Coating composition

Abstract

To provide: a paint composition that can form a wrinkle-pattern coat excellent in weather resistance and scratch resistance by clarifying the relationship between a matte shape such as a wrinkle pattern and coating film performance of the weather resistance and the scratch resistance; a method of forming the wrinkle-pattern coat using the paint composition; and a coated metal sheet.SOLUTION: The paint composition includes a hydroxyl group-containing resin (A), a crosslinking agent (B), a sulfonic acid compound (C), and an amine compound (D). The paint composition has an arithmetic average height (Ra) of 1.0 μm or more and a value PV (Pattern Value) of 1.0-150 on a surfaces of coat obtained by curing the paint composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a paint composition capable of forming a wrinkled pattern coating film with excellent weather resistance and scratch resistance, a method for forming a wrinkled pattern coating film using the paint composition, and a painted metal sheet. [Background technology]

[0002] Pre-coated steel sheets are widely used as painted steel sheets for various components such as building materials like shutters, storm shutters, doors, roofs, and siding, as well as exterior materials for electrical equipment such as outdoor units of air conditioners, and interior materials.

[0003] Pre-coated steel sheets are steel sheets used in applications where a coating is applied to the surface of the steel sheet to form a coating film, and then processed into the desired product.

[0004] Therefore, the coating formed on pre-coated steel sheets requires flexibility and high workability, and depending on the application, coating properties such as weather resistance, scratch resistance, and corrosion resistance are also required.

[0005] Furthermore, due to customer needs regarding the appearance of the aforementioned products, pre-coated steel sheets are required to have excellent design qualities.

[0006] As a matte finish decorative coating for pre-coated steel sheets, a coating with a surface shape featuring fine irregularities, known as a wrinkled pattern, is known.

[0007] It has been found that this crinkled pattern is composed of ridges that are visible to the naked eye (mm to cm in size) and ridges that are difficult to see with the naked eye (nm in size), and it varies greatly depending on the type and amount of material components of the paint that forms the crinkled pattern.

[0008] Patent Document 1 discloses a paint composition that forms a paint film with excellent design properties having a uniform matte appearance and excellent weather resistance, comprising at least a film-forming resin (A) and a crosslinking agent (B), characterized in that the arithmetic mean height (Ra) on the surface of the paint film cured from the paint composition is 1.2 μm or more, and the developed area ratio (Sdr) is 800% or more. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2022-84372 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In the paint composition described in Patent Document 1, a coating film with improved weather resistance and a matte appearance can be obtained. However, the relationship between the surface shape (wrinkle pattern) that constitutes the matte finish and the coating film performance such as weather resistance and scratch resistance is not adequately understood. Depending on the matte surface shape of the obtained coating film, the coating film performance such as weather resistance and scratch resistance may be insufficient.

[0011] The object of the present invention is to clarify the relationship between matte shapes such as wrinkle patterns and the weather resistance and scratch resistance of coating films, and to provide a coating composition capable of forming a wrinkle pattern coating film with excellent weather resistance and scratch resistance, a method for forming a wrinkle pattern coating film using the coating composition, and a coated metal sheet. [Means for solving the problem]

[0012] The inventors have been diligently researching methods for quantitatively evaluating the matte finish of matte (wrinkle pattern) coatings, which have a high correlation with the results of sensory evaluation by visual observation, in conjunction with paint compositions. By capturing the pattern of a matte coating as a "pattern" (perception of random shading represented by an aggregate of uneven shapes of tens to hundreds of microns on the coating surface) from sensory evaluation by visual observation, they have discovered a new index (parameter value), a value called PV (Pattern Value), which is different from conventional micro-roughness values ​​such as Ra, Rz, and Sdr.

[0013] The PV value is derived from the 2D power spectrum value obtained by performing a Fourier transform on an image of the coating film. This parameter value, the PV value, makes it possible to quantitatively evaluate the matte finish (crinkled pattern), which was previously done by subjective visual inspection.

[0014] Furthermore, it was revealed that there is a range, indicated by the PV value (a measure of matte finish, or crinkled pattern), in which weather resistance and scratch resistance are good.

[0015] This invention was completed by applying the above-mentioned new findings to the prior art.

[0016] In other words, the present invention provides the following:

[0017] 1. A paint composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), a sulfonic acid compound (C), and an amine compound (D), A paint composition characterized in that the arithmetic mean height (Ra) on the surface of the paint film cured from the paint composition is 1.0 μm or more, and the Pattern Value (PV) is 1.0 to 150.

[0018] 2. The coating composition according to Item 1 above, wherein the PV (Pattern Value) is a value derived from a two-dimensional power spectrum integral value obtained by integrating the power of low spatial frequency components and normalizing with a direct current component from a spatial frequency spectrum obtained by subjecting a grayscale 8-bit gradation image obtained by irradiating a coating film surface with light and photographing the irradiated coating film surface with a CCD camera at an angle at which specular reflected light of the irradiated light does not enter to two-dimensional Fourier transform.

[0019] 3. The coating composition according to Item 2 above, wherein the PV is calculated by the following formula.

[0020] PV=(IPSL-0.25)×1000 (wherein, IPSL is a two-dimensional power spectrum integral value) 4. A coated metal plate having a metal plate and a coating film on at least one surface of the metal plate, wherein the coating film is formed from the coating composition according to Item 1 above, a coated metal plate characterized in that, on the surface of the coating film, the arithmetic mean height (Ra) is 1.0 µm or more, and the PV (Pattern Value) is 1.0 to 150.

[0021] 5. A method for forming a coating film, comprising: a coating step of applying the coating composition according to Item 1 above to an object to be coated; and drying and / or curing the applied coating composition at a temperature of 170°C to 270°C.

Effects of the Invention

[0022] According to the present invention, by using PV, which is a quantitative evaluation parameter for the matte feeling (wrinkled pattern) of a matte coating film surface, as an index, not only the range in which not only the matte feeling (wrinkled pattern) but also weather resistance and scratch resistance are favorable can be clarified, and it is possible to provide a coating composition capable of forming a wrinkled pattern coating film excellent in weather resistance and scratch resistance, a method for forming a wrinkled pattern coating film using the coating composition, and a coated metal plate.

Mode for Carrying Out the Invention

[0023] Hereinafter, the coating composition of the present invention will be specifically described.

[0024] The present invention relates to a coating composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), a sulfonic acid compound (C), and an amine compound (D), The paint composition is characterized in that the arithmetic mean height (Ra) on the surface of the paint film cured from the paint composition is 1.0 μm or more, and the Pattern Value (PV) is 1.0 to 150.

[0025] Arithmetic mean height (Ra) is a parameter that indicates the surface roughness of a paint film. It represents the average of the absolute differences in height between each point relative to the average surface of the paint film. A small Ra indicates a flatter paint film surface and a less matte finish.

[0026] Ra can be measured in accordance with JIS B 0601-2001, for example, using a surface roughness measuring instrument such as the Surfcom 130A (manufactured by ACCRETECH (Tokyo Seimitsu)).

