Process for the continuous preparation of copolyamides from lactams, diamines and dimer acids

Abstract

A process for the continuous production of a copolyamide by copolymerization of at least one lactam (A) and monomers (M), said process comprising the steps of a) mixing at least one lactam (A) with monomers (M) at a temperature of from 60 to 150°C, and b) passing the mixture obtained in step a) from the top downwards through a vertical polymerization tube at a temperature at which the polyamide is formed to obtain a copolyamide, wherein the monomers (M) comprise at least one C32-C40-dicarboxylic acid (B1) and at least one C4-C12-diamine (B2) and optionally at least one C4-C20-dicarboxylic acid (B3).

Description

[0001] A method for the continuous preparation of copolyamides from a salt of caprolactam and diamine dissolved in water and a dicarboxylic acid is known from WO 2010 / 066769 A2 (BASF SE), wherein an aqueous solution of the caprolactam and diamine salt of the dicarboxylic acid (which has been pretreated in a mixing unit and a spiral evaporator) is fed from above into a VK tube. The two carboxyl groups of the dicarboxylic acid used are linked by an alkylene group or a 1,3- or 1,4-phenylene group having 4 to 12 carbon atoms. The dimer acid is not disclosed.

[0002] US 5,013,518 A discloses a copolyamide comprising C32-C40 dimer fatty acids, a diamine, and caprolactam, wherein the amount is 85.0 to 99.5 parts by weight of caprolactam units and 0.5 to up to 15 parts by weight of equimolar amounts of C32-C40 dimer fatty acids and diamine. A continuous process is not disclosed in detail.

[0003] WO 2018 / 050487 A1 (BASF SE) discloses a copolyamide obtained by polymerizing a lactam, a C32-C40 dimer acid, and a C4-C12 diamine. The polymerization is carried out in a stirred reactor. A VK tubular reactor and continuous process steps are not disclosed.

[0004] The object of the present invention is to provide a continuous method for preparing an optically improved transparent copolyamide from a lactam (A) (especially caprolactam) and a monomer (M), wherein the monomer (M) comprises at least one C32-C40 dimer acid (B1) and at least one C4-C12 diamine (B2) and optionally at least one C4-C20 diacid (B3).

[0005] This objective is achieved by a method for the continuous preparation of copolyamides by copolymerizing at least one lactam (A) and a monomer (M), the method comprising the following steps:

[0006] a) Mixing at least one lactam (A) with a monomer (M) at a temperature of 60 to 150°C, and

[0007] b) Pass the mixture obtained in step a) through a vertical polymerization tube from top to bottom at the temperature at which the polyamide is formed to obtain a copolyamide.

[0008] The monomer (M) comprises at least one C32-C40 dimer acid (B1), at least one C4-C12 diamine (B2), and optionally at least one C4-C20 diacid (B3).

[0009] The objective is also achieved by a method for the continuous preparation of copolyamides by copolymerizing at least one lactam (A) and a monomer (M), the method comprising the following steps:

[0010] a) Mixing at least one lactam (A) with a monomer (M) at a temperature of 60 to 150°C, and

[0011] b) Pass the mixture obtained in step a) through a vertical polymerization tube from top to bottom at the temperature at which the polyamide is formed to obtain a copolyamide.

[0012] The monomer (M) comprises at least one C32-C40 dimer acid (B1), at least one C4-C12 diamine (B2), and optionally at least one C4-C20 diacid (B3).

[0013] And the mixing in step a) comprises premixing at least one lactam (A) with component (B1) to obtain a premix, and then

[0014] Component (B2) and optionally (B3) are added to the premix.

[0015] The objective is also achieved by the copolyamides available by the method and their use in the preparation of films, fibers and molding articles, in each case as defined and described in the patent claims and herein.

[0016] The comonomer units of the copolyamides obtained by the method of the present invention exhibit an improved distribution in the polymer chain, and the copolymers are preferably random copolymers.

[0017] Furthermore, the method of the present invention has the advantage of providing copolyamides that can be further processed to obtain molding articles, films, or fibers, wherein the molding articles, films, or fibers, especially the molding articles or films, have unexpectedly high optical purity and a low number of defects (also referred to in this art as "fisheyes"). Defects or fisheyes are fractures that occur under mechanical stress and are negatively perceived by consumers in transparent applications. The copolyamides prepared by the method of the present invention can be processed, for example, to obtain transparent molding articles or films up to 2 mm thick, which is very unexpected for semi-crystalline materials and also has advantages, especially in terms of the coloring and color depth of the molding articles or films.

[0018] According to the present invention, the copolyamide is prepared by polymerizing at least one lactam (A) (preferably in an amount of 15 to 84 wt%) and a monomer (M) (preferably in an amount of 16 to 85 wt%), wherein the monomer (M) comprises at least one C32-C40 dimer acid (B1) and at least one C4-C12 diamine (B2) and optionally at least one C4-C20 diacid (B3), wherein the sum of the weight percentages of components (A) and (M) is 100 wt%.

[0019] According to another embodiment of the invention, the copolyamide is preferably prepared by polymerizing at least one lactam (A) (preferably in an amount of 18 to 83 wt%) and a monomer (M) (preferably in an amount of 17 to 82 wt%), wherein the monomer (M) comprises at least one C32-C40 dimer acid (B1) and at least one C4-C12 diamine (B2) and optionally at least one C4-C20 diacid (B3), wherein the sum of the weight percentages of components (A) and (M) is 100 wt%.

[0020] In the context of this invention, "at least one lactam (A)" means either exactly one lactam (A) or a mixture of two or more lactams (A). Preferably, it is exactly one lactam.

[0021] According to the invention, a copolyamide is preferably prepared by polymerizing 40 to 83 wt% of a lactam (A) and 17 to 60 wt% of a monomer (M), and particularly preferably by polymerizing 60 to 80 wt% of a lactam (A) and 20 to 40 wt% of a monomer (M), wherein the monomer (M) comprises at least one C32-C40 dimer acid (B1) and at least one C4-C12 diamine (B2) and optionally at least one C4-C20 diacid (B3), wherein the weight percentages of components (A) and (M) are based on the sum of the weight percentages of components (A) and (M) in each case, and wherein the sum of the weight percentages of components (A) and (M) is 100 wt%.

[0022] It is evident that the weight percentages of lactam (A) and monomer (M) are based on the weight percentages of lactam (A) and monomer (M) prior to polymerization (i.e., before lactam (A) and monomer (M) have reacted with each other). During polymerization, the weight ratios of lactam (A) and monomer (M) may change.

[0023] According to the present invention, the copolyamide prepared by the method of the present invention preferably does not contain polyether groups.

[0024] Preferably, the monomer (M) does not contain polyoxyalkylene groups.

