Crosslinked and chain-extended films and foams based on biodegradable polyesters for improved hydrolysis

Abstract

The present invention relates to a process for producing a biodegradable polyester product, comprising the following steps: a) providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) extruding, calendering and / or injection molding the mixture from step a), and c) irradiating the extruded, calendered and / or injection-molded mixture from step b) with ionizing radiation. The invention also relates to a biodegradable polyester product obtainable therefrom, and to a foam or film comprising such a biodegradable polyester product.

Description

[0001] 202403249

[0002] 1

[0003] Description

[0004] Cross-linked and chain-extended films and foams based on biodegradable polyesters for improved hydrolysis

[0005] Field of invention

[0006] The invention relates to a method for producing a biodegradable polyester product, a biodegradable polyester product obtainable by such a method, and a film or foam comprising such a polyester product.

[0007] State of the art

[0008] Polyesters are used in a wide variety of industries because they possess several desirable properties, including low weight, thermal insulation, processability, and shock absorption. Since cross-linked polyesters, especially in the form of films or foams, are usually only marginally biodegradable, they are typically incinerated or landfilled at the end of their service life, resulting in significant environmental pollution and wasted land.

[0009] However, cross-linked polyesters with improved biodegradability are already known. Such biodegradable polyesters currently lack sufficient melt strength, which makes foaming films with chemical blowing agents difficult or impossible.

[0010] By using radiation crosslinking with ionizing radiation (10-500 kGy) of the biodegradable polyester with the aid of crosslinking agents, the mechanical and thermal properties of the biodegradable polyester can be improved, so that the foams obtained from it have the desired 202403249

[0011] 2

[0012] Properties (thickness, expansion rate, surface appearance, (bio)degradability, etc.) can be produced.

[0013] However, the use of radiation crosslinking with ionizing radiation has the disadvantage that the resulting crosslinking is influenced by the amount of crosslinking agent and the intensity and duration of the irradiation. This leads to the formation of non-biodegradable substances, mostly resulting from the reacted crosslinking agent. These non-biodegradable substances can be measured by the gel content in the crosslinked biodegradable polyester. The higher the degree of crosslinking of the biodegradable polyester and the higher the gel content within it, the less biodegradable the resulting crosslinked polyester will be. A high gel content is typically caused by a high proportion of crosslinking agent and high kGy values ​​during radiation crosslinking.Therefore, the biodegradability of polyester currently contrasts with the advantageous mechanical and thermal properties of radiation-crosslinked polyester, so that usually only one of the desired properties can be achieved.

[0014] Description of the invention

[0015] The object of the present invention is to provide a method for producing a biodegradable polyester product which provides polyester products with improved mechanical and thermal properties, in particular sufficient melt strength, wherein the polyester products exhibit good biodegradability in accordance with DIN EN 14995 - 2007-03 despite improved mechanical and thermal properties.

[0016] The above problem is surprisingly solved by a method according to claim 1, i.e., by a method for producing a biodegradable polyester product, comprising the following steps: 202403249

[0017] 3 a) Providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) Extrusion, calendering and / or injection molding of the mixture from step a) and c) Irradiation of the extruded, calendered and / or injection molded mixture from step b) with ionizing radiation.

[0018] Such a process is particularly distinguished by its ability to produce biodegradable polyester products with improved mechanical and thermal properties, especially their melt strength. The improved melt strength results in better foamability of the biodegradable polyester product, enabling the production of stable foams containing such a polyester product. Furthermore, this process minimizes the amount of crosslinking agents required and reduces the need for intense and prolonged irradiation, thereby significantly minimizing the formation of non-biodegradable substances and maximizing the biodegradability of the resulting polyester product.

[0019] In particular, foams, including a polyester product obtainable through this process, are especially advantageous because such foams have a particularly high melting strength and are largely biodegradable.

[0020] Advantageous embodiments of the invention are described in the dependent claims.

[0021] Numerous specific details are discussed below to enable a comprehensive understanding of the subject matter. However, it is obvious to the person skilled in the art that the subject matter can also be practiced and replicated without these specific details.

