FR2993273A1 - STARCH-BASED THERMOPLASTIC COMPOSITION COMPRISING A FUNCTIONALIZED POLYETHYLENE WAX - Google Patents

Abstract

The invention relates to a thermoplastic composition comprising: at least one starch; . at least one plasticizer of the starch; . and at least one functional polyolefin; in which the functional polyolefin is a functional polyolefin mixture comprising a functionalized polyethylene comprising at least one functional compound carrying at least one polar function and a functionalized polyethylene wax comprising at least one functional compound carrying at least one polar function. This composition with improved properties allows in particular the manufacture of films.

Description

Field of the invention The invention relates to a composition based on polyolefin and thermoplastic starch with improved properties. This composition can be advantageously used for the manufacture of all types of articles, especially films. State of the art The development of plastics derived from renewable resources in the short term has become an economic imperative, in the face of the depletion and rising prices of fossil fuels such as oil. In addition, these plastics are often incinerated at the end of their life, which implies a release of carbon dioxide that was previously stored as fossil carbon. It has been shown by the scientific community that the carbon dioxide emitted contributes significantly to the global warming observed in recent decades. In the field of packaging, these phenomena are particularly important because this field uses large quantities of plastic material, and the packaging is rarely recycled at the end of its life and is generally incinerated. Most of these packages are currently made from polyolefins, such as polyethylene or polypropylene. Some of these polyolefins have rheological properties which allow them to be converted, at relatively low temperature for thermoplastic polymers, into monolayer or multilayer films. The films thus obtained have very interesting properties of permeability and mechanical strength, and this in particular for the manufacture of film and packaging bag. However, a disadvantage of these polyolefins is that they are currently obtained for the most part by polymerization of olefins of petrochemical origin. It is therefore necessary to develop plastics that can be developed from renewable resources, called "biobased", in order to reduce the quantities of plastics obtained from petroleum.

Thus, it has been proposed in recent years to develop polyesters which have a shaping temperature close to that of polyolefins, such as polybutylene succinate, and whose mechanical properties of the films are also similar. However, these polymers are biodegradable, which makes their use in some applications impossible, especially applications where the life of the product must be important. In addition, the price of these polymers is currently significantly higher than that of polyolefins. One of the solutions envisaged is to manufacture compositions based on thermoplastic starch, which consists of starch and plasticizer of this starch such as glycerol. Indeed, the manufacture of these compositions is advantageous because starch is one of the biobased polymers which is naturally the most widespread in the environment. However, these thermoplastic starches have insufficient properties, especially in terms of water resistance.

To counteract these drawbacks, compositions based on polyolefin and plasticized starch have been developed. In these compositions, the thermoplastic starch phase is dispersed in the polyolefin phase. These compositions have numerous advantages, such as, for example, being at least partially biobased and having a very improved resistance to water relative to thermoplastic starch. However, in these compositions, polyolefins naturally have poor compatibility with thermoplastic starch. These compositions therefore very generally also comprise a functional polyolefin for improving the compatibility between the two phases. In particular, compositions which can be used for the production of films have been described in document EP 554939, which relates to a composition having particular dynamic G 'and dissipative G' modules, comprising polyethylene, thermoplastic starch and a functional polyolefin selected from a polyethylene grafted with maleic anhydride and a copolymer of ethylene comprising ethylene and maleic anhydride US Patent 5314934 relates to a composition, useful for the manufacture of films, this composition being based on thermoplastic starch, polyolefin which is preferably high density polyethylene, and further comprising a functional polyolefin which is an ethylene-acrylate-maleic anhydride terpolymer, WO 2010012041 describes compositions which can be used to make films, including very low density polyethylene, starch thermoplastic and a functional polyolefin which is an ethylene acrylic acid copolymer. In the document by Bikiaris et al., LDPE / Starch blends compatibilized with PE-gMA copolymers, Journal of Applied Polymer Science, 1998, Vol.70, Pages 1503-1521 have also been described various compositions comprising low density polyethylene, polyethylene grafted with maleic anhydride and thermoplastic starch.

WO 2009022195 A1 discloses a composition comprising a polyolefin, thermoplastic starch and a functional polyolefin. The functional polyolefin may be a polyethylene grafted with maleic anhydride, a polypropylene grafted with maleic anhydride or a polybutene grafted with maleic anhydride.

Despite these improved properties compared to compositions not comprising functional polyolefin, these compositions have at least one of the following disadvantages. Some of these compositions are difficult to transform by known techniques because they are too viscous. In addition, the water resistance of the compositions may be insufficient, which limits the scope of application, for example for indoor use. Some of these compositions may comprise amounts of thermoplastic starch, and therefore of biobased material, quite limited.

On the other hand, another problem is that the compositions may have poor mechanical properties. Indeed, these compositions are generally fragile and not very deformable. This is particularly disadvantageous for films since their insufficient tear strength prevents them from being used in many applications. In addition, although filmable, these compositions can not be easily used in extrusion blowing of sheath, or even extrusion of flat die films (English cast extrusion). Indeed, using these compositions, we can observe many holes (also called "tears") in the films obtained. It can also be noted that the film obtained generally has aesthetic defects, including the presence of gels. These phenomena are exacerbated when the composition is converted into a film with a conversion machine using high industrial rates. Another disadvantage is that these compositions are not always suitable for the manufacture of multilayer films.

The Applicant has therefore conducted research to solve these problems and found a composition to solve at least one of the drawbacks mentioned above.

SUMMARY OF THE INVENTION The subject of the invention is thus a thermoplastic composition comprising: at least one starch; at least one plasticizer for the starch; at least one functional polyolefin mixture; said mixture comprising a functionalized polyethylene comprising at least one functional compound carrying at least one polar function and a functionalized polyethylene wax comprising at least one functional compound carrying at least one polar function.

Without being bound by any theory, the Applicant explains these best properties by the fact that this particular mixture of functional polyolefins binds very well with the thermoplastic starch within the thermoplastic composition, and this although the chemical nature of the mixture of functional polyolefins is very different from that of the starch or the plasticizer of the starch. It follows that the composition has improved mechanical properties. Moreover, this composition can be advantageously used for the manufacture of films, since it is particularly well filmable, including on film shaping machines such as extruders jacket blowing, or even flat-film extruders .

The functionalized polyethylene or the functionalized polyethylene wax can be obtained by different methods, either by polymerization of the functional compound with ethylene or by grafting the functional compound, respectively on a polyethylene or a polyethylene wax.

Functional compounds of functionalized polyethylene and functionalized polyethylene wax preferably have, before polymerization or grafting, a dipole moment greater than 1, preferably greater than 2, most preferably greater than 3 Debyes.

