WO2025237923A1 - Process for recovering valuable substances from isocyanurate-containing polyurethane products - Google Patents

Abstract

The present invention relates to a process for recovering valuable substances from polyurethane products, comprising the steps of: (A) providing an isocyanurate-containing polyurethane product, the polyol component of which comprises polyester polyols and/or polyether ester polyols, comprising extraction of the isocyanurate-containing polyurethane product using an organic solvent that does not react with urethane groups and isocyanurate groups during the extraction; (B) mixing the polyurethane product with water, a basic catalyst and optionally an organic chemolysis reagent to obtain a reaction mixture, reacting the reaction mixture at a reaction temperature of 90°C to 220°C to obtain a chemolysis product; and (C) processing the chemolysis product to obtain (I) at least one amine and/or (II) at least one polyol and/or at least one reaction product of a polyol, wherein the type and amount of the basic catalyst are selected such that there is always a pH value of 12 or more in the reaction mixture during the reaction.

Description

METHOD FOR RECOVERING VALUE MATERIALS FROM ISOCYANURATE-

CONTAINING POLYURETHANE PRODUCTS

The present invention relates to a process for recovering valuable materials from polyurethane products comprising the steps (A) providing an isocyanurate-containing polyurethane product, the polyol component of which comprises polyester polyols and/or polyether ester polyols, comprising extracting the isocyanurate-containing polyurethane product with an organic solvent that does not react with urethane groups and isocyanurate groups during extraction, (B) mixing the polyurethane product with water, a basic catalyst and optionally an organic chemolysis reagent to obtain a reaction mixture, reacting the reaction mixture at a reaction temperature of 90 °C to 220 °C to obtain a chemolysis product and (C) working up the chemolysis product to obtain (I) at least one amine and/or (II) at least one polyol and/or at least one reaction product of a polyol, wherein the type and amount of the basic catalyst are selected such that the reaction mixture always has a pH of 12 or more during the reaction.

Polyurethane products find diverse applications in industry and 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 typically divided into rigid and flexible foams. Despite their differences, all these products share the basic polyurethane structure, which is formed by the polyaddition reaction of a polyhydric isocyanate and a polyol. For example, a polyurethane based on a diisocyanate O=C=N-R-N=C=O and a diol H-O-R'-O-H (where R and R' denote organic groups) can be described as follows:

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

Under certain conditions, the isocyanates react not only with the polyols, but also with themselves, forming isocyanurate structures:

This process produces an isocyanurate-containing polyurethane product. This is particularly relevant for polyurethane products based on the di- and polyisocyanates of the diphenylmethane series (methylenediphenylene diisocyanate and polymethylene-polyphenylene polyisocyanate, MDI).

Polyurethane products containing isocyanurates are mostly produced as foams and are used particularly in building insulation because they offer higher fire safety than polyurethane insulation materials without isocyanurates. In applications where flame retardancy is less important, such as in refrigerator insulation, polyurethane products without isocyanurates are common. As thermal insulation of buildings becomes increasingly important and even the highest-quality materials have a limited lifespan, the recycling of polyurethane products containing isocyanurates is also gaining in significance.

The technically simplest form of reuse is incineration, utilizing the released heat of combustion for other processes, such as industrial manufacturing. However, this method does not allow for closing the raw material cycles. Another type of reuse is so-called "physical recycling," in which polyurethane waste is mechanically shredded and used in the production 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 breaking down the polyurethane bonds (so-called "chemical recycling"). The raw materials recoverable through such chemolysis include polyols (in the example above, H-O-R'-O-H) and their reaction products formed during chemolysis, as well as amines (in the example above, H₂N-R-NH₂) obtained through hydrolytic cleavage of the urethane bond. Amines obtained in this way can be phosgenated again to isocyanates (in the example above to O=C=N-R-N=C=O) after processing.

Methods of chemical recycling and devices for carrying them out have already been frequently the subject of literature, especially patent literature.

For example, Japanese patent application JP 2004-115631 A describes an apparatus for decomposing foamed plastics. The foamed plastics are processed during the The material is kneaded as it passes through the apparatus at elevated temperature. Suitable decomposition reagents include amines, polyols, and water. In the case of water as the decomposition reagent (hydrolysis), alkali or alkaline earth metals or their compounds, amines, and the like are described as suitable catalysts. Polyurethane flexible or rigid foams, or foams containing isocyanurates, are specifically mentioned as foamed plastics that can be decomposed using the described apparatus. The application of the apparatus is demonstrated in the examples by the chemolysis of a polyurethane rigid foam from refrigerator insulation with mono- 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 foams containing isocyanurates 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 high mechanical stress. The application does not disclose whether and how amines can be isolated from the resulting chemolysis product.

DE 2443 387 describes a process for the continuous hydrolytic decomposition of plastic waste, in which waste consisting of hydrolyzable plastic material is fed into a screw conveyor together with water and, optionally, hydrolysis catalysts. In a reaction zone, the mixture of water and plastic waste is subjected to intensive mass and heat exchange for 2 to 100 minutes at a temperature of 100 to 300 °C and a pressure of 5 to 100 bar. The liquid-gas mixture produced during hydrolysis is continuously conveyed into a nozzle permanently connected to the screw conveyor. The gas exits the nozzle via a control valve, which maintains a constant screw conveyor pressure, and the liquid exits via a control valve, which maintains a constant liquid level within the nozzle. The process is demonstrated using the example of the decomposition of a soft, elastic polyurethane foam.

DE 29 02 509 Al describes a process for producing polyol-containing liquids from polyurethane and/or polyisocyanurate-containing foam waste by heating optionally crushed 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 residue with 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 at temperatures of 150 to approximately 220°C, wherein at least one compound of a metal of group IV of the periodic table of elements is used as the catalyst. EP 0 011 662 Al describes the hydrolysis of polyurethanes, in particular polyurethane flexible foams, with superheated steam in the presence of basic alkali or alkaline earth compounds.

EP 0 753 535 Al deals with a process for obtaining recycled polyols by glycolysis of polyisocyanurates. For this purpose, the polyisocyanurates are reacted with short-chain, hydroxyl-group-containing compounds in the presence of carrier polyols with an OH number of at most 500 mg KOH/g and a molar mass of at least 450 g/mol.

EP 0 976 719 Al (also published as US 6,630,517) describes an apparatus and a process for the hydrolysis of polyisocyanate derivatives, in which the polyisocyanate derivative to be hydrolyzed is reacted with liquid water at a temperature of 190 to 370 °C and a pressure of 30 to 300 bar. The hydrolysis is carried out without the use of a catalyst. EP 0976 719 Al (US 6,630,517) explicitly aims to eliminate the need for catalysts. Polyisocyanate derivatives are defined as compounds with 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 that are formed by the oligomerization of isocyanate-containing compounds and that are present in distillation residues from chemical plants used to produce the isocyanate-containing compounds. Examples of oligomeric compounds found in the waste streams of chemical plants producing isocyanate-containing compounds include dimers, trimers, and higher oligomers such as carbodiimide, uretidione, urethanimine, 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 toluene diisocyanate (TDI) production. The polyurethane foams are compressed at elevated temperatures prior to hydrolysis. Whether isocyanate-containing polyurethane products (to be distinguished from residue streams from isocyanate production), particularly PUR-PIR foams, can be hydrolyzed using this process is not addressed in EP 0 976 719 Al (US 6,630,517).