[0025] According to the present invention, it is also preferred that components (B1), (B2) and (B3) do not contain polyoxyalkylene groups.

[0026] In particular, each of the preferred components (B1), (B2) and (B3) does not contain at least one polyoxyalkylene group.

[0027] Lactam (A)

[0028] Component (A) is at least one lactam.

[0029] Lactams are known to those skilled in the art. In the context of this invention, “lactam” should be understood to mean a cyclic amide having 2 to 12, preferably 4 to 12, and particularly preferably 5 to 8 carbon atoms in the ring.

[0030] Suitable lactams are selected from, for example, 3-aminopropionic lactam (propionic-3-lactam; β-lactam; β-propionic lactam), 4-aminobutyrolactam (butionic-4-lactam; γ-lactam; γ-butyrolactam), 5-aminopentanolactam (2-piperidinone; δ-lactam; δ-pentanolactam), 6-aminocaprolactam (hexo-6-lactam; ε-lactam; ε-caprolactam), and 7-aminoheptanolactam (heptionic-7-lactam; δ-lactam; δ-heptanolactam). Amides), 8-aminooctanolactam (oct-8-lactam; ε-lactam; ε-octanolactam), 9-aminononanolactam (non-9-lactam; ζ-lactam; ζ-nonanolactam), 10-aminodecanolactam (dec-10-lactam; ω-decanolactam), 11-aminoundecanolactam (undecane-11-lactam; ω-undecanolactam), and 12-aminododecanolactam (dodecane-12-lactam; ω-dodecanolactam).

[0031] The lactam may be unsubstituted or at least monosubstituted. If at least monosubstituted lactam is used, its nitrogen atom and / or cyclic carbon atom may carry one, two or more substituents independently selected from the following: C1- to C10-alkyl, C5- to C6-cycloalkyl and C5- to C10-aryl.

[0032] Suitable C1- to C10-alkyl substituents are, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl. Suitable C5- to C6-cycloalkyl substituents are, for example, cyclohexyl. Preferred C5- to C6-aryl substituents are phenyl and anthracene.

[0033] Unsubstituted lactams are preferred, especially γ-lactam (γ-butyrolactam), δ-lactam (δ-valeractam), and ε-lactam (ε-caprolactam). δ-lactam (δ-valeractam) and ε-lactam (ε-caprolactam) are particularly preferred, and 6-aminocaprolactam (hexyl-6-lactam; ε-lactam; ε-caprolactam) is especially preferred.

[0034] According to the present invention, the lactam (A) contains 0 to 10% by weight of water, preferably 0.5 to 5% by weight of water, more preferably 1 to 3% by weight of water, and most preferably 1.5 to 2% by weight of water, based on the total weight of the lactam (A).

[0035] Monomer (M)

[0036] The monomer (M) comprises at least one C32-C40 dimer acid (B1), at least one C4-C12 diamine (B2), and optionally at least one C4-C20 diacid (B3).

[0037] The monomer (M) comprises, 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 molar percentages of components (B1) and (B2), preferably based on the total molar amount of monomer (M).

[0038] The monomer (M) preferably comprises 47 to 53 mol% of component (B1) and 47 to 53 mol% of component (B2), in each case based on the sum of the molar percentages of components (B1) and (B2), preferably based on the total molar amount of monomer (M).

[0039] The monomer (M) particularly preferably comprises 49 to 51 mol% of component (B1) and 49 to 51 mol% of component (B2), in each case based on the sum of the molar percentages of components (B1) and (B2), preferably based on the total molar amount of monomer (M).

[0040] The sum of the molar percentages of components (B1) and (B2) present in monomer (M) is typically 100 mol%.

[0041] The monomer (M) may also additionally contain component (B3), namely at least one C4-C20 diacid.

[0042] When the monomer (M) further comprises component (B3), it is preferred that the monomer (M) comprises 25 to 54.9 mol% of component (B1), 45 to 55 mol% of component (B2) and 0.1 to 25 mol% of component (B3), in each case based on the total molar amount of monomer (M).

[0043] Particularly preferred is that the monomer (M) comprises 13 to 52.9 mol% of component (B1), 47 to 53 mol% of component (B2), and 0.1 to 13 mol% of component (B3) in each case based on the total molar amount of monomer (M).

[0044] The monomer (M) preferably contains 7 to 50.9 mol% of component (B1), 49 to 51 mol% of component (B2), and 0.1 to 7 mol% of component (B3) in each case based on the total molar amount of monomer (M).

[0045] When monomer (M) additionally contains component (B3), the total molar percentage of components (B1), (B2) and (B3) is typically 100 mol%.

[0046] The monomer (M) may be almost anhydrous or may contain water. The monomer (M) may contain 0 to 10%, preferably 0.1 to 5% by weight, of water, based on the sum of the components of the monomer (M).

[0047] Components (B1) and (B2) and optionally (B3) of component (B) can react with each other to obtain an amide. This reaction is known to those skilled in the art. Therefore, the monomer (M) may comprise components (B1) and (B2) and optionally (B3) in fully reacted, partially reacted, or unreacted forms. Preferably, the monomer (M) comprises components (B1) and (B2) and optionally (B3) in unreacted forms.

[0048] Therefore, in the context of this invention, "unreacted form" means that component (B1) exists as at least one C32-C40 dimer acid, component (B2) exists as at least one C4-C12 diamine, and component (B3) (if present) exists as at least one C4-C20 diacid.

[0049] If components (B1) and (B2) and optionally present (B3) react at least partially with each other, then components (B1) and (B2) and optionally present (B3) are at least partially present in the form of amides.

[0050] Component (B1)

[0051] According to the present invention, component (B1) is at least one C32-C40 dimer acid or preferably a mixture of C32-C40 dimer acids as defined herein.

[0052] In the context of this invention, "at least one C32-C40 dimer acid" means either exactly one C32-C40 dimer acid or a mixture of two or more C32-C40 dimer acids.

[0053] In the context of this invention, "C32-C40 dimer acid mixture" means a mixture that can be obtained by dimerizing unsaturated fatty acids and optionally hydrogenating the resulting mixture, wherein the unsaturated fatty acids are selected from unsaturated C16 fatty acids, unsaturated C18 fatty acids and unsaturated C20 fatty acids, with unsaturated C18 fatty acids being particularly preferred.

[0054] Dimer acids are also known as dimer fatty acids. C32-C40 dimer acids are known to those skilled in the art and are typically prepared by dimerizing unsaturated fatty acids. This dimerization can be catalyzed, for example, by alumina.

[0055] Based on current knowledge, the bonding of dimer acids primarily occurs via the Diels-Alder mechanism. Depending on the number and position of double bonds in the fatty acids used to prepare the dimer acid, the resulting mixture is predominantly a dimer product containing alicyclic, linear, branched, and C6-aromatic hydrocarbon groups between carboxyl groups. Depending on the mechanism and / or any subsequent hydrogenation, the aliphatic groups can be saturated or unsaturated, and the proportion of aromatic groups can also vary.

