JPH10235287A - Coating and protecting method of metallic base body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable coating and protection of a metallic base body with a water-based coating material having excellent performances as a coating film comparable to a solvent-based coating material by preparing a water-based coating material containing an acryl polymer of a specified compsn. and a specified org. solvent and then applying the coating material to specified film thickness as a topcoat of a metal base. SOLUTION: Nonfunctional (meth)acrylates (a-1) having 4 to 12C hydrocarbon groups or these esters (a-1) and aromatic vinyl monomers (a-2), monofunctional unsatd. monomers (b) having polyethylene glycol groups, and α,β-ethylenically unsatd. carboxylic acids (c) are used as the monomer component. The water- based coating material is prepared from a water-based resin dispersion (A) described below and an org. solvent (B) having >100 solubility with water at 20 deg.C. The water-based resin dispersion (A) contains (a-1) or (a-2) b about >=65wt.% of the whole polymerizable unsatd. monomers and about 3 to about 6wt.% of the sum of (b) and (c), 6wt.% and has the weight ratio of (b)/(c) ranging from about 1 to about 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention provides a new and useful
The present invention relates to a method of protecting the coating of metal materials. More specifically, the present invention uses, as a so-called top coat, an aqueous coating based on an aqueous dispersion of a specific composition and an aqueous resin dispersion of a vinyl solvent having a low solvent content,

[0002] Primarily to various metal structures, such as bridges, tanks, ships or towers, or various so-called metal members, such as accessories, road signs, fences or vehicle bodies, or parts, respectively. By letting it be painted on the surface, etc., the organic solvent content is small, and the coating film is especially excellent in stain resistance and gloss,

[0003] It is also excellent in other physical properties of the coating film. It not only improves the appearance but also improves the stain resistance and the function of preventing the deterioration of the base material such as corrosion over a long period of time. The present invention relates to a method for protecting a metal base material, which is extremely practical and very valuable, which can be maintained.

[0004]

2. Description of the Related Art Various paints have been studied and proposed for improving the appearance and protection of various metal materials and various metal products. Of these, solvent-based alkyd paints have been applied as top coats, but the coatings, in particular, are inferior in weather resistance, chemical resistance and stain resistance, and are frequently Currently, solvent-based acrylic paints are mainly used because of the necessity of repainting.

[0005] In recent years, as a part of measures to prevent environmental pollution, it has become a place where a reduction in the amount of evaporated organic solvent at the time of coating has started to be demanded, and various aqueous paints have been studied. I have.

[0006] Such aqueous paints are based on emulsion polymers and so-called colloidal dispersions in which the resin is self-emulsified and dispersed (or dissolved) in the presence of a water-soluble co-solvent. Are roughly divided into

However, the water-based paint based on the emulsion polymer, which is conventionally used, has a low organic solvent content, but is formed by a process in which resin particles are fused together to form a film. In, the smoothness and the like of the coating film surface is impaired, and in turn, the gloss is impaired, and as a result, it is extremely difficult to obtain a coating film having good stain resistance and the like. ,
Due to the effect of the emulsifier contained, the foamability of the coating material is increased, and in addition, the coating film has, in particular, poor water resistance and poor adhesion to a substrate.

On the other hand, in the case of an aqueous coating based on a colloidal dispersion, the smoothness of the surface of the coating film can be improved more easily than that based on an emulsion polymer. It is generally inferior to the resin-based form, and if it is to be further improved, the content of the water-soluble solvent must be increased, It is an unfavorable paint for environmental pollution prevention.

Further, because of a so-called polar group such as a carboxyl group introduced to obtain self-emulsifying dispersibility,
It was also difficult to obtain sufficient coating properties such as sufficient water resistance, corrosion resistance and chemical resistance.

[0010] Among the various coating properties, the smoothness of the dried coating film is not limited to the high-gloss appearance, but also to prevent contamination of the coating film after coating. It is needless to say that the performance is also important from the viewpoint.

[0011]

As described above, as long as the conventional technology as described above is followed, a low acid value, which is suitable for protection and appearance of a metal substrate, and
Water-based paint for metal substrates, which has a low solvent content, is high in gloss, has good water resistance, etc., and provides various coating properties as solvent-based paint, The reality was that it could not be obtained.

However, in view of the above-mentioned various drawbacks in the conventional technology, the present inventors have sought a water-based paint capable of providing a coating film having extremely high practicality as described above. Diligently, the research has begun.

[0013] Therefore, the problem to be solved by the present invention is, on the one hand, to have excellent coating properties of a specific composition, which are comparable to solvent-based paints. A water-based coating for room temperature drying or forced drying, which has high gloss and low organic solvent content, is used as a top coat for metal substrates, especially with a constant film thickness. An object of the present invention is to provide an extremely practical method for protecting a metal substrate by coating.

[0014]

[Means for Solving the Problem] Accordingly, the present inventors have
As a result of intensive studies to solve various unresolved problems in the conventional technology, a vinyl polymer having a specific composition, particularly an acrylic polymer (acrylic resin), The kind and the amount of the organic solvent, as an essential component, and further, an aqueous paint comprising a curing agent also as an essential component, with a constant film thickness, for a metal substrate Only by applying it as a top coat, there is little so-called danger such as prevention of environmental pollution and fire during painting, and construction can be done easily,
In addition, the present inventors have found that they exhibit an excellent protective effect on the substrate, which is unprecedented, and completed the present invention.

That is, the present invention basically comprises, as one part, non-functional (meth) acrylates (a-1) each having a hydrocarbon group having 4 to 12 carbon atoms.
Or the non-functional (meth) acrylates (a-1) and the aromatic vinyl monomer (a-2)
And a monofunctional unsaturated monomer (b) having a polyethylene glycol group and an α, β-ethylenically unsaturated carboxylic acid (c) as essential polymerizable unsaturated monomer components, Each of the monomers (a-1) is used alone or in combination with the monomer (a-1).
In the form of a combination of the monomer (a-1) and the monomer (a-
The combination of cases 2) is also referred to as monomer (a). About 65% by weight or more in all polymerizable unsaturated monomers, and the sum of the above-mentioned monomer (b) and the above-mentioned monomer (c) is about 3 to 6% by weight. And an aqueous resin dispersion (A) having a self-water dispersibility, in which the ratio by weight of (b) / (c) is in the range of about 1 to about 5,

An organic solvent (B) having a boiling point in the range of about 130 to about 220 ° C. under normal pressure and a solubility of water of 100 or more at 20 ° C. as an essential component,

Furthermore, this organic solvent (B) is added to the above-mentioned aqueous resin dispersion (A) in a proportion of 100 parts by weight of solids.
About 20% by weight or more, and the total amount of organic solvent in the water-based paint is about 15% by weight or less.
This water-based paint is used as a top coat for metal substrates.
It is intended to provide a method for protecting the coating of a metal substrate, which comprises applying a coating having a film thickness of about 20 to about 150 micrometers or microns (μm).

