Value chain return process for recovering phosphorus ester flame retardants from polyurethane rigid foams

Abstract

A polyurethane rigid foam containing at least one phosphorus ester flame retardant is returned to the value chain by hydrogenating the polyurethane rigid foam to obtain a hydrogenation product containing polyamines and polyols from the polyurethane rigid foam and recovering the flame retardant from the hydrogenation product. The hydrogenation is carried out in an aprotic organic solvent under a hydrogen atmosphere in the presence of at least one homogeneous transition metal catalyst complex, wherein the transition metal is selected from metals of groups 7, 8, 9 and 10 of the Periodic Table of the Elements according to IUPAC, at a reaction temperature of at least 120°C.

Description

[Technical field]

[0001] The present invention relates to a value chain return process for polyurethane rigid foams that allows for the recovery of phosphorus ester flame retardants contained therein.

[0002] Over the last 30 years, there has been an enormous increase in the global demand for plastics. For example, over the last decade, the amount of plastic produced worldwide has increased by almost 50%. It has almost quadrupled in 30 years, reaching a volume of 359 million metric tons in 2018. It is clear from these facts that this huge amount of plastic production inevitably leads to the need to dispose of or recycle used plastics. Therefore, priority should be given to recycling in which valuable materials, such as compounds that can act as monomers, can be returned to the value chain, for example by direct reuse in plastic production. Plastics are used with additional components that are incorporated with the aim of giving the resin various functions. For example, resins are mixed with flame retardants in proportions of up to 25% by weight with a view to preventing the spread of fire, since they are highly flammable themselves. If the flame retardants could be returned to the industrial cycle, it would be promising both from a resource-saving and economic point of view.

[0003] In addition, polyurethane (PU) rigid foam waste is generated in the industrial production of polyurethane rigid foam. For example, such waste of PU rigid foam is obtained when a block of PU rigid foam is cast and then cut, trimmed or sized to obtain the desired PU workpiece. In addition, rejects of PU rigid foam, such as off-spec products, are also generated.

[0004] Therefore, there is a need to develop processing technologies to recover materials from plastic waste. The recycling process should reduce both the waste and the carbon footprint of the materials. Furthermore, it should also be an economical and energy-efficient process that gives valuable materials with high technical characteristics. In contrast, disposal, for example by combustion, has a negative impact on both the environment and the carbon footprint.

[0005] Among the above plastics, polyurethanes (PU) are an important representative example. In general, polyurethanes are produced by polyaddition of (poly)isocyanates with polyols. The characteristic chain linkage is the urethane group. There are many types of polyurethanes, such as foams, elastomers, or thermosets, among which foams are particularly important.

[0006] The 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 stage of the reaction spontaneously decomposes to an amine with the elimination of carbon dioxide. This amine then reacts with excess isocyanate to give a symmetrically substituted urea. This reaction is the fundamental reaction that leads to polyurethane foams.

[0007] These foams can be made in a wide range of densities and can have a flexible or rigid foam structure. In general terms, a "flexible foam" is one that recovers its shape after deformation. In addition to being reversibly deformable, flexible foams tend to have limited resistance to applied loads and tend to have primarily open cells. A "rigid foam" is one that generally retains its deformed shape without significant recovery after deformation. Rigid foams tend to have primarily closed cells. Whether a PU soft or rigid foam is formed during polyaddition depends primarily on the type of polyisocyanate and polyol components used. For example, the starting material can affect the crosslinking of the polymer, meaning that the polymer consists of a three-dimensional network. Long flexible segments contributed by the polyol result in the formation of a PU soft foam. PU rigid foams are obtained from short chains with many crosslinks. Further 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.

[0008] Polyurethane rigid foams provide excellent thermal insulation. They are therefore of great importance in the construction sector and are often used as thermal insulation materials, for example for building insulation. However, the application of polyurethane rigid foams as thermal insulation materials in buildings requires the addition of flame retardants for fire protection reasons. For this purpose, flame retardants are added in the production process of polyurethane rigid foams. Nowadays, mainly phosphorus esters such as tris(2-chloroethyl) phosphate, tris(chloroisopropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(2-ethylhexyl) phosphate, triethyl phosphate, tricresyl phosphate, tris(2,3-dibromo)phosphate, tetrakis(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethyl propylphosphonate, diphenylcresyl phosphate, and mixtures thereof are used as flame retardants in construction polyurethane rigid foams (see Chemosphere, 2012, 88, 1119-1153 and WO 2015 / 121057).

[0009] Recycling of polyurethane rigid foams into valuable monomer compounds and recovery of phosphorus ester flame retardants remains challenging. Polyol compounds can be recovered and recycled by glycolysis or hydrolysis (see Ullmann's Encyclopedia of Industrial Chemistry, Plastics recycling and Polyurethanes, 2020, DOI:10.1002 / 14356007.a21_057.pub2).

[0010] US Pat. No. 4,196,148 describes a process for the hydrolysis of polyurethane foam and the recovery of diamines and polyethers (or polyesters) from the hydrolysis product, carried out at near atmospheric pressure and at temperatures above 185° C.

[0011] Although the hydrolysis of polyurethane foams allows recycling of the constituent monomers, phosphorus-based flame retardants are degraded under harsh hydrolysis reaction conditions (see Ullmann's Encyclopedia of Industrial Chemistry, Phosphorus Compounds, Organic, 2012, DOI: 10.1002 / 14356007.a19_545.pub2). Such degradation is not only disadvantageous in terms of the flame retardant no longer being available for reuse, but the hydrolysis products of the esters may contaminate the polyols and / or polyamines, which may result in more complex, resource-intensive and costly downstream processes.

[0012] Therefore, it would be of great economic importance to depolymerize polyurethane rigid foams in a manner that would provide phosphorus ester flame retardants in addition to polyols and polyamines.

[0013] T. Schaub et al., ChemSusChem, 2020, DOI:10.1002 / cssc.202002465, describe the depolymerization of nylon and polyurethane using homogeneous ruthenium catalysts with P,N,N tridentate ligands in tetrahydrofuran as solvent. So far, good results have been obtained using ruthenium catalysts in tetrahydrofuran as solvent at 200 °C and 100 bar H2 to obtain amine components and polyols from toluene diisocyanate-based polyurethane soft foams. However, the hydrogenation of methylene di(phenyl isocyanate)-based polyurethane rigid foams containing phosphorus ester flame retardants has not been disclosed.

[0014] T. Skrydstrup et al., JACS Au, 2021, DOI: 10.1021 / jacsau.1c00050, describe the depolymerization of polyurethanes using 2 mol% homogeneous iridium catalyst with P,N,P tridentate ligands at 150 °C and 30 bar H2 pressure in 2-propanol as solvent. In this work, methylene di(phenyl isocyanate)-based polyurethane rigid foam from refrigerator insulation was hydrogenated to give the corresponding diamines and polyols. The authors found that in the polyol fraction, 31 A phosphorus compound with a signal at 20.00 ppm was detected in the P NMR spectrum. It was suggested that this phosphorus compound may be due to a phosphorus-based flame retardant, but no further confirmation, characterization, or isolation of this unknown phosphorus compound was performed. However, PU rigid foams used for refrigerator insulation do not usually contain phosphorus-based flame retardants.

[0015] In addition, phosphorus ester flame retardants that are commonly used in polyurethane rigid foams are 31 They do not have a chemical shift around 20 ppm in the P NMR spectrum, and are usually less than 1 ppm: tris(2-chloroethyl)phosphate -2.5 ppm (see Zhurnal Obshchei Khimii, 1978, 78, 694-695), tris(chloroisopropyl)phosphate -4.2 ppm (measured on a standard), tris(2-ethylhexyl)phosphate -0.24 ppm (see J. Chem. Eng. Data, 2008, 53, 2718-2720), and triethylphosphate -0.8 ppm (see Phosphorus, Sulfur and Silicon and the Related Elements, 1991, 61, 31-39). Skrydstrup et al. therefore do not disclose the recovery of phosphorus ester flame retardants from polyurethane rigid foams. The authors probably convert the phosphine oxide of the phosphine ligand of the catalyst used into 31 The oxide of the PNP ligand, Ph2P(O)C2H4NHC2H4P(O)Ph2, 31The P NMR spectrum has a phosphine oxide signal at 20 ppm (measured with an authentic sample of the oxidized PNP ligand).

