Stepwise thermosetting polyester resin prepn. - from branched unsatd. polyester dispersed in vinyl monomer to cause crosslinking of the polyester

摘要

A thermosetting moulding resin is made from a branched unsatd. polyester dispersed in an ethylenically unsatd. vinyl monomer to cause crosslinking of the polyester. In the prepn. (1) on a relative molar basis, 1 mole dipropylene glycol and 0.3-1.5 mole trimethylol ethane or penacrythritol are esterified with 1.0-3.5 moles isophthalic acid, to give a branched prepolymer with an acid value 10, and with 10-50 u (20-40)% of the OH gps. available for reaction with carboxylic gps., (2) the prepolymer is esterified with 0.87-2.25 moles of an alpha-beta ethylenically unsatd. dicarboxylic acid, pref. maleic anhydride, to give a polymer with acid value 40; (3) the polymer is dispersed in vinyl monomer to give a thermosetting resin mixt. contg. 20-65 wt.% vinyl monomer. The polyester is partic. suitable for cars, instruments and electrical components for which large changes in heat are encountered. Such polyesters can support simultaneously a high stress and strain.