PREPARATION METHOD OF PVDF HOMOPOLYMER OR COPOLYMER BY POLYMERIZATION USING PERSULFATE AS INITIATOR IN AQUEOUS DISPERSION AND ADDITION OF SODIUM ACETATE IN INITIATION OF, DURING OR AFTER POLYMERIZATION AND OPTIONALLY POTASSIUM ALKYL SULFONATE AFTER POLYMERIZATION, AND THERMALLY STABLE PVDF HOMOPOLYMER OR COPOLYMER THEREOF

摘要

PURPOSE: Provided are a method for preparing a PVDF homopolymer or copolymer and a PVDF homopolymer or copolymer prepared by the method which is improved in thermal stability. CONSTITUTION: The method comprises the steps of radical polymerizing vinylidene fluoride and optionally a comonomer in an aqueous dispersion in the presence of a transfer agent, a persulfate as a radical initiator, optionally a surfactant and optionally a paraffin wax; adding sodium acetate in the initiation of, during or after polymerization; optionally adding potassium alkyl sulfonate after polymerization; obtaining an aqueous PVDF dispersion; and pulverizing the dispersion with an air of 120-220 deg.C to obtain a PVDF powder. Preferably the surfactant is represented by ZCnF2nCOOM, wherein Z is F or Cl; n is an integer of 6-13; and M is H, an alkali metal, an ammonium ion, or an ammonium ion having at least one low molecular weight alkyl group. Preferably the amount of sodium acetate is 50-600 ppm based on the prepared PVDF.