Method for cleaving urethanes

Abstract

The invention relates to a method for the chemical cleavage of urethanes, in particular polyurethanes, by reacting with a chemolysis alcohol (alcoholysis). The method is characterised in that a (poly)urethane is reacted with a chemolysis alcohol which has a boiling point of no greater than 200°C at 1013 mbar, wherein a mass ratio of the chemolysis alcohol to the urethane is set between 0.50 and 15 and a chemolysis product containing a carbamate is obtained, wherein the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol that is connected to two or three C atoms at (at least) one β position or γ-position (preferably β-position) other C atom relative to the hydroxy group of the monoalcohol, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the above-mentioned chemolysis alcohols.

Description

[0001] PROCESS FOR CLEAVING URETHANES

[0002] The present invention relates to a process for the chemical cleavage of urethanes, in particular polyurethanes, by reaction with a chemolysis alcohol. The process is characterized in that a (poly)urethane is reacted with a chemolysis alcohol which has a boiling point of not more than 200 °C at 1013 mbar, wherein a mass ratio of the chemolysis alcohol to the urethane is set at 0.50 to 15 and a chemolysis product containing a carbamate is obtained, wherein the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at (at least) one C atom which is in the ß-position or γ-position (preferably ß-position) to the hydroxy group of the monoalcohol, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.

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

[0004] - [O-R'-O-(O=C)-HN-R-NH-(C=O)] - can be represented. Simple (non-polymeric) urethanes are also characterized by the urethane bond. Polyurethanes are the most economically important among the urethanes.

[0005] In addition to the basic polyurethane structure, many polyurethanes contain additional structural units. These include, in particular, urea, isocyanurate, allophanate, and biuret structural units.

[0006] Precisely because of the great economic success of polyurethanes in particular, large quantities of polyurethane waste (e.g., from old mattresses, seating furniture, or insulation materials) are generated, which must be put to sensible use. The technically simplest method of reuse is incineration, using the released combustion heat for other processes, such as industrial manufacturing. However, this method does not allow for closing the raw material cycle. Another type of reuse is so-called "physical recycling," in which polyurethane waste is mechanically shredded and used in the manufacture of new products.This type of recycling naturally has its limits, which is why there has been no shortage of attempts to recover the raw materials underlying polyurethane production by splitting back the urethane bonds (and any additional bond structures such as isocyanurate, urea, allophanate, or biuret bonds) (so-called "chemical recycling"). The raw materials to be recovered primarily include polyols (in the above example, HO-R'-OH) or their degradation products (e.g., the monomers underlying a polyester polyol). In addition, amines can be obtained by hydrolytic cleavage of the urethane bond (in the above example, H2N-R-NH2), which can be phosgenated after processing to form isocyanates (in the above example, O=C=NRN=C=O).

[0007] Various approaches to chemical recycling have been developed in the past. The three most important are briefly summarized below:

[0008] 1. Hydrolysis of urethanes by reaction with water to produce amines and polyols with formation of carbon dioxide.

[0009] 2. Glycolysis of urethanes by reaction with alcohols, whereby the polyols incorporated into the urethane groups are replaced by the alcohol used and thus released. This process is usually referred to in the literature as transesterification (more precisely: transurethanization). This type of chemical recycling, regardless of the exact type of alcohol used, is usually referred to in the literature as glycolysis, although this term actually only applies to glycol or glycol derivatives. (In the context of the present invention, therefore, the term alcoholysis is generally used.) Glycolysis can be followed by hydrolysis. If the hydrolysis is carried out with the direct process product of glycolysis (i.e., without prior separation of polyols and carbamates), it is referred to as

[0010] 3. Hydroglycolysis (hydroalcoholysis) of urethane bonds by reaction with alcohols and water. It is, of course, also possible to add alcohol and water from the beginning, with the glycolysis and hydrolysis processes described above occurring in parallel. A summary of known polyurethane recycling processes is provided in the review article by Simon, Borreguero, Lucas, and Rodriguez in Waste Management 2018, 76, 147-171 [1].

[0011] WO 2022 / 171586 A1 describes a process for recovering raw materials (i.e., polyols and optionally additional amines) from polyurethane foams, comprising chemolysis. The chemolysis is characterized in that a polyurethane foam is reacted with an alcohol and water in the presence of a catalyst at a temperature in the range from 130°C to 195°C, wherein the mass ratio of (total alcohol used) and (total water used) on the one hand to the polyurethane foam on the other hand is in the range from 0.5 to 2.5, and wherein the mass of the water is 4.0% to 10% of the mass of the alcohol. The catalyst comprises a metal salt selected from a carbonate, a bicarbonate, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, or a mixture of two or more of the aforementioned metal salts.

[0012] WO 2023 / 285545 A1 describes a process for recycling a polyurethane, in which the polyurethane is reacted with a first alcohol, and the low-molecular-weight carbamate formed during this reaction or in a further transurethanization with a second alcohol is thermally cleaved into the parent alcohol and the parent isocyanate. Particularly preferred first and / or second alcohols are propanol, pentanol, isopropyl alcohol, butanol, hexanol, nonanol, octanol, glycerol, ethylene glycol, diethylene glycol, and triethylene glycol. In the examples, a flexible polyurethane foam is reacted once with octanol (mass ratio of foam to alcohol 1:2, under reflux in a pressureless apparatus) and once with isopropanol (mass ratio of foam to alcohol 1:5, in a pressure reactor at an argon pressure of 30 bar).

[0013] EP 3 590 999 B1 describes a process for the degradation of plastics using methanol or ethanol in the presence of methanolate as a catalyst. The examples describe the degradation of flexible polyurethane foam.

[0014] US 4,316,992 describes a process for recovering polyether polyols from polyurethane foams. In the process, the polyurethane foam is dissolved in an alcohol at 225°C to 280°C, and superheated steam at 185°C to 220°C is then passed through the resulting solution. Suitable alcohols are saturated mono- or polyalcohols with boiling points between 225°C and 280°C. These can be straight-chain, branched, cyclic, or aromatic. Diols or triols with ether bridges are preferred, especially diethylene glycol, dipropylene glycol, dibutylene glycol, glycerol, and propylene-ethylene glycol, with diethylene glycol being emphasized as being particularly advantageous. In practice, only the use of diethylene glycol (Examples 1 and 2), glycerol (Example 3), and 1,6-hexanediol (Example 4) is demonstrated. The patent does not indicate any connection between the choice of alcohol and the formation of by-products.

[0015] US Patent No. 4,336,406 describes the hydroalcoholysis of polyurethane foams by dissolving them in an alcohol at 225°C to 280°C, followed by reaction with water (here, liquid water) at 185°C to 220°C. Suitable alcohols are described as saturated alcohols with a boiling point between 225°C and 280°C, with diethylene glycol being preferred. In this case, too, the patent does not disclose any connection between the choice of alcohol and the formation of by-products. US Patent No. 5,104,932 describes a process for obtaining improved asphalt or bitumen compositions containing polymeric residues. For this purpose, partial alcoholysis (e.g., with tert-butyl alcohol), hydrolysis, or hydroalcoholysis of polyurethane and / or polyester waste, followed by reaction of the resulting polymer residue with molten asphalt and / or bitumen, is disclosed.

[0016] US 2016 / 0145409 A1 describes a process for recovering organic fibers from composite materials containing a polymer matrix and organic fibers. The process comprises reacting the composite material in an alcohol-water mixture. The polymer is, in particular, an epoxy or phenolic resin. Water and alcohol are preferably used in equal volumes, and the alcohol is preferably selected from methanol, ethanol, n-propanol, iso-propanol, glycerol, or a mixture thereof.

[0017] DE 42 17 024 A1 describes a process for recovering polyols from polyurethane, polyurethane-urea, and / or polyurea plastics, in which the plastics are reacted with a di- and / or polyfunctional alcohol and water. Only glycols are described as alcohols.

[0018] EP 0 601 596 A1 describes a process for recovering polyols from polyurethane foams by glycolysis. The process is characterized by the fact that primary amines, which are formed as a result of the presence of urea bonds in the polyurethane foam during glycolysis, are converted into secondary amines by an alkoxylation reaction.

