SK279572B6 - Biodegradable material, process for producing the same, use thereof - Google Patents

Abstract

The invention relates to a biodegradable material which contains from 30 to 85 percent by weight of a biodegradable polysaccharide-based plastic, from 15 to 70 percent by weight of native starch or unmodified cellulose, and optionally conventional auxiliaries. Said biodegradable plastic is melt down at temperature ranging from the melting point of plastics to 240 degrees Celsius, simultaneously or subsequently to, starch or unmodified cellulose is added with the proviso that water content present in starch does not exceed 20 percent. Thus obtained mixture is subjected to granulation, then is moulded according to known methods, or the biodegradable plastic is dissolved in such a solvent that prevents starch dissolving, then starch is added and organosol thus obtained is moulded according to known methods.

Description

Technical field

The invention relates to biodegradable material, to a process for its production and to its use.

BACKGROUND OF THE INVENTION

For a long time, the packaging industry has been looking for alternatives to the previously known plastics, which, on the one hand, have very good performance properties and can generally be produced at low cost, but on the other hand cause problems in getting rid of them because do not rot and cause waste pile to grow. It has already been proposed to use biodegradable materials to alleviate garbage problems. The disadvantage of these substances, however, is that they are several times more expensive than the known packaging materials. In order to overcome this disadvantage, it has been proposed to incorporate starch into the polyethylene film as a filler, which, on the one hand, lowers production costs as a low-priced filler and, on the other hand, is intended to improve biodegradability. However, since the degradability of the polyethylene itself does not change, this extension does not solve the problem of garbage and, on the other hand, the mechanical properties of the polyethylene film are reduced by the addition of starch.

The object of the present invention was to provide a biodegradable material which, by its mechanical and physical properties, is comparable to films of pure filled plastics, which is rapidly biodegradable and cost-effective to produce.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention solves this problem by a biodegradable material comprising 30-85% by weight of a biodegradable plastic based on polysaccharide, 15-70% by weight of natural starch or unmodified cellulose, or a conventional substance which can be prepared by melting the biodegradable plastic. at a temperature ranging from melting point of plastic up to about 240 ° C, starch or unmodified cellulose, if any, with or without the water content of the starch not exceeding 20% is added, the resulting mixture is granulated and the granulate is then shaped in the usual manner; the biodegradable plastic is dissolved in a starch-insoluble solvent, starch is added to the solution, and the organosol formed is then formed in a known manner.

Surprisingly, it has been found that a mixture of natural starch or unmodified cellulose with a polysaccharide-based plastic provides products with excellent mechanical properties, which are degraded up to 10 times faster than the known biodegradable plastics.

An essential component of the inventive material is a biodegradable polysaccharide-based plastic. Such plastics are known and any biodegradable polysaccharide-based plastics that can be processed into shaped articles are suitable herein. Preferably, thermoplastic cellulose derivatives are used as biodegradable plastics. Cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetobutyrate and ethylcellulose have proven to be particularly advantageous. These derivatives are commercially available products and therefore do not need to be described in detail. The biodegradable plastic is present in an amount of from 30 to 85% by weight. Preferably, the proportion of plastic is from 40 to 70% by weight.

Biodegradable plastic means a plastic which, in an experiment in which it is buried in the ground, loses at least 20 g / yr of weight per year, preferably at least 30 g / m 2 per year as a result of microbacterial effects. The method for determining the weight loss is described in Example 4.

The second essential component of the material of the invention is natural starch or unmodified cellulose. Natural starch can be obtained from all known vegetable, starch-containing materials, such as potatoes, corn, rice or grain. The starch obtained from these substances is in the form of grains. Unmodified cellulose can also be obtained from plant material such as cotton, jute, flax, hemp, ramia (Chinese grass), as well as from coniferous and deciduous wood and straw. Pure cellulose, like starch, is built up from glucose units, but it is not in the form of spheres but because of the beta-glycosidic linkage, but in the form of long chains, i.e. fibers. The proportion of natural starch or unmodified cellulose in the material according to the invention may range from 1 to 70% by weight, preferably from 30 to 60% by weight. A share of less than 15% is also possible, but does not show any economic benefits. A share of approximately 70% by weight represents the upper limit of concentration for spatial reasons. The ratio of the two components according to the invention, most suitable for the intended use, can be readily determined by the skilled person in only a few experiments.