[0022] All features of one embodiment can be combined with features of another embodiment if the features of the different embodiments are compatible. 202403249

[0023] 4

[0024] The terminology used in the description of this disclosure serves only to describe certain embodiments and is not to be understood as limiting the subject matter. As used in this description and the claims, the singular forms "a", "an", and "the" are to be understood as including the plural forms unless the context clearly indicates otherwise. The reverse is also true; that is, the plural forms include the singular forms. It is also understood that the term "and / or", as used herein, refers to and includes all possible combinations of one or more of the associated listed elements.

[0025] It is further understood that the terms "include", "include", "comprise" and / or "comprehensive", when used in the present description and the claims, specify the presence of the specified features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or groups thereof.

[0026] In the present description and claims, the terms "includes", "comprises" and / or "comprising" may also mean "consisting of", i.e., the presence or addition of one or more other features, steps, operations, elements, components and / or groups is excluded.

[0027] The method according to the invention is explained in more detail below.

[0028] In step a), a mixture comprising at least one polyester and at least one polycarbodiimide is provided. 202403249

[0029] 5

[0030] Polyesters are known to experts as polymers with ester functional groups (RI-C(O)-O-R2) in their main chain. Polyesters can be natural or synthetic.

[0031] Natural polyesters occur in nature and can be found, for example, on the surface of plants.

[0032] Synthetic polyesters are typically produced by the esterification of polyols, usually diols, with polycarboxylic acids, usually dicarboxylic acids, or their derivatives. However, synthetic polyesters can also be produced by transesterification or other methods. Perhaps the best-known synthetic polyester is polyethylene terephthalate (PET), which is obtained by the polycondensation of terephthalic acid and ethylene glycol.

[0033] Polycarbodiimides are known to those skilled in the art as compounds or polymers with several carbodiimide units (-N=C=N-).

[0034] Polycarbodiimides with fewer than three carbodiimide units per polycarbodiimide molecule, when reacting with the polyester, only result in chain elongation of the polyester without any significant branching.

[0035] Preferably, the at least one polycarbodiimide has at least three carbodiimide units per polycarbodiimide molecule.

[0036] Preferably, the at least one polycarbodiimide is miscible with the at least one polyester in the molten state.

[0037] Suitable polycarbodiimides are known under the trade names Stabaxol P110, Lubio AS 15-PLA or Stabilizer 9000 from RASCHIG GmbH.

[0038] In step b), the mixture from step a) is extruded, calendered and / or injection molded, preferably extruded. 202403249

[0039] 6

[0040] Extrusion is a process familiar to those skilled in the art. In extrusion, a reaction mixture is typically forced out of a die under pressure and elevated temperature. The reaction mixture typically reacts during the pressing process. The mass formed by the pressing process is called the extrudate and usually hardens upon exiting the die through cooling and / or chemical reaction. In some cases, the extrudate reacts further with additional reactants before hardening.

[0041] Examples of extrusions include pipe extrusion and film extrusion, especially blown film extrusion.

[0042] Calendering is a familiar process to experts. It is a method that enables the production of high-quality films in large batches. In calendering, a reaction mixture is melted and blended under heat and pressure in an extruder / kneader. The mixture is then rolled out into a film or sheet using calender rollers.

[0043] Injection molding processes are familiar to those skilled in the art. In injection molding, the reaction mixture is first made malleable by heating in an injection unit of an injection molding machine and then transferred to a clamping unit of the machine, where it is formed. Unlike extrusion, the molded product is manufactured discontinuously in the injection molding process.

[0044] Examples of injection molding processes include multi-component injection molding, internal pressure injection molding, molten core injection molding, powder injection molding, extrusion injection molding, and injection stretch blow molding.

[0045] Preferably, the extrusion, calendering, and / or injection molding, in particular the extrusion, in step b) takes place at a temperature of 100 to 300 °C, preferably 120 to 260 °C. 202403249

[0046] 7

[0047] During extrusion, calendering and / or injection molding, carboxyl groups of the at least one polyester react with the carbodiimide groups of the at least one polycarbodiimide, causing the at least one polyester to be partially crosslinked.