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 polyether polyol formed with a hydrocarbon. The examples describe the hydrolysis of TDI-based polyurethane foams.

CN 111 533 873 A describes a process for recycling polyurethane sieves. CN 113 429 540 A describes a process for the production of a polyurethane thermal insulation material by using a polyol alcohol lysis agent for the degradation of polyurethane waste.

WO 96/26236 Al describes a method for separating polymeric materials from a plastic part, in particular a motor vehicle part, which consists of thermoplastic polymers and at least one thermosetting polymer made of polyurethane foam.

WO 2022/042909 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 pKa 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 containing an ammonium cation comprising 6 to 30 carbon atoms and (ii) an organic sulfonate containing at least 7 carbon atoms is 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 the alkali and alkaline earth metals and an activating agent selected from quaternary ammonium salts with at least 15 carbon atoms or organic sulfonates with at least 7 carbon atoms has already been described in US 5,208,379.

WO 2022/042910 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 pKa value of less than 1 at 25 °C, and wherein a (phase-transfer) catalyst selected from the group consisting of (i) a quaternary ammonium salt containing an ammonium cation with 6 to 14 carbon atoms, provided the ammonium cation does not include a benzyl group, and (ii) a quaternary ammonium salt containing an ammonium cation with 6 to 12 carbon atoms, provided the ammonium cation includes a benzyl group. The hydrolysis yields polyether polyols and polyamines. The recycling of PIR-containing polyurethanes is not described.

WO 2024/104963 Al (also published as EP 4 372 036 Al) describes a process for the hydrolysis of a polyisocyanurate. The polyisocyanurate is produced by reacting a polyol selected from the group consisting of polyester polyols, mixtures of polyester polyols, and mixtures of polyester and polyether polyols with an excess of an isocyanate. The hydrolysis is carried out by contacting the polyisocyanurate with water in the presence of an organic amine base, whereby carboxylic acids, which are the same as the carboxylic acids used to produce the polyester polyols, are reacted. The reaction yields polyols corresponding to those used to produce polyester polyols, as well as amines corresponding to the isocyanate used to produce polyisocyanurate. During hydrolysis, the reaction mixture is a stirred homogeneous or heterogeneous mixture, preferably a solution, an emulsion, a dispersion, or a combination thereof.

WO 2024/104964 Al (also published as EP 4 372 024 Al) describes a process for the hydrolysis of a polyisocyanurate. The polyisocyanurate is produced by reacting a polyol selected from the group consisting of polyester polyols, mixtures of polyester polyols, and mixtures of polyester and polyether polyols with an excess of an isocyanate. The hydrolysis is carried out by contacting the polyisocyanurate with water in the presence of a base, yielding carboxylic acids and polyols corresponding to those used in the production of the polyester polyols, as well as amines corresponding to the isocyanate used in the production of the polyisocyanurate. The base used is selected from the group consisting of a base containing an alkali metal cation and/or an ammonium cation and having a pKβ value at 25°C of 1 to 10, preferably containing no primary, secondary and/or tertiary amino groups, and a strong inorganic base with a pKβ value at 25°C of less than 1.

In their article "Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis-Hydrolysis Demonstration" in Sustainability 2021, 13, 3583 (https://doi.org/10.3390/sul3063583), Pegah Zahedifar et al. discuss the recycling of polyurethanes through chemical depolymerization. They describe how glycolysis is beginning to gain traction in industry, with the primary goal of polyurethane glycolysis being the recovery of the polyols used. However, they note that there have been only limited attempts to date to recover the aromatic dicarbamate residues and derivatives from the isocyanates used. This article describes work on combined glycolysis and hydrolysis (hydrolysis of the carbamates formed in glycolysis after their separation from the polyols obtained by urethane hydrolysis; to be distinguished from hydroglycolysis, in which the reaction product of glycolysis is hydrolyzed without separation of carbamates and polyols). Amine production yields of approximately 30% were obtained for model systems.

WO 2023/275029 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 amine and/or phenolic antioxidants in a mass fraction of 0.001 to 10%. The recycled polyol is preferably combined with a Hydrolysis process as described in WO 2022/042909 Al or WO 2022/042910 Al.

WO 2023/275036 Al describes a process for the production 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 Al or WO 2022/042910 Al.

WO 2023/275038 Al 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 Al or WO 2022/042910 Al.

EP 1 149 862 A1 describes a process in which rigid polyurethane foam from a used refrigerator is pulverized, liquefied by glycolysis or aminolysis, and then treated with supercritical or non-supercritical water. The raw product obtained in this way is fractionated and used in the manufacture of new refrigerators.

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 include, 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 polyisocyanates (such as isocyanurates and carbodiimides).

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

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. In the introductory section, in addition to glycolysis, they also mention steam hydrolysis and pyrolysis, both of which are described as disadvantageous because, according to the authors, they result in complex product mixtures. They argue that separating the amines formed during hydrolysis is not practical, whereas glycolysis yields reusable polyol mixtures in a single-stage process. P.N. Gribkova et al. describe in Polymer Science USSR, 1980, 22, 299-304 the decomposition of polyisocyanurate obtained by polycyclotrimerization of 4,4'-methylenediphenyl diisocyanate (4,4'-mMDI) (i.e., containing no urethane groups). The investigated polyisocyanurate could be cleaved, among other methods, in saturated steam at high temperatures (decomposition begins at temperatures above approximately 300 °C) without a catalyst (i.e., purely thermally).

WO 2023/208946 describes the recycling of isocyanurate-containing polyurethane products, in particular the well-known polyurethane-polyisocyanurate rigid foams. The process is characterized by the reaction of the isocyanurate-containing polyurethane product 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, yielding a chemolysis product. Subsequently, the chemolysis product is 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. The process requires comparatively high temperatures (at least 130 °C).

WO 2023/083968 Al deals with the aminohydrolysis of polyurethane products, in particular rigid polyurethane foams.

M. Modesti et al. describe in "Valuable secondary raw material by chemical recycling of polyisocyanurate foams", published in Polymer Degradation and Stability 2018, 156, 151 - 160, a glycolysis of polyisocyanurate foams with dipropylene glycol in the presence of potassium acetate.

None of the aforementioned processes are entirely satisfactory for recovering valuable materials from polyurethane products. In particular, the known processes for recovering amines from isocyanurate-containing polyurethane products, insofar as they even attempt this goal and are not limited to the recovery of polyols, still have drawbacks. Such polyurethane products are mostly based on MDI and, at least partially, polyols with ester links (polyester polyols or polyether ester polyols). Recovering the MDA formed by hydrolytic cleavage presents challenges, including the formation of N-alkylated byproducts.

