Stable colorant compositions

Details Stable colorant compositions Stable colorant compositions

1998-09-25

2000-06-27

Liott, Caroline D.

Bleaching and dyeing; fluid treatment and chemical modification

Dyeing involving animal-derived natural fiber material ,...

Leather dyeing

8436, 8557, 8558, 86371, 8676, 8681, 8682, 8683, 8685, 8687, D06P 332

Patent

active

06080209&

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The present invention relates to stable aqueous colorant compositions comprising at least one anionic dye, at least one pigment and a polyanionic thickener.
The present invention further relates to the use of these colorant compositions for dyeing leather and to a process for dyeing leather with the aid of the colorant compositions.
Aqueous colorant compositions, eg. colorant liquors for leather dyeing, comprising pigments and anionic dyes are long known. These colorant liquors are usually prepared by mixing solid or liquid pigment and dye preparations with water immediately prior to the leather dyeing. Such aqueous colorant compositions are described for example in EP-B1-0 377 409 and EP-A2-0 344 555.
The disadvantage of this process is that an additional mixing operation has to take place before every dyeing. This mixing operation requires costly metering means and harbors the risk of variable colorant compositions and hence of inconsistent dyeing results. Aqueous mixtures of water, suspended pigments and anionic dyes are ready prepared to avoid these problems. However, the use of these colorant compositions is difficult because the aqueous pigment suspensions are not stable to storage. Existing colorant compositions sediment or tend to spontaneous crystallization on storage, which leads to difficulties with the colorant metering and to nonuniform dyeing results.
There are also colorant compositions, for example Trupocor.RTM. Black N liquid from Trumpler, which are thixotropic because of thixotropicizing additives. True, such compositions are stable in storage, but they are difficult to handle and cause problems in automatic metering means, for example.
It is an object of the present invention to provide aqueous colorant compositions which overcome these disadvantages, exhibit satisfactory storage stability and permit uncomplicated handling and metering.
We have found that this object is achieved by the colorant compositions described at the beginning.
The colorant compositions of this invention preferably comprise
The colorant compositions particularly preferably comprise
Very particular preference is given to colorant compositions comprising
The diluent in the colorant composition is generally water, but other, water-miscible solvents may be present in the diluent, too. Suitable solvents include for example alcohols such as methanol, ethanol, n-propanol or isopropanol and glycols such as ethylene glycol, diethylene glycol or propylene glycol.
Suitable dyes include all water-soluble acid dyes, for example the well known azo, metal phthalocyanine or anthraquinone dyes which contain at least one sulfonic acid group. Of course, metal complexes of anionic azo dyes are also embraced by the claims.
Preferred anionic dyes for the colorant compositions of this invention are acid dyes of the general formula I ##STR1## where R.sup.1 and R.sup.2 are each hydroxyl, amino or hydrogen, one of the radicals being hydroxyl, being SO.sub.3 H, substituent being an amino or hydroxyl group, and ##STR2## where the aromatic rings are substituted or unsubstituted, for example by sulfo, C.sub.1 -C.sub.4 -alkyl and/or C.sub.1 -C.sub.4 -alkoxy groups.
R.sup.1 and R.sup.2 are each preferably hydroxyl or amino; it is particularly preferred for R.sup.1 to be amino and R.sup.2 to be hydroxyl.
R.sup.3 and R.sup.4 are each preferably SO.sub.3 H preferably disposed ortho to the diazo group.
Examples of radicals suitable as R.sup.5 include substituted naphthyl or phenyl radicals, preferably substituted phenyl radicals. The aromatic ring systems can be monosubstituted or polysubstituted, for example monosubstituted, disubstituted or trisubstituted. Suitable substituents include for example nitro, cyano, halogen such as chlorine or bromine, SO.sub.3 H, hydroxyl, amino, C.sub.1 -C.sub.4 -alkylamino, dialkylamino, N-morpholino, anilino, toluidino or C.sub.1 -C.sub.4 -alkyl, of which nitro is preferred. p-Nitrophenyl is particularly preferred for R.sup.5. A further suitable substituent for the phenyl or naphthyl radicals R.sup.5

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