Gear oil composition having improved copper corrosion properties

Abstract

A gear oil additive composition and gear oil composition comprising a organic polysulfide having at least 30 wt % of a dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds, a thiadiazole; and at least one ashless phosphorus-containing wear inhibitor compound is disclosed as having low yellow corrosion in axles and transmissions.

What is claimed is:  
     
         1 . A gear oil additive composition comprising: 
 a) an organic polysulfide containing greater than 30 wt % of a dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds of the formula:    R 1 —(S) x —R 2      wherein R 1  and R 2  are independently an alkyl group of about 4 to 12 carbon atoms and x is about 4 or greater;    b) a thiadiazole; and    c) at least one ashless phosphorus-containing wear inhibitor compound.    
     
     
         2 . The gear oil composition according to  claim 1 , wherein the composition comprises from about 35 to 75 wt % of the organic polysulfide, about 0.5 to 15 wt % of the thiadiazole, and about 5.0 to 40 wt % of the ashless phosphorus-containing wear inhibitor compound.  
     
     
         3 . A gear oil additive composition according to  claim 1 , further comprising a dispersant additive selected from the group consisting of alkenyl succinimides, alkenyl succinimides modified with other organic compounds, alkenyl succinimides modified by post-treatment with ethylene carbonate or boric acid, pentaerythritol alkenyl succinates, phenate-salicylates and their post-treated analogs, alkali metal or mixed alkali metal, alkaline earth metal borates, dispersions of hydrated alkali metal borates, dispersions of alkaline-earth metal borates, polyamide ashless dispersants, or mixtures of such dispersants.  
     
     
         4 . A gear oil additive composition according to  claim 3 , wherein the dispersant additive is present in a range from about 3.0 to 45 wt %.  
     
     
         5 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide is present from about 45 to 70 wt %.  
     
     
         6 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide is present from about 50 to 65 wt %.  
     
     
         7 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide contains at least 40 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         8 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide contains at least 50 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         9 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide contains at least 55 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         10 . The gear oil additive composition according to  claim 1 , wherein R 1  and R 2  are independently an alkyl group of about 4 to 10 carbon atoms.  
     
     
         11 . The gear oil additive composition according to  claim 1 , wherein R 1  and R 2  are independently an alkyl group of about 4 to 6 carbon atoms.  
     
     
         12 . The gear oil additive composition according to  claim 1 , wherein R 1  and R 2  are each a tertiary-butyl group.  
     
     
         13 . The gear oil additive composition according to  claim 1 , wherein x is about 4 to 8.  
     
     
         14 . The gear oil additive composition according to  claim 1 , wherein x is about 4 to 7.  
     
     
         15 . The gear oil additive composition according to  claim 1 , wherein the organic polysulfide is di-tertiary-butyl polysulfide.  
     
     
         16 . The gear oil additive composition according to  claim 15 , wherein the organic polysulfide is a mixture of di-tertiary-butyl-tri-, tetra-, and penta-sulfide.  
     
     
         17 . The gear oil additive composition according to  claim 1 , wherein the thiadiazole is present from about 0.7 to 12 wt %.  
     
     
         18 . The gear oil additive composition according to  claim 1 , wherein the thiadiazole is present from about 1.0 to 10 wt %.  
     
     
         19 . The gear oil additive composition according to  claim 1 , wherein the thiadiazole comprises at least one of 2,5-dimercapto-1,3,4-thiadiazole; 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles; 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles; 2,5-bis(hydrocarbyl and 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles.  
     
     
         20 . The gear oil additive composition according to  claim 1 , wherein the ashless phosphorus-containing wear inhibitor compound is present from about 7.0 to 35 wt %.  
     
     
         21 . The gear oil additive composition according to  claim 1 , wherein the ashless phosphorus-containing wear inhibitor compound is present from about 10 to 35 wt %.  
     
     
         22 . The gear oil additive composition according to  claim 1 , wherein the ashless phosphorus-containing wear inhibitor compound is at least one compound selected from the group consisting of an amino phosphorus compound and a trialkyl phosphite.  
     
     
         23 . The gear oil additive composition according to  claim 22 , wherein the amino phosphorus compound is amine dithiophosphate.  
     
     
         24 . The gear oil additive composition according to  claim 22 , wherein the trialkyl phosphate is trilauryl phosphite.  
     
     
         25 . The gear oil additive composition according to  claim 24 , wherein the trilauryl phosphite contains at least 75 wt % of the structure (RO) 3  P, wherein R is a hydrocarbyl of about 4 to 24 carbon atoms.  
     
     
         26 . A gear oil composition comprising: 
 a) a major amount of a base oil of lubricating viscosity; and    b) a minor amount of a gear oil additive composition comprising: 
 (i) an organic polysulfide containing greater than 30 wt % of a dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds of the formula:  
 R 1 —(S) x —R 2    
 wherein R 1  and R 2  are independently an alkyl group of about 4 to 12 carbon atoms and x is about 4 or greater;  
 (ii) a thiadiazole; and  
 (iii) at least one ashless phosphorus-containing wear inhibitor compound.  
   