Advantageously, the functional polyolefin mixture is a mixture of functionalized polyethylene obtained by grafting at least one functional compound carrying at least one polar function and a functionalized polyethylene wax obtained by grafting at least one carrier functional compound. at least one polar function. Preferably, the mixture of functional polyolefins is obtained by cografting a mixture of polyethylene and a polyethylene wax with a functional compound carrying at least one polar function. The functional polyolefin mixture may comprise, based on the weight of functional polyolefins: from 60 to 99% functionalized polyethylene; from 1 to 40% of functionalized polyethylene wax. Advantageously, the mixture of functional polyolefins comprises, based on the weight of functional polyolefins: from 70 to 96% of functionalized polyethylene; from 4 to 30% of functionalized polyethylene wax. Preferably, the mixture of functional polyolefins comprises, relative to the weight of functional polyolefins: from 80 to 95% of functionalized polyethylene; from 5 to 20% of functionalized polyethylene wax. According to an advantageous variant, the composition according to the invention further comprises at least one additional polyethylene having a density of between 0.865 and 0.935.

This additional polyethylene that may be present may be chosen from very low density polyethylene, low density polyethylene, linear low density polyethylene or a mixture of these polymers. Preferably, this additional polyethylene has a density of between 0.890 and 0.935, most preferably between 0.910 and 0.935. The plasticizer of the starch may be chosen from glycerol, sorbitol, mannitol, maltitol, oligomers of these polyols, polyethylene glycol, urea or a mixture of these plasticizers.

Advantageously, the composition comprises, with respect to its total mass, from 5 to 90% of the functional polyolefin mixture, advantageously from 10 to 30%. Advantageously, the composition additionally comprises between 0 and 20% of optional constituent other than starch, the plasticizer of the starch, the mixture of functional polyolefins and the optional additional polyethylene, this optional constituent being able to be chosen from polymers and additives. According to one variant, the composition comprises, relative to its total mass: from 5 to 40% of starch, advantageously from 8 to 35%; from 5 to 40% of plasticizer, advantageously from 8 to 30%; from 5 to 90% of functional polyolefin mixture, advantageously from 10 to 30%; optionally between 0 and 85% of polyethylene, for example between 5 and 80%, advantageously from 20 to 60%; optionally between 0 and 20% of an additive; the sum of the constituents making 100%. The composition may also comprise, as an optional component, an additive acting as a starch binding agent, the plasticizer and / or the functional polyolefin blend. This linking agent may be chosen from compounds bearing at least two free or masked functions, which are identical or different, chosen from isocyanate functions, carbamoylcaprolactams, aldehydes, epoxides, halogen, protonic acids, acid anhydrides, halides of acyl, oxychlorides, trimetaphosphates, alkoxysilanes and combinations thereof.

This binding agent makes it possible to further improve the mechanical properties and the shaping of the composition in the form of a film. The functional compound included in the functionalized polyethylene or functionalized polyethylene wax may be polymerized or grafted. This functional compound carries a polar function and preferably comprises at least one carbon-carbon double bond. Functional compounds of functionalized polyethylene and functionalized polyethylene wax are preferably chosen from unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids, unsaturated oxiranes, unsaturated silanes and mixtures thereof, preferably maleic anhydride. Advantageously, the mixture of functional polyolefins comprises, relative to its total weight, from 0.1 to 5% by weight of functional compounds, advantageously from 0.5 to 2% by weight.

The functional polyolefin blend can have a density of from 0.855 to 0.950, e.g. from 0.890 to 0.920. The functionalized polyethylene wax may have a number-average molecular weight ranging from 500 to 10,000 g / mol, for example from 800 to 6,000 g / mol. Advantageously, the functionalized polyethylene wax has a fluidity greater than 100, for example greater than 200, preferably greater than 400 cm3 / 10min (ASTM D 1238, 190 ° C., 2.16 kg). The functionalized polyethylene has a number-average molar mass greater than that of the functionalized polyethylene wax, for example greater than 10,000 g / mol, typically ranging from 11,000 to 10,000,000 g / mol, for example from 20,000 g / mol to 300,000 g / mol. mol. The fluidity of the functionalized polyethylene is advantageously from 0.1 to 90, for example from 0.5 to 50 cm3 / 10min (ASTM D 1238, 190 ° C., 2.16 kg).

When the morphology of the composition according to the invention is observed, for example by scanning electron microscopy, this composition is generally in the form of dispersions of thermoplastic starch domains in a continuous phase of polyolefin. Advantageously, at least 90% by number of the plasticized starch domains have a size of less than 11 μm, preferably less than 0.8 μm.

Another subject of the invention relates to a film comprising the composition according to the invention. Indeed, as explained above, the composition according to the invention has a very good filmability and the properties of the films obtained, in particular its mechanical and appearance properties, are excellent.

The properties of said composition allow it to be advantageously used for the manufacture of monolayer or multilayer films. The composition according to the invention can be manufactured very simply, for example by a process comprising at least one step of mixing in the molten or softened state of the various constituents and a step of recovering the composition. It is specified that the various variants of the invention presented above and below are of course combinable with each other.

The invention relates to a thermoplastic composition comprising: at least one starch; at least one plasticizer for the starch; at least one functional polyolefin mixture as defined above. A thermoplastic composition is a composition that reversibly softens under the action of heat and hardens on cooling to room temperature. It has at least one 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 -150 ° C to 30 ° C. This starch-based composition can, of course, be shaped by the processes traditionally used in plastics, such as extrusion, injection, molding, blowing and calendering. Its viscosity, measured at a temperature of 100 ° C. to 200 ° C., is generally between 10 and 106 Pa.s.

The starch included in the composition may be of any type. If it is desired to obtain a composition of lower cost, the starch preferentially used for the manufacture of the composition is a granular starch, preferably a native starch. The term "granular starch" is used herein to mean a starch which is native or physically modified, chemically or enzymatically, and which has retained, within the starch granules, a semicrystalline structure similar to that evidenced in starch grains. naturally occurring in reserve organs and tissues of higher plants, particularly in cereal grains, legume seeds, potato or cassava tubers, roots, bulbs, stems and fruits. In the native state, the starch grains have a degree of crystallinity which varies from 15 to 45%, and which depends essentially on the botanical origin of the starch and the possible treatment that it has undergone. Granular starch, placed under polarized light, has a characteristic black cross, so-called Maltese cross, typical of the granular state.

