A method for producing a perfluoroelastomer, which includes carrying out polymerization of a perfluoromonomer in an aqueous medium in the presence of a polymer (1) having a number average molecular weight of 0.3×10.sup.4 or more to provide a perfluoroelastomer, the polymer (1) containing a polymerized unit (1) derived from a monomer represented by the following general formula (1):

CX.sub.2═CY(—CZ.sub.2—O—Rf-A)   (1)

wherein X, Y, Z, Rf and A are as defined herein, with the proviso that at least one of X, Y, and Z contains a fluorine atom.

Provided is a fluoropolymer comprising tetrafluoroethylene unit (1) and a monomer unit (2) derived from a perfluoroalkadlene represented by formula (2):

CF.sub.2═CF(CF.sub.2).sub.nCF═CF.sub.2

where n represents an integer of 2 to 10, wherein a content of tetrafluoroethylene unit (1) is 98.0 to 99.999 mol % or more based on total monomer units constituting the fluoropolymer, and a content of the monomer unit (2) is 0.001 to 2.0 mol % based on total monomer units constituting the fluoropolymer.

Provided is a fluoropolymer comprising tetrafluoroethylene unit (1) and a monomer unit (2) derived from a perfluoroalkadlene represented by formula (2):

CF.sub.2═CF(CF.sub.2).sub.nCF═CF.sub.2

where n represents an integer of 2 to 10, wherein a content of tetrafluoroethylene unit (1) is 98.0 to 99.999 mol % or more based on total monomer units constituting the fluoropolymer, and a content of the monomer unit (2) is 0.001 to 2.0 mol % based on total monomer units constituting the fluoropolymer.

A method for producing a fluoropolymer, which includes polymerizing a fluoromonomer in an aqueous medium in the presence of a polymer (1), the polymer (1) including a polymerized unit derived from a monomer CX.sub.2═CY(—CZ.sub.2—O—Rf-A), wherein X is the same or different and is —H or —F; Y is —H, —F, an alkyl group, or a fluorine-containing alkyl group; Z is the same or different and is —H, —F, an alkyl group, or a fluoroalkyl group; Rf is a C1-C40 fluorine-containing alkylene group or a C—C100 fluorine-containing alkylene group and having an ether bond; and A is —COOM, —SO.sub.3M, or —OSO.sub.3M, wherein M is —H, a metal atom, —NR.sup.7.sub.4, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein R.sup.7 is H or an organic group, providing that at least one of X, Y, and Z contains a fluorine atom.

A method for producing a fluoropolymer, which includes polymerizing a fluoromonomer in an aqueous medium in the presence of a polymer (1), the polymer (1) including a polymerized unit derived from a monomer CX.sub.2═CY(—CZ.sub.2—O—Rf-A), wherein X is the same or different and is —H or —F; Y is —H, —F, an alkyl group, or a fluorine-containing alkyl group; Z is the same or different and is —H, —F, an alkyl group, or a fluoroalkyl group; Rf is a C1-C40 fluorine-containing alkylene group or a C—C100 fluorine-containing alkylene group and having an ether bond; and A is —COOM, —SO.sub.3M, or —OSO.sub.3M, wherein M is —H, a metal atom, —NR.sup.7.sub.4, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein R.sup.7 is H or an organic group, providing that at least one of X, Y, and Z contains a fluorine atom.

A composition contains ethylenically unsaturated quaternary ammonium cations with acetate counterions, where each of the ethylenically unsaturated ammonium cations contain only one non-aromatic carbon-carbon double bond and the composition contains less than one mole-percent chloride relative to quaternary ammonium cations can be polymerized to form a cationic polymer acetate.

A composition including a polytetrafluoroethylene and a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I), the composition having a standard specific gravity of 2.200 or less:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m   (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; A.sup.0 is an anionic group; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.

A composition including a polytetrafluoroethylene and a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I), the composition having a standard specific gravity of 2.200 or less:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m   (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; A.sup.0 is an anionic group; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.

A method for producing modified polytetrafluoroethylene including: polymerizing tetrafluoroethylene and a modifying monomer in an aqueous medium in the presence of a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I) to obtain a modified polytetrafluoroethylene:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m  (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A.sup.0 is an anionic group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more. Also disclosed is a composition containing the modified polytetrafluoroethylene and the polymer (I).

A method for producing modified polytetrafluoroethylene including: polymerizing tetrafluoroethylene and a modifying monomer in an aqueous medium in the presence of a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I) to obtain a modified polytetrafluoroethylene:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m  (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A.sup.0 is an anionic group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more. Also disclosed is a composition containing the modified polytetrafluoroethylene and the polymer (I).