Value chain return process for recovering unbonded additives and depolymerizing polyurethane rigid foams by extraction from polyurethane or polyisocyanurate rigid foams

Abstract

The 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-based flame retardants, polymerization catalysts and surfactants, the method comprises the steps of: providing a composition comprising a 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 of the uncomminuted polyurethane or polyisocyanurate rigid foam; and extracting the additive (A1) with a solvent at a temperature below 190 DEG C.

Description

[0001] The present invention relates to a method for the value chain return of rigid polyurethane foams, which allows the recovery by extraction of the phosphite-based flame retardants and other additives contained therein, which are not bonded in the polymer chains.

[0002] Specifically, the present invention relates to a method for the value chain return of rigid polyurethane and polyisocyanurate foams containing at least one additive (A1) not chemically bonded to the polymer chains, the at least one additive (A1) being selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprising the steps of: providing a composition comprising comminuted rigid polyurethane or polyisocyanurate foam, wherein the comminuted foam has a content of intact cells of less than 10% based on the total number of intact cells of the non-comminuted rigid polyurethane or polyisocyanurate foam; and extracting the additive (A1) with a solvent at a temperature below 190 °C.

[0003] The present invention also relates to phosphite-based flame retardants obtained or obtainable according to the method and their use for the preparation of polyurethanes or polyisocyanurates. In addition, the present invention also relates to polymerization catalysts obtained or obtainable according to the method and surfactants obtained or obtainable according to the method and their use for the preparation of polyurethanes or polyisocyanurates.

[0004] In the past thirty years, the demand for plastics worldwide has increased enormously. For example, in the past 10 years, the amount of plastics produced worldwide has increased by almost 50%. In 30 years, it has even become almost four times as much, reaching a volume of 359 million metric tons in 2018. From these facts it becomes clear that there is a need to dispose of or recycle waste plastics after the production of said large amounts of plastics. Recycling should preferably be carried out, since valuable materials (such as compounds that can act as monomers) can thus be added back to the value chain (for example by direct reuse in plastics production). For the purpose of imparting various functions to the resin, plastics are used together with incorporated additive components. For example, since the resin itself has high flammability, the resin is mixed with a flame retardant in a proportion of up to 25% by weight from the viewpoint of preventing the spread of fire. In terms of resource conservation and from an economic point of view, the possibility of returning the flame retardant to the industrial cycle seems promising.

[0005] In addition, rigid polyurethane (PU) foam waste is generated in the industrial production of rigid polyurethane foams. For example, such PU foam waste is obtained when casting rigid PU foam blocks and then cutting, trimming or sizing the blocks to obtain the desired PU workpieces. In addition, PU foam rejects such as non-conforming products are also generated.

[0006] Therefore, there is a need to develop treatment technologies for recycling materials from plastic waste. The recycling method should reduce both material waste and the carbon footprint. Additionally, it should be an economical and energy-efficient method for delivering valuable materials including high-tech features. In contrast, disposal by combustion, for example, has a negative impact on the environment and on the carbon footprint.

[0007] Among the above-mentioned plastics, polyurethane (PU) is an important representative. Generally speaking, polyurethane is produced by the addition polymerization of (poly) isocyanates and polyols. The characteristic link is the urethane group. Polyurethanes exist in many types, such as foams, elastomers or thermosetting plastics, among which foams are particularly important.

[0008] (Poly) isocyanates and polyols undergo addition polymerization to cause the formation of linear, branched or crosslinked polyurethanes. As an alternative form of alcohols, the most important group of NCO-reactive compounds are amines that cause the formation of disubstituted or trisubstituted ureas. Ureas are also formed by the reaction of water with isocyanates, in which the carbamic acid formed in the first step of the reaction spontaneously decomposes into an amine and eliminates carbon dioxide. The amine then reacts with the excess isocyanate to produce symmetrically substituted ureas. If no external blowing agent such as low-boiling hydrocarbons is used, this reaction is the basic reaction for producing polyurethane foams.

[0009] These foams can be formed with a wide range of densities and can have flexible or rigid foam structures. Generally speaking, "flexible foams" are those foams that recover their shape after deformation. In addition to being able to deform reversibly, flexible foams also tend to have a limited resistance to the applied load and tend to have mostly open cells. "Rigid foams" are those foams that generally retain the deformed shape and do not recover significantly after deformation. Rigid foams tend to have mostly closed cells. Whether a PU flexible foam or a PU rigid foam is formed during addition polymerization mainly depends on the types of polyisocyanates and polyol components used. For example, the starting materials can affect the crosslinking of the polymer, and the crosslinking of the polymer means that the polymer consists of a three-dimensional network. The long flexible chain segments contributed by the polyol cause the formation of PU flexible foams. PU rigid foams are obtained from short chains with many crosslinked parts. More details on the polyurethane rigid foams suitable for use according to the present invention can be found in Polyurethane Handbook, 2nd Edition, 1993, Chapter 6.

[0010] Rigid polyurethane foams provide excellent insulation properties. Therefore, they are very important in the construction industry and are commonly used as insulation materials, for example, for building insulation. However, for the application of rigid polyurethane foams as insulation materials in buildings, the addition of flame retardants is necessary for fire protection reasons. For this purpose, flame retardants are added during the production of rigid polyurethane foams. Nowadays, mainly phosphite 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, tetra(2-chloroethyl)-ethylenediphosphonate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenyltolyl phosphate, and their mixtures) are used as flame retardants in rigid polyurethane foams for building applications (see: Chemosphere, 2012, 88, 1119-1153 and WO 2015 / 121057). These flame retardants do not chemically bond to the polymer chains of polyurethanes.

[0011] In addition to these flame retardants, there are also other valuable additives from polymer synthesis that do not chemically bond to the polymer chains of polyurethanes, such as polymerization catalysts and surfactants, which, stretching the point slightly, are present. It is also desirable to recycle these additives together with the flame retardants and reuse them in the synthesis of new rigid polyurethane foams.

[0012] Recycling rigid polyurethane foams into valuable monomer compounds and recovering phosphite ester flame retardants and other additives remains challenging. Polyol compounds and amines can be recovered and recycled by glycolysis or hydrolysis (see: Plastics recycling and Polyurethanes, 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] US4196148A describes a method for hydrolyzing polyurethane foams at a temperature close to atmospheric pressure and above 185 °C and recovering diamines and polyethers (or polyesters) from the hydrolysis products. The recovery of flame retardants is not proposed in this work.

[0014] Although the hydrolysis of polyurethane foams allows for the recycling of the constituent monomers, phosphorus-based flame retardants decompose under the harsh hydrolysis reaction conditions (see: Ullmann's Encyclopedia of Industrial Chemistry, Phosphorus Compounds, Organic, 2012, DOI: 10.1002 / 14356007.a19_545.pub2). Such decomposition is not only disadvantageous in terms of the flame retardant no longer being available for reuse, but also the hydrolysis products of the esters may contaminate the polyol and / or polyamine, which can lead to a more complex, resource-intensive, and expensive post-treatment process.

[0015] Therefore, recycling and depolymerizing rigid polyurethane foams in a way that allows for the recovery of polyols, polyamines, and phosphite-based flame retardants would be of high economic benefit.

