JP6466874B2 - Manufacturing method of decorative building board - Google Patents

Description

  The present invention relates to a method for manufacturing a decorative building board having a surface coating layer on the surface of a metal siding substrate.

  Conventionally, a decorative building board in which a surface layer such as a printed layer or a clear layer is formed on a metal siding base material is known as a building exterior material. The printed layer is formed for the purpose of imparting design properties to the decorative building board, and examples of the printed layer include a layer having irregularities, a layer having a specific pattern, and the like. On the other hand, the surface coating layer such as a clear layer is formed for the purpose of protecting the metal siding substrate and the printing layer from external moisture etc., for example, by applying a water-based resin emulsion paint in which synthetic resin particles are dispersed in water. Formed. Examples of the water-based resin emulsion paint include a water-based silicone-modified acrylic resin emulsion paint, a water-based acrylic resin emulsion paint, and a water-based acrylic styrene resin emulsion paint (see, for example, Patent Document 1). These water-based resin emulsion paints include synthetic resin particles and film-forming aids.

  Here, as for the general metal siding base material, a metal plate, a core material, and a back surface material are laminated | stacked in this order, and a core material consists of resin foams, such as a polyurethane and an isocyanurate. Therefore, after applying the water-based resin emulsion paint on the metal siding substrate, if this is dried at a high temperature, the metal siding substrate warps, the interface peeling occurs between the metal plate and the core, the back surface Defects may occur in the metal siding base material, such as swelling of the material or wrinkles on the back material. On the other hand, if the water-based resin emulsion paint is not sufficiently dried and the film-forming aid remains in the surface coating layer, the water resistance of the decorative building board is reduced, or the surface coating layer and the metal siding substrate are Adhesion may be insufficient.

  Here, ceramic siding is mentioned as a general building exterior material other than metal siding. In ceramic siding, the material of the substrate surface is ceramic, and its heat capacity is large. Therefore, once the ceramic siding substrate is heated, it is difficult to lower the temperature, and the film-forming aid and water in the water-based resin emulsion paint can be effectively evaporated with a short heating. On the other hand, since the surface of a metal siding base material is a metal, its heat capacity is small, and the temperature tends to decrease even when heated. Therefore, with a metal siding base material, it has been difficult to sufficiently evaporate the film-forming aid and water in the water-based resin emulsion paint by heating in a short time.

  Therefore, as a method of forming a surface coating layer on a metal siding substrate, a method of heating the metal siding substrate under mild conditions after applying a water-based resin emulsion paint, and further irradiating near infrared rays or mid infrared rays has been proposed. (See Patent Document 2). According to the method, it is possible to heat only the metal plate side of the metal siding substrate. Therefore, according to the method, the film-forming aid in the aqueous resin emulsion paint can be sufficiently removed.

  On the other hand, in recent years, the exterior building materials are also required to have stain resistance such as rain-stain stain prevention, and the surface covering layer of the decorative building board is also required to have stain resistance. In response to such demands, it has been proposed to add colloidal silica particles as hydrophilic antifouling components to water-based resin emulsion paints (see Patent Document 3 and Patent Document 4).

JP 2003-53258 A Japanese Patent No. 5567167 Japanese Patent No. 4812902 JP2012-210605A

  The colloidal silica particles described in Patent Document 3 and Patent Document 4 described above exhibit antifouling performance by forming (concentrating) a layer having a high concentration on the surface side of the surface coating layer. However, when colloidal silica particles are added to the conventional water-based resin emulsion paint, the colloidal silica particles are difficult to move to the surface side, and it is difficult to obtain sufficient antifouling performance. This phenomenon was remarkable when the surface coating layer was formed on the metal siding substrate.

  The reason is guessed as follows. Colloidal silica particles usually move to the coating surface side together with the film-forming aid when the film-forming aid in the water-based resin emulsion paint evaporates. However, when the surface coating layer is formed on the metal siding substrate, it is difficult to set the drying temperature of the water-based resin emulsion paint high as described above. For this reason, it is considered that the film-forming auxiliary does not evaporate sufficiently, or it is difficult to sufficiently evaporate the film-forming auxiliary, and the colloidal silica particles cannot move to the surface side of the surface coating layer. Even if the surface coating layer is formed by the method described in Patent Document 2, the evaporation rate of the film-forming aid is not sufficient, and it is difficult to sufficiently improve the antifouling property.

  In view of such circumstances, an object of the present invention is to provide a method for producing a decorative building board having a surface coating layer that is excellent in water resistance and adhesion, and also in antifouling properties, on a metal siding substrate. .

The present invention provides the following method for producing a decorative building board.
[1] A method for producing a decorative building board, comprising: a metal siding base material having a metal plate, a core material, and a back surface material in this order; and a surface covering layer formed on the metal plate side surface of the metal siding base material. A water-based resin emulsion paint containing a film-forming aid, a hydrophilic antifouling component, and synthetic resin particles is applied to the surface of the metal siding substrate on the metal plate side and then heated to form the surface coating layer. The film-forming aid contains ethylene glycol monobutyl ether, the hydrophilic antifouling component contains colloidal silica particles and / or colloidal silica / resin composite particles, and the amount of the ethylene glycol monobutyl ether However, it is 2-10 mass% with respect to the total amount of the said water-system resin emulsion coating material, The manufacturing method of a decorative building board.

[2] The film-forming aid further includes an alcohol-based organic solvent that is soluble in water and has a boiling point of 150 ° C. or higher, and the amount of the alcohol-based organic solvent is 4 mass based on the total amount of the water-based resin emulsion paint. % Of the decorative building board production method according to [1].
[3] The method for manufacturing a decorative building board according to [1] or [2], wherein the synthetic resin particles include silicone-modified acrylic resin particles and / or acrylic resin particles.
[4] The method for producing a decorative building board according to any one of [1] to [3], wherein the coating is performed at a temperature of 50 to 90 ° C. for 10 minutes or less after the application of the water-based resin emulsion paint.

