Method for recovering raw materials from polyurethane products

Abstract

The present invention relates to a method for recovering at least one raw material from a polyurethane product, comprising: (A) providing an isocyanate component at a concentration of 1013 mbar of the corresponding amine; (abs.) (B) preparing a polyurethane product based on an isocyanate component and a polyol component, the polyurethane product containing only isocyanates having a boiling point of at most 410°C at 10°C; (C) carrying out a chemical decomposition of the polyurethane product using alcohol and water; and (D) carrying out a chemical decomposition of the polyurethane product using alcohol and water at a temperature in the range of 10°C to 60°C at 1013 mbar. (abs.) (C.II) treating the products of the chemical decomposition comprising extracting the amines with an organic solvent having a boiling point at 40° C. to 120° C. at room temperature, followed by phase separation into a first product phase and a second product phase; and (D) treating the first product phase to obtain a polyol comprising (DI) separating the organic solvent by distillation and / or stripping, and (D.II) separating the amines dissolved in the first product phase by distillation to obtain a polyol.

Description

[Technical field]

[0001] The present invention relates to a method for recovering at least one raw material from a polyurethane product, comprising the steps of: (A) providing a polyurethane product based on an isocyanate component and a polyol component, wherein the isocyanate component is at least 1013 mbar of the corresponding amine; (abs.) (B) chemically decomposing the polyurethane product with alcohol and water; and (C) (CI) at a temperature in the range of 10°C to 60°C and 1013 mbar. (abs.) (C) extracting the product of chemical decomposition with an organic solvent having a boiling point at 40° C. to 120° C. at room temperature, followed by (C.II) a step of post-treating the product of chemical decomposition, comprising phase separation into a first product phase and a second product phase; and (D) a step of post-treating the first product phase to obtain a polyol, comprising (DI) separating and removing the organic solvent by distillation and / or stripping, and (D.II) separating and removing the amine dissolved in the first product phase by distillation to obtain a polyol. [Background technology]

[0002] Polyurethane products have a variety of applications in industry and in everyday life. A distinction is usually made between polyurethane foams and what are known as "CASE" products, the latter being a general term for polyurethane coatings (e.g. paints), adhesives, sealants and elastomers. Polyurethane foams are usually divided into rigid and flexible foams. Despite their heterogeneity, the basic polyurethane structure is common to all these products, which is formed by the polyaddition reaction of multifunctional isocyanates with polyols, for example in the case of polyurethanes based on diisocyanates O=C=NRN=C=O and diols HO-R'-OH, where R and R' represent organic groups: ~~~[O-R'-O-(O=C)-HN-R-NH-(C=O)]~~~ It can be expressed as:

[0003] The great economic success of polyurethane products is the reason for the generation of large amounts of polyurethane waste (e.g. from old mattresses or seating furniture), which must be used rationally. The technically easiest method of recycling to implement is incineration, where the heat of combustion released is utilized in other processes, for example industrial processes. However, this does not allow the raw material cycle to be completed. Another method of recycling is the so-called "physical recycling", in which polyurethane waste is mechanically comminuted and used to manufacture new products. This type of recycling, of course, has its limitations, which does not eliminate attempts to recover the basic raw materials for polyurethane production by retrocleavage of polyurethane bonds (so-called "chemical recycling"). The raw materials recovered are firstly polyols (i.e. HO-R'-OH in the above example, or polyols formed therefrom in chemical decomposition). Secondly, it is also possible to recover amines by hydrolytic cleavage of urethane bonds (i.e. H2N-R-NH2 in the above example), which can be phosgenated after workup to give isocyanates (O=C=NRN=C=O in the above example).

[0004] A variety of chemical recycling approaches have been developed so far. The three most important can be briefly summarized as follows: 1. Hydrolysis of urethanes by reaction with water to recover amines and polyols and form carbon dioxide. 2. Glycolysis of urethanes by reaction with alcohols, whereby the polyol incorporated in the urethane group is replaced by the alcohol used, releasing the polyol. This process is generally referred to in the literature as transesterification (more correctly, transurethanization). Regardless of the exact nature of the alcohol used, this method of chemical recycling is usually referred to in the literature as glycolysis, a term that in fact applies only to glycols. Therefore, in the context of the present invention, the term alcoholysis is generally used. Glycolysis may be followed by hydrolysis. If the hydrolysis is carried out in the presence of the still unchanged glycolysis mixture, it is called hydroglycolysis. 3. Hydroglycolysis of urethane bonds by reaction with alcohol and water. Of course, it is also possible to add alcohol and water from the beginning, in which case the above-mentioned glycolysis and hydrolysis processes will proceed in parallel.

[0005] An overview of known polyurethane recycling methods is given in a review by ., who highlights that glycolysis (2. above) is particularly important. In glycolysis, a distinction is made between the "biphasic" and "monophasic" regimes, depending on whether the crude product obtained in the reaction with alcohol separates into two phases or not. This depends in particular on the choice of the alcohol used and on the process conditions (in particular the proportion of alcohol used in the reaction mixture and the temperature). In , the biphasic regime with crude glycerol (e.g. a waste product from biodiesel production) is preferred, as it offers the highest possibility of recovering a high-quality product at low production costs (polyol recovery is clearly the focus).

[0006] As a result of the additional use of water, the products of hydroglycolysis (3. above) are always biphasic. 2001, pp. 1111-1115 describes a work-up of the products of this type of process, which includes removal of water (either by phase separation on a laboratory scale or by evaporation in a process recommended for industrial scale applications and called the "Ford hydroglycolysis process") and extraction of the remaining organic phase with hexadecane to form an alcohol phase from which amines can be recovered and a hexadecane phase from which polyols can be recovered. Although the option of recovering amines is mentioned, 2001, pp. 1111-1115 also focuses on the recovery of polyols.

