Cracking method of (poly) urethane

Abstract

The invention relates to a method for the chemical decomposition of a urethane based on an isocyanate component and an alcohol component, in particular a polyurethane, by reaction with a chemically decomposed alcohol to form an isocyanate of the isocyanate component and a urethane of the chemically decomposed alcohol, in particular for obtaining a starting material for the production of chemical products, wherein the urethane is chemically decomposed with a chemically decomposed alcohol at a temperature of 185 DEG C to 245 DEG C in the absence of a chemical decomposition catalyst, and the chemically decomposed alcohol is selected from the group consisting of unbranched monoalcohols having 1 to 4 carbon atoms, and wherein the mass ratio of the chemically decomposed alcohol to the urethane is 1.0 to 4.5.

Description

[0001] The present invention relates to the chemical decomposition of urethanes (in particular polyurethanes) based on an isocyanate component and an alcohol component by reaction with a chemical decomposition alcohol to form an isocyanate of the isocyanate component and a carbamate of the chemical decomposition alcohol, in particular a process for obtaining starting materials for producing chemical products, wherein the urethane is chemically decomposed with the chemical decomposition alcohol at a temperature of 185° C. to 245° C. in the absence of a chemical decomposition catalyst, and the chemical decomposition alcohol is selected from unbranched monohydric alcohols having 1 to 4 carbon atoms, wherein the mass ratio of chemical decomposition alcohol to urethane is 1.0 to 4.5.

[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 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).

[0013] 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.

[0014] 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 demonstrated.

[0015] US Patent No. 4,336,406 describes the hydrolysis of polyurethane foams, wherein the polyurethane foam is dissolved in an alcohol at 225° C. to 280° C. and then reacted with water (here, liquid water) at 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.

[0016] 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.

[0017] 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.

[0018] The article Methanolysis investigation of commercially available polyurethane foam by N.Asahi et al. in Polymer Degradation and Stability 2004, 86, 147–151 describes the methanolysis of polyurethane at temperatures ranging from 160 to 305°C and pressures up to 15 MPa, where the methanol is partially in a supercritical state. The aim of this study was to perform methanolysis on commercially available polyurethane foam without the use of a catalyst. This study investigated

[0019] Chemical decomposition of model polyurethane 1

[0020]

[0021] and commercially available polyurethane foam Chemical decomposition at a methanol to polyurethane mass ratio of 5:1 (i.e., m(methanol / m(polyurethane)=5) or 16:1 (i.e., m(methanol / m(polyurethane)=16). The article concludes that at temperatures above 200°C, polyurethane can be successfully decomposed into methyl carbamate in a high proportion, while a catalyst is required at lower temperatures.

[0022] The article "tert-Amyl Alcohol-Mediated Deconstruction of Polyurethane for Polyol and Aniline Recovery" by Martin B.Johansen et al. in ACSSustainable 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 about 16:1 (i.e., m(methanol / m(polyurethane)=16).

[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 to carry out the chemical decomposition with the highest possible economic feasibility.For example, it is desirable to reduce the amount of the chemical decomposition reagent (which, of course, also serves as a solvent) as much as possible and to avoid the use of other substances, such as catalysts, as much as possible.

[0025] The selection of the chemical decomposition process to be used depends, among other factors, on the primary raw materials to be recovered. If the focus is on recovering polyols, as described in numerous publications on the subject, a chemical decomposition method can be employed in which low-molecular-weight carbamates do not even appear as intermediates or are immediately cleaved into the parent amine and alcohol, such as by hydrolysis or hydrolysis. Conversely, if further raw materials are desired in addition to polyols, it may be advantageous to generate low-molecular-weight carbamates in a targeted and as selective a manner as possible and to separate them from the polyols in the highest possible purity. The most selective formation of low-molecular-weight carbamates involves suppressing side reactions that generate carbonates rather than carbamates and directly release the amine corresponding to the originally used isocyanate. The targeted and selective formation of carbamates allows for further processing in forms other than hydrolysis to amines. Even when hydrolysis to amines is the goal, separating the carbamates that appear as intermediates before hydrolysis may be advantageous, for example, when carbamates and polyols are easier to separate than amines and polyols. To date, the prior art has not adequately considered this aspect.

