PEA STARCH POLYMER COMPOSITION

Description

[0001] The present invention relates to a polymer composition, a process for producing a polymer composition, the use of a polymer composition and molded parts, films or fibers containing a polymer composition.

[0002] Plastics are materials composed of macromolecules. Their versatility and technical properties, such as formability, elasticity, tensile strength, and durability, make them suitable for numerous applications. Depending on the application, plastics are subject to very different mechanical requirements. For example, when using plastics in carrier bags, high tensile strength, high elongation at break, high tear propagation resistance, and high dart drop of the plastic films used are desirable.

[0003] Conventional plastics have a number of undesirable properties: their production consumes large quantities of fossil resources such as oil and natural gas, many are not or only minimally biodegradable, and they often have a poor carbon footprint. To reduce the consumption of fossil resources and achieve a better carbon footprint, plastics made from renewable raw materials, such as plants, have been increasingly produced in recent years. Polymers that are at least partially or entirely based on renewable raw materials are also called "bio-based" polymers.

[0004] Many plastics are very durable and degrade in nature only very slowly, sometimes over decades or even centuries. In light of current environmental developments, such as ocean pollution, the demand for biodegradable plastics is increasing. These are plastics that can be broken down by naturally occurring microorganisms, such as fungi or bacteria, using enzymes. The biodegradability of plastics depends solely on the chemical structure of the plastic and its ability to be transformed into naturally occurring metabolic end products through biological activity. Therefore, bio-based plastics are not necessarily biodegradable.

[0005] The main applications of biodegradable polymer compositions are in the packaging and catering sectors. Applications also exist in agriculture and horticulture, as well as in the pharmaceutical and medical fields. Biodegradable polymer compositions are particularly relevant for the production of waste bags, carrier bags, disposable tableware (cups, mugs, plates, cutlery), packaging films, bottles, fruit and vegetable trays, loose-fill packing peanuts, mulch films, flower pots, and similar products.

[0006] Especially in the area of ​​waste bags and carrier bags, particularly high mechanical requirements are placed on the plastic films made from polymer compositions with regard to tear resistance and load-bearing capacity.

[0007] For the reasons mentioned above, plastics that have good mechanical properties and are at least partially bio-based and / or biodegradable are particularly desirable.

[0008] Polymer compositions for the production of such plastics based on starch and aliphatic-aromatic copolyesters are known from the prior art.

[0009] For example, a plasticizer-free thermoplastic polymer composition based on potato starch, which is particularly suitable for blown film extrusion, flat film extrusion and injection molding of biodegradable products, is commercially available under the trade name BIOPLAST ®< GF 106 / 02 from the company BIOTEC GmbH & Co. KG in Emmerich (Germany).

[0010] The production and properties of plasticizer-free thermoplastic polymer blends based on starch and aliphatic-aromatic copolyesters are described, for example, in the publication EP 0 596 437 B1.

[0011] As described on page 265 of the "Handbook of Biodegradable Polymers, 2nd Edition", published by Smithers Rapra Technology, 2014, the usual and most important sources of starch are crops such as maize, wheat, potatoes, tapioca and rice.

[0012] WO 2005 / 120808 A1 describes a process for producing biodegradable plastic films, comprising the production of a biodegradable blown film and subsequent monoaxial or biaxial cold drawing. The biodegradable polymer used can be an aliphatic-aromatic copolyester, for example, polybutylene adipate terephthalate. The polymer composition used can also contain starch. CN 108 948 681 A discloses starch-modified PBAT copolyesters. The manufacture of waste bags is mentioned. Furthermore, claim 4 mentions in a list that the starch can be pea starch.

[0013] Disadvantages of the polymer compositions known from the prior art are that the mechanical properties of molded parts, films and fibers produced from them are in need of improvement, or that they are not or only to a small extent bio-based and / or are not or only slowly or incompletely biodegradable.

[0014] The present invention was based on the objective of providing a polymer composition that at least partially overcomes one or more disadvantages of the prior art. The polymer composition should result in excellent mechanical properties for molded parts, films, and fibers produced from it, and should be at least partially bio-based and / or biodegradable. The polymer composition should be particularly suitable for the production of especially stable and durable waste bags and carrier bags. In particular, films produced from the polymer composition should exhibit high tensile strength, high elongation at break, high tear propagation strength, and high dart drop.

