Lubricant compositions, their preparation and use

Abstract

A lubricating composition that has improved air release characteristics is based on a lubricating base oil comprising an oil or mixture of oils derived from waxy hydrocarbons produced in an F-T synthesis process. The composition is substantially free of a viscoelastic fluid having a shear stress greater than 11 kPa and a viscosity greater than 30 cSt at 100° C. It is further characterized as entraining less than 1.7% air in 2 minutes and having an air release rate greater than 0.3%/min. when measured at 50° C. by ASTM D 3427.

1 . A method for improving the air release characteristics of a lubricating composition comprising a major amount of a lubricating base oil and a minor amount of at least one additive, the method comprising using as the base oil an effective amount of one or more oils derived from a waxy hydrocarbon produced in an F-T process. 
   
   
       2 . The method of  claim 1  wherein the base oil has a kinematic viscosity in the range of 2 mm 2 /s to about 50 mm 2 /s at 100° C. 
   
   
       3 . The method of  claim 2  wherein the oil has a VI in the range of 130 to 140 or more. 
   
   
       4 . A lubricating composition comprising:
 a major amount of a lubricating base oil comprising an oil or mixture of oils derived from waxy hydrocarbons produced in an F-T process; and   a minor amount of at least one lubricant additive,   the composition being substantially free of viscoelastic fluids having both a shear stress greater than 11 kPa and a viscosity greater than 30 cSt at 100° C. and further characterized as entraining less than 1.7%/min. air and having an initial air release rate greater than 0.3%/min. when measured at 50° C. by ASTM D 3427.   
   
   
       5 . The composition of  claim 4  wherein the base oil has a viscosity of 2 to 50 mm 2 /s at 100° C. 
   
   
       6 . The composition of  claim 5  wherein the base oil has a VI in the range of 130 to 140 or more. 
   
   
       7 . The composition of  claim 6  including a plurality of additives. 
   
   
       8 . The composition of  claim 7  wherein the additives include one or more of alkaline earth metal detergents, ashless dispersants, antioxidants, antiwear agents, pour point depressants and VI improvers. 
   
   
       9 . The composition of  claim 8  wherein the composition has a TBN less than 10, a phosphorous content less than 0.08 wt % and calcium content less than 0.3 wt %, each based on the total weight of the composition and a sulfated ash of 1% or less. 
   
   
       10 . The composition of  claim 8  wherein the additives comprise, on an active ingredient basis, from 0.5 wt % to 25 wt % based on the total weight of the composition. 
   
   
       11 . The composition of  claim 10  wherein the additives comprise from 2 wt % to 10 wt % of the composition. 
   
   
       12 . In the lubrication of an engine with a crankcase lubricant wherein the lubricant additionally is used to perform a hydraulic function, the improvement comprising using as the crankcase lubricant a lubricating composition according to  claims 4  to  11 . 
   
   
       13 . A method for formulating an engine oil lubricant having an air entrainment of less than 1.7% in 2 minutes and an air release rate greater than 0.3%/min. when measured at 50° C. by ASTM D 3427 without adding to the formulation a viscoelastic fluid having a shear rate greater than 1 kPa and a viscosity greater than 30 cSt at 100° C., the method comprising blending a major amount of a base oil consisting essentially of an oil or mixture of oils derived from waxy hydrocarbons produced in an F-T process with one or more engine oil additives. 
   
   
       14 . The use of one or more oils derived from a waxy hydrocarbon produced in an F-T process to improve the air release characteristics of a lubricating composition. 
   
   
       15 . The use according to  claim 14 , wherein the one or more oils derived from a waxy hydrocarbon produced in an F-T process is used in an amount of at least 50 wt % based on the total weight of the lubricating composition. 
   
   
       16 . The use according to any of  claims 14  or  15 , wherein the one or more oils derived from a waxy hydrocarbon produced in an F-T process have a kinematic viscosity in the range of 2 mm 2 /s to 50 mm 2 /s at 100° C. 
   
   
       17 . The use according to any of  claims 14  to  16 , wherein the one or more oils derived from a waxy hydrocarbon produced in an F-T process have a VI in the range of 130 to 140 or more. 
   
   
       18 . The use according to any of  claims 14  to  17 , wherein the lubricating composition has an air entrainment of less than 1.7% in 2 minutes and an air release rate greater than 0.3%/min. when measured at 50° C. by ASTM D 3427 without adding to the formulation a viscoelastic fluid having a shear rate greater than 1 kPa and a viscosity greater than 30 cSt at 100° C.