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 μm/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., 20 Newton load, and 1.1 nm/s rolling speed. 
   
   
       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 16.0 GPa −1  in a temperature range of 70-100° C., 20 Newton load, and 1.1 μm/s rolling speed. 
   
   
       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 15.7 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 15.5 GPa −1  in a temperature range of 70-100° C., 20 Newton load, and 1.1 m/s rolling speed.