GB465589A - Improved process for the emulsification of tars - Google Patents

Abstract

Stable aqueous emulsions of road tars, pitch, bitumen and like materials are obtained by first preparing an inverted emulsion of the "water-in-oil" type from the whole of the tar &c., and a quantity of water not less than 5 per cent by weight of the tar &c. used and an emulsifying agent, and this emulsion is then added to and dispersed in a concentrated aqueous solution of an emulsifying agent, which contains not less than one-eighth part by weight of the emulsifying agent, whereby the first emulsion is reverted into an emulsion of the "oil-in-water" type. Suitable emulsifying agents are water-soluble and include alkalies, soaps, alkali-soluble proteins, alkali salts of weak acids, e.g. sodium acetate, formate, borate, stearate or tri-basic phosphates, sodium alginate, potassium chromate or bichromate, resin soaps, triethanolamine oleate or stearate, turkey red oil, glue, size or starch or mixtures thereof. The emulsions are prepared in tanks fitted with suitable stirring gear, and preferably heating means such as steam coils, and arranged so that the contents of the first tank can be discharged into the second. According to examples: (1) the first emulsion is prepared from 1500 lbs. tar, 150 lbs. water at 85 DEG C. and 40 lbs. of 25 per cent ammonium rosin soap. This emulsion is then reverted by addition to a solution prepared from 40 lbs. of 25 per cent ammonium rosin soap, 20 lbs. soluble casein, 60 lbs. water at 85 DEG C. and 1,9 lbs. ammonia (s.g. ,880). When reversion is complete, 190 lbs. of water are added to obtain a product containing 75 per cent by weight of tar. When further dilution is required, a potassium bichromate solution is added to the second emulsifying agent; (2) the first emulsion is prepared by adding in this order, 40 lbs. of 25 per cent sodium rosin soap (having a pH value of 9), 140 lbs. water at 85 DEG C. and 1,25 lbs. tri-sodium phosphate dissolved in 10 lbs. water followed by 1500 lbs. of continuous vertical retort road tar. This emulsion was then added to a mixture of 40 lbs. of 25 per cent. sodium rosin soap, 20 lbs. soluble casein, 130 lbs. water at 85 DEG C., \ba1/8\beth gallon of 5N caustic soda solution and 1 lb. tri-sodium phosphate dissolved in 10 lbs. water. The final emulsion was diluted with 415 lbs. water to obtain a product containing 65 per cent of tar; (3) the first emulsion is prepared by mixing 20 lbs. sodium alginate (10 per cent), 170 lbs. water at 85 DEG C. and 1500 lbs. of tar, and was reverted by addition to a mixture of 25 lbs. sodium alginate (10 per cent), 25 lbs. casein, 100 lbs. water and 1,9 lbs. ammonia (s.g. ,880). If the tar is very viscous, extra water may be added during the reversion. The emulsion may be further diluted if desired; (4) a casein/sodium rosin soap mixture is used for the preparation of the \water-in-oil" emulsion and also for its reversion into an "oil-in-water" emulsion.