[0026] Therefore, further improvements are needed in the field of chemical decomposition of urethanes, especially polyurethanes. It is particularly desirable to be able to achieve the highest possible selectivity for cleaving the urethane bonds, so that low molecular weight urethanes are primarily formed from low-boiling alcohols and the parent amines of the (poly)urethanes. Furthermore, it is desirable to be able to carry out the chemical decomposition with the highest possible economic viability with respect to the consumption of reagents (i.e., raw materials and auxiliaries, especially catalysts).

[0027] 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.

[0028] In particular, a method for obtaining starting materials for producing chemical products,

[0029] The method comprises the following steps:

[0030] (A) Provide urethane and

[0031] (B) chemically decomposing the urethane from (A) with a chemical decomposition alcohol (without added water) at a temperature of 185° C. to 245° C., preferably 195° C. to 240° C., more preferably 205° C. to 235° C., most preferably 215° C. to 230° C. in the absence of a chemical decomposition catalyst, wherein the chemical decomposition alcohol is selected from unbranched monohydric alcohols having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, and wherein the mass ratio of chemical decomposition alcohol to urethane, m(chemical decomposition alcohol) / m(urethane) (m=mass), is set to 1.0 to 4.5, preferably 1.0 to 4.0, to form a chemical decomposition product comprising urethane.

[0032] Surprisingly, it has been found that the use of unbranched monohydric alcohols having 1 to 4 carbon atoms allows the corresponding carbamates to be formed with good selectivity (considerably improved compared to other alcohols), in particular with respect to avoiding amine formation, and correspondingly in good yields without the addition of chemical decomposition catalysts.

[0033] The present invention therefore further provides for the use of an unbranched monohydric alcohol having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, 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 at temperatures of 185° C. to 245° C., preferably 195° C. to 240° C., more preferably 205° C. to 235° C., most preferably 215° C. to 230° C., without the use of a chemical decomposition catalyst, for reducing the formation of amines corresponding to the isocyanate of the isocyanate component, wherein the mass ratio of chemical decomposition alcohol to urethane, m(chemical decomposition alcohol) / m(urethane) (m=mass), is from 1.0 to 4.5, preferably from 1.0 to 4.0.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In the context of the present invention, "in the absence of a chemical decomposition catalyst" means that only the chemical decomposition alcohol (i.e. methanol, ethanol, n-propanol and / or n-butanol) is added to the (poly)urethane to be cleaved, but not the chemical decomposition catalyst. It is known that, for example, polyurethane foams may still contain residual components of the blowing catalyst (in the case of the above For example, these components are tertiary amines and, in smaller proportions, tin and lead compounds. The presence of such catalysts originating from the original use of the (poly)urethane to be cleaved does not constitute a departure from the scope of the present invention. The only essential aspect of the present invention is that no further catalysts are added (more specifically, no compounds that catalyze chemical cleavage, i.e., no chemical cleavage catalysts), other than the catalysts that may already be present in the original use of the (poly)urethane to be cleaved, are added. This example, carried out with a model urethane that does not contain the aforementioned blowing catalyst, demonstrates that it is not the presence of such catalyst residues that enables chemical cleavage.

[0039] 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.

[0040] First, a brief overview of various possible embodiments of the present invention is given:

[0041] 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):

[0042] (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.

[0043] 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:

[0044] (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;

[0045] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0046] (D.III) cleaving the carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0047] (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.

[0048] In a third embodiment of the invention, which is combinable with all other embodiments except the embodiment providing for the isolation of carbamates, the process comprises the following steps:

[0049] (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

[0050] (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).

[0051] In a fourth embodiment of the invention, which may be combined with all embodiments providing for hydrolysis, said hydrolysis is carried out in the presence of a hydrolysis catalyst comprising

[0052] (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,

[0053] and / or

[0054] (II) an aminase, in particular one of the aminases described in EP 3587570 A1.

[0055] In a fifth embodiment, which is a special configuration of the second embodiment, step (D.II) is carried out, wherein the hydrogenolysis catalyst comprises copper, palladium (especially Pd / C, PdCl2 or Pd(OAc)2), 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).

[0056] 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

[0057] (I) Metal-free or metal-containing Bronsted or Lewis acidic catalysts

[0058] or

[0059] (II) Metal-free or metal-containing Brønsted basic or Lewis basic catalysts.

