GB928451A - Improvements in thermosetting material - Google Patents

Abstract

A shell moulding material comprises a granular refractory material, usually sand, the grains of which are coated with a thermosetting resinous product obtained from a reaction between at least one carbohydrate or at least one polyhydrate alcohol containing at least three carbon atoms and at least one tannin. Specified carbohydrates and polyhydric alcohols are glucose, fructose, cane sugar molasses, sucrose, maltose, dextrose, starch, dextrins, cellulose, glycosides, glycerol and sorbitol. Numerous tannins are specified of both the hydrolysable and condensed types. Free-flow promoting agents such as zinc oxide, aluminium hydroxide, calcium oxide and hydroxide; sodium, magnesium, ammonium and zinc chlorides; calcium, zinc and aluminium stearates; magnesium, zinc and the alkali and alkaline-earth metal carbonates; ammonium persulphate, manganese dioxide, potassium and sodium nitrates and other inorganic oxidizing agents, the isocyanates, sodium acetate and complex hydrated alumino-silicates such as montmorillonites, may be included. Examples 6-9 describe this embodiment of the invention; in these examples quartz sand is mixed and coated with a mixture of molasses or cane sugar, sulphited quebracho extract, aniline and concentrated hydrochloride acid (hardening agents). In Example 7 the coated sand is additionally coated with a solution of fatty acid pitch dissolved in carbon tetrachloride; in Example 8 it is mixed with hexamethylene tetramine and zinc stearate; and in Example 9 it is mixed with an uncured novolac and Wyoming bentonite. The thermosetting resinous products referred to above may also be used to bond fuels, e.g. coal to make coal briquettes. Specifications 274,146, 481,819, 520,913, 539,581, 545,147 and U.S.A. Specifications 1,949,831, 1,949,832, 1,974,064 are referred to.ALSO:A resinous liquid or solid thermosetting product is obtained from a reaction between at least one carbohydrate or at least one polyhydric alcohol containing at least 3 carbon atoms and at least one tannin. When the carbohydrate is a polysaccharide it may first be hydrolysed into mono- or di-saccharide units. Specified carbohydrates and polyhydric alcohols are glucose, fructose, cane sugar molasses, dextrose, sucrose, maltose, starch, dextrins, cellulose, glycosides, glycerol and sorbitol. Specified tannins are numerous including both the hydrolysable and condensed types; utilized in the examples are sulphited quebracho extract, myrabolam extract and quebracho extract. Optional additives include tackiness reducing agents talc, stearates, clays, zinc oxide strengthening agents phenol-formaldehyde condensates, urea-formaldehyde condensates, silicone resins and melamine-formaldehyde resins natural or synthetic thermoplastic materials to increase resiliency and resistance to thermal shock stripping agents plumbago, talc, silicones and diatomaceous earth hardening agents sulphuric, phosphoric, chromic, hydrochloric, hydriodic, hydrobromic, lactic, acetic, formic, citric, oxalic, gallic, phthalic and salicyclic acids and anhydrides as well as hexamethylenetetramine, aniline, anhydroformaldehyde aniline, the naphthylamines, thiocarbonilamide, p-aminophenol, p-phenylene diamine, pyridine, thiourea, isoamylamine, hydroxylamine, ammonia, paraformaldehyde, polyoxymethylene derivatives and formaldehyde fillers wood meal, pine wood flour, cotton linters, mica, asbestos and mineral powders. The thermosetting products may be used for bonding finely divided metals, fuels, and micas in such processes as the production of sintered products, coal briquettes and tiles; a particular use is in the preparation of shell moulds either by applying a moulding mixture containing a granular refractory substance (usually sand) and the thermosetting binder in granular form or by applying a granular substance coated with the thermosetting binder. For shell-moulding applications the following additives may be employed:- finely divided substances such as iron oxide, manganese oxide and silica flour to impart a smoother finish to the castings inhibiting agents ammonium borofluoride, boric acid and sulphur and free-flow promoting agents (in the coated granular substance application) zinc oxide, aluminium hydroxide, calcium oxide and hydroxide; sodium, magnesium, ammonium and zinc chlorides; calcium, zinc and aluminium stearates; magnesium, zinc and the alkali and alkaline earth metal carbonates; ammonium persulphate, manganese dioxide, potassium and sodium nitrates and other inorganic oxidizing agents, the isocyanates, sodium acetate and complex hydrated alumino-silicates such as the montmorillonites.ALSO:Resinous solid thermosetting products, which may be in the form of foams, are obtained from the reaction between at least one carbohydrate or at least one polyhydric alcohol containing at least 3 carbon atoms and at least one tannin. Specified carbohydrates and polyhydric alcohols are glucose, fructose, cane sugar molasses, sucrose, maltose, dextrose, starch, dextrins, cellulose, glycosides, glycerol and sorbitol. Numerous tannins are specified including both the condensed and hydrolysable types. Numerous other additives are specified (see Group IV(a)). In Example 5, cane sugar molasses are mixed with aniline (hardening catalyst), sulphited quebracha extract and concentrated hydrochloric acid (hardening catalyst) and the resultant mass heated to produce a hard, brittle foam.