METHOD FOR PRODUCING A POLYMER FILM

Description

[0001] The present invention relates to a method for producing a polymer film (P) containing at least one copolyamide by extruding the copolyamide through an annular die and subsequently stretching the resulting tube by blowing in air. Furthermore, the present invention relates to the polymer film (P) obtainable according to the inventive method.

[0002] Polyamides are of particular industrial importance due to their excellent mechanical properties, especially high strength and toughness, good chemical resistance, and high abrasion resistance. They are used, for example, in the production of fishing lines, climbing ropes, and carpets. Furthermore, polyamides are used in the manufacture of packaging films and packaging sleeves.

[0003] An overview of its use as packaging films and packaging sleeves, as well as methods for their production, can be found, for example, in Encyclopedia of Polymer Science and Engineering, 2nd Ed., Vol. 7, pp. 73-127. , Vol. 10, pp. 684-695 (John Wiley & Sons, Inc., 1987 ) described. However, the polyamide films described therein are very stiff, have low tear strength and high density.

[0004] Copolyamides, which combine the positive properties of various polyamides, are therefore frequently used for packaging films and packaging sleeves. Several copolyamides are described in the prior art.

[0005] EP 0 352 562 describes films made of copolyamides, wherein the copolyamides are produced from ε-caprolactam and preferably 1 to 10 parts by weight of a dimeric acid and a diamine. The copolyamides can then be used to produce flat or blown films. They are also suitable for the production of composite films.

[0006] A disadvantage of the copolyamide films described in EP 0 352 562 is that they have a relatively low tear strength, a high modulus of elasticity and low puncture energy.

[0007] EP 2 993 041 A1 describes multilayer shrink films for packaging foodstuffs, which may contain a base layer of polyamides. The polyamides described do not contain dimer acid.

[0008] DE 28 46 596 describes molded bodies made of a copolyamide consisting of caprolactam, fatty acid dimers, and hexamethylenediamine. However, the described thermoplastics cannot be extruded into a film.

[0009] A disadvantage of polymer films produced using state-of-the-art methods is that they often have a high restoring force and are frequently very stiff.

[0010] The present invention therefore aims to provide a method for producing a polymer film (P) that does not exhibit the disadvantages of the methods described in the prior art, or only to a very limited extent. The method should also be as simple and cost-effective as possible.

[0011] This task is solved by a process for producing a polymer film (P), comprising the steps i) Providing at least one copolyamide produced by polymerizing components (A) 15 to 84 wt% of at least one lactam, (B) 16 to 85 wt% of a monomer mixture (M) containing components (B1) at least one C32-C40 dimer acid and (B2) at least one C4-C12 diamine, wherein the wt% of components (A) and (B) are based on the sum of the wt% of components (A) and (B), in molten form in a first extruder; ii) Extruding the at least one copolyamide provided in step i) in molten form from the first extruder through an annular die to obtain a tube containing the at least one copolyamide in molten form; iii) Cooling the tube obtained in step ii) containing the at least one copolyamide in molten form in a water bath to a first temperature (T1), wherein the at least one Copolyamide solidifies, forming a first tubular film.which contains the at least one copolyamide, wherein the tube is guided over a first roller system during cooling, whereby the tube is stretched in its length, iv) heating the first tube film obtained in step iii) to a second temperature (T 2 ) to obtain a heated first tube film containing the at least one copolyamide, v) blowing air into the heated first tube film obtained in step iv), wherein the heated first tube film is stretched in its width, and wherein the heated first tube film cools to a third temperature (T 3 ) to obtain the polymer film (P) containing the at least one copolyamide. ,

[0012] A polymer film (P) produced by the process according to the invention surprisingly exhibits high tear resistance both in the extrusion direction and perpendicular to it. This is particularly advantageous when the polymer film (P) produced according to the invention is used in a food packaging process.

[0013] The polymer film (P) produced by the inventive method also has a lower restoring force according to DIN 53369 and is also characterized by good shrinkage properties.

[0014] Furthermore, the polymer film (P) produced according to the invention exhibits high transparency and high low-temperature toughness. It is also advantageous that the polymer film (P) produced by the process according to the invention is less stiff than polymer films produced by processes described in the prior art. The polymer film (P) produced according to the invention also exhibits a low modulus of elasticity and high puncture resistance in the dry state. The high puncture resistance is particularly important when the polymer film (P) is used for packaging food products.

[0015] The method according to the invention is explained in more detail below. Step i)

[0016] In step i), at least one copolyamide is provided in molten form in an extruder. The at least one copolyamide is produced by polymerization of components (A), 15 to 84 wt% of at least one lactam, and (B), 16 to 85 wt% of a monomer mixture (M), wherein the wt% of components (A) and (B) are based on the sum of the wt% of components (A) and (B). The monomer mixture (M) contains components (B1), at least one C32-C40 dimer acid, and (B2), at least one C4-C12 diamine.

[0017] In the context of the present invention, "at least one copolyamide" means exactly one copolyamide as well as a mixture of two or more copolyamides.

[0018] In the context of the present invention, "a first extruder" means exactly one first extruder as well as two or more first extruders. Typically, in the process according to the invention, as many first extruders are used as there are first layers containing the at least one copolyamide that are to be included in the polymer film (P) to be produced.

[0019] If the polymer film (P) produced according to the inventive process is to contain, for example, exactly one first layer containing the at least one copolyamide, then exactly one first extruder is used. If the polymer film (P) is to contain exactly two first layers containing the at least one copolyamide, then exactly two first extruders are used. If the polymer film (P) is to contain exactly five first layers containing the at least one copolyamide, then exactly five first extruders are used.

[0020] For example, the at least one copolyamide is provided in one to eleven first extruders, preferably in one to five first extruders and particularly preferably in one to three first extruders.

[0021] According to the invention, the at least one copolyamide is provided in molten form.

[0022] "In molten form" within the scope of the present invention means that the at least one copolyamide is provided at a temperature (TC) that is above the melting temperature (TM(C)) of the at least one copolyamide. "In molten form" therefore means that the at least one copolyamide has a temperature (TC) that is above the melting temperature (TM(C)) of the at least one copolyamide. If the at least one copolyamide is in molten form, it is flowable.

[0023] "Flowable" means that at least one copolyamide can be conveyed in the first extruder, and that at least one copolyamide can be extruded from the first extruder.

[0024] For example, the at least one copolyamide is provided in step i) at a temperature (TC ) in the range of 170 to 300 °C, preferably in the range of 200 to 290 °C and particularly preferably in the range of 230 to 280 °C, in each case provided that the temperature (TC ) at which the at least one copolyamide is provided is above the melting temperature (TM(C) ) of the at least one copolyamide.

[0025] The at least one copolyamide can be provided in molten form in the first extruder using any method known to a person skilled in the art.

[0026] For example, the at least one copolyamide can be fed to the first extruder in molten or solid form. If the at least one copolyamide is fed to the first extruder in solid form, it can be, for example, granules and / or powder. The at least one copolyamide is then melted in the first extruder and thus provided in molten form. This embodiment is preferred.

[0027] Furthermore, it is possible that components (A) and (B) are polymerized directly in the first extruder, thus providing at least one copolyamide in molten form in the extruder. Methods for this are known to those skilled in the art.

[0028] Furthermore, it is possible that in step i) additives are provided in the first extruder together with the at least one copolyamide in molten form. The additives are usually compounded (mixed) with the at least one copolyamide in molten form in the first extruder. Methods for this are known to those skilled in the art.

[0029] Suitable additives are known to those skilled in the art and are selected, for example, from the group consisting of stabilizers, dyes, antistatic agents, tackifiers, antiblocking agents, processing aids, antioxidants, light stabilizers, UV absorbers, lubricants and nucleating aids.

[0030] Suitable colorants include organic and inorganic pigments, such as titanium dioxide with a sizing. Suitable tackifiers include polyisobutylene (PIB) or ethyl vinyl acetate (EVA). Suitable antiblocking agents include silicon dioxide or calcium carbonate particles. Suitable light stabilizers include hindered amine light stabilizers (HALS). Ethylene bisstearamide (EBS) wax can be used as a processing aid or lubricant. Nucleation aids can include all types of organic or inorganic crystallization nucleating agents, such as talc.

[0031] The following section describes at least one copolyamide in more detail. Copolyamide

[0032] According to the invention, the at least one copolyamide is produced by polymerization of the components. (A) 15 to 84 wt% of at least one lactam, (B) 16 to 85 wt% of a monomer mixture (M) comprising the components (B1) at least one C 32 -C 40 dimer acid and (B2) at least one C 4 -C 12 diamine, wherein the wt% of components (A) and (B) are each based on the sum of the wt% of components (A) and (B).

[0033] The terms "component (A)" and "at least one lactam" are used synonymously within the scope of the present invention and therefore have the same meaning.

[0034] The same applies to the terms "component (B)" and "monomer mixture (M)". These terms are also used synonymously within the scope of the present invention and therefore have the same meaning.

[0035] According to the invention, the at least one copolyamide is produced by polymerization of 15 to 84 wt.% of component (A) and 16 to 85 wt.% of component (B), preferably the at least one copolyamide is produced by polymerization of 40 to 83 wt.% of component (A) and 17 to 60 wt.% of component (B), and particularly preferred is the at least one copolyamide produced by polymerization of 60 to 80 wt.% of component (A) and 20 to 40 wt.% of component (B), wherein the wt. percent of components (A) and (B) are each based on the sum of the wt. percent of components (A) and (B).