[0015] A further object of the present invention is to provide a method for producing such a polymer composition. In particular, the method should be fast and efficient.

[0016] All or some of these problems are solved according to the invention by a polymer composition according to claim 1, a method according to claim 9, a polymer composition according to claim 14, a use according to claim 15, and molded parts, films, or fibers according to claim 16. Advantageous embodiments of the invention are specified in the dependent clauses and are explained in detail below.

[0017] The invention provides a polymer composition which, based on the total dry weight of the polymer composition, contains at least the following components: a) 25.5 wt.% to 50 wt.% starch, b) 30 wt.% to 74.5 wt.% aliphatic-aromatic copolyester, wherein the starch contains at least 25 wt.% pea starch, based on the total dry weight of the starch.

[0018] Surprisingly, it has been found that films produced from the polymer composition according to the invention exhibit particularly high tensile strength, elongation at break, tear propagation strength, and a particularly high dart drop. Tensile strength is a measure of the film's strength and denotes the maximum mechanical tensile stress that a material can withstand. It is therefore an important measure of the mechanical load that a film, for example as a material in a carrier bag, can withstand. Elongation at break is a measure of a material's elasticity. It expresses the existing elongation at the moment of tearing. Elongation at break is given as a percentage relative to the original length before stretching. Tear propagation strength describes the property of a material not to tear further, even if an indentation is present.High tear resistance is therefore important to prevent, for example, a carrier bag from tearing further if it is damaged at a single point by a sharp object during transport. The dart drop is a measure of a material's impact resistance. It refers to the weight of a drop hammer that punctures the film in 50% of drop tests. A high dart drop is therefore important to prevent a film from being punctured under mechanical stress, for example, by a heavy object in a carrier bag. Due to these mechanical properties, films made from the composition according to the invention are particularly well-suited for garbage bags and carrier bags. Furthermore, a polymer composition according to the invention is preferably at least partially bio-based and biodegradable.

[0019] Without wishing to be bound to a specific scientific theory, the advantageous properties of the polymer composition according to the invention appear to be attributable to the pea starch content in the polymer composition.

[0020] In particular, the amylose / amylopectin ratio, the molecular weight and / or the molecular fine structure of pea starch, compared to other starches such as potato starch, appear to be crucial.

[0021] Tests have shown that a polymer composition with a starch content of 25.5 wt.% to 50 wt.% (based on the total dry weight of the polymer composition) provides particularly good mechanical properties while simultaneously ensuring a high bio-based content and good biodegradability. A lower starch content reduces the bio-based content in the polymer composition and also decreases biodegradability. A higher starch content impairs the processability of the polymer composition and, in film production, leads to films with low stability and poor mechanical properties such as low tensile strength, elongation at break, tear resistance, and low dart drop. With excessively high starch content, films cannot be produced at all.

[0022] A proportion of 30 wt.% to 74.5 wt.% aliphatic-aromatic copolyester, based on the total dry weight of the polymer composition, ensures good processability of the polymer composition and good mechanical properties of molded parts, films, or fibers produced from it, especially blown films. Furthermore, the aliphatic-aromatic copolyester can be partially or completely bio-based. The aliphatic-aromatic copolyester also increases the biodegradability of the polymer composition and of the molded parts, films, and fibers produced from it. If the proportion of aliphatic-aromatic copolyester in the polymer composition is too high or too low, molded parts, films, or fibers with the desired mechanical properties cannot be produced from the polymer composition.

[0023] The term "starch" as used herein also includes starch derivatives. Starch derivative, as used here, means modified or functionalized starch. Preferably, starch whose free OH groups are at least partially substituted is used as the starch derivative. For example, starch modified with ether and / or ester groups is suitable. Further examples of suitable starch derivatives are hydrophobized or hydrophilized starch, in particular, for example, hydroxypropyl starch or carboxymethyl starch. The starch can be obtained, for example, from potatoes, corn, tapioca, or rice. Preferably, native starch, i.e., unmodified or non-functionalized starch, is used for the production of the polymer compositions according to the invention.