[0007] A process operating on these principles has been patented in US Pat. No. 5,399,633, which is a process for recovering polyether polyols from polyurethanes, comprising the steps of: (a) dissolving said polyurethane in a saturated alcohol having a boiling point of 225° C.-280° C. at a temperature of 185° C.-220° C. under a non-oxidizing atmosphere to form a solution; (b) refluxing said solution with water in the presence of an alkali metal hydroxide catalyst under said non-oxidizing atmosphere while maintaining said solution at a temperature of 175° C.-220° C. for a time required to substantially hydrolyze the hydrolyzed solution products to amines and alcohols; A metal hydroxide catalyst is contained in the solution in an amount in the range of at least 0.1% by weight based on the weight of the polyurethane foam; (c) removing water remaining after hydrolysis from the solution under a non-oxidizing atmosphere; (d) extracting the polyol from the hydrolysis solution using an alkane (particularly hexadecane) that is substantially immiscible with the alcohol and has a boiling point of 230°C to 300°C under a non-oxidizing atmosphere; and (e) subjecting the extracted polyol to vacuum purification at a temperature of less than about 230°C.

[0008] In step (a), the polyurethane is reacted with an alcohol group of a saturated alcohol to form a polyol, a urea, and a carbamate (see column 3, lines 42-46).

[0009] In step (b), water and an alkali metal hydroxide catalyst are added to the solution obtained in step (a) either separately or in the form of an aqueous catalytic solution, to decompose the carbamates and ureas into amines and alcohols. Steps (a) and (b) are generally described as hydroglycolysis (more precisely hydroalcoholysis), including the time delay between the addition of the alcohol and the addition of the water. Water is added in such an amount that the solution boils at a temperature between 175°C and 200°C. When the alcohol is diethylene glycol, water is added in an amount between 2.4% and 0.6%, preferably 1.1%, of the mass of diethylene glycol used (see column 4, lines 39-46). The water consumed in the hydrolysis is replenished by the addition of further water to keep the water content constant. After the hydrolysis, the water used must be removed in step (c) before the extraction of step (e) can be carried out (column 5, lines 31-33).

[0010] Patent Document 2 describes a process in which polyurethane foam is first dissolved in alcohol, then water and a catalyst are added, and the reaction mixture is heated under reflux. The resulting reaction product is either monophasic (in which case it is purified by vacuum distillation) or biphasic (in which case the polyol phase is removed and purified by vacuum distillation). The polyol thus recovered can be used to produce new polyurethane foam.

[0011] Of the chemical recycling processes known from the literature, only a few are operating sustainably on an industrial scale, and many have not even reached pilot scale (Non-Patent Document 1). Given the general increase in environmental awareness and the growing efforts to make industrial processes as sustainable as possible, both of which basically support chemical recycling, it is clearly shown that chemical recycling of polyurethane products is still by no means mature from a technical and economic point of view. There are challenges, especially with regard to the purity of the recovered products. In case of reuse in the production of polyurethane foams, it is necessary to recover polyols as free as possible from amine impurities, in order not to have a negative effect on, for example, the foaming properties. If the additional aim is the recovery of amines, these must also be obtained of course in maximum purity. In addition, the polyurethane products to be reused usually still contain various auxiliaries and additives (stabilizers, catalysts, etc.), which must be separated and disposed of in an economically viable and environmentally friendly way from the actual product to be recycled. Furthermore, an economical recycling process must ensure that the reagents used (e.g. the alcohols used) are recovered as completely as possible and can be reused (i.e. following a closed loop).

[0012] Patent document 3 relates to a solution to such difficulties. Patent document 3 describes a method for recovering raw materials from a polyurethane product, comprising the steps of (A) preparing a polyurethane product based on isocyanate and polyol, (B) reacting the polyurethane product with a (monohydric or polyhydric) alcohol in the presence of a catalyst to obtain a first product mixture, (C) recovering the polyol from the first product mixture, including (CI) combining the first product mixture obtained in step (B) with an organic solvent that is not completely miscible with the alcohol used in step (B) without prior removal of the water present in the first product mixture, and carrying out a phase separation into a first alcohol phase and a first solvent phase, and (C.II) working up the first solvent phase to recover the polyol, and preferably (D) recovering the amine. Although the described method offers a promising approach to the solution with respect to the mentioned problems, and shows a particularly efficient and environmentally friendly way to recover the amine, while at the same time neatly discharging the accompanying substances (e.g. stabilizers) originating from the polyurethane product, it is not without drawbacks. For example, the polyol phase is obtained in admixture with (small amounts of) carbamates, which must be separated off and have very high boiling points which make them difficult to remove by simple distillation. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 4,336,406 [Patent Document 2] U.S. Patent No. 4,317,939 [Patent Document 3] International Publication No. 2020 / 260387 [Non-patent literature]

[0014] [Non-Patent Document 1] Simon, Borreguero, Lucas and Rodriguez in Waste Management 2018, 76, 147-171 [Non-Patent Document 2] Braslaw and Gerlock in Ind. Eng. Chem. Process Des. Dev. 1984, 23, 552-557 Summary of the Invention [Problem to be solved by the invention]

[0015] For this reason, further improvements were needed in the field of chemical recycling of polyurethanes. In particular, it would be desirable to be able to recover polyols, preferably also amines, from polyurethane products in high purity and efficiently, in a manner that makes their use economically achievable, especially on an industrial scale. To this end, a method is desirable in which the chemical decomposition and the post-treatment of the crude product from the chemical decomposition are arranged in such a way that the maximum purity of the polyols can be recovered with a minimum of complexity. [Means for solving the problem]