[0036] Preferably, the sum of the weight percent of components (A) and (B) equals 100 wt.%.

[0037] It goes without saying that the weight percentages of components (A) and (B) refer to their weight percentages before polymerization, i.e., before components (A) and (B) have reacted with each other. During polymerization, the weight ratio of components (A) and (B) may change.

[0038] According to the invention, the at least one copolyamide is produced by polymerization of components (A) and (B). The polymerization of components (A) and (B) is known to those skilled in the art. Typically, the polymerization of components (A) with (B) is a condensation reaction. During the condensation reaction, component (A) reacts with components (B1) and (B2) contained in component (B), as well as optionally with component (B3), which may also be contained in component (B) and is described below. Amide bonds are formed between the individual components. Typically, component (A) exists at least partially in an open-chain form, i.e., as an amino acid, during the polymerization.

[0039] The polymerization of components (A) and (B) can take place in the presence of a catalyst. Suitable catalysts include any catalyst known to those skilled in the art that catalyzes the polymerization of components (A) and (B). Such catalysts are known to those skilled in the art. Preferred catalysts are phosphorus compounds such as sodium hypophosphite, phosphorous acid, triphenylphosphine, or triphenylphosphite.

[0040] The polymerization of components (A) and (B) forms at least one copolyamide, which therefore contains building blocks derived from component (A) and building blocks derived from component (B). Building blocks derived from component (B) contain building blocks derived from components (B1) and (B2), and optionally from component (B3).

[0041] The polymerization of components (A) and (B) forms the copolyamide as a copolymer. This copolymer can be a statistical copolymer or a block copolymer.

[0042] In a block copolymer, blocks of units derived from component (B) and blocks of units derived from component (A) are formed. These alternate. In a statistical copolymer, building blocks derived from component (A) alternate with building blocks derived from component (B). This alternation occurs statistically. For example, two building blocks derived from component (B) may be followed by a building block derived from component (A), which in turn may be followed by another building block derived from component (B), which may then be followed by a building block containing three building blocks derived from component (A).

[0043] Preferably, at least one copolyamide is a statistical copolymer.

[0044] The present invention therefore also relates to a process in which the at least one copolyamide is a statistical copolymer.

[0045] The production of the at least one copolyamide preferably comprises the following steps. I) Polymerization of components (A) and (B) to obtain at least one first copolyamide, II) Granulation of the at least one first copolyamide obtained in step I) to obtain at least one granulated copolyamide, III) Extraction of the at least one granulated copolyamide obtained in step II) with water to obtain at least one extracted copolyamide, IV) Drying of the at least one extracted copolyamide obtained in step III) at a temperature (TT ) to obtain the at least one copolyamide.

[0046] The present invention therefore also relates to a process in which the at least one copolyamide is produced in a process comprising the following steps: I) Polymerization of components (A) and (B) to obtain at least one first copolyamide, II) Granulation of the at least one first copolyamide obtained in step I) to obtain at least one granulated copolyamide, III) Extraction of the at least one granulated copolyamide obtained in step II) with water to obtain at least one extracted copolyamide, IV) Drying of the at least one extracted copolyamide obtained in step III) at a temperature (TT ) to obtain the at least one copolyamide.

[0047] The polymerization in step I) can take place in all reactors known to those skilled in the art. Stirred tank reactors are preferred. Additional aids known to those skilled in the art can be used to improve reaction control, such as defoamers like polydimethylsiloxane (PDMS).

[0048] In step II), the at least one first copolyamide obtained in step I) can be granulated according to all methods known to those skilled in the art, for example by strand granulation or underwater granulation.

[0049] The extraction in step III) can be carried out using any method known to a person skilled in the art.

[0050] During the extraction in step III), by-products formed during the polymerization of components (A) and (B) in step I) are typically extracted from the at least one granulated copolyamide.

[0051] In step IV), the at least one extracted copolyamide obtained in step III) is dried. Drying methods are known to those skilled in the art. According to the invention, the at least one extracted copolyamide is dried at a temperature (TT). The temperature (TT) is preferably above the glass transition temperature (TG(C)) of the at least one copolyamide and below the melting temperature (TM(C)) of the at least one copolyamide.

[0052] The drying in step IV) is usually carried out for a period of time in the range of 1 to 100 hours, preferably in the range of 2 to 50 hours and particularly preferably in the range of 3 to 40 hours.

[0053] The idea is that drying in step IV) further increases the molecular weight of the at least one copolyamide.

[0054] The at least one copolyamide typically has a glass transition temperature (TG(C) ). The glass transition temperature (TG(C) ) is, for example, in the range of 20 to 50 °C, preferably in the range of 23 to 47 °C and particularly preferably in the range of 25 to 45 °C, determined according to ISO 11357-2:2014.

[0055] The present invention therefore also relates to a method in which the at least one copolyamide has a glass transition temperature (TG(C) ), wherein the glass transition temperature (TG(C) ) is in the range of 20 to 50 °C.

[0056] The glass transition temperature (TG(C) ) of the at least one copolyamide refers, in accordance with ISO 11357-2:2014, to the glass transition temperature (TG(C) ) of the dry copolyamide within the scope of the present invention.

[0057] In the context of the present invention, "dry" means that the at least one copolyamide contains less than 1 wt.%, preferably less than 0.5 wt.%, and particularly preferably less than 0.1 wt.% water, based on the total weight of the at least one copolyamide. More preferably, "dry" means that the at least one copolyamide contains no water, and most preferably, that the at least one copolyamide contains no solvent.

[0058] The at least one copolyamide also typically has a melting temperature (TM(C) ). The melting temperature (TM(C) ) of the at least one copolyamide is, for example, in the range of 150 to 210 °C, preferably in the range of 160 to 205 °C and particularly preferably in the range of 160 to 200 °C, determined according to ISO 11357-3:2014.

[0059] The present invention therefore also relates to a method in which the at least one copolyamide has a melting temperature (TM(C) ), wherein the melting temperature (TM(C) ) is in the range of 150 to 210 °C.

[0060] The at least one copolyamide generally has a viscosity number (VZ (C) ) in the range of 150 to 300 ml / g, determined in a 0.5 wt% solution of the at least one copolyamide in a mixture of phenol / o-dichlorobenzene in a wt ratio of 1 : 1.

[0061] Preferably, the viscosity number (VZ (C) ) of the at least one copolyamide is in the range of 160 to 290 ml / g and particularly preferably in the range of 170 to 280 ml / g, determined in a 0.5 wt% solution of the at least one copolyamide in a mixture of phenol / o-dichlorobenzene in a weight ratio of 1 : 1.

[0062] The present invention therefore also relates to a process in which the at least one copolyamide has a viscosity number (VZ (C) ) in the range of 150 to 300 ml / g, determined in a 0.5 wt% solution of the at least one copolyamide in a mixture of phenol / o-dichlorobenzene in a ratio of 1 : 1. Component (A)

[0063] According to the invention, component (A) is at least one lactam.

[0064] In the context of the present invention, "at least one lactam" means both exactly one lactam and a mixture of two or more lactams.

[0065] Lactams are known as such to those skilled in the art. According to the invention, lactams with 4 to 12 carbon atoms are preferred.

[0066] Within the scope of the present invention, "lactams" are understood to be cyclic amides which preferably have 4 to 12, and particularly preferably 5 to 8, carbon atoms in the ring.

[0067] Suitable lactams are selected, for example, from the group consisting of 3-aminopropanoic acid lactam (propio-3-lactam; β-lactam; β-propiolactam), 4-aminobutanoic acid lactam (butyro-4-lactam; γ-lactam; γ-butyrolactam), aminopentanoic acid lactam (2-piperidinone; δ-lactam; δ-valerolactam), 6-aminohexanoic acid lactam (hexano-6-lactam; ε-lactam; ε-caprolactam), 7-aminoheptanoic acid lactam (heptano-7-lactam; ζ-lactam; ζ-heptanolactam), 8-aminooctanoic acid lactam (octano-8-lactam; η-lactam; η-octanolactam), 9-aminononanoic acid lactam (Nonano-9-lactam; θ-Lactam; θ-Nonanolactam), 10-Aminodecanoic acid lactam (Dekano-10-lactam; ω-Decanolactam), 11-Aminoundecanoic acid lactam (Undekano-11-lactam; ω-Undecanolactam) and 12-Aminododecanoic acid lactam (Dodekano-12-lactam; ω-Dodecanolactam).

[0068] The present invention therefore also relates to a process in which the component (A) is selected from the group consisting of 3-aminopropanoic acid lactam, 4-aminobutanoic acid lactam, 5-aminopentanoic acid lactam, 6-aminohexanoic acid lactam, 7-aminoheptanoic acid lactam, 8-aminooctanoic acid lactam, 9-aminononanoic acid lactam, 10-aminodecanoic acid lactam, 11-aminoundecanoic acid lactam and 12-aminododecanoic acid lactam.

[0069] The lactams can be unsubstituted or at least monosubstituted. In the case that at least monosubstituted lactams are used, they can bear one, two, or more substituents on the nitrogen atom and / or on the carbon atoms of the ring, which are independently selected from the group consisting of C1 to C10 alkyl, C5 to C6 cycloalkyl, and C5 to C10 aryl.

