JP2014009288A - Metallic coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition that can form a metallic coat excellent in chemical resistance and weather resistance, particularly a coating composition suitable to form matte metallic topcoat films on metal plates.SOLUTION: A coating composition comprises: a resin binder component including a polyester resin component containing an aliphatic acid-modified polyester resin in which the total content of alicyclic polybasic acid is within a particular range relative to the total amount of a polybasic acid component and a melamine resin component containing a butyl-etherified melamine resin; and a metallic pigment component.

Description

  The present invention relates to a metallic coating composition capable of forming a coating film excellent in weather resistance, particularly a metallic coating composition suitable for forming a top coating film on a coated metal plate, and a coating film excellent in weather resistance using the coating composition. And a coated metal plate on which a cured coating film is formed by the coating composition.

  Conventionally, outdoor base materials (for example, buildings, display objects, guard fences, appliances, machines, etc.) have been coated with an outdoor paint for the purpose of decoration or protection. In these paints, the coating film deteriorates due to the effects of dust, iron powder, rain (acid rain), sunlight, etc. when exposed outdoors. It is required to have excellent properties.

  Examples of paints used for outdoor use include polyurethane resin paints, fluororesin paints, silicon resin paints, acrylic resin paints, polyester paints, and the like. In paint specifications, metallic pigments typified by aluminum pigments do not have sufficient weather resistance and chemical resistance, and thus are susceptible to deterioration and further deterioration due to corrosion by acids and alkalis.

  The deterioration and deterioration of the metallic pigment in the coating film promotes the deterioration of the entire coating film, the coating film cohesively breaks down, and the adhesion to the lower layer coating film such as a primer coating film decreases. There was a problem that the metallic coating film peeled off.

  For example, Patent Document 1 is characterized in that the surface of aluminum particles is coated with a resin composition containing a copolymerizable resin and a phenol-based antioxidant, as a solution to such problems. An aluminum pigment composition, and a coating composition containing the aluminum pigment composition, a binder, and a solvent have been proposed.

  However, since the coating composition of Patent Document 1 treats an aluminum pigment, it requires man-hours for manufacturing, and also requires an antioxidant, which is an expensive raw material, and thus manufacturing costs. From the viewpoint of, it is not preferable. Moreover, the improvement effect of the chemical resistance of a metallic coating film and a weather resistance may be inadequate.

  Further, in particular, the matte-specification coating film has a problem that the deterioration is more likely to proceed as compared with the glossy coating film, and problems such as cohesive failure and peeling of the coating film are likely to occur.

JP 2003-64283 A

  An object of the present invention is to provide a coating composition capable of forming a metallic coating film excellent in chemical resistance and weather resistance, particularly a coating composition suitable for forming a top coating film of a glossy metallic coating metal plate. That is.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a resin containing a polyester resin component containing a specific fatty acid-modified polyester resin and a melamine resin component containing a butyl etherified melamine resin. A coating composition containing a binder component and a metallic pigment component is particularly suitable for a chemical coating and a weather resistance in a metallic coating film having a matte specification (particularly a gloss less than semi-gloss (60 ° gloss value is about 60 or less)). The present inventors have found that a coating film having excellent properties can be formed, and have completed the present invention.

That is, the present invention
The total content of the alicyclic polybasic acid (a1-1) obtained by the reaction of the polybasic acid component (a1), the alcohol component (a2) and the fatty acid (a3) and the polybasic acid component (a1) is The total content of the trihydric or higher polyhydric alcohol (a2-1) in the alcohol component (a2) is within the range of 50 to 100 mol% based on the total amount of the polybasic acid component (a1). 50 fatty acid-modified polyester resins (A1) having a number average molecular weight of 5,000 to 30,000, a hydroxyl value of 5 to 100 mgKOH / g, and an oil length of 3 to 30% based on the total amount of a2) ~ 100 mass% polyester resin component (A),
A coating composition comprising a melamine resin component (B) containing 50 to 100% by mass of a butyl etherified melamine resin (B1) and a metallic pigment component (C) is provided.

  In addition, the present invention forms a primer coating with a chromium-free primer coating not containing a chromium-based rust preventive component on a metal plate, and forms a top coating with the coating composition on the primer coating. The coating-film formation method characterized by becoming is provided.

  Further, in the present invention, a primer coating film made of a chromium-free primer coating not containing a chromium-based anticorrosive component is formed on a metal plate, and a top coating film made of the coating composition is formed on the primer coating film. The present invention provides a painted metal plate characterized by:

  Furthermore, the present invention provides a matte coated metal sheet on which a coating film is formed by the coating composition further containing a matting agent (D).

  The coating composition of the present invention comprises a resin binder component containing a polyester resin component containing a specific fatty acid-modified polyester resin, a melamine resin component containing a butyl etherified melamine resin, and a metallic pigment component. With this coating composition, a coating film excellent in chemical resistance and weather resistance can be formed even in a coating film having a matte specification (60 ° gloss value of about 60 or less).

  In general, it is presumed that when the metallic pigment present in the metallic coating film corrodes, a corrosion product is formed on the surface of the metallic pigment, and the water absorption as the whole coating film is remarkably increased. By increasing the water absorption rate of the metallic coating film, hydrolysis of the resin component in the coating film is promoted. As a result, the coating film changes in quality, and the cohesive failure of the coating film progresses due to a decrease in cohesive force. Further, the adhesion force between the lower coating film and the lower coating film also decreases, and it is considered that peeling occurs.

  Further, it is considered that the peeling of the coating film due to the decrease in the adhesion force is accelerated as the coating film is affected by the light transmittance of the metallic coating film and the interlayer coating film and the lower coating film are more likely to deteriorate.

  In such an estimation mechanism, even in an environment where hydrolysis of the resin component due to corrosion of the metallic pigment is promoted, the specific fatty acid-modified polyester resin that is an essential component of the coating composition of the present invention is a polybasic acid. Since 50 mol% or more of the components is an alicyclic polybasic acid, it has better weather resistance and hydrolysis resistance than ordinary polyester resins, thus preventing coating deterioration and cohesive failure. As a result, it is presumed that the metallic coating film has good chemical resistance and weather resistance.

  In addition, it is presumed that the fatty acid-modified portion acts as an adsorption functional group of the metallic pigment component, which contributes to suppression of corrosion of the metallic pigment, and further suppression of increase in water absorption as a whole metallic coating film. It is also possible.

  The reason why a coating film excellent in chemical resistance and weather resistance can be formed even when the coating film by the coating composition of the present invention is a matte coating film is not clear, I think as follows.

  Coating films with matting specifications with matting agents etc. have a rough surface compared to glossy coatings, are easily wetted with water, and are exposed to more severe conditions regarding hydrolysis resistance. When the polyester paint system is used, in the matte-colored metallic paint, the deterioration of the painted surface is further accelerated, and the appearance is not good.