[0060] 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

[0061] 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.

[0062] 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).

[0063] In a ninth embodiment of the invention, which can be combined with all embodiments, the chemical decomposition alcohol is selected from methanol, ethanol, or a mixture of methanol and ethanol, and is in particular methanol.

[0064] In a tenth embodiment of the invention, which may be combined with all embodiments, the isocyanate component comprises an isocyanate selected from the group consisting of:

[0065] 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 12Phosgenation of MDA to produce diaminodicyclohexylmethane H 12 MDA, in turn, can be produced by ring hydrogenation of bicyclic MDA), xylylenediisocyanate (XDI; can be produced by phosgenation of xylylenediamine XDA), p-phenylene diisocyanate (PPDI; can be produced by phosgenation of p-phenylenediamine), or a mixture of two or more of the foregoing isocyanates.

[0066] 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 comprise any other isocyanates than the above-mentioned substances.

[0067] In an eleventh 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:

[0068] Polyether monool, polyether polyol, polyester polyol, polyether ester polyol, polyacrylate polyol, polycarbonate polyol, polyether carbonate polyol, or a mixture of two or more of the above polyols.

[0069] The alcohol component preferably comprises polyester polyol, polyether polyol and / or polyetherester polyol, more preferably polyether polyol. More preferably, the alcohol component is a polyether polyol (i.e., does not contain any other monohydric alcohol or polyol other than polyether polyol; however, mixtures of two or more different polyether polyols are also included without departing from the scope of this embodiment).

[0070] In a twelfth embodiment of the invention, which may be combined with all embodiments, the urethane is a polyurethane.

[0071] In a thirteenth embodiment of the invention, which can be combined with all embodiments, the chemical decomposition in step (B) is carried out in a pressure range of 5.0 bar to 100 bar (wherein pressure and temperature are particularly matched to one another so that the chemical decomposition can be carried out under reflux of the chemical decomposition alcohol).

[0072] In a fourteenth 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 25, more preferably from 8.0 to 20. 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 value by titration with 0.1 molar perchloric acid.

[0073] In a fifteenth 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.

[0074] 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.

[0075] Providing (poly)urethane for chemical recycling

[0076] In step (A), the (poly)urethane to be chemically recovered is provided in preparation for chemical decomposition. The urethane provided in step (A) is also referred to below as "starting urethane". In principle, it can be any type of urethane.

[0077] 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.

[0078] Preferred are urethanes or polyurethanes wherein the isocyanate component comprises an isocyanate selected from the group consisting of,

[0079] 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) 12MDI, especially the 4,4' isomer; can be obtained by diaminodicyclohexylmethane H 12 Phosgenation of MDA to produce diaminodicyclohexylmethane H 12 MDA, in turn, is obtainable by ring hydrogenation of bicyclic MDA), xylylenediisocyanate (XDI; producible from xylylenediamine XDA), p-phenylene diisocyanate (PPDI; producible from p-phenylenediamine PPDA) or a mixture of two or more of the aforementioned isocyanates.

[0080] 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.

[0081] As for the alcohol component, it preferably comprises monohydric alcohols and / or polyhydric alcohols selected from the group consisting of:

[0082] 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.

[0083] The alcohol component preferably comprises polyester polyols, polyether polyols and / or polyetherester polyols, more preferably polyether polyols. More preferably, the alcohol component is a polyether polyol (i.e., does not contain any other monohydric alcohol or polyol other than polyether polyol; however, a mixture of two or more different polyether polyols may be included without departing from the scope of this embodiment).

[0084] The polyether polyol may also be a polyether polyol 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). 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.

[0086] 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.

[0087] Chemical decomposition of (poly)urethane

[0088] 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.

[0089] The chemical decomposition is carried out at a reaction temperature of 185°C to 245°C, preferably 195°C to 240°C, more preferably 205°C to 235°C, and most preferably 215°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 operated 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 5.0 bar to 100 bar (absolute 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).

[0090] An example of a suitable reactor is a stirred tank reactor, which can also be operated continuously. It is also possible to use a cascade of a plurality of continuously operated stirred tank reactors. In another preferred embodiment, to complete the conversion, a portion of the liquid phase from one stirred tank reactor (in the case of a stirred tank reactor cascade, from the last stirred tank reactor in the cascade) is introduced into a downstream tubular reactor, in particular so that the reaction mixture flows through the tubular reactor with plug flow.

