JP5366628B2 - MULTILAYER COATING FORMATION METHOD AND COATED METAL PLATE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a dual layer coat on a coated metallic plate which shows excellent coat outlook, coat hardness, workability, weathering properties and corrosion resistance, as well as a coated metallic plate. <P>SOLUTION: This method of forming a dual layer coat is to form a primer cured coat with a dry coat thickness of 1 to 10 &mu;m, using a primer coating material (A) which features that it contains no chromium-based rust-proof component, on one side surface or both side surfaces of the metallic plate whose surface may be given a chemical treatment. Further, the method is to apply a facing material (B) to at least, one side surface of the primer cured coat and thermally cure the facing material (B) and thereby, form an overlay cured coat with a dry coat thickness of 5 to 30 &mu;m. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for forming a multi-layer coating film of a coated metal sheet and a coated metal sheet that are excellent in coating film appearance, coating film hardness, workability, weather resistance and corrosion resistance.

  Conventionally, pre-coated metal sheets such as pre-coated steel sheets painted by coil coating, etc., building materials such as roofs, walls, shutters, garages, various household appliances, switchboards, refrigerated showcases, steel furniture, kitchen appliances, etc. Widely used as a housing related product.

  In order to manufacture these housing-related products from a pre-coated metal plate, the pre-coated steel plate is usually cut, press-molded and joined. Therefore, these housing-related products often have a metal exposed portion that is a cut surface and a crack generating portion due to press working. The above metal exposed part and crack generation part are likely to have a corrosion resistance lower than other parts, so in order to improve the corrosion resistance, it is common to include a chromium-based anticorrosive pigment in the primer coating of the pre-coated steel sheet Has been done.

  However, chromium-based rust preventive pigments contain or produce hexavalent chromium having excellent rust prevention properties, and the use of this hexavalent chromium has been restricted from the viewpoint of human health and environmental protection. ing. Therefore, many non-chromium rust preventive pigments such as zinc phosphate, tripolyaluminum phosphate, and zinc molybdate have been put on the market, and various types such as primers combining non-chromium pigments have been proposed. .

On the other hand, the topcoat that is applied over the precoat film is directly affected by the external environment such as sunlight and acid rain, so it not only has excellent processability of the paint film but also cracks and peeling of the paint film due to weather resistance deterioration. Therefore, a coating film excellent in weather resistance that does not cause discoloration or choking (chalking) is required, and therefore selection of a resin composition and a pigment component is important.
As a top coat for recoating on such a pre-coat film, a paint using a polyester containing at least 50 mol% of hexahydrophthalic acid as an acid component and further using neopentyl alcohol is conventionally used. (Patent Document 1) discloses a coated metal plate that is coated and exhibits excellent durability.
However, in the coated metal plate according to Patent Document 1, when the primer coating film does not contain a chromium-based anticorrosive pigment, the corrosion resistance at the processed portion and end surface portion of the coated metal plate was insufficient.

  In addition, a primer coating and a hue coating are provided on a metal plate, and a multilayer coating on which a clear coating including a polyester resin containing hexahydrophthalic anhydride and neopentyl glycol is provided on the hue coating. A coated metal plate is disclosed (Patent Document 2).

  However, the coated metal plate described in Patent Document 2 is a top coating film simply using a polyester resin containing hexahydrophthalic anhydride and neopentyl glycol when the primer coating does not contain a chromium-based rust preventive pigment. As a result, the corrosion resistance in the processed part and end face part of the coated metal sheet was insufficient.

  From such a background, a method for forming a multilayer coating film on a coated metal sheet and a coated metal sheet that are excellent in coating film appearance, coating film hardness, workability, weather resistance, and corrosion resistance have been demanded.

JP-A-5-239196 JP 2007-55137 A

  The problem to be solved by the invention is to find a method for forming a multilayer coating film excellent in coating film appearance, coating film hardness, workability, weather resistance and corrosion resistance, and to provide a coated metal plate excellent in the above-mentioned various performances.

  As a result of intensive studies, the present inventors have found that a primer cured coating film having a dry film thickness of 1 to 10 μm by the primer coating (A) is formed on one or both surfaces of a metal plate that may be subjected to chemical conversion treatment on the surface. A multi-layer formed by coating a specific top coating (B) on at least one side of the primer cured coating film and curing by heating to form a top coating cured film having a dry film thickness of 5 to 30 μm. By the coating film formation method, it came to obtain the coating metal plate excellent in coating-film external appearance, coating-film hardness, workability, weather resistance, and corrosion resistance.

That is, the present invention
1. A primer-cured coating film having a dry film thickness of 1 to 10 μm is formed on one or both surfaces of a metal plate that may be subjected to chemical conversion treatment by coating and curing the primer paint (A) having the following characteristics. And a top coat paint (B) having the following characteristics is applied on at least one surface of the primer cured coating film and cured by heating to form a top coat cured film having a dry film thickness of 5 to 30 μm. Film forming method.
Primer paint (A):
At least one of an aliphatic polybasic acid having 4 to 36 carbon atoms (a11), an acrylic resin (a12) having a glass transition temperature of -20 to 50 ° C, and a polyester resin (a13) having a glass transition temperature of -20 to 50 ° C. Primer paint top coating (B): acid component containing a bisphenol type epoxy resin (A1) modified with a soft organic component of (A1), a crosslinking agent (A2), and a rust preventive component (A3) not containing a chromium-based rust preventive pigment A hydroxyl group-containing polyester resin (B1) comprising (b1) and an alcohol component (b2) as constituent components, i) based on the total mass of the acid component (b1), hexahydrophthalic acid or its anhydride, hexahydro The total proportion of at least one polybasic acid selected from isophthalic acid, tetrahydrophthalic acid or its anhydride and 1,4-cyclohexanedicarboxylic acid is Of at least one alcohol component selected from neopentyl glycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A, based on 0-100% by mass and (ii) the total mass of the alcohol component (b2) A hydroxyl group-containing polyester resin (B1) obtained by reacting an acid component (b1) and an alcohol component (b2), a blocked aliphatic polyisocyanate and / or a blocked fat having a total ratio of 50 to 100% by mass. Inorganic composite oxide pigment (B3) having infrared reflectivity with respect to 100 parts by mass of the solid content of the crosslinking agent (B2) containing the cyclic polyisocyanate compound and the resin (B1) and the crosslinking agent (B2). 1 to 100 parts by mass of a top coating composition, Inorganic composite oxide pigment (B3) having infrared reflectivity contains at least one metal selected from Mg, Zn, Li and Mn as a metal element and Fe, Co and Al, Bi- Mn-based inorganic composite oxide pigment, Fe-Cu-Mn-based inorganic composite oxide pigment, Mn-Sr-based inorganic composite oxide pigment, Fe-Cr-based inorganic composite oxide pigment, Fe-Cr-Co-based inorganic composite oxide The method for forming a multilayer coating film according to item 1, which is at least one inorganic composite oxide pigment selected from pigments,
3. The alcohol component (b2) contains at least one selected from neopentyl glycol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, and contains at least one compound selected from trimethylolpropane and glycerin. The method for forming a multilayer coating film according to item 1 or 2,
4). The method for forming a multilayer coating film according to any one of items 1 to 3, wherein the top coating material (B) contains an ultraviolet absorber and / or a light stabilizer,
5. The rust preventive component (A3) is at least one of at least one vanadium compound (1) of vanadium pentoxide, calcium vanadate and ammonium metavanadate, metal phosphate (2), metal silicate and silica fine particles. Item 5. The method for forming a multilayer coating film according to any one of items 1 to 4, which comprises a silicon-containing compound (3).
It is related with the coating metal plate obtained by the multilayer coating-film formation method of any one of 6.1-5.

The coated metal plate obtained by the method for forming a multilayer coating film of the present invention is excellent in coating film appearance, coating film hardness, workability, weather resistance and corrosion resistance.
Specifically, a top coating (B) containing a specific polyester resin (B1), a specific cross-linking agent (B2), and an inorganic complex oxide pigment (B3) having infrared reflectivity on a coating film made of a primer paint (A). The multilayer coating film obtained by coating is excellent in workability and coating film hardness.

  In addition, it can suppress hydrolysis caused by resin irradiation and acid rain due to light irradiation, and has the effect of suppressing coating film deterioration (fading, fading, gloss reduction, etc.), so the coating film has excellent coating appearance, weather resistance, and corrosion resistance. Is obtained.

  Furthermore, as the primer paint (A), a primer paint containing a bisphenol type epoxy resin (A1) modified with a soft organic component, a curing agent (A2), and a rust preventive component (A3) not containing a chromium-based rust preventive pigment By using, workability can be further imparted to the coating film. Furthermore, a multilayer coating film excellent in corrosion resistance can be formed not only in the corrosion resistance of the flat portion but also in the processed portion and the end surface portion of the coated metal plate. From such a thing, even if it is a chromium free multilayer coating film, the coating metal plate which was fully excellent in the said various performance can be obtained.

  The present invention forms a primer cured coating film having a dry film thickness of 1 to 10 μm by the primer coating (A) on one surface or both surfaces of a metal plate which may be subjected to chemical conversion treatment on the surface, A method for forming a multi-layer coating film and a coated metal plate, characterized in that a specific top-coating paint (B) is applied on at least one side of the coating and cured by heating to form a top-coating cured film having a dry film thickness of 5 to 30 μm It is. Details will be described below.

[Metal coating]
The metal plate to be coated is iron, aluminum alloy, brass, copper plate, stainless steel plate, tin plate, galvanized steel plate, alloyed zinc (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel plate, aluminum Metal plates such as plated steel plates; surface-treated metal plates obtained by subjecting the surfaces of these metal plates to chemical conversion treatment such as phosphate treatment and chromate treatment. In addition to the above metal plate, a metal resin composite plate having a layer configuration of “metal plate / adhesive layer / resin layer / adhesive layer / metal plate” having a metal plate on the outermost layer on one or both sides is used. it can.
In addition, a metal resin composite plate in which the surface of a non-metallic substance such as resin is coated with a metal layer by vapor deposition or the like can also be used as an object to be coated. Further, by melting the resin and sandwiching it between the metal resin composite plates, What is referred to as “plate / resin layer / metal plate” can also be used as an object to be coated.

  From the viewpoint of lightness and durability, a metal resin composite plate having a layer configuration of “metal plate / adhesive layer / resin layer / adhesive layer / metal plate” having a metal plate on the outermost layer on one or both sides is provided. Preferably, aluminum is more preferable as the metal plate from the viewpoint of workability and corrosion resistance.

[Primer paint (A)]
A coating film of the primer coating (A) is formed on the above metal coating, which does not contain a rust preventive component that does not contain a chromium-based rust preventive pigment. The primer paint (A) is a bisphenol type epoxy resin (A1) modified with a soft organic component obtained by reacting a soft organic component (a1) with a bisphenol type epoxy resin (a2) from the viewpoint of improving processability and corrosion resistance. (Hereinafter, it may be abbreviated as “modified resin (A1)”).

