WO1996041838A1 - Totally biodegradable material and preparation thereof - Google Patents

Abstract

A totally biodegradable material particularly suitable for packaging materials, and especially for storing compostables, and a method for making said material, are disclosed. The material is made from biodegradable matter consisting of at least one natural or synthetic polymer and non-toxic additives, said natural or synthetic polymers being arranged to form a physical gel in the presence of a solvent. Said matter may also be used in a composite material made from a second biodegradable matter consisting of at least one polyester-type synthetic resin. The synthetic resin comprises at least one saturated aliphatic polyester and, in particular, at least one high molecular weight aliphatic linear polyester, e.g. a tetramethylene adipate or a copolymer obtained by reaction with a diisocyanate or a diepoxide. Said polymers may for example be gelatin, starch, carrageenan, carob and gum arabic. Gelatin is preferred. The additives preferably comprise a plasticizer, particularly a hydroxy compound such as glycerol and/or a cross-linking agent.

Description

 TOTALLY BIODEGRADABLE MATERIAL AND ITS PREPARATION

The present invention relates to a completely biodegradable material which can be used in particular for packaging products and in particular for storing compostable organic waste, produced from a biodegradable material formulated from at least one natural or synthetic polymer and non-toxic additives . It also relates to a process for the manufacture of this material.

Today plastics are part of our everyday environment. Their development is explained by the many advantages of use that their multiple properties allow them: low density, ease of implementation and excellent adaptability, low cost of production and processing, etc. Plastics are widely used by households and follow, at the end of their life, the traditional ways of treating household waste, currently falling under three philosophies: recovery, disposal or storage.

The first two treatment channels are not yet in the majority and landfill remains the most widespread solution. In this case, the plastic waste appears to be relatively annoying since it occupies a very large volume and generates a distressing visual pollution.

Plastics, in France as in Europe, are responsible for around 10% of the weight of landfills but occupy more than 25% of the volume of household waste. These plastics come mainly from packaging, a sector which generates a massive problem of waste management. In the fight for the establishment of a waste management system, plastic therefore appears to be the main enemy.

The packaging uses plastic like other materials to produce almost exclusively objects with a short functional life cycle (a few hours to a few weeks). This sector therefore poses a major problem of post-use waste disposal. In the other industrial sectors, users of plastics, they are rather used for medium to long-term applications. The building or transport mainly produces massive objects and, therefore, easily collectable. In this case, the problem of managing the waste generated by packaging does not arise in the same terms: an industry whose cycle is short, creates a very acute waste problem. This is all the more true as plastic is used more and more for the production of lost packaging which amplifies the volume of waste. Unlike buildings and transport, the packaging industry produces films or containers of low weight and low resistance which make their collection and management more difficult after consumption.

The consumer packaging or household consumption packaging sector may find an interest in biodegradable materials. These can, in fact, respond perfectly to applications with a short and poorly controllable functional life cycle.

The very current concern to live in a preserved environment, the growing ecological conscience, the directives in particular European in terms of environmental protection, as well as the demand of the general public in search of "nature" products have led researchers to find solutions in the field of biodegradable materials, in particular polymers used in the various packaging of consumer products.

There is currently no universally accepted definition or standards for biodegradable materials. Biodegradation cannot therefore be demonstrated by the simple experimentation of a standard biodegradation test. We can currently distinguish three types of definitions:

- A biodegradable plastic must degrade, under the action of microorganisms, in a significantly shorter time than a conventional polymer. Biodegradation implies a loss of mechanical properties, then a bio-assimilation. The degradation of the mechanical properties plus the presence within the material of a biodegradable phase suffices to justify this designation.

- Biodegradable plastic must fragment and quickly lead to fragments that can be bio-assimilated. In this definition, there is no commitment to reach the stage of carbon monoxide, water and non-harmful biological products. - A biodegradable plastic must quickly transform, under the effect of microorganisms, into carbon monoxide, water and humus, this mixture being able to allow the growth of a plant. Such a material deserves the designation "fully biodegradable".

There are currently three main types of so-called "biodegradable" plastics, these materials essentially corresponding to the first two definitions mentioned above. The first type is a product obtained by additive.

A biodegradable plastic material by additive is mainly composed of three phases:

- A traditional polymer of petrochemical origin which gives the overall structure.

- A starch phase (approximately 10% by weight) dispersed within the structure.

- Producing agents, chemical agents of degradation (less than 1% by weight).

This additive technology has given rise to numerous industrial developments. These additive products are in fact biofragmentable products. This fragmentation is mainly due to the producing agents and, only to a lesser extent, to the starch they contain. The chemical agents used are, for some, compounds of heavy metals causing pollution since they are considered toxic.

The second type is a so-called majority starch product. Unlike the previous products, starch is no longer a filler but becomes the basic raw material. In the starch network is dispersed a polymer of petrochemical origin, specially developed to ensure the mechanical cohesion of the whole. Currently, the products obtained correspond to a definition which is intermediate between the last two definitions above. In this type of product, starch is used either in the modified state or gektinized. "Modified" means that the starch becomes a thermoplastic material, for example by virtue of an esterification, as described in the publication WO 95/04108, WO 94/07953 or WO 92/09654. However, the modification of starch has in particular the disadvantage of reducing the biodegradability of starch. "Gelatinized" means, as described in the publications EP-A-606,923, EP-A-535,994, WO 92/19680 and WO 93/00399, that the chains which constitute the starch are destructured by heating to high temperatures and in the presence of water in order to burst the starch grains. The chains, in recrystallizing, give a thermoreversible crystalline starch. This method has the particular disadvantage of working at high temperatures, which represents a significant energy consumption.

A third type is based on polymers obtained by synthesis.

The grafting or copolymerization, by chemical means, of biodegradable sequences onto weakly biodegradable synthetic sequences or molecules makes it possible to obtain products, called biodegradable, which meet the second definition.

