JP2018167174A - Method for manufacturing coated metal plate - Google Patents

Abstract

To provide a fluorine resin-based coated metal plate having workability, designability and low glossiness sufficiently even after long-term storage.SOLUTION: A method for manufacturing a coated metal plate having a metal plate and a colored coated film arranged thereon, includes: heating a film of a colored coating material comprising pigment particles containing colored pigment particles and a base material resin containing 50 mass% or more of a fluorine resin, on a metal plate up to a specific temperature; and then cooling the heated film to a specific temperature at a specific cooling rate. The colored coated material further has a content and a particle diameter of the specific pigment particles and a content of the colored pigment particles.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a coated metal plate.

  The painted metal plate is generally excellent in durability, weather resistance, and design properties, and is suitably used for, for example, exterior building materials. Among painted metal plates for exterior building materials, painted metal plates having a coating film made of fluororesin are suitable for painted metal plates that require long-term durability. Such a fluororesin-based coated metal plate has a transparent coating film made of a mixed resin of polyvinylidene fluoride and an acrylic resin on a stainless steel plate surface, and the transparent coating film has a specific crystallinity and hardness. A fluororesin-based coated stainless steel plate is known (for example, see Patent Document 1), and has a fluoro-colored layer containing a fluororesin, an acrylic resin, an inorganic fired pigment, and an organic pigment on the surface of the steel plate. A fluororesin-based coated steel sheet having a coating film made of polyester having a specific glass transition temperature on the back surface of the steel sheet is known (for example, see Patent Document 2).

JP 2001-009367 A JP 2008-087242 A

  However, in a fluororesin-based coating film, generally, the crystallization of the fluororesin proceeds with time, so that the ductility of the coating film may decrease. That is, in a fluororesin, its molecules move relatively easily in a temperature range higher than its glass transition temperature (for example, about −40 ° C. for polyvinylidene fluoride). Fluororesin is generally a polymer having crystallinity, and in a temperature range above the glass transition temperature, from an irregular molecular arrangement structure (amorphous structure) to a regular molecular arrangement structure (crystal structure). Has a changing nature. The crystallized fluororesin has a strong bond between the molecular chains. Therefore, the ductility of the fluororesin-based coating film on the fluororesin-based coated metal plate stored for a long time tends to be low.

  Therefore, in the fluororesin-based coated metal plate, the ductility of the fluororesin-based coating film is high immediately after its production, so the coating film does not break during coating (coating cracking). When it is molded after being stored, the ductility of the fluororesin-based coating film is reduced, so that the coating film may break. For this reason, fluororesin-based coated metal plates after long-term storage may not satisfy the required performance, for example, the three performances of workability, design (freedom of coloring), and low glossiness at the same time. The exterior building material produced by using may not exhibit desired performance.

  An object of the present invention is to provide a fluororesin-based coated metal plate having sufficient workability, designability and low gloss even after long-term storage.

  It is known that the decrease in ductility of the fluororesin-based coating film over time is a phenomenon that is observed only when a pigment is included in the fluororesin-based coating film. The present inventor has studied in detail the relationship between the pigment in the fluororesin-based coating film and the ductility reduction of the coating film, and as a result, the particle size and content of the pigment in the coating film are in a specific range. It has been found that if it is within, the deterioration of workability over time is suppressed.

  The present invention provides, as one means for solving the above-mentioned problems, a method for producing a coated metal plate having a metal plate and a colored coating film disposed on the metal plate, pigment particles containing colored pigment particles, and The film on the metal plate of the colored paint containing the base resin containing the fluororesin in a content of 50% by mass or more is heated to a temperature at which the ultimate temperature of the metal plate is equal to or higher than the melting temperature Tm of the fluororesin. And cooling the film of the colored paint to a temperature not higher than the crystallization temperature Tc of the fluororesin at a cooling rate of 10 ° C./second or less. In the colored paint, the pigment particles in the colored paint Content is 12 volume% or less in content in the said colored coating film, Content of the said color pigment particle in the said colored coating material is 2 volume% or more in content in the said colored coating film, The said coloring The content of particle size 3μm greater of the particles in charge is to provide a manufacturing method, the coated metal plate is 1 vol% or less in content of the colored coating.

  According to the present invention, it is possible to provide a fluororesin-based coated metal plate having sufficient processability, designability and low gloss even after long-term storage.

It is a photographic image which shows an example of the spherulite in the said colored coating film which expanded the colored coating film in the coating metal plate manufactured by this invention 2000 times, and image | photographed with the scanning electron microscope.

  The manufacturing method of the coating metal plate which concerns on one embodiment of this invention is a method of manufacturing the coating metal plate which has a metal plate and the colored coating film arrange | positioned on the said metal plate.

  The said metal plate can be selected from a well-known metal plate in the range in which the effect in this Embodiment is acquired. Examples of the metal plate include cold rolled steel sheet, galvanized steel sheet, Zn—Al alloy plated steel sheet, Zn—Al—Mg alloy plated steel sheet, aluminum plated steel sheet, stainless steel sheet (austenite, martensite, ferrite, ferrite -Including martensite two-phase systems), aluminum plates, aluminum alloy plates and copper plates.

  The metal plate is preferably a plated steel plate or a stainless steel plate from the viewpoint of corrosion resistance and weight reduction, and is preferably a plated steel plate from the viewpoint of cost effectiveness. The metal plate is preferably a molten 55% Al—Zn alloy plated steel plate, a Zn—Al—Mg alloy plated steel plate or an aluminum plated steel plate from the viewpoint of corrosion resistance and suitability as an exterior building material. is there.

  The thickness of the metal plate can be appropriately determined based on the application of the coated metal plate. For example, the thickness of the metal plate is preferably 0.2 to 3.0 mm when the application of the coated metal plate is an exterior building material, and from the viewpoint of workability therefor, 0.25 to 2 0.0 mm is preferred.

  The manufacturing method includes a step of heating a film of a colored paint on a metal plate to a temperature at which the metal plate reaches a temperature equal to or higher than a melting temperature Tm of the fluororesin (hereinafter also referred to as “heating step”), and the coloring And a step of cooling the coating film to a temperature not higher than the crystallization temperature Tc of the fluororesin at a cooling rate of 10 ° C./second or less (hereinafter also referred to as “cooling step”).

  The colored paint contains pigment particles and a base resin. The colored paint is a liquid composition containing the material of the colored coating film.

  The base resin includes a fluororesin. One or more fluororesins may be used. Examples of the fluororesin component include a fully fluorinated resin such as polytetrafluoroethylene, a partially fluorinated resin such as polyvinyl fluoride, polyvinylidene fluoride, and ethylene trifluoride chloride. The fluororesin is excellent in durability, chemical resistance, heat resistance, abrasion resistance, stain resistance, etc. Among them, it has high workability and mechanical strength, and therefore it may be polyvinylidene fluoride (PVDF). preferable.

  The base resin may further contain a resin other than the fluororesin. The base resin may be bonded to each other or may not be bonded. One or more of the other resins may be used, and examples thereof include an acrylic resin. The said acrylic resin contributes to the improvement of coating-film adhesiveness. The acrylic resin is preferably a thermoplastic acrylic resin or a thermosetting acrylic resin having compatibility with polyvinylidene fluoride. Examples of the acrylic resin include polymers of acrylic monomers such as methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and butyl methacrylate, or copolymers of monomers containing the acrylic monomer.

  Content of the said fluororesin in the said base resin is 50 mass% or more. When there is too little content of the said fluororesin in the said base resin, the workability after a long-term storage may become inadequate. The content of the fluororesin in the base resin can be appropriately determined within a range of 50% by mass or more in a range where the effects of the present embodiment can be obtained. For example, sufficient low gloss in a colored coating film From the viewpoint of achieving the above, it is preferably 50 to 85% by mass, and from the viewpoint of further achieving sufficient weather resistance and workability of the coated metal plate, it is preferably 70 to 85% by mass.

  For example, the base resin may be composed of 50 to 85% by mass of a fluororesin and the remaining acrylic resin. For example, the base resin is preferably a resin having a mass ratio (PVDF: AR) of polyvinylidene fluoride (PVDF) and acrylic resin (AR) of 50:50 to 85:15. If the weight ratio of polyvinylidene fluoride is too low, the properties of the fluororesin such as weather resistance, corrosion resistance, and contamination resistance may not be fully exhibited. If the weight ratio of polyvinylidene fluoride is too high, coloring coating The adhesion of the film may decrease, and the workability of the coated metal plate may decrease.

  The pigment particles include colored pigment particles, and may further include other pigment particles. The color pigment particles may be one kind or more, and may be any of organic color pigments and inorganic color pigment particles that are generally available as color pigments for paints. The colored pigment particles are non-transparent and give a color tone to the colored coating film.

  Examples of the inorganic coloring pigments include titanium oxide, chromium oxide, carbon black, iron black, iron oxide yellow, titanium yellow, bengara, bitumen, cobalt blue, cerulean blue, ultramarine, cobalt green, and molybdenum red. included.

  Examples of the organic coloring pigments include quinacridone red, resol red B, brilliant scarlet G, pigment scarlet 3B, brilliant carmine 6B, lake red C, lake red D, permanent red 4R, Bordeaux 10B, fast yellow G, fast yellow. 10G, para red, watching red, benzidine yellow, benzidine orange, bon maroon L, bon maroon M, brilliant fast scarlet, vermillion red, phthalocyanine blue, phthalocyanine green, fast sky blue, and aniline black.