[0056] The group connecting the carboxyl group of the dimer fatty acid preferably does not contain unsaturated bonds or aromatic hydrocarbon groups.

[0057] Suitable unsaturated fatty acids for preparing at least one C32-C40 dimer acid are known to those skilled in the art and are, for example, unsaturated C16 fatty acids, unsaturated C18 fatty acids, and unsaturated C20 fatty acids.

[0058] Suitable unsaturated C16 fatty acids include, for example, palmitoleic acid ((9Z)-hexadec-9-enoic acid).

[0059] Suitable unsaturated C18 fatty acids are selected from, for example, apiric acid ((6Z)-octadec-6-enoic acid), oleic acid ((9Z)-octadec-9-enoic acid), transoleic acid ((9E)-octadec-9-enoic acid), isoleic acid ((11E)-octadec-11-enoic acid), linoleic acid ((9Z,12Z)-octadec-9,12-dienoic acid), α-linolenic acid ((9Z,12Z,15Z)-octadec-9,12,15-trienoic acid), and γ-linolenic acid ((6Z)-octadec-6-enoic acid). (9Z,12Z)-octadecano-6,9,12-trienoic acid, octadecano-trienoic acid ((8E,10E,12Z)-octadecano-8,10,12-trienoic acid), punicic acid ((9Z,11E,13Z)-octadecano-9,11,13-trienoic acid), α-tungstic acid ((9Z,11E,13E)-octadecano-9,11,13-trienoic acid) and β-tungstic acid ((9E,11E,13E)-octadecano-9,11,13-trienoic acid). The unsaturated C18 fatty acids are particularly preferred from the following: phellic acid ((6Z)-octadec-6-enoic acid), oleic acid ((9Z)-octadec-9-enoic acid), transoleic acid ((9E)-octadec-9-enoic acid), isoleic acid ((11E)-octadec-11-enoic acid), and linoleic acid ((9Z,12Z)-octadec-9,12-dienoic acid).

[0060] Suitable unsaturated C20 fatty acids are selected from serotonic acid ((9Z)-eicosenoic acid), eicosenoic acid ((11Z)-eicosenoic acid), arachidonic acid ((5Z,8Z,11Z,14Z)-eicosenoic acid-5,8,11,14-tetraenoic acid) and eicosopentaenoic acid ((5Z,8Z,11Z,14Z,17Z)-eicosenoic acid-5,8,11,14,17-pentaenoic acid).

[0061] C36 dimer acids are prepared, for example, from unsaturated C18 fatty acids. Particularly preferred are C36 dimer acids prepared from C18 fatty acids selected from: phellic acid ((6Z)-octadec-6-enoic acid), oleic acid ((9Z)-octadec-9-enoic acid), transoleic acid ((9E)-octadec-9-enoic acid), isoleic acid ((11E)-octadec-11-enoic acid), and linoleic acid ((9Z,12Z)-octadec-9,12-dienoic acid).

[0062] Component (B1) prepared from unsaturated fatty acids can additionally form trimeric acids; alternatively, unreacted residual unsaturated fatty acids can be retained.

[0063] The formation of trimeric acids is known to those skilled in the art.

[0064] According to the invention, component (B1) preferably contains up to 0.5% by weight of unreacted unsaturated fatty acids and up to 0.5% by weight of trimeric acid, particularly preferably up to 0.2% by weight of unreacted unsaturated fatty acids and up to 0.2% by weight of trimeric acid, in each case based on the total weight of component (B1).

[0065] The proportions of monomer, dimer, and trimer molecules and other byproducts in dimer acids can be determined, for example, by gas chromatography (GC). The dimer acid is converted to the corresponding methyl ester by the boron trifluoride method (see DIN EN ISO 5509) prior to GC analysis, followed by GC analysis.

[0066] The dimer acid or C32-C40 dimer acid mixture to be used is available in the form of commercially available products. Examples include Radicacid 0970, Radicacid 0971, Radicacid 0972, Radicacid 0975, Radicacid 0976 and Radicacid 0977 from Oleon, Pripol 1006, Pripol 1009, Pripol 1012 and Pripol 1013 from Croda, and Unidyme 10 and Unidyme TI from Arizona Chemical.

[0067] The acid value of component (B1) is, for example, 190 to 200 mg KOH / g.

[0068] According to the present invention, the preferred component (B1) contains 0.1 to 5% by weight of water.

[0069] According to the present invention, component (B1) is more preferably substantially free of water. In the context of the present invention, "free of water" means less than 1% by weight, preferably less than 0.5% by weight, and especially preferably less than 0.2% by weight of water, based on the total weight of component (B1).

[0070] Component (B2)

[0071] According to the present invention, component (B2) is at least one C4-C12 diamine.

[0072] In the context of this invention, "at least one C4-C12 diamine" means either exactly one C4-C12 diamine or a mixture of two or more C4-C12 diamines.

[0073] In the context of this invention, "C4-C12 diamine" should be understood to mean an aliphatic and / or aromatic compound having four to twelve carbon atoms and two amino groups (-NH2 groups). The aliphatic and / or aromatic compound may be unsubstituted or additionally at least monosubstituted. If the aliphatic and / or aromatic compound is additionally at least monosubstituted, it may have 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. They are known to those skilled in the art. At least one C4-C12 diamine is preferably unsubstituted.

[0074] The preferred component (B2) is selected from 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-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane (decamethylenediamine), 1,11-diaminoundecane (undecamethylenediamine), and 1,12-diaminododecane (dodecylmethylenediamine).

[0075] Particularly preferred component (B2) is selected from 1,4-diaminobutane (tetramethylenediamine), 1,5-diaminopentane (pentamethylenediamine), 1,6-diaminohexane (hexamethylenediamine), 1,10-diaminodecane (decamethylenediamine) and 1,12-diaminododecane (dodecylethylenediamine), with component (B2) being particularly 1,6-diaminohexane (hexamethylenediamine).

[0076] According to the present invention, the preferred component (B2) contains 0.1 to 50% by weight of water, more preferably 5 to 45% by weight of water, and more preferably 5 to 30% by weight of water.

[0077] Component (B3)

[0078] According to the present invention, the component (B3) optionally present in the monomer (M) is at least one C4-C20 diacid.

[0079] In the context of this invention, "at least one C4-C20 diacid" means either exactly one C4-C20 diacid or a mixture of two or more C4-C20 diacids.

