Лако-красочные материалы — производство

The water-soluble reactive phthalocyanine dyes (see Section 2.8) yield brilliant turquoise and green shades not available from any other dye category. The most important reactive phthalocyanine dyes contain copper or nickel as their central atom; they are substituted with sulfonic acid groups and also with reactive groups joined via sulfonamide bridges. An example is C. I. Reactive Blue 15, 74459 [12225-39-7] (23):

3.1.2 Synthesis

The synthesis of selected reactive dyes is illustrated by the following examples taken from the patent literature.

Azo Dyes. The dye obtained by coupling diazotized 4-(2-sulfooxyethylsulfonyl)ani- line with 1-amino-8-naphthol-3,6-disulfonic acid at pH 1 — 2 is coupled at pH 6 — 7 with a diazonium compound synthesized from the condensation product derived from 1,3-diaminobenzene-6-sulfonic acid and 2,4,6-trifluoro-5-chloropyrimidine. The crude material is salted out of the solution and isolated. This product (24) gives a blue solution in water and dyes cotton in a marine blue to black color:

Metal-Complex (Formazan) Dyes. The hydrazone from 2-carboxyphenylhydra — zine-4-sulfonic acid and benzaldehyde is suspended in water and then dissolved by adding aqueous sodium hydroxide to obtain pH 6.5 -7.0. This solution is added to the aqueous diazonium salt solution obtained from a typical aqueous diazotiza — tion of 4-(2-sulfooxyethylsulfonyl)-2-aminophenyl-6-sulfonic acid. The mixture is then dripped into an aqueous solution of copper sulfate, while the pH is main­tained with soda at 5.5 — 6.5. After complete coupling the pH is adjusted to 1 with concentrated hydrochloric acid. The strongly acidic solution is then neutralized with alkali to pH 5.5. The copper — formazan complex is salted out along with sodium chloride, filtered, washed with dilute aqueous sodium chloride solution, and dried. A dark powder results which gives a dark blue solution in water. It consists of an electrolyte-containing powdered sodium salt of the acid 25:

This compound is a very effective dye that renders cotton and regenerated cel­lulose fibers a clear blue shade on prolonged treatment in the presence of an acid-binding agent. The resulting color prove to be very light — and waterfast.

Dioxazine Dyes. The synthetic routes (see below) to almost all dioxazines yield products with a symmetrical structure, resulting in at least two reactive anchors. The highly reactive double-anchor dyes are suitable for both the exhaust and the padding processes. Ecological limits for wastewater are satisfied as a result of a high degree of fixation and low salt requirements in the exhaust process, whereby the latter also has a positive influence on leveling.

The most important industrial process for synthesizing triphenodioxazines for cellulose fibers involves reaction of two equivalents of an aromatic amine with 2,3,5,6-tetrachloro-1,4-benzoquinone ( ^-chloranil) [ 118-75-2] and subsequent oxi­dative closure of the ring. All commercially available dioxazines thus contain chlor­ine atoms at the 6- and 13-positions. The process was discovered in 1911 [46], and its simplicity, coupled with excellent availability of raw materials, was the basis for the commercial success of early dioxazines. In the first reaction step the starting materi­als are condensed in the presence of an acid-binding agent such as soda ash or magne­sium oxide to form the 2,5-diarylamino-3,6-dichloro-1,4-benzoquinone (26). Ring closure is then induced by heating either with a metal halide or an acid halide catalyst in a high-boiling solvent (e. g., nitrobenzene) or, in the case of sulfonated dyes, by heating with an oxidant in concentrated sulfuric acid.

The cyclization process needs a very careful choice of starting materials and reac­tion parameters to obtain a product with the desired brilliance and tinctorial strength. The use of oleum in the second step is a significant improvement, because oleum serves not only as a solvent but also as an oxidant, permitting cyclization to proceed at or below room temperature. Ring closure continued to prove difficult with starting materials containing sulfonic acid groups, which are of great importance in reactive dyes, but this problem was overcome by resorting to a mixture of oleum and peroxosulfate compounds [47]. Later patents describe the use of halogens [48], manganese dioxide [49], and aqueous hydrogen peroxide [50] as alternatives to peroxosulfate.

The triphenodioxazine chromophore can be converted to a reactive dye by in­corporating anchors that are attached to the dioxazine core either directly or via bridging groups. The first patents, like the first commercial products, were based almost exclusively on the use of bridging groups. The usual starting material is 2- chloro-5-nitrobenzenesulfonic acid (27), which is treated with a diamine (28).

Reduction produces the p — phenylenediamine derivative 29, which is con­densed with chloranil, and the resulting diarylamino-3,6-dichloro-1,4-benzoqui — none (30) is isolated, dried, and then cyclized in oleum containing peroxosulfate to yield the desired dye base. The base is converted to a reactive dye by reaction of the two primary amino groups with two equivalents of an acylating agent Z-Cl. Typical diamine bridges include 1,4-phenylenediamine-2-sulfonic acid, ethylene — diamine, and 1,3-diaminopropane. The reactive anchors are almost always deriva­tives of s-triazines [51-58] (Scheme 3.1).

Scheme 3.1

Because of their symmetry, all such triphenodioxazine reactive dyes feature double or even fourfold anchor systems. However, dyes with only one anchor group can be prepared by adding a single equivalent of acylating agent. Most asymmetric products of this type are based on 1,4-phenylenediamine-2-sulfonic

Red dioxazines can be synthesized by substituting an amino alcohol for the diamine derivative [60].

Replacing the sulfonic acid 27 with the appropriate carboxy-, carboxamido-, sulfonyl-, or sulfon-amido-4-nitrochlorobenzene leads to analogues described in [61], [62].

Another alternative is attaching the reactive anchor to the dioxazine ring via sulfonamide or carboxamide groups instead of via amine groups, as in 33 [62], [63]:

Compound 27 or one of the above-mentioned derivatives can also be reacted with a 2-hydroxyethylsulfonylaniline instead of with a diamine. After reduction of the 4-nitroaniline product 34 followed by condensation with chloranil, the cyclization takes place in oleum where, besides ring closure, the 2-hydroxyethyl — sulfonyl groups are also esterified to |3-sulfooxyethylsulfonyl groups [vinylsulfone (VS) groups]. Thus, the reactive anchor is formed concurrently during the cycliza­tion reaction [64,65] (Scheme 3.2):

Cl ho3s H

H SO, H Cl

R’ = so2-ch2-ch2-oso3h

Other similar fiber-reactive triphenodioxazines are prepared by replacing the sulfonic acid group in 26 with a 2-hydroxyethylsulfonyl group. The starting mate­rial here is 4-chloro-3-(2-hydroxyethylsulfonyl) nitrobenzene (35), which leads to products containing a VS group bound directly to the dioxazine ring (36) [64,66] (Scheme 3.3).

NO,

‘SO,-CH,-CH,-OH

35

+ H. NR

NO,

‘SO,-CH,-CH,-OH

NHR

RHN

HO, SO-CH,-CH,-SO

so,-ch2-ch2-oso3h

NHR

Scheme 3.3

In an analogous reaction, use of a diamine affords dyes with both VS and amino groups. Subsequent acylation of the free amino groups produces the four — anchor system 37 [67].

Because of the symmetrical nature of the chloranil condensation product 7, all the syntheses described so far afford exclusively symmetrical triphenodioxazines; i. e., the two phenyl rings fused onto the dioxazine skeleton bear the same substi­tuents. An elegant synthesis for an asymmetric chloranil condensation product has not yet been developed.