PURPOSE: To obtain a curablepolymer compsn. which is a long-stable one- component system, has an excellent curability, and gives a coating film with excellent properties by incorporating a specific nonaq. dispersion of a vinyl polymer and a specific compd. into the compsn.

CONSTITUTION: This polymer compsn. contains a nonaq. dispersion of a vinyl polymer and at least one compd. selected from the group consisting of an aryldiazonium salt, a diaryliodinium salt, a triarylsulfonium salt, a triarylselenonium salt, a phenacylsulfonium salt, a 4-hydroxyphenylsulfonium salt, and a sulfonic ester (e.g. diphenyliodinium hexafluorophosphonate). The dispersion contains a dispersion-stabilizing resin and dispersed resin particles, each of them being a vinyl polymer and at least one of them having hydrolyzable silyl groups of the formula (wherein R1 is alkyl, aryl, or aralkyl; X is halogen, alkoxy, acyloxy, or hydroxyl; and (k) is 1-3) (e.g. a polymer produced by using γ-methacryloxypropyltrimethoxysilane).