Only the use of the two essential components according to the invention achieves the advantages of the material according to the invention. If the starch or unmodified cellulose is mixed with other biodegradable plastics, but which do not have a polysaccharide structure, the mechanical strength decreases as the proportion of starch or unmodified cellulose increases. On the other hand, the mechanical strength of the combination according to the invention is higher than the mechanical values for the biodegradable plastics material, corresponding to the proportion of the biodegradable plastics material.

The material according to the invention may contain, in addition to the two essential constituents of the invention, other additives customary for the production of packaging materials, such as fillers, colorants or other auxiliaries. The type and amount of suitable additives are known and do not require further explanation.

Particularly preferred in the materials of the invention is the amount of biodegradable amount as a function of time. Up to 10 times the rate of degradation is achieved in comparison with the biodegradation of the biodegradable plastic itself. Particularly advantageous results are obtained using starch.

Further, the invention describes methods for producing the material of the invention as defined. This material can preferably be made by compounding or forming an organosol. If the starch content is in the lower range of the range, the material according to the invention can be prepared simply by mixing the two components and then forming

SK 279572 van6 by a known method. Higher proportions of starch may result in the mixture obtained clogging the molding equipment. Therefore, for the production of materials according to the invention which contain more than about 20 to 25% starch, a method is proposed in which these problems can be avoided.

Therefore, a further object of the invention is a method for producing a biodegradable material, the method being characterized in that the biodegradable plastic is melted, at the same time or subsequently the starch or unmodified cellulose is added, after which the obtained mixture is granulated and

Preferably, the degradable plastic and starch or unmodified cellulose are mixed and the plastic is melted in the presence of starch.

For shaping, the granulate is preferably further processed by compression molding, injection molding or extrusion.

In this way, the material according to the invention can be produced simply and at low production costs. When mixing the molten plastic with starch, conditions are applied such that the granular structure of the starch does not substantially change. Temperatures ranging from the melting point of the plastic to about 240 ° C are suitable. The water content of the starch should not exceed 20%, preferably 15%.

A further alternative to the process for producing the material according to the invention is a process characterized in that the biodegradable plastic is dissolved in a non-starch-insoluble solvent or unmodified cellulose, then starch or unmodified cellulose is added and the organosol obtained is shaped. in a known way

Solvents suitable for this variant of the process for producing the material of the invention are known to those skilled in the art; acetone and ethanol are preferably used.

The shaping of the organosol is preferably carried out by coating, casting, spreading or spraying in a known manner by evaporating the solvent.

The material according to the invention can be processed, for example, into containers for various materials. Due to its composition, this material is particularly suitable for packaging food, cosmetics, cleaning products and household utensils. Preferably, this material is used for packaging solids. For the packaging of, for example, aggressive materials such as acids, cleaning and polishing agents, a layer impermeable to these media may be formed on the material of the invention.

Preferably, the cartridges of the present invention are molded or processed into shapes that are used as lids or bottoms of wound paper boxes. The invention provides a material that is particularly ecologically suitable since it is produced from naturally-recovering substances and can biodegrade very quickly again. In addition, it has particular advantages over mechanical properties as well as for economic reasons over the known packaging materials.

The invention is illustrated by the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

1 kg of granular cellulose propionate is mixed with 0.2 kg of starch powder. The resulting mixture is poured into an injection molding machine and then injection molded to produce components that are suitable as a lid or bottom of a carton made from paper.

Example 2

1 kg of granular cellulose propionate is mixed with 1 kg of natural potato starch powder. The resulting mixture is heated to such an extent that the cellulose propionate softens, then is granulated. The granulate obtained is poured into an injection molding machine and formed into shaped pieces suitable as lids or box bottoms produced by the roll of paper.

Example 3 kg of cellulose acetate is dissolved in 9 kg of acetone. 1 kg of natural starch is added to the resulting solution. The organosol obtained is decanted and the acetone is evaporated. A film with good strength properties is formed.

Example 4

The degradability of plastics is tested in an experiment involving their burial into the ground. To this end, a test specimen of 45 x 22 x x 2 mm consisting of an aluminum core and a layer of the biodegradable plastic of interest is buried in the ground. The earth has the following composition:

Biological-organic carbon 29.0%

Organic nitrogen 0.2%

Organic compounds 50.0% pH 5.5 - 6.5

Resistance (conductivity) 2000 ohms

Gross dry weight 37.0% (consisting of peat obtained from amelioration works and vegetable products) Organic gross weight 20.0%

Absorbency 600.0%

The rest is sand and water.

