A value chain return method for recovering polymeric methylene phenylene amine (pMDA) as its HCl salt from the depolymerization of post-consumer polyurethane and polyisocyanurate rigid foams

Abstract

The present invention relates to a method for producing a polyurethane and polyisocyanurate rigid foam based on polymeric methylene diphenyl diisocyanate (pMDI) by depolymerization to obtain a mixture (M1), a method for removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) containing pMDA and at least one polyol, and a method for producing a mixture (M2) containing pMDA and at least one polyol by distillation of the mixture (M2) at a concentration of 0.5×10 -30 Cm~7.8×10 -30 The present invention relates to a value chain return process comprising dissolving pMDA in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, followed by the addition of HCl to isolate the pMDA-HCl salt. The present invention also relates to polymeric methylene phenylene amines (pMDA) and polymeric methylene diphenyl diisocyanates (pMDI) obtained or obtainable according to the above process, as well as their use for the preparation of polyurethanes or polyisocyanurates.

Description

[Technical Field]

[0001] The present invention relates to a method for returning polyurethane rigid foam value chains, which allows polymeric methylene phenylene amines to be recovered as their HCl salts from the depolymerization of used polyurethane rigid foams and reused as starting materials in the synthesis of polymeric methylene phenylene isocyanates (pMDI) for the synthesis of new polyurethane rigid foams.

[0002] The present invention particularly relates to the depolymerization of polyurethane and polyisocyanurate rigid foams based on polymeric methylene diphenyl diisocyanate (pMDI) to obtain a mixture (M1), distilling off volatile compounds from the mixture (M1) to obtain a mixture (M2) comprising pMDA and at least one polyol, and distilling the mixture (M2) to obtain a mixture (M2) comprising 0.5×10 -30 Cm~7.8×10 -30 The present invention relates to a value chain return process comprising dissolving pMDA in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, followed by the addition of HCl to isolate the pMDA-HCl salt. The present invention also relates to polymeric methylene phenylene amines (pMDA) and polymeric methylene diphenyl diisocyanates (pMDI) obtained or obtainable according to the above process, as well as their use for the preparation of polyurethanes or polyisocyanurates.

[0003] Global demand for plastics has skyrocketed over the past 30 years. For example, the amount of plastic produced worldwide over the past decade increased by nearly 50%. In less than 30 years, it has even nearly quadrupled, reaching 359 million metric tons in 2018. These facts clearly demonstrate that the production of such a large amount of plastics entails the need for disposal or recycling of used plastics. In this regard, it is desirable to prioritize recycling, since useful materials, such as compounds that can function as monomers, can be returned to the value chain, for example, by direct reuse in plastic production. Plastics are often used with additives incorporated to impart various functionalities to the resin. For example, because resins themselves are highly flammable, flame retardants are often mixed into them at a rate of up to 25% by weight to prevent the spread of fire. The possibility of returning flame retardants to the industrial cycle seems promising, both in terms of resource conservation and economics.

[0004] Additionally, in the industrial production of polyurethane rigid foams, polyurethane (PU) rigid foam waste is generated. For example, such PU rigid foam waste is obtained during the casting of PU rigid foam blocks and subsequent cutting, trimming, or sizing of the blocks to obtain the desired PU workpieces. Furthermore, rejected PU rigid foam products, such as off-spec products, are generated.

[0005] Disposing of waste through combustion, for example, has a negative impact on the environment as well as the carbon footprint.

[0006] To reduce waste and its negative impact on the environment, processing technologies need to be developed to recover materials from plastic waste. Recycling processes should preferably reduce both material waste and the carbon footprint. Furthermore, they should be economical and energy-efficient, resulting in valuable materials with high technical characteristics.

[0007] Among the above-mentioned plastics, polyurethanes (PU) are important representatives. Generally, polyurethanes are produced by the polyaddition of (poly)isocyanates with polyols. The characteristic chain bond is the urethane group. Polyurethanes exist in many forms, for example as foams, elastomers or thermosets, of which foams are particularly important.

[0008] Polyaddition of (poly)isocyanates with polyols leads to the formation of linear, branched, or crosslinked polyurethanes. As an alternative to alcohols, the most important group of NCO-reactive compounds are amines, which lead to the formation of di- or trisubstituted ureas. Ureas are also formed by the reaction of water with isocyanates, where the carbamic acid formed in the first step of the reaction spontaneously decomposes to form the amine, with the elimination of carbon dioxide. This amine then reacts with excess isocyanate to give the symmetrically substituted urea. This reaction is the basis for polyurethane foams.

[0009] These foams are produced in a wide range of densities and can have either flexible or rigid structures. Generally, "flexible" foams are those that recover their shape after deformation. In addition to being reversibly deformable, flexible foams tend to have limited resistance to applied loads and tend to have mostly open cells. "Rigid" foams generally retain their deformed shape without significant recovery after deformation. Rigid foams tend to have mostly closed cells. Whether a PU flexible or PU rigid foam is formed during polyaddition depends primarily on the type of polyisocyanate and polyol components used. For example, the starting materials can affect crosslinking of the polymer, meaning that the polymer consists of a three-dimensional network structure. Long flexible segments from the polyol result in the formation of PU flexible foams. PU rigid foams are obtained from short chains with many crosslinks. Details of polyurethane rigid foams suitable for use in accordance with the present invention can be found in Kunststoffhandbuch, Band 7, Polyurethane, Carl-Hanser-Verlag, 3. Auflage, 1993, Kapitel 6. In rigid foams, pMDI is often used as the polyisocyanate component.

