GB908498A - Improvements in or relating to exothermic mixtures and the use thereof - Google Patents

Abstract

An exothermic composition, in the form of a shaped solid mass, for lining the riser cavities, feeding head cavities or head boxes in the production of metal castings or ingots, comprises finely-divided aluminium, an oxidizing agent, e.g. alkali metal nitrate or chlorate, manganese dioxide and/or iron oxide, preferably in a stoichiometric insufficient amount, a refractory filler such as sand, grog or crushed firebrick, and a resinous binding material consisting of or containing a water-insoluble furan resin. The composition may further contain a catalyst for hardening the resin, such as one or more of ammonium chloride, sugar, urea, aluminium phthalate, sodium dihydrogen orthophosphate, acid aluminium phosphate, and/or ammonium thiocyanate, carbon black, e.g. 1 to 15% by weight, 0.1 to 15% by weight of a fluoride such as NaF, sodium or potassium aluminium fluoride, and green strength additives such as gum arabic or dibutyl phthalate. The shaped solid mass may be produced from a powdered composition which contains, besides the aluminium, oxidizing agent and refractory filler, a precursor for the water-insoluble furan resin, which forms upon heating; at least one of the reactants needed to form the resin is included in the powdered composition. Other resins, e.g. urea-formaldehyde or phenol-formaldehyde resins, may be mixed with the furan resin or precursor thereof, e.g. furfural, furfuryl alcohol, furfuramide or tetrahydrofurfuryl alcohol; the furan resin may be a condensation product of furfural with a phenol, amine, aldehyde or ketone, catalysed by acids or alkalis. Reducing agents additional to aluminium may be employed, e.g. ferrosilicon or carbon. Specification 627,678 is referred to.