Transparent copolyamide from isophorone diamine and substituted undecane diamine

A thermoplastic, transparent copolyamide obtained by reacting a diamine of the formula I ##STR7## and an aliphatic diamine with isophthalic acid or terephthalic acid or amide-forming derivatives thereof or with a mixture of isophthalic acid and terephthalic acid or amide-forming derivatives thereof, which copolyamide has a reduced specific viscosity of not less than 0.5 dl/g, measured on an 0.5% solution in m-cresol at 25.degree. C., and is obtained by reacting a mixture (A) of the diamine of the formula I and isophthalic acid or terephthalic acid or mixtures or amide-forming derivatives thereof either with a mixture (B) of an aliphatic diamine of the formula II ##STR8## and terephthalic acid or an amide-forming derivative thereof or a mixture of terephthalic acid and isophthalic acid or amide-forming derivatives thereof in a molar ratio of terephthalic acid or derivative:

• isophthalic acid or derivative of 8:2 to 10:0 or with a mixture C of an aliphatic diamine of the formula III ##STR9## and terephthalic acid or isophthalic acid or mixtures or amide-forming derivatives thereof, in which formulae R' and R", independently of one another, are each hydrogen or methyl, R.sub.1 is alkyl having 2-12 C atoms or is substituted or unsubstituted aryl, R.sub.2 is alkyl having 1-8 C atoms, R.sub.3 is hydrogen or alkyl having 1-5 C atoms, R.sub.4 is unsubstituted or C.sub.1-4 -alkyl-substituted cycloalkyl having 5-12 ring C atoms, R.sub.5 is hydrogen or methyl and R.sub.6 is methyl or R.sub.5 and R.sub.6 together are alkylene having 4-11 C atoms, the proportion of mixture (C) being 60-80 percent by weight and the proportion of mixture (B) being 50-80 percent by weight, relative to the total weight of the reactants, and these percentages by weight relating, in the case of amide-forming derivatives of isophthalic acid or terephthalic acid, to identical functional groups.