COMPOSITION COMPRISING THERMOPLASTIC STARCH AND ALIPHATIC POLYESTER

- Roquette Freres

The invention relates to a thermoplastic composition comprising at least one polyester (A) which is an aliphatic polyester; at least one starch (B); at least one organic plasticiser (C) for starch; and at lest one monoester compound (D) of fatty monoacid comprising at least 12 carbon atoms and glycerol. The composition is characterised in that the amount by weight of compound (D) varies between 0.05 and 1.7 parts per 100 parts of the dry weight of the different constituents (A), (B) and (C).

Skip to: Description  ·  Claims  · Patent History  ·  Patent History
Description
FIELD OF THE INVENTION

A subject of the invention is a thermoplastic composition comprising thermoplastic starch, an aliphatic polyester and at least one monoester of a fatty acid and of glycerol. Another subject of the invention is a granule of the composition, a manufacturing process for manufacturing said composition and a process for manufacturing a film by film blowing using the composition.

TECHNICAL BACKGROUND OF THE INVENTION

Because of their numerous advantages, plastics have become inescapable in the mass manufacture of objects. Indeed, because of their thermoplastic nature, it is possible to manufacture objects of any type from these polymers, at a high rate. To manufacture these objects, small pieces of these thermoplastic polymers are used, that are melted by providing heat and mechanical stresses in forming machines. For example, it is possible to manufacture film by introducing these pieces into a blown film extruder or a flat die extruder (cast extrusion) or else to manufacture bottles by introducing said pieces into a blow-molding extruder. These small pieces are in most cases in the form of granules, since said granules are very easy to handle.

These objects are generally made of non-biodegradable thermoplastics, such as polyolefins or polyamides. However, these plastics are still today not recycled a great deal. Thus, this causes environmental problems since they are generally incinerated and this incineration can cause toxic gases to be given off. Thus, one of the important preoccupations today in the polymer field is to provide polymers which are biodegradable or at least compostable.

Among the biodegradable and/or compostable polymers, mention may be made of aliphatic polyesters, such as poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBSA), poly-ε-caprolactone (pCAPA), polylactic acid (PLA) and also polyhydroxyalkanoates of polyhydroxybutyrate (PHB) or poly(hydroxy butyrate-co-valerate) (PHVB) type. Aliphatic polyesters generally have melting points close to those of polyolefins, thereby allowing, inter alia, their use in the fields of films and packaging, the biodegradability of which is an obvious advantage for single-use applications.

However, one of the problems of these polyesters is that they are relatively expensive. One of the solutions envisioned for providing biodegradable compositions which are more economical is to manufacture compositions based on thermoplastic starch, this consisting of starch and of a plasticizer for this starch, such as glycerol. Specifically, the manufacture of these compositions is advantageous since starch is one of the biosourced polymers that is naturally the most widespread in the environment. However, these thermoplastic starches have insufficient properties, in particular in terms of water resistance. Furthermore, transforming starch into thermoplastic starch is not easy since it requires the use of substantial constraints and/or temperatures during the thermomechanical mixing, which has a tendency to degrade the thermoplastic starch thus formed.

To counter these drawbacks, compositions based on aliphatic polyesters and plasticized starch have been developed. In these compositions, the thermoplastic starch phase is generally dispersed in the polyester phase. These compositions have numerous advantages, for instance that of being able to be composted or and/or biodegradable and of having water resistance that is very much improved relative to thermoplastic starch.

In industrial practice, films are mainly manufactured by blown film extrusion (or extrusion blow molding) since this technique allows the manufacture of films of large size and at a high rate. The applicant has been able to note that one of the problems of these compositions based on thermoplastic starch and aliphatic polyester is that they can, at high rate, be tacky during the forming of the film by extrusion blow molding. This creates problems of separation of the blown tube during or after manufacture, once this blown tube is in the form of a spool. This phenomenon prevents, for example, the production of fine bags or films. This problem is specific to compositions comprising aliphatic polyester since, contrary to other polyesters such as semi-aliphatic polyesters, they have a slow crystallization speed. The blown tube remains in the molten state and has a tendency to stick during the extrusion blow molding process.

These problems are worsened when the amount of thermoplastic starch in the composition and/or the amount of plasticizer in the thermoplastic starch are high.

The applicant has succeeded in providing novel compositions which make it possible to overcome these problems.

SUMMARY OF THE INVENTION

A subject of the invention is thus a thermoplastic composition comprising at least one polyester (A) which is an aliphatic polyester, at least one starch (B), at least one organic plasticizer for starch (C) and at least one compound which is a monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, the amount by weight of monoester (D) of which ranges from 0.05 to 1.7 parts, these amounts by weight being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C).

The applicant has been able to note that, when compositions based on starch and aliphatic polyester comprise this monoester (D) in these particular proportions, they have, in particular when they are in blown tube form, a much less tacky aspect than the compositions free of this compound (D) or else comprising these compositions in greater proportions.

Application EP 950 690 A2 describes a composition based on thermoplastic starch and a thermoplastic polymer which is incompatible with this thermoplastic starch, which can be an aliphatic polyester, in which the thermoplastic starch is dispersed in a continuous phase of thermoplastic polymer, and an interfacial agent in order to improve the water resistance and its resistance to ageing. According to sub-variant c) of the family of compositions A), this interfacial agent may be of the type of a monoester of a fatty acid comprising from 12 to 22 carbon atoms and of glycerol. In this case, this interfacial agent must be introduced in proportions of at least 10% by weight relative to the weight of the thermoplastic starch.

