Recycling process

Abstract

The present invention relates to a process for recycling polyurethane from a composition comprising an elastic polyurethane (PU1) and at least one other material, the process comprising the steps of: providing a composition (CW) comprising polyurethane (PU1) and at least one other material; the composition (CW) is brought into contact with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1). The invention also relates to polyurethanes obtained or obtainable according to the method and to the use of the polyurethanes according to the invention for producing shaped articles.

Description

[0001] The present invention relates to a method for recycling polyurethane from a composition comprising an elastic polyurethane (PU1) and at least one other material, comprising the steps of: providing a composition (CW) comprising the polyurethane (PU1) and at least one other material; contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from cyclic amides at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1). The invention also relates to a polyurethane obtained or obtainable according to the method and to the use of the polyurethane according to the invention for producing shaped articles.

[0002] As the polyurethane production industry booms, the problem of removing and reusing polyurethane waste or off-specification goods also increases. Therefore, there is considerable interest in the industry to utilize the increasing amount of polyurethane waste for both ecological and economic reasons.

[0003] Different strategies have been proposed in the literature. US Pat. No. 4,115,298 A discloses a method for decomposing polyurethane waste into activated polyols that can be reused in the production of polyurethane plastics. The method broadly involves reacting polyurethane waste with a lactam or an equilibrium association of a lactam with an active hydrogen-containing compound at elevated temperature.

[0004] US Pat. No. 4,160,749 A also relates to a process for dissociating cellular and non-cellular polyurethane resins into reusable starting products for isocyanate polyaddition processes, wherein the polyurethane is reacted at elevated temperature with an association of a lactam and an adduct former having at least two Zerevitinoff-active hydrogen atoms.

[0005] Depolymerization is one way to recycle waste products. However, it is preferred to reuse the polyurethane without depolymerization, thereby reducing the cost of the process. For example, US 2005 / 0096400 A1 discloses a method for recycling polyurethane-containing materials. The method includes mixing the polyurethane-containing material with a solvent to form a solution of the polyurethane-containing material and the solvent.

[0006] Multi-material systems are difficult to recycle because not all waste components can be recycled using the same methods. Examples of multi-material systems are shoe scraps, mixed-material fibers, or composite materials. Classic polar organic solvents cannot be used on an industrial scale due to their cost, toxicity, explosion hazard, and high boiling point. There are no energy-efficient, non-toxic separation methods for the selective extraction of polyurethane (PU) from multi-material systems.

[0007] In particular, mixed fibers containing polyurethane (Spandex, PU) and polyamide are a problem for the textile industry, since even slight contamination with spandex (PU) is sufficient to prevent the recycling of polyamide fibers.

[0008] It is therefore an object of the present invention to provide a process for separating elastomeric polyurethane from other materials and additives that may be present in waste compositions.

[0009] This object is achieved by a method for recycling polyurethane from a composition comprising elastic polyurethane (PU1) and at least one other material, the method comprising the following steps

[0010] (a) providing a composition (CW) comprising a polyurethane (PU1) and at least one other material;

[0011] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from cyclic amides at a temperature below the boiling point of the alcohol,

[0012] To obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0013] Surprisingly, it has been found that polyurethanes can be selectively dissolved in a solvent mixture (SM) comprising an alcohol and a cyclic amide (e.g., a lactam) using the process according to the invention. It has been found that elastomeric polyurethanes can be dissolved without degrading the polymeric structure. This allows the polyurethane to be recovered from the composition without depolymerizing it. Consequently, the polyurethane can be easily separated from other materials, such as polyamide- or polyester-based fibers.

[0014] The polyurethane (PU1) is an elastic polyurethane, preferably a heat-processable polyurethane, in particular a thermoplastic polyurethane. It has been found that thermoplastic polyurethanes based on aromatic isocyanates can be readily dissolved in the solvent mixture (SM) and thus separated from other materials. Depending on the process conditions used, thermoplastic polyurethanes based on aromatic isocyanates can be separated from other polyurethane materials, such as thermoplastic polyurethanes based on aliphatic isocyanates.

[0015] Generally speaking, polyurethanes are produced by the reaction of a polyisocyanate component with a polyol component. Particularly suitable foams are, for example, thermoplastically processable foams, such as those disclosed in WO 2019 / 122122A1. Other materials such as flame retardants, polymerization catalysts, fillers, pigments, and surfactants may be added during the preparation of the polymer.

[0016] The organic polyisocyanate that can be used to prepare the polyurethane is any of the known organic diisocyanates and polyisocyanates, preferably aromatic isocyanates. Preferably, according to the present invention, an isocyanate component having a functionality in the range of 1.9 to 2.2, especially in the range of 1.95 to 2.1, more preferably in the range of 1.95 to 2.05, most preferably in the range of 1.96 to 2.03 is used.

[0017] Individual examples that may be mentioned are toluene 2,4- and 2,6-diisocyanate (TDI) and the corresponding isomer mixtures, diphenylmethane 4,4'-, 2,4'-, and 2,2'-diisocyanate (MDI) and the corresponding isomer mixtures, mixtures of diphenylmethane 4,4'- and 2,4'-diisocyanate, polyphenylpolymethylene polyisocyanate, and mixtures of diphenylmethane 4,4'-, 2,4'-, and 2,2'-diisocyanate. Organic diisocyanates and organic polyisocyanates can be used individually or in mixtures. If isocyanates with higher functionality are used in these mixtures, the functionality of the mixture preferably does not exceed 2.2. Furthermore, the proportion of the higher-functionality isocyanate, based on the total isocyanate mixture, must not exceed 10% by weight, preferably not more than 5% by weight.