Bisphenol type epoxy resin (A1):
The soft organic component (a1) in the production of the bisphenol type epoxy resin (A1) is an organic component having a functional group that reacts with the bisphenol type epoxy resin and capable of plasticizing the bisphenol type epoxy resin (a2). -36 aliphatic polybasic acid (a11), an acrylic resin (a12) having a glass transition temperature of -20 to 50 ° C, and a polyester resin (a13) having a glass transition temperature of -20 to 50 ° C. .

  The aliphatic polybasic acid having 4 to 36 carbon atoms (a11) is a saturated or unsaturated aliphatic polybasic acid having 4 to 36 carbon atoms, preferably 8 to 36, including alicyclic polybasic acids. For example, hexahydroisophthalic acid, hexahydroterephthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, methylhexahydroterephthalic acid, 1-tetrahydrophthalic acid, 2-tetrahydrophthalic acid, 3-tetrahydrophthalic acid, 4-tetrahydrophthalic acid, 3-tetrahydroisophthalic acid, 4-tetrahydroisophthalic acid, 1-tetrahydroterephthalic acid, 2-tetrahydroterephthalic acid, methyltetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, hexachloroendo Methylenetetrahydrophthal Alicyclic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dodecanedicarboxylic acid, suberic acid, pimelic acid, maleic acid, fumaric acid, itaconic acid, Aliphatic dicarboxylic acids such as brassic acid, citraconic acid, chloromaleic acid and dimer acid and their anhydrides; trivalent or higher aliphatic polybasic acids such as hexahydrotrimellitic acid; methyl esters and ethyl esters of these acids And lower alkyl esters.

  Examples of the acrylic resin (a12) that can be used as the soft organic component in the production of the modified resin (A1) include an acrylic resin (a12) having a reactive group that reacts with the epoxy group of the bisphenol-type epoxy resin. The acrylic resin (a12) includes a modified acrylic resin such as a urethane-modified acrylic resin. Examples of the reactive group include a carboxyl group, an amino group, a hydroxyl group, and the like. Among the acrylic resins, an acrylic resin having a carboxyl group is preferably used.

  The acrylic resin having a carboxyl group is obtained by copolymerizing a polymerizable unsaturated monomer having a carboxyl group and other polymerizable unsaturated monomers by a known method such as a solution polymerization method, a suspension polymerization method, or a bulk polymerization method. Among them, the solution polymerization method is preferable because of easy control of polymerization. The other polymerizable unsaturated monomer contains a (meth) acrylic acid ester. It is preferable that the amount of (meth) acrylic ester used is in the range of 30 to 98% by mass based on the total amount of copolymerization monomer components constituting the modified resin (A). Examples of the polymerizable unsaturated monomer having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid.

  Examples of the other polymerizable unsaturated monomers include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and ε-caprolactone modified. Tetrahydrofurfuryl (meth) acrylate, ε-caprolactone modified hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- Hydroxyl group-containing polymerizable unsaturated monomers such as hydroxy-3-butoxypropyl (meth) acrylate and monohydroxyethyl (meth) acrylate phthalate; methyl (meth) acrylate , Ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate , Alkyl (meth) acrylates such as tridecyl (meth) acrylate; cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate; benzyl (meth) acrylate, phenyl (meth) acrylate; dimethylaminoethyl (meth) acrylate, diethylamino Di (alkyl) aminoalkyl (meth) acrylates such as ethyl (meth) acrylate; glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether Epoxy group-containing polymerizable unsaturated monomers such as styrene, α-methylstyrene, vinyl toluene, and other vinyl aromatic compounds; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, methacrylamide, methylolacrylamide, methylolmethacrylamide , Diacetone acrylamide, acryloyl morroline, N-vinyl-2-pyrrolidone, γ-acryloxypropyltrimethoxylane, γ-methacryloxypropyltrimethoxylane, vinyl chloride, propylene, ethylene, C4-C20 α-olefin Etc. These can be used alone or in combination of two or more. In the present specification, “(meth) acrylate” means “acrylate or methacrylate”.

The number average molecular weight of the acrylic resin (a12) is 2,000 to 40,000, particularly 3,000, when it is synthesized by solution polymerization from the viewpoint of compatibility with the bisphenol type epoxy resin and reactivity. Within the range of ~ 30,000 is preferred.
In the present specification, the average molecular weight of the resin is a value calculated based on the molecular weight of standard polystyrene from the chromatogram measured by gel permeation chromatography. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: under the conditions of RI.

  The acrylic resin (a12) preferably has an acid value of 3 to 50 mgKOH / g, particularly 5 to 40 mgKOH / g, from the viewpoints of reactivity and adhesion to the bisphenol type epoxy resin (a2). Further, the hydroxyl value of the acrylic resin (a12) is preferably 10 to 300 mgKOH / g, particularly preferably 30 to 250 mgKOH / g, from the viewpoint of the curability and water resistance of the coating film. Furthermore, the glass transition temperature (Tg) of the acrylic resin (a12) is in the range of −20 ° C. to 50 ° C., preferably −20 ° C. to 40 ° C., from the viewpoint of the balance between processability and hardness of the resulting coating film. Is preferred. In the present specification, the glass transition temperature (Tg) of the resin is determined by using a scanning differential thermal analysis (DSC), a scanning scanning calorimeter “DSC-60A” (trade name, manufactured by Shimadzu Corporation). Is a value measured at a heating rate of 10 ° C./min.

  Examples of the polyester resin that can be used as the soft organic component (a1) in the production of the bisphenol type epoxy resin (A1) include a polyester resin (a13) having a reactive group that reacts with the epoxy group of the bisphenol type epoxy resin. The polyester resin (a13) includes both oil-free polyester resins and oil-modified polyester resins, and may be modified polyester resins such as silicon-modified polyester resins and urethane-modified polyester resins. Examples of the reactive group include a carboxyl group, an amino group, a hydroxyl group, and the like, and a polyester resin having a carboxyl group is particularly preferably used as the polyester resin.

Of the polyester resin (a13), the oil-free polyester resin can be produced using a known method such as a direct esterification method, a transesterification method, or a ring-opening polymerization method. As a specific example of the direct esterification method, a method in which an acid component and an alcohol component are mainly polycondensed can be mentioned.
As the acid component, one or more dibasic acids selected from phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and the like; Tribasic acid or more polybasic acid such as trimellitic anhydride, methylcyclohexylic carboxylic acid, pyromellitic anhydride, etc. is used, and benzoic acid, crotonic acid, p-tertbutylbenzoic acid, etc. are used as the acid component as required. Monobasic acids can also be used.

  As the alcohol component, dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, hexanediol, and 1,6-hexanediol are mainly used. Trivalent or higher alcohol components such as methylolethane, trimethylolpropane and pentaerythritol may be used in combination.

  The production of the polyester resin (a13) can be carried out by a known method using a compounding ratio in which the acid group and the alcohol component are excessive in terms of the hydroxyl group with respect to the hydroxyl group. It can also be carried out by post-adding an acid component such as trimellitic anhydride or phthalic anhydride.

  The oil-free polyester resin can also be produced by condensation polymerization by transesterification of a lower alkyl ester of an acid component and an alcohol. Furthermore, the oil-free polyester resin can also be produced by ring-opening polymerization of lactones such as δ-valerolactone and ε-caprolactone.

  Of the polyester resin (a13), an oil-modified polyester resin is obtained by reacting an oil fatty acid with the oil-free polyester resin. Examples of the oil fatty acid include coconut oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, Flower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, tung oil fatty acid and the like can be mentioned. The reaction between the polyester resin and the oil fatty acid can also be carried out by a known method, and the oil length is usually preferably 30% or less. .

  The number average molecular weight of the polyester resin (a13) may be in the range of 1,000 to 30,000, particularly 2,000 to 20,000, from the viewpoint of compatibility with the bisphenol-type epoxy resin and reactivity. Is preferred. The acid value of the polyester resin is preferably from 3 to 100 mgKOH / g, particularly preferably from 5 to 70 mgKOH / g, from the viewpoints of reactivity and adhesion with the bisphenol-type epoxy resin. Moreover, the glass transition temperature (Tg) of the polyester resin (a13) is in the range of −20 ° C. to 50 ° C., preferably −20 ° C. to 40 ° C. from the viewpoint of compatibility between the workability of the obtained coating film and the coating film hardness. Preferably it is.

  The bisphenol-type epoxy resin (a2) used in the production of the bisphenol-type epoxy resin (A1) modified with a soft organic component is a bisphenol-type epoxy resin having one or more, preferably two or more epoxy groups in one molecule. Yes, for example, a resin obtained by condensing epichlorohydrin and bisphenol up to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, epichlorohydrin and bisphenol, if necessary, in the presence of a catalyst such as an alkali catalyst. Any of resins obtained by condensation to form a low molecular weight epoxy resin and a polyaddition reaction of the low molecular weight epoxy resin and bisphenol may be used.

  The bisphenol type epoxy resin (a2) usually has a number average molecular weight of 350 to 5,000, preferably 400 to 4,000, and an epoxy group content of 0.5 to 15.4 mmol / g, preferably 0.8-10 mmol / g is preferred.

  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, bis ( 2-hydroxy-tert-butyl-phenyl) -2-hydroxy-1,3-oxy-propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, bis (2-hydroxynaphth Le), etc. can be mentioned methane, bisphenol A, bisphenol F are preferably used among others. The bisphenols can be used alone or as a mixture of two or more.

  As a commercial item of bisphenol type epoxy resin, for example, manufactured by Japan Epoxy Resin Co., Ltd., jER828, jER812, jER815, jER820, jER834, jER1001, jER1004, jER1007, jER1009, jER1010, jER4004P, jER4007P, jER4210; , Araldite AER6099; and Mitsui Chemicals, Inc.'s Epomic R-309.

  The method for producing the modified resin (A) by reacting the soft organic component (a1) with the bisphenol type epoxy resin (a2) is not particularly limited. For example, when two types of soft organic component (a1) are used, a method in which two types of soft organic component (a1) and bisphenol-type epoxy resin (a2) are simultaneously reacted together, a soft organic component ( a1) After reacting 1 type and bisphenol type epoxy resin (a2), the method of making the remaining soft organic component react can be mentioned.

  The above reaction can be suitably carried out, for example, by reacting usually at 100 to 150 ° C. for 1 to 5 hours in the presence of a reaction catalyst as necessary in a solvent capable of dissolving these components.

Examples of the reaction catalyst include quaternary salt catalysts such as tetraethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrabutylphosphonium bromide and triphenylbenzylphosphonium chloride; amines such as triethylamine and tributylamine Etc.
In the above reaction, when the reactive group of the soft organic component (a1) is a carboxyl group, the equivalent ratio of (epoxy group in the bisphenol type epoxy resin) / (carboxyl group in the soft organic component) is 10 / It is suitable to be in the range of 1-1 / 1, preferably 5/1 to 2/1.

