JP2003138225A - Coating composition for primer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition for a primer which, when applied to a steel sheet, can form a coating film excellent in properties such as workability and resistances to scratch, corrosion, and boiling water. SOLUTION: This coating composition for a primer comprises (A) 100 pts.wt. hydroxyl-group-containing resin, (B) 10-40 pts.wt. at least one cross-linker selected from among amino resins and blocked polyisocyanate compounds, and (C) 1-10 pts.wt. resol phenol resin cross-linker. A coated steel sheet is prepared by using the composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to scratch resistance,
The present invention relates to a primer coating composition capable of forming a coating film having excellent corrosion resistance, boiling water resistance, processability, and the like.

[0002]

2. Description of the Related Art Conventionally, precoated metal sheets such as precoated steel sheets coated by coil coating are used for building materials such as roofs, walls, shutters and garages of buildings, various home appliances, switchboards, and freezer showcases. Widely used as housing-related products such as steel furniture and kitchen appliances.

In recent years, in order to improve the workability of precoated steel sheets, it has been required to improve the workability of the primer used therein, and a part or all of the base resin is changed from an epoxy resin to a polyester resin having good workability. They are replaced (see Japanese Patent Laid-Open No. 6-220355) or the cross-linking agent is replaced with an amino resin by a polyisocyanate resin. However, the primer coating film thus obtained becomes soft, which causes problems such as a reduction in coating film hardness and a reduction in corrosion resistance. In order to compensate for this, increasing amounts of pigments such as rust preventive pigments and extender pigments and increasing the crosslink density have been studied, but with these methods, the adhesion between the coating film and the metal material decreases and scratch resistance Tends to decrease significantly.

The object of the present invention is to maintain the processability of the coating film,
Another object of the present invention is to provide a coating composition for a primer having good scratch resistance, and to provide a coated metal plate using the coating composition for a primer.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a coating composition containing a hydroxyl group-containing resin and an amino resin or a blocked polyisocyanate compound is further used as a resol-type phenol resin. By adding a cross-linking agent, it was found that the adhesion with the material can be improved without lowering the workability, and the scratch resistance can be greatly improved, and the present invention has been completed.

Thus, according to the present invention, 10 to 40 parts by weight of at least one crosslinking agent selected from (B) an amino resin and a blocked polyisocyanate compound, and ( There is provided a coating composition for a primer, which comprises C) 1 to 10 parts by weight of a resol type phenol resin crosslinking agent.

Also provided is a coated metal plate using the above coating composition for a primer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The coating composition for a primer of the present invention comprises at least one cross-linking agent (B) selected from a hydroxyl group-containing resin (A), an amino resin and a blocked polyisocyanate compound, and a resol type phenol resin cross-linking agent. The agent (C) is contained as an essential component.

Hydroxyl group-containing resin (A) The hydroxyl group-containing resin, which is the component (A) of the present invention, is a resin containing a hydroxyl group in the molecule, such as epoxy resin,
Examples thereof include polyester resins, acrylic resins, and modified products of these resins, and these can be used in combination. Generally, epoxy resins have excellent hardness and corrosion resistance but poor processability, while polyester resins have excellent processability but tend to have poor hardness and corrosion resistance.
Epoxy-modified polyester resin having the characteristics of both resins is particularly preferable among them.

The hydroxyl group-containing polyester resin is an acid component mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid,
Also, it can be obtained by reacting an alcohol component mainly containing dialcohol.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, or their lower alkyl esters and acid anhydrides, and one or more of them can be used. As the aliphatic dicarboxylic acid, adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, hymic acid, 1,6-cyclohexanedicarboxylic acid and the like can be used. Lower alkyl esters of these dicarboxylic acids, acid anhydrides and the like may be used. These may be used alone or in combination of two or more.
As the acid component, a small amount of monocarboxylic acid or trivalent or higher carboxylic acid can be used in addition to the above dicarboxylic acid. Examples of monocarboxylic acids include pt-butylbenzoic acid, and examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, trimesic acid, methylcyclohexene tricarboxylic acid, and acid anhydrides of these acids. And so on.

