CN118139918A

CN118139918A - Method for cleaving (poly) urethanes

Info

Publication number: CN118139918A
Application number: CN202280070893.XA
Authority: CN
Inventors: M·莱文; N·海因茨; J·兰甘克; T·海涅曼; K·拉默霍尔德; D·欣兹曼; T·纳班托格鲁; N·沃格特; W·莱特纳; E·迪克森
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2021-10-29
Filing date: 2022-10-26
Publication date: 2024-06-04

Abstract

The invention relates to a method for cleaving carbamates, in particular polyurethanes, by chemical decomposition (alcoholysis, hydrolysis or hydroalcoholysis) in the presence of a catalyst. The chemical decomposition is characterized in that the catalyst used is a salt of an oxyacid of an element of group five, fourteenth or fifteenth of the periodic table of elements or a mixture of two or more of these salts, the anion of the oxyacid salt having a pK _b in the range of 0.10 to 6.00, preferably 0.25 to 5.00, especially 0.50 to 4.50, wherein in the case of the chemical decomposition carried out to alcoholysis (Ia), the catalyst does not comprise any carbonate; where the chemical decomposition is carried out as hydroalcoholysis, the catalyst does not comprise any carbonate, phosphate or metaphosphate.

Description

Method for cleaving (poly) urethanes

The invention relates to a method for cleaving carbamates, in particular polyurethanes (polyurethanes), by chemical decomposition (alcoholysis, hydrolysis or hydroalcoholysis (hydroalcoholysis)) in the presence of a catalyst. The chemical decomposition is characterized in that the catalyst used is a salt of an oxyacid of a fifth, fourteenth or fifteenth group of the periodic table of elements, or a salt of a mixture of two or more such oxyacids, wherein the anion of the oxyacid salt has a pK _B in the range of 0.10 to 6.00, preferably 0.25 to 5.00, more preferably 0.50 to 4.50, wherein in the case of the chemical decomposition carried out to alcoholysis (Ia), the catalyst does not contain any carbonate; in the case of the chemical decomposition carried out into hydroalcoholysis, the catalyst does not comprise any carbonate, any phosphate or any metaphosphate. The process of the invention makes it possible to recover valuable raw materials from industrially produced carbamates, in particular polyurethanes, which have previously completed their original use, thus avoiding the losses of these raw materials in the case of disposal, for example by incineration or by landfill.

Carbamates are a wide range of products. Polyurethanes are particularly widely used in industry and daily life. Polyurethane foam is generally different from so-called "CASE" products, where "CASE" is a generic term for polyurethane coatings (e.g., paints), adhesives, sealants, and elastomers. Polyurethane foams are generally classified into rigid foams and flexible foams. Despite the differences between them, all these products have in common the basic structure of the polyurethane, which is produced by the addition reaction of a polyfunctional isocyanate with a polyol, which can be represented, for example, in the case of polyurethanes based on diisocyanates o=c=n-R-n=c=o and diols H-O-R '-O-H (where R and R' represent organic groups)

～～～[O-R‘-O-(O＝C)-HN-R-NH-(C＝O)]～～～

Even simple (non-polymeric) urethanes are characterized by urethane linkages.

It is precisely with the great success of polyurethane in terms of economics that a particularly large amount of polyurethane waste (e.g. from old mattresses or seating furniture) is produced, which must be reasonably utilized. The most technically feasible way of recycling is incineration, wherein the released heat of combustion is used in other processes, such as industrial production processes. However, this does not complete the closed loop of the raw material cycle. Another recycling mode is the so-called "physical recycling", i.e. the mechanical comminution of polyurethane waste materials for the production of new products. This type of recycling has its limitations in nature and therefore lacks attempts to recover the raw materials on which polyurethane production is based by reverse cleavage of the polyurethane bonds (so-called "chemical recycling"). These raw materials to be recovered mainly comprise polyols (i.e., H-O-R' -O-H in the examples above). In addition, amines (i.e., H ₂N-R-NH₂ in the examples above) can also be recovered by hydrolytic cleavage of the urethane linkage, and these amines can be phosgenated to give isocyanates (o=c=n-R-n=c=o in the examples above) after work-up.

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

1. hydrolysis of the carbamate is carried out by reaction with water to recover the amine and polyol, wherein carbon dioxide is formed.

2. Glycolysis (glycolysis) of the carbamate proceeds by reaction with an alcohol, wherein the polyol incorporated in the carbamate group is replaced by the alcohol used, thereby releasing the polyol. This process is generally referred to in the literature as transesterification (more precisely: transesterification of urethane (transurethanization). This mode of chemical recycling is referred to in the literature as glycolysis, regardless of the specific nature of the alcohol used, and this term is actually only applicable to ethylene glycol. Accordingly, in the context of the present invention the term alcoholysis (alcoholysis) is generally used, which may be followed by hydrolysis.

3. Glycolysis of urethane linkages (hydroglycolysis) proceeds by reaction with alcohol and water. Of course, the alcohol and water may be present simultaneously from the beginning of the chemical decomposition, in which case the glycolysis and hydrolysis processes described above would proceed simultaneously. In the present invention, the term hydroalcoholysis is used similarly to item 2.

In the context of the present invention, for these three methods, a generic chemical decomposition is used.

A review article of Sim-n, borreguero, lucas and Rodr i-guez in WASTE MANAGEMENT 2018,76,147-171[1] provides an overview of known polyurethane recycling processes.

International patent application WO 2022/171586 A1 describes the use of carbonates, bicarbonates, phosphates, hydrogen phosphates, metaphosphates or mixtures of two or more of the above metal salts as catalysts for hydroalcoholysis (clause 3) for the cleavage of polyurethanes.

Of the chemical recycling processes known from the literature, only a few are continuously operable on an industrial scale; many of the methods did not even reach pilot scale [1]. In view of the increased environmental awareness and the continual effort to construct industrial processes as sustainable as possible, both of which support chemical recycling at all, it is clear that chemical recycling of polyurethane products is still immature from a technical and economic point of view. For example, challenges remain with respect to the catalytic cracking efficiency of polyurethanes. The treatment of conventional processes requires a reaction temperature of about 200 ℃, which generally results in severe discoloration of the product and contains a large amount of by-products such as N-alkylated amines, thereby making recycling of the recovered raw materials very difficult or even making recycling economically inefficient.

Troev et al, "Chemical degradation of polyurethanes,3.,Degradation of microporous polyurethane elastomer by diethyl phosphonate and tris(1-methyl-2-chloroethyl)phosphate", in Polymer Degradation and Stability, 70, 43-48, describes polyurethane elastomers based on diphenylmethane diisocyanate and polyester polyol (Bayflex 2003E) that are subject to cleavage under superstoichiometric amounts of diethyl phosphonate ((CH ₃CH₂O)₂ P (O) H, diesters of phosphonic acid) and tris (1-methyl-2-chloroethyl) phosphate ((CH ₂ClCH(CH₃)O)₃ P (O), triesters of phosphoric acid). The process for polyurethane cleavage is part of a series of papers differing from the known processes of hydrolysis (see item 1 above), glycolysis (see item 2 above) and ammonolysis (not described above) (see introduction to this document).

The reaction products which have been formed are chemically characterized, including first the products 1 to 3, which can be immediately regarded as transesterification products of the polyester blocks of the polyurethane elastomer with alkoxyphosphite compounds (the "repeat units" shown in the article do not correspond to the other details described in the article in relation to the polyurethane elastomer; it can be assumed that the polyester blocks are considerably longer than shown). Secondly, N-alkylated polyurethanes (in the form of salts, the nitrogen of the polyurethanes carrying a positive charge-product 4) are also formed.

Mention is made in this article of: thus, the "exchange reaction" between ethoxy or 1-methyl-2-chloroethoxy groups and urethane groups is based at least predominantly, if not entirely, on cleavage of ester bonds within the polyester blocks, i.e. not essentially of the polyurethane structure, but of the polyester structure. For diethyl phosphonate, the resulting products 1 to 3 together were 30.6% and the N-alkylated salt (product 4) was 51.6%. Moreover, more than half of this product mixture consists of N-alkylated compounds which cannot be hydrolyzed to amines and thus cannot be used for regasification, so that the product mixture is completely unusable for meaningful chemical recycling.