  When the acrylic resin (a12) has a reactive group that reacts with an epoxy group other than a carboxyl group in the synthesis reaction of the modified resin (A1), the ratio of each reactive group is “in the soft organic component” It is preferable to be within the range of the formula in which “the carboxyl group of” is replaced with “a reactive group that reacts with an epoxy group other than the carboxyl group”.

  The blending ratio of the soft organic component (a1) and the bisphenol type epoxy resin (a2) when producing the modified resin (A1) is within the following range based on a total of 100 parts by mass of both. Soft organic component (a1): 5 to 50 parts by mass, preferably 10 to 40 parts by mass, bisphenol type epoxy resin (a2): 50 to 95 parts by mass, preferably 60 to 90 parts by mass.

  Further, the modified resin (A1) is composed of benzoic acid, salicylic acid, or a secondary grade, because when the epoxy group remains after the soft organic component (a1) and the bisphenol type epoxy resin (a2) are reacted, the epoxy group is blocked. It may be obtained by reacting a blocking agent such as an amine compound. Moreover, depending on the case, a blocking agent can also be made to react at the time of reaction of a soft organic component (a1) and a bisphenol-type epoxy resin (a2). It is considered that the modified resin (A1) has a soft component in the structure, thereby contributing to the development of stress relaxation ability of the crosslinked coating film and contributing to improvement of workability and corrosion resistance.

Cross-linking agent (A2):
The cross-linking agent (A2) reacts with the modified resin (A1) to form a cured coating film, and is particularly limited as long as it can be cured by reacting with the modified resin (A1) by heating or the like. Among them, amino resins, phenol resins and polyisocyanate compounds which may be blocked are suitable. These crosslinking agents can be used alone or in combination of two or more. Examples of the amino resin include amino resins obtained by the reaction of amino components such as melamine, urea, benzoguanamine, acetogranamamine, steroguanamine, spiroguanamine, and dicyandiamide with aldehyde, and among these, melamine resin is preferable from the viewpoint of processability. .

  The melamine resin is a monohydric alcohol having 1 to 8 carbon atoms, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i, part or all of the methylol group of methylolated melamine. Examples thereof include partially etherified or fully etherified melamine resins etherified with butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

  These may be used in which all methylol groups are etherified or partially etherified so that methylol groups or imino groups remain. Examples include alkyl etherified melamines such as methyl etherified melamine, ethyl etherified melamine, and butyl etherified melamine, and only one kind may be used or two or more kinds may be used in combination. Of these, methyl etherified melamine resin in which at least a part of methylol group is alkyl etherified is preferable.

  Commercially available products of such melamine resins include, for example, Cymel 202, Cymel 232, Cymel 235, Cymel 238, Cymel 254, Cymel 266, Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325, Cymel 325 327, Cymel 350, Cymel 370, Cymel 701, Cymel 703, Cymel 1141 (manufactured by Nihon Cytec Industries, Inc.), Uban 20SE60 (manufactured by Mitsui Chemicals, trade name, average polymerization degree exceeding 3), and the like are commercially available. .

  The phenol resin that can be used as the crosslinking agent (A2) crosslinks with the modified resin (A) and introduces a methylol group by heating and condensing the phenol component and formaldehyde in the presence of a reaction catalyst. And a resol type phenol resin obtained by alkylating a part or all of the methylol group of the methylolated phenol resin obtained with the alcohol with an alcohol.

  In the production of a resol type phenol resin, a bifunctional phenol compound, a phenol compound of a trifunctional phenol compound, or the like can be used as the phenol component that is a starting material.

  As the above-mentioned phenol compound, for example, as a bifunctional phenol compound, o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, bis (4- Hydroxyphenyl) -2,2-propane [bisphenol A], bis (4-hydroxyphenyl) methane [bisphenol F] and the like. Examples of the trifunctional phenol compound include carboxylic acid, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol and the like. Among these, in order to improve the scratch resistance, it is preferable to use a trifunctional phenol compound, particularly carboxylic acid and / or m-cresol. These phenol compounds may be used alone or in combination of two or more.

  Examples of formaldehydes used in the production of phenol resins include formaldehyde, paraformaldehyde, trioxane, and the like, which can be used alone or in combination of two or more.

  As the alcohol used for alkyl etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, can be suitably used. Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

  A phenol resin having an average of 0.5 or more, preferably 0.6 to 3.0, alkoxymethyl groups per benzene nucleus is suitable from the viewpoint of reactivity with the modified resin (A1). Yes.

  Examples of the non-blocked polyisocyanate compound in the optionally-blocked polyisocyanate compound that can be used as the crosslinking agent include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; hydrogenated xylylene diisocyanate or Cycloaliphatic diisocyanates such as isophorone diisocyanate; organic diisocyanates themselves such as tolylene diisocyanate, xylylene diisocyanate or 4,4'-diphenylmethane diisocyanate, aromatic diisocyanates such as crude MDI, or each of these organic diisocyanates and polyvalent Adducts with alcohol, low molecular weight polyester resin or water, or as described above Cyclic polymerization of an organic diisocyanate comrades, further include isocyanate-biuret, or the like.

  The blocked polyisocyanate compound is obtained by blocking free isocyanate groups of the polyisocyanate compound with a blocking agent. Examples of the blocking agent include phenols such as phenol, cresol and xylenol; ε-caprolactam; lactones such as δ-valerolactam and γ-butyrolactam; methanol, ethanol, n-, i- or t-butyl alcohol, ethylene Alcohols such as glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and benzyl alcohol; oximes such as formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime System: Active methylene such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, acetylacetone It can be suitably used blocking agent, such as. By mixing the polyisocyanate compound and the blocking agent, free isocyanate groups of the polyisocyanate compound can be easily blocked.

  The blending ratio of the bisphenol type epoxy resin (A1) and the cross-linking agent (A2) is based on 100 parts by mass of the total solid content of the components (A1) and (A2), and the bisphenol type epoxy resin (A1) is 55 to 55 parts. It is 95 mass parts, Furthermore, it is 60-95 mass parts, Comprising: It is sclerosis | hardenability, workability, corrosion resistance, etc. that a crosslinking agent (A2) exists in the range of 5-45 mass parts, and also 5-40 mass parts. From the point of view, it is preferable.

  In addition, in order to improve the sclerosis | hardenability of primer coating material (A), a curing catalyst can be mix | blended as needed. When the crosslinking agent (A2) contains an amino resin, particularly a low molecular weight, methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether, sulfonic acid compound or amine neutralization of sulfonic acid compound as a curing catalyst A thing is used suitably. Representative 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 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, the reaction promoting effect, and the physical properties of the obtained coating film. .

  When the crosslinking agent (A2) is a phenol resin, the sulfonic acid compound or an amine neutralized product of the sulfonic acid compound is preferably used as the curing catalyst.

  When the crosslinking agent (A2) is a blocked polyisocyanate compound, a curing catalyst that promotes dissociation of the blocking agent of the blocked polyisocyanate compound, which is a curing agent, is suitable. As a suitable curing catalyst, for example, octyl Tin oxide, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate And organometallic catalysts such as When the crosslinking agent (A2) combines two or more kinds of crosslinking agents, an effective curing catalyst can be used in combination with each crosslinking agent.

Rust preventive component (A3) not containing chromium-based rust preventive pigment:
The primer coating (A) uses a rust preventive component (A3) that does not contain a chromium-based rust preventive pigment from the viewpoint of health to the human body and environmental protection. Examples of the anticorrosive component (A3) not containing a chromium-based anticorrosive pigment include zinc phosphate, aluminum tripolyphosphate, calcium molybdate silicate, vanadium pentoxide, calcium vanadate, ammonium metavanadate, phosphorus vanadate, phosphorus Aluminum phosphate, calcium phosphate, dibasic magnesium phosphate, calcined product of manganese oxide and vanadium oxide, calcined product of calcium phosphate and vanadium oxide, oil absorption of 30 to 200 ml / 100 g, pore volume of 0.05 to 1.2 ml Examples thereof include silica fine particles that are / g. These rust preventive components (A3) can be used alone or in combination of two or more.

  The anticorrosive component (A3) containing no chromium-based anticorrosive pigment in the primer paint (A) is a combination of the following vanadium compound (1), phosphate metal salt (2) and silicon-containing compound (3). Can be suitably used.

Vanadium compound (1)
The vanadium compound (1) is at least one vanadium compound selected from vanadium pentoxide, calcium vanadate, and ammonium metavanadate. Vanadium pentoxide, calcium vanadate and ammonium metavanadate are excellent in elution of pentavalent vanadium ions into water, and the pentavalent vanadium ions released from the vanadium compound (1) react with the material metal, It works effectively to improve corrosion resistance by reacting with ions from other antirust pigment mixtures.

Phosphate metal salts (2)
The phosphoric acid metal salt (2) is at least one of a phosphoric acid metal salt, a hydrogen phosphate metal salt, and a tripolyphosphate metal salt. The metal of the phosphate metal salt is not particularly limited, and examples of suitable metals include Ca, Zn, Al, and Mg. Among these, Ca is particularly suitable.

  Examples of the phosphate metal salt include calcium phosphate, calcium ammonium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate phosphate, zinc phosphate, aluminum phosphate, magnesium phosphate, hydrogen phosphate Examples thereof include zinc, aluminum phosphate, magnesium phosphate, aluminum hydrogen phosphate, magnesium hydrogen phosphate, magnesium ammonium phosphate, and aluminum dihydrogen triphosphate. Of these, calcium phosphate, calcium monohydrogen phosphate, and calcium dihydrogen phosphate are particularly preferred from the viewpoint of corrosion resistance. Phosphate ions released from the phosphate metal salt (2), metal ions such as Ca, Zn, Al, or Mg effectively work to improve corrosion resistance.

Silicon-containing compound (3)
The silicon-containing compound (3) is at least one of metal silicate and silica fine particles. The metal silicate is a salt made of silicon dioxide and a metal oxide, and may be any of orthosilicate, polysilicate, and the like. Examples of the silicate include zinc silicate, aluminum silicate, aluminum orthosilicate, aluminum hydroxide silicate, aluminum calcium silicate, sodium aluminum silicate, beryllium aluminum silicate, sodium silicate, calcium orthosilicate, calcium metasilicate, sodium calcium silicate, and silicic acid. Zirconium, magnesium orthosilicate, magnesium metasilicate, magnesium calcium silicate, manganese silicate, barium silicate, olivine, garnet, tortovite, cyllite, benitoite, neptunite, nymphite, turquoise, quartzite, barracite, tosen Stones, zonotorite, talc, gyoganite, aluminosilicate, borosilicate, beryllosilicate, cholite, fluorite and the like. Among them, calcium orthosilicate and calcium metasilicate are preferable as the metal silicate.

