Process for recovering aliphatic polyamides

Abstract

The present invention relates to a process for recovering an aliphatic polyamide from polyamide materials, which comprises treating said polyamide material with an organic solvent comprising a saturated monocyclic N-C1-C4-alkyl lactam to obtain a solution of said aliphatic polyamide in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide with respect to the content of aliphatic polyamide in the polyamide material before the treatment. The invention relates in particular to a process for recovering an aliphatic polyamide A having a melting point as determined by differential scanning calorimetry of less than 230°C from a polyamide material containing said polyamide A and at least one further component selected from polyamides B having a melting point of more than 230°C, fibrous reinforcing fillers, pigments and non-fibrous fillers, which comprises treating said polyamide material with an organic solvent comprising a saturated monocyclic N-C1-C4-alkyl lactam, in particular a N-C1-C4-alkyl-2-pyrrolidone, especially N-methyl-2- pyrrolidone, to obtain a solution of said polyamide A in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide A with respect to the content of aliphatic polyamide A in the polyamide material before the treatment.

Description

[0001] BASF SE 241069W001

[0002] 1

[0003] Process for Recovering Aliphatic Polyamides

[0004] The present invention relates to a process for recovering an aliphatic polyamide from polyamide materials, in particular polyamide waste materials, containing aliphatic polyamides. The invention relates in particular to the recovery of an aliphatic polyamide A having a melting point as determined by differential scanning calorimetry of less than 230°C from a polyamide material, in particular a polyamide waste material, containing said polyamide A and at least one further component selected from polyamides B having a melting point of more than 230°C, pigments and fillers.

[0005] Background of Invention

[0006] The use of plastics in packaging materials and also as a construction material has increased dramatically in recent decades, as has the amount of plastic waste produced. The disposal of plastic waste from both industrial production and consumer goods is therefore an increasing environmental impact. The recycling of plastic waste is therefore becoming increasingly important. Recycling helps to ensure that less plastic waste ends up in landfills or in the environment. Moreover, recycling can reduce the need for new raw materials, which reduces the pressure on natural resources and minimizes the environmental impact of plastic production.

[0007] The recycling of plastic is predominantly carried out by mechanical recycling and involves the melting and reforming of the pre-sorted plastic into other items. This can cause polymer degradation at the molecular level and requires that waste be sorted by colour and polymer type before processing, which is often complicated and expensive and may even be impossible in case of black colored plastics. Alternatives are feedstock recycling, also called chemical recycling or thermal recycling, where the polymers are depolymerized by heat or solvolysis to their monomers or smaller building blocks which can then be used as starting materials for fresh polymers.

[0008] Polyamide 6 (PA6, polycaprolactam) and polyamide 6.6 (PA 66, poly-(hexamethylenadipamid)) are semicrystalline thermoplastic polyamides having melting points of about 220°C and 260°C, respectively, with excellent thermal, mechanical and chemical resistance properties. They are used in various application sectors, such as textiles, automotive construction parts, electrical and electronic components, construction, coatings, films etc. Polyamide 6 and polyamide 6.6 are widely used in the engineering sector to produce composite products, i.e. materials in which the aforementioned polymer is used in combination with one or more additional fibrous reinforcing materials, such as glass fibers, carbon fibers, polymeric fibers and the like, which increase the mechanical properties thereof.

[0009] Even though polyamide 6 and polyamide 6.6 have a comparable property profile, they are usually processed separately. In plastic materials, such as plastic waste, however, they are present as mixtures even after pre-

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[0012] sorting. For an efficient recycling of plastic waste containing polyamide, it is therefore necessary to separate polyamide 6 from polyamide 6.6.

[0013] While recycling is slowly starting for some other types of plastic, plastic materials containing aliphatic polyamides, such as polyamide 6 and / or polyamide 6.6, is very difficult to recycle, e. g. because waste streams of polyamide are mixed or contaminated with other materials. Incineration for energy recovery is also out of the question, as large quantities of CO2 emissions are generated and the goal of a closed-cycle economy cannot be achieved in this way. Moreover, toxic compounds such as hydrocyanic acid may be produced.

[0014] Recycling of plastic materials containing aliphatic polyamides, such as polyamide 6 and polyamide 6.6, is currently mainly carried out by thermomechanical means. That is, plastic waste materials of both postindustrial and post-consumer origin are subjected to processes of shredding, grinding, screening, washing, densification, etc. to obtain a material in a size suitable for use in new production cycles as a partial replacement of the virgin polymer.

[0015] WO 2023 / 084441 describes a process for the recycling of polyamide 6, which comprises the treatment of a composite material containing polyamide 6 with a polyol to obtain a solution of the polyamide 6 in the polyol, treating the solution with a coagulating agent to obtain a coagulate of a partially depolymerized polyamide 6 followed by hydrolytic depolymerization of the coagulate to obtain epsilon-caprolactone, which can be used for producing fresh polyamide 6 or caprolactam containing copolyamides. The process described in WO 2023 / 084441 is laborious and time-consuming because of the large number of steps involved and does not yield undecomposed polyamide 6, but caprolactam, which then has to be polycondensed again.

[0016] US 5,994,417 discloses the recovery of nylon, I. e. aliphatic polyamides, such as polyamide 6 and polyamide 6.6, from a commingled polymer material by a solvent based treatment, which comprises subjecting the commingled polymer material with an organic solvent, such as formic acid, phenol or acetic acid, to obtain a solution of nylon in said solvent followed by the precipitation of the nylon by the treatment of the solution with an anti-solvent such supercritical carbon dioxide.

[0017] N. Kartalis et al, J. Appl. Polym. Sci. , 86, 2004, p 1924-1930 describe the recovery of polyamide 6 from a mixture of pellets of polyamide 6 and pellets of polyamide 6.6 by treating the mixture with dimethylsulfoxide at a temperature of 125°C to dissolve polyamide 6. However, a selective dissolution of polyamide 6 could not be achieved under the conditions reported by N. Kartalis et al.

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[0020] Summary of Invention

[0021] There is an ongoing need for a process to recycle polyamide materials, in particular the polyamide waste materials, containing aliphatic polyamides, such as polyamide 6 and polyamide 6.6, that provides an essentially non-degraded aliphatic polyamide that can be used directly for further processing.

[0022] It was surprisingly found that aliphatic polyamides are soluble in organic solvents comprising a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, without degradation. Therefore, aliphatic polyamides can be recovered essentially non-degraded from polyamide materials, in particular from polyamide waste materials, containing said aliphatic polyamide by treating the polyamide material, in particular the polyamide waste material, with an organic solvent comprising said saturated monocyclic N-Ci-C4-alkyl lactam, whereby a solution of said aliphatic polyamide in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide with respect to the content of aliphatic polyamide in the polyamide material before the treatment are obtained.

[0023] Therefore, the present invention relates to a process for recovering an aliphatic polyamide from polyamide materials, in particular from polyamide waste materials, which comprises treating said polyamide material, in particular the polyamide waste material, with an organic solvent comprising a saturated monocyclic N-C1-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, to obtain a solution of said aliphatic polyamide in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide with respect to the content of aliphatic polyamide in the polyamide material before the treatment.

[0024] Furthermore, it was found that aliphatic polyamides A having a melting point of less than 230°C, such as polyamide 6, can be selectively dissolved from polyamide materials containing said polyamide A and one or more further materials selected from polyamides B having a melting point of more than 230°C, pigments and fillers by treating the polyamide material with an organic solvent comprising a saturated monocyclic N-C1-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone. Thereby aliphatic polyamides A can be selectively extracted from polyamide materials.

[0025] Therefore, the present invention relates in particular to a process for recovering an aliphatic polyamide A having a melting point as determined by differential scanning calorimetry of less than 230°C from a polyamide material, in particular from a polyamide waste material, containing said polyamide A and at least one further component selected from polyamides B having a melting point of more than 230°C, fibrous reinforcing fillers, pigments and non-fibrous fillers, which comprises treating said polyamide material with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, to obtain a solution of said polyamide A in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide A with respect to the content of aliphatic polyamide A in the polyamide material before the treatment

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[0028] The process of the present invention provides several benefits. The organic solvent which comprises the saturated monocyclic N-Ci-C4-alkyl lactam, in particular the N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-py rrolidone, is capable of selectively dissolving the aliphatic polyamide from the polyamide material that contains the aliphatic polyamide. In this way, aliphatic polyamides can be simply extracted from polyamide materials and thereby recovered. In particular, the organic solvent which comprises the saturated monocyclic N-Ci-C4-alkyl lactam, in particular the N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, is capable of selectively dissolving the polyamide A from the polyamide material, even if it contains aliphatic polyamides having a melting point above 230°C and / or other polyamides with a melting point above 230°C, which are herein also referred to as polyamides B. In this way, mixtures of the aliphatic polyamide A and the polyamide B can be efficiently separated in a simple manner, as the polyamide A is essentially or completely dissolved during the treatment of the polyamide material with the organic solvent while the polyamide B, the filler and / or the pigments remain essentially or completely in the undissolved residue. The treatment of the polyamide material with the organic solvent does not result in noticeable degradation of the aliphatic polyamide, regardless of whether it is an aliphatic polyamide A or an aliphatic polyamide from the group of the polyamides B. In particular, no noticeable decrease of the molecular weight of the aliphatic polyamide is observed after the treatment. Rather an increase is observed, as low molecular weight fragments of the aliphatic polyamide may at least partly stay dissolved and do not precipitate. Since pigment and / or fillers, if present, remain at least partly, in particular essentially or completely in the undissolved residue, the aliphatic polyamide is depleted in pigments and fillers as well as polymer materials which are insoluble in saturated monocyclic N-Ci-C4-alkyl lactams, such as cotton or wool. If the polyamide material, which is subjected to the treatment with the organic solvent, contains one or more pigments, the recovered aliphatic polyamide obtained from the treatment thus has a lower discoloration, e. g. higher lightness as expressed as an increased L-value in the Cl ELAB color space, than the polyamide material before the treatment. For example, the inventive process may result in an increase of the L-value of the aliphatic polyamide by at least 50% with respect to the L-value before the treatment step or by at least 5 L-units or more.