[0048] The reaction between carboxyl groups and carbodiimide groups is known to those skilled in the art. The carbodiimide units of the polycarbodiimide react with free carboxylic acids of the polyester via O-acetylurea derivatives to form N-acetylurea derivatives, thus causing crosslinking of the polyester.

[0049] In step c), the extruded, calendered and / or injection-molded mixture from step b) is irradiated with ionizing radiation, in particular short-wave UV radiation, extremely short-wave UV radiation, electron radiation and / or gamma radiation.

[0050] Preferably, the ionizing radiation is electron radiation.

[0051] Ionizing radiation, in particular short-wave UV radiation, extremely short-wave UV radiation, electron radiation, and gamma radiation, is known to those skilled in the art. Ionizing radiation is typically radiation with a kinetic energy of approximately 5 eV or higher. Short-wave UV radiation describes radiation with a wavelength of 280 to 315 nm. Extremely short-wave UV radiation describes radiation with a wavelength of 200 to 280 nm.

[0052] Irradiation of the extruded, calendered and / or injection-molded mixture from step b) further cross-links the extruded, calendered and / or injection-molded mixture.

[0053] Preferably, at least one crosslinking agent is added to the mixture in step a) or to the extruded, calendered and / or injection-molded mixture in step b). 202403249

[0054] 8

[0055] It is further preferred that at least one crosslinking agent is added to the extruded, calendered and / or injection-molded mixture in step b).

[0056] If the at least one crosslinking aid is added to the mixture in step a), the at least one crosslinking aid preferably does not react with the at least one polyester and / or the at least one polycarbodiimide under extrusion conditions, calendering conditions and / or injection molding conditions.

[0057] Typically, at least one crosslinking agent comprises a monomer with several functional groups, in particular at least two unsaturated bonds.

[0058] Crosslinking the at least one polyester using ionizing radiation and at least one crosslinking agent has the advantage that the thermal and mechanical properties of the at least one polyester are improved after crosslinking, while biodegradability is not significantly affected.

[0059] Preferably, the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polylactides, polyhydroxyalkanoates, polyhydroxybutyrate, polycaprolactone, polybutylene (adipatterephthalate) and their copolymers with polyethers and mixtures thereof, preferably polybutylene succinates, polyhydroxyalkanoates and mixtures thereof.

[0060] Preferably, the at least one polycarbodiimide in step a) is selected from the group consisting of poly(tolylcarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-biphenylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide), polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their 202403249

[0061] 9 aryl- and / or alkyl-substituted analogues, and mixtures thereof, preferably polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof.

[0062] Particularly preferably, the at least one polycarbodiimide in step a) comprises polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or aryl- and / or alkyl-substituted analogues and diisopropylphenyl diisocyanate and / or aryl- and / or alkyl-substituted analogues in a ratio of 70:30 to 99.9:1, preferably from 80:20 to 99:1.

[0063] Preferably, the at least one polycarbodiimide in step a) has a melting temperature of 40 to 90 °C, preferably of 60 to 70 °C.

[0064] Preferably, the carbodiimide group is contained in the at least one polycarbodiimide from step a) in an amount of at least 7 wt.%, preferably at least 12 wt.%, based on the total weight of the at least one polycarbodiimide.

[0065] Preferably, the at least one polycarbodiimide is contained in the mixture from step a) in an amount of 0.1 to 10 wt.%, preferably 0.5 to 5 wt.%, based on the total weight of the mixture.

[0066] In a further preferred embodiment, the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polyhydroxyalkanoates and mixtures thereof, wherein the at least one polycarbodiimide in step a) is selected from the group consisting of polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof.

[0067] Preferably, the at least one crosslinking agent in step a) and / or step b) is selected from the group consisting of acrylates or 202403249

[0068] 10

[0069] Methacrylates, such as 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetramethylol methane triacrylate, 1,9-nonanediol dimethacrylate and 1,10-decanediol dimethacrylate; allyl esters of carboxylic acids, such as trimellitic acid triallyl ester, pyromellitic acid triallyl ester and oxalic acid diallyl ester; allyl esters of cyanulic acid or isocyanulic acid, such as triallyl cyanurate, trimethylolpropane trimethacrylate and triallyl isocyanurate; maleimide compounds, such as N-phenylmaleimide and N,N'-m-phenylenebismaleimide; compounds with at least two triple bonds, such as phthalic acid dipropagyl and maleic acid dipropagyl; divinylbenzene and mixtures thereof, preferably triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate and mixtures thereof.

