Method for recovering valuable materials from polyurethane foams
The described process effectively addresses the challenge of separating methylenediphenylenediamine and polyphenylenepolymethylenepolyamine from MDI-based polyurethane foams by hydrolysis and controlled solvent use, achieving high-purity isolation through solvent selection and distillation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- COVESTRO DEUTSCHLAND AG
- Filing Date
- 2025-11-05
- Publication Date
- 2026-05-15
AI Technical Summary
The challenge in recycling MDI-based polyurethane foams lies in the complex separation of polyols and amines, particularly due to the low water solubility of methylenediphenylenediamine (MDA) and polyphenylenepolymethylenepolyamine, which are difficult to isolate with high purity using existing extraction or precipitation methods.
A process involving hydrolysis of polyurethane foams with water at specific temperatures, followed by the addition of solvents and pyrostatic acid to form salts, then distilling under controlled conditions to precipitate these compounds, allowing for their isolation in a simple and pure manner.
Enables the efficient and high-purity separation of methylenediphenylenediamine and polyphenylenepolymethylenepolyamine from polyurethane hydrolysates, overcoming the limitations of existing methods by maintaining these compounds in solution until distillation, thereby simplifying their recovery.
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Abstract
Description
[0001] METHOD FOR RECOVERING VALUE MATERIALS FROM POLYURETHANE FOAM
[0002] The project that led to this application has received funding under grant agreement no. 101036854 from the European Union’s Horizon 2020 research and innovation programme.
[0003] The present invention relates to the hydrolysis of an MDI- and polyether polyol-based polyurethane foam with water to obtain a hydrolysate containing the polyether polyol, methylenediphenylenediamine and polyphenylenepolymethylenepolyamine and optionally solid components, wherein the hydrolysate is processed by the following steps: Optionally, separation of any solid components that may be present;Addition of a first solvent and optionally a second solvent, wherein the second solvent is added at least when the hydrolysate contains no more than 50% water by mass, wherein the first solvent is an aprotic organic solvent that boils at a higher temperature than the second solvent, but at least at a higher temperature than water, and wherein at least 50 g of water dissolve in 1000 g of the first solvent at 20 °C, wherein the second solvent is selected from a C1 to C4 alcohol, water, or a mixture thereof, wherein the first solvent is added in such an amount that, after mixing all components, only a liquid phase, optionally containing solid components, is present; separation of any solid components that may be present; addition of a pyrostatic acid, wherein at least a first part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts formed remain in solution;Distillation of volatile components at a temperature and pressure such that the boiling point of the first solvent is undershot and the first part of the methylenediphenylenediamine salts and polyphenylenepolymethylene polyamine salts of Brensted acid precipitates; and separation of the precipitated methylenediphenylenediamine salts and polyphenylenepolymethylene polyamine salts, leaving a polyether polyol phase comprising the polyether polyol.
[0004] Polyurethane foams have a wide range of applications in industry and everyday life. They are typically divided into rigid and flexible foams. All foam types share the basic polyurethane structure, which is formed by the polyaddition reaction of a polyhydric isocyanate and a polyol. For example, a polyurethane (PU) based on a diisocyanate O=C=NRN=C=O and a dihydric polyol HO-R'-OH (where R denotes a low-molecular-weight or oligomeric organic residue and R' a polymeric organic residue) can be described as follows:
[0005] [O-R'-O-(O=C)-HN-R-NH-(C=O)]. Many polyurethanes contain additional structural units besides the polyurethane base structure. These include, in particular, urea, isocyanurate, allophanate, and biuret structural units.
[0006] An important isocyanate is MDI. MDI is a collective term for methylenediphenyl diisocyanate (mMDI – “monomeric MDI”) and polymethylene-polyphenylene polyisocyanate, which refers to the higher homologs of mMDI (also called “polymeric MDI”, pMDI). Methylenediphenyl diisocyanate exists in several isomers, of which 2,4'-methylenediphenyl diisocyanate and 4,4'-methylenediphenyl diisocyanate are the most important.
[0007] Pure mMDI and mixtures of mMDI and pMDI are technically important. Such mixtures (hereinafter referred to as MDI) are widely used, for example, in the production of rigid foams. The industrial production of MDI starts with aniline, which undergoes an acid-catalyzed reaction with formaldehyde, yielding mixtures of methylenediphenylenediamine ("monomeric MDA," mMDA) and polymethylenepolyphenylenepolyamine ("polymeric MDA," pMDA). Analogous to MDI, the collective term MDA is used below for mixtures of mMDA and pMDA. These mixtures are usually phosgenated without prior separation, thus obtaining corresponding mixtures of mMDI and pMDI. Typically, fractions of essentially pure mMDI are distilled off from these mixtures, leaving behind mixtures of pMDI and mMDI with an increased pMDI content compared to the starting mixtures.
[0008] Precisely because of the great economic success of polyurethanes, large quantities of polyurethane waste (e.g., from old mattresses, seating furniture, or insulation) are generated, which must be put to good use. The technically simplest form of reuse is incineration, utilizing the heat released for other processes, such as industrial manufacturing. However, this method does not allow for closing the material cycle. Another form of reuse is so-called "physical recycling," in which polyurethane waste is mechanically shredded and used in the production of new products. This type of recycling naturally has its limitations, which is why there has been no shortage of attempts to recover the basic chemicals underlying polyurethane production through chemical cleavage (chemolysis) of the polyurethane bonds (so-called "chemical recycling").The chemical raw materials to be recovered primarily comprise polyols (in the example above, HO-R'-OH). In addition, amines can also be obtained by hydrolytic cleavage of the urethane bond (in the example above, H₂N-R-NH₂), which, after processing, can be phosgenated to isocyanates (in the example above, to O=C=NRN=C=O). A summary of the polyurethane recycling processes known up to 2017 is provided in the review article by Simon, Borreguero, Lucas, and Rodriguez in Waste Management 2018, 76, 147–171 [1]. Glycolysis (see section 2 below) is highlighted therein as being particularly important.
[0009] Various approaches to chemical recycling have been developed in the past. Five of them are briefly summarized below:
[0010] 1. Hydrolysis of polyurethanes by reaction with water to obtain amines and polyols with the formation of carbon dioxide.
[0011] 2. Glycolysis (alcohollysis) of polyurethanes by reaction with alcohols, whereby the polyols incorporated into the urethane groups are replaced by the alcohol used and thus released (umurethanization). This type of chemical recycling is commonly referred to as glycolysis in the literature, regardless of the specific type of alcohol used, although this term is actually only applicable to glycols, and one should therefore more generally speak of alcoholysis. Glycolysis can be followed by hydrolysis. If the unchanged product mixture of a glycolysis (i.e., without prior separation of the polyols formed) is hydrolyzed, it is called hydrolysis.
[0012] 3. Hydroglycolysis (hydroalcohollysis) of polyurethanes. It is also possible, of course, to add alcohol and water from the beginning, in which case the hydrolysis and glycolysis processes described above occur in parallel.
[0013] 4. Aminolysis of polyurethanes by reaction with primary or secondary amines, whereby the polyols incorporated into the urethane groups can be replaced by the amine used and thus released. In this case, the urethane groups are converted to urea groups. Similarly, the R-NH (C=O) bonds in the urethanes can also be cleaved, and the R-NH groups replaced by the amine used in the aminolysis, releasing the amine R-NH₂ corresponding to the originally used isocyanate. If amino acids with primary or secondary amino groups are used, the alcohol groups of the amino alcohol used can also react with urethane bonds, potentially leading to the formation of carbamates. According to most of the prior art, aminolysis can be followed by hydrolysis in a separate step.
