GB560317A - Improvements in or relating to the manufacture of low-density cellular material - Google Patents

Abstract

A low-density cellular material is prepared by forming a froth of an aqueous solution of an alginate, and treating the froth so as to render it insoluble. A solution of sodium or ammonium alginate may be used and the foam rendered insoluble by calcium chloride or a salt of chromium, beryllium, strontium or zinc or by formaldehyde solution. The alginate solution may be mixed with a foam-stabilizing agent such as saponin or sodium isopropyl naphthalene sulphonate, and with a gelling agent such as calcium citrate or calcium sulphite which produces a slow conversion to calcium alginate. The mixture is agitated to form a foam which becomes gelled and is hardened by being soaked for some days in calcium chloride or formaldehyde solution, and is then washed and dried. Before hardening, the foam may have incorporated into it, a dispersion of synthetic resin such as phenolurea- or melamine-formaldehyde resin or polymethyl methacrylate resin or rubber latex. Fillers such as carbon black, wood flour or paper pulp may also be incorporated. The gelling of the foam may be controlled by addition of sodium hexa-metaphosphate or other phosphate or sodium carbonate, and the hardening may be hastened by passing electric current through the mass. Drying may be assisted by passing alternating current.ALSO:A low-density cellular material is prepared by forming a froth of an aqueous solution of an alginate and treating the froth so as to render it insoluble. A solution of sodium or ammonium alginate may be used and the foam rendered insoluble by calcium chloride or a salt of chromium, beryllium, strontium or zinc or by formaldehyde solution. The alginate solution may be mixed with a foam-stabilizing agent such as saponin or sodium isopropyl naphthalene sulphonate, and with a gelling agent such as calcium citrate or calcium sulphite which produces a slow conversion to calcium alginate. The mixture is agitated to form a foam which becomes gelled and is hardened by being soaked for some days in calcium chloride or formaldehyde solution, and is then washed and dried. Before hardening the foam may have incorporated into it a dispersion of synthetic resin such as phenol-, urea- or melamineformaldehyde resin or polymethyl methacrylate resin or rubber latex. Fillers such as carbon black, wood flour or paper pulp may also be incorporated. The gelling of the foam may be controlled by addition of sodium hexametaphosphate or other phosphate or sodium carbonate, and the hardening may be hastened by passing electric current through the mass. Drying may be assisted by passing alternating current.