Method for recovering valuable substances from polyurethane foams

Abstract

The present invention relates to a method for recovering valuable substances from polyurethane foams, the method comprising: (A) providing a polyurethane foam based on toluene diisocyanate and polyether polyol; (B) performing chemolysis of the polyurethane foam by reacting it with an organic chemolysis reagent and water, wherein the organic chemolysis reagent is selected from (i) a primary or secondary chemolysis amine, (ii) a chemolysis amino alcohol having a primary or secondary amino group, (iii) a chemolysis alcohol, or (iv) a mixture of two or more of the aforementioned organic chemolysis reagents; (C) distilling off the organic chemolysis reagent and optionally also the toluenediamine formed in (B) or portions thereof, wherein the distilling off may be preceded and / or followed by separation of solid components; (D) extracting polyether polyol using an organic solvent, wherein an acid and water are added, and, after separation of an acidic aqueous phase, a polyol phase is obtained; and (E) processing the polyol phase to recover at least one polyether polyol.

Description

[0001] PROCESS FOR RECOVERING VALUABLE MATERIALS FROM POLYURETHANE FOAMS

[0002] The present invention relates to a process for the recovery of valuable materials from polyurethane foams, comprising (A) providing a toluene diisocyanate- and polyether polyol-based polyurethane foam, (B) chemolysis of the polyurethane foam by reacting it with an organic chemolysis reagent and water, wherein the organic chemolysis reagent is selected from (i) a primary or secondary chemolysis amine, (ii) a chemolysis amino alcohol having a primary or secondary amino group, (iii) a chemolysis alcohol, or (iv) a mixture of two or more of the aforementioned organic chemolysis reagents, (C) distilling off the organic chemolysis reagent and optionally also the toluenediamine formed in (B) or portions thereof, wherein the distillation may be preceded and / or followed by a separation of solid components, (D) extracting the polyether polyol with an organic solvent,wherein an acid and water are added and, after separation of an acidic aqueous phase, a polyol phase is obtained, and (E) working up the polyol phase to obtain at least one polyether polyol.

[0003] Polyurethane foams are used in a wide variety of applications in industry and in everyday life. Polyurethane foams are usually divided into rigid foams and flexible foams. Despite their differences, all these products have in common the basic polyurethane structure, which is formed by the polyaddition reaction of a polyfunctional isocyanate and a polyol. For example, for a polyurethane based on a diisocyanate O=C=NRN=C=O and a diol HO-R'-OH (where R and R' are organic radicals),

[0004] - [O-R'-O-(O=C)-HN-R-NH-(C=O)] - can be represented.

[0005] Precisely because of the great economic success of polyurethane products, large quantities of polyurethane waste (e.g., from old mattresses or seating furniture) are generated, which must be put to sensible use. The technically easiest method of reuse is incineration, using the released combustion heat for other processes, such as industrial manufacturing. However, this method does not allow for closing the raw material cycle. Another type of reuse is so-called "physical recycling," in which polyurethane waste is mechanically shredded and used in the manufacture of new products. This type of recycling naturally has its limitations, which is why there has been no shortage of attempts to recover the raw materials underlying polyurethane production by splitting the polyurethane bonds (so-called "chemical recycling").The raw materials to be recovered primarily include polyols (in the above example, HO-R'-OH). In addition, amines can also be obtained by hydrolytic cleavage of the urethane bond (in the above example, H2N-R-NH2), which can be phosgenated after processing to isocyanates (in the above example, O=C=NRN=C=O). A summary of the known processes for polyurethane recycling is provided in the review article by Simon, Borreguero, Lucas, and Rodriguez in Waste Management 2018, 76, 147-171 [1]. Glycolysis (see below, No. 2) is highlighted as being particularly important.

[0006] Various approaches to chemical recycling have been developed in the past. Five of them are briefly summarized below:

[0007] 1. Hydrolysis of urethanes by reaction with water to produce amines and polyols with formation of carbon dioxide.

[0008] 2. Glycolysis (alcoholysis) of urethanes by reaction with alcohols, whereby the polyols incorporated into the urethane groups are replaced by the alcohol used and thus released. This process is usually referred to in the literature as transesterification (more precisely: transurethanization). This type of chemical recycling, regardless of the exact type of alcohol used, is usually referred to in the literature as glycolysis, although this term is actually only applicable to glycol and one should therefore speak more generally of alcoholysis. Glycolysis can be followed by hydrolysis. If the hydrolysis is carried out in the presence of the unchanged glycolysis mixture (i.e., without prior separation of the polyols formed), it is referred to as

[0009] 3. Hydroglycolysis (hydroalcoholysis) of urethane bonds. It is, of course, also possible to add alcohol and water from the beginning, in which case the hydrolysis and glycolysis processes described above occur in parallel.

[0010] 4. Aminolysis of urethane bonds by reaction with primary or secondary amines, whereby the polyols incorporated into the urethane groups can be replaced by the amine used and thus released. In this case, the urethane groups are converted to urea groups. Similarly, the R-NH-(C=O) bonds in the urethanes can be cleaved, and the R-NH groups can be replaced by the amine used in the aminolysis, releasing the amine R-NH2 corresponding to the isocyanate originally used. If amino acids with primary or secondary amino groups are used, the alcohol groups of the amino alcohol used can naturally also react with urethane bonds, resulting in the formation of carbamates. According to the teachings of most of the prior art, aminolysis can be followed by hydrolysis in a separate step.

[0011] 5. A reaction procedure corresponding to hydroglycolysis, in which amines or amino alcohols and water are used as reagents without prior separation of the released polyols, is described in WO 2023 / 083968 A1 (see below for details) and is referred to there as aminohydrolysis.

[0012] EP 0 013 350 A1 describes a process for the separation of chemolysis products obtained by hydrolysis (according to the teaching of the laid-open specification DE 2442 387, ie at 100 °C to 300 °C and 5 bar to 100 bar) of polyurethanes into polyols or polyamines which can be reused for the production of polyurethane plastics by introducing hydrogen chloride gas into the hydrolysate mixture which is preferably diluted with an inert solvent, in particular toluene, and filtering off the precipitated amine salt, wherein the hydrogen chloride precipitation takes place fractionally (in several partial steps).

[0013] DE 2 207 379 discloses a process for recovering polyether polyols from polyurethane plastics, in which the comminuted plastic is heated in an autoclave at 150 to 220 °C under direct steam pressure at approximately 20 atm (19.6 bar) for at least 1 hour. For processing, the reaction product treated in this way can be dissolved in an organic solvent, such as toluene, treated with dilute hydrochloric acid, and filtered. The remaining organic solution is evaporated and filtered, yielding the polyether polyol as the residue.

[0014] US 3,404,103 describes a process for the decomposition of a polyether polyol-based polyurethane with an amine in the presence of basic catalysts such as alkali or alkaline earth metal oxides or hydroxides. Urethane and urea bonds of the polyurethane are converted to ureas of the amine used in the chemolysis, releasing the polyether polyol. These ureas are cleaved under the influence of the basic catalysts into amines (namely, the amine corresponding to the isocyanate used in the synthesis of the polyurethane and the amine used in the chemolysis) and carbonates (e.g., sodium carbonate). When ethanolamine (2-aminoethanol, also called monoethanolamine) is used, 2-oxazolidinone is formed as an intermediate. This is cleaved into ethanolamine and carbonate under the influence of the basic catalysts.EP 0 990 674 B1 describes a two-stage chemolysis process in which a polyurethane starting material, in particular a foam (flexible or rigid foam, preferably flexible foam) is dissolved in a first stage by adding a glycol, a polyamine or an amino alcohol at 120 °C to 250 °C and then, optionally after filtration to separate solids, in a second stage in an autoclave with water at 200 to 320 °C at pressures of 49 to 76 bar(g) (50 to 78 kg / cm). 2 G; see examples). For processing, water is removed in gaseous form, distilled off, or expelled with an inert gas. The solvent is removed by distillation. The resulting polyol and polyamine are separated by distillation, centrifugation, or solvent extraction. Amine-containing hydrolysate can also be reacted with alkylene oxides to form a polyol.

[0015] EP 1 142 945 A2 describes a process in which a polyurethane starting material, in particular a polyurethane foam (flexible or rigid foam, preferably flexible foam), is first mixed with a polyamine and heated to 120°C to 250°C. This forms a liquid phase containing the polyol and dissolved polyurea fractions, as well as a solid phase containing undissolved polyurea fractions. The liquid phase is then hydrolyzed in an autoclave at temperatures of 200 to 320°C and high pressure (in the examples at least 4.7 MPa = 47 bar). The solid phase can be dissolved in additional polyamine and then, optionally after separation of insoluble fractions, also hydrolyzed. For workup, water is stripped off in gaseous form, distilled off, or expelled with an inert gas. The solvent is removed by distillation.The resulting polyol and polyamine are separated by distillation, centrifugation, or solvent extraction. Amine-containing hydrolysate can also be reacted with alkylene oxides to form a polyol. The description mentions that the process is also applicable to rigid foams. However, their isocyanate components regularly contain mixtures of methylenediphenylene diisocyanate (mMDI, comprising two isocyanate groups) and polymethylenepolyphenylene polyisocyanate (pMDI, comprising three or more isocyanate groups—mixtures of mMDI and pMDI are also referred to as MDI below). The amines corresponding to pMDI (polymethylenepolyphenylenepolyamines, pMDA), which are formed in the chemolysis, cannot be distilled without decomposition. A practical method for recovering such amines is not disclosed.