[0014] 5. A reaction procedure corresponding to hydroglycolysis, in which amines or amino alcohols and water are used as reagents without prior separation of the released polyols, is described in WO 2023 / 083968 Al and referred to there as aminohydrolysis. The present application deals with hydrolysis (No. 1), specifically with the processing of MDI-based polyurethane foam hydrolysates. A major challenge in the chemical recycling of polyurethanes is the clean separation of the resulting chemolysis products into polyols and amines formed by hydrolysis. The development of usable processing concepts has been and continues to be the subject of numerous investigations. Particular challenges arise when the isocyanate component used in the production of the polyurethane contains the isocyanate MDI discussed above. In contrast to toluene diisocyanate (TDI), which is found in so-calledIn the broad application of flexible foams, the hydrolysis of an MDI-based polyurethane product (for example, from old, used, so-called "end-of-life" (Eo\_-) products or from offcuts generated during the production of polyurethane foams) yields an amine (MDA) that is only very poorly soluble in water. This makes its isolation through extractive processes, especially the separation of polyols (which is important in the case of polyurethane recycling), complex. Switching to distillation processes is not possible in the case of pMDA (which is regularly the case in the recycling of rigid foams) due to its high boiling point, which makes the isolation of pMDA in high purity very difficult.
[0015] In the past, various approaches have therefore been developed for the purification of MDA-containing chemolysis products, which involve the protonation of the MDA to a salt, in particular chloride. The resulting “MDA hydrochloride” can be transferred to an aqueous phase by extraction or precipitated from an organic medium.
[0016] EP 0013 350 Al describes a process for separating chemolysis products (hydrolysates) obtained by hydrolysis (particularly at 100 °C to 300 °C and 5 bar to 100 bar) of polyurethanes into polyols or polyamines that can be reused for the production of polyurethane plastics. This is achieved by introducing hydrogen chloride gas into the hydrolysate mixture, preferably diluted with an inert solvent, especially toluene, and filtering off the amine salt precipitated in this way, wherein the hydrogen chloride precipitation is carried out fractionally (in several steps). The described process is considered particularly suitable for processing the hydrolysates of polyetherurethane foams.
[0017] DE 2 207 379 discloses a process for recovering polyether polyols from polyurethane plastics, in which the comminuted plastic is heated under direct steam pressure at approximately 20 atm (19.6 bar) for at least one hour in an autoclave at 150 to 220 °C. For work-up, the treated reaction product can be dissolved in an organic solvent, such as toluene, in particular, treated with dilute hydrochloric acid, and filtered. The remaining organic solution is evaporated and filtered, yielding the polyether polyol as a residue.WO 2023 / 083968 describes the aminohydrolysis of polyurethanes with an amine chemolysis reagent and water in the presence of a catalyst, followed by work-up of the resulting chemolysis product by liquid-liquid extraction with an extraction solvent and phase separation into a first product phase containing an amine formed from the polyurethane in the aminohydrolysis or a salt of such an amine, and a second product phase containing a polyol formed from the polyurethane in the aminohydrolysis. The liquid-liquid extraction may be preceded by distillation to separate the amine chemolysis reagent from the chemolysis product. If the polyurethane is based on methylenediphenyl diisocyanate or a mixture of methylenediphenyl diisocyanate and polymethylenepolyphenylene polyisocyanate, the extraction solvent preferably comprises (i) an organic solvent selected from a hydrocarbon or a halogen-substituted hydrocarbon and (ii) hydrochloric acid.
[0018] WO 2024 / 094787 describes a value chain recycling process comprising: a) “depolymerization” of a polyurethane and polyisocyanurate rigid foam based on polymeric methylenediphenyl diisocyanate (pMDI) to produce a first mixture (Ml), b) distillative removal of volatile compounds from mixture Ml to produce a second mixture (M2) comprising pMDA and at least one polyol, c) dissolving mixture M2 in an aprotic organic solvent (Sl) with a dipole moment in the range of 0.5 x IO -30 cm up to 7.8 x 10" 30 Cm, and d) addition of HCl and separation of the pMDA-HCl salt formed. The solvent Sl is preferably selected from aliphatic hydrocarbons, halogenated hydrocarbons, ethers, aromatic hydrocarbons, esters, ketones and mixtures thereof.
[0019] All these processes involve either the extraction of MDA salt into an aqueous phase or its precipitation from an organic MDA solution by adding acid. Both methods have drawbacks. Extraction processes generally suffer from the problem that, due to prevailing solubility equilibria, some product inevitably ends up in the "wrong phase"; for example, an aqueous amine phase may be contaminated with small amounts of polyol, the complete separation of which is not at all trivial. While precipitation of MDA salt from an organic solution by lowering the pH is possible in principle, it can lead to the formation of a pasty solid that is difficult to separate, especially with significant amounts of pMDA, as is common in rigid foams.
[0020] There was therefore a need for further improvements in the field of recycling MDI-based polyurethane foams. In particular, it would be desirable to be able to isolate mMDA and pMDA formed by hydrolysis from the hydrolysate of a polyurethane foam in the simplest possible way and with the highest possible purity. Addressing this need, the invention provides the following:
[0021] A process for recovering valuable materials from polyurethane foams, comprising the following steps:
[0022] (A) Providing a polyurethane foam based on an isocyanate component and a polyol component, wherein the isocyanate component comprises methylene diphenyl end isocyanate and polyphenylene polymethylene polyisocyanate and in particular does not comprise any other isocyanates other than methylene diphenyl end isocyanate and polyphenylene polymethylene polyisocyanate (such as toluene diisocyanate, TDI), and wherein the polyol component comprises (at least) one polyether polyol and in particular does not comprise any other polyols other than polyether polyols (such as polyester polyols);
[0023] (B) Hydrolyzing the polyurethane foam with water, wherein water is added such that a mass ratio of water to polyurethane foam of at least 0.1 : 1, in particular of 0.1 : 1 to 20 : 1, is obtained, at a temperature of 180 °C to 260 °C, in particular without the addition of a hydrolysis catalyst, to obtain a hydrolysate containing the (at least one) polyether polyol, methylenediphenylenediamine and polyphenylenepolymethylenepolyamine and optionally (at the temperature of step (B)) solid components (such as, for example, metal residues from the original application of an EoL PU foam);
[0024] (C) Comprehensive work-up of the hydrolysate
[0025] (I) optional, separation of any solid components that may be present, in particular by filtration, centrifugation, sedimentation or a combination of these methods, preferably at a temperature in the range of 100 °C up to the temperature of step (B),
[0026] (II) Addition of a first solvent and optionally a second solvent, wherein the second solvent is added at least when the hydrolysate supplied to step (C) (II) (optionally pretreated according to step (C)(1) and / or - see below - according to step (C)(1.0)) contains no more than 50 wt% water, based on its total mass, wherein the first and the second solvents may be added in any order, wherein the first solvent is an aprotic organic solvent that boils at a higher temperature than the second solvent, but at least at a higher temperature than water, and wherein at least 50 g of water, preferably at least 200 g of water, dissolve in 1000 g of the first solvent at 20 °C, and wherein the first solvent is preferably selected from an ether, an ester, a ketone,a halogenated (aromatic or a I iphatic) hydrocarbon or a mixture of two or more of the aforementioned organic solvents (where ethers, esters or mixtures thereof are particularly preferred and ethers are most particularly preferred), wherein the second solvent is selected from a C1 to C4 alcohol, water or a mixture thereof, wherein the first solvent is added in such an amount that, after mixing all components (i.e., including the second solvent which may be used), only one (1) liquid phase remains, optionally containing solid components (such as, for example, metal residues, non-hydrolyzable polymers from polymer-filled PU foams or from additives used in the original application of a PU foam),
[0027] (III) Separation of any solid components that may be present,
[0028] (IV) Addition of a pyrostatic acid with formation of methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of the pyrostatic acid, wherein a first part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of the pyrostatic acid remains in solution and, if applicable, a second part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of the pyrostatic acid precipitates,
[0029] (V) Distilling off volatile components (i.e., any excess water remaining from step (B) and any second solvent added, where at least one of both is still present at this point) at such a temperature and pressure that the boiling point of the first solvent is reduced (in particular by at least 10 °C, preferably by at least 20 °C and in particular by at most 100 °C) (i.e., at the temperature and pressure chosen for step (C)(V)) and the first part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of bromstedtic acid precipitates, and
[0030] (VI) Separation of the precipitated methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of Brensted acid, leaving a polyether polyol phase comprising the (at least one) polyether polyol. It was quite unexpectedly found that the complete precipitation of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts (hereinafter also referred to collectively as MDA salts) obtained during a known acidic work-up of a PU hydrolysate only requires distillation of volatile compounds under deliberately chosen work-up conditions such that a significant proportion of the MDA salts remain in solution before distillation, thus allowing the isolation of these salts in a simple manner and with high purity.
