GB1106281A - Gelled compositions - Google Patents

Abstract

A clay capable of base exchange and of swelling in water is treated in the aqueous phase with an ammonium compound to give a modified clay, there being used from 40 to 500 (preferably from 100 to 300) milliequivalents of ammonium compound per 100 grams of clay. Clays which are suitable for the treatment are naturally-occurring clays containing high proportions of montmorillonite, for example Wyoming bentonite, hectorite and other bentonites, which clays may be activated, for example by soda ash, to replace cations other than sodium ions, for example calcium ions, by sodium ions thereby to enhance the ability to swell in water. The ammonium compound has a cation of the general formula R1R2R3R4N+ wherein R1 is a substituted or unsubstituted lower alkyl group and R2, R3 and R4 are hydroge atoms or substituted or unsubstituted lower alkyl groups, the lower alkyl groups being the same or different and each containing from one to four carbon atoms, or wherein R1R2 represent not more than four carbon atoms in a cyclic saturated group containing the ammonium nitrogen atom and R3 and R4 are as defined above, the total number of carbon atoms in R1, R2, R3 and R4 in either of the above alternatives not exceeding six. The lower alkyl groups, examples of which are methyl, ethyl, propyl, n-butyl and isobutyl groups, may be substituted with, for example, amino or hydroxyl groups (which groups themselves may be substituted) or halogen atoms. The anion of the ammonium compound may be the chloride, bromide, iodide, formate, acetate, nitrate, sulphate or hydroxyl ion. The ammonium compound may be a salt formed from methylamine, dimethylamine, trimethylamine, tetramethyl ammonium hydroxide, ethylamine, diethylamine, triethylamine, n- or isopropylamine, n-, sec-, tert- or iso-butylamine, ethanolamine, diethanolamine, triethanolamine, 2 - aminoethylethanolamine, methyldiethanolamine, N,N - dimethylaminoethanol, isopropanolamine, di - isopropanolamine, 2 - amino - 2 - ethylpropane - 1,3 - diol, 3-dimethylaminopropane - 1 - ol, 1 - dimethylaminopropane - 2 - ol, 2 - amino - 1 - butanol, ethylenediamine, 1,2 - propylenediamine or morpholine. A gelled aqueous composition, in which is dispersed from 1.5 to 20 (preferably from 2 to 6) per cent by weight, based on the aqueous content of the composition, of clay modified with an ammonium compound as defined above, may be prepared by dispersing unmodified clay in the aqueous composition which is to be gelled and then adding thereto either the ammonium compound or, separately and preferably in equivalent amounts, a base and an acid which together form the ammonium compound, for example as an aqueous solution or solutions. The gelled aqueous composition should have a yield value (the minimum force which must be applied to the gel to cause it to flow) greater than 20 dynes per square centimetre.