Lubricating oil for refrigerators and hydraulic fluid composition for refrigerator using the same

Abstract

The present invention proposes a lubricating oil for refrigerators comprising, as the base oil, a polyester-based derivative or a polyvinyl ether derivative and a polycarbonate-based oxygenated compound; a polyoxyalkylene glycol derivative; or a polyester-based derivative or a polyvinyl ether derivative and a polyoxyalkylene glycol derivative. The lubricating oil exhibits excellent miscibility with a refrigerant having one carbon atom and no chlorine atoms and, in particular, with difluoromethane and provides a hydraulic fluid composition exhibiting excellent antiwear, lubricity and stability.

1 . A lubricating oil for refrigerators which comprises, as a base oil, (a) a polyvinyl ether-based derivative with a kinematic viscosity of 3 to 500 mm 2 /s at 40° C. and (b) a polycarbonate-based oxygenated compound with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. in an amount of 0.1% by weight or more and less than 60% by weight based on an amount of the entire base oil, wherein a temperature of phase separation at a low temperature side of a mixture comprising the lubricating oil and a refrigerant having one carbon atom and no chlorine atoms is 5° C. or lower in at least any one of the case where the lubricating oil is contained within a range of 3 to 50% by weight based on an amount of the entire mixture.  
     
     
         2 . A lubricating oil for refrigerators which comprises, as a base oil, (a) a polyester-based derivative with a kinematic viscosity of 3 to 500 mm 2 /s at 40° C. and (b) a polycarbonate-based oxygenated compound with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. in an amount of 0.1% by weight or more and less than 60% by weight based on an amount of the entire base oil, wherein a temperature of phase separation at a low temperature side of a mixture comprising the lubricating oil and a refrigerant having one carbon atom and no chlorine atoms is 10° C. or lower in at least any one of the case where the lubricating oil is contained within a range of 3 to 50% by weight based on an amount of the entire mixture.  
     
     
         3 . The lubricating oil for refrigerators according to  claim 1  or  claim 2 , wherein a kinematic viscosity at 40° C. of said lubricating oil is 7 to 200 mm 2 /s and a viscosity index of said lubricating oil is 40° C. or greater.  
     
     
         4 . The lubricating oil for refrigerators according to any one of  claims 1  to  3 , wherein said polycarbonate-based oxygenated compound is a polycarbonate having at least two carbonate bonds in one molecule which is at least one compound selected from: 
 (i) compounds represented by general formula (I):  
                     
  wherein Z represents a residue group obtained by eliminating hydroxyl group from an alcohol having 1 to 12 carbon atoms and a functionality of n, R 1  represents a linear or branched alkylene group having 2 to 10 carbon atoms, R 2  represents a monovalent hydrocarbon group having 1 to 12 carbon atoms or a group having ether bond represented by R 4 (O—R 3 ) p —, R 4  representing hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms, R 3  representing a linear or branched alkylene group having 2 to 10 carbon atoms and p representing an integer of 1 to 20, k represents an integer of 1 to 30, m represents an integer of 1 to 50 and n represents an integer of 1 to 6; and  
 (ii) compounds represented by general formula (II):  
                     
  wherein R 5  represents a linear or branched alkylene group having 2 to 10 carbon atoms, q represents an integer of 1 to 20 and Z, R 1 , R 2 , k, m and n are the same as described for general formula (I).  
 
     
     
         5 . The lubricating oil for refrigerators according to  claim 4 , wherein said compound represented by general formula (I) is a compound represented by general formula (I-a):  
       
         
           
           
               
               
           
         
       
       wherein R 6  represents a residue group obtained by eliminating hydroxyl group from a monohydric alcohol having 1 to 12 carbon atoms and R 1 , R 2 , k and m are as described for general formula (I); and/or said compound represented by general formula (II) is a compound represented by general formula (II-a):  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 5 , R 6 , k, m and q are the same as described for general formulae (I), (II) and (I-a).  
     
     
         6 . The lubricating oil for refrigerators according to  claim 5 , wherein R 1  in general formula (I-a) and general formula (II-a) represents an alkylene group having 2 to 6 carbon atoms.  
     
     
         7 . The lubricating oil for refrigerators according to  claim 6 , wherein R 1  represents ethylene group or propylene group.  
     
     
         8 . The lubricating oil for refrigerators according to any one of  claims 5  to  7 , wherein, in general formula (I-a) and general formula (II-a), R 2  and/or R 6  represents a linear or branched alkyl group having 1 to 6 carbon atoms.  
     