US 4,159,972 describes a process for recycling flexible polyurethane foam, which process comprises: (a) Dissolving the foam in a low molecular weight glycol; (b) Mixing a high molecular weight polyol suitable for use in the production of flexible polyurethane foam; (c) Removing the low molecular weight glycol solvent from the resulting mixture under reduced pressure; (d) recovering the remaining polyol product. The polyol product thus recovered can be used to produce new polyurethane foams. The disclosed blowing catalyst is dibutyl [ bis (dodecanoyloxy) ] stannane.

EP 0 835 901 A2 describes a process for producing recycled polyols by glycolysis using a catalyst. Suitable catalysts described are: lewis acids (such as zinc chloride, ferric chloride, aluminum chloride, or mercuric chloride), carboxylic acids (such as acetic acid, formic acid, propionic acid, butyric acid, or benzoic acid), inorganic acetates (such as magnesium acetate, lead acetate, calcium acetate, potassium acetate, zinc acetate, sodium acetate, or "phosphorous acetate"), and alkali metal salts (such as sodium carbonate, sodium bicarbonate, calcium hydroxide, potassium hydroxide, or sodium hydroxide).

The chemical recovery of polyols from flexible polyurethane foam waste by glycolysis with diethylene glycol under the catalysis of Zn/Sn/Al Hydrotalcite (HTC) as heterogeneous catalyst is described in article "Polyurethane flexible foam recycling via glycolysis using Zn/Sn/AI hydrotalcites as heterogeneous catalyst" by Morcillo-boost et Al, revista Facultad DE INGENIERIA, universidad de Antioquia,2018,87,77-85.

M.M Alavi Nikje et al, journal of Cellular Plastics,2008, 44, 367-380, entitled "Microwave-assisted Polyurethane Bond CLEAVAGE VIA Hydroglycolysis Process at Atmospheric Pressure" relates to the glycolysis of flexible polyurethane foams under the action of Microwave radiation. This includes the use of a mixture of glycerol, water and sodium hydroxide.

Various methods of recycling polyurethane are outlined by Zia et al in Reactive & Functional Polymers, article "Methods of polyurethane and polyurethane composites RECYCLING AND recovery: A review" published by 2007,67,675-692.

Accordingly, there is a need for further improvements in the field of chemical recycling of polyurethane products. In particular, it is desirable to provide a process in which chemical decomposition is efficiently catalysed and can therefore preferably be carried out at relatively low temperatures.

In view of this requirement, the present invention provides a process for cleaving a carbamate, in particular a polyurethane, by chemical decomposition (I), comprising: (A) Providing a urethane (particularly polyurethane) based on an isocyanate component and an alcohol component, and then (B) subjecting the urethane to chemical decomposition (I) with a chemical decomposition reagent, wherein the chemical decomposition (I) is carried out with the addition of a catalyst as one of the following conversions (in this regard, see the description in the sections "chemical decomposition methods (Ia), (Ib) and (Ic)") below:

(Ia) alcoholysis of polyurethane (poly) wherein the chemical decomposing agent is an alcohol,

(Ib) hydrolysis of polyurethane, wherein the chemical decomposition agent is water,

The hydroalcoholysis of the polyurethane (Ic), wherein the chemical decomposing agent comprises an alcohol and water, preferably added sequentially in this order,

Wherein the catalyst comprises a salt of an oxyacid of group five, fourteenth or fifteenth element of the periodic table of elements, or a mixture of two or more such oxyacids, wherein the anion of the oxyacid salt has a pK _B (as defined in the section "determination of pK _B value" hereinbelow) within the range of 0.10 to 6.00, preferably 0.25 to 5.00, more preferably 0.50 to 4.50, wherein the catalyst does not comprise any carbonate in the event of a chemical decomposition to alcoholysis (la); in the case of the chemical decomposition carried out into hydroalcoholysis (lc), the catalyst does not comprise any carbonate, any phosphate or any metaphosphate.

Quite unexpectedly, it has been found that the hydrolysis of the urethane bond is possible under the conditions of using anionic compounds having low to medium pK _B values, even if it is used in catalytic-grade amounts instead of stoichiometric amounts.

In the context of the present invention, a urethane is an addition product (sometimes also referred to as condensation product, although not entirely correct) formed by reacting an isocyanate (=isocyanate component in the preparation of the urethane) with a monohydric or polyhydric alcohol (=alcohol component in the preparation of the urethane). In the case of using a polyfunctional isocyanate and a polyol, the above polyurethane may be produced. In particular, polyurethanes generally include not only the above-described polyurethane basic structure but also other structures, for example, structures having urea linkages. These structures, including polyurethane structures, which are present in distinction to the pure polyurethane base structure, are also within the scope of the invention.

In the generic term according to the invention, the term isocyanate covers all isocyanates known in all the technical fields related to urethane chemistry, such as, in particular, phenyl isocyanate (PHI, obtainable by phosgenation of aniline ANL), toluene diisocyanate (TDI; obtainable by phosgenation of toluene TDA diamine), di-and polyisocyanates of the diphenylmethane series (MDI; obtainable by phosgenation of diamines of the diphenylmethane series and polyamine MDA), pentane-1, 5-diisocyanate (PDI; obtainable by phosgenation of pentane-1, 5-diamine PDA), hexamethylene-1, 6-diisocyanate (HDI; obtainable by phosgenation of hexamethylene-1, 6-diamine), isophorone diisocyanate (IPDI; obtainable by phosgenation of isophorone diamine IPDA) and xylylene diisocyanate (XDI; obtainable by phosgenation of xylylene diamine XDA). The expression "isocyanate" of course also covers embodiments in which two or more different isocyanates (e.g. mixtures of MDI and TDI) are used in the production of the polyurethane product, unless explicitly stated otherwise, for example by using the expression "exactly one isocyanate". All isocyanates used to produce polyurethanes are collectively referred to as the isocyanate component (of the polyurethane). The isocyanate component comprises at least one isocyanate. Similarly, all monohydric or polyhydric alcohols used to produce polyurethane are collectively referred to as the alcohol component (of the polyurethane). The alcohol component comprises at least one monohydric or polyhydric alcohol.

In the sense of the present invention, the term mono-or polyol covers all mono-or polyols known in the art relating to urethane chemistry, such as in particular polyether mono-alcohols, polyether polyols, polyester polyols, polyether ester polyols and polyether carbonate polyols. The expression "monohydric alcohol" or "polyhydric alcohol" of course also covers embodiments in which two or more different monohydric alcohols or polyhydric alcohols are used in the production of the carbamate. Thus, if reference is made hereinafter to, for example, "polyether polyol" (or "polyester polyol" etc.), this terminology of course 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 the polyurethane.

In the special expression of the invention, carbamates (carbamates) refer to carbamates (urethane) produced by reaction with alcohols in the case of a chemical decomposition carried out into alcoholysis or hydroalcoholysis, in order to be able to distinguish them from the carbamates used.

The amine corresponding to isocyanate is one which can be phosgenated according to R-NH ₂+COCl₂ → R-n=c=o+2hcl to obtain isocyanate. Similarly, the nitro compound corresponding to an amine is one that can be reduced according to R-NO ₂+3H₂→R-NH₂+2H₂ O to yield an amine.

In the process of the invention, water and alcohol chemical decomposition reagents are used in superstoichiometric amounts. This means that in the case of hydrolysis, the amount of water is that which is theoretically necessary for hydrolyzing all the urethane bonds of the polyurethane to produce an amine and a monohydric or polyhydric alcohol while simultaneously releasing carbon dioxide. Similarly, a superstoichiometric amount of alcohol means that in the case of alcoholysis, the amount of alcohol is that which is theoretically sufficient to cause all urethane bonds of the polyurethane to switch to give the alcohol and the carbamate of the monohydric or polyhydric alcohol. In the case of hydroalcoholysis, the amount of alcohol and water each is that which is theoretically sufficient to hydrolyze all of the urethane linkages of the polyurethane to amine and polyol, or to form the carbamate of the alcohol and mono-or polyol, and at the same time to liberate carbon dioxide.