  The fatty acid-modified polyester resin using a large amount of alicyclic polybasic acid as the polybasic acid component, which is the base resin of the coating composition of the present invention, has good weather resistance and hydrolysis resistance, and further, a metallic pigment component It is considered that it also has an advantageous effect on inhibiting the deterioration of the pigment component.

  As described above, the coating film obtained by the coating composition of the present invention has excellent hydrolysis resistance and suppresses deterioration of the metallic pigment component, and thus is particularly excellent as compared with conventional polyester-based metallic coating compositions. It is considered that the chemical resistance and weather resistance can be exhibited.

  The coating composition of the present invention is a coating composition containing the following polyester resin component (A), melamine resin component (B), and metallic pigment component (C).

Polyester resin component (A)
In the coating composition of the present invention, the polyester resin component (A) contains 50 to 100% by mass of the following fatty acid-modified polyester resin (A1).

Fatty acid-modified polyester resin (A1)
The fatty acid-modified polyester resin (A1) that is an essential component of the polyester resin component (A) is obtained by a reaction of the following polybasic acid component (a1), alcohol component (a2), and fatty acid (a3).

Polybasic acid component (a1)
In this invention, a polybasic acid component (a1) contains an alicyclic polybasic acid (a1-1), and is the sum total of the alicyclic polybasic acid (a1-1) in a polybasic acid component (a1). The content is in the range of 50 to 100 mol%, preferably 70 to 100 mol%, more preferably 80 to 100 mol%, based on the total amount of the polybasic acid component (a1).

  The alicyclic polybasic acid (a1-1) is generally a compound having one or more alicyclic structures (mainly 4 to 6 membered rings) and two or more carboxyl groups in one molecule, Acid anhydrides and esterified products of the compounds, for example, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, Cycloaliphatic polyvalents such as 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, etc. Carboxylic acid; anhydride of the alicyclic polyvalent carboxylic acid; lower alkyl esterified product of the alicyclic polyvalent carboxylic acid, and the like. Rhohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2- Dicarboxylic acid anhydride can be preferably used.

  Among the above, 1,2-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic acid anhydride are particularly preferable from the viewpoint of hydrolysis resistance.

  The said alicyclic polybasic acid (a1-1) can be used individually or in combination of 2 or more types.

  As a polybasic acid component, an aromatic polybasic acid (a1-2) and an aliphatic polybasic acid (a1-3) can be used in addition to the alicyclic polybasic acid (a1-1).

  The aromatic polybasic acid (a1-2) is generally an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and an esterified product of the aromatic compound. For example, aromatic polyvalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid; anhydride of the aromatic polyvalent carboxylic acid A lower alkyl esterified product of the aromatic polyvalent carboxylic acid. The aromatic polybasic acid (a1-2) can be used alone or in combination of two or more.

  The aliphatic polybasic acid (a1-3) is generally an aliphatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound. Aliphatic polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid, citric acid; An anhydride of the aliphatic polyvalent carboxylic acid; a lower alkyl esterified product of the aliphatic polyvalent carboxylic acid, and the like. The above aliphatic polybasic acids can be used alone or in combination of two or more.

  As said aliphatic polybasic acid (a1-3), it is preferable to use the dicarboxylic acid which has a C4-C18 alkyl chain. Examples of the dicarboxylic acid having an alkyl chain having 4 to 18 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, and octadecanedioic acid. Among them, adipic acid can be preferably used.

Alcohol component (a2)
In the present invention, the alcohol component (a2) contains a trihydric or higher polyhydric alcohol (a2-1), and the total content of the trihydric or higher polyhydric alcohol (a2-1) in the alcohol component (a2). Is in the range of 10 to 70 mol%, preferably 20 to 65 mol%, more preferably 30 to 60 mol%, based on the total amount of the alcohol component (a2).

  Examples of the trihydric or higher polyhydric alcohol (a2-1) include glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, Trihydric or higher alcohols such as sorbitol and mannitol; polylactone polyols obtained by adding lactones such as ε-caprolactone to these trihydric or higher alcohols; tris (2-hydroxyethyl) isocyanurate, tris (2- And tris (hydroxyalkyl) isocyanurate such as hydroxypropyl) isocyanurate and tris (2-hydroxybutyl) isocyanurate.

  Among these, trimethylolpropane is particularly preferable from the viewpoint of increasing the molecular weight and improving the reactivity of the modification reaction with the fatty acid (a3).

  As the alcohol component, a trihydric or higher polyhydric alcohol (a2-1), a dihydric alcohol (a2-2), and a monoalcohol (a2-3) can be used.

  Examples of the dihydric alcohol (a2-2) include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, and 1,3-butanediol. 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1, 5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-1,5 -Pentanediol, 2,2,4-trimethyl-1,3- Nthanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, water Dihydric alcohols such as hydrogenated bisphenol A and hydrogenated bisphenol F; polylactone diols obtained by adding lactones such as ε-caprolactone to these dihydric alcohols; ester diols such as bis (hydroxyethyl) terephthalate; alkylene of bisphenol A Examples include oxide adducts, polyether diols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol.

  Examples of the monoalcohol (a2-3) include monoalcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, stearyl alcohol, and 2-phenoxyethanol; glycidyl esters of propylene oxide, butylene oxide, and synthetic highly branched saturated fatty acids (trade names) Examples thereof include alcohol compounds obtained by reacting a monoepoxy compound such as “Cardura E10” (made by HEXION Specialty Chemicals) with an acid.

Fatty acid (a3)
In the present invention, the fatty acid (a3) is a linear hydrocarbon monovalent carboxylic acid, such as coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid. Fatty acids such as linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc. Can be mentioned. The said fatty acid can be used individually or in combination of 2 or more types.

Of these, those having a low degree of unsaturation, specifically those having an iodine value of 20 or less, particularly 10 or less, are preferred from the viewpoint of weather resistance. The iodine value is a numerical value serving as an index representing the degree of unsaturation of the compound, and is represented by the number of g of iodine absorbed by 100 g of the sample. The measurement can be performed according to the standard of JIS K 5421.
From the viewpoint of the degree of unsaturation, coconut oil fatty acid, lauric acid, myristic acid, palmitic acid, stearic acid, especially coconut oil fatty acid can be suitably used as the fatty acid (a3).

  The production of the fatty acid-modified polyester resin (A1) is not particularly limited, and can be performed according to a usual method. For example, the polybasic acid component (a1), the alcohol component (a2), and the fatty acid (a3) are reacted at 150 to 250 ° C. for 5 to 10 hours in a nitrogen stream to perform an esterification reaction or a transesterification reaction. A method is mentioned.

