EP2247662A2 - Thermoplastic compositions based on soluble starch and method for preparing such compositions - Google Patents

Abstract

The subject matter of the present invention is a novel starch-based composition comprising: (a) at least 45% by weight of at least one soluble starch, (b) at most 55% by weight of at least one non-biodegradable, non-amylaceous polymer, and (c) a bonding agent carrying at least two functional groups capable of reacting with molecules carrying functions comprising an active hydrogen, these amounts being expressed with respect to solids and relative to the sum of (a) and (b). The present invention also relates to a method for preparing such a starch-based composition and to a thermoplastic composition prepared by heating such a composition.

Description

 SOLUBLE STARCH THERMOPLASTIC COMPOSITIONS AND PROCESS FOR PREPARING SUCH COMPOSITIONS

The present invention relates to novel starch-based compositions and thermoplastic starch compositions obtained therefrom, as well as processes for the preparation thereof.

The term "thermoplastic composition" in the present invention means a composition which reversibly softens under the action of heat and hardens on cooling. It has at least one so-called glass transition temperature (Tg) below which the amorphous fraction of the composition is in the brittle glassy state, and above which the composition can undergo reversible plastic deformations. The glass transition temperature or at least one of the glass transition temperatures of the starch-based thermoplastic composition of the present invention is preferably from -50 to 150 ^° C. This starch-based composition can, of course, be shaped by the processes traditionally used in plastics (extrusion, injection, molding, blowing, calendering, etc.). Its viscosity, measured at a temperature of 100 ⁰ C to 200 ⁰ C, is generally between 10 and 10 ⁶ Pa. S.

Preferably, said composition is "hot melt", that is to say that it can be shaped without applying significant shear forces, that is to say by simple flow or by simply pressing the melt. Its viscosity, measured at a temperature of 100 ⁰ C to 200 ⁰ C, is generally between 10 and 10 ³ Pa. S. For the purposes of the invention, the term "soluble starch" means any polysaccharide material derived from starch, having, at 20 ^° C., a fraction soluble in a solvent chosen from demineralized water, ethyl acetate, propyl acetate, butyl acetate, diethyl carbonate, propylene carbonate, dimethyl glutarate, triethyl citrate, dibasic esters, dimethyl sulfoxide (DMSO), dimethyl isosorbide, glycerol triacetate, diacetate isosorbide, isosorbide dioleate and methyl esters of vegetable oils, at least 5% by weight. This soluble fraction is preferably greater than 20% by weight and in particular greater than 50% by weight. Of course, the soluble starch may be totally soluble in one or more of the solvents indicated above (soluble fraction = 100%).

Soluble starch is used according to the invention in solid form, preferably substantially anhydrous, that is to say not dissolved in an aqueous or organic solvent. It is therefore important not to confuse, throughout the description that follows, the term "soluble" with the term "dissolved".

The term "plasticizer of starch" means any molecule, preferably organic, of low molecular weight, that is to say preferably having a molecular weight of less than 5000, in particular less than 1000, which, when it is incorporated into the starch by thermomechanical treatment at a temperature between 20 and 200 ^° C. results in a decrease in the glass transition temperature and / or a reduction in the crystallinity of this starch. In the case of a soluble starch in the meaning of the invention, generally weakly crystalline, the incorporation of the plasticizer leads to a disappearance of a possible crystallinity residual and to obtain a totally amorphous state. The plasticizer preferably does not include water.

The term "non-biodegradable non-starchy polymer" means any organic polymer other than starch or starch derivatives, considered as non-biodegradable or non-compostable in the sense of EN standards.

13432, ASTM D6400 and ASTM 6868.

This non-biodegradable non-starchy polymer does not include, in particular, natural polymers extracted from plants, animal tissues or microorganisms, polyvinyl alcohol and biodegradable polyesters such as poly (lactic acid) (PLA), polycaprolactones (PCL), poly (butylene succinate adipate) (PBSA), poly (butylene adipate terephthalate) (PBAT), polyhydroxyalkanoate (PHA), especially polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV).

Preferably, the non-biodegradable non-starchy polymer carries active hydrogen functions, that is to say functions having at least one hydrogen atom that can be displaced if a chemical reaction takes place between the carrier atom. of this hydrogen atom and another reactive function. The functions with active hydrogen are, for example, hydroxyl, protonic acid, urea, urethane, amide, amine or thiol functions. This definition also encompasses in the present invention any non-starchable non-biodegradable polymer carrying functional groups capable of giving, in particular by hydrolysis, such active hydrogen functions. The functions which can give, in particular by hydrolysis, such active hydrogen functions are, for example, the alkoxy functional groups, in particular the alkoxysilanes, or the acyl chloride, acid anhydride, epoxide or ester functions. By "binding agent" is meant any molecule carrying at least two functional groups, free or masked, capable of reacting with molecules carrying active hydrogen functions, such as, in particular, macromolecules of starch. This binding agent therefore allows, by formation of covalent bonds, the bridging of at least a portion of the soluble starch macromolecules with each other and optionally with the non-starchable non-starchy polymer present in the composition. When the composition contains a plasticizer carrying active hydrogen functional groups, the binding agent is advantageously capable of reacting with this plasticizer to fix it on the starch and / or on the non-biodegradable non-starchy polymer. This binding agent is distinguished from adhesion agents, physical compatibilizers or grafting agents in that they either create weak bonds (non-covalent) or carry only a single reactive function .

In the current context of climatic disturbances due to the greenhouse effect and the global warming, of the evolution upwards of the costs of the fossil raw materials, in particular of the oil from which the plastics originate, of the state of the public opinion in search of sustainable development, more natural products, cleaner, healthier and less expensive in energy, and the evolution of regulations and taxation, it is necessary to have new compositions from renewable resources , which are particularly suitable for the field of plastic materials, and which are both competitive, designed from the outset to have little or no negative impact on the environment, and technically as efficient as polymers prepared from raw materials of fossil origin.

Starch is a raw material with the advantages of being renewable, biodegradable and available in large quantities at an economically attractive price compared to the oil and gas used as raw materials for today's plastics.

The biodegradable nature of starch has already been exploited in the manufacture of plastics, according to two main technical solutions.

