Here a few general colorants for food contact plastics are introduced.
White. Titanium dioxide (TiO2). Don’t forget white color of plastics is made via adding white colorants. Normal plastic’s natural color is from transparent to translucent. TiO2 is the mostly used one among all commercial colorants. It is non-toxicity (LD50 Oral – Rat > 10,000 mg/kg).
Black. Carbon Black. In a general example, carbon black is just the black powder at the bottom of a pot after the pot is used for cooking. However, the food safety colorant is collected via professional industrial procedures instead of via living channel. The key point of carbon black is the purity with limits on aromatic hydrocarbons. It is non-toxicity (LD50 Oral – Rat > 8,000 mg/kg).
Red. Unlike White and Black colorants, Red color actually includes series of colorants. Two series of colorants for red color are Quinacridone and Azo. Quinacridone has very strong red color. Toxicity is LD50 Oral – Rat > 10,000 mg/kg. Azo includes mono-azo, bis-azo, and metal-azo complexes. Not all azo series of compounds are red color. And not all azo series of compounds are non-toxic. However, there are some commercial azo series of compounds with non-toxicity (LD50 Oral – Rat > 5,000 mg/kg).
Yellow. Yellow color also includes many compounds. One organic colorant is Benzimidazolone series. Normally Benzimidazolone group connects to azo group to form the yellow colorant, such as pigment yellow 151. Pigment yellow 151 is non-toxic (LD50 Oral – Rat > 5,000 mg/kg). A general inorganic colorant is Zinc Ferrite Oxide. Acutally Zinc Ferrite colorant is almost brown instead of yellow. Toxicity of Zinc Ferrite colorant is LD50 Oral – Rat > 2,000 mg/kg.
Blue. The main series of organic blue pigment is copper phthalocyanine. This series also include green color as well as blue color. The color strenght is strong but decrease when it is used toghther with TiO2. It is non-toxice (LD50 Oral – Rat > 2,000 mg/kg). Another blue pigment is an inorganic pigment named as Ultramarine Blue (Pigment Blue 29). It is a zeolite-based mineral container small amount of polysulfides. It is non-toxice (LD50 Oral – Rat > 10,000 mg/kg).
A point is necessary to be noted. There are too many commercial colorants. Many of them are the mixiture of a few chemcials instead of one single pure chemcial. Such mixtures allow to make almost all colors what our eyes can see.
A separated kind of colorant is effect pigment. It is used as additives to the mass tone to let the packaging more attractive or shiny. Effect pigment contains Aluminum normally. Cosmetics packaing is offten added with effect pigment but pharmaceutical packaging doesn’t contain effect pigment.
Here, we mainly concern the toxicity because it is most important for a food contact plastics. However, there are also other features to allow the best applications of a colorant. Therefore, do discuss with the colorant suppliers before develop a colored plastics.
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