Powdery molding compositions capable of being sintered made from polyvinyl chloride, which are especially suitable for the manufacture of separator plates for electric cells, and which substantially consist of a suspension polyvinyl chloride, from 0.003 to 0.45 weight %, relative to the molding composition, of free sulfonic acids selected from the group of alkylarylsulfonic acids and/or alkylsulfonic acids, and 1/9 to 7/3 of said 0.003 to 0.45 weight % of anions of said sulfonic acids, in the form of their salts with organic cations, selected from the group of quaternary ammonium cations.