[0010] Polyurethane rigid foams exhibit excellent thermal insulating properties, which is why they are of great importance in the construction sector and are commonly used, for example, to insulate buildings or as insulation in refrigerators.

[0011] Recycling polyurethane rigid foams into useful monomer compounds remains challenging. In principle, polyurethanes can be depolymerized into polyol and polyamine compounds by glycolysis or hydrolysis (see Plastics Recycling and Polyurethanes, in Ullmann's Encyclopedia of Industrial Chemistry, 2020, DOI: 10.1002 / 14356007.a21_057.pub2 and Waste Management, 2018, 76, 147-171). Isolation of the polyol and amine components in the glycolysis or hydrolysis approach can be achieved, for example, by extraction / phase separation methods. Alternatively, if the PU is based on the diisocyanate MDI (methylene bisphenyl isocyanate) or TDI (toluene diisocyanate), the corresponding amines MDA (methylene bisphenyl isocyanate) and TDA (toluene diamine) have vapor pressures that allow their separation from the polyol components by distillation under reduced pressure. Unfortunately, extraction and phase separation methods from glycolysis or hydrolysis methods have failed for pMDA, which also cannot be separated by distillation due to its negligible vapor pressure.

[0012] German Patent Application Publication No. 2854940 discloses a method for precipitating toluenediamine HCl salt. This can be achieved by first removing water by azeotropic distillation with toluene. Then, in a fractional precipitation, toluenediamine HCl is precipitated stepwise by adding gaseous HCl and separated by filtration. A drawback of this approach is the need for multiple precipitation steps to remove toluenediamine HCl from the polyol fraction. This approach requires precise quantitative control of the amount of HCl used in each precipitation step, as well as control of the amine content at each step. Furthermore, there is no disclosure that this approach can be successful when the amine component is a polymeric amine compound such as pMDA.

[0013] To avoid the fractional precipitation of polyamine HCl salts, German Patent Application Publication No. 3034680 discloses a method in which the majority of the diamine components from hydrolytic polyurethane depolymerization are first continuously distilled off from the reaction mixture under reduced pressure at temperatures above 200°C. Because this removal is not complete, the remaining diamines (less than 1%) in the polyol component are subsequently precipitated by first dissolving them in toluene and adding HCl to precipitate the diamine HCl salts. A significant drawback of this approach is that it is only viable for diamines from polyurethane hydrolysis, which have a high vapor pressure, but not for pMDA, which cannot be distilled off under these conditions.

[0014] Another approach is the hydrogenation of polyurethane in a protic organic solvent using a hydrogenation catalyst, as described in ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705. This is also the only method disclosed to date that can isolate pMDA from the polyol component after depolymerization of pMDI-based polyurethane rigid foams. After hydrogenation at 50 bar, the reaction mixture was first purified by column chromatography to obtain a polyol fraction containing pMDA. This was then dissolved in an aqueous HCl / brine solution to form the pMDA HCl salt. This aqueous phase containing the dissolved pMDA HCl salt was then extracted several times with dichloromethane to extract the polyol. The dissolved pMDA HCl salt then had to be neutralized with aqueous NaOH to form free pMDA dissolved in this aqueous phase, which then had to be isolated by further extraction with dichloromethane. The disadvantages of this approach are the large consumption of organic solvent in the initial column chromatography and the need to extract not only pMDA but also the polyol in this system. Additionally, a stoichiometric amount of NaOH is required to release free pMDA prior to extraction.

[0015] Therefore, it would be of great economic interest to depolymerize pMDI-based polyurethane rigid foams so that polyols and pMDA can be obtained simply and efficiently. Furthermore, it is an object of the present invention to provide a method that is easy to apply and can be applied on an industrial scale.

[0016] The purpose of this is to a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; This was achieved through value chain return methods, including:

[0017] "Value chain return" is intended to mean that the low molecular weight products obtained by the process of the present invention can be reintegrated into the value chain that leads to polyurethanes or can be used as raw materials in another value chain.

[0018] Surprisingly, in the value chain return method according to the invention, after depolymerization of the pMDI-based polyurethane foam, the depolymerization mixture is distilled to remove volatile compounds, followed by distilling the remaining polyol-pMDA mixture into a 10×10 -30It has been found that pMDA can be easily separated in the form of its HCl salt from the polyol component in a single step by dissolving it in an organic solvent having a dipole moment less than Cm, adding HCl to precipitate pMDA as its HCl salt, and separating the pMDA-HCl salt. According to the method of the present invention, pMDA can be separated from the depolymerized mixture and directly reused in the synthesis of new pMDI in a simple manner with a minimum number of steps.

