| 摘要 |
PURPOSE:To obtain an expanded novolak type phenol resin molding free of uneven expansion and packing by a method in which a composition consisting of a novolak type phenol resin precondensate and given amounts of a decomposable blowing agent and a hardening agent is partly expanded and hardened to form secondarily expandible granules which are in turn expanded and molded in molds. CONSTITUTION:A composition consisting of a novolak type phenol resin precondensate and given amounts of a decomposable blowing agent (e.g., dinitrosopentamethylenetetramine, etc.) and a hardening agent (e.g., hexamethylenetetramine, etc.) is partly expanded and hardened to form secondarily expandible novolak type phenol resin granules. The resin granules are packed into wooden molds and covered, and the molds are held in a hot wster circulation type constant temperature tank to expand and mold the resin granules to obtain an expanded novolak type phenol resin molding. |