[0027] From the viewpoint of matte appearance and weather resistance, Ra is 1.0 μm or more, preferably 1.5 μm or more, more preferably 2.0 μm or more, and most preferably 2.5 μm or more. The upper limit of Ra is preferably 13.0 μm, more preferably 11.5 μm, and even more preferably 10.0 μm.

[0028] In wrinkle patterns, the wrinkle shapes formed include, for example, grid-like convex parts (called "one," which can be seen with the naked eye) that can be observed in images at a magnification of about 20x, and convex and concave parts (called "une," which are difficult to see with the naked eye) that can be observed in images at a magnification of about 150x (Figure 1).

[0029] The PV (Pattern Value) is a parameter that quantitatively quantifies the size of the shape described above, known as the "pattern," which is formed by the crinkled pattern.

[0030] A larger PV value indicates a larger "pattern" shape.

[0031] The following explains the value PV.

[0032] To measure the PV value, the coating surface is first irradiated with light. This light is preferably simulated (artificial) sunlight, and suitable light sources include, for example, LED lights, halogen lamps, and metal halide lamps. The angle of light irradiation onto the coating surface is suitable within the range of 5 to 60 degrees, preferably 30 to 60 degrees, based on the vertical line of the coating surface, with 45 degrees relative to the vertical line being particularly preferable. While the shape of the light irradiation area is not particularly limited, it is usually circular, and the irradiation area on the coating surface is typically 1 to 10,000 mm². 2 While the range is suitable, it is not limited to this range. The illuminance of the irradiated light is usually preferably in the range of 100 to 2,000 lux.

[0033] Light is shone onto the coating surface in this manner, and the illuminated coating surface is photographed with a CCD (Charge Couple Device) camera at an angle where specular reflected light does not enter the surface. This shooting angle can be any angle where specular reflected light does not enter, but a direction perpendicular to the coating surface is particularly preferred. Furthermore, the angle between the CCD camera's shooting direction and the specular reflected light is preferably within the range of 10 to 60 degrees. The measurement range of the CCD camera on the illuminated coating surface is not particularly limited as long as the area is uniformly illuminated, but typically it includes the center of the illuminated area, with a measurement area of ​​1 to 10,000 mm². 2 Preferably 500-5000mm 2 It is appropriate that it be within the range.

[0034] To measure the PV value, images captured by a CCD camera are analyzed to quantitatively evaluate the matte finish.

[0035] The following describes a preferred method for measuring the PV value.

[0036] In a preferred method for measuring PV (Value Perception), an image captured by a CCD camera is a two-dimensional image, divided into a large number of sections (pixels, image pixels) (usually 10,000 to 10,000,000), and the brightness of each section is measured. In measuring PV, "brightness" means "the digital gradation that indicates the grayscale value of each section of a two-dimensional image obtained by capturing with a CCD camera, and is a digital quantity corresponding to the brightness of the subject." The digital gradation (8-bit grayscale gradation) that represents the brightness of each section output from an 8-bit resolution CCD camera shows values ​​from 0 to 255.

[0037] In the 2D image captured by the CCD camera described above, the areas corresponding to the strongly reflected light of the matte coating have an uneven shape, with the convex parts being flat and highly reflective, resulting in high brightness. Naturally, the areas corresponding to the other areas have lower brightness. Furthermore, even within the areas corresponding to the strongly reflected light of the uneven shape, the brightness changes depending on the height difference, shape, and continuity of the unevenness. In other words, brightness can be displayed for each area, and based on the brightness in each area, it is possible to display the brightness distribution of the 2D image captured by the CCD camera in three dimensions. This three-dimensional brightness distribution diagram (Figure 2) is divided into peaks and valleys, indicating that the greater the difference between the height of the peaks and the depth of the valleys, the more pronounced the matte finish.

[0038] The images captured by the above-mentioned CCD camera can be analyzed using an image analysis device connected to the CCD camera. A suitable image analysis software for this device is, for example, "WINROOF" (product name) from Mitani Corporation.

[0039] In measuring the PV value, the matte finish (pattern) of the matte coating is quantitatively evaluated based on the brightness of each section obtained by analyzing the image.

[0040] The quantitative measurement of the "pattern" of the matte finish is performed as described above by capturing a 2D image of the light-irradiated matte coating surface with a CCD camera, integrating the power of the low spatial frequency components from the spatial frequency spectrum obtained by performing a 2D Fourier transform on this 2D image, and normalizing it with the DC component to obtain a 2D power spectrum integral value. The "pattern" of the matte finish of the coating is then quantitatively evaluated from this 2D power spectrum integral value.

[0041] When measuring the integrated value of a two-dimensional power spectrum obtained by extracting low spatial frequency components from an image of the spatial frequency spectrum after a two-dimensional Fourier transform, and then performing integration and normalization by the DC component, it is appropriate to set the extraction region of the low spatial frequency components extracted from the spatial frequency spectrum image to a region where the linear density representing the resolution is within the range of a lower limit of 0 lines / mm to an upper limit of 0.1 to 6.2 lines / mm, preferably a region with a lower limit of 0.03 lines / mm to an upper limit of 1.55 lines / mm, from the viewpoint of achieving a high correlation with the results of the sensory evaluation of "matte finish" obtained by visual observation.

[0042] The integral value of the two-dimensional power spectrum can be calculated using the following formula.

[0043]

number

[0044] (In the formula, ν is the spatial frequency, θ is the angle, P is the power spectrum, 0 to L is the extracted low spatial frequency region, and L represents the upper limit of the extracted frequency.) The correlation between the two-dimensional power spectrum integral values ​​obtained as described above and the sensory evaluation results of "matte finish" obtained through visual observation is high.

[0045] The Pattern Value (PV) is a parameter value derived by the following equation, assuming the above two-dimensional power spectrum integral value is IPSL.

[0046] IPSL stands for Integration of Power Spectrum of Low frequency.

[0047] PV = (IPSL - 0.25) × 1000 Since the 2D power spectrum integral value, IPSL, is approximately between 0.25 and 0.4, the value PV is a parameter value set to be within an easily understandable range (0 (small) to 150 (large)).

[0048] Next, I will explain the equipment used for measuring the PV value.

[0049] The apparatus may be, for example, a matte finish quantitative evaluation apparatus comprising a light irradiation device (1) that irradiates light onto the coating surface, a CCD camera (2) that photographs the irradiated coating surface at an angle where the irradiated light does not enter and forms an image, and an image analysis device (3) connected to the CCD camera that analyzes the image.

[0050] The image analysis device (3) includes, at least during image analysis, means such as image analysis software and a computer to obtain a spatial frequency spectrum by performing a two-dimensional Fourier transform on an image obtained by converting the above image to an 8-bit grayscale image, and to obtain a two-dimensional power spectrum integral value by integrating the power of the low spatial frequency components from the spectrum and normalizing it with the DC component.

[0051] Based on the data obtained by the image analysis device described above, the value PV can be calculated using the above formula.

