Value chain return method for recovery of unbound additives by extraction from polyurethane or polyisocyanurate rigid foam and depolymerization of polyurethane rigid foam

Abstract

The present invention relates to a value chain return method for polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bonded to the polymer chain, selected from the group consisting of phosphite flame retardants, polymerization catalysts, and surfactants, the method comprising the steps of: preparing a composition comprising ground polyurethane or polyisocyanurate rigid foam, wherein the ground foam has a content of intact cells of less than 10% based on the number of intact cells in the unground polyurethane or polyisocyanurate rigid foam; and extracting the additive (A1) with a solvent at a temperature below 190°C.

Description

[Technical Field]

[0001] The present invention relates to a value chain return method for polyurethane rigid foams, which allows the phosphite flame retardants and other additives not bound to the polymer chain to be recovered by extraction.

[0002] In particular, the present invention relates to a value chain return method for polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bound to the polymer chain and is selected from the group consisting of phosphite flame retardants, polymerization catalysts and surfactants, the method comprising the steps of: preparing a composition comprising ground polyurethane or polyisocyanurate rigid foam, wherein the ground foam has a content of intact cells of less than 10% based on the number of intact cells in the unground polyurethane or polyisocyanurate rigid foam; and extracting the additive (A1) with a solvent at a temperature below 190°C.

[0003] The present invention also relates to a phosphite flame retardant obtained or obtainable by the above process and its use for the preparation of polyurethanes or polyisocyanurates.Furthermore, the present invention also relates to a polymerization catalyst obtained or obtainable by the above process and a surfactant obtained or obtainable by the above process and their use for the preparation of polyurethanes or polyisocyanurates.

[0004] 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.

[0005] 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.

[0006] Therefore, there is a need to develop processing technologies to recover materials from plastic waste. It is desirable that the recycling process reduce both material waste and the carbon footprint. Furthermore, it should be economical and energy-efficient, resulting in useful materials with high technical characteristics. In contrast, disposal, for example by combustion, has a negative impact on the environment as well as the carbon footprint.

[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 basic reaction leading to polyurethane foams, provided no external blowing agents, such as low-boiling hydrocarbons, are used.

[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 result from short chains with many crosslinks. Further details on polyurethane rigid foams suitable for use in accordance with the present invention can be found in the Polyurethane Handbook, 2nd edition, 1993, chapter 6.

[0010] Polyurethane rigid foams exhibit excellent thermal insulation properties. For this reason, they are very important in the construction sector, and are commonly used as thermal insulation materials for, for example, insulating buildings. However, in order to apply polyurethane rigid foams as thermal insulation materials in buildings, the addition of flame retardants is required for fire prevention reasons. For this purpose, flame retardants are added during the production process of polyurethane rigid foams. Currently, phosphites, such as tris(2-chloroethyl)phosphate, tris(chloroisopropyl)phosphate, tris(1,3-dichloro-2-propyl)phosphate, tris(2-ethylhexyl)phosphate, triethylphosphate, tricresylphosphate, tris(2,3-dibromo)phosphate, tetrakis(2-chloroethyl)ethylenediphosphate, dimethylphosphonate, dimethylpropylphosphonate, diphenylcresylphosphate, and mixtures thereof, are primarily used as flame retardants in polyurethane rigid foams for construction applications (see Chemosphere, 2012, 88, 1119-1153 and WO 2015 / 121057). These flame retardants are not chemically bound to the polyurethane polymer chain.

[0011] In addition to these flame retardants, there are also a few other beneficial additives that come from the polymer synthesis, such as polymerization catalysts and surfactants, that are not chemically bound to the polyurethane polymer chain. It would also be desirable to recover these additives along with the flame retardants and reuse them in the synthesis of new polyurethane rigid foams.

[0012] Recycling polyurethane rigid foams into useful monomer compounds and recovering phosphite flame retardants and other additives remains challenging. Polyol compounds and amines can be recovered and recycled not only by glycolysis or hydrolysis (see "Plastics recycling and Polyurethanes," in Ullmann's Encyclopedia of Industrial Chemistry, 2020, DOI: 10.1002 / 14356007.a21_057.pub2), but also by hydrogenation in the presence of a hydrogenation catalyst (see ChemSusChem, 2020, DOI: 10.1002 / cssc.20200246 or ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705).

[0013] U.S. Patent No. 4,196,148 describes a method for hydrolyzing polyurethane foam and recovering diamines and polyethers (or polyesters) from the hydrolyzate, carried out at near atmospheric pressure and temperatures above 185° C. The work does not demonstrate recovery of flame retardants.

[0014] While hydrolysis of polyurethane foams allows for the recycling of constituent monomers, phosphorous 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 that the flame retardant cannot be reused, but the hydrolysis products of the esters can also contaminate polyols and / or polyamines, potentially leading to more complex, resource-intensive, and costly workup methods.

[0015] Therefore, there would be great economic interest in recycling and depolymerizing polyurethane rigid foams so that the polyols, polyamines, and phosphite flame retardants could be obtained.

[0016] T. Skrydstrup et al., JACS Au, 2021, DOI: 10.1021 / jacsau.1c00050, describes the depolymerization of polyurethanes using a 2 mol% homogeneous iridium catalyst with tridentate P,N,P ligands in 2-propanol as solvent at 150 °C and 30 bar H2 pressure. In this work, methylene di(phenyl isocyanate)-based polyurethane rigid foams derived from refrigerator insulation were hydrogenated to give the corresponding diamines and polyols. The authors: 31 A phosphorous compound with a signal at 20.00 ppm in the P NMR spectrum was detected in the polyol fraction. It was suggested that this phosphorous compound may be a phosphorous flame retardant, but further confirmation, characterization, or isolation of this unknown phosphorous compound was not attempted. However, PU rigid foams used in refrigerator insulation typically do not contain phosphorous flame retardants. Furthermore, the phosphite ester flame retardants commonly used in polyurethane rigid foams are: 31They do not have chemical shifts around 20 ppm in the P NMR spectrum, and are usually less than 1 ppm: -2.5 ppm for tris(2-chloroethyl)phosphate (see Zhurnal Obshchei Khimii, 1978, 78, 694-695), -4.2 ppm for tris(chloroisopropyl)phosphate (measured on a reference sample), 0.24 ppm for tris(2-ethylhexyl)phosphate (see J. Chem. Eng. Data, 2008, 53, 2718-2720), or -0.8 ppm for triethylphosphate (see Phosphorus, Sulfur and Silicon and the Related Elements, 1991, 61, 31-39). Therefore, Skrydstrup et al. do not disclose the recovery of phosphite flame retardants from polyurethane rigid foams. The authors state: 31 In the P NMR spectrum, the phosphine oxide of the phosphine ligand of the catalyst used was most likely detected. The oxide of the PNP ligand, Ph2P(O)C2H4NHC2H4P(O)Ph2, is 31 It has a phosphine oxide signal at 20 ppm in the P NMR spectrum (measured on a reference sample of the oxidized PNP ligand).

