| 摘要 |
PURPOSE:To improve the cushioning characteristics due to the local change of packing of fine foam strands and consequently extends the field of application of the strands by a method wherein the relationship of the diameter and interval of the extrusion holes of a mouth piece to the extent of free expansion ratio from the extrusion hole is specified and further the relationship of the extrusion speed and taking-up speed to the diameter and interval of the extrusion holes and the extent of free expansion ratio is specified. CONSTITUTION:A large number of extrusion holes 51 with the hole diameter of Dmm is regularly arranged on the resin discharging surface of a mouth piece 5 provided at the tip of an extruder 1. A mouth piece 5 provided at the tip of an extruder l consists of a sheet-like body, or the resin discharging surface of which a large number of extrusion holes 51 with the hole diameter of Dmm is provided at regular intervals L so as to realize a similar shape scaled-down from the sectional shape of foams. The interval L of the arrangement of the extrusion holes is determined by the attached formula (1). In this case, the extent of free expansion ratio of a fine foam strand freely extruded from the extrusion hole of the mouth piece. The thermoplastic resin kneaded with foaming agent in the extruder 1 is extruded from the extrusion holes 51 of the mouth piece 5 in the form of fine strands and led in a shaping device 6 and finally taken off by a puller 7. In this case, the fine foam strands 8 are taken off at the extrusion rate or take-off speed (v), which is controlled so as to satisfy the attached formula (2), in which V represents the extrusion speed of the fine foam strand freely extruded from the extrusion hole. |