  The modification with the fatty acid (a3) is performed simultaneously with the esterification reaction or transesterification reaction of the polybasic acid component (a1) and the alcohol component (a2), or after the esterification reaction or after the transesterification reaction. Can do.

  The polybasic acid component (a1), alcohol component (a2), and fatty acid (a3) may be added at once, or may be added in several portions. Moreover, after synthesize | combining a carboxyl group-containing fatty acid modified polyester resin first, you may esterify this carboxyl group-containing fatty acid modified polyester resin using the said alcohol component (a2). Furthermore, after first synthesizing a hydroxyl group-containing fatty acid-modified polyester resin, the acid anhydride may be reacted to half-esterify the hydroxyl group-containing fatty acid-modified polyester resin.

  In the esterification or transesterification reaction, a catalyst may be used to promote the reaction. As the catalyst, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used.

  The fatty acid-modified polyester resin (A1) can also be modified with a monoepoxy compound during or after preparation of the resin. As the monoepoxy compound, for example, a glycidyl ester of a synthetic highly branched saturated fatty acid (trade name “Cardura E10” manufactured by HEXION Specialty Chemicals) can be suitably used.

  The fatty acid-modified polyester resin (A1) may have a number average molecular weight in the range of 5000 to 30000, preferably 7000 to 25000, and more preferably 10000 to 20000, from the viewpoint of processability and smoothness of the resulting coating film. Is preferred.

  The fatty acid-modified polyester resin (A1) is generally a hydroxyl group in the range of 5 to 100 mgKOH / g, preferably 10 to 90 mgKOH / g, more preferably 40 to 80 mgKOH / g, from the viewpoint of curability of the resulting coating film. It is preferable to have a valence.

  The fatty acid-modified polyester resin (A1) preferably has an oil length in the range of 3 to 30%, preferably 5 to 20%, from the viewpoint of the weather resistance of the resulting coating film. Here, the oil length is mass% of the fatty acid component (a3) with respect to the total amount of the acid component (a1), the alcohol component (a2) and the fatty acid component (a3) which are constituent components.

  In addition, the fatty acid-modified polyester resin (A1) preferably has a glass transition temperature in the range of 0 to 50 ° C., preferably 10 to 40 ° C., from the viewpoint of the hardness and workability of the resulting coating film. .

  The adjustment of the number average molecular weight and the hydroxyl value of the fatty acid-modified polyester resin (A1) is, for example, equivalent of the carboxyl group in the polybasic acid component (a1) and the fatty acid component (a3) and the hydroxyl group in the alcohol component (a2). The ratio (COOH / OH) can be adjusted, or the reaction time in the esterification reaction or transesterification reaction can be adjusted.

  The equivalent ratio (COOH / OH) of the carboxyl group in the polybasic acid component (a1) and the hydroxyl group in the alcohol component (a2) is generally 0.5 to 0.98, preferably 0.6 to It is preferable to be within the range of 0.95.

  In addition, the number average molecular weight and the weight average molecular weight in this specification are based on the number average molecular weight and the weight average molecular weight measured with a gel permeation chromatograph (manufactured by Tosoh Corporation, “HLC8120GPC”) based on the molecular weight of standard polystyrene. It is a converted value. In this measurement, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, and “TSKgel G-2000HXL” (both trade names, manufactured by Tosoh Corporation) were used as columns. The measurement conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow rate 1 mL / min, detector RI were used.

  Moreover, in this specification, glass transition temperature (Tg) is based on a differential thermal analysis (DSC).

  As the polyester resin component (A), in addition to the fatty acid-modified polyester resin (A1), a fatty acid-modified polyester resin having an oil length of less than 3% based on the fatty acid component (a3) in the fatty acid-modified polyester resin (A1) can also be used.

  Further, an oil-free polyester resin (A2) that is not modified with fatty acid can also be used.

  The oil-free polyester resin (A2) is a polyester resin obtained by an esterification reaction or a transesterification reaction of the polybasic acid component (a1) and the alcohol component (a2) by a conventional method, and the polybasic acid component (a1) and As an alcohol component (a2), it can manufacture in the same way as the method illustrated by the said fatty acid modified polyester resin (A1), using what was illustrated by the said fatty acid modified polyester resin (A1).

  In the present invention, the amount of the fatty acid-modified polyester resin (A1) relative to the total amount of the polyester resin component (A) is 50 to 100% by mass, preferably from the viewpoint of weatherability and corrosion resistance retention of the resulting coating film. Is in the range of 60 to 100% by mass, more preferably 70 to 100% by mass.

Melamine resin component (B)
In the coating composition of the present invention, the melamine resin component (B) contains 50 to 100% by mass of the following butyl etherified melamine resin (B1).

Butyl etherified melamine resin (B1)
The butyl etherified melamine resin is a part of the methylol group in the methylolated melamine resin, which is an addition reaction product of melamine and aldehyde components such as formaldehyde and paraformaldehyde (which may be either a monomer or a multimer). Alternatively, it is a melamine resin that is etherified with n-butyl alcohol or isobutyl alcohol, and has a number average molecular weight of 800 to 8000, particularly 1000 to 5000, in terms of the processability and stain resistance of the resulting coating film. It is preferable to be in the range. The butyl etherified melamine resin (B1) can be used alone or as a mixture of two or more.

  Commercially available products of butyl etherified melamine resin (B1) include, for example, Uban 20SE, 225 (all of which are manufactured by Mitsui Chemicals, Inc.), Super Becamine J820-60, L-117-60, L- 109-65, 47-508-60, L-118-60, G821-60 (all are manufactured by DIC Corporation).

  As the melamine resin component (B), a melamine resin (melamine resin (B2)) other than the butyl etherified melamine resin (B1) can be used.

Specifically, for example, a methylol group in a methylolated melamine resin, which is an addition reaction product of melamine and an aldehyde component such as formaldehyde or paraformaldehyde (which may be either a monomer or a multimer). Mention may be made of melamine resins in which part or all are etherified with one or more alcohols other than n-butyl alcohol or isobutyl alcohol. Examples of alcohols used for etherification include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, 2-ethylbutanol, and 2-ethylhexanol.
Examples of the melamine resin etherified with methyl alcohol include Sumimar M-100, M-40S, and M-55 (all trade names, manufactured by Sumitomo Chemical Co., Ltd.), Cymel 300, 303, 325, and 327. 350, 370, 730, 736, 738 (above, both are made by Nippon Cytec Industries, Inc., trade name), Melan 522, 523 [above, both are made by Hitachi Chemical Co., Ltd.], Methyl such as Nicarak MS17, MS15, MS001, MX430, MX650 (both manufactured by Sanwa Chemical Co., Ltd., trade names), Resimin 740, 741, 747 (all of which are manufactured by Monsanto Co., Ltd.) Mention may be made of etherified melamine resins.