[0029] If the polyamide material, which is in particular a polyamide waste material, which is subjected to the treatment with the organic solvent, contains one or more polyamides B, the polyamide B remains essentially or completely in the undissolved residue, if a proper temperature is chosen for the treatment.

[0030] Therefore, the present invention also provides a method for separating the aliphatic polyamide A from the polyamide B by a process comprising treating a polyamide material containing said polyamide A and said polyamide B with an organic solvent comprising the saturated monocyclic N-Ci-C4-alkyl lactam, in particular the N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, at a temperature, where the polyamide A becomes soluble but where the polyamide B remains insoluble, to obtain a solution of said polyamide A in the organic solvent and an undissolved residue which is depleted in the polyamide A with respect to the polyamide material before the treatment and which essentially or completely contains the polyamide B present in the polyamide material before the treatment. The separation of polyamide A from polyamide B, in particular

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[0033] the separation of polyamide 6 from polyamide 6.6, renders the process particularly useful for the recycling of post-consumer waste, which often contains different polyamides.

[0034] Detailed Description of Invention

[0035] Here and in the following the melting point of the polyamides A and B refer to the melting points as determined by differential scanning calorimetry, also referred to as DSC. For determining the melting point, the DSC is typically carried out in accordance with the requirements of ASTM D3418 with heating rate of 10 K / min. For further details we refer to the examples.

[0036] Here and in the following, the term "essentially” means "at least 90%, in particular at least 95%”. For example, the phrase "the undissolved residue essentially or completely contains the polyamide B present in the polyamide material before the treatment” means that at least 90% by weight, in particular at least 95% by weight of the polyamide B present in the polyamide material before the treatment is contained in the undissolved residue obtained by the treatment.

[0037] Here and in the following, the term "aliphatic polyamide” is referred to polyamides essentially made of aliphatic amide-forming monomers. Herein, the term "aliphatic monomer” refers to monomers having saturated hydrocarbon radicals, which may be linear or branched and typically have 4 to 20 carbon atoms and amide forming functional groups, namely primary amino groups (NH2), amide groups (NH-CO), carboxyl groups (COCH), alkoxycarbonyl groups and carbonylcloride groups (COCI).

[0038] The aliphatic amide-forming monomers include in particular

[0039] saturated lactams having in particular 5 to 14 carbon atoms, such as delta-valerolactam, epsilon- caprolactam, decanolactam, undecanolactam and laurolactam;

[0040] a,co-aminoalcanoic acids having in particular 5 to 14 carbon atoms, such as 10-aminodecanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and 14-aminotetratecanoic acid;

[0041] aliphatic dicarboxylic acids having in particular 4 to 20 carbon atoms, especially 4 to 14 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, acelaic acid, sebacic acid, undecanedioic acid, dodecandioic acid, tridecanedioic acid, tetradecandioic acid, pentadecanoic acid, hexadecanedioic acid and octadecandioic acid, as well as their alkyl esters, e. g. their methyl esters or ethyl esters and the corresponding acid chlorides;

[0042] diamoalkanes having in particular 4 to 20 carbon atoms, especially 4 to 14 carbon atoms, such as 1,3- diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane,

[0043] 1 , 4-d I ami no-1 , 1 , -dimenty I butane, 1 , 4-d i amino-1 -ethylbutane, 1 , 4-d i ami no-1 , 2-d i methyl butane, 1,4- diamino-1 , 3-d i methy Ibutane, 1 , 4-d i amino- 1 , 4-di methyl butane, 1 , 4-diami no-2, 3-d i methyl butane, 1,2- diamino-1 -butylethane, 1,6-diaminohexane, 1,8-amidooctane, 1,9-diaminononane, 1,10- diaminodecane,

[0044] 1,11 -diaminoundecane, 1 , 12 -diaminododecane, 1 , 13-tridecanediamine,

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[0047] 1,14-tetradecanediamine, 1,16-hexadecanediamine, 1,18-octadecanediamine, 1,20-eicosanediamine, 1,22-docosanediamine, 2,2,4-trimethylhexane-1 ,6-diamine, 2,4,4-trimethylhexane-1 ,6-diamine, 2- methyl-1 ,8-octanediamine,

[0048] 1.3-d i methyloctane- 1 ,8-diamine, 1 , 4-d i methyloctane- 1 ,8-diamine,

[0049] 2.4-d I methyloctane- 1 ,8-diamine, 3, 4-dimethyloctane-1 ,8-diamine,

[0050] 4.5-dimethyloctane-1 ,8-diamine, 2, 2-dimethyloctane-1 ,8-diamine,

[0051] 3.3-dimethyloctane-1 ,8-diamine, 4, 4-dimethyloctane-1 ,8-diamine, and

[0052] 2.4-diethylhexane-1 ,6-diamine and 5-methylnonane-1,9-diamine.

[0053] The aliphatic polyamides may be made of repeating units of the formulae (I) or of repeating units of the formula (II)

[0054] }NH— R1— CO} Formula (I)

[0055] }NH— R2— NH— CO— R3— CO} Formula (II)

[0056] where

[0057] R1is an aliphatic radical having 4 to 14 carbon atoms, in particular 5 to 14 carbon atoms;

[0058] R2is an aliphatic radical having 4 to 20 carbon atoms, in particular 6 to 14 carbon atoms;

[0059] and

[0060] R3is an aliphatic radical having 2 to 18 carbon atoms, in particular 4 to 12 carbon atoms;

[0061] Examples of aliphatic polyamides include polyamide 6, polyamide 10, polyamide 11, polyamide 12, polyamide 6, 10, polyamide 6, 11 , polyamide 6, 12, polyamide 6.6 and polyamide 4.6.

[0062] According to the invention, the aliphatic polyamide A contained in the polyamide material has a melting point of below 230°C, in particular of at most 225°C, e. g. in the range of 160 to < 230°C and especially in the range of 170 to 225°C.

[0063] The aliphatic polyamides A are typically made of repeating units of the formula (I), where R1is an aliphatic radical having 4 to 14 carbon atoms, in particular 5 to 14 carbon atoms, or of repeating units of the formula (II), where R2is an aliphatic radical having 6 to 20 carbon atoms and R3is an aliphatic radical having 8 to 18 carbon atoms, in particular 8 to 12 carbon atoms. Examples of polyamides A include polyamide 6, polyamide 10, polyamide 11, polyamide 12, polyamide 6,10, polyamide 6,11 and polyamide 6,12.

[0064] In particular, the polyamide A is polyamide 6, i. e. poly caprolactam or poly(E-caprolactam), respectively.

[0065] The polyamide B may be an aliphatic polyamide, an araliphatic polyamide, also termed semi-aromatic polyamides, or an aromatic polyamide. According to the invention, the polyamide B has a melting point of above 230°C, e. g. in the range of 235 to 480°C, in particular in the range of 240 to 450°C.

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[0068] Aliphatic polyamides B, hereinafter also referred to as polyamides B1, can be described by the formula (II) above, where R2is an aliphatic radical having 4 to 7 carbon atoms and R3is an aliphatic radical having 2 to 6 carbon atoms. Examples of aliphatic polyamides B are polyamide 6.6 and polyamide 4.6.

[0069] Semi-aromatic polyamides can be described by the following formula (Ila),

[0070] }NH— R2— NH— CO— R4— CO} Formula (Ila)

[0071] where

[0072] R2is an aliphatic radical having 4 to 10 carbon atoms, in particular 4 to 8 carbon atoms;

[0073] and

[0074] R4is an aromatic radical having 6 to 10 carbon atoms, such as 1 ,4-phenylene or 1 ,3-phenylene or a combination thereof.

