WO2004000929A1

WO2004000929A1 - Biodegradable grafted block copolymer matrix compound having high content of steam-exploded biomass, a porducing method thereof, and method of producing molded article using the same

Info

Publication number: WO2004000929A1
Application number: PCT/KR2003/001188
Authority: WO
Inventors: Fijeau Kim
Original assignee: NEXSOL TECHNOLOGIES Inc
Current assignee: NEXSOL TECHNOLOGIES Inc
Priority date: 2002-06-19
Filing date: 2003-06-18
Publication date: 2003-12-31
Anticipated expiration: 2004-12-19
Also published as: AU2003241858A1

Abstract

The present invention relates to a biodegradable grafted block copolymer matrix compound of slurry type containing biomass and grain powders as main components, and also to also to production and molding methods thereof. This matrix compound has a water-plasticizing property, a curing property according to dehydration crosslinking caused by polycondensation occurring in a drying process, and a composite characteristic of thermoplastic resin.

Description

BIODEGRADABLE GRAFTED BLOCK COPOLYMER MATRIX COMPOUND HAVING

HIGH CONTENT OF STEAM-EXPLODED BIOMASS, A PRODUCING METHOD

THEREOF, AND METHOD OF PRODUCING MOLDED ARTICLE USING THE SAME

Technical Field

The present invention relates to a biodegradable natural polymer matrix compound containing biomass and grain powders as main components, and more particularly, to a biodegradable grafted block copolymer matrix compound of slurry type having a water-plasticizing property, a curing property according to dehydration crosslinking caused by polycondensation occurring in a drying process, and a composite characteristic* of thermoplastic resin, also to production and molding methods thereof.

Background Art

With, a growing interest in environment, social and international pressure from environmental .organizations is being intensified to develop materials that can substitute non-biodegradable plastics produced and abandoned excessively. Owing to such pressure, there have been various attempts to manufacture biodegradable plastics and products. Biodegradable polymers are being studied in the following three categories:

(a) natural polymer obtained from plants and animals (for example, cellulose, starch, protein, collagen and the like) ,

(b) polymer generated by fermentation of bacteria or microorganisms (for example, polyhydroxy alkanoates) , and

(c) synthetic polymer having biodegradability (for example, polycaprolactone and polylactic acid) .

Those studied up to now follow. It has been reported that a filler was manufactured by injection and expansion moldings of various biodegradable materials with starch as their main component.

It has been reported that biodegradable containers were molded and commercialized with starch as their main component. It has been reported that biodegradable materials were molded and commercialized by mixing thermoplastic resins with natural materials such as chaff, wheat flour, starch, etc.

There has been an attempt to manufacture biodegradable/difficult-to-decompose resins by esterifying/etherifying natural materials of xylem powder, etc. and mixing the resulting material with liquefied materials.

There has been a report in which starch was destructurized to give thermal plasticity to starch matrix compounds so that the compounds could be easily molded and commercialized with the prior plastic molder.

There has been a report in which many companies manufactured thermoplastic composite resins by mixing starch with olefin resins and various non-decomposable resins to give biodegradability to the resulting mixture.

Biodegradable containers of pulp mold are being commercialized, in which pulp slurry is manufactured by using plant pulp, regenerated pulp, etc. that are made of wood pulp, annual plants, etc. There has been an attempt to use, as a biodegradable plastic, poly-3-hydroxy lactic acid ester (PHB) obtained through fermentation.

There has been an attempt to manufacture biodegradable plastics by using polyamino acid, particularly gluten, zein, collagen, fermented polyglutamic acid (PGA) , synthesized amino acid, etc. There has been an attempt to manufacture biodegradable plastics by treating pulp, a raw material of cellulose, chemically with ester or ether.

There has been an attempt to manufacture biodegradable plastics by making viscous solutions that are obtained by dissolving cellulose, natural resin, with solvents of polar aprotic amide, especially N,N-dimethylacetamide (DMA) , n- methyl morpholine-n-Oxide (NMMO) , n-methyl caprolactam, dimethyl sulfoxide (DMSO), para-formaldehyde, etc. in the presence of lithium halide salts. Such processes produce the viscous solutions more easily and cheaply than esterification and etherification through treatment with the prior inorganic compound.

There has been an attempt to make biodegradable plastics by polymerizing caprolactone to form polycaprolactone or mixing, compounding, and dispersing caprolactone with other materials .

There has been an attempt to manufacture biodegradable plastics by using chitin and chitosan that are rich in nature and available easily.

There has been an attempt to manufacture biodegradable plastics by using alginic acid that is rich in nature and available easily.

Biodegradable plastics of aliphatic polyester, etc. made by mediation of aliphatic polyester are commercialized and in sale.

There has been an attempt to manufacture biodegradable plastics by using natural saccharide or lignin, which is a waste of the pulp industry. There has been an attempt to manufacture biodegradable plastics by fermenting or processing, and polymerizing amino acid.

An attempt has been reported to manufacture biodegradable plastics by polymerizing soybean milk, fish oil, etc. There has been a report in which lactic acid is polymerized to manufacture polylactic acid, a biodegradable polymer, for the purpose of constructing a plant for commercialization in a large scale.

As described above, an innumerable plurality of studies on biodegradability are being performed now and many kinds of products are already commercialized and in market. Nevertheless, biodegradable plastics are still not widely used mainly because compared to the prior commercialized products, molded products are very expensive, - production is still not in a large scale,

- molding processes are difficult due to relatively complicated molding and processing, the quality of newly developed products is relatively bad compared to the molded articles commercialized already, or the shapes of molded products are not acceptable to users or chosen by users, in the aspect of usage and beauty, compared to the prior molded articles. This is because users would like biodegradable plastics to have the same properties as the difficult-to- decompose plastics they are now familiar with and to be cheaper than them.

Disclosure of Invention Recently, there have been many attempts to use xylem, pulp, processed materials of various plants, products fermented by various bacteria, starch and starch derivatives as biodegradable polymer matrixes. A method of simply forming steam-exploded biomass, a main component of an inventive compound, into a molded article using aqueous thermoplastic resin and carbohydrates contained in grain powder or potatoes, particularly starch, as a basic mixture binder, includes the traditional method that the human race has used for several thousand years as a method of molding foods such as similar agricultural products. That is the method of molding, by heating, wheat flour containing water, starch, and the dough or slurry of pulverized grain or potatoes in a heated container. When the method is applied to foods, they can have countless plurality of shapes of bread, scorched rice, pie, pancake, potato powder cake steamed on a layer of pine needles, an additive, etc. Biomass is one of important components of the compound according to the present invention. Also, as for the known arts on biodegradable sheets and molded products, there are Korea Patents Publication No. 1999- 0087469, 1999-0087468, etc.

However, the prior arts such as the patents have the following disadvantages: 1. starch that is not gelatinized should be used and should be gelatinized during the processes,

2. organic additives should inevitably be used so that the surfaces of sheets molded out of matrix compounds does not stick to the rollers during the processes. A wide range of temperature should necessarily be used for organic additives so that the possibility of bad temperature control and a high defective fraction are accepted,

3. Combination should be precise so that molding can be finished without flowing down or being scattered by self- adhesion power, 4. A high content of starch should be used due to the dependence only on starch' s adhesion power, and

5. The resistance to water is very weak after molding. On the other hand, according to the present invention, -any starch may be used in the present invention, -a sheet is cast on an isolation film being continuously supplied, so that it is not stuck on processing equipment and thus not interferes with process flow,

-a sheet is cast on an isolation film by gravity, and thus, only the physical and chemical strengths, and morphological stability of a finished product after drying other than self-adhesion powder may be considered so that there is a margin against bad characteristics,

-a process is conducted by gravity so that there is required structural adhesion powder only after drying without requiring great adhesion powder from a coagulant during the process,

-a sheet has improved water resistance such that it can be used for a considerable period of time, even if it is in contact with water after molding, and -in a great improvement, other optional biodegradable fillers, which can be available at low prices, can be widely used.

Therefore, giving hydrophobicity to the surfaces by molding biodegradable natural products, such as steam-exploded biomass, with carbohydrate binders, can generate containers that can be useful enough in our daily life. The object of the present invention is to provide a biodegradable compound by using natural polymer having a high content of steam-exploded biomass (biomass made of vegetable material) and ^Λgrain powder' easily found and abundantly existing are directly steam-exploded and pre-treated, in consideration of their biodegradability, by then adding a functional additive' to the resulting material, by reinforcing with a fibroid material,' and by then binding the resulting material with a group of binders,' and a method of molding molded articles. The bound material is used in manufacturing a biodegradable natural polymer matrix compound

(hereinafter, referred to as compound' in a sense and thus compound and composition will be used in a mutually interchangeable manner) of slurry type, wherein the biodegradable compound is cheap, beautiful, and not inferior physically, chemically and morphologically than the prior petrochemical products.

An improved composition and method for producing a sheet, which is inexpensive and eco-friendly and has similar properties with paper, board, polystyrene and plastics, are required in the art. If a molded article containing eco- friendly steam-exploded biomass and grain powder in addition to water and fibroid material contained in typical pulp slurry used in paper production can be produced, it will be an improvement in the field of production of biodegradable molded articles. Furthermore, if this sheet, and containers or products made of the sheet, can be easily biodegradable or degradable in soil, it will be a considerable improvement in the relevant field of art. Particularly, in producing the same article, it is preferred to reduce energy and initial investment necessary for the production of products having the essential properties of paper, plastic and metal. In view of practical use, if a composition and method, which allow sheets, containers and other molded articles to be produced at low costs, are provided, it will be a considerable improvement.

Moreover, providing a composition and method, which allow considerable amounts of steam-exploded biomass, grain powders and bulbous plants, etc. to be directly used in the sheet as described above and can contain natural fillers, is also an improvement. Particularly, if a sheet filled with such inorganic materials has higher flexibility, tensile strength, stretchability, moldability, water resistance and mass production than the prior material containing high contents of inorganic materials, it will be a great improvement in the art. The present invention provides a biodegradable natural grafted block copolymer matrix containing high contents of steam-exploded biomass, a sheet molded with this compound

(called "three-layered composite sheet") , and production and molding methods thereof.

Brief Description of Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 shows a commercial steam-exploder, which allows biomass to be continuously steam-exploded;

FIGS. la, lb and lc are illustrative diagrams of commercial compounding machines that can continuously make slurry that can be directly input to molding processes;

FIG. Id is an illustrative diagram of a commercialized 1188

9

compounding machine that can compound any slurry for each lot; FIG. 3 shows rollers and process where slurry supplied from a continuous compounding machine is continuously formed into a sheet; FIG. 4 shows rollers and process that sheet continuously the slurry cast in an extruder on a one-sided or both-sided film that is supplied after completion;

FIG. 5a is an illustrative diagram of a mixer or extruder of cylinder type; FIG. 5b is a diagram showing the states of processes that show the appearance of fine adjusting the cast sheet between various rollers; and

FIG. 6 is an inner structural diagram of molded articles.

Best Mode for Carrying Out the Invention

A method of simply forming steam-exploded biomass, a main component of an inventive compound, into a molded article using aqueous thermoplastic resin and carbohydrates contained in grain powder or potatoes, particularly starch, as a basic mixture binder, includes the traditional method that the human race has used for several thousand years as a method of molding foods such as similar agricultural products. That is the method of molding, by heating, wheat flour containing water, starch, and the dough or slurry of pulverized grain or potatoes in a heated container. When the method is applied to foods, they can have countless plurality of shapes of bread, scorched rice, porridge, soup, pie, pancake, potato powder cake steamed on a layer of pine needles, an additive, etc. Here, proteins and carbohydrates, especially starch, contained in the dough, is not only a component of molded article, but they play a role of binders and exist in an aqueous mixture of polymer matrixes.

Therefore, giving hydrophobicity to the surfaces by molding biodegradable natural products such as wood-based materials with carbohydrate binders can generate containers that can be useful enough in our daily life.

The object of the present invention is to provide a biodegradable compound by using natural polymer having a high content of steam-exploded biomass (biomass made of vegetable material) and 'grain powder' easily found and abundantly existing are directly steam-exploded and pre-treated, in consideration of their biodegradability, by then adding a 'functional additive' to the resulting material, by reinforcing with a 'fibroid material,' and by then binding the resulting material with a group of 'binders,' and a method of molding molded articles. The bound material is used in manufacturing a biodegradable natural polymer matrix compound

(hereinafter, referred to as 'compound' in a sense and thus compound and composition will be used in a mutually interchangeable manner) of slurry type, wherein the biodegradable compound is cheap, beautiful, and not inferior physically, chemically and morphologically than the prior petrochemical products.

The present invention provides a biodegradable grafted block copolymer matrix of slurry type containing high contents of steam-exploded biomass and having water-plasticizing property, a curing property according to dehydration crosslinking, and a composite characteristic of thermoplastic resin, and also provides a producing method thereof, a method for producing a three-layered composite sheet using the same and a molded article produced from the same. The compound having high contents of steam-exploded biomass according to the present invention has superior water- resistance, strength and performance that are superior physically, chemically, morphologically, and functionally, to papers made of the prior pulp. The composition of the compound used for forming a sheet mostly comprises steam-exploded biomass as a main component, aqueous polymer having thermal plasticity (also referred to as thermal gelling or syneresis hardening) as a primary binder, starch granules contained in grain powder as a secondary binder, a homogeneously dispersed fibroid material, a functional additive, additive components, and water as a solvent and a viscosity controller.

Here, the dehydration crosslinking, which can also be referred to as 'syneresis' , means that two molecules bind together by driving water out. Condensation polymerization is a similar phenomenon.

The present invention provides a biodegradable polymer matrix composition having high contents of steam-exploded biomass, which is used for sheets having properties similar to those of papers, cardboards, polystyrene, and plastic foam sheets and being environmentally friendly, and also provides a method of forming a compound made of the composition into the desired shape. Also, the present invention provides a composition for manufacturing sheets that can be formed into various containers or other products and a method thereof, by using manufacturing facilities and technologies used for manufacturing papers, cardboards, polystyrene, or plastic sheets .

The matrix for manufacturing the compound having high contents of steam-exploded biomass according to the present invention consists of steam-exploded biomass, grain powders, a fibroid material, a binder including water-soluble (or water- dispersible) thermoplastic resin and a group of carbohydrates (especially, starch) , an additive, a functional additive, and water acting as a solvent and a plasticizer. To form the compound having intended properties with the components mentioned above, the compound for molding is manufactured through the step of mixing them in a prescribed ratio.

A group of binders is mixed in the compound, as a part of the components used for manufacturing the matrix. The matrix comprises fibroid material homogeneously dispersed for reinforcing elasticity, drawing property, and strength. To provide physical-chemical and dimensional stabilities for the molded article, a hydrophobic coating is formed on or attached to the surfaces. Unless otherwise defined herein, the term 'water- soluble' means both 'water-soluble' and 'water-dispersible' .

Comprising various materials that can provide related properties to increase property of the components of the matrix, the present invention can produce inherent molded articles having significant strength, drawing property, environmental friendliness, large scale productivity, and cheap price. These examples can be easily found in ABS resins and ABR rubbers to be described later.

The term 'steam-exploded biomass' or shortly 'biomass' means a fibroid material, which is obtained from naturally occurring celluloses by an explosion method. It is contained in the compound of the present invention before compounding. Unless otherwise defined or explained herein, 'biomass' means 'steam-exploded biomass' . A 'group of binders' means the combination of binders used for the production of molded articles or sheets of the present invention. In order words, the group means a mixture of an organic binder contained in the combination and a natural binder supplied from grain powder.

A 'composite component' is an extended concept of compound and means that the composition used for manufacturing sheets comprises various chemically or physically different materials or phases such as steam-exploded biomass, water- soluble, thermoplastic (or thermo-gelling or thermo-curing) binder resins, biodegradable grain powder, fibroid material, inorganic additives, function additives, and water. This wide range of materials each and every way allows both the composition used for sheeting and the final sheets to have more than one inherent property.

The term 'to reinforce with fibroid material' mean to add fibroid material literally. But the sheet or molded article of the present invention is different from pulp papers and plastic sheets. Pulp papers depends not only on the binding of papers but on hydrogen bonding (condensation reaction) due to mutual entanglement of fibers based on 'Web' physics to provide 3-dimensional matrix and weight. In particular, to give papers a shape and weight, it is manufactured by adding thermally hardening resins and a filler together with materials for hydrogen bonding to occur.

The terms 'slurry,' 'polymer matrix,' or 'molding composition, ' 'moldable composition, ' or 'polymer matrix having a high content of steam-exploded biomass' are differentiated depending on the amount of water content, can be used in a mutually exchangeable way, and mean 'biodegradable polymer matrix compound' having a high content of steam-exploded biomass that can be molded into a shape of sheet or other shapes. This has a characteristic in that it contains water as a solvent and a plasticizer that forms a mixture having plasticity similar to plastics, by mixing a significant amount of steam-exploded biomass and grain powders, a small amount of organic synthetic binders, various amounts of fibroid materials and mineral additives. The compound can contain additives such as plasticizers as a functional additive, lubricants, dispersants, water-curing materials, and foaming agents.

The term 'total solids' include all solids regardless of whether they are suspended or dissolved in a mixture. Of course, the total solids do not include compounding water.

The compound having high contents of steam-exploded biomass according to the present invention has a limited range of plasticity and adhesive property, but has a characteristic in that it is stabilized after molding into a desired shape to have a relatively high bearing power. The 'polymer matrix,' 'compound, ' or 'mixture of steam-exploded biomass' refers to the compound irrespective of the degree of dryness. This compound thus comprises dried polymer matrixes and completely dried compounds (even though a certain amount of water may remain as binding water within the group of binders in the sheet..)

Formed after the compound forms sheets, the binders harden then by heat, the functional additives play their role, and the sheets are dried partially, the sheet or molded product will have the 'polymer matrix having a high content of steam-exploded biomass' .

The composition for making matrix comprises 5 to 90 wt% of steam-exploded biomass; 1 to 90 wt% of a starch binder contained in grain among the group of binders and an aqueous organic synthetic resin; 1 to 40 wt% of fibroid materials; 0 to 90 wt% of a filler; and the amount of water enough for producing the compound, by mixing with slurry, with all the percentages being relative to the total solids. Water-soluble resins in the compound increase the bearing power of the matrix to function as a thickener that allows homogeneous dispersion of fibers in the entire polymer matrix.

There are in general many methods in molding plastics, which mostly include injection, extrusion, calendaring through casting, etc. For injection and extrusion of the compound of the present invention, conventional plastic processing methods can be used by virtue of the constituents of the present invention. And the compound is formed into an initial sheet since the compound mentioned above is cast to laminate on an isolation membrane continuously supplied through a conveyer in the calendaring process.

The biodegradable polymer matrix mixed completely is laminated in a uniform thickness on a coated film continuously supplied or an isolation film supplied continuously through a conveyer. Afterward, the sheet passes through a heating means heated up to more than the gelatinization temperature of starch. For example, the starch such as potato starch is gelatinized at 65 °C, corn starch at 95 °C and wax corn starch at 70 °C.

The compound cast on the isolation film flattens with its surfaces being uniform by a heated compression roller. The sheet hardens to a significant degree by evaporating a considerable amount of water. The heating means hot enough to remove water gelatinizes starch granules. The initial sheet passes through heated rollers to be dispersed with other binders and the components of the compound homogeneously so as to bind to the isolation film and, afterward, is completely molded by removing a considerable amount of water through evaporation. Then another isolation film is laminated on the surfaces of the initial sheet that is being almost dried, and the heated rollers presses the sheet to let the membrane to stick to the initial sheet, thereby completing the process of producing the biodegradable sheet with both surfaces being coated with the films.