  Examples of melamine resins etherified with methyl alcohol and butyl alcohol include Cymel 232, 235, 202, 238, 254, 266, 272, 1130, XV-514, XV805 (both Examples include methyl / butyl mixed etherified melamine resins such as Nippon Cytec Industries, Ltd. (trade name), Sumimar M66B (trade name, Sumitomo Chemical Co., Ltd.), Resimin 753, 755 (all of which are manufactured by Monsanto). be able to.

  In the present invention, the amount of the butyl etherified melamine resin (B1) is 50 to 100% by mass with respect to the total amount of the melamine resin component (B) from the viewpoint of the workability of the resulting coating film and the stain resistance retention. , Preferably it is 70-100 mass%, More preferably, it exists in the range of 80-100 mass%.

  Moreover, in order to accelerate | stimulate the hardening reaction of a polyester resin component (A) and a melamine resin component (B), a curing catalyst can be used as needed. As a curing catalyst for promoting this curing reaction, a sulfonic acid compound or a neutralized product of a sulfonic acid compound is generally used.

Examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and the like. Examples of the neutralizing agent in the neutralized product of the sulfonic acid compound include basic compounds such as primary amine, secondary amine, tertiary amine, ammonia, caustic soda, and caustic potash.
In the coating composition of the present invention, the ratio of the polyester resin component (A) and the melamine resin component (B) is based on the total amount of the polyester resin component (A) and the melamine resin component (B). A) is 50 to 90% by mass, in particular 60 to 80% by mass, and the melamine resin component (B) is 10 to 50% by mass, in particular 20 to 40% by mass, the curability of the resulting coating film, From the viewpoints of mechanical strength, workability, solvent resistance, chemical resistance, corrosion resistance, weather resistance, etc., it is preferable.

Metallic pigment component (C)
Metallic pigments are pigments that reflect the received light to give the coating a glittery feeling and light interference pattern. Specifically, non-leafing type or leafing type aluminum (including vapor deposited aluminum), copper Metal powder such as zinc, brass, nickel, aluminum oxide, flake iron oxide (MIO), stainless steel powder, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide, At least one pigment selected from metal flakes, mica, pearl pigments, glass flakes and the like can be used.

  The shape of the metallic pigment may be various shapes such as a granular shape, a plate shape, a lump shape, and a flake shape (scale shape). From the viewpoint of imparting an excellent metallic feeling and luminance to the coating film, it may be a flake shape. preferable.

  The amount of the metallic pigment may be arbitrarily selected according to the kind of pigment to be used and the glitter, color tone, brightness, saturation, etc. required for the coating film, but from the relationship with the light transmittance and water resistance of the coating film. Based on the total amount of the components (A) and (B), it is preferably in the range of 10 to 60% by mass, particularly 15 to 50% by mass, and more particularly 20 to 40% by mass.

  The light transmittance in the wavelength range of 310 to 350 nm of the coating film having a dry film thickness of 15 μm obtained from the coating composition of the present invention is 5% or less, particularly 3% or less, more particularly 2% or less. From the viewpoint of sex.

  The average particle diameter of the metallic pigment is not particularly limited, but is preferably within the range of 5 to 100 μm, particularly 10 to 40 μm, from the viewpoint of achieving both the finished appearance and the concealing property of the coating film.

  The average particle size of the metallic pigment can be determined by calculating the volume average from the particle size distribution measured by a known particle size distribution measurement method such as a laser diffraction method, a micromesh sieve method, a Coulter counter method or the like.

  The average particle diameter of the metallic pigment in the present invention is a median diameter (d50) of a volume-based particle size distribution measured by a laser diffraction scattering method, and is a value measured using a Nikkiso Co., Ltd. Microtrac particle size distribution measuring device. is there.

  The average thickness of the metallic pigment is not particularly limited, but is preferably in the range of 0.1 to 5 μm, particularly 0.3 to 2.0 μm from the viewpoint of the finished appearance of the coating film.

  A grinding aid may be attached to the surface of the metallic pigment. As a grinding aid, unsaturated fatty acids are generally used. Examples of the unsaturated fatty acid include oleic acid, linoleic acid, linolenic acid, ricinoleic acid, elaidic acid, zomarinic acid, gadoleic acid, erucic acid and the like. The amount of the grinding aid is not particularly limited, but in general, it is preferably in the range of 0.1 to 20% by mass, particularly 0.5 to 10% by mass with respect to the amount of the metallic pigment.

  In the coating composition of the present invention, among the above-described materials, the aluminum pigment (C1) can be suitably used as the metallic pigment component from the viewpoint of the finished appearance and cost.

  As the aluminum pigment (C1), a pigment surface-treated one can be used, but the coating composition of the present invention is an untreated aluminum pigment, in particular, having no pigment surface. Is characterized in that a metallic coating film excellent in chemical resistance and weather resistance can be obtained.

  Examples of the surface treatment of the aluminum pigment (C1) include the following methods (1) to (5).

  (1) A method of treating with an inorganic acid or an ammonium salt of an inorganic acid (for example, JP-A-6-57171).

  Examples of inorganic acids include carbonic acid, boric acid, sulfuric acid, nitric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, silicic acid, chromic acid, molybdic acid, tungstic acid, titanic acid, vanadic acid, tantalum acid, and condensates thereof. Can be mentioned.

  Particularly preferred inorganic acids include phosphoric acid, molybdic acid, tungstic acid, vanadic acid, and their condensates such as pyrophosphoric acid, polyphosphoric acid, polymolybdic acid, polytungstic acid, phosphomolybdic acid, and phosphotungstic acid. Can do.

  The method of treating the surface of the aluminum pigment with an inorganic acid is not particularly limited. For example, these inorganic acids or ammonium salts of inorganic acids are dissolved in a hydrophilic solvent such as water or alcohol, and the aluminum pigment is in a slurry state or a paste state. Can be suitably carried out by stirring and mixing or kneading.

  The amount of inorganic acid or inorganic acid ammonium salt for treating the surface of the aluminum pigment is suitably in the range of 0.05 to 5% by mass relative to the total amount of aluminum pigment.

  (2) A method of treating with an inorganic phosphate compound or the like (for example, JP-A-10-130545).

  (3) A method of coating with a resin (for example, JP-A-51-137725, JP-B-57-35214, JP-A-62-81460, JP-A-2002-105381).

  (4) A method of further treating the resin coating with a phosphorus compound (for example, JP-A No. 2002-121423).

  (5) A method of surface coating with a silica layer. Particularly preferably, a method of treating with an silane coupling agent after coating the aluminum surface (Japanese Patent Laid-Open No. 2003-12964, etc.).

