THE HAGUE, NETHERLANDS - Polyurethane raw material suppliers have been working hard on vacuum insulation panel technology for appliances, as ICI Polyurethanes and Bayer AG indicated at UTECH '96 in The Hague. Bayer's contribution has been to develop technology for using recycled rigid polyurethane foam from old appliances as the insulating material in vacuum insulation panels for new refrigerators.
And the process is in practical use at Telwest Recycling GmbH of Bretten, Germany.
Describing details of this technology to the UTECH audience, Karl Werner Dietrich, section manager of the technical insulation department for home appliances in Bayer AG's PU marketing group, pointed out that vacuum panels need open-celled foam, which can be evacuated to give the insulation effect. Diffusion of gases from closed cells would reduce the long-term insulating effect.
Recycled foam must be ground up finely to produce open cells. Recycled PU is a substitute for standard vacuum panel substrates, such as silica gel, fiberglass, or new open-cell foams, Dietrich said.
In refrigerators, the panels are used like normal vacuum panels as an insert in walls, etc., and are foamed in place using virgin polyurethane foam, Dietrich said.
ICI has developed its Vacpac technology for refrigerators and freezers very rapidly, Patrick Thomas, European business director for ICI Polyurethanes, said in an interview at UTECH.
``Eighteen months ago we went out and attacked this market,'' he said.
ICI's package, which enables appliance makers to set up in-house Vacpac production, consists of an open-celled foam; a high-quality film laminate; what it calls ``getter'' technology, which removes volatile elements; and foam encapsulation systems for sealing the panels into the walls of appliances.
Originally this technology used heavy steel panels, but Vacpac technology, being used by Scottish freezer maker Norfrost Ltd., makes very light panels and has boosted thermal performance of its 100-liter chest freezers to A - the highest rating on the European scale.
Appliances made using this technology can meet the highest U.S. energy standards, Thomas added. Vacuum panels have thermal conductivity of about 30 percent that of conventional PU foam, according to ICI.
Encouraging results also have resulted from Vacpac trials in building panels with welded stainless steel envelopes, performed by Thyssen Vakuum Isolationstechnik, according to ICI.
Dietrich pointed out that use of recycled appliance foam in vacuum panels, ``solves the two major problems currently facing the appliance industry regarding polyurethane insulating foam: recycling and improvement in energy efficiency.''
He added that all the PU foam
from an old refrigerator can be incorporated into a new one.
The old foam is ground to a fine open-celled fluff, which is then molded with polymeric methylene diphenyl diisocyanate as a binder, using heat and pressure, into sheets.
The sheets are evacuated and sealed within a gas-impermeable plastic film to give 25mm-thick vacuum insulation panels.
Dietrich said that in Germany about 6.61 million pounds of urethane foam waste is recovered from old appliances annually, a figure expected to rise to 33.1 million pounds by 2000.