Two, the above-mentioned specific aqueous resin dispersion (A) having self-water dispersing ability, the above-mentioned specific organic solvent (B), and the curing agent (C) are indispensable. And the organic solvent (B)
Is contained in an amount of about 20% by weight or more based on 100 parts by weight of the solid content of the aqueous resin dispersion (A), and the total amount of the organic solvent in the aqueous paint is about 15% by weight or less. At the same time, this water-based paint is
It is an object of the present invention to provide a method for protecting a metal substrate from coating, which comprises applying a coating to a film thickness of about 20 to about 150 μm.

Specifically, according to the present invention, each of the aqueous resin dispersions (A) described above has a number average molecular weight of about 100% in terms of polystyrene equivalent by gel permeation chromatography (GPC). 8,000 to about 20,000 and a weight average molecular weight of about 15,000
0 to about 50,000 and an acid value in terms of solid content of about 3 to about 18 mgKOH / g. To offer,

Further, the above-mentioned aqueous resin dispersion (A)
In particular, the number average molecular weight is about 8,000 to about 20,000 in terms of polystyrene equivalent molecular weight by GPC,
And having a weight average molecular weight of about 15,000 to about 50,000.
0, the aqueous resin dispersion (A)
Has a hydroxyl value of about 30 to about 120 mg in terms of solid content.
KOH / g, and a polyisocyanate compound is used as the curing agent (C), and the polyisocyanate compound has an NCO group / O
An object of the present invention is to provide a method for protecting a metal substrate from coating, which is formulated so that the equivalent ratio of H groups is in the range of about 0.5 to about 2. It is.

[0021]

DETAILED DESCRIPTION OF THE INVENTION Thus, the present application provides, in part,
Nonfunctional (meth) acrylates (a-1) having a hydrocarbon group having 4 to 12 carbon atoms, or the nonfunctional (meth) acrylates (a-1) and aromatic vinyl A monomer (a-2), a monofunctional unsaturated monomer having a polyethylene glycol group (b),
-The ethylenically unsaturated carboxylic acid (c) as an essential monomer component, and these (a-1) or (a-2)
Is contained in the total polymerizable unsaturated monomer in an amount of about 65% by weight or more, and the sum of the monomer (b) and the monomer (c) is about 3 to about 6% by weight. And an aqueous resin dispersion (A) having a self-water dispersibility having a weight part ratio of (b) / (c) in the range of about 1 to about 5; In the range of 130 to about 220 ° C., and
An organic solvent (B) having a solubility of water of 100 or more at 20 ° C. is contained as an essential component, and the organic solvent (B) is mixed with the solid content of the aqueous resin dispersion (A). It comprises about 20% by weight or more based on 100 parts by weight, and the total amount of organic solvent in the water-based paint is about 15% by weight or less. As a coat, about 20 to about 200 micro
It claims that a method for protecting the coating of a metal substrate, which comprises applying a coating to a thickness of a meter or a micron (μm),

Second, non-functional (meth) acrylic acid esters having a hydrocarbon group having 4 to 12 carbon atoms (a)
-1) or the nonfunctional (meth) acrylates (a-1) and the aromatic vinyl monomer (a-2)
And a monofunctional unsaturated monomer (b) having a polyethylene glycol group, and an α, β-ethylenically unsaturated carboxylic acid (c) as essential monomer components.
1) or (a-2) is contained in the total polymerizable unsaturated monomer in an amount of about 65% by weight or more, and the sum of the above-mentioned monomer (b) and the above-mentioned monomer (c) Is about 3 to about 6% by weight, and the ratio by weight of (b) / (c) is in the range of about 1 to about 5; And the boiling point under normal pressure is about 130 to about 220
The organic solvent (B) having a solubility of water within 100 ° C. and 20 ° C. of 100 or more, and a curing agent (C) as essential components. ) Is adjusted to a solid content of 10 of the above aqueous resin dispersion (A).
0% by weight, containing about 20% by weight or more, and the total amount of organic solvent in the water-based paint is about 15% by weight or less.
As a coat, it is also claiming a method of protecting the coating of the metal base material, which comprises applying a coating having a thickness of about 20 to about 200 μm,

In the present invention, the aqueous resin dispersion (A) has a number average molecular weight of about 8,000 to about 20,000 in terms of polystyrene-equivalent molecular weight by GPC.
00 and a weight average molecular weight of about 15,000 to about 5
It claims that a specific coating protection method for a metal substrate, which comprises using an acid value in the range of 000 and an acid value in terms of solid content of about 3 to about 18 mgKOH / g, is claimed. Is the thing,

Further, the present invention relates to the aqueous resin dispersion (A) having a number average molecular weight of about 8,000 to about 20,000 in terms of polystyrene equivalent molecular weight by GPC.
00 and a weight average molecular weight of about 15,000 to about 5
Within a range of about 000, and a hydroxyl value in terms of solid content of about 3 to about 120 mgKOH / g, and a polyisocyanate compound is used as the curing agent (C). , The polyisocyanate compound has an NCO group /
Claimed is a specific method of protecting a metal substrate, which is formulated so as to have an equivalent ratio of OH groups within a range of about 0.5 to about 2. Things.

In the following, the present invention will be described in more detail, particularly the constitution and effects of the present invention.

That is, in carrying out the method for protecting a metal substrate from coating according to the present invention, the above description is of the aqueous resin dispersion (A). It is necessary that the composition be composed of a polymerizable unsaturated monomer.

First, examples of the polymerizable unsaturated monomer include non-functional (meth) acrylates (a-1) having a hydrocarbon group having 4 to 12 carbon atoms. The monomer (a-1) itself is an essential component in order to improve the water resistance, chemical resistance, weather resistance, and the like of the obtained coating film.

As typical examples of the nonfunctional (meth) acrylates (a-1), only typical (non-functional) (meth) acrylates (a-1) are exemplified by normal (n-) butyl (meth) acrylate and iso (i- ) Butyl (meth) acrylate, tertiary (tert-) butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate, as well as cyclohexyl (meth) acrylate or benzyl (meth) acrylate or lauryl (meth) acrylate But these are 1
Used as a seed or a mixture of two or more.

The use of (meth) acrylic esters having a hydrocarbon group having more than 12 carbon atoms inevitably reduces the adhesion of the obtained coating film, especially the adhesion to a substrate, and therefore, such The overuse of a class of (meth) acrylates is truly discouraged.

In addition, styrene, vinyltoluene, p-tert-butylstyrene, and the like may be mentioned as examples of only the above-mentioned aromatic vinyl monomers. The monomers are of a class used as necessary, particularly for improving the corrosion resistance and chemical resistance of the coating film.

The amount of these aromatic vinyl monomers to be used in the total polymerizable unsaturated monomer, that is, the polymerizable unsaturated monomer, Desirably, it is less than about 40% by weight, based on monomers.

