Patent GB-573025-A (GB)
Title: Manufacture of trisazo dyestuffs
IPC: C09B31/16
Filed: 1942-08-19
Abstract: Trisazo dyes are obtained by coupling, in an alkaline medium, a diazotised aminoazo compound of the general formula R1-N = N-R2-NH2, wherein R1 and R2 represent residues of the benzene series, free from hydroxy, sulphonic or carboxylic acid groups, and in which the azo and amino groups are in m- or p-position to each other on the residue R2, with an aminonaphtholsulphonic acid of the general formula <FORM:0573025/IV/1> wherein one Z represents a primary amino group and the other Z's each represent H, diazotising the resulting disazo compound and coupling with resorcinol or m-aminophenol (1 mol.).  The products have affinity for natural or regenerated cellulose fibres and the shade and fastness to wet treatments of the resulting dyeings may be improved by an after-treatment with formaldehyde or with a diazotised aromatic amine.  Specified aminoazo compounds are 4-aminoazobenzene and its 3-and 41-methyl, 2 : 21 and 2 : 5-dimethyl, 3-methoxy, 2 - methyl - 5 - methoxy or ethoxy, 2 : 41-dimethyl-5-methoxy, 2 : 5-dimethoxy or diethoxy, 2 - methyl - 21 - or 41 - methoxy and 2-methyl-5 : 41-dimethoxy derivatives, 3-amino-41 - methoxy - azobenzene, 4 - acetylamino - 41 - aminoazobenzene and its 21-methyl, 21-methyl-51 - methoxy, 2 : 21 - dimethyl - 51 - methoxy, 2 - chloro-21-methyl-51-methoxy and 2 : 6-dichloro-21-methyl - 51 - methoxy derivatives, 3 - acetyl - amino - 21 - methyl - 51 - methoxy - 41 - aminoazo - benzene, 4 - formylamino - 21 - methyl - 41 - amino - azobenzene, 4-aminoazobenzene-41-oxamic acid and its 2-methyl and 2-methyl-5-methoxy derivatives, 4 - nitro - 41 - aminoazobenzene and its 2-, 21- and 31 - methyl, 21 : 51 - dimethyl, 21 - methyl - 51 - methoxy, 2- and 31 - methoxy, 21 : 51 - dimethoxy and 2 - chloro derivatives, 5-nitro-2-methyl-41-aminoazobenzene, 3-nitro-21 - methyl - 51 - methoxy - 41 - aminoazobenzen and 4 - amino - 2 - methyl - azobenzene - 31 - oxamic acid and its 5-methoxy derivative.  Specified aminonaphtholsulphonic acids are the 1 : 5 : 7-, 2 : 5 : 7- and 2 : 8 : 6-acids.  Examples relate to the production of the dyestuffs, (1) 4-amino-3-methoxy-azobenzene --> (alkaline) 2 : 8 : 6-acid --> resorcinol, which dyes cotton brown violet, becoming a readily dischargeable olive brown, fast to washing, on development with diazotised 4-nitroaniline; (2) 4-amino-2-methyl-5-methoxy-azobenzene --> (alkaline) 1 : 5 : 7-acid --> resorcinol, which dyes cotton grey-violet, becoming a readily dischargeable olive brown, fast to washing, on development with diazotised 4-nitroaniline; (3) 4-amino-2-methyl-41-methoxy-azobenzene --> (alkaline) 2 : 8 : 6-acid --> 3-aminophenol, which dyes cotton violet brown, becoming a readily-dischargeable brown, fast to washing, on development with diazotised 4-nitroaniline; (4) 4-acetylaminoaniline --> 3-toluidine --> (alkaline) 2 : 8 : 6-acid --> resorcinol, which dyes cotton violet brown, becoming fast to washing on after-treatment with formaldehyde and becoming a dischargeable brown, fast to washing, on development with diazotised 4-nitroaniline; if the 3-toluidine is replaced by cresidine, the product dyes cotton grey green, becoming fast to washing on after-treatment with formaldehyde and becoming a dischargeable olive black, fast to washing, on development with diazotised 4-nitroaniline.  A table is given showing the shades obtainable on cotton on development with diazotised 4-nitroaniline of the dyeings with the dyestuffs from various combinations of components.  Examples are also given of the dyeing process as applied to cotton with (a) development with diazotised 4-nitroaniline, (b) after-treatment with formaldehyde.  The Specification as open to inspection under Sect. 91 comprises also the use as amino-azo compound of 4-amino-41-hydroxy-21-methyl-azobenzene.  This subject - matter does not appear in the Specification as accepted.  3 - Amino - 41 - methoxy - azobenzene is obtained by reducing the nitro group in the product obtained by methylating the dyestuff, 3-nitroaniline --> phenol.