[0024] The term "total dry weight" here refers to the total weight of the respective component or composition excluding water. This means that the water content of the respective starch is not taken into account when stating the total dry weight and the respective weight percentages. In a mixture of 50 g of "moist" pea starch with a water content of 10% by weight (based on the total weight of the pea starch) and 50 g of aliphatic-aromatic copolyester, the dry weight of the pea starch is therefore 45 g, and the total dry weight of the mixture is 95 g. The proportion of pea starch, based on the total dry weight of the mixture, is therefore 45 divided by 95, or 47.4% by weight. This specification allows for a better comparison of different starches with varying water contents, as well as the starch content after processing steps such as drying or extrusion.

[0025] The term "pea starch" here refers to starch obtained from peas, regardless of any prior processing steps. "Pea" here refers to the plant genus Pisum. The pea starch can therefore originate from any plant species, variety, or convarietal within this genus, such as garden peas, field peas, shelling peas, garden peas, and sugar snap peas. The pea starches used to produce the polymer compositions according to the invention may, for example, contain a residual water content of 8 to 12% by weight, based on the total weight of the pea starch. Preferably, native pea starch, i.e., unmodified or non-functionalized pea starch, is used to produce the polymer compositions according to the invention.

[0026] The term "aliphatic-aromatic copolyester" here refers to a polyester, i.e., a polymer with multiple ester groups (COO) in its main chain, composed of at least two different types of monomer units, where at least one monomer unit is an aliphatic hydrocarbon and at least one monomer unit is an aromatic hydrocarbon. When "aliphatic-aromatic copolyester" is mentioned here, it also includes mixtures of different aliphatic-aromatic copolyesters.

[0027] Preferably, the polymer composition contains a water content of 0.01 wt.% to 5 wt.%, based on the total weight of the polymer composition, particularly 0.03 wt.% to 3 wt.%, 0.04 wt.% to 1.5 wt.%, or 0.05 wt.% to 1 wt.%. The water content influences the properties of molded parts, films, or fibers produced from the polymer composition. It also directly affects the processing properties of the polymer composition. If the water content is too low, there is a risk that the components of the polymer composition will burn when heated. If the water content is too high, molded parts, films, and fibers with the desired mechanical properties cannot be produced from the polymer composition; in particular, undesirable blistering may occur during further processing.

[0028] According to a preferred embodiment of the polymer composition according to the invention, the starch contains at least 30 wt.%, in particular at least 40 wt.%, at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, at least 90 wt.%, at least 95 wt.%, at least 97 wt.%, or at least 99 wt.% pea starch, in each case based on the total dry weight of the starch. Such a proportion of pea starch in the starch ensures that films produced from the polymer composition exhibit particularly good mechanical properties, such as high tensile strength, elongation at break, tear resistance, and high dart drop.

[0029] According to a further preferred embodiment of the polymer composition according to the invention, the starch is present in a destructured form. Preferably, the destructured starch contained in the polymer composition according to the invention is formed during the production of the polymer composition from native starch by mechanical and / or thermal destructuring. Destructured in this context means that the granular, crystalline structure of native starch has been completely or at least largely destroyed. This can be easily determined, for example, by examining cross-sectional sections under a scanning electron microscope. Alternatively, the starch phase of the polymer composition can be isolated and examined under a polarizing microscope for the presence of crystalline components.

[0030] Destructured starch within the meaning of this invention must be distinguished from cases in which native starch is used merely as a filler and the granular structure of the starch is at least partially retained.

[0031] Destructured starch can advantageously be present in the form of (optionally pre-fabricated) plasticizer-containing thermoplastic starch (TPS) in the polymer composition according to the invention. Suitable plasticizers include, in particular, carbon-containing plasticizers such as glycerin and / or sorbitol. However, the destructured starch in the polymer composition according to the invention is preferably as free of plasticizers as possible.

[0032] To obtain destructured starch without the addition of carbon-containing plasticizers, native starch is preferably homogenized together with at least one hydrophobic polymer and at a sufficiently high water content under the influence of high shear forces and temperatures. The water is preferably completely or, more preferably, partially removed by drying during or at the end of the homogenization process. The production of such a plasticizer-free destructured starch in polymer blends with aliphatic-aromatic copolyesters is described, for example, in publication EP 0 596 437 B1.