[0070] Suitable C1 to C10 alkyl substituents include, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl. A suitable C5 to C6 cycloalkyl substituent is, for example, cyclohexyl. Preferred C5 to C10 aryl substituents are phenyl or anthranyl.

[0071] Unsubstituted lactams are preferably used, with γ-lactam (γ-butyrolactam), δ-lactam (δ-valerolactam), and ε-lactam (ε-caprolactam) being preferred. δ-lactam (δ-valerolactam) and ε-lactam (ε-caprolactam) are particularly preferred, with ε-caprolactam being especially preferred. Monomer mixture (M)

[0072] According to the invention, component (B) is a monomer mixture (M). The monomer mixture (M) contains components (B1), at least one C32-C40 dimer acid, and (B2), at least one C4-C12 diamine.

[0073] In the context of the present invention, a monomer mixture (M) is understood to be a mixture of two or more monomers, wherein at least the components (B1) and (B2) are contained in the monomer mixture (M).

[0074] The terms "component (B1)" and "at least one C32-C40 dimer acid" are used synonymously within the scope of the present invention and therefore have the same meaning. The same applies to the terms "component (B2)" and "at least one C4-C12 diamine". These terms are also used synonymously within the scope of the present invention and therefore have the same meaning.

[0075] The monomer mixture (M) contains, for example, 45 to 55 mol% of component (B1) and 45 to 55 mol% of component (B2), in each case based on the sum of the mol% of components (B1) and (B2), preferably based on the total amount of substance of the monomer mixture (M).

[0076] Preferably, component (B) contains 47 to 53 mol% of component (B1) and 47 to 53 mol% of component (B2), respectively, based on the sum of the mol% of components (B1) and (B2), preferably based on the total amount of component (B).

[0077] Particularly preferably, component (B) contains 49 to 51 mol% of component (B1) and 49 to 51 mol% of component (B2), respectively, based on the sum of the mol% of components (B1) and (B2), preferably based on the total amount of component (B).

[0078] The present invention therefore also relates to a method in which component (B) contains in the range of 45 to 55 mol% of component (B1) and in the range of 45 to 55 mol% of component (B2), in each case based on the total amount of component (B).

[0079] The sum of the mol percent of components (B1) and (B2) contained in component (B) usually adds up to 100 mol percent.

[0080] Component (B) may additionally contain a component (B3), at least one C4-C20 diacid.

[0081] The present invention therefore also relates to a method in which the component (B) additionally contains a component (B3), at least one C 4 -C 20 diacid.

[0082] The terms "component (B3)" and "at least one C4-C20 diacid" are used synonymously within the scope of the present invention and therefore have the same meaning.

[0083] If component (B) additionally contains component (B3), it is preferred that component (B) contains component (B1) in the range of 25 to 54.9 mol%, component (B2) in the range of 45 to 55 mol% and component (B3) in the range of 0.1 to 25 mol%, in each case based on the total amount of component (B).

[0084] Particularly preferably, component (B) contains in the range of 13 to 52.9 mol% of component (B1), in the range of 47 to 53 mol% of component (B2) and in the range of 0.1 to 13 mol% of component (B3), in each case based on the total amount of component (B).

[0085] The component (B) most preferably contains in the range of 7 to 50.9 mol% of component (B1), in the range of 49 to 51 mol% of component (B2) and in the range of 0.1 to 7 mol% of component (B3), in each case based on the total amount of component (B).

[0086] If component (B) also contains component (B3), the molar percent of components (B1), (B2) and (B3) usually add up to 100 molar percent.

[0087] The monomer mixture (M) may also contain water.

[0088] Components (B1) and (B2), and optionally (B3), of component (B) can react with each other to form amides. This reaction is known to those skilled in the art. Therefore, component (B) can contain components (B1), (B2), and optionally (B3) in fully reacted form, in partially reacted form, or in unreacted form. Preferably, component (B) contains components (B1) and (B2), and optionally (B3), in unreacted form.

[0089] "In unreacted form" within the scope of the present invention means that the component (B1) is present as the at least one C 32 -C 40 dimer acid and the component (B2) as the at least one C 4 -C 12 diamine and optionally the component (B3) as the at least one C 4 -C 20 dia acid.

[0090] If components (B1) and (B2) and, if applicable, (B3) have reacted at least partially, then components (B1) and (B2) and, if applicable, (B3) are present at least partially as amides. Component (B1)

[0091] According to the invention, component (B1) is at least one C 32 -C 40 dimer acid.

[0092] "At least one C 32 -C 40 dimer acid" within the scope of the present invention means both exactly one C 32 -C 40 dimer acid and a mixture of two or more C 32 -C 40 dimer acids.

[0093] Dimer acids are also known as dimer fatty acids. C32-C40 dimer acids are well-known to those skilled in the art and are usually produced by the dimerization of unsaturated fatty acids. This dimerization can be catalyzed, for example, by aluminas.

[0094] Suitable unsaturated fatty acids for the production of at least one C 32 -C 40 dimer acid are known to those skilled in the art and include, for example, unsaturated C 16 fatty acids, unsaturated C 18 fatty acids and unsaturated C 20 fatty acids.

[0095] The component (B1) is therefore preferably produced starting from unsaturated fatty acids selected from the group consisting of unsaturated C 16 fatty acids, unsaturated C 18 fatty acids and unsaturated C 20 fatty acids, wherein the unsaturated C 18 fatty acids are particularly preferred.

[0096] The present invention therefore also relates to a process in which the component (B1) is produced starting from unsaturated fatty acids selected from the group consisting of unsaturated C 16 fatty acids, unsaturated C 18 fatty acids and unsaturated C 20 fatty acids.

[0097] A suitable unsaturated C 16 fatty acid is, for example, palmitoleic acid ((9Z)-hexadeca-9-enoic acid).

[0098] Suitable unsaturated C18 fatty acids are, for example, selected from the group consisting of petroselinic acid ((6Z)-octadeca-6-enoic acid), oleic acid ((9Z)-octadeca-9-enoic acid), elaidic acid ((9E)-octadeca-9-enoic acid), vaccenic acid ((11E)-octadeca-11-enoic acid), linoleic acid ((9Z,12Z)-octadeca-9,12-dienoic acid), α-linolenic acid ((9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid), γ-linolenic acid ((6Z,9Z,12Z)-octadeca-6,9,12-trienoic acid), calendic acid ((8E,10E,12Z)-octadeca-8,10,12-trienoic acid), and punicic acid. ((9Z,11E,13Z)-Octadeca-9,11,13-trienoic acid), α-Elaeostearic acid ((9Z,11E,13E)-Octadeca-9,11,13-trienoic acid) and β-Elaeostearic acid ((9E,11E,13E)-Octadeca-9,11,13-trienoic acid). Particularly preferred are unsaturated C18 fatty acids selected from the group consisting of petroselinic acid ((6Z)-Octadeca-6-enoic acid), oleic acid ((9Z)-Octadeca-9-enoic acid), elaidic acid ((9E)-Octadeca-9-enoic acid), vaccenic acid ((11E)-Octadeca-11-enoic acid), linoleic acid ((9Z,12Z)-Octadeca-9,12-dienoic acid).

[0099] Suitable unsaturated C 20 fatty acids are selected, for example, from the group consisting of gadoleic acid ((9Z)-eicosa-9-enoic acid), icosenoic acid ((11Z)-eicosa-11-enoic acid), arachidonic acid ((5Z,8Z, 11Z, 14Z)-eicosa-5,8, 11, 14-tetraenoic acid) and timnodonic acid ((5Z,8Z,11Z,14Z,17Z)-eicosa-5,8,11,14,17-pentaenoic acid).

[0100] The component (B1) is in particular preferably at least one C 36 dimer acid.

[0101] The at least one C36 dimer acid is preferably produced starting from unsaturated C18 fatty acids. Particularly preferably, the C36 dimer acid is produced starting from C18 fatty acids selected from the group consisting of petroselinic acid ((6Z)-octadeca-6-enoic acid), oleic acid ((9Z)-octadeca-9-enoic acid), elaidic acid ((9E)-octadeca-9-enoic acid), vaccenic acid ((11E)-octadeca-11-enoic acid) and linoleic acid ((9Z, 12Z)-octadeca-9, 12-dienoic acid).

[0102] During the production of component (B1) from unsaturated fatty acids, trimeric acids can also be formed, and residues of unreacted unsaturated fatty acid may remain.

[0103] The formation of trimeric acids is known to experts.

[0104] According to the invention, preferably the component (B1) contains at most 0.5 wt.% unreacted unsaturated fatty acid and at most 0.5 wt.% trimeric acid, particularly preferably at most 0.2 wt.% unreacted unsaturated fatty acid and at most 0.2 wt.% trimeric acid, each based on the total weight of the component (B1).