[0019] WO 2010 / 130652 A2 describes a process for the hydrolysis of isocyanate adducts, which in the terminology of this publication refers in particular to residues from isocyanate production (e.g., distillation residue from the production of toluene diisocyanate). The hydrolysis is carried out in the presence of an imidazole. If the isocyanate adduct is a residue from isocyanate synthesis (= not a polyurethane), the hydrolysis can be preceded by contact with a primary or secondary alcohol. The article "tert-Amyl Alcohol-Mediated Deconstruction of Polyurethane for Polyol and Aniline Recovery" by Martin B. Johansen et al. in ACS Sustainable Chem. Eng., 2022, 10 (34), 11191 - 11202 describes the chemolysis of polyurethanes with tert-amyl alcohol with direct formation of the amine, which was the precursor of the isocyanate used in polyurethane synthesis.A reaction mechanism is proposed in which the polyurethane used is first thermally cleaved back to isocyanate and polyol, and the resulting isocyanate reacts with the amyl alcohol to form a carbamate as an intermediate. The carbamate reacts with the elimination of 2-methyl-1-butene and 2-methyl-2-butene to form the unstable carbamic acid, from which the amine is formed with the release of carbon dioxide. The reactions take place with a mass ratio of alcohol to polyurethane of 16 at temperatures between 200 and 225 °C. The influence of the choice of chemolysis alcohol on the formation of N-alkylated by-products is not discussed.

[0020] Only a few of the chemical recycling processes known in the literature are operated permanently on a large-scale; many have not even reached pilot scale [1]. Given the generally increased environmental awareness and increased efforts to make industrial processes as sustainable as possible – both of which fundamentally speak in favor of chemical recycling – this clearly shows that the chemical recycling of polyurethane products is far from mature from a technical and economic perspective. Challenges exist, in particular, with regard to the purity of the recovered products. Polyols must be recovered with as little amine contamination as possible to avoid adversely affecting the foam formation behavior when reused, for example, in the production of polyurethane foams.If the recovery of amines is also desired, these must, of course, also be obtained in the highest possible purity. In addition, the polyurethane products to be recycled usually contain various auxiliary materials and additives (stabilizers, catalysts, flame retardants, etc.), which must be separated and disposed of economically and in an environmentally friendly manner from the actual target products of the recycling. Furthermore, an economically viable recycling process must ensure that the reagents used (e.g., alcohols used) can be recovered as completely as possible and reused (i.e., recycled). Due to the large volumes of polyurethane waste generated from used polyurethane foams (e.g., mattresses, seating furniture, vehicle seats, insulation materials, etc.), the recycling of polyurethane foams is particularly important.

[0021] Another important aspect concerns the avoidance of by-products during chemolysis. Interfering by-products can be, in particular, N-alkylated compounds. Such compounds can arise, for example, in the industrial production process of di- and polyamines of the diphenylmethane series, the amine precursors of the di- and polyisocyanates of the diphenylmethane series. It is known that an increased concentration of N-alkylated products leads to an increased HC value of the produced isocyanates. Depending on the application of the isocyanates, specified HC limits apply. This means that even substrate streams whose proportion of N-alkylated groups relative to the free amine groups is not significantly below 1% are generally unsuitable for a conventional phosgenation reaction, as the product streams no longer meet the required specifications.The recovery of aromatic amines from polymer waste streams through chemical recycling enables additional reaction pathways for the formation of N-alkylated compounds. The resulting byproducts will have a correspondingly negative impact on the phosgenation process. This aspect has not yet been adequately addressed in the current state of the art.

[0022] There was therefore a need for further improvements in the field of chemolysis of urethanes, especially polyurethanes. In particular, it would be desirable to minimize the formation of N-alkylated compounds during chemolysis.

[0023] Taking this need into account, the present invention relates to a process for the chemolysis (= chemical cleavage) of a urethane (in particular polyurethane) based on an isocyanate component and an alcohol component by reaction with a chemolysis alcohol to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, in particular for the purpose of obtaining starting materials for the production of chemical products, the process comprising the steps:

[0024] (A) Providing the urethane and

[0025] (B) Chemolysis of the urethane from (A) with the chemolysis alcohol in the presence or absence of a chemolysis catalyst, wherein the chemolysis alcohol has a boiling point of not more than 200 °C (preferably from 82 °C to 200 °C, particularly preferably from 82 °C to 185 °C) at 1013 mbar, and wherein a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane) (with m = mass), is set in the range from 0.50 to 15 (and consequently the chemolysis alcohol is present in stoichiometric excess with respect to the urethane groups), to form a chemolysis product containing the carbamate, wherein the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol which is (at least) one C-atom in the ß-position or y-position (preferably ß-position) to the hydroxy group of the monoalcohol is connected to two or three further C-atoms,(iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.

[0026] Completely surprisingly, it was found that the use of branched monoalcohols as described above as chemolysis reagents can suppress or even completely prevent the formation of N-alkylated by-products.

[0027] Use of a monoalcohol having a boiling point at 1013 mbar of not more than 200 °C (preferably from 82 °C to 200 °C, particularly preferably from 82 °C to 185 °C) and selected from

[0028] (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at (at least) one C atom in the ß-position or γ-position (preferably ß-position) to the hydroxy group of the monoalcohol, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned monoalcohols as chemolysis alcohol in a chemolysis (chemical cleavage) of a urethane (in particular polyurethane) based on an isocyanate component and an alcohol component in a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane), in the range from 0.50 to 15, preferably 0.75 to 10, particularly preferably 1.0 to 5.0 (and consequently the chemolysis alcohol in stoichiometric excess with respect to the urethane groups are present), forming a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol,To reduce the formation of N-alkylated by-products, i.e., by-products in which (at least) one organic radical is bonded to a nitrogen atom via an aliphatic carbon atom (in particular originating from the chemolysis alcohol or the alcohol component), this is therefore a further subject of the invention. All aspects described in connection with the process according to the invention (for example, preferred chemolysis alcohols, temperatures, pressures, proportions of the starting materials, etc.) are of course also applicable to the use according to the invention, which will not be specifically mentioned below to avoid unnecessary repetition.

[0029] According to the invention, the mass ratio of the chemolysis alcohol to the urethane is at least 0.50:1 and at most 15:1, preferably at least 0.75:1 and at most 10:1, particularly preferably 1.0:1 and at most 5.0:1.

[0030] In the terminology of the present invention, the term isocyanates encompasses all isocyanates known in the art in connection with urethane chemistry. The expression "one isocyanate" naturally also encompasses embodiments in which two or more different isocyanates (e.g., mixtures of MDI and TDI) were used in the preparation of the (poly)urethane, unless expressly stated otherwise, for example by the formulation "exactly one isocyanate." The totality of all isocyanates used in the preparation of the (poly)urethane is referred to as the isocyanate component (of the (poly)urethane). The isocyanate component comprises at least one isocyanate. Analogously, the totality of all mono- or polyols used in the preparation of the (poly)urethane is referred to as the alcohol component (of the (poly)urethane). The alcohol component comprises at least one mono- or polyol.

[0031] In the terminology of the present invention, the term mono- or polyols encompasses all mono- or polyols known in the art in connection with urethane chemistry. The expression "a mono- or polyol" naturally also encompasses embodiments in which two or more different mono- or polyols were used in the preparation of the urethane. Therefore, if reference is made below, for example, to "a polyether polyol" (or "a polyester polyol," etc.), this terminology naturally also encompasses embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) were used in the preparation of the (poly)urethane.

[0032] In the terminology of the present invention, the carbon atom bearing the hydroxyl group of the monoalcohol is referred to as the α-carbon atom. The next carbon atom is β-positioned to the hydroxyl group, the carbon atom after that is γ-positioned, and so on.

[0033] The chemolysis of the urethane from (A) with the chemolysis alcohol is carried out at a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane), in the range from 0.50 to 15. The mass ratio m(chemolysis alcohol) / m(urethane) can assume any value within this range, including the endpoints. A smaller selection range within the range from 0.50 to 15 can also be used, for example, 0.75 to 15 or 0.75 to 10 or 1.0 to 10 or 1.0 to 5.0 or 1.0 to 4.8 or 1.0 to 4.5 or 1.0 to 4.4. Selection ranges resulting from a combination of the aforementioned lower and upper limits can also be applied, such as 0.50 to 4.8 or 0.50 to 4.5 or 0.50 to 4.4 or 0.75 to 4.8 or 0.75 to 4.5 or 0.75 to 4.4. Each selection range of the mass ratio m(chemolysis alcohol) / m(urethane) can be combined with any other embodiment / configuration / variant of the invention.

[0034] In the terminology of the present invention, the urethanes formed during the chemolysis as a result of the reaction with the chemolysis alcohol are referred to as carbamates in order to distinguish them from the urethane used. This choice of terminology serves merely to simplify the discussion.

[0035] An amine corresponding to an isocyanate refers to the amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCl2 —> RN=C=O + 2 HCl.

