Compositions – Vaporization – or expansion – refrigeration or heat or energy...
Reexamination Certificate
1998-03-26
2001-08-07
Ogden, Necholus (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
C062S114000, C510S410000
Reexamination Certificate
active
06270689
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to compositions which may be used in place of chlorofluorocarbons (CFCs) and/or hydrochlorofluorocarbons (HCFCs) in various applications. The compositions of the invention may also be used partially or entirely in place of hydrofluorocarbons (HFCs). More particularly, the present invention is directed to compositions comprising blends of trifluoroiodomethane, 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane, and the use of such compositions for providing refrigeration.
BACKGROUND OF THE INVENTION
Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and/or blends containing these compounds have conventionally been used as refrigerants, solvents, foam blowing agents, propellants and the like. However, because of their high chemical stability and long atmospheric lifetimes, such compounds, when released to the atmosphere, migrate to the stratosphere where they undergo photolysis and deplete the earth's protective ozone layer. CFCs particularly contribute to depletion of the ozone layer, with the HCFCs depleting the ozone layer to a lesser extent. As a result, production of CFCs and HCFCs has been and continues to be severely limited and is scheduled for phase out in many industrialized and non-industrialized countries.
Accordingly, a need exists to develop materials which can be used as efficient and economical substitutes for CFC and/or HCFCs in a wide variety of applications, including refrigeration, solvent use (for example in chemical manufacturing and solvent cleaning applications), polymer foam blowing, and propulsion (for example, aerosol propellants), and the like. The Nimitz et al U.S. Pat. Nos. 5,444,102, 5,562,861, 5,605,647 and 5,611,210 broadly disclose blends of fluoroiodocarbon compounds and various additives as substitutes for CFCs, HCFCs and/or Halons. The fluoroiodocarbon blends of Nimitz et al are disclosed as advantageous for use in a variety of applications, including refrigeration, solvent cleaning, foam blowing, aerosol propulsion and firefighting, owing to the desirable combinations of properties provided by such blends. For example, the blends are disclosed as nonflammable, non-toxic and environmentally benign in having zero ozone depletion potentials, low global warming potentials and negligible atmospheric and terrestrial environmental impacts.
While the compositions broadly disclosed by Nimitz et al are useful in a variety of applications, a need still exists for developing compositions with a particular combination of properties for more specific applications. For example, in the refrigeration area, suitable replacements for CFCs, HCFCs and/or HFCs must be non-flammable and unreactive and substantially non-fractioning over a wide range of temperatures, for example from about −98° C. to about 90° C., or even wider. While the majority of residential, commercial and institutional refrigeration devices operate in the range of from about −23° C. to about 8° C., and in extraordinary cases, higher temperatures may be experienced. Thus, suitable compositions for refrigeration must not significantly fractionate or change composition over these temperature ranges to avoid becoming flammable. Additionally, for compositions to be suitable refrigerant replacements for CFCs, HCFCs and/or HFCs, the compositions must exhibit good miscibility with refrigeration lubricants such as polyol ester lubricants. Further, in order for a composition to adequately serve as a replacement for CFCs, HCFCs and/or HFCs, the substitute compositions must be effective under the operating conditions of conventional refrigeration equipment, thereby serving as “drop in” replacements for CFCs, HCFCs and/or HFCs or “near drop in” replacements for such materials, requiring only minor changes in lubricant, equipment, for example expansion valves, or the like. In view of this combination of necessary properties, a need still exists for further development of suitable replacement materials, particularly for refrigeration applications.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide new compositions, and particularly compositions which may be used in place of conventionally employed CFCs and/or HCFCs in one or more applications. It is a further object of the invention to provide fluoroiodocarbon-containing compositions which may be used as replacements for CFCs and/or HCFCs. It is an additional object to provide fluoroiodocarbon-containing compositions which may be used to partially or fully replace hydrofluorocarbon (HFC) compositions. It is yet a further object to provide compositions which are suitable for providing refrigeration and to provide refrigeration methods employing such compositions.
These and additional objects are provided by the compositions and methods of the present invention. Broadly, the present invention is directed to compositions comprising blends of trifluoroiodomethane, 1,1,1,2-tetrafluoroethane, and 1,1-difluoroethane, and to methods employing such compositions for providing refrigeration. The compositions of the invention exhibit an advantageous combination of physical properties which allow the compositions to be economically and efficiently useful for, inter alia, providing refrigeration. More specific embodiments of the compositions and methods of the invention, and further advantages thereof, will be apparent in view of the following detailed description.
DETAILED DESCRIPTION
The compositions of the present invention comprise blends of trifluoroiodomethane, 1,1,1,2-tetrafluoroethane (commonly referred to as HFC-134a) and 1,1-difluoroethane (commonly referred to as HFC-152a). It has been determined that compositions comprising blends of these three specific compounds are particularly advantageous for use in refrigeration applications. In a preferred embodiment, the compositions comprise blends of from about 25 mol percent to about 45 mol percent trifluoroiodomethane and a balance of 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane. In a further preferred embodiment, the balance of 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane comprises equal molar amounts of the two compounds 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane.
In an alternate embodiment, the compositions of the invention are directed to blends of from about 25 mol percent to about 45 mol percent trifluoroiodomethane, from about 25 mol percent to about 50 mol percent 1,1,1,2-tetrafluoroethane, and from about 25 mol percent to about 50 mol percent 1,1-difluoroethane. More preferably, such compositions comprise blends of from about 30 mol percent to about 40 mol percent trifluoroiodomethane, from about 25 mol percent to about 35 mol percent 1,1,1,2-tetrafluoroethane and from about 25 mol percent to about 35 mol percent 1,1-difluoroethane. Even more preferred, the compositions are directed to blends of from about 30 mol percent to about 40 mol percent trifluoroiodomethane, from about 30 mol percent to about 35 mol percent 1,1,1,2-tetrafluoroethane and from about 30 mol percent to about 35 mol percent 1,1-difluoroethane. Further preferred compositions comprise from about 34 mol percent to about 38 mol percent trifluoroiodomethane and from about 30 mol percent to about 35 mol percent each of 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane.
In further embodiments of the invention, the compositions consist essentially of the indicated blends of trifluoroiodomethane, 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane, whereby other components which might materially effect the essential characteristics of the compositions are excluded. For example, in preferred embodiments, the compositions of the invention are nonflammable and are azeotropic or near azeotropic, whereby the compositions are physically stable and do not substantially fractionate during use. Within the context of the present invention, near-azeotropic compositions are those in which the difference in vapor pressures of the components at room temperature is less than 10 psi. Accordingly, the compositions according to the p
Dinsmore & Shohl LLP
IKON Corporation
Ogden Necholus
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