# US 5,347,034 A · Process for the production of poly(O-alkylurethanes) of the diphenyl methane series

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- Number: US 5,347,034 A
- Document ID: US5347034A
- Status: Granted
- Kind: A
- Application number: 07/871,914
- Filed: 1992-04-21
- Granted: 1994-09-13
- Earliest claimed: 1991-04-23
- Assignees: Bayer Aktiengesellschaft
- Inventors: Gunter Hammen; Thomas Schieb; Stefan Wershofen
- Web page: https://patentgrep.com/patent/US5347034A

## CPC

- C07C 269/04: from amines with formation of carbamate groups
- C07C 263/04: from or via carbamates or carbamoyl halides
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

The present invention relates to an improved process for the production of monomeric and polymeric poly(O-alkylurethanes) of the diphenyl methane series. The process comprises the reaction of the corresponding amines with dialkyl carbonates in the presence of a catalyst, followed by the isolation of the products in a highly pure form. The invention also relates to the use of the produced monomeric and polymeric poly(O-alkylurethanes) for the production of the corresponding isocyanates.

## Claims

### Claim 1

A process for the production of monomeric and/or polymeric poly(O-alkylurethanes) of the diphenyl methane series comprising reacting
a) amines selected from the group consisting of 4,4'-diaminodiphenyl methane, 2,4'-diaminodiphenyl methane, 2,2'-diaminodiphenyl methane, higher homologs thereof formed in the condensation of aniline with formaldehyde, and mixtures thereof; with
b) a dialkyl carbonate containing from 1 to 2 carbon atoms per alkyl group;
in the presence of
c) a catalyst;
wherein said dialkyl carbonate is present in a quantity such that the molar ratio of dialkyl carbonate to amine is at least 40:1, and the formed monomeric and/or polymeric poly(O-alkylurethanes) crystallize out in a highly pure form upon cooling.

### Claim 2 (depends on 1)

The process of claim 1, wherein said catalyst is a metal compound selected from the group consisting of Groups 1 to 15 of the periodic table.

### Claim 3 (depends on 1)

The process of claim 1, wherein said catalyst is a metal compound selected from the group consisting of Group 12 of the periodic table, and Group 14 of the periodic table.

### Claim 4 (depends on 1)

The process of claim 1, wherein said catalyst is a metal compound selected from the group consisting of tin, zinc, and lead.

### Claim 5 (depends on 1)

The process of claim 1, wherein said formed monomeric and/or polymeric poly(O-alkylurethanes) are separated off after partial concentration of the reaction mixture.

### Claim 6 (depends on 1)

In a process for the production of an isocyanate comprising heating a urethane, the improvement wherein said urethane is a monomeric and/or polymeric poly(O-alkylurethane) produced by the process of claim 1.