GB636602A - Improvements relating to the production of pitch mastic - Google Patents

Abstract

An oil for use in the preparation of a pitch mastic (see Group V) is prepared from the middle tar oil fraction produced in the low-temperature carbonization of coal. The fraction is washed successively with 30 DEG Tw. caustic soda solution to remove tar acids, 3 per cent by volume of 40 per cent sulphuric acid, 1 1/2 per cent by volume of 80 per cent sulphuric acid, water, 30 per cent caustic soda solution to neutralize free acid, and 4 per cent by volume of 60 DEG Tw. caustic soda solution. The resultant is then distilled at 190-225 DEG C. under reduced pressure to produce a product of initial boiling-point of over 300 DEG C.ALSO:Pitch mastic for use particularly as flooring is prepared by incorporating a coarse and a fine aggregate into a coal-tar pitch to which has been added a fluxing oil consisting mainly of aromatic hydrocarbons compatible with pitch, having an initial boiling point of approximately 300 DEG C., and evolving no noxious or irritant fumes when heated during laying of the mastic. The pitch is preferably one produced during the low-temperature carbonization or distillation of coal and has a full carbon content of not more than 10 per cent, while the fluxing oil may be obtained from the middle oil fraction boiling between 200 DEG C. and 330 DEG C. produced during low temperature carbonization or from a mineral oil fraction. The middle oil fraction from which the fluxing oil is obtained is composed of 45 per cent by volume of crude phenols, 12 per cent paraffin hydrocarbons, 14 per cent olefines, 26 per cent aromatic hydrocarbons and 3 per cent crude bases, and of the fluxing oil obtained therefrom 15-40 per cent distils at 345 DEG C. and 3.6 per cent is lost by evaporation at 325 DEG C.; corresponding figures for the mineral oil fraction are 3.5 and 0.6 per cent respectively. The fluxing oil is obtained from the middle oil fraction by treating chemically for the removal of the acids and bases and then distilling under reduced pressure (see Group III). The mastic is prepared by mixing the substances together at a temperature not exceeding 160 DEG C., there being present 9-19 per cent of pitch 1-3 per cent of fluxing oil and the remainder aggregate which may include an absorbent filler such as sawdust (preferably from a hard, non-resinous, and low moisture-content wood) up to 50 per cent by weight of the mastic, and a pigment. Specification 568,705 is referred to. According to the Provisional Specification, the fluxing-oil may be incorporated in an asphalt mastic.