Method for decomposing polyether polyurethane

Abstract

The present invention relates to a process which can be used to decompose a polyurethane formed from a polyether polyol and an aromatic isocyanate into a polyether polyol and an aromatic amine.

Description

[0001] The present invention relates to a method that can be used to decompose polyurethanes formed from polyether polyols and isocyanates into polyether polyols and amines.

[0002] Polyurethanes are used particularly in large quantities for the production of rigid and flexible foams. When these materials are incinerated at the end of their service life, CO is released. 2 Since the raw materials used for the production of polyurethanes are mainly or completely made from crude oil, the combustion of polyurethanes leads to an increase in the CO content in the atmosphere. 2 Therefore, it is highly desirable to reuse polyurethane waste as comprehensively as possible in terms of substances.

[0003] Polyurethanes are formed from an isocyanate component and a polyol component. They form urethane bonds through an addition reaction, which connect these two components and thus form a polymer network. Isocyanates having aromatically bonded isocyanate groups, in particular toluene diisocyanate, methylene diphenyl diisocyanate, and polycyclic derivatives of methylene diphenyl diisocyanate, are mainly used in foam production. Polyether polyols are commonly used as the polyol component.

[0004] In order to recover polyether polyols from polyurethanes, methods already exist, some of which have been tested on an industrial scale. These methods are based on the reaction of polyurethanes with low molecular weight alcohols such as diols. Here, the polyether polyol is replaced by the low molecular weight alcohol. Similar to transesterification, the replacement of the polyol as part of the urethane group by another polyol is referred to as "urethane exchange" in this patent application. The reaction product of this urethane exchange is a polyether for the production of polyurethanes and a urethane derived from the aromatic polyisocyanate used for the synthesis of polyurethanes and the low molecular weight alcohol used for urethane exchange. The newly formed urethane is of low molecular weight because the urethane exchange uses a large molar excess of low molecular weight polyols relative to the polyether content of the polyurethane, so most of the low molecular weight polyol molecules react only with one molecule derived from the isocyanate used for the production of the polyether polyurethane. Simon et al. (2018), Waste Management, 76: 147 - 171 describe the details and variants of this method.

[0005] However, only the polyether polyols released from the polyurethane are utilized materially. The low molecular weight urethanes formed during the transesterification are by-products for which no satisfactory use has been found so far. Simon et al. (2014), Journal of Material Cycles and Waste Management, 16: 523-525 describe a method for separating unreacted low molecular weight alcohols from the transesterification product by distillation. The distillation residue consists of an ill-defined mixture of aromatic amines and low molecular weight urethanes. This residue can be used as an initiator for the synthesis of polyether polyols. The diversity of the compounds present therein is disadvantageous for the use of this distillation residue in other fields of application.

[0006] Mirror-symmetric to the above method, Beneš, H., Černá, R., Ďuračková, A., & Látalová, P. (2012). Utilization of natural oils for decomposition of polyurethanes. Journal of Polymers and the Environment, 20(1), 175-185 describe a method using fish oil or castor oil as the alcohol for transesterification. The aim of this method is to obtain low molecular weight urethanes as raw materials for further chemical reactions. Since the alcohols used are strongly hydrophobic, this product is present in the phase together with the released polyether at the end of the method.

[0007] The object of the present invention is to provide a method capable of decomposing polyether polyurethanes as completely as possible into chemically as precisely defined compounds as possible.

[0008] This object is achieved by a method comprising the following steps

[0009] a) subjecting the polyether polyurethane to transesterification with at least one low molecular weight alcohol to form polyether polyols and low molecular weight urethanes; and

[0010] b) enzymatically cleaving the low molecular weight urethanes formed in process step a) to release at least one amine and the at least one low molecular weight alcohol used in process step a).

[0011] Method step a) has two objectives: (i) The polyether polyol used for synthesizing polyurethane should be released from the polyurethane as a separable compound. (ii) The isocyanate used for synthesizing polyurethane should be present as a component of the low molecular weight carbamate. Different from the polyurethane with its high molecular weight, the low molecular weight carbamate is very suitable as a substrate for the enzymatic cleavage occurring in method step b) due to its lower molecular weight and thus better solubility.

[0012] In method step b), by the enzymatic cleavage of the low molecular weight carbamate, amines and low molecular weight alcohols for carbamate exchange in method step a) are released. In addition, CO is released in this method step 2 . These compounds can be separated by suitable separation methods and then further used. Preferably, the released low molecular weight alcohol is reused for the carbamate exchange occurring in method step a). The released amines can be used as pure and well-defined raw materials for new syntheses.

