JP5833871B2 - Manufacturing method of painted metal plate - Google Patents

Description

  The present invention relates to a coated metal plate that is excellent in both stain resistance and scratch resistance and has a matte appearance and a method for producing the same.

  When a metal plate is used as an exterior building material or the like, the metal plate is often painted in order to improve corrosion resistance, design properties, and the like. Until now, various paints suitable for improving the corrosion resistance and design properties have been developed and used.

  In recent years, dirt on painted metal plates due to oily carbon-based pollutants has become apparent due to air pollution caused by automobile exhaust gas or factory smoke. With respect to stains resulting from such environmental deterioration, the conventional coated metal plate has insufficient stain resistance adhesion. For this reason, when a conventional coated metal plate is used as an exterior building material, dirt is noticeable in a relatively short period of time. Under such circumstances, there is a need for a coated metal plate that is excellent in stain resistance.

  As a technique for improving the stain resistance of a coated metal plate, a technique for making the coating film surface hydrophilic has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses that a coating film is formed using an organic solvent-based paint blended with a silane compound. On the surface of the coating film thus formed, the silane compound is concentrated. In the silane compound concentrated on the surface of the coating film, the alkoxyl group is hydrolyzed by moisture in the environment and has a hydroxy group. Thereby, the coating-film surface becomes hydrophilic. As a result, oily carbon-based contaminants are less likely to adhere to the surface of the coated metal plate, and the stain resistance of the painted metal plate is improved.

JP 2002-294154 A

  Painted metal plates used as exterior building materials are required to have scratch resistance and design properties in addition to stain resistance. Accordingly, the present inventors have attempted to produce a coated metal plate that is excellent in scratch resistance in addition to stain resistance and has a matte appearance.

  It is well known that the porous silica particles are blended in various organic solvent-based paints as a matting agent and can improve the scratch resistance of the coating film. When blending porous silica particles in an organic solvent-based paint, the porous silica particles are easily dispersed in the organic solvent-based paint even if they are as they are. Therefore, the untreated porous silica particles are blended in the organic solvent-based paint as they are. It is common.

  Therefore, the present inventor can form a matte coating film excellent in stain resistance and scratch resistance by blending an untreated porous silica particle with an organic solvent-based paint containing a silane compound. I thought that. However, when a coated metal plate is produced using a paint that further contains silica particles in addition to the silane compound, the coating film surface has insufficient hydrophilicity, and the stain resistance can be sufficiently improved. There wasn't. Moreover, the coating material which mix | blended the silica particle had a viscosity rising with progress of time, and was inferior to storage stability.

  As described above, even when a conventional organic solvent-based paint containing a silane compound is blended with untreated porous silica particles, it has both excellent stain resistance and scratch resistance, and is matte. It was not possible to produce a coated metal plate showing the appearance of.

  This invention is made | formed in view of this point, and it aims at providing the coating metal plate which is excellent in both stain-resistant adhesion and damage resistance, and shows the matte appearance.

  The present inventor, when blended with an untreated porous silica particle in an organic solvent-based paint containing a silane compound, the hydrophilicity of the coating film surface is not improved, and the storage stability of the paint is reduced We studied earnestly. As a result, the present inventors have found that the cause is that the hydroxy group present on the surface of the porous silica particles reacts with the silane compound.

  And this inventor discovered that the said problem could be solved by coat | covering the surface of the porous silica particle to mix | blend with organic resin, and completed this invention.

That is, this invention relates to the following coated metal plates.
[1] A coated metal plate having a coating film formed on the surface of the metal plate, wherein the coating film comprises an organic resin, a silane compound or a condensate of a silane compound, organic resin-coated silica particles, and a pigment. The pH of the suspension of the mixture of the organic resin-coated silica particles and the pigment measured in accordance with JIS K5101-17-2 is in the range of 5.5 to 8.5; Board.
[2] The coated metal plate according to [1], wherein the organic resin-coated silica particles are porous particles obtained by coating the surface of porous silica particles having a number average particle diameter of 1 to 15 μm with an organic resin.
[3] The coated metal plate according to [1] or [2], wherein the coating film includes 1 to 20 parts by mass of the organic resin-coated silica particles with respect to 100 parts by mass of the organic resin contained in the coating film.
[4] The silane compound is a silane represented by the general formula R ¹⁴ _-n Si (OR ² ) _n [where R ^{1 is} an alkyl group or an alkoxyl group, R ^{2 is} an alkyl group, n is 3 or 4]. The painted metal plate according to any one of [1] to [3], which is a compound.