[0017] T. Schaub et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101606, describes the depolymerization of polyurethanes using 2-4 mol% of a homogeneous manganese catalyst bearing a tridentate P,N,N ligand in toluene or THF at 130-200 °C and 60 bar H2 pressure. This system was applied to methylene di(phenyl isocyanate)-based polyurethane rigid foams, affording the corresponding diamines and polyols, which could be isolated. The rigid foams did not contain phosphorous-based flame retardants.

[0018] T. Skrydstrup et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705, describes the depolymerization of polyurethanes using 1 mol% of a homogeneous manganese catalyst with tridentate P,N,P ligands in 2-propanol as solvent at 180 °C and 50 bar H2 pressure. The system was applied to methylene di(phenyl isocyanate)-based polyurethane rigid foams derived from refrigerator insulation and decorative polyurethane rigid foams. In both cases, the corresponding diamines and polyols could be obtained and isolated. The authors report: 31 In the P NMR spectra, a phosphorous acid compound with a signal at 31.00 ppm was detected in the polyol fraction obtained from decorative PU rigid foam, and a phosphorous acid compound with a signal at 32.05 ppm was detected in the polyol fraction obtained from PU rigid foam derived from refrigerator insulation. As mentioned above, the authors also suggested that the signals for these unknown phosphorous acid compounds might be derived from phosphorous-based flame retardants. Again, no further confirmation, characterization, or isolation of the unknown phosphorous acid compounds was performed. However, as discussed in more detail above, PU rigid foams used in refrigerator insulation and decoration typically do not contain phosphorous-based flame retardants. Furthermore, the phosphite-based flame retardants commonly used in polyurethane rigid foams are: 31 They do not have a chemical shift around 31 ppm in the P NMR spectrum, which is typically below 1 ppm (see above). Therefore, this work also does not disclose the recovery of phosphite flame retardants from polyurethane rigid foams.

[0019] In the plastic recycling processes described above, a method for recycling polyurethane rigid foam in a manner that recovers the phosphite flame retardant while simultaneously obtaining both the valuable amine and polyol components has not been disclosed.

[0020] It was therefore an object of the present invention to depolymerize polyurethane rigid foams containing additives that are not chemically bound to the polymer chain, such as flame retardants, stabilizers or catalysts, in particular phosphite flame retardants, to obtain polyols, aromatic amines and phosphite flame retardants, and other additives, which can preferably also be reused.

[0021] This objective has been achieved by a value chain return method for the extraction of polyurethane rigid foams containing at least one additive (A1) that is not chemically bound to the polymer chain, in particular at least one phosphite flame retardant, selected from the group consisting of phosphite flame retardants, polymerization catalysts, and surfactants. The method comprises extracting the phosphate flame retardant and other unbound additives with a solvent, in particular an organic aprotic solvent, at a temperature below 190°C and recovering them, followed by depolymerizing the remaining polyurethane rigid foam, preferably after extraction of the polyol and amine components, and separating the amine and polyol components.

[0022] The present invention relates to a value chain return method for polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bonded to the polymer chain and is selected from the group consisting of a phosphite flame retardant, a polymerization catalyst, and a surfactant, the method comprising the steps of: a) providing a composition comprising pulverized polyurethane or polyisocyanurate rigid foam, wherein the pulverized foam has an intact cell content of less than 10% based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam; b) extracting the additive (A1) with a solvent at a temperature below 190°C The present invention relates to a method, comprising:

[0023] "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 other value chains.

[0024] In the context of the present invention, "ground thermoplastic polyurethane or polyisocyanurate rigid foam" means that the material is obtained from a rigid foam and the ground thermoplastic polyurethane or polyisocyanurate is used, for example, in chopped form, in granular form, as an agglomerate, or as a powder. The polyurethane or polyisocyanurate rigid foam can be ground by conventional methods, for example, by chopping in a tumbling or rotary mill at room temperature, typically to a particle size of less than 20 mm, or by known cold grinding processes, for example. Preferably, a particle size of less than 5 mm is selected, for example, in the range of 0.01 mm to 5 mm, preferably 0.01 mm to 1 mm.

[0025] The method of the present invention includes steps a) and b) and may include further steps. According to step a), a composition comprising a pulverized polyurethane or polyisocyanurate rigid foam is prepared, wherein the pulverized foam has an intact cell content of less than 10% based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam. Suitable methods for preparing compositions comprising pulverized polyurethane or polyisocyanurate rigid foam are known in principle from the state of the art. "Intact cells" in the context of the present invention means that the cell structure and shape are similar, and preferably identical, to those of the unpulverized foam. According to the present invention, the cell structure of the pulverized rigid foam is preferably destroyed, and the resulting material has a closed cell content of less than 10%, preferably less than 5%, particularly less than 2%, more preferably less than 1%, and particularly preferably less than 0.5%, based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam. The composition may contain further components, such as a solvent.

[0026] Unless otherwise specified, in the context of the present invention, intact cell content is determined by optical microscopy of a sample of the material and comparison of the cell counts of each sample of unmilled and milled foam.

[0027] According to step b), the additive (A1) is extracted with a solvent at a temperature below 190°C. It is also possible to extract two or more additives in the extraction step according to the invention. Usually, at least 20%, preferably at least 30%, more preferably at least 40%, and in particular at least 50% of the additive (A1) present in the polyurethane or polyisocyanurate rigid foam is extracted in step b). Preferably, 50% to 100%, in particular 80% to 99.9%, more preferably 90% to 99% of the at least one additive (A1) is extracted in step b).

[0028] According to the present invention, the method may comprise two or more extraction steps using different solvents and / or different temperature ranges.

[0029] According to step b), a solvent containing the additive (A1) is obtained together with the remaining ground polyurethane or polyisocyanurate.

[0030] Preferably, the polyurethane or polyisocyanurate rigid foam obtained in step b) is subjected to a further process according to the invention, in particular a depolymerization process.

[0031] According to a further embodiment, the present invention provides a method for producing a medicament comprising the steps of: c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b) The present invention also relates to the method as disclosed above, further comprising:

[0032] The extraction step and the depolymerization of the comminuted polyurethane rigid foam can also be combined according to the present invention. It may also be possible for depolymerization or partial depolarization to occur during step b. Preferably, the extraction step and the depolymerization step are separate steps according to the present invention.

[0033] Suitable methods for depolymerization are known in principle to those skilled in the art. Preferably, depolymerization is achieved by hydrolysis, glycolysis, hydrogenation, or aminolysis according to the present invention. Preferably, depolymerization is achieved by glycolysis or hydrolysis according to the present invention.

[0034] Depending on the method used for depolymerization, different products are obtained. Typically, the isocyanate component is obtained and can be separated, but sometimes the polyol component is also separated, especially when depolymerization is achieved by glycolysis. The process of the present invention may include further separation steps.

[0035] According to a further embodiment, the present invention also relates to the process as disclosed above, wherein the depolymerization according to step c) is carried out by a process selected from hydrolysis, glycolysis, hydrogenation, or by aminolysis.

