Pigment Black 7 (CI 77266), also known as Carbon black, is chemically classified as an inorganic colorant. This pigment is composed of finely divided particles of elemental carbon obtained by the incomplete combustion of hydrocarbons. It is widely used in various industrial and cosmetic applications.

Chemical Composition and Structure

Pigment Black 7 is an inorganic compound primarily composed of elemental carbon (C). The particles of carbon black are formed through the process of incomplete combustion or thermal decomposition of hydrocarbons, resulting in extremely fine particles that provide a deep black pigment.

Physical Properties

This pigment typically appears as an extremely fine black powder. It has a high surface area and strong tinting strength, offering excellent covering power. Pigment Black 7 is known for its exceptional resistance to light and heat, making it suitable for long-lasting applications. Its high stability and non-reactivity contribute to its versatility.

Chemical Industrial Synthesis Process

• Preparation of reagents. The main raw materials include liquid or gaseous hydrocarbons such as coal tar oil, natural gas, or mineral oil.
• Incomplete combustion. The production of Pigment Black 7 begins with the incomplete combustion of hydrocarbons. This combustion is carried out in a controlled environment where the amount of oxygen is limited, allowing the formation of finely divided carbon particles.
• Cooling. The gas containing the carbon particles is rapidly cooled to stop further combustion reactions.
• Collection. The carbon particles are collected using filters, cyclones, or electrostatic precipitators.
• Washing and purification. The collected particles are washed with water and, if necessary, treated with acids to remove impurities such as ash or metals.
• Drying. The purified carbon particles are dried at controlled temperatures to remove residual moisture.
• Grinding. The dried carbon black is ground to obtain a fine and uniform powder.
• Classification. The ground powder is classified to ensure a uniform particle size using sieves or air classifiers.
• Stabilization. The Pigment Black 7 powder is stabilized to ensure its stability during transportation and storage, preventing aggregation and degradation.
• Quality control. The Pigment Black 7 undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.

What it is used for and where

Cosmetics

Restricted cosmetic ingredient as IV/126  a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Ingredients reported:

• Carbon black. Wording of conditions of use and warnings.  Purity > 97 %, with the following impurity profile: Ash content ≤ 0,15 %, total sulphur ≤ 0,65 %, total PAH ≤ 500 ppb and benzo(a)pyrene ≤ 5 ppb, dibenz(a,h)anthracene ≤ 5 ppb, total As ≤ 3 ppm, total Pb ≤ 10 ppm, total Hg ≤ 1 ppm.
• Carbon black (nano). Maximum concentration in ready for use preparation 10%. Wording of conditions of use and warnings    Not to be used in applications that may lead to exposure of the end user's lungs by inhalation. Only nanomaterials having the following characteristics are allowed: — Purity > 97 %, with the following impurity profile: Ash content ≤ 0,15 %, total sulphur ≤ 0,65 %, total PAH ≤ 500 ppb and benzo(a)pyrene ≤ 5 ppb, dibenz(a,h)anthracene ≤ 5 ppb, total As ≤ 3 ppm, total Pb ≤ 10 ppm, and total Hg ≤ 1 ppm; — Primary particle size ≥ 20 nm.’

Cosmetics - INCI Functions

Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Pigment Black 7 is widely used in cosmetic products such as eyeliners, mascaras, eyeshadows, and lipsticks due to its intense black color and high opacity.

Industrial Applications

Paints and Coatings: In the paint industry, carbon black is used to achieve deep black shades and enhance UV resistance. Its stability and strong tinting properties make it ideal for both decorative and protective coatings.

Plastics and Polymers: This pigment is employed in the production of plastics and polymers to improve color uniformity, opacity, and UV resistance. It is commonly used in products like automotive parts, packaging materials, and consumer goods.

Inks: Pigment Black 7 is extensively used in printing inks for its high color strength and permanence. It ensures sharp, dark prints and is used in various types of inks including those for newspapers, magazines, and packaging.

Rubber: In the rubber industry, carbon black is a crucial component in the manufacturing of tires and other rubber products. It enhances the durability, strength, and wear resistance of rubber materials.

