GB447710A - Improved manufacture of highly swellable inorganic substances - Google Patents

Abstract

Bentonites or similar minerals which are only slightly swellable are treated to replace their exchangeable cations by monovalent cations such as Na, K, and Li, the product being freed from water and dried. It is highly swellable. The quantity of exchangeable cation is determined and the mineral such as calcium bentonite treated with a compound of a monovalent base to replace sufficient Ca by monovalent ion. The compounds may be added in solid or solution form. Sodium, potassium or lithium salts which form sparingly soluble compounds with the exchangeable cations, for example carbonates, sulphates, phosphates or oxalates, may be employed. Thus, 1000 kg. of Ca-bentonite, moist as mined, with 80 milli-equivalents of exchangeable calcium per 100 g. dry substance, is made into a slurry with water and mixed with 20--25 kg. anhydrous soda. The slurry is agitated for 15 mins., de-watered, dried, and ground. Bentonites, that is all clays containing the mineral montmorillonite, and bentonite-like minerals such as smectite, beidelite, ehrenbergite, damontherolite, fuller's earth and bole are suitable starting materials. The addition of a few per cent of the products to non-plastic substances such as cori-moulding sand in foundry work gives an intimate binding or prevents settling of glazes, colours, enamels or the like in the ceramic industry. One-fifth of the amount of clay usually employed suffices.ALSO:Slightly swellable bentonites and like earths are treated with compounds of monovalent bases to replace their exchangeable cations by monovalent cations such as Na, K, and Li. The addition of a few per cent of the products to non-plastic substances such as core-moulding sand gives an intimate binding.