Application WO 2007/012142 A1 describes a composition comprising polycaprolactone, polycaprolactone-grafted starch, corn starch, sorbitol and glycerol and also glucose stearate. This composition has improved properties conferred by the presence of the grafted starch. This document does not describe a composition comprising the monoester (D) described above.

DETAILED DESCRIPTION OF THE INVENTION

A subject of the invention is a thermoplastic composition based on polyester (A) which is aliphatic, thermoplastic starch and a monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol.

A thermoplastic composition is a composition which, reversibly, softens under the action of heat and hardens on cooling to ambient temperature. It has at least one glass transition temperature (Tg) below which the amorphous fraction of the composition is in the brittle vitreous state, and above which the composition may 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 between −150° C. and 40° C. This starch-based composition may, of course, be formed via processes conventionally used in plastics engineering, such as extrusion, injection, molding, blow-molding and calendering. Its viscosity, measured at a temperature from 100° C. to 200° C., is generally between 10 and 106 Pa·s.

The composition according to the invention also has the advantage of being able to be biodegradable.

The composition according to the invention comprises at least one aliphatic polyester, which is a polyester that comprises exclusively non-aromatic monomers. The term “comprises monomers” is intended to mean that the polyester can be obtained by polycondensation of these monomers. For example, if the polyester comprises succinic acid and 1,4-butanediol, this means that it can be obtained by polycondensation of monomers comprising succinic acid and 1,4-butanediol. It is also specified that, when it is indicated that the polyester “comprises x % of a monomer (X)”, this means that it can be obtained from a mixture of monomers comprising, relative to the total weight of the monomers, x % of monomer (X).

An aliphatic polyester is a polyester that can be obtained using non-aromatic monomers, said monomers being chosen from polyols, polyacids and monomers bearing at least one carboxylic acid function and at least one alcohol function. These non-aromatic monomers may be linear, cycloaliphatic or branched. It is also possible to obtain these polyesters via enzymatic or fermentation routes, as in the case of the polyhydroxyalkanoates.

These polyols are generally aliphatic diols, preferably saturated linear aliphatic diols. As linear aliphatic diol, mention may be made of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, or a mixture of aliphatic diol units comprising at least one of these units, preferentially ethylene glycol and 1,4-butanediol or a mixture of these diols, most preferentially 1,4-butanediol.

The polyacids are generally aliphatic diacids, preferably saturated aliphatic diacids. By way of example, these diacids may be succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or a mixture of these diacids. Preferably, the aliphatic diacid is chosen from succinic acid and adipic acid or a mixture of these acids. The polyesters can also be obtained from esters, anhydrides or chlorides of these polyacids.

The monomers bearing at least one carboxylic acid function and at least one alcohol function are generally hydroxy acids. By way of example, the hydroxy acids may be glycolic acid, lactic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, or a mixture of these hydroxy acids. The polyesters may also be obtained from dilactone such as glycolide or lactide, or from lactone such as caprolactone.

Preferably, the composition comprises, as polyester (A), an aliphatic polyester or a mixture of aliphatic polyesters.

According to the variant wherein the composition comprises, as polyester (A), an aliphatic polyester, this aliphatic polyester advantageously comprises 1,4-butanediol and succinic acid and/or adipic acid. The polyester (A) is most preferentially chosen from PBS and PBSA.

According to the variant, the composition comprises a mixture of aliphatic polyesters; the composition advantageously comprises a mixture:

    • of at least one polyester (A1) which is an aliphatic polyester comprising 1,4-butanediol and succinic acid and/or adipic acid, this polyester (A1) being most preferentially chosen from PBS and PBSA;
    • of at least one polyester (A2) which is polylactic acid.

Preferably, the polylactic acid is a semi-crystalline polylactic acid. Polylactic acid is generally obtained by polymerization of lactide, by ring opening. The lactide can be in the form of D-lactide or L-lactide or else in the form of meso-lactide. The crystallinity of the polylactic acid is mainly controlled by the amount of D-lactide and of L-lactide and to a lesser extent by the type of catalyst used. Thus, the polymerization of a racemic mixture of L-lactide and D-lactide generally leads to the synthesis of an amorphous polylactic acid, whereas the polymerization of pure D-lactide or of pure L-lactide leads to the synthesis of a semi-crystalline polylactic acid. A synthesis process using a racemic mixture can also lead to a heterotactic PLA exhibiting crystallinity by using stereospecific catalysts. Preferably, the polylactic acid exhibits a crystallinity ranging from 30% to 75%, most preferentially from 40% to 60%. The degree of crystallinity of the PLA can be determined by differential scanning calorimetry analysis on the basis of the calculation of the ratio of the Cp jump values at Tg of the semi-crystalline product that it is sought to characterize and of the same product made completely amorphous.

According to the variant wherein the composition comprises a blend of polyesters (A1) and (A2), the weight percentage of (A2) relative to the weight of (A1) and (A2), expressed by dry weight, advantageously ranges from 2% to 70%, advantageously from 10% to 50%, preferably from 18% to 30%. More preferentially, the weight percentage of (A2), relative to the weight of (A1) and (A2), expressed by dry weight, ranges from 5% to 90%, preferably from 15% to 45%.

