Process for improving the light fastness of polyamide dyeings

The light fastness of dyed polyamide fibre materials, in particular of the type used for manufacturing car seat covers, can be substantially improved by treating these materials, before, during or after the dyeing, with copper compounds of the compounds of the formula ##STR1## wherein R=H, OH, alkyl or cycloalkyl. The compounds (I) are distinguished by low self-colour and good stability to acid conditions.

For some years the automotive sector has been making increasingly tough 
demands on the light fastness of dyed textile materials which are based on 
preferably synthetic polyamide fibres and are used to prepare seat covers. 
This high fastness level, however, is not attained by most commercially 
available polyamide dyestuffs. This is particularly true even of the metal 
complex dyestuffs which, because of their outstanding light fastness, are 
used for said purpose to the virtual exclusion of other dyestuffs. 
Proposals have therefore already been made to meet the high requirements 
of car manufacturers by using the metal complex dyestuffs together with UV 
absorbers. 
German Patent Specification A No. 3,041,153, for example, recommends that 
the polyamide textile materials should be treated, before, during or after 
the dyeing, with copper complexes of Schiff's bases. 
However, this method, which is well proven in itself, has the disadvantage 
that the light fastness improvers it makes use of have an undesirable 
self-colour and a not fully adequate stability to acid conditions. 
The reason why this acid stability is so critical is that, in practice, the 
dyeing frequently needs to be followed by finish-application treatments 
within the acid range of pH 4-6 to finish the dyed material in full. 
It has now been found that the light fastness of polyamide dyeings can be 
improved with, preferably metal complex dyestuffs without having to accept 
the abovementioned disadvantages of an aftertreatment in an acid medium if 
copper compounds of phenols of the formula 
##STR2## 
wherein R=H, OH, alkyl or cycloalkyl and 
the ring A can optionally contain further substituents customary in the 
chemistry of UV absorbers, 
are used. 
Suitable alkyl radicals are those having 1 to 4 C atoms. Suitable 
cycloalkyl radicals are cyclohexyl and methylcyclohexyl radicals. Suitable 
substituents in the ring A are methyl, methoxy or chlorine. However, this 
ring is preferably unsubstituted. 
A further advantage of the copper compounds according to the invention is 
their lower self-colour, compared with, for example, the abovementioned 
copper complexes of Schiff's bases. 
The copper compounds according to the invention are used in amounts of 
0.01-2%, preferably 0.05 to 0.1%, on weight of polyamide. They are 
preferably added to the dyebath. 
The copper compounds to be used in the manner of the invention are known 
(for example the salicylaldoxime-copper(II) complex from Ber. 63, 1928-30 
(1930), the 2-hydroxyacetophenoxime-copper(II) complex from Ber. 64, 
1210-1215 (1931)) or can be obtained in a manner which is known in itself, 
namely by reacting compounds of the formula I with a copper(II) salt, in 
particular with a salt of a mineral acid, such as copper(II) chloride or 
copper(II) sulphate, or copper(II) oxide (hydroxide), in a preferably 
alcoholic, aqueous alcoholic or aqueous medium. Preferably 1 to 2 mol of 
compound I are reacted per mol of copper compound. The reaction products 
are accordingly the corresponding 1:1 and 1:2 copper complexes or (in the 
case of the hydroxamic acid derivatives) presumably the corresponding acid 
and neutral copper salts. 
It is also known in principle that transition metal complexes of compounds 
(I) are suitable for use as light fastness improvers, but they have so far 
always been used for other substrates, such as, for example, cellulose 
fibres (cf. British Patent Specification Nos. 1,321,645 and 1,392,953), 
modified polyolefine or polyacetal fibres (cf. U.S. Pat. No. 3,203,752) or 
ethylcellulose polymers (cf. German Patent Specification A No. 2,625,386). 
These patent specifications, moreover, did not describe the copper 
complexes--if mentioned at all--by way of examples or as particularly 
preferred, but almost exclusively the nickel complexes, which forces the 
conclusion that the copper complexes are less suitable. 
For this reason it has to be regarded as very surprising that, in improving 
the light fastness of polyamide dyeings, it is solely the copper 
derivatives of (I) which give the desired effect, while the nickel 
complexes have a much smaller effect, if any. 
"Polyamide" is, incidentally, to be preferably understood as meaning 
synthetic polyamide fibres. 