Examples of dialcohols used in the polyester resin include ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol and neopentyl. Glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentanediol, diethylene glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 2-methyl-1,3 -Propanediol, 2,
2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, xylylene glycol or hydrogenated bisphenol A, and ethylene oxide or propylene oxide adduct of bisphenol A. You can These are a kind,
Alternatively, two or more kinds may be mixed and used. As the alcohol component, a trihydric or higher alcohol can be used in addition to the dialcohol. Examples of the alcohol include trimethylolethane, trimethylolpropane, glycerin, pentaerythritol and the like.

Further, a part of the above acid component and alcohol component is replaced with dimethylolpropionic acid, oxypivalic acid, paraoxybenzoic acid, etc .; lower alkyl esters of these acids; oxyacid components such as lactones such as ε-caprolactone. You can also The polyester resin can be produced by a conventionally known esterification reaction or ester conversion reaction using the above acid component and alcohol component, and optionally an oxyacid component.

Examples of the epoxy resin include a bisphenol type epoxy resin and a novolac type epoxy resin; and modified epoxy resins obtained by reacting various modifying agents with the epoxy groups or hydroxyl groups in these epoxy resins. In the production of the modified epoxy resin, the timing of modification with the modifying agent is not particularly limited, and the modification may be performed at an intermediate stage of the epoxy resin production or at a final stage of the epoxy resin production.

The above bisphenol type epoxy resin is, for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, epichlorohydrin and bisphenol. It may be any resin obtained by condensing into a low molecular weight epoxy resin in the presence of a catalyst such as a catalyst and subjecting the low molecular weight epoxy resin and bisphenol to a polyaddition reaction.

Examples of the bisphenol include bis (4-
Hydroxyphenyl) methane [bisphenol F],
1,1-bis (4-hydroxyphenyl) ethane, 2,
2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-) Hydroxy-tert-butyl-phenyl) -2,2-propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, Examples thereof include bis (2-hydroxynaphthyl) methane, and among them, bisphenol A and bisphenol F are preferably used. The above bisphenols can be used alone or as a mixture of two or more.

Commercially available bisphenol type epoxy resins include, for example, Epicoat 828, 812, 815, 820, 834, manufactured by Yuka Shell Epoxy Co., Ltd.
Same 1001, same 1004, same 1007, same 1009, 1010; Araldite AER609 manufactured by Asahi Chiba.
9; and Epomic R-309 manufactured by Mitsui Chemicals, Inc., and the like.

As the novolac type epoxy resin which can be used as the epoxy resin, for example, various novolacs such as phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol glyoxal type epoxy resin having many epoxy groups in the molecule, etc. A type epoxy resin may be mentioned.

Examples of the modified epoxy resin include an epoxy ester resin obtained by reacting the above bisphenol type epoxy resin or novolac type epoxy resin with a drying oil fatty acid; a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid. An epoxy acrylate resin reacted with an isocyanate compound; a urethane-modified epoxy resin reacted with an isocyanate compound; an amine compound is reacted with an epoxy group in the bisphenol type epoxy resin, the novolac type epoxy resin, or the various modified epoxy resins to give an amino group or Examples thereof include amine-modified epoxy resin obtained by introducing a quaternary ammonium salt.

As the epoxy-modified polyester resin,
For example, a reaction product obtained by reacting a polyester resin and an epoxy resin by addition, condensation, grafting or the like can be mentioned. Specifically, a reaction product of a carboxyl group in a polyester resin and an epoxy group-containing resin such as the above-mentioned epoxy resin, a hydroxyl group in the polyester resin and a hydroxyl group in the epoxy resin through a polyisocyanate compound. And the like. The epoxy-modified polyester resin has a glass transition temperature of 10 to 100 ° C., preferably 20 to 70 ° C., and a hydroxyl value of 5 to 50, preferably 10 to 40 in terms of processability and chemical resistance. And a number average molecular weight of 2,000 to 30,000, preferably 30,
The range of 00 to 20,000 is preferable from the viewpoint of workability and coating workability.

