Paints Pigment Violet

Paint pigments do not change colors on appHcation. Other common colors are violet from cobalt(II) phosphate [18475-47-3] pink from cobalt and magnesium oxides, aureolin yellow from potassiuim cobalt(III) nitrite [13782-01-9], KCo(N02)4, and cerulean blue from cobalt staimate [6546-12-5]. Large quantities of cobalt are used at levels of a few ppm to decolori2e or whiten glass and ceramics. Iron oxide or titanium dioxide often impart a yellow tint to various domestic ware. The cobalt blue tends to neutrali2e the effect of the yellow. 

Fig. 36 Dispersion of Pigment Violet 19, (l-modification, in an alkyd-melamine resin baking enamel with a paint shaker. Reduction 1 2 with Ti02. Tinctorial strength-time curve.

Pigment Violet 37 also exhibits a considerably more reddish shade and reduced tinctorial strength in paints compared to Pigment Violet 23, with equivalent fastness properties. 

Resembling indigo, the colour is not remarkably brilliant, and, unless several precautions are carefully observed, is rather violet than blue. He also implies that it was unlikely to have been used as a painting pigment. 

These pigments are obtained by coupling substituted aryl diazonium salts with ary-lides of 2-hydroxy-3-naphthoic acid (2-hydroxy-3-naphthoic acid anilide = Naph-tol AS). They provide a broad range of colors from yellowish and medium red to bordeaux, carmine, brown, and violet their solvent fastness and migration resistance are only marginal. Naphthol AS pigments are used mainly in printing inks and paints. 

Commercial interest inP.V.5 l, Constitution No. 58055 1,has declined considerably. The pigment continues to be used in industrial paints, especially throughout the USA. Its full shade is a brilliant, deep bluish maroon. In white reductions, the pigment produces clean, reddish violet shades. It lacks tinctorial strength and the coatings are fast to neither acid nor alkali. P.V.5 1 is also not very lightfast, which practically precludes its use in products for exterior application, particularly in reduced shades. 

P.V.23, also referred to as Carbazole Violet, is a universally useful product. Its color, a bluish violet shade, is not accessible with other Pigments. P.V.23 is used in almost all media which are typically colored with pigments. The list of suitable systems ranges from coatings and paints to plastics, printing inks, and other special-purpose media. P.V.23 is entirely fast to many organic solvents. At standardized conditions (Sec. 1.6.2.1), it is fast to alcohols, esters, and aliphatic hydrocarbons as well as to plasticizers such as dibutyl and dioctyl phthalate. Other solvents, such as ketones, are colored slightly (step 4). 

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