Chemical decomposition methods (Ia), (Ib) and (Ic)

In the context of the present invention, alcoholysis (Ia) refers to chemical decomposition using (at least) an alcohol without (intentional) addition of water as a chemical decomposition reagent. Since alcohols are generally not completely anhydrous (unless they are dried and stored under humid conditions prior to use), small amounts of water may be present in the alcoholysis used in the present invention even if water is not deliberately used as a chemical decomposition reagent. However, in the alcoholysis for the purposes of the invention, the water introduced into the chemical decomposition is at most in such an amount: the mass of water present during the alcoholysis is from 0% to <4.0%, in particular from 0% to 3.5%, preferably from 0% to 3.4%, more preferably from 0% to 3.0%, most preferably from 0% to 2.0% of the mass of alcohol used. The water content of the alcohol can be determined by karl fischer (KARL FISCHER) titration, which is a key method 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. Within the scope of the object of the invention, various possible configurations of the basic principle of karl fischer titration may generally give results with sufficient consistency. The karl fischer titration method as described in DIN 51777 (part 1,3 of 1983) is of critical importance for the purposes of the present invention if it is in question. When determining the amount of alcohol to be used and the maximum allowable amount of water, the key value is mainly the mass of "pure" alcohol (=alcohol minus water present therein). However, if only trace amounts of water are contained in the alcohol, those skilled in the art will immediately appreciate that this water content can be ignored in determining the amount of alcohol to be used and the maximum allowable amount of water, which does not create significant errors. In the case of doubt, however, the key value is the mass of alcohol from which the mass of water present is subtracted and the amount of water present in the alcohol should be taken into account when determining the maximum allowable amount of water. If only "excessively moist" alcohols are available, but the chemical decomposition to be carried out is alcoholysis (instead of hydroalcoholysis), the excess water in the alcohol can be removed by drying methods known per se.

In the context of the present invention, hydrolysis (Ib) refers to chemical decomposition using only water as a chemical decomposition reagent. In contrast to alcoholysis, water may be used directly but does not deliberately contain other chemical decomposition reagents.

In the context of the present invention, hydroalcoholysis (Ic) refers to chemical decomposition using alcohols and water (without other chemical decomposing agents), where the mass of water represents at least 4.0%, preferably from 4.0% to 15%, more preferably from 4.0% to 10%, very particularly preferably from 5.0% to 7.0% of the mass of the alcohol. The above description regarding alcoholysis applies correspondingly to the quantification of the total amount of water present when using moist alcohols. In practice, therefore, it is often sufficient to consider the mass of water that is deliberately added. If, contrary to expectations, doubt is made as to whether the water content thus determined is within the above-mentioned range, which is caused by the significant water content in the alcohol used, the water content of the alcohol should be determined and taken into account in accordance with the method proposed in the above-mentioned alcoholysis (Ia). The alcohol and water may (but are not required to) be added simultaneously to the carbamate to be cleaved. For the purposes of the present invention, hydroalcoholysis involves first adding water to the processed product thus obtained only to the carbamate so that it is as far as possible in solution (in which case transesterification has already taken place).

Regarding salts of oxy acids of the fifth, fourteenth or fifteenth group of the periodic table of elements (hereinafter referred to as salts of oxy acids), the oxy acids themselves need not be stable, separable compounds for the purposes of the present invention. For example, the carbonate may be formally derived from "H ₂CO₃ carbonate"; the fact that this is in a pure form that cannot be isolated is not an obstacle and does not depart from the scope of the invention.

In the context of the present invention, the suffix "ate" is used to identify the salt, and does not represent an ester. For example, the term "alkylphosphonate (alkylphosphonate)" refers to a salt having the anion RP (O) O ₂ ^2-, which anion may be derived from complete deprotonation of alkylphosphonate RP (O) (OH) ₂. In the case of salts derived from partial deprotonation of a polyprotic acid, the amount of hydrogen remaining is explicitly stated, for example H ₂SiO₄ ^2- represents the dihydrogen orthosilicate. However, in the case where one hydrogen atom remains, the prefix "a" may be omitted, for example HSiO ₄ ^3- represents a hydrogen silicate (instead of a monohydrogen orthosilicate).

Determination of pK _B value

In the present context, the pK _B value is understood to mean the pK _B value in "ideal diluted" aqueous solution, i.e. the pK _B value in the case of negligible interactions between the cation and the anion in the salts of oxy acids, in the temperature range from 23 ℃ to 25 ℃. The following equations for the corresponding acid-base pairs are known to be applicable here with sufficient accuracy, pK _A+pK_B =14.00. Thus, for example, for the purposes of the present invention, the pK _B (irrespective of the counterion) of all hydroxides is equal to 0.00 and is therefore not within the range of 0.10 to 6.00 of the present invention. The pK _A values of many oxo acids and the pK _B values of their salts (via pK _A+pK_B =14.00) are known from the literature. Reference is made herein in particular to the standard textbook "Holleman, arnold f; wiberg Egon; wiberg, nils: inorganic chemistry, stage 101, de Gruyter ", wherein the pK _A values of a number of oxo acids are reported in the section of the corresponding element; for example: phosphoric acid, pK _A =12.3 in the third dissociation stage (page 771); orthosilicic acid, pK _A =11.7 in the second dissociation stage (page 923); carbonic acid, pK _A =10.3 in the second dissociation stage (page 862).

If literature values cannot be used, pK _B in the context of the present invention is determined by acid-base titration. This is achieved by analytically determining the base constant (K _B) of the oxyacid anion and calculating pK _B therefrom. Such acid-base titration procedures are well known to those skilled in the art. Please refer to the relevant technical literature, in particular "Gerhart Jander, KARL FRIEDRICH Jahr, gerhard Schulze, mu rgen Simon (code )：Maβanalyse.Theorie und Praxis der Titrationen mit chemischen und physikalischen Indikationen[Quantitative Analysis:Theorie und Praxis der Titration mit chemischen und physikalischen Indikationen],, 16 th edition, walter de Gruyter, berlin, 2003, pages 67 to 128". Alkali constant K _B is obtained by the method described in section "SEHR SCHWACHE)Und Basen "[ very weak acid and base ] (pages 86 and 87). The equation for solving for K _B is as follows:

K_B＝[c²(OH^-)-K_W]/c₀(B)， (I)

Wherein c (OH ^-) represents the hydroxide ion concentration determined by titration with an acid, K _W represents the ion product constant of water (10 ^-14mol²/l²), and c ₀ (B) represents the starting concentration of base (=anion of oxo acid), i.e. the concentration calculated from the starting weight. In many cases, in particular in the lower region of the pK _B range of 0.10 to 6.00 according to the invention, the effect of the self-hydrolysis of water is very small, so that the calculation can also be carried out using a simplified equation:

K_B＝c²(OH^-)/c₀(B) (II)；

However, in case of doubt, an accurate calculation of equation (I) is crucial for the purposes of the present invention. For the purposes of the present invention, titration with 0.1N hydrochloric acid was carried out using phenolphthalein.

The following first briefly summarizes the various possible embodiments of the invention:

in a first embodiment of the method of the invention, which may be combined with all other embodiments, the method further comprises the steps of:

(C) The chemical decomposition products are subjected to a post-treatment to obtain a first product phase comprising monohydric and/or polyhydric alcohols, i.e. the alcohol component and/or other alcohols resulting therefrom in the chemical decomposition, and a second product phase comprising (i) in the case of the chemical decomposition carried out into alcoholysis (Ia), carbamate (optionally together with small amounts of amine, which is produced, for example, due to traces of water present in the alcohol), or (ii) in the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic).

In a second embodiment of the method of the present invention, which is a specific configuration of the first embodiment, step (C) comprises separating the chemically decomposed product phase into a first product phase and a second product phase.

In a third embodiment of the process of the present invention, which is another specific configuration of the first embodiment, the process comprises in case the chemical decomposition performed is hydrolysis (Ib), wherein step (C) comprises blending the chemical decomposition product with an organic solvent and phase separating into a first product phase and a second product phase.

In a fourth embodiment of the process of the present invention, which is another specific configuration of the first embodiment, the process comprises in case the chemical decomposition is carried out as alcoholysis (Ia) or hydroalcoholysis (Ic), wherein step (C) comprises blending the chemical decomposition product with an organic solvent which is not completely miscible with the alcohol used in step (B) and phase separating into a first product phase and a second product phase.

