Aqueous fluoropolymer dispersion
The present invention aims to provide an aqueous dispersion that contains particles of a fluoropolymer at high concentrations and has a less variable pH, and in which aggregates are less likely to be generated even after the aqueous dispersion has been stored for a long time. The present invention relates to an aqueous dispersion, including: particles of a fluoropolymer having an average primary particle size of 0.1 to 0.5 μm in an amount of 50 to 70% by mass; a nonionic surfactant in an amount of 2 to 10% by mass based on the amount of the fluoropolymer; and ammonium lauryl sulfate in an amount of 0.0001 to 1% by mass based on the amount of the fluoropolymer, wherein an amount of a fluorine-containing anionic surfactant is less than 10 ppm.
1. A production method of an aqueous dispersion comprising the steps of:
(a) polymerizing fluoromonomers in the presence of a fluorine-containing anionic surfactant to obtain an aqueous dispersion containing particles of a fluoropolymer;
(b) adding a nonionic surfactant into the aqueous dispersion;
(c) removing the fluorine-containing anionic surfactant from the aqueous dispersion and condensing the aqueous dispersion; and
(d) adding, only after removing the fluorine-containing anionic surfactant and condensing the aqueous dispersion, 0.01 to 0.1% by mass, which is based on the amount of fluoropolymer, of ammonium lauryl sulfate into the aqueous dispersion from which the fluorine-containing anionic surfactant has been removed.
2. The production method according to claim 1 ,
wherein said condensing comprises separating the aqueous dispersion into a fluoropolymer-non-containing supernatant phase and a condensed phase containing the fluoropolymer particles.
3. The production method according to claim 1 ,
wherein the fluoropolymer is polytetrafluoroethylene.
4. The production method according to claim 1 ,
wherein the nonionic surfactant is a polyoxyethylene alkyl ether.
5. The production method according to claim 1 ,
wherein the aqueous dispersion comprises:
particles of a fluoropolymer having an average primary particle size of 0.1 to 0.5 μm in an amount of 50 to 70% by mass;
a nonionic surfactant in an amount of 2 to 10% by mass based on the amount of the fluoropolymer; and
ammonium lauryl sulfate in an amount of 0.01 to 0.1% by mass based on the amount of the fluoropolymer,
wherein an amount of a fluorine-containing anionic surfactant is less than 10 ppm.
6. The production method according to claim 1 ,
wherein the ammonium lauryl sulfate is added in an amount of 0.05 to 0.1% by mass, based on the amount of fluoropolymer.