  According to the production method of the present invention, a decorative building board having a surface coating layer having high adhesion to a metal siding substrate and the like, and having high water resistance and antifouling properties can be obtained.

  The present invention relates to a method for manufacturing a decorative building board having a metal siding base material and a surface coating layer formed on the metal siding base material. The “surface covering layer” in the present specification refers to a film disposed on the outermost side when a decorative building board is used in a building. In the present invention, the surface coating layer may be formed directly on the metal siding substrate, but other layers such as an undercoat layer, an overcoat layer, and an ink layer are formed on the metal siding substrate. The surface coating layer may be formed on these layers.

  As described above, when the surface coating layer is formed on the surface of the metal siding substrate, if excessive heat is applied, the metal siding substrate may be defective, for example, the metal siding substrate may be warped. On the other hand, if the water-based resin emulsion paint for forming the surface coating layer is insufficiently dried and the film-forming aid remains in the surface coating layer, the adhesion between the surface coating layer and the metal siding substrate is reduced. Or the water resistance of the surface coating layer was liable to decrease. Further, even when a hydrophilic antifouling component was added to the water-based resin emulsion paint, it was difficult for the hydrophilic antifouling component to move to the surface side of the surface coating layer, and it was difficult to sufficiently exhibit the antifouling property.

  In contrast, the present invention provides a metal siding of a water-based resin emulsion paint containing colloidal silica particles and / or colloidal silica / resin composite particles as a hydrophilic antifouling component and containing a certain amount of ethylene glycol monobutyl ether as a film-forming aid. It is applied onto a substrate and heated to form a surface coating layer. As a result, even when the water-based resin emulsion paint is dried at a relatively low temperature, it is possible to sufficiently evaporate the film-forming aid from the surface coating layer, and the adhesiveness to the metal siding substrate is high and the water resistance is high. And a surface coating layer having high antifouling properties can be obtained.

  The reason is as follows. Ethylene glycol monobutyl ether is completely compatible with water, and even if it is contained in a relatively large amount in the water-based resin emulsion paint, phase separation is difficult. Moreover, although the boiling point is 171 ° C., the vapor pressure is 0.8 mmHg, and it has the property of being easily evaporated. Therefore, even if the heating temperature at the time of forming the surface coating layer is relatively low, the film-forming auxiliary (ethylene glycol monobutyl ether) is likely to evaporate from the coating film of the water-based resin emulsion paint, and the film-forming auxiliary is present in the surface coating layer. It is hard to remain. Colloidal silica particles and colloidal silica / resin composite particles move to the surface of the coating as the ethylene glycol monobutyl ether evaporates. However, since ethylene glycol monobutyl ether evaporates from the coating at a relatively high rate, It becomes possible to move to the surface side of the coating film before the film is cured. Therefore, the concentration of the hydrophilic antifouling component on the surface side of the surface coating layer is sufficiently high, and the antifouling performance of the surface coating layer is increased.

  Hereinafter, the metal siding and water-based resin emulsion used in the method for manufacturing a decorative building material of the present invention will be described first, and then the method for manufacturing a decorative building board will be described.

(Metal siding base material)
The metal siding base material only needs to have a metal plate, a core material, and a back surface material laminated in this order. For example, another member may be further included. The layer structure of the metal siding substrate can be a layer structure obtained by removing a surface coating layer and a printing layer from a known metal siding substrate. As the metal siding substrate, a commercially available metal siding substrate may be used as it is, or may be produced by a known method.

  The type of the metal plate is not particularly limited, and specific examples thereof include hot dip zinc-5% aluminum alloy plated steel plate, hot dip zinc-55% aluminum alloy plated steel plate, aluminum alloy plate, stainless steel plate, and these coated steel plates. It is.

  The shape of the metal plate is not particularly limited, and may be a flat plate shape or may be bent into a desired shape according to the use of the decorative building board. Furthermore, the metal plate may be subjected to embossing, drawing molding, uneven processing, and the like. When such a process is applied to the metal plate, a decorative building board having various surface shapes such as a tile tone, a brick tone, and a wood grain tone can be manufactured.

  Further, the metal plate may be subjected to a surface treatment, and the metal plate may have a chemical conversion treatment film formed by a chemical conversion treatment of a metal. When the metal plate is subjected to chemical conversion treatment, adhesion of a surface coating layer or the like formed on the metal plate is increased, or the corrosion resistance of the metal plate is increased. Examples of the chemical conversion treatment include chromate treatment, chromium-free treatment, phosphate treatment and the like.

The adhesion amount of the chemical conversion treatment film is appropriately selected according to the type of chemical conversion treatment. For example, when the chemical conversion film is a chromate film, the amount of adhesion can be 5 to 100 mg / m ^{2 in} terms of total Cr. Examples of the coating by the chromium-free treatment include a Ti—Mo composite coating and a fluoroacid coating. And when a chemical conversion treatment film is a Ti-Mo composite film, the adhesion amount can be 10-500 mg / m < ² > in conversion of the total amount of Ti and Mo. On the other hand, when the chemical conversion film is a fluoroacid-based film, the adhesion amount can be 3 to 100 mg / m ^{2 in} terms of fluorine or total metal elements. When the chemical conversion treatment film is a phosphate film, the adhesion amount can be 5 to 500 mg / m ^{2 in} terms of phosphorus.

  On the other hand, the core material of the metal siding base material can be a synthetic resin foam. Examples of the core material include polyurethane foam, polystyrene foam, polyisocyanurate foam, phenol urethane foam, phenol foam, and urea foam.

