JP6061783B2 - Multi-layer coating film and method for forming multi-layer coating film - Google Patents

Description

  The present invention relates to a multilayer coating film and a method for forming a multilayer coating film.

  Conventionally, from the viewpoint of reducing environmental burden and cost, energy saving is also demanded in buildings such as houses.

  Therefore, in order to reduce the energy consumed in buildings such as houses, it has heat insulation and heat insulation by coating the exterior surface such as the roof and outer wall of the building with heat insulation and heat insulation paint. It is conceivable to form a coating film and suppress an increase in room temperature. As such a heat-insulating or heat-shielding coating film, a heat-insulating undercoat formed by an undercoat material containing a base material layer (A), a binder, and hollow particles sequentially formed on the exterior surface. Particles having a layer (B), a decorative material layer (C) formed by a decorative coating material containing an organic binder and colored particles, and the basic particles covered with infrared reflective powder as colored particles In addition, a heat-insulating and heat-insulating laminate (multilayer coating film) containing particles composed of an aggregate of infrared reflective powder is known (see Patent Document 1).

  Also known is a technique for coating a building with a heat-shielding coating composition comprising a hollow resin in which calcium carbonate and talc are adhered to a shell, hollow glass, cryogenic stone, and a synthetic resin emulsion. (See Patent Document 2).

JP 2009-90527 A JP 2011-79999 A

However, the multilayer coating film of Patent Document 1 has a heat insulating property because it contains hollow particles, and further has a heat insulating property because it also contains an infrared reflective powder, but has a satisfactory heat insulating property and heat insulating property. Is not obtained.
Moreover, since the heat-insulating undercoat layer (B) of the multilayer coating film of patent document 1 mix | blends a hollow particle and infrared reflective powder separately, in order to improve the heat insulation and heat insulation of a coating film. It is necessary to increase the pigment weight content (PWC) of the paint. However, when the PWC of the paint is increased, the coating film tends to be fragile and the water adhesion resistance is also deteriorated.
In addition, in the multilayer coating film of Patent Document 1, since the heat insulating property and the heat shielding property are not sufficient, water vapor from the base material layer (A) is likely to be generated. When water vapor from the base material layer (A) is generated, the water vapor accumulates at the interface between the heat-insulating undercoat layer (B) and the decorative material layer (C), so that the decorative material layer (C) swells. Therefore, the decorative material layer (C) is limited to those having water vapor permeability.

Since the coating film of Patent Document 2 does not contain an infrared reflective powder, sufficient heat insulating properties and heat shielding properties are not obtained.
In addition, the hollow resin having calcium carbonate and talc attached to the shell disclosed in Patent Document 2 has a high specific gravity in order to eliminate the problem that the hollow resin alone has a low specific gravity and is easily scattered during compounding. Or talc is attached to the shell. In Patent Document 2, the shell surface of the hollow resin is not coated for the purpose of improving the heat insulating properties and heat shielding properties of the coating film.

  Thus, it is the present condition that it is a coating film formed on the exterior surface of a building, which has satisfactory heat insulating properties and heat shielding properties, and has good water-resistant adhesion properties.

  The present invention has been made in view of the above, and an object of the present invention is to form a multilayer coating film that is formed on an exterior surface of a building, has both heat insulation and heat shielding properties higher than conventional ones, and has good water resistance. And it is providing the formation method of a multilayer coating film.

  In order to achieve the above object, the present invention provides a multilayer coating film formed on an exterior surface of a building, comprising a base layer (A) and an overcoat layer (A) formed on the base layer (A). B), and the base layer (A) is formed of a base paint, and the base paint contains particles having a hollow portion and a resin, and the particles having the hollow portion are infrared reflective. At least a part of the surface is coated with the powder, and the infrared reflective powder contains a metal oxide having a refractive index of 1.7 to 3.0.

  Moreover, it is preferable that content of the said particle | grain in solid content of the said base coating material is 10-70 mass%.

  Further, the resin contained in the base paint is synthetic resin emulsion particles, the base paint further includes a particle cross-linking agent, and the particle cross-linking agent further includes a particle cross-linking agent that cross-links the synthetic resin emulsion particles. It is preferable.

  The synthetic resin emulsion particles are obtained by polymerizing a monomer mixture containing a ketone group or an aldehyde group-containing acrylic monomer, and the particle cross-linking agent is a compound having two or more hydrazide groups in one molecule. The content of the ketone group or aldehyde group-containing acrylic monomer in the monomer mixture is preferably 0.1 to 30% by mass.

  The synthetic resin emulsion particles are obtained by polymerizing a monomer mixture containing a carboxyl group-containing acrylic monomer, and the particle cross-linking agent is a compound having two or more carbodiimide groups in one molecule, and the monomer It is preferable that content of the said carboxyl group-containing acrylic monomer in a mixture is 0.1-5 mass%.

  The topcoat layer (B) is formed by a topcoat, and the topcoat is substantially free of black pigment and is a coating film formed by the topcoat according to JIS K 5675 7.8 c). The required brightness is preferably 50 or less.

  The top coating material preferably contains a resin and an infrared reflective powder, and the content of the infrared reflective powder in the solid content of the top coating material is preferably 30% by mass or less.

