Antioxidant mixture for low viscous polyalkylene glycol basestock

Abstract

The invention relates to a lubricant comprising a polyalkylene glycol basestock, an aromatic amine of the formula (I) as defined hereinafter, and a thioether of the formula (II) as defined hereinafter. The invention further relates to a method for preparing the lubricant comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II); and to a method for reducing the oxidative degradation of the lubricant comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II).

1 .- 14 . (canceled) 
     
     
         15 . A lubricant comprising a polyalkylene glycol basestock,
 an aromatic amine of the formula (I)   
       
         
           
           
               
               
           
         
         wherein R1 and R2 are H or together represent the group A 
       
       
         
           
           
               
               
           
         
         and R3 and R4 are independently H or C 2 -C 30  alkyl, and 
         a thioether of the formula (II) 
       
       
         
           
           
               
               
           
         
       
     
     
         16 . The lubricant according to  claim 15 , comprising 0.05-5 wt % of the aromatic amine. 
     
     
         17 . The lubricant according to  claim 16 , comprising 0.5-1.0 wt % of the aromatic amine. 
     
     
         18 . The lubricant according to  claim 15 , comprising 0.05-5 wt % of the thioether. 
     
     
         19 . The lubricant according to  claim 18 , comprising 0.5-1.0 wt % of thioether. 
     
     
         20 . The lubricant according to  claim 15 , where the weight ratio between the thioether and the aromatic amine is from 1.5:1 to 1:1.5. 
     
     
         21 . The lubricant according to  claim 20 , where the weight ratio between the thioether and the aromatic amine is from 5:1 to 1:5. 
     
     
         22 . The lubricant according to  claim 15 , where the polyalkylene glycol basestock has a kinematic viscosity at 40° C. in the range from 10-300 mm 2 /s. 
     
     
         23 . The lubricant according to  claim 15 , where the polyalkylene glycol basestock is an ethoxylated and propoxylated C 1 -C 20  alkanol or C 2 -C 20  alkandiol. 
     
     
         24 . The lubricant according to  claim 15 , where the polyalkylene glycol basestock is an ethoxylated and propoxylated C 1 -C 8  alkanol. 
     
     
         25 . The lubricant according to  claim 15 , where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 400 to 10 000 Da. 
     
     
         26 . The lubricant according to  claim 15 , where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 1000 to 1500 Da. 
     
     
         27 . The lubricant according to  claim 23 , where the alkoxylated alcohol contains 30 to 70 wt-% ethylene oxide units, and 70 to 30 wt-% of propylene oxide units. 
     
     
         28 . The lubricant according to  claim 15 , where R1 and R2 together represent the group A, R3 is H, and R4 is C 2 -C 30  alkyl. 
     
     
         29 . The lubricant according to  claim 15 , where R1 and R2 are H, and R3 and R4 are independently C 2 -C 30  alkyl. 
     
     
         30 . The lubricant according to  claim 15 , where R3 and R4 are independently H or n-propyl, isopropyl, n-, iso-, or tert-butyl, n-pentyl, isoamyl, neopentyl, 2-ethylbutyl, n-hexyl, 1-methylpentyl, 1,3-dimethylbutyl, n-heptyl, isoheptyl, n-octyl, 1,4,4-trimethyl-2-pentyl, 3,4-, 3,5- or 4,5-dimethyl-1-hexyl, 3- or 5-methyl-1-heptyl, 1,1,3,3-tetramethylbutyl, 2-ethylhexyl, branched octyl, branched octyl as obtained from a dimer of isobutylene, n-nonyl, 1,1,3-trimethylhexyl, branched nonyl as obtained from a trimer of tripropylene, 1-methylundecyl, 2-n-butyl-n-octyl, branched dodecyl obtained from a trimer of isobutylene or a tetramer of propylene, branched pentadecyl obtained from a pentamer of propylene, 2-n-hexyl-n-decyl or 2-n-octyl-n-dodecyl. 
     
     
         31 . A method for preparing the lubricant as defined in  claim 15  comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II). 
     
     
         32 . A method for reducing the oxidative degradation of the polyalkylene glycol basestock as defined in  claim 15  comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II).