VACUUM HEAT-INSULATING MATERIAL, METHOD FOR PRODUCING VACUUM HEAT-INSULATING MATERIAL, AND OUTER PACKAGING MATERIAL FOR VACUUM HEAT-INSULATING MATERIAL

摘要

Provided are a vacuum heat-insulating material that has high heat-insulation properties from an initial stage and that can maintain said heat-insulation properties for a long period of time, a method for producing the same, and an outer packaging material used in said vacuum heat-insulating material. This vacuum heat-insulating material is plate-shaped and is provided with a core material and an outer packaging material that seals the core material in a vacuum state, wherein: the outer packaging material has a heat fusion layer that contains a vinyl alcohol resin and that is disposed furthest inward, and a gas barrier layer that is layered over the outer-surface side of the heat fusion layer; and the change over time in thermal conductivity between the front surface and the rear surface satisfies formula (1). In formula (1), T₁ is the minimum value of said thermal conductivity. T₂ is the maximum value within the range from the initial value to the minimal value of said thermal conductivity.