Some polymers are designed to be bio-assimilable. They are obtained biotechnologically and are synthesized by bacteria from carbon substrates. Currently, some of these biotechnological products fully meet the third definition. If the biotechnological way seems to give satisfaction as for an "ecological" biodegradation leaving no toxicity appearing, it is not the same for the three others. In fact, after "bibfragmentation" of the products, the weakly biodegradable synthetic components remain, causing fragmentary pollution which can hardly be prevented by a recovery or revalorization treatment. There are also photodegradable polymers sensitive to UV rays which can also cause fragmentary pollution. They are photofragmentary polymers. Currently, there are no 100% biodegradable products at sufficiently low production costs to allow use on an industrial scale.

The challenge is therefore to obtain real biodegradability, namely complete assimilation by the ambient environment, generating only products such as CO2, H2O and humus.

The main object of the invention is to produce such a material which is completely biodegradable.

A secondary but nevertheless essential goal for the material to find an industrial application which is part of an economic process is to achieve such material at equivalent or lower costs than non-biodegradable plastic materials.

Finally, another aim is to produce a material which is transformed in a conventional manner, that is to say like known thermoplastic materials, with equipment or according to conventional methods, for example by extrusion, extrusion blow molding, calendering, injection, molding, thermoforming, etc.

These aims are achieved by the material as defined in the preamble and characterized in that said natural or synthetic polymers are arranged to form a physical gel in the presence of a solvent.

The invention also provides a fully biodegradable composite material, produced from a mixture of said biodegradable material formulated from at least one natural or synthetic polymer and non-toxic additives, said natural or synthetic polymers being arranged to form a physical gel in the presence of a solvent and a second biodegradable material consisting of at least one synthetic resin of the polyester type.

Said solvent is chosen from water, alcohols, pory alcohols and in particular glycerol, ethylene glycol, a polymer of ethylene glycol, propylene glycol, a polymer of propylene glycol.

Said physical gel can be concentrated by elimination of solvent.

In a preferred embodiment, said natural or synthetic polymers forming a physical gel in the presence of solvent are chosen from: gelatin obtained by hydrolysis of collagen contained in the skin, connective tissue and / or bones of animals, starch , carageenane, alginate, pectin, guar, xanthan, carob, gum arabic, starch derivatives obtained by fractionation of corn, wheat, potato.

Said additives advantageously comprise a plasticizer of at least one of said polymers. Preferably, the plasticizers are chosen from molecules comprising several -OH bonds, and more specifically from alcohols, polyalcohols and in particular glycerol, sorbitol, mannitol, retylene glycol, a polymer of ethylene glycol, propylene glycol , a polymer of propylene glycol, sugars and in particular sucrose, glucose, dextrose and their derivatives.

In the preferred embodiment, said additives comprise crosslinkers for insolubilizing the polymers, these crosslinkers being chosen from aldehydes and in particular formaldehyde, glutaraldehyde, metal salts and in particular chromium salts.

The additives may also include pigments, stabilizers, antioxidants, lubricants and substances which protect against ultraviolet radiation.

According to the preferred embodiment, said synthetic resin comprises at least one saturated aliphatic polyester and in particular at least one linear aliphatic polyester of high molecular weight.

Said aliphatic polyester can be a poly-hydroxy-butyrate, a po-hydroxy-butyrate-valerate or a polycaprolactone.

Said aliphatic polyester is preferably obtained by a reaction of polyacids and polyalcohols according to a global scheme:

HO-R-OH + HOOC-R'-COOH <—> OR-OOC-R-COO + H ₂ O

Advantageously, the polyacids are di-carboxylic of the HOOC- (CH2) _n - COOH type, in particular succinic (n = 2), glutaric (n = 3), adipic (n = 4), pimelic (n = 5), suberic (n = 6), azealic (n = 7), sebacic (n = 8).

Similarly, the polyalcohols are diols, in particular ethylene glycol HO- (CH2) 2-OH, 1,4 butane-diol or tetramethylene glycol HO- (CH2) 4-OH, diethylene glycol HO-CH2- CH2 -O-CH2-CH2-OH, propylene glycol HO-CH ₂ -CH (CH ₃ OH, neopentyl glycol HO-CH2-C (CH ₃ ) 2-CH2-OH, triethylene glycol HO-CH2-CH2- O-CH2-CH2-O-CH2- CH ₂ -OH The polyester can be a poly-tetramethylene-adipate or a poly-ethylene-succinate or else a poly-tetramethylene-succinate.

In the preferred embodiment, said high molecular weight polyester is obtained by addition copolymerization from high molecular weight polyester precursors with difunctional reagents.

This polyester precursor reacts with a difunctional reagent which comprises diisocyanate and diepoxy reacting respectively according to the following reactions: H - [- OR-OOC-R'-CO-] _n -OR-OH + OCN-R "-NCO ->

[-OR-OOC-R'-CO-] _n -OR-OOC-HN-R "- H-CO - [- OR-OOC-R'-CO-] _n and,

HOOC-R'-CO - [- OR-OOC-R'-CO-] _n -OH + CH2- (O> CH-R "-CH- (O CH ₂ ->

[-OR-OOC-R'-CO-] nO-CH2-CH (OH) -R "-CH (OH) -CH 2-OOC-R'-CO - [- OR-OOC-R'- CO- ] _n .

According to an alternative embodiment, said polyester can be a copoly-tetramethylene-adipate-hexamethylene isocyanate or a copoly-tetramethylene-adipate-hexamethylene diglycidyl ether.

These aims are also achieved by the manufacturing process according to the invention, using at least one natural or synthetic polymer and non-toxic additives constituting a biodegradable material, characterized in that a physical gel is formed with said natural or synthetic polymers in the presence of a solvent.

Advantageously, said biodegradable material consisting of at least one natural or synthetic polymer and non-toxic additives can be mixed, said natural or synthetic polymers being arranged to form a physical gel in the presence of a solvent, with a second biodegradable material consisting of at least one synthetic resin of the polyester type.

Said natural or synthetic polymers are heated in the presence of the solvent and in that the composition obtained is cooled so as to obtain a physical gel. The solvent can be concentrated in the physical gel so as to obtain a concentrated physical gel.