In a fifth embodiment of the method of the present invention, which is another specific configuration of the first embodiment, the method comprises in case the chemical decomposition performed is alcoholysis (Ia) or hydroalcoholysis (Ic), wherein step (C) comprises:

(C.I) mixing the chemical decomposition product with an organic solvent miscible with the alcohol used in step (B) to obtain a product mixture, and

(C.II) washing the product mixture with an aqueous washing liquid and phase separating into a first product phase and a second product phase.

In a sixth embodiment of the process of the present invention, which is one specific configuration of the first embodiment and can be combined with all other configurations of the first embodiment, the process comprises the step (D) of obtaining the monohydric and/or polyhydric alcohols from the first product phase.

In a seventh embodiment of the method of the present invention, which is one specific configuration of the sixth embodiment, step (D) comprises distillation and/or stripping.

In an eighth embodiment of the process of the present invention, which is one specific configuration of the first embodiment and can be combined with all other configurations of the first embodiment, the process comprises step (E), i.e. obtaining the amine from the second product phase.

In a ninth embodiment of the process of the present invention, which is a specific configuration of the eighth embodiment, the process comprises in the case of the chemical decomposition carried out into alcoholysis (Ia), wherein step (E) comprises hydrolyzing the carbamate to amine and distilling off the alcohol and water, and then subjecting the remaining amine after the distillation off to distillative purification.

In a tenth embodiment of the process of the present invention, which is another specific configuration of the eighth embodiment, the process comprises in case of a chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic), wherein step (E) comprises distillative removal of alcohol and water from the second product phase, followed by distillative purification of the remaining amine after distillative removal.

In an eleventh embodiment of the process of the invention, which can be combined with all other embodiments (except embodiments limited to hydrolysis (Ib)), the process comprises in the case of the chemical decomposition performed into alcoholysis (Ia) or hydroalcoholysis (Ic), wherein the alcohol used for the chemical decomposition is selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, triethylene glycol, glycerol, 2-methylpropane-1, 3-diol or a mixture of two or more of the alcohols mentioned above.

In a twelfth embodiment of the method of the invention, which may be combined with all other embodiments, the elements of group five, fourteenth or fifteenth of the periodic table of elements are selected from vanadium, carbon, silicon and phosphorus.

In a thirteenth embodiment of the method of the present invention, which is a specific configuration of the twelfth embodiment, the method comprises in case of a chemical decomposition performed into alcoholysis (Ia), wherein the salt of the oxy acid comprises an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Phosphate (PO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Metaphosphoric acid radical ([ PO ₃)^-]_n) ],

Alkyl phosphonates (RP (O) O ₂ ^2-, wherein R represents an alkyl radical having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms),

Aryl phosphonate (ArP (O) O ₂ ^2- wherein Ar represents aryl, in particular phenyl),

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

Alkylsilanolato (R _xSiO_4-x ^(4-x)-; where R denotes alkyl having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms; x is 1, 2 or 3, preferably 1 or 2, more preferably 1) or

Arylsilanolate (Ar _xSiO_4-x ^(4-x)-; wherein Ar represents aryl, in particular phenyl, and x is 1,2 or 3, preferably 1 or 2, more preferably 1).

In particular, the salts of oxy acids do not comprise any other anions than the anions described above. More preferably, the anion of the salt of the oxo acid is selected from phosphate and orthovanadate.

In a fourteenth embodiment of the method of the present invention, which is another specific configuration of the twelfth embodiment, the method comprises in case of a chemical decomposition performed into hydrolysis (Ib), wherein the salt of an oxy acid comprises an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Carbonate (CO ₃ ^2-),

Phosphate (PO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Metaphosphoric acid radical ([ PO ₃ ^-]_n) ],

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

Alkylsilanolato (R _xSiO_4-x ^(4-x)-; where R denotes alkyl having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, and x is 1,2 or 3, preferably 1 or 2, more preferably 1) or

Arylsilanolate (Ar _xSiO_4-x ^(4-x)-; wherein Ar represents aryl, in particular phenyl; and x is 1,2 or 3, preferably 1 or 2, more preferably 1).

In particular, the oxyacid salt does not contain any other anions other than the anions described above.

In a fifteenth embodiment of the method of the present invention, which is another specific configuration of the twelfth embodiment, the salt of an oxy acid (regardless of the chemical decomposition method selected) comprises an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Alkyl phosphonates (RPO ₃ ^2-; wherein R represents an alkyl radical having from 1 to 18 carbon atoms, preferably from 1 to 10 carbon atoms),

Aryl phosphonate (ArPO ₃ ^2-; wherein Ar represents aryl, in particular phenyl),

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

The anions mentioned above are particularly suitable in the case of the chemical decomposition carried out into hydroalcoholysis (Ic). In particular, the salts of oxy acids do not comprise any other anions than the anions described above.

In a sixteenth embodiment of the method of the invention, which may be combined with all other embodiments, the salt of an oxy acid is an alkali metal salt or a quaternary ammonium salt.

In a seventeenth embodiment of the method of the present invention, which is a specific configuration of the sixteenth embodiment, the alkali metal salt is a sodium salt or a potassium salt.

In an eighteenth embodiment of the method according to the present invention, which can be combined with all other embodiments, the chemical decomposition is carried out at a pressure in the range of 200 mbar _{( Absolute value (Absolute) )} to 50 bar _{( Absolute value (Absolute) )}, preferably 500 mbar _{( Absolute value (Absolute) )} to 50 bar _{( Absolute value (Absolute) )}, more preferably 900 mbar _{( Absolute value (Absolute) )} to 1.8 bar _{( Absolute value (Absolute) )}, in particular at ambient pressure.

In a nineteenth embodiment of the method of the present invention, which may be combined with all other embodiments, the chemical decomposition is performed at a temperature in the range of 50 ℃ to 195 ℃, preferably 80 ℃ to 150 ℃, more preferably 100 ℃ to 130 ℃, most preferably 110 ℃ to 120 ℃.

In a twentieth embodiment of the method of the present invention, it may be combined with all other embodiments wherein the isocyanate component comprises an isocyanate selected from the group consisting of:

Phenyl isocyanate (PHI; prepared from aniline ANL; TDI; prepared from toluene diamine TDA), di-and polyisocyanates of the diphenylmethane series (MDI; prepared from diamines of the diphenylmethane series and polyamines MDA), pentane-1, 5-diisocyanate (PDI; prepared from pentane-1, 5-diamine PDA), hexamethylene-1, 6-diisocyanate (HDI; prepared from hexamethylene-1, 6-diamine HDA), isophorone diisocyanate (IPDI; prepared from isophorone diamine IPDA), xylylene diisocyanate (XDI; prepared from xylylene diamine XDA), or mixtures of two or more of the isocyanates mentioned above.

In a twenty-first embodiment of the method of the invention, which is a specific configuration of the twentieth embodiment, the isocyanate component comprises toluene diisocyanate, or a mixture of toluene diisocyanate and di-and polyisocyanates of the diphenylmethane series (in particular does not comprise any other isocyanate than the above-mentioned isocyanates).

In a twenty-second embodiment of the method of the invention, which may be combined with all other embodiments, the alcohol component comprises a monohydric or polyhydric alcohol selected from the group consisting of

Polyether monols, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polyether carbonate polyols or mixtures of two or more of the polyols mentioned above. The alcohol component preferably contains a polyether polyol. More preferably, the alcohol component is a polyether polyol (i.e., does not contain any monol or polyol other than polyether polyol; but contains a mixture of two or more different polyether polyols, which is within the scope of this embodiment).

In a twenty-third embodiment of the method of the invention, which can be combined with all other embodiments, the alcohol component comprises a styrene-acrylonitrile copolymer filled polyether polyol.

In a twenty-fourth embodiment of the method of the invention, which may be combined with all other embodiments, the salt of an oxy acid is present in an amount of 0.10% to 20%, preferably 1.0% to 15%, more preferably 5.0% to 10% by mass of the polyurethane.

In a twenty-fifth embodiment of the method of the invention, which may be combined with all other embodiments, the mass ratio of chemical decomposition reagent (total amount) to polyurethane

In the range of 0.05 to 90, preferably 1.0 to 80.

In a twenty-sixth embodiment of the method of the invention, which may be combined with all other embodiments, the chemical decomposition is performed in the presence of (at least) a phase transfer catalyst.

