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Polyurethanes conference highlights "soft" CFCs, new materials.

POLYURETHANES CONFERENCE HIGHLIGHTS "SOFT" CFCs, NEW MATERIALS

The consensus among chlorofluorocarbon (CFC) and foam producers at The Society of the Plastics Industry's Polyurethanes Conference in San Francisco, October 1 - 4, is that the industry may have lost a battle but won the war.

The battle was to stop the enactment of a tax - meant to hasten the introduction of alternative blowing agents with lower ozone depletion potential (ODP) - on the expected windfall profits arising from the sharply higher prices of CFCs as their production is wound down according to the Montreal Protocol. The tax will rise to $3.10/lb by 1993. CFC use in polystyrene foam and packaging and polyurethane flexible foam and packaging is expected to be phased out by that date. In recognition of their price sensitivity and energy conservation value - polyurethane and polyisocyanurate (PIR) foam boards have the highest R-value of any insulation product - the effective tax on foam board manufacturers will be only 25[cents]lb. Major appliance designs also rely on the structural value of the rigid boards.

The struggle to synthesize alternative blowing agents and the consequent polyurethane and PIR reformulations may have been won by extensive industry R & D and by the work of an industry/government consortium consisting of the U.S. Department of Energy, U.S. Environmental Protection Agency, SPI's Polyurethane Division, the Polyisocyanurate Insulation Manufacturers Association, the National Roofing Contractors Association, and the Massachussetts Institute of Technology. Test boards made with HCFC-141b and - 123, "soft" CFCs, have the same insulation value per inch as the CFC-11 blown products at 2% to 10% of CFC-11's ODP. Overall properties remain to be determined. Dan Madinabeitia, market manager, blowing agents, Du Pont Co., reported that results for the first stage of toxicity testing on three HCFCs are favorable, but that two-year animal studies have just started. Nevertheless, Madinabeitia said, Du Pont has made an "unprecedented commitment of funds" to build HCFC production facilities prior to completion of toxicity testing.

Even so, other combatants have entered the fray. The United Nations Environmental Programme's scenarios project a return to a stratospheric "pre-hole" chlorine level with 4%-ODP HCFCs by the year 2030; and by 2050 the level predicted for the "best-case" scenario, that of 0%-ODP usage, will be achieved. But Elizabeth Cook, of Friends of the Earth Inc., Washington, D.C., said that her organization is dissatisfied with those schedules. It regards HCFCs as "bridging" chemicals between CFCs and totally inert substances, and believes HCFCs should be phased out by the year 2000 and replaced by 0%-ODP agents, leading to a return to the pre-hole level in 30 years. Industry participants claim that such a scenario would discourage investment in HCFC production and worsen the problem.

Perhaps even more significant is the role of industrially developing nations. SPI reports that China and India, nonsigners of the Montreal Protocol, have proposed massive refrigeration programs based on CFCs. Such programs would partially defeat the best efforts of the signatory nations. Thus, SPI says, worldwide participation and attitudes accepting the rapid introduction of HCFCs are crucial.

MATERIALS

Although much of the technical program was understandably devoted to alternative blowing agents and reformulated systems, several 100%-solids materials were also introduced. ICI Polyurethanes has combined proprietary MDI-based isocyanate prepolymers with imine-terminated polyols and chain extenders to develop new polyurea/RIM systems. The imine-isocyanate reaction exhibits an induction period that allows a more controlled process at lower mold temperatures than conventional polyureas. The novel prepolymers can be formulated to give up to 70% hardblock content, resulting in broad ranges of physical and mechanical properties. Automotive applications, therefore, include low-modulus fascias, medium-modulus bumpers, and high-modulus body panels.

Two-component, 100%-solids spray systems that offer good properties and negligible volatile organic compounds content were also featured. Catalyst-free polyurea systems from Texaco Chemical Co. have been formulated with both aromatic and aliphatic MDI-based isocyanates to yield coatings with a range of hardnesses and better hydrolytic and thermal stability. Reaction times and cures are extremely fast for high productivity.

Mobay Corp.'s polyurethane systems can be sprayed, cast, or poured, need no bonding agents, and also are claimed to have fast cures and excellent physical properties. PU laminating resins with pot lives of a few minutes were described for manufacturing structural sandwich composites. The resin is sprayed or poured over a fiber mat; the soaked mat is then wrapped around the core (which can be foam, wood, or pitted metal) and cured by low-temperature compression molding. Normal gel coats or films can be used, and because of the low temperatures, economical epoxy molds.

Concerning CFCs, Union Carbide announced in September that its new Hyperlite foam chemistry eliminates the need for CFCs during production of molded foams for automotive seats and backs. The foam is also said to provide better cushioning and lower weight than existing high resilience or hot mold foam systems. Further, the company's Sert Release System technology cuts volatile organic compound emissions by 90% compared with current foam-molding processes.
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Title Annotation:Plastics News Supplement, part 1; chlorofluorocarbons
Author:Kates, D.F.
Publication:Plastics Engineering
Date:Dec 1, 1989
Words:830
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