  Moreover, this invention is a formation method of the multilayer coating film which forms a multilayer coating film in the exterior surface of a building, Comprising: The particle | grains which have a hollow part in the exterior surface of the said building, and resin are included. A particle having a hollow portion, which includes a step of forming a base layer (A) by applying a base paint, and a step of forming a top coat layer (B) on the base layer (A). A multilayer coating film characterized in that at least a part of the surface is coated with an infrared reflective powder, and the infrared reflective powder contains a metal oxide having a refractive index of 1.7 to 3.0. A forming method is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the formation method of the multilayer coating film and multilayer coating film which are formed in the exterior surface of a building, have both heat insulation and heat insulation higher than before, and have favorable water-resistant adhesion property can be provided. . In the present invention, the conventional hollow particles and the infrared reflective powder are blended into the base layer of the multilayer coating film by adding particles having a hollow portion at least part of the surface of which is coated with the infrared reflective powder. It is considered that the pigment weight content (PWC) of the coating material can be lowered and the fragility of the coating film is improved, so that the water resistance of the coating film is improved. In the present invention, the particles having hollow portions are coated with at least a part of the surface with the infrared reflecting powder, so that the surface reflectance is increased, and the coating film is formed by blending the infrared reflecting powder alone. It is considered that the heat shielding property of the is improved.

  Hereinafter, embodiments of the present invention will be described in detail.

<Multilayer coating film>
The multilayer coating film which concerns on embodiment of this invention is formed in the exterior surface of a building, and includes the base layer (A) and the overcoat layer (B) formed on the said base layer (A). The base layer (A) is formed of a base paint, and the base paint includes particles having a hollow portion at least a part of the surface of which is coated with an infrared reflective powder, and a resin. The infrared reflective powder in a paint contains a metal oxide having a refractive index of 1.7 to 3.0. The multilayer coating film which concerns on this embodiment is formed in the exterior surface of a building, and has high heat insulation and heat insulation.

  It does not specifically limit as the exterior surface (base material) of the building in which the multilayer coating film which concerns on this embodiment is formed. As a base material with which the multilayer coating film of this embodiment is formed, a metal base material, a plastic base material, an inorganic material base material etc. can be mentioned, for example. Examples of the metal substrate include an aluminum plate, an iron plate, a galvanized steel plate, an aluminum galvanized steel plate, a stainless steel plate, and a tin plate. Examples of the plastic substrate include an acrylic plate, a polyvinyl chloride plate, a polycarbonate plate, an ABS plate, a polyethylene terephthalate plate, and a polyolefin plate. Examples of the inorganic material base material include concrete, mortar, cement board, extrusion-formed board, slate board, PC board, ALC board, ceramic siding material and fiber reinforced cement board described in JIS A 5422, JIS A 5430, and the like. Examples of ceramic building materials and glass base materials. Further, a so-called old paint film may be present on the exterior surface. The multilayer coating film according to the present embodiment is preferably formed on the surface of an inorganic material base material used for exterior walls such as outer walls and roofs of houses and buildings, etc., ceramic building materials, concrete, mortar, ALC, other More preferably, it is formed on the surface of the inorganic building material.

[Base layer (A)]
The base layer (A) is formed on the exterior surface of the building. The base layer (A) is formed of a base paint, and the base paint includes particles having a hollow portion, at least a part of the surface of which is coated with an infrared reflective powder, and a resin.

  Particles having a hollow portion covered with at least a part of the surface thereof with an infrared reflective powder (hereinafter sometimes referred to as “infrared reflective particles”) contained in the base coating are one or more particles in the particles. A particle having a hollow portion. The infrared reflective powder contains a metal oxide having a refractive index of 1.7 to 3.0. Examples of the metal oxide of 1.7 to 3.0 include titanium dioxide (refractive index: 2.76), zinc oxide (refractive index: 1.95), magnesium oxide (refractive index: 1.72), zirconium oxide ( Examples include refractive index: 2.76), yttrium oxide (refractive index: 1.82), and alumina (refractive index: 1.76). When the refractive index of the metal oxide contained in the infrared reflective powder is less than 1.7, the infrared diffused reflection in the base layer (A) tends to be insufficient, and the desired heat shielding function cannot be obtained. When the refractive index is larger than 3.0, a non-white metal oxide such as a petal or vermilion is contained, and therefore, when a white top coat is applied, there is a risk of causing a decrease in design properties due to see-through. . The metal oxide of the infrared reflective powder is preferably titanium dioxide. When the infrared reflective powder contains titanium dioxide, the multilayer coating film exhibits high heat shielding performance. The refractive index of calcium carbonate is 1.57, and the refractive index of talc is 1.59.

  The infrared reflective particles may be those in which at least a part of the surface of particles made of an organic substance or an inorganic substance having a hollow portion is coated with an infrared reflective powder, or formed by the infrared reflective powder itself. The particle | grains which have a hollow part may be sufficient.

  Infrared reflective particles made of an organic material are produced, for example, as follows. First, a shell made of vinyl chloride resin, vinyl alcohol resin, acrylic resin, or the like is encapsulated with a liquid that becomes a gas at or below the softening temperature of the shell. Next, in the hollow resin in which the shell is heated and expanded by heating to a temperature higher than the softening temperature of the shell, titanium dioxide, which is one of infrared reflective powders, is applied to the shell surface while the shell is heated and softened. By making it adhere, infrared reflective particles made of an organic substance can be obtained (see, for example, JP-A No. 05-285376). Infrared reflective particles made of an inorganic material are produced, for example, as follows. First, an inorganic fine hollow body made of a glassy raw material is heated and softened. Next, in the state that the inorganic micro hollow body is softened, the titanium dioxide, which is one of the infrared reflecting powders, is adhered to the surface to obtain the infrared reflecting particles made of an inorganic substance (for example, Japanese Patent Laid-Open No. 10-101). No. 25139).

