Manufacture of rigidized convoluted foam from flexible polyurethane foam and resultant product

Claim 1

A process for the manufacture of a convoluted polyurethane foam self-standing filter which comprises the steps of: (a) passing a sheet of air-permeable flexible polyurethane foam that is capable of being impregnated with a thermosetting resin, said sheet having a thickness of from about 11/4 inches to about 8 inches, through a convoluting machine whereby two unnested sheets of convoluted foam are provided, each of said sheets being convoluted on only one side; (b) nesting said two unnested sheets of convoluted foam; (c) impregnating one of said nested sheets, by means of immersion, reverse-roll coating, or gravure roll coating, from the flat surface of the sheet almost to the closest valley surface of the sheet with a thermosetting melamine, urea, or benzoguanamine resin, and a cross-linker, the combined dry weight of said thermosetting resin and said cross-linker after reaction being from about 10 percent to about 300 percent of the dry weight of said polyurethane foam and being an amount to not appreciably impair said foam permeability and to increase the rigidity of said polyurethane foam sufficiently that said unnested sheet will be self-standing; (d) reacting said thermosetting resin and said cross-linker without separating said nested sheets; (e) repeating steps (c) and (d) on the other of said nested sheets; and, (f) separating said nested sheets, thereby providing convoluted polyurethane foam which is rigid enough to be self-standing.