The first starch-based compositions developed were about thirty years ago. The starches were then employed in the form of mixtures with synthetic polymers such as polyethylene, as filler, in the native granular state. Before dispersion in the synthetic polymer constituting the matrix, or continuous phase, the native starch is then preferably dried to a moisture content of less than 1% by weight, to reduce its hydrophilicity. For the same purpose, it can also be coated with fatty substances (fatty acids, silicones, siliconates) or be modified on the surface of the grains by siloxanes or isocyanates. The materials thus obtained generally contained approximately 10%, at most 20% by weight of granular starch, because beyond this value, the mechanical properties of the composite materials obtained became too imperfect and lowered compared with those of the synthetic polymers forming the matrix. In addition, it has been found that such polyethylene-based compositions are only biodegradable and non-biodegradable as expected, so that the expected growth of these compositions has not occurred. To palliate in the absence of biodegradability, developments were also carried out later on the same principle but replacing only conventional polyethylene with oxidatively degradable polyethylenes or with biodegradable polyesters such as polyhydroxybutyrate-co-hydroxyvalerate (PHBV) or poly (lactic acid) (PLA). Again, the mechanical properties of such composites obtained by mixing with granular starch have been found to be insufficient. Reference may be made to the excellent book "Green Chemistry", Paul Colonna, Edition TEC & DOC, January 2006, Chapter 6 entitled "Materials based on starches and their derivatives" by Denis Lourdin and Paul Colonna, pages 161 to 166. Subsequently, the starch has been used in a substantially amorphous and thermoplastic state. This state is obtained by plastification of the starch using a suitable plasticizer incorporated into the starch at a level generally between 15 and 25% relative to the granular starch, by supply of energy at a time. mechanical and thermal. US Pat. Nos. 5,095,054 to Warner Lambert and EP 0,497,706 B1 of the Applicant describe in particular this destructured state, with reduced or absent crystallinity, and means for obtaining such thermoplastic starches.

However, the mechanical properties of the thermoplastic starches, although they may be to some extent modulated by the choice of starch, plasticizer and the rate of use of the latter, are generally rather poor because the materials thus obtained are always very highly viscous at high temperature (120 ⁰ C to 170 ⁰ C) and very fragile, too brittle and very hard and low film-forming at low temperature, that is to say below the temperature of glass transition or the highest glass transition temperature.

Thus, the elongation at break of such thermoplastic starches is very low, still less than about 10%, and this even with a very high plasticizer content of the order of 30%. By way of comparison, the elongation at break of low density polyethylenes is generally between 100 and 1000%.

In addition, the maximum breaking stress of thermoplastic starches decreases dramatically as the level of plasticizer increases. It has an acceptable value, of the order of 15 to 60 MPa, for a plasticizer content of 10 to 25%, but decreases unacceptably beyond 30%. As a result, these thermoplastic starches have been the subject of numerous studies aimed at developing biodegradable and / or water-soluble formulations having better mechanical properties by physical mixing of these thermoplastic starches, or with polymers of petroleum origin such as polyvinyl acetate (PVA), polyvinyl alcohol

(PVOH), ethylene / vinyl alcohol copolymers (EVOH), biodegradable polyesters such as polycaprolactones (PCL), poly (butylene adipate terephthalate) (PBAT) and poly (butylene succinate adipate) (PBS), or with polyesters of renewable origin such as poly (lactic acid) (PLA) or microbial polyhydroxyalkanoates (PHA, PHB and PHBV), or with natural polymers extracted from plants or animal tissues. We can refer again to the book "Green Chemistry", Paul Colonna, TEC & DOC Edition, pages 161 to 166, but also for example to patents EP 0 579 546 B1, EP 0 735 104 B1 and FR 2 697 259 of the Applicants who describe compositions containing thermoplastic starches.

Under the microscope, these biodegradable resins appear to be very heterogeneous and have large islands of plasticized starch in a continuous phase of synthetic polymers. This is because thermoplastic starches are very hydrophilic and are therefore very incompatible with synthetic polymers. It follows that the mechanical properties of such mixtures, even with the addition of compatibilizing agents such as, for example, copolymers comprising hydrophobic units and alternating hydrophilic units such as ethylene / acrylic acid (EAA) copolymers, or even cyclodextrins. or organosilanes, remain quite limited.

By way of example, the commercial product MATER-BI grade Y has, according to the information given by its manufacturer, an elongation at break of 27% and a maximum breaking stress of 26 MPa. As a result, these composite materials today find limited use, that is to say, limited mainly to the sectors of the overpack, trash bags, crate bags and certain rigid mass objects, biodegradable.

The destructuring of the native semicrystalline granular state of the starch to obtain thermoplastic amorphous starches can be carried out in a medium that is poorly hydrated by the extrusion processes. Obtaining a melted phase from the starch granules requires not only a large supply of mechanical energy and thermal energy but also the presence of a plasticizer at the risk, otherwise, to carbonize the starch. Such plasticizers may be sugars, polyols or other low molecular weight organic molecules.

The amount of energy to be applied to plasticize the starch can be advantageously reduced by increasing the amount of plasticizer. In practice, however, the use of a plasticizer at a high level relative to the starch induces various technical problems among which may be mentioned the following: a release of the plasticizer from the plasticized matrix at the end of manufacture or at the end of the manufacturing process; during the storage, so that it is impossible to retain a quantity of plasticizer as high as desired and therefore to obtain a sufficiently flexible and film-forming material, o a strong instability of the mechanical properties of the plasticized starch which hardens or softens depending on the humidity of the air, respectively when its water content decreases or increases, o whitening or opacification of the surface of the composition by crystallization of the plasticizer used at high dose, such as by example in the case of xylitol, o a tacky or oily nature of the surface, as in the case of glycerol for example, o very poor resistance to water, all the more It is problematic that the plasticizer content is high. A loss of physical integrity is observed in the water, so that the plasticized starch can not, at the end of manufacture, be cooled by immersion in a water bath as for conventional polymers. As a result, its uses are very limited. To extend its possibilities of use, it is necessary to mix it with large quantities, generally superior or 60%, of polyesters or other expensive polymers. o a possible premature hydrolysis of the polyesters (PLA, PBAT, PCL, PET) possibly associated with the thermoplastic starch.

The present invention provides an effective solution to the problems stated above.

Its object is, in the first place, a starch composition comprising: (a) at least 45% by weight of at least one soluble starch,

(b) not more than 55% by weight of at least one non-biodegradable non-starchy polymer, and

(c) a binding agent carrying at least two functional groups capable of reacting with molecules carrying active hydrogen functions, these amounts being expressed as solids and based on the sum of (a) and (b).

The present invention also relates to a process for preparing a starch-based composition as described above. This process comprises the following steps:

(i) selecting at least one soluble starch (a), (ii) incorporating into this soluble starch (a) a non-starchable non-starchy polymer (b) in an amount such that the soluble starch (a) ) represents at least 45% by weight and the non-biodegradable non-starchy polymer (b) represents at most 55% by weight, these quantities being expressed as solids and referred to the sum of (a) and (b), and

(iii) incorporation into the composition thus obtained of at least one linking agent carrying at least two functional groups capable of reacting with molecules carrying active hydrogen functions, step (ii) can be implemented before, during or after step (iii), that is to say after intermediate storage of the compositions obtained at the end of one or the other of these steps. The process according to the invention preferably comprises drying the composition obtained in step (ii), before the incorporation of the binding agent, to a residual moisture content of less than 5%, preferably less than 1%, in particular less than 0.1% by weight. Depending on the amount of water to be removed, this drying step can be carried out batchwise or continuously during the process.

The starch-based compositions obtained by this process contain the various ingredients, namely starch, non-starchable, non-biodegradable polymer, binding agent and optionally plasticizer, intimately mixed with each other. In these compositions, the binding agent has, in principle, not yet reacted with the other ingredients carrying active hydrogen functions.

