# US 4,394,500 A · Bead polymerization process for preparing polybenzimidazole

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- Number: US 4,394,500 A
- Document ID: US4394500A
- Status: Granted
- Kind: A
- Application number: 06/290,865
- Filed: 1981-08-07
- Granted: 1983-07-19
- Earliest claimed: 1981-08-07
- Assignees: E. I. Du Pont de Nemours and Company
- Inventors: George N. Milford, Jr.
- Web page: https://patentgrep.com/patent/US4394500A

## CPC

- C08G 73/18: Polybenzimidazoles
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

## Abstract

Polybenzimidazoles are prepared in the form of small particles by reaction of bis(o-diamine) substituted compounds with dicarboxylic acids or of o-diamino-substituted carboxylic acids in the presence of an inert, nonsolvent, liquid medium and polyphosphoric acid.

## Claims

### Claim 1

Process for the preparation of polybenzimidazole in the form of small particles from at least one aromatic compound selected from the group consisting of o-diamino-substituted carboxylic acid compounds by contacting at least one o-diamino-substituted carboxylic acid compound with an excess of polyphosphoric acid dehydrating agent in an inert, nonsolvent, liquid medium, heating to 120.degree.-230.degree. C. for 1-4 hours with stirring, cooling to room temperature with continued stirring and filtering to remove polybenzimidazole which is washed to remove impurities.

### Claim 2 (depends on 1)

The process of claim 1 wherein the inert, nonsolvent liquid medium is mineral oil.

### Claim 3 (depends on 2)

The process of claim 2 wherein the reaction mixture contains a surface-active agent.

### Claim 4 (depends on 2)

The process of claim 2 wherein the aromatic compound is 3,4-diaminobenzoic acid.

### Claim 5 (depends on 4)

The process of claim 4 wherein the reaction is carried out at 120.degree.-200.degree. C. for two hours.