[0018] Compounds that can be used to prepare polyurethanes having at least two hydrogen atoms reactive toward isocyanate groups are those having at least two reactive groups selected from OH groups, SH groups, NH groups, NH2 groups, and acidic CH groups. Preferably, polyols are used, and in particular polyether alcohols and / or polyester alcohols having an OH value in the range of 25 mg KOH / g to 800 mg KOH / g. According to the present invention, preferably a polyol component having a functionality in the range of 1.7 to 2.2, especially in the range of 1.7 to 2.1, more preferably in the range of 1.7 to 2.05, and most preferably in the range of 1.7 to 2.03 is used. Mixtures of polyols can also be used herein. If polyols with higher functionality are used in these polyol mixtures, the functionality of the mixture is preferably no more than 2.2. In addition, the proportion of the polyols with higher functionality must not exceed 10% by weight, preferably no more than 5% by weight, based on the total mixture of polyols.

[0019] The polyesterols used are prepared predominantly via condensation of polyols (preferably diols) having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, with polycarboxylic acids having 2 to 12 carbon atoms, for example succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid or preferably phthalic acid, isophthalic acid, terephthalic acid or the isomeric naphthalenedicarboxylic acids.

[0020] Polyether polyols of particular use are those prepared by known methods, for example by anionic polymerization of alkylene oxides onto H-functional starter substances in the presence of catalysts, preferably alkali metal hydroxides or double metal cyanide catalysts (DMC catalysts). The alkylene oxides used are primarily ethylene oxide or propylene oxide, or tetrahydrofuran, various butylene oxides or styrene oxide, and preferably pure 1,2-propylene oxide. The alkylene oxides can be used individually, in alternating succession, or in the form of mixtures. Starter substances of particular use are compounds having at least two, preferably two to eight, hydroxyl groups or at least two primary amino groups in the molecule. Preferred starting substances having at least two, preferably 2 to 8, hydroxyl groups in the molecule are trimethylolpropane, glycerol, pentaerythritol, sugar compounds (such as glucose, sorbitol, mannitol and sucrose), polyphenols, resols (for example, oligomeric condensates of phenol and formaldehyde, and Mannich condensates of phenol, formaldehyde and dialkanolamines), and melamine. Preferred starting substances having at least two primary amino groups in the molecule are aromatic diamines and / or polyamines, such as phenylenediamine, 2,3-toluenediamine, 2,4-toluenediamine, 3,4-toluenediamine and 2,6-toluenediamine, as well as 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane and 2,2'-diaminodiphenylmethane, and aliphatic diamines and polyamines, such as ethylenediamine. The polyether polyols preferably have a functionality of 2 to 8 and their preferred hydroxyl number is from 25 mg KOH / g to 800 mg KOH / g, in particular from 150 mg KOH / g to 570 mg KOH / g.

[0021] Other compounds having at least two isocyanate-reactive hydrogen atoms are chain extenders, which can be used concomitantly, if appropriate. Preferred chain extenders are alkanolamines and, in particular, diols having a molecular weight of less than 400, preferably from 60 to 300. The chain extenders or their mixtures are usefully employed in amounts of 1 to 20% by weight, preferably 2 to 5% by weight, based on the polyol component.

[0022] Common polyols used in large quantities are, for example, polyester polyols, low molecular weight polyols such as ethylene glycol or propylene glycol, or high molecular weight polyether polyols based on glycerol, ethylene glycol, polypropylene glycol, polytetramethylene glycol and polyester polyols.

[0023] Furthermore, one or more blowing agents may be present during the preparation of the elastic polyurethanes used. The blowing agents may be chemically active blowing agents and / or physically active compounds. Chemical blowing agents are understood to mean compounds which form gaseous products by reaction with isocyanates, for example water and carboxylic acids or carboxylic acid derivatives, for example hydrogen citrates, hydrogen carbonates or azodicarbonamides, such as or mixtures thereof, water being the preferred blowing agent.

[0024] Physical blowing agents are understood to mean compounds which are dissolved or emulsified in the raw materials for polyurethane production and which evaporate under the polyurethane formation conditions. These are, for example, hydrocarbons, halogenated hydrocarbons and other compounds, for example perfluorinated alkanes, such as perfluorohexane, hydrochlorofluorocarbons, as well as ethers, esters, ketones and / or acetals, for example (cyclo)aliphatic hydrocarbons with 4 to 8 carbon atoms, hydrofluoroolefins (HFOs), or gases, such as carbon dioxide, or mixtures thereof. In a preferred embodiment, the blowing agent used is a mixture of these blowing agents comprising water, more preferably only water.

[0025] In a preferred embodiment, the water content is 0.1% to 6% by weight, preferably 1% to 5% by weight, more preferably 2.5% to 4% by weight, based on the total weight of the elastic polyurethane foam.

[0026] Preferably, the polyurethane (PU1) is based on an isocyanate component having a functionality in the range from 1.9 to 2.2 and a polyol component having a functionality in the range from 1.7 to 2.2.

[0027] The term "aromatic diisocyanate" refers to a molecule having two isocyanate groups attached directly and / or indirectly to an aromatic ring. Aromatic diisocyanates typically have 8 to 18 carbon atoms. Examples of aromatic diisocyanates include, but are not limited to, 1,2-, 1,3-, and 1,4-phenylene diisocyanate, naphthylene-1,5-diisocyanate, 2,4- and 2,6-toluene diisocyanate, 2,4'-, 4,4'-, and 2,2'-diphenyl diisocyanate, 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate, 1,2-, 1,3-, and 1,4-phenylenediisocyanate, and meta-tetramethylphenylenediisocyanate (TMXDI), and mixtures thereof. Preferred aromatic diisocyanates are 2,4- and 2,6-toluene diisocyanate, 2,4′-, 4,4′- and 2,2′-diphenyl diisocyanate, 2,2′-, 2,4′- and 4,4′-diphenylmethane diisocyanate, 1,2-, 1,3- and 1,4-phenylenediisocyanate, meta-tetramethylxylylene diisocyanate (TMXDI), and mixtures thereof.

