Recycling methods

Abstract

The present invention relates to a method for recycling polyurethanes from a composition comprising an elastomeric polyurethane (PU1) and at least one further material, the method comprising the steps of providing a composition (CW) comprising a polyurethane (PU1) and at least one further material, and contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of 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 the polyurethanes obtained or obtainable by said method, as well as to the use of the polyurethanes according to the invention for preparing molded articles.

Description

[Technical Field]

[0001] The present invention relates to a method for recycling polyurethanes from a composition comprising an elastomeric polyurethane (PU1) and at least one further material, the method comprising the steps of providing a composition (CW) comprising a polyurethane (PU1) and at least one further material, and contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of 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 the polyurethanes obtained or obtainable by said method, as well as to the use of the polyurethanes according to the invention for preparing molded articles.

[0002] With the vigorous growth of the polyurethane manufacturing industry, the problem of removing and recycling polyurethane waste or rejects has increased simultaneously. Therefore, there is great interest in industrially utilizing the ever-increasing amount of polyurethane waste from both an environmental and economic standpoint.

[0003] Various strategies have been proposed in the literature. U.S. Pat. No. 4,115,298 discloses a method for splitting polyurethane waste into activated polyhydroxyl compounds that can be reused in the production of polyurethane plastics. The method generally involves reacting polyurethane waste with lactams or equilibrium associates of lactams and active hydrogen-containing compounds at high temperatures.

[0004] Also, U.S. Pat. No. 4,160,749 is directed to a method for dissociating foamed and non-foamed polyurethane resins into reusable starting products for an isocyanate polyaddition process, in which the polyurethane is reacted at elevated temperatures with a combination of a lactam having at least two Zerewitinoff-active hydrogen atoms and an adduct-forming agent.

[0005] Depolymerization is one method for recovering waste materials. However, it would be preferable to reuse polyurethane without depolymerization to reduce the cost of the process. For example, U.S. Patent Application Publication No. 2005 / 0096400 discloses a method for recycling polyurethane-containing materials. The method includes combining 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 in the same way. Examples of multi-material systems are shoe scraps, mixed material fibers, or composites. Conventional polar organic solvents cannot be used on an industrial scale due to their cost, toxicity, explosion risk, and high boiling point. No energy-efficient, non-toxic separation method exists to selectively extract polyurethane (PU) from multi-material systems.

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

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

[0009] The object is to provide a method for recycling polyurethane from a composition comprising an elastomeric polyurethane (PU1) and at least one further material, the method comprising: (a) providing a composition (CW) comprising a polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); The problem is solved by a method including:

[0010] Surprisingly, it has been found that the method of the present invention can be used to selectively dissolve polyurethane in a solvent mixture (SM) containing an alcohol and a cyclic amide, such as a lactam. It has been found that elastomeric polyurethanes can be dissolved without decomposition of the polymer structure. This allows the polyurethane to be recovered from the composition without depolymerization. Therefore, polyurethanes can be easily separated from other materials, such as polyamide- or polyester-based fibers.

[0011] The polyurethane (PU1) is an elastic polyurethane, preferably a heat-processable polyurethane, particularly a thermoplastic polyurethane. It has been found that aromatic isocyanate-based thermoplastic polyurethanes in particular can be easily dissolved in the solvent mixture (SM) and thus separated from other materials. Depending on the process conditions used, for example, aromatic isocyanate-based thermoplastic polyurethanes can be separated from other polyurethane materials, such as aliphatic isocyanate-based thermoplastic polyurethanes.

[0012] Generally, polyurethanes are produced by the reaction between a polyisocyanate component and a polyol component. For example, particularly suitable foams are those that can be thermoplastically processed, such as those disclosed in WO 2019 / 122122. Additional materials, such as flame retardants, polymerization catalysts, fillers, pigments, and surfactants, can be added during the polymer production process.

[0013] The organic polyisocyanates that can be used in preparing the polyurethanes are any of the known organic diisocyanates and polyisocyanates, preferably aromatic isocyanates. Preferably, the present invention uses an isocyanate component having a functionality in the range of 1.9 to 2.2, particularly in the range of 1.95 to 2.1, more preferably in the range of 1.95 to 2.05, and most preferably in the range of 1.96 to 2.03.

[0014] Examples that may be mentioned include tolylene 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. The organic diisocyanates and polyisocyanates can be used individually or in the form of mixtures. When higher-functionality isocyanates are used in these mixtures, the functionality of the mixture is preferably 2.2 or less. Furthermore, the proportion of higher-functionality isocyanates should be 10% by weight or less, preferably 5% by weight or less, based on the total isocyanate mixture.

[0015] Compounds that can be used to prepare polyurethanes having at least two hydrogen atoms reactive with isocyanate groups are compounds having at least two reactive groups selected from OH, SH, NH, NH2, and acidic CH groups. Polyols, particularly polyether alcohols and / or polyester alcohols with an OH value in the range of 25 to 800 mg KOH / g, are preferably used. According to the present invention, polyol components having a functionality in the range of 1.7 to 2.2, particularly 1.7 to 2.1, more preferably 1.7 to 2.05, and most preferably 1.7 to 2.03, are preferably used. Mixtures of polyols can also be used. When polyols with higher functionality are used in these polyol mixtures, the functionality of the mixture is preferably 2.2 or less. Furthermore, the proportion of the higher functionality polyols should be 10% by weight or less, preferably 5% by weight or less, based on the entire polyol mixture.

