Aqueous polymerization of perfluoromonomer using hydrocarbon surfactant

摘要

A process is provided for the polymerization of fluoromonomer to an dispersion of fluoropolymer particles in an aqueous medium in a polymerization reactor, by (a) providing the aqueous medium in the reactor, (b) adding the fluoromonomer to the reactor, (c) adding initiator to the aqueous medium, the combination of steps (b) and (c) being carried out essentially free of hydrocarbon-containing surfactant and resulting in the kickoff of the polymerization of the fluoromonomer, and (d) metering hydrocarbon-containing surfactant into the aqueous medium after the kickoff of polymerization, e.g. after the concentration of the fluoropolymer in the aqueous medium is at least 0.6 wt %, the metering being at a rate reducing the telogenic activity of said surfactant while maintaining surface activity.

主权项

1. Process for polymerizing one or more fluoromonomers to form a dispersion of fluoropolymer particles in an aqueous medium in a polymerization reactor, wherein the fluoropolymer is selected from the group consisting of polytetrafluoroethylene, modified polytetrafluoroethylene, and melt-processible copolymer comprising at least 40-99 mol % tetrafluoroethylene units and about 1-60 mol % of at least one other monomer, said process comprising
(a) providing an aqueous medium in said reactor, (b) adding said one or more fluoromonomers to said reactor, (c) adding polymerization initiator to said aqueous medium to commence polymerizing of said one or more fluoromonomers, (d) metering hydrocarbon surfactant into said aqueous medium during the polymerization at a metering rate of at least 0.005 g/l-hr and that provides an amount of hydrocarbon surfactant in the aqueous medium sufficient to stabilize the dispersion of fluoropolymer particles formed during polymerization, wherein 100% of the monovalent substituents on the carbon atoms of the hydrocarbon surfactant are hydrogen, said metering of hydrocarbon surfactant being commenced when the concentration of said fluoropolymer in said aqueous medium is at least 0.6 wt %, andsaid process further comprising providing polymerization sites dispersed in said aqueous medium prior to commencement of polymerization, said polymerization sites forming loci for the precipitation of fluoropolymer, wherein said aqueous medium contains no fluorosurfactant or contains an amount of fluorosurfactant insufficient to stabilize the dispersion of fluoropolymer particles formed during polymerization.