The total of the above-mentioned non-functional (meth) acrylic acid esters and the aromatic vinyl monomers is included in the total amount of the polymerizable unsaturated monomers, that is, the amount of the polymerizable unsaturated monomer. It is absolutely necessary, and preferably not less than about 70% by weight, based on the total amount of the body.
It is appropriate to use it in such a way.

Next, the above-mentioned monofunctional unsaturated monomer (b) having a polyethylene glycol group will be described, but only typical examples of such polymerizable unsaturated monomers will be described below. By way of example only, mono (meth) acrylates of polyethylene glycol and the like, and further, their terminal hydroxyl groups can be formed by various alkoxyl groups such as methoxy groups and ethoxy groups by a conventional method. It is in the form of a blockade.

Further, among the polyethylene glycol group-containing monofunctional unsaturated monomers (b), specific examples of commercially available products are described as follows: "Blemmer PME400, PME4000, AE350 or PE350 "[the above products are products of Nippon Oil & Fats Co., Ltd.] or" NK Ester M-90G "," the same M-230G "[the above products are products of Shin-Nakamura Chemical Co., Ltd.], or" NF Visomer S " -10W, S-20W, MPEG
350MA or PEM6E [the above are products of Daiichi Kogyo Seiyaku Co., Ltd.].

These improve not only the hydrophilicity and the like of the aqueous resin dispersion (A), but also the water dispersibility thereof, and also improve the pigment dispersibility and the like.
From the viewpoint of improving the water retention, etc., the polymerizable unsaturated is essential in the sense that the resulting coating film, in particular, delays the surface drying property and contributes to the development of high gloss. It is a monomer component.

The molecular weight of the polyethylene glycol group in the polyethylene glycol group-containing monofunctional unsaturated monomer (b) is as follows.
When a compound having a molar addition product or less, that is, a compound obtained by adding 3 moles or less of ethylene oxide is used, the effect of improving hydrophilicity, pigment dispersibility, water retention, etc., as described above, respectively, is low. Easy to become,

On the other hand, when a compound having an ethylene oxide adduct of 50 mol or more, that is, a compound to which at least 50 mol of ethylene oxide has been added, is used, the obtained coating film, particularly, the adhesion to a substrate is reduced. In each case, special attention is required.

In the case of a non-crosslinked type paint, that is, in the case of a non-crosslinked type water-based paint (hereinafter, also simply referred to as a paint), there are two types: one having a terminal hydroxyl group and one having a terminal alkoxyl group-blocking type. Can be used without discrimination, but in the case of an isocyanate cross-linking paint, the use of a form having a terminal hydroxyl group is faster in the cross-linking reaction,
It is even more preferred.

Next, the α, β-ethylenically unsaturated carboxylic acid (c) will be described. The polymerizable unsaturated monomer is used in the aqueous resin dispersion (A). In particular, hydrophilicity, water dispersion stability and pigment dispersibility are improved, and in addition, the resulting coating film, in particular, is an essential polymerizable unsaturated monomer component for imparting substrate adhesion and the like. Yes,

Of those, only typical ones are exemplified, and various unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid, and further, fumaric acid, maleic acid and the like can be used. Various unsaturated dicarboxylic acids, such as acids, itaconic acids or citraconic acids;
Alternatively, there are various monoalcohol esters (half esters) of these unsaturated dicarboxylic acids, and these are used as one kind or as a mixture of two or more kinds.

The monofunctional unsaturated monomer (b) having a polyethylene glycol group described above and the α, β-
The sum of the amounts used with the ethylenically unsaturated carboxylic acid (c) is
The resulting coating film, among others, such as gloss, water resistance and substrate adhesion, etc., should be determined from the balance of various coating film properties,

The sum of the amounts of these monomers (b) and (c) used in the total monomers is about 3 to about 6
% By weight and the ratio by weight of these monomers (b) / monomers (c) is suitably in the range of about 1 to about 5. .

If the sum of the amounts of the components (b) and (c) is too large, exceeding about 6% by weight,
In particular, the resulting coating film has high hydrophilicity and the like, and thus tends to have poor corrosion resistance and water resistance. On the other hand, if the sum is less than about 3% by weight, the water dispersibility of the resin itself is low. Either case is not preferred because it becomes inferior.

In both of these components, the above (b)
When the weight part ratio of / (c) is less than about 1, the obtained coating material has insufficient water retention, and it becomes easy to obtain a smooth coating film or a high gloss coating film. On the other hand, if the ratio by weight exceeds 5 and becomes too large, the pigment dispersibility of the resin itself and the adhesion of the obtained coating material to the base material tend to be deteriorated.

The aqueous resin dispersion (A) itself has an acid value of about 3 to 3 from the viewpoint of water resistance, alkali resistance and adhesion to a substrate.
Suitably in the range of about 18 mg KOH / g, preferably in the range of 6 to 15 mg KOH / g.

In addition, only typical representative examples of other polymerizable unsaturated monomers capable of being copolymerized include methyl (meth) acrylate, ethyl (meth) acrylate and n. (Meth) acrylates having various alkyl groups having 3 or less carbon atoms, such as -propyl (meth) acrylate or i-propyl (meth) acrylate;

Various vinyl esters, such as vinyl acetate, vinyl benzoate or "Veova" (trade name of vinyl versatate, Shell Co., Netherlands); perfluorocyclohexyl (meth) acrylate or di-perfluoro Various perfluoroalkyl group-containing monomers such as cyclohexyl fumarate; or various cyano group-containing monomers such as (meth) acrylonitrile;

Various (halogenated) olefins such as ethylene or propylene, vinyl chloride or vinylidene chloride or vinyl fluoride, as well as glycidyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) ) Acrylamide,
(Meth) acryloyloxyalkyl acid phosphate or N, N-dimethylaminoethyl (meth) acrylate,

Methacryloxypropyltrimethoxysilane, alkoxylated polypropylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate,
2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate or di-2-hydroxyethyl fumarate,

Polyethylene glycol (meth) acrylate having a polyethylene glycol group having a molecular weight of less than 250, cyclohexyl dimethanol mono (meth) acrylate or “Placcel FM or FE monomer” [ε-caprolactone-added monomer manufactured by Daicel Chemical Industries, Ltd.] And other functional group-containing monomers, for example, as represented by the following, but the present invention is by no means limited to only these illustrative examples.

In particular, the above-mentioned (meth) acrylic esters do not at all hinder the use of a polymerizable unsaturated monomer having a hydrocarbon group having more than 12 carbon atoms. Such other copolymerizable unsaturated monomers that can be copolymerized are used for the purpose of improving the hardness, pigment dispersibility, substrate adhesion, etc. of the resulting coating film. It is appropriately selected and used in the monomer, that is, in an amount of about 32% by weight or less based on the total amount of the polymerizable unsaturated monomers.

