Basic dyes

Diacetin is chiefly the 1 3-diacelate CH3OOCCH3.CHOH.CH2OOCCH3. Used as plasticizer for cellulose acetate lacquers and as a solvent for basic dyes. 

Most xanthene dyes are classified as basic dyes by their method of appHcation acid dyes can be produced by introduction of sulfonic acid groups. The fluoresceins, which contain carboxy and hydroxy substituents, are also acid dyes for coloration of silk. Some of the fluoresceins in which the carboxy group has been esterified, are soluble in alcohol or other organic solvents and can be classified as solvent dyes. Mordant dyes can be produced by introducing o-dihydroxy or sahcyhc acid groups (2), which when metallised can have very good lightfastness. 

Sa.ccha.rein, Sacchareia [6837-69-0] (36) is a basic dye prepared by the condensation of y -diethylaminophenol with sacchatin at 165°C. 

Parameter Basic dyes Acid dyes Direct dyes... 

Table 5. Typical Basic Dyes Used as Complexes with Heteropolyacids...

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

Statistics for the production of basic dyes include those products hsted as cationic dyes, eg, cyanines, for dyeing polyacrylonitrile fibers and the classical triaryhnethane dyes, eg, malachite green, for coloring paper and other office apphcations (2,53). Moreover, statistics for triaryhnethane dyes are also hidden in the production figures for acid, solvent, mordant, and food dyes, and also organic pigments. Between 1975 and 1984, the aimual production of basic dyes in the United States varied from 5000—7700 t. However, from 1985—1990, aimual production of basic dyes varied from 5000—5700 t, and the annual sales value increased from 56 to 73 million per year. 

Commercially, heteropolytungstates, particulady the heteropolytungstates, are produced in large quantities as precipitants for basic dyes, with which they form colored lakes or toners (see also Dyes and dye intermediates). They are also used in catalysis, passivation of steel, etc. 

Dyes in these classes are generally basic dyes ie, the chiomophoie is cationic. Some stmctures have been sulfonated to acid dyes, eg, the Nigrosine, (Cl Solvent Black 5 Cl 50415), (8) to Cl Acid Black 2 [8005-03-6] (Cl 50420) (9). 

There are approximately one dozen references to azine dyes reported in Chemicaly hstracts traceable literature since 1976. Of these references, all but one refers to titration indicators. One basic dye is reported, but it is not a commercial product (6) ... 

Cationic azo dyes carry a positive charge ia the chromophore portion of the molecule. The salt-forming counterion is usually a chloride or acetate. Cl basic dyes are ammonium, sulfonium, or oxonium salts. Commercial basic azo dyes for which chemical stmctures are revealed by U.S. producers are listed ia Table 15. 

Reaction with vatious nucleophilic reagents provides several types of dyes. Those with simple chromophores include the hernicyanine iodide [16384-23-9] (20) in which one of the terminal nitrogens is nonheterocyclic enamine triearbocyanine iodide [16384-24-0] (21) useful as a laser dye and the merocyanine [32634-47-2] (22). More complex polynuclear dyes from reagents with more than one reactive site include the trinuclear BAB (Basic-Acidic-Basic) dye [66037-42-1] (23) containing basic-acidic-basic heterocycles. Indolizinium quaternary salts (24), derived from reaction of diphenylcyclopropenone [886-38-4] and 4-picoline [108-89-4] provide trimethine dyes such as (25), which absorb near 950 nm in the infrared (23). 

Cyclohexanoae is miscible with methanol, ethanol, acetone, benzene, / -hexane, nitrobenzene, diethyl ether, naphtha, xylene, ethylene glycol, isoamyl acetate, diethylamine, and most organic solvents. This ketone dissolves cellulose nitrate, acetate, and ethers, vinyl resias, raw mbber, waxes, fats, shellac, basic dyes, oils, latex, bitumea, kaure, elemi, and many other organic compounds. 

In the 1950s acid dyes were successively developed to dye nylon carpet with excellent fastness and uniform leveling. Development of polyacrylonitrile fiber stimulated the invention of anthraquinone basic dyes, modified disperse dyes in which quaternary ammonium groups are introduced. 

Basic Dyes. These are usuaUy the salts of organic bases where the colored portion of the molecule is the cation. They are therefore sometimes referred to as cationic dyes. They are appHed from mild acid, to induce solubUity, and appHed to fibers containing anionic groups. Thein main outiet is for dyeing fibers based on polyacrylonitrile (see Fibers, acrylic). 

A20 dyes can also be positively charged to form basic dyes by quatemi2iag the nitrogen ia a heterocycHc dia2onium component or by incorporating a quatemi2ed group ia a side chain. 

Langmuir isotherms are typically found with ionic synthetic fibers and ionic dyes, eg, dyeing polyacrylonitrile with modified basic dyes, and on hydrophilic fibers in situations when the number of sites becomes very low. This may arise when the internal pH is such that only a small number of sites ionise. 

Dyeing Mechanism. The original basic dyes were characterized by a delocalized charge in the molecule. As the importance of acryHc fibers grew basic dyes were developed with localized charge in one specific part of the molecule allowing stronger salt links to be formed than with the delocalized type. 

These newei dyes aie often lefeiied to as modified basic dyes. Essentially thek stmctuie is that of a dispeise dye that has been piotonated. These dyes theiefoie have high rates of diffusion into the fiber, and thek mode of attraction is almost entkely ionic. 

The compatibihty value is mainly related to the affinity of the dye for the particular fiber because for basic dyes on modified acryhc fibers there is htde possibihty for migration and therefore this does not play a significant part in determining compatibihty. The rate of dyeing of a specific mixture of dyes of the same compatibihty value is not determined by the value itself. The adsorption of cationic dyes is induenced by the presence of others in the dyebath the presence of cationic retarding agents and electrolytes also induences the rate of exhaustion. It is therefore possible to have a combination of dyes with a compatibihty value 5 that under specific dyebath conditions exhausts more rapidly than a combination based on dyes of compatibihty value 3. 

Basic (Cationic) Dyes. The use of basic dyes is confined mainly to acryUc textile fibers, acetate, and as complementary dyes for acid-modified polyester fibers that accept this class of dyes. 

Transfer of Basic Dyes on Acrylics. This test is identical in concept to the transfer of disperse dye on polyester except that basic dyes, acryhc fiber, and a standard dyebath for dyeing acryflc is used. 

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