Hair dye is the main functional ingredient in hair dye products, which can change the color of hair. According to its duration of action, it can be divided into temporary hair dyes, semi-permanent hair dyes, and long-lasting hair dyes; according to the composition, it can be divided into metal hair dyes (inorganic hair dyes), oxidative hair dyes (synthetic hair dyes); according to the principle of hair dyes It can be divided into oxidative hair dyes and non-oxidative hair dyes. Among them, metal hair dyes mostly use heavy metals such as lead acetate as raw materials, which are less used now because of their accumulated toxicity. At present, most of the products on the market are long-lasting oxidative hair dyes. The hair dyes commonly used in this kind of hair dyes are phenylenediamines, among which p-phenylenediamine is the most important one in oxidative hair dyes because of its fast dyeing and long-lasting coloring. One of the raw materials for dyeing.
p-Phenylenediamine (PPD for short), also known as Wuersi D. Due to the presence of amino groups, p-phenylenediamine is weakly basic and can react with acids to obtain a series of derivatives, such as p-phenylenediamine hydrochloride, p-phenylenediamine sulfate, toluene-2,5 di Amine, toluene-2,5 diamine sulfate, etc.
In 1883, Monnet Company in Paris, France launched the world's first oxidative hair dye containing p-phenylenediamine, and this type of hair dye spread to all over the world; in 1925, various phenylenediamine hair dyes appeared on the market After 1950, various formulations of hair dye products such as hair dye cream and hair dye shampoo appeared in the international market one after another. At present, all kinds of hair dyeing products are emerging in the market, but phenylenediamine hair dyes still occupy a place, which is an important stroke in the history of hair dyeing and has an unshakable position.
With the gradual increase of national supervision, the conditions for the use of phenylenediamine substances in cosmetics are becoming more and more stringent. Amines and their salts have been banned from being added to cosmetics. At present, there are 9 kinds of phenylenediamine substances in the hair dyes approved for cosmetics in the "Safety and Technical Specifications for Cosmetics" (2015 edition), and these substances have basically the same physical and chemical properties and dyeing principles as p-phenylenediamine.