Therefore, there was a need for further improvements in the field of recovering valuable materials from polyurethane products containing isocyanurate. In particular, it would be desirable to produce amines with as few N-alkylated amines as possible. To recover by-products from polyurethane products so that, after purification, they can be phosgenated back into isocyanates.

Taking this need into account, the present invention relates to a method for recovering valuable materials from polyurethane products, comprising the following steps:

(A) Providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component, wherein the polyol component comprises a polyester polyol, a polyether ester polyol or a mixture thereof, comprising extraction of the isocyanurate-containing polyurethane product with an organic solvent which does not react with urethane groups and isocyanurate groups during extraction;

(B) Mixing the polyurethane product with water, a basic catalyst and optionally an organic chemolysis reagent to obtain a reaction mixture (the addition of the components of the reaction mixture need not necessarily be in this order),

Reaction (= chemolysis) of the reaction mixture at a reaction temperature of 90 °C to 220 °C, preferably 100 °C to 160 °C, particularly preferably 110 °C to 125 °C (whereby the temperature adjustment does not necessarily have to take place only after the addition of the last component of the reaction mixture) to obtain a chemolysis product containing

(i) (at least) an amine corresponding to an isocyanate of the isocyanate component and

(ii) (at least) one polyol of the polyol component and/or (at least) one reaction product of a polyol of the polyol component, wherein the type and amount of the basic catalyst are selected such that the reaction mixture always has a pH of 12 or more, preferably 13 or more, during the reaction (whereby compliance with this requirement is checked, if necessary, as described below, by measuring the pH while neglecting the influence of temperature); and

(C) Processing of the chemolysis product to obtain

(I) of (at least one) amine and/or (II) of (at least one) polyol and/or of (at least one) reaction product of a polyol.

Within the scope of the present invention, it was found that the chemolysis of isocyanurate-containing polyurethane products is particularly successful when the pH value during the reaction is consistently sufficiently high (at least 12, preferably at least 13). This allows the use of comparatively low temperatures and promotes the selective formation of the underlying amines while reducing undesired N-alkylation.

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

In the terminology of the present invention, the term isocyanates includes those isocyanates familiar to those skilled in the art in connection with polyurethane chemistry. The expression "one isocyanate" naturally also includes embodiments in which two or more different isocyanates (e.g., mixtures of different MDI types) are used in the manufacture of the isocyanate-containing polyurethane product, unless otherwise expressly stated, for example by the formulation "exactly one isocyanate". The entirety of all isocyanates used in the manufacture of the isocyanate-containing polyurethane product is referred to as the isocyanate component (of the isocyanate-containing polyurethane product). The isocyanate component comprises at least one isocyanate.

Similarly, the entirety of all polyols used in the manufacture 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 "one polyol" naturally also includes embodiments in which two or more different polyols were used in the manufacture of the isocyanurate-containing polyurethane product. Therefore, when, for example, "one polyether polyol" (or "one polyester polyol," etc.) is used below, this terminology naturally also includes embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) were used in the manufacture of the isocyanurate-containing polyurethane product. An amine corresponding to an isocyanate is that amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCI2 —> RN=C=O + 2 HCl.

According to the invention, the chemolysis takes place in the presence of a basic catalyst. This refers to a catalyst added within the framework 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 accompanying substances from the original production. Within the scope of the present invention, it is provided that one does not rely on such potentially present catalyst residues, but rather—in the interest of a reliable and reproducible reaction—a basic catalyst is added for carrying out step (B).

In a particularly preferred embodiment, the hydrolysis takes place in the presence of a catalyst which is not one of the following compounds (i) to (ii): (i) a guarantor 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 guarantor ammonium salts containing an ammonium cation comprising 6 or more carbon atoms (such as (a) guarantor ammonium salts containing an ammonium cation with 6 to 30 carbon atoms, (b) guarantor ammonium salts containing an ammonium cation with 6 to 14 carbon atoms, provided that the ammonium cation does not comprise a benzyl group, (c) guarantor ammonium salts containing an ammonium cation with 6 to 12 carbon atoms, provided that the ammonium cation comprises a benzyl group, (d) guarantor ammonium salts containing an ammonium cation with 15 to 30 carbon atoms) and organic sulfonates containing at least 7 carbon atoms is excluded for chemolysis, i.e., the chemolysis takes place in the absence of the aforementioned compounds. Organic sulfonates are understood to be the salts of organic sulfonic acids with the anion R-Sch", where "R" denotes an organic residue containing 7 or more carbon atoms.

According to the invention, the type and amount of the basic catalyst are selected such that the reaction mixture always maintains a pH of 12 or higher, preferably 13 or higher, during the reaction. With regard to the maximum pH value, the process according to the invention is not subject to any special limitations. The maximum pH value during the reaction is limited only by the dissociation capacity (i.e., the ability to dissolve in water, releasing hydroxide ions) of the basic catalyst used. Chemolysis therefore takes place at pH values in the range of 12 (preferably 13) up to the maximum pH value achievable due to the dissociation capacity of the basic catalyst used. For economic reasons, one will naturally strive to avoid unnecessarily high pH values. It is therefore preferable to maintain the pH value during the reaction process consistently between 12 and 14, and particularly between 13 and 14.

For a polyurethane product with a precisely known composition (e.g., offcuts from the manufacturing process), experts can predict which base-consuming reactions will occur and to what extent. Therefore, given a specific basic catalyst, the required amount can be calculated based on its basicity (pKa value). If this is not possible (for example, for a polyurethane product whose composition is unknown or only qualitatively known), compliance with the required pH value can be monitored by measurement, and additional basic catalyst can be added as needed. Such measurements can be taken during the reaction (in particular, by regular sampling at least hourly, preferably at least every half hour, and external analysis). However, the simplest method is to determine the required amount of basic catalyst in preliminary tests. For this purpose, in a preliminary test after completion of the reaction, the pH value of the aqueous phase that forms (resulting from the superstoichiometric addition of water) is measured ("first aqueous phase"; see below for details). If the pH value after the reaction is equal to or greater than 12, preferably 13, it must have been higher during the reaction, since base is consumed in the chemolysis (and thus the pH value decreases), so that the requirement of the invention is met in any case. The actual measurement of the pH value can be carried out using any method known in the art, as these usually provide a result that is sufficiently accurate for the purposes of the present invention. In case of doubt, the measurement of the pH value with a pH electrode at 25 °C is decisive (pH changes due to the increased temperature during the reaction are negligible for the purposes of the present invention). Since the solution to be measured is very strongly alkaline and this can affect the measurement accuracy of the pH electrode, the pH value is reduced to about 10 before the measurement. This is done by adding a defined volume of hydrochloric acid of a defined concentration to a defined volume of the aqueous phase. The pH value present after the addition of hydrochloric acid is then measured precisely with the pH electrode, and the pH value before the addition of hydrochloric acid is calculated from the result.

