A novel ‘permanent’ acid‐type hair color made possible with dye–metal ion complex technology

Abstract

The advantages and disadvantages of oxidative permanent and acid‐type semi‐permanent hair colors are evident. The former provides a long‐lasting ‘permanent’ color, while the latter imparts less damage to the hair. We developed a novel acid‐type hair color technology that can allow an acid dye and a metal ion to form a complex inside the hair similar to the oxidative hair color. It is well known that acid dye diffuses into the hair and creates an ionic bond with the positively charged amino acid residues of hair protein. However, the dye can be extracted easily from the hair by daily shampooing due to the weakness of the bond. In order to strengthen this bond and to prevent the extraction of the dye by shampooing, an aluminum chloride ion was chosen as the metal ion component to form the dye–metal complex. A proper composition of penetration enhancers, benzyl alcohol and ethyl alcohol, was required to allow acid dyes to interact with the aluminum chloride ion after each component penetrates deeply into the hair to form a complex inside the hair. To provide color brightness and a color longevity effect to hair color, glycolic acid was also selected due to the observation that a weak acid with a small molecular weight would enhance those effects.

Coloration, Hair

“…Permanent dyes essentially last until new hair growth appears, which is every 4-6 weeks for the average consumer [3,11,12]. Dyes that are less permanent tend to be larger and adsorb onto the surface of hair [13] or diffuse only into the cuticle, or the outermost region of the hair fiber [11]. The precursors that give rise to permanent hair dyes are capable of diffusing into the cortex (an inner region of the hair fiber), due to their small size, where they react to form oligomers that aggregate and become too large to be desorbed from the hair [2,4,5,12].…”

“…The precursors that give rise to permanent hair dyes are capable of diffusing into the cortex (an inner region of the hair fiber), due to their small size, where they react to form oligomers that aggregate and become too large to be desorbed from the hair [2,4,5,12]. In each case, some dye can remain adsorbed onto the surface of hair [11,13]. Dye adsorbed onto the surface or within the outer layers of hair can more easily be removed upon shampoo treatment [1,4,5,[9][10][11], especially if dye is weakly bound and the cuticle is damaged (more porous).…”

“…Another interesting hair dyeing technology was proposed by Ochiai and co-workers, who examined the viability of certain acid dyes as novel permanent hair colorants when applied to hair with metal salts such as AlCl 3 [13]. Acid dyes studied included C.I.…”

Dyeing Human Hair

“…Ochiai et al [60] reported that permanent dyes can be developed in hair using dye-metal ion complexes. These scientists used aluminum chloride as the metal ion which was allowed to penetrate into the hair so that the aluminum ion could complex with the acid dyes in the hair.…”

“…Wool dyeing is very different from hair dyeing because of the high temperatures involved in the former. In fact, low temperature dyeing in wool is [80][81][82][83][84][85] C. Solvent assist dyeing permits wool to be dyed at [60][61][62][63][64][65][66][67][68][69][70] still too high a temperature for dyeing human hair. Prototype systems have been developed based on chemistry related to that of natural melanin pigment formation [10].…”