  The base layer (A) exhibits both high heat insulating properties and heat shielding properties by including particles having a hollow portion at least part of the surface of which is coated with an infrared reflective powder as described above. Specifically, the air in the hollow of the particle gives heat insulation to the base layer (A), and the infrared reflecting powder (metal oxide) on the particle surface diffuses and reflects infrared rays to the base layer (A). Gives heat insulation. Here, in the present embodiment, the base layer (A) including hollow particles having a metal oxide having a refractive index of 1.7 to 3.0 on the surface has the metal oxide and the hollow particles separately in the coating film. Compared with the case where it exists, the infrared rays are diffusely reflected. The reason is not necessarily clear, but the diffuse reflection of infrared rays is caused by the fact that an air layer and a resin layer having different refractive indexes are adjacent to each other through a metal oxide having a refractive index of 1.7 to 3.0. Expected to be amplified.

  The average particle diameter of the infrared reflective particles is preferably 0.1 to 300 μm. When the average particle diameter of the infrared reflective particles is less than 0.1 μm, the heat shielding property of the multilayer coating film tends to be lowered. In addition, if the average particle diameter of the infrared reflective particles is larger than 300 μm, the hollow part is ruptured when adjusting the base paint and the heat insulating property tends not to be exhibited, and the infrared reflective particles are not sufficiently covered with the resin. There exists also a tendency for the intensity | strength of a coating film to fall. In addition, the average particle diameter of infrared reflective particles is a laser diffraction type particle size distribution measuring apparatus (for example, Horiba, Ltd.) having the measurement principle [light scattering method (25 ° C.)] described in JIS Z 8825-1: 2001. Manufactured by LA-920, Shimadzu Corporation SALD-1100, etc.).

The content of the infrared reflective particles in the solid content of the base paint is preferably 10 to 70% by mass. When the content of the particles in the solid content of the base coating is less than 10% by mass, the heat insulating property and heat shielding property of the coating film tend to be reduced. When the content is more than 70% by mass, the base layer (A) When the hollow part in the inside increases, the strength of the coating film tends to decrease.
The content of the particles is more preferably 20 to 50% by mass.

  The resin contained in the base paint is not particularly limited. The resin contained in the base paint is synthetic resin emulsion particles, and the base paint preferably further includes a particle cross-linking agent that cross-links the synthetic resin emulsion particles. When the base paint contains the synthetic resin emulsion particles and the particle cross-linking agent, they can be cross-linked at room temperature to form a strong coating film when forming the base layer (A).

  The synthetic resin emulsion particles are obtained by polymerizing a monomer mixture containing a ketone group or aldehyde group-containing acrylic monomer, and the particle crosslinking agent preferably contains a compound having two or more hydrazide groups in one molecule. . By adopting such a combination of synthetic resin emulsion particles and particle cross-linking agent, ketone groups and aldehyde groups react with hydrazide groups at room temperature, and a cross-linked structure is formed between synthetic resin emulsion particles. A smooth coating film can be formed.

  Specific examples of the above ketone group or aldehyde group-containing acrylic monomer include acrolein, diacetone (meth) acrylamide, formylstyrene, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone). Vinyl butyl ketone), acetoacetoxyethyl methacrylate, and the like. Of these, diacetone (meth) acrylamide is preferably used because the resulting synthetic resin emulsion particles are highly reactive with the particle crosslinking agent.

  As described above, when the base paint includes synthetic resin emulsion particles obtained by polymerizing a monomer mixture containing a ketone group or aldehyde group-containing acrylic monomer, the content of the ketone group or aldehyde group-containing acrylic monomer in the monomer mixture Is preferably 0.1 to 30% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1 to 10% by mass. When the content of the ketone group or aldehyde group-containing acrylic monomer in the monomer mixture is less than 0.1% by mass, the strength of the coating film tends to decrease due to insufficient degree of crosslinking, and 30% by mass. If it is more than%, the physical properties of the coating film may be adversely affected.

  Further, a synthetic resin emulsion particle obtained by polymerizing a monomer mixture containing a carboxyl group-containing acrylic monomer and a particle cross-linking agent containing a compound having two or more carbodiimide groups in one molecule. It is also preferable to include. By adopting such a combination of synthetic resin emulsion particles and particle cross-linking agent, the carboxyl group reacts with the carbodiimide group at room temperature, and a cross-linked structure is formed between the synthetic resin emulsion particles. Can be formed.

  Specific examples of the carboxyl group-containing acrylic monomer include (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid and the like. Of these, it is preferable to use (meth) acrylic acid because the resulting synthetic resin emulsion particles are highly reactive with the particle crosslinking agent.

  As described above, when the base paint includes synthetic resin emulsion particles obtained by polymerizing a monomer mixture containing a carboxyl group-containing acrylic monomer, the content of the carboxyl group-containing acrylic monomer in the monomer mixture is from 0.1 to 0.1%. It is preferably 5% by mass, and more preferably 0.1 to 3% by mass. When the content of the ketone group or aldehyde group-containing acrylic monomer in the monomer mixture is less than 0.1% by mass, the stability of the emulsion particles tends to decrease, and when the content is more than 5% by mass, it is formed. The water resistance of the coating film tends to decrease.