In the present invention, the Tg point is measured by
It is based on differential thermal analysis (DSC) using a differential scanning calorimeter, and the number average molecular weight is measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene.

Cross-linking Agent (B) The cross-linking agent (B) of the present invention is added to the above hydroxyl group-containing resin (A) in order to cross-link and cure.
At least one crosslinking agent selected from amino resins and blocked polyisocyanate compounds.

Examples of the amino resin include methylol amino resins obtained by the reaction of an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetogramamine, sterogtanamine, spiroguanamine, and dicyandiamide. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, the above methylolated amino resin etherified with a suitable alcohol can also be used as the amino resin. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

The blocked polyisocyanate compound is a compound obtained by blocking free isocyanate groups of the polyisocyanate compound with a blocking agent.

Examples of the polyisocyanate compound before blocking are aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cyclic aliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; tolylene diisocyanate. Alternatively, an organic diisocyanate itself such as an aromatic diisocyanate such as 4,4′-diphenylmethane diisocyanate, or an adduct of each of these organic diisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or each of the above-mentioned organic compounds Examples thereof include cyclized polymers of diisocyanates, and isocyanate / biuret.

Examples of the blocking agent for blocking the isocyanate group include phenols such as phenol, cresol and xylenol; ε-caprolactam; δ-
Valerolactam, γ-butyrolactam, β-propiolactam and other lactams; methanol, ethanol, n-
Or i-propyl alcohol, n-, i- or t-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Alcohols such as benzyl alcohol; formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime and other oximes; dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, etc. A blocking agent such as the active methylene-based compound can be preferably used. By mixing the polyisocyanate compound and the blocking agent, the free isocyanate group of the polyisocyanate compound can be easily blocked.

Resole type phenolic resin cross-linking agent (C) The phenolic resin cross-linking agent which is the component (C) of the present invention causes a cross-linking reaction with the above-mentioned hydroxyl group-containing resin (A) and greatly contributes to the adhesion to the raw material. Greatly improves scratch resistance. The phenol resin cross-linking agent (C) is a part or all of the methylol group of a methylolated phenol resin obtained by introducing a methylol group by heating a phenol component and formaldehydes in the presence of a reaction catalyst to cause a condensation reaction. Is a resol-type phenolic resin obtained by alkylating ether with alcohol.

In the production of the phenol resin cross-linking agent (C), as the above-mentioned phenol component as a starting material, a bifunctional phenol compound, a trifunctional phenol compound, a
A phenolic compound having a functionality or higher can be used.

As the above-mentioned phenol compound, for example, 2
Examples of the functional phenol compound include o-cresol, p
-Cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, and other bifunctional phenols can be cited. Examples of the trifunctional phenol compound include carboxylic acid, m-
Examples include cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol. Examples of the tetrafunctional phenol compound include bisphenol A and bisphenol F. Among them, scratch resistance is improved. For this purpose, it is preferable to use a trifunctional or higher functional phenol compound, particularly carboxylic acid and / or m-cresol. These phenolic compounds are one kind,
Alternatively, two or more kinds can be mixed and used.

The formaldehydes used in the production of the phenol resin crosslinking agent (C) include formaldehyde, paraformaldehyde, trioxane and the like, and they can be used alone or in admixture of two or more.

The alcohol used for alkyl-etherifying a part of the methylol groups of the methylolated phenolic resin has 1 to 8 carbon atoms, preferably 1 to
Four monohydric alcohols can be preferably used.
Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

The phenol resin cross-linking agent (C) has an average of 0.5 or more, preferably 0.6 or more alkoxymethyl groups per benzene nucleus in view of reactivity with the hydroxyl group-containing polyester resin (A). Those having up to 3.0 are suitable.