[0019] The method of the present invention provides polyamines containing amino groups bonded to the carbon atoms to which the isocyanate groups were bonded in the original polyisocyanate, such as oligomeric and polymeric methylenephenylamines. Polyols commonly used in the preparation of polyurethane and polyisocyanurate rigid foams based on polymeric methylenediphenyldiisocyanate (pMDI) can also be preferably reisolated. Therefore, the method preferably also provides polyester polyols, low molecular weight polyols such as ethylene glycol or propylene glycol, or high molecular weight polyether polyols based on glycerol, sorbitol, ethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0020] This method allows the reuse of pMDA in the form of its HCl salt, which can be easily converted, for example by phosgenation, into new polyisocyanate pMDI and used to produce new pMDI based on used polyurethane rigid foam. Furthermore, by removing the organic solvent from the liquid phase obtained by precipitation of the pMDA-HCl salt, the polyol component can also be recycled for the synthesis of new polyurethanes.

[0021] The method according to the invention comprises steps a), b), c) and d), but may also comprise further steps. The method may, for example, comprise a further purification step or a heat treatment. According to a further embodiment, the invention also relates to the method disclosed above, which comprises a further purification step.

[0022] Suitable processing steps are known in principle to those skilled in the art. Suitable processing and / or purification steps can be carried out between steps a) and b), between steps b) and c), or between steps c) and d). In the context of the present invention, step b) can also be carried out immediately after step a). Step c) can also be carried out immediately after step b). Step d) can also be carried out immediately after step c).

[0023] Suitable purification steps include, for example, washing and drying steps.

[0024] Therefore, according to a further embodiment, the present invention provides a method for producing a medicament comprising the steps of: d1) purifying the pMDA-HCl salt by washing with fresh solvent and / or drying at elevated temperature and / or drying in vacuo; The present invention also relates to the method disclosed above, including:

[0025] According to a preferred embodiment, the process comprises a further step of treating the salt obtained in step d): the pMDA-HCl salt can be subjected to a phosgenation step, for example, to obtain polymeric methylene diphenyl diisocyanate.

[0026] Therefore, according to a further embodiment, the present invention provides a method for producing a medicament comprising the steps of: e) Phosgenating pMDA HCl salt to obtain pMDI The present invention also relates to the method disclosed above, including:

[0027] According to the invention, it is also possible to subject the pMDA HCl salt to phosgenation in a mixture containing further components such as fresh pMDA or a solvent.

[0028] In the context of the present invention, it is also possible to treat the pMDA-HCl salt obtained in step d) with formaldehyde. Thus, according to a further embodiment, the present invention provides a method for the preparation of pMDA-HCl salt obtained in step e) * ) e *) condensation reaction of pMDA HCl salt with formaldehyde, preferably formaldehyde and aniline, to obtain pMDA. The present invention also relates to the method disclosed above, including:

[0029] According to step a), polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foams are depolymerized to obtain a mixture (M1).

[0030] According to the present invention, any polyurethane and polyisocyanurate rigid foam based on polymeric methylene diphenyl diisocyanate (pMDI) can be used for depolymerization. Generally, waste foam is used as starting material in step a) of the process of the present invention.

[0031] The polyurethane rigid foam used in the present invention is typically obtained from articles made from polyurethane rigid foam after they have been used for the purpose for which they were made, or from polyurethane rigid foam waste from the manufacturing process. Before being subjected to step a) of the method of the present invention, the articles can be subjected to mechanical comminution, and the articles can be further sorted to an appropriate size, for example, by shredding, sieving, or density separation, i.e., air, liquid, or magnetic separation. Optionally, these fragments can then be subjected to a process to remove impurities, such as paper labels. Depending on the composition of the polyurethane rigid foam, extraction can be performed to remove soluble additives, such as flame retardants, surfactants, or catalysts, leaving a pure polymeric polyurethane material before hydrolysis, thereby avoiding the additives from being hydrolyzed or becoming contaminated with MDA.

[0032] The properties of the foam used as starting material in the process according to the invention can vary within wide limits.

[0033] Generally, polyurethane rigid foams are produced by the reaction of a polyisocyanate component with a polyol component.

[0034] The properties of polyurethane rigid foams are influenced by the type of polyisocyanate and polyol components used. For example, the starting materials can affect the cross-linking of the polymer, meaning that the polymer is composed of a three-dimensional network structure. Rigid polymers are typically obtained from short chains with many cross-links.

[0035] According to the present invention, polyurethane and polyisocyanurate rigid foams based on polymeric methylene diphenyl diisocyanate (pMDI) are used in step a). For representative compositions of these PU rigid foams, see WO 2015 / 121057 and WO 2013 / 139781.

[0036] Common polyols used in large amounts are, for example, polyester polyols, low molecular weight polyols such as ethylene glycol or propylene glycol, or high molecular weight polyether polyols based on glycerol, ethylene glycol, polypropylene glycol, polytetramethylene glycol and polyester polyols.

