Method of producing fluorine-containing polymer, aqueous dispersion, particle, and composition

A method of producing a fluorine-containing polymer, the method comprising:

• preparing an aqueous dispersion A that contains a first perfluoropolymer having a glass transition temperature of 10° C. or lower, and an aqueous medium;
• and
• producing a second fluoropolymer different from the first perfluoropolymer, by polymerizing, in the aqueous dispersion A, a monomer that contains tetrafluoroethylene and a compound represented by Formula (1) below,
• before starting the polymerization of the monomer, a content of the first perfluoropolymer being from 0.01 to 4.0 mass % with respect to a total mass of the aqueous dispersion A, and
• before starting the polymerization of the monomer, the aqueous dispersion A being free of a fluorine-containing emulsifier, or a content of the fluorine-containing emulsifier being 100 ppm by mass or less, with respect to the total mass of the aqueous dispersion A:
• wherein, in Formula (1), Rf represents a perfluoroalkyl group having from 1 to 10 carbon atoms, and optionally having an etheric oxygen atom between carbon atoms in the perfluoroalkyl group.

An aqueous dispersion comprising an aqueous medium and a melt-moldable particle,

• the particle having an average particle size of 1 μm or smaller;
• the particle containing one or more kinds of fluorine-containing polymer;
• the fluorine-containing polymer containing a tetrafluoroethylene-based constitutional unit, a perfluoro (alkyl vinyl ether)-based constitutional unit, and a constitutional unit ascribed to a compound represented by Formula (1) below;
• a content of the perfluoro (alkyl vinyl ether)-based constitutional unit being from 0.05 to 5.0 mol %, with respect to all constitutional units of the fluorine-containing polymer;
• a content of the particle being from 1 to 50 mass % with respect to a total mass of the aqueous dispersion;
• and
• the aqueous dispersion being free of a fluorine-containing emulsifier, or a content of the fluorine-containing emulsifier being 100 ppm by mass or less, with respect to a content of the fluorine-containing polymer:
• wherein, in Formula (1), Rf represents a perfluoroalkyl group having from 1 to 10 carbon atoms, and optionally having an etheric oxygen atom between carbon atoms in the perfluoroalkyl group.

A melt-moldable particle,

• the particle having an average particle size of 1 μm or smaller;
• the particle containing one or more kinds of fluorine-containing polymer;
• the fluorine-containing polymer containing a tetrafluoroethylene-based constitutional unit, a perfluoro (alkyl vinyl ether)-based constitutional unit, and a constitutional unit ascribed to a compound represented by Formula (1) below;
• a content of the perfluoro (alkyl vinyl ether)-based constitutional unit being from 0.05 to 5.0 mol %, with respect to all constitutional units of the fluorine-containing polymer;
• the particle being free of a fluorine-containing emulsifier, or a content of the fluorine-containing emulsifier being 100 ppm by mass or less, with respect to a content of the fluorine-containing polymer;
• and
• with respect to the fluorine-containing polymer, a content of a compound represented by Formula (S1) being from 1 to 10000 ppb by mass, and a content of a compound represented by Formula (S2) being 100 ppb by mass or less:
• wherein, in Formula (S1) and Formula (S2), each M independently represents a hydrogen atom, Na, K, or NH4, n represents from 7 to 11, and m represents from 8 to 12.