[0016] T. Skrydstrup et al., JACS Au, 2021, DOI: 10.1021 / jacsau.1c00050 describe the depolymerization of polyurethane using a homogeneous iridium catalyst with a tridentate P,N,P-ligand at 150 °C and 30 bar H 2 pressure in 2-propanol as the solvent. In this work, a methylene bis(phenyl isocyanate)-based rigid polyurethane foam from refrigerator insulation was hydrogenated to yield the corresponding diamine and polyol. The authors detected a phosphorus compound in the polyol fraction with a signal at 20.00 ppm in the 31 P NMR spectrum. It was proposed that this phosphorus compound might be due to the phosphorus-based flame retardant, but no further confirmation, characterization, or isolation of this unknown phosphorus compound was carried out. However, the rigid PU foams used in refrigerator insulation typically do not contain phosphorus-based flame retardants. Additionally, the commonly used phosphite-based flame retardants for rigid polyurethane foams are 31The chemical shift of about 20 ppm is not present in the ³¹P NMR spectrum, but is usually below 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 at the reference sample), 0.24 ppm for tris(2-ethylhexyl) phosphate (see: J. Chem. Eng. Data, 2008, 53, 2718 - 2720) or -0.8 ppm for triethyl phosphate (see: Phosphorus, Sulfur and Silicon and the Related Elements, 1991, 61, 31 - 39). Therefore, Skrydstrup et al. did not disclose the recovery of phosphite-based flame retardants from rigid polyurethane foams. Most likely, the authors detected phosphine oxides of the phosphine ligands of the catalysts used in the 31 ³¹P NMR spectrum. The oxide of the PNP-ligand Ph 2 ³¹P(O)C 2 H 4 NHC 2 H 4 ³¹P(O)Ph 2 has a phosphine oxide signal at 20 ppm in the 31 ³¹P NMR spectrum (measured at the reference sample of the oxidized PNP-ligand).

[0017] T. Schaub et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101606 described the depolymerization of polyurethanes using 2 mol% to 4 mol% of a homogeneous manganese catalyst with a tridentate P,N,N-ligand at 130 °C to 200 °C and 60 bar H 2 pressure in toluene or THF as solvents. When this system was applied to rigid polyurethane foams based on methylene bis(phenyl isocyanate), the corresponding diamines and polyols could be obtained and separated. The rigid foams did not contain phosphorus-based flame retardants.

[0018] T. Skrydstrup et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705 described the depolymerization of polyurethanes using 1 mol% of a homogeneous manganese catalyst with a tridentate P,N,P-ligand at 180 °C and 50 bar H 2 pressure in 2-propanol as a solvent. This system was applied to rigid polyurethane foams based on methylene bis(phenyl isocyanate) from refrigerator insulation and rigid polyurethane foams for decoration. In both cases, the corresponding diamines and polyols could be obtained and separated. The authors in31 Phosphorus compounds in the polyol fraction obtained from PU rigid foam for decoration, which exhibit a signal at 31.00 ppm in the ³¹P NMR spectrum, and phosphorus compounds in the polyol fraction obtained from PU rigid foam from refrigerator insulation, which exhibit a signal at 32.05 ppm, were detected. As described above, for these unknown phosphorus compounds, the authors proposed that the signals might originate from phosphorus-based flame retardants. Similarly, no further confirmation, characterization, or separation of the unknown phosphorus compounds was carried out. However, as described in further detail above, the PU rigid foams used in refrigerator insulation and decoration generally do not contain phosphorus-based flame retardants. Additionally, the commonly used phosphite-based flame retardants for rigid polyurethane foams do not have a chemical shift of approximately 31 ppm in the 31 ³¹P NMR spectrum, but are generally below 1 ppm (see above). Therefore, this work also did not disclose the recovery of phosphite-based flame retardants from rigid polyurethane foams.

[0019] The above-described plastic recycling method has not hitherto disclosed a method for recycling rigid polyurethane foam and recovering phosphite-based flame retardants in such a way as to obtain both valuable amine and polyol components.

[0020] Accordingly, an object of the present invention is to depolymerize rigid polyurethane foam containing additives (such as flame retardants, stabilizers, or catalysts, especially phosphite-based flame retardants) that are not chemically bonded to the polymer chain in such a way that polyols, aromatic amines, and phosphite-based flame retardants and other additives can be obtained and preferably also reused.

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

[0022] The present invention relates to a value chain return method for rigid polyurethane and polyisocyanurate foams containing at least one additive (A1) that is not chemically bonded to the polymer chain selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprising the following steps:

[0023] a) Provide a composition comprising comminuted rigid polyurethane or polyisocyanurate foam, wherein the comminuted foam has a closed cell content of less than 10% based on the number of intact cells of the non-comminuted rigid polyurethane or polyisocyanurate foam,

[0024] b) Extract the additive (A1) with a solvent at a temperature below 190 °C.

[0025] "Value chain return" is intended to mean that the low molecular weight products obtained by the process of the invention can be reintegrated into the value chain for producing polyurethanes or used as raw materials in other value chains.

[0026] In the context of the present invention, "comminuted thermoplastic polyurethane or polyisocyanurate rigid foam" means that the material is obtained from a rigid foam and the comminuted thermoplastic polyurethane or polyisocyanurate is used, for example, in chopped form, in particulate form, as an agglomerate or as a powder. The rigid polyurethane or polyisocyanurate foam can be comminuted by conventional methods, for example by chopping, for example comminuting at room temperature in a rotary mill or a rolling ball mill to a particle size which is generally less than 20 mm, or by known cold grinding methods, for example. Preferably, a particle size of less than 5 mm is selected, for example in the range from 0.01 mm to 5 mm, and preferably in the range from 0.01 mm to 1 mm.

[0027] The process of the invention comprises steps a) and b) and can comprise further steps. According to step a), a composition comprising comminuted rigid polyurethane or polyisocyanurate foam is provided, wherein the comminuted foam has a closed cell content of less than 10% based on the number of intact cells of the non-comminuted rigid polyurethane or polyisocyanurate foam. Suitable methods for preparing a composition comprising comminuted rigid polyurethane or polyisocyanurate foam are in principle known from the prior art. In the context of the present invention, "intact cell" means that the cell structure and shape of the cell are similar, preferably identical, to the cell structure and shape of the cells of the non-comminuted foam. According to the invention, the cell structure of the comminuted rigid foam is preferably disrupted and the material provided has a closed cell content of less than 10%, preferably less than 5%, in particular less than 2%, more preferably less than 1%, particularly preferably less than 0.5%, in each case based on the number of intact cells of the non-comminuted rigid polyurethane or polyisocyanurate foam. The composition can contain further components, for example a solvent.

[0028] Unless otherwise stated, in the context of the present invention, the content of intact cells is determined by optical microscopic examination of a sample of the material and comparison of the cell counts of samples of the non-comminuted foam and the comminuted foam.

[0029] According to step b), the additive (A1) is extracted with a solvent at a temperature below 190 °C. Two or more additives can also be extracted in the extraction step according to the invention. Generally, at least 20%, preferably at least 30%, more preferably at least 40%, especially at least 50% of the additive (A1) present in the rigid polyurethane or polyisocyanurate foam is extracted in step b). Preferably, 50% to 100%, especially 80% to 99.9%, more preferably 90% to 99% of at least one additive (A1) is extracted in step b).

[0030] According to the invention, the method can also include two or more extraction steps using different solvents and / or different temperature ranges.

[0031] According to step b), a solvent containing the additive (A1) and the remaining ground polyurethane or polyisocyanurate are obtained.

[0032] Preferably, the rigid polyurethane or polyisocyanurate foam obtained in step b) is subjected to a further step according to the invention, especially a depolymerization step.

[0033] According to another embodiment, the invention also relates to the method as disclosed above, wherein the method further comprises step c)

[0034] c) depolymerizing the ground polyurethane or polyisocyanurate obtained in step b).

[0035] According to the invention, the extraction step and the depolymerization of the ground rigid polyurethane foam can also be combined. Depolymerization or partial depolarization can also occur during step b. Preferably, according to the invention, the extraction step and the depolymerization step are separate steps.

[0036] Suitable depolymerization methods are in principle known to those skilled in the art. Preferably, the depolymerization is achieved by hydrolysis, glycolysis, hydrogenation or ammonolysis according to the invention. Preferably, the depolymerization is achieved by glycolysis or hydrolysis according to the invention.

[0037] Depending on the method used for depolymerization, different products are obtained. Generally, an isocyanate component is obtained and the isocyanate component can be separated, but the polyol component can also be separated, especially in the case where depolymerization is achieved by glycolysis. The method of the invention can also include additional separation steps.