[0052] The PV value may, and preferably may, be obtained by means of a computer or other means constituting the image analysis device described above. The PV value can be determined using this matte finish quantitative evaluation device.

[0053] The light irradiation device is a device that can irradiate simulated (artificial) sunlight, and its light source can be, for example, an LED, a halogen lamp, or a metal halide lamp. The image analysis software for the image analysis device can be, for example, "WINROOF" (product name) manufactured by Mitani Corporation. In addition to image analysis software, known calculation software can also be used.

[0054] The above-described image analysis device may, at least during image analysis, further have means to obtain a spatial frequency spectrum by performing a two-dimensional Fourier transform on an image of the light-illuminated coating surface captured by a CCD camera, converted to an 8-bit grayscale image, and then obtaining a two-dimensional power spectrum integral value by integrating the power of the low spatial frequency components from the spectrum and normalizing it with the DC component. Examples of such means include image analysis software and a computer.

[0055] The PV value is in the range of 1.0 to 150 from the viewpoint of good matte (crinkled) appearance, weather resistance, and scratch resistance. The lower limit of the PV value is preferably 1.3, more preferably 1.5. The upper limit of the PV value is preferably 140, more preferably 130.

[0056] <Hydroxygroup-containing resin (A)> The hydroxyl group-containing resin (A) is a resin having two or more hydroxyl groups in one molecule, and may optionally have carboxyl groups.

[0057] Specific examples of hydroxyl group-containing resin (A) include polyester resin, acrylic resin, epoxy resin, polyurethane resin, etc., but hydroxyl group-containing polyester resin is preferred from the viewpoint of processability and weather resistance of the coating film.

[0058] Examples of hydroxyl group-containing polyester resins include oil-free polyester resins, alkyd resins, urethane-modified polyester resins, and silicone-modified polyester resins.

[0059] The above oil-free polyester resin can usually be produced by an esterification or transesterification reaction with a polybasic acid component (a1) and a polyhydric alcohol component (a2).

[0060] As the polybasic acid component (a1) mentioned above, compounds commonly used as polybasic acid components in the manufacture of polyester resins can be used. Specifically, for example, alicyclic polybasic acids, aliphatic polybasic acids, aromatic polybasic acids, etc., can be used.

[0061] Alicyclic polybasic acids are compounds having one or more alicyclic structures (mainly 4-6 membered rings) and two or more carboxyl groups in one molecule, as well as acid anhydrides of said compounds and esterified products of said compounds.

[0062] Examples of the alicyclic polybasic acid include alicyclic polycarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 1,3,5-cyclohexanetricarboxylic acid; anhydrides of these alicyclic polycarboxylic acids; and lower alkyl esters of these alicyclic polycarboxylic acids. The alicyclic polybasic acid can be used alone or in combination of two or more types.

[0063] As alicyclic polybasic acids, 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and 4-cyclohexene-1,2-dicarboxylic acid anhydride can be preferably used.

[0064] Aliphatic polybasic acids are aliphatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of said aliphatic compounds, and esters of said aliphatic compounds. Specifically, examples include aliphatic polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, brassic acid, octadecanediic acid, and citric acid; anhydrides of these aliphatic polycarboxylic acids; and lower alkyl esters of these aliphatic polycarboxylic acids. Aliphatic polybasic acids can be used alone or in combination of two or more types.

[0065] As the aliphatic polybasic acid, it is preferable to use a dicarboxylic acid having an alkyl chain with 4 to 18 carbon atoms. Examples of dicarboxylic acids having an alkyl chain with 4 to 18 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, brassic acid, octadecanediic acid, etc., and among these, adipic acid can be preferably used.

[0066] Aromatic polybasic acids are aromatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of said aromatic compounds, and esters of said aromatic compounds. Specifically, examples include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, trimellitic acid, and pyromellitic acid; anhydrides of these aromatic polycarboxylic acids; and lower alkyl esters of these aromatic polycarboxylic acids. Aromatic polybasic acids can be used alone or in combination of two or more types.

[0067] As the alcohol component (a2), polyhydric alcohols having two or more hydroxyl groups in one molecule can be suitably used. Examples of such polyhydric alcohols include alicyclic diols, aliphatic diols, aromatic diols, and the like.

[0068] Alicyclic diols are compounds that have one or more alicyclic structures (mainly 4- to 6-membered rings) and two hydroxyl groups in a single molecule. Examples of alicyclic diols include dihydric alcohols such as 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F; and polylactone diols obtained by adding lactone compounds such as ε-caprolactone to these dihydric alcohols. These can be used individually or in combination of two or more.

[0069] Aliphatic diols are aliphatic compounds having two hydroxyl groups in one molecule. Examples of aliphatic diols include 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, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol, and 1 Examples include ,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol, etc. These can be used individually or in combination of two or more.

[0070] Aromatic diols are aromatic compounds having two hydroxyl groups in one molecule. Examples of aromatic diols include ester diol compounds such as bis(hydroxyethyl) terephthalate; and alkylene oxide adducts of bisphenol A. These can be used individually or in combination of two or more.

[0071] Other polyhydric alcohols besides the alicyclic diols, aliphatic diols, and aromatic diols mentioned above include, for example, polyether diol compounds such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; trihydric or higher alcohols such as glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris(2-hydroxyethyl) isocyanurate, sorbitol, and mannitol; and polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these trihydric or higher alcohols.

[0072] Among the other polyhydric alcohols mentioned above, trihydric or higher alcohols can be suitably used from the viewpoint of increasing molecular weight and improving reactivity. Examples of trihydric or higher polyhydric alcohols include trihydric or higher alcohols such as glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannitol; polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these trihydric or higher alcohols; and tris(hydroxyalkyl) isocyanurates such as tris(2-hydroxyethyl) isocyanurate, tris(2-hydroxypropyl) isocyanurate, and tris(2-hydroxybutyl) isocyanurate. Of these, trimethylolpropane is particularly preferred.

[0073] In addition, as an alcohol component other than the polyhydric alcohol (a2) mentioned above, other alcohols such as monoalcohols including methanol, ethanol, propyl alcohol, butyl alcohol, stearyl alcohol, and 2-phenoxyethanol; and alcohol compounds obtained by reacting monoepoxy compounds such as propylene oxide, butylene oxide, and glycidyl esters of synthetic highly branched saturated fatty acids (trade name "Cardura E10," manufactured by HEXION Specialty Chemicals) with acids may be used as needed.

[0074] The method for producing hydroxyl group-containing polyester resin is not particularly limited and can be carried out according to conventional methods. For example, it can be produced by reacting the polybasic acid component and the polyhydric alcohol component in a nitrogen stream at 150 to 250°C for 5 to 10 hours to carry out an esterification reaction or transesterification reaction.

[0075] In the above esterification or transesterification reaction, the acid component and alcohol component may be added all at once or in several stages. Alternatively, a carboxyl group-containing polyester resin may be synthesized first, and then a portion of the carboxyl groups in the carboxyl group-containing polyester resin may be esterified using the alcohol component. Furthermore, a hydroxyl group-containing polyester resin may be synthesized first, and then the hydroxyl group-containing polyester resin may be partially esterified by reacting it with an acid anhydride.