According to another embodiment, the weight percentage of (A2) relative to the weight of (A1) and (A2) is low, that is to say that this weight percentage, expressed by dry weight, ranges from 2% to 20%, advantageously according to this mode from 3% to 15%, for example from 4% to 10%.

According to this variant, and in particular according to these preferred sub-variants, it is possible to manufacture films from this composition by blown film extrusion, using particularly high production rates.

The various constituents of the composition, in particular the starch, and also the composition obtained, may comprise moisture. The weight proportions can be expressed in the present application either by “dry weight”, that is to say that the water possibly included in the constituents or the composition is not taken into consideration for the calculation of the weight proportion, or by “wet weight”, that is to say that the water possibly included in the constituents or the composition is taken into consideration for the calculation of the weight proportion.

Preferably, the polyester(s) (A) has (have) a flow index ranging from 0.1 to 50 g/10 min, advantageously from 0.5 to 15 g/10 min (ISO 1133, 190° C., 2.16 kg).

The composition according to the invention also comprises starch (B) and an organic plasticizer for starch (C), the two forming thermoplastic starch.

With regard to the starch (B), it may be of any type. If it is desired to obtain a less expensive composition, the starch preferentially used for the manufacture of the composition is a granular starch, preferably a native starch.

The term “granular starch” is intended to mean herein a native or physically, chemically or enzymatically modified starch, which has conserved, within the starch granules, a semicrystalline structure similar to that revealed in the starch grains naturally present in the storage organs and tissues of higher plants, in particular in cereal grains, legume grains, potato or cassava tubers, roots, bulbs, stalks and fruit. In the native state, starch grains generally have a degree of crystallinity that ranges from 15% to 45%, and which depends essentially on the botanical origin of the starch and on the possible treatment that it has undergone.

Granular starch, placed under polarized light, has a characteristic black cross, known as the Maltese cross, typical of the granular state.

According to the invention, the starch may come from any botanical origin, including a granular starch rich in amylose or, conversely, rich in amylopectin (waxy). It may be native starch of cereals such as wheat, maize, barley, triticale, sorghum or rice, tubers such as potato or cassava, or legumes such as pea and soybean, and mixtures of such starches.

The starch may also be modified, chemically or physically.

The function of the organic plasticizer for starch (C) is to make the starch thermoplastic.

It may be an organic plasticizer chosen from diols and polyols such as glycerol, polyglycerols, sorbitans, sorbitol, mannitol, and hydrogenated glucose syrups, urea, polyethers with a molar mass below 800 g/mol, and any mixtures of these products, preferably glycerol, sorbitol or a mixture of glycerol and sorbitol.

According to the invention, the composition may comprise relatively high amounts of plasticizer. Thus, advantageously, the starch/plasticizer weight ratio, expressed by dry weight, ranges from 90/10 to 40/60, for example from 85/15 to 40/60, advantageously from 85/15 to 50/50, preferably from 80/20 to 60/40. The range from 90/10 to 40/60 can be broken down into two sub-ranges: a sub-range from 90/10 to 85/15 (85/15 limit excluded) and a sub-range from 85/15 to 40/60. According to another preferred embodiment, the starch (B)/organic plasticizer (C) weight ratio, expressed by dry weight, ranges from 90/10 to 80/20, or even from 90/10 to 85/15 (85/15 limit excluded). According to this mode, the weight percentage of (A2) relative to the weight of (A1) and (A2) is preferably low. The compositions of this preferred mode make it possible to be subsequently converted, for example in the form of a film, without any fumes being given off during the conversion. Moreover, the films obtained exhibit excellent mechanical properties, in particular when the amount of (A2) is low.

Even when the amounts of plasticizer are high, the composition according to the invention can be converted into the form of a blown tube, without said blown tube sticking to itself, this being even when the blown tube is produced at a high rate. The composition then exhibits a greater flexibility.

According to the invention, the composition may comprise very variable amounts of thermoplastic starch. Thus, the total amount by weight of polyester (A) may be included in the range of from 35 to 75 parts, these amounts by weight being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C). It may comprise a total amount by weight of polyester (A) ranging from 40 to 70 parts, advantageously in the range of from 40 to 60 parts, preferably in the range of from 48 to 58 parts.

The composition according to the invention can be characterized by a morphology which is in the form of co-continuous domains of thermoplastic starch and of polyester. The morphology of the composition can be observed by scanning electron microscopy.

Even when the amounts of thermoplastic starch are high, the composition according to the invention may be made into the form of films, without said films being tacky. In certain proportions such as those defined above, the morphology of the composition exhibits co-continuous domains of polyester and of thermoplastic starch. These compositions exhibit improved biodegradability compared with compositions in which the thermoplastic starch is dispersed in a continuous phase of polyester.

According to another preferred mode, the composition comprises a total amount by weight of polyester (A) included in the range of from 60 to 75 parts, preferentially from 62 to 72 parts, these amounts by weight being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C). Generally, this composition is characterized by a morphology which is in the form of thermoplastic starch domains dispersed in a polyester matrix. According to this mode, the films obtained from these compositions exhibit better tear strength properties.

Even when the amounts of thermoplastic starch are high, the composition according to the invention can be converted into the form of films, without said films sticking to themselves, this being possible even when the production rate is high. In certain proportions such as those defined above, the morphology of the composition exhibits co-continuous domains of polyester and of thermoplastic starch. These compositions exhibit improved biodegradability compared with compositions in which the thermoplastic starch is dispersed in a continuous phase of polyester.

