Solvation of linear polyurethane materials via caprolactam / alcohol mixtures

Abstract

The present invention relates to a method for recovering elastic polyurethane from a composition comprising elastic polyurethane foam, the method comprising the steps of providing a composition comprising polyurethane foam, heating the composition comprising polyurethane foam to a temperature in the range of 140°C to 220°C, and contacting the composition comprising polyurethane foam 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. The present invention also relates to the polyurethane obtained or obtainable by said method, as well as to the use of the polyurethane according to the invention for preparing a molded article.

Description

[Technical Field]

[0001] The present invention relates to a method for recovering elastic polyurethane from a composition comprising elastic polyurethane foam, the method comprising the steps of providing a composition comprising polyurethane foam, heating the composition comprising polyurethane foam to a temperature in the range of 140°C to 220°C, and contacting the composition comprising polyurethane foam 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. The invention also relates to the polyurethane obtained or obtainable by said method, as well as to the use of the polyurethane according to the invention for preparing a molded article.

[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 approach to recovering waste materials. However, it would be preferable to reuse polyurethanes without depolymerization, reducing the cost of the process. Therefore, it was an object of the present invention to provide a method for separating elastomeric polyurethanes from other additives that may be present in waste compositions.

[0006] The object is to provide a method for recovering elastic polyurethane from a composition containing elastic polyurethane foam, comprising the steps of: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam 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; The problem is solved by a method including:

[0007] Surprisingly, it was found that larger samples of block foam could not be completely dissolved in solvent mixtures containing caprolactam and methanol as described by Wagner et al., and in particular, the core was not dissolved (K. Wagner, Angew. Makromol. Chem. 1974, 37, 59-88). Surprisingly, using the method according to the invention, it is possible to completely dissolve elastomeric polyurethanes in solvent mixtures (SM) containing lactams or cis-amides and alcohols. It was found that even elastomeric foams from large samples were completely solubilized after being subjected to a tempering step.

[0008] Tempering of block foams after production is an established technique used to induce crosslinking in the core region by locally increasing the reaction temperature during the reaction, thereby completely reacting the incompletely reacted material in the outer regions. Surprisingly, it has been found that this tempering step results in improved solubility.

[0009] It has been discovered that elastomeric polyurethanes can be dissolved without decomposing the polymer structure, which allows the polyurethane to be recovered from the composition without depolymerizing it, thus allowing the polyurethane to be easily recycled.

[0010] The method according to the present invention comprises steps (a), (b), and (c). The method may also comprise further steps. In step (a), a composition comprising a polyurethane foam is provided. In step (b), the composition comprising the polyurethane foam is heated to a temperature in the range of 140°C to 220°C. In step (c), the heat-treated composition comprising the polyurethane foam 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.

[0011] The composition comprising the polyurethane foam may contain further additives or solid particles that are not soluble in the solvent mixture used. For example, the composition may contain additives frequently used in polyurethane foams, such as fillers such as chalk, flame retardants such as melamine, or pigments.

[0012] The properties of suitable compositions, including polyurethane foams, that can be used in the method of the present invention can vary widely. Any polyurethane foam, including elastomeric polyurethanes, can be used in accordance with the present invention. For example, waste foam can be used as the starting material in step (a) of the method of the present invention.

[0013] A suitable foam may be, for example, a flexible polyurethane foam. According to a further embodiment, the present invention is also directed to the above disclosed method, wherein the resilient polyurethane foam is a flexible polyurethane foam.

[0014] The polyurethane foam used in the present invention can be obtained from articles made from polyurethane foam after their intended use, or from polyurethane foam waste from the manufacturing process. Prior to step (a) of the method of the present invention, the articles can be subjected to mechanical comminution, i.e., by 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, such as IR spectroscopy. Optionally, these fragments can then be subjected to a process to remove impurities, such as paper labels. Depending on the polyurethane foam's composition, it can be subjected to extraction to remove soluble additives, such as flame retardants, surfactants, or catalysts, leaving a pure polymeric polyurethane material prior to step (a).

[0015] The properties of the foam used as starting material in the process according to the invention may vary widely. Preferably, the elastomeric polyurethane is thermoplastic and heat-processable.

[0016] Generally, polyurethane foams are produced by the reaction of a polyisocyanate component with a polyol component, and the properties of the polyurethane foam are affected by the type of polyisocyanate and polyol components used.

[0017] The polyurethane foams can be comminuted by conventional methods, for example by chopping in a tumbling or rotary mill at room temperature, typically to a particle size of 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 particle sizes 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.

[0018] According to a further embodiment, the present invention is also directed to the method disclosed above, wherein the composition comprising the polyurethane foam 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 prior to step (a).

[0019] According to the invention, in step (b), the composition is 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 invention, step (b) can be carried out continuously or batchwise.