[0105] Dimer acids (also known as dimerized fatty acids or dimer fatty acids) are generally, and particularly within the scope of the present invention, defined as mixtures produced by the oligomerization of unsaturated fatty acids. They can be produced, for example, by the catalytic dimerization of unsaturated fatty acids from plants, using, in particular, unsaturated C16 to C20 fatty acids as starting materials. The linkage proceeds primarily according to the Diels-Alder type, and, depending on the number and position of the double bonds of the fatty acids used to produce the dimer acids, mixtures of predominantly dimeric products result, which exhibit cycloaliphatic, linear-aliphatic, branched-aliphatic, and also C6 aromatic hydrocarbon groups between the carboxyl groups.Depending on the mechanism and / or any subsequent hydrogenation, the aliphatic residues can be saturated or unsaturated, and the proportion of aromatic groups can also vary. The residues between the carboxylic acid groups then contain, for example, 32 to 40 carbon atoms. Preferably, fatty acids with 18 carbon atoms are used for the preparation, so that the dimeric product has 36 carbon atoms. Preferably, the residues that link the carboxyl groups of the dimeric fatty acids have no unsaturated bonds and no aromatic hydrocarbon residues.

[0106] In accordance with the present invention, C18 fatty acids are preferably used in the production process. Linolenic, linoleic, and / or oleic acids are particularly preferred.

[0107] Depending on the reaction procedure, the oligomerization described above produces mixtures containing mainly dimeric molecules, but also trimeric molecules, monomeric molecules, and other byproducts. Purification is usually carried out by distillation. Commercially available dimeric acids generally contain at least 80 wt% dimeric molecules, up to 19 wt% trimeric molecules, and a maximum of 1 wt% monomeric molecules and other byproducts.

[0108] It is preferred to use dimer acids which consist of at least 90 wt.%, preferably at least 95 wt.%, most preferably at least 98 wt.% dimer fatty acid molecules.

[0109] The proportions of monomeric, dimeric, and trimeric molecules, as well as other byproducts, in dimeric acids can be determined, for example, by gas chromatography (GC). In this process, the dimeric acids are converted to the corresponding methyl esters using the boron trifluoride method prior to GC analysis (see DIN EN ISO 5509) and then analyzed by GC.

[0110] Within the scope of the present invention, a fundamental characteristic of "dimer acids" is that their production involves the oligomerization of unsaturated fatty acids. This oligomerization process predominantly yields, that is, preferably, at least 80 wt.%, particularly preferably at least 90 wt.%, most preferably at least 95 wt.%, and particularly preferably at least 98 wt.% dimeric products. The fact that the oligomerization process predominantly produces dimeric products containing exactly two fatty acid molecules justifies this already common designation. An alternative term for the relevant concept of "dimer acids" is therefore "mixture containing dimerized fatty acids."

[0111] The dimer acids to be used are available as commercial products. Examples include Radiacid 0970, Radiacid 0971, Radiacid 0972, Radiacid 0975, Radiacid 0976 and Radiacid 0977 from Oleon, Pripol 1006, Pripol 1009, Pripol 1012, and Pripol 1013 from Croda, Empol 1008, Empol 1012, Empol 1061 and Empol 1062 from BASF SE, and Unidyme 10 and Unidyme TI from Arizona Chemical.

[0112] Component (B1), for example, has an acid number in the range of 190 to 200 mg KOH / g. Component (B2)

[0113] According to the invention, component (B2) is at least one C4-C12 diamine.

[0114] "At least one C4-C12 diamine" within the scope of the present invention means both exactly one C4-C12 diamine and a mixture of two or more C4-C12 diamines.

[0115] In the context of this compound, "C4-C12 diamine" refers to aliphatic and / or aromatic compounds with four to twelve carbon atoms and two amino groups (-NH2 groups). The aliphatic and / or aromatic compounds can be unsubstituted or, additionally, at least monosubstituted. If the aliphatic and / or aromatic compounds are additionally at least monosubstituted, they can bear one, two, or more substituents that do not participate in the polymerization of components (A) and (B). Such substituents include, for example, alkyl or cycloalkyl substituents. These are known to those skilled in the art. Preferably, the at least one C4-C12 diamine is unsubstituted.

[0116] Suitable components (B2) are, for example, selected from the group consisting of 1,4-diaminobutane (butane-1,4-diamine; tetramethylenediamine; putrescine), 1,5-diaminopentane (pentamethylenediamine; pentane-1,5-diamine; cadaverine), 1,6-diaminohexane (hexamethylenediamine; hexane-1,6-diamine), 1,7-diaminoheptane, 1,8-diaminoctane, 1,9-diaminononane, 1,10-diaminodecane (decamethylenediamine), 1,11-diaminoundecane (undecamethylenediamine) and 1,12-diaminododecane (dodecamethylenediamine).

[0117] The component (B2) is preferably selected from the group consisting of tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine and dodecamethylenediamine.

[0118] The present invention therefore also relates to a process in which the component (B2) is selected from the group consisting of tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine and dodecamethylenediamine. Component (B3)

[0119] The component (B3) which may be contained in component (B) is, according to the invention, at least a C4-C20 diacid.

[0120] "At least one C4-C20 diacid" within the scope of the present invention means both exactly one C4-C20 diacid and a mixture of two or more C4-C20 diacids.

[0121] Within the scope of the present invention, "C4-C20 diaacid" refers to aliphatic and / or aromatic compounds with two to eighteen carbon atoms and two carboxyl groups (-COOH groups). The aliphatic and / or aromatic compounds can be unsubstituted or additionally at least monosubstituted. If the aliphatic and / or aromatic compounds are additionally at least monosubstituted, they can bear one, two, or more substituents that do not participate in the polymerization of components (A) and (B). Such substituents are, for example, alkyl or cycloalkyl substituents. These are known to those skilled in the art. Preferably, the at least one C4-C20 diaacid is unsubstituted.

[0122] Suitable components (B3) are, for example, selected from the group consisting of butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), octanedioic acid (corticic acid, suberic acid), nonanedioic acid (azelaic acid), decanodioic acid (sebacic acid), undecandioic acid, dodecandioic acid, tridecandioic acid, tetradecandioic acid and hexadecandioic acid.

[0123] The component (B3) is preferably selected from the group consisting of pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), decanodioic acid (sebacic acid) and dodecanedioic acid. Step ii)

[0124] In step ii), the at least one copolyamide provided in step i) is extruded in molten form from the first extruder through an annular die to obtain a tube containing the at least one copolyamide in molten form.

[0125] Within the scope of the present invention, "a ring nozzle" means exactly one ring nozzle as well as two or more ring nozzles. According to the invention, exactly one ring nozzle is preferred.

[0126] All ring dies known to those skilled in the art that allow the extrusion of a tube from at least one copolyamide in molten form are suitable. Suitable ring dies are known to those skilled in the art.

[0127] In a preferred embodiment of the present invention, if step i1) described below is carried out, it is preferred that in step ii) the at least one copolyamide in molten form from the first extruder is combined with the at least one further polymer (wP) in molten form from the further extruder described below in the annular die.

[0128] In particular, preferably in step ii) the at least one copolyamide in molten form from the first extruder is combined with the at least one further polymer (wP) in molten form from the further extruder in the die such that the tube obtained in step ii), which contains the at least one copolyamide in molten form, contains at least a first layer containing the at least one copolyamide in molten form, and contains at least one further layer containing the at least one further polymer (wP) in molten form.

[0129] For example, the thickness of the tube containing the at least one copolyamide in molten form is in the range of 10 to 1 mm, preferably in the range of 20 to 700 µm and particularly preferably in the range of 50 to 500 µm.

[0130] The present invention therefore also relates to a method in which the hose obtained in step ii) has a thickness in the range of 10 µm to 1 mm. Step iii)

[0131] In step iii), the tube obtained in step ii), which contains the at least one copolyamide in molten form, is cooled in a water bath to a first temperature (T 1 ), whereby the at least one copolyamide solidifies to obtain a first tube film containing the at least one copolyamide.

[0132] The first temperature (T 1 ) to which the hose is cooled is, for example, below the melting temperature (TM(C) ) of the at least one copolyamide, preferably the temperature (T 1 ) is below the glass transition temperature (TG(C) ) of the at least one copolyamide.

[0133] For example, the first temperature (T 1 ) in step iii) is in the range of 5 to 50 °C, preferably in the range of 10 to 45 °C and particularly preferably in the range of 15 to 40 °C.

[0134] The present invention therefore also relates to a method in which the first temperature (T 1 ) in step iii) is in the range of 5 to 50 °C.

[0135] The water bath contains water. The water bath may also contain other components such as alcohols.

[0136] According to the invention, the water bath preferably consists of water.

[0137] The temperature of the water bath in step iii) is, for example, in the range of 5 to 70 °C, preferably in the range of 10 to 50 °C and particularly preferably in the range of 15 to 40 °C.

[0138] Steps ii) and iii) can be carried out sequentially or simultaneously. It is understood that if steps ii) and iii) are carried out simultaneously, the tube containing the at least one copolyamide in molten form is only obtained briefly and in an intermediate state. Typically, during extrusion in step ii), the at least one copolyamide in molten form is directly extruded as a tube into the water bath in step iii), cooled therein, and solidifies, yielding the first tube film.

[0139] The tube containing the at least one copolyamide is guided over a first roller system during cooling in step iii). This stretches the tube along its length.

[0140] The present invention therefore relates to a method in which the tube containing the at least one copolyamide is guided over a first roller system during cooling in step iii), whereby the tube is stretched in its length.

[0141] When the hose is stretched, the polymer chains of the at least one copolyamide align, and the crystallinity of the at least one copolyamide can increase. This process is known to those skilled in the art.

[0142] Furthermore, it is possible that the polymer chains of at least one other polymer (wP) potentially contained in the tube may also align during stretching. This can also increase the crystallinity of at least one other polymer (wP).

