Lubricating oil for refrigerating machine and hydraulic composition containing the same for use in refrigerating machine

Abstract

A lubricating oil for refrigerators which comprises a compound having oxygen as a base oil and is miscible with a refrigerant having no chlorine atoms and one carbon atom at a temperature of −10° C. or lower when the lubricating oil is comprised at least in one content within the range of 3 to 50% by weight based on the entire amount of a mixture comprising the lubricating oil and the refrigerant; and a hydraulic fluid composition for refrigerators which comprises a refrigerant having no chlorine atoms and one carbon atom and the lubricating oil described above. The hydraulic fluid composition exhibits excellent miscibility of the lubricating oil with the above refrigerant and, in particular, with difluoromethane and also exhibits excellent antiwear, lubricity and stability.

1 . A lubricating oil for refrigerators which comprises a compound having oxygen as a base oil and is miscible with a refrigerant having no chlorine atoms and one carbon atom at a temperature of −10° C. or lower when the lubricating oil is comprised at least in one content within a range of 3 to 50% by weight based on an entire amount of a mixture comprising the lubricating oil and the refrigerant.  
     
     
         2 . A lubricating oil for refrigerators according to  claim 1 , which comprises a compound having oxygen as a base oil and is miscible with a refrigerant having no chlorine atoms and one carbon atom at a temperature of −10° C. or lower when the lubricating oil is comprised at least in one content within a range of 10 to 15% by weight based on an entire amount of a mixture comprising the lubricating oil and the refrigerant.  
     
     
         3 . A lubricating oil for refrigerators according to claims  1  and  2 , which comprises a compound having oxygen as a base oil and is miscible with a refrigerant having no chlorine atoms and one carbon atom at a temperature of −10° C. or lower when the lubricating oil is comprised in a content in a range of 3 to 50% by weight based on an entire amount of a mixture comprising the lubricating oil and the refrigerant.  
     
     
         4 . A lubricating oil for refrigerators according to any one of  claims 1  to  3 , wherein the compound having oxygen is a polycarbonate compound having at least two carbonate bonds in one molecule.  
     
     
         5 . A lubricating oil for refrigerators according to  claim 4 , wherein the polycarbonate compound is at least one compound selected from: 
 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    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 as described for general formula (I).    
     
     
         6 . A lubricating oil for refrigerators according to  claim 5 , wherein the 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 the 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 as described for general formulae (I), (II) and (I-a).  
     
     
         7 . A lubricating oil for refrigerators according to  claim 6 , wherein R 1  in general formulae (I-a) and (II-a) represents an alkylene group having 2 to 6 carbon atoms.  
     
     
         8 . A lubricating oil for refrigerators according to  claim 7 , wherein R 1  represents ethylene group or propylene group.  
     
     
         9 . A lubricating oil for refrigerators according to any one of claims  6 ,  7  and  8 , wherein, in general formulae (I-a) and (II-a), R 2  represents a monovalent hydrocarbon group having 1 to 6 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 6 carbon atoms, R 3  representing a linear or branched alkylene group having 2 to 6 carbon atoms and p representing an integer of 1 to 10; and R 6  represents a linear or branched alkyl group having 1 to 6 carbon atoms.  
     
     
         10 . A lubricating oil for refrigerators according to any one of  claims 1  to  9 , which has a kinematic viscosity at 40° C. of 2 to 2,000 mm 2 /s.  
     
     
         11 . A lubricating oil for refrigerators according to any one of  claim 10 , which has a kinematic viscosity at 40° C. of 10 to 1,000 mm 2 /s.  
     
     
         12 . A lubricating oil for refrigerators according to any one of  claims 1  to  11 , which comprises an acid catcher.  
     
     
         13 . A lubricating oil for refrigerators according to any one of  claims 1  to  12 , which comprises at least one additive selected from a group consisting of extreme pressure agents, oiliness agents and antioxidants.  
     
     
         14 . A hydraulic fluid composition for refrigerators which comprises (A) a refrigerant having no chlorine atoms and one carbon atom and (B) a lubricating oil for refrigerators described in any one of  claims 1  to  13 .  
     
     
         15 . A hydraulic fluid composition for refrigerators according to  claim 14 , which comprises component (A) and component (B) in amounts such that a ratio of an amount by weight of component (A) to an amount by weight of component (B) is in a range of 5:95 to 99:1.  
     
     
         16 . A hydraulic fluid composition for refrigerators according to any one of claims  14  and  15 , wherein the refrigerant of component (A) is difluoromethane.