[0036] In a further embodiment described below, the chemolysis according to the invention is carried out in the absence of a chemolysis catalyst. In the context of the present invention, this means that only the chemolysis alcohol, but no chemolysis catalyst, is added to the (poly)urethane to be cracked. It is known that, for example, polyurethane foams can still contain residual components of foaming catalysts (for example, tertiary amines). The presence of such catalysts originating from the original application of the (poly)urethane to be cracked does not exceed the scope of this embodiment of the present invention.The only important point in this context is that no additional catalysts (more precisely: no compounds that would catalyze the chemolysis, i.e., no chemolysis catalysts) are added beyond the catalysts already present in some cases from the original application of the (poly)urethanes to be cleaved. The present examples were carried out using a model urethane that was free of foaming catalysts such as those mentioned above. A brief summary of various possible embodiments of the invention follows:

[0037] In a first embodiment of the invention, which can be combined with all other embodiments except those which do not provide for isolation of the carbamate, the process comprises step (C):

[0038] (C) the separation of the carbamate formed in (B) from the chemolysis product using an extraction with an organic solvent, optionally with the addition of water, and / or a solid-liquid phase separation, whereby in addition to the carbamate a liquid alcohol phase (in particular a polyol phase) is obtained.

[0039] In a second embodiment of the invention, which is a particular embodiment of the first embodiment, the carbamate separated in (C), optionally after purification, is further reacted in a step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions:

[0040] (DI) hydrolysis of the carbamate in the presence or absence of a hydrolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0041] (D.II) hydrogenolysis of the carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0042] (DI II) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or

[0043] (D.IV) Reaction of the carbamate with a polyol in the presence or absence of a catalyst to form a further OH-terminated carbamate, in particular - in the case that the urethane from step (A) is a polyurethane - to form an OH-terminated prepolymer.

[0044] In a third embodiment of the invention, which can be combined with all other embodiments except those providing for isolation of the carbamate, the process additionally comprises the steps:

[0045] (Bl) hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture; and (Cl) extraction of the hydrolyzed product mixture with an organic (in particular halogenated) solvent to obtain an amine phase and a liquid alcohol phase (in particular a polyol phase).

[0046] In a fourth embodiment of the invention, which can be combined with all embodiments that provide for hydrolysis of the carbamate, the hydrolysis is carried out in the presence of a hydrolysis catalyst comprising

[0047] (I) an (organic or inorganic) Brpnsted base selected from (i) a hydroxide (in particular sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (in particular an alkali metal carbonate such as sodium or potassium carbonate), (iii) a bicarbonate (in particular an alkali metal bicarbonate such as sodium or potassium bicarbonate),

[0048] (iv) an orthophosphate or metaphosphate, preferably orthophosphate (in particular an alkali metal phosphate or alkali metal hydrogen phosphate) or

[0049] (v) a mixture of two or more of the aforementioned Brpnsted bases, and / or

[0050] (II) a urethanase, in particular one of the urethanases described in EP 3 587 570 A1.

[0051] In a fifth embodiment of the invention, which is a particular embodiment of the second embodiment, step (D. II) is carried out, wherein the hydrogenolysis catalyst comprises copper, palladium (in particular Pd / C, PdO2 or PdfOAc), nickel (in particular Raney nickel), manganese (in particular Mn complexes having a tridentate chelate ligand bonding via P and N donor atoms and CO and / or halogen ligands) or platinum (in particular platinum(IV) oxide).

[0052] In a sixth embodiment of the invention, which is a further particular embodiment of the second embodiment, step (D.III) is carried out, wherein the cleavage of the carbamate is carried out in the presence of a carbamate cleavage catalyst comprising

[0053] (I) a metal-free or metal-containing Brpnsted or Lewis acid catalyst or

[0054] (II) a metal-free or metal-containing Brpnsted or Lewis basic catalyst. In a seventh embodiment of the invention, which is a further particular embodiment of the second embodiment, step (D.IV) is carried out, wherein the reaction of the carbamate with the polyol is carried out in the presence of a catalyst comprising a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, an orthovanadate (all of the aforementioned chemolysis catalysts are preferably used in the form of their sodium or potassium salts), a titanium alkoxide (in particular tetra-n-butyl titanate, Ti(O-nBu)4), a tertiary amine (in particular 1,4-diazabicyclo(2.2.2)octane, "DABCO"), cesium fluoride, a stannate (in particular dibutyltin dilaurate, "DBTL", or monobutyltin oxide, n-Bu-Sn(O)OH, "MBTO"), or a mixture of two or more of the aforementioned chemolysis catalysts.

[0055] In an eighth embodiment of the invention, which can be combined with all embodiments comprising step (C) or (Cd), the liquid alcohol phase from (C) or (Cd) is distilled and / or stripped in a step (E) to obtain (at least) one chemical product selected from (i) an alcohol of the alcohol component and / or (ii) a reaction product formed from an alcohol of the alcohol component in the chemolysis (B).

[0056] In a ninth embodiment of the invention, which can be combined with all embodiments, provided that they do not provide for a catalytic implementation of step (B), the chemolysis of the urethane (in particular polyurethane) is carried out in the absence of a chemolysis catalyst.

[0057] In a tenth embodiment of the invention, which can be combined with all embodiments, provided they do not provide for an uncatalyzed implementation of step (B), the chemolysis of the urethane (in particular polyurethane) is carried out in the presence of a chemolysis catalyst, wherein the chemolysis catalyst is a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, an orthovanadate (all of the aforementioned chemolysis catalysts are preferably used in the form of their sodium or potassium salts), a titanium alcoholate (in particular tetra-n-butyl titanate, Ti(O-nBu)4), a tertiary amine (in particular 1,4-diazabicyclo(2.2.2)octane, "DABCO"), cesium fluoride, a stannate (in particular dibutyltin dilaurate, "DBTL"), or monobutyltin oxide, n-Bu-Sn(O)OH, "MBTO") or a mixture of two or more of the aforementioned chemolysis catalysts.In an eleventh embodiment of the invention, which can be combined with all embodiments except those which exclude the use of an aromatic chemolysis alcohol, the chemolysis alcohol is selected from / so-propanol, sec-butanol, / so-butanol, tert-butanol, 2-pentanol, 3-pentanol, / so-amyl alcohol (3-methyl-.

[0058] 1-butanol), 2-methyl-2-butanol, neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, 3-methyl-2-butanol, 2-methyl-l-butanol, cyclopentanol, hexan-2-ol, hexan-3-ol,

[0059] 2-methylpentan-l-ol, 2-methylpentan-2-ol, 2-methylpentan-3-ol, 4-methylpentan-l-ol, 3-methylpentan-l-ol, 3-methylpentan-2-ol, 3-methylpentan-3-ol, 2,2-dimethylbutan-l-ol,

[0060] 3,3-Dimethylbutan-l-ol, 3,3-Dimethylbutan-2-ol, 2,3-Dimethylbutan-l-ol,

[0061] 2.3-Dimethylbutan-2-ol, 2-Ethylbutan-l-ol, 4-Methylpentan-2-ol, Cyclohexanol, Phenol, 2- Ethylhexan-l-ol oder einer Mischung aus zwei oder mehr der vorgenannten Chemolysealkohole. (Bevorzugt sind: / so-Propanol, sec-Butanol, / so-Butanol, 2-Pentanol, 3- Pentanol, / so-Amylalkohol (3-Methyl-l-butanol), neo-Pentanol (2,2-Dimethyl-l-propanol), 2-Methyl-l-butanol, 3-Methyl-2-butanol, Pentaerythritol, 2-Methyl-l-butanol, Cyclopentanol, Hexan-2-ol, Hexan-3-ol, 2-Methylpentan-l-ol, 2-Methylpentan-3-ol, 4- Methylpentan-2-ol, 3-Methylpentan-l-ol, 3-Methylpentan-2-ol, 2,2-Dimethylbutan-l-ol,

[0062] 3.3-Dimethylbutan-l-ol, 3,3-Dimethylbutan-2-ol, 2,3-Dimethylbutan-l-ol, 2-Ethylbutan-l- ol, 4-Methylpentan-2-ol, Cyclohexanol, Phenol und 2-Ethylhexanol.)

[0063] In a twelfth embodiment of the process according to the invention, which can be combined with all embodiments except those which provide for the use of an aromatic chemolysis alcohol, the chemolysis alcohol is selected from

[0064] (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol,

[0065] (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at (at least) one C atom in the ß-position or γ-position (preferably ß-position) to the hydroxy group of the monoalcohol, or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.

