Leather lightfastness

The practical route for oxidizing leuco diphenylmethanes 15 demands inital conversion to an imine salt 16. The imine salt is obtained by heating a mixture of diphenylmethane, sulfur, ammonium chloride, and sodium chloride at 175°C in a current of ammonia or by heating a mixture of diphenylmethane, urea, sulfamic acid, sulfur, and ammonia at 175°C (Scheme 3). Dyes 16 can be represented as the quinonoid resonance structure 17. Dyes of this class, known as auramines, are all yellow, with the only commercial representative being auramine O 16a. Due to its poor lightfastness and instability to hot acids and bases, its use has been restricted to dyeing and printing cotton, paper, silk, leather, and jute. 

P.O.38 is frequently employed in combination with P.Y.83 to provide brilliant and very lightfast shades of orange. P.O.38 is particularly useful to produce shades of brown in PVC and PUR imitation leather. 1/3 SD HDPE formulations con-... 

In PVC, most benzimidazolone pigments are heat stable up to 220°C. They have excellent to outstanding lightfastness. Some representatives are very weather-fast in impact resistant PVC types and in rigid PVC and even withstand long-term weathering. Various benzimidazolone pigments are used, for instance by the automobile industry, in PVC plastisols to lend color to synthetic leather. 

Hydrazone Dyes If the diazonium salts of aromatic amines are coupled with the methylene derivatives of N heterocycles, hydrazone dyes (i.e., the monoaza derivatives of the enamine dyes) are obtained. Paper and leather can be dyed in yellow to red shades with these dyes [23], They are moderately lightfast on polyacrylonitrile. If the diazo components contain substituents in the 2-position relative to the amino group that can form a hydrogen bond (e.g., 2-nitroaniline [24] or 1-ami-noanthraquinone [25]), lightfastness is improved considerably (10). 

The first synthetic leather dyes were cationic. Mauveine, discovered by W. H. Perkin, marked the start of the synthetic dye industry. The cationic dyes were characterized by a previously unknown brightness. Nevertheless, the introduction of the new synthetic dyes was not a simple matter. The lightfastness properties were poor. However, the presence of Perkin at the first International Leather Congress in 1897 in London, undoubtedly ensured the breakthrough in the use of synthetic dyes for leather. 

Soluble sulfonated triarylmethane compounds are still used today as single dyes. They are brilliant blue, but with medium lightfastness. There are therefore often used in leather dye mixtures as shading components or as brightening dyes. 

In 1869 Caro succeeded in performing the sulfonation step, and the anthraqui-none dyes could be used to color leather. These bright acid dyes have excellent lightfastness and a bright, mostly blue to reddish shade. The arylaminoanthraqui-none types are chiefly utilized for coloring leather. The sulfo groups can be present in the anthraquinone or/and in the substituent. An example is C.I. Acid Blue 25, 62055 [6408-78-2] (6). 

Metallization of azo dyes enhances lightfastness, reduces water solubility, causes a bathochromic shift in color, and dulls the shade. Iron complexes generally give brown shades (e.g., C.I. Acid Brown 98) and are most often used to dye leather. 

The cis-trans isomerisation process in the photofading of azo dyes has been found to be a first-order process in polypropylene and independent of polymer crystallinity l. oye lightfastness on leather has however been found to depend upon the colour of the dye lS while alkyl and peroxy radicals have been observed in the photofading of Rhodamine and azo dyes in solution . More specifically basic triphenylmethane dyes have been found to give benzophenone products on photofading 20 structure of a series... 

Uses Metalized dye for leather spray dyeing applies., wood stains, solvent inks, decorative coatings on metal foils and polymeric films Features Provides high lightfastness Properties Sol. in alcohol and various polar soivs. 

Chem. Descrip. Methyl methacrylate-based polymer Uses Binder for mfg. of hard, lightfast coatings for plastics (esp. plasticized PVC) also for strippable coatings, PVC finishing (e.g., artificial leather) heat-sealing raw material for pkg. of foods and pharmaceuticals... 

Uses Fatliquoring agent for pickle, chrome tannage, rechrome of leathers Features Dry handle exc. stability to electrolytes, acids, hard water, chrome tanning salts exc. lightfastness Properties Yel./brn. liq. pH 5.0-6.5 (10%) 75% act. 

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