To produce a solution of a dicarboxylic acid useful as a raw material for producing a copolyamide without producing a polycondensate even when water is contained at the time of storage for a long period and without causing decomposition or discoloration by dissolving a specific dicarboxylic acid in a lactam.
This solution comprises (A) a 6-44C, especially a 6-13C dicarboxylic acid (e.g. adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 2,6-dinaphthalenedicarboxylic acid or 4,4'-biphenyldicarboxylic acid) dissolved in (B) a lactam of a 6-16C, especially a 6-12C aliphatic α,ω-aminocarboxylic acid (e.g. caprolactam, laurolactam or pelargolactam). The amount of the component (A) is preferably up to 4 times, especially preferably up to 1.5 times based on the component (B).
FURANTSUUEERITSUHI BAUMAN
