Common varieties of organic pigments

The common varieties of organic pigments are mainly as follows:

1. Azo pigment

A water-insoluble organic compound containing the azo group (-n =N-) in its molecular structure. It is one of the most varied and productive organic pigments. Azo pigment is the diazo component prepared by diazotization of aromatic amine or heterarylamine and then coupled with acetylarylamine, 2-naphthol, pyrazolone, 2-hydroxy-3-naphthol carboxylic acid or 2-hydroxy-3-naphthol aromatic amine by coupling components, resulting in water insoluble precipitation, that is, the general azo pigment. Its synthesis method is basically the same as that of azo dyes, but the latter is water soluble. Commonly used azo pigments for orange, yellow, red pigments such as permanent orange RN (C.I. Pigment orange 5), gold bright red (C.I. pigment red 21), benzidine yellow G (C.I. Pigment yellow 12). In order to improve the properties of pigment such as fast sunlight, heat resistance and organic solvent resistance, two molecules can be condensed into macromolecules by aromatic diamine. Pigments made in this way are called macromolecular pigments or condensed azo pigments such as: macromolecular orange. Pigment Orange 31), macromolecular red R (C.I. Pigment Red 166).

2. Color lake

Water-soluble dyes (such as acid dyes, direct dyes, alkaline dyes, etc.) produced by the action of precipitant water insoluble pigment. Its color light is more brilliant, the chromatography is more complete, the production cost is low, and the fast fastness is higher than the original water soluble dyes. The precipitant is mainly inorganic salt, acid, carrier and so on. Inorganic salt precipitation is the reaction of barium chloride, calcium chloride and manganese sulfate as precipitating agents with water-soluble dyes to produce water-insoluble salts such as barium, calcium and manganese, such as permanent red F5R(C.I). Pigment Red 48:2), golden red C(C.I. pigment red 53:1). Acid precipitation is the use of phospho-molybdic acid, phospho-tungstic acid, tannic acid and other as precipitant and water-soluble alkaline dyes reaction to produce insoluble lake, such as: fast rose lake (C.I. Pigment purple 1), light green lotus (C.I. pigment purple 3). Carrier precipitation is to deposit water-soluble dyes on the surface of carriers such as aluminum hydroxide and barium sulfate to form water-insoluble lake, such as acid golden lake (C.I.). Pigment orange 17), fast lake blue Lake (C.I. pigment blue 17).

3. Phthalocyanine pigment

The main body of the molecule is phthalocyanine, and the structural formula is:

They are water insoluble organic matter, mainly blue and green pigments. In 1934, the first variety — phthalocyanine blue was produced by the British Chemical Industry company and the German Farben Company respectively. The vast majority of products contain divalent metals, such as copper, nickel, iron, manganese, etc., also change the benzene ring in the molecule to pyrrole ring or other rings, and introduce other groups in the molecule, different structures have different properties and uses. The main variety of phthalocyanine pigments is copper phthalocyanine blue (C.I. pigment Blue 15). The main industrial production method is to phthalic anhydride and urea (also directly using phthalonitrile) in the presence of ammonium molybdate catalyst, reaction with cuprous chloride, the crude product commonly known as “copper phthalocyanine”. Different products can be obtained by different methods of pigment post-treatment. If the coarse product is dissolved in concentrated sulfuric acid, and then slowly precipitated in water, α crystal can be obtained, which is a kind of blue organic pigment with red light; If the crude product is dissolved in concentrated sulfuric acid, and then through a small amount of chlorine gas, so that the molecule with 1 ~ 2 chlorine atoms, the product color light than without chlorine some green; If the coarse product is ground with dry sodium chloride in the ball mill, the stable green light β crystal product can be obtained. The crude product is heated to about 220°C in aluminum trichloride and sodium chloride melt, and chlorine gas is introduced into the molecule, so that 14 ~ 16 chlorine atoms are introduced into the product for bright green pigment; If a small amount of bromine is introduced, the resulting product is more yellowish and vivid.

4. Quinacridone pigment

A pigment whose basic molecular structure is quinacridone:

It was produced by DuPont in 1958. The production method is from diethyl succinate through self condensation, condensation with aniline, closed loop, refining, oxidation to obtain γ crystalline quinacridone pigment. Because its heat resistance, fast sunlight, brightness and other properties are comparable to phthalocyanine pigments, so the commodity is called phthalocyanine red (C.I. The pigment purple 19), in fact, the molecular structure of the two is completely different. If different conditions are used in oxidation, the bluer β-crystal quinacridone pigment can be obtained, which is commercially known as phthalocyanine purple.

In addition to the above mentioned varieties, there are some excellent performance varieties, such as dioxazine pigments, represented by the variety permanent purple RL(C.I. Pigment purple 23); Isoindolinone pigment, represented by pigment yellow 2GLT (C.I. Pigment Yellow 109); Benzimidazolone pigment, represented by the variety permanent orange HSL (C.I. Pigment Orange 36).

The research focus of organic pigment workers is on the improvement of pigment post-treatment, such as the selection of better crystal type, the manufacture of finer particles with small particle size distribution, the improvement of pigment wetness, so that organic pigment can play a greater role.

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