| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a good productivity without necessitating a large high vacuum device by forming a molding body which is tobermorite potassium silicate, and which is composed of a particle in which a spheroidal shell is not formed on an external shell by secondary particle as a main component, as a heat insulating core material, vacuum-exhausting the inside of a container filled the heat insulating material therein, and make the inside thereof in low vacuum condition of a specified value and less. SOLUTION: A heat insulating core material is a tobermorite potassium silicate molding body formed by dehydrating and drying tobermorite slurry obtained by hydrothermal synthesis reacting calcareous raw material and siliceous raw material, and is used which is composed of particle in which a spheroidal shell is not formed by secondary particle as a main component. After a molding body composing tobermorite potassium silicate as a main component is housed in a container manufactured by using a gas barrier film, vacuum exhaust treatment is carried out in the container in a pressure reducing condition. At a time point where the pressure reducing condition in the vacuum container attains a predetermined vacuum degree, an opening end of the container is heat-sealed so as to tightly pack the molding body by the container in the pressure reducing condition. The pressure reducing condition is set so as to hold a vacuum degree of 2Torr and less.</p> |