According to the invention, the composition also comprises a compound which is a monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol.

The mono fatty acid may be saturated or unsaturated and in particular may be stearic acid, lauric acid, myristic acid, palmitic acid, erucic acid, oleic acid or linoleic acid. Preferably, the compound (D) is glyceryl monostearate.

Preferably, the amount by weight of compound (D) ranges from 0.3 to 1.65 parts, advantageously from 0.5 to 1.5 parts, preferentially from 0.65 to 1.3 parts, these amounts by weight being expressed relative to 100 parts of the dry weight of the various constituents (A), (B) and (C).

In these particular variants, the compound (D) makes it possible to obtain films, by extrusion blow molding, with particularly low tackiness.

Preferably, the amount by weight of compound (D) is less than 8 parts, preferably less than 5 parts, most preferentially less than 2.5 parts, these amounts by weight being expressed relative to 100 parts of the dry weight of the various constituents (B) and (C).

The composition according to the invention may also comprise other additives or additional polymers, termed additional constituents, or a mixture thereof.

The composition according to the invention can in particular also comprise a bonding agent bearing several functions capable of reacting with the polyester and/or the starch and/or the organic plasticizer for starch, it being possible for this function to be chosen from carboxylic acid, carboxylic acid ester, isocyanate or epoxy functions. This bonding agent, in particular citric acid, can be present in an amount by weight ranging from 0.01 to 0.45 part, these amounts by weight being expressed relative to 100 parts of the total dry weight of (A), (B) and (C). Advantageously, the composition comprises from 0.05 to 0.3 part of citric acid, preferentially from 0.06 to 0.20 part, most preferentially from 0.07 to 0.15 part, these amounts by weight being expressed relative to 100 parts of the total dry weight of (A), (B) and (C). The presence of citric acid in the composition makes it possible to improve the homogeneity thereof and thus to improve the properties of the composition. In the citric acid proportions selected and particularly in the preferred proportions, the composition is easy to granulate, in comparison with the compositions based on polyester and thermoplastic starch comprising larger amounts of citric acid.

The composition according to the present invention can also comprise, as other additive or additional constituent, fillers or fibers of organic or inorganic nature, which are optionally nanometric and optionally functionalized. They may be silicas, zeolites, glass fibers or beads, clays, mica, titanates, silicates, graphite, calcium carbonate, talc, carbon nanotubes, wood fibers, carbon fibers, polymer fibers, proteins, cellulose-based fibers, lignocellulosic fibers and non-destructured granular starch. These fillers or fibers can make it possible to improve the hardness, the rigidity or the water- or gas-permeability. Preferably, the composition comprises from 0.1 to 200 parts of fillers and/or fibers, for example from 0.5 to 50 parts, this amount being expressed relative to 100 parts of the total dry weight of (A), (B) and (C). The composition may also be of composite type, i.e. may comprise large amounts of these fillers and/or fibers.

The additive that is of use in the composition according to the invention may also be chosen from opacifiers, dyes and pigments. They may be chosen from cobalt acetate and the following compounds: HS-325 Sandoplast® Red BB (which is a compound bearing an azo function, also known under the name Solvent Red 195), HS-510 Sandoplast® Blue 2B which is an anthraquinone, Polysynthren® Blue R, and Clariant® RSB Violet.

The composition according to the invention may also comprise other additives, such as stabilizers, for example light stabilizers, UV stabilizers and heat stabilizers, fluidizers, flame retardants and antistatic agents. It may also comprise primary and/or secondary antioxidants. The primary antioxidant may be a sterically hindered phenol, such as the compounds Hostanox® 0 3, Hostanox® 0 10, Hostanox® 0 16, Ultranox® 210, Ultranox®276, Dovernox® 10, Dovernox® 76, Dovernox® 3114, Irganox® 1010 or Irganox® 1076. The secondary antioxidant may be trivalent phosphorus compounds such as Ultranox® 626, Doverphos® S-9228, Hostanox® P-EPQ or Irgafos® 168.

The composition may also comprise, as additive, an additional processing aid, different than the compound (D), making it possible to reduce the pressure in the processing tool. These aids can also have the function of demolding agents making it possible to reduce the adhesion to the materials for forming the composition, such as molds or calendering cylinders. These aids may be selected from fatty acid esters and fatty acid amides different than the compound (D), metal salts, soaps, paraffins and hydrocarbon-based waxes. Particular examples of these aids are zinc stearate, calcium stearate, aluminum stearate, stearamides such as ethylene bis(stearamide) (EBS), erucamide such as Incromax®, behenamide, beeswaxes or candelilla wax. According to this preferred variant, this additional processing aid may be present in an amount by weight of less than 0.2 part, advantageously in an amount by weight of less than 0.1 part, these amounts by weight being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C). However, the composition according to the invention is preferably free of additional processing aid. Processing aids such as erucamides can be difficult to meter out and can lead to problems during the use of the films (difficulty with printing, bubble instability during the extrusion blow molding step).

The composition may also comprise an additional polymer, different than the polyester(s) (A). This polymer may be chosen from polyamides, polystyrene, styrene copolymers, styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene copolymers, poly(methyl methacrylate)s, acrylic copolymers, poly(ether-imide)s, poly(phenylene oxide)s, such as poly(2,6-dimethylphenylene oxide), poly(phenylene sulfate)s, poly(ester-carbonate)s, polycarbonates, polysulfones, polysulfone ethers, polyether ketones, and mixtures of these polymers.