[0091] According to the present invention, the chemical decomposition alcohol is selected from unbranched monohydric alcohols having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms. Methanol, ethanol, or a mixture thereof is particularly preferred; methanol is very particularly preferred. The mass ratio of chemical decomposition alcohol to (poly)urethane is 1.0 to 4.5, preferably 2.0 to 4.0. This allows the amount of chemical decomposition alcohol to be limited without the addition of a chemical decomposition catalyst, which is highly advantageous from a process engineering perspective (lower costs and less complex post-processing). The molar ratio is typically superstoichiometric at the stated mass ratio to ensure complete reaction. The mass ratio is preferably selected within the aforementioned range to ensure a molar excess of chemical decomposition alcohol (i.e., the molar ratio n(chemical decomposition alcohol) / n(urethane groups), where 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., to reuse polyurethane of unknown origin), it can be easily determined by hydrolyzing a representative sample of the (poly)urethane provided in (A) and determining the amine value of the hydrolysis product. 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.

[0092] 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 KOH per gram of analyzed sample and is calculated as follows:

[0093]

[0094] in

[0095] AZ represents amine value,

[0096] V represents the volume of perchloric acid solution consumed,

[0097] m represents the mass of the titration sample,

[0098] M(KOH) represents the molar mass of KOH (56.11 g·mol –1 ),

[0099] b i represents the molar concentration of perchloric acid solution,

[0100] f represents the dimensionless factor (titer) of the perchloric acid solution.

[0101] Post-treatment of chemical decomposition products

[0102] 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.

[0103] 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 processes. 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).

[0104] 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.

[0105] If extraction is used, the carbamate is obtained as a solution; depending on the nature of the (poly)urethane used and the type of organic solvent used, it 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 type of further processing of the carbamate desired, the solution can be used directly. However, the carbamate can also be easily isolated from the solution by evaporation of the solvent and / or crystallization.

[0106] 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:

[0107] (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;

[0108] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0109] (D.III) cleaving the carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0110] (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.

[0111] 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.

[0112] 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:

[0113] (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,

[0114] and / or

[0115] (II) an aminase, in particular one of the aminases described in EP 3587570 A1.

[0116] The amine corresponding to the isocyanate of the isocyanate component can also be obtained by hydrogenolysis of the carbamate of (D.II). Hydrogenative Depolymerization of Polyurethanes Catalyzed by Manganese Pincer Complex, Viktoriia Zubar et al., published in ChemSusChem 2022, 15, e202101606 [2] describes a method starting directly from polyurethane and 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:

[0117] 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).

[0118] 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.

[0119] 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:

[0120] (I) Metal-free or metal-containing Bronsted acidic catalysts or Lewis acidic catalysts

[0121] or

[0122] (II) Metal-free or metal-containing Bronsted basic catalysts or Lewis basic catalysts.

[0123] 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.

[0124] 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, or in particular consists of, toluene diisocyanate (TDI) (i.e., contains no other isocyanates besides TDI).

[0125] Another possibility for further processing the carbamates is to react the carbamates from step (C) with polyols according to (D.IV) 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.

[0126] 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 comprises 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.

[0127] 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.

[0128] 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.

[0129] 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 can be advantageous to conduct carbamate formation as selectively as possible, as this often facilitates subsequent workup, especially the separation of the individual chemical decomposition product components. Reactions that reduce selectivity are therefore particularly those that directly ("uncontrolled") form amines in step (B).

[0130] There are three possible pathways for the formation of amines: (i) partial hydrolysis due to the presence of trace amounts of water; (ii) chemical decomposition of alcohols by reaction with urea groups (urea groups are present in small quantities, for example in water-blown polyurethane foams, in addition to urethane groups); and (iii) chemical decomposition of alcohols by reaction with urethane groups to form carbonates and release amines.

