Copolymerized PVDF resin for lithium ion battery binders and its preparation method

A preparation method of a copolymerized PVDF resin for lithium ion battery binders, comprising the following steps:

• (1) preparing reaction raw materials for later use:
• by weight, the reaction raw materials including:
• 300 to 600 parts of deionized water, 0.04 to 0.25 part of a pH buffer regulator, 85 to 99.5 parts of a VDF monomer, 0.5 to 15 parts of a comonomer, 0.3 to 3 parts of a metallocene synergist, 0.2 to 1.0 part of an initiator, and 0.08 to 0.35 part of a dispersant;
• (2) preparing an aqueous solution of the pH buffer regulator and an aqueous solution of the dispersant:
• combining the pH buffer regulator and 0.3 to 5 wt % of the deionized water to prepare the aqueous solution of the pH buffer regulator for later use;
• and combining the dispersant and 10 to 40 wt % of the deionized water to prepare the aqueous solution of the dispersant for later use;
• (3) adding remaining deionized water and the aqueous solution of the pH buffer regulator and the aqueous solution of the dispersant obtained in step (2) to a reactor, reducing a temperature in the reactor to 8 to 12° C., vacuumizing the reactor, and replacing with nitrogen to control an oxygen content in the reactor to ≤20 ppm;
• (4) adding the initiator, the comonomer, the metallocene synergist and 10 to 30 wt % of the VDF monomer to the reactor;
• and
• (5) heating the reactor up to 40 to 65° C. to carry out a polymerization reaction, and controlling a polymerization pressure at 5.5 to 8.0 MPa by adding remaining VDF monomer during the polymerization reaction;
• then, holding temperature of the reactor and continuing the polymerization reaction;
• when a reactor pressure drops to 4.0 MPa, cooling down to stop the polymerization reaction;
• recovering unreacted monomers, and then carrying out washing, filtering, and drying, thus obtaining the copolymerized PVDF resin.