Method for recovering raw materials from isocyanurate-containing polyurethane products

Abstract

The invention relates to a method for recovering raw materials from isocyanurate-containing polyurethane products, in particular from known rigid polyurethane-polyisocyanurate foams (PUR-PIR foams or PIR foams for short). The method is characterized in that an isocyanurate-containing polyurethane product is reacted with liquid water in the presence of a catalyst at a temperature of 130 DEG C to 260 DEG C and a pressure of 1.0 bar to 100 bar to obtain a chemical decomposition product, which is subsequently post-treated to obtain (I) an amine corresponding to the isocyanate of the isocyanate component, and optionally (II) a polyol of a polyol component or a reaction product of a polyol of a polyol component.

Description

[0001] The present invention relates to a method for recovering raw materials from isocyanurate-containing polyurethane products, in particular the well-known rigid polyurethane-polyisocyanurate foams (PUR-PIR foams or PIR foams for short). The method is characterized in that the isocyanurate-containing polyurethane product is reacted with liquid water in the presence of a catalyst at a temperature of 130° C. to 260° C. and a pressure of 1.0 bar to 100 bar to obtain a chemical decomposition product, which is then post-treated to obtain (I) an amine corresponding to the isocyanate of the isocyanate component and optionally (II) a polyol of the polyol component or a reaction product of the polyols of the polyol component.

[0002] Polyurethane products have a wide range of applications in industry and everyday life. A distinction is often 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 the differences, all these products share a basic polyurethane structure, which is formed by the polyaddition reaction of polyfunctional isocyanates and polyols and, in the case of polyurethanes based on diisocyanates O=C=NRN=C=O and diols HO-R'-OH (where R and R' represent organic groups), can be expressed, for example, as

[0003] ~~~[O-R'-O-(O=C)-HN-R-NH-(C=O)]~~~.

[0004] Under certain conditions, isocyanates react not only with polyols but also with themselves to form isocyanurate structures:

[0005]

[0006] In this way, isocyanurate-containing polyurethane products are formed. This is particularly relevant for polyurethane products based on diisocyanates and polyisocyanates of the diphenylmethane series (methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, MDI).

[0007] Isocyanurate-containing polyurethane products are typically produced as foams and are particularly used in the field of building insulation because they offer a higher level of fire safety compared to polyurethane insulation materials without isocyanurate groups. In applications where flame retardancy plays a lesser role, such as in refrigerator insulation, polyurethane products without isocyanurate groups are often used. As building insulation becomes increasingly important and even the highest-quality materials cannot be used indefinitely, the recycling of isocyanurate-containing polyurethane products is becoming increasingly important.

[0008] The most technically feasible recycling model is incineration, where the heat released by combustion is used in other processes, for example industrial processes. However, this does not close the loop on the recycling of raw materials. Another recycling model is so-called "physical recycling," in which polyurethane waste is mechanically shredded and used to make new products. This type of recycling naturally has its limitations, so attempts have been made to recover the basic raw materials for polyurethane production by reverse cleavage of polyurethane bonds (so-called "chemical recycling"). The raw materials obtainable in this chemical decomposition include polyols (i.e., HO-R'-OH in the above example) and / or their reaction products formed in the chemical decomposition, and amines formed by the hydrolytic cleavage of polyurethane bonds (i.e., H2N-R-NH2 in the above example). After post-processing, the amines obtained in this way can be rephosgenated to give isocyanates (O=C=NRN=C=O in the above example).

[0009] Methods for chemical recovery and apparatus for their implementation frequently appear in the literature, in particular in the patent literature.

[0010] For example, Japanese patent application JP 2004-115631A discloses an apparatus for decomposing expanded plastics. The expanded plastics are kneaded at high temperatures as they pass through the apparatus. Amino compounds, polyols, and water are listed as suitable decomposition agents. In the case of water as the decomposition agent (hydrolysis), alkali or alkaline earth metals or their compounds, amino compounds, etc. are listed as suitable catalysts. Expanded plastics that can be decomposed using the apparatus include, in particular, soft or rigid polyurethane foams or foams containing isocyanurates. The apparatus is described in examples for the chemical decomposition of rigid polyurethane foams used for refrigerator insulation using monoethanolamine or diethanolamine at 210°C or 250°C. Therefore, it is unclear whether the apparatus can actually be successfully applied to the decomposition of isocyanurate-containing foams under these conditions. The application clearly focuses on the apparatus described, in which the expanded plastics are "kneaded," that is, subjected to significant mechanical stress. The application does not disclose whether or how the amines can be separated from the resulting chemical decomposition products.

[0011] DE 24 43 387 A1 describes a method for the continuous hydrolytic cleavage of polymer waste, wherein waste consisting of hydrolyzable plastic material is introduced into a screw unit together with water and, optionally, a hydrolysis catalyst. The mixture of water and plastic waste is subjected to intense mass and heat transfer in a reaction zone at a temperature of 100° C. to 300° C. and a pressure of 5 to 100 bar for 2 to 100 minutes. The liquid-gas mixture formed during the hydrolysis is then continuously conveyed to a die fixedly connected to the screw unit. The gas escapes from the die through a control valve that maintains a constant screw pressure, and the liquid escapes through a control valve that maintains a constant liquid level in the die. The method is illustrated using the example of the cleavage of flexible, elastic polyurethane foam.

[0012] DE 29 02 509 A1 describes a process for preparing a polyol-containing liquid from polyurethane-containing and / or polyisocyanurate-containing foam waste, by heating the optionally comminuted foam waste and at least one aliphatic diol of the general formula HO—R—OH, where R is a linear or branched alkylene group having 2 to 20 carbon atoms, the main chain of which may be interrupted by one or more oxygen atoms, to a temperature of 150° C. to about 220° C. in the presence of a catalyst, wherein the catalyst used is at least one compound of a metal of transition group IV of the periodic table.

[0013] EP 0 011 662 A1 describes the hydrolysis of polyurethanes, in particular flexible polyurethane foams, using superheated steam in the presence of basic alkali metal or alkaline earth metal compounds.

[0014] EP 0 753 535 A1 relates to a process for preparing recycled polyols by glycolysis of polyisocyanurates. For this purpose, polyisocyanurates are reacted with short-chain, hydroxyl-containing compounds in the presence of a carrier polyol having an OH number of up to 500 mg KOH / g and a molar mass of at least 450 g / mol.