     
     
         27 . The gear oil composition according to  claim 26 , wherein the composition comprises from about 0.1 to 3.6 wt % of the organic polysulfide, about 0.01 to 0.6 wt % of the thiadiazole, and about 0.1 to 2.5 wt % of the ashless phosphorus-containing wear inhibitor compound.  
     
     
         28 . The gear oil composition according to  claim 26 , further comprising a dispersant additive selected from the group consisting of alkenyl succinimides, alkenyl succinimides modified with other organic compounds, alkenyl succinimides modified by post-treatment with ethylene carbonate or boric acid, pentaerythritol alkenyl succinates, phenate-salicylates and their post-treated analogs, alkali metal or mixed alkali metal, alkaline earth metal borates, dispersion of hydrated alkali metal borates, dispersion of alkaline-earth metal borates, polyamide ashless dispersants, or mixtures of such dispersants.  
     
     
         29 . The gear oil composition according to  claim 28 , wherein the dispersant additive is present in a range from about 0.1 to 2.7 wt %.  
     
     
         30 . The gear oil composition according to  claim 26 , wherein the organic polysulfide is present from about 0.6 to 2.5 wt %.  
     
     
         31 . The gear oil composition according to  claim 26 , wherein the organic polysulfide is present from about 1.5 to 2.2 wt %.  
     
     
         32 . The gear oil composition according to  claim 26 , wherein the organic polysulfide contains at least 40 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         33 . The gear oil composition according to  claim 26 , wherein the organic polysulfide contains at least 50 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         34 . The gear oil composition according to  claim 26 , wherein the organic polysulfide contains at least 55 wt % of the dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds.  
     
     
         35 . The gear oil composition according to  claim 26 , wherein R 1  and R 2  are independently an alkyl group about 4 to 10 carbon atoms.  
     
     
         36 . The gear oil composition according to  claim 26 , wherein R 1  and R 2  are independently an alkyl group of about 4 to 6 carbon atoms.  
     
     
         37 . The gear oil composition according to  claim 26 , wherein R 1  and R 2  are each a tertiary-butyl group.  
     
     
         38 . The gear oil composition according to  claim 26 , wherein x is about 4 to 8.  
     
     
         39 . The gear oil composition according to  claim 26 , wherein x is about 4 to 7.  
     
     
         40 . The gear oil composition according to  claim 26 , wherein the organic polysulfide is a di-tertiary-butyl polysulfide.  
     
     
         41 . The gear oil composition according to  claim 40 , wherein the organic polysulfide is a mixture of di-tertiary-butyl tri-, tetra-, and penta-sulfide.  
     
     
         42 . The gear oil composition according to  claim 26 , wherein the thiadiazole is present from about 0.05 to 0.4 wt %.  
     
     
         43 . The gear oil composition according to  claim 26 , wherein the thiadiazole is present from about 0.1 to 0.3 wt %.  
     
     
         44 . The gear oil composition according to  claim 26 , wherein the thiadiazole comprises at least one of 2,5-dimercapto-1,3,4-thiadiazole; 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles; 2-mercapto-5-hydrocarbyidithio-1,3,4-thiadiazoles; 2,5-bis(hydrocarbyl and 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles.  
     
     
         45 . The gear oil composition according to  claim 26 , wherein the ashless phosphorus-containing wear inhibitor compound is present from about 0.2 to 1.7 wt %.  
     
     
         46 . The gear oil composition according to  claim 26 , wherein the ashless phosphorus-containing wear inhibitor compound is present from about 0.5 to 1.2 wt %.  
     
     
         47 . The gear oil composition according to  claim 26 , wherein the ashless phosphorus-containing wear inhibitor compound is at least one compound selected from the group consisting of an amino phosphorus compound and a trialkyl phosphite.  
     
     
         48 . The gear oil composition according to  claim 47 , wherein the amino phosphorus compound is amine dithiophosphate.  
     
     
         49 . The gear oil composition according to  claim 47 , wherein the trialkyl phosphite is trilauryl phosphite.  
     
     
         50 . The gear oil composition according to  claim 49 , wherein the trilauryl phosphite contains at least 75 wt % of the structure (RO) 3  P, wherein R is a hydrocarbyl of about 4 to 24 carbon atoms.  
     
     
         51 . The gear oil composition according to  claim 26 , having chlorine levels below 50 ppm.  
     
     
         52 . A method of reducing yellow metal corrosion in axles and transmissions, said method comprising contacting the metal components of the axle and transmission with a gear oil composition comprising: 
 c) a major amount of a base oil of lubricating viscosity; and    d) a minor amount of a gear oil additive composition comprising: 
 (i) an organic polysulfide containing greater than 30 wt % of a dialkyl polysulfide compound or mixture of dialkyl polysulfide compounds of the formula:  
 R 1 —(S) x —R 2    
 wherein R 1  and R 2  are independently an alkyl group alkyl of about 4 to 12 carbon atoms and x is about 4 or greater;  
 (ii) a thiadiazole; and  
 (iii) at least one ashless phosphorus-containing wear inhibitor compound.