Transmission Fluid Compositions for Improved Energy Efficiency

Abstract

Transmission fluid compositions are provided having improved power transmission properties through the presence therein of certain defined additives, which increase the energy efficiency of the transmission during operation. The invention further provides a process for the manufacture of such transmission fluid compositions, a method of improving the energy efficiency of a transmission, and an additive concentrate for a transmission fluid.

What is claimed is: 
     
         1 . A transmission fluid composition consisting of:
 (i) a lubricating oil, or blend of lubricating oils;   (ii) a viscosity modifier additive or blend of viscosity modifier additives;   (iii) a polyalphaolefin compound or compounds; and   (iv) one or more detergent/inhibitor additives, at least one of which comprises one or more alkaline earth metal detergent compounds,
 wherein the or each polyalphaolefin compound (iii) is made by the metallocene-catalysed polymerisation of an alphaolefin feedstock, and wherein the total amount of the polyalphaolefin compound(s) (iii) in the transmission fluid composition does not exceed 4 percent by weight of the composition; and 
 wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound. 
   
     
     
         2 . The transmission fluid composition of  claim 2 , wherein the total amount of the polyalphaolefin compound or compounds (iii) in the composition is in the range of 2 to 3 percent by weight of the composition. 
     
     
         3 . The transmission fluid of  claim 1 , wherein each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound. 
     
     
         4 . The transmission fluid composition of  claim 1 , wherein each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound, and wherein the total amount of the calcium salicylate compound(s) present is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition. 
     
     
         5 . The transmission fluid composition of  claim 1 , wherein the composition is an automotive transmission fluid. 
     
     
         6 . The transmission fluid composition of  claim 1 , wherein at least one detergent/inhibitor additive (iv) also comprises one or more dispersant, oxidation inhibitor and/or friction modifier compounds. 
     
     
         7 . The transmission fluid of  claim 2 , wherein each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound. 
     
     
         8 . The transmission fluid composition of  claim 2 , wherein each alkaline earth metal detergent compound present in the transmission fluid composition is a neutral or overbased calcium salicylate compound, and wherein the total amount of the calcium salicylate compound(s) present is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition. 
     
     
         9 . The transmission fluid composition of  claim 2 , wherein the composition is an automotive transmission fluid. 
     
     
         10 . The transmission fluid composition of  claim 2  wherein at least one detergent/inhibitor additive (iv) also comprises one or more dispersant, oxidation inhibitor and/or friction modifier compounds. 
     
     
         11 . A process for the manufacture of a transmission fluid composition, the composition consisting of:
 (i) a lubricating oil, or blend of lubricating oils;   (ii) a viscosity modifier additive or blend of viscosity modifier additives;   (iii) a polyalphaolefin compound or compounds, each made by the metallocene-catalysed polymerisation of an alphaolefin feedstock; and   (iv) one or more detergent/inhibitor additives, at least one of which comprises one or more alkaline earth metal detergent compounds wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound;
 the process comprising the following steps:
 a) obtaining (by manufacture or otherwise) a lubricating oil or blend of lubricating oils containing no polyalphaolefin compound(s) made by the metallocene-catalysed polymerisation of an alphaolefin feedstock; and 
 b) mixing with this lubricating oil or blend of lubricating oils the following: 
 (b)(1) the viscosity modifier additive or blend of viscosity modifier additives (ii), 
 (b)(2) the polyalphaolefin compound(s) (iii) in a total amount not exceeding 4 percent by weight of the transmission fluid composition, and 
 (b)(3) one or more detergent/inhibitor additives (iv); to provide the transmission fluid composition. 
 
   
     
     
         12 . The process of  claim 11 , wherein the total amount of the polyalphaolefin compound or compounds (iii) mixed with the lubricating oil or blend of lubricating oils is in the range of 2 to 3 percent by weight of the transmission fluid composition. 
     
     
         13 . The process of  claim 11 , wherein each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound. 
     
     
         14 . The process of  claim 11 , each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound, and wherein the total amount of calcium salicylate compound(s) mixed with the lubricating oil or blend of lubricating is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition. 
     