[0038] According to another embodiment, the invention also relates to the method as disclosed above, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation or ammonolysis.

[0039] Surprisingly, in the value chain return method according to the invention, additives (A1) not chemically bonded to the polymer chain, selected from the group consisting of phosphite-based flame retardants, polymerization catalysts and surfactants, in particular phosphite-based flame retardants, are recovered in a chemically unchanged form by extraction from waste rigid polyurethane foam with a suitable solvent, in particular an aprotic organic solvent, below 190 °C. Surprisingly, under these conditions, the polymerization catalyst, surfactant and phosphite-based flame retardant do not decompose under the extraction conditions applied in this method. This allows the recovery of the additives, in particular phosphite-based flame retardants, before the polymeric polyurethane material is depolymerized into the polyol component and the isocyanate or its amine component.

[0040] Furthermore, in the value chain return method, by extracting the phosphite-based flame retardant, other additives not chemically bonded to the polymer chain, such as polymerization catalysts (e.g., tertiary amines) and surfactants (e.g., siloxanes), can also be extracted together with the phosphite-based flame retardant. They can be obtained together with the phosphite-based flame retardant after removal of the aprotic organic solvent used for extraction, and the obtained mixture of phosphite-based flame retardant, polymerization catalyst and surfactant is used for the synthesis of new rigid polyurethane foam.

[0041] Thus, the method of the invention enables the reuse of phosphite-based flame retardants, polymerization catalysts and surfactants. The value chain return method of the invention for polyurethane rigid foam containing at least one phosphite-based flame retardant and additional unbonded additives yields a remaining polyurethane material in which at least the phosphite-based flame retardant is removed before extraction with a suitable solvent, in particular an aprotic organic solvent.

[0042] Preferably, the remaining ground polyurethane or polyisocyanurate obtained in step b) of the method is subjected to depolymerization, and thus two raw material components can be recovered from the polyurethane. The polyurethane component is either directly recovered (e.g., polyol) or obtained as a valuable synthetic building block (such as a polyamine that can be easily converted into polyisocyanate).

[0043] The method according to the invention comprises steps a) and b) and optionally c), but may also comprise additional steps. The method may, for example, comprise additional purification steps or heat treatment. According to another embodiment, the invention also relates to the method as disclosed above, wherein the method comprises an additional purification step.

[0044] 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 directly after step a). Step c) can also be carried out directly after step b).

[0045] According to the present invention, steps a) and b) can also be combined and carried out in the same apparatus. The composition provided in step a) can also contain a solvent, such as the solvent that can be used in step b) of the method according to the present invention.

[0046] According to the present invention, at least one additive (A1) that is not chemically bonded to the polymer chain is extracted, and the at least one additive (A1) is selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants. According to the present invention, phosphite-based flame retardants, polymerization catalysts, and surfactants that are commonly used as additives not bonded to the polymer chain in rigid polyurethane or polyisocyanurate foams can be extracted.

[0047] Generally speaking, phosphite-based flame retardants for rigid polyurethane foams (for example, for building applications) conform to the compounds of general formula (i):

[0048]

[0049] wherein R 1 and R 2 are independently selected from C 1 -C 12 -alkyl, C 5 -C 8 -cycloalkyl, and aryl, wherein

[0050] C 1 -C 12 -alkyl is unsubstituted or carries 1, 2, 3, 4, or 5 identical or different substituents selected from hydroxyl and halogen (such as Cl or Br), and

[0051] C 5 -C 8 -cycloalkyl or aryl is unsubstituted or carries 1, 2, 3, 4, or 5 identical or different substituents selected from alkyl, hydroxyl, and halogen (such as Cl or Br), and

[0052] wherein R 3 is selected from C 1 -C 12 -alkyl, C 5 -C 8 -cycloalkyl, and aryl, wherein

[0053] C1 -C 12 - The alkyl group is unsubstituted or bears 1, 2, 3, 4 or 5 identical or different substituents selected from hydroxyl and halogen (such as Cl or Br), and

[0054] C 5 -C 8 - The cycloalkyl or aryl group is unsubstituted or bears 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, hydroxyl and halogen (such as Cl or Br), or

[0055] wherein R 3 is selected from -O-C 1 -C 12 -alkyl, -O-C 5 -C 8 -cycloalkyl and -O-aryl, wherein

[0056] -O-C 1 -C 12 -alkyl is unsubstituted or bears 1, 2, 3, 4 or 5 identical or different substituents selected from hydroxyl and halogen (such as Cl or Br), and

[0057] -O-C 5 -C 8 -cycloalkyl or -O-aryl is unsubstituted or bears 1, 2, 3, 4 or 5 identical or different substituents selected from alkyl, hydroxyl and halogen (such as Cl or Br).

[0058] Preferably, the aryl group is selected from phenyl and naphthyl.

[0059] In one embodiment, the phosphite-based 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, tetra(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenylcresyl phosphate, and mixtures thereof.

[0060] Thus, according to another embodiment, the present invention also relates to the method as disclosed above, wherein the at least one phosphite-based 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, tetra(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenylcresyl phosphate, triethyl phosphate, and mixtures thereof.

[0061] Suitably, the phosphite-based flame retardant is present in the rigid polyurethane foam in an amount of 1% to 15% by weight, preferably 3% to 10% by weight, more preferably 5% to 8% by weight.

[0062] Suitably, the polymerization catalyst is present in the rigid polyurethane foam or polyisocyanurate foam in an amount of 0.1% to 10% by weight, preferably 0.25% to 5% by weight, more preferably 0.5% to 2.5% by weight. Generally, the surfactant is present in the rigid polyurethane foam or polyisocyanurate foam in an amount of 0.1% to 8% by weight, preferably 0.25% to 5% by weight, more preferably 0.5% to 2.5% by weight.

[0063] In addition to the phosphite-based flame retardant, the rigid polyurethane foam typically also contains a polymerization catalyst (such as a trialkylamine) and a surfactant (such as a silicone), which can also be extracted in the step of extracting the flame retardant and obtained in the form of a mixture with them after removing the extraction solvent (preferably by distillation). Suitable methods for separating the corresponding compounds are known to those skilled in the art.

[0064] According to another embodiment, the invention also relates to the method as disclosed above, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0065] Preferably, the polymerization accelerator is selected from tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N’,N’-tetramethyldiaminoethyl ether, bis-(dimethylaminopropyl)-urea, N-methylmorpholine 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-dimethyl-aminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo-(2,2,0)-octane, 1,4-azabicyclo-(2,2,2) octane (Dabco) and alkanolamines such as triethanolamine, triisopropanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)-ethanol, N,N’,N”-tris-(dialkylaminoalkyl) hexahydrotriazine, e.g. N,N’,N”-tris-(dimethylamino-propyl)-s-hexahydrotriazine and triethylamine.

[0066] According to another embodiment, the invention also relates to the method as disclosed above, wherein the at least one surfactant is selected from the group consisting of silicone cell stabilizers.