[0036] Surprisingly, in the value chain return method according to the present invention, additives (A1), particularly phosphite flame retardants, selected from the group consisting of phosphite flame retardants, polymerization catalysts, and surfactants, which are not chemically bound to the polymer chain, are recovered in a chemically unchanged form when extracted from used rigid polyurethane foams by extraction with a suitable solvent, particularly an aprotic organic solvent, at temperatures below 190°C. Surprisingly, using these conditions, the polymerization catalyst, surfactant, and phosphite flame retardant are not decomposed under the extraction conditions applied in the method. This allows the additives, particularly phosphite flame retardants, to be recovered before the polymeric polyurethane material is depolymerized into polyol components and isocyanates or their amine components.

[0037] Furthermore, the value chain return method described above allows for the extraction of phosphite flame retardants, which in turn extracts other additives that are not chemically bound to the polymer chain, such as polymerization catalysts (e.g., tertiary amines) and surfactants (e.g., siloxanes), along with the phosphite flame retardant. These can be obtained together with the phosphite flame retardant after removing the aprotic organic solvent used for extraction. The resulting mixture of the phosphite flame retardant, polymerization catalyst, and surfactant can then be used to synthesize new polyurethane rigid foams.

[0038] The process therefore allows for the recycling of the phosphite flame retardant, the polymerization catalyst and the surfactant.The value chain return process of the present invention for polyurethane rigid foams containing at least one phosphite flame retardant and further non-bonded additives results in a residual polyurethane material from which at least the phosphite flame retardant has previously been removed by extraction with a suitable solvent, in particular an aprotic organic solvent.

[0039] Preferably, the remaining ground polyurethane or polyisocyanurate obtained in step b) of the process is subjected to depolymerization, which allows recovery of both starting material components from the polyurethane. The polyurethane components, e.g., polyols, are recovered directly or as valuable synthetic building blocks, such as polyamines, which can be easily converted to polyisocyanates.

[0040] The method according to the invention comprises steps a) and b) and optionally c), 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.

[0041] 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) or between steps b) and c). 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 c) can also be carried out immediately after step b).

[0042] According to the invention, steps a) and b) can also be combined and carried out in the same apparatus. It is also possible that the composition provided in step a) comprises a solvent, for example a solvent that can be used in step b) of the method according to the invention.

[0043] According to the present invention, at least one additive (A1) that is not chemically bound to the polymer chain and is selected from the group consisting of a phosphite flame retardant, a polymerization catalyst, and a surfactant is extracted. According to the present invention, the additives that are not chemically bound to the polymer chain include phosphite flame retardants, polymerization catalysts, and surfactants that are commonly used in polyurethane or polyisocyanurate rigid foams.

[0044] Generally, the phosphite flame retardants used in polyurethane rigid foams, such as polyurethane rigid foams for construction applications, are represented by the general formula (i): [ka] [In the formula, R 1 and R 2 are 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, for example 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, for example Cl or Br, R 3 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, for example 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 R 3 -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, for example 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, for example Cl or Br. This applies to compounds of the formula:

[0045] Preferably, aryl is selected from phenyl and naphthyl.

[0046] In one embodiment, the phosphite flame retardant is selected from tris(2-chloroethyl)phosphate, tris(chloroisopropyl)phosphate, tris(1,3-dichloro-2-propyl)phosphate, tris(2-ethylhexyl)phosphate, triethylphosphate, tricresyl phosphate, tris(2,3-dibromo)phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, dimethyl phosphonate, dimethyl propyl phosphonate, diphenyl cresyl phosphate, and mixtures thereof.

[0047] Therefore, according to a further embodiment, the present invention also relates to the method as disclosed above, wherein the at least one phosphite flame retardant is selected from the group consisting of 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)ethylene diphosphate, dimethyl phosphonate, dimethyl propyl phosphonate, diphenyl cresyl phosphate, triethyl phosphate, and mixtures thereof.

[0048] Suitably, the phosphite flame retardant is present in the polyurethane rigid foam in an amount of 1 to 15% by weight, preferably 3 to 10% by weight, more preferably 5 to 8% by weight.

[0049] Suitably, the polymerization catalyst is present in the polyurethane rigid or polyisocyanurate foam in an amount of 0.1 to 10 wt%, preferably 0.25 to 5 wt%, more preferably 0.5 to 2.5 wt%. Typically, the surfactant is present in the polyurethane rigid or polyisocyanurate foam in an amount of 0.1 to 8 wt%, preferably 0.25 to 5 wt%, more preferably 0.5 to 2.5 wt%.

[0050] In addition to the phosphite flame retardant, polyurethane rigid foams typically also contain polymerization catalysts such as trialkylamines and surfactants such as siloxanes, which are also extracted during the flame retardant extraction process and can be obtained in admixture with the catalysts after removing the extraction solvent, preferably by distillation. Suitable methods for separating the individual compounds are known to those skilled in the art.

[0051] According to a further embodiment, the present invention also relates to the above disclosed method, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0052] Preferably, the polymerization catalyst is a tertiary amine, such as triethylamine, tributylamine, 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, dimethylpiperazine, N-dimethyla The alkylaminomethylpiperidine, 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.

[0053] According to a further embodiment, the present invention also relates to the method disclosed above, wherein the at least one surfactant is selected from the group consisting of silicone-based cell stabilizers.

[0054] Silicone-based cell stabilizers include silicone-based compounds that reduce the surface tension of polyesterols. These compounds are preferably amphiphilic, i.e., they have two molecular moieties with different polarities. Silicone-based cell stabilizers preferably have one molecular moiety with an organosilicon unit, such as dimethylsiloxane or methylphenylsiloxane, and one molecular moiety with a chemical structure somewhat similar to that of the polyol used. These are preferably polyoxyalkylene units. Silicone-based cell stabilizers particularly preferably include polysiloxane-polyoxyalkylene block copolymers with an oxyethylene content of less than 75% by weight, based on the total content of polyoxyalkylene units. These preferably contain polyethylene oxide and / or polypropylene oxide units. The molar mass of the polyoxyalkylene side chains is preferably at least 1000 g / mol of side chain. These compounds are known and are described, for example, in Plastics Handbook, Volume 7, Polyurethane, Carl Hanser Verlag, 3rd Edition 1993, Chapter 3.4.4.2. They can be produced, for example, by reacting a siloxane, such as polydimethylsiloxane, with a polyoxyalkylene, particularly polyethylene oxide, polypropylene oxide, or a copolymer of polyethylene oxide and polypropylene oxide. Here, it is possible to obtain a polysiloxane-polyoxyalkylene block copolymer having an oxyalkylene chain as a terminal group or one or more side chains. The silicone-based cell stabilizer (e) may contain OH groups, but preferably does not. This can be achieved by using a monofunctional alcohol, such as butanol, as a starter to produce the polyoxyalkylene.By way of example, silicone-based cell stabilizers used may be known foam stabilizers based on silicone, such as Niax Silicone L1501, L 1505, L 1540, L 1593, L 1602 or L 1609 from Monentive, Dabco® DC 193, Dabco® DC 3041, Dabco® DC 3042, Dabco® DC 3043, Dabco® DC 5000, Dabco® DC 5169, Dabco® DC 2525, Dabco® DC 2584 or Dabco® DC 5160 from Air Products, Tegostab® BF 2270, Tegostab® BF 2370, Tegostab® BF 2470, Tegostab® BF 2584 from Evonik, or Tegostab® BF 2670, Tegostab® BF 2770, Tegostab® BF 2870, Tegostab® BF 2970, Tegostab® BF 3070, Tegostab® BF 3170, Tegostab® BF 3270, Tegostab® BF 3370, Tegostab® BF 3470, Tegostab® BF 3570, Tegostab® BF 3670, Tegostab® BF 3770, Tegostab® BF 3870, Tegostab® BF 3970, Tegostab® BF 4070, Tegostab® BF 4170, Tegostab® BF 4270, Tegostab® BF 4370, Tegostab® BF 4470, Tegostab® BF 4570, Tegostab® BF 4670, Tegostab® BF 8110, Tegostab® B 8225, Tegostab® B 8255, Tegostab® B 8317, Tegostab® B 8325, Tegostab® B 8905, Tegostab® B 8946 PF, Tegostab® B 8948, Tegostab® B 8950, Tegostab® B 8952, Tegostab® B 8960, Tegostab® B 8498 or Tegostab® B 8486.

