Aqueous functional fluids with antioxidants

Abstract

The present invention relates to an aqueous functional fluid comprising an antioxidant of the hindered phenol type and a water-soluble polyalkylene glycol. The aqueous functional fluids are especially suitable for use as hydraulic or metal working fluids. The present invention also relates to the use of the aqueous functional fluid for improving the performance properties of hydraulic or metal working fluids.

1 . A functional fluid comprising 
 a) A 4-hydroxyphenylpropionic acid ester:                        wherein    one of R 1  and R 2  represents hydrogen or C 1 -C 9 alkyl; and the other one represents C 3 -C 9 alkyl;    R 3  represents hydrogen or methyl;    R 4  represents hydrogen, C 1 -C 30 alkyl, (C 1 -C 4 alkyl) 1-3 phenyl, phenyl or a group:                          wherein    R 1 ′ and R 2 ′ have the same meanings as R 1  and R 2  defined above; and    n represents a numeral from 1 to 60;      b) Water soluble polyalkylene glycol or mixtures thereof; and    c) Water.    
     
     
         2 . A functional fluid according to  claim 1  comprising as component a) a 4-hydroxyphenylpropionic acid ester (I), wherein 
 one of R 1  and R 2  represents methyl; and the other one represents tert-butyl; or    both of R 1  and R 2  represent tert-butyl;    R 3  represents hydrogen or methyl;    R 4  represents hydrogen, C 1 -C 9 alkyl, or the group (A), wherein    one of R 1 ′ and R 2 ′ represents methyl; and the other one represents tert-butyl; or    both of R 1 ′ and R 2 ′ represent tert-butyl; and    n represents a numeral from 2 to 15.    
     
     
         3 . A functional fluid according to  claim 1  comprising as component a) 
 a 4-hydroxyphenylpropionic acid ester:                          wherein    one of R 1  and R 2  represents methyl and the other one represents tert-butyl;    R 1 ′ and R 2 ′ are as defined as R 1  and R 2 ; and the index n represents a numeral from 2 to 15; or    R 1 , R 1 ′, R 2  and R 2 ′ represent tert-butyl; or the index n represents a numeral from 2 to 15.    
     
     
         4 . A functional fluid according to  claim 1  comprising as component a) a compound:  
       
         
           
           
               
               
           
         
       
     
     
         5 . A functional fluid according to  claim 3  comprising 
 a) A 4-hydroxyphenylpropionic acid ester (I′);    b) High viscosity, water soluble polyalkylene glycol or mixtures thereof;    c) Water; and, optionally,    d) Further additives suitable for aqueous hydraulic or metal working fluids.    
     
     
         6 . A concentrate comprising 
 a) A 4-hydroxyphenylpropionic acid ester (I), wherein R 1 -R 4  and n are as defined in  claim 1;     b) High viscosity, water soluble polyalkylene glycol or mixtures thereof; and    d) Further additives suitable for aqueous hydraulic or metal working fluids.    
     
     
         7 . A method for improving the performance properties of a functional fluid which comprises adding to an aqueous phase a 4-hydroxyphenylpropionic acid ester (I), wherein R 1 -R 4  and n are as defined in  claim 1 .  
     
     
         8 . A method for improving the performance properties of a functional fluid which comprises adding to an aqueous phase a concentrate according to  claim 6 .  
     
     
         9 . The use of an aqueous functional fluid according to  claim 1  for improving the performance properties of hydraulic or metal working fluids.