Patent GB-441384-A (GB)
Title: Improvements in the manufacture and production of metal oxides colloidally soluble in water
IPC: B01J13/00
Filed: 1934-07-16
Abstract: Hydroxides of trivalent metals, e.g. iron and chromium but particularly aluminium, colloidally soluble in water are obtained by treating metal salts with stoichiometrical amounts of reagents which decompose the salts with the formation of hydroxides, preferably in several stages with an intermediate solidifying treatment if desired, treating the hydroxides with peptizing agents, e.g. acids, and at the same time or subsequently protectively withdrawing water to form a concentrated solution, a soluble jelly or a soluble solid gel containing at least sufficient water to correspond to a product consisting of hydroxide.  The salts formed are removed at any stage after the precipitation.  The peptization is effected by the use of 10--20 per cent of the acid required for salt formation. Hydrochloric acid or nitric acid solutions of aluminium hydrate obtained by the alkaline decomposition of bauxite are preferably treated with ammonia to give a pH value of 6--8 and peptized with 5--15 per cent of hydrochloric or acetic acids, or the alkali aluminate solutions obtained as above may be directly precipitated with acids.  When the final product may contain iron, the solutions obtained by decomposing clays, bauxite, laucite, glauconite, labradorite or feldspar may be used, and the mother liquors containing ammonium salts may be used as fertilizers.  Aluminium hydroxide insoluble in water may be worked up, e.g. in a ball mill, with an amount of acid or alkali hydroxide insufficient for complete solution, the mass is then treated with the stoichiometrical amount of alkali or acid, washed and protectively dried in the presence of peptizing agents.  In this case, the product dissolves to form a suspension in which the colloidal fraction acts as a protective colloid for the coarser insoluble residue.  To facilitate recovery of the salts in the mother liquors, the hydroxide to be peptized is obtained in a readily filterable and washable form by subjecting the precipitated product to a mechanical treatment, e.g. grinding, beating, rolling, kneading or pounding, then separating the alkali salts and thoroughly washing the hydroxides with further mechanical treatment if desired.  Gaseous ammonia may also be used as a precipitant, in this case the aluminium salt solution, not too concentrated, is saturated with ammonia and the final quantity of ammonia added in solution, or the reactants may be run continuously into a vessel provided with an overflow.  In all cases, the concentration of the mass to be peptized and of the peptizing agent is so selected that the mixture before drying contains at least 30 gms. anhydrous oxide per litre.  The colloidal hydroxides may also be freed from soluble salts by extraction with organic solvents, e.g. ethyl or methyl alcohols, or liquid ammonia, or this treatment may be combined with a filtering and washing process.  Iron salts may be removed by extraction with solvents such as acetone, cyclohexanol or ether, and ammonium and iron salts may be removed by a mixture of ethyl alcohol and acetone, and if necessary hydrochloric acid may be added to the solvent, or treatment with acid precede the extraction. Ammonium salts may also be removed by protectively drying the reaction mass, after separation of mother liquor, the dried mass then being lixiviated with water, and again filtered. The mass is then dried or mixed with water whereby some acid formed during the protective drying acts as peptizing agent, additional acid being added if desired.  According to examples: (1) 160 kgms. of iron-free Al(OH)3 obtained by the alkaline decomposition of bauxite are dissolved at 90 to 100 DEG  C. in 945 kgms. of 40 per cent nitric acid and 135 kgm. water.  A small amount of undissolved alumina is worked up with the next batch, and the aluminium nitrate solution contains about 0.5 to 0.9 per cent free acid.  This solution is then treated with 510 kgm. of a 20 per cent (by wt.) ammonia solution in a ball mill lined with aluminium or rubber, heat being applied.  The mass is filtered, washed with a little hot water, ground again in the ball mill with the addition of a little hot water and again filtered. The mother liquor and washing waters are worked up into a fertilizer in a multiple evaporator.  The washed cake is heated while kneading vigorously with 73 kgms. of 30 per cent hydrochloric acid.  The paste is then dried at 100--120 DEG  C. until it possesses a water content of 50--55 per cent and then comminuted.  (2) The aluminium nitrate prepared as above is reacted with ammonia in two stages, a sol being formed in the first stage.  440 Kgm. of a 20 per cent (by wt.) ammonia solution are added to the aluminium nitrate solution at 65--70 DEG  C. while stirring, any hydroxide precipitated being redissolved before adding fresh ammonia.  The crude sol is cooled to 25 DEG  C. and 65 kgm. of 50 per cent potassium acetate solution are added.  