JPS6484870A - Shock absorbing packaging sheet - Google Patents

Abstract

PURPOSE:To permit the sealing treatment by thermal shrinkage of a packaging sheet, simultaneously with the formation of a shock absorbing foam layer by providing a base material consisting of a thermally shrinkable film with a foam agent retaining layer on one side or both sides thereof. CONSTITUTION:A shock absorbing packaging sheet is provided with a foam agent retaining layer 2 on one side or both sides of a base material 1. A thermally shrinkable film of a thickness over 10-500mum range indicating the thermal shrinkage rate of 5-80% at a temperature of 50-200 deg.C is preferable as the base material 1. The foam agent retaining layer 2 formed on the base material 1 does not create much hindrance to the thermal shrinking ability of the base material consisting of the thermally shrinkable film and is expanded by heat treatment with the formation and retention of the shock absorbing foam layer. The amount of foam agent use is determined appropriately by the thickness of the shock absorbing foam layer, etc., and, in general, the foam agent is used in such an amount as to be expandable by not less than 1.2 times, preferably 1.5-10 times, the original volume of the foam agent retaining layer, according to the foaming characteristics dependent upon the type of foam agent used or heating conditions. Upon heat treatment of the shock absorbing packaging sheet, the base material 1 is shrunk into a thermally shrunk material 1' and the foam agent retaining layer 2 is expanded into the shock absorbing foam layer 2'.