Polycondensn of low mol polyesters - in mild reaction conditions to give high mol products

摘要

Low- or medium molecular polyesters e.g. PET (rel. visc. 1.25 - 2.10 measured as 1% soln. in 3/2 phenol/tetrachloroethane at 25 degrees C) contg. terminal hydroxyl-grps. are mixed with carbonic acid esters e.g. diphenylcarbonate or aromatic, aliphatic and/or cycloaliphatic alcohols, and reacted in solid phase at 5 - 80 degrees C below the m.p. of the polyesters under mild reaction condns. Prod. has excellent degree of whiteness and resistance to hydrolysis, and low carboxyl content.