Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
2002-02-28
2004-02-17
McAvoy, Ellen M. (Department: 1764)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C508S421000, C508S460000, C508S485000, C508S501000
Reexamination Certificate
active
06692654
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to refrigerating machine oils and more particularly to refrigerating machine oils for use with a refrigerant containing carbon dioxide (CO
2
).
Due to the recent issues concerning the ozone shield depletion, conventional refrigerants for refrigerating machine such as CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon) have been targeted for regulation. In place of these refrigerants, HFC (hydrofluorocarbon) has been used as such a refrigerant. However, since the HFC refrigerant also has a problem that it is high in Global Warming Potential (GWP), it has been considered to use refrigerants containing natural materials as alternative refrigerants for the fluorocarbon type refrigerants. Among these alternative refrigerants, carbon dioxide (CO
2
) has conventionally been used as a refrigerant for refrigerating machines because it is harmless to the environment, superior in safety, advantageous in miscibility with refrigerating machine oils and the materials forming a refrigerating machine, and has availability. Recently, it has been considered to apply carbon dioxide as a refrigerant for air conditioners of automobiles using an open- or hermetic-type compressor.
It also has been considered to use hydrocarbon base oils as disclosed in Japanese Patent Laid-Open Publication No. 10-46168 and ether oils such as polyalkylene glycol or polyvinyl ether, as disclosed in Japanese Patent Laid-Open Publication No. 10-46169, as a refrigerating machine oil to be used together with a CO
2
refrigerant. However, these conventional refrigerating oils are not satisfactory in use with the CO
2
refrigerant because of its poor miscibility therewith, resulting in various malfunctions in practical use, such as the deterioration of an important property, that is, the returnability of the oil in the refrigerating system and in poor lubricity leading to seizure of a compressor and a reduction in refrigerating efficiency.
Since a refrigerating machine oil is also required to perform a role of an insulating oil, when used in a hermetic type compressor, a refrigerating machine oil containing polyalkylene glycol which is poor in electric insulation is not appropriate for such hermetic type compressors. Therefore, it is hastened to develop a refrigerating machine oil which meets all of the requirements such as lubricity, miscibility with a refrigerant, stability and electric insulation, in a well-balanced manner.
In view of the foregoing, an object of the present invention is to provide a refrigerating machine oil which can exert excellent properties such as lubricity, miscibility with a refrigerant, stability and electric insulation when used together with a refrigerant containing carbon dioxide.
It has now been found after extensive research that use of an ester oil makes it possible to produce a refrigerating machine oil for use with a CO
2
refrigerant which is superior in various properties, such as lubricity, miscibility with a refrigerant, stability and electric insulation.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, there is provided a refrigerating machine oil which comprises a carbonic ester for use with a refrigerant containing carbon dioxide. A fluid composition comprising the refrigerating machine oil and a refrigerant containing carbon dioxide is also provided.
DETAILED DESCRIPTION OF THE INVENTION
The refrigerating machine oil according to the present invention comprises an ester oil.
Eligible ester oils for the present invention are an aromatic ester, a dibasic ester, a polyol ester, a complex ester, a carbonic ester and a mixture thereof.
The aromatic ester may be an ester of an aromatic carboxylic acid having 1 to 6, preferably 1 to 4, more preferably 1 to 3 valencies and an aliphatic alcohol having 1 to 18, preferably 1 to 12 carbon atoms. Specific examples of such an aromatic carboxylic acid are benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid and a mixture thereof. The aliphatic alcohol having 1 to 18 carbon atoms may be straight-chain or branched. Specific examples of such aliphatic alcohols are methanol, ethanol, straight or branched propanol, straight or branched butanol, straight or branched pentanol, straight or branched hexanol, straight or branched heptanol, straight or branched octanol, straight or branched nonanol, straight or branched decanol, straight or branched undecanol, straight or branched dodecanol, straight or branched tridecanol, straight or branched tetradecanol, straight or branched pentadecanol, straight or branched hexadecanol, straight or branched heptadecanol, straight or branched octadecanol and a mixture thereof.
Specific examples of the aromatic ester are dibutyl phthalate, di(2-ethylhexyl)phathalate, dinonyl phthalate, didecyl phthalate, didodecyl phthalate, ditridecyl phthalate, tributyl trimellitate, tri(2-ethylhexyl) trimellitate, trinonyl trimellitate, tridecyl trimellitate, tridodecyl trimellitate and tritridecyl trimellitate.
Needless to mention, when an aromatic carboxylic acid having at least two valences is used, it may be a simple ester made from one kind of an aliphatic alcohol or a complex ester made from at least two kinds of aliphatic alcohols.
The dibasic ester may be an ester obtained by reacting a dibasic acid having 5 to 10 carbon atoms such as glutamic acid, adipic acid, pimelic acid, suberic acid, azealic acid or sebacic acid, with a monohydric alcohol having 1 to 15 carbon atoms and a straight or branched alkyl group, such as methanol, ethanol, propanol, butanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol or pentadecanol, or a mixture of these esters. Specific examples of these esters are ditridecyl glutarate, di 2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di 2-ethylhexyl sebacate and a mixture thereof.
The polyol esters may be esters of a diol or a polyol having 3 to 20 hydroxyl groups and a fatty acid having 6 to 20 carbon atoms. Specific examples of the diol are ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butane diol, 1,2-butane diol, 2-methyl-1,3-propane diol, 1,5-pentane diol, neopentyl glycol, 1,6-hexane diol, 2-methyl-2-methyl-1,3-propane diol, 1,7-heptane diol, 2-methylol-2-propyl-1,3-propane diol, 2,2-diethyl-1,3-propane diol, 1,8-octane diol, 1,9-nonane diol, 1,10-decane diol, 1,1,1-undecane diol and 1,12-dodecane diol. Specific examples of such polyols are polyalcohols such as trimethylol ethane, trimethylol propane, trimethylol butane, di-(trimethylol propane), tri-(trimethylol propane), pentaerythritol, di-(pentaerythritol), tri-(penthaerythritol), glycerin, polyglycerin (glycerin dimers to icosomer), 1,3,5-penthaerythritol, sorbitol, sorbitan, sorbitol-glycerin condensate, adonitol, arabitol, xylitol and mannitol; saccharides such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose and melezitose; the partially etherified products of these polyalcohols and saccharides; and methylglucoside. Among these, preferred polyols are hindered alcohols such as neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di-(trimethylol propane), tri-(trimethylol propane), penthaerythritol, di-(pentaerythritol) and tri-(penthaerythritol).
Although the carbon number of the fatty acid is not particularly restricted, a fatty acid having 1 to 24 carbon atoms is usually used. Among such fatty acids, preferred are those having more than 3 carbon atoms, more preferred are those having more than 4 carbon atoms, further more preferred are those having more than 5 carbon atoms, and the most preferred are those having more than 10 carbon atoms in view of lubricity. In view of miscibility with a refrigerant, preferred fatty acids are those having fewer than 18 carbon atoms, more preferred are those having fewer than 12 carbon atoms, further more preferred are those having fewer than 9 carbon atoms.
Furthermore,
Hirano Hiroyuki
Osumi Tomomasa
Watanabe Yasuyuki
Akin Gump Strauss Hauer & Feld L.L.P.
McAvoy Ellen M.
Nippon Mitsubishi Oil Corporation
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