[0037] In an embodiment of the present invention, the polyurethane rigid foam is based on a polyfunctional polyisocyanate based on polymeric diphenylmethane diisocyanate (MDI). Suitable diphenylmethane diisocyanates are in particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI, or oligomeric MDI, also known as polyphenylpolymethylene isocyanate, or a mixture of two or three of the above-mentioned diphenylmethane diisocyanates, or crude MDI produced during the production of MDI, or a mixture of at least one oligomer of MDI with at least one of the above-mentioned low molecular weight MDI derivatives.

[0038] According to the present invention, polymeric diphenylmethane diisocyanate (MDI) may contain up to 80% by weight of monomeric MDI, preferably less than 50% by weight, more preferably less than 30% by weight, especially less than 20% by weight.

[0039] Polyurethane rigid foams are often made from modified polyisocyanates, i.e., products obtained by chemical reaction of organic polyisocyanates and containing two or more reactive isocyanate groups per molecule. Particular mention may be made of polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate, and / or urethane groups, which may also be depolymerized in the process of the present invention.

[0040] Methylenedi(phenylisocyanate) (MDI)-Based Polyurethanes and Polymers Methylenedi(phenylisocyanate)-based polyurethanes are technical polymers and are mass-produced as described, for example, in Polyurethanes, in Ullmann's Encyclopedia of Industrial Chemistry, 2012, DOI: 10.1002 / 14356007.a21_665.pub2).

[0041] In step a) according to the present invention, the pMDI-based polyurethane rigid foam can be depolymerized using any suitable method, for example by hydrolysis, preferably in the presence of a catalytically active organic nitrogen component such as a tertiary amine or an N-heterocycle.

[0042] Therefore, according to a further embodiment, the present invention also relates to the process as disclosed above, wherein in step a) depolymerization is achieved by hydrolysis in the presence of a catalytically active organic nitrogen component.

[0043] The catalytically active organic nitrogen compounds are typically of formula I or formula II [ka] [In the formula, R 1 and R 2 , R 3 , R 4 and R 5 are, independently of each other, substituted or unsubstituted C1 to C12 -Alkyl, C1-C 12 -alkenyl, C5-C8-cycloalkyl and aryl, and the residue R 1 , R 2 and R 3 , or R 4 and R 5 two of which may form a ring or be part of a ring system] The compound comprises an organic compound containing at least one nitrogen functional group according to

[0044] Preferably, the active organic nitrogen compound is a tertiary amine, such as triethylamine, tributylamine, pyridine, 1-methylimidazole, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis(dimethylaminopropyl)urea, N-methyl- or N-ethylmorpholine, N-cyclohexyl-morpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexanediamine, 1,6-pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl)ether, dimethylpiperidine, The alkyl amines are selected from methyl amine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo(2,2,0)octane, 1,4-diazabicyclo(2,2,2)octane (Dabco), and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N''-tris(dialkylaminoalkyl)hexahydrotriazines such as N,N',N''-tris(dimethylamino-propyl)-s-hexahydrotriazine, and triethylenediamine.

[0045] In a preferred embodiment, the active organic nitrogen compound has a boiling point of less than 200° C. at ambient pressure.

[0046] In a preferred embodiment, the active organic nitrogen compound is selected from pyridine, 1-methylimidazole or triethylamine.

[0047] Therefore, according to a further embodiment, the present invention also relates to the process disclosed above, wherein the catalytically active organic nitrogen compound is selected from the group consisting of pyridine, 1-methylimidazole and triethylamine.

[0048] According to the present invention, the active nitrogen compound is preferably used in an amount of 1 to 100 weight equivalents, more preferably 2 to 20 weight equivalents, depending on the polyurethane rigid foam.

[0049] According to the present invention, water is preferably used in combination with an active organic nitrogen compound for hydrolysis, typically in an amount of 0.1 to 100 weight equivalents, preferably 1 to 10 weight equivalents, depending on the polyurethane rigid foam.

[0050] The hydrolysis is usually carried out at a temperature in the range of 50 to 250°C, preferably in the range of 80 to 200°C, and more preferably in the range of 100 to 180°C.

[0051] The hydrolysis is usually carried out at a pressure ranging from ambient pressure to 100 bar, depending on the vapor pressure of water and the active organic compound at the selected temperature. Preferably, the hydrolysis is carried out at a pressure of 1 to 20 bar.

[0052] The hydrolysis time is usually selected from the range of 0.1 to 100 hours, preferably 2 to 50 hours, and more preferably 1 to 20 hours.

[0053] The hydrolysis can be carried out in any reactor suitable for such reactions, for example a stirred batch reactor or a tubular reactor, and can be carried out discontinuously or continuously.

[0054] According to step a), a mixture (M1) is obtained which comprises pMDA and at least one polyol, usually also comprises further volatile compounds, and may also comprise unreacted starting materials. Preferably, mixture (M1) comprises pMDA and at least one polyol, usually also comprises further volatile compounds. If the mixture obtained in step a) comprises solid residues, these can be separated by a suitable separation step, for example a filtration step.

[0055] The process of the present invention further comprises a step b) of distilling off volatile compounds from the mixture (M1) to obtain a mixture (M2) comprising pMDA and at least one polyol.

