Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Halogenated hydrocarbon doai
Reexamination Certificate
1998-03-27
2001-10-09
Clardy, S. Mark (Department: 1616)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Halogenated hydrocarbon doai
C252S067000, C252S068000
Reexamination Certificate
active
06300378
ABSTRACT:
FIELD OF THE INVENTION
The invention described and claimed herein is generally related to bromine-containing halocarbon additives used to decrease or eliminate the flammability of refrigerants, foam blowing agents, cleaning agents (solvents), aerosol propellants, and sterilants. Specific and novel to this invention are the combined properties of these additives: (1) The halocarbon additives claimed are destroyed or otherwise removed rapidly by natural processes in the earth's troposphere and thus have short atmospheric lifetimes, low ozone depletion potentials (ODPs), and low global warming potentials (GWPs). (2) These additives are chemically active flammability reducing agents and do not operate merely by dilution of a flammable substance with a nonflammable substance. In this document, I refer to atmospheric lifetimes, ODPs, and GWPs as “global environmental properties” since they determine the potential environmental impact on the earth as a whole rather than just one area. The additives claimed are called “tropodegradable” since they are removed rapidly from the earth's troposphere.
BACKGROUND
Flammability and Explosivity
It is important at this point to briefly discuss what is meant by flammability and explosivity. Materials used in the applications of interest here (refrigeration, foam blowing, solvents, aerosol propulsion, and sterilization) are liquids or gases. In many cases, they are stored in one form and used in another or they are present in both forms during use. When flammable liquids burn, combustion actually occurs in the vapor phase, which is formed above the surface of the liquid by evaporation of the liquid. When flammable gases or vapor from evaporated flammable liquids are allowed to mix with air, the mixture can be explosive. (In this document, I use the terms “vapor” and “gas” as synonymous.) In fact, for the materials of interest here, explosions are just rapid combustion in the gaseous state. Explosions are often termed “deflagrations” if the combustion is relatively slow and as “detonations” if it is extremely fast. Thus “burning,” “combustion,” “explosion,” “deflagration,” and “detonation” all involve a rapid oxidation and differ primarily in the rapidity of the process and the results (explosions are often highly destructive). For the materials of interest here, flammability is often determined by introducing the material as a gas or as a vapor from an evaporated liquid into a container with air or oxygen and determining whether deflagration occurs. Thus, throughout this document, I use the term “flammable” to indicate whether combustion can occur without regard for whether the combustion occurs in the vapor phase above the liquid/vapor interface of a liquid or as a deflagration or explosion in a gas/air mixture. Halocarbons
The broad class of halocarbons consists of all molecules containing carbon and one or more of the following halogen atoms: fluorine, chlorine, bromine, and/or iodine. Halocarbons, as the term is used here, may also contain other chemical features such as hydrogen, oxygen, and/or nitrogen atoms; carbon-to-carbon multiple bonds; and aromatic rings.
Due to their generally low toxicities and low or non-existent flammability, one family of halocarbons—the chlorofluorocarbons (CFCs), which contain only carbon, chlorine, and fluorine atoms—has been used for many years in a variety of applications. Refrigerants
Air conditioning, refrigerating, and heat pump appliances transfer heat from one area to another. In vapor compression systems, a chemical or mixture of chemicals, the refrigerant or “working fluid”, is compressed in one area (the high-pressure side), where heat is given off, and then allowed to expand in a second area (the low-pressure side), where heat is taken up. In most cases, the working fluid condenses in the high pressure area and then evaporates in the low pressure area. A schematic of a typical refrigeration system is shown in FIG.
1
.
CFCs have been the refrigerants of choice in many air conditioning, refrigerating, and heat pump appliances. Thus, CFC-12 (See
Halocarbon Nomenclature
, Center for Global Environmental Technologies, New Mexico Engineering Research Institute, The University of New Mexico, Albuquerque, N. Mex., Revised September 1997 for a discussion of this “halocarbon number” and other halocarbon nomenclature), also known as R-12 or dichlorodifluoromethane (CCl
2
F
2
), has been a widely used medium-pressure refrigerant for commercial and residential refrigeration, medium-pressure centrifugal chillers, and automobile air conditioners. CFC-11 (R-11, trichlorofluoromethane, CCl
3
F) has been widely used in low-pressure centrifugal chillers, and CFC-114 (R-114, 1,2-dichloro-1,1,2,2-tetrafluoroethane, CCIF
2
CCIF
2
) is widely used by the U.S. Navy for centrifugal chillers. Other CFCs have also been used as refrigerants, either pure or in mixtures
Foam Blowing Agents
The manufacture of plastic foams for insulation, cushioning, and packaging foams requires the use of gas or volatile liquid blowing agents to create bubbles or cells. CFC-11, CFC-12, CFC-113 (1,1,2-trichloro-1,2,2-trifluoroethane, CCl
2
FCCIF
2
), and CFC-114 have been used as blowing agents in the manufacture of foam plastic products. In addition to their remarkably low toxicities and lack of flammability, CFCs provide plastic closed-cell foams with excellent insulating ability and generally have good materials compatibility.
Solvents
CFC-113 has been widely used as a solvent in metals, electronic, and precision cleaning and/or decreasing. In this application, in addition to acceptable toxicities and low flammability, rapid evaporation is desired. Rapid evaporation decreases or eliminates energy consumption for drying cleaned parts. All CFCs in common use evaporate rapidly. CFCs and related materials have also been used for dissolution of solutes (dissolving) in many applications including aerosol sprays.
Aerosol Propellants and Sterilants
CFCs have also been used as aerosol propellants though this use is decreasing and is nearly absent in some areas of the world, and a mixture of CFC-12 and ethylene oxide (C
2
H
4
O) is used for gas sterilization of medical equipment and devices. Ethylene oxide is the actual sterilant; CFC-12 is added only to decrease the ethylene oxide flammability. It is estimated that in 1989, 95 percent of all U.S. hospitals used an ethylene oxide/CFC-12 mixture as a sterilant.
Global Environmental Problems
CFCs and many other halocarbons, have come to be recognized as serious global environmental threats due to their ability to cause stratospheric ozone depletion and global warming and their significant atmospheric lifetime. The ozone depletion and global warming impact of chemicals such as these is measured by the ozone depletion potential (ODP) and global warming potential (GWP). ODP and GWP give the relative ability of a chemical to deplete stratospheric ozone or to cause global warming on a per-pound-released basis. ODP and GWP are usually calculated relative to a reference compound (usually CFC-11 for ODP and either CFC-11 or carbon dioxide for GWP) and are usually calculated based on a release at the earth's surface. It is important to note that ODP and GWP values must be calculated by computer models; they cannot be measured. As models, theory, and input parameters change, the calculated values vary. For that reason, many different values of ODP and GWP are often found in the literature for the same compound. Nevertheless, the calculation results are very accurate in predicting which compounds are highly detrimental to ozone depletion or global warming, which are only moderately detrimental, and which have very low or essentially zero impacts.
Despite the wide utility of CFCs, their production has been severely restricted due to concerns about stratospheric ozone depletion. In fact, under the Montreal Protocol, an international treaty enacted in 1987 and amended in 1990, 1992, and 1995, the production of CFCs was phased out in all industrialized nations at the end of 1995. Moreover, the productio
Clardy S. Mark
Pryor Alton
Robert W. Becker & Associates
University of New Mexico
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