Hydrochloro fluorocarbons

The phasing-out of fully halogenated CFCs is a success story of international cooperation in ameliorating an environmental hazard created by anthropogenic activities. In part, this success was achieved because chemical manufacturers found ready substitutes for the fully halogenated CFCs, the partially halogenated hydrochloro-fluorocarbons (HCFCs), for example HCFC-22,... 

Solvents, like contaminants, may be polar or nonpolar. As a general rule, polar solvents dissolve polar residues while nonpolar solvents dissolve nonpolar residues. Thus, ionic residues such as chlorides, salts, acids, acid fluxes, and alkalis are best dissolved and removed with polar solvents such as water, isopropyl alcohol, ethanol, or methylethyl ketone. Greases, oils, silicones, rosin flux, and low-molecular-weight monomers are best dissolved and removed with solvents such as hydrocarbons, Freons , hydrochloro-fluorocarbons, xylene, terpenes, and naphtha. To remove both polar and nonpolar residues, a two-step process using both types of solvents may be used or, more conveniently, an azeotrope mixture of the two solvents can be used in a one-step process. Most of the chlorofluorocarbon solvents (Freons ) and their azeotropes with alcohols, methylene chloride, or ketones are being phased out due to their high ozone-depletion potentials. Solvent blends and azeotropes of hydro-fluoroethers and hydrochlorofluorocarbons (HCFC) are now replacing these solvents. 

Ci-derivatives Trichloromethane Monochloromethane Tetrachloromethane Phosgene Hydrochloro-fluorocarbons Polytetrafluoroethylene (PTFE) Silicones, methylcellulose Industrial processes Polycarbonates, diisocyanates, polyurethanes... 

FIGURE 46.8 Ozone-depleting potential and global warming potential of chlorofluorocarbons (CFC) and hydrochloro-fluorocarbons (HCFC) relative to Rll = 1. 

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. 

---