FR2993274A1 - STARCH-BASED THERMOPLASTIC COMPOSITION COMPRISING A FUNCTIONALIZED POLYPROPYLENE OF SELECTED FLUIDITY - 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 polypropylene comprising at least one functional compound carrying at least one polar function, and whose melt volume melt index is from 120 to 155 cm / 10 min (ASTM D 1238 190 ° C, 2.16 kg). 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, VoL70, Pages 1503-1521 have also been described various compositions comprising low density polyethylene, polyethylene grafted by 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; said functional polyolefin being a polypropylene comprising at least one functional compound carrying at least one polar function, and whose melt volume melt index is from 120 to 155 cm3 / 10 min (ASTM D 1238, 190 ° C, 2.16 kg).

Without being bound by any theory, the Applicant explains these best properties in that this particular functional polyolefin binds very well with the thermoplastic starch within the thermoplastic composition, and this although the chemical nature of the functional polyolefin 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 polypropylene can be obtained by various methods, either by polymerization of the functional compound with propylene, or by grafting the functional compound onto a polypropylene. The functional compound carrying a polar function preferably has, before polymerization or grafting, a dipole moment greater than 1, preferably greater than 2, most preferably greater than 3 Debyes. Preferably, the melt volume melt index is 130 to 152 cm3 / 10 min, most preferably 135 to 150 cm3 / 10 min.

According to an advantageous variant, the composition according to the invention further comprises at least one polyethylene having a density of between 0.865 and 0.935. This polyethylene which 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 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 functional polyolefin, advantageously from 10 to 30%. Advantageously, the composition further comprises between 0 and 20% of optional constituent other than the starch, the plasticizer of the starch, the functional polyolefin and the optional polyethylene, this optional component 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, 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 binding agent between the starch, the plasticizer and / or the functional polyolefin. 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 polar function of the functional compound included in the functional polyolefin can be polymerized or grafted. This functional compound carries a polar function and 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 can be obtained by various methods, either by polymerization of the functional compound with propylene or by grafting the functional compound onto a polypropylene.

Preferably, the functional polyolefin is obtained by grafting a polypropylene with a functional compound. In other words, the functional polyolefin is preferably a polypropylene grafted with a functional compound. The latter may be chosen from unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids, unsaturated oxiranes and unsaturated silanes, preferentially maleic anhydride. Advantageously, the functional polyolefin comprises, relative to its total weight, from 0.1 to 5% by weight of functional compound, advantageously from 0.5 to 2% by weight.

The functional polyolefin may have a density ranging from 0.855 to 0.950, for example from 0.890 to 0.920. The functional polyolefin of the composition advantageously has a melting temperature of 140 ° C to 200 ° C, for example 150 ° C to 195 ° C. 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 as defined above. A thermoplastic composition is a composition which 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 may 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 trademark P REG E FLO®. 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. Selection of the functional polyolefin has allowed the Applicant to obtain a thermoplastic composition with improved properties.

This functional polyolefin is a polypropylene comprising at least one functional compound and whose melt volume melt index is from 120 to 155 g / 10 min (ASTM D 1238, 190 ° C., 2.16 kg). 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 preferentially chosen from unsaturated carboxylic acid anhydrides, unsaturated carboxylic acids, unsaturated oxiranes and unsaturated silanes, preferably maleic anhydride. The functional polyolefin may be obtained by different methods, or by polymerization of the functional compound with propylene. or by grafting the functional compound onto a polypropylene. 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 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, 4-methylenecyclohex- 4-ene-1,2-dicarboxylic, 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 be chosen in particular 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 alkyl (meth) acrylates. 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, mention may be made of vinyl acetate, vinyl versatate, vinyl propionate, vinyl butyrate or vinyl maleate. Unsaturated oxirane, also known as 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, 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 chosen 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 functional compound in the functional polyolefin can be determined by conventional methods, typically by Fourier transform infrared spectroscopy.