[0015] EP 0 976 719 A1 (also published as US Pat. No. 6,630,517) describes a device and method for the hydrolysis of polyisocyanate derivatives, wherein the polyisocyanate derivative to be cleaved is reacted with liquid water at a temperature of 190° C. to 370° C. at a pressure of 30 to 300 bar. The hydrolysis process can be carried out without the use of a catalyst. In fact, EP 0 976 719 A1 (US Pat. No. 6,630,517) explicitly seeks to avoid the use of a catalyst. Polyisocyanate derivatives are understood to be compounds containing at least one isocyanate group or a functional group derived therefrom, such as polyurethanes. In the context of this application, polyisocyanate derivatives are also compounds formed by oligomerization of compounds containing isocyanate groups, which are present in the distillation residues of chemical plants used to prepare compounds containing isocyanate groups. The example of this type of oligomeric compound that is present in the waste stream of the chemical plant for the preparation of the compound containing isocyanate groups comprises dimer, trimer or higher oligomer, for example carbodiimide, uretdione, ureaamine (urethanimin), isocyanurate etc.This method has been described by the embodiment of the hydrolysis of the residue prepared by relevant flexible polyurethane foam, rigid polyurethane foam and toluene diisocyanate (TDI).Polyurethane foam is compressed at high temperature before hydrolysis.From EP 0 976 719 A1 (US 6,630,517), it is not clear whether the polyurethane product (being different from the residue stream prepared by isocyanate), especially PUR-PIR foam, that contains isocyanate groups can be hydrolyzed by this method.

[0016] US Pat. No. 3,441,616 describes the recovery of polyether polyols from polyurethane products by hydrolysis in a mixture of water and dimethyl sulfoxide in the presence of a strong base, such as an alkali metal oxide or alkaline earth metal oxide or hydroxide, at a temperature of 100° C. to 190° C., followed by extraction of the formed polyether polyol with a hydrocarbon. The examples describe the hydrolysis of TDI-based polyurethane foams.

[0017] CN 111 533 873A describes a method for recycling polyurethane screens.

[0018] CN 113 429 540A describes a method for preparing polyurethane thermal insulation materials by degrading polyurethane waste using a polyol alcoholysis agent.

[0019] WO 96 / 26236 A1 describes a method for separating polymer materials from plastic components, in particular motor vehicle parts, which consist of a thermoplastic polymer and at least one thermosetting polymer of a polyurethane foam.

[0020] WO 2022 / 042909 A1 describes a process for the hydrolysis of polyurethanes in the presence of a base comprising alkali metal cations and / or ammonium cations, wherein the base has a pK of 1 to 10 at 25°C. B The invention relates to a process for preparing polyurethanes based on polyether polyols, wherein the polyurethanes are prepared by a process comprising a polyol having a carbon number of 15 or more and a polyol having a carbon number of 15 or more. The process further comprises a method for preparing polyurethanes based on polyether polyols, wherein the polyols are prepared by a process comprising a polyol having a carbon number of 15 or more and a polyol having a carbon number of 15 or more. The process further comprises a method for preparing polyurethanes based on polyether polyols, wherein the polyols are prepared by a process comprising a polyol having a carbon number of 15 or more and a polyol having a carbon number of 15 or more. The process further comprises a method for preparing polyurethanes based on polyether polyols, wherein the polyurethanes are prepared by a process comprising a polyol having a carbon number of 15 or more and ...

[0021] WO 2022 / 042910 A1 describes a process for the hydrolysis of polyurethanes in the presence of a base comprising alkali metal cations and / or ammonium cations, wherein the base has a pK of less than 1 at 25°C. B The invention relates to a process for preparing a polyurethane containing polyol having a carbon number of 6 to 14 carbon atoms, wherein the process further comprises a (phase transfer) catalyst selected from (i) a quaternary ammonium salt comprising an ammonium cation having 6 to 14 carbon atoms (if the ammonium cation does not contain a benzyl group) and (ii) a quaternary ammonium salt comprising an ammonium cation having 6 to 12 carbon atoms (if the ammonium cation contains a benzyl group). The hydrolysis produces a polyether polyol and a polyamine. Recovery of the PIR-containing polyurethane is not described.

[0022] WO 2023 / 275029 A1 describes a method for preparing polyurethane foam by reacting an isocyanate component with a polyol component, wherein the polyol component comprises 0.001% to 10% by weight of a recycled polyol containing amino and / or phenolic antioxidants. The recycled polyol is preferably obtained by a hydrolysis method such as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0023] WO 2023 / 275036 A1 describes a process for preparing aromatic and / or aliphatic diisocyanates and / or polyisocyanates by phosgenation of diamines and / or polyamines, wherein the diamines and / or polyamines are obtained by a hydrolysis process as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0024] WO 2023 / 275038 A1 describes a process for the ring hydrogenation of aromatic amines at least partially produced by a polyurethane decomposition process. Preferred polyurethane decomposition processes are hydrolysis processes as described in WO 2022 / 042909 A1 or WO 2022 / 042910 A1.

[0025] EP 1 149 862 A1 describes a process in which rigid polyurethane foam from used refrigerators is comminuted, liquefied by glycolysis or aminolysis, and then treated with supercritical or non-supercritical water. The crude product obtained in this way is fractionated and used to produce new refrigerators.

[0026] GB 991,387 A describes the hydrolysis of non-volatile polyisocyanate reaction products with superheated steam at 200° C. to 400° C. Non-volatile polyisocyanate reaction products are understood to mean reaction products of polyisocyanates with compounds containing active hydrogen atoms, such as polyureas and polyurethanes, and oligomeric reaction products of polyisocyanates, such as isocyanurates and carbodiimides.

[0027] US Pat. No. 3,708,440 describes a method for post-processing waste polyisocyanurate foam to obtain polyols that can be used as the polyol component in the preparation of polyurethane foam without further treatment. The method comprises heating the waste foam to a temperature of 175° C. 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% by weight of the mixture.

[0028] H. Ulrich et al., in Polymer Engineering and Science, 1978, 18, 844-848, describe the glycolysis of polyurethane and (polyurethane) polyisocyanurate foams for the recovery of polyols that can be reused in foam production. The introduction mentions not only glycolysis but also steam hydrolysis and thermal decomposition. However, both methods are described as disadvantageous because, according to the authors, they result in complex product mixtures. Therefore, separation of the amines formed during hydrolysis was considered impractical, while glycolysis was considered to produce a recyclable polyol mixture in a single-stage process.

[0029] PNGribkova et al. describe the decomposition of polyisocyanurates obtained by polycyclic trimerization of 4,4'-methylenediphenylene diisocyanate (4,4'-mMDI) (i.e., without urethane groups) in Polymer Science USSR, 1980, 22, 299-304. The polyisocyanurates studied can be cracked in saturated steam at high temperatures (decomposition begins at temperatures above about 300° C.) without catalysts (i.e., by a purely thermal process).

[0030] None of the above methods is completely satisfactory for recovering raw materials from isocyanurate-containing polyurethane products. In particular, there is still a lack of feasible methods for recovering amines from isocyanurate-containing polyurethane products.

[0031] Therefore, there is a need for further improvement in the field of recycling raw materials from isocyanurate-containing polyurethane products. In particular, it is desirable to recover amines from isocyanurate-containing polyurethane products so that they can be phosgenated to produce isocyanates after purification.