[0016] EP 1 149 862 A1 describes a process in which a rigid foam is dissolved in an amine or glycol at 100°C to 250°C and ambient pressure and then hydrolyzed. Suitable polyurethane foams disclosed are those based on tolylene diisocyanate (TDI) and / or methylenediphenylene diisocyanate (mMDI). Hydrolysis is carried out using supercritical or subcritical water. The pressure range for hydrolysis is disclosed to be 100 to 250 bar. Reprocessing is carried out by fractionation. Recovered amines can be used in the production of new isocyanate or as starters for polyol synthesis.

[0017] Patent application CN 116 041 191 A claims a process for the "extraction" of toluenediamine (TDA) from the "alcoholysis product" of a flexible polyurethane foam, comprising the following steps:

[0018] • Separation of a mixture of TDA and the alcoholysis reagent used (e.g. diethylene glycol) by vacuum distillation;

[0019] • Reaction of the mixture of TDA and the alcoholysis reagent with a carboxylic acid chloride to precipitate a TDA amide salt and separation of the salt by filtration;

[0020] • Expelling hydrogen chloride from the alcoholysis reagent remaining after filtration by nitrogen stripping and introducing the stripped gas stream into water to form hydrochloric acid; and

[0021] • Dissolution of the TDA amide salt in the hydrochloric acid and phase separation into an organic phase containing the carboxylic acid chloride and an aqueous TDA phase.

[0022] Although the application consistently refers to "alcoholysis," it is clear from the context that hydroalcoholysis must be meant, because otherwise the "alcoholysis product" would have to contain large proportions not of TDA, but of carbamates of the alcoholysis reagent used and of TDI. Irrespective of this, the multi-step process of amide salt formation using an organic acid chloride and the recovery of the TDA and the acid chloride involves considerable effort.

[0023] Patent application CN 115 785 520 A claims a process for extracting a polyether polyol from the "alcoholysis product" of a flexible polyurethane foam, comprising the following steps:

[0024] • Acidifying the “alcoholysis product” with an inorganic acid to obtain a moderately acidic emulsion;

[0025] • Breaking the emulsion by adding a demulsifier, in particular a polyoxyethylene-polyoxypropylene alkyl alcohol (with an ethylene oxide degree of polymerization of preferably 6 to 10, a propylene oxide degree of polymerization of preferably 10 to 15 and a chain length of the alkyl alcohol of preferably 12 to 18 carbon atoms), and separating the resulting phases; and • Extracting the polyether polyol from the resulting organic phase with a polar solvent.

[0026] This application also consistently refers to "alcoholysis," although all specifically disclosed compositions of the alcoholysis product contain large amounts of TDA and no carbamates are identified, meaning that it must be a hydroalcoholysis. Irrespective of this, the necessity of using a comparatively high-molecular-weight demulsifier, which is therefore difficult or impossible to distill, is disadvantageous.

[0027] Patent application WO 2023 / 099420 A1 describes a process for recovering at least one raw material from a polyurethane product, comprising the steps of (A) providing a polyurethane product based on an isocyanate component and a polyol component, wherein the isocyanate component comprises only those isocyanates whose corresponding amines have a boiling point at 1013 mbapabs.) of at most 410°C, preferably in the range from 170°C to 400°C; (B) chemolysis of the polyurethane product with an alcohol and water; (C) working up the product of the chemolysis, comprising (Cl) extraction with an organic solvent whose boiling point is 1013 mbapabs.) in the range of 40 °C to 120 °C, at a temperature in the range of 10 °C to 60 °C, followed by (C.ll) phase separation into a first product phase and a second product phase and (D) working up the first product phase to obtain the polyol, comprising (D.I) Separation of organic solvent by distillation and / or stripping and (DI I) Separation of amine dissolved in the first product phase by distillation to obtain the polyol.

[0028] The patent application WO 2023 / 083968 A1 describes a process for the recovery of raw materials from polyurethane products, in particular polyurethane foams, comprising chemolysis. The chemolysis is characterized in that the polyurethane products are reacted with (i) an aminic chemolysis reagent selected from (a) a primary or secondary organic amine, (b) an amino alcohol having a primary or secondary amino group or (c) a mixture of (a) and (b) and (ii) water in the presence of (iii) a catalyst at a temperature of 100 °C to 195 °C and at a pressure of 900 mbapabs.) to 2000 mbapabs.), wherein the mass ratio of aminic chemolysis reagent and water on the one hand and the polyurethane product on the other hand is in the range of 0.5 to 2.5 and the mass of water is 3.0% to 22% of the mass of the aminic chemolysis reagent.In the case of TDI-based polyurethane foams, the chemolysis product is preferably processed by extraction with an extractant comprising (i) an organic solvent selected from an (aliphatic or aromatic) hydrocarbon or a halogen-substituted, in particular chlorinated, (aliphatic or aromatic) hydrocarbon and (ii) water, followed by phase separation into a first product phase (TDA-water phase containing the aminic chemolysis reagent) and a second product phase (polyol-solvent phase). The valuable substances TDA and polyol are preferably recovered from these two phases by distillation and / or stripping.

[0029] Only a few of the chemical recycling processes known from the literature are operated permanently on a large-scale; many have not even reached the pilot scale [1]. Given the generally increased environmental awareness and increased efforts to make industrial processes as sustainable as possible – both of which fundamentally speak in favor of chemical recycling – this clearly shows that the chemical recycling of polyurethane products is far from mature from a technical and economic perspective. Challenges exist, in particular, with regard to the purity of the recovered products. Furthermore, an economically viable recycling process must ensure that the reagents used (e.g., alcohols, amino alcohols, or amines) can be recovered as completely as possible and reused (i.e., recycled).Due to the large volumes of polyurethane waste generated from used polyurethane foams (e.g., refrigerators, hot water storage units, mattresses, seating, vehicle seats, etc.), the recycling of polyurethane foams is becoming increasingly important. In addition, the polyurethane products to be recycled usually contain various auxiliary materials and additives (stabilizers, catalysts, etc.), which must be separated and disposed of economically and environmentally friendly from the actual target products of the recycling.

[0030] The recycling processes described above can still be improved. Challenges remain, particularly with regard to the most complete separation of polyols and amines. This is particularly important for products produced in very large quantities, such as TDI and polyether polyol-based polyurethane foams.

[0031] There was therefore a need for further improvements in the field of chemical recycling of polyurethane foams. In response to this need, the present invention provides a process for recovering valuable materials from polyurethane foams, comprising the following steps:

[0032] (A) Providing a polyurethane foam based on an isocyanate component and a polyol component, in particular a flexible foam, wherein the isocyanate component comprises tolylene diisocyanate and in particular does not comprise any further isocyanates other than tolylene diisocyanate (such as methylenediphenyl diisocyanate and / or polymethylenepolyphenylene polyisocyanate) (ie in particular consists of tolylene diisocyanate), and wherein the polyol component comprises (at least) one polyether polyol and in particular does not comprise any further polyols other than polyether polyols (such as polyester polyols) (ie in particular consists of (at least) one polyether polyol);

[0033] (B) chemolysis of the polyurethane foam by reacting with an organic chemolysis reagent and water, wherein the organic chemolysis reagent is selected from (i) a primary or secondary chemolysis amine, (ii) a chemolysis amino alcohol having a primary or secondary amino group, (iii) a chemolysis alcohol or (iv) a mixture of two or more of the aforementioned organic chemolysis reagents, wherein (iii) is preferred, to obtain a chemolysis product comprising the (at least one) polyether polyol, toluenediamine and the organic chemolysis reagent (which is released again by hydrolytic cleavage of the intermediately formed carbamates and / or ureas of the toluene diisocyanate and the organic chemolysis reagent);

[0034] (C) distilling off organic chemolysis reagent and optionally also the toluenediamine or portions thereof from the chemolysis product to obtain a chemolysis product depleted in organic chemolysis reagent (and optionally also in toluenediamine), wherein the distillation may be preceded and / or followed by a separation of solid components;

[0035] (D) Extracting the (at least one) polyether polyol with a, in particular halogenated, organic solvent from the chemolysis product depleted in organic chemolysis reagent (and optionally in toluenediamine and optionally also in solid components), wherein an acid and water are added (wherein the order of addition of the, in particular halogenated, organic solvent, the acid and the water is variable), in particular such that an aqueous acid (and optionally further water) is added (wherein the order of addition of the, in particular halogenated, organic solvent, the aqueous acid and optionally further water is variable) and, after separation of an acidic aqueous phase, a polyol phase comprising the (in particular halogenated) organic solvent and the (at least one) polyether polyol is obtained; and

[0036] (E) Processing the polyol phase to obtain the (at least one) polyether polyol.

