Лако-красочные материалы — производство

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(a) Sodium Antkraquinone-2-tulfonate (“Silver Salt”)

To 125 grains of oleum containing 18 per cent S03 is added, with stirring, 100 grams of anthraquinone of highest purity. The mixture is heated gradually to 135°C., while being stirred slowly, and held at this temperature for 3 hours. The mixture is then allowed to cool to 50°, and 80 grams of 66 per cent oleum is added during the course of 5 min­utes, after which the whole is heated for 4 hours more at 110°. The
sulfonation mixture is then cooled and poured into 1.5 liters water, the aqueous suspension is heated to 80°, and the unchanged anthra — quinone is filtered off and washed with hot water. The hot filtrate is treated with 150 grams of salt and cooled with stirring. After at least 10 hours, the sodium anthraquinone-2-sulfonate, which separates as plates, is filtered off, washed with a small amount of 10 per cent salt solution, pressed out, and dried. The yield is about 73 grams, and about 37 grams of anthraquinone is recovered.

Sodium anthraquinone-2-sulfonate, which is called “silver salt” in the industry because of its appearance, can be recrystallized from water to produce a material which is almost chemically pure. The air-dried material contains one molecule of water of crystallization.

(b) 2-Aminoanthraquinone

50 grams of sodium anthraquinone-2-sulfonate, 120 grams of 25 per cent ammonia, 25 grams of ammonium chloride, and 36 grams of sodium arsenate are placed in a rotating autoclave (page 359) which is heated slowly to 120°C. The temperature is then raised to 200° over a period of 1 hour and held at this point for 12 hours. The pressure increases to about 40 atmospheres. The autoclave is then cooled, and the residual pressure is released through the valve. The 2-aminoanthraquinone, which has separated, is filtered off, washed with water, boiled with about 200 cc. water containing 3 to 4 cc. 40° Be sodium hydroxide solu­tion, filtered off again, and washed with water. Further purification is effected by treating the crude product with several 200- to 300-cc. por­tions of boiling 5 per cent hydrochloric acid, cooling to 50-60°, fil­tering, and washing thoroughly with hot water. The product, after drying, weighs about 30 grams and melts at 300-301°. It is almost chemically pure, but can be improved by reprecipitation from concen trated sulfuric acid[48] or by crystallization from boiling chlorobenzene.77 It has been shown that the completely pure 2-aminoanthraquinone gives an indanthrene blue which is purer and has better fastness to chlorine (see page 321).

Technical Observations. The solution of ammonium sulfite formed by the action of ammonia on anthraquinonesulfonic acid has a deleterious action on the end product. The sulfite must be removed, therefore, by oxidizing it to the sulfate.

Previously, this was done with pyrolusite, but modem processes use arsenic acid (with 2-aminoanthraquinone) and sodium m-nitrobenzenesulfonate (with 1-amino­anthraquinone). The sulfite can also be removed by precipitation with alkaline earth chlorides, e. g., barium chloride. The procedure given above has the advan­tage that it yields a product which is practically ash-free. The ammonium chloride is added to neutralize the alkali formed in the reaction (the arsenite formed acts as free sodium hydroxide). The mother liquors, which contain arsenious acid, are poisonous, of course, and must be handled carefully. They are usually treated with milk ef lime to render them harmless. The toxicity of such waste products is fre­quently overemphasized; if they are discharged into large streams, for example, they rarely poison the fish. In plant operations, the excess ammonia is collected and used over without further treatment.78 For a general discussion of the sulfonation of anthraquinone, see page 56 ff.