[0028] According to another embodiment, the present invention also relates to a process as disclosed above, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates.

[0029] Surprisingly, it has been found that the process according to the invention allows the selective dissolution of elastic polyurethanes, in particular thermally processable polyurethanes, using mild conditions and the separation of the remaining residues, such as polyamides, rubber, EVA, paint, soot, pigments, flame retardants, talc, glass fibers, textiles or even polyurethanes based on aliphatic isocyanates or thermosetting polyurethanes, by simple filtration.

[0030] In particular, thermoplastic polyurethanes with a low content of chain extenders are highly soluble in the solvent mixture (SM). Preferably, the content of chain extenders in the polyurethane (PU1) is less than 40%, more preferably less than 30%, and in particular less than 20%. In particular, the content of aliphatic chain extenders in the polyurethane (PU1) is less than 20%, more preferably less than 15%, and in particular less than 12.5%.

[0031] The method according to the present invention comprises steps (a) and (b). The method may further comprise other steps. According to step (a), a composition (CW) comprising a polyurethane (PU1) and at least one other material is provided. According to step (b), the composition (CW) is contacted with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from cyclic amides to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0032] The composition (CW) typically comprises other materials, such as other polymers or other waste materials. The composition may also comprise additives commonly used in polyurethanes, such as fillers such as chalk, flame retardants such as melamine or pigments.

[0033] The properties of suitable compositions (CW) which can be used in the process according to the invention may vary within wide ranges. Preferably, the elastomeric polyurethane is heat-processable, in particular thermoplastic and heat-processable.

[0034] According to the invention, any waste composition comprising elastic polyurethane, in particular comprising heat-processable polyurethane, can be used.For example, waste foam or mixed fibers comprising polyurethane can be used as starting material in step (a) of the process according to the invention.

[0035] The waste composition used in the present invention can generally be obtained from the following: articles produced at a certain time after the polyurethane has been used for the purpose for which it was manufactured. Before being subjected to step (a) of the method of the present invention, the articles can be subjected to mechanical crushing, that is, for example, by chopping, screening or separation by density ratio, that is, by air, liquid or magnetic force, to further sort the articles and make them into suitable sizes. Suitable separation methods can be supported by spectral analysis (such as, for example IR spectroscopy). Optionally, these fragments can then be treated to eliminate impurities, such as paper labels. Depending on the composition of the waste material, it can be extracted to remove soluble additives before step (a). The composition (CW) can, for example, contain other polymeric materials, but can also contain inorganic materials. Depending on the process conditions applied, different polyurethanes can also be separated, in particular, thermoplastic polyurethanes based on aliphatic isocyanates can be separated from thermoplastic polyurethanes based on aromatic isocyanates using mild conditions.

[0036] According to another embodiment, the present invention also relates to a process as disclosed above, wherein the composition (CW) comprises a polyurethane, a polyester and / or a cellulose-based polymer. According to another embodiment, the present invention also relates to a process as disclosed above, wherein the composition (CW) comprises a material selected from polyurethanes based on aliphatic isocyanates, thermosetting polyurethanes, rubber, ethylene-vinyl acetate copolymers, soot, talc, pigments or cellulose-based polymers.

[0037] The nature of the waste composition used as starting material in the process according to the invention can vary within wide ranges.

[0038] The waste compositions can be comminuted by conventional methods, for example as described in "Recycling von Polyurethan-Kunststoffen", W. (Heidelberg), 1994", for example by chopping at room temperature in a rotary mill or a tumbling ball mill to a particle size of typically less than 100 mm, or even less than 20 mm, or for example by grinding by known cold grinding methods. Particle sizes of less than 5 mm may also be selected, for example in the range of 0.01 mm to 5 mm, and preferably in the range of 0.01 mm to 1 mm.

[0039] According to another embodiment, the present invention also relates to a process as disclosed above, wherein before step (a) the composition (CW) is subjected to a mechanical treatment selected from grinding, beating, chopping, tearing and a mixture of two or more of these treatments.

[0040] According to the present invention, the composition (CW) can also be subjected to a heat treatment before step (a) of the method according to the present invention or between step (a) and step (b). The composition can be heated to a temperature in the range of 150°C to 220°C, preferably in the range of 150°C to 200°C, and more preferably in the range of 150°C to 170°C. Heating can be carried out, for example, for a duration of 1 minute to 120 minutes, preferably 10 minutes to 90 minutes, or particularly preferably 30 minutes to 60 minutes. Suitable techniques are generally known to those skilled in the art and include, for example, heating the composition in an oven. According to the present invention, the treatment can be carried out continuously or intermittently.

[0041] According to step (b), a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from cyclic amides is used. It has been found that the elastic polyurethane can be dissolved in the solvent mixture under mild conditions. Step (b) is carried out at a temperature below the boiling point of the alcohol used, for example at a temperature of 20°C to 50°C, preferably at a temperature of 15°C to 40°C, more preferably at a temperature of 20°C to 30°C. Typically, the treatment according to step (b) is carried out for a duration of 1 minute to 48 hours, preferably for a duration of 1 hour to 24 hours, in particular for a duration of 1 hour to 10 hours. According to the present invention, typically at least 50% by weight of the polyurethane (PU1) present in the composition is dissolved in the solvent mixture (SM), for example at least 60% by weight, preferably at least 70% by weight, and particularly preferably up to 100% by weight of the polyurethane (PU1) is dissolved in the solvent mixture (SM).