The solvent is chosen from water, alcohols, polyalcohols and in particular glycerol, ethylene glycol, a polymer of ethylene glycol, propylene glycol, a polymer of propylene glycol.

According to a first manufacturing process, said mixture is made in equal parts, the first material being in the form of granules, in an extruder at a temperature of the order of 100 to 120 ° C.

According to a second manufacturing process, 100 parts of polyester, 39.5 parts of gelatin with 10% water, 39.5 parts with 10% of apple starch water are mixed at room temperature. earth, 10 parts of glycerin, 0.5 parts of stearic acid, and 0.5 parts of glycerol stearate, the mixture is left to stand and then the mixture is introduced into an extruder at a temperature of the order of 100 to 120 ° C. , then allow the rods obtained at the outlet of the die to cool so as to obtain a physical gel.

The invention, its main characteristics and its advantages will be better understood with reference to the description of exemplary embodiments and variants, given by way of non-limiting example.

As mentioned above, the material according to the invention is formulated from a biodegradable material formulated from at least one natural or synthetic polymer having the characteristic of giving a physical gel in the presence of solvent.

Said biodegradable material can be produced either by chemical means, that is to say by synthesis of new molecules with biodegradable character, or by bio-technological way, that is to say by synthesis of new molecules with biodegradable character with from bacteria, either by dry physical route, that is to say by temperature mixing of solid particles involving a polymer of weakly biodegradable petrochemical origin and a natural polymer such as for example starch which is biodegradable. In the context of the invention, the choice is made on the wet physical route. Said biodegradable material produced by the wet physical process is a complex having the characteristic of forming a physical gel of biodegradable polymers of synthetic or natural origin.

The mixture of polymers + additives is heated and homogenized in a solvent medium at a temperature X. The mixture homogenized at temperature X is then cooled to a temperature Y in order to obtain a physical gel having the characteristic of being heat-reversible. This is in the form of a visco-elastic solid that can be chopped, ground, cut, etc. in the form of granules, cubes, grains, powders, etc. These pieces of gels of various shapes are then dried by evaporation of the solvent using, for example, a vacuum dryer or a fluidized bed dryer. The pieces of dried gels, containing between 5% and 30% by weight of water, can thus be conventionally transformed as a thermoplastic material: extrusion, extrusion-blowing, calendering, injection, molding, thermoforming, etc.

The natural or synthetic polymers and the non-toxic additives from which said material is made are:

* Natural or synthetic polymers forming a physical gel in the presence of solvent such as, for example, gelatin obtained by partial hydrolysis of collagen contained in the skin, connective tissue and bones of animals. Among the polymers of natural origin with gelling properties, mention may also be made of: starch, carageenane, alginate, pectin, guar, xanthan, locust bean, gum arabic.

* Natural or synthetic polymers which may or may not have aptitudes for gef fi cation such as for example starch and its derivatives obtained by fractionation of corn, wheat, potato, etc.

* A plasticizer for one or more polymers, in general molecules containing one or more -OH bonds, such as alcohols or polyalcohols such as glycerol, sorbitol, mannitol, ethylene glycol (or its polymer), propylene glycol (or its polymer), etc. or else sugars in general, such as sucrose, glucose, dextrose, etc. and their derivatives. All of these additives are considered non-toxic.

* To make such a specific application, crosslinking agents making it possible to insolubilize the polymer or polymers such as aldehydes such as, for example, foaldehyde, glutaraldehyde, etc. or else metal salts such as, for example, chromium salts, etc. These additives do not will be used only for specific applications and in small quantities because they can present a toxic and polluting character.

* For certain specific applications, different additives can be added such as pigments, stabilizers, antioxidants, anti-ultraviolet, lubricants.

The solvents used to form the gel with the natural or synthetic polymer are for example water, alcohols or polyalcohols such as glycerol, sorbitol, mannitol, ethylene glycol (or its polymer), propylene glycol (or its polymer).

The material is obtained from a physical gel. The physical gel can be defined as a two-phase system consisting of a solid, namely the natural or synthetic polymer, and a liquid, namely the solvent. The gel can be characterized by a three-dimensional network, presenting nodes or thermoreversible junction zones generating a specific order, and retaining between its meshes the liquid phase. These junction zones are themselves characterized by an association of chains or macromolecular segments together or by a polymer-solvent complex.

The physical gel, which represents a polymer-solvent complex, is generally produced from a solution of polymers + additives (between 5 and 50% by weight) in water or another solvent (between 50 and 95% by weight), heated and homogenized at a temperature between 50 ° C and 160 ° C and then cooled to a temperature below the melting temperature of the gel, to produce gelation.

The gel block obtained is then put into the form of granules whose size can be variable. This shaping is carried out mechanically, for example using a meat grinder. The granules thus obtained can be dried by applying a vacuum or by a fluidized bed, that is to say by ventilating air blown through the granules. In both cases, the room temperature can be gradually increased to around 80 ° C as it dries, in order to avoid sticking between the fragments.

To illustrate the manufacturing process for this material, two examples of preparation are described below.

According to a first example, the preparation is done in a 500 cm3 beaker. 200 parts of demineralized water are poured into the beaker and brought to a water bath at a temperature of 70 ° C. At stabilized temperature, 6 parts of glycerin are added thereto, with stirring, then 50 parts of food-type gelatin (200 bloom). At this temperature, the solution is homogenized with stirring for half an hour. The beaker is removed from the water bath and cooled to a temperature of 20 ° C for 12 hours in order to obtain complete gelation of the product. The gelled product is then extracted from the beaker.

In the form of gel, the product can be put in the form of granules using a meat grinder. By this process, the product is introduced into an orifice leading to an endless screw actuated by a motor. This pushes the material, through a die composed of a plate comprising holes with a diameter of 6 mm, which is cut regularly by a rotary knife in contact with the plate.

The "gel granules" thus obtained are placed in a crystallizer which is itself brought to a vacuum oven at a temperature of 20 ° C. After introduction and at this temperature, the vacuum is made for 12 hours. The temperature is then brought to 50 ° C. for 8 hours, the vacuum being always made.

