Lubricant additive
A hydrogenated styrene butadiene star copolymer is incorporated in a lubricant additive package. The star copolymer can include about 3 to 25% and about 97 to 75% butadiene. The star copolymer may further be incorporated in a lubricant additive in the amount of about 12 wt % of the star copolymer as compared to the base oil.
1. A lubricant comprising a viscosity index improver wherein
a. the viscosity index improver comprises:
a hydrogenated styrene butadiene star copolymer, wherein the star copolymer is formed from styrene and butadiene monomers in a ratio of about 5 to 13% styrene to about 95 to 87% butadiene by weight, further wherein the star copolymer has greater than 50% of 1,2 polymerization of the butadiene monomer;
wherein the star copolymer core comprises divinylbenzene;
wherein the degree of hydrogenation of the star copolymer is at least 95%;
wherein the star copolymer has 3 or more arms and the molecular weight of each arm is more than 50,000;
a base oil; and
wherein the star copolymer is provided in an amount to be approximately 0.5 to 1.5 wt % of the lubricant; and
b. the lubricant has a mini-rotary viscometer (MRV TP-1) value improvement of at least 5000 cP over a lubricant containing a hydrogenated styrene isoprene star polymer or an olefin copolymer at generally equivalent kinematic viscosity at 100° C.
2. The lubricant of claim 1 , wherein the hydrogenated star polymer has about a 98% degree of hydrogenation.
3. The lubricant of claim 1 , wherein the star copolymer has an average molecular weight (Mw) of at least about 700,000.
4. The lubricant of claim 1 , wherein the ratio of styrene and butadiene monomers is about 10% styrene and 90% butadiene.
5. The lubricant of claim 1 , wherein the star polymer comprises a hydrogenated, random styrene-butadiene copolymer.
6. The lubricant of claim 1 , wherein the star polymer comprises a hydrogenated, styrene-butadiene block copolymer.
7. The lubricant of claim 1 , wherein the base oil is a Group I base oil.
8. The lubricant of claim 1 having a mini-rotary viscometer value improvement of at least 8000 cP.
9. The lubricant of claim 1 , wherein the lubricant comprises a Group I, Group II, Group III, or Group IV oil.
10. A method of improving the mini-rotary viscometer value (MRV TP-1) of a lubricant comprising the step of:
mixing a lubricant with a viscosity index improver,
wherein the viscosity index improver comprises:
a. a hydrogenerated styrene butadiene star copolymer, wherein the star copolymer is formed from styrene and butadiene monomers in a ratio of about 5 to 13% styrene to about 95 to 87% butadiene by weight, further wherein the star copolymer has greater than 50% of 1,2 polymerization of the butadiene monomer, and still further wherein the star copolymer core comprises divinylbenzene;
b. wherein the degree of hydrogenation of the star copolymer is at least 95% and further wherein the star copolymer has 3 or more arms and the molecular weight of each arm is more than 50,000;
c. a base oil; and
wherein the star copolymer is provided in an amount to be approximately 0.5 to 1.5 wt % of the lubricant.
11. The method of claim 10 , further wherein the star copolymer comprises a hydrogenated, random styrene-butadiene copolymer.
12. The method of claim 10 , further wherein the star copolymer comprises a hydrogenated, styrene-butadiene block copolymer.
13. The lubricant of claim 1 , wherein the star copolymer is provided in an amount to be approximately 0.3 to 2 wt % of the lubricant.
14. The method of claim 10 , wherein the star copolymer is provided in an amount to be approximately 0.3 to 2 wt % of the lubricant.
15. The method of claim 14 , wherein the star copolymer is provided in an amount to be approximately 0.5 to 1.5 wt % of the lubricant.