The following is a brief summary of various possible embodiments of the invention:

In a first embodiment of the invention, which can be combined with all other embodiments, the implementation in step (B) is carried out in a pressure range of Ambient pressure (especially 1.0 bar) up to 100 bar (preferably 1.0 bar to 5.0 bar, particularly preferably 1.0 bar to 1.5 bar, most preferably 1.0 bar to 1.2 bar or preferably > 5.0 bar to 100 bar, particularly preferably 10 bar to 80 bar) is carried out (all pressure values refer to absolute pressures in the gas space above the reaction mixture).

In a second embodiment of the invention, which can be combined with all other embodiments, the organic solvent used in the extraction comprises an aromatic hydrocarbon (in particular toluene), a halogenated aromatic (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 (and is in particular such an organic solvent, i.e. in particular no other solvents are present besides those mentioned).

In a third embodiment of the invention, which can be combined with all other embodiments, the extraction is carried out at a temperature in the range of ambient temperature (especially 20 °C) to 180 °C, preferably in the range of 50 °C to 180 °C, and particularly preferably at ambient pressure (especially 1.0 bar) and the boiling point of the organic solvent.

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

In a fifth embodiment of the invention, which can be combined with all other embodiments, the basic catalyst comprises a hydroxide, a carbonate, a hydrogen carbonate, a phosphate, a hydrogen phosphate, a carboxylate, an acetate, an alcoholate, ammonia, in particular in the form of ammonia gas, a metal oxide or a mixture of two or more of the aforementioned basic catalysts (and is in particular such a basic catalyst, i.e. in particular no further basic catalysts are present other than those mentioned).

In a sixth embodiment of the invention, which is a particular embodiment of the fifth embodiment, the basic catalyst comprises an alkali or alkaline earth metal salt of a hydroxide, a carbonate, a hydrogen carbonate, a phosphate, a hydrogen phosphate, a carboxylate, an acetate or an alcoholate (and is in particular such a basic catalyst, i.e. in particular no further basic catalysts are present other than those mentioned).

In a seventh embodiment of the invention, which can be combined with all other embodiments, provided that these are not limited to pure hydrolysis, The conversion in step (B) is carried out in the presence of the organic chemoyl reagent.

In an eighth embodiment of the invention, which is a particular embodiment of the seventh embodiment, the organic chemolysis reagent is selected from an alcohol, a primary or secondary amine, or a mixture of two or more of the aforementioned organic chemolysis reagents.

In a ninth embodiment of the invention, which is a particular embodiment of the seventh and eighth embodiments, the polyurethane product is placed in the organic chemolysis reagent in step (B), and water is added stepwise at the reaction temperature such that the reaction temperature decreases by a maximum of 15 °C, preferably by a maximum of 10 °C.

In a tenth embodiment of the invention, which can be combined with all other embodiments, provided that these are not limited to chemolysis using organic chemolysis reagents, the reaction in step (B) is carried out in the absence of an organic chemolysis reagent.

In an eleventh embodiment of the invention, which can be combined with all other embodiments, provided that these do not exclude the precipitation of a first solid organic (amine) phase from the chemolysis product, 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.

In a twelfth embodiment of the invention, which is a special embodiment of the eleventh embodiment, any organic chemoyl reagent used is distilled off before the liquid-solid phase separation.

In a thirteenth embodiment of the invention, which is a special embodiment of the eleventh and twelfth embodiments, the first solid organic (amine) phase is processed to obtain the amine.

In a fourteenth embodiment of the invention, which is a particular embodiment of the thirteenth embodiment, the processing of the first solid organic (amine) phase comprises washing the same with an aqueous washing liquid.

In a fifteenth embodiment of the invention, which is a particular embodiment of the thirteenth and fourteenth embodiments, the first solid organic (amine) phase, optionally washed, is dissolved in an organic solvent, yielding a first liquid organic (amine) phase. In a sixteenth embodiment of the invention, which can be combined with all other embodiments, provided that these do not exclude an organic extraction of the chemolysis product, the chemolysis product is extracted in step (C), optionally after distilling off any organic chemolysis reagent used, with an organic solvent, followed by a liquid-liquid phase separation into a first aqueous phase and a first liquid organic (amine) phase.

In a seventeenth embodiment of the invention, which is a special embodiment of the fifteenth and sixteenth embodiments, the first liquid organic (amine) phase is processed to obtain the (at least one) amine.

In an eighteenth embodiment of the invention, which is a particular embodiment of the seventeenth embodiment, the processing of the first liquid organic (amine) phase comprises washing the same with an aqueous washing liquid.

In a nineteenth embodiment of the invention, which is a particular embodiment of the seventeenth and eighteenth embodiments, the first liquid organic (amine) phase, optionally washed, 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 by precipitation of a second solid organic (amine) phase, followed by work-up of the second solid organic (amine) phase to obtain the amine.

In a twentieth embodiment of the invention, which is a particular embodiment of the nineteenth embodiment, the second solid organic (amine) phase is separated by a liquid-solid phase separation or absorbed in an organic solvent and obtained after separation by a liquid-liquid phase separation and evaporation of the organic solvent.

In a twenty-first embodiment of the invention, which is a particular embodiment of the nineteenth and twentieth embodiments, step (C. II) is included, wherein step (C. II) comprises a work-up of the second liquid organic phase by distillative separation of organic solvent while leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

In a twenty-second embodiment of the invention, which is a particular embodiment of the eleventh to twenty-first embodiments, step (C. II) is included, wherein step (C. II) is a work-up of the first aqueous phase by means of includes the distillative separation of water while leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping.

In a twenty-third embodiment of 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. Preferably, the isocyanate component does not include toluene diisocyanate in addition to these, and particularly preferably, no other isocyanates at all.

In a twenty-fourth embodiment of the invention, which can be combined with all other embodiments, the polyol component additionally comprises a polyether polyol.

In a twenty-fifth embodiment of the invention, which can be combined with all other embodiments, the polyurethane product provided in step (A) is a polyurethane foam, in particular a rigid polyurethane foam, preferably originating from building insulation.

In a twenty-sixth embodiment of the invention, which can be combined with all other embodiments, the conversion in step (B) is carried out in a stirred tank reactor.

In a twenty-seventh embodiment of the invention, which can be combined with all other embodiments, step (C.1) is included, and the obtained (at least one) amine is phosgenated to the corresponding isocyanate in a step (D).

In a twenty-eighth embodiment of the invention, which is a particular embodiment of the twenty-seventh embodiment, the isocyanate, optionally in mixture with (at least) an isocyanate of other origin (in particular from a new production), is reacted with a polyol to form a polyurethane.

In a twenty-ninth embodiment of the invention, which can be combined with all other embodiments, in the implementation of step (B) compounds are selected from the group consisting of

(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 not used. The embodiments and further possible configurations of the invention briefly described above are explained in more detail below. Unless the context clearly indicates otherwise to a person skilled in the art, or unless expressly stated otherwise, all previously described embodiments and the further configurations of the invention can be combined with one another as desired.

PREPARATION FOR CHEMICAL RECYCLING

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 in whose infrared spectra in the spectral range of 1650 ^cm⁻¹ to 1800 ^cm⁻¹ (range of the C=O stretching vibration) the signal maximum lies at a wavenumber of 1712 ^cm⁻¹ or less.

