Viscosity index improver for lubricant compositions
AssigneeDow Global Technologies LLC
InventorsColin Li Pi Shan, Roger L. Kuhlman, Gary L. Rath, Pamela J. Kenny, Morgan M. Hughes, Rongjuan Cong
Life of this patent
Estimating the term…
Abstract
A lubricant composition comprises a base oil and a viscosity modifier including an ethylene/α-olefin interpolymer. The ethylene/α-olefin interpolymer has at least a hard segment and at least a soft segment. The soft segment contains a higher amount of comonomers than the hard segment. The hard segment has low crystallinity. The copolymer has a number of unique characteristics disclosed herein. Such copolymers offer the possibility of improved low temperature performance and flexibility in formulating motor oil, gear lubricants and greases, etc.
Claims15
A lubricant composition comprising:
- (i) a base oil;
- and
- (ii) an ethylene/α-olefin interpolymer comprising a hard segment and a soft segment, wherein the ethylene/α-olefin interpolymer:
- (a) has a Mw/Mn from about 1.7 to about 3.5;
- (b) has an ethylene content in the hard segment in the range of from 70 wt % to 85 wt % based on total monomer content in hard segment;
- (c) (i) has a hard segment composition of at least 40%, at least one melting point, Tm, in degrees Celsius and an amount of ethylene in weight percent, wt % C2, wherein the numerical values of Tm and wt % C2 correspond to the relationship:
- 90° C.≧Tm≧4.1276(wt % C2)−244.76;
- or
- (ii) has a hard segment composition of less than 40%, at least one melting point, Tm, in degrees Celsius and an amount of ethylene in weight percent, wt % C2, wherein the numerical values of Tm and wt % C2 correspond to the relationship:
- 80° C.≧Tm≦4.1276(wt % C2)−264.95;
- or
- (iii) is characterized by an average block index greater than zero and up to about 1.0;
- or
- (iv) has a molecular fraction which elutes between 0° C. and 130° C. when fractionated using low temperature TREF, characterized in that the fraction has a molar comonomer content of at least 5 percent higher than that of a comparable random ethylene interpolymer fraction eluting between the same temperatures, wherein said comparable random ethylene interpolymer has the same comonomer(s) and has a melt index, density, and molar comonomer content (based on the whole polymer) within 10 percent of that of the ethylene/α-olefin interpolymer;
- or
- (v) has a relationship between ethylene content in wt % and log molecular weight such that a line plotted of ethylene content vs log molecular weight as measured by GPC-IR has an absolute slope, m, of equal to or less than 4;
- and,
- (d) has a turbidity measurement of a 1.0 wt % solution of the ethylene/α-olefin interpolymer in oil or a 1.5 wt % solution in dodecane of less than or equal to that of a comparable copolymer wherein the comparable copolymer has the same DSC enthalpy (J/g) at greater than 55° C. within ±5 J/g, and the same overall ethylene content within 10%;
- and
- wherein the soft segment comprises 35 wt % to 80 wt % comonomer.
Dependencies are inferred from the claim text.