Safety

Many scientific studies have examined the Carbon black and the actions that this chemical compound derived from coal puts in place in the human body and have found that this chemical compound acts as a weak genotoxic agent (1) and can, in the form of nanoparticles, accelerate the development of lung cancer (2).

Other studies believe that Carbon black "should" not be considered a direct genotoxic (3).

Considering the mixed results of the numerous scientific studies, it remains, in my opinion, a danger that is difficult to overcome and, since it is about health, I exclude this ingredient from my positive choices.

References_____________________________________________________________________

(1) Di Ianni E, Jacobsen NR, Vogel UB, Møller P. Systematic review on primary and secondary genotoxicity of carbon black nanoparticles in mammalian cells and animals. Mutat Res Rev Mutat Res. 2022 Jul-Dec;790:108441. doi: 10.1016/j.mrrev.2022.108441.

(2) Chang CY, You R, Armstrong D, Bandi A, Cheng YT, Burkhardt PM, Becerra-Dominguez L, Madison MC, Tung HY, Zeng Z, Wu Y, Song L, Phillips PE, Porter P, Knight JM, Putluri N, Yuan X, Marcano DC, McHugh EA, Tour JM, Catic A, Maneix L, Burt BM, Lee HS, Corry DB, Kheradmand F. Chronic exposure to carbon black ultrafine particles reprograms macrophage metabolism and accelerates lung cancer. Sci Adv. 2022 Nov 18;8(46):eabq0615. doi: 10.1126/sciadv.abq0615. 

Abstract. Chronic exposure to airborne carbon black ultrafine (nCB) particles generated from incomplete combustion of organic matter drives IL-17A-dependent emphysema. However, whether and how they alter the immune responses to lung cancer remains unknown. Here, we show that exposure to nCB particles increased PD-L1+ PD-L2+ CD206+ antigen-presenting cells (APCs), exhausted T cells, and Treg cells. Lung macrophages that harbored nCB particles showed selective mitochondrial structure damage and decreased oxidative respiration. Lung macrophages sustained the HIF1α axis that increased glycolysis and lactate production, culminating in an immunosuppressive microenvironment in multiple mouse models of non-small cell lung cancers. Adoptive transfer of lung APCs from nCB-exposed wild type to susceptible mice increased tumor incidence and caused early metastasis. Our findings show that nCB exposure metabolically rewires lung macrophages to promote immunosuppression and accelerates the development of lung cancer.

(3) Chaudhuri I, Fruijtier-Pölloth C, Ngiewih Y, Levy L. Evaluating the evidence on genotoxicity and reproductive toxicity of carbon black: a critical review. Crit Rev Toxicol. 2018 Feb;48(2):143-169. doi: 10.1080/10408444.2017.1391746. 

Abstract. Carbon black is produced industrially by the partial combustion or thermal decomposition of gaseous or liquid hydrocarbons under controlled conditions. It is considered a poorly soluble, low toxicity (PSLT) particle. Recently, results from a number of published studies have suggested that carbon black may be directly genotoxic, and that it may also cause reproductive toxicity. Here, we review the evidence from these studies to determine whether carbon black is likely to act as a primary genotoxicant or reproductive toxicant in humans. For the genotoxicity endpoint, the available evidence clearly shows that carbon black does not directly interact with DNA. However, the study results are consistent with the mechanism that, at high enough concentrations, carbon black causes inflammation and oxidative stress in the lung leading to mutations, which is a secondary genotoxic mechanism. For the reproductive toxicity endpoint for carbon black, to date, there are various lung instillation studies and one short-term inhalation study that evaluated a selected number of reproduction endpoints (e.g. gestational and litter parameters) as well as other general endpoints (e.g. gene expression, neurofunction, DNA damage); usually at one time point or using a single dose. It is possible that some of the adverse effects observed in these studies may be the result of non-specific inflammatory effects caused by high exposure doses. An oral gavage study reported no adverse reproductive or developmental effects at the highest dose tested. The overall weight of evidence indicates that carbon black should not be considered a direct genotoxicant or reproductive toxicant.