This can, in principle, be any type of polyurethane product containing isocyanurate. 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 has been foamed into a cellular structure with low raw material density and low thermal conductivity. It is generally closed-cell and exhibits the following properties:

Under compressive stress, the foam exhibits a relatively high resistance to deformation. Its thermosetting nature is evident in the fact that the foam is not meltable, has a high softening point, and offers good resistance to chemicals and solvents. Polyurethane rigid foams according to the present invention exhibit a compressive stress at 10% compression (do) of 10 kPa or more, as measured according to DIN EN 826:2013-05.

Furthermore, polyurethane products are preferred which, with respect to the isocyanate component, are based on an isocyanate comprising methylenediphenylene diisocyanate (“monomeric MDI”; mMDI), polymethylenepolyphenylene polyisocyanate (“polymeric MDI”; pMDI), or 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], polymethylenepolyphenylene polyamine (“polymeric MDA”; pMDA)), or a mixture of methylenediphenylenediamine and polymethylenepolyphenylene polyamine [hereinafter collectively referred to as MDA]). Preferably, the isocyanate component comprises MDI, i.e., a mixture of mMDI and pMDI. In one embodiment of the invention, The isocyanate component of the process does not include toluene diisocyanate and, in particular, does not include any isocyanate other than MDI.

With regard to the polyol component, the polyurethane product is based on a polyol selected from at least polyester polyols, polyether ester polyols, or a mixture thereof. In one embodiment, the polyol component contains, in addition to polyester polyols and/or polyether ester polyols, also polyether polyols. Preferably, the polyol component contains no other polyols besides those mentioned above.

The process according to the invention can be applied both to the recycling of used (so-called £nd-o/-£//e-) polyurethane products and to that of polyurethane waste from polyurethane production. In the latter case, the chemical nature of the isocyanate component used in the production and that of the polyol component are, of course, known. In the case of the reuse of a used polyurethane product, suitable sorting can ensure that the nature of the polyurethane product is at least qualitatively known. If the original application of a used polyurethane product to be recycled is known, it will regularly be known, for example, whether it is an MDI- or TDI-based polyurethane product and what type of polyols are to be expected. In case of doubt, the underlying isocyanates and polyols can be identified analytically.

For this purpose, the polyurethane product to be analyzed is examined for functional groups using ATR infrared spectroscopy (ATR = attenuated total reflection). The infrared spectrum (IR spectrum) provides a qualitative composition of the polyurethane product. This allows determination of whether the polyurethane product is based on polyether and/or polyester polyols. The IR spectrum also indicates whether the polyurethane product is partially or completely MDI-based, as such polyurethane products can be identified by characteristic bands at 1410 ^cm⁻¹ , 1010 ^cm⁻¹ , and 510 ^cm⁻¹ .

Preferably, step (A) comprises preparatory steps for the cleavage of the urethane bonds and, optionally, isocyanurate bonds in step (B). This particularly involves the mechanical comminution of the isocyanurate-containing polyurethane products. Such preparatory steps are known in the field.

In particular, polyurethane products containing isocyanurate, especially those used in building insulation, regularly contain additives, particularly flame retardants, but also stabilizers and activators. It has proven effective to remove these in an extraction step before starting the chemical recycling process in step (B). For this purpose, the isocyanurate-containing polyurethane foam, preferably already shredded, is treated with a The extract is obtained using an organic solvent that does not react with urethane groups (or isocyanurate groups) during extraction. This is ensured either by using a solvent that is (in principle) chemically inert towards urethane and isocyanurate groups (preferred), or by selecting a temperature and/or extraction time so low that no significant chemical reaction occurs. Suitable organic solvents include aromatic hydrocarbons (especially toluene), halogenated aromatics (especially monochlorobenzene or [preferably: ortho-]dichlorobenzene, where dichlorobenzene, preferably used as an ortho-isomer, is 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. Halogenated aromatics are preferred. Suitable extraction temperatures range, for example, from ambient temperature (room temperature, particularly 20 °C) to 180 °C, preferably 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, especially with one of the aforementioned organic solvents (the same solvent used for extraction may, but need not, be used). Any remaining solvent is preferably removed by drying before carrying out step (B).

Chemical cleavage of urethane bonds and, if applicable, isocyanurate bonds

Step (B) comprises the chemolysis of the isocyanurate-containing polyurethane product with water and optionally an organic chemolysis reagent. According to the invention, this chemolysis is carried out at a temperature in the range of 90 °C to 220 °C, preferably 100 °C to 160 °C, and particularly preferably 110 °C to 125 °C. The (absolute) pressure is preferably in the range of ambient pressure (in particular 1.0 bar) to 100 bar, more preferably 1.0 bar to 5.0 bar, wherein the pressure values refer to the gas space above the reacting mixture. At reaction temperatures of up to 125 °C, regardless of whether the chemolysis is carried out as pure hydrolysis or in the presence of an organic chemolysis reagent, it is preferred to carry out the reaction at 1.0 bar to 5.0 bar, more preferably 1.0 bar to 1.5 bar, more preferably 1.0 bar to 1.2 bar, and particularly at ambient pressure. Loss of water and/or organic chemolysis reagent due to evaporation is replenished, if necessary, by condensation. The evaporated components and their return to the reaction mixture ("reflux") were counteracted.

Suitable basic catalysts include hydroxides, carbonates, hydrogen carbonates, phosphates, hydrogen phosphates, carboxylates, alcoholates, ammonia, especially in the form of ammonia gas (which can be easily added during the reaction if necessary), and metal oxides. While not preferred, mixtures of different basic catalysts can be used. Alkali or alkaline earth metal salts are preferred as basic catalysts.

As already mentioned, it is possible to carry out chemolysis in the presence of an organic chemolysis reagent. Alcohols (hydroalcohollysis, for example with glycols (= hydroglycolysis; a special case of hydroalcohollysis) such as diethylene glycol, Ci-C4 monoalcohols such as methanol, or branched monoalcohols such as isopropanol), primary or secondary amines (also in the form of amino alcohols; aminohydrolysis, for example with ethanolamine, N-methylethanolamine, or 1,2-ethylenediamine), and mixtures thereof have proven particularly suitable. When using an organic chemolysis reagent with a sufficiently high boiling point, it is possible to pretreat (dissolve or suspend) the isocyanurate-containing polyurethane product to be cleaved in the organic chemolysis reagent, heat the reaction mixture to the reaction temperature, and then gradually add the water in such a way that the temperature does not drop too much, in particular not by more than 15.0 °C, preferably not by more than 10 °C. In this case, the reaction is usually carried out at low pressures of preferably 1.0 bar to 5.0 bar, more preferably 1.0 bar to 1.5 bar, more preferably 1.0 bar to 1.2 bar, and particularly at ambient pressure.

However, it is also possible to carry out the reaction without an organic chemolysis reagent. This simplifies the work-up. The reaction is then carried out either at comparatively low temperatures, particularly up to 125 °C, and at comparatively low pressures (particularly 1.0 bar to 5.0 bar, preferably 1.0 bar to 1.5 bar, and most preferably 1.0 bar to 1.2 bar), or 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 (absolute pressures in the gas space above the reacting mixture). Of course, carrying out the reaction in a pressure-resistant reactor is not limited to pure hydrolysis; hydroalcohollysis and aminohydrolysis can also be performed in such a reactor.