[0055] According to the present invention, the extraction of additive (A1) is carried out using a suitable solvent.Suitable solvents are known in principle, and include, for example, organic aprotic solvents, water, polyols and alcohols.Suitable polyols include those that can also be used as starting materials for the preparation of polyisocyanates or polyisocyanurates, such as diethylene glycol (DEG) or dipropylene glycol (DPG).

[0056] According to the invention, the mixture of solvent and additive (A1) obtained in the extraction step can also be used directly in the process for preparing polyurethanes or polyisocyanurates without further purification steps.

[0057] According to a further embodiment, the present invention also relates to the method disclosed above, wherein the solvent is selected from organic aprotic solvents, water, polyols and alcohols.

[0058] According to the present invention, extraction of the phosphite flame retardant is preferably carried out using an organic aprotic solvent. Suitable solvents are known in principle to those skilled in the art. In principle, any solvent suitable for dissolving the phosphite flame retardant but not depolymerizing the polyurethane polymer chains under extraction conditions can be used. For an economical process, an organic solvent with a boiling point at ambient pressure of less than 200°C, preferably less than 150°C, is preferably selected.

[0059] A suitable solvent is preferably 10×10 -30 It may have a dipole moment less than Cm.

[0060] In one embodiment, the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0061] Therefore, according to a further embodiment, the present invention also relates to the process as disclosed above, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones and mixtures thereof.

[0062] Suitable aliphatic hydrocarbons are selected from pentane and its isomers, hexane and its isomers, heptane and its isomers, octane and its isomers, cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane, and mixtures thereof.

[0063] Suitable halogenated hydrocarbons are selected from dichloromethane, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane and mixtures thereof.

[0064] Suitable ethers are selected from tetrahydrofuran, 1,4-dioxane, anisole, diethyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether (MTBE) and diethylene glycol dimethyl ether, and mixtures thereof.

[0065] Suitable aromatic hydrocarbons are selected from benzene, toluene, ortho-xylene, meta-xylene, para-xylene, ethylbenzene, mesitylene and chlorobenzene and mixtures thereof.

[0066] Preferred esters are selected from methyl formate, methyl acetate, ethyl acetate and butyl acetate, and mixtures thereof.

[0067] Suitable ketones are selected from acetone, methyl ethyl ketone, diethyl ketone, cyclopentanone and mixtures thereof.

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

[0069] In a preferred embodiment, the extraction solvent is selected from cyclohexane, methylcyclopentane, methylcyclohexane, THF, MTBE, toluene, acetone and mixtures thereof.

[0070] Suitably, the ratio of solvent, especially organic aprotic solvent, to polyurethane rigid foam is in the range of 0.1 to 100 L of solvent per kg of polyurethane rigid foam, preferably 1 to 20 L per kg.

[0071] According to the present invention, the extraction according to step b) is carried out at a temperature below 190° C. To allow an efficient and rapid extraction, the extraction is preferably carried out at an elevated reaction temperature of at least 20° C. but not exceeding 190° C., preferably 50-180° C., in particular 80-170° C., most preferably 100-160° C., in order to prevent degradation of the PU polymer chains.

[0072] Therefore, according to a further embodiment, the present invention also relates to the method disclosed above, wherein the extraction is carried out at a temperature in the range of 20-190°C.

[0073] If a solvent is used for extraction at a temperature above its boiling point at ambient pressure, the extraction is carried out in a pressure vessel, for example an autoclave, at the given vapor pressure of the solvent used at the selected extraction temperature.

[0074] The method of the present invention for extracting additive (A1), especially phosphorus ester flame retardants, can be carried out using conventional equipment for extracting used polyurethanes in a liquid phase and / or equipment known to those skilled in the art. In principle, any equipment suitable for liquid extraction of solids at a specified temperature and pressure can be used in the method of the present invention. Suitable equipment for liquid-solid extraction is described, for example, in "Liquid-Solid Extraction" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag GmbH & Co. KGaA, DOI 10.1002 / 1436007.b03_07.pub2. Suitable examples include, for example, rotary extractors, pot extractors, autoclave extractors, extraction columns, bucket elevator extractors, carousel extractors, and sliding cell extractors. The polyurethane rigid foam and solvent can be fed simultaneously or separately. The reaction may be carried out batchwise, continuously, or semi-continuously, with or without solvent recycling. The mean residence time in the reaction space can be varied over a wide range, preferably from 15 minutes to 100 hours, more preferably from 1 to 50 hours.

[0075] The extraction in step b) yields additive (A1), in particular a phosphite flame retardant. Preferably, additional unbound components, such as catalysts and surfactants, are also extracted from the polyurethane. If the phosphite flame retardant is extracted together with additional components, a suitable separation step can be carried out to obtain different components. It is also possible to combine the separation step with a purification step, such as a washing step.

[0076] Therefore, according to a further embodiment, the present invention also relates to the method disclosed above, wherein a further additive selected from the group consisting of a polymerization catalyst and a surfactant is extracted together with the phosphite flame retardant.

[0077] Therefore, according to a further embodiment, the present invention also relates to the method disclosed above, wherein the further additive is selected from a tertiary amine as polymerization catalyst and a siloxane as surfactant.

[0078] In step b), the remaining ground polyurethane or polyisocyanurate is obtained, which can be subjected to further processing. In the context of the present invention, it is preferred to subject the remaining ground polyurethane or polyisocyanurate to a treatment suitable for obtaining the individual building blocks, which can be separated and reused, for example, for the preparation of polyurethanes.

[0079] The method of the present invention may comprise further steps. Suitable purification steps include, for example, washing and drying steps.

[0080] Preferably, the method of the present invention also includes a step c) of depolymerizing the remaining ground polyurethane. As mentioned above, suitable conditions for depolymerization are known in principle to those skilled in the art. Preferably, the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or by aminolysis.

[0081] Preferably, the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base. The resulting products of depolymerization can be separated using suitable separation techniques.

[0082] According to a further embodiment, the present invention also relates to the process disclosed above, wherein the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base.

[0083] Methods for depolymerization by glycolysis are also known in principle. Preferably, glycolysis is carried out in the presence of a base. Thus, according to a further embodiment, the present invention also relates to the above-disclosed method, in which glycolysis is carried out in the presence of a metal catalyst.

