| 摘要 |
PURPOSE:To obtain the titled core with fine uniform independent bubbles by directly mixing a foaming agent into a thermoplastic resin, into which an inorganic foamed nucleus forming agent is mixed, under pressure, extruding and applying the mixture to the outer circumferential surface of a conductor and forming a specific foamed insulating layer. CONSTITUTION:The inorganic foamed nucleus forming agent such as superfine magnesium silicate is added to the thermoplastic resin such as low-density polyethylene, heated and melted at a temperature higher than the melting point of the thermoplastic resin, and kneaded by a screw. Fluorocarbon, permeability thereof is 2.5l/m<2> or more for twenty-four hrs, is mixed directly into the kneaded thermoplastic resin under pressure by a mechanical pressure means such as a pressure pump as the foaming agent. The mixture is extruded and applied on the pipe conductor in copper to which an adhesive layer is formed previously, and the highly foamed plastic insulating layer, an expansion ratio thereof is three or seven times and thickness thereof is 6mm. or more, is formed, thus obtaining the aimed core for the highly foamed plastic insulating coaxial cable. |