  In addition to the above-mentioned ketone group or aldehyde group-containing acrylic monomer and carboxyl group-containing acrylic monomer, the monomer mixture used as a raw material for the synthetic resin emulsion particles may contain any monomer component. Optional monomer components include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) having a hydroxyl group M90G, M230G (both manufactured by Shin-Nakamura Chemical Co., Ltd.), Bremer AE-350, having polyalkylene oxide units, such as (meth) acrylamide, having an amide group, such as acrylate, Renma PE-90, Blemmer PE-200, Blemmer PE-350 (all manufactured by NOF Corporation) and the like. These monomer components may be used in combination of two or more monomers.

  The synthetic resin emulsion particles in the present embodiment can be obtained by emulsion polymerization of a ketone group or aldehyde group-containing acrylic monomer, a carboxyl group-containing acrylic monomer, and other monomer components. The method of emulsion polymerization for obtaining a synthetic resin emulsion is not particularly limited, and methods generally known to those skilled in the art can be used.

  The glass transition temperature (Tg) of the resin of the synthetic resin emulsion particles in this embodiment is preferably -20 ° C to 50 ° C. When the glass transition temperature (Tg) of the synthetic resin emulsion particles is lower than -20 ° C, the coating film is softened by heat generated by sunlight or the like when it is applied to the exterior surface of the building, and sufficient coating film strength is obtained. However, when the temperature is higher than 50 ° C., the flexibility of the coating film is insufficient and the coating film tends to be cracked. In addition, Tg of the polymer which consists of n types of monomers can be calculated | required by FOX formula (following formula (1)). In the following formula (1), the glass transition temperature of the homopolymer of each monomer constituting the polymer composed of n types of monomers is Tgi (° C.), and the mass fraction of each monomer is Wi. That is, the relationship of W1 + W2 + ... + Wi + ... Wn = 1 holds.

  As a compound (particle cross-linking agent) having two or more hydrazide groups in one molecule used together with synthetic resin emulsion particles obtained by polymerizing a monomer mixture containing a ketone group or aldehyde group-containing acrylic monomer. Oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanoic acid dihydrazide, carbonic acid dihydrazide, phthalic acid dihydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide 20 Polyhydrazide of polyacrylic acid having -100 hydrazide groups, nitrilotriacetic acid trihydrazide, ethylenediaminetetraacetic acid tetrahydrazide, ditrihydrazine-triazine, Lihydrazine-triazine, thiocarbohydrazide, N, N′-diaminoguanidine, 2-hydrazinopyridine-5-carboxylic acid hydrazide, 3-chloro-2-hydrazinopyridine-5-carboxylic acid hydrazide, 6-chloro-2 -Hydrazinopyridine-4-carboxylic acid hydrazide, 2,5-dihydrazinopyridine-4-carboxylic acid, 1,4-dihydrazinobenzol, 1,3-dihydrazinobenzol, 2,3-dihydrazine naphthalene Maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin and the like. Among these, it is preferable to use adipic acid dihydrazide from the viewpoint of availability and 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin from the viewpoint of high water solubility.

  As a compound (particle crosslinking agent) having two or more carbodiimide groups in one molecule used together with the synthetic resin emulsion particles obtained by polymerizing the monomer mixture containing the carboxyl group-containing acrylic monomer, The modified polycarbodiimide compound to be described is mentioned. The modified polycarbodiimide compound has a polyalkylene oxide unit having at least two carbodiimide groups in one molecule and blocked at one end with a monoalkoxy group having 4 or more carbon atoms. The amount of the carbodiimide group contained in one molecule of the modified polycarbodiimide compound is at least 2, and is preferably 20 or less in view of reaction efficiency. Specific examples of compounds having two or more carbodiimide groups in one molecule include carbodilite V-02-L2 (polyvalent carbodiimide, manufactured by Nisshinbo Chemical Co., Ltd.), carbodilite E-01 (multivalent carbodiimide, Nisshinbo Chemical Co., Ltd.) Company-made).

  Examples of the combination of the synthetic resin emulsion particles used when forming the base layer (A) and the crosslinking reactive groups of the particle crosslinking agent include the combinations of ketone groups or aldehyde groups and hydrazide groups, carboxyl groups and carbodiimide groups mentioned above. In addition, an epoxy group and an amino group, an epoxy group and a carboxyl group, a carboxyl group and an aziridine group, a carboxyl group and an oxazoline group, an alkoxyl group, and the like can be given. In addition, you may use the substance which produces | generates a metal ion as a particle | grain crosslinking agent used with respect to the synthetic resin emulsion particle | grains which have a carboxyl group. In this case, the carboxyl group of the synthetic resin emulsion particles is coordinated to the metal ion, so that a crosslinked structure is generated.

[Overcoat layer (B)]
The topcoat layer (B) is formed on the base layer (A). The topcoat layer (B) preferably absorbs or transmits infrared rays without absorbing infrared rays as much as possible. If the top coating layer (B) reflects a large amount of infrared rays, the entire multi-layer coating film exhibits high heat shielding properties. Further, even if the overcoat layer (B) does not reflect infrared rays so much, the base layer (A) containing the infrared reflective particles reflects a large amount of infrared rays as long as it transmits infrared rays, and The heat storage due to infrared absorption of the top coat layer (B) can be reduced. Even in this case, high thermal barrier properties can be exhibited as a whole multilayer coating film.