[0066] In a thirteenth embodiment of the invention, which is a particular embodiment of the twelfth embodiment, the chemolysis alcohol is selected from sec-butanol, / iso-butanol, / iso-amyl alcohol (3-methyl-l-butanol), neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol and 2-ethylhexanol. (Preferred are: / so-propanol, 2-butanol, neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, / so-amyl alcohol (3-methyl-l-butanol), 2-ethyl-l-butanol and cyclohexanol. Particularly preferred are: / so-propanol, 2-butanol, neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, 2-ethyl-l-butanol and cyclohexanol.)

[0067] In a fourteenth embodiment of the invention, which can be combined with all embodiments, the isocyanate component comprises an isocyanate selected from phenyl isocyanate (PHI; producible by phosgenation of aniline, ANL), toluene diisocyanate (TDI; producible by phosgenation of toluenediamine, TDA), the di- and polyisocyanates of the diphenylmethane series (MDI; producible by phosgenation of the di- and polyamines of the diphenylmethane series, MDA), 1,5-pentane diisocyanate (PDI; producible by phosgenation of 1,5-pentanediamine, PDA),

[0068] 1,6-Hexamethylene diisocyanate (HDI; produced by phosgenation of

[0069] 1,6-hexamethylenediamine, HDA), isophorone diisocyanate (IPDI; preparable by phosgenation of isophoronediamine, IPDA), diisocyanatodicyclohexylmethane ("saturated methylenediphenyl diisocyanate", H12MDI, in particular the 4,4'-isomer; preparable by phosgenation of diaminodicyclohexylmethane, H12MDA, which in turn is obtainable by ring hydrogenation of 2-ring MDA), xylylene diisocyanate (XDI; preparable by phosgenation of xylylenediamine, XDA), para-phenylene diisocyanate (PPDI; preparable by phosgenation of para-phenylenediamine) or a mixture of two or more of the aforementioned isocyanates. (The isocyanate component preferably contains toluene diisocyanate, di- and polyisocyanates of the diphenylmethane series or a mixture of toluene diisocyanate and the di- and polyisocyanates of the diphenylmethane series and in particular does not comprise any other isocyanates besides those mentioned above.)

[0070] In a fifteenth embodiment of the invention, which can be combined with all embodiments, the alcohol component comprises a mono- and / or polyol selected from a polyether monool, a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol, a polycarbonate polyol, a polyether carbonate polyol, or a mixture of two or more of the aforementioned polyols. (The alcohol component preferably contains a polyester polyol, polyether polyol, and / or a polyether ester polyol, particularly preferably a polyether polyol. Most preferably, the alcohol component is a polyether polyol (i.e., it contains no other mono- or polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is included and does not depart from the scope of this embodiment.)

[0071] In a sixteenth embodiment of the invention, which can be combined with all embodiments, the urethane is a polyurethane.

[0072] In a seventeenth embodiment of the invention, which can be combined with all embodiments, step (B) is carried out in a temperature range from 150°C to 270°C, preferably from 170°C to 250°C, particularly preferably from 180°C to 230°C, and at a pressure in the range from 1.0 bar (in particular ambient pressure) to 85 bar (wherein pressure and temperature are particularly coordinated such that the chemolysis can be carried out under reflux of the selected chemolysis alcohol). In an eighteenth embodiment of the invention, which can be combined with all embodiments, the mass ratio of the chemolysis alcohol to the urethane is selected such that a molar ratio n(chemolysis alcohol) / n(urethane groups) (where n = molar amount) of 4.5 to 30, preferably 5.0 to 20, particularly preferably 8.5 to 15, results.If necessary, the molar amount of urethane groups, n(urethane groups), is determined by hydrolyzing a sample of the urethane provided in (A) and then determining the amine number by titration with 0.1-molar perchloric acid.

[0073] In a nineteenth embodiment of the invention, which can be combined with all embodiments, the chemolysis in step (B) is carried out in a reactor which is inertized with an inert gas, in particular nitrogen, before the start of the chemolysis, wherein preferably an inert gas partial pressure of 1.0 bar (in particular ambient pressure) to 20 bar, preferably up to 10 bar, is set.

[0074] In a twentieth embodiment of the invention, which can be combined with all embodiments, in (B) a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane) (with m = mass), is set in the range from 0.50 to 4.5, in particular 0.50 to 4.0, or in the range from 1.0 to 4.5, in particular 1.0 to 4.0.

[0075] The embodiments briefly described above and other possible configurations of the invention are explained in more detail below. All of the embodiments described above and the other configurations of the invention described below can be combined with each other as desired, unless the context clearly indicates otherwise to a person skilled in the art or unless expressly stated otherwise.

[0076] PROVISION OF (POLY-)URETHANE FOR CHEMICAL RECYCLING

[0077] In step (A), the (poly)urethane to be chemically recycled is prepared in preparation for chemolysis. This can, in principle, be any type of urethane.

[0078] Preferred are polyurethanes, i.e., urethanes derived from polyisocyanates (two or more isocyanate groups per molecule) and polyols (two or more alcohol groups per molecule). These can, in principle, be any type of polyurethane, i.e., polyurethane foams as well as polyurethane products from the so-called CASE applications described above. Polyurethane foams can be both flexible and rigid foams, with flexible foams (e.g., from old mattresses, upholstered furniture, or car seats) being preferred. Polyurethane foams are typically produced using propellant gases such as pentane or carbon dioxide. Polyurethane elastomers, polyurethane adhesives, and polyurethane coatings are preferred for polyurethanes from CASE applications.

[0079] Preferred are those urethanes or polyurethanes whose isocyanate component is an isocyanate selected from

[0080] Phenyl isocyanate (PHI; producible by phosgenation of aniline, ANL), toluene diisocyanate (TDI; producible by phosgenation of toluenediamine, TDA), the di- and polyisocyanates of the diphenylmethane series (MDI; producible by phosgenation of the di- and polyamines of the diphenylmethane series, MDA), 1,5-pentane diisocyanate (PDI; producible by phosgenation of 1,5-pentanediamine, PDA),

[0081] 1,6-Hexamethylene diisocyanate (HDI; produced by phosgenation of

[0082] 1,6-hexamethylenediamine, HDA), isophorone diisocyanate (IPDI; preparable by phosgenation of isophoronediamine, IPDA), diisocyanatodicyclohexylmethane ("saturated methylenediphenyl diisocyanate", H12MDI, in particular the 4,4'-isomer; preparable by phosgenation of diaminodicyclohexylmethane, H12MDA, which in turn is obtainable by ring hydrogenation of 2-ring MDA), xylylene diisocyanate (XDI; preparable by phosgenation of xylylenediamine, XDA), para-phenylene diisocyanate (PPDI; preparable by phosgenation of para-phenylenediamine, PPDA) or a mixture of two or more of the aforementioned isocyanates. In the case of polyurethanes, it is particularly preferred that the isocyanate component comprises tolylene diisocyanate, di- and polyisocyanates of the diphenylmethane series or a mixture of tolylene diisocyanate and the di- and polyisocyanates of the diphenylmethane series and in particular does not comprise any further isocyanates besides those mentioned above.

[0083] As regards the alcohol component, this preferably comprises a mono- and / or polyol selected from a polyether monool, a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol, a polycarbonate polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols.

[0084] The alcohol component preferably contains a polyester polyol, polyether polyol, and / or a polyether ester polyol, particularly preferably a polyether polyol. The alcohol component is most preferably a polyether polyol (i.e., it contains no other mono- or polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is encompassed and does not exceed the scope of this embodiment). A polyether polyol can also be one filled with a styrene-acrylonitrile copolymer (SAN copolymer).

[0085] Preferably, step (A) already includes preparatory steps for the cleavage of the urethane bonds in step (B). In the case of polyurethanes, this particularly involves mechanical comminution. Such preparatory steps are known to the person skilled in the art; reference is made, for example, to the literature cited in [1]. Depending on the nature of the polyurethane (particularly in the case of polyurethane foams), it may be advantageous to "freeze" it prior to mechanical comminution in order to facilitate the comminution process.

[0086] It is also conceivable to carry out the preparatory steps described above at a location spatially separate from the chemolysis site. In this case, the prepared foam is loaded into suitable transport vehicles, such as silo vehicles, for further transport. For further transport, the prepared foam can also be compressed to achieve a higher mass-to-volume ratio. At the chemolysis site, the foam is then loaded into the reaction facility intended for chemolysis. It is also conceivable to connect the transport vehicle used directly to the reaction facility.

[0087] CHEMOLYSIS OF (POLY-)URETHANE

[0088] The chemolysis of the (poly)urethane, step (B), is preferably carried out under the exclusion of oxygen. This means that the reaction is carried out in an inert gas atmosphere (especially in a nitrogen, argon, or helium atmosphere). Preferably, the chemolysis alcohol used is also freed of oxygen by inert gas saturation.