The molecular weight of the aqueous resin dispersion (A) depends on the balance of durability and film forming property of the resulting coating film, the viscosity of the aqueous resin dispersion (A) itself, and the paint quality. The number average molecular weight is about 8.0 in terms of polystyrene-equivalent molecular weight determined by gel permeation chromatography (GPC) in consideration of the viscosity and the like.
Suitably, the weight average molecular weight is in the range of about 15,000 to about 50,000.

The method for preparing the dispersion (A) and the method for polymerization are not particularly limited, but the solution polymerization is carried out in the presence of a part or all of a so-called water-soluble organic solvent (B) as described later. It is desirable in the process to disperse in water or carry out dispersion polymerization in the presence of water-soluble organic solvent (B) and water.

The glass transition temperature (Tg) of the aqueous resin dispersion (A) is not particularly limited, and is determined in consideration of, for example, the base material, the application, the drying method, and the coating composition. First, in the case of a non-crosslinked paint, the theoretical Tg is about 40 in consideration of the balance of stain resistance, water resistance and toughness of the obtained coating film.
It is preferably in the range of from about to about 80C, while in the case of a cross-linking paint in combination with polyisocyanate, the theoretical Tg is preferably in the range of from about 10 to about 60C.

The carboxyl group in the aqueous resin dispersion (A) is desirably neutralized with a volatile basic substance also from the viewpoint of, for example, stability and pigment dispersibility of the paint. If only typical representative examples of such basic substances are given, ammonia, triethylamine, monoethanolamine, diethanolamine, dimethylethanolamine or 2-amino-
Such as 2-methyl-1-propanol,

The present invention is by no means limited to only these illustrative examples. However, in the case of crosslinking with a polyisocyanate curing agent type, it is better to avoid using a base having a reactive hydrogen atom in the molecule, such as ammonia.

Also, these basic substances are:
For iron-based substrates, directly, when painted, is a compound that is also useful as a primary rust inhibitor, but on the other hand, it can also be a volatile organic solvent component, it can also cause odor, Excessive use should truly be refrained.

Next, in carrying out the method for protecting the coating of a metal substrate according to the present invention, the above-mentioned organic solvent (B), which is one of the other essential components, will be described.

The organic solvent (B) is mainly distributed in the particles of the aqueous resin dispersion (A) and the aqueous phase in the aqueous paint used in carrying out the method of the present invention. It improves the film-forming properties of the body (A), and at the time of drying the coating film, delays the drying property of the coating film surface, and develops a high gloss of the coating film, and is further obtained by mixing with water. It is an essential component that lowers the surface tension of the paint, thereby improving the dispersibility of the pigment and the wettability of the paint to the base material, as well as improving the coating workability and the base material adhesion.

From such a viewpoint, it is necessary to select a solvent having a sufficient hydrophilicity and at the same time having a boiling point within an optimum range.
That is, the solubility of water at 20 ° C. needs to be 100 or more.

Such a solvent having a water solubility of less than 100 is
In general, although the swelling effect of resin particles is high, it is difficult to obtain a high gloss coating film, and therefore, a large amount of solvent must be used, which is not desirable in preventing environmental pollution. That is.

On the other hand, the boiling point is about 13 at normal pressure.
It must be in the range of 0 to about 220 ° C. When the boiling point is less than about 130 ° C., in any case, during the drying process of the coating film, it becomes easy to volatilize with water as the main solvent,
Eventually, a coating film having both high smoothness and gloss tends to be difficult to obtain, while if the boiling point is too high beyond about 220 ° C., by any means, even after forming the coating film, Either case is not preferable because the solvent easily remains in the coating film, and as a result, the coating film contaminant accompanying the softening of the coating film and the initial water resistance tend to decrease.

As the organic solvent (B) which can be used in the present invention, only typical ones are exemplified, and 3-methoxybutanol, 3-methoxy-3-methylbutanol, ethylene glycol monoethyl ether, ethylene glycol Glycol mono (n- or i-) propyl ether, ethylene glycol mono (n-, i- or tert-) butyl ether,

Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono (n- or i-) propyl ether or propylene glycol mono (n-, i- or tert-)
Butyl ether,

Or dimethylformamide or the like, or N-methylpyrrolidone or ethylene glycol methyl ether acetate, but the present invention is by no means limited to only these examples.

The amount of these solvents to be used may be one or two or more in consideration of the coating (drying) conditions and the solubility based on the composition and molecular weight of the aqueous resin dispersion (A) itself. The mixture is appropriately selected and used.
It is desirable to use about 20% by weight or more based on 100 solids of the aqueous resin dispersion (A). If the amount used is less than about 20% by weight, the effect of use becomes insufficient.

The content of the organic solvent in the obtained paint includes the specific organic solvent (B) as described above from the viewpoint of measures against disasters such as ignition and burning of the paint and measures against environmental pollution. In form, it should be no more than about 15% by weight, preferably no more than 12% by weight.

If too much is used in excess of about 15% by weight, depending on the type of solvent, generally,
The paint ignites and burns easily, and thus the storage of the paint, the coating method and the drying step are greatly restricted, and it is also undesirable in terms of environmental pollution prevention measures.

Organic solvents other than the above-mentioned specific organic solvent (B) may be added in an amount as described above in order to improve, for example, drying properties, leveling, film forming properties and freeze stability. It does not in any way prevent them from being used together within the limits of the above. When carrying out polyisocyanate crosslinking, it is preferable to use a large amount of aprotic solvent.

Next, the pigment will be described. When carrying out the method for protecting the coating of a metal substrate according to the present invention, it can be used as a clear coating in the form of no pigment, but it is mainly used for coloring, concealment, hardness of a coating film, drying property, and adhesion of a substrate. For the purpose of imparting various functionalities such as properties, rust prevention, ultraviolet shielding, and design, various known and commonly used pigments can be used as needed.

Of those, only typical ones are exemplified, and titanium oxide, calcium carbonate, barium sulfate, mica, silica, talc, clay,
Various inorganic pigments such as red iron oxide, iron black, zinc oxide, mapico yellow, carbon black, aluminum powder, barium metaborate or calcium phosphate;

Alternatively, in addition to various organic pigments such as quinacridone red or phthalocyanine blue, commercially available aqueous dispersion pigments in which these various pigments are dispersed in an aqueous medium can be used.

The amount of the pigment used is not particularly limited, but it is appropriate to use the pigment within a range of about 120 parts by weight or less based on 100 parts by weight of the solid content of the aqueous resin dispersion (A). is there.

In particular, if it is used in excess of about 120 parts by weight, the resulting coating film is liable to deteriorate in smoothness and gloss, and as a result, the appearance of the coating film, particularly,
This is not preferred because not only does the visual clarity tend to be inferior, but also the stain resistance after outdoor exposure significantly deteriorates.

However, it does not prevent the pigments and the like from being appropriately selected and used for a specific purpose or the like, and intentionally lowering the gloss value.

