Patent GB-807015-A (GB)
Title: Method of producing porous materials suitable for building insulation and other purposes
IPC: C04B18/02
Filed: 1955-03-07
Abstract: 807,015. Porous compositions; moulding pellets. WIKNE, S. March 7, 1955, No. 6641/55. Classes 22 and 87(2). Porous concrete or other porous building material, which may or may not contain aggregates, is preferred by adding to a mortarcontaining mix pellets of hardened jelly, the evaporation of the water in which forms pores during the setting of the material. The added pellets may have been previously expanded by bubbles of air, or other gas, and may comprise alone or in combination, alginic acid, alginates, carboxy-methyl-cellulose, methyl cellulose, hydroxy-ethyl-cellulose, agar agar, starch and its viscous degraded products, defatted soya and peanut flour, hide and bone glue, gum arabic, gum karaya and other gums, waterglass, polyvinyl alcohol, and china and other clays. A urea formaldehyde-condensation product may be added to strengthen the pellets. In one Example pellets of sodium aliginate are prepared by washing 60 kg. of seaweed in running water for 1 to 2 hours, and then adding a solution of 3-4 k.g. calcined sodium carbonate in 30 gallons of water. After stirring for 5 to 6 hours the liquor which contains sodium alginate is strained from the solids and the pH value thereof adjusted to 7-3 by adding dilute acetic acid, and 125 gallons water and 5 grams copper sulphate in 100 ml. of water added. The liquor is then caused to flow as jets beneath the surface of a 2 per cent. aqueous solution of calcium chloride, whereby a hardened jelly containing sodium alginate is produced which is divided into pellets within the solution. Alternatively the alginate liquor is added in the form of drops to the calcium chloride solution to form hardened pellets. Before adding the calcined sodium carbonate solution the seaweed may be softened by treatment with dilute hydrochloric acid. In other Examples the pellets are prepared from water-soluble cellulose, a foamed solution in caustic soda of fish or fish waste, and potato starch, respectively. The pellets may be further hardened by treatment with beryllium and chromium salts and formalin. A composition for making porous building material may comprise 200 litres pellets, 50 kg. Portland cement, water, and either 150 kg. sand or 200 litres fermented sawdust. Apparatus for preparing the pellets may comprise a tank 4, Fig. 1, containing the hardening liquid and within which is a receptacle 5 to which is fed viscous liquid or jelly either from a tank 8 by compressed air supplied through a pipe 11, or from a tank 1 by a piston 2. The mixture is forced from the receptacle 5 through holes 28 in the uppper wall thereof into the hardening liquid to be formed into pellets by brushes or knives 24, 25 mounted on a shaft 6 rotated by a pulley 7 and belt 30. Springs 26, 27 hold the brushes or knives against said upper wall. In an alternative construction the viscous solution or jelly is fed through a hollow shaft 33, Fig. 3, to a hollow cylinder 35 to be discharged through peripheral holes 37 into a hardening liquid. The cylinder 35 and shaft 33 are rotated by a belt 46 and pulley 32 so that the jets discharged through the holes 37 are cut into pellets by stationary brushes or knives 38,39.