Moreover, this invention relates to the manufacturing method of the following coated metal plates.
[5] preparing a metal plate, preparing an organic resin, a silane compound or a condensate of a silane compound, organic resin-coated silica particles, a pigment, and an organic solvent-based paint containing a dehydrating agent; Applying the organic solvent-based paint to the surface of the metal plate and drying to form a coating film; and measuring the organic resin-coated silica particles measured according to JIS K5101-17-2 and The pH of the suspension of the pigment mixture is in the range of 5.5 to 8.5;
[6] The method for producing a coated metal plate according to [5], wherein the organic resin-coated silica particles are porous particles obtained by coating the surface of porous silica particles having a number average particle diameter of 1 to 15 μm with an organic resin. .
[7] The organic solvent-based paint according to [5] or [6], in which the organic resin-coated silica particles include 1 to 20 parts by mass with respect to 100 parts by mass of the organic resin included in the organic solvent-based paint. Manufacturing method of painted metal sheet.
[8] The silane compound is a silane represented by the general formula R ¹⁴ _-n Si (OR ² ) _n [wherein R ^{1 is} an alkyl group or an alkoxyl group, R ^{2 is} an alkyl group, n is 3 or 4]. The manufacturing method of the coating metal plate as described in any one of [5]-[7] which is a compound.
[9] The method for producing a coated metal plate according to any one of [5] to [8], wherein the dehydrating agent is trialkyl orthoformate, trialkyl orthoacetate, trialkyl orthoborate, or a combination thereof. .

  ADVANTAGE OF THE INVENTION According to this invention, the coating metal plate which is excellent in both stain-resistant adhesion and damage resistance, and shows the matte appearance can be provided. The coated metal plate of the present invention is excellent in stain resistance, scratch resistance and design, and is suitable for, for example, exterior building materials.

  The coated metal plate of the present invention includes a metal plate (painted original plate) and a coating film formed on the surface of the metal plate. The coated metal plate of the present invention is mainly characterized in that the surface of porous silica particles to be blended for imparting scratch resistance and having a matte appearance is coated with an organic resin.

  Hereinafter, each component of the coated metal plate of this invention is demonstrated.

[Painted original plate]
The kind of metal plate used as a coating original plate is not specifically limited. Examples of the coating original plate include cold rolled steel plate, galvanized steel plate, Zn-Al alloy plated steel plate, Zn-Al-Mg alloy plated steel plate, aluminum plated steel plate, stainless steel plate, aluminum plate, aluminum alloy plate, copper plate and the like. . The metal plate may be subjected to known coating pretreatments such as degreasing, pickling, chromate treatment, chromium-free treatment, and phosphate treatment as necessary.

[Coating]
The coating film is formed on the surface of the metal plate. The coating film may have a one-layer configuration, a two-layer configuration of an undercoat / topcoat, or a three-layer configuration of an undercoat / intermediate / topcoat. May be. In any case, a matte coating film having excellent scratch resistance and stain resistance, which will be described later, is formed on the outermost layer. The composition and film thickness of the undercoat film and the intermediate coat film are not particularly limited, and may be appropriately selected according to the properties to be imparted (for example, corrosion resistance and coating film adhesion). Moreover, the kind of antirust pigment mix | blended with an undercoat coating film is not specifically limited, Either of a chromium system and a chromium free system may be sufficient.

  The coating film (hereinafter also simply referred to as “coating film”) formed on the outermost layer is composed of an organic resin (base resin), a silane compound or a condensate thereof (hydrophilizing agent), organic resin-coated silica particles, and a pigment. Including.