Additionally, the present invention provides a composition having high contents of steam-exploded biomass and a manufacturing method thereof for manufacturing environmentally friendly sheets that comprises a part of water contained in the slurry used for manufacturing pulp papers, is unnecessary for excessive dehydration during the sheet-forming process, and can be formed out of moldable compositions. Also, the present invention provides sheets, containers, and other products that can be decomposed by materials contained in soil or are biodegradable. The invention also provides a method of manufacturing sheets, containers, and other products with the cost cheaper than that of manufacturing papers, plastics, or other metal products, and a composition obtained therefrom. It additionally provides a composition that can reduce the energy and the initial investment expenditure for manufacturing molded articles having the identical characteristics to those found in papers or plastic sheets and especially that can comprise a high content of steam-exploded biomass, and a method thereof. Lastly, it provides a composition and a method for manufacturing inorganic material-filled sheets that can comprise a significant amount of natural additives in them and can have bigger elasticity, tensile strength, drawing property, moldability, large scale productivity.

The molded article, especially sheet, molded using the method of manufacturing the polymer matrix compound having high contents of steam-exploded biomass according to the present invention can be 0.1 mm to 100 mm thick. But to have the quality similar to that of papers or cardboards, the thickness should be less than 1 cm, preferably less than 5 mm, more preferably less than 3 mm, and most preferably less than 1 mm.

The sheets produced according to the present invention have similar properties to paper, cardboards, and plastic sheets, and can be used for forming articles, such as containers or other packing materials.

As a result of the present invention, various products that have been manufactured with papers, cardboards, or polystyrene, when using the materials described above, can be manufactured in a large scale, with the cost cheaper than that of the prior costs. The cost reduction is not only due to the reduction in unit price of materials but a rational result of using the manufacturing processes that require less energy and the initial capital investment. Especially, the composition used for manufacturing the sheets having high contents of steam-exploded biomass • according to the present invention requires dehydration less than that in the case of manufacturing papers . Thus compared to the case of manufacturing plastics or metals, the cost of obtaining raw materials is low in the present invention.

Also, the sheets of the polymer compound matrix having a high content of steam-exploded biomass contain only environmentally friendly components. Thus this method of manufacturing sheets using this compound matrix affects environment less than the method of manufacturing sheets from the prior materials. The sheets having high contents of steam- exploded biomass according to the present invention require wood pulp of high concentration, products for petro-chemistry, or other natural resources less than the cases of manufacturing papers, plastics, or metal sheets. Since starch or water-soluble resin components dissolve in water easily, recycling or biodegradability is promoted. If abandoned to ambient environment, starch and aqueous resins absorb water quickly to be dissolved, thereby leaving biomass having a small amount of fibers and a composition similar to soil and functional additives. Microorganisms existing in soil degrade dissolved starch and water-soluble resins and dispersed fibers easily.

Starch granules used as a natural binder in processing biodegradable molded articles having high contents of steam- exploded biomass according to the present invention are not soluble in water in general. Thus, if a composition containing these starch granules is not heated above the gelling temperature of starch, the granules function only as a passive particle filler. Otherwise, a mixture should contain far more water to increase the viscosity of gelatinized starch in the molded article and to maintain the same molding properties as those before gelatinization.

The molded article produced from a polymer matrix compound containing steam-exploded biomass as a main component is manufactured such that it has properties similar to papers, cardboards, or other sheet materials. The sheets described above have excellent dimensional stability and hydrophobicity since an isolation film is coated uniformly on the surfaces of the sheet. The molded article containing high contents of steam- exploded biomass according to the present invention can be described as a composite component to be mentioned later, especially a thermoplastic sheet or a molded article reinforced with fibers. In other words, the article is a thermoplastic complex or a molded article in which a composite component reinforced with fibers is bound with the group of binders.

The most important goal set for the present invention is to give plasticity and flexibility to the components of the present invention, even though they are natural materials, so that they can be molded freely even after the initial molding. The examples include acrylonitrile butadiene styrene (ABS) resin, ABR synthetic rubber, etc. that are composite block compounds. Since each component contained in ABR resin is plastic resin and has many disadvantages, it is not frequently manufactured alone (except PS resin) . But three (four, substantially) components are mixed to have synergy effects. Similarly, SBR synthetic resin shows better rubber properties, a third characteristic, when mixed with styrene monomers and butadiene monomers . Therefore, this is a realization of the 'grafted block copolymer' matrix compound consisting of biodegradable slurry that can be molded thermo-plastically, which is a goal of the present invention.

According to the definitions and the principles, a biodegradable polymer matrix compound comprising steam- exploded biomass and grain powders, a group of binders, a fibroid material, and other additives is formed into various products having the properties similar to those of pulp papers or cardboards. The molded articles or sheets having high contents of steam-exploded biomass according to the present invention can substitute for sheets made of plastics or polystyrene. The inventive sheets can be cut to manufacture various containers and other products by forming processes such as bending, folding, and rolling. The composition having high contents of steam-exploded biomass, method, and molded article according to the present invention are especially useful for large scale production of disposable containers and food wrappers in the fast food industry.

The compound having high contents of steam-exploded biomass according to the present invention has the following characteristics different from those of other molded articles. In the cases of the prior starch and molded articles of a high content of inorganic materials, at the instant when the molded articles contact water, especially hot water, the binding force reduces considerably such that the molded articles themselves can be sustained, thus limiting the usage. In the case of an alloy with olefin resins, starch decomposes easily, but olefin_. resins not decompose but collapse biologically, thus confirming that olefin resins still exist.

The decomposition mechanism of the molded article having high contents of steam-exploded biomass according to the present invention is as follows. First the molded article is dissolved initially by the water in the aqueous binder. Afterward, as the binding force of the composite components added, etc. reduces, collapse occurs slowly. Then, the steam- exploded biomass is decomposed by microorganisms. Therefore, the lifetime of the article is long sufficiently, compared to the biodegradable molded articles manufactured out of other natural materials. The article has a characteristic in that its composite components have physically strong resistance to water. But after decomposition, they decompose completely to become fertilizers, thus aiding a beneficial circulation of nature .

Outline of cellulose

Steam-exploded biomass that is one of main components used in the present invention is cellulose. Strong binding force of paper, a representative of pulps, is because of the cohesive strength between a sizing agent and a thermosetting resin contained in paper, and also the OH bonding between fibrils of re-bound pulps.

The characteristics of fibroid materials of plants, especially cellulose, are being continuously studied. Cellulose is dissolved in a solvent under a special environment. For example, polar aprotic amide solvents, especially N,N-dimethylacetamide (DMA), n-metyhl morpholine-n- oxide (NMMO) , n-methyl caprolactam, dimethyl sulfoxide (DMSO) , para-formaldehyde, etc. in the presence of lithium halide can dissolve cellulose. There are attempts to manufacture biodegradable plastics by making viscose through the prior treatment processes of inorganic materials using such dissolution or by obtaining viscose or cellulose solution in the processes cheaper and simpler than esterification and etherification. However, even though many progresses have been made, such dissolution cannot be considered as being perfect. The reason is that except spinning or film, it is difficult to freely mold and process using such dissolution like plastics. For reference, the production processes of papers made from pulp are explained. In manufacturing pulp papers, the kraft or hydrogen sulfite process is mostly used for forming pulp.

In the kraft process, pulp fibers are 'cooked' for dismantling during the NaOH process. In the hydrogen sulfite process, acid is used for dismantling fibers. To release lignin kept inside the fiber walls in these processes, fibers are processed primarily. However, the removal of lignin from fibers reduces the strength of fibers. Since the hydrogen sulfite process is much severer than the primary process, the papers manufactured by the sulfite process have only about 70% of the strength of those by the kraft process.

If woods become wood pulp in the kraft or hydrogen sulfite process, they are processed in beater to release hemicellulose and lignin inside the fiber and to unbind by chafing the fibers. In general, pulp slurry consists of 99.5% of water and about 0.5% of wood pulp. Such pulp slurry are further beat to release hemicellulose and to form a fiber mixture in which molecules binds to themselves through a web effect (web physics) and hydrogen bonding by which fibers entangle mutually when chafed. However, this severe treatment in pulp production causes defect to be generated along the length of the entire fibers, thus losing most of tensile, tearing, and bursting strengths. Pulp manufacturing depends on web physics to obtain bonding and structural integrities necessary for sheeting papers. Thus a relatively high ratio (more than 80%) of fibers should be added to the paper sheets.

The slurry beaten in water is put on a screen net and extrusion rollers squeeze out water for primary dehydration. This dehydration process generates the sheet having 50 to 60% of water contents. After the primary dehydration, the paper sheets are further dried by heat with heated rollers. Here, to obtain typical properties of papers, substituting fiber materials can be added to the sheets. The materials include various plant fibers (known as secondary fibers) such as reeds, bamboos, straw, flax hemp fibers, Manila hemp, hemp, and sugar canes. The resulting papers are called 'plant papers.' However, in the paper industry, pulp is obtained from trees and papers are made from pulp. This requires too much energy and contaminates environment.

Considering the level of the current technologies, to mold for a desired purpose by using the characteristics of pulp fibers, starch, and steam-exploded biomass as they are, are much economical and realistic than to mold by transforming or substituting glucose molecules. However, despite advanced modern paper production methods, there exists no fiber slurry in the 'moldable' state that can be molded like plastics having plasticity, at any instant of paper manufacturing stages. This is so because cellulose does not have thermal plasticity and does not dissolve in any solvent as perfectly as to allow molding. The sheets having high contents of steam-exploded biomass according to the present invention have so many characteristics in that they can substitute papers. Nevertheless, their manufacturing processes differ from the prior processes of manufacturing pulp papers, in many aspects. At first, compared to the pulp paper slurry containing more than 97% of water, even 99.9%, a far less amount of water is used in manufacturing the compound of the present invention

(less than 50 wt%) . Also, the sheets having high contents of steam-exploded biomass according to the present invention are more cohesive than the aqueous pulp slurry and are formed together with the polymer matrix in the compound. Thus once molded, they maintain the shapes as long as no more molding or actions are applied.

In paper production, only cellulose is extracted and hemicellulose and lignin are removed. But different from that, the present invention removes water and absorbed water from wood-based materials and the remnants are pulverized for use. Thus the use ratio of raw materials is high and the loss ratio is relatively low. Preferably, this is more environmentally friendly, that the paper manufacturing industry. Another characteristic of the compound having high contents of steam- exploded biomass according to the present invention is that it does not depend on web physics to bind the components of the sheet. Bur rather, the binding and cohesive forces of the group of binders provide most of tensile and bending strengths. The group of binders interacts not only other solid components to a certain degree but themselves as a binding matrix.

As a result, a smaller ratio of fibers can be included inside the fibroid material, while maintaining the advantages of tensile, tearing, and bursting strengths given to the material. Since a smaller amount of fibroid materials are used while the good strength characteristics are maintained, sheets, containers, or other related molded articles can be manufactured out of the compound, which is more economical than papers . The reasons for being more economical are:

(1) the steam-exploded biomass to be used in the present invention is much cheaper that pulp,

(2) the unprocessed grain powder, potatoes, etc. to be used in the present invention are much cheaper than processed starch and organic synthetic binders,

(3) the capital investment for processing facilities is much smaller than that of the paper industry,

(4) hydrophobicity of the surfaces of the steam-exploded biomass is removed and the amount of fiber contents is minimized with the pretreatments that do not use acid and alkali, thus reducing the amount of contaminants related to fiber manufacturing, and (5) the energy consumption is low since the amount of water used in the processes of the present invention is small. The L/D ratio and strength of a fibroid material are important factors in determining the amount of fibroid materials to be used.

The higher the tensile strength, the smaller the amount of fibroid materials is used for obtaining the tensile strength necessary for the molded articles. Some fibers have higher tensile, tearing, and bursting strengths and other kinds of fibers having lower tensile strength may be more elastic. In the case where sheet are used for bending at a large angle, a high concentration of fibroid materials are required. Fibers with a smaller L/D ratio or short length are mixed easily with the compound. Fibers such as the kraft pulp and

Manila hemp have high tearing and bursting strengths . Fibers such as cotton have lower strength and higher elasticity. When better mixing, higher elasticity, higher tearing and bursting strengths are required, the combination of fibers having various L/D ratios is added to the mixture.

The fibroid materials used for manufacturing the sheets of the present invention and other products are favored to have a large ratio of 'length/diameter (L/D) , since thinner and longer fibers can give larger strength. The ratio is 10: 1, preferably 100: 1.

Cotton, wood fibers, flax hemp, Manila hemp, and Indian millet are favored since they decompose easily under normal conditions. Depending on the usage, recycled paper fibroid materials may also be used.

The sheets having high contents according to the present W

26

invention contain about 1/100 to about 1/3 of the amount of fibroid materials that are required in papers. Nevertheless, the sheets have the tensile, tearing, and cohesive strengths similar to those of papers. A reason is that the fibroid materials used in the present invention experience less processing than those in manufacturing papers. Another reason is that grain powder contains a certain amount of fibers as a binder and a structural constituent.

In any case, fibers contained in high contents of steam- exploded biomass used in the present invention maintain their initial strength, since they do not undergo the severe processing used in the production in pulp paper, unlike fibers contained in paper. Fibers in the steam-exploded biomass used in the present invention require little or no chemical processing, unlike those in the paper industry.

In the following, we turn to detailed description of the components of steam-exploded biomass used in the present invention and their role and function. A. Biomass and pretreatment 'Steam-exploded biomass' , a main component of the present invention, is defined in the following way. It is a collection of stem cells of perennial and annual plants and consists of cellulose, hemicellulose, and lignin. It refers to fine power obtained by steam explosion of wood-based materials, having property more than the physical strength of a certain requirement . Depending on the kind of raw material and the usage of molded articles, it can be processed additionally, which will be described later.

Plants accumulate a great deal of xylem (stem cells) in the stem as they live for several years or for more than a thousand years sometimes. This life activity of plants affects environment in a very ingenious way. Especially the activity affects human life much in an unavoidably inevitable manner. The products generated in these plants return to nature after they stop life activities and decompose biologically. Generation and decomposition are mutually related to form a cycle, thus providing nutrition for new organisms.

However, since manmade high quality plastics do not decompose in natural environment, the cycle of generation and decomposition is broken to hinder environmental circulation. Xylem (biomass) is regenerated annually as carbohydrates and is very cheap, is abundantly supplied, and is a limited resource that cannot be used up. It is innumerably plentiful from perennial woods and bamboos to perennial trees that are not economical, to stems of annual reeds, to annual grasses that are stepped on at mountains and fields, to fallen leaves, to vegetables that are cultivated, to cuticles of grain and dried nuts, to stems, to leaves, to byproducts of food manufacturing, and to wastes from wood processing and food manufacturing. But those that are used in reality in our life are at the very least and extremely restricted.

Except fruits, most of stem plants in any species are divided into the following three categories: 35 to 45% of cellulose, 25 to 35% of hemicellulose, and 20 to 30% of lignin. Except for the cases where woods are used as they are, only celluloses are extracted among them to manufacture pulp papers, cellophane films, artificial fibers (viscose) , and plastics, and hemicellulose and lignin are extracted to disappear during hydrolysis with acid and alkali or are used as fuels or abandoned almost, thus causing other environmental problems. The existing wood pulping processes include mechanical pulping, chemical pulping and semi-chemical pulping processes. More specifically, they include alkali treatment, sulfur dioxide (sulfite) treatment, hydrogen peroxide treatment, freeze-explosion, weak acid extraction, and steam explosion. However, these pulping processes are unsuitable for the treatment of filament biomass.

Among such traditional treatment processes, the steam explosion is recently widely studied, and considered as an environmentally and functionally excellent process. Furthermore, the steam explosion process is advantageous in that it allows hemicellulose and lignin to be dissociated.

Among the processes described above, the steam explosion process of making the steam-exploded cellulose, a main component of the inventive compound, is a method in which biomass is heated with high pressure steam, and then explosively emitted. This steam explosion process shows remarkably low corrosion as compared to the prior acid or alkali treatment process, and allows lignin to be decomposed into relatively small pieces such that it can be easily dissolved. Before explaining the treatment of biomass in details, thermal decomposition by dry distillation and methods of surface treatment of wood-based materials are described further. An 'absorbed water' contained in woods is evaporated when heated to about 100 °C. But when the temperature exceeds 100 °C, thermal decomposition sets in slowly as a structurally absorbed water is released and at 150 °C, decomposition rate become fast. At 180 to 300 °C, . hemicellulose decomposes rapidly. As cellulose decompose at 240 to 400 °C and lignin at 250 to 550 °C, peaks of heat generation appear near 250, 300, and 400 °C. At this time, decomposition is vigorous and exothermal reaction occurs simultaneously. At 500 to 1000 °C, hydrogen is separated from carbides of 3 main components to become wood charcoal and peaks of wood gas generated near 700 °C are due mainly to this hydrogen. The specific gravity of trees differs depending on the kind of trees. The kind having the greatest specific gravity is African ironwood, which is 1.49 g/cm². The kind having the lowest is Cuban Aeschynomene Hispidad, which is 0.044 g/cm². The specific gravity of chaff is 1.10 g/cm², and the apparent specific gravity of bulked chaff is 0.17 g/cm².

Any biomass can be used in the present invention, but biomass of 0.1 to 1.5 g/cm² is preferably used. When the biomass is compared to general plastics, plastics are nothing more than the biomass foamed 1 to 5 times. This means that the biomass materializes more strength than the plastics having the same strength and weight. This is an additional advantage and characteristic. It is lighter because of pores generated in wood-based materials by the drying of absorbed water.

The wood-based material prepared in this manner is used widely .as a plastic filler. In general, it is compounded in 20 to 60 wt% relative to plastics. Such plastics are injected materials of general-purpose plastics of PVC, PE, PP, etc. This is so because they can be made light in weight by using the average specific gravity of wood-based biomass of 0.3 to 0.9 g/cm², wood-based biomass is environmentally friendly and available in a cheaper price than plastics, and its property is not worse than that of plastics. Wood-based biomass is mixed with the general-purpose resins mentioned above and molded such that it has characteristics similar to those of woods. And the powder is used for purposes similar to those of woods, but more excellent performances than those of woods are taken out for use. However in this case, wood-based biomass and plastic alloys lose biodegradability. Also for one disadvantage, even though the wood-based biomass mentioned above is environmentally friendly, the direct use of woods obtained from cut trees without pretreatment is destructive to environment and consumes energy too much. Therefore, the present invention make it possible to use the stem cells of annual plants that are low in commercial value.

One of the most important reasons why steam-exploded biomass is used in the present invention is that trees have a strength of 400 to 700 kg/cm² whereas general-purpose plastics have a strength same as or lower than that. Also for another reason, cellulose, a component of steam-exploded biomass, does not dissolve in water, differently from starch. Thus after molding, the shape does not collapse rapidly or property does not lower immediately, even though the biomass contacts directly with water.

Meanwhile, the gelatinization temperature or the glass transition temperature of starch is 55 to 95 °C. Thus if starch is used as a main biodegradable binder, starch is melted due to the temperature obtained from the contents higher than the glass transition temperature, in the case where the molded article is put in hot water or high frequency wave heaters (microwave oven) are used. Here, the physical shape of the molded article changes. When this happens, biomass blocks heat conduction. Thus even though it is used at a temperature higher than the transition temperature, the stability of shape is not hampered much.

Another very important point is that steam-exploded biomass is rather competitive naturally even when considering the cost of treatment chemicals and the processes necessary for changing starch properties in order to provide with a specific property.

As known very well, even though water contact the molded article having a high content of biomass during storage, transportation, and usage, the property of wood-based biomass do not lower immediately, and its resistance to water is excellent compared to the sheets having a high content of starch. This is one of the characteristics of the molded articles having high contents of steam-exploded biomass according to the present invention.

Specifically, the steam explosion process, which is applied in the present invention, is a method in which cellulose, a component of wood-based (cellulose-based) biomass, is extracted by steam explosion in a relatively simple manner, and at the same time, components of the biomass are sorted, thereby obtaining fibers. Particularly, this is one of good processes for effectively sorting the components of wood-based or non-wood-based biomass having low economical efficiency.

Hereinafter, the term 'wood-based biomass' or 'non-wood- based biomass' will also be termed 'xylem' or 'biomass' according to usage or convenience.

