Method for recovering raw materials from polyurethane products

Abstract

This invention relates to a method for recovering raw materials from polyurethane products, comprising the steps of: (A) providing a polyurethane product based on an isocyanate component and a polyol component; (B) reacting the polyurethane product with an alcohol in the presence of a catalyst to obtain a first product mixture containing an alcohol, a polyol, a urethane, and optionally water; (C) post-processing the first product mixture, comprising: (CI) mixing the first product mixture obtained in step (B) with an organic solvent miscible with the alcohol used in step (B), optionally subsequently removing solid components, thereby obtaining a second product mixture; (C.II) washing the second product mixture obtained in step (CI) with an aqueous washing solution, thereby partially hydrogenating the urethane contained in the second product mixture to release an amine and an alcohol, and separating the phases into a first solvent phase containing the organic solvent and the polyol used in step (CI) and a first aqueous phase containing water, an alcohol, a urethane, and an amine; and (C.III) post-processing the first solvent phase to obtain a polyol; and optionally, (D) post-processing the first aqueous phase to obtain an amine corresponding to the isocyanate from the isocyanate component.

Description

[0001] The project for which this application was made was funded under grant agreement number 814543 of the EU Horizon 2020 research and innovation programme.

[0002] This invention relates to a method for recovering raw materials (i.e., polyols and optionally additional amines) from polyurethane products, comprising the steps of: (A) providing a polyurethane product based on an isocyanate component and a polyol component; (B) reacting the polyurethane product with an alcohol in the presence of a catalyst to produce a first product mixture containing an alcohol, a polyol, and a urethane, and optionally water; (C) post-processing the first product mixture, comprising: (CI) mixing the first product mixture obtained in step (B) with an organic solvent miscible with the alcohol used in step (B), optionally subsequently removing solid components to obtain a second product mixture; (C.II) washing the second product mixture obtained in step (CI) with an aqueous washing solution, thereby partially hydrolyzing the urethane contained in the second product mixture to release the amine and alcohol, and separating the phases into a first solvent phase containing the organic solvent and polyol used in step (CI) and a first aqueous phase containing water, an alcohol, a urethane, and an amine; and (C.III) post-processing the first solvent phase to obtain a polyol; and optionally, (D) post-processing the first aqueous phase to obtain an amine corresponding to the isocyanate from the isocyanate component.

[0003] Polyurethane products have diverse applications in industry and daily life. A distinction is often made between polyurethane foam and so-called "CASE" products, where "CASE" is a general term for polyurethane coatings (such as paints), adhesives, sealants, and elastomers. Polyurethane foam is generally classified into rigid foam and flexible foam. Despite their differences, all these products share the basic polyurethane structure, which is formed through the addition polymerization reaction of polyfunctional isocyanates and polyols, and can be represented, for example, in the case of polyurethanes based on diisocyanates O=C=NRN=C=O and diols HOR'-OH (where R and R' refer to organic groups).

[0004] ~~~[OR'-O-(O=C)-HN-R-NH-(C=O)]~~~.

[0005] The enormous economic success of polyurethane products has ironically resulted in a significant amount of polyurethane waste (e.g., from old mattresses or seating furniture) that must be properly utilized. The most technically feasible recycling method is incineration, where the released heat is used in other processes, such as industrial manufacturing. However, this does not complete the raw material loop. Another utilization method, known as "physical recycling," involves mechanically crushing polyurethane waste and using it in the manufacture of new products. This recycling method naturally has limitations, and there has been ongoing effort to recover the raw materials upon which polyurethane production is based by re-breaking polyurethane bonds (known as "chemical recycling"). These recycled raw materials primarily consist of polyols (i.e., HOR'-OH in the example above). Additionally, amines (i.e., H2N-R-NH2 in the example above) can be obtained through the hydrolytic cracking of urethane bonds, which, after post-treatment, can be phosgenated to form isocyanates (O=C=NRN=C=O in the example above).

[0006] Various chemical recycling methods have been developed in the past. The three main ones are briefly summarized below:

[0007] 1. The urethane is hydrolyzed by reacting with water to obtain amines and polyols, which in turn form carbon dioxide.

[0008] 2. Glykolyse is performed on urethanes by reacting them with an alcohol, in which the polyol incorporated into the urethane group is replaced by the alcohol used and thus released. This method is commonly referred to in the literature as transesterification (more precisely: urethane transesterification). Regardless of the exact nature of the alcohol used, this mode of chemical recycling is commonly referred to in the literature as glycolysis—although this term actually applies only to diols. Therefore, in this invention, the term commonly used is alcoholysis (Alkoholyse). Hydrolysis can be performed after glycolysis. If hydrolysis is performed in the presence of an unaltered mixture of glycolysates, this is referred to as...

[0009] 3. Hydrolyzed urethane bonds can be hydrated by reacting with alcohol and water. Alternatively, alcohol and water can be added from the beginning, in which case the hydrolysis and hydration processes described above occur in parallel.

[0010] The review article by Simón, Borreguero, Lucas, and Rodríguez in Waste Management 2018, 76, 147–171[1] provides an overview of known polyurethane recycling methods. The article emphasizes the particular importance of diollysis (2. above). In diollysis, two-phase and single-phase schemes are distinguished based on whether the crude process product obtained from the reaction with the alcohol separates into two phases. This depends particularly on the choice of alcohol used and the process conditions (especially the proportion of alcohol used in the reaction mixture and the temperature). The aforementioned review article endorses the two-phase scheme using crude glycerol (e.g., waste from biodiesel production) because it has the greatest potential to recover high-quality products at low production costs (with a specific focus on the recovery of polyols).

[0011] The additional use of water ensures that the process products of hydrodiolosis (3. above) are always two-phase. Braslaw and Gerlock describe the post-treatment of such process products in Ind. Eng. Chem. Process Des. Dev. 1984, 23, 552–557 [2], which includes the removal of water (by laboratory-scale phase separation or by evaporation in the so-called "Ford Hydrodiolosis Process" recommended for industrial applications) and extraction of the remaining organic phase with hexadecane to form an alcohol phase and a hexadecane phase, from which amines can be obtained and polyols can be obtained from the hexadecane phase. Although the possibility of amine recovery is mentioned, the focus of the article is also on the recovery of polyols.

[0012] A patent for a method operating based on these principles is granted under US Patent No. 4,336,406. It describes a method for recovering polyether polyols from polyurethane through the following stages:

[0013] (a) A solution is formed by dissolving the polyurethane in a saturated alcohol with a boiling point of 225°C to 280°C in a non-oxidizing atmosphere at a temperature of 185°C to 220°C.

[0014] (b) Allowing the solution to react with water in the presence of an alkali metal hydroxide catalyst in a non-oxidizing atmosphere for a time required to largely hydrolyze the hydrolyzable dissolved products to form amines and alcohols, while maintaining the solution at a temperature of 175°C to 220°C, wherein the alkali metal hydroxide catalyst is added to the solution in an amount of approximately at least 0.1% by mass based on the mass of the polyurethane foam.

[0015] (c) Remove the water remaining after hydrolysis from this solution under a non-oxidizing atmosphere;

[0016] (d) Extracting the polyol from the hydrolysis solution with an alkane (especially hexadecane) that is substantially immiscible with the alcohol and has a boiling point of 230°C to 300°C under a non-oxidizing atmosphere;

[0017] and

[0018] (e) The extracted polyols were purified under vacuum at a temperature below 230°C.

[0019] In step (a), the polyurethane is reacted with the alcohol groups of a saturated alcohol to form a polyol, a urea, and a urethane (see column 3, lines 42 to 46).

[0020] In step (b), water and the alkali metal hydroxide catalyst are added separately or as an aqueous solution of the catalyst to the solution obtained in step (a), thereby decomposing the carbamate and urea to produce amines and alcohols. Steps (a) and (b) as a whole should be considered as hydrodiolization (more precisely: hydroalcolysis), in which the alcohol and water are added in staggered time. The amount of water added is such that the solution boils at a temperature of 175°C to 200°C. In the case of diethylene glycol as the alcohol, the amount of water added is 2.4% to 0.6% of the mass of diethylene glycol used, preferably 1.1% (see column 4, lines 39 to 46). The water content is kept constant by adding additional water to replace the water consumed in the hydrolysis. After the hydrolysis is complete, the water used must be removed in step (c) before extraction in step (e) (column 5, lines 31 to 33).

