Patent ID: 8450439

Claim:
A process for preparing a vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and has a number average degree of polymerization of 4 to 15, in which vinylidene fluoride is subjected to radical polymerization in the presence of a radical polymerization initiator and at least one of perfluoro iodides represented by the formula (2): X 2 —(CF 2 ) n —I (2) wherein X 2 is a fluorine atom or iodine atom, n is an integer of 1to 20, wherein in the vinylidene fluoride homopolymer comprising crystal form I alone or as main component, when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal form I, II or III which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1): 100≧I-form/(I-form+II-form)≧50% by weight (Equation 1) and (Equation 2): 100≧I-form/(I-form+III-form)≧50% by weight (Equation 2).