Patent GB-654367-A (GB)
Title: Calcareous silicious material and method of preparation thereof
IPC: C04B28/18
Filed: 1947-07-28
Abstract: 654,367. Moulding cementitious material. TRIGGS, W. W. (Paraffine Cos., Inc.). July 28, 1947, No. 20247. [Classes 22, 70 and 87 (ii)] A method of making a lightweight mass of porous heatinsulating material set substantially without shrinkage from a relatively thin aqueous slurry consisting substantially of lime and silica and which slurry, if desired, may also contain an inorganic hydrophillic colloid and/or a strong alkali comprises (1) pouring said slurry into a mould prior to substantial thickening thereof ; (2) effecting chemical reaction between the said materials ; (3) rapidly setting said slurry to a firm self-supporting mass in the mould which shapes it, said chemical reaction and setting being effected by initially applying heat to the slurry and in addition applying heat to the mould to maintain the heated condition of the slurry to cause substantially all thickening of the slurry to said self-supporting mass to occur substantially undisturbed in the mould, said heating of the mould being maintained during the setting period, whereby the setting is completed in a comparatively short time ; (4) removing said self-supporting mass from the mould after the slurry has set, and (5) subjecting the self-supporting mass to an indurating treatment out of the mould. The slurry is composed of about 1 part of dry solids to about 2¢-6 parts of.water by weight, and usually has reinforcing fibres added, the density of the final product being determined by the quantity of water. Preferably the materials are first dry mixed and the dry fibre added in a dry atmosphere not more than 2 hours before adding the water. It is advantageous to add a colloidal earth (1-4 per cent by weight), to the mixture. The slurry is preferably made by adding boiling water and mixing in a heated vessel, and should be transferred to the mould within 4 minutes. The pre-setting may be accelerated by dissolving a strong alkali, e.g. sodium hydroxide (¢ per cent by weight of dry solids), in the water. For a tubular product the mould comprises a closed cylinder 2 with a steam or hot water jacket 4, a hollow cylindrical mandrel 8 within which steam or hot water is circulated through an inlet pipe 10 and an overflow pipe 10<SP>1</SP>, and a tubular ejecting ram 11. The preferred temperature range of the mould is 180-212‹ F. A crosshead 13 carries circumferentially arranged rods 12 and is connected to a mechanism (not described), whereby the rods enter the space 9, into which the slurry containing fibres has been poured, reach nearly to the ram and are given a limited but rapid back and forth movement for a short time to straighten the fibres in the general direction of the axis of the tube. To make a slab the mould is rectangular with correspondingly shaped jacket and ejecting ram and rods similar to 12 in a straight line and is without a hollow mandrel. The final setting is preferably accomplished by indurating the mass in an autoclave in steam at 100-125 pounds per square inch pressure. A tubular mass may be cut in two after final setting to make pipe covering halves. The indurated mass is dried either naturally or by heating until all uncombined moisture is removed.