[0032] In view of this demand, the present invention provides a method for recovering raw materials from a polyurethane product containing isocyanurate, comprising the following steps:

[0033] (A) providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component;

[0034] (B) in the absence of an organic solvent or in the presence of an organic solvent inert to urethane groups and isocyanurate groups,

[0035] At a temperature of 130° C. to 260° C., in particular 130° C. to 240° C., preferably 135° C. to 230° C., particularly preferably 140° C. to 220° C., and at a pressure of 1.0 bar to 100 bar, preferably 5.0 bar to 100 bar, particularly preferably 10 bar to 80 bar,

[0036] In the presence (ie added) of a catalyst, the catalyst is in particular not or does not comprise the following compounds (i) to (ii):

[0037] (i) a quaternary ammonium salt containing an ammonium cation containing 6 or more carbon atoms, (ii) an organic sulfonate containing 7 or more carbon atoms;

[0038] chemical decomposition (= hydrolysis) of an isocyanurate-containing polyurethane product with liquid water to obtain chemical decomposition products,

[0039] as well as

[0040] (C) post-processing the chemical decomposition products to obtain

[0041] (I) (at least) one amine corresponding to the isocyanate of the isocyanate component, and optionally

[0042] (II) a polyol of (at least) one polyol component or a reaction product of a polyol of (at least) one polyol component.

[0043] Surprisingly, it has been found that the chemical decomposition of isocyanurate-containing polyurethane products proceeds successfully under the conditions described above and that the amine can be recovered as pure hydrolyzate, ie without using reactive organic solvents.

[0044] In the context of the present invention, polyurethane products are polyaddition products of polyfunctional isocyanates (=isocyanate component of polyurethane production) and polyols (=polyol component of polyurethane production). The present invention relates to the recovery of polyurethane products that, in addition to the pure polyurethane base structure, also contain isocyanurate structures (see above). Furthermore, other structures, such as those containing urea bonds, may also be present without departing from the scope of the present invention.

[0045] In the terminology of the present invention, the term isocyanate encompasses isocyanates commonly known to a person skilled in the art in the context of isocyanurate chemistry. Obviously, the expression "isocyanate" also encompasses embodiments in which two or more different isocyanates (e.g., a mixture of different MDI types) are used in the preparation of an isocyanurate-containing polyurethane product, unless otherwise expressly indicated, for example, by the expression "exactly one isocyanate". The total number of all isocyanates used to prepare an 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.

[0046] Similarly, all polyols used to prepare isocyanurate-containing polyurethane products are referred to as polyol components (of isocyanurate-containing polyurethane products). The polyol component comprises at least one polyol. It should be understood that the expression "polyol" also encompasses embodiments in which two or more different polyols are used in the preparation of isocyanurate-containing polyurethane products. Therefore, if, for example, "polyether polyol" (or "polyester polyol" etc.) is mentioned hereinafter, it should be understood that this term also encompasses embodiments in which two or more different polyether polyols (or two or more different polyester polyols etc.) are used in the preparation of isocyanurate-containing polyurethane products.

[0047] The amine corresponding to the isocyanate is an amine which can be phosgenated to give the isocyanate according to R—NH 2 + COCl 2 → RN = C = O + 2HCl.

[0048] According to the invention, the chemical decomposition of the isocyanurate-containing polyurethane product is carried out hydrolytically, i.e., using liquid water. This is to be understood as meaning that the chemical reaction of the hydrolysis is carried out by the action of liquid water on the isocyanurate-containing polyurethane product (in contrast to, for example, the use of steam). The chemical decomposition is carried out in the absence of an organic solvent or in the presence of an organic solvent that is inert toward carbamate and isocyanurate groups (i.e., the organic solvent does not lead to the cleavage of carbamate and / or isocyanurate groups), and is therefore a "true" hydrolysis rather than a hydroalcoholic acid reaction.

[0049] According to the present invention, the hydrolysis is carried out in the presence of a catalyst. In the context of the process according to the invention, this is understood to mean the addition of a catalyst. Depending on the origin of the isocyanurate-containing polyurethane product to be recovered, the presence of traces of catalytically active concomitant products from the original preparation cannot be ruled out. In the context of the present invention, there is no need to rely on the presence of such catalyst residues, but rather—given reliable and reproducible reaction management—the addition of a catalyst to carry out step (B).

[0050] In a particularly preferred embodiment, the hydrolysis is carried out in the presence of a catalyst (= addition of a catalyst) which is not or does not comprise the following compounds (i) to (ii): (i) a quaternary ammonium salt containing an ammonium cation containing 6 or more (e.g. up to 30) carbon atoms, (ii) an organic sulfonate containing 7 or more (e.g. up to 25) carbon atoms. Thus, this embodiment does not include the addition of a quaternary ammonium salt containing an ammonium cation containing 6 or more carbon atoms (e.g. (a) a quaternary ammonium salt containing an ammonium cation with 6 to 30 carbon atoms, (b) a quaternary ammonium salt containing an ammonium cation with 6 to 14 carbon atoms (if the ammonium cation does not contain a benzyl group) and (c) a quaternary ammonium salt containing an ammonium cation with 6 to 12 carbon atoms (if the ammonium cation contains a benzyl group)) and an organic sulfonate containing at least 7 carbon atoms for the chemical decomposition, i.e. the chemical decomposition is carried out in the absence of said compounds. An organic sulfonate is understood to be a quaternary ammonium salt containing an anion R-SO3 - An organic sulfonate wherein "R" is an organic group containing 7 or more carbon atoms.

[0051] The following are various possible embodiments of the present invention. Overview :

[0052] In a first embodiment of the process according to the invention, which can be combined with all other embodiments, step (A) comprises extracting the polyurethane product with an organic solvent which does not react with urethane groups or isocyanurate groups during the extraction.

[0053] In a second embodiment of the process according to the invention, which is a special embodiment of the first embodiment, the organic solvent used for the extraction comprises (in particular is) an aromatic hydrocarbon (in particular toluene), a halogenated aromatic compound (in particular monochlorobenzene or dichlorobenzene [preferably o-dichlorobenzene]), an aliphatic ether (in particular tetrahydrofuran or dioxane [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.

[0054] In a third embodiment of the process according to the invention, which is a special embodiment of the first and second embodiments, the extraction is carried out at a temperature of from ambient temperature (in particular 20° C.) to 180° C., preferably from 50° C. to 180° C. and particularly preferably at ambient pressure (in particular 1.0 bar) and at the boiling point of the organic solvent.

[0055] In a fourth embodiment of the process according to the invention, which can be combined with all the other embodiments, step (A) comprises mechanical comminution of the polyurethane product.

[0056] 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 hydrogenphosphate, a carboxylate, an alkoxide, a metal oxide or a mixture of two or more of the aforementioned catalysts.

