To increase the vertical compression strength of a corrugated fiberboard sheet and improve its printability without increasing the weight per m2 of a base paper by a method wherein the weight per m2 of a corrugating medium, the height of a flute and the number of flutes of a flute near the inside of a box are specified and the flute structure of a flute near the outside of the box is specified.
In a double wall corrugated fiberboard, the weight per m2 of the corrugating medium of a flute near the inside of a box is 160g/m2 or more, its height of a flute is 5.5mm or higher and its number of flutes is 20 or more per 30cm while a flute near the outside of the box is an A-flute, C-flute or B-flute. The flute, the height of a flute of which is higher, is used as the flute near the inside of the box so as to play a roll for heighten the strength of the box, while the A-, B- or C-flute excellent in planeness is arranged near the outside of the box so as to coexist the strength and external appearance of the box with its printability. When the rear linerboard and the front linerboard having the weight per m2 of 337g/m2 or more are employed in this double wall corrugated fiberboard, the resistance to impact punching and printability of the box are further improved as well as the compression strength of the box, resulting in obtaining a double wall corrugated fiberboard suitable for transporting a heavier matter.
TAKEYAMA SABURO
HAMAZAKI KOHEI
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