These starch-based compositions are then used to prepare compositions in which at least a portion of the binding agent has reacted with the non-biodegradable starch and / or non-starchy polymer and optionally with the plasticizer. It is this binding of the various ingredients to one another which gives the thermoplastic starch compositions of the present invention the interesting properties specified hereinafter. The Applicant merely wishes to emphasize here that, although the two types of compositions of the present invention (before and after reaction of the binding agent) contain starch and have a thermoplastic character, the compositions before The reaction of the linking agent will hereinafter be referred to systematically as "starch-based compositions" while the compositions obtained by heating thereof and containing the reaction product of the binding agent, starch and / or or non-biodegradable non-starchy polymer, and optionally plasticizer, will be called "thermoplastic compositions" or "thermoplastic starch compositions".

The subject of the present invention is therefore also a process for the preparation of such a "thermoplastic starchy composition" comprising the heating of a starch-based composition, as defined above, to a sufficient temperature and during a period of time. sufficient time to react the binding agent with the soluble starch (a) and / or the non-biodegradable non-starchy polymer (b), and a thermoplastic starchy composition obtainable by such a method.

Both types of compositions mentioned above (before and after reaction of the binding agent) have a structure of "solid dispersion" type. In other words, the compositions of the present invention, despite their high starch content, contain this starch in the form of domains dispersed in a continuous polymer matrix. This dispersion-type structure must be distinguished in particular from a structure in which the starch and the non-starchy polymer are perfectly miscible or compatible with each other, or else compositions containing two co-continuous starch networks. and polymer. The object of the present invention is indeed not to prepare biodegradable materials but bio-sourced plastics with high starch content having excellent rheological and mechanical properties. To the best knowledge of the Applicant, such soluble starches have not, as such, the object of significant development work of thermoplastic compositions, or only very little. This was due to the widespread and unfavorable prejudice that their mechanical properties and water-resistance would necessarily be particularly poor.

Preferably, the starch-based composition comprises at least 49% by weight of at least one soluble starch (a) and at most 51% by weight of at least one non-biodegradable non-starchy polymer (b).

The amount of soluble starch (a), expressed as solids and based on the sum of (a) and (b), is advantageously between 51% and 99.8% by weight, preferably between 55% and 99%, 5% by weight, and in particular between 60% and 99% by weight, the ideal being an even greater quantity, which can even reach 70%. Fillers and other additives, detailed below, may be incorporated into the starch compositions of the present invention. Although the proportion of these additional ingredients may be quite large, the total amount of the sum of soluble starch (a) and non-starchy non-biodegradable polymer

(b) starch-based composition, expressed in dry matter, is at least 25%, preferably at least equal to

30% and more preferably at the month equal to 40% by weight of the dry matter thereof. The total amount of non-starchy non-starchy polymer (s) (s) (b) is preferably between 0.1 and 49%, in particular between 0.2 and 45% and more preferably between 1 and 40%, these values being expressed in dry matter and referred to the sum of (a) and (b).

It should be noted that the Applicant has found after many works that, surprisingly, the presence of a binding agent advantageously improves the properties of the thermoplastic composition and that, moreover, against all odds, thanks to the use of a binding agent, the final thermoplastic composition obtained had a very good resistance to water and steam, while remaining sufficiently flexible and truly thermoplastic in the sense of the present invention.

The amount of binding agent depends in particular on the type of soluble starch used. This quantity, expressed as solids and based on the sum of (a) and (b), is preferably between 0.1 and 15% by weight, preferably between 0.1 and 12% by weight, better still between 0.2 and 9% by weight and in particular between 0.5 and 5% by weight. This amount of binding agent is for example between 0.5 and 3% by weight.

The molecular weight of the binding agent is preferably less than 5000, in particular less than 1000. In fact, the low molecular weight of the binding agent enables its quick and easy incorporation into the plasticized starch composition. plasticizer. The binding agent preferably has a molecular weight of between 50 and 5000, in particular between 90 and 300.

Unexpectedly, very small amounts of binding agent considerably reduce the sensitivity to water and water vapor of the final thermoplastic composition obtained according to the invention and thus make it possible to to cool it rapidly at the end of manufacture by immersion in water, which is not possible without the use of a binding agent capable of forming bonds between the soluble starch molecules and between them and the non-starchy polymer.

The binding agent may be chosen for example from compounds carrying at least two functions, free or masked, identical or different, chosen from isocyanate, carbamoylcaprolactam, epoxide, halogen, protonic acid, acid anhydride and halide functions. acyl, oxychloride, trimetaphosphate and alkoxysilane. It may advantageously be the following compounds:

diisocyanates and polyisocyanates, preferably 4,4'-dicyclohexylmethane diisocyanate (H12MDI), methylenediphenyl diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate; (HMDI) and lysine diisocyanate (LDI), dicarbamoyl caprolactams, preferably 1-1'-carbonyl bis caprolactam,

diepoxides,

compounds comprising an epoxide functional group and a halogen functional group (= halohydrins), preferably epichlorohydrin, organic diacids, preferably succinic acid, adipic acid, glutaric acid, oxalic acid, malonic acid, maleic acid and the corresponding anhydrides, - the oxychlorides, preferably phosphorus oxychloride,

trimetaphosphates, preferably sodium trimetaphoshate,

alkoxysilanes, preferably tetraethoxysilane, and any mixtures of these compounds.

In a preferred embodiment of the invention, the linking agent is a diisocyanate, in particular methylenediphenyl diisocyanate (MDI) and 4,4'-dicyclohexylmethane diisocyanate (H12MDI).

The use of diisocyanates in the presence of starch and non-starch polymers has certainly been described but under conditions and for purposes very different from those of the present invention. The non-starchy polymers were generally biodegradable polymers which, for high starch contents, did not make it possible to obtain thermoplastic compositions having the same performances as those of the present invention. Thus, international application WO 97/03120 describes the preparation of starch derivatives by grafting biodegradable polyesters (poly (lactic acid) and polycaprolactone) via diisocyanates. The biodegradable compositions obtained are perfectly monophasic, the starch having been made completely compatible with the grafted biodegradable polyester.

Yu et al., Green Polymeric Blends and Composites from Renewable Resources, Macromol. Sym. 2007, 249-250, 535-539, discloses the preparation of biodegradable materials by extrusion of a mixture of gelatinized starch and biodegradable polyesters (PLA, PCL and PBSA) containing methylene diisocyanate introduced either in admixture with the starch either in admixture with the biodegradable polyester. The proportion of starch in the compositions is significantly lower than that of the compositions of the present invention.

Application FR 2 640 274 describes the preparation of a film of polyvinyl alcohol and of starch. During the preparation of the film, a crosslinking agent comprising at least two functions capable of reacting with the hydroxyl groups of starch and PVA can be added to the composition. PVA, a biodegradable polymer, however, does not provide materials having the rheological performance of the present invention, nor its high stability with respect to water.

International application WO 2004/005365 describes rigid foams of polyisocyanurates obtained by reaction of a composition containing an aromatic polyester polyol, a polyisocyanate, a carbohydrate having a molecular weight of less than 2000 and an expanding agent. The only example of application using a soluble starch is Example 11 in which a maltodextrin (Maltrin M150) is used at a rate of only a few percent.