As used herein, the term 'low economical efficiency' means that biomass available at low prices, such as sawdust, byproducts in wood processing, chaffs, rice-straws, byproducts of processed foods, and the like, have low prices even after processed, since they are unsuitable for use as high value- added articles in a given application, unlike relatively expensive forest resources. However, since these wood-based byproducts still have cellulose suitable for use in a certain use, they are changed into a suitable shape by separate processing such that they can be used as a component of the compound having high contents of steam-exploded biomass, thereby increasing their value.

Celluloses having low economical efficiency, which can be selectively extracted by steam explosion, include various biomasses. However, typical celluloses suitable for use in the compound of the present invention include chaffs, rice- straws, sawdust, rye straws, Indian millet straws, sugar cane straws, bean stems, and bamboos. Long fibers include Kenaf, flax hemp, hemp, yellow hemp, Manila hemp, and the like. Such cellulose-based (wood-based) biomasses are leaves, stems and roots of naturally occurring plants, and their main components consist of three components of cellulose, hemicellulose and lignin. Decomposition or conversion of these biomasses gives materials useful for human life, such as cellulose (cellulose, pulp) , glucose, xylose, purified lignin, and derivatives thereof, including ethanol, xylitol, and the like.

However, the cellulose-based biomass contains the three components at a given ratio. For example, oaks growing in Korea contain cellulose at 45-50%, hemicellulose at 12-25%, and lignin at 23-35%, which are bound closely together to form wood tissues. For separation and use of such three components, cutting of the tissues between them, breakdown of the binding between them and purification must be carried out, so that these components are separated from each other.

Among the cellulose-based materials, chaffs, rice-straws, wheat straws, sugar cane straws and woods, etc. were analyzed for their celluloses. The results indicated that the celluloses contain the following components. Also, needle-leaf trees as woods for pulp are 3.0 mm in length (diameter: 15 microns, L/D: 75) , broad-leaf trees are 1.2 mm in length (diameter: 26 microns, L/D: 46), Kenaf (Bast) is 2.6 mm in length (diameter: 20 microns, L/D: 130) and Kenaf

(Core) is 0.6 mm in length (diameter: 30 microns, L/D: 33), whereas bamboos are 3.0 mm in length (diameter: 15 microns, L/D: 200), rye straws are 1.5 mm in length (diameter: 13 microns, L/D: 110), and sugar canes are 1.5 mm in length

(diameter: 20 microns, L/D: 75) . Thus, it can be found that the non-wood biomasses can also be sufficiently used in the matrix compound having high contents of steam-exploded biomass according to the present invention.

Accordingly, there are various attempts to use cellulose, hemicellulose and lignin in such a biomass intact by the breakdown or change of the binding between the three components, or to make their separation easy by additional decomposition or conversion of these components.

Among the materials as described above, materials forming the surface of seeds, such as chaffs, act to protect contents of the seeds unlike wood byproducts (particles) , and have a curved shape and contain wax and silica layers in their inside. Thus, they have a characteristic in that their low tensile strength is about 1/3 lower than fibers produced from woods.

There are no study or attempt to fibrillate short fibers of the biomass as described above and knit them into threads or mats, or to use them in woven fibers. This is because their length is too short to knit them into threads. There were only attempts to use them in making papers or cardboards. However, it is known to use xylem powders crushed into 100 meshes as carriers and additives for thermoplastic resins. However, when they were steam-exploded to separate celluloses, they have a L/D of 10-100 and stand comparison 03 001188

34

with other fillers in their use as a reinforcing agent for plastics.

In the principle of steam explosion, cellulose- containing biomass is contacted with acid or alkali to activate its surface. Then, the biomass is heated to 180-230 °C for a given period with water or water steam to swell it to a given level, after which it is put in a closed reactor which is then pressurized to about 20 atm (actual process pressure: 14-30 atm) for 1-10 minutes. Then, if the reactor is suddenly opened to reduce its pressure to atmospheric pressure, condensed steam (water) and adsorbed water inside the biomass will be instantaneously expanded into steam due to the heat from heated steam and the vapor pressure (evaporation pressure) of absorbed water caused by this heat. The expanded water evaporates with the absorbed water inside the biomass.

The term 'activate' herein means that a hydroxyl group on the biomass surface is ready to hydrogen-bind with other components by dehydration. This term has a physically similar meaning to 'swelling' and is used in the same manner as the 'swelling' .

When a pressure of 15-30 atm is applied for steam- exploding the biomass, 180-230 °C steam, most of adsorbed water and liquid lignin are dissociated together, and at the same time, sites where adsorbed water or moisture had been present, particularly cell and stem structures, are broken down and swollen. Thus, cellulose contained in the biomass is fibrillated to become a network-like three-dimensional shape. Particularly, hemicellulose and lignin, which had been contained together, are steam-exploded and dissociated such that they can be easily separated.

The surface of the fibrils, which were steam-exploded and dissociated as described above, is more activated such that it can be easily hydrolyzed or dehydration-cured with water, enzyme, components and additives, etc.

Here, the saturated steam heated to about 180-230 °C has a steam pressure of 10-28 kg/cm². This process is closely similar to a popping process of cereals, which can frequently see in ambient environment. The fibrils, which had been steam-exploded as described above, are used in various applications, such as pulps, plastic additives, microcrystalline celluloses and the like, depending on the length of fibers.

In order to improve the steam explosion process such that given physical properties can be obtained by only one steam explosion process, the biomass can be subjected to suitable pre-steam explosion before introduction into the reactor. The pre-steam explosion includes a method wherein the biomass surface is activated by heating with steam or the dissociation of hemicellulose and lignin is more accelerated by alkali treatment, particularly treatment in 1% caustic soda solution for one hour.

In order to obtain given celluloses from biomass, wood (cellulose) -based biomass crushed into a given size is introduced into an extractive reactor equipped with a heating jacket allowing temperature control, via a hopper. Steam heated through a pre-heater is introduced at given temperature and pressure while the biomass is activated such that hemicellulose and part of lignin are dissociated from the biomass. And an open/close valve at the lower portion of the reactor is closed and a steam valve at the upper portion of the reactor is opened so that steam is applied into the reactor to a given pressure. Immediately after closing the steam valve, the open/close valve at the lower portion of the reactor is opened so that extracted solids including cellulose and -lignin within the reactor are explosively spouted in a flash tank and thus exploded. These procedures are repeated to give large amounts of exploded biomasses.

Due to heat and pressure transferred during the steam explosion process as described above, an acetyl group in hemicellulose can be free to reduce the pH of process steam to 3.0. As a result, hemicellulose is hydrolyzed into monosaccharides and oligosaccharides such that it can be soluble in water. At the same time, lignin is opened at the alkyl allyl ether linkage to reduce its molecular weight such that it is mostly soluble in organic solvent or weak alkali. By modification of such components, the structure of cellular walls is broken down, so that cellulose is exposed and hemicellulose and lignin are modified to increase their reactivity with enzymes, etc.

Depending on the use of extracts or the purpose of processes, there will be a need to minimize the breakdown of cellulose or to accelerate the saccharification of treated materials. This can be achieved by controlling the kind of biomass, heat and pressure in processes, and process time.

After steam explosion, polysaccharide slurry liquid containing large amounts of water and fiber is obtained. The steam-exploded biomass is discharged from the pressure vessel, and then separated into fiber and slurry in a refiner, and the separated fiber is pulped according to its use.

Hereinafter, a steam explosion process and apparatus of the fibroid material used as a main material in the present invention will be described in detail. In order to charge a material to be steam-exploded into a cylinder or reactor, a hatch that can be easily opened/closed is mounted in an introduction portion or upper portion of the reactor. For the standardization of terms, the cylinder is also called the reactor.

In order to maintain the internal temperature (180-230 °C) of the reactor uniformly, a steam jacket is mounted outside of the reactor, and also a pre-heater heated with an electric heater is operated to prevent fresh clod biomass or ^' condensed water from being introduced into the reactor. The temperature of such elements is automatically controlled with an automatic temperature control heater. Meanwhile, in order to prevent excessive steam introduction upon steam introduction into the reactor after extraction, an automatic temperature control sensor is disposed at the upper portion of the reactor.

The most important requirements in reactor operation are as follows. (1) Reactor internal temperature and process time are maintained uniformly during extraction operation, (2) a pump, a pre-heater and a reactor are stably maintained at high pressure (10-28 kg/cm²) in connection with the requirement (1) , and (3) the apparatus operation is ^' maintained precisely under such conditions.

An apparatus for carrying out the continuous steam explosion process as described above is preferably structured with reference to Stake Technologies, USA and Canada, as shown in FIG. 1.

First, in order to heat the reactor (cylinder) to pre- steam explosion temperature, saturated steam heated with a steam generator is introduced into the reactor. When the internal temperature of the reactor reaches the desired temperature by operation of an automatic temperature control sensor connected with a jacket inside the reactor and the outside of the reactor, a valve for introducing high pressure steam is controlled to maintain the reached temperature. For example, hearted chaffs as biomasses are introduced into the reactor via a hopper, and all valves connected with the inside of the reactor to close an inlet to the reactor. Then, only valves for steam introduction and discharge are opened, and heated saturated steam is introduced. This steam is introduced for one minute such that the biomass reaches a given temperature and pressure. Immediately, the open/close valve at the lower portion of the reactor is opened to extract materials including cellulose and lignin, and the resulting solids are explosively spouted into a flash tank, thereby steam-exploding the biomass. In this way, a fibroid material of steam-exploded chaffs can be obtained. The exploded material is physically separated into fiber and slurry such that it can be blended in the compound.

Machinery and related processes can be structured such that this process can be conducted by batch or continuously. In order to obtain large amounts of biomasses or steam- exploded materials, the introduction, heating, pressurization and steam explosion processes as described above are repeated. When cellulose-based biomass is subjected to steam explosion according to the above-described steam process, the biomass, which was not finely crushed, can be decomposed in an easy and efficient manner to give fibrillated solids at high yield. This has the following advantages as compared to pulps obtained by the existing chemical pulping process or simply crushed xylem powders.

First, various biomass particles having a particle size of about 1-100 mm depending on the kind of used biomass can be treated to give fibrillated solids intact without cutting or breakdown of fiber.

Second, the steam-exploded fibrillated biomass can be used just after the process without drying such that activated cellulose can be blended in slurry to give a compound having good reactivity. This allows the productivity of blending of slurry with treated solids to be increased, since the demand and supply of raw materials are achieved in a smooth and rapid manner and also temperature is conveniently maintained.

Third, since biomasses cheaper than woods are used, raw materials having an increased competitive price can be provided.

In the processed fibrous solids, adsorbed water inside thereof is dissociated inside by steam explosion, the fibroid material is bulked and softened to be three-dimensionally spread, and a hydroxyl group on the fiber is activated by exposure to water. Thus, the fibrillated solids can be kneaded uniformly with components of the inventive compound, so that it can be more strongly bound with other components through crosslinking that is hydrogen binding according to drying.

Applying the biomass fibrillated by this steam explosion as a main component of the inventive compound and inducing the crosslinking via hydrogen binding of the fibrillated biomass show the same effect as the case where a silane or titanate coupling agent is used to induce the stronger binding between glass fiber and unsaturated polyester resin in producing SMC (sheet molding compound) using glass fiber. A good example where a molded article made of the fibril subjected to the steam explosion as described above shows higher strength than the case of simply crushed biomass can be seen in Hwa-hyung, LEE and Ki-sun, HAN, "studies on physical and mechanical properties of boards made of steam-exploded and pretreated chaffs", Korean Society of Wood Science and Technology, pp. 19-24, 1999; and Hwa-hyung, LEE and Ki-sun, HAN, "studies on suitable pretreatment conditions for production of chaff board", Wood Science and Technology, 28(3):9-13, 2000. In such studies, the steam-exploded chaffs showed improved properties over non-treated chaffs in the production of chaff-wood boards. Here, in steam explosion conditions, explosion pressure was 25 kgf/cm², explosion time was one minute, and the mixing ratio between chaffs and woods was 25:75.

The fibrous solid, a product of the steam explosion process as described above, can be widely used in the production of papers, now-woven fabrics, crude feedstuffs and cellulose-based structural materials, in addition to the biodegradable thermoplastic matrix compound of the present invention. Moreover, since the steam explosion process must be carried out at high reaction temperature (180-230 °C) , even cellulose as the desired material can be decomposed into sugar so that the yield of cellulose is reduced and glucose (70-80%, including xylane) as a byproduct is made. Therefore, the slurry, as a byproduct, from which fiber was extracted, may also be used as a raw material for the production of sweetenings or seasonings, i.e., xylane-based chemicals (xylane, xylose and xylitol oligomers, etc.).

The very important reason why the biomass is subjected to pretreatment, particularly, boiling in water, dissociation or pulping, is that this pretreatment makes crosslinking conditions such that the fibroid material forms strong physical or chemical binding with the binder group. This induces the chemical binding, i.e., hydrogen binding between steam-exploded biomass fiber, starch and binder group via condensation reaction.

Similarly, in the case of FRP resin or SMC resin, a coupling agent, such as silan or titanate, is added to increase the binding force between polyester resin and glass fiber. The addition of the coupling agent provides the strong binding between the glass fiber surface and the resin, thereby giving a molded article of glass fiber-reinforced polyester having higher strength. Like coupling in the FRP molded article, the hydrogen binding between glucoses via condensation reaction provides the crosslinking between the components to enhance physical property of a molded article.

In order that the biomass steam-exploded as described above is physically and chemically bound with other polysaccharide components of the inventive polymer matrix, it is preferable to blend one where a hydroxyl group on the xylem surface is dissociated in water, as shown in Chemical Formula 3 to be described later. The situation where the xylem-based biomass is dissociated in water means a situation similar to that where pulp is at a colloidal state in water. However, since it is physically impossible to completely dissolve the steam-exploded biomass in water like refined pulp liquor, it is sufficient for the usage of the present invention to soak the surfaces of the biomass in water.

If water is dried again in this case, cellulose molecules in the surfaces and molecules of the fibroid materials and starch molecules give up water to undergo condensation reaction like Chemical Formula 4 to be described later. As a result, a strong binding forms mutually between three molecules in cellulose (in xylem and fibroid materials), starch, and the group of binders.

The sheets coupled in a mutually organic manner can be processed in various shapes at the instant when the binding get loose due to the supply of heat or water. It is said in this case that the sheets 'have plasticity.' This characteristic is unique to the present invention and cannot be found in other woods or papers. The molded articles manufactured with the compound having high contents of steam-exploded biomass according to the present invention can have a limited plasticity because the group of binders contains (water-soluble) thermoplastic resins, starch chain and organic synthetic binder resins, and hydrogen bonding gets loose as they contact with water and heat, and thus a part of them become soft.

These materials can be restored to materials having strong binding force again by drying. They show the binding force of polymer matrixes stronger than the binding force of the group of binders alone. This is a characteristic of the present invention, which is one of its very important functions.

Papers having the same hydrogen bonding do not show plasticity by heat or water. This is so because they consist of pulp fibers not having drawing property and elasticity at all. In the compound having high contents of steam-exploded biomass according to the present invention, starch and the group of binders play the role of cohesive agents, thus showing other physical phenomena differently from hydrogen bonded materials such as papers. In the present invention, the degree of thermal plasticity is affected absolutely by the amounts of starch, synthetic binders, and plasticizers.

Among pretreatments of xylem, purification includes the removal of lignin, which can show change in time (change of properties as time passes by) if it is present in the compound. Especially, as time progresses after molding, lignin can turn into yellow or can cause chemical, physical, or morphological change. For another disadvantage, pores within cells can exist in xylem from which water or absorbed water is evaporated after a drying process. Those pores can sustain inside of them water or other components during the processes. Therefore, they may contain the materials that can cause change in time or may require much time and energy for drying the inside of xylem even though they are dried in a forced way. This is why the treatment of the surfaces is preferable. Lignin is not used in the present invention, but as mentioned above, lignin decomposes at the highest temperature. Therefore, it is not possible to separate lignin by using heat, before cellulose or hemicellulose .

The steam explosion and the pre-treatments described above make it possible to properly utilized the biomass having low economical efficiency that is wasted until now and to use the xylem that has been used for insignificant purposes and the natural material wastes for the purposes in which added value is high. In the present invention, the biomass is used at the amount of 1 to 90 wt% relative to the total solids. B. Group of binders In the present invention, a binder plays a very important role in that it coheres all the composite components contained in the polymer matrix compound to provide a physical strength so as to sustain, the shape of molded articles. Another important role of binder is that plasticity generated when heated allows the compound or the primary molded articles to be molded again into other shapes through re-processing.

The binding force of molded articles maintains the shape basically with the cohesive force of binder before molding and in addition to the cohesive force, the hydrogen bonding between constituents generated after drying makes the molded articles stronger. Starch and organic synthetic binders are distributed homogeneously- in the matrix constituents. Thus it is preferable to compound them in such a way that the cohesive force and the hydrogen bonding force are balanced due to the arrangement of the compounded amounts of constituents.

The 'binders' mentioned above are mixed in the matrix before use to make a group of binders, i.e., a mixture of organic synthetic binders as a main binder and natural binders as a supplementary binder. Here in the present invention, a 'binder' means a group of binders, if a separate modification or explanation is not expressed.

The polymer matrix having high contents of steam- exploded biomass displays its strength and properties by drying aqueous or water-dispersed organic synthetic polymer binders and starch binders that are dissolved in water. Polymer compositions can exhibit workability and fluidity by adding water to the matrix in an amount proper for forming a mixture that has properties similar to those of plastics. Afterward, the group of aqueous binders is induced to show a synergy effect such that it is bound to the compound through the removal of water by evaporation so as to exhibit maximum strength. The compounding ratio of components of the polymer matrix compound and the addition of water as a solvent and a viscosity controller affect significantly rheology of a mixture that is compounded for moldability, especially the matrix containing 'a group of binders' that can be dissolved under the presence of water. The group of aqueous or water-dispersed polymer binders considered in the present invention is classified into the following categories, which are compounded properly for each usage before use.

(1) aqueous and water-dispersed synthetic resin that has thermal plasticity at a prescribed temperature;

(2) aqueous and water-dispersed natural resin that has thermal plasticity at a prescribed temperature;

(3) aqueous and water-dispersed resin that has the characteristics of hardening by heat (gelling by heat or syneresis hardening)

(4) starch, generally non-denatured starch granules

(5) polysaccharides compatible with starch and cellulose, and other organic thickeners or binders such as proteins and synthetic organic materials. A 'group of binders' combined in this manner has softening point or glass transition temperature, etc. to induce to compound the matrix having thermal plasticity, thereby having a prescribed temperature characteristic. The latter characteristic means that the compound having high contents of steam-molded biomass according to the present invention is molded to an initial molded article, which is then given plasticity by heating like plastics, and finally the resulting material can be processed for molding. 1. Main binder (organic synthetic binder) The organic synthetic binder as a main binder of the present invention is contained in the compound, in an amount far smaller than that of steam-exploded biomass and grain powders as main components of the compound. Any aqueous resins that have thermal plasticity and syneresis hardening property can be used for this purpose. Therefore, water-dispersed organic synthetic binders can be used. Good examples of them include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polyvinylmethyl ether, polyacrylic acid, polyacrylate, polyvinylacrylic acid, polyvinylacrylate, polyacrylimide, ethyleneoxide polymer, polylactic acid, latex (containing various polymerizable materials that can form aqueous emulsions like styrene- butadiene copolymer), and a mixture or a derivative thereof.

Among the polymers mentioned above, the present inventors have noted biodegradability of various aqueous synthetic resins such as polyvinyl alcohol, cellulose ether, etc., simultaneously polymer performance when dried, thermal plasticity and syneresis hardening property when heated. The present invention is completed by noting that strong binding force appears when constituents of these polymers are interacted, plasticity or syneresis hardening property is exhibited when heated, thus they can be formed in a required shape, and they decompose easily when abandoned. a) Polyvinyl alcohol (PVA) Polyvinyl alcohol is a synthetic polymer expressed in Chemical Formula 1 and is a representative product among aqueous synthetic polymers. Its appearance is white to pale yellow powder and its softening point 220 °C (144 °C for recently developed one) and its specific gravity about 1.19 to 1.31. It is frequently used for various usages in addition to Vinylon fiber. Its biodegradability is widely known already and is still being studied in detail for decomposition structures and enzymes in relation to environmental contamination problems .

