An organic pigment is an organic molecule that acts as a pigment, which means that it changes the color of reflected or transmitted light as the result of wavelength-selective absorption. Furthermore, it is insoluble in coating systems and polymers.
In most cases, organic pigments have a lower covering power than inorganic pigments, but exhibit higher color strength and gloss.
They are mainly based on carbon, hydrogen, and nitrogen and can be classified in three main groups: azo pigments, polycyclic pigments, and anthraquinone pigments.
1– Azo Pigments:
A– Monoazo Pigments (PY 183, PY 191)
These high-performance pigments cover the spectral range of reddish yellow and exhibit good light fastness and durability combined with very good heat stability up to 320 °C. PY 183 and PY 191 are specialty products for the coloration of plastics and are mostly used in masterbatches for olefins, polystyrenes, and engineering polymers as well as for the direct coloring of PVC. Their excellent hiding power and clean, brilliant full and medium shades make some of these pigments suitable for replacing chrome yellow in chromium free pigmentation. Furthermore, they offer the best available alternative to match lead chromates, especially in combination with nickel and chrome rutiles.
B– Disazo Pigments (Diarylide) (PY 83)
This product covers the color range of extremely reddish yellow. It has a very high color strength compared to all other yellows and therefore offers excellent opportunities for use in alternatives to lead chromates. Disazo pigments exhibit weak light and weather fastness but satisfactory solvent and migration fastness as well as a high tinctorial strength (twice as high compared to monoazo yellow pigments, which cover the same range of colors). Typical applications for diarylide yellows are paints, especially industrial finishes. Some types are suitable for automotive finishes and other industrial coatings.
C– ß-Naphthol Pigments (PO 5)
The color of the range varies from yellowish orange to bluish red, while Heubach’s PO 5 exhibits a yellow orange color shade. ß-naphthol pigments exhibit a low tinctorial strength but a good light fastness, combined with limited solvent and migration resistance. Pigment orange 5 is a cost-effective orange pigment for all applications which do not require a high fastness against light and weather. These organic pigments are mainly used in paints and printing inks such as packaging, flexo, and offset printing.
D– Naphthol AS Pigments (PR 112, PR 2)
The color of PR 112 and PR 2 ranges from a yellowish to medium red. Even if solvent fastness and migration resistance are limited, pigment red 2 is the most cost-effective red pigment for the printing industry, providing clear and brilliant red colors. A very important use of naphthol AS pigments are offset, flexo, and packaging gravure printing inks as well as paints, textile printings, cleaning agents, detergents, and the coloration of paper.
E– Benzimidazolone Pigments (PY 151, PY 154, PY 180, PY 181, PR 176)
This range of pigments covers the spectrum from greenish to reddish yellow as well as a bluish red depending on the coupling component. They offer outstanding fastness to light, weather, solvents, and chemicals accompanied by good migration fastness. Due to a wide spectrum of physical characteristics, benzimidazolone pigments vary considerably in their tinctorial strength. Most of these pigments meet the major heat stability standards, while some are even among the most heat-stable organic pigments available. Benzimidazolone pigments are suitable for the highest demands such as high-end industrial coatings, automotive coatings, long-lasting plastic applications, and high-grade printing inks. Some pigments, such as PR 176, are ideally suited to the coloration of wood laminate applications.
E– Metal Complex Pigments (PY 150)
The color of PY150 is a medium shaded yellow. Due to its very good light and weather fastness as well as enhanced solvent resistance and migration fastness, pigment yellow 150 is best suited to be used in paints, especially industrial finishes. Some types are also suitable for automotive finishes and other industrial coatings. Metal complex pigments can be used together with stable blue pigments to give artificial grass the right color in polyamide applications and fibres.
F– Isoindoline Pigments (PY 139)
PY 139 organic pigments enable reddish yellow shades. As with the metal complex pigments, isoindolines exhibit good fastness to weather and light as well as good solvent and migration fastness, heat stability, and chemical inertness. Pigment yellow 139 is used in general and high-grade industrial paints including original automobile and automotive refinishes, in plastics for spin dyeing, and in high-grade printing inks, especially for metal deco, laminated plastic sheets, and in printing inks for bank notes and securities. It represents the most reddish yellow pigment and thus offers outstanding suitability for use in orange applications.
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2– Polycyclic Pigments
A– Phthalocyanine Blues (PB 15:1, 15:2, 15:3, 15:4, Blue Crude) and Greens (PG 7, PG 36)
While copper phthalocyanine blue pigments range in shades from greenish to reddish blue, the halogenated copper phthalocyanine green series covers the bluish to yellowish green portion of spectrum. This class of organic pigments exhibits excellent fastness properties, especially regarding light- and weather fastness, as well as very good heat stability and overall stability to organic solvents. Phthalocyanine pigments, which exhibit high tinctorial strength, provide an excellent ratio of tinting strength versus price. Their excellent general chemical and physical properties, combined with good cost effectiveness, make them the largest share of organic pigments in the market today. Phthalocyanine blues and greens are very versatile pigments which can be used in high-end automotive coating systems as well as in everyday printing applications. Their high temperature resistance makes them suitable for all kinds of plastic applications, and their relatively high transparency also permits them to be used in combination with effect pigments.
B– Quinacridone Reds (PR 122, PV 19)
These organic pigments cover the spectral range from a bluish red shade to a reddish violet shade. Quinacridone reds are very light and weather fast and practically insoluble in most common solvents. They further provide extensive migration resistance in all application media. These very stable pigments are suitable for use in high-grade industrial coatings, such as automotive finishes and refinishes, emulsion paints such as house paints, in plastic applications that require high fastness properties, in special printing inks for purposes such as metal deco and poster printing, in textile printing, and in spin dyeing.
C– Diketopyrrolo-Pyrrole (DPP) Pigments (PR 254, PR 264)
These organic pigments enable shades in the color range from orange to medium reds. Diketopyrrolo-pyrrole (DPP) pigments exhibit excellent light fastness and weather fastness combined with good to very good solvent fastness and heat stability. The DPP reds are the most stable and brilliant organic red pigments and are suitable for a variety of applications such as plastics, printing inks, and high-grade industrial coatings, including automotive finishes. This pigment class is now used in a majority of red applications and has replaced other red pigments in applications requiring fastness properties.
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3– Anthraquinone Pigments
A– Indanthrone Blues (PB 60)
PB 60 are reddish shaded blue pigments that exhibit excellent weather fastness, good transparency, high tinctorial strength, and very good fastness to organic solvents. Due to their high transparency and brilliance combined with their fastness properties, indanthrone blue pigments are suitable for effect colors. They are therefore mainly applied in industrial paints such as automotive finishes, especially in metallic finishes. Heubach is the only pigment producer that manufactures indanthrone crude blue globally.
B– Anthanthrone (PR 168)
PR 168 provides a clean yellowish shade of scarlet. These pigments are almost entirely resistant to most of the organic solvents which are commonly found in typical binder systems. Furthermore, they offer outstanding light and weather fastness along with a comparatively low tinting strength. The pigment red 168 is probably the only red pigment stable enough for red plaster applications in the decorative field. In addition, it can be used for high-grade industrial coatings such as automotive finishes, in architectural paints and emulsion paints, and in coil and PVC coatings.