In the present invention, by introducing a hydroxyl group into the above-mentioned aqueous resin dispersion (A), a crosslinked paint in a form combined with a polyisocyanate crosslinker can be obtained. In particular, it is a desirable place to improve weather resistance, water resistance, stain resistance and solvent resistance. In particular, in the case of an object to be coated which may be unavoidably applied with a solvent-based paint in the future, it is a desirable place to prevent lifting.

In order to introduce a hydroxyl group into this aqueous resin dispersion (A), it is most convenient to copolymerize the above-mentioned hydroxyl group-containing polymerizable monomer. Could be done.

Here, if only typical representative examples of the polyisocyanate compound are given,
Various aromatic diisocyanates, such as tolylene diisocyanate or diphenylmethane diisocyanate; various alicyclic diisocyanates, such as hexamethylene diisocyanate or trimethylhexane diisocyanate;

Or isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6) -diisocyanate, 4,4′-methylenebis (cyclohexyl diisocyanate) or 1,3- (isocyanatomethyl) cyclohexane cycloaliphatic isocyanates;

Alternatively, these diisocyanates and various polyhydric alcohols such as ethylene glycol, polyether polyols (polyethylene glycol, polypropylene glycol, polycaprolactone polyol, etc.), trimethylolethane or trimethylolpropane may be further used. Is a so-called low-molecular-weight polyester resin having a functional group reactive with an isocyanate group, a so-called low-molecular-weight acrylic copolymer, or an adduct with water or the like;

Alternatively, a burette form or a multimer, etc., which is particularly representative of them, and a specific example of such a form may be mentioned as "Barnock D-
750, D-800, DN-950 or DN-90
1S "[the above is a product of Dainippon Ink and Chemicals, Inc.] and the like.

Here, each of these polyisocyanate compounds may be used in the form of an emulsified dispersion thereof, or may be used in the form of a water-soluble or water-dispersible polyisocyanate compound, for example, "BAY
HYDUR LS-2980 or LS-2032 "
(These are Bayer products) or "Aquanate 10
0, 110, 200 or 210 "[the above products are products of Nippon Polyurethane Industry Co., Ltd.], and may be used in the form of various aqueous polyisocyanate compounds. It is not limited only to the illustrated example.

In the form of using such a polyisocyanate compound as a so-called curing agent or crosslinking agent,
In the case of a so-called polyisocyanate cross-linking system, the hydroxyl value per solid content of the aqueous resin dispersion (A) described above (hereinafter, also referred to as a solid content hydroxyl value) is an improvement in various physical properties of the obtained coating film. Is suitably in the range of about 30 to about 120, and preferably 50 to 10
Suitably, it is in the range of zero.

At this time, the mixing ratio of the polyisocyanate compound (C) and the above-mentioned aqueous resin dispersion (A) is such that the NCO group in the former compound (C) and the latter resin dispersion (A) Ratio to the OH groups in the
The equivalent ratio of group / OH group is suitably in the range of about 0.5 to about 2, and is preferably compounded in the range of 0.8 to 1.3.

In carrying out the method for protecting the coating of a metal substrate according to the present invention, iron, a plated steel sheet, an iron-based alloy, aluminum And various products such as, for example, bridges, tanks and their piping;

Various metal structures such as ships and steel towers or their attached members; various automobile parts such as for repairing automobile exteriors, chassis, etc .; various industries such as bulldozers Machinery; furthermore, various construction members such as metal fences, etc., and the drying and curing means at that time is suitably room temperature drying or forced drying.

The coating method at this time is also not limited at all, and may be, for example, brush coating, spray coating or roller coating, or a shower coater or curtain coater.
Various known coating methods or means can be used.

In addition, there is no restriction on applying a rust preventive paint or a primer as an undercoat depending on the purpose of coating. Regarding the coating thickness at that time, in order to express the excellent properties of the coating film of the water-based coating used in the present invention, the coating is applied within a range of about 20 to about 150 μm with an average dry film thickness. It is desirable.

The water-based paint used in the present invention may contain various known and commonly used paint additives within a range not departing from the object of the present invention and within a range not impairing the effects of the present invention. Can be used.

If only typical examples of such additives are given as examples, defoamers, leveling agents,
Thixants, rust inhibitors, drying regulators, dispersants, thickeners, ultraviolet absorbers, antioxidants, preservatives, fungicides, antistatic agents, charge regulators, film forming aids, plasticizers , A crosslinking catalyst, a freeze stabilizer, a water repellent or a wetting agent.

[0091]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples. However, the present invention is by no means limited to only these illustrative examples. Absent. In the following, all parts and percentages are by weight unless otherwise specified.

Reference Example 1 (Preparation example 1 of aqueous resin dispersion)

In a reaction vessel equipped with a reflux condenser, a stirrer and a nitrogen inlet tube, ethylene glycol mono-n-
330 parts of butyl ether was charged, and stirring was started while the temperature was raised to 110 ° C.

In a nitrogen stream, at the same temperature, 330 parts of styrene and 39 parts of 2-ethylhexyl methacrylate
5 parts, 240 parts of methyl methacrylate, 10 parts of acrylic acid and "NK ester M230G" [Methoxylated polyethylene glycol (23, manufactured by Shin-Nakamura Chemical Co., Ltd.)
Mol), a monomer mixture consisting of 25 parts of

An initiator mixture consisting of 20 parts of tert-butylperoxy-2-ethylhexanoate and 10 parts of tert-butylperoxybenzoate and 30 parts of ethylene glycol mono-n-butyl ether were added for 3 hours. And added in parallel.

Thereafter, the reaction was completed by further adding 5 parts of tert-butyl peroxybenzoate and maintaining the same temperature for 6 hours.
After cooling to 80 ° C., 13 parts of triethylamine was added, and 1,130 parts of ion-exchanged water was further added, followed by mixing and dispersing with a homogenizer.

The desired aqueous resin dispersion thus obtained is a milky white liquid having a solid content of 40%
And the viscosity at 25 ° C. (the same applies hereinafter) is 4,000 mP
a.sec. The acid value of the solid content is 8, and the number average molecular weight is 1 as determined by molecular weight measurement in terms of polystyrene by gel permeation chromatography (GPC).
The molecular weight was 1,000, the weight average molecular weight was 25,000, and the organic solvent content was 15%. Hereinafter, this is abbreviated as DS-1.

Reference Example 2 (Preparation example 2 of aqueous resin dispersion)

The monomer mixtures were respectively 200 parts of 2-ethylhexyl methacrylate, 350 parts of n-butyl methacrylate, 200 parts of cyclohexyl methacrylate, 200 parts of methyl methacrylate, 20 parts of methacrylic acid, and “NK-ester”. M90G ”(trade name of methoxylated polyethylene glycol (9 mol) methacrylate manufactured by Shin-Nakamura Chemical Co., Ltd.) and 15 parts of“ Blemmer PME4000 ”[manufactured by NOF Corporation
Methoxylated polyethylene glycol (90 mol) methacrylate].