  The kind of organic resin used as a base is not specifically limited, What is necessary is just to select suitably from the well-known organic resin currently used for the precoat metal plate. The base organic resin may be a thermosetting resin or a thermoplastic resin. Examples of such organic resins include mixed resins of polyvinylidene fluoride resin and acrylic resin, solvent-soluble fluororesin, polyester resin, silicone polyester resin, acrylic resin, urethane resin, vinylidene chloride resin, and the like. . Moreover, as an example of a thermosetting resin, the hardened | cured material of the resin composition containing the regular polyester resin (OH value: 1-250KOHmg / g) whose average molecular weight is about several thousand, and a hardening | curing agent is contained. A hardening | curing agent bridge | crosslinks between organic resins at the time of baking. As the type of the curing agent, a known one can be appropriately selected depending on the type of organic resin to be used, baking conditions, and the like. Examples of the curing agent include melamine compounds and isocyanate compounds. When a melamine compound is used as a curing agent, it is more preferable to use a methylol group type or fully alkyl group type melamine compound than an imino group type or methylol imino group type melamine compound. Methylol group-type and fully alkyl group-type melamine compounds are less reactive with silane compounds and more advantageous in terms of storage stability of paints, compared to imino group-type melamine compounds and methylol-imino group-type melamine compounds. is there. In addition, a curing catalyst may be added as appropriate as long as it does not affect the storage stability of the paint.

  The silane compound or the condensate thereof is concentrated on the surface of the coating film and hydrophilizes the surface of the coating film to impart stain resistance. When a paint containing the silane compound or its condensate is applied to the surface of the metal plate and baked, the silane compound or its condensate moves to the surface of the coating film to be formed and thickens. The silane compound or its condensate concentrated on the surface of the coating film has hydroxy groups due to hydrolysis of alkoxy groups by moisture in the environment. As a result, a coating film having a large number of hydroxy groups on the surface and excellent hydrophilicity and antifouling adhesion is obtained.

As the silane compound, those represented by the general formula R ¹⁴ _-n Si (OR ² ) _n [where R ^{1 is} an alkyl group or alkoxyl group, R ^{2 is} an alkyl group, n is 3 or 4] are used. The Examples of such silane compounds include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and the like. A condensation product (oligomer) of a silane compound can be prepared by adding water and a catalyst to these silane compounds (monomer) to cause dehydration condensation. In consideration of the compatibility with the paint, the storage stability of the paint, and the balance of imparting hydrophilicity to the coating film surface, the degree of polymerization of the condensate of the silane compound is preferably about 1 to 5 on average.

  The amount of the silane compound or the condensate thereof is preferably in the range of 1 to 20% by mass relative to the base organic resin. When the blending amount of the silane compound or the condensate thereof is less than 1% by mass, the surface of the coating film cannot be sufficiently hydrophilized, and there is a possibility that the stain resistance cannot be sufficiently imparted. On the other hand, when the blending amount of the silane compound or the condensate thereof is more than 20% by mass, the processability of the coating film is lowered, and there is a risk that cracks are likely to occur during processing.

  The organic resin-coated silica particles are dispersed in the coating film, improving the scratch resistance of the coating film and matting the appearance of the coating film. The organic resin-coated silica particles are obtained by coating the surface of porous silica particles having a number average particle diameter of 1 to 15 μm with an organic resin.

  As described above, the coated metal plate of the present invention is characterized in that the surface of the porous silica particles blended in the coating film is coated with an organic resin in order to improve the scratch resistance and to make the appearance of the coating film matt. And Thus, by covering the surface of the porous silica particles with an organic resin, it is possible to prevent a decrease in hydrophilic addition function and a decrease in the storage stability of the paint due to the silane compound or a condensate thereof.

  The porous silica particles have a large number of hydroxy groups on the surface and have a very large specific surface area. Therefore, for the purpose of improving scratch resistance and matting the appearance of the coating film, when porous silica particles are blended with a paint containing a silane compound or its condensate, the silane compound or its condensate and porous silica are mixed. It reacts with the hydroxy groups of the particles. As a result, the viscosity of the paint increases and the storage stability of the paint decreases. Further, since the silane compound or the condensate thereof is consumed, it becomes impossible to sufficiently impart antifouling adhesion.