[0016] T. Schaub et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101606, describes the depolymerization of polyurethanes using 2-4 mol% homogeneous manganese catalysts with P,N,N tridentate ligands at 130-200 °C and 60 bar H2 pressure in toluene or THF as solvent. The application of this system to methylene di(phenyl isocyanate)-based polyurethane rigid foams afforded the corresponding diamines and polyols, which could be isolated. The rigid foams did not contain phosphorus-based flame retardants. Thus, the recovery of phosphorus-based flame retardants from polyurethane rigid foams is neither disclosed nor suggested in this document.

[0017] T. Skrydstrup et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705, describe the depolymerization of polyurethanes using 1 mol% homogeneous manganese catalyst with P,N,P tridentate ligands at 180 °C and 50 bar H2 pressure in 2-propanol as solvent. The system was applied to methylene di(phenyl isocyanate)-based polyurethane rigid foams from refrigerator insulation and decorative polyurethane rigid foams. In both cases, the corresponding diamines and polyols were obtained, which could be isolated.

[0018] The authors, 31In the P NMR spectrum, phosphorus compounds with a signal at 31.00 ppm were detected in the polyol fraction obtained from the decorative PU rigid foam, and a signal at 32.05 ppm in the polyol fraction obtained from the PU rigid foam from refrigerator insulation. As mentioned above, for these unknown phosphorus compounds, the authors also suggested that the signals could be derived from phosphorus-based flame retardants. Again, no further confirmation, characterization or isolation of these unknown phosphorus compounds was performed. However, as further detailed above, PU rigid foams used for refrigerator insulation and decoration do not usually contain phosphorus-based flame retardants. Also, phosphorus ester-based flame retardants commonly used in polyurethane rigid foams are 31 It does not have a chemical shift around 31 ppm in the P NMR spectrum, which is typically less than 1 ppm (see above). Therefore, this work also does not disclose the recovery of phosphorus ester flame retardants from polyurethane rigid foams.

[0019] The above-mentioned plastic recycling processes have not so far disclosed a method for recycling polyurethane rigid foams in such a way that both the valuable amine and polyol components are obtained while recovering the phosphorus ester flame retardant. Heretofore, it was unclear whether phosphorus ester flame retardants are susceptible to decomposition under hydrogenation conditions, i.e., at relatively high reaction temperatures, and in protic solvents such as 2-propanol.

[0020] Therefore, it would be of great economic importance to depolymerize polyurethane rigid foams containing phosphorus ester flame retardants in a manner that would provide the phosphorus ester flame retardant in addition to the polyols, aromatic amines, etc.

[0021] This objective was achieved by a back-in-the-value-chain process for polyurethane rigid foams containing at least one phosphorus ester flame retardant. in an aprotic organic solvent, - under hydrogen atmosphere, in the presence of at least one homogeneous transition metal catalyst complex, in which the transition metal is selected from the metals of groups 7, 8, 9 and 10 of the Periodic Table of the Elements according to IUPAC, -Reaction temperature of at least 120°C The method includes hydrogenating the polyurethane rigid foam to obtain a hydrogenated product containing a polyamine and a polyol from the polyurethane rigid foam, and recovering the flame retardant from the hydrogenated product.

[0022] "Return to value chain" 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 resulting in polyurethanes or else used as feedstock in other value chains.

[0023] Surprisingly, in the value chain reintroduction process, the phosphorus ester flame retardants are recovered in a chemically unchanged form, in other words they do not react and are not decomposed under the hydrogenation reaction conditions applied in the process, which allows them to be recovered after the hydrogenation reaction.

[0024] Thus, the method allows for the recycling of both the starting material components and the phosphorus ester flame retardants, which can either be directly recovered (polyols) or obtained as valuable synthetic building blocks such as polyamines that can be easily converted to polyisocyanates.

[0025] The inventive value chain return process for polyurethane rigid foams containing at least one phosphorus ester flame retardant results in a hydrogenated product, which contains the polyamine and polyol from the polyurethane rigid foam. In addition to the polyamine and polyol, the phosphorus ester flame retardant is present as a further component in the hydrogenated product.

[0026] Work-up of the hydrogenated product, in particular isolation of the polyamine, polyol and phosphorus ester flame retardant, can be achieved, depending on the case, for example, by aqueous extractive work-up, chromatography or vacuum distillation, etc. Preferably, the work-up comprises several steps.

[0027] In the distillation workup, the compounds are separated according to their volatility, with the more volatile compounds being separated first. In general, 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, polyamine and phosphorus ester flame retardants are generally more volatile than polyols.

[0028] If the polyamine is more volatile than the polyol and the flame retardant, the polyamine is recovered from the hydrogenation product by distillation, preferably by vacuum distillation. After distillation of the polyamine, a distillation bottom remains, which contains the polyol together with the flame retardant. In a next step, the flame retardant can be recovered from the distillation bottom by distillation to obtain a fraction essentially consisting of the flame retardant and a distillation bottom containing the polyol. Alternatively, the flame retardant can be left in the polyol, which can later be used in the synthesis of new polyurethanes. In the synthesis of PU rigid foams, it is customary to mix the flame retardant with the polyol component prior to reaction with the isocyanate component.

[0029] If the flame retardant has a higher volatility than the polyol and polyamine, the flame retardant can be recovered from the hydrogenation product by distillation, preferably by vacuum distillation. After distillation of the flame retardant, a distillation bottom containing the polyol together with the polyamine remains. In a next step, the polyamine can be recovered from the distillation bottom by distillation to obtain a fraction consisting essentially of polyamine and a distillation bottom containing the polyol.

[0030] After removal of volatile components according to the above embodiments, the polyol is suitably recovered as distillation bottoms.

[0031] Alternatively, the polyol can be recovered by extraction from the distillation bottoms using a suitable extractant. This procedure is also advantageous in terms of further components other than the polyol contained in the distillation bottoms, such as hydrogenation catalyst. For example, after extraction of the distillation bottoms, the water-soluble polyol can be obtained from the aqueous phase, and the hydrogenation catalyst can be recovered from the organic phase after extraction. Once separated from the product, the catalyst can be returned to the reactor for reuse. Alternatively, the catalyst solution can be diluted with a solvent and reused.

[0032] Alternatively, the polyol can be recovered by extraction from the hydrogenation product, i.e. before carrying out the recovery of the volatile compounds mentioned above, and the polyamine and flame retardant can then be obtained from the remaining portion in the same manner as above, i.e. by distillation.

[0033] In yet another alternative, the polyol may be recovered by extraction from the distillation bottoms obtained after distilling off the volatile components as described above.

[0034] It is understood that the above separation processes can be combined with any of the various embodiments of the inventive process described herein.

[0035] The present invention can be applied to polyurethane rigid foam waste containing at least one phosphorus ester flame retardant as a starting material. In this specification, the term "polyurethane rigid foam waste" includes used polyurethane rigid foam and PU rigid foam waste. In this context, the term "used polyurethane rigid foam" refers to an item resulting from a polyurethane rigid foam that has already been used for its manufacturing purpose. The term "polyurethane rigid foam waste" refers to polyurethane rigid foam waste resulting from the production process of PU rigid foam.

[0036] Generally, polyurethane rigid foams are produced by the reaction of a polyisocyanate component with a polyol component. Additional materials, such as phosphorus ester flame retardants, are added during the polymer production process.

[0037] The properties of polyurethane rigid foams depend on the type of polyisocyanate and polyol components used. For example, the starting materials can affect the crosslinking of the polymer, meaning that the polymer consists of a three-dimensional network. Rigid polymers result from short chains with many crosslinks.

[0038] In particular, methylene di(phenyl isocyanate) (MDI) or its polymeric forms are used industrially, and therefore in large quantities, as polyisocyanate components for the production of PU rigid foams. To a lesser extent, 1,6-hexane diisocyanate, isophorone diisocyanate, and 1,5-naphthyl diisocyanate are also used as polyisocyanate components for this purpose.

[0039] For representative compositions of these PU rigid foams, see WO 2015 / 121057 and WO 2013 / 139781.

[0040] 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.

