| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a phenolic foam adaptable to a vacuum insulating material core which has an open-cell structure with a small average cell diameter and high open-cell percentage and can reveal excellent heat insulating performance by subjecting a foamed and hardened material made from a hardenable liquid phenolic resin to high-temperature heat treatment. SOLUTION: A foamable mixture obtained by uniformly mixing ingredients comprising, e.g. a hardenable liquid phenolic resin, a foaming agent, a foam stabilizer and, if necessary, a foam breaker, an agent for forming fine cells, and other additives is hardened while foamed to give a foamed and hardened material. This phenolic foam precursor is heat treated at 100-200 deg.C until the rate of decrease in weight reaches a constant (for 10min to 5hr). The obtained phenolic foam has a cell structure with an average cell diameter of less than 90μm and an open-cell percentage of at least 99.5%.</p> |