[0143] When the tube is stretched lengthwise, this means that the tube is stretched in the extrusion direction. The polymer chains of the at least one copolyamide and, if applicable, of the at least one further polymer (wP), align themselves parallel to the direction in which the tube is stretched. Step iv)

[0144] In step iv) the first tubular film obtained in step iii) is heated to a second temperature (T 2 ) to obtain a heated first tubular film containing the at least one copolyamide.

[0145] The heating of the first film of the hose can be carried out using any method known to the expert, for example by infrared emitters or a heating ring surrounding the hose.

[0146] The second temperature (T2), to which the first tubular film is heated, is preferably above the glass transition temperature (TG(C)) of the at least one copolyamide. It is further preferred that the second temperature (T2) is below the melting temperature (TM(C)) of the at least one copolyamide.

[0147] The present invention therefore also relates to a method in which the at least one copolyamide has a glass transition temperature (TG(C) ) and a melting temperature (TM(C) ), and the second temperature (T 2 ) in step iv) is above the glass transition temperature (TG(C) ) and below the melting temperature (TM(C) ) of the at least one copolyamide.

[0148] For example, the second temperature (T 2 ) in step iv) is in the range of 50 to 200 °C, preferably in the range of 60 to 190 °C and particularly preferably in the range of 70 to 180 °C.

[0149] The present invention therefore also relates to a method in which, in step iv), the first tubular film obtained in step iii) is heated to a second temperature (T 2 ) which is in the range of 50 to 200 °C.

[0150] It goes without saying that the second temperature (T 2 ) to which the first tube film is heated in step iv) is above the first temperature (T 1 ) to which the tube is cooled in step iii). Step v)

[0151] In step v) air is blown into the heated first tube film obtained in step iv), whereby the heated first tube film is stretched in its width and the heated first tube film cools to a third temperature (T 3 ) while retaining the polymer film (P) which contains the at least one copolyamide.

[0152] In the context of the present invention, "air" is understood to mean the gas mixture of the Earth's atmosphere.

[0153] In a further embodiment of the present invention, in step v) at least one gas selected from the group consisting of nitrogen, argon and carbon dioxide is blown into the heated first tube film obtained in step iv).

[0154] The blowing of air into the heated first film of tubing obtained in step iv) can be carried out using any method known to a person skilled in the art.

[0155] The heated first tube film is stretched in width. This means that it is stretched perpendicular to the extrusion direction.

[0156] During step v), the heated first tube film can additionally be guided over a second roller system, whereby the heated first tube film is additionally stretched in length.

[0157] The present invention therefore also relates to a method in which the heated first tube film containing the at least one copolyamide is guided over a second roller system during the blowing of air in step v), whereby the heated first tube film is stretched in its length.

[0158] If the heated first tube film is passed over a second roller system during step v) and / or the tube is passed over a first roller system during cooling in step iii), then the polymer film (P) obtained in step v) is a polymer film (P) that is stretched both in its extrusion direction and perpendicular to it. It is then a biaxially oriented polymer film (P).

[0159] "Biaxially oriented" means that the polymer chains are essentially aligned in two different directions, preferably perpendicular to each other.

[0160] In step v), the first tube film cools down to a third temperature (T3). This cooling to the third temperature (T3) can be achieved solely by blowing air into the heated first tube film. Alternatively, the heated first tube film can be cooled further during step v).

[0161] The third temperature (T 3), to which the heated first tube film is cooled, is preferably below the glass transition temperature (TG(C) ) of the at least one copolyamide.

[0162] For example, the third temperature (T 3 ) is in the range of 5 to 50 °C, preferably in the range of 10 to 45 °C and particularly preferably in the range of 15 to 40 °C.

[0163] It goes without saying that the third temperature (T 3 ), to which the heated first tube film is cooled in step v), is below the second temperature (T 2 ), to which the first tube film is heated in step iv).

[0164] According to the invention, the following steps are preferably carried out following step v): vi) Passing the polymer film (P) obtained in step v) over at least one third roller, vii) Heating the polymer film (P) obtained in step v) to a fourth temperature (T 4) which is above the glass transition temperature (TG(C) ) of the at least one copolyamide, obtaining a heated polymer film (P), viii) Passing the heated polymer film (P) obtained in step vii) over at least one fourth roller, wherein the heated polymer film (P) is cooled between step vii) and step viii), during step viii) and / or following step viii) to a fifth temperature (Ts) which is below the glass transition temperature (TG(C) ) of the at least one copolyamide.

[0165] The present invention therefore also relates to a method in which the following steps are carried out following step v): vi) Passing the polymer film (P) obtained in step v) over at least one third roller, vii) Heating the polymer film (P) obtained in step v) to a fourth temperature (T 4 ) which is above the glass transition temperature (TG(C) ) of the at least one copolyamide, obtaining a heated polymer film (P), viii) Passing the heated polymer film (P) obtained in step vii) over at least one fourth roller, obtaining the polymer film (P) wherein the heated polymer film (P) is cooled between step vii) and step viii), during step viii) and / or following step viii) to a fifth temperature (Ts) which is below the glass transition temperature (TG(C) ) of the at least one copolyamide.

[0166] Steps vi) to viii), which may be carried out following step v), are also referred to as "annealing".

[0167] In step vi) the polymer film (P) is guided over at least one third roller.

[0168] "At least one third roller" means, within the scope of the present invention, both exactly one third roller and a third roller system.

[0169] Preferably, the polymer film (P) is guided over a third roller system in step vi).

[0170] Suitable third rollers are known to those skilled in the art. Likewise, suitable third roller systems are known to those skilled in the art.

[0171] The at least one third roller usually has a first rotational speed.

[0172] In one embodiment of the present invention, steps v) and vi) are carried out simultaneously. Then, in step v), the heated first tubular film is additionally guided over a second roller system, and the second roller system is identical to the at least third roller over which the polymer film (P) is guided in step vi).

[0173] The present invention therefore also relates to a method in which the heated first tube film containing the at least one copolyamide is guided over a second roller system during the blowing of air in step v), whereby the heated first tube film is stretched in length, and the following steps are carried out after step v). vii) Heating the polymer film (P) obtained in step v) to a fourth temperature (T 4) which is above the glass transition temperature (TG(C) ) of the at least one copolyamide, obtaining a heated polymer film (P), viii) Passing the heated polymer film (P) obtained in step vii) over at least a fourth roller, obtaining the polymer film (P) wherein the heated polymer film (P) is cooled between step vii) and step viii), during step viii) and / or following step viii) to a fifth temperature (T 5) which is below the glass transition temperature (TG(C) ) of the at least one copolyamide.

[0174] In step vii) the polymer film (P) is heated to a fourth temperature (T 4 ).

[0175] Heating is preferably carried out after the polymer film (P) has been guided over the at least one third roller in step vi). If the heated first tubular film is guided over a second roller system during step v) and the at least one third roller is identical to the second roller system, heating is preferably carried out after guiding the film over the second roller system.

[0176] Heating the obtained polymer film (P) to the fourth temperature (T 4 ) in step vii) can be carried out using any method known to a person skilled in the art.

[0177] According to the invention, the fourth temperature (T4) is above the glass transition temperature (TG(C)) of the at least one copolyamide. It is further preferred that the fourth temperature (T4) is below the melting temperature (TM(C)) of the at least one copolyamide.

[0178] The present invention therefore also relates to a method in which the fourth temperature (T 4 ) is below the melting temperature (TM(C) ) of the at least one copolyamide.

[0179] It goes without saying that the fourth temperature (T 4 ), to which the polymer film (P) is heated if necessary in step vii), is above the third temperature (T 3 ), to which the heated first tubular film is cooled in step v).

[0180] In step viii) the heated polymer film (P) is guided over at least a fourth roller.

[0181] "At least a fourth roller" means, within the scope of the present invention, both exactly a fourth roller and a fourth roller system.

[0182] The at least one fourth roller usually has a second rotational speed.

[0183] According to the invention, preferably the first rotational speed of the at least one third roller is higher than the second rotational speed of the at least one fourth roller.

[0184] The heated polymer film (P) is cooled to a fifth temperature (T5) between step vii) and step viii) during and / or following step viii). The fifth temperature (T5) is below the glass transition temperature (TG(C)) of the at least one copolyamide.

[0185] It goes without saying that the fifth temperature (T 5 ) is below the fourth temperature (T 4 ).

[0186] Cooling to the fifth temperature (T 5 ) can be carried out using any method known to a person skilled in the art, for example by cooling with air.

[0187] By carrying out steps vi) to viii), a polymer film (P) is obtained that exhibits a particularly low pre-shrinkage. The polymer film (P) therefore shrinks little or not at all between its production and its use, for example as a packaging film. The same applies if the heated first tubular film is passed over a second roller system in step v) and steps vi) to viii) are then carried out. Polymer film (P)

[0188] The polymer film (P) produced according to the invention contains the at least one copolyamide.

[0189] The polymer film (P) has, for example, a thickness in the range of 0.1 µm to 1 mm, preferably a thickness in the range of 5 to 500 µm and particularly preferably in the range of 20 to 100 µm.

[0190] The present invention therefore also relates to a method in which the polymer film (P) has a thickness in the range of 0.1 µm to < 1 mm.

[0191] The polymer film (P) can contain at least one additional polymer (wP) besides the at least one copolyamide.