[0057] In a sixth embodiment of the process according to the invention, which is a special embodiment of the fifth embodiment, the catalyst comprises (in particular is) an alkali metal or alkaline earth metal hydroxide, carbonate, bicarbonate, phosphate, hydrogenphosphate, carboxylate or alkoxide.

[0058] In a seventh embodiment of the process according to the invention, which can be combined with all other embodiments, without being restricted to a solvent-free chemical decomposition, the chemical decomposition is carried out in the presence of an organic solvent which is inert toward urethane and isocyanurate groups.

[0059] In an eighth embodiment of the process according to the invention, which is a special embodiment of the seventh embodiment, in step (B), the polyurethane product is firstly added to an organic solvent inert toward urethane and isocyanurate groups, and water is gradually added.

[0060] In a ninth embodiment of the process according to the invention, which is a special embodiment of the seventh and eighth embodiments, the organic solvent inert to carbamate groups and isocyanurate groups comprises (in particular is) dimethyl sulfoxide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dichlorobenzene (in particular the ortho isomer), trichlorobenzene, ethylmethylbenzene (in particular 1-ethyl-2-methylbenzene), mesitylene, decane (in particular n-decane), undecane (in particular n-undecane) and / or dodecane (in particular n-dodecane).

[0061] In a tenth embodiment of the process according to the invention, which can be combined with all other embodiments, the chemical decomposition is carried out in the absence of an organic solvent, provided that it is not restricted to the presence of a solvent.

[0062] In an eleventh embodiment of the process according to the invention, which is a special embodiment of the eighth and ninth embodiments, the chemical decomposition is carried out at a pressure in the range 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, in particular at ambient pressure (in particular 1.0 bar).

[0063] In a twelfth embodiment of the process according to the invention, which is a special embodiment of the tenth embodiment, the chemical decomposition is carried out without pressure equalization at autogenous pressure, in particular at an autogenous pressure of 5.0 bar to 100 bar, preferably 10 bar to 80 bar.

[0064] In a thirteenth embodiment of the process according to the invention, which is a specific embodiment of the first to twelfth embodiments, in step (c), the chemical decomposition product is cooled (by active cooling or by allowing it to cool) to precipitate a first solid organic (amine) phase, followed by liquid-solid phase separation into a first aqueous phase and a first solid organic (amine) phase, and the first solid organic (amine) phase is further worked up to obtain the amine.

[0065] In a fourteenth embodiment of the process according to the invention, which is a special embodiment of the thirteenth embodiment, the further workup of the first solid organic (amine) phase comprises washing it with an aqueous washing liquid.

[0066] In a fifteenth embodiment of the process according to the invention, which is a specific 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 worked up to obtain the amine.

[0067] In a sixteenth embodiment of the process according to the invention, which is another specific embodiment of the first to twelfth embodiments, in step (C), the chemical decomposition product is extracted with an organic solvent, followed by liquid-liquid phase separation to obtain a first aqueous phase and a first liquid organic (amine) phase, and the first liquid organic (amine) phase is further worked up to obtain the amine.

[0068] In a seventeenth embodiment of the process according to the invention, which is a special embodiment of the fifteenth and sixteenth embodiments, the further treatment of the first liquid organic (amine) phase comprises washing it with an aqueous washing liquid.

[0069] In an eighteenth embodiment of the process according to the invention, which is a specific 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 to obtain a second liquid organic phase and a second aqueous phase (containing the protonated amine), the second aqueous phase is then neutralized or alkalized to precipitate a second solid organic (amine) phase, and the second solid organic (amine) phase is then worked up to obtain the amine.

[0070] In a nineteenth embodiment of the process according to the invention, which is a special embodiment of the eighteenth embodiment, the second solid organic (amine) phase is separated by liquid-solid phase separation or dissolved in an organic solvent.

[0071] In a twentieth embodiment of the process according to the invention, which is a specific embodiment of the eighteenth and nineteenth embodiments, step (C.II) is comprised, wherein step (C.II) comprises working up the second liquid organic phase, separating the organic solvent by distillation to retain an alcoholic phase, and subsequently purifying the alcoholic phase by distillation or stripping.

[0072] In a twenty-first embodiment of the process according to the invention, which is a specific embodiment of the thirteenth to twentieth embodiments, step (C.II) is included, wherein step (C.II) comprises post-treatment of the first aqueous phase, separating the water by distillation to retain the alcoholic phase, and subsequently purifying the alcoholic phase by distillation or stripping.

[0073] In a twenty-second embodiment of the process according to the invention, which can be combined with all other embodiments, the isocyanate component comprises methylene diphenylene diisocyanate, polymethylene polyphenylene polyisocyanate, or a mixture of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate. The isocyanate component preferably does not contain toluene diisocyanate and particularly preferably does not contain any other isocyanates besides toluene diisocyanate.

[0074] In a twenty-third embodiment of the process according to the invention, which is combinable 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.

[0075] In a twenty-fourth embodiment of the process according to the invention, which is combinable with all other embodiments, the isocyanurate-containing polyurethane product provided in step (A) is a polyurethane foam, in particular a rigid polyurethane foam, preferably derived from building insulation.

[0076] In a twenty-fifth embodiment of the process according to the invention, which can be combined with all other embodiments, the chemical decomposition is carried out in a stirred tank reactor.

[0077] In a twenty-sixth embodiment of the process according to the invention, which is combinable with all other embodiments, the amine obtained in step (CI) is phosgenated to the corresponding isocyanate in step (D).

[0078] 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 the following compounds (i) to (ii):

[0079] (i) quaternary ammonium salts containing an ammonium cation containing 6 or more carbon atoms, (ii) organic sulfonates containing 7 or more carbon atoms.

[0080] The embodiments briefly outlined above and further possible configurations of the present invention will be discussed below. More specifically Explanation All of the above-described embodiments and further configurations of the invention described below can be combined with one another and collectively as desired, unless this is obvious to a person skilled in the art from the context or is explicitly stated to the contrary.

[0081] Preparation for chemical recycling

[0082] Step (A) of the process according to the invention comprises providing an isocyanurate-containing polyurethane product to be chemically recovered. Isocyanurate-containing polyurethane products in the context of the present invention are in particular those polyurethane products which have a -1 to 1800cm -1 The infrared spectrum in the spectral range (C=O stretching vibration range) is at 1712 cm -1 The signal maximum occurs at wave numbers of 0.001 or less.

