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Types of Organic Pigments

Organic pigments are a class of vividly colored, highly tinting insoluble organic compounds. With a wide variety and comprehensive color spectrum, organic pigments encompass the entire visible light spectrum. Common types of organic pigments include azo pigments (which can be further classified into monoazo, diazo, azo lake, and azo condensation pigments), phthalocyanine pigments, naphthol pigments, quinacridone pigments, dioxazine pigments, and other special pigments.

I. Azo Pigments

Azo pigments refer to organic pigments containing azo groups in their chemical structure. They are a major category of organic pigments, constituting approximately 60% of the total organic pigment production. 

Azo pigments exhibit a wide color range, bright hues, strong tinting strength, and relatively good lightfastness. As such, they find extensive applications in coloring various products such as inks, coatings, rubber, plastics, printing inks, paper, stationery, and cosmetics.

Azo pigments can be further classified based on the number of azo groups in the pigment molecule or the structural characteristics of their diazo and coupling components, into categories such as monoazo, diazo, azo lake, and condensed azo pigments.

Azo Pigments Powder Photo

1. Monoazo Pigments

Monoazo pigments contain only one azo group in their molecule as the coloring system. Typically, they include insoluble azo and azo lake pigments, primarily featuring yellow, orange, and red hues. These pigments exhibit relatively low molecular weight, simple structures, vibrant colors, high tinting strength, moderate durability, and application fastness, mainly used in ink coloring.

2. Diazo Pigments

Diazo pigments contain two azo groups in the molecule. Their production process is relatively complex, and while their lightfastness is not ideal, they exhibit good solvent resistance and migration resistance. They are mainly used in general-purpose printing inks and plastics, with limited applications in coating products.

3. Azo Lake Pigments

Azo lake pigments are water-insoluble pigments formed by the interaction of water-soluble dyes with precipitants. They exhibit bright colors, a wide color range, and higher lightfastness compared to the original water-soluble dyes. Their production difficulty is similar to that of typical monoazo pigments. The color spectrum mainly comprises yellow and red hues. Azo lake pigments are primarily used in industries such as coatings, inks, printing, plastics, papermaking, rubber products, and ceramics.

4. Condensation Azo Pigments

Condensation azo pigments structurally resemble typical diazo pigments but are formed by the condensation of two monoazo pigments containing carboxylic acid groups. These pigments have complex production processes and exhibit excellent lightfastness, solvent resistance, and migration resistance. They are primarily used for liquid coloring of plastics and synthetic fibers.

Phthalocyanine Pigments

II. Phthalocyanine Pigments

Phthalocyanine pigments are organic compounds containing phthalocyanine molecules insoluble in water. They are predominantly blue and green, with copper phthalocyanine being the main variety. Industrially, copper phthalocyanine is produced by the reaction of phthalic anhydride and urea catalyzed by ammonium molybdate, with cuprous chloride yielding the crude product known as copper phthalocyanine.

Phthalocyanine pigments are polycrystalline compounds, with common α-crystal (red light) and β-crystal (cyan light) types. These pigments offer vibrant hues, high tinting strength, excellent heat resistance, and lightfastness. They are finely granulated, easily dispersed, and processed, finding primary applications in inks, iron inks, coatings, watercolor paints, oil paints, and coating printing, as well as rubber and plastic products coloring.

III. Naphthol Pigments

Chemically, naphthol pigments also belong to monoazo pigments but use naphthol as the coupling component, with orange and red hues predominantly. To distinguish them from yellow and orange monoazo pigments, they are classified as naphthol series pigments. These pigments exhibit excellent lightfastness, solvent resistance, and migration resistance but are not alkali-resistant. Therefore, they are mainly used in paints and coating products requiring high lightfastness.

IV. Quinacridone Pigments

Quinacridone pigments are derived from the condensation and cyclization of diethyl phthalate with aniline, followed by refining and oxidation. Most quinacridone pigments are red and purple-red. They offer vibrant hues, excellent comprehensive color fastness, migration resistance, and solvent resistance, withstanding temperatures of up to 300°C. Widely used in high-grade printing inks, spray paints, plastics, and coloring of synthetic fibers.

Quinacridone Pigments Powder

V. Dioxazine Pigments

Dioxazine pigments mainly feature a carbazole dioxazine structure, offering vivid purple hues, high tinting strength, excellent heat resistance, lightfastness, and solvent resistance. They are excellent coloring pigments for plastics.

Conclusion

In conclusion, organic pigments encompass a diverse range of compounds with various chemical structures and color properties, catering to a wide array of applications across industries. Understanding the types of organic pigments and their characteristics is crucial for achieving the desired coloring effects and ensuring product performance in various applications.

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