Provided are methods for removing a perfluorinated alkanoic acid from solutions containing the perfluorinated alkanoic acid and a fluorinated alkoxy acid. These methods include contacting the first solution with an anion-exchange resin to produce a second solution and a resultant anion-exchange resin having perfluorinated alkanoic acid adsorbed thereto, wherein the perfluorinated alkanoic acid is present in the first solution at a first concentration and is present in the second solution at a second concentration which is lower than the first concentration, and separating the second solution from the resultant anion-exchange resin.

A method for producing an aqueous dispersion of purified polytetrafluoroethylene, the method including: removing or reducing a compound represented by Formula (1) or (2) below from an aqueous dispersion of polytetrafluoroethylene obtained using a hydrocarbon surfactant: Formula (1): (H(CF.sub.2).sub.mCOO).sub.pM.sup.1; or Formula (2): (H(CF.sub.2).sub.nSO.sub.3).sub.qM.sup.2.

Also disclosed is a composition containing polytetrafluoroethylene substantially free from a compound represented by Formula (3) below and a molded body including the composition: Formula (3): (H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2.

A method for producing an aqueous dispersion of purified polytetrafluoroethylene, the method including: removing or reducing a compound represented by Formula (1) or (2) below from an aqueous dispersion of polytetrafluoroethylene obtained using a hydrocarbon surfactant: Formula (1): (H(CF.sub.2).sub.mCOO).sub.pM.sup.1; or Formula (2): (H(CF.sub.2).sub.nSO.sub.3).sub.qM.sup.2.

Also disclosed is a composition containing polytetrafluoroethylene substantially free from a compound represented by Formula (3) below and a molded body including the composition: Formula (3): (H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2.

To provide a fluorinated elastic copolymer having a low content of metal elements and being excellent in crosslinkability. This fluorinated elastic copolymer has iodine atoms and has units a based on tetrafluoroethylene, units b based on a monomer having one polymerizable unsaturated bond (but excluding tetrafluoroethylene), and units c based on a fluorinated monomer having at least two polymerizable unsaturated bonds, wherein the metal content is at least 0.3 ppm by mass and at most 20.0 ppm by mass.

To provide a fluorinated elastic copolymer having a low content of metal elements and being excellent in crosslinkability. This fluorinated elastic copolymer has iodine atoms and has units a based on tetrafluoroethylene, units b based on a monomer having one polymerizable unsaturated bond (but excluding tetrafluoroethylene), and units c based on a fluorinated monomer having at least two polymerizable unsaturated bonds, wherein the metal content is at least 0.3 ppm by mass and at most 20.0 ppm by mass.

A method for producing purified fine polymer particles (A), includes an organic solvent mixing step of mixing an organic solvent (B) and a latex that contains fine polymer particles (A) and an emulsifying agent having a polyethylene group to obtain a mixture, and a mixed state maintaining step of allowing the mixture to stand and/or stirring the mixture. The method can efficiently purify fine polymer particles from a latex and has reduced environmental impact.

A method for producing purified fine polymer particles (A), includes an organic solvent mixing step of mixing an organic solvent (B) and a latex that contains fine polymer particles (A) and an emulsifying agent having a polyethylene group to obtain a mixture, and a mixed state maintaining step of allowing the mixture to stand and/or stirring the mixture. The method can efficiently purify fine polymer particles from a latex and has reduced environmental impact.

A composition containing polytetrafluoroethylene and substantially free from a compound represented by Formula (3):

(H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2

wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4 (where R.sup.5s may be the same as or different from each other and are each H or an organic group having 1 to 10 carbon atoms), an imidazolium optionally having a substituent, a pyridinium optionally having a substituent, or a phosphonium optionally having a substituent, and q is 1 or 2. Also disclosed is a molded boy including the composition.

A composition containing polytetrafluoroethylene and substantially free from a compound represented by Formula (3):

(H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2

wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4 (where R.sup.5s may be the same as or different from each other and are each H or an organic group having 1 to 10 carbon atoms), an imidazolium optionally having a substituent, a pyridinium optionally having a substituent, or a phosphonium optionally having a substituent, and q is 1 or 2. Also disclosed is a molded boy including the composition.

A composition containing polytetrafluoroethylene and substantially free from a compound represented by Formula (3):

(H(CF.sub.2).sub.8SO.sub.3).sub.qM.sup.2

wherein M.sup.2 is H, a metal atom, NR.sup.5.sub.4 (where R.sup.5s may be the same as or different from each other and are each H or an organic group having 1 to 10 carbon atoms), an imidazolium optionally having a substituent, a pyridinium optionally having a substituent, or a phosphonium optionally having a substituent, and q is 1 or 2. Also disclosed is a molded boy including the composition.