  About this problem, in this invention, the reaction of the silane compound or its condensate, and the hydroxy group of a porous silica particle is suppressed by coat | covering the surface of the porous silica particle with an organic resin. Thereby, the fall of the hydrophilic addition function and the storage stability of a coating material by reaction with the silane compound or its condensate, and the hydroxyl group of porous silica particle can be prevented.

  The type of organic resin that coats the surface of the porous silica particles is not particularly limited as long as it is stable in the solvent (organic solvent) of the paint and can coat the hydroxy groups on the surface of the porous silica particles. Examples of such organic resins include acrylic resins, urethane resins, polyester resins, polyethylene resins, polycarboxylic acid type resins, and the like. As the organic resin-coated silica particles, commercially available ones may be used, or they may be prepared by themselves. The method for coating the surface of the porous silica particles with the organic resin is not particularly limited, and for example, the porous silica particles may be coated by a gas phase method, a liquid phase method, an autoclave method, a mechanochemical method, or the like. Examples of the mechanochemical method include a method of coating pulverized particles while pulverizing porous silica particles with a jet mill or the like.

  The blending amount of the organic resin-coated silica particles is preferably in the range of 1 to 20% by mass with respect to the base organic resin. When the blending amount of the organic resin-coated silica particles is less than 1% by mass, the scratch resistance cannot be sufficiently improved, and the appearance of the coating film may not be matted. On the other hand, when the compounding amount of the organic resin-coated silica particles is more than 20% by mass, the processability may be lowered or the production cost may be increased.

  The pigment is a coloring pigment, an extender pigment or the like blended in addition to the organic resin-coated silica particles. Only one type of pigment may be used, or a combination of two or more types may be used.

  The kind of pigment is not particularly limited, and can be appropriately selected from known pigments so as to satisfy the pH conditions described later. Examples of coloring pigments include inorganic pigments such as titanium oxide, calcium carbonate, carbon black, iron black, titanium yellow, bengara, bitumen, cobalt blue, cerulean blue, ultramarine blue, cobalt green, and molybdenum red; CoAl, CoCrAl, CoCrZnMgAl , CoNiZnTi, CoCrZnTi, NiSbTi, CrSbTi, FeCrZnNi, MnSbTi, FeCr, FeCrNi, FeNi, FeCrNiMn, composite oxide calcined pigments containing metallic components such as CoCr, Mn, Co, SnZnTi; Metals such as Al, resin coating Al, Ni Pigment: 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, Vermilion Red, Phthalocyanine Blow, Phthalocyanine Green, Fast Sky Blue, Aniline Black Organic pigments such as are included. Examples of extender pigments include clay, talc, barium sulfate, and silica.

  It is preferable that the compounding quantity of a pigment exists in the range of 5-150 mass% with respect to the organic resin used as a base. When the blending amount of the pigment is less than 5% by mass, a necessary color tone may not be obtained. On the other hand, when the amount of the pigment is more than 150% by mass, the processability and paintability may be lowered.

  The pH of the entire pigment including the organic resin-coated silica particles and the pigment (colored pigment, extender pigment, etc.) is preferably in the range of 5.5 to 8.5. Here, “the pH of the whole pigment including the organic resin-coated silica particles and the pigment” is based on JIS K5101-17-2 (Pigment Test Method—Part 17: pH Value—Section 2: Room Temperature Extraction Method). It refers to the pH of the suspension of the mixture of organic resin-coated silica particles and pigment that is measured. Specifically, it is determined by measuring the pH of a 5 mass% suspension prepared by adding organic resin-coated silica particles and pigment to water from which carbon dioxide has been removed.

  The problem here is whether the pH of the entire pigment is within the range of 5.5 to 8.5. That is, even if the pH of one of the plurality of pigments is outside the range of 5.5 to 8.5, the pH of the entire pigment combined with the other pigments is 5.5 to 8.5. It may be within the range.