  The silica fine particles can be used without any limitation as long as they are silica fine particles. For example, silica fine powder whose surface is not treated, silica fine powder whose surface is treated with organic matter, calcium ion-exchanged silica fine particles, organic solvent-dispersible colloidal silica And so on.

  Examples of the silica fine particles whose surface is not treated or treated with an organic substance include silica fine powder having an average particle size of 0.5 to 15 μm, preferably 1 to 10 μm, and organic solvent-dispersible colloidal silica. As the silica fine powder, those having an oil absorption of 30 to 350 ml / 100 g, preferably 30 to 150 ml / 100 g can be suitably used. As such commercially available products, silicia 710, silicia 740, Examples include Silysia 550, Aerosil R972 (all of which are manufactured by Fuji Silysia Chemical Co., Ltd.), Mizukasil P-73 (manufactured by Mizusawa Chemical Co., Ltd.), Gasil 200DF (manufactured by Crossfield).

  Calcium ion exchanged silica is silica fine particles in which calcium ions are introduced into a fine porous silica carrier by ion exchange. Examples of commercially available calcium ion exchanged silica include SHIELDEX (Shielddex, registered trademark) C303, AC-3, AC-5 (all of which are manufactured by WR Grace & Co.). it can.

  Calcium ions released from calcium ion exchanged silica are involved in electrochemical action and various salt forming actions, and effectively work to improve corrosion resistance. Moreover, the silica fixed in the coating film effectively works to suppress peeling of the coating film in a corrosive atmosphere. The organic solvent-dispersible colloidal silica is also called an organosilica sol, in which silica fine particles having a particle size of about 5 to 120 nm are stably dispersed in an organic solvent such as alcohols, glycols, and ethers. Examples of commercially available products include the OSCAL series (manufactured by Catalyst Kasei Co., Ltd.) and organosols (manufactured by Nissan Chemical Co., Ltd.). Of these, calcium ion exchanged silica fine particles are preferred. Each metal silicate and each silica fine particle can be used as a silicon-containing compound (3) by 1 type or in combination of 2 or more types.

  In addition, in primer coating material (A), the quantity of the antirust component (A3) which does not contain a chromium-type antirust pigment with respect to 100 mass parts of total solid content of the said bisphenol type epoxy resin (A1) and a crosslinking agent (A2). Is preferably from 10 to 150 parts by mass, preferably from 15 to 90 parts by mass, from the viewpoint of corrosion resistance. Among them, as the anticorrosive component (A3) not containing a chromium-based anticorrosive pigment, the vanadium compound (1), From the viewpoint of improving the corrosion resistance, it is preferable that the silicon-containing compound (2) and the phosphate metal salt (3) are within the following ranges.

Vanadium compound (1): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Phosphate metal salt (2): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Silicon-containing compound (3): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
In the coating composition of the present invention, as a rust-preventive pigment mixture, a combination of these (1), (2) and (3) in a predetermined amount can synergistically improve the corrosion resistance, in particular, the corrosion resistance of the blackboard. It is.

  In addition to the bisphenol-type epoxy resin (A1), the cross-linking agent (A2), the rust preventive component (A3) not containing a chromium-based rust preventive pigment, and the curing catalyst blended as necessary, the primer paint (A) Additives such as adhesion imparting agents, color pigments that can be used in the paint field, extender pigments, organic solvents, anti-settling agents, antifoaming agents, and coating surface conditioners can be blended as necessary.

  Examples of the adhesion-imparting agent include an epoxy resin having a secondary or tertiary amino group, an acrylic resin having a secondary or tertiary amino group, and a silane coupling agent. The resol type phenol resin described in the section of the crosslinking agent (A2) also has a function as an adhesion imparting agent.

  The epoxy resin having a secondary or tertiary amino group is a resin having an epoxy resin skeleton and a secondary or tertiary amino group. Examples of the epoxy resin skeleton include a bisphenol type epoxy resin skeleton and a novolac epoxy resin. Examples include skeletons.

  The epoxy resin having a secondary or tertiary amino group is, for example, a secondary compound obtained by adding an amine compound to an epoxy group such as a glycidyl group in an epoxy resin such as a bisphenol type epoxy resin, a novolac epoxy resin or a urethane-modified epoxy resin. Alternatively, it can be obtained by introducing a tertiary amino group. As an epoxy resin, it is usually preferable that the epoxy equivalent is 200 to 1,000 from the viewpoint of reactivity with an amine compound, and among them, a bisphenol type epoxy resin and a novolac epoxy resin are preferable.

  When a bisphenol type epoxy resin is used, a secondary or tertiary amino group is usually present in the resin skeleton or at the end by reacting a bisphenol type epoxy resin having an epoxy equivalent of about 400 to 1000 with a primary or secondary amine compound. Can be obtained. When a novolac epoxy resin is used, a novolac epoxy resin having an epoxy equivalent of about 200 to 500 is usually used. However, if it is reacted with a primary amine compound, it is easily gelled in production, and therefore a secondary or tertiary amine having a high amine concentration. When obtaining a novolak type epoxy resin having an amino group, it is usually preferable to react a secondary amine compound such as N-methylethanolamine or diethanolamine with a novolak epoxy resin.

  The acrylic resin having an amino group can be obtained, for example, by reacting an acrylic resin copolymerized with an acrylic monomer having an epoxy group such as glycidyl methacrylate and a primary or secondary amine compound. Moreover, the acrylic resin which copolymerized the acrylate or methacrylate monomer which has tertiary amino groups like N, N- dimethylamino ethyl (meth) acrylate and N, N- dimethylaminopropyl (meth) acrylate may be sufficient.

  Of the adhesion-imparting agents, an epoxy resin system is preferable from the viewpoint of the toughness of the coating film required for scratch resistance and the like, and an acrylic resin system is preferable from the viewpoint of water resistance and chemical resistance. If necessary, two or more kinds of adhesion imparting resins can be used in combination.

  Examples of the colored pigment include organic colored pigments such as cyanine blue, cyanine green, organic red pigments such as azo and quinacridone; and inorganic colored pigments such as titanium white, titanium yellow, bengara, carbon black, and various fired pigments. Among them, titanium white can be preferably used. Examples of the extender pigment include talc, clay, mica, alumina, calcium carbonate, barium sulfate and the like.

  The said organic solvent which can be mix | blended with primer paint (A) is mix | blended as needed, and can melt | dissolve or disperse | distribute the bisphenol type | mold epoxy resin (A1) and crosslinking agent (A2) which were modified | denatured with the soft organic component. Specifically, for example, hydrocarbon solvents such as toluene, xylene, high boiling petroleum hydrocarbons, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, ethyl acetate, butyl acetate, ethylene Ester solvents such as glycol monoethyl ether acetate and diethylene glycol monoethyl ether acetate, alcohol solvents such as methanol, ethanol, isopropanol and butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, And ether alcohol-based solvents such as ethylene glycol monobutyl ether can be cited, which may be used alone or in combination of two or more.

  For the coating film formation with the primer paint (A), the primer paint (A) is usually coated on a metal plate with a roll coater or the like so that the dry film thickness is 1 to 10 μm, preferably 2 to 8 μm. A cured coating film is formed by baking and drying at a maximum temperature (PMT) of 160 to 250 ° C. for 15 to 180 seconds, particularly at a PMT of 180 to 230 ° C. for 20 to 120 seconds.

[Top coat (B)]
The multi-layer coating film forming method of the present invention is characterized in that the top coating material (B) is applied to at least one surface of the cured coating film by the primer coating material (A) and is heat-cured to form a top coating cured coating film. It is said.

  The top coating (B) includes a specific hydroxyl group-containing polyester resin (B1), a crosslinking agent (B2) containing a blocked aliphatic isocyanate compound, and a solid content of the resin (B1) and the crosslinking agent (B2). 5 to 120 parts by mass of the pigment component (B3) is contained with respect to 100 parts by mass in total. Hereinafter, each component will be described in detail.

Hydroxyl group-containing polyester resin (B1):
The hydroxyl group-containing polyester resin (B1) used in the present invention is composed of an acid component (b1) and an alcohol component (b2), and (i) hexahydrophthalic acid based on the total mass of the acid component (b1). Alternatively, the ratio of at least one polybasic acid selected from anhydrides thereof, hexahydroisophthalic acid, tetrahydrophthalic acid or anhydrides thereof, and 1,4-cyclohexanedicarboxylic acid is 90 to 100% by mass, preferably 92 to 100%. It is contained by mass%, and further 95-100 mass%. Further, (ii) at least one alcohol component selected from neopentyl glycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A is 50 to 100% by mass based on the total mass of the alcohol component (b2), preferably Is characterized by containing 70-100% by mass, more preferably 85-100% by mass. By using the hydroxyl group-containing polyester resin (B1) obtained by reacting these specific acid component (b1) and alcohol component (b2), a coating having excellent coating film hardness, workability, weather resistance and corrosion resistance is obtained. A membrane can be obtained.

  In addition, as acid components (b1) other than hexahydrophthalic acid or its anhydride, hexahydroisophthalic acid, tetrahydrophthalic acid or its anhydride, and 1,4-cyclohexanedicarboxylic acid, for example, phthalic acid, isophthalic acid, Terephthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4,4′-dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, heptic acid, maleic acid, fumaric acid, itaconic acid, triconic acid Examples thereof include compounds having two or more carboxyl groups in one molecule such as merit acid, pyromellitic acid, tetrahydrophthalic acid, and anhydrides thereof.

On the other hand, as alcohol components (b2) other than neopentyl glycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A, for example, ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, Dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,5-pentanediol, 2,2,4 -Trimethyl-1,3 Glycols such as pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, and neopentyl glycol ester of hydroxypivalic acid, these glycols Lactones such as ε-caprolactone and polyester diols such as bis (hydroxyethyl) terephthalate; glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6- Examples include hexanetriol, pentaerythritol, dipentaerythritol, dipentaerythritol, sorbitol, mannitol and the like.
Here, when at least one alcohol component (b2) selected from neopentyl glycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A is an essential component, and when other alcohol components are used, trimethylolpropane and In order to obtain a coating film excellent in coating film hardness, processability, weather resistance and corrosion resistance, glycerin is also preferred.

  The number average molecular weight (Note 1) of the hydroxyl group-containing polyester resin (B1) is 1,000 to 35,000, preferably 2,000 to 25,000, hydroxyl value 5 to 80 mgKOH / g, preferably 10 to 70 mgKOH / g. g is preferred. Furthermore, the glass transition temperature (Note 2) of the polyester resin (B) is 5 ° C to 50 ° C, preferably 10 ° C to 40 ° C. By being the said range, the coating film excellent in coating-film hardness, workability, a weather resistance, and corrosion resistance can be obtained.

  (Note 1) Number average molecular weight: Measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve as described above for the primer paint (A).

  (Note 2) Glass transition temperature: It was determined by differential scanning thermal analysis (DSC) in the same manner as described above for the primer paint (A).