A desired aqueous resin dispersion was obtained in the same manner as in Reference Example 1, except that the addition amount of triethylamine was changed to 23 parts. The aqueous resin dispersion obtained here was milky white and had a solid content of 40% and a viscosity of 5,000 mPa · sec. And the acid value of the solid content was 13, and the number average molecular weight was 12,000 as determined by GPC based on polystyrene-equivalent molecular weight.
And the weight average molecular weight is 27,000, and
The organic solvent content was 16%. Hereinafter, this is abbreviated as DS-2.

Reference Example 3 (Preparation example 3 of aqueous resin dispersion)

As the initially charged solvent, 150 parts of ethylene glycol mono-i-propyl ether and 180 parts of ethylene glycol methyl ether acetate were changed to be used, and as a monomer mixture,
In each case, 300 parts of styrene, 400 parts of n-butyl methacrylate, 100 parts of methyl methacrylate, β
-150 parts of hydroxyethyl methacrylate, 10 parts of acrylic acid, 10 parts of "NK-ester M230G" and "NF-Visomer PME6E" [polyethylene glycol (6 mol) monomethacrylate manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] An aqueous resin dispersion was obtained in the same manner as in Reference Example 1, except that 30 parts of [Product Name] was changed to use.

The target aqueous resin dispersion thus obtained was milky white and had a solid content of 40%
And the viscosity is 5,000 mPa · sec. The acid value of the solid content is 8, the hydroxyl value of the solid content is 70, and the number average molecular weight is 1
It was 1,000, the weight average molecular weight was 27,000, and the organic solvent content was 15%. Hereinafter, this is abbreviated as DS-3.

Reference Example 4 (Preparation example 4 of aqueous resin dispersion)

In a reaction vessel equipped with a reflux condenser, a stirrer and a nitrogen inlet tube, ethylene glycol mono-i-
200 parts of propyl ether and 70 parts of N-methylpyrrolidone were charged, and stirring was started while heating to 110 ° C.

Under a nitrogen stream, 505 parts of n-butyl methacrylate, 200 parts of i-butyl methacrylate, 90 parts of methyl methacrylate, 155 parts of β-hydroxyethyl methacrylate, 20 parts of acrylic acid, “NK
—Ester M230G ”, 10 parts,“ NF-Visomer P ”
ME6E "[trade name of polyethylene glycol (6 mol) monomethacrylate manufactured by Daiichi Kogyo Seiyaku Co., Ltd.]
A monomer mixture consisting of 0 parts,

Tert-butyl peroxy-2-ethylhexanoate (25 parts) dissolved in 30 parts of N-methylpyrrolidone with an initiator mixture in the form of 6 parts each
0% was added over 2 hours while maintaining the same temperature.

Thereafter, the temperature was maintained at the same temperature for one hour, and then, while adding 1,170 parts of ion-exchanged water and 13 parts of triethylamine, the inside of the reaction vessel was heated to 95%.
The temperature was lowered to ° C.

Further, the remainder of the monomer mixture and the initiator mixture are added at the same temperature over 1 hour.
The polymerization reaction was continued by adding 5 parts of tert-butylperoxy-2-ethylhexanoate and maintaining the same temperature for 2 hours.

After cooling to 80 ° C., 13 parts of triethylamine were added thereto. Then, it was treated with a homogenizer to obtain an intended aqueous resin dispersion.

The aqueous resin dispersion obtained here was milky white and had a solid content of 40% and a viscosity of 2,5.
00 mPa · sec. And the solid content acid value is 15, and
The hydroxyl value of the solid content was 70, and the number average molecular weight was 13,00 as determined by molecular weight measurement in terms of polystyrene by GPC.
0, the weight average molecular weight was 45,000, and the organic solvent content was 13%. Hereinafter, this is abbreviated as DS-4.

Reference Example 5 (Preparation example 5 of aqueous resin dispersion)

As the monomer mixture, 200 parts of 2-ethylhexyl methacrylate, 350 parts of n-butyl methacrylate, and 200 parts of cyclohexyl methacrylate were used.
Parts, 200 parts of methyl methacrylate and 50 parts of methacrylic acid, and the control was carried out in the same manner as in Reference Example 1 except that the addition amount of triethylamine was changed to 59 parts. An aqueous resin dispersion was obtained.

The aqueous resin dispersion thus obtained is milky white and has a solid content of 40% and a viscosity of 5,
000 mPa · sec. The acid value of the solid content was 32, and the polystyrene-equivalent molecular weight measured by GPC was:
The number average molecular weight is 11,000, the weight average molecular weight is 24,000, and the organic solvent content is 17
%. Hereinafter, this is abbreviated as DS-5 '.

Reference Example 6 (Preparation example 6 of aqueous resin dispersion)

600 parts of ethylene glycol mono-n-butyl ether was charged, and stirring was started while the temperature was raised to 110 ° C. In a nitrogen stream, at the same temperature, a monomer mixture consisting of 300 parts of styrene, 400 parts of 2-ethylhexyl methacrylate, 280 parts of methyl methacrylate and 20 parts of acrylic acid, and tert-butyl peroxy-2-ethyl An initiator mixture consisting of 15 parts of hexanoate and 10 parts of tert-butyl peroxybenzoate, ethylene glycol mono-n
30 parts of butyl ether were added in parallel over 4 hours.

Thereafter, 5 parts of tert-butyl peroxybenzoate was further added, and the temperature was maintained at the same temperature for 8 hours to complete the reaction. After cooling to 80 ° C, triethylamine 2
6 parts and 860 parts of ion-exchanged water were further added and mixed and dispersed by a homogenizer.

The obtained aqueous resin dispersion for control was a translucent liquid having a solid content of 40%.
% And a viscosity of 6,000 mPa · sec. And the acid number of the solid content is 13, the number average molecular weight is 11,000, and the number average molecular weight is 11,000,
The weight average molecular weight was 23,000, and the organic solvent content was 27%. Hereafter, this is DS
Abbreviated as -6 '.

Reference Example 7 (Preparation example 7 of aqueous resin dispersion)

As the monomer mixture, 400 parts of ethyl acrylate and 55 parts of methyl methacrylate were used, respectively.
0 parts, 20 parts of methacrylic acid, "NK-ester M90
G "and 15 parts of" Blemmer PME4000 "
A control aqueous resin dispersion was obtained in the same manner as in Reference Example 1, except that 5 parts were used and the addition amount of triethylamine was changed to 23 parts.

The aqueous resin dispersion thus obtained was milky white and had a solid content of 40% and a viscosity of 6,
000 mPa · sec. The acid value of the solid content is 13, and the polystyrene-equivalent molecular weight is measured by GPC.
Number average molecular weight is 12,000 and weight average molecular weight is 2
6,000, and the organic solvent content was 16%. Hereinafter, this is abbreviated as DS-7 '.

