High build dispersions
AssigneeE. I. Du Pont de Nemours and Company
InventorsClay Jones, Robert Cavanaugh, Walter Krakowiak, Richard Morgan, Theodore Treat
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Abstract
An aqueous dispersion of non-melt-processible fluoropolymer, process for making same and concentrated dispersion and powder obtained from the dispersion. The fluoropolymer particles of the dispersion have a standard specific gravity (SSG) of less than 2.225 and comprise a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene. At least about 1.5 weight % of the fluoropolymer particles comprise substantially rod-shaped particles having a length to diameter ratio greater than about 5.
Claims49
A dispersion comprising non-melt-processible fluoropolymer particles having an SSG of less than about 2.225 in aqueous medium, said fluoropolymer particles comprising a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene, wherein at least about 1.5 weight % of said fluoropolymer particles comprise substantially rod-shaped particles having a length to diameter ratio of greater than about 5.
A coating composition comprising a concentrated dispersion of non-melt-processible fluoropolymer particles having an SSG of less than about 2.225 in aqueous medium containing a surfactant, said dispersion containing about 30 to about 70 weight % fluoropolymer, said fluoropolymer particles comprising a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene, wherein at least about 1.5 weight % of said fluoropolymer particles consists of substantially rod-shaped particles having a length to diameter ratio of greater than about 5.
A batch process for producing non-melt-processible fluoropolymer dispersion comprising polymerizing tetrafluoroethylene in an aqueous medium in the presence a dispersing agent to produce fluoropolymer having an SSG of less than 2.225, said polymerizing being carried out in first stage during which a first amount of free radical initiator is added and second stage during which a second amount free radical initiator and a telogenic agent are added, said first amount of initiator producing polytetrafluoroethylene having an average melt creep viscosity greater than about 1.2×1010 Pa·s, and said second amount of initiator being at least about 10 times said first amount and being added before about 95% of the total tetrafluoroethylene has been polymerized, said second amount of initiator producing polytetrafluoroethylene or modified polytetrafluoroethylene, and wherein said polymerizing in said first stage is carried out so that at least about 1.5 weight % of said fluoropolymer particles comprise substantially rod-shaped particles having a length to diameter ratio of greater than about 5.
Fine powder comprising non-melt-processible fluoropolymer particles having an SSG of less than about 2.225, said fluoropolymer particles comprising a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene, wherein at least about 1.5 weight % of said fluoropolymer particles comprise substantially rod-shaped particles having a length to diameter ratio of greater than about 5.
Dependencies are inferred from the claim text.