Abstract: The present invention provides a production of 2-hydroxynaphthalene-6-carboxylic acid improved in the yield and the selective ratio, in which .beta.-naphthol and water formed in the reaction system are eliminated therefrom through the reaction.

Abstract: The present invention provides a method of production of aromatic hydroxycarboxylic acids by the reaction of alkaline metal salts of phenols or naphthols with carbon dioxide, in which free phenols or free naphthols produced as by-products in the reaction system are removed from the system so as to control the content of free phenols or free naphthols at a suitable level, by which a purer objective compound can be obtained at high yield under the condition of lower temperature and shorter time.

Abstract: A melt-processable copolyester composed of the following structural units (I), (II) and (III) and/or (IV) as main structural components, whereinunit (I) is represented by the formula ##STR1## wherein X.sub.1, X.sub.2, X.sub.3 and X.sub.4, independently from each other, represent H, F, Cl, Br, CH.sub.3 or C(CH.sub.3).sub.3, provided that X.sub.1 to X.sub.4 do not simultaneously represent H, and n is 2 or 4,unit (II) is at least one unit selected from the group consisting of ##STR2## wherein at least one of the hydrogen atoms in each aromatic ring in units (II), (III) and (IV) may be substituted by an alkyl or alkoxy group having 1 to 4 carbon atoms or a halogen atom.The proportion of unit (I) is 2.5 to 35 mole %, the proportion of unit (II) is 2.5 to 35 mole %, and the proportion of unit (III), (IV) or a combination of units (III) and (IV) is 30 to 95 mole %.