[0067] Silicone-based cell stabilizers include silicone compounds that reduce the surface tension of polyester polyols. These compounds are preferably compounds having an amphiphilic structure, and this means that they have two molecular moieties with different polarities. Preferably, the silicone-based cell stabilizer has a molecular moiety having a silicone unit, examples being dimethylsiloxane or methylphenylsiloxane, and has a molecular moiety having a chemical structure somewhat similar to the polyol used. These are preferably polyoxyalkylene units. The silicone-based cell stabilizer particularly preferably contains a polysiloxane-polyoxyalkylene block copolymer having an ethylene oxide content of less than 75% by weight based on the total content of polyoxyalkylene units. These preferably contain polyethylene oxide units and / or polypropylene oxide units. The molar mass of the polyoxyalkylene side chain is preferably at least 1000 g / mol per side chain. These compounds are known and are described, for example, in Plastics handbook, Chapter 7, Polyurethane, Carl Hanser Verlag, 3rd edition, 1993, Chapter 3.4.4.2, and for example they can be produced by the reaction of siloxanes such as polydimethylsiloxane with polyoxyalkylene, especially with polyethylene oxide, with polypropylene oxide, or with a copolymer of polyethylene oxide and polypropylene oxide used. Here, polysiloxane-polyoxyalkylene block copolymers having oxyalkylene chains as end groups or as one or more side chains can be obtained. The silicone-based cell stabilizer (e) may have OH groups, but preferably does not contain OH groups. This can be achieved by using a monofunctional alcohol such as butanol as a raw material to produce polyoxyalkylene. For example, the silicone-based cell stabilizers used may include known silicone foam stabilizers, such as Niax Silicone L1501, L1505, L1540, L1593, L1602 or L1609 from Monentive; DC 193, DC 3041, DC 3042, DC 3043, DC 5000, DC 5169, DC 2525, DC2584 or DC 5160; from Evonik BF 2270, BF 2370, BF 2470, B 8110, B 8225, B 8255, B 8317, B 8325, B 8905, B 8946PF, B 8948, B8950, B 8952, B 8960, B 8498 or B 8486.

[0068] According to the invention, the extraction of the additive (A1) is carried out using a suitable solvent. Suitable solvents are in principle known and include, for example, organic aprotic solvents, water, polyols and alcohols. Suitable polyols include those which can also be used as raw materials for the preparation of polyisocyanates or polyisocyanurates, such as diethylene glycol (DEG) or dipropylene glycol (DPG).

[0069] 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 the preparation of polyurethanes or polyisocyanurates without further purification steps.

[0070] According to another embodiment, the invention also relates to the process as disclosed above, wherein the solvent is selected from organic aprotic solvents, water, polyols and alcohols.

[0071] In the present invention, the extraction of the phosphite-based flame retardant is preferably carried out using an organic aprotic solvent. Suitable solvents are in principle known to the person skilled in the art. In principle, any solvent which is suitable for dissolving the phosphite-based flame retardant but which does not depolymerize the polyurethane polymer chains under the extraction conditions can be used. For an economical process, an organic solvent with a boiling point below 200 °C, preferably below 150 °C, at ambient pressure is preferably selected.

[0072] The suitable solvent may preferably have a dipole moment of less than 10*10 -30 Cm.

[0073] In one embodiment, the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones and mixtures thereof.

[0074] Thus, according to another embodiment, the 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.

[0075] Suitable aliphatic hydrocarbons are selected from pentane and its isomers, hexane and its isomers, heptane and isomers, octane and its isomers, cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane and mixtures thereof.

[0076] Suitable halogenated hydrocarbons are selected from methylene chloride, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, and mixtures thereof.

[0077] Suitable ethers are selected from tetrahydrofuran, 1,4-dioxane, anisole, diethyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether (MTBE), diethylene glycol dimethyl ether, and mixtures thereof.

[0078] Suitable aromatic hydrocarbons are selected from benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, mesitylene, chlorobenzene, and mixtures thereof.

[0079] Suitable esters are selected from methyl formate, methyl acetate, ethyl acetate, butyl acetate, and mixtures thereof.

[0080] Suitable ketones are selected from acetone, methyl ethyl ketone, diethyl ketone, cyclopentanone, and mixtures thereof.

[0081] If desired, mixtures of two or more of the aforementioned organic aprotic solvents can be used.

[0082] In a preferred embodiment, the extraction solvent is selected from cyclohexane, methylcyclopentane, methylcyclohexane, THF, MTBE, toluene, acetone, and mixtures thereof.

[0083] Suitably, the ratio of the solvent (especially the organic aprotic solvent) to the rigid polyurethane foam is in the range of 0.1 L to 100 L of solvent / 1 kg of rigid polyurethane foam, preferably 1 L to 20 L / 1 kg.

[0084] According to the present invention, the extraction according to step b) is carried out at a temperature below 190 °C. To allow for effective and rapid extraction, the extraction is preferably carried out at an elevated reaction temperature of at least 20 °C but not higher than 190 °C to prevent decomposition of the PU polymer chains, preferably at 50 °C to 180 °C, especially 80 °C to 170 °C, and most preferably 100 °C to 160 °C.

[0085] Thus, according to another embodiment, the present invention also relates to the method as disclosed above, wherein the extraction is carried out at a temperature of 20 °C to 190 °C.

[0086] If the solvent is used for extraction at a temperature above its boiling point at ambient pressure, the extraction is carried out in a pressure vessel (such as an autoclave) at the selected extraction temperature at the vapor pressure of the solvent used subsequently.

[0087] The inventive method for extracting additive (A1), in particular a phosphite-based flame retardant, can be carried out in conventional equipment and / or is known to those skilled in the art for extraction, wherein waste polyurethane is extracted with a liquid phase. For the inventive method, in principle, any equipment that is substantially suitable for extracting a solid with a liquid at a specified temperature and a specified pressure can be used. For suitable equipment for liquid-solid extraction, see, for example: Liquid-Solid Extraction, 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, tank extractors, autoclave extractors, extraction towers, bucket elevator extractors, disk conveyor extractors, and sliding cell extractors. The supply of rigid polyurethane foam and solvent can be carried out simultaneously or separately from each other. The reaction can be carried out discontinuously in batch mode with or without solvent recycling or continuously or semi-continuously. The average residence time in the reaction space can vary within a wide range, preferably within the range of 15 minutes to 100 hours, more preferably within the range of 1 hour to 50 hours.

[0088] In the extraction according to step b), additive (A1), in particular a phosphite-based flame retardant, is obtained. Preferably, other unbonded components such as catalysts and surfactants are also extracted from the polyurethane. In the case where the phosphite-based flame retardant is extracted together with other components, suitable separation steps can be carried out to obtain the different components. Separation and purification steps such as washing steps can also be combined.

[0089] Accordingly, according to another embodiment, the invention also relates to the method as disclosed above, wherein additional additives selected from the group consisting of polymerization catalysts and surfactants are extracted together with the phosphite-based flame retardant.

[0090] Accordingly, according to another embodiment, the invention also relates to the method as disclosed above, wherein the additional additives are selected from tertiary amines as polymerization catalysts and siloxanes as surfactants.

[0091] In step b), the remaining ground polyurethane or polyisocyanurate is obtained, and the remaining ground polyurethane or polyisocyanurate can be subjected to additional steps. In the context of the present invention, it is preferred that the remaining ground polyurethane or polyisocyanurate is subjected to a treatment suitable for obtaining individual structural units, and the individual structural units can in turn be separated and reused, for example, for the preparation of polyurethanes.

[0092] The method of the present invention may further include additional steps. Suitable purification steps include, for example, washing steps and drying steps.

[0093] Preferably, the method of the present invention further includes step c) of depolymerizing the remaining ground polyurethane. As described above. Suitable depolymerization conditions are in principle known 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 ammonolysis.

[0094] 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 depolymerization products can be separated using suitable separation techniques.

[0095] According to another embodiment, the present invention also relates to the method as 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.

[0096] The method of depolymerization by glycolysis is also known in principle. Preferably, the glycolysis is carried out in the presence of a base. Thus, according to another embodiment, the present invention also relates to the method as disclosed above, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0097] Suitable methods of depolymerization by hydrogenation include hydrogenation in the presence of a hydrogenation catalyst. Thus, according to another embodiment, the present invention also relates to the method as disclosed above, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0098] The remaining polyurethane material can be cracked, for example, into synthetic structural unit polyols and polyamines using known proton conditions for polyurethane depolymerization such as hydrolysis, post - ammonolysis hydrolysis, glycolysis, as given for rigid foams in Waste Management, 2018, 76, 147 - 171.

[0099] Another possibility is to depolymerize the remaining polyurethane by hydrolysis in the presence of a combination of water with a reusable organic nitrogen base such as 1 - alkylimidazole (as described in WO2010 / 130652A2) or pyridine / water or a combination of a nitrogen - containing ionic liquid with water to allow hydrolysis at a lower temperature and shorter reaction time.

