JP2008106177A - One-pack undercoat composition and coating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-pack undercoat composition which causes, in using as an undercoat of a multilayered coating film, no topcoat exfoliation due to aging even when a coat film having excellent light transmittance such as a metallic or blue paint color is used as a topcoat, and exhibits excellent durability and fine appearance keeping property. <P>SOLUTION: 1. A one-pack undercoat composition comprising (A) an epoxy resin and/or a modified epoxy resin, (B) an ultraviolet light absorber and a photostabilizer, (C) a rust preventing pigment and (D) a solvent, as essential ingredients, is provided. 2. A coating composition described in the section 1 and further comprising (E) a silane coupling agent is provided. 3. A coating composition described in the section 1 or the section 2, wherein, based on 100 pts.mass total resin solid of the (A) epoxy resin and the modified epoxy resin, the compounding amount of the (B) ultraviolet light absorber is 0.1-10 pts.mass and the compounding amount of the photostabilizer is 0.2-20 pts.mass, is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a one-component undercoating composition that is particularly excellent in rust prevention of iron parts, and this coating composition does not cause peeling of the upper coating film over time when used as an undercoat of a multilayer coating film. Gives excellent durability and aesthetic maintenance.

  One-component undercoat paints that use epoxy resin as a binder and rust-preventive pigments are available on the market as general-purpose primers that can be selected from any material type (Reference: Nippon Paint Co., Ltd., “Nippe Show-Biz Product Information”, [on line], [October 6, 2006 search], Internet <URL: http://www.nippe-showbiz.com/function/power_b.html>). Patent Document 1 discloses a one-part primer composition in which an epoxy resin, an aminoalkoxysilane, and a monoepoxy compound are combined. In claim 4, a silane coupling agent having an epoxy group at the end is used as the monoepoxy compound. It is disclosed. The purpose of blending these silane compounds is to improve the adhesion to the steel substrate, and the silane coupling agent terminated with an epoxy group improves the adhesion to steel by comparing with the conventional paint combining epoxy and aminosilane. It discloses that it is effective. There is also a description in the text that it may be combined with an antioxidant. However, there is no description of the effect on the adhesion with the top coat.

  Patent Document 2 discloses a water-based rust preventive coating composition comprising a vinyl polymer having a silyl group, an epoxy resin, and a rust preventive pigment, which contains an ultraviolet absorber, an antioxidant, and the like. Also good things are mentioned. However, the antirust coating composition of the examples does not contain an ultraviolet absorber or an antioxidant, and no mention is made of the effects of using these ultraviolet absorbers and antioxidants. Moreover, evaluation is performed by the single layer coating film, and it is not mentioned about the recoating of topcoat.

Japanese Patent Laid-Open No. 01-92775 Japanese Patent Laid-Open No. 06-41471

  The present invention relates to an undercoating composition comprising (A) an epoxy resin and / or a modified epoxy resin, (B) an ultraviolet absorber and a light stabilizer, (C) an antirust pigment and (D) a solvent as essential components. It is.

  A one-component undercoating paint containing an epoxy resin as a binder and a rust-preventive pigment is used as a two-layer undercoating, and a coating with high light transmittance, such as a metallic or blue-based paint, is applied to the overcoat. In some cases, there was a problem that peeling of the upper coating film was likely to occur over time.

  One-pack type epoxy-based undercoating paint comprising a UV absorber, a light stabilizer and a rust preventive pigment can solve the conventional problems. That is, the features of the present invention are as follows.

  1. A one-component undercoating composition comprising (A) an epoxy resin and / or a modified epoxy resin, (B) an ultraviolet absorber and a light stabilizer, (C) a rust preventive pigment, and (D) a solvent as essential components.

  2. The coating composition according to Item 1, further comprising (E) a silane coupling agent.

  3. (A) The blending amount of the ultraviolet absorber (B) is 0.1 to 10 parts by weight and the blending amount of the light stabilizer is 0 with respect to 100 parts by weight of the total resin solids of the epoxy resin and the modified epoxy resin. 3. The coating composition according to item 1 or 2, which is 2 to 20 parts by mass.

  4). Item 4. The coating composition according to any one of Items 1 to 3, wherein the light stabilizer is a hindered amine compound.

  5. Furthermore, (F) Coating composition as described in any one of said claim | item 1-4 which contains a talc as an essential component.