[0013] Polyether carbamate

[0014] Polyurethane is a compound formed from polyols and polyisocyanates. The totality of all polyols used for forming polyurethane is also referred to as the "polyol component" in this application. The totality of all polyisocyanates used for forming polyurethane is also referred to as the "isocyanate component" in this application. One hydroxyl group of each polyol and one isocyanate group of each polyisocyanate form a carbamate group through an addition reaction, thereby crosslinking the structural components of the polyurethane.

[0015] The polyurethane decomposed by the method of the present invention is a polyether polyurethane. This term refers to a polyurethane in which the polyol component contains polyether polyols. Preferably, at least 40% by weight of the hydroxyl groups contained in the polyol component are components of polyether polyols. More preferably, this is at least 60% by weight, even more preferably at least 80% by weight, and most preferably at least 95% by weight. When following the above dosage ratios of polyether polyols, the polyether polyurethane according to the present invention may also contain other polyols as structural components. This is preferably a polyester polyol.

[0016] Isocyanate groups can in principle also react with other functional groups containing Zerewitinoff active hydrogen atoms. Such functional groups are in particular amino and thiol groups. In this case, urea groups and thiocarbamate groups are formed by addition reactions, respectively. However, in the "polyether urethanes" according to the present application, the proportion of urethane bonds and urea bonds in the total amount of urethane bonds, urea bonds and thiocarbamate bonds is at least 60 mol%, preferably at least 80 mol%, more preferably at least 90 mol%. In the total amount of urethane bonds, urea bonds and thiocarbamate bonds, the proportion of urethane bonds is at least 20 mol%, preferably at least 40 mol%, more preferably at least 60 mol%.

[0017] Furthermore, "polyurethanes" for the purposes of the present application have at least 3, preferably at least 5 urethane groups per molecule. The resulting crosslinking of multiple molecules of the structural components involved gives rise to the high molecular weight of the polyurethanes. The number-average molecular weight of the polyurethanes to be decomposed by the method according to the invention is therefore preferably at least 1350 g / mol.

[0018] Polyether polyols

[0019] The term "polyether polyols" is well known to those skilled in the art. It is a polyether having an average hydroxyl functionality of 1.5 to 6.0. The polyether polyols contained in polyether polyurethanes are preferably addition polymers of one or more alkylene oxides having 2 to 4 carbon atoms by using at least one initiator molecule containing 2 to 8, preferably 2 to 6 bonded reactive hydrogen atoms.

[0020] Preferred alkylene oxides are styrene oxide, ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide and epichlorohydrin. More preferred are 1,3-propylene oxide, 1,2- or 2,3-butylene oxide and styrene oxide. Particularly preferred are ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used alone, successively in alternation or as a mixture.

[0021] The initiator molecules used for the addition polymerization are preferably water, organic dicarboxylic acids, aliphatic and aromatic, optionally N-mono-, N,N- or N,N'-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl group, diols and polyols.

[0022] Preferred organic dicarboxylic acids are succinic acid, adipic acid, phthalic acid and terephthalic acid.

[0023] Preferred diamines are mono- and dialkyl-substituted ethylenediamines, diethylenetriamine, triethylenetetramine, propan-1,3-diamine, butan-1,3-diamine or butan-1,4-diamine, hexan-1,2-diamine, hexan-1,3-diamine, hexan-1,4-diamine, hexan-1,5-diamine and hexan-1,6-diamine, phenylenediamine, toluene-2,3-diamine, toluene-2,4-diamine and toluene-2,6-diamine, and 2,2'-, 2,4'- and 4,4'-diaminodiphenylmethane.

[0024] Preferred diols and polyols are ethylene glycol, propan-1,2- and -1,3-diols, diethylene glycol, dipropylene glycol, butan-1,4-diol, hexan-1,6-diol, triethanolamine, bisphenol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose.

[0025] Isocyanates

[0026] Polyurethanes in which the isocyanate component comprises isocyanates having isocyanate groups with aliphatic, cycloaliphatic, aromatic or araliphatic bonding are in principle suitable for decomposition by the process according to the invention.

[0027] In isocyanates having isocyanate groups with aliphatic bonding, all isocyanate groups are bonded to carbon atoms which are part of an open carbon chain. This may be unsaturated at one or more positions. Aliphatic-bonded isocyanate groups or – in the case of polyisocyanates – a plurality of aliphatic-bonded isocyanate groups are preferably bonded to the terminal carbon atoms of the carbon chain.

[0028] Particularly suitable polyisocyanates having isocyanate groups with aliphatic bonding according to the invention are 1,4-butane diisocyanate (BDI), 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2-methyl-1,5-pentane diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-hexane diisocyanate and 1,10-decane diisocyanate.

[0029] In isocyanates having isocyanate groups with cycloaliphatic bonding, all isocyanate groups are bonded to carbon atoms which are part of a closed ring of carbon atoms. The ring may be unsaturated at one or more positions, provided that it does not acquire aromatic character due to the presence of double bonds.