The functional polyolefin can be obtained by grafting the functional compound onto a polypropylene. These polypropylenes are generally obtained by catalytic polymerization of propylene. The polypropylene is preferably a homopolymer of propylene.

These grafted polypropylenes are marketed for example under the brand name Bondyrame by Polyram, Orevace by Arkema® or by Fusabonde by DuPontTM. The grafting of polypropylene is a known operation in itself and the skilled person will be able to adapt the following process for obtain the functional polyolefin desired and useful to the invention. The grafting reaction can be carried out according to a batch process in solution or, preferably, in a continuous process with a melt mixing 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 polypropylene is introduced in the presence of a radical generator and the functional compound in the tool, whose body temperature is regulated, this temperature being chosen in line with the decomposition kinetics of the radical generator. 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 polypropylene, 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 polypropylene main supply, 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 polypropylene grafting agent, for example styrene. This fraction of polypropylene grafting agent is intended to facilitate and accelerate the grafting of the functional agent and thus improve the yield of the reaction. 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 graft polypropylene 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 polyethylene having a density of between 0.865 and 0.935. This 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 polyethylene is between 0.890 and 0.935, preferably between 0.910 and 0.935. Polypropylene and polyethylene are naturally very little compatible. The resulting mixtures generally have lower mechanical properties than polyethylene alone or polypropylene alone. Surprisingly, although the functional polyolefin is a polypropylene comprising a functional compound, the Applicant has achieved, according to the preferred variant where the composition comprises polyethylene, to obtain a composition having excellent properties, superior to those of a composition. identical with the difference that the functional polyolefin is a polypropylene comprising a functional compound of different melt index. The polyethylene may 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 functional polyolefin and the optional polyethylene.

This optional component may be selected from among the additives and polymers other than starch, functional polyolefin and 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-fungants 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 process for preparing the composition comprising introducing the starch and a plasticizer thereof into a reactor containing a mixture of softened or fused polyolefin and functional polyolefin 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 of hollow body, co-extrusion inflation also called blowing of sheath (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 may have a thickness ranging from 5 to 500 μm. The composition may be used for the manufacture 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 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 track the loss of mass for 2 minutes (mass measurement every 20 seconds) (vii) Determine the mass of the swollen sample by graphing the measurements previous 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 rate Tg, in percent, according to the formula (Mg-Ms1) / Ms1. Measurement of Mechanical Properties: Conditioning of Test Pieces For carrying out the 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 next). the NF T51-014 standard.

Tensile test The mechanical tensile characteristics of a composition are determined according to standard NF T51-034 (Determination of tensile properties) using a Lloyd Instrument LR5K test bench, a pulling speed: 50 mm / min and standard H2 specimens.

From the tensile curves (stress = f (elongation), obtained at a stretching speed of 50 mm / min, the elongation and the stress at the threshold, elongation and stress are recorded for the composition tested. Bending test The measurement of the flexural 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). The melt volume volume index (MVR) of the functional polyolefin is determined: The melt index is determined at 190 ° C. under a mass of 2.16 kg. different samples using a Kayeness 4001 Dynasco grader according to ASTM D 1238.

Measurement of melt volume melt flow rate (MVR) of the compositions: The melt flow rate at 190 ° C. under a mass of 10 kg of the different samples is determined using a Kayeness 4001 Dynasco grader. Measurement of the density: The density of the various samples is determined by weighing in the air (mass in the air) and in the water (mass in the 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 pocket Shore D durometer.

