Polymerization of vinyl monomers employing liquid acyl sulfonyl peroxide formulations derived from solid acyl alkylsulfonyl peroxides

In a method of polymerizing a vinyl monomer in the presence of an initiator, the improvement comprising using in an initiating amount in the temperature range of 0.degree. C. to 80.degree. C. a liquid solution composition which is a storable stable liquid at 0.degree. to -40.degree. C. consisting essentially of

• a. 10 to 70% by weight of a solid acyl alkylsulfonyl peroxide with a melting point between -10.degree. and 70.degree. C. having the formula ##STR3## where (1) R.sub.1 is an alkyl of 1 to 4 carbons and
• (2) R.sub.2 is selected from the group consisting of an alkyl or monochloroalkyl radical of 3 to 18 carbons and a cycloalkyl or cyclomonochloroalkyl radical of 4 to 12 carbons, and
• b. 90 to 30% by weight of a polar or polarizable solvent or solvent system having a complete solidification temperature below about -10.degree. C and a miscibility number of greater than 8 and less than 21, which solvent or solvent system possesses at least about 20% by weight based on the solid acyl sulfonyl peroxide of a solvent which has a boiling point of at least 165.degree. C at 760 torr.