Hoechst Aktiengesellschaft

Martin Schott

Hans-Peter Rieck

Jurgen Russow

Gunther R Schimmel

Reinhard Gradl

Werner Gohla

Willy Ott

For the preparation of crystalline sodium silicates having a sheet structure and an SiO.sub.2 /Na.sub.2 O molar ratio of 1.9:1 to 3.5:1 from waterglass solutions having a solids content of 20 to 65% by weight, the waterglass solutions are first treated in a spray-drying zone. This gives a pulverulent amorphous sodium silicate having a maximum ignition loss of 20% by weight, while the waste gas leaving the spray-drying zone is at a temperature of at least 140.degree. C. Thereafter, the spray-dried sodium silicate is heated in an ignition zone containing an agitated solid bed at temperatures of 500.degree. to 800.degree. C. for 1 to 60 minutes in the presence of at least 10% by weight of recycled material. This recycled material was obtained by mechanical comminution of crystalline sodium silicate discharged from the ignition zone.

Process for the preparation of crystalline sodium silicates having a

X-ray crystalline sodium silicates having a sheet structure and an SiO.sub.2 :Na.sub.2 O molar ratio of 1.9 to 3.5 are prepared by dissolving an X-ray crystalline sodium silicate having a sheet structure and an SiO.sub.2 /Na.sub.2 O molar ratio of 1.9:1 to 3.5:1 in water and evaporating the solution at temperatures of 20.degree. to 445.degree. C. For the preparation of detergents or cleaners, a mixture of surfactants and builders, which may also contain fillers, bleaching agents, bleach activators and enzymes, is made into a paste with water, mixed with an X-ray crystalline sheet sodium silicate having an SiO.sub.2 /Na.sub.2 O molar ratio of 1.9:1 to 3.5:1, mixed thoroughly and then spray-dried.

Process for the preparation of crystalline sheet sodium silicates

A process for the preparation of a crystalline sheet-type alkali metal silicate is described, in which an aqueous solution of an alkali metal silicate or a suspension of an amorphous alkali metal silica having a molar ratio M.sub.2 O (unneutralized)/SiO.sub.2, where M represents an alkali metal, of 0.05:1 to 0.8:1 is allowed to react at temperatures of 70.degree. to 250.degree. C. until the sheet-type alkali metal silicate crystallizes out. After the beginning of crystallization, an acidic compound is added in an amount such that an M.sub.2 O (unneutralized)/SiO.sub.2 ratio of 0.05:1 to 0.8:1 is constantly maintained in the mother liquor of a filtered sample. However, at least an amount corresponding to 5 milliequivalents of H.sup.+ per mole of SiO.sub.2 in the alkali metal silicate used is added. The use of seed crystals of the desired sheet silicate is advantageous.

Process for the preparation of crystalline sheet-type alkali metal

Moldings are described which are composed of a silicic acid with a layer structure, or salts thereof with the general formula (H,M).sub.2 Si.sub.y O.sub.2y+1, or the corresponding hydrates, M representing lithium, sodium, potassium or ammonium and y being 1.7 to 24. They can be prepared for example by extruding pulverulent layer silicic acids, or salts thereof with the general formula (H,M).sub.2 Si.sub.y O.sub.2y+1, or the corresponding hydrates, M representing lithium, sodium, potassium or ammonium and y being 1.7 to 24, to produce cylindrical blanks, if appropriate after moistening with water or an organic solvent, and then drying the blanks, or by introducing the same starting materials into a mold, as dry or moist powders, converting them to moldings with the application of pressure and, if appropriate, drying the moldings.

Moldings made of silicate material and processes for their preparation

A process for the production of shaped articles from silicate material by extrusion and/or pelleting and subsequent annealing is described. In this process, pulverulent layered silicic acids of the general formula H.sub.2 Si.sub.y O.sub.2y+1, in which y is a number from 1.7 to 24, or salts thereof, in which all or some of the H is replaced by at least one cation from the group comprising Li.sup.+, Na.sup.+, K.sup.+, NH.sub.4.sup.+, Ca.sup.2+, Cu.sup.2+, Co.sup.2+, Ni.sup.2+ and Mg.sup.2+, are mixed with water or an organic solvent, the mixture is extruded and/or pelleted to give roll-shaped or tube-shaped pieces and these are then dried and annealed under conditions such that the starting material is chiefly converted into cristobalite and/or tridymite. The same material can also be pressed in a molding tool under pressure. Under these conditions, shaped articles which predominantly consist of cristobalite or tridymite and have a Shore hardness of at least 70 can be obtained.

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Steinbach, Germany

Martin Schott