Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1995-10-04
2003-06-24
Diamond, Alan (Department: 1753)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C252S067000, C508S485000, C508S495000
Reexamination Certificate
active
06582621
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lubricating oil for compressors of refrigerators using therein a hydrogen-containing halogenocarbon as a refrigerant (the oil being hereinafter referred to as “a refrigerator oil for use with a hydrogen-containing halogenocarbon refrigerant”) and, more specifically, it relates to such a refrigerator oil which comprises a specific ester as a base oil and is superior in various properties.
2. Prior Art
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° 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, hydrogen-containing halogenocarbons, such as HFC-134a and HFC-152a, have been being 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.
Refrigerator oils require various properties, among which their compatibility with refrigerants is extremely important in regard to lubricity and system efficiency in refrigerators. However, conventional refrigerator oils comprising, as the base oils, naphthenic oils, paraffinic oils, alkylbenzenes, heretofore known ester oils and the like, are hardly compatible with hydrogen-containing halogenocarbons such as HFC-134a. Therefore, if said conventional refrigerator oils are used in combination with HFC-134a, the resulting mixture will separate into two layers at normal temperature so as to degrade the oil-returnability which is the most important within the refrigeration system and cause various troubles such as a decrease in refrigeration efficiency, the deterioration of lubricity and the consequent seizure of the compressor within the system whereby the refrigerator oils are made unsuitable for use as such. In addition, polyglycolic oils are also known as refrigerator oils for their high viscosity index and are disclosed in, for example, JP-A-57-42119 and JP-A-61-52880 and JP-A-57-51795. However, the polyglycolic oils disclosed in these prior art publications are not fully compatible with HFC-134a thereby raising the same problems as above and rendering them unusable.
Further, U.S. Pat. No. 4,755,316 discloses polyglycolic refrigerator oils which are compatible with HFC-134a and U.S. Pat. No. 4,851,144 discloses refrigerator oils comprising a mixture of an ester and a polyglycol which are compatible with HFC-134a. In addition, the present inventors developed polyglycolic refrigerator oils which have excellent compatibility with HFC-134a as compared with conventional known refrigerator oils, filed an application for a patent for the thus developed polyglycolic refrigerator oils and have already obtained a patent (U.S. Pat. No. 4,948,525) therefor. It has been found, however, that the polyglycolic oils raise problems as to their high compatibility with water and inferior electrical insulating property.
On the other hand, refrigerator oils used in compressors of home refrigerators and the like are required to have a high electrical insulating property. Among the known refrigerator oils, alkylbenzenes and the mineral oils have the highest insulating property, but they are hardly compatible with hydrogen-containing halogenocarbons such as HFC-134a as mentioned above. WO 90/12849 describes a composition comprising a hydrogen-containing halogenocarbon and a specific ester lubricant. Therefore, no refrigerator oil having both high compatibility with hydrogen-containing halogenocarbons such as HFC-134a and a high insulating property has been developed prior to the present invention.
SUMMARY OF THE INVENTION
The present inventors made various intensive studies in attempts to develop refrigerator oils which can meet the aforesaid requirements and, as the result of their studies, they found that esters having specific structures have excellent compatibility with hydrogen-containing halogenocarbons such as HFC-134a, and a high electrical insulating property as well as excellent lubricity. This invention is based on this finding.
The object of this invention is to provide refrigerator oils for use with hydrogen-containing halogenocarbons refrigerants, the oils comprising as a major component (or a base oil) at least one kind of ester having a specific structure and an epoxy compound and having excellent compatibility with hydrogen-containing halogenocarbons such as HFC-134a, high electrical insulating property, high wear resistance, low hygroscopicity, and high thermal and chemical stability.
The present invention provides a refrigerator oil for use in compressors using therein a hydrogen-containing halogenocarbon as a refrigerant, consisting essentially of as a base oil at least one ester selected from the group consisting of:
[I] a pentaerythritol ester represented by the general formula (1)
wherein R
1
-R
4
may be identical with or different from each other and are each selected from the group consisting of straight-chain alkyl groups having 3 to 11 carbon atoms, branched-chain alkyl groups having 3 to 15 carbon atoms and cycloalkyl groups having 6 to 12 carbon atoms, the straight-chain alkyl groups being present in a ratio of not more than 60% of the total alkyl groups, and a is an integer of 1 to 3;
[II] a polyol ester represented by the general formula (2)
wherein R
5
-R
7
may be identical with or different from each other and are each selected from the group consisting of straight-chain alkyl groups having 3 to 11 carbon atoms, branched-chain alkyl groups having 3 to 15 carbon atoms and cycloalkyl groups having 6 to 12 carbon atoms, the straight-chain alkyl groups being present in a ratio of not more than 60% of the total alkyl groups, R
8
is selected from the group consisting of methyl, ethyl and propyl groups, and b is an integer of 1 to 3;
[III] an ester represented by the general formula (3)
wherein X
1
is a group represented by the general formula —OR
11
or
X
2
is a group represented by the general formula
R
9
and R
15
are each a divalent hydrocarbon group having 1 to 8 carbon atoms, R
10
and R
12
are each a divalent saturated hydrocarbon group having 2 to 16 carbon atoms, R
11
and R
16
are each a branched-chain alkyl group having 3 to 15 carbon atoms, R
13
and R
14
are each a branched-chain alkyl group having 3 to 14 carbon atoms, c and e are each an integer of 0 or 1 and d is an integer of 0 to 30; and
[IV] a polyol ester obtained by the synthesis of, as raw materials, (a) a neopentyl type polyhydric alcohol having 5 to 6 carbon atoms and 3 to 4 hydroxyl groups, (b) a straight-chain monocarboxylic acid and/or a branched-chain monocarboxylic acid, the branched-chain monocarboxylic acid being present in a ratio of not less than 50 mol % of the total monocarboxylic acids, (c) a dicarboxylic acid: and further comprising at least one epoxy compound.
First, the pentaerythritol esters [I] will be explained in detail. In the formula (1), R
1
-R
4
may be identical with, or different from, each other and are each a group selected from the group consisting of straight-chain alkyl groups having 3-11 carbon atoms, preferably 3-7 carbon atoms, branched-chain alkyl groups having 3-15 carbon atoms, preferably 4-11 carbon atoms and cycloalkyl groups having 6-12 carbon atoms, preferably 6-8 carbon atoms. The cycloalkyl groups in this invention may include alkylcycloalkyl groups. In ad
Hasegawa Hiroshi
Ishida Noboru
Ishikawa Tatsuyuki
Sasaki Umekichi
Bucknam and Archer
Diamond Alan
Nippon Mitsubishi Oil Corporation
LandOfFree
Refrigerator oils for use with chlorine-free fluorocarbon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Refrigerator oils for use with chlorine-free fluorocarbon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Refrigerator oils for use with chlorine-free fluorocarbon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3156537