[0080] In the context of this invention, "C4-C20 diacid" should be understood to mean an aliphatic and / or aromatic compound having 2 to 18 carbon atoms and two carboxyl groups (-COOH groups). The aliphatic and / or aromatic compound may be unsubstituted or additionally at least monosubstituted. If the aliphatic and / or aromatic compound is additionally at least monosubstituted, it may have 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. At least one C4-C12 diacid is preferably unsubstituted.

[0081] Examples of suitable components (B3) are selected from succinic acid, glutaric acid, adipic acid, pimelic acid, succinic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid and hexadecanoic acid.

[0082] Preferably, component (B3) is selected from glutaric acid, adipic acid, sebacic acid and dodecanoic acid.

[0083] Preferably, component (B3) contains 0.1 to 40% by weight of water, more preferably 5 to 30% by weight of water.

[0084] According to the present invention, a copolyamide is prepared by polymerizing a lactam (A) and a monomer (M). The polymerization of the lactam (A) and the monomer (M) is known in principle to those skilled in the art. Typically, the polymerization of the lactam (A) and the monomer (M) is a condensation reaction. During the condensation reaction, the lactam (A) reacts with components (B1) and (B2) present in the monomer (M) and (if present) component (B3) (which may optionally be present in component (M)). This results in the formation of amide bonds between the components. Typically, the lactam (A) is at least partially open-chain in form during polymerization, i.e., in the form of amino acids.

[0085] The polymerization of lactam (A) and monomer (M) can be carried out in the presence of a catalyst. Suitable catalysts are all catalysts known to those skilled in the art for catalyzing the polymerization of lactam (A) and monomer (M). Such catalysts are known to those skilled in the art. Preferred catalysts are phosphorus compounds, such as sodium hypophosphite, phosphorous acid, triphenylphosphine, or triphenyl phosphite.

[0086] According to the present invention, in step a), at a temperature of 60 to 150°C, at least one lactam (A) is mixed with a monomer (M) typically by means of a mixing element (e.g., a mixing element in a feed line or a separate mixing tank), wherein the at least one lactam (A) is selected, for example, from 3-aminopropionic lactam, 4-aminobutyrolactam, 5-aminopentanolactam (2-piperidinone; δ-lactam; δ-pentanolactam), 6-aminocaprolactam (hexyl-6-lactam; ε-lactam; ε-caprolactam), 7-aminoheptanolactam (heptyl-7-lactam; δ-lactam; δ-heptanolactam), 8-aminooctanolactam ( Octyl-8-lactam; ε-lactam; ε-octyllactam), 9-aminononanolactam (non-9-lactam; ζ-lactam; ζ-nonanolactam), 10-aminodecanolactam (dec-10-lactam; ω-decanolactam), 11-aminoundecanolactam (undecane-11-lactam; ω-undecanolactam), and 12-aminododecanolactam (dodecane-12-lactam; ω-dodecanolactam), preferably 5-aminopentanolactam (2-piperidinone; δ-lactam; δ-pentanolactam), 6-aminocaprolactam (hexane-6-lactam; ε-lactam; ε-caprolactam), 7-amino Heptanolactam (hept-7-lactam; δ-lactam; δ-heptanolactam), 8-aminooctanolactam (oct-8-lactam; ε-lactam; ε-octanolactam), 9-aminononanolactam (non-9-lactam; ζ-lactam; ζ-nonanolactam), 10-aminodecanolactam (dec-10-lactam; ω-decanolactam), 11-aminoundecanolactam (undecane-11-lactam; ω-undecanolactam), and 12-aminododecanolactam (dodecane-12-lactam; ω-dodecanolactam), with particular preference for 6-aminocaprolactam (hexane-6-lactam; ε-lactam; ε- The monomer (M) preferably comprises an unhydrogenated or hydrogenated mixture of C32-C40 dimer acids (B1) and one or more diamines (B2), wherein the diamine (B2) is selected, for example, from 1,4-diaminobutane (butane-1,4-diamine; tetramethylenediamine; putrescine), 1,5-diaminopentane (pentamethylenediamine; pentane-1,5-diamine; cadaverine), 1,6-diaminohexane (hexamethylenediamine);The monomers (M) preferably comprise an unhydrogenated or hydrogenated mixture of C32-C40 dimer acids (B1) and a diamine (B2) of 1,6-diaminohexane (hexamethylenediamine or hexane-1,6-diamine).

[0087] In a preferred embodiment, in step a), at least one lactam (A) is first added and a monomer (M) is added separately. This embodiment explicitly includes all lactams (A) and monomers (M) and their components (B1), (B2) and (B3) that are identified herein as preferred, particularly preferred, especially or exemplary.

[0088] When monomer (M) is added alone, the mixing in step a) preferably includes the following steps: premixing at least one lactam (A) with component (B1) to obtain a premix, and then adding component (B2) and optionally (B3) to the premix.

[0089] According to the method of the present invention, at least one lactam (A) is mixed with a monomer (M) at a temperature of 60 to 150°C, preferably 80 to 120°C, more preferably 90 to 100°C.

[0090] Preferably, at least one lactam (A) is premixed with component (B1) at a temperature of 60 to 150°C, preferably 80 to 120°C, to obtain a premix, and then component (B2) and optionally (B3) are added to the premix.

[0091] It is particularly preferred that the lactam (A) and component (B1) be preheated separately to the temperature for premixing before premixing.

[0092] The premixed solution is preferably a transparent solution.

[0093] Preferably, in step a), after adding component (B2) and optionally (B3) to the premix, the resulting mixture is heated to 190 to 210°C, more preferably to 195 to 201°C, and most preferably to 200 to 205°C.

[0094] In step a), the following combination of lactam (A) and monomer (M) comprising components (B1) and (B2) is preferred:

[0095] 6-Aminocaprolactam (A) + C32-C40 dimer acid mixture (B1), 1,6-diaminohexane (B2) or 6-aminocaprolactam (A) + hydrogenated C32-C40 dimer acid mixture (B1) and 1,6-diaminohexane (B2).

[0096] In this document, components (B1), (B2), and optionally (B3) are preferably used in such amounts that the molar number of amino groups from (B2) is substantially equal to the sum of the molar numbers of carboxyl groups from (B1) and optionally (B3).

[0097] This embodiment explicitly includes all lactams (A) and monomers (M) and their components (B1), (B2) and (B3) that are identified herein as preferred, particularly preferred, special or exemplary.

[0098] In another particularly preferred embodiment, in step a), at least one lactam (A) is first added and monomer (M) is added separately, wherein the lactam (A) comprises 0 to 10% by weight of water based on the lactam (A), the monomer (M) comprises 0 to 10% by weight of water based on the sum of monomers (M), and wherein the molar number of amino groups from (B2) is substantially equal to the molar number of carboxyl groups from (B1) and optionally (B3). This embodiment explicitly includes all lactams (A) and monomers (M) and their components (B1), (B2) and (B3) that are identified herein as preferred, particularly preferred, especially, or exemplary.

