Dyes from 2-amino-3-nitro-5-acyl thiophenes have been described in numerous patent disclosures such as U.S. 2,805,218 and German 2,818,101. A problem which has existed with many of these dyes is that they generally are temperature sensitive in their application to fibers, particularly polyester, and cannot be satisfactorily applied at low tempera¬ tures. On the other hand, those dyes which do appear to have adequate application properties are, in general, the wrong shade which is, of course, a critical feature for commercial success of dyes of this type on polyester. This has been found to be exceptionally important with neutal blue dyes for polyester fibers which must meet very stringent shade, flare and brightness standards.

It has also been observed that these dyes in general have good light fastness and other general fastness properties, however, as aforesaid, the energy of application, i.e., sensitivity to the temperatures of dyeing, as well as crockfastness, and barre coverage are generally undesirable.

The term "crockfastness" relates to the resistance of colors in dyed fabrics to transfer by rubbing. A standard test which measures this pro¬ perty is Test Method 8 of the American Association of Textile Chemists and Colorists. The term "barre coverage" relates to ability of a dyeing composition to evenly dye a fabric, including imperfections, such as barre stripes.

The problem to be solved is therefore to provide dyeing compositions with generally improved

OMPI ^ WIPO

properties such as greater crockfastness and lower energy of application. This problem is solved by providing a mixture of two or more dyes of the formul :

wherein R is alkyl of 1-4 carbon atoms; R ¹ is H or alkyl of 1-4 carbon atoms; R ² is alkyl of 1-7 carbon atoms including substituted alkyl such as methylphenyl, or ethoxyethyl; R ³ is H or methoxy; and R* is H, methyl, or -NHCOCH3 wherein each dye is present in at least 1 percent by weight of the total mixture weight. These mixtures of dyes derived from 2-amino-3-nitro-5-acyl thiophenes surprisingly have much lower energy of application than the indi¬ vidual components. This enables dyes of the correct shade to be selected and mixed, the energy levels of which individually would otherwise be undesirably high. Further, by selection individual components of different shade but undesirably high energy level, a combination can be matched exactly to the shade required and the energy level simultaneously improved to an acceptable level.

The mixture of two or more of the present dyes may be made by mixing the individual dyes. Alternatively, the dye mixture can be prepared in situ by mixing the coupling components. For example, a mixture according to the invention is prepared in situ by diazotizing a 2-amino-3-nitro-5-acyl thio- phene with a mixture of aniline couplers. (An aniline coupler is a compound derived from aniline which is unsubstituted in the position para to the amino group of the aniline so that the para position can diazotize the amino group of the thiophene.) The currently preferred thiophene is 2-amino-3-nitro-5-

acetyl thiophene. The currently preferred aniline couplers are N,N-diethyl-m-acetamido aniline; N,N-di- propyl-m-acetamido aniline; N,N-diethyl-m-toluidine; and 2-methoxy-5-methyl-N-isobutylaniline. In gen- eral, the latter process may be more desirable for economic considerations and also for the fact that the mixtures so prepared are intimate and homo¬ geneous and indeed mixed crystals may even result upon precipitation. The amount of each dye can vary between 1 percent and 99 percent by weight of the total weight of the mixture, with from 20 percent to 80 percent of each dye being preferred.

Among the general advantages of the present invention are that the mixtures have lower dyeing energy levels and dyeings therewith show better crockfastness than the individual components, the use of mixtures allows the selection of the exact shade required which neither of the individual components have, and the mixtures allow a marginally acceptable fastness property of one component to be improved by ensuring that the second component is well above the acceptable level in this property. For example, one component may have marginal light fastness but have excellent pH stability and by ensuring that the second component has high lightfastness, some defi¬ ciency in the overall pH stability could be toler¬ ated. Moreover, by selection of the appropriate components of a mixture, the economics can be improved, i.e., an expensive coupling component yielding high fastness dyes can be "diluted" with a less expensive coupling component giving a conse¬ quently lower cost final dyestuff.

Example 1 Two dyes were prepared by normal diazotiza- tion and coupling techniques. The dyes were as follows :

₂

NHCOCH

and

NHCOCHa

Each dye has a neutral greenish-blue shade and excellent technical properties on textured polyester, except for temperature sensitivity and poor crockfastness when dyed at 115°C, as opposed to 130°C, as evidenced by a depth difference in the dyeing carried out at both temperatures. When the two dyes were mixed, 1:1 by weight, the shade and fastness properties remained as the single com¬ ponents; but the temperature sensitivity, as evi¬ denced by the dyeings at 115°C as opposed to 130°C, was much improved showing no depth difference at the two temperatures. Also, the crockfastness of the low temperature dyeing was excellent and equivalent to the high temperature dyeing.