[0016] The polyester alcohols used are mainly prepared by condensation of polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, with polybasic carboxylic acids having 2 to 12 carbon atoms, such as 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.

[0017] The polyether polyols used in particular are those prepared by known methods, for example, by anionic polymerization of alkylene oxides to H-functional starting materials in the presence of a catalyst, preferably an alkali metal hydroxide or a double metal cyanide catalyst (DMC catalyst). The alkylene oxides used are primarily ethylene oxide or propylene oxide, or tetrahydrofuran, various butylene oxides, or styrene oxide, preferably pure propylene 1,2-oxide. The alkylene oxides can be used alone, alternating in succession, or in the form of mixtures. The starting materials used in particular are compounds having at least two, preferably 2 to 8, hydroxy groups or at least two primary amino groups in the molecule. The starting materials used, which have at least two, preferably 2 to 8, hydroxyl groups in the molecule, are preferably trimethylolpropane, glycerol, pentaerythritol, sugar compounds such as glucose, sorbitol, mannitol, and sucrose, polyhydric phenols, resols, such as oligomeric condensates of phenol with formaldehyde, and Mannich condensates of phenol, formaldehyde, and dialkanolamines, and also melamine.The starting materials used, which have at least two primary amino groups in the molecule, are preferably aromatic diamines and / or polyamines, such as phenylenediamine, 2,3-, 2,4-, 3,4-, and 2,6-tolylenediamine, and 4,4'-, 2,4'-, and 2,2'-diaminodiphenylmethane, and also aliphatic diamines and polyamines, such as ethylenediamine. The preferred functionality of the polyether polyols is 2 to 8, and their preferred hydroxyl number is 25 to 800 mg KOH / g, in particular 150 to 570 mg KOH / g.

[0018] Other compounds having at least two hydrogen atoms reactive with isocyanates are chain extenders which can be used in combination if appropriate. Preferably used chain extenders are alkanolamines, in particular diols with a molecular weight of less than 400, preferably 60 to 300. The amount of chain extender or mixtures thereof which are advantageously used is 1 to 20% by weight, preferably 2 to 5% by weight, based on the polyol component.

[0019] Common polyols used in large amounts 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.

[0020] Furthermore, one or more blowing agents may also be present in the preparation of the elastic polyurethanes used. The blowing agents used may be chemically active blowing agents and / or physically active compounds. Chemical blowing agents are understood to mean compounds that form gaseous products by reaction with isocyanates, such as water and carboxylic acids or carboxylic acid derivatives, such as hydrogen citrates, hydrogen carbonates or azodicarbonamides, such as Celegoene®, Tracel®, Hydrocerol® or mixtures thereof, with water being the preferred blowing agent.

[0021] Physical blowing agents are understood to mean compounds that are dissolved or emulsified in the raw materials for polyurethane production and evaporate under the conditions of polyurethane formation. These include, for example, hydrocarbons, halogenated hydrocarbons, and other compounds, such as perfluorinated alkanes such as perfluorohexane, hydrochlorofluorocarbons, and ethers, esters, ketones, and / or acetals, such as (cyclo)aliphatic hydrocarbons having 4 to 8 carbon atoms, hydrofluoroolefins (HFO), or gases such as carbon dioxide, or mixtures thereof. In a preferred embodiment, the blowing agent used is water, more preferably a mixture of these blowing agents containing only water.

[0022] 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 resilient polyurethane foam.

[0023] Preferably, the polyurethane (PU1) is based on an isocyanate component having a functionality in the range of 1.9 to 2.2 and a polyol component having a functionality in the range of 1.7 to 2.2.

[0024] 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'-biphenyl diisocyanate, 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate, 1,2-, 1,3-, and 1,4-xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI), and mixtures thereof. Preferred aromatic diisocyanates are 2,4- and 2,6-toluene diisocyanate, 2,4'-, 4,4'- and 2,2'-biphenyl diisocyanate, 2,2'-, 2,4'- and 4,4'-diphenylmethane diisocyanate, 1,2-, 1,3- and 1,4-xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI), and mixtures thereof.

[0025] According to a further embodiment, the present invention is also directed to the method as disclosed above, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate.

[0026] Surprisingly, it has been found that the method according to the invention selectively dissolves elastic polyurethanes, in particular heat-processable polyurethanes, using mild conditions, allowing the remaining residues, such as polyamides, rubber, EVA, paints, soot, pigments, flame retardants, talc, glass fibers, textiles, or even polyurethanes based on aliphatic isocyanates or thermosetting polyurethanes, to be separated by simple filtration.