The topcoat layer (B) is formed by a topcoat paint. The top coat is not particularly limited.
Carbon black can be included as a black pigment in the top coat, but heat-shielding black pigment is used instead of carbon black as a method of adjusting any hue without containing carbon black in the top coat. And a method for toning. Examples of the heat shielding black pigment include composite metal oxides such as iron chromium and bismuth manganese, and organic black pigments such as perylene black pigments and azomethiazo pigments. All of these have almost no reflection in the visible light wavelength region of 350 nm to less than 780 nm, and are nearly black, that is, the brightness defined by JIS K 5675 7.8 c) is less than 30, but the near infrared wavelength region of 780 nm to 2500 nm In infrared rays, infrared rays are reflected or transmitted, and the amount of infrared rays absorbed is reduced as compared with carbon black.

In addition, as a method for toning an arbitrary hue, a method for toning by subtractive color mixing using a plurality of coloring pigments may be used.
As a method of subtractive color mixing using a plurality of colored pigments, one or two from a colored pigment group consisting of a red pigment, a yellow pigment, an orange pigment, a blue pigment, a green pigment, a purple pigment, etc. There is a method of toning using the above pigment and titanium dioxide which is an infrared reflective powder.

As described above, the top coating material in the present embodiment can contain various pigments, but it is preferable that the top coating material contains substantially no black pigment. Examples of the black pigment include carbon black and the above heat-shielding black pigment. Absorption of infrared rays in the coating film (the top coating layer (B)) can be suppressed by not using a black pigment as the pigment type to be blended in the top coating material. By suppressing the absorption of infrared rays in the topcoat layer (B), most of the infrared rays irradiated to the topcoat layer (B) are reflected on the surface of the topcoat layer (B) or the topcoat layer (B) Since it is transmitted and reflected at the base layer (A), heat storage by infrared absorption of the top coating layer (B) is reduced, and the heat shielding property as the whole multilayer coating film is also improved.
“Substantially no black pigment” is not intended to exclude the inclusion of a small amount of black pigment. Specifically, the black pigment content in the solid content of the top coat is preferably less than 3.0% by mass.

  Here, the inorganic color pigment generally has a higher infrared reflectance in the near-infrared wavelength region of 780 nm to 2500 nm than the organic color pigment, but also exhibits some infrared absorption. On the other hand, organic color pigments have a low infrared reflectance, but also have a smaller infrared absorption and a greater infrared transmission. Therefore, if the overcoat layer is toned by subtractive color mixture (hereinafter referred to as “organic subtractive color mixture”) that selectively uses organic pigments as the color pigment, more infrared rays are transmitted through the overcoat layer. Since it is reflected by the layer, it is possible to increase the solar reflectance as a multilayer coating film.

  As described above, since the top coating is not particularly limited, the brightness of the coating film formed by the top coating is not limited, but the brightness of the coating formed by the top coating layer (B) may be 50 or less. preferable. Here, “brightness” is determined according to JIS K 5675 7.8 c). When the brightness of the topcoat layer (B) is 50 or less, the amount of titanium dioxide, which is an infrared reflective powder blended in the topcoat layer (B), decreases. In this case, the reflective performance of the base layer (A) is effectively exhibited by organic subtractive color mixing without using a black pigment, and color matching using an inorganic color pigment or color matching using an alternative black pigment is performed. It is possible to increase the solar reflectance as a multilayer coating film.

  Examples of the red pigment used in the top coating material in the present embodiment include Color Index Pigment Number (hereinafter referred to as “CI No.”) of The Society of Dyer and Colorists. Pigment Red (hereinafter referred to as “PR”) 3, PR5, PR48, PR58, PR63, PR88, PR112, PR122, PR123, PR144, PR146, PR149, PR168, PR170, PR171, PR175, PR177, PR179, PR189, PR190, PR194, PR202, PR207, PR209, PR214, PR216, PR224, PR255, PR242, PR254, PR260, PR264, etc. It is.

  Examples of the orange pigment used in the top coat in the present embodiment include C.I. I. No. Pigment Orange (hereinafter referred to as “PO”) 5, PO13, PO16, PO34, PO36, PO38, PO43, PO60, PO62, PO64, PO65, PO69, PO73, and the like.

  Examples of yellow pigments used in the top coat in this embodiment include C.I. I. No. Pigment Yellow (hereinafter referred to as “PY”) 1, PY3, PY12, PY13, PY14, PY16, PY17, PY55, PY73, PY74, PY81, PY83, PY93, PY95, PY97, PY98, PY108, PY109 , PY110, PY116, PY117, PY120, PY127, PY128, PY129, PY130, PY137, PY138, PY139, PY147, PY150, PY151, PY153, PY154, PY155, PY165, PY168, PY173, PY173, PY173, PY173, PY173, PY173, PY173, PY173 , PY184 and the like.

  Examples of the green pigment used in the top coat in this embodiment include C.I. I. No. Pigment Green (hereinafter referred to as “PG”) 7, PG8, PG10, PG36, etc.

  Examples of the blue pigment used in the top coat in this embodiment include C.I. I. No. Pigment Blue (hereinafter referred to as PB) 15: 1, PB15: 2, PB15: 3, PB15: 4, PB15: 6, PB60, PB75, PB76, PB80, and the like.

