Urethane cracking method

Abstract

The invention relates to a method for the chemical cleavage of urethane esters, in particular polyurethanes, by reaction (alcoholysis) with chemically decomposed alcohols. The process is characterized in that a (poly) urethane is reacted with a chemically decomposed alcohol having a boiling point of no more than 200 DEG C at 1013 mbar, the mass ratio of chemically decomposed alcohol to urethane being set in the range of 0.50 to 15, and a chemically decomposed product comprising urethane is obtained, the chemically decomposed alcohol being selected from (i) aliphatic secondary or tertiary (preferably secondary) monohydric alcohols, (ii) aliphatic secondary or tertiary (preferably secondary) monohydric alcohols, (ii) aliphatic secondary or tertiary (preferably secondary) monohydric alcohols, (ii) aliphatic secondary or tertiary (preferably secondary) monohydric alcohols, and (ii) aliphatic secondary or tertiary (preferably secondary) monohydric alcohols; (ii) an aliphatic primary monohydric alcohol bonded to two or three further carbon atoms at the (at least one) carbon atom at the beta or gamma (preferably beta) position of the monohydric alcohol hydroxyl group, (iii) an aromatic monohydric alcohol or (iv) a mixture of two or more of the above chemically decomposed alcohols.

Description

[0001] The present invention relates to a method for chemically cleaving urethanes, in particular polyurethanes, by reaction with a chemical decomposition alcohol. The method is characterized in that (poly)urethane is reacted with a chemical decomposition alcohol having a boiling point of not more than 200° C. at 1013 mbar, wherein the mass ratio of chemical decomposition alcohol to urethane is set at 0.50 to 15, and a chemical decomposition product containing carbamate is obtained, wherein the chemical decomposition alcohol is selected from: (i) aliphatic secondary or tertiary (preferably secondary) monoalcohols; (ii) aliphatic primary monoalcohols bonded to (at least one) carbon atom in the β-position or γ-position (preferably the β-position) of the monoalcohol hydroxyl group and to two or three additional carbon atoms; (iii) aromatic monoalcohols; or (iv) a mixture of two or more of the aforementioned chemical decomposition alcohols.

[0002] Urethanes are products with a wide range of uses. Polyurethanes in particular have a wide range of applications in industry and everyday life. In the case of polyurethanes, they are usually divided into polyurethane foams and so-called "CASE" products, where "CASE" is a general term for polyurethane coatings (such as paints), adhesives, sealants and elastomers. Polyurethane foams are usually divided into rigid foams and flexible foams. Although these products are different, what they all have in common is the polyurethane basic structure, which is formed by polyaddition reactions of polyfunctional isocyanates and polyols. For example, taking a polyurethane based on a diisocyanate O=C=NRN=C=O and a diol HO-R'-OH (where R and R' represent organic groups), its basic structure can be expressed as

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

[0004] Simple (non-polymeric) urethanes are also characterized by urethane bonds. Polyurethanes are the most economically significant of all urethanes.

[0005] Many polyurethanes contain other structural units in addition to the polyurethane base structure, including in particular urea, isocyanurate, allophanate and biuret structural units.

[0006] Because of the huge economic benefits of polyurethane in particular, a large amount of polyurethane waste (for example from old mattresses, seats or insulation materials) is generated, which must be sent for rational use. The most technically feasible recycling method is incineration, so that the released combustion heat can be used for other processes, such as industrial production processes. However, this method cannot achieve a closed-loop circulation of raw materials. Another recycling method is so-called "physical recycling", in which polyurethane waste is mechanically crushed and used to produce new products. This recycling method naturally has limitations, so people have been trying to recycle the raw materials based on polyurethane production by re-cracking urethane bonds (and optionally additional bond structures, such as isocyanurate bonds, urea bonds, allophanate bonds or biuret bonds) (so-called "chemical recycling"). The raw materials to be recycled mainly include polyols (i.e. HO-R'-OH in the above example) or their degradation products (such as the monomers based on polyester polyols). In addition, amines (i.e., H2N-R-NH2 in the above example) can be obtained by hydrolytic cleavage of the urethane bond, which can be phosgenated to form isocyanates (i.e., O=C=NRN=C=O in the above example) after post-treatment.

[0007] In the past, a variety of chemical recovery methods have been developed. The three most important methods are briefly summarized below:

[0008] 1. Urethane hydrolysis by reaction with water to give amines and polyols with formation of carbon dioxide.

[0009] 2. Glycolysis of the urethane by reaction with an alcohol, wherein the polyol incorporated into the urethane group is replaced by the alcohol used and thereby released. This process is generally referred to in the literature as transesterification (more precisely: transurethane transesterification). Regardless of the specific nature of the alcohol used, this mode of chemical recovery is referred to in the literature as glycolysis, although this term is actually only applied to diols or diol derivatives. (Thus, in the present invention, the term "alcoholysis" is generally used.) The glycolysis can be followed by a hydrolysis. If the hydrolysis is carried out using the direct process product of the glycolysis (i.e. without prior separation of the polyol and the urethane), it is called

[0010] 3. Aqueous diololysis of the urethane bond by reaction with alcohol and water (hydroalcoholysis). Of course, alcohol and water can also be added from the beginning, wherein the diololysis and hydrolysis processes described above are carried out simultaneously.

[0011] Simón, Borreguero, Lucas and A review article in Waste Management 2018, 76, 147–171 [1] summarizes known polyurethane recycling methods.

[0012] WO 2022 / 171586 A1 describes a method for recovering raw materials (i.e., polyols and, optionally, additional amines) from polyurethane foam, comprising chemical decomposition. This chemical decomposition is characterized in that the polyurethane foam is reacted with an alcohol and water in the presence of a catalyst at a temperature of 130°C to 195°C, wherein the mass ratio of the alcohol (total amount) on the one hand and the water (total amount) to the polyurethane foam on the other hand is 0.5 to 2.5, and the mass of the water is 4.0% to 10% of the mass of the alcohol. The catalyst comprises a metal salt selected from carbonates, bicarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, or mixtures of two or more of these metal salts.

[0013] WO 2023 / 285545 A1 describes a method for recovering polyurethanes, wherein the polyurethane is reacted with a first alcohol, and the low molecular weight carbamate generated here or in a further aminoester exchange with a second alcohol is thermally cracked into the alcohol based on and the isocyanate based on. Particularly preferred first and / or second alcohols are propanol, amyl alcohol, isopropanol, butanol, hexanol, nonanol, octanol, glycerol, ethylene glycol, diethylene glycol and triethylene glycol. In an embodiment, a polyurethane flexible foam is reacted once with octanol (foam to alcohol mass ratio of 1:2, reflux in a device operated at normal pressure) and once with isopropanol (foam to alcohol mass ratio of 1:5, in a pressure reactor with an argon pressure of 30 bar).

[0014] EP 3590999 B1 describes a process for the degradation of plastics using methanol or ethanol in the presence of methoxide catalysts. The examples describe the degradation of flexible polyurethane foams.

[0015] US Pat. No. 4,316,992 describes a method for recovering polyether polyols from polyurethane foam. In this method, 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 monohydric or polyhydric alcohols with a boiling point of 225°C to 280°C. These alcohols can be linear, branched, cyclic, or aromatic. Diols or triols with ether bridges are preferred, especially diethylene glycol, dipropylene glycol, dibutylene glycol, glycerol, and propylene glycol, with diethylene glycol being particularly advantageous. The use of only diethylene glycol (Examples 1 and 2), glycerol (Example 3), and 1,6-hexanediol (Example 4) is actually demonstrated. The patent document does not provide any information on the relationship between the choice of alcohol and the formation of by-products.

[0016] US Patent No. 4,336,406 describes the hydrolysis of polyurethane foams, wherein the polyurethane foam is dissolved in an alcohol at a temperature of 225°C to 280°C and then reacted with water (here, liquid water) at a temperature of 185°C to 220°C. Suitable alcohols are described as saturated alcohols with a boiling point of 225°C to 280°C, with diethylene glycol being preferred. However, in this case, the patent document does not reveal any correlation between the choice of alcohol and the formation of by-products.

[0017] US Pat. No. 5,104,932 describes a method for obtaining an improved bitumen composition or bitumen composition containing a polymer residue. For this purpose, partial alcoholysis (e.g. with tert-butyl alcohol), hydrolysis or hydroalcoholysis of polyurethane and / or polyester waste is disclosed, followed by reaction of the resulting polymer residue with molten bitumen and / or bitumen.