[0192] "At least one further polymer (wP)" within the scope of the present invention means both exactly one further polymer (wP) and a mixture of two or more further polymers (wP).

[0193] All polymers known to those skilled in the art are suitable as at least one additional polymer (wP). It goes without saying that the at least one additional polymer (wP) is different from the at least one copolyamide.

[0194] Preferably, at least one further polymer (wP) is selected from the group consisting of polyolefins, poly(ethyl vinyl alcohols), poly(ethyl vinyl acetates), polyethylene terephthalates, polyvinylidene chlorides, polyolefins grafted with maleic anhydride, polyesters and ionomers.

[0195] Particularly preferred is at least one further polymer (wP) selected from the group consisting of polyolefins, poly(ethyl vinyl alcohols), poly(ethyl vinyl acetates), polyethylene terephthalates, polyvinylidene chlorides and polyolefins grafted with maleic anhydride.

[0196] The most preferred polymer is at least one other polymer (wP) selected from the group consisting of polyolefins, polyolefins grafted with maleic anhydride and ethyl vinyl alcohols.

[0197] If at least one further polymer (wP) is selected from the group consisting of polyolefins, it is preferred that maleic anhydride-grafted polyolefins are additionally used as at least one further polymer (wP). It is possible that the at least one further polymer (wP) is a mixture of polyolefins and maleic anhydride-grafted polyolefins.It is also possible that, if the polymer film (P) is a multilayer film as described below, the polymer film (P) contains at least one first further layer of at least one further polymer (wP), wherein the at least one further polymer (wP) of the first further layer is selected from the group consisting of polyolefins grafted with maleic anhydride, and the polymer film (P) contains at least one second further layer of at least one further polymer (wP), wherein the at least one further polymer (wP) of the second further layer is selected from the group consisting of polyolefins. The polymer film (P) then preferably contains the first further layer between the first layer containing the at least one copolyamide and the second further layer.

[0198] Polyolefins as such are known to those skilled in the art. Preferred polyolefins are polypropylene (PP), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and very low-density polyethylene (VLDPE).

[0199] Linear low-density polyethylene (LLDPE) is a copolymer of ethylene and at least one C₄-C₈-α-olefin. Linear low-density polyethylene (LLDPE) is characterized by long polymer chains with short side chains. The side chain lengths in linear low-density polyethylene (LLDPE) are typically shorter than in low-density polyethylene (LDPE) and medium-density polyethylene (MDPE). The melting point of linear low-density polyethylene (LLDPE) is preferably in the range of 110 to 130 °C, and its density is in the range of 0.91 to 0.93 g / cm³.

[0200] Very-low-density polyethylene (VLDPE) is a copolymer of ethylene and at least one C₄-C₈α-olefin. It typically has a melting point in the range of 110 to 130 °C and a density in the range of 0.86 to < 0.91 g / cm³. The proportion of C₄-C₈α-olefins in VLDPE is generally higher than in LLDPE.

[0201] Within the scope of the present invention, "C4-C8-α-olefins" are understood to be linear and branched, preferably linear, alkylenes with 4 to 8 carbon atoms that are unsaturated at the α-position, i.e., possess a C-C double bond at the α-position. Examples include 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. 1-Butene, 1-hexene, and 1-octene are preferred.

[0202] Copolymers of ethylene and vinyl acetate are preferred as poly(ethylene vinyl acetates). For example, ethylene in the range of 82 to 99.9 wt.% and vinyl acetate in the range of 0.1 to 18 wt.% are used for production, preferably ethylene in the range of 88 to 99.9 wt.% and vinyl acetate in the range of 0.1 to 12 wt.%.

[0203] Preferred poly(ethylene vinyl alcohols) are obtained by complete or partial sintering of the poly(ethylene vinyl acetates) described above. For example, the poly(ethylene vinyl alcohols) contain 50 to 75 mol% ethylene and 25 to 50 mol% vinyl alcohol, based on the total amount of poly(ethylene vinyl alcohols).

[0204] The polymer film (P) can contain at least one other polymer (wP) as a blend (mixture) with the at least one copolyamide.

[0205] Furthermore, it is possible and preferred according to the invention that the polymer film (P) contains at least one first layer containing the at least one copolyamide, and the polymer film (P) contains at least one further layer containing the at least one further polymer (wP).

[0206] In this embodiment, it is preferred that the at least one first layer containing the at least one copolyamide does not contain any further polymer (wP).

[0207] In the context of the present invention, "at least one first layer" means exactly one first layer as well as two or more first layers.

[0208] As described above, the number of first layers results from the number of first extruders used in step i) of the process according to the invention.

[0209] In the context of the present invention, "at least one additional layer" means exactly one additional layer as well as two or more additional layers. Two or more additional layers are preferred.

[0210] As explained below, the number of additional layers results from the number of additional extruders used in an embodiment of the inventive method.

[0211] It is therefore preferred that the polymer film (P) contains at least one first layer containing the at least one copolyamide, and that the polymer film (P) also contains at least one further layer, wherein the at least one further layer contains at least one further polymer (wP) selected from the group consisting of polyolefins, poly(ethylene vinyl alcohols), poly(ethylene vinyl acetates), polyethylene terephthalates, polyvinylidene chlorides and polyolefins grafted with maleic anhydride.

[0212] The present invention therefore also relates to a method in which the polymer film (P) contains at least one first layer containing the at least one copolyamide, and the polymer film (P) contains at least one further layer, wherein the at least one further layer contains at least one further polymer (wP) selected from the group consisting of polyolefins, poly(ethylene vinyl alcohols), poly(ethylene vinyl acetates), polyethylene terephthalates, polyvinylidene chlorides and polyolefins grafted with maleic anhydride.

[0213] If the polymer film (P) contains no further layers other than the at least one first layer, the polymer film (P) is also referred to as a "monofilm". If the polymer film (P) is a monofilm, it can contain exactly one first layer and no further layers, or it can contain two or more first layers and no further layers. If the polymer film (P) contains two or more first layers and is a monofilm, the two or more first layers all have the same composition.

[0214] If the polymer film (P) contains at least one first layer containing the at least one copolyamide and at least one further layer containing the at least one further polymer (wP), the polymer film (P) is also referred to as a multilayer film.

[0215] For example, the polymer film (P) then contains 1 to 11 first layers containing the at least one copolyamide, and 1 to 13 further layers containing the at least one further polymer (wP). Preferably, the polymer film (P) contains 1 to 5 first layers containing the at least one copolyamide, and 1 to 11 further layers containing the at least one further polymer (wP). Particularly preferably, the polymer film (P) contains 1 to 3 first layers containing the at least one copolyamide, and 1 to 7 further layers containing the at least one further polymer (wP).

[0216] In a preferred embodiment of the present invention, the at least one first layer consists of the at least one copolyamide. It is also preferred that the at least one further layer consists of the at least one further polymer (wP).

[0217] Within the scope of the present invention, the term "polymer film (P)" therefore includes both monofilms and multilayer films.

[0218] The present invention therefore also relates to a method in which the polymer film (P) is a monofilm or a multilayer film.

[0219] As described above, the polymer film (P) typically has a thickness in the range of 0.1 µm to 1 mm, preferably in the range of 5 to 500 µm and particularly preferably in the range of 10 to 100 µm.

[0220] If the polymer film (P) is a monofilm and contains exactly one first layer, the first layer has the same thickness as the polymer film (P), for example, in the range of 0.1 µm to 1 mm, preferably in the range of 5 to 500 µm, and particularly preferably in the range of 10 to 100 µm. If the polymer film (P) is a monofilm and contains two or more first layers, the thickness of each first layer is typically less than the thickness of the polymer film (P). The sum of the thicknesses of the individual first layers then generally corresponds to the thickness of the polymer film (P). For example, the at least one first layer containing the at least one copolyamide then has a thickness in the range of 0.1 to 100 µm, preferably in the range of 0.5 to 50 µm, and particularly preferably in the range of 0.5 to 15 µm.

[0221] If the polymer film (P) is a multilayer film, the thickness of the individual layers of the polymer film (P), i.e., the thickness of the at least one first layer containing the at least one copolyamide and the thickness of the at least one further layer containing the at least one further polymer (wP), is usually less than the thickness of the polymer film (P). The sum of the thicknesses of the individual layers then generally corresponds to the thickness of the polymer film (P).

[0222] For example, the at least one first layer containing the at least one copolyamide then has a thickness in the range of 0.1 to 100 µm, preferably in the range of 0.5 to 50 µm and particularly preferably in the range of 0.5 to 15 µm.

[0223] The at least one further layer containing the at least one further polymer (wP) then has, for example, a thickness in the range of 0.1 to 100 µm, preferably in the range of 0.5 to 50 µm and particularly preferably in the range of 0.5 to 15 µm.

[0224] The polymer film (P) can contain at least one adhesion promoter. This embodiment is preferred if the polymer film (P) is a multilayer film.

[0225] In the context of the present invention, "at least one adhesion promoter" means both exactly one adhesion promoter and a mixture of two or more adhesion promoters.

[0226] If the polymer film (P) is a multilayer film, the at least one adhesion promoter can be contained together with the at least one copolyamide in the at least one first layer. It is also possible that the at least one adhesion promoter is contained together with the at least one further polymer (wP) in the at least one further layer. Furthermore, it is possible that the at least one adhesion promoter is contained as at least one additional layer in the polymer film (P). This embodiment is preferred.

