| 摘要 |
PROBLEM TO BE SOLVED: To prevent water droplets from dropping, foodstuffs from becoming sticky and the taste of foodstuffs from being spoiled, by a method wherein a skin layer of a foamed sheet itself of a container lid which is formed from a polystyrenic resin foamed sheet having the fraction of interconnecting cells at a specific rate or more, and which is positioned on the side facing to the interior of a container, and a part of covering layers arbitrarily laminated on the skin layer are broken or removed to form passages for moisture. SOLUTION: A polystyresnic resin (PS) and a foaming agent necessary for foaming are supplied to an extruder and, after melting and kneading the resin and the foaming agent, they are extruded from a die provided at a forward end of the extruder into ambient air to produce a PS sheet with has the fraction of interconnecting cells of at least 50%, and for which a foaming condition is set so that the PS expands to break cell walls. The PS formed sheet has a non-foamed skin layer formed on a surface layer, but has a favorable water vapor-absorbing performance imparted by notching the skin layer with a multitude of fixed flat-blades set at desired intervals to form notched slits 11, or by breaking or removing at least a part of the skin layer with the arrangement of a needle-crest roll. Accordingly, since the PS foamed sheet does not release moisture once absorbed, moisture adhering to an inner face of a lid 1 can be prevented from dropping on foodstuffs in a container so as not to spoil the taste of the foodstuffs. |