[0083] In principle, this can be any type of isocyanurate-containing polyurethane product. However, preference is given to polyurethane foams, in particular rigid polyurethane foams, preferably derived from building insulation materials. Rigid polyurethane foam is a highly crosslinked thermosetting plastic, the cellular structure obtained by foaming has a low raw material density (especially at 20 kg / m 3 Up to 90kg / m 3 In the range of 30kg / m 3 Up to 45kg / m 3Rigid polyurethane foams have a high thermal conductivity (typically in the range of 0.016 W / (m·K) to 0.030 W / (m·K) according to DIN 52616 1977-11) and a low thermal conductivity (typically in the range of 0.016 W / (m·K) to 0.030 W / (m·K) according to DIN 52616 1977-11). They are generally closed-cell and have a relatively high resistance to deformation under compressive stress. Their thermosetting properties are reflected in the foam's infusibility, high softening point, and good chemical and solvent resistance. Rigid polyurethane foams typically have a compressive strength of 50 kPa to 300 kPa, measured at 10% according to DIN EN 826 2013-05, and a tensile strength of 30 kPa to 250 kPa, measured according to EN 1607 2013-05.

[0084] Furthermore, polyurethane products are preferred, which Isocyanate component They are based on isocyanates selected from the group consisting of methylene diphenylene diisocyanate ("monomeric MDI", mMDI), polymethylene polyphenylene polyisocyanates ("polymeric MDI", pMDI), and mixtures of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanates (hereinafter collectively referred to as MDI). They are prepared by phosgenation of the corresponding amines (methylene diphenylene diamine ["monomeric MDA", mMDA], polymethylene polyphenylene polyamines ("polymeric MDA", pMDA)), or mixtures of methylene diphenylene diamine and polymethylene polyphenylene polyamines (hereinafter collectively referred to as MDA)).

[0085] Furthermore, polyurethane products are preferred, which Polyol components Based on a polyol selected from the group consisting of polyether polyols, polyester polyols, polyether ester polyols, polyether carbonate polyols or mixtures of two or more of these polyols. Particular preference is given to polyester polyols and polyether ester polyols, especially in mixtures with polyether polyols.

[0086] Step (A) preferably includes preparatory steps for cleaving the urethane and isocyanurate bonds in step (B). These preferably include mechanical comminution of the isocyanurate-containing polyurethane product. These preparatory steps are known to those skilled in the art.

[0087] In particular, isocyanurate-containing polyurethane products from building insulation materials often contain additives, particularly flame retardants, as well as stabilizers and activators. It has proven advantageous to remove these substances in an extraction step before the chemical recovery in step (B) begins. For this purpose, the previously comminuted isocyanurate-containing polyurethane foam is preferably extracted using an organic solvent that does not react with urethane or isocyanurate groups during the extraction process. This can be ensured by using a solvent that is (preferably) essentially chemically inert toward urethane and isocyanurate groups or by selecting a sufficiently low temperature and / or a sufficiently short extraction time to ensure that chemical reactions do not occur to a significant extent. Organic solvents that have proven advantageous include, in particular, aromatic hydrocarbons (especially toluene), halogenated aromatic compounds (especially monochlorobenzene or dichlorobenzene [preferably o-dichlorobenzene], with dichlorobenzene, preferably as the ortho isomer, being more preferred than monochlorobenzene), aliphatic ethers (especially tetrahydrofuran or dioxane [preferably 1,4-dioxane]), ketones (especially acetone), aromatic ethers (especially anisole), or mixtures of two or more of the aforementioned solvents. Halogenated aromatic compounds 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"). Once the extraction is complete, 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 (it is possible, but not necessary, to use the same solvent as used for the extraction). Before carrying out step (B), adhering solvent residues are preferably removed by drying. However, a less preferred embodiment using a reactive solvent (eg ethanol) for extraction and / or washing removes said solvent before step (B).

[0088] Chemical cleavage of urethane and isocyanurate bonds

[0089] Step (B) involves chemically decomposing the isocyanurate-containing polyurethane product with liquid water. According to the invention, the hydrolysis is carried out in the presence of a catalyst at a temperature of 130° C. to 260° C., in particular 130° C. to 240° C., preferably 135° C. to 230° C., particularly preferably 140° C. to 220° C., and at a pressure of 1.0 bar to 100 bar, preferably 5.0 bar to 100 bar, particularly preferably 10 bar to 80 bar.

[0090] Catalysts that have proven to be advantageous include hydroxides, carbonates, bicarbonates, phosphates, hydrogenphosphates, carboxylates, alkoxides, and metal oxides. Although not preferred, mixtures of different catalysts can also be used. Catalysts in the form of alkali metal salts or alkaline earth metal salts are preferably used.

[0091] As mentioned above, the chemical decomposition can be carried out in the presence of an organic solvent that is inert toward urethane and isocyanurate groups. Solvents that have proven advantageous include, in particular, dimethyl sulfoxide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dichlorobenzene (especially the ortho-isomer), trichlorobenzene, ethylmethylbenzene (especially 1-ethyl-2-methylbenzene), mesitylene, decane (especially n-decane), undecane (especially n-undecane), and dodecane (especially n-dodecane). When using an organic solvent, the isocyanurate-containing polyurethane product to be cleaved can first be added (dissolved or suspended) in the solvent, the reaction mixture heated to the reaction temperature, and then water gradually added, ensuring that the temperature does not drop excessively, in particular, not by more than 15.0°C. During this process, the water that hydrolyzes the PUR and PIR bonds reacts rapidly enough to ensure that it does not evaporate to a degree that impairs the reaction. In this case, the reaction is generally carried out at reduced pressure, preferably from 1.0 bar to <5.0 bar, preferably from 1.0 bar to 1.5 bar, particularly preferably from 1.0 bar to 1.2 bar, and in particular at ambient pressure.

[0092] However, it is also possible and preferred to carry out the reaction completely without organic solvents. This facilitates post-processing. In this case, it has proven advantageous to carry out the hydrolysis in a pressure-resistant reactor without pressure equalization under autogenous pressure, in particular at an autogenous pressure of 5.0 to 100 bar, preferably 10 to 80 bar. In this case, the relatively high pressure ensures that the chemical decomposition is carried out with liquid water.

[0093] Therefore, the chemical decomposition is carried out in particular in such a way that:

[0094] Step (B) comprises firstly adding the polyurethane product to an organic solvent inert toward urethane groups and isocyanurate groups and gradually adding water, wherein the pressure is maintained at 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 atmospheric pressure,

[0095] or

[0096] Step (B) comprises reacting the polyurethane product with water without organic solvent under autogenous pressure without pressure equalization, especially under autogenous pressure of 5.0 bar to 100 bar, preferably 10 bar to 80 bar.

[0097] With regard to the apparatus that can be used, all reactor types known in the art are suitable in principle. Preference is given to stirred tank reactors.

[0098] Post-treatment of chemical decomposition products

[0099] Step (C) comprises post-processing the chemical decomposition product obtained in step (B) to obtain (I) (at least) one amine corresponding to the isocyanate of the isocyanate component, and optionally (II) (at least) one polyol of the polyol component or (at least) one reaction product of the polyols of the polyol component.