According to the invention, the granular starch can come from all botanical origins, including a granular starch rich in amylose or conversely, rich in amylopectin (waxy). It may be starch native to cereals such as wheat, maize, barley, triticale, sorghum or rice, tubers such as potato or cassava, or legumes such as peas and soybeans, and mixtures of such starches. According to one variant, the granular starch is an acid hydrolyzed, oxidizing or enzymatic starch, or an oxidized starch. It can be a starch commonly called fluidized starch or a white dextrin. According to another variant, it may also be a starch modified physico-chemically but having essentially retained the structure of the native starch starting, such as in particular esterified and / or etherified starches, in particular modified by acetylation , hydroxypropylation, cationization, crosslinking, phosphatation, or succinylation, or starches treated in aqueous medium at low temperature (in English "annealing"). Preferably, the granular starch is a native, hydrolysed, oxidized or modified starch, in particular corn, wheat or pea.

Granular starch generally has a degree of soluble at 20 ° C in demineralized water, less than 5% by weight. It is preferably almost insoluble in cold water.

According to a second variant, the starch selected as starch useful in the manufacture of the composition is a water-soluble starch, which may also come from all botanical origins, including a water-soluble starch rich in amylose or conversely, rich in amylopectin (waxy). This water-soluble starch can be introduced as a partial or total replacement of the granular starch.

For the purposes of the invention, the term "water-soluble starch" means any starchy component which, at 20 ° C. and with mechanical stirring for 24 hours, has a soluble fraction in demineralized water of 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 water-soluble starch can be totally soluble in demineralized water (soluble fraction = 100%). Such water-soluble starches can be obtained by pregelatinization on a drum, by pregelatinization on an extruder, by spraying a suspension or a starch solution, by precipitation with a non-solvent, by hydrothermal cooking, by chemical functionalization or the like. It is in particular a pregelatinized, extruded or atomized starch, a highly converted dextrin (also called yellow dextrin), a maltodextrin, a functionalized starch or any mixture of these products. The pregelatinized starches may be obtained by hydrothermal treatment of gelatinization of native starches or modified starches, in particular by steam cooking, jet-cooker cooking, drum cooking, cooking in kneader / extruder systems, then drying for example. in an oven, by hot air on a fluidized bed, on a rotating drum, by atomization, by extrusion or by lyophilization. Such starches generally have a solubility in demineralized water at 20 ° C. of greater than 5% and more generally of between 10 and 100% and a starch crystallinity level of less than 15%, generally less than 5% and most often less than 1%, or even none. By way of example, mention may be made of the products manufactured and marketed by the Applicant under the brand name PREGEFLO®. Highly processed dextrins can be prepared from native or modified starches by dextrinification in a weakly acidic acid medium. 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® C 072 products manufactured and marketed by the Applicant. Such dextrins have demineralized water at 20 ° C, a solubility generally between 10 and 95% and a starch crystallinity of less than 15% and generally less than 5%. Maltodextrins can be obtained by acid, oxidative or enzymatic hydrolysis of starches in an aqueous medium. They may in particular have an equivalent dextrose (DE) of between 0.5 and 40, preferably between 0.5 and 20 and better still between 0.5 and 12. Such maltodextrins are for example manufactured and marketed by the Applicant under the trade name GLUCIDEX® and have a solubility in demineralized water at 20 ° C generally greater than 90%, or even close to 100%, and a starch crystallinity generally less than 5% and usually almost zero. The functionalized starches can be obtained from a native or modified starch. The functionalization can for example be carried out by esterification or etherification at a sufficiently high level to confer a solubility in water. Such functionalized starches have a soluble fraction as defined above, greater than 5%, preferably greater than 10%, more preferably greater than 50%. The functionalization can be obtained in particular by acetylation in aqueous phase with acetic anhydride, by reaction with mixed anhydrides, by hydroxypropylation in the glue phase, by cationization in dry phase or glue phase, by anionization in dry phase or glue phase. by phosphatation or succinylation. The water-soluble highly functionalized starches obtained may have a degree of substitution of between 0.01 and 3, and more preferably between 0.05 and 1. Preferably, the reagents for modifying or functionalizing the starch are of renewable origin. According to another advantageous variant, the water-soluble starch is a water-soluble starch of corn, wheat or peas, or a water-soluble derivative thereof. In addition, it advantageously has a low water content, generally less than 10%, preferably less than 5%, in particular less than 2.5% by weight, and ideally less than 0.5%, or even less than 0%, 2% by weight. According to a third variant, the amylaceous component selected for the preparation of the composition is an organomodified starch, preferably organosoluble, which may also come from all botanical origins, including an organomodified starch, preferably organosoluble, rich in amylose or, conversely, rich in amylopectin (waxy). This organosoluble starch may be introduced as partial or total replacement of the granular starch or of the water-soluble starch.

For the purposes of the invention, the term "organomodified starch" means any starchy component other than a granular starch or a water-soluble starch according to the definitions given above. Preferably, this organomodified starch is almost amorphous, that is to say having a starch crystallinity level of less than 5%, generally less than 1% and especially zero. It is also preferably "organosoluble", that is to say having at 20 ° C, a fraction soluble in a solvent selected from ethanol, ethyl acetate, propyl acetate, butyl acetate , diethyl carbonate, propylene carbonate, dimethyl glutarate, triethyl citrate, dibasic esters, dimethyl sulfoxide (DMSO), dimethyl isosorbide, glycerol triacetate, isosorbide diacetate, isosorbide dioleate and methyl esters of vegetable oils, at least equal to 5% by weight. This soluble fraction is preferably greater than 20% by weight and in particular greater than 50% by weight. Of course, the organosoluble starch may be totally soluble in one or more of the solvents indicated above (soluble fraction = 100%). The organomodified starch may be used according to the invention in solid form, including having a low water content, ie less than 10% by weight. It may especially be less than 5%, in particular less than 2.5% by weight and ideally less than 0.5%, or even less than 0.2% by weight.

