Method for recovering raw materials from polyurethane foam

Abstract

The present invention relates to a process for recovering raw materials (i.e. polyols and optionally additionally amines) from polyurethane foam, comprising chemical degradation, which comprises reacting polyurethane foam with alcohol and water in the presence of a catalyst at a temperature between 130°C and 195°C, characterized in that the mass ratio of (total) alcohol and (total) water to polyurethane foam (i.e. m(alcohol+water) / m(polyurethane foam), where "m" is mass) is between 0.5 and 2.5, and the mass of water is between 4.0% and 10% of the mass of alcohol. The catalyst comprises a metal salt selected from carbonates, hydrogen carbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates or a mixture of two or more of said metal salts.

Description

[Technical Field]

[0001] The present invention relates to a method for recovering raw materials (i.e., polyols and optionally further amines) from polyurethane foam, including chemical decomposition. In the chemical decomposition, the polyurethane foam is reacted with alcohol and water at a temperature in the range of 130°C to 195°C in the presence of a catalyst, where the mass ratio of one (all used) alcohol and water to the other polyurethane foam (i.e., m(alcohol + water) / m(polyurethane foam), where "m" is mass) is in the range of 0.5 to 2.5, and the mass of water is 4.0% to 10% of the mass of alcohol. The catalyst comprises a metal salt selected from two or more of the following: carbonates, bicarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, or mixtures of the above metal salts. It is also possible to initially mix only the alcohol and catalyst with the polyurethane foam, and then add water after the polyurethane foam has dissolved. Alternatively, it is also possible to add a portion of the water together with the alcohol and catalyst at the start of the chemical decomposition, and then add the remaining amount of water after the polyurethane foam has dissolved. [Background technology]

[0002] Polyurethane foams have a wide range of applications in industry and daily life. Typically, polyurethane foams are distinguished from what are known as "CASE" products, which are a general term for polyurethane coatings (e.g., paints), adhesives, sealants, and elastomers. Polyurethane foams are typically divided into rigid and flexible foams. Despite their heterogeneity, the basic polyurethane structure is common to all these products, formed by the polyaddition reaction of a polyfunctional isocyanate and a polyol. For example, in the case of polyurethanes based on diisocyanate O=C=NRN=C=O and diol 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 follows.

[0003] The great economic success of polyurethane products is precisely what generates large amounts of polyurethane waste (e.g., from old mattresses or chairs / seating furniture), which needs to be used rationally. The easiest technically feasible reuse method is incineration, where the heat released from combustion is used in other processes, such as industrial processes. However, this does not close the raw material loop. Another reuse method is so-called "physical recycling," in which polyurethane waste is mechanically crushed and used to manufacture new products. This type of recycling naturally has its limitations, so attempts to recover the basic raw materials for polyurethane production by retrocleavage of polyurethane bonds (so-called "chemical recycling") will not disappear. These raw materials to be recovered mainly consist of polyols (i.e., HO-R'-OH in the above example). In addition, 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 post-treatment to obtain isocyanates (O=C=NRN=C=O in the above example).

[0004] Various chemical recycling approaches have been developed to date. The three most important can be summarized as follows: 1. Hydrolysis of urethane, in which amines and polyols are recovered through reaction with water, and carbon dioxide is formed. 2. Glycolysis of urethane by reaction with alcohol, in which polyols incorporated into the urethane group are released by being replaced by the alcohol used. This process is generally referred to in the literature as transesterification (more precisely, transurethanization). Regardless of the exact properties of the alcohol used, this method of chemical recycling is called glycol decomposition in the literature, a term that actually applies only to glycols. Therefore, in the context of the present invention, the term alcohol decomposition is generally used. Hydrolysis may be performed following glycol decomposition. When hydrolysis is performed in the presence of an unchanged glycol decomposition mixture, it is called hydrolyzed glycol decomposition. 3. Hydroglycolic decomposition of urethane bonds by reaction with alcohol and water. Naturally, it is also possible to add alcohol and water from the beginning, in which case the glycol decomposition and hydrolysis processes described above proceed in parallel.

[0005] An overview of known polyurethane recycling methods is given in the review in Non-Patent Document 1. Non-Patent Document 1 emphasizes that glycol decomposition (2. above) is particularly important. In glycol decomposition, a distinction is made between "two-phase" and "one-phase" regimes depending on whether the crude product obtained from the reaction with alcohol separates into two phases. This depends particularly on the choice of alcohol used and the process conditions (in particular, the proportion of alcohol used in the reaction mixture and the temperature). Non-Patent Document 1 prefers the two-phase regime using crude glycerol (e.g., waste from biodiesel production) because it is considered to have the highest potential for recovering high-quality products at low production costs (the recovery of polyols is clearly the focus).

[0006] As a result of the additional use of water, the products of glycol hydrolysis (3. above) are always biphasic. Non-patent document 2 describes a post-treatment of such products, comprising the removal of water (by phase separation on a laboratory scale or by evaporation in a process recommended for industrial-scale applications and known as the "Ford glycol hydrolysis process") and extraction of the remaining organic phase with hexadecane, forming an alcohol phase from which amines can be recovered and a hexadecane phase from which polyols can be recovered. While the option of recovering amines is mentioned, Non-patent document 2 also places emphasis on the recovery of polyols.

