Method for recovering raw materials from isocyanurate-containing polyurethane products

Abstract

The present invention relates to a method for recovering raw materials from isocyanurate-containing polyurethane products, especially from the known polyurethane-polyisocyanurate rigid foams (PUR-PIR foams or PIR foams for short). The method is characterized by reacting the isocyanurate-containing polyurethane product with liquid water at a temperature in the range of 130°C to 260°C and a pressure in the range of 1.0 bar to 100 bar in the presence of a catalyst, thereby obtaining a chemolysis product, and subsequently reprocessing the chemolysis product and as a result obtaining (I) an amine that corresponds to an isocyanate of the isocyanate component, and optionally (II) a polyol of the polyol component or a reaction product of a polyol of the polyol component.

Description

[0001] Process for the recovery of raw materials from polyurethane products containing isocyanurate

[0002] The present invention relates to a process for the recovery of raw materials from isocyanurate-containing polyurethane products, in particular the known polyurethane-polyisocyanurate rigid foams (PUR-PIR foams or PIR foams for short). The process is characterized in that the isocyanurate-containing polyurethane product is reacted with liquid water at a temperature in the range of 130 °C to 260 °C and at a pressure in the range of 1.0 bar to 100 bar in the presence of a catalyst to obtain a chemolysis product. The chemolysis product is then processed to obtain (I) an amine corresponding to an isocyanate of the isocyanate component and optionally (II) a polyol of the polyol component or a reaction product of a polyol of the polyol component.

[0003] Polyurethane products have a wide range of applications in industry and in everyday life. A distinction is usually made between polyurethane foams and so-called "CASE" products, where "CASE" is a collective term for polyurethane coatings (e.g., paints), adhesives, sealants, and elastomers. Polyurethane foams are usually divided into rigid foams and flexible foams. Despite their differences, all of these products share the same basic polyurethane structure, which is formed by the polyaddition reaction of a polyfunctional isocyanate and a polyol. For example, a polyurethane based on a diisocyanate O=C=NRN=C=O and a diol HO-R'-OH (where R and R' are organic radicals) is

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

[0005] Under certain conditions, the isocyanates react not only with the polyols, but also with themselves to form isocyanurate structures: This creates a polyurethane product containing isocyanurate. This is particularly relevant for polyurethane products based on the di- and polyisocyanates of the diphenylmethane series (methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate, MDI).

[0006] Polyurethane products containing isocyanurate are typically produced as foams and are used primarily in building insulation, as they offer greater fire safety than polyurethane insulation materials without isocyanurate groups. In applications where flame retardancy plays a lesser role, such as refrigerator insulation, polyurethane products without isocyanurate groups are common. As thermal insulation of buildings becomes increasingly important and even the highest-quality materials are not reusable indefinitely, the recycling of isocyanurate-containing polyurethane products is becoming increasingly important.

[0007] The technically easiest way to implement reuse is incineration, using the released combustion heat for other processes, such as industrial manufacturing processes. 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 obtainable in such chemolysis include polyols (in the above example, HO-R'-OH) or their reaction products formed in chemolysis, and, through hydrolytic cleavage of the urethane bond, amines (in the above example, H2N-R-NH2).Amines obtained in this way can be phosgenated again to isocyanates (in the above example to O=C=NRN=C=O) after processing.

[0008] Methods of chemical recycling and devices for their implementation have often been the subject of literature, particularly patent literature.

[0009] For example, Japanese patent application JP 2004-115631 A describes an apparatus for decomposing foamed plastics. The foamed plastics are kneaded at elevated temperatures while passing through the apparatus. Suitable decomposition reagents include amine compounds, polyols, and water. In the case of water as the decomposition reagent (hydrolysis), alkali or alkaline earth metals or their compounds, amine compounds, and the like are described as suitable catalysts. Foamed plastics that can be decomposed using the described apparatus include, in particular, flexible or rigid polyurethane foams or foams containing isocyanurate. The use of the apparatus is demonstrated in the examples using the chemolysis of a rigid polyurethane foam from refrigerator insulation with monoethanolamine or diethanolamine at 210 °C or 250 °C.It is therefore unclear whether the described apparatus can actually be successfully applied to the decomposition of isocyanurate-containing foams under the described conditions. The focus of the application is clearly on the described apparatus, in which the foamed plastics are "kneaded," i.e., subjected to great mechanical stress. The application does not disclose whether and how amines can be isolated from the resulting chemolysis product.

[0010] DE 2443 387 A1 describes a process for the continuous hydrolytic decomposition of plastic waste, in which waste made of hydrolysable plastic material is fed into a screw extruder together with water and optionally hydrolysis catalysts, where the mixture of water and plastic waste is exposed to a temperature of 100 to 300 °C at a pressure of 5 to 100 bar for 2 to 100 minutes in a reaction zone with intensive mass and heat exchange, and the liquid-gas mixture resulting from the hydrolysis is continuously conveyed into a nozzle fixedly connected to the screw extruder, from which the gas emerges via a control valve which maintains the constant screw extruder pressure in the nozzle, and the liquid emerges via a control valve which maintains a constant liquid level within the nozzle.The process is demonstrated using the example of splitting a soft elastic polyurethane foam.

[0011] DE 29 02 509 A1 describes a process for producing polyol-containing liquids from polyurethane and / or polyisocyanurate-containing foam waste by heating optionally comminuted foam waste with at least one aliphatic diol of the general formula HO-R-OH, in which R is a straight-chain or branched alkylene radical having 2 to approximately 20 carbon atoms, the main chain of which may be interrupted by one or more oxygen atoms, in the presence of a catalyst to temperatures of 150 to approximately 220°C, wherein at least one compound of a metal of subgroup IV of the Periodic Table of the Elements is used as catalyst.

[0012] EP 0 011 662 A1 describes the hydrolysis of polyurethanes, in particular flexible polyurethane foams, with superheated steam in the presence of basic alkali or alkaline earth compounds.

[0013] EP 0 753 535 A1 deals with a process for obtaining recycled polyols by glycolysis of polyisocyanurates. For this purpose, the polyisocyanurates are reacted with short-chain, hydroxyl-containing compounds in the presence of carrier polyols with an OH number of at most 500 mg KOH / g and a molecular weight of at least 450 g / mol. EP 0 976 719 A1 (also published as US Pat. No. 6,630,517) describes an apparatus and a process for the hydrolysis of polyisocyanate derivatives, in which the polyisocyanate derivative to be cleaved is reacted with liquid water at a temperature of 190 to 370 °C at a pressure of 30 to 300 bar. The hydrolysis is carried out without the use of a catalyst. EP 0976 719 A1 (US 6,630,517) has explicitly set itself the goal of doing without catalysts.Polyisocyanate derivatives are understood to be compounds having at least one isocyanate group or a functional group derived therefrom, for example, polyurethanes. Polyisocyanate derivatives within the meaning of the application also include compounds formed by the oligomerization of compounds containing isocyanate groups and contained in distillation residues from chemical plants for the production of the compounds containing isocyanate groups. Examples of such oligomeric compounds contained in the waste streams of a chemical plant for the production of compounds containing isocyanate groups include dimers, trimers, or higher oligomers, such as carbodiimide, uretidione, urethane imine, isocyanurate, and the like. The process is demonstrated in the examples using the hydrolysis of a flexible polyurethane foam, a rigid polyurethane foam, and a residue from the production of toluene diisocyanate (TDI).The polyurethane foams are compressed at elevated temperatures prior to hydrolysis. Whether polyurethane products containing isocyanate groups (to be distinguished from residue streams from isocyanate production), particularly PUR-PIR foams, are hydrolyzable using this process is not clear from EP 0 976 719 A1 (US Pat. No. 6,630,517).