The sol is flowed into flat aluminium vats in which it gradually solidifies.  After standing, the jelly is broken up and treated with the quantity of ammonia necessary for the conversion of the nitrate in the jelly, i.e. 70 kgm. of a 20 per cent solution, diluted with 748 kgm. of water.  When the reaction is completed, the granular mass is filtered and washed, with treatment in a ball mill if desired.  It is subsequently treated as in the first example.  The products may be used for waterproofing building materials, e.g. concrete, cement or lime mortar; or waterproofing insulating materials, e.g. those prepared according to Specification 336,318, [Class 70]; waterproofing buildings or elements made of porous materials, e.g. bricks, stones, tiles, plates, pipes, walls, wall and floor coverings, asbestos plates, cork or gypsum plates, diatomite, if desired with other materials as silica sol, lime water or ammonia. The materials are subsequently heated to 100--400 DEG  C. or treated with ammonia.  The sols are also suitable for coatings, if desired transparent, on various materials, e.g. glass, especially show window panes and spectacle glasses, e.g. in gas masks, to render them moisture proof; for glazing ceramic bodies, e.g. silicon articles, the bodies being afterwards fired; as a varnish on wood or tapestry; for the impregnation of wood, textiles, threads, fabrics, paper or pasteboard, with other materials if desired, to render them waterproof, prevent putrefaction or reduce combustibility.  They may also be used, together with gelatine if desired, to prepare or stabilize petroleum, wax, oil or paraffin emulsions or as protective colloids in the preparation of colloidal sols of inorganic materials, e.g. sulphur or sulphur and latex suspensions.  The sols or jellies are also suitable for the preparation of concentrable thick juice from sugar beet slices; for the precipitation of floating substances in solutions, e.g. fats, starch, yeast, albumen and gelatinous raw materials; for the enrichment of enzymes; as mordants for fabrics and leather; for use in the lacquer and dye industries; in the preparation of yeast, wine, beer; as substitutes for lubricants; for the refining, desulphurizing and deodorizing of solutions, oils and hydrocarbons; and as initial materials for the preparation of salts of organic acids, e.g. acetic, formic, lactic, citric, tartaric, stearic, salicylic acids or pyrogallol.  The sols of the hydroxides of iron, chromium and aluminium are suitable as tanning agents, alumina sols being especially suitable for tanning, the products being washable.  They may also be used in the manufacture of coloured leathers.  The products may also be employed as agents for combating pests, preventing dry rot and rust, putrefaction, preserving eggs, as polishing, washing and cleaning agents or as additions to the same; as coagulating agents, e.g. for latex; as fillers for rubber and rubber-like substances, pasteboard and paper and for weighting silk; as adhesives and cements for glass, metals and ceramic masses; as binding agents in the sizing of paper; in the preparation of silicon bricks, metal bricks, magnet cores, safety glass, fireproof tiles and artificial compositions and compressed masses, e.g. urea condensation products; and in the briquetting of coal or coke.  They may also be used as the framework for making alcosols, alcogels, benzene sols and gels and other organosols and organogels, e.g. in the production of solid or pasty burning spirits, or in the solidification of perfumes or scouring water, the tube in the latter case being provided with a filter so that only the liquid is pressed therefrom.  The pure sols or jellies may also be used for medicinal purposes, e.g. as a substitute for aluminium acetate; sols peptized with organic acids, e.g. acetic acid being particularly suitable.  They may also be worked up with fats and oils, e.g. wool grease, to form salves. Specification 398,517 also is referred to.  The Specification as open to inspection under Sect. 91 also includes the subject-matter of Specification 441,206.  This subject-matter does not appear in the Specification as accepted.ALSO:Hydroxides of trivalent metals, e.g. iron and chromium, but particularly aluminium, colloidally soluble in water are obtained by treating metal salts with stoichiometrical amounts of reagents which decompose the salts with the formation of hydroxides, preferably in several stages with an intermediate solidifying treatment if desired, treating the hydroxides with peptizing agents, e.g. acids, and at the same time or subsequently protectively withdrawing water to form a concentrated solution, a soluble jelly or a soluble solid gel containing at least sufficient water to correspond to a product consisting of hydroxide.  The salts formed are removed at any stage after the precipitation.  The peptization is effected by the use of 10-20 per cent of the acid required for salt formation.  Hydrochloric acid or nitric acid