Cross-linking agent (B2) containing a blocked aliphatic polyisocyanate compound and / or a blocked alicyclic polyisocyanate compound:
The top coat (B) of the present invention may be abbreviated as “crosslinking agent (B2) (hereinafter referred to as“ crosslinking agent (B2) ”) containing a blocked aliphatic polyisocyanate compound and / or a blocked alicyclic polyisocyanate compound. The blocked polyisocyanate compound is an addition reaction product of a polyisocyanate compound and a blocking agent.

  Here, examples of the aliphatic polyisocyanate compound include ethylene diisocyanate, tetramethylene diisocyanate, and hexamethylene diisocyanate (HDI). Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), and cyclohexylene diisocyanate. Among these, it is preferable to use a blocked product of hexamethylene isocyanate (HDI) as the crosslinking agent (B2) in terms of coating film hardness, workability, weather resistance, and corrosion resistance.

The blocking agent is added to the isocyanate group of the polyisocyanate compound to block, and the blocked polyisocyanate compound produced by the addition is stable at normal temperature, but the baking temperature of the coating film (usually 100 to 200 ° C. It is desirable that the blocking agent can be dissociated to regenerate free isocyanate groups when heated to).
Examples of the blocking agent used in the blocked aliphatic isocyanate compound include oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; n-butanol, 2- Aliphatic alcohols such as ethyl hexanol; Aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; Ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; ε-caprolactam, γ-butyrolactam, etc. Lactam compounds; and the like.

The ratio of the blocked aliphatic isocyanate compound in the crosslinking agent (B2) is 50 to 100% by mass, preferably 60 to 100% by mass, more preferably 70 to 70% by mass, based on the resin solid content of the crosslinking agent (B2). 100% by mass is also preferable for obtaining a coating film excellent in coating film hardness, workability, weather resistance and corrosion resistance in combination with the specific hydroxyl group-containing polyester resin (B1). Furthermore, a conventionally known blocked polyisocyanate compound, melamine resin, benzoguanamine resin, urea resin and the like can be used in combination with the crosslinking agent (B2).
As a conventionally known blocked polyisocyanate compound, for example, a blocked polyisocyanate compound blocked with an aromatic polyisocyanate by the blocking agent can be used.

  Aromatic polyisocyanates include 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (TDI), 2,4'- and / or 4,4. '-Diphenylmethane diisocyanate (MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanato Examples include diphenylmethane, 1,5-naphthylene diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, m- and p-isocyanatophenylsulfonyl isocyanate.

  Moreover, as a melamine resin which can be used together, some or all of the methylol groups of methylolated melamine are monohydric alcohols having 1 to 8 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n- Examples include partially etherified or fully etherified melamine resins etherified with butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like. These may be used in which all methylol groups are etherified or partially etherified so that methylol groups or imino groups remain.

  Examples include alkyl etherified melamines such as methyl etherified melamine, ethyl etherified melamine, and butyl etherified melamine, and only one kind may be used or two or more kinds may be used in combination. Of these, methyl etherified melamine resin in which at least a part of methylol group is alkyl etherified is preferable.

Commercially available products of such melamine resins include, for example, Cymel 202, Cymel 232, Cymel 235, Cymel 238, Cymel 254, Cymel 266, Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325, Cymel 325 327, Cymel 350, Cymel 370, Cymel 701, Cymel 703, Cymel 1141 (manufactured by Nihon Cytec Industries, Inc.), Uban 20SE60 (manufactured by Mitsui Chemicals, trade name, average polymerization degree exceeding 3), and the like are commercially available. . Among these, a melamine resin in which a hydrophilic group (for example, imino group) does not remain is preferable for improving corrosion resistance. For example, a combined use of a methyl etherified melamine resin is good for improving corrosion resistance.
Here, as a blending ratio of the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2), 65 to 95 parts by mass of the hydroxyl group-containing polyester resin (B1), preferably based on 100 parts by mass of the total solid content of both components, preferably Is 70 to 90 parts by mass, 5 to 35 parts by mass, preferably 10 to 30 parts by mass of the crosslinking agent (B2).

  Moreover, the ratio of the blocked aliphatic polyisocyanate compound and / or the blocked alicyclic polyisocyanate compound in the crosslinking agent (B2) is preferably 50 to 100% by mass, based on the solid content of the crosslinking agent (B2). Is preferably from 100 to 100% by mass from the viewpoints of coating stability, coating film hardness, processability, weather resistance and corrosion resistance.

Inorganic composite oxide pigment (B3) having infrared reflectivity:
The top coat (B) used in the coating film forming method of the present invention contains an inorganic composite oxide pigment (B3) having infrared reflectivity in addition to the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2). Thus, the effect of further improving the weather resistance and the corrosion resistance is exhibited, and the weather resistance and the corrosion resistance which are not found in the conventional precoated steel sheet can be obtained.

  Infrared composite oxide face (B3) with infrared reflectivity improves reflectivity in the infrared region (780-2500 nm), can suppress the temperature rise of the coated steel sheet, and suppress the decomposition and deterioration of the resin In addition, since there is an effect of suppressing deterioration (discoloration, gloss reduction) due to light irradiation, a coating film having excellent coating film appearance, weather resistance and corrosion resistance can be obtained. The average particle size of the inorganic composite oxide pigment (B3) is preferably 0.1 μm to 20 μm, and more preferably 0.2 μm to 10 μm, from the viewpoint of balance between processability, hiding property, and infrared reflectivity. The average particle diameter in this specification is the median diameter (d50) of the volume-based particle size distribution measured by a laser diffraction scattering method using a microtrack particle size distribution measuring device (trade name “MT3300”, manufactured by Nikkiso Co., Ltd.). Value.

  As a specific example of the inorganic complex oxide face (B3) having infrared reflectivity, an inorganic complex oxide pigment containing at least one metal selected from Mg, Zn, Li and Mn as a metal element and Fe, Co and Al (Hereinafter referred to as “inorganic composite oxide pigment (B31)”).

  The production of the inorganic composite oxide pigment (B31) can be obtained by mixing each metal compound at an appropriate ratio, firing at 800 ° C. or higher in the atmosphere, and pulverizing the obtained powder. Examples of commercially available inorganic oxide pigments (B31) include SA11-2HS and HR-B (manufactured by Toda Kogyo Co., Ltd., Fe—Co—Al—Mg pigments).

  In addition, the inorganic complex oxide pigment (B3) having infrared reflectivity includes, for example, a Bi-Mn based inorganic complex oxide pigment and / or a Fe—Cu—Mn based inorganic complex oxide pigment (hereinafter referred to as “inorganic complex oxide pigment”). Oxide pigments (referred to as “B32)” can be used.

The inorganic composite oxide pigment (B32) can be produced by mixing a Bi—Mn-based inorganic composite oxide pigment, for example, by mixing Bi ₂ O ₃ and MnO ₂ in an appropriate ratio and then firing the mixture. For _example, Bi ₂ O 3 by mixing 57.3 wt% and _MnO 2 42.7 wt%, then use the _Bi 2 _Mn 4 _{O 10} obtained by firing. Other examples include Bi ₁₂ MnO ₂₀ obtained by mixing 97% by mass of Bi ₂ O ₃ and 3% by mass of MnO ₂ and firing the mixture.
On the other hand, the Fe—Cu—Mn-based inorganic composite oxide pigment can be produced, for example, by mixing Fe ₂ O ₃ , MnO ₂ and Cu ₂ O at an appropriate ratio and then firing the mixture. In addition, the Mn—Sr-based inorganic composite oxide pigment can be produced, for example, by mixing MnO ₂ and SrO in an appropriate ratio and then firing the mixture.

  An example of a commercially available Bi-Mn inorganic composite oxide pigment is Black 6301 (manufactured by Asahi Kasei Kogyo Co., Ltd.). Examples of commercially available Fe-Cu-Mn inorganic composite oxide pigments include Black 30C933 and Black 3300 (manufactured by Shepherd). As a commercially available product of the Mn—Sr based inorganic composite oxide pigment, Black 6302 (manufactured by Asahi Kasei Kogyo Co., Ltd.) can be mentioned.

  In addition, the inorganic composite oxide pigment (B3) having infrared reflectivity is selected from Fe-Cr inorganic composite oxide pigments, Fe-Co inorganic oxide pigments, and Fe-Cr-Co inorganic oxide pigments. At least one inorganic oxide pigment (B33) (hereinafter referred to as “inorganic composite oxide pigment (B33)”) can be used.

  The inorganic composite oxide pigment (B33) can be produced by mixing each metal compound at an appropriate ratio, firing at 800 ° C. or higher in the atmosphere, and pulverizing the obtained powder. Specifically, commercially available Fe-Cr inorganic composite oxide pigments include Black 6350 (manufactured by Asahi Kasei Kogyo Co., Ltd.), Black 30C940 (manufactured by Shepherd), and AG235 (manufactured by Kawamura Chemical Co., Ltd.). Examples of commercially available oxide pigments include KR900 (manufactured by Kawamura Chemical Co., Ltd.). Examples of commercially available Fe-Cr-Co inorganic composite oxide pigments include Black 3500 (manufactured by Asahi Kasei Kogyo Co., Ltd.), KR350, NC90Z, AE801, and AB820 (manufactured by Kawamura Chemical Co., Ltd.).

The blending ratio of the inorganic composite oxide pigment (B3) having infrared reflectivity in the top coat (B) used in the present invention is 100 parts by mass in total of the solid content of the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2). From the viewpoint of weather resistance, workability and corrosion resistance, a range of 10 to 100 parts by mass, preferably 20 to 80 parts by mass is preferable for improving weather resistance and corrosion resistance.
In addition to the hydroxyl group-containing polyester resin (B1), the crosslinking agent (B2), and the inorganic composite oxide pigment (B3) having infrared reflectivity, the top coating material (B) may contain other pigment components as necessary. Organic resin fine particles, ultraviolet absorbers and light stabilizers, curing catalysts, surface conditioners, antifoaming agents, organic solvents and other additives and solvents may be contained.

  The other pigment components include, for example, white pigments such as titanium white and zinc white; blue pigments such as cyanine blue and indanthrene blue; green pigments such as cyanine green and patina; organic red pigments such as azo and quinacridone Red pigments such as Bengala; organic yellow pigments such as benzimidazolone, isoindolinone, isoindoline, and quinophthalone; yellow pigments such as titanium yellow and yellow lead; black pigments such as carbon black, graphite, and pine smoke Color pigments such as; Luminous pigments such as aluminum powder, copper powder, nickel powder, titanium oxide-coated mica powder, iron oxide-coated mica powder and glittering graphite. Examples include extender pigments such as clay, talc, barita, calcium carbonate, and silica.

  The organic resin fine particles are not completely melted by baking at the time of coating film formation, and do not contain a color pigment in the resin fine particles. Examples of the resin species include fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, polyamides, acrylic resins, polyurethanes, phenol resins, silicone resins, polypropylene, and polyamides such as nylon 11 and nylon 12. .

