INORGANIC HOLLOW POWDER, PROCESS FOR PRODUCING THE SAME, AND COMPOSITION CONTAINING THE SAME

摘要

An inorganic hollow powder is provided which has a reduced particle size and higher purity and is reduced in the unevenness of hollowness percentage. Also provided are: a process for producing the powder; and a resin composition containing the inorganic hollow powder. The inorganic hollow powder comprises 60-100 mass% hollow particles having a percentage of hollowness of 60-80 vol.% and up to 5 mass% (including 0 mass%) hollow particles having a percentage of hollowness of 0-20 vol.%. In the powder, the hollow particles have a maximum particle diameter of 25 µm or smaller, a specific surface area as determined by the BET method of 30 m2/g or smaller, and an average sphericity of 0.85 or higher. In the process for producing the inorganic hollow powder, an inorganic raw powder having a pore volume of 0.1-1.0 mL/g and a maximum particle diameter of 10 µm or smaller is fed at a powder concentration of 50-500 g/Nm3 through a raw-material supply pipe of a doughnut structure having a slit width of 0.1-2.0 mm, and is made hollow with a flame.