  As the back material, a sheet-like member usually used as a back material of metal siding, such as laminated paper, can be used. Specific examples of the back material include laminated paper of aluminum foil and kraft paper, kraft paper heat-sealed with polyethylene, laminated paper of calcium carbonate impregnated paper and aluminum foil, and iron plate.

  Here, as described above, an undercoat layer, an overcoat layer, an ink layer, and the like may be formed on the surface of the metal plate of the metal siding substrate.

  The undercoat layer is a layer formed on the metal plate or the chemical conversion film, and is a layer for improving the corrosion resistance of the metal plate or the like and the adhesion of the overcoat layer. The undercoat layer may be formed on the entire surface of the metal plate, or may be formed only in a partial region. The undercoat layer is formed by applying an undercoat paint to the surface of a metal plate or chemical conversion treatment film and drying (or curing) it. Examples of the type of resin contained in the undercoat paint include polyester, epoxy resin, and acrylic resin. Epoxy resins are particularly preferred because of their high polarity and good adhesion to metal plates or chemical conversion coatings. The film thickness of the undercoat layer is not particularly limited, and can be about 5 μm, for example.

  The topcoat layer is a layer that is formed on the undercoat layer and imparts designability and the like to the decorative building board. The overcoat layer may be formed on the entire surface of the metal plate, or may be formed only in a partial region. The topcoat layer may be a layer having surface irregularities from the viewpoint of imparting design properties to the decorative building board. The topcoat layer is formed by applying a topcoat paint to the surface of the undercoat layer and drying (or curing). Examples of the top coat for forming the top coat layer include a composition containing polyester and one or both of a melamine resin and a urethane resin. The overcoat layer may further contain extender pigments, colored pigments, and the like. The film thickness of the overcoat layer is not particularly limited and can be, for example, 10 to 40 μm.

  The ink layer is formed on the top coat layer and is a layer for enhancing the design of the decorative building board. The ink layer may be formed on the entire surface of the metal plate, or may be formed only in a partial region. The ink layer is formed, for example, by applying ink containing a curable resin and a colorant to the surface of the topcoat layer and curing it by heating, UV irradiation, or the like. Examples of the ink application method include an inkjet method.

  Examples of the ink include a composition containing an epoxy group-containing silane coupling agent, a hydroxyl group-containing oxetane compound, a colorant, a cationic polymerizable compound, and a photopolymerization initiator. Examples of the colorant include various pigments such as organic pigments and inorganic pigments. Examples of the cationically polymerizable compound include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides. The film thickness of the ink layer is not particularly limited.

(Water-based resin emulsion paint)
The water-based resin emulsion paint applied on the metal siding substrate contains at least a film-forming aid, a hydrophilic antifouling component, and synthetic resin particles. In the water-based resin emulsion paint, the synthetic resin particles and the hydrophilic antifouling component are dispersed in water or a film-forming aid. The water-based resin emulsion paint may contain other components as necessary.

  Synthetic resin particles contained in water-based resin emulsion paints, when forming a surface coating layer, the particles are bonded to each other (for example, fusion, adhesion, chemical bonding, etc.) to cover the surface of a metal siding substrate, etc. If it is possible, there is no particular limitation. The kind of the synthetic resin particles is appropriately selected according to the physical properties required for the surface coating layer.

  Examples of synthetic resins constituting the synthetic resin particles include acrylic resins, polyester resins, alkyd resins, silicone-modified acrylic resins, silicone-modified polyester resins, silicone resins, and fluorine resins. The water-based resin emulsion paint may contain only one kind of synthetic resin particle or two or more kinds. When the synthetic resin particles are made of an acrylic resin or a silicone-modified acrylic resin, the weather resistance and transparency of the surface coating layer are likely to increase.

  As described above, since the synthetic resin particles are bonded to each other when forming the surface coating layer, the average particle diameter is not particularly limited, and is appropriately selected according to the desired film thickness of the surface coating layer, etc. Is done. Moreover, it is preferable that the quantity of the synthetic resin particle with respect to the total amount in a water-system resin emulsion coating material is 30-70 mass%, and it is preferable that it is 40-60 mass%. When the amount of the synthetic resin particles is 30% by mass or more, it becomes easy to efficiently form a surface coating layer having a desired film thickness. On the other hand, when the amount of the synthetic resin particles is 70% by mass or less, the amount of the film-forming aid and the hydrophilic antifouling component is relatively large, and a layer excellent in antifouling property is easily obtained.

  The film-forming aid contained in the water-based resin emulsion paint fulfills a function of improving the surface smoothness of the coating film and a function of improving the binding property between the synthetic resin particles when the water-based resin emulsion paint is applied. The film forming aid contains at least ethylene glycol monobutyl ether. By including ethylene glycol monobutyl ether, the water-based resin emulsion paint can be dried at 60 to 80 ° C. as described later. Also, as described above, ethylene glycol monobutyl ether is highly evaporable, so even if a little monoethylene glycol butyl ether remains in the coating film immediately after the surface coating layer is formed, it will evaporate from the coating film in a few weeks. It is possible.

