| 摘要 |
1,251,656. Moulding plastic substances. MONSANTO CHEMICALS Ltd. 13 Aug., 1969 [26 Aug., 1968], No. 40665/68. Heading B5A. [Also in Division C3] A ceramic article is produced by (a) making a porous ceramic mould by forming a slurry of a particulate refractory material is a hydrolysed alkyl silicate solution into the desired shape of the mould, the particulate refractory material being a uniform blend of a material having a particle size range of from - 16 to + 80 BSS mesh and a material having a particle size of less than 200 BSS mesh, the proportions by weight of the two refractory materials being from 2 : 3 to 3 : 2 and the two particulate refractories together forming at least 80% by weight of the total solids content of the slurry, gelling the shaped slurry to form a given mould, drying and firing the given mould; and (b) shaping theceramic article in the porous ceramic mould. The mould may be a block mould formed by pouring the slurry into a moulding box round a pattern, or a shell mould formed by applying alternate slurry and stucco coatings to a disposable pattern. The hydrolysed alkyl silicate solution is preferably prepared from ethyl silicates containing 39-43% by weight silica hydrolysed with 8-12% by weight, of the alkyl silicate, of water, in the presence of a catalytic amount of hydrochloric acid and an alcohol. The particulate refractory material may be a refractory oxide such as silica, alumina, zirconia; refractory aluminate or silicate minerals such as sillimanite, mullite, molochite, zircon or forsterite; and refractory clays such as calcined Ayrshire or Stourbridge clays of which molochite is the preferred. |
