| abstract |
A two-step process for preparing latices containing no emulsifier comprises (1) polymerizing a 30-50% portion of the monomers in aqueous emulsion containing 0.4-1.5 parts of persulfate and 0.5-2.0 parts of N-methylolacrylamide per 100 parts of monomer, and (2) adding the remaining portion of the monomers, 0.4-1.5 parts of persulfate, and 0.5-2.0 parts of Nmethylolacylamide per 100 parts of monomer and polymerizing to complete conversion. The latices have unusually good stability to mechanical shear and multivalent ions at low pH. Latices made with large amounts of persulfate but no N-methylolacrylamide are not stable; N-methylolacrylamide by itself has no capacity for stabilizing latices. |