In the coating composition of the present invention, the above (A),
The blending amount of the components (B) and (C) is 10 to 40 parts by weight, preferably 15 to 30 parts by weight, and the component (C) 1 to 10 with respect to 100 parts by weight of the hydroxyl group-containing resin (A).
Parts by weight, preferably in the range of 2 to 7 parts by weight, are excellent in terms of workability, hardness and scratch resistance of the coating film.

A curing catalyst may be added, if necessary, in order to enhance the curability of the coating composition of the present invention. When the curing agent (B) contains an amino resin, particularly a low molecular weight methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether, a sulfonic acid compound or amine neutralization of the sulfonic acid compound as a curing catalyst. The thing is used suitably. Typical examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and the like. The amine in the amine neutralized product of the sulfonic acid compound is 1
It may be any of primary amine, secondary amine, and tertiary amine. Among these, the amine neutralized product of p-toluenesulfonic acid and / or the amine neutralized product of dodecylbenzenesulfonic acid is preferable from the viewpoints of the stability of the coating material, the reaction accelerating effect, and the physical properties of the resulting coating film. .

When the curing agent (B) is a blocked polyisocyanate compound, a curing catalyst that promotes the dissociation of the blocking agent of the blocked polyisocyanate compound that is the curing agent is suitable. As a suitable curing catalyst, For example, tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, 2-ethyl. Examples thereof include organometallic catalysts such as lead hexanoate. Since the curing catalyst for amino resin is also effective as a curing catalyst for the phenol resin crosslinking agent (C), the curing catalyst may be used in combination with a curing catalyst that promotes dissociation of the blocking agent.

In the composition of the present invention, a rust preventive pigment is contained as the component (D) in the above resin composition, if necessary. Anticorrosion pigments include chromate pigments such as calcium chromate, strontium chromate, barium chromate, zinc potassium chromate, and tetrabasic zinc chromate; aluminum phosphorus molybdate, aluminum tripolyphosphate dihydrogen phosphate, phosphoric acid. Examples thereof include non-chromium rust preventive pigments such as zinc, barium metaborate, zinc phytate, calcium phytate, organic nitro compound zinc salt, and calcium ion-exchanged amorphous silica. Chromate pigments when corrosion resistance is required,
Of these, calcium chromate, strontium chromate and zinc potassium chromate are preferable. For safety and health,
If a chrome-based pigment cannot be used, a non-chrome-based pigment may be used.

In the composition of the present invention, the rust preventive pigment (D)
Is 120 parts by weight or less, preferably 1 part by weight based on 100 parts by weight of the total solid content of the components (A), (B) and (C).
It is suitable to blend within the range of 0 to 80 parts by weight.

In the composition of the present invention, coloring pigments that can be used in the coating field, such as cyanine blue, cyanine green,
Organic coloring pigments such as azo-based and quinacridone-based organic red pigments; inorganic coloring pigments such as titanium white, titanium yellow, red iron oxide, carbon black, yellow lead, various baked pigments, etc.
If necessary, extender pigments such as talc, clay, silica, mica, and alumina, pigment dispersants, fillers, additives, organic solvents and the like can be added.

As the article to be coated with the composition of the present invention, cold rolled steel sheet, hot dip galvanized steel sheet, galvanized steel sheet, alloy plated steel sheet, aluminum zinc alloy plated steel sheet, aluminum sheet, stainless steel sheet, copper sheet, copper sheet A metal plate such as a steel plate and a tin-plated steel plate is suitable, but it is also applicable to plastics, wood, cement and the like. As a coating method, curtain coating, roll coating, dip coating, spray coating, or the like can be used, and the coating is usually performed so that the coating thickness after drying is within the range of 2 to 10 μm.