[0027] In particular, thermoplastic polyurethanes with a low content of chain extender can be easily dissolved in the solvent mixture (SM). Preferably, the content of chain extender in polyurethane (PU1) is less than 40%, more preferably less than 30%, and particularly less than 20%. In particular, the content of aliphatic chain extender in polyurethane (PU1) is less than 20%, more preferably less than 15%, and particularly less than 12.5%.

[0028] The method according to the present invention comprises steps (a) and (b). This method may also comprise further steps. According to step (a), a composition (CW) is provided comprising a polyurethane (PU1) and at least one further material. 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 the group consisting of cyclic amides, to obtain a solution (S1) rich in dissolved polyurethane (PU1).

[0029] The composition (CW) typically comprises further materials such as further polymers or further waste materials. The composition may also comprise additives frequently used in polyurethanes, such as fillers such as chalk, flame retardants such as melamine, or pigments.

[0030] The properties of suitable compositions (CW) that can be used in the method of the present invention may vary widely. Preferably, the elastomeric polyurethane is heat-processable, in particular thermoplastic and heat-processable.

[0031] According to the present invention, any waste composition containing elastomeric polyurethane, especially heat-processable polyurethane, can be used, for example, waste foam or mixed fibers containing polyurethane can be used as starting material in step (a) of the method of the present invention.

[0032] The waste composition used in the present invention can be obtained from articles made from polyurethane after their use for the purpose for which they were manufactured. Before subjecting the articles to step (a) of the method of the present invention, the articles can be subjected to mechanical comminution, i.e., for example, shredding, sieving, or density separation, i.e., air, liquid, or magnetic separation, to further classify the articles into appropriate sizes. Suitable separation methods can be assisted by spectroscopic analysis, for example, IR spectroscopy. Optionally, these fragments can then be subjected to a process to remove impurities, such as paper labels. Depending on the composition of the waste material, it can be subjected to extraction to remove soluble additives before step (a). Composition (CW) can, for example, contain not only additional polymeric materials but also 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 milder conditions.

[0033] According to a further embodiment, the present invention is also directed to the above-disclosed method, wherein composition (CW) comprises a polyamide, a polyester, and / or a cellulose-based polymer. According to a further embodiment, the present invention is also directed to the above-disclosed method, wherein composition (CW) comprises a material selected from an aliphatic isocyanate-based polyurethane, a thermoset polyurethane, a rubber, an ethylene-vinyl acetate copolymer, soot, talc, a pigment, or a cellulose-based polymer.

[0034] The characteristics of the waste composition used as starting material in the method according to the invention may vary widely.

[0035] The waste composition can be comminuted by conventional methods, for example by chopping in a tumbling or rotary mill at room temperature, to a particle size typically less than 100 mm, or even less than 20 mm, as disclosed, for example, in "Recycling von Polyurethan-Kunststoffen", W. Rasshofer, Huethig (Heidelberg), 1994, or can be cut, for example, by known cold cutting processes. It is also possible to select a particle size of less than 5 mm, for example in the range of 0.01 mm to 5 mm, preferably in the range of 0.01 mm to 1 mm.

[0036] According to a further embodiment, the present invention is also directed to the method disclosed above, wherein composition (CW) is subjected to a mechanical treatment selected from the group consisting of crushing, beating, shredding, tearing, and combinations of two or more of these treatments before step (a).

[0037] According to the present invention, it is also possible to subject the composition (CW) to a heat treatment before step (a) or between steps (a) and (b) of the method according to the present invention. The composition can be heated to a temperature in the range of 150 to 220°C, preferably in the range of 150 to 200°C, more preferably in the range of 150 to 170°C. Heating can be carried out, for example, for a duration of 1 to 120 minutes, preferably 10 to 90 minutes, or particularly preferably 30 to 60 minutes. Suitable techniques are known in principle 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 batchwise.

[0038] According to step (b), a solvent mixture (SM) containing at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides is used. It has been found that it is possible to dissolve the elastomeric polyurethane 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 in the range of 20 to 50°C, preferably at a temperature in the range of 15 to 40°C, and more preferably at a temperature in the range of 20 to 30°C. Typically, the treatment in step (b) is carried out for 1 minute to 48 hours, preferably 1 hour to 24 hours, and particularly preferably 1 to 10 hours. According to the present invention, typically, at least 50% by weight of the polyurethane (PU1) present in the composition is dissolved, 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).

[0039] Compound (A1) is selected from cyclic amides. In principle, any cyclic amide can be used according to the invention, as long as it is capable of forming a solvent mixture (SM) with an alcohol.

[0040] The cyclic amide is preferably selected from the group consisting of lactams, such as caprolactam and / or valerolactam, at least one cyclic urea, or mixtures thereof, particularly preferably caprolactam.

