Lubricant composition

Abstract

A lubricant composition is suitable for use in diesel engines and is resistant to degradation by oxidative by-products of biodiesel fuel. The composition includes (A) a base oil, (B) at least one diphenylamine antioxidant, and (C) at least one antioxidant. The antioxidant (C) is selected from the group consisting of a sulfur containing phenolic antioxidant, a phenyl-alpha-naphthylamine antioxidant, and combinations thereof. The lubricant composition is formed using a method. In the method, the (A) base oil has an initial oxidation value measured according to ASTM D 6186. In addition in the method, the lubricant composition includes up to about 6 wt % of the biodiesel fuel and has a final oxidation value measured according to ASTM D 6186 that is equal to or greater than the initial oxidation value of the (A) base oil.

1 . A lubricant composition suitable for use in a diesel engine and resistant to degradation by oxidative by-products of biodiesel fuel, said composition comprising:
 A. a base oil;   B. at least one diphenylamine antioxidant; and   C. at least one antioxidant selected from a sulfur containing phenolic antioxidant, a phenyl-alpha-naphthylamine antioxidant, and combinations thereof.   
     
     
         2 . A lubricant composition as set forth in  claim 1  wherein said (C) at least one antioxidant comprises both said sulfur containing phenolic antioxidant and said phenyl-alpha-naphthylamine antioxidant. 
     
     
         3 . A lubricant composition as set forth in  claim 1  wherein said (C) at least one antioxidant comprises said sulfur containing phenolic antioxidant 
     
     
         4 . A lubricant composition as set forth in  claim 1  wherein said (C) at least one antioxidant consists essentially of said sulfur containing phenolic antioxidant. 
     
     
         5 . A lubricant composition as set forth in  claim 4  wherein said (C) at least one antioxidant is free of said phenyl-alpha-naphthylamine antioxidant. 
     
     
         6 . A lubricant composition as set forth in  claim 1  wherein said (C) at least one antioxidant comprises said phenyl-alpha-naphthylamine antioxidant. 
     
     
         7 . A lubricant composition as set forth in  claim 1  wherein said (C) at least one antioxidant consists essentially of said phenyl-alpha-naphthylamine antioxidant. 
     
     
         8 . A lubricant composition as set forth in  claim 7  wherein said (C) at least one antioxidant is free of said sulfur containing phenolic antioxidant. 
     
     
         9 . A lubricant composition as set forth in  claim 1  wherein said phenyl-alpha-naphthylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         and wherein R 1  is an aryl radical having from 6 to 12 carbon atoms or an aryl radical having from 6 to 20 carbon atoms and substituted by one, two or three straight or branched chain alkyl radicals each having from 1 to 18 carbon atoms. 
       
     
     
         10 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         wherein each R′ is independently a hydrogen atom, a straight or branched chain alkyl radical having from 1 to 18 carbon atoms, or an aralkyl radical having 7 to 14 carbon atoms; 
         wherein said (C) at least one antioxidant comprises said sulfur containing phenolic antioxidant and said sulfur containing phenolic antioxidant is further defined as having the formula: 
       
       
         
           
           
               
               
           
         
         and wherein x is a number from 0 to 6, y is a number from 2 to 20 and R is a straight or branched chain alkyl radical having from 1 to 6 carbon atoms. 
       
     
     
         11 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant is further defined as comprising at least one octylated/butylated diphenylamine antioxidant and also comprising thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. 
     
     
         12 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         wherein each R′ is independently a hydrogen atom, a straight or branched chain alkyl radical having from 1 to 18 carbon atoms, or an aralkyl radical having 7 to 14 carbon atoms; 
         wherein said (C) at least one antioxidant comprises said phenyl-alpha-naphthylamine antioxidant and said phenyl-alpha-naphthylamine antioxidant is further defined as having the formula: 
       
       
         
           
           
               
               
           
         
         and wherein R 1  is an aryl radical having from 6 to 12 carbon atoms or an aryl radical having from 6 to 20 carbon atoms and substituted by one, two or three straight or branched chain alkyl radicals each having from 1 to 18 carbon atoms. 
       
