Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1999-08-20
2001-05-08
Einsmann, Margaret (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C252S067000
Reexamination Certificate
active
06228282
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 polycarboxylic acid ester compound and a specific epoxy 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, refrigerant miscibility, heat stability/hydrolysis resistance, 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 hydrolysis resistance.
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 hydrolysis resistance.
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 hydrolysis resistance. However, even the ester having this structure has not sufficient heat stability and hydrolysis resistance when the viscosity thereof is lowered.
Further, it is generally known that hydrolysis resistance can be improved by incorporating an acid scavenger into an ester refrigerating machine oil. However, the majority of acid scavengers used in conventional ester refrigerating machine oils have substantially no effect or insufficient effect on alicyclic polycarboxylic acid esters.
Therefore, an ester refrigerating machine oil that has both low viscosity for obtaining a high efficiency and high heat stability/hydrolysis resistance, 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/hydrolysis resistance, 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 performances can be obtained by blending a specific epoxy compound into a base oil containing a specific ester oil.
The refrigerating machine oil composition according to the present invention comprises:
(A) an alicylic polycarboxylic acid ester compound having an alicyclic ring and at least two ester groups represented by formula (1) bonded to adjacent carbon atoms of the alicyclic ring:
—COOR
1
(1)
wherein R
1
represents a hydrocarbon group having 1-30 carbon atoms, and R
1
of each of the ester groups may be the same or different from each other; and
(B) at least one epoxy compound selected from the group consisting of glycidyl ester epoxy compounds and alicyclic epoxy compounds.
The alicylic polycarboxylic acid ester compound has preferably two ester groups represented by the formula (1). Further, the refrigerating machine oil composition according to the present invention preferably further comprises a phosphorus compound.
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.
DESCRIPTION OF THE PREFFERRED EMBODIMENTS
The best modes for carrying out the present invention will be explained in detail hereinafter.
The alicylic polycarboxylic acid ester compound according to the present invention has an alicyclic ring and at least two ester groups represented by formula (1) bonded adjacent carbon atoms of the alicyclic ring:
—COOR
1
(1)
wherein R
1
represents a hydrocarbon group having 1-30 carbon atoms, and R
1
of each of the ester groups may be the same or different from each other.
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 under severe conditions, whereas cyclohexene ring is preferable since the rise of its total acid value is small in the use for a long term or under severe conditions.
In addition to the alicyclic ring, the alicyclic polycarboxylic acid ester compound must have at least two ester groups represented by formula (1). The carboxylic acid ester compound only having one ester group is not preferable since its miscibility with the refrigerant and heat stability/hydrolysis resistance are insufficient. Further, there is no particular restriction on the number of the ester groups, however, when taking into consideration the low temperature fluidity, the carboxylic acid ester compound has preferably 4 or less, more preferably 3 or less, and the most preferably 2 ester groups.
Further, the at least two ester groups represented by formula (1) must be bonded to adjacent carbon atoms of the alicyclic ring. The carboxylic acid ester compound, wherein the ester groups are not bonded to adjacent carbon atoms of the alicyclic ring, is not preferable since its heat stability/hydrolysis resistance is insufficient.
There is no particular restriction on the stereo configuration of the ester groups. For example, if the carboxylic acid ester compound has two ester groups represented by formula (1), these two ester groups may be in cis- or trans-form. However, when consideration is given to heat stability and hydrolysis resistance, cis-form is preferable, whereas when consideration is given to both heat stability/hydrolysis resistance and lubricity, trans-form is preferable.
R
1
in formula (1) is a hydrocarbon group having 1-30, preferably 2-24 and more preferably 3-18carbon atoms. The hydrocarbon group mentioned here includes alkyl groups, alkenyl groups, cycloalk
Hirano Hiroyuki
Shimomura Yuji
Suda Satoshi
Einsmann Margaret
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Nippon Mitsubishi Oil Corp.
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