| abstract |
A process for preparing polymer non-aqueous dispersions to be formulated together with a binder component in coating compositions, which comprises the steps of: (1) emulsion polymerizing a hydroxy group containing α,β-ethylenically unsaturated monomer, a polyfunctional α,β-ethylenically unsaturated monomer and an α,β-ethylenically unsaturated monomer different therefrom by using a water-soluble polymerization initiator, preferably a persulphate, in a soap free system or in the presence of an ester group containing anionic or cationic surfactant; adding an organic solvent, preferably comprising an amphipathic organic solvent, to a resultant polymer aqueous dispersion; and then adding a basic compound catalyst when anionic surfactant is used or an acidic compound catalyst when the cationic surfactant is used, to thereby hydrolyze completely said surfactant and water-soluble polymerization initiator at a temperature not exceeding 95° C. as in the condition of suspension; (2) adding an acidic or basic compound to said suspension to neutralize said basic or acidic compound catalyst: then after adding dispersion stabilizing resin, further adding an amine salt of organic acid, followed by leaving said suspension to stand to separate into organic and water layers; and isolating the organic layer from the water layer; and (3) removing residual water in the organic layer. The resultant polymer non-aqueous dispersion comprises polymer particles having a total ionic group concentration (I) less than 2×10 -5 mol/g particle, a hexane tolerance (HT) from 5 to 40 exclusive and a degree of swelling in acetone (S) less than 10, and used with a binder component comprising a polyol resin and a curing agent for preparing coating compositions. |