An aqueous resin dispersion useful as a primer capable of providing
plastics products, in particular polyolefin plastics products, with good
coatability characteristics. A thermocrosslinkable resin dispersion
having a continuous phase having an aqueous medium and a dispersed phase
distributed therein, the dispersed phase having particles (I) of a resin
component and particles (II) of a crosslinking agent as separately
dispersed from the particles (I), the resin component having, as an
essential constituent thereof, a modified polyolefin resin (a) or a
mixture thereof with a vinyl resin (b), the resin (a) having a number
average molecular weight of at least 1,500 and having at least one
functional group species selected from the group of carboxyl, hydroxyl,
mercapto, amino, isocyanate and carbodiimide groups, the resin (b) having
a number average molecular weight of 700 to 40,000 and a glass transition
temperature of -65 to 40.degree. C., and the crosslinking agent having at
least two groups reactive with the resin (a).