[0227] If the at least one adhesion promoter is contained as at least one additional layer in the polymer film (P), the at least one adhesion promoter is usually provided in an additional extruder in the inventive method and then also extruded from this through the annular die in step ii).

[0228] If the at least one adhesion promoter is included as at least one additional layer in the polymer film (P), this at least one additional layer is preferably arranged between the at least one further layer containing the at least one further polymer (wP) and the at least one first layer containing the at least one copolyamide. The at least one layer of the adhesion promoter has, for example, a thickness of 0.1 to 100 µm, preferably in the range of 0.5 to 50 µm and particularly preferably in the range of 0.5 to 15 µm.

[0229] Suitable adhesion promoters are known to those skilled in the art. Copolymers of ethylene with maleic anhydride or a copolymer of ethylene with vinyl acetate are preferred as adhesion promoters. A copolymer of linear low-density polyethylene (LLDPE) and maleic anhydride or a copolymer of ethylene and vinyl acetate is preferred, wherein > 18 wt% vinyl acetate and < 82 wt% ethylene are used in the preparation of the copolymer. These copolymers are commercially available, for example under the trade name [trade name missing in original text]. Bynel 4105 the company DuPont or Escorene FL00119 the company Exxon.

[0230] Ethylene copolymers with maleic anhydride, polymers grafted with maleic anhydride, or ethylene copolymers are preferred as adhesion promoters.

[0231] The polymer film (P) may also contain additives if these were provided in the first extruder together with the at least one copolyamide and / or in the subsequent extruder together with the at least one further polymer (wP). The previously described specifications and preferences apply accordingly to the additives.

[0232] The additives can be contained in at least one first layer as well as in at least one further layer. They can be contained in only one of these layers, or they can be contained in all of them.

[0233] It is clear to those skilled in the art that if the additives are provided together with at least one copolyamide in the first extruder, the additives are contained in the first layer. If the additives are provided together with at least one further polymer (wP) in the subsequent extruder, the additives are contained in the subsequent layer.

[0234] The subject matter of the present invention is therefore also a polymer film obtainable according to the inventive method.

[0235] If the polymer film (P) is to contain at least one further polymer (wP), the process according to the invention preferably additionally comprises a step i1), providing at least one further polymer (wP) in molten form in a further extruder, wherein step i1) is carried out before step ii).

[0236] The subject matter of the present invention therefore also includes a method in which the additional step i1) Providing at least one further polymer (wP) in molten form in a further extruder, where step i1) is performed before step ii).

[0237] It is particularly preferred that step i1) be carried out simultaneously with step i).

[0238] It goes without saying that if step i1) is carried out, then the tubing obtained in step ii) will additionally contain the further polymer (wP) in molten form. Likewise, the first tubing film obtained in step iii) and the heated first tubing film obtained in step iv) will then additionally contain at least one further polymer.

[0239] Preferably, the process for producing the polymer film (P) then comprises the steps i) Providing at least one copolyamide produced by polymerizing components (A) 15 to 84 wt% of at least one lactam, (B) 16 to 85 wt% of a monomer mixture (M) containing components (B1) at least one C32-C40 dimer acid and (B2) at least one C4-C12 diamine, wherein the wt% of components (A) and (B) are based on the sum of the wt% of components (A) and (B) in molten form in an extruder. i1) Providing at least one further polymer (wP) in molten form in a further extruder. ii) Extruding the at least one copolyamide provided in step i) in molten form from the first extruder through an annular die and extruding the at least one further polymer (wP) provided in molten form from the further extruder through the annular die to obtain a tube.which contains the at least one copolyamide and the at least one further polymer (wP) each in molten form, iii) Cooling the tube obtained in step ii), which contains the at least one copolyamide and the at least one further polymer (wP) each in molten form, in a water bath to a first temperature (T1), wherein the at least one copolyamide and the at least one further polymer (wP) solidify to obtain a first tube film containing the at least one copolyamide and the at least one further polymer (wP), wherein the tube is guided over a first roller system during cooling, whereby the tube is stretched in length; iv) Heating the first tube film obtained in step iii) to a second temperature (T2), obtaining a heated first tube film containing the at least one copolyamide and the at least one further polymer (wP).v) Blowing air into the heated first tubular film obtained in step iv), wherein the heated first tubular film is stretched in width and wherein the heated first tubular film cools to a third temperature (T 3 ) while retaining the polymer film (P) containing the at least one copolyamide and the at least one further polymer (wP).

[0240] The present invention therefore also relates to a method for producing a polymer film (P) comprising the steps i) Providing at least one copolyamide produced by polymerizing components (A) 15 to 84 wt% of at least one lactam, (B) 16 to 85 wt% of a monomer mixture (M) containing components (B1) at least one C32-C40 dimer acid and (B2) at least one C4-C12 diamine, wherein the wt% of components (A) and (B) are based on the sum of the wt% of components (A) and (B) in molten form in an extruder. i1) Providing at least one further polymer (wP) in molten form in a further extruder. ii) Extruding the at least one copolyamide provided in step i) in molten form from the first extruder through an annular die and extruding the at least one further polymer (wP) provided in molten form from the further extruder through the annular die to obtain a tube.which contains the at least one copolyamide and the at least one further polymer (wP) each in molten form, iii) Cooling the tube obtained in step ii), which contains the at least one copolyamide and the at least one further polymer (wP) each in molten form, in a water bath to a first temperature (T1), wherein the at least one copolyamide and the at least one further polymer (wP) solidify to obtain a first tube film containing the at least one copolyamide and the at least one further polymer (wP), wherein the tube is guided over a first roller system during cooling, whereby the tube is stretched in length; iv) Heating the first tube film obtained in step iii) to a second temperature (T2), obtaining a heated first tube film containing the at least one copolyamide and the at least one further polymer (wP).v) Blowing air into the heated first tubular film obtained in step iv), wherein the heated first tubular film is stretched in width and wherein the heated first tubular film cools to a third temperature (T 3 ) while retaining the polymer film (P) containing the at least one copolyamide and the at least one further polymer (wP).

[0241] In the context of the present invention, "another extruder" means exactly one additional extruder as well as two or more additional extruders. Two or more additional extruders are preferred.

[0242] Preferably, as many additional extruders are used as there are additional layers containing the at least one additional polymer (wP) that is to be included in the polymer film (P). For example, 1 to 13 additional extruders are used, preferably 1 to 11 additional extruders, and particularly preferably 1 to 7 additional extruders.

[0243] For example, if the polymer film is to contain exactly one additional layer containing at least one additional polymer (wP), then exactly one additional extruder is used. If the polymer film (P) is to contain exactly two additional layers containing at least one additional polymer (wP), then exactly two additional extruders are used. If the polymer film (P) is to contain exactly five additional layers containing at least one additional polymer (wP), then exactly five additional extruders are used.

[0244] The same specifications and preferences described above for the first extruder apply to the second extruder.

[0245] The above-described explanations and preferences apply accordingly to the at least one further polymer (wP) that may be contained in the polymer film (P).

[0246] According to the invention, the at least one further polymer (wP) is provided in molten form in step i1). "In molten form" means that the at least one further polymer (wP) is provided at a temperature above its melting point (TM(wP)). "In molten form" therefore means that the at least one further polymer (wP) has a temperature above its melting point (TM(wP)). If the at least one further polymer (wP) is in molten form, it is fluid.

[0247] "Flowable" means that at least one further polymer (wP) can be conveyed in the further extruder, and that at least one further polymer (wP) can be extruded from the further extruder.

[0248] For example, the at least one further polymer (wP) is provided in step i1) at a temperature in the range of 120 to 350 °C, preferably in the range of 130 to 300 °C and particularly preferably in the range of 140 to 250 °C, in each case provided that the temperature at which the at least one further polymer (wP) is provided is above the melting temperature (TM(wP) ) of the at least one further polymer (wP).

[0249] The at least one additional polymer (wP) can be supplied to the further extruder in molten form using any method known to a person skilled in the art. For example, the at least one additional polymer (wP) can be fed to the further extruder in molten or solid form. If the at least one additional polymer (wP) is fed to the further extruder in solid form, it can be supplied, for example, as granules and / or as a powder. The at least one additional polymer (wP) is then melted in the further extruder and thus supplied to the further extruder in molten form.

[0250] Furthermore, it is possible that in step i1) additives are provided in the subsequent extruder together with the at least one further polymer (wP) in molten form. The additives are usually compounded (mixed) with the at least one further polymer (wP) in molten form in the subsequent extruder. Methods for this are known to those skilled in the art.

[0251] The specifications and preferences previously described for the additives that may be provided in molten form together with the further polymer (wP) in the further extruder shall apply accordingly to the additives that may be provided in molten form together with the at least one copolyamide in the first extruder.

[0252] The additives that are optionally provided in molten form together with the further polymer (wP) in the further extruder, and the additives that are optionally provided in molten form together with the at least one copolyamide in the first extruder, can be the same or different. Preferably, the additives that are optionally provided in molten form together with the further polymer (wP) in the further extruder are different from the additives that are optionally provided in molten form together with the at least one copolyamide in the first extruder.