  Ethylene glycol monobutyl ether is contained in an amount of 2 to 10% by mass, more preferably 3 to 9% by mass, based on the total amount of the water-based resin emulsion paint. If the amount of ethylene glycol monobutyl ether is excessively small, the synthetic resin particles are difficult to bind to each other, and cracks or the like may occur in the resulting surface coating layer. Further, when the amount of ethylene glycol monobutyl ether is small, it is difficult for the hydrophilic antifouling component to move to the surface side during the formation of the surface coating layer, and sufficient antifouling performance is hardly exhibited. On the other hand, when the amount of ethylene glycol monobutyl ether is 2% by mass or more, particularly 3% by mass or more, the hydrophilic antifouling component easily moves to the surface side of the surface coating layer, and the antifouling performance of the surface coating layer. Is likely to increase. Further, when the surface coating layer is formed, the synthetic resin particles are easily bound to each other, and cracks are hardly generated in the obtained surface coating layer. On the other hand, if the amount of ethylene glycol monobutyl ether is excessive, the synthetic resin particles tend to swell and the storage stability of the water-based resin emulsion paint tends to decrease, but the amount of ethylene glycol monobutyl ether is 10% by mass or less. If so, the storage stability of the water-based resin emulsion paint is sufficiently high. Further, when the amount of ethylene glycol monobutyl ether is 9% by mass or less, not only the adhesion of the obtained surface coating layer is increased, but also the pencil hardness of the surface coating layer is easily increased.

  It is preferable that the film-forming aid further contains an alcohol-based organic solvent having a boiling point of 150 ° C. or higher and soluble in water. When an alcohol-based organic solvent is contained in the film-forming aid, leveling properties when a water-based resin emulsion paint is applied tend to be good. The boiling point of the alcoholic organic solvent is preferably 270 ° C. or lower. If the boiling point of the film-forming aid is excessively high, the alcohol-based organic solvent tends to remain in the coating film even when the water-based resin emulsion paint is heated, and the resulting surface coating layer has insufficient water resistance and adhesion. May be.

  Examples of alcohol solvents having a boiling point of 150 ° C. or more and soluble in water include 1-butoxy-2-propanol, texanol, carbitol, butyl carbitol acetate, butyl carbitol, tripropylene glycol monomethyl ether, dipropylene Propylene glycol monobutyl ether and the like are included.

  Here, the total amount of the alcohol solvent is preferably 4% by mass or less, and more preferably 1 to 3% by mass with respect to the total amount of the aqueous resin emulsion paint. When the amount of the alcohol solvent is 4% by mass or less, the alcohol solvent hardly remains in the surface coating layer, and the adhesion between the metal siding substrate and the surface coating layer is likely to increase. In addition, the storage stability of the water-based resin emulsion paint is also increased.

  A hydrophilic antifouling component is a component which prevents that a pollutant adheres to the surface of a decorative building board (surface coating layer), and a substance with a low contact angle with water is used as a hydrophilic antifouling component. By disposing such a hydrophilic antifouling component on the surface side of the surface coating layer, the hydrophilicity of the surface coating layer is increased. As a result, contaminants with high hydrophobicity are less likely to adhere to the decorative building board, and even if contaminants adhere to the surface of the decorative building board, the contaminants attached due to rainwater tend to flow down.

  Such hydrophilic antifouling components include at least colloidal silica particles and / or colloidal silica / resin composite particles. In the present specification, “colloidal silica particles” refers to particles that have silicon dioxide as a basic unit and can be dispersed in water having an average particle diameter of 5 to 120 nm. When the average particle size of the colloidal silica particles is 120 nm or less, the storage stability of the water-based resin emulsion paint tends to be good. The average particle diameter is more preferably 60 nm or less. The average particle diameter is a value specified by observation with an electron microscope.

  The shape of the colloidal silica particles is not particularly limited, and may be any shape such as a spherical shape, a chain shape, a rod shape, or a pearl like shape.

  Specific examples of colloidal silica include, for example, Snowtex ST-20, ST-O, ST-C, ST-S, ST-N, ST-20L, ST-AK, ST-UP, manufactured by Nissan Chemical Industries, Ltd. ST-ZL: Adelite AT-20, AT-30, AT-20N, AT-30N, AT-20N, AT-20S, AT-20Q, AT-30A, AT-30S, AT-40, AT manufactured by ADEKA -50, AT-300; Cataloid S-20H, Cataloid S-30, Cataloid S-30H, Cataloid SI-500, Cataloid SN, Cataloid SA manufactured by Catalyst Kasei Kogyo Co., Ltd .; Dole 20, Silica Doll 20A, Silica Doll 20B; Clevosol 30R9, Clevosol 30R50 manufactured by Clariant Japan, Rebozoru 50R50; DuPont Ludox HS-40, Ludox HS-30, Ludox LS, Ludox SM-30, Ludox AS, Ludox AM, and the like. The water-based resin emulsion paint may contain only one kind of these colloidal silica particles or two or more kinds.

  The colloidal silica particles are preferably contained in an amount of 0.2 to 8 mass%, more preferably 2 to 6 mass%, based on the total amount of the water-based resin emulsion paint. When the colloidal silica particles are included in the above range, the hydrophilicity of the surface of the surface coating layer is likely to be sufficiently increased.

  On the other hand, in the present specification, “colloidal silica / resin composite particles” refers to particles in which the surface of resin particles is covered with colloidal silica. The colloidal silica / resin composite particles are added, for example, by adding 1 to 300 parts by mass of the above-mentioned colloidal silica particles to 100 parts by mass of the α, β-ethylenically unsaturated monomer. The monomer can be prepared by emulsion polymerization by a known method. An example of a method for preparing such colloidal silica / resin composite particles is the method described in JP-A-2008-23979.