[0037] Completely surprisingly, it was found that the addition of an acid and water, preferably in the form of an aqueous acid and optionally additional water, to the extraction step improves the separation of polyether polyols and toluenediamine. Toluenediamine is soluble in both polar organic solvents and (unlike methylenediphenylenediamine, for example) in water and therefore does not necessarily need to be protonated for conversion to an aqueous phase. However, protonation of toluenediamine leads to a nearly quantitative conversion to the aqueous phase, which was not foreseeable.

[0038] In the terminology of the present invention, the term polyols encompasses all polyols known in the art in connection with urethane chemistry. The term "a polyol" naturally also encompasses embodiments in which two or more different polyols were used in the production of the polyurethane foam. Therefore, if reference is made below to "a polyether polyol," this terminology naturally also encompasses embodiments in which two or more different polyether polyols were used in the production of the polyurethane foam. For reasons of linguistic simplification, this will not necessarily be specifically mentioned below, but is deemed to be included unless expressly stated otherwise. The totality of all polyols used in the production of the polyurethane foam is referred to as the polyol component (of the polyurethane foam). The polyol component comprises at least one polyol.If the polyol component comprises exactly one (1) polyol, this polyol is a polyether polyol.

[0039] In the terminology of the present invention, the term isocyanates encompasses all isocyanates known in the art in connection with urethane chemistry. The expression "one isocyanate" naturally also encompasses embodiments in which two or more different isocyanates (e.g., mixtures of MDI and TDI) were used in the production of the polyurethane foam, unless expressly stated otherwise, for example, by the phrase "exactly one isocyanate." The totality of all isocyanates used in the production of the polyurethane foam is referred to as the isocyanate component (of the polyurethane foam). The isocyanate component comprises at least one isocyanate.

[0040] An amine corresponding to an isocyanate refers to the amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCl2 —> RN=C=O + 2 HCl.

[0041] The addition of an "acid and water" in step (D) can be realized by adding an aqueous acid (i.e., a solution of an acid in water). The addition of further water (i.e., in addition to the water content of the aqueous acid) is possible in this case, but not mandatory.

[0042] First, a brief summary of various possible embodiments of the invention follows:

[0043] In a first embodiment of the invention, which can be combined with all other embodiments, the (at least one) polyether polyol comprises (at least) one polyether polyol filled with a polymer, wherein the polymer comprises a polymer of (at least) one vinyl group-containing monomer, a polyurea and / or a polyurethane.

[0044] In a second embodiment of the invention, which is a particular embodiment of the first embodiment, the polymer comprises a polymer of (at least) one vinyl group-containing monomer and is in particular such a polymer of (at least) one vinyl group-containing monomer.

[0045] In a third embodiment of the invention, which is a particular embodiment of the second embodiment, the polymer of (the at least one) vinyl group-containing monomer comprises a styrene-acrylonitrile copolymer and is in particular such a styrene-acrylonitrile copolymer.

[0046] In a fourth embodiment of the invention, which is a particular embodiment of the first to third embodiments, the (at least one) polyether polyol contains no further polyether polyols besides the (at least one) polymer-filled polyether polyol.

[0047] In a fifth embodiment of the invention, which can be combined with all other embodiments, the polyol component contains no other polyols other than the polyether polyol (at least one polyol optionally filled with a polymer). In a sixth embodiment of the invention, which can be combined with all other embodiments, the isocyanate component comprises, in addition to tolylene diisocyanate, methylenediphenylene diisocyanate or mixtures of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate, particularly those with a high proportion of methylenediphenylene diisocyanate.

[0048] In a seventh embodiment of the invention, which can be combined with all other embodiments, the isocyanate component comprises no further isocyanates besides toluene diisocyanate.

[0049] In an eighth embodiment of the invention, which is a particular embodiment of the sixth embodiment, the isocyanate component comprises polyisocyanurates.

[0050] In a ninth embodiment of the invention, which is a particular embodiment of the sixth to eighth embodiments, the isocyanate component comprises prepolymers of the said isocyanates (ie tolylene diisocyanate, polymethylene polyphenylene polyisocyanate and / or methylene diphenylene diisocyanate) and polyols.

[0051] In a tenth embodiment of the invention, which can be combined with all other embodiments,

[0052] (i) the primary or secondary chemolysis amine is an aliphatic primary or secondary organic amine and in particular 1,2-ethylenediamine, 1,4-diaminobutane and / or 1,6-hexamethylenediamine,

[0053] (ii) the chemolysis amino alcohol is an aliphatic amino alcohol having a primary or secondary amino group and in particular ethanolamine, N-methylethanolamine and / or 3-amino-l-propanol, and / or

[0054] (iii) the chemolysis alcohol methanol, ethanol, propanol (all isomers, preferably n-propanol), butanol (all isomers, preferably n-butanol), isopropanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol or a mixture of two or more of the aforementioned alcohols.

[0055] In an eleventh embodiment of the invention, which can be combined with all other embodiments, the mass ratio of (1) organic chemolysis reagent and water on the one hand and (2) the polyurethane foam on the other hand (m(l) / m(2); i.e. [m(organic chemolysis reagent) + m(water)] / m(polyurethane product); where m stands for mass) is in the range from 0.5 to 2.5, the mass of water being 3.0% to 22% of the mass of the chemolysis reagent.

[0056] In a twelfth embodiment of the invention, which can be combined with all other embodiments, step (B) is carried out at a temperature of 100°C to 195°C, preferably 110°C to 190°C, particularly preferably 115°C to 160°C and at a pressure of 900 mbapabs.) to 2000 mbapabs.), preferably 950 mbapabs.) to 1500 mbapabs.), particularly preferably 1000 mbapabs.) to 1300 mbapabs.) and in particular at ambient pressure, if necessary with reflux cooling.

[0057] In a thirteenth embodiment of the invention, which can be combined with all other embodiments, the polyurethane foam in step (B)

[0058] (I) firstly with (1) the organic chemolysis reagent, but not yet with the water, or (2) the organic chemolysis reagent and a first part of the water, and then

[0059] (II) the water (1) or a second part of the water (2) is added.

[0060] In a fourteenth embodiment of the invention, which is a particular embodiment of the thirteenth embodiment, in step (II) the water (1) or the second part of the water (2) is added continuously or in portions such that the temperature of the liquid phase during step (II) deviates from the temperature of the liquid phase in step (I) by a maximum of 20 °C, preferably by a maximum of 15 °C, particularly preferably by a maximum of 10 °C, very particularly preferably by a maximum of 5.0 °C and extraordinarily very particularly preferably by a maximum of 1.0 °C.

[0061] In a fifteenth embodiment of the invention, which is a particular embodiment of the thirteenth and fourteenth embodiments, in (l)(2) the first part of the water amounts to up to 4.0%, in particular 2.0% to 4.0%, of the mass of the total water added in step (B) (i.e. in (I) and (II) together).

[0062] In a sixteenth embodiment of the invention, which can be combined with all other embodiments, the organic solvent comprises an aromatic hydrocarbon, a water-insoluble ether, a halogenated (aliphatic or aromatic) hydrocarbon, or a mixture of two or more of the aforementioned solvents. In a seventeenth embodiment of the invention, which can be combined with all other embodiments, the extraction in step (D) is carried out at 10°C to 80°C, preferably at 20°C to 60°C.

[0063] In an eighteenth embodiment of the invention, which can be combined with all other embodiments, in step (D) the ratio of the mass m(3) of the chemolysis product depleted in organic chemolysis reagent (and optionally in toluenediamine and / or further amine and optionally also in solid components) and the mass m(4) of the organic solvent present in the extractant is, m(3) / m(4) = m[chemolysis product depleted in organic chemolysis reagent (and optionally in toluenediamine and / or further amine and optionally in solid components)] m[organic solvent]

[0064] (where m = mass), 0.03 to 3.0, preferably 0.04 to 2.8, particularly preferably 0.10 to 2.0, wherein the (total) extractant comprises, based on its total mass, 20 mass% to 80 mass% organic solvent and 20 mass% to 80 mass% aqueous constituents. The term "aqueous constituents" refers to the sum of all aqueous constituents, i.e., in the preferred embodiment with the addition of the acid in the form of an aqueous acid, to the sum of aqueous acid and any additional water added.