[0030] Polyisocyanates having alicyclic-bonded isocyanate groups that are particularly suitable according to the invention are 1,3- and 1,4-cyclohexane diisocyanate, 1,4-diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane (NBDI), 4,4'-diisocyanato-3,3'-dimethyl dicyclohexylmethane, 4,4'-diisocyanato-3,3',5,5'-tetramethyl dicyclohexylmethane, 4,4'-diisocyanato-1,1'-bis(cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-bis(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetramethyl-1,1'-bis(cyclohexyl), 1,8-diisocyanato-p-menthane, 1,3-adamantane diisocyanate and 1,3-dimethyl-5,7-adamantane diisocyanate.

[0031] In the isocyanates having araliphatic-bonded isocyanate groups, all the isocyanate groups are bonded to a methylene group which is in turn bonded to an aromatic ring.

[0032] Polyisocyanates having araliphatic-bonded isocyanate groups that are particularly suitable according to the invention are 1,3- and 1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate; XDI), 1,3- and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI) and bis(4-(1-isocyanato-1-methylethyl)phenyl) carbonate.

[0033] The polymerizable composition according to the invention can comprise any mixture of the above isocyanates in monomeric and / or oligomeric form.

[0034] In the isocyanates having aromatic-bonded isocyanate groups, all the isocyanate groups are directly bonded to a carbon atom which is part of an aromatic ring.

[0035] Isocyanates having aromatic-bonded isocyanate groups that are particularly suitable according to the invention are toluene diisocyanate (TDI), methylene diphenyl isocyanate (MDI) and naphthalene diisocyanate.

[0036] The term "toluene diisocyanate" means toluene-2,4-diisocyanate (2,4-TDI), toluene-2,6-diisocyanate (2,6-TDI), and any mixture of these two isomers. The term "methylene diphenyl diisocyanate" means all isomers of MDI, in particular 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, all mixtures containing at least two of the above isomers, and polycyclic derivatives of MDI.

[0037] The term "naphthalene diisocyanate" means naphthalene-1,4-diamine, naphthalene-1,5-diamine, and naphthalene-1,6-diamine, and any mixture of the above isomers.

[0038] However, it is preferred to decompose an isocyanate in which the isocyanate component contains an isocyanate group having an aromatic bond or a polyether polyurethane composed of such an isocyanate.

[0039] The isocyanate component of the polyether polyurethane particularly preferably contains TDI, MDI, or any mixture of these two isocyanates.

[0040] In a particularly preferred embodiment of the present invention, at least 50 mol% of the isocyanate groups contained in the isocyanate component are components of TDI and / or MDI. This is more preferably at least 65 mol%, and even more preferably at least 80 mol%.

[0041] Low molecular weight alcohol

[0042] Various compounds having at least one hydroxyl group per molecule are in principle suitable for use as the low molecular weight alcohol in method step a). However, for the success of the entire method, certain properties of the low molecular weight alcohol are advantageous, and thus the preferably used low molecular weight alcohol satisfies one or more of the conditions defined below.

[0043] In order for the low molecular weight carbamate from method step a) to be suitable as a substrate for the enzymatic cleavage of the carbamate bond, the molecular weight of the low molecular weight alcohol must not be too high. This is preferably at most 700 g / mol, more preferably at most 500 g / mol, and most preferably at most 200 g / mol.

[0044] Advantageously, the urethane formation of the low molecular weight alcohol used forms a separate phase from the polyether polyol released from the polyether urethane. Low molecular weight alcohols whose esters form a separate phase upon addition of an additional solvent can also be used here. This promotes the formation of a separate polyether phase, whereby the released polyether polyol can be easily separated from the reaction mixture. For the reasons stated, low molecular weight alcohols with a higher polarity are preferred. Preferably, the low molecular weight alcohol contains at least 2 hydroxyl groups per molecule. Particularly preferably, the low molecular weight alcohol contains at least 2 hydroxyl groups per molecule and has a molecular weight of at most 500 g / mol, more preferably at most 200 g / mol.

[0045] Furthermore, from a technical perspective, low molecular weight alcohols with a low melting point such that there is no risk of them solidifying in the equipment pipelines and causing pipeline blockages are particularly suitable. Therefore, low molecular weight alcohols with a melting point of at most 45 °C are preferably used. More preferably, the low molecular weight alcohol used has a melting point of at most 20 °C.

[0046] The at least one low molecular weight alcohol is preferably selected from methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, glycerol, 2-methylpropane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, polyethylene glycol 400, and mixtures of two or more of the above alcohols. More preferably, it is particularly preferably selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, and mixtures of two or more of the above alcohols. Very particularly preferably, the low molecular weight alcohol is diethylene glycol.