[0076] In the esterification or transesterification reaction described above, a catalyst may be used to accelerate the reaction. Known catalysts such as dibutyltin dibenzoate, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used.

[0077] Furthermore, hydroxyl group-containing polyester resins can be modified with fatty acids, oils and fats, polyisocyanate compounds, organopolysiloxane compounds, etc., during the preparation of the resin, after the esterification reaction, or after the transesterification reaction.

[0078] Alkyd resins can be obtained by modification with fatty acids or oils. Urethane-modified polyester resins can be obtained by modification with polyisocyanate compounds. Silicone-modified polyester resins can be obtained by modification with organopolysiloxanes.

[0079] Examples of fatty acids used in the production of the aforementioned alkyd resin include coconut oil fatty acids, cottonseed oil fatty acids, hemp seed oil fatty acids, rice bran oil fatty acids, fish oil fatty acids, tall oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, tung oil fatty acids, rapeseed oil fatty acids, castor oil fatty acids, dehydrated castor oil fatty acids, and safflower oil fatty acids; as well as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. Examples of oils and fats include coconut oil, cottonseed oil, hemp seed oil, rice bran oil, fish oil, tall oil, soybean oil, linseed oil, tung oil, rapeseed oil, castor oil, dehydrated castor oil, and safflower oil.

[0080] Polyisocyanate compounds used to modify urethane-modified polyester resins include, for example, aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,3-(isocyanatomethyl)cyclohexane. Examples include alicyclic diisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate; organic polyisocyanates themselves, such as trivalent or higher polyisocyanates like lysine triisocyanate; adducts of these organic polyisocyanates with polyhydric alcohols, low molecular weight polyester resins, or water; or cyclized polymers (e.g., isocyanurates) and billet-type adducts of the above-mentioned organic diisocyanates. These can be used individually or in combination of two or more.

[0081] Examples of organopolysiloxane compounds used for modifying silicon-modified polyester resins include organopolysiloxane (i) represented by the following formula (1), and organopolysiloxane (ii) having a hydrolyzable silyl group.

[0082] R 2 a Si(OH) b O (4-a-b) / 2 ···Formula (1) (wherein R 2 each represents the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and a and b satisfy the relationships: 0.2≦a≦2, 0.1≦b≦3, and a+b<4.

[0083] R 2 is preferably a substituted hydrocarbon group selected from alkyl groups having 1 to 4 carbon atoms, a phenyl group, a vinyl group, a 3-glycidoxypropyl group, a 3-methacryloyloxypropyl group, a 3-aminopropyl group, and a 3,3,3-trifluoropropyl group, and is more preferably an alkyl group such as a methyl group or an ethyl group.

[0084] Such organopolysiloxane (i) can be obtained, for example, by hydrolyzing one or a mixture of two or more of methyltrichlorosilane, dimethyldichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, or alkoxysilanes corresponding thereto with a large amount of water by a known method.

[0085] Examples of commercially available products of the organopolysiloxane (i) include KR-311, KR-282, and KR-271 (all are product names manufactured by Shin-Etsu Chemical Co., Ltd.).

[0086] Organopolysiloxane (ii) is an organopolysiloxane having a hydrolyzable silyl group at the terminal or side chain of the molecule, wherein the hydrolyzable silyl group in the molecule, such as an alkoxysilyl group, reacts with moisture or water in the air and is hydrolyzed to form a silanol group. Any known compound can be used without limitation as organopolysiloxane (ii), as long as it undergoes hydrolytic condensation at normal temperature. As organopolysiloxane (ii), those having a weight average molecular weight in the range of 200 to 28,000, particularly 300 to 18,000 are generally suitable.

[0087] The weight-average molecular weight of the hydroxyl group-containing resin is preferably 3,000 to 60,000, and particularly preferably has a number-average molecular weight in the range of 5,000 to 40,000, from the viewpoint of processability, chemical resistance, and finished appearance of the resulting coating film.

[0088] In this specification, the number-average molecular weight and weight-average molecular weight are calculated by converting the number-average molecular weight and weight-average molecular weight measured using gel permeation chromatography (GPC) to the molecular weight of standard polystyrene.

[0089] Specifically, the measurement can be performed using the "HLC8120GPC" (product name, manufactured by Tosoh Corporation) as the gel permument chromatograph, and four columns: "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (product names, all manufactured by Tosoh Corporation), under the conditions of tetrahydrofuran mobile phase, measurement temperature of 40°C, flow rate of 1 mL / min, and radioisotope detector.

[0090] The hydroxyl value of the hydroxyl group-containing resin is preferably in the range of 5 to 250 mgKOH / g, and particularly 10 to 200 mgKOH / g, from the viewpoint of processability of the coating film.

[0091] From the viewpoint of the finished appearance, the acid value of the hydroxyl group-containing resin is preferably within the range of 30 mg KOH / g or less, and particularly 20 mg KOH / g or less.

[0092] <Crosslinking agent (B)> The crosslinking agent (B) is a component that contributes to the formation of a cured coating film by reacting with the hydroxyl group-containing resin (A). Examples of crosslinking agents (B) include amino resins; polyisocyanate compounds; blocked polyisocyanate compounds (compounds in which the isocyanate group of a polyisocyanate compound is blocked with an active hydrogen-containing compound); and phenolic resins.

[0093] Crosslinking agent (B) can be used alone or in combination of two or more types.

[0094] As the crosslinking agent (B), an amino resin can be suitably used from the viewpoint of crosslinking reactivity and finished appearance.

[0095] Examples of amino resins include melamine resin and urea resin, with melamine resin being preferred.

[0096] Melamine resin is generally a thermosetting resin synthesized from melamine and aldehydes, with a triazine core and three reactive functional groups (-NX) per triazine core. 1 X 2 The melamine resin has the following characteristics: 1. A fully alkylated type containing -N(CH2OR)2 [where R is preferably an alkyl group having 1 to 8 carbon atoms, the same applies hereinafter] as a reactive functional group; 2. A methylol group type containing -N(CH2OR)(CH2OH) as a reactive functional group; 3. An imino group type containing -N(CH2OR)(H) as a reactive functional group; and 4. A methylol / imino group type containing both -N(CH2OR)(CH2OH) and -N(CH2OR)(H), or containing -N(CH2OH)(H) as reactive functional groups.

[0097] Among the melamine resins mentioned above, it is preferable to use a fully alkylated melamine resin from the viewpoint of forming a matte coating.

[0098] Examples of fully alkylated melamine resins include methylated melamine resins, butylated melamine resins, methyl / butyl mixed melamine resins, and isobutylated melamine resins. Among these, methylated melamine resins, butylated melamine resins, and methyl / butyl mixed melamine resins are preferred.