[0041] Suitable cyclic amides include, for example, those of the general formula (I): [ka] wherein -X- is a 1- to 6-membered, preferably 2- to 4-membered, particularly preferably 3-membered, optionally substituted radical. This results in a cyclic urea structure according to formula (I), the ring having 4 to 9 members, especially 6 members, including the urea structure -NH-C(O)-NR-. Preferably, the members of the X radical are -NR 1 -, -O-, -CR 2 R3 -, -N=, and -CR 4 -CR = 4 For = or -N= radicals, the adjacent members must also be -CR 4 = or -N= members, so that a double bond can form between the two members. Radical R 1 ~R 4 are each independently hydrogen, an alkyl radical, preferably ethyl or methyl, or a halogen, such as a fluoride radical or a chloride radical. In a very particularly preferred embodiment, X is -(CH2)3-. The radical 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 alkylaryl or heteroalkylaryl group. Examples of possible substituents are halogen groups, alkyl groups, hydroxyl groups, or amine groups. In a preferred embodiment of the present invention, R contains at least one isocyanate-reactive hydrogen atom, such as an -OH or -NH2 group. Preferably, R is methyl, ethyl, propyl, pentyl, hexyl, one or more alkylene oxide moieties, such as oxyethylene, oxypropylene, or a mixture of oxyethylene and oxypropylene, and phenyl, or phenyl ether. R is particularly preferably methyl, ethyl, oxyethylene, oxypropylene, or phenyl methoxy ester, and very particularly preferably methyl. Bridged cyclic urea structures can also be used as cyclic urea compounds, in which two cyclic urea structures are bridged via a radical R.

[0042] R is very particularly preferably a linear unsubstituted hydrocarbon radical selected from methyl, ethyl, propyl, pentyl and hexyl, in particular R is a methyl radical.

[0043] Preferably, compound (A1) is a lactam. According to a further embodiment, the present invention is also directed to the above disclosed method, wherein compound (A1) is a lactam.

[0044] Particularly suitable examples include lactams of omega-aminocarboxylic acids such as 3-aminopropionic acid, 4-aminobutyric acid, 5-aminovaleric acid, 6-aminocaproic acid, or 10-aminocapric acid; N-substituted azalactams such as 1-N-methyl-hexahydro-1,4-diazepinone-(3), 1-N-butyl-hexahydro-1,4-diazepinone-(3), 1-N-alpha-pyridyl-hexahydro-1,4-diazepinone-(3);

[0045] For example, 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam are particularly suitable. According to a further embodiment, the present invention is also directed to the above-disclosed method, wherein the lactam is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0046] Suitable alcohols for the solvent mixture (SM) are in particular mono- and diols having 1 to 12 carbon atoms, in particular 1 to 6 carbon atoms, such as methanol, ethanol, propanol, butanol, ethanediol, propanediol, or butanediol. According to a further embodiment, the present invention is also directed to the process disclosed above, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0047] According to the present invention, the solvent mixture (SM) may contain two or more lactams or two or more alcohols. The mixing ratio of lactam to alcohol can vary over a wide range, as long as a homogeneous solution is obtained. Preferably, the molar ratio of at least one lactam to 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, and more preferably in the range of 1.2:1 to 1:1.2.

[0048] According to a further embodiment, the present invention is also directed to the process 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.

[0049] The solvent mixture (SM) is used in an amount appropriate for dissolving the polyurethane (PU1) in step (b) of the method according to the present invention. The appropriate amount depends on the solvent mixture and 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.

[0050] According to a further embodiment, the present invention is also directed to the method disclosed above, wherein the weight ratio of composition (CW) to solvent mixture (SM) is in the range of 1:2 to 1:20.

[0051] Step (b) results in a solution (S1) rich in dissolved polyurethane (PU1). Typically, the composition (CW) does not dissolve completely, leaving behind a residue that is insoluble in the solvent mixture (SM) used under the process conditions applied. The solution (S1) is preferably separated from the insoluble residue by a suitable separation step.

[0052] According to a further embodiment, the present invention provides a method comprising step (c): (c) Separating the solution (S1) obtained in (b), rich in dissolved polyurethane (PU1), from the residue of composition (CW). Also covered is the method as disclosed above, further comprising:

[0053] The separation can be carried out in a conventional device in a manner known to those skilled in the art. Suitable methods are in particular physical separation methods such as filtration, decantation or centrifugation, in particular filtration. According to a further embodiment, the present invention also relates to the method disclosed above, wherein the separation according to step (c) is carried out by a physical separation method.

[0054] The separation, in particular the filtration, can be carried out batchwise, discontinuously, or continuously, semi-continuously.

[0055] After separation, an appropriate washing step can be applied according to the method of the present invention.

[0056] According to the invention, it is also possible to combine steps (b) and (c), and optionally a washing step. For example, it is possible to combine step (b) with step (c) as a washing or extraction step. Suitable devices are known in principle to those skilled in the art.

[0057] In this case, it is also possible to remove the polyurethane from further components of composition (CW), such as fibers present in composition (CW), such as glass fibers or polyamide fibers, and to recycle said further components.

[0058] Step (c) results in a solution (S1). 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, it is also possible to add a suitable compound to the solution (S1) that causes the polyurethane to precipitate. For example, water can be added to the solution in an appropriate amount to precipitate the polyurethane, which can then be isolated using a filtration step.