[0033] Preferably, the polymer composition according to the invention can contain 27 wt.% to 45 wt.%, in particular 28.5 wt.% to 40 wt.% or 30 wt.% to 35 wt.%, of starch, based on the total dry weight of the polymer composition. Such a proportion of starch ensures particularly good mechanical properties and simultaneously a high bio-based content and good biodegradability. A lower proportion of starch results in a lower bio-based content in the polymer composition and simultaneously reduces biodegradability. A higher proportion of starch impairs the processability of the polymer composition and, in film production, leads to films with low stability and poor mechanical properties such as low tensile strength, elongation at break, tear propagation resistance, and low dart drop. With excessively high starch content, films cannot be produced at all.

[0034] For the polymer composition according to the invention, aliphatic-aromatic copolyesters are particularly suitable which are biodegradable according to EN 13432 and / or have a glass transition temperature (Tg) below 0 °C, in particular below -4 °C, more preferably below -10 °C, even more preferably below -20 °C and most preferably below -30 °C. The aliphatic-aromatic copolyesters contained in the polymer composition according to the invention are also preferably thermoplastic.

[0035] According to the polymer composition according to the invention, the aliphatic-aromatic copolyester is a copolyester based on at least one aliphatic dicarboxylic acid with 7 to 22 carbon atoms, one aromatic dicarboxylic acid with 8 to 20 carbon atoms and a diol with 2 to 12 carbon atoms.

[0036] According to a particularly preferred embodiment of the polymer composition according to the invention, the aliphatic-aromatic copolyester is a statistical copolyester.

[0037] According to a further preferred embodiment of the polymer composition according to the invention, the aliphatic-aromatic copolyester is a copolyester based on at least adipic and / or sebacic acid, in particular based on at least adipic acid.

[0038] According to a particularly preferred embodiment of the polymer composition according to the invention, the aliphatic-aromatic copolyester is a copolyester or statistical copolyester based on 1,4-butanediol, adipic acid and / or sebacic acid, and terephthalic acid or a terephthalic acid derivative, in particular dimethyl terephthalate (DMT). This copolyester can, in particular, have a glass transition temperature (Tg) of -25 to -40 °C, in particular -30 to -35 °C, and / or a melting range of 100 to 120 °C, in particular 105 to 115 °C. Such an aliphatic-aromatic copolyester ensures that the polymer composition is biodegradable and compostable.Furthermore, such an aliphatic-aromatic copolyester ensures excellent mechanical properties in molded parts, films, or fibers produced from this polymer composition. Additionally, such an aliphatic-aromatic copolyester provides high tensile strength, elongation at break, tear resistance, and high dart drop in films produced from this polymer composition.

[0039] According to a further preferred embodiment of the polymer composition according to the invention, the polymer composition contains, based on the total dry weight of the polymer composition, 40 wt.% to 74.5 wt.%, in particular 50 wt.% to 74.5 wt.%, 55 wt.% to 70 wt.%, or 60 wt.% to 70 wt.% aliphatic-aromatic copolyester. Such an amount of aliphatic-aromatic copolyester ensures good processability of the polymer composition and results in good mechanical properties of molded parts, films, or fibers produced from the polymer composition, in particular blown films, while simultaneously ensuring good biodegradability. If the proportion of aliphatic-aromatic copolyester in the polymer composition is too high or too low, molded parts, films, or fibers with the desired mechanical properties cannot be produced from the polymer composition.

[0040] Furthermore, the polymer composition according to the invention can contain 0.1 wt.% to 5 wt.%, in particular 0.2 wt.% to 2 wt.% or 0.3 wt.% to 1 wt.% processing aids, in particular sorbitan monostearate, based on the total dry weight of the polymer composition. Such a processing aid assists in the further processing of the polymer composition, for example in blown film extrusion for the production of blown films.