[0021] US 4,317,939 describes a method in which polyurethane foam is first dissolved in an alcohol, followed by the addition of water and a catalyst, and the reaction mixture is heated under reflux. The resulting reaction product is either single-phase, in which case it is purified by vacuum distillation, or biphase, in which case the polyol phase is removed and purified by vacuum distillation. The polyol recovered in this manner can be used to produce new polyurethane foam.

[0022] Only a few known chemical recycling methods in the literature operate sustainably on an industrial scale; many have never even reached a pilot scale [1]. This clearly demonstrates that chemical recycling of polyurethane products remains technically and economically immature, given the growing environmental awareness and efforts to make industrial processes as sustainable as possible (both of which largely support chemical recycling). The challenge lies particularly in the purity of the recycled products. Polyols must be recovered as free of amine impurities as possible to avoid adverse effects on foaming properties, for example, when reused in the production of polyurethane foam. If amines are also to be recovered, they must, of course, be obtained with the highest possible purity. Furthermore, polyurethane products intended for reuse often still contain various auxiliaries and additives (stabilizers, catalysts, etc.), which must be separated from and disposed of in an economically and environmentally friendly manner from the actual target products of recycling. In addition, economically viable recycling methods must ensure that the reagents used (e.g., the alcohols used) can be recovered and reused as completely as possible (i.e., recycling).

[0023] Therefore, further improvements are needed in the chemical recycling of polyurethane products. In particular, there is a desire to recover polyols from polyurethane products with high purity and efficiency, preferably also amines, especially in a manner and manner that makes industrial-scale application economically feasible. Additionally, there is a desire to provide economically and environmentally acceptable outlets for auxiliaries and additives present in polyurethane products.

[0024] In view of this requirement, the subject of this invention is a method for recovering raw materials (i.e., polyols and optional amines) from polyurethane products, comprising the steps (see also...) Figure 1 ):

[0025] (A)–1000–Provides polyurethane products based on isocyanate components and polyol components (1);

[0026] (B)–2000– React polyurethane product (1) with (mono- or poly) alcohol (2) in the presence of a catalyst to produce a first product mixture (3) containing (unreacted) alcohol, polyol (i.e., the polyol constituting the polyol component and / or optionally the polyol formed by the original polyol component in the reaction with alcohol (2)) and urethane and optionally water.

[0027] (C)–3000–Post-processing first product mixture (3), comprising:

[0028] (CI)–3100– The first product mixture (3) obtained in step (B) is mixed with a (water-insoluble) organic solvent (4) that is miscible with the alcohol (2) used in step (B), and optionally the solid components are subsequently removed to obtain a second product mixture (5);

[0029] (C.II)–3200–A second product mixture (5) obtained in a washing step (CI) using an aqueous washing solution (6) (single-stage or multi-stage, especially two-stage) wherein the urethane fraction contained in the second product mixture (5) is partially hydrolyzed to release amines and alcohols, and the phase is separated into a first solvent phase (41) containing the organic solvent and polyol used in step (CI) (i.e., a first portion of the polyol from at least the first product mixture; therefore, the first solvent phase may also be referred to as the first polyol phase), and

[0030] A first aqueous phase (61) containing water, alcohols (used in step (B) but not converted and released in step (C.II) during partial hydrolysis of the urethane), urethanes and amines (and impurities derived from the polyurethane product);

[0031] (C.III)–3300– Post-treatment of the first solvent phase to obtain polyols;

[0032] And optionally (and preferably)

[0033] (D)–4000– Post-treatment of the first aqueous phase to (at least) obtain an amine (8) corresponding to the isocyanate from the isocyanate component.

[0034] In this invention, polyurethane products are addition polymerization products (although not entirely accurate, sometimes referred to as condensation polymerization products) of polyfunctional isocyanates (i.e., the isocyanate component in polyurethane preparation) and polyols (i.e., the polyol component in polyurethane preparation). In addition to the basic polyurethane structure described above, polyurethane products typically contain other structures, such as structures with urea bonds. The presence of these structures, different from the pure polyurethane basic structure, does not depart from the scope of this invention.

[0035] In the terminology of this invention, the term isocyanate includes all isocyanates known to those skilled in the art in relation to polyurethane chemistry, particularly, for example, toluene diisocyanate (TDI; which can be prepared and is preferably prepared from toluene diamine, TDA), diphenylmethane series diisocyanates and polyisocyanates (MDI; which can be prepared and is preferably prepared from diphenylmethane series diamines and polyamines, MDA), pentane-1,5-diisocyanate (PDI; which can be prepared and is preferably prepared from pentane-1,5-diamine, PDA), 1,6-hexane diisocyanate (HDI; which can be prepared and is preferably prepared from hexane-1,6-diamine, HDA), isophorone diisocyanate (IPDI; which can be prepared and is preferably prepared from isophorone diamine, IPDA), and phenyl dimethyl diisocyanate (XDI; which can be prepared and is preferably prepared from phenyl dimethyl diamine, XDA). The term "isocyanate" naturally includes embodiments in the preparation of polyurethane products that use two or more different isocyanates (e.g., a mixture of MDI and TDI), unless otherwise explicitly stated, such as by expressing "exactly one isocyanate." The same applies within an isocyanate category (i.e., it also applies to, for example, different types of MDI). All isocyanates used in the preparation of polyurethane products are collectively referred to as the isocyanate component (of the polyurethane product). An isocyanate component contains at least one isocyanate. Similarly, all polyols used in the preparation of polyurethane products are collectively referred to as the polyol component (of the polyurethane product). A polyol component contains at least one polyol.

[0036] In the terminology of this invention, isocyanate categories are understood to refer to isocyanates having the same basic chemical structure, wherein differences in substitution are not considered deviations from the basic chemical structure. For example, TDI and MDI belong to different isocyanate categories, but their respective isomers do not belong to different isocyanate categories relative to each other. For example, all isomers of TDI (of which 2,4-TDI and 2,6-TDI are the most important) belong to the same "TDI isocyanate category," and similarly, all isomers of diphenylmethane diisocyanates (of which 2,4'-MDI and 4,4'-MDI are the most important) belong to the same "MDI isocyanate category." MDI types having three or more "benzene rings" are also classified into the "MDI isocyanate category." This also applies to amine categories.

[0037] In the terminology of this invention, the term polyol includes all polyols known to those skilled in the art in relation to polyurethane chemistry, particularly, for example, polyether polyols, polyester polyols, polyether ester polyols, and polyether carbonate polyols. The term "a polyol" naturally also includes embodiments in which two or more different polyols are used in the production of a polyurethane product. The same applies within a category of polyols. Therefore, if, for example, "polyether polyol" (or "polyester polyol," etc.) is mentioned, the term naturally also includes embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) are used in the preparation of a polyurethane product.

[0038] In the terminology of this invention, urethane refers to the urethane formed in step (B) by reaction with an alcohol.

[0039] The amines corresponding to isocyanates are those that can be converted to isocyanates through phosgenation according to the reaction R-NH2 + COCl2 → RN=C=O + 2HCl. Similarly, the nitro compounds corresponding to amines are those that can be converted to amines through reduction according to the reaction R-NO2 + 3H2 → R-NH2 + 2H2O.

[0040] The requirement of the present invention that "the organic solvent used in step (CI) is miscible with the alcohol used in step (B)" means that, under the conditions of the temperature present in step (CI) and the ratio of organic solvent to alcohol from step (B), the mixture of the organic solvent and the alcohol from step (B) does not spontaneously separate into two phases.

[0041] The first aqueous phase is typically a clear aqueous phase. However, without excluding and without departing from the scope of the invention, the first aqueous phase may contain an emulsion (i.e., it comprises both a clear phase and an emulsion phase, in which case, in the terminology of the invention, the entirety of the clear phase and the emulsion phase should be considered the first aqueous phase) or even an emulsion (i.e., its entirety is an emulsion phase). An emulsion in this respect refers to an emulsion of organic components emulsified in an aqueous medium.