The composition may also comprise, as additional polymer, a polymer for improving the impact properties of the polymer, in particular functional polyolefins such as functionalized ethylene or propylene polymers and copolymers, core-shell copolymers or block copolymers.

The compositions according to the invention may also comprise polymers of natural origin, such as cellulose, chitosans, alginates, carrageenans, agar-agar, proteins such as gluten, pea proteins, casein, collagen, gelatin or lignin, these polymers of natural origin possibly being physically or chemically modified.

According to one variant of the invention, the composition comprises by dry weight:

    • from 10 to 80 parts of at least one polyester (A1) from condensation of ethylene glycol and of 1,4-butanediol and of succinic acid and/or of adipic acid, preferably from 30 to 55 parts, most preferentially from 30 to 50 parts;
    • from 5 to 50 parts of at least one starch (B), preferably from 20 to 40 parts;
    • from 5 to 50 parts of at least one organic plasticizer (C) for starch, preferably from 10 to 35 parts;
    • optionally from 1 to 70 parts of polylactic acid (A2), preferably from 5 to 35 parts; the sum of the amounts of constituents (A1), (A2), (B) and (C) coming to 100 parts; the composition also comprising:
    • from 0.05 to 1.7 parts of monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, advantageously from 0.3 to 1.65 parts, preferentially from 0.5 to 1.5 parts, most preferentially from 0.65 to 1.3 parts;
    • optionally from 0.01 to 200 parts of additional constituent(s) chosen from the additives and polymers, different than (A1), (A2), (B), (C) and (D).

The composition according to the invention can be manufactured using a manufacturing process comprising:

    • a step a) of introducing into a mixing system constituents comprising at least one aliphatic polyester (A), at least one starch (B), at least one organic plasticizer for starch (C), at least one monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, and optionally water;
    • a mixing step b) in which the constituents are thermomechanically mixed so as to obtain the thermoplastic composition;
    • a step c) of recovering the thermoplastic composition.

The amounts of the various constituents can obviously be varied in such a way as to obtain the compositions described above. In the case where constituents comprising moisture are used, those skilled in the art can easily, in order to carry out the process, determine the amounts by weight of the various constituents by wet weight to be introduced into the mixing system, by measuring beforehand the moisture content in each constituent, for example by carrying out an assay using the Karl-Fisher method, this being in order to obtain the compositions in the proportions described above. By way of illustration, the Examples section contains the description of compositions expressed by dry weight, with the amounts of each of the constituents used during the process which are, for their part, expressed by wet weight.

With regard to the mixing system, it may involve internal blade or rotor mixers, external mixers, or single-screw or co-rotating or counter-rotating twin-screw extruders. However, it is preferred to prepare this mixture by extrusion, in particular using a co-rotating twin-screw extruder. In the case of an extruder, the various constituents of the composition may be introduced by means of feed hoppers located along the extruder.

The process described in WO 2010/010282 A1 may in particular be used to prepare the composition.

The mixing system may comprise a drying system, for example a system for extracting the volatile compounds, such as a vacuum pump. In this case, the moisture content of the composition at the end of the process may be reduced in comparison with the total moisture content of the constituents introduced in step a).

Preferably, the moisture content of the composition is adjusted so as to be between 2.5% and 9% relative to the total weight (and thus wet weight) of the constituents introduced during step a).

Advantageously, the process comprises at least one drying step, such that the moisture content of the composition is between 0.2% and 1.4%. Preferably, the mixing of step b) is carried out simultaneously with the drying step, for example by connecting a vacuum pump to the reactor. The process may also comprise a distinct drying step, which takes place subsequent to the recovering step c).

According to the invention, the mixing temperature during step b) advantageously ranges from 90 to 210° C., preferentially from 110 to 190° C.

The mixing of the constituents of the composition may take place under an inert atmosphere.

With regard to the mixing system, it may involve internal blade or rotor mixers, external mixers, or single-screw or co-rotating or counter-rotating twin-screw extruders. Preferably, the mixing step b) takes place in an extruder, in particular using a co-rotating twin-screw extruder. When it is by extrusion, the step a) of introducing the various constituents of the composition can be carried out by means of introduction hoppers located along the extruder.

When the mixing is carried out by extrusion, the composition recovered in step c) is in the form of a rod of polymer.

Preferably, the manufacturing process also comprises a step d) of granulating the composition recovered in step c). At the end of this granulating step d), granules of composition are obtained.

This granulating step can be carried out by means of any type of granulator, for example a water ring granulator, an underwater granulator or a rod granulator. The composition recovered can be very easily granulated, this being without bead formation, in particular when the composition comprises citric acid.

The invention also relates to granules of polymer consisting of the composition according to the invention.

The invention also relates to an article comprising the composition according to the invention.

This article may be of any type and may be obtained using conventional transformation techniques.

It may be, for example, fibers or threads that are of use in the textile industry or other industries. These fibers or threads may be woven so as to form fabrics, or else nonwovens.

The article according to the invention may also be a film or a sheet. These films or sheets may be produced by calendering, film cast extrusion or blown film extrusion techniques.