[0099] Commercially available melamine resins can be used. Examples of commercially available products include Cymel 303, Cymel 254, Cymel 1170, Cymel 235, Cymel 238, Cymel 1123, Mycoat 715 (all manufactured by Daicel Ornex), Sumimaru M-40S (manufactured by Sumitomo Chemical), Super Beccamine J-820-60, Super Beccamine L-121-60 (both manufactured by DIC), and Yuban 20SE-60 (manufactured by Mitsui Chemicals).

[0100] The above-mentioned melamine resins can be used individually or in combination of two or more types.

[0101] The polyisocyanate compound is a compound having two or more free isocyanate groups in one molecule, and includes, for example, aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate; alicyclic diisocyanate compounds such as hydrogenated xylylene diisocyanate, cyclohexylene diisocyanate, methylenebis(cyclohexyl isocyanate), and isophorone diisocyanate; and tolylene diisocyanate and phenylene diisocyanate. Examples include aromatic diisocyanate compounds such as 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, and naphthalene diisocyanate; and trivalent or higher organic polyisocyanate compounds such as 2-isocyanatoethyl-2,6-diisocyanatocaproate, 3-isocyanatomethyl-1,6-hexamethylene diisocyanate, and 4-isocyanatomethyl-1,8-octamethylene diisocyanate (commonly known as triaminononane triisocyanate). Furthermore, examples include cyclized polymers or burettes of these polyisocyanate compounds; or combinations thereof.

[0102] Among the above polyisocyanate compounds, aliphatic polyisocyanate compounds are preferred from the viewpoint of obtaining a wrinkled pattern coating film with excellent processability and weather resistance, and among these, the nurate form of aliphatic polyisocyanate compounds, the adduct form of aliphatic polyisocyanate compounds, and the burette form of aliphatic polyisocyanate compounds are preferred.

[0103] In particular, the nurate form of hexamethylene diisocyanate, the adduct form of hexamethylene diisocyanate compounds, and the burette form of hexamethylene diisocyanate are preferred.

[0104] The above-mentioned blocked polyisocyanate compound is a compound obtained by blocking the isocyanate group of the above-mentioned polyisocyanate compound with an active hydrogen-containing compound.

[0105] Examples of blocking agents as active hydrogen-containing compounds include pyrazoles such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-nitro-3,5-dimethylpyrazole, and 4-bromo-3,5-dimethylpyrazole; oximes such as methyl ethyl ketoxime, methyl amyl ketoxime, and cyclohexanone oxime; phenols such as phenol, para-t-butylphenol, and cresol; lactams such as ε-caprolactam and γ-butyrolactam; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol; ether alcohols such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; and active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone.

[0106] Among these blocking agents, pyrazoles, oximes, phenols, and lactams, particularly oximes, can be suitably used to obtain a wrinkled pattern coating film with excellent processability and weather resistance.

[0107] Commercially available blocked polyisocyanate compounds include, for example, nurates of hexamethylene diisocyanates such as Barnock D-500, Barnock D-550, Barnock DB-980K (all manufactured by DIC Corporation, trade names), Sumijoule N3300, Desmodule N3600, Desmodule N3790BA, Desmodule N3900, and Desmodule XP2840; burettes of hexamethylene diisocyanates such as Desmodule N75MPA / X and Desmodule N3200; and hexamethylene diisocyanates such as Desmodule HT. Examples include Anate adduct bodies (all manufactured by Sumika Bayer Urethane Co., Ltd., product names), Takenate D-102, Takenate D-202, Takenate D-110N or Takenate D-123N (all manufactured by Mitsui Chemicals, product names), Coronate L, Coronate HL, Coronate EH, Coronate 203, Millionate MT (manufactured by Nippon Polyurethane Industry Co., Ltd., product names), Duranate MF-K60B, SBN-70D, MF-B60B, 17B-60P, TPA-B80E, E402-B80B (all manufactured by Asahi Kasei Chemicals, product names), etc.

[0108] In the paint composition of the present invention, the mixing ratio of the hydroxyl group-containing resin (A) and the crosslinking agent (B) is preferably such that, based on the total solid content of components (A) and (B), the hydroxyl group-containing resin (A) is 50 to 95% by mass, preferably 60 to 90% by mass, and the crosslinking agent (B) is 5 to 50% by mass, preferably 10 to 40% by mass, from the viewpoint of obtaining a wrinkled pattern coating film with excellent processability, weather resistance, and scratch resistance.

[0109] <Sulfonic acid compound (C)> The sulfonic acid compound (C) acts as a catalyst to promote the reaction between the hydroxyl group-containing resin (A) and the crosslinking agent (B). Furthermore, the sulfonic acid compound (C) and the amine compound (D) can form a salt. The salt of sulfonic acid (C) and amine compound (D) increases the difference between surface hardening and internal hardening of the coating film formed from the paint composition, promoting the uneven hardening of the entire coating film.

[0110] Examples of sulfonic acid compounds include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, methanesulfonic acid, and dinonylnaphthalenesulfonic acid. These can be used individually or in combination of two or more.

[0111] From the viewpoint of forming a good matte appearance (wrinkle pattern), dodecylbenzenesulfonic acid and p-toluenesulfonic acid are particularly suitable for use among the above.

[0112] From the viewpoint of forming a good matte appearance (wrinkle pattern) of the coating film, the content of the sulfonic acid compound (C) is preferably in the range of 0.1 to 3.0% by mass, particularly 0.2 to 2.5% by mass, and even more preferably 0.3 to 2.0% by mass, based on the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B).

[0113] <Amine compound (D)> The amine compound (D) contributes to the neutralization of the sulfonic acid compound (C), and at least a portion of it may exist in the paint composition of the present invention as a salt with the sulfonic acid compound (C). Furthermore, an excess amount of the amine compound (D) promotes the uneven curing of the paint film and contributes to the formation of a good matte appearance (wrinkle pattern).

[0114] Examples of amine compounds (D) include secondary amines such as diethylamine, diisopropylamine, di-n-propylamine, diallylamine, diamylamine, diamylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, N-ethyl-1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, piperidine, 2-pipecolin, 3-pipecolin, 4-pipecolin, 2,4-,2,6-,3,5-lupetidine, and 3-piperidinemethanol; tertiary amines such as triethylamine, tributylamine, triallylamine, N-methyldiallylamine, N-methylmorpholine, N,N,N',N'-tetramethyl-1,2-diaminoethane, N-methylpiperidine, pyridine, and 4-ethylpyridine; and amines having secondary and tertiary amino groups such as N-methylpiperazine. These can be used individually or in combination of two or more.

[0115] In amine compound (D), the boiling point, type, and amount added are important for obtaining a good matte appearance (uniform wrinkle pattern) of the coating film.

[0116] The boiling point of the amine compound (D) is preferably in the range of 30 to 250°C, particularly 70 to 200°C, and even more preferably 75 to 160°C.

[0117] Triethylamine, diisopropylamine, and di-n-butylamine are particularly preferred as the amine compound (D).

[0118] The amount of amine compound (D) added is preferably in the range of amine compound (D) / sulfonic acid compound (C) = 1.5 to 30, particularly 3 to 25, and even more particularly 5 to 20, in terms of molar ratio.

