Patent ID: 7521514

Claim:
A semi-batch emulsion polymerization process for the manufacture of a dipolymer of tetrafluoroethylene and 3,3,3-trifluoropropene, said process comprising: A) charging a reactor with a quantity of an aqueous solution; B) pressurizing said reactor to a pressure between 0.3 and 10.0 MPa with a first gaseous monomer mixture consisting of between 100 and 95 mole percent tetrafluoroethylene and between 0 and 5 mole percent 3,3,3-trifluoropropene to form a reaction mixture; C) polymerizing said reaction mixture in the presence of a free radical initiator to form a polymer dispersion while maintaining said reactor at said pressure and at a temperature between 25° C. and 130° C.; and D) feeding to said reactor a quantity of a second gaseous monomer mixture at a rate so as to maintain said pressure in said reactor, said second gaseous monomer mixture consisting of between 45 and 95 mole percent tetrafluoroethylene and between 5 and 55 mole percent 3,3,3-trifluoropropene to form a dispersed dipolymer of between 45 and 95 mole percent copolymerized units of tetrafluoroethylene and between 5 and 55 mole percent copolymerized units of 3,3,3-trifluoropropene.