| 摘要 |
A flexible polyimide foam having an apparent density of 70 kg/m3 or less and a glass transition temperature of 300° C. or higher can be prepared by mixing an aromatic tetracarboxylic acid comprising 2,3,3',4'-biphenyltetracarboxylic dianhydride a portion of which is converted into its mono- or di-lower primary alcohol ester with an aromatic polyamine containing diaminodisiloxane in an amount of 0.1 to 10 mol. %, based on the amount of total amine compounds, to give a solid of polyimide precursor; and heating the solid of polyimide precursor to a temperature of 300° C. to 500° C.
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