Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-09
2002-02-05
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...
C525S107000, C525S285000, C525S327500, C525S507000
Reexamination Certificate
active
06344500
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to: an aqueous primer coating composition that is fit for such as plastic materials; and a thing coated with this aqueous primer coating composition.
B. Background Art
Plastic materials used for automobile bumpers, molds and so on, generally, have bad wetting ability to coating compositions and are inferior in coatability. Especially, if the plastic materials are polyolefin resin molding materials such as a polypropylene resin, coatability and adhesion of an overcoating paint is extremely low. Therefore, a method of coating a primer before coating a paint is often adopted in order to ensure adhesion between the materials and the paint, and various solvent type or aqueous primers are proposed.
In recent years, developments of the aqueous primer are eagerly carried out. However, the aqueous primer has a demerit that the coatability and adhesion thereof is generally inferior to those of the solvent type primer. Therefore, various researches and developments are carried out in order to obtain an aqueous primer that is excellent in coatability and adhesion.
For example, various studies about aqueous primers comprising non-modified poly(olefin chloride) were performed (JP-A-214188/1993, JP-A-258596/1995 and so on). However, adhesion of the aqueous primer is not improved enough because the none-modified poly(olefin chloride) has low cohesive forces.
In addition, a primer comprising a modified poly(olefin chloride), obtained by modifying a poly(olefin chloride) with unsaturated polycarboxylic acid and/or acid anhydride in order to improve adhesion enough, is disclosed (JP-A-182534/1991 etc.). However, there was a demerit that water resistance became low because of modifying the poly(olefin chloride) with the highly water-soluble unsaturated polycarboxylic acid and/or acid anhydride.
On the other hand, it is disclosed that various capacities of the aqueous primer can be improved by mixing various other resins with the non-modified or modified poly(olefin chloride) in order to jointly use them. For example, an aqueous primer, comprising a urethane resin and an epoxy resin in addition to the modified poly(olefin chloride) in order to improve paint stability and capacities of coating film, is disclosed in JP-A-72337/1992. However, in this case, gasohol resistance is not enough, and further, pigment dispersion stability when mixing a pigment is not either enough. These gasohol resistance and pigment dispersion stability are, for example, capacities particularly demanded when the aqueous primer is applied to the automotive plastic materials. In addition, an aqueous primer comprising a carboxylic-acid-functional resin, an amine compound and water in addition to the specific poly(olefin chloride), is disclosed in JP-A-509383/1994. However, in this case, water resistance was not enough.
Thus, an aqueous primer having enough capacities in respect to all of adhesion, water resistance, gasohol resistance and pigment dispersion stability enough, has not yet been obtained.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide an aqueous primer coating composition of which the deterioration of the water resistance is prevented with the high adhesion maintained, and which is excellent in the gasohol resistance and the pigment dispersion stability.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above-mentioned problems. As a result, they have found that an aqueous primer coating composition obtained by mixing an emulsion resin containing acid anhydride-modified poly(olefin chloride) with an aqueous alkyd resin and an aqueous novolac-type epoxy resin in a specific ratio can solve all the above-mentioned problems. The present invention has been completed in this way.
That is to say, an aqueous primer coating composition, according to the present invention, comprises acid anhydride-modified poly(olefin chloride) emulsion resin (A), aqueous alkyd resin (B) and aqueous novolac-type epoxy resin (C), wherein the contents of the (A), (B), and (C) are (A) 20 to 60 weight %, (B) 10 to 60 weight %, and (C) 10 to 60 weight % in terms of solid content weight % to the total resin solid content in the composition.
In addition, a coated thing, according to the present invention, is coated with the aqueous primer coating composition according to the present invention.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
The aqueous primer coating composition, according to the present invention, comprises acid anhydride-modified poly(olefin chloride) emulsion resin (A), aqueous alkyd resin (B) and aqueous novolac-type epoxy resin (C), wherein the contents of the (A), (B), and (C) are (A) 20 to 60 weight %, (B) 10 to 60 weight %, and (C) 10 to 60 weight % in terms of solid content weight % to the total resin solid content in the composition. Hereinafter, to begin with, each component of this composition is described.
(Acid Anhydride-modified poly(olefin chloride))
The acid anhydride-modified poly(olefin chloride), as used in the present invention, is a polyolefin derivative comprising a poly(olefin chloride) moiety and an acid anhydride moiety as bonded to this poly(olefin chloride) moiety. The acid anhydride-modified poly(olefin chloride) preferably has a chlorine content of 10 to 30 weight %, an acid anhydride moiety content of 1 to 10 weight %, and a weight-average molecular weight of 20,000 to 200,000.
The poly(olefin chloride) moiety is a moiety comprising a polyolefin including a chlorine atom substituent. In addition, the acid anhydride moiety, for example, comprises a group as derived from an acid anhydride such as maleic anhydride, citraconic anhydride or itaconic anhydride, and is a modified moiety as obtained by grafting. The acid anhydride moiety may be a moiety comprising a group as derived either from only one acid anhydride or from two or more acid anhydrides.
Because the acid anhydride-modified poly(olefin chloride) preferably has an acid anhydride moiety content in the range of 1 to 10 weight % and a relatively low chlorine content in the range of 10 to 30 weight %, it improves the gasohol resistance.
The acid anhydride-modified poly(olefin chloride) is a polyolefin as internally modified by reacting a polyolefin with an acid anhydride and chlorine, and is, for example, produced by reacting chlorine and an acid anhydride upon a polyolefin, wherein either one of the chlorine and the acid anhydride may be reacted upon the polyolefin earlier than the other. The reaction with the chlorine is, for example, carried out by introducing a chlorine gas into a solution containing a polyolefin. In addition, the reaction with the acid anhydride is, for example, carried out by reacting the acid anhydride upon a polyolefin (or poly(olefin chloride)) in the presence of a peroxide.
Examples of the polyolefin include: polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-propylene-diene copolymers and polybutene; and hydrogenated products from copolymers such as styrene-butadiene-isoprene copolymers. These may be used either alone respectively or in combinations with each other. Among these, polypropylene is preferable because it is easily available and gives high adhesion.
Examples of the acid anhydride, as used for the modification, include maleic anhydride, citraconic anhydride and itaconic anhydride.
The acid anhydride-modified poly(olefin chloride) has a chlorine content in the range of preferably 10 to 30 weight %, more preferably 18 to 22 weight %. In the case where the chlorine content is less than 10 weight %, the composition has a low solubility into solvents, and the acid anhydride-modified poly(olefin chloride) is difficult to emulsify. On the other hand, in the case where the chlorine content is more than 30 weight %, the adhesion to the plastic materials is inferior and the gasohol resistance is also deteriorated.
Iida Hiroshi
Itakura Tatsuya
Mizuguchi Katsumi
Nishimura Izumi
Ogawa Takeshi
Aylward D.
Dawson Robert
Honda Giken Kogyo Kabushihi Kaisha
Roylance Abrams Berdo & Goodman L.L.P.
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