None of the above documents discloses or suggests a thermoplastic composition similar to that of the present invention comprising a reactive at least bifunctional binding agent in a composition comprising a substantial fraction of a soluble starch and a non-starch-free polymer. biodegradable having rheological and mechanical properties and water resistance comparable to those of the present invention.

The soluble starch according to the invention is a polysaccharide material derived from starch, in particular granular starches, by means of a suitable solubilization treatment of a physical, chemical and / or enzymatic nature. In the native state, that is to say, as naturally occurring in the reserve organs and tissues of higher plants, the starches are in the form almost insoluble in water and organic solvents because of their semi structure. - crystalline granules. Their level of solubles in demineralised water or in organic solvents is in fact still well below 5%. The semi-crystalline state within the starch granules is essentially due to amylopectin and the degree of crystallinity generally varies from 15 to 45%, essentially depending on the botanical origin of the starch. The native granular starch, placed under polarized light, presents under the microscope a characteristic black cross, called "Maltese Cross", typical of the crisalline granular state. For a more detailed description of granular starch, reference may be made in Chapter II entitled "Structure and morphology of the starch grain" of S. Perez, in the book "Initiation to chemistry and physico- Macromolecular Chemistry ", First Edition 2000, Volume 13, pages 41 to 86, French Group for Polymer Studies and Applications.

The solubilization treatment of starch is usually accompanied by a significant reduction in amylopectin crystallinity. Therefore, soluble starch in the sense of the invention can be in the form of granules, but the granules then appear without visible Maltese cross in polarized light. In any case, the amylopectin crystallinity level of the soluble starch is therefore always less than 15% and preferably close to 0%.

Moreover, this soluble starch generally has an average molecular weight between 500 and 10 ⁷ Daltons, preferably between 800 and 500 000 daltons and in particular between 2000 and 500 000 daltons.

The soluble starch according to the invention can come from all botanical origins. It can be a starch obtained by physical, chemical or enzymatic treatment of granular native starch of cereals such as wheat, maize, barley, triticale, sorghum or rice, tubers such as potato or cassava or legumes such as pea and soy, and mixtures of such starches.

According to one preferred variant, this soluble starch is obtained from a starch which has undergone acid, oxidizing or enzymatic hydrolysis, an oxidation, a chemical modification, in particular an esterification and / or etherification, acetylation, hydroxypropylation, cationisation, crosslinking, phosphating, or succinylation, or a low temperature aqueous treatment ("annealing"), or from a mixture of such starches.

It may be in particular a soluble starch obtained from a granular starch chosen from fluidized starches, oxidized starches, physicochemically modified starches, white dextrins, and mixtures thereof.

Finally, it can be obtained from a modified starch by a combination of the above-mentioned treatments or from any mixture of these native starches, hydrolyzed starches, oxidation-modified starches and physico-chemically modified starches. Preferably, the soluble starch is a derivative of native or modified starches, wheat or peas.

The soluble starch according to the invention can be rendered soluble, in particular by the application of a pre-gelatinization treatment on a drum, atomization, hydrothermal cooking or chemical functionalization.

This starch soluble in water or organic solvents, is preferably a pregelatinized starch, a highly converted dextrin usually called yellow dextrin, maltodextrin, highly functionalized starch or a mixture of these starches.

The pregelatinized starches can be obtained by hydrothermal treatment of gelatinization of native starches or modified starches, in particular by steam cooking, jet-cooker cooking, cooking on drums, cooking in kneader / extruder systems and then dried for example in an oven, by hot air on a fluidized bed, on rotating drums, by atomization, by extrusion or by lyophilization. Such starches usually have a solubility in demineralized water at 20 ⁰ C greater than 5% and more generally between 10 and 100%. For example, there may be mentioned the products manufactured and sold by the Applicant under the trade name PREGEFLO ^®, having a water content of less than 10% and generally between 4 and 8%.

Dextrins can be prepared from native starches or modified starches by dextrinification in acid medium with little hydration. It may be in particular soluble white dextrins or yellow dextrins. By way of example, mention may be made of the STABILYS ^® A 053 or TACKIDEX ^® C072 products manufactured and marketed by the Applicant. Such dextrins present in demineralized water at 20 ^° C., a solubility of usually between 10 and 95%.

Maltodextrins can be obtained by acid, oxidative or enzymatic hydrolysis of starches in an aqueous medium. They may have in particular an equivalent dextrose of between 0.5 and 40, preferably between 0.5 and 20 and better still between 2 and 19. Such maltodextrins are for example manufactured and marketed by the Applicant under the trade name GLUCIDEX ^® . They present in the water demineralized at 20 ^° C., a solubility generally greater than 90%, or even close to 100%.

Highly functionalized starches can be obtained from a native or modified starch. The high functionalization may be carried out for example by esterification or etherification to a sufficiently high level to make it soluble in the sense defined above. Such functionalized starches have a solubility at 20 ^° C. of greater than 5%, preferably greater than 10%, more preferably greater than 50% and are ideally completely soluble in demineralized water or in an organic solvent, for example in ethyl acetate, propyl acetate, butyl acetate, diethyl carbonate, propylene carbonate, glutarated dimethyl, triethyl citrate, dibasic esters (DBE), dimethylisosorbide, glycerol triacetate or isosorbide diacetate, isosorbide dioleate and methyl esters of vegetable oils. The high functionalization can be obtained in particular by acetylation in solvent phase of acetic anhydride and acetic acid, grafting by use for example of acid anhydrides, mixed anhydrides, fatty acid chlorides, oligomers of caprolactones or lactides, hydroxypropylation in glue phase, cationization in dry phase or glue phase, anionization in dry phase or glue phase by phosphatation or succinylation. These highly functionalized starches can be water-soluble and then have a degree of substitution of between 0.1 and 3, and more preferably between 0.25 and 3.

In the case of highly functionalized organosoluble starches, such as starch, dextrin or maltodextrin acetates, the degree of substitution is usually higher and greater than 0.1, preferably between 0.2 and 3, more preferably between 0.80 and 2.80 and most preferably between 1.5 and 2.7.

Preferably, the reagents for modifying or functionalizing the starch are of renewable origin.

Preferably, the soluble starch has a low water content, less than 10%, in particular less than 8%, better still less than 5% and ideally less than 2%, if possible less than 0.5%, or even less at 0.2%.

According to an advantageous variant, the soluble starch has a low content of reducing sugars, that is to say an equivalent dextrose (DE) of less than 0.5, preferably less than 0.2. This low content of reducing sugars can be obtained in a known manner by reducing the soluble starch, for example by catalytic hydrogenation or by treatment with sodium borohydride. Such hydrogenated or reduced soluble starches advantageously have a better heat stability.

According to one variant of the starch-based composition of the present invention, the soluble starch (a) is partially replaced by a plasticized starchy composition, consisting of starch and a plasticizer thereof, and obtained by mixing thermomechanical process of a granular starch selected from native starches, fluidized starches, oxidized starches, chemically modified starches, white dextrins and mixtures of these starches and a plasticizer of this granular starch.