  The colored pigment particles may be composite oxide fired pigment particles containing a metal component. Examples of the fired pigment include CoAl, CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr. FeCrNi, FeNi, FeCrNiMn, FeZn, CoCr, MnCo, and SnZnTi.

  The colored pigment particles may be metallic pigment particles. Examples of the metallic pigment particles include Al flakes, resin-coated Al flakes, metal oxide-coated Al flakes, Ni flakes, Cu flakes, and Stainless steel flakes are included.

  The colored pigment particles may be pearl pigment particles, and examples of the pearl pigment particles include titanium oxide-coated mica, iron oxide-coated mica, and titanium oxide-iron oxide-coated mica.

  Examples of the other pigment particles include gloss adjusting agent particles and extender pigment particles.

  The gloss modifier particles can be used from the viewpoint of imparting a desired gloss to the colored coating film, or from the viewpoint of forming irregularities on the upper surface of the colored coating film. The gloss adjusting agent particles may be one kind or more, and examples of the material include inorganic materials such as silica and calcium carbonate, acrylic resin, urethane resin, benzoquamine resin, styrene resin, polyethylene resin, polypropylene resin, Resin materials such as fluororesin are included.

  The particle size of the gloss modifier particles contained in the colored coating film is 3 μm or less. Since the average particle size of commercially available gloss modifier particles is usually more than 3 μm, when using commercially available gloss modifier particles, particles having a particle size of 3 μm or less are separated and used by classification, or The content is preferably less than 1% by volume.

  The content of the gloss modifier particles in the colored coating film varies depending on, for example, the particle size of the gloss modifier particles, but the desired design is achieved by blending the gloss modifier particles in the colored coating film. From this viewpoint, the content is preferably 0.2 to 1.0% by volume.

  Alternatively, from the viewpoint of adjusting the gloss in the colored coating film, the particle size of the gloss modifier particles in the colored coating film is preferably larger (for example, the above particle size is more than 3 μm), and the content thereof is It is preferable that it is 0.2 volume% or more. In addition, as above-mentioned, it is preferable that the said content is 1.0 volume% or less from a viewpoint of the workability after storage.

  The extender pigment particles are pigments contained in the coating film from the viewpoints of adjusting the hardness of the coating film and reducing the cost of the coating (the effect of increasing the bulk), and generally do not affect the color tone of the coating film. Since extender pigment particles are usually less expensive than fluororesin, it is preferable that the colored coating film contains extender pigment particles within the range where the effects of the present embodiment can be obtained. The extender pigment particles preferably have a high visible light transmittance. The extender pigment particles may be one kind or more, and examples thereof include particles of barium sulfate, titanium oxide, silica, and calcium carbonate. For example, the number average particle diameter of the extender particles is 0.01 to 1 μm, and the content of extender particles in the colored coating film is 0.1 to 10% by volume, for example.

  Content of the said pigment particle in the said colored coating material is 12 volume% or less by content in the said colored coating film. The pigment particles are not deformed even when the colored coating film is deformed in the colored coating film, and the deformation of the coating film is suppressed. Therefore, when the content exceeds 12% by volume, the effect of suppressing deformation of the coating film by the pigment particles is enhanced, and the ductility of the colored coating film may be insufficient.

  Content of the said color pigment particle in the said colored coating material is 2 volume% or more by content in the said colored coating film. The colored pigment particles are contained in the colored coating film for the purpose of imparting design properties. Therefore, when the content is less than 2% by volume, color development and color concealment by the colored pigment particles are insufficient, the color of the base is transparent, and the designability may be insufficient. Moreover, the said fluororesin has a property which permeate | transmits an ultraviolet-ray, and comprises a film | membrane structure in a colored coating film. If the content of the colored pigment particles is less than 2% by volume, the amount of ultraviolet light applied to the base of the colored coating film increases in an outdoor environment, and the adhesion at the interface between the base and the colored coating film decreases early. In addition, the colored coating film may be peeled off from the base.

  The content of particles having a particle size of more than 3 μm in the colored coating is 1% by volume or less in terms of the content in the colored coating film. Here, “particle size” means the size of the particles in the colored coating film, and when the pigment particles are present as primary particles in the colored coating film, they may be the primary particle diameter or the pigment. When the particles are aggregated, the particle diameter of the aggregated particles may be used.

  In forming a painted metal plate, tensile stress is applied to the surface of the coating film it has. When the extensibility of the coating film is low, the coating film may be broken and the underlying metal plate may be partially exposed. When exposed to an outdoor environment for a long period of time, a situation occurs in which the metal plate and a factor that promotes corrosion of the metal such as water and chloride ions are in direct contact with each other for a long period of time. Corrosion may progress. On the other hand, when the elongation of the coating film is high, the coating film is not broken and the underlying metal plate is not exposed to the outside. For this reason, the progress of corrosion of the underlying metal plate can be suppressed for a long period of time, and long-term durability is exhibited.

  If the content of the particles having a particle size of more than 3 μm in the colored coating film exceeds 1% by volume, the ductility of the colored coating film may be insufficient, and the above-described underlying metal plate may be corroded. From the viewpoint of the long-term durability, the content is preferably as small as possible, and most preferably the colored coating film does not contain the particles.

  The number average particle diameter of the colored pigment particles can be appropriately determined within a range in which the effect of the present embodiment can be obtained, and is usually 3 μm or less, for example, 0.01 to 1.5 μm. If the particle size of the colored pigment particles is smaller, the content of the colored pigment particles in the colored coating film can be increased. From this viewpoint, the average particle size of the colored pigment particles is 2.0 μm or less. It is preferable that it is 0.5 μm or less. For example, if the average particle diameter is 2.0 μm or less, it is usually possible to contain colored pigment particles in a colored coating film up to 5% by volume. If the average particle diameter is 0.5 μm or less, coloring is performed. It becomes possible to contain the colored pigment particles in the coating film up to 10% by volume.

  The colored paint may further contain components other than the base resin and the pigment particles as long as the effects of the present embodiment are obtained. Examples of such other components include solvents, ultraviolet absorbers, light stabilizers, plasticizers, dyes, antioxidants, antistatic agents, surfactants, dispersion aids, curing agents, curing catalysts, and hydrophilic Agent.

  Examples of the solvent include hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, ethers such as cellosolve, and ketones such as methyl isobutyl ketone, methyl ethyl ketone, isophorone, and cyclohexanone.

  The curing agent crosslinks the base resins when the paint is cured (baked). The curing agent can be appropriately selected from known crosslinking agents and curing agents according to the type of base resin, baking conditions, and the like. Examples of curing agents include melamine compounds, isocyanate compounds, and both. Examples of the melamine compound include an imino group type, a methylol imino group type, a methylol group type or a fully alkyl group type melamine compound. The isocyanate compound may be aromatic, aliphatic, or alicyclic, and examples include m-xylene diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, and block compounds thereof.

  One or more of the other components may be used, and they are used in an amount corresponding to a desired action. For example, from the viewpoint of further improving the weather resistance of the colored coating film, the colored coating material may contain 10% by volume or less of an ultraviolet absorber and a light stabilizer in a content of the colored coating film. Good.

  Further, for example, the curing catalyst is a component that accelerates the curing of the film or the crosslinking of the base resin, and can be appropriately selected from known components having such a catalytic action. The content of the curing catalyst in the colored paint can be determined as appropriate as long as sufficient storage stability of the colored paint is obtained, and is, for example, 10 to 30% by volume.

  Moreover, the said hydrophilizing agent is suitable as an additive of a colored coating film, and can be contained in the gloss adjusting paint in an amount of, for example, 30% by volume or less from the viewpoint of preventing rain stains on the colored coating film. Examples of the hydrophilizing agent include a partial hydrolysis condensate of tetraalkoxysilane.

  The thickness of the colored coating film can be appropriately determined according to the desired thickness (dry film thickness) of the colored coating film to be produced. The thickness of the colored coating film is determined in a timely manner within the above-mentioned thickness range based on various factors such as the content of the color pigment, the color tone, the ultraviolet shielding degree, and the degree of processing at the time of forming the coated metal plate. It is possible to decide.

  The thickness of the colored coating film is preferably 50 μm or less. The thickness of the colored coating film can be represented by an average value of the distance from the bottom surface to the surface at a plurality of locations (for example, 10 locations arbitrarily selected) of the colored coating film. When the thickness exceeds 50 μm, it is necessary to increase the coating amount of the colored paint when producing a colored coating film. When the film of the paint is heated and cured, ) Is likely to occur as a coating defect. Moreover, since the said coating amount increases, it becomes disadvantageous in terms of cost.

  In addition, for example, the thickness of the colored coating film increases as the content of the colored pigment increases, as the color brightness of the colored pigment (L value defined in JIS) decreases, or as the ultraviolet shielding degree increases. The film can be made small because it has excellent color developability (color concealment with respect to the color of the base) and an ultraviolet shielding rate to the base. Moreover, when the said process degree is low, since the ductility calculated | required by a colored coating film becomes low, it is possible to make the thickness of a colored coating film small.

  In addition, for example, from the viewpoint of maintaining long-term adhesion between the colored coating film and the base (suppressing interfacial fracture for a long time), it is preferable to lower the ultraviolet transmittance of the colored coating film. It is preferable to increase the thickness. In general, when tensile stress is applied to the coating film, even if the elongation displacement is the same, the elongation deformation strain increases as the film thickness decreases. For this reason, it is preferable that the thickness of the colored coating film is large from the viewpoint of reducing the elongation deformation strain.