The experiment is carried out at a temperature of about 20 ° C. The weight loss of the sample, i.e. the loss on 1 µl of the surface, is determined at time intervals. The experiment is carried out with the following polymeric materials: cellulose acetate (CA), cellulose propionate (CP), cellulose acetobutyrate (CAB) and polycaprolactone (PCL - for comparison), as well as always a combination of degradable material with starch (inventive material). The results are evident from the attached diagrams in FIG. 1 to 4.

In FIG. 1 is a diagram showing the weight loss (Δ mv mg) of test specimens coated with (1) cellulose acetate (CA) alone and (2) cellulose acetate in combination with 50% starch, from the time they were buried in the ground (expressed in days) ).

In FIG. 2 is a diagram showing the weight loss (Δ mv mg) of test specimens coated with (3) cellulose propionate (CP) and (4) cellulose propionate in combination with 50% starch, from the time they were buried in the ground (expressed in days) ).

In FIG. 3 is a diagram showing the weight loss (Δ mv mg) of test specimens coated with (5) cellulose acetobutyrate (CAB) alone and (6) cellulose acetobutyrate in combination with 50% starch, from the time they were buried in the ground (expressed in days) ).

SK 279572 Β6

In FIG. 4 is a diagram showing the weight loss (Δ m in mg) of test specimens coated with (7) polycaprolactone (PCL) alone and (8) polycaprolactone in combination with 50% starch, from the time they were buried in the ground (expressed in days).

In these diagrams, weight loss is always plotted against the time of burial of test specimens in the ground (time is expressed in days). A comparison of the diagrams shows that the combination of the biodegradable material of the invention with starch exhibits an excellent degradation rate which is much greater compared to the degradation rate of the cellulose derivative itself. The results obtained with individual cellulose derivatives alone, or combinations thereof with 50% starch, are re-assembled in the diagram in FIG. 5th

Fig. 5 is a diagram showing the degradation rate (weight loss in g / mTrok) for each of the materials designated (1) to (8), wherein (1) is a sample coated with cellulose acetate (CA) alone, (2) a sample coated with cellulose acetate in in combination with 50% starch, (3) means a sample coated with cellulose propionate (CP) alone, (4) means a sample coated with cellulose propionate in combination with 50% starch, (5) means a sample coated with cellulose acetobutyrate (CA) alone, (6) means a sample coated with cellulose acetobutyrate in combination with 50% starch; (7) means a sample coated with polycaprolactone (PCL) alone; and (8) means a sample coated with polycaprolactone in combination with 50% starch.

5. A process for the production of a biodegradable material as claimed in claims 1 to 4, characterized in that the biodegradable plastic is melted, with or without the addition of starch or unmodified cellulose, the resulting mixture is granulated and the granulate is then shaped in a conventional manner.

A process according to claim 5, characterized in that the plastic is mixed with starch or unmodified cellulose and the plastic is melted in the presence of starch or unmodified cellulose.

Method according to claim 5 or 6, characterized in that the shaping is carried out by pressing, injection molding or extrusion.

A process for the production of a biodegradable material according to claims 1 to 4, characterized in that the biodegradable plastic is dissolved in a starch-insoluble solvent, starch is added to the solution and the resulting organosol is formed in a manner known per se

9. The method of claim 8, wherein the organosol is formed by coating, casting, spreading or spraying the solvent.

Use of a biodegradable material according to claims 1 to 4 for the packaging of foodstuffs, cosmetics and cleaning agents.

drawings

Claims (4)

PATENT CLAIMS A biodegradable material comprising 30 to 85% by weight of a biodegradable plastic based on polysaccharide and 15 to 70% natural starch or unmodified cellulose, which can be prepared by melting the biodegradable plastic at a temperature ranging from the melting point of the plastic starch or unmodified cellulose, wherein the water content of the starch does not exceed 20%, the mixture obtained is granulated and the granulate is then molded in the usual manner, or that the biodegradable plastic is dissolved in a solvent starch-insoluble, starch is added to the solution and the organosol formed is formed in a known manner. The biodegradable material of claim 1, wherein the biodegradable plastic is a thermoplastic cellulose derivative. Biodegradable material according to claim 1 or 2, characterized in that the biodegradable plastic is cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetobutyrate or ethylcellulose. Biodegradable material according to claims 1 to 3, characterized in that potato starch is used as natural starch.