[0018] US2016 / 0145409 A1 describes a method for recovering organic fibers from a composite material comprising a polymer matrix and organic fibers. The method comprises reacting the composite material in an alcohol-water mixture. The polymer is preferably an epoxy resin or a phenolic resin. Equal volumes of water and alcohol are preferably used, and the alcohol is preferably selected from methanol, ethanol, n-propanol, isopropanol, glycerol, or mixtures thereof.

[0019] DE 4217024 A1 describes a process for recovering polyols from polyurethane plastics, polyurethaneurea plastics and / or polyurea plastics, wherein the plastics are reacted with difunctional and / or polyfunctional alcohols and water. Only diols are described as alcohols.

[0020] EP 0601596 A1 describes a process for recovering polyols from polyurethane foams by glycolysis. This process is characterized in that the primary amines produced during the glycolysis due to the presence of urea bonds in the polyurethane foam are converted into secondary amines by an alkoxylation reaction.

[0021] WO 2010 / 130652 A2 describes a process for the hydrolysis of isocyanate adducts, which in this publication are understood to mean in particular residues from isocyanate production processes (e.g., distillation residues from toluene diisocyanate production). The hydrolysis is carried out in the presence of imidazole. If the isocyanate adduct is a residue from isocyanate synthesis (= not a polyurethane), it can be contacted with a primary or secondary alcohol before the hydrolysis.

[0022] 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 chemical decomposition of polyurethane with tert-amyl alcohol to directly form amines, which are precursors of isocyanates used in polyurethane synthesis. The proposed reaction mechanism is that the polyurethane used is first thermally re-cleaved into isocyanates and polyols, and the isocyanates thus formed react with amyl alcohol to form carbamates as intermediates. The carbamates react and eliminate 2-methyl-1-butene and 2-methyl-2-butene to form unstable carbamic acid, from which amines are then generated and carbon dioxide is released. The reaction is carried out at a temperature of 200 to 225°C, with a mass ratio of alcohol to polyurethane of 16. The influence of the choice of chemical decomposition alcohol on the formation of N-alkylated by-products is not discussed.

[0023] Of the chemical recycling processes known from the literature, only a few are in continuous operation on an industrial scale; many have not even reached pilot scale [1]. In view of the general growing environmental awareness and the increasing efforts to make industrial processes as sustainable as possible – both of which are fundamentally referred to as chemical recycling – it is clear that the chemical recycling of polyurethane products is still far from mature from a technical and economic point of view. The purity of the recycled products is particularly challenging. The recycled polyols must be as free as possible from amine impurities so that they do not adversely affect the foaming properties when used again, for example, in the production of polyurethane foam. If another goal is to recover the amines, then of course the highest possible purity must also be obtained. In addition, the polyurethane products to be reused usually still contain various auxiliary agents and additives (stabilizers, catalysts, flame retardants, etc.), which must be separated from the actual target product of the recovery and disposed of in an economically viable and environmentally friendly manner. In addition, an economically operating recycling process must ensure that the reagents used (e.g. the alcohols used) can be recovered and reused (i.e. recycled) as completely as possible. Recycling of polyurethane foam is particularly important due to the large volume of polyurethane waste generated after use (e.g., in mattresses, chairs, car seats, insulation, etc.).

[0024] Another important aspect is avoiding the formation of by-products during the chemical decomposition process. Interfering by-products can be N-alkylated compounds in particular. Such compounds can be formed, for example, during the industrial production of di- and polyamines from the diphenylmethane series (amine precursors for di- and polyisocyanates from the diphenylmethane series). It is known that an increased concentration of N-alkylated products leads to an increased HC value in the resulting isocyanates. Fixed HC limits apply depending on the area of ​​use of the isocyanates. Consequently, even if the ratio of N-alkylated groups to free amine groups in the substrate stream is not significantly below 1%, conventional phosgenation reactions are generally unsuitable, as the product stream would no longer meet the necessary specifications. Chemical recycling of aromatic amines from polymer waste streams can create additional reaction pathways for the formation of N-alkylated compounds. The resulting by-products can have correspondingly negative effects on the phosgenation process. This aspect has not been adequately considered in the prior art.

[0025] Therefore, further improvements are needed in the field of chemical decomposition of urethanes (especially polyurethanes), in particular, to suppress the formation of N-alkylated compounds during the chemical decomposition process as much as possible.

[0026] Taking this requirement into account, the present invention provides a process for chemically decomposing (=chemically cleaving) urethanes (in particular polyurethanes) based on an isocyanate component and an alcohol component to form an isocyanate of the isocyanate component and a carbamate of the chemically decomposition alcohol by reaction with a chemically decomposition alcohol.

[0027] In particular, to obtain raw materials for the production of chemical products,

[0028] The method comprises the following steps:

[0029] (A) Provide urethane and

[0030] (B) chemically decomposing the urethane from (A) with a chemical decomposition alcohol in the presence or absence of a chemical decomposition catalyst, wherein the boiling point of the chemical decomposition alcohol at 1013 mbar does not exceed 200° C. (preferably 82° C. to 200° C., more preferably 82° C. to 185° C.), and wherein the mass ratio of chemical decomposition alcohol to urethane, m(chemical decomposition alcohol) / m(urethane), is set to 0.50 to 15 (the chemical decomposition alcohol is therefore present in a stoichiometric excess relative to the urethane groups), to form a chemical decomposition product comprising urethane,

[0031] The chemical decomposition alcohol is selected from (i) aliphatic secondary or tertiary (preferably secondary) monoalcohols, (ii) aliphatic primary monoalcohols bonded to two or three additional carbon atoms at (at least one) carbon atom in the β-position or γ-position (preferably β-position) of the hydroxyl group of the monoalcohol, (iii) aromatic monoalcohols or (iv) mixtures of two or more of the above chemical decomposition alcohols.

[0032] Surprisingly, it has been found that the formation of N-alkylated by-products can be suppressed or even completely prevented by using the above-mentioned branched monoalcohols as chemical decomposition agents.

[0033] Therefore, the present invention further provides for the use of a monohydric alcohol having a boiling point of not more than 200° C. (preferably from 82° C. to 200° C., more preferably from 82° C. to 185° C.) at 1013 mbar as a chemical decomposition alcohol in the chemical decomposition (chemical cleavage) of urethanes (in particular polyurethanes) based on an isocyanate component and an alcohol component to form an isocyanate of the isocyanate component and a carbamate of the chemical decomposition alcohol for reducing the formation of N-alkylated by-products, i.e. by-products.

[0034] (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol bonded to (at least one) carbon atom in the beta or gamma position (preferably the beta position) to the hydroxyl group of the monoalcohol to two or three further carbon atoms, (iii) an aromatic monoalcohol, or (iv) a mixture of two or more of the above monoalcohols,

[0035] wherein the mass ratio of chemical decomposition alcohol to urethane, m(chemical decomposition alcohol) / m(urethane), is from 0.50 to 15, preferably from 0.75 to 10, more preferably from 1.0 to 5.0 (thus, the chemical decomposition alcohol is present in a stoichiometric excess relative to the urethane groups),

[0036] In the by-product, the (at least one) organic group is bonded to the nitrogen atom via an aliphatic carbon atom, in particular an aliphatic carbon atom originating from the chemical decomposition of the alcohol or an alcohol component.

[0037] All aspects described about the method of the present invention (such as the preferred chemical decomposition alcohol, temperature, pressure, amount ratio of raw materials, etc.) are of course also applicable to the purposes of the present invention and will not be mentioned separately below in order to avoid unnecessary repetition.

[0038] According to the present invention, the mass ratio of chemical decomposition alcohol to urethane is at least 0.50:1 and at most 15:1, preferably at least 0.75:1 and at most 10:1, more preferably 1.0:1 and at most 5.0:1.

[0039] In the terminology of the present invention, the term "isocyanate" encompasses all isocyanates known in the professional field of urethane chemistry. The expression "isocyanate" naturally also encompasses embodiments in which two or more different isocyanates (e.g., a mixture of MDI and TDI) are used in the production of (poly)urethane, unless otherwise expressly stated, such as the expression "exactly one isocyanate". The sum of all isocyanates used in the production of (poly)urethane is referred to as the isocyanate component of the (poly)urethane. This isocyanate component contains at least one isocyanate. Similarly, the sum of all mono- or polyols used in the production of (poly)urethane is referred to as the alcohol component of the (poly)urethane. This alcohol component contains at least one mono- or polyol.

