Multilayer coating film and method for producing the same

Abstract

To provide a multilayer coating film capable of retaining heat-shielding performance for an extended period.SOLUTION: A multilayer coating film includes a substrate, a heat-shielding layer, and a protective layer in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-layer coating film and a method for producing the same. [Background technology]

[0002] The size of the domestic paint market is estimated to be approximately 600 billion yen per year. Of this, architectural paints are the largest at 150 billion yen per year, and within that, the non-residential renovation market, a business category, is a huge market at 45 billion yen per year. Non-residential renovation here refers to renovations of factories, warehouses, buildings, etc. other than homes.

[0003] Galvalume, a zinc-aluminum alloy plated steel sheet, is often used for the roofs of factories and warehouses. These have high thermal conductivity, and in summer the surface temperature rises to nearly 80°C, raising the temperature inside the factory that is in direct contact with the metal roof. Although it is possible to regulate the temperature inside the factory or warehouse using air conditioners, there is a demand for technology that can keep the temperature inside comfortable while suppressing CO2 emissions. One solution is to paint the roof with a heat-insulating paint that contains metal oxides such as titanium oxide and nickel oxide (Patent Documents 1 and 2). Furthermore, in order to maintain the heat-insulating function for a long period of time, heat-insulating paints based on highly weather-resistant paints such as silicon-based paints and fluorine-based paints have been introduced to the market.

[0004] However, due to their nature, the heat-shielding paints described in Patent Documents 1 and 2 have been thought to need to be applied to the outermost surface of the coated object that is exposed to sunlight. Therefore, the period during which the heat-shielding function is exhibited depends on the durability of the coating film, and the heat-shielding function tends to deteriorate in a relatively short period of time. In addition, on the roofs of factories and warehouses, which are relatively flat, pollutants such as automobile exhaust gas suspended in the air accumulate, which increases the absorption rate of near-infrared rays in sunlight and makes the heat-shielding function prone to deterioration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 59-31545 [Patent Document 2] Patent No. 2593968 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a multi-layer coating film capable of maintaining heat-shielding performance for a long period of time. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by examining the layer structure and functions of the coating film, and have thus completed the present invention.

[0008] That is, the present invention includes the following aspects. <1> A multi-layer coating film comprising a substrate, a thermal barrier layer, and a protective layer in this order. <2> Item 2. The multilayer coating film according to item 1, wherein the heat shielding layer is substantially free of an ultraviolet absorbing material. <3> Item 3. The multilayer coating film according to item 1 or 2, wherein the protective layer is made of a polyurea resin. <4> Item 3. The multilayer coating film according to item 1 or 2, wherein the substrate is made of metal. <5> Item 3. A method for producing a multilayer coating film according to item 1 or 2, comprising the steps of forming a heat shielding layer on a substrate and forming a protective layer on the heat shielding layer. <6> Item 6. The method for producing a multilayer coating film according to item 5, wherein in the step of forming a protective layer on the heat shielding layer, a coating composition for forming a polyurea is applied onto the heat shielding layer and cured to form a protective layer made of a polyurea resin. <7> Item 7. The method for producing a multilayer coating film according to item 6, wherein the coating composition for forming a polyurea is a one-component type. Effect of the Invention

[0009] The multi-layer coating film of the present invention can maintain its heat-shielding performance for a long period of time. [Brief description of the drawings]

[0010] [Figure 1] 1 shows one embodiment of the multi-layer coating film of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <<Multi-layer coating>> The multilayer coating film of the present invention is characterized by comprising a substrate, a heat-shielding layer, and a protective layer in this order. In the present invention, the heat-shielding layer is substantially free of ultraviolet absorbing materials such as carbon black, and when applied over a wide area, has a heat-shielding function of lowering the surface temperature of the substrate. By providing such a heat-shielding layer, sufficient heat-shielding performance can be obtained without using a coating film with a heat-shielding function on the outermost exterior part. By forming a protective layer on this heat-shielding layer, it is possible to maintain the heat-shielding function for a long period of time. The multilayer coating film is produced by a method including a step of forming a heat-shielding layer on the substrate, and a step of forming a protective layer on the heat-shielding layer.