[0042] Compound (A1) is selected from cyclic amides. In principle, any cyclic amide can be used according to the invention as long as it can form a solvent mixture (SM) with an alcohol.

[0043] The cyclic amide is preferably selected from lactams, such as caprolactam and / or valerolactam, at least one cyclic urea or mixtures thereof, particularly preferably caprolactam.

[0044] Suitable cyclic amides are also, for example, cyclic ureas containing at least one cyclic urea of the general formula (I):

[0045]

[0046] Wherein -X- is a 1 to 6-membered group, preferably a 2 to 4-membered group and particularly preferably a 3-membered group, which may be substituted. This produces a cyclic urea structure according to formula (I), the ring of which (including the urea structure -NH-C(O)-NR-) has 4 to 9 members, in particular 6 members. Preferably, the members of the X group are selected from -NR 1 -、-O-、-CR 2 R 3-, -N= and -CR 4 =. In -CR 4 = or -N= group, the adjacent member is also composed of -CR 4 = or -N= members, so that a double bond can be formed between the two members. 1 to R 4 Each independently is hydrogen, an alkyl group, preferably ethyl or methyl, or a halogen, such as a fluoro group or a chloro group. In a very particularly preferred embodiment, X is -(CH2)3-. The group R according to formula (I) represents a substituted or unsubstituted alkyl or heteroalkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl-aryl or heteroalkyl-aryl group. Examples of possible substituents are halogen groups, alkyl groups, hydroxyl groups or amino groups. In a preferred embodiment of the present invention, R contains at least one isocyanate-reactive hydrogen atom, such as -OH or -NH2 group. Preferably, R is methyl, ethyl, propyl, pentyl, hexyl, one or more alkylene oxide moieties, such as ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide, and phenyl or phenyl ether. R is particularly preferably -methyl, ethyl, ethylene oxide, alkylene oxide or phenyl methoxy ester, and very particularly preferably methyl. Bridged cyclic urea structures can also be used as cyclic urea compounds, wherein two cyclic urea structures are bridged via the group R.

[0047] R is very particularly preferably a straight-chain, unsubstituted hydrocarbon radical selected from the group consisting of methyl, ethyl, propyl, pentyl and hexyl, in particular R is a methyl radical.

[0048] Preferably, compound (A1 ) is a lactam. According to another embodiment, the present invention also relates to a process as disclosed above, wherein compound (A1 ) is a lactam.

[0049] Particularly suitable examples include lactams of ω-aminocarboxylic acids, such as 3-aminopropionic acid, 4-aminobutyric acid, 5-aminopentanoic acid, 6-aminohexanoic acid or 10-aminodecanoic acid; N-substituted azalactams, such as 1-N-methyl-hexahydro-1,4-diazepinone-(3); 1-N-butyl-hexahydro-1,4-diazepinone-(3); 1-N-α-pyridyl-hexahydro-1,4-diazepinone-(3); and the like.

[0050] Particularly suitable are, for example, 2-pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam. According to another embodiment, the present invention also relates to a process as disclosed above, wherein the lactam is selected from the group consisting of 2-pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam.

[0051] Suitable alcohols for the solvent mixture (SM) are in particular monohydric alcohols and diols having 1 to 12 carbon atoms, in particular 1 to 6 carbon atoms, such as methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol or butanediol. According to another embodiment, the present invention also relates to a process as disclosed above, wherein the alcohol is selected from methanol, ethanol and propanol.

[0052] According to the invention, the solvent mixture (SM) may also contain two or more lactams or two or more alcohols. The mixing ratio of the lactams and alcohols can vary within a wide range as long as a homogeneous solution is obtained. Preferably, the molar ratio of the at least one lactam to the at least one alcohol in the solvent mixture (SM) is in the range of 2:1 to 1:2, in particular in the range of 1.5:1 to 1:1.5, more preferably in the range of 1.2:1 to 1:1.2.

[0053] According to another embodiment, the present invention also relates to a process as disclosed above, wherein the molar ratio of the at least one lactam to the at least one alcohol in the solvent mixture (SM) is in the range of 2:1 to 1:2.

[0054] The solvent mixture (SM) is used in an amount suitable for dissolving the polyurethane (PU1) in step (b) of the process according to the invention. The appropriate amount depends on the solvent mixture and the polyurethane used. Typically, the weight ratio of the composition (CW) to the solvent mixture (SM) is in the range of 1:2 to 1:20, preferably in the range of 1:2 to 1:10.

[0055] According to another embodiment, the present invention also relates to a process as disclosed above, wherein the weight ratio of the composition (CW) to the solvent mixture (SM) is in the range of 1 :2 to 1 :20.

[0056] According to step (b), a solution (S1) rich in dissolved polyurethane (PU1) is obtained. Typically, the composition (CW) is not completely dissolved, and the residue is not soluble in the solvent mixture (SM) used under the applied process conditions. The solution (S1) is preferably separated from the insoluble residue by a suitable separation step.

[0057] According to another embodiment, the present invention also relates to the method as disclosed above, wherein the method further comprises the step (c)

[0058] (c) separation of the solution (S1) enriched in dissolved polyurethane (PU1) and the residue of the composition (CW) obtained in (b).

[0059] This separation can be carried out in a manner known to those skilled in the art in conventional apparatus. Suitable methods are in particular physical separation methods, such as filtration, decantation or centrifugation, in particular filtration. According to another embodiment, the invention also relates to a method as disclosed above, wherein the separation according to step (c) is carried out by a physical separation method.

[0060] The separation, in particular the filtration, can be carried out discontinuously in batch mode or continuously or semi-continuously.