[0075] Examples of semi-aromatic polyamides are polyamides of the formula (II), where R2is 1 ,6-hexanediyl and R3is 1,4 phenylene or a combination of 1 ,3-phenylene and 1 ,4-phenylene, which are referred to as polyamide 6T and polyamide 6T / 6I (copolyamide of 1,6-hexanediamine, phthalic acid and isophthalic acid). These semiaromatic polyamides are obtained by polycondensation of 1,6-diaminohexane with phthalic acid or an ester forming derivative thereof or by polycondensation of 1,6-diaminohexane with phthalic acid and isophthalic acid or ester forming derivatives thereof.

[0076] Preferably, the polyamide B is selected from aliphatic polyamides B1, in particular from the group consisting of polyamide 6.6 and polyamide 4.6, semi-aromatic polyamides, such as polyamide 6T / I and aromatic polyamides, such as aramide. Especially, the polyamide B comprises or is an aliphatic polyamide B1, especially a polyamide 6.6.

[0077] Generally, the total amount of the aliphatic polyamide in the polyamide material used in the treatment is in the range of 10 to 99% by weight, in particular in the range of 40 to 98% by weight, especially in the range of 60 to 97% by weight or 70 to 97% by weight, based on the total weight of the polyamide material.

[0078] Generally, the total amount of the further components, such as polyamides other than aliphatic polyamides, pigments, fillers, additives and polymers other than polyamides, is in the range of 1 to 90% by weight, in particular in the range of 2 to 60% by weight, especially in the range of 3 to 30% by weight, based on the total weight of the polyamide material used in the treatment.

[0079] Examples of polymers other than polyamides include, polyurethanes, polyurea, in particular polyetherurea, such as Spandex®, Lycra® or Elastan®, acrylonitrile-butadiene-styrene terpolymers (ABS), polyvinylchloride (PVC), polyethylene therephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC),

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[0082] polydimethylsiloxan (PDMS), polyoxymethylene (POM), polystyrene (PS), polymethylmethacrylate (PMMA), polyethylene (PE) and polypropylene (PP). These other polymers may be contained as contaminants in the polyamide material, e. g. due to incomplete sorting of the polymer material or due to being composites, interwoven and / or glued together with the polyamides. The total amount of said polymers will typically not exceed 20% by weight, in particular 10% by weight, of the polyamide material.

[0083] Further polymers other than polyamides are impact modifiers. The amount of impact modifiers will generally not exceed 20% by weight, based on the aliphatic polyamide present in the polyamide material. The amount of additives will typically not exceed 10% by weight, based on the total weight of the aliphatic polyamide present in the polyamide material, and is typically present in an amount of not more than 2% by weight, e. g. in an amount of 0.2 to 2% by weight, based on the weight of the polyamide material.

[0084] In a particular group (1) of embodiments, the polyamide material, in particular the polyamide waste material, contains at least one aliphatic polyamide A. In a subgroup (1a) of the group (1) of embodiments, the polyamide material, in particular the polyamide waste material, contains essentially no aliphatic polyamide B1 , i. e. the weight ratio of polyamide B1 to polyamide A is less than 1:10 and in particular less than 1:20 or less than 1:100.

[0085] In a particular group (2) of embodiments, the polyamide material, in particular the polyamide waste material .contains at least one aliphatic polyamide, selected from the group B of polyamides, i. e. and aliphatic polyamides B1 having a melting point above 230°C, e. g. in the range of 235 to 350°C, in particular in the range of 240 to 300°C, e. g. polyamide 6.6 or polyamide 4.6. In a subgroup (2a) of the group (2) of embodiments, the polyamide material, in particular the polyamide waste material, contains essentially no aliphatic polyamide A, i. e. the weight ratio of polyamide A to polyamide B1 is less than 1:10 and in particular less than 1:20 or less than 1:100.

[0086] In a particular group (3) of embodiments, the polyamide material, in particular the polyamide waste material, contains at least one polyamide B in addition to the polyamide A.

[0087] In the group (3) of embodiments, the polyamide A is in particular selected from polyamide 6, polyamide 10, polyamide 11, polyamide 12, polyamide 6,10, polyamide 6,11 and polyamide 6,12. Especially, the polyamide A is polyamide 6.

[0088] In the group (3) of embodiments, the polyamide B is preferably selected from aliphatic polyamides B1, in particular from the group consisting of polyamide 6.6 and polyamide 4.6, semi-aromatic polyamides, such as polyamide 6T / 6I, and aromatic polyamides, such as aramide. In particular, the polyamide B is selected from aliphatic polyamides B1. Especially, the polyamide B comprises or is polyamide 6.6.

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[0091] In a subgroup (3a) of the group (3) of embodiments, the polyamide material, in particular the polyamide waste material, contains a combination of polyamide 6 as a polyamide A and a polyamide B. In the group (3a) of embodiments, the polyamide B is preferably selected from aliphatic polyamides B1, in particular from the group consisting of polyamide 6.6 and polyamide 4.6, semi-aromatic polyamides, such as polyamide 6T / 6I, and aromatic polyamides, such as aramide. In particular, the polyamide B comprises or is an aliphatic polyamide B1, especially polyamide 6.6.

[0092] In a subgroup (3b) of the group (3) of embodiments the polyamide material, in particular the polyamide waste material, contains a combination of polyamide 6 as the polyamide A and polyamide 6.6 as the polyamide B.

[0093] In the group (3) of embodiments, and likewise in the groups (3a) and (3b) of embodiments, the weight ratio of the polyamide A to the polyamide B in the polyamide material, in particular the polyamide waste material, before the treatment is typically in the range of 20:1 to 1:20, in particular in the range of 10:1 to 1:10.

[0094] Typically, the total amount of polyamide A and polyamide B is in the range of 10 to 100% by weight, in particular 20 to 100% by weight, especially 30 to 100% by weight, based on the total weight of organic polymers in the polyamide material before the treatment.

[0095] In the polyamide material, in particular the polyamide waste materials, of the group (3) of embodiments, and likewise in the groups (3a) and (3b) of embodiments, the polyamide A and the polyamide B may be present as a blend or in form of a mixture of particles of a polyamide A containing material and particles of a polyamide B containing material.

[0096] The further component in the polyamide material, in particular the polyamide waste material, which is subjected to the treatment of the present invention, may comprise one or more fibrous reinforcing fillers. Fibrous reinforcing fillers are typically glass fibers and mineral fibers but may also be fibers of organic high melting polymers. Examples of reinforcing fillers are glass fibers, carbon fibers, aramid fibers and potassium titanate fibers. Glass fibers, such as E-glass are particularly preferred reinforcing fillers. These can be used as rovings or in particular as cut glass in the commercially available forms. These fibers have in general a diameter of from 3 to 30 pm, preferably from 6 to 20 pm and particularly preferably from 8 to 15 pm. The fiber length in the compound is as a rule from 20 pm to 1000 pm, preferably from 180 to 500 pm and particularly preferably from 200 to 400 pm.

[0097] The further component in the polyamide material, in particular the polyamide waste material, which is subjected to the treatment of the present invention, may comprise one or more non-fibrous fillers. Suitable non-fibrous fillers which may contained in the polyamide material include, but are not limited to inorganic fillers, such as chalk, precipitated calcium carbonate, graphite, gypsum, carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc, glass meal and hollow glass spheres. In particular, the fillers are selected from the group consisting of chalk, precipitated calcium carbonate, graphite, gypsum, carbon black, and talc.

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[0100] The total amount of the fillers in the polyamide material, in particular the polyamide waste material, may generally be as high as 70% by weight, in particular not more than 50% by weight, and is typically in the range of 0 to 70% by weight, in particular in the range of 0 to 50% by weight or 1 to 50% by weight, especially in the range of 0 to 40% by weight or 4 to 40% by weight, based on the total weight of the polyamide material.

[0101] Suitable pigments which may be contained in the polyamide materials include, but are not limited to inorganic pigments, such as titanium dioxide pigments, which may be coated or uncoated, carbon black, iron oxide, ultramarin blue, and organic pigments, such as phthalocyanines, quinacridones, perylenes, nigrosine and anthraquinones.

[0102] The total amount of the pigments in the polyamide material, in particular the polyamide waste material, may generally be as high as 20 % by weight, in particular not more than 10% by weight, and is typically in the range of 0 to 20% by weight, in particular in the range of 0 to 10% by weight or 0.1 to 10% by weight, based on the total weight of the polyamide material.

[0103] Besides the aforementioned components of the polyamide materials, i. e. the aliphatic polyamides, in particular, the polyamide A, the polyamide B, the pigment and fillers, the polyamide material, in particular the polyamide waste material, may contain one or more impact modifiers. If present, the amount of the impact modifier is typically in the range of 0.1 to 20% by weight, in particular in the range of 0.5-15% by weight, especially in the range of 1 to 10% by weight, based on the total weight of the polyamide material.