[0042] In this invention, the term "impurities derived from polyurethane products" is understood to refer to substances produced from polyurethane products that cannot be recovered as polyols or amines in chemical recycling, i.e., particularly auxiliaries and additives (stabilizers, catalysts, polymer particles, etc.) produced from polyurethane products.

[0043] The attached image shows:

[0044] Figure 1 A schematic diagram of the method of the present invention in its simplest configuration (where the recovery of amine (8) from the first aqueous phase (61) is optional);

[0045] Figure 2A schematic diagram of a preferred embodiment of the step (= step (D)) for obtaining an amine;

[0046] Figure 3 A schematic diagram of an amine preparation method that can be combined with step (D);

[0047] Figure 4 A possible configuration for the combination of amine preparation method and step (D); and

[0048] Figure 5 Another possible configuration of the combination of amine preparation method and step (D).

[0049] The various possible embodiments of the present invention are first outlined below:

[0050] In a first embodiment of the invention, which can be combined with all other embodiments, the first product mixture and the organic solvent are mixed in step (CI) at a mass ratio of 5:1 to 1:3.

[0051] In a second embodiment of the invention, which can be combined with all other embodiments, the first solvent phase is distilled and / or stripped with a stripping gas (particularly nitrogen or water vapor, preferably nitrogen) in step (C.III).

[0052] In a third embodiment of the invention, which is a specific configuration of the second embodiment, the method in step (C.III) includes distillation in an evaporator selected from falling film evaporators, thin film evaporators, flash evaporators, rising film evaporators, natural circulation evaporators, forced circulation evaporators, and batch evaporators.

[0053] In a fourth embodiment of the invention, which is a specific configuration of the third embodiment, the method in step (C.III) includes stripping with steam downstream of distillation.

[0054] In a fifth embodiment of the invention, which can be combined with all other embodiments except those that set up multi-stage washing in step (C.II), step (C.II) includes exactly one washing stage, wherein a second product mixture is followed at a mass ratio of 20:1 to 1:1 to the aqueous washing solution.

[0055] In a sixth embodiment of the invention, which can be combined with all other embodiments except those that provide a single-stage wash in step (C.II), step (C.II) includes at least (preferably exactly) two wash stages, wherein phase separation is performed after each wash stage to obtain a solvent phase and an aqueous phase, wherein the solvent phase obtained in the last wash stage is a first solvent phase, and the first aqueous phase (at least) comprises the aqueous phase obtained in the first wash stage.

[0056] In a seventh embodiment of the invention, which is a specific configuration of the sixth embodiment, in each washing stage, the mass ratio of the second product mixture to be washed in the washing stage or the solvent phase to be washed to the aqueous washing liquid used in the washing stage is followed from 20:1 to 1:1.

[0057] In the eighth embodiment of the invention, which is a specific configuration of the sixth to seventh embodiments, the solvent phase obtained after phase separation following the first washing stage is subjected to evaporation of organic solvent, and the organic solvent-poor (concentrated) phase obtained in this way is sent to the second washing stage.

[0058] In a ninth embodiment of the invention, which is a specific configuration of the eighth embodiment, the organic solvent obtained by evaporation (optionally after purification) is recycled to step (CI).

[0059] In a tenth embodiment of the invention, which is a specific configuration of the sixth to ninth embodiments, the aqueous phases obtained in at least (preferably exactly) two washing stages are combined to obtain a first aqueous phase.

[0060] In an eleventh embodiment of the invention, which can be combined with all other embodiments, the method includes step (D).

[0061] In a twelfth embodiment of the invention, which is a specific configuration of the eleventh embodiment, step (D) includes:

[0062] (DI) The first aqueous phase is mixed with an organic solvent (especially the same organic solvent used in step (CI)) and the phases are separated.

[0063] The second solvent phase contains the organic solvent used in step (DI) and the polyol (i.e., the second portion of the polyol from the first product mixture, which is smaller than the first portion of the polyol; therefore, the second solvent phase may also be referred to as the second polyol phase), and

[0064] The second aqueous phase contains alcohols, urethanes, and amines (and impurities derived from polyurethane products).

[0065] In a thirteenth embodiment of the invention, which is a specific configuration of the eleventh and twelfth embodiments, step (D) includes:

[0066] (D.II.a) Hydrolyze (especially in the presence of a catalyst) the urethane contained in the first aqueous phase or, if step (DI) is performed, the second aqueous phase to obtain a third product mixture containing water, an alcohol (released during hydrolysis and already contained in the first or second aqueous phase) and an amine (released during hydrolysis and already contained in the first or second aqueous phase) (as well as impurities derived from the polyurethane product).

[0067] (D.III.a) Evaporate water from the third product mixture (optionally – especially if step (DI) is performed – along with the residual components of the organic solvent) to leave an amine-alcohol mixture (containing impurities derived from the polyurethane product);

[0068] (D.IV.a) Evaporate the alcohol fraction from the amine-alcohol mixture to leave the amine phase (which contains impurities derived from polyurethane products);

[0069] (DV) Obtain (at least) an amine from the amine phase corresponding to the isocyanate from the isocyanate component.

[0070] In a fourteenth embodiment of the invention, which is a specific configuration of the thirteenth embodiment, the water evaporated in step (D.III.a) (optionally after purification) is recycled to step (C.II) as a component of the aqueous washing solution.

[0071] In a fifteenth embodiment of the invention, which is a specific configuration of the thirteenth and fourteenth embodiments, the alcohol fraction evaporated in step (D.IV.a) is recycled to step (B).

[0072] In a sixteenth embodiment of the invention, which is another specific configuration of the eleventh and twelfth embodiments, step (D) includes:

[0073] (D.II.b) Evaporate the water-alcohol fraction from the first aqueous phase or, if step (DI) is performed, from the second aqueous phase to leave the urethane phase (which contains impurities derived from the polyurethane product);

[0074] (D.III.b) Hydrolyze (especially in the presence of a catalyst) the urethane contained in the urethane phase to obtain a third product mixture containing water, an alcohol (released during hydrolysis and already contained in the first or second aqueous phase), and an amine (released during hydrolysis and already contained in the first or second aqueous phase) (as well as impurities derived from the polyurethane product); (D.IV.b) Evaporate the alcohol fraction from the third product mixture to obtain an amine phase (containing impurities derived from the polyurethane product);

[0075] (DV) Obtain (at least) an amine from the amine phase corresponding to the isocyanate from the isocyanate component.

[0076] In a seventeenth embodiment of the invention, which is a specific configuration of the sixteenth embodiment, the water-alcohol fraction evaporated in step (D.II.b) (optionally after purification) is recycled to step (C.II) as a component of the aqueous washing solution.

[0077] In an eighteenth embodiment of the invention, which is a specific configuration of the sixteenth and seventeenth embodiments, the alcohol fraction evaporated in step (D.IV.b) is recycled to step (B).

[0078] In a nineteenth embodiment of the invention, which is a specific configuration of the thirteenth to eighteenth embodiments, these embodiments include the steps (DI) of the twelfth embodiment.

[0079] In a twentieth embodiment of the invention, which is a specific configuration of the nineteenth embodiment, in step (DI), the mass ratio of the first aqueous phase to the organic solvent is followed as 20:1 to 1:3.

[0080] In the twenty-first embodiment of the invention, which is a specific configuration of the nineteenth and twentyth embodiments, the second solvent phase is washed together with the second product mixture in step (C.II).

[0081] In a twenty-second embodiment of the invention, which is a specific configuration of the thirteenth to twenty-first embodiments, the method includes the steps of:

[0082] (E) Provide a crude product fraction of an amine, the same amine obtained in step (DV), wherein the crude product fraction contains (at least) organic impurities with boiling points higher than that amine in addition to the amine;

[0083] The steps (DV) include:

[0084] (DV1) A mixture of the amine phase and the crude product fraction, and the post-treatment mixture, is obtained together with the amine obtained from the amine phase to give the amine contained in the crude product fraction.

[0085] In a twenty-third embodiment of the invention, which is a specific configuration of the twenty-second embodiment, the crude product fraction is taken from the bottom fraction of a distillation column used to purify the amine contained in the crude product fraction, wherein in step (DV1) a solid residue is obtained in addition to (i.e., in addition to the amine contained in the crude product fraction and the amine obtained from the amine phase), which contains organic impurities with boiling points higher than such amines (and impurities derived from polyurethane products).