  The reason why the pH of the entire pigment is in the range of 5.5 to 8.5 is to prevent the silane compound or the condensate thereof from being polymerized in the paint. Some of the commonly used color pigments and extender pigments are sources of hydrogen ions and hydroxide ions when they come into contact with moisture derived from the raw material of paint and moisture absorbed in the paint from outside air There are many. The hydroxide ion substitutes the alkoxy group of the silane compound or its condensate with a hydroxy group. As a result, the silane compound or the condensate thereof is dehydrated and condensed to become a polymer. In addition, the hydrogen ions accelerate the dehydration condensation of the silane compound or the condensate thereof to increase the molecular weight. When the silane compound or the condensate thereof is polymerized in the paint as described above, the silane compound or the condensate thereof cannot move to the coating film surface during baking of the paint due to steric hindrance due to an increase in molecular weight. As a result, the surface of the coating film cannot be made hydrophilic, and the stain resistance cannot be sufficiently imparted. In addition, the viscosity of the paint increases excessively.

  On the other hand, by setting the pH of the entire pigment within the range of 5.5 to 8.5, even when the pigment comes into contact with moisture, generation of hydrogen ions and hydroxide ions can be remarkably suppressed. . As a result, the silane compound or the condensate thereof can be moved to the surface of the coating film at the time of baking the coating, and the stain resistance adhesion on the coating film surface can be sufficiently imparted.

  In addition, from the viewpoint of improving paintability, coating film hardness, designability, and corrosion resistance, the coating film includes inorganic aggregates such as glass beads, glass flakes, scaly iron oxide powder, mica; pearl mica, scaly metal powder Glittering powder such as metal-coated scale powder; organic resin aggregates such as polyacrylonitrile (PAN) beads, acrylic beads, nylon beads, polytetrafluoroethylene (PTFE) particles; leveling agents, ultraviolet absorbers, light stabilizers Various additives such as; For example, the scratch resistance of the coating film can be further improved by blending PTFE particles having a number average particle diameter of 1 to 15 μm with the coating film. These aggregate powders and additives are also preferably used in combination so as to be neutral (pH: 5.5 to 8.5) for the same reason as the pigment. Moreover, by using the PTFE particles in combination with one or more aggregates selected from the group consisting of PAN beads, acrylic beads and mica, the scratch resistance can be further improved. At this time, the number average particle diameters of PAN beads, acrylic beads, and mica are each preferably 10 μm or more.

  Although the film thickness of a coating film is not specifically limited, Usually, it exists in the range of 3-30 micrometers. When a coating film is too thin, there exists a possibility that durability and concealment property of a coating film may become inadequate. On the other hand, when the coating film is too thick, the manufacturing cost increases, and there is a possibility that a crack is likely to occur during baking.

  The coating film can be formed by a general method. For example, an organic solvent-based paint containing an organic resin, a silane compound or a condensate thereof, organic resin-coated silica particles, a pigment, and a dehydrating agent may be applied to the surface of the metal plate (coating substrate) and baked. .

  The kind of organic resin, silane compound or its condensate, organic resin-coated silica particles, and pigment, and the blending amount in the paint may be appropriately set according to the composition of the coating film.

  The dehydrating agent has a function of removing moisture contained in the paint. Thus, by removing the water | moisture content in a coating material, a dehydrating agent suppresses that a silane compound or its condensate reacts with a water | moisture content, and polymerizes in a coating material. As described above, when the silane compound or the condensate thereof is polymerized, the viscosity of the coating increases, and the storage stability decreases. In addition, it is difficult to concentrate the silane compound or its condensate on the surface of the coating film when baking the coating, and the stain resistance adhesion on the surface of the coating film cannot be sufficiently improved.

  As the dehydrating agent, one that does not react with the hydroxy group of the silane compound but reacts only with water is preferable. Examples of such a dehydrating agent include trialkyl orthoformate, trialkyl orthoacetate, trialkyl orthoborate and the like. Examples of trialkyl orthoformates include trimethyl orthoformate, triethyl orthoformate, tributyl orthoformate. Examples of trialkyl orthoacetate include trimethyl orthoacetate, triethyl orthoacetate, tributyl orthoacetate. Examples of trialkyl orthoborate include trimethyl orthoborate, triethyl orthoborate, and tributyl orthoborate. These dehydrating agents may be used alone or in combination of two or more.

