WO2024170559A1 - Method for cleaving (poly)urethanes - Google Patents

Abstract

The invention relates to a method for the chemolysis of a urethane (in particular polyurethane) based on an isocyanate component and an alcohol component by reacting with a chemolysis alcohol to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, in particular for the purpose of obtaining starting materials for the production of chemical products, wherein the chemolysis of the urethane with the chemolysis alcohol is carried out in the absence of a chemolysis catalyst at a temperature in the region of 185°C to 245°C, and the chemolysis alcohol is selected from unbranched monoalcohols with 1 to 4 carbon atoms, wherein a mass ratio of the chemolysis alcohol to the urethane is set between 1.0 and 4.5.

Description

METHOD FOR CLEAVAGE OF

The present invention relates to a process for the chemolysis of a urethane (in particular polyurethane) based on an isocyanate component and an alcohol component by reaction with a chemolysis alcohol to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, in particular for the purpose of obtaining starting materials for the production of chemical products, wherein the chemolysis of the urethane with the chemolysis alcohol is carried out in the absence of a chemolysis catalyst at a temperature in the range of 185 °C to 245 °C and the chemolysis alcohol is selected from unbranched monoalcohols having 1 to 4 carbon atoms, wherein a mass ratio of the chemolysis alcohol to the urethane is set at 1.0 to 4.5.

Urethanes are versatile products. Polyurethanes in particular have a wide range of applications in industry and in everyday life. Polyurethanes are usually divided into polyurethane foams and so-called "CASE" products, with "CASE" being a collective term for polyurethane coatings (e.g. paints), adhesives, sealants and elastomers. Polyurethane foams are usually divided into rigid foams and flexible foams. Despite their differences, all of these products have the basic polyurethane structure in common, which is created by the polyaddition reaction of a polyvalent isocyanate and a polyol and is suitable, for example, for a polyurethane based on a diisocyanate O=C=N-R-N=C=O and a diol H-O-R'-O-H (where R and R' are organic radicals) as

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

Many polyurethanes contain additional structural units in addition to the basic polyurethane structure. These include urea, isocyanurate, allophanate and biuret structural units.

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

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

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

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

3. Hydroglycolysis (hydroalcoholysis) of urethane bonds by reaction with alcohols and water. It is of course also possible to add alcohol and water from the beginning, whereby the processes of glycolysis and hydrolysis described above take place in parallel.

A summary of the known processes of polyurethane recycling is provided in the review article by Simon, Borreguero, Lucas and Rodriguez in Waste Management 2018, 76, 147 - 171 [1], WO 2023/285545 A1 describes a process for recycling a polyurethane in which the polyurethane is reacted with a first alcohol and the low molecular weight carbamate formed in the process or in a further transurethanization with a second alcohol is thermally split into the underlying alcohol and the underlying isocyanate. Particularly preferred first and/or second alcohols are propanol, pentanol, isopropyl alcohol, butanol, hexanol, nonanol, octanol, glycerin, ethylene glycol, diethylene glycol and triethylene glycol. In the examples, a flexible polyurethane foam is reacted once with octanol (mass ratio of foam to alcohol 1:2, under reflux in a pressureless apparatus) and once with isopropanol (mass ratio of foam to alcohol 1:5, in a pressure reactor at an argon pressure of 30 bar).

EP 3 590 999 Bl describes a process for the degradation of plastics using methanol or ethanol in the presence of methoxide as a catalyst. The examples describe the degradation of flexible polyurethane foam.

US 4,316,992 describes a process for recovering polyether polyols from polyurethane foams. In the process, the polyurethane foam is dissolved in an alcohol at 225 °C to 280 °C, then superheated steam is passed through the resulting solution at 185 °C to 220 °C. Suitable alcohols are saturated mono- or polyalcohols with boiling points between 225 °C and 280 °C. These can be straight-chain, branched, cyclic or aromatic. Diols or triols with ether bridges are preferred, in particular diethylene glycol, dipropylene glycol, dibutylene glycol, glycerin and propylene-ethylene glycol, with diethylene glycol being highlighted as being particularly advantageous. In practice, only the use of diethylene glycol (Examples 1 and 2), glycerin (Example 3) and 1,6-hexanediol (Example 4) is shown.

The patent US 4,336,406 describes the hydroalcoholysis of polyurethane foams by dissolving in an alcohol at 225 °C to 280 °C followed by reaction with water (here liquid water) at 185 °C to 220 °C. Suitable alcohols are described as saturated alcohols with a boiling point between 225 °C and 280 °C, with diethylene glycol being preferred. US 2016/0145409 A1 describes a process for recovering organic fibers from composite materials containing a polymer matrix and organic fibers. The process comprises reacting the composite material in an alcohol-water mixture. The polymer is in particular an epoxy or phenolic resin. Water and alcohol are preferably used in equal volumes, and the alcohol is preferably selected from methanol, ethanol, n-propanol, /iso-propanol, glycerin or a mixture thereof.

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

The article Methanolysis investigation of commercially available polyurethane foam by N. Asahi et al., published in Polymer Degradation and Stability 2004, 86, 147 - 151, describes the methanolysis of polyurethanes in the temperature range from 160 to 300 °C at pressures of up to 15 MPa, with the methanol partially in a supercritical state. The aim was to realize the methanolysis of a commercially available polyurethane foam without the use of a catalyst. The chemolysis of the model polyurethane 1,

1 and that of the commercially available polyurethane foam "Sofran®" at mass ratios of methanol to polyurethane of 5 : 1 (i.e. m(methanol/m(polyurethane) = 5) or 16 : 1 (i.e. m(methanol/m(polyurethane) = 16). The article comes to the conclusion that the decomposition of polyurethane to methyl carbamate is successful in high proportions at temperatures above 200 °C and that the use of catalysts is necessary at lower temperatures.