[0020] According to step (c), a solvent mixture (SM) is used that contains at least one alcohol and at least one compound (A1) selected from the group consisting of cyclic amides. It has been found that after the composition is heated according to step (b), it is possible to dissolve the elastomeric polyurethane in the solvent mixture. According to the present invention, typically, at least 50% by weight of the elastomeric polyurethane present in the composition is dissolved, for example, at least 60% by weight, preferably at least 70% by weight, particularly preferably up to 100% by weight of the elastomeric polyurethane is dissolved in the solvent mixture (SM).

[0021] Step (c) is carried out at a temperature below the boiling point of the alcohol used, for example, a temperature in the range of 20 to 50°C, preferably a temperature in the range of 15 to 40°C, more preferably a temperature in the range of 20 to 30°C.

[0022] 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.

[0023] 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.

[0024] 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 member 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.

[0025] R is very preferably a linear unsubstituted hydrocarbon radical selected from methyl, ethyl, propyl, pentyl and hexyl, and in particular R is a methyl radical.

[0026] 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.

[0027] 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);

[0028] 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 compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The solvent mixture (SM) is used in step (c) of the process according to the present invention in an amount suitable for dissolving the elastomeric polyurethane. The suitable amount depends on the solvent mixture and polyurethane used. Typically, the weight ratio of the polyurethane foam-containing composition 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.

[0033] According to a further embodiment, the present invention is also directed to the method as disclosed above, wherein the weight ratio of the composition comprising polyurethane foam to the solvent mixture (SM) is in the range of 1:2 to 1:20.

[0034] According to step (c), a solution (S1) rich in dissolved polyurethane is obtained. If the composition does not dissolve completely and leaves behind residues that are not soluble in the solvent mixture (SM) used, the solution (S1) is preferably separated from the insoluble residues by a suitable separation step.

[0035] According to a further embodiment, the present invention provides a method comprising step (d): (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the residue of the composition containing polyurethane foam. Also covered is the method disclosed above, further comprising:

[0036] 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. Thus, according to a further embodiment, the present invention also relates to the above-disclosed method, wherein the separation according to step (d) is carried out by a physical separation method.

[0037] The separation, in particular the filtration, can be carried out batchwise, discontinuously, or continuously, semi-continuously.

[0038] After separation, an appropriate washing step can be applied according to the method of the present invention.

[0039] Step (d) results in a solution (S1). The polyurethane 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 that causes the precipitation of the polyurethane can be added to the solution (S1). 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.

[0040] According to a further embodiment, the present invention provides a method comprising step (e): (e) removing the solvent mixture from the dissolved polyurethane-rich solution (S1) to obtain polyurethane; Also covered is the method disclosed above, further comprising:

[0041] 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.

[0042] According to an alternative embodiment, the present invention relates to a method comprising the steps (e * ): (e * ) adding water to the solution (S1) to obtain polyurethane; Also covered is the method disclosed above, further comprising:

[0043] According to the present invention, the step (e *) can be carried out after step (d). According to a further embodiment of the present invention, one or more components of the solvent mixture can be carried out after step (e * ), or the solvent mixture is removed before step (e * ) is partially removed before

[0044] The method of the present invention may also include further steps, such as washing or drying steps to remove traces of residual solvent.

[0045] 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.

[0046] The method according to the invention comprises steps (a), and (b), (c) and optionally (d) and / or (e) / (e * ), 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.

[0047] 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).

[0048] The method according to the present invention is also applicable to polyurethane foam waste. In this specification, "polyurethane foam waste" includes end-of-life polyurethane foam and PU foam rejects. In this context, the term "post-consumer polyurethane foam" refers to articles made from polyurethane foam at a point where the polyurethane foam has already been used to make the article. "Polyurethane foam rejects" refers to polyurethane foam waste generated in the PU foam manufacturing process.

[0049] Generally, polyurethane foams 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.

[0050] The organic polyisocyanates that can be used to prepare the polyurethanes are any of the known organic diisocyanates and polyisocyanates, preferably aromatic polyfunctional 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Other compounds having at least two hydrogen atoms reactive with isocyanates are crosslinkers and 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 advantageously used amount of chain extender, crosslinker or mixture thereof is 1 to 20% by weight, preferably 2 to 5% by weight, based on the polyol component.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Preferably, the foam 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.

[0061] 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.

[0062] The polyurethanes obtained by the process of the present invention can be used in any suitable application without further modification. It is also possible to use the polyurethanes in admixture with further compounds, in particular with further polyurethanes or additives for the preparation of molded articles.

[0063] In principle, methods for preparing moldings from polyurethanes are known to those skilled in the art.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 1. A method for recovering elastomeric polyurethane from a composition containing elastomeric polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; A method comprising:

[0068] 2. The method of embodiment 1, wherein the polyurethane foam is a flexible polyurethane foam.