The invention relates in particular to a process for manufacturing a film by film blowing, comprising:

    • a step of extruding the composition or granules according to the invention so as to form a molten composition;
    • a step of forming a blown tube by blowing the molten composition obtained in the following step;
    • a step of drawing the blown tube;
    • a step of recovering a film.

Advantageously, the drawing speed is greater than 5 m/s, preferably greater than 10 m/s. The compositions according to the invention, in particular in the preferred variants, make it possible to keep excellent production rates and to obtain high drawing speeds, in particular when the composition comprises a blend of polyesters (A1) and (A2).

The article according to the invention may also be a container for transporting gases, liquids and/or solids. The containers concerned may be bottles, for example sparkling or still water bottles, juice bottles, soda bottles, carboys, alcoholic drink bottles, small bottles, for example small medicine bottles, small bottles for cosmetic products, dishes, for example for ready meals, microwave dishes, or lids. These containers may be of any size. They may be produced by extrusion-blow molding, thermoforming or injection-blow molding.

The articles may also be multilayer articles, at least one layer of which comprises the composition according to the invention. These articles may be produced via a process comprising a coextrusion step in the case where the materials of the various layers are placed in contact in the molten state. By way of example, mention may be made of the techniques of tube coextrusion, profile coextrusion, coextrusion blow-molding of a bottle, a small bottle or a tank, generally collated under the term “coextrusion blow-molding of hollow bodies”, coextrusion blow-molding also known as film blowing, and cast coextrusion.

They may also be manufactured according to a process comprising a step of applying a layer of molten composition onto a layer based on organic polymer, paper, metal or adhesive composition in the solid state. This step may be performed by pressing, by overmolding, stratification or lamination, extrusion-lamination, coating, extrusion-coating or spreading.

The invention will now be illustrated in the examples hereinafter. It is pointed out that these examples do not in any way limit the present invention.

EXAMPLES Constituents

The constituents of the various compositions illustrated are presented below.

(A): Polyesters

(A1): Aliphatic polyester from condensation of succinic acid, of adipic acid and of 1,4-butanediol, melting point of 95° C., flow index equal to 1.2 g/10 min.

(A2): Semi-crystalline poly(lactic acid) (L-lactic acid content equal to 9.75 mol %, D-lactic acid content equal to 4.3 mol %, melting point of 150° C., flow index equal to 2.6 g/10 min).

(B): Starch

Starch a: Wheat starch (containing 12.5% water)

Starch b: Potato flour (containing 20% water)

(C): Plasticizer

Plasticizer c: Glycerol

Plasticizer d: Mixture of glycerol and sorbitol containing 16% of water with the distribution by dry weight glycerol=60%, sorbitol=40%.

(D) Monoester Compound

(D)=Glyceryl monostearate

Additives

Processing aids other than compound (D)

Incromax®

EBS: ethylene bis(stearamide)

Bonding agent

CA=Citric acid

Composition Manufacturing Process

The compositions according to the invention and comparative compositions were prepared using an extruder of the Leistritz brand, ZSE27MAXX60D, Diameter 28, Length L/D=60, for a flow rate of: 20 kg/h.

    • Temperature profile (fifteen heating zones Z1 to Z15, temperature in ° C.): 20/60/60/80/90/110/130/130/180/160/180/150/130/130/130 with a variable screw speed of 200 rpm to 400 rpm.

In the case where the composition envisioned comprises an additional polyester, physical mixing of the granules of the polyesters (A1) and (A2) is carried out prior to the introduction into the extruder.

During the process, the following are introduced into the extruder:

    • the polyester (A) or the blend of the polyesters (A1) and (A2) in the main hopper of the extruder, following which said blend passes through all of the heating zones of the extruder,
    • the plasticizer for starch (C) in zone Z3 (9 to 12 D),
    • the starch (B), and also the additives at zone Z4 (13 to 16 D).

A partial vacuum is applied in zone Z9 (33-36 D) and in zone 11 (41-44 D) (vacuum of 100 mbar) making it possible to remove the water.

The granules are obtained by means of a conventional underwater granulation system.

The granules are dried in a basket dryer for 2 hours at 80° C. Moisture content is assayed using the Karl-Fisher method. All the compositions obtained have a moisture content of approximately 0.5%.

Details of the Compositions

The compositions according to the invention and the comparative compositions were prepared using the process described above. The amounts of the various constituents introduced into the extruder are given in table 1. The proportions of all the constituents are given relative to the wet weight of the sum of the constituents (A), (B) and (C).

In order to facilitate reading, it is specified that a composition according to the invention is named EX and a comparative composition is named Comp EX.