[0253] For steps i), ii), iii), iv) and v) for the production of the polymer film (P) containing the at least one copolyamide and the at least one further polymer (wP), the previously described explanations and preferences for steps i), ii), iii), iv) and v) for the production of the polymer film (P) containing the at least one copolyamide apply accordingly.

[0254] The tube obtained in step ii), which contains the at least one copolyamide and the at least one other polymer (wP) each in molten form, contains the at least one copolyamide in at least one first layer and the at least one other polymer (wP) in at least one further layer. Typically, the tube obtained in step ii) contains as many first layers containing the at least one copolyamide in molten form as there were first extruders used in step i) and as many further layers containing the at least one other polymer (wP) in molten form as there were additional extruders used in step i1).

[0255] The first temperature (T 1 ) in step iii) is, when step i1) is carried out, preferably also below the melting temperature (TM(wP) ) of the at least one further polymer (wP).

[0256] The second temperature (T 2 ) in step iv) is, when step i1) is carried out, preferably also above the glass transition temperature (TG(wP) ) of the at least one further polymer (wP) and particularly preferably also below the melting temperature (TM(wP) ) of the at least one further polymer (wP).

[0257] The third temperature (T 3 ) in step v) is, when step i1) is carried out, preferably below the melting temperature (TM(wP) ) of the at least one further polymer (wP).

[0258] It goes without saying that if step i1) is carried out, the polymer film (P) obtained in step v) is a multilayer film. Food packaging

[0259] The polymer film (P) produced according to the invention can be used in a process for packaging food.

[0260] The present invention therefore also relates to the use of the polymer film (P) according to the invention for packaging foodstuffs.

[0261] For example, the process for packaging food includes the following steps. a) Providing a foodstuff that is encased by at least one polymer film (P) according to the invention, wherein the at least one polymer film (P) has a provision temperature (TB). b) Heating the at least one polymer film (P) to a shrinkage temperature (TS), whereby the at least one polymer film (P) shrinks while retaining the foodstuff that is encased by the at least one shrunken polymer film (P).

[0262] A process for packaging food is also described, including the steps involved. a) Providing a foodstuff that is encased by at least one polymer film (P) according to claim 11, wherein the at least one polymer film (P) has a provision temperature (TB), b) Heating the at least one polymer film (P) to a shrinkage temperature (TS) whereby the at least one polymer film (P) shrinks while retaining the foodstuff that is encased by the at least one shrunken polymer film (P).

[0263] In step a), the food is provided which is coated by at least one polymer film (P).

[0264] The provisions and preferences previously described for the polymer film (P) apply accordingly to the at least one polymer film (P).

[0265] All known foods are suitable as foodstuffs. Cheese products, meat products and sausage products are particularly suitable.

[0266] "Covered by the at least one polymer film (P)" within the scope of the present invention means that at least 20%, preferably at least 50%, particularly preferably at least 80%, and most preferably 100% of the surface of the food is covered by the at least one polymer film (P). "Covered" means that the at least one polymer film (P) and the surface of the food can be in direct contact with each other. It is also possible that there is at least some air between the surface of the food and the at least one polymer film (P).

[0267] The at least one polymer film (P) has a provisioning temperature (TB) in step a).

[0268] The provision temperature (TB ) is preferably below the glass transition temperature (TG(C) ) of the at least one copolyamide contained in the at least one polymer film (P).

[0269] For example, the polymer film (P) has a provision temperature (TB) in the range of 5 to 50 °C, preferably in the range of 10 to 45 °C and particularly preferably in the range of 15 to 40 °C.

[0270] A method for packaging foodstuffs is also disclosed, wherein the provision temperature (TB ) is below the glass transition temperature (TG(C) ) of the at least one copolyamide contained in the at least one polymer film (P).

[0271] In the food packaging process, the provision temperature (TB ) is in the range of 5 to 50 °C.

[0272] In step b), the at least one polymer film (P) is heated to a shrinkage temperature (TS). The shrinkage temperature (TS) is therefore above the supply temperature (TB) of the polymer film (P).

[0273] Preferably, the shrinkage temperature is above the glass transition temperature (TG(C) ) of the at least one copolyamide contained in the at least one polymer film (P). For example, the shrinkage temperature (TS ) is in the range of 50 to 200 °C, preferably in the range of 60 to 180 °C and particularly preferably in the range of 70 to 120 °C.

[0274] A process is also described in which the shrinkage temperature (TS ) in step b) is above the glass transition temperature (TG(C) ) of the at least one copolyamide contained in the at least one polymer film (P).

[0275] In the food packaging process, the shrinkage temperature (TS ) in step b) is in the range of 50 to 200°C.

[0276] The at least one polymer film (P) can be heated to the shrinkage temperature (TS) using any method known to a person skilled in the art. For example, it can be heated to the shrinkage temperature (TS) by steam or hot air. In step b), the at least one polymer film (P) shrinks. The at least one polymer film (P) can begin to shrink while being heated to the shrinkage temperature (TS). It is also possible that the at least one polymer film only begins to shrink once its temperature reaches the shrinkage temperature (TS).

[0277] In the context of the present invention, "shrinkage" means that the volume of the at least one polymer film (P) becomes smaller compared to the volume of the at least one polymer film (P) at the supply temperature (TB). For example, the volume of the at least one polymer film (P) becomes 10 to 80% smaller, preferably 20 to 70% smaller, and particularly preferably 30 to 60% smaller, in each case relative to the volume of the at least one polymer film (P) at the supply temperature (TB).

[0278] The at least one shrunken polymer film (P) can completely or partially envelop the food in step b).

[0279] For example, the at least one shrunken polymer film (P) covers at least 20%, preferably at least 50%, particularly preferably at least 80%, and most preferably 100% of the surface of the food. "Covered" means that the at least one shrunken polymer film (P) and the surface of the food can be in direct contact with each other. It is also possible that there is at least some air between the surface of the food and the at least one shrunken polymer film (P).

[0280] The at least one shrunken polymer film (P) that encases the food exhibits a particularly high oxygen barrier and therefore protects the food very effectively from oxygen ingress. This high oxygen impermeability is maintained even at high humidity and high temperatures, for example above 25 °C.

Claims

1. A process for producing a polymer film (P), comprising the steps of i) providing at least one copolyamide produced by polymerizing the following components: (A) 15% to 84% by weight of at least one lactam, (B) 16% to 85% by weight of a monomer mixture (M) comprising the following components: (B1) at least one C32-C40 dimer acid and (B2) at least one C4-C12 diamine, where the percentages by weight of components (A) and (B) are each based on the sum total of the percentages by weight of components (A) and (B), in molten form in a first extruder, ii) extruding the at least one copolyamide provided in step i) in molten form from the first extruder through a ring die to obtain a tube comprising the at least one copolyamide in molten form, iii) cooling the tube obtained in step ii) which comprises the at least one copolyamide in molten form in a water bath to a first temperature (T1), solidifying the at least one copolyamide to obtain a first tubular film comprising the at least one copolyamide, where the tube is guided through a first roller system during the cooling, where the tube is stretched lengthwise, iv) heating the first tubular film obtained in step iii) to a second temperature (T2) to obtain a heated first tubular film comprising the at least one copolyamide, v) blowing air into the heated first tubular film obtained in step iv) to extend the width of the heated first tubular film, and cooling the heated first tubular film to a third temperature (T3) to obtain the polymer film (P) comprising the at least one copolyamide.

2. The process according to claim 1, wherein component (A) is selected from the group consisting of 3-aminopropanolactam, 4-aminobutanolactam, 5-aminopentanolactam, 6-aminohexanolactam, 7-aminoheptanolactam, 8-aminooctanolactam, 9-aminononanolactam, 10-aminodecanolactam, 11-aminoundecanolactam and 12-aminododecanolactam.

3. The process according to claim 1 or 2, wherein component (B2) is selected from the group consisting of tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine and dodecamethylenediamine.

4. The process according to any of claims 1 to 3, wherein the tube obtained in step ii) has a thickness in the range from 10 µm to 1 mm.

5. The process according to any of claims 1 to 4, wherein the first temperature (T1) in step iii) is in the range from 5 to 50°C.

6. The process according to any of claims 1 to 5, wherein the at least one copolyamide has a glass transition temperature (TG(C)) and a melting temperature (TM(C)), and the second temperature (T2) in step iv) is above the glass transition temperature (TG(C)) and below the melting temperature (TM(C)) of the at least one copolyamide.

7. The process according to any of claims 1 to 6, wherein the heated first tubular film comprising the at least one copolyamide is guided through a second roll system during the blowing-in of air in step v) to extend the length of the heated first tubular film.

8. The process according to any of claims 1 to 6, wherein the polymer film (P) has a thickness in the range from 0.1 µm to < 1 mm.

9. The process according to any of claims 1 to 8, wherein the following steps are conducted after step v): vi) guiding the polymer film (P) obtained in step v) through at least one third roll, vii) heating the polymer film (P) obtained in step v) to a fourth temperature (T4) above the glass transition temperature (TG(C)) of the at least one copolyamide to obtain a heated polymer film (P), viii) guiding the heated polymer film (P) obtained in step vii) through at least one fourth roll to obtain the polymer film (P), where the heated polymer film (P), between step vii) and step viii), during step viii) and / or after step viii), is cooled to a fifth temperature (T5) below the glass transition temperature (TG(C)) of the at least one copolyamide.

10. A polymer film (P) obtainable by a process according to any of claims 1 to 9.