Functional fluid composition for improving lubricity of a braking system

Abstract

The functional fluids of the present invention comprise about 50 parts by weight to about 99 parts by weight of a glycol component and about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content. Desirably, in one aspect of this invention, the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.05 mm to about 0.45 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.

1 . A functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising:
 about 50 parts by weight to about 99 parts by weight of a glycol component; and   about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content;   wherein the functional fluid composition exhibits an average scar width as measured according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both, and   wherein the functional fluid is optionally free of silicone;   wherein the one or more additives includes
 (i) a first additive including an ester of phosphoric acid, 
 (ii) a second additive including an ethoxylated phosphate ester, or 
 (iii) both (i) and (ii). 
   
   
   
       2 . The functional fluid composition of  claim 1 , wherein the first additive consists essentially of a tricresyl phosphate. 
   
   
       3 . The functional fluid composition of  claim 2 , wherein the second additive includes an ethoxylated phosphate ester selected from the group consisting of a polyoxyethylene octadadecenyl ether phosphate. a polyoxyethylene lauryl ether phosphate, a linear alcohol ethoxy phosphate, a polyethylene phenyl ether phosphate, a dialkylphenol phosphate ester or any combination thereof. 
   
   
       4 . The functional fluid composition of  claim 3 , wherein the second additive includes a polyethylene glycol phenyl ether phosphate. 
   
   
       5 . The functional fluid composition of  claim 3 , wherein the second additive consists essentially of a polyethylene glycol phenyl ether phosphate. 
   
   
       6 . The functional fluid composition of  claim 3 , wherein the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mg KOH/kg of the first additive. 
   
   
       7 . The functional fluid composition of  claim 3 , wherein the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 mg KOH/kg of the second additive and a nonionic content less than about 15%. 
   
   
       8 . The functional fluid composition of  claim 3 , wherein the first additive, the second additive, or both is present in the amount of about 0.005 to about 0.7 parts by weight of the fluid composition. 
   
   
       9 . The functional fluid composition of  claim 3 , wherein the one or more additives includes a corrosion inhibitor that is present in the amount of about 0.5 parts by weight to about 2 parts by weight of the one or more additives. 
   
   
       10 . The functional fluid composition of  claim 6 , wherein the glycol component comprises the formula: 
     
       
         
         
             
             
         
       
     
     wherein R 1  is H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, the glycol component including at least one glycol wherein at least one of R 2 , R 3 , R 4 , and R 5  is an alkyl group containing 1 to 8 carbon atoms. 
   
   
       11 . The functional fluid composition according to  claim 10 , wherein the glycol component includes at least one glycol having at least one first repeat unit wherein R 2 , R 3 , R 4 , and R 5  are each H and at least one second repeat unit wherein at least one (e.g., one, two, three, or all four) of R 2 , R 3 , R 4 , and R 5  are each an alkyl group containing 1 to 8 carbon atoms. 
   
   
       12 . The functional fluid composition according to  claim 10  wherein the at least one glycol include glycol where n=2 is present in an amount of from about 0.25 parts by weight to about 10 parts by weight of the glycol component and glycol where n=4 or more in an amount from about 0 parts by weight to about 30 parts by weight of the glycol component. 
   
   
       13 . The functional fluid composition according to  claim 10  wherein the composition is substantially free of glycol borate esters. 
   
   
       14 . The functional fluid composition according to  claim 10  further comprising from about 0.1 parts by weight to about 70 parts by weight of a glycol borate ester comprising the formula: 
     
       
         
         
             
             
         
       
     
     wherein each R 1  R 2 , R 3 , R 4 , and R 5  is independently H or an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, n is 1 to 4. 
   
   
       15 . The functional fluid composition according to  claim 10  wherein the glycol component comprises one or more high purity glycol components. 
   
   
       16 . The functional fluid composition according to  claim 10  wherein:
 about 0.5 parts by weight to about 10 parts by weight of the glycol component has R 1  contains 4 carbon atoms and n=2;   about 40 parts by weight to about 60 parts by weight of the glycol component has R 1  contains 1 carbon atom and n=3;   about 5 parts by weight to about 15 parts by weight of the glycol component has R 1  contains 4 carbon atoms and n=3;   about 5 parts by weight to about 15 parts by weight of the glycol component wherein R 1  contains 4 carbon atoms and n=4 or more;   about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content,   wherein the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.1 mm to about 0.3 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 8, or both.   
   
   
       17 . The functional fluid composition according to  claim 10 , wherein the functional fluid composition is free of silicone. 
   
   
       18 . The functional fluid composition according to  claim 10 , wherein the fluid power system is a brake system. 
   
   
       19 . An additives package for imparting lubricity in a fluid power system comprising:
 about 5 parts by weight to about 75 parts by weight of at least one of (i) a first additive including an ester of phosphoric acid and (ii) a second additive including an ethoxylated phosphate ester;   about 30 parts by weight to about 99 parts by weight of two or more corrosion inhibitors that includes at least one of (a) propanediamine and xylene, (b) hydroxyethylpiperazine, (c) dodecenyl succinic anhydride, (d) Di-(2-ethylhexyl)phosphoric acid, (e) poly(diethoxysiloxane), (e) oleic acid, and (f) propylene glycol and borax 5 mol component,   wherein the first additive exhibits a melting point that ranges from about −45° C. to about −25° C., a boiling point (at 4 mm Hg) that ranges from about 230° C. to about 265° C., a flash point that is at least about 375° C., a specific gravity (at 25° C.) that ranges from about 1.1 to about 1.25, and an acid number of less than about 0.5 mgKOH/kg,   wherein the second additive exhibits an acid number (KOH to first inflection point) that ranges from about 90 to about 115 and a nonionic content less than about 15%, and   wherein a functional fluid composition includes the additive package, the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 0.35 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both.   
   
   
       20 . The additive package of  claim 19 , wherein the first additive consists essentially of a tricresyl phosphate. 
   
   
       21 . The additive package of  claim 20 , wherein the second additive consists essentially of a polyethylene glycol phenyl ether phosphate. 
   
   
       22 . A method for imparting lubricity comprising the steps of:
 contacting one or more rubber components of a fluid power system with a functional fluid composition free of silicone and including about 0.3 parts by weight to about 10 parts by weight of one or more additives including a phosphate content,
 wherein the functional fluid composition exhibits an average scar width according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) that ranges from about 0.05 mm to about 0.45 mm, an average tooth count according to ASTM D 2670 (100 lb break-in for 1 min, 200 lb load for 30 minutes) of less than about 15, or both. 
   
   
   
       23 . A functional fluid composition for imparting lubricity in a fluid power system having metal/rubber contact comprising:
 about 50 parts by weight to about 99 parts by weight of a glycol component; and   about 0.3 parts by weight to about 10 parts by weight of one or more additives;   wherein the functional fluid is further characterized either or both of
 i) the glycol component includes a polyethylene-propylene glycol monomethyl ether having an average molecular weight of about 500 at a concentration from about 10 wt. % to about 30 wt. % based on the total weight of the functional fluid; or 
 ii) the one or more additives includes oleic acid at a concentration from about 0.02 wt. % to about 0.5 wt. % based on the total weight of the functional fluid; 
   wherein the one or more additives optionally contains a polyethylene phenyl ether phosphate, the functional fluid is optionally is free of silicone, the glycol component includes methoxytriglycol present a concentration greater than about 25 wt. % based on the total weight of the functional fluids, and the functional fluid has one or any combination of the following characteristics: an average scar width less than about 0.36 mm, a tooth count less than about 10, an ERBP greater than about 250° C., or a viscosity at −40° C. of less than about 800 cSt.