[0059] According to a further embodiment, the present invention provides a method comprising step (d): (d) adding water to the solution (S1) to obtain polyurethane; Also covered is the method as disclosed above, further comprising:

[0060] According to the invention, step (d) can be carried out by adding water to solution (S1) either directly or after a suitable treatment, for example after at least partial removal of the solvent. According to a further embodiment of the invention, one or more components of the solvent mixture are removed before step (d), or the solvent mixture is partially removed before step (d).

[0061] According to an alternative further embodiment, the present invention relates to a method comprising the steps (d * ): (d * ) removing the solvent mixture from the solution (S1) to obtain polyurethane (PU1); Also covered is the method as disclosed above, further comprising:

[0062] According to the invention, it is also possible to remove one or more components of the solvent mixture or to only partially remove the solvent mixture, in particular the alcohol present in the solvent mixture can be easily removed, for example, under reduced pressure at ambient temperature.

[0063] The method of the present invention may also include further steps, such as washing or drying steps to remove traces of residual solvent.

[0064] According to the invention, the solution (S1) obtained in step (d) can also be used directly to prepare molded articles. Methods for preparing molded articles from solutions containing dissolved polyurethanes are known in principle to those skilled in the art and include, for example, methods for preparing membranes or methods for producing synthetic leather or methods for preparing fibers from solutions, such as spinning methods. Suitable methods are disclosed, for example, in "New materials permeable to water vapor", H. Traeubel, Springer-Verlag, 1999, chapter 8.

[0065] The method according to the invention comprises steps (a), and (b), and optionally (c) and / or (d) / (d *), but may also include further steps. The method may, for example, include a further purification step or a heat treatment. According to a further embodiment, the present invention is also directed to the method disclosed above, which method further includes a purification step.

[0066] Suitable processing steps are known in principle to those skilled in the art. Suitable processing and / or purification steps can be carried out between steps (a) and (b), or between steps (b) and (c), or between steps (c) and (d).

[0067] According to a further aspect, the present invention is also directed to a polyurethane obtained or obtainable by the method disclosed above. Preferably, the polyurethane obtained is thermoplastic and preferably thermally processable, for example by extrusion or injection molding.

[0068] The polyurethane obtained by the method of the present invention can be used in any suitable application without further modification.The polyurethane can also be used in combination with other compounds, in particular with other polyurethanes or additives for the preparation of molded articles.It is also possible to prepare blends containing the polyurethane obtained by the present invention.

[0069] In principle, methods for preparing moldings from polyurethanes are known to those skilled in the art.

[0070] According to a further aspect, the present invention is also directed to the use of a polyurethane according to the invention or a polyurethane obtained or obtainable by the process of the present invention for the preparation of a molded article.

[0071] In principle, the polyurethane (PU1) obtained in this way can be reused as is. However, in some applications, it may be advantageous to subject the polyurethane (PU1) to a suitable treatment to obtain its individual components, which can then be separated and reused, for example, in the preparation of polyurethanes. For example, it is possible to depolymerize the polyurethane (PU1) and reuse the components obtained. Methods for depolymerizing polyurethanes are in principle known to those skilled in the art and include, for example, hydrolysis, glycolysis, or aminolysis.

[0072] According to a further embodiment, the present invention provides a method comprising step (e): (e) Depolymerizing polyurethane (PU1) Also covered is the method as disclosed above, further comprising:

[0073] Suitable conditions for depolymerization 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 by aminolysis. According to a further embodiment, the present invention is also directed to the above-disclosed method, wherein the depolymerization according to step (e) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or by aminolysis.

[0074] 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 products can be separated using appropriate separation techniques.

[0075] According to a further embodiment, the present invention is also directed to the process 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.

[0076] Methods for depolymerization by glycolysis are also known in principle. Preferably, glycolysis is carried out in the presence of a base. Thus, according to a further embodiment, the present invention is also directed to the above-disclosed methods, in which glycolysis is carried out in the presence of a metal catalyst.

[0077] Suitable methods for depolymerization by hydrogenation include hydrogenation in the presence of a hydrogenation catalyst. Thus, according to a further embodiment, the present invention is also directed to the above-disclosed methods, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0078] Depolymerization typically results in a mixture of components that can be separated using appropriate separation techniques. The process according to the invention may also include a step of separating the isocyanate component or its amine derivative from the polyol component.

[0079] According to a further embodiment, the present invention provides a method comprising step (f): (f) A step of separating the isocyanate component or its amine derivative obtained by depolymerization from the polyol component. Also covered is the method as disclosed above, further comprising:

[0080] Work-up of the depolymerized products, in particular isolation of the polyamines and polyols, can be achieved, as the case may be, by, for example, extractive work-up, precipitation of the amine components as hydrochlorides, as ureas (in the case of aminolysis), chromatography, or distillation under reduced pressure. Preferably, the work-up comprises several steps.

[0081] In the distillation process, 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 processing of the polyol polyamine mixture. In general, the "volatility" of a liquid can be described using its vapor pressure; a high vapor pressure indicates a high volatility, and vice versa.

