Patent ID: 6228819
Filing Date: 2001-05-08
Classification: C08F,C10M

Abstract:
A method for making a viscosity index improving copolymer solution, comprising:polymerizing a monomer mixture in an oil soluble diluent and in the presence of a polymerization initiator to form a polymerization intermediate, said monomer mixture comprising:from about 5 parts by weight to about 70 parts by weight of a first (meth)acrylate monomer having the structural formula: ##STR3##wherein:each R.sub.1 is independently H or CH.sub.3 ; andeach R.sub.2 is independently selected from (C.sub.16 -C.sub.24)alkyl;from about 5 parts by weight to about 85 parts by weight of a second (meth)acrylate monomer having the structural formula: ##STR4##wherein:each R.sub.3 is independently H or CH.sub.3 ; andeach R.sub.4 is independently selected from (C.sub.7 -C.sub.15)alkyl; andfrom about 5 parts by weight to about 50 parts by weight of a styrenic monomer; andpolymerizing from about 2 parts by weight to about 20 parts by weight additional (meth)acrylate monomer per 100 parts by weight of the combined first and second (meth)acrylate monomers of the monomer mixture, said additional (meth)acrylate monomer consisting essentially of the first (meth)acrylate monomer, the second (meth)acrylate monomer or a mixture thereof, in the presence of the polymerization intermediate, provided that the combined monomers of the monomer mixture and the additional monomer comprise from about 5 weight percent to about 70 weight percent of the first (meth)acrylate monomer, from about 5 weight percent to about 85 weight percent of the second (meth)acrylate monomer and from about 5 weight percent to about 50 weight percent of the styrenic monomer, to provide a solution of from about 30 weight percent to about 90 weight percent of a viscosity index improving copolymer in the diluent, said solution including less than or equal to 1000 parts by weight residual styrene monomer per one million parts by weight solution.