When the object to be coated is a metal, the metal surface may be applied as it is if it is not contaminated with a pollutant such as oil. However, in order to improve the adhesion and corrosion resistance of the coating film, a known metal surface is used. It is preferable to perform a treatment, for example, a phosphate-based surface treatment, a chromate-based surface treatment, or a chromic acid-based coating agent.

The coating composition of the present invention is suitable for a primer because it has excellent corrosion resistance. Corrosion resistance can be obtained by applying a top coating composition on the coating film of the coating composition of the present invention in a dry film thickness of about 8 to 50 μm. It is possible to form a comprehensive coating film which is excellent in appearance and good in cosmetic properties. As the top coating, any top coating usually used in the coating field may be used, and examples thereof include oil-free polyester coatings, alkyd resin coatings such as coconut oil-modified alkyd resin coatings, silicone-modified polyester resin coatings, and fluororesin coatings. The curing can be performed under baking conditions suitable for each paint. The coating composition of the present invention can also be used as a so-called double-coating primer in which both surfaces of a metal plate are coated and an overcoat coating film is formed thereon.

When the coating composition of the present invention is roll-coated by the coil coating method, it can be coated by a normal two-roll coating method (so-called reverse coating or natural coating) or a three-roll coating method. For baking, the maximum material temperature (PMT) is usually 1
It can be performed under the conditions of 60 to 250 ° C. and 15 to 60 seconds.

[0043]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. In the following, "part" and "%"
All are based on weight.

Production of Resol-Type Phenolic Resin Crosslinking Agent Production Example 1 100 parts of bisphenol A, 178 parts of 37% aqueous formaldehyde solution and 1 part of sodium hydroxide were added, and the mixture was added at 60 ° C.
After reacting for 3 hours at 50 ° C., it was dehydrated under reduced pressure at 50 ° C. for 1 hour. Then, 100 parts of n-butanol and 3 parts of phosphoric acid were added and reacted at 110 to 120 ° C. for 2 hours. After the completion of the reaction, the obtained solution was filtered to separate the sodium phosphate produced by filtration to obtain a resol-type phenol resin crosslinking agent solution C1 having a solid content of about 50%. The obtained resin had a number average molecular weight of 880, an average number of methylol groups per benzene nucleus of 0.4, and an average number of alkoxymethyl groups of 1.0.

Production Example 2 Production Example 1 except that 100 parts of bisphenol F was used instead of 100 parts of bisphenol A in Production Example 1.
In the same manner as described above, a resol type phenol resin crosslinking agent solution C2 having a solid content of about 50% was obtained. The resulting resin had a number average molecular weight of 750, an average number of methylol groups per benzene nucleus of 0.3, and an average number of alkoxymethyl groups of 1.2.

Production Example 3 The procedure of Production Example 1 was repeated except that 100 parts of m-cresol was used in place of 100 parts of bisphenol A, and a resol type phenol resin crosslinking agent solution C3 having a solid content of about 50% was prepared. Obtained. The resulting resin had a number average molecular weight of 750, an average number of methylol groups per benzene nucleus of 0.3, and an average number of alkoxymethyl groups of 1.2.

Production Example 4 188 parts of carboxylic acid, 324 aqueous 37% formaldehyde solution
Parts were placed in a flask and heated to 50 ° C. to uniformly dissolve the contents. Next, add zinc acetate and mix to adjust the pH of the system.
Was adjusted to 5.0, heated to 90 ° C. and reacted for 5 hours. Then, after cooling to 50 ° C. and slowly adding a 32% calcium hydroxide aqueous dispersion to adjust the pH to 8.5,
The reaction was carried out at 50 ° C for 4 hours. After the reaction was completed, the pH was adjusted to 4.5 with 20% hydrochloric acid, and then the resin component was extracted with a mixed solvent of xylene / n-butanol / cyclohexanone = 1/2/1 (weight ratio) to neutralize the catalyst. The salt was removed, and then azeotropic dehydration was performed under reduced pressure to obtain a resol-type phenol resin crosslinking agent solution C4 having a solid content of about 60%. The obtained resin is
It had a number average molecular weight of 320, an average number of methylol groups of 1.3 and an average number of alkoxymethyl groups of 0.2 per benzene nucleus.