  6). A coating method in which the coating composition according to any one of the above items 1 to 5 is applied as an undercoat paint, and after being uncured or cured, a topcoat paint is applied again thereon.

  7. Item 7. The coating method according to Item 6, wherein an aminoalkyd coating or aminoacrylic coating is used as the top coating.

  8). Item 7. The coating method according to Item 6, wherein a two-component room temperature curing coating is used as the top coating.

9. An article coated by the coating method according to any one of Items 6 to 8.

As an undercoat paint, it is excellent in rust prevention and material adhesion, and even when a coating film having a high light transmittance is applied repeatedly, peeling of the upper coating film due to aging hardly occurs. As a result, the paint repainting interval can be made longer, which is economical.

  The present invention relates to a primer coating composition. Usually, even if it is a base coat, when combined with a top coat having a high light transmittance, the surface of the base coat film deteriorates due to the ultraviolet rays transmitted through the top coat, which causes weathering peeling of the top coat. In particular, the problem is remarkable when an epoxy resin whose undercoat is easily photodegraded is used as a binder. In order to solve this, it is necessary to suppress the photodegradation of the undercoat coating film. In general, in order to suppress photodegradation, it is a known method to use an ultraviolet absorber and / or a light stabilizer as an additive. However, in the case of outdoor use, which is the intended use of the undercoat coating composition of the present invention, high effect persistence may not be obtained due to the spillage of the additive due to rainwater or the like. Light stabilization, which is generally a polar compound and has a lower molecular weight than UV absorbers, which generally have a π-electron conjugated structure and are hydrophobic and relatively high in molecular weight, with many aromatic and heterocyclic rings. Agent spillage was considered to be the main problem. In addition, it should not impair the substrate adhesion and anticorrosion properties, which are essential properties required for undercoating as well as suppressing light degradation.

As a result of intensive studies, the inventors have invented the primer coating composition of the present invention as satisfying the conditions. The constituent elements will be described below in order.

(A) Epoxy resin or modified epoxy resin The undercoat paint composition of the present invention uses an epoxy resin as its binder. Conventionally, epoxy resins are known to have excellent adhesion to metal materials, and are the resins that have been most adopted as binders for undercoat paints. It is widely known that when it is used as a one-part lacquer paint, it is clearly superior to other types of resin in terms of adhesion (Reference: Daiwa Paint Co., Ltd., N Pro Division, “Paint Joy Communications” 2nd basic knowledge of sealers (undercoating paint) ”, [on line], [October 6, 2006 search], Internet <URL: https://www.diyna.com/webshop/paintjoy/pjm-2. html>).

  Examples of the epoxy resin that can be used in the present invention include an epoxy resin obtained by reacting a polyhydric alcohol, polyhydric phenol, or the like with an excess of epichlorohydrin or alkylene oxide. Examples of polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diglycerol, sorbitol, etc. Examples of phenol include 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], halogenated bisphenol A, 4,4-dihydroxyphenylmethane [bisphenol F], tris (4-hydroxyphenyl) propane, resorcinol , Tetrahydroxyphenylethane, novolac polyhydric phenol, cresol polyhydric phenol, and the like.

  These epoxy resins are commercially available, for example, jER-1001, jER-1004, jER-1007H, jER-404P, jER-1256, jER-154, jER-872 (the above are products manufactured by Japan Epoxy Resin Co., Ltd.), AER, etc. -6003, AER-6071, AER-6072, AER-6097, AER-ECN1273, etc. (above asahi Kasei Chemicals products), EPICLON-N-740-80M, EPICLON-FQ-065-P, etc. Ink Chemical Industry Co., Ltd.).

The modified epoxy resin is a resin obtained by reacting an epoxy resin with some compound. In the present invention, a urethane-modified epoxy resin, an amine-modified epoxy resin, an acrylic-modified epoxy resin, a polyester-modified epoxy conventionally used for one-pack type paints. Resins, dimer acid-modified epoxy resins, and the like can be suitably used. Of these, it is particularly preferable to use a urethane-modified epoxy resin.
Examples of the urethane-modified epoxy resin include those obtained by reacting an amine-added epoxy resin obtained by reacting an amine with an epoxy resin and a polyisocyanate compound or a monoisocyanate compound. As the epoxy resin, those similar to the above-mentioned epoxy resin can be used, and as the amines, alkanolamines, aliphatic amines, aromatic amines, alicyclic amines and the like can be used. As the polyisocyanate compound, conventionally known aliphatic, aromatic or alicyclic polyisocyanate compounds can be used, and as the monoisocyanate compound, aliphatic monoamine or aromatic monoamine reacted with phosgene, or diisocyanate compound. Those obtained by reacting one isocyanate group with a hydroxyl group-containing compound can be used.

