PURPOSE: To obtain an anthraquinone vat dye which has excellent fastness and a blue tint without using any harmful material such as MnO2, by chlorinating dianthraquinone-N,N'-dihydroazine in the absence of a catalyst in conc. sulfuric acid.
CONSTITUTION: An alkaline condensation agent is added to 1-aminoanthraquinone in the presence of dimethyl sulfoxide or 1,3-dimethyl-2-imidazolidinone and an oxidizing agent to effect a condensation reaction, thus obtaining dianthraquinone-N,N'-dihydroazine (A) of formula I. 1pt.wt. component A is dissovled in 90W95% sulfuric acid in a quantity of 3W20 times by weight that of component A. Chlorine is made to bubble through the soln. to chlorinate component A. Water is added thereto to adjust the concn. of sulfuric acid to 83%. The soln. is filtered at room temp. The resulting filter cake is dissolved in 98% sulfuric acid and reduced with aluminum powder to obtain a vat dye of formula II (wherein n is 1W2).
NAKAJIMA YOSHIHIKO
TAGASHIRA HIROMASA
HIRAYAMA AKIRA
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