[0082] When the polyamine is more volatile than the polyol, as is the case for example with TDA, MDA, and NDA, the polyamine is recovered from the depolymerization product by distillation, preferably at reduced pressure. After the polyamine is distilled off, a still bottoms containing the polyol remains.

[0083] Suitable conditions for the distillation are known in principle to those skilled in the art.

[0084] Alternatively, the polyol can be recovered by extraction from the depolymerization mixture using a suitable extractant or pair of extractants. It is also possible to precipitate the polyamine component in the form of its hydrochloride by adding HCl and extracting the polyol component with a suitable solvent, preferably one that dissolves the polyol component but not the hydrochloride salt of the polyamine component, as described, for example, in DE-A-2854940. The hydrochloride salt of the polyamine component can then be converted to free polyamine by adding a base after separation, or it can be used directly in phosgenation to produce new polyisocyanates for polyurethane synthesis. MDA * In the case of HCl, the hydrochloride salt can be used in the MDA synthesis step by condensation of aniline with formaldehyde.

[0085] It is understood that the above separation processes can be combined with any of the various embodiments of the methods of the present invention described herein.

[0086] The polyol composition obtained in the depolymerization process, as well as the isocyanates, can be reused, for example, for the preparation of polyurethanes. According to a further aspect, the present invention is also directed to a polyol composition obtained or obtainable by a method according to any one of the above-disclosed claims.

[0087] According to a further aspect, the present invention is also directed to the use of said polyol composition or of a polyol composition obtained or obtainable by the process of the present invention for the preparation of a polyurethane or a polyisocyanurate.

[0088] Further embodiments of the present invention can be found in the claims and examples. It will be understood that the features of the subject matter / method / use according to the present invention mentioned above and detailed 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 present invention. Thus, for example, combinations of preferred features with particularly preferred features or combinations of features not further characterized with particularly preferred features are implicitly encompassed even if this combination is not explicitly mentioned.

[0089] Exemplary embodiments of the present invention are listed below without limiting the present invention, and in particular the present invention also encompasses embodiments resulting from the reference to dependencies and hence combinations specified below.

[0090] 1. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

[0091] 2. The method of embodiment 1, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate.

[0092] 3. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0093] 4. The method of any one of embodiments 1 to 3, wherein the composition (CW) comprises a polyamide, polyester, and / or cellulose-based polymer.

[0094] 5. The method of any one of embodiments 1 to 4, wherein composition (CW) comprises a material selected from an aliphatic isocyanate-based polyurethane, a thermosetting polyurethane, a rubber, an ethylene-vinyl acetate copolymer, soot, talc, a pigment, or a cellulose-based polymer.

[0095] 6. The method of any one of embodiments 1 to 5, wherein compound (A1) is a lactam.

[0096] 7. The method of any one of embodiments 1 to 6, wherein compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0097] 8. The method of any one of embodiments 1 to 7, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0098] 9. The method of any one of embodiments 1 to 8, wherein the lactam is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam, and the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0099] 10. The method of any one of embodiments 1 to 9, wherein the lactam is epsilon-caprolactam and the alcohol is selected from the group consisting of methanol, ethanol, and propanol, preferably methanol.

[0100] 11. The process of any one of embodiments 1 to 10, 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.

[0101] 12. The method further comprises step (c): (c) Separating the solution (S1) obtained in (b), rich in dissolved polyurethane (PU1), from the residue of composition (CW). 12. The method of embodiment 1 or 11, further comprising:

[0102] 13. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); A method comprising:

[0103] 14. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0104] 15. The method of any one of embodiments 12 to 14, wherein the separation according to step (c) is carried out by a physical separation method.

[0105] 16. The method of any one of embodiments 1 to 15, wherein composition (CW) is subjected to a mechanical treatment selected from the group consisting of crushing, beating, shredding, tearing, and combinations of two or more of these treatments before step (a).

[0106] 17. The method further comprises step (d): (d) adding water to the solution (S1) to obtain polyurethane; 17. The method of any one of embodiments 1 to 16, further comprising:

[0107] 18. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; A method comprising:

[0108] 19. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0109] 20. The method comprises the steps of: * ): (d * ) removing the solvent mixture from the solution (S1) to obtain polyurethane (PU1); 17. The method of any one of embodiments 1 to 16, further comprising:

[0110] 21. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d * ) removing the solvent mixture from the solution (S1) to obtain polyurethane (PU1); A method comprising:

[0111] 22. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d * ) removing the solvent mixture from the solution (S1) to obtain polyurethane (PU1); Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0112] 23. A method comprising step (e): (e) Depolymerizing polyurethane (PU1) 23. The method of any one of embodiments 17 to 22, further comprising:

[0113] 24. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; (e) depolymerizing the polyurethane (PU1); A method comprising:

[0114] 25. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; (e) depolymerizing the polyurethane (PU1); Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0115] 26. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d * ) removing the solvent mixture from the solution (S1) to obtain a polyurethane (PU1); (e) depolymerizing the polyurethane (PU1); A method comprising:

[0116] 27. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d *) removing the solvent mixture from the solution (S1) to obtain a polyurethane (PU1); (e) depolymerizing the polyurethane (PU1); Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0117] 28. The method of any one of embodiments 23 to 27, wherein the depolymerization according to step (e) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or by aminolysis.