Regarding the equipment that can be used, all reactor types commonly used in the field are generally suitable. Stirred tank reactors are preferred. PROCESSING OF THE CHEMOLOGY PRODUCT

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

After hydrolysis, the chemolysis product is first cooled (by active cooling or by allowing it to cool), whereby a first solid organic (amine) phase precipitates. If an organic chemolysis reagent is used, it can be advantageous to distill off unreacted portions of it to promote the precipitation of the amine phase. In the context of the present invention, the term "solid phase" is not limited to "crystalline solids." Often, pasty, "dough-like" phases will be formed, which in the terminology used here are subsumed under the general term "solid phase." The first solid organic (amine) phase is separated from the chemolysis product by a liquid-solid phase separation (in particular, filtration), leaving a first aqueous phase. The resulting first solid organic phase is further processed to obtain the amine.

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

As an alternative to liquid-solid phase separation of the chemolysis product, it is also possible to extract the entire chemolysis product with an organic solvent, followed by liquid-liquid phase separation into a first aqueous phase and a first liquid organic (amine) phase. Any organic chemolysis reagent used can be distilled off before extraction. Suitable organic solvents for this purpose include halogenated aliphatic hydrocarbons (such as dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as monochlorobenzene and (preferably) ortho-)dichlorobenzene), cycloaliphatic alcohols (such as cyclohexanol), and aromatic ethers (such as anisole). Regardless of how exactly the first liquid organic phase was obtained, it is further processed to obtain the amine. This further processing preferably begins with washing with an aqueous washing liquid.

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

It is preferred to first separate the second solid organic phase by liquid-solid phase separation (especially filtration). Particularly if the nature of this solid phase makes liquid-solid phase separation difficult, it can also be directly dissolved in an organic solvent and separated from the aqueous components by liquid-liquid phase separation. Suitable organic solvents for this purpose include halogenated aliphatic hydrocarbons (such as dichloromethane and chloroform), halogenated aromatic hydrocarbons (such as monochlorobenzene and (preferably) ortho-)dichlorobenzene), cycloaliphatic alcohols (such as cyclohexanol), and aromatic ethers (such as 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.

The amine obtained in step (C. II) can be subjected to phosgenation to yield the corresponding isocyanate. Such phosgenation can be carried out according to a process known from the prior art (step (D)). For example, such a process is described in WO 2017/055311 Al (see in particular page 15, line 10 to page 19, line 17). Isocyanates obtained in this way can advantageously be reacted with polyols to form polyurethanes, optionally in combination with isocyanates of other origin (especially from a new production).

Naturally, the polyol component of the isocyanurate-containing polyurethane product also represents a valuable material that should preferably be recycled as much as possible. The type of recovered material 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) undergo hydrolytic degradation in step (B). Cleavages. The resulting low-molecular-weight or oligomeric reaction products are also valuable substances that can be used in the production of new polyols. The process according to the invention offers the advantage that, due to the high pH value during chemolysis, the cleavage of the ester bonds proceeds predominantly or completely down to the monomeric building blocks, and the formation of difficult-to-handle oligomeric cleavage products is largely or completely avoided.

Polyols and/or their reaction products can be obtained by processing the first aqueous phase. The previously mentioned second liquid organic phase may also contain them in substantial proportions.

The work-up of the first aqueous phase to obtain the polyols and/or their reaction products preferably comprises the distillative removal of water, leaving an alcohol phase, followed by purification of the alcohol phase by distillation or stripping. The work-up of the second liquid organic phase to obtain the polyols and/or their reaction products preferably comprises the distillative removal of organic solvent, leaving an alcohol phase, followed again by purification of the alcohol phase by distillation or stripping.

Concepts and methods

Key figure: Denotes the molar ratio of NCO- to nCO- multiplied by 100.

NCO-reactive groups of a formulation.

Amine count: The amine count was determined according to the EN standard.

ISO 9702 (August 1998). pH value: The pH values were determined after the reaction in the aqueous phase obtained after filtration at room temperature. pH paper with a pH scale from 1 to 14 (maximum error ±1) was used for this purpose.

N-Alkylation: The percentage of N-alkylation was determined by NMR using a Bruker Ascend 400 NMR spectrometer at 400 MHz. The sample was dissolved in deuterated DMSO. 100 mg of pyrazine was weighed into 1 mL of the resulting solution as an internal standard for quantification. T 1H and T 1 H,13C-HMBC spectra of the sample were recorded. The integrals of the sample signals were compared to the integrals of the standard, and the amount of N-alkylation was calculated from the sample weight.

chemicals

Desmodur 44V70L from Covestro Deutschland AG, a mixture of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate (MDI) with an NCO content of 30 to 32 wt%.

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

Desmophen V657 from Covestro Deutschland AG, a 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.

Additive 1132 from Covestro Deutschland AG, a reaction product of phthalic anhydride and diethylene glycol with an acid number of 89 mg KOH/g. Stabilizer 21AS08 silicone polyether copolymer with an OH number of 12 mg KOH/g from Covestro Deutschland AG.

Desmorapid 1792 potassium acetate, 25 wt% in diethylene glycol (DEG). n-Pentane from Sigma Aldrich.

Diethylene glycol from Brenntag GmbH.

Potassium hydroxide from Sigma Aldrich.

Sodium hydroxide from Sigma Aldrich.

Potassium carbonate from Sigma Aldrich.

Ethanolamine from Sigma Aldrich.

TBAHS* from Sigma Aldrich.

Tetra-butyl ammonium hydrogen sulfate

Production of a PIR-containing rigid foam

The PIR-containing foam was produced on a laboratory scale by hand mixing in test packets with a square base and sides of 20 cm, according to the formula specified in Table 1. The polyol component, containing the polyols, was prepared together with the additives and catalysts. Shortly before mixing, the polyol component was heated to 23–25 °C, while the isocyanate component was heated to 30–35 °C. The isocyanate component was then added to the polyol mixture while stirring. The amount of n- ^pentane required to achieve a core density of approximately 38 kg/m³ had been weighed out beforehand. The mixing time was 6 seconds, and the mixing speed of the stirrer (of the "pendraulik" type) was 4200 ^min⁻¹ . The foam was then stored for a further 24 hours at 20–23 °C to allow for post-reaction.

Table 1: Formulation of the PIR-containing PUR rigid foam

Extraction prior to hydrolysis

260 g of a powdered PIR foam (prepared as described above) were heated under reflux in ortho-dichlorobenzene for 4 h, then filtered, washed with acetone and dried.

Preparation for hydrolysis experiments

A dark brown, pasty solid precipitated from the aqueous phase and was dissolved in chloroform. The chloroform solution was washed twice with water. The organic chloroform phase obtained after phase separation was washed with 10% aqueous hydrochloric acid until the aqueous phase reached a pH of 2. The aqueous phase was then washed with chloroform and, after phase separation, adjusted to a pH of 10 using KOH plates. After evaporation of the water, a brownish, pasty solid was obtained. The product was analyzed by amine number titration and ^¹H NMR.