[0099] In one embodiment of the method of the present invention (in the form of a spiral tube), the mixture obtained in step a) can be introduced into the spiral tube evaporator in step (aa) at an increased pressure of 3 to 9 bar, preferably 4 to 8 bar, more preferably 6 to 7 bar, through a pressure regulating valve. Preferably, water is simultaneously evaporated through the spiral tube evaporator to form both a vapor phase and a liquid phase.

[0100] A pre-reactor (e.g., a stirred tank) may be connected upstream of a spiral reactor, or a pre-reactor may replace a spiral reactor. Such a pre-reactor is typically operated at 200 to 300°C, preferably 250 to 290°C, and the cleavage of lactam (A) causes its prepolymerization and allows polymerization in the spiral or VK tube to proceed at an accelerated rate.

[0101] In step a) of the method of the present invention, and optionally also in or at the top of the VK tube, an additive known to those skilled in the art can be used to improve the reaction conditions, such as an antifoaming agent, like polydimethylsiloxane (PDMS). Water vapor and / or an inert gas can also be optionally introduced into the mixture upstream of the spiral tube. The inert gas is, for example, nitrogen, carbon dioxide, or argon, or a mixture of these gases.

[0102] The spiral tube evaporator is preferably a jacketed tube in which the heating medium is transported and used for temperature control within a heating jacket. According to the invention, the industrial jacketed tubes preferably used typically have a length of 20 to 100 m, particularly preferably 40 to 80 m, and an inner diameter preferably 10 to 150 mm, particularly 15 to 60 mm. The spiral tube evaporator evaporates the water in the mixture obtained in step a). A core flow of gas (water vapor) is typically present in the discharge zone of the spiral tube evaporator, while the wall film exists as the liquid phase. If desired, an inert gas, such as water vapor, nitrogen, carbon dioxide, or argon, or a mixture of gases containing them, such as 16 bar of water vapor, can be metered at the inlet or “top” of the spiral tube to generate or enhance the core flow. This may be necessary, for example, if the water content in the mixture obtained in step a) is insufficient, for example, if the total concentration of organic components is above 98%. The added gas then serves as a carrier gas. At the end of the spiral tube evaporator, phase separation typically exists between the vapor and liquid phases. For example, based on the cross-sectional area of ​​the helical tube, the core flow of gas can account for 15% to 35%, particularly about 25% of the area, while the wall film (i.e., the liquid phase) can account for 65% to 85% of the cross-sectional area, particularly about 75%. In this form of the method according to the invention, the helical tube evaporator can be used as a valve because high pressure, for example 5 to 20 bar, dominates at the evaporator inlet, while near atmospheric pressure dominates at the reactor outlet. Therefore, the pressure decreases continuously along the length of the helical tube. The helical tube evaporator can be constructed as described in WO 2008 / 049786.

[0103] During the passage of the reaction mixture through a spiral evaporator, a temperature of 140 to 300°C, preferably 170 to 220°C, and particularly preferably 190 to 210°C is typically established. Simultaneously, the pressure is reduced to approximately atmospheric pressure (1 bar), and the gas phase is separated to obtain the liquid phase. Therefore, the depressurization of the mixture obtained in step a) to approximately atmospheric pressure is carried out via a spiral evaporator. The gas phase mainly consists of water vapor, which separates from the organic components upon exiting the spiral evaporator. The vapor phase can be removed, for example, by passing it through a column.

[0104] The expression "approximate atmospheric pressure" usually describes atmospheric pressure (1 bar) with a deviation of -0.5 to +1 bar, especially ±0.5 bar.

[0105] For the advantageous operating mode of the spiral tube, the residence time of the mixture obtained in step a) is preferably 40 to 120 seconds. If a longer residence time of 3 to 10 minutes is used, the spiral tube evaporator is advantageously equipped with internal components such as random packing, Raschig rings or Pall rings, especially wire mesh rings, to achieve a high surface area.

[0106] Preferably, no chemical reaction, such as polymerization, occurs in the spiral tube evaporator; instead, only the separation of the vapor / gas and liquid phases takes place. Water is preferably removed from the mixture obtained in step a) in the form of steam.

[0107] Subsequently, in step (ab), the two-phase mixture exiting the spiral tube and consisting of a vapor phase and a liquid phase is separated, wherein the liquid phase consists of or contains components (B1) and (B2) as well as lactam (A). Ideally, the two-phase mixture of vapor and liquid phases is introduced into the vapor space at the top of the tubular polymerization zone of the vertical polymerization tube (VK tube), where the separation of the vapor and liquid phases takes place.

[0108] Also advantageously, in step (ab), the obtained vapor phase is separated in the column into water vapor, components (B1) and (B2) and optionally (B3) and lactam (A), and all organic components are recycled to polymerization, i.e., step b). The separation of the vapor phase is advantageously carried out in a column with distillation. Suitable columns are, for example, columns with random packing, columns with structured packing, bubble cap columns, valve plate columns, or sieve plate columns with 5-15 theoretical plates. The column is advantageously operated under the same conditions as for separating the vapor and liquid phases, for example, at an absolute pressure of 0.5 to 2.5 bar or at the pressure in the polymerization zone. Advantageously, 0.1 to 0.5 L of water per kg of vapor is introduced to the top of the column to improve the separation effect. A liquid phase containing components (B1) and (B2) and lactam (A), or composed of components (B1) and (B2) and lactam (A), is obtained as the column effluent. Water vapor is obtained at the top of the column.

[0109] If the separation is performed at the top of the VK tube according to the preferred operating mode, the liquid phase containing diamine, dicarboxylic acid, and lactam or composed thereof is returned to the top of the VK tube.

[0110] The organic phase (which comprises components (B1) and (B2) and optionally (B3) and lactam (A) or composed thereof) from the spiral tube and the return from the separation column are preferably mixed by stirring at the top of the vertical polymerization tube (VK tube).

[0111] The mixture obtained in step a) (optionally in a pre-reactor), or, if steps (aa) and (ab) are performed, the liquid phase from step (aa) and the organic component from step (ab) are passed from top to bottom through a vertical polymerization tube at the temperature at which the polyamide is formed, and a copolyamide is obtained. This method is carried out continuously as described below.

[0112] Vertical tubular reactors (also referred to herein as “polymerization tubes”) for the continuous preparation of polyamides are known and are also referred to herein and in the art as “VK tubes”, and the methods for the continuous preparation of polyamides or copolyamides using them are also referred to herein and in the art as “VK methods” (V = vereinfacht [simplified], K = kontinuierlich [continuous]). For example, VK tubes and VK methods are described in Kunststoff-Handbuch [Plastics Handbook], Volume VI (Polyamide [Polyamides]), Carl Hanser Verlag München, 1966, Chapter 2.11.6.6, pp. 190-194, or in Kunststoff-Handbuch 3 / 4, Technische Thermoplaste (Polyamide) [Industrial Thermoplastics (Polyamides)], Carl Hanser Verlag München, 1998, pp. 65-70. All publicly available content of these citations is included here in this article by way of citation.

