Patent GB-843794-A (GB)
Title: A process for the preparation of moulding sand for the shell moulding process
IPC: B22C1/22
Filed: 1957-10-22
Abstract: Sand coated with a resinous condensation product for use in the shell moulding process is prepared by mixing the sand with the resin, before or after the resin has been plasticised with a liquid mixture comprising one or more liquids having a b.p. below 100 DEG C. and one or more plasticiser liquids having a b.p. above 100 DEG C., e.g. 150-220 DEG C. the lower and/or higher b.p. liquid or liquids optionally being capable of forming a resinous partial condensation product having plasticizer properties, removing the liquid of lower b.p. from the resin by evaporation and/or conversion into a resinous partial condensation product, and allowing at least a portion of the liquid of higher b.p. to remain in the resin as such and/or in the form of a resinous partial condensation product.  15-40 parts of liquid mixture may be used per 100 parts of sand.  The liquid mixture may contain 70-95% of lower b.p. liquid or liquids and 5-30% of higher b.p. liquid or liquids.  Synthetic resins specified are a novolak resin, a lignin-novolak resin consisting of 40% lignin and 60% of novolak resin and a novolak resin modified with 10% of butyl phenol. Hardeners specified are hexamethylene tetramine and paraformaldehyde.  Lower b.p. liquids specified are methanol and acetone.  Higher b.p. liquids specified are ethylene glycol, cyclohexanone, acetophenone, acetonyl acetone and acetyl phenyl ketone.  The ketones specified may form resinous condensation products in the presence of the hardeners specified and/or added formaldehyde, preferably at a pH of 12, which pH may be produced by the addition of sodium hydroxide.ALSO:Sand coated with a resinous condensation product for use in the shell moulding process is prepared by mixing the sand with the resin, before or after the resin has been plasticized with a liquid mixture comprising one or more liquids having a b.p. below 100 DEG C. and one or more plasticizer liquids having a b.p. above 150 DEG C., e.g. 150-220 DEG C., the lower and/or higher b.p. liquid or liquids optionally being capable of forming a resinous partial condensation product having plasticizer properties, removing the liquid or liquids of lower b.p. from the resin by evaporation and/or conversion into such a resinous partial condensation product, and allowing at least a portion of the liquid or liquids of higher b.p. to remain in the resin as such and/or in the form of such a resinous partial condensation product, 15-40 parts of liquid mixture may be used per 100 parts of sand.  The liquid mixture may contain 70-95% of lower b.p. liquid or liquids and 5-30% of higher b.p. liquid or liquids.  Synthetic resins specified are a novolak resin, a lignin-novolak resin consisting of 40% lignin and 60% of novolak resin, and a novolak resin modified with 10% of butyl phenol.  Hardeners specified are hexamethylene tetramine and paraformaldehyde.  Lower b.p. liquids specified are methanol and acetone.  Higher b.p. liquids specified are ethylene glycol, cyclohexanone, acetophenone, acetonyl acetone and acetyl phenyl ketone.  The ketones specified may form resinous condensation products in the presence of the hardeners specified and/or added formaldehyde at a temperature of 20-50 DEG C., preferably at a pH of 12, which pH may be produced by the addition of sodium hydroxide.