Preparation for hydroalcoholesis experiments

The reaction mixture was dissolved in water and the pH was measured. A dark brown, pasty solid precipitated from the aqueous phase and was separated by decantation. The same work-up procedure as described for the hydrolysis was then carried out. The product (also a brownish, pasty solid) was analyzed by amine number titration and ^¹H NMR. Preparation for amino hydrolysis experiments

The excess ethanolamine was distilled off after the reaction (no further CO₂ formation). The residue was dissolved in chloroform and washed with water. The organic chloroform phase was washed with 10% aqueous hydrochloric acid until the aqueous phase obtained after phase separation had a pH of 2. The aqueous phase was then washed with chloroform. The organic chloroform phase obtained after phase separation was processed as described for hydrolysis, yielding a brownish, pasty solid. The product was analyzed by amine number titration and ^¹H NMR.

Examples 1 to 8: Hydrolysis

Example 1 (comparative example with too low a concentration of KOH)

In a 2.1 L pressure autoclave, 600 mL of demineralized water, 20 g of powdered PIR foam (prepared as described above), and 50 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 120 °C for 15 h and then cooled to room temperature. A beige solid precipitated from the aqueous phase and was separated by decantation. The residue was washed with water and dried under vacuum. An amine number could not be determined due to insolubility.

Example 2 (comparative example at a higher temperature and lower concentration of KOH than in Example 1)

In a 2.1 L pressure autoclave, 600 mL of demineralized water, 20 g of powdered and extracted PIR foam (prepared as described above), and 10 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 160 °C for 15 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 6.5) and was separated by decantation. The residue was washed with water and dried under vacuum. The amine titration yielded a value of 430 mg KOH/g.

Example 3 (comparative example with too low a concentration of KOH)

In a 2.1 L pressure autoclave, 600 mL of demineralized water, 20 g of powdered and extracted PIR foam (prepared as described above), and 40 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 160 °C for 15 h. The solution was heated and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase (pH 6.5) and was separated by decantation. The residue was washed with water and dried under vacuum. The amine number titration yielded a value of 495 mg KOH/g.

Example 4 (Comparative example with too low a concentration of KOH, addition of phase transfer catalyst)

In a 2.1 L pressure autoclave, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), 5 g of potassium hydroxide (KOH) platelets, and 0.5 g of tetrabutylammonium hydrogen sulfate (TBAHS) were placed. The reactor contents were heated to 150 °C for 7 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 6.5) and was separated by decantation. The residue was extracted as described above and dried under vacuum. The amine number titration yielded a value of 330 mg KOH/g.

Example 5 (according to the invention, 160 °C, concentration of KOH sufficiently high)

In a 2.1 L pressure autoclave, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), and 234 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 160 °C for 6 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yielded a value of 525 mg KOH/g, and NMR spectroscopy revealed an N-alkylation of 4.6%.

Example 6 (according to the invention, 140 °C, concentration of KOH sufficiently high)

In a 2.1 L pressure autoclave, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), and 234 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 140 °C for 6 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yielded a value of 510 mg KOH/g, and NMR spectroscopy revealed an N-alkylation of 4.5%. Example 7 (according to the invention, 110 °C, concentration of KOH sufficiently high)

In a 1000 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), and 234 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 110 °C under nitrogen clouding for 7.5 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yielded a value of 515 mg KOH/g, and NMR spectroscopy revealed an N-alkylation of 3.5%.

Example 8 (according to the invention, 100 °C, concentration of KOH sufficiently high)

In a 1000 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), and 234 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 100 °C under nitrogen clouding for 7.5 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yielded a value of 510 mg KOH/g, and NMR spectroscopy revealed an N-alkylation of 2.7%.

Table 2: Hydrolysis of isocyanurate-containing PUR foams (produced as described above)

(V) Comparative example n.b. not determined [a] 2% TBAHS added

[b] 100 • m(KOH)/m(PUR rigid foam)

[c] absolute pressure in the gas space above the reaction mixture

[d] Theoretically maximum achievable amine number: 566 mg KOH/g

[e] Mass % based on the total mass of the dried solid

The results in Table 2 show that with small amounts of KOH, even at temperatures up to 160 °C, only incomplete conversion occurs (Examples 1, 2, and 3). Example 4 shows that the addition of a phase-transfer catalyst does not lead to improved conversion. Only the addition of KOH to the foam in such a quantity that a very high pH value is present after the reaction is complete leads to more complete hydrolysis, even at low temperatures (Examples 5 to 8). The lower the temperature, the fewer N-alkylated byproducts are found. Examples 9 to 11: Hydroalcohollysis

Example 9 (comparison, 140 °C, insufficient concentration of KOH)

In a 50 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 3.3 g of powdered and extracted PIR foam (prepared as described above), 15.0 g of diethylene glycol, and 1.92 g of potassium hydroxide were placed. The contents of the flask were heated to 140 °C. Water was added gradually, in small increments to ensure the temperature of the reaction mixture did not fall below 140 °C. After adding 0.8 g of water, another 4.2 g of powdered PIR foam was added. The foam dissolved within moments, yielding a clear, orange liquid in 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 then dissolved in 400 g of water. A dark brown, pasty solid separated from the aqueous phase (pH 7) and was separated by decantation. The residue was extracted as described above and dried under vacuum. The amine number titration yielded a value of only 475 mg KOH/g.

Example 10 (according to the invention, 125 °C, sufficiently high concentration of NaOH)

In a 1000 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 200 mL of demineralized water, 25 g of powdered and extracted PIR foam (prepared as described above), 30 g of diethylene glycol, and 1132 g of sodium hydroxide (NaOH) platelets were placed. The reactor contents were heated to 125 °C for 11.5 h and then cooled to room temperature. A dark brown, pasty solid precipitated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yielded a value of 515 mg KOH/g, and NMR spectroscopy revealed an N-alkylation of 3.5%.

Example 11 (according to the invention, 110 °C, sufficiently high concentration of KOH)

In a 1000 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 200 mL of demineralized water, 574 g of diethylene glycol, 50 g of powdered and extracted PIR foam (prepared as described above), and 237 g of potassium hydroxide (KOH) platelets were placed. The reactor contents were heated to 110 °C for 5.5 h and then cooled to room temperature. A dark brown, pasty solid separated from the aqueous phase (pH 14) and was separated by decantation. The residue was extracted as described above and dried under vacuum. Amine number titration yields a value of 510 mg KOH/g, and NMR revealed an N-alkylation of 1.6%.