     
         15 . The process of  claim 11 , wherein the transition fluid composition is an automotive transmission fluid. 
     
     
         16 . The process of  claim 11 , wherein the additions in step b) improve the efficiency of power transmission provided by the composition when in use as an automotive transmission fluid, as demonstrated by an increase in the fuel efficiency of the vehicle during operation. 
     
     
         17 . The process of  claim 12 , wherein the polyalphaolefin compound(s) (iii) are mixed with one or more of the detergent/inhibitor additives (iv) to form a single additive concentrate prior to addition to the lubricating oil or blend of oils. 
     
     
         18 . The process of  claim 12 , wherein each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound. 
     
     
         19 . The process of  claim 12 , each alkaline earth metal detergent compound mixed with the transmission fluid composition is a neutral or overbased calcium salicylate compound, and wherein the total amount of calcium salicylate compound(s) mixed with the lubricating oil or blend of lubricating is such as to provide the transmission fluid composition with a calcium content of between 50 and 250 parts per million by weight, per weight of the transmission fluid composition. 
     
     
         20 . The process of  claim 12 , wherein the transition fluid composition is an automotive transmission fluid. 
     
     
         21 . The process of  claim 12 , wherein the additions in step b) improve the efficiency of power transmission provided by the composition when in use as an automotive transmission fluid, as demonstrated by an increase in the fuel efficiency of the vehicle during operation. 
     
     
         22 . The process of  claim 12 , wherein the polyalphaolefin compound(s) (iii) are mixed with one or more of the detergent/inhibitor additives (iv) to form a single additive concentrate prior to addition to the lubricating oil or blend of oils. 
     
     
         23 . A method of improving the energy efficiency of a transmission, comprising the use therein of the transmission fluid composition defined in  claim 1 . 
     
     
         24 . The method of  claim 23 , wherein the transmission is a transmission for an automotive vehicle, and the improvement in energy efficiency is an increase in fuel economy of the vehicle during operation. 
     
     
         25 . A method of improving the energy efficiency of a transmission, comprising the use therein of the transmission fluid composition obtained by the process of  claim 11 . 
     
     
         26 . The method of  claim 25 , wherein the transmission is a transmission for an automotive vehicle, and the improvement in energy efficiency is an increase in fuel economy of the vehicle during operation. 
     
     
         27 . An additive concentrate for a transmission fluid, the concentrate consisting of a suitable carrier liquid, (ii) a viscosity modifier or blend of viscosity modifiers, and (iii) a polyalphaolefin compound or mixture of polyalphaolefin compounds made by the metallocene-catalysed polymerisation of an alphaolefin feedstock, and (iv) one or more detergent/inhibitor additives, at least one of which comprises one or more alkaline earth metal detergent compounds wherein at least one alkaline earth metal detergent compound is an alkaline earth metal salicylate or sulphonate compound. 
     
     
         28 . The additive composition of  claim 27  wherein the total amount of polyalphaolefin compound(s) (iii) present in the concentrate is such that, after addition of the concentrate at its specified treat rate to the transmission fluid, said compounds (iii) constitute no more than 4 percent by weight of the resulting transmission fluid composition. 
     
     
         29 . The additive concentrate of  claim 27 , wherein each alkaline earth metal detergent compound present in the concentrate is a neutral or overbased calcium salicylate compound. 
     
     
         30 . The additive concentrate of  claim 27 , wherein the total amount of the polyalphaolefin compound or compounds (iii) in the concentrate is such that, after addition of the concentrate at its specified treat rate to the transmission fluid, said compounds (iii) constitute 2 to 3 percent by weight of the resulting transmission fluid composition. 
     
     
         31 . The additive concentrate of  claim 28 , wherein each alkaline earth metal detergent compound present in the concentrate is a neutral or overbased calcium salicylate compound. 
     
     
         32 . The additive concentrate of  claim 28 , wherein the total amount of the polyalphaolefin compound or compounds (iii) in the concentrate is such that, after addition of the concentrate at its specified treat rate to the transmission fluid, said compounds (iii) constitute 2 to 3 percent by weight of the resulting transmission fluid composition.