  Thus, although the lower limit value of the thickness of the colored coating film cannot be generally specified, for example, the processing degree is equivalent to a 4T bending degree, and the L value of the colored pigment particles (for example, titanium oxide particles) is If it exceeds 80, the thickness of the colored coating film is preferably 20 μm or more, and more preferably 25 μm. If the L value of the color pigment particles (for example, iron-chromium-based calcined pigment particles) is 70 or less, the thickness of the colored coating film is preferably 15 μm or more, and 18 μm or more. It is more preferable that

  The content of the pigment particles in the colored coating film is determined by, for example, observing a cross section of the colored coating film with a microscope or the like, and cutting off the pigment and resin in an arbitrary range (for example, a colored coating film thickness × 200 μm width range). It can be determined by measuring the area and calculating this ratio.

  The heating step can be performed by a known apparatus and method for baking a paint on a metal plate in the production of a coated metal plate. Generally, the coating film is cured by the heating step. In the heating step, the colored paint film on the metal plate is heated to a temperature at which the ultimate temperature of the metal plate is equal to or higher than the melting temperature Tm of the fluororesin. The heating step may be baking of the colored paint, or may be a step of heating the film after baking. The crystal structure of the fluororesin in the film substantially disappears at a temperature equal to or higher than the melting temperature of the fluororesin.

  From the viewpoint of sufficiently eliminating the crystal structure, in the heating step, it is preferable that the film is heated to a temperature of the ultimate temperature of Tm + 20 ° C. or higher. The temperature of the film in the heating step can be appropriately determined within a range in which substantial denaturation due to heat does not occur in the film. From this viewpoint, for example, in the heating step, the film is It is preferable that the heating is performed within a range of Tm + 100 ° C. or less.

  In the cooling step, the colored paint film is cooled to a temperature not higher than the crystallization temperature Tc of the fluororesin at a cooling rate of not more than 10 ° C./second. The said cooling process can be performed by a well-known method in the range with which said cooling rate is satisfy | filled. Examples of cooling methods include cooling in a normal temperature atmosphere, blowing cold air (wind cooling), blowing low temperature liquid such as water or immersing in the cooling liquid (water cooling), and cooling by contact with a low temperature solid. (For example, contact with a cooling roll or a cooling plate).

  The cooling step can be started from the temperature at the end of the heating step. That is, the cooling start temperature in the cooling step is a temperature equal to or higher than the melting temperature Tm of the fluororesin, and is preferably a temperature from Tm to Tm + 20 ° C. from the above viewpoint.

  The cooling end temperature in the cooling step can be appropriately determined within a range where a sufficient amount of crystals (spherulites) of the fluororesin are generated in the colored coating film. The cooling end temperature is preferably a temperature from Tc to Tc-20 ° C. from the viewpoint of sufficiently storing the generated crystals in the colored coating film. The cooling end temperature may be normal temperature (for example, 30 ° C.).

  The cooling rate in the cooling step is 10 ° C./second or less. When the cooling rate is too high, the generation of the fluororesin crystals in the colored coating film becomes insufficient, and the desired low glossiness may not be obtained. The cooling rate is, for example, an average value of the cooling rate from the cooling start temperature to the cooling end temperature. The actual cooling rate is preferably within the range of ± 2 ° C./second of the average value from the viewpoint of appropriately controlling the crystallization of the fluororesin. From the viewpoint of sufficiently exhibiting low glossiness, the cooling rate is preferably 6 ° C./second or less.

  For example, when the fluororesin is polyvinylidene fluoride, the melting point of polyvinylidene fluoride is 180 ° C., and the crystallization temperature is 130 ° C. Therefore, the film of the colored coating film reaches the temperature reached by the metal plate in the heating step. At a temperature of at least 180 ° C. or more, and in the cooling step, the temperature is gradually cooled at a rate of 10 ° C./second or less between a temperature of at least 180 ° C. and 130 ° C. The cooling rate of the colored coating film after the cooling step may be faster than the cooling rate in the cooling step.

  According to the said manufacturing method, the coating metal plate which has a colored coating film whose arithmetic mean roughness of the surface is 50 nm or more is obtained by crystallization of the said fluororesin in the said colored coating film. When the surface roughness is 50 nm or more, moderate unevenness is formed on the surface of the colored coating film, the specular gloss at 60 ° of the coated metal plate is 40 or less, and a low-gloss painted metal plate is realized. Is done. The surface roughness can be appropriately determined from the viewpoints of glossiness and design required for the coated metal plate, but is more preferably 100 nm or more from the viewpoint of reducing the specular glossiness. More preferably, it is 300 nm or more. On the other hand, it is preferably 400 nm or less from the viewpoint that the effect of reducing the gloss reaches a peak.

  The surface roughness can be determined using any known measuring device of a contact type or a non-contact type. Examples of the contact-type measuring device include a contact-type roughness meter and an atomic force microscope. Examples of the non-contact type measuring device include a white interferometer, a laser microscope, and an electron microscope.

  The crystallization of the fluororesin will be described. Usually, in the process of cooling a crystalline polymer from a melting temperature to a crystallization temperature or lower, a part of the molecular chain forms a crystal structure. For example, in polyvinylidene fluoride, crystals (spherulites) called α crystals having a large crystal grain size (particle size: 0.1 to several tens of μm) are generated and grown in the crystallization temperature range. In the crystallization temperature range, the time required for producing α crystals having a particle size of about 10 μm is, for example, about 1 second. Therefore, by producing a colored coating film by slow cooling, the time for staying in the crystallization temperature range at the time of cooling becomes longer, and many large α crystals are generated in the coating film.

  However, when a colored coating film is produced by rapid cooling, since the time for staying in the crystallization temperature range is short, α crystals in the coating film are small and the number of crystal grains is small. In addition to the α crystal, a crystal having a small particle size (1 μm or less) called a β crystal is likely to be generated. For example, in the colored coating film composed of polyvinylidene fluoride, the phases of the α crystal, β crystal, and amorphous part may exist depending on the cooling rate in the production. In addition, crystals grow even below the crystallization temperature range, for example, at room temperature, but the growth rate is much slower than the growth rate in the crystallization temperature range, and the crystal grain size produced is usually less than 1 μm.

  When the fluororesin crystallizes in the colored coating film in the production process, the volume of the coating film shrinks, and irregularities are formed on the surface thereof. When the spherulites are large and the number of spherulites is increased, the area of the portion where the irregularities extend is increased, and the arithmetic average roughness can be sufficiently increased. In order to obtain a low-gloss surface in the colored coating film, irregularities due to large α crystals are preferable. The unevenness formed by the β crystal has a small height, and a surface with a low specular gloss may not be obtained.

  In the colored coating, the average value of the size of the spherulites is preferably 10 μm or more from the viewpoint of sufficiently increasing the arithmetic average roughness, and the colored coating when the colored coating is viewed in plan. It is preferable from the above viewpoint that the area ratio of the spherulites in is 50% or more.

  FIG. 1 is a photographic image showing an example of a spherulite in the colored coating film, which was obtained by magnifying the colored coating film having the spherulite with an electron microscope at a magnification of 2000 times. As shown in FIG. 1, the spherulites can be individually confirmed from the appearance, for example, by a radial pattern. The size of the spherulite may be the length of a portion representing the size of the spherulite, and is represented by, for example, the maximum diameter. The area ratio can be obtained by determining an arbitrary range including a plurality of (for example, five or more) spherulites as a measurement region.

  The size of the spherulite and the area ratio can be measured and determined by observation with an optical microscope or an electron microscope, for example, based on an enlarged image of the surface of the colored coating film.

  The manufacturing method may further include other steps than the heating step and the cooling step described above as long as the effects of the present embodiment can be obtained. Examples of the other steps include a chemical conversion treatment step for forming a chemical conversion treatment film, a step for forming an undercoat coating, a step for forming an intermediate coating, and a step for applying a colored paint.

  The chemical conversion treatment step is a step of producing a chemical conversion treatment film. For example, an aqueous chemical conversion solution for forming a chemical conversion treatment film is formed by a known method such as a roll coating method, a spin coating method, or a spray method. It can be carried out by applying to the surface of the metal plate and drying the metal plate after washing without washing. From the viewpoint of productivity, the drying temperature and drying time of the metal plate are preferably, for example, 60 to 150 ° C. and 2 to 10 seconds at the ultimate temperature of the metal plate.

  The chemical conversion treatment film is disposed directly on the metal plate, that is, between the metal plate and the colored coating film, for the purpose of improving the adhesion and corrosion resistance of the coated metal plate. A chemical conversion treatment film is a layer on a metal plate, and is comprised with the composition adhering to the surface of the metal plate by the pre-coating process. Examples of the chemical conversion coating include a non-chromate coating and a chromate coating. Both are films formed by rust prevention treatment.

  The non-chromate film is preferable from the viewpoint of enhancing the corrosion resistance and reducing the environmental load in the production and use of the coated metal plate, and the chromate film is preferable from the viewpoint of increasing the corrosion resistance.

  Examples of the non-chromate coating include Ti-Mo composite coating, fluoroacid coating, phosphate coating, resin coating, resin and silane coupling agent coating, silica coating, silica and silane coupling agent coating Films, zirconium-based films, zirconium and silane coupling agent-based films are included.