Soluble starch can itself be plasticized by a plasticizer. The starch-based composition can therefore be any mixture of soluble and insoluble starch (s) and plasticizer (s) thereof.

The plasticizer is preferably chosen from diols, triols and polyols such as glycerol, polyglycerols, isosorbide, sorbitans, sorbitol, mannitol, hydrogenated glucose syrups, organic acid salts such as sodium lactate, the methyl, ethyl or fatty esters of organic acids such as lactic, citric, succinic, adipic or glutaric acids or the acetic or fatty esters of monoalcohols, diols, triols or polyols such as ethanol, diethylene glycol, glycerol or sorbitol, and mixtures of these products.

When the soluble starch is a highly functionalized organosoluble starch, the plasticizer is preferably chosen from the methyl, ethyl or fatty esters of organic acids such as lactic, citric, succinic, adipic or glutaric acids or the acetic or fatty esters of mono-alcohols, diols, triols or polyols such as ethanol, diethylene glycol, glycerol or sorbitol. By way of example, mention may be made of glycerol diacetate (diacetin), glycerol triacetate (triacetin), isosorbide diacetate, isosorbide dioctanoate, isosorbide dioleate and DBE.

The plasticizer advantageously has a molar mass of less than 5000, preferably less than 1000, and in particular less than 400. The plasticizer preferably has a molar mass greater than 18, that is, it preferably does not include 'water. The plasticizer is incorporated in the starch preferably in a ratio by weight, on a dry basis, of plasticizer with soluble starch between 1/100 and 150/100, preferably between 5/100 and 120/100 and better including 10/100 and 60/100.

The amount of plasticizer used in the context of the invention may be zero or low, especially when using fluidized soluble starches, dextrins or maltodextrins.

The non-starchable non-biodegradable polymer can be of any kind and be a mixture of polymers.

It is advantageously a functional polymer carrying active hydrogen functional groups and / or functions which give, in particular by hydrolysis, such active hydrogen functions.

It may be synthetic polymers obtained from monomers of fossil origin but also, and preferably, from monomers of biological origin

(biobased monomers). These synthetic polymers are preferably of the polyolefin, polystyrenic, polyvinyl, polyacrylic, fluorinated, polyacetal, polyester, polycarbonate, polyether, polyamide, polyimide, polyurethane, polysulfone, silicone and epoxy type.

This non-starchy, non-biodegradable polymer may be chosen from synthetic polymers of polyester, polyacrylic, polyacetal, polycarbonate, polyamide, polyimide, polyurethane, functionalized polyolefin, functionalized styrenic, functionalized vinylic, functionalized fluorinated, functionalized polysulfone, functionalized poly (phenylene ether) functionalized poly (phenylene sulfide), functionalized silicone and functionalized polyether. By way of example, mention may be made of PETs, polyamides 6, 6-6, 6-10, 6-12, 11 and 12, polyacrylates, polyvinyl acetate, ethylenevinylacetates ( EVA), ethylene-methyl acrylate (EMA) copolymers, ethylene-alcohol copolymers vinylic acid (EVOH), polyoxymethylenes (POM), acrylonitrile-styrene-acrylate copolymers (ASA), thermoplastic polyurethanes (TPU), polyethylenes or polypropylenes functionalized for example with silane, acrylic or maleic anhydride units and styrene block copolymers -ethylene-butylene-styrenes

(SEBS) functionalized for example by maleic anhydride units, and mixtures of these polymers.

The non-biodegradable, preferably functionalized, non-starchy polymer is advantageously a polymer synthesized or functionalized, partially or totally, by using biosourced monomers, that is to say from short-term natural renewable resources such as plants, microorganisms or gases, especially from sugars, glycerin, oils or their derivatives such as alcohols or acids, mono-, di- or polyfunctional.

It may be in particular polyethylene obtained from bioethanol, polypropylene derived from bio-propanediol, non-biodegradable polyesters based on lactic acid or succinic acid biosourced, non-biodegradable polyesters based on butane-diol, biosourced isosorbide or succinic acid, SORONA ^® type polyesters based on 1,3-propanediol biosourced, polycarbonates containing isosorbide, polyethylene glycols based on bio-ethylene glycol, polyamides based on castor oil or plant polyols, and polyurethanes based on diols or diacids derived from vegetable or animal fats, glycerol, isosorbide, sorbitol or sucrose.

The non-starchy non-biodegradable polymer may also be chosen from polymers of natural origin obtained directly by extraction from plants, algae, microorganisms or animal tissues and modified or functionalized so as to lose their biodegradability. It may be in particular protein polymers, cellulosic, lignocellulosic, chitosan type and natural rubbers.

Such a non-biodegradable non-starchy polymer, modified or functionalized, can be chosen from flour, modified proteins, celluloses modified in particular by carboxymethylation, ethoxylation, hydroxypropylation, cationization, acetylation, alkylation, hemicelluloses, modified lignins and guars, chitins and chitosans, gums and natural resins such as natural rubbers, rosins, shellacs and terpene resins, polysaccharides extracted from algae such as alginates and carrageenans, polysaccharides of bacterial origin such as modified xanthanes or modified PHAs, lignocellulosic fibers such as flax, hemp, sisal, coconut or miscanthus fibers.

Preferably, the non-starchy non-biodegradable polymer is chosen from ethylene-vinyl acetate copolymers (EVA), polyethylenes (PE) and polypropylenes (PP), polyethylenes (PE) and polypropylenes (PP) functionalized with silane units, acrylic or maleic anhydride, thermoplastic polyurethanes (TPU), styrene-ethylene-butylene-styrene block copolymers (SEBS) functionalized with maleic anhydride units, synthetic polymers obtained from biosourced monomers and extraction polymers of natural resources (secretion or extracts of plants, tissues animals and microorganisms), modified or functionalized, and mixtures thereof.

Particularly preferred examples of non-starchable, non-biodegradable polymers that can be used in the present invention are polyethylenes.

(PE) and polypropylenes (PP), preferably functionalized, thermoplastic polyurethanes, polyamides, styrene-ethylene / butylene-styrene triblock block copolymers (SEBS) and amorphous poly (ethylene terephthalate) (PETG).

Advantageously, the non-biodegradable non-starchy polymer has a weight average molecular weight of between 8500 and 10,000,000 daltons, in particular between 15,000 and 1,000,000 daltons. The starch composition according to the invention may also comprise various other additional products. It may be products intended to improve its physico-chemical properties, in particular its implementation behavior and its durability or its mechanical, thermal, conductive, adhesive or organoleptic properties.

The additional product may be an improving or adjusting agent for the mechanical or thermal properties chosen from minerals, salts and organic substances, in particular from nucleating agents such as talc, compatibilizing agents such as surfactants, impact or scratch-resistant improvers such as calcium silicate, shrinkage control agents such as magnesium silicate, scavengers or deactivators of water, acids, catalysts, metals, oxygen , infra-red rays, UV rays, hydrophobic agents such as oils and fats, hygroscopic agents such as pentaerythritol, flame retardants and fireproofing agents, such as halogenated derivatives, anti-smoke agents, reinforcing fillers, mineral or organic, such as clays, carbon black, talc, vegetable fibers, glass fibers , polyacrylonitrile or Kevlar.

