Use of surfactants with low molecular weight for improving the filterability in hydraulic lubricants

Abstract

A hydraulic oil, a predominant amount of an oil having a viscosity suitable for lubrication and from 0.03% to 0.06% of an agent improving filterability, corresponding to the formula R—Z. Z represents a polar group containing one or more substituents chosen from phosphoric esters, amides, ethers, amino alcohols, ethoxylated amines, and mixtures thereof. R represents a lipophilic chain having 14 to 24 carbon atoms.

What is claimed is:  
     
         1 . A lubricating fluid comprising 
 1) a predominant amount of an oil having a viscosity suitable for lubrication; and    2) from 0.03% to 0.06% of an agent improving filterability or a mixture thereof, corresponding to the following formula:   R—Z   wherein Z represents a polar group containing one or more substituents chosen from the group consisting of    a) phosphoric esters;    b) amides;    c) ethers;    d) amino alcohols;    e) ethoxylated amines;    f) mixtures thereof,    and R represents a lipophilic chain having 14 to 24 carbon atoms.    
     
     
         2 . A lubricating fluid according to  claim 1 , wherein R contains 17 to 19 carbon atoms.  
     
     
         3 . A lubricating fluid according to  claim 1 , wherein Z is chosen from the group consisting of: 
 a) phosphoric esters;    b) polyethers;    c) ethoxylated amines;    d) mixtures thereof.    
     
     
         4 . A lubricating fluid according to  claim 1 , wherein the agent improving filterability is a phosphoric ester corresponding to the following formula:  
       
         
           
           
               
               
           
         
       
       wherein X represents H or R and at least one of the symbols X represents R, and R represents a saturated or unsaturated hydrocarbyl chain which may contain ether groups, said hydrocarbyl chain having 14 to 24 carbon atoms and preferably 17 to 19 carbon atoms.  
     
     
         5 . A lubricating fluid according to  claim 1 , wherein the agent improving filterability is a compound corresponding to the formula R—O—(CH 2 —CH 2 O) x H wherein X represents an integer from 3 to 12, preferably equal to 9, and R represents a hydrocarbyl chain having 14 to 24 carbon atoms, R representing preferably a C 11 H 23  or C 15 H 31  group.  
     
     
         6 . A lubricating fluid according to  claim 3 , wherein the ethoxylated amine contains at least two ethoxy groups.  
     
     
         7 . A lubricating fluid according to  claim 6 , wherein the agent improving filterability is a compound corresponding to the following formula:  
       
         
           
           
               
               
           
         
       
       wherein R represents a hydrocarbyl chain having 14 to 24 carbon atoms, and R represents preferably an aliphatic chain C 18 H 35 .  
     
     
         8 . A lubricating fluid according to  claim 1 , wherein the agent improving filterability is an unsubstituted fatty amide corresponding to the following formula: 
       H 2 N—CO—R 
       wherein R represents a hydrocarbyl chain having 14 to 24 carbon atoms and preferably 17 to 19 carbon atoms.  
     
     
         9 . A lubricating fluid according to  claim 1 , said lubricating fluid consisting in a hydraulic oil.  
     
     
         10 . An additive for a lubricating fluid, comprising an effective quantity of an agent improving filterability according to  claim 1 .  
     
     
         11 . The use of an effective quantity of an agent improving filterability according to  claim 1  as additive intended to improve the filterability of a lubricating fluid.  
     
     
         12 . The use according to  claim 11 , wherein the lubricating fluid is a hydraulic oil.  
     
     
         13 . The use according to  claim 11  or  12 , wherein the concentration of the agent improving filterability in the said fluid is equal to 0.03% to 0.06% by weight.  
     
     
         14 . The use according to any one of  claims 11  to  13 , the said use being intended for a hydraulic system containing a piston pump having wear surfaces containing copper or a copper alloy and, optionally, a vane pump having wear surfaces containing steel.  
     
     
         15 . A process for the production of a hydraulic fluid with improved filterability which comprises the mixture of the following constituents: 
 a) a predominant amount of an oil having a viscosity suitable for lubrication; and    b) from 0.03% to 0.06% of an agent improving filterability, corresponding to the following formula   R—Z   wherein Z represents a polar group containing one or more substituents chosen from the group consisting of:    a) phosphoric esters;    b) amides;    c) ethers;    d) amino alcohols;    e) ethoxylated amines;    f) mixtures thereof,    and R represents a lipophilic chain having 14 to 24 carbon atoms.