  Similarly, an amine-modified epoxy resin, an acrylic-modified epoxy resin, and a polyester-modified epoxy resin each have a functional group capable of reacting with an epoxy group, such as an amino group, a hydroxyl group, or an acid group, on the epoxy resin. A polymer and polyester are reacted. The dimer acid-modified epoxy resin is obtained by reacting a dimer acid, which is a long-chain dibasic acid having a branch formed by bonding two oleic acids, with the epoxy resin.

  These modified epoxy resins are also commercially available, for example, Arachid 9205, Arachid 9208 and the like (above Arakawa Chemical Industries products), EPICLON H-405-40, EPICLON FK753 etc. (above Dainippon Ink and Chemicals products) Epokey 803, Epokey 813, Epokey 820-40CX, Epokey 833-40SC, etc. (the above are Mitsui Chemicals products), jER872X75 (Japan epoxy resin product), etc. are mentioned.

  The epoxy resin and / or modified epoxy resin used in the present invention preferably has a number average molecular weight of 1000 to 300,000 in consideration of the balance of adhesion, water resistance, coating workability, storage stability, and the like. The range is preferably 2000 to 150,000, more preferably 5000 to 100,000.

  The number average molecular weight of the resin in the present specification is a value calculated based on the molecular weight of standard polystyrene from the chromatogram measured by gel permeation chromatography. The gel permeation chromatograph used was “HLC8120GPC” (manufactured by Tosoh Corporation), and the columns were “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL”. Measurement was performed under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI.

  Hereinafter, the epoxy resin and / or modified epoxy resin used as the component (A) in the present invention will be collectively referred to as an epoxy resin.

Moreover, you may add a small amount of other resin, a hardening | curing agent, etc. as needed, such as pigment dispersion. The small amount here is an amount of 10 parts or less when the total solid mass of the epoxy resin is 100 parts. If this range is exceeded, metal material adhesion, which is a feature of epoxy resins, may be hindered.

(B) Ultraviolet Absorber and Light Stabilizer Ultraviolet absorbers absorb other wavelength components (ultraviolet rays shorter than 360 nm) that promote the deterioration of organic substances contained in natural light by efficiently absorbing them. In this case, the organic resin used as a binder is used for the purpose of preventing ultraviolet deterioration. There are many commercially available products, and they are classified by chemical structure. Benzotriazole series: TINUVIN P, TINUVIN 234, TINUVIN 326, TINUVIN 900, etc., triazine series: TINUVIN 1577FF, etc., benzophenone series: CHIMASORB 81, etc., benzoate series: TINUVIN 120 Etc. are known. (All the absorbents under the trade names given as examples are products of Ciba Specialty Chemicals Co., Ltd.)
In the present invention, the chemical structure of the ultraviolet absorber is not limited, and when the total amount of the solid content of the epoxy resin is 100, the addition amount is 0.1 to 10 parts because a sufficient ultraviolet absorption effect can be obtained. Is preferable. On the other hand, when it is more than this, when the top coat is applied, it may bleed at the interface between the top coat and the undercoat and inhibit adhesion.

Light stabilizers have the effect of stopping the progress of resin degradation by stabilizing radicals generated in the process of degradation of organic matter due to light absorption, and synergistic degradation when used in combination with the aforementioned UV absorbers. The prevention effect is expressed. Its action is mainly radical scavenging and detoxification, and the main mode of photodegradation of organic matter is sometimes referred to as an antioxidant because it is oxidative degradation mediated by oxygen in the air. There are many commercially available products, and when classified by chemical structure, hindered amines: CHIMASORB 944, TINUVIN 144, TINUVIN 292, TINUVIN 770, etc., and hindered phenols: IRGANOX 1010, IRGANOX 1098 are known. (All light stabilizers under the trade names given as examples are products of Ciba Specialty Chemicals Co., Ltd.)
In the present invention, the light stabilizer is used in combination with the ultraviolet absorber in order to obtain a synergistic deterioration preventing effect. Thereby, the addition amount of expensive ultraviolet absorbers and light stabilizers can be reduced. The addition amount of the light stabilizer is preferably 0.2 to 20 parts when the total solid mass of the epoxy resin is 100, because a sufficient light stabilization effect (antioxidation effect) can be obtained. . On the other hand, when it is more than this, when the top coat is applied, it may bleed at the interface between the top coat and the undercoat and inhibit adhesion.

