Patent ID: 6121387
Filing Date: 2000-09-19
Classification: B29C,C08G

Abstract:
A process for preparing a thermosetting cross-linkable protective coating composition containing an organic functionalized cross-linkable polymeric binder having functionally active crosslinking groups adapted to crosslink upon heating the protective coating when applied to a substrate, the process comprising:(a) providing a reaction mixture of (i) a cleavable, high molecular weight carbonyl polymer, and (ii) a low molecular weight, multifunctional compound, where the cleavable carbonyl polymer (i) has a cleavable unit of an activated carbonyl group in the polymer backbone adjacent to an electronegative atom of an oxygen or a nitrogen, the cleavable carbonyl polymer having a weight average molecular weight greater than 5,000, where the cleavable carbonyl polymer is heated above its softening point in the reaction mixture,where the multifunctional compound (ii) has a weight average molecular weight of less than 5,000, and at least one functionally reactive group capable of reacting with the cleavable carbonyl polymer in the reaction mixture to cleave the carbonyl polymer at the activated carbonyl group, the multifunctional compound having at least one other functionally active reactive group consisting of a functionally active crosslinking group for crosslinking the protective coating;(b) reacting the reaction mixture while intimately mixing in an extruder to provide a continuous reaction mixture under conditions of shear at temperatures between about 150 and 350.degree. C. for a short reaction time period between about 15 and 600 seconds to cleave the carbonyl polymer at the carbonyl group to produce a reduced molecular weight cleaved polymer, and partially reacting the cleaved polymer with the multifunctional compound to less than equilibrium reaction between the cleaved polymer and the multifunctional compound to form a bond between the multifunctional compound and the cleaved polymer;(c) quenching the continuous reaction mixture by rapid cooling prior to the equilibrium reaction of the cleaved polymer and the multifunctional compound to avoid crosslinking of the cleaved polymer and the multifunctional compound, the continuous reaction producing a functionalized polymer of cleaved polymer and multifunctional compound, where said functionalized polymer has functionally active crosslinking groups derived from the multifunctional compound; and(d) producing a heat reactive, thermosetting, protective coating containing the functionalized polymer having functionally active crosslinking groups adapted to crosslink upon heating with a coreactive crosslinking agent.