SEDIMENTATION POLYMERIZATION

An aqueous monomer solution, also containing a crosslinker (methyleneb isacrylamide) and an initiator (ammonium persulfate), was introduced d ropwise with a syringe into a vertical glass column containing hot par affin oil. The partial gelation of the droplets, which took place duri ng their sedimentation (about 7-9 s), allowed them to maintain their s pherical shape and not coalesce during their polymerization (for 2 h a t about 50 degrees C) at the bottom of the column. A narrow size distr ibution of beads was achieved for droplets between 1 and 2.5 mm in siz e. Six hydrophilic monomers (acrylamide, acrylic acid, 2-acrylamino-2- methyl-1-propanesulfonic acid, 2-hydroxyethyl-methacrylate, 2-vinyl-1- pyrrolidone and sodium styrenic sulfate) were used to illustrate the n ew methodology.