Patent ID: 8686066

Claim:
A process for producing core-shell polytetrafluoroethylene-based powder comprising polytetrafluoroethylene-based cores and styrene/acrylonitrile copolymer-based shells, the process comprising: a polymerisation process comprising: introducing an aqueous dispersion of polytetrafluoroethylene into a reactor; introducing an emulsifier into the reactor,; introducing a catalyst into the reactor; and introducing a styrene monomer, an acrylonitrile monomer, and a copolymer of styrene and acrylonitrile into the reactor, wherein the polymerisation process produces a core-shell polytetrafluoroethylene-based latex; wherein the polymerisation process comprises introducing between about 45% and 55% by weight of polytetrafluoroethylene, about 10% to 20% by weight of the copolymer of styrene and acrylonitrile, about 25% and 27.5% by weight of styrene monomer and about 5% and 10% by weight of acrylonitrile monomer into the reactor; wherein the emulsifier comprises potassium hydroxide and a mixture of oleic acid and stearic acid; wherein the catalyst is potassium persulfate; and a flocculation process comprising: introducing the core-shell polytetrafluoroethylene-based latex to a coagulant, a color stabilizer, and an antioxidant at a temperature of between about 85Â° C. and 90Â° C.; wherein the coagulant comprises magnesium sulfate and phosphoric acid; and increasing the temperature to between about 90Â° C. and 100Â° C. for one of facilitating and effectuating flocculation of the core-shell polytetrafluoroethylene-based latex, wherein the flocculation process produces core-shell polytetrafluoroethylene-based powder.