[0016] Considering this requirement, the present invention provides a method for recovering at least one raw material from a polyurethane product, comprising: (A) providing a polyurethane product based on an isocyanate component and a polyol component; The isocyanate component is reacted with the corresponding amine at 1013 mbar. (abs.) contains only isocyanates having a boiling point at 410°C or less, preferably in the range of 170°C to 400°C; (B) reacting the polyurethane product in the presence of a catalyst in the liquid phase with a stoichiometric excess of alcohol and a stoichiometric excess of water (=chemical decomposition) to obtain chemical decomposition products comprising alcohol (unconverted alcohol in the chemical decomposition), water (unconverted water in the chemical decomposition), (at least) polyol (in particular from the polyol component or optionally formed from the polyol component in the chemical decomposition) and (at least) amines corresponding to the isocyanates of the isocyanate component; (C) (CI) Chemical decomposition products at temperatures ranging from 10°C to 60°C and 1013 mbar (abs.) Extraction with an organic solvent having a boiling point in the range of 40°C to 120°C at room temperature, optionally with the addition of water, followed by (C.II) a first product phase comprising (at least a majority of) an organic solvent, (at least a majority of) a polyol and a first (relatively small) portion of an amine, and optionally a first (relatively small) portion of an alcohol; a second product phase comprising alcohol (at least a majority thereof, possibly only a second (larger) portion of the alcohol), water (at least a majority thereof) and a second portion (=most) of the amine; 4. Phase separation into post-treating the chemical decomposition products, comprising: (D) separating and removing (at least a majority of) the organic solvent by (DI) distillation and / or stripping; (D.II) isolating and removing a first portion of the amine by distillation to obtain a polyol (i.e., at least one feedstock); post-treating the first product phase to obtain a polyol; The present invention provides a method comprising:

[0017] Quite surprisingly, in the case of the polyurethane product designated in (A), the chemical decomposition constitutes hydrolysis, and is at a temperature in the range of 10°C to 60°C and a pressure of 1013 mbar (abs.)It has been found that if the work-up of the chemical decomposition products is constituted by extraction with an organic solvent having a boiling point in the range of 40°C to 120°C at room temperature, it is possible to obtain high-purity polyols in a simple manner in the subsequent work-up steps.

[0018] A polyurethane product in the context of the present invention is a polyaddition product (sometimes also called, although not entirely correctly, a polycondensation product) of a polyfunctional isocyanate (=isocyanate component in the polyurethane preparation) and a polyol (=polyol component in the polyurethane preparation). A polyurethane product generally contains not only the polyurethane basic structure outlined above, but also other structures, for example structures with urea bonds. The presence of such structures that deviate from the pure polyurethane basic structure, in addition to the polyurethane structure, does not depart from the scope of the present invention.

[0019] The amines corresponding to the isocyanates are those amines which can be phosgenated to give isocyanates according to R-NH2+COCl2→RN=C=O+2HCl. In the terminology of the present invention, the term isocyanate includes all isocyanates known to those skilled in the art in connection with polyurethane chemistry, in so far as their corresponding amines fulfill the conditions specified in (A). Isocyanates in the context of the present invention are in particular tolylene diisocyanate (TDI; the corresponding amine is tolylene diamine, TDA), diisocyanates of the diphenylmethane series ("monomeric MDI", mMDI; the corresponding amine is diamine of the diphenylmethane series, mMDA), pentane 1,5-diisocyanate (TDI; the corresponding amine is pentane-1,5-diamine, PDA), hexamethylene 1,6-diisocyanate (HDI; the corresponding amine is hexamethylene-1,6-diamine, HDA), isophorone diisocyanate (IPDI; the corresponding amine is isophorone diamine, IPDA) and xylylene diisocyanate (XDI; the corresponding amine is xylylene diamine, XDA). The term "isocyanate" naturally encompasses embodiments in which two or more different isocyanates (e.g., a mixture of MDI and TDI) are used in the preparation of the polyurethane product, unless expressly stated otherwise, e.g., by the term "exactly one isocyanate". Collectively, all isocyanates used in the preparation of the polyurethane product are referred to as the isocyanate component (of the polyurethane product). The isocyanate component comprises at least one isocyanate. Similarly, collectively, all polyols used in the preparation of the polyurethane product are referred to as the polyol component (of the polyurethane product). The polyol component comprises at least one polyol.

[0020] In the terminology of the present invention, the term polyol includes all polyols known to the skilled person in the art in relation to polyurethane chemistry, such as, in particular, polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols and polyether carbonate polyols. The expression "polyol" naturally also includes the embodiment in which two or more different polyols are used in the manufacture of the polyurethane product. Thus, for example, when referring hereinafter to "polyether polyol", this term naturally also includes the embodiment in which two or more different polyether polyols are used in the manufacture of the polyurethane product. The term polyol may also refer to the polyol formed during chemical decomposition from the polyol originally used in the manufacture of the polyurethane product. However, as will be explained in more detail further below, the polyol of the polyol component is preferably a polyether polyol or a polyacrylate polyol that can be recovered as such during chemical decomposition.

[0021] The expression "reacting the polyurethane product with a stoichiometric excess of alcohol and a stoichiometric excess of water" does not necessarily mean that all of the water used in step (B) must be added immediately at the beginning of step (B). Instead, the present invention encompasses embodiments in which no water or only a portion of the water is added initially at the beginning of step (B) and water / the remainder of the water is added continuously during the reaction time. In principle, it is also conceivable to gradually add the alcohol or a mixture of water and alcohol.