[0100] Once the hydrolysis is complete, the chemical decomposition product is first cooled (either by active cooling or by allowing it to cool) to precipitate a first solid organic (amine) phase. In the context of the present invention, the term "solid phase" is not limited to a "crystalline solid." A pasty, "clay-like" phase is typically produced and is included in the general term "solid phase" in the terminology used herein. The first solid organic (amine) phase is separated from the chemical decomposition product by liquid-solid phase separation (especially filtration), retaining the first aqueous phase. The obtained first solid organic phase is further post-processed to obtain the amine.

[0101] The further post-treatment preferably comprises washing with an aqueous washing liquid. In addition, the optionally washed first solid organic phase is preferably dissolved in an organic solvent to obtain a first liquid organic amine phase, which is further post-treated to obtain the amine. Suitable organic solvents for this purpose include, in particular, halogenated aliphatic hydrocarbons (such as, in particular, dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as, in particular, monochlorobenzene and dichlorobenzene (preferably o-dichlorobenzene), alicyclic alcohols (such as, in particular, cyclohexanol) and aromatic ethers (such as, in particular, anisole).

[0102] As an alternative to liquid-solid phase separation of the chemical decomposition products, the chemical decomposition products can also be completely extracted with an organic solvent and then liquid-liquid phase separated to obtain a first aqueous phase and a first liquid organic (amine) phase. Suitable organic solvents for this purpose include, in particular, halogenated aliphatic hydrocarbons (such as, in particular, dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as, in particular, monochlorobenzene and dichlorobenzene (preferably o-dichlorobenzene), cycloaliphatic alcohols (such as, in particular, cyclohexanol) and aromatic ethers (such as, in particular, anisole).

[0103] Regardless of how the first liquid organic phase is obtained, it is subjected to further workup to obtain the amine. This further workup preferably first comprises washing with an aqueous washing liquid.

[0104] The first liquid organic phase, which is optionally washed, is then preferably extracted with an aqueous mineral acid, followed by phase separation to obtain a second liquid organic phase and a second aqueous phase (containing the protonated amine). The second aqueous phase is neutralized or alkalized (preferably to a pH of 9.0 to 14, preferably 10 to 14) to precipitate a second solid organic (amine) phase. The resulting second solid organic phase is further post-processed to obtain the amine.

[0105] For this purpose, it is preferred to first separate the second solid organic phase by liquid-solid phase separation (particularly filtration). In particular, when the properties of the solid phase make liquid-solid phase separation difficult to carry out, it can also be directly dissolved in an organic solvent and separated from the aqueous component by liquid-liquid phase separation. Suitable organic solvents for this purpose include, in particular, halogenated aliphatic hydrocarbons (for example, especially dichloromethane and chloroform), halogenated aromatic hydrocarbons (for example, especially monochlorobenzene and dichlorobenzene (preferably o-dichlorobenzene), alicyclic alcohols (for example, especially cyclohexanol) and aromatic ethers (for example, especially anisole). After evaporation of the solvent, the second solid organic phase is retained. It is preferably washed and dried. The solid obtained in this way contains amines, which can be returned to phosgenation to produce the corresponding isocyanate. This phosgenation can be carried out according to methods known in the prior art (step (D)). This method is described in, for example, WO2017 / 055311A1 (see in particular page 15, line 10 to page 19, line 17).

[0106] Of course, the polyol component of the isocyanurate-containing polyurethane product also represents a valuable product that is preferably subjected to the greatest possible degree of material recovery. In this context, the nature of the raw materials to be recovered depends on the nature of the polyol component initially used. While pure polyether polyols can be recycled as such, polyols with more reactive functional groups (e.g., especially ester groups) are hydrolytically cleaved in step (B). However, the resulting low-molecular-weight or oligomeric reaction products are also valuable raw materials for the preparation of new polyols.

[0107] The polyols and / or their reaction products can be obtained by post-treatment of the first aqueous phase. The second liquid organic phase may also contain a considerable proportion of these.

[0108] To obtain the polyols and / or reaction products thereof, the workup of the first aqueous phase preferably comprises distillative separation of the water to retain the alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

[0109] To obtain the polyols and / or reaction products thereof, the workup of the second liquid organic phase preferably comprises distillative separation of the organic solvent to retain the alcohol phase, followed by purification of the alcohol phase by distillation or stripping. Example

[0110] Index: This refers to the molar ratio of NCO groups to NCO-reactive groups in the formulation multiplied by 100.

[0111] Amine value: The determination of the amine value is carried out in accordance with EN ISO 9702 (August 1998).

[0112] Chemicals

[0113] Desmodur VP.PU 1806 is available from Covestro Deutschland AG, a mixture of diphenylmethane 4,4′-diisocyanate and diphenylmethane 2,4′-diisocyanate, with an NCO content of 31.4% by mass.

[0114] Desmodur 44V70L from Covestro Deutschland AG, polymeric MDI with an NCO content of 30% to 32% by weight

[0115] Desmophen 2382 was purchased from Covestro Deutschland AG, an aromatic polyester polyol with an OH value of 240 mg KOH / g

[0116] Desmophen V657 is available from Covestro Deutschland AG, a reactive trifunctional polyether polyol having an OH value of 255±15 mgKOH / g, an acid value of up to 0.35 mgKOH / g and a viscosity of (265±20) mPa·s at 25°C.

[0117] Additive 1132 was purchased from Covestro Deutschland AG, a reaction product of phthalic anhydride and diethylene glycol, with an acid value of 89 mgKOH / g

[0118] Stabilizer 21AS08 silicone-polyether copolymer with an OH value of 12 mgKOH / g, purchased from Covestro Deutschland AG

[0119] Desmorapid 1792 potassium acetate, 25 mass % in diethylene glycol (DEG)

[0120] n-Pentane was purchased from Sigma Aldrich

[0121] Dimethyl sulfoxide was purchased from Sigma Aldrich

[0122] Diethylene glycol was purchased from Brenntag GmbH

[0123] Potassium hydroxide was purchased from Sigma Aldrich

[0124] Potassium phosphate was purchased from Sigma Aldrich

[0125] Potassium carbonate was purchased from Sigma Aldrich

[0126] Preparation of model substances

[0127] Model substance 1

[0128] First, 172.1 g of Desmodur VP.PU 1806 was added to a 250 ml four-necked flask equipped with a gas inlet, reflux condenser, stirrer, and dropping funnel. The mixture was then filled with nitrogen and heated to 80°C with stirring. 77.9 g of Desmophen 2382 was added to this solution, ensuring that the temperature did not exceed 80°C. Once the addition was complete, the mixture was stirred at 80°C for 2 hours. 200 g of the resulting NCO-containing prepolymer was then mixed with 1 g of Desmorapid 1792, mixed in a high-speed mixer, and then cast onto an aluminum sheet and cured in an oven at 80°C overnight to convert excess NCO groups.