[0040] In the terminology of the present invention, the term "monool or polyol" encompasses all monools or polyols known in the field of urethane chemistry. The expression "monool" or "polyol" naturally also encompasses embodiments in which two or more different monools or polyols are used in the production of urethane. Thus, if, for example, "polyether polyol" (or "polyester polyol", etc.) is mentioned below, this term naturally also encompasses embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) are used in the production of (poly)urethane.

[0041] In the terminology of the present invention, the carbon atom bearing the monohydric alcohol hydroxyl group is referred to as the alpha carbon atom. The next carbon atom is located in the beta position to the hydroxyl group, the next carbon atom is located in the gamma position, and so on.

[0042] The chemical decomposition of the aminoester from (A) and the chemical decomposition alcohol is carried out with a mass ratio m (chemical decomposition alcohol) / m (aminoester) of chemical decomposition alcohol to aminoester of 0.50 to 15. The mass ratio m (chemical decomposition alcohol) / m (aminoester) can take any value within this range, including endpoint values. A smaller selection range in 0.50 to 15 can also be adopted, such as 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. A selection range drawn by combining the above upper and lower limits can also be adopted, 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. Any selection range of the mass ratio m (chemical decomposition alcohol) / m (aminoester) can be combined with any other embodiment / configuration / variant of the present invention.

[0043] In the terminology of the present invention, carbamate refers to the urethane formed by the reaction with the chemical decomposition alcohol in the chemical decomposition to distinguish it from the urethane used. This terminology is chosen only to simplify the discussion.

[0044] The amine corresponding to isocyanate refers to an amine that can be phosgenated to give isocyanate according to R-NH2+COCl2→RN=C=O+2HCl.

[0045] In another embodiment described below, the chemical decomposition according to the invention is carried out in the absence of a chemical decomposition catalyst. In the context of the present invention, this means that only the chemical decomposition alcohol is added to the (poly)urethane to be cracked, without the addition of a chemical decomposition catalyst. It is known that, for example, polyurethane foams may still contain residual components of a blowing catalyst (e.g., tertiary amines). The presence of such catalysts originating from the original use of the (poly)urethane to be cracked does not constitute a deviation from the scope of this embodiment of the invention. In this regard, it is only important that no additional catalyst is added (more precisely: no compound that catalyzes the chemical decomposition, i.e., a chemical decomposition catalyst, is added) by way of the catalyst originating from the original use of the (poly)urethane to be cracked, which is present anyway in some cases. This example was carried out using a model urethane that does not contain the above-mentioned blowing catalyst.

[0046] First, a brief overview of various possible embodiments of the present invention is given:

[0047] In a first embodiment of the invention, which is combinable with all other embodiments except those not providing for the isolation of the carbamate, the process comprises step (c):

[0048] (C) Separating the carbamate formed in (B) from the chemical decomposition products using organic solvent extraction (optionally with addition of water) and / or solid-liquid phase separation, wherein a liquid alcohol phase (especially a polyol phase) is obtained in addition to the carbamate.

[0049] In a second embodiment of the invention, which is a special configuration of the first embodiment, the carbamate separated in (C), optionally after purification, is further reacted in step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions:

[0050] (DI) hydrolyzing the carbamate in the presence or absence of a hydrolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0051] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0052] (D.III) cleaving a carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0053] (D.IV) reacting the urethane with a polyol in the presence or absence of a catalyst to give a further OH-terminated urethane, in particular - if the urethane from step (A) is a polyurethane - to give an OH-terminated prepolymer.

[0054] In a third embodiment of the invention, which is combinable with all other embodiments except those not providing for the isolation of the carbamate, the process additionally comprises the following steps:

[0055] (B1) hydrolyzing the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemical decomposition product obtained in (B) with water, thereby obtaining a hydrolyzate mixture; and

[0056] (CI) Extracting the hydrolyzate mixture with an organic (especially halogenated) solvent to obtain an amine phase and a liquid alcohol phase (especially a polyol phase).

[0057] In a fourth embodiment of the invention, which is combinable with all embodiments providing for the hydrolysis of carbamates, said hydrolysis is carried out in the presence of a hydrolysis catalyst comprising

[0058] (I) an (organic or inorganic) Brønsted base selected from: (i) a hydroxide (especially sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (especially an alkali metal carbonate, for example sodium carbonate or potassium carbonate), (iii) a hydrogen carbonate (especially an alkali metal hydrogen carbonate, such as sodium hydrogen carbonate or potassium hydrogen carbonate), (iv) an orthophosphate or a metaphosphate, preferably an orthophosphate (especially an alkali metal phosphate or an alkali metal hydrogen phosphate), or (v) a mixture of two or more of the aforementioned Brønsted bases,

[0059] and / or

[0060] (II) an aminase, in particular one of the aminases described in EP 3587570 A1.

[0061] In a fifth embodiment of the invention, which is a special configuration of the second embodiment, step (D.II) is carried out, wherein the hydrogenolysis catalyst comprises copper, palladium (in particular Pd / C, PdCl2 or Pd(OAc)2), nickel (in particular Raney nickel), manganese (in particular an Mn complex with a tridentate chelating ligand bound via P and N donor atoms and CO and / or halogen ligands) or platinum (in particular platinum(IV) oxide).

[0062] In a sixth embodiment of the present invention, which is a further particular configuration of the second embodiment, step (D.III) is performed wherein the cleavage of the carbamate is performed in the presence of a carbamate cleavage catalyst comprising

[0063] (I) Metal-free or metal-containing Bronsted or Lewis acidic catalysts

[0064] or

[0065] (II) Metal-free or metal-containing Brønsted basic or Lewis basic catalysts.

[0066] In a seventh embodiment of the present invention, which is a further specific configuration of the second embodiment, step (D.IV) is performed wherein the reaction of the urethane with the polyol is carried out in the presence of a catalyst comprising

[0067] Carbonates, bicarbonates, hydroxides, orthophosphates, monohydrogen orthophosphates, metaphosphates, orthovanadates (where all of the above chemical decomposition catalysts are preferably used in the form of their sodium or potassium salts), titanium alkoxides (in particular tetra-n-butyl titanate, Ti(O-nBu)4), tertiary amines (in particular 1,4-diazabicyclo(2.2.2)octane, "DABCO"), cesium fluoride, stannates (in particular dibutyltin dilaurate, "DBTL", or monobutyltin oxide, n-Bu-Sn(O)OH, "MBTO") or mixtures of two or more of the above chemical decomposition catalysts.

[0068] In an eighth embodiment of the present invention, which can be combined with all embodiments comprising step (C) or (CI), the liquid alcohol phase from (C) or (CI) is distilled and / or stripped in step (E) to obtain (at least one) chemical product selected from (i) alcohols of the alcohol component and / or (ii) reaction products formed by the chemical decomposition of alcohols of the alcohol component in (B).

[0069] In a ninth embodiment of the invention, which can be combined with all the embodiments as long as they do not provide for a catalytic performance of step (B), the chemical decomposition of the urethane, in particular the polyurethane, is carried out in the absence of a chemical decomposition catalyst.

[0070] In a tenth embodiment of the invention, which can be combined with all embodiments (as long as they do not provide for the non-catalytic implementation of step (B)), the chemical decomposition of the urethane (in particular the polyurethane) is carried out in the presence of a chemical decomposition catalyst, wherein the chemical decomposition catalyst comprises a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, an orthovanadate (wherein all of the above chemical decomposition 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"), a 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 above chemical decomposition catalysts.

[0071] In an eleventh embodiment of the invention, which is combinable with all embodiments except the embodiment excluding the use of an aromatic chemical decomposition alcohol, the chemical decomposition alcohol is selected from the group consisting of isopropyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 2-pentanol, 3-pentanol, isopentanol (3-methyl-1-butanol), 2-methyl-2-butanol, neopentyl alcohol (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-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2,3-dimethylbutan-1-ol, 2,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, 4-methylpentan-2-ol, cyclohexanol, phenol, 2-ethylhexan-1-ol or a mixture of two or more of the above chemically decomposed alcohols. (Preferred are isopropanol, sec-butanol, isobutanol, 2-pentanol, 3-pentanol, isopentanol (3-methyl-1-butanol), neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 3-methyl-2-butanol, pentaerythritol, 2-methyl-1-butanol, cyclopentanol, hexan-2-ol, hexan-3-ol, 2-methylpentan-1-ol, 2-methylpentan-3-ol, 4-methylpentan-2-ol, 3-methylpentan-1-ol, 3-methylpentan-2-ol, 2,2-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2,3-dimethylbutan-1-ol, 2-ethylbutan-1-ol, 4-methylpentan-2-ol, cyclohexanol, phenol, and 2-ethylhexanol.)

