SHEET MATERIAL, PRESS BOARD, THEIR PRODUCTION AND USE THEREOF

摘要

PURPOSE:To obtain a sheet material having a bulk specific gravity falling within a specific range and suitable as an insulation board to be used in a transformer by pressing fibers of a methylpentene polymer (or a polyolefin resin composition containing the polymer). CONSTITUTION:A nonwoven fabric having a bulk specific gravity of <=0.5g/cm<3> is produced from fibers composed of (A) a 4-methyl-1-pentene polymer or (B) a polyolefin resin composition containing the component A. The nonwoven fabric is pressed to a bulk specific gravity of 0.01-0.8g/cm<3> to obtain the objective sheet material. Preferably, two or more sheet materials are laminated one upon another and (hot) pressed.