  Examples of purple pigments used in the top coat in this embodiment include C.I. I. No. Pigment Violet (hereinafter referred to as PV) 19, PV23, PV27, PV29 and the like classified by.

  The total amount of pigments used in the top coating composition in this embodiment is preferably 2 to 70% by mass in the solid content of the top coating composition. When the total of the pigments used in the top coating is less than 2% by mass in the solid content of the top coating, the coloring power is reduced and the film thickness necessary for obtaining the target color is increased. Further, when the total amount of pigments used in the top coating exceeds 70% by mass in the solid content of the top coating, the weather resistance tends to deteriorate.

  In addition to the pigment, the top coating material in the present embodiment includes a resin component in the vehicle and other additives added as necessary, as a solid component.

  Moreover, it is preferable that top coat paint contains resin and infrared reflective powder. Since the top coating material contains the infrared reflective powder together with the resin, the top coating layer (B) also has a heat shielding property in addition to the base layer (A), so that the heat shielding property of the entire multilayer coating film is also improved. The infrared reflective powder contained in the top coat contains a metal oxide. The metal oxide contained in the infrared reflective powder of the top coat is the same as the metal oxide contained in the infrared reflective powder of the base paint.

  Further, even when the top coat contains an infrared reflective powder together with the resin, the content of the infrared reflective powder in the solid content of the top coat is preferably 30% by mass or less, and 20% by mass. The following is more preferable. When the content of the infrared reflective powder in the solid content of the top coating is more than 30% by mass, the weather resistance tends to be deteriorated.

<Formation method of multilayer coating film>
It is the formation method of the multilayer coating film which concerns on this embodiment, and the method of forming the multilayer coating film which concerns on the said embodiment. That is, the method for forming a multilayer coating film according to the present embodiment includes a particle having a hollow portion at least a part of the surface of which is coated with an infrared reflective powder on the exterior surface of a building, and a resin. A step of forming a base layer (A) by applying a base paint; and a step of forming a top coat layer (B) on the base layer (A), wherein the infrared reflectivity in the base paint The powder is characterized by containing a metal oxide having a refractive index of 1.7 to 3.0.

  The method for forming the base layer (A) and the top coat layer (B) of the multilayer coating film according to the present embodiment (a method for applying the base paint and the top coat) is not particularly limited, and for example, dipping, brush, roller Examples of commonly used coating methods include roll coaters, air sprays, airless sprays, curtain flow coaters, roller curtain coaters, and die coaters. These coating methods can be appropriately selected depending on the object to be coated and the application.

The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, an intermediate coating layer may be formed between the base layer (A) and the top coating layer (B) in the above embodiment. In addition, after forming the base layer (A), an intermediate coating layer and a top coating layer (B) having different hues may be formed to form a tile-like coating film having different joints and top coating colors. Further, a clear layer may be formed on the top coat layer (B).

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” are all based on mass.

[Preparation of synthetic resin emulsions 1-3]
Preparation Example 1
In a beaker, 45 parts by weight of deionized water, 2 parts by weight of Aqualon HS-10 (Reactive emulsifier, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 30 parts by weight of styrene, 25 parts by weight of methyl methacrylate, 2 parts by weight of n-butyl acrylate, 2- 20 parts by mass of ethylhexyl acrylate, 3 parts by mass of diacetone acrylamide, and 2 parts by mass of acrylic acid were added and stirred to obtain an emulsion. Separately, 60 parts by mass of deionized water and 0.4 part by mass of Aqualon HS-10 were charged in a reaction vessel equipped with a stirrer, a cooling tube, a dropping funnel and a thermometer, and the temperature was raised to 80 ° C. The product was added dropwise over 3 hours, and at the same time, 20 parts by mass of a 10% aqueous solution of ammonium persulfate was added dropwise. After completion of the dropping, the temperature was kept at 80 ° C. for 2 hours, and then the reaction solution was cooled to room temperature, and then 10% ammonia water was added to adjust the pH to 8. Subsequently, the synthetic resin emulsion 1 was prepared by filtering with a 200 mesh metal-mesh. The solid content NV in the synthetic resin emulsion 1 was 45%.

Preparation Example 2
A synthetic resin emulsion 2 was prepared in the same manner as in Preparation Example 1 except that the amount of each monomer in the emulsion was changed as shown in Table 1. The solid content NV in the synthetic resin emulsion 2 was 45%.

Preparation Example 3
50 parts by mass of deionized water and 0.5 part by mass of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive emulsifier were placed in a reaction vessel, and the temperature of the contents was 85 ° C. Among them, pre-emulsification comprising 20 parts by mass of styrene, 45 parts by mass of n-butyl acrylate, 5 parts by mass of glycidyl methacrylate, 40 parts by mass of deionized water and 1 part by mass of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.). The core part was prepared by dripping the liquid and the polymerization initiator aqueous solution which consists of 0.1 mass part of ammonium persulfate and 10 mass parts of deionized water as a water-soluble polymerization initiator in 2 hours. During the emulsion polymerization, the pH of the polymerization reaction solution was kept at 3.0. Thereafter, pre-emulsification comprising 10 parts by mass of styrene, 17 parts by mass of n-butyl acrylate, 3 parts by mass of methacrylic acid, 20 parts by mass of deionized water and 0.3 part by mass of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.). A liquid and a polymerization initiator aqueous solution consisting of 0.2 parts by mass of ammonium persulfate and 10 parts by mass of deionized water were dropped in 2 hours, and stirring was continued for 3 hours to prepare a shell part. Subsequently, the temperature of the reaction solution was cooled to 30 ° C., and 10% aqueous ammonia was added to adjust the pH to 8. Subsequently, the synthetic resin emulsion 3 was prepared by filtering with a 200 mesh metal-mesh. The solid content NV of the synthetic resin emulsion 3 was 44%.