In a twenty-seventh embodiment of the method of the invention, which is one specific configuration of the twenty-sixth embodiment, the phase transfer catalyst comprises a charged organic molecule.

In a twenty-eighth embodiment of the method of the invention, which is one specific configuration of the twenty-seventh embodiment, the phase transfer catalyst comprises a quaternary ammonium salt, a quaternary phosphonium salt, or a mixture of both.

The embodiments and other possible configurations briefly summarized above of the present invention are set forth in more detail below. All of the above-described embodiments of the invention, as well as other configurations described hereinafter, may be combined and assembled as desired, unless the context clearly indicates otherwise, or clearly, the contrary is intended to be contrary.

In particular, the method of the invention comprises the steps of: post-treating (II) the process product of the chemical decomposition (I) to obtain (at least) one starting material selected from (a) monohydric and/or polyhydric alcohols, (b) carbamates and/or (c) amines. The working-up (II) is preferably carried out in a step (C) in which a first product phase comprising monohydric and/or polyhydric alcohols (i.e. the alcohol component and/or other alcohols formed therefrom in chemical decomposition) and a second product phase comprising: (i) In the case of the chemical decomposition carried out into the glycolysis (Ia), the carbamate (optionally together with small amounts of amine, which are formed, for example, as a result of traces of water present in the alcohol), or (ii) in the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic). Thus, in this preferred embodiment, the method of the invention comprises the steps of:

(A) Providing a urethane (especially a polyurethane) based on an isocyanate component and a polyol component;

(B) The chemical decomposition as described above is performed, that is, with the addition of a catalyst as one of the following reactions, to obtain a chemical decomposition product:

(Ia) alcoholysis of polyurethane with alcohol (without deliberate addition of water);

(Ib) hydrolysis of polyurethane with water (without deliberate addition of alcohol);

Or (b)

(Ic) hydroalcoholysis of polyurethane with alcohol and water;

Wherein the catalyst comprises a salt of an oxyacid of an element of group five, fourteenth or fifteenth of the periodic table of elements, or a mixture of two or more of these salts, wherein the anion of the salt has a pK _B in the range of 0.10 to 6.00, preferably 0.25 to 5.00, more preferably 0.50 to 4.50, and wherein the catalyst does not comprise any carbonate in the case of the chemical decomposition carried out to alcoholysis (Ia); in the case of chemical decomposition into hydroalcoholysis (Ic), the catalyst does not comprise any carbonate, any phosphate or any metaphosphate;

And

(C) Post-treating the chemical decomposition product to obtain a first product phase comprising a monohydric and/or polyhydric alcohol (i.e., an alcohol component and/or other alcohols produced by its chemical decomposition) and a second product phase comprising: (i) In the case of the chemical decomposition carried out into alcoholysis (Ia), the carbamate (optionally together with small amounts of amine, which are formed, for example, as a result of traces of water present in the alcohol), or (ii) in the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic).

The carbamate is the other carbamate formed by the transesterification reaction, and the amine is the amine corresponding to the isocyanate formed by the hydrolysis reaction, as described above.

Providing polyurethanes for chemical recycling

Step (a) in the above embodiment comprises providing the polyurethane to be chemically recycled in preparation for chemical decomposition. In principle any kind of carbamate is possible.

Polyurethanes, i.e., urethanes derived from polyisocyanates (having 2 or more isocyanate groups per molecule) and polyols (having 2 or more alcohol groups per molecule) are preferred. In principle, this can be any polyurethane, i.e. polyurethane foam or polyurethane product in the so-called CASE application described at the outset. The polyurethane foam may be either a flexible foam or a rigid foam, preferably a flexible foam (e.g., from a used mattress, furniture cushion, or car seat). Polyurethane foams are generally produced using foaming gases such as pentane or carbon dioxide. For polyurethanes in CASE applications, polyurethane elastomers, polyurethane adhesives and polyurethane coatings are preferred.

As regards the isocyanate component, those urethanes or polyurethanes containing isocyanates selected from the following are preferred:

In the case of polyurethanes, it is particularly preferred that the isocyanate component comprises toluene diisocyanate or a mixture of toluene diisocyanate and di-and polyisocyanates of the diphenylmethane series, in particular does not comprise any other isocyanate than the isocyanates mentioned above.

As for the alcohol component, it is particularly preferable to include a monohydric alcohol or polyhydric alcohol selected from the group consisting of:

Polyether monols, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polyether carbonate polyols or mixtures of two or more of the polyols mentioned above.

The alcohol component preferably contains a polyether polyol. More preferably, the alcohol component is a polyether polyol (i.e., does not contain any monol or polyol other than polyether polyol; but contains a mixture of two or more different polyether polyols), which is within the scope of this embodiment.

The polyether polyol may also be a polyether polyol filled with a styrene-acrylonitrile copolymer (SAN copolymer). In this case, it is advantageous to carry out the chemical decomposition in the manner of hydrolysis (Ib) or hydroalcoholysis (Ic). In the chemical decomposition of polyurethanes with such polyol components based on SAN copolymer filled polyether polyols, the difficulty encountered is that the SAN copolymer released during chemical decomposition is a fine polymer particle. This SAN polymer, present as fine polymer particles, presents problems for subsequent separation (e.g., by extraction methods) in the reaction mixture. Moreover, in view of the fineness of the polymer particles, the filter can clog quickly and cannot be separated further, so that filtration is almost impossible. When the chemical decomposition is carried out in the form of hydrolysis (Ib) or hydroalcoholysis (Ic), after release of the SAN polymer from the polyether polyol, a portion of the SAN polymer is converted back into soluble form by the hydrolysis step, which facilitates the work-up of the reaction mixture by extraction after the chemical decomposition.

Preferably, this step (a) even comprises a preparation step for cleavage of the urethane bond in step (B). For polyurethanes, this is in particular mechanical comminution. These preparatory steps are known to those skilled in the art; reference is made, for example, to the literature mentioned in [1 ]. Depending on the characteristics of the polyurethane (especially polyurethane foam), it may be advantageous to "freeze" the polyurethane prior to mechanical comminution in order to facilitate the comminution operation.

The polyurethane may be treated with an aqueous or alcoholic disinfectant before, during or after mechanical comminution. The disinfectant is preferably hydrogen peroxide, chlorine dioxide, sodium hypochlorite, formaldehyde, N-chloro- (4-methylbenzene) sulfonamide sodium salt (chloramine T) and/or peracetic acid (aqueous disinfectant) or ethanol, isopropanol and/or 1-propanol (alcohol disinfectant).

It is also conceivable to carry out the above preparation step in a space location separate from the location where the chemical decomposition is carried out. In this case, the ready foam is transferred to a suitable transport vehicle (e.g., a silo vehicle) for further transport. For further transport, the ready foam can also be compressed to achieve a higher mass-to-volume ratio. The foam is then transferred to a reaction device for chemical decomposition at the site of chemical decomposition. The transport vehicle used can also be connected directly to the reaction device.

Chemical decomposition of polyurethane

The chemical decomposition of the polyurethane, step (B), is preferably carried out under anaerobic conditions. This means that the reaction is carried out in an inert atmosphere, in particular in a nitrogen, argon or helium atmosphere. It is also preferred that the chemical decomposition reagent (alcohol, water or alcohol and water) used is free of oxygen by inert gas saturation.

According to the invention, the chemical decomposition can be carried out in the form of alcoholysis (Ia), hydrolysis (Ib) or hydroalcoholysis (Ic). The terms "alcoholysis (alcoholysis)" and "hydroalcoholysis (hydroalcoholysis)" herein generally refer to glycolysis (glycolysis) and hydroglycolysis (hydroglycolysis), respectively, mentioned in the literature; see clauses 2 and 3 above. However, since this is true only if ethylene glycol (glycol) is used as the alcohol, the more general terms alcoholysis and hydroalcoholysis are used in the context of the present invention. In the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), the alcohol used for the chemical decomposition is preferably selected from the group consisting of: methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, triethylene glycol, glycerol, 2-methylpropan-1, 3-diol or a mixture of two or more of the alcohols mentioned above. Diethylene glycol and propylene glycol are particularly preferred. In the case of glycolysis, water and alcohol may be premixed, but this is not mandatory.

