Sakai Chemical Industry Co., Ltd.

Yoshihiko Nakane

Akira Kotone

Kenzo Konishi

Shigefumi Kamisaka

Iwao Yamazaki

Susumu Iwasaki

Tutomu Hatanaka

Iro Yamase

Takeshi Hori

Masahiro Hoda

Teijiro Kitao

A process for producing microcrystalline barium ferrite platelets which comprises: forming an aqueous alkaline dispersion containing coprecipitates of hydroxides of barium ions, iron (III) ions, and optionally ions of a substituent element; heating the dispersion to a temperature of not less than 50.degree. C. and not more than the boiling point of the dispersion under an atmospheric pressure to convert the coprecipitates to precursors of the barium ferrite; calcining the precursors to provide microcrystalline barium ferrite platelets; the improvement comprising the step of adding a carbonating agent such as sodium carbonate to the aqueous alkaline dispersion before or after the heating of the aqueous dispersion to insolubilize water soluble barium ions therein, and the step of calcining the barium ferrite precursors in the presnece of sodium sulfate at temperatures of 700.degree.-900.degree. C., to provide microcrystalline barium ferrite platelets of about 0.03-0.1 .mu.m in average particle size and 2-5 in planarity ratio.

Process for producing microcrystalline barium ferrite platelets

A polyazo dye represented by the formula ##SPC1## Wherein A is an optionally substituted aromatic ring; B is an aromatic ring having at least one substituent selected from the group consisting of amino, substituted amino and hydroxy; Y is hydrogen, alkali metal, --NH.sub.4 or amine salt residue; n is 1 or 2; and one of R.sup.1 and R.sup.2 is hydroxy and the other is amino.

Trisazo dye containing a diphenylenesulfone structure

A polyazo dye represented by the formula ##SPC1## Wherein A is an aromatic ring having or not having a substituent, B is an aromatic ring having at least one substituent selected from the group consisting of amino, substituted amino and hydroxyl, Y is hydrogen, alkali metal, --NH.sub.4 or an amine salt residue, n is 1 or 2, and each of R.sup.1 and R.sup.2 is hydroxyl or amino, R.sup.1 being amino when R.sup.2 is hydroxyl and hydroxyl when R.sup.2 is amino. The polyazo dye has outstanding utility in the dyeing of fibers having hydroxyl and/or amide groups and are not carcinogenic.

Trisazo compounds containing a diphenyl-tetrazinyl component

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Yao, Japan

Yoshihiko Nakane