[0100] Another possibility is to depolymerize 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.

[0101] Typically, depolymerization yields a mixture of components that can be separated using suitable separation techniques.

[0102] The product of the depolymerization of polyurethane after extraction of the flame retardant may contain polyamines and optionally polyols from rigid polyurethane foams.

[0103] The method according to the invention may further comprise step d) of separating the isocyanate component or its amine derivative from the polyol component.

[0104] Work-up of the depolymerization product, in particular separation of the polyamines and polyols, can be effected as appropriate, for example by extraction work-up, precipitation of the amine component as a hydrochloride, precipitation as a urea (in the case of ammonolysis), chromatography or vacuum distillation. Preferably, the work-up comprises several steps.

[0105] In work-up by distillation, the 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 prior to further work-up of the polyol-polyamine mixture. Generally speaking, the "volatility" of a liquid can be described using its vapor pressure, where a high vapor pressure indicates high volatility, and vice versa.

[0106] In the case where the polyamine is more volatile than the polyol, as is the case for TDA, MDA and NDA, for example, the polyamine is recovered from the depolymerization product by distillation, preferably by vacuum distillation. After distilling off the polyamine, a distillation residue containing the polyol remains.

[0107] Suitable distillation conditions are in principle known to those skilled in the art.

[0108] Alternatively, the polyol can be recovered from the depolymerization mixture by extraction using a suitable extractant or pair of extractants. The polyamine component can also be precipitated in the form of its hydrochloride by adding HCl and extracting the polyol component with a suitable solvent, such as described in DE2854940A1, preferably a solvent that dissolves the polyol component but not the hydrochloride of the polyamine component. As described in CN107337615B, the hydrochloride of the polyamine component can then be converted to the free polyamine by adding a base after separation, but can also be used directly for phosgenation to produce a new polyisocyanate for polyurethane synthesis. In the case of MDA*HCl or PMDA*HCl, the hydrochloride can be used in the MDA / PMDA synthesis step by condensation of aniline and formaldehyde.

[0109] It should be understood that the above separation methods can be combined with any of the various embodiments of the method according to the invention described herein.

[0110] According to step a), a shredded polyurethane or polyisocyanurate rigid foam containing at least one phosphite-based flame retardant is used. In principle, the properties of the foam can vary within a wide range.

[0111] The polyurethane or polyisocyanurate rigid foam used in the present invention is preferably obtained from: articles generated at some time after the polyurethane rigid foam has been used for the purpose for which it was manufactured, or polyurethane rigid foam waste from the production process. Before being subjected to the method of the present invention, these articles can be subjected to mechanical shredding. That is, the articles are further sorted and made into appropriate sizes, for example, by chopping, screening, or separation by density rate (i.e., by air, liquid, or magnetically). Optionally, these fragments can then be treated to remove impurities, such as paper labels. In addition, a step of removing the blowing agent can be included in the method. Suitable methods are in principle known to those skilled in the art.

[0112] The method according to the present invention is also applicable to polyurethane rigid foam waste containing at least one additive (A1), especially at least one phosphite-based flame retardant, as a raw material. Herein, the term "polyurethane rigid foam waste" includes polyurethane rigid foam at the end of its service life and PU rigid foam production rejects or waste generated during construction. In this context, the term "discarded polyurethane rigid foam" means the articles generated from the polyurethane rigid foam when the polyurethane rigid foam has been used for the purpose for which it was manufactured. "PU rigid foam production rejects" means polyurethane rigid foam waste generated during the production process of PU rigid foam.

[0113] Generally speaking, polyurethane rigid foam is produced by the reaction between a polyisocyanate component and a polyol component. Additional materials, such as phosphite-based flame retardants, polymerization catalysts (such as tertiary amines), and surfactants (such as siloxanes), are added during the production process of the polymer.

[0114] The properties of the polyurethane rigid foam are affected by the types of polyisocyanate and polyol components used. For example, the starting materials can affect the crosslinking of the polymer, and the crosslinking of the polymer means that the polymer consists of a three-dimensional network. The rigid polymer is obtained from short chains with many crosslinked parts.

[0115] Especially methylene bis(phenyl isocyanate) (MDI) or its polymeric form is used industrially and thus in large quantities as the polyisocyanate component for the production of PU rigid foam.

[0116] For representative compositions of these PU rigid foams, see WO 2015 / 121057 and WO 2013 / 139781.

[0117] The organic polyisocyanates which can be used for the preparation of polyurethanes are any of the known organic diisocyanates and polyisocyanates, preferably aromatic polyfunctional isocyanates.

[0118] Individual examples which may be mentioned are toluene 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 consisting of diphenylmethane 4,4’- and 2,4’-diisocyanate, polyphenyl polymethylene polyisocyanates, mixtures consisting of diphenylmethane 4,4’-, 2,4’- and 2,2’-diisocyanate and polyphenyl polymethylene polyisocyanates (crude MDI) and mixtures consisting of crude MDI and toluene diisocyanate. The organic diisocyanates and polyisocyanates can be used individually or in the form of mixtures.

[0119] So-called modified polyfunctional isocyanates are also often used, i.e. products obtained via the chemical reaction of organic diisocyanates and / or polyisocyanates. For example, mention may be made of diisocyanates and / or polyisocyanates containing uretdione groups, carbamate groups, isocyanurate groups, carbodiimide groups, urethane groups and / or allophanate groups. If appropriate, the modified polyisocyanates can be mixed with one another or with unmodified organic polyisocyanates such as diphenylmethane 2,4’ or 4,4’-diisocyanate, crude MDI or toluene 2,4- and / or 2,6-diisocyanate.

[0120] The compounds which can be used for the preparation of polyurethanes having at least two hydrogen atoms reactive towards isocyanate groups are those carrying at least two reactive groups selected from OH groups, SH groups, NH groups, NH2 groups and acidic CH groups. Polyols are preferably used and especially polyether alcohols and / or polyester alcohols having an OH value in the range from 25 mg KOH / g to 800 mg KOH / g.

[0121] The polyester alcohols used are mainly prepared by the condensation of polyols (preferably diols) having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, with polycarboxylic acids having 2 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decane dicarboxylic acid, maleic acid, fumaric acid, or preferably phthalic acid, isophthalic acid, terephthalic acid or isomeric naphthalene dicarboxylic acids. The polyester alcohols mainly used have a functionality of 1.5 to 4.

[0122] The polyether polyols used in particular are those prepared by known methods, for example by anionic polymerization of alkylene oxides onto H-functional starting materials in the presence of a catalyst, preferably an alkali metal hydroxide or a double metal cyanide catalyst (DMC catalyst). The alkylene oxides used are mainly ethylene oxide or propylene oxide, or tetrahydrofuran, various butylene oxides or styrene oxide, and preferably pure 1,2-propylene oxide. The alkylene oxides can be used individually, used alternately in succession or used in the form of a mixture. The starting materials used in particular are compounds having at least 2, preferably 2 to 8, hydroxyl groups in the molecule or having at least two primary amino groups. The starting materials used having at least 2, preferably 2 to 8, hydroxyl groups in the molecule are preferably trimethylolpropane, glycerol, pentaerythritol, saccharide compounds (such as glucose, sorbitol, mannitol and sucrose), polyhydric phenols, novolac resins (such as oligomeric condensates composed of phenol and formaldehyde, and Mannich condensates composed of phenol, formaldehyde and dialkanolamine), and melamine. The starting materials used having at least two primary amino groups in the molecule are preferably aromatic diamines and / or polyamines, such as phenylenediamine, 2,3-toluenediamine, 2,4-toluenediamine, 3,4-toluenediamine and 2,6-toluenediamine and 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane and 2,2'-diaminodiphenylmethane, and aliphatic diamines and polyamines, such as ethylenediamine. The preferred functionality of the polyether polyols is from 2 to 8 and their preferred hydroxyl value is from 25 mg KOH / g to 800 mg KOH / g, especially from 150 mg KOH / g to 570 mg KOH / g.