Chemical Formula 1

- (CH₂-CH)m - (CH₂-CH)n- I I

OH O I

CO I. CHs

As shown in Chemical Formula 1, polyvinyl alcohol has in reality a structure where vinylacetate and vinyl alcohol are polymerized in a mixed manner, and a copolymer of their combination. Depending on their constituent ratio, the characteristics vary and have various SVs

Like pulp, starch, and steam-exploded biomass, polyvinyl alcohol can form hydrogen bonding with steam-exploded biomass, starch, and fibroid materials through syneresis reaction of an OH group contained in a straight chain. If water is removed from aqueous solution and it binds to constitutents of the matrix, resistance to water is generated and the physical phase and property is strengthened. This is also one of the most important phenomena noticed by the present inventor.

Through the OH group, polyvinyl alcohol decomposes slowly in aqueous solution. But in air, the decomposition mechanism does not function. The evidence for this is that Vinylon fiber does not change its properties even though it is manufactured by spinning, processing by heat treatment, and drawing polyvinyl alcohol as a raw material. Polyvinyl alcohol is used in various usages for construction, reinforcing agents of cements, heat isolation fibers for agriculture, etc. It has been used as it is since it does not change in air for several years.

However, film of polyvinyl alcohol molded after heat treatment as well as general polyvinyl alcohol is degraded biologically or deteriorated in water by enzymes. This mechanism is known to be a decomposition mechanism same as that of polyhydrooxybutylate (PHB) . For a reference, polyvinyl alcohol film having a thickness of 40 μ starts to be deteriorated by Pseudomonas bacteria at 30 °C in water, in 21 days. It is confirmed that on the 28^th day, the strength reduces to 1/2, with the appearance unchanged. (Practical Technologies of Biodegradable Plastics, p 70-81, Japan, CMC 2001)

Polyvinly alcohol has the characteristics of film moldability, transparency, rigidity, surface activity. Therefore, it can be used in various fields of papers, woods, adhesives, milks, suspension liquids, etc. Especially, polyvinyl alcohol film has excellent air isolation property. Completely saponified PVA has a softening point that is very close to thermal decomposition temperature. Thus the PVA lacks melting moldability. Partially saponified PVA is lower in thermal stability. Thus it is modified to have thermal plasticity for use.

Currently, PVA resin is manufactured by molding film through melting in aqueous solution. However, PVA has various disadvantages in that it is difficult to manufacture using thermal plasticity. The disadvantages include that since general PVA has the softening point near 225 °C and decomposes at 230 to 300 °C, it is difficult to process by heating it to the temperature similar to the case of carbohydrate binders, and since the PVA is hygroscopic, the dimensional stability of molded articles become very bad.

The reason why PVA resin having very bad moldabilities can be used in the present invention is that since it is used as a functional assistant, whose added amount is small, molding is possible, and the sheets of the present invention require strong cohesive force and biodegradability as a disposable rather than precise processing and dimensional stability after molding that are needed in engineering plastics. However, the property is not fatal enough to exclude its use in the present invention. Therefore, we have looked for various PVAs and were able to find aqueous PVAs that are modified to have a softening point of 144 °C, at which constituents of the present invention do not decompose. PVA is used in the present invention for very important reasons that follow. The resin is aqueous. The OH functional existing in the straight chain can be substituted with various functional materials. Thus it can be modified to PVA polymers having various characteristics. When cured, all the OH groups of constituents undergo condensation polymerization with neighboring constituents .to form crosslinkings so as to provide very strong binding force and hydrophobicity. Especially in this case, the molecules of constituents use up their OH groups that can bind to other constituents. Thus the polymerized PVA has a strong hydrophobicity and a structural characteristic that do not allow binding to or penetration by water or other materials. Also, other very important characteristics of PVA are limited plasticity and flexibility exhibited without water when temperature reaches a prescribed temperature. Thus the compound of the present invention can be molded through re-processing. The PVA resin modified for a particular purpose is completely dissolved alone in water and shows 22 MI (melt index, g/10 min, ASTM D 1238) at maximum at 195 to 225 °C inside the cylinder of the processor. This is a melt index similar to those of general olefin resin for blow molding and resin for casting, meaning that PVA resin can be molded to film or laminated without separate addition of water.

As described above, PVA is compounded as a main binder to the sheets having high contents of steam-exploded biomass according to the present invention to exhibit a prescribed binding force and a sufficient molding effect.

Therefore, it is possible to mold an intermediate molded article and to re-process the intermediate after water is dried, using the polymer matrix compound having high contents of steam-exploded biomass according to the present invention that is compounded to constituents in a type of aqueous and water-dispersed slurry. In this case, if the molded article is extruded again or heated when processed, it can show a melt index of 0.1 to 25 MI. Depending on the combination of a group of binders and the amount of compounding, the compound can be molded into a final molded article in the initial stage.

Since PVA has strong viscosity and adhesive force, it is widely used as aqueous adhesives. Therefore, when molding with the compound containing PVA, it may be difficult to design processing processes since it may stick to molders. When this phenomenon occurs, it is preferable to mold after hardening the surfaces at first, by mixing with the binder having the thermal gelling (syneresis hardening) characteristic. b) Cellulose derivatives Cellulose derivatives soluble in water can be utilized as a binder in the present invention. Cellulose derivatives preferable for the present invention are celluloses that can be esterified and have thermal gelling characteristic. These include methylhydroxymethylcellulose, hydroxymethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, hydoxyethylcellulose, hydroxyethylpropylcellulose, hydroxypropylmethylcellulose or a mixture or a derivative thereof. Other celluloses can be used that have the thermal gelling property when heated.

Cellulose ethers are soluble in water. If a specific cellulose soluble in water increases in temperature, its viscosity increases and thermal gel appears. A particular cellulose has thermal gelling temperature. When the cellulose ether is heated above a prescribed gelling temperature, the OH functional of the ether in the compounded material releases water (called syneresis phenomenon) to be hardened by bindings between molecules. This phenomenon is called 'thermal gelling' or 'hardening by the syneresis phenomenon' , which is a kind of thermal hardening. This phenomenon is similar to the phenomenon and type where amylose molecules retrograded in starch give up water to be condensed. When this phenomenon occurs, it accompanies chemical and structural changes in the matrix. In other words, a specific cellulose ether is a polymer that has a gelling temperature due to the syneresis phenomenon between molecules, is aqueous at room temperature, and contracts and hardens as viscosity increases when a prescribed temperature is reached.

Preferred cellulose ethers are based on methylcellulose and a mixture of celluloses having various syneresis gelling temperatures can be used. The Methocel catalogue of Dow Chemicals, USA show various cellulose ether products that can be used for foods. These include the SG A series at 38 to 44 °C and the A series at 50 to 55 °C of methylcellulose and the E series at 58 to 64 °C, the F series at 62 to 68 °C, and the K series at 70 to 90 °C of hydroxypropylmethylcellulose, etc., having each inherent thermal gelling temperature.

If cellulose ether is heated above the inherent gelling temperature to be gelled, its binding force to and its compatibility with starch increase but lubricating and isolating properties also increase in relation to the outside. These phenomena are due to bridging by condensation of cellulose molecules. There are many research reports showing that by using these phenomena, cellulose is coated on the surfaces of various foods to give a rich feeling to the products, to lower the adhesive forces of the surfaces, and to increase the preservation power due to the increased adhesive forces .

A person having ordinary skills in the art would know that in order to reduce the adhesion between the rollers and the sheets during the sheet formation process, it is preferable to choose, for designing the processes of the present invention, appropriate cellulose ethers that have the thermal gelling temperature lower than the gelatinization temperature of starch granules. c) Assistant binder Biodegradable natural polymers that are dissolved or dispersed in water or alcohol can be added to the main binder of the present invention for supplementary use.

Natural polysaccharide binders that can be used include alginic acid, picocolloid, agar, Arabian gum, guar gum, locust bean gum, karaya gum, xanthan gum, tragacanth rubber, and a mixture or derivative thereof. Appropriate binders based on proteins include zein (prolamine derived from zein corn) , collagen (extracted from stroma or bones of animals) , derivatives of gelatin or glue, casein (main proteins of milk) , a mixture or derivative thereof.

Additionally when the natural polymer mentioned above is used as an assistant binder for compounding, it delays starch's dissolution in water. d) Function and role of main binders One of the largest characteristics of the present invention is that by using condensation reaction between various types of glucoses, mutually organic binding force is derived, whereas PVA and cellulose ether use another type of condensation reactions. The syneresis phenomenon can reduce adhesive forces between the compound surfaces and processing machines by hardening the surfaces of molded articles through the hardening of the wet compound surfaces. In other words, when heated the cast compound, the compound surfaces harden. Thus during the subsequent stages of the formation process, starch is gelatinized and dried. But this prevents the compound having adhesive property from being stuck to the rollers of forming sheets.

A specific study on compatibilities between cellulose ether and PVA can be found in Journal of Applied Polymer Science (USA), vol. 80, no. 10, pp. 1825-1834, June 2001. Here, one can find the resulting materials of hydrogen bonding between two molecules in details.

Simultaneously, hydrogen bonding between starch and pulp cellulose is a known fact. Therefore, mutual hydrogen bonding between PVA, cellulose ether, pulp and starch produces grafted block copolymerization. In addition to this, the steam- exploded biomass in which cellulose molecules on the surfaces are activated shows a synergy effect.

Differently from compounding water, this induces binding between active OH groups in the branches of polysaccharide molecules that have OH groups among the constituents of the present invention, including PVA, starch, steam-exploded biomass, and pulp fiber. And the binder itself is kicked out by condensation reaction to make thermoplastic grafted block copolymers of natural materials -that have dried biodegradability.

In other words, the functions and roles of binders, i.e., 'main binders,' 'supplementary binders,' and 'assistant binders' is to make thermoplastic grafted block copolymers of natural materials that have dried biodegradability, by inducing binding between active OH groups in the branches of polysaccharide molecules that have OH groups among the constituents of the present invention, including steam- exploded biomass and pulp fiber. Molded using the method described above, the sheets of high quality have larger elasticity, tensile strength, and hydrophobicity.

2. Supplementary binder a. Outline As used herein, the term 'grain' is a common name of unprocessed carbohydrates, especially the source of starch. As starch of carbohydrates contained inside grain, the grain not only plays a binder role in cohering strongly composite components inside the biodegradable polymer matrix having high contents of steam-exploded biomass according to the present invention. But as the volume of grain added, it plays a good filler and contributes to strengthening cohesive forces of the compound by providing fibroid materials supplied from the cuticles of grain.

Grain powder, especially starch contained in the grain powder, also exhibits a certain limited thermal plasticity when heated, just like the organic synthetic binders mentioned above. Thus it makes re-molding possible.

The natural binders of the present invention use cohesive forces of starch, which will be supplied from grain powder obtained by pulverizing grain, or pure starch. To use for compounding, direct pulverization of grain is an attempt to ensure a competitive edge in price. But it is also preferable to choose pure starch depending on the use of molded articles and the desired property. The representative grain that can be used in the present invention includes grain crops such as rice, glutinous rice, barley, wheat, corn, glutinous corn, Indian millet, millet, and oat. But for convenience, it also includes potatoes such as white potato, sweet potato, tapioca, etc. In addition to them, plants containing starch are also included in the category of grain, since all the crops mentioned above are the sources of unprocessed starch for the present invention.

In the present invention, grain has another characteristic in that after removing foreign materials, it can be pulverized for a direct use.

However when grain contains much unnecessary materials that do not have an effective value to the present invention or can hamper the performance of the present invention, such as proteins, lignin, milk fat, embryo, etc., they can be separated, selected, modified, denatured, or treated in advance before use when necessary according to the usage. The amount of starch content contained in grain, especially the ratio of amylose to amylofactin, and the amount of fibroid contents, water, unnecessary materials, etc. should be measured precisely beforehand. It is compounded properly together with other mixtures by controlling the amount with water of desired compounding. Naturally for using it in the next processes, an artisan having ordinary skill in the field should precisely measure the glass transition and gelatinization temperatures of starch before compounding and the sheeting process.

Grain is naturally cheaper than processed starch and rather more excellent in the performance and the resulting synergy effect than pure starch.

In the present invention, starch is supplied as carbohydrates contained in grain. Grain powder in the present invention contains fibroid materials, but at the same time, the starch contained in grain powder also belongs to the category of binger group. Therefore, starch plays both a supplementary binder and a filler of the compound in the present invention. When forming sheets filled with composite components, only a main binder of aqueous organic synthetic binders can be used without a supplementary binder. Even so, the cost of using a main binder only is far higher than that of using a group of binders in which main and supplementary binders are mixed. Hence, it is economically rational to use a mixture of starch and a small amount of organic synthetic binders.

The compound of the present invention shows the strength required for hardening of organic synthetic binders through water removal due to evaporation, hardening of gelatinized starch, and crossinking of cellulose on the surface of steam- exploded biomass and starch.

Starch is a chain of natural carbohydrates that contain polymerized glucose molecules found in the granule type.

Starch granules contain two different kinds of glucose units: branchless single chain amylose and branched multiple chain amylofactin. Two different glucoses show different property.

The role of binders of carbohydrates, fibroid materials, etc. contained in grain, especially starch, will be mentioned again later. b. Pretreatment of grain

Grain is treated in advance due to various reasons. The first pretreatment is pulverization. Grains should be pulverized in a prescribed size homogeneously, so that various additives should be mixed uniformly in the compound. Pretreatment is to obtain property enough for the molded articles to be used in the daily life after mixing grain with other components. Especially, the molded articles should have the strength such that they can maintain their initial shapes until they are used. And by giving the molded articles, especially the starch component, hydrophobicity, their property should not be reduced abruptly, which might occur when component are dissolved in contact with water. Therefore, this pretreatment is to ensure enough property that is expected when compounding. Additional treatment is to physically coat and chemically treat the starch by using the property of polymers in starch contained in grain powder. For example, hydrophobicity and fluidity are given, starch is decolorized and dyed, the gel strength is modified, etc. All this can be called the denaturation of starch.

Starch are classified into water resistant starch, acid- processed starch, oxidized starch, derived starch, etc., depending on the denaturation method. Denatured starches are the starch where grain powder is provided with strong water repellency by mixing grain with a water repellant agent, the alpha starch obtained by dehydrating rapidly after the starch component is gelatinized in advance before compounding, the decomposition product by heat, acid, and enzymes, - the starch derivatives in which the chains of starch are attached to various functionals, by esterfication or etherification, etc., - the starch provided with hydrophobicity by substituting the OH groups of starch molecules, etc. There are many pretreatment methods known in the art, which are commercialized in the market and used widely, c. Binding function of grain powder Starch and cellulose have a structure that is made from a polysaccharide molecule unit shown in Chemical Formula 2. In the structure of Chemical Formula 2 wherein Rl, R2, and R3 are basically an OH functional, but when denatured, they can be substituted with the same or different functional.

Chemical Formula 2

CH2- Ri I 0 - ® - <5> - O I I - - Φ - o - i I I

R₂ Ra H

' Different from starch having a similar structure, cellulose has different hydrophilicity and solubility in water. These differences are due to the difference of the bonding methods of carbons 1 and 4 of the straight chain in the arrangement of connection loops between polysaccharide molecules. On the contrary, starch shows a very rapid biodegradability and solubility in water. Therefore, the characteristics of starch need to be changed such that shape deformation and decomposition of molded articles are delayed even in contact with water.

As described above, denaturation methods of starch are known and commercialized according to the usage.

To provide hydrophobicity for the above structured starch, starch (grain power in reality) can be treated in advance. As explained in b above, there are many pretreatment (denaturation) methods of starch. This means that the three OH functionals indicated as Rl, R2, and R3 are substituted with acetic acid, nitric acid, or other polyhydric alcohol, or the surfaces of starch is coated.

Surface characteristics of starch and cellulose The surface of pulp or steam-exploded biomass, i.e. cellulose, is anionic. Therefore, if cationic starch is used where the OH groups of starch molecules are substituted with quaternary amine-based organic compounds, then the binding force between additives is increased to improve the physical strength by which starch interacts with cellulose, since the starch has a strong affinity with cellulose fibrils and additives. In this case, the substituent that binds to the OH functionals of starch through ether bonding is quaternary amine. In this manner, one can induce a 3-dimensioally stable bonding .

This characteristic is widely used currently in paper manufacturing processes, especially the process of strengthening the bond between starch and pulp and the process of pulp sizing.

Gelatinization of starch

In general, starch granules are not soluble in cold water. But if the outside membranes of the granules are destructed by grinding, etc., then starch is swelled to form gel. The precise temperature where starch binders are swelled and gelatinized depends on the kind of starch. Gelatinization results from swelling due to decomposition of linear amylose polymer granules that were compressed in the granules initially. Many changes occur during the process of increasing temperature to 100 °C in the suspended state in enough water. When non-denatured granules are exposed in warm water, they swell and soluble starch (amylose) diffuses through the wall of the granules to form paste. In hot water, the granules break down to swell enough to gelatinize the mixture. Initially, swelling is slow, but if a specific temperature is reached, irreversible change occurs more rapidly to increase the viscosity of starch liquid. This accompanies the collapse of molecular configuration inside. At this point, the crystallinity of starch particles is lost and the sensitivity to hydrolysis by enzymes and the solubility change of starch are accompanied.

Various natural starches have a great variety of gelatinization temperatures. For example, potato starches have the temperature of 59 to 68 °C, corn starches that of 62 to 95 °C, and glutinous corn starches that of 63 to 72 °C. All grain crops and potatoes are used for supply of starch in the present invention. At the temperature, starch granules start to swell irreversibly. Swelling increases with temperature. The viscosity of starch liquid increases depending on the swelling and bursting of starch granules and the degree of exposure of materials inside.

In the aspect of processability, the gelatinization temperature is one of the important characteristics that require a strict management in the binder molding process. Gelatinization implies that starch granules become more compatible and sensitive to enzyme actions, and this is an important characteristic in the molding stage of the present invention. Especially the gelatinization temperature is intimately utilized in applying the temperature to control cohesive forces in the processes that use starch as a binder. The cohesive forces before and after gelatinization and the force after drying, especially the difference in viscoelasticity should be grasped before using starch in the molding processes of the present invention. Otherwise, unexpected variations in the shape stability, the dimensional stability, and the foaming magnification ratio of the molded articles might occur.

Completely gelatinized starch can be used for the constituents of the biodegradable polymer matrix compound having high contents of steam-exploded biomass according to the present invention. However in this case, the starch tends inevitably to stick to the molding machine during the processes. Thus the processes should be designed in preparation for such incidences .

Non-denatured starch-based binders of are cheap in price and thus they are favored compared to denatured starch-based binders. Especially, non-denatured starch is not gelatinized until the instant when temperature is heated to the gelatinization temperature.

Since a pure starch composition can absorb water vapor from the air near by, water exists in 10 to 12 wt% of the total weight of the composition. When an additive is added to a starch composition, water exists in 3 to 6 wt% of the total weight since the composition contains a smaller amount of starch. d. Pulverization of grain and size As for grain pulverization, the grain mentioned above should be pulverized enough to have a proper size for each usage before use. By using known methods, cuticles and contents should be pulverized homogeneously. When grain is pulverized, the temperature increase should be prevented to avoid the gelatinization of starch contained in the grain. When pulverized, temperature increases due to the frictional heat of grain, which may cause grain to be gelatinized.

Grain is pulverized to be more than 50 mesh, preferably more than 100 mesh. By mixing it with other components evenly, it can be used, as a compound component, for direct compounding. e. Amount of grain powder for compounding

In the present invention, the concentration of natural binders in the form of grain powder is 5 to 90 wt% relative to the total solid binder group, preferably 20 to 80 wt%, more preferably 30 to 70 wt%. f. Physical property of molded articles

When the polymer matrix having high contents of steam- exploded biomass according to the present invention and containing grain powder, fibroid materials, starch and a group of binders forms a solid material, the matrix can have a tensile strength of 40 to 50 MPa. The sheets of the present invention reinforced with fibroid materials can have the tensile strength of 100 Mpa at maximum, depending on the kind and concentration of the starch, fibroid materials, and binders in the sheets.

