| 摘要 |
To provide a microheater which gives a desired temperature and starts an exothermic reaction upon immediate contact with air and in which plural microheaters can be chained or incorporated in a packaging material. A microheater having a heat generating composition molded body made of a moldable heat generating composition containing surplus water as a connecting substance accommodated in an air-permeable accommodating bag, which is characterized in that the accommodating bag is made of a heat seal layer-containing substrate and a covering material and has an exothermic part as formed by laminating a heat generating composition molded body as molded on the substrate which is substantially planar and does not have a pocket, an accommodating division and an accommodating section, covering by the covering material and heat sealing the periphery of the heat generating composition molded body; that the moldable heat generating composition contains, as essential components, an iron powder, a carbon component, a reaction accelerator and water, has a content of water in the moldable heat generating composition of from 1 to 60%, does not contain a flocculant aid, a flocculant, an agglomeration aid, a dry binder, a dry binding agent, a dry binding material, a sticky raw material, a thickener and an excipient, contains surplus water so as to have a water mobility value of from 0.01 to 20, with the water in the heat generating composition not functioning as a barrier layer, and is capable of causing an exothermic reaction upon contact with air; that a volume of the heat generating composition molded body is from 0.1 to 30 cm3, and a ratio of a capacity of the exothermic part to the volume of the heat generating composition molded body is from 0.6 to 1.0; and that a maximum height of the exothermic part is from 0.1 to 10 mm.
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