A process for preparing a
polymer having a 2,5-furandicarboxylate
moiety within the
polymer backbone and having a number average molecular weight of at least 10,000 (as determined by GPC based on
polystyrene standards) includes a first step where a
prepolymer is made having the 2,5-furandicarboxylate
moiety within the
polymer backbone, followed in a second step by a
polycondensation reaction. In the first step a 2,5-furandicarboxylate ester is transesterified with a compound or mixture of compounds containing two or more hydroxyl groups, in the presence of a
tin(IV) based
transesterification catalyst. In the second step at reduced pressure and under melt conditions the
prepolymer prepared in the first step is polycondensed in the presence of a
tin (II) based polycondensation catalyst until the polymer is obtained. This polymer may then be subjected to
Solid State Polycondensation. Polymers so produced may have a 2,5-furandicarboxylate
moiety within the polymer backbone, and having a number average molecular weight of at least 20,000 (as determined by GPC based on
styrene standards), and an
absorbance as a 5 mg / mL solution in a
dichloromethane:hexafluoroisopropanol 8:2 at 400 nm of below 0.05.