Specifically, Techpolymer MBX-12 (manufactured by Sekisui Plastics Co., Ltd., average particle size 12 μm, acrylic resin), Techpolymer MBX-15 (manufactured by Sekisui Plastics Kogyo Co., Ltd., average particle size 15 μm, acrylic resin) , Techpolymer MBX-20 (manufactured by Sekisui Plastics Co., Ltd., average particle size 20 μm, acrylic resin), techpolymer MB30X-20 (manufactured by Sekisui Plastics Co., Ltd., average particle size 20 μm, acrylic resin), techpolymer BM30X -20 (manufactured by Sekisui Plastics Co., Ltd., average particle size 20 μm, acrylic resin), Diasphere MPB-X10 (manufactured by KOLON, trade name, average particle size 10 μm, acrylic resin).
Either one or both of the ultraviolet absorber and the light stabilizer can be added to the coating composition. Examples of such ultraviolet absorbers include benzotriazole, triazine, anilide, benzophenone, oxalate anilide, and cyanoacrylate. Commercially available products include “Tinuvin 1130” and “Tinuvin 400” (above, Ciba Specialty). Chemicals), “CYASORBUV-1164L” (Nippon Cytec Industries), “Hostabin 3206” (Clariant). As the light stabilizer, hindered amines are suitable, and commercially available products are “Tinuvin 123”, “Tinuvin 144” (above, manufactured by Ciba Specialty Chemicals), “Sanol LS-292” (Sankyo Lifetech Co., Ltd.). Product), “Hostabin 3070”, “Hostabin 3058”, “Hostabin PR-31” (manufactured by Clariant).

  The curing catalyst is blended as necessary to accelerate the curing reaction with the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2), and is appropriately selected according to the type of the crosslinking agent (B2). Can be used.

When a melamine resin is used in combination with the crosslinking agent (B2), an acid catalyst such as a sulfonic acid is used as a curing catalyst, particularly in the case of a low molecular weight methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether. A compound or a neutralized amine of a sulfonic acid compound is preferably used. Representative 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 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, the reaction promoting effect, and the physical properties of the resulting coating film.
For the crosslinking agent (B2) containing the blocked aliphatic polyisocyanate compound and / or the blocked alicyclic polyisocyanate compound, a curing catalyst that promotes dissociation of the blocking agent can be suitably used. For example, octyl Tin oxide, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, tetra-n-butyl-1,3-di And organometallic catalysts such as acetoxy distanoxane. Among these, tetra-n-butyl-1,3-diasecitodistanoxane is preferable from the viewpoints of curability and corrosion resistance.
The curing catalyst is 0.1 to 5.0 parts by mass, preferably 0.2 to 1.5 parts by mass, based on 100 parts by mass of the total solid content of the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2). Is suitable from the viewpoint of improving the stability of the paint and the hardness of the coating film.

  The organic solvent blended in the top coating (B) is blended as necessary for improving paintability, and those capable of dissolving or dispersing the film-forming resin component can be used. For example, hydrocarbon solvents such as toluene, xylene, high boiling petroleum hydrocarbons, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, diethylene glycol Ester solvents such as monoethyl ether acetate, alcohol solvents such as methanol, ethanol and butanol, ether alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether Solvents, etc. can be mentioned water, which may be used alone or in combination of two or more.

  The top coating (B) is applied by coating the top coating (B) on the cured coating of the primer coating (A) by a curtain coating method or a roll coating method, and a cured film thickness of 5 to 30 μm, preferably 10 to 20 μm. The material is reached at a maximum material temperature (PMT) of 160 to 250 ° C. within a range of 15 to 180 seconds, particularly at a material maximum temperature of the material (PMT) of 180 to 230 ° C. within a range of 20 to 120 seconds. A dry coating film is formed by baking and drying. By the above process, a multilayer coating film in which the coating film of the top coating material (B) is formed on the coating film of the primer coating material (A) is obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited at all by the following examples, unless the summary is exceeded. Hereinafter, both “parts” and “%” are based on mass.

[Production example of primer paint (A)]
Synthesis Example 1 Production of acrylic resin AC1 solution (acrylic resin (a12))
65.0 parts of Swazol 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high-boiling aromatic petroleum solvent) was added to a flask equipped with a stirrer, condenser, thermometer, nitrogen inlet tube and dropping device, and reacted while stirring. The temperature in the container was raised to 110 ° C., and a mixture of raw materials such as monomers shown below was added dropwise over 3 hours while maintaining the temperature at 110 ° C.

Styrene 18.4 parts Methyl methacrylate 31.2 parts N-butyl acrylate 37.5 parts 2-hydroxyethyl acrylate 11.0 parts Acrylic acid 1.9 parts 2,2'-Azobisisobutyronitrile 7 parts After the completion of dropping, 0.5 parts of 2,2′-azobisisobutyronitrile was further added, and the reaction was further continued for 2 hours at the same temperature. Then, 35.0 parts of cyclohexanone was added, and the solid content was 50%. An acrylic resin AC1 solution was obtained. The acrylic resin AC1 had an acid value of 15 mgKOH / g, a hydroxyl value of 53 mgKOH / g, a glass transition temperature of 5 ° C., and a number average molecular weight of about 10,000.

Synthesis Example 2 Production of Modified Bisphenol Type Epoxy Resin ME1 Solution In a flask equipped with a stirrer, a condenser, and a thermometer, 43 parts of cyclohexanone and 70 parts of jER1004P (Note 3) (solid content) were blended and heated to a temperature of 130 ° C. After confirming that the epoxy resin was dissolved, 15.0 parts of dimer acid, 30 parts of the 50% soft acrylic resin AC1 solution obtained in Synthesis Example 1 (15 parts in solid content) and 0.5 part of tetraethylammonium bromide were added. In addition, the temperature was maintained at 130 ° C. and reacted for 3 to 4 hours. Confirming that the resin acid value is 1 mgKOH / g or less, mixed solvent 1 [cyclohexanone / swazol 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high boiling aromatic petroleum solvent) = 1/2 (mass ratio)] In addition, a modified bisphenol type epoxy resin solution ME1 having a solid content of 40% was obtained.

  (Note 3) jER1004: bisphenol A type epoxy resin manufactured by Japan Epoxy Resin, epoxy equivalent of about 925.

Synthesis Example 3 Polyester resin No. 1 solution The following raw material mixture was put into the reaction apparatus provided with the stirring apparatus, the heating apparatus, the thermometer, the separation apparatus, and the distillate storage tank, and the heating was started.

Neopentyl glycol 729 parts Hexahydrophthalic anhydride 704 parts After stirring, when stirring became possible, stirring was started, the temperature was raised to 240 ° C while removing condensed water, and the reaction was continued at the same temperature. When the outflow of water stopped after about 1.5 hours, 40 parts of xylene was added to promote the reaction, dehydration condensation was continued, and the reaction was carried out until the acid value reached 51 mgKOH / g. Next, the mixture was cooled, 417 parts of cyclohexanone was added for dilution, and a polyester resin No. 70 having a solid content of 70% was obtained. One solution was obtained. The obtained polyester resin No. 1 had a glass transition temperature of 30 ° C. and a number average molecular weight of 2,200.

Synthesis Example 4 Production of Modified Bisphenol Type Epoxy Resin ME2 Solution In a flask equipped with a stirrer, a condenser and a thermometer, 60 parts of cyclohexanone and 70 parts of jER4004P (Note 4) (solid content) were blended and heated to a temperature of 130 ° C. The epoxy resin was dissolved. After confirming that the epoxy resin was completely dissolved, 15.0 parts of dimer acid and a polyester resin No. 70 having a solid content of 70% obtained in Synthesis Example 3 were used. 21.4 parts of 1 solution (15 parts by solid content) and 0.5 part of tetraethylammonium bromide were added, and the temperature was maintained at 130 ° C. and reacted for 3 to 4 hours. Confirming that the resin acid value is 1 mgKOH / g or less, mixed solvent 1 [cyclohexanone / swazol 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high boiling aromatic petroleum solvent) = 1/2 (mass ratio)] In addition, a modified bisphenol type epoxy resin solution ME2 having a solid content of 40% was obtained.

  (Note 4) jER4004P: manufactured by Japan Epoxy Resin Co., Ltd., trade name, bisphenol F type epoxy resin, epoxy equivalent of about 880.

Synthesis Example 5 Production of Modified Bisphenol Type Epoxy Resin ME3 Solution In a reaction vessel equipped with a stirrer and a heating / temperature control device, 43 parts of cyclohexanone and 90 parts of jER1001 (Note 5) were charged and heated to 130 ° C. while stirring. did. After confirming that the epoxy resin was dissolved, 10 parts of adipic acid and 0.5 part of tetraethylammonium bromide were added, and the reaction was continued for 4 hours. After confirming that the resin acid value was 1 or less, 67.7 parts of cyclohexanone and SWAZOL 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high-boiling aromatic petroleum solvent) were added, and a modified bisphenol having a solid content of 40% Type epoxy resin solution ME3 was obtained.

  (Note 5) jER1001: Bisphenol A type epoxy resin manufactured by Japan Epoxy Resin, trade name, epoxy equivalent 475.

Synthesis Example 6 Production of Modified Bisphenol Epoxy Resin ME4 Solution In Synthesis Example 5, except that jER1001 (Note 5) is changed to jER1007 (Note 6) and adipic acid is changed to the acrylic resin AC1 solution obtained in Synthesis Example 1. It carried out similarly to the synthesis example 5, and obtained the modification | denaturation bisphenol type | mold epoxy resin solution ME4 of 40% of solid content.

  (Note 6) jER1007: manufactured by Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent of about 1,800.

Synthesis Example 7 Production of Modified Bisphenol-Type Epoxy Resin ME5 Solution In Synthesis Example 5, jER1001 (Note 5) was changed to jER1007 (Note 6), and adipic acid was obtained from Synthesis Resin No. 3 obtained in Synthesis Example 3. Except changing to 1 solution, it carried out similarly to the synthesis example 5, and obtained modified | denatured bisphenol type | mold epoxy resin solution ME5 of 40% of solid content.
Synthesis Example 8 Production of resol type phenol resin D solution
In a reaction vessel, 100 parts of p-cresol, 178 parts of a 37% aqueous formaldehyde solution and 1 part of sodium hydroxide were blended and reacted at 60 ° C for an hour, and then dehydrated at 50 ° C for 1 hour under reduced pressure.
Subsequently, 100 parts of n-butanol and 3 parts of phosphoric acid were added and reacted at 110 to 120 ° C. for 2 hours. After completion of the reaction, the sodium phosphate produced by filtering the resulting solution was filtered off to obtain a resol type phenolic resin D solution having a solid content of 50% by mass. 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.

