Abstract: This invention relates to a laminate which changes in dimension to such a small extent as not to cause curling and warpage when the ambient humidity changes and is useful for flexible printed wiring boards. The laminate possesses a polyimide layer or layers of polyimides formed on a conductor by coating and at least one of the polyimide layers is composed of polyimide of low hygroscopic expansion obtained by the reaction of diamines containing 20 mol % or more of 4,4?-diamino-2,2?-dimethylbiphenyl with a tetracarboxylic acid compound and exhibiting a coefficient of linear hygroscopic expansion of 15×10?6/% RH or less.

Abstract: The process of this invention for preparing 2,6-naphthalene-dicarboxylic acid comprises a reaction step (Step A) wherein 2,6-naphthalene-dicarboxylic acid potassium salts consisting of 2,6-naphthalene-dicarboxylic acid dipotassium salt and/or 2,6-naphthalene-dicarboxylic acid monopotassium salt are allowed to react with benzene-carboxylic acids in the presence of water to yield 2,6-naphthalene-dicarboxylic acid and benzene-carboxylic acid potassium salts and a separation step (Step B) wherein the crystallized 2,6-naphthalene-dicarboxylic acid is separated from the benzene-carboxylic acid potassium salts dissolved in the aqueous solution and provides 2,6-naphthalene-dicarboxylic acid, useful as raw material for polymers, at low cost on a commerical scale with recycle of potassium.