The organomodified starch that can be used in the composition according to the invention can be prepared by functionalization of the native or modified starches such as those presented above. This functionalization can for example be carried out by esterification or etherification at a sufficiently high level to make it essentially amorphous and to confer on it an insolubility in water and preferably a solubility in one of the organic solvents above. Such functionalized starches have a soluble fraction as defined above, greater than 5%, preferably greater than 10%, more preferably greater than 50%. The functionalization can be obtained in particular by acetylation in the solvent phase with acetic anhydride, grafting, for example in the solvent phase or by reactive extrusion of acid anhydrides, mixed anhydrides, fatty acid chlorides, oligomers of caprolactones or lactides, hydroxypropylation and crosslinking in the glue phase, cationization and crosslinking in the dry phase or in the glue phase, anionization by phosphatation or succinylation, and crosslinking in the dry phase or in the glue phase, silylation, butadiene telomerization. These organomodified, preferably organosoluble, highly functionalized starches can be, in particular, acetates of starches, dextrins or maltodextrins or fatty esters of these starchy materials (starches, dextrins, maltodextrins) with fatty chains of 4 to 22 carbons, all of these products preferably having a degree of substitution (DS) between 0.5 and 3.0, preferably between 0.8 and 2.8 and in particular between 1.0 and 2.7. It may be, for example, hexanoates, octanoates, decanoates, laurates, palmitates, oleates and stearates of starch, dextrins or maltodextrins, in particular having a DS between 0 , 8 and 2.8. According to another advantageous variant, the organomodified starch is an organomodified starch of corn, wheat or peas or an organomodified derivative thereof.

The composition comprises, based on its total mass, from 5 to 40% by weight of starch. Preferably, the composition comprises from 8 to 35% starch. The composition further comprises a starch plasticizer, whose function is to destructure the starch. This plasticizer may be of any type and is advantageously chosen from glycerol, sorbitol, mannitol, maltitol, oligomers of these polyols, polyethylene glycol, urea or a mixture of these plasticizers. The plasticizer advantageously has a molar mass of less than 1000 g / mol, and in particular less than 400 g / mol / l. The plasticizer of the starch, especially when the latter is organomodified, is preferably chosen from methyl, ethyl or fatty esters of organic acids such as lactic, citric, succinic, adipic and glutaric acids and acetic esters. or fatty esters of monoalcohols, diols, triols or polyols such as ethanol, diethylene glycol, glycerol and sorbitol. By way of example, mention may be made of glycerol diacetate (diacetin), glycerol triacetate (triacetin), isosorbide diacetate, isosorbide dioctanoate, isosorbide dioleate, isosorbide dilaurate, esters of dicarboxylic acids or dibasic esters (DBE of English dibasic esters) and mixtures of these products. The plasticizer is generally present in the composition in a proportion of 1 to 150 parts by weight, preferably in a proportion of 10 to 120 parts by weight and in particular in a proportion of 25 to 120 parts by weight per 100 parts by weight of starch. The composition comprises, relative to its total mass, from 5 to 40% of at least one plasticizer of the starch. Preferably, the composition comprises from 8 to 30% of plasticizer.

The selection of the functional polyolefin mixture has allowed the Applicant to obtain a thermoplastic composition with improved properties.

The functional compound comprises a polar function. It preferably has, before polymerization or grafting, a dipole moment greater than 1, preferably greater than 2, most preferably greater than 3 Debyes. This functional compound preferably comprises at least one carbon-carbon double bond. It is preferably selected from unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids, unsaturated oxiranes and unsaturated silanes, preferentially maleic anhydride. The functional polyolefin mixture useful for the invention comprises a functionalized polyethylene and a functionalized polyethylene wax, each of which comprises a functional compound carrying at least one polar function. According to the invention, when a polymer comprises a functional compound, it means that the polymer comprises units resulting from the polymerization or grafting of a compound of this type.

The functionalized polyethylene can thus be obtained either by polymerization of the functional compound with ethylene or by grafting the functional compound onto a polyethylene. The functionalized polyethylene wax can also be obtained either by polymerization of the functional compound with ethylene or by grafting the functional compound onto a polyethylene wax. As explained above, the functionalized polyethylene wax differs mainly from functionalized polyethylene in that its molar mass is lower. As a result, the melt viscosity is also higher than that of a functionalized polyethylene.

The functional compound is capable of polymerizing with propylene or is capable of reacting by grafting a polypropylene to form a functional polyolefin useful for the invention. The functional compound carries a chemical function having a dipole moment.

The functional compound preferably comprises at least one oxygen atom. This functional compound is, for example, an unsaturated carboxylic acid anhydride, an unsaturated carboxylic acid or salts thereof, an unsaturated carboxylic acid ester, a carboxylic acid vinyl ester, an unsaturated oxirane or an unsaturated silane.

The carboxylic acid anhydride preferably comprises from 4 to 30 carbon atoms: it can be chosen, for example, from maleic, itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic anhydrides. Methylenecyclohex-4-ene-1,2-dicarboxylic acid and bicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid. The unsaturated carboxylic acid or its salts preferably comprises from 2 to 30 carbon atoms, and may in particular be chosen from acrylic acid or methacrylic acid and the salts of these same acids. The unsaturated carboxylic acid ester is advantageously chosen from alkyl acrylates or alkyl methacrylates, grouped under the term (meth) acrylates of alkyls. The alkyl groups of these (meth) acrylates can have up to 30 carbon atoms. Mention may be made, as an alkyl group, of methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl and tridecyl groups. , tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, hencosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl. As an example of a carboxylic acid vinyl ester, there may be mentioned vinyl acetate, vinyl versatate, vinyl propionate, vinyl butyrate or vinyl maleate. The unsaturated oxirane, also called unsaturated epoxide, may be chosen from aliphatic glycidyl esters and ethers such as glycidyl allyl glycidyl ether, vinyl glycidyl ether, maleate and itaconate, glycidyl acrylate and methacrylate, and the like. alicyclic glycidyl esters and ethers such as 2-cyclohexene-4,5-diglycidylcarboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene-2-methyl-2-glycidyl carboxylate and endo-cis-bicyclo (2 , 2,1) -5-heptene-2,3-diglycidyldicarboxylate. Preferably, the unsaturated oxirane is chosen from acrylate and glycidyl methacrylate. The unsaturated silane may be selected from 3-methacryloyloxypropyltrialkoxysilanes, 3-methacryloyloxypropyldialkoxyalkylsilanes, methacryloyloxymethyltrialkoxysilanes, (methacryloyloxymethyl) dialkoxysilanes, vinyldialkoxyalkylsilanes and vinyltrialkoxysilanes. Most preferably, maleic anhydride is used as a functional compound. The functional polyolefin may comprise, relative to its total mass, more than 0% and less than 20%, advantageously from 0.05% to 10%, preferentially from 0.1 to 5%, most preferably from 0.5 to 2% by weight of functional compound. The functional polyolefin has a melt volume melt index of from 120 to 155 g / 10 min (ASTM D 1238, 190 ° C, 2.16 kg). The amounts of the functional compound in the functional polyolefin can be determined by conventional methods, typically by Fourier transform infrared spectroscopy.

The functionalized polyethylene and the functionalized polyethylene wax may be obtained by grafting a polyethylene or a polyethylene wax with a functional compound, respectively.