[0041] In one embodiment, the polyurethane rigid foam is selected from aromatic isocyanate-based polyurethane rigid foams, preferably methylene di(phenyl isocyanate)-based polyurethane rigid foams, polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams, and 1,5-naphthyl diisocyanate-based polyurethane rigid foams, with methylene di(phenyl isocyanate)-based polyurethane rigid foams and polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams being especially preferred.

[0042] Polyfunctional isocyanates based on diphenylmethane diisocyanate (MDI) are in particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI, or oligomeric MDI, also called polyphenylpolymethylene isocyanates, or a mixture of two or three of said diphenylmethane diisocyanates, or crude MDI obtained during the production of MDI, or a mixture of at least one oligomer of MDI and at least one of said low molecular weight MDI derivatives.

[0043] In methylene di(phenylisocyanate)-based polyurethane rigid foams, an isomeric mixture of 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanate; an isomeric mixture of 4,4'-, and 2,2'-diphenylmethane diisocyanate; polyphenylpolymethylene polyisocyanate; or a mixture of 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanate and polyphenylpolymethylene polyisocyanate (crude MDI) may also be used.

[0044] Modified polyisocyanates, i.e. products obtained by chemical reaction of organic polyisocyanates and having two or more reactive isocyanate groups per molecule, are also frequently used. Mention may in particular be made of polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups.

[0045] Aromatic isocyanates are compounds in which the isocyanate functionality is attached directly to an aromatic core, whereas compounds such as p-xylylene diisocyanate are not considered aromatic isocyanates because the isocyanate functionality is attached to a methylene spacer and therefore not directly to the aromatic core.

[0046] Methylenedi(phenylisocyanate) (MDI)-based polyurethanes and polymeric methylenedi(phenylisocyanate)-based polyurethanes are technical polymers and are produced on a large scale (see Ullmann's Encyclopedia of Industrial Chemistry, Polyurethanes, 2012, DOI: 10.1002 / 14356007.a21_665.pub2).

[0047] The process of the present invention gives polyamines containing amino groups attached to the carbon atoms to which the isocyanate groups were attached in the initial polyisocyanate, such as methylenediphenyldiamine, oligomeric and polymeric methylenephenyleneamines and toluenediamines (1,2-toluenediamine or 1,4-toluenediamine) or 1,5-naphthyldiamine. The commonly used polyols, such as those mentioned above, can be reisolated. Thus, the process further gives low molecular weight polyols, such as polyester polyols, ethylene glycol or propylene glycol, or high molecular weight polyether polyols based on glycerol, sorbitol, ethylene glycol, polypropylene glycol and polytetramethylene glycol.

[0048] The polyurethane rigid foams used in the present invention are obtained from the products resulting from polyurethane rigid foams after they have been used for their manufacturing purpose, or from polyurethane rigid foam waste from the production process. Before being subjected to hydrogenation, the products may be subjected to mechanical comminution, i.e., the products are further selected and sized, for example by shredding, sieving, or density ratio separation, i.e., air, liquid or magnetic separation. Optionally, these pieces may then undergo a process to remove impurities, for example paper labels.

[0049] Generally, phosphorus ester flame retardants used in polyurethane rigid foams, such as construction polyurethane rigid foams, are compounds of the general formula (i): [ka] [In the formula, R 9 and R 10 are independent of each other, C1 to C 12 -alkyl, C5-C8-cycloalkyl and aryl, C1~C 12 -alkyl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from hydroxy and halogen, such as Cl or Br; C5-C8-cycloalkyl or aryl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, hydroxy and halogen, such as Cl or Br; In the formula, R 11 is C1~C 12 -alkyl, C5-C8-cycloalkyl and aryl, C1~C 12 -alkyl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from hydroxy and halogen, such as Cl or Br; C5-C8-cycloalkyl or aryl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, hydroxy and halogen, such as Cl or Br, or In the formula, R 11 is -O-C1~C 12 -alkyl, -O-C5-C8-cycloalkyl and -O-aryl, -O-C1~C 12 -alkyl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from hydroxy and halogen, such as Cl or Br; -O-C5-C8-cycloalkyl or -O-aryl is unsubstituted or carries 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, hydroxy and halogen, such as Cl or Br. Follow.

[0050] Preferably, aryl is selected from phenyl and naphthyl.

[0051] In certain embodiments, the phosphorus ester flame retardant is selected from tris(2-chloroethyl)phosphate, tris(chloroisopropyl)phosphate, tris(1,3-dichloro-2-propyl)phosphate, tris(2-ethylhexyl)phosphate, triethyl phosphate, tricresyl phosphate, tris(2,3-dibromo)phosphate, tetrakis(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethyl propylphosphonate, diphenylcresyl phosphate, and mixtures thereof.

[0052] Suitably, in the polyurethane rigid foam, the phosphorus ester flame retardant is present in the polyol component in an amount of 1 to 40% by weight, preferably 5 to 30% by weight, and more preferably 8 to 25% by weight.

[0053] According to the present invention, the hydrogenation is carried out in an aprotic organic solvent, which must have certain properties, including the ability to dissolve the polyurethane rigid foam used as starting material under the hydrogenation conditions, and the chemical inertness under the hydrogenation conditions.

[0054] In one embodiment, the aprotic organic solvent is selected from ethers, aromatic hydrocarbons, and mixtures thereof.

[0055] Suitable ethers are selected from tetrahydrofuran, 1,4-dioxane, anisole, diethyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether, diethylene glycol dimethyl ether, and diphenyl ether.

[0056] Suitable aromatic hydrocarbons are selected from benzene, toluene, ortho-xylene, meta-xylene, para-xylene, ethylbenzene, mesitylene, pyridine, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine, 3,5-lutidine, collidine, 2-picoline, 3-picoline, 4-picoline.

[0057] Mixtures of two or more of the above aprotic organic solvents may be used if desired.

[0058] In certain preferred embodiments, the ether is selected from tetrahydrofuran, 1,4-dioxane and anisole, and the aromatic hydrocarbon is selected from benzene, toluene, xylene and mesitylene.

[0059] The net energy balance of the hydrogenation reaction is exothermic, but the initiation requires the supply of energy (activation energy). Also, the higher the temperature, the more readily the polyurethane rigid foam is subjected to hydrogenation, as the solubilization of the polyurethane rigid foam by the aprotic organic solvent defined above is promoted. In order to provide the necessary activation energy and to solubilize a sufficient amount of the polyurethane rigid foam, the hydrogenation reaction is carried out at a high reaction temperature of at least 120°C. In one embodiment, the reaction temperature is 120-220°C, preferably 140-200°C.

[0060] The hydrogenation is carried out under a hydrogen atmosphere, since molecular hydrogen is consumed during the hydrogenation reaction of the polyurethane rigid foam. The hydrogen pressure affects the outcome of the reaction. Typically, the lower the pressure, the slower the reaction rate, and the higher the pressure, the faster the reaction rate. It is therefore appropriate that the hydrogen atmosphere is present at a high pressure level. The hydrogenation reaction is therefore carried out in a pressurized reaction vessel, for example an autoclave. In one embodiment, the hydrogenation reaction is carried out at a pressure of 30 to 500 bar absolute, preferably 40 to 300 bar absolute, more preferably 50 to 200 bar absolute.

[0061] The hydrogenation reaction is carried out in the presence of at least one homogeneous transition metal catalyst complex (hereinafter also referred to as "hydrogenation catalyst") that contains at least one multidentate ligand having at least one nitrogen atom and at least one phosphorus atom capable of coordinating to a transition metal.

[0062] In general, the amount of hydrogenation catalyst present in the hydrogenation reaction may vary within wide limits. Suitably, the hydrogenation catalyst is present in the hydrogenation reaction in an amount of 0.1 to 5000 ppm (parts by weight calculated as catalytic metal), preferably 1 to 2000 ppm, more preferably 50 to 1000 ppm.

[0063] The hydrogenation catalyst comprises a transition metal selected from metals of groups 7, 8, 9 and 10 of the Periodic Table of the Elements according to IUPAC, preferably group 7 or 8.

[0064] In one embodiment, the homogeneous transition metal catalyst complex comprises a transition metal selected from manganese, iron, cobalt, rhodium, osmium, rhenium, ruthenium, iridium, nickel, palladium and platinum. Preferred transition metals are ruthenium and iridium. More preferred transition metal is manganese due to its wide availability.

