| 摘要 |
PROBLEM TO BE SOLVED: To attain pure black color and small glossiness and to improve writing feeling and flexural strength by using a specific born nitride powder as an inorganic extender of a fired pencil lead. SOLUTION: The boron nitride powder 1-5μm in average particle diameter, 25-50m<2> /g in specific surface area, >=700Åin the size of crystallite and >=97% in purity is dispersed, mixed and kneaded as the inorganic extender with an organic binder and if necessary, a plasticizer, a stabilizer or the like. Next, a lead body obtained by extruding into fine line state to form, drying and firing at 800-1,400 deg.C in a gaseous nitrogen atmosphere is impregnated with oils and fats.
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