[0086] In a twenty-fourth embodiment of the invention, which is a specific configuration of the twenty-second embodiment, the crude product fraction is taken from the crude product of a method for producing an amine contained in the crude product fraction, and contains organic impurities with boiling points below the amine and water, and is supplied to distillation to remove water, wherein a bottom fraction containing the amine, organic impurities with boiling points below the amine and organic impurities with boiling points above the amine (and impurities derived from polyurethane products) and a top fraction (optionally containing the removed water in addition to residual organic impurities with boiling points below the amine) are obtained.

[0087] In a specific configuration of the twenty-third and twenty-fourth embodiments of the invention, in the twenty-fifth embodiment, step (E) includes:

[0088] (EI) The nitro compound corresponding to the amine contained in the crude product fraction is optionally catalytically hydrogenated in the presence of a solvent to obtain a crude product, which contains, in addition to the amine, organic impurities with boiling points higher than the amine, organic impurities with boiling points lower than the amine, and water.

[0089] (E.II) Remove water from the crude product to obtain a water-poor process product;

[0090] (E.III) Distill the product of the water-poor process to obtain a distillate fraction containing the amine (i.e. the desired amine) in the crude product fraction and a bottom fraction containing organic impurities with boiling points higher than the amine in addition to the amine.

[0091] In a twenty-sixth embodiment of the invention, which can be combined with all other embodiments, the isocyanate component comprises an isocyanate selected from toluene diisocyanate (TDI), diphenylmethane series diisocyanates and polyisocyanates (MDI), pentane 1,5-diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), isophorone diisocyanate (IPDI), phenyl dimethyl diisocyanate (XDI), and mixtures of two or more of the above isocyanates. The isocyanate component is preferably a mixture of TDI and MDI (i.e., a mixture containing TDI and MDI but without other isocyanates). More preferably, the isocyanate component is TDI (i.e., containing TDI but without other isocyanates).

[0092] In a twenty-seventh embodiment of the invention, which can be combined with all other embodiments, the polyol component comprises a polyol selected from polyether polyols, polyester polyols, polyether ester polyols, polyether carbonate polyols, and mixtures of two or more of the above polyols. The polyol component is preferably a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., a polyol that does not contain non-polyether polyols; but contains a mixture of two or more different polyether polyols and does not depart from the scope of this embodiment).

[0093] In a twenty-eighth embodiment of the invention, which can be combined with all other embodiments, the organic solvent in step (CI) is selected from halogenated aliphatic hydrocarbons (particularly, for example, tetrachloromethane, chloroform, and hexachloromethane), halogenated alicyclic hydrocarbons (particularly, for example, chlorocyclohexane), halogenated aromatic hydrocarbons (particularly, for example, monochlorobenzene and dichlorobenzene), and mixtures of two or more of the above organic solvents.

[0094] The alcohol in step (B) is selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, glycerol, 2-methylprop-1,3-diol and mixtures of two or more of the above alcohols.

[0095] In a twenty-ninth embodiment of the invention, which is a specific configuration of the twenty-eighth embodiment, the organic solvent comprises a halogen-substituted aromatic hydrocarbon, and the alcohol comprises ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, and / or triethylene glycol.

[0096] In a thirtieth embodiment of the invention, which is a specific configuration of the twenty-ninth embodiment, the organic solvent is dichlorobenzene (especially the ortho-isomer), and the alcohol is diethylene glycol.

[0097] In the thirty-first embodiment of the invention, which can be combined with all other embodiments, the catalyst in step (B) is selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal salts of carboxylic acids (especially acetates), alkaline earth metal salts of carboxylic acids (especially acetates), Lewis acids (especially dibutyltin dilaurate), organic amines (especially diethanolamine), organometallic compounds (especially tetrabutoxide titanium), and tin compounds (especially tin octoate).

[0098] In the thirty-second embodiment of the invention, which is a specific configuration of the thirty-first to thirty-first embodiments, the catalyst used in step (D.II.a) or step (D.III.b) is selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal salts of carboxylic acids (especially acetates), alkaline earth metal salts of carboxylic acids (especially acetates), Lewis acids (especially dibutyltin dilaurate), organic amines (especially diethanolamine), organometallic compounds (especially tetrabutoxide titanium), and tin compounds (especially tin octoate).

[0099] In the thirty-third embodiment of the invention, which can be combined with all other embodiments except those involving polyurethane products that are not polyurethane foams, the polyurethane product is a polyurethane foam.

[0100] In a thirty-fourth embodiment of the invention, which is a specific configuration of the thirty-third embodiment, the polyurethane foam is a flexible polyurethane foam.

[0101] In the thirty-fifth embodiment of the invention, which is a specific configuration of the thirty-third embodiment, the polyurethane foam is a rigid polyurethane foam.

[0102] In the thirty-sixth embodiment of the invention, which can be combined with all other embodiments except those involving polyurethane products that are not polyurethane elastomers, the polyurethane product is a polyurethane elastomer.

[0103] In the thirty-seventh embodiment of the invention, which can be combined with all other embodiments except those involving polyurethane products that are not polyurethane adhesives, the polyurethane product is a polyurethane adhesive.

[0104] In the thirty-eighth embodiment of the invention, which can be combined with all other embodiments except those involving polyurethane products that are not polyurethane coatings, the polyurethane product is a polyurethane coating.

[0105] In the thirty-ninth embodiment of the invention, which can be combined with all other embodiments, water is supplied to the reaction in step (B) in an amount such that the mass percentage of water is 0% to 5.0%, preferably 0% to 3.0%, more preferably 0% to 2.0%, and most preferably 0% to 1.6%, based on the total mass of the polyurethane product, catalyst, alcohol, and water present in step (B) (i.e., immediately after the reactants are mixed, i.e. before the start of the urethane cracking reaction). Here, no additional water is added after the reaction of the polyurethane product with the (mono- or poly-)ol in the presence of the catalyst (i.e., no water is added to replace the water consumed in the polyurethane cracking reaction).

[0106] under More detailed explanation The above outlines the embodiments and further possible configurations of the invention. Various embodiments can be combined with each other in any way, provided that the contrary is not obvious from the context to those skilled in the art.

[0107] Figure 1 A schematic diagram of the method of the present invention is shown in the form of a simple block flowchart. It has the following meanings:

[0108] 1: Polyurethane products;

[0109] 2: Alcohol;

[0110] 3: The mixture of the first products;

[0111] 4: Organic solvent; 41: First solvent phase;

[0112] 5: Second product mixture;

[0113] 6. Aqueous washing solution; 61: First aqueous phase;

[0114] 7: Polyols;

[0115] 8: Amine;

[0116] 1000: Step (A) [Provide polyurethane products];

[0117] 2000: Step (B) [Reaction of polyurethane products with alcohols];

[0118] 3000: Step (C) [Post-treatment to obtain polyols]; 3100: Step (CI) [Washing]; 3200: Step (C.II) [Washing including phase separation]; 3300: Step (C.III) [Further post-treatment to polyols];

[0119] 4000: Step (D) [Post-treatment to obtain amine];

[0120] Figure 2 A schematic diagram showing one embodiment of the method of the present invention is provided, emphasizing step (D). The reference numerals used have the same meaning as... Figure 1 It has the same meaning as in the text. In addition, it has the following meanings:

[0121] 9: A mixture of third-generation products;

[0122] 10: Amine-alcohol mixture;

[0123] 11: Carbamate phase;

[0124] 12: Amine phase;

[0125] 42: Second solvent phase;

[0126] 62: Second aqueous phase; 63: Evaporated water, which may optionally contain a certain proportion of solvent; 64: Water-alcohol fraction;

[0127] 4100: Step (DI) [mixing with solvent, including phase separation];

[0128] 4201: Step (D.II.a) [Hydrolysis]; 4301: Step (D.III.a) [Evaporation]; 4401: Step (D.IV.a) [Evaporation];

[0129] 4202: Step (D.II.b) [Evaporation]; 4302: Step (D.III.b) [Hydrolysis]; 4402: Step (D.IV.b) [Evaporation];

[0130] 4500: Step (DV) [Amine Acquisition].