The article "tert-Amyl Alcohol-Mediated Deconstruction of Polyurethane for Polyol and Aniline Recovery" by Martin B. Johansen et al. in ACS Sustainable Chem. Eng., 2022, 10 (34), 11191 - 11202 describes the chemolysis of polyurethanes with tert-amyl alcohol with direct formation of the amine, which was the precursor of the isocyanate used in the polyurethane synthesis. A reaction mechanism is proposed in which the polyurethane used is first thermally split back to isocyanate and polyol and the isocyanate thus formed forms a carbamate as an intermediate with the amyl alcohol. The carbamate reacts with the splitting off of 2-methyl-l-butene and 2-methyl-2-butene to form the unstable carbamic acid, from which the amine is formed with the release of carbon dioxide. The reactions take place with a mass ratio of alcohol to polyurethane of approximately 16:1 (i.e. m(alcohol/m(polyurethane) = 16) at temperatures of 200 to 225 °C.

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

Another important aspect is to carry out the chemolysis as economically as possible. It is therefore desirable to keep the amount of chemolysis reagent used (which also serves as a solvent) as low as possible and to avoid using other substances such as catalysts if possible.

The choice of chemolysis process to be used depends, among other things, on which raw materials are to be recovered first. If the focus is on the recovery of polyols, as is the case in numerous publications on this topic, a chemolysis process can be used in which low molecular weight carbamates either do not occur as intermediates at all or are immediately split into the underlying amines and alcohols, e.g. hydrolysis or hydroalcoholysis. If, on the other hand, other raw materials are to be obtained in addition to the polyols, it can also be advantageous to aim for the formation of low molecular weight carbamates in a targeted and as selective manner as possible and to separate them from the polyols in as pure a form as possible. The most selective formation of a low molecular weight carbamate involves suppressing a side reaction in which a carbonate is formed instead of the carbamate and the amine corresponding to the originally used isocyanate is released directly. A targeted and selective formation of carbamates enables their further processing in a form other than hydrolyzing them to the amines. Even if hydrolysis to the amines is desired, it can be advantageous to separate intermediate carbamates before hydrolysis, for example if carbamate and polyol can be separated more easily than amine and polyol. This aspect has not yet been sufficiently taken into account in the prior art. There was therefore a need for further improvements in the field of chemolysis of urethanes, particularly polyurethanes. In particular, it would be desirable to cleave the urethane bonds in such a way that low-molecular carbamates are initially formed from low-boiling alcohols and the amines on which the (poly)urethanes are based, and this as selectively as possible. Furthermore, it would be desirable for the chemolysis to be carried out as economically as possible in terms of the use of reagents (i.e. starting materials and auxiliary materials such as catalysts in particular).

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

(A) Providing the urethane and

(B) Chemolysis of the urethane from (A) with the chemolysis alcohol (without addition of water) in the absence of a chemolysis catalyst at a temperature in the range from 185 °C to 245 °C, preferably 195 °C to 240 °C, particularly preferably 205 °C to 235 °C, very particularly preferably 215 °C to 230 °C, wherein the chemolysis alcohol is selected from unbranched monoalcohols having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, and wherein a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol)/m(urethane) (with m = mass), is set in the range from 1.0 to 4.5, preferably 1.0 to 4.0, to form a chemolysis product containing the carbamate.

Completely surprisingly, it was found that the use of unbranched monoalcohols with 1 to 4 carbon atoms leads to the formation of corresponding carbamates with good selectivity (significantly improved compared to other alcohols), in particular with regard to the avoidance of amine formation, and correspondingly good yield, without the addition of a chemolysis catalyst. The

Use of an unbranched monoalcohol having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, as chemolysis alcohol in a chemolysis of a urethane based on an isocyanate component and an alcohol component, carried out without the use of a chemolysis catalyst at a temperature in the range from 185 °C to 245 °C, preferably 195 °C to 240 °C, particularly preferably 205 °C to 235 °C, very particularly preferably 215 °C to 230 °C, in a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol)/m(urethane) (with m = mass), in the range from 1.0 to 4.5, preferably 1.0 to 4.0, with formation of a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol to reduce the formation of an amine corresponding to an isocyanate of the isocyanate component is therefore a further Subject of the invention.

All aspects described in connection with the process according to the invention (for example preferred chemolysis alcohols, temperatures, pressures, quantitative ratios of the starting materials, etc.) are of course also applicable to the use according to the invention, which will not be specifically referred to below in order to avoid unnecessary repetition.

In the terminology of the present invention, the term isocyanates includes all isocyanates known in the art in connection with urethane chemistry. The expression "an isocyanate" naturally also includes embodiments in which two or more different isocyanates (e.g. mixtures of MDI and TDI) were used in the production of the (poly)urethane, unless something else is expressly stated, for example by the formulation "exactly one isocyanate". The totality of all isocyanates used in the production of the (poly)urethane is referred to as the isocyanate component (of the (poly)urethane). The isocyanate component comprises at least one isocyanate. Analogously, the totality of all mono- or polyols used in the production of the (poly)urethane is referred to as the alcohol component (of the (poly)urethane). The alcohol component comprises at least one mono- or polyol. In the terminology of the present invention, the term mono- or polyols includes all mono- or polyols known in the art in connection with urethane chemistry. The expression "a monool" or "a polyol" naturally also includes embodiments in which two or more different mono- or polyols were used in the production of the urethane. Therefore, if in the following we refer to "a polyether polyol" (or "a polyester polyol", etc.), this terminology naturally also includes embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) were used in the production of the (poly)urethane.