[0041] Preferably, the polymer composition according to the invention contains, based on the total dry weight of the polymer composition, less than 5 wt.%, in particular less than 3 wt.% or less than 1 wt.%, carbon-containing plasticizers, in particular glycerin or sorbitol. Other examples of carbon-containing plasticizers are arabinose, lycose, xylose, glucose, fructose, mannose, allose, altrose, galactose, gulose, lodose, inositol, sorbose, talitol and monoethoxylate, monopropoxylate and monoacetate derivatives thereof, as well as ethylene, ethylene glycol, propylene glycol, ethylene diglycol, propylene diglycol, ethylene triglycol, propylene triglycol, polyethylene glycol, polypropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-, 1,3-, 1,4-butanediol, 1,5-pentanediol, 1,6-, 1,5-hexanediol, 1,2,6-, 1,3,5-hexanetriol, neopentyl glycol, trimethylolpropane, pentaerythritol, sorbitol and their derivatives. Acetate, ethoxylate and propoxylate derivatives.The polymer composition according to the invention preferably does not contain carbon-containing plasticizers. Although the polymer composition according to the invention preferably does not contain carbon-containing plasticizers, it has good processing properties and is particularly well suited for the production of elastic products, such as films.

[0042] The polymer composition according to the invention preferably contains, based on the total weight of the polymer composition, less than 10 wt.% low-molecular-weight substances and is therefore essentially free of plasticizers. Low-molecular-weight substances within the meaning of the invention are understood to be substances with a molecular weight of less than 500 g / mol, in particular less than 250 g / mol. Low-molecular-weight substances within the meaning of the invention are, in particular, water, glycerin, sorbitol and / or mixtures thereof.

[0043] The polymer composition according to the invention may contain further components, in particular further polymers and / or conventional additives, such as processing aids, stabilizers, flame retardants, antiblocking agents and / or fillers.

[0044] According to a further preferred embodiment of the polymer composition according to the invention, the polymer composition is biodegradable according to EN 13432, in particular completely biodegradable. This prevents any risk to flora and fauna if the polymer composition according to the invention or products made from it, such as carrier bags or waste bags, enter the environment.

[0045] According to a further preferred embodiment of the invention, the polymer composition according to the invention possesses thermoplastic properties. Preferably, the polymer composition is thermoplastically processable.

[0046] The invention further provides a method by which it is possible to obtain the polymer compositions described above.

[0047] Basically, the methods according to the invention comprise the following steps, wherein the individual steps can be carried out simultaneously or successively and in any order and frequency: (i) Producing a mixture by mixing, in each case based on the total dry weight of the mixture, at least: (a) 25.5 wt.% to 50 wt.% starch, (b) 30 wt.% to 74.5 wt.% aliphatic aromatic copolyester, wherein the starch contains at least 25 wt.% pea starch, based on the total dry weight of the starch; (ii) Homogenizing the mixture by supplying thermal and / or mechanical energy; (iii) Adjusting the water content of the mixture so that the final product has a water content of less than 5 wt.%, based on the total weight of the mixture.

[0048] Preferably, the process steps are carried out in the order given above.

[0049] The above statements regarding the polymer composition according to the invention apply analogously to the aliphatic-aromatic copolyester. The above statements regarding the quantities contained in the polymer composition according to the invention, each based on the total dry weight of the mixture, apply analogously to the quantities used to produce the mixture, each based on the total dry weight of the mixture. The above statements regarding the polymer composition according to the invention apply analogously to the proportion of pea starch, based on the total dry weight of the starch.

[0050] The process according to the invention provides for the homogenization of the mixture. Homogenization can be carried out by any method known to those skilled in the art in plastics engineering. Preferably, the mixture is homogenized by dispersion, stirring, kneading, and / or extrusion. According to a preferred embodiment of the invention, shear forces act on the mixture during homogenization. Suitable manufacturing processes for starch-containing thermoplastic polymers, which are also analogously applicable to the production of the polymeric material according to the invention, are described, for example, in EP 0 596 437 B1 EP. This ensures uniform homogenization of the mixture.

[0051] According to a preferred embodiment of the invention, the mixture is heated during homogenization (e.g., in the extruder). According to a further preferred embodiment of the invention, the mixture is heated to a temperature of 90 to 250 °C, in particular 130 to 220 °C, during homogenization or extrusion.

[0052] According to a further preferred embodiment of the process according to the invention, the water content of the mixture is adjusted to less than 3 wt.%, in particular less than 1.5 wt.% or less than 1 wt.%, based on the total weight of the mixture. It is preferred to keep the water content of the polymer composition low in order to enable good further processing.

[0053] The water content values ​​given here refer to the material exiting the extruder. To determine the water content, a sample of molten extrudate is collected at the die outlet as it exits the extruder in a sealable container, which is then hermetically sealed. Care should be taken to ensure that the container is filled as completely as possible with extrudate to minimize air entrapment. After the sealed container has cooled, it is opened, a sample is taken, and the water content is determined using Karl Fischer titration.