[0069] 3. The method of embodiment 1 or 2, wherein compound (A1) is a lactam.

[0070] 4. The method of any one of embodiments 1 to 3, wherein compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0071] 5. The method of any one of embodiments 1 to 4, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0072] 6. The method of any one of embodiments 1 to 5, wherein compound (A1) is a lactam and the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0073] 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, and the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0074] 8. The method of any one of embodiments 1 to 7, wherein compound (A1) is epsilon-caprolactam and the alcohol is selected from the group consisting of methanol, ethanol, and propanol, preferably methanol.

[0075] 9. The method of any one of embodiments 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 2:1 to 1:2.

[0076] 10. The method of any one of embodiments 1 to 9, wherein the weight ratio of the polyurethane foam-containing composition to the solvent mixture (SM) is in the range of 1:2 to 1:20.

[0077] 11. The method further comprises step (d): (d) separating the solution (S1) obtained in (c), rich in dissolved polyurethane, from the remainder of the composition comprising the polyurethane foam. 11. The method of any one of embodiments 1 to 10, further comprising:

[0078] 12. A method for recovering elastomeric polyurethane from a composition containing elastomeric polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising polyurethane foam; A method comprising:

[0079] 13. The method of embodiment 11 or 12, wherein said separation according to step (d) is carried out by a physical separation method.

[0080] 14. The method of any one of the preceding claims, wherein the polyurethane foam-containing composition 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 prior to step (a).

[0081] 15. The method further comprises step (e): (e) removing the solvent mixture from the solution (S1) rich in dissolved polyurethane to obtain polyurethane; 15. The method of any one of embodiments 1 to 14, further comprising:

[0082] 16. A method for recovering elastomeric polyurethane from a composition containing elastomeric polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising the polyurethane foam; (e) removing the solvent mixture from the solution (S1) rich in dissolved polyurethane to obtain polyurethane; A method comprising:

[0083] 17. The method further comprises the steps of: * ): (e * ) adding water to the solution (S1) to obtain polyurethane; 15. The method of any one of embodiments 1 to 14, further comprising:

[0084] 18. A method for recovering elastomeric polyurethane from a composition containing elastomeric polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising the polyurethane foam; (e * ) adding water to the solution (S1) to obtain polyurethane; A method comprising:

[0085] 19. A polyurethane obtained or obtainable by the method of any one of embodiments 1 to 18.

[0086] 20. A method for recovering elastomeric polyurethane from a composition containing elastomeric polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; 1. A polyurethane obtained or obtainable by a process comprising:

[0087] 21. The polyurethane of embodiment 20, wherein the polyurethane foam is a flexible polyurethane foam.

[0088] 22. The polyurethane of embodiment 20 or 21, wherein compound (A1) is a lactam.

[0089] 23. The polyurethane of any one of embodiments 20 to 22, wherein compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

[0090] 24. The polyurethane of any one of embodiments 20 to 23, wherein the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0091] 25. The polyurethane of any one of embodiments 20 to 24, wherein compound (A1) is a lactam and the alcohol is selected from the group consisting of methanol, ethanol, and propanol.

[0092] 26. The polyurethane of any one of embodiments 20 to 25, wherein compound (A1) 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.

[0093] 27. The polyurethane of any one of embodiments 20 to 26, wherein compound (A1) is epsilon-caprolactam and the alcohol is selected from the group consisting of methanol, ethanol, and propanol, preferably methanol.

[0094] 28. The polyurethane of any one of embodiments 20 to 27, 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.

[0095] 29. The polyurethane of any one of embodiments 20 to 28, wherein the weight ratio of the polyurethane foam-containing composition to the solvent mixture (SM) is in the range of 1:2 to 1:20.

[0096] 30. The method comprises step (d): (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the residue of the composition containing polyurethane foam. 30. The polyurethane of embodiment 20 or 29, further comprising:

[0097] 31. The method, (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising the polyurethane foam; 31. The polyurethane of any one of embodiments 20 to 30, comprising:

[0098] 32. The method of embodiment 30 or 31, wherein said separation according to step (d) is carried out by a physical separation method.

[0099] 33. The method of any one of embodiments 20 to 32, wherein the composition comprising the polyurethane foam 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 prior to step (a).

