Amine-treated pigments

However, amine-treated pigments also have their problems. The treatment process affords dark red compounds which are easily soluble in toluene and appreciably enhance the tinctorial strength of the resulting printing ink (Sec. 2.4.1.4). The same pigment formulation, however, will be considerably less soluble and thus weaker in printing inks based on aliphatic hydrocarbons or in media which contain blends of toluene and aliphatic hydrocarbons. As the ink is printed on to the... 

Curve 1 Pigment Yellow 12, Curve 2 Pigment Yellow 12, amine treated. 

Although treated as separate classes in the Colour Index, these structural types are closely related and the few diphenylmethane dyes such as auramine (1.28 Cl Basic Yellow 2) are now of little practical interest. Commercial usage of the triarylmethane dyes and pigments has also declined considerably in favour of the major chemical classes. They were formerly noteworthy contributors to the acid, basic, mordant and solvent ranges, primarily in the violet, blue and green sectors. Numerous structural examples are recorded in the Colour Index. The terminal groupings can be amine/quinonimine, as in auramine and crystal violet (1.29 Cl Basic Violet 3), hydroxy/quinone, or both. The aryl nuclei are not always benzenoid (section 6.5). 

The influence of mixed coupling on the properties of Cl Pigment Yellow 12 has been studied recently [12]. Carboxy- or sulpho- substituted derivatives of acetoacetanilide were evaluated as co-coupling components and analysis revealed that the state of the crystal and the particle size were changed and new diffraction peaks were observed. When these modified pigments were treated with a fatty amine such as stearylamine, the hydrocarbon chains enclosed the anionic groups in the co-coupler so that properties such as flowability, wettability and dispersibility in nonpolar solvents were greatly improved. 

The pigments are obtained by treating the appropriate amine with water/hy-drochloric acid to form the amine hydrochloride. In most cases, subsequent dia-zotization is carried out in the cold (0 to 5°C) with an aqueous sodium nitrite solution (a). The resulting diazonium salt solution is then transferred onto sodium... 

The customary method of preparing perylene pigments is by reaction of perylene tetracarboxylic dianhydride with primary aliphatic or aromatic amines in a high boiling solvent. The dianhydride itself is also used as a pigment. Di-methylperylimide may also be obtained by treating the diimide with methyl chloride or dimethyl sulfate. 

Route B of this process may be substantially improved in terms of yield and product quality (purity) of the resulting triarylaminoarylcarbonium pigment. To this end, the solution of the free dye base is treated with an excess of aqueous sulfuric acid (20 to 40% ) in a solvent such as chlorobenzene or an aromatic amine. This method produces the sulfate of the basic dye, which is insoluble in this medium, together with the soluble sulfates of the primary aromatic amines, which can therefore easily be separated. The isolated sulfate of the basic dye is then washed and in dry or wet condition monosulfonated with 85 to 100% sulfuric acid. Based on the dye base sulfate, this step affords 96 to 98% yield, compared to only 83 to 89% achieved by the previously described method. The entire synthesis, including the intermediate isolation of the triarylaminoarylmethane sulfate, may also be performed by continuous process [3]. 

Chem. Descrip. Unsat. polyamide and acid ester salts Uses Wetting agent/dispersant for pigments/organically treated bentonites in solv. or solv.-free coatings Features Solv.-free shorfer disp. fime improved storage stability Properties Dk. brn. liq. dens. 0.98-1.02 g/cm cid no. 58-72 amine no. 10-30 anionic/cationic 100% act. 

The most usual in house method would be to disperse the pigments/extenders into a suitable solution dispersed resin with the use of additives to improve efficiency and increase loadings. The resins available for this kind of dispersion are usually solubilised by the addition of bases (amines are the most common). Some come wiA the amine added. Others require addition on site to make them soluble. They can then be treated in many respects as if they were solvent based systems. 

---