[0118] 29. A method, comprising step (f): (f) A step of separating the isocyanate component or its amine derivative obtained by depolymerization from the polyol component. 29. The method of any one of embodiments 23 to 28, further comprising:

[0119] 30. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; (e) depolymerizing the polyurethane (PU1); (f) separating the isocyanate component or its amine derivative from the polyol component obtained by the depolymerization; A method comprising:

[0120] 31. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d) adding water to the solution (S1) to obtain polyurethane; (e) depolymerizing the polyurethane (PU1); (f) separating the isocyanate component or its amine derivative from the polyol component obtained by the depolymerization; Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0121] 32. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d * ) removing the solvent mixture from the solution (S1) to obtain a polyurethane (PU1); (e) depolymerizing the polyurethane (PU1); (f) separating the isocyanate component or its amine derivative obtained by depolymerization from the polyol component; A method comprising:

[0122] 33. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides at a temperature below the boiling point of the alcohol to obtain a solution (S1) rich in dissolved polyurethane (PU1); (c) separating the solution (S1) obtained in (b) rich in dissolved polyurethane (PU1) from the residue of composition (CW); (d * ) removing the solvent mixture from the solution (S1) to obtain a polyurethane (PU1); (e) depolymerizing the polyurethane (PU1); (f) separating the isocyanate component or its amine derivative from the polyol component obtained by the depolymerization; Including, Polyurethane (PU1) is a thermoplastic polyurethane based on aromatic isocyanates, method.

[0123] 34. A polyurethane obtained or obtainable by the method of any one of embodiments 1 to 22.

[0124] 35. Use of the polyurethane according to embodiment 34 or obtained or obtainable by the method according to any one of embodiments 1 to 22 for the preparation of a molded article.

[0125] 36. A polyol composition obtained or obtainable by the process of any one of embodiments 23 to 33.

[0126] 37. Use of the polyol composition according to embodiment 36 or the polyol composition obtained or obtainable by the method according to any one of embodiments 23 to 33 for the preparation of a polyurethane or a polyisocyanurate.

[0127] 38. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

[0128] 39. The method of embodiment 38, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate.

[0129] 40. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

[0130] 41. The method of any one of embodiments 38 to 40, wherein the content of chain extender in polyurethane (PU1) is less than 40%.

[0131] 42. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate, and the content of chain extenders in the polyurethane (PU1) is less than 40%; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

[0132] 43. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material, wherein the content of chain extender in the polyurethane (PU1) is less than 40%; (b) contacting the composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

[0133] 44. The method of any one of embodiments 38 to 43, wherein composition (CW) comprises a polyamide, polyester, and / or cellulose-based polymer.

[0134] 45. The method of any one of embodiments 38 to 44, wherein composition (CW) comprises a material selected from an aliphatic isocyanate-based polyurethane, a thermoset polyurethane, a rubber, an ethylene-vinyl acetate copolymer, soot, talc, a pigment, or a cellulose-based polymer.

[0135] 46. ​​The method of any one of embodiments 38 to 45, wherein compound (A1) is a lactam.

[0136] 47. The method of any one of embodiments 38 to 46, wherein compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0137] 48. The method of any one of embodiments 38 to 47, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0138] 49. The method of 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 in the range of 2:1 to 1:2.

[0139] 50. The method comprises step (c): (c) Separating the solution (S1) obtained in (b), rich in dissolved polyurethane (PU1), from the residue of composition (CW). 50. The method of any one of embodiments 38 to 49, further comprising:

[0140] 51. The method of embodiment 50, wherein the separation according to step (c) is carried out by a physical separation method.

[0141] 52. The method of any one of embodiments 38 to 51, wherein composition (CW) is subjected to a mechanical treatment selected from the group consisting of crushing, beating, shredding, tearing, and combinations of two or more of these treatments before step (a).

[0142] 53. The method comprises step (d): (d) adding water to the solution (S1) to obtain polyurethane; 53. The method of any one of embodiments 38 to 52, further comprising:

[0143] 54. The method comprises the steps of: * ): (d * ) removing the solvent mixture from the solution (S1) to obtain polyurethane (PU1); 53. The method of any one of embodiments 38 to 52, further comprising:

[0144] 55. A method comprising step (e): (e) Depolymerizing polyurethane (PU1) 55. The method of embodiment 53 or 54, further comprising:

[0145] 56. The method of embodiment 55, wherein the depolymerization according to step (e) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or by aminolysis.

[0146] 57. A method comprising step (f): (f) A step of separating the isocyanate component or its amine derivative obtained by depolymerization from the polyol component. 57. The method of embodiment 55 or 56, further comprising:

[0147] 58. A polyurethane obtained or obtainable by the method of any one of embodiments 38 to 54.

[0148] 59. Use of the polyurethane according to embodiment 58 or obtained or obtainable by the method according to any one of embodiments 38 to 54 for the preparation of a molded article.

