Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
1998-09-28
2002-11-26
Webb, Gregory E. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C252S067000
Reexamination Certificate
active
06486114
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to azeotrope-like or essentially constant-boiling mixtures of pentafluoropropane and a perfluorinated fluorocarbon having 5 to 7 carbon atoms or N-methylperfluoromorpholine or N-ethylperfluoromorpholine. These mixtures are useful as refrigerants for heating and cooling.
BACKGROUND OF THE INVENTION
Fluorocarbon based fluids have found widespread use in industry for refrigeration applications such as air conditioning and heat pump applications.
Vapor compression is one type of refrigeration. In its simplest form, vapor compression involves changing the refrigerant from the liquid to the vapor phase through heat absorption at a low pressure and then from the vapor to the liquid phase through heat removal at an elevated pressure.
While the primary purpose of refrigeration is to remove energy at low temperature, the primary purpose of a heat pump is to add energy at higher temperature. Heat pumps are considered reverse cycle systems because for heating, the operation of the condenser is inter-changed with that of the refrigeration evaporator.
Certain chlorofluoromethane and chlorofluoroethane derivatives have gained widespread use in refrigeration applications including air conditioning and heat pump applications owing to their unique combination of chemical and physical properties. The majority of refrigerants utilized in vapor compression systems are either single components fluids or azeotropic mixtures. Moreover, certain applications, such as centrifugal chillers, can only use pure or azeotropic refrigerants, since non-azeotropic mixtures will separate in pool boiling evaporators, causing undesirable performance.
Azeotropic or azeotrope-like compositions are desired because they do not fractionate upon boiling. This behavior is desirable because in the previously described vapor compression equipment with which these refrigerants are employed, condensed material is generated in preparation for cooling or for heating purposes. Unless the refrigerant composition exhibits a constant boiling point, i.e. is azeotrope-like, fractionation and segregation will occur upon evaporation and condensation and undesirable refrigerant distribution may act to upset the cooling or heating. If a leak occurs in a refrigeration system during use or service the composition of the azeotrope-like mixture does not change and thus, system pressures and system performance remain unaffected.
The art is continually seeking new fluorocarbon based azeotrope-like mixtures which offer alternatives for refrigeration and heat pump applications. Currently, of particular interest, are fluorocarbon based azeotrope-like mixtures which are considered to be environmentally safe substitutes for the presently used fully halogenated chlorofluorocarbons (CFC's), such as trichlorofluoromethane (R-11), which are suspected of causing environmental problems in connection with the earth's protective ozone layer.
The substitute materials must also possess those properties unique to the CFC's including chemical stability, low toxicity, non-flammability, and efficiency in-use. The latter characteristic is important in refrigeration and air-conditioning especially where a loss in refrigerant thermodynamic performance or energyefficiency may have secondary environmental impacts through increase fossil fuel usage arising from an increased demand for electrical energy. Furthermore, the ideal CFC refrigerant substitute would not require major engineering changes to conventional vapor compression technology currently used with CFC refrigerants.
Mathematical models have substantiated that hydro-fluorocarbons, such as pentafluoropropane, including 1,1,2,2,3-pentafluoropropane (HFC-245ca), 1,1,2,3,3-pentafluoropropane (HFC-245ea), 1,1,1,2,3-pentafluoropropane (HFC-245eb) and 1,1,1,3,3,-pentafluoropropane (HFC-245fa) will not adversely affect atmospheric chemistry, because they are a negligible contributor to ozone depletion and to green-house global warming in comparison to the fully halogenated species.
However, HFC-245eb has been found to have flame limits under normal ambient conditions, and HFC-245ca has been found to have flame limits under humid conditions, but not under dry conditions. It has not been confirmed whether or not other pentafluoropropane isomers also exhibit some finite flame propagation behavior in specific, but yet undetermined, environments. This flame propagation behavior would significantly limit the potential use of the pentafluoropropane isomer as an R-11 replacement in chiller applications.
SUMMARY OF THE INVENTION
In accordance with the present invention, novel mixtures have been discovered comprising pentafluoropropane and a perfluorocarbon having 5 to 7 carbon atoms or N-methylperfluoromorpholine or N-ethylperfluoromorpholine. Also, novel azeotrope-like compositions have been discovered comprising pentafluoropropane and a perfluorocarbon selected from the group consisting of perfluoropentane, perfluorohexane and perfluoroheptane or N-methylperfluoromorpholine or N-ethylperfluoromorpholine.
Preferably, the novel azeotrope-like compositions comprise effective amounts of pentafluoropropane and a perfluorocarbon having 5 to 7 carbon atoms or N-methylperfluoromorpholine or N-ethylperfluoromorpholine. The term “effective amounts” as used herein means the amount of each component which upon combination with the other component, results in the formation of the present azeotrope-like compositions.
The preferred, more preferred and most preferred embodiments for each azeotrope-like composition of the invention are set forth in Table I below. The numerical ranges, boiling point and pressures are understood to be prefaced by “about”.
TABLE 1
MORE
MOST
PREF.
PREF.
PREF.
BOILING
RANGE
RANGE
RANGE
POINT
COMPONENTS
(WT. %)
(WT.%)
(WT.%)
(° C.)
HFC-245ca
90-50
80-50
70-50
perfluoro-
10-50
20-50
30-50
18
pentane
HFC-245ca
90-50
80-50
70-50
perfluoro-hexane
10-50
20-50
30-50
23
HFC-245ca
99-75
95-80
90-80
perfluoro-heptane
1-25
5-20
10-20
25
HFC-245ca
99-75
95-80
90-80
N-ethyl-perfluoro
1-25
5-20
10-20
25
morpholine
HFC-245fa
99-50
90-60
85-70
perfluoro-pentane
1-50
10-40
15-30
10
HFC-245fa
99-50
95-50
90-60
perfluoro-hexane
1-50
5-50
10-40
15
HFC-245eb
99.90-80
99.9-85
perfluoro-heptane
0.1-20
0.1-15
22
HFC-245eb
90-30
80-40
70-50
perfluoro-pentane
10-70
20-60
30-50
15
HFC-245eb
99-50
90-60
85-70
perfluoro-hexane
1-50
10-40
15-30
21
HFC-245ea
99.9-65
99-70
90-75
N-methylperfluoro-
0.1-35
1-30
10-25
36
morpholine
HFC-245ea
99.9-75
99-80
95-85
N-ethylperfluoro-
0.1-25
1-20
5-15
36.5
morpholine
All compositions within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.
The precise azeotropic compositions have not been determined but have been ascertained to be within the above ranges. Regardless of where the true azeotropes lie, all compositions within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.
Moreover, these compositions were determined to be nonflammable in air at ambient conditions using the ASTM E-681 method as specified in the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 34-1992.
Because the present novel compositions exhibit essentially constant-vapor pressure characteristics as the liquid mixture is evaporated and show relatively minor shifts in composition during evaporation, the present compositions are advantageous in a vapor compression cycle as they mimic the performance of a constant-boiling single component or azeotropic mixture refrigerant.
From fundamental principles, the thermodynamic state of a fluid is defined by four variables: pressure, temperature, liquid composition and vapor composition, or P-T-X-Y, respectively. An azeotrope is a unique characteristic of a system
Lund Earl A. E.
Lund Hilde
Nalewajek David
Wilson David P.
Electric Power Research Institute Inc.
Lund Hilde
Peters Howard M.
Peters, Verny, Jones & Schmitt, L.L.P.
Webb Gregory E.
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