Suspension polymerization using 2-stage buffer salt addition to prevent clustering and to regulate bead size

Claim 1

A PROCESS FOR THE PRODUCTION OF POLYMER COMPRISING METHYL METHACRYLATE UNITS BY SUSPENSION POLYMERIZATION IN WHICH THE POLYMER BEAD SIZE IS REGULATED AND IN WHICH THE TENDENCY OF THE POLYMER BEADS TO CLUSTER IS INHIBITED WHICH COMPRISES: (A) FORMING AN AQUEOUS SUSPENSION OF A MONOMER TO BE POLYMERIZED IN AN AQUEOUS SOLUTION HAVING A PREDETERMINED BUFFER SALT CONCENTRATION WITHIN THE RANGE OF 1.5 TO 8.8 PARTS PER THOUSAND PARTS OF WATER, THE RATIO OF MONOMER TO AQUEOUS SOLUTION BEING OF THE ORDER OF .55 TO 1.5; (B) POLYMERIZING SAID MONOMER UNTIL THE POLYMERMONOMER BEADS REACH THE TACKY STAGE AT WHICH THERE IS NO LONGER A TOTAL EXCHANGE OF MATERIAL WHEN POLYMER-MONOMER PARTICLES COLLIDE WITH EACH OTHER; (C) AND THEN ADDING ADDITIONAL BUFFER SALT TO THE AQUEOUS SUSPENSION, THE AMOUNT OF SAID ADDITION BEING FROM 1/3 TO 3 TIMES THE AMOUNT OF BUFFER SALT INITIALLY ADDED; (D) CONTINUING THE POLYMERIZATION REACTION UNTIL THE REACTION IS COMPLETE AND RECOVERING UNCLUSTERED POLYMER BEADS.