Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1998-12-18
2002-01-22
Copenheaver, Blaine (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S220000, C428S314400, C427S373000, C427S388100, C427S409000, C521S076000, C523S218000
Reexamination Certificate
active
06340519
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to water-based chipping-resistant paint which improves chipping resistance, anti-corrosiveness, and soundproof performance of metal board; and its application to automobiles.
BACKGROUND OF THE INVENTION
The underfloor, wheel house, and side sill of automobile outside are usually painted with underbody coating materials for improving their chipping resistance, anti-corrosiveness, and soundproof performance. The major conventional underbody coating material applied for the purpose is vinyl-chloride-based plastisol containing vinyl chloride resin as a major component, a plasticizer, and a filler. Such plastisol has been painted and baked to be changed into coating film after painted on metal substrate. Such vinyl-chloride-based plastisol has been required to have a viscosity of 40,000 cPs or more in order to be painted into sufficient thickness, 200 to 1000 &mgr;m, which is necessary to achieve desirable performance as underbody coating film.
Contrary to the above high-viscosity paint, low-viscosity vinyl-chloride-based paints containing thermoexpandable microcapsules were proposed in Japanese Patent Provisional Publication No. 25419 of 1993 and U.S. Pat. No. 5,520,961.
When an automobile is scrapped to be recycled into raw materials for steel making or casting, vinyl-chloride-based plastisol painted on metal parts is burnt to generate hydrogen chloride. The hydrogen chloride causes environmental hazard, and in addition, organic solvent contained in vinyl-chloride-based paints in considerable amount pollutes air in work place and threats occupational safety in painting operation.
Recently, a new chipping-resistant paint for automobiles substitutable for vinyl-chloride-based paints has been demanded for preventing the above hazard. And water-based paint, in which solid matters are dispersed in water, is paid much attention. A desirable chipping-resistant paint must form sufficiently thick film like as the above vinyl-chloride-based paint, in other words, it must have thixotropy. For imparting such property required for chipping-resistant paint to water-based paint, a water-dispersible inorganic filler blended in paint is proposed in Japanese Patent Provisional Publication No. 214269 of 1993, and hollow microspheres blended for reducing high specific gravity of chipping-resistant paint is proposed in European Patent Application No. 0026388A1 and Japanese Patent Provisional Publication No. 166093 of 1995.
The water in the inside of the thick film of water-based chipping resistant paint cannot be evaporated as fast as the water on the film surface. Because the energy required for water evaporation is so great that the thermal energy applied to the film in drying process is insufficient to dry up both the surface and inside of thick paint film simultaneously. And the water in thick film of water-based paint boils when heated at 100° C. or higher, or remains in the inside of the paint film after the surface of the paint film is dried into coating film through drying and baking process. Such behavior of water causes crack, split, or swell of coating film.
For preventing such troubles, several methods are proposed: blending a heat sensitizing agent proposed in Japanese Patent Provisional Publication No. 166094 of 1995; controlling the average particle size of film forming polymer dispersed in aqueous emulsion in 0.3 &mgr;m or more and blending hollow microspheres proposed in Japanese Patent Provisional Publication No. 166096 of 1995; and blending inorganic fibers proposed in Japanese Patent Provisional Publication No. 166097 of 1995. However, those preventive measures may bear other troubles, such as unstable dispersion of paint ingredients, or big bubbles, 200 to 500 &mgr;m in diameter, generated in paint film.
The present invention provides water-based resin paint which has superior chipping resistance; forms underbody coating film without crack, split, and swell; and is safe and free from environmental pollution.
DESCRIPTION OF THE INVENTION
The chipping-resistant paint of the present invention contains 30 to 65 weight percent, preferably 30 to 60 weight percent, of solid matter, and 0.1 to 10 weight percent of low-volatility solvent, both of which are dispersed in water. The said solid matter comprises 15 to 75 weight percent of film-formable resin, 0.2 to 25 weight percent of thermoexpandable microspheres, and 20 to 80 weight percent of chipping-resistant material.
And the present invention includes chipping-resistant film of 0.2 to 5 &mgr;m thickness formed by painting and heating the said chipping-resistant paint, and containing separate hollows inside.
The present invention also includes the method for forming chipping-resistant film, wherein the said chipping-resistant paint is spread on a metal substrate and heated to the temperature higher than the expansion temperature of the thermoexpandable microspheres contained for expanding the microspheres so as to increase the thickness of the paint film.
The advantage of the present invention is the forming of thick paint film from thin paint film by expanding the contained thermoexpandable microspheres with heat applied in drying and baking process. The method does not require spreading thick paint film on metal surface and thus can avoid the troubles involved in painting thick film.
Further the paint of the present invention can release water easily when painted on a surface owing to the function of low-temperature volatility solvent blended as a film-forming agent, and thus can prevent water from remaining in paint film, and the crack or swell of paint film due to the evaporation of water from the inside of baked paint film.
Another advantage of the paint of the present invention is its improved chipping resistance owing to the inorganic chipping resistant agent blended.
THE BEST MODE OF THE EMBODIMENT
The present invention is further explained in detail.
The water-based chipping-resistant paint of the present invention contains film-formable resin being dispersed in water into emulsion and the like. Almost all of the aqueous emulsion of resins conventionally used as water-based paint can be applied as the above-mentioned emulsion of the film-formable resin. Those are polyvinyl acetate emulsion, vinyl acetate copolymer emulsion, acrylic ester copolymer emulsion, polyethylene emulsion, paraffin wax emulsion, epoxy resin emulsion, urethane resin emulsion, butadiene-styrene copolymer latex, and butadiene-acrylonitril copolymer latex.
The most preferable emulsions are vinyl acetate copolymer emulsion, acrylic ester copolymer emulsion, and urethane resin emulsion, because of their superior film-forming performance, compatibility to pigments, film strength, and film hardness.
The ratio of the film-formable resin in the water-based chipping-resistant paint is 15 to 75 weight percent, preferably 20 to 60 weight percent. The ratio lower than 15 weight percent is insufficient to attain desirable strength as underbody coating paint, because low resin content results in insufficient adhesion of resin to microspheres expanded in paint film or to fillers, and decreases the strength of the vehicle of chipping-resistant paint. The ratio more then 75 weight percent is not preferable because of the increased cost of the paint beyond an acceptable range. In addition, excessive resin content simultaneously decreases the ratio of thermoexpandable microspheres below the level necessary to achieve sufficient cushioning effect, and thus such paint fails to attain sufficient chipping resistance and low specific gravity of coating film.
The water-based chipping-resistant paint of the present invention contains thermoexpandable microspheres, and low-volatility solvent which functions as a film-forming agent.
The chipping-resistant paint of the present invention, in which thermoexpandable microspheres is contained, can attain sufficient performance being painted into thin film, and water can evaporate from thin film in a short time. In addition, the low-volatility solvent facilitates the evaporation of wat
Kitano Kenichi
Masuda Toshiaki
Tanaka Koji
Foley & Lardner
Matsumoto Yushi Seiyaku Co., Ltd.
LandOfFree
Chipping-resistant paint does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chipping-resistant paint, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chipping-resistant paint will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2836831