| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject aqueous solution which contains water as a solvent, has a high concentration and a low viscosity, and can exhibit excellent storage stability by reacting a specific tetracarboxylic acid with a specified diamine in the water to form the salt. SOLUTION: This polyimide precursor aqueous solution comprises water as a solvent and a salt as a solute. The salt comprises a diamine of formula I (R is a divalent aliphatic residue or the like) and a tetracarboxylic acid of formula II (R' is a tetravalent aromatic residue or aliphatic residue, wherein the four carboxyl groups are directly to different carbon atoms in the residual group, and form two pairs which are bound to the adjacent carbon atoms, respectively; R"1, R"2 are each H, a 1 to 12C alkyl or the like, provided that at least one of R"1, R"2 is H) or its diester derivative. The aqueous solution has a solute concentration of >=20 wt.% and a viscosity of <=100 poises. The aqueous solution can be prepared by reacting the diamine of formula I with the tetracarboxylic acid of formula II or its diester derivative in the water.
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