Process for depolymerizing hydroxycarboxylic polymers

Process for obtaining a hydroxycarboxylic polymer of reduced molecular weight from a corresponding polymer of higher molecular weight, the hydroxycarboxylic polymer containing monomer units of the formula ##STR3## in which R.sub.1 and R.sub.2 represent hydrogen or an alkyl group containing from 1 to 3 carbon atoms which can be substituted by a hydroxyl group or by a halogen atom, and R.sub.1 and R.sub.2 can be identical or different, and where M represents hydrogen, an alkali metal atom or an ammonium group comprising heating the said polymer of higher molecular weight in a gaseous medium to a temperature of between 60.degree. and 240.degree. C., said polymer of higher molecular weight having a Flory average molecular weight greater than about 3,000.