[0131] Reaction pathway (i) can be suppressed by appropriate drying measures. It is therefore preferred to use a chemical decomposition alcohol with a water content as low as possible. It is particularly preferred that the chemical decomposition alcohol used has a water content of a maximum of 0.500 mass %, preferably a maximum of 0.200 mass %, more preferably a maximum of 0.050 mass %, and most preferably a maximum of 0.005 mass %, based on its total mass. If necessary, this can be achieved by drying measures known per se. In the present invention, the mass of the chemical decomposition alcohol refers to the total mass including any water present. If necessary, 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 has been described many times and is well known to those skilled in the art. Various possible configurations of the basic principle of the Karl-Fischer titration generally provide results with sufficiently good consistency within the scope of the present invention. In case of doubt, the Karl-Fischer titration described in DIN 51777 Part 1 (March 1983) is key for the purposes of the present invention.

[0132] The importance of reaction pathway (ii) depends on the type of polyurethane raw material used; if the raw material contains urea groups, these will always also give rise to amines in the event of complete chemical decomposition (although in smaller amounts, since urethane groups are usually present in significantly more abundance than urea groups).

[0133] Without wishing to be bound by any theory, it is believed that the present invention inhibits reaction pathway (iii). This explains the experimental observation that in the practice of the present invention, the chemical decomposition of the urethane group occurs with a higher selectivity. Formation of carbamate (rather than carbonate) ester).

[0134] If the acquisition of carbamates is not essential for the desired (poly)urethane recovery, the chemical decomposition products formed in step (B) can likewise be hydrolyzed directly, i.e. without isolating the carbamates formed. In this case, step (B) comprises a step (B1) of hydrolyzing the carbamates formed in step (B) in the presence or absence of a hydrolysis catalyst to form amines by reacting the (unchanged) chemical decomposition products 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 carbamates.

[0135] 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:

[0136] (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:

[0137] (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;

[0138] (D.II) hydrogenolyzing a carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component;

[0139] (D.III) cleaving the carbamate into an isocyanate component and a chemical decomposition alcohol in the presence or absence of a carbamate cleavage catalyst; or

[0140] (D.IV) reacting the carbamate with a polyol in the presence or absence of a catalyst to obtain a further OH-terminated carbamate;

[0141] Among them, variants (DI), (D.II) and (D.IV) are preferred, and variant (DI) is particularly preferred;

[0142] or

[0143] (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).

[0144] 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.

[0145] The above invention will be described in more detail below through examples. Example:

[0146] Chemicals

[0147]

[0148]

[0149] Unless stated otherwise, the water content of the chemical splitting alcohols used was in each case from 100 to 300 ppm.

[0150] analyze

[0151] GC method

[0152] 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).

[0153] GC yield and conversion were calculated using the following formula with tetradecane as internal standard:

[0154]

[0155] m i = mass of substance i

[0156] m intStd = internal standard mass

[0157] A i = Area integral of substance i

[0158] A intStd = Area integral of internal standard

[0159] kf = correction factor (FID response factor)

[0160] This method was used to quantitatively determine the mass ratio of 2-ethoxyethyl N-phenylcarbamate (substrate; see below) and the target carbamate (for the alcohols according to the invention: MeOH, EtOH, n-PrOH, and n-BuOH; for the target carbamates of all other examples, a kf value of 1 was assumed).

[0161] Experimental part

[0162] The model reaction chosen is 2-ethoxyethyl N-phenylcarbamate

[0163]

[0164] The advantage of using a model carbamate is that the presence of urea groups can be eliminated.

[0165] Synthesis of 2-ethoxyethyl N-phenylcarbamate

[0166] 2-Ethoxyethanol (59.8 g, 64.3 mL, 0.66 mol, 6.00 equiv) was initially charged to a 250 mL round-bottom flask, and phenyl isocyanate (13.2 g, 12.1 mL, 0.11 mol, 1.00 equiv) was rapidly added 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 solution 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%).

[0167] Alcoholysis reaction in autoclave

[0168] In the glass insert of magnetic stirring apparatus is housed, catalyzer of packing (optional (see Table 1 to 3), based on the total mass meter 1.0 quality %) of substrate and chemical decomposition alcohol), substrate (700mg), chemical decomposition alcohol (with the mass ratio of substrate as shown in the table) and interior mark tetradecane (20mg), put into stainless steel autoclave (capacity 20mL) then.Use N Purge three times (setting the nitrogen pressure of 50 bar, then be decompressed to ambient pressure) and close, then by adding nitrogen pressure is increased to 10 bar.Autoclave is heated the time (seeing table) of regulation under the temperature of regulation in the aluminum cone of preheating stirring (900 rev / mins).Subsequently, autoclave was cooled 10 minutes in ice bath, decompression then.With THF (2mL) diluted reaction mixture, filter by syringe filter (Chromafil O-20 / 15MS), and analyze by GC-FID.

