GB1096477A - Production of aromatic polyamides with high melting points. - Google Patents

Abstract

The invention comprises linear polyamides having recurring units of formula: <FORM:1096477/C3/1> in which Ar is an aromatic radical the valencies of which stem directly from the benzene ring, R represents a non-amide-forming atom or group all of which may or may not be the same and m and n are 0-4. They may be prepared by heating the corresponding di-isocyanate, e.g. 1,1-bis(p-iso-cyanatophenyl) cyclohexane, and dicarboxylic acid, e.g. iso-or terephthalic acid at 170 DEG C. in a solvent, e.g. dimethyl acettamide under normal pressure, concentration of the resulting solution and precipitation of the product with a non-solvent. Alternatively the polymer may be prepared from the corresponding diamine and dicarboxylic acid dichloride. Dicarboxylic acid dichlorides preferred are those of formula: Cl CO Ar CO Cl where Ar is of formula: <FORM:1096477/C3/2> X is alkylene, cycloalkylidene, -SO2-, -O-, -CO-, -CYY1-, or -P(O)R1- and Y, Y1 and R1 are alkyl or cycloalkyl. They include iso- and tere-phthalyl chloride, 1,6-bis(4-carboxy-phenoxy hexane dichloride, 1,4 - bis(4 - carboxyphenoxymethyl) benzene di - chloride and bis(4 - carboxyphenyl) methane dichloride. R may be alkyl, alkoxy or halogen. The diamine may bis(4-aminophenyl) cyclohexane. The reaction may be carried out in a liquid which dissolves the reactants and is or contains a solvent or swelling agent for the product. A combination of immiscible solvents may be used. Sufficient base may be present to neutralize all the eliminated HCl. Bases specified are Na2 CO3, NH3 and tertiary amines. The products may be shaped into fibres, films or plates or used as adhesives for laminates or as varnishes. In Examples polymers are prepared in liquid media containing tetrahydrofuran, water, dimethyl-acetamide and N-methylpyrrolidone. The reaction mixture is cooled with a solid CO2/acetone mixture or an ice bath. The eliminated HCl is neutralized by passing NH3 gas through the reaction mixture and the polymer is precipitated by adding water. In Example 9, the reactants are mixed continuously in an agitated chamber joined by a throttle neck to the reaction chamber. From the reaction chamber the product overflows into a large volume of water to precipitate the polymer. The products of the invention are soluble in dimethyl formamide, dimethyl sulphoxide, hexamethyl phosphoramide, m-cresol and N-methyl pyrrolidone.