| 摘要 |
A method for making a continuous bilaminar planar sheet material utilized for packaging of goods and having raised pockets containing a gas. The sheet material is made by extruding a molten plastic through an extruder having a cylindrical nozzle with an annular circular slot opening, so that a tubular hollow element is formed. A plurality of heating elements are arranged around the circumference of the annular circular slot to maintain the temperature of the extruded material at different temperatures around the circumference of the annular slot.
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