Sulfonated bead polymers prepared from styrene, vinylpyridines, and crosslinkers

A process for preparing bead copolymers comprising

• (i) forming a suspension of a seed polymer and a monomer mixture in a continuous aqueous phase, wherein
• (1) the seed polymer is obtained by jetting a monomer mixture of components (A) and (B) or (A) and (B) and (C) as defined below in an aqueous phase and adjacent polymerization or is obtained in a hetero-disperse or homodisperse suspension of a monomer mixture of components (A) and (B) or (A) and (B) and (C) as defined below by stirring or jetting in a continuous aqueous phase, and
• (2) the monomer mixture comprises
• (A) from 67 to 99.45% by weight of styrene,
• (B) from 0.5 to 20% by weight of crosslinkers, which optionally are present as an isomer mixture and can contain up to 50% by weight of isomers of ethylstyrenes and up to 10% by weight of isomers of diethylbenzenes,
• (C) from 0.5 to 8% by weight of vinylpyridines, and
• (D) from 0.1 to 1.1 parts by weight, based on 100 parts by weight of the mixture of components (A)+(B)+(C), of a polymerization initiator,
• (ii) polymerizing the monomer mixture in the seed polymer or in a heterodisperse or homodisperse suspension to form a copolymer, and
• (iii) functionalizing the resulting copolymer by sulfonation.