Patent ID: 7083751

Claim:
A method for forming a solidified granular material ( 15 ) with granules bonded into a solid form, in a space within a frame member ( 11 ) and/or a space enclosed by said frame member and a surrounding panel member, said method comprising the steps of: mixing first granules ( 16 ) and second granules ( 17 ) together, each of said second granules having a thermoplastic resin shell ( 17 c ) enclosing a solid or liquid ( 17 b ) which expands by vaporization; charging the mixture of said first and second granules into said frame member; heating said first granules and said second granules together with said frame member so as to soften said second granules and make the same expand by internal pressures and become hollow, as well as to melt surfaces of said second granules for bonding with said first granules; and cooling said first granules and said second granules together with said frame member to thereby provide the solid granular material comprised of said first granules and said second granules being more collapsible than said first granules.