[0022] In the process of the present invention, water and alcohol are used in superstoichiometric amounts, which means that a theoretically sufficient amount of water is used to hydrolyze all of the polyurethane bonds to obtain amines and polyols with the release of carbon dioxide.Similarly, the use of a superstoichiometric amount of alcohol means that the alcohol is used in a theoretically sufficient amount to convert all of the polyurethane bonds to form carbamates and polyols. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic visualization of a method of the present invention for obtaining at least a polyol raw material 12. [Diagram 2] FIG. 2 is a schematic diagram of a preferred embodiment of the process of the present invention which also provides an amine feedstock 18. [Diagram 3] FIG. 2 shows the kinematic viscosity at different temperatures of the polyol recovered by the process of the present invention compared to fresh polyol of the same type. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] First, a summary of various possible embodiments of the present invention follows.

[0025] In a first embodiment of the invention, which can be combined with all other embodiments, in step (E) a first portion of the amine is added to the second product phase, which is together worked up in step (F) to give the amine.

[0026] In a second embodiment of the present invention, which can be combined with all other embodiments, in step (G), the organic solvent separated and removed in step (DI) is supplied to step (CI).

[0027] In a third embodiment of the invention, which can be combined with all other embodiments, in step (DI) the organic solvent is first separated off as a solvent fraction in a first stage and then an alcohol fraction (containing a first (relatively small) portion of alcohol and optionally a (relatively small) portion of organic solvent) is separated off in a second stage.

[0028] In a fourth embodiment of the invention, which is a specific configuration of the third embodiment, the second stage is carried out in a thin film evaporator, a short path evaporator or a flash evaporator.

[0029] In a fifth embodiment of the present invention, which is a specific configuration of the third and fourth embodiments, the alcohol fraction separated and removed in the second stage is supplied to step (B).

[0030] In a sixth embodiment of the present invention, which is a further specific configuration of the third and fourth embodiments, the alcohol fraction separated and removed in the second stage is separated into an alcohol phase and a solvent phase, and the alcohol phase is supplied to step (B) and the solvent phase is supplied to step (CI).

[0031] In a seventh embodiment of the present invention, which can be combined with all other embodiments, the separation and removal of the organic solvent in step (DI) is carried out in a falling film evaporator, a natural circulation evaporator, a tank evaporator, a forced circulation evaporator or a flash evaporator.

[0032] In an eighth embodiment of the present invention, which can be combined with all other embodiments, the separation off of the first part of the amine in step (D.II) is carried out in a thin-film evaporator, a short-path evaporator or a flash evaporator.

[0033] In a ninth embodiment of the present invention, which can be combined with all other embodiments, the separation and removal of the first portion of the amine in step (D.II) is carried out at a pressure of 0.1 mbar (abs.) ~5.0mbar (abs.) and a temperature of 140℃ to 240℃.

[0034] In a tenth embodiment of the present invention, which can be combined with all other embodiments, in step (B), (I) the polyurethane product is first mixed only with the (α) alcohol (= variant (α)) or (β) alcohol (= variant (β)) and water in a first portion, then (II) Water (α) or a second portion of water (β) is added, especially after the polyurethane product has gone into solution.

[0035] In an eleventh embodiment of the present invention, which is a particular configuration of the tenth embodiment, in step (II), water (α) or the second portion of water (β) is added continuously or in portions such that the temperature of the liquid phase in step (II) differs from the temperature of the liquid phase in the chemical decomposition reactor in step (I) by at most 20° C., preferably at most 15° C., more preferably at most 10° C., even more preferably at most 5.0° C., very exceptionally preferably at most 1.0° C.

[0036] In a twelfth embodiment of the present invention, which is a specific configuration of the tenth and eleventh embodiments, in variant (β), the first portion of water is up to 4.0%, in particular 2.0% to 4.0%, of the mass of water added in step (B) as a whole (i.e. (I) and (II) combined).

[0037] In a thirteenth embodiment of the present invention, which can be combined with all other embodiments, step (B) is carried out at a temperature in the range of 140°C to 220°C, preferably 170°C to 200°C.

[0038] In a fourteenth embodiment of the present invention, which can be combined with all other embodiments, the mass ratio of the alcohol (used in total) and water (used in total) on the one hand to the polyurethane product on the other hand (i.e. [m(alcohol)+m(water)] / m(polyurethane product), where m=mass) is in the range of 0.5 to 2.5, and the mass of the water is 2.0% to 10% of the mass of the alcohol.

[0039] In a fifteenth embodiment of the invention, which can be combined with all other embodiments, the alcohol is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methylpropane-1,3-diol or a mixture of two or more of the aforementioned alcohols.

[0040] In a sixteenth embodiment of the present invention, which can be combined with all other embodiments, the catalyst is selected from carbonates, hydrogen carbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, hydroxides (especially using the above-mentioned catalysts in the form of their alkali metal or alkaline earth metal salts), organic amines, organometallic compounds or a mixture of two or more of the above-mentioned catalysts.

[0041] In a seventeenth embodiment of the present invention which can be combined with all other embodiments, the mass of the catalyst is 0.1% to 3.5% of the mass of the polyurethane product.

[0042] In an eighteenth embodiment of the invention, which can be combined with all other embodiments, the isocyanate component comprises an isocyanate selected from tolylene diisocyanate, diisocyanates of the diphenylmethane series, pentane 1,5-diisocyanate, hexamethylene 1,6-diisocyanate, isophorone diisocyanate, xylylene diisocyanate or a mixture of two or more of the aforementioned isocyanates.

[0043] In a nineteenth embodiment of the invention, which is a specific configuration of the eighteenth embodiment, the isocyanate component comprises tolylene diisocyanate or a mixture of tolylene diisocyanate and a diphenylmethane type diisocyanate.

[0044] In a twentieth embodiment of the present invention, which is a specific configuration of the nineteenth embodiment, the isocyanate component comprises tolylene diisocyanate.

[0045] In a twenty-first embodiment of the present invention, which is a particular configuration of the twentieth embodiment, the isocyanate component does not include any further isocyanates other than tolylene diisocyanate.