  In the coating composition of the present invention, in addition to the components (A), (B) and (C) described above, for example, coloring pigments other than metallic pigments, extender pigments such as silica fine particles, organic resin powders, inorganic aggregates, Known materials conventionally used in paints such as pigment dispersants, UV absorbers, UV stabilizers, paint additives such as antifoaming agents and surface conditioners, and solvents can also be used.

Examples of the extender pigment include silica fine particles, talc, mica powder, and barita. The compounding amount of the extender pigment is 0.1 to 20% by mass, particularly 0.5 to 15% by mass, more particularly 1 to 10% by mass, based on the total amount of the component (A) and the component (B). preferable.
Further, the matting agent (D) can be used in the coating composition of the present invention for the purpose of adjusting the gloss so that the resulting coating film has a finished appearance with a matte specification. The matting agent (D) is used to lower the gloss of the resulting coating film, and may be either an organic matting agent or an inorganic matting agent. Or two or more types can be used in combination.

  The coating composition of the present invention can form a coating film excellent in chemical resistance and weather resistance even in a coating film having a finished appearance with reduced matte gloss.

  In the matte specification, the 60 ° gloss value is preferably in the range of 10 to 60, particularly 20 to 50, and more particularly 25 to 45, from the viewpoint of finished appearance and weather resistance.

  Examples of the organic matting agent include organic resin fine particles that are not completely melted by baking at the time of coating film formation. The organic resin fine particles usually have an average particle diameter of 3 to 80 μm, preferably 5 to 60 μm, from the viewpoint of coating film appearance, coating workability, and the like. Examples of organic matting agents include fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, acrylic resins, polyurethanes, phenol resins, silicone resins, polypropylene, and polyamides such as nylon 11 and nylon 12. it can.

  Examples of the inorganic matting agent include silica, mica, alumina, talc, clay, calcium carbonate, barium sulfate and the like.

  The said matting agent (D) can be used individually or in combination of 2 or more types. The blending amount of the matting agent (D) is preferably 0.1 to 30% by mass, particularly preferably 0.5 to 20% by mass, based on the total amount of the component (A) and the component (B).

  The coating composition of the present invention can be produced by uniformly mixing the components (A) to (C) and, if necessary, the other components. Preferably, the pigment component is preliminarily mixed and dispersed with a part of the polyester resin component (A) and / or a pigment dispersant to prepare a pigment paste, and the pigment paste is mixed with the remaining components. Can do.

  As a method of coating the coating composition of the present invention, the coating composition is adjusted to a desired viscosity by adding an organic solvent or the like as necessary, and then air spray, electrostatic air spray, roll coater, flow coater. Using a coating machine, brush, bar coater, applicator, etc. in a dipping format, the coating film thickness after drying is usually 0.5 to 300 μm, preferably 5 to 50 μm, and usually 80 to 300 ° C. And a method of curing by heating at a temperature of about 5 seconds to about 1 hour. As the coating method, spray coating or roll coater coating is preferable among the above methods.

Coating Film Forming Method The coating film forming method of the present invention comprises forming a primer coating film on a metal plate with a chromium-free primer coating that does not contain a chromium-based anticorrosive component, and forming the coating composition of the present invention on the primer coating film. It is a coating film forming method characterized by forming a top coat film by a composition.

  Examples of the metal plate to be coated in the coating film forming method of the present invention include cold rolled steel plate, hot dip galvanized steel plate, electrogalvanized steel plate, alloy galvanized steel plate (iron-zinc, aluminum-zinc, nickel-zinc, etc. Alloy galvanized steel plate), aluminum plate, stainless steel plate, copper plate, copper plated steel plate, tin plated steel plate and the like.

  When painting on metals, the metal surface, which is the material to be coated, may be painted as it is if it is not contaminated with oil or other pollutants, but it is well known for improving adhesion and corrosion resistance with the coating film. It is desirable to apply a metal surface treatment. These known surface treatment methods include phosphate surface treatment, chromate surface treatment, zirconium surface treatment and the like.

  As a primer for forming a primer coating film on a metal plate, a known primer used in the colored color steel sheet coating field, the industrial machine coating field, the metal part coating field, or the like can be applied.

  From the viewpoint of environmental protection, it is preferable to use a chromium-free primer coating that does not contain a chromium-based rust preventive component.

  The chrome-free primer coating is appropriately selected depending on the type of material to be coated and the type of metal surface treatment, but polyester-based, epoxy-based primer coatings and their modified primer coatings are particularly suitable, and workability is particularly required. In this case, a polyester primer paint is suitable.

In addition, when adhesion with a lower layer coating such as a primer coating is particularly required, an epoxy primer coating, particularly a modified epoxy resin primer coating is preferred. Specific examples of the modified epoxy resin primer include, for example,
(I) A bisphenol type epoxy resin modified with a soft organic component obtained by reacting 5 to 50% by mass of a soft organic component and 95 to 50% by mass of a bisphenol type epoxy resin, (II) a curing agent and (III) prevention A coating composition containing a rust pigment, wherein the soft organic component in the resin (I) is an aliphatic polybasic acid having 4 to 36 carbon atoms, an acrylic resin having a glass transition temperature of -20 to 50 ° C, and a glass transition Examples thereof include a rust preventive coating composition (A) (see JP 2009-256634 A), which is at least one of polyester resins having a temperature of -20 to 50 ° C.

  The primer coating is applied by a known coating method such as roll coating or spray coating so that the primer coating thickness is 1 to 30 μm, preferably 2 to 20 μm, and it is usually at an ambient temperature of 80 to 300 ° C. for 5 seconds. When pre-coating is applied for about 1 hour, it can be cured by heating for 15 seconds to 120 seconds, preferably under the condition that the maximum material arrival temperature is 140 to 250 ° C.

  The primer coating film may be a single layer or two layers in which a second primer coating film (intermediate coating film) is formed on the first primer coating film. When the primer film has two layers, the first primer film has an anticorrosion function, and the second primer film (intermediate film) has processability and chipping resistance. The primer coating can also have different functions.

  In the coating film forming method of the present invention, the coating composition of the present invention is applied on at least one surface of the primer coating film. Examples of the coating method include curtain coating, roll coater coating, dip coating, and spray coating. Usually, the coating thickness after drying is 5 to 50 μm, preferably 8 to 25 μm. Is done.

  When the coating composition of the present invention is pre-coated, the coating method is not limited, but curtain coating and roll coater coating are recommended in view of the economy of pre-coated steel sheet coating. When roll coater coating is applied, the bottom feed method (so-called natural reverse coating or natural coating) with a normal two-roll is practically performed, but the uniformity of the coating surface is best. Therefore, the top feed or bottom feed method using three rolls can be used.