[0089] The chemolysis is carried out at reaction temperatures of 150 °C to 270 °C, preferably 170 °C to 250 °C, particularly preferably 180 °C to 230 °C. The chemolysis is preferably carried out in a pressure-resistant reactor (autoclave) without pressure equalization, in particular such that the reaction is operated "under reflux" (chemolysis alcohol evaporates, condenses in cooler areas of the reactor, and flows back into the reacting mixture). In this procedure, a pressure is established in the gas space above the liquid reaction mixture that corresponds to the vapor pressure of the chemolysis alcohol used at the prevailing temperature, i.e., depending on the type of chemolysis alcohol and the temperature, the pressure is in the range of approximately 1.0 bar to 85 bar (absolute). However, it is also possible to carry out the chemolysis under pressure equalization, i.e., at ambient pressure.It is preferable to inertize the reactor used for the chemolysis with an inert gas, especially nitrogen, before the start of the chemolysis. The inert gas is preferably used to set an inert gas partial pressure of 1.0 bar (especially ambient pressure) to 20 bar, preferably up to 10 bar (absolute).

[0090] A suitable reactor, for example, is a stirred tank reactor, which can also be operated continuously. The use of a cascade of several continuously operated stirred tank reactors, optionally with a downstream tubular reactor (especially operated with plug flow), is also possible.

[0091] According to the invention, the mass ratio of the chemolysis alcohol to the (poly)urethane is in the range of 0.50 to 15 (for example, it is in the range of 0.50 to 4.5 or 1.0 to 4.5 or 0.50 to 4.0 or 1.0 to 4.0). This makes it possible to limit the mass of chemolysis alcohol used, which is a major advantage from a process engineering perspective (lower costs, less complex processing). Regarding the molar ratios, these are generally superstoichiometric at the stated mass ratios, so that complete conversion can be ensured. Preferably, the mass ratios within the stated ranges are selected such that a molar excess of the chemolysis alcohol (i.e. a molar ratio n(chemolysis alcohol) / n(urethane groups), where n = molar amount) of 4.5 to 30, particularly preferably 5.0 to 20, very particularly preferably 8.5 to 15, is ensured.If the molar amount of urethane groups is unknown (e.g., because polyurethanes of unknown origin are to be recycled), it can be easily determined by hydrolyzing a representative sample of the (poly)urethane provided in (A) and determining the amine number of the hydrolysis product. Since one mole of amine is released per mole of cleaved urethane groups, the molar amount of urethane groups can be determined from the amine number. The exact method of conducting the hydrolysis naturally depends on the type of (poly)urethane. Using the information and literature references compiled in [1], it is easy for the skilled person to find a suitable process.

[0092] The amine number indicates how many mg of potassium hydroxide are required to neutralize the free organic amines present in 1 g of substance. Primary, secondary, and tertiary amino groups are included. The amino groups are weak bases. Concentrated acetic acid (glacial acetic acid, 99% to 100%) is used as the solvent. The amine is protonated by the solvent and thus converted into the corresponding acid, which now forms an ion pair with the deprotonated acid of the glacial acetic acid. The titration is then carried out using 0.1 molar perchloric acid as the titrant, with the perchloric acid displacing the anion of the solvent (glacial acetic acid). The perchloric acid consumed is equated with the consumption of potassium hydroxide. The amine number is usually expressed in milligrams of KOH per gram of sample and is calculated as follows: wherein

[0093] • AZ for the amine number,

[0094] • V is the volume of perchloric acid solution consumed,

[0095] • m is the mass of the titrated sample,

[0096] • M(KOH) for the molar mass of KOH (56.11 g • mol -1 ),

[0097] • bi is the molarity of the perchloric acid solution and

[0098] • f stands for the dimensionless factor (titer) of the perchloric acid solution.

[0099] According to the invention, the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at (at least) one C atom in the ß-position or γ-position (preferably ß-position) to the hydroxy group of the monoalcohol, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.The use of such a chemolysis alcohol in a chemolysis (chemical cleavage) of a urethane (in particular polyurethane) based on an isocyanate component and an alcohol component to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol to reduce the formation of by-products in which (at least) one organic radical is bonded to a nitrogen atom via an aliphatic carbon atom (in particular originating from the chemolysis alcohol or the alcohol component) is a further subject of the present invention.

[0100] Als Chemolysealkohole eignen sich bevorzugt / so-Propanol, sec-Butanol, / so-Butanol, tert- Butanol, 2-Pentanol, 3-Pentanol, / so-Amylalkohol (3-Methyl-l-butanol), 2-Methyl-2- butanol, neo-Pentanol (2,2-Dimethyl-l-propanol), 2-Methyl-l-butanol, 3-Methyl-2- butanol, 2-Methyl-l-butanol, Cyclopentanol, Hexan-2-ol, Hexan-3-ol, 2-Methylpentan-l-ol, 2-Methylpentan-2-ol, 2-Methylpentan-3-ol, 4-Methylpentan-2-ol, 3-Methylpentan-l-ol, 3- Methylpentan-2-ol, 3-Methylpentan-3-ol, 2,2-Dimethylbutan-l-ol, 3,3-Dimethylbutan-l- ol, 3,3-Dimethylbutan-2-ol, 2,3-Dimethylbutan-l-ol, 2,3-Dimethylbutan-2-ol, 2-Ethylbutan- l-ol, 4-Methylpentan-2-ol, Cyclohexanol, Phenol, 2-Ethylhexan-l-ol oder Mischungen aus zwei oder mehr der vorgenannten Chemolysealkohole. Besonders bevorzugt sind / so-Propanol, sec-Butanol, / so-Butanol, 2-Pentanol, 3-Pentanol, / so-Amylalkohol (3-Methyl-

[0101] 1-butanol), neo-Pentanol (2,2-Dimethyl-l-propanol), 2-Methyl-l-butanol, 3-Methyl-

[0102] 2-butanol, Pentaerythritol, 2-Methyl-l-butanol, Cyclopentanol, Hexan-2-ol, Hexan-3-ol,

[0103] 2-Methylpentan-l-ol, 2-Methylpentan-3-ol, 4-Methylpentan-2-ol, 3-Methylpentan-l-ol,

[0104] 3-Methylpentan-2-ol, 2,2-Dimethylbutan-l-ol, 3,3-Dimethylbutan-l-ol, 3,3-

[0105] Dimethylbutan-2-ol, 2,3-Dimethylbutan-l-ol, 2-Ethylbutan-l-ol, 4-Methylpentan-2-ol, Cyclohexanol, Phenol und 2-Ethylhexanol.

[0106] Of the non-aromatic chemolysis alcohols whose use is generally preferred, sec-butanol, / so-butanol, / so-amyl alcohol (3-methyl-l-butanol), neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol and 2-ethylhexanol are preferred. Particularly preferred are / so-propanol, 2-butanol, neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, / so-amyl alcohol (3-methyl-l-butanol), 2-ethyl-l-butanol and cyclohexanol, very particularly preferred are / so-propanol, 2-butanol, neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, 2-ethyl-l-butanol and cyclohexanol.

[0107] The chemolysis can, but does not necessarily have to, be carried out in the presence of a catalyst. In one embodiment, the addition of a chemolysis catalyst is deliberately omitted. If a catalyst is used, it preferably comprises a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, an orthovanadate (all of the aforementioned chemolysis catalysts are preferably used in the form of their sodium or potassium salts), a titanium alkoxide (in particular tetra-n-butyl titanate, Ti(O-nBu)4), a tertiary amine (in particular 1,4-diazabicyclo(2.2.2)octane, "DABCO"), cesium fluoride, a stannate (in particular dibutyltin dilaurate, "DBTL," or monobutyltin oxide, n-Bu-Sn(O)OH, "MBTO"), or a mixture of two or more of the aforementioned chemolysis catalysts.

[0108] PROCESSING OF THE CHEMOLYSIS PRODUCT

[0109] The chemolysis yields a chemolysis product containing the carbamate. The chemolysis product is preferably processed by separating the carbamate formed in (B) from the chemolysis product in step (C) using extraction with an organic solvent, optionally with the addition of water, and / or solid-liquid phase separation, yielding a liquid alcohol phase (especially a polyol phase) in addition to the carbamate. Excess chemolysis alcohol is removed by distillation before or after the separation, preferably before. Separation by solid-liquid phase separation is limited to those carbamates that precipitate as solids from the chemolysis product (possibly after cooling). Whether this is the case depends on the exact nature of the carbamate, i.e., in particular, on the nature of the (poly)urethane to be cleaved. Separation by extraction, however, is applicable in any case.The separation of alcohols (especially polyols) and carbamates, which are present in a mixture in the product of alcoholysis, by extractive processes is generally known in the prior art. Reference is made, for example, to the international patent applications WO 2020 / 260387 A1 (use of very nonpolar organic solvents, such as, in particular, hydrocarbons) and WO 2022 / 063764 A1 (use of moderately polar organic solvents, such as, in particular, halogenated hydrocarbons, in combination with an aqueous washing liquid).

