METHOD FOR CLEAVING POLYURETHANE PRODUCTS

Abstract

The invention relates to a method for cleaving polyurethane products, having the steps of (A) providing a polyurethane product which is based on isocyanate components and a polyol component; (B) reacting the polyurethane product with a monofunctional araliphatic alcohol in the presence of an alcoholysis catalyst, thereby obtaining a product mixture containing a liquid polyol phase and a solid carbamate of an isocyanate of the isocyanate component and the monofunctional araliphatic alcohol; and (C) separating the carbamate from the product mixture, thereby leaving the liquid polyol phase.

Claims

1. A process for cleavage of polyurethane products comprising: (A) providing a polyurethane product based on an isocyanate component and a polyol component; (B) reacting the polyurethane product with a monofunctional araliphatic alcohol in the presence of an alcoholysis catalyst to obtain a product mixture containing a liquid polyol phase and a solid carbamate of an isocyanate of the isocyanate component and of the monofunctional araliphatic alcohol; And (C) separating the carbamate from the product mixture, leaving behind the liquid polyol phase.

2. The process as claimed in claim 1, wherein the polyurethane product comprises a polyurethane foam.

3. The process as claimed in claim 1, wherein the polyol component comprises a polyether polyol, a polyester polyol, a polyether ester polyol, a polyether carbonate polyol, a polyacrylate polyol or a mixture of two or more of the abovementioned polyols.

4. The process as claimed in claim 1, wherein the isocyanate component comprises tolylene diisocyanate, methylenediphenylene diisocyanate, polymethylenepolyphenylene polyisocyanate, a mixture of methylenediphenylene diisocyanate and polymethylenepolyphenylene polyisocyanate, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate or a mixture of two or more of the abovementioned isocyanates.

5. The process as claimed in claim 1, wherein the araliphatic monofunctional alcohol comprises benzyl alcohol, furfuryl alcohol or a mixture of both alcohols.

6. The process as claimed in claim 1, wherein step (B) is performed at a temperature in the range from 130 C. to 195 C.

7. The process as claimed in claim 1, wherein the monofunctional araliphatic alcohol and the polyurethane product are employed in a mass ratio [m(monofunctional araliphatic alcohol)/m(polyurethane product)] in the range from 0.30 to 10 in step (B).

8. The process as claimed in claim 1, wherein step (C) is followed by: (D) further reaction of the carbamate separated in (C), wherein the further reaction comprises: (D.I) hydrolysis of the carbamate with water in the presence of a hydrolysis catalyst to form an amine corresponding to an isocyanate of the isocyanate component; (D.II) cleavage of the carbamate into the isocyanate of the isocyanate component and the monofunctional araliphatic alcohol; or (D.III) hydrogenolysis of the carbamate with hydrogen to form an amine corresponding to an isocyanate of the isocyanate component in the presence of a hydrogenolysis catalyst.

9. The process as claimed in claim 8 comprising step (D.I), wherein the hydrolysis catalyst comprises an organic or inorganic Brnsted base.

10. The process as claimed in claim 9, wherein the organic or inorganic Brnsted base comprises a hydroxide, a carbonate or a hydrogencarbonate.

11. The process as claimed in claim 8 comprising step (D.I), wherein the hydrolysis catalyst comprises a urethanase.

12. The process as claimed in claim 11, wherein the urethanase comprises a polypeptide comprising SEQ ID no. 3, SEQ ID no. 4, SEQ ID no. 10, SEQ ID no. 11 or a variant of any thereof, wherein the polypeptide exhibits urethanase activity.

13. The process as claimed in claim 8, comprising step (D.II), wherein step (D.II) is performed at a temperature in the range from 150 C. to 280 C. and at a pressure in the range from 0.001 bar.sub.(abs.) to 2.00 bar.sub.(abs.).

14. The process as claimed in claim 8, comprising step (D.III), wherein and the hydrogenolysis is performed in the presence of a solvent at a temperature in the range from 20 C. to 100 C.

15. The process as claimed in claim 1, further comprising: (E) obtaining polyols from the polyol phase.

Description

EXAMPLES

A. Examples for Alcoholysis of an MDI-Based Rigid Foam

General Comments

[0127] The following examples 1 to 6 were performed with benzyl alcohol and the comparative examples 7 to 8 with ethanol/phenylethanol as monofunctional alcohol. In all examples an MDI-based rigid polyurethane foam was used as the polyurethane product to be cleaved. The MDI-based carbamate compounds corresponding to the employed alcohols were analyzed by LC-MS. The method employed was as follows:

[0128] 5-95% of water-acetonitrile (+0.1% formic acid) gradient on an Agilent EC-C18 503 mm 2.7 m dp separating column at 35 C. and a flow rate of 0.8 ml/min. Recording of positive and negative mass spectra and tandem mass spectra at a resolution of 35000 Th at m/z 200 Th. Th is short for the unit Thomson which describes the mass-charge ratio m/z.

[0129] The rigid polyurethane foam was produced according to the following formulation.

