Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2006-05-09
2006-05-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S545000, C526S242000, C526S250000
Reexamination Certificate
active
07041728
ABSTRACT:
The present invention provides a method of making an aqueous dispersion of non-melt processible polytetrafluoroethylene, the method comprising:(a) an aqueous emulsion polymerization of an amount of tetrafluoroethylene to produce a final amount of polytetrafluoroethylene solids and optionally up to 1% by weight based on the amount of tetrafluoroethylene of a perfluorinated comonomer, wherein said aqueous emulsion polymerization is initiated with a free radical initiator and the polymerization is carried out in the presence of a fluorinated surfactant, and wherein before completing the feeding of said amount of tetrafluoroethylene but after feeding at least 80% by weight of said amount of tetrafluoroethylene, free radicals capable of introducing ionic end groups or precursors thereof in the polytetrafluoroethylene polymer are caused to be formed at a rate that without counter measures would cause an increase in the polymerization rate of at least 20%;(b) reducing the amount of fluorinated surfactant in the thus obtained aqueous dispersion to an amount of not more than 200 ppm, preferably not more than 100 ppm and more preferably not more than 50 ppm based on the amount of polytetrafluoroethylene solids. The invention further provides an aqueous dispersion of polytetrafluoroethylene particles and the use thereof in coating a substrate.
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Dadalas Michael C.
Hintzer Klaus
Loehr Gernot
Zipplies Tilman
3M Innovative Properties Company
Hu Henry S.
Szymanski Brian E.
Wu David W.
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