[0084] Suitable methods for depolymerization by hydrogenation include hydrogenation in the presence of a hydrogenation catalyst. Thus, according to a further embodiment, the present invention also relates to the above-disclosed method, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0085] The remaining polyurethane material can be cleaved into the synthetic building blocks polyol and polyamine using known protic conditions for depolymerization of polyurethanes, such as hydrolysis, aminolysis followed by hydrolysis, or glycolysis, as described for rigid foams in, for example, Waster Management, 2018, 76, 147-171.

[0086] Another possibility is the depolymerization of the remaining polyurethane by hydrolysis using water in the presence of reusable organic nitrogen bases such as 1-alkylimidazoles in combination with water as described in WO 2010 / 130652, or pyridine / water, or a combination of nitrogen-containing ionic liquids with water to allow hydrolysis at lower temperatures and shorter reaction times.

[0087] Another possibility is the depolymerization of the remaining polyurethane by hydrogenation in the presence of a transition metal-containing hydrogenation catalyst, as described, for example, in ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705 or ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705.

[0088] Typically, depolymerization results in a mixture of components, which can be separated using suitable separation techniques.

[0089] The products of depolymerization of polyurethane after extraction of the flame retardant may contain polyamines and optionally polyols from the polyurethane rigid foam.

[0090] The process according to the invention may also comprise a step d) of separating the isocyanate component or its amine derivative from the polyol component.

[0091] Workup of the depolymerized products, particularly isolation of the polyamines and polyols, can be achieved, as the case may be, by, for example, extractive workup, precipitation of the amine components as hydrochlorides, precipitation as ureas (in the case of aminolysis), chromatography, or distillation under reduced pressure. Preferably, the workup comprises several steps.

[0092] In distillation workup, compounds are separated according to their volatility, with the more volatile compounds being separated first. Additives, water, or solvents used in the depolymerization can also be removed by distillation before further workup of the polyol-polyamine mixture. In general, the "volatility" of a liquid can be described using its vapor pressure; a high vapor pressure indicates high volatility, and vice versa.

[0093] When the polyamine is more volatile than the polyol, as is the case with TDA, MDA, and NDA, the polyamine is recovered from the depolymerization product by distillation, preferably vacuum distillation. After the polyamine is distilled off, a distillation bottom containing the polyol remains.

[0094] Suitable conditions for distillation are known in principle to those skilled in the art.

[0095] Alternatively, the polyol can be recovered by extraction from the depolymerization mixture using a suitable extractant or set of extractants. It is also possible to precipitate the polyamine component in its hydrochloride form by extracting the polyol component with a suitable solvent, such as that described in German Patent Application Publication No. 2854940, which preferably dissolves the polyol component but not the hydrochloride salt of the polyamine component, by adding HCl. The hydrochloride salt of the polyamine component can then be converted to the free polyamine by adding a base after separation, or it can be directly used in phosgenation to produce new polyisocyanates for polyurethane synthesis, as described in Chinese Patent No. 107337615. In the case of MDA·HCl or PMDA·HCl, the hydrochloride salt can be used in the MDA / PMDA synthesis process by condensation of aniline with formaldehyde.

[0096] It will be understood that the above separation methods can be combined with any of the various embodiments of the methods of the present invention described herein.

[0097] According to step a), a pulverized polyurethane or polyisocyanurate rigid foam containing at least one phosphite flame retardant is used. In principle, the properties of the foam can vary within wide limits.

[0098] The polyurethane or polyisocyanurate rigid foam used in the present invention is preferably obtained from an article made from polyurethane rigid foam after it has been used for the purpose for which it was made, or from polyurethane rigid foam waste from the manufacturing process. Before being subjected to the method of the present invention, the article can be subjected to mechanical comminution. That is, the article can be further sorted to a suitable size, for example, by shredding, sieving, or density separation, i.e., air, liquid, or magnetic separation. Optionally, these fragments can be subsequently subjected to a process to remove impurities, such as paper labels. Furthermore, a step of removing the blowing agent can be included in the process. Suitable methods are known in principle to those skilled in the art.

[0099] The method according to the present invention is also applicable to polyurethane rigid foam waste containing at least one additive (A1), in particular at least one phosphite flame retardant, as a starting material. In this specification, the term "polyurethane rigid foam waste" includes post-consumer polyurethane rigid foam and PU rigid foam production rejects or waste generated during construction. In this context, the term "post-consumer polyurethane rigid foam" refers to an article produced from polyurethane rigid foam that has already been used for the purpose for which it was produced. "Polyurethane rigid foam production rejects" refers to polyurethane rigid foam waste generated during the PU rigid foam production process.

[0100] Generally, polyurethane rigid foams are produced by the reaction of a polyisocyanate component with a polyol component, and additional materials are added during the polymer production process, such as phosphite flame retardants, polymerization catalysts such as tertiary amines, and surfactants such as siloxanes.

[0101] The properties of rigid polyurethane foams are influenced by the type of polyisocyanate and polyol used. For example, the starting materials can influence the cross-linking of the polymer, meaning that the polymer is composed of a three-dimensional network structure. Rigid polymers are obtained from short chains with many cross-links.

[0102] Industrially, and consequently in large quantities, especially methylene di(phenyl isocyanate) (MDI) or its polymeric forms are used as the polyisocyanate component in the production of PU rigid foams.

[0103] For representative compositions of these PU rigid foams, see WO 2015 / 121057 and WO 2013 / 139781.

[0104] The organic polyisocyanates which can be used in preparing the polyurethanes are any of the known organic diisocyanates and polyisocyanates, preferably aromatic polyfunctional isocyanates.

[0105] Specific examples that may be mentioned are tolylene-2,4- and 2,6-diisocyanate (TDI) and the corresponding isomer mixtures, diphenylmethane-4,4'-, 2,4'- and 2,2'-diisocyanate (MDI) and the corresponding isomer mixtures, mixtures composed of diphenylmethane-4,4'- and 2,4'-diisocyanate, polyphenylpolymethylene polyisocyanate, mixtures composed of diphenylmethane-4,4'-, 2,4'- and 2,2'-diisocyanate and polyphenylpolymethylene polyisocyanate (crude MDI), and mixtures composed of crude MDI and tolylene diisocyanate. The organic diisocyanates and polyisocyanates can be used alone or in the form of mixtures.

[0106] Modified polyfunctional isocyanates, i.e., products obtained by chemical reaction of organic diisocyanates and / or polyisocyanates, are also frequently used. Examples include diisocyanates and / or polyisocyanates containing uretdione, carbamate, isocyanurate, carbodiimide, allophanate, and / or urethane groups. The modified polyisocyanates can be mixed, if appropriate, with each other or with unmodified organic polyisocyanates, such as diphenylmethane-2,4'- or 4,4'-diisocyanate, crude MDI, or tolylene-2,4- and / or 2,6-diisocyanate.

[0107] Compounds that can be used to prepare polyurethanes having at least two hydrogen atoms reactive with isocyanate groups are those having at least two reactive groups selected from OH groups, SH groups, NH groups, NH2 groups, and acidic CH groups. Preferably, polyols are used, and in particular polyether alcohols and / or polyester alcohols having an OH value in the range of 25 to 800 mg KOH / g.