[0007] A patent for a process that operates based on these principles is granted in Patent Document 1. This process recovers polyether polyols from polyurethane, (a) A step of dissolving this polyurethane in a saturated alcohol having a boiling point of 225°C to 280°C at a temperature of 185°C to 220°C in a non-oxidizing atmosphere to form a solution, (b) A step in which the solution is reacted with water for a required time in a non-oxidizing atmosphere in the presence of an alkali metal hydroxide catalyst while maintaining the temperature of this solution at 175°C to 220°C, thereby hydrolyzing most of the hydrolyzable dissolution products to amines and alcohols, Furthermore, this alkali metal hydroxide catalyst is added to the solution in an amount of at least 0.1% by mass relative to the mass of the polyurethane foam; (c) A step of removing the water remaining after hydrolysis from this solution in a non-oxidizing atmosphere, (d) A step of extracting the polyol from the hydrolysis solution using an alkane (especially hexadecane) that is substantially immiscible with the alcohol and has a boiling point of 230°C to 300°C, in a non-oxidizing atmosphere. (e) A step of subjecting the extracted polyol to vacuum purification at a temperature of less than 230°C, A process including this is described in Patent Document 1.

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

[0009] In step (b), water and an alkali metal hydroxide catalyst are added to the solution obtained in step (a) separately or in the form of an aqueous catalyst solution to decompose the carbamate and urea into an amine and an alcohol. Steps (a) and (b) are sometimes described together as hydrolyzed glycol decomposition (more precisely, hydroalcoholysis) by alternating addition of alcohol and water. Water is added in an amount such that the solution boils at a temperature of 175°C to 200°C. When diethylene glycol is used as the alcohol, water is added in an amount of 2.4% to 0.6%, preferably 1.1%, of the mass of diethylene glycol used (see column 4, lines 39 to 46). Water consumed in hydrolysis is replenished by adding further water to maintain a constant water content. After hydrolysis is complete, the water used must be removed in step (c) before extraction in step (e) (see column 5, lines 31 to 33).

[0010] Of the chemical recycling processes known from the literature, only a few are sustainably operating on an industrial scale, and many have not even reached a pilot scale (Non-Patent Literature 1). Given the general rise in environmental awareness and the increasing effort to make industrial processes as sustainable as possible, both fundamentally support chemical recycling, but it is clear that the chemical recycling of polyurethane products is far from mature from a technical and economic standpoint. There are particular challenges regarding the purity of the recovered products. When reused in the manufacture of polyurethane foam, for example, to avoid adverse effects on foaming properties, it is necessary to recover polyols that are as free of amine impurities as possible. If the goal is further recovery of amines, these must also be obtained at the highest possible purity. In addition, recycled polyurethane products usually still contain various auxiliary agents and additives (stabilizers, catalysts, etc.), which must be separated from the actual recycled product and disposed of in an economically viable and environmentally friendly manner. Furthermore, economical recycling processes must ensure that the reagents used (e.g., alcohol used) can be recovered and reused as completely as possible (i.e., follow a closed-loop system). The recycling of polyurethane foam is particularly important due to the large amount of polyurethane waste generated from used polyurethane foam (e.g., mattresses, chairs, car seats, etc.). [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] U.S. Patent No. 4,336,406 [Non-patent literature]

[0012] [Non-Patent Document 1] Simon, Borreguero, Lucas and Rodriguez in Waste Management 2018, 76, 147 - 171 [Non-Patent Document 2] Braslaw and Gerlock, Ind. Eng. Chem. Process Des. Dev. 1984, 23, 552 - 557

Summary of the Invention

Problems to be Solved by the Invention

[0013] Therefore, further improvements are needed in the field of chemical recycling of polyurethane foams. In particular, it is desirable to be able to recover polyols, preferably further amines, from polyurethane foams in a highly pure and efficient manner, especially in a way that is economically valuable for industrial scale use. Furthermore, it is desirable to have available outlets for auxiliaries and additives present in polyurethane products that are acceptable from an economic and environmental perspective.

Means for Solving the Problems

[0014] In view of this requirement, the present invention is a method for recovering raw materials (i.e., polyols and optionally further amines) from polyurethane foams, comprising: (A) (Preparation for Chemical Decomposition) preparing a polyurethane foam based on an isocyanate component and a polyol component; (B) (Execution of Chemical Decomposition) chemically decomposing the polyurethane foam with alcohol and water in the presence of a catalyst at a temperature in the range of 130°C to 195°C, preferably in the range of 135°C to 190°C, particularly preferably in the range of 140°C to 190°C, and most preferably in the range of 165°C to 185°C to obtain a first product mixture containing: (at least) one amine corresponding to the isocyanate of the isocyanate component; a polyol (i.e., the polyol constituting the polyol component and / or a polyol optionally formed from the original polyol component during the reaction with alcohol and / or alcohol); (an alcohol that is used in a superstoichiometric amount and is thus incompletely converted); (water that is used in a superstoichiometric amount and is thus incompletely converted); and Furthermore, the mass ratio of one component (all of the alcohol and water used) to the other component (polyurethane foam) (i.e., m(alcohol + water) / m(polyurethane foam), where "m" represents mass) is in the range of 0.5 to 2.5. The mass of water is 4.0% to 10% of the mass of alcohol. The catalyst comprises (preferably consists solely of) a metal salt selected from carbonates, bicarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, or a mixture of two or more of the above metal salts; (C) (Separation of polyol and amine) A step of post-treating the first product mixture to obtain a polyol phase containing a polyol and an amine phase containing an amine, water and an alcohol, (D) (Isolation of polyols) A step of recovering polyols from the polyol phase, (E) (Isolation of amines) The present invention provides a method comprising the step of optionally (preferably) recovering an amine from the amine phase.

[0015] Surprisingly, it was found that both urethane exchange, resulting from the reaction of urethane groups with alcohol, and the subsequent in situ hydrolysis of the carbamate intermediate with water, could be catalyzed using the same catalyst listed. The listed catalysts are characterized by their ability to catalyze both urethane exchange and hydrolysis because they are not deactivated by carbonization due to carbon dioxide formed during the reaction.

