Process for the preparation of crystalline sodium disilicates

In order to prepare crystalline sodium disilicates having a sheet structure, a molar ratio of SiO2 to Na2O of (from 1.9 to 2.1):1 and a water content of less than 0.3% by weight, a water glass solution is first obtained by reacting sand with aqueous sodium hydroxide in a molar ratio SiO2 to Na2O of...

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Bibliographic Details
Main Authors MICHAEL KOTZIAN, GUENTHER SCHIMMEL, ALEXANDER TAPPER, KNUT BAUER
Format Patent
LanguageEnglish
Published 24.06.1993
Edition5
Subjects
CHEMISTRY
COMPOUNDS THEREOF
INORGANIC CHEMISTRY
METALLURGY
NON-METALLIC ELEMENTS
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Summary:In order to prepare crystalline sodium disilicates having a sheet structure, a molar ratio of SiO2 to Na2O of (from 1.9 to 2.1):1 and a water content of less than 0.3% by weight, a water glass solution is first obtained by reacting sand with aqueous sodium hydroxide in a molar ratio SiO2 to Na2O of (from 2.0 to 2.3):1 at temperatures of from 180 to 240 DEG C and pressures of from 10 to 30 bar. This water glass solution having a solids content of at least 20% by weight is treated in a spray dryer with hot air of from 200 to 300 DEG C to form a powdered amorphous sodium disilicate having a water content (determined as loss at red heat at 700 DEG C) of from 15 to 23% by weight and a bulk weight of at least 300 g/l. The spray-dried powdered amorphous sodium disilicate is pre-ground. The pre-ground sodium disilicate is introduced into a rotary kiln which is equipped with devices for moving solids, is heated externally via its wall and in its interior has a plurality of different temperature zones, the sodium disilicate being treated therein at temperatures of from 400 to 800 DEG C for from 1 to 60 minutes to form crystalline sodium disilicate.
Bibliography:Application Number: ZA19920009886