[0110] Within the scope of the process according to the invention, both halogen-substituted (especially chlorinated) organic solvents such as, for example, halogen-substituted aliphatic hydrocarbons, halogen-substituted alicyclic hydrocarbons, halogen-substituted aromatic hydrocarbons or mixtures of two or more of the aforementioned organic solvents, as well as non-halogenated solvents such as, for example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons or mixtures of two or more of the aforementioned organic solvents, can be used. The choice of solvent depends on the circumstances of the individual case, in particular on the nature of the (poly)urethane to be cleaved, and can be determined by the person skilled in the art, if necessary, through simple preliminary tests.

[0111] When the carbamate is separated using an extraction, the carbamate is obtained as a solution, specifically, depending on the nature of the (poly)urethane used and the type of organic solvent used, dissolved in the extraction solvent or - as described in WO 2020 / 260387 A1 - in excess chemolysis alcohol or - as described in WO 2022 / 063764 A1 - in an aqueous phase obtained after adding an aqueous wash liquid to the extraction. Depending on the type of further processing of the carbamate desired, this solution can be used directly. Isolation of the carbamate from this solution by evaporation of the solvent and / or crystallization is also easily possible.

[0112] The carbamate thus obtained can then, optionally after purification, be further reacted in a step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions: (Dl) hydrolysis of the carbamate in the presence or absence of a hydrolysis catalyst to form an amine which corresponds to the isocyanate of the isocyanate component;

[0113] (D.II) hydrogenolysis of the carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0114] (D.III) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or

[0115] (D.IV) Reaction of the carbamate with a polyol in the presence or absence of a catalyst to form another OH-terminated carbamate, in particular - if the starting urethane is a polyurethane - to form an OH-terminated prepolymer.

[0116] The reactions according to (Dl) to (D.IV), hydrolysis, hydrogenolysis, carbamate cleavage and transurethanization, are well known in the art and are therefore only briefly outlined here.

[0117] The hydrolysis according to (Dl) yields the amine corresponding to the isocyanate of the isocyanate component. In principle, such a hydrolysis can be carried out analogously to the direct hydrolysis of polyurethanes (see the literature cited above, in particular the review article [1]). The amines thus formed can then be used for all applications known in the art for such amines, including phosgenation to the corresponding isocyanates. The isocyanate thus obtained can then be recycled to the production of a (poly)urethane. The hydrolysis can be assisted by the use of a hydrolysis catalyst. The following is particularly suitable for this purpose:

[0118] (I) an (organic or inorganic) Brpnsted base selected from (i) a hydroxide (in particular sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (in particular an alkali metal carbonate such as sodium or potassium carbonate), (iii) a hydrogen carbonate (in particular an alkali metal hydrogen carbonate such as sodium or potassium hydrogen carbonate), (iv) an orthophosphate or metaphosphate, preferably orthophosphate (in particular an alkali metal phosphate or alkali metal hydrogen phosphate) or (v) a mixture of two or more of the aforementioned Brpnsted bases, and / or (II) a urethanase, in particular one of the urethanases described in EP 3 587 570 A1.

[0119] The amine corresponding to the isocyanate of the isocyanate component can also be obtained by hydrogenolysis of the carbamate according to (D.II) with hydrogen. A process that starts directly from polyurethanes and is also applicable for the present step (D.II) is described in Hydrogenative Depolymerization of Polyurethanes Catalyzed by Manganese Pincer Complex by Viktoriia Zubar et al., published in ChemSusChem 2022, 15, e202101606 [2]. Reference is also made to the literature cited in [2]. The possible uses of the amine are the same as described for (DI). The hydrogenolysis is preferably supported by the use of a catalyst. A particularly suitable hydrogenolysis catalyst is a catalyst that

[0120] Palladium (in particular Pd / C, PdÜ2 or PdfOAc), copper, nickel (in particular Raney nickel), manganese (in particular Mn complexes having a tridentate chelate ligand binding via P and N donor atoms as well as CO and / or halogen ligands) or platinum (in particular platinum(IV) oxide).

[0121] The processing variants according to (DI) and (D.II) thus yield the amine corresponding to the isocyanate of the isocyanate component. This amine can be used for all applications known in the art; in particular, it can be phosgenated and used in the production of new (poly)urethane.

[0122] However, it is also conceivable to obtain the isocyanate of the isocyanate component directly from the carbamate by splitting the carbamate—either purely thermally or in the presence of a carbamate cleavage catalyst—into the isocyanate of the isocyanate component and the chemolysis alcohol (carbamate cleavage according to (D.III)). For catalytic implementation, the following are particularly suitable as carbamate cleavage catalysts:

[0123] (I) a metal-free or metal-containing Brpnsted or Lewis acid catalyst or

[0124] (II) a metal-free or metal-containing Brpnsted or Lewis basic catalyst.

[0125] For further details, see W. Leitner et al., Carbon2Polymer - Chemical Utilization of CC in the Production of Isocyanates, Chapter 4, "Carbamate Cleavage," published in Chem. Ing. Tech. 2018, 90, 1504–1512, and the references cited therein.

[0126] The processing variant according to (D.III) directly yields the isocyanate of the isocyanate component, thus eliminating the need for further phosgenation. This isocyanate can be used for all applications known in the art; in particular, it can be reacted again with H-functional compounds to form polyaddition products, preferably (poly)urethanes. Carbamate cleavage according to (D.III) may be the variant of choice, especially when the isocyanate component of the urethane or polyurethane comprises and, in particular, consists of toluene diisocyanate (TDI) (i.e., does not comprise any other isocyanates besides TDI).

[0127] The reaction of the carbamate from step (C) with a polyol to form another OH-terminated carbamate according to (D.IV) is another possible way of further processing the carbamate. Chemically, this is a transurethanization and thus essentially the same type of reaction that underlies the glycolysis of polyurethanes (see the literature cited above, in particular the review article [1]). It is particularly advantageous when the urethane provided in step (A) is a polyurethane. For this purpose, the carbamate is reacted with a polyol, with the OH groups of the polyol being used stoichiometrically or superstoichiometrically, in particular slightly superstoichiometrically (e.g., 5 to 10% excess on a molar basis), relative to the existing carbamate functionalities. If the starting urethane is a polyurethane, which is preferred, this reaction leads to OH-terminated prepolymers.These can be used for all purposes known in the professional world, in particular as prepolymers for flexible and rigid foam applications, thermoplastic polyurethanes, coatings and adhesives.

[0128] The polyol used for step (D.IV) preferably has a boiling point higher than that of the chemolysis alcohol used. In a particularly preferred embodiment, the chemolysis alcohol is continuously removed from the reaction mixture by distillation during the reaction with the polyol. The reaction can optionally be carried out in the presence of a catalyst. This preferably comprises a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a mono-hydrogen orthophosphate, a metaphosphate, an orthovanadate (all of the aforementioned catalysts preferably being used in the form of their sodium or potassium salts), a titanium alcoholate (in particular tetra-n-butyl titanate, Ti(O-nBu)4), a tertiary amine (in particular 1,4-diazabicyclo(2.2.2)octane, "DABCO"), cesium fluoride, a stannate (in particular dibutyltin dilaurate, "DBTL", or monobutyltin oxide, n-Bu-Sn(O)OH, "MBTO") or a mixture of two or more of the aforementioned catalysts.

[0129] Typical suitable polyols are dihydric polyols (in particular ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-butenediol, 1,4-butynediol, neopentyl glycol, 1,5-pentanediol, methylpentanediols (such as 3-methyl-1,5-pentanediol), 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, bis-(hydroxymethyl)-cyclohexanes (such as 1,4-bis-(hydroxymethyl)cyclohexane), triethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, tripropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols), trihydric polyols (in particular trimethylolpropane, Glycerol, trishydroxyethyl isocyanurate), tetravalent polyols (especially pentaerythritol) and polyols that can be obtained from renewable raw materials (especially sorbitol, hexitol, sucrose, starch, starch hydrolysates, cellulose, cellulose hydrolysates and hydroxy-functionalised fats and oils, especially castor oil),as well as all modification products of these aforementioned polyols with varying amounts of ε-caprolactone. Polyether polyols can also be used as polyols for step (D.IV), especially those with a number-average molecular weight M, determined according to DIN 55672-1 (2016-03). n in the range from 18 g / mol to 8000 g / mol and a functionality (calculated from the H-functional starters used in the preparation of the polyether polyols) of 2 to 3. Preferred polyether polyols are those composed of repeating ethylene oxide and propylene oxide units, preferably with a proportion of 35% to 100% propylene oxide units, particularly preferably with a proportion of 50% to 100% propylene oxide units. These can be random copolymers, gradient copolymers, alternating or block copolymers of ethylene oxide and propylene oxide.