According to the invention, the catalyst used for the chemical decomposition is a salt of an oxo acid of an element of the fifth, fourteenth or fifteenth group of the periodic table of the elements, or a salt of a mixture of two or more of these acids, wherein the anion of the salt has a pK _B in the range of 0.10 to 6.00, preferably 0.25 to 5.00, more preferably 0.50 to 4.50, and wherein the catalyst does not comprise any carbonate in the case of the chemical decomposition carried out into alcoholysis (Ia), and does not comprise any carbonate, any phosphate or any metaphosphate in the case of the chemical decomposition carried out into hydroalcoholysis (Ic). Preferably, the element selected from group five, fourteenth or fifteenth elements of the periodic table is vanadium, carbon, silicon or phosphorus. In the case of the chemical decomposition carried out into alcoholysis (Ia), the salt of the oxo acid preferably comprises an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Phosphate (PO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Metaphosphoric acid radical ([ PO ₃ ^-]_n) ],

Alkylphosphonate (RP (O) O ₂ ^2-, wherein R represents an alkyl radical having from 1 to 18 carbon atoms, preferably from 1 to 10 carbon atoms),

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

Arylsilanolate (Ar _xSiO_4-x ^(4-x)-; wherein Ar represents aryl, in particular phenyl,

And x is 1, 2 or 3, preferably 1 or 2, more preferably 1).

Of the above anions, orthovanadate (VO ₄ ^3-), phosphate (PO ₄ ^3-) and orthosilicate (HSiO ₄ ^3-) are particularly preferred. Very particular preference is given to orthovanadate (VO ₄ ^3-) and phosphate (PO ₄ ^3-).

In the case of the chemical decomposition carried out into hydrolysis (Ib), the salt of the oxo acid preferably comprises an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Carbonate (CO ₃ ^2-),

Phosphate (PO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Metaphosphoric acid radical ([ PO ₃ ^-]_n) ],

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

Of the above anions, orthovanadate (VO ₄ ^3-), carbonate (CO ₃ ^2-), phosphate (PO ₄ ^3-) and orthosilicate (HSiO ₄ ^3-) are particularly preferred. Very particular preference is given to orthovanadate (VO ₄ ^3-), carbonate (CO ₃ ^2-) and phosphate (PO ₄ ^3-), in particular when used in combination with a phase transfer catalyst (see below).

In the case of all the chemical decomposition processes (Ia) to (Ic) described, in particular in the case of the chemical decomposition carried out into hydroalcoholysis (Ic), the salt of the oxo acid may be an anion selected from the group consisting of:

orthovanadate (VO ₄ ^3-),

Diphosphate (P ₂O₇ ^4-),

Triphosphate (P ₃O₉ ^5-),

Tetraphosphate (P ₄O₁₁ ^6-),

Hydrogen orthosilicate (HSiO ₄ ^3-),

Silicate ([ SiO ₃ ^2-]_n ]),

Hydrogen silicate ([ HSiO ₃ ^-]_n) ],

Dihydrogen orthosilicate (H ₂SiO₄ ^2-),

Trisilicate (H ₃SiO₄ ^-),

Of the above anions, orthovanadate (VO ₄ ^3-) and hydrogen orthosilicate (HSiO ₄ ^3-) are particularly preferred.

Regardless of the chemical decomposition method selected, the following applies: it is preferred to use only one salt of the (1) oxy acid as catalyst, instead of a mixture. It is also preferred that other catalysts not enumerated above are also not used. It has been found useful to meter in the salt of the oxy acid such that its mass is from 0.10% to 20%, preferably from 1.0% to 15%, more preferably from 5.0% to 10% of the mass of the polyurethane to be converted. Finally, alkali metal salts are preferably used as salts of oxo acids, in particular sodium or potassium salts, or quaternary ammonium salts. Sodium or potassium salts are particularly preferred.

In the chemical decomposition, it is preferable to observe a reaction temperature in the range of 50 to 195 ℃, more preferably 80 to 150 ℃, even more preferably 100 to 130 ℃, very particularly preferably 110 to 120 ℃. The chemical decomposition can be carried out in an autoclave without pressure compensation, in which a pressure of up to 50 bar _{( Absolute value (Absolute) )} can be established. However, the reaction is not particularly limited to pressure, but it may also be carried out at ambient pressure or at slightly reduced pressure (in particular at a lower pressure limit of 200 mbar _{( Absolute value (Absolute) )}, preferably 900 mbar _{( Absolute value (Absolute) )}), which facilitates the removal of the carbon dioxide formed. In particular, the pressure can also be increased slightly, up to 1.8 bar _{( Absolute value (Absolute) )}.

The chemical decomposition generally ends within 1.0 to 48 hours, preferably 1.5 to 24 hours, more preferably 2.0 to 10 hours, even more preferably 2.5 to 6.0 hours, very particularly preferably 3.0 to 5.5 hours; in other words, after the reaction time of this period, at most only a few further transformations, if any, take place.

In a preferred embodiment, the mass ratio of the chemical decomposition agent used (total amount) to the polyurethane,

In the range of 0.05 to 90, preferably 1.0 to 80.

In the case of hydroalcoholysis (Ic), this amount should be split into an amount of water and an amount of alcohol, wherein the mass of water represents at least 4.0%, preferably from 4.0% to 15%, more preferably from 4.0% to 10%, very particularly preferably from 5.0% to 7.0% of the mass of the alcohol. Advantageously, the water to be used in the hydroalcoholysis should not be added at the beginning of the reaction. It has been found to be advantageous to add only alcohol first and dissolve the polyurethane therein (in which case, of course, the transesterification reaction has already taken place), and then to add water. Small amounts of water (in particular 2% to 4% of the total amount of water used in the chemical decomposition) may also be added to the polyurethane together with the alcohol. The addition of water in the former case, or in the latter case the addition of the majority of water, is then preferably not completed immediately, but rather in a manner with a time delay for the further progress of the chemical decomposition within the reaction time. In the case of adding water in a time-delayed manner, the requirement "the mass of water represents at least 4.0%, preferably 4.0% to 15%, more preferably 4.0% to 10%, very particularly preferably 5.0% to 7.0% of the mass of alcohol" is related to the total amount of water added as a part of the chemical decomposition reagent.

In the case where the chemical decomposition performed is alcoholysis (Ia), water is not used as the chemical decomposing reagent. Small amounts of water introduced from other sources, in particular from the moisture in the alcohol, are not excluded. Nor does it exclude the dissolution of the catalyst in water. In the context of the alcoholysis of the invention, the amount of water introduced into the chemical decomposition is at most such that the mass of water present during the alcoholysis is from 0% to <4.0%, in particular from 0% to 3.5%, preferably from 0% to 3.4%, more preferably from 0% to 3.0%, most preferably from 0% to 2.0% of the mass of alcohol used. Alcoholysis first generates carbamates and mono-and/or polyols. If the aim is to isolate the amine, the hydrolysis must be carried out in a separate process step from the alcoholysis, as will be explained in more detail below.

In chemical decomposition, it may be advantageous to add at least one phase transfer catalyst in addition to the catalyst (i.e. in addition to the chemical decomposition catalyst) to increase the yield and/or shorten the reaction time. Without wishing to be bound by any theory, it is believed that the phase transfer catalyst promotes the transport of the actual catalyst (chemical decomposition catalyst) into the (hydrophobic) polyurethane, thereby accelerating the degradation reaction. Suitable phase transfer catalysts are preferably compounds having charged organic molecules, preferably quaternary ammonium salts ([ R ₄N]⁺X^-) or quaternary phosphonium salts ([ R ₄P]⁺X^-) having an organic group (R) and a counterion (X ^-). Quaternary ammonium salts having an organic group and a counter ion are particularly preferred. The organic radical (R) is preferably methyl, propyl, butyl, pentyl, hexyl, octyl, hexadecyl or octadecyl or benzyl, the four radicals of the quaternary ammonium or phosphonium salts being each different or identical. The counter ion (X ^-) is preferably chloride, bromide, sulfate, chlorate or triflate. Suitable phase transfer catalysts are, for example, trimethylbenzyl ammonium chloride, tetra (1-propyl) ammonium chloride, tetra (1-butyl) ammonium chloride, tetra (1-pentyl) ammonium chloride, tetra (1-hexyl) ammonium chloride, dimethyl dioctadecyl ammonium chloride, tetraphenyl phosphonium chloride, hexa (1-decyl) tributyl phosphonium chloride, methyltri (1-octyl) phosphonium chloride and/or methyltri (1-octyl) ammonium chloride ("Aliquat 336"), preferably tetra (1-butyl) ammonium chloride, tetra (1-pentyl) ammonium chloride, tetra (1-hexyl) ammonium chloride and methyltri (1-octyl) ammonium chloride ("Aliquat 336"). Most preferably, the phase transfer catalyst used is tetra (1-hexyl) ammonium chloride and/or methyltri (1-octyl) ammonium chloride ("Aliquat 336").