[0070] Preferably, the ionizing radiation in step c) has an energy dose of 10 to 500 kGy, preferably of 25 to 125 kGy.

[0071] Preferably the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:1.

[0072] Preferably, the mass ratio of the at least one polyester and the at least one polycarbodiimide to the at least one crosslinking aid in the mixture from step a) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a).

[0073] Preferably, the mass ratio of the extruded calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a).

[0074] Alternatively, the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one 202403249

[0075] 11

[0076] Crosslinking aids in the mixture from step b) 5:1 to 300:1, preferably 6:1 to 200:1, if the at least one crosslinking aid has been added to the extruded, calendered and / or injection-molded mixture from step b).

[0077] In a preferred embodiment, the mass ratio of the at least one polyester and the at least one polycarbodiimide to the at least one crosslinking aid in the mixture from step a) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a), and the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a).

[0078] In a further preferred embodiment, the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:1; the mass ratio of the at least one polyester and the at least one polycarbodiimide to the at least one crosslinking aid in the mixture from step a) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a); and the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a).

[0079] In a further preferred embodiment, the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 20:1 to 200:1, 202403249

[0080] 12 the mass ratio of the at least one polyester and the at least one polycarbodiimide to the at least one crosslinking aid in the mixture from step a) 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a), and the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) 6:1 to 200:1, when the at least one crosslinking aid has been added to the mixture from step a).

[0081] In an alternative embodiment, the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:1, and the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid has been added to the extruded, calendered and / or injection-molded mixture from step b).

[0082] In a preferred alternative embodiment, the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 20:1 to 200:1, and the mass ratio of the extruded, calendered and / or injection-molded mixture to the at least one crosslinking aid in the mixture from step b) is 6:1 to 200:1 when the at least one crosslinking aid has been added to the extruded, calendered and / or injection-molded mixture from step b).

[0083] Preferably, at least one foaming agent is added to the mixture in step a) or to the extruded, calendered and / or injection-molded mixture in step b).

[0084] Preferably, the at least one foaming agent is a physical or chemical foaming agent, in particular a chemical foaming agent. 202403249

[0085] 13

[0086] Physical foaming agents are usually low-boiling liquids, such as pentane or chlorofluorocarbons (CFCs). Gases such as carbon dioxide or nitrogen can also be used as physical foaming agents.

[0087] Chemical foaming agents are mostly organic compounds that decompose at elevated temperatures, releasing gases, especially nitrogen or carbon dioxide.

[0088] Preferably, the foaming agent is selected from a group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, in particular sodium bicarbonate, citrates, in particular citric acid, and mixtures thereof.

[0089] In a preferred embodiment, at least one foaming agent is additionally added to the mixture in step a) or to the extruded, calendered and / or injection-molded mixture in step b), wherein the foaming agent is selected from the group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, citrates, in particular citric acid, in particular sodium bicarbonate, and mixtures thereof.

[0090] In a preferred embodiment, at least one foaming agent is additionally added to the mixture in step a), wherein the foaming agent is selected from the group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, citrates, in particular citric acid, in particular sodium bicarbonate, and mixtures thereof. 202403249

[0091] 14

[0092] In an alternative embodiment, at least one foaming agent is additionally added to the extruded, calendered and / or injection-molded mixture in step b), wherein the foaming agent is selected from a group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, citrates, in particular citric acid, in particular sodium bicarbonate, and mixtures thereof.