[0131] Preparation for chemical recycling

[0132] In step (A) of the method of the present invention (=1000 in the figure), a polyurethane product (1) for chemical recycling is provided.

[0133] In principle, it can be any type of polyurethane product, that is, it can be polyurethane foam or polyurethane products from so-called CASE applications. For polyurethane foam, both flexible foam and rigid foam can be considered, with flexible foam being preferred (e.g., from old mattresses, furniture padding, or car seats). For polyurethane products from CASE applications, polyurethane elastomers, polyurethane adhesives, and polyurethane coatings are preferred.

[0134] Furthermore, polyurethane products based on isocyanates selected from toluene diisocyanate (TDI), diphenylmethane diisocyanates and polyisocyanates (MDI), pentane 1,5-diisocyanate (PDI), 1,6-hexanediisocyanate (HDI), isophorone diisocyanate (IPDI), and phenyl dimethyl diisocyanate (XDI), and mixtures of two or more of the above isocyanates, are preferred in terms of the isocyanate component. Polyurethane products based on mixtures of TDI and MDI, in terms of the isocyanate component, are particularly preferred. Very particularly preferred are polyurethane products based solely on TDI, in terms of the isocyanate component.

[0135] Preferably, step (A) includes a preparatory step for breaking the urethane bonds in step (B). This is particularly true for the mechanical crushing of polyurethane products. Such preparatory steps are known to those skilled in the art; see, for example, the literature cited in [1].

[0136] Chemical breaking of urethane bonds

[0137] Step (B) of the method of the present invention (=2000 in the figures) involves actual chemical recycling, namely the breaking of the urethane bond. Step (B) is carried out as alcoholysis (commonly referred to in the literature as diollysis; see number 2 above), particularly at temperatures between 160°C and 240°C, i.e., as a reaction with an alcohol without the addition of a significant proportion of water, which differs from the process referred to in the literature as aqueous diollysis. “Without the addition of a significant proportion of water” in this respect means that water is not intentionally added in an amount that would cause a significant degree of aqueous diollysis (more precisely: aqueous alcoholysis). This does not preclude the introduction of small amounts of water, which may be in a dissolved form, for example, contained in the alcohol used in step (B), introduced by a polyurethane product, or used as a solvent as a catalyst. It is also conceivable that a small amount of water is added in step (B) to dissolve any salts that may precipitate. Here, it is preferable to add carbon dioxide to the water to be added, especially to saturate it with carbon dioxide. This promotes the dissolution of basic salts. Water is introduced into step (B) from the aforementioned sources in such an amount that the mass percentage of water is 0% to 5.0%, preferably 0% to 3.0%, more preferably 0% to 2.0%, and most preferably 0% to 1.6%, based on the total mass of the polyurethane product, catalyst, alcohol, and water (from any source) present in step (B) (i.e., immediately after the reactants are mixed, i.e. before the start of the urethane cracking reaction). In particular, because these proportions are significantly lower than those commonly used for hydrolysis in the method of the present invention, the reaction in step (B) proceeds as “pure hydrolysis” very early, even in the presence of a small amount of water initially.

[0138] Even after alcoholysis, water can be added in a cooled state (especially after cooling to ambient temperature) to dissolve the salt. In this case, the mass ratio of water used for this purpose may be higher than the aforementioned mass ratio, especially up to 20%, based on the total mass of the reaction mixture in a cooled state before and after alcoholysis. It is also preferable to add carbon dioxide to the water to be added, especially to saturate it with carbon dioxide, to promote the dissolution of the basic salt.

[0139] This alcoholysis produces a first product mixture (3), which contains a polyol, a urethane, and the unconverted portion of the alcohol used, as well as optional water. In the reaction of the urethane bond of the polyurethane product to be reused with the alcohol used in step (B), the polyol bound to the urethane bond is released and forms a new urethane with the alcohol used. For this new urethane, the term urethane is used in this invention to distinguish it from the original urethane. In the case of polyols, all alcohol groups can, in principle, participate in such a urethane formation reaction.

[0140] The first product mixture (3) may already contain amines. This is especially true when the polyurethane product provided in step (A) contains a significant amount of urea (e.g., formed by water-driven foaming). Such urea then reacts with the alcohol used in step (B) to release the amine.

[0141] The alcoholysis can, in principle, be carried out as is known in the prior art.

[0142] The alcohol particularly suitable for step (B) is methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, glycerol, 2-methylprop-1,3-diol, or a mixture of two or more of the above alcohols. Particularly preferred are ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, or a mixture of two or more of these. Diethylene glycol is very particularly preferred.

[0143] Particularly suitable catalysts for step (B) are alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal salts of carboxylic acids (especially acetates), alkaline earth metal salts of carboxylic acids (especially acetates), Lewis acids (especially, for example, dibutyltin dilaurate), organic amines (especially, for example, diethanolamine), organometallic compounds (especially tetrabutoxide titanium), and tin compounds (especially, for example, tin octoate). Step (B) is preferably carried out at a temperature of 160°C to 270°C in the presence of 0.1% to 5% by mass of catalyst based on the mass of the added polyurethane product.

[0144] The first product mixture obtained in this manner can be (and preferably is) single-phase. A major advantage of the present invention is that the post-treatment for separating the chemically cleaved products of the urethane bond, i.e., at least polyols (see step (C)), preferably polyols and amines (see step (D)), is not based on the preliminary separation of the product mixture already achieved in step (B), as is the case in many prior art methods that pursue two-phase products (see [1] and the references cited therein). This significantly increases the freedom in the selection of alcohols. However, the multiphase nature of the first product mixture (including possible solid precipitation) is not intrusive and does not depart from the scope of the present invention.

[0145] Obtaining polyols

[0146] Step (C) of the method of the present invention (=3000 in the figure) includes obtaining a polyol from the first product mixture obtained in step (B), i.e., without dehydration between steps (B) and (C) as in the so-called "Ford hydrolysis method" of the prior art. For this purpose, in the first step... (CI) In (=3100 in the figure), the first product mixture (3) obtained in step (B) is mixed with an organic solvent (4), which is miscible with the alcohol (2) used in step (B).

[0147] Suitable organic solvents for step (CI) are, in particular, halogenated aliphatic hydrocarbons (especially tetrachloromethane, chloroform, and hexachloromethane), halogenated alicyclic hydrocarbons (especially chlorocyclohexane), halogenated aromatic hydrocarbons (especially monochlorobenzene and dichlorobenzene), or mixtures of two or more of the above-mentioned organic solvents. Of the above examples, halogenated aromatic hydrocarbons are particularly preferred. Dichlorobenzene (especially the ortho-isomer) is very particularly preferred.

[0148] In any case, the alcohol used in step (B) and the organic solvent used in step (CI) should be selected such that they are miscible under the conditions of step (CI) (temperature and ratio of organic solvent to alcohol). Preferably, in step (CI), the first product mixture and the organic solvent are mixed in a mass ratio of 5:1 to 1:3, preferably at a temperature of 30°C to 80°C. To achieve the desired miscibility, it is particularly preferred to use halogenated aromatic hydrocarbons as organic solvents and ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, and / or triethylene glycol as alcohols. In particular, the combination of dichlorobenzene (of which the ortho isomer is preferred) and diethylene glycol has been found to be useful. In case of doubt, a suitable combination of alcohol and solvent can be quickly determined by simple preliminary tests. Due to the mutually miscible organic solvent and the combination of alcohol according to the invention, the second product mixture (5) obtained in step (CI) is generally present in a single-phase form (which is also preferred). However, given the exact properties of the polyurethane product provided in step (A), it is not possible to completely rule out the formation of a second phase (optionally even a solid phase, for example, when the polyurethane product is based on a styrene-acrylonitrile copolymer polyol – also known as a polymeric polyol [PMPO]). This does not depart from the scope of the invention.

[0149] Second Step (C.II) In step (CI), the second product mixture (5) obtained in step (CI) is washed with a first washing solution (6) in one or more stages. Here, after phase separation, a first solvent phase (41) (which contains the solvent used in step (CI) in addition to the polyol) and a first aqueous phase (61) are obtained.