[0061] After separation, suitable washing steps may be applied according to the process of the invention.

[0062] According to the present invention, step (b) and step (c) and optionally, a washing step can also be combined. For example, step (b) and step (c) can be combined as a washing step or an extraction step. Suitable devices are in principle known to those skilled in the art.

[0063] In this case, it is also possible to remove the polyurethane from the other components of the composition (CW), for example the fibers present in the composition (CW), such as glass fibers or polyamide fibers, and allow recycling of said other components.

[0064] According to step (c), a solution (S1) is obtained. The polyurethane (PU1) can be recovered from the solution (S1) using a suitable method. For example, the solvent can be removed to obtain the polyurethane itself. According to the present invention, a suitable compound can also be added to the solution (S1) to cause the precipitation of the polyurethane. For example, water can be added to the solution in a suitable amount to cause the precipitation of the polyurethane, which can then be separated using a filtration step.

[0065] According to another embodiment, the present invention also relates to the method as disclosed above, wherein the method further comprises the step (d)

[0066] (d) adding water to the solution (S1) to obtain polyurethane.

[0067] According to the present invention, step (d) can be carried out by adding water to the solution (S1) as is or after suitable treatment, for example after at least partial removal of the solvent. According to another embodiment of the present invention, one or more components of the solvent mixture are removed before step (d), or the solvent mixture is partially removed before step (d).

[0068] According to another alternative embodiment, the present invention also relates to the process as disclosed above, wherein the process further comprises step (d*)

[0069] (d*) Removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1).

[0070] According to the invention, it is also possible to remove one or more components of the solvent mixture or to remove only part of the solvent mixture. In particular, alcohols present in the solvent mixture can be easily removed, for example at ambient temperature under reduced pressure.

[0071] The process of the present invention may also comprise additional steps, such as a washing step or a drying step for removing traces of residual solvent.

[0072] According to the invention, the solution (S1) obtained in step (d) itself can also be used to produce shaped articles. Methods for producing shaped articles from solutions containing dissolved polyurethane are known in principle to those skilled in the art and include, for example, methods for producing films or methods for producing synthetic leather, or methods for producing fibers from solutions, such as spinning methods. Suitable methods are disclosed, for example, in "New materials permeable to water vapor", H. Springer-Verlag, 1999, Chapter 8.

[0073] The method according to the invention comprises steps (a) and (b), and optionally (c) and / or (d) / (d*), but may also comprise further steps. The method may, for example, comprise further purification steps or heat treatment. According to another embodiment, the invention also relates to the method as disclosed above, wherein the method comprises further purification steps.

[0074] Suitable work-up steps are known in principle to the person skilled in the art. Suitable work-up and / or purification steps can be carried out between steps (a) and (b), between steps (b) and (c) or between steps (c) and (d).

[0075] According to another aspect, the present invention also relates to a polyurethane obtainable or obtainable according to the process as disclosed above. Preferably, the polyurethane obtained is thermoplastic and preferably heat treatable, for example by extrusion or injection molding.

[0076] The polyurethane obtained according to the inventive method can be used in any suitable application without further modification. It is also possible to use polyurethane mixed with other compounds, in particular other polyurethanes or additives, to prepare shaped articles. It is also possible to prepare blends comprising the polyurethane obtained according to the present invention.

[0077] In principle, processes for producing shaped articles from polyurethanes are known to those skilled in the art.

[0078] According to a further aspect, the present invention also relates to the use of the polyurethane according to the invention or the polyurethane obtainable or obtainable by the process according to the invention for producing shaped articles.

[0079] In principle, the polyurethane (PU1) obtained in this process can be reused as is. However, for some applications, it may be advantageous to subject the polyurethane (PU1) to a treatment suitable for obtaining individual building blocks, which can in turn be separated and reused, for example, for the preparation of polyurethanes. For example, the polyurethane (PU1) can be depolymerized and the resulting components reused. Methods for depolymerizing polyurethanes are generally known to those skilled in the art and include, for example, hydrolysis, glycolysis, or aminolysis.

[0080] According to another embodiment, the present invention also relates to the method as disclosed above, wherein the method further comprises the step (e)

[0081] (e) Depolymerization of polyurethane (PU1).

[0082] Suitable depolymerization conditions are known in principle to those skilled in the art. Preferably, the depolymerization according to step (e) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation or aminolysis. According to another embodiment, the present invention also relates to a method as disclosed above, wherein the depolymerization according to step (e) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation or aminolysis.

[0083] Preferably, the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base. The resulting depolymerization product can be separated using a suitable separation technique.

[0084] According to another embodiment, the present invention also relates to a process as disclosed above, wherein the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base.

[0085] Methods for depolymerization by glycolysis are also known in principle. Preferably, the glycolysis is carried out in the presence of a base. Therefore, according to another embodiment, the present invention also relates to a method as disclosed above, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0086] Suitable methods for depolymerization by hydrogenation include hydrogenation in the presence of a hydrogenation catalyst.Thus, according to another embodiment, the present invention also relates to a process as disclosed above, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0087] Typically, depolymerization produces a mixture of components that can be separated using suitable separation techniques.The process according to the invention may also comprise separating the isocyanate component or its amine derivative from the polyol component.

[0088] According to another embodiment, the present invention also relates to the process as disclosed above, wherein the process further comprises the step (f)

[0089] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0090] The work-up of the depolymerization products, in particular the separation of the polyamines and polyols, can be achieved as appropriate, for example, by extractive work-up, precipitation of the amine component as a hydrochloride, precipitation as a urea (in the case of aminolysis), chromatography or distillation under reduced pressure. Preferably, the work-up comprises several steps.