  The curing condition of the top coat film by the coating composition of the present invention is usually about 15 seconds to 30 minutes at a material maximum temperature of 120 to 260 ° C. In the field of pre-coating that is applied by coil coating or the like, it is usually possible to carry out at a raw material maximum temperature of 160 to 260 ° C. for a baking time of 15 to 90 seconds.

  Hereinafter, the present invention will be described more specifically with reference to production examples and examples. The present invention is not limited to the following examples. Hereinafter, “parts” and “%” are based on mass.

Production and production example 1 of polyester resin
The following raw materials were charged into a flask equipped with a thermometer, a stirrer, a heating device, and a rectifying tower.
1,2-cyclohexanedicarboxylic anhydride 150.9 parts (0.98 mol)
Neopentyl glycol 38.9 parts (0.37 mol)
9.6 parts (0.06 mol) of butylethylpropanediol
77.8 parts (0.57 mol) of trimethylolpropane
Coconut fatty acid 44.1 parts (0.21 mol)
Dibutyltin oxide (catalyst) 0.03 part Next, the temperature was raised to 160 ° C. while stirring the contents, the temperature was gradually raised from 160 ° C. to 230 ° C. over 3 hours, and the reaction was continued at 230 ° C. for 30 minutes. In order to replace the rectification column with a water separator and promote removal of by-product condensed water, 5% xylene was added to the total charge, and the reaction was further proceeded at 230 ° C., with an acid value of 4 mgKOH / When it became g, the heating was stopped, and swathol 1500 (hydrocarbon solvent) was added to dilute to obtain a fatty acid-modified polyester resin (A1-1) solution having a solid content of 65%.

  The obtained resin had a number average molecular weight of 15,000, a hydroxyl value (mg number of potassium hydroxide required to neutralize 1 g of resin) 75 mgKOH / g, oil length 14.7%, iodine value 5>. .

Production Examples 2 to 13
In the same manner as in Production Example 1 with the formulation shown in Table 1 below, solutions of each fatty acid-modified polyester resin (A1-2) to (A1-13) having a solid content of 65% were obtained. The composition ratio of each component in Table 1 is a molar ratio.

  Table 1 shows the number average molecular weight, hydroxyl value, oil length, and iodine value of each resin. In addition, the fatty acid modified polyester resins (A1-7) to (A1-13) in Production Examples 7 to 13 are resins for comparative examples.

Production of coating composition and performance test Examples 1-22, Comparative Examples 1-10 and Reference Examples 1-2
A paint was prepared with the composition shown in Table 2 below. 1-32 were obtained. Coating composition No. 21 to 30 are for comparative examples, coating composition Nos. 31 to 32 are coating compositions for reference examples.

  In addition, the mixing | blending of Table 2 is a solid content. The amount of component C (aluminum pigment) is an amount as an aluminum pigment component.

  The following primer coating 1 is coated on a molten 55% aluminum-zinc-plated steel sheet (galvalume steel sheet) having a thickness of 0.35 mm that has been subjected to chemical conversion treatment so that the dry film thickness is 5 μm. It was heated to 220 ° C. and baked for 40 seconds to obtain a primer-coated steel sheet. Each of the coating compositions obtained as described above was coated on this primer-coated steel sheet with a bar coater so that the dry film thickness was about 15 μm, and heated so that the maximum material temperature reached 230 ° C. Each coated steel sheet was obtained by baking for 2 seconds. The following performance test was done about each obtained coated steel plate.

(Undercoat 1)
In 200 parts of modified bisphenol type epoxy resin ME1 solution modified with a soft organic component (80 parts in solid content), 20 parts of vanadium pentoxide, 20 parts of calcium metasilicate, 20 parts of calcium phosphate, 20 parts of titanium white, 20 parts of barita And an appropriate amount of mixed solvent A [swazol 1500 / cyclohexanone = 1/1 (mass ratio)] was mixed, and pigment dispersion was performed until the tub (particle diameter of the coarse pigment particles) became 20 microns or less. Next, 26.7 parts (20 parts by solid content) of Desmodur BL-3175 (manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate type polyisocyanate compound solution blocked with methyl ethyl ketoxime, solid content of about 75%) was added to this dispersion. ), 2 parts of Takenate TK-1 (manufactured by Takeda Pharmaceutical Co., Ltd., organotin blocking agent dissociation catalyst, solid content of about 10%) and mixed uniformly, and further mixed solvent B [cyclohexanone / ethylene glycol monobutyl ether / swazole 1500 (manufactured by Maruzen Petrochemical Co., Ltd., high-boiling aromatic hydrocarbon solvent) = 3/1/1 (mass ratio)] to adjust the viscosity to about 80 seconds (Ford Cup # 4/25 ° C.) Undercoat paint 1 was obtained.

(Modified bisphenol type epoxy resin ME1 solution)
In a flask equipped with a stirrer, a condenser and a thermometer, 60 parts of cyclohexanone and 90 parts of jER1007 (Japan Epoxy Resin bisphenol A type epoxy resin, epoxy equivalent of about 1800) are blended and heated to a temperature of 130 ° C. Dissolved. After confirming that the epoxy resin was completely dissolved, an epoxy resin solution having a solid content of 60% was obtained. To 150 parts of the obtained epoxy resin solution having a solid content of 60%, 20 parts of a 50% soft acrylic resin AC1 solution (10 parts in terms of solid content) and 0.5 part of tetraethylammonium bromide are added, and the temperature is maintained at 130 ° C. 3 Reacted for ~ 4 hours. Confirm that the resin acid value is 1 or less, and add mixed solvent 1 [cyclohexanone / swazol 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high boiling aromatic petroleum solvent) = 1/2 (mass ratio)] A resin solution ME1 having a solid content of 40% was obtained.

(Soft acrylic resin AC1 solution)
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%. A soft acrylic resin AC1 solution was obtained. The soft 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.

  The undercoat paint 1 used in the preparation of the coated steel plate of Example 2 is the following undercoat paint 2 in Example 21, and undercoat paint 3 in Example 22 (KP Color 8510 Primer (manufactured by Kansai Paint Co., Ltd., precoat). Each coated steel sheet was prepared in the same manner by changing to an epoxy resin primer for steel sheet)).

(Undercoat 2)
Undercoat paint 1 was prepared in the same manner as undercoat paint 1 except that the modified bisphenol type epoxy resin ME1 solution was changed to a modified bisphenol type epoxy resin ME11 solution.