[0014] US 3,441,616 describes the recovery of polyether polyols from polyurethane products by hydrolysis at temperatures between 100 °C and 190 °C in the presence of strong bases such as alkali metal or alkaline earth metal oxides or alkali metal or alkaline earth metal hydroxides in a mixture of water and dimethyl sulfoxide, followed by extraction of the resulting polyether polyol with a hydrocarbon. The examples describe the hydrolysis of TDI-based polyurethane foams.

[0015] CN 111 533 873 A describes a process for recycling polyurethane screens.

[0016] CN 113 429 540 A describes a process for producing a polyurethane thermal insulation material by using a polyol alcoholizing agent to degrade polyurethane waste.

[0017] WO 96 / 26236 A1 describes a process for separating polymeric materials from a plastic part, in particular a motor vehicle part, consisting of thermoplastic polymers and at least one thermosetting polymer from polyurethane foam. WO 2022 / 042909 A1 describes a process for hydrolyzing polyurethanes in the presence of a base comprising an alkali metal cation and / or an ammonium cation, wherein the base has a pKß value at 25°C of 1 to 10, and wherein a (phase transfer) catalyst selected from the group consisting of (i) a quaternary ammonium salt comprising an ammonium cation comprising 6 to 30 carbon atoms and (ii) an organic sulfonate comprising at least 7 carbon atoms is additionally used. The hydrolysis yields polyether polyols and polyamines. The recycling of PIR-containing polyurethanes is not described.Hydrolysis of polyether polyol-based polyurethanes in the presence of strong bases such as the oxides and hydroxides of alkali and alkaline earth metals and an activating agent selected from quaternary ammonium salts having at least 15 carbon atoms or organic sulfonates having at least 7 carbon atoms has already been described in US 5,208,379.

[0018] WO 2022 / 042910 A1 describes a process for the hydrolysis of polyurethanes in the presence of a base comprising an alkali metal cation and / or an ammonium cation, wherein the base has a pKß value at 25°C of less than 1, and wherein a (phase transfer) catalyst selected from the group consisting of (i) a quaternary ammonium salt comprising an ammonium cation having 6 to 14 carbon atoms, provided the ammonium cation does not comprise a benzyl radical, and (ii) a quaternary ammonium salt comprising an ammonium cation having 6 to 12 carbon atoms, provided the ammonium cation comprises a benzyl radical, is additionally used. The hydrolysis yields polyether polyols and polyamines. The recycling of PIR-containing polyurethanes is not described.

[0019] WO 2023 / 275029 A1 describes a process for producing polyurethane foams by reacting an isocyanate component with a polyol component, wherein the polyol component comprises a recycled polyol containing certain aminic and / or phenolic antioxidants in a mass fraction of 0.001 to 10%. The recycled polyol is preferably obtained by a hydrolysis process as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0020] WO 2023 / 275036 A1 describes a process for the preparation of aromatic and / or aliphatic di- and / or polyisocyanates by phosgenation of di- and / or polyamines obtained by a hydrolysis process as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0021] WO 2023 / 275038 A1 describes a process for the core hydrogenation of aromatic amines that result at least partially from a polyurethane decomposition process. The preferred polyurethane decomposition process is a hydrolysis process as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0022] EP 1 149 862 A1 describes a process in which a rigid polyurethane foam from a used refrigerator is pulverized, liquefied by glycolysis or aminolysis, and subsequently treated with supercritical or non-supercritical water. The resulting crude product is fractionated and used in the manufacture of new refrigerators.

[0023] GB 991,387 A describes the hydrolysis of non-volatile polyisocyanate reaction products with superheated steam at 200 to 400 °C. Non-volatile polyisocyanate reaction products are understood to be, on the one hand, the reaction products of polyisocyanates with compounds containing active hydrogen atoms (such as polyureas and polyurethanes) and, on the other hand, the products of oligomerization reactions of the polyisocyanates (such as isocyanurates and carbodiimides).

[0024] US 3,708,440 describes a process for processing a waste polyisocyanurate foam to obtain a polyol that can be used without further steps as a polyol component in the production of a polyurethane foam. The process comprises heating the waste foam to 175 to 250 °C in the presence of (a) an aliphatic diol having 2 to 6 carbon atoms and a boiling point above about 180 °C and (b) a dialkanolamine having 4 to 8 carbon atoms, wherein the dialkanolamine constitutes about 2 to 20 weight percent of the mixture.

[0025] H. Ulrich et al. describe in Polymer Engineering And Science, 1978, 18, 844-848, the glycolysis of polyurethane and (polyurethane) polyisocyanurate foams for the recovery of polyols that can be reused in foam production. In the introductory section, in addition to glycolysis, the possibilities of steam hydrolysis and pyrolysis are mentioned, but both are described as disadvantageous, as, according to the authors, they produce complex product mixtures. For example, the separation of the amines formed during hydrolysis is impractical, whereas glycolysis produces recyclable polyol mixtures in a single-step process.

[0026] P.N. Gribkova et al. describe in Polymer Science USSR, 1980, 22, 299-304 the decomposition of polyisocyanurate obtained by polycyclotrimerization of 4,4'-methylenediphenylene diisocyanate (4,4'-mMDI) (i.e., one that contains no urethane groups). The polyisocyanurate investigated could be decomposed, among other things, in saturated steam at high temperatures (decomposition begins at temperatures above approximately 300 °C) without a catalyst (i.e., purely thermally). None of the aforementioned processes is entirely satisfactory for the recovery of raw materials from isocyanurate-containing polyurethane products. In particular, a practical process for the recovery of amines from isocyanurate-containing polyurethane products is still lacking.

[0027] There was therefore a need for further improvements in the recovery of raw materials from isocyanurate-containing polyurethane products. In particular, it would be desirable to recover amines from isocyanurate-containing polyurethane products so that they can be phosgenated back to the isocyanates after purification.

[0028] In response to this need, the present invention provides a process for recovering raw materials from isocyanurate-containing polyurethane products, comprising the steps:

[0029] (A) providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component;

[0030] (B) Chemolysis (= hydrolysis) of the isocyanurate-containing polyurethane product with liquid water in the absence of an organic solvent or in the presence of an organic solvent inert towards urethane groups and isocyanurate groups at a temperature in the range from 130 °C to 260 °C, in particular up to 240 °C, preferably 135 °C to 230 °C, particularly preferably 140 °C to 220 °C and at a pressure in the range from 1.0 bar to 100 bar, preferably 5.0 bar to 100 bar, particularly preferably 10 bar to 80 bar, in the presence of (i.e. with the addition of) a catalyst which in particular is not or comprises none of the following compounds (i) to (ii):

[0031] (i) a quaternary ammonium salt containing an ammonium cation comprising 6 or more carbon atoms, (ii) an organic sulfonate comprising 7 or more carbon atoms, to obtain a chemolysis product; and

[0032] (C) Processing of the chemolysis product to obtain

[0033] (I) (at least) one amine corresponding to an isocyanate of the isocyanate component, and optionally (II) (at least) one polyol of the polyol component or (at least) one reaction product of a polyol of the polyol component.