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

In the context of the present invention, the absence of a chemolysis catalyst means that only the chemolysis alcohol (i.e. methanol, ethanol, n-propanol and/or n-butanol) is added to the (poly)urethane to be split, but no chemolysis catalyst. It is known that, for example, polyurethane foams can still contain residual components of foaming catalysts (in the case of the above-mentioned "Sofran®", these are, for example, tertiary amines and smaller amounts of tin and lead compounds). The presence of such catalysts originating from the original application of the (poly)urethane to be split does not go beyond the scope of the present invention. According to the invention, it is only essential that no additional catalysts (more precisely: no compounds that would catalyze the chemolysis, i.e. no chemolysis catalysts) are added beyond the catalysts that are already present in some cases from the original application of the (poly)urethanes to be split. The present examples were carried out with a model urethane that was free of foaming catalysts such as those mentioned above, which proves that it is not such catalyst residues that enable the chemolysis.

An amine corresponding to an isocyanate is the amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCl2 —> R-N=C=O + 2 HCl.

First, a brief summary of various possible

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

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

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

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

(D.I II) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or

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

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

(B.l) hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture; and

(Cl) Extraction of the hydrolyzed product mixture with an organic (in particular halogenated) solvent to obtain an amine phase and a liquid alcohol phase (in particular a polyol phase). In a fourth embodiment of the invention, which can be combined with all embodiments that provide for hydrolysis, the hydrolysis is carried out in the presence of a hydrolysis catalyst comprising

(I) an (organic or inorganic) Br0nsted base selected from (i) a hydroxide (in particular sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (in particular an alkali metal carbonate such as sodium or potassium carbonate), (iii) a hydrogen carbonate (in particular an alkali metal hydrogen carbonate such as sodium or potassium hydrogen carbonate), (iv) an orthophosphate or metaphosphate, preferably orthophosphate (in particular an alkali metal phosphate or alkali metal hydrogen phosphate) or (v) a mixture of two or more of the aforementioned Br0nsted bases, and/or

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

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

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

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

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

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

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

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

In a tenth embodiment of the invention, which can be combined with all embodiments, the isocyanate component comprises an isocyanate selected from

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

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

1,6-hexamethylenediamine, HDA), isophorone diisocyanate (IPDI; preparable by phosgenation of isophoronediamine, IPDA), diisocyanatodicyclohexylmethane ("saturated methylenediphenyl diisocyanate", H12MDI, in particular the 4,4'-isomer; preparable by phosgenation of diaminodicyclohexylmethane, H12MDA, itself obtainable by ring hydrogenation of 2-ring MDA), xylylene diisocyanate (XDI; preparable by phosgenation of xylylenediamine, XDA), poro-phenylene diisocyanate (PPDI; preparable by phosgenation of para-phenylenediamine) or a mixture of two or more of the aforementioned isocyanates.

The isocyanate component preferably contains toluene diisocyanate, di- and polyisocyanates of the diphenylmethane series or a mixture of toluene diisocyanate and the di- and Polyisocyanates of the diphenylmethane series and in particular does not include any other isocyanates besides those mentioned above.

In an eleventh embodiment of the invention, which can be combined with all embodiments, the alcohol component comprises a mono- and/or polyol selected from a polyether monool, a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol, a polycarbonate polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols

The alcohol component preferably contains a polyester polyol, polyether polyol and/or a polyether ester polyol, particularly preferably a polyether polyol. The alcohol component is most preferably a polyether polyol (i.e. does not contain any other mono- or polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is included and does not go beyond the scope of this embodiment).

In a twelfth embodiment of the invention, which can be combined with all embodiments, the urethane is a polyurethane.

In a thirteenth embodiment of the invention, which can be combined with all embodiments, the chemolysis in step (B) is carried out at a pressure in the range from 5.0 bar to 100 bar (wherein pressure and temperature are in particular coordinated such that the chemolysis can be operated under reflux of the chemolysis alcohol).

In a fourteenth embodiment of the invention, which can be combined with all embodiments, the mass ratio of the chemolysis alcohol to the urethane is selected such that a molar ratio n(chemolysis alcohol)/n(urethane groups) (where n = molar amount) of 4.5 to 30, preferably 5.0 to 25, particularly preferably 8.0 to 20, results. If necessary, the molar amount of urethane groups, n(urethane groups), is determined by hydrolysis of a sample of the urethane provided in (A) and subsequent determination of the amine number by titration with 0.1 molar perchloric acid.

In a fifteenth embodiment of the invention, which can be combined with all embodiments, the chemolysis in step (B) is carried out in a reactor which is inertized with an inert gas, in particular nitrogen, before the start of the chemolysis, preferably an inert gas partial pressure of 1.0 bar (in particular ambient pressure) to 20 bar, preferably up to 10 bar, being set. The embodiments briefly described above and other possible embodiments of the invention are explained in more detail below. All of the embodiments described above and the other embodiments of the invention described below can be combined with one another as desired, unless the context clearly indicates the opposite to a person skilled in the art or unless something else is expressly stated.