[0065] In a nineteenth embodiment of the invention, which can be combined with all other embodiments, the acid and the water are added in step (D) such that a pH in the range of 0.0 to 5.0, in particular 2.5 to 5.0, preferably 3.0 to 4.5 and particularly preferably 3.7 to 4.2 is established.

[0066] In a twentieth embodiment of the invention, which can be combined with all other embodiments, step (E) comprises distillation and / or stripping.

[0067] In a twenty-first embodiment of the invention, which can be combined with all other embodiments, the (at least one) polyether polyol obtained in step (E) is reacted with an isocyanate to form a polyurethane, in particular a polyurethane foam. In a twenty-second embodiment of the invention, which can be combined with all other embodiments, the process comprises

[0068] (F) workup of the acidic aqueous phase to obtain toluenediamine (and optionally any other amines present which correspond to other isocyanates of the isocyanate component other than toluene diisocyanate).

[0069] In a twenty-third embodiment of the invention, which is a particular embodiment of the twenty-second embodiment, the workup of the acidic aqueous phase comprises a (optionally "over-") neutralization with a base followed by phase separation and / or distillation and / or stripping.

[0070] In a twenty-fourth embodiment of the invention, which can be combined with all other embodiments except those which provide for complete separation of the toluenediamine in step (C), toluenediamine is also partially distilled off from the chemolysis product in step (C).

[0071] In a twenty-fifth embodiment of the invention, which can be combined with all other embodiments except those which provide for only partial separation of the toluenediamine in step (C), the toluenediamine is also (completely) distilled off from the chemolysis product in step (C).

[0072] In a twenty-sixth embodiment of the invention, which is a particular embodiment of the twenty-second to twenty-fifth embodiments, the toluenediamine obtained in step (F) (and optionally the further amines optionally obtained in step (F) which correspond to isocyanates of the isocyanate component other than toluene diisocyanate) and / or the toluenediamine distilled off in step (C), optionally after purification, is used in the production of toluene diisocyanate (or in the production of other isocyanates of the isocyanate component).

[0073] In a twenty-seventh embodiment of the invention, which is a particular embodiment of the twenty-sixth embodiment, the toluene diisocyanate is reacted with a polyol to form a polyurethane, in particular a polyurethane foam.

[0074] In a twenty-eighth embodiment of the invention, which is a particular embodiment of the twenty-seventh embodiment, the polyol comprises the (at least one) polyether polyol obtained in step (E). In a twenty-ninth embodiment of the invention, which can be combined with all other embodiments, the chemolysis is carried out in the presence of a catalyst.

[0075] In a thirtieth embodiment of the invention, which is a particular embodiment of the twenty-ninth embodiment, the catalyst is selected from a (particularly alkali metal or alkaline earth metal) hydroxide, a (particularly alkali metal or alkaline earth metal) carboxylate (particularly acetate), a tin compound (particularly dibutyltin dilaurate or tin(II) octoate [= tin(II) 2-ethylhexanoate]), a zinc compound (particularly zinc acetate), a (particularly alkali metal or alkaline earth metal) carbonate, a (particularly alkali metal or alkaline earth metal) orthophosphate, a (particularly alkali metal or alkaline earth metal) monohydrogen orthophosphate, a (particularly alkali metal or alkaline earth metal) metaphosphate or a mixture of two or more of the aforementioned catalysts.Preferably, the catalyst is selected from a (particularly alkali metal or alkaline earth metal) carbonate, a (particularly alkali metal or alkaline earth metal) orthophosphate, a (particularly alkali metal or alkaline earth metal) monohydrogen orthophosphate or a mixture of two or more of the aforementioned catalysts.

[0076] In a thirty-first embodiment of the invention, which is a particular embodiment of the twenty-ninth and thirtieth embodiments, the mass ratio of catalyst to polyurethane foam is in the range of 0.001 to 0.035.

[0077] In a thirty-second embodiment of the invention, which can be combined with all other embodiments, organic chemolysis reagent distilled off in step (C), optionally after purification, is recycled to step (B).

[0078] In a thirty-third embodiment of the invention, which can be combined with all other embodiments, the (at least one) polyether polyol contains secondary OH end groups in a (by means of 13 C-NMR spectroscopy as described in the section "Foam Analysis"), molar fraction of > 45%, in particular 46% to 100%, preferably 80% to 100%.

[0079] In a thirty-fourth embodiment of the invention, which can be combined with all other embodiments, the acid is selected from hydrogen chloride gas, hydrochloric acid, sulfuric acid, phosphoric acid, a sulfonic acid (in particular para-toluenesulfonic acid and / or methanesulfonic acid), a carboxylic acid (in particular trifluoroacetic acid, oxalic acid, formic acid and / or acetic acid, with formic acid and acetic acid being preferred) or a mixture of two or more of the aforementioned acids.

[0080] The embodiments briefly described above and other possible configurations of the invention are explained in more detail below. All of the embodiments described above and the other configurations of the invention described below can be combined with one another as desired, unless the context clearly indicates otherwise to a person skilled in the art or unless expressly stated otherwise.

[0081] PREPARATION OF POLYURETHANE FOAM FOR CHEMOLYSIS

[0082] In step (A) of the process according to the invention, the polyurethane foam to be recycled by chemolysis is prepared. According to the invention, the isocyanate component used in the production of the polyurethane foam contains at least toluene diisocyanate, and the polyol component contains at least one polyether polyol. Provided these conditions are met, the polyurethane foam can in principle be any type of polyurethane foam. In particular, both flexible and rigid foams are suitable, with flexible foams (e.g., from old mattresses, upholstered furniture, or car seats) being preferred.

[0083] The process according to the invention can be applied both to the recycling of used (so-called £nd-o / -£ / / e-) polyurethane foams and to the recycling of foam waste from foam production. In the latter case, the chemical nature of the isocyanate component and the polyol component used in production is, of course, known.

[0084] When reusing used polyurethane foam, appropriate sorting is particularly important to ensure that it is a polyurethane foam suitable for the purposes of the process according to the invention. Knowing the original application of a used polyurethane foam to be recycled will generally reveal whether or not it is a TDI- and polyether-based polyurethane foam. The same applies to other properties of the polyol and isocyanate components used in the production of the polyurethane foam listed below. By collecting different foam types separately, the identification of suitable foams can therefore be easily ensured.If the exact properties of an available polyurethane foam are not known (for example, because it is a used polyurethane foam with an unspecified origin), this can be determined as described in the section "Foam Analysis". In particular, TDI-based polyurethane foams can be determined by. 1 H NMR spectroscopy. The chemical nature of the polyol component can be determined by IR spectroscopy.

[0085] According to the invention, the polyol component contains at least one polyether polyol. It is preferred that this is a so-called "inactive" polyether polyol. In this context, "inactive" polyether polyols are understood to mean polyether polyols with a considerable molar fraction of secondary OH end groups, which (by means of 13C-NMR spectroscopy as described in the section "Foam Analysis") is greater than 45% and preferably 46% to 100%, particularly preferably 80% to 100%.

[0086] As already mentioned, in one embodiment of the process according to the invention, the polyol component comprises at least one polymer-filled polyether polyol (PMPO), wherein the polymer comprises a polymer of at least one vinyl-containing monomer, a polyurea, and / or a polyurethane. It is particularly preferred that the polymer comprises a polymer of at least one vinyl-containing monomer and, in particular, is such a polymer. The polymer of the vinyl-containing monomer comprises (preferably, is) in particular a styrene-acrylonitrile copolymer (SAN copolymer). In one embodiment of the process according to the invention, no other polyether polyols are present besides the polymer-filled polyether polyol. The distillation of the organic chemolysis reagent according to the invention prevents swelling of the polymer.

[0087] The optional removal of solid constituents before and / or after performing step (C) comprises, in particular, a separation of such polymers. It is preferred to remove solid constituents at least after performing step (C). It may also be necessary to perform two solid separations: a first before performing step (C) to remove the majority of solid constituents and a second after performing step (C) to remove any remaining residues. In addition to the polymers mentioned, the solid separation may also comprise the separation of other solid constituents, such as, for example, the catalyst used in the chemolysis or solid constituents from used (so-called £nd-o / -£ / / e-) polyurethane foams.Such solid components can include, for example, inorganic fillers (such as calcium carbonate, barium sulfate, aluminum trihydrate, silicates), flame retardants (such as melamine, ammonium polyphosphate), or paints (such as pigments, carbon black). Solids separation prevents entrained solids from causing problems in subsequent process steps, for example, by forming solid deposits on equipment such as pumps or evaporators.

[0088] Regardless of whether the polyol component contains polymer-filled polyether polyols or not, the polyol component preferably does not comprise any other polyols other than polyether polyols. Particularly preferably, all polyether polyols are inactive polyether polyols as defined above.

