| 摘要 |
PROBLEM TO BE SOLVED: To obtain a porous body excellent in heat insulation and dielectric properties by preparing a wet polyimide gel from a polyimide precursor as the starting material and drying the wet gel to obtain a dry polyimide gel. SOLUTION: This porous body comprises a dry gel of a polyimide resin and has an apparent density of 800 kg/m3 and an average pore size of 1μm or lower. The polyimide resin preferably has a three-dimensional crosslinked structure. The porous body is produced e.g. by preparing a polyimide precursor, imidizing the precursor by a thermal or chemical treatment to give a polyimide resin, dissolving or swelling the polyimide resin in or with a solvent, preparing a wet gel from the resultant solution or swelled resin, and drying the wet gel to obtain a dry gel. Preferably, the drying step is done by supercritical drying since the gel is thereby prevented from shrinking in the step.
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