BASE PAPER FOR FOLDING

PURPOSE:To provide the title base paper having high mechanical strength in the form of a folding box, humidity resistance and water resistance and generating no configurational deformation due to the restoring repulsion of a bent part, by using a foamed thermoplastic resin sheet having a thickness of 0.3-2mm and foaming magnification of 105-210%. CONSTITUTION:It is necessary to set the thickness of a foamed thermoplastic resin sheet used as base paper for a folding box to 0.3-2mm. When said thickness is less than 0.3mm, stiffness is too weak and strength is insufficient and a predetermined shape can not be held when said sheet is assembled into a folding box and durability is inferior. Further, it is necessary to use a thermoplastic resin having foaming magnification of 105-210%, pref., 110-180%. Foaming at this time may be either one of physical foaming and chemical foaming. When said foaming magnification is below 105%, a defect is reproduced which is generated when a resin single sheet is used, such that the restoring repulsion of a bent part becomes large to make configurational deformation easy by generate. When the foaming magnification becomes larger than 210%, the lowering in the hinge durability or heat sealing property of the bent part is brought about and various mechanical strengths are lowered generally.