Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1998-07-09
2001-04-24
Einsmann, Margaret (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C252S067000, C062S114000, C510S408000, C510S410000, C510S411000, C510S412000
Reexamination Certificate
active
06221273
ABSTRACT:
The present invention relates to working fluids based on hydrofluorocarbons (HFC) as substitutes of CClF
2
-CClF
2
(R 114)
More particularly the present invention relates to binary and ternary azeotropic or near azeotropic mixtures to be used in combination with suitable lubricants as substitutes of R 114 (1, 2-dichlorotetrafluoroethane), environmental friendly, that is, completely inert towards the stratospehric ozone layer (ODP=0) and which are charaterized by a low global warming power (low GWP) and any how lower than that of R 114.
It is well known that R 114 was widely used as refrigerating fluid in circuits for the conditioning of buildings and especially as fluid for heat pumps for industrial applications with condensation temperatures up to 120° C. In this last application the refrigerating machine is used for heating; indeed the heat drawn from the evaporator, from a source whose temperature is lower than the desired one, is transferred at a higher temperature to the condenser, by means of a mechanical work carried out by the compressor.
The heat pumps allow, therefore, the recovery of thermal energy at a higher temperature by using energy sources at low temperature.
Since Jan. 1st, 1995 the production and commercialization of R 114, and in general of chlorofluorocarbons (CFC) have been banned for applications of this kind due to the high depleting potential on the ozone layer.
Therefore it is particularly felt the need to find other fluids able to replace R 114 in the above applications while respecting and protecting the environment. For this purpose the use of hydrofluorocarbons (HCFC) has been proposed, in which has thermodynamic characteristics similar to R 114 ones, but still showing the disadvantage of a destroying effect on the ozone layer. R 124 is considered a transition product and its use will be limited in the time, since subjected, as all the HCFCs, to regulation.
It is therefore evident the need to have an alternative fluid able to definitively overcome the still present environmental problems, even though in a more contained extent, by using HCFC type substitutes and able to give a definitive alternative to the substitution of R 114 both for applications on new equipments, and for the recovery of those existing.
The Applicant has unexpectedly and surprisingly found HFC-based azeotropic mixtures characterized by vapour pressure curves particularly suitable as substitutes of R 114 which have an environmental impact expressed in ODP terms equal to zero and very low GW values, which allow applications on new circuits and the economic recovery of the existing ones.
It is a remarkable advantage to have available azeotropic compositions since it allows to avoid the component segregation in binary and ternary systems, in practice a refrigerating fluid maintaining the same behaviour also in the case of leak is available. Indeed, in the case of non azeotropic mixtures, due to the different volatility of the components, there is segregation during the change from the liquid to the vapour phase or viceversa, with consequent variation of the evaporation and condensation temperature, so as to also sensibly compromise the efficiency of the thermal exchange and therefore the performances of the refrigerating circuit.
Moreover, due to often unavoidable leaks from the refrigerating plant, it is necessary to carry out the total substitution of the remaining fluid, in order to recover the initial performances (such as volumetric capacity and coefficient of performance (COP), vapour pressure, solubility with lubricants)).
Moreover, if the mixture contains more volatile flammable components, the vapour phase becomes rich in such a component until reaching the flammability limit, with evident dangers for the use safety.
Likewise, if the flammable component is less volatile, it concentrates in the liquid phase, giving a flammable liquid.
In order to avoid such drawbacks it is necessary to have available azeotropic mixtures.
It has been unexpectedly found that the azeotropic mixture has also a combination of performances which are particularly suitable to replace R 114.
The Applicant has also found that mixtures around the azeotrope have a near azeotropic behaviour, as defined hereinafter, and that therefore they too can be used as substitutes of R 114. A near azeotrope blend is a mixture of two or more fluids which has a vapour composition substantially equal to that of the liquid and undergoes phase changes without substantially modifying its composition and temperature.
An object of the present invention consists therefore in azeotropic or near azeotropic compositions based on hexafluoropropane (R 236) as substituents of R 114 which consist essentially of:
I)
1,1,1,2,3,3-hexafluoropropane (R 236ea)
15-95%
by wt.
bis (difluoromethyl)ether (RE 134)
5-85%
by wt.
II)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
30-90%
by wt.
bis (difluoromethyl)ether (RE 134)
10-70%
by wt.
III)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
90-98%
by wt.
n-butane (R 600)
2-10%
by wt.
IV)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
35-85%
by wt.
n-butane (R 600)
2-10%
by wt.
bis (difluoromethyl)ether (RE 134)
5-63%
by wt.
V)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
40-88%
by wt.
n-butane (R 600)
2-10%
by wt.
1,1,1,2,3,3-hexafluoropropane (R 236ea)
2-58%
by wt.
The azeotropes have the followinq compositions:
I)
1,1,1,2,3,3-hexafluoropropane (R 236ea)
54.9%
by wt.
bis (difluoromethyl)ether (RE 134)
45.1%
by wt.
II)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
65.2%
by wt.
bis (difluoromethyl)ether (RE 134)
34.8%
by wt.
III)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
94.1%
by wt.
n-butane (R 600)
5.9%
by wt.
IV)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
57.8%
by wt.
n-butane (R 600)
4.9%
by wt.
bis (difluoromethyl)ether (RE 134)
37.3%
by wt.
V)
1,1,1,3,3,3-hexafluoropropane (R 236fa)
81.6%
by wt.
n-butane (R 600)
3%
by wt.
1,1,1,2,3,3-hexafluoropropane (R 236ea)
15.4%
by wt.
An azeotrope is a particular blend having specific, unexpected and unforeseeable chemical physical properties, the most important are reported hereinafter. An azeotrope is a mixture of two or more fluids which has the same composition in the vapour and in the liquid phase. The azeotropic composition is defined by particular temperature and pressure values; in these conditions the mixtures undergo phase changes at a constant composition and temperature as though they were pure compounds.
A near azeotrope is mixture of two or more fluids having a vapour composition substantially equal to that of the liquid and undergoes phase changes without substantially modifying its composition and temperature. According to the present invention a composition is near azeotropic when, after evaporation at a constant temperature of 50% of the initial liquid mass, the per cent variation of the vapour pressure between that of the initial and that of the final composition results lower than about 10%. See on the matter the paper of Didion and D. B. Bivens in Int.J. Of Refrigeration, (vol.13, page 163, 1990).
In the case of an azeotrope no variation of the vapour pressure between that of the initial composition and that obtained after evaporation of 50% of the liquid is noticed.
The azeotropic or near azeotropic mixtures fall within the cases which show sufficiently positive or negative deviation from the Raoult's law valid for ideally behaving systems.
Deviations with respect to the ideality are caused by unexpected and unforeseeable intermolecular interactions among the components of the binary or ternary system such as to generate higher or lower interactions than those existing among the molecules of the pure products. When such deviations are sufficiently marked, the vapour pressure of the mixture in the azeotropic point is charaterized by either lower or higher values than that of the pure components.
It is evident that, if the mixture vapour pressure curve shows a maximum, this corresponds to a minimum of the boiling temperature; viceversa to a minimum value of the vapour pressure it corresponds a maximum of the boiling temperature.
There is a range of co
Basile Giampiero
Musso Ezio
Arent Fox Kintner & Plotkin & Kahn, PLLC
Ausimont S.p.A.
Einsmann Margaret
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