Hydroxylated acrylic resins prodn - by soln polymn and use with etherified melamine-formaldehyde resins for stoving enamels

摘要

An 0H-contg. acrylic resin (I) is produced by soln. polmysn. using a polymsn. initiator (IIe and a chain transfer agent (III) by (a) heating a solvent mixt. of 50-80 (wt.) pts. xylene and 50-20 pts. white spirit, with 15-20% aromatics content and boiling range 130-175 degrees C, to boiling under reflux; and (b) adding a mixt. of 12-16% hydroxyethyl methacrylate (IV), 25-35% styrene (V), 30-40% n-butyl acrylate (VI), 10-2% ethyl acrylate (VIIe and 1-2% acrylic acid (VIII), (II) and (III), 10-35% of the mixt. being added initially and the rest gradually, over about 3 h. after polymsn. of the first part (after ca. 1h), and heating being continued until the conversion is >98%. The (I) soln. is used as binder component in conjunction with etherified melamine-HCHO resins for the prodn. of new stoving enamels, esp. for use in the automobile industry. The enamels are suitable for thick film spraying, even on vertical surfaces, and allow the prodn. of dry film thicknesses of 60 mum or more, without intermediate stoving.