Preparation of azo pigments with low PCB content by coupling in the presence of olefins
AssigneeHoechst Aktiengesellschaft
InventorWolfgang Rieper
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Abstract
The production which is customary in practice of monoazo compounds based on dichloro- and trichloroanilines or disazo compounds of the chlorinated biphenyl series by conventional coupling methods meets with difficulties in that the resulting pigments are contaminated by traces of polychlorinated biphenyls. According to the invention, it has now been found that by addition of water-soluble olefins of the type ##STR1## (R =H, alk or Oalk; X =--COOR.sup.1, --CONHR.sup.2 or --NR.sup.3 COR.sup.4) in the azo coupling, the side reactions which form PCBs can be decidedly suppressed during synthesis of the pigments.
Claims11
A process for the preparation of a monoazo pigment of the formula (I) ##STR4## or of a disazo pigment of the formula II ##STR5## in which n is 1, 2 or 3, m is 1 or 2, K.sup.1 and K.sup.2 are each the radical of an acidic CH coupling component H--K.sup.1 or H--K.sup.2 from the acetoacetic acid arylamide or naphthol series or of a heterocyclic structure and K.sup.1 and K.sup.2 are identical or different, which contains not more than 25 .mu.g of polychlorinated biphenyls (PCBs) per gram of pigment, by azo coupling in an aqueous medium, which comprises carrying out the coupling reaction in the presence of olefins of limited or unlimited water-solubility of the formula III ##STR6## in which R is a hydrogen atom or an alkyl or alkoxy group and
- X is a radical of the formula --COOR.sup.1, --CONHR.sup.2 or --NR.sup.3 COR.sup.4 or--if R is not alkoxy--is also the radical --CN, in which
- R.sup.1 is hydrogen, alkyl or alkyl which is substituted by 1 or more radicals from the group comprising hydroxyl, alkoxy, amino, alkylamino and dialkylamino,
- R.sup.2 is hydrogen, alkyl or alkyl which is substituted by 1 or more radicals from the group comprising hydroxyl, alkoxy, amino, alkylamino, dialkylamino, sulfo, carboxyl, alkoxycarbonyl and saturated or unsaturated alkanoylamino as well as corresponding N-alkanoyl-N-alkyl-amino,
- R.sup.3 is hydrogen or alkyl and
- R.sup.4 is alkyl.
Dependencies are inferred from the claim text.