[0089] In industrial practice, polyether polyols on which the polyurethane foams to be recycled according to the invention are based often have the following number-average molecular weights and functionalities:

[0090] Number average molecular weight: 2000 g / mol to 8000 g / mol, in particular 2500 g / mol to 6500 g / mol and

[0091] Functionality: 2 to 8, especially 3 to 6.

[0092] These values ​​can also be achieved within the scope of the present invention. However, polyurethane foams based on polyols whose properties deviate from these values ​​can also be recycled using the process according to the invention.

[0093] Regarding the isocyanate component of the polyurethane foam, one embodiment of the process according to the invention provides that, in addition to tolylene diisocyanate (TDI), it additionally comprises (i) methylenediphenylene diisocyanate (mMDI) or (ii) mixtures (MDI) of methylenediphenylene diisocyanate (mMDI) and polymethylenepolyphenylene polyisocyanate (pMDI), particularly those with a high proportion of methylenediphenylene diisocyanate (mMDI). Particularly in this embodiment, it is furthermore possible for the polyurethane foam to also comprise polyisocyanurates.

[0094] Particularly preferably, TDI is the sole isocyanate of the isocyanate component.

[0095] Prepolymers made from the isocyanates and polyols mentioned above can of course also be used in the production of the polyurethane foam.

[0096] Foam Analysis The polyurethane foam (PU) to be analyzed is first analyzed for functional groups using ATR infrared spectroscopy (ATR = attenuated total reflection). The infrared spectrum (IR spectrum) provides a qualitative composition of the polyurethane foam. This allows it to be determined whether the polyurethane foam is based on polyether and / or polyester polyols. All polyether polyurethanes are characterized by their COC vibration band at 1100 cm 1 If propylene oxide polyether is present, the reaction occurs at 2960 cm 1 the CH3 stretching vibration band typical for this material. The IR spectrum also provides information about which fillers (such as calcium carbonate, silicates, SAN polymers) may be present. For example, SAN polymers are characterized by the nitrile band at approximately 2240 cm 1 and the styrene band at about 705 cm -1identifiable. The IR spectrum also provides information about whether the polyurethane foam is partially or completely MDI-based, because such polyurethane foams are characterized by characteristic bands at 1410 cm' 1 , 1010 cm 1 and 510 cm 1 Partially or fully TDI-based polyurethane foams are produced after chemical decomposition of the polyurethane foam (see below) by 1 H NMR spectroscopy has demonstrated this. The methyl group of the TDA formed during cleavage (measured in CDCl3; chemical shift relative to the residual proton signal) is located at approximately 2.10 ppm in the case of the 2,4-isomer and approximately 1.97 ppm in the case of the 2,6-isomer. The aromatic range of 2,4-TDA extends from 6.0 ppm to 7.0 ppm, that of 2,6-TDA from 6.2 ppm to 7.0 ppm.

[0097] The polyurethane foam is then subjected to extraction in a Soxhlet extractor with acetone as solvent (LM) in a mass ratio LM:PU of 130:1 for 4 h at reflux (boiling point of acetone) in order to separate low molecular weight auxiliaries used in PU production, such as flame retardants, antioxidants, etc.

[0098] For a complete investigation of the polyether polyol composition, the polyurethane foam thus freed from impurities must be completely chemically digested. The solid PU residue (PU-RS) remaining after removal of the acetone is reacted with a water-moist methanolic KOH solution (KOH(MeOH); c = 4 mol / l; water content approx. 1 mass %) in a KOH(MeOH) : PU-RS mass ratio of 27 : 1 at 150 °C for 15 h. The resulting reaction mixture is filtered, and the filter residue is washed with MeOH. The resulting filtrate I is neutralized with hydrogen chloride gas or a methanolic hydrogen chloride solution against phenolphthalein and filtered again. The resulting filtrate II is freed from methanol using a rotary evaporator. The remaining residue is dissolved in CDCl3. 1H-NMR spectroscopic detection of TDA can be carried out with the resulting CDCH phase I. For further investigation, the CDCH phase I is extracted with hydrochloric acid (c = 1 mol / l), followed by separation into an aqueous hydrochloric acid phase, which contains the amines formed by hydrolytic cleavage as hydrochlorides, and an organic CDCH phase II. The aqueous hydrochloric acid phase obtained after phase separation can also be 1 H-NMR spectroscopy.

[0099] The resulting organic CDCH phase II is 13C-NMR spectroscopy using chromium(III) acetylacetonate as a relaxation accelerator was used to determine the molar fraction of primary OH end groups as follows: Secondary and primary OH end groups can be clearly identified by their chemical shift. Carbon atoms with secondary OH groups lie (measured against the carbon atom of the CDCH solvent) in a range of 65 ppm to 67 ppm, and those with primary OH groups in a range of 60 ppm to 62 ppm. By integrating the respective signal areas and calculating the ratio, the molar ratio b of the corresponding carbon atoms to each other, which corresponds to the molar ratio of primary to secondary OH end groups, can be determined: b = n(sec.) / n(prim.), where n = molar amount, sec. = secondary OH end groups, prim. = primary OH end groups.

[0100] The mole fraction of secondary OH end groups, x(sec.), is then given by the equation: x(sec.) = n(sec.) / (n(sec.) + n( pri m .)) = b / (b + 1).

[0101] Multiplying by 100 gives the corresponding percentage value.

[0102] Preferably, step (A) already comprises preparatory steps for the chemolysis in step (B). This involves, in particular, mechanical comminution of the polyurethane foams. Such preparatory steps are known to the person skilled in the art; reference is made, for example, to the literature cited in [1]. Depending on the nature of the polyurethane foam, it may be advantageous to "freeze" it before mechanical comminution in order to facilitate the comminution process.

[0103] Before, during, or after mechanical comminution, the polyurethane foam can be treated with (aqueous or alcoholic) disinfectants. Such disinfectants are preferably hydrogen peroxide, chlorine dioxide, formaldehyde, alkali metal hypochlorites (especially sodium hypochlorite), and / or peracetic acid (aqueous disinfectants) or ethanol, isopropanol, and / or 1-propanol (alcoholic disinfectants). It is also conceivable to carry out the described preparatory steps at a location spatially separate from the chemical lysis site. In this case, the prepared foam is loaded into suitable transport vehicles, such as silo vehicles, for further transport. For further transport, the prepared foam can also be compressed to achieve a higher mass-to-volume ratio.

[0104] CHEMOLYSIS OF POLYURETHANE FOAM

[0105] Step (B) of the process according to the invention involves the chemolysis of the polyurethane foam prepared in step (A) by reaction with an organic chemolysis reagent and water. The chemolysis takes place as aminohydrolysis (use of a primary or secondary amine or an amino alcohol with a primary or secondary amino group as the organic chemolysis reagent), as hydroalcoholysis (use of an alcohol as the organic chemolysis reagent), or as a combination of the aforementioned processes. Hydroalcoholysis is preferred. This also applies in particular to the chemolysis of polyurethane foams that are not filled with a polymer.In each case, a chemolysis product is formed which comprises the at least one polyether polyol (and optionally further polyols), TDA (and optionally further amines which correspond to isocyanates of the isocyanate component other than TDI) and the organic chemolysis reagent (which is released again by hydrolytic cleavage of the intermediately formed carbamates and / or ureas of the isocyanate(s) of the isocyanate component and the organic chemolysis reagent).

[0106] If the chemolysis reagent used comprises a chemolysis amine, this is preferably selected from an aliphatic primary or secondary organic amine, in particular 1,2-ethylenediamine, 1,4-diaminobutane and / or 1,6-hexamethylenediamine.

[0107] If the chemolysis reagent used comprises a chemolysis amino alcohol, this is preferably selected from an aliphatic amino alcohol having a primary or secondary amino group, in particular ethanolamine, N-methylethanolamine and / or 3-amino-l-propanol.

[0108] If the chemolysis reagent used comprises a chemolysis alcohol, this is preferably selected from methanol, ethanol, propanol (all isomers, preferably n-propanol), butanol (all isomers, preferably n-butanol), isopropanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol and / or 2-methyl-1,3-propanediol. Preferably, in step (B), a mass ratio of (1) organic chemolysis reagent and water on the one hand and (2) the polyurethane foam on the other hand (m(l) / m(2); i.e. [m(organic chemolysis reagent) + m(water)] / m(polyurethane product); where m stands for mass) is set in the range of 0.5 to 2.5, wherein the mass of the water is 3.0% to 22% of the mass of the chemolysis reagent.

[0109] Step (B) is preferably carried out at a temperature of 100°C to 195°C, preferably 110°C to 190°C, particularly preferably 115°C to 160°C and at a pressure of 900 mbapabs.) to 2000 mbapabs.), preferably 950 mbapabs.) to 1500 mbar(abs.), particularly preferably 1000 mbapabs.) to 1300 mbapabs.) and in particular at ambient pressure, if necessary with reflux cooling.

