Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
2000-08-04
2002-03-12
Medley, Margaret (Department: 1714)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C508S465000, C508S484000
Reexamination Certificate
active
06355186
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a refrigerating machine oil composition, particularly relates to a refrigerating machine oil composition characterized in containing a specific alicyclic dicarboxylic acid ester compound.
2. Related Background Art
Owing to the restriction of fluorocarbons for prevention of ozone layer destruction and prevention of global -warming, efforts are being made to replace chlorine-containing refrigerants such as CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon) with HFC (hydrofluorocarbon), and to realize high efficiency of a refrigerating system. On the other hand, since HFC refrigerants are also the objects under the restriction for preventing global warming, the application of natural refrigerants such as carbon dioxide, ammonia, hydrocarbons have been researched.
In accordance with the efforts to substitute the above-mentioned refrigerants for the conventional refrigerants, various refrigerating machine oils have been developed. These refrigerating machine oils must satisfy a number of performance requirements including lubricity (lubricating action), refrigerant miscibility, heat stability/hydrolytic stability, electric insulating ability, low hygroscopicity and the like. Therefore, the compounds contained in the refrigerating machine oils are selected to meet the required performances on the basis of the type and the use of the refrigerants. For example, refrigerating machine oils for HFC refrigerants may contain oxygen compounds such as esters, ethers and carbonates that are miscible with the refrigerant, or they may contain alkylbenzene having inferior miscibility with the refrigerant but having excellent lubricity, heat stability and hydrolytic stability.
In order to achieve a high efficiency of a refrigerating system, the efforts have been made to lower the viscosity of the refrigerating machine oil. The ester refrigerating machine oils, such as polyol ester obtained from the reaction between an aliphatic polyhydric alcohol and a fatty acid, are disclosed in Japanese Translation Publication No. Hei 3-505602 (JP-A 3-505602) of International Publication for Patent Application and Japanese Patent Kokai (Laid-Open) Publication No. Hei. 3-128991 (JP-A 3-128991). One effective means for lowering viscosity of such kinds of ester refrigerating machine oils is to select a fatty acid having a small number of carbon atoms in its alkyl group. However, in general, an ester obtained from a fatty acid with a small alkyl group would have low heat stability and hydrolytic stability.
Japanese Patent Kokai (Laid-Open) Publication No. Hei 9-221690 (JP-A 9-221690) discloses an alicyclic polycarboxylic acid ester which is an ester refrigerating machine oil having excellent heat stability and hydrolytic stability. However, problems still exist. The miscibility with a refrigerant is insufficient when the number of carbon atoms of the terminal alkyl group on the ester site is large. On the other hand, the heat stability/hydrolytic stability of the refrigerating machine oil is inferior and the lubricity is insufficient when the number of carbon atoms of the terminal alkyl group on the ester site is small.
Therefore, an ester refrigerating machine oil that has all of low viscosity (for obtaining a high efficiency), high lubricity, high heat stability/hydrolytic stability and high refrigerant miscibility, and can also satisfy other required performances has not be developed yet.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned technical problems. Therefore, an object of the present invention is to provide a refrigerating machine oil composition having excellent lubricity, refrigerant miscibility, heat stability/hydrolytic stability, electric insulating ability and other performances, and can achieve a high efficiency of a refrigerating system when it is used together with an HFC refrigerant or a natural refrigerant such as carbon dioxide and hydrocarbon.
As the results of intensive researches conducted by the present inventors to achieve the above described object, it is found that an excellent refrigerating machine oil composition having the above-mentioned various excellent performances can be obtained by using a base oil comprising a specific ester oil.
The refrigerating machine oil composition according to the present invention comprises an alicylic dicarboxylic acid ester compound having an alicyclic ring and two ester groups represented by formula (1) bonded to adjacent carbon atoms of the alicyclic ring:
—COOR
1
(1)
wherein R
1
represents an alkyl group having 1-18 carbon atoms. This alicyclic dicarboxylic acid ester compound is obtained by using an alcohol component comprising:
(a) at least one alcohol selected from a group consisting of fatty alcohols each having 1 to 5 carbon atoms; and
(b) at least one alcohol selected from a group consisting of fatty alcohols each having 6 to 18 carbon atoms.
The fatty alcohol in foregoing (a) is preferably:
(i) at least one alcohol selected from a group consisting of n-butanol and n-pentanol; or
(ii) at least one alcohol selected from a group consisting of iso-butanol and iso-pentanol.
Further, the fatty alcohol in the foregoing (b) is at least one alcohol selected from a group consisting of fatty alcohols preferably having 6 to 12 carbon atoms and more preferably having 7 to 9 carbon atoms.
Furthermore, the ratio (mole ratio) between the fatty alcohol (a) and fatty alcohol (b) employed as the alcohol component is preferably 1:99 to 99:1.
The refrigerating machine oil composition according to the present invention further preferably comprises an epoxy compound and/or a phosphorus compound. The epoxy compound is preferably at least one compound selected from a group consisting of phenylglycidyl ether epoxy compounds, glycidyl ester epoxy compounds, alicyclic epoxy compounds and epoxidized aliphatic acid monoesters, among which glycidyl ester epoxy compounds and/or alicyclic epoxy compounds are more preferable.
A fluid composition for refrigerating machines according to the present invention comprises the above-described refrigerating machine oil composition according to the present invention and a chlorine-free fluorocarbon.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.
DESCRIPTION OF THE PREFFERRED EMBODIMENTS
The best modes for carrying out the present invention. will be explained in detail hereinafter.
The alicylic dicarboxylic acid ester compound according to the present invention has an alicyclic ring and two ester groups represented by formula (1) bonded to adjacent carbon atoms of the alicyclic ring:
—COOR
1
(1)
wherein R
1
represents an alkyl group having 1-18 carbon atoms.
This alicyclic dicarboxylic acid ester compound is obtained by using an alcohol component comprising:
(a) at least one alcohol selected from a group consisting of fatty alcohols each having 1 to 5 carbon atoms; and
(b) at least one alcohol selected from a group consisting of fatty alcohols each having 6 to 18 carbon atoms.
Here, the examples of the alicyclic ring include cyclopentane ring, cyclopentene ring, cyclohexane ring, cyclohexene ring, cycloheptane ring, cycloheptene ring, etc., among which cyclohexane ring and cyclohexene ring are preferable. Further, cyclohexane ring is preferable since the rise of its viscosity is small in the use for a long term or
Hirano Hiroyuki
Shimomura Yuji
Suda Satoshi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Medley Margaret
Nippon Mitsubishi Oil Corporation
Toomer Cephia D.
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