| 摘要 |
1,248,756. Foundry mould composition. BORDEN CHEMICAL CO. (U.K.) Ltd. 24 Nov., 1969 [5 Dec., 1968], No. 57913/68. Heading C3N. A two-part cold-setting foundry moulding composition comprises a mixture of (i) a granular refractory material coated with a methylolated product and (ii) a granular refractory material coated with a suspension or solution of a phenolic novolak resin and an acid material. The methylolated product may be a reaction product of a phenol, a urea, a triazine or dicyandiamide with formaldehyde or may be furfuryl alcohol or furfuryl alcohol partial polymer or a reaction product of furfuryl alcohol with formaldehyde. Mixtures or co-condensates of any of these products may also be employed and in this respect co-condensates of urea with formaldehyde and furfuryl alcohol are particularly preferred. The phenolic component of the phenol novolak may be phenol, m-cresol, 3,5- xylenol, or resorcinol. Typical novolaks employed are phenolformaldehydes having a molar ratio of phenol to formaldehyde within the range 1:0À2-1:0À9. The acid material may be a mineral acid such as sulphuric acid; an organic acid such as p-toluene sulphonic acid; acidic salts such as zinc chloride or aluminium chloride; or mixtures thereof. The granular refractory material is desirably silica sand but ground quartz, zircon or chromite sands may also be used together with additives such as mill scale and plumbago. The moulding composition may be produced by coating one portion of a granular refractory material with 0À5-5% by weight of methylolated product in a mixer, coating the second portion of granular refractory material with the phenolic novolak and acid material in another mixer, charging both coated products to separate feed chambers, subsequently simultaneously discharging the two coated products, preferably in approximately equal quantities, into a common chamber where mixing is effected and finally discharging the mixed product into a core-box or mould before the mixture sets. |