As a light stabilizer, any of hindered amines, hindered phenols, and other structures can be suitably used, but when using hindered amines, the deterioration preventing effect is high, Particularly preferred. As a result, the same effect persistence can be obtained with addition of a smaller amount of light stabilizer than other structures. This is because the epoxy resin and / or modified epoxy resin used as a binder for the hindered amine and the paint has a strong interaction including a chemical reaction, so that the effect of suppressing the outflow of the hindered amine light stabilizer from the coating film is manifested. I think it is because.

(C) Rust preventive pigment Although the rust preventive pigment used in the present invention can be those commonly used in the past, it contains harmful metals such as lead and chromium that have been widely used from the viewpoint of preventing environmental pollution. Those that do not are preferred. Examples of such pigments include zinc phosphate, zinc phosphite / zinc oxide complex, aluminum phosphate, calcium phosphate, phosphate such as magnesium phosphate, and molybdate such as calcium molybdate and zinc molybdate. Is mentioned. The addition amount of the antirust pigment is preferably in the range of 10 parts to 200 parts when the total solid mass of the epoxy resin is 100. If it is less than 10 parts, sufficient rust prevention effect may not be obtained, and if it exceeds 200 parts, the coating workability of the paint and the water resistance of the formed coating film may be impaired.

In the undercoat paint composition of the present invention, in order to obtain a desired paint color, it is possible to use a color pigment, extender pigment, or bright pigment (metal flake pigment) that is usually used in paints in combination with a rust preventive pigment.

(D) Solvent The solvent used in the present invention is a good solvent for the epoxy resin as a binder. For example, alcohols such as methanol, ethanol, propanol, butanol, 2-methoxyethanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monoethyl ether, ethers such as diethylene glycol monobutyl ether, acetone, methyl ethyl ketone, Ketones such as 2-pentanone, 2-hexanone, methyl isobutyl ketone, isophorone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol mono Esters such as ethyl ether acetate, toluene, xylene (o , M-, p-) aromatics, and a mixed solvent of two or more of these, and the like. Moreover, you may use water together suitably.

The undercoat coating composition of the present invention is applied after being diluted with a solvent so as to have an appropriate viscosity according to the coating method.

(E) Silane coupling agent The undercoat coating composition of the present invention may contain a silane coupling agent. Silane coupling agents are known to have the effect of improving the adhesion between inorganic substances (metals) and organic compounds, and it is possible to further enhance the adhesion to the base metal by blending with the undercoat paint. .

  Although the coating composition of the present invention exhibits high adhesion even when it is used as an binder with an epoxy resin, the coating film thickness may vary from the set value depending on the material shape and the coating method. For example, even if the film thickness is set to 50 μm, depending on the coating method, the film thickness exceeding 200 μm may be deposited on the inner side of the corner or in the recessed portion. Thus, when there is an abnormal film thickness portion, the coating film distortion generated due to the volatilization of the solvent at the time of drying concentrates and the coating film peeling may occur. By blending a silane coupling agent to enhance the adhesion of the coating film, there is an effect of preventing such peeling.

  On the other hand, the coating film thickness may be thinner than the set film thickness at the corner outer side or the convex part. In this case, for example, when a water resistant load is applied, the thin film portion tends to collect water at the interface with the material, and peeling or rusting may occur. Against this, there is an effect of preventing such peeling and rusting by adding a silane coupling agent to further improve the adhesion of the coating film.

  As described above, the coating film adhesion to the substrate can be increased by blending the silane coupling agent, and the substrate peeling resistance can be further improved.

  Examples of the silane coupling agent that can be used in the present invention include vinylmethoxysilane, vinylethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltri. Methoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N -Β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyl Methyl Methoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, p-styryl Trimethoxysilane, γ-acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide , Γ-isocyanatopropyltriethoxysilane, γ-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- (vinylbenzylamine) -β-aminoethyl γ- aminopropyltrimethoxysilane etc. may be mentioned, these one may be used alone or in combination of two or more.