[0065] Generally, homogeneous transition metal catalyst complexes contain at least one ligand to solubilize the transition metal in the reaction solution and maintain the transition metal in a form active for hydrogenation. Preferred ligands are multidentate ligands having at least one nitrogen atom and at least one phosphorus atom capable of coordinating to the transition metal.

[0066] The hydrogenation catalyst may further comprise one or more additional ligands, such as anions selected from the group consisting of hydrides, alkoxides, aryloxides, carboxylates and acyl, or neutral ligands selected from the group consisting of carbon monoxide, triarylphosphines, amines, N-heterocyclic carbenes and isonitriles. Preferably, the hydrogenation catalyst further comprises a carbon monoxide ligand, a halide or a hydride.

[0067] In one embodiment, the at least one polydentate ligand has the general formula (I): [ka] [In the formula, Each R' is independently H or C1-C4-alkyl; R 1 and R 2 are independent of each other, C1 to C 12 - alkyl, cycloalkyl or aryl, The alkyl is unsubstituted or has 1, 2, 3, 4 or 5 identical or different substituents R 7 Hold The cycloalkyl and aryl are unsubstituted or have 1, 2, 3, 4 or 5 identical or different substituents R 8Hold R 3 and R 4 are each independently H or C1-C 12 -alkyl (which is unsubstituted or heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl, NE 1 E 2 and PR 1 R 2 and bearing 1, 2, 3, 4 or 5 identical or different substituents selected from R 5 is H or C1~C 12 -alkyl, which is unsubstituted or has 1, 2, 3, 4 or 5 identical or different substituents R 7 (which holds) R 6 is H or C1-C4-alkyl, or R 4 and R 6 does not exist, and R 3 and R 5 is R 3 The nitrogen atom to which R is attached 5 together with the carbon atom to which it is attached form a six-membered heteroaromatic ring (It may be unsubstituted or C1-C 12 - carrying 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, cycloalkyl, aryl and hetaryl, The alkyl is unsubstituted or has 1, 2, 3, 4 or 5 identical or different substituents R 7 Hold The cycloalkyl, aryl and hetaryl are unsubstituted or can be substituted with an alkyl substituent, which can be unsubstituted or can be substituted with an alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl, NE, 1 E 2 and PR 1 R 2(holding a substituent selected from) Forming Each R 7 is independently cycloalkyl, heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl or NE 1 E 2 and Each R 8 are independently C1-C4-alkyl, cycloalkyl, heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl or NE 1 E 2 and E 1 and E 2 are independent of each other and for each occurrence, H, C1 to C 12 - is a group selected from alkyl, cycloalkyl and aryl. Follow.

[0068] The term "cycloalkyl" (as well as in combinations such as "cycloalkyloxy") refers to a saturated cyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms, preferably 4 to 7 carbon atoms, more preferably 5 to 6 carbon atoms. Cyclopentyl or cyclohexyl is preferred.

[0069] The term "heterocycloalkyl" (as well as in combinations such as "heterocycloalkoxy") refers to a saturated 3-8 membered cyclic hydrocarbon in which one or more carbon atoms are replaced with a heteroatom selected from O, S, N and P or combinations thereof. Pyrrolidinyl, imidazolidinyl, pyrazolidinyl, piperidyl, piperazinyl, morpholinyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothiophene, and the like are preferred, as are the methyl-, ethyl-, propyl-, isopropyl- and tert-butyl substituted derivatives thereof.

[0070] The term "aryl" (also in combinations such as aryloxy) denotes a monocyclic or fused aromatic carbocyclic ring, preferably a phenyl or naphthyl group, more preferably a phenyl group.

[0071] The term "hetaryl" (also in combinations such as hetaryloxy) refers to a 3- to 8-membered aromatic carbocyclic ring in which one or more carbon atoms are replaced by a heteroatom selected from O, S, N and P or combinations thereof, and which may be fused to one or two aromatic rings. Furyl, thienyl, pyrrolyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl, pyrimidinyl, pyrazinyl, and the like are preferred, as are their methyl-, ethyl-, propyl-, isopropyl- and tert-butyl-substituted derivatives. Most preferably, the hetaryl is pyridyl.

[0072] Preferably, R' is H.

[0073] Preferably, R 1 and R 2 are the same and are selected from the group consisting of isopropyl, cyclohexyl, tert-butyl and phenyl, with tert-butyl and phenyl being particularly preferred.

[0074] Preferably, R 3 is H or C1-C3-alkyl, with H being particularly preferred.

[0075] Preferably, R 4 is H or -(CH2)2-PR 1 R 2 , for example -(CH2)2-PPh2 or -(CH2)2-P i Pr2 or C1-alkyl bearing one hetaryl substituent, such as -(CH2)-(2-pyridyl) or -(CH2)-(1-methyl-imidazol-2-yl), with -(CH2)2-PPh2 being particularly preferred.

[0076] Preferably, R 5is H or C1-C3-alkyl, with H being particularly preferred.

[0077] Preferably, R 6 is H.

[0078] In a further preferred embodiment, R 6 and R 4 does not exist and R 3 and R 5 is R 3 The nitrogen atom to which R is attached 5 together with the carbon atom to which it is attached form a six-membered heteroaromatic ring. Preferably, the six-membered heteroaromatic ring has a heteroatom at position 1, -CR'R'-PR 1 R 2 is in the 2-position, one substituent is preferably held in the 6-position.

[0079] In one embodiment, the at least one polydentate ligand has the general formula (II) [ka] [In the formula, D is H, C1~C 12 -alkyl, cycloalkyl, aryl or hetaryl; The alkyl is unsubstituted or has 1, 2, 3, 4 or 5 identical or different substituents R 7 Hold The cycloalkyl, aryl or hetaryl may be unsubstituted or may be substituted with an alkyl substituent, which may be unsubstituted or may be substituted with an alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl, NE 1 E 2 and PR 1 R 2 , preferably NE 1 E 2 and PR 1 R 2 (holding a substituent selected from the group consisting of Follow.

[0080] In a preferred embodiment, D is NE 1 E 2 C1 to C substituted with 12 -Alkyl, unsubstituted hetaryl, or NE 1 E 2 Or PR 1 R 2 C1~C substituted with 12 - Hetaryl bearing an alkyl group, with unsubstituted hetaryl being particularly preferred.

[0081] In a more preferred embodiment, D is NE 1 E 2 substituted methyl group, unsubstituted 2-pyridyl, or -CH2-NE at the 6-position 1 E 2 or -CH2-PR 1 R 2 and particularly preferred is unsubstituted 2-pyridyl.

[0082] In one embodiment, the at least one polydentate ligand is one of compounds A to L. [In the formula, Et is ethyl, i Pr is isopropyl, t where Bu is tert-butyl, Cy is cyclohexyl, and Ph is phenyl. [ka] is selected from.

[0083] Homogeneous hydrogenation catalyst complexes, for example based on ruthenium, are known per se. Such catalyst complexes allow catalytically active ruthenium in an environment favorable for hydrogenation. Various ligand systems have been investigated for this purpose. For example, BINAP- (Noyori), P,N,N- (Milstein) or P,N,P- (Takasago) ligands have been used successfully in hydrogenation reactions.

[0084] Similarly, manganese-based hydrogenation catalyst complexes are known per se.

[0085] In a preferred embodiment, the transition metal is ruthenium and the polydentate ligand is according to one of compounds A to G or J, with E, F and J being particularly preferred.

[0086] In another embodiment, the transition metal is manganese and the polydentate ligand is according to one of compounds A, E, or H through L, with E and J being particularly preferred.

[0087] The hydrogenation catalyst may be used in the form of a preformed metal complex comprising a metal compound and one or more ligands.

[0088] In a preferred embodiment, the hydrogenation catalyst is a compound of Ru-1 to Ru-10 [In the formula, Et is ethyl, i Pr is isopropyl, t where Bu is tert-butyl, Cy is cyclohexyl, and Ph is phenyl. [ka] or a preformed ruthenium catalyst selected from Or the hydrogenation catalyst is a compound Mn-1 to Mn-8 [In the formula, i Pr is isopropyl, Cy is cyclohexyl, and Ph is phenyl]: [ka] A preformed manganese catalyst is selected from the group consisting of:

[0089] No special or specialized techniques are necessary to prepare the catalysts used in the present invention, although it is preferable to carry out the operation under an inert atmosphere, for example nitrogen, argon, etc., in order to obtain highly active catalysts.

