Ultramarine Blue Derived from Linde A Molecular Sieves

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  • Ｌｉｎｄｅ　Ａモレキュラーシーブよりウルトラマリン・ブルーの合成法
  • Linde A モレキュラー シーブ ヨリ ウルトラマリン ブルー ノ ゴウセ

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Ultramarines have the crystal structure made up of close packings of a sodalite-type cage which is also a main constituent in the structure of Linde A molecular sieves (MS). The formation of ultramarines from MS should be easy from this reason and in fact ultramarine blues were able to be derived from MS5A and MS4A via the following processes (1) to (4); (1) impregnation of MS with Na2S in the saturated aqueous solution of Na2S and drying the resulting MS-Na2S (in N2 gas), (2) absorption of sulfur vapor on the MS-Na2S at 500°C (in N2 gas), (3) heating of the MS-Na2S-S up to 820°C (in N2 gas, heating rate 17°C/min), (4) cooling of the MS-Na2S-S from 820°C to 500°C followed by the air oxidation at 500°C.<br>The oxidized products from MS5A and MS4A were sky-blue and green, respectively and they turned blue by re-heating in air for a few hours at 820°C. The formation of the ultramarine from MS4A was found much easier than that from the sintered product between kaolin and Na2CO3 with the composition of NaAlSiO4 which has no sodalite-like structure. It was presumed from the above result that the formation of ultramarine green was caused by the intrusion of polysulfides into sodalite-type cages in MS4A.<br>This method for the synthesis of ultramarine blue is not practical for industrial manufacturing at present because of the high cost of molecular sieves and the low concentration of blue chromophor in the produets, but this method has an advantage for the study of the reaction mechanisms involved in the ultramarine synthesis.

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