Dyeing of polyamide substrates with an organic N-nitroso-hydroxylamine as light stabilizer

DETAILED DESCRIPTION We claim: 1.
A process for dyeing a polyamide substrate from an aqueous bath with a suitable dye and with a copper complex as light stabilizer for the dyed polyamide, which comprises using the copper complex of an organic N-nitrosohydroxylamine.
2.
A process as claimed in claim 1, wherein the copper complex used has the formula I ##STR5## in which each R is C.
sub.
1 -C.
sub.
20 -alkyl, C.
sub.
3 -C.
sub.
20 -alkenyl, C.
sub.
7 -C.
sub.
12 -aralkyl, C.
sub.
5 -C.
sub.
12 -cycloalkyl or aryl, of which the cycloalkyl may be substituted by up to 3 C.
sub.
1 -C.
sub.
4 -alkyl groups and the aryl by up to 3 C.
sub.
1 -C.
sub.
12 -alkyl groups, C.
sub.
1 -C.
sub.
12 -alkoxy groups, C.
sub.
2 -C.
sub.
8 -alkenyl groups, or chlorine or amino radicals.
3.
A process as claimed in claim 2, wherein R is phenyl or cyclohexyl.
4.
A process as claimed in claim 1, wherein the polyamide substrate is a sheetlike structure consisting of or containing polyamide fiber material.
5.
A dye formulation for dyeing a polyamide substrate, containing a copper complex of an organic N-nitrosohydroxylamine as light stabilizer for the dyed polyamide.




Description:
The present invention relates to an improved process for dyeing polyamide substrates from aqueous baths with suitable dyes and with copper complexes as light stabilizers for the dyed polyamide.
The present invention also relates to dye formulations which contain a copper complex of an organic N-nitrosohydroxylamine as light stabilizer for the dyed polyamide.
It is common knowledge that the light fastness of dyed polyamide deteriorates as a consequence of the catalytic effect of the dye; that is, under the action of light, in particular light and heat, the dyed polyamide undergoes chemical changes which have an adverse effect on the mechanical and thermal properties and also bring about undesirable discolorations.
Therefore, to remedy this disadvantage, light fastness stabilizers have been used in the dyeing, chiefly copper complexes, for example of salicylaldehydes (EP-A-252 368) salicyloximes (EP-A-113 856 and EP-A- 162 811) and water-soluble azo dyes (EP-A-255 481) and of hydroxamic acids (DE-A-3 326 640)