Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2001-03-01
2002-06-25
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C252S068000, C508S304000
Reexamination Certificate
active
06410492
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a lubricating oil for heat transfer devices (the oil being hereinafter referred to as “a refrigerator oil”) and, more specifically, it relates to a refrigerator oil having a number of satisfactory and well-balanced performances including lubricity, hydrolysis resistance, heat stability, refrigerant miscibility, electric insulating ability and the like.
BACKGROUND ART
Owing to the restriction of fluorocarbons for preventing ozone layer destruction, efforts are being made to replace chlorine-containing fluorocarbon refrigerant such as CFC-11, CFC-12, HCFC-22 or the like used in refrigerating and air conditioning machines with chlorine-free fluorocarbon refrigerants such as HFC-32, HFC-125, HFC-134a or the like. Since naphthenic oils or paraffinic oils that have been conventionally used as refrigerator oils have not satisfactory refrigerant miscibility, which is one of the requisite performances of a refrigerator oil, when a chlorine-free fluorocarbon refrigerant is used, the researches have been executed to use ester oils instead of naphthenic or parafinic oils. Such ester oil-containing refrigerator oils (referred to as “ester refrigerator oil(s)” hereinafter) are disclosed, for example, in National Publication No. Hei 3-505602 (JP-A 3-505602) of International Publication for Patent Application and Japanese Patent Kokai (Laid-Open) Publication No.3-128992 (JP-A 3-128992).
In addition to the refrigerant miscibility, the refrigerator oils are required to have a number of performances including lubricity, hydrolysis resistance, heat stability, electric insulating ability and the like. However, an ester refrigerator oil having all the above-mentioned performances which are satisfactory and well-balanced has not developed heretofore.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned technical problems, namely, to develop an excellent ester refrigerator oil having all requisite performances including refrigerant miscibility, lubricity, hydrolysis resistance, heat stability, electric insulating ability and the like. Accordingly, an object of the present invention is to provide a refrigerator oil having all the above-mentioned performances which are achieved in good balance.
As a results of the intensive researches conducted by the present inventors to attain the above described object, it is found that an excellent refrigerator oil having the above-mentioned various performances can be obtained by using a specific ester oil as the base oil.
The refrigerator oil according to the present invention comprises an ester obtained from:
pentaerythritol; and
a carboxylic acid mixture comprising n-pentanoic acid in an amount of 20 to 50% by mass; n-heptanoic acid in an amount of 20 to 50% by mass and 3,5,5-trimethylhexanoic acid in an amount of 5 to 60% by mass, of the total amount of the carboxylic acid mixture.
In the refrigerator oil according to the present invention, the contents of n-pentanoic acid, n-heptanoic acid and 3,5,5-trimethylhexanoic acid are preferably within ranges of 25 to 45% by mass, 25 to 45% by mass and 10 to 50% by mass, respectively.
The refrigerator oil 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 phenylglycidyl ether epoxy compounds and/or glycidyl ester epoxy compounds are more preferable.
A fluid composition for refrigerators according to the present invention comprises the above-described refrigerator oil according to the present invention and a chlorine-free fluorocarbon.
BEST MODE FOR CARRYING OUT THE INVENTION
The best modes for carrying out the present invention will be explained in detail hereinafter.
The refrigerator oil according to the present invention comprises an ester (hereinafter referred to as “specificester”) obtained from pentaerythritol and a carboxylic acid mixture comprising n-pentanoic acid in an amount of 20 to 50% by mass; n-heptanoic acid in an amount of 20 to 50% by mass and 3,5,5-trimethylhexanoic acid in an amount of 5 to 60% by mass, of the total amount of the carboxylic acid mixture.
Taking into particular consideration the miscibility with the refrigerant, the content of n-pentanoic acid in the carboxylic acid mixture is not less than 20% by mass, more preferably not less than 25% by mass and further more preferably not less than 30% by mass, of the total amount of the carboxylic acid mixture. On the other hand, taking into particular consideration the hydrolysis resistance, the content of n-pentanoic acid in the carboxylic acid mixture is not more than 50% by mass, preferably not more than 45% by mass, more preferably not more than 40% by mass, and further more preferably not more than 35% by mass, of the total amount of the carboxyl acid moisture.
Further, taking into particular consideration the lubricity, the content of n-heptanoic acid in the carboxylic acid mixture is not less than 20% by mass, preferably not less than 25% by mass and more preferably not less than 30% by mass, of the total amount of the carboxyl acid mixture. On the other hand, taking into particular consideration the hydrolysis resistance, the content of n-heptanoic acid in the carboxylic acid mixture is not more than 50% by mass, preferably not more than 45% by mass, more preferably not more than 40% by mass and further more preferably not more than 35% by mass, of the total amount of the carboxyl acid mixture.
Further, taking into particular consideration of the hydrolysis resistance, the content of 3,5,5-trimethylhexanoic acid in the carboxylic acid mixture is not less than 5% by mass, preferably not less than 10% by mass and more preferably not less than 15% by mass, of the total amount of the carboxyl acid mixture. On the other hand, taking into particular consideration the miscibility with the refrigerant and the lubricity, the content of 3,5,5-trimethylhexanoic acid in the carboxylic acid mixture is not more than 60% by mass, preferably not more than 50% by mass, more preferably not more than 40% by mass and further more preferably not more than 30% by mass, of the total amount of the carboxyl acid mixture.
The specific ester according to the present invention may be a partial ester wherein a part of hydroxyl groups of pentaerythritol remain un-esterified, whereas a complete ester wherein all the hydroxyl groups of pentaerythritol are esterified is preferable. Further the specific ester according to the present invention may be a mixture of a partial ester and a complete ester.
There is no particular limit in respect to the content of the specific ester in the refrigerator oil according to the present invention, but in order to attain all the well-balanced requisite performances including refrigerant miscibility, lubricity, hydrolysis resistance, heat stability, electric insulating ability and so on, the content of the specific ester is preferably not less than 50% by mass, more preferably not less than 70% by mass, further more preferably not less than 80% by mass and most preferably less than 90% by mass, of the total amount of the refrigerator oil.
The refrigerator oil according to the present invention is an oil comprising the above-described specific ester, whereas it may be used in combination with a hydrocarbon oil such as mineral oils, olefin polymers, naphthalene compounds or alkylbenzenes; or an oxygen-containing synthetic oil such as polyglycols, polyvinyl ethers, ketones, polyphenyl ethers, silicone, polysiloxanes, perfluoro ethers or esters other than the above-described specific esters. The preferable ones among the above-listed oxygen-containing synthetic oils are polyglycols, polyvinyl ethers and ketones.
The refrigerator oil according to the present invention comprising the specific ester and, if required, the hydrocarbon oil and/or the o
Hirano Hiroyuki
Shimomura Yuji
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
McAvoy Ellen M.
Nippon Mitsubishi Oil Corporation
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