This invention provides a process for producing an aqueous resin
dispersion in which the average particle diameter of the dispersed resin
is not more than 500 nm, comprising finely dispersing a monomeric mixture
(I) containing (A) fatty acid-modified polymerizable unsaturated monomer
and (B) other polymerizable unsaturated monomer which is copolymerizable
with the monomer (A) in an aqueous medium in such a manner that the
dispersed particles have an average particle diameter not more than 500
nm, and polymerizing the resulting emulsified product. The invention also
provides aqueous resin compositions which comprise the aqueous resin
dispersions, and water-based paint compositions which comprise the
aqueous resin compositions.