[0016] In the context of this invention, polyurethane foam is a polyaddition product (sometimes referred to as a polycondensation product, though not entirely accurate) formed by the reaction of a polyfunctional isocyanate (= isocyanate component in polyurethane production) and a polyol (= polyol component in polyurethane production) in the presence of a blowing agent. Polyurethane foam generally includes not only the basic polyurethane structure outlined above, but also other structures, such as structures having urea bonds. The presence of such structures, which deviate from the pure basic polyurethane structure, in addition to the polyurethane structure does not depart from the scope of this invention.

[0017] In the terminology of the present invention, the term isocyanate encompasses all isocyanates known to those skilled in the art in connection with polyurethane chemistry, for example, particularly tolylene diisocyanate (TDI; produced from tolylenediamine (TDA)), diphenylmethane-based diisocyanates and polyisocyanates (MDI; produced from diphenylmethane-based diamines and polyamines (MDA)), pentane 1,5-diisocyanate (PDI; produced from pentane-1,5-diamine (PDA)), hexamethylene 1,6-diisocyanate (HDI; produced from hexamethylene-1,6-diamine (HDA)), isophorone diisocyanate (IPDI; produced from isophorone diamine (IPDA)), and xylylene diisocyanate (XDI; produced from xylylenediamine (XDA)). The term "isocyanate" naturally includes embodiments in which two or more different isocyanates (e.g., a mixture of MDI and TDI) are used in the manufacture of polyurethane products, unless otherwise explicitly stated, for example, by the expression "strictly one isocyanate." All isocyanates used in the manufacture of polyurethane products are collectively referred to as the isocyanate component (of polyurethane foam). The isocyanate component contains at least one isocyanate. Similarly, all polyols used in the manufacture of polyurethane foam are collectively referred to as the polyol component (of polyurethane foam). The polyol component contains at least one polyol.

[0018] In the terminology of this invention, the term "polyol" encompasses all polyols known to those skilled in the art in relation to polyurethane chemistry, such as polyether polyols, polyester polyols, polyether ester polyols, and polyether carbonate polyols. The expression "polyol" naturally also encompasses embodiments in which two or more different polyols are used in the manufacture of polyurethane products. Therefore, when referring to, for example, "polyether polyol" (or "polyester polyol," etc.), this term naturally also encompasses embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) are used in the manufacture of polyurethane foams.

[0019] In the technical terminology of this invention, carbamate is a urethane formed by a reaction with alcohol in step (B).

[0020] An amine corresponding to an isocyanate is an amine that can be phosgenated to produce an isocyanate via the reaction R-NH2 + COCl2 → RN=C=O + 2HCl. Similarly, a nitro compound corresponding to an amine is a nitro compound that can be reduced to produce an amine via the reaction R-NO2 + 3H2 → R-NH2 + 2H2O.

[0021] In the context of the method according to the present invention, water and alcohol are used in hyperstoichiometric quantities. This is understood to mean that a theoretically sufficient amount of water is used to hydrolyze all polyurethane bonds and obtain amines and polyols by liberating carbon dioxide. Similarly, the use of hyperstoichiometric quantities of alcohol is understood to mean that a theoretically sufficient amount of alcohol is used to convert all polyurethane bonds and form alcohol and polyol carbamates. When using the mass fractions of water and alcohol required according to the present invention, both of the above usually apply.

[0022] The phrase "chemical decomposition of polyurethane foam in the presence of a catalyst with alcohol and water" does not necessarily mean that all the water used in step (B) must be added immediately at the start of step (B). Rather, embodiments of this invention include cases in which no water is added at the start of step (B), or only a portion of the water is added, and then the water / remaining water is added continuously during the reaction time. In this case, a specified amount of 4.0% to 10%, preferably 5.0% to 7.0%, relative to the mass of alcohol, refers to the amount of water added before the end of the reaction time in step (B). In principle, it is also conceivable to add alcohol or an alcohol-water mixture continuously. In any case, the specified amounts related to step (B) refer to the total amount added by the end of the reaction time in that step, in each case.

[0023] The quantitative expression for water in step (B) refers to the water added as a reagent for hydrolytic carbamate cleavage. Any amount of water already present in the alcohol and / or polyurethane foam used is relatively small. The alcohol / polyurethane foam used is understood to mean trace amounts of water that may occur on an industrial scale. It is certainly possible to pre-mix the alcohol with the water used for hydrolytic carbamate cleavage or to wet the polyurethane foam with the water used for hydrolytic carbamate cleavage. Such embodiments do not depart from the scope of the present invention, and the water added in this manner is naturally taken into consideration in the quantitative expression of step (B), i.e., the amount of additional water added as needed is reduced accordingly. If the catalyst is used as an aqueous solution, the water used as a solvent is similarly taken into consideration in the quantitative expression of step (B), i.e., the amount of additional water added as needed is reduced accordingly.

[0024] The present invention includes "the chemical decomposition of a polyurethane foam in the presence of an alcohol and water catalyst, wherein the catalyst comprises (preferably consisting only of) a metal salt selected from two or more of the following metal salts: carbonates, bicarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, or mixtures thereof." Thus, according to the present invention, at the start of step (B), the polyurethane foam is mixed with an alcohol or an alcohol-water mixture and at least one of the listed metal salts to obtain a reaction mixture, which is then reacted at the above-mentioned temperature range by adding water as needed (provided that not all water has already been added in the mixing step).

[0025] Orthophosphate salts are salts of orthophosphate H3PO4, in which all hydrogen ions have been removed (=PO4). 3- Orthophosphate monohydrogen salt is a salt of orthophosphate, in which two hydrogen ions have been removed (=HPO4). 2- Metaphosphate is empirically formulated [(PO3) - ] n It is a condensation product of orthophosphate having n, where n represents a natural number (especially 3 or 4). [Modes for carrying out the invention]

[0026] First, an overview of various possible embodiments of the present invention will be provided.