[0123] Other compounds having at least two hydrogen atoms reactive towards isocyanate are crosslinking agents and chain extenders, which can be used in combination if appropriate. The addition of a difunctional chain extender, a trifunctional or higher functionality crosslinking agent, or, if appropriate, a mixture of these can prove advantageous for improving mechanical properties. The chain extender and / or crosslinking agent preferably used is an alkanolamine and especially a diol and / or triol having a molecular weight below 400, preferably from 60 to 300. The useful amount of the chain extender, crosslinking agent or a mixture thereof is from 1% by weight to 20% by weight, preferably from 2% by weight to 5% by weight, based on the polyol component.

[0124] 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.

[0125] In one embodiment, the rigid polyurethane foam is selected from rigid polyurethane foams based on aromatic isocyanates, preferably from rigid polyurethane foams based on methylene bis(phenyl isocyanate) and rigid polyurethane foams based on polymeric methylene bis(phenyl isocyanate). Rigid polyurethane foams based on methylene bis(phenyl isocyanate) and rigid polyurethane foams based on polymeric or oligomeric methylene bis(phenyl isocyanate) are particularly preferred.

[0126] Accordingly, according to another embodiment, the present invention also relates to the method as disclosed above, wherein the rigid polyurethane foam is selected from the group consisting of rigid polyurethane foams based on aromatic isocyanates, preferably selected from rigid polyurethane foams based on methylene bis(phenyl isocyanate), rigid polyurethane foams based on polymeric methylene bis(phenyl isocyanate), and 1 rigid polyurethane foam.

[0127] The polyfunctional isocyanate based on diphenylmethane diisocyanate (MDI) is in particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI or oligomeric MDI (which is also referred to as polyphenyl polymethylene polyisocyanate), or a mixture of two or three of the aforementioned diphenylmethane diisocyanates, or crude MDI produced in MDI production, or a mixture of at least one MDI oligomer and at least one of the aforementioned low molecular weight MDI derivatives.

[0128] In the rigid polyurethane foam based on methylene bis(phenyl-isocyanate), an isomeric mixture of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate; an isomeric mixture of 4,4'- and 2,2'-diphenylmethane diisocyanate; polyphenyl polymethylene polyisocyanate; or a mixture of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate can also be used.

[0129] Modified polyisocyanates are generally also used, i.e., products obtained by chemical reaction of organic polyisocyanates and having two or more reactive isocyanate groups per molecule. Particular mention may be made of polyisocyanates containing ester, urea, biuret, urethane, carbodiimide, isocyanurate, uretdione, carbamate and / or allophanate groups.

[0130] An aromatic isocyanate is a compound in which the isocyanate functional group is directly bonded to an aromatic core. In contrast, a compound such as p-phenylene diisocyanate is not considered an aromatic isocyanate because the isocyanate functional group is bonded to a methylene spacer and thus not directly bonded to an aromatic core.

[0131] After depolymerization, the process of the present invention generally produces polyamines containing amino groups attached to the carbon atoms to which the isocyanate groups were bonded in the initial polyisocyanate, for example, methylene diphenyl diamine, oligomeric and polymeric methylene polyphenylene amines, and toluene diamine (TDA), especially 2,4-toluene diamine or 2,6-toluene diamine or 1,5-naphthyl diamine (NDA). The polyols commonly used as described above can preferably also be re-separated. Thus, the process preferably further produces, for example, 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.

[0132] According to another aspect, the present invention also relates to a phosphite-based flame retardant, polymerization catalyst, or surfactant obtained or obtainable according to the method disclosed above, especially a phosphite-based flame retardant obtained or obtainable according to the method disclosed above. The present invention also relates to a polyol composition obtained or obtainable according to the method disclosed above.

[0133] Preferably, the obtained phosphite-based flame retardant, polymerization catalyst, or surfactant and the obtained polyurethane components can be reused, for example, in a process for preparing polyurethanes or polyisocyanurates.

[0134] Preferably, the obtained polyol composition can also be reused, for example, in a process for preparing polyurethanes or polyisocyanurates.

[0135] Thus, according to another aspect, the present invention also relates to the use of a phosphite-based flame retardant, polymerization catalyst, or surfactant according to the present invention, or a phosphite-based flame retardant, polymerization catalyst, or surfactant obtained or obtainable according to the method disclosed above, for preparing polyurethanes or polyisocyanurates.

[0136] Further embodiments of the present invention can be found in the claims and the examples. It should be understood that the features of the subject matter / method / use according to the present invention described above and elaborated below can be used not only in the combinations specified in each case, but also in other combinations without departing from the scope of the present invention. For example, combinations of preferred features with particularly preferred features or combinations of features not further characterized with particularly preferred features, etc., are thus also implicitly covered even if the combination is not explicitly mentioned.

[0137] Exemplary embodiments of the present invention are listed below, but these do not limit the present invention. In particular, the present invention also covers those embodiments resulting from the combinations specified by the dependent references and thus below.

[0138] 1. A method for the value chain return of polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bonded to the polymer chain, wherein the at least one additive (A1) is selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprising the following steps:

[0139] a) Providing a composition comprising comminuted polyurethane or polyisocyanurate rigid foam, wherein the comminuted foam has a complete cell content of less than 10% based on the number of complete cells of the uncomminuted polyurethane or polyisocyanurate rigid foam.

[0140] b) Extracting the additive (A1) with a solvent at a temperature below 190 °C.

[0141] 2. The method according to embodiment 1, wherein the method further comprises step c)

[0142] c) Depolymerizing the comminuted polyurethane or polyisocyanurate obtained in step b).

[0143] 3. The method according to embodiment 2, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or ammonolysis.

[0144] 4. The method according to 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.

[0145] 5. The method according to embodiment 4, wherein the method further comprises step d)

[0146] d) Separating the isocyanate component or its amine derivative from the polyol component.

[0147] 6. The method according to embodiment 3, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0148] 7. The method according to embodiment 3, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0149] 8. The method according to any one of embodiments 1 to 7, wherein the polyurethane rigid foam is selected from the group consisting of polyurethane rigid foams based on aromatic isocyanates, preferably selected from polyurethane rigid foams based on methylene bis(phenyl isocyanate) and polyurethane rigid foams based on polymeric methylene bis(phenyl isocyanate).

[0150] 9. The method according to any one of embodiments 1 to 8, wherein the at least one phosphite-based 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, tetra(2-chloroethyl) ethylenediphosphate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenyltolyl phosphate, triethyl phosphate, and mixtures thereof.

[0151] 10. The method according to any one of embodiments 1 to 9, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0152] 11. The method according to any one of embodiments 1 to 10, wherein the at least one surfactant is selected from the group consisting of silicone cell stabilizers.

[0153] 12. The method according to any one of embodiments 1 to 11, wherein the solvent is selected from organic aprotic solvents, water, polyols, and alcohols.

[0154] 13. The method according to embodiment 12, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0155] 14. The method according to any one of embodiments 1 to 6, wherein the extraction is carried out at a temperature in the range of 20 °C to 190 °C.

[0156] 15. A polyol composition obtained or obtainable by the method according to any one of embodiments 1 to 14.

[0157] 16. Use of the phosphite-based flame retardant obtained or obtainable by the method according to any one of embodiments 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

[0158] 17. Use of the polymerization catalyst obtained or obtainable by the method according to any one of embodiments 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

[0159] 18. Use of the stabilizer obtained or obtainable by the method according to any one of embodiments 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

[0160] 19. Use of the polyol composition according to embodiment 15 or a polyol composition obtainable or obtainable according to the method according to any one of embodiments 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

[0161] 20. A method for the value chain return of polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) not chemically bonded to the polymer chain, said at least one additive (A1) being selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprising the following steps:

[0162] a) Providing a composition comprising comminuted polyurethane or polyisocyanurate rigid foam, wherein the comminuted foam has a content of intact cells of less than 10% based on the number of intact cells of the non-comminuted polyurethane or polyisocyanurate rigid foam,

[0163] b) Extracting the additive (A1) with a solvent at a temperature below 190 °C,

[0164] c) Depolymerizing the comminuted polyurethane or polyisocyanurate obtained in step b).

