Batch polymerization process

In the batch process for preparing tetrafluoroethylene homopolymer or copolymers of tetrafluoroethylene and at least one copolymerizable fluorinated ethylenically unsaturated comonomer of the formula ##STR2## wherein R.sub.1 is --R.sub.f, --R.sub.f' X, --O--R.sub.f, or --O--R.sub.f' X in which R.sub.f is a perfluoroalkyl radical of 1-5 carbon atoms, --R.sub.f' is a linear perfluoroalkylenediradical of 1-5 carbon atoms in which the attaching valences are at each end of the linear chain, and X is H or Cl;

• and R.sub.2 is --R.sub.f or R.sub.f' X, by polymerizing tetrafluoroethylene alone or with at least one said comonomer present in an amount sufficient to produce a comonomer unit content in the copolymer of between 0.005 mole percent and 20 mole percent, in an aqueous polymerization medium containing a free-radical initiator and 0.01-0.5 percent dispersing agent, based on weight of aqueous medium, the improvement which comprises employing as the dispersing agent 1) a mixture of compounds of the formula
• F--CF.sub.2 --CF.sub.2).sub.n CH.sub.2 --CH.sub.2 --SO.sub.3 M
• wherein n is a cardinal number of between 2-8 and the average value of n is between 3-6, or 2) a compound of said formula wherein n is a cardinal number selected from 2-6, and M is a cation having a valence of 1.