GB1179241A - Soluble Cores. - Google Patents

Abstract

1,179,241. Water-soluble cores. UNILEVER Ltd. 14 July, 1967 [15 June, 1966], No. 26658/66. Heading B5A. [Also in Divisions B2, B3 and C3] Articles may be moulded by use of a watersoluble sintered mould core formed from a composition comprising a major amount of (a) a water-soluble material, and minor amounts of (b) a flux, (c) a fine particulate refractory, and (d) an organic binder. The composition is blended, compacted, e.g. at 145-290 kg/cm.<SP>2</SP> and sintered, e.g. at 450-675‹ C. (a) may be (i) basic, e.g. sodium or potassium metasilicate, forming 90-96% wt. of the composition; or (ii) neutral, e.g. NaCl, KCl, MgCl 2 , MgSO 4 , Na 2 SO 4 , forming 80-92% wt. of the composition; in this case up to 10% alkali metasilicate is preferably present. (b) may be B 2 O 3 , e.g. 1-3%; (c) may be SiO 2 , or MgO, Al 2 O 3 or ZrO 2 , e.g. 3-7%. (d) may be e.g. polyethylene glycol or paraffin wax in trichloroethylene; the solvent is evaporated before compaction, and the wax is vaporized before sintering. A coating material insert may be applied to the core e.g. by flamespraying, vapour deposition or dry transfer; or as a preform. The coating material subsequently becomes bonded to the casting; the material may be metal, e.g. bronze, stainless steel, Ni, Mo, Ni/Cr, Monel metal (Registered Trade Mark), W, tungsten carbide, " Stellite " (Registered Trade Mark), or Au, or graphite, ferrite, Al 2 O 3 , or quartz. A Zn coating may first be applied to the core. The core may be used in the casting of thermoplastic materials, e.g. polystyrene, polymethylmethacrylate, polyacrylate, or polyamide, or catalyst + monomer or precondensate e.g. epoxy condensate: or thermosetting materials, e.g. phenolformaldehyde; or metals, e.g. Al or Mg. The core may be dissolved with hot water.