.beta.-Alanine, N-(2-aminoethyl)-, monosodium salt, polymer with 2,2-dimethyl-1,3-propanediol, hexanedioic acid, 1,6-hexanediol, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, 1,1-methylenebis4-isocyanatocyclohexane and 1,5-pentanediol