Method for producing perfluoroelastomer and composition

A composition comprising a perfluoroelastomer and a polymer (1) having a number average molecular weight of 0.3×104 or more and containing a polymerized unit (1) derived from a monomer represented by the following general formula (1):

• CX2═CY(—CZ2—O—Rf-A) (1)
• 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 fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and having an ether bond;
• and A is —COOM, —SO3M, —OSO3M, or —C(CF3)2OM, where M is —H, a metal atom, —NR74, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent and R7 is —H or an organic group, with the proviso that at least one of X, Y, and Z contains a fluorine atom,
• wherein a content of the polymerized unit (1) in the polymer (1) is 90 mol % or more based on all polymerized units.