[0104] The polyamide material, in particular the polyamide waste material, which is subjected to the treatment of the present invention, may also comprise various additives conventionally used in polyamides. Such additives include e.g. surface effect additives, antioxidants, colorant other than pigments, heat stabilizers, light stabilizers, flow modifiers, plasticizers, demolding agents, flame retardants, anti-drip agents, radiation stabilizers, ultraviolet absorbing compounds, ultraviolet light stabilizers, release agents, and / or antimicrobial agents. The heat stabilizer may be any conventional heat stabilizer, such as copper heat stabilizer and / or organic amine heat stabilizer, for example Irganox 1098. The light stabilizer may be any conventional light stabilizer, such as hindered amine compounds, benzophenone, benzotriazole and / or salicylates light stabilizer. The preferred light stabilizer may be 2-hydroxy-4-n-octoxy benzophenone, 2-(2-hydroxy-5-methylphenyl) benzotriazole, aryl salicylates, and / or 2-(2-hydroxy-5-tert-octylphenyl) benzotri azole, etc. The lubricant may be any conventional lubricant for polyamide composition, such as stearate, polyethylene wax, ethylene bisstearamide (EBS), fatty acid ester, wax, phthalic acid ester and / or silicones, etc. The flame retardant may be any conventional flame retardant, for example the inorganic flame retardant and / or organic flame retardant. The organic flame retardant includes e. g. phosphorus, brominated, chlorinated and / or nitrogen flame retardant. Examples of nitrogen flame retardant are benzoguanamine, tris(hydroxyethyl)isocyanurate, isocyanurate, melamine, melamine cyanurate. Examples of phosphorus flame

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[0107] retardant are selected from the group consisting of ethylene-diamine phosphate, piperazine phosphate, piperazine pyrophosphate, dialkylphosphate.

[0108] The total content of the additives in the polyamide material is typically in the range of 0 to 10% by weight, based on the total weight of the aliphatic polyamides in the polyamide material or in the range of up to 2% by weight, e. g. in the range of 0.1 to 2% by weight, based on the total weight of the polyamide material.

[0109] According to the invention, the polyamide material, in particular the polyamide waste material, containing an alipahtic polyamide is treated with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone. Generally, the organic solvent comprises at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more preferably at least 90% by weight, especially at least 95% by weight, based on the total weight of the organic solvent, of a saturated monocyclic N-Ci-C4-alkyl lactam. The remainder of the organic solvent may be water, methanol or ethanol, butyrolactone or other organic solvents that are miscible with the saturated monocyclic N-Ci-C4-alkyl lactam. Typically, the organic solvent does not contain more than 2% by weight, based on the total weight of the organic solvent, of organic solvents different from N-C i-C4-alky I lactams.

[0110] Suitable N-Ci-C4-alkyl lactams are selected from the group of N-Ci-C4-alkyl 2-pyrrolidones, N-Ci-C4-alkyl caprolactams and N-Ci-C4-alkyl 2-piperidones. In particular, the N-Ci-C4-alkyl lactam is an N-Ci-C4-alkyl 2-pyrrolidone, such as N-methyl-2-pyrrolidone or N-ethyl-2-pyrrolidone or N-butyl-2-pyrrolidone. Especially the N-Ci-C4-alkyl lactam is N-methyl-2-pyrrolidone. In particular, the organic solvent does not contain more than 5% by weight, in particular not more than 2% by weight, based on the total weight f the organic solvent, of organic solvents different from N-Ci-C4-alkyl 2-pyrrolidones and especially not more than 2% by weight, based on the total weight of the organic solvent, of organic solvents different from N-methy I -2-py rrolidone .

[0111] The origin of the polyamide material, which is subjected to the recovery process of the present invention, is of minor importance as long as it contains the aliphatic polyamide and at least one other component as mentioned before. Typically, the polyamide material is a polyamide containing waste materials, hereinafter also termd polyamide waste material, such as polyamide containing industrial waste, polyamide containing pre-consumer waste and post-consumer waste, pretreated polyamide waste materials containing one or more aliphatic polyamides, presorted plastic waste materials containing one or more aliphatic polyamides, such as presorted automotive shredder materials or presorted textile materials. Polyamide materials subjected to the recovery process of the present invention may also polyamide material from other recycling processes.

[0112] In the technical field of the present invention the term "industrial waste materials” refers to waste occurring during industrial production of goods. The term "pre-consumer waste materials” refers to waste materials of unsold goods while post-consumer goods refer to used or sold goods as well as parts of used or sold goods.

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[0115] Frequently, the polyamide waste material is a pre-sorted plastic waste material which has been presorted with respect to the type of organic polymers contained therein, in particular with respect to polyamides. In particular, the pre-sorted plastic waste material contains at least 80% by weight, in particular at least 85% by weight by weight, especially at least 90% by weight of polyamides with respect to the organic polymers contained in the pre-sorted plastic waste material.

[0116] In particular embodiments, the plastic waste material is a pre-sorted waste material of industrial origin, preconsumer origin, or post-consumer origin, in particular a presorted automotive shredder material, also referred to as automotive shredder residue (ASR), and / or textile waste, which may be industrial textile waste, preconsumer textile waste and post-consumer textile waste.

[0117] For an efficient dissolution of the aliphatic polyamide from the polyamide material, it is beneficial if the polyamide material is a particulate material having a particle size of not more than 100 mm, in particular not more than 80 mm and especially not more than 50 mm, as determined by sieving. The determination of the particle size is typically carried out according to the methods described in DIN 66165-1:2022 and DIN 66165-2:2016.

[0118] To achieve an efficient dissolution of the aliphatic polyamide, the treatment of the polyamide material is carried out at a temperature, at which the aliphatic polyamide to be recovered has a sufficient solubility in the organic solvent. The temperature required for achieving an effective dissolution of the polyamide will depend on the kind of polyamide to be recovered polyamide waste material. Generally, the treatment is carried out at a temperature of at least 150°C, in particular at least 155°C, especially at least 158°C. The treatment may be carried out at temperatures of higher than 155°C. However, for economic reasons the treatment is generally carried out at a temperature of at most 250°C, in particular at most 240°C or at most 230°C.

[0119] If the polyamide material is a polyamide material, in particular a polyamide waste material, according to group (3) of embodiments, the treatment can be carried out in a manner to selectively dissolve the polyamide A and to avoid dissolution of the polyamide B. In this case, the treatment is preferably carried out at a temperature of at most 175°C in particular at most 173°C or at most 170°C to avoid a dissolution of the polyamide B, in particular of the polyamide 6.6. In particular, in case of N-Ci-C4-alkyl 2-pyrrolidones, and especially in case of N-methyl-2-pyrroldione, the treatment is carried out at a temperature in the range of 150°C to 175°C, in particular in the range of 155°C to 173°C and especially in the range of 158°C to 170°C.

[0120] In the groups (1) and (3) of embodiments, the treatment of the polyamide material is preferably carried out at a temperature in the range of 150°C to 175°C, in particular in the range of 155°C to 173°C and especially in the range of 158°C to 170°C. In particular if the polyamide A is polyamide 6, the treatment of the polyamide material is preferably carried out at a temperature in the range of 150°C to 175°C, in particular in the range of 155°C to 173°C and especially in the range of 158°C to 170°C.

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[0123] In the group (2) of embodiments, the treatment of the polyamide material is preferably carried out at a temperature above 175°C, e. g. at least 180°C or at least 185°C, in order to achieve an effective dissolution of the polyamide B1. In particular, the treatment of a polyamide material according to the group (2) of embodiments is carried out at a temperature in the range of >175 to 250°C, in particular in the range of 180°C to 240°C and especially in the range of 185 to 230°C. In particular, if the polyamide B1 is polyamide 6.6, the treatment of the polyamide material is preferably carried out at a temperature in the range >175 to 250°C, in particular in the range of 180°C to 240°C and especially in the range of 185 to 230°C.

[0124] The amount of organic solvent required for complete dissolution of the respective aliphatic polyamide to be recovered is generally at least 1 part by weight per 1 part by weight of the polyamide material. Of course, a higher amount of organic solvent may be used. Generally, the amount of organic solvent will not exceed 100 parts by weight per 1 part by weight of the polyamide material and is preferably in the range of 1 to 20 parts by weight, in particular in the range of 2 to 15 parts by weight per 1 part by weight of the polyamide material.

