| 摘要 |
PURPOSE: To reduce shrink characteristics to enhance a dimensional stability and to raise a compression strength and a resistance to repeated compression by a method wherein an average foam diameter in a thickness direction is determined to a specific value in a specific ratio to each of an average foam diameter in a width direction and an average foam diameter in an extrusion direction. CONSTITUTION: An average foam diameter in a thickness direction is determined to 0.65-1.00mm to be 1.0-1.25 times an average foam diameter in a width direction and 0.85-1.1 times an average foam diameter in an extrusion direction. For a specific foam structure, a foaming agent is selected out of a low-boiling hydrocarbon, a low-boiling halogenated hydrocarbon, a low-boiling halogenated carbon, and the mixture of these. A resin is supplied from a material supply port 2 of an extruder 1 and kneaded under heat by a screw 3. The foaming agent is injected from a foaming agent injection port 4. The melt gel of the foaming agent is once extruded into an accumulator 5, thereafter being extruded from a die 9 to a condition under atmospheric pressure to form a planar foam 10. |