The adhesion amount of the non-chromate film can be appropriately determined according to the type. For example, the adhesion amount of the Ti—Mo composite film is 10 to 500 mg / m ² in terms of total Ti and Mo, and the adhesion amount of the fluoroacid-based film is 3 to 100 mg / in terms of fluorine or total metal elements. m ² , the adhesion amount of the phosphate film is 0.1 to 5 g / m ² in terms of phosphorus element, and the adhesion amount of the resin film is 1 to 500 mg / m ² in terms of resin. The adhesion amount of the resin and the silane coupling agent-based film is 0.1 to 50 mg / m ² in terms of Si, and the adhesion amount of the silica-based film is 0.1 to 200 mg / m ² in terms of Si. There, the adhesion amount of the silica and silane coupling agent-based coating is 0.1 to 200 mg / ^{m 2} in terms of Si, adhesion quantity of the zirconium-based coating is 0.1-100 mg / ^{m 2} in terms of Zr And Adhesion amount of the serial zirconium and a silane coupling agent-based coating is preferably 0.1-100 mg / ^{m 2} in terms of Zr.

Examples of the chromate film include a coating type chromate film and a phosphoric acid-chromic acid system chromate rust preventive film. The adhesion amount of these chromate films is preferably ²⁰ to 80 g / m ² in terms of chromium element.

  The step of forming the undercoat coating film is a step of producing an undercoat coating film on a metal plate, and can be performed, for example, by applying a coating for the undercoating film (undercoating paint) and thereby curing the film. The undercoat paint may contain the solvent and the additive as necessary. The undercoat paint is prepared by uniformly mixing and dispersing the following undercoat paint materials. For example, the undercoat paint is applied to the metal plate by a known method described above for the overcoat paint in an application amount that provides a dry film thickness of 1 to 10 μm (preferably 3 to 7 μm). For example, the coating film of the paint is baked onto the metal plate by heating the metal plate at a temperature of 180 to 260 ° C. at the temperature reached by the metal plate.

  The said undercoat coating film is arrange | positioned between the said metal plate and the said colored coating film from a viewpoint of improving the adhesiveness and corrosion resistance with the colored coating film in a coating metal plate. The undercoat coating film is formed on the surface of the metal plate or, if the chemical conversion coating is prepared, on the surface of the chemical conversion coating.

  The film structure of the undercoat coating film is composed of a resin. Examples of the resin include the fully fluorinated resin, the partially fluorinated resin, the polyester resin, the modified silicon resin, the acrylic resin, the epoxy resin, the phenoxy resin, the urethane resin, and the vinyl chloride resin.

  The undercoat coating film may further contain additives such as rust preventive pigment particles, colored pigment particles, metallic pigment particles, pearl pigment particles, extender pigment particles, and gloss modifier particles. Examples of the rust preventive pigment particles include non-chromium rust preventive pigment particles such as modified silica, vanadate, magnesium hydrogen phosphate, magnesium phosphate, zinc phosphate, and aluminum polyphosphate, and chromic acid. Particles of chromium-based anticorrosive pigments such as strontium, zinc chromate, barium chromate and calcium chromate.

  Examples of the colored pigment particles include titanium oxide, chromium oxide, carbon black, iron black, iron oxide yellow, titanium yellow, bengara, bitumen, cobalt blue, cerulean blue, ultramarine, cobalt green, molybdenum red, quinacridone red, and risol. Red B, Brilliant Scarlet G, Pigment Scarlet 3B, Brilliant Carmine 6B, Lake Red C, Lake Red D, Permanent Red 4R, Bordeaux 10B, Fast Yellow G, Fast Yellow 10G, Para Red, Watching Red, Benzidine Yellow, Benzidine Orange, Bonn Maroon L, Bon Maroon M, Brilliant Fast Scarlet, Vermilion Red, Phthalocyanine Blue, Phthalocyanine Green, Fast Sky Blue, Anilyb Click, CoAl, CoCrAl, CoCrZnMgAl, CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr, FeCrNi, FeNi, FeCrNiMn, FeZn, CoCr, MnCo, and include SnZnTi, particles.

  Examples of the metallic pigment particles include Al flakes, resin-coated Al flakes, metal oxide-coated Al flakes, Ni flakes, Cu flakes, and stainless steel flakes. Examples of the pearl pigment particles include titanium oxide-coated mica, iron oxide-coated mica, and titanium oxide-iron oxide-coated mica. Examples of the extender pigment particles include particles of barium sulfate, titanium oxide, silica, and calcium carbonate. Examples of the gloss modifier particles include inorganic materials such as silica and calcium carbonate, and resin materials such as acrylic resin, urethane resin, benzoquamine resin, styrene resin, polyethylene resin, polypropylene resin, and fluororesin.

  The content of the pigment particles in the undercoat film can be determined as appropriate as long as the effect of the present embodiment can be obtained. By providing an undercoating film with low brightness between the metal plate and the metal plate, it is possible to impart a unique color tone and radiance to the pearl pigment. In addition, for example, by adding pigment particles having a large particle size of about several tens of μm in the undercoat coating, irregularities are formed at the interface between the undercoat coating and the colored coating, In addition, the low glossiness can be further enhanced by forming or developing irregularities on the surface of the coated metal plate. Moreover, for example, the content of the rust preventive pigment in the undercoat coating film is preferably 10 to 70% by volume.

  The step of forming the intermediate coating film is a step of producing an intermediate coating film between the undercoat coating film and the colored coating film in the laminating direction. For example, in the same manner as the process of forming the undercoat coating film, The coating can be carried out by applying a coating for a coating film (intermediate coating) and thereby curing the film. The intermediate coating material may also contain the solvent and the additive as required in addition to the material of the intermediate coating film described below. The intermediate coating is also prepared by uniformly mixing and dispersing the aforementioned materials. For example, the intermediate coating is preferably applied at a coating amount of 3 to 20 μm (preferably 5 to 15 μm) by the above-described known method. For example, the coating film of the paint is baked onto the metal plate by heating the metal plate at a temperature of 180 to 260 ° C. at the temperature reached by the metal plate.

  The said intermediate coating film is arrange | positioned between the said undercoat coating film and the said colored coating film from a viewpoint of improving the adhesiveness and corrosion resistance between the coating films in a coating metal plate.

  The film structure of the intermediate coating film is also made of resin. Examples of the resin include the fully fluorinated resin, the partially fluorinated resin, the polyester resin, the modified silicon resin, the acrylic resin, the epoxy resin, the phenoxy resin, the urethane resin, and the vinyl chloride resin. In the intermediate coating film, as in the case of the undercoating film, an additive may be appropriately contained as long as the effect of the present embodiment is obtained. The additive is the same as that described for the colored coating film, for example.

  The step of applying the colored coating includes the step of applying the colored coating on the surface of the metal plate, the chemical conversion coating, the undercoat or the intermediate coating, roll coating, curtain flow coating, spray coating, dip coating. It can carry out by well-known methods, such as. The coating amount of the colored paint is appropriately adjusted according to the desired thickness of the coating film.

  In the case of producing a coating film other than the colored coating film, the thickness of the colored coating film can be determined in consideration of the presence of the coating film. For example, when the coated metal plate has an undercoat coating and a colored coating described later, the thickness of the colored coating is preferably 10 to 35 μm from the viewpoints of design properties, corrosion resistance, and workability over time.

  It should be noted that the coating of at least the upper two of the two coatings that directly overlap is applied by a non-contact coating method such as curtain flow coating or spray coating (so-called wet-on-wet coating without contact with the object to be coated) When the coating method is possible, the lower coating film can be cured at the same time as the upper coating film, so apply the coating for the upper coating. It is possible to omit the step of previously curing the lower coating film. For example, in the case where the above-mentioned colored coating film is disposed directly on the above-described other coating film or coating film, a coating film film for another film is formed, and then the colored coating film is formed by a non-contact coating method. Once formed, the other film and the overlying film of colored paint can be cured (by heating).

  The coated metal plate produced by the above production method has sufficient ductility and design properties even though the colored coating film contains pigment particles, and thus has sufficient workability. In addition, the coated metal plate has sufficiently low gloss because the colored coating film has the above surface roughness. The reason will be described below.

  Generally, when a coated metal plate is formed and processed, a tensile stress acts on the coating film of the coated metal plate, and the coating film is stretched. This stretching is initially constricted, deformed and stretched at a certain point, and the region thus deformed (neck deformed portion) expands (propagates) in the tensile direction.

  In the constricted deformation portion, the molecular chains of the fluororesin constituting the coating film that are oriented randomly before the constriction deformation are oriented in the tensile direction due to the tensile stress. For this reason, when a certain amount of tensile stress is applied to the constricted deformed portion, the molecular chain that has already been oriented is not easily stretched any more, even if tensile stress is applied further. For this reason, the “parts that have not been constricted yet (molecular chains that are not oriented)” around the constricted deformed portion are constricted and deformed.

  Such propagation of molecular chain orientation is elongation deformation of the resin coating film. In other words, the high ductility of the resin-made coating film results from the propagation of the above-described orientation of the molecular chain progressing throughout the coating film without breaking the molecular chain. Note that the stress required for the orientation of the molecular chain is higher in the crystallized resin than in the amorphous resin. This is because the bond strength between regularly folded crystal molecular chains is high.

