Lubricating compositions with improved oxidation resistance containing a dispersant and an antioxidant

Abstract

This invention relates to a lubricating composition comprising a major amount of an oil of lubricating viscosity with an iodine number less than about 9, (A) one or more antioxidant, and (B) from about 0.01% to about 3% by weight of at least one dispersant or detergent, wherein the total amount of antioxidant is at least about 2% by weight. The additives are useful act controlling oxidation of lubricants. Further, these lubricants have reduced viscosity increase caused by oxidation, while maintaining favorable carbon/varnish ratings.

1 . A lubricating composition comprising a major amount of an oil of lubricating viscosity with an iodine number less than about 9, (A) one or more antioxidants, and (B) from about 0.01% to about 3% by weight of at least one dispersant or detergent, wherein the total amount of antioxidant is at least about 2% by weight.  
     
     
         2 . The composition of  claim 1  wherein the amount of antioxidant (A) is from about 2.5% up to about 8% by weight.  
     
     
         3 . The composition of  claim 1  wherein the antioxidant (A) is selected from the group consisting of amine antioxidants, dithiophosphoric esters, phenol antioxidants, dithiocarbamates, aromatic phosphites, and sulfurized fatty oils and olefins.  
     
     
         4 . The composition of  claim 1  wherein the antioxidant (A) is selected from the group consisting of aromatic substituted amines, hindered phenols, sulfur coupled phenols, aromatic phosphites, and alkylene coupled dithiocarbamates.  
     
     
         5 . The composition of  claim 1  wherein the antioxidant (A) is selected from the group consisting of a diphenylamine or an alkylene coupled dithiocarbamate.  
     
     
         6 . The composition of  claim 1  wherein the antioxidant (A) is a diphenylamine or a methylene coupled dithiocarbamate.  
     
     
         7 . The composition of  claim 1  wherein the antioxidant (A) is a dithiocarbamte ester which is the reaction product of a dithiocarbamic acid or salt and one or more unsaturated amide, carboxylic acid, anhydride, or ester, and ether.  
     
     
         8 . The composition of  claim 1  wherein the antioxidant (A) is a dithiocarbamate ester prepared by reacting a dithiocarbamic acid or salt with an acrylate or methacrylate.  
     
     
         9 . The composition of  claim 1  wherein the antioxidant (A) is a reaction product of nonene and diphenylamine.  
     
     
         10 . The composition of  claim 1  wherein (B) is at least one dispersant selected from the group consisting of an acylated amine, a carboxylic ester, a Mannich reaction product, and a hydrocarbyl substituted amine.  
     
     
         11 . The composition of  claim 1  wherein (B) is at least one dispersant which is a reaction product of a hydrocarbyl substituted carboxylic acylating agent and a polyamine.  
     
     
         12 . The composition of  claim 1  wherein (B) is at least one detergent which is an overbased metal salt.  
     
     
         13 . The composition of  claim 1  wherein (B) is at least one detergent which is an overbased sodium, calcium, or magnesium carboxylate or sulfonate.  
     
     
         14 . The composition of  claim 1  wherein the dispersant or detergent (B) contains boron.  
     
     
         15 . The composition of  claim 1  further comprising (C) at least one additive selected from the group consisting of (i) a sulfur containing antiwear or extreme pressure agent, (ii) a phosphorus or boron antiwear or extreme pressure agent, and (iii) mixtures thereof, provided that (C) is different from (A).  
     
     
         16 . The composition of  claim 15  wherein the additive (C) is (i).  
     
     
         17 . The composition of  claim 16  wherein (i) is an organic polysulfide.  
     
     
         18 . The composition of  claim 15  wherein the additive (C) is (ii), and wherein (ii) is selected from the group consisting of a metal thiophosphate; a phosphoric acid ester or salt thereof; a phosphite; a phosphorus-containing carboxylic acid, ester, ether, or amide; an alkali metal borate; a borated fatty amine; a borated phospholipid; and a borate ester.  
     
     
         19 . The composition of  claim 18  wherein (ii) is at least one phosphoric acid ester prepared by reacting a dithiophosphoric acid with an epoxide to form an intermediate, and the intermediate is further reacted with a phosphorus acid or anhydride, or a salt of the phosphoric acid ester.  
     
     
         20 . The composition of  claim 18  wherein (ii) is at least one phosphoric acid ester prepared by reacting a phosphorus acid or anhydride with at least one alcohol wherein each alcohol independently contains from about 1 to about 30 carbon atoms, or a salt of the phosphoric acid ester.  
     
     
         21 . The composition of  claim 18  wherein (ii) is at least one dihydrocarbyl or trihydrocarbyl phosphite independently containing from one to about 30 carbon atoms in each hydrocarbyl group.  
     
     
         22 . A lubricating composition comprising a major amount of an oil of lubricating viscosity having a iodine number less than about 9, (A) one or more antioxidant, and (B) from about 0.01% to about 3% by weight of at least one borated dispersant or detergent, wherein the total amount of antioxidant (A) is at least about 2% by weight and wherein the antioxidant (A) is selected from the group consisting of dithiophosphoric esters, amine antioxidants, phenol antioxidants, dithiocarbamates, phosphites, thioalkanols, and sulfurized fatty oils and olefins.  
     
     
         23 . The composition of  claim 22  wherein (B) is selected from the group consisting of a borated acylated amine, a borated carboxylic ester, a borated Mannich reaction product, and a borated hydrocarbyl substituted amine.  
     
     
         24 . The composition of  claim 22  wherein (B) is a borated acylated amine prepared by reacting a boron compound with a reaction product of a hydrocarbyl substituted carboxylic acylating agent and a polyamine.  
     
     
         25 . The composition of  claim 22  wherein (B) is a borated overbased metal salt.  
     
     
         26 . A lubricating composition comprising a major amount of an oil of lubricating viscosity having a iodine number less than about 9, (A) one or more antioxidant, and (B) from about 0.01% to about 2% by weight of at least one dispersant or detergent, wherein the total amount of antioxidant (A) is at least about 2.5% by weight and wherein the antioxidant (A) is phosphorus free.  
     
     
         27 . The composition of  claim 26  further comprising (C) at least one additive selected from the group consisting of (i) a sulfur containing antiwear or extreme pressure agent, (ii) a phosphorus or boron antiwear or extreme pressure agent, and (iii) mixtures thereof, provided that when (A) is a dithiocarbamate, then (C) is different from (A).  
     
     
         28 . A gear oil composition comprising a major amount of a gear oil base stock having an iodine number less than about 9, (A) one or more antioxidant, and (B) from about 0.01% to about 3% by weight of at least one borated dispersant or detergent, wherein the total amount of antioxidant is at least about 2% by weight.  
     
     
         29 . A lubricating composition comprising a major amount of an oil of lubricating viscosity with an iodine number less than about 9, (A) one or more antioxidants, and (B) from about 0.01% to about 3% by weight of at least one dispersant or detergent, wherein the total amount of antioxidant is at least about 1.5% by weight, provided that at least 1% by weight of the antioxidant is an amine antioxidant, dithiocarbamate antioxidant or a mixture thereof.