The chemical decomposition can be carried out in any reactor known in the art for this purpose. In particular, in addition to the autoclaves already mentioned, suitable chemical decomposition reactors are stirred tanks (stirred reactors) and tubular reactors.

Post-treatment of chemical decomposition products

The product mixture is obtained from the chemical decomposition (I) of polyurethane, the chemical decomposition product. In order to isolate the desired starting material, it is necessary to subject the chemical decomposition products to a working-up (II); preferably according to step (C) in the preferred embodiment described above. The purpose of the work-up (II) according to step (C) is to provide two product phases, one of which (hereinafter referred to as first product phase) contains monohydric and/or polyhydric alcohols (i.e. the alcohol component and/or other alcohols formed therefrom in the chemical decomposition) and/or according to the nature of the chemical decomposition, wherein the second product phase (hereinafter referred to as second product phase) contains the following:

(i) In the case of the chemical decomposition carried out into alcoholysis (Ia): carbamates (possibly together with small amounts of amines, produced, for example, due to traces of water contained in the alcohol), or

(Ii) In the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic): an amine.

It is obvious to a person skilled in the art that in this sense-all mono-or polyols go into the first product phase and all carbamates or amines go into the second product phase, the separation of the two product phases does not necessarily need to be done perfectly. For example, if a small amount of amine enters the first product phase (or a small amount of monohydric or polyhydric alcohol enters the second product phase) due to the dissolution equilibrium, this certainly does not depart from the scope of this embodiment.

Depending on the nature of the chemical decomposition reagent used, it is possible to obtain the chemical decomposition product directly in the form of two phases. This is generally the case when the chemical decomposition is carried out in the hydrolysis (Ib) or hydroalcoholysis (Ic) mode. This is often the case even when the chemical decomposition is carried out in the alcoholysis (Ia) mode, depending on the choice of alcohol. If one of the two phases contains a major part of the monohydric or polyhydric alcohol and the other of the two phases contains a major part of the carbamate or amine, the first and second product phases can be obtained by simple phase separation. The first product phase may then be passed directly to further work-up to isolate the monohydric or polyhydric alcohol (hereinafter referred to as step (D)). Accordingly, the second product phase may be directly subjected to further work-up to isolate the amine (hereinafter referred to as step (E)). This embodiment is contemplated, for example, under conditions where TDI-based polyurethane foam is used and chemical decomposition is carried out using diethylene glycol in the manner of hydroalcoholysis. The TDA produced (due to its water solubility) forms a second product phase (alcohol-water phase) together with diethylene glycol and unconverted water, which are also water-soluble, while the polyol recovered forms a first product phase (organic phase). Whether this embodiment can be applied or not can be easily determined by a person skilled in the art taking into account or by simple preliminary experiments.

However, the chemical decomposition products may not be able to provide the first product phase with sufficient mono-or polyol content and the second product with sufficient carbamate content by simple phase separation. In this case, it is preferable to extract all the chemical decomposition products using an organic solvent. This is also the method of choice when the chemical decomposition product is in single phase form. Several options for these extraction methods are as follows:

In a preferred embodiment, in the case of the chemical decomposition carried out into hydrolysis (Ib), the chemical decomposition products are extracted with an organic solvent and then separated into a first and a second product phase. Suitable organic solvents are aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, halogenated alicyclic hydrocarbons, halogenated aromatic hydrocarbons and mixtures of two or more of the foregoing organic solvents.

In a preferred embodiment, in the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), the work-up of the chemical decomposition product comprises admixing it with an organic solvent which is not completely miscible with the alcohol used in the chemical decomposition and phase separating into a first product phase and a second product phase. The requirement that the organic solvent used in the extraction is not fully miscible with the alcohol used in the chemical decomposition means that-in case of adjusting the temperature of the extraction and the ratio of organic solvent to alcohol from the chemical decomposition in the extraction-a miscibility gap (miscibility gap) must exist, making phase separation possible. This is the case, for example, under the following conditions: the organic solvent is selected from aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and mixtures of two or more of the above organic solvents, and the alcohol used in the chemical decomposition is selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, triethylene glycol, glycerol, 2-methylpropan-1, 3-diol or mixtures of two or more of the above alcohols. In case of doubt, it can be easily ascertained by a simple preliminary test whether a suitable miscibility gap is present.

In another preferred embodiment, in the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), the extraction process which can also be employed is: the work-up of the chemical decomposition products is also carried out by extraction, but the organic solvent used is miscible with the alcohol used in the chemical decomposition. In this case, the post-processing includes the steps of:

(1) Mixing the chemical decomposition product with an organic solvent miscible with the alcohol used in the chemical decomposition to obtain a product mixture, and

(2) The product mixture is washed with an aqueous wash and phase separated into a first product phase and a second product phase.

This requirement, the organic solvent used in step (1) is miscible with the alcohol used in step (B), means that-in the case of adjusting the temperature of step (1) and the ratio of the organic solvent to the alcohol from chemical decomposition in step (1) -the mixture of the organic solvent and the alcohol from chemical decomposition does not spontaneously separate into two phases. This is the case, for example, under the following conditions: when the organic solvent in step (1) is selected from the group consisting of halogenated aliphatic hydrocarbons, halogenated alicyclic hydrocarbons, halogenated aromatic hydrocarbons and mixtures of two or more of the foregoing organic solvents, and the alcohol used for chemical decomposition is selected from the group consisting of methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, triethylene glycol, glycerol, 2-methylpropan-1, 3-diol or mixtures of two or more of the foregoing alcohols.

Post-treatment of the first product phase

The first product phase comprises the monohydric and/or polyhydric alcohol, preferably it is isolated in a substantially very clean form for post-treatment (step (D) in the preferred embodiment described above). The treatment is preferably carried out by distillation and/or stripping with a stripping gas, such as in particular nitrogen or steam, preferably nitrogen. This comprises carrying out the distillation, preferably in an evaporator selected from the group consisting of falling film evaporators, thin film evaporators, flash evaporators, rising film evaporators, natural circulation evaporators, forced circulation evaporators or tank evaporators. It is particularly preferred to carry out the stripping operation with steam after distillation. Steam stripping can be achieved by passing steam through a stripping column known per se. Steam stripping, however, can also be achieved in such a way that: the water in liquid form is added to the first product phase (which optionally has been prepurified in distillation) and then superheated (pressure is regulated by a pressure valve sufficient to keep the water in liquid form) and depressurized downstream of the pressure valve, as a result of which the water in the polyol is evaporated and has a stripping effect.

Post-treatment of the second product phase

The second product phase comprises an amine or carbamate, which is preferably isolated in a substantially very clean form for work-up (step (E) in the preferred embodiment described above).

If the second product phase contains no carbamate at all, or only a negligible proportion of carbamate, as in the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic), the recovery of the amine advantageously first comprises distillative separation of the alcohol and water from the second product phase. This can be accomplished by known distillation techniques. The remaining crude amine is preferably subjected to further work-up, in particular by distillation.

If the second product phase is predominantly composed of carbamate, as is desired in the case of the chemical decomposition carried out into alcoholysis (Ia), it is advantageous if the recovery of amine comprises hydrolysis of carbamate into amine and distillative removal of alcohol and water, followed by distillative purification of the crude amine remaining after this distillative removal. The hydrolysis and the evaporation of water and alcohol do not have to be carried out in this order. It is also entirely possible to evaporate the alcohol fraction first (usually together with a portion of the water) and then to carry out the hydrolysis, finally removing the remaining water in the step of distilling the crude amine. In the work-up of the second product phase, the catalysts suitable for the hydrolysis step are those of the prior art which are suitable for hydrolysis and are likewise the catalysts used according to the invention in the chemical decomposition of step (B). The abovementioned possibilities of phase transfer catalysis in connection with step (B) can also be used in the same way in hydrolysis and working up of the second product phase.