[0150] Step (C.II) can be carried out using extraction apparatus known to those skilled in the art, particularly, for example, a mixer (rotary, pulsed, or static) and a downstream static separator or centrifuge with or without internal components. Temperatures from 20°C to 80°C, preferably at most 10 K below the boiling point of the solvent used, optionally with a slight increase in pressure by covering with nitrogen and preventing gas formation; cross-current extraction, especially countercurrent extraction for reducing the total water volume, is suitable as process conditions.

[0151] The washing can be carried out in a single stage, wherein a mass ratio of the second product mixture to the aqueous washing solution of 20:1 to 1:1 is preferably followed.

[0152] The washing can alternatively be carried out in multiple stages, particularly two stages. The multi-stage washing in step (C.II) can be performed using principles known to those skilled in the art, such as cross-flow extraction (also known as cross-current extraction) and / or countercurrent extraction, particularly countercurrent extraction. In the case of multi-stage washing, phase separation is performed after each washing stage to obtain a solvent phase and an aqueous phase, wherein the solvent phase obtained in the last washing stage is the first solvent phase (41), and the first aqueous phase (61) (at least) comprises the aqueous phase obtained in the first washing stage (in a preferred embodiment, all aqueous phases obtained are combined to obtain the first aqueous phase). Particularly preferred here is that, in each washing stage, the mass ratio of the second product mixture to be washed in the washing stage or the polyol phase to be washed to the aqueous washing solution used in the washing stage follows a ratio of 20:1 to 1:1.

[0153] In the case of multi-stage washing, it may be advantageous to subject the solvent phase obtained after phase separation in the first washing stage to evaporation of the organic solvent, and to send the organic solvent-poor (concentrated) (“solvent”) phase obtained in this way to the second washing stage. It is advantageous to recycle the organic solvent obtained from evaporation (optionally after purification) to step (CI).

[0154] The first solvent phase (41) thus obtained in Step (C.III) Post-processing (=3300 in the attached figure) yields the polyol, preferably by distillation and / or stripping with a stripping gas (particularly nitrogen or steam, preferably nitrogen). Here, distillation is preferably carried out in an evaporator selected from falling film evaporators, thin-film evaporators, flash evaporators, rising film evaporators, natural circulation evaporators, forced circulation evaporators, and batch evaporators. Stripping with steam after distillation is particularly preferred.

[0155] Steam stripping can be carried out by passing steam in a stripping column known to those skilled in the art. However, steam stripping can also be carried out by adding water in liquid form to a first polyol phase (which has optionally been pre-purified in distillation), followed by superheating (while following a pressure sufficient to keep the water in liquid form, regulated by a pressure valve) and depressurization downstream of the pressure valve, thus evaporating the water contained in the polyol and having a stripping effect.

[0156] Acquisition of amines

[0157] Preferably, the present invention further includes Step (D) The acquisition of amines (=4000 in the attached figure; see also...) Figure 2 ).

[0158] Preferably, firstly, in Step (DI) In step (4100), the first aqueous phase (61) is mixed with an organic solvent (especially the same solvent used in step (CI); 4), and then the phase is separated into a second solvent phase (42) containing the organic solvent used in step (DI) and a polyol (i.e., a second portion of the polyol from the first product mixture, which is smaller than the first portion of the polyol; therefore, the second solvent phase may also be referred to as the second polyol phase) and a second aqueous phase (62) containing alcohols, urethanes and amines (and impurities derived from the polyurethane product). In step (DI), a mass ratio of the first aqueous phase to the organic solvent of 20:1 to 1:3 is preferably followed. The second solvent phase obtained in the implementation of step (DI) is preferably introduced into step (C.II), combined with and washed with the second product mixture (5). For this purpose, the second solvent phase (41) (together with the solvent (4)) can be sent to step (CI) (3100) or directly to step (C.II) (3200). In the event of a (semi-stable) emulsion (i.e., a separation time that is technically too long) during phase separation in the washing process of step (C.II), the first aqueous phase containing the emulsifying component (or composed of the emulsifying component) is sent to step (DI), where the emulsion is demulsified to obtain a second aqueous phase and a second solvent phase. If the demulsification of the emulsion does not proceed spontaneously or proceeds too slowly, this can be accelerated by adding an alcohol (2). By recycling the second solvent phase, which now contains the emulsified organic component previously contained in the first aqueous phase, to the washing step (C.II), a certain proportion of polyols that were emulsified in the first aqueous phase are prevented from being obtained in step (C.III) due to polyols being obtained in the first aqueous phase.

[0159] for Step D.II Further post-treatment of the second aqueous phase in the solution presents two particularly preferred possibilities, which are shown in... Figure 2 middle:

[0160] exist variant a (shown) Figure 2 In the left side of the diagram, step (D.II) includes the following sub-steps:

[0161] (D.II.a)–4201– hydrolysis (Especially in the presence of a catalyst) the urethane [hydrolysis D.II.a] contained in the first aqueous phase or if step (DI) is performed, is used to obtain a third product mixture (9) containing water, alcohol (released during hydrolysis and already contained in the first or second aqueous phase) and amine (released during hydrolysis and already contained in the first or second aqueous phase) (and impurities derived from the polyurethane product);

[0162] (D.III.a)–4301–from the mixture of third products Evaporation Water (63) (optionally – especially if step (DI) is performed – along with the residual components of the organic solvent) to leave an amine-alcohol mixture (10) (containing impurities derived from the polyurethane product);

[0163] (D.IV.a)–4401–from an amine-alcohol mixture (10) (which contains impurities derived from polyurethane products) Evaporation Alcohol fraction (21).

[0164] The water (63) evaporated in step (D.III.a) – which, as described above, may be present in a mixture with the solvent in a particular embodiment – ​​can advantageously (optionally after purification) be recycled to step (C.II) and used therein as a component of the aqueous washing solution (6). The alcohol fraction (21) evaporated in step (D.IV.a) can advantageously be recycled to step (B) and used here as a component of the alcohol (2) to be used.

[0165] exist Variant b (shown) Figure 2 In the right-hand side of the diagram, step (D.II) includes the following sub-steps:

[0166] (D.II.b)–4202–from the first aqueous phase (61) or, if step (DI) is performed, from the second aqueous phase (62). Steam issue Water-alcohol fraction (64) was used to leave the urethane phase (11) (which contains impurities derived from polyurethane products);

[0167] (D.III.b)–4302– hydrolysis (Especially in the presence of a catalyst) the urethane contained in the urethane phase to obtain a third product mixture (9) containing water, alcohol (released during hydrolysis and already present in the first or second aqueous phase) and amine (released during hydrolysis and already contained in the first or second aqueous phase) (and impurities derived from the polyurethane product);

[0168] (D.IV.b)–4402–from the third product mixture (9) Evaporation Alcohol fraction (21) is used to obtain amine phase (12) (which contains impurities derived from polyurethane products).

[0169] In this variant, in step (D.II.b), a water-alcohol fraction (64) is obtained by evaporation, which, in a preferred configuration (optionally after purification), can be recycled as a component of the aqueous washing solution (6) to step (C.II). The alcohol fraction (21) evaporated in step (D.IV.b) is preferably recycled to step (B).

[0170] In both of these variants, Hydrolysis steps A catalyst is preferably used in steps (D.II.a) and (D.III.b). Particularly suitable are alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal salts of carboxylic acids (especially acetates), alkaline earth metal salts of carboxylic acids (especially acetates), Lewis acids (especially dibutyltin dilaurate), organic amines (especially diethanolamine), organometallic compounds (especially tetrabutoxide titanium), and tin compounds (especially tin octoate). In variant b, depending on how much water has already evaporated with the alcohol in step (D.IIb), it may be suitable to add (a certain amount) of water.

[0171] The main difference between these two variants is therefore the different order of the steps in hydrolysis and evaporation. Both variants contain... Steps (DV) Amines are obtained from the amine phase.

[0172] In a particularly advantageous embodiment of the invention, which provides an economical and environmentally friendly solution for impurities derived from polyurethane products, an amine is obtained from the amine phase and incorporated into the post-treatment of the newly prepared amine—this is done by mixing the amine phase (12) into the crude fraction of the amine to be prepared.

