1,3-Benzenedicarboxylic acid, polymer with hexanedioic acid, .alpha.-hydro-.omega.-hydroxypolyoxy(methyl-1,2-ethanediyl), 1,1-methylenebis4-isocyanatobenzene, 2,2-oxybisethanol, 1,2-propanediol and .alpha.,.alpha.,.alpha.-1,2,3-propanetriyltris.omega.-hyd