  Of these, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-, which have excellent miscibility with epoxy resins Glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltri Methoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N- (vinylbenzylamine) -β-aminoethyl-γ-aminopropyltrimethoxy Silane and the like are preferable.

  As described above, the addition of the silane coupling agent has the effect of preventing peeling problems due to fluctuations in the coating film thickness. Great effect when painting with coating methods that tend to cause thickness fluctuations.

When a silane coupling agent is blended, it is preferable that the total solid content of the epoxy resin is 100, so that a sufficient adhesion enhancing effect can be obtained in the range of 0.3 part to 10 parts. The range of 1 part to 5 parts is more preferable. On the other hand, if the amount exceeds 10 parts, the coating property of the top coating material may be deteriorated and the adhesion between the top coating layer may be impaired due to bleeding of the excessive coupling agent.

(F) Talc The undercoat paint composition of the present invention can contain talc as an extender pigment. Talc is a scaly pigment and is acidic. It is considered that talc is present in a layered manner in parallel with the material surface in the coating film, thereby obtaining the effect of reducing the substance permeability in the coating film, particularly the water permeability. Since water triggers the substrate peeling and is also a corrosion factor, blending of talc can suppress peeling and corrosion, and further improvement of the anticorrosion property as an undercoat can be expected.

  Also, when a hindered amine light stabilizer is used as the light stabilizer, the talc particles present in the layer form have an effect of suppressing the outflow of the hindered amine light stabilizer from the coating film due to the acid-base interaction. I believe. For this reason, a system in which an epoxy resin, a hindered amine, and talc are combined has overlapping interaction effects, and thus can exhibit higher durability against light degradation, that is, durability as a result.

In order to obtain excellent photodegradation prevention effect sustainability, substrate adhesion, and corrosion resistance, the amount of talc is preferably in the range of 10 to 50 parts when the total solid mass of the epoxy resin is 100. .

Coating and coating method In addition to the raw materials described so far, the primer coating composition of the present invention contains additives such as surface conditioners, color separation inhibitors and sagging inhibitors generally used in coatings without problems. I can do it.

  The method for producing the coating material of the present invention is not particularly limited, but usually, the pigment and the pigment dispersion resin and, if necessary, the pigment dispersant and solvent are dispersed by a conventional method using a disperser such as a disper, a ball mill, or a sand mill. The mill base is manufactured, and the remaining raw materials are added to the mill base. In this case, an epoxy resin as a binder is used as the pigment dispersion resin, but a small amount of other resin, a curing agent, or the like may be used. Further, instead of the mill base method, all the raw materials may be dispersed from the beginning to form a paint. The produced paint is usually applied to an object by diluting it with a solvent or water to a viscosity corresponding to a desired coating method. As a coating method, it can be finished by directly or once or twice by a conventionally known method such as roller coating, spray coating or brush coating.

  After the undercoat paint is applied, the desired topcoat paint is applied in a state where the surface of the coating film is dried by room temperature drying or baking drying to obtain an article coated with the desired multilayer coating film which may be room temperature drying or baking drying. The top coat may be applied immediately after the undercoat paint or a considerable period may be left after the undercoat paint is applied.

  The top coat can be used regardless of the type of coating, but as the baking finish top coat, amino alkyd paint or amino acrylic paint is used, and the coating film appearance, physical properties, durability and adhesion to the undercoat are excellent. A coated film can be obtained. At this time, the baking condition is preferably 5 to 100 minutes at an ambient temperature of 60 ° C. to 160 ° C. In addition, when a two-pack type room temperature curing coating is used as the normally dry top coating, it is possible to obtain a coating excellent in coating film appearance, physical properties, durability, and adhesion to the undercoat. The drying temperature at this time is room temperature to 80 ° C. (forced drying), and the drying time is preferably about 3 minutes to 7 days.

The material to be coated with the undercoat of the present invention is not particularly limited, but metal materials such as steel, aluminum and alloy materials are suitable. Steel structures, construction machines, machine tools, automobile bodies, automobile parts, fences It can be suitably used for painting gates, gardening supplies, furniture and joinery.

Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to these examples. In addition, “parts” and “%” in the description of the examples indicate mass parts and mass%, respectively.