[0072] In a twelfth embodiment of the process according to the invention, which is combinable with all embodiments except the embodiment providing for the use of an aromatic chemical decomposition alcohol, the chemical decomposition alcohol is selected from: (i) an aliphatic secondary or tertiary (preferably secondary) monoalcohol, (ii) an aliphatic primary monoalcohol bonded to (at least one) carbon atom in the beta position or gamma position (preferably the beta position) to the hydroxyl group of the monoalcohol to two or three additional carbon atoms, or (iv) a mixture of two or more of the aforementioned chemical decomposition alcohols.

[0073] In a thirteenth embodiment of the present invention, which is a specific configuration of the twelfth embodiment, the chemical decomposition alcohol is selected from the group consisting of sec-butanol, isobutanol, isopentanol (3-methyl-1-butanol), neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol, and 2-ethylhexanol. (Preferred are isopropanol, 2-butanol, neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, isopentanol (3-methyl-1-butanol), 2-ethyl-1-butanol, and cyclohexanol. Particularly preferred are isopropanol, 2-butanol, neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 2-ethyl-1-butanol, and cyclohexanol.)

[0074] In a fourteenth embodiment of the invention, which may be combined with all embodiments, the isocyanate component comprises an isocyanate selected from the group consisting of:

[0075] Phenyl isocyanate (PHI; can be produced by phosgenation of aniline ANL), toluene diisocyanate (TDI; can be produced by phosgenation of toluenediamine TDA), diisocyanates and polyisocyanates of the diphenylmethane series (MDI; can be produced by phosgenation of diamines and polyamines MDA of the diphenylmethane series), 1,5-pentane diisocyanate (PDI; can be produced by phosgenation of 1,5-pentanediamine PDA), 1,6-hexamethylene diisocyanate (HDI; can be produced by phosgenation of 1,6-hexamethylenediamine HDA), isophorone diisocyanate (IPDI; can be produced by phosgenation of isophoronediamine IPDA), diisocyanatodicyclohexylmethane ("saturated methylene diphenyl diisocyanate", HDI) 12 MDI, especially the 4,4' isomer; can be obtained by diaminodicyclohexylmethane H 12 Preparation of MDA by phosgenation, diaminodicyclohexylmethane H 12MDA (which can in turn be prepared by ring hydrogenation of bicyclic MDA), xylylenediisocyanate (XDI; which can be prepared by phosgenation of xylylenediamine XDA), p-phenylene diisocyanate (PPDI; which can be prepared by phosgenation of p-phenylenediamine), or a mixture of two or more of the above isocyanates. (The isocyanate component preferably comprises toluene diisocyanate, diisocyanates and polyisocyanates of the diphenylmethane series, or a mixture of toluene diisocyanate and diisocyanates and polyisocyanates of the diphenylmethane series, and in particular does not include any other isocyanates other than the above.)

[0076] In a fifteenth embodiment of the present invention, which may be combined with all embodiments, the alcohol component comprises monohydric and / or polyhydric alcohols selected from the group consisting of:

[0077] Polyether monools, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polycarbonate polyols, polyether carbonate polyols, or mixtures of two or more of the foregoing polyols. (Preferably, the alcohol component comprises a polyester polyol, a polyether polyol, and / or a polyether ester polyol, more preferably a polyether polyol. Most preferably, the alcohol component is a polyether polyol (i.e., it does not contain any other monools or polyols other than polyether polyols; however, mixtures of two or more different polyether polyols are also contemplated and do not depart from the scope of this embodiment).)

[0078] In a sixteenth embodiment of the invention, which may be combined with all embodiments, the urethane is a polyurethane.

[0079] In a seventeenth embodiment of the invention, which can be combined with all embodiments, step (B) is carried out in a temperature range of 150° C. to 270° C., preferably 170° C. to 250° C., more preferably 180° C. to 230° C. and in a pressure range of 1.0 bar (in particular ambient pressure) to 85 bar (wherein pressure and temperature are particularly matched to one another so that the chemical decomposition can be carried out under reflux of the selected chemical decomposition alcohol).

[0080] In an eighteenth embodiment of the invention, which can be combined with all embodiments, the mass ratio of chemical decomposition alcohol to urethane is selected so that the molar ratio n(chemical decomposition alcohol) / n(urethane groups) (n=molar amount) is from 4.5 to 30, preferably from 5.0 to 20, more preferably from 8.5 to 15. If desired, the molar amount of urethane groups n(urethane groups) can be determined by hydrolyzing a sample of the urethane provided in (A) and then determining the amine value by titration with 0.1 molar perchloric acid.

[0081] In a nineteenth embodiment of the invention, which can be combined with all embodiments, the chemical decomposition in step (B) is carried out in a reactor which is inertized with an inert gas, in particular nitrogen, before the start of the chemical decomposition, wherein preferably an inert gas partial pressure of 1.0 bar (in particular ambient pressure) to 20 bar, preferably to 10 bar, is set.

[0082] In a twentieth embodiment of the invention, which can be combined with all embodiments, the mass ratio of chemical decomposition alcohol to urethane in (B) m(chemical decomposition alcohol) / m(urethane) (m=mass) is set to 0.50 to 4.5, in particular 0.50 to 4.0, or 1.0 to 4.5, in particular 1.0 to 4.0.

[0083] The embodiments briefly described above and other possible configurations of the present invention are described in more detail below. Unless otherwise apparent to those skilled in the art from the context, or otherwise explicitly stated, all of the above embodiments and other configurations of the present invention described below may be combined with each other as needed.

[0084] Providing (poly)urethane for chemical recycling

[0085] In step (A), the (poly)urethane to be chemically recovered is provided in preparation for chemical decomposition. In principle, it can be any type of urethane.

[0086] Polyurethanes are preferred, i.e., urethanes derived from polyisocyanates (containing two or more isocyanate groups per molecule) and polyols (containing two or more alcohol groups per molecule). In principle, these can be any type of polyurethane, including, for example, polyurethane foams and polyurethane products for so-called CASE applications, as described at the outset. Polyurethane foams can be both flexible and rigid foams, with flexible foams (e.g., from old mattresses, furniture pads, or car seats) being preferred. Polyurethane foams are typically produced using a blowing gas such as pentane or carbon dioxide. Polyurethane elastomers, polyurethane adhesives, and polyurethane coatings are preferred for CASE applications.

[0087] Preferred are urethanes or polyurethanes wherein the isocyanate component comprises an isocyanate selected from the group consisting of,

[0088] Phenyl isocyanate (PHI; can be produced by phosgenation of aniline ANL), toluene diisocyanate (TDI; can be produced by phosgenation of toluenediamine TDA), diisocyanates and polyisocyanates of the diphenylmethane series (MDI; can be produced by phosgenation of diamines and polyamines MDA of the diphenylmethane series), 1,5-pentane diisocyanate (PDI; can be produced by phosgenation of 1,5-pentanediamine PDA), 1,6-hexamethylene diisocyanate (HDI; can be produced by phosgenation of 1,6-hexamethylenediamine HDA), isophorone diisocyanate (IPDI; can be produced by phosgenation of isophoronediamine IPDA), diisocyanatodicyclohexylmethane ("saturated methylene diphenyl diisocyanate", HDI) 12 MDI, especially the 4,4' isomer; can be obtained by diaminodicyclohexylmethane H 12 Phosgenation of MDA to produce diaminodicyclohexylmethane H 12 MDA, in turn, can be obtained by ring hydrogenation of bicyclic MDA), xylylenediisocyanate (XDI; producible by phosgenation of xylylenediamine XDA), p-phenylene diisocyanate (PPDI; producible by phosgenation of p-phenylenediamine PPDA) or a mixture of two or more of the aforementioned isocyanates.

[0089] For polyurethanes, it is particularly preferred that the isocyanate component comprises toluene diisocyanate, diisocyanates and polyisocyanates of the diphenylmethane series or a mixture of toluene diisocyanate and diisocyanates and polyisocyanates of the diphenylmethane series, and in particular does not comprise any other isocyanates than those mentioned above.

[0090] As for the alcohol component, it preferably comprises monohydric alcohols and / or polyhydric alcohols selected from the group consisting of:

[0091] Polyether monools, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polycarbonate polyols, polyether carbonate polyols or mixtures of two or more of the above polyols.

[0092] The alcohol component preferably comprises polyester polyols, polyether polyols and / or polyetherester polyols, more preferably polyether polyols. Most preferably, the alcohol component is a polyether polyol (i.e., does not contain any other monohydric alcohols or polyols other than polyether polyols; however, a mixture of two or more different polyether polyols may be included without departing from the scope of this embodiment).

