Heat sealable coating compositions

Abstract

A dispersion of polymer microparticles in organic liquid obtainable by a process comprising the steps of i) providing a mixture comprising a first polymer having functional groups capable of reacting with the carboxylic acid and/or carboxylic acid anhydride groups of a second, polypropylene polymer ii) causing the polymers to melt at a chosen temperature under conditions of high shear, preferably in an extruder, to form an intimate mixture iii) causing the carboxylic acid and/or carboxylic acid anhydride groups of the polypropylene polymer to react with at least some of the functional groups of the first polymer, under conditions of high shear, preferably in an extruder iv) diluting the resulting mixture of step iii) with an organic liquid at a temperature such that a substantially homogeneous solution is formed v) cooling the solution to a temperature whereby the polymer microparticles of the dispersion are formed.