Environmental concerns CFCs

Poor solubility in most common organic solvents represents an inherent problem in the synthesis and processing of many high molar mass fluoropolymers. In fact, CFCs and carbon dioxide are the best solvents for amorphous varieties of fluoropolymers. Due to the environmental problems associated with CFCs, the international community is seeking to replace them with more benign compounds such as hydrochlorofluorocarbons and hydrofluorocarbons. However, the environmental problems which will be created by the use of these replacement compounds such as the accumulation of trifluoroacetic acid in the atmosphere clouds this issue [71], Carbon dioxide presents an ideal inert solvent to effect the polymerization of these types of highly fluorinated monomers and obviates the use of solvents that are being phased out because of environmental concerns. 

Many of the changes in chlorine consumption in the past ten years have arisen out of the environmental concern about the use of chlorine in some processes such as pulp and paper as well as the concern of the loss of the ozone layer with the use of CFCs. 

The synthesis of fluoropolymers in C02 is of particular interest since these polymers have historically been prepared in chlorofluorocarbons (CFCs) and other fluorinated solvents, as well as in water. Due to the association of CFCs with ozone-layer depletion, these solvents have been banned and replacement solvents must be found. Alternative fluorinated solvents are expensive and also have environmental concerns. 

Because of environmental concerns about using chlorofluorocarbon (CFC) blowing agents, methylene chloride is being used as a blowing agent. A number of catalysts have been developed that are particularly compatible with methylene chloride. Several of these new catalysts work on the delayed-action principle to avoid splitting of the foams (22). 

However, there will always be situations where the introduction of a new excipient is inevitable. The candidate drug, for instance, maybe incompatible with the current range of excipients. Another reason might be the phasing out of existing excipients for safety or environmental concerns, such as chlorofluorocarbons (CFCs) in metered dose aerosols. There may be a need to introduce a new excipient for a novel drug delivery system or to overcome disadvantages with the currently available materials. 

HFCs and HCFCs both act as greenhouse gases, so environmental concerns about those effects have not yet been resolved by using them as replacements for CFCs. However, their atmospheric lifetimes are only a few years, in contrast to those of the CFC, which may be many decades. 

The other CFC of major environmental concern was CFC-113, C2F3CI3. It was used extensively for cleaning the glue, grease and solder residues from electronic circuit boards after their fabrication, up to 2 kg m . 

There are three reasons for environmental concern about CFCs... 

Hydrofluorocarbons have been proposed as CFC and HCFC substitutes since 1987, after the Montreal Protocol, with the aim of decreasing the ozone depletion. At present, these compounds are industrially produced by reaction of chlorinated hydrocarbons with HF. Environmental concerns have been raised regarding such processes, due to the co-production of huge amounts of HCl and the possible generation of dioxins and chlorinated compounds [1]. Due to their contribution to the greenhouse effect, fluorinated alkanes have often been replaced by other materials (e.g., natural refrigerants) in several UE countries... 

The combination of a spacer and face mask with a pMDI was the breakthrough that allowed the benefits of inhaled therapy to be offered to the large number of young patients with wheezing. However, pMDIs have significant disadvantages, including the irritant effect of additives, problems of dose consistency (see Chap. 10), and environmental concerns over both CFC and HFA propellants (see Chap. 11). 

The ban on CFC and the demand for a more efficient use of energy, both issues coming from environmental concerns, are therefore posing serious challenges to the Industry as a whole. 

The use of CFCs circumvents these problems however, CFCs have fallen under exceedingly strict regulation because of environmental concerns and, as a result, are no longer economically viable options as large-scale reaction media. Additionally, many of the fluorinated surfactants typically employed in aqueous... 

CFC propellants are no longer used in cosmetic products. The market has switched to a number of other delivery systems driven by the need to meet environmental concerns over CFCs. The aerosol industry has made enormous strides in reformulating its products to virtually eliminate CFCs from all but a few specialist (usually medical) applications. The aerosol is the major delivery system with condensed gas propellant systems based on hydrocarbons (propane/butane mixtures) or dimethyl ether (DME). Although compressed gas and pump delivery systems have been marketed by all the major companies, they have met with limited success largely on performance grounds and many have been withdrawn. In the deodorant segment, the aerosol is the preferred delivery system but roll-on, stick and pump systems have significant presence in the market. 

