GB341443A - Process for manufacturing dispersions - Google Patents

Abstract

Aqueous dispersions of asphalt, tar, pitch and the like, prepared with the aid of finely divided solids such as bentonite or colloidal oxides hydroxides or silicates, are treated with an electrolyte, in quantity sufficient normally to cause flocculation of the dispersion or with two or more electrolytes added in admixture or in succession, flocculation being prevented by adding the electrolytes gradually and with continued beating of the dispersion. The beating may be effected in the apparatus described in Specification 334,100, [Class 81 (i), Disinfecting &c.], and may be continued after the electrolytes have been added. Electrolytes may also be added to the dispersing agent. Protective colloids such as gums, starch dextrine, tapioca flour or tannin may be added before, during, or after the treatment. Suitable electrolytes are sulphuric, hydrochloric, phosphoric, chromic, oxalic, or benzoic acid; acid salts such as potassium dichromate, aluminium sulphate, or acid sodium or calcium phosphate; and magnesium or calcium oxide or hydroxide. In examples: (1) Mexican asphalt is dispersed with an aqueous suspension of equal parts of bentonite and New Jersey pottery clay, to which 10 per cent of potassium dichromate has been added. The dispersion, containing 20 to 50 times as much asphalt as dispersing agent is then beaten during the gradual addition of 0,3 per cent phosphoric, 0,4 per cent chromic, or 0,1 per cent hydrochloric acid, or 1 per cent potassium dichromate, relative to the weight of the dispersion. The addition is preferably made in small increments, each being added only when the beating action has dissipated the flocculation induced by the previous one. The dispersion gives a rust inhibiting coating to metal surfaces. (2) Coal tar is dispersed in water with a bentonite suspension made alkaline with sodium carbonate, or ammonium or trisodium phosphate. An acid salt, an acid, or a mixture of a basic and an acid substance, in similar quantities as are used in (1), is then added while beating.