  “Tg of synthetic resin emulsion” in Table 1 is a theoretical value obtained from the above-mentioned FOX equation from the glass transition temperature of the homopolymer of each monomer constituting the synthetic resin emulsion particles constituting the synthetic resin emulsion and the blending amount of each monomer. The glass transition temperature of

[Preparation of base paints 1-8 and intermediate paint 1]
With respect to the synthetic resin emulsion particles obtained by the above preparation examples, the infrared reflective particles, hollow particles, titanium dioxide as the infrared reflective powder, and the particle crosslinking agent in the amount shown in Table 2 (unit is “part by mass”) The base coating materials 1 to 8 and the intermediate coating material 1 were prepared by mixing and stirring uniformly.

As the hollow particles and particle crosslinking agents 1 and 2 shown in Table 2, the following hollow particles and particle crosslinking agents were used.
Hollow particles: closed cell hollow resin particles (acrylic-acrylonitrile copolymer resin, average particle diameter 45 μm, density 0.025 g / cm ³ )
Particle cross-linking agent 1: Adipic acid dihydrazide particle cross-linking agent 2: Carbodilite V-02-L2 (multivalent carbodiimide, manufactured by Nisshinbo Chemical Co., Ltd.)

  The infrared reflective particles shown in Table 2 were prepared as follows.

Infrared reflective particles 1
After uniformly mixing 340 parts by weight of deionized water, 10 parts by weight of a 10% adipic acid-diethanolamine condensate aqueous solution and 110 parts by weight of sodium chloride, 5.0 mmol parts of glycidyl methacrylate (GMA) (0.7 parts by weight) Parts), 1526 mmol parts (80.9 parts by mass) of acrylonitrile, 5.0 mmol parts (0.7 parts by mass) of hydroxyethyl methacrylate, 2.0 mmol parts (0.4 parts by mass) of ethylene glycol dimethacrylate, methacrylic acid A solution composed of 200 mmol parts of methyl (20 parts by weight), 20 parts by weight of n-pentane and 0.5 parts by weight of azobisisobutyronitrile was added, and a homomixer (manufactured by Special Machinery Co., Ltd., ROBOMICS, 4000 rpm) was used. Stir for 1 minute to obtain a suspension. The suspension was transferred to a pressure-resistant reaction vessel, polymerized at a gauge pressure of 0.3 MPa and 60 ° C. for 20 hours, and a volatile expansion agent (n-pentane) that became a gas at a temperature not higher than the softening temperature (160 ° C.) of the copolymerized resin. ) Was obtained. Next, the polymerization solution was filtered and dried at 30 ° C. for 3 hours to obtain thermally expandable resin particles (microcapsules). The shell is heated and expanded by heating the thermally expandable resin particles (microcapsules) at 160 ° C. for 3 minutes using a forward air dryer to form hollow particles (closed-cell type hollow resin particles: acrylic-acrylonitrile copolymer resin). ) Was formed. Subsequently, in the state where the heated and expanded hollow particles are softened, titanium dioxide (refractive index: 2.76) is attached to the surface of the hollow resin to obtain infrared reflective particles 1. The average particle diameter of the infrared reflective particles 1 is 51.1 μm.

Infrared reflective particles 2
Infrared reflective particles 2 were obtained by attaching titanium dioxide (refractive index: 2.76) to the surface in a state where an inorganic micro hollow body (shirasu balloon) made of a glassy raw material was heated to 1000 ° C. and softened. . The average particle diameter of the infrared reflective particles 2 is 42 μm.

  In addition, the average particle diameter of the hollow particle described in Table 2 and the infrared reflective particles 1 and 2 is a volume average particle diameter measured by Shimadzu Corporation SALD-1100 type.

[Top coat]
As the top coating, the following top coating was used. In addition, the value of the brightness of each coating film was measured according to JIS K 5675 7.8 c).
Topcoat 1: Thermo Eye 4F Cool Black (manufactured by Nippon Paint Co., Ltd., brightness: 10, content of infrared reflective powder in paint solids: 0% by mass, substantially free of black pigment)
Top coat 2: Thermo Eye 4F Neo Sapphire Blue (Nippon Paint Co., Ltd., brightness: 42, content of infrared reflective powder in paint solids: 30% by mass, substantially free of black pigment)
Top coating 3: Fine 4F Best Black (Nippon Paint Co., Ltd., brightness: 9, content of infrared reflective powder in paint solids: 0% by mass, including black pigment)

<Example 1>
The base paint 1 is uniformly applied to the slate plate to a dry film thickness of 500 μm, dried for 24 hours in an atmosphere of 23 ° C. and relative humidity 50% RH, and then the top coat 1 is applied to a dry film thickness of 50 μm. A test plate was obtained by curing for 10 days in an atmosphere of 23 ° C. and 50% RH.

