A Two-Step Emulsion Polymerization Process Catalyzed by an Organic Diperoxide

Abstract

Abstract An emulsion polymerization process is described which consists of consecutively polymerizing at least two olefinic monomers using an organic diperoxide with two independently functioning peroxy groups, namely 2,5-dimethyl-2-t-butylperoxy-5-hydroxy hexane. In the first polymerization step, the hydroperoxide group is activated by a redox reaction at low temperatures without decomposing the t-butyl peroxide portion of the initiator molecule. After charging fresh monomer, the t-butyl peroxide can then be thermally activated to initiate a second-stage polymerization reaction. This polymerization process employs conventional emulsion polymerization technology. It yields polymeric product with unique physical properties. Polymers with butadiene monomer in the first polymerization step, followed by styrene polymerization in the second step, resemble SBS tri-block polymers. They are thermoplastic, highly resilient and of good strength at high ultimate elongations. The consecutive polymerization of butadiene and acrylonitrile yields elastomers with a superior balance of low-temperature flexibility and resistance to swelling in organic solvents, when compared with random NBR copolymers of equivalent chemical composition. Combinations of butadiene and styrene in the first polymerization stage followed by styrene/acrylonitrile polymerization in the second, yield transparent ABS polymers with superior low-temperature impact resistance. Reference is also made to the polymerization of additional vinyl monomers.