     
     
         13 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant is further defined as comprising at least one octylated/butylated diphenylamine antioxidant, wherein said (C) at least one antioxidant comprises said phenyl-alpha-naphthylamine antioxidant, and said phenyl-alpha-naphthylamine antioxidant is further defined as octylated phenyl-alpha-naphthylamine. 
     
     
         14 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant and said (C) at least one antioxidant are present in a weight ratio of from about 9:1 to about 1:9 to each other, respectively. 
     
     
         15 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant and said (C) at least one antioxidant are present in a combined amount of from about 0.3 to 7 parts by weight per 100 parts by weight of said base oil. 
     
     
         16 . A lubricant composition as set forth in  claim 1  wherein said (B) at least one diphenylamine antioxidant and said (C) at least one antioxidant are present in a combined amount of from about 0.5 to 3 parts by weight per 100 parts by weight of said base oil. 
     
     
         17 . A lubricant composition as set forth in  claim 1  further comprising a biodiesel fuel. 
     
     
         18 . A lubricant composition as set forth in  claim 17  wherein said biodiesel fuel is present in said lubricant composition in an amount of from 1 to 50 weight percent. 
     
     
         19 . A lubricant composition as set forth in  claim 17  wherein said biodiesel fuel comprises at least one fatty acid methyl ester of a vegetable or oleaginous seed oil. 
     
     
         20 . A lubricant composition as set forth in  claim 19  wherein fatty acid methyl ester is further defined as a soy oil fatty acid methyl ester, a rapeseed oil fatty acid methyl ester, a palm oil fatty acid methyl ester, or a coconut oil fatty acid methyl ester. 
     
     
         21 . A lubricant composition as set forth in  claim 17  wherein said biodiesel fuel is further defined as a first, second, or third generation biodiesel fuel. 
     
     
         22 . A lubricant composition as set forth in  claim 1  wherein said base oil is further defined as an API Group II or Group III base oil. 
     
     
         23 . A lubricant composition as set forth in  claim 1  wherein said base oil is further defined as an API Group II base oil, said (B) at least one diphenylamine antioxidant is further defined as an octylated/butylated diphenylamine, and said (C) at least one antioxidant comprises octylated phenyl-alpha-naphthylamine, and (B) and (C) are present in a combined amount of from about 0.5 to 3 parts by weight per 100 parts by weight of said base oil 
     
     
         24 . A lubricant composition as set forth in  claim 23  further comprising a biodiesel fuel in an amount of from 0.5 to 6 parts by weight per 100 parts by weight of said lubricant composition. 
     
     
         25 . A lubricant composition as set forth in  claim 1  wherein the (A) base oil has an initial oxidation value measured according to ASTM D 6186 and wherein said lubricant composition comprises up to about 6 wt % of the biodiesel fuel and has a final oxidation value measured according to ASTM D 6186 that is equal to or greater than the initial oxidation value of the (A) base oil. 
     
     
         26 . A lubricant composition as set forth in  claim 25  comprising from 0.3 to 7 parts by weight of said (B) and (C) antioxidants per 100 parts by weight of said lubricant composition. 
     
     
         27 . A lubricant composition as set forth in  claim 25  comprising from 0.9 to 3.5 parts by weight of said (B) and (C) antioxidants per 100 parts by weight of said lubricant composition. 
     
     
         28 . A lubricant composition as set forth in  claim 25  comprising less than about 2.1 parts by weight of said (B) and (C) antioxidants per 100 parts by weight of said lubricant composition. 
     
     
         29 . A method of improving the performance of a lubricant composition suitable for use in diesel engines by improving resistance to degradation by oxidative by-products of a biodiesel fuel, wherein the lubricant composition comprises (A) a base oil, said method comprising the steps of:
 i. providing the (A) base oil;   ii. providing (B) at least one diphenylamine antioxidant;   iii. providing (C) at least one antioxidant selected from a sulfur containing phenolic antioxidant, a phenyl-alpha-naphthylamine antioxidant, and combinations thereof; and   iv. combining (A), (B), and (C) to form the lubricant composition;   wherein the (A) base oil has an initial oxidation value measured according to ASTM D 6186,   wherein the lubricant composition comprises up to about 6 wt % of the biodiesel fuel and has a final oxidation value measured according to ASTM D 6186 that is equal to or greater than the initial oxidation value of the (A) base oil.   
     