Fabrications of compositions according to the invention and comparative The constituents of the various compositions exemplified are presented below. - Polyolefin: LDPE Lupolen 2420 F 10 - Functional Polyolefin These functional polyolefins are commercially available products. PF1 = Polypropylene grafted with 1% by weight of maleic anhydride, having a modulus of 1400 MPa, an elongation at break of 5% and exhibiting a MVR of 146cc / 10min. PF2 = Polypropylene grafted with 1% by weight of maleic anhydride, 850 MPa module, elongation at break of 10% and having a VCR of 140 cc / 10 min. PF3 = Polypropylene grafted with 1% by weight of maleic anhydride, of 1200 MPa module, elongation at break of 10% and having a VCR of 149 cc / 10 min. PF4 = Polypropylene grafted with 1% by weight of maleic anhydride, of 1200 MPa modulus, elongation at break of 8% and having a VCR of 100 cc / 10 min. PF5 = Polypropylene grafted with 1% by weight of maleic anhydride, with a 1300 MPa modulus, an elongation at break of 10% and having a MVR of 220 cc / 10 min. PF6 = Polypropylene grafted with 1% by weight of maleic anhydride, 600 MPa module, elongation at break of 900% and having a MVR of 290 cc / 10 min. PF7 = Polypropylene grafted with 1% by weight of maleic anhydride, of 1200 MPa modulus, elongation at break of 20% and exhibiting an MVR of 160 cc / 10 min. PF8 = Polypropylene grafted with 1% by weight of maleic anhydride, of 1150 MPa modulus, elongation at break of 4% and having a MVR of 360 cc / 10 min. - Starch = Wheat starch (containing 12.5% water) - Plasticizer = Blend of plasticisers made up of sorbitol (34.5%), glycerol (51.7%) and water (13%) 8%) - Additives PA = Process Aid AOP = Primary Antioxidant AL = Diisocyanate Binding Agent Method of making 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 heating zones Z1 to Z16, temperature in ° C): 40/40/40/40/70/90/110/130/150/170/200 / 220/220/200/180 / 180for screw speed: 400 rpm. 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.

Details of the compositions The compositions of the examples differ only in the nature of their functional polyolefin and consist of: Polyolefin = 21.8% Functional polyolefin = 21.8% Starch = 32.4% Plasticizer = 21.6% PA = 1 , 15% - PDO = 0.35% - AL = 0.9% The compositions according to the invention (Examples 1 to 3) and comparative (Examples 4 to 8) were carried out using the method described above. The amounts of the various constituents of the compositions are shown in Table 1.

TABLE 1 Functional Polyolefin Used in the Compositions According to the Invention and Comparative Composition Functional Polyolefin Type Test Example 1 PF1 According to the invention Example 2 PF2 According to the invention Example 3 PF3 According to the invention Example 4 PF4 According to the invention Example 5 PF5 Comparative Example 6 PF6 Comparative Example 7 PF7 Comparative Example 8 PF8 Comparative The compositions of Examples 1 to 8 have a density of about 1.12.

Characterization of the Compositions Examples 1 to 3 demonstrate the benefits of the composition according to the invention: different compositions, which differ only in the choice of the functional polyolefin used, are thus compared.

The properties of the compositions of these examples are summarized in Table 2 and 3.

TABLE 2 Effect of the functional polyolefin useful in the invention: Mechanical properties of the compositions

Threshold composition Eseuil a rupt. (MPa) Erupt. Flexural modulus (MPa) Hardness (MPa) (%) (%) Shore D Example 1 11.6 26 16.8 680 345 56 Example 2 10.8 31.7 17.3 750 321 55 Example 3 9.4 27 Example 4 12.5 17 15 140 450 51 Example 5 9.7 23.5 16 220 310 49 Example 6 11.4 22.4 8 195 340 50 Example 7 12 21.9 6 210 EXAMPLE 8 10.8 22 6.3 260 357 Table 3: Effect of functional polyolefin useful in the invention: Other properties. MVR Composition Water Immersion (190 ° C / 1 Ok2) 72h cm3 / 10min Tg (%) T '(%) Example 1 3.5 3.5 99.7 Example 2 3.1 99.8 Example 3 12 2.7 99 Example 4 32 8.9 98.7 Example 5 8.3 7.5 99.2 Example 6 8.1 98.5 Example 7 36 5.6 99.4 Example 8 40 5.1 99.3 results obtained for the various compositions show that the compositions comprising the functionalized polyolefin useful in the invention are superior to the compositions of the prior art. Comparing the compositions of Examples 1 to 3 with those of Examples 4 to 8 show in particular that the use of the functionalized polyolefin useful in the invention allows a significant increase in the mechanical properties (increase by a factor of 4). elongation at break) and an increase in the water resistance of the composition (swelling rate after immersion for 72 hours in water divided by three and insoluble level of 1% greater).