[0119] The sulfonic acid compound (C) and the amine compound (D) may be mixed beforehand, or a mixture of these may be formulated. Blocked sulfonic acid compounds, in which the sulfonic acid is blocked with an amine compound (particularly a secondary or tertiary amine), can also be used and can be used in combination with amine compound (D).

[0120] Examples of commercially available blocked sulfonic acid compounds include Naicure 5225 (manufactured by King Industries, an amine-neutralized solution of dodecylbenzenesulfonic acid, containing 25% dodecylbenzenesulfonic acid) and Naicure 2500 (manufactured by King Industries, an amine-neutralized solution of p-toluenesulfonic acid, containing 25% p-toluenesulfonic acid).

[0121] In addition to the hydroxyl group-containing resin (A), crosslinking agent (B), sulfonic acid compound (C), and amine compound (D), the paint composition of the present invention may use, as necessary, known raw materials that have been conventionally used in paint compositions, such as aggregates, coloring pigments, gloss pigments, extender pigments, rust-preventive pigments, and heat-shielding pigments; paint additives such as defoamers, surface modifiers, ultraviolet absorbers (triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, etc.), light stabilizers, and waxes; anti-fouling agents such as organic silicates; metal catalysts such as tin compounds and titanium compounds; and solvents such as water and organic solvents.

[0122] Examples of aggregates include organic resin particles such as acrylic resin particles, nylon resin particles, acrylonitrile resin particles, urethane resin particles, and urea resin particles; glass beads, ceramic fibers, and silica particles. These can be used individually or in combination of two or more types.

[0123] The amount of aggregate is preferably in the range of 0.5 to 30% by mass, and particularly 2 to 20% by mass, based on the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B).

[0124] By including aggregate, a uniform matte coating can be stably produced in the coating film obtained from the paint composition of the present invention.

[0125] Examples of coloring pigments include inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and cold dust; organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone, perylene, anthrapyrimidine, carbazole violet, anthrapyridine, azo orange, flavanthrone yellow, isoindoline yellow, azo yellow, induthrone blue, dibromanzathrone red, perylene red, azo red, and anthraquinone red; and aluminum powder, alumina powder, bronze powder, copper powder, tin powder, zinc powder, iron phosphide, and finely atomized titanium.

[0126] Examples of luminous pigments include foil pigments such as aluminum foil, bronze foil, tin foil, gold foil, silver foil, titanium metal foil, stainless steel foil, nickel-copper alloy foil, and foil-like phthalocyanine blue.

[0127] Examples of extender pigments include calcium carbonate, barium sulfate, clay, talc, mica, and glass fibers.

[0128] The above pigments can be used individually or in combination of two or more types.

[0129] The amount of pigment is preferably in the range of 3 to 150% by mass, particularly 5 to 100% by mass, based on the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B).

[0130] As the wax, waxes known to those skilled in the art for use in paints can be used, such as microcrystalline, polyethylene, polytetrafluoroethylene, polypropylene, paraffin, carnauba, and modified versions thereof.

[0131] The above waxes can be used individually or in combination of two or more types.

[0132] The amount of wax is preferably in the range of 0.5 to 15% by mass, particularly 1 to 7% by mass, based on the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B).

[0133] By including wax, the coating film obtained from the coating composition of the present invention can stably exhibit good scratch resistance.

[0134] Examples of solvents include water; glycol-based organic solvents such as ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate; alcohol-based organic solvents such as methanol, ethanol, isopropyl alcohol, and Solfit (manufactured by Kuraray Co., Ltd.); ether-based organic solvents such as dioxane and tetrahydrofuran; ester-based organic solvents such as 3-methoxybutyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; ketone-based organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, and isophorone; and N-methyl-2-pyrrolidone, toluene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirits, and Swazole 1500 (aromatic hydrocarbon solvent, manufactured by ENEOS Corporation). The above solvents can be used individually or in combination of two or more.

[0135] The paint composition of the present invention may be a water-based paint or an organic solvent-based paint.

[0136] <Method for manufacturing paint composition> The method for producing the paint composition of the present invention is not particularly limited. For example, it can be produced by mixing each component using a mixer, disperser, kneader, etc., such as a sand grind mill, ball mill, blender, paint shaker, or disperser.

[0137] <Object to be coated> Examples of objects to be coated with the coating composition of the present invention include metal sheets such as galvanized steel sheets, zinc-aluminum alloy plated steel sheets, aluminum alloy plated steel sheets, hot-dip zinc-aluminum-magnesium alloy plated steel sheets, stainless steel sheets, and cold-rolled steel sheets, which are manufactured by methods such as melting or electrolysis.

[0138] In addition to these steel plates or plated steel plates, metal plates such as aluminum plates (including aluminum alloy plates) can also be used as the object to be coated.

[0139] The metal sheet described above is preferably surface-treated. Specifically, it is preferable that the metal sheet undergoes a pretreatment such as alkaline degreasing, hot water washing, or water washing, followed by a chemical conversion treatment. The chemical conversion treatment may be carried out by known methods, and specifically includes non-chromate treatments such as chromate treatment, zinc phosphate treatment, and zirconium treatment. The surface treatment can be appropriately selected depending on the steel sheet used, but treatments that do not contain heavy metals are preferred.

[0140] <Painted metal sheet> The painted metal sheet of the present invention comprises a metal sheet and a coating film formed from the coating composition of the present invention on at least one surface of the metal sheet. The coating composition contains a hydroxyl group-containing resin (A), a crosslinking agent (B), a sulfonic acid compound (C), and an amine compound (D). On the surface of the coating film, the arithmetic mean height (Ra) is 1.0 μm or more, and the Pattern Value (PV) is 1.0 to 150.

[0141] The thickness of the above coating film is preferably in the range of 1 μm to 40 μm, particularly 15 μm to 30 μm, and even more preferably 18 μm to 25 μm.

[0142] A painted metal sheet may have a coating film formed from the paint composition of the present invention on one surface, and a coating film formed from a known paint composition on the other surface.

[0143] For example, the other surface may have a coating film formed from a known coating composition, such as a coating composition containing epoxy resin.

[0144] The painted metal sheet may have an undercoat film (primer film) between the metal sheet and the coating film formed from the paint composition of the present invention.

[0145] The above-mentioned undercoat paint (primer paint) may be any conventionally known product.

[0146] The primer paint is selected appropriately depending on the type of material to be coated and the type of metal surface treatment, but epoxy resin-based primer paints, polyester resin-based primer paints, and modified primer paints thereof are particularly preferred, and polyester-based primer paints are preferred when processability is particularly required. From the viewpoint of environmental protection, it is preferable to use a chromium-free primer paint that does not contain chromium-based rust-preventive components.

[0147] The primer coating is typically applied by known coating methods such as roll coating or spray coating to a dry film thickness of 1 to 30 μm, preferably 2 to 20 μm. Furthermore, a cured primer coating film can be formed by heating at a temperature of 140 to 270°C, preferably 190 to 240°C, for 5 to 120 seconds, preferably 10 to 60 seconds, where the maximum temperature the material can reach.