[0027] In a first embodiment of the present invention, which can be combined with all other embodiments, the isocyanate component comprises an isocyanate selected from tolylene diisocyanate (TDI; produced from tolylenediamine (TDA)), diphenylmethane-based diisocyanates and polyisocyanates (MDI; produced from diphenylmethane-based diamines and polyamines (MDA)), pentane 1,5-diisocyanate (PDI; produced from pentane-1,5-diamine (PDA)), hexamethylene 1,6-diisocyanate (HDI; produced from hexamethylene-1,6-diamine (HDA)), isophorone diisocyanate (IPDI; produced from isophorone diamine (IPDA)), xylylene diisocyanate (XDI; produced from xylylenediamine (XDA)), or a mixture of two or more of the above-mentioned isocyanates.

[0028] In a second embodiment of the present invention, which is a specific configuration of the first embodiment, the isocyanate component includes tolylene diisocyanate or a mixture of tolylene diisocyanate and diphenylmethane-based diisocyanates and polyisocyanates.

[0029] In a third embodiment of the present invention, which is a specific configuration of the second embodiment, the isocyanate component comprises tolylene diisocyanate.

[0030] In the fourth embodiment of the present invention, which is a specific configuration of the third embodiment, the isocyanate component does not include any further isocyanates in addition to tolylene diisocyanate.

[0031] In a fifth embodiment of the present invention, which can be combined with all other embodiments, the polyol component includes polyether polyols, polyester polyols, polyether ester polyols, polyacrylate polyols and / or polyether carbonate polyols. The polyol component is preferably a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., it does not contain any polyols other than polyether polyols; however, mixtures of two or more different polyether polyols are included and do not fall outside the scope of this embodiment).

[0032] In a sixth embodiment of the present invention, which can be combined with all other embodiments, the polyol component comprises a styrene-acrylonitrile copolymer-filled polyether polyol.

[0033] In a seventh embodiment of the present invention, which can be combined with all other embodiments, the alcohol is selected from methanol, ethanol, 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 above alcohols.

[0034] In an eighth embodiment of the present invention, which can be combined with all other embodiments, the metal salt is a salt of an alkali metal or an alkaline earth metal.

[0035] In a ninth embodiment of the present invention, which can be combined with all other embodiments, the metal salt comprises a carbonate, a bicarbonate, a monohydrogen orthophosphate, an orthophosphate, or a mixture of two or more of the above-mentioned metal salts.

[0036] In the tenth embodiment of the present invention, which is a special configuration of the ninth embodiment, the metal salt comprises only one of the listed metal salts, preferably without any further metal salts.

[0037] In an eleventh embodiment of the present invention, which can be combined with all other embodiments, the mass ratio of one alcohol and water to the other polyurethane foam (m(alcohol + water) / m(polyurethane foam)) is in the range of 1.0 to 1.3.

[0038] In a twelfth embodiment of the present invention, which can be combined with all other embodiments, particularly the eleventh embodiment, the mass of water is 5.0% to 7.0% of the mass of alcohol.

[0039] In a thirteenth embodiment of the present invention, which can be combined with all other embodiments, the reaction in step (B) is carried out over a reaction time of 1.0 to 10 hours, preferably 1.5 to 7.5 hours, particularly preferably 2.0 to 6.0 hours, and very particularly preferably 2.5 to 5.5 hours.

[0040] In the 14th embodiment of the present invention, which is a special configuration of the 13th embodiment, in step (B), either only the alcohol and catalyst are initially mixed with the polyurethane foam, and water is added over the reaction time in a further step of step (B), or in step (B), the alcohol, catalyst, and 2% to 4% of the total amount of water used in step (B) are initially mixed with the polyurethane foam, and the remaining amount of water is added over the reaction time in a further step of step (B). The time for adding water is particularly 1.0 to 5.0 hours in both alternative forms. Therefore, the final addition of water is made before the end of the previously specified reaction time.

[0041] In a 15th embodiment of the present invention, which can be combined with all other embodiments, step (B) is performed at 900 mbar (abs.) ~1800 bar (abs.) This is done at pressures within a certain range, especially ambient pressure.

[0042] In a sixteenth embodiment of the present invention, which can be combined with all other embodiments, the catalyst is added in an amount such that its mass corresponds to 0.1% to 3.5% of the mass of the polyurethane foam used in step (B).

[0043] In the 17th embodiment of the present invention, which can be combined with all other embodiments except the 18th and 19th embodiments specified below, step (C) is: The first product mixture is separated into a polyol phase and an amine phase. Includes.

[0044] In the 18th embodiment of the present invention, which is an alternative to the 17th and 19th embodiments described below, but can otherwise be combined with all other embodiments, step (C) is: The first product mixture is combined with an organic solvent that is completely immiscible with the alcohol used in step (B), and then phase-separated into a polyol phase and an amine phase. Includes.

[0045] In the 19th embodiment of the present invention, which is an alternative to the 17th and 18th embodiments but can otherwise be combined with all other embodiments, step (C) is: (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) to obtain a second product mixture. (C.II) The second product mixture obtained in step (CI) is washed with an aqueous washing solution and separated into an amine phase and a polyol phase. Includes.

[0046] In a 20th embodiment of the present invention, which can be combined with all other embodiments, step (D) includes stripping by distillation and / or stripping gas (particularly nitrogen or vapor, preferably nitrogen, etc.).

[0047] In a 21st embodiment of the present invention, which can be combined with all other embodiments, step (E) is performed, which includes distilling off the alcohol and water from the amine phase, and then distilling and purifying the amine remaining after the distillation removal.