The additional product may also be an improving agent or an adjustment of the conductive or insulating properties with respect to electricity or heat, for example sealing against air, water or gases. , to solvents, to fatty substances, to essences, to aromas, to perfumes, chosen in particular from minerals, salts and organic substances, in particular from nucleating agents such as talc, compatibilizing agents such as surfactants, agents trapping or deactivating water, acids, catalysts, metals, oxygen or infrared radiation, hydrophobic agents such as oils and fats, pearling agents, hygroscopic agents such as pentaerythritol, heat conduction or dissipation agents such as metal powders, graphites and salts, and micrometric reinforcing fillers such as clays and carbon black.

The additional product may be an agent that improves the organoleptic properties, in particular:

- odorant properties (perfumes or odor masking agents), optical properties (glossing agents, whitening agents such as titanium dioxide, dyes, pigments, dye enhancers, opacifiers, matting agents such as carbonate calcium, thermochromic agents, phosporescence and fluorescence agents, metallizing or marbling agents and anti-fogging agents), sound properties (barium sulphate and barytes), and

- tactile properties (fat).

The additional product may also be an enhancing or adjusting agent for adhesive properties, including adhesion to cellulosic materials such as paper or wood, metal materials such as aluminum and steel, glass or ceramic materials, textiles and mineral materials, such as pine resins, rosin, ethylene / vinyl alcohol copolymers, fatty amines, lubricating agents, mold release agents, antistatic agents and anti-blocking agents. Finally, the additional product may be an agent improving the durability of the material or an agent for controlling its (bio) degradability, especially chosen from hydrophobing agents such as oils and greases, anti-corrosion agents, antimicrobial agents such as Ag, Cu and Zn, degradation catalysts such as oxo-catalysts and enzymes such as amylases.

The incorporation of the binding agent into the thermoplastic composition and the reaction with the starch and / or the functional polymer is preferably carried out by hot kneading at a temperature of between 60 ^° C. and 200 ^° C., and better still 100 to 160 ^° C.

Preferably, the thermomechanical mixture of the soluble starch and the optional plasticizer is made hot, at a temperature preferably between 60 and 200 ⁰ C, more preferably between 100 and 160 ⁰ C, discontinuously, for example by kneading mixing, or continuously, for example by extrusion. The duration of this mixture can be of some seconds to a few hours, depending on the mix mode selected.

Similarly, the incorporation, during step (ii) or step (iii), of the non-starchy polymer or of the binding agent in the composition may be carried out by thermomechanical mixing, batchwise or continuously and in particular online, by reactive extrusion. In this case, the mixing time can be short, from a few seconds to a few minutes.

As explained above, the invention relates both to the starch-based composition obtainable by the process before reaction by heating and the thermoplastic composition that can be obtained after reaction by heating.

Of course, the most interesting properties of the thermoplastic compositions of the present invention are those of the compositions obtained after heating to a temperature sufficient to react the binding agent with the starch and / or with the non-starchy polymer.

The Applicant has found that the thermoplastic starch compositions according to the invention have a lower sensitivity to water than the plasticized starches of the prior art. The latter, which are very sensitive to water, must necessarily be cooled in the air, which requires a lot more time than cooling with water. Moreover, this characteristic of water stability opens many new potential uses for the thermoplastic starchy composition according to the invention.

The composition according to the invention is thermoplastic in the sense defined above and therefore advantageously has a complex viscosity, measured on rheometer PHYSICA type MCR 501 or equivalent, between 10 and 10 ⁶ Pa. s, for a temperature between 100 and 200 ⁰ C. For injection uses for example, its viscosity at these temperatures can be rather low and the composition is then preferentially heat fusible in the sense specified above.

These thermoplastic compositions according to the invention have the advantage of being sparingly soluble, preferably insoluble in water, of hydrating with difficulty and of maintaining a good physical integrity after immersion in water. Their insoluble content after 24 hours in water at 20 ^° C., is preferably greater than 72%, in particular greater than 80%, more preferably greater than 90%. Very advantageously, it may be greater than 92%, especially greater than 95%. Ideally, this level of insolubles can be at least 98% and in particular be close to 100%.

Moreover, the degree of swelling of the thermoplastic compositions according to the invention, after immersion in water at 20 ^° C. for a period of 24 hours, is preferably less than 20%, in particular less than 12%, more preferably less than at 6%. Very advantageously, it may be less than 5%, especially less than 3%. Ideally, this swelling rate is at most equal to 2% and may especially be close to 0%.

In contrast to the compositions with high levels of thermoplastic starch of the prior art, the thermoplastic composition according to the invention advantageously has stress / strain curves characteristic of a ductile material, and not of a fragile type material. The elongation at break, measured for the compositions of the present invention, is greater than 40%, preferably greater than 80%, more preferably greater than 100%. This elongation at break can advantageously be at least 95%, especially at least equal to 120%. It can even reach or exceed 180% or even 250%. It is generally reasonably less than 500%.

The maximum tensile strength of the compositions of the present invention is generally greater than 4 MPa, preferably greater than 6 MPa, more preferably greater than 10 MPa. It can even reach or exceed 15 MPa, even 20 MPa. It is generally reasonably less than 80 MPa.

The thermoplastic composition of the present invention also has the advantage of being essentially renewable raw materials

(soluble starch) and having, after formulation adjustment, the following properties, useful in many applications in plastics or other fields: - suitable thermoplasticity, melt viscosity and glass transition temperature, in the usual ranges of known values of current polymers (Tg of -50 ° to 150 ^° C.), allowing an implementation thanks to the existing industrial installations and conventionally used for the usual synthetic polymers,

- sufficient miscibility with a wide variety of polymers of fossil origin or of renewable origin on the market or in development, - satisfactory physicochemical stability under the conditions of implementation,

- low sensitivity to water and water vapor,

- mechanical performance significantly improved compared to the thermoplastic compositions of starch the prior art (flexibility, elongation at break, maximum breaking stress)

- good barrier effect to water, water vapor, oxygen, carbon dioxide, UV, fats, aromas, essences, fuels,

- opacity, translucency or transparency adjustable according to the uses,

good printability and ability to be painted, in particular with water-based inks and paints,

- controllable removal,

- stability over time,

- adjustable recyclability.

In a very remarkable manner, the starch-based thermoplastic composition according to the invention can, in particular, present simultaneously:

an insoluble level of at least 98%,

an elongation at break of at least 100%, preferably at least 200%, and a maximum tensile strength greater than

10 MPa.

The thermoplastic composition according to the invention can be used as is or in admixture with synthetic, artificial or naturally occurring polymers, which may or may not be biodegradable.

The composition according to the invention is preferably non-biodegradable or non-compostable in the sense of the standards EN 13432, ASTM D6400 and ASTM 6868, and then comprises, for example, known synthetic polymers or highly functionalized starches or extraction polymers. crosslinked or etherified. It is possible to modulate the lifetime and the stability of the composition according to the invention by adjusting in particular its affinity for water, so as to suit the intended uses as material and the methods of recovery considered at the end of life.