[0113] In principle, the VK method operates by introducing a mixture of monomers or oligomers, typically liquid, to be polymerized to obtain polyamide or copolyamide into the upper part of a vertical, belt, or fully heated tube, typically 4 to 50 m long and usually made of V4A steel, so that the mixture flows vertically through the tube (which may include built-in internal devices), and the resulting polymer or copolymer is removed at the lower end. Specifically, the same amount of the mixture to be polymerized (typically a liquid mixture of monomers or oligomers) is introduced into the upper part of the VK tube for polymerization.

[0114] The VK method also includes, in principle, the arrangement of multiple VK tubes, as described in Kunststoff-Handbuch, Volume VI (Polyamide), Carl Hanser Verlag München, 1966, Chapter 2.11.6.6, page 192.

[0115] According to the method of the invention, for example, the mixture to be polymerized into a copolyamide obtained in step a) is introduced into the upper part of a vertical, belt, or fully heatable tube, typically 4 to 50 m long and typically made of V4A steel, so that the mixture flows vertically through the tube (which may include built-in internal devices), and the resulting copolymer is removed at the lower end, specifically, in the same amount as the mixture to be polymerized obtained in step a), the mixture to be polymerized is introduced into the upper part of a VK tube for polymerization, which is referred to as a continuous method.

[0116] One form of the method according to the invention comprises an arrangement of multiple VK tubes, as described in Kunststoff-Handbuch, Volume VI (Polyamide), Carl Hanser Verlag München, 1966, Chapter 2.11.6.6, page 192.

[0117] A very suitable embodiment of the method of the present invention is as follows: A temperature preferably between 250 and 285°C, especially 265 to 280°C, is maintained at the upper third of the VK tube. During the passage through the VK tube, the temperature of the melt is controlled so that a melt at a preferably 240 to 260°C is obtained at the lower end.

[0118] The preferred residence time in the VK tube is 8 to 30 hours.

[0119] Preferably, the copolyamide obtained according to the method of the present invention has a relative viscosity of 2.0 to 3.0 (determined according to the definition in the examples) and a water extractable fraction content of 3.5 to 12% by weight, especially 5 to 11% by weight.

[0120] The copolyamide melt obtained in this manner is typically cast into strands, cured and granulated, or directly granulated in flowing water by underwater granulation. Suitable methods are known to those skilled in the art.

[0121] The resulting granules can then be continuously extracted with countercurrent water at a preferred temperature of 80°C to 120°C. The resulting aqueous extract is then advantageously evaporated after the addition of 0.5 to 2 times the amount of fresh caprolactam (based on the amount of caprolactam in the extract). Suitable methods are described, for example, in DE-A 25 01 348.

[0122] Typically, the extracted copolyamide is then dried. Advantageously, temperature control is performed here, accompanied by the use of an inert gas such as nitrogen or superheated steam as a countercurrent heat carrier, until the desired viscosity is reached, for example at a temperature of 100 to 185°C.

[0123] According to the present invention, the polymerization of components (A) and (B) forms a copolyamide, thereby obtaining structural units derived from component (A) and structural units derived from component (B). The structural units derived from component (B) comprise structural units derived from components (B1) and (B2) and optionally component (B3).

[0124] The polymerization of component (A) and monomer (M) forms a copolyamide as a copolymer. The copolymer can be a random copolymer, but it can also be a block copolymer.

[0125] In block copolymers, blocks forming units derived from monomer (M) and blocks forming units derived from component (A) appear in an alternating sequence. In random copolymers, structural units derived from component (A) alternate with structural units derived from monomer (M). This alternation occurs randomly; for example, two structural units derived from monomer (M) may be followed by one structural unit derived from component (A), then another structural unit derived from monomer (M), followed by a structural unit containing three structural units derived from component (A).

[0126] Preferably, at least one copolyamide obtained by the method of the present invention is a random copolymer.

[0127] At least one copolyamide obtained by the method of the present invention typically has a glass transition temperature (T). G(C) The glass transition temperature (T) G(C) The temperature is, for example, 20 to 50°C, preferably 23 to 47°C and especially preferably 25 to 45°C, as determined according to ISO 11357-2:2014.

[0128] In the context of this invention, according to ISO 11357-2:2014, the glass transition temperature (Tg) of the at least one copolyamide is... G(C) ) refers to the glass transition temperature (T) of the dry copolyamide. G(C) ).

[0129] In the context of this invention, "dry" means that the at least one copolyamide contains less than 1% by weight, preferably less than 0.5% by weight, and particularly preferably less than 0.1% by weight of water, based on the total weight of the at least one copolyamide. More preferably, "dry" means that the at least one copolyamide does not contain any water, and most preferably, the at least one copolyamide does not contain any solvent.

[0130] In addition, the at least one copolyamide typically has a melting temperature (T). M(C) The melting temperature of the at least one copolyamide (T) M(C) The temperature is, for example, 150 to 210°C, preferably 160 to 205°C and especially preferably 160 to 200°C, as determined according to ISO 11357-3:2014.

[0131] The viscosity (VZ) of the at least one copolyamide (C) The concentration is typically 150 to 300 ml / g, determined by a 0.5% by weight solution of the at least one copolyamide in a phenol / o-dichlorobenzene mixture at a weight ratio of 1:1.

[0132] Preferably, the viscosity (VZ) of the at least one copolyamide is... (C)(Measured according to the examples) is 160 to 290 ml / g, and particularly preferably 170 to 280 ml / g, determined as a 0.5% by weight solution of the at least one copolyamide in a phenol / o-dichlorobenzene mixture at a weight ratio of 1:1.

[0133] The copolyamides that can be obtained according to the method of the present invention typically have 15 to 84% by weight, preferably 18 to 83% by weight, more preferably 40 to 83% by weight, and most preferably 60 to 80% by weight of nylon-6 units.

[0134] According to the present invention, the preferred copolyamide does not contain polyether groups.

[0135] The copolyamide of the present invention is used to prepare films, such as films for agricultural applications, films for food packaging applications, or films for industrial applications, such as coated films or VARTM (vacuum-assisted resin transfer molding) films, which have high acid and salt stability and reduced rigidity compared to films obtained using nylon-6, while having a high melting temperature; such films are generally obtained by extrusion.

[0136] The copolyamide of this invention can also be used to prepare molded articles by injection molding, profile extrusion, and blow molding. The prepared molded articles exhibit unexpectedly high transparency for semi-crystalline materials, especially for molded articles with a wall thickness of up to 2 mm, and therefore can also be dyed with excellent color depth.

