Copolymers of ethylene and ethylenically unsaturated monomers, process for their preparation and distillate oil containing said copolymers

In a method of preparing an oil-soluble copolymer of ethylene and vinyl acetate useful as a middle distillate fuel oil flow improver for depressing the pour point of said oil and limiting the size of wax crystals that form on cooling said oil below its cloud point, by free radical initiation, wherein said copolymer has a number average molecular weight by Vapor Phase Osmometry in the range of 1,000 to 5,000 and consists essentially of about 3 to 20 molar proportions of ethylene per molar proportion of vinyl acetate, which method comprises copolymerizing said monomers in a liquid phase reaction in about 100 to 600 parts by weight of C.sub.5 to C.sub.10 hydrocarbon solvent based upon 100 parts by weight of copolymer to be produced, at a temperature of about 200.degree. to 270.degree. F. under an ethylene pressure of about 700 to 3,000 psig sufficient to maintain a liquid phase medium and to maintain the desired concentration of ethylene in solution in the solvent, the improvement which comprises using about 0.1 to 5 parts by weight of t-butyl peroctanoate as initiator per 100 parts by weight of copolymer to be produced.