Patent ID: 7084225

Claim:
A process for the copolymerization of a tetrafluoroethylene copolymer of the fine powder type, said copolymer containing essentially from 99.4% by weight to 99.98% by weight tetrafluoroethylene monomer units and from 0.02% by weight to 0.6% by weight copolymerized (perfluorobutyl)ethylene comonomer units, comprising: (a) copolymerizing said monomer and comonomer in a pressurized reactor, and (b) initiating said copolymerization by adding potassium permanganate (KMnO 4 ), (c) carrying out the entire reaction in the absence of any ionic strength enhancer, and (d) stopping the addition of (KMnO 4 ) initiator at a point in the reaction no further than 80% of the reaction completion, wherein said polymerized comonomer units are present in an amount from 0.02% by weight to 0.6% by weight, based upon total copolymer weight; and said copolymer has a primary raw dispersion particle size (RDPS) in the range between 0.175 microns to and including 0.203 microns and has a standard specific gravity (SSG) of less than 2.143.