[0047] Reaction product

[0048] In a first process step, free polyether is formed, which can be separated from the reaction mixture by physical means.

[0049] If a low molecular weight alcohol with a sufficiently high polarity is used, a two-phase mixture is formed. The lower polarity phase consists mainly of polyether. The other higher polarity phase contains the unused low molecular weight alcohol, low molecular weight urethane, and reaction by-products, especially aromatic amines. The polyether polyol can be separated out particularly simply here.

[0050] The chemical structure of the resulting low molecular weight urethane depends on the reactants used in process step a). The urethane contains a first hydrocarbon group derived from the isocyanate component used for synthesizing the polyether urethane. The second hydrocarbon group is derived from the low molecular weight alcohol used in process step a). These two hydrocarbon groups are bonded by a urethane group, and the nitrogen atom of the urethane group is bonded to the first hydrocarbon group.

[0051] Reaction conditions

[0052] The reaction conditions and catalysts applicable in principle to urethane transesterification are described in Simon et al. (2018), Waste Management, 76: 147-171. Method step a) is carried out at a temperature of 140 °C to 300 °C, preferably 160 °C to 270 °C. The weight ratio of the low molecular weight alcohol to the polyether urethane is from 2:1 to 1:17. Particularly suitable as catalysts are alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal salts of carboxylic acids (especially acetates), alkaline earth metal salts of carboxylic acids (especially acetates), Lewis acids (especially dibutyltin dilaurate for example), organic amines (especially diethanolamine for example), organometallic compounds (especially titanium tetrabutoxide) and tin compounds (especially tin octoate). The urethane transesterification is preferably carried out at a temperature of 160 °C to 270 °C in the presence of 0.1% by mass to 5% by mass of catalyst based on the mass of the polyurethane product added.

[0053] Enzymatic cleavage

[0054] In addition to the actual enzymatic cleavage of the low molecular weight urethanes, method step b) may also comprise further sub-steps. This is particularly helpful for improving the efficiency of the enzymatic cleavage.

[0055] Since the cleavage of the urethane is a hydrolysis, water is preferably added to the product obtained in method step a).

[0056] In a preferred embodiment, the released polyether polyol is first separated from the product obtained in method step a) before adding the enzyme for enzymatic cleavage.

[0057] However, it is also possible to carry out the enzymatic cleavage in a mixture still containing the released polyether polyol.

[0058] In another preferred embodiment, the excess alcohol, i.e., the alcohol not yet bonded in the low molecular weight urethane, is separated before adding the enzyme. This can be particularly advantageously achieved by distillation.

[0059] In another preferred embodiment, at least one co-solvent and / or at least one detergent is added in method step b). This can increase the solubility of the low molecular weight urethane in water and thereby improve its accessibility to the enzyme. Preferred co-solvents are ethanol, acetone, dimethyl sulfoxide and dimethylformamide. Preferred detergents are sorbates.

[0060] The low molecular weight urethane may also be contaminated with salts after urethane transesterification, which interfere with the enzymatic cleavage. Therefore, in another preferred embodiment of the present invention, the salts present together with the low molecular weight urethane are completely or partially separated before adding the enzyme for enzymatic cleavage.

[0061] Since low molecular weight alcohols do not have an adverse effect on enzyme activity in many cases, this preparatory step can also be omitted in many cases. A person skilled in the art can determine the extent to which free low molecular weight alcohols must be separated before enzymatic cleavage by simple preliminary tests in the presence and absence of the low molecular weight alcohol used in method step a).

[0062] The enzymatic cleavage in method step b) can be carried out with various enzymes capable of cleaving carbamate bonds.

[0063] For example, enzymes having an amino acid sequence defined in SEQ ID No: 1 to 13 are suitable for this purpose. Particularly suitable is the enzyme defined by SEQ ID No: 3 or a variant thereof. When using the above enzymes, in a reaction buffer containing 100 mM K 2 HPO 4 / KH 2 PO 4 at pH 7 together with 20% by volume of ethanol is very suitable for the enzymatic cleavage of low molecular weight carbamates. However, it has been found that good results can also be achieved without using ethanol.

[0064] "Enzyme variants" are preferably obtained by adding, deleting or replacing up to 10%, more preferably up to 5% of the amino acids contained in the respective polypeptide. The above-mentioned modifications can in principle be carried out continuously or discontinuously at any arbitrary site in the polypeptide. However, they are preferably carried out only at the N-terminus and / or C-terminus of the polypeptide. However, each variant obtained according to the invention by adding, replacing or deleting amino acids is characterized by carbamate hydrolase activity. This is preferably confirmed by the test method in Example 1.

