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Researchers rushing to replace CFCs.

In response to consumer and government outcries, researchers are working fast to create products that will replace chlorofluorocarbons (CFCs), which deplete Earth's ozone layer.

Chemists at Philadelphia-based Atochem North America Inc. are developing products that replace CFCs in refrigeration, air conditioning, and foaming agent applications. After years of R&D, the company now manufactures the hydrochlorofluoro-carbons HCFC-142b and HCFC-22. It also produces HCFC-141b, which replaces CFC-11 in rigid polyurethane foams used as insulation.

R&D work on the hydrofluorocarbon HFC-134a is under way at Atochem's new industrial pilot-scale plant in Pierre-Benite, France, with full-scale production expected to begin in mid-1992.

HCFC-142b, HCFC-22, and HFC-134a replace CFC-12 in refrigeration, commercial and automotove air conditioning, polystyrene and polyethylene insulating foams, and other applications.

Changes are also taking place in the electronics industry, where for decades CFCs were used as cleaning solvents because of their stability and compatibility with most materials. But stability is also a main problem of CFCs: They are so stable they cannot be easily extracted from the atmosphere.

No-Clean fluxes from Alpha Metals Inc., Jersey City, NJ, eliminate the need for excessive rinsing of printed circuit boards and resulting wastewater treatment, the company says. The No-Clean technique leaves almost no residue on boards.

One of the company's fluxes is halide-free and rosin/resin-free with a 2.1% solids contents. Other Alpha Metals fluxes have 2.2% and 4.4% solid levels.

"Our challenge was to find organic materials that remove copper, lead, and other metals oxide from circuit boards and component surfaces," says Alpha Metal's John Stevenson, product manager of assembly chemicals. "Two to three years ago, traditional fluxes contained 30% to 40% solids. Today we rely on organic acids and materials that volatilize at soldering temperatures to reduce solids content. This process has resulted in totally gaseous products that leave virtually zero residue."

Too much residue can result in ionic contaminants that lower surface insulation resistance of the boards. The small amount of residue left on the No-Clean boards also eliminates problems during automatic pin testing procedures. Extensive residue can form insulating pads on boards, and during testing, the system might detect defects where there are none.

Another company, Zenon Environmental of Burlington, Ontario, is testing a membrane-based vapor permeation CFC recovery process that concentrates CFCs in liquid form. The process, developed primarily for refrigeration, pharmaceuticals, ink, and specialty chemicals was created to minimize the damaging effects of organic vapors produced by industrial processes that involve volatile hydrocarbons. Released into the atmosphere, such vapors and contaminants help create photochemical smog.

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Title Annotation:R&D News; chlorofluorocarbons
Author:Oluver, Joyce Anne
Publication:R & D
Date:Jan 1, 1992
Words:422
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