Generally, naphthenic mineral oils, paraffinic mineral oils, alkylbenzenes, polyglycolic oils, ester oils and mixtures thereof, which have each a kinematic viscosity of 10-200 cSt at 40.degree. C., as well as these oils incorporated with suitable additives have been used as refrigerator oils.
On the other hand, chlorofluorocarbons (CFCS) type refrigerants, such as CFC-11, CFC-12, CFC-113 and HCFC-22, have been used for refrigerators.
Of these CFCS, CFCS such as CFC-11, CFC-12 and CFC-113, which are obtained by substituting all the hydrogen atoms of hydrocarbons thereof by halogen atoms including chlorine atoms, may lead to the destruction of the ozone layer, and therefore, the use of the CFCS has been controlled. Accordingly, halohydrocarbons, such as HFC-134a and HFC-152a, have been used as substitutes for CFCs. HFC-134a is especially promising as a substitute refrigerant since it is similar in thermodynamic properties to CFC-12 which has heretofore been used in many kinds of refrigerators of home cold-storage chests, air-conditioners and the like.
A number of patents have discussed esters that are useful as refrigerator oils.
Sasaki et al., U.S. Pat. No. 6,582,621 disclose a refrigerator oil for us in compressors using there in a hydrogen-containing halogenocarbon as a refrigerant, consisting essentially of as a base oil at least one kind of ester selected from the group consisting of a specific pentaerythritol ester such as an ester of pentaerythritol with a mono- or dicarboxylic acid, a specific polyol ester such as an ester of trimethylolethane with a mono- or dicarboxylic, a specific ester such as an ester of ethylene glycol and a dicarboxylic acid, and a specific polyol ester synthesized from a neopentyl type polyhydric alcohol, a monocarboxylic acid and a dicarboxylic acid; and further comprising at least one kind of an epoxy compound.
Ankner et al., U.S. Patent Publication No. US 2004/0046146 disclose refrigerant compositions which comprise a hydrofluorocarbon based refrigerant, and mixed with the refrigerant, a polyol ester based lubricant. The polyol ester comprises a diol having a strong sterically hindered hydrogen attached to the carbon in position 2, said diol being esterified with a mixture of mono- and diabasic carboxylic acids.
Schnur, U.S. Pat. No. 6,551,523 discloses an ester blend, including an ester having neopentylglycol and a source of 2-ethylhexanoic acid as its reactive components and an ester having pentaerythritol and a source of 2-ethylhexanoic acid as its reactive components, is especially effective as a lubricant for chlorine-free fluorocarbon refrigerant heat transfer fluids, particularly Refrigerant 134a (1,1,1,2-tetrafluoroethane).
Shimomura et al., U.S. Pat. No. 7,045,490 disclose a refrigerating machine oil composition that comprises an alicyclic polycarboxylic acid ester compound obtained from the following compounds (a) to (c): (a) an alicyclic polycarboxylic acid having an alicyclic ring and two or more carboxyl groups are bonded to mutually adjacent carbon atoms on the alicyclic ring; (b) a compound with two or more hydroxyl groups or its derivative; and (c) a compound with one hydroxyl group or its derivative.
Glova U.S. Pat. No. 4,556,496 discloses a refrigeration lubricating oil composition comprising a branched-chain alkylbenzene or mixture of branched-chain alkylbenzenes containing a total of from 10 to 25 carbon atoms in the alkyl groups, and about 50 ppm to 5 weight percent of a dialkyl sulfosuccinate wherein each alkyl group has 3 to 7 carbon atoms.
Shimomura et al., U.S. Pat. No. 6,831,045 disclose a refrigerating machine oil composition comprising an alicyclic dicarboxylic acid ester compound containing an alicyclic ring and two ester groups represented by the following general formula: —COOR1 where R1 represents a hydrocarbon group of 1-30 carbons, where R1 represents a hydrocarbon group of 1-30 carbons, the two ester groups bonded to mutually adjacent carbon atoms on the alicyclic ring, wherein the molar ratio of cis-forms and trans-forms for the orientation of the two ester groups of the alicyclic dicarboxylic acid ester compound is from 20/80 to 80/20.
Kawahara, U.S. Publication 2006/0019840A1 is directed to a lubricating oil for bearings. It is not a refrigerator oil composition such as those disclosed in this invention.
Kawahara is directed to adipate and azelate diesters made from terminal diols, not the vicinal diesters of the current invention.