[0031] Polyurethane foams are the polyaddition products obtained by reacting polyhydric isocyanates (the isocyanate component of polyurethane production) with polyols (the polyol component of polyurethane production) in the presence of blowing agents. In general, polyurethane foams contain, in addition to the basic polyurethane structure described above, other structures, for example, urea, isocyanurate, allophanate, and biuret structural units. The presence of such structures, which deviate from the pure polyurethane basic structure, alongside polyurethane structures is not outside the scope of the present invention. Polyurethane foams that can be recycled according to the invention are preferably polyurethane rigid foams. Within the scope of the present invention, a rigid polyurethane foam is understood to be a polyurethane foam that exhibits a compressive stress at 10% compression (cw) of 10 kPa or more, as measured according to DIN EN 826:2013-05.
[0032] In the terminology of the present invention, the term polyols encompasses all polyols known to those skilled in the art in connection with polyurethane chemistry, but in particular polyether polyols. The expression "a polyol" naturally also includes embodiments in which two or more different polyols are used in the production of a polyurethane foam. Therefore, when, for example, "a polyether polyol" is mentioned below, this terminology naturally also includes embodiments in which two or more different polyether polyols are used in the production of a polyurethane foam. The entirety of all polyols used in the production of a polyurethane foam is referred to as the polyol component (of the polyurethane foam). The polyol component comprises at least one polyol and at least one polyether polyol.Therefore, if the polyol component contains exactly one (1) polyol, then according to the invention this polyol is a polyether polyol. It is preferred that the polyol component comprises no other polyols besides polyether polyols. Polyether polyols are comparatively unreactive and can be recovered (essentially) chemically unchanged.
[0033] In the terminology of the present invention, the term isocyanate encompasses all isocyanates known to those skilled in the art in connection with polyurethane chemistry and refers in particular to methylenediphenyl diisocyanate or a mixture of methylenediphenyl diisocyanate (mMDI) and polymethylenepolyphenyl polyisocyanate (pMDI). The expression "one isocyanate" naturally also includes embodiments in which two or more different isocyanates (e.g., mixtures of MDI and TDI) are used in the manufacture of a polyurethane foam, unless otherwise expressly stated, for example by the formulation "exactly one isocyanate". The entirety of all isocyanates used in the manufacture of a polyurethane foam is referred to as the isocyanate component (of the polyurethane foam). The isocyanate component contains at least one isocyanate.It contains exactly one (1) isocyanate, which according to the invention is selected from mMDI or - preferably - a mixture of mMDI and pMDI.
[0034] An amine corresponding to an isocyanate is that amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCI2 -^> RN=C=O + 2 HC / .
[0035] When the present invention refers to a device / assembly (e.g., in expressions such as "a reactor," etc.), this also includes embodiments in which several devices / assemblies of the aforementioned type are connected in series or in parallel (the example expression is therefore to be read as "at least one reactor"), unless expressly stated otherwise (e.g., by the formulation "exactly one"). The same applies to substances (see the above discussion of polyols and isocyanates).
[0036] The term distillation, as used in the context of the present invention, also includes rectification.
[0037] If the water solubility of the first solvent is unknown, it can be easily determined. For this purpose, 1000 g of the first solvent and a defined quantity (50 g or 200 g for the preferred embodiment) of deionized water are each heated to 20 °C and mixed in a vessel heated to 20 °C while stirring at 200 rpm. After 5 minutes, the stirrer is stopped. If a single homogeneous phase forms within 5 minutes of stopping the stirrer, the water solubility of the first solvent is sufficient.
[0038] The following is a brief summary of various possible embodiments of the invention:
[0039] In a first embodiment of the invention, which can be combined with all other embodiments, the first solvent is selected from an ether, an ester, a ketone, a halogenated (aromatic or aliphatic) hydrocarbon, or a mixture of two or more of the aforementioned organic solvents. Ethers, esters, or mixtures thereof are particularly preferred, and ethers are especially preferred.
[0040] In a second embodiment of the invention, which can be combined with all other embodiments, excess water (i.e., water not consumed in step (B)) is distilled off in step (C)(1 1.0) after step (B) and before step (C)(1 1.0) down to a residual content of a maximum of 50 wt%, in particular a maximum of 10 wt%, based on the total mass of the hydrolysate present after distillation of the water, wherein the second solvent (which is necessarily added in this embodiment as a result of the water separation) comprises a Ci to C4 alcohol.
[0041] In a third embodiment of the invention, which can be combined with all other embodiments, step (C) further comprises:
[0042] (VII) Purification of the polyether polyol phase comprising one or more of the following purification operations:
[0043] Distillation and / or stripping,
[0044] Removal of acidic impurities by washing with an aqueous alkaline solution and / or treatment with a resin containing basic functional groups,
[0045] Adsorption of impurities onto activated carbon.
[0046] In a fourth embodiment of the invention, which can be combined with all other embodiments, step (C) further comprises:
[0047] (VIII) Recovery of methylenediphenylenediamine and polyphenylenepolymethylenepolyamine (optionally as solution in a third organic solvent) from the salts separated in step (C)(VI), comprising their neutralization with a base.
[0048] In a fifth embodiment of the invention, which is a particular embodiment of the fourth embodiment, step (C)(VI 11) comprises:
[0049] 1) Mixing the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts, optionally after purification by washing and / or recrystallization, with water and a base; and
[0050] 2) Phase separation into an aqueous phase and an organic phase comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine.
[0051] In a sixth embodiment of the invention, which is a particular embodiment of the fifth embodiment, a third organic solvent is added in step 1); and / or in step 2), the aqueous phase obtained in the phase separation is extracted (once or several times) with a third organic solvent, and subsequently all organic phases are combined. In a seventh embodiment of the invention, which is a particular embodiment of the sixth embodiment, the process further comprises:
[0052] 3) Separation of the third organic solvent from the organic phase comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine, leaving methylenediphenylenediamine and polyphenylenepolymethylenepolyamine.
