GB816254A - Preparation of foamed bitumen - Google Patents

Abstract

In a method of making foamed bitumen, an asphaltic bitumen, in which are dispersed a blowing agent and a surface-active agent soluble in the bitumen, is heated to a temperature above the decomposition temperature of the blowing agent but below the temperature at which the viscosity of the bitumen falls to such a low value that a substantial escape of emitted gas occurs, the mixture is maintained at this temperature until the desired foam volume has been obtained, and is then cooled. Specific examples are given of surface active agents which can be used belonging to the following classes of compounds: quarternary ammonium compounds; alkyl amines and their salts; cyclic amines; partial amides of polyamines, and salts thereof; complex polyamino compounds derived from ammonolysis of chlorinated paraffin wax, the higher fatty acid salts of polyamines derived from reaction between acrolein and ammonia, adducts of hydrogen sulphide and diallyl amine; complex polyamines containing amino and hydroxyl groups, e.g. condensation products of epihalohydrins with ammonia or amino compounds; partial amides of these latter complex polyamines obtained by treatment with a variety of fatty, naphthenic, resin, and cyclic acids and certain mixtures thereof; salts of carboxylic and organic sulphonic acids and of acids derived from animal, plant, and fish oils; high molecular weight acids such as carboxylic, sulphinic, sulphonic, and organic sulphuric acids, e.g. sulphated fatty oils and sulphonated mineral oils; hydroxy fatty acids; hydroxyl-containing organic compounds, e.g. glycols, partially hydrolysed glycerides, monohydric alcohols, condensation products of ethylene or propylene glycol with alcohols or carboxylic acids; organic compounds or phosphorus. The surface-active agent may be added to the bitumen to be foamed after the latter has been warmed to facilitate mixing, or it may first be mixed with a small amount of softer grade bitumen which mixture is then added to the main bulk of bitumen. The blowing agent, which is stable at room temperature but decomposes below 450 DEG C., may be inorganic or organic, e.g. sodium bicarbonate, ammonium carbonate, hydrated ammonium alum, urea, diazoaminobenzene, dinitrosopentamethylene. The asphaltic bitumen is a solid or semi-solid product derived from asphaltic, semi-asphaltic, or non-asphaltic crude petroleum oils, and may be naturally-occurring or prepared by treating residual petroleum oils by steam or vacuum distillation; it may also be a straight-run, steam refined or a so-called blown asphaltic bitumen. The mixture of bitumen, blowing agent, and surface-active agent is heated in a mould preferably between 100 DEG and 180 DEG C. In two examples a dispersion of sodium bicarbonate in soft grade bitumen at 100 DEG C. is added to blown bitmen at 175 DEG C. containing aluminium stearate as surface-active agent, and the mix is heated to 135 DEG C. for 2 hours.