[0129] Preparation of rigid foam containing PIR

[0130] PIR-containing foams were prepared as shown in Table 1 and mixed manually on a laboratory scale in test bags with a square base area of ​​20 cm. The polyol component containing the polyols was first added along with the additives and catalyst. Shortly before mixing, the polyol component temperature was controlled at 23°C to 25°C, while the polyisocyanate component temperature was controlled at 30°C to 35°C. Subsequently, the polyisocyanate component was added to the polyol mixture, which had been previously mixed to achieve a density of approximately 38 kg / m². 3 The mixing time was 6 seconds and the mixing speed of the Pendraulik stirrer was 4200 min. -1 The foam was then stored at 20°C to 23°C for a further 24 hours to allow for post-reaction.

[0131] Table 1: Formulations of rigid PUR foams containing PIR

[0132] Desmophen 2382 [share] 63.8 Desmophen V657 [share] 5.0 PU additive 1132 [share] 2.2 Stabilizer 21AS08 [share] 4.0 Desmorapid 1792 [share] 5.0 n-pentane [share] 13.8 Desmodur 44V70L [share] 191.3 index [-] 350

[0133] Hydrolysis at atmospheric pressure

[0134] Example 1 (the present invention)

[0135] First, 7.5 g of model substance 1 and 2.0 g of potassium hydroxide in 7.5 g of dimethyl sulfoxide were added to a 50 mL two-necked round-bottom flask and heated to 140°C with stirring. 5 mL of water was added to the reaction mixture in 1.0 mL portions. The mixture was stirred after each addition of water until it reached the reaction temperature again. Subsequently, an additional 2.9 mL of water was added. Once 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 in vacuo, and then characterized by amine value.

[0136] Amine value = 520 mg KOH / g.

[0137] Example 2 (Comparative - Hydrolysis)

[0138] First, 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 added to a 50 ml two-necked round-bottom flask equipped with a thermometer and a powerful cooler. The contents of the flask were heated to 140°C. Water was gradually added. The water was added in small steps so that the temperature of the reaction mixture did not fall below 140°C. After 0.8 g of water, 4.2 g of powdered PIR foam (PS 436) was added. The foam dissolved after a while. A clear orange liquid formed at the bottom of the flask. An additional 4.8 g of water was gradually added. The mixture was then stirred for 2.4 hours. The total reaction time was 4 hours, and the reaction mixture was then added to 400 g of water. A dark brown, pasty solid precipitated from the aqueous phase and was isolated by decantation. The residue was washed with water and dried in vacuo. A titration of the amine value revealed only 475 mg KOH / g.

[0139] Pressure hydrolysis

[0140] Example 3 (present invention)

[0141] A 2.1 L autoclave was initially charged with 600 mL of demineralized water, 25 g of powdered PIR foam (prepared as described above), and 50 g of potassium hydroxide (KOH) pellets. The reactor contents were heated to 160°C for 5.5 hours and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase and was isolated by decantation. The residue was washed with water and dried under vacuum. Amine titration revealed a value of 510 mg KOH / g.

[0142] Example 4 (Comparative Example at Extremely Low Temperature)

[0143] 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 in vacuo. Due to insolubility, the amine value could not be determined.

[0144] Example 5 (present invention)

[0145] The experiment was carried out similarly to Example 3. However, the hydrolysis was carried out at 220°C for 1.5 h. A dark brown, pasty solid precipitated from the aqueous phase and was isolated by decantation. The residue was washed with water and dried in vacuo. Amine titration gave a value of 533 mg KOH / g.

[0146] Example 6 (present invention)

[0147] A 2.1 L autoclave was initially 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 hours and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase and was isolated by decantation. The residue was washed with water and dried in vacuo. Amine titration yielded a value of 510 mg KOH / g.

[0148] Example 7 (Comparative Example without Catalyst)

[0149] A 2.1 L autoclave was initially 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 hours and then cooled to room temperature. A brownish-yellow powder precipitated from the aqueous phase and was isolated by filtration. The residue was washed with water and dried under vacuum. Amine titration yielded a value of 295 mg KOH / g.

[0150] Example 8 (the present invention, extraction before hydrolysis)

[0151] 260 g of powdered PIR foam (prepared as described above) was heated under reflux in o-dichlorobenzene for 4 hours, then filtered, washed with acetone, and dried in a drying oven. 260 g of the extracted foam and 65 g of potassium carbonate were added to a 2.1 L autoclave along with 1500 mL of demineralized water. The reactor contents were heated to 220°C for 4.25 hours, then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase, which was dissolved 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 the pH adjusted to 10 with KOH tablets. The resulting precipitate was dissolved in chloroform. After solvent removal, a brown, pasty solid was obtained. Amine titration yielded a value of 515 mg KOH / g.

[0152] Example 9 (Comparative Example without Catalyst, Extraction Before Hydrolysis)

[0153] 25 g of powdered PIR foam (prepared as described above) was heated under reflux in o-dichlorobenzene for 4 hours, then filtered, washed with acetone, and dried in a drying oven. 25 g of the extracted PIR foam was first added to a 2.1 L autoclave along with 600 mL of demineralized water. The reactor contents were heated to 220°C for 5.5 hours, then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase, which was dissolved in chloroform and washed twice with water. The organic chloroform phase was washed with 10% aqueous HCl. The aqueous phase was washed with chloroform and the pH was adjusted to 10 with KOH tablets. The resulting precipitate was dissolved in chloroform. After solvent removal, a brown, pasty solid was obtained, which was dried under vacuum. Amine titration yielded a value of 260 mg KOH / g.

[0154] Table 2: Pressure hydrolysis of isocyanurate-containing PUR foams (prepared as described above)

[0155]

[0156] The results in Table 2 show that an incomplete reaction occurs at very low temperatures (Example 4). At a temperature of 220° C., a product with a particularly favorable amine number is obtained (Example 5). If the hydrolysis is carried out without a catalyst, an incomplete reaction also occurs, and even with relatively long reaction times and high temperatures, only products with low amine numbers are obtained (Examples 7 and 9).

[0157] Pressure hydrolysis at high temperature (250°C)

[0158] Compression of foam (Examples 10 and 11)

[0159] The foam was compressed in a heatable hydraulic press for 10 minutes at 160° C. The press used initially applied a force of 11 kN which decreased over time to 6 kN.

[0160] Example 10 (Comparative Example without Catalyst and Compressed Before Hydrolysis)

[0161] First, 180 mL of demineralized water and 7.5 g of compressed PIR foam (prepared as described above) were added to a 2.0 L autoclave purchased from Büchi AG. The reactor contents were heated to 250° C. for 1.5 hours and then cooled to room temperature. A dark brown pasty solid precipitated from the aqueous phase, which was dissolved in chloroform and washed twice with water. The organic chloroform phase was washed twice with 10% aqueous HCl. The aqueous phase was washed with chloroform and the pH was adjusted to 10 with KOH tablets. The resulting precipitate was dissolved in chloroform. After removing the solvent, a brown pasty solid was obtained, which was dried under vacuum. Amine titration gave a value of 278 mg KOH / g.

