Lubricant oil compositions containing GTL base stock(s) and/or base oil(s) and having improved resistance to the loss of viscosity and weight and a method for improving the resistance to loss of viscosity and weight of GTL base stock(s) and/or base oil(s) lubricant oil formulations

Abstract

The present invention is directed to a method for improving the performance of lubricating oils of high viscosity comprising GTL base stock(s) and/or base oil(s) and lubricating oil comprising such base stock(s) and/or base oil(s) in combination with an effective amount of a polyolefin fluid having a kinematic viscosity at 100° C. in the range between about 10 to about 200 mm 2 /s.

1 . A method for reducing the loss of viscosity and weight and improving the oxidation stability and low temperature properties of lubricating oil formulation by employing a base stock comprising a GTL base stock and/or base oil in combination with a polyolefin fluid, said polyolefin fluid being characterized by a viscosity in the range of about 2 to 1000 mm 2 /s at 100° C., a number average molecular weight in the range of about 200 to 10,000.  
   
   
       2 . The method of  claim 1  wherein the lubricating oil formulation has a viscosity in the range of about 2 to 1000 mm 2 /s at 100° C.  
   
   
       3 . The method of  claim 1  wherein the polyolefin fluid is combined with the GTL in an amount in the range of about 0.1 to 90 wt % based on the weight of the combination.  
   
   
       4 . The method of  claim 1  wherein the polyolefin fluid is a copolymer of a first alpha olefin selected from ethylene, propylene, 1-butylene and a second alpha olefin different from the first selected from the group of C 2 -C 30  straight or branched chain alphaolefins and mixtures thereof wherein when one of the alpha olefin used is ethylene the ethylene content of the poly olefin fluid is not more than 50 wt %.  
   
   
       5 . The method of  claim 1  wherein the polyolefin fluid is a poly alpha olefin homo or copolymer made from alpha olefins selected from the group of C 8  to C 18  alpha olefins and mixtures thereof.  
   
   
       6 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the polyolefin fluid has a molecular weight distribution (MWD) of from 1.00 to 4.  
   
   
       7 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the GTL base stock and/or base oil is a hydrodewaxed or hydroisomerized Fischer-Tropsch material.  
   
   
       8 . The method of  claim 7  wherein the Fischer-Tropsch material is Fischer-Tropsch wax.  
   
   
       9 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the lubricating oil formulation has a kinematic viscosity in the range of about 2 to 500 mm 2 /s at 100° C.  
   
   
       10 . The method of  claim 9  wherein the GTL base oil has a kinematic viscosity in the range of about 1.5 to 50 mm 2 /s at 100° C.  
   
   
       11 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the polyolefin fluid has a kinematic viscosity in the range about 4 to 800 mm 2 /s at 100° C.  
   
   
       12 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the polyolefin fluid has a kinematic viscosity in the range of about 10 to 500 mm 2 /s at 100° C.  
   
   
       13 . The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the polyolefin fluid has a kinematic viscosity in the range of about 10 to 200 mm 2 /s at 100° C.  
   
   
       14 . The method of  claim 1  wherein the base stock further contains a hydrodewaxate or hydroisomerate of waxy feed derived from mineral oil.  
   
   
       15 . The method of  claim 1  or  14  wherein the base stock further contains a mineral oil base stock, a Group V synthetic base stock or mixture thereof.  
   
   
       16 . The method of  claim 15  wherein the GTL base stock and/or base oil constitutes 5 to 100 wt % of the total of the base oil.  
   
   
       17 . The method of  claim 16  wherein the GTL base stock and/or base oil constitutes 40 to 100 wt % of the total of the base oil.  
   
   
       18 . The method of  claim 16  wherein the GTL base stock and/or base oil constitute 70 to 100 wt % of the total of the base oil.  
   
   
       19 . The method of  claim 16  wherein the GTL base stock and/or base oil constitutes 90 to 100 wt % of the total of the base oil.  
   
   
       20 . A base stock exhibiting an enhanced resistance to reduction in the loss of weight and viscosity and improved oxidation stability and low temperature properties comprising a mixture of GTL base stock and/or base oil in combination with a polyolefin fluid, said polyolefin fluid being characterized by a viscosity in the range of about 2 to 1000 mm 2 /s at 100° C. and a number average molecular weight in the range of about 200 to 10,000 and a molecular weight distribution of 1.00 to 4.  
   
   
       21 . The base stock of  claim 20  wherein the polyolefin fluid is present in an amount in the range of about 0.1 to 90 wt % based on the total weight of the base stock.  
   
   
       22 . The base stock of  claim 20  wherein the polyolefin fluid is a copolymer of a first alpha olefin selected from ethylene, propylene, 1-butylene and a second alpha olefin different from the first selected from the group of C 2 -C 30  straight or branched chain alpha-olefin and mixtures thereof wherein when one of the alpha olefins used is ethylene, the ethylene content of the polyolefin fluid is not more than 50 wt %.  
   
   
       23 . The base stock of  claim 20  wherein the polyolefin fluid is a polyalpha olefin homo- or copolymer made from C 8  to C 18  alpha olefin.  
   
   
       24 . The base stock of  claim 20 ,  21 ,  22  or  23  wherein the GTL base stock and/or base oil is a hydrodewaxed or hydroisomerized Fischer-Tropsch liquid hydrocarbon composition comprising paraffinic hydrocarbon components in which the extent of branching, as measured by the percentage of methyl hydrogens (BI), and the proximity of branching, as measured by the percentage of recurring methylene carbons which are four or more carbons removed from an end group or branch (CH2≧4), are such that: 
 (a) BI−0.5 (CH 2 ≧4)>15; and    (b) BI+0.85 (CH 2 ≧4)<45 as measured over said liquid hydrocarbon composition as a whole and further characterized as a mixture of branched paraffinic characterized in that the GTL base oil contains at least 90% of a mixture of branched paraffins wherein said branched paraffins are paraffinic having a carbon chain length of about C 20  to about C 40 , a molecular weight of about 280 to about 562, a boiling range of about 650° F. to about 1050° F., and wherein said branched paraffins contain up to four alkyl branches and wherein the free carbon index of said branched paraffins is at least about 3.    
   
   
       25 . The base stock of  claim 24  wherein the GTL base stock and/or base oil has a kinematic viscosity in the range of about 1.5 to 50 mm 2 /s @ 100° C.  
   
   
       26 . The base stock of  claim 25  wherein the polyolefin fluid has a kinematic viscosity in the range of about 4 to 800 mm 2 /s @ 100° C.  
   
   
       27 . The base stock of  claim 25  wherein the polyolefin fluid has a kinematic viscosity in the range of about 10 to 500 mm 2 /s @ 100° C.  
   
   
       28 . The base stock of  claim 25  wherein the polyolefin fluid has a kinematic viscosity in the range of about 10 to 200 mm 2 /s @100° C.