[0130] In all four variants, the chemolysis alcohol used is released again and can be recovered by distillation and reused in chemolysis.

[0131] The variants for further processing of the carbamate described above are all the more advantageous to implement, the more selectively the carbamate is formed in step (B). This applies in particular to variant (D.III), in which the isocyanate is obtained without the intermediate amine. However, in the other variants, it can also be advantageous if the formation of the carbamate is as selective as possible, because in many cases this facilitates subsequent workup, particularly the separation of the constituents of the chemolysis product from one another. Therefore, the direct ("uncontrolled") formation of the amine in step (B) is particularly noteworthy as a selectivity-reducing reaction. To reduce the formation of the amine, it is therefore preferable to use chemolysis alcohols with the lowest possible water content.In particular, it is preferred that the chemolysis alcohol used, based on its total mass, contains a maximum of 0.500 mass%, preferably a maximum of 0.200 mass%, particularly preferably a maximum of 0.050 mass%, and very particularly preferably a maximum of 0.005 mass% of water, which can be achieved, if necessary, by drying measures known per se. For the purposes of the present invention, the mass of the chemolysis alcohol is in any case the total mass including any water present. The water content of the chemolysis alcohol can be determined, if necessary, by Karl Fischer titration; this is the method relevant for the purposes of the present invention. Karl Fischer titration has been described many times and is well known to those skilled in the art. Various possible embodiments of the basic principle of Karl Fischer titration generally produce results that are sufficiently consistent within the framework for the purposes of the present invention.In case of doubt, the Karl Fischer titration as described in DIN 51 777, Part 1, March 1983 is decisive for the purposes of the present invention.

[0132] If the recovery of the carbamate is not important for the desired (poly)urethane recycling, it is also possible to hydrolyze the chemolysis product formed in step (B) directly, i.e., without separating the resulting carbamate. In this case, step (B) comprises a step (B1), the hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture. In this case, the workup comprises a step (C1), the extraction of the hydrolyzed product mixture with an organic (especially halogenated) solvent, yielding an amine phase and a liquid alcohol phase (especially a polyol phase). Suitable organic (especially halogenated) solvents are the same as those described above in connection with the extraction of the carbamate.

[0133] Within the scope of the process according to the invention, there are basically two possible ways for the processing of the chemolysis product: a first one involving the recovery of the carbamate followed by separate further processing of the same and the resulting liquid alcohol phase, and a second one involving direct hydrolysis of the chemolysis product. Regarding the processing of the chemolysis product, the process according to the invention therefore comprises either

[0134] (a) a step (C), the separation of the carbamate formed in (B) from the chemolysis product using an extraction with an organic solvent, optionally with the addition of water, and / or a solid-liquid phase separation, wherein in addition to the carbamate a liquid alcohol phase (in particular a polyol phase) is obtained, wherein preferably the carbamate separated in (C), optionally after purification, is further reacted in a step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions: (Dl) hydrolysis of the carbamate in the presence or absence of a hydrolysis catalyst to form an amine which corresponds to the isocyanate of the isocyanate component;

[0135] (Dl I) hydrogenolysis of the carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0136] (D.III) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or

[0137] (D.IV) reacting the carbamate with a polyol in the presence or absence of a catalyst to form a further OH-terminated carbamate; wherein variants (Dl), (D.II) and (D.IV) are preferred and variant (Dl) is particularly preferred; or

[0138] (ß) a step (B1), the hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture, and a step (C1), the extraction of the hydrolyzed product mixture with an organic (in particular halogenated) solvent to obtain an amine phase and a liquid alcohol phase (in particular a polyol phase).

[0139] Regarding the liquid alcohol phase from (C) or (Cl), it is preferred to distill and / or strip it in a step (E) to obtain (at least) one chemical product selected from (i) an alcohol of the alcohol component and / or (ii) a reaction product formed from an alcohol of the alcohol component in the chemolysis (B). The alcohols and / or reaction products thus obtained can be used for all purposes known in the art for such compounds. In particular, recovered polyether polyols can be used in the production of novel polyurethanes, and reaction products of polyester polyols can be used in the production of novel polyester polyols.

[0140] The invention described above is explained in more detail below using examples. Examples:

[0141] Chemicals

[0142] Name Related from Purity

[0143] Phenylisocyanat Sigma-Aldrich >98%

[0144] MeOH Sigma-Aldrich >99,9% iPrOH Sigma-Aldrich 99,5%

[0145] EG Sigma-Aldrich 99,8%

[0146] 2-Ethoxyethanol Alfa Aesar 99%

[0147] Anillin Ridel-de Haen 99,5%

[0148] THF Sigma-Aldrich (Merck) n.a.

[0149] Tetradecan Sigma-Aldrich (Merck) >99,0%

[0150] Na2CÜ3 Sigma-Aldrich >99,5%

[0151] 2-Butanol Fluka >99,5%

[0152] 2,2'-Dimethyl-l- r .. .. . . .

[0153] . Sigma-Aldrich 99% propanol

[0154] 2-Methyl-l-butanol Sigma-Aldrich > 99 %

[0155] 3-Methyl-l-butanol Sigma-Aldrich > 99 %

[0156] 2-Ethyl-l-butanol Sigma-Aldrich 98% cyclo-Hexanol Acros Organics 98%

[0157] Ethylenglykol Sigma-Aldrich 99.8 %

[0158] Diethylenglykol Sigma-Aldrich > 99 %

[0159] Analytik

[0160] GC method

[0161] Gas chromatography with a flame ionization detector (GC-FID) was used for the quantitative analysis of the samples. An Agilent 8890 GC system was used with an SSL inlet (275 °C, split ratio 80:1 with a constant flow of 5 mL / min), a GC column HP-5 (30 m, inner diameter 320 pm, film thickness 0.25 pm), and H2 as the carrier gas. At the beginning of the measurement, the temperature was held constant at 60 °C for 0.5 min and then increased to 300 °C with a ramp of 20 °C / min. Once the temperature was reached, the temperature was maintained at 300 °C for a further 10 min. Tetrahydrofuran (THF) was used as the solvent.

[0162] The following formula was used to calculate the GC yields and conversions using the internal standard tetradecane: rrij = mass of substance i mint std = mass of internal standard

[0163] Ai = surface integral of substance i

[0164] Aint std = area integral of internal standard kf = correction factor (FID response factor). The mass fractions of 2-ethoxyethyl-N-phenylurethane (substrate; see the following section), the target carbamate, and aniline were quantified in this way. A kf of 1 was assumed for the N-alkylated aniline derivatives. Part

[0165] The model reaction was the conversion of 2-ethoxyethyl-N-phenylurethane,

[0166] (henceforth substrate) with various chemolysis alcohols to form corresponding transurethanization products (henceforth target carbamates).

[0167] 2-Ethoxyethanol (59.8 g, 64.3 mL, 0.66 mol, 6.00 equiv.) was placed in a 250 mL round-bottom flask, and phenyl isocyanate (13.2 g, 12.1 mL, 0.11 mol, 1.00 equiv.) was rapidly added while stirring (at 500 rpm) at room temperature. The reaction solution was then stirred for 4.5 h at 100 °C. After the reaction solution had cooled to room temperature, CHCl3 (~60 mL) was added and extracted with deionized water (3 x 50 mL). The organic phase was washed with saturated brine and dried over MgSO. The volatile components were removed under reduced pressure before 2-ethoxyethyl N-phenylcarbamate was dried under high vacuum for 72 h and isolated as a yellowish, viscous liquid (16.7 g, 72.2%).

[0168] -Reactions in high-pressure autoclaves

[0169] A glass insert equipped with a magnetic stirrer is filled with catalyst (optional (see Tables 1 to 2), 28 mg, 1.0 mass% based on the total mass of substrate and chemolysis alcohol), substrate (700 mg), chemolysis alcohol (2.1 g), and the internal standard tetradecane (20 mg) and placed in the stainless steel autoclave (volume 20 mL). The autoclave is purged three times with N2 (setting a nitrogen pressure of 50 bar and then depressurizing to ambient pressure) and sealed before the pressure is increased to 10 bar by adding nitrogen. The autoclave is heated in a preheated aluminum cone for 4 h at 200 °C with stirring (900 rpm). The autoclave is then cooled in an ice bath for 10 min and then depressurized. The reaction mixture is diluted with THF (2 mL), filtered through a syringe filter (Chromafil O- 20 / 15 MS) and analyzed by GC-FID.