After 20 hours of drying, dried granules are obtained which, after reaching room temperature, are ready to be post-processed like a thermoplastic material. The granules obtained by the process described above are introduced into a machine to be extruded by means of a hopper. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for feeding the pellets, T2-T3-T4-T5: heating the sheath along the screw 70-90-110-110 ° C, T6: heating the flat film fihère 100 ° C, T7: cooling the poh-mirror cylinder with tap water 15 ° C. Finished products extruded in the form of a film are obtained through a cast-film system. The thicknesses of films obtained vary between 20 and 150 μm.

In a second example, the preparation is done in a 500 cm3 beaker. 200 parts of demineralized water are poured into the beaker and brought to a water bath at a temperature of 70 ° C. At stabilized temperature, 7 parts of sorbitol are added thereto, with stirring, and then 30 parts of food-type gelatin (200 bloom) and 30 parts of potato starch. At this temperature, the solution is homogenized, with stirring, for half an hour. The solution, with stirring, is then heated in a water bath at a temperature of 120 ° C for half an hour.

The beaker is removed from the water bath and cooled to a temperature of 20 ° C for 12 hours in order to obtain complete gelation of the product. The gelled product is then extracted from the beaker.

In the form of gel, the product can be put in the form of granules using a meat grinder. By this process, the product is introduced into an orifice leading to an endless screw actuated by a motor. This pushes the material, through a die composed of a plate comprising holes with a diameter of 6 mm _; which is cut regularly by a rotary knife in contact with the plate.

The "gel granules" thus obtained are introduced into a crystallizer which is itself carried in a vacuum oven at a temperature of 20 ° C. After introduction and at this temperature, the vacuum is made for 12 hours. The temperature is then brought to 50 ° C. for 8 hours, the vacuum being always made. After 20 hours of drying, dried granules are obtained which, after reaching room temperature, are ready to be post-processed like a thermoplastic material.

Said biodegradable material produced by a process called concentrated wet physical process which is a variant of that described above, is as before a complex of biodegradable polymers of synthetic or natural origin forming a concentrated physical gel in the presence of solvent.

The mixture of polymers + additives is heated and homogenized in the presence of solvent at a temperature X. The mixture homogenized at temperature X is then cooled to a temperature Y in order to obtain a "concentrated solid physical gel" having the characteristic of being thermoreversible . This is in the form of a solid which can be cut into granules. The granules of concentrated physical gels, containing between 5% and 30% by weight of water, can thus be conventionally transformed as a thermoplastic material extrusion, extrusion-blowing, calendering, injection, molding, thermoforming, etc. The natural or synthetic polymers and non-toxic additives from which said first material is produced are:

* Natural or synthetic polymers with gelling properties such as for example gelatin obtained by partial hydrolysis of collagen contained in the skin, connective tissue and bones of animals. Among the polymers of natural origin with gelling properties, there may also be mentioned: starch, carageenane, alginate, pectin, guar, xanthan, carob, gum arabic, etc.

* Natural or synthetic polymers which may or may not have gelation capacities such as, for example, starch and its derivatives obtained by fractionation of corn, wheat, potato, etc.

* A plasticizer for one or more polymers, in general molecules containing one or more -OH bonds, such as alcohols or polyalcohols such as glycerol, sorbitol, mannitoL, ethylene glycol (or its polymer), propylene glycol (or its polymer), etc. or else sugars in general, such as sucrose, glucose, dextrose, etc. and their derivatives. All of these additives are considered non-toxic.

* To make such a specific application, crosslinking agents making it possible to inhibit the polymer or polymers such as aldehydes such as for example formaldehyde, ghitaraldehyde, etc. or else metal salts such as for example chromium salts, etc. These additives will only be used for specific applications and in small quantities because they can be toxic and polluting.

* For certain specific applications, different additives can be added such as pigments, stabilizers, antioxidants, anti-ultraviolet, lubricants.

The solvents used to form the gel with the natural or synthetic polymer are, for example water, alcohols or polyalcohols such as glycerol, sorbitol, mannitol, ethylene glycol (or its polymer), propylene glycol (or its polymer).

The material is obtained from a concentrated physical gel. The physical gel can be defined as a two-phase system consisting of a solid, namely the natural or synthetic polymer, and a fluid, namely the solvent. The gel can be characterized by a three-dimensional network, presenting nodes or thermoreversible junction zones generating a specific order, and retaining between its meshes the hid phase. These junction zones are themselves characterized by an association of chains or macromolecular segments together or by a polymer-solvent complex. The concentrated physical gel, which represents a polymer-solvent complex, is generally produced from a mixture of polymers + additives (between 5 and 50% by weight) in the presence of water or other solvent (between 5 and 40% by weight), heated and homogenized in a worm extruder, at a temperature between 50 ° C and 200 ° C. The homogenized mass is passed through a rod filter and then cooled to a temperature below the melting point of the concentrated gel, to produce gelation. The concentrated gel obtained in the form of rods is then placed in the form of granules. This shaping is carried out mechanically, for example using a rod granulator. The forming of granules can be carried out directly at the outlet of the homogenized mass, for example using a hot head cut, then the granules are cooled to obtain concentrated gelling.

Two methods can be used: one to obtain an injection grade, the other an extrusion grade.

