Process for producing dibenzanthrone containing vat dyes

A process for producing a vat dye of the formula I ##STR55## wherein n is 1 or 2,

• Z is H, unsubstituted or substituted alkyl, unsubstituted or substituted aryl or a heterocyclic radical, when n is 1, or a direct bond, unsubstituted or substituted alkylene, unsubstituted or substituted arylene or a heterocyclic radical, when n is 2,
• X is H, Cl or a group of the formula --SO.sub.2 T, where T is the radical of an aliphatic or aromatic, primary or secondary amine, and
• Y is H or Cl,
• which process comprises condensing n equivalents of dihydroxydibenzanthrone of the formula II ##STR56## in chlorosulfonic acid, with an aldehyde of the formula III
• Z--(CHO).sub.n (III)
• wherein Z and n have the meanings defined above, and subsequently, if dyes of the formula I in which X and/or Y are (is) not hydrogen are being produced, chlorinating the reaction product and/or reacting it with thionyl chloride and an amine of the formula IV
• H--T (IV),
• where T has the meaning defined above.