[0048] The embodiments and further possible configurations briefly outlined above will be described in more detail below. Unless the opposite is clearly evident to those skilled in the art from the context or is explicitly stated otherwise, all of the above embodiments and the further configurations of the present invention described below can be used interchangeably and in combination with each other as desired.

[0049] Preparation of polyurethane foam for chemical recycling. Step (A) of the method according to the present invention includes preparing a polyurethane foam to be chemically recycled in preparation for chemical decomposition.

[0050] Polyurethane foam can be of any type in principle, with both flexible and rigid foams being particularly preferred, and flexible foam (e.g., from used mattresses, furniture cushioning, or car seats) being preferred. Such polyurethane foam is typically manufactured using pentane, chlorofluorocarbon, dichloromethane, and / or carbon dioxide as blowing agents.

[0051] In addition, with respect to the isocyanate component, polyurethane foams based on isocyanates selected from tolylene diisocyanate (TDI), diphenylmethane-based diisocyanates and polyisocyanates (MDI), pentane 1,5-diisocyanate (PDI), hexamethylene 1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), and mixtures of two or more of the above-mentioned isocyanates are preferred. With respect to the isocyanate component, polyurethane foams based on a mixture of TDI and MDI are particularly preferred. With respect to the isocyanate component, polyurethane products based solely on TDI are very particularly preferred.

[0052] With regard to 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-mentioned polyols are preferred. The polyol component is preferably a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., it does not contain any polyols other than polyether polyols; however, mixtures of two or more different polyether polyols are included and do not fall outside the scope of this embodiment). The polyether polyol may be filled with styrene-acrylonitrile copolymer (SAN copolymer). One of the advantages of the present invention is that it can also be used as such a polyol component. The problem in the chemical decomposition of polyurethane foams based on SAN copolymer-filled polyether polyols is that the SAN copolymer is released as fine polymer particles during chemical decomposition. This is true regardless of the chemical decomposition process selected. The SAN polymer present as fine polymer particles in the reaction mixture causes problems in subsequent extraction processes, for example. Furthermore, due to the fineness of the polymer particles, the filter clogs rapidly, making further removal impossible, thus rendering filtration virtually impossible. The advantage of the hydrolysis of alcohol according to the present invention is that, after liberation from the polyether polyol, the SAN polymer becomes partially soluble by hydrolysis, allowing for smooth post-treatment of the reaction mixture after chemical decomposition by extraction.

[0053] Most preferably, the polyurethane foam is a foam in which the isocyanate component contains tolylene diisocyanate (TDI), as well as diphenylmethane-based diisocyanates and polyisocyanates (MDI), particularly TDI only, and the polyol component contains a polyether polyol (particularly a polyether polyol, i.e., not containing any further polyols other than polyether polyols, but including a mixture of two or more different polyether polyols, which does not deviate from the scope of this embodiment).

[0054] Preferably, step (A) further includes a preparatory step for breaking the urethane bonds in step (B.II). This is in particular the mechanical grinding of the polyurethane foam. Such preparatory steps are known to those skilled in the art. See, for example, Non-Patent Document 1. Depending on the properties of the polyurethane foam, it may be advantageous to "freeze" the polyurethane foam before mechanical grinding to facilitate the grinding operation.

[0055] Before, during, or after mechanical grinding, the polyurethane foam may be treated with an aqueous or alcoholic disinfectant. Such disinfectants are preferably hydrogen peroxide, chlorine dioxide, sodium hypochlorite, formaldehyde, sodium N-chloro-(4-methylbenzene) sulfonamide (chloramine T) and / or peracetic acid (aqueous disinfectant), or ethanol, isopropanol and / or 1-propanol (alcoholic disinfectant).

[0056] It is also conceivable to carry out the above preparation steps at a location spatially separated from the chemical decomposition site. In that case, the prepared foam is transferred to a transport vehicle suitable for further transport, such as a silo vehicle. For further transport, the prepared foam may be further compressed to achieve a higher mass-to-volume ratio. The foam is then transferred to a reactor prepared for chemical decomposition at the chemical decomposition site. It is also conceivable to connect the transport vehicle used directly to the reactor.

[0057] Chemical decomposition of polyurethane foam to obtain the first product mixture Step (B) of the method according to the present invention includes the chemical decomposition of the polyurethane foam prepared in step (A).

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

[0059] According to the present invention, step (B) is carried out as hydrolysis of alcohol. The term hydrolysis of alcohol used here is usually referred to as hydrolysis of glycol in the literature (see item 3 above). However, since the term hydrolysis of glycol is correct only when glycol is used as the alcohol, the more comprehensive term hydrolysis of alcohol is used in the context of the present invention.

[0060] The alcohol used is preferably methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol, or a mixture of two or more of the above alcohols. Diethylene glycol and propylene glycol are particularly preferred. Water and alcohol may be mixed beforehand, but this is not necessary.

[0061] The metal salt used as a catalyst is preferably an alkali metal or alkaline earth metal salt, with sodium salt being particularly preferred. Regarding the metal salt anion, carbonate ions, bicarbonate ions, monohydrogen orthophosphate ions, orthophosphate ions, and mixtures of two or more of these are particularly preferred. It is especially preferable to use carbonate ions, bicarbonate ions, or orthophosphate ions (i.e., using only one of the above compounds, rather than a mixture). It is particularly preferable not to use any further catalysts not mentioned above in the reaction. It has been proven advantageous to add the catalyst in an amount such that its mass corresponds to 0.1% to 3.5% of the mass of the polyurethane foam converted in step (B).