We noted from the outset of this chapter that environmental concerns about ozone depletion arise from tbe increase in the rate of destruction of ozone in the stratosphere. This is a process apparently caused by man-made chemicals. Specifically, chlorofluorocarbons used as refrigerants have been cited as a cause of ozone depletion. Yet a look at the Chapman cycle does not show any obvious role for CFCs. So how can these molecules accelerate the destruction of ozone if they do not even appear in the underlying chemical equations Catalysis is a process in which a reaction rate is influenced by the presence of substances that are neither reactants nor products in the overall equation. A catalyst is a substance that increases the rate of the reaction but is neither created nor destroyed in the process. How can CFCs catalyze ozone depletion ... 

When first introduced, semi-permanent release agents were formulated in hydrocarbon solvents or chlorofluorocarbon (CFC) aerosol propellants for application. However, with the environmental concerns about the use of solvents, and the Montreal Protocol banning the use of CFC, semi-permanent release agents are produced with a water base, that are equal in their properties to the solvent borne materials. 

Recent environmental concerns have led to significant changes in the flexible slabstock foam industry. Replacement of environmentally damaging CFCs by carbon dioxide produced by the reaction between isocyanate and water has placed new demands on the stabilization packages used in this application. The use of higher levels of water to induce carbon dioxide formation and release result in increased curing temperatures. In inadequately stabilized foams, this can lead to scorch and potentially selfignition. 

Selecting appropriate substitutes for an industry that has developed over 50 years is no trivial task. Many factors must be considered and thoroughly evaluated. Foremost is environmental acceptability for the ozone and other environmental concerns such as global warming and acid rain, but economic factors are important as well. There is an estimated 135 billion worth of equipment in the U.S. which depends on CFCs, with an expected lifetime of 20-40 years. Therefore, it is very important that the physical properties of the alternatives closely match those of the CFCs they are replacing. 

Traditionally, fiuorinated polymers have been synthesized in chlorofluoro-carbons (CFCs) as they are insoluble in common organic solvents. Due to the environmental concerns associated with CFCs, CO2 was investigated as a solvent for the synthesis of poly(FOA) by DeSimone et al. (30). Poly(FOA) was synthesized under homogeneous conditions to high molecular weight (about 2.7 x 10 g/mol), demonstrating the potential of CO2 as a solvent for fluoropolymer modification (30). 

There have been a number of subsitutions of chemicals in recent years, many of them driven by environmental concerns and regulations resulting from those concerns. One of the greater of these has been the substitution of hydrochloro-fluorocarbons (HCFCs) and hydrofluorocarbons (MFCs) for chlorofluorocarbons (Freons or CFCs) driven by concerns over stratospheric ozone depletion. Substitutions of nonhalogenated solvents, supercritical fluid carbon dioxide, and even water with appropriate additives for chlorinated hydrocarbon solvents will continue as environmental concerns over these solvents increase. 

Chlorinated solvents (cleaning) Solvents containing carbon and chlorine, such as trichloroethylene (TCE), methylene chloride (MEC), Perchloroethylene (PERC), and 1,1,1 trichloroethane (TCA). Very effective solvents but regulated because of health and environmental concerns. Example Carbon tetrachloride (CCI4), a fully chlorinated solvent. See also Chlorofluorocarbon (CFC) solvents Hydrochlorofluorocarbon (HCFC) solvents. 

Adsorption of ozone-depleting chlorofluorocarbons (CFG) over zeolite is of major global environmental concern. To investigate the nature of CFCs including fluoro. 

Evidence that many of these compounds can have adverse effects on the immune, endocrine and nervous systems and that some are carcinogenic has grown during the last decade. The role of chlorofluorocarbons (CFCs) and of methyl bromide in the ozone layer depletion is well established (ref. 3).It is therefore not surprising that many halogenated derivatives are cast as environmental and health villains by various concerned groups who call for total phase out of chlorine and chlorinated hydrocarbons. 

Substitutes for the CFCs that cause depletion of stratospheric ozone are being developed. Those which will be used in the near future (hydrochlorofluorocarbons, HCFCs) are of concern because a decomposition product, trifluoroacetic acid, might be very persistent and, under extreme conditions, have the potential to cause an undesirable environmental impact. 

---