[0137] The copolyamides available according to the present invention are particularly suitable for the production of films, including multilayer films consisting of or containing copolyamide film layers. Examples of methods for producing such films include casting, blow molding, biaxially oriented polyamide film (BOPA) production, or multilayer blow molding. These methods, and the films made from copolyamides, are known in principle to those skilled in the art and are described, for example, in WO 2018 / 050487 A1 (BASF SE), the disclosure of which is expressly incorporated herein by reference. Typically, when using these methods, a film composed of a copolyamide available according to the present invention is stretched to obtain a stretched copolyamide film composed of a copolyamide available according to the present invention.

[0138] Films made of copolyamides available according to the present invention (including multilayer films consisting of or containing copolyamide film layers) are used, for example, as packaging films, such as food packaging films. For example, the films can also be used in the food industry as tubular bag packaging, side-sealed bag packaging, thermoformed packaging, sealable bags, and / or pillow-shaped packaging.

[0139] The present invention will be described in more detail below with reference to the embodiments. Example:

[0140] The properties of the polymer film were determined as follows.

[0141] According to DIN EN ISO 307:2007, the viscosity of the copolyamide is determined at 25°C in a 1% by weight solution of phenol / o-dichlorobenzene at a weight ratio of 1:1. Unlike DIN EN ISO 307:2007, a different solvent must be selected to make the copolyamide a solution. Also unlike DIN EN ISO 307:2007, a 1% by weight solution is used instead of a 0.5% by weight solution.

[0142] As described on page 15 of DIN EN ISO 307:2007, the relative viscosity is determined by the arithmetic mean of the flow times, and the relative viscosity is (RV) = (t - tc / T0 – T0c). Unlike DIN EN ISO 307:2007, a different solvent must be selected to make the copolyamide a solution. The selected solvent is phenol / o-dichlorobenzene in a 1:1 weight ratio. Furthermore, the polyamide solution used contains 1% by weight of polyamide, instead of the 0.5% by weight solution disclosed in DIN EN ISO 307:2007.

[0143] The melting temperature was determined according to ISO 11357 1:2009 and ISO 11357-3:2011. Two heating cycles were performed, and the melting temperature was determined based on the second heating cycle.

[0144] The density of polyamide was determined using water as a solvent according to the impregnation method described in EN ISO 1183-1A:2012.

[0145] To determine the proportion of nylon-6,36 in the copolyamide, the copolyamide was hydrolyzed in dilute hydrochloric acid (20%). This protonated the unit derived from hexamethylenediamine, where chloride ions from the hydrochloric acid formed counterions. These chloride ions were then exchanged for hydroxide ions using an ion exchanger, releasing hexamethylenediamine. The concentration of hexamethylenediamine was then quantified by titration with 0.1 mol of hydrochloric acid, from which the proportion of nylon-6,36 in the copolyamide could be calculated.

[0146] Copolyamide according to the method of the present invention:

[0147] Example E-1

[0148] At 95°C, 70 kg / h of Pripol 1009 (C36 dimer acid mixture, hydrogenated) from Croda was added to 185 kg / h of caprolactam containing 2% water, which was also heated to 95°C. Subsequently, a 70% aqueous solution of hexamethylenediamine was added to the clear solution at a rate of 20 kg / h. The still clear mixture was heated to 200–205°C and transferred to a spiral evaporator through a pressure regulating valve at 7 bar. The pressure at the inlet of the spiral evaporator was approximately 1–2 bar. The mixture discharged from the spiral evaporator at a temperature of 195–205°C and a slightly increased pressure of 250 mbar was transferred to the top of the VK tube. Simultaneously, an antifoaming agent was injected into the top of the VK tube at a concentration of 30–40 ppm relative to the total input. The temperature at the top of the VK tube was approximately 260°C. The vapor phase was introduced into the column at the top of the VK tube and discharged after condensation. The remaining monomer mixture is passed through a VK tube (which is segmentally heated), with the temperature gradually decreasing from 265-280°C to approximately 250°C at the tube outlet. The VK tube is operated under hydrostatic pressure established by the system itself. At the VK tube outlet, a Nylon-6 / 6.36 melt is obtained and transferred directly via a discharge pump to an underwater granulation system, which includes subsequent extraction and drying steps. Post-condensation is then performed after drying.

[0149] The obtained copolyamide exhibited a viscosity of 218 ml / g and a melting temperature of 199 °C. The proportion of nylon-6,36 in the copolyamide was 30.4% by weight, and the density was 1.052 g / ml based on the total weight of the copolyamide.

[0150] Example E-2

[0151] The method described in Example 1 was modified to use a flux of 160 kg / h caprolactam, 60 kg / h Pripol 1012 (a mixture of C36 dimer acids, unhydrogenated) and 17 kg / h hexamethylenediamine aqueous solution.

[0152] The obtained copolyamide had a viscosity of 217 ml / g and a melting temperature of 198°C. The proportion of nylon-6,36 in the copolyamide was 28.0% by weight, and the density was 1.054 g / ml based on the total weight of the copolyamide.

[0153] Example E-3

[0154] The method described in Example 1 was modified to use 260 kg / h of caprolactam, 50 kg / h of Pripol 1012 (a mixture of C36 dimer acids, unhydrogenated) and 16 kg / h of hexamethylenediamine aqueous solution.

[0155] The obtained copolyamide had a viscosity of 222 ml / g and a melting temperature of 208°C. The proportion of nylon-6,36 in the copolyamide was 16.7% by weight, and the density was 1.084 g / ml based on the total weight of the copolyamide.

[0156] Comparison with copolyamides:

[0157] Comparative Example C-4

[0158] 932 kg of caprolactam, 323.2 kg of Pripol 1009 (a mixture of C36 dimer acids, hydrogenated) from Croda (C36 dimer acid, hydrogenated), 77.84 kg of 85% hexamethylenediamine aqueous solution, and 153 kg of water were mixed in a 1930 L container and covered with nitrogen. The container was heated to an external temperature of 290 °C, and the mixture was stirred at this temperature for 11 hours. Stirring was first carried out under increased pressure for 7 hours, followed by continued stirring under decreased pressure for 4 hours, while distilling off the water formed. The resulting copolyamide was discharged from the container, extruded, and granulated. The resulting copolyamide granules were extracted four times with hot water at 95 °C for 6 hours each time, and then dried at 90–140 °C under a nitrogen stream for 10 hours.

[0159] The obtained copolyamide has a viscosity of 200 ml / g and a melting temperature of 201℃. The proportion of nylon-6,36 in the copolyamide is 29.3% by weight, and the density is 1.057 g / ml based on the total weight of the copolyamide.