[0056] In step b) of the present invention, all volatile compounds after depolymerization are removed by distillation. Generally, the "volatility" of a liquid can be described using its vapor pressure, where a high vapor pressure indicates a high volatility, and vice versa. In the context of the present invention, the volatile components after depolymerization are mainly active organic nitrogen compounds and water used in hydrolysis.

[0057] The distillation can be carried out at a pressure of 1 bar to 0.001 bar, preferably 1 bar to 0.01 bar.

[0058] The distillation can be carried out at a temperature of 20°C to 250°C, preferably 50°C to 200°C.

[0059] Therefore, according to a further embodiment, the present invention also relates to the process as disclosed above, wherein step b) is carried out at a pressure in the range of 1 bar to 0.001 bar and at a temperature in the range of 20°C to 250°C.

[0060] The active organic nitrogen compounds separated in step b) can be reused for further depolymerization.

[0061] In step b), a mixture (M2) is obtained comprising pMDA and at least one polyol. The remaining high-boiling / non-volatile fraction from the distillation, consisting of polyol components and pMDA, is further used in step c) of the present invention.

[0062] According to step c), the mixture (M2) was diluted with 10 × 10 -30 It dissolves in an organic solvent (S1) with a dipole moment less than Cm.

[0063] In step c) according to the present invention, the remaining polyol-pMDA mixture is 0.5×10 -30 Cm~7.8×10 -30 Cm range, preferably 0.5 x 10 -30 ~6.27×10 -30 It is incorporated into aprotic organic solvents with dipole moments in the range of Cm.

[0064] Suitable solvents are known in principle. According to the invention, -30 Cm~7.8×10 -30 It has been found that an aprotic organic solvent (S1) having a dipole moment in the range of Cm is suitable for dissolving at least the polyol component, but not the pMDA-HCl salt. For an economical process for separating the pure polyol from the organic solvent used in step c), preferably an organic solvent is chosen having a boiling point at ambient pressure below 200°C, more preferably below 150°C.

[0065] In one embodiment, the organic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0066] Suitable halogenated hydrocarbons are selected from dichloromethane, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene and mixtures thereof.

[0067] Therefore, according to a further embodiment, the present invention also relates to the process disclosed above, wherein the organic solvent (S1) is selected from the group consisting of aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, aromatic halogenated hydrocarbons, esters, ketones and mixtures thereof.

[0068] If desired, mixtures of two or more of the above organic aprotic solvents may be used.

[0069] This step is typically carried out at an elevated reaction temperature of at least 0°C but generally not exceeding 150°C, preferably 10-100°C.

[0070] The method of the present invention further comprises step d), in which HCl is added to precipitate pMDA as its HCl salt, followed by separation of pMDA-HCl.

[0071] According to the present invention, HCl can be added as a gas or as a solution of HCl in any given solvent suitable for step c). The ratio of HCl used is preferably at least 1 equivalent of HCl per equivalent of pMDA and up to 100 equivalents of HCl per equivalent of pMDA. Unreacted HCl can also be subsequently recycled from the polyol phase, for example by distillation or flashing.

[0072] Therefore, according to a further embodiment, the present invention also relates to the process disclosed above, wherein HCl is added as a gas or as a solution of HCl in solvent (S1).

[0073] If a solvent is used in this process at a temperature above its boiling point under ambient or HCl pressure, the extraction is carried out in a pressure vessel, e.g., an autoclave, at the given vapor pressure of the solvent used at the selected extraction temperature.

[0074] Preferably, this step is carried out at an elevated reaction temperature of at least 0°C but not exceeding 150°C, more preferably 10-100°C.

[0075] The method of the present invention for separating the solid pMDA-HCl thus formed can be carried out using conventional equipment for separating solids from liquids and / or equipment known to those skilled in the art.In principle, any equipment suitable for separating solids from liquids at a specified temperature and pressure, such as filtration, decanting, or centrifugation, can be used in the method of the present invention.Suitable equipment for filtration is disclosed, for example, in Filtration, 2. Equipment, in Ullmann's Encyclopedia of Industrial Chemistry, 2013, Wiley-VCH Verlag GmbH & Co. KGaA, DOI 10.1002 / 1436007.n11_n01.pub2.

[0076] Filtration may be carried out discontinuously in a batch mode, or continuously or semi-continuously.

[0077] After separating the pMDA-HCl salt, the liquid phase containing the organic solvent added in step c) typically contains the polyol component and, if used in excess, also HCl. The HCl and organic solvent are then separated from the polyol by distillation, and the polyol component can be reused in the synthesis of new polyurethane rigid foams, while the organic solvent can be reused in step c) and the HCl can be reused in step d).

[0078] After separation, the pMDA-HCl may be further purified. Suitable purification steps may include washing with fresh solvent to remove traces of polyols, and / or drying at elevated temperature and / or in vacuo.

[0079] Preferably, the method of the present invention comprises step d1): d1) purifying the pMDA-HCl salt by washing with fresh solvent and / or drying at elevated temperature and / or drying in vacuo; Includes.

[0080] The pMDA-HCl salt may be isolated or subjected to further processing, such as phosgenation, to obtain pMDI, which may be isolated and used in further processes.

