| 摘要 |
PURPOSE:To flatten frequency characteristics by lessening fluctuations by heat- sealing a surface material sheet of thermoplastic resin, obtained by mixing carbon fiber and adhesive fiber, on the surface of a foamed material sheet consisting essentialy of thermoplastic resin. CONSTITUTION:A surface sheet 1 while superposed on the surface of a core material sheet 2 is passed between heater-incorporated rollers 3 and 3'. Then, since those rollers 3 and 3' are heated at low temperature, the core material sheet 2 and surface material sheet 1 are heat-sealed. The resulting composite sheet 6 is heated at high temperature by heaters 4 and 4' for several seconds. A foamed material in the core material sheet 2 is heated above its foaming start temperature by the heaters 4 and 4' to be foamed, and polyethylene short fiber of the surface material sheet 1 and polyethylene which is the base material of the core material sheet 2 are molten. Thus, the composite sheet 6 is treated by cold press between dies 5 and 5' to be formed in a diaphragm shape. |