[0090] Alternatively, the hydrogenation catalyst is formed in situ in the reaction mixture by combining a metal compound (hereinafter also referred to as a "pre-catalyst") with at least one suitable ligand to form a catalytically active metal complex ("hydrogenation catalyst") in the reaction medium. The hydrogenation catalyst can also be formed in situ in the presence of ancillary ligands by combining a metal compound with at least one ancillary ligand to form a catalytically active metal complex in the reaction medium.

[0091] Suitable pre-catalysts are selected from neutral metal complexes, oxides and salts of transition metals. Preferred pre-catalysts are selected from metal complexes, oxides and salts of manganese, rhenium, ruthenium, iridium, nickel, palladium and platinum.

[0092] In the context of this application, "COD" denotes 1,5-cyclooctadiene, "Cp" denotes cyclopentadienyl, "Cp*" denotes pentamethylcyclopentadienyl, and "binap" denotes 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl.

[0093] Suitable rhenium precatalysts are selected from ammonium perrhenate, chlorotricarbonyl(2,2'-bipyridine)rhenium(I), chlorotricarbonyl(4,4'-di-t-butyl-2,2'-bipyridine)rhenium(I), cyclopentadienylrhenium tricarbonyl, iododioxobis(triphenylphosphine)rhenium(V), methyltrioxorhenium(VII), pentamethylcyclopentadienylrhenium tricarbonyl, rhenium carbonyl, rhenium chloride(V), rhenium pentacarbonyl bromide, and trifluoromethylsulfonatotricarbonyl(2,2'-bipyridine)rhenium(I).

[0094] Suitable ruthenium precatalysts are [Ru(methylallyl)2COD], [Ru(p-cymene)Cl2]2, and [Ru(benzene)Cl2] n , [Ru(CO)2Cl2] n, [Ru(CO)3Cl2]2, [Ru(COD)(allyl)], [RuCl3·H2O], [Ru(acetylacetonato)3], [Ru(DMSO)4Cl2], [Ru(PPh3)3(CO)(H)Cl], [Ru(PP h3)3(CO)Cl2], [Ru(PPh3)3(CO)(H)2], [Ru(PPh3)3Cl2], [Ru(Cp)(PPh3)2Cl], [Ru(Cp)(CO)2Cl], [Ru(Cp)(CO)2H], [Ru(Cp )(CO)2]2, [Ru(Cp*)(CO)2Cl], [Ru(Cp*)(CO)2H], [Ru(Cp*)(CO)2]2, [Ru(indenyl)(CO)2Cl], [Ru(indenyl)(CO)2H], [Ru(indenyl)(CO)2]2, ruthenocene, [Ru(binap)(Cl)2], [Ru(2,2'-bipyridine)2(Cl)2·H2O], [Ru(COD)(Cl)2H]2, [Ru(Cp*)(COD)Cl], [Ru3(CO) 12 ], [Ru(tetraphenylhydroxycyclopentadienyl)(CO)2H], [Ru(PMe3)4(H)2], [Ru(PEt3)4(H)2], [Ru(Pn-Pr3)4(H)2], [Ru(Pn-Bu3)4(H)2], and [Ru(Pn-octyl3)4(H)2], preferably selected from [Ru(methylallyl)2COD], Ru(COD)Cl2]2, [Ru(Pn-Bu3)4(H)2], [Ru(Pn-octyl3)4(H)2], [Ru(PPh3)3(CO)(H)Cl], and [Ru(PPh3)3(CO)(H)2], more preferably [Ru(PPh3)3(CO)(H)Cl.

[0095] Suitable iridium pre-catalysts are selected from [IrCl3·H2O], KIrCl4, K3IrCl6, [Ir(COD)Cl]2, [Ir(cyclooctene)2Cl]2, [Ir(ethene)2Cl]2, [Ir(Cp)Cl2]2, [Ir(Cp*)Cl2]2, [Ir(Cp)(CO)2], [Ir(Cp*)(CO)2], [Ir(PPh3)2(CO)Cl], and [Ir(PPh3)3Cl], preferably selected from [Ir(COD)Cl]2, [Ir(cyclooctene)2Cl]2 and [Ir(Cp*)Cl2]2.

[0096] Suitable nickel precatalysts include [Ni(COD)2], Ni(CO)4, NiCl2, NiBr2, NiI2, Ni(OAc)2[Ni(AcAc)2], [Ni(Cl)2(TMEDA)], [Ni(Cl)2(DME)], [Ni(Br)2(DME)], [Ni(Cl)2(PPh3)2], [Ni(CO)2(PPh3)], [Ni(Cl)(methallyl)]2, [Ni(CO3)], nickel(II) diethylglyoxime, 2-ethylhexyl The nickel(II) oxalate, nickel(II) hexafluoroacetate, nickel(II) hexafluoroacetotriacetonate, bis(N,N'-di-t-butylacetamidinato)nickel(II), nickel(II) oxalate, Ni(NO3)2, nickel(II) stearate, Ni(SO4), nickel(II) tetrafluoroborate hexahydrate, nickel(II) trifluoroaceylacetonate dehydrate, and nickel(II) trifluoromethanesulfonate.

[0097] Suitable palladium precatalysts include allyl(cyclopentadienyl)palladium(II), bis[(trimethylsilyl)methyl](1,5-cyclooctadiene)palladium(II), allylpalladium chloride dimer, ammonium tetrachloropalladate(II), bis[1,2-bis(diphenylphosphino)ethane]palladium(0), bis(dibenzylideneacetone)palladium(0), trans-bis(dicyclohexylamine)bis(acetato)palladium(II), and bis[1,2-bis(diphenylphosphino)ethane]palladium(0). Diacetato[1,3-bis(diphenylphosphine)propane]palladium(II), diacetatobis(triphenylphosphine)palladium(II), bis(2-methylallyl)palladium chloride dimer, bis(tri-t-butylphosphine)palladium(0), bis(tricyclohexylphosphine)palladium(0), bis(tri-o-tolylphosphine)palladium(0), chloromethyl(1,5-cyclooctadiene)palladium(II), diacetato[1,3-bis(diphenylphosphino)propane]palladium(II), diacetatobis(triphenylphosphine)palladium(I I), diacetato(1,10-phenanthroline)palladium(II), di-μ-bromobis(tri-t-butylphosphino)dipalladium(I), trans-dibromobis(triphenylphosphine)palladium(II), dibromo(1,5-cyclooctadiene)palladium(II), dichlorobis(benzonitrile)palladium(II), dichlorobis(di-t-butylphenylphosphino)palladium(II), di-μ-chlorobis{2-[(dimethyl trans-dichlorobis(tricyclohexylphosphine)palladium(II), trans-dichlorobis(triphenylphosphine)palladium(II), dichloro(1,5-cyclooctadiene)palladium(II), dichloro(norbornadiene)palladium(II), cis-dichloro(N,N,N',N'-tetramethylethylenediamine)palladium(II), cis-dimethyl(N,N,N',N'-tetramethylethylenediamine)palladium(II), (1-methylallyl)palladium chloride dimer, palladium(II) acetate, palladium(II) acetylacetonate, palladium(II) benzoate, palladium(II) bromide, palladium(II) chloride, palladium(II) hexafluoroacetylacetonate, palladium(II) iodide, palladium(II) sulfate, palladium(II) trifluoroacetate, palladium(II) trimethylacetate, tetrakis(triphenylphosphine)palladium(0), and tris(dibenzylideneacetone)dipalladium(0).

