| 摘要 |
PURPOSE:To heighten the whiteness of a writing material, by using silica sand of low titanium compound and iron contents for sandblasting. CONSTITUTION:Silica sand which does not contain ilmenite and iron sand is used for sandblasting, to heighten the whiteness of a writing material. To be concrete, the silica sand is subjected to magnetic separation in a magnetic field of scores of thousands of gauss by a magnet and/or gravity separation by being caused to quietly flow in water, so that the ilmenite and the iron sand are removed from the silica sand. A film subjected to the sandblasting is dissolved with concentrated hydrochloric acid to check the titanium content of the film. The removed quantity of the ilmenite is such that the titanium content of the film is 16mg or less per 1m<2> of the film.
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