Monoazo pigments

Monoazo Pigments. Monoazo yellow pigments ate represented by the foUowiag general formula ... 

Monoazo Pigments. In combination with other groups, the a2o linkage, —N=N—, imparts color to many dyes and pigments (see Azo Dyes). The simplest of these, ie, the Hansa yellows, toluidine reds, and naphthol reds, do not have the lightfastness and heat stabiUty required for plastics. Permanent YeUow FGL and Permanent Red 2B are stable enough for vinyls, polyethylene, polypropylene, and ceUulosics (11). Permanent Red 2B is available as the calcium, barium, or manganese salt. 

Monoazo pigments, 79 430, 431-432 MonoazopyrazoloneYellow, Calcium Salt pigment for plastics, 7 366t Monoazo Red, colorant for plastics, 7 374t Monoazo Yellow, colorant for plastics, 7 374t... 

These are the only ranges of precursor products in the Colour Index that are still commercially significant. Azoic dyes have a close formal relationship to those monoazo pigments derived from BON acid or from acetoacetanilides (section 2.3.1) and some are chemically identical with them, although they are used in a totally different way. Azoic components are applied to produce insoluble azo dyes within the textile substrate, which is almost always cotton. Corresponding azoic components for the dyeing of cellulose acetate, triacetate and polyester fibres were once commercially important, but are now obsolete because of environmental hazards and the time-consuming application procedure. 

Benzidine is an aromatic diamine that can be tetrazotised and coupled to two molecules of a coupler such as acetoacetanilide. This gives a yellow disazo pigment that can be regarded as a double molecule of the monoazo pigments described above. The possibilities of making a... 

Both molecules favor the o-quinone-hydrazone form over the o-hydroxyazo form. Corresponding studies on a selection of monoazo pigments and several (i-naphthol and Naphthol AS pigments are described in the respective chapters. 

Yellow monoazo pigments were discovered by Meister Lucius Bruiting in Germany (later Hoechst AG) in 1909 and entered the market in 1910 under the trade name of Hansa Yellows . 

A number of commercially available yellow monoazo pigment lakes are based on a pyrazolone sulfonic acid derivative as a coupling component. An example is the aluminum tartrazine lake, listed in the Colour Index as Pigment Yellow 100,... 

Recent patents [5-7] also describe yellow pyrazolone monoazo pigment lakes based on the general structure... 

This monoazo pigment exhibits a yellow shade. It is recommended for use in paints and printing inks as a substitute for lead containing pigments. P.Y.203 is scarcely found on the European market. 

The paint industry shows only limited interest in either P.Y.13 or 12. Although the redder varieties of P.Y.13 are more lightfast than the P.Y.12 types by a few steps on the Blue Scale, they do not reach the lightfastness of Hansa Yellow type monoazo pigments. P.Y.13 is not fast to overpainting. 

BONA pigment lakes are monoazo pigments, characterized primarily by the following general chemical structure ... 

P.R.211 is offered only in the Japanese market. It is the calcium salt of a monoazo pigment. P.R.211 affords shades of scarlet which resemble those provided by Lake Red C types (P.R.53 1). The list of suitable media includes plastics and printing inks. Incorporated in these media, P.R.211 presents application and fastness prop-... 

Table 22 shows the monoazo pigment lakes which are based on naphthalene sulfonic acid (CP = coupling position). 

The pigment affords medium yellow shades. Regarding shades and performance it competes with some other pigments, such as the monoazo pigment P.Y.97 and the bisacetoacetarylide pigment P.Y.16. 

The number of carbonamide groups is thus doubled in relation to the monoazo pigment. 

The formal structure is exemplified by the red disazo condensation pigments. The structure may be visualized as resulting from the dimerization of two monoazo pigments of the Naphthol AS type ... 

The nitrogen atom which is connected to the least nucleophilic aromatic moiety is always the one to serve as a ligand. As is the case with yellow and red monoazo pigments, which have been studied by three dimensional X-ray diffraction analysis (Sec. 2.3.1.1 and 2.5.1), the chelate-6-rings of azo metal complexes prefer the quinonehydrazone structure over the hydroxyazo form [4],... 

This is a bluish red monoazo pigment of which the chemical structure has not yet been disclosed. P.R.278 is recommended for use in printing inks. 

Benzimidazolone pigments are actnally monoazo pigments but the convention within the indnstry is to not use the azo descriptor they are classified as high-performance pigments. All the pigments in this class are derived from coupling... 

Diarylides show significandy greater tinctorial strength and superior bleed and heat resistance than the conventional monoazo pigments. However, they are generally inferior to the monoazo pigments in lightfastness. 

Most dyes and pigments are unreactive. One exception, however, is lead chromate, which can act as an oxidizer in the presence of certain monoazo pigments, and following intimate mixing, produce fires. ... 

USA Patent 2,644,814). A monoazo pigment that has gained significant use in trade sales finishes. It is very similar in color to dalamar yellow and somewhat more bleed-resistant. 

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