Synthesis Example 9 Production of amino group-containing epoxy resin D solution In a reaction vessel equipped with a stirrer and a heating / temperature control device, 65 parts by weight of methoxybutyl acetate solvent, 35 parts of jER1002 (Note 7), 1.09 of 2-aminoethanol The reaction was carried out for 2 hours with stirring and stirring at 90 ° C. under a nitrogen atmosphere. Next, 1.89 parts of diethanolamine was added, and the reaction was further carried out at 90 ° C. for 1 hour, followed by dilution with a methoxybutyl acetate solvent to obtain an amino group-containing epoxy resin D solution having a solid content of 35%.

  (Note 7) jER1002: bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd., trade name, epoxy equivalent 650.

Production Example A Production of backside paint
jER1009F (Note 8) 80 parts mixed solvent 2 [cyclohexanone / ethylene glycol monobutyl ether / swazol 1500 (manufactured by Maruzen Petrochemical Co., Ltd., high boiling aromatic hydrocarbon solvent) = 3/1/1 (mass ratio)] An appropriate amount of 40 parts of titanium white, 40 parts of varita and mixed solvent 3 [cyclohexanone / swazole 1500 = 1/1 (mass ratio)] was mixed with 200 parts of the epoxy resin solution dissolved in 120 parts. The pigment dispersion was carried out until the particle diameter of the particle was 20 μm or less.
Next, 26.7 parts of Sumidur BL-3175 (Note 9) (20 parts in solid content) and 2 parts of Formate TK-1 (Note 10) were added to this dispersion and mixed uniformly. Further, the above mixed solvent 2 was added to adjust the viscosity to about 80 seconds (Ford Cup # 4/25 ° C.) to obtain a paint for the back surface.

  (Note 8) jER1009F: manufactured by Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent of about 2,000.

  (Note 9) Sumidur BL-3175: Sumika Bayer Urethane, trade name, blocked hexamethylene diisocyanate.

  (Note 10) Formate TK-1: manufactured by Mitsui Chemicals Polyurethanes, trade name, organotin blocking agent dissociation catalyst, solid content of about 10%.

Production Example 1 of Primer Paint A Production Example 1 (corresponding to Example)
To 80 parts (solid content) of a bisphenol-type epoxy resin ME1 modified with the soft organic component obtained in Synthesis Example 2, 20 parts of vanadium pentoxide, 20 parts of calcium phosphate, 20 parts of calcium metasilicate, 20 parts of titanium white, and barita 20 Part and mixed solvent 3 [swazol 1500 / cyclohexanone = 1/1 (mass ratio)] were mixed in an appropriate amount, and pigment dispersion was performed until the tub (particle diameter of the coarse pigment particles) became 20 μm or less.
Next, 20 parts (solid content) of Sumidur BL-3175 (Note 9) in this dispersion, 5 parts (solid content) of the resol type phenol resin D obtained in Synthesis Example 8, and the amino group content obtained in Synthesis Example 9 25 parts of epoxy resin D (solid content) and 2 parts of formate TK-1 (Note 10) are added and mixed uniformly. Further, the above mixed solvent 3 is added and the viscosity is about 80 seconds (Ford Cup # 4/25 ° C. ) Primer paint No. 1 was obtained.

Production Examples 2 to 6 (equivalent to Examples)
Production Example 1 was carried out in the same manner as Production Example 1 except that it was as shown in Table 1. 2-No. 6 was obtained.

Comparative production example 1
Production Example 1 was carried out in the same manner as Production Example 1 except that it was as shown in Table 1. 7 was obtained.

(Note 11) Ca ion exchange silica: R. Grace & Co. SHIELDEX (Shielddex, registered trademark) C303
[Production example of top coat (B)]
Synthesis Example 10 Hydroxyl-containing polyester resin Synthesis Example 1 (PE No. 1) In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator,
The following “monomer mixture” was charged, and the temperature was raised from 160 ° C. to 230 ° C. over 3 hours. Then, the condensed water was distilled off with a water separator and maintained at 230 ° C. for 1 hour, and then xylene was refluxed. While dehydrating, the esterification reaction was carried out.
Hexahydrophthalic anhydride 146.3 parts Neopentyl glycol 105.0 parts When the acid value reached about 0, it was cooled to 140 ° C and held for 2 hours. After cooling, the solid content was adjusted with cyclohexanone to obtain a solid content of 55 % Hydroxyl group-containing polyester resin No. 1 1 was obtained.
The obtained hydroxyl group-containing polyester resin No. 1 (hereinafter sometimes abbreviated as “PE No. 1”) had a hydroxyl value of 24.0 mgKOH / g, a glass transition temperature of 22.0 ° C., and a number average molecular weight of 2,300.

Synthesis Examples 11-16 Hydroxyl-containing polyester resin solution No. 2-No. 7 (PE No. 2 to PE No. 7) Synthesis Example (for Examples)
A polyester resin solution No. 1 was prepared in the same manner as in Synthesis Example 10 except that the content of the monomer mixture shown in Table 2 was used. 2-No. 7 (PE No. 2 to PE No. 7) was obtained.

Synthesis Examples 17-20 Hydroxyl-containing polyester resin solution No. 8-No. 11 Synthesis Example A hydroxyl group-containing polyester resin solution No. 11 was prepared in the same manner as in Synthesis Example 10 except that the content of the monomer mixture in Table 3 was used. 8-No. 11 (PE No. 8 to PE No. 11) was obtained.

[Manufacture of top coat]
Production Example 7 Production of 1A (for Examples)
Hydroxyl-containing polyester resin solution No. 1 obtained in Synthesis Example 7 1 part (PE No. 1) 80 parts (solid content), CR-93 (Note 23) 5.3 parts, Todacolor KN-V (Note 25) 0.1 part, TAROX HY-100 (Note 26) 0. 9 parts, 50 parts of Black30C940 (Note 20), and an organic solvent (Swazole 1500 / cyclohexanone = 40/60 mixed solvent) are mixed in an appropriate amount, and the pigment is dispersed until the tube (particle diameter of coarse pigment particles) is 10 μm or less. Went.
Next, 20 parts (solid content) of Sumidur BL3175 (Note 9) and 0.2 part of Formate TK-1 (Note 10) were added to this dispersion and mixed uniformly to obtain an organic solvent (Swazole 1500 / cyclohexanone = 40). / 60 mixed solvent) was added to dilute, and the top coating No. of viscosity 80 seconds (Ford Cup # 4, 25 ° C.) was applied. 1A was obtained.

Production Examples 8 to 35 Topcoat No. 2A-No. Production of 29A (for Examples)
Except for the contents of Table 4 and Table 5, the top coating No. 2A-No. 29A was obtained.

(Note 12) Cymel 303: Nippon Cytec Industries, Inc., trade name, methyl etherified melamine resin (Note 13) Takenate B830N: Mitsui Chemicals Polyurethanes, trade name, tolylene diisocyanate blocked isocyanate (Note 14) Takenate B842N: Mitsui Chemicals Polyurethane Co., Ltd., trade name, xylylene diisocyanate-based blocked isocyanate (Note 15) Takenate B870N: Mitsui Chemicals Polyurethanes Co., Ltd., trade name, isophorone diisocyanate-based blocked isocyanate (Note 16) Black30C933: Shepherd Manufactured, trade name, Fe-Cu-Mn pigment, inorganic composite oxide pigment (B32)
(Note 17) Black 6301: manufactured by Asahi Kasei Kogyo Co., Ltd., trade name, Bi-Mn pigment, inorganic composite oxide pigment (B32)
(Note 18) Black 6302: manufactured by Asahi Kasei Kogyo Co., Ltd., trade name, Sr—Mn pigment, inorganic composite oxide pigment (B32)
(Note 19) HR-B: manufactured by Toda Kogyo Co., Ltd., trade name, Fe-Co-Al-Mg pigment, inorganic composite oxide pigment (B31)
(Note 20) Black 30C940: manufactured by Shepherd, trade name, Fe-Cr pigment, inorganic composite oxide pigment (B33)
(Note 21) Black 3500: manufactured by Shepherd, trade name, Fe-Cr-Co pigment, inorganic composite oxide pigment (B33)
(Note 22) KR-900: manufactured by Kawamura Chemical Co., Ltd., trade name, Fe-Co pigment, inorganic composite oxide pigment (B33)
(Note 23) CR-93: Ishihara Sangyo Co., Ltd., trade name, titanium white (Note 24) Mitsubishi Carbon MA-100: Mitsubishi Chemical Corporation, trade name, carbon black (Note 25) Toda Color KN-V: Toda Kogyo Co., Ltd. Manufactured, trade name, iron oxide bengara (Note 26) TAROX HY-100: manufactured by Titanium Industry Co., Ltd., trade name, yellow iron oxide (Note 27) LIONOL GREEN 8930: manufactured by Toyo Ink Manufacturing Co., Ltd., trade name, green organic pigment (Note) 28) Fastgen Super RED500RG: Toyo Ink Mfg. Co., Ltd., trade name, red organic pigment (Note 29) Necure 5225: King Industries, Inc. (USA), trade name, amine neutralized solution of dodecylbenzenesulfonic acid (Note 30) ) Tinuvin 400: Ciba Specialty Chemicals, trade name, UV absorber (Note 31) Sanol LS2 92: Sankyo Lifetech Co., Ltd., trade name, light stabilizer.

Comparative Production Example 2 Production of 1B (for comparative example)
Hydroxyl-containing polyester resin solution No. obtained in Synthesis Example 17 8 solution (PE No. 8) 80 parts (solid content), CR-93 (Note 23) 5.3 parts, Todacolor KN-V (Note 25) 0.1 part, TAROX HY-100 (Note 26) 0. 9 parts, 50 parts of Black30C940 (Note 20), and an organic solvent (Swazole 1500 / cyclohexanone = 40/60 mixed solvent) are mixed in an appropriate amount, and the pigment is dispersed until the tube (particle diameter of coarse pigment particles) is 10 μm or less. Went.
Next, 20 parts (solid content) of Sumidur BL3175 (Note 9) and 0.2 part of Formate TK-1 (Note 10) were added to this dispersion and mixed uniformly to obtain an organic solvent (Swazole 1500 / cyclohexanone = 40). / 60 mixed solvent) was added to dilute, and the top coating No. of viscosity 80 seconds (Ford Cup # 4, 25 ° C.) was applied. 1B was obtained.

Comparative Production Examples 3 to 25 2B-No. Production of 24B (for comparative example)
Except for the contents of Table 6 and Table 7, the top coating No. 2B-No. 24B was obtained.

Example 1 Painted metal plate No. 1 Create 1
The primer paint No. obtained in Production Example 1 was applied on a hot-dip galvanized steel sheet having a thickness of 0.5 mm × 70 mm × 150 mm subjected to zinc phosphate treatment. No. 1 was coated so that the dry film thickness was about 5 μm, and baked for 30 seconds so that the maximum material reached temperature was 220 ° C. to obtain a primer-coated metal plate.
On the above-mentioned primer-coated metal plate, the top coating paint No. obtained in Production Example 7 was obtained. 1A was coated with a roll coater so as to have a dry film thickness of 20 μm and baked for 60 seconds at a maximum material reaching temperature of 190 ° C. 1 was obtained.