[0110] Regarding the order of addition of the reactants in step (B), the polyurethane foam is preferably added

[0111] (II) firstly treated with (1) the organic chemolysis reagent, but not yet with the water, or (2) the organic chemolysis reagent and a first portion of the water, and then

[0112] (II) adding the water (1) or a second part of the water (2).

[0113] This facilitates the hydrolytic cleavage of the polyurethane bonds or intermediately formed carbamates or ureas from the isocyanate of the isocyanate component and the organic chemolysis reagent. In this embodiment, it is particularly preferred if, in step (II), the water (1) or the second portion of the water (2) is added continuously or in portions such that the temperature of the liquid phase during step (II) deviates from the temperature of the liquid phase in step (I) by a maximum of 20 °C, preferably by a maximum of 15 °C, particularly preferably by a maximum of 10 °C, very particularly preferably by a maximum of 5.0 °C, and extraordinarily very particularly preferably by a maximum of 1.0 °C. In variant (2) of step (I), it is preferred that the first portion of the water amounts to up to 4.0%, in particular 2.0% to 4.0%, of the total mass of the water added in step (B) (i.e., in (I) and (II) together).

[0114] It is preferred to carry out the chemolysis in step (B) in the presence of a catalyst. Suitable catalysts include (in particular alkali metal or alkaline earth metal) hydroxides, (in particular alkali metal or alkaline earth metal) carboxylates (in particular acetates), tin compounds (in particular dibutyltin dilaurate or tin(II) octoate [= tin(II) 2-ethylhexanoate]), zinc compounds (in particular zinc acetate), (in particular alkali metal or alkaline earth metal) carbonates, (in particular alkali metal or alkaline earth metal) orthophosphates, (in particular alkali metal or alkaline earth metal) monohydrogen orthophosphates, (in particular alkali metal or alkaline earth metal) metaphosphates, or mixtures of two or more of the aforementioned catalysts.The catalyst is preferably selected from a carbonate (especially an alkali metal or alkaline earth metal), an orthophosphate (especially an alkali metal or alkaline earth metal), a monohydrogen orthophosphate (especially an alkali metal or alkaline earth metal), or a mixture of two or more of the aforementioned catalysts. The mass ratio of catalyst to polyurethane foam is preferably in the range from 0.001 to 0.035 (for all catalysts).

[0115] DISTILLATION OF THE ORGANIC CHEMOLYSING REAGENT AND OPTIONALLY THE AMINE

[0116] In step (C) of the process according to the invention, organic chemolysis reagent is distilled from the chemolysis product to obtain a chemolysis product depleted in organic chemolysis reagent. Distillation can be preceded and / or followed by the removal of solid components, as described above. Suitable distillation conditions depend on the type of organic chemolysis reagent used and can be easily determined by a person skilled in the art. Preferably, organic chemolysis reagent distilled in step (C) is recycled to step (B), optionally after purification (in particular by distillation).

[0117] It is also possible, in step (C), to additionally distill off the toluenediamine (TDA) formed in step (B) and optionally any other amines present (in particular methylenediphenylenediamine) from the chemolysis product. Since TDA and any other amines present generally have a higher boiling point than the organic chemolysis reagent, it is preferable to first distill off the chemolysis reagent and then, at a higher temperature, the TDA or the TDA and any other amines present. Alternatively to and / or in combination (namely, if only a portion of the TDA / any other amines present is distilled off in step (C)) with this procedure, TDA formed in step (B) and any other amines formed in step (B) can also be recovered from the acidic aqueous phase obtained in the extraction according to step (D) (see step (F) below).

[0118] Regardless of whether the TDA formed in step (B) and optionally any other amines present are also distilled off completely or partially from the chemolysis product in step (C), the evaporator types described in WO 2023 / 099420 A1 for step (DI) therein can preferably be used to distill off the organic chemolysis reagent, namely falling-film evaporators, natural circulation evaporators, kettle evaporators, forced circulation evaporators, or flash evaporators. If only the chemolysis reagent and not TDA (and any other amines) are to be distilled off at this point, care must be taken to ensure a sufficient boiling point difference between the chemolysis reagent used and the amine with the lowest boiling point (which in practice will usually be TDA).If the TDA and optionally any other amines present are also to be distilled off, this of course does not matter, and a joint distillation of the chemolysis reagent and amine(s) is possible.

[0119] It is preferred that a first distillation using one of the aforementioned evaporator types is followed by a second distillation and / or stripping. Such a second distillation is preferably carried out using one of the evaporator types described in WO 2023 / 099420 A1 for step (D. II) therein, namely thin-film evaporators, short-path evaporators, or flash evaporators, in particular thin-film or short-path evaporators. Stripping serves to remove any residues of chemolysis reagent and, if desired, TDA (and any other amines present) that may still be present and have not yet been separated off by previous distillation steps and is preferably carried out using steam or an inert gas such as nitrogen, in particular in columns, preferably columns filled with random packing or structured packing.

[0120] Regardless of the source of the recovered TDA / further amine, it is preferred to use it, optionally after purification, in particular by distillation (by means of which different amines can also be separated from one another), in the production (new production) of an isocyanate (= the corresponding isocyanate). Known processes are suitable for this purpose, in particular comprising phosgenation of the recovered TDA / further amine. Isocyanate produced in this way can be easily converted into a polyol to form a polyurethane, in particular a polyurethane foam. The at least one polyether polyol obtained in step (E) is also particularly suitable as a polyol.

[0121] EXTRACTION OF THE POLYETHER POLYOL

[0122] Step (D) of the process according to the invention comprises the extraction of the at least one polyether polyol from the chemolysis product depleted in organic chemolysis reagent (and optionally in solid components and optionally in TDA / further amine). The extraction is carried out using a (water-insoluble) organic solvent. An acid and water are added, in particular in such a way that an aqueous acid is added, optionally in combination with further water. Suitable acids include, for example, hydrogen chloride gas, hydrochloric acid, sulfuric acid, phosphoric acid, sulfonic acids (in particular para-toluenesulfonic acid, methanesulfonic acid) and carboxylic acids (in particular trifluoroacetic acid, oxalic acid, formic acid, acetic acid, with formic acid and acetic acid being preferred). The order in which the organic solvent, the acid and the water are added is variable, i.e.it is not critical for the successful application of the process according to the invention. Although the process according to the invention can in principle be carried out using any addition sequence, it may be advantageous to first add the organic solvent and then the acid / water to accelerate the subsequent phase separation. If an aqueous acid is used, the addition sequence is preferably (1) organic solvent, (2) optional additional water, and (3) aqueous acid. If the acid used is non-aqueous, the addition sequence is preferably (1) organic solvent, (2) water, and (3) acid.

[0123] After separation of an acidic aqueous phase, a polyol phase comprising the organic solvent and the at least one polyether polyol is obtained. The acid and the water are preferably added (in particular in the form of an aqueous acid and optionally further water) such that a pH in the range from 0.0 to 5.0, in particular 2.5 to 5.0, preferably 3.0 to 4.5 and particularly preferably 3.7 to 4.2 is established. The organic solvent is preferably selected from an aromatic hydrocarbon, a water-insoluble ether, a halogenated (aliphatic or aromatic) hydrocarbon or a mixture of two or more of the aforementioned solvents. The extraction is preferably carried out at 10 °C to 80 °C, particularly preferably at 20 °C to 60 °C.

[0124] In the extraction according to step (D), a ratio of the mass m(3) of the chemolysis product depleted in organic chemolysis reagent (and optionally in solid components and optionally in amine) and the mass m(4) of the organic part of the extraction agent, m(3) / m(4) = m[chemolysis product depleted in organic chemolysis reagent (and optionally in solid components and optionally in TDA / further amine)] m[organic solvent]

[0125] (where m = mass) in the range of 0.03 to 3.0. "m[organic solvent]" denotes the mass of the organic solvent present in the extractant. Depending on the circumstances of the individual case, various values ​​within this range may be advantageous, for example, values ​​from 0.04 to 2.8 or from 0.10 to 2.0. Which values ​​are most appropriate in a specific case can easily be determined through simple preliminary tests. In general, one strives to keep the amount of organic solvent used as low as possible. The total extractant used comprises, based on its total mass, 20% to 80% organic solvent and 20% to 80% aqueous components by mass.The term "aqueous components" refers to the sum of all aqueous components, i.e., in the preferred embodiment with the addition of the acid in the form of an aqueous acid, to the sum of aqueous acid and any additional water added.

[0126] PROCESSING THE POLYOL PHASE TO OBTAIN THE POLYETHER POLYOL AND, IF NECESSARY, THE TDA

[0127] The polyol phase obtained in step (D) is subsequently processed in step (E) to obtain at least the polyether polyol. This processing preferably comprises distillation and / or stripping. Regardless of the precise type of processing, it is preferred to react the polyether polyol obtained in step (E) with an isocyanate to form a polyurethane, in particular a polyurethane foam.