[0100] 34. The method further comprises step (e): (e) removing the solvent mixture from the solution (S1) rich in dissolved polyurethane to obtain polyurethane; 34. The method of any one of embodiments 20 to 33, further comprising:

[0101] 35. The method comprises: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising the polyurethane foam; (e) removing the solvent mixture from the solution (S1) rich in dissolved polyurethane to obtain polyurethane; 35. The polyurethane of embodiment 20 or 34, comprising:

[0102] 36. The method further comprises the steps (e * ): (e * ) adding water to the solution (S1) to obtain polyurethane. 36. The method of any one of embodiments 20 to 35, further comprising:

[0103] 37. The method comprises: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising said polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of said alcohol, to obtain a solution (S1) rich in dissolved polyurethane; (d) separating the solution (S1) obtained in (c) rich in dissolved polyurethane from the remainder of the composition comprising the polyurethane foam; (e * ) adding water to the solution (S1) to obtain polyurethane; 37. The polyurethane of embodiment 20 or 36, comprising:

[0104] 38. Use of the polyurethane according to any one of embodiments 19 to 37 or obtained or obtainable by the method according to any one of embodiments 1 to 18 for the preparation of a molded article.

[0105] 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]

[0106] 1. Materials used [Table 1]

[0107] 2. Example 1 2.1 Foams were prepared using the A component summarized in Table 1 and isocyanate 1 as the B component having an index of 90-115.

[0108] [Table 2]

[0109] The first sample was prepared in a beaker (0.56 L). The foam was completely soluble in a mixture of caprolactam / MeOH (1:1.2 mol) using a solvent mixture in a ratio of 1:10.

[0110] Additional samples with larger blocks were prepared (64 L and 2600 L). Each sample was only partially soluble, with the core region of the block foam not being soluble in the solvent mixture.

[0111] 2.2 Samples from the block form were subjected to a tempering step at temperatures above 150°C for durations ranging from 10 minutes to 1 hour, and an improvement in solubility could be observed.

[0112] 3. Example 2 An MDI-based linear foam was also developed. All tests were conducted as cup tests (0.65 L).

[0113] The A component consisted of polyol 2, an amine catalyst, and tap water. The B component was based on a mixture of isocyanate 2 and isocyanate 3. The proportion of isocyanate 3 in the B component was successively increased to increase the overall functionality of the B component. At compositions of 87 parts isocyanate 2 and 13 parts isocyanate 3 in the B component, the foams were all immediately soluble. At 15, 18, and 22 parts isocyanate 3 in the B component, the foams were no longer immediately soluble. Therefore, the foams were tempered at 150°C for 1 hour and were then soluble at room temperature. At more than 27 parts isocyanate 3 in the B component, the foams were no longer soluble, even after the tempering step. These results are summarized in Table 2.

[0114] [Table 3]

[0115] 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. Trauubel, Springer-Verlag, 1999, chapter 8 K. Wagner, Angew. Makromol. Chem. 1974, 37, 59-88

Claims

1. 1. A method for recovering resilient polyurethane from a composition comprising resilient polyurethane foam, comprising: (a) providing a composition comprising a polyurethane foam; (b) heating the polyurethane foam-containing composition to a temperature in the range of 140°C to 220°C; (c) contacting the composition comprising the polyurethane foam with a solvent mixture (SM) comprising at least one alcohol and at least one compound (A1) selected from the group of cyclic amides, at a temperature below the boiling point of the alcohol, to obtain a solution (S1) rich in dissolved polyurethane; A method comprising:

2. The method of claim 1 , wherein the polyurethane foam is a flexible polyurethane foam.

3. 3. The method according to claim 1 or 2, wherein compound (A1) is a lactam.

4. The process according to any one of claims 1 to 3, wherein the compound (A1) is selected from the group consisting of 2-pyrrolidone, 2-piperidone, epsilon-caprolactam, and laurolactam.

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

6. 6. The process according to any one of claims 1 to 5, 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.

7. 7. The method according to claim 1, wherein the weight ratio of the composition comprising the polyurethane foam to the solvent mixture (SM) is in the range of 1:2 to 1:

20.

8. The method further comprises step (d): (d) separating the solution (S1) obtained in (c), rich in dissolved polyurethane, from the residue of the composition comprising the polyurethane foam.

10. The method of claim 1 or 7, further comprising:

9. The method of claim 8 , wherein said separating according to step (d) is performed by a physical separation method.

10. 10. The method of claim 1, wherein the polyurethane foam-containing composition 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 prior to step (a).

11. The method further comprises step (e): (e) removing the solvent mixture from the solution (S1) rich in dissolved polyurethane to obtain the polyurethane.

11. The method of claim 1, further comprising:

12. The method further comprises the step (e ＊ ): (e ＊ ) adding water to the solution (S1) to obtain the polyurethane.

11. The method of claim 1, further comprising:

13. A polyurethane obtained or obtainable by the process according to any one of claims 1 to 12.

14. 14. Use of a polyurethane according to claim 13 or a polyurethane obtained or obtainable by a process according to any one of claims 1 to 12 for the preparation of a molded article.

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