[0160] Comparative Example C-5

[0161] 932 kg of caprolactam, 322 kg of Pripol 1012 (a C36 dimer mixture, unhydrogenated) from Croda, 77.84 kg of 85% hexamethylenediamine aqueous solution, 100 g of Polyapp 2557-CTW defoamer from Polystell do Brazil, and 153 kg of water were mixed in a 1930 L container and covered with nitrogen. The container was heated to an external temperature of 290 °C, and the mixture was stirred at this temperature for 11 hours. Stirring was first carried out under increased pressure for 7 hours, followed by continued stirring under decreased pressure for 4 hours, while distilling off the water formed. The resulting copolyamide was discharged from the container, extruded, and granulated. The resulting copolyamide granules were extracted four times with hot water at 95 °C for 6 hours each time, and then dried at 90–140 °C under a nitrogen stream for 10 hours.

[0162] The obtained copolyamide has a viscosity of 184 ml / g and a melting temperature of 199°C. The proportion of nylon-6,36 in the copolyamide is 30.1% by weight, and the density is 1.060 g / ml based on the total weight of the copolyamide.

[0163] Comparative Example C-6

[0164] 1039 kg of caprolactam, 216 kg of Pripol 1009 (a C36 dimer acid mixture, hydrogenated) from Croda, 51.7 kg of 85 wt% hexamethylene diamine solution, 100 g of defoamer Polyapp 2557-CTW from Polystell do Brazil, and 142 kg of water were mixed in a 1930 L container and covered with nitrogen. The external temperature of the container was heated to 290 °C, and the mixture was stirred at this temperature for 11 hours. Stirring was first carried out under increased pressure for 7 hours, followed by continued stirring under decreased pressure for 4 hours, while distilling off the water formed. The resulting copolyamide was discharged from the container, extruded, and granulated. The resulting copolyamide granules were extracted four times with hot water at 95 °C for 6 hours each time, and then dried at 90–140 °C under a nitrogen stream for 10 hours.

[0165] The obtained copolyamide has a viscosity of 240 ml / g and a melting temperature of 206°C. The proportion of nylon-6,36 in the copolyamide is 19.8% by weight, and the density is 1.078 g / ml based on the total weight of the copolyamide.

[0166] The optical quality of films obtained using the copolyamides prepared in Examples E-1 to E-3 and Comparative Examples C-4 to C-6 was determined:

[0167] From The optical quality of the thermoplastic (copolyamide) obtained in the above experiments was determined using a commercially available FQTS SFA-100 system. For this purpose, a polymer film was prepared by casting using a nozzle head width of 100 mm. The system has a screw with a diameter of 25 mm and a length of 625 mm. Different extruder zone temperatures were set at 240–260 °C, and the nozzle temperature was 260 °C. The cooling roller was then cooled to room temperature. Subsequently, a 50 μm thick transparent polymer film was continuously irradiated with a 50 W halogen lamp, and defects in the film were monitored using a 2048-pixel CCD line scan camera from Nikon. The pixel resolution on the cast film was 10 x 10 μm. 2 Two square meters of film were inspected for each material. The optical defects counted on these two square meters, according to their size, are listed in Table 1:

[0168] Table 1:

[0169]

[0170] Compared to the discontinuous methods described in the literature, the copolyamide prepared by the continuous method according to the present invention has significantly improved optical quality and makes it possible to use copolyamide in optically transparent molded products.

Claims

1. A method for continuously preparing a copolyamide by copolymerizing at least one lactam (A) and a monomer (M), the method comprising the following steps: a) Mixing at least one lactam (A) with a monomer (M) at a temperature of 60 to 150°C, and b) Pass the mixture obtained in step a) through a vertical polymerization tube from top to bottom at the temperature at which the polyamide is formed to obtain a copolyamide. The monomer (M) comprises at least one C32-C40 dimer acid (B1), at least one C4-C12 diamine (B2), and optionally at least one C4-C20 diacid (B3). in The mixing in step a) comprises premixing at least one lactam (A) with component (B1) to obtain a premix, and then... Component (B2) and optionally (B3) are added to the premix. The presence of at least one lactam (A) is 60 to 80 wt%, and the presence of monomer (M) is 20 to 40 wt%, wherein the weight percentages of components (A) and (M) are based on the sum of the weight percentages of components (A) and (M) in each case, and wherein the sum of the weight percentages of components (A) and (M) is 100 wt%.

2. The method according to claim 1, wherein the component (B1) is a C32-C40 dimer acid mixture, which can be obtained by dimerizing unsaturated fatty acids selected from unsaturated C16 fatty acids, unsaturated C18 fatty acids and unsaturated C20 fatty acids.

3. The method according to claim 1 or 2, wherein the lactam (A) comprises 0 to 10% by weight of water, based on the lactam (A), and the monomer (M) comprises 0 to 5% by weight of water, based on the sum of the components of the monomer (M).

4. The method according to claim 1 or 2, wherein the number of moles of amino groups from (B2) is equal to the sum of the number of moles of carboxyl groups from (B1) and optionally (B3).

5. The method according to claim 1 or 2, wherein the lactam (A) is selected from 3-aminopropionic lactam, 4-aminobutyrolactam, 5-aminopentanolactam, 6-aminocaprolactam, 7-aminoheptanolactam, 8-aminooctanolactam, 9-aminononanolactam, 10-aminodecanolactam, 11-aminoundecanolactam, and 12-aminododecanolactam.

6. The method according to claim 1 or 2, wherein 6-aminocaprolactam (ε-caprolactam) is used as lactam (A).

7. The method according to claim 1 or 2, wherein component (B2) is selected from 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane.

8. The method according to claim 1 or 2, wherein component (B2) is 1,6-diaminohexane (1,6-hexamethylenediamine).

9. The method according to claim 1 or 2, wherein the monomer (M) does not contain polyoxyalkylene.

10. The method according to claim 1 or 2, wherein prior to step b). (aa) The mixture obtained in step a) is supplied to a heated spiral evaporator, wherein a liquid phase and a vapor phase are formed at a temperature of 140 to 300°C, wherein optionally a feed stream consisting of water vapor and / or inert gas is introduced into the mixture upstream of the spiral tube, and (ab) The vapor phase formed in step (aa) is separated from the liquid phase and separated in a column into water vapor and an organic component containing components (B1), (B2), optionally (B3), and lactam (A). and (ac) The liquid phase from the spiral tube in step (aa) is mixed with the organic components in step (ab).

11. The copolyamide obtained by the method of any one of claims 1 to 10.

12. Use of the copolyamide as defined in claim 11 in the preparation of fibers, films and molding articles.

13. The use according to claim 12, for preparing films in the agricultural field, films in the food packaging field, and films in the industrial application field.

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