TABLE-US-00001 TABLE 1 Formulation of the polyurethane foam cleaved in the examples (in parts by weight) Desmophen 21AP17 (1) 41.71 Tegostab BF 8465 (2) 0.43 Desmorapid PV (3) 0.09 Desmorapid 726 B (4) 0.43 Water 0.65 Cyclopentane (5) 4.34 Desmodur 44V20L (6) 52.34 Index (7) 110 Key: (1) Polyether polyol from Covestro Deutschland AG (2) Polyether siloxane additive from Evonik AG (3) Desmorapid PV is an amine catalyst from Covestro Deutschland AG (4) Desmorapid 726 B is an amine catalyst from Covestro Deutschland AG (5) Cyclopentane is a physical blowing agent (6) Desmodur 44V20L is an MDI from Covestro Deutschland AG (7) Ratio of NCO to OH groups

General Experimental Procedure

[0130] In a 1000 mL 4-necked flask fitted with a stirrer, thermometer and cooler, alcohol and catalyst are initially charged and heated to 180 C. to 190 C. under nitrogen. A rigid foam produced according to the formulation from table 1 is added at this temperature and after dissolution thereof the resulting mixture is stirred at 180 C. to 190 C. for 3 hours. Table 2 shows the conditions and the results achieved.

TABLE-US-00002 TABLE 2 Results of examples Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 (inv.) (inv.) (inv.) (inv.) (inv.) (inv.) (comp.) (comp.) m(benzyl 300 300 300 300 900 141 alcohol)/g m(ethanol)/g 60 m(phenyl- 300 ethanol)/g m(DBU)/g 0.9 m(DABCO)/g 0.9 m(Na.sub.2CO.sub.3)/g 12.15 m(tetrabutyl 0.23 0.3 0.22 0.18 0.3 titanate)/g Rigid foam/g 150 150 150 300 450 300 300 300 1,2-dichloro- 400 400 benzene/g Yield of MDI 18.4 18.4 29.0 40.0 84.0 38.8 biscarbamate/g Key: inv. = inventive; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; DABCO = 1,4-diazabicyclo[2.2.2]octane. (Methylenedi-p-phenylene)bis(phenylmethylcarbamate) (examples 1 to 6) having a molar mass of 466.5 g/mol was in each case demonstrated as the main product by LC-MS. (The polymeric carbamates from pMDI were likewise demonstrated but not quantified).

[0131] In comparative example 7 the rigid polyurethane foam was not dissolvable. In comparative example 8 the MDA-phenylethanol carbamate obtained was not solid but viscous and was therefore inseparable from the reaction mixture and from the polyol.

B. Examples for Enzymatic Hydrolysis of MDI Carbamates

General Comments and Experimental Procedure

[0132] The following examples employed urethanases from WO 2019/243293 A1. The enzymes were expressed in Escherichia coli BL21 (DE3), digested and lyophilized. 0.9% (w/w) of this preparation was admixed with 1% (w/w) of substrate (here carbamates) in phosphate buffer (preferably between 50 to 200 mM, pH 7.5). Dimethyl sulfoxide is employed as cosolvent for the substrate (not more than 10% (w/w) of the final reaction). An esterase from Sigma Aldrich was also investigated: PLE (esterase from porcine liver (E2884-5kU)) (SEQ ID no. 11, WO 2019/243293). The reaction is carried out for 24 h at 40 C. and a further 24 h at 50 C. in 1.5 mL reaction vessels in a Thermoblock at 1000 rpm. The enzymatic reaction is stopped by diluting the reaction batch in acetonitrile or stopping solution (50 mM NaOH, 20% acetic acid, 50% acetonitrile). The samples are filtered and analyzed by HPLC (ZORBAX Eclipse C18 column (particle size 3.5 m, 4.675 mm (Agilent Technologies, Santa Clara, USA), 40 C., eluent A: acetonitrile with 5% ultrapure water, eluent B: 10 mM sodium phosphate buffer pH 7.0 with 5% ACN, flow: 1 mL/min). The profile of the HPLC method is shown in table 3. Table 4 shows the elution times of the components with this measurement method.

TABLE-US-00003 TABLE 3 Profile of HPLC method Time/ Flow/ Maximum allowable min A % B % ml .Math. min.sup.1 pressure/bar 0.00 0 100 1 300 2.00 0 100 1 300 10.00 95 5 1 300 11.00 95 5 1 300 11.50 0 100 1 300 17.00 0 100 1 300

TABLE-US-00004 TABLE 4 Elution times in HPLC analysis for the employed carbamate pMDI-benzyl alcohol and the expected products 4,4-MDA and pMDA. Component Elution time [min] Benzyl alcohol 7.3 4,4-MDA 8.4 Regioisomers and polymers of MDA (pMDA) between 8.8-9.4

Examples 9 to 12

[0133] As is apparent from table 5 which follows, liberation of 4,4-MDA and pMDA from pMDI-benzyl alcohol was identified in three enzymatic reactions: with Aes72 (SEQ ID no. 3, WO 2019/243293 A1), PLE (SEQ ID no. 11, WO 2019/243293 A1) and Aes170 (SEQ ID no. 4, WO 2019/243293). Liberation of benzyl alcohol was also demonstrated. These results were achievable both with synthetically produced carbamate and with carbamate from the benzyl alcoholysis from the preceding examples. The carbamate from example 1 and example 3 (table 2) served as starting material.

TABLE-US-00005 TABLE 5 Results of examples for enzymatic hydrolysis a) hydrolysis of pMDA-benzyl alcohol b) hydrolysis of (synthetically the carbamate produced from from the pMDI with alcoholysis SEQ ID no. (WO Designation excess benzyl with benzyl Ex. 2019/243293 A1) in study alcohol) alcohol.sup.1 9 3 Aes72 yes yes 10 11 PLE yes.sup.2 yes.sup.2 11 4 Aes170 yes.sup.2 yes.sup.2 12 10 AesG56 partial partial .sup.1Examples 9b to 12b were each performed once with the carbamate from example 1 and once with the carbamate from example 3. The results were identical. .sup.2In addition to 4,4-MDA the liberation of benzyl alcohol was also detected.