[0012] <Base material> The substrate is not particularly limited as long as it is used as a building material, and examples thereof include metal materials such as galvalume steel plate, zinc-plated steel plate, tinplate steel plate, aluminum, and stainless steel plate, inorganic materials such as concrete, calcium silicate plate, ALC plate, gypsum board, and slate plate, fiber materials such as glass wool, rock wool, and cellulose fiber, resin materials such as polyethylene foam, polystyrene foam, polyurethane foam, and polyvinyl chloride, wood materials, and any combinations thereof. Among these, metal materials that particularly require heat-shielding performance are preferred, and galvalume steel plate and zinc-plated steel plate are more preferred.

[0013] <Heat barrier layer> The heat shielding layer reflects near infrared rays. The wavelength region of near infrared rays is 750 nm or more and 1000 nm or less. The heat shielding layer preferably contains a pigment that reflects near infrared rays. Methods for reflecting near infrared rays include a method of using a white pigment, as well as a method of performing subtractive color mixing by appropriately combining cyanine, magenta, and yellow pigments. In particular, a combination of a magenta pigment and a cyanine pigment is preferable because it significantly increases the light reflectance in the near infrared region.

[0014] Examples of pigment materials include inorganic pigments such as iron oxide, lead oxide, titanium dioxide, infrared shielding titanium oxide, talc, barium sulfate, chrome yellow, bismuth dimanganese pentoxide, titanium black, aluminum flakes, etc., and organic pigments such as phthalocyanine blue, Shinkasha red, etc. The content of the pigment in the heat-shielding paint for forming the heat-shielding layer is preferably 0.05:1 to 1.1:1 when expressed as a weight ratio of pigment:non-volatile content in the paint.

[0015] The heat-shielding coating material preferably does not substantially contain an ultraviolet absorbing material such as carbon black. The content of the ultraviolet absorbing material in the non-volatile components of the coating material is preferably 0.01% by weight or less, more preferably 0.001% by weight or less, and even more preferably is not contained at all.

[0016] Resins used to disperse the pigment contained in the heat-shielding paint include acrylic resins, epoxy resins, polyurethane resins, polyester resins, polybutadiene resins, and modified products of these resins. The paint form can be any of solvent-based, water-dispersed, and emulsion-based. The coating method can be any of known methods such as spray coating, brush coating, and roller coating. The wet film thickness of the heat-shielding layer is preferably 100 to 300 μm, more preferably 100 to 200 μm, and even more preferably 140 to 180 μm. The wet film thickness can be measured with a commonly used film thickness gauge such as a hexagonal stainless steel wet film comb. The dry film thickness of the heat-shielding layer is preferably 50 to 150 μm, more preferably 50 to 100 μm, and even more preferably 70 to 90 μm. The dry film thickness can be measured with an electromagnetic film thickness gauge or an eddy current film thickness gauge.

[0017] The multilayer coating film of the present invention preferably reflects 40% or more, and more preferably 80% or more, of the near-infrared wavelength region.

[0018] <Protective layer> The protective layer is formed on the heat shield layer for the purpose of maintaining the heat shielding performance for a long period of time. The protective layer is preferably formed of a highly durable resin. Examples of such resins include polyurea resin, silicone resin, and fluororesin, and among them, polyurea resin is preferable.

[0019] The protective layer made of a polyurea resin is formed by applying a coating composition for forming a polyurea on the heat shield layer and curing it. The coating composition for forming a polyurea is not particularly limited as long as it can form a polyurea coating film, and examples thereof include a two-liquid type coating composition made of an isocyanate compound and an amine compound, and a one-liquid type coating composition in which an isocyanate compound and an amine compound are mixed in a state where they do not react with each other.