[0098] Suitable platinum precatalysts are ammonium tetrachloroplatinate(II), bis(tri-t-butylphosphine)platinum(0), bis(ethylenediamine)platinum(II) chloride, dibromo(1,5-cyclooctadiene)platinum(II), dichlorobis(benzonitrile)platinum(II), cis-dichlorobis(diethylsulfide)platinum(II), cis-dichlorobis(pyridine)platinum(II), cis-dichlorobis(triethylphosphine)platinum(II), dichloro(1,5-cyclooctadiene)platinum(II), cis-dichlorodiammineplatinum(II), and dichlorodichlorobiphenyl(μ-chlorodichlorobiphenyl). The platinum(II) salt is selected from the group consisting of bis(ethylene)diplatinum(II), dichloro(dicyclopentadienyl)platinum(II), di-μ-iodobis(ethylenediamine)diplatinum(II) nitrate, diiodo(1,5-cyclooctadiene)platinum(II), dimethyl(1,5-cyclooctadiene)platinum(II), platinum(II) acetylacetonate, platinum(II) acetylacetonate, platinum(II) bromide, platinum(II) chloride, platinum(II) iodide, potassium bis(oxalato)platinate(II) dihydrate, tetrakis(triphenylphosphine)platinum(0) and tris(dibenzylideneacetone)diplatinum(0).

[0099] Suitable manganese precatalysts are MnCl2, MnCl2·4H2O, MnBr2, MnBr2·4H2O, MnBr2·2THF, manganocene, [Mn(cyclopentadienyl)(CO)3], [Mn(methylcyclopentadienyl)(CO)3], [Mn(pentamethylcyclopentadienyl)(CO)3], MnOAc2, MnOAc2·4H2O, MnOAc3·2H2O, Mn(II) acetylacetonate, Mn(III) acetylacetonate, Mn(CO) 10 , Mn(NO3)2, [Mn(Br)(CO)5], and Mn(ClO4)2 6H2O.

[0100] The hydrogenation catalysts comprising the polydentate ligand according to general formula (I) may be used in hydrogenation reactions without the need for an additional base, however, higher activity is usually obtained by combining a catalytic amount of a base with the hydrogenation catalyst.

[0101] In one embodiment, the hydrogenation reaction is carried out in the presence of a base, preferably an alkali metal or alkaline earth metal carbonate, an alkali metal or alkaline earth metal hydroxide or an alkali metal or alkaline earth metal alcoholate. Preferably, the base is an alkali metal alcoholate, such as potassium tert-butoxide.

[0102] Generally, a base is present in the hydrogenation reaction within the amount of hydrogenation catalyst used. Suitably, the base is present in an amount of 1 to 50 equivalents, preferably 1 to 10 equivalents, more preferably 1 to 4 equivalents based on the amount of hydrogenation catalyst.

[0103] The process of the invention for hydrogenating polyurethane rigid foams can be carried out in conventional equipment and / or reactors known to the skilled person for gas-liquid reactions in which the hydrogenation catalyst is in the liquid phase. It is in principle possible to use any reactor for the process of the invention which is basically suitable for gas-liquid reactions at the stated temperatures and the stated pressures. For standard reactors suitable for gas-liquid and liquid-liquid reaction systems, see, for example, Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH Verlag GmbH&Co.KGaA, chapter 3.3, Reactor Types and Their Industrial Applications and Reactors for gas-liquid reactions. Suitable examples include, for example, stirred tank reactors, tubular reactors or bubble column reactors. The feeding of the polyurethane rigid foam, the hydrogenation catalyst, the organic solvent and the base can take place simultaneously or separately from one another. The reaction can be carried out discontinuously in batch mode, with or without recycle, or continuously, semi-continuously. The average residence time in the reaction space can be varied within a wide range, preferably within the range of 15 minutes to 100 hours, more preferably within the range of 1 to 50 hours.

[0104] Generally, the aprotic organic solvent is used in an amount sufficient to swell or partially dissolve the polyurethane rigid foam. As the hydrogenation reaction proceeds, the polyurethane rigid foam gradually dissolves in the reaction solution. Suitably, the ratio of the aprotic organic solvent to the polyurethane rigid foam is in the range of 0.1-100 L of aprotic organic solvent per kg of polyurethane rigid foam, preferably 1-20 L of aprotic organic solvent per kg.

[0105] The present invention can be further explained and illustrated by the following examples, although it will be understood that these examples are provided for illustrative purposes only and are not intended to limit the scope of the invention in any way. [Brief description of the drawings]

[0106] [Figure 1] FIG. 1 shows a comparison of the 31P NMR spectra of a sample of flame retardant TCPP (top) and the flame retardant obtained after hydrogenation of PU rigid foam Index 100 (bottom). EXAMPLES

[0107] material All chemicals and solvents were purchased from Sigma-Aldrich or ABCR unless otherwise stated and used without further purification. 1 H, 13 C and 31 P NMR spectra were recorded on a Bruker Avance 200 MHz or 400 MHz spectrometer and were determined by subtracting residual protons ( 1 H) or carbon ( 13 C) Resonance peaks were used as reference. Chemical shifts (δ) are reported in ppm. 31 P NMR spectra were referenced to an external standard (sufficient D3PO4).

[0108] In the following hydrogenation examples, a PU rigid foam index of 100 was used. The PU rigid foam index of 100 is based on 74 parts by weight of Lupranol 3422 (a commercial polyether polyol based on sorbitol and propylene oxide, containing only secondary hydroxyl groups, available from BASF SE, Germany), 20 parts by weight of Lupragen TCPP (flame retardant tris(2-chloroisopropyl) phosphate), 3 parts by weight of Tegostab B 842045 (a silicone surfactant, available from Evonik Industries AG), 0.5 parts by weight of Lupragen N600 (a tertiary amine, available from BASF SE, Germany), 2.5 parts by weight of water, 5 parts by weight of cyclopentane, and 100 parts by weight of Lupranat MP 102 (a short-chain prepolymer based on pure 4,4'-diphenylmethane diisocyanate, available from BASF SE, Germany), thus containing 9.4% by weight of flame retardant TCPP in the final PU rigid foam. The results are summarized in Table 1.

[0109] Hydrogenation catalysts P and Q were prepared according to literature protocols: E. Balaraman, J. Am. Chem. Soc. 2010, 132, 16756-16758 and D. Srimani, Adv. Synth. Catal. 2013, 355, 2525-2530. Hydrogenation catalyst Mn-1 was prepared similarly to literature protocols: W. Zhou, ChemSusChem 2021, 14, 4176-4180 (ligand synthesis) and V. Zubar, Angew. Chem. Int. Ed. 2018, 57, 13439-13443 (complex synthesis) using Mn(CO)5Br as the metal precursor. The hydrogenation catalyst Mn-5 was prepared according to literature protocols: W. Zhou, ChemSusChem 2021, 14, 4176-4180 and UKDas, ACS Catal. 2018, 9, 479-484.

[0110] Reference Example 1: Synthesis of hydrogenation catalyst H [ka]

[0111] First step: In a 50 mL Schlenk tube, 6-methyl-2,2'-bipyridine (511 mg, 3.00 mmol) was dissolved in 15 mL of Et2O, cooled to 0°C, and LDA (3.50 mL, 1 M, in THF / hexanes) was added dropwise. After stirring at 0°C for 1 hour, the system was i Cooled to -80°C with PrOH / liquid N2, ClPCy2 (815 g, 3.50 mmol) in 5 mL of Et2O was added slowly. After 1 h, the cooling bath was removed and the mixture was allowed to warm slowly to room temperature and stirred overnight. The reaction mixture was quenched by adding 10 mL of degassed water to the yellow slurry. The organic phase was separated and the aqueous phase was extracted with ether (5 mL x 2). The combined organic phase was dried over Na2SO4, filtered and the solvent was removed to give the crude ligand as a viscous orange oil. 31 52% purity based on P NMR, which was used directly in the next step without further purification.