[0053] In an eighth embodiment of the invention, which is a particular embodiment of the fifth to seventh embodiments, in step 1) the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts are washed with a polar aprotic solvent, wherein the polar aprotic solvent is selected from an ether, an ester, a ketone, a halogenated (aromatic or aliphatic) hydrocarbon, a nitrile or a mixture of two or more thereof, wherein the polar aprotic solvent is in particular the same organic solvent used as the first solvent in step (C)(11), and / or from a solvent selected from a Ci to C4 alcohol, water, a mixture of a Ci to C4 alcohol and water or a mixture of a Ci to C4 alcohol, water and an aprotic solvent (in particular as defined above), and are subsequently recrystallized in water.
[0054] In a ninth embodiment of the invention, which is a particular embodiment of the fifth to eighth embodiments, the base is selected from an alkali metal hydroxide (in particular LiOH, NaOH, KOH, RbOH), an alkaline earth metal hydroxide (in particular Be(OH)₂, Mg(OH)₂, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂), an alkali metal oxide (in particular Li₂Ü, Na₂Ü, K₂O, Rb₂O), an alkaline earth metal oxide (in particular BeO, MgO, CaO, SrO, or BaO), or a mixture of the aforementioned bases. (NaOH, KOH, Mg(OH)₂, and Ca(OH)₂ are preferred).
[0055] In a tenth embodiment of the invention, which can be combined with all embodiments providing for the use of the third organic solvent, the third organic solvent is selected from a halogenated aromatic compound (such as, in particular, chlorobenzene or dichlorobenzene, preferably chlorobenzene), a halogenated aliphatic hydrocarbon (such as, in particular, dichloromethane or chloroform), an ether (such as, in particular, diethyl ether, methyl tert-butyl ether, or diisopropyl ether, preferably diethyl ether), an ester (such as, in particular, ethyl acetate), or a mixture thereof. (Chlorobenzene is most preferred.)) In an eleventh embodiment of the invention, which is a particular embodiment of the fifth to tenth embodiments, the organic phase comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine is dried to a water content (determined by Karl Fischer titration) of a maximum of 1000 ppm, preferably a maximum of 500 ppm, particularly preferably a maximum of 300 ppm.
[0056] In a twelfth embodiment of the invention, which can be combined with all embodiments which provide step (C)(VIII), the methylenediphenylenediamine and polyphenylenepolymethylenepolyamine are phosgenated to methylenediphenylene diisocyanate and polyphenylenepolymethylenepolyisocyanate, optionally after drying and optionally after removal of the third organic solvent, followed optionally by separation of methylenediphenylene diisocyanate, leaving a mixture of methylenediphenylene diisocyanate and polyphenylenepolymethylenepolyisocyanate.
[0057] In a thirteenth embodiment of the invention, which is a particular embodiment of the twelfth embodiment, the process further comprises the reaction of the methylenediphenylene diisocyanate and / or the mixture of methylenediphenylene diisocyanate and polyphenylenepolymethylenepolyisocyanate with (each) (at least) one polyol to form a polyurethane.
[0058] In a fourteenth embodiment of the invention, which is a particular embodiment of the thirteenth embodiment, the (at least one) polyol comprises the optionally purified polyether polyol phase and optionally consists thereof.
[0059] In a fifteenth embodiment of the invention, which can be combined with all other embodiments, the pyrostatic acid is selected from sulfuric acid, hydrochloric acid or hydrogen chloride, preferably sulfuric acid or hydrochloric acid, particularly preferably sulfuric acid.
[0060] In a sixteenth embodiment of the invention, which can be combined with all other embodiments, the first solvent comprises a C1-C4 alkyl ether of a diol and is in particular such a solvent.
[0061] In a seventeenth embodiment of the invention, which is a particular embodiment of the sixteenth embodiment, the diol is selected from diethylene glycol, triethylene glycol, tetraethylene glycol, dimethylene glycol, trimethylene glycol, tetramethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol or a mixture of two or more of the aforementioned diols.
[0062] In an eighteenth embodiment of the invention, which is a particular embodiment of the seventeenth embodiment, the first solvent comprises, in particular, diglyme, the optionally used second solvent water, and the pyrolytic acid sulfuric acid. In a nineteenth embodiment of the invention, which is a particular embodiment of the eighteenth embodiment, the addition of the second solvent in step (C)(11) comprises a mass ratio of the first solvent to the second solvent in the range of 1:1 to 5:1, preferably 1.3:1 to 3:1.
[0063] In a twentieth embodiment of the invention, which can be combined with all other embodiments except those providing for a catalytic execution of the hydrolysis, no hydrolysis catalyst is added in step (B).
[0064] In a twenty-first embodiment of the invention, which can be combined with all other embodiments except those that exclude a catalytic carrying out of the hydrolysis, a hydrolysis catalyst is added in step (B) which is selected from a (in particular alkali metal or alkaline earth metal) hydroxide, a (in particular alkali metal or alkaline earth metal) carboxylate (in particular acetate), a tin compound (in particular dibutyltin dilaurate or tin(II) octoate [= tin(II)-2-ethylhexanoate]), a zinc compound (in particular zinc acetate), a (in particular alkali metal or alkaline earth metal) carbonate, a (in particular alkali metal or alkaline earth metal) hydrogen carbonate, an (in particular alkali metal or alkaline earth metal) orthophosphate, a (in particular alkali metal or alkaline earth metal) monohydrogen orthophosphate, an (in particular alkali metal or alkaline earth metal) orthovanadate, a titanium alkoxide, a tertiary amine,Cesium fluoride or a mixture of two or more of the aforementioned catalysts.
[0065] In a twenty-second embodiment of the invention, which can be combined with all other embodiments, step (B) is carried out in a reactor selected from a stirred tank reactor, a tubular reactor (optionally with integrated stirring unit) or a rotary tube reactor.
[0066] In a twenty-third embodiment of the invention, which is a special embodiment of the twenty-second embodiment, the reactor has a device for conveying solids.
[0067] In a twenty-fourth embodiment of the invention, which can be combined with all other embodiments except those providing for hydrolysis in the gas phase, the polyurethane foam is suspended in the water in step (B).
[0068] In a twenty-fifth embodiment of the invention, a particular embodiment of the twenty-fourth embodiment, the hydrolysis in step (B) is carried out at a pressure in a gas space above the polyurethane foam suspended in water of 12 bar to 60 bar.
[0069] In a twenty-sixth embodiment of the invention, which can be combined with all other embodiments except those providing for hydrolysis in the liquid phase, in step (B) the water is brought into a gaseous state to react with the polyurethane foam. In a twenty-seventh embodiment of the invention, a particular embodiment of the twenty-fifth embodiment, the reaction of the gaseous water with the polyurethane foam is carried out at a pressure of 1.0 bar to 60 bar.
[0070] In a twenty-eighth embodiment of the invention, which can be combined with all other embodiments, the separation of the precipitated methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts comprises filtration, centrifugation, sedimentation or a combination of the aforementioned methods.
[0071] The embodiments and further possible configurations of the invention briefly described above are explained in more detail below. Unless the context clearly indicates otherwise to a person skilled in the art, or unless expressly stated otherwise, all previously described embodiments and the further configurations of the invention can be combined with one another as desired.