[0170] Examples 1 to 36 The following Table 1 summarizes the results of the alcoholysis reactions.

[0171] Table 1: Alcoholysis of a glycol-based urethane as a substrate with different chemolysis alcohols at 200 °C and 120 to 360 min reaction time [a] Table 2: Alcoholysis of a glycol-based urethane as substrate with different chemolysis alcohols at 200-220 °C and 240-480 min reaction time (compared to Table 1, higher temperatures and longer reaction times). [a]

[0172] Explanations of the table:

[0173] [a] Substrate: Ph-NH-CO-O-fCl-hh-OEt; mass ratio of chemolysis alcohol to substrate of 3:1. If a catalyst is used, it is employed in a mass fraction of 1.0%, based on the total mass of substrate and chemolysis alcohol. The reaction conditions are optimized to maximize the yield of the target carbamate in the case of the uncatalyzed reaction with methanol (Example 1).

[0174] [b] Amount-related percentage of the substrate or target carbamate or aniline in the product in relation to the amount of substrate used:

[0175] Ysubstrate = (100% ■ [n(SubStrat)product / n(SubStrat)used] or

[0176] Yzc = 100 % ■ [n(target carbamate) product / n(substrate) used] or YAniline = 100 % • [n(product / n(substrate) used].

[0177] [c] Quotient of (i) the sum of the area percentages (GC) of the detected N-alkylated aniline derivatives R 1 R 2NCeH5 (where R 1 an alkyl part of the chemolysis alcohol or a (CFhh-OEt group from the substrate and R 2 is either hydrogen, an alkyl part of the chemolysis alcohol or a (CFhh-OEt group from the substrate, where R 1 also equal to R 2 can be) and

[0178] (ii) the sum of the area percentages (GC) of the detected N-alkylated aniline derivatives, the free aniline, the substrate, and the target carbamate; multiplied by 100%.

[0179] [d] V = comparative example.

[0180] As the examples in Tables 1 and 2 show, the use of simple linear C1- to C4-alcohols leads to the formation of N-alkylated by-products (Examples 1 to 6). Replacing n-propanol with iso-propanol leads to a reduction of N-alkylated by-products to zero (Examples 7 to 8). Even with longer reaction times and higher reaction temperatures, with or without the use of an additional catalyst, no N-alkylation is observed when using the alcohols according to the invention (Table 2).

[0181] The use of methyl- and ethyl-substituted butanols in the presence of a catalyst leads to very good yields of the target carbamate in the product mixture of around 90%, despite non-optimized reaction conditions and even a reaction time halved compared to Example 2, also without N-alkylation (Examples 14, 16, and 18). A comparable yield is achieved with iso-propanol even without a catalyst (Example 7).

[0182] Glycols, traditionally used as chemolysis alcohols, yield enormous amounts of N-alkylated by-products and are unusable under the chosen reaction conditions (Examples 21 and 22).

Claims

1. A process for the chemolysis of a urethane based on an isocyanate component and an alcohol component by reaction with a chemolysis alcohol to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, comprising the steps of: (A) Providing the urethane and (B) Chemolysis of the urethane from (A) with the chemolysis alcohol in the presence or absence of a chemolysis catalyst, wherein the chemolysis alcohol has a boiling point of not more than 200 °C at 1013 mbar, and wherein a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane), is set in the range from 0.50 to 15, to form a chemolysis product containing the carbamate, wherein the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at (at least) one C atom in the β-position or γ-position (preferably β-position) to the hydroxy group of the monoalcohol, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.

2. A process according to claim 1, comprising (C) separating the carbamate formed in (B) from the chemolysis product using extraction with an organic solvent and / or solid-liquid phase separation, whereby a liquid alcohol phase is obtained in addition to the carbamate.

3. A process according to claim 2, wherein the carbamate separated in (C), optionally after purification, is further reacted in a step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions: (DI) hydrolysis of the carbamate in the presence or absence of a hydrolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component; (D.II) hydrogenolysis of the carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component; (D.III) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or (D.IV) Reaction of the carbamate with a polyol in the presence or absence of a catalyst to form another OH-terminated carbamate.

4. The method according to claim 1, comprising the steps: (Bl) hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture; and (Cd) Extraction of the hydrolyzed product mixture with an organic solvent to obtain an amine phase and a liquid alcohol phase.

5. Process according to one of claims 2 to 4, in which the liquid alcohol phase from (C) or (Cd) is distilled and / or stripped in a step (E) to obtain a chemical product selected from (i) an alcohol of the alcohol component and / or (ii) a reaction product formed from an alcohol of the alcohol component in the chemolysis (B).

6. A process according to any one of claims 1 to 5, wherein the chemolysis of the urethane is carried out in the absence of a chemolysis catalyst.

7. A process according to any one of claims 1 to 5, wherein the chemolysis of the urethane is carried out in the presence of a chemolysis catalyst, wherein the chemolysis catalyst comprises a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a mono-hydrogen orthophosphate, a metaphosphate, an orthovanadate, a titanium alkoxide, a tertiary amine, cesium fluoride, a stannate or a mixture of two or more of the aforementioned chemolysis catalysts.

8. A process according to any one of claims 1 to 7, wherein the chemolysis alcohol is selected from iso-propanol, sec-butanol, iso-butanol, tert-butanol, 2-pentanol, 3-pentanol, iso-amyl alcohol (3-methyl-1-butanol), 2-methyl-2-butanol, neo-pentanol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, cyclopentanol, hexan-2-ol, hexan-3-ol, 2-methylpentan-1-ol, 2-methylpentan-2-ol, 2-methylpentan-3-ol, 4-methylpentan-2-ol, 3-methylpentan-1-ol, 3-Methylpentan-2-ol, 3-Methylpentan-3-ol, 2,2-Dimethylbutan-l-ol, 3,3-Dimethylbutan-l-ol, 3,3-Dimethylbutan-2-ol, 2,3-Dimethylbutan-l-ol, 2,3-dimethylbutan-2-ol, 2-ethylbutan-l-ol, 4-methylpentan-2-ol, cyclohexanol, phenol, 2-ethylhexan-l-ol or a mixture of two or more of the aforementioned chemolysis alcohols.

9. A process according to any one of claims 1 to 7, wherein the chemolysis alcohol is selected from (i) an aliphatic secondary or tertiary monoalcohol, (ii) an aliphatic primary monoalcohol which is bonded to two or three further C atoms at a C atom in the ß-position or y-position to the hydroxy group of the monoalcohol, or (iv) a mixture of two or more of the aforementioned chemolysis alcohols.

10. The process according to claim 9, wherein the chemolysis alcohol is selected from sec-butanol, iso-butanol, iso-amyl alcohol (3-methyl-l-butanol), neo-pentanol (2,2-dimethyl-l-propanol), 2-methyl-l-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol and 2-ethylhexanol.

11. A process according to any one of the preceding claims, wherein the isocyanate component is an isocyanate selected from Phenyl isocyanate, toluene diisocyanate, the di- and polyisocyanates of the diphenylmethane series, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, diisocyanatodicyclohexylmethane, xylylene diisocyanate, para-phenylene diisocyanate or a mixture of two or more of the aforementioned isocyanates.

12. A process according to any one of the preceding claims, wherein the alcohol component comprises a mono- and / or polyol selected from a polyether monool, a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol, a polycarbonate polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols.

13. A process according to any one of the preceding claims, wherein step (B) is carried out in a temperature range of 150°C to 270°C.

14. A process according to any one of the preceding claims, wherein in (B) m(chemolysis alcohol) / m(urethane) is adjusted to 0.50 to 4.5 or 1.0 to 4.

5.

15. Use of a monoalcohol having a boiling point at 1013 mbar of not more than 200 °C, which is selected from (i) an aliphatic secondary or tertiary monoalcohol, (ii) an aliphatic primary monoalcohol which is linked to a C-atom in the ß- or y-position to the hydroxy group of the monoalcohol with two or three further C atoms, (iii) an aromatic monoalcohol or (iv) a mixture of two or more of the aforementioned monoalcohols, as a chemolysis alcohol in a chemolysis of a urethane based on an isocyanate component and an alcohol component in a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol) / m(urethane), in the range from 0.50 to 15 to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, to reduce the formation of by-products in which an organic radical is bonded to a nitrogen atom via an aliphatic carbon atom.

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