[0062] According to the present invention, a reaction temperature in the range of 130°C to 195°C is maintained in step (B). The reaction temperature is preferably 135°C to 190°C, particularly preferably 140°C to 190°C, and very particularly preferably 165°C to 185°C. Regardless of the selected temperature, it is preferable to carry out the reaction at ambient pressure. However, lower pressures (especially up to 900 mbar) are preferable. (abs.) ) or higher pressures (especially up to 1800 mbar) (abs.) ) is similarly possible. The reaction in step (B) is generally completed within a period of 1.0 to 10 hours, preferably 1.5 to 7.5 hours, particularly preferably 2.0 to 6.0 hours, and very particularly preferably 2.5 to 5.5 hours, i.e., after the reaction time within this period, any further reaction, if any, occurs only very slightly.

[0063] As described above, it is advantageous not to immediately add the water, or at least all of it, used in the hydrolysis of the alcohol in step (B) at the start of the reaction. It has been proven advantageous to initially mix a small portion, if any, of the total amount of water used in (B), i.e., 2% to 4%, with the remaining reactants (alcohol, catalyst, and polyurethane foam), and then add the remaining or all of the water over the reaction time during further steps in step (B). The addition of water for the hydrolytic cleavage of the carbamate formed as an intermediate is carried out continuously or in small amounts at intervals such that the boiling point of the reaction mixture is always maintained within a specified range, particularly the especially preferred range of 165°C to 185°C. The water addition time is preferably in the range of 1.0 to 5.0 hours (depending on the boiling point of the alcohol used).

[0064] In preferred embodiments, a mass ratio (m(alcohol + water) / m(polyurethane foam)) of one (all used) alcohol and / or water (all used) to the other polyurethane foam, ranging from 1.1 to 1.3, is used. When water is added gradually as described above, rather than all at once, this applies to the total amount of water used in step (B).

[0065] The amount of water used in process (B) is preferably 5.0% to 7.0% of the mass of alcohol used in process (B). This is especially true for the aforementioned range of 1.0 to 1.3 for the mass ratio (m(alcohol + water) / m(polyurethane foam)). If the water is added gradually as described above, rather than all at once, this applies to the total amount of water used in process (B).

[0066] Step (B.II) can be carried out in any reactor known in the art for such purposes. Particularly preferred chemical decomposition reactors are stirred tanks (stirred reactors) and tubular reactors.

[0067] Post-treatment of the first product mixture Process (B) is, The isocyanate component consists of (at least) one amine corresponding to the isocyanate, Polyols (i.e., polyols arbitrarily formed from the original polyol components during the reaction with polyols and / or alcohols that constitute the polyol components), (Because it is used hyperstoichiometrically, the alcohol is incompletely converted) and (Because it is used hyperstoichiometrically, it is incompletely converted) water and, This yields a first product mixture containing [the specified substance].

[0068] In step (C), the first product mixture is post-treated to obtain a polyol phase containing a polyol and an amine phase containing an amine, water, and alcohol (separation of polyol and amine). It goes without saying that this separation does not need to proceed completely in the sense that all of the polyol migrates to the polyol phase and all of the amine (as well as all of the water and all of the alcohol) migrates to the amine phase. For example, if, as a result of general solubility equilibrium, a small amount of amine migrates to the polyol phase (or a small amount of polyol migrates to the amine phase), this does not, of course, deviate from the scope of the present invention.

[0069] Due to the reaction mode in step (B) as hydrolysis of alcohol, the first product mixture is usually biphasic. The two phases are an alcohol-aqueous phase and an organic phase. Depending on the exact properties of the polyurethane foam used and the alcohol used in step (B), the organic phase in the first product mixture may contain a polyol, and the alcohol-aqueous phase may contain an amine, in each case, to such an extent that the separation of the amine and polyol in step (C) can be achieved by simply separating the first mixture into an organic phase and an alcohol-aqueous phase. In this case, the organic phase in the first product mixture is the polyol phase required in step (C) and may be supplied directly to step (D). Similarly, the alcohol-aqueous phase in the first product mixture is the amine phase required in step (C) and may be supplied directly to step (E) insofar as the recovery of the amine is required. This embodiment is conceivable, for example, in the case of TDI foam, where TDA readily dissolves in water and forms an alcohol-aqueous phase with similarly water-soluble diethylene glycol, while the recovered polyol forms an organic phase, and is used when hydrolytic alcohol decomposition is performed using diethylene glycol as the alcohol. Whether this embodiment can be used can be easily determined by examination by those skilled in the art or by simple preliminary experiments.

[0070] However, simple phase separation of the first product mixture obtained in step (B) may not yield a polyol phase and an amine phase with a sufficient polyol / amine ratio. In such cases, it is preferable to extract the entire first product mixture with an organic solvent. There are numerous options for this.

[0071] In a preferred embodiment, step (C) includes combining the first product mixture obtained in step (B) with an organic solvent that is completely immiscible with the alcohol used in step (B), and phase separation into an alcohol phase, which in this embodiment contains not only the alcohol but also an amine and water, and corresponds to the amine phase, and a solvent phase, which in this embodiment contains not only the solvent used for extraction but also a polyol, and corresponds to the polyol phase. The requirement that the organic solvent used in step (C) is completely immiscible with the alcohol used in step (B) means that, under the conditions of the temperature used in step (C) and the ratio of the organic solvent to the alcohol from step (B), there must be a miscibility gap that allows for phase separation. This applies, for example, when the organic solvent is selected from a mixture of two or more aliphatic hydrocarbons, alicyclic hydrocarbons (e.g., cyclohexane), aromatic hydrocarbons (e.g., toluene) and the organic solvents mentioned above, and the alcohol is selected from a mixture of two or more methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol and the alcohols mentioned above.