[0065] Other enzymes that are suitable in principle are described in WO 2006 / 019095, WO / 2013 / 134801, Shigeno et al. (2006), Applied Microbiology and Biotechnology, 70: 422-429, Gamerith et al. (2016), Polymer Degradation and Stability, 132: 69-77 and Magnin et al. (2019), Waste Management, 85: 141-150.

[0066] The reaction product resulting from the enzymatic cleavage of the low molecular weight carbamate in method step b) is the at least one low molecular weight alcohol and an amine or amine mixture used in method step a). The chemical structure of the amine formed depends on the nature of the isocyanate component used for synthesizing the polyurethane. The amine is released, which can be eliminated by adding water and subsequent elimination of CO 2and derived from the isocyanates used in the isocyanate component.

[0067] The process of the invention thus provides compounds having a well-defined structure and suitable as raw materials for novel syntheses for high-value products.

[0068] The following examples are only illustrative of the invention. They should in no way limit the scope of protection of the claims.

[0069] Examples

[0070] Example 1 (of the invention)

[0071] Implementation:

[0072] Model substrates for enzyme reactions

[0073] Enzymes with putative carbamate hydrolase activity were tested in the hydrolysis of exemplary carbamate model compounds to characterize the substrate spectrum. This was done using carbamates that can form during the glycolysis of polyurethanes. All model substrates and screening substrates for this purpose are shown below. To the reaction buffer (100 mM KH 2 PO 4 / K 2 HPO 4 , pH 7.0) was added 20% (v / v) ethanol and 0.2 mg / mL substrate. The reaction was carried out in 200 µL batches in glass tubes by adding 1 - 3 mg of the enzyme lyophilized product. The batch was incubated with shaking at room temperature for about 20 hours and then at 37 °C for about 16 hours. After incubation, the plate was left to stand at room temperature, whereby the suspended particles sedimented (5 minutes), and the supernatant was centrifuged in a high-capacity centrifuge at 4000 rpm and 20 °C for 5 minutes into a 96-well polypropylene plate via a 96-well filter plate (Corning, Kaiserslautern) with a PVDF membrane and a pore size of 0.2 µm. Samples were measured by HPLC using the "dansylamide" method to detect the amines formed.

[0074]

[0075] Enzyme reactions with oligomers from PU foams

[0076] It was also investigated whether the carbamate hydrolase was able to hydrolyze the soluble oligomers formed in the hydrolysis of the ester bonds of the polyester PU foam. The glycolysis of the polyether polyurethane of diethylene glycol produced the same products. For this purpose, 1 g of the foam was added to a 50 mL centrifuge tube together with 20 mL of a potassium phosphate buffer at pH 7.0 and approximately 30 mg of the freeze-dried product "Chirazyme L2" of CalB (Roche, Basel, Switzerland) and incubated at 37 °C and 200 rpm for 5 days. Then the turbid solution was centrifuged in a large-capacity centrifuge at 25 °C and 4000 rpm for 10 minutes. The clear supernatant was adjusted to pH 7.0 with 1 M NaOH. After approximately 6 hours at room temperature, the slightly decreased pH value was retitrated to 7.0 and the solution was sterile filtered.

[0077] This led to the formation of the oligomers shown below. For each oligomer mixture (OM), the isomers based on 2,4-TDA are shown exemplarily, but isomers based on 2,6-TDA and various regioisomers formed by different bonding of the amino group to diethylene glycol are also present in this mixture. The hydrolytic activity of the confirmed carbamate hydrolase towards these carbamates was tested.

[0078] The soluble oligomers were stored at 4 °C until use. 20 μL of DMF was added to 150 μL of this solution. Then 30 μL of undiluted purified carbamate hydrolase was added to each, and these batches were shaken on a heating block at 30 °C and 1000 rpm. The batch containing the enzyme storage buffer served as a negative control. After 3 days, these batches were filtered through a filter plate (Corning, Kaiserslautern) with a PVDF membrane and a pore size of 0.2 µm, and the 2,4- and 2,6-TDA formed in the filtrate were analyzed by HPLC using the "dansylamide 95" method.

[0079]

[0080] HPLC analysis

[0081] High-performance liquid chromatography was performed on an 1100 series instrument from Agilent Technologies (Santa Clara, USA) with an autosampler and a DAD (diode array detector) for ultraviolet and visible range light. All measurements were carried out using a "Zorbax XDB-C18" column (Agilent Technologies, Santa Clara, USA) with a particle size of 3.5 μm and a size of 4.6 x 75 mm. In all methods, 5 μL of the sample was injected and the column was temperature-controlled to 40 °C. The flow rate was generally 1.5 mL / min. Since a reverse-phase column was used, elution was carried out with increasing concentrations of organic solvents in all methods.