TABLE 1 Proportion of the constituents of the compositions by wet weight introduced into the extruder (A1) (A2) (B) (C) (D) EBS Incromax CA Ex 1 32.12 13.77 35.17a 18.94c 0.66 0 0 0.1 Ex 2 32.12 13.77 35.17a 18.94c 0.95 0 0 0.1 Ex 3 32.12 13.77 35.17a 18.94c 1.18 0 0 0.1 Ex 4 32.12 13.77 35.17a 18.94c 1.41 0 0 0.1 Ex 5 26.6 17.74 36.18a 19.48d 0.92 0 0 0.09 Ex 6 26.6 17.74 36.18a 19.48d 1.14 0 0 0.09 Ex 7 26.6 17.74 36.18a 19.48d 1.37 0 0 0.09 Ex 8 34.77 23.18 27.33a 14.71c 0.67 0 0 0.1 Ex 9 31.74 21.6 30.62a 16.49c 0.67 0 0 0.1 Ex 10 27.53 18.35 35.13a 18.93c 0.67 0 0 0.1 Ex 11 27.53 18.35 35.13a 18.93c 0.29 0 0 0.1 Ex 12. 34.94 8.7 34.94b 11.26c 0.95 0 0 0.1 Ex 13 32.12 13.77 35.17a 18.94c 0.95 0 0 0.18 Comp 32.12 13.77 35.17a 18.94c 0 0 0 0.1 Ex 1 Comp 32.12 13.77 35.17a 18.94c 0 0.29 0 0.1 Ex 2 Comp 32.12 13.77 35.17a 18.94c 0 0.48 0 0.1 Ex 3 Comp 32.12 13.77 35.17 to 18.94c 0 0.95 0 0.1 Ex 4 12 Comp 32.12 13.77 35.17a 18.94c 1.88 0 0 0.1 Ex 5 Comp 32.12 13.77 35.17a 18.94c 0 0 0.29 0.1 Ex 6 Comp 32.12 13.77 35.17a 18.94c 0 0 0.95 0.1 Ex 7

Table 2 expresses the proportions by weight of the various constituents of the composition recovered in the form of dry granules, these amounts being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C).

TABLE 2 Proportion of the constituents by dry weight in the compositions extruded (A1) (A2) (B) (C) (D) EBS Incromax CA Ex 1 33.6 14.4 32.19a 19.81c 0.7 0 0 0.1 Ex 2 33.6 14.4 32.19a 19.81c 1 0 0 0.1 Ex 3 33.6 14.4 32.19a 19.81c 1.25 0 0 0.1 Ex 4 33.6 14.4 32.19a 19.81c 1.5 0 0 0.1 Ex 5 28.8 19.2 34.28a 17.72d 1 0 0 0.1 Ex 6 28.8 19.2 34.28a 17.72d 1.25 0 0 0.1 Ex 7 28.8 19.2 34.28a 17.72d 1.5 0 0 0.1 Ex 8 36 24 24.76a 15.24c 0.7 0 0 0.1 Ex 9 33 22 27.86a 17.14c 0.7 0 0 0.1 Ex 10 28.8 19.2 32.19a 19.81c 0.7 0 0 0.1 Ex 11 28.8 19.2 32.19a 19.81c 0.3 0 0 0.1 Ex 12. 38.4 9.6 39.6b 12.38c 1 0 0 0.1 Ex 13 33.6 14.4 32.19a 19.81c 1 0 0 0.2 Comp Ex 1 33.6 14.4 32.19a 19.81c 0 0 0 0.1 Comp Ex 2 33.6 14.4 32.19a 19.81c 0 0.3 0 0.1 Comp Ex 3 33.6 14.4 32.19a 19.81c 0 0.5 0 0.1 Comp Ex 4 33.6 14.4 32.19a 19.81c 0 1 0 0.1 Comp Ex 5 33.6 14.4 32.19a 19.81c 2 0 0 0.1 Comp Ex 6 33.6 14.4 32.19a 19.81c 0 0 0.3 0.1 Comp Ex 7 33.6 14.4 32.19a 19.81c 0 0 1 0.1

In addition, comparative compositions 8, 9, 10 and 11 were prepared. These compositions differ from the compositions of the examples according to the invention 2, 5, 12 and 13 in that glucose stearate is used instead of glyceryl monostearate.

The granules of the compositions obtained above were converted into the form of a blown tube according to the following protocol: the granules of the compositions are converted into films on a blow-molding extruder of the Collin brand (Diameter 20, Length L/D=18, five heating zones Z1 to Z5) using the following temperature profile (160° C./160° C./160° C. /160° C. /160° C.) and a screw speed of 60 revolutions per minute. The maximum blown tube manufacturing speed, and also the ratio of this speed relative to the maximum speed of the machine are reported in table 3.

The tacky aspect of the blown tubes was evaluated in two ways:

    • the tendency of the blown tube to stick to itself after having been rolled up;
    • the tacky feel of the blown tube.

The mechanical properties were also measured when the blown tube could be separated so as to form a 50 μm film. The evaluation of the tacky aspect and also the mechanical properties are also reported in table 3.

TABLE 3 Evaluation of the film-forming ability and of the films obtained by blown film extrusion Tacky Stickiness Drawing Ds/Ds Modulus elongation feel to itself speed (m/s) max. % (MPa) at break (%) ++ ++ 13 100 250 250 Ex 2 ++ ++ 13 100 280 225 Ex 3 ++ ++ 13 100 220 225 Ex 4 ++ ++ 7.8 60 195 190 Ex 5 ++ ++ 13 100 260 220 Ex 6 ++ ++ 13 100 215 190 Ex 7 ++ ++ 7.15 55 255 195 Ex 8 ++ ++ 13 100 275 230 Ex 9 ++ ++ 13 100 240 195 Ex 10 ++ ++ 13 100 170 165 Ex 11 + + 13 100 295 270 Ex 12. ++ ++ 13 100 140 245 Ex 13 ++ + 13 100 340 115 Comp Ex 1 −− −− 9.1 70 NA NA Comp Ex 2 − −− 13 100 NA NA Comp Ex 3 − −− 13 100 NA NA Comp Ex 4 − −− 13 100 NA NA Comp Ex 5 NA NA NA Film NA NA formation not possible Comp Ex 6 − −− 13 100 NA NA Comp Ex 7 − −− 13 100 NA NA Tackiness grading Feel: ++does not stick, non-greasy +slightly greasy feel −greasy and waxy −−tacky Blown tube: ++Blown tube separated +Blown tube can be easily separated −Blown tube can be separated by tensile force −−Blown tube stuck and cannot be separated

The tests show that the use of a monoester of a mono fatty acid and of glycerol in compositions based on thermoplastic starch and aliphatic polymer makes it possible, when the amount is less than 2 parts, this amount being expressed relative to 100 parts of the total dry weight of the constituents (A), (B) and (C), to form non-tacky films by film blowing.