These fibres can be conventionally dyed not only with metal complex 
dyestuffs but also with acid dyestuffs. The preferred dyestuffs are the 
metal complex dyestuffs, in particular the 1:2 chromium or 1:2 cobalt 
complexes of monoazo or diazo compounds, of which a large number have been 
described in the literature and are commercially available. These 
dyestuffs can also contain 1-2 sulpho groups. 
Suitable acid dyestuffs are in particular those types which are usually 
used in combination with metal complex dyestuffs. 
The polyamide materials can be treated with the copper compounds to be used 
according to the invention before, during or after--preferably during--the 
dyeing. 
If they are not water-soluble, the copper compounds, which will normally 
have been prepared separately, are of course used in a finely divided form 
as is obtained by grinding in the presence of customary dispersants. 
In a special embodiment of the process according to the invention, the 
process is carried out as a one-vessel process, as it were, in which the 
copper compounds for treating the fibre materials are not added in their 
solid, isolated form, but are produced, principally in any order, in situ 
on the fibre from the corresponding starting materials. 
In this version of the process the fibres are preferably first dyed with a 
dyeing liquor which, in addition to the dyestuff and customary dyeing 
auxiliaries, contains the metal-free compounds of the formula I, and are 
then aftertreated with a copper(II) salt solution.

PREATION EXAMPLES 
Example 1 
A (2:1) salicylhydroxamic acid/copper compound 
76.5 g (0.5 mol) of commercially available salicylhydroxamic acid are 
introduced into 500 ml of water and are dissolved by adding 40 g of a 50% 
strength sodium hydroxide solution (0.5 mol), and 62.5 g (0.25 mol) of 
CuSO.sub.4 .times.5H.sub.2 O are added dropwise with stirring in the form 
of a saturated aqueous solution. The mixture is stirred for 10 minutes, 
and the green precipitate is filtered off, is taken up in water, is 
reprecipitated by stirring and is filtered once more. Drying in vacuo (200 
mbar) at 60.degree. C. leaves 92.5 g (theoretical: 91.9 g) of a greenish 
grey powder. The copper content in the product was measured as 18.1%. 
Example 2 
A (1:1) salicylhydroxamic acid/copper compound 
58 g (0.38 mol) of salicylhydroxamic acid are introduced into 380 ml of 
water, and 60.7 g of a 50% strength sodium hydroxide solution (0.76 mol) 
are added. 94.8 g (0.38 mol) of CuSO.sub.4 .times.5H.sub.2 O are added 
dropwise with stirring at 50.degree. C. in the form of a saturated aqueous 
solution. The mixture is stirred for 10 minutes, and the green precipitate 
is filtered off, is taken up in 300 ml of water, is reprecipitated by 
stirring and is filtered once more. Drying in vacuo (200 mbar) at 
60.degree. C. leaves 80.5 g (theoretical: 81.5 g) of a greenish grey 
powder. The copper content in the product was measured as 28.9%. 
APPLICATION EXAMPLES 
Example 1a 
100 parts of a nylon 6 fibre material are entered into 2,000 parts of an 
aqueous dyeing liquor which contains 0.065 part of the copper complex 
##STR3## 
and 0.15 part of the metal complex dyestuff of the formula 
##STR4## 
Disodium phosphate and monosodium phosphate are added to bring the dye 
liquor to pH 8. The liquor temperature is then slowly raised to 
98.degree.-100.degree. C. and is held at this temperature for 60 minutes, 
the textile material being agitated all the while. 
The dyeing is then removed from the dyebath, is rinsed and is dried. 
The dyeing, and a comparative dyeing prepared without (1), are exposed for 
250 hours in a Xenon test instrument as stipulated by 
Adam Opel AG 
Russelsheim/West Germany 
GM (Engineering Standards Europe) 
GME No 60 202 A/B 
The dyeing treated with (1) has a much better light fastness than the 
comparison. 
Example 1b 
A similar light fastness improvement is obtained by bringing the liquor not 
to pH 8, but, by means of trisodium phosphate, to pH 10. 
Example 1c 
The light fastness improvement is retained in full if the dyeings prepared 
in 1a and 1b are finally heat-set at 180.degree. C. in the course of 30 
seconds. 
Example 2 
100 parts of nylon 6 material are entered into 2,000 parts of an aqueous 
dyeing liquor which contain 0.1 part of the copper complex (1) described 
in Example 1 and 0.5 part of the dyestuff of the formula 
##STR5## 
The dyeing liquor is brought to pH 6 by means of a buffer mixture 
consisting of monosodium phosphate and acetic acid. The textile material 
is treated at 98.degree.-100.degree. C. for 1 hour, is rinsed and is 
dried. 