[0034] Completely surprisingly, it was found that the chemolysis of isocyanurate-containing polyurethane products succeeds as pure hydrolysis, i.e. without the use of reactive organic solvents, under the conditions mentioned and allows the recovery of amines.

[0035] Polyurethane products within the meaning of the present invention are the polyaddition products of polyfunctional isocyanates (= isocyanate component of polyurethane production) and polyols (= polyol component of polyurethane production). The invention concerns the recycling of such polyurethane products that contain isocyanurate structures (see above) in addition to the pure polyurethane base structure. Other structures, for example, structures with urea bonds, may also be present, which of course does not exceed the scope of the present invention.

[0036] In the terminology of the present invention, the term "isocyanates" encompasses the isocyanates familiar to the person skilled in the art in connection with isocyanurate chemistry. The expression "one isocyanate" naturally also encompasses embodiments in which two or more different isocyanates (e.g., mixtures of different MDI types) were used in the preparation of the isocyanurate-containing polyurethane product, unless expressly stated otherwise, for example, by the phrase "exactly one isocyanate." The totality of all isocyanates used in the preparation of the isocyanurate-containing polyurethane product is referred to as the isocyanate component (of the isocyanurate-containing polyurethane product). The isocyanate component comprises at least one isocyanate.

[0037] Analogously, the totality of all polyols used in the production of the isocyanurate-containing polyurethane product is referred to as the polyol component (of the isocyanurate-containing polyurethane product). The polyol component comprises at least one polyol. The term "a polyol" naturally also encompasses embodiments in which two or more different polyols were used in the production of the isocyanurate-containing polyurethane product. Therefore, if reference is made below, for example, to "a polyether polyol" (or "a polyester polyol," etc.), this terminology naturally also encompasses embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) were used in the production of the isocyanurate-containing polyurethane product.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.

[0038] According to the invention, the chemolysis of the isocyanurate-containing polyurethane product is carried out as a hydrolysis, specifically with liquid water. This means that the chemical reaction of hydrolysis occurs through the action of liquid water on the isocyanurate-containing polyurethane product (in contrast, for example, to the use of steam). The chemolysis takes place in the absence of an organic solvent or in the presence of an organic solvent that is inert toward urethane groups and isocyanurate groups (i.e., the organic solvent does not contribute to the cleavage of urethane groups and / or isocyanurate groups); it is therefore a "true" hydrolysis and not a hydroglycolysis.

[0039] According to the invention, the hydrolysis takes place in the presence of a catalyst. This refers to a catalyst added within the scope of the process according to the invention. Depending on the origin of the isocyanurate-containing polyurethane product to be recycled, it cannot be ruled out that it contains trace amounts of catalytically active impurities originating from the original production. Within the scope of the present invention, it is intended not to rely on such potentially present catalyst residues, but rather – in the interests of a reliable and reproducible reaction – to add a catalyst for carrying out step (B).

[0040] In a particularly preferred embodiment, the hydrolysis takes place in the presence of (= with the addition of) a catalyst which is not or comprises none of the following compounds (i) to (ii): (i) a quaternary ammonium salt containing an ammonium cation comprising 6 or more (for example up to 30) carbon atoms, (ii) an organic sulfonate comprising 7 or more (for example up to 25) carbon atoms.In this embodiment, therefore, the addition of quaternary ammonium salts containing an ammonium cation comprising 6 or more carbon atoms (such as (a) quaternary ammonium salts containing an ammonium cation having 6 to 30 carbon atoms, (b) quaternary ammonium salts containing an ammonium cation having 6 to 14 carbon atoms, provided that the ammonium cation does not comprise a benzyl radical, (c) quaternary ammonium salts containing an ammonium cation having 6 to 12 carbon atoms, provided that the ammonium cation comprises a benzyl radical) and organic sulfonates containing at least 7 carbon atoms is excluded for chemolysis, ie the chemolysis takes place in the absence of the compounds mentioned. Organic sulfonates are understood to be the salts of organic sulfonic acids with the anion R-SCh-, where "R" denotes an organic radical containing 7 or more carbon atoms.First, a brief summary of various possible embodiments of the invention follows:.

[0041] In a first embodiment of the process according to the invention, which can be combined with all other embodiments, step (A) comprises an extraction of the polyurethane product with an organic solvent which does not react with urethane groups or isocyanurate groups during the extraction.

[0042] In a second embodiment of the process according to the invention, which is a particular embodiment of the first embodiment, the organic solvent used in the extraction comprises (in particular is) an aromatic hydrocarbon (in particular toluene), a haloaromatic (in particular mono- or [preferably: ortho-]dichlorobenzene), an aliphatic ether (in particular tetrahydrofuran or [preferably: 1,4-]dioxane), a ketone (in particular acetone), an aromatic ether (in particular anisole) or a mixture of two or more of the aforementioned organic solvents.

[0043] In a third embodiment of the process according to the invention, which is a particular embodiment of the first and second embodiments, the extraction is carried out at a temperature in the range from ambient temperature (in particular 20 °C) to 180 °C, preferably in the range from 50 °C to 180 °C, and particularly preferably at ambient pressure (in particular 1.0 bar) and the boiling temperature of the organic solvent.

[0044] In a fourth embodiment of the process according to the invention, which can be combined with all other embodiments, step (A) comprises a mechanical comminution of the polyurethane product.

[0045] In a fifth embodiment of the process according to the invention, which can be combined with all other embodiments, the catalyst comprises (in particular: is) a hydroxide, a carbonate, a bicarbonate, a phosphate, a hydrogen phosphate, a carboxylate, an alkoxide, a metal oxide or a mixture of two or more of the aforementioned catalysts.

[0046] In a sixth embodiment of the process according to the invention, which is a particular embodiment of the fifth embodiment, the catalyst comprises (in particular: is) an alkali or alkaline earth metal salt of a hydroxide, a carbonate, a bicarbonate, a phosphate, a hydrogen phosphate, a carboxylate or an alkoxide.

[0047] In a seventh embodiment of the process according to the invention, which can be combined with all other embodiments, provided that they are not limited to a solvent-free chemolysis, the chemolysis is carried out in the presence of an organic solvent inert towards urethane groups and isocyanurate groups.

[0048] In an eighth embodiment of the process according to the invention, which is a particular embodiment of the seventh embodiment, the polyurethane product in step (B) is initially introduced into the organic solvent which is inert towards urethane groups and isocyanurate groups and the water is added stepwise.

