Patent ID: 8513349

Claim:
A binder composition comprising: polymer alloy particles comprising (i) a polymer A having a recurring unit derived from at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride, and (ii) a polymer B having a recurring unit derived from an unsaturated carboxylic acid ester; and water, wherein: the average particle diameter of the polymer alloy particles is 50 to 400 nm; the polymer alloy particles are synthesized by absorbing a monomer for constituting the polymer B to the polymer A and polymerizing the monomer for constituting the polymer B to synthesize the polymer B; the monomer for constituting the polymer B is an unsaturated carboxylic acid ester, or a mixture of an unsaturated carboxylic acid ester and at least one monomer selected from the group consisting of an α,β-unsaturated nitrile compound, an unsaturated carboxylic acid, a conjugated diene compound, styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, a carboxylic vinyl ester and an acid anhydride of an ethylenically unsaturated dicarboxylic acid; the polymer alloy particles comprise 1 to 60 wt % of the polymer A, based on the weight of the polymer alloy particles; the polymer alloy particles have only a single Tg or Tm in a temperature range of −50° C. to 250° C., based on a differential scanning calorimetry measurement performed in accordance with JIS K7121; the polymer alloy particles are not core-shell particles; and the binder composition is for use as a positive electrode of an electric storage device.