[0169] Examples 1 to 26

[0170] Tables 1 to 3 below summarize the results of the alcoholysis reactions.

[0171] Table 1: Alcoholysis of diol-based urethanes with various monofunctional and difunctional alcohols without catalyst [a]

[0172]

[0173] Description of the table:

[0174] [a] Substrate: Ph-NH-CO-O-(CH2)2-OMe; mass ratio of chemical decomposition alcohol to substrate: 3.0:1; reaction temperature: 200°C; reaction time: 240 min.

[0175] [b] The molar percentage of the rediscovered substrate relative to the amount of substrate used (Y 底物 =100%·[n(substrate) 重新发现 / n(substrate) 使用 ).

[0176] [c] Theoretical yield of target carbamate (ZC).

[0177] [d] The molar percentage of the amine found relative to the amount of substrate used (Y 胺 =100% [n(amine) 重新发现 / n(substrate) 使用 ).

[0178] [e] Determine the selectivity of the target carbamate (S ZC = Y ZC / [100%-Y 底物 ]).

[0179] [f] V = comparative example (inventive examples are highlighted in bold).

[0180] The experiments summarized in Table 1 show that, compared to difunctional alcohols (especially diols), significantly better selectivities for the desired target carbamates are achieved when using short-chain monofunctional alcohols for non-catalytic alcoholysis. Due to the constant mass ratio of chemical decomposition alcohol to substrate, the yield values ​​for the target carbamates are therefore lower with increasingly longer alkyl chains. However, it is crucial that the selectivity for the target carbamates remain correspondingly high for the alcohols according to the invention.

[0181] Table 2: Alcoholysis of diol-based urethanes with unbranched primary C1-C4 alcohols without and with different catalysts [a]

[0182]

[0183] Description of the table:

[0184] [a] Substrate: Ph-NH-CO-O-(CH2)2-OMe; mass ratio of chemical decomposition alcohol to substrate: 3.0:1; reaction temperature: 200°C; reaction time: 240 min. The mass proportion of catalyst used was 1.0%, based on the total mass of substrate and chemical decomposition alcohol.

[0185] [b] The molar percentage of the rediscovered substrate relative to the amount of substrate used (Y 底物 =100%·[n(substrate) 重新发现 / n(substrate) 使用 ).

[0186] [c] Theoretical yield of target carbamate (ZC).

[0187] [d] The molar percentage of the amine found relative to the amount of substrate used (Y 胺 =100% [n(amine) 发现 / n(substrate) 使用 ).

[0188] [e] Determine the selectivity of the target carbamate (S ZC = Y ZC / [100%-Y 底物 ]).

[0189] [f] V = comparative example (inventive examples are highlighted in bold).

[0190] The experiments summarized in Table 2 show that short-chain monofunctional alcohols can not only be successfully used without catalysts, but also achieve better selectivity for the target carbamate than when catalysts are used. The reaction conditions selected here were optimized for the chemical decomposition of the alcohol MeOH in order to achieve the highest possible yield of the target carbamate (i.e., the most complete reaction of the carbamate possible with the highest possible selectivity S). ZC ). Under the same conditions, for the other chemical decomposition alcohols, selectivity was at least improved compared to the catalytic reaction, and in three of the four cases, yield was also improved. Combined with the results of Table 3 (see below), it can be expected that for C2 to C4 alcohols, the conversion can be optimized by increasing the temperature proportionally without reducing the selectivity or at least without significantly reducing the selectivity, and thus, ultimately, significantly higher yields of the target carbamate can also be expected.

[0191] Table 3: Alcoholysis of diol-based urethanes with methanol at different methanol-substrate ratios and temperatures without catalyst [a]

[0192]

[0193]

[0194] Description of the table:

[0195] [a] Substrate: Ph-NH-CO-O-(CH2)2-OMe; no additional catalyst was added; reaction time: 120 min.

[0196] [b] The molar percentage of the rediscovered substrate relative to the amount of substrate used (Y 底物 =100%·[n(substrate) 重新发现 / n(substrate) 使用 ).