[0112] Step 2: The ligand from step 1 was dissolved in 20 mL of THF. RuHCl(CO)(PPh3)3 (952 mg, 1.00 mmol) was added and the mixture was stirred at 70 °C for 5 h and then cooled to room temperature. The solvent was reduced to approximately 10 mL under vacuum and 20 mL of Et2O was added to the remaining red-orange dispersion. The solution was removed via cannula and the solid was washed with Et2O (10 mL x 2) and dried under vacuum to give 465.2 mg of orange product (87% yield based on Ru). 31 P{ 1 H}NMR (122MHz, CD2Cl2) δ83.68. 1H NMR(301MHz,CD2Cl2)δ9.22-9.13(m,1H),8.07-7.97(m,1H),7.93(d,J=8.0Hz,1H),7.86(td,J=8.0,1.6Hz,1H),7.82(td,J=8.0,0.9H z,1H),7.49(d,J=7.7Hz,1H),7.45-7.39(m,1H),3.82-3.56(m,2H),2.46-2.27(m,2H),2.08-0.99(m,20H),-14.83(d,J=23.6Hz,1H). 13 C{ 1 H}NMR(126MHz,CD2Cl2)δ207.71(d,J=14.9Hz),161.70(d,J=5.1Hz),156.38,154.78(d,J=2.7Hz),153.51(d,J=1.7 Hz),137.30,136.51,126.42(d,J=1.9Hz),123.13(d,J=9.6Hz),122.76(d,J=1.6Hz),119.73,40.59(d,J=22.2Hz),3 8.59(d,J=23.4Hz),35.76(d,J=28.9Hz),31.01(d,J=2.9Hz),29.60(d,J=4.2Hz),28.61(d,J=4.5Hz),28.20(d,J=1 3.6Hz), 27.73, 27.56 (d, J = 9.2 Hz), 26.82 (d, J = 4.4 Hz), 26.74 (d, J = 3.5 Hz), 26.71 (d, J = 2.0 Hz), 26.35 (d, J = 1.5 Hz). HRMS(ESI): m / z calculated value C 24 H 32 N2OPRu as [M-Cl] + :497.1296, actual value:497.1291.

[0113] Reference Example 2: Synthesis of hydrogenation catalyst Mn-1 [ka]

[0114] Step 1: Cy-PNN ligand was synthesized in a similar manner to the procedure described above for hydrogenation catalyst H and used in the next step without further purification.

[0115] Second step: To a solution of Cy-PNN ligand (406 mg, 1.11 mmol) in 4 mL of THF was added an orange solution of Mn(CO)5Br (240 mg, 0.88 mmol) in 10 mL of THF under argon atmosphere and the reaction mixture was kept stirring at room temperature for 24 h (Note: liberated CO gas needs to be removed occasionally under vacuum). The solution was evaporated under vacuum. The solid residue was washed with pentane (10 mL) and evaporated to give a dark brown solid product. The brown crude product was dissolved in THF (15 mL) and the solution was filtered, concentrated, overlaid with pentane and kept in the refrigerator (-30 °C) to give a dark red solid in 71% (350 mg, based on Mn) yield. 31 P{ 1 H}NMR (162 MHz, CDCl3) δ 89.77.

[0116] Example 1: Hydrogenation of polyurethane rigid foam containing phosphorus ester flame retardant A stainless steel autoclave (Premex) equipped with a Teflon insert was charged with PU rigid foam index 100 (1.00 g). Catalyst and base were added in the glove box. The walls were rinsed with the indicated solvent and the autoclave was closed. Outside the glove box, the autoclave was flushed with hydrogen gas (5 bar x 2) and charged with hydrogen gas (50 bar). The autoclave was heated to 200 °C under stirring (preheated metal block, 750 RPM) for 21 h. After cooling to room temperature (ice bath), the residual pressure was carefully released. The suspension was filtered through a suction filter and the remaining solid was washed with dichloromethane (5 mL x 3) and EtOH (5 mL x 3). The solid residual polymer was dried under reduced pressure (room temperature, <5.0 10 -2The conversion was determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the δ-NMR spectroscopy (δ-δ) δ-δ ... 1 H and 31 It was analyzed by P NMR spectroscopy. 1 In H NMR, the amount of TCPP in the corresponding sample was determined by integration of the TCPP signal (δ = 4.67 ppm) relative to the 1,1,2,2-tetrachloroethane signal (δ = 6.00 ppm). The samples listed in Table 1 contained undecomposed flame retardant.

[0117] [Table 1]

[0118] As can be seen from Figure 1, the phosphorus ester flame retardants in Table 1 are 31 It remained undecomposed as evident from the P NMR. Figure 1 shows the comparison of the flame retardant TCPP sample (top) and the flame retardant obtained after hydrogenation of PU rigid foam index 100 (bottom). 31 A comparison of the P NMR spectra is shown. All relevant signals in the range of -4.10 to -3.55 ppm are 31 It is also detected in the P NMR spectrum.

[0119] Example 2: Hydrogenation of polyurethane rigid foam (5 g) containing phosphorus ester flame retardant A stainless steel autoclave (Premex) equipped with a Teflon insert was charged with PU rigid foam index 100 (5.12 g). Mn-5 (200 μmol) and KOtBu (400 μmol) were added in the glove box. The walls were rinsed with THF (40 mL) and toluene (40 mL) and the autoclave was closed. Outside the glove box, the autoclave was flushed with hydrogen gas (15 bar × 2) and finally filled with hydrogen gas (50 bar). The autoclave was heated to 200 °C under stirring (preheated metal block, 750 RPM) for 21 h. After cooling to room temperature (ice bath), the residual pressure was carefully released. The suspension was filtered through a suction filter and the remaining solid was washed with dichloromethane (20 mL × 3). The solid residual polymer was dried under reduced pressure (room temperature, <5.0·10 -2 mbar) was used to determine the conversion (conversion = [(polymer used - polymer recovered) / polymer used] x 100). The conversion of the hydrogenation of PU rigid foam index 100 was 62%. After removing the solvent of the filtrate under reduced pressure (45 °C, minimum pressure 80 mbar), the residue was diluted with 1.4·10 -1 The resulting fractions were purified by distillation in a Kugelrohr oven at 150-170 °C (pressure 1000 psi, mbar). 1 H and 31 Analysis by P NMR spectroscopy. TCPP was obtained as a pale yellowish oil (404 mg).

[0120] Comparative Example 1: Hydrolytic depolymerization of polyurethane rigid foam containing phosphorus ester flame retardant As a comparative example, hydrolytic depolymerization of polyurethane rigid foam was carried out instead of hydrogenative depolymerization. For this purpose, a sample of PU rigid foam containing phosphorus ester flame retardant (index 100, composition see above) was hydrolyzed with a mixture of pyridine and water at 160 °C in a sealed glass pressure tube. [ka]

[0121] After the reaction, a reaction mixture containing no solids was obtained in the form of a dark brown solution. 4,4'-methylenedianiline was detected by analyzing the reaction mixture by GC / MS. However, the GC / MS data 31 P NMR data showed that the reaction mixture contained no phosphorus ester flame retardants, which were thus hydrolyzed under these conditions.

[0122] Experimental details: In air, a stainless steel autoclave (Premex) equipped with a Teflon insert was filled with PU rigid foam index 100 (1.00 g). The walls were rinsed with pyridine (20 mL) and water (2 mL). The autoclave was closed and heated to 160° C. for 16 h. After cooling to room temperature (ice bath), the brown solution was filtered through a suction filter and the filter was rinsed with EtOH (5 mL×3). No solids remained on the filter. The solvent was removed under reduced pressure (45° C., minimum pressure 60 mbar). 1 H and 31 No flame retardants were detected in the crude or isolated samples by P NMR analysis.

[0123] Comparative Example 2: Hydrogenolysis of polyurethane rigid foam containing phosphorus ester flame retardant using MACHO catalyst in isopropanol The results and conditions of the following procedures are summarized in Table 2.

[0124] A stainless steel autoclave (Premex) equipped with a Teflon insert was charged with PU rigid foam index 100 (1.00 g). Catalyst and base were added in the glove box. The walls were rinsed with isopropanol and the autoclave was closed. Outside the glove box, the autoclave was flushed with hydrogen gas (15 bar x 2) and finally filled with hydrogen gas (50 bar). The autoclave was heated to 180 °C under stirring (preheated metal block, 750 RPM) for 21 h. After cooling to room temperature (ice bath), the residual pressure was carefully released. The suspension was filtered through a suction filter and the remaining solid was washed with dichloromethane (5 mL x 3) and EtOH (5 mL x 3). The solid residual polymer was dried under reduced pressure (room temperature, <5.0 10 -2 The conversion was determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the NMR spectroscopy (NMR spectroscopy) at 1000 Hz and 100 Hz, respectively. The conversion was then determined by the NMR spectroscopy (NMR spectroscopy) and the δ-NMR spectroscopy (δ-δ) δ-δ ... 1 H and 31 It was analyzed by P NMR spectroscopy. 1 In H NMR, the amount of TCPP in the corresponding sample was determined by integration of the TCPP signal (δ = 4.67 ppm) relative to the 1,1,2,2-tetrachloroethane signal (δ = 6.00 ppm).