Even with the methods described above, the current technology does not allow starch to be perfectly hydrophobic and to have a perfect polymeric binding with other components, like the prior plastics. However, starch can prevent water penetration for a significant period of time and can have a binding force sufficient to be used for the period. Thus it does not present many difficulties to be used as a disposable. 3. Supplementation of function for binders In the matrix compound having high contents of steam- exploded biomass according to the present invention, water- soluble synthetic binders and starch binders are favored and used basically. Even so, additional organic binders can be used in a supplementary manner.

Having various properties and thermal deformation characteristics, cellulose ether can be used as a supplementary member. When PVA is a main binder, a cellulose ether-based resin can be preferably an assistant binder. When cellulose resin is a main binder, PVA is preferably an assistant binder. Cellulose ether dissolves in water. Proper cellulose ethers include methylhydroxyethylcellulose, hydroxymethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxyethylpropylcellulose, a mixture or derivative thereof.

Cellulose ether as a favored assistant binder is methylcellulose. Most of methylcellulose ethers have the hardening temperature of about 70 to 85 °C. Other cellulose ethers having the thermal gelling characteristic can be used as an assistant binder.

As an assistant binder, a synthetic binder selected from the group consisting of polyvinyl pyrrolidone, polyethylene glycol, polyvinylmethyl ether, polyacrylic acid, polyacrylate, polyvinylacrylic acid, polyvinylacrylate, polyacryl i ide, polylactic acid, ethylene oxide polymer, latex, a mixture or a derivative thereof can be used as a supplementary member.

Polysaccharide selected from the group consisting of alginic acid, picocolloid, agar, Arabian gum, guar gum, locust bean gum, karaya gum, xanthan gum, tragacanth rubber, and a mixture or a derivative thereof can be used as a supplementary member.

Natural proteins selected from the group consisting of prolamine, collagen, gelatin, glue, casein, a mixture or a derivative thereof can be used as a supplementary member.

An artisan having ordinary skills in the field would know how to choose cellulose ether that has the syneresis hardening temperature lower than the gelatinization temperature of starch granules.

4. Function and role of binders during the hardening reaction of the compound

When sheet are manufactured using extrusion and roller processes, organic synthetic binders (including cellulose- based resin) may provide the optimal performance. Even so, they are very expensive, compared to other constituents used in manufacturing sheets.

Starch is a good binder and cheaper than organic synthetic binders are. But when starch is used as a binder in the sheet formation process, it sticks sheets to rollers due to the strong sticking property. Thus starch makes large scale production difficult.

The present invention uses, as the supply source of starch, grain powder instead of a large amount of organic synthetic binders. The combination of a small amount of organic synthetic binders and a large amount of grain powder binders alleviates the disadvantages that appear when each is used separately. Also, the combination prevents the adhesion of starch to the rollers during the formation process of molded articles and thus reduces the cost of manufacturing sheets greatly. Additionally, if a large amount of grain powder is included, the sheets are stronger than those including a large amount of organic synthetic binders, and are not much fragile.

Therefore, when a specific organic synthetic binder is used, it acts as a binder of forming coated films in the formed sheets. When the starch inside the sheets is gelatinized and is dried by water removal due to vaporization afterward, the starch becomes a main binder to bind other solid components inside the matrix of the sheet. Since steam-exploded biomass and grain powders themselves have fibroid materials, they can provide an additional dimensional stability to molded articles. At the same time, biomass or grain powder is not only less expensive than processed starch, but an excellent natural binder. Thus with the cost far less than that of the sheets using organic synthetic binders as an only binder, a fairly high quality of sheets can be manufactured.

Therefore, the method of molding the composition used for forming the composition or sheets having high contents of steam-exploded biomass of the present invention includes the step of mixing water, fibroid materials, and binders using a high shear mixing method, in order to form a mixture in which steam-exploded biomass and fibroid materials are dispersed homogeneously. Afterward, non-denatured starch granules contained in the grain powder, additives, and other assistant additives are mixed to form the compound. The fibroid materials in the dried sheet are dispersed homogeneously, as a reinforcing agent, in the entire matrix. Here, water can be added additionally to control the viscosity.

If not the process of casting on the coated films supplied by a conveyer, sheets are formed through molding rollers. In this case, the sheets formed out of the compound in the sheet formation process pass through between a set of heated rollers. Starch granules are protected by the coated films hardened on the surfaces of the sheets. This protection prevents starch from being stunk to the rollers when starch granules are gelatinized.

In order to form the surfaces of organic synthetic binders on the surfaces of the sheets before gelatinization of starch, the starch-based binders favored in this process are non-denatured starch that is gelatinized at a temperature higher than the syneresis hardening temperature of organic synthetic binders.

5. Chemical bonding between steam-exploded biomass, pulp cellulose, and a group of binders Binder achieves the role and purpose by materializing the binding strength between constituents. After molded in a desired shape, it is better to maintain the shape stronger.

The reason why steam-exploded biomass and grain powders are mixed for use in the present invention is very important and different from that the same volume of inorganic additives is mixed as an organic synthetic binder to a mixture to manufacture a matrix. One of the important reasons is explained with the following Chemical Formulae.

Chemical Formulae 3a and 3b:

Chemical Formula 4 :

Chemical Formula 3a shows HO and H of two hydrated glucose molecules loosely held together. As they are dehydrated, water (H₂0) is condensed out as shown in Chemical Formula 3b to form a strong ether bond in the type of single oxygen link as shown in Chemical Formula 4. If starch is coated on a paper, a part of starch reacts with cellulose pulp to form a bridge on the surfaces of the paper. Similarly, parts of OH groups on the surface of steam-exploded biomass undergo condensation reaction with starch monomers, pulp fibers and organic synthetic resins in the dehydration process to form very strong physicochemical bonds.

The case where steam-exploded biomass and starch undergo grafted polymerization through organic bridging shows a physical strength in molded articles, as if they form grafted polymerization, much significantly different from that where inorganic additives are added to a mixture and just occupy a volume. The 'dehydration bridging' phenomenon due to condensation reaction is the source of the difference-. As described above and will .be done again later, the increase in the bursting strength of paper due to hydrogen bonding between dissociated pulp and starch, and the bridging between PVA and cellulose ether, namely the reaction shown in Chemical Formulae 3 and 4, is widely known already. The present inventor understands that the polymer matrix compound is a very characteristic polymer obtained by condensation polymerization between natural materials, and is a thermoplastic grafted block copolymer of steam-exploded biomass/pulp/starch/binders . C. Fibroid material

In the present invention, fibroid materials are contained in the steam-exploded biomass and grain components. Nevertheless, various types of fibroid materials are used in the present invention to entail a good result. 'Fibroid materials' are a common name for various 'fibers.' 'Fibers,' 'fibroid materials,' and 'fibroid raw materials' means both inorganic and organic fibers. Fibroid materials are added to the compound in order to increase elasticity, ductility, flexibility, cohesive property, drawing property, bending property, rupture energy, bending and tensile strengths. Sheets or products manufactured thereform are damaged when cutting molded articles (when section forces are applied) .

Fibroid materials that can be contained in sheets or the matrix of^' molded products include naturally produced organic fibers such as pulp, hemp, cotton, leaves of plants, cellulose extracted from woods or stems. Rich fibers harvested in agriculture and the industry related to forestry can be utilized in the present invention.

Depending on the situation, 'regenerated fibers' can be used instead. 'Regenerated fibers' include waste papers, regenerated papers, regenerated pulp, regenerated fibers, viscous fibers, 'twined fibers,' etc.

Among constituents of plants, especially cellulose exists in fibrous resin inherently. There are three OH groups in the resin molecule in such a way that antihydrophilicity and antihydrophobicity coexist. Cellulose, especially pulp fibers, swells in water. When they swell, shapes are formed and then by removing water, papers are manufactured. When swelled cellulose fibers are dried, they give off water and form strong bonds between OH groups of cellulose fibers through condensation reaction.

The binding mechanism of the polymer matrix sheets having high contents of steam-exploded biomass according to the present invention is due to hydrogen bonding between cellulose and starch contained in steam-exploded biomass, and mutual bonding between the composite components of the group of binders, fibroid materials, and other mixtures. However, fibroid materials act as a component to reinforce cohesive forces and to provide tensile strength and elasticity. But the binding is not as strong as hydrogen bonding. Thus fibroid materials do not provide a strong binding to the extent that the prior papers depend solely on hydrogen.

In harmony of the physicochemical binding forces, for example, the cohesive force between organic synthetic binders and starch, the physical cohesive force due to the viscoelasticity between cellulose contained in steam-exploded biomass, starch, binders, and pulp fibers, and the hydrogen bonding force, the sheets molded out of the polymer matrix compound of the present invention shows strength and property, not worse than those of the prior polymers produced by the prior petro-chemistry.

In order to use the sheets having high contents of steam-exploded biomass according to the present invention for a specific usage, especially for a thick and strong material quality, for example, for substitutions of wrapping boxes, corrugated cardboards, or fiber drums, one can utilize processed 'twined fibroid materials.' The processed 'twined fibroid materials' are twined strings of Manila hemp, twined straw ropes, those that can withhold stronger forces by papers twining after slitting in one direction, Korean paper ropes twined after slitting in one direction, films twined after slitting in the length direction, yarns of twined fibers, waste fiber yarns, etc. These are similar to fine twined ribbons. The raw materials of processed twined fibroid materials may include those that can give the sheet more dimensional stability and vertical strength, such as the Kraft paper, plastic films, synthetic fibers, regenerated papers, waste papers, news papers, regenerated fibers, glass fibers, animal fibers, metal fibers, etc.

At the same time when three OH groups in the glucose molecules are dried together with steam-exploded biomass and starch, glucose molecules of starch and steam-exploded biomass are also mixed with them to allow polymer chains to be connected by bridging as shown in Chemical Formula 4 above. This enables stronger polymer matrix compounds to be formed.

The polymer matrix has a strong three dimensional structure in which the fibroid materials are dispersed in steam-exploded biomass and starch to form hydrogen bonding, thus they are strongly interconnected, and organic synthetic binders cohere in between the bonds.

This can be inferred from the enlarged view of the foam sheet shown in FIG. 6.

The amount of fibroid materials added to the compound having high contents of steam-exploded biomass according to the present invention depends on the properties of the final molded article such as the required tensile strength, drawing property, and elasticity. The cost is one of the criteria that determine the amount. Hence, the concentration of the fibroid materials in the sheet of the present invention is 0.1 to 50 wt% of the total solids, preferably 0.5 to 40 wt%, and more preferably 1 to 30 wt%.

D. Functional additives To supplement performances required for the sheet of the matrix compound having high contents of steam-exploded biomass according to the present invention, various function additives and a filler can be used. As described above, the required performances include hydrophobicity (or water resistance) providers, agents of supplementing flexibility, agents of strengthening elasticity, agents of expanding surface areas, filler, etc.

As used herein, a filler can be one of additives and one additive may have two functions or may be a filler that performs filling only. 1. Plasticizer

In the matrix compound having high contents of steam- exploded biomass according to the present invention, water, especially compounding water, is an excellent plasticizer. In addition to compounding water, various plasticizers can be added to the compound, to provide plasticity necessary for the final sheets and products. Plasticity plays a very significant role in exhibiting elasticity without the sheets or the molded articles of the present invention being deformed or destroyed by outside forces for the time of use.

Plasticity, i.e., elasticity and flexibility obtained by softening, can be increased by adding plasticizers to the matrix. To soften the formed sheets or the matrix of molded articles, plasticizers are preferably the materials that can be dispersed by a group of binders. These plasticizers, also acting as a lubricant, have boiling points high enough not to be vaporized from the matrix during the molding processes. And they remain stable, being evenly distributed in the polymer matrix even after the molded articles or the sheets are formed. Favored plasticizers do not evaporate during the formation processes and remain in the formed sheets and products.

The appropriate plasticizers used in the present invention include polyethylene glycol (less than 600 of MW) , glycerin, sorbitol, fumaric acid ester, and soybean milk, which function as plasticizers with compounding water. Glycerin is also removed in part during the water removal process. In the next sheet formation treatment process, glycerin is applied to provide increased elasticity and acts as a wetting agent. Glycerin treatment gives the sheets elasticity, thus stabilizing them against a certain impact or deformation.

A specific study on compatibilities between cellulose ether and PVA can be found in Journal of Applied Polymer Science (USA), vol. 80, no. 10, pp. 1825-1834, June 2001. Here, one can find the resulting materials of hydrogen bonding between two molecules in details. Simultaneously, hydrogen bonding between starch and pulp cellulose is a known fact. In addition to this, steam-exploded biomass in which cellulose molecules on the surfaces are activated shows a synergy effect. Therefore, mutual hydrogen bonding between PVA, cellulose ether, pulp and starch produces grafted block copolymer.

Differently from compounding water, this induces binding between active OH groups in the branches of polysaccharide molecules that have OH groups among the constituents of the present invention, including PVA, starch, steam-exploded biomass, and pulp fiber. And the binder itself is kicked out by condensation reaction to make thermoplastic grafted block copolymers of natural materials that have dried biodegradability.

2. Foaming agents (formation of pores) When thermal isolation is required more than strength, elasticity, or flexibility in molded articles (i.e., when required to thermally isolate hot or cold materials), it may be preferable to include small pores in the sheet in addition to light weight filler, in order to increase the thermal isolation property of the molded articles. Pores should be included with a careful control to provide required thermal isolation without serious reduction of the sheet strength. When thermal isolation is not important, it is preferable to minimize pores so as to maximize the strength and minimize the volume. The pores can be filled with air by high-speed shear upon mixing of the compound. The foaming agent contributes to the formation and maintenance of pores.

The foaming ratio of the compound of the present invention can be controlled by the compounding machine of high shear, by the foaming method in which high pressure gas is added, or by the foaming method using chemical foaming agents such as calcium carbonate. And it is easy to ensure its property such as proper tensile strength. Thus it is possible to mold the compound and manufacture its products. Chemical foaming agents that are available in the market and can be used in the present invention, and their chemical reaction temperatures are shown below.

Azodicarbonamide 205 to 215 °C

4, 4' -Oxybis (benzenesulfohydrazide) 150 to 160 °C

Diphenlysulfon-3, 3' -disulfohydrazide 155 °C

Trihydrazinotriazine 275 °C p-Toluenesulfonylsemicarbazide 228 to 235 °C

5-phenyltetrazole 240 to 250 °C

Isatoic Anhydride 210 to 225 °C

Resin particles containing foaming gas can be also used and are available easily in the foaming polystyrene resin makers or in the market.

Another foaming agent that can be used in the present invention is a mixture of citric acid and bicarbonate, which is pulverized to small particles and coated with wax, starch, or aqueous coating. This can be used for forming pores in the following two manners:

(1) A cell type structure is generated in the matrix by forming the carbon dioxide gas through the reaction with water.

(2) Particles are filled as a part of the matrix, which is hardened. Afterward, the molded article is heated to above 180 °C, for the foaming particles to be reacted, thereby generating a well controlled lightweight structure of cell type (that can decompose the particles by absorbing heat) .

As another simple foaming agent, the powder of calcium carbonate can be used. The liquid existing in the compound penetrates in the apertures of the carbonate. In this state, vaporization by heat is in equilibrium due to the balance between the evaporation of the foaming agents and the vapor pressure of water. When the pressure is reduced abruptly, the foaming agents undergo thermal expansion, thus allowing the foaming agent to be evaporated.

Pores can be introduced in the compound by adding to the matrix the foaming agents that expand when heat is applied to the matrix during the molding processes. These pores are mixed homogeneous in the compound and are maintained under pressure while heated, thus allowing homogeneous foaming to be achieved.

While sheets are formed out of the compound, it is preferable to compress the compound with heated rollers in order to remove water that is generated in the compound. If the surfaces of sheets are not compressed, apertures or weak parts can be formed on the surfaces. It is necessary to form skins stronger than the inside by increasing the density of the surfaces through compression. 3. Inorganic filler

The inorganic fillers that are generally used in the paper, paint and coating industries may be used in manufacturing the compound having high contents of steam- exploded biomass according to the present invention. The inorganic fillers used in the paper industry have an average particle diameter less than 2 μ. But the average diameter of the particles used in the present invention may be more than 100 μ, depending on the wall thickness of sheets. Thus they are generally cheap and have lower specific surface areas. The inorganic fillers used in the paper industry in general have more uniform sizes that those of the present invention.

To increase the natural particle filling density of additives in a mixture, various ranges of additive particle sizes will be used. By using larger particles with various sizes, the cost of inorganic additives can be reduced in the present invention, compared to the paper industry.

The allowance of various ranges of particle sizes makes it possible to use additives and fillers far more various in the present invention than in the paper industry. Therefore, the additives included in the polymer matrix having high contents of steam-exploded biomass according to the present invention may be chosen such that they provide far various properties for the final products such as sheets or molded articles. The raw materials of the present invention can contain far more functional additives or fillers than those of paper. The reason is that the binding force of binders to cohere sheets mutually is stronger than hydrogen bonding force of web physics.

Functional additives having different characteristics can provide their own inherent characteristics for sheets. Thus they may be chosen properly. For example, kaolin is sleek and requires less processing in finishing, and materials such as clay provide surfaces. The fillers having large particles such as calcium carbonate generate lusterless surfaces. The favored fillers in the present invention are calcium carbonate that is dry and pulverized. It is because wet pulverized calcium carbonates are available at the price of 1/3 of other fillers. The calcium carbonates are favored to have the particle sizes of 10 to 150 μ and the average sizes of about 50 μ.

Clay and gypsum can be easily purchased and cheap. They have a good workability and can be formed in various shapes. Also, they can provide the binding and cohesive properties and strength. Thus they are very useful fillers. Due to the properties of the compound and the sheet manufactured, it is possible to include porous light weight fillers in them. Thus they can provide the thermal isolation effect for the molded sheets, more than that the foamed materials. The fillers that can provide lightweight and thermal isolation to the sheets include Perlite, vermiculite, hollow glass beads, cork, clay, etc.

Other kinds of fillers that can be added to the compound include inorganic gel such as silica gel, calcium silicate gel, and aluminum silicate gel, and micro gel. Gel and micro gel absorb water. Thus in order to reduce the amount of water content, they may be added to increase cohesive forces. Additionally, the high hygroscopic property of silica gel allows it to be used as a water controller in the final gelled sheets. Gel and micro gel absorb water from air, thus maintaining the expected amount of water under the normal conditions in the sheets. Of course, the water absorption speed from air is related to the relative humidity of air. The control over the water content in the sheets makes it possible to more carefully control drawn down, elasticity modulus, flexibility, folding property, elasticity, and drawing property of sheets.

It is preferable to include various sizes and classes of fillers that can fill the narrow spaces between constituents of the compound. If the particle density is optimized, the narrow spaces filled with water ( 'capillary water' ) can be removed to reduce the amount of water required in the processes to a proper level.

Considering the explanations above, the amount of inorganic fillers that are added to the compound having high contents of steam-exploded biomass according to the present invention depend not only on their usage and particle density but various factors including the kind and amount of other additive components. Therefore, their concentration in the sheet of the present invention is 10 to 90 wt% of the total solids, preferably 20 to 70 wt%, and more preferably 30 to 50 wt% 4. Dispersing agents

A 'dispersing agent' refers to a material that can be added for homogeneous dispersion and for reducing viscosity and bearing power of the matrix. By dispersing constituents, especially inorganic filler particles or fibroid materials, dispersing agents reduce the viscosity of a mixture. They maintain the proper level of workability so as to reduce the amount of water used. However, they act against the group of binders that bind solid materials in liquid phase. Thus they tend to weaken the binding force also in solid phase. Dispersing agents act by being adsorbed on the surfaces or near the colloidal double layers of particles. They generate negative charges on the particle surfaces to prevent the cohesion of the particles by repelling them. The repelling of the particles reduces attractive or frictional force that lets them to have larger interaction, thereby 'lubricating' them. This increases the material density to a less degree to maintain the workability. Thus even with a smaller amount of water, the compound can be worked on smoothly enough.