(Modified bisphenol type epoxy resin ME11 solution)
In a flask equipped with a stirrer, a condenser and a thermometer, 53.3 parts of cyclohexanone and 80 parts of jER1007 (bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent of about 1800) are blended and heated to a temperature of 130 ° C. The resin was dissolved. After confirming that the epoxy resin was completely dissolved, an epoxy resin solution having a solid content of 60% was obtained. To 150 parts of the obtained epoxy resin solution with a solid content of 60%, 28.6 parts of a 70% soft polyester resin PE1 solution (20 parts in terms of solid content) and 0.5 part of tetraethylammonium bromide are added, and the temperature is maintained at 130 ° C. And reacted for 3 to 4 hours. After confirming that the resin acid value is 1 or less, mixed solvent C [cyclohexanone / swazol 1000 (manufactured by Maruzen Petrochemical Co., Ltd., high boiling aromatic petroleum solvent) = 1/2 (mass ratio)] was added, A resin solution ME11 having a solid content of 40% was obtained.

(Soft polyester resin PE1 solution)
The following raw material mixture was put into a reactor equipped with a stirrer, a heating device, a thermometer, a separation device, and a distillate storage tank, and heating was started.
Neopentyl glycol 105 parts 1,6-Hexanediol 354 parts Hexahydrophthalic anhydride 564 parts Adipic acid 123 parts After starting heating, when stirring becomes possible, stirring is started and the temperature is raised to 240 ° C while draining condensed water 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 continued until the acid value reached 52. Next, the mixture was cooled, and 417 parts of cyclohexanone was added for dilution to obtain a soft polyester resin PE1 solution having a solid content of 70%. The obtained resin had a number average molecular weight of 2100 and a glass transition temperature of 35 ° C.

  Among the undercoat paints 1 to 3, the undercoat paint 1 and the undercoat paint 2 are modified epoxy resin primer paints and are paint compositions corresponding to the rust preventive paint composition (A).

  The test results are also shown in Table 2. In addition, the quantity of each component in Table 2 is solid content mass. Further, a mixed solvent of cyclohexanone / swazol 1500 (manufactured by Maruzen Petroleum Co., Ltd., aromatic high-boiling solvent) = 60/40 (mass ratio) was used for adjusting the viscosity of the coating composition. During coating, the viscosity of the coating composition was adjusted to about 100 seconds (25 ° C.) with Ford Cup # 4.

  Moreover, the light transmittance of the coating film obtained with each coating composition is also shown.

  The light transmittance was measured as follows.

Each paint composition was applied to a tin plate so as to have a dry film thickness of 15 μm, and the light transmittance at a wavelength of 320 nm was measured using a visible to ultraviolet spectrophotometer for the free coating film peeled by the mercury amalgam method. The transmittance for the blank (air) was also measured and evaluated according to the following categories.
A: 0.5% or less B: More than 0.5% and less than 2% C: More than 2% and less than 5% D: More than 5%

  In Table 2, (Note 1) to (Note 17) are as follows.

  Uban 20SE-60 (Note 1): Mitsui Chemicals, butyl etherified melamine resin, number average molecular weight of about 4000.

  Super Becamine J820-60 (Note 2): Trade name “Super Becamine J-820-60”, manufactured by Dainippon Ink & Chemicals, Inc., n-butyl etherified melamine resin solution.

  Super Becamine L-118-60 (Note 3): Trade name “Super Becamine L-118-60”, manufactured by Dainippon Ink & Chemicals, Inc., n-butyl etherified melamine resin solution.

  Cymel 303 (Note 4): Low molecular weight methylated melamine resin, manufactured by Nippon Cytec Industries, Ltd. The content of hexakis (methoxymethyl) melamine is 60% by weight or more.

  Sumidur BL3175 (Note 5): A methyl ethyl ketone oxime block compound of trimethylolpropane adduct type hexamethylene diisocyanate manufactured by Sumika Bayer Urethane Co., Ltd.

  1200M (Note 6): manufactured by Toyo Aluminum Co., Ltd., trade name “aluminum paste 1200M”, untreated product, average particle size 12 μm.

  1100NA (Note 7): manufactured by Toyo Aluminum Co., Ltd., trade name “aluminum paste 1100NA”, untreated product, average particle size 22 μm.

  1109M (Note 8): manufactured by Toyo Aluminum Co., Ltd., trade name “aluminum paste 1109M”, untreated product, average particle size 33 μm.

  1200M-Mo (Note 9): Molybdic acid-treated product of “aluminum paste 1200M”.

  1100NA-Mo (Note 10): Molybdic acid treated product of “aluminum paste 1100NA”.

  1109M-Mo (Note 11): “Aluminum paste 1109M” treated with molybdic acid.

  1100NA-P (Note 12): Processed as follows using “aluminum paste 1100NA” as a raw material.

  In the stirring and mixing vessel, 21.2 parts (aluminum paste 1100NA) 21.2 parts (solid content 14 parts), 2-ethyl-1-hexanol 35 parts, the following phosphoric acid group-containing resin solution 8 parts (solid content 4 parts) and 2- (Dimethylamino) ethanol 0.2 part was mixed uniformly to obtain 1100NA-P which is an aluminum pigment dispersion.

  Phosphoric acid group-containing resin solution: put a mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen gas inlet tube and dropping device. , Heated to 110 ° C., 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of “isostearyl acrylate” (trade name, Osaka Organic Chemical Industries, Ltd., branched higher alkyl acrylate), 4-hydroxybutyl acrylate 7 121.5 parts of a mixture comprising 5 parts, 15 parts of the following phosphoric acid group-containing polymerizable monomer, 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol, and 4 parts of t-butylperoxyoctanoate In addition to the above mixed solvent over 4 hours, 0.5 parts of t-butylperoxyoctanoate A mixture of isopropanol 20 parts was added dropwise for 1 hour. Thereafter, the mixture was aged and stirred for 1 hour to obtain a phosphate group-containing resin solution having a solid concentration of 50%. The acid value due to the phosphoric acid group of this resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.

  Phosphoric acid group-containing polymerizable monomer: put 57.5 parts monobutyl phosphoric acid and 41 parts isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen gas inlet tube and dropping device, and bring it to 90 ° C. After raising the temperature, 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, followed by stirring and aging for another hour. Thereafter, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution having a solid content concentration of 50%. The acid value of the obtained monomer was 285 mgKOH / g.

  Thyroid 161W (Note 13): manufactured by GRACE GMBH, trade name, finely treated silica fine powder, oil absorption 170 ml / 100 g.

  Nacure 5225 (Note 14): An isopropanol solution of a neutralized secondary amine of dodecylbenzenesulfonic acid, manufactured by King Industries, USA. The degree of neutralization of dodecylbenzenesulfonic acid / amine is about 1.1 (molar ratio). The active ingredient is about 33% by weight, of which dodecylbenzenesulfonic acid / amine (mass ratio) is about 8/25. The numerical values in Table 2 are parts by mass of solid content of dodecylbenzenesulfonic acid.

  Formate TK-1 (Note 15): A curing catalyst which is an organic tin solution manufactured by Takeda Pharmaceutical Co., Ltd., and a dissociation catalyst for a blocked polyisocyanate compound.