To make an injection grade, we mix together at room temperature, 42 parts of gelatin (200 bloom) with 10% water, 42 parts with 10% water of potato starch, 5 parts of glycerin, 0 , 5 parts of stearic acid, 0.5 parts of glycerol stearate in a mixer for 30 minutes. The mixture obtained in the form of powder is left to stand for 12 hours. Then it is introduced via a hopper into a co-rotating twin-screw extender. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for feeding the material, T2-T3-T4-T5: heating the sheath along the screws 100-120-120- 100 ° C, T6-T7: heating of gorse fihère 100-100 ° C. The rods obtained at the outlet of the fihère are cooled to obtain solid gelling by passing through rings with air ventilation. The granules are shaped by means of a gorse granulator in line behind the extender. The granules obtained by the process described above are introduced into an injection-molding machine through a hopper. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for re-feeding the pellets, T2-T3: heating the sheath along the screw 110-110 ° C, T4: heating the nozzle d injection 100 ° C, T5: cooling of the mold with tap water 15 ° C. Finished molded fork products are obtained. To make an extrusion grade, 34.5 parts of gelatin (200 bloom) with 10% water, 34.5 parts with 10% potato starch water, 10 parts are mixed together at room temperature. of water, 20 parts of glycerin, 0.5 parts of stearic acid, 0.5 parts of glycerol stearate in a mixer for 30 minutes. The mixture obtained in the form of powder is left to stand for 12 hours. Then it is introduced through a hopper, into a co-rotating twin-screw extender. The fixed temperatures are: Tl: cooling with city water 15 ° C under the hopper for re-feeding the material, T2-T3- T4-T5: heating of the sheath along the screws 100-120-120-100 ° C, T6-T7: heating the gorse fihère 100-100 ° C. The rods obtained at the outlet of the fiher are cooled to obtain solid gelation by passing through rings with air ventilation. The granules are shaped by means of an in-line rod granulator behind the extruder. The granules obtained by the process described above are introduced into a machine to be extruded by means of a hopper. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for re-feeding the pellets, T2-T3-T4-T5: heating the sheath along the screw 70-90-110-110 ° C , T6: heating of the flat film fihère 100 ° C, T7: cooling of the poh-mirror cylinder with tap water 15 ° C. Finished products extruded in the form of film are obtained by means of a cast-film system. The film thicknesses obtained varied between 20 and 150 μm.

The biodegradable material described above, called the first biodegradable material, makes it possible to obtain a composite material based on the mixture of said first biodegradable material and a second material consisting of a synthetic polymer, preferably specially synthesized bio-assimilable by action. bacteriological generating non-toxic biological elements.

Said second material consists of a fully biodegradable polymer or synthetic resin.

Currently, the main applications of polyesters are in the field of cosmetics, primers, polishes and plasticizers. For the latter use, they have the advantage of migrating little and are, in particular, used as plasticizers for PVC. Numerous industrial developments mainly concern low molecular weight polyesters since, depending on the applications, they rarely exceed 4000 g / mole. These molecular weights allow use as an additive or crosslinking polymerization precursor. Only polyesters with molecular weights from around 30,000 g / mole allow use as a technical polymer which can undergo transformation by extrusion, injection-molding, etc. and having acceptable mechanical characteristics.

Saturated ahphatic polyesters can be obtained both by conventional polycondensation reaction (acid or derivative + alcohol) and by ring opening polymerization. The polyesterification process by reaction of polyacids and polyalcohols or also called direct, remains the simplest. Ω corresponds to the following overall diagram: HO - R- OH + HOOC - R '- COOH <=> O - R - OOC - R' - COO + H ₂ O The corresponding pofycondensations are made by simple heating, generally in the presence of 'A catalyst, at temperatures generally in the range 150-250 ° C but which can reach, especially at the end of the operation, 280 ° C. They obey the general rules of condensation, in particular, the degree of polymerization depends closely on the following parameters:

- Stoichiometry of functional groups and possible presence of monofunctional reagents. - Degree of progress of the reaction: it is necessary to have a high conversion rate of the functional groups to obtain polymers of high molar masses and it is only in the last stages of the reaction that these are reached .

One of the essential characteristics of the reaction is to be balanced, this means that the degree of polymerization depends very much on the efficiency with which the water is removed. In the case of saturated polyesters used as basic products in the preparation of polyurethanes, we are generally satisfied with degrees of polymerization from 5 to 20, which makes it possible to be satisfied with an ehmination of water by simple distillation with l assistance, in general, of effective agitation or the bubbling of an inert gas. When it is desired to obtain products with a high molar mass, it is necessary to proceed either with an azeotropic entrainment of the water formed, with a solvent, or with distillation under reduced pressure which may correspond to a very high vacuum in the last phases of the reaction. Observing a rigorous stoichiometry can be made difficult by the following parasitic phenomena: - Physical elimination of volatiles or more or less bound to water, this is the case for the diols, which must often be introduced in excess compared to the stoichiometry.

- Secondary reactions: they can be significant and in general, disturb both the progress of the synthesis and the final properties of the product obtained.

The preparation can be done by an acid-alcohol reaction using the following raw materials:

- Di-carboxyhic acids of the HOOC- (CH2) _n -COOH type: succinic (n = 2), ghitaric (n = 3), adipic (n = 4), punqueque (n = 5), suberic ( n = 6), azéahque (n = 7), sebacique (n = 8).

- Diols: Ethylene glycol HO- (CH2) 2 "OH, 1,4 Butane-diol or tetramethylene glycol HO- (CH ₂ ) 4-OH, diethylene glycol HO-CH ₂ -CH ₂ -O-CH2-CH2- OH, propylene glycol HO-CH ₂ - CH (CH ₃ OH, Neopentyl glycol HO-CH ₂ -C (CH ₃ ) 2-CH ₂ -OH, triethylene glycol HO-CH ₂ - CH2-O-CH2-CH2-O -CH2-CH2-OH, etc. are the most used.

High molecular weight aliphatic linear polyesters can be obtained by direct polyesterification. As indicated before, the difficulty in obtaining high molecular weight polyesters lies in the good choice of the catalyst, of respecting the stoichiometry between the diacid and the diol (mainly at the end of the reaction), of eliminating as efficiently as possible the water and work with high purity reagents.