Reference Example 8 (Preparation example 8 of aqueous resin dispersion)

As the monomer mixture, 300 parts of styrene and 3 parts of 2-ethylhexyl methacrylate were used, respectively.
50 parts, 280 parts of methyl methacrylate, 50 parts of “NK ester M230G” and “Blemmer PME4
000 ", except for using 20 parts
A control aqueous resin dispersion was obtained in the same manner as in Reference Example 1.

The aqueous resin dispersion obtained here was milky white and had a solid content of 40% and a viscosity of 3.0%.
00 mPa · sec. And the solid content acid value is 0, and G
The number average molecular weight was 12,000, and the weight average molecular weight was 2
It was 8,000, and the organic solvent content was 15%. Hereinafter, this is abbreviated as DS-8 '.

Examples 1 to 8 and Reference Examples 1 to 10

Each of the aqueous resin dispersions obtained above was formed into a paint by the following procedure, and further, as a comparative product,
Solvent paint and acrylic emulsion gloss paint
Each was applied to various substrates and dried and cured.
Evaluation tests for various properties of each coating film were performed.

The results are collectively shown in Tables 1, 2 and 3. Table 1 shows the physical properties of the non-crosslinked paint at the time of coating (drying at room temperature), and Table 2 shows the results. Table 3 shows the physical properties of the isocyanate crosslinked paint at the time of application (normal temperature drying), and Table 3 shows the physical properties of the crosslinked and non-crosslinked paint at the time of application (forced drying).

Formulation Example 1 of non-crosslinked water-based paint

Aqueous resin dispersion (solid content = 40%) 125 parts “Typek R930” [trade name of titanium oxide manufactured by Ishihara Sangyo Co., Ltd.] 82 parts “Nopco 8034” [manufactured by San Nopco Co., Ltd.] Product name of foaming agent] 0.2 parts Ion-exchanged water 0 to 10 parts サ ン ド Sand mill dispersion, 1 hour ────────────

(Let down prescription)

Aqueous resin dispersion 125 parts Deionized water 0 to 20 parts

Paint solids 52-54% Pigment weight concentration (PWC) 45% Paint viscosity Adjusted to 70-76 KU (Stomer viscometer; the same applies hereinafter) by ion-exchanged water in the mixing ratio table.

Resins used DS1 and 2 and DS5 ', 6', 7 'and 8'

Formulation Example 2 of non-crosslinked solvent-based paint

Using “Acrydic A181X” [trade name of acrylic-styrene resin for lacquer, manufactured by Dainippon Ink and Chemicals, Ltd .; solid content = 45%, xylene solvent] A target paint having a solid content of 40% and a PWC of 45% was prepared according to Formulation Example 1 of the aqueous paint (where the diluting solvent was changed to xylene).

Formulation Example 3 of Crosslinked Water-based Paint

Aqueous resin dispersion (solid content = 40%) 125 parts “Taipec R930” 100 parts “Nopco 8034” 0.2 parts Ion exchange water 10 parts {Sand mill dispersion, 1 hour} ───────────

(Let down prescription)

Aqueous resin dispersion 125 parts Ion-exchanged water 10 to 30 parts 配合 Hardener compound ──────────── “Aquanate 210” / water = 1 / 150 to 74 parts

Paint solids 52-55% PWC 42-44% NCO / OH equivalent ratio 0.8-1.2 Paint viscosity Adjusted to 70-76 KU by ion-exchanged water in the mixing ratio table.

Resin used DS3 and 4

"Aquanate 210": trade name of water-dispersible polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd .; free isocyanate group content (NCO = 17%)

Formulation Example 4 of Crosslinking Solvent-Based Paint

"Acrydic A801" (trade name of acrylic polyol manufactured by Dainippon Ink and Chemicals, Inc .; solid content = 50%, solid content hydroxyl value = 100, toluene / n-butyl acetate solvent) One piece, "Barnock DN
-950 "(a polyisocyanate compound manufactured by the same company;
Using solid content = 75%, ethyl acetate solvent, NCO = 12%), the solid content is 44%, the PWC is 43%, and the NCO / OH equivalent ratio is 1 (the diluent solvent is n-butyl acetate). ) Was prepared.

Formulation Example 5 of Emulsion Paint

Using “Boncoat EC889” [trade name of acrylic / styrene-based emulsion for glossy paint manufactured by Dainippon Ink and Chemicals, Inc .; solids content = 50%], the following compounding ratio was used. Was prepared.

Ion-exchanged water 42 parts 10% aqueous solution of sodium tripolyphosphate 1.6 parts "Demol NL" [dispersant manufactured by Kao Corporation] 1.2 parts Ethylene glycol 5.2 parts "Best Side FX" [Large] Nippon Ink Co., Ltd., trade name of preservative] 0.3 parts "SN Deformer 373" [San Nopco Co., Ltd., defoamer trade name] 0.2 parts "Typek R930" 81 parts分散 Dispersing dispersion, 2 hours ──────────── “Boncoat EC889” 200 parts “Texanol” (film-forming aid) 15 parts 3% “cellosize QP4400H” aqueous solution (Thickener) 5 parts 28% ammonia water 0.3 part 15% "UH438" (thickener) 6 parts "SN deformer 373" 0.7 parts Ion exchange water 22 parts ─────── ──── ─ stirring ────────────

Paint solids 48% PWC 45% Paint viscosity 73 KU

“Texanol”: trade name of a solvent for a film-forming aid manufactured by Eastman Kodak Company, USA

[0150] "Cellosize QP4400H" ... A brand name of hydroxyethylcellulose manufactured by Union Carbide, USA

"UH438": trade name of a thickener manufactured by Asahi Denka Co., Ltd.

Formulation Example 6 of water-based rust-proof undercoat

"Watersol CD-550LA"
[Product name of aqueous vinyl-modified epoxy ester resin manufactured by Dainippon Ink and Chemicals, Inc .; solid content = 40%, solid content acid value = 25, solvent = water / ethylene glycol mono i-
Propyl ether] and the PWC is 40%
Calcium carbonate = 1/1 (parts by weight)].

(Application Test Conditions)

Preparation of base material:

○ Polished mild steel sheet [Japan Test Panel Co., Ltd.]
And a size of 150 × 70 × 0.6 mm], which is hereinafter abbreviated as a substrate I.

Undercoated polished mild steel sheet The above-mentioned polished mild steel sheet was coated with the above-mentioned undercoating composition as in the water-based rust-preventive undercoating composition example 6 so as to have a dry film thickness of 60 μm. After that, it was prepared by leaving it at room temperature for one week and drying it. Hereinafter, this is abbreviated as substrate II.

ア ル ミ An aluminum plate [having a size of 150 × 70 × 0.6 mm, manufactured by Japan Test Panel Co., Ltd.], which is hereinafter abbreviated as substrate III.

