Power steering fluid

Abstract

Provided are power steering fluids made from a waxy feed and with improved low temperature properties, such as, for example, a viscosity index of greater than 290 and a Brookfield Viscosity at −40° C. of less than 1900 mPa·s. In an embodiment, the power steering fluid comprises greater than 50 weight % base oil, viscosity index improver, and less than about 1.0 weight % pour point depressant.

1 . A power steering fluid comprising:
 a) greater than 50 weight % base oil, wherein the base oil has consecutive numbers of carbon atoms and has a viscosity index greater than a Viscosity Index Factor calculated by the following equation:
   28×ln(Kinematic Viscosity at 100° C.)+101; and 
   b) viscosity index improver;   wherein the power steering fluid has a viscosity index of greater than 290 and a Brookfield Viscosity at −40° C. of less than 1900 mPa·s.   
   
   
       2 . The power steering fluid of  claim 1 , further comprising less than about 1.0 weight % pour point depressant. 
   
   
       3 . The power steering fluid of  claim 1 , wherein the base oil is made from a waxy feed. 
   
   
       4 . The power steering fluid of  claim 1 , wherein the base oil has a kinematic viscosity at 100° C. between about 1.2 and about 4.0 mm 2 /s. 
   
   
       5 . The power steering fluid of  claim 1 , wherein the base oil has a kinematic viscosity at 100° C. between about 1.5 and about 3.5 mm 2 /s. 
   
   
       6 . The power steering fluid of  claim 1 , wherein the base oil has greater than 5.0 weight % molecules with cycloparaffinic functionality. 
   
   
       7 . The power steering fluid of  claim 1 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 5. 
   
   
       8 . The power steering fluid of  claim 1 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 10. 
   
   
       9 . The power steering fluid of  claim 1 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 15. 
   
   
       10 . The power steering fluid of  claim 1 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 20. 
   
   
       11 . The power steering fluid of  claim 1 , comprising greater than 70 weight % base oil. 
   
   
       12 . The power steering fluid of  claim 1 , comprising viscosity index improver in an amount less than 13 weight %. 
   
   
       13 . The power steering fluid of  claim 1 , comprising viscosity index improver in an amount less than 12 weight %. 
   
   
       14 . The power steering fluid of  claim 1 , wherein the power steering fluid comprises approximately 0 weight % pour point depressant. 
   
   
       15 . The power steering fluid of  claim 1 , wherein the Brookfield Viscosity at −40° C. is less than 1500 mPa·s. 
   
   
       16 . The power steering fluid of  claim 1 , further comprising a detergent-inhibitor additive package. 
   
   
       17 . The power steering fluid of  claim 16 , comprising 2 to 6 weight % detergent-inhibitor additive package. 
   
   
       18 . The power steering fluid of  claim 16 , comprising less than 5 weight % detergent-inhibitor additive package. 
   
   
       19 . The power steering fluid of  claim 1 , wherein the base oil is Fischer-Tropsch derived. 
   
   
       20 . The power steering fluid of  claim 1 , wherein the power steering fluid meets the requirements of one or more power steering fluid specifications for automotive power steering systems. 
   
   
       21 . A process for producing the power steering fluid of  claim 1  comprising:
 a) obtaining a base oil having:
 i) a consecutive numbers of carbon atoms; 
 ii) a viscosity index greater than a Viscosity Index Factor calculated by the following equation:
   28×ln(Kinematic Viscosity at 100° C.)+101; and 
 
   b) blending the base oil with viscosity index improver to form the power steering fluid;   wherein the power steering fluid comprises greater than 50 weight % base oil and has a viscosity index of greater than 290 and a Brookfield Viscosity at −40° C. of less than 1900 mPa·s.   
   
   
       22 . A process for producing a power steering fluid comprising:
 a) obtaining a base oil having:
 i) a consecutive numbers of carbon atoms; 
 ii) a kinematic viscosity at 100° C. of less than about 4 mm 2 /s; and 
 iii) a Noack volatility less than a Noack Volatility Factor calculated by the following equation:
   160−40(Kinematic Viscosity at 100° C.); and 
 
   b) blending the base oil with viscosity index improver to form the power steering fluid;   wherein the power steering fluid comprises greater than 50 weight % base oil and has a viscosity index of greater than 290 and a Brookfield Viscosity at −40° C. of less than 1900 mPa·s.   
   
   
       23 . The process of  claim 22 , wherein forming a power steering fluid further comprises blending the base oil with pour point depressant, wherein the power steering fluid comprises less than about 1.0 weight % pour point depressant. 
   
   
       24 . The process of  claim 22 , wherein the base oil has a viscosity index greater than a Viscosity Index Factor calculated by the following equation:
   28×ln(Kinematic Viscosity at 100° C.)+101.   
   
   
       25 . The process of  claim 22 , wherein the base oil has a kinematic viscosity at 100° C. between about 1.2 and about 4.0 mm 2 /s. 
   
   
       26 . The process of  claim 22 , wherein the base oil has a kinematic viscosity at 100° C. between about 1.5 and about 3.5 mm 2 /s. 
   
   
       27 . The process of  claim 22 , wherein the base oil is Fischer-Tropsch derived. 
   
   
       28 . The process of  claim 22 , wherein the base oil has greater than 5.0 weight % molecules with cycloparaffinic functionality. 
   
   
       29 . The process of  claim 22 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 5. 
   
   
       30 . The process of  claim 22 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 10. 
   
   
       31 . The process of  claim 22 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 15. 
   
   
       32 . The process of  claim 22 , wherein the base oil has a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality of greater than 20. 
   
   
       33 . The process of  claim 22 , wherein forming a power steering fluid further comprises blending the base oil with a detergent-inhibitor additive package. 
   
   
       34 . The process of  claim 33 , wherein the detergent-inhibitor additive package is blended in an amount of 2 to 6 weight %. 
   
   
       35 . The process of  claim 33 , wherein the detergent-inhibitor additive package is blended in an amount of less than 5 weight %. 
   
   
       36 . The process of  claim 22 , wherein the base oil has an aniline point greater than
   36×ln(Kinematic Viscosity at 100° C.)+200.   
   
   
       37 . The process of  claim 22 , wherein the base oil has a Noack volatility between 0 and 100. 
   
   
       38 . The process of  claim 37 , wherein the base oil has a Noack volatility less than a Noack Volatility Factor calculated by the following equation:
   900×(Kinematic Viscosity at 100° C.) −2.8 −15.   
   
   
       39 . A power steering fluid produced by the process of  claim 22  comprising:
 a) greater than 50 weight % base oil, wherein the base oil has consecutive numbers of carbon atoms, a kinematic viscosity at 100° C. of less than about 4 mm 2 /s, and a Noack volatility less than a Noack Volatility Factor calculated by the following equation:
   160−40(Kinematic Viscosity at 100° C.); and 
   b) viscosity index improver;   wherein the power steering fluid has a viscosity index of greater than 290 and a Brookfield Viscosity at −40° C. of less than 1900 mPa·s.