The polyethylene and the polyethylene wax may be obtained by radical polymerization, in particular by high-pressure polymerization or catalytically, for example by Phillips, Ziegler-Natta or metallocene catalysis. Functionalized polyethylenes are sold, for example, under the brand name Bondyram® by the company Polyram, Orevac® by the company Arkema® or by Fusabond® by the company DuPontTM. Functionalized polyethylene waxes are marketed under the trademark Licocene® by the company Clariant® . The grafting of polyethylene or polyethylene wax is an operation known per se and the skilled person will adapt the following process to obtain functionalized polyethylene, functionalized polyethylene wax or functionalized polyethylene mixture and functionalized polyethylene wax useful to the invention. According to the invention, it is possible to perform the grafting of the polyethylene and the polyethylene wax separately or by co-grafting a mixture of polyethylene and a polyethylene wax, that is to say the simultaneous grafting of this mixture. The grafting reaction can be carried out according to a batch process in solution or, preferably, according to a continuous process with a melt blending tool, these processes being well known to those skilled in the art. As a melt-blending tool, it is possible to use internal mixers, cylinder mixers, single-screw, twin-screw contra or co-rotating extruders, planetary extruders, continuous co-kneaders. The grafting tool can be one of the tools mentioned above or their combination, such as for example a co-ordinator associated with a single-screw extruder, or a co-rotating twin-screw extruder associated with a pump. In the case of an extrusion, the tool preferably comprises a melting zone of the polymer, a zone of mixing and reaction between the species present and an expansion / degassing zone for eliminating the volatile compounds. The tool may be equipped with a pumping system for the melt and / or a filtration system and / or a granulation system with rushes or underwater. The polyethylene and / or the polyethylene wax are introduced in the presence of a radical generator and the functional compound in the tool, the body temperature of which is regulated, this temperature being chosen in line with the decomposition kinetics of the generator. radicals. As the radical generator for continuous grafting organic peroxides such as dialkyl peroxides, hydroperoxides or peroxyketals can be used. Preferentially, a temperature ranging from 100 to 300 ° C., more preferably from 180 to 250 ° C., is used. The polyethylene and / or polyethylene wax, the functional compound and the radical generator can be introduced simultaneously or separately into the extrusion tool. In particular, the functional compound and / or the radical generator can be introduced simultaneously with the polyethylene and / or polyethylene wax as a main feed, or separately injection along the tool. In the injection step, the functional compound and / or the radical generator may be combined with a fraction of a polyethylene grafting co-agent and / or polyethylene wax, for example styrene. This fraction of grafting co-agent of polyethylene and / or polyethylene wax is intended to facilitate and accelerate the grafting of the functional agent and thus improve the reaction yield. During a relaxation / degassing step, a vacuum is applied adapted to devolatilize volatile compounds, the vacuum level may range from a few millibars to several hundred. The polyethylene and / or the grafted polyethylene wax useful in the invention can be recovered at the outlet of the extrusion tool in the form of a granule using a granulation tool. According to a preferred variant, the composition according to the invention further comprises at least one additional polyethylene having a density of between 0.865 and 0.935.

This additional polyethylene may be chosen from very low density polyethylene, low density polyethylene, linear low density polyethylene or a mixture of these polymers. Advantageously, the density of the additional polyethylene is between 0.890 and 0.935, preferably between 0.910 and 0.935. Like the functionalized polyethylene described above, the additional polyethylene can be obtained by radical polymerization, in particular by high-pressure polymerization or catalytically, for example by Phillips, Ziegler-Natta or metallocene catalysis. The composition according to the invention may furthermore comprise, relative to its total mass, between 0 and 20% of optional constituent other than starch, the plasticizer of the starch, the mixture of functional polyolefins and any additional polyethylene. .

This optional constituent may be chosen from additives and polymers other than starch, functional polyolefin mixture and additional polyethylene. The additives, customary in the manufacture of thermoplastics, are capable of improving at least one of the final properties of the composition and / or of facilitating the method of manufacturing said composition. The usual additives may be chosen from antioxidants, stabilizers, UV absorbers, antistatic agents, optical brighteners, dyes or pigments, nucleating agents, flame retardants, lubricating agents, antiblocking agents, printing promoters, anti-electrostatic agents, release agents, anti-caking agents, antimicrobials, plasticizers, anti-fog and blowing agents. The composition may also comprise as usual additives reinforcements or fillers, for example natural plant fibers such as sawdust, wood fibers or hemp fibers.

The optional constituent may also be an additive acting as a binding agent between the starch, the plasticizer and / or the functional polyolefin, this binding agent being chosen from compounds carrying at least two functions, free or masked. , identical or different, chosen from isocyanate functions, carbamoylcaprolactams, aldehydes, epoxides, halo, protonic acids, acid anhydrides, acyl halides, oxychlorides, trimetaphosphates, alkoxysilanes and combinations thereof. Advantageously, the amount of binding agent ranges from 0.01 to 15% by weight of the composition, preferably from 0.1 to 5%. A list of these agents of connections appears in the application WO2009095618 in the name of the Applicant.

This additive can be introduced into the composition according to the manufacturing method described below. The composition according to the invention can be manufactured by conventional methods for transforming thermoplastics. These conventional methods comprise at least one step of melt blending or softening of the various constituents and a step of recovering the composition. This method can be carried out in internal mixers with blades or rotors, an external mixer, co-rotating or counter-rotating single-screw, twin-screw extruders. However, it is preferred to carry out this mixture by extrusion, in particular by using a co-rotating extruder.

The mixture of the constituents of the composition may be at a temperature ranging from 80 to 300 ° C, for example from 100 to 250 ° C.

In the case of an extruder, the various constituents of the composition can be introduced by means of introducing hoppers located along the extruder. The process described in application WO2009095618 in which the thermoplastic starch is thermomechanically mixed with the polyolefin and the functional polyolefin can be used. However, it is particularly preferred to use a method for preparing the composition comprising introducing the starch and a plasticizer thereof into a reactor containing a mixture of polyolefin and softened or fused functional polyolefins and kneading. of the mixture obtained under conditions sufficient to obtain the plasticization of the starch by the plasticizer in order to obtain the composition according to the invention. This process is described in detail in application WO2010010282 in the name of the Applicant. The process for preparing the composition preferably comprises a step of removing volatiles such as water, for example using a vacuum pump.

The composition thus obtained can be used as it is, or can be subsequently mixed with other constituents before use. The composition thus obtained advantageously has a melt flow volume index (MVR) (190 ° C., 10 kg) advantageously from 1 to 50 cm3 / 10 min, advantageously from 2 to 30 cm3 / 10 min. In general, the invention also relates to an article comprising said thermoplastic composition.

