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.