[0125] The treatment of the polyamide material is typically carried out until the polyamide material is depleted in the respective aliphatic polyamide to be recovered to at least 50% by weight, in particular at least 80% by weight or at least 90% by weight, based on the content of the respective aliphatic polyamide to be recovered in the starting polyamide material before the treatment. In other words, the treatment is carried out until at least 50% by weight, in particular at least 80% by weight or at least 90% by weight of the respective aliphatic polyamide to be recovered contained in the polyamide material before the treatment is dissolved in the organic solvent. Consequently, the undissolved residue obtained in the treatment contains at most 50% by weight, in particular at most 20% by weight and especially at most 10% by weight of the respective aliphatic polyamide to be recovered contained in the polyamide material before the treatment. Especially, the treatment is carried out until the respective aliphatic polyamide to be recovered contained in the polyamide material is completely dissolved in the organic solvent and the undissolved residue does not contain the respective aliphatic polyamide to be recovered. The time required for this will depend on the kind of polyamide material and the temperature and can be determined routinely by a skilled person. It may be in the range of 5 minutes to 2 h.

[0126] The treatment of the polyamide material, in particular of the polyamide waste material, with the organic solvent can be carried out in a batch procedure or in a continuous procedure. For example, the treatment may be carried out in stirred vessels, agitated or rotating extraction vessels, which can be operated batchwise or continuously. The organic solvent can be circulated to minimize the amount of solvent required for complete dissolution of the respective aliphatic polyamide to be recovered. Of course, continuously operated systems such as cascades of extraction vessels can be employed for the treatment.

[0127] The treatment of the polyamide material with the organic solvent is preferably carried out in an inert atmosphere, such as nitrogen or argon, in order to avoid oxidative degradation of the polyamides. It may also be possible to degas the organic solvent before it is used in the treatment of the polyamide material.

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[0130] By the treatment, a solution of the respective aliphatic polyamide to be recovered in the organic solvent and an undissolved residue is obtained, which is depleted in the respective aliphatic polyamide to be recovered with respect to its content in the polyamide material before the treatment.

[0131] Generally, the solution of the respective aliphatic polyamide to be recovered will then be separated from the undissolved residue by conventional solid-liquid separations. For example, the separation may be achieved by filtration and / or centrifugation. Preferably, the solid liquid separation is carried out at an elevated temperature to avoid a precipitation of the polyamide A from the solution. In particular, the solid-liquid separation of the obtained solution from the undissolved residue is carried out at a temperature of at least 145°C, in particular at last 150°C or at least 155°C, e. g. in the range of 145°C to 250°C, in particular in the range of 150°C to 240°C and especially in the range of 155°C to 230°C.

[0132] If the respective aliphatic polyamide to be recovered is a polyamide A, the solid-liquid separation of the obtained solution from the undissolved residue is carried out at a temperature of at least 145°C, in particular at last 150°C or at least 155°C, e. g. in the range of 145°C to 175°C, in particular in the range of 150°C to 173°C and especially in the range of 155°C to 170°C. If the respective aliphatic polyamide to be recovered is a polyamide B1, the solid-liquid separation of the obtained solution from the undissolved residue is carried out at a temperature of above 175°C, in particular at least 180°C and especially at least 185°C, e. g. at a temperature in the range of >175°C to 250°C, in particular in the range of 180°C to 240°C and especially in the range of 180 to 230°C.

[0133] To recover the aliphatic polyamide, I. e. the polyamide A or the polyamide B1, it is generally separated from the organic solvent. Preferably, the separation comprises the precipitation of the respective aliphatic polyamide to be recovered from the solution of said aliphatic polyamide by cooling the solution or by addition of an anti-solvent to the solution or by combinations of these measures. For example, the cooling may be achieved by allowing the solution of said aliphatic polyamide to cool without temperature control. However, it is also possible to control the cooling rate. For example, controlled cooling rates in the range of 0.1 to 10 K / min can be applied.

[0134] Anti-solvents are solvents, wherein the respective aliphatic polyamide to be recovered is insoluble. Typical antisolvents are aliphatic hydrocarbons, cycloaliphatic hydrocarbons, water, alcohols, such as methanol, ethanol and mixtures thereof.

[0135] Preferably, the precipitation of the aliphatic polyamide to be recovered from the solution of said aliphatic polyamide in the organic solvent is achieved by cooling of the solution. For this, the solution of the aliphatic polyamide to be recovered is cooled to a temperature of below 110°C, in particular to a temperature in the range of 0 to 110°C especially in the range of 10 to 100°C.

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[0138] The precipitated aliphatic polyamide to be recovered is generally separated from the organic solvent. The separation can be carried out by conventional solid-liquid separation measures, such as filtration and / or centrifugation. The separated solid aliphatic polyamide to be recovered may be washed by suitable solvents, such as acetone or N-methy l-2-py rrolidone, to remove impurities and to foster the drying of the respective aliphatic polyamide.

[0139] The thus recovered aliphatic polyamide is typically dried to remove the organic solvent before it is further used. The drying can be carried out by conventional drying techniques, such as vented drying ovens at elevated temperature of e. g. up to 150°C, in particular in the range of 20 to 150°C or at reduced pressure, e. g. in the range of 5 to 200 mbar, and optionally elevated temperatures of e.g. up to 120°C, e. g. 20 to 120°C.

[0140] The organic solvent which has been separated from the aliphatic polyamide can be recycled into the process of the present invention, in particular into the treatment step, to reduce the amount of solvent required for the treatment. In order to avoid a build-up of impurities, the organic solvent can be purified, for example by distillation, before being recycled to the process according to the invention.

[0141] In case of a polyamide material according the group (3) of embodiments, the treatment of the polyamide material is typically treated with the organic solvent at a temperature in the range of 150°C to 175°C, in particular in the range of 155°C to 173°C and especially in the range of 158 to 170°C to obtain a solution of the polyamide A in the organic solvent and an undissolved residue containing the polyamide B, in particular the aliphatic polyamide B1. The polyamide A recovered from the solution is essentially free of the polyamide B contained in the polyamide material that is subjected to the treatment. In particular, the recovered polyamide A does not contain more than 10% by weight, in particular not more than 5% by weight and especially not more than 2% by weight of the polyamide B, based on the total weight of the recovered polyamide A.

[0142] Moreover, the amounts of pigments and fillers, if contained in the polyamide material that is subjected to the treatment is typically reduced to a level of less than 20%, in particular less than 15% or less than 10% of the amount contained in the polyamide material prior to the treatment of the present invention.

[0143] The process of the present inventio may also include a pretreatment of the polyamide material, in particular of the polyamide waste material, to remove organic polymers which are different from polyamides (hereinafter also referred to as non-polyamide polymers), such as the aforementioned polymer contaminants contained in the polyamide material, including e. g. polyurethanes, polyurea, in particular polyetherurea, such as Spandex®, Lycra® or Elastan®, aery lonitrile-butadiene-sty rene terpolymers (ABS), polyvinylchloride (PVC), polyethylene therephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polydimethylsiloxan (PDMS), polyoxymethylene (POM), polystyrene (PS), polymethylmethacrylate (PMMA), polyethylene (PE) and polypropylene (PP). These polymers can be removed from the polymer material by extracting the polyamide material with an organic solvent under conditions, where these non-polyamide polymers are soluble in the organic solvent, while the aliphatic polyamides contained in the polyamide material are not. In particular, it was found that organic solvents containing gamma-valerolactone are suitable

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[0146] for this purpose, because the aforementioned polymers show a better solubility in said solvents compared to aliphatic polyamides.

[0147] For example, it is possible to pretreat the polyamide material with an organic solvent comprising gammavalerolactone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent.

[0148] As an alternative, it is also possible to pretreat the polyamide material with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam, in particular the N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-py rrolidone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent.

[0149] Hereby the non-poly amide polymers are extracted from the polyamide material, whereby a polyamide material is obtained which is depleted in said non-polyamide polymers. The pretreatment is typically carried out at a temperature, wherein the aliphatic polyamide to be recovered, is still not soluble, while the non-polyamide polymer is sufficiently soluble in the organic solvent. Thereby a solution of the non-polyamide polymers is obtained which can be separated from the solid polyamide material which is depleted in the non-polyamide polymers. The treatment and separation steps can be carried out by analogy to the treatment and separation steps described above.

[0150] If the polyamide material, e. g. the polyamide waste material, contains one or more of the aforementioned non-polyamide polymers which are different from polyamides, it may be desirable that the process of the invention comprises the following the following additional pretreatment, which comprises:

[0151] treatment of the polyamide material, in particular of the polyamide waste material, with an organic solvent at a temperature T1, where the non-polyamide polymer to be removed from the polyamide material is sufficiently soluble in the respective organic solvent and where the temperature T 1 is lower than the temperature T2, where the aliphatic polyamide to be recovered becomes sufficiently soluble in the respective organic solvent, to obtain a solution containing said organic polymer to be removed dissolved in the organic solvent and a pretreated polyamide material which is depleted in the organic polymer to be removed with respect to the content of organic polymer to be removed in the polyamide material before the pretreatment.

[0152] The term "sufficiently soluble” means that the solubility of the respective non-polyamide polymer to be removed in the respective organic solvent at the temperature T1 is at least 10 g / L. At the temperature T 1 the solubility in the respective organic solvent of any aliphatic polyamide contained in the polyamide material should be less than 10 g / L, in particular at most 5 g / L.

