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 crankcase lubricating composition comprising a major amount of an oil of lubricating viscosity wherein substantially all of the oil of lubricating viscosity in the composition has an iodine number less than about 4, (A) at least about 2% by weight of one or more antioxidants selected from amine antioxidants, dithiocarbamate antioxidants, phenol antioxidants and mixtures thereof, (B) from about 0.01% to about 3% by weight of at least one boron-containing dispersant or detergent, and (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). 
   
   
       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 amine antioxidants, hindered phenols, and mixtures thereof. 
   
   
       4 . The composition of  claim 3  wherein the amine antioxidant comprises an alkaryl amine. 
   
   
       5 . The composition of  claim 3  wherein the hindered phenol comprises an alkylated phenol. 
   
   
       6 . The composition of  claim 1  wherein the antioxidant (A) comprises an alkaryl amine and an alkylated phenol. 
   
   
       7 . The composition of  claim 1  wherein the antioxidant (A) comprises an alkaryl amine and at least two alkylated phenols. 
   
   
       8 . 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. 
   
   
       9 . 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. 
   
   
       10 . The composition of  claim 1  wherein (B) is at least one detergent which is an overbased metal salt. 
   
   
       11 . The composition of  claim 1  wherein (B) is at least one detergent which is an overbased sodium, calcium, or magnesium carboxylate or sulfonate. 
   
   
       12 . The composition of  claim 1  wherein the dispersant or detergent (B) contains boron. 
   
   
       13 . The composition of  claim 1  wherein the additive (C) is (i). 
   
   
       14 . The composition of  claim 13  wherein (i) is an organic polysulfide. 
   
   
       15 . The composition of  claim 1  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. 
   
   
       16 . The composition of  claim 15  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. 
   
   
       17 . The composition of  claim 15  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. 
   
   
       18 . The composition of  claim 15  wherein (ii) is at least one dihydrocarbyl or trihydrocarbyl phosphite independently containing from one to about 30 carbon atoms in each hydrocarbyl group. 
   
   
       19 . A crankcase lubricating composition comprising a major amount of an oil of lubricating viscosity wherein substantially all of the oil of lubricating viscosity in the composition has an iodine number less than about 4, (A) at least about 2.5% by weight of one or phosphorus-free antioxidant, selected from amine antioxidants, dithiocarbamate antioxidants, phenol antioxidants and mixtures thereof, (B) from about 0.01% to about 2% by weight of at least one boron-containing dispersant or detergent, and (C) at least one polysulfide. 
   
   
       20 . A gear oil composition comprising a major amount of a gear oil basestock wherein substantially all of the gear oil basestock in the composition has an iodine number less than about 4, (A) at least about 2% by weight of one or more antioxidants selected from amine antioxidants, dithiocarbamate antioxidants, phenol antioxidants and mixtures thereof, (B) from about 0.01% to about 3% by weight of at least one borated dispersant or detergent, and (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). 
   
   
       21 . A crankcase lubricating composition comprising a major amount of an oil of lubricating viscosity with an iodine number less than about 4, (A) one or more antioxidants selected from amine antioxidants, dithiocarbamate antioxidants, phenol antioxidants and mixtures thereof, (B) from about 0.01% to about 3% by weight of at least one boron-containing dispersant or detergent; and (C) at least one additive selected from (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), and wherein the total amount of antioxidant is from about 2% by weight up to about 10% by weight.