1,3-Benzenedicarboxylic acid, polymer with 1,4-benzenedicarboxylic acid, 1,4-butanediol and hexahydro-1,3-isobenzofurandione 1,4-Butanediol, terephthalic acid, isophthalic acid, hexahydrophthalic anhydride polymer 68133-51-7