[0072] In a further preferred embodiment, step (C) is: (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) to obtain a second product mixture. (C.II) The second product mixture obtained in step (CI) is washed with an aqueous washing solution, and phase separation is performed into an aqueous phase which contains not only water but also alcohol and amine, and in this embodiment corresponds to the amine phase, and a solvent phase which contains not only the solvent used for extraction but also a polyol, and in this embodiment corresponds to the polyol phase. Includes.

[0073] The requirement 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 used in step (CI) and the ratio of the organic solvent to the alcohol from step (B), the mixture of the organic solvent and the alcohol from step (B) does not spontaneously separate into two phases. This applies, for example, when the organic solvent in step (CI) is selected from a mixture of two or more halogen-substituted aliphatic hydrocarbons, halogen-substituted alicyclic hydrocarbons, halogen-substituted aromatic hydrocarbons and the aforementioned organic solvents, and the alcohol in step (B) is selected from a mixture of two or more methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol and the aforementioned alcohols.

[0074] Post-treatment of the polyol phase In step (D), the organic polyol phase obtained in step (C) is post-treated to recover the polyol (isolation of the polyol). This is preferably done by distillation and / or stripping with a stripping gas (particularly nitrogen or vapor, preferably nitrogen, etc.). This preferably involves performing distillation in an evaporator selected from a falling film evaporator, thin film evaporator, flash evaporator, rising film evaporator, natural circulation evaporator, forced circulation evaporator, or tank evaporator. It is particularly preferable to perform a vapor stripping operation following the distillation.

[0075] Steam stripping can be performed by passing steam through a stripping column, which is itself a known stripping column. However, steam stripping can also be performed by adding water in liquid form to a polyol phase (optionally pre-purified by distillation), then superheating the mixture (while maintaining sufficient back pressure to keep the water in liquid using a pressure valve), and reducing the pressure downstream of the pressure valve, thereby causing the water present in the polyol to evaporate and producing a stripping effect.

[0076] Amine phase post-treatment In step (E), it is preferable to post-treat the aqueous amine phase obtained in step (C) to recover the amine (isolation of the amine).

[0077] The recovery of the amine preferably includes first distilling off the alcohol and water from the amine phase. This can be achieved by known distillation techniques. The remaining crude amine is preferably further post-treated by distillation. It is particularly preferable to incorporate the recovery of the amine into the post-treatment of the newly produced amine by mixing the crude amine with the crude product fraction of the amine obtained from the new production of the same amine. This embodiment provides an economical and environmentally friendly outlet for impurities resulting from polyurethane products. This is described in more detail in WO 2020 / 260387.

Example

[0078] The reaction conversion rate was verified by determining the amine value of the reaction mixture after glycolysis with water. The acid value indicates how many milligrams of potassium hydroxide are required to neutralize the free organic amines present in 1 g of the substance. Primary amino groups, secondary amino groups, and tertiary amino groups are captured. The amino group is a weak base. The solvent used is concentrated acetic acid (glacial acetic acid, 99% - 100%). The amine is protonated by the solvent and converted into the corresponding acid, and exists as an ion pair with the deprotonated acid of glacial acetic acid. The mixture is then titrated with 0.1 mol of perchloric acid as the titrant, and the perchloric acid replaces the anion of the solvent (glacial acetic acid). The perchloric acid consumed during the process is equal to the consumption of potassium hydroxide. The amine value is usually reported as the number of milligrams of KOH per gram of the analytical sample, AZ / (mg·g -1 )=(V / ml·[b i / (mol·l -1 )]·[M(KOH) / (g·mol -1 )]·f) / (m / g) (where AZ represents the amine value, V represents the volume of the perchloric acid solution consumed, m represents the mass of the titration sample, M(KOH) is the molar mass of KOH (56.11 g × mol). -1 ) represents, b i This is the molar concentration of the perchloric acid solution, f is calculated according to the dimensionless coefficient (titer) of the perchloric acid solution.

[0079] Example 1: In a 1000 mL four-necked flask equipped with a stirrer, thermometer, and condenser, 300 g of diethylene glycol and 5.5 g of sodium carbonate are initially added and heated to 180 °C under nitrogen. 300 g of flexible PU foam having the composition reported in Table 1 is added and dissolved while stirring. After dissolution, the mixture is stirred at 180 °C for 2 hours, and then 16.5 g of water is added over 1 hour, ensuring that the reaction temperature does not fall below 170 °C. After the addition of water is complete, the mixture is stirred at 180 °C for a further 2 hours, and the reaction conversion rate is determined by the amine value as described above. The theoretically expected amine value of the reaction mixture when all amines are completely recovered is 86.0 mg KOH / g. Amine value of the reaction mixture (measured value): 93.0 mg KOH / g

[0080] Reaction mixture 1 In the 1H-NMR spectrum, TDI-based carbonates were no longer detected, and only TDA was detected.

[0081] [Table 1]

[0082] Examples 3 to 7: Further experiments were conducted using a different catalyst than in Example 1, but with the same procedure otherwise. The results are summarized in Table 2.

[0083] [Table 2]

[0084] In Comparative Example 5, a solid precipitate formed in the reaction vessel, indicating an incomplete conversion. In Comparative Example 7, the amine value was excessively low.

[0085] Example 8: Production of flexible foam from r-polyether polyol The polyol was recovered from the reaction mixture ("r-polyether polyol") produced in Example 1 as follows:

[0086] The reaction mixture was mixed with 3 parts by weight of cyclohexane and vigorously homogenized. The mixture was separated into two phases, an organic cyclohexane-polyether phase and a diethylene glycol-amine phase, using a separatory funnel. The organic phase was separated, and the r-polyol was recovered by removing the solvent by distillation. Flexible foams were prepared using the obtained r-polyether polyols and compared with flexible foams based solely on the original polyether polyol Arcol 1108. The formulations used are reported in Table 3, and the results are compared in Table 4.