PROVISION OF (POLY-)URETHANE FOR CHEMICAL RECYCLING

In step (A), the (poly)urethane to be chemically recycled is prepared in preparation for chemolysis. The urethane provided in step (A) is also referred to below as the "starting urethane". In principle, this can be any type of urethane.

Polyurethanes, i.e. urethanes derived from polyisocyanates (2 or more isocyanate groups per molecule) and polyols (two or more alcohol groups per molecule) are preferred. In principle, this can be any type of polyurethane, i.e. both polyurethane foams and polyurethane products from the so-called CASE applications described at the beginning. Polyurethane foams can be both flexible and rigid foams, with flexible foams (e.g. from old mattresses, upholstered furniture or car seats) being preferred. Polyurethane foams are usually produced using propellants such as pentane or carbon dioxide. Polyurethane elastomers, polyurethane adhesives and polyurethane coatings are preferred for polyurethanes from CASE applications.

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

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

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

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

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

The alcohol component preferably contains a polyester polyol, polyether polyol and/or a polyether ester polyol, particularly preferably a polyether polyol. The alcohol component is most preferably a polyether polyol (i.e. does not contain any other mono- or polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is included and does not go beyond the scope of this embodiment).

A polyether polyol can also be one that is filled with a styrene-acrylonitrile copolymer (SAN copolymer).

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

It is also conceivable to carry out the preparatory steps described above at a location that is spatially separated from the chemolysis site. In this case, the prepared foam is filled into suitable transport vehicles, such as silo vehicles, for further transport. The prepared foam can also be compressed for further transport in order to achieve a higher mass-volume ratio. At the chemolysis site, the foam is then filled into the reaction device intended for chemolysis. It is also conceivable to connect the transport vehicle used directly to the reaction device. CHEMOLYSIS OF (POLY-)URETHANE

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

The chemolysis is carried out at reaction temperatures in the range of 185 °C to 245 °C, preferably 195 °C to 240 °C, particularly preferably 205 °C to 235 °C, very particularly preferably 215 °C to 230 °C. The chemolysis is preferably carried out in a pressure-resistant reactor (autoclave) without pressure equalization, in particular such that the reaction is operated "under reflux" (chemolysis alcohol evaporates, condenses in cooler areas of the reactor and flows back into the reacting mixture). In this procedure, a pressure is established in the gas space above the liquid reaction mixture which corresponds to the vapor pressure of the chemolysis alcohol used at the prevailing temperature, i.e. depending on the type of chemolysis alcohol and the temperature, the pressure is in the range of about 5.0 bar to 100 bar (absolute). It is preferred to inertize the reactor used for the chemolysis with an inert gas, in particular nitrogen, before the start of the chemolysis. The inert gas is preferably used to set an inert gas partial pressure of 1.0 bar (in particular ambient pressure) to 20 bar, preferably up to 10 bar (absolute).

A suitable reactor is, for example, a stirred tank reactor, which can also be operated continuously. The use of a cascade of several continuously operated stirred tank reactors is also possible. In a further preferred embodiment, in order to complete the conversion, part of the liquid phase from a stirred tank reactor (in the case of a cascade of stirred tank reactors, from the last stirred tank reactor in the cascade) is passed into a downstream tubular reactor, in particular in such a way that the reaction mixture flows through the tubular reactor with a plug flow.

According to the invention, the chemolysis alcohol is selected from unbranched monoalcohols with 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms. Methanol, ethanol or mixtures of both are particularly preferred; methanol is very particularly preferred. The mass ratio of the chemolysis alcohol to the (poly)urethane is in the range from 1.0 to 4.5, preferably 2.0 to 4.0. It is therefore possible to limit the mass of chemolysis alcohol to be used without adding a chemolysis catalyst, which is a great advantage in terms of process technology (lower costs, less complex processing). As far as the molar ratios are concerned, these are regularly overstoichiometric at the mass ratios mentioned, so that a complete Implementation can be ensured. Preferably, the mass ratios within the ranges mentioned are selected so that a molar excess of the chemolysis alcohol (i.e. a molar ratio n(chemolysis alcohol)/n(urethane groups), where n = molar amount) of 4.5 to 30, particularly preferably 5.0 to 20, very particularly preferably 8.5 to 15, is ensured. If the molar amount of urethane groups is not known (for example because polyurethanes of unknown origin are to be recycled), this can easily be determined by hydrolyzing a representative sample of the (poly)urethane provided in (A) and determining the amine number of the hydrolysis product. Since one mole of amine is released per mole of urethane groups split, the molar amount of urethane groups can be determined from the amine number. The exact manner in which the hydrolysis is carried out naturally depends on the type of (poly)urethane. With the help of the information and literature references compiled in [1], it is easy for the expert to find a suitable procedure.

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

wherein

• AZ for the amine number,

• V is the volume of perchloric acid solution consumed,

• m is the mass of the titrated sample,

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

• bi is the molarity of the perchloric acid solution and

• f is the dimensionless factor (titer) of the perchloric acid solution. PROCESSING OF THE CHEMOLYSIS PRODUCT

The chemolysis yields a chemolysis product containing the carbamate. The chemolysis product is preferably worked up by separating the carbamate formed in (B) from the chemolysis product in a step (C) using an extraction with an organic solvent, optionally with the addition of water, and/or a solid-liquid phase separation, whereby a liquid alcohol phase (in particular a polyol phase) is obtained in addition to the carbamate. Excess chemolysis alcohol is separated off by distillation before or after the separation, preferably before.