[0125] The reaction mixture of entry 2 was further purified by flash column chromatography (EtOAc-hexanes) to determine the amount of amine. Finally, the polyol fraction was eluted by flushing the silica pad with EtOH.

[0126] [Table 2]

[0127] Comparative Example 3: Stability of TCPP (mixture of isomers, flame retardant) under Mn- or Ru-catalyzed hydrogenation conditions in various solvents The results and conditions of the following procedures are summarized in Table 3.

[0128] Inside the glove box, a stainless steel autoclave (Premex) was charged with catalyst, base and TCPP (mixture of isomers, flame retardant). The walls were rinsed with solvent and the autoclave was closed. Outside the glove box, the autoclave was flushed with hydrogen gas (15 bar x 2) and finally filled with hydrogen gas (50 bar). The autoclave was heated to the indicated temperature under stirring (preheated metal block, 750 RPM) for 21 h. After cooling to room temperature (ice bath), the residual pressure was carefully released. The resulting mixture was filtered through a short Celite pad in a Pasteur pipette and the pad was washed with dichloromethane (5 mL x 3). After removal of the solvent under reduced pressure (45 °C, minimum pressure 80 mbar), the residue was weighed and 1 H and 31 The amount of recovered flame retardant was determined by analysis with P NMR (recovery rate = [(amount of TCPP detected) / (amount of TCPP used)] × 100).

[0129] [Table 3]

[0130] Under hydrogenation conditions in the presence of an aprotic solvent, 31 As is evident from the P NMR (−4.10 to −3.55 ppm), the phosphorus ester flame retardant (see Table 3 ) remained undecomposed.

[0131] However, under hydrogenation conditions in the presence of a protic solvent such as isopropanol, 31 In the 1H NMR spectrum, only a nonspecific and very broad flat signal (δ -31.76 to +20.82 ppm) was detected.

Claims

1. A value chain recovery process for polyurethane rigid foam containing at least one phosphate ester flame retardant, - In aprotic organic solvent, - Under a hydrogen atmosphere, - In the presence of at least one homogeneous transition metal catalyst complex [wherein the transition metal is selected from metals of Group 7, Group 8, Group 9 and Group 10 of the periodic table according to IUPAC], - At a reaction temperature of at least 120°C Hydrogenating the polyurethane rigid foam to obtain a hydrogenation product containing a polyamine and a polyol from the polyurethane rigid foam, and To recover the flame retardant from the hydrogenation product. A process that includes this.

2. The process according to claim 1, wherein the polyamine is recovered from the hydrogenation product by distillation.

3. The process according to claim 1 or 2, wherein the flame retardant is recovered by distillation from the hydrogenation product or its distillation bottom.

4. The process according to claim 1 or 2, wherein the polyol is recovered from the hydrogenation product or from the distillation bottom thereof by extraction, or recovered as a distillation bottom after removal of volatile components.

5. The process according to claim 1 or 2, wherein the polyurethane rigid foam is selected from aromatic isocyanate-based polyurethane rigid foams, preferably from methylenedi(phenylisocyanate)-based polyurethane rigid foam, polymeric methylenedi(phenylisocyanate)-based polyurethane rigid foam, and 1,5-naphthyldiisocyanate-based polyurethane rigid foam.

6. The process according to claim 1 or 2, wherein the at least one phosphate ester flame retardant is selected from tris(2-chloroethyl) phosphate, tris(chloroisopropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(2-ethylhexyl) phosphate, tricresyl phosphate, tris(2,3-dibromo) phosphate, tetrakis(2-chloroethyl)ethylenediphosphate, dimethyl phosphonate, dimethyl propylphosphonate, diphenylcresyl phosphate, triethyl phosphate, and mixtures thereof.

7. The process according to claim 1 or 2, wherein the aprotic organic solvent is selected from ethers, aromatic hydrocarbons, and mixtures thereof.

8. The process according to claim 7, wherein the ether is selected from tetrahydrofuran, 1,4-dioxane, and anisole, and the aromatic hydrocarbon is selected from benzene, toluene, xylene, and mesitylene.

9. The process according to claim 1 or 2, wherein the homogeneous transition metal catalyst complex comprises a transition metal selected from manganese, rhenium, ruthenium, iridium, nickel, palladium, and platinum, preferably a transition metal selected from manganese, ruthenium, and iridium.

10. The process according to claim 1 or 2, wherein the homogeneous transition metal catalyst complex comprises at least one polydentate ligand having at least one nitrogen atom and at least one phosphorus atom that can coordinate to the transition metal.

11. The above at least one polydentate ligand is given by general formula (I) 【Chemistry 1】 [In the formula, Each R' is independently H or C １ ~C ４ -It is alkyl, R １ and R ２ They are independent of each other, C １ ~C １２ - Alkyl, cycloalkyl, or aryl, The alkyl group is either unsubstituted or has one, two, three, four, or five identical or different substituents R. ７ Hold, The cycloalkyl and aryl atoms are either unsubstituted or have one, two, three, four, or five identical or different substituents R. ８ Hold, R ３ and R ４ are, independently of each other, H or C １ ~C １２ -alkyl (which is unsubstituted or holds 1, 2, 3, 4 or 5 identical or different substituents selected from heterocycloalkyl, aryl, hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy, hydroxyl, NE １ E ２ and PR １ R ２ ). R ５ is H or C １ ~C １２ -Alkyl (this is either unsubstituted or has 1, 2, 3, 4, or 5 identical or different substituents R) ７ (holds) R ６ is H or C １ ~C ４ - Is it alkyl? or R ４ and R ６ It does not exist, R ３ and R ５ R ３ The nitrogen atom and R to which it is bonded ５ Along with the carbon atom to which it is bonded, a six-membered heteroaromatic ring (which is either unsubstituted or C) １ ~C １２ - It retains one, two, three, four, or five identical or different substituents selected from alkyl, cycloalkyl, aryl, and hetalil, wherein the alkyl is either unsubstituted or has one, two, three, four, or five identical or different substituents R ７ The cycloalkyl, aryl and hetalil are either unsubstituted or alkyl substituents (which are either unsubstituted or alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaliloxy, hydroxyl, NE １ E ２ and PR １ R ２ Forms a substituent that is selected from, Each R ７ These are independently cycloalkyl, heterocycloalkyl, aryl, hetalyl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetalyloxy, hydroxyl or NE １ E ２ And, Each R ８ Independently, C １ ~C ４ - Alkyl, cycloalkyl, heterocycloalkyl, aryl, hetalyl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetalyloxy, hydroxyl or NE １ E ２ And, E １ and E ２ H and C are independent of each other and appear independently of each other. １ ~C １２ - A group selected from alkyl, cycloalkyl, and aryl groups. The process according to claim 10.

12. The above at least one polydentate ligand is given by General Formula (II) 【Chemistry 2】 [In the formula, D is H, C １ ~C １２ - Alkyl, cycloalkyl, aryl, or hetalil, The alkyl group is either unsubstituted or has one, two, three, four, or five identical or different substituents R. ７ Hold, The cycloalkyl, aryl, or hetalil may be unsubstituted or have an alkyl substituent (this may be unsubstituted or have an alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaliloxy, hydroxyl, NE １ E ２ and PR １ R ２ Preferably NE １ E ２ and PR １ R ２ [Holds a substituent selected from] The process according to claim 11.

13. The aforementioned at least one polydentate ligand is compound A to L [In the formula, Et is ethyl, ｉ Pr is isopropyl, ｔ [Bu is tert-butyl, Cy is cyclohexyl, and Ph is phenyl] 【Transformation 3】 A process according to claim 10, selected from the following.

14. The process according to claim 1 or 2, wherein the hydrogenation reaction is carried out at an absolute pressure of 30 to 500 bar, preferably 40 to 300 bar, and more preferably 50 to 200 bar.

15. The process according to claim 1 or 2, wherein the hydrogenation reaction is carried out in the presence of a base, preferably an alkali metal carbonate or alkaline earth metal carbonate, an alkali metal hydroxide or alkaline earth metal hydroxide, or an alkali metal alkoxide or alkaline earth metal alkoxide, more preferably an alkali metal tert-butoxide.

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