[0087] [Table 3]

[0088] [Table 4]

[0089] Legend: Cream time: Determined when the mixture is in the mold. This is the elapsed time from the start of mixing (polyol and isocyanate components) to the start of visible foaming. Rise time: Determined at the point when the mixture is in the mold. This is the elapsed time from the start of mixing (polyol and isocyanate components) until the foam reaches its final height. Blow-off: Refers to the gas generation and formation of open-cell characteristics after the foam reaches its final height. Shrinkage at RT (room temperature): 1 = The sides of the foam have shrunk slightly. Air permeability: The apparatus used to measure air permeability consists of a glass cylinder with an inner diameter of 36 mm and a scale of 0 to 350 mm, and an inner tube with an inner diameter of 7 mm. The inner tube has a T-shaped end, with an air inlet attached to one end and a hose with a measuring head attached to the other end. The hose for the measuring head has an inner diameter of 12 mm and a length of 1.80 m. The glass cylinder has a closed bottom and can be filled with water through a funnel attached to the back. The test apparatus is connected to a compressed air source via two taps, a pressure reducer, and hoses of arbitrary length and diameter, with the pressure reducer set to approximately 3.0 bar. (abs.) Set to this.

[0090] As is clear, the recovered r-polyol can be reused in flexible foam formulations as a polyether polyol in amounts up to 100% after the chemical recycling process. The visual properties, as well as the cream time and rise time, of the examples using r-polyol exhibit comparable behavior to the reference example. The mechanical properties of r-polyol, such as elasticity and compressive strength, are comparable to those of the reference polyether polyol. The lower permeability values ​​of Examples 8 and 10 using r-polyol indicate a higher open-cell content compared to Reference Examples 6 and 9.

Claims

1. A method for recovering raw materials from polyurethane foam, (A) A step of preparing a polyurethane foam based on isocyanate and polyol components, (B) The polyurethane foam is chemically decomposed with alcohol and water at a temperature in the range of 130°C to 195°C in the presence of a catalyst. The amine corresponding to the isocyanate of the aforementioned isocyanate component, Polyols and, Alcohol and, Water and, A step of obtaining a first product mixture containing, The mass ratio of one component, alcohol and water, to the other, polyurethane foam, is in the range of 0.5 to 2.

5. The mass of water is 4.0% to 10% of the mass of alcohol. The catalyst comprises a metal salt selected from carbonates, bicarbonates, orthophosphates, monohydrogen orthophosphates, metaphosphates, or a mixture of two or more of the above-mentioned metal salts; (C) A step of post-treating the first product mixture to obtain a polyol phase containing a polyol and an amine phase containing an amine, water and an alcohol, (D) A step of recovering the polyol from the polyol phase, (E) A step of optionally recovering the amine from the amine phase, Methods that include...

2. The method according to claim 1, wherein the isocyanate component contains an isocyanate selected from tolylene diisocyanate, diphenylmethane-based diisocyanates and polyisocyanates, pentane 1,5-diisocyanate, hexamethylene 1,6-diisocyanate, isophorone diisocyanate, xylylene diisocyanate, or a mixture of two or more of the above-mentioned isocyanates.

3. The method according to claim 2, wherein the isocyanate component comprises tolylene diisocyanate, or a mixture of tolylene diisocyanate and diphenylmethane-based diisocyanates and polyisocyanates.

4. The method according to claim 3, wherein the isocyanate component comprises tolylene diisocyanate.

5. The method according to claim 4, wherein the isocyanate component does not contain any further isocyanates in addition to tolylene diisocyanate.

6. The method according to any one of claims 1 to 5, wherein the polyol component comprises a polyether polyol, a polyester polyol, a polyether ester polyol, a polyacrylate polyol and / or a polyether carbonate polyol.

7. The method according to any one of claims 1 to 6, wherein the polyol component comprises a styrene-acrylonitrile copolymer-filled polyether polyol.

8. The method according to any one of claims 1 to 7, wherein the alcohol is selected from methanol, ethanol, 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 above alcohols.

9. The method according to any one of claims 1 to 8, wherein the metal salt is a salt of an alkali metal or an alkaline earth metal.

10. The method according to any one of claims 1 to 9, wherein the metal salt comprises a carbonate, a bicarbonate, a monohydrogen orthophosphate, an orthophosphate salt, or a mixture of two or more of the above-mentioned metal salts.

11. The method according to claim 10, wherein the metal salt comprises only one of the enumerated metal salts.

12. The method according to any one of claims 1 to 11, wherein the mass of the catalyst is 0.1% to 3.5% of the mass of the polyurethane foam used in step (B).

13. Process (C) is The first product mixture is separated into a polyol phase and an amine phase. Does it include, Or process (C) The first product mixture is combined with an organic solvent that is completely immiscible with the alcohol used in step (B), and then phase-separated into a polyol phase and an amine phase. Does it include, Or process (C) (C.I) The first product mixture obtained in step (B) is mixed with an organic solvent that is miscible with the alcohol used in step (B) to obtain a second product mixture. (C.II) The second product mixture obtained in step (C.I) is washed with an aqueous washing solution and phase separation is performed into the amine phase and the polyol phase. A method according to any one of claims 1 to 12, including the method described in any one of claims 1 to 12.

14. The method according to any one of claims 1 to 13, wherein step (D) includes distillation and / or stripping with stripping gas.

15. The method according to any one of claims 1 to 14, wherein step (E) is performed, and step (E) is performed by distillation to remove alcohol and water from the amine phase, and subsequently by distillation to purify the amine remaining after distillation.

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