[0020] When using a two-liquid coating composition, the isocyanate compound and the amine compound are mixed and applied immediately before painting. After painting, a urea structure is formed by a chemical reaction. There is a wide range of isocyanate compounds and amine compounds to choose from, making it easy to control the quality of the coating film. As a method for applying a two-liquid coating composition, a two-head spray gun method is available in which the isocyanate compound and the amine compound are stored in separate containers, sent to the tip of a spray gun at high pressure, and mixed by colliding with each other at the tip and applied. This allows good storage stability to be achieved even in compositions using highly reactive isocyanate compounds and amine compounds.

[0021] Examples of one-liquid type coating compositions include those that are made into one liquid by encapsulation or the like to prevent contact between the isocyanate compound and the amine compound, those that have low concentrations of isocyanate compounds and / or amine compounds, those that use isocyanate compounds and / or amine compounds with low reactivity, moisture-curing paints that generate amine compounds due to moisture, etc. One-liquid type coating compositions are easy to handle and the quality can be easily controlled.

[0022] In both the two-liquid type coating composition and the one-liquid type coating composition, examples of the isocyanate compound include linear, branched, or cyclic aliphatic isocyanates and aromatic isocyanates. Examples of the aliphatic isocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of the aromatic diisocyanates include toluene diisocyanate, naphthylene diisocyanate, and xylylene diisocyanate. These isocyanates can be used alone or in combination of two or more.

[0023] In both the two-component coating composition and the one-component coating composition, examples of the amine compound include aromatic amines such as aniline, toluidine, phenylenediamine, anisole, benzylamine, and naphthalenediamine; aliphatic amines such as diethylamine, triethylamine, dipropylamine, cyclohexylamine, stearylamine, and octadecylamine; polyamines such as polyethylene polyamine, polypropylene polyamine, and polyamidoamine; and amine resins such as epoxy amine resins and polyurethane amine resins.

[0024] The mixing ratio of the isocyanate compound and the amine compound, in terms of the ratio of isocyanate group:amino group, is preferably 1:0.3 to 0.3:1, and more preferably 1:0.5 to 0.5:1.

[0025] The thickness of the protective layer is defined as the wet film thickness. The wet film thickness of the protective layer may be thick to enhance the protective function, and is preferably 200 to 600 μm, and more preferably 300 to 500 μm. Also, the wet film thickness may be thin to enhance the smoothness of the protective layer, and is preferably 160 to 500 μm, and more preferably 200 to 400 μm. The wet film thickness can be measured by a commonly used film thickness meter such as a hexagonal stainless steel wet film comb.

[0026] In addition, when the substrate is made of a metal material, the film thickness of the protective layer can be specified as a dry film thickness. The dry film thickness of the protective layer may be a thick film in order to enhance the protective function, and is preferably 100 to 300 μm, and more preferably 150 to 250 μm. In addition, the dry film thickness may be a thin film in order to enhance the smoothness of the protective layer, and is preferably 80 to 250 μm, and more preferably 100 to 200 μm. The dry film thickness can be measured by a commonly used electromagnetic film thickness meter.

[0027] As the protective layer, either a thick protective layer or a thin protective layer may be provided, but it is preferable to provide both. In order to maintain the heat-shielding performance for a long period of time, it is preferable to form a thick protective layer on the heat-shielding layer, and further form a thin protective layer on the thick protective layer. By forming a thick protective layer on the heat-shielding layer, waterproofing is imparted, and the influence of moisture on the substrate can be eliminated, and for example, rust of the steel plate used as the substrate can be suppressed. By forming a thin protective layer on the top layer, the weather resistance of the coating film can be dramatically improved, and at the same time, a decrease in heat-shielding performance can be prevented by imparting low contamination properties that prevent adhesion of contaminants.