Production Example of Pigment Dispersed Paste Epokey 813 (Note 1): 640 parts, Disparon 6900-20X (Note 2): 36 parts, BYK-P104S (Note 3): 3 parts in a stirring vessel equipped with a rotary blade, propylene glycol Monomethyl ether acetate (hereinafter abbreviated as PMA): 300 parts, xylene 400 parts, butanol: 150 parts, TITANIX JR-605 (Note 4): 420 parts, Mitsubishi Carbon Black MA-100 (Note 5): 2 parts, LF Rust prevention ZP-50S (Note 6): 300 parts, Microace L-1 (Note 7): 120 parts, Precipitated barium sulfate 100 (Note 8): 240 parts, Tankar 85 (Note 9): 450 parts , After pre-stirring at about 1000 rpm for 20 minutes, the entire content was charged into a sand mill, and the sand mill was dispersed to obtain a particle size of 20 μm or less (Note 10). To obtain a fee dispersed paste. The obtained paste had a solid content of about 60% and a pigment / resin ratio (mass) of 5.3 / 1.

Note 1: Modified epoxy resin varnish manufactured by Mitsui Chemicals, solid content 45%.
Note 2: Anti-settling agent manufactured by Enomoto Chemical Co., Ltd., solid content 20%.
Note 3: BYK Hemy's surface conditioner, solid content 50%.
Note 4: Titanium dioxide pigment manufactured by Teika Co., Ltd.
Note 5: Graphite pigment manufactured by Mitsubishi Chemical.
Note 6: Zinc phosphate rust preventive pigment manufactured by Kikuchi Color Co., Ltd.
Note 7: Hydrous magnesium silicate (talc) manufactured by Nippon Talc Co., Ltd.
Note 8: Barium sulfate manufactured by Sakai Chemical Industry Co., Ltd.
Note 9: Calcium carbonate manufactured by Takehara Chemical Co., Ltd.
Note 10: According to JIS K-5400 degree of dispersion A method.

Paint production example 1
Pigment dispersion paste obtained above in a stirring vessel equipped with rotating blades: 300 parts, Epokey 803 (Note 11): 76.4 parts, 1% BYK-240S (Note 12): 0.3 part, Silicone KBM- 403 (Note 13): 1.8 parts, TINUVIN 900 (Note 14): 1.6 parts, TINUVIN 144 (Note 15): 3.4 parts, PMA: 9.8 parts, methyl isobutyl ketone: 6.9 parts, butanol : 7.8 parts and 11.8 parts of xylene were charged and sufficiently stirred and mixed to prepare paint 1. The solid content of the paint is about 53%, the blending amount of the UV absorber is 2.7 PHR (PHR is used for the mass part of the blend with respect to 100 parts by mass of the resin), the blending amount of the light stabilizer is 5.8 PHR, The amount of the silane coupling agent is 3.1 PHR.

Note 11: Urethane-modified epoxy resin varnish manufactured by Mitsui Chemicals, solid content 40%.
Note 12: BYK Heme Co. color separation inhibitor, commercial product has a solid content of 52%, but solidified with xylene.
Dilute to 1% form.
Note 13: Silane coupling agent manufactured by Shin-Etsu Chemical Co., Ltd.
Note 14: Benzotriazole UV absorber manufactured by Ciba Specialty Chemicals.
Note 15: Hindered amine light stabilizer manufactured by Ciba Specialty Chemicals Co., Ltd.

Paint production examples 2-8
According to the formulation shown in Table 1, paints 2 to 8 were produced in the same manner as paint production example 1. Table 1 also shows the solid content of the produced coating material, the ultraviolet absorber, the light stabilizer, and the amount of the silane coupling agent.

In addition, jER-1007H used in paint production examples 3 and 5 was obtained by diluting bisphenol A type solid epoxy resin manufactured by Japan Epoxy Resins Co., Ltd. to a solid content of 40% with a 1: 1 (mass) mixed solvent of methyl isobutyl ketone and xylene. Is. IRGANOX 1010 used in Production Example 8 is a hindered phenol light stabilizer manufactured by Ciba Specialty Chemicals.











































Table 1

Example 1
After degreasing the surface of a polished mild steel sheet having a width of 70 mm, a length of 150 mm, and a thickness of 0.8 mm, the paint 1 obtained in Paint Production Example 1 was spray-coated to a dry film thickness of 20 μm, and then at 50 ° C. for 20 minutes. It was forcibly dried to obtain an undercoat plate. On top of that, Asukabake NEO G Metallic (Aminoacrylic paint with silver metallic color made by Kansai Paint) was spray-coated to a dry film thickness of 5 μm, 10 μm and 15 μm, respectively, set for 3 minutes and then heated at 140 ° C. for 30 minutes with a hot air dryer. Baking was performed to obtain three types of test coated plates of Example 1. Thus, performance evaluation was performed by the accelerated test using the test plate from which the film thickness of top coat differs (it changed the light transmittance of the top coat film).