     
         9 . A lubricating oil for refrigerators used for a refrigerant having one carbon atom and no chlorine atoms which comprises, as a base oil, a polyoxyalkylene glycol derivative with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. and, as a main component thereof, having at least one constituting unit represented by general formula (III):  
       
         
           
           
               
               
           
         
       
       wherein R 7  to R 10  each independently represent hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or a group represented by general formula (IV):  
       
         
           
           
               
               
           
         
       
       wherein R 11  and R 12  each independently representing hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, R 13  representing an alkylene group having 2 to 5 carbon atoms, a substituted alkylene group having an alkyl group as a substituent and 2 to 5 carbon atoms in an entire group or a substituted alkylene group having an alkoxyalkyl group as a substituent and 4 to 10 carbon atoms in an entire group, R 14  representing a monovalent hydrocarbon group having 1 to 10 carbon atoms and n representing an integer of 0 to 20; and at least one of R 7  to R 10  represents a group represented by general formula (IV).  
     
     
         10 . A lubricating oil for refrigerators which comprises, as a base oil, (a) a polyvinyl ether-based derivative with a kinematic viscosity of 3 to 500 mm 2 /s at 40° C. and (b) a polyoxyalkylene glycol derivative with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. in an amount of 0.1% by weight or more and less than 60% by weight based on an amount of the entire base oil, and having at least one constituting unit represented by general formula (III):  
       
         
           
           
               
               
           
         
       
       wherein R 7  to R 10  each independently represents hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or a group represented by general formula (IV):  
       
         
           
           
               
               
           
         
       
       wherein R 11  and R 12  each independently representing hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, R 13  representing an alkylene group having 2 to 5 carbon atoms, a substituted alkylene group having an alkyl group as a substituent and 2 to 5 carbon atoms in an entire group or a substituted alkylene group having an alkoxyalkyl group as a substituent and 4 to 10 carbon atoms in an entire group, R 14  representing a monovalent hydrocarbon group having 1 to 10 carbon atoms and n representing an integer of 0 to 20; and at least one of R 7  to R 10  represents a group represented by general formula (IV); 
 characterized that a temperature of phase separation at a low temperature side of a mixture comprising the lubricating oil and a refrigerant having one carbon atom and no chlorine atoms is 5° C. or lower in at least any one of the case where the lubricating oil is contained within a range of 3 to 50% by weight based on an amount of the entire mixture.  
 
     
     
         11 . A lubricating oil for refrigerators which comprises, as a base oil, (a) a polyester-based derivative with a kinematic viscosity of 3 to 500 mm 2 /s at 40° C. and (b) a polyoxyalkylene glycol derivative with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. in an amount of 0.1% by weight or more and less than 60% by weight based on an amount of the entire base oil, having at least one constituting unit represented by general formula (III):  
       
         
           
           
               
               
           
         
       
       wherein R 7  to R 10  each independently represent hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or a group represented by general formula (IV):  
       
         
           
           
               
               
           
         
       
       wherein R 11  and R 12  each independently representing hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, R 13  representing an alkylene group having 2 to 5 carbon atoms, a substituted alkylene group having an alkyl group as a substituent and 2 to 5 carbon atoms in an entire group or a substituted alkylene group having an alkoxyalkyl group as a substituent and 4 to 10 carbon atoms in an entire group, R 14  representing a monovalent hydrocarbon group having 1 to 10 carbon atoms and n representing an integer of 0 to 20; and at least one of R 7  to R 10  represents a group represented by general formula (IV); 
 characterized that a temperature of phase separation at a low temperature side of a mixture comprising the lubricating oil and a refrigerant having one carbon atom and no chlorine atoms is 10° C. or lower in at least any one of the case where the lubricating oil is contained within a range of 3 to 50% by weight based on an amount of the entire mixture.  
 
     
     
         12 . The lubricating oil for refrigerators according to any one of  claims 9  to  11 , wherein a kinematic viscosity at 40° C. of said lubricating oil is 7 to 200 mm 2 /s and a viscosity index of said lubricating oil is 40 or greater.  
     
     
         13 . The lubricating oil for refrigerators according to any one of  claims 1  to  12 , which further comprises an acid catcher.  
     
     
         14 . The lubricating oil for refrigerators according to any one of  claims 1  to  13 , which further comprises at least one additive selected from a group consisting of extreme pressure agents, oiliness agents and antioxidants.  
     
     
         15 . The hydraulic fluid composition for refrigerators which comprises (A) a refrigerant having one carbon atom and no chlorine atoms and (B) a lubricating oil for refrigerators described in any one of  claims 1  to  14 .  
     
     
         16 . The hydraulic fluid composition for refrigerators according to  claim 15 , which comprises said (A) and said (B) in amounts such that a ratio of an amount by weight of said (A) to an amount by weight of said (B) is in a range of 5:95 to 99:1.  
     
     
         17 . The hydraulic fluid composition for refrigerators according to  claim 15  or  claim 16 , wherein said (A) is difluoromethane.