Separation by solid-liquid phase separation is limited to those carbamates that precipitate as solids from the chemolysis product (possibly after cooling). Whether this is the case depends on the exact nature of the carbamate, i.e. in particular on the nature of the (poly)urethane to be split. Separation by extraction, on the other hand, is applicable in any case. The separation of alcohols (in particular polyols) and carbamates, which are present in a mixture with one another in the product of an alcoholysis, by extractive processes is basically known in the prior art. Reference is made, for example, to the international patent applications WO 2020/260387 Al (use of very non-polar organic solvents such as in particular hydrocarbons) and WO 2022/063764 Al (use of moderately polar organic solvents such as in particular halogenated hydrocarbons in conjunction with an aqueous washing liquid).

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

When separated using an extraction, the carbamate is obtained as a solution, in particular depending on the nature of the (poly)urethane used and the type of organic solvent used, dissolved in the extraction solvent or - as described in WO 2020/260387 Al - in excess chemolysis alcohol or - as described in WO 2022/063764 Al - in an aqueous phase which, after addition of a aqueous washing liquid in the extraction. Depending on the type of further processing of the carbamate desired, this solution can be used directly. However, the carbamate can also be easily isolated from this solution by evaporation of the solvent and/or crystallization.

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

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

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

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

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

The hydrolysis according to (D.I) yields the amine corresponding to the isocyanate of the isocyanate component. In principle, such a hydrolysis can be carried out analogously to the direct hydrolysis of polyurethanes (see the literature cited above, in particular the review article [1]). The amines formed in this way can then be used in all applications known in the specialist world for such amines, including being phosgenated again to give the corresponding isocyanates. The isocyanate obtained in this way can then be used again to produce a (poly)urethane. The hydrolysis can be supported by using a hydrolysis catalyst. The following is particularly suitable for this:

(I) a (organic or inorganic) Brpnstedbase selected from (i) a

Hydroxide (especially sodium hydroxide, tetramethylammonium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide), (ii) a carbonate (in particular an alkali metal carbonate such as sodium or potassium carbonate), (iii) a hydrogen carbonate (in particular an alkali metal hydrogen carbonate such as sodium or potassium hydrogen carbonate), (iv) an orthophosphate or metaphosphate, preferably orthophosphate (in particular an alkali metal phosphate or alkali metal hydrogen phosphate) or (v) a mixture of two or more of the aforementioned Brpnsted bases, and/or

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

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

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

The processing variants according to (D.I) and (D.II) therefore provide the amine corresponding to the isocyanate of the isocyanate component. This amine can be used for all purposes known in the professional world, in particular it can be phosgenated and used in the production of new (poly)urethane.

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

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

(II) a metal-free or metal-containing Br0nsted or Lewis basic catalyst.

For further details, please refer to W. Leitner et al., Carbon2Polymer - Chemical Utilization of CC in the Production of Isocyanates, Chapter 4, "Carbamate Cleavage", published in Chem. Ing. Tech. 2018, 90, 1504 - 1512 and the literature cited therein.

The processing variant according to (D.III) directly delivers the isocyanate of the isocyanate component, so that further phosgenation is unnecessary. This isocyanate can be used for all purposes known in the specialist world, in particular it can be reacted again with H-functional compounds to form polyaddition products, preferably (poly)urethanes. The carbamate cleavage according to (D.III) can be the variant of choice in particular when the isocyanate component of the urethane or polyurethane comprises toluene diisocyanate (TDI) and in particular consists of it (i.e. does not comprise any other isocyanates in addition to TDI).

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

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

Typical suitable polyols are divalent polyols (in particular ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-butenediol, 1,4-butynediol, neopentyl glycol, 1,5-pentanediol, methylpentanediols (such as 3-methyl-1,5-pentanediol), 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, bis-(hydroxymethyl)-cyclohexanes (such as 1,4-bis-(hydroxymethyl)cyclohexane), triethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, tripropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols), trivalent polyols (in particular trimethylolpropane, Glycerol, trishydroxyethyl isocyanurate), tetravalent polyols (especially pentaerythritol) and polyols that can be obtained from renewable raw materials (especially sorbitol, hexitol, sucrose, starch, starch hydrolysates, cellulose, cellulose hydrolysates and hydroxy-functionalized fats and oils, especially castor oil), as well as all modification products of these aforementioned polyols with different amounts of e-caprolactone. Polyether polyols can also be used as polyols for step (D.IV), in particular those that have a number-average molar mass M _n determined in accordance with DIN55672-1 (2016-03) in the range of 18 g/mol to 8000 g/mol and a functionality of 2 to 3 (calculated from the H-functional starters used in the production of the polyether polyols). Preference is given to polyether polyols which are composed of repeating ethylene oxide and propylene oxide units, preferably with a proportion of 35% to 100% propylene oxide units, particularly preferably with a proportion of 50% to 100% propylene oxide units. These can be statistical copolymers, gradient copolymers, alternating or block copolymers of ethylene oxide and propylene oxide.

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

The variants described above for further processing the carbamate are all the more advantageous to implement, the more selectively the carbamate is formed in step (B). This applies in particular to variant (D.III), in which the isocyanate is obtained without the intermediate amine. But it can also be advantageous in the other variants if the formation of the carbamate is as selective as possible, because in many cases this simplifies the subsequent processing, in particular the separation of the components of the chemolysis product from each other. The direct ("uncontrolled") formation of the amine in step (B) is therefore particularly worthy of mention as a selectivity-reducing reaction.

