Copolymerization of tetrafluoroethylene and hexafluoropropylene

Claim 1

IN A PROCESS FOR THE PREPARATION OF A COPOLYMER OF HEXAFLUOROPROPYLENE AND TETRAFLUOROETHYLENE IN AN AQUEOUS DISPERSION,SAID COPOLYMER HAVING A SPECIFIC MELT VISCOSITY, AS MEASURED AT 380*C. UNDER A SHEAR STRESS OF 6.5 POUNDS PER SQUARE INCH, OF BETWEEN 1.5X10**3 AND 1.5X10**6 POISES AND A SPECIFIC I.R. RATIO, AS MEASURED ON FILM OF ABOUT 0.002 INCH THICKNESS WATER-QUENCHED FROM THE MOLTEN PRODUCT, BY NET ABSORBANCE AT 10.18 MICRONS WAVE LENGTH DIVIDED BY NET ABSORBANCE AT 4.25 MICRONS WAVE LENGTH, IN THE RANGE OF 1.5 TO 6, THE STEPS WHICH COMPRISE POLYMERIZING A MIXTURE OF HEXAFLUOROPROPYLENE AND TETRAFLUOROETHYLENE HAVING A VAPOR DENSITY OF 0.18 TO 0.30 G/CC. AT 95 TO 138*C. AND A TOTAL PRESSURE OF 400 TO 750 P.S.I.G. IN AN AQUEOUS SYSTEM CONTAINING A DISPERSING AGENT HAVING A SOLBILITY IN WATER OF AT LEAST 0.1 WT. PERCENT AT REACTION CONDITIONS AND USING A WATER SOLUBLE, FREE RADICAL-PRODUCING INITIATOR HAVING A HALF LIFE AT 95 TO 138*C. OF LESS THAN 9.0 MINUTES, SAID INITIATOR BEING PRESENT IN QUANTITIES WHICH ARE AT LEAST 6.5 WT. PERCENT IN EXCESS OF THAT REQUIRED TO ACHIEVE THE DESIRED MOLECULAR WEIGHT, WITH THE EXCESS BEING CONTACTED WITH THE INITIAL CHARGE OF HEXAFLUOROPROPYLENE PRIOR TO THE ADDITION OF TETRAFLUOROETHYLENE.