[0072] PREPARATION OF THE PU FOAM FOR HYDROLYSIS
[0073] In step (A) of the process according to the invention, the polyurethane foam to be recycled is provided. The process of providing is to be understood broadly and also includes the mere delivery of recycled polyurethane foam that has been generated elsewhere and may also have been prepared elsewhere for hydrolysis (see below for details).
[0074] The process according to the invention can be applied both to the recycling of used (so-called Enc / -o / -L( / e-) polyurethane foams) and to the recycling of polyurethane waste from polyurethane production. In the latter case, the chemical nature of the isocyanate component used in the production and that of the polyol component is, of course, known. In the case of the recycling of used polyurethane foam, suitable sorting can ensure that the nature of the polyurethane foam is at least qualitatively known. If the original application of a used polyurethane foam to be recycled is known, it will regularly be known, for example, whether it is an MDI- or TDI-based polyurethane foam and what type of polyols are to be expected. In case of doubt, the underlying isocyanates and polyols can be identified analytically.
[0075] For this purpose, the polyurethane foam to be analyzed is examined for functional groups using ATR infrared spectroscopy (ATR = attenuated total reflection). The infrared spectrum (IR spectrum) provides a qualitative composition of the polyurethane foam. This allows determination of whether the polyurethane foam is based on polyether and / or polyester polyols. The IR spectrum also indicates whether it is a partially or completely MDI-based polyurethane foam, as such polyurethane foams exhibit characteristic bands at 1410 cm⁻¹. 1 , 1010 cm 1 and 510 cm 1 identifiable.
[0076] Prior to hydrolysis in step (B), the polyurethane foam to be recycled is preferably subjected to preparatory steps. These steps primarily involve the mechanical comminution of the polyurethane foam. Such preparatory steps are known in the field.
[0077] Polyurethane foams regularly contain additives, especially flame retardants, but also stabilizers and activators. It has proven effective to remove these in an extraction step before starting the chemical recycling process in step (B). For this purpose, the polyurethane foam, preferably already shredded, is extracted with an organic solvent that does not react with urethane groups (or other functional groups present, such as isocyanurate groups) during extraction. This is ensured either by using a solvent that is chemically inert towards urethane groups (and, if applicable, other functional groups) (preferred), or by selecting a temperature and / or extraction time that is low enough to prevent any significant chemical reaction from occurring.Suitable organic solvents include aromatic hydrocarbons (especially toluene), halogenated aromatics (especially monochlorobenzene or [preferably: ortho-]dichlorobenzene, where dichlorobenzene, preferably used as an ortho-isomer, is more preferred than monochlorobenzene), aliphatic ethers (especially tetrahydrofuran or [preferably: 1,4-]dioxane), ketones (especially acetone), aromatic ethers (especially anisole), or a mixture of two or more of the aforementioned solvents. Halogenated aromatics are preferred. Suitable extraction temperatures range, for example, from ambient temperature (room temperature, especially 20 °C) to 180 °C, preferably from 50 °C to 180 °C. Extraction can be carried out, in particular, at ambient pressure and the boiling point of the chosen organic solvent ("reflux").After extraction, the polyurethane foam to be split is separated from the extraction solvent by solid-liquid separation, in particular filtration, and preferably washed, especially with one of the aforementioned organic solvents (the same solvent used for extraction may, but need not, be used). Any remaining solvent is preferably removed by drying before carrying out step (B). HYDROLYSIS OF THE POLYURETHANE FOAM.
[0078] In step (B) of the process according to the invention, the polyurethane foam provided in step (A) and, if necessary, prepared as described, is hydrolyzed. According to the invention, water is added such that a mass ratio of water to polyurethane foam of at least 0.1 : 1, in particular of 0.1 : 1 to 20 : 1, is achieved, and the hydrolysis is carried out at a temperature of 180 °C to 260 °C, in particular without the addition of a hydrolysis catalyst. The hydrolysate obtained contains the polyether polyols of the polyol component as well as methylenediphenylenediamine and polyphenylenepolymethylenepolyamine formed by hydrolytic cleavage. Furthermore, solid components (such as, for example, metal residues from the original application of an EoL PU foam) may be present (at the temperature of step (B)).
[0079] Preferably, the hydrolysis is carried out without the addition of a hydrolysis catalyst. However, if a
[0080] If a catalyst is used, then all hydrolysis catalysts known per se can be used.
[0081] They are used, for example, (especially alkali metal or alkaline earth metal) hydroxides,
[0082] (especially alkali metal or alkaline earth metal) carboxylates (especially acetate),
[0083] Tin compounds (especially dibutyltin dilaurate or tin(II) octoate [= tin(II)-2-ethyl hexanoate]), zinc compounds (especially zinc acetate), (especially alkali metal or alkaline earth metal) carbonates, (especially alkali metal or
[0084] Erda I ka I i meta 11-) Hydrogen carbonates, (especially Al ka limeta 11- or Erda potassium metal) orthophosphates, (especially Al ka limeta 11- or
[0085] alkaline earth metal monohydrogen orthophosphates, (especially alkali metal or
[0086] Alkaline earth metal orthovanates, titanium alcoholates, tertiary amines, cesium fluoride or a mixture of two or more of the aforementioned catalysts.
[0087] In principle, all reactor types known in the field for chemolysis are suitable for carrying out step (B), in particular stirred tank reactors, tubular reactors (optionally with an integrated stirring unit) or rotary kiln reactors. Preferably, the reactor used has a solids conveying system to convey the polyurethane foam into the reaction chamber.
[0088] In one embodiment, the hydrolysis takes place in the liquid phase. For this purpose, the polyurethane foam is suspended in water. The pressure in the gas space above the reacting mixture is preferably 12 bar to 60 bar (absolute).
[0089] In another embodiment, water in a gaseous state is reacted with the polyurethane foam, preferably at a pressure of 1.0 bar to 60 bar (absolute). PROCESSING THE HYDROLYSATE
[0090] In step (C) of the process according to the invention, the hydrolysate obtained in step (B) is processed.
[0091] If the hydrolysate contains solid components, these are separated before the acid treatment in step (IV). This is done in step (I) and / or step (III). Step (I) is optional and can therefore be omitted even if solid components are present. Step (III) is only omitted if all solid components have already been separated at this point in the process or if no solid components were present in the first place. The essential point is that all solid components have been removed before the acid treatment in step (IV). The separation of solid components, whether carried out in step (I) and / or step (III), can be achieved using well-known liquid-solid separation methods such as filtration, centrifugation, sedimentation, or a combination of these methods.
[0092] In step (II) of the process according to the invention, the first and optionally the second solvent is added. This ensures that in step (IV) not all of the MDA salt precipitates, but that a significant portion (in particular at least 10%) remains in solution.
[0093] The first solvent is an organic solvent that boils at a higher temperature than the second solvent, but at least higher than water, exhibits the solubility properties with respect to water specified above, and is preferably selected from an ether, an ester, a ketone, a halogenated (aromatic or aliphatic) hydrocarbon, or a mixture of two or more of the aforementioned organic solvents, wherein ethers, esters, or mixtures thereof are particularly preferred, and ethers are very preferred. Most preferably, the first solvent comprises a Ci-C4 alkyl ether of a diol and is, in particular, such a diol. Suitable diols include, for example, diethylene glycol, triethylene glycol, tetraethylene glycol, dimethylene glycol, trimethylene glycol, tetramethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, or mixtures thereof.
[0094] The second solvent is a C1 to C4 alcohol (preferably methanol), water, or a mixture thereof.
