Production of aromatic polyamides from dicarboxylic acid and diamine

Claim 1

In a process for producing a fiber forming aromatic polyamide by polycondensing a dicarboxylic acid of the formula, HOOC -- R.sup.2 -- COOH (II) wherein R 2 is a straight chain, branched chain or alicylic hydrocarbon radical, an aryl group with or without at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a nitro group and a cyano group, or a radical in which two or more radicals selected from the group consisting of the above-mentioned radicals are bonded through an alkylene group having 1 to 4 carbon atoms, an alkylidene group having 2 to 4 carbon atoms, --CONH-- or --SO 2 NH--, with an aromatic diamine of the formula, H.sub.2 N -- R.sup.3 -- NH.sub.2 (III) wherein R 3 is an aromatic hydrocarbon radical which may contain one or more substituents on the aromatic nuclei, said substituent being an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a nitro group or a cyano group, and which may contain two or more aromatic hydrocarbon radicals bonded through an alkylene group having 1 to 4 carbon atoms, an alkylidene group having 2 to 4 carbon atoms, --O--, --SO 2 --, --S--, --NH--, --NR"-- wherein R" is an alkyl group having 1 to 4 carbon atoms, --CONH--, --CO-- or --SO 2 NH--, in the presence of a phosphorus compound of the formula, R.sup.4 -- P (OR.sup.5).sub.2 (IV) wherein R 4 is OR 5 , a hydroxyl group, an alkyl group having 1 to 6 carbon atoms or an aryl group with or without at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a nitro group and a cyano group; and R 5 is an aryl group with or without at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a nitro group and a cyano group, and a teriary amine in the liquid phase, wherein the tertiary amine is used in an amount of 1 mole or more per mole of the phosphorus compound and the phosphorus compound is used in an amount of 2 moles or more per mole of the dicarboxylic acid or diamine, the improvement which comprises carrying out the polycondensation using a solvent selected from the group consisting of N-methylpyrrolidone and dimethylacetamide as the reaction medium and a metal halide selected from the group consisting of a lithium halide and a calcium halide wherein the metal halide is used in an amount of 1 to 15% by weight based on the weight of the mixture of the tertiary amine and the solvent.