Process for producing water-soluble vinyl high-polymers by reversed-phase emulsion polymerization

Claim 1

A process for producing powdery, water-soluble, vinyl polymers having a high degree of polymerization, by W/O emulsion polymerization, which comprises the steps of: in a reaction vessel having a reflux condenser at its top, forming a reaction mixture consisting essentially of (1) an oil phase consisting essentially of a mixture of at least two non-polar organic solvents which are soluble with each other, and substantially immiscible with water and which have different boiling points, said solvent mixture having a boiling temperature in the range of from 30° to 60° C, said boiling temperature being in the temperature range for effecting polymerization of water-soluble vinyl monomers, (2) a W/O emulsifier and (3) a water phase consisting essentially of an aqueous solution of a water-soluble vinyl monomer or mixture of said monomers, said emulsifier being effective to emulsify said water phase in said oil phase, the amount of said water phase being less than twice the amount of said emulsifier whereby said water phase is solubilized by said emulsifier and is dispersed in said oil phase to form a W/O emulsion; heating said W/O emulsion reaction mixture to the boiling temperature of said solvent mixture, and simultaneously agitating said reaction mixture, and maintaining said reaction mixture at said boiling temperature under stable reflux conditions to start polymerization of said monomer to form vinyl polymer in the dispersed water phase of said reaction mixture; and then intermittently or continuously adding to said reaction mixture, while it is maintained under said reflux and agitation and in said W/O emulsion state, additional quantities of said aqueous solution of water-soluble vinyl monomer whereby to effect polymerization of said monomer, said additional quantities being added at such a rate that the concentration of the vinyl polymer present in the dispersed water phase of said W/O emulsion reaction mixture is continuously maintained at not less than 20 percent by weight, based on the weight of the water phase of said reaction mixture, during said adding step and until completion of the polymerization period.