This article can be of any type of object, in particular a film, a sheet, a tray, a bottle, a bottle, a tank, a pocket, a tube, a pipe, a bucket, a box, a dashboard, a tool handle, a door handle or a carpet. These articles can be manufactured by conventional thermoplastic processing methods. It can thus be films obtained by extrusion-inflation or by extrusion on a flat die, molded parts, profiles obtained by extrusion, injected parts, parts obtained by thermoforming or rotational molding. The articles according to the invention may also include articles comprising a multilayer structure and wherein at least one of the layers comprises the composition according to the invention.

The other layer (s) of the structure according to the invention may comprise at least one layer based on metal or organic polymer. It is specified that the term "based on" means that the layer comprises at least 10% by weight of said constituent (metal or organic polymer). Preferably, the organic polymer-based layer comprises at least 50% by weight of organic polymer, preferably at least 70%, in particular at least 90% of organic polymer. As organic polymers, mention may be made of: Homopolymers and copolymers of ethylene (PE) such as high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LDPE), ethylene-co-vinyl acetate copolymer (EVA), ethylene-alkyl coacrylate copolymers, ethylene-co-alkyl methacrylate copolymers, ethylene-co-acrylic acid copolymer, ethylene-co-methacrylic acid copolymer ethylene-co-vinyl alcohol copolymer (EVOH); polyvinyl alcohol (PVOH); homopolymers or copolymers of propylene (PP) such as isotactic polypropylene (iPP) or atactic polypropylene (aPP); homopolyamides and copolyamides (PA) such as polyamide 6 (PA6), polyamide 6.6 (PA6.6), polyamide 11 (PA11), polyamide 12 (PA12); homopolymers and copolymers of styrene such as crystal polystyrene, poly (styrene-co-butadiene), poly (styrene-co-acrylonitrile) (SAN), poly (acrylonitrile-co-butadiene-co-styrene) (ABS), poly (acrylonitrile-co-styrene-co-acrylate) (ASA); polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly (glycolic acid) (PGA), poly (lactic acid) (PLA), polycaprolactone (PCL), poly (butylene succinate) ) (PBS), poly (butylene adipate) (PBA), poly (ethylene succinate) and poly (ethylene adipate); chlorinated polymers and fluoropolymers; thermoplastic starches (TPS); or a mixture thereof. Cellulose can also be mentioned as an organic polymer that is useful for the invention. Among the cellulose-based materials, there may be mentioned all types of modified celluloses, paper or cardboard. Preferably, the cellulose-based material is chosen from modified cellulose or not, paper or cardboard. The organic polymer-based layer may be in the form of a film, a woven or a nonwoven. The metal-based layer may be metal, a metal alloy or a non-metallic component mixed with a metal. As an example of a metal that can be used in the multilayer structure, mention may be made of aluminum. These articles can be manufactured by a process comprising a coextrusion step in the case where the materials of the different layers are brought into contact in the molten state. By way of example, mention may be made of tube coextrusion techniques, coextrusion of profiles, coextrusion blow molding (in English "blowmolding") of bottles, flasks or tanks, generally grouped under the term coextrusion blow molding, co-extrusion inflation also called blowing film (in English "film blowing") and co-extrusion flat ("English" castcoextrusion ").

They can also be manufactured by a method comprising a step of applying a layer of polymer in the molten state to a layer based on an organic polymer, a metal or a solid state adhesive composition. This step may be carried out by pressing, overmolding, lamination or lamination, extrusion-rolling, coating, extrusion-coating or coating. The conditions for converting the composition according to the invention to form monolayer or multilayer articles depend on the processing techniques employed. The article according to the invention may in particular be produced by a process comprising a thermomechanical mixing step at a temperature of between 100 and 250 ° C., preferably between 130 and 210 ° C., followed by a shaping step. The skilled person will find the conditions for the implementation of articles according to the invention.

The invention also relates to a film comprising the composition according to the invention. Indeed, the films obtained have excellent properties, superior to those of known films based on thermoplastic starch and polyolefin. These films can have a thickness ranging from 5 to 500. The composition can be used for the production of monolayer or multilayer films. Indeed, an advantage of this composition is that it is very easily converted into monolayer film or multilayer film, especially by extrusion inflation or flat extrusion. This is not always the case for compositions based on thermoplastic starch and polyolefin: in this case, it is then necessary to reduce the rate of production in order to obtain a good quality film. An advantage of the composition according to the invention is that it can be used for the production of monolayer and multilayer films while maintaining production rates quite satisfactory. Embodiments of the invention will now be described in detail in the following nonlimiting examples.

Examples Analytical Methods The properties of the various compositions detailed below were determined according to the analytical methods described below. Measurement of insoluble levels and degree of swelling: The level of insolubles in water is determined according to the following protocol: (i) Dry the sample of composition to be characterized (12 hours at 80 ° C. under vacuum) (ii) ) Measure the mass of the sample (= Ms1) 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 quickly as possible. (vi) Place the sample on a precision scale and track the loss of mass for 2 minutes (mass measurement every 20 seconds) (vii) Determine the mass of the inflated sample by graphing the previous measurements as a function of time and extrapolation to t = 0 of 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 T ', expressed in percent, according to the formula Ms2 / Ms1. (X) Calculate the swelling ratio Tg, in percent, according to the formula (Mg-Ms1) / Ms1.

Measurement of mechanical properties: Conditioning of test pieces For carrying out tests of characterization of the mechanical properties, the test pieces used are conditioned for 24 hours at 20 ° C ± 2 ° C and 65% ± 5 (3/0 relative humidity according to the standard NF T51-014 Traction test The tensile mechanical characteristics of a composition are determined according to standard NF T51-034 (Determination of tensile properties) using a Lloyd Instrument LR5K test bench, a test speed of tensile strength: 50 mm / min and standard test specimens of type H. From the tensile curves (stress = f (elongation), obtained at a stretching speed of 50 mm / min, the composition under test shows that elongation and threshold stress, elongation and tensile stress.

Bending test The measurement of the bending modulus is carried out according to the ISO 178 standard, using a Lloyd Instrument LR5K test bench, a deformation speed of 2 mm / min and standard bending test specimens (NF T58-001).

