Patent ID: 7307138

Claim:
A process for the preparation of a polyether ketone of the formula (II) [Ar—O—Ar′—CO—Ar′—O—Ar—CO—Ar″—CO—] (II) in which from 1% to 100% of the O-phenylene-CO units are substituted with an SO 3 M group and sulfonated and unsulfonated O-phenylene-CO units can be in any desired sequence with respect to one another, the radicals Ar, Ar′ and Ar″ independently of one another are substituted or unsubstituted 1,2-, 1,3- or 1,4-phenylene rings, and M taking into account the ionic valencies, comprises one or more elements selected from the group consisting of H, NR where R is H or C 1 -C 4 -alkyl, or an alkali metal or alkaline earth metal or a metal from subgroup 8, by dissolving the corresponding unsulfonated polyetherketone of the formula (II) in from 94 to 97% strength by weight sulfuric acid, adding a sulfonating agent to the solution thus obtained, at an appropriate temperature, until the concentration of sulfuric acid is from 98 to 100% by weight or the concentration of oleum is from 0.01 to 15% by weight SO 3 , and working up the reaction mixture as soon as the desired degree of sulfonation has been reached and optionally converting the sulfonic acid groups into their salt form.