C.I. Pigment Black 1
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Product Description
C.I. Pigment Black 1, also known as Aniline Black, is a complex organic pigment characterized by its deep, bluish, and transparent black color. It is an azine derivative primarily used in coatings, inks, and dyes due to its excellent resistance to solvents, acids, and light. Historically significant as one of the first synthetic black pigments. However, its use is now limited due to modern safety and environmental standards. Aniline Black may release carcinogenic aromatic amines during synthesis or use, posing potential health risks. Additionally, its synthesis process is similar to that of banned azo dyes, further restricting its application.
Synthesis Methods
General Synthesis:
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Typically prepared by reacting chromium salts with diazotized aromatic amines and coupling agents, followed by complexation and precipitation.
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The exact process is proprietary and varies by manufacturer.
Uses and Applications
Historical and Common Uses:
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Printing Inks: Staple for black printing inks, especially in letterpress and lithographic printing.
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Coatings and Paints: Used in various industrial and decorative paints.
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Plastics and Rubber: For coloring these materials.
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Artist's Materials: Historically used in some artist's paints and inks.
Modern Applications:
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Industrial Coatings: Automotive, machinery, and anticorrosive coatings.
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Printing Inks: Especially for offset and gravure inks requiring high opacity.
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Plastics: For coloring polyethylene, polypropylene, and PVC.
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Artist Pigments: Occasionally used in oil and acrylic paints.
Properties and Characteristics
Color and Appearance:
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Produces a deep, rich black with high tinting strength and opacity.
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The complexation of multiple dark-colored azo dye molecules with the chromium ion shifts the absorption spectrum to cover the entire visible range, resulting in a black appearance.
Chemical Composition:
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Formula: C₆₆H₅₁Cr₃N₁₁O₁₂.
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Consists of three Chromium (Cr³⁺) ions acting as a coordination center, binding to organic dye ligands through oxygen and nitrogen atoms.
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The organic dye ligands are typically derived from diazotized aniline derivatives coupled with molecules like BON (Beta-Oxy-Naphthoic) Acid.
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The N11 in the formula points to multiple azo groups (-N=N-), which are the chromophores responsible for the initial intense color.
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The O12 includes oxygen atoms from carboxylic acid (-COOH) and hydroxyl (-OH) groups on the dye molecules.
Solubility:
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Insoluble in common solvents (water, oil, etc.), which is a key distinction from soluble dyes.
Stability:
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Offers good lightfastness, weather stability, and chemical resistance.
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Has moderate heat stability, suitable for many applications but may decompose at very high temperatures.
Safety and Handling
Toxicity:
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Contains chromium (Cr³⁺), which is less toxic than Cr⁶⁺ compounds, but should still be handled with care.
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Potential release of carcinogenic aromatic amines (such as benzidine and dimethylbenzidine) during synthesis or use.
Regulations:
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Restricted or banned in many applications, especially those involving toys, food packaging, and consumer goods, by regulations like REACH in Europe.
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Subject to restrictions in some regions due to chromium content.
Environmental Impact:
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Stable and non-bleeding, but chromium content requires controlled disposal.
Safety Notes:
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Avoid inhalation of pigment dust; use protective equipment during industrial handling.
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Handling requires precautions such as dust control and personal protective equipment (PPE).