Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1994-03-24
2001-05-22
Einsmann, Margaret (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C252S067000, C062S114000
Reexamination Certificate
active
06235215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluorocarbon refrigerant used as a working fluid medium in a refrigerator and other refrigeration cycles. More particularly, the present invention relates to a so-called “Freon (Fron) substitute” containing no chlorine or bromine. The Freon substitute disclosed herein is a mixed refrigerant of fluorocarbons which is able to obtain a refrigeration temperature of −30° C. or less.
2. Discussion of Background Information
Chlorofluorocarbons (CFC) have been widely used as the working fluid medium in various refrigeration cycles such as, for example, a refrigerator. However, it was recently found that CFC can damage the ozone layer of the earth. Also, to preserve the environment of the earth, each country has established its own regulations and schedules of regulations to inhibit and/or control the use of specified Freons including CFC in accordance with the provisions of international conventions. In addition to the control of specified Freons, research and development for providing a Freon substitute which does not contain chlorine, i.e., the detrimental substance which causes ozone layer damage, are being carried out in a great many companies and institutes. Moreover, as a result of recent studies, the ozone layer damage caused by the specified Freons was noted to be a very important and severe problem which must be promptly solved, and accordingly each country started to practice the established regulations earlier than scheduled.
On the other hand, Freon 502 (azeotropic mixture of HClF
2
and C
2
ClF
5
) and Freon 13B1 (CBrF
3
) are known to obtain a refrigeration temperature of −30° C. or less. However, both of these Freons cannot be used or are listed high on the schedule of regulations, because they contain chlorine or bromine. A Freon substitute (HFC) having an evaporation temperature (boiling point) of −30° C. or less has not yet been developed.
SUMMARY OF THE INVENTION
In view of the above-described technical background, one object of the present invention is to provide a novel refrigerant which does not contain chlorine or bromine, and which can obtain a refrigeration temperature of −30° C. or less.
According to the present invention, the above object can be attained by a mixed fluorocarbon refrigerant which is characterized by containing Freon 134a (namely, 1,1,1,2-tetrafluoroethane; CH
2
FCF
3
) and Freon 23 (namely, trifluoromethane; CHF
3
).
Note that the present invention was made as a result of careful and thorough studies concerning the combined use of two or more fluorocarbons which contain hydrogen, but are free from chlorine and bromine, to thereby obtain a Freon working fluid medium having a boiling point of −30° C. or less.
The present disclosure relates to subject matter contained in Japanese patent application No. 04-48704 (filed on Mar. 5, 1992) which is expressly incorporated herein by reference in its entirety.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The fluorocarbon refrigerant according to the present invention, as mentioned above, comprises two types of fluorocarbons or Freons. One Freon is Freon 134a, having a boiling point of −26.3° C. Another Freon is Freon 23, having a boiling point of −82.0° C. A mixture of these Freons is a non-azeotropic mixture. It should be noted, however, that the non-azeotropic mixture of Freon 134a and Freon 23 can provide a boiling point (refrigeration temperature) of −30° C. or less. The term “refrigeration temperature” used herein means the temperature typically occurring in a refrigerator or other machine.
Surprisingly, although a detailed mechanism thereof has not yet been clarified, it was noted that the boiling point of −30° C. or less can always be obtained, even if Freon 134a is mixed with a very small quantity of Freon 23.
The fluorocarbon refrigerant according to the present invention contains preferably 60 to 95% by weight of Freon 134a and 5 to 40% by weight of Freon 23. The preferred compositions should have a when the boiling point of −40° C. or less.
As described above, Freon 134a is preferably used in a mixing ratio of 60 to 95% by weight of the refrigerant to obtain the boiling point of −40° C. or less. If its mixing ratio exceeds 95% by weight, namely, if an amount of Freon 23 is used which is less than 5% by weight, it becomes difficult to obtain a stable refrigeration temperature of −40° C. or less. And, if the mixing ratio of Freon 23 exceeds 40% by weight, namely, if an amount of Freon 134a is used which is less than 60% by weight, the discharging pressure of the refrigerator or compressor might increase excessively. To avoid problems due to increased pressure, it is necessary to use a specially designed compressor. Note, if it is desired to obtain a refrigeration temperature of −45° C. or less without excessive increase in pressure, it is preferred to combine 80±5% by weight of Freon 134a and 20±5% by weight of Freon 23. Preferably, the best results will be obtained when 76±2% by weight of Freon 134a is combined with 24±2% by weight of Freon 23.
The mixed fluorocarbon refrigerant of the present invention may contain at least one additive selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons and aromatic hydrocarbons. These additions to further reduce the refrigeration temperature and also reduce, rather than increase, the discharge pressure.
The saturated hydrocarbons used herein as an additive are generally represented by the formula: C
n
H
2n+2;
wherein n represents an integer, and typical examples thereof include methane, ethane, propane, butane, pentane and isopentane. Preferably, isopentane is used as the additive. Moreover, very good results will be obtained if a refrigerant additive of high molecular weight hydrocarbons, trade name “SDG” commercially available from Daiei Yakuhin Kogyo Kabushiki Kaisha, is used herein.
The unsaturated hydrocarbons used herein are generally represented by the formula: C
n
H
2n
; wherein n is as defined above, and typical examples thereof include ethylene, propylene, butylene and pentene. Preferably, pentene is used.
The aromatic hydrocarbons used herein include, for example, benzene, toluene and ethylbenzene.
It was found that these hydrocarbon additives can increase the mixability of Freon 134a and Freon 23, further reduce the boiling point of the resultant refrigerant, and also reduce the discharging temperature of the machine.
The hydrocarbon additives could be added to either one of or both the refrigerant mixture or a refrigerator oil. By adding these additives to the refrigerator oil, it becomes possible to prevent sludge formation because of a high solubility of the additives in the oil. Accordingly stable operation of the refrigerator can be attained for a long period of time. It was also found that recycling of the oil was improved.
The isopentane additive can be present in the refrigerant in an amount of about 1.4 to 50.7 percent by weight of the total weight of the refrigerant. In this regard, the additive(s) can be present in an amount of at least about 7 percent by weight of the total weight of the refrigerant, and still yet in an amount of at least about 14 percent by weight of the total weight of the refrigerant.
The amount of additives, when added to a refrigerator oil, is preferably 1 to 30% and more preferably 3 to 30% by weight with regard to the amount of the oil. An amount less than 1% by weight is not enough to give an advantageous effect on the refrigerator oil, and also it does not cause a significant change in the refrigeration capacity of the refrigerator. Contrary to this, when the amount of the additives exceeds 30% by weight, both the compression rate and refrigeration capacity tend to be reduced.
The present invention will be further described with reference to working examples thereof. Note that Freon 134a and Freon 23 used herein each have the following physical properties, and as is appare
Seino Toshio
Yosioka Masanov
Dairei Co. Ltd.
Einsmann Margaret
Greenblum & Bernstein P.L.C.
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