[0081] Preferably, the method of the present invention further comprises step e): e) Phosgenating pMDA HCl salt to obtain pMDI Includes.

[0082] In step e) according to the present invention, the pure pMDA-HCl salt obtained in step d1) of step d) can, in one embodiment, then be used directly as starting material for phosgenation to produce new pMDI. Suitable conditions for phosgenation are known in principle to those skilled in the art. The phosgenation of amine-HCl salts is disclosed, for example, in U.S. Pat. No. 8,455,695, EP 0 424 836 or CN 107337615.

[0083] According to an alternative embodiment, the resulting pMDA-HCl salt may be reacted with formaldehyde. For this reason, the method of the present invention comprises step e * ): e * ) condensation reaction of pMDA HCl salt with formaldehyde, preferably formaldehyde and aniline, to obtain pMDA. It may also include.

[0084] According to this embodiment, the isolated pMDA-HCl salt is used in a condensation reaction with aniline and formaldehyde to obtain fresh pMDA, which can then be reused in a state-of-the-art phosgenation for the production of pMDI, as described, for example, in Isocyanates, Organic, in Ullmann's Encyclopedia of Industrial Chemistry, 2012, DOI: 10.1002 / 14356007.a14_611.

[0085] According to a further aspect, the present invention also relates to polymeric methylene phenylene amines (pMDAs) obtained or obtainable according to the process disclosed above.

[0086] According to one aspect, the present invention also relates to polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the method disclosed above.

[0087] The polymeric methylene diphenyl diisocyanates (pMDI) obtained or obtainable according to the process of the present invention can be reused as starting material in processes for preparing, for example, polyurethanes or polyisocyanurates.

[0088] According to a further aspect, the present invention also relates to the use of a polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the process of the present invention, or a polymeric methylene diphenyl diisocyanate (pMDI) according to the invention, for the preparation of a polyurethane or a polyisocyanurate.

[0089] Further embodiments of the invention can be found in the claims and the examples. It will be understood that the features of the subject matter / method / use according to the invention mentioned above and described below can be used not only in the combination specified in each case but also in other combinations without departing from the scope of the invention. Thus, for example, combinations of preferred features with particularly preferred features, or combinations of features not further characterized with particularly preferred features, etc. are implicitly encompassed even if this combination is not explicitly mentioned.

[0090] Exemplary embodiments of the present invention are listed below, but are not intended to limit the present invention. In particular, the present invention also encompasses embodiments resulting from the dependent references and thus combinations defined below.

[0091] 1. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; Value chain return methods, including:

[0092] 2. Process e) e) Phosgenating pMDA HCl salt to obtain pMDI 2. The method of embodiment 1, comprising:

[0093] 3. The method of embodiment 1 or 2, comprising a further purification step.

[0094] 4.Process d1) d1) purifying the pMDA-HCl salt by washing with fresh solvent and / or drying at elevated temperature and / or drying in vacuo; 4. The method of any one of embodiments 1 to 3, comprising:

[0095] 5.Process e * ) e * ) condensation reaction of pMDA HCl salt with formaldehyde, preferably formaldehyde and aniline, to obtain pMDA. 4. The method of any one of embodiments 1 to 3, comprising:

[0096] 6. The method of any one of embodiments 1 to 5, wherein in step a), depolymerization is achieved by hydrolysis in the presence of a catalytically active organic nitrogen component.

[0097] 7. The method of embodiment 6, wherein the catalytically active organic nitrogen compound is selected from the group consisting of pyridine, 1-methylimidazole, and triethylamine.

[0098] 8. The method of any one of the preceding embodiments, wherein step b) is carried out at a pressure ranging from 1 bar to 0.001 bar and at a temperature ranging from 20°C to 250°C.

[0099] 9. The process of any one of embodiments 1 to 8, wherein the aprotic organic solvent (S1) is selected from the group consisting of aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0100] 10. The method of any one of embodiments 1 to 9, wherein HCl is added as a gas or as a solution of HCl in solvent (S1).

[0101] 11. A polymeric methylene phenylene amine (pMDA) obtained or obtainable according to the method of any one of embodiments 1 to 10.

[0102] 12. Polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the method of any one of embodiments 1 to 10.

[0103] 13. Use of the polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the method of any one of embodiments 1 to 10, or the polymeric methylene diphenyl diisocyanate (pMDI) according to embodiment 12, for the preparation of a polyurethane or polyisocyanurate.

[0104] 14. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; e) Phosgenating pMDA HCl salt to obtain pMDI Value chain return methods, including:

[0105] 15. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; A value chain return method comprising: Process d1) d1) purifying the pMDA-HCl salt by washing with fresh solvent and / or drying at elevated temperature and / or drying in vacuo; A method comprising:

[0106] 16. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; A value chain return method comprising: Process e * ) e * ) condensation reaction of pMDA HCl salt with formaldehyde, preferably formaldehyde and aniline, to obtain pMDA. A method comprising:

[0107] 17. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) Mixture (M2), 0.5×10 -30 Cm~7.8×10 -30 dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm, d) adding HCl to separate the pMDA-HCl salt; e) Phosgenating pMDA HCl salt to obtain pMDI A value chain return method comprising: A process wherein in step a) depolymerization is achieved by hydrolysis in the presence of a catalytically active organic nitrogen component.