<Examples 2 to 8 and Comparative Examples 1 and 2 >
A test plate was obtained in the same manner as in Example 1 except that the base paint and the top coat were changed to those shown in Table 3.

<Example 9 >
Apply the base paint in the same manner as in Example 1, and after drying, apply the intermediate coating 1 to a dry film thickness of 50 μm, dry it in an atmosphere of 23 ° C. and 50% RH for 24 hours, and then apply the top coating. A test plate was obtained in the same manner as in Example 1 except that.

<Measurement of near-infrared solar reflectance of multi-layer coating film>
Instead of the slate plate, an evaluation plate was obtained on the black and white concealment rate paper in the same coating process as the test plate obtained in the examples and comparative examples. The evaluation plates obtained in the same coating process as the test plates obtained in Examples 1 to 9 and Comparative Examples 1 and 2 were used as the evaluation plates of Examples 1 to 9 and Comparative Examples 1 and 2 , respectively. For the evaluation plates of Examples 1 to 9 and Comparative Examples 1 and 2 , near infrared solar radiation reflectance was measured according to JIS K 5675 (high solar reflectance paint for roofs). The results are shown in Table 3. The results in Table 3 are based on the following criteria.
A: Reflectance of 50% or more B: Reflectance of 40% or more and less than 50% C: Reflectance of 20% or more and less than 40% D: Reflectance of less than 20%

<Evaluation of water resistance>
The test plates obtained in the examples and comparative examples were cut out to 70 mm × 150 mm, immersed in water that was left still for a day or more, and left in a test room at 23 ° C. and a relative humidity of 50% RH for one week. Thereafter, the moisture is wiped off, a 25 mm square cut is made on the test plate, a transparent pressure-sensitive adhesive tape described in JIS K 5600-5, -6 is applied to the test plate, and then the adhesive is removed by peeling. evaluated. In the 25th square of the test plate, the number of squares remaining without being peeled off by the transparent pressure-sensitive adhesive tape was evaluated according to the following criteria. The results are shown in Table 3.
A: 25 squares B: 22-24 squares C: 20-21 squares D: Less than 20 squares

As is apparent from Table 3, the infrared ray reflective powder (titanium dioxide, refractive index: 2) includes a base layer (A) and an overcoat layer (B) formed on the base layer (A). .76) a multilayer coating film in which a base layer is formed by a base coating material including a particle having a hollow portion coated at least a part of the surface and a resin, and an overcoat layer is formed thereon. Infrared solar reflectance is high and water-resistant adhesion tends to be good. Further, the multilayer coating film of Example 1 has higher near-infrared solar reflectance than the multilayer coating film of Comparative Example 2 . From this result, it was shown that the effect of reflecting the infrared rays of the base layer formed by the base coating material including the infrared reflective particles is more strongly exhibited when the top coating material contains substantially no black pigment.

Claims (7)

A multilayer coating film formed on the exterior surface of a building,
A base layer (A) and an overcoat layer (B) formed on the base layer (A),
The base layer (A) is formed of a base paint,
The base paint includes particles having a hollow portion and a resin,
The particles having the hollow part are at least partly coated with an infrared reflective powder,
The infrared reflective powder contains a metal oxide having a refractive index of 1.7 to 3.0 ,
The top coat layer (B) is formed of a top coat paint,
The top coat is substantially free of black pigment.
A multi-layer coating film characterized by having a lightness determined by JIS K 5675 7.8 c) of a coating film formed by the top coating composition of 50 or less .   2. The multilayer coating film according to claim 1, wherein the content of the particles in the solid content of the base coating is 10 to 70% by mass. The resin contained in the base paint is synthetic resin emulsion particles,
The base paint further includes a particle cross-linking agent,
The multilayer coating film according to claim 1 or 2, wherein the particle crosslinking agent crosslinks the synthetic resin emulsion particles. The synthetic resin emulsion particles are obtained by polymerizing a monomer mixture containing a ketone group or an aldehyde group-containing acrylic monomer,
The particle crosslinking agent is a compound having two or more hydrazide groups in one molecule,
The multilayer coating film according to claim 3, wherein the content of the ketone group or aldehyde group-containing acrylic monomer in the monomer mixture is 0.1 to 30% by mass. The synthetic resin emulsion particles are obtained by polymerizing a monomer mixture containing a carboxyl group-containing acrylic monomer,
The particle crosslinking agent is a compound having two or more carbodiimide groups in one molecule,
The multilayer coating film according to claim 3, wherein the content of the carboxyl group-containing acrylic monomer in the monomer mixture is 0.1 to 5% by mass. The top coating includes a resin and an infrared reflective powder,
The multilayer coating film according to claim 5 , wherein the content of the infrared reflective powder in the solid content of the top coating is 30% by mass or less. It is a method of forming a multilayer coating film that forms a multilayer coating film on the exterior surface of a building,
Forming a base layer (A) by coating a base paint containing particles having hollow portions and a resin on the exterior surface of the building; and
Forming a top coat layer (B) on the base layer (A),
The particles having the hollow part are at least partly coated with an infrared reflective powder,
The infrared reflective powder contains a metal oxide having a refractive index of 1.7 to 3.0 ,
The top coat layer (B) is formed of a top coat paint,
The top coat is substantially free of black pigment.
A method for forming a multilayer coating film, wherein the coating film formed by the top coating has a brightness determined by JIS K 5675 7.8 c) of 50 or less .