[0128] If the TDA formed in the chemolysis has not already been distilled off in step (C), it is present in protonated form in the acidic aqueous phase obtained in step (D). In this case, it is preferable to process the acidic aqueous phase in a step (F) to obtain the TDA. This process comprises, in particular, a (possibly "over-") neutralization with a base followed by phase separation and / or distillation and / or stripping. The recovered TDA is preferably used, optionally after purification (in particular by distillation), in the new production of an isocyanate. If, in addition to TDA, other amines are present in the acidic aqueous phase, these can be separated using conventional separation techniques.For example, methylenediphenylenediamine and polymethylenepolyamine can be separated after neutralization by phase separation (these amines, unlike TDA, are not water-soluble), optionally assisted by the addition of an organic solvent (in particular, the same organic solvent used in the extraction according to step (D)). Feedstocks:

[0129] For the following tests, a polyurethane foam was used, manufactured according to the following

[0130] Recipe as starting material for chemolysis:

[0131] 1) Polyether polyol with secondary OH end groups from Covestro Deutschland AG.

[0132] 2) Polymer-filled (styrene-acrylonitrile) polyether polyol with secondary OH end groups from Covestro Deutschland AG.

[0133] 3) Demineralized water.

[0134] 4) Polyethersiloxane additive from Evonik AG.

[0135] 5) Amine catalyst from Momentive Performance Materials.

[0136] 6) Tin catalyst from Air Products.

[0137] 7) Desmodur T80 is an isomer mixture of 2,4- and 2,6-TDI from Covestro Deutschland AG.

[0138] 8) Amount of NCO groups used per 100 mol of OH groups.

[0139] Analytics:

[0140] Amine number determination. The amine number indicates how many mg of potassium hydroxide are required to neutralize the free organic amines present in 1 g of substance. Primary, secondary, and tertiary amino groups are detected. The amino groups are weak bases. Concentrated acetic acid (glacial acetic acid, 99% to 100%) is used as the solvent. The amine is protonated by the solvent and thus converted into the corresponding acid, which now forms an ion pair with the deprotonated acid of the glacial acetic acid. The titration is then carried out using 0.1 molar perchloric acid as the titrant, with the perchloric acid displacing the anion of the solvent (glacial acetic acid). The perchloric acid consumed is equated with the consumption of potassium hydroxide. The amine number is usually expressed in milligrams of KOH per gram of sample and is calculated as follows: wherein

[0141] • AZ for the amine number,

[0142] • V is the volume of perchloric acid solution consumed,

[0143] • m is the mass of the titrated sample,

[0144] • M(KOH) for the molar mass of KOH (56.11 g • mol -1 ),

[0145] • bi is the molarity of the perchloric acid solution and

[0146] • f stands for the dimensionless factor (titer) of the perchloric acid solution.

[0147] Degree of protonation. The degree of protonation is a measure of the amount of added acid. If the amount of added acid corresponds to the amount theoretically required to protonate all amine groups, the degree of protonation is said to be 100%. pH values ​​were determined at the specified temperature using an Accumet AP 110 pH meter and a glass electrode.

[0148] NMR spectroscopy. For analysis by 1For H-NMR spectroscopy, the samples to be measured were dissolved in deuterated solvents such as chloroform, DMSO, or acetone. The choice of deuterated solvent was based on the position of the signals of the compounds under investigation. Pyrazine was used as an internal standard.

[0149] Overview of the examples:

[0150] Examples la and lb: hydroalcoholysis and aminohydrolysis of the PU foam, respectively.

[0151] Examples 2a and 2b: Distillation of the organic chemolysis reagent and filtration.

[0152] Examples 3a to 3c: Extraction with prior distillation and filtration (as in Examples 2a and 2b) and with the addition of acid (extraction experiments according to the invention). Example 4: Extraction without distillation and without the addition of acid (comparative experiment).

[0153] Example 5: Extraction with prior distillation and filtration (as in

[0154] Example 2b), but without the addition of acid (comparative experiment). and (B) of the

[0155] In a 1000 ml, 4-neck flask equipped with a stirrer, thermometer, and cooling attachment, 300 g of diethylene glycol (DEG) and 5.5 g of sodium carbonate were placed and heated to 180 °C under nitrogen. While stirring, 300 g of the polyurethane foam with the above composition were added and dissolved. After dissolution, the mixture was stirred at 180 °C for 2 hours, and then 17 g of water was added over a period of 1 hour so that the reaction temperature did not fall below 160 °C. After the water addition was complete, the mixture was stirred for a further 2 hours at 160 °C to 180 °C.

[0156] In a 1 H-NMR spectrum of the reaction mixture showed no TDI-based carbamates, but only TDA. Thus, complete hydrolysis has occurred. and (B) of the

[0157] In a 1000 ml, 4-neck flask equipped with a stirrer, thermometer, and cooling attachment, 300 g of ethanolamine and 3 g of sodium carbonate were placed and heated to 150 °C under nitrogen. While stirring, 300 g of the polyurethane foam with the above composition were added and dissolved. After dissolution, the mixture was stirred at 150 °C for 2 hours, and then 18 g of water were added over a period of 30 minutes, ensuring that the reaction temperature did not fall below 150 °C.

[0158] In a 1 H-NMR spectrum of the reaction mixture showed no TDI-based carbamates, only TDA. Thus, complete hydrolysis has occurred. of the and filtration - Instructions After completion of the hydroalcoholysis (Ex. la) or aminohydrolysis (Ex. lb), the organic chemolysis reagent used and the excess water used are removed by distillation from the chemolysis product obtained at a temperature of 150 to 180 °C while continuously reducing the pressure to less than 20 mbar, typically leaving a residual content of organic chemolysis reagent of < 5 mass%.

[0159] The resulting chemolysis product from Example 1a, which is depleted of organic chemolysis reagent, typically has the following composition according to analysis by 1H-NMR / 2D-NIVIR spectroscopy with internal standard:

[0160] 3.7% TDA; 6.0% SAN polymer; 88.0% polyether polyols; 2.3% DEG.

[0161] The resulting chemolysis product from Example 1b, which is depleted of organic chemolysis reagent, typically has the following composition according to analysis by 1H-NMR / 2D-NIVIR spectroscopy with internal standard:

[0162] 4.6% TDA; 5.9% SAN polymer, 74.4% polyether polyol; 4.6% 2-oxazolidinone (ethanolamine by-product).

[0163] In both cases, distillation is followed by filtration. A pressure filter apparatus is used for this, which carries out filtration through a Pall T5500 depth filter previously coated with diatomaceous earth at an overpressure of 0.5 to 2.5 bar. The filter is pre-coated as follows:

[0164] A 5% slurry of diatomaceous earth (“Celite 545”) in diethylene glycol is prepared using a Pendraulik laboratory dissolver Disperlux LR 34 at 1000 rpm and then filtered through the depth filter T5500 so that at 140 mm 2A coating of approximately 25 g of Celite 545 is created for each filter diameter.

[0165] The filtered chemolysis product from Example 1a, which is depleted of organic chemolysis reagent, typically has the following composition according to 1H-NMR / 2D-NIVIR spectroscopy with internal standard:

[0166] 3.7% TDA; 0.5% SAN polymer; 95.2% polyether polyols; 0.6% DEG.

[0167] The filtered chemolysis product from Example 1b, which is depleted of organic chemolysis reagent, typically has the following composition according to 1H-NMR / 2D-NIVIR spectroscopy with internal standard:

[0168] 3.8% TDA; 0.2% SAN polymer; 93% polyether polyols; 3.2% 2-oxazolidinone (ethanolamine by-product). Example 3a: Extraction (Step (D) of the process according to the invention)

[0169] A product mixture remaining after distillation (according to Example 2a) of the chemolysis product of the hydroalcoholysis according to Example 1a was mixed with dichloromethane and water in the following mass ratio, whereby the amine number was determined after addition of the dichloromethane:

[0170] Product mixture: dichloromethane: water = 0.11:1:1. Subsequently, based on the result of the amine number determination, a protonation degree of 100% was adjusted by adding 32% hydrochloric acid.

[0171] The resulting mixture was shaken at 50 °C, followed by phase separation into the acidic aqueous phase and the organic polyol phase. Both phases were concentrated on a rotary evaporator at approximately 20 mbar and 120 °C until no further evaporation of volatile components was visible, and then 1 H-NMR spectroscopy. The following compositions were determined:

[0172] • Concentrated acidic aqueous phase: 96.4% TDA hydrochloride; 0.1% polyether polyol; 3.5% diethylene glycol.

[0173] • Concentrated polyol phase: 92.0% polyether polyols; 8.0% diethylene glycol.