By way of nonlimiting example, the following procedure is indicated for the manufacture of a poly-tetramethylene-adipate but it can be applied with some modifications to other polyesters. The polymerization is carried out in a four-necked reactor with a capacity of 0.5 liters. The reactor is equipped with a nitrogen inlet per tube, a thermometer, an agitator and a distillation head connected to a condenser, a flask receptacle and a vacuum pump. The empty reactor is heated to 80 ° C and purged with nitrogen for 15 minutes. The reagents, 1.05 moles (94.5 g) of tetramethylene glycol and 1 mole (146 g) of adipic acid, are then added. The mixture is mechanically stirred under a stream of nitrogen and the temperature rises slowly until the acid is completely dissolved. The catalyst (0.5% of the total weight of the reactants), tetraisopropyltitanate, is then added. The temperature is gradually increased over 1 hour to 175 ° C. and maintained at this temperature for 6 hours. During this time, most of the water released from the polymerization is evaporated, condensed and collected in the flask receptacle. The temperature then rose to 190-195 ° C and held for 6 hours or until there was no more water distilling. At this time, the temperature is lowered to 165 ° C, the nitrogen flow is suppressed and a vacuum is created. These temperature conditions are maintained with mechanical stirring under vacuum for 6 hours, characterized by obtaining a viscous melt. In order to keep the stoichiometry, the necessary amount of diol is increased by 5%, this in order to make up for the loss in diol during the distillation reaction where the risks of coevaporation with water are present.

By way of nonlimiting example, the following procedure is indicated for the manufacture of a po y-ethylene-succinate but it can be applied with some modifications to other polyesters.

The polymerization is carried out in a four-necked reactor with a capacity of 0.5 liters. The reactor is equipped with a nitrogen inlet per tube, a thermometer, an agitator and a distillation head connected to a condenser, a flask receptacle and a vacuum pump. The reagents, 1 mole (174g) of diethyl succinate, 1.5 moles (93g) of ethylene glycol, 0.280g of zinc acetate and 0.070g of antimony trioxide, are introduced into the reactor, after purging with l 'nitrogen, under a flow of nitrogen. The contents of the reactor are brought to a temperature of 180 ° C., with mechanical stirring. These conditions are maintained for 1 hour 30 minutes. The reaction temperature is then gradually brought over 1 hour to 240 ° C. Then the apparatus connected to the vacuum pump is gradually put on 30 minutes under vacuum of 0.5 mmHg. These conditions are maintained for 6 hours 30 minutes, characterized by obtaining a viscous melt. In order to keep the stoichiometry, the necessary amount of diol is increased by 50%, this in order to make up for the loss in diol during the distillation reaction where it coevapes with water.

By way of non-limiting example, the following procedure is indicated for the manufacture of a poly-tetramethylene succinate but it can be applied with some modifications to other polyesters. The polymerization is carried out in a four-necked reactor with a capacity of 0.5 liters. The reactor is equipped with a nitrogen inlet per tube, a thermometer, an agitator and a distillation head connected to a condenser, a flask receptacle and a vacuum pump. The reagents, 1 mole (174g) of diethyl succinate, 1.5 moles (135g) of termethylene glycol, 0.270g of zinc acetate and 0.10g of antimony trioxide, are introduced into the reactor, after purging with nitrogen, under a stream of nitrogen and stirred for 20 minutes at room temperature. The contents of the reactor are then brought to a temperature of 190-200 ° C, with mechanical stirring. These conditions are maintained for 1 hour 30 minutes. The reaction temperature is then gradually brought over 30 minutes to 240 ° C. Then the apparatus connected to the vacuum pump is gradually put over 40 minutes under vacuum of 0.5 mmHg. These conditions are maintained for 5 hours 30 minutes, characterized by obtaining a viscous melt. In order to keep the stoichiometry, the necessary amount of diol is increased by 50%, this in order to make up for the loss in diol during the distillation reaction where it coevaporates with water.

In the following procedures, obtaining very high molecular weight polyesters can be achieved by addition copolymerization from high molecular weight polyester precursors with difunctional reagents.

H - [- OR-OOC-R'-CO-] _n -OR-OH + OCN-R "-NCO (Diisocyanate) => [- OR-OOC-R'-CO-] _n -OR-OOC-HN -R "- H-CO - [- OR-OOC-R'-CO-] _n

HOOC-R * -CO - [- OR-OOC-R'-CO-] _n -OH + CH2- (O CH-R "-CH- (O CH2 (Diepoxy)>

[-OR-OOC-R'-CO-] nO-CH2-CH (OH R "-CH (OH) -CH 2-OOC-R'-CO - [- OR-OOC-R'- CO-] _n

By way of nonlimiting example, the following procedure is indicated for the manufacture of a copoly-tetramethylene-adipate-hexamethylene isocyanate but it can be apphquee with some modifications to other polyesters: H - [- O- (CH2) 4-OOC- (CH ₂ ) 4-CO-] _n -O- (CH ₂ ) 4-OH + OCN- (CH ₂ ) 6 "NCO The polymerization is carried out in a four-necked reactor with a capacity of 0.5 liters. The reactor is equipped with a nitrogen inlet per tube, a thermometer, an agitator and a distillation head connected to a condenser, a flask receptacle and a vacuum pump. The empty reactor is heated to 80 ° C and purged with nitrogen for 15 minutes. The reagents, 1.10 moles (99 g) of tetramethylene glycol and 1 mole (146 g) of adipic acid, are then added. The mixture is mechanically stirred under a stream of nitrogen and the temperature rises slowly until the acid is completely dissolved. The catalyst (0.5% of the total weight of the reactants), tetraisopropyltitanate, is then added. The temperature is gradually brought over 1 hour to 175 ° C. and maintained at this temperature for 6 hours. During this time, most of the water released from the polymerization is evaporated, condensed and collected in the flask receptacle. The temperature then rose to 190-195 ° C and held for 6 hours or until no more water was distilled. The molten mixture obtained is then treated with 5 g of hexamethylene diisocyanate (HMDI) for 2 hours.