  The compounding quantity of a dehydrating agent should just be in the range of 1-200 mass% with respect to the organic resin used as a base. When the blending amount of the dehydrating agent is less than 1% by mass, there is a possibility that water in the paint cannot be removed sufficiently. On the other hand, when the compounding amount of the dehydrating agent exceeds 200% by mass, the viscosity of the coating material is excessively lowered, and it may be difficult to paint. The timing at which the dehydrating agent is added to the paint is not particularly limited. For example, the mixture of the dehydrating agent and the pigment may be added to the coating material after the dehydrating agent is brought into contact with the pigment and the moisture on the pigment surface is previously dehydrated. Further, a dehydrating agent may be added when or after the organic resin is dissolved in the paint (solvent). Moreover, you may add the mixture of a silane compound or its condensate, and a dehydrating agent to a coating material. By doing so, since a dehydrating agent exists around the silane compound or its condensate, the condensation reaction (polymerization) of the silane compound or its condensate can be suppressed even after the paint kneading. And the storage stability of the paint can be enhanced. Thus, the dehydrating agent may be added at the time of kneading the paint, or may be added after the kneading. The dehydrating agent evaporates together with the solvent during baking of the paint and does not remain in the coating film after baking.

  The kind of the organic solvent is not particularly limited as long as each component can be dissolved or dispersed. Examples of the organic solvent include aromatic solvents such as xylene, alkane solvents such as hexane, ketone solvents such as acetone, and the like.

  The coating method of the paint is not particularly limited, and may be appropriately selected from the methods used for producing the precoated steel sheet. Examples of the coating method include a roll coating method, a curtain coating method, a spray coating method, and a die coating method. The baking condition may be, for example, baking at an ultimate plate temperature of 150 to 300 ° C. for 20 to 120 seconds.

  As described above, the coated metal plate of the present invention has a silane compound or a condensate thereof and an organic resin-coated silica particle in the outermost layer coating film, so that it is resistant to dirt and scratches. Excellent and matt appearance.

  In the present invention, the surface of the porous silica particles is coated with an organic resin. Therefore, the silane compound or its condensate is neither consumed nor polymerized in the paint before baking. Therefore, when baking the paint, the silane compound or the condensate thereof can be appropriately concentrated on the surface of the coating film, and the stain resistance can be sufficiently imparted. Further, the viscosity of the paint does not increase over time, and the storage stability of the paint is good.

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

1. Preparation and Evaluation of Top Coating Material 10 parts by mass of a regular polyester resin having an average molecular weight of 3000 (Byron G802; Toyobo Co., Ltd.) was added to 100 parts by mass of cyclohexanone and heated to dissolve. To the resulting solution, 20 parts by mass of each of fully methylated melamine (Cymel 303; Nippon Cytec Industries, Inc.) and methylolated melamine (Cymel 370; Nippon Cytec Industries, Inc.) were added. Further, two types of curing catalysts (Catalyst 4050 and Catalyst 296-9; both from Nippon Cytec Industries Co., Ltd.) were added in an amount of 0.1 parts by mass with respect to the regular polyester resin. 1-22 and paint no. 27-33 base resins were prepared.

Next, an oligomer of tetramethoxysilane (condensate of a silane compound; methyl silicate 40 or methyl silicate 51; Colcoat Co., Ltd.), porous silica particles (surface-treated silica particles) appropriately diluted with ethyl orthoformate are obtained on the obtained base resin. Or untreated silica particles), white TiO ₂ pigment (Taipeke CR90; Ishihara Chemical Co., Ltd.) and rain-stained stains that are easily noticeable, and triethyl orthoformate (dehydrating agent). 1-22 and no. A top coat of 27-31 was prepared. For comparison, No. 1 added with calcium carbonate (Sunlite SL2200; Takehara Chemical Industry Co., Ltd.) having a pH of 9.5 instead of the TiO ₂ pigment. No. 32 No. 32 top coating and carbon black (# 2350; Mitsubishi Chemical Corporation) with a pH of 2.5 added together with TiO ₂ pigment. 33 topcoats were also made.