[0162] Example 11 (Present invention, compression before hydrolysis)

[0163] First, 180 mL of demineralized water, 7.5 g of compressed PIR foam (prepared as described above), and 1.88 g of potassium carbonate were added to a 2.0 L autoclave purchased from Büchi AG. The reactor contents were heated to 250°C for 1.5 hours and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase, which was dissolved in chloroform and washed twice with water. The organic chloroform phase was washed twice with 10% aqueous HCl. The aqueous phase was washed with chloroform and the pH was adjusted to 10 using KOH tablets. The resulting precipitate was dissolved in chloroform. After removing the solvent, a brown, pasty solid was obtained, which was dried under vacuum. Amine titration gave a value of 534 mg KOH / g.

[0164] Example 12 (present invention, not compressed before hydrolysis)

[0165] First, 180 mL of demineralized water, 7.5 g of powdered (uncompressed) PIR foam (prepared as described above), and 1.88 g of potassium carbonate were added to a 2.0 L autoclave purchased from Büchi AG. The reactor contents were heated to 250°C for 1.5 hours and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase, which was dissolved in chloroform and washed twice with water. The organic chloroform phase was washed twice with 10% aqueous HCl. The aqueous phase was washed with chloroform and the pH was adjusted to 10 using KOH tablets. The resulting precipitate was dissolved in chloroform. After removing the solvent, a brown, pasty solid was obtained, which was dried under vacuum. Amine titration gave a value of 508 mg KOH / g.

[0166] Table 3: Pressure hydrolysis of isocyanurate-containing PUR foams (prepared as described above) at elevated temperatures

[0167]

[0168] The reaction conditions in Example 10 correspond to those described in claim 1 of US Pat. No. 6,630,517 (temperature range 190° C. to 370° C., pressure range 30 to 300 bar). The foam was also compressed before hydrolysis (the examples of US Pat. No. 6,630,517 also include compression before hydrolysis). Example 10 demonstrates that the method described in US Pat. No. 6,630,517 yields poor results for isocyanurate-containing PUR foams.

Claims

1. A method for recovering raw materials from a polyurethane product containing isocyanurate, wherein The following steps are involved: (A) providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component; (B) in the absence of an organic solvent or in the presence of an organic solvent inert to urethane groups and isocyanurate groups, At a temperature of 130°C to 260°C and a pressure of 1.0 bar to 100 bar, In the presence of a catalyst, Chemically decomposing the isocyanurate-containing polyurethane product with liquid water to obtain a chemical decomposition product, as well as (C) post-processing the chemical decomposition products to obtain (I) an amine corresponding to the 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.

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

3. The method according to claim 2, wherein the organic solvent used for 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 above organic solvents.

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

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

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

7. The method according to any one of claims 1 to 6, wherein the catalyst comprises 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 above catalysts.

8. The process according to claim 7, wherein the catalyst is a hydroxide, carbonate, bicarbonate, phosphate, hydrogenphosphate, carboxylate or alkoxide of an alkali metal or alkaline earth metal.

9. The process according to any one of claims 1 to 8, wherein the chemical decomposition is carried out in the presence of an organic solvent which is inert toward urethane groups and isocyanurate groups.

10. The method according to claim 9, wherein in step (B), the polyurethane product is first added to an organic solvent inert to carbamate groups and isocyanurate groups, and water is gradually added.

11. The method according to claim 9 or 10, wherein the organic solvent inert to carbamate groups and isocyanurate groups comprises dimethyl sulfoxide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dichlorobenzene, trichlorobenzene, ethylmethylbenzene, mesitylene, decane, undecane and / or dodecane.

12. The process according to any one of claims 1 to 8, wherein the chemical decomposition is carried out in the absence of an organic solvent.

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

14. The method according to claim 12, wherein the chemical decomposition is carried out under autogenous pressure without pressure equalization.

15. The method according to any one of claims 1 to 14, wherein in step (C), the chemical decomposition product is cooled to precipitate a first solid organic phase, followed by liquid-solid phase separation to obtain a first aqueous phase and a first solid organic phase, and the first solid organic phase is further post-treated to obtain the amine.

16. The process according to claim 15, wherein the further post-treatment of the first solid organic phase comprises washing it with an aqueous washing liquid.

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

18. The process according to any one of claims 1 to 14, wherein in step (C), the chemical decomposition product is extracted with an organic solvent, followed by liquid-liquid phase separation to obtain a first aqueous phase and a first liquid organic phase, and the first liquid organic phase is further post-treated to obtain the amine.

19. A process according to claim 17 or 18, wherein the further work-up of the first liquid organic phase comprises washing it with an aqueous washing liquid.

20. The process according to any one of claims 17 to 19, wherein the optionally washed first liquid organic phase is extracted with an aqueous mineral acid, followed by phase separation to obtain a second liquid organic phase and a second aqueous phase, the second aqueous phase is then neutralized or alkalized to precipitate a second solid organic phase, and the second solid organic phase is then post-treated to obtain the amine.

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

22. The method according to claim 20 or 21, comprising step (C.II), wherein step (C.II) comprises working up the second liquid organic phase by separating the organic solvent by distillation to retain an alcoholic phase, which is subsequently purified by distillation or stripping.

23. The process according to any one of claims 15 to 22, comprising step (C.II), wherein step (C.II) comprises working up the first aqueous phase by separating off the water by distillation so as to retain an alcoholic phase, which is subsequently purified by distillation or stripping.

24. The method of any one of the preceding claims, wherein the isocyanate component comprises methylene diphenylene diisocyanate, Polymethylene polyphenylene polyisocyanate, or A mixture of methylene diphenylene 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 contains no other isocyanates.

27. The method of any one 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 foregoing polyols.

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

29. The method of claim 28, wherein the polyurethane foam is a rigid polyurethane foam.

30. The method of claim 29, wherein the rigid polyurethane foam is derived from building insulation.

31. The process according to any one of the preceding claims, wherein the chemical decomposition is carried out in a stirred tank reactor.

32. The process according to any one of the preceding claims, wherein the amine obtained in step (CI) is phosgenated in step (D) to give the corresponding isocyanate.

33. A method according to any one of the preceding claims, wherein the chemical decomposition is carried out at a temperature in the range of 130°C to 240°C.

34. The process according to any one of the preceding claims, wherein the catalyst is not or does not comprise the following compounds (i) to (ii): (i) quaternary ammonium salts containing an ammonium cation containing 6 or more carbon atoms, (ii) organic sulfonates containing 7 or more carbon atoms.

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