[0082] The detection and quantification of aromatic amines and carbamates were performed using the "dansylamide" and "dansylamide 95" methods. As the eluent, except for AcN, 10 mM sodium phosphate buffer at pH 7.0 was used, to which 0.005% (w / v) sodium azide was added to prevent microbial growth. The data were analyzed using "OpenLAB CDS ChemStation LC" software, version A.02.09

[017] (Agilent Technologies, Santa Clara, USA).

[0083] Dansylamide : Eluent: Acetonitrile and 10 mM Na 2 HPO 4 / NaH 2 PO 4 , pH 7.0

[0084] t [min] Acetonitrile 0 5 6.5 85 8.0 5

[0088] 10.0 5。

[0089] Dansylamide 95 : Eluent: Acetonitrile containing 5% (v / v) ddH 2 O and 10 mM Na 2 HPO 4 / NaH 2 PO 4 , pH7.0

[0090] t [min] % Acetonitrile (+ 5% (v / v) ddH 2 O) 0 5 6.5 90 8.0 5

[0094] 10.0 5。

[0095] Results

[0096] Model substrates for enzyme reactions

[0097] Active carbamate hydrolases were added to the model substrates MDEC, MDBC, TDBC, and TDMC, which can be made from polyurethane by chemical carbamate exchange, and at least one carbamate hydrolase capable of catalytic hydrolysis cleavage to amines was found for each model substrate (Table 1). In addition, two carbamate hydrolases showed activity towards the oligomer mixtures OM-1, OM-2, and OM-3, in which both 2,4-TDA and 2,6-TDA were released.

[0098] Table 1: Summary of the study on the substrate spectrum of carbamate hydrolases. Enzymes showing significant activity in the MDEC screening and Ure were used for the screening of other carbamate compounds. 3: (Almost) only the fully hydrolyzed product (diamine) could be detected, 2: hydrolysis into the final product and intermediate product, 1: hydrolysis into intermediate product (monoamine), 0: (Almost) no hydrolysis product could be detected. "-" means that a significant amount of the substrate was still present. n.b.: Not determined. PLE: Porcine liver esterase

[0099] Enzyme MDEC MDBC TDBC TDMC OM-1 OM-2 OM-3 Ure (SEQ ID No. 13) 0 0 0 1- 0 0 0 Lip250 (SEQ ID No. 9) 1- 0 0 3 0 0 0 Porcine liver esterase 2- 3- 3- 2 n.b. n.b. n.b. B 2- 0 0 0 n.b. n.b. n.b. Lip72 (SEQ ID No. 3) n.b. n.b. n.b. n.b. 3 3- 3- Lip197 (SEQ ID No. 7) n.b. n.b. n.b. n.b. 3- 3- 1-

[0100] Example 2 (of the present invention): Tests on different reaction conditions for the cleavage of carbamates with Aes72

[0101] Introduction

[0102] In this experiment, the carbamates present in the lower phase after the chemical glycolysis of TDI flexible foam (carbamate exchange with diethylene glycol) should be hydrolyzed enzymatically. By the glycolysis of TDI flexible foam, long-chain polyether polyols are released, which sediment as a second phase above the excess glycol and the formed carbamates and amines after the reaction. The lower phase of the reaction product thus obtained is used as the substrate solution. By the enzymatic hydrolysis of the carbamate bond, 2,4-TDA and 2,6-TDA as well as diethylene glycol and CO are released 2 . In Example 1, a cosolvent was used. Since the additional solvent has to be separated out laboriously in industrial applications, it should be tested whether the reaction can also be carried out in the absence of a cosolvent. The higher the substrate concentration in the reaction, the more concentrated the TDA solution is after the reaction, which is advantageous for the subsequent post-treatment. Accordingly, Aes72 (SEQ ID No. 3) was tested at a substrate concentration of up to 40% (w / v). In addition, the temperature was increased to study whether this affects the reaction rate.

[0103] Implementation

[0104] Chemical glycolysis

[0105] Preload 250 g of diethylene glycol and heat to 200 °C. Then meter in 250 g of TDI flexible foam. After the foam has dissolved, keep the temperature constant for an additional 3 hours. Use 2.5 g of tin(II) 2-ethylhexanoate as a catalyst.

[0106] Enzyme preparation

[0107] For the preparation of the enzyme, Escherichia coliBL21(DE3) was transfected with plasmid pET21a-Aes72. 100 mg / L ampicillin was added to all cultures. MagicMedia (Thermofisher) was inoculated with a single colony and then cultured with shaking at 30 °C and 130 rpm for 24 h. Cells were separated by centrifugation at 4000 x g and 4 °C for 10 min. The cell pellet was placed in 10 mL of 50 mM potassium phosphate buffer at pH 7.5 and disrupted by sonication (amplitude 50%, pulse 1 s then pause 1 s, total sonication time 2 min). After separating the insoluble components by centrifugation (9500 rpm, 4 °C, 20 min), the crude enzyme solution was frozen at -80 °C and then lyophilized. The lyophilized product was stored at 4 °C. In addition, a blank vector control was prepared as an enzyme preparation in which the corresponding blank vector was used instead of pET21a-Aes72.