[0149] 60. A polyol composition obtained or obtainable by the method of any one of embodiments 55 to 57.

[0150] 61. Use of the polyol composition according to embodiment 60 or the polyol composition obtained or obtainable by the method according to any one of embodiments 55 to 57 for the preparation of a polyurethane or a polyisocyanurate.

[0151] The present invention is further illustrated by examples, which relate to practical, possibly preferred, embodiments of the invention and which do not limit the scope of the invention. [Example]

[0152] 1. Example 1 Various samples of used sports shoe waste were tested, consisting of different materials (PU, textile, EVA, rubber, styrene block copolymer). Different samples contained different amounts of elastic PU.

[0153] 300 g of each sample was added to 1.5 L of caprolactam / MeOH solution, and the mixture was stirred overnight at room temperature. The resulting suspension was then filtered to remove all insoluble components. The insoluble components of the sample were washed with water and emerged unchanged from the process, allowing the materials to be recycled separately.

[0154] Upon adding 1.5 L of water to the solution, a precipitate formed. The precipitate was removed by filtration and washed with water. Depending on the sample, up to 65 wt. % of the material was isolated, based on the weight of the waste composition. The material was characterized by IR spectroscopy and processed in an extruder. For comparison, a thermoplastic polyurethane with a similar composition as determined by IR spectroscopy was processed in an extruder in the same manner.

[0155] The sample characteristics are summarized in Table 1.

[0156] [Table 1]

[0157] 2. Solubility of thermoplastic polyurethanes The solubility of different TPU samples was tested. 1 g of TPU sample was cut into small pieces and 15 g of a mixture of caprolactam and methanol was added. The mixture was stirred at room temperature.

[0158] These results are summarized in Table 2.

[0159] [Table 2]

[0160] Surprisingly, only aromatic isocyanate-based TPUs were soluble in the caprolactam / methanol mixture. Under the conditions applied, none of the aliphatic TPUs were dissolved in a series of tests.

[0161] Furthermore, it was observed that a higher content of aliphatic chain extender reduces the solubility: if the content of each is too high, the TPU is no longer soluble at room temperature (see Samples H and I or Samples P and R (Samples P, R, and S are made from the same raw materials and differ only in the weight percentages of the raw materials)).

[0162] References U.S. Patent No. 4,115,298 U.S. Patent No. 4,160,749 "Recycling von Polyurethan-Kunststoffen", W. Rasshofer, Huethig (Heidelberg), 1994 “New materials permeable to water vapor”, H. Traeubel, Springer-Verlag, 1999, chapter 8

Claims

1. 1. A method for recycling polyurethane from a composition comprising polyurethane (PU1) and at least one further material, comprising: (a) providing a composition (CW) comprising an elastomeric polyurethane (PU1) and at least one further material; (b) contacting said composition (CW) with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane (PU1); A method comprising:

2. 2. The method of claim 1, wherein the polyurethane (PU1) is a thermoplastic polyurethane based on an aromatic isocyanate.

3. 3. The method according to claim 1, wherein the content of chain extenders in the polyurethane (PU1) is less than 40%.

4. 4. The method according to claim 1, wherein the composition (CW) comprises a polyamide, a polyester, and / or a cellulose-based polymer.

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

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

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

8. 8. The method of claim 1, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

9. 9. The process according to any one of claims 1 to 8, 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 from 2:1 to 1:

2.

10. The method further comprises step (c): (c) separating the solution (S1) obtained in (b), rich in dissolved polyurethane (PU1), from the residue of the composition (CW); 10. The method of any one of claims 1 to 9, further comprising:

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

12. 12. The method according to any one of claims 1 to 11, wherein the composition (CW) is subjected to a mechanical treatment selected from the group consisting of crushing, beating, shredding, tearing, and combinations of two or more of these treatments before step (a).

13. The method further comprises step (d): (d) adding water to the solution (S1) to obtain the polyurethane.

13. The method of any one of claims 1 to 12, further comprising:

14. The method further comprises the step (d ＊ ): (d ＊ ) removing the solvent mixture from the solution (S1) to obtain the polyurethane (PU1); 13. The method of any one of claims 1 to 12, further comprising:

15. The method further comprises step (e): (e) depolymerizing the polyurethane (PU1).

15. The method of claim 13 or 14, further comprising:

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

17. The method further comprises step (f): (f) A step of separating the isocyanate component or its amine derivative and the polyol component obtained by the depolymerization.

17. The method of claim 15 or 16, further comprising:

18. A polyurethane obtained or obtainable by the process according to any one of claims 1 to 14.

19. 19. Use of a polyurethane according to claim 18 or a polyurethane obtained or obtainable by a process according to any one of claims 1 to 14 for the preparation of a molded article.

20. A polyol composition obtained or obtainable by the process of any one of claims 15 to 17.

21. 21. Use of a polyol composition according to claim 20 or a polyol composition obtained or obtainable by the process according to any one of claims 15 to 17 for the preparation of a polyurethane or a polyisocyanurate.

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