[0173] (1) This particularly advantageous embodiment of the method of the present invention is especially applicable when the isocyanate component of the polyurethane product is based on exactly one isocyanate class. In such a case, the amine phase (12) obtained from the polyurethane product in the method of the present invention contains only the amine corresponding to the isocyanate of that isocyanate class (and no other amines), and therefore can be mixed without any problem with the crude product fraction obtained in the preparation method of the same amine (of the same amine class) (i.e., fresh preparation, rather than recycling).

[0174] (2) If the isocyanate component of the polyurethane product is based on isocyanates from different isocyanate classes, a particularly advantageous embodiment of the method of the present invention is applicable especially when the boiling points of the amine classes corresponding to the isocyanate classes differ such that (exactly) the boiling point level of one amine class is significantly lower than that of the lowest boiling point amine class that would otherwise exist (i.e., at least 20°C lower). In such cases, this embodiment can be used to recover the lowest boiling point amine class in the post-treatment of newly prepared amines of the same amine class, wherein the amines of higher boiling point amine classes are removed in the post-treatment—this is done by converting them into a bottom fraction or residue (details below). For example, in the case of polyurethane products based on a mixture of TDI and MDI in terms of their isocyanate component, the amine phase can be incorporated into the post-treatment of the crude TDA product fraction—this is done by mixing the amine phase with such crude TDA product fraction and post-treating it together. In this post-treatment, newly prepared TDA and TDA originally derived from the polyurethane product are obtained together, while MDA from the polyurethane product is removed as a bottom fraction in distillation purification. It can be obtained from this bottom fraction in a further distillation step (at least diamines of the diphenylmethane series), or the (physical) recovery of MDA can be omitted and allowed to enter the solid residue from TDA production (details below).

[0175] For simplicity, the following details the language based on case (1), but also applicable to case (2).

[0176] The preparation of amines, which are important for polyurethane synthesis, regularly produces crude product fractions—for example, as the bottom fraction from distillation used to purify the desired amine or as the crude product of the preparation itself (optionally after solvent removal), which contain impurities or byproducts in addition to the desired amine (e.g., organic impurities with boiling points above the amine (so-called high-boiling impurities), organic impurities with boiling points below the amine (so-called low-boiling impurities) and / or (reaction) water).

[0177] In this embodiment of the invention, the method of the invention therefore includes the following step (E):

[0178] (E) Provide a crude product fraction of an amine, which is the same amine obtained in step (DV), wherein the crude product fraction contains (at least) organic impurities with boiling points higher than that amine in addition to the amine.

[0179] The steps (DV) include:

[0180] (DV1) A mixture of the amine phase and the crude product fraction, and the post-treatment mixture, is obtained together with the amine obtained from the amine phase to give the amine contained in the crude product fraction.

[0181] In the first preferred configuration of step (D.V.1), the crude product fraction is taken from the bottom fraction of the distillation for purifying the amine contained in the crude product fraction, wherein in step (D.V.1), a solid residue is additionally obtained (i.e., in addition to the amine contained in the crude product fraction and the amine obtained from the amine phase), which comprises organic impurities having a boiling point higher than that of the amine (and impurities derived from polyurethane products).

[0182] Regardless of the specific configuration of step (D.V.1), step (E) preferably comprises the following:

[0183] (E.I) catalytic hydrogenation of the nitro compound corresponding to the amine contained in the crude product fraction, optionally in the presence of a solvent, to obtain a crude product which, in addition to said amine, further comprises organic impurities having a boiling point higher than that of said amine, organic impurities having a boiling point lower than that of said amine, and water;

[0184] (E.II) removing water from the crude product to obtain a water-lean process product;

[0185] (E.III) distilling the water-lean process product to obtain a distillate fraction of the amine (i.e., the desired amine) contained in the crude product fraction and a bottom fraction which, in addition to said amine, further contains organic impurities having a boiling point higher than that of said amine.

[0186] Steps (E.I) to (E.III) are schematically shown in Figure 3 . It has the following meanings:

[0187] 13: hydrogen for hydrogenation;

[0188] 14: nitro compound corresponding to the amine;

[0189] 15: crude hydrogenation product;

[0190] 16: removed water;

[0191] 17: water-lean process product;

[0192] 18: distillate fraction of the amine formed in hydrogenation;

[0193] 19: distillation bottom fraction;

[0194] 5100: hydrogenation (step (E.I)); 5200: water removal (step (E.II)); 5300: distillation (step (E.III))

[0195] In one embodiment of the invention, the amine phase (12) is mixed with the hydrogenated crude product (15) obtained in step (EI) (which has only had the optionally present solvent removed), i.e., the crude product fraction from step (E) is obtained as the crude product from hydrogenation (step EI) = 5100). The amine (8) from the polyurethane product is here distilled together with the (freshly) prepared amine (18). This shows Figure 4 In the figures, the reference numerals used have the same meaning as before, and 4510 represents step (DV1).

[0196] In this embodiment, the amine phase (12) is incorporated into the crude hydrogenated product from step (EI), particularly before or during the dehydration step (step E.II), wherein water is preferably removed by distillation as described, for example, in EP 0236839A2. In this embodiment, the crude product fraction of the amine corresponding to the isocyanate contains, in addition to the amine, organic impurities with boiling points below the amine and water, and is sent for distillation to remove water. In this distillation, a bottom fraction containing the amine, organic impurities with boiling points below the amine, and organic impurities with boiling points above the amine (and impurities derived from the polyurethane product) and (optionally, in addition to residual organic impurities with boiling points below the amine) containing the removed water are obtained. Impurities derived from the polyurethane product enter the bottom fraction in the dehydration step – step (E.II). They also enter the bottom fraction in the subsequent distillation step – step (E.III).

[0197] In another embodiment of the invention, the amine phase (12) is incorporated into the bottom fraction (19) obtained in step (E.III), i.e., the crude product fraction from step (E) is obtained as the bottom fraction from amine distillation (step E.III) = 5300. An example of such a crude product fraction obtained as the bottom fraction from amine distillation is International Patent Application WO 02 / 48075A1. Figures 1 to 3 Streams 5, 50, and 51 are included, wherein further post-processing of these streams may be carried out as described in this document or, differently, in a drying apparatus as described below. Another example of such crude product fractionation is found in U.S. Patent Specification US 7,307,190 B2. Figures 1 to 5The feed stream P4. These bottom fractions are post-processed in the prior art to recover the amines contained therein. For this purpose, the bottom fractions are concentrated in a drying unit to produce a solid residue, from which the amines can be distilled and thus recovered. In an embodiment of the method of the present invention mentioned above, due to the mixing of the amine phase (12) with the bottom fraction (19), the recovery of the (freshly) prepared amine (20) from the amine is now combined with the acquisition of amine (8) from the polyurethane product. Here, in addition to the amines (20, 8), a solid residue (21) is also obtained, which contains high-boiling substances present in the crude product fraction and impurities derived from the polyurethane product. This shows Figure 5 In this context, the reference numerals used have the same meaning as before, and 6000 represents post-treatment of residues. Applicable to such post-treatment... Device This is known to those skilled in the art and is described, for example, in patent applications DE 10 2012 108 261 A1 (kneader dryer, also mentioned in US 3,307,190 B2 for post-treatment of flow P4), EP 2 540 702 A2 (fluidized bed dryer), and WO 2018 / 114846 A1 (various dryer types). (The mentioned DE, EP, and WO documents describe the post-treatment of TDI residues, but these devices can also be used for the post-treatment of TDA residues). The solid residues obtained in such a post-treatment process can be further processed as before; for example, they can be incinerated, gasified (i.e., heated under oxygen-deficient conditions, unlike combustion), or pyrolyzed.

[0198] Through the particularly advantageous embodiments of the invention outlined above, impurities in polyurethane products are thus successfully transferred to the residues that would otherwise be generated, thereby reducing or avoiding additional waste streams.