[0049] In a ninth embodiment of the process according to the invention, which is a particular embodiment of the seventh and eighth embodiments, the organic solvent inert towards urethane groups and isocyanurate groups comprises (in particular: is) dimethyl sulfoxide, / V, / V-dimethylformamide, / V-methyl-2-pyrrolidone, dichlorobenzene (in particular the ortho isomer), trichlorobenzene, ethylmethylbenzene (in particular l-ethyl-2-methylbenzene), mesitylene, (in particular n-)decane, (in particular n-)undecane and / or (in particular n-)dodecane.

[0050] In a tenth embodiment of the process according to the invention, which can be combined with all other embodiments, provided that they are not limited to chemolysis in the presence of a solvent, the chemolysis is carried out in the absence of an organic solvent.

[0051] In an eleventh embodiment of the process according to the invention, which is a particular embodiment of the eighth and ninth embodiments, the chemolysis is carried out at a pressure in the range from 1.0 bar to < 5.0 bar, preferably 1.0 bar to 1.5 bar, particularly preferably 1.0 bar to 1.2 bar and in particular at ambient pressure (in particular 1.0 bar).

[0052] In a twelfth embodiment of the process according to the invention, which is a particular embodiment of the tenth embodiment, the chemolysis is carried out without pressure equalization under autogenous pressure, in particular in the range from 5.0 bar to 100 bar, preferably 10 bar to 80 bar.

[0053] In a thirteenth embodiment of the process according to the invention, which is a particular embodiment of the first to twelfth embodiments, the chemolysis product is cooled in step (C) (by active cooling or allowing to cool), whereby a first solid organic (amine) phase precipitates, followed by a liquid-solid phase separation into a first aqueous phase and the first solid organic (amine) phase and the first solid organic (amine) phase is further processed to obtain the amine.

[0054] In a fourteenth embodiment of the process according to the invention, which is a particular embodiment of the thirteenth embodiment, the further processing of the first solid organic (amine) phase comprises washing it with an aqueous washing liquid.

[0055] In a fifteenth embodiment of the process according to the invention, which is a particular embodiment of the thirteenth and fourteenth embodiments, the optionally washed first solid organic (amine) phase is dissolved in an organic solvent to obtain a first liquid organic (amine) phase which is further processed to obtain the amine.

[0056] In a sixteenth embodiment of the process according to the invention, which is a further particular embodiment of the first to twelfth embodiments, the chemolysis product in step (C) is extracted with an organic solvent, followed by a liquid-liquid phase separation into a first aqueous phase and a first liquid organic (amine) phase and the first liquid organic (amine) phase is further processed to obtain the amine.

[0057] In a seventeenth embodiment of the process according to the invention, which is a particular embodiment of the fifteenth and sixteenth embodiments, the further processing of the first liquid organic (amine) phase comprises washing it with an aqueous washing liquid.

[0058] In an eighteenth embodiment of the process according to the invention, which is a particular embodiment of the fifteenth to seventeenth embodiments, the optionally washed first liquid organic (amine) phase is extracted with an aqueous mineral acid, followed by phase separation into a second liquid organic phase and a second aqueous (protonated amine-containing) phase, after which the second aqueous phase is neutralized or made alkaline to precipitate a second solid organic (amine) phase, followed by workup of the second solid organic (amine) phase to obtain the amine.

[0059] In a nineteenth embodiment of the process according to the invention, which is a particular embodiment of the eighteenth embodiment, the second solid organic (amine) phase is separated by liquid-solid phase separation or taken up in an organic solvent.

[0060] In a twentieth embodiment of the process according to the invention, which is a particular embodiment of the eighteenth and nineteenth embodiments, step (C. II) is included, wherein step (C. II) comprises working up the second liquid organic phase by distillative removal of organic solvent to leave an alcohol phase, followed by purification of the alcohol phase by distillation or stripping. In a twenty-first embodiment of the process according to the invention, which is a particular embodiment of the thirteenth to twentieth embodiments, step (C. II) is included, wherein step (C. II) comprises working up the first aqueous phase by distillative removal of water to leave an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

[0061] In a twenty-second embodiment of the process according to the invention, which can be combined with all other embodiments, the isocyanate component comprises methylenediphenylene diisocyanate, polymethylenepolyphenylene polyisocyanate, or a mixture of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate. The isocyanate component preferably does not comprise any tolylene diisocyanate besides these, and particularly preferably does not comprise any other isocyanates.

[0062] In a twenty-third embodiment of the process according to the invention, which can be combined with all other embodiments, the polyol component comprises a polyether polyol, a polyester polyol, a polyether ester polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols.

[0063] In a twenty-fourth embodiment of the process according to the invention, which can be combined with all other embodiments, the isocyanurate-containing polyurethane product provided in step (A) is a polyurethane foam, in particular a rigid polyurethane foam, preferably originating from building insulation.

[0064] In a twenty-fifth embodiment of the process according to the invention, which can be combined with all other embodiments, the chemolysis is carried out in a stirred tank reactor.

[0065] In a twenty-sixth embodiment of the process according to the invention, which can be combined with all other embodiments, the amine obtained in step (Cl) is phosgenated in a step (D) to the corresponding isocyanate.

[0066] In a twenty-seventh embodiment of the process according to the invention, which can be combined with all other embodiments, the catalyst does not comprise any of the following compounds (i) to (ii):

[0067] (i) a quaternary ammonium salt containing an ammonium cation comprising 6 or more carbon atoms, (ii) an organic sulfonate comprising 7 or more carbon atoms. The embodiments briefly described above and further possible configurations of the invention are explained in more detail below. All of the embodiments described above and the further configurations of the invention described below can be combined with one another as desired, unless the context clearly indicates the opposite to a person skilled in the art or unless expressly stated otherwise.

[0068] PREPARATION FOR CHEMICAL RECYCLING

[0069] In step (A) of the process according to the invention, the isocyanurate-containing polyurethane product to be chemically recycled is provided. Isocyanurate-containing polyurethane products within the meaning of the present invention are, in particular, those polyurethane products whose infrared spectra in the spectral range of 1650 cm 1 up to 1800 cm 1 (C=O stretching range) the signal maximum at a wavenumber of 1712 cm 1 or smaller.

[0070] In principle, this can be any type of isocyanurate-containing polyurethane product. However, polyurethane foams, especially rigid polyurethane foams, preferably derived from building insulation, are preferred. Rigid polyurethane foam is a highly cross-linked thermosetting plastic that forms a cellular structure with a low raw material density (especially in the range of 20 kg / m³). 3 up to 90 kg / m 3 , preferably 30 kg / m 3 up to 45 kg / m3 , determined according to DIN EN ISO 845:2009-10) and low thermal conductivity (usually in the range of 0.016 W / (m • K) to 0.030 W / (m • K), determined according to DIN 52616 1977-11). It is usually closed-cell and has a relatively high resistance to deformation under compressive stress. The thermosetting character is reflected in the fact that the foam is not meltable, has a high softening point and good resistance to chemicals and solvents. Rigid polyurethane foams in particular have a compressive stress (also called compressive strength) at 10% of 50 kPa to 300 kPa determined according to DIN EN 826 2013-05 and a tensile strength of 30 kPa to 250 kPa determined according to EN 1607 2013-05.

