GB798577A - Improvements in or relating to the manufacture of magnesia cement - Google Patents

Abstract

Porous magnesia cement is prepared by adding a frothing agent, whilst intensively beating to a mixture of water and an artificial resin and/or bitumen, and adding to the foam, whilst continuously stirring, a solution of a water-soluble sulphate of a bivalent metal and, subsequently, magnesium oxide and at least one filler. The magnesium oxide may be crystalline or amorphous, and ferrous, magnesium, or zinc sulphate is preferred. The filler may be selected from wood dust, pine or fir wood chips, paper fibre, paper meal, cork dust, cork meal, talc, stone dust, quartz powder, kieselguhr, asbestos, or sand. The preferred artificial resins are polyvinyl esters, e.g., polyvinylacetate. The frothing agent may be an ammonium or other salt of an alkylarylsulphonic acid, to which may be added a stabilizer such as a polyacrylic acid ester. To improve the waterproofing properties of the cement a silicone or silicones, e.g., the sodium salt of methylsilicic acid, or a solution of organosilicon chlorides, may be added to the artificial resin and/or bitumen. After mixing the cement it is preferably intensively heated, e.g., by infra red radiation, at a temperature above 80 degrees Centigrade.