In any case, it is preferred to integrate the recovery of the amine into the post-treatment of the newly produced amine by mixing the crude amine with the crude product fraction of the amine resulting from the newly produced same amine. This embodiment provides an economical and environmentally friendly scheme for impurities derived from polyurethane products. International patent application WO 2020/260387 A1 describes this in more detail.

The present invention will be described in more detail with reference to examples.

Examples:

the test reactions selected were cleavage of 2- (2-ethoxyethoxy) ethyl N-phenylcarbamate to (i) aniline or a carbamate formed from aniline and monoethylene glycol (MEG) and (ii) 2- (2-ethoxyethoxy) ethane-1-ol. In each case, 0.25 mmol of 2- (2-ethoxyethoxy) ethyl phenylcarbamate was converted in an autoclave. The catalyst and the phase transfer catalyst used were commercial products and no further purification was required.

The experimental conditions and experimental results are summarized in the following table:

table 1: chemical decomposition general test result overview

[A] (I) =the present experiment; (C) Comparative experiment [ b ] conversion of 2- (2-ethoxyethoxy) ethyl N-phenylcarbamate, determined by gas chromatography

Table 2: overview of experimental results under the influence of Phase Transfer Catalysts (PTC)

[A] Conversion of 2- (2-ethoxyethoxy) ethyl phenylcarbamate was determined by gas chromatography.

[B] methyl tris (1-octyl) ammonium chloride

Claims

1. A method for cleaving a carbamate by chemical decomposition (I), comprising (a) providing a carbamate based on an isocyanate component and an alcohol component, and then (B) subjecting the carbamate to chemical decomposition (I) with a chemical decomposition reagent to obtain a chemical decomposition product, wherein the chemical decomposition (I) is performed with the addition of a catalyst that is one of the following conversions:

(Ia) alcoholysis of carbamates, wherein the chemical decomposing agent is an alcohol

(Ib) hydrolysis of the carbamate, wherein the chemical decomposition agent is water,

Or (b)

(Ic) hydroalcoholysis of carbamates, wherein the chemical decomposing agent comprises an alcohol and water,

Wherein the catalyst comprises a salt of an oxyacid of a fifth, fourteenth or fifteenth group of the periodic table of elements, or a mixture of two or more such oxyacids, wherein the anion of the oxyacid salt has a pK _B in the range of 0.10 to 6.00, and wherein the catalyst does not comprise any carbonate in the case of chemical decomposition to alcoholysis (Ia); in the case of the chemical decomposition carried out into hydroalcoholysis (Ic), the catalyst does not comprise any carbonate, any phosphate or any metaphosphate.

2. The method according to claim 1, comprising

(C) Post-treating (II) the chemical decomposition product to obtain a first product phase comprising monohydric and/or polyhydric alcohols, and a second product phase comprising:

(i) In the case of the chemical decomposition carried out into alcoholysis (Ia), carbamate, or (ii) in the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic), amine.

3. The method of claim 2, wherein step (C) comprises phase separating the chemical decomposition products into a first product phase and a second product phase.

4. The method of claim 2, wherein

(I) In the case of the chemical decomposition carried out into hydrolysis (Ib), step (C) comprises blending the chemical decomposition product with an organic solvent and phase separating into a first product phase and a second product phase.

(Ii) In the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), step (C) comprises blending the chemical decomposition product with an organic solvent which is not completely miscible with the alcohol used in step (B) and phase separating into a first product phase and a second product phase,

Or (b)

(Iii) In the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), step (C) comprises:

5. The method according to any one of claims 2 to 4, comprising:

(D) The monohydric and/or polyhydric alcohol is obtained from the first product phase.

6. The method according to any one of claims 2 to 5, comprising:

(E) The amine is obtained from the second product phase.

7. The method according to claim 6, wherein:

(i) In the case of the chemical decomposition carried out into alcoholysis (Ia), step (E) comprises hydrolyzing the carbamate to an amine and distilling off the alcohol and water, followed by distillative purification of the remaining amine after the distillative removal;

Or (b)

(Ii) In the case of the chemical decomposition carried out into hydrolysis (Ib) or hydroalcoholysis (Ic), step (E) comprises distillative removal of alcohol and water from the second product phase and then distillative purification of the remaining amine after this distillative removal.

8. The process according to any of the preceding claims, wherein in the case of the chemical decomposition carried out into alcoholysis (Ia) or hydroalcoholysis (Ic), the alcohol used for the chemical decomposition is selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, triethylene glycol, glycerol, 2-methylpropan-1, 3-diol or a mixture of two or more of the alcohols mentioned above.

9. The method of any one of the preceding claims, wherein the element of group five, fourteenth or fifteenth of the periodic table is selected from vanadium, carbon, silicon and phosphorus.

10. The method according to claim 9, wherein:

(i) In the case of the chemical decomposition carried out into alcoholysis (Ia), the salt of the oxo acid comprises an anion selected from the group consisting of orthovanadate, phosphate, diphosphate, triphosphate, tetraphosphate, metaphosphate, alkylphosphonate, arylphosphonate, hydrogen orthosilicate, silicate, hydrogen silicate, dihydrogen orthosilicate, trihydrogen orthosilicate, alkylsilanol and arylsilanol;

(ii) In the case of the chemical decomposition carried out into hydrolysis (Ib), the salt of the oxo acid comprises an anion selected from orthovanadate, carbonate, phosphate, diphosphate, triphosphate, tetraphosphate, metaphosphate, alkylphosphonate, arylphosphonate, orthosilicate, silicate, hydrogen silicate, dihydrogen orthosilicate, trihydrogen orthosilicate, alkylsilanol and arylsilanol; or alternatively

(Iii) In the case of the chemical decomposition carried out into hydroalcoholysis (Ic), the salt of the oxo acid comprises an anion selected from the group consisting of orthovanadate, diphosphate, triphosphate, tetraphosphate, alkylphosphonate, arylphosphonate, hydrogen orthosilicate, silicate, hydrogen silicate, dihydrogen orthosilicate, trihydrogen orthosilicate, alkylsilanol and arylsilanol.

11. The method of claim 9, wherein the salt of an oxy acid comprises an anion selected from the group consisting of orthovanadate, diphosphate, triphosphate, tetraphosphate, alkylphosphonate, arylphosphonate, hydrogen orthosilicate, silicate, hydrogen silicate, dihydrogen orthosilicate, trihydrogen orthosilicate, alkylsilanol, and arylsilanol.

12. The method of claim 10 or 11, wherein the salt of an oxy acid does not comprise any other anions than the anions described above.

13. The method of any of the preceding claims, wherein the isocyanate component comprises an isocyanate selected from the group consisting of:

Phenyl isocyanate (PHI; prepared from aniline ANL), toluene diisocyanate (TDI;

Prepared from toluenediamine TDA), di-and polyisocyanates of the diphenylmethane series (MDI; prepared from diamines and polyamines MDA of the diphenylmethane series), pentane-1, 5-diisocyanate (PDI; prepared from pentane-1, 5-diamine PDA), hexamethylene-1, 6-diisocyanate (HDI; prepared from hexamethylene-1, 6-diamine HDA), isophorone diisocyanate (IPDI; prepared from isophorone diamine IPDA), xylylene diisocyanate (XDI; prepared from xylylenediamine XDA), or a mixture of two or more isocyanates mentioned above;

and/or wherein the alcohol component comprises a monohydric or polyhydric alcohol selected from the group consisting of:

Polyether monols, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols, polyether carbonate polyols, or mixtures of two or more of the polyols mentioned above.

14. The method according to any of the preceding claims, wherein the mass of the salt of the oxo acid is 0.10 to 20% of the mass of the carbamate, and/or wherein the mass ratio of the chemical decomposition reagent to the carbamate is in the range of 0.05 to 90.

15. The method according to any of the preceding claims, wherein a phase transfer catalyst is used in addition to the catalyst in the chemical decomposition.