Patent ID: 6479591
Filing Date: 2002-11-12
Classification: C08F

Abstract:
Fine powders of modified polytetrafluoroethylene (PTFE) having a â€œcore-shellâ€  structure; the fine powder being formed by:1) a â€œcoreâ€  of tetrafluoroethylene (TFE) modified by one or more monomers selected from: a) dioxoles of formula: wherein W1 and W2, equal to or different from each other, represent F or CF3; W4&boxH;F, Rf, ORf, with Rf equal to a perfluoroalkyl radical containing from 1 to 5 carbon atoms; b) one or more perfluorinated monomers which cyclize during the polymerization; 2) a â€œshellâ€  of TFE modified by perfluoropropene (PFP); the amount, referred to the core+shell total particle, of comonomers 1) in the â€œcoreâ€  being in the range 0.01-0.06% by weight; the amount, referred to the core+shell total particle, of perfluoropropene 2) in the â€œshellâ€  being in the range 0.002-0.06% by weight; the thermal instability index (TII) of the fine powder being equal to or lower than 5, determined according to ASTM D4895.