| 摘要 |
PROBLEM TO BE SOLVED: To provide a cured spherical phenolic resin having high density and containing little nitrogen. SOLUTION: The cured spherical phenolic resin has a specific gravity of 1.20-1.35 measured by a gas-substitution process using helium gas as a medium and a nitrogen content of <=0.5 wt.%. It can be produced by reacting phenol with formaldehyde in the presence of an alkali catalyst and curing the product using an acid catalyst. |
