Patent GB-1003291-A (GB)
Title: Polybenzimidazoles and their preparation
IPC: C08G73/18
Filed: 1961-10-12
Abstract: Linear polybenzimidazoles having recurring structural units of formula <FORM:1003291/C3/1> in which R is an aromatic group free of imidazol rings, are prepared by melt polymerizing for at least 30 minutes under a pressure low enough to ensure removal of phenol, either (a) an aromatic compound containing two amino groups in ortho relationship and a phenol carboxylate group, or (b) a mixture of an aromatic compound containing two pairs of ortho amino groups and the diphenyl ester of an aromatic dicarboxylic acid.  The solid polymers may be pulverized and heated above 250 DEG  C. under low pressure to raise their molecular weight.  Particularly desirable polymers have structural units of formulae <FORM:1003291/C3/2> or <FORM:1003291/C3/3> in which R1 is a carbon-carbon bond, an oxygen atom or a lower alkylene chain, R3 is a divalent aromatic radical which is carbocyclic or derived from pyridine, pyrazine, furan or quinoline, and R4 is a tetravalent aromatic radical, containing one or more rings which may be fused or connected by linkages.  Examples describe the preparation of polymers from I phenyl-3,4-diaminobenzoate; II, VI 3,31-diaminobenzidine and diphenylisophthalate; III, VII 1,2,4,5-tetramino benzene and diphenylisophthalate; IV 3,31-diaminobenzidine and the diphenyl ester of pyridine-3,5-dicarboxylic acid; V 3,31-diaminobenzidine and diphenyl furan-2,5-dicarboxylate; VIII 3,31diaminobenzidine and phenyl-(biphenyl-4,41dicarboxylate); IX 3,31-diaminobenzidine and the diphenyl ester of biphenyl-2,21-dicarboxylic acid; X 3,31-diaminobenzidine and the diphenyl ester of naphthalene-1,6-dicarboxylic acid; XI 3,31-diaminobenzidine and diphenyl phthalate.  Other starting materials mentioned are (a) the phenyl esters of 6,7-diamino-b -naphthoic acid; m-(3,4-diaminophenyl) benzoic acid; and m-(3,4-diaminophenoxy) benzoic acid, and (b) 2,3,6,7 - tetra - aminonaphthalene; 3,4,31,41tetra - amino diphenyl ether; 3,4,31,41 -tetraamino diphenyl methane; and phenyl esters of terephthalic acid; naphthalene-1,4- or -2,6dicarboxylic acid; pyridine-2,5- or -2,6-dicarboxylic acid; pyrazine-2,5-dicarboxylic acid; quinoline - 2,6 - dicarboxylic acid; tribenzoic acid; diphenyl ether-4,41-dicarboxylic acid; and diphenylmethane-4,41-dicarboxylic acid. The starting materials may carry non-reactive substituents and may be used in admixture.  The polymers may be shaped to form articles, e.g. fibres or films.  Reference has been directed by the Comptroller to Specification 798,004.ALSO:In examples: (I) phenyl-3,4-diaminobenzoate is prepared from p-aminobenzoic acid by acetylation, nitration, formation of the acid chloride with thionyl chloride, esterification with phenol, hydrolysis and reduction; (II) benzidene is acetylated, nitrated, hydrolysed, reduced with acid stannous chloride to form 3,31-diaminobenzidine; (III) m-dichlorobenzene is nitrated, reacted with ammonia and reduced to yield 1,2,4,5-tetraaminobenzene; (IV) diphenyl pyridine-3,5-dicarboxylate was prepared by treating pyridine-3,5-dicarboxylic acid with thionyl chloride and then with phenol; (V) diphenylfuran-2,5-dicarboxylat was prepared by dehydrating and cyclizing mucic acid to dehydromucic acid, reaction with phosphorus oxychloride and phenol.  Reference has been directed by the Comptroller to Specification 798,004.