[0165] 21. A method for the value chain return of polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) not chemically bonded to the polymer chain, said at least one additive (A1) being selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprising the following steps:

[0166] a) Providing a composition comprising comminuted polyurethane or polyisocyanurate rigid foam, wherein the comminuted foam has a content of intact cells of less than 10% based on the number of intact cells of the non-comminuted polyurethane or polyisocyanurate rigid foam,

[0167] b) Extracting the additive (A1) with a solvent at a temperature below 190 °C, wherein the solvent is selected from organic aprotic solvents, water, polyols, and alcohols.

[0168] 22. The method according to embodiment 21, wherein the method further comprises step c)

[0169] c) Depolymerizing the comminuted polyurethane or polyisocyanurate obtained in step b).

[0170] 23. The method according to embodiment 22, wherein the depolymerization according to step c) is carried out by a method selected from hydrolysis, glycolysis, hydrogenation, or ammonolysis.

[0171] 24. The method according to 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.

[0172] 25. The method according to embodiment 24, wherein the method further comprises step d)

[0173] d) separating the isocyanate component or its amine derivative from the polyol component.

[0174] 26. The method according to embodiment 23, wherein the glycolysis is carried out in the presence of a metal catalyst.

[0175] 27. The method according to embodiment 23, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst.

[0176] 28. The method according to any one of embodiments 21 to 27, wherein the rigid polyurethane foam is selected from the group consisting of rigid polyurethane foams based on aromatic isocyanates, preferably selected from rigid polyurethane foams based on methylene bis(phenyl isocyanate), rigid polyurethane foams based on polymeric methylene bis(phenyl isocyanate).

[0177] 29. The method according to any one of embodiments 21 to 28, wherein the at least one phosphite-based 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, tetra(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenyltolyl phosphate, triethyl phosphate, and mixtures thereof.

[0178] 30. The method according to any one of embodiments 21 to 29, wherein the at least one polymerization catalyst is selected from the group consisting of tertiary amines.

[0179] 31. The method according to any one of embodiments 21 to 30, wherein the at least one surfactant is selected from the group consisting of silicone-based cell stabilizers.

[0180] 32. The method according to embodiment 21, wherein the organic aprotic solvent is selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones, and mixtures thereof.

[0181] The present invention can be further explained and illustrated based on the following examples. However, it should be understood that including these examples is for illustrative purposes only and is not intended to limit the scope of the present invention in any way. Examples

[0182] 1. Materials used

[0183] Polyol 1: A polyether polyol with an OH value of 490 obtained by the propoxylation of a mixture of sucrose and glycerol.

[0184] Elastopir: A polyisocyanurate rigid foam (Index = 330) from BASF Polyurethanes, obtained by reacting a P-containing flame retardant-containing polyol component

[0185] (Elastopir 1132 / 509) with Lupranat M50.

[0186] Elastocool: A rigid polyurethane foam (Index = 120) from BASF Polyurethanes, obtained by reacting a polyol component (Elasto-

[0187] cool F 2030 / 310) with Lupranat M20.

[0188] 2. General description

[0189] In the extraction experiment, different PU rigid foams containing at least one phosphite-based flame retardant were used. PU rigid foam Index 100 is 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 purchased from Evonik Industries AG), 0.5 part by weight of Lupragen N600 (a tertiary amine purchased from BASF SE, Germany), 2.5 parts by weight of water, 5 parts by weight of cyclopentane, and 100 parts by weight of Lu-pranat MP 102 (a short-chain prepolymer based on pure 4,4'-diphenylmethane diisocyanate purchased from BASF SE, Germany), so that the final PU rigid foam contains 9.4% by weight of the flame retardant TCPP. PU rigid foam Elastopir is based on 70% polymeric MDI and 25% of a polyol component (a mixture of polyester polyol and polyether polyol), 3.5% by weight of the TCPP (tris(2-chloroisopropyl) phosphate) flame retardant, and a total of 2.5% by weight of a tertiary amine catalyst and a silicone surfactant as other extractable components in addition to the phosphite-based flame retardant.

[0190] For comparison, Elastocool, a PU rigid foam made from pMDI (60%) and polyether polyol, was also used as a reference material to demonstrate the stability of the PU polymer chain under these conditions. This PU rigid foam does not contain an extractable phosphite-based flame retardant.

[0191] These rigid foams are used as comminuted foams in powder form, and based on the number of intact cells of the non-comminuted rigid foam, their intact cell content is less than 1%. The intact cell content is determined using an optical microscope.

[0192] 3. Procedure for pre-extracting flame retardants :

[0193] Charge the polymer into a 38 mL Ace tube (without stir bar). Rinse the walls with cyclohexane (CyH). Seal the Ace tube and heat for a specified time to a specified temperature (preheated metal block, without stirring). After cooling to room temperature, filter the suspension through a suction filter. The remaining polymer is rinsed with additional cyclohexane (2 x 10 mL, 1 x 5 mL). Transfer the polymer to a vial and dry overnight at 60 °C (oven) to obtain a certain amount of recovered polymer. Remove the solvent from the filtrate under reduced pressure (47 °C, minimum pressure 60 mbar). By 1 H. 31 P and 13 C NMR spectroscopy (CDCl 3 3) and GC-FID analysis, a colorless oil is obtained.

[0194]

[0195]

[0196] [1] The separated oil contains residual solvent.

[0197] [2] In addition to the flame retardant (TCPP) as the main component, the separated oil also contains a small amount of other unidentified

[0198] substances.

[0199] [3] Experiments are carried out in a 300 mL stainless steel autoclave (Premex) equipped with a Teflon insert under stirring

[0200] (750 RPM).

[0201] [4] The separated oil contains other unidentified substances.

[0202] CyH = cyclohexane; RPM = revolutions per minute.

[0203] Index 100 and Elastopir extracts contain the flame retardant (TCPP - tris(2-chloroisopropyl) phosphate). Elastopir and Elastocool samples contain a small amount of silicon stabilizer and a small amount of amine catalyst.

[0204] 4. Procedure for pre-extracting flame retardants using different solvents :

[0205] Charge a 38 mL Ace tube (without stir bar) with the polymer (1.00 g). Rinse the walls with the specified solvent. Seal the Ace tube and heat for 16 h to 150 °C (preheated metal block, without stirring). After cooling to room temperature, filter the suspension through a suction filter. Wash the remaining polymer with the specified solvent (2 x 10 mL, 1 x 5 mL). Transfer the polymer to a vial and dry overnight at 60 °C (oven) to obtain a certain amount of recovered polymer. Remove the solvent from the filtrate under reduced pressure (47 °C, minimum pressure 60 mbar). By 1 H. 31 P and 13 C NMR spectroscopy (CDCl 3 ) and a colorless oil obtained by GC-FID analysis.

[0206]

[0207]

[0208] [1] The separated oil contains residual solvent.

[0209] [2] The separated oil contains a small amount of other unidentified substances in addition to the flame retardant (TCPP) as the main component.

[0210] [3] Experiments were carried out in a stainless-steel autoclave (Premex) equipped with a Teflon insert under stirring (750 RPM).

[0211] [4] Some polymers are lost during transfer.

[0212] EtOAc = ethyl acetate; THF = tetrahydrofuran; PhMe = toluene; EtOH = ethanol; MTBE = methyl tert-butyl ether; DCM = dichloromethane; CPME = cyclopentyl methyl ether; RPM = revolutions per minute.

[0213] Index 100 and Elastopir extracts contain the flame retardant (TCPP - tris(2-chloroisopropyl) phosphate). Elastopir and Elastocool samples contain a small amount of silicon stabilizer and a small amount of amine catalyst.