[0046] In a twenty-second embodiment of the invention, which can be combined with all other embodiments, the polyol component comprises a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol and / or a polyether carbonate polyol. The polyol component preferably contains a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., it does not contain polyols other than polyether polyols, but includes a mixture of two or more different polyether polyols without departing from the scope of this embodiment).

[0047] In a twenty-third embodiment of the present invention, which is a specific configuration of the twenty-second embodiment, the polyether polyol is a styrene-acrylonitrile copolymer-filled polyether polyol.

[0048] In a 24th embodiment of the invention, which can be combined with all other embodiments, the organic solvent is selected from aliphatic hydrocarbons (especially hexane), cycloaliphatic hydrocarbons (especially cyclohexane), aromatic hydrocarbons (especially toluene) or a mixture of two or more of the aforementioned solvents.

[0049] The above briefly outlined embodiments of the present invention and possible further configurations are elucidated in more detail below. All the above embodiments and the below further configurations of the present invention can be combined together as desired, unless the contrary is clearly visible from the context or explicitly stated to the skilled person.

[0050] Preparing Polyurethane Products for Chemical Recycling Step (A) of the method of the present invention (1000 in FIG. 1) involves providing a polyurethane product 1 to be chemically recycled in preparation for chemical decomposition.

[0051] This may in principle be any type of polyurethane product, but polyurethane foams, in particular flexible polyurethane foams, are preferred.Polyurethane foams are typically produced using pentane, dichloromethane and / or carbon dioxide as blowing agents.

[0052] In addition, for the isocyanate component, polyurethane products based on isocyanates selected from tolylene diisocyanate (TDI), diphenylmethane diisocyanates (mMDI), pentane 1,5-diisocyanate (PDI), hexamethylene 1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI) and mixtures of two or more of the abovementioned isocyanates are preferred. For the isocyanate component, polyurethane products based on TDI and / or mMDI are particularly preferred, with TDI being very particularly preferred. Very exceptionally preferred, the isocyanate component does not contain any further isocyanates other than TDI. When the isocyanates of the isocyanate component are in the form of various isomers, as is the case for example with TDI and mMDI, which are particularly preferred isocyanates, the isomer distribution is not critical to the present invention.

[0053] As regards the polyol component, polyurethane foams based on polyols selected from polyether polyols, polyester polyols, polyether ester polyols, polyether carbonate polyols, polyacrylate polyols or mixtures of two or more of the above polyols are preferred, with polyether polyols and polyacrylate polyols being particularly preferred. Most preferably, the polyol component contains a polyether polyol. Very exceptionally preferably, the polyol component is a polyether polyol (i.e., does not contain any polyols other than polyether polyols, but a mixture of two or more different polyether polyols is included and does not depart from the scope of this embodiment). The polyether polyol may be one filled with styrene-acrylonitrile copolymers (SAN copolymers). It is an advantage of the present invention that it can also be applied to such polyol components. A problem in the chemical degradation of polyurethane products whose polyol component is based on SAN copolymer-filled polyether polyols is that the SAN copolymer may be released as fine polymer particles during chemical degradation. This is true regardless of the chemical degradation method selected. The presence of SAN polymers as fine polymer particles in the reaction mixture causes problems in their separation, for example by subsequent extraction methods. Moreover, the fineness of the polymer particles makes filtration almost impossible, since the filters quickly become clogged and no further removal is possible. The advantage of the hydrolysis according to the invention is that after liberation from the polyether polyol, the SAN polymers are in a partially soluble form due to the hydrolysis step, so that the work-up of the reaction mixture after chemical decomposition by extraction can proceed without problems.

[0054] Most preferably, the polyurethane product is one in which the isocyanate component contains either TDI or mMDI, especially TDI (and not any other isocyanate), and the polyol component contains a polyether polyol (especially a polyether polyol, i.e., no further polyols other than the polyether polyol, although mixtures of two or more different polyether polyols are included without departing from the scope of this embodiment).

[0055] Preferably, step (A) further comprises a preparatory step for the cleavage of the urethane bonds in step (B), which is in particular the mechanical grinding of the polyurethane product. Such preparatory steps are known to those skilled in the art, see, for example, "Freezing" the polyurethane product before mechanical grinding, depending on the properties of the polyurethane product, in order to facilitate the grinding operation. This is particularly true for polyurethane foams.

[0056] It is also conceivable that the above preparation step is carried out at a location that is spatially separated from the site of chemical decomposition. In that case, the prepared polyurethane product is transferred to a suitable transport vehicle, for example a silo vehicle, for further transportation. For further transportation, the prepared polyurethane product, especially in the case of polyurethane foam, may be additionally compressed to achieve a higher mass-to-volume ratio. The polyurethane product is then transferred to a reactor prepared for chemical decomposition at the site of chemical decomposition. It is also conceivable that the transport vehicle used is directly connected to the reactor.

[0057] Chemical Degradation of Polyurethane Products to Obtain Chemical Degradation Products Step (B) (2000 in FIG. 1) of the method of the present invention involves the chemical decomposition of the polyurethane product prepared in step (A) with alcohol 2 and water 3.

[0058] The chemical decomposition is preferably carried out in the absence of oxygen. This means that the reaction is carried out in an inert gas atmosphere, in particular a nitrogen, argon or helium atmosphere. It is also preferable to remove oxygen from the chemical decomposition reagents used (water and alcohols) by inert gas saturation.

[0059] The chemical decomposition is preferably carried out at temperatures between 140° C. and 220° C., preferably between 170° C. and 200° C. There are no special requirements regarding the pressure. The reaction can be carried out either at reduced or elevated pressure, e.g. up to 200 mbar. (abs.) ~2000mbar (abs.) , preferably 500 mbar (abs.) ~1500mbar (abs.) , more preferably 900 mbar (abs.) ~1300mbar (abs.) The reaction can be carried out at a pressure of 1000 MPa, in particular at ambient pressure.

