Alcohol-and Ester-Soluble Dyes

As far as chemical constitution is concerned, there is no precise delineation between alcohol- and ester-soluble dyes, nor between these two groups and the fat- and oil-soluble dyes described below. 

With the exception of the blue copper phthalocyanine derivatives, these products are azo dyes that are soluble in polar solvents such as alcohols, glycols, esters, glycol ethers, and ketones. Dyes soluble in alcohols and esters are used in protective lacquers for the transparent coating of metal (aluminum) foils and other materials, such as wood (greening lacquers) in flexographic inks for the printing of metal foils, cellophane, and paper as well as for the coloration of cellulose esters, celluloid, and poly(vinyl acetates), and, in the office supplies sector, for 

In accordance with chemical aspects, the most important alcohol- and ester-soluble azo dyes can be divided into three groups. 

1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

Second, 1 1 metal-complex azo dyes that contain sulfonic acid or carboxylic acid groups and are present in the form of internal salts. Here, azamethine-metal complexes are also of importance. An examples is C.I. Solvent Yellow 32, 48045 [61931-84-8] (2). 

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Fat- and oil-soluble dyes are also soluble in waxes, resins, lacquers, hydrocarbons, halogenated hydrocarbons, ethers, and alcohols, but not in water. It is not possible to differentiate clearly between them and the alcohol- and ester-soluble dyes. With the exception of blue anthraquinone derivatives, fat- and oil-soluble dyes are azo dyes, generally based on simple components. According to their degree of solubility they usually contain hydroxyl and/or amino groups, but not sulfonic acid and carboxylic acid groups. Examples of fat- and oil-soluble azo dyes are C.I. 

Solvent Dyes (see also Section 3.10). The 1 2 chromium and cobalt complex dyes devoid of any hydrophilic substituent have a considerable solubility in organic solvents, especially alcohols, ketones, and esters. Enhanced solubility can be achieved by converting the metal-complex sodium salts into salts of organic cations [57], Such cations may be cationic dyes, long-chain aliphatic ammonium ions, or protonated guanidines. For example, the bluish red solvent dye 34 reaches a solubility in organic solvents of up to 1000 g/L [58],... 

Both acrylic acid and methacrylic acid polymerise to give water soluble hard resins. The viscous solutions so formed have been used as emulsifying agents, adhesives and as thickening agents for inks and dyes. Polymers of esters of these acids are of greater commercial importance. Esters can be prepared from cyanhydrins by reaction with an alcohol ... 

Chlorophyll. Chemically pure chlorophyll is difficult to prepare, since it occurs mixed with other colored substances such as carotenoids. Commercially it is solvent extracted from the dried leaves of various plants such as broccoli or spinach. Chlorophyll is water-iosoluble. It has none of the characteristics of a dye in that it has no aflinity for the usual libers such as cotton or wool. Chlorophyll is properly classified as a pigment tCI Natural Green 3 Cl 75810), As such. It finds use lor coloring soaps, waxes, inks. fats, or nils. Chlorophyll is an ester composed of an acidic pint, chlorophyllin, esterilied by an aliphatic alcohol known as phylol. Hydrolysis of chlorophyll using sodium hydroxide produces the moderately water-soluble sodium salts of chlorophyllin. phytol. and methanol. The magnesium in chlorophyllin may be replaced by copper. The sodium copper chlorophyllin salt is heat-stable, and is ideal for coloring foods where heat is involved, such as in canning. 

There are quite a number of water-soluble esters, such as ethyl formate, diethyl tartrate, and ethyl lactate, which hydrolyse in a boiling dye liquor with the liberation of the organic acid and the alcohol, most of which distils away in the steam. The use of such esters in the application of acid dyes... 

The second type is comprised of 2 1 metal complexes of o -dihydroxy azo dyes which generally do not contain sulfo or other strongly hydrated groups as found in the premetallized 2 1 complexes for wool. Thus their solubility in esters, ketones, and alcohols is relatively increased. Cl Solvent Violet 1... 

Quinoline is a liquid, soluble in alcohol, ether, carban disulfide, and in most of the common organic solvents, but only partially soluble in water. It is o solvent for cellulose esters and ethers when used with other solvents. It is used in the manufacture of dyes, photographic sensitizers, nicotinic acid, and drugs. It is also used as an extraction agent and in organic synthesis. 

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