Hydrolytically stable viscosity index improves
An acrylic acid ester polymer having improved characteristics and oleaginous compositions containing the acrylic acid ester polymer. The acrylic acid ester polymer includes a copolymer derived from a first acrylic acid ester monomer having from about 1 to about 4 carbon atoms, a second acrylic acid ester monomer having from about 12 to about 14 carbon atoms, and a third acrylic acid ester monomer having from about 16 to about 20 carbon atoms. The copolymer has a weight average molecular weight ranging from about 20,000 to about 100,000 daltons and contains no more than about 1 weight percent unreacted monomer.
1 . An acrylic acid ester polymer having improved characteristics comprising a copolymer derived from a first acrylic acid ester monomer having from about 1 to about 4 carbon atoms, a second acrylic acid ester monomer having from about 12 to about 14 carbon atoms, and a third acrylic acid ester monomer having from about 16 to about 20 carbon atoms, wherein the copolymer has a weight average molecular weight ranging from about 20,000 to about 100,000 daltons and wherein the copolymer contains no more than about 1 weight percent unreacted monomer.
2 . The acrylic acid ester polymer of claim 1 , wherein the copolymer contains from about 15 to about 35 percent by weight of a first monomeric unit containing from about 1 to about 4 carbon atoms.
3 . The acrylic acid ester polymer of claim 1 , wherein the copolymer contains from about 30 to about 60 percent by weight of a second monomeric unit containing from about 12 to about 14 carbon atoms.
4 . The acrylic acid ester polymer of claim 1 , wherein the copolymer contains from about 1 to about 20 percent by weight of a third monomeric unit containing from about 16 to about 20 carbon atoms.
5 . The acrylic acid ester polymer of claim 1 , wherein the copolymer contains less than about 1 weight percent unreacted monomer.
6 . A viscosity index improver comprising the acrylic acid ester polymer of claim 1 .
7 . A finished lubricant having improved hydrolytic stability comprising from about 1 to about 15 percent by weight of the acrylic acid ester polymer of claim 1 .
8 . The finished lubricant of claim 5 , further comprising an effective amount of an antiwear additive package.
9 . The finished lubricant of claim 8 , wherein the antiwear additive package comprises a Zinc dialkyl dithiophosphate antiwear agent.
10 . The finished lubricant of claim 8 , wherein the antiwear additive package comprises an ashless antiwear agent.
11 . An automatic transmission fluid containing the finished lubricant of claim 7 .
12 . A hydraulic oil composition comprising the finished lubricant of claim 8 .
13 . A hydraulic system containing the hydraulic oil composition of claim 11 .
14 . The hydraulic system of claim 13 , wherein the hydraulic system is operable at a pressure above about 200 atmospheres.
15 . A lubricant composition having improved hydrolytic stability comprising an effective amount of an antiwear additive package and an acrylic acid ester polymer, wherein the acrylic acid ester polymer comprises a reaction product produced by polymerizing more than about 90 weight percent of monomers in a reaction mixture containing a first acrylic acid ester monomer having from about 1 to about 4 carbon atoms, a second acrylic acid ester monomer having from about 12 to about 14 carbon atoms, and a third acrylic acid ester monomer having from about 16 to about 20 carbon atoms, in the presence of a polymerization initiator, a chain transfer agent, and a hydrocracked group II process oil having a sulfur content of less than about 0.03 wt. %, and wherein the reaction product as made contains less than about 1 weight percent unreacted monomer.
16 . The lubricant composition of claim 15 , wherein the reaction product contains from about 15 to about 35 percent by weight of a first monomeric unit containing from about 1 to about 4 carbon atoms.
17 . The lubricant composition of claim 15 , wherein the reaction product contains from about 30 to about 60 percent by weight of a second monomeric unit containing from about 12 to about 14 carbon atoms.
18 . The lubricant composition of claim 15 , wherein the reaction product contains from about 1 to about 20 percent by weight of a third monomeric unit containing from about 16 to about 20 carbon atoms.
19 . The lubricant composition of claim 15 , wherein the antiwear additive package comprises a Zinc dialkyl dithiophosphate.
20 . A method of operating a high pressure hybrid hydraulic pump comprising inserting the lubricant composition of claim 15 into the pump and operating the pump.
21 . A method of passing a hydrolytic stability test for a lubricant composition comprising providing the lubricant composition of claim 15 and conducting a hydrolytic stability test on the lubricant composition.
22 . A vehicle containing the lubricant composition of claim 15.