[0093] In a preferred embodiment, the process for producing a biodegradable polyester product comprises the following steps: a) providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) extruding the mixture from step a), and c) irradiating the extruded mixture from step b) with electron and / or gamma radiation, wherein at least one crosslinking agent is additionally added to the mixture in step a) or to the extruded mixture in step b), and / or wherein the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polylactides, polyhydroxyalkanoates, polyhydroxybutyrate, polycaprolactone, polybutylene (adipatterephthalate) and their copolymers with polyethers and mixtures thereof, preferably polybutylene succinates, polyhydroxyalkanoates and mixtures thereof.and / or wherein the at least one polycarbodiimide in step a) is selected from the group consisting of poly(tolylcarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-biphenylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide), polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof, preferably polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof and / or 202403249,

[0094] 15 wherein the at least one crosslinking agent in step a) and / or step b) is selected from the group consisting of acrylates or methacrylates, such as 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetramethylolmethane triacrylate, 1,9-nonanediol dimethacrylate and 1,10-decanediol dimethacrylate; allyl esters of carboxylic acids, such as trimellitic acid triallyl ester, pyromellitic acid triallyl ester and oxalic acid diallyl ester, allyl esters of cyanulic acid or isocyanulic acid, such as triallyl cyanurate, trimethylolpropane trimethacrylate and triallyl isocyanurate, maleimide compounds, such as N-phenylmaleimide and N,N'-m-phenylenebismaleimide; compounds with at least two triple bonds, such as phthalic acid dipropagyl and maleic acid dipropagyl;Divinylbenzene and mixtures thereof, preferably triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate and mixtures thereof, and / or wherein the ionizing radiation in step c) has an energy dose of 10 to 500 kGy, preferably 25 to 125 kGy, and / or wherein the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:1, and / or wherein at least one foaming agent is additionally added to the mixture in step a) or to the extruded mixture in step b), wherein the foaming agent is preferably selected from the group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, bicarbonates, 5-Phenyltetrazol, in particular sodium bicarbonate, citrates, in particular citric acid, and mixtures thereof.;

[0095] In a particular embodiment, the process for producing a biodegradable polyester product comprises the following steps: a) providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) extruding the mixture from step a), and c) irradiating the extruded mixture from step b) with electron and / or gamma radiation.

[0096] 16, wherein at least one crosslinking aid is added to the mixture in step a) or to the extruded mixture in step b), wherein the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polylactides, polyhydroxyalkanoates, polyhydroxybutyrate, polycaprolactone, polybutylene (adipatterephthalate) and their copolymers with polyethers and mixtures thereof, preferably polybutylene succinates, polyhydroxyalkanoates and mixtures thereof, wherein the at least one polycarbodiimide in step a) is selected from the group consisting of poly(tolylcarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-biphenylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide) polycarbodiimides based on 1,3,5- Triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues,and mixtures thereof, preferably polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof, wherein the at least one crosslinking aid in step a) and / or step b) is selected from the group consisting of acrylates or methacrylates such as 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetramethylolmethane triacrylate, 1,9-nonanediol dimethacrylate and 1,10-decanediol dimethacrylate; Allyl esters of carboxylic acids, such as trimellitic acid triallyl ester, pyromellitic acid triallyl ester and oxalic acid diallyl ester, allyl esters of cyanulic acid or isocyanulic acid, such as triallyl cyanurate, trimethylolpropane trimethacrylate and triallyl isocyanurate, maleimide compounds,such as N-phenylmaleimide and N,N'-m-phenylenebismaleimide; compounds with at least two triple bonds such as phthalic dipropagyl and maleic dipropagyl; divinylbenzene and mixtures thereof, preferably of triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate and mixtures thereof, wherein the ionizing radiation in step c) has an energy dose of 10 to 500 kGy, preferably of 25 to 125 kGy, 202403249,

[0097] 17 wherein the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:1, and wherein at least one foaming agent is additionally added to the mixture in step a) or to the extruded mixture in step b), wherein the foaming agent is preferably selected from the group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, in particular sodium bicarbonate, citrates, in particular citric acid, and mixtures thereof.