[0108] Enzyme reaction

[0109] An enzyme solution was prepared by dissolving 4.5% (w / v) of the enzyme lyophilized product in 50 mM potassium phosphate buffer at pH 7.5. These batches were prepared with a total volume of 300 μL. 60 μL of the enzyme solution and 5% (w / v), 10% (w / v), 20% (w / v), and 40% (w / v) of the lower phase after glycolysis were used as substrates respectively. The remainder was made up of 50 mM potassium phosphate buffer at pH 7.5. Incubation was carried out at 40 °C, 50 °C or 60 °C and 800 rpm in a heating block. Reactions with the blank vector control preparation were prepared in the same way. After 3 h, the total amount of TDA was quantified by HPLC. The TDA concentration in the negative control was subtracted from the value in the enzyme reaction to obtain the total amount of TDA released by Aes72.

[0110] Stop the enzyme reaction

[0111] The samples were diluted 1:2 with 50 mM NaOH / 20% acetic acid to inactivate the enzyme. The inactivated samples were incubated at room temperature for at least 5 min or longer at 4 °C and then diluted 1:10 with 140 mM NaOH.

[0112] HPLC analysis

[0113] 2,4-TDA and 2,6-TDA formed by HPLC analysis. Standards and samples were centrifuged before analysis (2 min, 13300 rpm, room temperature), and the supernatant was filtered through a 0.22 µm PES filter. 5 µL of the sample was injected by an autosampler in each case. The column used was a Zorbax Eclipse C18 (15 cm) with a corresponding guard column. Acetonitrile served as eluent A, and 10 mM sodium phosphate buffer at pH 7.0 served as eluent B. The total flow rate was 1 mL / min. The eluent gradient is shown in Table 2.

[0114] Table 2: HPLC gradient

[0115] t [min] Eluent A [%] Eluent B [%] 0.00 5 95 2.00 5 95 10.00 95 5 11.00 95 5 11.50 5 95 16.00 5 95

[0116] Results

[0117] The components in the lower phase after chemical glycolysis quantified by NMR are listed in Table 3.

[0118] Table 3: Composition of the lower phase after glycolysis. Determined by 1 1H-NMR spectrometry. The weight percentages of the TDA carbamates refer only to the TDA part of the compound; the DEG part is shown as "carbamylated DEG".

[0119] Component Content Polyol 3.61 wt% DEG 67.2 wt% TDA (diaminotoluene) 1.92 wt% TCA (toluene-carbamate-amine) 5.57 wt% TDC (toluene diisocyanate) 6.01 wt% Carbamoylated DEG 15.3 wt%

[0120] The concentrations of TDA released under various conditions in the enzyme reaction are shown in Table 4. It was found that high conversion rates could be achieved. It was also found that cosolvents were not essential for enzyme activity. A significant amount of TDA was released at all temperatures, and at the two lowest substrate concentrations, the reaction rate increased with increasing temperature.

[0121] Table 4: Total TDA released after 3 h. The quantified amount of TDA in the negative control was subtracted from the amount in the enzyme reaction to obtain the amount of TDA released.

[0122]

[0123] Experiment 3 (comparative, not of the invention): Replication of Beneš et al., 2012 to check phase formation

[0124] Introduction

[0125] The following experiments should confirm the extent to which the urethanes described in Beneš, H., Černá, R., Ďuračková, A., & Látalová, P. (2012). Utilization of natural oils for decomposition of polyurethanes. Journal of Polymers and the Environment, 20(1), 175 - 185 are suitable as raw materials for the two - stage decomposition method disclosed in this application. Here, as good as possible phase separation between the newly formed urethanes and the polyols released from the decomposed polyurethanes is crucial.

[0126] According to Beneš et al., 2012, the trans - urethanization of polyether polyurethanes based on pMDI with natural fats / oils releases the original polyether polyols. Due to the excessive use of long - chain and hydrophobic oils such as castor oil, phase separation between the released polyether polyols, the newly formed urethanes, and the excess oil as used in the present invention is not possible after this trans - urethanization. To verify this, urethanes described as products by Beneš et al., 2012 were synthesized from pMDI and castor oil, and mixing experiments with the polyether polyols used therein were carried out. Thereby, the product mixture existing after the glycolysis described therein should be replicated.

