Coal tar pitch and the preparation and use thereof
AssigneeRutgerswerke Aktiengesellschaft
InventorsWinfried Boenigk, Hans-Dieter Behrens, Hans Spengler
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Abstract
An isotropic coal tar pitch having a low content of carcinogenic compounds is prepared by distilling a coal tar pitch in an evaporator having a specific evaporator surface of from 330 to 10,000 m.sup.2 /m.sup.3, at a temperature in the range of from 300.degree. to 380.degree. C., under a pressure not exceeding 1 mbar, whereby the average stay period is from 2 to 10 minutes. The isotropic pitch thus obtained contains less that 50 ppm of benzo[a]pyrene and is suitable, optionally after adding an oil, resin or other modifying agents having a low benzo[a]pyrene content, for use as binding and impregnating agent and also as protecting agent in construction materials or as varnish (painting agent).
Claims10
A coal tar pitch which has an optical anisotropy below 2% comprising benzo[a]pyrene, wherein the concentration of said benzo[a]pyrene is less than 50 ppm.
A coal tar pitch which has an optical anisotropy below 2% wherein said coal tar pitch contains benzo[a]pyrene and wherein the concentration of said benzo[a]pyrene is less than 50 ppm.
A coal tar pitch which has an optical anisotropy below 2% comprising benzo[a]pyrene, wherein the concentration of said benzo[a]pyrene is 20 to 40 ppm.
Dependencies are inferred from the claim text.