  Desparon L1982 (Note 16): An acrylic resin-based surface conditioner manufactured by Enomoto Kasei Co., Ltd.

  BYK1790 (Note 17): Polyethylene antifoaming agent manufactured by Big Chemie.

  In addition, the performance test in Table 2 was performed according to the following methods and evaluation criteria.

  60 ° gloss value: 60 ° specular reflectance was measured in accordance with the 60 ° specular gloss specified in JIS K-5600.4.7 (1999).

Workability: In a room at 20 ° C., the test plate was bent 180 degrees with the coating surface facing outside, and the T number at which no crack occurred at the bent portion was displayed. The T number is 0T when bending 180 degrees without anything inside the bent part, 1T, 2 when a sheet of the same thickness as the test plate is folded. In the case of a sheet, 2T,... (The same applies hereinafter)... The results were determined by:
(Double-circle): A crack is hardly recognized in 4T bending process.
○: Slight cracking is observed in 4T bending, but cracking is not observed in 6T bending.
Δ: Clear cracks are observed in 4T bending. Slight cracking is also observed for 6T bending.
X: Clear cracking is observed in 6T bending process Boiling water resistance: Each test coating plate cut to a size of 5 cm × 10 cm is immersed in boiling water at about 100 ° C. for 5 hours, and then pulled up to the surface side. The appearance of the coating film was evaluated according to the following criteria by measuring the color difference (ΔE) from the test plate before immersion in boiling water.
◎: ΔE is less than 0.5 ○: ΔE is 0.5 or more and less than 2.0 Δ: ΔE is 2.0 or more and less than 5.0 ×: ΔE is 5.0 or more Salt spray resistance: Salt spray test The appearance of the coating film after 1000 hours was evaluated according to the following criteria.
A: No abnormality is observed. B: Slight swelling is observed. Or, when the cello tape (registered trademark) is peeled off from the coated plate in the cello tape (registered trademark) adhesion test, slight adhesion of rust is recognized.
Δ: Swelling is observed. Or, when the cello tape (registered trademark) is peeled off from the coated plate in the cello tape (registered trademark) adhesion test, the coating film is slightly peeled off.
X: Remarkable swelling is recognized. Or peeling of a coating film is recognized when the cello tape (registered trademark) is peeled off from the coated plate in the cello tape (registered trademark) adhesion test.

  Accelerated weather resistance: xenon accelerated weather resistance tester 3000 test appearance after test (measure the color difference (ΔE) from the test plate before the test) and adhesion (cross-cut (100 × 2 mm × 2 mm) cello tape ( (Registered trademark) peel test) was evaluated according to the following criteria.

<Appearance change>
：: ΔE is less than 1.5 ○: ΔE is 1.5 or more and less than 3.0 Δ: ΔE is 3.0 or more and less than 7.0 ×: ΔE is 7.0 or more <Adhesiveness>
A: No separation is observed B: 90 or more grids remain.
Δ: 50 or more and less than 90 grids remain.
X: Less than 50 grids remain.

Claims (12)

The total content of the alicyclic polybasic acid (a1-1) obtained by the reaction of the polybasic acid component (a1), the alcohol component (a2) and the fatty acid (a3) and the polybasic acid component (a1) is The total content of the trihydric or higher polyhydric alcohol (a2-1) in the alcohol component (a2) is within the range of 50 to 100 mol% based on the total amount of the polybasic acid component (a1). 50 fatty acid-modified polyester resins (A1) having a number average molecular weight of 5,000 to 30,000, a hydroxyl value of 5 to 100 mgKOH / g, and an oil length of 3 to 30% based on the total amount of a2) ~ 100 mass% polyester resin component (A),
Containing a melamine resin component (B) containing 50 to 100% by mass of a butyl etherified melamine resin (B1) and a metallic pigment component (C),
A coating composition comprising 10 to 60% by mass of a metallic pigment component (C) based on the total amount of the polyester resin component (A) and the melamine resin component (B).   In the fatty acid-modified polyester resin (A1), the total content of the alicyclic polybasic acid (a1-1) in the polybasic acid component (a1) is 85 to 85 based on the total amount of the polybasic acid component (a1). The coating composition according to claim 1, which is in the range of 100 mol%.   The polyester resin component (A) is contained in an amount of 50 to 90% by mass and the melamine resin component (B) is contained in an amount of 10 to 50% by mass based on the total amount of the polyester resin component (A) and the melamine resin component (B). Or the coating composition of 2.   The coating composition according to any one of claims 1 to 3, wherein the metallic pigment component (C) contains an aluminum pigment (C1).   The coating composition according to claim 4, wherein the pigment surface of the aluminum pigment (C1) is untreated.   Furthermore, the coating composition of any one of Claims 1-5 containing a matting agent (D).   The coating composition according to any one of claims 1 to 6, wherein a light transmittance in a wavelength range of 310 to 350 nm of a coating film having a dry film thickness of 15 µm is less than 5%.   A primer coating with a chromium-free primer coating that does not contain a chromium-based anticorrosive component is formed on a metal plate, and the coating with the coating composition according to any one of claims 1 to 7 is applied on the primer coating. A method for forming a coating film, comprising forming a coating film. Chrome-free primer paint
(I) A bisphenol type epoxy resin modified with a soft organic component obtained by reacting 5 to 50% by mass of a soft organic component and 95 to 50% by mass of a bisphenol type epoxy resin, (II) a curing agent and (III) prevention A coating composition containing a rust pigment, wherein the soft organic component in the resin (I) is an aliphatic polybasic acid having 4 to 36 carbon atoms, an acrylic resin having a glass transition temperature of -20 to 50 ° C, and a glass transition The method for forming a coating film according to claim 8, which is a rust-proof coating composition (I), which is at least one of polyester resins having a temperature of -20 to 50 ° C.   A primer coating with a chromium-free primer coating that does not contain a chromium-based rust preventive component is formed on the metal plate, and the top coating with the coating composition according to any one of claims 1 to 7 is performed on the primer coating. A coated metal plate, characterized in that a coating film is formed. Chrome-free primer paint
(I) A bisphenol type epoxy resin modified with a soft organic component obtained by reacting 5 to 50% by mass of a soft organic component and 95 to 50% by mass of a bisphenol type epoxy resin, (II) a curing agent and (III) prevention A coating composition containing a rust pigment, wherein the soft organic component in the resin (I) is an aliphatic polybasic acid having 4 to 36 carbon atoms, an acrylic resin having a glass transition temperature of -20 to 50 ° C, and a glass transition The coated metal sheet according to claim 10, which is a rust preventive coating composition (I), which is at least one of polyester resins having a temperature of -20 to 50 ° C.   A matte-coated metal sheet having a 60 ° gloss value of 60 or less, wherein a coating film of the coating composition of claim 6 is formed.