High viscosity index comb polymer viscosity modifiers and methods of modifying lubricant viscosity using same

A lubricant composition comprising:

• a lubricating oil basestock consisting essentially of a Group I basestock, a Group II basestock, a Group III basestock, or a mixture thereof, and optionally a Group IV basestock;
• a lubricant additive comprising one or more of an antioxidant, a corrosion inhibitor, an anti-wear additive, a friction modifier, a dispersant, a detergent, a defoaming agent, an extreme pressure additive, a pour point depressant, and a seal-swelling control agent;
• and
• a comb copolymer viscosity modifier made by polymerization comprising at least the following monomers:
• (a) a hydrogenated polybutadiene-based (alk)acrylate ester macromonomer;
• (b) a C3-C8 alkyl (alk)acrylate ester monomer;
• (c) a C12-C24 alkyl (alk)acrylate ester monomer;
• and
• (d) a C6-C20 aryl-, aralkyl-, or alkaryl-endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer having the following structure (II):
• in which R2 represents hydrogen or C1-C2 alkyl, m is from 2 to 6, such that —(CH2)m— represents a linear, branched, and/or cyclic alkyl group between oxygens, n is from 1 to 10, and R1 represents a C6-C20 aryl, aralkyl, or alkaryl endcap,
• wherein a sum of the C12-C24 alkyl (alk)acrylate ester monomer repeat units plus the C6-C20 aryl-, aralkyl-, or alkaryl-endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer repeat units collectively comprise at least 21.0 wt % of repeat units of the comb copolymer viscosity modifier, but where the C6-C20 aryl-, aralkyl-, or alkaryl-endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer repeat units comprise only up to 20 wt % of the repeat units of the comb copolymer viscosity modifier and wherein the lubricant composition is free of a Group V basestock.

A method of modifying a viscosity and a dispersancy of a lubricant composition comprising:

• forming a viscosity and dispersancy modified mixture by combining a viscosity and dispersancy modifying amount of a comb copolymer viscosity modifier with one of the following lubricant composition components:
• (1) a lubricating oil basestock comprising at least 75% by weight of one or more basestocks selected from the group consisting of Group I, Group II, and Group III basestocks;
• (2) a concentrated lubricant additive package comprising a minor amount of a lubricating oil basestock and one or more of an antioxidant, a corrosion inhibitor, an anti-wear additive, a friction modifier, a dispersant, a detergent, a defoaming agent, an extreme pressure additive, a pour point depressant, and a seal-swelling control agent;
• or (3) a lubricant composition comprising both (1) and (2), the comb copolymer viscosity modifier being made by polymerization comprising at least the following monomers:
• (a) a hydrogenated polybutadiene-based (alk)acrylate ester macromonomer;
• (b) a C3-C8 alkyl (alk)acrylate ester monomer;
• (c) a C12-C24 alkyl (alk)acrylate ester monomer;
• and
• (d) a C6-C20 aryl-, aralkyl-, or alkaryl-endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer having the following structure (II):
• in which R2 represents hydrogen or C1-C2 alkyl, m is from 2 to 6, such that —(CH2)m— represents a linear, branched, and/or cyclic alkyl group between oxygens, n is from 1 to 10, and le represents a C6-C20 aryl, aralkyl, or alkaryl endcap,
• wherein repeat units based on the C12-C24 alkyl (alk)acrylate ester monomer comprise at least 21.0 wt % of repeat units of the comb copolymer viscosity modifier, and
• wherein repeat units based on the C6-C20 aryl-, aralkyl-, or alkaryl-endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer comprise from 3.0 wt % to 20 wt % of the repeat units of the comb copolymer viscosity modifier, wherein the viscosity and dispersancy modified mixture exhibits:
• (i) at least a 25% improvement, relative to the lubricant composition components (1), (2), or (3) without the comb copolymer viscosity modifier, with regard to soot dispersancy, wherein soot dispersancy is measured using a non-linear model applied yield stress (APY) value and/or a linear model soot rating, when measured in the presence of an additional ˜6 wt % carbon black;
• and
• (ii) at least a 5% difference, relative to the lubricant composition components (1), (2), or (3) without the comb copolymer viscosity modifier, with regard to one or more of HTHS150, HTHS100, HTHS80, KV100, KV40, KV20, and VI.