Patent ID: 8080617

Claim:
A method for increasing the molecular weight of a polymer comprising the steps of providing a reaction mixture including (i) an initial polymer with a molecular weight of less than 2000 g/mol which initial polymer comprises a first repeat unit, which comprises the residual of a condensation reaction of either a volatile or non-volatile aliphatic dicarboxylic acid with a bisamide diol prepared from a diamine having 6 or fewer carbon atoms or a volatile or non-volatile diol with a diamide diester, and a second repeat unit, which comprises the residual of a condensation reaction of a volatile or non-volatile diol and a volatile or non-volatile aliphatic dicarboxylic acid, provided that at least one of the volatile or non-volatile diol or the volatile or non-volatile aliphatic dicarboxylic acid is the volatile diol or volatile aliphatic dicarboxylic acid, which are characterized in that when found independently in a reaction mixture they may be distilled out of the reaction mixture and (ii) a reactant selected from high boiling point diacid esters having the formula R′OOC—HA-COOR′ where HA is an aliphatic or heteroaliphatic, alicyclic or heteroalicyclic or aromatic or heteroaromatic group of 5 or more carbon atoms and R′ is a monovalent organic group, non-volatile diols and non-volatile aliphatic dicarboxylic acids, wherein each of the non-volatile aliphatic dicarboxylic acids has 5 or more carbon atoms, wherein the first repeat unit and the second repeat unit are different, heating the reaction mixture to increase the molecular weight of the polymer to 4000 g/mol or more.