[0060] Suitable alcohols 2 for step (B) are in particular ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methylpropane-1,3-diol or a mixture of two or more of the aforementioned alcohols.

[0061] Suitable catalysts for step (B) are in particular carbonates, hydrogencarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, hydroxides (in particular using the abovementioned catalysts in the form of their alkali metal or alkaline earth metal salts), organic amines, organometallic compounds or mixtures of two or more of the abovementioned catalysts. The catalyst is preferably used in an amount such that its weight is between 0.1% and 3.5% of the weight of the polyurethane product.

[0062] Step (B) is preferably carried out in such a way that the mass ratio of the alcohol (used as a whole) and water (used as a whole) on the one hand to the polyurethane product on the other hand (i.e. [m(alcohol)+m(water)] / m(polyurethane product), where m=mass) is in the range of 0.5-2.5, the mass of water being 2.0%-10% of the mass of the alcohol. The quantitative figures for water in the context of the present invention relate to the water added as a reagent for the hydrolytic carbamate cleavage. In comparison, the amount of water originating from the moisture present in the alcohol used and / or in the polyurethane product used is small in each case. By the alcohol used or the moisture in the polyurethane product used is meant the trace amounts of moisture that may occur on an industrial scale. It is of course possible to premix the alcohol and the water used for the hydrolytic cleavage or to wet the polyurethane product with the water used for the hydrolytic cleavage. Such an embodiment does not depart from the scope of the present invention, and the water added in this way should of course be taken into account in the quantitative figures given above, i.e. the amount of water added additionally, if necessary, should be reduced accordingly. If the catalyst is used in the form of an aqueous solution, the water used as solvent should likewise be taken into account in the abovementioned quantitative figures, i.e. the amount of water additionally added, if necessary, should be reduced accordingly.

[0063] As already mentioned, it is not necessary to add all the water exactly at the beginning of step (B). In this case, the amount "2.0% to 10% of the mass of the alcohol" mentioned above relates to the amount of water added in total by the end of the reaction time of step (B). The same applies if the alcohol is added gradually.

[0064] In particular, in step (B), (I) first mixing the polyurethane product with only a first portion of the (α) alcohol or (β) alcohol and water, then (II) It is also possible to add the water (α) or a second portion of the water (β), especially once the polyurethane product has gone into solution.

[0065] The term "goes into solution" in this context does not necessarily imply the presence of a "true" solution in the sense of a completely homogeneous mixture. It is entirely possible that a "cloudy" solution of the polyurethane product exists. This does not depart from the scope of the present invention.

[0066] In the course of carrying out step (B) in steps (I) and (II), it is particularly preferred to add water (α) or the second portion of water (β) continuously or in small portions in step (II) so that the temperature of the liquid phase in step (II) differs from the temperature of the liquid phase in step (I) by at most 20° C., preferably at most 15° C., more preferably at most 10° C., even more preferably at most 5.0° C., very exceptionally preferably at most 1.0° C. A temperature always sufficiently high to ensure the progress of the chemical decomposition is thereby achieved. If a portion of the water is already added at the beginning of the chemical decomposition (= variant (β)), it is preferred that the first portion of water is at most 4.0% by mass, in particular 2.0% to 4.0% by mass, of the total amount of water added in step (B) (i.e. (I) and (II) taken together).

[0067] Obtaining polyol By the process (B), at least one amine corresponding to the isocyanate of the isocyanate component; (At least) one polyol (derived from the polyol component or formed from the polyol component in step (B)); Alcohol (used superstoichiometrically and therefore incompletely converted) Water (used superstoichiometrically and therefore incompletely converted) Chemical decomposition products 4 containing

[0068] In a subsequent step, the chemical decomposition products are post-treated to recover the raw polyol.

[0069] This work-up initially involves a step (C) (3000 in FIG. 1) (see also FIG. 1), followed by extraction (step (CI) - 3100 in FIG. 1) and phase separation (step (C.II) - 3200 in FIG. 1) of the chemical decomposition products. According to the invention, the extractant used in step (CI) is a 1013 mbar (abs.) The organic solvent 5 has a boiling point at 50° C. in the range of 40° C. to 120° C. Suitable organic solvents are in particular aliphatic hydrocarbons (e.g. hexane), cycloaliphatic hydrocarbons (e.g. cyclohexane), aromatic hydrocarbons (e.g. toluene) or a mixture of two or more of the abovementioned solvents. The extraction is carried out at a temperature of 10° C. to 60° C. (e.g. room temperature).

[0070] The process product 6 of the extraction is biphasic and is separated into its phases in step (C.II). To facilitate this phase separation, it may be advantageous to add additional water in the extraction. One of the phases obtained in step (C.II) contains the organic solvent (at least the majority), the polyol (at least the majority) and a first (relatively small) portion of the amine and optionally a first (relatively small) portion of the alcohol. This phase is called in the terminology of the present invention the first product phase 7. This phase may also be called the polyol phase since it contains at least the majority of the polyol. The second phase contains the alcohol (at least the majority, and possibly only a second (larger) portion of the alcohol), the water (at least the majority) and a second (=major) portion of the amine. This phase is called in the terminology of the present invention the second product phase 8. This phase may also be called the amine phase since it contains the majority of the amine. In this way, in step (C), separation of the (major) portion of the amine and the polyol is achieved. It is clear to those skilled in the art that this separation does not necessarily have to proceed completely in the sense that all the polyol enters the first product phase and all the amine enters the second product phase. As a result of general solubility equilibrium, it is usually the case that a small amount of the amine enters the first product phase. It is not uncommon for a small amount of the polyol to enter the second product phase, which of course does not depart from the scope of the present invention.