By way of nonlimiting example, the following procedure is indicated for the manufacture of a copoly-tetramet ylene-adipate-tetramethylene diglycidyl ether but it can be apphquee with some modifications to other polyesters: HOOC- (CH ₂ ) 4 -CO - [- O- (CH ₂ ) 4-OOC- (CH ₂ ) 4-CO-] _n -OH + CH2- (O CH-CH2-O- (CH ₂ ) 4-O-CH2-CH- (O CH ₂ (Tetramethylene diglycidyl ether) The polymerization is carried out in a four neck reactor with a capacity of 0.5 liters. The reactor is equipped with a nitrogen inlet per tube, a thermometer, a stirrer and a distillation head connected to a condenser, a flask receptacle and a vacuum pump. The empty reactor is heated to 80 ° C. and purged with nitrogen for 15 minutes. Reagents, 1 mole ( 94 g) of tetramethylene glycol and 1 mole (146 g) of adipic acid are then added The mixture is mechanically stirred under a flow of nitrogen and the temperature rises slowly until the acid is co Completely dissolved The catalyst (0.5% of the total weight of the reactants), tetraisopropyltitanate, is then added. The temperature is gradually brought over 1 hour to 175 ° C. and maintained at this temperature for 6 hours. During this time, most of the water released from the polymerization is evaporated, condensed and collected in the flask receptacle. The temperature then rose to 190-195 ° C and held for 6 hours or until no more water was distilled. The molten mixture obtained is then treated with 10 g at 0.8 equiv. tetramethylene epoxy diglycidyl ether for 2 hours in the presence of an additional catalyst (0.5% of the total weight of the reagents) triphenylphosphine.

In principle, the polymerization monitoring is carried out by means of the monitoring of the viscosity, the determination of the acid and hydroxy index and the determination of the molecular mass.

In all cases, the polymer is in the form of a melt and can be recovered either by dissolution in a solvent system (acetone, dioxane, etc.) or non-solvent (methanol) after filtering and drying or by casting and or pushing through a die with hot header cutter and cooling to obtain granules. The polymers obtained have a melting point between 60 and 190 ° C and the molecular weight obtained is high enough to allow processing on conventional plastics processing equipment (extrusion, injection-molding, etc.).

The fully biodegradable composite material according to the invention is the result of a mixture of said first and said second material described above. In other words, it results from the mixture of natural or synthetic polymers constituting said first material and one or more synthetic polymers of the polyester type constituting said second material.

As an example of an embodiment, to manufacture an extrusion grade, 100 parts of polyester and 100 parts of granules obtained are mixed together at room temperature as described above. This mixture is then introduced via a hopper into a co-rotating twin-screw extender. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for re-feeding the material, T2-T3-T4-T5: heating the sheath along the screws 100-120-120-100 ° C , T6-T7: heating of the rod filter 100-100 ° C. The rods obtained at the outlet of the fiher are cooled to obtain solid gelation by passing through rings with air ventilation. The granules are shaped by means of a gorse granulator in line behind the extender. The granules obtained by the process described above are introduced into a machine to be extruded by means of a hopper. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for re-feeding the pellets, T2-T3-T4-T5: heating the sheath along the screw 80-100-110-110 ° C , T6: heating of the flat fihère to film 100 ° C, T7: cooling of the poh-mirror cylinder with tap water 15 ° C. Finished products extruded in the form of a film are obtained through a cast-film system. The thicknesses of films obtained vary between 20 and 150 μm.

According to an alternative embodiment, 100 parts of polyester and 39.5 parts of gelatin (200 bloom) with 10% water, 39.5 parts with 10% water of apple starch are mixed together at room temperature. of soil, 10 parts of water, 10 parts of glycerin, 0.5 parts of stearic acid, 0.5 parts of glycerol stearate in a mixer for 30 minutes. The mixture obtained in the form of powder is left to stand for 12 hours. Then it is introduced via a hopper into a co-rotating twin-screw extender. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper to feed the material, T2-T3-T4-T5: heating the sheath along the screws 100-120- 120-100 ° C, T6-T7: heating the gorse fihère 100-100 ° C. The rods obtained at the outlet of the die are cooled to obtain solid gelation by passing through rings with air ventilation. The granules are shaped by means of an in-line rod granulator behind the extruder.

The granules obtained by the process described above are introduced into an extruding machine via a hopper. The fixed temperatures are: Tl: cooling with tap water 15 ° C under the hopper for feeding the pellets, T2-T3-T4-T5: heating the sheath along the screw 80-100-110-110 ° C, T6: heating the flat film fihère 100 ° C, T7: cooling the poh-mirror cylinder with tap water 15 ° C. Finished products extruded in the form of a film are obtained through a cast-film system. The thicknesses of films obtained vary between 20 and 150 μm.

The biodegradation capacity of natural products such as gelatin and starch is well known. However, biodegradation tests of the materials obtained according to the above exemplary embodiments were carried out. Films extruded from the materials obtained were placed in a container containing potable city water at a temperature of 25 ° C. After swelling in water, the film biologically degraded after 3 weeks and disappeared leaving humus at the bottom of the container. An observation of the residual water under an optical microscope has revealed numerous bacteria making it possible to conclude that the film material is bio-assimilated. Biodegradation tests carried out by burying the films in the ground gave the same results. In order to verify the biodegradation of the synthetic resin, other biodegradation tests were carried out. Films extradited from materials obtained were buried in the mass of a fermented (aerobic) compost brat, originating from the grinding of fermentable waste from households from selective collection. The films were identified using warning nets. The test was very successful because after a week, the films have completely disappeared.

The invention is not limited to the embodiments described above but extends to any modification and variant obvious to a person skilled in the art.