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[0155] If the organic solvent comprises gamma-valerolactone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent, typical temperatures T1 are in the range of 110°C to 187.5°C, in particular in the range of 115°C to 187°C or 130°C to 187°C or 140 to 187°C. For example, the non-polyamide polymers listed in the following table A are sufficiently soluble at the temperatures T given therein:

[0156] Table A

[0157] > >>

[0158]

[0159] 1) Temperature, where the polymer is readily soluble in the organic solvent containing at least 90 % by weight of gamma valerolactone.

[0160] 2) Preferred operating temperature range T 1 for pretreatment of the polyamide material with the organic solvent containing gamma valerolactone.

[0161] 3) Higher temperatures T1 of up to 220°C, in particular up to 210°C are possible, if the polyamide material is according to the group (2) of embodiments.

[0162] If the organic solvent comprises a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent, typical temperatures T1 are in the range of 40°C to 157.5°C preferably in the range of 45°C to 157.5°C, especially in the range of 48°C to 157°C or 90°C to 157°C or 95°C to 157°C. For example, the non-polyamide polymers listed in the following table B are sufficiently soluble at the temperatures T given therein:

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[0165] Table B

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[0167]

[0168] 1) Temperature, where the polymer is readily soluble in the organic solvent containing at least 90 % by weight of N-methyl pyrrolidone.

[0169] 2) Preferred operating temperature range T 1 for pretreatment of the polyamide material with the organic solvent containing at least 90% by weight of saturated monocyclic N-Ci-C4-alkyl lactam, especially N-methyl pyrrolidone.

[0170] 3) Higher temperatures T1 of up to 175°C, in particular up to 170°C are possible, if the polyamide material is according to the group (2) of embodiments.

[0171] The pretreatment can be carried out by analogy to the treatment according to the present invention. The amount of the organic solvent used in the pretreatment is typically in the range of 0.5 to 20 parts by weight, in particular 1 to 10 parts by weight per 1 part by weight of the polyamide material or in the range of 1 to 100 parts by weight or 2 to 20 parts by weight per 1 part by weight of polymer to be recovered from the polyamide material.

[0172] Recovering the non-poly amide polymer in the pretreatment step may be carried out in two or more separate sequential pretreatment steps of the polyamide material with the organic solvent at different T 1 temperatures to recover at least non-polyamide materials from the group of PVC, PET / PBT and polyetherurethane.

[0173] If the organic solvent comprises gamma-valerolactone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent the pretreatment steps include:

[0174] a pretreatment at a temperature in the range of 110°C to 187.5°C, in particular

[0175] 110°C to 170°C or 115°C to 170°C or 130 to 170°C and especially 140°C to 149°C, or 110°C to 149 °C, in particular 110°C to 140 °C, especially 115°C to 125°C to dissolve PVC and / or polyetherurethane, depending on which one is present in the polyamide material, with subsequent separation of the thus obtained solution containing dissolved PVC and polyetherurethane and / or

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[0178] a pretreatment at a temperature in the range of 170°C to 187.5°C,

[0179] in particular 180°C to 187°C C to dissolve PET / PBT with subsequent separation of the thus obtained solution containing dissolved PET / PBT from the pretreated polyamide material.

[0180] If the organic solvent comprises N-methylpyrrolidone, preferably in an amount of at least 50% by weight or at least 60% by weight, in particular at least 70% by weight or at least 80% by weight, more particularly at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent the pretreatment steps include:

[0181] a pretreatment at a temperature in the range of 40°C to 157.5°C, in particular 40°C to 149°C, preferably 45°C to 80°C, especially 48°C to 70°C or in particular 90°C to 149°C, preferably 95°C to 130°C, especially 95°C to 120°C to dissolve PVC and / or polyetherurethane, depending on which one is present in the polyamide material, with subsequent separation of the thus obtained solution containing polyetherurethane from the pretreated polyamide material and / or

[0182] a pretreatment at a temperature in the range of 150°C to 157.5°C, in particular 152°C to 157°C to dissolve PET / PBT with subsequent separation of the thus obtained solution containing dissolved PET / PBT from the pretreated polyamide material.

[0183] The thus obtained solution which contains the non-polyamide polymer to be removed in the organic solvent is typically separated from the pretreated polyamide material at the temperature T1 or a temperature slightly lower than the temperature T1 but at a temperature, where the polymer to be removed remains dissolved.

[0184] The organic solvent may be separated from the non-polyamide polymer by distillation or by precipitation. Precipitation of the non-polyamide polymer from the solution is typically achieved by cooling and / or by addition of an anti-solvent as described above in the context of the precipitation of the aliphatic polyamide to be recovered from its solution in the organic solvent.

[0185] The thus obtained pretreated material is then subjected to the process of the present invention.

[0186] The recovered aliphatic polyamide can be used in the same way as fresh aliphatic polyamide for numerous purposes. For this, the recovered aliphatic polyamide, which is typically obtained as a powder, may be converted into a granulate, e. g. by hot knock off granulation, hot-melt granulation, strain granulation or underwater granulation. If required, an annealing step can be performed in between in order to increase the chain length. Typically, the annealing step is carried out at a temperature in the range of 160 to 220 °C Typically, the annealing step is carried out under vacuum or in an inert atmosphere, I. g. under a blanket of inert gas, such as nitrogen or argon.

[0187] For example, the recycled aliphatic polyamide can be incorporated into the article as part of mobile electronic devices, as automobile components, into textiles or as films, e. g. packaging films for food products or films for

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[0190] agricultural purposes. As used herein, a mobile electronic device refers to an electronic device that its user can easily carry and used in various locations. A mobile electronic device can include, but not limited to mobile computers such as a tablet computer, a laptop computer, a pocket calculator, portable media player, mobile internet device (MID), handheld PC, handheld game console, digital media player, mobile phones such as a smart phone, a phablet, wearable computers such as a smart watch, a head-mounted display, a virtual reality headsets, a digital camera, a global positioning system receiver, a portable power source, a portable Wi-Fi, a portable media player, a pocket calculator, and a e-book reader. The part herein is the one that at least partially comprises the polyamide composition. In some embodiments, the part could be a frame, housing, connector, cover, circuit board of the mobile electronic device. As used herein, the automobile component includes but not limited to interior and exterior automobile components, for example hoods, trunks, bumpers, grilles, side claddings, rocker panels, fenders, tail-gates, in wire and cable applications, instrument panels, consoles, interior trim, exterior trim, door panels, heater housings, battery supports, headlight housings, front ends, ventilator wheels, reservoirs, and soft pads. In some embodiments, the automobile component is an interior trim, console, and exterior trim. The recovered aliphatic polyamide may also be used for producing textiles.

[0191] If the polyamide material that has been subjected to the process of the invention contains a polyamide B, the undissolved residue contains the polyamide B and optionally pigments and fillers, if present in the polyamide material. Since the process of the present invention does not affect the molecular weight, the undissolved residue can be used in the same way as compounds of the polyamide B, e. g. in the above manner, optionally after drying, which is typically carried out as described above for the polyamide A.

[0192] However, it is also possible to isolate the polyamide B from the undissolved residue by conventional techniques which will depend on the type of polyamide B in a known manner. For example, it will be possible to extract certain polyamides B, in particular aliphatic polyamides B1, such as polyamide 6.6, from undissolved residue by the treatment of the undissolved residue with polar organic solvents in which the polyamide B becomes soluble.

[0193] In particular, it is possible to recover the aliphatic polyamides B1, such as polyamide 6.6, from the undissolved residue by treating the undissolved residue with an organic solvent or solvent mixture. The treatment of the undissolved residue with the organic solvent is generally carried out at a temperature, where the polyamide B1 is soluble in the said organic solvent. Typical solvents for dissolving polyamides B1 include formic acid, acetic acid and mixtures thereof with water, alcohols, such as methanol or ethanol, or gylcols, such as ethylene glycol or propylene glycol and organic solvents containing a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, preferably in an amount of at least 50% by weight, in particular at least 60% by weight or at least 70 by weight or at least 80 by weight or at least 90% by weight or at least 95% by weight. The remainder of the organic solvent for the treatment of the undissolved residue containing the polyamide B1 may be water, methanol or ethanol, butyrolactone or other organic solvents that are miscible with the N-Ci-C4-alkyl lactam.

[0194] M / BASFTR-4207-PCBASF SE 241069W001

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[0196] According to a preferred embodiment, the organic solvent used for treating the undissolved residue, I. e. for dissolving the aliphatic polyamide B1 , contains a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, preferably in an amount of at least 50% by weight or at least 60% by weight, more preferably at least 70% by weight or at least 80% by weight, in particular at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent. The remainder of the organic solvent used in the treatment of the undissolved residue may be water, methanol or ethanol, butyrolactone or other organic solvents that are miscible with the with the N-Ci-C4-alkyl lactam. In particular, the organic solvent used for the treatment of the undissolved residue does not contain more than 5% by weight, in particular not more than 2% by weight, based on the total weight f the organic solvent, of organic solvents different from N-Ci-C4-alkyl 2-py rrolidones and especially not more than 2% by weight, based on the total weight f the organic solvent, of organic solvents different from N-methyl-2-pyrrolidone.