The composition according to the invention usually contains at least 33%, preferably at least 50%, in particular at least 60%, more preferably at least 70%, or more than 80% of renewable carbon in the sense of ASTM D6852 relative to the total carbon of the composition. This carbon of renewable origin is essentially that constitutive of the starch necessarily present in the composition according to the invention but can also be advantageously, by a judicious choice of the constituents of the composition, that present in the plasticizer of the starch as in the case for example glycerol or sorbitol, but also that present in the non-starch polymer (s) or any other constituent of the thermoplastic composition, when they come from renewable natural resources such as those defined preferentially above. It is in particular conceivable to use the thermoplastic compositions based on starch according to the invention, as barrier films for oxygen, carbon dioxide, flavorings, fuels and / or fats, alone or in multilayer structures obtained by coextrusion for the field of food packaging in particular.

The compositions of the present invention can also be used to increase the hydrophilicity, electrical conductivity, permeability to water and / or water vapor or resistance to organic solvents and / or fuels, synthetic polymers in the context of, for example, the manufacture of membranes, films or printable electronic labels, textile fibers, containers or reservoirs, or to improve the adhesive properties of synthetic hot melt films on hydrophilic supports.

It should be noted that the hydrophilic character of the thermoplastic composition according to the invention considerably reduces the risk of bioaccumulation in the adipose tissue of living organisms and therefore also in the food chain.

The composition according to the invention may be in pulverulent, granular or bead form and form the matrix of a dilutable masterbatch in a bio-sourced matrix or not.

The invention also relates to a plastic or elastomeric material comprising the thermoplastic composition of the present invention or a finished or semi-finished product obtained therefrom.

EXAMPLES

Comparison of starch compositions based on water-soluble maltodextrins according to the prior art (without binding agent) and according to the invention (with binding agent)

For these examples, the following are used: as soluble starches, various maltodextrins marketed by the Applicant under the brand name GLUCIDEX 1, GLUCIDEX 2, GLUCIDEX 6, GLUCIDEX 12 and GLUCIDEX 19, having a water content of about 4%. These maltodextrins have a fraction soluble in water at 20 ⁰ C close to 100%; as a non-biodegradable non-starchy polymer, a thermoplastic polyurethane (TPU) marketed by LUBRISOL under the name ESTANE 58300, and and as a linking agent, methylene diphenyl diisocyanate (MDI) sold under the name Suprasec 1400 by the company Hunstman.

A TSA twin-screw extruder (diameter (D) 26 mm, length 56D) is fed with a 50/50 maltodextrin (undried) / TPU mixture at a total material flow rate of 15 kg / h.

The extrusion conditions are as follows: - Temperature profile (ten heating zones Zl to

ZlO): 160 ⁰ C

- Screw speed: 400 rpm.

At the extruder outlet, it is found, in all cases, that the compositions obtained under these conditions are weakly hydrophilic and can be cooled in a cold water tank although they then become slightly tacky on the surface.

To eliminate this stickiness on the surface, extruded and cooled rods are dried at 80 ⁰ C in a vacuum oven for 24 hours and then granulated.

These granular starchy compositions are subjected to a second extrusion, under the same conditions as above,

in the absence of a binding agent (comparative compositions),

or in the presence of 1 part of MDI per 100 parts of granules (phr) (compositions according to the invention).

Water stability tests: Tests are carried out to measure the water and moisture sensitivity of these same compositions. These tests make it possible to evaluate fairly precisely the hydrophilic or hydrophobic nature of the compositions thus prepared. Water recovery rate:

The rate of water uptake is determined by measuring the mass of the comparative compositions and compositions according to the invention above, after one month of storage, before drying (M _h ) and after drying under vacuum at 80 ^° C. for 24 hours. (M _s ). Humidity rate

(expressed as a percentage) is calculated according to the following formula:

Moisture content (%) = (1-M _s / M _h ) x 100. Insoluble levels and swelling rate:

The level of insolubles and the degree of swelling in water of the compositions obtained according to the following protocol are determined:

(i) Dry the sample to be characterized (12 hours at 80 ^° C. under vacuum)

(ii) Measure the mass of the sample (= MsI) with a precision scale.

(iii) Immerse the sample in water at 20 ^° C. (volume of water in ml equal to 100 times the mass in g of sample). (iv) Take the sample after a defined time of several hours.

(v) Remove excess surface water with absorbent paper as soon as possible.

(vi) Place the sample on a precision scale and follow the loss of mass for 2 minutes (measure the mass every 20 seconds)

(vii) Determine the mass of the inflated sample by graphical representation of the previous measurements taken as a function of time and extrapolation to t = 0 of the mass (= Mg).

(viii) Dry the sample (for 24 hours at 80 ° C under vacuum). Measure the mass of the dry sample (= Ms2)

(ix) Calculate the insoluble content, expressed in percent, according to the formula Ms2 / Msl. (x) Calculate the swelling rate, in percent, according to the formula (Mg-MsI) / MsI.

The results obtained are summarized in Table 1 below.

Table 1:

Moisture uptake rate and insoluble levels measured for GLUCIDEX® / TPU 58300 compositions

It is found that the compositions according to the invention GLUCIDEX / TPU 58300 containing 1 phr of MDI (results in bold) are practically insoluble in water (levels of insoluble greater than 95%) and hydrophobic, whereas compositions according to prior art, free of MDI, are very hydrophilic and disintegrate.

Mechanical properties: The tensile mechanical characteristics of the various samples are determined according to standard NF T51-034 (Determination of tensile properties) using a Lloyd Instrument LR5K test bench, a tensile speed of 300 mm / min and specimens. normalized type H2. Table 2: Stress and elongation at break of the compositions GLUCIDEX ^® / TPU 58300

These results show that the use of a difunctional linker (MDI) results in an increase in breaking stress of about 50% compared to the corresponding MDI-free compositions. The elongations at break of all compositions prepared in the presence of MDI are greater than 200%. These values are equivalent to those obtained with low density polyethylenes.

The mass spectrometric analysis has furthermore shown that the compositions thus prepared in accordance with the invention using a binding agent (MDI) contain specific entities attesting to the binding of starchy chains to each other. contained in the maltodextrin used and this via the binding agent.

The use of the maltodextrins Glucidex 12 and Glucidex 19 gives starchy compositions having particularly advantageous mechanical properties. These two maltodextrins have weight average molecular weights between 800 and 1600, lower than the other three dextrins, which are between 3000 and 20,000. These results clearly show the very beneficial effect of the use of a binding agent in the preparation of a thermoplastic composition based on soluble starchy material such as maltodextrin, in terms of improving the stability of the moisture and water and improvement of mechanical properties.

Claims

A starch composition comprising:

(a) at least 45%, preferably at least 49% by weight of at least one soluble starch,

(b) at most 55%, preferably at most 51% by weight of at least one non-biodegradable non-starchy polymer, and

(c) a binding agent carrying at least two functional groups capable of reacting with molecules carrying active hydrogen functions, these amounts being expressed as solids and based on the sum of (a) and (b).