Three pathways are possible for the formation of the amine: (i) partial hydrolysis due to the presence of traces of water, (ii) reaction of the chemolysis alcohol with urea groups (which are present in small amounts, for example, in water-foamed polyurethane foams alongside the urethane groups) and (iii) reaction of the chemolysis alcohol with a urethane group to form a carbonate and release an amine.

Reaction path (i) can be suppressed by suitable drying measures. It is therefore preferable to use chemolysis alcohols with the lowest possible water content. In particular, it is preferred that the chemolysis alcohol used contains, based on its total mass, a maximum of 0.500 mass %, preferably a maximum of 0.200 mass %, particularly preferably a maximum of 0.050 mass %, very particularly preferably a maximum of 0.005 mass % of water, which can be achieved if necessary by drying measures known per se. For the purposes of the present invention, the mass of the chemolysis alcohol is in any case the total mass including any water present. The water content of the chemolysis alcohol can be determined if necessary by Karl Fischer titration; this is the method relevant for the purposes of the present invention. Karl Fischer titration has been described many times and is well known to those skilled in the art. Various possible embodiments of the basic principle of Karl Fischer titration generally produce results that are sufficiently consistent within the framework for the purposes of the present invention. In case of doubt, the Karl Fischer titration as described in DIN 51 777, Part 1, March 1983 is decisive for the purposes of the present invention.

The importance of reaction pathway (ii) depends on the type of polyurethane starting material used; if it contains urea groups, these will always also form amines upon complete chemolysis (albeit in minor amounts, since there are usually considerably more urethane groups than urea groups).

Without wishing to be bound by theory, it is believed that the present invention reduces reaction path (iii). This explains the experimental observation that the chemolysis of urethane groups, when carried out according to the invention, leads to the formation of a carbamate (and not a carbonate) with higher selectivity. If the recovery of the carbamate is not important for the desired (poly)urethane recycling, it is also possible to hydrolyze the chemolysis product formed in step (B) directly, i.e. without separating the carbamate formed. In this case, step (B) comprises a step (B1), the hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the (unchanged) chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture. In this case, the processing comprises a step (Cl), the extraction of the hydrolyzed product mixture with an organic (in particular halogenated) solvent, whereby an amine phase and a liquid alcohol phase (in particular a polyol phase) are obtained. Suitable organic (in particular halogenated) solvents are the same as those described above in connection with the extraction of the carbamate.

Within the framework of the process according to the invention, there are basically two possible ways of working up the chemolysis product, namely a first one involving recovery of the carbamate followed by separate further processing of the same and the resulting liquid alcohol phase and a second one involving direct hydrolysis of the chemolysis product. As far as the workup of the chemolysis product is concerned, the process according to the invention therefore comprises either

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

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

(D.III) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or (D.IV) reacting the carbamate with a polyol in the presence or absence of a catalyst to form a further OH-terminated carbamate; variants (DI), (D.II) and (D.IV) are preferred and variant (DI) is particularly preferred; or

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

As regards the liquid alcohol phase from (C) or (C.1), it is preferred to distill and/or strip it in a step (E) to obtain (at least) one chemical product selected from (i) an alcohol of the alcohol component and/or (ii) a reaction product formed from an alcohol of the alcohol component in the chemolysis (B). The alcohols and/or reaction products obtained in this way can be used for all purposes known in the art for such compounds. In particular, recovered polyether polyols can be used in the production of new polyurethanes and reaction products of polyester polyols in the production of new polyester polyols.

The invention described above is explained in more detail below using examples.

Examples:

Chemicals

Name Related to Purity

Phenyl Isocyanates Sigma-Aldrich >98%

2-Ethoxyethanol Alfa Aesar 99%

MeOH Sigma-Aldrich >99.9%

EtOH Sigma-Aldrich >99.9% n-PrOH Sigma-Aldrich >99.9% n-BuOH Sigma-Aldrich >99%

Etylene glycol Sigma-Aldrich 99.8%

Diethylene glycol Sigma-Aldrich >99.9%

1.3-Propanediol Roth >98%

1.4-Butanediol Sigma-Aldrich >99.9%

Anillin Ridel-de Haen 99.5%

THF Sigma-Aldrich (Merck) n.a.

Tetradecane Sigma-Aldrich (Merck) >99.0%

NazCCh Sigma-Aldrich >99.5%

K3PO4 Sigma-Aldrich >98%

Ti(O-nBu)4 Sigma-Aldrich (Merck) n.a.

The water content of the chemolysis alcohols used was 100 to 300 ppm in all cases unless otherwise stated.

Analytics

GC method

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

rrij = Masse Substanz i rriintstd = Masse interner Standard The following formula was used to calculate the GC yields and conversions using the internal standard tetradecane:

rrij = mass of substance i rriintstd = mass of internal standard

Ai = surface integral substance i

Aintstd = area integral internal standard kf = correction factor (FID response factor)

Teil In this way, the mass fractions of 2-ethoxyethyl-N-phenylurethane (substrate; see the following section) and the target carbamates (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) were quantified.

Part

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

(henceforth substrate) with various chemolysis alcohols to form corresponding transurethanization products (henceforth target carbamates). The use of a model urethane has the advantage that the presence of urea groups can be excluded.