[0071] Following step (C.II), a polyol is then obtained from the first product phase in step (D) (4000 in FIG. 1). For this purpose, the organic solvent is first largely or completely separated off in step (DI) (4100 in FIG. 1) by distillation and / or stripping (10). For this purpose, it is preferred to use falling film evaporators, natural circulation evaporators, tank evaporators, forced circulation evaporators or flash evaporators. The separated off organic solvent is preferably fed in step (G), optionally after purification, to step (CI) where it is used as extractant (indicated by the dotted arrow in FIG. 1).

[0072] After separating off the organic solvent, the amine dissolved in the first product phase (=first portion of amine) 11 is separated by distillation, leaving the purified polyol 12 (step (D.II); 4200 in FIG. 1). This separation off of the first portion of amine 11 is preferably carried out in a thin film evaporator, a short path evaporator or a flash evaporator, in particular at 0.1 mbar (abs.) ~5.0mbar (abs.) This is achieved at a pressure of 1000 and a temperature of 140°C to 240°C.

[0073] As already mentioned, the first product phase may contain a fraction of the alcohol used for the chemical decomposition. This can be separated off together with the first portion of the amine in step (D.II) and subsequently becomes part of stream 11. As will be explained in more detail further below, in order to obtain the amine, it is preferred to feed the first portion of the amine 11 in step (E) to the second product phase and work it up together therewith. This is also possible without problems in the described cases in which stream 11 contains a fraction of the alcohol, since the second product phase contains the majority of the alcohol in each case.

[0074] However, it is also possible in step (DI) to first separate off the organic solvent in a first stage as a solvent fraction (which is advantageously fed to step (CI)) and then separate off the alcohol fraction (containing a first (relatively small) portion of alcohol and possibly a (relatively small) portion of organic solvent) in a second stage. Suitable apparatuses for the second stage are in particular the same as for step (D.II), namely thin-film evaporators, short-path evaporators or flash evaporators. The alcohol fraction separated off in the second stage may still contain a solvent fraction and may possibly separate spontaneously into two phases, namely an alcohol phase and a solvent phase. The alcohol phase is preferably fed to step (B) and the solvent phase (such as the solvent fraction) is fed to step (CI). If no spontaneous phase separation occurs, it is preferred to feed the alcohol fraction to step (B). The described two-stage implementation of step (DI) allows the separate recovery of a fraction of unconverted alcohol dissolved in the first product phase and is therefore particularly desirable when such a proportion is relatively large.

[0075] Obtaining amines It is preferred to work up the second product phase 8 obtained in step (C.II) in order to recover further amine raw material. Expediently (see also FIG. 2 in this respect), in step (E) (5000 in FIG. 2), the first portion of amine 11 separated off in step (D.II) is mixed with the second product phase 8 and the resulting mixture 13 is worked up to obtain amine 18 (step (F); 6000 in FIG. 2). As already mentioned, the second product phase 8 contains the alcohol used for the chemical decomposition (at least the majority thereof, and possibly only the second (relatively large) portion of alcohol), the water (at least the majority thereof) and the second portion (=the majority) of amine, as well as the first portion of amine 11, and amine, and possibly also a fraction of the alcohol used for the chemical decomposition, so that the mixture 13 essentially consists of amine, water and alcohol.

[0076] This amine-water-alcohol mixture 13 is subjected to an evaporation process to obtain the amine. This is preferably achieved in two stages: in a first stage (step (FI); 6100 in FIG. 2), the water 14 is evaporated, leaving the amine-alcohol mixture 15, and in a second stage (step (F.II); 6200 in FIG. 2), the alcohol fraction 16 is evaporated, leaving the unpurified amine phase 17. If the amine-water-alcohol mixture 13 still contains a fraction of organic solvent 5 (which cannot be excluded depending on the position of the solvent equilibrium), this is preferably distilled off before the evaporation of the water or, depending on the position of the boiling point (or the presence of an azeotrope), optionally together with the water (followed by phase separation) or after the water has been separated off. The water separated off in step (F) is preferably used as a constituent of the water 3 used in step (B) (2000 in FIG. 2). The additionally required water can come from other conventional water sources (e.g. fresh water or condensate).

[0077] The alcohol fraction 16 obtained in the second evaporation stage (step (F.II); 6200 in FIG. 2) is preferably recycled (optionally after purification) to step (B) (2000 in FIG. 2), where it is used as a constituent of the alcohol 2 used in the chemical decomposition.

[0078] The amine 18 is then isolated from the crude amine phase 17. The work-up required for this purpose (step (F.III); 6300 in FIG. 2) is preferably achieved by distillation.

[0079] In a particularly advantageous configuration of the amine work-up, which provides an economical and environmentally friendly outlet for impurities originating from the polyurethane product, the obtaining of amines from the amine phase 8 is integrated into the work-up of freshly prepared amines by mixing the amine phase with a crude fraction of amines originating from a fresh production of amines. This embodiment is described in detail in patent application WO 2005 / 023991 (page 23, line 31 to page 27, line 7), to which reference is now made.

[0080] The following examples are intended to further illustrate the invention. EXAMPLES

[0081] analysis Hydroxyl Number (also called OHN, with units of mg KOH / g) is a standard method for determining the properties of polyols and was determined as follows.

[0082] Polyol is mixed with excess phthalic anhydride (PA). The remaining PA is hydrolyzed with water. Each OH group reacts with an anhydride group to form an ester. The COOH groups released from the PA can be titrated with KOH solution, allowing the number of OH groups to be calculated.

[0083] Amine value was determined by titration of the amine nitrogen with 0.1 M perchloric acid in acetic acid and, like OHN, is reported in mg KOH per gram of material tested.