Examples 1 to 3 show that the modules of the functionalized polyolefin (which vary according to the examples of 850 MPa to 1400 MPa) or its elongation at break have surprisingly little effect on the final properties of the composition. The comparison of the initial properties of the maleic anhydride grafted polypropylenes employed shows a significant link between the viscosity of the functionalized polyolefin and the final properties of the composition obtained. By way of example, when the MVR is about 160 cm3 / 10 min, a strong degradation of the properties is observed as shown in Example 7. Conversely, when the MVR is too weak, the properties are also degraded ( see example 4).

Finally, the compositions according to the invention have a viscosity and a melt strength allowing it to be easily filmed using a jacket blowing extruder.

Claims (7)

CLAIMS1 Thermoplastic composition comprising: - at least one starch; at least one plasticizer for the starch; at least one functional polyolefin; characterized in that the functional polyolefin is a polypropylene comprising at least one functional compound carrying at least one polar function, and whose melt volume melt index is from 120 to 155 cm3 / 10 min (ASTM D 1238, 190 ° C, 2.16 kg). Composition according to the preceding claim, characterized in that the melt volume melt index of the functional polyolefin ranges from 130 to 152 cm3 / 10 min. 3. Composition according to the preceding claim, characterized in that the melt volume melt index of the functional polyolefin ranges from 135 to 150 cm3 / 10 min. 4 Composition according to one of the preceding claims, characterized in that the functional compound carrying a polar function has a dipole moment greater than 1 Debye. 5. Composition according to one of the preceding claims, characterized in that the functional polyolefin is a polypropylene which is grafted with a functional compound carrying the polar function, said functional compound being selected from unsaturated carboxylic acid anhydrides, carboxylic acids. unsaturated, unsaturated oxiranes and unsaturated silanes, preferentially maleic anhydride. 6. Composition according to one of the preceding claims, characterized in that the functional polyolefin comprises, relative to its total weight, from 0.1 to 5% by weight of functional compound, advantageously from 0.5 to 2% by weight. Composition according to one of the preceding claims, in which the functional polyolefin has a density ranging from 0.855 to 0.950, for example from 0.890 to 0.920. Composition according to one of the preceding claims, in which the functional polyolefin has a melting point of 140 ° C to 200 ° C, for example from 150 ° C to 195 ° C. 9 Composition according to one of the preceding claims, characterized in that it further comprises at least one polyethylene having a density between 0.865 and 0.935. Composition according to Claim 9, characterized in that the polyethylene is chosen from very low density polyethylene, low density polyethylene, linear low density polyethylene or a mixture of these polymers. 11 Composition according to one of claims 9 or 10, characterized in that the polyethylene has a density between 0.890 and 0.935, preferably between 0.910 and 0.935. 12 Composition according to one of the preceding claims, characterized in that it comprises, relative to its total mass, from 5 to 90% of functional polyolefin, preferably from 10 to 30%. 13 Composition according to one of the preceding claims, characterized in that it comprises, relative to its total mass: - 5 to 40% of starch, preferably 8 to 35%; from 5 to 40% of plasticizer, advantageously from 8 to 30%; from 5 to 90% of functional polyolefin, 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 13. Use of the composition according to one of Claims 1 to 13, for the production of monolayer or multilayer films. Process for manufacturing the composition according to one of the preceding claims. Claims 1 to 13, comprising at least one step of melt or softened mixing of the various constituents and a step of recovering the composition.