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

A glass insert equipped with a magnetic stirrer is filled with catalyst (optional (see Tables 1 to 3), 1.0 mass% based on the total mass of substrate and chemolysis alcohol), substrate (700 mg), chemolysis alcohol (mass ratio to substrate as given in the table) and the internal standard tetradecane (20 mg) and placed in the stainless steel autoclave (volume 20 mL). This is flushed three times with N2 (setting a nitrogen pressure of 50 bar and then relaxing to ambient pressure) and sealed before the pressure is increased to 10 bar by adding nitrogen. The autoclave is heated in a preheated aluminum cone for a defined period of time at a defined temperature (see tables) while stirring (900 rpm). The autoclave is then cooled in an ice bath for 10 min and then relaxed. The reaction mixture is diluted with THF (2 mL), filtered through a syringe filter (Chromafil 0-20/15 MS) and analyzed by GC-FID.

Examples 1 to 26

The following Tables 1 to 3 summarize the results of the alcoholysis reactions.

Table 1: Alcoholysis of a glycol-based urethane with different mono- and bifunctional alcohols without catalyst ^[a]

Explanations of the table:

[a] Substrate: Ph-NH-CO-O-fCHzh-OMe; mass ratio of chemolysis alcohol to substrate of 3.0:1; reaction temperature 200 °C; reaction time 240 min.

[b] Amount-related percentage of the substrate recovered in relation to the amount of substrate used (Ysubstrate = 100 % ■ [n(substrate _{) recovered} / n(substrate) used). [c] Theoretical yield of target carbamate (ZC).

[d] Amount-related percentage of the amine found in relation to the amount of substrate used (YAmin = 100 % ■ [n(amine) _found /n(substrate) used).

[e] Determination of the selectivity to the target carbamate (Szc = Yzc / [100 % - Ysubstrate]).

[f] V = Comparative example (examples according to the invention are highlighted in bold).

The experiments compiled in Table 1 show that an uncatalyzed alcoholysis using short-chain monofunctional alcohols delivers significantly better selectivities to the desired target carbamates compared to difunctional alcohols, especially glycols. Due to the consideration of a constant mass ratio of chemolysis alcohol to substrate, the yield values for the target carbamate are consequently smaller as the alkyl chain becomes increasingly longer. However, it is crucial that the selectivity to the target carbamate remains correspondingly high with the alcohols according to the invention.

Table 2: Alcoholysis of a glycol-based urethane with unbranched primary C1-C4

Alcohols without catalyst and with various catalysts ^[a]

Explanations of the table:

[a] Substrate: Ph-NH-CO-O-(CHz)z-OMe; mass ratio of chemolysis alcohol to substrate of 3.0:1; reaction temperature 200 °C; reaction time 240 min. A catalyst is used in a mass fraction of 1.0%, based on the sum of the masses of substrate and chemolysis alcohol.

[b] Amount-related percentage of the substrate recovered in relation to the amount of substrate used (Ysubstrate = 100 % ■ [n(substrate _{) recovered} / n(substrate) used). [c] Theoretical yield of target carbamate (ZC).

[d] Amount-related percentage of the amine found in relation to the amount of substrate used (YAmin = 100 % ■ [n(amine) _found /n(substrate) used).

[e] Determination of the selectivity to the target carbamate (Szc = Yzc / [100 % - Ysubstrate]).

[f] V = Comparative example (examples according to the invention are highlighted in bold).

The experiments summarized in Table 2 show that the short-chain monofunctional alcohols can not only be used successfully without a catalyst, but that the selectivities achieved for the target carbamate are better than with catalysts. The reaction conditions chosen here are optimized for the chemolysis alcohol MeOH to achieve the highest possible yield of target carbamate (i.e. the most complete conversion of the urethane possible in conjunction with the highest possible selectivity Szc). Under the same conditions, at least an improvement in selectivity is achieved for the other chemolysis alcohols compared to the catalyzed reaction, and in three out of four cases an improvement in yield. In conjunction with the results from Table 3 (see below), it can be expected that the conversions for the C2 to C4 alcohols can be optimized by a moderate increase in temperature without a deterioration in selectivity or at least without a significant deterioration in selectivity, so that ultimately significantly higher yields of target carbamate can be expected.

Erläuterungen zu der Tabelle: Table 3: Alcoholysis of a glycol-based urethane with methanol without catalyst at different methanol-substrate ratios and temperatures ¹

Explanations of the table:

[a] Substrate: Ph-NH-CO-O-fCHzh-OMe; no additional catalyst added; reaction time 120 min.

[b] Amount-related percentage of the substrate recovered in relation to the amount of substrate used (Ysubstrate = 100 % ■ [n(substrate _{) recovered} / n(substrate) used).

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

[d] Determination of the selectivity to the target carbamate (Szc = Yzc / [100 % - Ysubstrate]).

The experiments summarized in Table 3 show that maximum selectivities to the target carbamate are achieved at about 210 °C, while maximum yields of target carbamate are achieved at about 230 °C under the given reaction conditions.

Table 4: Alcoholysis of a glycol-based urethane with methanol without catalyst at different methanol-substrate ratios ^[a]

Explanations of the table:

[a] Substrate: Ph-NH-CO-O-fCHzh-OMe; no additional catalyst added; reaction time 120 min, temperature 220 °C, water content of methanol 5098 ppm.

[b] Amount-related percentage of the substrate recovered in relation to the amount of substrate used (Ysubstrate = 100 % ■ [n(substrate _{) recovered} / n(substrate) used).