Similarly, commercially available acrylic resin-based clear paint (C951 type; Nippon Fine Coatings Co., Ltd.) is mixed with oligomers of tetramethoxysilane, porous silica particles, TiO ₂ pigment and triethyl orthoformate appropriately diluted with ethyl orthoformate. No. A top coating of 23-26 was prepared.

  Part of the top coat was further mixed with PTFE particles having an average particle diameter of 5 μm (Lublon L5; Daikin Industries, Ltd.) or 9 μm PTFE particles (Fullon L150J; Asahi Glass Co., Ltd.). In some top coats, polyacrylonitrile (PAN) fine particles (Toughtic A20; Toyobo Co., Ltd.), polymethyl methacrylate (PMMA) fine particles (Tuftic ARS650S; Toyobo Co., Ltd.), or mica are used as aggregates. (MK300; Corp Chemical Co., Ltd.) was further blended.

  Tables 1 and 2 show the compositions of the prepared top coats. The pH of the silica particles and pigments shown in Table 1 and Table 2 was measured according to JIS K5101-17-2.

  The silica particles of the surface treatment 1, the silica particles of the surface treatment 2 and the silica particles of the surface treatment 4 shown in Table 1 and Table 2, respectively, are obtained by coating the surface of the porous silica particles with an acrylic resin. And Silysia 476 (both Fuji Silysia Chemical Co., Ltd.) were used. In addition, Nipgel AZ260 (Tosoh Silica Co., Ltd.), which is organic resin-coated porous silica, was used as the silica particles for surface treatment 3. Untreated silica particles used were Silicia 430 (Fuji Silysia Chemical Co., Ltd.), a porous silica particle. Table 3 shows the results of elemental analysis of the surface of each porous silica particle by X-ray electron spectroscopy.

  Each prepared paint was examined for storage stability. Specifically, each paint was stored at 40 ° C. for 18 days, and the change in viscosity before and after storage was examined. The viscosity of each paint was measured using a B-type viscometer.

  For example, No. 1 blended with porous silica whose surface is coated with an organic resin. In the paint of 2, the initial viscosity was 495 mPa · s, and the viscosity after storage was 515 mPa · s. As described above, in the paint blended with the porous silica whose surface was coated with the organic resin, there was almost no change in viscosity before and after storage. On the other hand, No. containing untreated porous silica. In the paint of 29, the initial viscosity was 549 mPa · s, and the viscosity after storage was 1023 mPa · s. As described above, the viscosity of the paint containing untreated porous silica was greatly increased.

2. Preparation and Evaluation of Painted Steel Sheet As a coating original sheet, a molten 55% aluminum-zinc plated steel sheet (plate thickness: 0.3 mm) having a plating adhesion amount of 125 g / m ^{2 on} one side was prepared.

  The surface of the plated steel sheet was subjected to alkali degreasing and then subjected to surface conditioning treatment and chromate treatment. Next, an epoxy primer paint (700P primer; Dainippon Ink & Chemicals, Inc.) is applied to the surface of the plated steel sheet and baked at a maximum reached plate temperature of 200 ° C. for 20 seconds to form an undercoat film having a dry film thickness of 5 μm. did.

  Next, the top coat shown in Table 1 was applied on the undercoat and baked at a maximum plate temperature of 215 ° C. for 30 seconds to form a top coat of 15 μm in dry film thickness. In addition, No. With respect to the paint No. 31, the viscosity became very high, and a top coat film could not be formed.

  A test piece was cut out from each coated steel plate, and the hydrophilicity and stain resistance of the coating film surface were examined. About hydrophilicity, after immersing a test piece in warm water for 30 minutes and hydrolyzing an alkoxyl group, the static contact angle of the coating-film surface and water was measured using the contact angle measuring device. For stain resistance, a 20cm long vinyl chloride corrugated sheet is attached to each specimen at an angle of 15 ° so that rainwater flows down on each specimen placed vertically toward the south. An outdoor exposure test was conducted in Ichikawa City. Three months after the start of the test, the surface of each test piece was visually observed from a position 2 m away from the test piece. The evaluation was “◯” when there was no rain streak, “Δ” when some rain streak was observed, and “x” when clear rain streak was observed.