[0148] The above-mentioned primer coating may be a single layer, or it may be a two-layer coating with a second primer coating (intermediate coating) formed on top of the first primer coating. When there are two layers of primer coating, it is possible to give the two primer coatings different functions, such as providing corrosion protection to the first primer coating and workability or chipping resistance to the second primer coating (intermediate coating).

[0149] By having an undercoat film, the adhesion and corrosion resistance of the coating film formed from the paint composition of the present invention can be improved.

[0150] The thickness of the undercoat film is preferably in the range of 1 μm to 20 μm, and particularly 3 μm to 7 μm.

[0151] <Method for manufacturing coating film> The present invention provides a method for manufacturing a coating film, comprising the steps of applying the coating composition of the present invention to an object to be coated, and drying and / or curing the coating composition at a temperature in the range of 170°C to 270°C.

[0152] It is preferable to apply a chemical conversion treatment, such as phosphate treatment or chromate treatment, to the surface of the object to be coated as a paint base treatment, and then apply the paint composition thereon. By applying the paint composition of the present invention to a metal plate that has undergone such chemical conversion treatment, the adhesion and corrosion resistance of the coating film to the metal plate can be improved.

[0153] Alternatively, a primer coating can be formed on a metal plate that has undergone chemical conversion treatment, and then painted over.

[0154] A coating film made from the coating composition of the present invention can be formed by applying the coating composition to an object to be coated, such as a metal plate, and then performing a baking treatment by heating the object to be coated.

[0155] The application of the paint composition is not particularly limited and can be done on the substrate using a bar coater, roll coater, roll curtain coater, curtain flow coater, die coater, or spray gun.

[0156] Furthermore, the baking treatment method for heating the workpiece after painting is not particularly limited, but a cured coating can be obtained by baking the coating and crosslinking the resin using heating means such as hot air heating, infrared heating, or induction heating. The baking temperature (the highest temperature reached by the workpiece, such as a steel plate) is usually in the range of 180°C to 250°C, preferably 200°C to 235°C, and the baking time is usually in the range of 5 seconds to 100 seconds, preferably 25 seconds to 60 seconds.

[0157] The film thickness (dry film thickness) of the coating obtained using the coating composition of the present invention is usually in the range of 1 μm to 40 μm, and for example, in the case of a topcoat coating, it is preferably in the range of 15 μm to 30 μm, and more preferably in the range of 18 μm to 25 μm. [Examples]

[0158] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[0159] Manufacturing of paint compositions Example 1 85 parts (solids) of polyester resin 1 (Note 1), 15 parts of Cymel 303 (Note 4), 0.5 parts of dodecylbenzenesulfonic acid, 1.5 parts of diisopropylamine, 2 parts of UVA1130 (Note 7), 1.5 parts of polyethylene dispersion, 2 parts of DYNEON TF9205 (Note 8), 5 parts of Toughtic AR650M (Note 9), 7 parts of GASIL HP560 (Note 11), and 10 parts of carbon MA-100 (Note 12) were mixed and diluted with an organic solvent (a mixed solvent of cyclohexanone / Swazole 1500 = 40 / 60 (mass ratio)) to obtain paint composition No. 1 with a viscosity of 80 seconds (Ford Cup #4, 25℃).

[0160] Examples 2-16 and Comparative Examples 1-6 Paint compositions No. 2 to 22 were obtained in the same manner as in Example 1, except for the formulations shown in Table 1. Paint compositions No. 17 to 22 are for comparative examples. In Table 1, the amounts of components excluding amine compounds are the solid content.

[0161] Furthermore, the notes in the table are as follows:

[0162] (Note 1) Polyester resin 1 The polyester resin is synthesized with acid components of isophthalic acid / phthalic anhydride / adipic acid and alcohol components of 1,3-butylene glycol / neopentyl glycol / glycerin, with a DBR ratio of 0.91. It has a weight-average molecular weight of approximately 8000, a hydroxyl value of 100 mgKOH / g, and an acid value of 2.9 mgKOH / g.

[0163] (Note 2) Polyester resin 2 The polyester resin is synthesized with acid components of terephthalic acid / isophthalic acid / adipic acid and alcohol components of ethylene glycol / neopentyl glycol / glycerin, with a DBR ratio of 0.98. It has a weight-average molecular weight of approximately 19,000, a hydroxyl value of 20 mgKOH / g, and an acid value of 8.1 mgKOH / g.

[0164] (Note 3) Polyester resin 3 The acid component is 1,2-cyclohexanedicarboxylic acid anhydride, and the alcohol component is neopentyl glycol / 2-butyl-2-ethyl-1,3-propanediol / trimethylolpropane. The polyester resin, synthesized with a DBR ratio of 0.98, is modified with coconut oil fatty acids to form an alkyd resin. It has a weight-average molecular weight of approximately 30,000, a hydroxyl value of 75 mgKOH / g, and an acid value of 6.0 mgKOH / g.

[0165] (Note 4) Cymel 303: Manufactured by Japan Cytec Industries Co., Ltd., product name, fully alkyl-type methylated melamine resin (Note 5) Cymel 325: Manufactured by Japan Cytec Industries Co., Ltd., product name, imino-based methylated melamine resin (Note 6) Super Beccamine L-121-60: Manufactured by DIC Corporation, product name, butylated melamine resin (Note 7) UVA1130: UV absorber, trade name, manufactured by BASF (Note 8) DYNEON TF9205:3M, manufactured by DYNEON, trade name, polytetrafluoroethylene (Note 9) ToughTic AR650M: Manufactured by Toyobo Co., Ltd., product name, polymethyl methacrylate copolymer fine particles (Note 10) ToughTic A-20: Manufactured by Toyobo Co., Ltd., product name, polyacrylonitrile-based fine particles (Note 11) GASIL HP560: Manufactured by PQ Corporation, product name, silicon dioxide, synthetic amorphous silica (Note 12) Carbon MA-100: Manufactured by Mitsubishi Chemical Corporation, product name, carbon black Preparation of test boards A primer coating with a dry film thickness of 4 μm (KP Color 8635 Primer, manufactured by Kansai Paint Co., Ltd., product name, polyester resin-based primer) was formed on an aluminum-zinc alloy galvanized steel sheet (GL material, sheet thickness 0.35 mm).

[0166] Next, each of the paint compositions No. 1 to 22 obtained in the above examples and comparative examples was applied to the primer coating using a bar coater to a dry film thickness of 22 μm, and the plates were baked for 40 seconds under conditions where the maximum temperature achievable by the material was 220°C to obtain each test plate. The results of tests conducted using each test plate according to the test conditions described below are also shown in Table 1. In the evaluation criteria of S, A, B, and C, S and A represent practical levels.

[0167] 60°G: This value represents the gloss level (60° gloss value) of each painted surface, measured in accordance with the specular gloss level (60°) of JIS K5600-4-7 (1999).

[0168] Crinkled pattern, visual evaluation of the pattern Pattern size: The appearance of the test plate was observed with the naked eye and evaluated according to the following criteria.