[0108] The polyester alcohols used are primarily prepared by condensation of polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, with polybasic carboxylic acids having 2 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, or preferably phthalic acid, isophthalic acid, terephthalic acid, or isomeric naphthalenedicarboxylic acids. The polyester alcohols used mostly have a functionality of 1.5 to 4.

[0109] The polyether polyols used in particular are those prepared by known processes, such as the anionic polymerization of alkylene oxides onto H-functional starter substances in the presence of a catalyst, preferably an alkali metal hydroxide or double metal cyanide catalyst (DMC catalyst). The alkylene oxides used are primarily ethylene oxide or propylene oxide, or alternatively tetrahydrofuran, various butylene oxides, or styrene oxide, preferably pure propylene 1,2-oxide. The alkylene oxides can be used alone, alternating in succession, or in the form of mixtures. The starter substances used in particular are compounds having at least two, preferably 2 to 8, hydroxy groups or at least two primary amino groups in the molecule. The starter substances used, which have at least two, preferably two to eight, hydroxyl groups in the molecule, are preferably trimethylolpropane, glycerol, pentaerythritol, sugar compounds such as glucose, sorbitol, mannitol, and sucrose, polyhydric phenols, resols such as oligomeric condensates of phenol and formaldehyde, and Mannich condensates of phenol, formaldehyde, and dialkanolamines, as well as melamine.The starter substances used, which have at least two primary amino groups in the molecule, are preferably aromatic diamines and / or polyamines, such as phenylenediamine, 2,3-, 2,4-, 3,4-, and 2,6-tolylenediamine, and 4,4'-, 2,4'-, and 2,2'-diaminodiphenylmethane, as well as aliphatic diamines and polyamines, such as ethylenediamine. The polyether polyol preferably has a functionality of 2 to 8, and a hydroxyl value of 25 to 800 mg KOH / g, particularly 150 to 570 mg KOH / g.

[0110] Other compounds having at least two hydrogen atoms reactive with isocyanates are crosslinkers and chain extenders, which can be used in combination if appropriate. The addition of difunctional chain extenders, trifunctional or higher functional crosslinkers, or mixtures thereof, if appropriate, proves advantageous for improving the mechanical properties. The chain extenders and / or crosslinkers preferably used are alkanolamines, in particular diols and / or triols with a molecular weight of less than 400, preferably 60 to 300. The amount of chain extender, crosslinker or mixtures thereof advantageously used is 1 to 20% by weight, preferably 2 to 5% by weight, based on the polyol component.

[0111] 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.

[0112] 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 and polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams, with methylene di(phenyl isocyanate)-based polyurethane rigid foams and polymeric or oligomeric methylene di(phenyl isocyanate)-based polyurethane rigid foams being particularly preferred.

[0113] Therefore, according to a further embodiment, the present invention also relates to the method disclosed above, wherein the polyurethane rigid foam is selected from the group consisting of 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 polyurethane rigid foams.

[0114] Polyfunctional isocyanates based on diphenylmethane diisocyanate (MDI) are in particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI, oligomeric MDI, also known as polyphenylpolymethylene isocyanates, or mixtures of two or three of the above-mentioned diphenylmethane diisocyanates, or crude MDI produced during the production of MDI, or mixtures of at least one oligomer of MDI with at least one of the above-mentioned low molecular weight MDI derivatives.

[0115] In methylene di(phenyl-isocyanate) 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 may also be used.

[0116] Modified polyisocyanates, i.e. products obtained by chemical reaction of organic polyisocyanates and containing two or more reactive isocyanate groups per molecule, are also often used. Particular mention may be made of polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups.

[0117] Aromatic isocyanates are compounds in which the isocyanate functionality is attached directly to an aromatic core. In comparison, 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.

[0118] After depolymerization, the process of the present invention typically yields polyamines containing amino groups bonded to the carbon atoms to which the isocyanate groups were bonded in the original polyisocyanate, such as methylenediphenyldiamine, oligomeric and polymeric methylenephenylamines, and toluenediamines (TDA), particularly 2,4-toluenediamine or 2,6-toluenediamine, or 1,5-naphthyldiamine (NDA). Commonly used polyols such as those mentioned above can also be preferably re-isolated. For this reason, the process preferably also yields 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.

[0119] According to a further aspect, the present invention also relates to a phosphite flame retardant, a polymerization catalyst or a surfactant obtained or obtainable according to the process disclosed above, in particular a phosphite flame retardant obtained or obtainable according to the process disclosed above.The present invention also relates to a polyol composition obtained or obtainable according to the process disclosed above.

[0120] Preferably, the resulting phosphite flame retardant, polymerization catalyst or surfactant, as well as the components of the resulting polyurethane, can be reused in processes for preparing, for example, polyurethanes or polyisocyanurates.

[0121] Preferably, the resulting polyol composition can also be reused in processes for preparing, for example, polyurethanes or polyisocyanurates.

[0122] Thus, according to a further aspect, the present invention also relates to the use of a phosphite flame retardant, a polymerization catalyst or a surfactant according to the invention, or obtained or obtainable according to the process disclosed above, for the preparation of a polyurethane or a polyisocyanurate.

[0123] 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.

[0124] 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.

[0125] 1. A value chain return method for polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bonded to the polymer chain and is selected from the group consisting of phosphite flame retardants, polymerization catalysts and surfactants, comprising: a) providing a composition comprising pulverized polyurethane or polyisocyanurate rigid foam, wherein the pulverized foam has an intact cell content of less than 10% based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam; b) extracting the additive (A1) with a solvent at a temperature below 190°C A method comprising:

[0126] 2. Process c) c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b) 2. The method of embodiment 1, further comprising:

[0127] 3. The method of embodiment 2, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or aminolysis.

[0128] 4. The method of embodiment 3, wherein the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base.

[0129] 5. Process d) d) A step of separating the isocyanate component or its amine derivative from the polyol component. 5. The method of embodiment 4, further comprising:

[0130] 6. The method of embodiment 3, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0131] 7. The method of embodiment 3, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0132] 8. The method of any one of embodiments 1 to 7, wherein the polyurethane rigid foam is selected from the group consisting of aromatic isocyanate-based polyurethane rigid foams, preferably methylene di(phenyl isocyanate)-based polyurethane rigid foams, polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams.

[0133] 9. The method of any one of embodiments 1 to 8, wherein the at least one phosphite flame retardant is selected from the group consisting of 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)ethylene diphosphate, dimethyl phosphonate, dimethyl propyl phosphonate, diphenyl cresyl phosphate, triethyl phosphate, and mixtures thereof.

[0134] 10. The method of any one of embodiments 1 to 9, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0135] 11. The method of any one of the preceding embodiments, wherein the at least one surfactant is selected from the group consisting of silicone-based cell stabilizers.

[0136] 12. The method of any one of embodiments 1 to 11, wherein the solvent is selected from organic aprotic solvents, water, polyols and alcohols.

[0137] 13. The method of embodiment 12, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0138] 14. The method of any one of embodiments 1 to 6, wherein the extraction is carried out at a temperature ranging from 20 to 190°C.