[0098] In a particular embodiment, the process for producing a biodegradable polyester product comprises the following steps: a) providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) extruding the mixture from step a), and c) irradiating the extruded mixture from step b) with electron and / or gamma radiation, wherein at least one crosslinking agent is additionally added to the mixture in step a) or to the extruded mixture in step b), wherein the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polyhydroxyalkanoates, and mixtures thereof, and wherein the at least one polycarbodiimide in step a) is selected from the group consisting of polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof.wherein the at least one crosslinking agent in step a) and / or step b) is selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate and mixtures thereof, wherein the ionizing radiation in step c) has an energy dose of 25 to 125 kGy, 202403249,

[0099] 18 wherein the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 20:1 to 200:1, and wherein at least one foaming agent is additionally added to the mixture in step a), wherein the foaming agent is preferably selected from a group consisting of azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, in particular sodium bicarbonate, citrates, in particular citric acid, and mixtures thereof.

[0100] The present invention also relates to a biodegradable polyester product obtainable by a method as described above.

[0101] Preferably, the polyester product has a gel content of 30 to 70 wt.%, preferably 35 to 55 wt.%, based on the total weight of the polyester product.

[0102] The gel content was determined according to DIN EN ISO 6427. For this purpose, the cross-linked films were first cut into 10 mm x 10 mm pieces. Then, 0.1 ± 0.01 g of these film pieces were weighed into a previously balanced stainless steel mesh. The mesh size of the stainless steel mesh was 16 pm. Multiple folds of the mesh were used to prevent sample leakage. The film sample weighed into the stainless steel mesh was placed in a large test tube along with 50 ml of solvent. Cyclohexanone was used as the solvent. The test tube was then tightly sealed with aluminum foil to prevent significant solvent evaporation. The test tube was then placed in an oil bath at 160°C for 24 hours. During this time, the uncross-linked components of the film dissolved.After extraction, the metal mesh, now containing only the cross-linked parts of the sample, was removed from the test tube. The metal mesh was then dried for 5 h at 160 °C to evaporate any remaining cyclohexanone and subsequently 202403249.

[0103] 19. Weighed again. The difference in weight of the foil piece before and after cyclohexanone treatment corresponds to the gel content.

[0104] Such a biodegradable polyester product has the advantage of improved mechanical and thermal properties, particularly its melt strength. The improved melt strength results in better foamability of the biodegradable polyester product, enabling the production of stable foams made from it.

[0105] All definitions and embodiments described above apply analogously to the biodegradable polyester product.

[0106] The present invention also relates to a film or foam comprising a biodegradable polyester product as described above.

[0107] Such films and foams, especially foams, have the advantage of having a particularly high melting strength and being particularly biodegradable.

[0108] Preferably, the film is calendered.

[0109] Preferably, the foam has a density of 30 to 300 kg / m³. 3 , especially from 50 to 250 kg / m² 3The density was determined in accordance with ISO 845. The density of the foam sheets was determined using die-cut test specimens (70 mm x 45 mm). For this purpose, the test specimens were weighed on an analytical balance (L 420 D from Sartorius AG, Göttingen). The foam thickness was measured at six different points using a thickness gauge (Sylvac SA, Malleray, Switzerland), and the arithmetic mean was calculated. The density was then calculated from the mass, test specimen area, and thickness using the following equation: Density = Mass / (Test specimen area x Test specimen thickness). 202403249

[0110] 20

[0111] Preferably, the foam has a cell-to-area ratio of 3 cells per 3 mm². 2 up to 100 cells per 3 mm 2 , preferably 5 cells per 3 mm 2 up to 40 cells per 3 mm 2 , on. Preferably the foam has an average cell diameter.

[0112] All definitions and embodiments described above apply analogously to the film or foam. The present invention is explained in more detail below with reference to some non-limiting examples.

[0113] 202403249

[0114] 21

[0115] Examples

[0116] Foam production:

[0117] A polyester (polybutylene succinate (PBS)) was extruded with a crosslinking agent (trimethylolpropane triacrylate) and / or a polycarbodiimide (ratio of 1,3,5-triisopropylphenyl diisocyanate to diisopropylphenyl diisocyanate is 9:1 by weight) and a foaming agent (azodicarbonamide). The extruded, foam-loaded compact film was then electron beam crosslinked and foamed by thermal decomposition of the foaming agent.

