Patent ID: 8753471

Claim:
A method of producing a vacuum heat insulating material, the method comprising: covering a core member with envelope members, each of the envelope members having a gas barrier layer and a heat-seal layer, wherein the envelope members are opposed to each other in such a manner to form an inside within which the core member is disposed, evacuating the inside of the envelope members; and subsequently first melting and sealing for heat sealing only the peripheries of the envelope members to provide heat-sealed peripheries by uniformly applying heat to the entire envelope members sufficient to melt the heat-seal layer, and second melting and sealing to melt and seal the heat-seal layer by uniformly applying heat and pressure from outside to inside the envelope members to the entire envelope members by introducing an atmosphere outside the envelope members having a higher pressure than the inside of the envelope members, wherein the heat is applied out of contact with the envelope members, and wherein heat sealing occurs a) where the envelope members are in contact with each other, and b) inside the heat-sealed peripheries, forming a heat sealed portion extending as far as the edges of the core member.