[0095] The second solvent is added at least when the water content of the hydrolysate supplied to step (II) (possibly pretreated according to step (I) and / or - see below - according to step (11.0)) does not exceed 50 wt%, based on its total mass.
[0096] It may be advantageous to distill off excess water (i.e., water not consumed in step (B)) in step (ILO) after step (B) and before step (II), reducing the residual water content to a maximum of 50% by mass, and in particular a maximum of 10% by mass, based on the total mass of the hydrolysate remaining after distillation. In this case, the second solvent is mandatory and comprises a Ci- to C-alcohol. The use of a Ci-C-alcohol simplifies the recovery of the MDA salt in high purity.
[0097] The first solvent is added in such an amount that (at the temperature of addition) after mixing all components (including any second solvent that may be added) only one (1) liquid phase is present. A single (1) liquid phase means that no two-phase aqueous-organic system forms. This formulation does not preclude the possible presence of solid components (such as metal residues, non-hydrolyzable polymers from polymer-filled PU foams, or from additives used in the original application of a PU foam), which would then have to be separated in step (III).
[0098] In step (IV), a Brønsted acid is added to the process product obtained in step (II) or step (III). Suitable Brønsted acids include sulfuric acid, hydrochloric acid, or hydrogen chloride, preferably sulfuric acid or hydrochloric acid, and particularly preferably sulfuric acid. A particularly preferred embodiment uses diglyme as the first solvent, water as the optional second solvent, and sulfuric acid as the Brønsted acid. In this case, the addition of the second solvent is preferred, with a mass ratio of the first solvent to the second solvent in the range of 1:1 to 5:1, preferably 1.3:1 to 3:1, being maintained. For other cases, the most suitable mass ratio can be easily determined by simple preliminary tests. Generally, it is advantageous to use a larger quantity of the first solvent than the second.According to the invention, in this step only a partial precipitation of MDA salts occurs.
[0099] Brønsted acid is added in such an amount that the molar ratio of HsCT ions to amino groups is 1.0:1 or more, preferably 1.0:1 to 1.3:1, whereby the amount of amino groups can be determined by an amine number determination. With very strong monohydric acids such as hydrochloric acid, the amount of HsCT ions corresponds to the amount of acid used (complete dissociation). With weaker acids, the degree of dissociation and thus the proportion of released HsCT ions can be determined from tabulated pKa values. The amine number indicates how many mg of potassium hydroxide are necessary to neutralize the free organic amines present in 1 g of substance. This includes primary, secondary, and tertiary amino groups. The amino groups are weak bases. Concentrated acetic acid (glacial acetic acid, 99–100%) is used as the solvent.The amine is protonated by the solvent and thus converted into the conjugate acid, which now exists as an ion pair with the deprotonated acid of the glacial acetic acid. Subsequently, titration is carried out with 0.1 M perchloric acid as the titrant, whereby the perchloric acid displaces the anion of the solvent (glacial acetic acid). The perchloric acid consumed in this process is considered equivalent to the potassium hydroxide consumed. The amine number is usually expressed in milligrams of KOH per gram of sample and is calculated as follows: wherein
[0100] • AZ for the amine number,
[0101] • V for the volume of perchloric acid solution consumed,
[0102] • m for the mass of the titrated sample,
[0103] • M(KOH) for the molar mass of KOH (56.11 g • mol -1 ),
[0104] • bj for the molarity of the perchloric acid solution and
[0105] • f represents the dimensionless factor (titer) of the perchloric acid solution.
[0106] In step (V), volatile components are distilled off, i.e., any excess water remaining from step (B) and any second solvent added (where, by the nature of the process, at least one of both is still present at this point). This is done at a temperature and pressure such that the boiling point of the first solvent is reduced (in particular by at least 10 °C, preferably by at least 20 °C, and particularly by no more than 100 °C) (i.e., at the temperature and pressure chosen for step (V)), so that the second solvent can be distilled off without substantial entrainment of the first solvent, and the first fraction of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of bromstedtic acid, which remained in solution until now, also precipitates.For the particularly preferred embodiment using diglyme as the first solvent and water (in the form of excess hydrolysis water and / or optionally added second solvent), step (V) can be carried out, for example, at 60 °C and 40 mbar. If diglyme is used as the first solvent and methanol as the second solvent, step (V) can be carried out, for example, at 60 °C and 100 mbar.
[0107] The precipitated MDA salts are finally separated in step (VI), leaving a polyether polyol phase. This is advantageously done by filtration, centrifugation, sedimentation, or a combination of the aforementioned methods. The polyether polyol phase obtained in step (VI) is preferably purified in step (VII) for its reuse in PU production. Such purification preferably comprises one or more of the following purification operations:
[0108] Distillation and / or stripping,
[0109] Removal of acidic impurities (to reduce the acid number) by washing with an aqueous base solution and / or treatment with a resin containing basic functional groups,
[0110] Adsorption of impurities onto activated carbon.
[0111] The MDA salts separated in step (VI) must be converted back into the free amines before being used in PU production. For this purpose, in step (VIII), MDA is obtained from the salts separated in step (V) by neutralizing them with a base (optionally as a solution in an organic solvent).
[0112] In one embodiment, this step (VIII) comprises:
[0113] 1) Mixing the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts, optionally after purification by washing and / or recrystallization, with water, a base and optionally a third organic solvent; and
[0114] 2) Phase separation into an aqueous phase and an organic phase comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine, optionally followed by (single or multiple) extraction of the aqueous phase with an organic solvent (which is selected according to the same criteria as the third organic solvent to be used if necessary; see below for details) and combining all organic phases into a common organic phase comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine.
[0115] The addition of an organic solvent in step 1) has the advantage of reducing viscosity. If sufficient flowability of the MDA formed can be ensured by other measures, in particular a sufficiently high temperature, the use of the third organic solvent at this point is unnecessary.
[0116] In step 1), prior to the addition of the base, the MDA salts are preferably washed with a polar aprotic solvent, wherein the polar aprotic solvent is selected from an ether, an ester, a ketone, a halogenated (aromatic or aliphatic) hydrocarbon, a nitrile, or a mixture of two or more thereof, wherein the polar aprotic solvent is in particular the same organic solvent used as the first solvent in step (C)(1 I). Alternatively or in addition to such a wash, the MDA salt can also be recrystallized from a Ci to C4 alcohol, water, a mixture of a Ci to C4 alcohol and water, or a mixture of a Ci to C4 alcohol, water, and an aprotic solvent (in particular as defined above).
[0117] The MDA salt thus pretreated is then dissolved in water, followed by the addition of the base, and when using the third organic solvent, this is done before, simultaneously with, or (preferably) after its addition.
[0118] In any case, the base is preferably selected from an alkali metal hydroxide (in particular LiOH, NaOH, KOH, RbOH), an alkaline earth metal hydroxide (in particular Be(OH)₂, Mg(OH)₂, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂), an alkali metal oxide (in particular Li₂Ü, Na₂Ü, K₂O, Rb₂O), an alkaline earth metal oxide (in particular BeO, MgO, CaO, SrO, or BaO), or a mixture of the aforementioned bases. NaOH, KOH, Mg(OH)₂, and Ca(OH)₂ are particularly preferred.
