Aqueous Polymerization of Fluorinated Monomer Using Polymerization Agent Comprising Fluoropolyether Acid or Salt and Short Chain Fluorosurfactant

A process for polymerizing fluoropolymer comprising:

• mixing fluoropolyether acid having a number average molecular weight of at least about 800 g/mol with fluorosurfactant to form an acid mixture, said fluorosurfactant having the formula:
• [R1—On-L-A−]Y+
• wherein:
• R1 is a linear or branched partially or fully fluorinated aliphatic group which may contain ether linkages;
• n is 0 or 1;
• L is a linear or branched alkylene group which may be nonfluorinated, partially fluorinated or fully fluorinated and which may contain ether linkages;
• A− is an anionic group selected from the group consisting of carboxylate, sulfonate, sulfonamide and phosphonate;
• and
• Y+ is hydrogen;
• with the proviso that the chain length of R1—On-L- is not greater than 6 atoms;
• dispersing said acid mixture in an aqueous polymerization medium to provide dispersed fluoropolyether acid or salt and surfactant or salt of said surfactant;
• polymerizing in said aqueous polymerization medium at least one fluorinated monomer in the presence of initiator and said dispersed fluoropolyether acid or salt and fluorosurfactant or salt of said surfactant to form an aqueous dispersion of particles of fluoropolymer.

A process for polymerizing fluoropolymer comprising:

• dispersing fluoropolyether acid or salt and fluorosurfactant in an aqueous medium to form a aqueous polymerization agent concentrate comprising dispersed fluoropolyether acid or salt and fluorosurfactant, said fluoropolyether acid or salt having a number average molecular weight of at least about 800 g/mol, said fluorosurfactant having the formula:
• [R1—On-L-A−]Y+
• wherein:
• R1 is a linear or branched partially or fully fluorinated aliphatic group which may contain ether linkages;
• n is 0 or 1;
• L is a linear or branched alkylene group which may be nonfluorinated, partially fluorinated or fully fluorinated and which may contain ether linkages;
• A− is an anionic group selected from the group consisting of carboxylate, sulfonate, sulfonamide anion, and phosphonate;
• and
• Y+ is hydrogen, ammonium or alkali metal cation;
• with the proviso that the chain length of R1—On-L- is not greater than 6 atoms;
• adding said aqueous polymerization agent concentrate to an aqueous polymerization medium to provide dispersed fluoropolyether acid or salt and fluorosurfactant in said medium;
• and
• polymerizing at least one fluorinated monomer in said aqueous polymerization medium in the presence of initiator and said dispersed fluoropolyether acid or salt and said fluorosurfactant to form an aqueous dispersion of particles of fluoropolymer.