| 摘要 |
PURPOSE:To provide an inorg. sphere which has excellent flow characteristics, fillability, warkability, etc., is suitable for use as a filler for resins, and contains little alkali ions which can be leached with warm water, by forming a fused quartz layer on the surface of a fine particulate core. CONSTITUTION:The titled inorg. sphere has at least a surface layer composed of fused quartz and a particle size of 500mu or below and contains alkali ions in such a quantity that the quantity of the alkali ions leached out after immersing it in warm water at 90 deg.C for 24hr is 10ppm or below. The inorg. sphere can be prepd. in such a manner that a core (e.g. sintered alumina) having a particle size of 500mu or below and a low alkali compd. content is mixed with colloidal silica, the mixture is dried, the dried material from the central raw material feed tube 2 of the oxyhydrogen burner 5 of a flame spray furnace 6 together with a combustible gas 3 (e.g. hydrogen or acetylene) and oxygen 4 is flame-sprayed into the flame spray furnace 6 to heat it at a high temp. and then cooled.
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