[0199] The invention will be further illustrated below with reference to specific examples. Example:

[0200] TDI-based polyurethane foam was alcoholyzed with diethylene glycol (DEG) at a 1:1 mass ratio (steps (A) and (B) of the method of the present invention). The results were obtained from analysis performed using 1H NMR / 2D NMR spectroscopy with an internal standard. First Product mixture It has the following composition (based on the mass ratio of the total mass of the first product mixture):

[0201] 38% polyols, 42% DEG and a total of 20% TDA and carbamates.

[0202] 60 grams of this first product mixture were packed into a sample vial, and 40 grams of o-dichlorobenzene (ODB) were added. The vial was closed and shaken by hand for 5 minutes (step (CI) of the method of the present invention). The resulting product... Second product mixture It is single-phase. Subsequently, the single-phase second product mixture was transferred to a new sample vial. After adding 100 g of softened (VE) water, the sample vial was closed and shaken by hand for 5 minutes. A two-phase mixture was formed. 69 g of the lower heavy phase ( solvent phase It mainly contains polyols and ODB; 131 grams of the upper light phase (= First aqueous phase It mainly contains DEG, water, amines, and carbamate compounds. The two phases are separated from each other in a separatory funnel (step (C.II) of the method of the present invention, the first washing stage).

[0203] Transfer 37g of the lower phase (containing polyol and ODB) to a sample vial and add 37g of vitamin E water. Close the sample vial and shake by hand for 5 minutes. Add the upper light phase (… First solvent phase The heavy phase below (the aqueous phase from the second stage) is separated from each other (step (C.II) of the method of the present invention, the second washing stage).

[0204] The following compositions were determined by ¹H NMR / 2D NMR analysis with internal standard (based on the mass proportions of each phase):

[0205] First solvent phase:

[0206] 24% polyols, 74% ODB, 0.5% DEG, balance: TDA and carbamates.

[0207] First aqueous phase:

[0208] 20% DEG, approximately 75% water, 0.6% ODB, <0.1% polyols, balance: TDA and carbamates.

[0209] The composition of the first solvent phase makes the polyols easy to separate, for example by distillation (step (CIII) of the method of the present invention).

Claims

1. A method for recovering raw materials from polyurethane products, comprising the steps of: (A) Provide polyurethane products based on isocyanate components and polyol components; (B) React the polyurethane product with an alcohol in the presence of a catalyst to produce a first product mixture containing an alcohol, a polyol and a urethane ester and optionally water. (C) A post-processed first product mixture, comprising: (CI) The first product mixture obtained in step (B) is mixed with an organic solvent that is miscible with the alcohol used in step (B), and optionally the solid components are then removed to obtain a second product mixture; (C.II) The second product mixture obtained in step (CI) is washed with an aqueous washing solution, thereby partially hydrolyzing the carbamate contained in the second product mixture to release amines and alcohols, and separating the phases into The first solvent phase contains the organic solvent and polyol used in step (CI), and The first aqueous phase contains water, alcohol, carbamate, and amine; (C.III) Post-treatment of the first solvent phase to obtain polyols; and optional (D) Post-treatment of the first aqueous phase to obtain an amine corresponding to the isocyanate from the isocyanate component.

2. The method of claim 1, wherein step (D) is performed and includes the following: (DI) The first aqueous phase is mixed with an organic solvent and the phases are separated. The second solvent phase contains the organic solvent and polyol used in step (DI), and The second aqueous phase contains alcohols, carbamates, and amines.

3. The method of claim 1, wherein step (D) comprises: (D.II.a) Hydrolyze the carbamate contained in the first aqueous phase to obtain a third product mixture containing water, alcohol and amine; (D.III.a) Evaporate water from the third product mixture to leave an amine-alcohol mixture; (D.IV.a) Evaporate the alcohol fraction from the amine-alcohol mixture, leaving the amine phase; (DV) Obtain the amine corresponding to the isocyanate from the isocyanate component from the amine phase.

4. The method of claim 2, wherein step (D) comprises: (D.II.a) Hydrolyze the carbamate contained in the second aqueous phase to obtain a third product mixture containing water, alcohol and amine; (D.III.a) Evaporate water from the third product mixture to leave an amine-alcohol mixture; (D.IV.a) Evaporate the alcohol fraction from the amine-alcohol mixture, leaving the amine phase; (DV) Obtain the amine corresponding to the isocyanate from the isocyanate component from the amine phase.

5. The method as described in claim 3 or 4, wherein the water evaporated in step (D.III.a) is recycled as a component of the aqueous detergent to step (C.II).

6. The method of claim 3 or 4, wherein the alcohol fraction evaporated in step (D.IV.a) is recycled to step (B).

7. The method of claim 1 or 2, wherein step (D) comprises: (D.II.b) Evaporate the water-alcohol fraction from the first aqueous phase or, if step (DI) is performed, from the second aqueous phase to leave the carbamate phase; (D.III.b) Hydrolyzing the carbamate contained in the carbamate phase yields a third product mixture containing water, alcohol, and amine; (D.IV.b) Evaporate the alcohol fraction from the third product mixture to obtain the amine phase; (DV) Obtain the amine corresponding to the isocyanate from the isocyanate component from the amine phase.

8. The method of claim 7, wherein the water-alcohol fraction evaporated in step (D.II.b) is recycled as a component of the aqueous detergent to step (C.II).

9. The method of claim 7, wherein the alcohol fraction evaporated in step (D.IV.b) is recycled to step (B).

10. The method of claim 3 or 4, further comprising the step of (E) Provide a crude product fraction of an amine, the same amine obtained in step (DV), wherein the crude product fraction contains, in addition to the amine, organic impurities with boiling points higher than the amine; The steps (DV) include: (DV1) A mixture of the amine phase and the crude product fraction, and the post-treatment mixture, is obtained together with the amine obtained from the amine phase to give the amine contained in the crude product fraction.

11. The method as described in claim 10, The crude product fraction is taken from the bottom fraction of the distillation column used to purify the amine contained in the crude product fraction, wherein a solid residue containing organic impurities with boiling points higher than that of the amine is further obtained in step (DV1). or The crude product fraction is taken from the crude product of a method for producing an amine contained in the crude product fraction, and contains organic impurities with boiling points lower than that of the amine and water, and is supplied to distillation to remove water, thereby obtaining a bottom fraction containing the amine, organic impurities with boiling points lower than that of the amine and organic impurities with boiling points higher than that of the amine, and a top fraction containing the removed water.

12. The method of claim 11, wherein step (E) comprises: (EI) The nitro compound corresponding to the amine contained in the crude product fraction is optionally catalytically hydrogenated in the presence of a solvent to obtain a crude product, which contains, in addition to the amine, organic impurities with boiling points higher than the amine, organic impurities with boiling points lower than the amine, and water. (E.II) Remove water from the crude product to obtain a water-poor process product; (E.III) Distill the water-poor process product to obtain a distillate fraction containing the amine in the crude product fraction and a bottom fraction containing organic impurities with boiling points higher than the amine in addition to the amine.

13. The method as described in any one of claims 1-4, The isocyanate component therein comprises an isocyanate selected from toluene diisocyanate, diphenylmethane series diisocyanates and polyisocyanates, pentane 1,5-diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, phenyl dimethyl diisocyanate, and mixtures of two or more of the above isocyanates. and / or one of them The polyol component contains a polyol selected from polyether polyols, polyester polyols, polyether ester polyols, polyether carbonate polyols, and mixtures of two or more of the above polyols.

14. The method according to any one of claims 1-4, wherein The organic solvent in step (CI) is selected from halogenated aliphatic hydrocarbons, halogenated alicyclic hydrocarbons, halogenated aromatic hydrocarbons, and mixtures of two or more of the above organic solvents. The alcohol in step (B) is selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, glycerol, 2-methylprop-1,3-diol, and mixtures of two or more of the above alcohols.

15. The method as described in any one of claims 1-4, wherein the polyurethane product is a polyurethane foam, a polyurethane elastomer, a polyurethane adhesive, or a polyurethane coating.

16. The method as described in any one of claims 1-4, wherein water is supplied to the reaction in step (B) in an amount such that the mass percentage of water is 0% to 5.0% based on the total mass of the polyurethane product, catalyst, alcohol, and water present in step (B), wherein no additional water is added after the reaction of the polyurethane product with the alcohol in the presence of the catalyst has begun.

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