Dispersing agents are preferably added to mix before addition of a group of binders and water.

The amount of dispersing agents added is 5 wt% relative to water at maximum, preferably 0.1 to 4 wt%, more preferably 0.5 to 2 wt%.

5. Water repellents Water repelling is a concept different from hydrophobicity, one in which water is repelled. The method of adding water repellents to raw materials are widely known especially in the fields of weaved fibers, papers, and pulp molds. The repellents widely used currently include fluoride- based resin or silicon-based products. The examples are Lodyne of a multinational enterprise, Ciba Specialty Chemicals Inc., Fluorad of 3M Inc., silicon-based oil or resin thereof of Dow- Corning Inc., etc.

To obtain a repelling effect requires simple addition. Thus the process is very simple. However, the problems that have to be overcome are the lowering of property such as binding force due to a large amount of addition and the high price.

6. Chromaticity controllers

To materialize the desired color of molded articles completed, pigments or dyes can be used. The prior known dyes can be used to colorize or white pigments can be used. Preferable whit pigments are calcium carbonate, oxidated titanium, talc, etc. E. Water Water is added to the compound, to dissolve the constituents in a mixture, especially binders, or at least to disperse them. The added water having such a function is called 'compounding water' to distinguish it from the water contained in the constituents. Also, water aids in homogeneously dispersing in an entire mixture other solid components such as fibroid materials and additives. Such water plays a very important role in generating the compound that has required rheological properties including viscosity and cohesive force. Also, another important role of water is to provide a cause of condensation reaction, that is, an environment for bridging, as shown in Chemical Formula 3 above. The OH and H between two glucoses form water under the influence of the supply of physical energy such as heat, to be kicked out of them. The water is then evaporated after letting them to be bound, as shown in Chemical Formula 4 above.

The important components of the compound of the present invention, that is, steam-exploded biomass, fibroid materials, and grain powder (starch) all are modifications of glucose molecules . The condensation reaction between glucose molecules is a very important reaction for inducing dehydrated hardening in the present invention.

In order to provide proper workability, water should be added to constituent particles, fibroid materials or other solid particles at an appropriate time to dissolve or at least disperse binders, thereby filling apertures. When dispersing agents or lubricants are added, a smaller amount of water can be used initially to maintain proper workability.

The amount of water added to the compound should be controlled so that the mixture has enough workability. One has to recognize the fact that if the initial amount of water is lowered, the amount of water to be removed for formation of hardened sheets is also lowered.

Water may be supplied though grain that is directly input. Especially unprocessed white or sweet potatoes in storage have a large amount of water.

In a certain case, it may be preferable to supply a relatively large amount of water initially. The reason is that an excessive amount of water can be evaporated. Nevertheless, one of the important characteristics of the present invention can be compared to the case of manufacturing papers. The fact is that the initial amount of water is far less in the present invention than in the water found in the fiber slurry used in manufacturing pulp papers. This brings a mixture that have bearing power and stability larger than those of paper slurry. To obtain self adhesive raw materials (i.e., morphologically stable) , the total amount of water to be removed is far less in the compound of the present invention than in the slurry of pulp papers. Furthermore, the intermediate sheets of the present invention have inner cohesive property far higher than the wet pulp slurry does. The amount of water necessary to be added in a mixture depends on the amounts of starch or other water-absorbing components, fibroid materials, and additives, and the particle filling density of additives. Also, the amount depends on the rheology of the compound. In most cases, a minimal amount of water preferably is added to provide the workability necessary for the compound. Thus the amount of water to be removed from the processed sheets is reduced. If so, the manufacturing cost is reduced since water removal requires energy. Pores were discussed in the section of the foaming agent above, but water is also an important foaming agent in the present invention. In other words, the relationship between water and pores involves the magnification ratio of foaming. When compounding, steam-exploded biomass, a group of binders, fibroid materials, functional additives and water are dispersed uniformly. In the compounding process, the shear force of rotation with a high speed may let a certain amount of air to be included.

The sheet in which air is included is heated. The heat increases the vapor pressure of water contained in the compound, thereby let it to evaporate. As water evaporates, the space of water becomes empty. Therefore, as water does so, the sheet of the present invention develops pores that are distributed homogeneously in the sheet.

Using the processes described above, one can control the magnification ratio of foaming by controlling the amount of water content. Without using a separate foaming agent, one can control the magnification ratio of apertures and foaming of the sheet to be molded, by controlling the water content in the total compounding amount. This is one of the very important characteristics in the present invention.

Therefore in the present invention, water play various roles such as a plasticizer, a bridging aiding agent through condensation reaction, a foaming agent by drying, a viscosity controller of the compounded material, a adhesive that provides the composite components with a basic binding force. The amount of water added for forming the compound having high contents of steam-exploded biomass according to the present invention may differ depending on the drying method and process, but it is 5 to 80 wt% of the compound when the magnification ratio of foaming is low, preferably 10 to 70 wt%, and more preferably 20 to 50 wt%. When the magnification ratio is desired to increase, instead of requiring the strength of molded articles, up to 10 times the total solid material of slurry may be added. A person skilled in the art would be able to control the preferable amount of compounding water in order to obtain the proper strength and workability necessary for molded articles in the manufacturing processes. Manufacturing of the compound The terms 'slurry,' 'polymer matrix,' 'compound,' 'moldable composition, ' or 'biodegradable polymer having a high content of steam-exploded biomass' can be used in a mutually interchangable way and they are a mixture filled with steam-exploded biomass that can be molded in any shapes. The mixture has a characteristics in that it has considerable amounts of steam-exploded biomass and grain powder, a small amount of natural or organic synthetic binders, various amounts of fibroid materials and function additives, and water as a solvent and a plasticizer that forms a mixture to have plasticity like plastics. The total solid material includes all the solid phase materials regardless of whether they are suspended or dissolved in the mixture.

The compound may include functional additives such as plasticizers, lubricants, dispersing agents, and aqueous gelling material, and other mixing agents such as foaming agents. The matrix that contains water has thermal plasticity after drying. Thus even after the matrix is molded in a desired shape by heat, it has a relatively high inner bearing power characteristically. Irrespective of the degree of drying, 'polymer matrix, ' 'compound, ' 'polymer mixture having a high content of steam-exploded biomass,' or 'slurry' refers to the compound. The compound of the present invention has water- solubility or thermal plasticity and includes the polymer matrix of slurry type that is partially dried and the compound that is completely dried (even though a certain amount of water may remain as binding water within the group of binders in the sheet. )

The polymer matrix of slurry type that contains a large amount of water forms a sheet and the binders harden when heated to function as an additive. Formed at least when the matrix is partially dried, the sheets or products may have the 'matrix having a high content of steam-exploded biomass.' The proper compounding of the compound can be designed to rationalize the processes by using in an appropriate way the apparatuses of mixing, extruding, and molding, and to minimize the controlling of various components. A. Constitution of the compounding ratio of the compound The first step of manufacturing the compound out of the matrix constituents is to mold in such a way that not only the molded articles have strength, elasticity, drawing and decomposing properties but the compound has a necessary workability and self-adhesion power. The preferable properties of the compound are proper workability, those similar to plastics, self-adhesion power for ^'extrusion, stamping, and molding, and the same property precisely reproduced according to temperature, water content, and compounding ratio. The amounts of water, binders, and dispersing agents determine workability and the extrusion property of a mixture. So do those of the fibroid- materials, plasticizers, and other- fillers such as hollow glass beads, inside the mixture. However, any single component cannot completely determine the rheology and other properties of the compound. Rather, each component is constituted to exhibit a synergy effect in an interrelated way.

Even with the compounding of a similar matrix, the result might be a highly viscous dough if water is compounded less and a slurry if it is compounded more.

B. Effect of components in the matrix process To obtain a mixture having a proper workability and fluidity in the matrix molding process, the amount of water to be added depends on the concentration of additives, the particle density, the kinds and amounts of fibroid materials and binders. However in general, as water is added more, the viscosity and bearing power of a mixture are reduced more. Thus the fluidity of the mixture increases and the dimensional stability decreases. Especially the energy consumption of a heating means is high. Binders can considerably affect the rheology of a mixture, depending on the degree of their gelatinization and dissolution, and their kind and concentration. The binders used in the present invention can be dissolved or at least dispersed well in water generally. The starch granules of grain powder directly pulverized are maintained to be not at the gelatinized state in the mixture containing water until they are molded.

The binders used in the present invention may have not only various cohesive forces, viscosities, and bearing powers but also various solubilities or dispersivenesses.

The starch granules contained in grain are gelatinized and hardened in the sheet formation process. Natural polymer binders like starch are not polymerized or decomposed when added to the compound. But if they are heated to a proper degree, they are gelatinized simultaneously with drying and then hardened. As for gelatinization, most aqueous resins are easily gelatinized in water of room temperature. Starch is gelatinized only in water of temperature higher than that. However, a part of denatured starch is gelatinized at the temperature. Although aqueous resins show maximum rheological effects instantly, starch-based binders become thick when the temperature of a mixture increases.

The functional additives that can directly affect the rheology of the compound are dispersing agents, plasticizers, lubricants, etc.

The amount, kind, and particle density of fillers can greatly affect the rheology and workability of the compound. The fillers that are porous or have large surface area tend to absorb water more than non-porous fillers do. Thus they reduce the amount of water that can be used for lubricating particles. This causes the mixture to be highly viscous.

The particle density of constituents also affects the volume of the space for other liquids such as water, lubricants, polymers, or the mixture to flow (move) , thereby affecting the rheology of the mixture greatly. The aqueous hardening additives like calcium carbonate can be used as a water absorber. They react with water to reduce the effective amount of water inside the mixture, thus affecting the rheology of the mixture greatly according to the hydration degree, which is a function of time. By holding molded articles together, cohesiveness allows sheets to be expanded or pulled through rollers and maintains the morphology until the materials are dried to have enough tensile strength.

Also, the solid materials such as steam-exploded biomass and grain powder affect the rheology in a manner similar to those of additives. Some fibroid materials may absorb water depending the porosity and the swelling tendency.

C. Function and ability of the components that provide a certain characteristics Mostly, the sheet that has lower concentrations of binders and fibroid materials is harder, has higher thermal isolation property and lower cohesiveness, is more resistant to damages by heat, has lower tensile strength, and is decomposed less in water. The sheet that has lower concentration of binders and higher concentration of fibroid materials has higher tensile strength and drawing property, lower compression and bending strengths, lower elastic modulus, higher elasticity, and is considerably resistant to decomposition by water.

The sheet that has higher concentration of binders and lower concentration of fibroid materials is more aqueous and decomposable, and easier to mold (this allows the sheet to be thin) , has relatively higher compression and tensile strengths, higher drawing property, and lower elastic modulus. It also has proper elasticity. The sheet that has higher concentrations of binders and fibroid materials has the properties most similar to those of pulp papers, and has higher tensile strength, drawing property, inner flexibility, and elasiticity, and lower elastic modulus. It also has proper compression strength, very low resistance to water and low resistance to heat.

By adding rosin and alum to the compound, the final molded articles may be provided with a certain degree of waterproof. These interact with constituents to form components that have high resistance to water in the matrix. D. Organic relationship of molded articles with composite components

The properties that can affect the property of the final molded articles and are preferably included in the polymer matrix are high tensile strength, elasticity, drawing property, bending property, and flexibility. According to the final usage, it may be preferable to manufacture the sheet having the properties of papers or cardboard products. However, it may be preferable to the matrix having the properties that cannot be obtained from general wood pulp or other raw materials of papers. These properties include resistance to water, increased drawing property, higher elastic modulus, or lower density.

Differently from papers, cardboard, or pulp molds that depend greatly on the properties of used pulp, the molded articles or sheets of the present invention have the properties relatively less correlated with those of used fibroid materials. Longer and more elastic fibers can provide the sheet with more elasticity than shorter and harder fibers do. However, one can include in the sheet of the present invention the properties that depend greatly on pulp, by controlling the processing technologies of the present invention and the concentrations of non-fibroid components. The properties such as surface strength, rigidity, surface finish, and porosity are irrelevant to the kind of fibroid materials used. Elasticity, tensile strength, or elastic modulus can be controlled such that the sheets or the molded articles manufactured therefrom satisfy the performance criteria. Depending on the usage, a higher tensile strength would be more important. Sometimes, the usage requires elasticity and at other times hardness. A certain sheet should be dense and another- should be thick, light, and isolating thermally. The important point is to target a material that is proper for a specific usage, in consideration of the cost and the parameters of other manufacturing process. In general, if the concentration of fibroid materials is increased in a mixture, the tensile, tearing, and bursting strengths and the elasticity of the final sheet are increased.

The kind of additives also affects the properties of the sheet. In general, light weight additives such as Perlite or hollow glass beads that is hard and inelastic entail the sheet that is low in density, high in thermal isolation, and not easily fragile. The additives such as silica, gypsum or clay are very cheap. Thus they can greatly reduce the cost of manufacturing a sheet .

E. Mixing of the compound The compound-manufacturing facility of integrated molding type includes the extrusion unit in which the raw materials contained in the matrix are continuously measured, mixed, mixed again after removal of air, and output, in an automatic fashion. Or a part of components are mixed beforehand in a container, and the mixed components are then pumped into a mixer of dough and slurry.

Various mixers for mixing the compound of the present invention are known and commercialized. For example, drum mixers, Banary mixers, Henschel mixers, Wigweg mixer, Hobart mixers, kneaders, and extruders having twin screws are preferably used.

Generally, a compound is produced by a method comprising the steps of: (a) metering components, (b) kneading dispersed components, (c) adding water to the kneaded components, (d) dispersing the metered components, and (e) discharging the dispersed slurry into a molding machine.

In the case of compounding the slurry matrix of low viscosity, various machines can be used in mixing the compound of the present invention. The Wigweg mixer shown in FIG. 2a is one of the proper low viscosity mixers.

In the case of compounding of high viscosity, extruders of twin screw are preferable. These mixers can be controlled to provide various rotation powers and different shear forces for different components . The low and high viscosity compoundings all have advantages and disadvantages. To obtain the most ideally mixed compound, composite components should have been homogeneously dispersed. To do so, additive components should be mixed in the order of mixing first those that are difficult to mix and should be prepared in a proper agreement of the characteristics necessary for the desired final molded articles. These requirements should be determined by the viscous state due to the proper amount of water added, depending on the -environment of the casting and drying processes . To form a mixture that is dispersed well and homogeneous, it may be preferable to mix in a powerful mixer of high shear the components that are difficult to mix.

When the added materials are not mixed well due to their long lengths and hardness, it is preferable to use stronger mixing methods in order to disperse homogeneously.

For example, some fibers may need to be separated completely. Since the mixing with high shear results in a more homogeneously mixed mixture, it increases the viscosity of the compound in the middle of mixing. Therefore, it increases the strength of the final hardened sheet. This is so because such mixing disperses fibroid materials, particles and binders more homogeneously to generate more homogeneous matrixes in the hardened sheets.

For the balance between the excessive mixing that may cause the damage in fibers and the homogeneous mixing, it is preferable to mix most of the compounds ' for 10 minutes at maximum and to cast with the extrusion of 3 minutes at maximum out of the mixture.

F. Completion and storage of the matrix To mix the constituents of the compounding ratio described above and to then supply the mixed matrix to the next molding process, the matrix is stored in the state where compounding is completed or the shape is modified properly. It is also required to store and maintain in a homogeneous state inside the hopper. For the proper shape, the matrix can be supplied directly to the sheeting process by extrusion like plastic master badges or the mixed dough can be supplied directly to the hopper of the caster in the case of the low viscosity matrix. If the mixing process, and the casting or molding process of the matrix are separated, the matrix should be stored in such as way that the mixed state does not change. This means that the water contained in the matrix compound, which is mostly organic materials and carbohydrates, should not be dried and the changes in time such as viscosity change, viscoelasticity change, dehydration reaction, foaming, fermentation, bridging, layer separation, phase change, etc. due to the gelatinization of starch should not occur.

The compound completed in this manner is stored in the state of the slurry containing water such that it can be molded into sheets or primary molded articles. Or, as the compounding water of the slurry is dried through the extruder, moldable pellets can be made to use for molding purposes. The primary molded articles should have a properly high melt index in the molder by increasing the binder content among the constituents. The moldable pellets can have function additives such as dispersing agents or wax added, in order to be proper for molding.

The matrix having the constituents and completed by processing methods, as described above, can be called a grafted block copolymer matrix compound of slurry type, consisting of natural raw materials such as biodegradable biomass, fibroid material, grain powder (starch), and binder. The difference of the compound undergone the process of the slurry of the present invention from the compound undergone the dry process through the extruder without containing water is whether it is through the bridging or the constituents play a simple filler. Note that this difference is very big. The molding through the slurry of the present invention exhibits far more excellent physical and structural strengths, resistance to water, relative stability of changes in time than that of the dry process does. Manufacturing of intermediate molded articles out of the compound

The compound of the present invention can be molded by various known methods, which include the molding process of slurry (similar to the manufacturing of carbon copies of bread) , the paper manufacturing process, the casting process of plastic sheets, the manufacturing process of PVA films or foam sheets, the manufacturing process of polyethylene or polystyrene foam sheets, the foaming process of sheets containing ethylenevinylacetate, etc. As for the process very similar to that of the present invention, one can refer to US patent no. 5545450 entitled 'Molded articles having an inorganically filled organic polymer matrix' , issued on 13 August 1996, where detailed explanations can be found on the formation process of starch sheets having a high content of inorganic materials.

The term 'sheet' molded out of the compound of the present invention includes a plate that is flat, circular, bended, and organized. The compound is one that is manufactured by homogeneously mixing the group of binders and the constituents. The sheets may include other layered sheets, surface coatings, printed matters, etc. The sheet may have various shapes according to its usage. It may be as thin as 0.01 mm and may be thicker than 1 cm, when its strength, durability, and size are important.

The present invention forms primary sheets by continuously casting the matrix compound containing a high ratio of steam-exploded biomass and the sheets are hardened by evaporating water through a drying means, thereby completing stable sheets. Thus the present invention relates to a novel composition for which a technological problem is solved to manufacture sheets in a large scale by using such a method of manufacturing stable sheets.

A. Formation of intermediate articles (initial sheets) The polymer matrix sheets, i.e., the intermediate molded articles to be molded into other products, can be manufactured by sheeting the compound mixed as described in details above. The present inventor presents the following four methods of molding sheets.

The first method consists of the steps of forming sheets by casting the compound on the already molded isolation film that is continuously supplied on a conveyer; then stabilizing the shapes of the formed sheets by promoting the bridging between binders, steam-exploded biomass, and fibroid materials through water removal by heating; and completely hardening the binders by complete evaporation. The sheet formed in this manner consists of one surface having a coated film and the other surface being a dried polymer sheet. Thus when completing by remolding, the other surface is coated properly for use. In this case, whether the starch constituents are gelatinized does not affect- the next processes much. The second method casts the compound on the conveyer coated with a biodegradable coating liquid that can be dried quickly, as in the first method. Then increasing the temperature of the conveyer hardens the coated film of the liquid and heats the compound, thus progressing the molding. Due to the heated conveyer in this case, the coating liquid between the compound and the conveyer hardens and the film in- between hardens, thus preventing the adhesion of the compound to the molder or rollers. The surfaces of the conveyer or rollers are coated with fluoride resin, etc. Thus the adhesion power to other materials is not strong and the molded sheets are easily separated together with the fluoride resin. In this case, whether or not the starch constituents are gelatinized does not affect the next processes.