[0197] Therefore, a particular subgroup of the group (3) embodiments of the invention relates to a process, where the insoluble residue obtained from the treatment of the polyamide material with the organic solvent is subjected to a further treatment with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, preferably in an amount of at least 50% by weight or at least 60% by weight, more preferably at least 70% by weight or at least 80% by weight, in particular at least 90% by weight, especially at least 95% by weight based on the total weight of the organic solvent, at a temperature, where the polyamide B1 becomes soluble in the organic solvent to obtain a solution of said polyamide B1 in the organic solvent.

[0198] The temperature required for dissolving the polyamide B1 will depend on the kind of polyamide B1. Generally, the minimum temperature where polyamide B1 becomes soluble in the organic solvent containing at least 50% by weight, preferably at least 80% by weight, in particular at least 90% by weight, especially at least 95% by weight, based of the total weight of the organic solvent, of a saturated monocyclic N-Ci-C4-alkyl lactam, in particular a N-Ci-C4-alkyl-2-pyrrolidone, especially N-methyl-2-pyrrolidone, is above 175°C, e. g. at least 180°C or at least 185°C. In particular, the treatment of the undissolved residue is carried out at a temperature of up to 250°C. In particular, in case of polyamide 6.6, the treatment of the undissolved residue is carried out at a temperature in the range of >175 to 250°C, in particular in the range of 180°C to 240°C and especially in the range of 185 to 230°C.

[0199] The amount of said organic solvent required for complete dissolution of polyamide B1, in particular polyamide 6.6, is generally at least 1 part by weight per 1 part by weight of the undissolved residue. Of course, a higher amount of organic solvent may be used. Generally, the amount of organic solvent will not exceed 100 parts by weight per 1 part by weight to the polyamide material and is preferably in the range of 1 to 20 parts by weight, in particular in the range of 2 to 15 parts by weight per 1 part by weight to the undissolved residue.

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[0202] Generally, the further treatment with the organic solvent is carried out until the undissolved residue is depleted in the polyamide B1 , in particular in polyamide 6.6, to at least 50% by weight, in particular at least 80% by weight or at least 90% by weight, based on the content of the polyamide B1, e. g. the polyamide 6.6 content, in the undissolved residue before the treatment. Especially, the further treatment is carried out until the polyamide B1, in particular the polyamide 6.6, contained in the undissolved residue is completely dissolved in the organic solvent and the undissolved residue does not contain polyamide B1. The time required for this will depend on the temperature and can be determined routinely by a skilled person. It may be in the range of 5 minutes to 2 h.

[0203] Apart from that, the treatment of the undissolved residue with the organic solvent, which preferably contains the gamma-valerolactone, can be carried out as described above for the treatment of the polyamide material.

[0204] Generally, the solution of the polyamide B1, in particular the polyamide 6.6, will then be separated from any undissolved material, if present, by conventional solid-liquid separations. For example, the separation may be achieved by filtration and / or centrifugation. Preferably, the solid liquid separation is carried out at an elevated temperature to avoid a precipitation of the polyamide B1 from the solution. In particular, the solid-liquid separations of the obtained solution from the undissolved residue is carried out at a temperature of above 175°C, e. g. at least 180°C or at least 185°C., e. g. at a temperature in the range of >175 to 250°C, in particular in the range of 180°C to 240°C and especially in the range of 185 to 230°C.

[0205] To recover the polyamide B1, in particular the polyamide 6.6, it is generally separated from the organic solvent. Preferably, the separation comprises the precipitation of the polyamide B1 from the solution of the polyamide B1 by cooling the solution or by addition of an anti-solvent to the solution or by combinations of these measures. For example, the cooling may be achieved by allowing the solution of the polyamide B1 without temperature control. However, it is also possible to control the cooling rate. For example, controlled cooling rates in the range of 0.1 to 10 K / min can be applied.

[0206] Anti-solvents are solvents, wherein the polyamide B1, e. g. the polyamide 6.6, is insoluble. Typical antisolvents are aliphatic hydrocarbons, cycloaliphatic hydrocarbons, water, alcohols, such as methanol, ethanol and mixtures thereof.

[0207] Preferably, the precipitation of the polyamide B1 from the solution of the polyamide B1 in the organic solvent is achieved by cooling of the solution. For this, the solution of the polyamide B is cooled to a temperature of below 110°C, in particular to a temperature in the range of 0 to 110°C especially in the range of 10 to 100°C.

[0208] The precipitated polyamide B1 is generally separated from the organic solvent, which can be carried out as described above for the separation of the polyamide A from the organic solvent. The thus recovered polyamide B1 is typically dried to remove the organic solvent before it is further used. The drying can be carried as described herein for the drying of the polyamide A.

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[0210] 23

[0211] The organic solvent which has been separated from the polyamide B1 can also be purified and / or recycled into the process of the present invention as described above.

[0212] The recovered polyamide B1, such as polyamide 6.6, can be used in the same way as fresh polyamide B1 for numerous purposes. For this, the recovered polyamide B1, which is typically obtained as a powder, may be converted into a granulate, e. g. by hot knock off granulation, hot-melt granulation, strain granulation or underwater granulation. If required, an annealing step can be performed in between in order to increase the chain length. Typically, the annealing step is carried out at a temperature in the range of 160 to 220 °C Typically, the annealing step is carried out under vacuum or in an inert atmosphere, I. g. under a blanket of inert gas, such as nitrogen or argon.

[0213] For example, the recycled polyamide B1, such as polyamide 6.6, can be incorporated into the article as part of mobile electronic devices, as automobile components, into textiles or as films. As used herein, a mobile electronic device refers to an electronic device that its user can easily carry and used in various locations. A mobile electronic device can include, but not limited to mobile computers such as a tablet computer, a laptop computer, a pocket calculator, portable media player, mobile internet device (MID), handheld PC, handheld game console, digital media player, mobile phones such as a smart phone, a phablet, wearable computers such as a smart watch, a head-mounted display, a virtual reality headsets, a digital camera, a global positioning system receiver, a portable power source, a portable Wi-Fi, a portable media player, a pocket calculator, and a e-book reader. The part herein is the one that at least partially comprises the polyamide composition. In some embodiments, the part could be a frame, housing, connector, cover, circuit board of the mobile electronic device. As used herein, the automobile component includes but not limited to interior and exterior automobile components, for example hoods, trunks, bumpers, grilles, side claddings, rocker panels, fenders, tail-gates, in wire and cable applications, instrument panels, consoles, interior trim, exterior trim, door panels, heater housings, battery supports, headlight housings, front ends, ventilator wheels, reservoirs, and soft pads. In some embodiments, the automobile component is an interior trim, console, and exterior trim. The recovered polyamide 6.6 may also be used for producing textiles.

[0214] The following figures and examples illustrate the invention.

[0215] Figure 1. IR spectra of polyamid 6 (rPA6) obtained as precipitate of the filtrate from example 3 in reference to virgin PA6 (Ultramid® B27).

[0216] Figure 2. IR spectra of polyamid 6.6 (rPA66) obtained as a residue of the NMP treatment in example 3 in reference to virgin PA66 (Ultramid® A27).

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[0219] Abbreviations:

[0220] ATR Attenuated total reflection

[0221] FTIR Fourier transform infrared spectroscopy

[0222] GPC Gel permeation chromatography

[0223] NMP: N-methyl-2-pyrrolidone

[0224] Mn number average molecular weight

[0225] Mw weight average molecular weight

[0226] PMMA Polymethylmethacrylate

[0227] Analytical methods:

[0228] Molecular weight:

[0229] Molecular weight of the polyamides was determined by gel permeation chromatography: Gel permeation chromatography measurements were carried out to observe changes in the molecular weight distribution of the original and recycled polyamides. For this, the dried polyamide samples were dissolved in hexafluoroisopropanol +0.1% trifluoroacetic acid potassium salt in a concentration of 10 mg / 4 mL and filtered through a 0.2 m filter. The sample were analyzed via a refractive index detector calibrated with PMMA-standards ranging from a molecular weight of 800 g / mol to 2200000 g / mol. A styrene-divinylbenzene column with exclusion limits of 100 and 100000 g / mol was used for sample separation. The measurement conditions were as follows: column temperature = 35 °C, eluent: hexafluoroisopropanol +0.1% trifluoroacetic acid potassium salt, column flow = 1 mL / min, injection volume = 50 piL

[0230] IR spectroscopy:

[0231] IR spectroscopy was carried out as ATR IR spectroscopy. The ATR spectra were obtained by FTIR spectrometers equipped with ATR units (Thermo Nicolet IS50 + diamond ATR unit). For measurement the samples were placed directly onto the ATR crystal without further preparation and were fixed with the unit's stamp. All measurements were performed at room temperature (25 °C) using 32 scans and a resolution of 4 cm’1.