[0119] The third organic solvent should be one that forms two phases with water under the given conditions of temperature and mixing ratio and has the lowest possible water solubility (in particular, the aqueous phase should be able to dissolve no more than 5% by mass of the third organic solvent, preferably no more than 1%, based on the total mass of the aqueous phase). The third organic solvent is preferably selected from a halogenated aromatic compound (such as, in particular, chlorobenzene or dichlorobenzene, preferably chlorobenzene), a halogenated aliphatic hydrocarbon (such as, in particular, dichloromethane or chloroform), an ether (such as, in particular, diethyl ether, methyl tert-butyl ether, or diisopropyl ether, preferably diethyl ether), an ester (such as, in particular, ethyl acetate), or a mixture thereof. Chlorobenzene is most preferred.
[0120] The organic phase (MDA phase) obtained in step 2), comprising methylenediphenylenediamine and polyphenylenepolymethylenepolyamine, is preferably dried by methods known per se before further use, in particular to a water content (determined by Karl Fischer titration) of a maximum of 1000 ppm, preferably a maximum of 500 ppm, and most preferably a maximum of 300 ppm. Karl Fischer titration is well-documented and familiar to those skilled in the art. Various embodiments of the basic principle of Karl Fischer titration generally yield sufficiently consistent results for the purposes of the present invention. In case of doubt, Karl Fischer titration as described in DIN 51 777, Part 1, March 1983, is decisive for the purposes of the present invention.
[0121] To isolate MDA, the third organic solvent is separated from the MDA phase in step 3). The dried MDA, optionally freed from the third organic solvent, is available for re-phosgenation using methods known per se. Optionally, a fraction of mMDI can be separated from the MDI thus obtained. MDI and / or mMDI obtained in this way can be reacted with polyols to form polyurethanes. The polyols recovered by the process according to the invention are particularly suitable as polyols.
[0122] Examples:
[0123] Chemicals and materials
[0124] Name related to purity 131
[0125] H2O (deionized)
[0126] THF VWR chemicals >99.9%, unstabilized
[0127] HCIaq Thermo Scientific 37% solution in water
[0128] H2SO4 Fisher Science 96% solution in water diglyme Fisher Science 99+%
[0129] MeOH aber GmbH 99.8%
[0130] Toluene Sigma-Aldrich (Merck) 99.85%
[0131] Appliance PUR foam Covestro
[0132] PUR foam appliance
[0133] (“End of life”)
[0134] Table 1: Formulation of the polyurethane rigid foam used in all examples (data are in parts by weight, except for the key figure)
[0135] (1) Polyether polyols from Covestro Deutschland AG.
[0136] (2) Polyethersiloxane additive from Evonik AG.
[0137] (3) Amine catalyst from Covestro Deutschland AG.
[0138] (4) Amine catalyst from Evonik AG.
[0139] (5) Physical propellant.
[0140] (6) Desmodur 44V20L is a mixture of mMDI and pMDI from Covestro Deutschland AG.
[0141] (7) Amount of NCO groups used per 100 mol of OH groups.
[0142] Analytics
[0143] HPLC
[0144] Manufacturer (device and column): Agilent
[0145] HPLC-UV: 254 nm
[0146] Separation column: EC-C18
[0147] Column temperature: 35 °C Injection: 1 pL
[0148] Eluent A: 20 mM CH3COONH4 (pH5.4)
[0149] Eluent B: Acetonitile
[0150] Gradient:
[0151] FT-IR
[0152] Each ID-IR (FTIR) spectrum was an average of 24 scans and was acquired in the wavelength range of 400 to 4000 cm⁻¹. -1 with a spectral resolution of 4 cm -1 Measured using a Bruker Alpha FTIR.
[0153] ^-NMR spectroscopy
[0154] The measurements were performed on a Bruker Avance III 400 (400 MHz); the calibration of the chemical shifts was performed relative to the residual proton signal (DMSO-d6: 5 1H = 2.50 PPm).
[0155] To determine the compositions of the individual phases after precipitation and solid / liquid separation, the amine and polyether polyol fractions in the two phases were determined using a calibration curve.
[0156] To determine the amine / polyol mass ratios, the proton signals in the aromatic region were integrated. These were corrected for the contribution of ortho-TDA in this signal region when using polyether polyols with ortho-TDA as the starter molecule. The -CHj- signal in the aliphatic region was integrated as representative of the polyether polyol (mixture) used. Pressure hydrolysis procedure - step (B), general operating procedure
[0157] The hydrolysis experiments are carried out in a 20 ml stainless steel pressure reactor with a glass inlet. The polyurethane foam is first comminuted using a mixer, and then 0.35 g of the comminuted foam is placed in the reactor along with varying amounts of water (see Table 2). The reactor is then inertized with nitrogen at room temperature and placed in an aluminum block heated to reaction temperature at a set nitrogen partial pressure of 10 bar. The reaction mixture is stirred at 900 rpm for the required reaction time at the reaction temperature. After the reaction time is complete, the reactor is cooled in an ice bath. Following pressure release, the reactor is opened, yielding a heterogeneous, multiphase product mixture.
[0158] For analytical purposes, 2 g of THF are added to the product mixture to convert the individual building blocks, pMDA and polyols, together with the aqueous phase into a homogeneous organic solution. Insoluble components are filtered off. The homogenized phase is analyzed for purity by HPLC with UV detection.
[0159] In the case of steam hydrolysis, 230 mg of PU foam are placed in a metal cage positioned above the aqueous phase in the glass inlet. The lower part of the glass inlet is filled with 690 mg of water. The glass inlet is placed in the reactor, and the procedure is then carried out analogously to the pressure hydrolysis experiments described above. The reaction parameters used are listed in Table 2.
[0160] To obtain larger quantities for the polyol-MDA separation experiments from Table 3 (Examples 28 to 30), the PU foam is treated analogously to the pressure hydrolysis described above in a 300 mL stainless steel reactor with glass inlet and 10.0 g PU-containing substrate.
[0161] Procedures of - Step (C), general operating procedure:
[0162] In a first step, the first and second solvents are added to the substrate mixture in the ratios specified in Table 3, and the mixture is homogenized by stirring in a glass vessel. The acid is then added dropwise at room temperature while stirring constantly. Initial solid formation can already be observed at this stage. After the acid has been completely added, volatile components are removed by distillation under reduced pressure (quantity of distillate to be separated according to Table 3; the distillate mainly contains excess hydrolysis water and the second solvent). After separation of the distillate, the mixture is present as a suspension in the examples according to the invention and is separated into a filter cake and an eluate by filtration. The filter cake can be washed with further solvent. Process for the purification of MDA salt by washing - general operating procedure:
[0163] The filter cake obtained after MDA / polyol separation is washed with an organic solvent according to Table 4. For this purpose, the solid and the solvent are mixed, homogenized, stirred for 2 minutes, and separated into solid and liquid by filtration. The solid is then dried.
[0164] Method for the purification of MDA salt by recrystallization - general operating procedure:
[0165] The filter cake obtained after MDA / polyol separation is recrystallized from an organic solvent according to Table 4. For this purpose, the solid and solvent are mixed and dissolved by increasing the temperature. The temperature of the mixture is raised to a maximum of the solvent's boiling point and stirred under reflux for approximately 15 minutes. If necessary, insoluble residues are removed while the mixture is hot. The solution is then cooled to initiate solid formation. Once complete, the solid and liquid are separated by filtration. The solid is then dried.
[0166]
[0167] Explanations regarding the table:
[0168] [a] Substrate: Rigid foam according to the formulation in Table 1.
[0169] [b] Specification in mass / mass.