  Here, in the case of a resin-made coating film containing no pigment particles (for example, a clear coating film), although there is some difference in deformation resistance depending on the crystal state of the resin, the coating film is stretched and deformed due to tensile stress. The ductility of is high. On the other hand, the pigment particles are extremely hard compared to the resin and do not deform due to elongation.

  Therefore, when the resin coating film contains pigment particles and the resin is a crystalline resin, the resin constituting the coating film is crystallized (the amorphous portion is reduced), and deformation resistance is reduced. It becomes even larger and voids are likely to be created between the molecular chains to be oriented and the pigment particles. For this reason, stress concentrates in the void generated in the constricted deformed portion, and the void grows. As a result, the coating film is broken. That is, the ductility of the coating film is low.

  Among the voids generated in the constricted deformed portion, when the size of the initially generated void is a size that cannot be ignored with respect to the thickness (about 3 to 5 μm) of the constricted deformed portion of the coating film, stress is applied to the void. Concentrate and grow the voids. The size of the void generated in the initial stage is considered to be equal to the particle size of the pigment particles in the coating film, and the initial size of the void is sufficiently small with respect to the thickness of the constricted deformation portion of the coating film. In this case, it is considered that the stress concentration in the void does not substantially occur.

  That is, if the particle size of the pigment particles in the coating exceeds a certain threshold, the stress concentration in the voids occurs, and if the pigment particle content in the coating exceeds a certain threshold, Since the small voids are sufficiently dense, the same effect as that of the large voids is exhibited, and the growth and coalescence of the voids due to the stress concentration occur, and the coating film is easily broken. That is, the ductility of the coating film is lowered. In the present embodiment, as a result of examining the threshold value, it was found that the pigment particle diameter threshold value is 3 μm, and the pigment particle content threshold value is 1% by volume.

  As described above, the coated metal plate produced in the present embodiment has a colored coating film, but this colored coating film is sufficient to exhibit design properties, but small pigment particle particles are used. Contains less than a certain amount. For this reason, the said colored coating film expresses sufficient ductility at the time of the process of a coating metal plate, and the crack of the colored coating film by said stress concentration is prevented. Therefore, even if the coated metal plate is subjected to processing after long-term storage, the colored coating film does not crack, exhibits sufficient corrosion resistance, and further has a design property by the colored coating film and low gloss by the colored coating film. Is expressed.

  Conventional fluororesin paints for exterior building materials usually exceed the above threshold. For example, gloss adjustment pigments are added to general paints for the purpose of adjusting the gloss of the coating surface. In order to impart unevenness to the surface of the coating film, the gloss adjusting pigment generally has an average particle diameter of about 5 to 30 μm, and the content in the coating film is generally more than 1% by volume.

  In addition, the pigment particles generally have a property of aggregating in the paint, and the aggregated particles of the pigment particles cause a large void in the constricted deformation portion. The present inventor confirmed that the agglomerated particles having a particle diameter of more than 3 μm were present in the paint when the paint having a particle diameter of 3 μm or less was allowed to stand, and the content thereof was a dry coating film. 1% by volume or more was confirmed. As described above, it has been found that the workability of the conventional fluororesin-based coated metal sheet for exterior building materials may be extremely lowered with time.

  As is clear from the above description, the method for producing a coated metal plate in the present embodiment includes pigment particles including colored pigment particles, and a base resin including a fluorine resin in a content of 50% by mass or more. Heating the film of the colored paint on the metal plate to a temperature at which the metal plate reaches a temperature equal to or higher than the melting temperature Tm of the fluororesin, and the film of the colored paint below the crystallization temperature Tc of the fluororesin Cooling to a temperature at a cooling rate of 10 ° C./second or less. And in the said colored paint, content of the said pigment particle in the said colored paint is 12 volume% or less by content in the said colored coating film, and content of the said colored pigment particle in the said colored paint is in the said colored paint film The content is 2% by volume or more, and the content of particles having a particle size of more than 3 μm in the colored coating is 1% by volume or less in the colored coating film. Therefore, according to the present embodiment, it is possible to provide a fluororesin-based coated metal plate having sufficient workability, designability and low gloss even after long-term storage.

  The cooling start temperature in the cooling step is Tm + 20 ° C. or less, which is more effective from the viewpoint of sufficiently generating the fluororesin spherulites, and the cooling end temperature in the cooling step is the Tc− A temperature of 20 ° C. or higher is more effective from the viewpoint of sufficiently maintaining the produced spherulites, and a cooling rate in the cooling step of 6 ° C./second or less is sufficient for the spherulites. More effective from the viewpoint of growth.

  Moreover, it is much more effective from the viewpoint of achieving sufficient low glossiness by the said spherulite in a colored coating film that content of the said fluororesin in the said base resin is 50-85 mass%. When the amount is less than 50% by mass, the amount of fluororesin spherulites is reduced, and the particle size or area ratio of the spherulites becomes insufficient. On the other hand, if it exceeds 85% by mass, the fluororesin concentration in the fluorocoating material is excessive, which may reduce the long-term storage stability of the coating material, which is disadvantageous in cost.

  Moreover, it is much more effective from a viewpoint of achieving sufficient weather resistance and workability of a coating metal plate that content of the said fluororesin in the said base resin is 70-85 mass%. When the amount is less than 70% by mass, the amount of the acrylic resin component harder than that of the fluororesin is increased, so that the initial processability and aging processability of the colored coating film are deteriorated. On the other hand, if it exceeds 85% by mass, the fluororesin concentration in the fluorocoating material is excessive, so that the long-term storage stability of the coating material may be reduced, which is disadvantageous in terms of cost and has little effect on improving weather resistance.

  Further, the pigment particles further include gloss modifier particles, and the content of the gloss modifier particles in the colored coating film is 0.2 to 1.0% by volume. The design property by coexistence with is realized, and is more effective from the viewpoint of realizing such a specific design property of the coated metal sheet.

  The average particle diameter of the colored pigment particles is 2.0 μm or less, from the viewpoint of increasing the content of the colored pigment particles (up to 5% by volume) and improving the workability of the painted metal plate after storage. The average particle diameter of the colored pigment particles is 0.5 μm or less from the viewpoint of increasing the content of the colored pigment particles (up to 10% by volume) and after storage of the coated metal plate This is more effective from the viewpoint of improving the workability.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Preparation of painted master plates 1 to 4]
A molten 55% Al—Zn alloy-plated steel sheet having a thickness of 1.0 mm and a double-sided adhesion amount of 150 g / m ² was alkali degreased. This is referred to as a coating original plate 1.

Apply chromate-based anti-rust treatment liquid (“Surf Coat NRC300” manufactured by Nippon Paint Surf Chemicals Co., Ltd.) on the surface of the painted original plate 1 and dry it at 100 ° C. without washing with water. Then, chromate rust prevention treatment with an adhesion amount of 20 mg / m ² was performed.

An epoxy resin-based paint containing the following components in the following amounts is applied to the surface of the coating original plate 2 after the above-described chromate rust prevention treatment so that the ultimate temperature of the plated steel plate on the coating original plate 2 is 200 ° C. The coated original sheet 2 after application was heated to obtain a plated steel sheet having a chromate-based coating film having a dry film thickness of 5 μm. This is referred to as a coating original plate 3. The following clear paint is “NSC680” manufactured by Nippon Paint Industrial Coatings Co., Ltd.
Strontium chromate 15% by volume
Barium sulfate 5% by volume
Silica 1% by volume
Clear paint

A non-chromate antirust treatment liquid containing the following components in the following amounts is applied to the surface of the coating original plate 1, and the coated original plate 1 after application is dried at 100 ° C. without being washed with water. A non-chromate anti-rust treatment with an adhesion amount of ² was performed.
Hexafluorotitanic acid 55g / L
Hexafluorozirconic acid 10g / L
Aminomethyl-substituted polyvinylphenol 72g / L
Water rest

Next, an epoxy resin-based coating material containing the following components in the following amounts is applied to the surface of the coating original plate 1 after the above-described non-chromate rust prevention treatment. The coated original sheet 1 after application was heated so as to obtain a plated steel sheet having a chromate-free coating film with a dry film thickness of 5 μm. This is referred to as a coating original plate 4. The following clear paint is “NSC680” manufactured by Nippon Paint Industrial Coatings Co., Ltd.
Phosphate mixture 15% by volume
Barium sulfate 5% by volume
Silica 1% by volume
Above clear paint

[Preparation of clear paints 1-8]
The clear paint 1 is a fluorine resin clear paint “Dick Flow C” manufactured by Nippon Paint Industrial Coatings Co., Ltd. The clear paint 1 is a blend paint of polyvinylidene fluoride and acrylic resin, and the weight ratio of polyvinylidene fluoride and acrylic resin is 85:15. The melting temperature of the resin component in the clear paint 1 is 180 ° C., and the crystallization temperature is 130 ° C.

  In addition, polyvinylidene fluoride ("Kynar 500" manufactured by Arkema, "KYNAR" is a registered trademark of the company), acrylic resin ("Pararoid B-44" manufactured by Rohm and Haas, "Pararoid" is a registered trademark of the company), and paint solvent The components (isophorone) were mixed to obtain clear paints 2-8. The weight ratios of the polyvinylidene fluoride and the acrylic resin in the clear paints 2 to 8 are 40:60, 50:50, 60:40, 70:30, 80:20, 85:15, and 90:10, respectively. The melting temperatures of the resin components in the clear paints 2 to 8 are all 180 ° C., and the crystallization temperatures are all 130 ° C.

