To provide a method for closing the opened end of a plastic cellular board, which is obtained by pasting up a flat back sheet and a flat liner sheet on the bottom and top surfaces of the caps of a cap sheet having a large number of cap-like projections obtained by molding a plastic sheet extruded in a molten state, using a simple technique and an apparatus comprising common constituent parts.
The end of the cellular board is heated by the irradiation with heat rays using an infrared heater (4) to soften the walls of the caps exposed to the end, the walls (31) of the caps arranged in the vicinity of the end, the edge (11) of the back sheet and the edge (21) of the liner sheet, and the softened edges (11) and (21) of both of the back sheet and the linear sheet are bonded under pressure by a press bonding stand (5) and a press bonding press (6) to close the end of the cellular board.
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