Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-03
2002-07-09
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S409000, C523S412000, C524S803000, C524S832000, C524S839000
Reexamination Certificate
active
06417252
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to resin compositions for use in proofing, such as waterproofing, dust-proofing or rust-proofing, of steel plates having metal coating of zinc, aluminum or the like. More specifically, the present invention relates to aqueous resin compositions that are particularly suitable for filling or sealing up a clearance defined in a joint portion of steel plates forming a car body or the like, or as hemming sealers.
2. Description of the Related Art
Steel plates plated with zinc, aluminum or an alloy containing such a metal are used in a great quantity as incorporated in vehicles, building materials, electric household appliances and the like.
Water or dust is likely to collect in a clearance defined in a joint portion of such plated steel plates, or in a bent portion or a like portion of such a plated steel plate, and such collected water or dust causes the steel plates to rust.
In the case of a car body, for instance, a clearance defined in a joint portion of steel plates is filled with a resin composition so-called “body sealer” in order to waterproof or dust-proof the steel plates. Various resin compositions each containing a polyvinyl chloride resin as a major ingredient are widely used as body sealer resin compositions (refer to Japanese Patent Applications No. HEI 4-80382 and No. HEI 7-345483).
Recent environmental issues, however, demand for resins replacing polyvinyl chloride resins containing chlorine or any plasticizer. Further, the recent trend toward improved working environments or the like demands for resin compositions not containing any organic solvent.
Aqueous emulsion type compositions are known as such resin compositions not containing any organic solvent. Most of such aqueous emulsion type resin compositions, however, are used as coated onto paper sheets or films. In this case, the viscosity of such a resin composition in a water-dispersed state is often intentionally lowered to ensure desired coating properties. Such resin compositions thus prepared are in no way suitable as sealers.
A surface-treated steel plate having a superior resistance to white rust has been proposed (refer to Japanese Patent Laid-Open Gazette No. 2000-000519). The surface treatment described in this Gazette comprises coating a steel plate plated with zinc or a zinc alloy or aluminum or an aluminum alloy with a protective film formed from a composition of which major components are a water-dispersible resin and/or a water-soluble resin and a polymer chelating agent having a chelate-forming group bonded to a polymer matrix. The protective film thus formed has a close tissue because the chelate-forming group contained in the protective film is adsorbed by the surface of the plating film.
The aforementioned surface treatment, however, is merely capable of forming a close protective film and hence cannot be expected to rust-proof a portion that is not coated with the film.
It is naturally conceivable to use an aqueous resin composition prepared by dispersing a resin in an aqueous dispersion medium without using any organic solvent as a sealer in attempt to lower the possibility of affecting the environment. Any one of known aqueous resin compositions, however, is not suitable for use as a sealer due to its very low viscosity.
Sealers are required to have a viscosity such as to allow relatively thick coating and good adherence to a subject to be sealed. Aqueous resin compositions, however, inherently have properties opposite to such requirements because they contain water in themselves. Further, where the subject to be sealed is a steel plate, aqueous resin compositions are more disadvantageous in terms of adherence because oil film is usually present on a surface of such a steel plate.
The inventors of the present invention have intensively studied in pursuit of an aqueous resin composition which is improved to overcome the foregoing inconveniences and made the present invention.
Accordingly, it is an object of the present invention to provide an aqueous resin composition for use as a sealer which is suited for waterproofing and rust-proofing of steel plates plated with zinc or a zinc alloy to be used in car bodies, building materials, electric household appliances or the like. The resin composition does not contain chlorine or any organic solvent and hence does not affect the environment while exhibiting a positive rust-proofing capability as well as water-proofing or dust-proofing capability.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an aqueous resin composition for use as a sealer, comprising an aqueous resin as a major component, and a viscosity modifier adjusting the viscosity of the aqueous resin composition to a value ranging from 5,000 to 100,000 mPa·s, the aqueous resin being an aqueous emulsion polyolefin resin which comprises a polyolefin not containing chlorine as a constituent element while exhibiting a viscosity of 1,000 mPa·s or higher in a water-dispersed state having a solid resin content of 20% to 40% by weight.
In the above aqueous resin composition, the aqueous resin as a major component is an aqueous emulsion polyolefin resin which comprises a polyolefin not containing chlorine as a constituent element while exhibiting a viscosity of 1,000 mPa·s or higher in a water-dispersed state having a solid resin content of 20to 40% by weight, and the overall viscosity of the aqueous resin composition is adjusted to a value ranging from 5,000 to 100,000 mPa·s by the viscosity modifier. The composition thus constituted exhibits proper viscosity, heat resistance, durability and strength as a sealer. Further, since the composition does not contain chlorine or any organic solvent, it does not emit any harmful substance during preparation, coating and disposal thereof or on other occasions and hence will not raise any environmental pollution problem or like problems.
The aqueous resin composition for use as a sealer may further comprise a water-soluble magnesium compound in a proportion of 0.1% to 10% by weight.
When the water-soluble magnesium compound is added to the foregoing aqueous resin composition, the resulting composition has an advantage of remarkably rust-proofing a steel plate plated with zinc or a zinc alloy as well as the advantages described above.
These and other objects, features and attendant advantages of the present invention will become apparent from the reading of the following detailed description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in detail.
The viscosity of the aqueous resin composition according to the present invention is adjusted to a value ranging from 5,000 to 100,000 mPa·s. If the viscosity of the composition is higher than 100,000 mPa·s, the coating property of the composition is unsatisfactory. If, on the other hand, the viscosity of the composition is lower than 5,000 mPa·s, the composition, if applied to a steel plate surface stained with oil, may flow down without fixing to a desired portion of the steel plate.
The aqueous emulsion polyolefin resin used as a major component in the aqueous resin composition of the present invention is preferably a dispersion of a particulate polyolefin having a particle diameter of several &mgr;m in water.
The aqueous emulsion polyolefin resin exhibits a viscosity of 1,000 mPa·s or higher at normal temperature when the solid resin content thereof is 20% to 40% by weight. If the solid resin content is less than 20% by weight, the aqueous resin composition has a viscosity lower than the predetermined value and hence cannot serve as a sealer for sealing up a clearance defined, for example, in a joint portion of steel plates or in a bent portion of a steel plate. If the solid resin content is more than 40% by weight, the aqueous resin composition undesirably exhibits too high a viscosity to ensure a satisfactory coating property.
Though a viscosity of about 10,000 mPa·s is practical as the viscosity of the aqueous emulsion polyolefin resin, there
Hiraoka Teruyoshi
Yoshihara Ryoichi
Aylward D.
Breiner & Breiner L.L.C.
Dawson Robert
Hiraoka Teruyoshi
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