Solvent fastness

In the red to violet sector Naphtol AS and its derivatives are widely used. Simple monoazo combinations such as 2,5-dichloroaniline and Naphtol AS serve where high heat and solvent fastness are not essential, but for better properties polar features, such as amide linkages, are incorporated. Cl Pigment Red 245 (4.119), Cl Pigment Red 188 (4.120) and... 

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. 

Particle size distribution analyses in organic solvents may show dissolution and recrystallization effects when pigments with poor solvent fastness are measured. 

A number of potential users, such as the printing industry, are interested in the solvent fastness not only of a pigment but of an entire pigment-vehicle system. Standardized tests are available. A proof print of a certain size is placed inside a test tube and allowed to remain in the target solvent at 20°C for 5 minutes. The change in solvent color is determined and the print dried and compared with an untreated specimen. Standard solvents [14] are ethanol or the following mixture ... 

Another facet that is affected by the particle size of a pigment is its tendency to recrystallize, a direct result of poor solvent fastness (Sec. 1.6.5). This is illustrated by three samples which differ in terms of particle size distribution (Sec. 1.7.3). The... 

P.Y.10 provides clean, reddish yellow hues. Its very good lightfastness makes it almost as fast as P.Y.97. However, its solvent fastness is poor and in this respect in-... 

P.Y.191 displays excellent solvent fastness in aliphatic and in aromatic hydrocarbons, as well as in the commonly used plasticizers. The pigment is almost completely fast to alcohols and esters but not to water, ketones and methylglycol. 

P.Y.13 and its chemically modified derivatives, due to their higher solvent fastness compared to P.Y.12, are used in much greater volume in packaging gravure inks. P.Y.13 is also fast to protective clear lacquer overcoatings and may be sterilized and calandered. 

P.R.146 is somewhat yellower than P.R.57 1 it therefore fails to match the standard magenta for three and four color printing. However, P.R.146 prints have the advantage of good application performance (Sec. 1.6.2.3), corresponding to the above-mentioned solvent fastnesses. 

The next step consisted of introducing groups to improve the hydrophilicity of the parent structure to a certain extent, but not enough to render it soluble in water. Best results were achieved by the carbonamide function. Additional introduction of several such groups, for instance into Naphthol AS pigments, resulted in very solvent fast and migration resistant pigments (Sec. 2.6.2). 

P.R.175 has stimulated interest throughout the printing ink industry wherever high lightfastness, excellent solvent fastness, fastness to sterilization, and very high heat stability (up to 220°C) are a requirement. 

In printing inks P.Y.173 it is a very green shade opaque yellow with excellent light, weather and solvent fastness properties, but low color strength. It is recommended for paste and liquid inks where high fastness properties are required as well as for water based decorative inks. 

Under the designation P.B.15 4, the Colour Index lists (3-Copper Phthalocyanine Blue types which are stabilized towards flocculation. These products show largely the same coloristic and fastness properties as P.B.15 3 types, but often exhibit much better rheology. As with stabilized a-Copper Phthalocyanine Blue types, stabilization through surface treatment has proven to decrease the solvent fastness of 3-Copper Phthalocyanine Blue, sometimes considerably so, making the pigment more sensitive to aromatics, alcohols, ethylene glycol, and ketones. 

Commercial types exhibit a surprisingly wide range of shades. A new version has been introduced recently which, although performing like other versions of P.R.224 in terms of weatherfastness, solvent fastness, and fastness to overcoating, is substantially yellower and noticeably cleaner than traditional types. Opaque va-... 

Pyranthrone may be halogenated, for instance, in chlorosulfonic acid in the presence of small amounts of sulfur, iodine, or antimony as a catalyst. This procedure necessitates intermediate separation and purification of pyranthrone after manufacture, because the products, unless purified, fail to furnish the solvent fastness which is characteristic of a typical pigment. 

While 7,15- and 3,11-dichloropyranthrone demonstrate such poor solvent fastness as to be unsuitable for use as pigments, 6,14-dichloropyranthrone possesses excellent solvent resistance. 

Dimethylformamide, as other amides, offers some unique features as a halogenation solvent. Fast reaction rates and high selectivities are repeatedly noticed. This is attributed to the in situ formation of remarkable intermediates, several of which have been isolated and characterized. 

Cl pigment orange 38, Cl No. 12367, is a very yellow shade, bright red with good solvent fastness. 

These pigments combine excellent tinctorial properties with outstanding durability, solvent fastness, lightfastness, heat fastness, and chemical resistance. Table 8.1 lists those shades currently available commercially. 

PY 13 MX yellow Redder shade than PY 12, offers improved heat stability and solvent fastness PVC and polyolefins are major outlets... 

PY 16 Yellow NCG Bright green shade improved heat and solvent fastness very limited use in plastics... 

PY 60 Arylide yellow Very red shade moderate light and solvent fastness... 

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