[0093] The polyether polyol may also be a polyether polyol filled with a styrene-acrylonitrile copolymer (SAN copolymer).

[0094] Preferably, step (A) already includes preparatory steps for the cleavage of the urethane bonds in step (B). For polyurethanes, these include, in particular, mechanical comminution. Such preparatory steps are known to those skilled in the art; for example, reference is made to the literature cited in [1]. Depending on the properties of the polyurethane (especially polyurethane foam), it may be advantageous to "freeze" it before mechanical comminution to facilitate the comminution operation.

[0095] It is also conceivable to carry out the above-mentioned preparation steps at a location spatially separate from the chemical decomposition site. In this case, the prepared foam is loaded into a suitable transport vehicle (e.g., a silo transport vehicle) for further transportation. For further transportation, the prepared foam can be additionally compressed to achieve a higher mass-to-volume ratio. At the chemical decomposition site, the foam is then loaded into the reaction device for the chemical decomposition. It is also conceivable to connect the transport vehicle directly to the reaction device.

[0096] Chemical decomposition of (poly)urethane

[0097] The chemical decomposition of (poly)urethane, i.e. step (B), is preferably carried out under oxygen-free conditions. This means that the reaction is carried out in an inert gas atmosphere (especially in a nitrogen, argon or helium atmosphere). In addition, the chemical decomposition alcohol used is preferably deoxygenated by saturation with an inert gas.

[0098] The chemical decomposition is carried out at a reaction temperature of 150°C to 270°C, preferably 170°C to 250°C, and more preferably 180°C to 230°C. The chemical decomposition is preferably carried out in a pressure-resistant reactor (autoclave) without pressure equalization, in particular so that the reaction is run under "reflux" (the chemical decomposition alcohol evaporates, condenses in the cooler areas of the reactor, and flows back into the reaction mixture). During this process, the pressure generated in the gas phase above the liquid reaction mixture corresponds to the vapor pressure of the chemical decomposition alcohol used at the current temperature, i.e., depending on the nature of the chemical decomposition alcohol and the temperature, the pressure is approximately 1.0 bar to 85 bar (absolute pressure). Alternatively, the chemical decomposition can also be carried out under pressure equalization, i.e., at ambient pressure. The reactor used for the chemical decomposition is preferably inertized with an inert gas (especially nitrogen) before the start of the chemical decomposition. The inert gas preferably sets an inert gas partial pressure of 1.0 bar (especially ambient pressure) to 20 bar, preferably to 10 bar (absolute pressure).

[0099] Suitable reactors are, for example, stirred tank reactors, which can also be operated continuously. It is also possible to employ cascades of a plurality of continuously operated stirred tank reactors, optionally with a downstream tubular reactor (especially operated with plug flow).

[0100] According to the present invention, the mass ratio of chemical decomposition alcohol to (poly)urethane is 0.50 to 15 (e.g., 0.50 to 4.5 or 1.0 to 4.5 or 0.50 to 4.0 or 1.0 to 4.0). Thus, the amount of chemical decomposition alcohol is successfully limited, which is very advantageous from a process engineering perspective (lower cost, lower post-processing complexity). With respect to the molar ratio, it is generally superstoichiometric at the mass ratio to ensure complete reaction. The mass ratio is preferably selected within the above range to ensure a molar excess of chemical decomposition alcohol (i.e., the molar ratio n (chemical decomposition alcohol) / n (urethane groups), wherein n = molar amount) of 4.5 to 30, more preferably 5.0 to 20, and most preferably 8.5 to 15. If the molar amount of urethane groups is unknown (e.g., because a polyurethane of unknown origin is to be reused), it can be easily determined by hydrolyzing a representative sample of the (poly)urethane provided in (A) and determining the amine value of the hydrolyzate. Since one mole of urethane groups is released per mole of amine cleaved, the amine value can be used to determine the molar amount of urethane groups. The specific manner in which the hydrolysis is carried out will of course depend on the nature of the (poly)urethane. With the help of the information summarized in [1] and the literature references, a person skilled in the art can easily find a suitable process scheme.

[0101] The amine value indicates how many milligrams of potassium hydroxide are required to neutralize the free organic amines present in 1 gram of a substance. This covers primary, secondary, and tertiary amino groups. Amino groups are weak bases. The solvent used is concentrated acetic acid (glacial acetic acid, 99% to 100% strength). The amine is protonated by the solvent and is thus converted into the corresponding acid, which now exists as an ion pair with the deprotonated acid of the glacial acetic acid. Subsequently, the titrant is titrated with 0.1 molar perchloric acid, where the perchloric acid replaces the anion of the solvent (glacial acetic acid). The perchloric acid consumed in this process is equal to the amount of potassium hydroxide consumed. The amine value is usually expressed in milligrams of potassium hydroxide per gram of analyzed sample and is calculated as follows:

[0102]

[0103] in

[0104] AZ represents amine value,

[0105] V represents the volume of perchloric acid solution consumed,

[0106] m represents the mass of the titration sample,

[0107] M(KOH) represents the molar mass of KOH (56.11 g·mol –1 ),

[0108] b i represents the molar concentration of perchloric acid solution,

[0109] f represents the dimensionless factor (titer) of the perchloric acid solution.

[0110] According to the present invention, the chemical decomposition alcohol is selected from the group consisting of: (i) aliphatic secondary or tertiary (preferably secondary) monoalcohols, (ii) aliphatic primary monoalcohols bonded to two or three further carbon atoms at (at least one) carbon atom in the β- or γ-position (preferably β-position) to the hydroxyl group of the monoalcohol, (iii) aromatic monoalcohols, or (iv) mixtures of two or more of the aforementioned chemical decomposition alcohols. The present invention also provides the use of such chemical decomposition alcohols in the chemical decomposition (chemical cleavage) of urethanes (in particular polyurethanes) based on an isocyanate component and an alcohol component to form an isocyanate of the isocyanate component and a carbamate of the chemical decomposition alcohol, for reducing the formation of by-products in which (at least one) organic group is bonded to a nitrogen atom via an aliphatic carbon atom (in particular an aliphatic carbon atom originating from the chemical decomposition alcohol or the alcohol component).

[0111] Suitable chemical decomposition alcohols are preferably isopropanol, sec-butanol, isobutanol, tert-butanol, 2-pentanol, 3-pentanol, isopentanol (3-methyl-1-butanol), 2-methyl-2-butanol, neopentyl alcohol (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-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2,3-dimethylbutan-1-ol, 2,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, 4-methylpentan-2-ol, cyclohexanol, phenol, 2-ethylhexan-1-ol or a mixture of two or more of the above chemically decomposed alcohols. Particular preference is given to isopropanol, sec-butanol, isobutanol, 2-pentanol, 3-pentanol, isopentanol (3-methyl-1-butanol), neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 3-methyl-2-butanol, pentaerythritol, 2-methyl-1-butanol, cyclopentanol, hexan-2-ol, hexan-3-ol, 2-methylpentan-1-ol, 2-methylpentan-3-ol, 4-methylpentan-2-ol, 3-methylpentan-1-ol, 3-methylpentan-2-ol, 2,2-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2,3-dimethylbutan-1-ol, 2-ethylbutan-1-ol, 4-methylpentan-2-ol, cyclohexanol, phenol and 2-ethylhexanol.

[0112] Among the non-aromatic chemical decomposition alcohols generally used with preference, preference is given to sec-butanol, isobutanol, isopentanol (3-methyl-1-butanol), neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol, and 2-ethylhexanol. Particular preference is given to isopropanol, 2-butanol, neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, isopentanol (3-methyl-1-butanol), 2-ethyl-1-butanol, and cyclohexanol, and very particular preference is given to isopropanol, 2-butanol, neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 2-ethyl-1-butanol, and cyclohexanol.

[0113] The chemical decomposition can (but does not necessarily) be carried out in the presence of a catalyst. In one embodiment, the addition of a chemical decomposition 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 (wherein all of the above chemical decomposition catalysts are preferably used in the form of their sodium or potassium salts), a titanium alkoxide (especially tetra-n-butyl titanate, Ti(O-nBu)4), a tertiary amine (especially 1,4-diazabicyclo(2.2.2)octane, "DABCO"), a cesium fluoride, a stannate (especially dibutyltin dilaurate, "DBTL", or monobutyltin oxide n-Bu-Sn(O)OH, "MBTO") or a mixture of two or more of the above chemical decomposition catalysts.