Melt flow volume rate (MVR) measurement of the functional polyolefin: The melt index at 190 ° C. under a mass of 2.16 kg of the different samples was determined using A Kayness 4001 Dynasco grader according to ASTM D 1238. Measurement of melt volume melt flow rate (MVR) of the compositions: The melt index is determined at 190 ° C. under a mass of 10 kg. of the different samples using a Kayeness 4001 Dynasco scale according to ASTM D 1238. Density measurement: The density of the various samples is determined by weighing in the air (mass in the air) and in the water (mass in water) of a standard H2 specimen. The density is calculated directly from the formula Mass in air d - (Mass in air - Mass in water) Hardness measurement: The Shore D hardness is determined according to the NF T46-052 standard. using a Shore D pocket durometer. Fabrications of compositions according to the invention and comparative The constituents of the various examples presented to illustrate the invention are as follows. Polyolefin = PEBDRiblene® MP3OR (MFI = 7.5 g / 10 min) Functional Polyolefin Functional polyolefin or functional polyolefin blend is carried out on a TSA brand extruder, Diameter 32, Length L / D = 50, for a flow rate of: 25 kg / h. The temperature profile of the extruder (ten heating zones Z1 to 25 Z10, temperature in ° C) is as follows: 140/140/140/140/140/220/220/240/200/200 for a speed of screw: 300 rpm. The polyolefin or polyolefin mixture is introduced into the main hopper in the presence of 500 ppm organic peroxide and maleic anhydride is introduced into zone 4 of the extruder. Riblene MT10: LDPE (MFI = 40 g / 10min) Riblene MR30: LDPE (MFI = 20 g / 10min) Riblene MR10: LDPE (MFI = 20g / 10min) Ceraflour 990: polyethylene wax 35 PF1 = Mixture [90% Riblene MT10 / 10% Ceraflour 990] cografted at 1% maleic anhydride (MVR = 30 cm3 / 10min). PF2 = Mixture [95% Riblene MR30 / 5% Ceraflour 990] cografted with 1% maleic anhydride (MVR = 25 cm3 / 10min). PF3 = Mixture [80% Riblene MR10 / 20% Ceraflour 990] cografted with 1% maleic anhydride (MVR = 20 cm3 / 10min).

PF4 = Mixture [80% LDPE grafted with 1% maleic anhydride (MVR = 10 cm3 / 10min) / 20% Ceraflour 990 grafted with 1% maleic anhydride] (MVR = 20 cm3 / 10min) PF5 = Mixture [90 % LDPE grafted with 1% maleic anhydride (MVR = 15 cm3 / 10min) / 10% PE wax Ceraflour 990 grafted with 1% maleic anhydride] (MVR = 20 cm3 / 10m in) CPF1 = LDPE grafted at 1% of maleic anhydride (MVR = 1 cm3 / 10min) CPF2 = LDPE grafted with 1% maleic anhydride (MVR = 22 cm3 / 10min) CPF3 = LDPE grafted with 1% maleic anhydride (MVR = 60 cm3 / 10min) CPF4 = PE Ceraflour 990 wax grafted with 1% maleic anhydride (MVR> 400 cm3 / 10min) CPF5 = Mixture [90% LDPE grafted to 1% maleic anhydride (MVR = 15 cm3 / 10min) / 10% Ceraflour 990] (MVR = 22 cm3 / 10min) - Starch = Wheat starch (containing 12.5% water) - Plasticizer = Mix of plasticizers consisting of sorbitol (34.5%), glycerol (51.7%) and water (13.8%) - Additives PA = Process aid PDO = Primary antioxidant AL = Agent diisocyanate link Manufacturing process of the composition The examples of this invention were carried out on a TSA brand extruder, Diameter 32, Length L / D = 80, for a flow rate of: 50 kg / h - Temperature profile (sixteen zones of heater Z1 to Z16, temperature in ° C): 40/40/40/40/70/90/110/130/150/170/200/220/220/200/180/180 for screw speed: 400 rpm min.

The polyolefin and the functional polyolefin are premixed in a bag to form a polymer mixture. In the course of this process, the polymer mixture (polyolefin + functional polyolefin) is introduced into the extruder: the extruder, after which said mixture passes through all the heating zones of the extruder, the plasticizer of the starch at the Z6 zone (26-27D), the starch at the zone Z7 (32-33 D) and the bonding agent at zone Z14 (66-67D) The degassing is carried out by the application of a partial vacuum in Z 12 (100 mbar vacuum) making it possible to eliminate the volatile compounds like water. The compositions of the examples of this invention consist of: Polyolefin = 21.76% Blend of functional polyolefins = 21.76% Starch = 32.43% Plasticizer = 21.62% PA. = 1.17% PDO = 0.36% A.0 = 0.90% The functional polyolefin mixture used for each example is shown in Table 1. The properties of the products thus obtained are summarized in Table 2. The All compositions have a density of about 1.13.25 Table 1: Functional polyolefin blend used in the various compositions based on polyethylene and thermoplastic starch. Composition Functional Polyolefin Type Test Example 1 CPF1 Comparative Example 2 CPF2 Comparative Example 3 CPF3 Comparative Example 4 CPF4 Comparative Example 5 CPF5 Comparative Example 6 PF1 According to the invention Example 7 PF2 According to the invention Example 8 PF3 According to the invention Example 9 PF4 According to the invention Example 10 PF5 According to the invention Characterization of the compositions Table 2: Technical characteristics of the compositions based on polyethylene and thermoplastic starch. Composition aseuil Cseuil Grupt. Crupt. Flexural Module (MPa) MVR Hardness ShD Immersion (MPa) (%) (MPa) (%) cm3 / 10min 72h Tg T '(%) (%) Example 1 6 18.5 9 19 184 0.1 48 12.8 80.3 Example 2 11.8 27.5 15.5 162 305 9 55 5.2 99.1 Example 3 11.3 24.3 13.5 410 160 95 52 3.2 99.2 Example 4 12.5 14.3 16.2 50 500 0.5 57 15.1 80.8 Example 5 11.9 28.1 15.4 90 390 8 55 10.1 95.2 Example 6 10.3 22.2 18.4 450 160 23 54 3.2 99.6 Example 7 8.9 23.1 13.1 510 155 21 55 5.1 99.8 Example 8 11.3 21.5 17.2 490 165 18 55 4.3 99 Example 9 7.9 25.1 18.4 480 120 22 54 2.8 99.3 Example 10 8.4 24.8 17.8 500 140 19 54 3.7 99.4 The results obtained for the compositions Comparative examples 1 to 5, in which the functional polyolefins used are not a mixture of functional polyolefins useful in the invention, show that: A low density maleic anhydride grafted polyethylene of low viscosity (MVR = 1 cm3 / 10 min) leads at elongation at break very low (Example 1). The water resistance of the composition is also very low. The inflation extrusion tests have also revealed that the composition is too viscous, has no melt stretchability (melt strength or excessive meltstrength) and is therefore not filmable.

