タイ国産ボールクレーの性質 : 鉛筆用ドイツ産粘土との比較

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The properties of a ball clay from Lansaka, Thailand, were compared with those of Klingenberg clay from Germany, which is used in manufacturing pencil leads due to its high plasticity. The clay fraction under 2μm in size in Klingenberg clay is mainly composed of kaolinite with a small amount of illite, and has a mean particle size of 0.4μm and a specific surface area of approximately 90m^2/g. This clay is also characterized by a thermal property that the metastable transition period, from the temperature at which mullite begins to form to the temperature at which its growth stops, is long during heating. Lansaka ball clay resembles Klingenberg clay in some properties; both clays are composed of disordered kaolinite with fine particle size and are black due to the presence of carbonaceous organic substances. Furthermore, round grains with size on the micrometer order are commonly present in coarse fractions, presumably resulting from the disintegration during transport processes of the source rocks in rivers where fedspar is finely ground. On the other hand, the clay particles of Lansaka clay have a wider particle size distribution than those of Klingenberg clay because of the presence of a relatively large amount of illite, which results in a narrow metastable transition period during heating. Good moldability of pencil leads during the trial preparation was achieved by using Lansaka clay fractions under 10μm in size, which have a mean particle size of 1.7μm and a specific surface area of 27.1m^2/g. The resuiting pencil lead provided smoothness in writing with blackness of HB grade, although its bending strength was rather low because its firing temperature was above the optimum range.
日本粘土学会の論文
2000-11-30

タイ国産ボールクレーの性質 : 鉛筆用ドイツ産粘土との比較

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