2. Composition according to claim 1, characterized in that the soluble starch is obtained by physical treatment, chemical or enzymatic, from a granular starch selected from native starches, the starches having undergone acid, oxidizing or enzymatic hydrolysis. , an oxidation or a chemical modification, in particular an acetylation, hydroxypropylation, cationisation, crosslinking, phosphatation, or succinylation, or the starches treated in an aqueous medium at low temperature ("annealing"), and the mixtures these starches.

3. Composition according to claims 1 or 2, characterized in that the soluble starch is obtained from a granular starch selected from fluidized starches, oxidized starches, physicochemically modified starches, white dextrins and mixtures of these starches.

4. Composition according to any one of the preceding claims, characterized in that the soluble starch is chosen from pre-gelatinized starches, highly-processed dextrins, maltodextrins, highly functionalized starches and mixtures of these starches.

5. Composition according to any one of the preceding claims, characterized in that the soluble starch (a) is partially replaced by a plasticized starchy composition, consisting of starch and a plasticizer thereof, and obtained by mixing thermomechanical process of a granular starch selected from native starches, fluidized starches, oxidized starches, chemically modified starches, white dextrins and mixtures of these starches and a plasticizer of this granular starch.

6. Composition according to any one of the preceding claims, characterized in that it further comprises a plasticizer selected from glycerol, polyglycerols, isosorbide, sorbitans, sorbitol, mannitol, hydrogenated glucose syrups. sodium lactate, methyl, ethyl or fatty esters of organic acids such as lactic, citric, succinic, adipic or glutaric acids or the acetic or fatty esters of monoalcohols, diols, triols or polyols such as ethanol, diethylene glycol, glycerol or sorbitol and mixtures thereof.

7. Composition according to any one of the preceding claims, characterized in that the weight ratio of the plasticizer to the soluble starch is between 1/100 and 150/100, preferably between 5/100 and 120/100. 8. Composition according to any one of the preceding claims, characterized in that the amount of soluble starch (a), expressed as solids and relative to the sum of (a) and (b), is between 51% and 99

8% by weight, preferably between 55% and 99.5% by weight, and in particular between 60% and 99% by weight.

9. Composition according to any one of the preceding claims, characterized in that the binding agent is chosen from compounds carrying at least two functions, free or masked, identical or different, chosen from isocyanate functions, carbamoylcaprolactam, epoxide, halo, protonic acid, acid anhydride, acyl halide, oxychloride, trimetaphosphate, alkoxysilane and mixtures thereof.

10. Composition according to Claim 9, characterized in that the binding agent is chosen from the following compounds: - diisocyanates and polyisocyanates, preferably 4,4'-dicyclohexylmethane diisocyanate (H12MDI), methylenediphenyl diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HMDI) and lysine diisocyanate (LDI), dicarbamoyl caprolactams, preferably 1,1'-carbonyl- caprolactam,

diepoxides,

compounds comprising an epoxide functional group and a halogen functional group, preferably epichlorohydrin, organic diacids, preferably succinic acid, adipic acid, glutaric acid, oxalic acid, malonic acid, maleic acid and the corresponding anhydrides, the oxychlorides, preferably phosphorus oxychloride,

trimetaphosphates, preferably sodium trimetaphoshate,

alkoxysilanes, preferably tetraethoxysilane, and mixtures of these compounds.

11. Composition according to Claim 10, characterized in that the binding agent is a diisocyanate, preferably methylenediphenyl diisocyanate.

12. Composition according to any one of the preceding claims, characterized in that the amount of binding agent, expressed as solids and based on the sum of (a) and (b), is between 0.1 and 15. % by weight, preferably between 0.1 and 12% by weight, more preferably between 0.2 and 9% by weight and in particular between 0.5 and 5% by weight.

13. Composition according to any one of the preceding claims, characterized in that the non-starchy non-biodegradable polymer is selected from ethylene-vinyl acetate copolymers (EVA), polyethylenes (PE) and polypropylenes (PP), polyethylenes ( PE) and polypropylenes (PP) functionalized with silane units, acrylic units or maleic anhydride units, thermoplastic polyurethanes (TPU), styrene-ethylene / butylene-styrene copolymers (SEBS) functionalized with maleic anhydride units, polymers non-biodegradable synthetic syntheses obtained by using bio-source monomers and modified or functionalized natural resource extraction polymers, as well as mixtures of these polymers.

14. Composition according to any one of the preceding claims, characterized in that it contains at least 33% of carbon of renewable origin within the meaning of ASTM D6852.

Process for the preparation of a starch composition according to any one of the claims preceding, characterized in that it comprises the following steps:

(i) selecting at least one soluble starch (a),

(ii) incorporation in this soluble starch (a) of a non-biodegradable non-starchy polymer (b) in an amount such that the soluble starch (a) is at least 45% by weight and the non-starchy non-biodegradable polymer (b) represents not more than 55% by weight, these quantities being expressed as solids and referred to the sum of (a) and (b), and

(iii) incorporation into the composition thus obtained of at least one linking agent carrying at least two functional groups capable of reacting with molecules carrying active hydrogen functional groups, step (ii) being able to be implemented before, during or after step (iii).

16. The method of claim 15, characterized in that it further comprises drying the composition obtained in step (ii), before the incorporation of the binding agent, to a rate of residual moisture less than 5%, preferably less than 1%, in particular less than 0.1% by weight.

A process for preparing a thermoplastic composition comprising heating a starch composition according to any one of claims 1 to 14 to a temperature sufficient and for a time sufficient to react with the agent. binding with the soluble starch (a) and / or the non-biodegradable non-starchy polymer (b).

18. Thermoplastic composition obtainable according to the method of claim 17.

19. Thermoplastic composition according to claim 18, characterized in that it has a elongation at break greater than 40%, preferably greater than 80% and in particular greater than 100%.

20. Thermoplastic composition according to claim 18 or 19, characterized in that it has a maximum tensile strength greater than 4 MPa, preferably greater than 6 MPa and in particular greater than 10 MPa.

21. Thermoplastic composition according to any one of claims 18 to 20, characterized in that it has a level of insoluble, after 24 hours of immersion in water at 20 ⁰ C, at least 90 % by weight, preferably at least 95% by weight, and in particular at least 98% by weight.

22. Thermoplastic composition according to any one of claims 18 to 21, characterized in that it has, after immersion in water at 20 ⁰ C for 24 hours, a swelling rate of less than 20%, preferably less than 20%. 12%, better still less than 6%.

23. Thermoplastic composition according to any one of claims 18 to 22, characterized in that it has:

an insoluble level of at least 98%,

an elongation at break of at least 100%, and

a maximum stress at break greater than 10 MPa.

24. Thermoplastic composition according to any one of claims 18 to 23, characterized in that it is non-biodegradable or non-compostable in accordance with EN 13432, ASTM D6400 and ASTM 6868.

Thermoplastic composition according to one of Claims 18 to 24, characterized in that it contains at least 33% renewable carbon as defined in ASTM D6852.