Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Patent
1990-10-15
1993-06-22
Skane, Christine
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
252 54, 252 546, 252 67, C10M10554, C10M10738, C10N 4030
Patent
active
052214940
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a refrigerant composition. More particularly, the present invention relates to a lubricant-containing refrigerant composition suitable for use in a refrigeration system employing as a refrigerant a tetrafluoroethane, preferably HFC-134a (1,1,1,2-tetrafluoroethane), which is promising as a substitute for CFC-12 (1,1-dichloro-1,1-difluoromethane) with a viewpoint of environment protection.
BACKGROUND ART
At present, CFC-12 is mainly used as a refrigerant for car air conditioners and refrigerators. However, development of a refrigerant which can be used as a substitution for CFC-12 has been desired with a viewpoint of protection of the ozone layer.
HFC-134a as a refrigerant has properties similar to those of CFC-12, and it can be used as a substitute for CFC-12 with only minor changes of equipment being necessary. Likewise, HFC-134 (1,1,2,2-tetrafluoroethane), which is an isomer of HFC-134a, can also be used.
In a refrigeration system using CFC-12, mineral oil is used as a lubricant for a compressor. CFC-12 is miscible with mineral oil over a wide temperature range and therefore, even in the refrigeration system where evaporation and condensation of the refrigerant are repeated, phase separation of the refrigerant from the lubricant does not occur.
However, HFC-134a is not satisfactorily miscible with mineral oil. Therefore, when mineral oil is used, the mineral oil is replaced by the refrigerant, for example, in a compressor, causing various serious problems. For example, the lubrication becomes unsatisfactory and the lubricant adheres to the inner wall of a heat exchanger, leading to a lowering of the heat exchange efficiency.
The lubricant for a refrigerator using HFC-134a as the refrigerant should be miscible with HFC-134a at least over a temperature range of from 0.degree. to 50.degree. C., preferably over a wide temperature range of from -20.degree. to 70.degree. C., more preferably over a wider temperature range of from -40.degree. to 90.degree. C., and most preferably over a still wider temperature range.
The lubricant should have a kinetic viscosity of from 3 to 500 centistokes (hereinafter, frequently abbreviated as "cst") at 40.degree. C., preferably from 5 to 300 cst at 40.degree. C., more preferably from 5 to 170 cst at 40.degree. C., and most preferably form 10 to 150 cst at 40.degree. C., for exerting excellent lubricating performances.
Accordingly, development of a lubricant having a desired viscosity and being miscible with HFC-134a over a wide temperature range has been desired.
Various polyoxyalkylene glycol substances have been proposed as the lubricant to be used in combination with HFC-134a. Particularly, a polyoxyalkylene glycol having at least two hydroxyl groups (specifically, polyoxypropylene glycol), disclosed in the specification of U.S. Pat. No. 4,755,316, is taught to exhibit a good miscibility with HFC-134a over a wide temperature range. However, the temperature range over which this lubricant is miscible with HFC-134a is still unsatisfactory, and improvement of the miscibility, especially at high temperatures, is required.
Polyoxyalkylene glycols have not only unsatisfactory lubrication properties under application conditions, but also high moisture absorption properties and therefore, various problems are likely to arise with respect to, for example, the freezing of water, corrosion of metals, and lowering of the volume resistivity (such a lowering of the volume resistivity causes a problem in the case of a closed type freezer, such as a refrigerator). Accordingly, polyoxyalkylene glycols are not an excellent lubricant for a refrigeration system from a practical point of view.
A perfluoropolyether oil appears to be a lubricant miscible with HFC-134a which is a fluorine-containing compound.
Various perfluoroether oils having different structures can be mentioned. For example, there can be mentioned oils comprised mainly of recurring units, which may be either of a single type or of a plurality of types, represented by the fol
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Fukui Hiroyuki
Ikeda Masanori
Suzuki Yoshio
Asahi Kasei Kogyo Kabushiki Kaisha
Skane Christine
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