Production Example 5 In a four-necked flask equipped with a reflux tube, a thermometer and a stirrer,
108 parts of p-cresol, 216 parts of 37% aqueous formaldehyde solution and 160 parts of 25% aqueous sodium hydroxide solution were charged and reacted at 50 ° C. under a nitrogen stream, and then 10
The temperature was raised to 0 ° C., the reaction was continued at 100 ° C. for an additional 1 hour, the mixture was neutralized with hydrochloric acid, the resin component was extracted with a mixed solvent of n-butanol / xylene = 1/1 (weight ratio), and then coexisting under reduced pressure It was dehydrated by boiling to obtain a resol-type phenol resin crosslinking agent solution C5 having a solid content of about 60%. The obtained resin had a number average molecular weight of 350, an average number of methylol groups per benzene nucleus of 0.7, and an average number of alkoxymethyl groups of 0.1.

Preparation Example of Coating Composition for Primer Example 1 Byron 96CS (manufactured by Toyobo Co., Ltd., epoxy modified polyester resin solution, solid content 40%, number average molecular weight of resin is about 14,000 and glass transition temperature is about 70 ° C.) ) 250
Parts (100 parts by solid content), titanium white 36 parts, aluminum tripolyphosphate 60 parts and mixed solvent [Solvesso 1
50 (manufactured by Esso Oil Co., Ltd., aromatic hydrocarbon solvent) / cyclohexanone = 1/1] were mixed in an appropriate amount and dispersed until the lump (particle diameter of coarse pigment particles) was 20 μm or less. This dispersion is then placed on the desmodul BL-3
175 (Sumitomo Bayer Urethane Co., HDI isocyanurate type polyisocyanate compound solution blocked with methyl ethyl ketoxime, solid content 75%) 26.7
Parts (20 parts by solid content), 10 parts of the resol-type phenolic resin crosslinking agent solution C1 obtained in Production Example 1 (5 by solid content).
Part), NACURE 5225 (manufactured by King Industries, USA, amine salt of dodecylbenzenesulfonic acid,
0.5% of active ingredient 25%, Takenate TK-1 (manufactured by Takeda Pharmaceutical Co., Ltd., organotin blocking agent dissociation catalyst, solid content about 10)
%) 2 parts and uniformly mixed, and further the above mixed solvent was added to adjust the viscosity to about 80 seconds (Ford cup # 4/25 ° C.) to obtain a primer coating composition.

Examples 2-14 and Comparative Examples 1-6 Coating compositions for primers were obtained in the same manner as in Example 1 except that the compositions shown in Table 1 below were used.

The blending amount in Table 1 is NACURE.
5225 is indicated by the amount of active ingredient, and other components are indicated by parts by weight of solid content.

[0052]

[Table 1]

[0053]

[Table 2]

Each note in Table 1 is as follows. Beckolite M-6159-60: manufactured by Dainippon Ink and Chemicals,
Polyester resin solution, solid content 60%, number average molecular weight of resin is about 2,600 Epokey 820-40CX: Mitsui Chemicals, urethane modified bisphenol A type epoxy resin solution, solid content 40
%, The number average molecular weight of the resin is about 6,000, the glass transition temperature is about 64 ° C. Sumimar M-55: Sumitomo Chemical Co., Ltd., methylated methylol melamine resin solution, solid content 70% Melan 28: Hitachi Chemical Co., Ltd., Butyl etherified melamine resin solution, solid content 60%.