[0054] According to a preferred embodiment of the process according to the invention, the water content of the mixture is adjusted by degassing the mixture, in particular by degassing the melt, and / or by drying the mixture during homogenization or extrusion. This saves energy and costs, as no further process step is required to adjust the water content.

[0055] The invention further relates to a polymer composition obtainable according to the inventive method. Such a polymer composition is particularly well suited for producing films with exceptionally high tensile strength, elongation at break, tear resistance, and dart drop. Due to these mechanical properties, films produced from such a composition, especially blown films, are particularly well suited for waste bags and carrier bags. Furthermore, a polymer composition obtainable according to the inventive method is at least partially bio-based and biodegradable.

[0056] The invention further relates to the use of a polymer composition according to the invention, or a polymer composition obtainable according to the inventive process, for the production of molded parts, films, or fibers, in particular by blown film extrusion, flat film extrusion, or injection molding, especially for the production of films by blown film extrusion. This use enables the production of molded parts, films, or fibers with particularly good mechanical properties that are at least partially bio-based and biodegradable. In particular, this use enables the production of films with high tensile strength, elongation at break, tear propagation strength, and high dart drop.

[0057] The invention also relates to molded parts, films, or fibers containing a polymer composition according to the invention or a polymer composition obtainable according to the inventive method. These molded parts, films, or fibers exhibit particularly good mechanical properties, are at least partially bio-based, and biodegradable. Films according to the invention can be blown, flat, or cast films. Preferred film thicknesses for blown films according to the invention are from 10 to 100 µm, for flat films according to the invention from 150 to 500 µm, and for cast films according to the invention from 10 to 500 µm. In particular, such films, especially blown films, exhibit high tensile strength, elongation at break, tear propagation strength, and a high dart drop. Therefore, they are particularly well-suited for the production of carrier bags and waste bags.

[0058] The principle of the invention will be explained below using examples that do not restrict the subject matter of the invention, with reference to the five figures ( Fig. 1 - Fig. 5 ) will be explained in more detail. Fig. 1 shows a comparison of the tensile strengths of a blown film (film A) made from a pea starch-containing polymer composition, a blown film (film B) made from a pea and potato starch-containing polymer composition, and a blown film (film C) made from a potato starch-containing polymer composition in the longitudinal and transverse directions, as well as at the seam in the longitudinal direction. Fig. 2shows a comparison of the elongation at break of a blown film (film A) made from a pea starch-containing polymer composition, a blown film (film B) made from a pea and potato starch-containing polymer composition, and a blown film (film C) made from a potato starch-containing polymer composition in the longitudinal and transverse directions, as well as at the seam in the longitudinal direction. Fig. 3 shows a comparison of the tear strength of a blown film (film A) made from a pea starch-containing polymer composition, a blown film (film B) made from a pea and potato starch-containing polymer composition, and a blown film (film C) made from a potato starch-containing polymer composition. Fig. 4shows a comparison of the specific dart drop of a blown film (film A) made from a pea starch-containing polymer composition, a blown film (film B) made from a pea and potato starch-containing polymer composition, and a blown film (film C) made from a potato starch-containing polymer composition. Fig. 5 shows a comparison of the dart drop of a blown film (film A) made from a pea starch-containing polymer composition, a blown film (film B) made from a pea and potato starch-containing polymer composition, and a blown film (film C) made from a potato starch-containing polymer composition. Examples of implementation

[0059] The following materials were used for the comparison and implementation examples: poly(butylene adipate co-terephthalate), PBAT (ECOFLEX F Blend 1201, BASF); native pea starch; native potato starch (EMSLANDSTÄRKE); sorbitan monostearate (Atmer 103, Croda).

