Aqueous polymerization of fluorinated monomer using polymerization agent comprising fluoropolyether acid or salt and short chain fluorosurfactant

A process comprising polymerizing at least one fluorinated monomer in an aqueous medium containing initiator and polymerization agent to form an aqueous dispersion of particles of fluoropolymer, said polymerization agent comprising:

• fluoropolyether acid or salt thereof having a number average molecular weight of at least about 800 g/mol;
• and
• 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 1;
• L is a linear or branched alkylene group which may be non-fluorinated, partially fluorinated or fully fluorinated and which may contain ether linkages;
• A−is a carboxylate;
• 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,
• wherein said polymerization agent comprises a minor amount of said fluoropolyether acid or salt thereof and a major amount of said fluorosurfactant;
• wherein said polymerizing produces less than about 3 wt % undispersed fluoropolymer based on the total weight of fluoropolymer produced;
• and
• said process further comprising forming a mixture of a polymerization agent comprising a fluoropolyether acid or salt in acid form and a fluorosurfactant in acid form and dispersing said mixture in an aqueous medium.