Example 2

As in Example 1, the two dyes were prepared from N,N-diethyl-m-toluidine and N,N-diethyl-m-acet- amido aniline as the aniline couplers. The dyes were as follows :

Dye A

CH ₃

Dye B

NHCOCH ₃

In each case the energy level on polyester was high. Additionally, although both dyes were blue, the N,N-diethyl-m-toluidirte dye A was much redder and brighter than the dye B from N,N-diethyl-m-acetamido aniline and, further, had inferior light'fastness. A very desirable shade required by the trade is that given by the anthraquinone dye CI Disperse Blue 56, which is midway between the two dyes of this example and has very low energy of application. By mixing the two dyes A/B in the ratio of 3:2 a combination very close in shade to CI Disperse Blue 56 can be obtained having much improved energy of application over either of the individual components. Moreover, the light fastness of A and the economics of B are noticeably improved in the mixture.

Example 3 Two dyes A and C were prepared ^n situ where the aniline couplers comprised a 1:1 mixture of N,N-diethyl-m-toluidine and 2-methoxy-5-methyl-N-iso- butyl acetyl aniline, respectively, and the thiophene was 2-amino-3-nitro-5-thiophene. Dye C therefore had the structure:

Dye C

CH=

The dyes were similar in shade to CI Disperse Blue 56. The dye A had high energy as mentioned in Example 2, and dye C was much lower in energy but did not have good pH stability. The mixture of dyes showed very similar shade and brightness to CI Disperse Blue 56 and was of low energy. The pH stability of dye C was improved and also its eco¬ nomics, while the energy level of Dye A was much improved. ^*

Examples 4-12

A variety of dye mixtures (1:1 by weight except Example 2 which was 3:2 and Example 5 which was 1:1:1) were tested as in Examples 1-3. The results are listed belo in table form, including the results from Examples 1-3 for completeness. In the table, TS refers to the temperature sensitivity of the composition (as explained in Example 1) on a scale of from 1-5. A TS of 1 or 2 represents a composition having lower temperature of application than a single dye having a TS of 4 or 5. ^R are in the positions indicated on the structural formula identified earlier in this specification. R in each- case is methyl.

- θREΛ O PI

tt

Table

TS Shade

Exa - Mix¬ Mix¬

P ^le . R ¹ R ² R ³ R- TS Shade ture) ture)

1 C ₂ H ₅ C ₂ Hs H NHCOCH3 5 Blue 2 Blue

C3H7 C3H7 H NHCOCH3 5 ^* Blue

2 C ₂ H ₅ C ₂ H ₅ H NHCOCH3 5 Blue 2 Reddish

C ₂ H ₅ C ₂ H ₅ H CHs 5 Bluish Blue Violet

3 C2H5 C ₂ Hs H CH ₃ 5 Violet 1 Reddish

H iso- OCH3 CH ₃ 3 Reddish Blue Bu. Blue

4 C ₂ H ₅ C ₂ H ₅ H CH3 5 Bluish 2 Bluish Violet Violet

C3H7 C3H7 H CH ₃ 5 Bluish

Table Continued

TS Shade

Exam¬ Mix¬ Mix¬ ple R ¹ R ² R ³ R" TS Shade ture) ture)

5 C ₂ H ₅ C2.H5 H NHCOCH3 5 Blue 2 Blue

C3H7 C3H7 H NHCOCH3 5- Blue

C ₂ H ₅ CH ₂ Ph H NHCOCH3 5 Reddish Blue ^*

6 C2H5 C ₂ H ₅ H NHCOCHs 5 Blue 2 Greenish

Blue

H CsHxi OCH3 NHCOCH3 5 Green

7 H G\H ₉ OCH3 NHCOCHs 5 Green 2 Green

H CSH OCH3 NHCOCHs 5 Green

8 C ₂ H ₅ C2H5 H H 4 Violet 2 Violet

C ₂ H ₅ C2H5 H CHs 5 Bluish

<*

to t tn tπ O O Ui.

Λ V . IU TS Shade

Exam¬ Mix¬ Mix¬ ple R ¹ R ² R ³ R* TS Shade ture) ture)

9 C ₂ H _S C ₂ H ₅ H NHCOCHs 5 Blue 2 Blue

C ₂ H _S C ₂ H_ - H NHCOCHs 4 Blue 0C ₂ H ₅

10 C ₂ H _S C2H5 H NHCOCHs 5 Blue 2 Greenish

H C ₂ Hι»- OCH3 NHCOCHs 4 Green 0C ₂ H ₅

11 C3H7 C3H7 H NHCOCHs 5 Blue 2 Blue

C ₂ H _S C ₂ H.- H NHCOCH3 5 Blue .0C ₂ H ₅

12 C3H7 C3H7 H NHCOCHs 5 Blue 2 Greenish

H CsHu H NHCOCHs 5 Green Blue