[0084] The viscosities of the tested polyols (initial polyol and recovered polyol) were measured using an Anton Paar heatable MCR 301 rotational viscometer in the temperature range 20°C to 180°C.

[0085] Example 1 (present invention) 300 g of diethylene glycol (DEG, 2) and 5.4 g of Na2CO3 were initially charged into a round bottom flask and heated to 180°C. Subsequently, 300 g of TDI-based polyurethane foam 1 was added stepwise. After the entire amount of foam was added, the resulting reaction mixture was held at 180°C for an additional 3 hours. After the reaction time, 17 g of demineralized (DM) water 3 was added stepwise to the reaction mixture at 180°C (hydroglycolysis step). Subsequently, the reaction mixture was held at 180°C for an additional 2.5 hours (step (A) and step (B); (1000 and 2000 in Figure 1)).

[0086] The resulting reaction mixture 4 was continuously contacted with 3 parts by weight of cyclohexane 5 (step (CI); 3100 in FIG. 1 )), resulting in the formation of a polyol-rich phase (light phase, first product phase, 7) and a DEG-rich phase (heavy phase, second product phase, 8). The phases were separated (step (C.II); (3200 in FIG. 1 )).

[0087] First, most of the cyclohexane 10 was removed from the light phase by batch evaporation using a rotary evaporator. For this purpose, the mixture was heated at 120° C. and 20 mbar. (abs.) The mixture was heated in a round-bottom flask heated by an oil bath until condensation was completed (Step (DI); 4100 in FIG. 1).

[0088] The cyclohexane-depleted mixture thus obtained was subjected to heating at 190° C. and 5 mbar (abs.) The evaporable vapor (11, a first portion of the amine, containing DEG and TDA) was continuously fed to a short-path evaporator at 4200° C. where it was condensed onto an internal water-cooled cooling coil (Step (D.II); 4200 in FIG. 1 ).

[0089] The polyol thus obtained (12, recycled polyol) was analyzed, and the following OH value and amine value were confirmed: OHN: 49.1 mg KOH / g, Amine value: 0.36 mg KOH / g.

[0090] The polyol originally used to prepare the converted polyurethane foam (original polyol) has the following values: OH value: 48.0 mg KOH / g, amine value: 0.00 mg KOH / g.

[0091] It can be seen that the recycled polyol is very similar to the original polyol with regard to the essential properties of OH number and amine number. This is confirmed by a comparison of the viscosities at different temperatures. In this respect, reference is made to Figure 3, where the temperature θ (°C) is shown on the horizontal axis and the kinematic viscosity η (mPa·s) on the vertical axis. The values ​​of the recycled polyol are displayed as "x"s and those of the original polyol as black triangles. The lines (dashed for the original polyol, solid for the recycled polyol) represent power functions fitted to the measurement points. It can be seen that these functions are almost congruent.

Claims

1. 1. A method for recovering at least one raw material from a polyurethane product, comprising: (A) providing a polyurethane product based on an isocyanate component and a polyol component; The isocyanate component has a viscosity of 1013 mbar of the corresponding amine. （ａｂｓ．） Contains only isocyanates having a boiling point at 410°C or less; (B) reacting the polyurethane product with a stoichiometric excess of alcohol and a stoichiometric excess of water in the liquid phase in the presence of a catalyst to obtain chemical decomposition products including alcohol, water, polyol, and amines corresponding to the isocyanates of the isocyanate component; (C) (C.I) The chemical decomposition product is subjected to a temperature of 10°C to 60°C and a pressure of 1013 mbar. （ａｂｓ．） Extraction with an organic solvent having a boiling point in the range of 40°C to 120°C at room temperature, followed by (C.II) a first product phase comprising the organic solvent, a first portion of the polyol and the amine, and optionally a first portion of the alcohol; a second product phase comprising a second portion of the alcohol, the water, and the amine; phase separation into post-treating the chemical decomposition products, comprising: (D) (D.I) separating and removing the organic solvent by distillation and / or stripping; (D.II) separating and removing a first portion of the amine by distillation to obtain a polyol; post-treating the first product phase to obtain a polyol, comprising: A method comprising:

2. 10. The method of claim 1, wherein in step (E) a first portion of the amine is added to the second product phase, which is then worked up in step (F) to provide an amine.

3. 3. The method according to claim 1 or 2, wherein in step (D.I), the organic solvent is first separated and removed as a solvent fraction in a first stage, and then an alcohol fraction is separated and removed in a second stage.

4. The alcohol fraction separated and removed in the second stage is fed to step (B), or The method according to claim 3, wherein the alcohol fraction separated and removed in the second stage is separated into an alcohol phase and a solvent phase, and the alcohol phase is supplied to step (B) and the solvent phase is supplied to step (C.I).

5. In step (B), (I) first mixing the polyurethane product with only a first portion of (α) the alcohol or (β) the alcohol and the water, and then 3. The method according to claim 1 or 2, wherein (II) water (α) or the second portion of water (β) is added, in particular after the polyurethane product has gone into solution.

6. 6. The method according to claim 5, wherein in step (II), the water (α) or the second portion of water (β) is added continuously or in small portions so that the temperature of the liquid phase in step (II) differs by at most 20° C. from the temperature of the liquid phase in the chemical decomposition reactor in step (I).

7. 3. The method of claim 1 or 2, wherein the isocyanate component comprises an isocyanate selected from tolylene diisocyanate, diisocyanates of the diphenylmethane series, pentane 1,5-diisocyanate, hexamethylene 1,6-diisocyanate, isophorone diisocyanate, xylylene diisocyanate, or a mixture of two or more of the foregoing isocyanates.

8. 3. The method of claim 1 or 2, wherein the polyol component comprises a polyether polyol, a polyester polyol, a polyetherester polyol, a polyacrylate polyol, and / or a polyethercarbonate polyol.

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