[0197] [c] Theoretical yield of target carbamate (ZC).

[0198] [d] Determine the selectivity of the target carbamate (S ZC = Y ZC / [100%-Y 底物 ]).

[0199] The experiments summarized in Table 3 show that the maximum selectivity of the target carbamate is achieved at about 210°C, while the maximum yield of the target carbamate is achieved at about 230°C under the given reaction conditions.

[0200] Table 4: Alcoholysis of diol-based urethanes with methanol at different methanol-substrate ratios without catalyst[a]

[0201]

[0202] Description of the table:

[0203] [a] Substrate: Ph-NH-CO-O-(CH2)2-OMe; no additional catalyst; reaction time: 120 min, temperature: 220°C, methanol water content: 5098 ppm.

[0204] [b] The molar percentage of the rediscovered substrate relative to the amount of substrate used (Y 底物 =100%·[n(substrate) 重新发现 / n(substrate) 使用 ).

[0205] [c] Theoretical yield of target carbamate (ZC).

[0206] [d] Determine the selectivity of the target carbamate (S ZC = Y ZC / [100%-Y 底物 ]).

[0207] [f] V = comparative example (inventive examples are highlighted in bold).

[0208] Table 4 shows that, under existing reaction conditions, although the conversion rate increases when using a large amount of excess chemical decomposition alcohol, the price is that the selectivity decreases significantly (the amount of aniline formed in Example 28 is 6.8 times that of Example 27). Therefore, even when using chemical decomposition alcohol with a relatively high water content, the method of the present invention can also achieve good to excellent selectivity. Drying can thus be avoided, or it can be at least made less complicated.

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 at a temperature of 185° C. to 245° C. in the absence of a chemical decomposition catalyst, wherein the chemical decomposition alcohol is selected from unbranched monohydric alcohols having 1 to 4 carbon atoms, and wherein the mass ratio of the chemical decomposition alcohol to the urethane, m(chemical decomposition alcohol) / m(urethane), is set to 1.0 to 4.5, to form a chemical decomposition product comprising a urethane.

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 3, comprising step (DI), or the process according to claim 4, wherein the hydrolysis is carried out in the presence of a hydrolysis catalyst comprising (I) a Bronsted base selected from the group consisting of: (i) a hydroxide, (ii) a carbonate, (iii) a bicarbonate, (iv) an orthophosphate or a metaphosphate, or (v) a mixture of two or more of the foregoing Bronsted bases, and / or (II) Aminase.

6. The process of claim 3, comprising step (D.II), wherein the hydrogenolysis catalyst comprises copper, palladium, nickel, manganese or platinum.

7. The process according to claim 3, comprising step (D.III), wherein the cleavage of the carbamate is carried out in the presence of a carbamate cleavage catalyst comprising (I) Metal-free or metal-containing Bronsted or Lewis acidic catalysts or (II) Metal-free or metal-containing Brønsted basic or Lewis basic catalysts.

8. The method of claim 3, comprising step (D.IV), 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, a titanium alkoxide, a tertiary amine, cesium fluoride, a stannate, or a mixture of two or more of the above chemical decomposition catalysts.

9. The process according to claim 2 , wherein in step (E), the liquid alcohol phase from (C) or (CI) is distilled and / or stripped 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).

10. The process according to any one of the preceding claims, wherein the chemical decomposition alcohol is selected from methanol, ethanol, or a mixture of methanol and ethanol.

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 the chemical decomposition in step (B) is carried out at a pressure of 5.0 bar to 100 bar. 14 . The process according to claim 1 , wherein the mass ratio of chemical decomposition alcohol to urethane is selected so that the molar ratio n(chemical decomposition alcohol) / n(urethane groups) is from 4.5 to 30.

15. Use of an unbranched monohydric alcohol having 1 to 4 carbon atoms as a chemical decomposition alcohol in chemically decomposing a urethane based on an isocyanate component and an alcohol component at a temperature of 185° C. to 245° C. to form an isocyanate of the isocyanate component and a urethane of the chemical decomposition alcohol without using a chemical decomposition catalyst, for reducing the formation of amines corresponding to the isocyanate of the isocyanate component, wherein the mass ratio of the chemical decomposition alcohol to the urethane, m(chemical decomposition alcohol) / m(urethane), is 1.0 to 4.5.

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