[0127] Implementation

[0128] Exemplarily, the product mixtures from Run 4BK and 4BK of Beneš et al., 2012 should be replicated. A pMDI mixture containing 32.25% NCO was used for this synthesis. 7.935 parts by weight of pMDI (10 - fold OH excess) were added to 210 parts by weight of castor oil and stirred at 80 °C until an NCO value of 0.03% was measured (OH value = 138.2 mg KOH / g; viscosity at 25 °C = 1570 mPas). A homogeneous phase was obtained in which the MDA urethane was completely dissolved in the excess castor oil. 11.06 g of Desmophen 5035 BT (trifunctional polypropylene ether polyol having a hydroxyl value of 35 mg KOH / g, a hydroxyl content of 1.1 wt%, and an OH equivalent weight of approximately 1600 g, manufactured by Covestro Deutschland AG, Leverkusen, Germany) (in the ratio after glycolysis as in 4BK and 4BK from D3) was added to 26.14 g of this urethane solution.

[0129] Results

[0130] After mixing the urethane solution and the polyether polyol, only a homogeneous liquid phase was observed, which did not separate even after 24 hours at room temperature. This indicates that the method described by Beneš et al., 2012 is not applicable to phase-separating glycolysis. Therefore, it is not possible to separate the polyether polyol as a separate phase after transurethanization, nor was a separate phase of the urethane and the excess diol obtained that could be used per se for the recovery of the aromatic amine. The method described by Beneš et al., 2012 thus precisely fails to cleave polyurethanes in two stages to recover monomers that can be used flexibly. The product therein is a specific type of polyol that is only suitable as a raw material for very specific reactions.

Claims

1. A method comprising the steps of a) subjecting a polyether polyurethane to urethanization with at least one low molecular weight alcohol having at least 2 hydroxyl groups per molecule and a molecular weight of up to 500 g / mol to form a polyether polyol and a low molecular weight urethane, wherein the low molecular weight urethane forms a separate phase from the polyether polyol released from the polyether urethane; and b) enzymatic cleavage of the low molecular weight carbamate formed in process step a) to release at least one amine and the at least one low molecular weight alcohol used in process step a).

2. The method of claim 1, wherein the isocyanate component of the polyether polyurethane comprises at least one aromatic polyisocyanate.

3. The process as claimed in claim 2, wherein the aromatic polyisocyanate is selected from the group consisting of toluene diisocyanate (TDI), methylene diphenyl isocyanate (MDI) and naphthalene diisocyanate.

4. The method of claim 1, wherein the isocyanate component of the polyether polyurethane comprises at least one aliphatic polyisocyanate.

5. The method of claim 4, wherein the aliphatic polyisocyanate is selected from 1,4-butane diisocyanate (BDI), 1,5-pentane diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2-methyl-1,5-pentane diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,4'- or 4,4'-dicyclohexylmethane diisocyanate (H12MDI) and 1,10-decane diisocyanate.

6. A method as claimed in any one of claims 1 to 5, wherein at least 50% by weight of the polyol component used to form the polyether polyurethane is a component of the polyether polyol.

7. The method as claimed in any one of claims 1 to 5, wherein the proportion of urethane bonds and urea bonds in the total amount of urethane bonds, urea bonds and thiourethane bonds in the polyether polyurethane is at least 60 mol%.

8. The method as claimed in claim 7, wherein the proportion of urethane bonds and urea bonds in the total amount of urethane bonds, urea bonds and thiourethane bonds in the polyether polyurethane is at least 80 mol%.

9. The method as claimed in claim 7, wherein the proportion of urethane bonds and urea bonds in the total amount of urethane bonds, urea bonds and thiourethane bonds in the polyether polyurethane is at least 90 mol%.

10. A process as claimed in any one of claims 1 to 5, wherein the low molecular weight alcohol has a melting point of at most 45°C.

11. The method of any one of claims 1 to 5, wherein the low molecular weight alcohol is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl ethylene glycol, triethylene glycol, glycerol, 2-methylpropane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, polyethylene glycol 400, and a mixture of two or more of the above alcohols.

12. The process as claimed in any one of claims 1 to 5, wherein the low molecular weight alcohol is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol and mixtures of two or more of the aforementioned alcohols and is used in such a quantitative ratio relative to the polyether polyurethane that at the end of process step a) there is a phase separate from the low molecular weight alcohol containing the released polyether.

13. The process as claimed in any one of claims 1 to 5, wherein the low molecular weight carbamate is separated from the at least one low molecular weight alcohol before process step b) is carried out.

14. The process as claimed in claim 1, wherein the low molecular weight alcohol formed in process step b) is reused in process step a).

15. The process as claimed in claim 1, wherein at least part of the low molecular weight alcohol released in process step b) is reused in process step a).

Images