  Examples of α, β-ethylenically unsaturated monomers used in preparing colloidal silica / resin composite particles include acrylic acid, (meth) acrylic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid Carboxy group-containing monomers such as itaconic anhydride and crotonic acid; 2-aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, 3-aminopropyl (meth) acrylate, 2-butylaminoethyl (meta ) Acrylate, and amino group-containing monomers such as 4-vinylpyridine; acrylamide, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and N-vinyl Amide group-containing monomers such as 2-pyrrolidone; allyl alcohol, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate, 2-hydroxybutyl (meth) acrylate, polyethylene Hydroxyl group-containing monomers such as glycol (meth) acrylate and polypropylene glycol (meth) acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, γ- (meth) acryloxy Propyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, β- (meth) acryloxyethyltrimethoxysilane, β- (meth) acryloxyethyltriethoxysilane, γ- (meta ) Acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxybutylphenyldimethoxysilane, γ- (meta ) Alkoxysilyl group-containing monomers such as acryloxypropyldimethylmethoxysilane and γ- (meth) acryloxypropyldiethylmethoxysilane;

  The colloidal silica / resin composite particles are preferably contained in the water-based resin emulsion paint in an amount of 0.5 to 18% by mass, and more preferably 3 to 9% by mass. When the colloidal silica / resin composite particles are included in the above range, the hydrophilicity of the surface coating layer is likely to be sufficiently increased.

  In addition, the water-based resin emulsion paint usually contains water as a dispersion medium. The amount of water is appropriately selected according to the desired viscosity of the water-based resin emulsion paint and the drying (heating) conditions.

  The water-based resin emulsion paint may further contain other components as necessary. Examples of other components include resin beads such as acrylic beads, inorganic particles such as hydrophilic silica, surfactants, ultraviolet absorbers, thickeners, waxes, antifoaming agents, and light stabilizers.

  When resin beads or inorganic particles are included, the gloss of the surface coating layer can be adjusted. Moreover, when these particles are contained, the mechanical strength of the surface coating layer tends to increase. The average particle diameter of the resin beads and inorganic particles is not particularly limited, but can be set to about 1 to 10 μm, for example. When the average particle diameter of these particles is within the above range, the gloss of the surface coating layer is easily adjusted and the mechanical strength of the surface coating layer is likely to increase. The amount of resin beads and inorganic particles is appropriately selected according to the desired properties of the surface coating layer. The average particle diameter is a value measured by a laser diffraction scattering method.

  On the other hand, when the amount of the thickener contained in the aqueous resin emulsion is excessive, the movement of the hydrophilic antifouling component to the coating film surface may be inhibited. On the other hand, if the amount of the thickener is small, the dispersed state of various particles may not be maintained. Therefore, the amount of the thickener is preferably 0.2 to 5% by mass and more preferably 0.5 to 2.0% by mass with respect to the total amount of the aqueous resin emulsion.

  Further, the minimum film-forming temperature of the water-based resin emulsion paint is preferably a sufficiently low temperature, specifically, preferably 0 to 50 ° C. If the minimum film-forming temperature is too low, the storage stability of the water-based resin emulsion paint may be insufficient. On the other hand, when the minimum film-forming temperature is too high, it is necessary to heat to a high temperature when forming the surface coating layer, and deformation or the like may occur in the metal siding substrate. The minimum film-forming temperature of the water-based resin emulsion paint can be adjusted by the type and amount of the film-forming aid.

  The method for preparing the water-based resin emulsion paint is not particularly limited, and for example, it can be prepared as follows. First, dilute emulsions containing synthetic resin particles, colloidal solution of colloidal silica particles and / or emulsions of colloidal silica / resin composite particles, and other additives with water as necessary, and mix and disperse them uniformly. Let Thereafter, a film-forming aid is added to the mixed solution and mixed uniformly. Thereby, it is possible to prepare a water-based resin emulsion paint in which each component is uniformly dispersed.

(Manufacturing method of decorative building board)
In the method for producing a decorative building board of the present invention, the above-described aqueous resin emulsion paint is applied onto the above-mentioned metal siding substrate, and this is heated to form a surface coating layer on the metal siding substrate. Is included.

  The method for applying the water-based resin emulsion paint on the metal siding substrate is not particularly limited, and can be appropriately selected from known methods. Examples of the method for applying the water-based resin emulsion paint include a roll coating method, a curtain flow method, a spin coating method, an air spray method, an airless spray method, and a dip-up method.

  On the other hand, the method for heating the coating film of the water-based resin emulsion coating applied on the metal siding substrate is not particularly limited, and can be performed by a known method such as heating with warm air or irradiation with near infrared rays. By heating, the synthetic resin particles in the water-based resin emulsion paint are bound to form a film, and the hydrophilic antifouling component moves to the coating surface side as the film-forming aid evaporates.

  Here, the heating temperature of the water-based resin emulsion paint is preferably 50 ° C to 90 ° C, more preferably 60 to 80 ° C. By setting the heating temperature to 90 ° C. or lower, warpage of the metal siding substrate, peeling between the metal plate and the core material, and the like can be suppressed. On the other hand, when the heating temperature is 50 ° C. or higher, water and the film-forming aid can be sufficiently evaporated. Moreover, it is preferable that heating time is 10 minutes or less, and it is more preferable that it is 3 to 8 minutes.

  As an example of the heating method, the plate surface wind speed of the metal siding substrate (the wind speed on the surface of the metal plate) is controlled while the ultimate temperature of the metal plate of the metal siding substrate to which the water-based resin emulsion paint is applied is controlled to 60 to 80 ° C. ) Is hot air treatment so that it becomes 4 m / sec or less. When the plate surface wind speed exceeds 4 m / sec, water and the film-forming aid evaporate too quickly from the coating film of the water-based resin emulsion paint, so that the hydrophilic antifouling component is sufficiently applied to the surface of the surface coating layer. You may not be able to move.

  Here, although the film thickness of a surface coating layer is suitably set according to the manufacturing method of a decorative building board, the film thickness of a surface coating layer can be about 10-40 micrometers, and shall be 20-40 micrometers. Is more preferable. When the film thickness of the surface coating layer is in the above range, the metal siding substrate can be sufficiently protected from external humidity, water, and the like.

