Method for producing fluororesin

A method for producing a fluororesin, comprising:

• polymerizing a mixture including a radical polymerization initiator and a monomer to produce the fluororesin including a residue unit of a formula (1), and when dissolved in perfluorohexane to obtain a 10 wt % perfluorohexane solution, having a transmittance of at least 50% as measured at an optical path length thereof of 10 mm and a wavelength of 275 nm,
• wherein the fluororesin has a weight average molecular weight Mw of from 5×104 to 9.5×104, and a molecular weight distribution Mw/Mn, which is a ratio of the weight average molecular weight Mw to a number average molecular weight Mn, of from 1.2 to 8,
• wherein in the formula (1), Rf1, Rf2, Rf3 and Rf4 each independently represent one of the groups consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, and a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group may have an ethereal oxygen atom, Rf1, Rf2, Rf3 and Rf4 may be linked to each other to form a ring having 4 or more and 8 or less carbon atoms, and the ring may include an ethereal oxygen atom,
• the radical polymerization initiator has a formula (2):
• wherein in the formula (2), Rf9, Rf10, Rf11, and Rf12 each independently represent a perfluoroalkyl group having 1 to 20 carbon atoms, the perfluoroalkyl group may have an ethereal oxygen atom, Rf9 and Rf10 may be linked to each other to form a ring having 4 or more and 20 or less carbon atoms, Rf11 and Rf12 may be linked to each other to form a ring having 4 or more and 20 or less carbon atoms, and the ring may include an ethereal oxygen atom, and
• the monomer has a formula (3):
• wherein in the formula (3), Rf5, Rf6, Rf7 and Rf8 each independently represent one of the groups consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, and a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group may have an ethereal oxygen atom, Rf5, Rf6, Rf7 and Rf8 may be linked to each other to form a ring having 4 or more and 8 or less carbon atoms, and the ring may include an ethereal oxygen atom.