Intermediates:Dyeing (dyeing) intermediates are an extremely important branch of the fine chemical industry, and the rapid development of the dyeing (dyeing) industry relies on the development of intermediates that are complementary to them. The production of dyeing and pigment intermediates in China has made significant progress since the 1950s. With the increasingly fierce market competition, there have been innovations in the production technology of dyeing and pigment intermediates; Breakthroughs have been made in developing new varieties, improving production processes, researching new methods, developing new uses for old varieties, and protecting the environment. Clean processes have been adopted for intermediate production of dyes and pigments.
1. Development of intermediate applications
In fact, the development of intermediate applications is multifaceted. A certain intermediate used in dyes is called a dye intermediate, while used in pesticides and pharmaceuticals is also called a pesticide or pharmaceutical intermediate. Intermediates should be considered as a whole branch of the fine chemical industry, and should not be rigidly divided into dye intermediates, pesticide intermediates, and pharmaceutical intermediates according to the industry. This will reduce the scope of use of some intermediates and affect their development.
The characteristic of the research on fine chemical intermediates is the wide variety. Except for a few varieties with particularly large production scales, most varieties have relatively small tonnages, but the preparation process is often complex, involving many unit reactions and separation processes, and a considerable amount of "three wastes" need to be properly treated during production. Therefore, it is necessary to conduct process research on serialized products and organize intermediate production reasonably in order to achieve good economies of scale.
From the situation abroad, the research and production of intermediates tend to be appropriately centralized to achieve serial production. A set of production equipment can produce several to more than ten intermediate varieties. Such research and production are also relatively easy to implement through overall development and the adoption of new technologies, which will achieve twice the result with half the effort. The situation in Japan can serve as a reference for us. The production of intermediates in Japan was originally very scattered, and has undergone seven adjustments and centralization since the 1960s.
Through transformation and development, China's dyeing and pigment intermediate industry has reached a higher level in terms of production scale, technology, equipment level, etc. It can not only meet the needs of domestic dyeing and pigment industry development, but also provide more high-quality intermediate products for foreign countries.
The raw materials required for synthesizing intermediates are mainly obtained from the products of the petroleum and coking chemical industries, with the vast majority being benzene, naphthalene, anthraquinone compounds, as well as some heterocyclic compounds. In recent years, the use of heterocyclic compound intermediates to prepare organic pigments has been on the rise. In addition, the use of complex raw materials such as phenanthrene, pyridine, oxyfluorene, quinoline, indole, carbazole, and biphenyl series compounds in dye manufacturing will become more extensive and widespread.
2. The most commonly used chemical reactions for intermediates
The most commonly used chemical reactions for processing raw materials into dye (pigment) industrial intermediates are as follows:(1) Sulfonation reaction
(2) Nitration reaction
(3) Halogenation reaction
(4) Preparation of Amino through Reduction Reaction
(5) Diazotization reaction (often accompanied by coupling reaction)
(6) Replacing sulfonic acid groups with hydroxyl groups through alkali melting reaction
(7) Acylation reaction
(8) Oxidation reaction
(9) Condensation and carbonation reactions
(10) Aromatization reaction (mainly amino)
(11) Mutual displacement reaction between hydroxyl and amino groups
(12) Alkylation reaction of hydroxyl or amino groups
According to the aromatic ring structure of fine chemical intermediates, they can be classified into fatty, benzene, naphthalene, anthraquinone, heterocyclic, and fused ring systems. China can produce over 400 varieties of dye and pigment intermediates, including benzene, naphthalene, anthraquinone, heterocyclic, etc., which can basically meet the development needs of the dye and pigment industry.
3. Main varieties of benzene series
2,4-dinitrochlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, p-nitrophenol, N, N-dimethylaniline, p-aminobenzyl ether, p-nitroaniline, o-toluidine, 2-bromo-6-chlorop-nitroaniline, N-ethylaniline, m-hydroxydiethylaniline, 2,4-dinitro-6-bromoaniline, ortho -, p-phenylenediamine, 3,3-dichlorobenzidine, anetholidine, p-aminobenzenesulfonic acid, ortho -, para aminobenzyl ether DSD acid, para aminophenethyl ether, CTL acid, ortho cyano para nitroaniline, acetylaceto-methoxyaniline, hydroquinone, meta phenylenediamine, N-methyl meta toluidine, N-ethyl meta toluidine, N, N-dimethyl meta toluidine, N, N-diethyl meta toluidine, N-methyl hydroxyethyl meta toluidine, N-ethyl hydroxyethyl meta toluidine, N-methyl cyano ethyl meta toluidine, N-methyl phenyl meta toluidine, para methyl, ethoxy aniline, 2-4 dimethylaniline, 4-chloro-3-aminobenzamide, 4-methyl-3-aminobenzamide, 4-methoxy-3-aminobenzamide, 4-methoxy-3-aminobenzamide N, N-diethylbenzenesulfonamide, 2,4,5-trichloroaniline, meta - and para esters, etc.
4. Main varieties of naphthalene intermediates
2-Naphthol, H-acid, K-acid, 2,3-acid, 2,6-acid, Tourette's acid, 6-nitro-1,2,4-oxide, J-acid, cyclic acid, gamma acid, G-salt, R-salt, amino K-acid, 2-naphthylamine-1,5-disulfonic acid, 1-naphthol-5-sulfonic acid, 1,5-dihydroxynaphthalene, 2,6-naphthalic acid, 2R acid, etc. The main varieties of anthraquinone intermediates include anthraquinone, 1-aminoanthraquinone, 1,4-diaminoanthraquinone, bromoamino-1,5-dimethylanthraquinone, 1,5-diaminoanthraquinone, 1-amino-5-benzoylanthraquinone, 1,5-dihydroxyanthraquinone, 1,8-hydroxyanthraquinone, 1,8-dihydroxy-4,5-diaminoanthraquinone, etc.
5. Main varieties of heterocyclic and polycyclic systems
Cyanuric chloride, barbituric acid, 2-amino-6-nitrobenzothiazole, 2-amino-5,6-dichlorobenzothiazole, 2-aminothiazole, dehydrothio p-toluidine disulfonic acid, 3-cyano-4-methyl-6-hydroxy-N-ethylpyridone, 3-formylamino-4-methyl-6-hydroxy-N-ethylpyridone, 4-chloro-1,8-naphthalene, naphthalic anhydride! Tetraacetic anhydride, etc.