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

[Production of metal siding substrate]
(Formation of undercoat layer, topcoat layer, and ink layer)
A hot-dip Zn-55% Al alloy-plated steel plate (metal plate) having an A4 size with a plate thickness of 0.27 mm and a plating adhesion amount per side of 90 g / m ² was prepared. The surface of the metal plate was alkali degreased, and a coating type chromate treatment solution (NRC300NS, manufactured by Nippon Paint Co., Ltd.) was applied to the surface. At this time, the total Cr conversion adhesion amount of the chemical conversion coating was 50 mg / m ² .

  Next, an epoxy-based undercoat paint (700P, manufactured by Nippon Fine Coatings Co., Ltd.) was applied onto the chemical conversion film with a bar coater and baked at a final plate temperature of 215 ° C. Thereafter, an undercoat layer having a dry film thickness of 5 μm was formed on the chemical conversion film.

  Then, using a bar coater, an overcoat was applied on the undercoat layer and baked at a final plate temperature of 225 ° C. for 1 minute to form an overcoat layer of 18 μm dry thickness having fine irregularities on the surface. . The top coating was prepared by blending a base resin with a catalyst, an amine, and a pigment. The base resin is a mixture of polyester (number average molecular weight 5000, glass transition temperature 30 ° C., hydroxyl value 28 mg KOH / g, manufactured by DIC) and methylated melamine resin (Cymel 303, manufactured by Mitsui Cytec) at 70:30. It was. The catalyst was dodecylbenzenesulfonic acid, and the amount of the catalyst added was 1% by mass with respect to the resin solid content. The amine was dimethylaminoethanol, and the amount of amine added was 1.25 times the amount of amine equivalent to the acid equivalent of dodecylbenzenesulfonic acid. As the pigment, 45% by mass of titanium oxide (JR-603, manufactured by Teica) having an average particle diameter of 0.28 μm and hydrophobic silica A having an average particle diameter of 5.5 μm (Cycilia) with respect to the solid content of the top coating material, respectively. 456, manufactured by Fuji Silysia Chemical Co., Ltd.), 6% by mass of mica (SJ-010, manufactured by Yamaguchi Mica Co., Ltd.) having an average particle size of 10 μm, and acrylic resin beads (Tuffic AR650S, Toyobo Co., Ltd.) having an average particle size of 40 μm. 2 mass%) was used.

Next, a cationic polymerization type UV ink was uniformly applied to the surface of the overcoat layer by an ink jet method to form a 100% solid image of the UV ink. Next, the applied UV ink is irradiated with ultraviolet rays to cure the UV ink, and then the cured UV ink is heated in a hot air oven at a furnace temperature of 70 ° C. for 5 minutes, followed by heat treatment. It was. Thus, a UV ink layer having an ink coating amount of 8.4 g / m ² was formed on the surface of the topcoat layer.

  The UV ink was prepared as follows. First, 3.5 parts by mass of a polymer dispersant (PB822, manufactured by Ajinomoto Fine Techno Co.), 25 parts by mass of an oxetane compound having a hydroxyl group (OXT-101, manufactured by Toagosei Co., Ltd.), an epoxy compound (CEL2021P, CEL3000). 10 parts by mass of Daicel), 35.5 parts by mass of oxetane compound (OXT-221, manufactured by Toa Gosei Co., Ltd.), and 3.0 parts by mass of black pigment (Channel Black RCF # 33, manufactured by Mitsubishi Chemical Corporation) 200 parts by mass of zirconia beads (diameter 1 mm) were added to the mixture, and the glass bottle was sealed. The mixture was then dispersed for 4 hours on a paint shaker. After the dispersion treatment, zirconia beads were removed from the mixture to obtain a pigment dispersion. The pigment dispersion was mixed with 18 parts by mass of a cationic photopolymerization initiator (CPI-100P, manufactured by San Apro).

  In the ink jet method, an ink jet printer (patterning jet, manufactured by Tritech) was used. The nozzle diameter of the inkjet head is 35 μm, the temperature of the inkjet head during inkjet printing is 45 ° C., the applied voltage is 11.5 V, the pulse width is 10.0 μs, the drive frequency is 3483 Hz, the volume of the ink droplet is 42 pL, and the resolution is 360 dpi.

Ultraviolet rays were irradiated with a high-pressure mercury lamp (H bulb, manufactured by Fusion UV Systems Japan). The lamp output was 200 W / cm, and the integrated light quantity was 600 mJ / cm ² . The integrated light quantity was measured with an infrared light quantity meter UV-351-25, manufactured by Oak Manufacturing Co., Ltd. For the post-heating treatment, an automatic discharge dryer AT0-101, manufactured by Tojo Thermal Engineering Co., Ltd. was used.

(Metal plate forming)
The metal plate (hereinafter also referred to as “painted metal plate”) on which the above-described undercoat layer, topcoat layer, and ink layer were formed was subjected to surface processing by embossing, and a fitting shape was formed by roll forming. Specifically, the above-described coated metal plate wound around an uncoiler was continuously fed out, and an embossed shape having a height of 1.8 mm to 4.0 mm was continuously formed on a brick pattern by a roll-type embossing machine. Thereby, the painted metal plate which has the external appearance of a tile pattern was obtained. Subsequently, a coated metal plate was formed by a roll forming machine to form a fitting convex portion and a fitting concave portion.