[0108] 18. The method of embodiment 17, wherein the catalytically active organic nitrogen compound is selected from the group consisting of pyridine, 1-methylimidazole, and triethylamine.

[0109] 19. The method of any one of embodiments 14 to 18, wherein step b) is carried out at a pressure ranging from 1 bar to 0.001 bar and a temperature ranging from 20°C to 250°C.

[0110] 20. The process of any one of embodiments 14 to 19, wherein the aprotic organic solvent (S1) is selected from the group consisting of aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0111] 21. The method of any one of embodiments 14 to 20, wherein HCl is added as a gas or as a solution of HCl in solvent (S1).

[0112] The present invention can be further explained and illustrated by reference to the following examples, however, it will be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0113] Example 1. Materials used Polyol 1: A polyetherol obtained by propoxylation of propylene glycol with an OH number of 56.

[0114] Polyol 2: A polyetherol obtained by propoxylation of propylene glycol with an OH number of 248.

[0115] Polyol 3: A polyetherol obtained by propoxylation of glycerin with an OH number of 42.

[0116] Polyol 4: A polyetherol obtained by propoxylation of glycerin with an OH number of 400.

[0117] Polyol 5: A polyetherol obtained by propoxylation of toluenediamine with an OH number of 400.

[0118] Polyol 6: A polyetherol obtained by propoxylation of sorbitol with an OH number of 490.

[0119] Polyol 7: A polyetherol obtained by propoxylation of a mixture of sucrose and glycerin with an OH number of 490.

[0120] Elastopir: A polyisocyanurate rigid foam (index = 330) from BASF Polyurethanes obtained by reacting a polyol component (Elastopir 1132 / 509) containing a P-containing flame retardant with Lupranat M50.

[0121] Elastocool: Polyurethane rigid foam (index = 120) from BASF Polyurethanes obtained by reacting a polyol component (Elastocool F 2030 / 310) with Lupranat M20.

[0122] Various pMDI-based PU rigid foams were used in the extraction experiments. The PU rigid foam Elastopir is based on 70% polymeric MDI and 30% polyol (a mixture of polyesterols and polyetherols). The PU rigid foam Elastocool is based on 60% pMDI and 40% propylene oxide-based polyetherols. The PU rigid foam "used polymer" was a material used as insulation in refrigerators. While its exact composition is unknown, it is a typical polyurethane rigid foam used for this purpose, made primarily from pMDI and shorter-chain polyetherols and polyesterols. This could be confirmed by reverse engineering using the method of the present invention through hydrolysis and separation of pMDA-HCl.

[0123] 2. Precipitation of polymeric diaminodiphenylmethane (pMDA) with HCl. [ka] Polymer MDA (368 mg, 1.86 mmol) was weighed into a 20 mL vial. The wall was rinsed with CHCl (5 mL). Under stirring, an ethereal solution of HCl (2 M in EtO, 5 mL) was added to the yellow solution. The formation of a viscous precipitate could be immediately observed. [Note: The last 3 mL of the solution was injected directly into the solution to ensure contact with the DCM phase.] After sealing with a screw cap, the vial was further shaken to homogeneously mix all phases. The suspension was filtered through a suction filter, and the remaining solid was washed with DCM (3 × 5 mL) and EtO (2 × 2 mL). After drying in air for 20 min, the yellow solid was transferred to a flask and stirred under reduced pressure (room temperature, 2.0·10 -2 The resulting solution was further dried at 45° C. and 70 mbar overnight to give a highly electrostatic solid (502 mg, 1.85 mmol, >99%). The colorless filtrate was dried under reduced pressure (45° C., 70 mbar). No residue was detected in the flask.

[0124] 3. Separation of polymeric diaminodiphenylmethane (pMDA) from polyols in premixed samples by precipitation with HCl. The results are summarized in Table 1. Polymeric 4,4'-diaminodiphenylmethane and polyol were mixed in a 20 mL screw-cap vial. Each sample was dissolved in either the specified amount of dichloromethane. After homogeneous mixing, the specified amount of ethereal HCl (2 M in Et2O) was added. The sample was diluted with the specified amount of dichloromethane and mixed by shaking for 20 seconds. A large amount of precipitate could be observed in each sample. All samples were filtered through a suction filter. The remaining solid was washed with dichloromethane (3 x 10 mL) and dried at 60 °C (oven) for 5 hours to obtain polymeric 4,4'-diaminodiphenylmethane as the polyhydrochloride salt. The solvent of all filtrates was removed under reduced pressure (47 °C, minimum pressure 60 mbar). The masses of all fractions can be extracted from the table below. All samples were 1 H& 13 Analyzed by C NMR spectroscopy (MeOD-d4 for the hydrochloride salt and CDCl3 for the polyol).