[0091] In post-processing by distillation, the compounds are separated according to their volatility, with the more volatile compounds being separated first. Additives, water, or solvents used in the depolymerization can also be removed by distillation before further post-processing of the polyol-polyamine mixture. Generally speaking, the "volatility" of a liquid can be described using its vapor pressure, with a high vapor pressure indicating high volatility, and vice versa.

[0092] In the case where the polyamine is more volatile than the polyol, as is the case for TDA, MDA and NDA, the polyamine is recovered from the depolymerization product via distillation, preferably via reduced pressure distillation. After the polyamine has been distilled off, a distillation residue containing the polyol remains.

[0093] Suitable distillation conditions are known in principle to those skilled in the art.

[0094] Alternatively, the polyols can be recovered from the depolymerization mixture by extraction using a suitable extractant or a pair of extractants. The polyamine component can also be precipitated as its hydrochloride salt by adding HCl and extracting the polyol component with a suitable solvent, such as described in DE 2854940 A1, which preferably dissolves the polyol component but not the hydrochloride salt of the polyamine component. The hydrochloride salt of the polyamine component can then be converted to the free polyamine after separation by adding a base, but can also be used directly for phosgenation to produce new polyisocyanates for polyurethane synthesis. In the case of MDA*HCl, the hydrochloride salt can be used in the MDA synthesis step by condensation of aniline and formaldehyde.

[0095] It will be understood that the above-described separation methods may be combined with any of the various embodiments of the methods of the present invention described herein.

[0096] The polyol composition obtained during the depolymerization process as well as the isocyanate can be reused, for example, in the preparation of polyurethanes. According to another aspect, the present invention also relates to a polyol composition obtainable or obtainable according to a process as claimed in any one of the claims disclosed above.

[0097] According to another aspect, the present invention also relates to the use of the polyol composition or the polyol composition obtainable or obtainable according to the process of the present invention for preparing polyurethanes or polyisocyanurates.

[0098] Further embodiments of the invention can be found in the claims and examples. It is understood that the features of the subject matter / method / use according to the invention described above and explained below can be used not only in the combination specified in each case, but also in other combinations without departing from the scope of the invention. For example, the combination of preferred features with particularly preferred features or the combination of features not further characterized with particularly preferred features, etc., is also implicitly included, even if this combination is not explicitly mentioned.

[0099] The following lists exemplary embodiments of the present invention, but these do not limit the present invention. In particular, the present invention also covers those embodiments resulting from the dependent references and the combinations specified below.

[0100] 1. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, the method comprising the following steps

[0101] (a) providing a composition comprising elastic polyurethane (PU1) and at least one other material

[0102] (CW);

[0103] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0104] 2. The method according to embodiment 1, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates.

[0105] 3. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0106] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0107] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0108] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0109] 4. The method according to any one of embodiments 1 to 3, wherein the composition (CW) comprises polyamide, polyester and / or cellulose-based polymer.

[0110] 5. The method according to any one of embodiments 1 to 4, wherein the composition (CW) comprises a material selected from polyurethanes based on aliphatic isocyanates, thermosetting polyurethanes, rubber, ethylene-vinyl acetate copolymers, soot, talc, pigments or cellulose-based polymers.

[0111] 6. The method according to any one of embodiments 1 to 5, wherein compound (A1) is a lactam.

[0112] 7. The method according to any one of embodiments 1 to 6, wherein compound (A1) is selected from

[0113] 2-Pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam.

[0114] 8. The method according to any one of embodiments 1 to 7, wherein the alcohol is selected from methanol,

[0115] Ethanol and propanol.

[0116] 9. The process according to any one of embodiments 1 to 8, wherein the lactam is selected from 2-pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam, and the alcohol is selected from methanol, ethanol and propanol.

[0117] 10. The process according to any one of embodiments 1 to 9, wherein the lactam is ε-caprolactam and the alcohol is selected from methanol, ethanol and propanol, preferably methanol.

[0118] 11. The process according to any one of embodiments 1 to 10, wherein the molar ratio of at least one lactam to the at least one alcohol in the solvent mixture (SM) is from 2:1 to 1:2.

[0119] 12. The method according to any one of embodiments 1 to 11, wherein the method further comprises step (c)

[0120] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and the residue of said composition (CW) obtained in (b).

[0121] 13. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0122] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0123] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0124] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b).

[0125] 14. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0126] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0127] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0128] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0129] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0130] 15. The method according to any one of embodiments 12 to 14, wherein the separation according to step (c) is performed by a physical separation method.

[0131] 16. The method according to any one of embodiments 1 to 15, wherein before step (a) the composition (CW) is subjected to a mechanical treatment selected from grinding, beating, chopping, tearing and a mixture of two or more of these treatments.

[0132] 17. The method according to any one of embodiments 1 to 16, wherein the method further comprises step (d)

[0133] (d) adding water to the solution (S1) to obtain polyurethane.

[0134] 18. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0135] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0136] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0137] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0138] (d) adding water to the solution (S1) to obtain polyurethane.

[0139] 19. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0140] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0141] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0142] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0143] (d) adding water to the solution (S1) to obtain polyurethane.

[0144] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0145] 20. The method according to any one of embodiments 1 to 16, wherein the method further comprises step (d*)

[0146] (d*) Removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1).

[0147] 21. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0148] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0149] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0150] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0151] (d*) Removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1).

[0152] 22. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0153] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0154] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0155] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0156] (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1),

[0157] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0158] 23. The method according to any one of embodiments 17 to 22, further comprising step (e)

[0159] (e) Depolymerization of polyurethane (PU1).

[0160] 24. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0161] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0162] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0163] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0164] (d) adding water to the solution (S1) to obtain polyurethane.