[0071] Furthermore, those polyurethane products are preferred which, with regard to the isocyanate component, are based on an isocyanate selected from the group consisting of methylenediphenylene diisocyanate ("monomeric MDI"; mMDI), polymethylenepolyphenylene polyisocyanate ("polymeric MDI; pMDI)"), and a mixture of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate (hereinafter collectively referred to as MDI). These are produced by phosgenation of the corresponding amines (methylenediphenylenediamine ["monomeric MDA"; mMDA], polymethylenepolyphenylenepolyamine ("polymeric MDA; pMDA)), or a mixture of methylenediphenylenediamine and polymethylenepolyphenylenepolyamine [hereinafter collectively referred to as MDA]).

[0072] Furthermore, polyurethane products are preferred which, with regard to the polyol component, are based on a polyol selected from polyether polyols, polyester polyols, polyetherester polyols, polyethercarbonate polyols, or a mixture of two or more of the aforementioned polyols. Polyester polyols and polyetherester polyols are particularly preferred, especially in blends with polyether polyols.

[0073] Preferably, step (A) comprises preparatory steps for the cleavage of the urethane bonds and isocyanurate bonds in step (B). This involves, in particular, mechanical comminution of the isocyanurate-containing polyurethane products. Such preparatory steps are known to the person skilled in the art.

[0074] Isocyanurate-containing polyurethane products from building insulation, in particular, regularly contain additives, especially flame retardants, but also stabilizers and activators. It has proven effective to remove these in an extraction step before chemical recycling begins in step (B). For this purpose, the isocyanurate-containing polyurethane foam, preferably already shredded, is extracted with an organic solvent that does not react with urethane groups or isocyanurate groups during extraction. This is ensured by either using a solvent that is fundamentally chemically inert toward urethane groups and isocyanurate groups (preferred), or by selecting the temperature and / or extraction time so low that no significant chemical reaction occurs.Suitable organic solvents include, in particular, aromatic hydrocarbons (especially toluene), haloaromatics (especially monochlorobenzene or [preferably: ortho-]dichlorobenzene, with dichlorobenzene, preferably used as the ortho isomer, being more preferred than monochlorobenzene), aliphatic ethers (especially tetrahydrofuran or [preferably: 1,4-]dioxane), ketones (especially acetone), aromatic ethers (especially anisole), or a mixture of two or more of the aforementioned solvents. Haloaromatics are preferred. Suitable temperatures for the extraction are, for example, in the range from ambient temperature (room temperature, especially 20 °C) to 180 °C, preferably in the range from 50 °C to 180 °C. The extraction can be carried out, in particular, at ambient pressure and the boiling point of the selected organic solvent ("under reflux").After extraction, the isocyanurate-containing polyurethane product to be cleaved is separated from the extraction solvent by solid-liquid separation, in particular filtration, and preferably washed, in particular with one of the aforementioned organic solvents (the same solvent as used in the extraction may, but need not, be used). Adhering solvent residues are preferably removed by drying before step (B). However, in the less preferred embodiment using reactive solvents (e.g., alcohols) for the extraction and / or washing, their removal is provided before step (B).

[0075] CHEMICAL CLEAVAGE OF URETHANE AND ISOCYANURATE BONDS

[0076] Step (B) comprises the chemolysis of the isocyanurate-containing polyurethane product with liquid water. According to the invention, this hydrolysis takes place at a temperature in the range of 130°C to 260°C, in particular up to 240°C, preferably 135°C to 230°C, particularly preferably 140°C to 220°C, and at a pressure in the range of 1.0 bar to 100 bar, preferably 5.0 bar to 100 bar, particularly preferably 10 bar to 80 bar, in the presence of a catalyst.

[0077] Hydroxides, carbonates, bicarbonates, phosphates, hydrogen phosphates, carboxylates, alcoholates, and metal oxides have proven effective catalysts. Although not preferred, various catalysts can also be used as mixtures. Catalysts in the form of alkali or alkaline earth metal salts are preferred.

[0078] As already mentioned, it is possible to carry out the chemolysis in the presence of an organic solvent that is inert towards urethane groups and isocyanurate groups. Particularly suitable solvents for this purpose are dimethyl sulfoxide, / V, / V-dimethylformamide, N-methyl-2-pyrrolidone, dichlorobenzene (especially the ortho isomer), trichlorobenzene, ethylmethylbenzene (especially l-ethyl-2-methylbenzene), mesitylene, (especially n-)decane, (especially n-)undecane, and (especially n-)dodecane. When using an organic solvent, it is possible to initially dissolve or suspend the isocyanurate-containing polyurethane product to be cleaved in the solvent, heat the reaction mixture to reaction temperature, and then add the water gradually so that the temperature does not drop too much, in particular by more than 15.0 °C.In this procedure, the water reacts so rapidly by hydrolyzing the PUR and PIR bonds that it does not evaporate to an extent that would impair the reaction. In this case, the reaction is typically carried out at low pressures, preferably 1.0 bar to <5.0 bar, preferably 1.0 bar to 1.5 bar, particularly preferably 1.0 bar to 1.2 bar, and especially at ambient pressure.

[0079] However, it is also possible and preferred to carry out the reaction entirely without organic solvent. This simplifies workup. In this case, it has proven advantageous to carry out the hydrolysis without pressure equalization in a pressure-resistant reactor under autogenous pressure, particularly in the range of 5.0 bar to 100 bar, preferably 10 bar to 80 bar. In this procedure, the comparatively high pressure ensures that the chemolysis takes place with liquid water.The chemolysis is therefore carried out in particular either by initially introducing the polyurethane product in step (B) into an organic solvent which is inert towards urethane groups and isocyanurate groups and gradually adding the water, maintaining a pressure of 1.0 bar to < 5.0 bar, preferably 1.0 bar to 1.5 bar, particularly preferably 1.0 bar to 1.2 bar and in particular ambient pressure, or by reacting the polyurethane product in step (B) with the water in the absence of an organic solvent without pressure equalization under autogenous pressure, in particular in the range from 5.0 bar to 100 bar, preferably 10 bar to 80 bar.

[0080] In terms of equipment, any reactor type commonly used in the field is suitable. Stirred tank reactors are preferred.

[0081] PROCESSING OF THE CHEMOLYSIS PRODUCT

[0082] Step (C) comprises the workup of the chemolysis product obtained in step (B) to obtain (I) (at least) one amine corresponding to an isocyanate of the isocyanate component, and optionally (II) (at least) one polyol of the polyol component or (at least) one reaction product of a polyol of the polyol component.

[0083] After hydrolysis, the chemolysis product is first cooled (by active cooling or cooling), whereby a first solid organic (amine) phase precipitates. The term "solid phase" in the context of the present invention is not limited to "crystalline solids." Often, pasty, "playful" phases are obtained, which in the terminology used here are subsumed under the generic term "solid phase." The first solid organic (amine) phase is separated from the chemolysis product by liquid-solid phase separation (particularly filtration), leaving behind a first aqueous phase. The resulting first solid organic phase is further processed to recover the amine.