[0169] Small: Only nm-sized wrinkled patterns (ridges) that are difficult to distinguish with the naked eye are formed. Middle: Ribs are formed, with visible ridges measuring in millimeters. Large: Ribs are formed that are visible to the naked eye and measured in centimeters. ×: No wrinkle pattern will appear on the painted surface. Pattern uniformity: The appearance of the test plates was observed visually and evaluated according to the following criteria.

[0170] S: The painted surface has an uneven texture, resulting in a dense and uniform wrinkle pattern.

[0171] A: A wrinkled pattern with an uneven texture appears on the painted surface, but the density or uniformity of the wrinkled pattern is slightly inferior to that of the test plate S described above.

[0172] B: A wrinkle pattern appears on the painted surface, but the density or uniformity of the wrinkle pattern is inferior to that of the test panel in A above.

[0173] C: No wrinkle pattern appears on the painted surface.

[0174] Ra: This is the Ra value of a test plate measured in accordance with JIS B 0601-2001 using a surface roughness measuring instrument Surfcom 130A (manufactured by ACCRETECH (Tokyo Seimitsu) Co., Ltd.) under the conditions of an evaluation length of 12.5 mm and a measurement speed of 0.3 mm / s.

[0175] PV: As shown in Figure 3, the measurement device included an LED light as a light source, a CCD camera to capture an image of the light-irradiated coating surface, and an image analysis device. The image analysis device used consisted of the image analysis software "WINROOF" (manufactured by Mitani Corporation) and a personal computer for control and management.

[0176] The measurement conditions were set with a 45-degree angle between the light emitted from the LED and the light incident on the CCD camera, and the CCD camera was positioned perpendicular to the painted surface of the test panel. The illuminance was set to 500 lux on the painted surface of the test panel.

[0177] The brightness setting for the CCD camera was configured so that the gray level of the image captured from test panel J was 66.

[0178] Images of the coated surface of a light-illuminated test panel were captured with a CCD camera, converted to 8-bit grayscale, and analyzed using an image analysis device. For the image analysis, the average brightness of the black matte coated panel was set to 66. The measurement surface of the image to be analyzed was 33mm x 33mm in size, and this was decomposed into 2048 x 2048 sections (pixels) for data processing to obtain the PV value corresponding to the pattern.

[0179] For each test panel, an image of the light-irradiated coating surface was captured with a CCD camera, converted to an 8-bit grayscale image, and then subjected to a 2D Fourier transform to obtain the spatial frequency spectrum. From this spatial frequency spectrum, the power of the low spatial frequency component (0 to 1.55 lines / mm) in the region where the linear density representing resolution is 0 to 31.03 lines / mm was integrated, and then normalized by the DC component to obtain the 2D power spectrum integral value. The 2D power spectrum integral value in the above region is obtained using the aforementioned formula for obtaining the 2D power spectrum integral value.

[0180]

number

[0181] In this calculation, the value PV for each test plate was obtained by defining 0 to L as the frequency range where the line density representing the resolution is 0 to 1.55 lines / mm.

[0182] Accelerated Weathering: Each test panel was subjected to continuous irradiation for 3,000 hours using a xenon weatherometer under repeated cycle conditions (18 minutes wet - 102 minutes dry), based on Method A of the accelerated weathering (xenon lamp method) test for long-term durability of coating films as specified in JIS K 5600 7.7. Subsequently, the surface condition of each test panel was evaluated based on the following criteria.

[0183] S: No surface abnormalities such as blistering, cracking, clouding, or chalking are observed on the painted surface.

[0184] A: No surface abnormalities such as blistering, cracking, or chalking are observed on the painted surface, but cloudiness is present. B: Any of the following coating surface abnormalities are observed: blistering, cracking, chalking, etc. C: Significant surface abnormalities such as blistering, cracking, or chalking are observed on the painted surface. Scratch resistance: Evaluated by the rotational scratch test described below.

[0185] For each test plate, two 5cm x 5cm square test plates were prepared, and the painted surfaces were placed together and attached to the pressure surface of the test machine (simple test press, model THP-IU, manufactured by Sanki Seisakusho), with a hydraulic pump pressure of 20kgf / cm². 2 Pressurization was applied, a load was placed on the sample, and the sample was rubbed horizontally and rotated twice. After that, the sample was removed and the surface condition was visually evaluated according to the following criteria.

[0186] S: A slight sheen is visible on a portion of the entire painted surface. A: A slight sheen can be observed across the entire painted surface. B: A thick sheen is visible across the entire painted surface. C: Scratching of the painted surface is observed.

[0187] [Table 1]

[0188] [Table 2]

[0189] [Table 3] [Industrial applicability]

[0190] This invention clarifies the relationship between matte shapes such as wrinkle patterns and the weather resistance and scratch resistance of the coating film, and provides a coating composition capable of forming a wrinkle pattern coating film with excellent weather resistance and scratch resistance, a method for forming a wrinkle pattern coating film using the coating composition, and a coated metal sheet. [Brief explanation of the drawing]

[0191] [Figure 1] This is an example of an image showing a wrinkled pattern (design). [Figure 2] This is an example of a 3D distribution map of the brightness distribution of a 2D image. [Figure 3] This figure shows an example of a device for measuring the Pattern Value (PV).

Claims

1. A coating composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), a sulfonic acid compound (C), an amine compound (D), and a wax, The aforementioned crosslinking agent (B) consists solely of melamine resin. The aforementioned crosslinking agent (B) contains a methylated melamine resin. The amount of the wax is within the range of 0.5 to 15% by mass, based on the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). The amount of amine compound (D) added is in molar ratio with sulfonic acid compound (C), where amine compound (D) / sulfonic acid compound (C) = 5 to 20. The arithmetic mean height (Ra) on the surface of the coating film cured with the coating composition is 1.0 μm or more, and the PV (Pattern Value) is 1.0 to 150. The aforementioned value PV (Pattern Value) is derived from the integral value of a two-dimensional power spectrum obtained by integrating the power of the low spatial frequency components and normalizing it with the DC component from the spatial frequency spectrum obtained by taking a picture of the light-irradiated coating surface with a CCD camera at an angle where specularly reflected light from the irradiation does not occur, and then performing a two-dimensional Fourier transform on the grayscale 8-bit gradation image. A paint composition characterized in that the aforementioned value PV is calculated by the following formula. PV=(IPSL-0.25)×1000 (In the formula, IPSL is the integral value of the two-dimensional power spectrum)

2. The paint composition according to claim 1, wherein the melamine resin is a fully alkylated melamine resin.

3. A painted metal plate having a coating on at least one surface of a metal plate, wherein the coating is formed by the paint composition described in claim 1. A painted metal sheet characterized in that the arithmetic mean height (Ra) on the surface of the coating film is 1.0 μm or more, and the PV (Pattern Value) is 1.0 to 150.

4. A method for forming a coating film, comprising a painting step of applying the coating composition described in claim 1 to an object to be coated, and drying and / or curing the coating composition after application at a temperature of 170°C to 270°C.

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