[0060] The properties of the manufactured films were determined according to the following standards. The film thickness was determined according to DIN EN ISO 2286-3:1998. The tensile strength was determined according to EN ISO 527. The elongation at break was determined according to EN ISO 527. The tear strength was determined according to EN ISO 6383. The dart drop was determined according to ASTM D 1709. The specific dart drop was determined by dividing the dart drop by the thickness of the film at its thinnest point. Example 1 (Production of polymer compositions)

[0061] Using a twin-shaft extruder (co-rotating extruder) of the type Werner & Pfleiderer ( COPERIONUsing a ZSK 40 screw press with a screw diameter of 40 mm and a length / diameter of 42 mm, the following formulations A, B, and C were compounded. The values ​​given refer to the proportions used in mass percent, based on the total weight of the formulations (not total dry weight). Formulation C serves as a comparison example. Table 1: Recipes A B C PBAT 68 65 65 pea starch 31,4 17,3 - potato starch - 17,3 34,6 Sorbitan monostearate 0,6 0,4 0,4

[0062] The following compounding parameters were adhered to: Table 2: Temperature profile of zones (Z) ZSK 40 (in °C) Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 Z11 Z12 0 190 190 190 190 170 160 160 160 150 140 0 Speed: 200 min -1< Throughput: 40 kg / h Example 2 (Production of blown films)

[0063] The polymer compositions A, B and C from Example 1 were produced using a single-shaft extruder of type Collin 30 ( DR. Collin ), screw diameter 30 mm, L / D = 33, melted and further processed into blown film.

[0064] The following processing parameters were set: Fan: 39-40 % Lying width of foil tube: 325 mm Throughput: 161 g / min Inflation ratio: 3,44 Mass temperature: 176 °C Mass pressure: 198 bar (A), 167 bar (B), 190 bar (C) Speed: 59 min -1< Example 3 (Mechanical properties of the films)

[0065] The mechanical properties of the films (film A, film B and film C) produced from polymer compositions A, B and C were determined at room temperature and ambient atmosphere as follows: Table 4: Mechanical properties of the films Polymer composition A B C Foil thickness Ø [µm] 14,4 13,3 13,85 Tensile strength [MPa] along 33,88 31,09 27,31 across 20,47 18,84 18,26 seam lengthwise 24 25,27 20,35 Elongation at break [%] along 543,6 471,04 508,04 across 500,73 537,35 497,31 seam lengthwise 273,44 274,74 275,9 Tear strength [N / mm] along 84,91 98,21 77,03 across 95,69 138,17 83,92 Specific Dart Drop [g / µm] 15,56 13,18 13,71 Dart Drop [g] 186,73 131,89 150,86

[0066] The films produced from polymer compositions A, B and C have comparable film thicknesses.

[0067] It is striking and surprising that the tensile strength of the pea starch-containing films (A and B) is significantly higher in all three directions (longitudinal direction, transverse direction and at the seam in the longitudinal direction) than the tensile strength of the pea starch-free film (C) ( Fig. 1The tensile strength of film A, which contains only pea starch, is highest in both the longitudinal and transverse directions. At the longitudinal seam, the tensile strength of film B, which contains a mixture of pea and potato starch, is highest.

[0068] When comparing the elongation at break of films A, B and C, no significant trend can be observed ( Fig. 2 The deviations are within the usual range of variation (±10%) of the method used.

[0069] It is striking that the pea starch-containing films A and B exhibit a significantly higher tear resistance in both the longitudinal and transverse directions than the pea starch-free film C ( Fig. 3 The tear resistance of film B, which contains both pea starch and potato starch, is particularly high.

[0070] Film A, which contains only pea starch as its starch component, exhibits a particularly high specific dart drop compared to films B and C. Fig. 4 ) and Dart Drop ( Fig. 5 ) on.

[0071] Surprisingly, the pea starch contained in the polymer compositions leads to improved mechanical properties, in particular improved tensile strength, tear resistance and improved dart drop of blown films produced from them.

Claims

1. Polymer composition containing - in each case relative to the total dry weight of the polymer composition - the following components: a) 25.5 wt% to 50 wt% starch, b) 30 wt% to 74.5 wt% aliphatic-aromatic co-polyester, characterized in that the starch is at least 25 wt% pea starch, relative to the total dry weight of the starch and that the aliphatic-aromatic co-polyester is a co-polyester based upon at least one aliphatic dicarboxylic acid having 7 to 22 carbon atoms, an aromatic dicarboxylic acid having 8 to 20 carbon atoms, and a diol having 2 to 12 carbon atoms.