[0084] This further workup preferably comprises washing with an aqueous wash liquid. It is further preferred to dissolve the optionally washed first solid organic phase in an organic solvent, obtaining a first liquid organic (amine) phase, which is further worked up to obtain the amine. Suitable organic solvents for this purpose are, in particular, halogenated aliphatic hydrocarbons (such as, in particular, dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as, in particular, monochlorobenzene and (preferably, ortho-)dichlorobenzene), cycloaliphatic alcohols (such as, in particular, cyclohexanol), and aromatic ethers (such as, in particular, anisole).

[0085] As an alternative to liquid-solid phase separation of the chemolysis product, it is also possible to extract the chemolysis product in its entirety with an organic solvent, followed by a liquid-liquid phase separation into a first aqueous phase and a first liquid organic (amine) phase. Suitable organic solvents for this purpose are, in particular, halogenated aliphatic hydrocarbons (such as, in particular, dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as, in particular, monochlorobenzene and (preferably, ortho-)dichlorobenzene), cycloaliphatic alcohols (such as, in particular, cyclohexanol), and aromatic ethers (such as, in particular, anisole).

[0086] Regardless of how the first liquid organic phase was obtained, it is further processed to recover the amine. This further processing preferably initially involves washing with an aqueous wash liquid.

[0087] The optionally washed first liquid organic phase is then extracted, preferably with an aqueous mineral acid, followed by phase separation into a second liquid organic phase and a second aqueous (protonated amine-containing) phase. This second aqueous phase is neutralized or rendered alkaline (pH preferably from 9.0 to 14, preferably 10 to 14) to precipitate a second solid organic (amine) phase. The thus obtained second solid organic phase is further processed to recover the amine.

[0088] For this purpose, it is preferable to first separate the second solid organic phase by liquid-solid phase separation (particularly filtration). Particularly if the nature of this solid phase is such that liquid-solid phase separation is difficult to carry out, it can also be taken up directly in an organic solvent and separated from the aqueous components by liquid-liquid phase separation. Suitable organic solvents for this purpose are, in particular, halogenated aliphatic hydrocarbons (such as, in particular, dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as, in particular, monochlorobenzene and (preferably ortho-)dichlorobenzene), cycloaliphatic alcohols (such as, in particular, cyclohexanol), and aromatic ethers (such as, in particular, anisole). After evaporation of the solvent, the second solid organic phase remains. This is preferably washed and dried.The solid obtained in this way contains the amine, which can be subjected to phosgenation to form the corresponding isocyanate. Such a phosgenation can be carried out by a process known from the prior art (step (D)). Such a process is described, for example, in WO 2017 / 055311 A1 (see in particular page 15, line 10 to page 19, line 17).

[0089] Naturally, the polyol component of the isocyanurate-containing polyurethane product also represents a valuable material that is preferably recycled as far as possible. The type of raw material to be recovered depends on the type of polyol component originally used. While pure polyether polyols can be recovered as such, polyols with more reactive functional groups (such as ester groups in particular) are subject to hydrolytic cleavage in step (B). However, the resulting low-molecular-weight or oligomeric reaction products are also valuable raw materials that can be used in the production of new polyols.

[0090] Polyols and / or their reaction products can be obtained by processing the first aqueous phase. The aforementioned second liquid organic phase can also contain them in substantial amounts.

[0091] The processing of the first aqueous phase to obtain the polyols and / or their reaction products preferably comprises a distillative separation of water while leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

[0092] The processing of the second liquid organic phase to obtain the polyols and / or their reaction products preferably comprises a distillative separation of organic solvent while leaving an alcohol phase, which in turn is followed by a purification of the alcohol phase by distillation or stripping.

[0093] Examples:

[0094] Key figure: Denotes the molar ratio of NCO to

[0095] NCO-reactive groups of a recipe

[0096] Amine number: The amine number was determined according to the EN

[0097] ISO 9702 (August 1998).

[0098] Chemicals

[0099] Desmodur VP. PU 1806 from Covestro Deutschland AG, mixture of

[0100] Diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate with an NCO content of 31.4% by mass

[0101] Desmodur 44V70L from Covestro Deutschland AG, polymer MDI with an NCO

[0102] Content of 30 to 32 wt.%

[0103] Desmophen 2382 from Covestro Deutschland AG, aromatic polyester polyol with an OH number of 240 mg KOH / g

[0104] Desmophen V657 from Covestro Deutschland AG, reactive trifunctional polyether polyol with an OH number of 255±15 mg KOH / g, an acid number of max. 0.35 mg KOH / g and a viscosity at 25 °C of (265±20) mPa • s

[0105] Additive 1132 from Covestro Deutschland AG, conversion product from

[0106] Phthalic anhydride and diethylene glycol with an acid number of 89 mg KOH / g

[0107] Stabilizer 21AS08 Silicone-polyether copolymer with an OH number of 12 mg KOH / g of

[0108] Covestro Deutschland AG

[0109] Desmorapid 1792 potassium acetate, 25% by mass in diethylene glycol (DEG) n-pentane from Sigma Aldrich

[0110] Dimethyl sulfoxide from Sigma Aldrich

[0111] Diethylene glycol from Brenntag GmbH

[0112] Potassium hydroxide from Sigma Aldrich

[0113] Potassium phosphate from Sigma Aldrich

[0114] Potassium carbonate from Sigma Aldrich PRODUCTION OF MODEL SUBSTANCES

[0115] Model substance 1

[0116] 172.1 g of Desmodur VP.PU 1806 were placed in a 250 mL four-necked flask equipped with a gas inlet, reflux condenser, stirrer, and dropping funnel, purged with nitrogen, and heated to 80 °C with stirring. 77.9 g of Desmophen 2382 were added to this solution, ensuring the temperature did not exceed 80 °C. After the addition was complete, the mixture was stirred at 80 °C for 2 hours. 200 g of the resulting NCO-containing prepolymer were then admixed with 1 g of Desmorapid 1792, mixed in a speed mixer, and then poured onto an aluminum tray and cured in an oven overnight at 80 °C to convert the excess NCO groups.

[0117] Production of a PIR-containing rigid foam

[0118] The PIR-containing foam was produced by hand mixing on a laboratory scale, as shown in Table 1, in test packages with a square base and a side length of 20 cm. The polyol component containing the polyols was initially introduced together with the additives and catalysts. Shortly before mixing, the polyol component was heated to 23 to 25 °C, whereas the polyisocyanate component was heated to a temperature of 30 to 35 °C. The polyisocyanate component was then added to the polyol mixture while stirring, to which the required amount of urea needed to achieve a core density of approximately 38 kg / m 3 The required amount of pentane had been previously weighed. The mixing time was 6 seconds and the mixing speed of the Pendraulik stirrer was 4200 min -1 The foam was then stored for another 24 hours at 20 to 23°C to allow it to react.

[0119] Table 1: Recipe of the PIR-containing PUR rigid foam HYDROLYSIS UNDER ATMOSPHERIC PRESSURE

[0120] Example 1 (according to the invention)

[0121] In a 50 mL two-necked round-bottom flask, 7.5 g of model substance 1 and 2.0 g of potassium hydroxide in 7.5 g of dimethyl sulfoxide were placed and heated to 140 °C with stirring. 5 mL of water was added to the reaction mixture in 1.0 mL portions. After each addition of water, the reaction mixture was stirred until it reached the reaction temperature again. A further 2.9 mL of water was then added. After the reaction was complete, the reaction mixture boiled at approximately 120 °C and could not be heated further. The amine-containing phase was precipitated by adding 100 mL of water and separated from the reaction mixture by filtration. The pasty filter residue was washed with water, dried under vacuum, and then characterized by its amine number.

