Process for the preparation of polyarylene sulphides

In the process for preparing a polyarylene sulphide by polycondensing at a temperature of from 160.degree.-285.degree. C. for up to 60 hours

• (a) a p-dihalogenobenzene which consists of 50-100 mol % of a compound of the formula ##STR3## and 0-50 mol % of a compound of the formula ##STR4## wherein X is fluorine, chlorine, bromine or iodine and each R is independently selected from the group consisting of hydrogen, C.sub.1 -C.sub.20 -alkyl, C.sub.5 -C.sub.20 -cycloalkyl, C.sub.6 -C.sub.24 -aryl, C.sub.7 -C.sub.24 -alkaryl and C.sub.7 -C.sub.24 -aralkyl with the proviso that at least one R is other than hydrogen;
• and
• (b) 0-2.0 mol %, based on (a), of a compound of the formula ArX.sub.n wherein Ar is an aromatic radical having 6 to 24 carbon atoms and at least 3 free valencies, X is as aforesaid and n is at least 3 with
• (c) an alkali metal sulphide in
• (d) a polar solvent, the molar ratio of (a) to (c) being from 0.98:1 to 1.02:1 and the molar ratio of (c) to (d) being from 1:2 to 1:10, the improvement wherein said polycondensation is carried out in the presence of 0.05-2.0 mols of tri-alkali metal phosphate per mol of (c).