Block copolyester in which the blocks consist of (1) units of at least one crystallisable polyester of intrinsic viscosity 0.1-0.5, and (2) units of at least on

摘要

Block copolyester in which the blocks consist of (1) units of at least one crystallisable polyester of intrinsic viscosity 0.1-0.5, and (2) units of at least one rubbery polyester of intrinsic viscosity 0.2-0.35, the ratio of (1):(2) being 10:65 to 95:35. The intrinsic viscosity of (1) is lower than that of (2), and the compsn. has a m. pt. of at least 150 deg.C. and intrinsic viscosity of 0.75-1.75 measured at 30 deg.C. in a 60/40 mixture of phenol and tetrachloroethane. The units of (1) are aromatic and those of (2) are aliphatic, part of (2) may be aliphatic acid dimer, and part may be aromatic acid, esp. butyl-naphthalic acid.