Disazo condensation pigments

Molecular dimerization, as in the transition from Hansa Yellow to disazo yellow pigments, increases the color strength considerably. A comparison of a Naph-thol AS/disazo condensation pigment pair gives similar results ... 

Only common aromatic amines are used as diazonium components. Coupling reactions between aminobenzamides or aminobenzanilides and bisacetoacetylamino-phenylenes are described under disazo condensation pigments (see Sec. 2.9). Bisacetoacetarylide pigments thus have the general chemical structure ... 

Enlarging the pigment molecule, as with disazo condensation pigments (Sec. 2.9). 

In the early 1950s, Ciba research succeeded in synthesizing red disazo compounds of relatively high molecular weight. These products were known as disazo condensation pigments [1,2], Such compounds may be structurally visualized as disazo pigments, formally composed of two monoazo units, which are attached to each other by an aromatic diamino carbonamide bridge ... 

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 ... 

Red disazo condensation pigments therefore have the following general structure ... 

Two possible chemical structures have been found for yellow disazo condensation pigments. The two monoazo units may be connected either via the coupling component (type 1) or via the diazo moiety (type 2). 

There are basically two routes leading to disazo condensation pigments. The two schemes will be exemplified by the synthesis of red pigments. 

The condensation principle makes it possible to synthesize a wide range of disazo condensation pigments. 

Disazo condensation pigments, whose manufacture is somewhat more demanding than that of diarylide yellow and Naphthol AS pigments, are correspondingly expensive. 

The paint industry is interested in individual representatives of this class, such as P.Y.128. These are used to color high grade paints, such as automobile (O.E.M) finishes and automotive refinishes. Other types are used in general industrial paints. As a rule, the fastness of disazo condensation pigments to overcoating is good to excellent in some media. The pigments are also used in architectural paints, sometimes also in emulsion paints. 

Various disazo condensation pigments are utilized in decorative printing on laminated plastic sheets. They are also applied in a number of special-purpose media outside the above-mentioned groups, such as oil colors for artists and crayons. 

Among yellow disazo condensation pigments, it is especially the ones that are based on the type I structure which enjoy widespread use. These pigments cover... 

Table 24 Commercially available disazo condensation pigments.

P.Y.94 is the greenest one of all available yellow disazo condensation pigments. It was only recently withdrawn from the market. With approximately equal cleanness, it is somewhat greener than P.Y.128, which is a member of the same class of pigments. However, P.Y.94 is only about half as strong tinctorially. 0.44% P.Y.94 is required to produce a 1/3 SD HDPE sample containing 1% TiOz, while the same end result is achieved by using only either 0.22% P.Y.128 or 0.2% of the somewhat redder P.Y.93. 

P.R.166 affords clean yellowish shades of red. It is broad in scope and in this respect resembles the somewhat bluer disazo condensation pigment P.R.144. Its main area of application, however, is in plastics and in spin dyeing. 

---