  Moreover, the test piece was cut out from each coated steel plate, and the scratch resistance was also examined. A diamond needle having a diameter of 125 μm was placed perpendicularly to the surface of the coating film, scratched using a Clemens type scratch hardness tester while applying a predetermined load, and the minimum load at which the metal surface of the plating layer was visible was taken as the evaluation value. When the evaluation value was 550 g or more, it was evaluated as “、”, when it was 500 g or more and less than 550 g, “◎ to ○”, when it was 450 g or more and less than 500 g, “◯”, and when it was less than 450 g, “×”.

  Moreover, the test piece was cut out from each coated steel plate, and the matte degree was also examined. About each test piece, 60 degree specular glossiness was measured using the gloss meter.

  Table 4 shows the evaluation results of hydrophilicity, dirt resistance, scratch resistance, and matte degree for each coated steel sheet. Table 4 also shows the evaluation results of the storage stability of each paint. In Table 4, the storage stability of each paint was evaluated as “◯” when the difference in viscosity before and after storage was less than 50 mPa · s, and “x” when 50 mPa · s or more.

  As shown in Table 4, in addition to the silane compound, the dehydrating agent and the pigment, the paints No. 1 to 26 to which the porous silica particles whose surfaces were coated with an organic resin were further added were excellent in storage stability. In addition, the formed coating film was excellent in stain resistance, scratch resistance and matte properties.

  On the other hand, the coating films formed using the paints No. 27 and 28 to which no porous silica particles were added were inferior in scratch resistance and matte properties. Moreover, the coating film formed using the coating materials of No. 29 and No. 30 to which untreated silica particles were added was inferior in stain resistance in addition to storage stability. This is presumably because the hydrophilizing tetramethoxysilane oligomer was consumed by reacting with the hydroxy groups on the surface of the silica particles. In addition, No. in which no dehydrating agent was added. The paint of No. 31 was poor in storage stability and could not form a coating film. Moreover, the pH of the pigment mixture is outside the range of 5.5 to 5.8. The paints of 32 and 33 were inferior in soil resistance in addition to storage stability.

  The coated metal plate of the present invention is excellent in stain resistance adhesion, scratch resistance and design, and is suitable as an exterior building material such as a roofing material or a wall material.

Claims (5)

Preparing a metal plate;
Preparing an organic solvent-based paint containing an organic resin, a silane compound or a condensate of a silane compound, organic resin-coated silica particles, a pigment other than the organic resin-coated silica particles, and a dehydrating agent;
Applying the organic solvent-based paint to the surface of the metal plate, and drying to form a coating film,
The pH of the suspension of the mixture of the organic resin-coated silica particles and the pigment, measured according to JIS K5101-17-2, is in the range of 5.5 to 8.5,
The ratio of the organic resin-coated silica particles in the suspension and the pigment is the same as the ratio of the organic resin-coated silica particles in the organic solvent-based paint and the pigment.
Manufacturing method of painted metal sheet. 2. The method for producing a coated metal plate according to claim 1 , wherein the organic resin-coated silica particles are porous particles obtained by coating the surfaces of porous silica particles having a number average particle diameter of 1 to 15 μm with an organic resin. The organic solvent-based paints, the comprises 1-20 parts by mass of the organic resin-coated silica particles of the organic resin 100 parts by weight contained in the organic solvent-based paints, method for manufacturing a coated metal sheet according to claim 1. The silane compound is a silane compound represented by a general formula R ¹⁴ _-n Si (OR ² ) _n [wherein R ^{1 is} an alkyl group or an alkoxyl group, R ^{2 is} an alkyl group, n is 3 or 4]. The manufacturing method of the coating metal plate of Claim 1 . The method for producing a coated metal sheet according to claim 1 , wherein the dehydrating agent is trialkyl orthoformate, trialkyl orthoacetate, trialkyl orthoborate, or a combination thereof.