The third method casts the compound on the conveyer coated with cellulose ether that has the thermal gel (syneresis hardening) characteristic, as in the first method. Simultaneously, the upper side of the sheet is coated and pressed down by the rollers that are coated with the coating liquid of cellulose ether, thus stabilizing the sheet. And increasing the temperature of the conveyer and rollers above the syneresis hardening temperature of the ether progresses the molding. Due to the heated conveyer, the coating liquid between the compound and the conveyer hardens and the film in- between hardens, thus preventing the adhesion of the compound to the molder or rollers. The surfaces of the conveyer or rollers are coated with fluoride resin, etc. Thus the adhesion power to other materials is not strong and the molded sheets are easily separated together with the cellulose films. Since both surfaces of the sheet formed in this way consists of the cellulose films, the sheets are fragile to the attack of water. The sheets are coated properly when remolding. In this case, it is inevitable to use the starch that is not gelatinized. The fourth method casts the compound under the condition that the temperature is lower than the gelatinization temperature of starch and higher than the thermal gel temperature by adding, to the binder compounding of the polymer matrix, the resin that has the thermal gel temperature characteristic, thus hardening the surfaces of the sheet, thereby removing the adhering property of the compound and forming the sheet.

B. Formation of the sheet out of the compound FIGS. 3a and 3b show the system for manufacturing the sheet out of the polymer matrix compound in details.

The polymer matrix compound that can be applied to the present invention can be formed, by using various polymer- processing technologies already known and widely used. The examples include: a process of drying papers and forming sheets, a process of sheeting PVC casting films, a process of foaming PVC sheets, a process of foaming low density polyethylene (LDPE) sheets, a process of molding polystyrene foam sheets, a process of manufacturing and processing various nonwovens, a process of drying resin pellets and mixing pigments, etc., a process of making functional master badges, and a process of making sheet molding compounds (SMC) .

The known machines and technologies used in the processes described above and other similar methods are preferably used. The examples of low viscosity mixer are preferably drum mixers, Banbary mixers, Henschel mixer, Wigweg mixers, Hobart mixers, etc. The examples of high viscosity mixer are preferably kneaders, extruders having twin screws, etc.

A series of slurry sheeting systems, as shown in FIGS.

3a and 3b of FIG. 3, may include mixers, twin screw extruders, various sheet forming rollers, drying means, compression rollers, additional drying means, a series of finishing rollers, and finishing spools.

The manufacturing processes used for manufacturing the polymer matrix sheets of the present invention that can be formed into containers or other products are shown in FIGS. 3,

4, and 5, which include the units performing the following steps of:

(1) preparing for extrusion by putting in the hopper the compound that is supplied in the mixed state; (2) extruding or casting the mixture in sheet or various shapes though a proper outlet (die) ;

(3) forming the desired thickness of casting sheets by passing the extruded mixture through formation and compression rollers; (4) gelatinizing the starch by passing the sheets through initial heating means, then removing a part of water from the mixture, and then drying the sheets with a heating means;

(5) increasing the strength of the sheets by removing undesired apertures through the compression of the sheets while the sheets are rather wet;

(6) further drying the sheets after the compression;

(7) finishing the sheets by passing them through more than one finishing roller; and (8) winding on spools the sheets dried to form the rolls that are stored to be used when needed. FIG. 2a is the favored mixing process of slurry and shows the 'Wigweg' extruder that supply rapidly back and forth the mixed slurry along the length of formation rollers. As shown in FIGs. 3a and 3b, the slurry compound can be injected directly into the space between formation rollers.

The second method for obtain a best mixture include the steps of:

(1) preparing for extrusion by putting in the hopper the compound that is supplied in the mixed state; (2) extruding the mixture and cutting the extruded mixture into separate units of proper shape;

(3) transferring the extruded units to the hopper;

(4) forming sheets by passing the units through a pair of self supplied compression rollers; and (5) drying or finishing the sheets.

The extrusion step assists the air removal from the compound and the extruded units are uniformly supplied for the inlet of the compression roller.

C. Fine adjustment of molding The slurry that is output with an initial thickness through the extruder die in the sheet formation step is compressed to the first desired thickness to mold sheets.

These sheets are passed through more than one group of compression or formation rollers (FIGS. 4b and 5b) to form the sheet of the second desired thickness out of the compound. Or, the compound can be input directly to the space between the sheet formation rollers of FIG. 4b or 5b.

FIG. 5a is an enlarged view of the extruder of screw type that includes an injector of injecting the compound onto the casting ^'extruder. The constituents put in the hopper are transferred to the inside of the cylinder to mix them homogeneously before being sent to the next steps.

The slurry constituents are injected into the hopper of FIG. 5a. The screws make the mixture progressed toward the oμtlet while mixing it. Extrusion should supply the compound for the molding facilities continuously and in a properly controlled manner. This can be achieved by the flow of materials though the outlet or by other mechanisms that induce 'extrusion.' For example, gravity can be used to make the compound flow. In FIGS. 3a and 3b, the slurry compound is injected directly to a group of extrusion and reduction rollers from the mixer to directly transform the compound of slurry state to sheets without using an extrusion die. The sheets that are formed by formation rollers like the systems shown in FIGS. 3a and 3b are transferred to drying rollers, compression rollers, additional drying rollers, a series of finishing rollers, and go through a spooling process afterward.

When a separate isolation or adhesion (sticking) prevention means is not provided, the binder having a thermal hardening characteristic is included in the compounding, to form the initial coating film of cellulose ether on the surfaces of the sheets, and the sheet formation rollers are then heated to the temperature at which starch granules are gelatinized. Also, a part of water can be removed by evaporation during the processes.

As shown in FIG. 5b, the reason for compressing the sheets is that compression can provide the dimensional stability for the sheets. At the same time, when the sheets are compressed, as shown in FIG. 6, flat and strong skins are formed on the surfaces of the sheets. As shown in FIG. 6a, the compression forms a denser layer on the surfaces than in the inside. Thus the denser layer has a characteristic in that it reduces the physical impact from the outside.

Directly after the compound is cast, water in liquid state is not removed almost at all in the initial formation stage of the sheets. But as shown in FIGS. 3a and 3b, a series of heated sheet formation rollers is used as a heating means during the sheet formation process to remove the water amount. The thickness of the sheets reduces as they are passed through rollers. Accordingly, the sheets are drawn down in the 'machine direction' with the width maintained uniform. As a result of drawing the sheets down, the fibroid materials are oriented in the machine direction. Combined with the initial extrusion processes, the reduction process can, in this manner, generate the sheets that are oriented singly in the machine direction. However, if the speed of the compression rollers increases, the fibroid materials become disordered in the sheets .

^• In the case of the matrix having the compounding that has very low adhering property to rollers and plasticity, the extruded sheets can be reduced to the final thickness in a single step using heated rollers of very large diameter and various rollers of small diameter.

To obtain the thinnest thickness of the sheets while preventing the molded sheets from being dried excessively, the optimization of roller diameter is favored more than the reduction in the number of the reduction processes in the manufacturing process. Not only the reduction of the space necessary for the processes but also the number reduction decrease the number of rollers that has to be synchronized for preventing the sheet accumulation behind the rollers (when the rollers rotate slowly) and the sheet tearing (when they rotate fast) .

In general, the adhesiveness of the compound increases as the water amount increases in a mixture. Therefore when a mixture contains a larger content of water, rollers should be heated to a higher temperature to prevent adhesion. This is an advantage because the sheets having a larger content of water should be heated to remove more water so as to obtain a proper self-adhesion power. Additionally, the increase in the roller temperature is permitted such that the increase in the roller speed prevents the sheets from being stuck to the rollers.

To reduce the adhesion between the rollers and the sheets, another method is to treat the surfaces of the rollers. The rollers are made of stainless steel with their surfaces treated with gloss and are coated with non-adhering materials such as chromium, nickel, or Teflon.

Finally, since the workability is high and the compound has plasticity, the stamping process does not compress the sheets much. In other words, when the sheets are dried excessively during the period of passing through the space between the compression rollers, a part of them may be expected to compress, but the density of the sheets will be maintained to a fixed value during the stamping process.

When compression is needed, the sheets may be passed through a group of compression rollers (FIG. 5b) after drying. Therefore, the important parameters in the stamping process are the diameter, speed, temperature and 'nip height' (or gap distance) of rollers. The increase in the diameter and nip height of rollers reduces the shear rate that is provided for the compound during the sheet formation process and the increase in the speed of rollers increases the shear rate.

In addition to the processes described above, one can apply, for the formation of the sheets of the present invention, the technology similar to mixing, heating, drying, melting, drawing, foaming, exfoliation, evaporation, winding, ultrasonic wave irradiation, ultraviolet ray irradiation, etc. If necessary, the technology may include the process such as mixing, kneading, surface coating, wet injection, wet removal, dissolution, fusion, addition reaction, clustering, granulation, hydrogenation, oxidation, reduction, hydrolysis, bridging, and cooling of the mixture, etc. An advantage of the sheets of the present invention is that they affect environment less than papers, cardboards, plastics, or polystyrene molded articles. The sheets and molded articles of the present invention can be regenerated. Even if they are not regenerated, they decompose easily when exposed to water, pressure, and other environmental factors, to become a component that is mutually supplementary to soil components. The components of organic synthetic binders dissolve in water more slowly that carbohydrates do, but decompose rapidly by the actions of microorganisms. Fibroid materials also decompose rapidly and are contained in a smaller amount in the compound of the present invention than in papers. Inorganic additives are inactive and compatible with soil in any cases. Comparatively, polyethylene or plastics continue to exist for several years or even several centuries. Papers or even cardboards may continue to exist for several months or even several years if decomposition conditions are not perfect. In comparison to this, the containers that are manufactured out of the sheets of the present invention decompose in several hours or days depending on the water content, to turn into compost, thus fertilizing soil. D. Drying process

By using a processor, especially an extruder, that has the removal function of air bubbles, compounding water and air bubbles are simultaneously removed from the compound for drying. But when the sheets are intermediate molded articles, compounding water and air bubble are not removed but dispersed in the mixer of low shear force and the formed sheets are dried with a separate heating means. When dried without the removal of air bubbles, the sites where air bubbles and compounding water have located remain as apertures to have foamed shapes. This means that the sheets 'are dried and hardened in the foaming magnification ratio as high as the compounding water is foamed. Thus the amount of compounding water added can determine the foaming magnification ratio of the molded article.

When the initial sheets are molded as an intermediate molded article, the sheets can be dried partially or even almost completely with a heating means by casting them on the conveyer. Even so, the sheets should be dried further to obtain a required tensile strength and a prescribed drawing property. Even though the sheets may be dried naturally as time passes by, it is impossible to wait for natural drying since a large scale production is aimed at in the process design. Drying can be performed with various methods of heating the sheet to discharge water quickly.

There may be various drying means of the sheets. But in the present invention, they are broadly classified into the methods of using heating rollers and a drying tunnel.

First, the method of using heating rollers is described. Contrary to more than one compression roller that are arranged in a group in a serial manner, the drying means are arranged in such a way that the sheets pass through the surface regions of rollers sequentially (various rollers shown in FIGS. 3a and 3b) .

In this method, two surfaces of the sheets are dried stepwise. The heating rollers of large diameter are favored.

Since the diameter is large, the contacted area is large and the heat efficiency is high. But many series of smaller rollers may be used.

Next, the method of using a drying tunnel (dryer) is explained. The matrix that is cast on the conveyer in the extruder is adjusted to a prescribed thickness in the compression roller to enter the drying tunnel. The entered conveyer is heated by various heating means and the length and line speed of the conveyer determine the duration time inside the heating means. The line speed is controlled according to the dried state. During the time, the matrix receives heat from the heating means and the water in the matrix is dried by the heat.

The heating means in the drying tunnel may include heating by electricity and gas, and a method of mixing high frequency wave (dielectric heating) irradiation with electricity or gas. As for heating by electricity and gas, one can use generally known methods.

High frequency wave dielectric heating is to heat an object in a strong high frequency electromagnetic field and is also called radio wave heating. If an object is placed in a high frequency electric field, the object itself generates heat due to the loss of dielectric substances of an insulator. This principle has been applied to drying or adhering of woods, vulcanization of rubbers, molding and processing of synthetic resin, gluing (high frequency wave gluing) of vinyl films, drying of fibers, processing, insects-killing and sterilization of agricultural and fishing products, cooking of foods (microwave oven), etc. The characteristics of this heating method is that even though the heated object has low thermal conductivity, the heated object itself generates heat and is heated in a good efficiency, and the desired location can be heated selectively.

The temperature of the drying means depends on various factors including the water content of the sheets when the sheets are passed through a specific roller. To prevent the damage and decomposition of the constituents of the matrix compound, the temperature of the drying means should be less than 300 °C. To prevent the destruction of organic components (organic binders or cellulose ether, etc.), the compound should not be heated above 250 °C. Nevertheless, the rollers can be heated above the temperature as long as a proper amount of water exist in the compound, since the vaporization of the water in the mixture can cool the materials. Still, since the amount of water reduces during the drying process, the roller temperature needs to be reduced in order to prevent the excessive heating of the sheet materials.

When the processes need to be quickened, one can use the drying tunnel, oven or chamber together with the drying means. To obtain the drying effect by thermal convection, one may favor to accelerate the drying process by circulating the heated air. The temperature inside the tunnel and the retention time of the sheets in the tunnel determine the speed and amount of evaporation of water in the sheet materials. The temperature inside the tunnel should not exceed 250 °C to prevent the destruction of organic binders . The drying tunnel is heated to 100 to 250 °C. In some cases, the final step is the drying process described above before the sheets are used for manufacturing containers or other products or are wound to the spool (the roll at the end of FIGS. 3a, 3b, 4a and 4b) . When the sheets are required to be smoother or to have finishing more like papers, additional steps can be added after the drying or finishing step.

Surface treatment (the difference between coating and lamination) Molded and dried as described above, the sheets may require additional surface treatment to supplement the performance according to the characteristics necessary for them and the final usage. According to the sheeting process described above, one side of the sheets may have been laminated initially and there may be sheets that are coated with a coating liquid and that have one surface of hardened binders. These additional surface treatment processes for supplementing the performance include coating, lamination, or a combination thereof. A. Lamination and lamination process

Surface treatment can provide molded articles with physicochemical protection and molded sheets with various properties. A 'lamination' sheet refers to the sheet that has more than two layers, at least one side of which is a sheet. A sheet can be formed by combining at least two layers . The thickness of a sheet varies according the desired usage and the required properties.

The lamination materials combined or adhered to the sheet include other sheets and the materials that provide the properties necessary for the sheets when two are laminated together, i.e., coating materials, adhesives, or a combination thereof. The examples of improving or strengthening the properties of the sheet are polymer sheets, metal foil sheets, ionomer sheets, elastic polymer sheets, nylon sheets, wax sheets, aqueous hardening sheets, and metalized film sheets. Wet starch may be used as an adhesive for lamination. By using adhesives through various methods such as wet gluing lamination, dry gluing lamination, heat and compression lamination, sheet-sheet and sheet-coated film mutual bindings can be formed. As useful adhesives, there are aqueous adhesives (natural and synthetic) , high temperature melting or dissolved adhesive.

Liquid adhesives that will combine two layers are used for wet binding lamination of the sheet and other layers. Natural aqueous adhesives useful for wet binding lamination include vegetable organic binder adhesives, protein-based adhesives, animal adhesives, casein and natural rubber latex. Useful synthetic aqueous adhesives include resin emulsions such as stable suspended liquids of polyvinyl acetate particles in water. Most of aqueous adhesives are weak in smell, taste, color, and toxicity, and have a wide range of adhesive properties and excellent performances.

Thermo-plastic adhesives are hot melt adhesives that are applied in the molten state and hardened when cooled. Hot melt adhesives harden more rapidly than other adhesives. Useful oily adhesives include polyurethane adhesives, oily ethyleneacetate systems, and other rubber resins.

Starch in the sheets also acts as a thermo-plastic material. If the sheets are heated above the glass transition temperature of starch, the sheets can be molten and deformed. Cooling of thermo-plastic materials makes molded articles fixed in a new shape. Molten and cooled starch acts as an adhesive that adheres and seals the sheet, so that pipes, tubes or cans can be manufactured.

The surface layers of the sheets that are supplied continuously by the conveyer should have higher drawing properties and melt flow viscosity than those of the compound at the temperature for remolding. Otherwise, the compound layers and the surface layers might be separated when remolded.

B. Coating and Coating process The sheets or the molded articles produced therefrom can be coated or applied for surface treatment with coating materials. By various methods including sealing and protection of sheets or articles, coating can be used for strengthening the surface characteristics of the sheets. Coating protects the surfaces from wet, base, acid, grease and organic solvents. It provides strengthened surfaces that are smoother and glossier, so that the sheets or their constituents are prevented from being scattered. It also provides thermal isolation and insulation. The coating materials of the surface layers reinforce the sheets at the lines of bending or folding. For the articles that are formed by folding, coating materials having plasticity and elasticity are favored. These materials can be used as lamination materials or adhesives. Some coating makes the matrix flexible, thus making the molded sheet more elastic. For example, coating based on the materials such as soybean milk or cellulose is applied on the sheet surface alone or in combination with polyethylene glycol, to make the sheets or the sites of folding in the sheets permanently flexible.

When these properties are provided for the sheets of the present invention through the surface treatment, they exhibit substantially the properties similar to those of polystyrene foam sheets, plastic sheet, or papers.

The purpose of coating process is to protect the content by forming a uniform film on the sheet surface. Coating can be applied during the sheet formation process or the production formation process, or after products are formed. A specific coating process and material can be chosen depending on the variables of the sheet surfaces and the coating compounding materials. The sheet variables are strength, wetting property, porosity, density, smoothness, homogeneity, etc. The compounding variables of the coating materials are the content amount of the total solid material, solvent (solubility and volatility of water), surface tension, rheology, etc. In the field of manufacturing papers, cardboards, plastics, polyethylene, metal sheets, or other wrapping materials, coating means such as blade, air-knife, Dahlgren (a coating machine using various rollers) , printing, and gravure, and coating methods such as powder coating, 'coating method using phase equilibrium' of Korea Patent Application No. 2001- 0060271, applied on 27 September 2001, and 'coating method of surface isolation materials using phase change and equilibrium during the molding process of starch molded articles' of Korean Patent Application No. 2001-0064858 can be applied for sheet coating.

Coating can be applied by pasting, smearing, or spraying coating materials on the sheet or articles, or by putting them in a container containing proper coating materials and then by performing post-treatments. Also, the coating methods of the sheet surfaces can integrate the coating and extrusion processes by casting through gluing the compound simultaneously with the molding of coating materials (hollow molding, lamination, casting, etc.) by casting (co-extruding) the compound on a coated film or a film that is molded on the conveyer, or

- by casting the compound on a film coating material that has become, ^' after hardening, a coated film, which was coated with a coating liquid on the surface of the conveyer contacting the compound. All these integrated coating methods maintain the initial shapes of the compound.

Proper organic coating materials include PVA, polyvinylacetate, polyacrylate, polyamide, nitrocellulose, cellulose acetate, cellulose acetate butylate, hydroypropylmethylcellulose, polyethyleneglycol, acryl resin of emulsion type, liquid phase polyurethane, polylactic acid, latex, starch, soybean protein, soybean milk, cellulose ether, synthetic polymer containing bidegradable polymer, rosins, wax

(beeswax, petroleum-based wax, or synthetic wax) , food oil, melamine, polyvinylchloride, elastic polymer, etc.

The compounding of PVA alone and monomers having plasticity, for example, copolymers with ethyl acrylate, butyl acrylate, dibutyl maleate, etc. can be used as a coating liquid. Vinylacetate resin alone has been used for being cheap. But, since coating materials using copolymers has low temperature of coated film formation, excellent weather resistance, water-resistance, and storage stability, they might be used. Nevertheless, the advantage may lower the biodegradability of the molded articles of the present invention. Thus, in order not to hamper the biodegradability, it is preferably to add a small amount of monomers. Proper inorganic coating materials include sodium silicate, calcium carbonate, aluminum oxide, silicon oxide, kaoline, clay, ceramics and a mixture thereof. Inorganic coating materials can be mixed with organic coating materials. In addition to these coating materials, proper coating materials can be used according to the usage.