A maleic anhydride grafted low density polyethylene of average viscosity (MVR = 22 cm3 / 10min) leads to a greater elongation at break which remains nevertheless low (Example 2). The material is more fluid and the inflation extrusion tests have revealed that the composition has sufficient melt stretchability to be filmable. However, the film obtained has a high heterogeneity including a significant presence of gels. The mechanical strength of the film is also very low (no resistance to tearing or perforation). A high viscosity maleic anhydride grafted polyethylene of low viscosity (MVR = 60 cm3 / 10min) also leads to a greater elongation at break. (Example 3) However, the material has a viscosity that is too low and can not be filmed by extrusion inflation due to insufficient melt strength. Furthermore, the results obtained for Example 4 show that a composition comprising solely as functional polyolefin a polyethylene wax grafted maleic anhydride does not provide a stable material over time. In fact, the grafted wax migrates on the surface and is exuded. The water resistance of the composition is very low. The elongation at break is also low and the material, too viscous, is not filmable by extrusion inflation.

Example 5 shows that a mixture, which comprises a nonfunctionalized polyethylene wax, does not provide satisfactory properties. The elongation at break is not satisfactory. The resistance to water is also low. The material has sufficient melt strength to be filmed by extrusion inflation, but the film thus obtained has a very high heterogeneity, including a significant presence of gels (phenomenon more marked than for Example 2). The mechanical strength of the film is also very low (no resistance to tearing or perforation). The results obtained for the compositions of Examples 6 to 8, in which use is made of a mixture cografted with maleic anhydride of polyethylene and of polyethylene wax, show that: the use of such a mixture makes it possible to obtain an elongation at the rupture is very important, the materials have a viscosity and a melt stretchability that allow them to be filmable by extrusion inflation. The films obtained are very homogeneous, without gel and have a very good mechanical strength (very good resistance to tearing and perforation). The results obtained for the compositions of Examples 9 and 10, in which the functional polyolefin mixture used is a mixture of maleic anhydride grafted polyethylene wax and maleic anhydride grafted polyethylene, show that: The use of such a mixture of functionalized polyolefins provides a very high elongation at break, - The viscosity of the material is close to those of Examples 6 to 8. The materials have good melt stretchability that allow them to be filmable by extrusion inflation. The films obtained are homogeneous, without frost with however a few streaks. These streaks do not affect the mechanical strength of the films (very good resistance to tearing and perforation). Examples 6 to 10 thus clearly show the advantage of using, as functional polyolefin, a mixture of functionalized polyethylene wax and of functionalized polyethylene instead of a maleic anhydride grafted polyethylene or a maleic anhydride grafted polyethylene wax, as is the case in compositions 1 to 4.

Claims (5)

REVENDICATIONS1. Thermoplastic composition comprising: - at least one starch; at least one plasticizer for the starch; at least one functional polyolefin mixture comprising a functionalized polyethylene comprising at least one functional compound carrying at least one polar functional group and a functionalized polyethylene wax comprising at least one functional compound carrying at least one polar function. 2. Composition according to the preceding claim, characterized in that the functional polyolefin mixture is a functionalized polyethylene mixture obtained by grafting at least one functional compound carrying at least one polar function and a functionalized polyethylene wax obtained. by grafting at least one functional compound carrying at least one polar function. 3 Composition according to the preceding claim, characterized in that the functional polyolefin mixture is obtained by co-grafting a mixture of polyethylene and a polyethylene wax with a functional compound carrying at least one polar function. Composition according to one of the preceding claims, characterized in that the mixture of functional polyolefins comprises, based on the weight of functional polyolefins: from 60 to 99% of functionalized polyethylene; from 1 to 40% of functionalized polyethylene wax. 5. Composition according to the preceding claim, characterized in that the mixture of functional polyolefins comprises, based on the weight of functional polyolefins: from 70 to 96% of functionalized polyethylene; from 4 to 30% of functionalized polyethylene wax. 2. Composition according to the preceding claim, characterized in that the functional polyolefin mixture comprises, based on the weight of functional polyolefins: from 80 to 95% of functionalized polyethylene; 5 - from 5 to 20% of functionalized polyethylene wax. Composition according to one of the preceding claims, characterized in that the functional compounds of functionalized polyethylene and functionalized polyethylene wax have a dipole moment greater than 1 Debye. Composition according to one of the preceding claims, characterized in that the functional compounds of the functionalized polyethylene and of the functionalized polyethylene wax are chosen from unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids, unsaturated oxiranes and silanes. Unsaturated and mixtures thereof, preferentially maleic anhydride. 9 Composition according to one of the preceding claims, characterized in that the mixture of functional polyolefins comprises, relative to its total weight, from 0.1 to 5% by weight of functional compounds, preferably from 0.5 to 2% in mass. Composition according to one of the preceding claims, in which the mixture of functional polyolefins has a density ranging from 0.855 to 0.950, for example from 0.890 to 0.920. 11. Composition according to one of the preceding claims, in which the functionalized polyethylene wax has a number-average molar mass ranging from 500 to 10,000 g / mol and the functionalized polyethylene has a number-average molar mass greater than 10,000 g / mol. . 12 Composition according to one of the preceding claims, characterized in that it further comprises at least one additional polyethylene having a density of between 0.865 and 0.935. 13. Composition according to claim 12, characterized in that the additional polyethylene is chosen from very low density polyethylene, low density polyethylene, linear low density polyethylene or a mixture of these polymers. 3014 Composition according to one of claims 12 or 13, characterized in that the additional polyethylene has a density between 0.890 and 0.935, preferably between 0.910 and 0.935. Composition according to one of the preceding claims, characterized in that it comprises, relative to its total mass, from 5 to 90% functional polyolefin mixture, preferably from 10 to 30%. Composition according to one of the preceding claims, characterized in that it comprises, with respect to its total mass: from 5 to 40% of starch, advantageously from 8 to 35%; from 5 to 40% of plasticizer, advantageously from 8 to 30%; from 5 to 90% of functional polyolefin mixture, advantageously from 10 to 30%; optionally between 0 and 85% of polyethylene, for example between 5 and 80%, advantageously from 20 to 60%; optionally between 0 and 20% of additive; the sum of the constituents making 100%. Film comprising the composition according to one of claims 1 to 16. 18 Use of the composition according to one of claims 1 to 16, for the manufacture of monolayer or multilayer films. Process for the production of the composition according to one of Claims 1 to 16, comprising at least one step of melt-blending or softening of the various constituents and a step of recovery of the composition.