Coating: On each substrate,
After coating with a bar coater so that the dry film thickness becomes 60 μm, the coating is dried under predetermined conditions, and then the polyester adhesive film (product of Nippon Test Panel Co., Ltd.) is used to seal the area other than the coating. Like that.

Drying at room temperature: After coating, under the conditions of a temperature of 20 ° C. and a relative humidity of 65%,
They were allowed to dry for weeks.

Forced drying: 80% after painting.
After drying at ℃ for 10 minutes, further under the condition that the temperature is 20 ℃ and the relative humidity is 65%,
They were allowed to dry for a week.

Flash point measurement: Measurement was performed using a creepland open type flash point measuring device.

Initial light spot: After the coated plate of the base material I was dried under predetermined conditions, the specular reflectivity became 20 ° and 60 °, respectively, with a reflection gloss meter.
Both gloss values were measured.

-Actual exposure contamination resistance: 1-Takasago, Takaishi-shi, Osaka
In the Sakai Plant of Dainippon Ink and Chemicals Co., Ltd., the contamination state of the appearance of the coated plate after six months of exposure was visually determined.

Accelerated weathering resistance: Each coated plate was subjected to a test for 1,000 hours using a sunshine weather meter, and a gloss value at 60 ° specular reflectance was measured. The gloss value after the test was measured. And its initial gloss value, and was expressed as gloss retention (GR%).

Water resistance: Each coated plate was
After immersion in tap water at 0 ° C. for 30 days, a change in the state of the coating film was visually determined.

Alkali resistance: each coated plate
After immersion in a 2% NaOH, saturated Ca (OH) ₂ aqueous solution at 0 ° C. for 30 days, a change in the state of the coating film was visually determined.

Oxidation resistance: Each coated plate was treated with 1
After being immersed in a 30% aqueous sulfuric acid solution for 30 days, the state change of the coating film was visually determined.

Solvent resistance: The coating on the glass coated plate was rubbed 20 times with gauze containing xylene, and the state change of the coating was visually determined.

Corrosion resistance: Each coating film was cross-cut with a cutter knife until it reached the substrate, and then subjected to a salt spray tester (5% saline solution at a temperature of 35 ° C.). The test is carried out for a predetermined period of time, followed by rinsing with water, drying for 2 hours, and then using cellophane tape to cross-
A peeling test was performed on the cut portion, and the width (mm) of the peeled piece at that time was measured.

[0171]

[Table 1]

<< Footnotes in Table 1 >> Evaluation criteria: ○: good △: slightly poor ×:
Bad

[0173]

[Table 2]

[0174]

[Table 3]

[0175]

[Table 4]

<< Footnotes in Table 2 >> Evaluation criteria: ○: good △: slightly poor ×:
Bad

[0177]

[Table 5]

[0178]

[Table 6]

<< Footnotes in Table 3 >> Evaluation criteria:…: good △: slightly poor
Bad

[0180]

[Table 7]

[0181]

As is clear from Tables 1, 2 and 3, the water-based paint used in the present invention, when applied to a metal substrate, is comparable to a solvent-based paint, Outstanding than conventional paints, unprecedented in the past, especially, with excellent protection effect of the substrate and excellent coating appearance,

In addition, the organic solvent content is low, so that the risk of ignition and the risk of combustion are both low,
It is easy to understand that the construction is simple and that it is extremely practical in terms of environmental pollution prevention measures and resource saving.

As described above, the present invention can be easily and easily found to be extremely practicable and innovative as a method for protecting a metal substrate from being coated. Like.

Claims (4)

[Claims] 1. A non-functional (meth) acrylate (a-1) having a hydrocarbon group having 4 to 12 carbon atoms or a non-functional (meth) acrylate (a)
-1) and an aromatic vinyl monomer (a-2), a monofunctional unsaturated monomer having a polyethylene glycol group (b), and an α, β-ethylenically unsaturated carboxylic acid (c)
And (a-1) or (a-2) in the total polymerizable unsaturated monomer in an amount of about 65%.
% By weight, and the sum of the monomer (b) and the monomer (c) is about 3 to about 6% by weight; and
An aqueous resin dispersion (A) having a self-water dispersibility having a weight part ratio of (b) / (c) in the range of about 1 to about 5; and a boiling point at normal pressure of about 130 to about 220. And an organic solvent (B) having a solubility of water of 100 or more at 20 ° C. in the range of 100 ° C. and an organic solvent (B). About 20% by weight or more based on 100 parts by weight of the solid content of the dispersion (A), and the total amount of the organic solvent in the aqueous paint is about 1%
The water-based paint is characterized in that the water-based paint has a thickness of about 20 to about 200 micrometers or micron (μm). A coating protection method for a metal substrate, characterized in that: 2. A non-functional (meth) acrylate (a-1) having a hydrocarbon group having 4 to 12 carbon atoms or a non-functional (meth) acrylate (a)
-1) and an aromatic vinyl monomer (a-2), a monofunctional unsaturated monomer having a polyethylene glycol group (b), and an α, β-ethylenically unsaturated carboxylic acid (c)
And (a-1) or (a-2) in the total polymerizable unsaturated monomer in an amount of about 65%.
% By weight, and the sum of the monomer (b) and the monomer (c) is about 3 to about 6% by weight; and
An aqueous resin dispersion (A) having a self-water dispersibility having a weight part ratio of (b) / (c) in the range of about 1 to about 5; and a boiling point at normal pressure of about 130 to about 220. The organic solvent (B) having a solubility of water within 100 ° C. and 20 ° C. of 100 or more, and a curing agent (C) as essential components. ) Based on 100 parts by weight of the solid content of the aqueous resin dispersion (A) described above, and the total amount of the organic solvent in the aqueous paint is about 15% by weight or less. In addition, the water-based paint is applied as a top coat of the metal base material so as to have a thickness of about 20 to about 200 micrometers or micron (μm). Paint protection method. 3. The water-based resin dispersion (A) has a number average molecular weight of about 8,000 as determined by gel permeation chromatography in terms of polystyrene equivalent molecular weight.
About 20,000 and a weight average molecular weight of about 15,
The method according to claim 1, wherein the acid value is in the range of 000 to about 50,000, and the acid value in terms of solid content is in the range of about 3 to about 18 mgKOH / g. 4. The method according to claim 1, wherein the aqueous resin dispersion (A) has a number average molecular weight of about 8,000 as determined by gel permeation chromatography in terms of polystyrene. ~ About 20,
000 and the weight average molecular weight is in the range of about 15,000 to about 50,000, and the aqueous resin dispersion (A) has a hydroxyl value of about 30 to
Within the range of about 120 mgKOH / g, and
The curing agent (C) is a polyisocyanate compound, and the polyisocyanate compound has an NCO group / O
A coating protection method for a metal substrate, characterized in that it is blended so as to have an equivalent ratio of H group within a range of about 0.5 to about 2.