Preparation of Test Coated Plates Examples 15-34 and Comparative Examples 7-18 The above Examples 1-
14 and the primer coating compositions obtained in Comparative Examples 1 to 6 were coated with a bar coater so that the dry film thickness was 5 μm, and the maximum material reaching temperature was 220 ° C.
Each primer coated plate was obtained by baking for 2 seconds. Then, a top coat paint was applied on these primer-coated plates by a bar coater so that the dry film thickness was about 15 μm, and baked for 30 seconds so that the maximum temperature reached to the material was 220 ° C. to obtain each test coated plate. It was

Table 2 below shows the combination of the material type, primer type, and top coating material of each test coated plate.

The contents of the materials and the topcoat paint in Table 2 are as follows.

[Material Type] M1: 0.35 mm hot-dip galvanized steel sheet, plating basis weight 250 g / m ² M2: 0.35 mm zinc-aluminum alloy-plated steel sheet (aluminum content in plating about 5% by weight) M3: 0 .35 mm zinc-aluminum alloy plated steel plate (aluminum content in plating about 55% by weight) M4: 0.5 mm aluminum plated steel plate M5: 0.5 mm aluminum plate.

[Top coating] T1: KP color 1580 blue (manufactured by Kansai Paint Co., Ltd.,
Polyester-based top coating, blue, glass transition temperature of cured coating approx. 70 ° C) T2: P color 1580 white (Kansai Paint Co., Ltd.,
Polyester-based top coating, white, glass transition temperature of cured coating about 70 ° C) T3: KP color 1510 blue (manufactured by Kansai Paint Co., Ltd.,
Polyester-based top coating, blue, glass transition temperature of cured coating is about 50 ° C).

Coating Film Performance Test Coating film performance tests were conducted on the coated test plates obtained in Examples 15 to 34 and Comparative Examples 7 to 18 in accordance with the following test method. The test results are shown in Table 2 below.

Test method Scratch resistance: At room temperature of 20 ° C., a coin scratch tester (manufactured by KOKAI Giken Kogyo Co., Ltd.) was used and the edge of a 10 yen copper coin was kept at an angle of 45 degrees on the coated surface of the coated plate and 3 kg
10mm copper coin 10mm /
The degree of scratches when the coated surface was scratched by pulling about 30 mm at a speed of 2 seconds was evaluated according to the following criteria. ⊚: No metal base is found on the scratched part ○: Slight metal base is found on the scratched part △: Metal base is considerably seen on the scratched part ×: Almost all coating film is on the scratched part You can see the metal base cleanly.

Corrosion resistance: The coated plate was cut into a size of 70 × 150 mm, and the back surface and the cut surface were sealed with a rust preventive paint. A cross cut that reaches the substrate is placed in the center of the sealed paint plate, and a 3T bending process is performed at a point approximately 1 cm from the end of the paint plate (fold with the surface of the paint plate facing outward and the same thickness as the paint plate inside). 3 pieces were sandwiched, and the coated plate was bent 180 degrees with a vise) and subjected to a salt spray test. The salt spray test is based on JIS Z-237.
The salt spray test time was set to 500 hours, and the degree of rust generation in the processed part and the average blistering width in the cross cut part of each coated plate were visually evaluated according to the following criteria. [Amount of rust generated in the processed part] ◎: No rust generated in the processed part ○: Degree of rust generated is recognized to be less than 10% of the length of the processed part △: Degree of rust generated is processed 10% or more, 30% of part length
X: less than 30% of the length of the processed portion. [Average blistering width of cross-cut part] ⊚: No blistering in cross-cut part ○: Average blistering width on one side from cut scratch is less than 1 mm Δ: Average blistering width on one side from cut scratch is 1 mm that's all,
Less than 5 mm x: The average blistering width on one side from the cut scratch is 5 mm or more.