[0114] Post-treatment of chemical decomposition products

[0115] The chemical decomposition results in chemical decomposition products comprising carbamates. For the post-processing of the chemical decomposition products, the following procedure is preferably employed: in step (C), the carbamate formed in step (B) is separated from the chemical decomposition products by extraction with an organic solvent, optionally with addition of water, and / or by solid-liquid phase separation, wherein a liquid alcohol phase (especially a polyol phase) is obtained in addition to the carbamate. Excess chemical decomposition alcohol is removed by distillation before or after the separation, preferably before the separation.

[0116] Separation by solid-liquid phase separation is limited to carbamates formed in solid form from the chemical decomposition products (optionally after cooling). Whether this is the case depends on the specific properties of the carbamate, in particular the properties of the (poly)urethane to be cleaved. However, extractive separation can be used in any case. In principle, it is known in the prior art to separate alcohols (especially polyols) and carbamates present in the form of a mixture with each other in the alcoholysis products by extractive methods. For example, reference can be made to international patent applications WO 2020 / 260387 A1 (using very non-polar organic solvents, such as especially hydrocarbons) and WO 2022 / 063764 A1 (using organic solvents of medium polarity, such as especially halogenated hydrocarbons, in combination with aqueous washing liquids).

[0117] In the process of the present invention, halogen-substituted (especially chlorinated) organic solvents, such as halogen-substituted aliphatic hydrocarbons, halogen-substituted alicyclic hydrocarbons, halogen-substituted aromatic hydrocarbons, or mixtures of two or more of the above organic solvents, can be used; non-halogenated solvents, such as aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, or mixtures of two or more of the above organic solvents can also be used. In some cases, the choice of solvent depends on the specific circumstances, in particular the properties of the (poly)urethane to be cleaved, and can be determined by a person skilled in the art by simple preliminary experiments as needed.

[0118] If the carbamate is isolated by extraction, it is obtained as a solution and, depending in particular on the nature of the (poly)urethane used and the type of organic solvent used, is dissolved in the extraction solvent, or (as described in WO 2020 / 260387 A1) in an excess of a chemical decomposition alcohol, or (as described in WO 2022 / 063764 A1) in an aqueous phase (which is obtained after addition of an aqueous washing liquid during the extraction process). Depending on the desired further processing of the carbamate, this solution can be used further directly. However, the carbamate can also be easily isolated from this solution by evaporation of the solvent and / or crystallization.

[0119] The carbamate thus obtained can now, optionally after purification, be reacted further in step (D) to obtain the chemical product, wherein (D) comprises one of the following reactions:

[0120] (DI) hydrolyzing the carbamate in the presence or absence of a hydrolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0121] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0122] (D.III) cleaving a carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0123] (D.IV) reacting the urethane with a polyol in the presence or absence of a catalyst to give a further OH-terminated urethane, in particular when the starting urethane is a polyurethane, to give an OH-terminated prepolymer.

[0124] The reactions (DI) to (D.IV), ie hydrolysis, hydrogenolysis, carbamate cleavage and transcarbamylase, are per se well known in the prior art and are therefore only briefly outlined here.

[0125] The hydrolysis of (DI) gives an 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 the uses known in the technical field for such amines and, in particular, can be phosgenated again to give the corresponding isocyanates. The isocyanates thus obtained can then be fed back into the production of (poly)urethanes. The hydrolysis can be assisted by the use of hydrolysis catalysts. The following catalysts are particularly suitable:

[0126] (I) an (organic or inorganic) Brønsted base selected from: (i) a hydroxide (especially sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (especially an alkali metal carbonate, for example sodium carbonate or potassium carbonate), (iii) a hydrogen carbonate (especially an alkali metal hydrogen carbonate, such as sodium hydrogen carbonate or potassium hydrogen carbonate), (iv) an orthophosphate or a metaphosphate, preferably an orthophosphate (especially an alkali metal phosphate or an alkali metal hydrogen phosphate), or (v) a mixture of two or more of the aforementioned Brønsted bases,

[0127] and / or

[0128] (II) an aminase, in particular one of the aminases described in EP 3587570 A1.

[0129] The amine corresponding to the isocyanate of the isocyanate component can also be obtained by hydrogenolysis of the carbamate of (D.II) with hydrogen. Hydrogenative Depolymerization of Polyurethanes Catalyzed by Manganese Pincer Complex, Viktoriia Zubar et al., published in ChemSusChem 2022, 15, e202101606 [2] describes a method that starts directly from polyurethane and is also applicable to this step (D.II). Reference is also made to the literature cited in [2]. Possible uses of amines are the same as outlined in (DI). Preferably, hydrogenolysis is assisted by the use of a catalyst. Suitable hydrogenolysis catalysts are, in particular, catalysts comprising the following substances:

[0130] Palladium (especially Pd / C, PdCl2 or Pd(OAc)2), copper, nickel (especially Raney nickel), manganese (especially Mn complexes with tridentate chelating ligands bound via P and N donor atoms and CO and / or halogen ligands) or platinum (especially platinum(IV) oxide).

[0131] The post-treatment variants (DI) and (D.II) thus give amines corresponding to the isocyanates of the isocyanate component. These amines can be used for all purposes known in the art; in particular, they can be phosgenated and used to produce novel (poly)urethanes.

[0132] However, it is also conceivable to obtain the isocyanate of the isocyanate component directly from the carbamate by cleaving the carbamate into the isocyanate of the isocyanate component and a chemical decomposition alcohol (carbamate cleavage of (D.III)). In the catalytic embodiment, suitable carbamate cleavage catalysts are in particular:

[0133] (I) Metal-free or metal-containing Bronsted acidic catalysts or Lewis acidic catalysts

[0134] or

[0135] (II) Metal-free or metal-containing Bronsted basic catalysts or Lewis basic catalysts.

[0136] For more detailed information, refer to W. Leitner et al., Carbon 2 Polymer–Chemical Utilization of CO 2 in the Production of Isocyanates, Chapter 4, “Carbamate Cleavage”, published in Chem. Ing. Tech. 2018, 90, 1504–1512 and the references cited therein.

[0137] The post-treatment variant (D.III) directly provides 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. The urethane cleavage variant (D.III) is particularly preferred, especially when the isocyanate component of the urethane or polyurethane comprises, in particular consists of, toluene diisocyanate (TDI) (i.e., contains no other isocyanates besides TDI).

[0138] (D.IV) Another possibility for further processing the carbamate is to react the carbamate from step (C) with a polyol to form further OH-terminated carbamates. From a chemical point of view, this is a transurethrization reaction and is therefore, in principle, the same type of reaction on which polyurethane diolization is also based (in this respect, see the literature cited above, especially the review article [1]). This method is particularly advantageous when the carbamate provided in step (A) is a polyurethane. For this purpose, the carbamate is reacted with a polyol, the OH groups of the polyol being used in a stoichiometric or superstoichiometric amount, in particular a slight superstoichiometric amount (e.g. a molar excess of 5% to 10%), relative to the carbamate functional groups present. If the starting carbamate is a polyurethane (which is preferred), the reaction forms OH-terminated prepolymers. These prepolymers can be used for all purposes known in the art; in particular, they can be used as prepolymers for flexible and rigid foam applications, thermoplastic polyurethanes, coatings, and adhesives.

[0139] The boiling point of the polyol used in step (D.IV) is preferably higher than the boiling point of the chemical decomposition alcohol used. In a particularly preferred embodiment, during the reaction with the polyol, the chemical decomposition alcohol is continuously removed from the reaction mixture by distillation. The reaction can optionally be carried out in the presence of a catalyst. The latter preferably includes carbonates, bicarbonates, hydroxides, orthophosphates, monohydrogen orthophosphates, metaphosphates, orthovanadates (wherein all of the above catalysts are preferably used in the form of their sodium or potassium salts), titanium alkoxides (particularly tetra-n-butyl titanate, Ti(O-nBu) 4 ), tertiary amines (particularly 1,4-diazabicyclo(2.2.2)octane, “DABCO”), cesium fluoride, stannates (particularly dibutyltin dilaurate, “DBTL”, or monobutyltin oxide, n-Bu-Sn(O)OH, “MBTO”) or a mixture of two or more of the above catalysts.

