| 摘要 |
PURPOSE: To provide a polymer composition containing baron nitride having respective specific particle diameter and specific surface area as a nucleating agent and useful for foaming extrusion molding use. CONSTITUTION: This polymer composition for foaming extrusion molding to extrude in the presence of a foaming agent contains at least a base resin containing a thermally meltable and extrudable polyolefin resin and boron nitride as a nucleating agent. The average particle diameter of the boron nitride is 3-50μm and the specific surface area is 1-10m<2> /g. A molded material containing fine and uniform cells and having high expansion ratio is produced from the polymer composition. When the molded material is used as a foamed insulating layer of a coaxial cable, the foamed insulating layer has excellent electrical characteristics, especially low tanδin high-frequency range and excellent insulation characteristic:s and, accordingly, excellent attenuation characteristics. Since the foamed insulating layer is producible without using a drying process, the production efficiency of coaxial cable can be improved and the production cost can be reduced. |