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

[d] Determination of the selectivity to the target carbamate (Szc = Yzc / [100 % - Ysubstrate]).

[f] V = comparative example (example according to the invention highlighted in bold).

Table 4 shows that when a large excess of chemolysis alcohol is used under the present reaction conditions, an improvement in conversion is achieved, but at the cost of a significantly reduced selectivity (in Example 28, 6.8 times the amount of aniline was formed compared to Example 27). The process according to the invention therefore makes it possible to achieve good to very good selectivities even when using comparatively water-rich chemolysis alcohols. This means that drying can be avoided or at least made less complex.

Claims

1. A process for the chemolysis of a urethane based on an isocyanate component and an alcohol component by reacting it with a chemolysis alcohol to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, comprising the steps of: (A) Providing the urethane and (B) chemolysis of the urethane from (A) with the chemolysis alcohol in the absence of a chemolysis catalyst at a temperature in the range of 185 °C to 245 °C, wherein the chemolysis alcohol is selected from unbranched monoalcohols having 1 to 4 carbon atoms and wherein a mass ratio of the chemolysis alcohol to the urethane, m(chemolysis alcohol)/m(urethane), is set in the range of 1.0 to 4.5, to form a chemolysis product containing the carbamate. 2. Process according to claim 1, comprising (C) separating the carbamate formed in (B) from the chemolysis product using an extraction with an organic solvent and/or a solid-liquid phase separation, whereby a liquid alcohol phase is obtained in addition to the carbamate. 3. Process according to claim 2, in which the carbamate separated in (C), optionally after purification, is further reacted in a step (D) to obtain a chemical product, wherein (D) comprises one of the following reactions: (D.I) 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) hydrogenolysis of the carbamate in the presence of a hydrogenolysis catalyst to form an amine corresponding to the isocyanate of the isocyanate component; (D.III) Cleavage of the carbamate in the presence or absence of a carbamate cleavage catalyst into the isocyanate of the isocyanate component and the chemolysis alcohol; or (D.IV) Reaction of the carbamate with a polyol in the presence or absence of a catalyst to form another OH-terminated carbamate. 4. The method according to claim 1, comprising the steps: (B.l) hydrolysis of the carbamate formed in (B) in the presence or absence of a hydrolysis catalyst to form an amine by reacting the chemolysis product obtained in (B) with water to obtain a hydrolyzed product mixture; and (Cd) Extraction of the hydrolyzed product mixture with an organic solvent to obtain an amine phase and a liquid alcohol phase. 5. The process according to claim 3, comprising step (D.I), or according to claim 4, wherein the hydrolysis is carried out in the presence of a hydrolysis catalyst comprising (I) a Brpnsted base selected from (i) a hydroxide, (ii) a carbonate, (iii) a hydrogen carbonate, (iv) an orthophosphate or metaphosphate, or (v) a mixture of two or more of the aforementioned Brpnsted bases, and/or (II) a urethanase is performed. 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) a metal-free or metal-containing Brpnsted or Lewis acid catalyst or (II) a metal-free or metal-containing Brpnsted or Lewis basic catalyst. 8. The process according to claim 3, comprising step (D.IV), wherein the reaction of the carbamate with a polyol is carried out in the presence of a catalyst comprising a carbonate, a hydrogen carbonate, a hydroxide, an orthophosphate, a mono-hydrogen orthophosphate, a metaphosphate, an orthovanadate, a Titana isocyanate, a tertiary amine, cesium fluoride, a stannate or a mixture of two or more of the aforementioned chemolysis catalysts. 9. Process according to one of claims 2 to 8, in which the liquid alcohol phase from (C) or (Cd) is distilled and/or stripped in a step (E) to obtain a chemical product selected from (i) an alcohol of the alcohol component and/or (ii) a reaction product formed from an alcohol of the alcohol component in the chemolysis (B). 10. A process according to any one of the preceding claims, wherein the chemolysis alcohol is selected from methanol, ethanol or a mixture of methanol and ethanol. 11. A process according to any one of the preceding claims, wherein the isocyanate component is an isocyanate selected from Phenyl isocyanate, toluene diisocyanate, the di- and polyisocyanates of the diphenylmethane series, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, diisocyanatodicyclohexylmethane, xylylene diisocyanate, para-phenylene diisocyanate or a mixture of two or more of the aforementioned isocyanates. 12. Process according to one of the preceding claims, wherein the alcohol component comprises a mono- and/or polyol selected from a polyether monool, a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol, a polycarbonate polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols. 13. A process according to any one of the preceding claims, wherein the chemolysis in step (B) is carried out at a pressure in the range of 5.0 bar to 100 bar. 14. Process according to one of the preceding claims, in which the mass ratio of the chemolysis alcohol to the urethane is selected such that a molar ratio n(chemolysis alcohol)/n(urethane groups) of 4.5 to 30 results. 15. Use of an unbranched monoalcohol having 1 to 4 carbon atoms as chemolysis alcohol in a chemolysis of a urethane based on an isocyanate component and an alcohol component, carried out without the use of a chemolysis catalyst at a temperature in the range of 185 °C to 245 °C, in a mass ratio of the chemolysis alcohol to Urethane, m(chemolysis alcohol)/m(urethane), in the range of 1.0 to 4.5 to form a carbamate of an isocyanate of the isocyanate component and the chemolysis alcohol, to reduce the formation of an amine corresponding to an isocyanate of the isocyanate component.