Examples 2-35 Painted metal plate No. 2-No. 35 The coated metal plate No. 35 was prepared in the same manner as in Example 1 except that the paint contents and heat curing conditions in Tables 8 and 9 were used. 2-No. 35 was obtained. Since the test according to the following test conditions was conducted, the results are also shown.

Comparative Examples 1-25
A coated metal plate No. 1 was prepared in the same manner as in Example 1 except that the paint contents and conditions in Tables 11 and 12 were used. 36-No. 60 was obtained. Since the test according to the following test conditions was conducted, the results are also shown.

(Note 30) Workability:
In a room at 20 ° C, the coating plate surface of the paint plate is folded outward, and the paint plate is bent 180 degrees with a vise without any inner part inside (4T bending process) The coating state of the folded part when the plate is folded 180 degrees in a vise with 4 sheets of the same thickness as the painted plate sandwiched between them is shown below. Evaluation was based on criteria.
◎ indicates that no abnormality of the coating film is observed in the processed part.
○, both or one of the occurrence of cracking of the coating film and peeling of the coating film is slightly observed in the processed part,
△ indicates that both or one of the occurrence of cracking of the coating film and peeling of the coating film is considerably observed in the processed part.
In the case of x, both or one of occurrence of cracking of the coating film and peeling of the coating film is remarkably observed in the processed part.

(Note 31) Accelerated weather resistance (hydrogen peroxide loaded xenon): “Xenon lamp irradiation and rain (21 hours) → Xenon lamp irradiation and 1% hydrogen peroxide (spray) (1 hour) → Rain in the dark ( In the coating film which was tested until 11 cycles (252 hours) with 1 cycle) as 1 cycle, the gloss retention (%) with respect to the initial gloss measured at 60 ° specular gloss was examined.
◎: Gloss retention exceeds 70% ○: Gloss retention exceeds 50% and 70% or less △: Gloss retention exceeds 30% and 50% or less ×: Gloss retention is less than 30%.

(Note 32) Weather corrosion resistance test: Method A of accelerated weathering (xenon lamp method) test for long-term durability of coating film specified in JIS K 5600 7.7 on a test coating plate cut to a size of 5 cm × 10 cm Based on the above, the xenon weatherometer was continuously irradiated for 750 hours under the repeated cycle conditions of (wet 18 minutes-dry 102 minutes).
Next, a cross cut with a narrow angle of 30 degrees and a line width of 0.5 mm reaching the substrate is put in the center of the surface side of each test paint plate using the back of the cutter knife, and JASO M609-91 (automobile material corrosion test) 1991), a combined cycle corrosion test (CCT test) was conducted by the following formula: “(35 ° C., 5% saline spray 2 hours) — (60 ° C., 4 hours, relative humidity 95%) — (50 ° C., wet 2 hours) The test was performed for 150 cycles (total of 1200 hours), with "humidity 95%)" as one cycle.
・ Plane part (B rank or higher is accepted)
A: No blistering, etc. No abnormality B: Small blister (less than 3 mm in diameter) is less than 1 to 10 points and no blistering is 3 mm or more in diameter C: Small blister (less than 3 mm in diameter) is 10 or more points Or, one or more bulges with a diameter of 3 mm or more
The average value of the edge creep width on the left and right sides of the long side of the painted plate was determined and evaluated according to the following criteria.
◎ is less than 5mm,
○ is 5 mm or more and less than 10 mm,
Δ is 10 mm or more and less than 20 mm,
X is 20 mm or more.
・ Cross cut part The corrosion state of the cross cut part is determined by the average ratio of the white rust occurrence length in the bare metal exposed part of 0.5 mm cut width and the left and right swelling width (sum of both sides) of the cut part. Evaluation based on the criteria.
◎ indicates that the white rust generation length ratio in the bare metal exposed portion is less than 50% and the swelling width is less than 3 mm,
○ is a white rust occurrence length ratio of 50% or more at the bare metal exposed portion and less than 3 mm in the bulge width, or a white rust occurrence length ratio of less than 50% in the bare metal exposed portion and the bulge width of 3 mm or more and less than 5 mm,
Δ is a white rust occurrence length ratio of 50% or more in the bare metal exposed part and a swelling width of 5 mm or more and less than 10 mm,
X indicates a white rust generation length ratio of 50% or more in the bare metal exposed portion and a swelling width of 10 mm or more.

  A coated metal plate excellent in coating film appearance, coating film hardness, workability, weather resistance and corrosion resistance can be provided.

Claims (10)

Chemical conversion treatment on one or both sides of which may metal plates have been applied to the surface, coating a primer coating composition (A), and by curing, to form a dry film thickness 1~10μm primer cured film Step, and
Step on at least one surface of the primer cured film was coated on the intermediate paint (B), and by causing heat curing, to form the topcoat cured film having a dry thickness of 5 to 30 [mu] m,
A method for forming a multilayer coating film , comprising :
Primer coating (A) is contained as the bisphenol type epoxy resin (A1), and the crosslinking agent (A2), and a rust preventive component containing no anticorrosive pigments chromium-based (A3),
The bisphenol type epoxy resin (A1) is an aliphatic polybasic acid (a11) having 4 to 36 carbon atoms, an acrylic resin (a12) having a glass transition temperature of -20 to 50 ° C, and a polyester resin having a glass transition temperature of -20 to 50 ° C. Modified with at least one soft organic component of (a13),
Overcoat Ri paint (B) is a hydroxyl-containing polyester resin (B1), blocked aliphatic polyisocyanate and / or blocked Kaabura alicyclic polyisocyanate compound crosslinking agent containing a (B2), Mg, Zn, Li and Mn Inorganic composite oxide pigment (B31) containing at least one metal selected from the group consisting of Fe, Co and Al, Bi-Mn based inorganic composite oxide pigment (B32), Fe-Cu-Mn based inorganic composite oxide pigment (B32), an inorganic composite oxide pigment selected from Mn—Sr based inorganic composite oxide pigment (B32), Fe—Cr based inorganic composite oxide pigment and Fe—Cr—Co based inorganic composite oxide pigment (B33) ( B3) containing and,
The hydroxyl group-containing polyester resin (B1) is based on i) hexahydrophthalic acid or its anhydride, hexahydroisophthalic acid, tetrahydrophthalic acid or its anhydride, and 1,4-based on the total mass of the acid component (b1). The total proportion of at least one polybasic acid selected from cyclohexanedicarboxylic acid is 90 to 100% by mass, and (ii) neopentyl glycol, 1,4-based on the total mass of the alcohol component (b2). It is obtained by reacting an acid component (b1) and an alcohol component (b2), wherein the total proportion of at least one alcohol component selected from cyclohexanedimethanol and hydrogenated bisphenol A is 50 to 100% by mass. Yes, and
The top coating (B) contains 10 to 100 parts by mass of the inorganic composite oxide pigment (B3) with respect to 100 parts by mass in total of the solid content of the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2).
The method for forming a multilayer coating film, wherein: Alcohol component (b2) is contained neopentyl glycol, at least one selected from 1,4-cyclohexane dimethanol and hydrogenated bisphenol A, and at least one selected from trimethylol propane and glycerin, claim 1 A method for forming a multilayer coating film according to 1. The method for forming a multilayer coating film according to claim 1 or 2, wherein in the hydroxyl group-containing polyester resin (B1), the acid component (b1) is hexahydrophthalic anhydride and the alcohol component (b2) is neopentyl glycol. Top coat (B) further contains an ultraviolet absorber and / or light stabilizers, multilayer coating film forming method according to any one of claims 1 to 3. Anticorrosive component (A3) is at least one vanadium compound selected from vanadium pentoxide, ammonium calcium vanadate and metavanadate (1), and phosphoric acid metal salt (2), selected from metal silicates and silica fine particles at least one silicon-containing compound containing a (3), a multilayer coating film forming method according to any one of claims 1 to 4 to be. The method for forming a multilayer coating film according to claim 5, wherein the metal phosphate (2) is calcium phosphate. The method for forming a multilayer coating film according to any one of claims 1 to 6, for producing a precoated metal sheet. A primer cured coating film having a dry film thickness of 1 to 10 μm formed from the primer coating (A) on one or both surfaces of a metal plate that may be subjected to chemical conversion treatment on the surface, and at least the primer cured coating film A multilayer coating film on a metal plate having a dry coating film thickness of 5 to 30 μm formed from the top coating material (B) on one side,
The primer paint (A) contains a bisphenol type epoxy resin (A1), a crosslinking agent (A2), and a rust preventive component (A3) not containing a chromium-based rust preventive pigment,
The bisphenol type epoxy resin (A1) is an aliphatic polybasic acid (a11) having 4 to 36 carbon atoms, an acrylic resin (a12) having a glass transition temperature of -20 to 50 ° C, and a polyester resin having a glass transition temperature of -20 to 50 ° C. Modified with at least one soft organic component of (a13),
The top coat (B) is composed of a hydroxyl group-containing polyester resin (B1), a crosslinking agent (B2) containing a blocked aliphatic polyisocyanate and / or a blocked alicyclic polyisocyanate compound, and Mg, Zn, Li, and Mn. Inorganic composite oxide pigment (B31) containing at least one selected metal, Fe, Co and Al, Bi-Mn inorganic composite oxide pigment (B32), Fe-Cu-Mn inorganic composite oxide pigment ( B32), an Mn—Sr inorganic composite oxide pigment (B32), an Fe—Cr inorganic composite oxide pigment and an Fe—Cr—Co inorganic composite oxide pigment (B3). Contains,
The hydroxyl group-containing polyester resin (B1) is based on i) hexahydrophthalic acid or its anhydride, hexahydroisophthalic acid, tetrahydrophthalic acid or its anhydride, and 1,4-based on the total mass of the acid component (b1). The total proportion of at least one polybasic acid selected from cyclohexanedicarboxylic acid is 90 to 100% by mass, and (ii) neopentyl glycol, 1,4-based on the total mass of the alcohol component (b2). It is obtained by reacting an acid component (b1) and an alcohol component (b2), wherein the total proportion of at least one alcohol component selected from cyclohexanedimethanol and hydrogenated bisphenol A is 50 to 100% by mass. Yes, and
The top coating (B) contains 10 to 100 parts by mass of the inorganic composite oxide pigment (B3) with respect to 100 parts by mass in total of the solid content of the hydroxyl group-containing polyester resin (B1) and the crosslinking agent (B2).
The multilayer coating film characterized by the above. A coated metal sheet comprising the multilayer coating film according to claim 8 and a metal sheet coated with the multilayer coating film. The painted metal plate according to claim 9, which is a precoated metal plate.