[0122] Amine number = 520 mg KOH / g

[0123] Example 2 (Comparison - Hydroglycolysis)

[0124] 3.3 g of powdered PIR foam (prepared as described above), 15.0 g of diethylene glycol, and 1.92 g of potassium hydroxide were placed in a 50 mL two-neck round-bottom flask equipped with a thermometer and intensive condenser. The contents of the flask were heated to 140 °C. Water was added gradually. The water was added in small increments so that the temperature of the reaction mixture did not fall below 140 °C. After adding 0.8 g of water, a further 4.2 g of powdered PIR foam (PS 436) was added. The foam dissolved after a few moments, resulting in a clear orange liquid at the bottom. A further 4.8 g of water was added gradually. The mixture was then stirred for 2.4 h. The total reaction time was 4 h. The reaction mixture was poured into 400 g of water. A dark brown, pasty solid settled from the aqueous phase and was separated by decantation. The residue was washed with water and dried in vacuo.The amine number titration yielded a value of only 475 mg KOH / g.

[0125] PRESSURE HYDROLYSIS

[0126] Example 3 (according to the invention)

[0127] A 2.1-L pressure autoclave was charged with 600 mL of demineralized water, 25 g of powdered PIR foam (prepared as described above), and 50 g of potassium hydroxide (KOH) flakes. The reactor contents were heated to 160 °C for 5.5 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was separated by decantation. The residue was washed with water and dried under vacuum. The amine number titration yielded a value of 510 mg KOH / g.

[0128] Example 4 (comparison example at too low a temperature)

[0129] The experiment was carried out analogously to Example 3. However, the hydrolysis was carried out at 120 °C for 15.5 h. The residue was washed with water and dried under vacuum. An amine number could not be determined due to insolubility.

[0130] Example 5 (according to the invention)

[0131] The experiment was carried out analogously to Example 3. However, the hydrolysis was carried out at 220 °C for 1.5 h. A dark brown, pasty solid settled from the aqueous phase, which was separated by decantation. The residue was washed with water and dried under vacuum. The amine number titration yielded a value of 533 mg KOH / g.

[0132] Example 6 (according to the invention)

[0133] A 2.1-L pressure autoclave was charged with 600 mL of demineralized water, 25 g of powdered PIR foam (prepared as described above), and 50 g of potassium phosphate. The reactor contents were heated to 160 °C for 6 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was separated by decantation. The residue was washed with water and dried under vacuum. The amine number titration yielded a value of 510 mg KOH / g.

[0134] Example 7 (comparative example without catalyst)

[0135] A 2.1-liter pressure autoclave was charged with 600 mL of demineralized water and 25 g of powdered PIR foam (prepared as described above). The reactor contents were heated to 200 °C for 7 h and then cooled to room temperature. A brownish-yellow powder settled from the aqueous phase, which could be separated by filtration. The residue was washed with water and dried under vacuum. The amine number titration yielded a value of 295 mg KOH / g. Example 8 (according to the invention, with extraction before hydrolysis)

[0136] 260 g of a powdered PIR foam (prepared as described above) was heated under reflux in ortho-dichlorobenzene for 4 h, then filtered, washed with acetone, and dried in a drying cabinet. 260 g of the extracted foam and 65 g of potassium carbonate were placed in a 2.1 L pressure autoclave together with 1500 mL of demineralized water. The reactor contents were heated to 220 °C for 4.25 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was taken up in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was then washed with chloroform and adjusted to a pH of 10 with KOH plates. The resulting precipitate was taken up in chloroform. After removal of the solvent, a brownish, pasty solid was obtained.The amine number titration yields a value of 515 mg KOH / g.

[0137] Example 9 (Comparative example without catalyst and with extraction before hydrolysis)

[0138] 25 g of a powdered PIR foam (prepared as described above) was heated under reflux in ortho-dichlorobenzene for 4 h, then filtered, washed with acetone, and dried in a drying cabinet. 25 g of the extracted PIR foam were placed in a 2.1 L pressure autoclave together with 600 mL of demineralized water. The reactor contents were heated to 220 °C for 5.5 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was taken up in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was then washed with chloroform and adjusted to a pH of 10 with KOH plates. The resulting precipitate was taken up in chloroform. After removal of the solvent, a brownish, pasty solid was obtained, which was dried under vacuum.The amine number titration yields a value of 260 mg KOH / g. Table 2: Pressure hydrolysis of isocyanurate-containing PUR foams (manufactured as described above).

[0139] The results in Table 2 show that at too low a temperature, an incomplete conversion occurs (Example 4). At temperatures of 220 °C, products with a particularly favorable amine number are obtained (Example 5). If the hydrolysis is carried out in the absence of a catalyst, an incomplete conversion also occurs, and even with a comparatively long reaction time and high temperature, only products with a low amine number are obtained (Example 7 and Example 9).

[0140] PRESSURE HYDROLYSIS AT HIGH TEMPERATURE (250 °C)

[0141] Compression of the foam (for examples 10 and 11)

[0142] The foam was compressed for 10 minutes at 160 °C in a heated hydraulic press. The press used initially exerted a force of 11 kN, which decreased to 6 kN over time.

[0143] Example 10 (Comparative example without catalyst and with compression before hydrolysis)

[0144] A 2.0 L pressure autoclave from Büchi AG was charged with 180 mL of demineralized water and 7.5 g of compressed PIR foam (prepared as described above). The reactor contents were heated to 250 °C for 1.5 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was taken up in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was then washed with chloroform and adjusted to a pH of 10 using KOH plates. The resulting precipitate was taken up in chloroform. After removal of the solvent, a brownish, pasty solid was obtained, which was dried under vacuum. The amine number titration yielded a value of 278 mg KOH / g.

[0145] Example 11 (according to the invention; with compression before hydrolysis)

[0146] A 2.0-L pressure autoclave from Büchi AG was charged with 180 mL of demineralized water, 7.5 g of compressed PIR foam (prepared as described above), and 1.88 g of potassium carbonate. The reactor contents were heated to 250 °C for 1.5 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was taken up in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was then washed with chloroform and adjusted to a pH of 10 using KOH plates. The resulting precipitate was taken up in chloroform. After removal of the solvent, a brownish, pasty solid was obtained, which was dried under vacuum. The amine number titration yielded a value of 534 mg KOH / g.

[0147] Example 12 (according to the invention; without compression before hydrolysis)

[0148] A 2.0-L pressure autoclave from Büchi AG was charged with 180 mL of demineralized water, 7.5 g of powdered (uncompressed) PIR foam (prepared as described above), and 1.88 g of potassium carbonate. The reactor contents were heated to 250 °C for 1.5 h and then cooled to room temperature. A dark brown, pasty solid settled from the aqueous phase, which was taken up in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was then washed with chloroform and adjusted to a pH of 10 using KOH plates. The resulting precipitate was taken up in chloroform. After removal of the solvent, a brownish, pasty solid was obtained, which was dried under vacuum. The amine number titration yielded a value of 508 mg KOH / g.Table 3: Pressure hydrolysis of isocyanurate-containing PUR foams at high temperature (prepared as described above).