[0232] PA6 and PA66 can be distinguished by characteristic bands in the fingerprint region with the major differences of PA6 to PA66 in the range of 500-550 cm1, 800-830 cm1, 850-950 erm1and 1100-1150 cm1.

[0233] Discoloration

[0234] The discoloration of the polyamide samples can be assessed by determining their L*a*b* values. For this, the samples were measured using an integrating sphere and UVA / IS-remission spectra (with a wavelength area of 400-700 nm). The data of these spectra were analyzed by the software OptLab-SPX using 2° standard observer and the standard light type C. The OptLab-SPX software calculates the L*a*b*-values based on DIN 5033 and DIN EN ISO 11664-1.6 from the years 2007-2014.

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[0237] Materials:

[0238] PA6 Ultramid® B27 of BASF SE

[0239] PA66 Ultramid® A27 of BASF SE

[0240] Example 1: Dissolution of PA6

[0241] 10 g of PA6 granules were placed in a reaction vessel (e.g. flask, tube, reaction vessel). 100 g of degassed NMP were added and the mixture was heated by use of a suitable heating system (e.g. oil bath, heating blocks, mini-plant vessels) to 160 °C under inert gas atmosphere, wherein PA6 fully dissolved upon visual inspection within 1-45 min. The hot solution was optionally filtered at 160°C over a heated solid-liquid separation unit (e. g. a heated filter plate) while PA6 was still dissolved. Thereafter the solution or filtrate was allowed to cool-down while the PA6 precipitated. The precipitate was filtrated and optionally washed with a small amount of NMP. For an easy removal of NMP and a faster drying process of the thus obtained PA6 powder, small amounts of acetone can optionally be used in a second washing step. The thus obtained powder was dried at 140°C and 20 mbar, for example in a vacuum compartment dryer. A probe of the thus obtained material was subjected to IR-spectroscopy and GPC.

[0242]

[0243]

[0244] Example 2: Dissolution of PA66 - 10 g of PA66 granules were placed in a reaction vessel (e.g. flask, tube, reaction vessel). 100 g of degassed NMP were added and the mixture was heated by use of a suitable heating system (e.g. oil bath, heating blocks, mini-plant vessels) to 185 °C under inert gas atmosphere, wherein PA66 was fully dissolved upon visual inspection within 1-45 min. The hot solution was optionally filtered at 185°C while over a heated solidliquid separation unit (e. g. a heated filter plate) while PA66 was still dissolved. Thereafter the solution or filtrate was allowed to cool-down while the PA66 precipitated. The precipitate was filtrated and optionally washed with a small amount of NMP. For an easy removal of NMP and a faster drying process of the reobtained PA66 powder, small amounts of acetone can optionally be used in a second washing step. The thus obtained powder was dried at 140°C and 20 mbar, for example in a vacuum compartment dryer. A probe of the thus obtained material was subjected to IR-spectroscopy and GPC.

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[0246]

[0247]

[0248] Example 3: Separation of PA6 and PA66

[0249] 10 g of a 1:1 mixture of PA66 granules and PA6 granules were placed in a reaction vessel (e.g. flask, tube, reaction vessel). 100 ml of degassed NMP were added and the mixture was heated by use of a suitable heating system (e.g. oil bath, heating blocks, mini-plant vessels) to 160 °C under inert gas atmosphere, so that a mixture was obtained, wherein PA6 was fully dissolved and PA66 remained as solid particles in the mixture after 60 min. The mixture was filtered at 160°C over a heated solid-liquid separation unit (e. g. a heated filter plate). The filter cake was optionally washed with pre-heated NMP. The PA6-enriched filtrate was allowed to cool-down while the PA6 precipitated. The precipitate was filtrated and optionally washed with a small amount of NMP. For an easy removal of NMP and a faster drying process of the re-obtained PA6 powder and the PA66-enriched residue of the solid-liquid separation, small amounts of acetone can optionally be used in an additional washing step. The thus obtained rPA6 powder and rPA66 were dried at 140°C and 20 mbar, for example in a vacuum compartment dryer. A probe of both the precipitate and the residue were subjected to IR-spectroscopy.

[0250] IR spectroscopy of both recovered polymers showed that the separation of PA6 and PA66 was successful. The rPA6 fraction is free of PA66 and the rPA66 fraction is free of PA6 (See Figures 1 and 2).

[0251] M / BASFTR-4207-PC

Claims

BASF SE 27 241069W001Claims1. A process for recovering an aliphatic polyamide from polyamide materials, which comprises treating said polyamide material with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam, to obtain a solution of said aliphatic polyamide in the organic solvent and an undissolved residue which is depleted in the aliphatic polyamide with respect to the content of aliphatic polyamide in the material before the treatment.

2. The process of claim 1 , where the polyamide material contains at least one aliphatic polyamide selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 6.10 and polyamide 6.12, polyamide 6.6, polyamide 4.6 and mixtures thereof.

3. The process of claim 1 , which is a process for recovering an aliphatic polyamide A having a melting point as determined by differential scanning calorimetry of less than 230°C from a polyamide material containing said polyamide A and at least one further component selected from polyamides B having a melting point of more than 230°C, pigments and fillers, which comprises treating said polyamide material with an organic solvent comprising saturated monocyclic N-Ci-C4-alkyl lactam, to obtain a solution of said polyamide A in the organic solvent and an undissolved residue which is depleted in the polyamide A with respect to the content of the polyamide A in the polyamide material before the treatment.

4. The process of claim 3, where the polymer A is selected from polyamide 6, polyamide 11 , polyamide 12, polyamide 6.10 and polyamide 6.12, and where the polyamide A is in particular polyamide 6.

5. The process of any one of claims 3 or 4, where the polyamide material contains at least one polyamide B.

6. The process of any one of claims 3 to 5, where the polyamide B is selected from aliphatic polyamides from the group of polyamide 6.6 and polyamide 4.6, semi-aromatic polyamides, such as polyamide 6T / 6I, and aromatic polyamides, such as aramide.

7. The process of any one of claims 3 to 6, where the polyamide A is separated from the organic solvent, where the separation comprises the precipitation of the polyamide A from the solution of the polyamide A, e. g. by cooling or by addition of an anti-solvent.

8. The process of any one of claims 3 to 7, where the polyamide material comprises a polyamide B and where the insoluble residue is subjected to a further treatment with an organic solvent at a temperature, where the polyamide B becomes soluble in the organic solvent to obtain a solution of said polyamide B.

9. The process of any one of the preceding claims, where the polyamide material contains polyamide 6 and polyamide 6.6.M / BASFTR-4207-PCBASF SE 28 241069W00110. The process of claim 9, which comprises treating said polyamide material with the organic solvent at a temperature in the range of 150 to 175°C to obtain a solution of polyamide 6 in the organic solvent and an undissolved residue which is depleted in polyamide 6 with respect to the content of the polyamide 6 in the polyamide material before the treatment, and a further treatment of the solid residue with an organic solvent comprising a saturated monocyclic N-Ci-C4-alkyl lactam at a temperature of above 180°C to obtain a solution of polyamide 6.6.

11. The process of any one of the preceding claims, where the organic solvent contains the saturated monocyclic N-Ci-C4-alkyl lactam in an amount of at least 50% by weight, based on the total weight of the organic solvent and where the organic solvent in particular consists of at least 95% by weight of N- methyl 2-py rrol idone, based on the total weight of the organic solvent.

12. The process of any one of the preceding claims, where the organic solvent is used in an amount of at least 1 part by weight, per 1 part by weight of the polyamide material.

13. The process of any one of the preceding claims, wherein the treatment is carried out until the polyamide material is depleted to at least 50% by weight with respect to the content of aliphatic polyamides in the starting polyamide material.

14. The process of any one of the preceding claims, wherein the polyamide material used in the treatment contains from 10 to 90% by weight of aliphatic polyamides, based on the total weight of the polyamide material.

15. The process of any one of the preceding claims, where the polyamide material is a particulate material having a particle size of not more than 50 mm, as determined by sieving.

16. The process of any one of the preceding claims, where the polyamide material comprises at least one of a polyamide containing waste materials, such as industrial waste, pre consumer waste and post consumer waste, pretreated polyamide containing waste materials, a presorted plastic waste materials containing polyamide, and polyamides or polyamide materials from other recycling processes.

17. The process of any one of the preceding claims, where the polyamide material is a pre-sorted plastic waste material containing at least 50% by weight of aliphatic polyamides with respect to the organic polymers contained in the pre-sorted plastic waste material.

18. The process of any one of the preceding claims, where the polyamide material is a presorted automotive shredder material or a presorted textile material.M / BASFTR-4207-PC

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