Abstract: Endothermic reaction (dissolution) of endothermic material to be packed in a cooling bag is retarded to avoid a large temperature gradient which results in a meaningless intake of ambient heat quantity and an excessively low temperature condition, so as to keep an adequately cooled condition for a long period of time. Column-like or tablet-like endothermic materials are prepared from granular starting materials to decrease their specific surface area and solution velocity in water. The products, either as they are alone, together with water absorbing resins and/or their granular starting endothermic materials, or as a stored state in a perforated inner bag, are packed in a bag made of synthetic resin film.

Abstract: A check valve comprises valve flaps formed by subjecting a front sheet and a rear sheet of synthetic resin, one of which is laid on top of the other, to heat sealing thereby sealing the same by thermal adhesion at the right and left sides thereof and at a plurality of curved heat sealings which are coupled to one another in such a way as to approximately form T-shapes at the junctions thereof so that the valve flaps have arabesque outlines. As a result, the lower parts of the heat sealings serve as fluid returning segments so as to improve the check valve in fluid sealing performance.