[0118] Foam 1 :

[0119] A polyester (PBS) was extruded with five parts of a foaming agent (azodicarbonamide) without crosslinking aids or chain extenders. Subsequent electron beam crosslinking at 25-125 kGy failed to crosslink the PBS (gel content of 4%), thus preventing foaming, as the film tore immediately due to insufficient melt strength.

[0120] Foam 2:

[0121] A polyester (PBS) was extruded with one part crosslinking agent (trimethylolpropane triacrylate), one part polycarbodiimide (ratio of 1,3,5-triisopropylphenyl diisocyanate to diisopropylphenyl diisocyanate is 9:1 by weight), and five parts foaming agent (azodicarbonamide). Due to the linear chain elongation of the polycarbodiimide, a low radiation dose (25 kGy) was sufficient to subsequently foam the film. The weakly electron-beam crosslinked foam is characterized by low density, homogeneous cell distribution, thermoformability, and thus cost reduction and improved processability (comparable to Foam 5), as well as improved biodegradability compared to Foam 5.

[0122] Foam 3: 202403249

[0123] 22

[0124] A polyester (PBS) was extruded with one part crosslinking agent (trimethylolpropane triacrylate) and five parts foaming agent (azodicarbonamide) without chain extenders. Electron beam crosslinking doses of 25–100 kGy did not sufficiently crosslink the PBS for foaming, as the film tore during the foaming process.

[0125] Foam 4:

[0126] A polyester (PBS) was extruded with four parts crosslinking agent (trimethylolpropane triacrylate) and five parts foaming agent (azodicarbonamide) without chain extenders. The subsequent electron beam dose of 125 kGy resulted in foaming of the film, but only with high density and a heterogeneous cell structure.

[0127] Foam 5:

[0128] A polyester (PBS) was extruded with one part crosslinking agent (trifunctional acrylate) and five parts foaming agent (azodicarbonamide) without chain extenders. The film was then foamed by an electron beam dose of 125 kGy. The resulting foam was characterized by a homogeneous cell structure and low density, but compared to foam 2, it is less biodegradable due to its stronger crosslinking.

[0129] The gel content was determined on cross-linked films in accordance with DIN EN ISO 6427. For this purpose, the cross-linked films were first cut into 10 mm x 10 mm pieces. Then, 0.1 ± 0.01 g of the film pieces were weighed into a previously balanced stainless steel mesh. The stainless steel mesh has a mesh size of 16 pm. Multiple folds of the mesh were used to prevent sample leakage. The film sample weighed into the stainless steel mesh was placed in a large test tube along with 50 ml of solvent. Cyclohexanone was used as the solvent. The test tube was then tightly sealed with aluminum foil to prevent significant solvent evaporation. The test tube was then immersed in an oil bath at 160°C for 24 h.

[0130] 23. During this time, the uncrosslinked components of the foil dissolve. After extraction, the metal mesh, now containing only the crosslinked parts of the sample, was removed from the test tube. The metal mesh was then dried for 5 h at 160 °C to evaporate any remaining cyclohexanone and subsequently weighed again. The difference in the weight of the foil piece before and after the cyclohexanone treatment corresponds to the gel content.

[0131] The gel content in Tables 1 to 3 refers to the weight fraction of the total weight of the foil piece before treatment with cyclohexanone.

[0132] The compositions and radiation doses of foams 1 to 5, as well as the resulting properties, are summarized in Tables 1 and 2. Table 1:

[0133] Table 2: 202403249

[0134] 24

[0135] Viscosity measurements show that the complex viscosity, and thus also the molecular weight, could be increased with the aid of a chain extender (polycarbodiimide). In contrast to electron-beam crosslinked PBS, the chain-extended PBS is meltable, thus proving that it is purely chain-extended and that no crosslinking has occurred.

[0136] The viscosities were measured as follows and summarized in Table 3.

[0137] The linear viscoelastic range (LVE range) for viscosity measurement was determined according to standard (ISO 6721-10 (2015)).

