Abstract: A method for producing a copolyamide, which comprises (1) heating either one dicarboxylic acid selected from the group consisting of adipic acid and a mixture containing 40 mol % or more of adipic acid to a temperature higher than the melting point of adipic acid but lower than a temperature lower by 30.degree. C. than the melting point of the resulting copolyamide, (2) dropping a diamine comprising paraxylylene diamine and metaxylylene diamine into the heated dicarboxylic acid before a conversion of the dicarboxylic acid reaches 90 mol %, (3) stopping dropping of the diamine before the conversion of the dicarboxylic acid reaches 90 mol %, and dropping metaxylylene diamine or a diamine mixture of metaxylylene diamine and paraxylylene diamine in place of the diamine until a molar ratio of the total of the diamines to the total of the dicarboxylic acids becomes 0.97 to 1.03, and (4) heating a reaction system to a temperature higher than a temperature lower by 30.degree. C.

Abstract: A process for the production of a polyamide, which comprises polycondensing adipic acid prepared by nitric acid oxidation and containing 1 ppm by weight or less of a free mineral acid as an impurity with a diamine represented by formula (1)H.sub.2 N--CH.sub.2 --R--CH.sub.2 --NH.sub.2 . . . (1)wherein R denotes a linear or branched alkylene group having 2 to 10 carbon atoms, a m-phenylene group, a p-phenylene group, a 1,3-cyclohexylene group or a 1,4-cyclohexylene group; a polyamide produced by said process; and a film or sheet made of the above polyamide.

Abstract: A hearing aid appliance has induction loops which are magnetically coupled to hearing aids held individually by hard-of-hearing persons. The number of induction loops is an integral multiple of two, and each induction loop is in the form of a rectangle having at least two parallel sides. The parallel sides of the induction loops are arranged in parallel with one another and equally spaced from one another so that signal currents flowing in adjacent parallel sides are shifted by 90.degree. in phase.