Method of producing fluorine-containing elastomer, composition, solid composition, and crosslinked rubber article

A composition, comprising:

• a compound represented by the following Formula (X);
• a first fluorine-containing polymer containing a structural unit based on a cyano group-containing monomer and a structural unit based on at least one selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, a fluorine-containing vinyl ether, and a fluorine-containing allyl ether;
• and
• a second fluorine-containing polymer containing a structural unit based on tetrafluoroethylene,
• wherein the composition substantially does not contain an emulsifier having a fluorine atom:
• wherein, in the Formula (X), each of X1 and X2 independently represents a hydrogen atom, a chlorine atom, or an alkyl group,
• X3 represents a hydrogen atom or an alkyl group,
• L represents a single bond or a divalent linking group, and
• Z represents an anionic group or a salt of an anionic group.

A solid composition, containing a fluorine-containing elastomer containing a structural unit based on a cyano group-containing monomer, a structural unit based on tetrafluoroethylene, and a structural unit based on at least one selected from the group consisting of a fluorine-containing vinyl ether and a fluorine-containing allyl ether, wherein:

• when heated in a nitrogen atmosphere under the following Condition 1, a weight reduction rate after a lapse of 1000 minutes from a start of temperature increase is 2.0% or less, and
• the solid composition substantially does not contain an emulsifier having a fluorine atom:
• (Condition 1)
• the temperature is raised from 40° C. to 90° C. at a heating rate of 20° C./min, maintained at 90° C. for 120 minutes, raised from 90° C. to 200° C. at a heating rate of 20° C./min, maintained at 200° C. for 240 minutes, raised from 200° C. to 305° C. at a heating rate of 20° C./min, and maintained at 305° C. for 720 minutes.