I want to render a polyester resin that is water soluble. What do I have to do? I know to use some materials like ammonia and amines but I don't know the procedure.
Varoon's answer is fully correct. Also hydroxycarboxylic acids would do the job when you use them as a monomer for co-condensation. Here a practical example which you can search via Google:
G. Walz, T. Wirth, W. Spengler, Water-thinnable polyester, process for its preparation and its use, EP 0060505, 1982 (Hoechst)