[0139] 15. A polyol composition obtained or obtainable according to the method of any one of embodiments 1 to 14.

[0140] 16. Use of a phosphite flame retardant obtained or obtainable according to the method of any one of embodiments 1 to 14 for the preparation of a polyurethane or polyisocyanurate.

[0141] 17. Use of a polymerization catalyst obtained or obtainable according to the method of any one of embodiments 1 to 14 for the preparation of a polyurethane or polyisocyanurate.

[0142] 18. Use of a stabilizer obtained or obtainable according to the method of any one of embodiments 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

[0143] 19. Use of the polyol composition according to embodiment 15, or the polyol composition obtained or obtainable according to the method according to any one of embodiments 1 to 14, for the preparation of a polyurethane or a polyisocyanurate.

[0144] 20. A value chain return method for polyurethane and polyisocyanurate rigid foams comprising at least one additive (A1) that is not chemically bonded to the polymer chain and is selected from the group consisting of phosphite flame retardants, polymerization catalysts, and surfactants, comprising: a) providing a composition comprising pulverized polyurethane or polyisocyanurate rigid foam, wherein the pulverized foam has an intact cell content of less than 10% based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam; b) extracting the additive (A1) with a solvent at a temperature below 190°C; c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b) A method comprising:

[0145] 21. A value chain return method for polyurethane and polyisocyanurate rigid foams comprising at least one additive (A1) that is not chemically bonded to the polymer chain and is selected from the group consisting of phosphite flame retardants, polymerization catalysts, and surfactants, comprising: a) providing a composition comprising pulverized polyurethane or polyisocyanurate rigid foam, wherein the pulverized foam has an intact cell content of less than 10% based on the number of intact cells in the unpulverized polyurethane or polyisocyanurate rigid foam; b) extracting the additive (A1) with a solvent at a temperature below 190°C, the solvent being selected from organic aprotic solvents, water, polyols and alcohols; A method comprising:

[0146] 22. Process c) c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b) 22. The method of embodiment 21, further comprising:

[0147] 23. The method of embodiment 22, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or aminolysis.

[0148] 24. The method of embodiment 23, wherein the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base.

[0149] 25.Step d) d) A step of separating the isocyanate component or its amine derivative from the polyol component. 25. The method of embodiment 24, further comprising:

[0150] 26. The method of embodiment 23, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0151] 27. The process of embodiment 23, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0152] 28. The method of any one of embodiments 21 to 27, wherein the polyurethane rigid foam is selected from the group consisting of aromatic isocyanate-based polyurethane rigid foams, preferably methylene di(phenyl isocyanate)-based polyurethane rigid foams, polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams.

[0153] 29. The method of any one of embodiments 21 to 28, wherein the at least one phosphite flame retardant is selected from the group consisting of 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)ethylene diphosphate, dimethyl phosphonate, dimethyl propyl phosphonate, diphenyl cresyl phosphate, triethyl phosphate, and mixtures thereof.

[0154] 30. The method of any one of embodiments 21 to 29, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0155] 31. The method of any one of embodiments 21 to 30, wherein the at least one surfactant is selected from the group consisting of silicone-based cell stabilizers.

[0156] 32. The method of embodiment 21, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0157] 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.

[0158] Example 1. Materials used Polyol 1: A polyetherol obtained by propoxylation of a mixture of sucrose and glycerin with an OH number of 490.

[0159] 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.

[0160] Elastocool: Polyurethane rigid foam (index = 120) from BASF Polyurethanes obtained by reacting a polyol component (Elastocool F 2030 / 310) with Lupranat M20.

[0161] 2. Overview In the extraction experiments, various PU rigid foams containing at least one phosphite flame retardant were used. PU rigid foam Index 100 was based on 74 parts by weight of Polyol 1, 20 parts by weight of 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 the flame retardant TCPP in the final PU rigid foam. The PU rigid foam Elastopir is based on 70% polymeric MDI and 25% polyol component (a mixture of polyesterols and polyetherols), 3.5% by weight of TCPP (tris(2-chloroisopropyl)phosphate) flame retardant, and a total of 2.5% by weight of tertiary amine catalyst, as well as siloxane surfactant as other extractable components apart from the phosphite flame retardant.

[0162] For comparison, Elastocool, a PU rigid foam made from pMDI (60%) and polyetherol, without extractable phosphite flame retardants, was also used as a reference material to demonstrate the stability of the PU polymer chains under these conditions.

[0163] The rigid foam was used as a ground foam in the form of a powder having an intact cell content of less than 1% based on the number of intact cells in the unground rigid foam. The intact cell content was determined using optical microscopy.

[0164] 3. Flame retardant pre-extraction procedure: The polymer was loaded into a 38 mL Ace tube (without a stir bar). The walls were rinsed with cyclohexane (CyH). The Ace tube was sealed and heated to the specified temperature for the specified time (preheated metal block, no stirring). After cooling to room temperature, the suspension was filtered through a suction filter. The remaining polymer was rinsed with additional cyclohexane (2 x 10 mL, 1 x 5 mL). The polymer was transferred to a vial and dried overnight at 60 °C (oven) to obtain the amount of recovered polymer. The solvent of the filtrate was removed under reduced pressure (47 °C, minimum pressure 60 mbar). The resulting colorless oil was 1 H, 31 The product was analyzed by P and 13C NMR spectroscopy (CDCl3) and GC-FID.

[0165] [Table 1]

[0166] The Index 100 and Elastopir extracts contained a flame retardant (TCPP - tris(2-chloroisopropyl)phosphate). The Elastopir and Elastocool samples contained small amounts of silicon stabilizers and small amounts of amine catalysts.

[0167] 4. Procedure for pre-extraction of flame retardants using different solvents: A 38 mL Ace tube (without a stir bar) was filled with polymer (1.00 g). The walls were rinsed with the specified solvent. The Ace tube was sealed and heated to 150 °C for 16 h (preheated metal block, no stirring). After cooling to room temperature, the suspension was filtered through a suction filter. The remaining polymer was rinsed with the specified solvent (2 × 10 mL, 1 × 5 mL). The polymer was transferred to a vial and dried overnight at 60 °C (oven) to obtain the amount of recovered polymer. The solvent of the filtrate was removed under reduced pressure (47 °C, minimum pressure 60 mbar). The resulting colorless oil was 1 H, 31 P and 13 The product was analyzed by C NMR spectroscopy (CDCl3) and GC-FID.

[0168] [Table 2]

[0169] The Index 100 and Elastopir extracts contained a flame retardant (TCPP - tris(2-chloroisopropyl)phosphate). The Elastopir and Elastocool samples contained small amounts of silicon stabilizers and small amounts of amine catalysts.