[0140] Typical suitable polyols are diols (especially 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, methylpentanediol (e.g. 3-methyl-1,5-pentanediol), 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, bis(hydroxymethyl)cyclohexane (e.g. 1,4-bis(hydroxymethyl)cyclohexane), triethylene glycol, The polyols used in step (D.IV) may also be polyether polyols, in particular polyether polyols having a number-average molar mass Mn, determined according to DIN 55672-1 (2016-03), of 18 to 8000 g / mol and a functionality (calculated based on the H-functional starter used to prepare the polyether polyol) of 2 to 3. The polyether polyols are preferably formed from repeating ethylene oxide and propylene oxide units, the proportion of propylene oxide units being preferably 35% to 100%, more preferably 50% to 100%. They may be random copolymers, gradient copolymers, alternating copolymers or block copolymers of ethylene oxide and propylene oxide.

[0141] In all four variants, the chemical decomposition alcohol used is released again and can be recovered by distillation and used again in the chemical decomposition.

[0142] The higher the selectivity of carbamate formation in step (B), the more advantageous the aforementioned variants for further processing of the carbamate are. This is particularly true for variant (D.III), in which the isocyanate is obtained without forming an amine intermediate. However, even in other variants, it may be advantageous to conduct carbamate formation as selectively as possible, as this often facilitates subsequent post-processing, especially the separation of the individual components of the chemical decomposition product. Therefore, a reaction that reduces selectivity is particularly the direct ("uncontrolled") formation of amines in step (B). To suppress amine formation, it is therefore preferred to use a chemical decomposition alcohol with the lowest possible water content. It is particularly preferred that the chemical decomposition alcohol used has a water content of no more than 0.500% by mass, preferably no more than 0.200% by mass, more preferably no more than 0.050% by mass, and most preferably no more than 0.005% by mass, based on its total mass. This can be achieved, if necessary, by drying measures known per se. In the present invention, the mass of the chemical decomposition alcohol refers in each case to the total mass including any water present. If desired, the water content of the chemical decomposition alcohol can be determined by Karl-Fischer titration; this is a key method for the purposes of the present invention. The Karl-Fischer titration method has been described many times and is well known to those skilled in the art. The various possible configurations of the basic principle of the Karl-Fischer titration method generally provide results with sufficiently good consistency within the scope of the present invention. In case of doubt, the Karl-Fischer titration method described in DIN 51777 Part 1 (March 1983) is crucial for the purposes of the present invention.

[0143] If the recovery of the carbamate is not essential for the desired (poly)urethane recovery, the chemical decomposition product formed in step (B) can also be hydrolyzed directly, i.e. without isolating the carbamate formed. In this case, step (B) comprises a step (B1) of hydrolyzing the carbamate formed in step (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemical decomposition product obtained in (B) with water, thereby obtaining a hydrolyzate mixture. In this case, the post-treatment comprises a step (C1) of extracting the hydrolyzate mixture with an organic (especially halogenated) solvent to obtain an amine phase and a liquid alcohol phase (especially a polyol phase). Suitable organic (especially halogenated) solvents are the same as those described above for the extraction of the carbamate.

[0144] Therefore, in principle, there are two possible approaches to the post-processing of the chemical decomposition products according to the present invention: first, obtaining the carbamate and then further processing it and the resulting liquid alcohol phase separately; second, direct hydrolysis of the chemical decomposition products. Therefore, with regard to the post-processing of the chemical decomposition products, the method according to the present invention comprises:

[0145] (a) step (C) of separating the carbamate formed in (B) from the chemical decomposition products by extraction with an organic solvent, optionally with addition of water, and / or solid-liquid phase separation, wherein a liquid alcohol phase (in particular a polyol phase) is obtained in addition to the carbamate, wherein preferably, the carbamate separated in (C) is further reacted in step (D), optionally after purification, to obtain a chemical product, wherein (D) comprises one of the following reactions:

[0146] (DI) hydrolyzing the carbamate in the presence or absence of a hydrolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0147] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0148] (D.III) cleaving a carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0149] (D.IV) reacting the carbamate with a polyol in the presence or absence of a catalyst to obtain a further OH-terminated carbamate;

[0150] Among them, variants (DI), (D.II) and (D.IV) are preferred, variant (DI) is particularly preferred; or

[0151] (β) a step (BI) of hydrolyzing the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the chemical decomposition product obtained in (B) with water, thereby obtaining a hydrolyzate mixture, and a step (CI) of extracting the hydrolyzate mixture with an organic (particularly halogenated) solvent to obtain an amine phase and a liquid alcohol phase (particularly a polyol phase).

[0152] The liquid alcohol phase from (C) or (CI) is preferably distilled and / or stripped in step (E) to obtain a chemical product selected from (i) an alcohol of the alcohol component and / or (ii) a reaction product formed by chemically decomposing the alcohol of the alcohol component in (B). The alcohol and / or reaction product thus obtained can be used for all purposes known in the art for such compounds. In particular, the recovered polyether polyol can be used to produce new polyurethanes, and the polyester polyol reaction product can be used to produce new polyester polyols.

[0153] The above invention will be described in more detail below through examples. Example:

[0154] Chemicals

[0155]

[0156] analyze

[0157] GC method

[0158] Samples were quantitatively evaluated using gas chromatography with a flame ionization detector (GC-FID). An Agilent 8890 GC system was used, equipped with an SSL inlet (275°C, split ratio 80:1, constant flow rate 5 mL / min), an HP-5 GC column (30 m, 320 μm inner diameter, 0.25 μm film thickness), and H2 as the carrier gas. At the start of the measurement, the temperature was held constant at 60°C for 0.5 minutes and then increased to 300°C at a rate of 20°C / min. Once this temperature was reached, it was maintained at 300°C for an additional 10 minutes. The solvent used was tetrahydrofuran (THF).

[0159] GC yield and conversion were calculated using the following formula with tetradecane as internal standard:

[0160]

[0161] m i = mass of substance i

[0162] m intStd = internal standard mass

[0163] A i = Area integral of substance i

[0164] A intStd = Area integral of internal standard

[0165] kf = correction factor (FID response factor)

[0166] This method was used to quantitatively determine the mass ratios of 2-ethoxyethyl N-phenylcarbamate (substrate; see below), the target carbamate, and aniline, assuming a kf of 1 for the N-alkylated aniline derivative.

[0167] Experimental part

[0168] The model reaction chosen is 2-ethoxyethyl N-phenylcarbamate

[0169]

[0170] (hereinafter referred to as substrate) reacts with various chemical decomposition alcohols to generate corresponding aminoester exchange products (hereinafter referred to as target carbamate).

[0171] Synthesis of 2-ethoxyethyl N-phenylcarbamate

[0172] A 250 mL round-bottom flask was initially charged with 2-ethoxyethanol (59.8 g, 64.3 mL, 0.66 mol, 6.00 equiv). Phenylisocyanate (13.2 g, 12.1 mL, 0.11 mol, 1.00 equiv) was added rapidly under stirring (500 rpm) at room temperature. The reaction solution was then stirred at 100°C for 4.5 hours. After the reaction solution cooled to room temperature, CHCl₃ (approximately 60 mL) was added, and the mixture was extracted with deionized water (3 x 50 mL). The organic phase was washed with saturated brine and dried over MgSO₄. Volatile components were removed under reduced pressure, and 2-ethoxyethyl N-phenylcarbamate was then dried under high vacuum for 72 hours and isolated as a pale yellow viscous liquid (16.7 g, 72.2%).

[0173] Alcoholysis reaction in autoclave

[0174] In the glass insert that magnetic stirring apparatus is housed, pack catalyzer (optional (see Table 1 and 2), 28mg, based on the total mass meter 1.0 quality % of substrate and chemical decomposition alcohol), substrate (700mg), chemical decomposition alcohol (2.1g) and internal standard tetradecane (20mg), put into stainless steel autoclave (capacity 20mL) then.Purge three times with N2 (setting the nitrogen pressure of 50 bar, then decompress to ambient pressure) and close, then by adding nitrogen pressure is increased to 10 bar.Autoclave is heated 4 hours down at 200 ℃ under stirring (900 rev / min) in preheating aluminum cone.Subsequently, autoclave is cooled 10 minutes in ice bath, decompression then.Dilute reaction mixture with THF (2mL), filter by syringe filter (Chromafil O-20 / 15MS), and analyze by GC-FID.

[0175] Examples 1 to 36

[0176] Table 1 below summarizes the results of the alcoholysis reactions.

