Abstract: The present invention is directed to a process for forming star shaped microgels which include a core of crosslinked polymer and multiplicity of substantially linear polymeric arms of macromonomers attached to the core. The process includes polymerizing monoethylenically unsaturated monomers in the presence of a chain transfer agent to form macromonomers each having a terminal polymerizable ethylenically unsaturated group and then polymerizing, in presence of the macromonomers, the monoethylenically unsaturated monomers and multi-olefinic crosslinking monomers. The microgels of the present invention can be used as rheology control agents in waterborne and solvent-borne coatings and in adhesives and cosmetics.

Abstract: A process for preparing microgel(s) that uses a wide range of activatable prepolymers. In the process, a polymer composition of crosslinked component A and soluble components B and C is formed from mono-olefinic and multi-olefinic monomers in the presence of catalyst and initiator. The process comprises: I) introducing mono-olefinic monomer, catalyst, and initiator into a reactor in the absence of multi-olefinic monomer and producing an activatable prepolymer, component B; II) contacting the product of I) with multi-olefinic monomer to produce components A and C, optionally in the presence of additional initiator; also optionally in the presence of additional mono-olefinic monomer and initiator. The ratio of components A/(B+C) can be controlled by varying the mole ratio of The Component B/multi-olefinic monomer from 0.05/1 up to 5/1, by decreasing the mole ratio to increase the ratio of A/(B+C), and increasing the mole ratio to decrease the ratio of A/(B+C).