Aviation phosphate ester functional fluids with enhanced acid scavenging properties

Abstract

The present invention is an aviation phosphate ester functional fluid of enhanced acid scavenging properties comprising a phosphate ester base oil and a mixture of aliphatic epoxide and carbodiimide acid scavengers.

1 . A functional fluid comprising: 
 a) a major amount of an organo phosphate ester base stock; b) from about 0.05 to 5 wt % based on the total weight of the fluid of a carbodiimide having the following structural formula     R 1 —(N ═C ═N) n —R 2      wherein R 1  and R 2  are the same or different and are hydrogen, hydrocarbyl groups or nitrogen and/or oxygen containing hydrocarbyl groups and n is 1 to 5;    c) from about 4 to 10 wt% based on the total weight of the fluid of an epoxide acid scavenger having the following structural formula                          wherein R is selected from the group consisting of alkyl having from 1 to 10 carbon atoms, substituted alkyl of from 1 to 10 carbon atoms and containing from 1 to 4 ether oxygen atoms; each R′ is independently selected from the group consisting of hydrogen, alkyl from 1 to 10 carbon atoms and C(O)—OR″ where R″ is selected from the group consisting of alkyl of from 1 to 10 carbon atoms optionally containing from 1 to 4 ether oxygen atoms, and cycloalkyl of from 3 to 10 carbon atoms.    
   
   
       2 . The functional fluid of  claim 1  wherein the organo phosphate ester base stock comprises: 
 i) from about 10 to 100% of a trialkyl phosphate;    ii) from 0 wt % to about 75 wt % of a dialkyl aryl phosphate;    iii) from 0 wt % to about 30 wt % of an alkyl diaryl phosphate; and iv) from 0 wt% to about 15 wt% of a triaryl phosphate.    
   
   
       3 . The functional fluid of  claim 2  wherein the alkyl groups of the esters have 4 to 5 carbon atoms.