[0174] Example 3b: Extraction (step (D) of the process according to the invention)

[0175] A portion of the product mixture remaining after distillation and filtration (according to Example 2a) of the chemolysis product of the hydroalcoholysis according to Example 1a was mixed with chloroform and water in the following mass ratio:

[0176] Product mixture: chloroform: water = 0.11:1:1. A pH value of 4.0 was then adjusted by adding 32% hydrochloric acid.

[0177] The resulting mixture was shaken at 50 °C, followed by phase separation into the acidic aqueous phase and the organic polyol phase. Both phases were concentrated on a rotary evaporator at approximately 20 mbar and 120 °C until no further evaporation of volatile components was visible, and then 1 H-NMR spectroscopy. The following compositions were determined:

[0178] • Concentrated acidic aqueous phase: 51.3% TDA hydrochloride; 48.0% TDA; 0.7% polyether polyols.

[0179] • Concentrated polyol phase: 97.0% polyether polyols; 0.8% TDA; 2.2% diethylene glycol. Example 3c: Extraction (Step (D) of the process according to the invention)

[0180] A portion of the product mixture remaining after distillation and filtration (according to Example 2b) of the chemolysis product of the aminohydrolysis according to Example 1b was mixed with chloroform and water in the following proportions:

[0181] Product mixture: chloroform: water = 0.11:1:1. Subsequently, a pH value of 4.0 was adjusted by adding 32% hydrochloric acid.

[0182] The resulting mixture was shaken at 50 °C, followed by phase separation into the acidic aqueous phase and the organic polyol phase. Both phases were concentrated on a rotary evaporator at approximately 20 mbar and 120 °C until no further evaporation of volatile components was visible, and then 1 H-NMR spectroscopy. The following compositions were determined:

[0183] • Concentrated acidic aqueous phase: 96% TDA hydrochloride; 0.2% polyether polyols, 3.8% 2-oxazolidinone (by-product of ethanolamine).

[0184] • Concentrated polyol phase: 99.0% polyether polyols; 1.0% TDA.

[0185] Example 4: Extraction without prior distillation of the organic chemolysis reagent and without addition of an acid for extraction (comparison)

[0186] A portion of the chemolysis product of the hydroalcoholysis according to Example 1a was mixed with cyclohexane in the following mass ratio:

[0187] Product mixture : cyclohexane = 1 : 3.

[0188] The resulting mixture was shaken at 25 °C, followed by phase separation into a DEG phase and a cyclohexane phase. Both phases were concentrated on a rotary evaporator at approximately 20 mbar and 120 °C until no further evaporation of volatile components was visible, and then TH-NMR spectroscopy was used to determine the following compositions:

[0189] • Concentrated DEG phase: 11.8% TDA; 79.7% diethylene glycol; 5.3% polyether polyols; 3.2% SAN polymer.

[0190] • Concentrated cyclohexane phase: 95.6% polyether polyols; 1.1% TDA; 3.3% diethylene glycol.

[0191] If the diethylene glycol and SAN polymer content is subtracted from the aqueous phase, the resulting TDA content is 69.0% and the polyether polyols 31.0%. The separation of TDA and polyether polyols is therefore considerably poorer than in the inventive examples. Example 5: Extraction with prior distillation and filtration (as in Example 2b), but without the addition of acid (comparative experiment)

[0192] A portion of the product mixture remaining after distillation and filtration (according to Example 2b) of the chemolysis product of the aminohydrolysis according to Example 1b was mixed with chloroform and water in the following mass ratio:

[0193] Product mixture: Chloroform: Water = 0.11:1:1.

[0194] The resulting mixture was shaken at 50 °C. An emulsion formed, which separated into two phases after approximately 1.5 hours of standing time. Both phases were concentrated on a rotary evaporator at approximately 20 mbar and 120 °C until no further evaporation of volatile components was visible. 1 H-NMR-

[0195] spectroscopy. The following compositions were determined:

[0196] • Concentrated aqueous phase: 40% TDA; 0.4% polyether polyols, 59.6% by-products of ethanolamine and TDA (e.g., 2-oxazolidinone, N,N'-bis(2-hydroxyethyl)urea, and other by-products). • Concentrated polyol phase: 90.0% polyether polyols; 7.0% TDA, 3.0%

[0197] Byproducts of TDA and ethanolamine.

[0198] Compared to Example 3c, a significantly poorer separation of TDA and polyol and a greatly increased proportion of by-products can be observed.

Claims

1. A process for the recovery of valuable materials from polyurethane foams, comprising the steps of: (A) providing a polyurethane foam based on an isocyanate component and a polyol component, wherein the isocyanate component comprises toluene diisocyanate and wherein the polyol component comprises a polyether polyol; (B) chemolysis of the polyurethane foam by reacting with an organic chemolysis reagent and water, wherein the organic chemolysis reagent is selected from (i) a primary or secondary chemolysis amine, (ii) a chemolysis amino alcohol having a primary or secondary amino group, (iii) a chemolysis alcohol or (iv) a mixture of two or more of the aforementioned organic chemolysis reagents, to obtain a chemolysis product comprising the polyether polyol, toluenediamine and the organic chemolysis reagent; (C) distilling off organic chemolysis reagent from the chemolysis product to obtain a chemolysis product depleted in organic chemolysis reagent, wherein the distillation may be preceded and / or followed by a separation of solid components; (D) extracting the polyether polyol with an organic solvent from the chemolysis product depleted in organic chemolysis reagent, wherein an acid and water are added and, after separation of an acidic aqueous phase, a polyol phase containing the organic solvent and the polyether polyol is obtained; and (E) Processing the polyol phase to obtain the polyether polyol.

2. The process according to claim 1, wherein the polyether polyol comprises a polymer-filled polyether polyol, the polymer comprising a polymer of a vinyl group-containing monomer, a polyurea and / or a polyurethane.

3. Process according to one of the preceding claims, in which the polyol component contains no further polyols other than polyether polyols besides the polyether polyol.

4. Process according to one of the preceding claims, in which the isocyanate component, in addition to toluene diisocyanate, further comprises methylenediphenylene diisocyanate or mixtures of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate, or in which the isocyanate component does not comprise any other isocyanates besides toluene diisocyanate.

5. Method according to one of the preceding claims, in which (i) the primary or secondary chemolysis amine comprises an aliphatic primary or secondary organic amine, (ii) the chemolysis amino alcohol comprises an aliphatic amino alcohol having a primary or secondary amino group, and / or (iii) the chemolysis alcohol comprises methanol, ethanol, propanol, butanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol or a mixture of two or more of the aforementioned alcohols.

6. A process according to any one of the preceding claims, wherein the mass ratio of (1) organic chemolysis reagent and water on the one hand and (2) the polyurethane foam on the other hand is in the range of 0.5 to 2.5 and wherein the mass of water is 3.0% to 22% of the mass of the chemolysis reagent.

7. A process according to any one of the preceding claims, wherein step (B) is carried out at a temperature of 100 °C to 195 °C and at a pressure of 900 mbar( a bs.) to 2000 mbapabs.) is carried out.

8. A process according to any one of the preceding claims, wherein the extraction in step (D) is carried out at 10°C to 80°C.

9. A process according to any one of the preceding claims, wherein in step (D) the ratio of the mass of the organic chemolysis reagent depleted chemolysis product and the mass of the organic solvent present in the extractant, m[chemolysis product depleted in organic chemolysis reagent] f mforganic solvent] with m = mass, is in the range from 0.03 to 3.0, wherein the extractant comprises, based on its total mass, 20 mass% to 80 mass% organic solvent and 20 mass% to 80 mass% aqueous components.

10. A process according to any one of the preceding claims, wherein the polyether polyol obtained in step (E) is reacted with an isocyanate to form a polyurethane.

11. Method according to one of the preceding claims, comprising (F) Workup of the acidic aqueous phase to obtain toluenediamine.

12. Process according to one of the preceding claims, in which in step (C) toluenediamine is also partially or completely distilled off from the chemolysis product.

13. The process according to any one of claims 11 to 12, wherein the toluenediamine obtained in step (F) and / or the toluenediamine distilled off in step (C), optionally after purification, is used in the production of toluene diisocyanate.

14. The process according to claim 13, wherein the toluene diisocyanate is reacted with a polyol to form a polyurethane.

15. A process according to any one of the preceding claims, wherein the polyether polyol contains secondary OH end groups in a molar fraction of > 45%.

16. A process according to any one of the preceding claims, wherein the acid is selected from hydrogen chloride gas, hydrochloric acid, sulfuric acid, phosphoric acid, a sulfonic acid, a carboxylic acid or a mixture of two or more of the aforementioned acids.

17. A process according to any one of the preceding claims, wherein the acid and water in step (D) are added in the form of an aqueous acid.

18. A process according to claim 17, wherein additional water is added in addition to the aqueous acid.

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