     
         30 . A method as set forth in  claim 29  wherein the lubricant composition comprises from 0.3 to 7 parts by weight of the (B) and (C) antioxidants per 100 parts by weight of the lubricant composition. 
     
     
         31 . A method as set forth in  claim 29  wherein the lubricant composition comprises from 0.9 to 3.5 parts by weight of the (B) and (C) antioxidants per 100 parts by weight of the lubricant composition. 
     
     
         32 . A method as set forth in  claim 29  wherein the lubricant composition comprises less than about 2.1 parts by weight of the (B) and (C) antioxidants per 100 parts by weight of the lubricant composition. 
     
     
         33 . A method as set forth in  claim 29  wherein the lubricant composition is diluted with the biodiesel fuel in a lubricant sump of a diesel engine. 
     
     
         34 . A method as set forth in  claim 29  wherein the (C) at least one antioxidant comprises both the sulfur containing phenolic antioxidant and the phenyl-alpha-naphthylamine antioxidant. 
     
     
         35 . A method as set forth in  claim 29  wherein the (C) at least one antioxidant comprises the sulfur containing phenolic antioxidant 
     
     
         36 . A method as set forth in  claim 29  wherein the (C) at least one antioxidant comprises the phenyl-alpha-naphthylamine antioxidant. 
     
     
         37 . A method as set forth in  claim 29  wherein the phenyl-alpha-naphthylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         and wherein R 1  is an aryl radical having from 6 to 12 carbon atoms or an aryl radical having from 6 to 20 carbon atoms and substituted by one, two or three straight or branched chain alkyl radicals each having from 1 to 18 carbon atoms. 
       
     
     
         38 . A method as set forth in  claim 29  wherein the (B) at least one diphenylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         wherein each R′ is independently a hydrogen atom, a straight or branched chain alkyl radical having from 1 to 18 carbon atoms, or an aralkyl radical having 7 to 14 carbon atoms; 
         wherein the (C) at least one antioxidant comprises the sulfur containing phenolic antioxidant and the sulfur containing phenolic antioxidant is further defined as having the formula: 
       
       
         
           
           
               
               
           
         
         and wherein x is a number from 0 to 6, y is a number from 2 to 20 and R is a straight or branched chain alkyl radical having from 1 to 6 carbon atoms. 
       
     
     
         39 . A method as set forth in  claim 29  wherein (B) at least one diphenylamine antioxidant is further defined as comprising at least one octylated/butylated diphenylamine antioxidant and also comprising thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. 
     
     
         40 . A method as set forth in  claim 29  wherein the (B) at least one diphenylamine antioxidant is further defined as having the formula: 
       
         
           
           
               
               
           
         
         wherein each R′ is independently a hydrogen atom, a straight or branched chain alkyl radical having from 1 to 18 carbon atoms, or an aralkyl radical having 7 to 14 carbon atoms; 
         wherein the (C) at least one antioxidant comprises the phenyl-alpha-naphthylamine antioxidant and the phenyl-alpha-naphthylamine antioxidant is further defined as having the formula: 
       
       
         
           
           
               
               
           
         
         and wherein R 1  is an aryl radical having from 6 to 12 carbon atoms or an aryl radical having from 6 to 20 carbon atoms and substituted by one, two or three straight or branched chain alkyl radicals each having from 1 to 18 carbon atoms. 
       
     
     
         41 . A method as set forth in  claim 29  wherein the (B) at least one diphenylamine antioxidant is further defined as comprising at least one octylated/butylated diphenylamine antioxidant, wherein the (C) at least one antioxidant comprises the phenyl-alpha-naphthylamine antioxidant, and the phenyl-alpha-naphthylamine antioxidant is further defined as octylated phenyl-alpha-naphthylamine. 
     
     
         42 . A method as set forth in  claim 29  wherein base oil is further defined as an API Group II base oil, the (B) at least one diphenylamine antioxidant is further defined as an octylated/butylated diphenylamine, and the (C) at least one antioxidant comprises octylated phenyl-alpha-naphthylamine, and (B) and (C) are present in a combined amount of from about 0.5 to 3 parts by weight per 100 parts by weight of the base oil.