Optical bleaching

Optical amplifiers Optical bleaches Optical brighteners... 

Naphthalenedicarboxylic Acid. NaphthaUc acid readily dehydrates on heating to 1,8-naphthalenedicarboxyhc acid anhydride [81-84-5] (naphthahc anhydride) (41). The anhydride and its imide naphthaUmide [81-83-4] (R = H) (42) are intermediates for important dyes, pigments, optical bleaches, and biologically active compounds. 

The reverse reaction, B returning to A, can be driven either by thermal or photochemical energy, or both. When the reversion is photochemicaHy driven, the process is called optical bleaching. Optical bleaching is a general characteristic and is a factor in almost all photochromic systems, even those normally thought of as being thermally reversible. 

The darkening reaction involves the formation of silver metal within the silver haUde particles containing traces of cuprous haUde. With the formation of metallic silver, cuprous ions are oxidized to cupric ions (1,4). The thermal or photochemical (optical bleaching) reversion to the colorless or bleached state corresponds to the reoxidation of silver to silver ion and the reduction of cupric ion to reform cuprous ion. 

Other miscellaneous materials also used occasionally include fire retardants, optical bleaches and blowing agents. 

Descriptive terms such as fluorescent whitening agents , optical brighteners and optical bleaches have all been used for the products described in this chapter as FBAs. Many of these terms have validity and the term fluorescent brightening agents is preferred here only because it has been adopted in the indexes of Chemical Abstracts. 

Optical bleaching sediment. Sunlight-reduced ESR signal intensity of the holes centres associated with A1 impurity and electron centres related to Ge impurities in quartz grains (sand). Whether sunlight bleached the optically sensitive centres completely is an issue in dating of sediments.45... 

So-called optical bleaches, such asBlankophor BA, a substituted amino stilbene sulfonic acid, like auramine O will show enhanced fluorescence in viscous media or when bound to polymers. The strong blue emission tends to give the dyed fabric, especially when viewed under sunlight illumination, an apparent whiteness to the fabric. This stilbene derivative is... 

Besides good heat resistance, FIBRAMOLL CN Liquid has a very good compatability with dye fixatives, resins, and optical bleaching agents and is suited for resin finishing. 

CNC SOFT XXX is exceptionally versatile as it is compatible with anionic, cationic or nonionic substances. It is compatible with resins, catalysts and optical bleaches also acrylic resins, polyvinyl acetate emulsions and starches. The product may be applied by padding or exhaust methods. 

CNC REZ K is fully compatible with other thermosetting resins, thermoplastics, softeners, dye fixatives, optical bleaches and almost all classes of organic and inorganic catalysts. 

Analogous to the photoreactivity of the A, B, C — series the b, c, d-series may be optically bleached. As a result a new series y, 6, e appears in the optical absorption spectra. This series is optically and thermally stable and therefore reacts neither upon UV-or resonant irradiation nor upon annealing of the crystal up to room temperature. This is in contrast to the intermediates A, B, C,... and b, c, d,... which finally form polymer chains. 

Fig. 6. Optical bleaching of the photoproduct A by resonant irradiation into the A absorption. The A absorption is transformed into the b and y absorptions (A -+ b y)...

Besides the direct generation of the monomer crystals by UV-irradiation AC molecules may also be produced indirectly by optical bleaching of the DR molecules. This has been demonstrated by example of the optical absorption A b in Fig. 6. The corresponding transformation of the ESR lines I - 2 during optical bleaching of A - b is shown in Fig. 14. The dimer DR molecule I is not transformed to the dimer AC molecule 1 but to the trimer AC molecule 2. Consequently, one monomer molecule is added in each resonant phototransformation reaction of DR molecules to AC molecules. 

The chain termination reactions are performed most effectively by resonant optical excitation of the DR and AC intermediates (optical bleaching) as shown in Figs. 6 and 14. The DR and AC reaction centres may be indirectly excited via energy transfer from the monomer matrix. The chain termination reactions are, therefore, in competition with the photoinitiation and photoinduced chain propagation reactions. 

Renilla (sea pansy) luciferin (and certain of its synthetic analogues) produces a brilliant blue chemiluminescence when dissolved in organic solvents such as dimethylformamide and involves the anion of 2-acetamido-3-benzyl-5-(p-hydroxy-phenyl)pyrazine (21) (1191). 5-Hydrazino-2-hydrazinocarbonylpyrazine is effective against mycobacterium tuberculosis and m. kansasii in vitro (1098). Aminonitro-pyrazines have been claimed as useful yellow dyes for wool (1180) and tetraamino-pyrazine (1180) and A -substituted amides of 2-carboxy-3,5-bismethylamino-6-(A -methylcarbamoyl)pyrazines (1192) as fluorescent brighteners (or optical bleaching agents) for textiles. 

Metanilic acid, the trivial name for m-aminobenzenesulfonic acid (aniline-3-sulfonic acid), is made by sulfonation of nitrobenzene, followed by B6champ reduction. It is used in reactive dyes and optical bleaching agents, or brighteners, that are added to detergents. 

Use Optical bleach in textile industry, in coatings for paper, labels, book covers, etc to lighten plastics, resins, varnishes, and lacquers invisible marking agent. 

Use Optical bleach on soaps, starches and laundry products, suntan lotions. 

Use Manufacture of dyes and optical bleaches, crystals are used as phosphors and scintillators. Note The cis form of a, (i-di phony lethy lone (isostilbene) is a yellow oil, bp 145C (13 mm Hg), mp 1C. 

There is opinion that stabilizing additives should be colorless [10, 76], on the other hand fluorescent additives (optical bleach) are introduced into polymer in order to compensate yellow painting, which appears at PA processing and also to increase luster and whiteness of products. However, there are works in literature in which there is opinion that it is more preferable to use dyes as stabilizers [77-81], especially if it is necessary to get dyed polymers. 

In some works direction of using different dyeing additives, including organic dyes, as PETP modifiers is being developed. Optical bleaches, disperse dyes, dyes of anthraquinone series, azo and phthalocyan dyes have found their application for this purpose. 

In order to detect radical ions, mass spectrometry, electron spectroscopy, and ESR are used in combination with optical bleaching. For example, according to mass spectrometric data, ethylene forms a dimer particle, C4H8, as a result of a primary ion-molecular reaction. This particle reacting with monomeric ethylene produces growing chains up to C14 with a radical-ion active centre ... 

---