Example 2
Using the paint 1 obtained in Paint Production Example 1, an undercoat coated plate was obtained in the same manner as in Example 1. On top of that, Cera M Retan Blue (acrylic / isocyanate two-component room temperature curable paint manufactured by Kansai Paint Co., Ltd., paint color is blue) is brushed to a dry film thickness of 10, 20, and 30 μm, respectively, and left at room temperature for 7 days. Curing was performed to obtain three types of test coated plates of Example 2. Thus, performance evaluation was performed by the accelerated test using the test plate from which the film thickness of top coat differs (it changed the light transmittance of the top coat film).

Examples 3 to 10 and Comparative Examples 1 to 6
Test coating plates of Examples 3 to 10 and Comparative Examples 1 to 6 were prepared by changing the types of the undercoat and topcoat, and performance evaluation was performed by an acceleration test. The paint combinations and performance evaluation results are shown in Tables 2a and 2b.

Here, the production process of the undercoat plate was the same as that in Example 1, and a test plate was prepared under the conditions of Example 1 when Asukabake NEO G metallic was applied to the top coat. In Table 2, “baked” is displayed in the top coat column. A test plate was prepared under the conditions of Example 2 when Cera M Retan Blue was applied to the top coat. In Table 2, “normally dry” is displayed in the top coat column. In the column of top coat thickness 1 in Table 2, the top coat thickness 2 of the test plate with the thinnest top coat thickness, that is, the test plate of 5 μm for the baking type Asuka Bake NEO G Metallic and 10 μm for the normal dry type Cera M Retan Blue. The column of No. 5 shows the performance evaluation results of the test plate of 10 μm by baking and 20 μm by normal drying, and the column of the top coat film thickness 3 by 15 μm by baking and 30 μm by normal drying, respectively.

Performance evaluation by accelerated test An adhesion test by accelerated exposure was performed to evaluate the outdoor aging effect between the undercoat and the topcoat. In the accelerated test, the combined cycle test shown below was performed, and the quality of aged peeling was evaluated by the number of cycles until peeling of the coating film occurred between the undercoat and the topcoat.
Combined cycle test A 60-hour light load is given by a sunshine carbon arc tester operated under the conditions of JIS K5600-7-5.
2. Next, it is immersed in warm water of 40 ° C. for 24 hours.
3. Pull up the water from the water, wipe off the surface water with a filter paper for qualitative analysis specified in JIS P3801, dry it for 30 minutes in a general state, and then perform the adhesion test by the method described in JIS K5628 6.10.

1 above. ~ 3. Was defined as one cycle, and the number of cycles until peeling between coatings with a width of 1 mm or more was recognized along a cut intersecting at an angle of 30 degrees on the surface of the test plate was taken as the score of the test plate. Therefore, the larger the numerical value of the score, the better the test piece is over time. (High performance)

Table 2a Example test results

Table 2b

Claims (9)

A one-component undercoating composition comprising (A) an epoxy resin and / or a modified epoxy resin, (B) an ultraviolet absorber and a light stabilizer, (C) a rust preventive pigment, and (D) a solvent as essential components. The coating composition according to claim 1, further comprising (E) a silane coupling agent. (A) The blending amount of the ultraviolet absorber (B) is 0.1 to 10 parts by weight and the blending amount of the light stabilizer is 0 with respect to 100 parts by weight of the total resin solids of the epoxy resin and the modified epoxy resin. The coating composition according to claim 1 or 2, wherein the coating composition is 2 to 20 parts by mass. The coating composition according to any one of claims 1 to 3, wherein the light stabilizer is a hindered amine compound. Furthermore, the coating composition as described in any one of Claims 1-4 which contains (F) talc as an essential component. A coating method in which the coating composition according to any one of claims 1 to 5 is applied as an undercoat, and after being uncured or cured, the overcoat is applied again. The coating method according to claim 6, wherein an aminoalkyd coating or an aminoacrylic coating is used as the top coating. The coating method according to claim 6, wherein a two-component room temperature curing coating is used as the top coating. An article coated by the coating method according to any one of claims 6 to 8.