Emulsion type water paint, process for its production, and proce

Details Emulsion type water paint, process for its production, and proce Emulsion type water paint, process for its production, and proce

1988-11-17

1992-02-11

Morgan, Kriellion

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

523409, 523412, 523413, 4272481, 4272556, 427348, 16628722, C08K 320, B32B 700

Patent

active

050876457

DESCRIPTION:

BRIEF SUMMARY
TECHNOLOGICAL FIELD

This invention relates to an emulsified-type water-base paint and processes for its production. More specifically, this invention relates to a water-base paint which is produced by a phase inversion emulsifying method utilizing the surface-activating action of an acrylic resin incorporated in a paint resin solution, and to processes for its production. The invention also pertains to a method of coating with this paint.


PRIOR ART

In the production of cans for canning, it has been the previous practice to coat metallic blanks or cans themselves with various paints in order to prevent dissolving of metal in can contents or inhibit corrosion of the metal. In the case of not only deep drawn cans produced from an uncoated metallic blank but also drawn cans or three-piece cans produced from a coated metallic blank, various paints are spray-coated and baked on can bodies or can closures in order to repair injuries caused to the coated film in the can-making process or to form top coats.
A paint comprising a combination of an epoxy resin and a curing agent resin and a vinyl-type paint are excellent in regard to adhesion to a metallic substrate, corrosion resistance, flavor characteristics and film processability. These paints exhibit good performance when coated in the form of an organic solvent solution. However, the solvent is dissipated in the working environment during spray coating, and problems of air pollution and environmental hygiene arise.
To eliminate these defects, water-base paints, namely paints in the form of an aqueous dispersion, have already been developed. A first type of such water-base paints comprises a paint resin rendered particulate by some means and dispersed in water using a surface-active agent or a water-soluble or hydrophilic resin as a dispersing agent (for example, Japanese Patent Publication No. 18076/1969). A second type is a paint obtained by reacting a paint resin having a functional group such as an epoxy resin with a resin having carboxyl groups such as an acrylic resin and neutralizing the modified resin with ammonia or an amine and causing it to self-emulsify in an aqueous medium (for example, Japanese Laid-Open Patent Publication No. 213718/1984).
However, the former type of water-base paint contains dispersed particles of the paint resin which generally tend to be large and non-uniform. Moreover, the water-base paint has low dispersion stability, and the properties of a coated film prepared from it is inferior to those of a film obtained from a solvent-base paint.
The later type of paint may have better dispersibility than the former type paint, but is greatly restricted in the composition of the paint resin. For example, in the case of an epoxy resin-type paint, it is difficult to secure a sufficiently high content of the resin curing agent, and the coated film cannot be fully cured. Consequently, the hardness and denseness of the coated film and its barrier property with respect to corrosive components cannot be improved to a satisfactory level.
Many coating methods have previously been proposed for forming good paint films using the above water-base paints.
For example, Japanese Laid-Open Patent Publication No. 133342/1977 describes that a slurry-like paint is coated on an article, and until the coated film is subjected to drying under heating, it is maintained in an atmosphere having a temperature of not more than 100.degree. C. at which, in addition, the resin particles do not melt, a relative humidity of at least 80%, and an air speed of not more than 0.3 m/sec thereby to prevent cracking during film formation.


PROBLEM SOUGHT TO BE SOLVED BY THE INVENTION

When a water-base paint containing emulsified resin particles is coated on the surface of a metallic substrate by such means as a roll coater, raised and depressed patterns such as ribs occur on the coated surface and remain there after drying and baking. Accordingly, the coated surface loses smoothness.
In the case of a paint in the form of an organic solvent solution, the resin solution h

REFERENCES:
patent: 4579888 (1986-04-01), Kodama et al.

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