Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1996-03-01
1998-06-16
Bell, Mark L.
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
4233301, 427150, 4273762, 4273835, C01B 3326, B41M 312, B05D 302
Patent
active
057665648
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for the production of aluminosilicates and to particular aluminosilicates having a high surface area and alumina content which are produced therefrom.
BACKGROUND OF THE INVENTION
Aluminosilicates useful in copy paper are known from Belgian patent publication 812,140. These aluminosilicates have a surface area of 300-800 m.sup.2 /g, an average pore volume of 0.5-1 ml/g, an average particle diameter of 3-15 .mu.m, and an alumina content of 7.5-28% by weight. Also disclosed is a process for the production of aluminosilicates which consists of reacting aluminum sulphate and sodium silicate in solution.
U.S. Pat. No. 3,915,734 discloses a sodium aluminosilicate useful as pigments in paper coatings, as fillers in rubber compounds, in inks, paints, plastics and the like. The reaction mixture from which the aluminosilicate is obtained includes an alkali metal silicate, an aluminum salt, and alkaline earth metal salt. The use of a reaction mixture not containing an alkaline earth metal salt in a similar process is mentioned in U.S. Pat. No. 2,739,073.
In a preferred process of U.S. Pat. No. 3,915,734, a portion of the solution of the alkali metal silicate, e.g., sodium meta- or disilicate, is added to the reaction media prior to the introduction of the aluminum salt solution, e.g., aluminum sulphate. In general, the pH should be maintained at 8-12 until all of the alkali metal silicate has been added. The addition of the aluminum salt solution may then be continued until the pH is reduced to 8-10. The temperature of the reaction vessel is maintained at 65.degree. C. throughout the reaction. In Example 4 the aluminum sulphate and sodium silicate solution are added simultaneously while the pH is maintained at 8.0 by adjusting the rate of addition of the two solutions.
The process disclosed in U.S. Pat. No. 3,915,734 differs from the present process in one important respect: the precipitation must be carried out at a pH from 8.0-10.0. This difference is critical since the pH at which precipitation is carried out exerts a strong influence on the properties of the aluminosilicate product.
British patent publication 1,477,557 discloses an aluminosilicate having a surface area of 185-622 m.sup.2 /gram. A process for making the same consists of mixing at high shear rate concentrated aqueous solutions of alkali metal silicate such as sodium silicate and of a metal salt other than an alkali or alkaline earth metal such as aluminum sulphate. The pH of the resulting aqueous composition is from 2-7.5. Preferably, the alkali metal silicate is sodium silicate and the metal salt is aluminium sulphate. These aluminosilicates can be used in water purification, as fillers in paper and textiles, as coatings for filaments and fibres in synthetic textiles, in the compression moulding industry, in water desalination, and as a filler in soap.
The process of the British patent publication differs from the present process in that it employs a far higher ratio of SiO.sub.2 :Na.sub.2 O than is used in the present process. Further, this patent does not have as a primary goal the production of high surface area products and thus states that equally good results are obtained at pH 2.5-3.5 as at pH 5.0-6.0 whereas in the present process, pH 2.5-3.5 cannot be successfully employed.
International patent publication WO 8,103,642 describes a record material carrying a colour developer composition comprising a hydrated silica/hydrated alumina composite. A process for making the coated record material consists of reacting hydrated silica and hydrated alumina together in an aqueous medium to produce a dispersion of said composite, applying a coating composition incorporating said composite to a substrate and drying the coated substrate to produce said record material, characterized in that the mean alumina content of the composite on a dried weight basis is up to 7.5%. For example the composite can be prepared by adding together sodium silicate and aluminium sulphate solution, and sub
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Konuksever Abdullah
Tijburg Ivo Ignatius Maria
Akzo-PQ Silica Vof
Bell Mark L.
Mancini Ralph J.
Morris Louis A.
Troilo Louis M.
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