[0028] Fig. 1 shows a cross-sectional view of one embodiment of the multilayer coating film of the present invention. 1 indicates a substrate. 2 indicates a heat shielding layer. 3 and 4 all indicate protective layers. Protective layer 3 is a thick protective layer that imparts waterproofing. Protective layer 4 is a thin protective layer that improves the weather resistance of the coating film.

[0029] A thick protective layer can be formed by applying a coating material for forming a polyurea having a high viscosity so that the coating thickness can be easily achieved. The viscosity of the coating material for forming a polyurea can be adjusted by using a thickener. The amount of the thickener is preferably 0.2 to 2.0% by weight, more preferably 0.5 to 1.5% by weight, of the non-volatile components in the coating material.

[0030] When forming the protective layer, the coating composition can be applied by any of the known methods such as spray coating, brush coating, roller coating, etc.

[0031] The dry thickness of the entire multilayer coating film of the present invention, including the heat shield layer and the protective layer, is preferably 150 to 400 μm, more preferably 200 to 300 μm, and the wet thickness of the entire multilayer coating film of the present invention, including the heat shield layer and the protective layer, is preferably 300 to 800 μm, more preferably 400 to 600 μm.

[0032] <Other additives> In addition to the components described above, various additives such as dispersants, solvents, leveling agents, curing catalysts and the like may be added to the coating compositions for forming the heat shielding layer and protective layer, as required.

[0033] The dispersant is not particularly limited, and examples thereof include polycarboxylic acid-based pigment dispersants, polyamine-based pigment dispersants, etc. The amount of the dispersant added may be 0.1 to 10 parts by weight per 100 parts by weight of the resin component.

[0034] The solvent is not particularly limited, and examples thereof include cyclohexanone, butyl acetate, ethyl acetate, xylene, toluene, methyl isobutyl ketone, and methyl ethyl ketone. These solvents can be used alone or in combination of two or more. The solid content rate (proportion of non-volatile content) of the paint can be adjusted by adjusting the amount of the solvent in the paint. The solid content rate of the paint is preferably 20 to 70% by weight, more preferably 30 to 60% by weight.

[0035] The leveling agent is not particularly limited, and examples thereof include polyether-based leveling agents, fluorine-based leveling agents, polyester-based leveling agents, siloxane-based leveling agents, silicone-based leveling agents, acrylic-based leveling agents, etc. The blending amount is not particularly limited, but is preferably 0.1 to 10 parts by weight per 100 parts by weight of the resin component.

[0036] <Paint hardening> The coating composition for forming the heat shield layer and the protective layer is cured for a certain period of time after application. The curing conditions are not particularly limited, but the drying time is preferably 0.1 minutes to 24 hours, more preferably 0.1 minutes to 16 hours. When the coating composition for forming the polyurea for forming the protective layer is a two-liquid type coating material consisting of a highly reactive isocyanate compound and an amine compound, the curing reaction proceeds in an extremely short time, for example, 1 to 60 seconds, after application. The drying temperature is preferably 5 to 40°C, more preferably 20 to 30°C.

[0037] Examples of objects to which the multilayer coating film of the present invention can be applied include roofing materials and wall surfaces of factories, warehouses, stadiums, gymnasiums, stations, schools, commercial buildings, agricultural facilities, houses, etc. EXAMPLES

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0039] (1) Example 1 A thermal barrier paint having the following composition was applied to a galvalume steel plate test piece of 150 mm x 70 mm x 0.8 mm and dried for 1 hour. The wet film thickness of the thermal barrier paint was 140 μm.