2. Polymer composition according to claim 1, characterized in that the polymer composition contains, in each case relative to the total weight of the polymer composition, water in an amount of 0.01 wt% to 5 wt%, and in particular 0.03 wt% to 3 wt%, 0.04 wt% to 1.5 wt%, or 0.05 wt% to 1 wt%.

3. Polymer composition according to claim 1 or 2, characterized in that the starch contains at least 30 wt%, and in particular at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 97 wt%, or at least 99 wt%, pea starch, in each case relative to the total dry weight of the starch and / or that the starch in the polymer composition is in destructured form.

4. Polymer composition according to one of the preceding claims, characterized in that the polymer composition contains, in each case relative to the total dry weight of the polymer composition, 27 wt% to 45 wt%, and in particular 28.5 wt% to 40 wt%, or 30 wt% to 35 wt%, starch.

5. Polymer composition according to one of the preceding claims, characterized in that the aliphatic-aromatic co-polyester is a statistical co-polyester and / or a co-polyester based upon at least adipic acid and / or sebacic acid, and in particular a co-polyester based upon at least adipic acid and / or a statistical co-polyester based upon 1,4-butanediol, adipic acid, and / or sebacic acid and terephthalic acid or a terephthalic acid derivative such as dimethyl terephthalate (DMT), and in particular a statistical co-polyester based upon 1,4-butanediol, adipic acid, and terephthalic acid or a terephthalic acid derivative, and in particular dimethyl terephthalate (DMT).

6. Polymer composition according to one of the preceding claims, characterized in that the polymer composition contains, in each case relative to the total dry weight of the polymer composition, 40 wt% to 74.5 wt%, and in particular 50 wt% to 74.5 wt%, 55 wt% to 70 wt%, or 60 wt% to 70 wt%, aliphatic-aromatic co-polyester and / or the polymer composition contains, in each case relative to the total dry weight of the polymer composition, 0.1 wt% to 5 wt%, and in particular 0.2 wt% to 2 wt%, or 0.3 wt% to 1 wt%, processing aids, and in particular sorbitan monostearate.

7. Polymer composition according to one of the preceding claims, characterized in that the polymer composition contains, relative to the total dry weight of the polymer composition, less than 5 wt%, and in particular less than 3 wt%, or less than 1 wt%, carbon-containing plasticizers, and in particular glycerol or sorbitol, or the polymer composition is free or substantially free of carbon-containing plasticizers.

8. Polymer composition according to one of the preceding claims, characterized in that the polymer composition is biodegradable, and in particular completely biodegradable, in accordance with EN 13432.

9. Process for producing a polymer composition according to one of claims 1 through 8, characterized by the following steps: (i) preparing a mixture by mixing, in each case relative to the total dry weight of the mixture, at least: a) 25.5 wt% to 50 wt% starch, b) 30 wt% to 74.5 wt% aliphatic-aromatic co-polyester, wherein the starch contains at least 25 wt% pea starch, relative to the total dry weight of the starch; (ii) homogenizing the mixture using thermal and / or mechanical energy; (iii) adjusting the water content of the mixture so that the end product has a water content of less than 5 wt%, relative to the total weight of the mixture.

10. Process according to claim 9, characterized in that the mixture is homogenized by dispersion, the action of shear forces on the mixture, stirring, kneading, and / or extruding and / or that the mixture is heated to a temperature of 90 to 250 °C, and in particular 130 to 220 °C, during the homogenization and / or extrusion.

11. Process according to one of claims 9 or 10, characterized in that the water content of the mixture is adjusted to less than 3 wt%, and in particular less than 1.5 wt% or less than 1 wt%, relative to the total weight of the mixture.

12. Process according to one of claims 9 through 11, characterized in that the water content of the mixture is adjusted during the homogenization.

13. Process according to one of claims 9 through 12, characterized in that the water content of the mixture is adjusted by degassing the mixture, and in particular by degassing the melt, and / or the water content of the mixture is adjusted by drying the mixture during the homogenization and / or extrusion.

14. Polymer composition obtainable by a process according to one of claims 9 through 13.

15. Use of a polymer composition according to one of claims 1 through 8 or 14 for producing moldings, films, or fibers - in particular, by blown film extrusion, flat film extrusion, or injection molding - and in particular for producing films by blown film extrusion.

16. Moldings, films, or fibers containing a polymer composition according to one of claims 1 through 8 or 14.