Abstract: In a process for preparing a polyarylene sulfide by reacting an alkali metal sulfide and at least one dihaloaromatic compound in an organic amide solvent at an elevated temperature: a highly pure anhydrous alkali metal sulfide reactant having a purity of at least 95% by weight and a content of alkali metal hydrosulfide impurity of not greater than 2% by weight is employed. The water is deliberately added in a proportion of 0.1 to 0.8 moles per each mole of the alkali metal sulfide used in the process. The alkali metal sulfide reactant is charged in a concentration of 2.5 to 5 moles per liter of the reaction mixture. The deliberate addition of water enables one to omit a dehydration stage which has been desirably or rather necessarily effected to obtain a satisfactory polymer product where a hydrous alkali metal sulfide reactant is employed.

Abstract: High molecular weight polyarylene sulfide prepared by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide solvent, wherein a gaseous phase part of a reactor is cooled to thereby condense a part of a gaseous phase in the reactor, and the condensed liquid is refluxed to a liquid phase in the reactor. Higher molecular weight is attained by copolymerization with 0.005 to 1.5 mole percent, based on the alkali metal sulfide, of a polyhaloaromatic compound.