(Lamination of painted metal plate, core material, and back material)
Sophane R-HIP and Toyosofuran R746-19D (both manufactured by Soflanwith), which are polyisocyanurate raw materials, were mixed at a mass ratio of 10: 7 in a foaming machine. And the said polyisocyanurate raw material was discharged to the back surface of the above-mentioned coating metal plate with the mixing extruder. And the aluminum kraft paper (back surface material) was sent out on the discharged polyisocyanurate raw material, and the foamed polyisocyanurate raw material was inserted | pinched between the coating metal plate and the aluminum kraft paper. In this state, heating and pressurization were performed to foam-mold the polyisocyanurate raw material. Thereby, the metal siding base material which has a coating metal plate, a core material (polyisocyanurate), and aluminum kraft paper (back surface material) in this order was obtained. The thickness of the core material was 17 mm. The thickness of the core material was adjusted by the distance between the conveyors of the double conveyor that sandwiches the metal-coated plate, the polyisocyanurate raw material layer, and the aluminum kraft paper in the laminating direction during foam molding (heating and pressing). The detailed foaming conditions of the polyisocyanurate raw material are as follows.

(Foaming conditions)
Conveyor line speed 40m / min
Flow rate (Discharge rate of polyisocyanurate raw material) 6kg / min
Polyisocyanurate raw material temperature 30 ° C
Preheating temperature of painted metal plate 35 ℃
Heating (oven cure) temperature 50 ° C
Foaming machine Low pressure agitator mixing foaming machine

[Examples 1 to 11 and Comparative Examples 1 to 11]
-Preparation of water-based resin emulsion paint Acrylic resin emulsion 7504 (resin content 55.5%, minimum film-forming temperature (MFT) 57 ° C., Tg 46 ° C., manufactured by BASF Japan Ltd.) 100 parts by mass, average particle size 18 μm acrylic beads ( Average particle size: 18 μm, Tuftic AR650S, manufactured by Toyobo Co., Ltd.) 3.8 parts by mass, hydrophilic silica particles having an average particle size of 12 μm (average particle size: 12 μm, Cicilia 470, manufactured by Fuji Silysia Chemical Ltd.), Nonionic surfactant (Adecoupler MPC-800, cloud point of about 30 ° C., manufactured by ADEKA) 0.1 part by mass, colloidal silica particle-containing emulsion (Snowtex C, manufactured by Nissan Chemical Industries, SiO ₂ content 20% by mass, 10 parts by mass of pH 8.8, average particle size 10-15 nm), UV absorber (TINUVIN 1130, B SF Japan Co., Ltd.) 5 parts by mass, polymer-type special nonionic thickener (Adecanol UH540, ADEKA Co., Ltd.) 0.07 parts by mass, and water 100 parts by mass are mixed and stirred for 10 minutes, and 80 mesh Filtered with a filter. This obtained the mixture which consists of components other than the film-forming aid.

  A film-forming aid was added to the mixture so that the composition shown in Table 1 was obtained. Specifically, ethylene glycol monobutyl ether (boiling point 171 ° C.) is 2.2 to 27.2 parts by mass, 1-butoxy-2-propanol (boiling point 170 ° C.) is 4.4 to 14 parts by mass, dipropylene glycol mono 4.4 to 14 parts by mass of butyl ether (boiling point 227 ° C.) or 4.4 to 14 parts by mass of tripropylene glycol monomethyl ether (boiling point 243 ° C.) was added to the above mixture, and the water-based resin of each Example and Comparative Example An emulsion paint was obtained.

Preparation Each aqueous resin emulsion paint and surface coating layer on the surface of the coated metal plate of the metal siding substrate (the ink layer) was coated by airless spray device so that the dry mass 30 g / m ^2. Thereafter, the coated metal siding base material was subjected to hot air treatment at a plate surface wind speed (wind speed on the surface of the metal plate of the metal siding base material) of 4 m / second, a metal plate temperature of 80 ° C., and a temperature hold time of 5 minutes.

[Example 12]
The amount of the acrylic resin emulsion was changed from 100 parts by weight to 96 parts by weight, except that 4 parts by weight of the colloidal silica / resin composite particle-containing emulsion prepared by the following method was added instead of the colloidal silica particle-containing emulsion. A mixture of components other than the film-forming aid was prepared in the same manner as described above. Thereafter, 9.2 parts by weight of ethylene glycol monobutyl ether (boiling point: 171 ° C.) as a film forming aid was added to the mixture to obtain an aqueous resin emulsion paint. Thereafter, a surface coating layer was formed on the metal siding substrate by the same method as in Example 1 and the like.

(Preparation of emulsion containing colloidal silica / resin composite particles)
In a reactor equipped with a stirrer, a thermometer, a cooling pipe and a dropping device, a colloidal silica particle-containing emulsion (trade name: Snowtex S, manufactured by Nissan Chemical Industries, Ltd., solid content 30% by mass, average particle size 8-11 nm , Na stable type) 500 parts by mass and 350 parts of deionized water were charged, and the temperature inside the reactor was increased to 80 ° C. while being replaced with nitrogen. Next, 2 parts of potassium persulfate was added, and a mixed solution of 210 parts of methyl methacrylate and 90 parts of 2-ethylhexyl acrylate which had been stirred and mixed in a separate container in advance was continuously added dropwise over 4 hours. After completion of dropping, the mixture was aged while continuing stirring at 80 ° C. for 2 hours, and cooled to room temperature. Thereafter, an aqueous ammonia solution was added to adjust the pH to 9 to 10 to obtain an emulsion containing colloidal silica / resin composite particles. The solid content of the colloidal silica / resin composite particles was 39% by mass.

[Comparative Example 12]
A mixture of components other than the film-forming aid was prepared in the same manner as in Example 1 except that the colloidal silica-containing emulsion and the colloidal silica / resin composite particle-containing emulsion were not added. Thereafter, 9.2 parts by weight of ethylene glycol monobutyl ether (boiling point: 171 ° C.) as a film forming aid was added to the mixture to obtain an aqueous resin emulsion paint. Thereafter, a surface coating layer was formed on the metal siding substrate by the same method as in Example 1 and the like.

