PURPOSE: To obtain extrusion-foamed sheet excellent in cutting workability by a method wherein the sheet concerned has specified compressive stress and flexural modulus and its cell structures in the longitudinal section in extrusion direction and in width direction show specified cell forms and the cell diameters in the direction of the thickness of respective cells at the surface layer part and the inner layer part of sheet are specified.
CONSTITUTION: The extrusion-foamed sheet concerned is produced by fixing the inner face of tubular foam extruded from an extruder by pressure into the form of sheet, the density (f) of which is 0.05-0.2g/cm3 and the corrected compressive stress of which and the corrected flexural modulus of elasticity Y of which satisfy the formulae 1 and 2. In the formulae, (x) represents 5% compressive stress (in kgf/cm2) of foamed sheet and (y) represents the flexural modulus (in kgf/cm2) in the extrusion direction. If X is not more than 0.7, the compressive strength is insufficient and consequently burr tends to develop at both sides of groove at grooving. If Y is not more than 1.2×103, the flexural strength in extrusion direction is not enough. Further, the average cell diameter in the longitudinal section in the extrusion direction (the direction indicated with the arrow (α)) of the sheet satisfies the formula 3, in which (a) represents the average cell diameter in the extrusion direction of the sheet and (b) is that in the direction of the thickness of the sheet. Furthermore, the average cell diameter in the longitudinal, section in the width direction (the direction indicated with the arrow (β)) normal to the extrusion direction of the sheet satisfies the formula 4, in which (c) represents the average cell diameter in width direction.
NAKATSUKA HIDETO
AOKI TAKESHI
KONISHI MAMORU