[0170] [c] Determined using the described IR analysis method. Comparison of the C=O band (1720 cm⁻¹). 1 ) determined via FT-IR at time to and t.
[0171] [d] Determined on a THF homogenized or diluted sample of the hydrolysate by dividing the area integrals of known product signals (aniline and derivatives of the methylenediphenylenediamine and polyphenylenepolymethylenepolyamine series) in the UV track of the HPLC by the sum of the area integrals of all signals.
[0172] [e] "Appliance" PUR foam ("End of life").
[0173] [f] Hydrolysis experiments with steam as described in the experimental procedure.
[0174] [g] No homogeneous solution possible after complete depolymerization due to metallic residues from the “End o / 7 / / e” foam material. na = not analyzed
[0175]
[0176] See table:
[0177] [a] H3O + -Mole equivalents of the -NH2 groups of the aromatic amines in the substrate mixture.
[0178] [b] [Polyol] / ([Polyol]+[M DA-Sa lz]) determined using 1 H NMR spectroscopy.
[0179] [c] [MDA salt] / ([Polyol]+[MDA salt]) determined using 1 H NMR spectroscopy.
[0180] [d] Model mixture of MDA, polyols and additives according to Table 1. Desmodur 44V20L is replaced by another MDA at the same mole fractions (n(-NH2) = n(NCO)).
[0181] [e] A mixture of a foam of the composition of Table 1 hydrolyzed according to Table 2, Example 19. Excess hydrolysis water was removed by distillation in one step (C)(l 1.0) before the addition of the first solvent (exception: if water is used as the second solvent, the water used in the hydrolysis was not removed beforehand, but only the amount of water added as the second solvent was adjusted computationally).
[0182] [f] Mixture of a hydrolyzed “end-of-life” foam according to Table 2, Example 21, from which inorganic foreign materials were removed by filtration. Excess hydrolysis water was removed by distillation in one step (C)(l 1.0) before the addition of the first solvent (exception: if water is used as the second solvent, the water used in the hydrolysis was not removed beforehand, but only the amount of water added as the second solvent was adjusted computationally).
[0183] [g] Formation of a two-phase liquid-liquid mixture after addition of the acid, which cannot be separated by filtration.
[0184]
[0185] Explanations for the table:
[0186] [a] Filter cake of the process from Table 3, Example 30.
[0187] [b] Determined by means of 1 H NMR spectroscopy by measuring the salts and converting to a neutralized mixture. [c] Mass ratio of solvent to salt.
[0188] [d] Isolated amount of purified MDA salt references the amount of MDA salt used.
Claims
1. Method for recovering valuable materials from polyurethane foams, comprising the steps: (A) Providing a product based on an isocyanate component and a Polyol component-based polyurethane foam, wherein the isocyanate component is methylenediphenyl endisocyanate and polyphenylenepolymethylene polyisocyanate comprises and wherein the polyol component comprises a polyether polyol; (B) Hydrolyzing the polyurethane foam with water, adding water in such a way as to achieve a mass ratio of water to polyurethane foam of at least 0.1 : 1, at a temperature of 180 °C to 260 °C, to obtain a hydrolysate containing the polyether polyol, methylenediphenylenediamine and polyphenylenepolymethylenepolyamine and optionally solid components; (C) Comprehensive work-up of the hydrolysate (I) optional, separation of any solid components that may be present, (II) Addition of a first solvent and optionally a second solvent, wherein the second solvent is added at least when the hydrolysate supplied to step (C)(11) contains no more than 50 wt% water, based on its total mass, wherein the first and the second solvent may be added in any order, wherein the first solvent is an aprotic organic solvent that boils at a higher temperature than the second solvent, but at least at a higher temperature than water, and wherein at least 50 g of water dissolve in 1000 g of the first solvent at 20 °C, wherein the second solvent is selected from a Ci to C4 alcohol, water or a mixture thereof, wherein the first solvent is added in such an amount that, after mixing all components, only a liquid phase, optionally containing solid components, is present. (III) Separation of any solid components that may be present, (IV) Addition of a pyrostatic acid to form methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine- Salts of Brønstedt acid, wherein a first part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of Brønstedt acid remains in solution and, if applicable, a second part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of Brønstedt acid precipitates, (V) Distilling off volatile components at such a temperature and pressure that the boiling point of the first solvent is undercut and the first part of the methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of Brønsted acid precipitates, and (VI) Separation of the precipitated methylenediphenylenediamine salts and polyphenylenepolymethylenepolyamine salts of Brønstedt acid leaving a polyether polyol phase comprising the polyether polyol.
2. The method of claim 1, wherein the first solvent is selected from an ether, an ester, a ketone, a halogenated hydrocarbon or a mixture of two or more of the aforementioned organic solvents.
3. A method according to claim 1 or 2, wherein, after step (B) and before step (C)(11), excess water is distilled off in a step (C)(11.0) to a residual content of a maximum of 50% by mass, based on the total mass of the hydrolysate present after distillation of the water, wherein the second solvent comprises a C1 to C4 alcohol.
4. Method according to any one of claims 1 to 3, wherein step (C) further comprises: (VIII) Recovery of methylenediphenylenediamine and polyphenylenepolymethylenepolyamine, optionally as solution in a third organic solvent, from the salts separated in step (C)(VI), comprising their neutralization with a base.
5. Method of claim 4, wherein the base is selected from an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal oxide, an alkaline earth metal oxide or a mixture of the aforementioned bases.
6. A method according to claim 4 or 5, wherein the third organic solvent is selected from a halogenated aromatic, a halogenated aliphatic hydrocarbon, an ether, an ester or a mixture thereof.
7. A method according to any one of claims 4 to 6, wherein the methylenediphenylenediamine and polyphenylenepolymethylenepolyamine, optionally after drying to a water content of a maximum of 1000 ppm and optionally after Separation of any third organic solvent used, which is phosgenated to methylenediphenyl diisocyanate and polyphenylenepolymethylene polyisocyanate, from which optional separation of Methylenediphenyl diisocyanate leaving a mixture of methylenediphenylene diisocyanate and polyphenylenepolymethylene polyisocyanate are connected.
8. The method of claim 7, further comprising the reaction of the methylenediphenylene diisocyanate and / or the mixture of methylenediphenylene diisocyanate and polyphenylenepolymethylene polyisocyanate with a polyol to form a polyurethane.
9. The method of claim 8, wherein the polyol comprises the optionally purified polyether polyol phase.
10. Method according to any one of claims 1 to 9, wherein the pyrostatic acid is selected from sulfuric acid, hydrochloric acid or hydrogen chloride.
11. A method according to any one of claims 1 to 10, wherein the first solvent comprises a Ci-C4 alkyl ether of a diol.
12. The method of claim 11, wherein the diol is selected from diethylene glycol, triethylene glycol, tetraethylene glycol, dimethylene glycol, trimethylene glycol, tetramethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol or a mixture of two or more of the aforementioned diols.
13. Method according to any one of claims 1 to 12, wherein no hydrolysis catalyst is added in step (B).
14. Method according to any one of claims 1 to 13, wherein in step (B) the polyurethane foam is suspended in the water or wherein in step (B) the water is brought into a gaseous state to react with the polyurethane foam.
15. Method according to any one of claims 1 to 14, wherein the separation of the precipitated methylenediphenylenediamine salts and Polyphenylene-polymethylenepolyamine salts include filtration, centrifugation, sedimentation or a combination of the aforementioned methods.