Abstract: In a process for producing polyarylene sulfide, comprising: reacting an alkali sulfide source and an aromatic dihalide compound in a polar organic solvent to obtain a polymerizate slurry containing polyarylene sulfide particles, by-produced alkali metal salt fine particles and the polar organic solvent, and recovering the polyarylene sulfide particles washed from the polymerizate slurry; the polymerizate slurry is separated by sieving into the polyarylene sulfide particles and a slurry containing the alkali metal salt fine particles, and the separated polyarylene sulfide particles are subjected to a washing step wherein the polyarylene sulfides are introduced into a countercurrent washing apparatus enclosing a movable part and subjected therein to continuous countercurrent contact with a washing liquid. As a result, polyarylene sulfide particles of good quality are produced at a good yield, while pursuing process rationalization.

Abstract: In a process for producing polyarylene sulfide, comprising: reacting an alkali sulfide source and an aromatic dihalide compound in a polar organic solvent to obtain a polymerizate slurry containing polyarylene sulfide particles, by-produced alkali metal salt fine particles and the polar organic solvent, and recovering the polyarylene sulfide particles washed from the polymerizate slurry; the polymerizate slurry is separated by sieving into the polyarylene sulfide particles and a slurry containing the alkali metal salt fine particles, and the separated polyarylene sulfide particles are subjected to a washing step wherein the polyarylene sulfides are introduced into a countercurrent washing apparatus enclosing a movable part and subjected therein to continuous countercurrent contact with a washing liquid. As a result, polyarylene sulfide particles of good quality are produced at a good yield, while pursuing process rationalization.

Abstract: A process for recovering N-methylpyrrolidone contained in an N-methylpyrrolidone-containing liquid formed in the process for preparing a polyarylene thioether by the dehalogenosulfidation of a dihalogeno-aromatic compound and an alkali metal sulfide in the presence of N-methylpyrrolidone as the polymerization solvent, which comprises (a) subjecting the N-methylpyrrolidone-containing liquid to distillation to distill and recover the majority of contained N-methylpyrrolidone while recovering a distillation residue having such a flowability that flow transferring of the distillation residue is possible, and (b) supplying the distillation residue to an air-tight mixer for a highly-viscous fluid, which has a vent and is provided with a heater, to treat the distillation residue under the conditions of a temperature in the mixer of 190.degree. to 310.degree. C.