Table 3: Hydroalcohollysis of isocyanurate-containing PUR foams (produced as described above)

(V) Comparative example n.b. not determined

[a] 100 • m(MOH)/m(PUR rigid foam); M = K or Na

[c] absolute pressure in the gas space above the reaction mixture [d] theoretically maximum achievable amine number: 566 mg KOH/g

[e] Mass % based on the total mass of the dried solid

The results in Table 3 show that even at 140 °C, with an insufficient amount of KOH, only incomplete conversion occurs (Example 9). Example 10 shows that adding sufficient NaOH to maintain a very high pH leads to a significantly improved conversion. Adding sufficient KOH to maintain a very high pH at lower temperatures (110 °C) results in even fewer N-alkylated byproducts (Example 11). Examples 12 to 14: Aminohydrolysis

Example 12 (comparison, 150 °C, too low base concentration)

In a 500 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 150 g of powdered and extracted PIR foam (prepared as described above), 150 g of ethanolamine, and 15 g of sodium carbonate were placed. The contents of the flask were heated to 150 °C. Two hours after the foam had dissolved, water was added gradually. The water was added in small increments so that the temperature of the reaction mixture did not fall below 150 °C. After another 4.5 hours, 60 g of sodium carbonate were added. After a further 4.5 hours, the excess ethanolamine was distilled off. The pH of the aqueous phase was 7, and the mixture was extracted as described above and dried under vacuum. The amine number titration yielded a value of 480 mg KOH/g.

Example 13 (according to the invention, 150 °C, sufficiently high concentration of KOH)

In a 500 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 50 g of powdered and extracted PIR foam (prepared as described above), 150 g of ethanolamine, and 75 g of KOH were placed. The contents of the flask were heated to 150 °C. Two hours after the foam had dissolved, water was added gradually. The water was added in small increments so that the temperature of the reaction mixture did not fall below 150 °C. After the initial addition of water, the experiment continued for another 5 hours. The total reaction time was 7.5 hours. The excess ethanolamine was distilled off. The pH of the aqueous phase was 14, and the mixture was extracted as described above and dried under vacuum. The amine number titration yielded a value of 505 mg KOH/g.

Example 14 (according to the invention, 110 °C, sufficiently high concentration of KOH)

In a 500 mL two-necked round-bottom flask equipped with a thermometer and intensive condenser, 50 g of powdered and extracted PIR foam (prepared as described above), 150 g of ethanolamine, and 75 g of KOH were placed. The contents of the flask were heated to 150 °C. Two hours after the foam had dissolved, water was added gradually. The water was added in small increments so that the temperature of the reaction mixture did not fall below 150 °C. After the initial addition of water, the experiment continued for another five hours. The total reaction time was 7.5 hours. The excess ethanolamine was distilled off. The pH of the aqueous phase was 14, and the mixture was extracted as described above and dried under vacuum. The amine number titration yielded a value of 525 mg KOH/g. Table 4: Aminohydrolysis of isocyanurate-containing PUR foams (produced as described above)

(V) Comparative example

_[ a] 100 • m(base)/m(PUR rigid foam); Base = KOH or _Na₂CO₃ [c] absolute pressure in the gas space above the reaction mixture

[d] Theoretically maximum achievable amine number: 566 mg KOH/g

The results in Table 4 show that incomplete conversion occurs when the amount of base is too low (Example 12). Example 13 shows that adding sufficient KOH to maintain a very high pH leads to a significantly improved conversion. This allows for a lower temperature, which in turn leads to an increased number of amines and thus an increased yield of MDA (Example 14). Example 13 shows that adding KOH in sufficient quantity to maintain a very high pH leads to a significantly improved conversion. This allows for a lower temperature, which in turn leads to an increased number of amines and thus an increased yield of MDA.

Claims

1. Process for recovering valuable materials from polyurethane products comprising the following steps: (A) Providing an isocyanurate-containing polyurethane product based on an isocyanate component and a polyol component, wherein the polyol component comprises a polyester polyol, a polyether ester polyol or a mixture thereof, comprising extraction of the isocyanurate-containing polyurethane product with an organic solvent which does not react with urethane groups and isocyanurate groups during extraction; (B) Mixing the polyurethane product with water, a basic catalyst and optionally an organic chemolysis reagent to obtain a reaction mixture, Reaction of the reaction mixture at a reaction temperature of 90 °C to 220 °C to obtain a chemolysis product containing (i) an amine corresponding to an isocyanate of the isocyanate component and (ii) a polyol of the polyol component and/or a reaction product of a polyol of the polyol component, wherein the type and amount of the basic catalyst are selected such that the reaction mixture always has a pH of 12 or higher during the reaction; and (C) Processing of the chemolysis product to obtain (I) of the amine and/or (II) of the polyol and/or the reaction product of a polyol. 2. The method of claim 1, wherein the conversion in step (B) is carried out in a pressure range from ambient pressure to 100 bar. 3. The method of claim 1 or 2, wherein the organic solvent used in the extraction comprises an aromatic hydrocarbon, a halogenated aromatic, an aliphatic ether, a ketone, an aromatic ether or a mixture of two or more of the aforementioned organic solvents. 4. Method according to one of the preceding claims, wherein the extraction is carried out at a temperature in the range of ambient temperature up to 180 °C. 5. Method according to any one of the preceding claims, wherein step (A) comprises mechanical comminution of the polyurethane product. 6. A method according to any of the preceding claims, wherein the basic catalyst comprises a hydroxide, a carbonate, a hydrogen carbonate, a phosphate, a hydrogen phosphate, a carboxylate, an acetate, an alcoholate, ammonia, a metal oxide or a mixture of two or more of the aforementioned basic catalysts. 7. Method according to any one of claims 1 to 6, wherein the reaction in step (B) is carried out in the presence of the organic chemoyl reagent. 8. The method of claim 7, wherein the organic chemolysis reagent is selected from an alcohol, a primary or secondary amine, or a mixture of two or more of the aforementioned organic chemolysis reagents. 9. Method according to claim 7 or 8, wherein the polyurethane product is placed in the organic chemolysis reagent in step (B) and water is added stepwise at the reaction temperature such that the reaction temperature decreases by a maximum of 15 °C. 10. Method according to any one of claims 1 to 6, wherein the reaction in step (B) is carried out in the absence of an organic chemoyl reagent. 11. A method according to any one of claims 1 to 10, wherein the chemolysis product is cooled in step (C), whereby a first solid organic phase precipitates, followed by a liquid-solid phase separation into a first aqueous phase and the first solid organic phase; or wherein the chemolysis product is extracted with an organic solvent in step (C), followed by a liquid-liquid phase separation into a first aqueous phase and a first liquid organic phase. 12. The method of claim 11, wherein the first solid organic phase or the first liquid organic phase is processed to obtain the amine. 13. The method of claim 11 or 12, wherein step (C.11) is comprised, wherein step (C.2) is a work-up of the first aqueous phase by means of distillation Separation of water while leaving an alcohol phase includes, followed by purification of the alcohol phase by distillation or stripping. 14. A method according to any of the preceding claims, wherein the isocyanate component is methylenediphenylene diisocyanate, polymethylenepolyphenylene polyisocyanate or a mixture of comprising methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate; and/or in which the polyol component additionally comprises a polyether polyol. 15. Method according to any of the preceding claims, wherein in the implementation of step (B) compounds are selected from the group consisting of (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 shall not be used.