The films can be formed at high speed, in particular when the amount of monoester of a mono fatty acid and of glycerol ranges from 0.3 to 1.25 parts. However, if films which do not stick at all are desired, it is advantageous to use amounts of 0.5 part or more. Conversely, when other processing aids, such as Incromax® or EBS, are used, this being regardless of the amount used, all the blown tubes formed are very tacky and it is thus not possible to open the blown tube. The same observations were made for comparative compositions 8 to 11. Thus, compared with the compositions of application WO2007/012142, which comprise glucose stearate, the compositions according to the invention can be converted at higher rate by blowing in the form of a blown tube, without said blown tube sticking to itself.

It may be noted that it was impossible to form a film (it was not possible to form the blown tube), when the amount of monoester of a mono fatty acid and of glycerol is 2 parts.

Claims

1. A thermoplastic composition comprising at least one polyester (A) which is an aliphatic polyester, at least one starch (B), at least one organic plasticizer for starch (C), and at least one compound which is a monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and glycerol wherein 0.05 to 1.7 parts of compound (D) by weight, relative to 100 parts of the dry weight of the various constituents (A), (B) and (C), are present.

2. The composition according to claim 1, wherein 0.3 to 1.65 parts of compound (D) are present.

3. The composition according to claim 1, wherein compound (D) is glyceryl monostearate.

4. The composition according to claim 1, wherein that the polyester said aliphatic polyester comprises polylactic acid (A2), polymers (A1) produced from condensation of ethylene glycol and/or of 1,4-butanediol and of succinic acid and/or of adipic acid, and mixtures thereof.

5. The composition according to claim 4, wherein said at least one polyester comprises a blend of polymers (A1) and (A2), a weight percentage of (A2) relative to a weight of (A1) and (A2), expressed by dry weight, ranges from 5% to 90%.

6. The composition according to claim 1, wherein said polyester (A) comprises from 35 to 75 parts relative to 100 parts of the total dry weight of the constituents (A), (B) and (C).

7. The composition according to claim 1, wherein a starch/plasticizer weight ratio, expressed by dry weight, ranges from 90/10 to 40/60.

8. The composition according to claim 1, wherein the organic plasticizer comprises diols and polyols, including glycerol, polyglycerols, sorbitans, sorbitol, mannitol, and hydrogenated glucose syrups, urea, polyethers with a molar mass below 800 g/mol, and mixtures thereof.

9. The composition according to claim 1 comprising a morphology including co-continuous domains of thermoplastic starch and polyester.

10. The composition according to claim 1, wherein polyester (A) has a flow index ranging from 0.1 to 50 g/10 min in accordance with ISO 1133, at 190° C. and 2.16 kg.

11. A granule of polymer comprising the composition of claim 1.

12. A process for manufacturing a thermoplastic composition, comprising:

introducing into a mixing system constituents comprising at least one aliphatic polyester (A), at least one starch (B), at least one organic plasticizer for starch (C), at least one monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, and optionally water;
thermomechanically mixing the constituents to obtain a thermoplastic composition; and
recovering the thermoplastic composition.

13. The process according to claim 12, further comprising

introducing water and adjusting moisture content of the constituents to between 2.5% and 9%; and wherein said thermomechanical mixing
is carried out simultaneously with drying to adjust the moisture content of the recovered composition between 0.2% and 1.4%.

14. The process according to claim 12, wherein a twin-screw extruder performs the thermomechanical mixing.

15. A process for manufacturing a film by film blowing, comprising:

extruding one of a composition comprising at least one aliphatic polyester (A), at least one starch (B), at least one organic plasticizer for starch (C), at least one monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, and optionally water, or a granulated thermoplastic composition comprising at least one aliphatic polyester (A), at least one starch (B), at least one organic plasticizer for starch (C), at least one monoester (D) of a mono fatty acid comprising at least 12 carbon atoms and of glycerol, and optionally water to form a molten composition;
forming a blown tube by blowing said molten composition;
drawing the blown tube; and
recovering a film
Patent History
Publication number: 20180327588
Type: Application
Filed: Nov 17, 2015
Publication Date: Nov 15, 2018
Applicant: Roquette Freres (Lestrem)
Inventors: Sophie Marcille (Lille), Hélène Amedro (Bethune), Nicolas Descamps (Sainghin-En-Melantois), Justine Leuwers (La Bassee), René Saint-Loup (Lomme)
Application Number: 15/527,306
Classifications
International Classification: C08L 67/02 (20060101); C08L 3/02 (20060101); C08J 3/20 (20060101); C08J 3/18 (20060101); C08J 5/18 (20060101);