[0149] The reaction conditions in Example 10 correspond to the reaction conditions described in claim 1 of US Pat. No. 6,630,517 (temperature in the range of 190 to 370 °C and pressure in the range of 30 to 300 bar). Furthermore, the foam was compressed prior to hydrolysis (in the examples of US Pat. No. 6,630,517, compression was also performed prior to hydrolysis). Example 10 shows that the process described in US Pat. No. 6,630,517 leads to poor results for an isocyanurate-containing PUR foam.

Claims

Patent claims:

1. Method for recovering raw materials from isocyanurate-containing polyurethane products, comprising the steps: (A) Providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component; (B) Chemolysis of the isocyanurate-containing polyurethane product with liquid water in the absence of an organic solvent or in the presence of an organic solvent inert to urethane and isocyanurate groups at a temperature in the range of 130 °C to 260 °C and at a pressure in the range of 1.0 bar to 100 bar, in the presence of a catalyst, to obtain a chemolysis product; and (C) Processing of the chemolysis product to obtain (I) of an amine corresponding to an isocyanate of the isocyanate component, and optionally (II) of a polyol of the polyol component or of a reaction product of a polyol of the polyol component.

2. The method of claim 1, wherein step (A) comprises an extraction of the polyurethane product with an organic solvent which does not react with urethane groups or isocyanurate groups during extraction.

3. The method of claim 2, wherein the organic solvent used in the extraction comprises an aromatic hydrocarbon, a halogenated aromatic compound, an aliphatic ether, a ketone, an aromatic ether or a mixture of two or more of the aforementioned organic solvents.

4. The method of claim 2 or 3, wherein the organic solvent used in the extraction comprises toluene, monochlorobenzene, dichlorobenzene, tetrahydrofuran, dioxane, acetone, anisole or a mixture of two or more of the aforementioned organic solvents.

5. Method according to any one of claims 2 to 4, wherein the extraction is carried out at a temperature in the range of ambient temperature to 180 °C or in the range of 20 °C to 180 °C or in the range of 50 °C to 180 °C.

6. Method according to any one of claims 1 to 5, wherein step (A) comprises a mechanical comminution of the polyurethane product.

7. A method according to any one of claims 1 to 6, wherein the catalyst comprises a hydroxide, a carbonate, a hydrogen carbonate, a phosphate, a hydrogen phosphate, a carboxylate, an alcoholate, a metal oxide or a mixture of two or more of the aforementioned catalysts.

8. The method of claim 7, wherein the catalyst comprises an alkali or alkaline earth metal salt of a hydroxide, a carbonate, a hydrogen carbonate, a phosphate, a hydrogen phosphate, a carboxylate or an alcoholate.

9. A method according to any one of claims 1 to 8, wherein the chemolysis is carried out in the presence of an organic solvent inert towards urethane groups and isocyanurate groups.

10. The method of claim 9, wherein in step (B) the polyurethane product is placed in the organic solvent which is inert with respect to urethane groups and isocyanurate groups and the water is added stepwise.

11. The method of claim 9 or 10, wherein the organic solvent inert with respect to urethane groups and isocyanurate groups comprises dimethyl sulfoxide, / V, / V-dimethylformamide, / V-methyl-2-pyrrolidone, dichlorobenzene, trichlorobenzene, ethyl methylbenzene, mesitylene, decane, undecane and / or dodecane.

12. A method according to any one of claims 1 to 8, wherein the chemolysis is carried out in the absence of an organic solvent.

13. Method according to claim 10 or 11, wherein the chemolysis is carried out at a pressure in the range of 1.0 bar to < 5.0 bar.

14. Method according to claim 12, wherein the chemolysis is carried out without pressure equalization under autogenous pressure.

15. A method according to any one of claims 1 to 14, wherein the chemolysis product is cooled in step (C) and a first solid organic phase precipitates, followed by a liquid-solid phase separation into a first aqueous phase and the first solid organic phase, and the first solid organic phase is further processed to obtain the amine.

16. The method of claim 15, wherein the further processing of the first solid organic phase comprises washing the same with an aqueous washing liquid.

17. Method according to claim 15 or 16, wherein the first solid organic phase, optionally washed, is dissolved in an organic solvent, yielding a first liquid organic phase which is further processed to obtain the amine.

18. A method according to any one of claims 1 to 14, wherein the chemolysis product is extracted in step (C) with an organic solvent, followed by a liquid-liquid phase separation into a first aqueous phase and a first liquid organic phase, and the first liquid organic phase is further processed to obtain the amine.

19. The method of claim 17 or 18, wherein the further processing of the first liquid organic phase comprises washing the same with an aqueous washing liquid.

20. A method according to any one of claims 17 to 19, wherein the first liquid organic phase, optionally washed, is extracted with an aqueous mineral acid and subsequently a phase separation into a second liquid organic phase and a second aqueous phase is carried out, after which the second aqueous phase is neutralized or made alkaline by precipitation of a second solid organic phase, followed by work-up of the second solid organic phase to obtain the amine.

21. The method of claim 20, wherein the second solid organic phase is separated by liquid-solid phase separation or absorbed in an organic solvent.

22. Method according to claim 20 or 21, comprising step (C.11), wherein step (C.11) comprises a work-up of the second liquid organic phase by distillative separation of organic solvent leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

23. Method according to any one of claims 15 to 22, comprising step (C.11), wherein step (C.11) comprises a work-up of the first aqueous phase by distillative separation of water while leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

24. Method according to one of the preceding claims, wherein the isocyanate component methylene diphenylene diisocyanate, comprises polymethylenepolyphenylene polyisocyanate or a mixture of methylenediphenylene diisocyanate and polymethylene-polyphenylene polyisocyanate.

25. The method of claim 24, wherein the isocyanate component does not comprise toluene diisocyanate.

26. The method of claim 24, wherein the isocyanate component does not comprise any further isocyanate.

27. A method according to any of the preceding claims, wherein the polyol component comprises a polyether polyol, a polyester polyol, a polyether ester polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols.

28. Method according to any of the preceding claims, wherein the isocyanurate-containing polyurethane product provided in step (A) is a polyurethane foam.

29. Method according to claim 28, wherein the polyurethane foam is a rigid polyurethane foam.

30. Method according to claim 29, wherein the rigid polyurethane foam originates from building insulation.

31. Method according to one of the preceding claims, wherein chemolysis is carried out in a stirred tank reactor.

32. Method according to one of the preceding claims, wherein the amine obtained in step (Cl) is phosgenated to the corresponding isocyanate in a step (D).

33. Method according to one of the preceding claims, wherein the chemolysis is carried out at a temperature in the range of 130 °C to 240 °C.

34. Method according to any of the preceding claims, wherein the catalyst is not or comprises none of the following compounds (i) to (ii): (i) a quaternary ammonium salt containing an ammonium cation comprising 6 or more carbon atoms, (ii) an organic sulfonate comprising 7 or more carbon atoms.

Images