The present invention relates to an aqueous dispersion composition and a method of producing the same. More particularly, the invention relates to an aqueous dispersion composition suited for use in various fields of painting, for example in decorating the interior and exterior of buildings or decorating automobiles, household electrical appliances, articles made of synthetic resin or the like, and capable of displaying good paint film performance characteristics in those fields of application where weather resistance and durability are required, and to a method of producing such composition.
In recent years, in the field of paints and adhesives, switchover from compositions comprising a resin and an organic solvent to compositions based on a water-soluble resin or water-dispersible resin (hereinafter referred to as "water-compatible resin") has been attempted for reasons of controlling pollution or saving resources.
However, the conventional water-compatible resins are produced exclusively by emulsion polymerization using surfactants and, as a result, cured products (paint films) formed therefrom tend to perform unsatisfactorily in weather resistance, water resistance and stain resistance due to the influences of said surfactants. Another disadvantage is that, owing to the difference in film formation mechanism, the gloss of paint films is inferior as compared with those cases where organic solvents are used.
Attempts have already been made to remove the above drawbacks. Thus, for instance, Japanese Kokai Patent Publication No. 02-178301 proposes a method of producing emulsion polymerizates which comprises subjecting, in an aqueous solution of a water-soluble resin having a hydrolyzable silyl function group, a vinyl monomer having a functional group capable of reacting with said silyl function group to emulsion polymerization.
However, such emulsion polymer having a hydrolyzable silyl function group can readily be crosslinked during polymerization and therefore the film-forming property obtainable therewith is very poor. To solve this problem, a measure is known which comprises adding a film formation aid such as Texanol or butyl carbitol acetate. However, mere addition of such an aid cannot produce a satisfactory level of film-forming ability, since such aid induces aggregation or fusion.