METHOD FOR PRODUCING POLYIMIDE ELECTRODEPOSITION COATING MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a suspension type polyimide electrodeposition coating material less liable to degenerate even in long-term storage and formable of an electrodeposited film having high uniformity of film properties at a high electrodeposition rate even after long-term storage.

SOLUTION: The method includes: a step wherein a polyimide solution in which a block-copolymerized polyimide having a siloxane bond in a molecular skeleton and having an anionic group in a molecule is dissolved in a water-soluble polar solvent at a concentration of the block-copolymerized polyimide of 15-25 wt.% is blended with a poor solvent for the block-copolymerized polyimide and a basic compound, and the resulting solution is allowed to stand at room temperature until a variation of electric conductivity of the solution per day becomes ≤0.1 mS/m; a first dilution step of pouring water in the polyimide solution after allowed to stand under stirring in an amount smaller than such a liquid amount as to deposit the block-copolymerized polyimide; and a second dilution step of further pouring water under stirring after the first dilution step to thereby deposit the block-copolymerized polyimide.

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