| 摘要 |
Hollow synthetic board which may be used to replace corrugated paper board is continuously extruded of relatively soft thermoplastic resin, such as polyolefin, by apparatus having replaceable mandrels disposed in the cavity of an extrusion die. These mandrels are fastened in operative position by hollow screws which are part of the passage means for maintaining the interior of the synthetic board at ambient pressure. After leaving the die the extrusion alternately passes through a plurality of cooling and sizing sections. In the latter a vacuum is applied to the outer surface of the board to prevent collapse thereof prior to hardening of the extrusion. Temperature within the cooling sections is regulated so that the upstream sections are warmer than the downstream sections. |
