Metal complex dyes - Kinzokusakuensenryo

A soluble azo dye in which the dye molecule is bonded to a metal ion such as chromium in the form of a complex salt. Dye molecules that dye wool fast need to be able to form complex salts, and generally have one of the following structures: o,o' -dihydroxyazo, o -hydroxy- o' -aminoazo, or o -hydroxy- o -carboxyazo. Metal ions that are used include Cr ^III , Cu ^II , Ni ^II , and Co ^III . Metal complex dyes are classified into two types, 1:1 and 2:1, depending on the bond ratio between the dye molecule and the metal ion. The former requires a fairly strong acidic bath to achieve even dyeing and has the disadvantage of easily causing embrittlement of the fiber, so the 2:1 type, which can be dyed in a weakly acidic to neutral bath, is mainly used. Originally, they were high-quality dyes for wool that have good lightfastness, but metal complex dyes for synthetic fibers, copper complex dyes for cotton, and reactive metal complex dyes have also been developed.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

染料分子とクロムなど金属イオンとが錯塩の形で結合している可溶性のアゾ染料をいう．羊毛を堅ろうに染める染料分子は，錯塩形成能をもつことが必要で，一般には，o,o′-ジヒドロキシアゾ，o-ヒドロキシ-o′-アミノアゾ，o-ヒドロキシ-o-カルボキシアゾ構造のいずれかをもっている．また，金属イオンとしては，Cr^Ⅲ，Cu^Ⅱ，Ni^Ⅱ，Co^Ⅲなどが用いられる．金属錯塩染料は，この染料分子と金属イオンとの結合比によって，1：1型と2：1型の2種類があるが，前者は均染性を得るためにかなり強い酸性浴を必要とし，繊維の脆化を生じやすい欠点があるので，弱酸性～中性浴から染色できる2：1型がおもに用いられている．元来は，耐光性のよい羊毛用高級染料であるが，合成繊維用の金属錯塩染料，木綿用の銅錯塩染料，反応金属錯塩染料も開発されている．

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