[Preparation of pigment particles 1 to 8]
Titanium oxide (“R-930” manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) was prepared. The average particle diameter can be confirmed by magnifying observation with a microscope or the like, or using an image analysis method, a Coulter method (for example, a precision particle size distribution measuring device “Multisizer 4” manufactured by Beckman Coulter, Inc.) It can be measured using a dynamic light scattering method (for example, a nanoparticle size distribution measuring device “SALD-7500 nano” manufactured by Shimadzu Corporation).

  Next, particles having the average particle diameter or more were removed from the titanium oxide by classification. Thus, pigment particles 1 which are colored pigment particles were obtained.

  Instead of titanium oxide “R-930”, iron-chromium composite oxide (“BLACK6350” manufactured by Asahi Kasei Kogyo Co., Ltd., average particle size: 0.5 μm) is used, and the average particle size (0.5 μm) is used. Except for performing the classification treatment, pigment particles 2 as colored pigment particles were obtained in the same manner as in the preparation of pigment particles 1. Further, instead of titanium oxide “R-930”, an iron-zinc composite oxide (“BROWN4123” manufactured by Asahi Kasei Kogyo Co., Ltd., average particle size: 1.8 μm) was used, and the above average particle size (1.8 μm) was used. The pigment particles 3 which are colored pigment particles were obtained in the same manner as in the preparation of the pigment particles 1 except that the classification treatment was performed in step (1). Further, instead of titanium oxide “R-930”, carbon black (“AUSTIN BLACK325” average particle size: 5.5 μm) manufactured by CoalFillers is used, and the pigment is subjected to classification treatment with the above average particle size (5.5 μm). In the same manner as the preparation of the particles 1, pigment particles 4 which are colored pigment particles were obtained.

  Further, instead of titanium oxide “R-930”, silica 1 (“Silicia 710” average particle size: 2.8 μm manufactured by Fuji Silysia Chemical Co., Ltd.), silica 2 (“Silicia 350” average particle manufactured by Fuji Silysia Chemical Co., Ltd.) Diameter: 4.0 μm), Silica 3 (“Silysia 770” average particle size: 6.0 μm manufactured by Fuji Silysia Chemical Co., Ltd.), Silica 4 (“Silicia 380” average particle size: 9.0 μm manufactured by Fuji Silysia Chemical Co., Ltd.) In the same manner as in the preparation of the pigment particle 1, the pigment which is a gloss modifier particle, except that the above-described average particle size (2.8 μm, 4.0 μm, 6.0 μm and 9.0 μm) is classified using Each of particles 5-8 was obtained.

[Preparation of colored paints 1 to 6]
The following components were mixed in the following amounts, and the obtained mixture was filtered through a 500 mesh filter to remove aggregated particles from the mixture. Thus, a colored paint 1 was obtained.
Pigment particle 1 15.0% by volume
Clear paint 1 remaining

  The colored paints 2 and 4 are the same as the preparation of the colored paint 1 except that the amount of the pigment particles 1 is changed to 12.0 vol%, 10.0 vol%, 7.5 vol% and 5.0 vol%, respectively. Each of ~ 6 was obtained.

  The colored paint 2 was allowed to stand for 30 days in a 28 ° C. environment. This is referred to as a colored paint 3. When the particle size distribution of the pigment particles 1 in the colored paint 3 is measured by a nano particle size distribution measuring device “SALD-7500 nano” manufactured by Shimadzu Corporation, the amount of the pigment particles 1 is 10.0% by volume. The amount of aggregated titanium oxide particles having an average particle diameter of 3.5 μm as the aggregate was 2.0% by volume, and it was confirmed that a part of the pigment particles 1 were aggregated.

[Preparation of colored paints 7 to 14]
Each of the colored paints 7 to 9, 11 and 12 was obtained in the same manner as the preparation of the colored paints 1, 2 and 4 to 6 except that the pigment particle 2 was used in place of the pigment particle 1. In addition, the colored paint is used in the same manner as the colored paint 1 except that the pigment particle 2 is used instead of the pigment particle 1 and the amount of the pigment particle 2 is changed to 2.0% by volume and 1.0% by volume, respectively. Each of 13 and 14 was obtained.

  The colored paint 9 was allowed to stand in an environment of 28 ° C. for 30 days. This is referred to as a colored paint 10. When the particle size distribution of the pigment particles 2 in the colored paint 10 is measured by a nano particle size distribution measuring device “SALD-7500 nano” manufactured by Shimadzu Corporation, the amount of the pigment particles 2 is 8.5% by volume. The amount of aggregated particles of the iron-chromium composite oxide having an average particle size of 4.0 μm, which is an aggregate, was 1.5% by volume, and it was confirmed that a part of the pigment particles 2 were aggregated. .

[Preparation of colored paints 15 to 22]
Colored paints 15, 16 and 18 to 20 were obtained in the same manner as in the preparation of colored paints 1, 2 and 4 to 6 except that pigment particles 3 were used instead of pigment particles 1. In addition, the colored paint is used in the same manner as the colored paint 1 except that the pigment particle 3 is used instead of the pigment particle 1 and the amount of the pigment particle 3 is changed to 2.0% by volume and 1.0% by volume, respectively. Each of 21 and 22 was obtained.

  The colored paint 16 was allowed to stand in an environment of 28 ° C. for 30 days. This is referred to as a colored paint 17. When the particle size distribution of the pigment particles 3 in the colored paint 17 was measured with a nanoparticle size distribution measuring device “SALD-7500 nano” manufactured by Shimadzu Corporation, the amount of the pigment particles 3 was 10.0% by volume, The amount of aggregated particles of iron-zinc composite oxide having an average particle size of 6.0 μm as the aggregate was 2.0% by volume, and it was confirmed that a part of the pigment particles 3 were aggregated.

[Preparation of colored paints 23 to 26]
Colored paints 23 and 24 were obtained in the same manner as in the preparation of the colored paints 5 and 6 except that the pigment particles 4 were used in place of the pigment particles 1. In addition, the colored paint is used in the same manner as the colored paint 1 except that the pigment particles 4 are used instead of the pigment particles 1 and the amount of the pigment particles 4 is changed to 2.0% by volume and 1.0% by volume, respectively. Each of 25 and 26 was obtained.

[Preparation of colored paints 27 to 36]
The following components were mixed in the following amounts, and the obtained mixture was filtered through a 500 mesh filter to remove aggregated particles from the mixture. In this way, a colored paint 27 was obtained.
Pigment particle 2 8.5% by volume
Pigment particle 5 12.0% by volume
Clear paint 1 remaining

  Except for changing the amount of the pigment particles 5 to 10.0% by volume, 7.5% by volume, 5.0% by volume, 2.0% by volume and 1.0% by volume, the same as the preparation of the colored paint 27. As a result, colored paints 28 to 32 were obtained.

  Colored paints 33 and 34 were obtained in the same manner as the preparation of the colored paint 32 except that the pigment particles 1 and the pigment particles 3 were used in place of the pigment particles 2, respectively. Further, colored paints 35 and 36 were obtained in the same manner as the preparation of the colored paint 27 except that the amount of the pigment particles 5 was changed to 0.5% by volume and 0.2% by volume, respectively.

[Preparation of colored paints 37 to 46]
Colored paints 37 to 46 were obtained in the same manner as the preparation of the colored paints 27 to 36 except that the pigment particles 6 were used instead of the pigment particles 5.

[Preparation of colored paints 47 to 51]
Each of the colored paints 47 to 51 was obtained in the same manner as the preparation of the colored paints 30 to 32, 35 and 36 except that the pigment particles 7 were used in place of the pigment particles 5.

[Preparation of colored paints 52-56]
Each of the colored paints 52 to 56 was obtained in the same manner as the preparation of the colored paints 47 to 51 except that the pigment particles 8 were used instead of the pigment particles 7.

  Tables 1 and 2 show the composition of the pigment particles of the colored paints 1 to 56.

[Preparation of colored paints 57 to 63]
Colored paints 57 to 63 were obtained in the same manner as the colored paint 5 except that the clear paints 2 to 8 were used in place of the clear paint 1.

[Preparation of painted metal plate 1]
The colored paint 1 is applied to the surface of the painted original plate 3, the coated original plate 3 coated with the colored paint 1 is heated so that the temperature reached by the plated steel sheet is 250 ° C., cooled according to condition 6, and then gauze is used. Water was wiped off and dried at 30 ° C. for 1 hour. Condition 6 is that a 250 ° C. metal plate coated with the colored paint 1 is cooled to 40 ° C. at a rate of 1 ° C./second by allowing it to cool in a 30 ° C. atmosphere, and then immersed in 30 ° C. water. This is a condition for cooling to 30 ° C. In this way, a coated metal plate 1 having a colored coating film with a thickness of 25 μm by the colored paint 1 on the surface of the coating original plate 3 was produced.

  The average particle diameter Rcg of resin crystals on the surface of the colored coating film of the coated metal plate 1 was 18 μm as determined by 5,000-times magnification observation with an electron microscope. Further, in the colored coating film of the coated metal plate 1, the area ratio Scg of the resin crystal when viewed in plan is obtained by obtaining the area of the spherulite region with respect to a photographic image magnified 5000 times using an electron microscope, It was 90% when calculated by dividing this by the area of the observation region. Furthermore, it was 119 nm when arithmetic mean roughness Ra of the surface (of a colored coating film) of the coating metal plate 1 was calculated | required by the three-dimensional measurement (three-dimensional electron microscope method) with an electron microscope.