[0125] [Table 1]

[0126] 4. Isolation of the monomer mixture obtained by precipitation of polymeric diaminodiphenylmethane from the polyol with HCl after hydrolysis in an amine base-water mixture. The results are summarized in Table 2. The polymer was filled into a 38 mL ace tube in air. The walls were rinsed with amine base and water. The tube was sealed and heated to 160 °C overnight under stirring. After 18 h of stirring at 160 °C, the deep orange solution was cooled to room temperature. The sample was filtered through a small pad of Celite (Pasteur pipette) and the pad was rinsed with used amine base (3 × 4 mL). The solvent was removed under reduced pressure (for pyridine: 47 °C, minimum pressure 60 mbar; for methylimidazole: 90 °C, minimum pressure 1.8·10 -2 The residue was suspended in dry dichloromethane (20 mL for small-scale reactions [1.00 g]; 150 mL for larger reactions). The specified amount of ethereal HCl was added at room temperature under stirring. The formation of a heavy precipitate could be observed. After stirring for 5 min at room temperature, the solid was filtered through a suction filter, washed with more dry dichloromethane (3 × 10 mL), and evaporated under reduced pressure (room temperature, 1.8·10 -2 The dried solid was weighed to determine the amount of ammonium polyhydrochloride isolated. The solvent of the filtrate was removed under reduced pressure (47°C, minimum pressure 50 mbar) and the polyol fraction was determined from the residual oil. All products were 1 H and 13 It was characterized by C NMR.

[0127] [Table 2]

[0128] 5. Solubility of polymeric diaminodiphenylmethane polyhydrochloride (pMDA·HCl) and polyol 7 in various solvents: 20 mL vials were filled with pMDA·HCl (approximately 20–40 mg) or polyol 7 (50–100 mg). The designated solvent (3–4 mL) was added, and the vials were sealed. All vials were allowed to stand at room temperature for 4 hours, followed by shaking for approximately 1 minute. The solubility of all samples was confirmed on the same day and over the weekend after standing at room temperature (a total of 68 hours).

[0129] [Table 3]

[0130] Citation of Prior Art Kunststoffhandbuch, Band 7, Polyurethane, Carl-Hanser-Verlag, 3. Auflage, 1993, Kapitel 6 Plastics recycling and Polyurethanes, in Ullmann's Encyclopedia of Industrial Chemistry, 2020, DOI: 10.1002 / 14356007.a21_057.pub2 and Waste Management, 2018, 76, 147-171 DE 2854940 A1 ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705 International Publication No. 2015 / 121057 International Publication No. 2013 / 139781 Ullmann's Encyclopedia of Industrial Chemistry, 2012, DOI: 10.1002 / 14356007.a21_665.pub2 U.S. Patent No. 8,455,695 European Patent Application Publication No. 0424836 Chinese Patent No. 107337615

Claims

1. a) depolymerizing a polymeric methylene diphenyl diisocyanate (pMDI) based polyurethane and polyisocyanurate rigid foam to obtain a mixture (M1); b) removing volatile compounds from the mixture (M1) by distillation to obtain a mixture (M2) comprising pMDA and at least one polyol; c) The mixture (M2) is 0.5×10 －３０ Cm ~ 7.8 x 10 －３０ dissolving in an aprotic organic solvent (S1) having a dipole moment in the range of Cm; d) adding HCl to separate the pMDA-HCl salt; Value chain return methods, including:

2. Step e) e) Phosgenation of pMDA HCl salt to obtain pMDI 2. The method of claim 1, comprising:

3. 3. The method of claim 1 or 2, comprising a further purification step.

4. Step d1) d1) purifying the pMDA-HCl salt by washing with fresh solvent and / or drying at elevated temperature and / or drying in vacuum.

4. The method of claim 1, comprising:

5. Engineering e ＊ ) e ＊ ) condensation reaction of pMDA HCl salt with formaldehyde, preferably formaldehyde and aniline, to obtain pMDA.

4. The method of claim 1, comprising:

6. 6. The process according to claim 1, wherein in step a) the depolymerization is achieved by hydrolysis in the presence of a catalytically active organic nitrogen component.

7. 7. The method of claim 6, wherein the catalytically active organic nitrogen compound is selected from the group consisting of pyridine, 1-methylimidazole and triethylamine.

8. 8. The process according to claim 1, wherein step b) is carried out at a pressure in the range from 1 bar to 0.001 bar and at a temperature in the range from 20°C to 250°C.

9. 9. The process according to claim 1, wherein the aprotic organic solvent (S1) is selected from the group consisting of aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones and mixtures thereof.

10. 10. The process according to claim 1, wherein HCl is added as a gas or as a solution of HCl in the solvent (S1).

11. 11. Polymeric methylene phenylene amine (pMDA) obtained or obtainable according to the process of any one of claims 1 to 10.

12. Polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the process of any one of claims 1 to 10.

13. Use of the polymeric methylene diphenyl diisocyanate (pMDI) obtained or obtainable according to the process of any one of claims 1 to 10, or the polymeric methylene diphenyl diisocyanate (pMDI) according to claim 12, for the preparation of polyurethanes or polyisocyanurates.

Images