Reduced molybdenum grease formulation

Abstract

Extreme pressure additives may be added to greases to improve their lubricating properties, particularly to decrease friction and wear of parts that are exposed to very high pressures. Molybdenum disulfide is frequently used as an extreme pressure additive. However, molybdenum disulfide is expensive, has limited availability, and may have adverse environmental effects. This invention discloses an extreme pressure additive and grease formulation where the amount of molybdenum disulfide is reduced through the addition of calcium carbonate while the performance characteristics of the grease are maintained or improved. The extreme pressure additive may comprise about 20% molybdenum sulfide and about 80% calcium carbonate, by weight.

We claim: 
     
         1 . An extreme pressure additive composition for a finished grease, the extreme pressure additive composition comprising:
 a first amount of molybdenum disulfide; and   a second amount of calcium carbonate,   
       wherein the first amount and the second amount are related according to a selected ratio. 
     
     
         2 . The additive described in  claim 1 , wherein the selected ratio of the first amount to the second amount is about 20% to about 80% by weight. 
     
     
         3 . The additive described in  claim 1 , wherein the calcium carbonate is coated with a coating agent. 
     
     
         4 . The additive described in  claim 3 , wherein the coating agent is stearic acid. 
     
     
         5 . The additive described in  claim 1 , wherein the calcium carbonate has a particle size that is in a range of from about 0.025 micrometers to about 1.75 micrometers. 
     
     
         6 . The additive described in  claim 5 , wherein the calcium carbonate has a particle size that is in a range of from 0.07 micrometers to 0.5 micrometers. 
     
     
         7 . The additive described in  claim 1 , wherein the calcium carbonate is precipitated calcium carbonate. 
     
     
         8 . A grease composition comprising:
 a first amount of finished grease; and   a second amount of a extreme pressure additive composition, wherein the grease composition contains a selected amount of the extreme pressure additive composition by weight.   
     
     
         9 . The grease composition described in  claim 8 , wherein the selected amount of the extreme pressure additive composition is between about 3% and about 5% by weight of the grease composition. 
     
     
         10 . The grease composition described in  claim 8 , wherein the selected amount of the extreme pressure additive composition is about 3% by weight of the grease composition. 
     
     
         11 . The grease composition described in  claim 8 , wherein the selected amount of the extreme pressure additive composition is about 5% by weight of the grease composition. 
     
     
         12 . The grease composition described in  claim 11 , wherein the finished grease is selected from commercially available greases. 
     
     
         13 . The grease composition described in  claim 8 , wherein the extreme pressure additive is comprised of about 20% molybdenum disulfide and about 80% calcium carbonate, by weight. 
     
     
         14 . The grease composition described in  claim 13 , wherein the calcium carbonate is coated with stearic acid. 
     
     
         15 . A method for formulating a reduced molybdenum grease, the method comprising the steps of:
 providing a finished grease;   preparing an extreme pressure additive composition, wherein the extreme pressure additive is comprised of about 20% molybdenum disulfide and about 80% calcium carbonate, by weight; and   mixing the base grease and the extreme pressure additive composition in selected amounts.   
     
     
         16 . The method for formulating a reduced molybdenum grease described in  claim 15 , wherein the selected amounts are about 95% of the finished grease and about 5% of the extreme pressure additive composition, by weight. 
     
     
         17 . The method for formulating a reduced molybdenum grease described in  claim 15 , wherein the selected amounts are about 97% of the finished grease and about 3% of the extreme pressure additive composition, by weight. 
     
     
         18 . The additive described in  claim 15 , wherein the calcium carbonate has a particle size that is in a range of from about 0.025 micrometers to about 1.75 micrometers. 
     
     
         19 . The additive described in  claim 19 , wherein the calcium carbonate has a particle size that is in a range of from 0.07 micrometers to 0.5 micrometers. 
     
     
         20 . The additive described in  claim 15 , wherein the calcium carbonate is precipitated calcium carbonate.