[0165] (e) Depolymerization of polyurethane (PU1).

[0166] 25. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0167] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0168] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0169] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0170] (d) adding water to the solution (S1) to obtain polyurethane.

[0171] (e) depolymerizing the polyurethane (PU1),

[0172] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0173] 26. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0174] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0175] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0176] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0177] (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1),

[0178] (e) depolymerizing the polyurethane (PU1).

[0179] 27. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0180] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0181] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0182] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0183] (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1),

[0184] (e) depolymerizing the polyurethane (PU1),

[0185] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0186] 28. The method according to any one of embodiments 23 to 27, wherein the depolymerization according to step (e) is performed by a method selected from hydrolysis, glycolysis, hydrogenation or aminolysis.

[0187] 29. The method according to any one of embodiments 23 to 28, wherein the method further comprises step (f)

[0188] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0189] 30. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0190] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0191] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0192] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0193] (d) adding water to the solution (S1) to obtain polyurethane.

[0194] (e) depolymerizing the polyurethane (PU1),

[0195] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0196] 31. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0197] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0198] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0199] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0200] (d) adding water to the solution (S1) to obtain polyurethane.

[0201] (e) depolymerizing the polyurethane (PU1),

[0202] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0203] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0204] 32. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0205] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0206] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0207] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0208] (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1),

[0209] (e) depolymerizing the polyurethane (PU1),

[0210] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0211] 33. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the following steps

[0212] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0213] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol, so as to obtain a solution (S1) rich in dissolved polyurethane (PU1),

[0214] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b),

[0215] (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1),

[0216] (e) depolymerizing the polyurethane (PU1),

[0217] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0218] The polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate.

[0219] 34. Polyurethane obtainable or obtainable according to a process according to any one of embodiments 1 to 22.

[0220] 35. Use of the polyurethane according to embodiment 34 or a polyurethane obtainable or obtainable by a process according to any one of embodiments 1 to 22 for producing shaped articles.

[0221] 36. Polyol composition obtainable or obtainable according to the process according to any one of embodiments 23 to 33.

[0222] 37. Use of the polyol composition according to embodiment 36 or the polyol composition obtainable or obtainable according to the process according to any one of embodiments 23 to 33 for the preparation of polyurethanes or polyisocyanurates.

[0223] 38. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the steps of

[0224] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material;

[0225] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0226] 39. The method according to embodiment 38, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates.

[0227] 40. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the steps of

[0228] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate;

[0229] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0230] 41. The process according to any one of embodiments 38 to 40, wherein the content of chain extender in the polyurethane (PU1) is lower than 40%.

[0231] 42. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the steps of

[0232] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanate and wherein the content of chain extender in the polyurethane (PU1) is less than 40%;

[0233] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0234] 43. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, said method comprising the steps of

[0235] (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material, wherein the content of chain extender in the polyurethane (PU1) is less than 40%;

[0236] (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0237] 44. The method according to any one of embodiments 38 to 43, wherein the composition (CW) comprises polyamide, polyester and / or cellulose-based polymer.

[0238] 45. The method according to any one of embodiments 38 to 44, wherein the composition (CW)

[0239] Contains a material selected from aliphatic isocyanate-based polyurethanes, thermosetting polyurethanes, rubber, ethylene-vinyl acetate copolymers, soot, talc, pigments or cellulose-based polymers.

[0240] 46. The method according to any one of embodiments 38 to 45, wherein compound (A1) is a lactam.

[0241] 47. The method according to any one of embodiments 38 to 46, wherein compound (A1) is selected from 2-pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam.

[0242] 48. The method of any one of embodiments 38 to 47, wherein the alcohol is selected from methanol, ethanol, and propanol.

[0243] 49. The process according to any one of embodiments 38 to 48, wherein the molar ratio of the at least one lactam to the at least one alcohol in the solvent mixture (SM) is from 2:1 to 1:2.

[0244] 50. The method according to any one of embodiments 38 to 49, further comprising step (c)

[0245] (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and said residue of said composition (CW) obtained in (b).

[0246] 51. The method according to embodiment 50, wherein the separation according to step (c) is performed by a physical separation method.

[0247] 52. The method according to any one of embodiments 38 to 51, wherein before step (a) the composition (CW) is subjected to a mechanical treatment selected from grinding, beating, chopping, tearing and a mixture of two or more of these treatments.

[0248] 53. The method according to any one of embodiments 38 to 52, further comprising step (d)

[0249] (d) adding water to the solution (S1) to obtain polyurethane.

[0250] 54. The method according to any one of embodiments 38 to 52, further comprising step (d*)

[0251] (d*) Removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1).

[0252] 55. The method according to embodiment 53 or 54, wherein the method further comprises step (e)

[0253] (e) depolymerizing the polyurethane (PU1).

[0254] 56. The method according to embodiment 55, wherein the depolymerization according to step (e) is performed by a method selected from hydrolysis, glycolysis, hydrogenation or aminolysis.

[0255] 57. The method according to any one of embodiments 55 or 56, wherein the method further comprises step (f)

[0256] (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

[0257] 58. Polyurethane obtainable or obtainable according to a process according to any one of embodiments 38 to 54.

[0258] 59. Use of the polyurethane according to embodiment 58 or the polyurethane obtainable or obtainable by the process according to any one of embodiments 38 to 54 for the preparation of shaped articles.

[0259] 60. Polyol composition obtainable or obtainable according to the process according to any one of embodiments 55 to 57.

[0260] 61. Use of the polyol composition according to embodiment 60 or a polyol composition obtainable or obtainable according to the process according to any one of embodiments 55 to 57 for the preparation of polyurethanes or polyisocyanurates.