[Preparation of painted metal plates 2 to 5]
Each of the painted metal plates 2 to 5 was produced in the same manner as the painted metal plate 1 except that each of the colored paints 2 to 5 was used instead of the colored paint 1. The Rcg of the coated metal plates 2 to 5 is 20 μm, 19 μm, 18 μm, and 20 μm, respectively, Scg is 90%, 90%, 85%, and 90%, respectively, and Ra is 126 nm, 129 nm, and 125 nm and 126 nm.

[Preparation of painted metal plate 6]
The coated metal plate 6 was prepared in the same manner as the coated metal plate 1 except that the colored coating 6 was used instead of the colored coating 1 and the coating amount of the colored coating 1 was adjusted to produce a colored coating film having a thickness of 35 μm. Produced. The Rcg of the coated metal plate 6 was 19 μm, the Scg was 90%, and Ra was 121 nm.

[Preparation of painted metal plates 7 to 56]
The coated metal plate 1 was used except that the colored paints 7 to 32, 34 to 42 and 44 to 56 were used in place of the colored paint 1 and the coating amount of the colored paint was adjusted to prepare a colored coating film having a thickness of 22 μm. Each of the coated metal plates 7 to 32, 34 to 42, and 44 to 56 was produced in the same manner as the production. Moreover, it replaced with the colored coating material 1, and each of the colored coating materials 33 and 43 was used similarly to preparation of the coating metal plate 1 except having adjusted the application quantity of the colored coating material and produced the 35-micrometer-thick colored coating film, Each of the painted metal plates 33 and 43 was produced.

  The Rcg of the coated metal plates 7 to 14 is 18 μm, 19 μm, 20 μm, 18 μm, 20 μm, 19 μm, 18 μm and 19 μm, respectively, and Scg is 90%, 85%, 90%, 90%, 90%, respectively. The Ra was 85%, 90%, and 90%, and Ra was 130 nm, 128 nm, 123 nm, 125 nm, 120 nm, 124 nm, 127 nm, and 120 nm, respectively.

  Moreover, Rcg of the coated metal plates 15 to 22 is 20 μm, 19 μm, 18 μm, 18 μm, 19 μm, 20 μm, 18 μm, and 20 μm, respectively, and Scg is 90%, 90%, 90%, 90%, 85, respectively. %, 90%, 85% and 85%, and Ra was 128 nm, 124 nm, 123 nm, 124 nm, 121 nm, 119 nm, 119 nm and 118 nm, respectively.

  The Rcg of the coated metal plates 23 to 26 is 19 μm, 19 μm, 20 μm, and 18 μm, respectively, Scg is 90%, 90%, 85%, and 90%, respectively, and Ra is 289 nm, respectively. They were 263 nm, 197 nm, and 154 nm.

  The Rcg of the coated metal plates 27 to 36 is 20 μm, 18 μm, 19 μm, 20 μm, 18 μm, 20 μm, 19 μm, 20 μm, 19 μm and 18 μm, respectively, and Scg is 90%, 90%, 90%, 90%, 85%, 90%, 85%, 85%, 90% and 85%, and Ra was 315 nm, 295 nm, 279 nm, 215 nm, 202 nm, 129 nm, 131 nm, 132 nm, 123 nm and 129 nm, respectively. .

  Moreover, Rcg of the coated metal plates 37 to 46 is 18 μm, 20 μm, 19 μm, 18 μm, 19 μm, 18 μm, 19 μm, 20 μm, 18 μm, and 20 μm, respectively, and Scg is 85%, 90%, 90%, 90%, 90%, 90%, 85%, 90%, 85% and 90%, and Ra was 407 nm, 389 nm, 367 nm, 343 nm, 230 nm, 150 nm, 164 nm, 169 nm, 145 nm and 134 nm, respectively. .

  The Rcg of the coated metal plates 47 to 51 is 19 μm, 19 μm, 18 μm, 20 μm and 19 μm, respectively, and the Scg is 90%, 90%, 90%, 90% and 85%, respectively, and Ra is 289 nm, 263 nm, 219 nm, 178 nm and 138 nm, respectively.

  The Rcg of the coated metal plates 52 to 56 is 18 μm, 19 μm, 20 μm, 18 μm and 19 μm, respectively, and the Scg is 90%, 85%, 90%, 90% and 90%, respectively, and Ra is 508 nm, 454 nm, 306 nm, 276 nm and 165 nm, respectively.

[Preparation of painted metal plates 57-63]
The painted metal plates 57 to 63 were produced in the same manner as the painted metal plate 5 except that the colored paints 57 to 63 were used in place of the colored paint 5. The Rcg of the coated metal plates 57 to 63 is 18 μm, 19 μm, 20 μm, 20 μm, 20 μm, 20 μm and 20 μm, respectively, and the Scg is 40%, 50%, 65%, 75%, 85% and 90%, respectively. And Ra were 43 nm, 59 nm, 98 nm, 133 nm, 142 nm, 184 nm and 207 nm, respectively.

[Preparation of painted metal plates 64-66]
Each of the painted metal plates 64 to 66 was produced in the same manner as the painted metal plate 5 except that the painted original plates 1, 2, and 4 were used in place of the painted original plate 3. The Rcg of each of the coated metal plates 64 to 66 was 20 μm, the Scg was 90%, and the Ra was 120 nm.

[Preparation of painted metal plates 67-77]
A coated metal plate 67 was produced in the same manner as the production of the coated metal plate 5 except that the cooling during the production of the colored coating film was performed under condition 1. The condition 1 is a condition in which a 250 ° C. metal plate coated with a colored paint is immersed in 30 ° C. water and cooled to 30 ° C. at a rate of 700 ° C./second.

  Further, each of the coated metal plates 68 to 77 is made in the same manner as the painted metal plate 67 except that the cooling at the time of producing the colored coating film is performed in each of the conditions 2 to 5 and 7 to 12 instead of the condition 1. Produced.

  The above condition 2 is that the water is cooled to 40 ° C. at a rate of 80 ° C./second by spraying 30 ° C. water only on the back surface of the 250 ° C. metal plate coated with the colored paint, and then immersed in 30 ° C. water. This is a condition for cooling to 30 ° C. The above condition 3 is that cooling is performed to 40 ° C. at a rate of 10 ° C./second by blowing cold air of 20 ° C. on both surfaces of a 250 ° C. metal plate coated with a colored paint, and then immersed in 30 ° C. water. This is a condition for cooling to 30 ° C. Condition 4 is that cooling is performed to 40 ° C. at a rate of 6 ° C./second by blowing cold air of 20 ° C. only on the back surface of a 250 ° C. metal plate coated with a colored paint, and then immersed in water at 30 ° C. This is a condition for cooling to 30 ° C. The above condition 5 is that a 30 ° C. steel plate (thickness 20 mm) is adhered to only the back surface of a 250 ° C. metal plate coated with a colored paint to cool to 40 ° C. at a rate of 2 ° C./second, and then 30 ° C. It is the conditions which cool to 30 degreeC by immersing in water.

  The above conditions 7 to 9 are the same as the condition 6 except that the cooling start temperature by cooling is changed from 250 ° C. to 180 ° C., 150 ° C. and 120 ° C., respectively. In addition, it cooled to the speed | rate of 80 degree-C / sec by spraying 30 degreeC water only on the back surface of a metal plate after the 250 degreeC heating to the cooling start temperature by standing_to_cool. In each of the above conditions 10 to 12, the start temperature of cooling by cooling is changed from 250 ° C. to 200 ° C. (After heating at 250 ° C. to 200 ° C., only 30 ° C. water is applied to the back surface of the metal plate. This is the same as Condition 6 except that the end temperature of cooling by cooling is changed from 40 ° C. to 160 ° C., 130 ° C., and 120 ° C., respectively.

  The Rcg of the coated metal plates 67 to 71 is 1 μm, 3 μm, 9 μm, 14 μm and 15 μm, respectively, and the Scg is 1%, 50%, 80%, 85% and 90%, respectively, and Ra is , 14 nm, 39 nm, 99 nm, 106 nm and 127 nm.

  Further, Rcg of the coated metal plates 72 to 74 is 20 μm, 1 μm, and 1 μm, respectively, Scg is 90%, 10%, and 10%, respectively, and Ra is 132 nm, 30 nm, and 25 nm, respectively. It was.

  The Rcg of the coated metal plates 75 to 77 is 1.5 μm, 10 μm, and 20 μm, respectively, Scg is 10%, 50%, and 90%, respectively, and Ra is 31 nm, 59 nm, and 132 nm, respectively. Met.

  Table 3 shows the cooling conditions 1 to 12.

[Evaluation]
(1) Initial workability Each of the coated metal plates 1 to 77 is bent by 4T, and subjected to a salt spray test specified in JISK5600-7-1 for 500 hours. Evaluation was made according to the following criteria. The evaluation of “◯” below is considered to have long-term outdoor durability at this level.
◎: No abnormalities such as rust and swelling ○: One or two places, minute swelling or rust is generated ×: Rust is generated in the entire processing part (practical problem)

(2) Workability after storage Each of the coated metal plates 1 to 77 is allowed to stand in an environment of 60 ° C. for 7 days, then subjected to the 4T bending process, and the salt spray test defined in JISK5600-7-1. The corrosion state of the processed part subjected to the above bending was evaluated according to the following criteria. In addition, the said stationary conditions are the conditions which reproduced the crystallization and ductility fall of the fluororesin by long-term normal temperature storage.
◎: No abnormalities such as rust and swelling ○: One or two places, minute swelling or rust is generated ×: Rust is generated in the entire processing part (practical problem)

(3) Color tone Each of the painted metal plates 1 to 77 and a reference coated metal plate having the same clear paint resin component and pigment particles are measured by JISZ8722 5 (spectral colorimetry method), and the color difference is obtained. It was. A case where the color difference is 1.5 or less is regarded as acceptable.

