Aqueous lubricant composition comprising a gallic acid ester

Abstract

The invention relates to an aqueous lubricant composition comprising at least: —water; —at least one polyalkylene glycol; —at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; —at least one gallic acid ester; and—at least one pH-regulating additive, making it possible to maintain the pH of said lubricant composition between (8) and (15). It also relates to the use of such an aqueous lubricant composition, for lubricating and/or cooling the moving parts in a mechanical system or as a hydraulic fluid. The invention also relates to the use of at least one gallic acid ester as an additive for improving the tribological properties of an aqueous lubricant composition.

1 . An aqueous lubricant composition comprising at least:
 water;   at least one polyalkylene glycol;
 at least one antifreeze compound chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; 
   at least one gallic acid ester; and   at least one pH-regulating additive for maintaining the pH of said lubricant composition between 8 and 15.   
     
     
         2 . The aqueous lubricant composition as claimed in  claim 1 , characterized in that the water is osmosed water, in particular deionized water. 
     
     
         3 . The aqueous lubricant composition as claimed in  claim 1 or 2 , comprising at least 20% by mass of water, in particular deionized water, preferably at least 30% by mass, notably between 35% and 90% by mass, more preferentially between 40% and 75% by mass of water, relative to the total mass of said composition. 
     
     
         4 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that the pH-regulating additive(s) are chosen from alkanolamines, in particular ethanolamines, and more particularly from dimethylethanolamine, triethanolamine, and a mixture thereof, and more particularly is dimethylethanolamine. 
     
     
         5 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that the content of pH-regulating additive(s) is between 0.1% and 10% by mass, preferably between 0.5% and 5% by mass, relative to the total mass of the composition. 
     
     
         6 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that said polyalkylene glycol(s) comprise at least 50% by mass, in particular at least 80% by mass, more preferentially at least 90% by mass of propylene oxide and/or ethylene oxide units, and in particular said polyalkylene glycol(s) are ethylene oxide/propylene oxide copolymers. 
     
     
         7 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that said polyalkylene glycol(s) have a kinematic viscosity measured at 100° C. (KV100), according to the standard ASTM D445, of between 100 and 25 000 mm 2 /s, in particular between 150 and 10 000 mm 2 /s. 
     
     
         8 . The aqueous lubricant composition as claimed in  any one of the preceding claims , comprising at least 5.0% by mass of polyalkylene glycol(s), preferably between 5.0% and 50% by mass, more preferentially between 10% and 40% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition. 
     
     
         9 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that said antifreeze compound is chosen from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, and in particular is diethylene glycol. 
     
     
         10 . The aqueous lubricant composition as claimed in  any one of the preceding claims , comprising at least 5.0% by mass of antifreeze compound(s), preferably between 5.0% and 45% by mass, more preferentially between 10% and 35% by mass, in particular between 20% and 35% by mass, relative to the total mass of said composition. 
     
     
         11 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that said gallic acid ester is obtained from a monoalcohol comprising between 1 and 24 carbon atoms, preferably between 3 and 20 carbon atoms, notably between 3 and 18 carbon atoms, more preferentially between 6 and 16 carbon atoms, for example between 8 and 14 carbon atoms, in particular chosen from 1-octanol and 1-dodecanol. 
     
     
         12 . The aqueous lubricant composition as claimed in  any one of the preceding claims , characterized in that said gallic acid ester is of formula (I): 
       
         
           
           
               
               
           
         
       
       in which R represents a linear or branched, saturated, mono- or polyunsaturated hydrocarbon-based chain, preferably a linear and saturated C 1 -C 24 , preferably C 3 -C 20 , more preferentially C 3 -C 18 , notably C 6 -C 16 , for example C 8 -C 14 , hydrocarbon-based chain, and preferably, said gallic acid ester is lauryl gallate. 
     
     
         13 . The aqueous lubricant composition as claimed in  any one of the preceding claims , comprising between 0.001% and 10% by mass of gallic acid ester(s), in particular between 0.01% and 5% by mass, more particularly between 0.1% and 2% by mass, relative to the total mass of the composition. 
     
     
         14 . The aqueous lubricant composition as claimed in  any one of the preceding claims , further comprising at least one additive chosen from antifoaming agents, biocides, corrosion inhibitors, antiwear and/or extreme-pressure additives, sequestrants, metal passivating agents, dyes, dispersants, emulsifying agents, and mixtures thereof, preferably chosen from antifoaming agents, corrosion inhibitors, metal passivating agents, dyes, and mixtures thereof. 
     
     
         15 . The aqueous lubricant composition as claimed in  any one of the preceding claims , comprising less than 5% by mass, preferably less than 2% by mass, more preferentially less than 1% by mass of water-insoluble oil(s), relative to the total mass of said composition, said composition more particularly being free of water-insoluble oil. 
     
     
         16 . The use of an aqueous lubricant composition as defined in  any one of the preceding claims , for the lubrication and/or cooling of moving parts in a mechanical system, for example for the lubrication and/or cooling of mobile or stationary drive systems, or as a hydraulic fluid. 
     
     
         17 . The use of at least one gallic acid ester, in particular as defined in  claim 11 or 12 , as an additive for improving the tribological properties, in particular in terms of friction reduction, of an aqueous composition further comprising at least: water, at least one polyalkylene glycol and at least one antifreeze compound chosen from glycols, and at least one pH-regulating additive which maintains the pH of said composition between 8 and 15.