Refrigerating machine oil for carbon dioxide refrigerant and fluid composition for refrigerating machine

Abstract

A refrigerating machine oil for a carbon dioxide refrigerant according to the present invention contains polyalkylene glycol represented by the following general formula (1): R 1 {—(OR 3 ) n —OR 2 ) m (1) [where R 1 represents a residue obtained by removing m hydroxyl groups from an organic compound having three to ten hydroxyl groups, R 2 hydrogen, an alkylene group of one to five carbons, or an acyl group of one to five carbons, R 3 an alkylene group of two to four carbons, m an integer of 3 to 10, and n such an integer that a number average molecular weight of the polyalkylene glycol (1) becomes 500 to 3000], wherein a kinematic viscosity at 100° C. of the polyalkylene glycol is 5-20 mm 2 /s.

What is claimed is:  
     
         1 . A refrigerating machine oil for a carbon dioxide refrigerant, comprising polyalkylene glycol represented by the following general formula (1): 
       R 1 {—(OR 3 ) n —OR R 2 } m   ( 1 ) [where R 1  represents a residue obtained by removing m hydroxyl groups from an organic compound having three to ten hydroxyl groups, R 2  hydrogen, an alkylene group of one to five carbons, or an acyl group of one to five carbons, R 3  an alkylene group of two to four carbons, m an integer of 3 to 10, and n such an integer that a number average molecular weight of the polyalkylene glycol represented by said formula (1) becomes 500 to 3000], 
 wherein a kinematic viscosity at 100° C. of said polyalkylene glycol is 5-20 mm 2 /s.  
   
     
     
         2 . A fluid composition for refrigerating machines, comprising the refrigerating machine oil for the carbon dioxide refrigerant as set forth in  claim 1 , and the carbon dioxide refrigerant.