  The reference coated metal plate has a coating original plate 3 and a colored coating film disposed on the surface thereof, and the colored coating film is a coating film of any one of the clear paints 1 to 8 and has 10 volumes. % Color pigment particles, and 1.5% by volume of gloss modifier particles (silica 4, “Silicia 770” manufactured by Fuji Silysia Chemical Ltd., average particle diameter: 6.0 μm). The configuration of the reference painted metal plate is one of the typical coating film configurations of conventional fluororesin-coated metal plates for exterior building materials. In addition, the thickness of the colored coating film in the reference coated metal plates for the coated metal plates 1 to 6 and 57 to 77 is 25 μm, and the thickness of the colored coating film in the reference coated metal plates for the painted metal plates 7 to 56 is 22 μm.

(4) Glossiness The specular glossiness (G60) at 60 degrees defined by JISK5600-4-7 of each of the coated metal plates 1 to 77 was measured. For exterior use, 40 or less can be accepted.

  Tables 4 to 8 show the structures, physical properties, and evaluation results of the painted metal plates 1 to 77.

[Machinability]
As is apparent from Tables 4 to 8, the initial workability is good in any of the coated metal plates. Immediately after the production, the fluororesin does not crystallize with time, and the colored coating is in a highly ductile state. Therefore, regardless of the particle size and content of the pigment particles in the colored coating. The colored coating film of any painted metal plate is considered to have high ductility.

  However, the total content of pigment particles in the colored coating film exceeds 12% by volume, or the content of particles having a particle size of the pigment particles exceeding 3 μm exceeds 1% by volume, or the substrate in the colored coating film Painted metal plate (painted metal plate 1, 3, 7, 10, 15, 17, 23-25, 27-30, 37-41, 47, 48, 52) in which the fluororesin content in the resin is less than 50% by mass 53 and 57), the workability after storage is insufficient. This is because crystallization of the fluororesin that constitutes the colored coating film progresses with storage, and voids formed in the colored coating film at the time of bending process grow due to stress concentration, which is a corrosion factor that crosses the colored coating film. Because the passage was formed, or when the content of the fluororesin is low, the content of the acrylic resin having a lower ductility than the crystallized fluororesin is relatively high, and the stress concentration in the voids is further increased. it is conceivable that.

  On the other hand, if the average particle diameter of the pigment particles in the colored coating film is 2.0 μm or less and the content of the fluororesin in the base resin in the colored coating film is 70% by mass or more, workability after storage is also achieved. It is enough. And, as is apparent from the coated metal plates 4 to 6, 9, 11 to 14, 20 to 22, 34 to 36, 46, and 60 to 77, the smaller the average particle diameter of the pigment particles, or the pigment The smaller the content of the particles, the smaller the content of the relatively large particles of the pigment particles, or the higher the content of the fluororesin in the base resin in the colored coating film, the more after storage. It can be seen that the workability becomes better. It is considered that when the content of the fluororesin is increased, the content of the acrylic resin having a lower ductility than the crystallized fluororesin is relatively decreased.

[Color tone]
As is apparent from Tables 4 to 8, if the content of the color pigment in the colored coating film is 2.0% by volume or more, the color difference from the reference coated metal plate is 1.5 or less, and the intended design It can be seen that sex is expressed. However, as apparent from the coated metal plates 14, 22 and 26, when the content was less than 2% by volume, the color difference from the reference plate was larger than 1.5. This is presumably because the color hiding property by the colored pigment particles in the colored coating film was insufficient, and the color tone of the base was seen through strongly.

[Low gloss]
As apparent from Tables 4 to 8, the higher the arithmetic average roughness Ra of the colored coating film, the lower the specular gloss G60, and the surface of the colored coating film has irregularities formed by the spherulites. In this case, it is understood that G60 is 40 or less when Ra is 50 nm or more. Moreover, the average particle diameter and surface area ratio of the crystal | crystallization of a fluororesin tend to become high, so that content of the fluororesin in base-material resin in a colored coating film is high. This is presumably because the higher the content of the fluororesin that forms spherulites, the easier the growth of spherulites, and the larger and more spherulites can be formed. More specifically, each of the coated metal plates 1 to 56 and 58 to 66 has a surface roughness Ra of the colored coating film adjusted to about 50 to 500 nm by the spherulite of the fluororesin in the colored coating film, A sufficiently low glossiness of 60 ° specular gloss G60 of 40 or less is exhibited.

  Further, as apparent from the coated metal plates 69 to 72, 76 and 77, the average particle size and the surface area ratio of the fluororesin crystals tend to increase as the cooling rate after baking during the production of the colored coating film decreases. Seen. This is considered to be because the fluororesin being cooled can stay in the crystallization temperature region for a long time by lowering the cooling rate, and a sufficient time for crystals (spherulites) to grow is secured.

  On the contrary, as apparent from the coated metal plates 67 and 68, when the cooling rate is fast, the temperature of the fluororesin becomes equal to or lower than the crystallization temperature during the crystal growth, and the crystal growth stops. As a result, it can be seen that sufficient size and number of irregularities are not formed on the surface of the colored coating film.

  Moreover, in the case where the cooling start temperature at the time of producing the colored coating film is higher than the melting point of the fluororesin, crystallization proceeds to such an extent that sufficient unevenness is formed. This is presumably because the molecular chain of the fluororesin can move freely before crystallization, so that it becomes easier to form a crystal structure in the subsequent cooling step.

  On the other hand, as is clear from the comparison of the coated metal plates 72 to 74, when the cooling start temperature is not higher than the melting point of the fluororesin, neither the average particle diameter of the crystal nor the surface ratio is sufficient. The reason is considered as follows. That is, when the reheating temperature is equal to or lower than the melting point, the arrangement structure of the fluororesin is a state in which α crystal, β crystal, and amorphous part are mixed. Since the crystal structure with large interaction is mixed, the barrier for recombination of this sequence is large, and a spherulite structure with a large particle size is formed even if it stays in the crystallization temperature range for a long time in the subsequent slow cooling process. It is thought that it was not reached.

  Furthermore, when the cooling end temperature is equal to or lower than the crystallization temperature of the fluororesin, a sufficiently large crystal grows, whereas when the cooling end temperature is equal to or higher than the crystallization temperature (for example, the coated metal plate 75), the crystal Both of the average particle size and the surface ratio of are insufficient. The reason is considered as follows. If the cooling end temperature is equal to or higher than the crystallization temperature, the formation of large grain crystals did not progress sufficiently at the end of cooling, and the insufficient crystal formation state was preserved by the subsequent rapid cooling. It is done.

  According to the present invention, the coated metal plate has a design property by the colored pigment particles even if it is a fluororesin-based coating film, has a low gloss, and has a high workability even after storage. can get. Therefore, further spread of fluororesin-based coated metal plates is expected, especially as a material for exterior building materials.

Claims (9)

In a method for producing a coated metal plate having a metal plate and a colored coating film disposed on the metal plate,
A film on a metal plate of a colored paint containing pigment particles containing colored pigment particles and a base resin containing a fluorine resin in a content of 50% by mass or more, and the temperature reached by the metal plate is that of the fluororesin Heating to a temperature equal to or higher than the melting temperature Tm;
Cooling the colored paint film to a temperature below the crystallization temperature Tc of the fluororesin at a cooling rate of 10 ° C./second or less,
In the colored paint,
The content of the pigment particles in the colored paint is 12% by volume or less in terms of the content in the colored coating film,
The content of the colored pigment particles in the colored paint is 2% by volume or more in terms of the content in the colored coating film,
The content of particles having a particle size of more than 3 μm in the colored paint is 1% by volume or less in terms of the content in the colored coating film.
Manufacturing method of painted metal sheet.   The manufacturing method of the coated metal plate according to claim 1, wherein a cooling start temperature in the cooling step is Tm + 20 ° C. or less.   The method for producing a coated metal sheet according to claim 1 or 2, wherein an end temperature of the cooling in the cooling step is Tc-20 ° C or higher.   The cooling rate in the said process to cool is a manufacturing method of the coating metal plate as described in any one of Claims 1-3 which is 6 degrees C / sec or less.   Content of the said fluororesin in the said base resin is a manufacturing method of the coating metal plate as described in any one of Claims 1-4 which is 70-85 mass%.   The manufacturing method of the coated metal plate as described in any one of Claims 1-5 whose average particle diameter of the said color pigment particle | grain is 2.0 micrometers or less.   The method for producing a coated metal sheet according to any one of claims 1 to 6, wherein an average particle diameter of the colored pigment particles is 0.5 µm or less.   The method for producing a coated metal sheet according to claim 6, wherein the content of the colored pigment particles in the colored coating film is 5% by volume or less.   The method for producing a coated metal sheet according to claim 7, wherein the content of the colored pigment particles in the colored coating film is 10% by volume or less.