[0261] The present invention is further described by way of examples. The examples relate to practical and in some cases preferred embodiments of the present invention and do not limit the scope of the invention. Example

[0262] 1. Example 1

[0263] Various samples of post-consumer athletic shoe waste composed of different materials (PU, textile fibers, EVA, rubber, styrene block copolymer) were tested. Different samples contained varying amounts of elastic PU.

[0264] 300 g of each sample was added to 1.5 L of caprolactam / MeOH solution and the mixture was stirred at room temperature overnight. The resulting suspension was then filtered and all insoluble components removed. The insoluble components of the sample were washed with water and emerged unchanged from the process, allowing the material to be recycled separately.

[0265] 1.5 L of water was added to the solution to form a precipitate. The precipitate was filtered out and washed with water. Depending on the sample, up to 65% by weight of material, based on the weight of the waste composition, was isolated. This material was characterized by IR spectroscopy and processed on an extruder. For comparison, a thermoplastic polyurethane having a similar composition according to IR spectroscopy was processed on the extruder in the same manner.

[0266] The characteristics of the samples are summarized in Table 1.

[0267] Table 1

[0268] New TPU Recirculated samples Molecular weight [g / mol] 82 000 84 000 Shore hardness 73 74 Tensile strength [MPa] 22 16 Elongation at break [%] 720 810

[0269] 2. Solubility of thermoplastic polyurethane

[0270] To test the solubility of different TPU samples, 1g of TPU sample was cut into small pieces and added to a mixture of 15g of caprolactam and methanol. The mixture was stirred at room temperature.

[0271] The results are summarized in Table 2.

[0272] Table 2

[0273]

[0274]

[0275] (*) Increase the amount of chain extender from sample P to sample S

[0276] Comparison of chain extender content :

[0277] Sample S > Sample R > Sample Q > Sample P

[0278] Sample C > Sample B > Sample A

[0279] Surprisingly, only TPUs based on aromatic isocyanates are soluble in a mixture of caprolactam and methanol. In the test series, no aliphatic TPUs dissolved under the conditions used.

[0280] Furthermore, it was observed that higher levels of aliphatic chain extenders reduced the solubility. If the respective content was too high, the TPU was no longer soluble at room temperature (see sample H vs. sample I or sample P vs. sample R (samples P, R, and S consist of the same raw materials and differ only in their weight ratios)).

[0281] References :

[0282] US4115298A

[0283] US4160749A

[0284] "Recycling von Polyurethan-Kunststoffen",W. (Heidelberg), 1994

[0285] "New materials permeable to water vapor",H. Springer-Verlag, 1999, Chapter 8

Claims

1. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one other material, the method comprising the following steps (a) providing a composition (CW) comprising an elastic polyurethane (PU1) and at least one other material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) chosen from cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1). 2 . The method according to claim 1 , wherein the polyurethane ( PU1 ) is a thermoplastic polyurethane based on aromatic isocyanates.

3. The process according to any one of claims 1 or 2, wherein the content of chain extenders in the polyurethane (PU1) is less than 40%.

4. The method according to any one of claims 1 to 3, wherein the composition (CW) comprises polyamide, polyester and / or cellulose-based polymer.

5. The method according to any one of claims 1 to 4, wherein the composition (CW) comprises a material selected from polyurethanes based on aliphatic isocyanates, thermosetting polyurethanes, rubber, ethylene-vinyl acetate copolymers, soot, talc, pigments or cellulose-based polymers.

6. The process according to any one of claims 1 to 5, wherein compound (A1) is a lactam.

7. The process according to any one of claims 1 to 6, wherein compound (A1) is selected from 2-pyrrolidone, 2-piperidone, ε-caprolactam and laurolactam.

8. The process according to any one of claims 1 to 7, wherein the alcohol is selected from methanol, ethanol and propanol.

9. The process according to any one of claims 1 to 8, wherein the molar ratio of at least one lactam to the at least one alcohol in the solvent mixture (SM) is in the range from 2:1 to 1:

2.

10. The method according to any one of claims 1 to 9, wherein the method further comprises step (c) (c) separating said solution (S1) enriched in dissolved polyurethane (PU1) and the residue of said composition (CW) obtained in (b).

11. The method according to claim 10, wherein the separation according to step (c) is performed by a physical separation method.

12. The process according to any one of claims 1 to 11, wherein before step (a) the composition (CW) is subjected to a mechanical treatment selected from grinding, beating, chopping, tearing and mixtures of two or more of these treatments.

13. The method according to any one of claims 1 to 12, wherein the method further comprises step (d) (d) adding water to the solution (S1) to obtain the polyurethane.

14. The method according to any one of claims 1 to 12, wherein the method further comprises step (d*) (d*) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1).

15. The method according to claim 13 or 14, wherein the method further comprises step (e) (e) depolymerizing the polyurethane (PU1).

16. The method according to claim 15, wherein the depolymerization according to step (e) is performed by a method selected from hydrolysis, glycolysis, hydrogenation or aminolysis.

17. The method according to any one of claims 15 or 16, wherein the method further comprises step (f) (f) separating the isocyanate component or its amine derivative from the polyol component obtained in the depolymerization.

18. Polyurethane obtainable or obtainable according to a process according to any one of claims 1 to 14.

19. Use of the polyurethane according to claim 18 or the polyurethane obtainable or obtainable by the process according to any one of claims 1 to 14 for producing shaped articles.

20. A polyol composition obtainable or obtainable according to a process according to any one of claims 15 to 17.

21. Use of the polyol composition according to claim 20 or a polyol composition obtainable or obtainable according to the process according to any one of claims 15 to 17 for the preparation of polyurethanes or polyisocyanurates.

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