Process for the preparation of improved polytetrafluoroethylene extrusion powder

Claim 1

IN THE HOMOPOLYMERIZATION OF TETRAFLUOROETHYLENE AT PRESSURE OF 1 TO 75 ATMOSPHERES IN AN AQUEOUS MEDIUM TO OBTAIN A COLLOIDAL DISPERSION OF POLYTETRAFLUOROETHYLENE BY POLYMERIZING SAID TETRAFLUORETHYLENE IN SAID AQUEOUS MEDIUM CONTAINING A WATER-SOLUBLE PEROXIDE INITIATOR AND A WATER-SOLUBLE DISPERSING AGENT COMPRISING A WATERSOLUBLE SALT SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL SALTS, THE AMMONIUM SALT AND THE SUBSTITUTED AMMONIUM SALTS OF A PERFLUOROALKANOIC ACID HAVING THE STRUCTURE B(CF2)NCOOH, WHEREIN B IS FROM THE GROUP CONSISTING OF HYDROGEN AND FLUORINE AND N IS AN INTEGER FROM 6 TO 20, THE STEP WHICH COMPRISES ADDING TO THE AQUEOUS MEDIUM, PRIOR TO POLYMERIZATION, LESS THAN 1% BY WEIGHT OF THE AQUEOUS MEDIUM OF COLLOIDALLY DISPERSED, SOLID, HIGH MOLECULAR WEIGHT POLYTETRAFLUOROETHYLENE HAVING A CRYSTALLINE MELTING POINT AT ABOUT 327*C. AND CONTINUING THE POLYMERIZATION BY MAINTAINING THE POLYMERIZATION PRESSURE UNTIL A POLYTETRAFLUOROETHYLENE CONCENTRATION OF ABOUR 35% BY WEIGHT OF THE AQUEOUS MEDIUM IS OBTAINED.