Gear Oil Compositions, Methods of Making and Using Thereof

Abstract

A gear oil composition is provided. The composition comprises a synergistic blend of mineral oil base stock and polyalphaolefin (PAO) base stock for the oil composition to have a traction coefficient at a slide to roll ratio of 40 percent at 15 mm 2 /s. of 0.030 or less and a pressure viscosity coefficient of at least 16.0 at 80° C., 20 Newton load, and 1.1 m/s rolling speed. In one embodiment, the synergistic amount of PAO base stock ranges from 5 to 48 wt. % based on the total weight of the gear oil composition.

1 . A gear oil composition, comprising:
 a) a base oil comprising a mixture of at least a polyalphaolefin (PAO) base stock and a mineral base stock having a kinematic viscosity of 3 to 120 mm 2 /s at 100° C. and a viscosity index of at least 60;   b) 0.001 to 30 wt % at least an additive selected from traction reducers, dispersants, viscosity modifiers, pour point depressants, antifoaming agents, antioxidants, rust inhibitors, metal passivators, extreme pressure agents, friction modifiers, and mixtures thereof;   wherein the polyalphaolefin base stock is present in a synergistic amount for the gear oil composition to have a traction coefficient at 15 mm 2 /s. of 0.030 or less at a slide to roll ratio of 40 percent and a pressure viscosity coefficient of at least 15.0 GPa −1  at 80° C., 20 Newton load, and 1.1 m/s rolling speed.   
   
   
       2 . The composition of  claim 1 , wherein the PAO base stock is present in a synergistic amount for the gear oil to have a pressure-viscosity coefficient of at least 15.5 GPa −1  in a temperature range of 70-100° C. 
   
   
       3 . The composition of  claim 1 , wherein the PAO base stock is present in an amount ranging from 5 to 48 wt. % based on the total weight of the gear oil composition. 
   
   
       4 . The composition of  claim 3 , wherein the PAO base stock is present in an amount ranging from 15 to 40 wt. % based on the total weight of the gear oil composition. 
   
   
       5 . The composition of  claim 4 , wherein the PAO base stock is present in an amount of 25 to 35 wt. % based on the total weight of the gear oil composition. 
   
   
       6 . The composition of  claim 5 , wherein the gear oil composition has a pressure viscosity coefficient of at least 16.5 GPa −1  in a temperature range of 70-100° C. 
   
   
       7 . The composition of  claim 1 , wherein the gear oil composition has a traction coefficient at a slide to roll ratio of 40 percent at 15 mm 2 /s. of less than 0.028. 
   
   
       8 . The composition of  claim 7 , wherein the gear oil composition has a traction coefficient at a slide to roll ratio of 40 percent at 15 mm 2 /s. of less than 0.026. 
   
   
       9 . The composition of  claim 1 , wherein the gear oil composition has a film thickness of at least 175 nm at 80° C. 
   
   
       10 . The composition of  claim 9 , wherein the gear oil composition has a film thickness of at least 160 nm at 90° C. or at least 130 nm at 100° C. 
   
   
       11 . The composition of  claim 1 , wherein the PAO base stock has a kinematic viscosity at 40° C. ranging from 40-500 mm 2 /s. 
   
   
       12 . The composition of  claim 1 , wherein the PAO base stock has kinematic viscosity at 100° C. of 10-16 mm 2 /s. and a viscosity index of 140-160. 
   
   
       13 . The composition of  claim 1 , wherein the mineral oil has a kinematic viscosity of 2.3 to 3.4 mm 2 /s at 100° C. and a % Cp defined by ASTM D 3238 (R2000) of 70 or higher. 
   
   
       14 . The composition of  claim 1 , wherein the mineral oil has a kinematic viscosity of less than 80 mm 2 /s at 40° C., comprising a mixture of at least a mineral oil and a synthetic oil having and a kinematic viscosity of 3.5 to 7 mm 2 /s at 100° C.; and at least a mineral oil and a synthetic oil having a kinematic viscosity of 20 to 52 mm 2 /s at 100° C. 
   
   
       15 . The composition of  claim 1 , wherein the mineral oil is a group II neutral base oil having a kinematic viscosity at 40° C. of 80-120 mm 2 /s., a kinematic viscosity at 100° C. of 10 to 14 mm 2 /s., and a viscosity index of 80-120. 
   
   
       16 . A method for improving the traction properties of a gear oil composition, the method comprises adding a synergistic amount of at least a polyalphaolefin (PAO) base stock to a base oil matrix comprising at least a mineral oil having a kinematic viscosity of 3 to 120 mm 2 /s at 100° C. and a viscosity index of at least 60, for the gear oil composition to have a traction coefficient at a slide to roll ratio of 40 percent at 15 mm 2 /s. of 0.030 or less, a pressure viscosity coefficient of 15.0 or higher at 80° C., 20 Newton load, and 1.1 m/s rolling speed, and a film thickness of greater than 175 nm at 80° C., wherein the PAO base stock has a kinematic viscosity at 40° C. in the range of 80-110 mm 2 /s. and a kinematic viscosity at 100° C. of 10-16 mm 2 /s. and a viscosity index of 140-160. 
   
   
       17 . The method of  claim 16 , wherein the synergistic amount of at least a polyalphaolefin (PAO) base stock ranges from 5 to 48 wt. % based on the total weight of the gear oil composition. 
   
   
       18 . The method of  claim 17 , wherein the synergistic amount of at least a polyalphaolefin (PAO) base stock ranges from 15 to 40 wt. % based on the total weight of the gear oil composition. 
   
   
       19 . The method of  claim 17 , wherein the synergistic amount of at least a polyalphaolefin (PAO) base stock ranges from 25 to 35 wt. % based on the total weight of the gear oil composition. 
   
   
       20 . The method of  claim 16 , wherein a synergistic amount of at least a polyalphaolefin (PAO) base stock is added to the base oil matrix for the composition to have a pressure viscosity coefficient of at least 16.5 GPa −1  in a temperature range of 70-100° C.