[0214] 5. Hydrolysis of pretreated / pre-extracted polymer samples :

[0215] In air, charge a pre-extracted Elastopir foam (7.70 g) into a stainless-steel autoclave (Premex) equipped with a Teflon insert. Rinse the walls with methylimidazole (80 mL) and water (8 mL). Close the autoclave and heat overnight with stirring to 160 °C. After stirring at 160 °C for 18 h, cool the autoclave to room temperature and slowly open to release the residual CO2 Pressure. A clarified purple-brown solution was obtained. The solution was transferred to a round-bottom flask and the autoclave was rinsed with additional 1-methylimidazole (3 × 5 mL). The solvent was removed under reduced pressure (slowly gradually heated to 100 °C, 2.5·10 –2 mbar). Under argon, the residue was dissolved in anhydrous dichloromethane (20 mL) and filtered (Whatman) into a 200 mL Schlenk tube. The flask was rinsed with DCM (4 × 10 mL) additionally. No solid remained in the initial flask or on the filter. The brown solution was diluted with DCM (90 mL, total volume of the solution = 150 mL). An ethereal solution of HCl (2 M in Et 2 O, 50 mL) was added dropwise slowly at room temperature. A large amount of yellow precipitate was observed. The suspension was transferred to a Schlenk filter frit ( ~500 mL, grade 3 filter). The remaining solid was washed with anhydrous dichloromethane (6 × 40 mL). After drying overnight under reduced pressure (r.t., 1.4·10 –2 mbar), the solid was transferred into the glove box and weighed. The separated pale yellow solid (6.62 g) consisted of the amine fraction of the polymer separated as the hydrochloride salt. The solvent of the filtrate was removed under reduced pressure (49 °C, minimum pressure 55 mbar). The obtained dark brown oil (1.55 g) consisted of the polyol fraction after hydrolysis. All products were characterized by 1 H and 13 C NMR.

[0216] 6. Comparative Example 1: Hydrolysis of rigid PU foam in the presence of phosphite-based flame retardants :

[0217]

[0218] After the reaction, the reaction mixture was obtained as a dark brown solution free of solids. By analyzing the reaction mixture via GC / MS, 4,4'-methylenedianiline was detected. However, according to the GC / MS or 31 P NMR data, the reaction mixture did not contain a phosphite-based flame retardant. Therefore, the phosphite-based flame retardant hydrolyzed under these conditions.

[0219] Experimental details: In air, untreated PU rigid foam Index 100 (1.00 g) was charged into a stainless-steel autoclave (Premex) equipped with a Teflon insert. The walls were rinsed with pyridine (20 mL) and water (2 mL). The autoclave was closed and heated for 16 h to 160 °C. After cooling to room temperature (ice bath), the brown solution was filtered through a suction filter and the filter was rinsed with EtOH (3 × 5 mL). No solid remained on the filter. The solvent was removed under reduced pressure (45 °C, minimum pressure 60 mbar). According to 1 H and31 P NMR analysis detected no flame retardant in either the crude or isolated materials.

[0220] 7. Comparative Example 2: Hydrogenolytic depolymerization of rigid polyurethane foam containing phosphite-based flame retardants using MACHO catalyst in the protic solvent isopropanol Cited literature

[0221] The results and conditions of the following procedures are summarized in Table 2.

[0222] Charge 1.00 g of PU rigid foam Index 100 into a stainless-steel autoclave (Premex) equipped with a Teflon insert. Inside the glove box, add the catalyst and base. Rinse the walls with isopropanol and close the autoclave. Outside the glove box, flush the autoclave with hydrogen (2 × 15 bar) and finally charge with hydrogen (50 bar). Heat the autoclave with stirring for 21 h to 180 °C (preheated metal block, 750 RPM). After cooling to room temperature (ice bath), carefully release the residual pressure. Filter the suspension through a suction filter and wash the remaining solid with dichloromethane (3 x 5 mL) and EtOH (3 x 5 mL). Dry the solid residual polymer under reduced pressure (room temperature, <5.0·10 –2 mbar) and use it to determine the conversion (conversion = [(polymer used - polymer recovered) / polymer used] × 100). After removing the solvent from the filtrate under reduced pressure (45 °C, minimum pressure 80 mbar), redissolve the residue in CDCl 3 (2 mL). Add an aliquot (50.0 μL) of 1,1,2,2-tetrachloroethane as an internal standard and homogenize the solution by vortexing. Analyze the sample by 1 H and 31 P NMR spectroscopy. In 1 H NMR, determine the amount of TCPP in the corresponding sample by integration of the TCPP signal (δ = 4.67 ppm) relative to the 1,1,2,2-tetrachloroethane signal (δ = 6.00 ppm).

[0223] Determine the amount of amine by additionally purifying the reaction mixture of entry 2 by flash column chromatography (EtOAc - hexane). Finally, rinse the silica pad with EtOH to elute the polyol fraction.

[0224]

[0225] ​

[0226] US4196148A

[0227] WO2010 / 130652A2

[0228] DE2854940A1

[0229] CN107337615B

[0230] WO 2015 / 121057

[0231] WO 2013 / 139781

[0232] Ullmann’s Encyclopedia of Industrial Chemistry, Phosphorus Compounds, Organic, 2012, DOI: 10.1002 / 14356007.a19_545.pub2

[0233] Chemosphere, 2012, 88, 1119 - 1153 and WO 2015 / 121057

[0234] Plastics recycling and Polyurethanes, in Ullmann’s Encyclopedia of Industrial Chemistry, 2020, DOI: 10.1002 / 14356007.a21_057.pu

[0235] ChemSusChem, 2020, DOI: 10.1002 / cssc.20200246 or ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705

[0236] T. Skrydstrup et al., JACS Au, 2021, DOI: 10.1021 / jacsau.1c0005

[0237] Zhurnal Obshchei Khimii, 1978, 78, 694 - 695

[0238] J. Chem. Eng. Data, 2008, 53, 2718 - 2720

[0239] T. Schaub et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101606

[0240] T. Skrydstrup et al., ChemSusChem, 2021, DOI: 10.1002 / cssc.202101705

Claims

1. A method for the value chain return of polyurethane and polyisocyanurate rigid foams containing at least one additive (A1) that is not chemically bonded to the polymer chain, said at least one additive (A1) being selected from the group consisting of phosphite-based flame retardants, polymerization catalysts, and surfactants, the method comprises the following steps: a) Providing a composition comprising comminuted polyurethane or polyisocyanurate rigid foam, wherein based on the number of intact cells of the non-comminuted polyurethane or polyisocyanurate rigid foam, the comminuted foam has an intact cell content of less than 10%. b) Extracting the additive (A1) with a solvent at a temperature below 190 °C.

2. The method according to claim 1, wherein the method further comprises step c) c) Depolymerizing the comminuted polyurethane or polyisocyanurate obtained in step b).

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

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. The method according to claim 4, wherein the method further comprises step d) d) Separating the isocyanate component or its amine derivative from the polyol component.

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

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

8. The method according to any one of claims 1 to 7, wherein the polyurethane rigid foam is selected from the group consisting of polyurethane rigid foams based on aromatic isocyanates, preferably selected from polyurethane rigid foams based on methylene bis(phenyl isocyanate), polyurethane rigid foams based on polymeric methylene bis(phenyl isocyanate).

9. The method according to any one of claims 1 to 8, wherein the at least one phosphite-based 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, tetra(2-chloroethyl)-ethylene diphosphate, dimethyl phosphonate, dimethylpropyl phosphonate, diphenyltolyl phosphate, triethyl phosphate, and mixtures thereof.

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

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

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

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

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

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

16. Use of the phosphite-based flame retardant obtained or obtainable by the method according to any one of claims 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

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

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

19. Use of the polyol composition according to claim 15 or a polyol composition obtained or obtainable by the method according to any one of claims 1 to 14 for the preparation of polyurethanes or polyisocyanurates.

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