Claims

claims 1. Fully biodegradable material which can be used in particular for packaging products and in particular for storing compostable organic waste, produced from a biodegradable material formulated from at least one natural or synthetic polymer and non-toxic additives, characterized in that said natural or synthetic polymers are arranged to form a physical gel in the presence of a solvent. 2. Material according to claim 1, characterized in that it is produced from a mixture of said biodegradable material formulated from at least one natural or synthetic polymer and non-toxic additives, said natural or synthetic polymers being arranged to form a physical gel in the presence of a solvent and a second biodegradable material consisting of at least one synthetic resin of the polyester type. 3. Material according to one of the preceding claims, characterized in that said solvent is chosen from water, alcohols, polyalcohols and in particular glycerol, ethylene glycol, a polymer of ethylene glycol propylene glycol, a polymer of propylene glycol. 4. Material according to claims 1 or 2, characterized in that said physical gel is concentrated. 5. Material according to claims 1 or 2, characterized in that said polymers forming a physical gel in the presence of solvent are chosen from: gelatin obtained by hydrolysis of collagen contained in the skin, connective tissue and / or bones of animals , starch, carageenane, alginate, pectin, guar, xanthan, carob, gum arabic, starch derivatives obtained by fractionation of corn, wheat, potato. 6. Material according to claims 1 or 2, characterized in that said additives comprise a plasticizer of at least one of said polymers. 7. Material according to claim 6, characterized in that said plasticizers are chosen from molecules comprising several -OH bonds. 8. Material according to claim 7, characterized in that said plasticizers are chosen from alcohols, polyalcohols and in particular glycerol, sorbitol, mannitol, ethylene glycol, a polymer of ethylene glycol, propylene glycol, a polymer of propylene glucol, sugars and in particular sucrose, glucose, dextrose and their derivatives. 9. Material according to claims 1 or 2, characterized in that said additives comprise crosslinking agents for insolubilizing the polymers. 10. Material according to claim 9, characterized in that said crosslinking agents are chosen from aldehydes and in particular formaldehyde, glutaraldehyde, metal salts and in particular chromium salts. 11. Material according to claims 1 or 2, characterized in that said additives include pigments, stabilizers, antioxidants, lubricants and substances protecting against ultraviolet radiation. 12. Material according to claim 2, characterized in that said synthetic resin comprises at least one saturated aliphatic polyester and in particular at least one linear aliphatic polyester of high molecular weight. 13. Material according to claim 12, characterized in that said ahphatic polyester is a poly-hydroxy-butyrate. 14. Material according to claim 12, characterized in that said ahphatic polyester is a poly-hydroxy-butyrate-valerate. 15. Material according to claim 12, characterized in that said ahphatic polyester is a polycaprolactone. 16. Material according to claim 12, characterized in that said ahphatic polyester is obtained by a reaction of polyacids and polyalcohols according to a global scheme: HO - R - OH + HOOC - R - COOH <-> O - R - OOC - R - COO + H ₂ O. 17. Material according to claim 16, characterized in that the polyacids are di-carboxyhques of the HOOC- (CH2) _rl -COOH type, in particular succinic (n = 2), ghitaric (n = 3), adipic (n = 4), pimelic (n = 5), suberic (n = 6), azéahque (n = 7), sebacique (n = 8). 18. Material according to claim 16, characterized in that the polyalcohols are diols, in particular retethylene glycol HO- (CH2) 2 ^_ OH, 1,4 butane-diol or tetramethylene glycol HO- (CH ₂ ) 4-OH, diethylene glycol HO-CH2-CH ₂ -O-CH ₂ -CH2-OH, propylene glycol HO-CH ₂ -CH (CH ₃ ) -OH, neopentyl glycol HO-CH ₂ -C (CH ₃ ) 2- CH ₂ -OH, triethylene glycol HO-CH2-CH2-O-CH2-CH2-O-CH2-CH2-OH 19. Material according to claim 12, characterized in that said polyester is a polytetramethylene adipate. 20. Material according to claim 12, characterized in that said polyester is a poryethylene ethyl succinate. 21. Material according to claim 12, characterized in that said polyester is a polytetramethylene succinate. 22. Material according to claim 12, characterized in that said high molecular weight polyester is obtained by addition copolymerization from high molecular weight polyester precursors with difunctional reagents. 23. Material according to claim 22, characterized in that said difunctional reagent is diisocyanate and diepoxy reacting respectively according to the following reactions: H - [- OR-OOC-R'-CO-] _n -OR-OH + OCN- R "-NCO => [-OR-OOC-R-CO-] _n -OR-OOC-HN-R" -NH-CO - [- OR-OOC-R'-CO-] _n and, HOOC-R '-CO - [- OR-OOC-R'-CO-] _n -OH + CH2- (O CH-R "-CH- (O) -CH ₂ -> [-OR-OOC-R'-CO-] nO-CH2-CH (OH R "-CH (OH CH ₂ -OOC-R'-CO - [- OR-OOC-R'- CO-] _n . 24. Material according to claim 22, characterized in that said polyester is a copolytetramethylene-adipate-hexamethylene isocyanate. 25. Material according to claim 22, characterized in that said polyester is a copofytetramethylene-adipate-hexamethylene diglycidyl ether. 26. A method of manufacturing a completely biodegradable material which can be used in particular for packaging products and in particular for storing compostable organic waste, using at least one natural or synthetic polymer and non-toxic additives constituting a biodegradable material according to claim 1, characterized in that a physical gel is formed with said natural or synthetic polymers in the presence of a solvent. 27. The method of claim 26, characterized in that said biodegradable material consisting of at least one natural or synthetic polymer and non-toxic additives is mixed, said natural or synthetic polymers being arranged to form a physical gel in the presence of 'a solvent, with a second biodegradable material consisting of at least one synthetic resin of the polyester type. 28. The method of claims 26 or 27, characterized in that said natural or synthetic polymers are heated in the presence of the solvent and in that the composition obtained is cooled so as to obtain a physical gel. 29. Method according to claims 26 or 27, characterized in that the solvent is concentrated in the physical gel so as to obtain a concentrated physical gel. 30. Method according to any one of claims 26 to 29, characterized in that the solvent is chosen from water, alcohols, polyalcohols and in particular glycerol, ethylene glycol, a polymer of ethylene glycol, propylene glycol, a polymer of propylene glycol. 31. The method of claim 27, characterized in that said mixing is done in equal parts, the first material being in the form of granules, in an extradeuse at a temperature of the order of 100 to 120 ° C. 32. Method according to claim 27, characterized in that 100 parts of polyester, 39.5 parts of gelatin with 10% water, 39.5 parts with 10% of water are mixed at room temperature. potato starch, 10 parts of glycerin, 0.5 parts of stearic acid, and 0.5 parts of glycerol stearate, the mixture is left to stand and then the mixture is introduced into an extender at a temperature of the order of 100 at 120 ° C., then the rods obtained are left to cool at the outlet of the die so as to obtain a physical gel.