[Problem to be Solved] To Provide a method for producing an acid-decomposable polymer having a reduced metal ion content, which suppresses decomposition and deprotection of the acid-decomposable polymer. [Means to Solve the Problem] The method for producing an acid-decomposable polymer according to the present invention comprises the steps of: preparing a polymer solution comprising an acid-decomposable polymer; washing an acidic cation exchanger with an organic solvent until the water content in the organic solvent discharged from the acidic cation exchanger falls to 400 ppm or less; and passing the polymer solution through the washed acidic cation exchanger to reduce the metal ion content of the polymer.

[Problem to be Solved] To Provide a method for producing an acid-decomposable polymer having a reduced metal ion content, which suppresses decomposition and deprotection of the acid-decomposable polymer. [Means to Solve the Problem] The method for producing an acid-decomposable polymer according to the present invention comprises the steps of: preparing a polymer solution comprising an acid-decomposable polymer; washing an acidic cation exchanger with an organic solvent until the water content in the organic solvent discharged from the acidic cation exchanger falls to 400 ppm or less; and passing the polymer solution through the washed acidic cation exchanger to reduce the metal ion content of the polymer.

The present disclosure provides a method for producing a perfluoroelastomer aqueous dispersion by polymerizing a perfluoromonomer in the presence of a polymer (1) and an aqueous medium to produce an aqueous dispersion of a perfluoroelastomer, the polymer (1) containing a polymerization unit (1) based on a monomer (1) represented by a general formula (1) and the polymer (1) having an ion exchange capacity of 1.50 meq/g or more.

The present disclosure provides a method for producing a perfluoroelastomer aqueous dispersion by polymerizing a perfluoromonomer in the presence of a polymer (1) and an aqueous medium to produce an aqueous dispersion of a perfluoroelastomer, the polymer (1) containing a polymerization unit (1) based on a monomer (1) represented by a general formula (1) and the polymer (1) having an ion exchange capacity of 1.50 meq/g or more.

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 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 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).

Provided is a method for producing an aqueous dispersion of a fluorine-containing elastomer, comprising polymerizing a fluorine-containing monomer in the presence of a polymer (1) containing a polymerization unit (1) based on a monomer (1) represented by general formula (1) and an aqueous medium,

CF.sub.2═CF—R—CZ.sup.1Z.sup.2—COOM  (1)

wherein R is a linking group, Z.sup.1 and Z.sup.2 are each independently F or CF.sub.3, and 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.

A method for producing a fluoropolymer aqueous dispersion, including a step A of performing ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof on a pretreatment aqueous dispersion containing a fluoropolymer obtained by polymerization in the presence of a polymer (I) including a polymerized unit (I) derived from a monomer represented by the following general formula (I), with the proviso that the fluoropolymer is other than the polymer (I):

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.