[0170] 5. Hydrolysis of pretreated / pre-extracted polymer samples: In air, a stainless steel autoclave (Premex Red) fitted with a Teflon insert was filled with pre-extracted Elastopir foam (7.70 g). The walls were rinsed with methylimidazole (80 mL) and water (8 mL). The autoclave was closed and heated to 160 °C overnight under stirring. After stirring at 160 °C for 18 h, the autoclave was cooled to room temperature and slowly opened to release residual CO pressure. A clear, purple-brown solution was obtained. The solution was transferred to a round-bottom flask, and the autoclave was rinsed with additional methylimidazole (3 × 5 mL). The solvent was removed under reduced pressure (slow and gradual heating to 100 °C, 2.5 × 10 mL). -2 mbar). The residue was dissolved in dry dichloromethane (20 mL) under argon and filtered into a 200 mL Schlenk tube (Whatman). The flask was rinsed with additional DCM (4 × 10 mL). No solid remained in the original flask or on the filter. The brown solution was further diluted with DCM (90 mL, total solution volume = 150 mL). An ethereal solution of HCl (2 M in EtO, 50 mL) was added slowly at room temperature. A large amount of ochre precipitate could be observed. The suspension was transferred to a Schlenk filter frit (φ 6.5 cm, approximately 500 mL, filter grade 3). The remaining solid was washed with dry dichloromethane (6 × 40 mL ... solution was then cooled under reduced pressure (room temperature, 1.4·10 -2After drying overnight at 49°C (200°F), the solid was transferred into the glove box and weighed. The isolated light tan solid (6.62 g) consisted of the amine fraction of the polymer, isolated as the hydrochloride salt. The solvent of the filtrate was removed under reduced pressure (49°C, minimum pressure 55 mbar). The resulting dark brown oil (1.55 g) consisted of the polyol fraction after hydrolysis. All products were 1 H and 13 It was characterized by C NMR.

[0171] 6. Comparative Example 1: Hydrolysis of PU Rigid Foam in the Presence of Phosphite Flame Retardants: [ka]

[0172] After the reaction, a reaction mixture was obtained in the form of a dark brown solution containing no solids. The reaction mixture was analyzed by GC / MS to detect 4,4'-methylenedianiline. However, GC / MS or 31 P NMR data indicated that the reaction mixture did not contain any phosphite flame retardants, which were therefore hydrolyzed under these conditions.

[0173] Experimental details: In air, a stainless steel autoclave (Premex) equipped with a Teflon insert was filled with untreated 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 (3 x 5 mL). No solid 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 either the crude or isolated material by P NMR analysis.

[0174] 7. Comparative Example 2: Hydrogenolysis of Polyurethane Rigid Foam Containing Phosphite Flame Retardant Using MACHO Catalyst in Protic Solvent Isopropanol The results and conditions of the following procedures are summarized in Table 2.

[0175] A stainless steel autoclave (Premex) equipped with a Teflon insert was filled with PU rigid foam Index 100 (1.00 g). The catalyst and base were added inside 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 (2 × 15 bar) 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 (3 × 5 mL) and EtOH (3 × 5 mL). The solid residual polymer was removed under reduced pressure (room temperature, 5.0·10 -2 The filtrate was dried at <100°C (<100°C) and used to determine the conversion (conversion = [(polymer used - polymer recovered) / polymer used] x 100). After removing the solvent from the filtrate under reduced pressure (45°C, minimum pressure 80 mbar), the residue was redissolved in CDCl3 (2 mL). An aliquot (50.0 μL) of 1,1,2,2-tetrachloroethane was added as an internal standard, and the solution was homogenized by swirling. The sample was 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).

[0176] The reaction mixture of entry 2 was further purified by flash column chromatography (EtOAc-hexane) to determine the amount of amine. Finally, the silica pad was flushed with EtOH to elute the polyol fraction.

[0177] Table 3

[0178] References U.S. Patent No. 4196148 International Publication No. 2010 / 130652 Universe Licensed Issuance Publication No. 2854940 Chinese Patent No. 107337615 Detail Book International Publication No. 2015 / 121057 International Publication No. 2013 / 139781 Ullmann's Encyclopedia of Industrial Chemistry, Phosphorus Compounds, Organic, 2012, DOI: 10.1002 / 14356007.a19_545.pub2 Chemosphere, 2012, 88, 1119-1153および International Publication No. 2015 / 121057 Plastics recycling and Polyurethanes, in Ullmann's Encyclopedia of Industrial Chemistry, 2020, DOI: 10.1002 / 14356007.a21_057.pu ChemSusChem, 2020, DOI: 10.1002 / cssc.20200246またはChemSusChem, 2021, DOI: 10.1002 / cssc.202101705 T. Skrydstrup et al., JACS Au, 2021, DOI: 10.1021 / jacsau.1c0005 Zhurnal Obshchei Khimii, 1978, 78, 694-695 J. Chem. Eng. Data, 2008, 53, 2718-2720 T. Schaub et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101606 T. Skrydstrup et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705

Claims

1. A value chain return method for polyurethane and polyisocyanurate rigid foams comprising at least one additive (A1) that is not chemically bonded to a polymer chain and is selected from the group consisting of a phosphite flame retardant, a polymerization catalyst, and a surfactant, the method comprising: a) providing a composition comprising comminuted polyurethane or polyisocyanurate rigid foam, wherein the comminuted foam has an intact cell content of less than 10% based on the number of intact cells in the uncomminuted polyurethane or polyisocyanurate rigid foam; b) extracting the additive (A1) with a solvent at a temperature below 190°C A method comprising:

2. Process c) c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b). The method of claim 1 further comprising:

3. 3. The process according to claim 2, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or aminolysis.

4. The method according to claim 3, wherein the hydrolysis is carried out in the presence of a catalytically active component, an ionic liquid or a phase transfer catalyst or a base.

5. Step d) d) A step of separating the isocyanate component or its amine derivative from the polyol component. The method of claim 4 further comprising:

6. The method of claim 3, wherein the glycolysis is carried out in the presence of a metal catalyst.

7. The process of claim 3, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

8. 8. The method according to claim 1, wherein the polyurethane rigid foam is selected from the group consisting of aromatic isocyanate-based polyurethane rigid foams, preferably methylene di(phenyl isocyanate)-based polyurethane rigid foams, polymeric methylene di(phenyl isocyanate)-based polyurethane rigid foams.

9. 9. The method of any one of claims 1 to 8, wherein the at least one phosphite flame retardant is selected from the group consisting of 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)ethylene diphosphate, dimethyl phosphonate, dimethyl propyl phosphonate, diphenyl cresyl phosphate, triethyl phosphate, and mixtures thereof.

10. 10. The process of any one of claims 1 to 9, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

11. 11. The method of any one of claims 1 to 10, wherein the at least one surfactant is selected from the group consisting of silicone-based cell stabilizers.

12. 12. The process according to any one of claims 1 to 11, wherein the solvent is selected from organic aprotic solvents, water, polyols and alcohols.

13. 13. The process of claim 12, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

14. 7. The process according to any one of claims 1 to 6, wherein the extraction is carried out at a temperature in the range of from 20 to 190°C.

15. A polyol composition obtained or obtainable according to the process of any one of claims 1 to 14.

16. 15. Use of a phosphite flame retardant obtained or obtainable according to the process of any one of claims 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

17. 15. Use of a polymerization catalyst obtained or obtainable according to the process of any one of claims 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

18. 15. Use of a stabilizer obtained or obtainable according to the process of any one of claims 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

19. 16. Use of a polyol composition according to claim 15, or a polyol composition obtained or obtainable according to the process according to any one of claims 1 to 14, for the preparation of a polyurethane or a polyisocyanurate.

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