Waterproof coating is preferable for the articles contacting water. If the sheets are used for the containers contacting foods, the coating materials will include those that are certified formally.

Polymer coating materials like polyethylene are useful for forming a thin layer of low density. Low density polyethylene is useful for generating the containers that seal water and are pressure-tight. Polymer coating materials can be utilized as an adhesive for heat sealing.

Wax and wax mixtures, especially natural and synthetic wax, provide a barrier to water, oxygen, and organic liquids such as grease or oil. These allow containers to be sealed thermally. Synthetic wax is useful for wrapping foods and drinks and includes paraffin wax and microcrystalline wax.

C. Post-processing

By optimizing the compounding of -the compound according to the purpose, one can manufacture the matrix that can be drawn down up to a prescribed ratio in the heated or wet state or even in the dried state. In other words, the sheet can be drawn down with the ratio range without being destructed.

The term 'draw down' means that the matrix of the sheet can be expanded without being destroyed to have a finished surface. In other words, the term implies that there exist a point to which the matrix can be deformed without being destroyed by the application of a drawing force. To obtain the sheet that has necessary strength, flexibility, drawing property, weight or other performance requirements, the thickness of the sheet can be modified by adjusting the gap (space) between the rollers of the molding facility. According to the thickness and performance, one can adjust the components of the matrix and their relative concentrations. The sheets can be designed to have various thicknesses. When thermal isolation, and higher elasticity or strength are required, the sheet may be 1 cm thick at maximum. Of course, compositions may be molded into the very thick sheets being more than 10 cm thick.

The sheets for wrapping boxes are preferably 2.5 mm thick and milk packs 5 mm and juice boxes 2.5 mm.

The sheets that require higher strength and elastic modulus and lower elasticity (covers of magazines or books) are preferably 0.1 to 2 mm thick. The thickness and elasticity of a specific sheet depends on the performance criteria required for the molded article and object in question.

As described above, the sheet can be molded to have various thicknesses and strengths to be used for various usages.

When boxes and containers with lids are manufactured out of the sheets, they need to be fold or bent. To form 'folding-inducing lines' where the sheets can be folded, it may be preferable to process the sheet in advance. Preprocessing is to first generate on the sheets the locations where the sheets can be folded or bend.

The pre-processed sheets prevent the exfoliation of the surface skins and intermediate layers that can occur when the sheet are bent in a forced manner. The processing generates in the sheets the 'folded locations (hinges)' that have larger flexibility and elasticity than the unprocessed sheets. Also it provides the locations where the sheets are naturally bent or first folded.

Depending on the usage, there are the cases where it is preferable to heighten resilience and provide resistance to folding by enriching more fibroid materials at the folded locations .

During the pre-processing, the sheets are preferably maintained in a dried or semi-dried state or in a semi- hardened state. It is because while lines are made on the sheets containing water, the rooms are provided for the locations compressed by a prescribed pressure to move without physical damages, since the contents have a prescribe viscosity. This induces the sheets to be compressed rather than cut. At the same time, the polymer matrix is condensed at the compressed locations. Thus the skins stronger in the compressed location than in the uncompressed location are formed to provide a force resistant to bending.

The pre-processing should be performed to a proper depth according to the cases and usages. The reason is that if too deep or shallow, the sheet might be cut instead of the increase in the resistant force to a prescribed bending. Also the pre-processing on both surfaces of the front and back is helpful in increasing the range and angle of bending movement. Articles manufactured as a sheet

By using the molding method of the sheet that utilizes the biodegradable polymer matrix compound of the present invention, one can manufacture various types of sheet having various properties. When very thin, elastic sheets of light weight are needed, the thickness of the sheets may be less than 0.1 cm. When relatively thick, strong, hardening sheets are required, the thickness may be about 1 cm. The sheets can have a density of 0.2 to 2 g/cm², depending on the kind of additives added in compounding. The, higher the density, the stronger the sheet is. If the density is low, thermal isolation is large. By designing the precise thickness and density in advance, one can manufacture the sheet that has necessary properties, in an economically possible method.

The sheet produced according to the present invention can be coiled around a large spool or cut into small sheets, and stacked on a pallet like papers or cardboards and stored for a necessary period.

The sheet having high contents of steam-exploded biomass according to the present invention can be re-heated or wetted to have plasticity in a limited range. After plasticized, the stacked or coiled sheet is cut, and formed into the desired shape by re-heating or re-wetting. Additionally, the sheet can be processed like plastics. If the sheet having high contents of steam-exploded biomass according to the present invention is heated above the glass transition temperature of starch, it can be formed into the desired shape. Upon cooling below the glass transition temperature, the sheet will be solidified.

The sheets of the present invention can be utilized in the fields where polystyrene foam material (Styrofoam) , pulp papers, or cardboards are used. Also, by virtue of the properties inherent to the raw materials of the compound of the present invention, one can manufacture various articles that can substitute for plastics, polystyrene, or metals.

Especially, the sheets of the present invention can be utilized for manufacturing the following various articles:

Disposable and non-disposable food or drink containers such as lunch containers, instantly fried noodle (instant noodle in-the-cup) containers, disposable take-out food containers, food containers heated instantly in microwave ovens (high frequency wave) for wrapping retort foods, cereal boxes, sandwich containers, 'clam shell' type containers (folding (hinge) type containers that are used for fast foods such as hamburgers and sandwiches) , freeze-dried food boxes, large wrappers for circulating fishes, food containers for exhibition in small packages at large general merchandise stores, food trays for exhibition in small packages, milk packs, fruit juice containers, yogurt containers, drink carriers (basket type carriers, '6 pack' ring type carriers) , ice cream boxes, cups (disposable drinking cups, corrugated cups, corn cups) , French fry containers; wrappers, wrapping materials such as space fillers, a filler, bags for snacks, bags having an opening end such as vegetable bags, bags inside dried cereal boxes, cosmetics wrappers, hardware wrappers, trays for supporting products such as cookies and candy bars, cans, tapes, cardboards, various boxes such as hard board corrugated boxes for wrapping, sweets boxes, and cosmetics boxes; molded article containers for condensed freeze-dried juice, oatmeal, potato chips, ice cream, salt, detergents, and motor oil; postal matters wrappers, books, magazines, envelopes, post cards, 3 ring binders, book covers, folders, trays, lids, straws, cases,, egg boxes, disposable plates, toys, Plamodel, etc. Examples

The following examples are given for the illustration of the matrix compound obtained according to the processes of the present invention and the method of forming sheets out of the matrix compound and the compositions thereof. In other words, the method of manufacturing sheets, containers, and other products having various properties and sizes and various mixture compositions thereof are described with reference to the examples. Example 1

To heat a reactor (cylinder) to 180-230 °C at which pre- explosion treatment is carried out, saturated steam heated to about 200 °C (pressure: 15.3 kg/cm²) in a steam generator is introduced into a reactor jacket and a reactor. An automatic temperature control sensor, which was connected with a jacket inside the reactor and the inside of the reactor, is operated so that the temperature inside the reactor reaches the desired temperature. Then, a valve for introducing high-pressure steam is operated such that the reached temperature can be maintained.

Chaffs, as biomasses, which were pre-heated to about 180 °C before introduction, are introduced into the reactor via a hopper, and all valves connected to the inside of the reactor are closed so that an inlet to the reactor is closed. Then, only open/close valves for introducing and discharging steam are opened, and saturated steam heated to 230 °C is introduced.

This steam is introduced into the reactor for one minute such that the biomasses within the reactor reach about 200 °C and 25 kg/cm². Immediately, an open/close valve at the lower portion of the reactor is opened, and solids within the reactor, including cellulose and lignin, are extracted and then explosively spouted into a flash tank, thereby steam- exploding the solids.

This gives a fibroid material of the steam-exploded chaffs. The resulting material is separated into fiber and slurry such that it can be blended in a compound. To obtain large amounts of steam-exploded biomass, the introduction, heating, pressurization and steam explosion processes as described above are repeated.

Example 2

A high content of steam-exploded biomass is manufactured into a compound out of a polymer matrix containing components given in the following table.

This example shows a standard compounding according to the present invention. As the biomass, the chaffs (specific gravity of 0.3 g/cm² and 0.7 g/cm²) of Examples 1 was used, and as the starch, corn starch was used. They were not gelatinated upon addition to the mixture. Organic binders were a mixture of PVA (Kuraray, Exceval CP-4104B1) and methylcellulose (For example, Dow' s Methocel F4M Grade, gel temperature is 62 to 68 °C, and it shows strong lubricating powder) in the ratio of 50: 50.

The steam-exploded biomass, starch, and fibers were mixed for 10 minutes under high shear in a Hobart mixer. Then a group of binders was added and the mixture was kneaded again for 5 minutes. After water of room temperature was added, the mixture was mixed under low shear until the components were mixed well, to complete slurry. The reason for using low shear is to protect the fibers in the components.

By using an extruder of screw type that can remove air, the mixture was extruded through an outlet of 30 cm x 0.6 cm, to form a continuous sheet having the corresponding width and thickness. Afterward, the extruded sheet had the gap corresponding to the thickness of the formed sheet and was passed through the space between the rollers that had been heated to about 70 °C. Afterward, the initial sheet was passed through the space between the rollers having a temperature above 100 °C to gelatinize starch and to remove water due to evaporation from the sheet. Since the steam-exploded biomass has low specific surface area and cellulose ether had been gelatinized, the mixture had a low sticking property to the rollers. Therefore, cellulose ether among the binder group prevented starch from being stuck to the rollers during the formation process.

The resulting sheets of a high content of steam-exploded biomass were completed as the initial molded articles of various thicknesses more than 1 mm.

Remolding was performed by heating the initial molded articles above 200-220 °C, to provide plasticity and flexibility and forming the molded articles into the desired shape. Example 3

A sheet filled with a high content of steam-exploded biomass is manufactured from the following composition.

The steam-exploded biomass, starch, pulp fibers were mixed for 10 minutes under high shear in a Hobart mixer. Afterward, a group of binders was added and the mixture was additionally kneaded. And water was added to the mixture, which was then mixed sufficiently under low shear. The mixture was extruded using an extruder through a die of 30 cm x 0.6 cm to form a continuous sheet having the corresponding width and thickness. Afterward, the extruded sheet was passed through a group of formation/reduction rollers that have the gap corresponding to the thickness of the formed sheet.

The sheets of this example were completed as the initial molded articles of various thicknesses of more than 1 mm.

Examples 4-8

Only the starch of Example 1 is substituted with the following grain powders, in the converted amount of starch.

A high content of steam-exploded biomass is produced into compounds from polymer matrixes having components given in the following table, particularly fiber pulp.

* The amount of water added = 6000 - (the converted amount of starch - 1500)

With foreign materials removed, the grain powders were homogeneously pulverized with the cuticles into a size smaller than 100 meshes and included in the compounding without separate pre-treatments. The cuticles of rice plants and barley and the embryos of corn were difficult to pulverize or separate in the lab. The processes were the same as those in Examples 2 and 3. The sheets are manufactured using the method described in Example 3. In these examples, the sheets were molded in thicknesses of more than 1 mm. Example 9 After increasing the amount of binders without containing grain powder, the sheets are manufactured out of the following compositions. Additionally, the compositions contain a large amount of steam-exploded biomass among all the components. 11 kg of water is contained in the compositions.

As natural filament, Manila hemp (string) was pulverized and compounded. It was confirmed that even though a large amount of steam-exploded biomass is contained, property can be maintained and molding was possible, if a large amount of organic binders and fibroid materials are used.

Example 10 The sheets, i.e., the intermediate molded articles that can be molded into various products (including foods or drinks containers) were manufactured. The hardened sheets were remolded to finish with coating and then manufactured into various foods and drinks containers. For the cups into which drinks are put in fast food stores, the sheets were cut in a proper size and the cut sheets were wound up in a cup shape and by using aqueous adhesives, they were glued to manufacture a pipe shape. For isolating heat, it is preferable to use the sheets of the present invention of a thickness of more than 1 mm in manufacturing the cups . Example 11

The sheets were heated to 220 °C and the heat provided the sheets with plasticity. The sheets that had been provided with plasticity and flexibility by heating were put on a female mold and then compressed with a male mold. They were cut in the neighbor afterward. After the shapes of the molded articles were stabilized, they were taken out. In this manner, the molded articles of tray shape were completed simply. Example 12

The sheets having various thicknesses were manufactured according to Examples described above. The dried sheets of each thickness were cut in a circular shape and molded into disposable trays by using facilities and machine presses that are used in manufacturing disposable plate with the raw material of papers. The formed plates are similar to the prior paper plates, trays and cups in the shape, strength, and appearance. However, the plates that are manufactured out of the sheet having a high content of steam-exploded biomass are harder than the prior paper plates and exhibit larger and stabler structural integration when foods are put on them. Example 13

By using the compositions, the sheets of corrugated cardboards that have an inner structure in which cardboards are put between two flat sheets were formed. The flat outer sheets were formed, by winding the raw materials with two flat sheets of proper thickness. The hardened cardboard sheets

(similar to the corrugated inner sheets of general pasteboard boxes) of a high content of steam-exploded biomass that are corrugated and have proper thickness were wetted again to be taut. The taut sheets were passed through the rollers having the corrugated surfaces or saw teeth that engage mutually, to form the corrugated sheets. Adhesives were applied on the corrugated sheets, which were then put between two taut sheets and hardened. The corrugated sandwich structures are more excellent in strength, toughness, and stiffness than the prior cardboard sheets. Example 14

After forming a plate and a tray, each weighing 20 g, they were coated with 1 to 5 g of a coating composition. The composition is a suspended liquid in which 20% nitrocellulose

(RS 1/2NC) , 20% glycerin, and 10% rosin are dissolved in 50% methanol. For coating, any known methods can be used. To prevent blushing, the coating composition were coated on the completely dried molded articles at room temperature and placed at the temperature. After coating, the containers were dried for a proper period of time. The physically stable biodegradable lacquer surfaces for which waterproof treatment was performed well were generated. Example 15 After a plate and a tray were formed, each weighing 20 g, they were coated with 1 to 5 g of a coating composition. The composition is a composition that contains 20% PVA, 20% glycerin, and 60% water. For coating, any known methods can be used. The composition is applied at 90 to 150 °C. After coating, the containers were dried for a proper period of time. Example 16

The molded articles such as the trays manufactured according to Example 11 were passed through a wax coating machine to apply wax on the surfaces. The wax layer was made waterproof by sealing the surfaces of the molded articles against moisture. Example 17

The containers such as the trays manufactured according to Example 11 were coated with acryl emulsion using a fine spray nozzle. Similar to the wax of Example 16, the acryl coating layers were made waterproof by sealing the surfaces of the molded articles against moisture. Since acryl coating does not meet the eye differently from was coating, it is an advantage. Since the thin acryl coating is possible, the gloss of the surfaces of the molded articles can be controlled by using different kinds of acryl coating. However, biodegradability might be disputed depending on the kind of acryl monomer.

Industrial Applicability

The present invention provides compositions and methods for manufacturing cheaply the sheets or molded articles that are manufactured from the compound having high contents of steam-exploded biomass and are environmentally friendly and simultaneously have the properties similar to those of papers, cardboards, polystyrene, plastics or metal sheets, which are modern conveniences but environmentally destructive. The sheets can be molded into various containers and other products by using manufacturing facilities and technologies that are used for manufacturing papers, cardboards, polystyrene, plastics, or metal sheets.

The present invention provides the compositions and methods for manufacturing the moldable biodegradable natural compositions, ^' especially the environmentally friendly sheets that can be formed from a high content of steam-exploded biomass. The invention also provides the sheets, containers, and other products that are decomposed into the materials existing in soil or biodegradable. It further provides the methods of manufacturing sheets, containers, and other products more cheaply than those of papers, plastics, or metal products. Moreover, it provides the composition and methods for manufacturing the sheets filled with a high content of steam-exploded biomass that consist of natural polymer but have large elasticity, tearing strength, toughness, and moldability, and large scale productivity. Since the compound and molded articles having high contents of steam-exploded biomass according to the present invention is biodegradable, they influence environment in a non-destructive manner.

Claims

What Is Claimed Is:

1. A biodegradable grafted block copolymer matrix compound in which a) steam-exploded biomass of 10 to 90 wt% relative to the total solids of the compound, b) a group of binders of 0 to 90 wt% relative to the total solids of the compound, c) a functional additive of 0 to 50 wt% relative to the total solids of the compound, and d) compounding water of 1 to 90 wt% relative t;o the total solids of the compound are homogeneously dispersed to form an aqueous slurry state.

2. The biodegradable compound according to Claim 1, wherein the binder group consists of: a) starch separated from grain powder, b) water-soluble or water-dispersible thermoplastic resin, and c) water-soluble or water-dispersible thermal gelling resin.

3. The biodegradable compound according to Claim 1, wherein the biomass is obtained by steam-exploding one or more selected from the group consisting of skins and stems of chaffs, rice straws, barley straws and wheat straws.

4. The biodegradable compound according to Claim 1, wherein the biomass is obtained by steam-exploding one or more selected from the group consisting of perennial trees, annual plant stems, fallen leaves, cultivated vegetables, stems of grains, cuticles of dried nuts, reed stems, leaves, byproducts of -food manufacturing having a high content of cellulose, and byproducts of wood processing.

5. The biodegradable compound according to Claim 1, wherein the biomass has a staple length of 0.1-0.5 mm.

6. The biodegradable compound according to Claim 1, wherein the biomass contains fibers having an L/D ratio of 10:1-100:1.

7. The biodegradable compound according to Claim 1, wherein the biomass has a specific gravity of 0.1 to 1.5 g/cm³.

8. The biodegradable compound according to Claim 1, wherein the biomass is steam-exploded under a steam explosion pressure of 5-25 atm, a steam explosion temperature of 100-250 °C, and a pressurization time of 1-10 minutes.

9. The biodegradable compound according to Claim 2, wherein a) the starch is contained at the amount of 0 to 90 wt% relative to the total solids of the binder group, b) the thermoplastic resin is contained at the amount of 0 to 90 wt% relative to the total solids of the binder groups, and c) the thermal gelling resin is contained at the amount of 0 to 90 wt% relative to the total solids of the binder group .

10. The biodegradable compound according to Claim 2 or 9, wherein the thermoplastic resin is selected from the group consisting of polyvinyl alcohol, polyvinyl alcohol derivatives, polyvinyl alcohol polymers, polyvinyl pryrrolidone polymers, polyvinyl acetate polymers, polyethylene oxide polymers, and a mixture thereof.

11. The biodegradable compound according to Claim 2, wherein the thermoplastic resin shows a Melt Index (ASTM D 1238) of 0.1 to 25 gram/lOmin.

12. A method of manufacturing a biodegradable grafted block copolymer matrix compound, which comprises the steps of: a) metering components including biomass, a group of binders, functional additives and compounding water; b) kneading the metered components; c) adding the compounding water to the kneaded components to. obtain slurry; d) uniformly dispersing the slurry; and e) discharging the uniformly dispersed slurry into a molding machine .

13. A method of manufacturing a biodegradable grafted block copolymer matrix compound, which comprises the steps of: a) forming a slurry compound in which biomass, a group of binders and compounding water are uniformly dispersed; b) kneading the compound in an extruder and casting the kneaded compound to a preselected thickness; c) drying the cast slurry compound by a drying means; d) forming the dried compound into a molded article.

14. The method of Claim 13, wherein the step b) of casting the kneaded compound comprises the sub-steps of: pressing the compound by rollers; drying the pressed compound by a heating means to cure it into a sheet; and adhering a coating or isolation film on the cured two- layered sheet to give a three-layered sheet.

15. The method of Claim 13, wherein the drying means is selected from a drying tunnel using electricity, a drying tunnel using gas, a drying tunnel using high frequency wave, and a drying means using heated rollers.

16. The method according to claim 13, wherein the molded article has a density of 0.1 to 2.0 g/cm².

17. The method according to claim 13, wherein the molded article has a thickness of 10 to 100 mm.