Improvements in or relating to moulding compositions

Abstract

Abstract A moulding or core composition is formed by coating individual granules of a refractory, nonabsorbent solid material a.g. foundry sand, silicon carbide, emery, glass and asbestos fibres, and metal powders, with a non-tacky layer of a potentially heat unstable thermosetting resin formed by the condensation of an isoalkylidene bisphenol with formaldehyde, in the presence or absence of a mononuclear phenol. The isoalkylidene bisphenol may be of the general formula <FORM:0950291/C1/1> where R = substituted or unsubstituted C1-C3 alkyl radical, R1 = methyl or ethyl radical. Examples are: 2,2-bis (4-hydroxyphenyl) propane, diphenolic acid (4,4-bis(4,hydroxyphenyl)pentanoic acid), 2(2-hydroxyphenyl)-2 (4-hydroxyphenyl) propane, 2,2-bis (2-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2 - bis (4 - hydroxyphenyl) 3 - methyl - butane. The bisphenol may be condensed with a phenol-formaldehyde resin which may be a resole. The bisphenol may constitute from 10-70% by weight of the resin solids. The composition may contain a latent acidic material which is degraded to yield acid only at the temperature of casting. The mould or core may be formed by depositing the composition on to a heated pattern and heating it to the curing temperature of the resin.ALSO:Isoalkylidene bis-phenol-formaldehyde resins are prepared by reacting a ketone with a phenol, and then reacting the crude condensate with formaldehyde in the presence of an alkali metal hydroxide, and removing part of the water by decantation or stripping. The reaction is preferably stopped when a viscosity of at least U at 68-72% solids on the Gardner scale is reached and cooled or concentrated to a viscosity of W to Z at 74-76% solids. Resins can also be made by adding a bisphenol to a convention mononuclear phenol-formaldehyde resin. The proportion of bisphenol may be from 10-70% by weight. Examples are given and the resins are used for coating sand.ALSO:The invention comprises granules of a refractory, non-absorbent solid material coated with a non-tacky layer comprising a potentially heat unstable thermosetting resin formed by the reaction of formaldehyde with an isoalkylidene bisphenol in the presence or absence of a mononuclear phenol. Suitable materials are foundry sand, silicon carbide, emery, glass and asbestos fibres, and metal powder. The isoalkylidene bisphenol is preferably of the formula: <FORM:0950291/B1-B2/1> in which R is a C1-C3 alkyl radical and R1 is methyl or ethyl. The composition may contain a latent acidic material which is degraded to yield acid only at the temperature of casting metals (composition used as a moulding or core composition).ALSO:A moulding or core composition is formed by coating individual granules of a refractory, non-absorbent material, e.g. glass and asbestos fibres with a non-tacky layer of a potentially heat unstable thermosetting resin formed by the condensation of an isoalkylidene bisphenol with formaldehyde, in the presence or absence of a mononuclear phenol. The isoalkylidene bisphenol is preferably of the formula:- <FORM:0950291/D1-D2/1> where R is a substituted or unsubstituted C1-C3 alkyl and R1 is methyl or ethyl.

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