[0177] Table 1: Alcoholysis of diol-based urethanes using different chemical decomposition alcohols at 200°C and reaction times ranging from 120 to 360 minutes [a]

[0178]

[0179]

[0180] Table 2: Alcoholysis of ethylene glycol-based urethanes using different chemical decomposition alcohols at 200-220°C and reaction times of 240-480 minutes (higher temperatures and longer reaction times compared to Table 1)[a]

[0181]

[0182] Description of the table:

[0183] [a] Substrate: Ph-NH-CO-O-(CH2)2-OEt; the mass ratio of the chemical decomposition alcohol to the substrate is 3:1. If a catalyst is used, the catalyst amount is 1.0% by mass based on the total mass of the substrate and the chemical decomposition alcohol. In the case of the uncatalyzed reaction with methanol (Example 1), the reaction conditions were optimized to maximize the yield of the target carbamate.

[0184] [b] The percentage of the molar amount of substrate or target carbamate or aniline in the product relative to the amount of substrate used:

[0185] Y 底物 =(100%·[n(substrate) 产物 / n(substrate) 使用 ]or

[0186] Y ZC =100%·[n(target carbamate) 产物 / n(substrate) 使用 ]or

[0187] Y 苯胺 =100% · [n(aniline 产物 / n(substrate) 使用 ].

[0188] [c] Multiply the quotient of (i) and (ii) by 100

[0189] (i) Detected N-alkylated aniline derivatives R 1 R 2 The total area percentage (GC) of NC6H5 (where R 1 is the alkyl portion of the chemically decomposed alcohol or the (CH2)2-OEt group from the substrate, R 2 is hydrogen, the alkyl portion of a chemically decomposed alcohol, or a (CH2)2-OEt group from a substrate, where R 1 Can also be used with R 2 same)

[0190] (ii) The sum of the area percentages (GC) of the detected N-alkylated aniline derivatives, free aniline, substrate, and target carbamate.

[0191] [d] V = comparative example.

[0192] As shown in the examples in Tables 1 and 2, the use of simple linear C1 to C4 alcohols leads to the formation of N-alkylated by-products (Examples 1 to 6). The use of isopropyl alcohol instead of n-propyl alcohol results in a reduction of N-alkylated by-products to zero (Examples 7 and 8). Even at longer reaction times and higher reaction temperatures, no N-alkylation was observed with the alcohols of the present invention, regardless of whether other catalysts were used (Table 2).

[0193] Even though the reaction conditions were not optimized and the reaction time was even shortened by half compared to Example 2, the use of methyl- and ethyl-substituted butanols in the presence of a catalyst still resulted in a good yield of the target carbamate in the product mixture of about 90%, and likewise without N-alkylation (Examples 14, 16, and 18). Using isopropanol, comparable yields were achieved even without the use of a catalyst (Example 7).

[0194] Ethylene glycol, which is conventionally used as the chemical decomposition alcohol, produces large amounts of N-alkylated by-products and cannot be used under the chosen reaction conditions (Examples 21 and 22).

Claims

1. A method for chemically decomposing a urethane based on an isocyanate component and an alcohol component by reacting with a chemical decomposition alcohol to form an isocyanate of the isocyanate component and a urethane of the chemical decomposition alcohol, comprising the following steps: (A) Provide urethane and (B) chemically decomposing the urethane from (A) with a chemical decomposition alcohol in the presence or absence of a chemical decomposition catalyst, wherein the boiling point of the chemical decomposition alcohol at 1013 mbar is not more than 200° C., and wherein the mass ratio of the chemical decomposition alcohol to the urethane, m(chemical decomposition alcohol) / m(urethane), is set to 0.50 to 15, to form a chemical decomposition product comprising a urethane, The chemical decomposition alcohol is selected from (i) aliphatic secondary or tertiary (preferably secondary) monoalcohols, (ii) aliphatic primary monoalcohols bonded to two or three additional carbon atoms at (at least one) carbon atom in the β-position or γ-position (preferably β-position) of the hydroxyl group of the monoalcohol, (iii) aromatic monoalcohols or (iv) mixtures of two or more of the above chemical decomposition alcohols.

2. The method according to claim 1, comprising: (C) Separation of the carbamate formed in (B) from the chemical decomposition products using organic solvent extraction and / or solid-liquid phase separation, wherein a liquid alcohol phase is obtained in addition to the carbamate.

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

4. The method according to claim 1, comprising the steps of: (BI) hydrolyzing the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the chemical decomposition product obtained in (B) with water to obtain a hydrolyzate mixture; as well as (CI) The hydrolyzate mixture is extracted with an organic solvent to obtain an amine phase and a liquid alcohol phase.

5. The process according to claim 2 , wherein in step (E), the liquid alcohol phase from (C) or (CI) is subjected to distillation and / or stripping to obtain chemical products selected from (i) alcohols of the alcohol component and / or (ii) reaction products formed from the alcohols of the alcohol component in the chemical decomposition (B).

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

7. The process according to any one of claims 1 to 5, wherein the chemical decomposition of the urethane is carried out in the presence of a chemical decomposition catalyst, wherein the chemical decomposition catalyst comprises a carbonate, a bicarbonate, a hydroxide, an orthophosphate, a monohydrogen orthophosphate, a metaphosphate, an orthovanadate, a titanium alkoxide, a tertiary amine, cesium fluoride, a stannate, or a mixture of two or more of the foregoing chemical decomposition catalysts.

8. The method according to any one of claims 1 to 7, wherein the chemical decomposition alcohol is selected from the group consisting of isopropyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 2-pentanol, 3-pentanol, isopentanol (3-methyl-1-butanol), 2-methyl-2-butanol, neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, cyclopentanol, hexanol, hexanol, 2-methylpentan-2-ol, 2-methylpentan-3-ol, 2-methylpentan-1-ol, 2-methylpentan-2-ol, 2-methylpentan-3-ol. -methylpentan-3-ol, 4-methylpentan-2-ol, 3-methylpentan-1-ol, 3-methylpentan-2-ol, 3-methylpentan-3-ol, 2,2-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2,3-dimethylbutan-1-ol, 2,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, 4-methylpentan-2-ol, cyclohexanol, phenol, 2-ethylhexan-1-ol or a mixture of two or more of the above chemically decomposed alcohols.

9. The process according to any one of claims 1 to 7, wherein the chemical decomposition alcohol is selected from: (i) aliphatic secondary or tertiary monoalcohols, (ii) aliphatic primary monoalcohols bonded to two or three additional carbon atoms at the carbon atom in the beta or gamma position of the monoalcohol hydroxyl group, or (iv) a mixture of two or more of the above chemical decomposition alcohols.

10. The method according to claim 9, wherein the chemical decomposition alcohol is selected from the group consisting of sec-butyl alcohol, isobutyl alcohol, isopentanol (3-methyl-1-butanol), neopentyl alcohol (2,2-dimethyl-1-propanol), 2-methyl-1-butanol, cyclopentanol, 4-methylpentan-2-ol, cyclohexanol and 2-ethylhexanol.

11. The method according to any one of the preceding claims, wherein the isocyanate component comprises an isocyanate selected from the group consisting of Phenyl isocyanate, toluene diisocyanate, diisocyanates and polyisocyanates of the diphenylmethane series, pentane-1,5-diisocyanate, hexamethylene-1,6-diisocyanate, isophorone diisocyanate, diisocyanatodicyclohexylmethane, xylylene diisocyanate, p-phenylene diisocyanate or mixtures of two or more of the aforementioned isocyanates.

12. The method according to any one of the preceding claims, wherein the alcohol component comprises a monohydric alcohol and / or a polyhydric alcohol selected from the group consisting of: Polyether monools, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polycarbonate polyols, polyether carbonate polyols or mixtures of two or more of the above polyols.

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

14. The method according to any one of the preceding claims, wherein m(chemical decomposition alcohol) / m(urethane) in (B) is set to 0.50 to 4.5 or 1.0 to 4.

5.

15. Use of a monohydric alcohol having a boiling point of not more than 200° C. at 1013 mbar as a chemical decomposition alcohol in the chemical decomposition of a urethane based on an isocyanate component and an alcohol component to form an isocyanate of the isocyanate component and a urethane of the chemical decomposition alcohol for reducing the formation of by-products (i) an aliphatic secondary or tertiary monoalcohol, (ii) an aliphatic primary monoalcohol bonded to two or three additional carbon atoms at the carbon atom in the beta or gamma position relative to the hydroxyl group of the monoalcohol, (iii) an aromatic monoalcohol, or (iv) a mixture of two or more of the foregoing monoalcohols, wherein the mass ratio of chemical decomposition alcohol to urethane, m(chemical decomposition alcohol) / m(urethane), is 0.50 to 15, In the by-product, the organic group is bonded to the nitrogen atom via an aliphatic carbon atom.

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