Boiling water resistance: The coated plate was immersed in boiling water at about 100 ° C. for 5 hours and then pulled up to evaluate the appearance of the coating film surface. ⊚: No abnormalities such as blistering are observed in the coating film ○: Slight blistering is observed in the coating film Δ: Significant blistering is observed in the coating film ×: The coating film is peeled off

Processing adhesion: The coated plate is cut into a size of 70 × 150 mm, and is bent at a room temperature of 20 ° C. for 3T (the surface of the coated plate is bent outward and the inside of the coated plate has the same thickness as the coated plate). 3 plates are sandwiched, the coated plate is bent 180 degrees with a vise, then cellophane adhesive tape is attached to the bent part, and when the tape is instantly peeled off, the coating film peels off at the bent part The degree was evaluated according to the following criteria. As the coated plate, two types were used: a coated plate not subjected to post-treatment (primary) and a coated plate immersed in boiling water for 5 hours after coating (secondary). ◎: No peeling of the coating film in the processed part ○: Slight peeling of the coating film in the processed part △: Significant peeling of the coating film in the processed part ×: Peeling of the coating film on the entire surface of the processed part To do.

[0065]

[Table 3]

[0066]

[Table 4]

[0067]

The coating composition of the present invention is applied to a steel sheet such as a galvanized steel sheet and baked and hardened in a short time to form a coating film excellent in scratch resistance, corrosion resistance, boiling water resistance, workability and the like. It can be formed and is particularly useful as a primer.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 161/06 C09D 161/06 161/20 161/20 175/04 175/04 (72) Inventor Masahiro Murata Kanagawa Paint 4-17-1 Higashi-Hachiman, Kanagawa Prefecture F-term in Kansai Paint Co., Ltd. (reference) 4D075 AE17 AE27 BB26Y BB26Z BB91Y BB92Y BB92Z BB93Y CA02 CA13 CA33 CA38 DA06 DB02 DB04 DB05 DB06 DB07 DB12 DB31 DC16 DC18 DC18 EA EB20 EB22 EB32 EB33 EB34 EB35 EB36 EB38 EB43 EB45 EB52 EB53 EB55 EB56 4F100 AB01A AB03 AB10 AK33B AK35B AK41B AL05B AL05C AL06B BA03 BA25B BA25C CC00B CC00C EH46B EH46C EH71 EJ42B EJ42C JA05B JB02 JK14 YY00B YY00C 4J038 CG141 CG142 DA051 DA052 DA161 DA162 DB061 DB062 DB071 DB072 DB081 DB082 DB391 DB392 DB471 DB472 DD051 DD052 DG301 DG302 GA03 KA03 KA04 MA13 MA14 NA03 NA04 NA11 NA12 PA19 PB0 2 PB05 PB06 PB09 PC02 PC04 PC06 PC08

Claims (5)

[Claims] 1. At least one crosslinking agent 10 to 4 selected from (B) amino resin and blocked polyisocyanate compound based on 100 parts by weight of (A) hydroxyl group-containing resin.
A coating composition for a primer, which contains 0 part by weight and 1 to 10 parts by weight of a (C) resol type phenolic resin crosslinking agent. 2. Resol type phenolic resin cross-linking agent (C)
Has a number average molecular weight of 200 to 200 obtained by reacting a trifunctional or higher functional phenol compound with formaldehydes.
The coating composition for a primer according to claim 1, which is 1,000 resol-type phenolic resin. 3. The trifunctional or higher functional phenol compound is m
-The coating composition for a primer according to claim 2, which is cresol and / or carboxylic acid. 4. The hydroxyl group-containing resin (A) is an epoxy-modified polyester resin having a number average molecular weight of 2,000 to 30,000, a hydroxyl value of 5 to 50, and a glass transition point of 10 to 100 ° C. Claims 1 to 1 characterized in that
The coating composition for a primer according to any one of 3 above. 5. On a metal plate which may be subjected to chemical conversion treatment,
After coating the coating composition according to any one of claims 1 to 4 so that the dry film thickness is 2 to 10 µm, and baking at the material reaching maximum temperature of 160 to 250 ° C for 15 to 60 seconds, Further, a coated metal plate, wherein an overcoat coating film having a dry film thickness of 8 to 50 μm is formed on the coating film.