[Evaluation]
(Adhesion)
About the obtained surface coating layer, according to JISK5600-5-6, the crosscut was put into the grid | lattice form, 100 squares were produced, and adhesiveness was evaluated. ○ If it is above, it is a usable level.
◎: No more than 5 peeled places ○: No less than 6 and no more than 29 places ×: 30 or more peeled places

(Pencil hardness)
About the obtained surface coating layer, the pencil hardness was measured according to the measuring method prescribed | regulated to JISK5600-5-4. ○ If it is above, it is at a usable level.
◎: H or more ○: HB or more and F or less ×: B or less

(Water resistant adhesiveness)
The decorative building board was immersed in boiling ion exchange water at 98 ° C. or higher for 2 hours, and then dried at room temperature for 2 hours. Thereafter, in the same manner as described above, 100 squares were prepared in the surface coating layer, and the adhesion was evaluated. ○ If it is above, it is at a usable level.
◎: No more than 5 peeled places ○: No less than 6 and no more than 29 places ×: 30 or more peeled places

(Film formability)
The surface of the surface coating layer was observed with a 20-fold magnifier, and the film forming property was evaluated based on the presence or absence of cracks. ○ If it is above, it is a usable level.
◎: No crack ○: There is a minute crack ×: There is a crack

(Water contact angle)
The water contact angle of the surface coating layer was measured with a droplet volume of 1 μL. ○ If it is above, the contamination resistance is a good level.
◎: Less than 35 ° ○: 35 ° or more and less than 50 ° ×: 50 ° or more

(Storage stability of water-based resin emulsion paint)
The aqueous resin emulsion paints prepared in Examples and Comparative Examples were stored in a thermostatic chamber at 50 ° C. for 4 weeks, and the viscosity of the paint at 25 ° C. before and after storage was measured with a B-type viscometer to calculate the rate of increase in viscosity.
A: Viscosity increase rate is less than 10% B: Viscosity increase rate is 10% or more and less than 20% X: Viscosity increase rate is 20% or more

  As shown in Table 1, a surface coating layer is formed by an aqueous resin emulsion paint containing 2 to 10% by mass of ethylene glycol monobutyl ether as a film-forming aid and colloidal silica particles and / or colloidal silica / resin composite particles. When it did, the adhesiveness of a surface coating layer and a metal siding base material was favorable (Examples 1-12). On the other hand, when the amount of ethylene glycol monobutyl ether was small, sufficient adhesion could not be obtained, and water-resistant adhesion and film-forming properties were also low (Comparative Example 1). This is probably because the film-forming aid was not sufficiently evaporated from the surface coating layer and remained in the film. At this time, water contact was also low. This is presumably because the colloidal silica particles or the colloidal silica / resin composite particles did not easily move to the surface of the surface coating layer because the evaporation rate of ethylene glycol monobutyl ether was slow.

  On the other hand, when the amount of ethylene glycol monobutyl ether was excessive, the adhesion was low, and the storage stability of the paint was further reduced (Comparative Example 2). If the amount of ethylene glycol monobutyl ether becomes excessive, it is presumed that the synthetic resin particles swell and the coating becomes unstable, the viscosity of the coating increases, and the storage stability of the coating decreases.

  In addition, when ethylene glycol monobutyl ether was replaced with another film-forming auxiliary, the adhesion of the surface coating layer was liable to decrease, and the water contact angle did not increase sufficiently (Comparative Examples 3 to 11). ). It is presumed that the film-forming auxiliary hardly evaporates from the surface coating layer, and the colloidal silica particles or the colloidal silica / resin composite particles did not move sufficiently to the surface of the surface coating layer.

  The surface coating film obtained by the method for producing a decorative building board of the present invention is excellent in water resistance and adhesion to a metal siding substrate, and is also excellent in antifouling properties. Accordingly, the decorative building board can be applied to various buildings.

Claims (5)

A metal siding substrate having a metal plate, a core material, and a back material in this order, and a surface covering layer formed on the metal plate side surface of the metal siding substrate,
After applying a water-based resin emulsion paint containing a film-forming aid, a hydrophilic antifouling component, and synthetic resin particles to the metal plate side surface of the metal siding substrate, the surface is heated to 60 ° C. or higher and 90 ° C. or lower to obtain the surface Forming a coating layer,
The film-forming aid contains ethylene glycol monobutyl ether,
The hydrophilic antifouling component contains colloidal silica particles and / or colloidal silica / resin composite particles,
The amount of the ethylene glycol monobutyl ether, Ri 2 to 10% by mass relative to the total amount of the aqueous resin emulsion paint,
During the heating, hot air with a plate surface wind speed of 4 m / sec or less is blown,
A method for manufacturing a decorative building board. The film-forming aid is at least one alcohol-based organic solvent selected from the group consisting of 1-butoxy-2-propanol, texanol, carbitol, butyl carbitol, tripropylene glycol monomethyl ether, and dipropylene glycol monobutyl ether Further including
The amount of the alcohol-based organic solvent is 4% by mass or less based on the total amount of the water-based resin emulsion paint.
The manufacturing method of the decorative building board of Claim 1. The synthetic resin particles include silicone-modified acrylic resin particles and / or acrylic resin particles.
The manufacturing method of the decorative building board of Claim 1 or 2. The heating time in the step of forming the surface coating layer is 10 minutes or less,
The manufacturing method of the decorative building board as described in any one of Claims 1-3.   The heating temperature in the step of forming the surface coating layer is 80 ° C.
  The manufacturing method of the decorative building board as described in any one of Claims 1-4.