[0138] The viscosity was determined by a frequency sweep measurement based on the determined LVE range at 0.1% deformation in the frequency range of 0.5 to 500 rad / s.

[0139] Rheological viscosity measurement method (measurement in oscillation): Temperature: 150°C, gap 1 mm, plate-plate measurement setup (25 mm diameter) 202403249

[0140] 25

[0141] Table 3:

Claims

202403249 26 Patent claims 1. A method for producing a biodegradable polyester product, comprising the following steps: a) providing a mixture comprising at least one polyester and at least one polycarbodiimide, b) extruding, calendering and / or injection molding the mixture from step a), and c) irradiating the extruded, calendered and / or injection molded mixture from step b) with ionizing radiation.

2. Method according to claim 1, wherein at least one crosslinking agent is additionally added to the mixture in step a) or to the extruded, calendered and / or injection-molded mixture in step b).

3. Method according to claim 1 or 2, wherein the at least one polyester in step a) is selected from the group consisting of polybutylene succinates, polylactides, polyhydroxyalkanoates, polyhydroxybutyrate, polycaprolactone, polybutylene (adipatterephthalate) and their copolymers with polyethers and mixtures thereof, preferably polybutylene succinates, polyhydroxyalkanoates and mixtures thereof.

4. A method according to any one of claims 1 to 3, wherein the at least one polycarbodiimide in step a) is selected from the group consisting of poly(tolylcarbodiimide), poly(4,4'-diphenylmethanecarbodiimide), poly(3,3'-dimethyl-4,4'-biphenylenecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide), polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof, preferably polycarbodiimides based on 1,3,5-triisopropylphenyl diisocyanate and / or diisopropylphenyl diisocyanate, as well as their aryl- and / or alkyl-substituted analogues, and mixtures thereof. 202403249 27 5. A method according to any one of claims 1 to 4, wherein the at least one compounding agent in step a) and / or step b) is selected from the group consisting of acrylates or methacrylates, such as 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetramethylolmethane triacrylate, 1,9-nonanediol dimethacrylate and 1,10-decanediol dimethacrylate; allyl esters of carboxylic acids, such as trimellitic acid triallyl ester, pyromellitic acid triallyl ester and oxalic acid triallyl ester, allyl esters of cyanulic acid or isocyanulic acid, such as triallyl cyanurate, trimethylolpropane trimethacrylate and triallyl isocyanurate, maleimide compounds, such as N-phenylmaleimide and N,N'-m-phenylenebismaleimide; Compounds with at least two triple bonds such as phthalic dipropagyl and maleic dipropagyl; divinylbenzene and mixtures thereof, preferably triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate and mixtures thereof.

6. Method according to any one of claims 1 to 5, wherein the ionizing radiation in step c) has an energy dose of 10 to 500 kGy, preferably of 25 to 125 kGy.

7. Method according to any one of claims 1 to 6, wherein the mass ratio of the at least one polyester to the at least one polycarbodiimide in the mixture from step a) is 10:1 to 300:1, preferably 20:1 to 200:

1.

8. Method according to any one of claims 1 to 7, wherein the mass ratio of the at least one polyester and the at least one polycarbodiimide to the at least one crosslinking aid in the mixture from step a) is 5:1 to 300:1, preferably 6:1 to 200:1, when the at least one crosslinking aid of the mixture from step a) has been added.

9. A method according to any one of claims 1 to 8, wherein at least one foaming agent is additionally added to the mixture in step a) or to the extruded mixture in step b), wherein the foaming agent is preferably selected from a group consisting of azodicarbonamide, 202403249 28 Benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, barium azodicarboxylate, 5-phenyltetrazol, bicarbonates, in particular sodium bicarbonate, citrates, in particular citric acid, and mixtures thereof.

10. Biodegradable polyester product obtainable by a process according to any one of claims 1 to 9.

11. Film or foam comprising a biodegradable polyester product according to claim 10.

12. Film according to claim 11, wherein the film is calendered.

13. Foam according to claim 11, wherein the foam has a density of 30 to 300 kg / m³ 3, especially from 50 to 250 kg / m² 3 , exhibits.

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