The dyeing thus prepared is found to have a much better light fastness than 
the one without (1) by the 250 hours of exposure in the Opel test. 
If the dyeing is carried out at pH 4 instead of at pH 6, the light fastness 
improvement is similar and much better than a dyeing prepared in 
accordance with the Application Example 2a.sub.1 of German Patent 
Specification No. 3,041,153 A1. 
Example 3a 
Example 1 is repeated, except that 0.75% (in the form of a 10% strength 
aqueous dispersion) of the salicylhydroxamic acid/copper compound 
described in Example 1 is used (on weight of fibre) in place of the copper 
complex (1), affording a marked improvement in light fastness not only at 
pH 8 but also at pH 6. 
Example 3b 
Example 3a is repeated, except that the salicylhydroxamic acid/copper 
compound described in the Preparation Example 2 is used, affording a 
marked improvement in light fastness not only at pH 8 but also at pH 6. 
Example 4 
A nylon 6 dye is conventionally prepared from a long liquor with the 
dyestuff Acid Yellow 151 (C.I. 14 906) and is dried. 
This dyeing is pad-mangled with a 100% liquor pick-up of a padding liquor 
which contains per liter 1 g of a 10% strength aqueous dispersion of the 
copper complex described in Example 1. 
The pad-mangling is followed by drying at about 100.degree. C. and then 
setting at 180.degree. C. in the course of 30 seconds. The yellow dyeing 
thus treated has a much higher light fastness than a dyeing prepared 
without using the copper complex described. 
Example 5a 
100 parts of nylon 6 fibre material are entered into 2,000 parts of an 
aqueous dyeing liquor which contains 0.1 part of the copper complex 
##STR6## 
and 0.15 part of the metal complex dyestuff of Example 1a. 
The dyeing liquor is brought to pH 8 by adding disodium phosphate and 
monosodium phosphate. The liquor temperature is then slowly raised to 
98.degree.-100.degree. C. and is held at this temperature for 1 hour, the 
textile material being agitated all the while. The dyeing is then rinsed 
and dried. 
The dyeing is exposed to light together with a dyeing prepared without (2). 
The dyeing treated with (2) has a much better light fastness. 
Example 5b 
An equally good light fastness is obtained by bringing the dyeing liquor 
not to pH 8 but to pH 6. 
Example 5c 
The light fastness improvement is fully retained if the dyeings prepared in 
5a and 5b are then heat-set at 180.degree. C. in the course of 30 seconds. 
Example 6 (comparative example) 
Example 1a is repeated, except that the copper complex (1) is replaced by 
the corresponding nickel complex, of which 0.1% are used on weight of 
fibre, affording no improvement in light fastness not only at pH 6 but 
also at pH 8. On exposure to light the dyeing behaves as though no optical 
stabiliser had been added to the dyeing liquor. 
Example 7a 
100 parts of nylon 6 textile material are entered into 2,000 parts of an 
aqueous dyeing liquor which contain 0.1 part of salicylaldoxime (I, R=H) 
and 0.2 part of the metal complex dyestuff of Example 1a. 
The dyeing liquor is brought to pH 8 by adding disodium phosphate and 
monosodium phosphate. While the textile material is being constantly 
agitated, the temperature of the dyeing liquor is gradually raised to 
98.degree.-100.degree. C. and is left at this value for 60 minutes. 
The liquor is cooled down, and the nylon material is removed, is briefly 
rinsed and is entered into 2,000 parts of a fresh dyeing liquor which 
contain 0.1 part of CuSO.sub.4.5H.sub.2 O. When the liquor has been 
gradually heated to 98.degree.-100.degree. C., the dyeing is treated at 
this final temperature for 30 minutes. The textile material is kept in 
uniform motion throughout the entire treatment period. 
The dyeing liquor is cooled down, and the dyed textile material is removed, 
is rinsed and is dried. 
The dyeing is exposed to light in the Opel test, together with a dyeing 
prepared without the salicylaldoxime/copper sulphate aftertreatment. The 
dyeing prepared in two baths by means of 
salicylaldoxime/CuSO.sub.4.5H.sub.2 O has a much better light fastness. 
Example 7b 
An equally good light fastness is obtained when the dyeing liquor 
containing the salicylaldoxime is brought to pH 6 and not pH 8. 
Example 7c 
A heat-setting of the dyeings prepared in 7a and 7b at 180.degree. C. for 
30 seconds--a treatment which is customary in the textile industry as a 
final treatment--has no adverse effect on the light fastness.