[0040] Heat-insulating coating composition Acrylic emulsion resin (non-volatile content 50%) 50.0% Infrared reflective pigment 1.5% (Benzimidazolone, Phthalocyanine, Quinacridone) Titanium dioxide 8.0% Extender pigment (talc) 5.0% Extender pigment (precipitated barium sulfate) 5.0% Additive (neutralizer) 0.5% Pure water 30.0% Total 100.0%

[0041] A thick-applied type one-component reactive curing urea resin paint, Strong Urea (manufactured by PL Japan Co., Ltd., mid-coat paint), was applied onto the heat-insulating paint film using a 22 mm long-hair roller and dried for 16 hours. Then, a thin-applied type one-component reactive curing urea resin paint, Resilience Urea (manufactured by PL Japan Co., Ltd., top-coat paint), was applied using a 22 mm long-hair roller and dried at room temperature of 23°C. The wet film thickness of the mid-coat paint was 220 μm, and the wet film thickness of the top-coat paint was 180 μm.

[0042] (2) Example 2 A thermal barrier paint having the following composition was applied to a tinplate steel test piece of 150 mm x 70 mm x 0.8 mm and dried for 3 hours. The wet thickness of the thermal barrier paint was 160 μm.

[0043] Heat-insulating coating composition Acrylic resin (non-volatile content 60%) 45.0% Pigment dispersant (BYK-161) 1.0% Infrared reflective pigment 2.5% (Bismuth dimanganese pentoxide system) Infrared shielding titanium dioxide 7.0% Extender pigment (talc) 5.0% Additive (anti-settling agent) 0.5% Mixed Thinner 5 39.0% Total 100.0%

[0044] A thick-applied one-component reactive curing urea resin paint, Strong Urea (manufactured by PL Japan, Ltd., mid-coat paint), was applied onto the heat-insulating paint film using a 22 mm long-hair roller, and after drying for 16 hours, a thin-applied one-component reactive curing urea resin paint, Resilience Urea (manufactured by PL Japan, Ltd., top-coat paint), was applied using a 22 mm long-hair roller and dried at room temperature of 23° C. The wet film thickness of the mid-coat paint was 240 μm, and the wet film thickness of the top-coat paint was 200 μm.

[0045] (3) Example 3 A thermal barrier paint having the following composition was applied to a tinplate steel test piece of 150 mm x 70 mm x 0.8 mm and dried for 1 hour. The wet thickness of the thermal barrier paint was 150 μm.

[0046] Heat-insulating coating composition Acrylic emulsion resin (non-volatile content 50%) 45.0% Infrared reflective pigment 2.5% (Phthalocyanine, Quinacridone) Titanium dioxide 10.0% Extender pigment (precipitated barium sulfate) 5.0% Additive (neutralizer) 0.5% Pure water 37.0% Total 100.0%

[0047] A thick-applied, one-component reactive curing urea resin paint, Strong Urea (PL Japan Co., Ltd., mid-coat paint), was applied onto the heat-insulating paint film using a 22 mm long-hair roller, and after drying for 16 hours, a thin-applied urea resin paint, Resilience Urea (PL Japan Co., Ltd., top-coat paint), was applied using a 22 mm long-hair roller and dried at room temperature of 23° C. The wet film thickness of the mid-coat paint was 240 μm, and the wet film thickness of the top-coat paint was 200 μm.

[0048] (4) Comparative Example 1 A paint having the following composition was applied to a tinplate steel test piece of 150 mm x 70 mm x 0.8 mm and dried for 1 hour. The wet film thickness of the heat insulating paint was 160 μm.

[0049] Heat-insulating coating composition Acrylic emulsion resin (non-volatile content 50%) 50.0% Carbon black 1.5% Titanium dioxide 10.0% Extender pigment (talc) 8.0% Extender pigment (precipitated barium sulfate) 7.0% Additive (neutralizer) 0.5% Pure water 23.0% Total 100.0%

[0050] On the coating containing carbon black, a thick-applied one-component reactive curing urea resin paint Strong Urea (PL Japan Co., Ltd., mid-coat paint) was applied with a 22 mm long-hair roller, and after drying for 16 hours, a thin-applied one-component reactive curing urea resin paint Resilience Urea (PL Japan Co., Ltd., top-coat paint) was applied with a 22 mm long-hair roller and dried at room temperature of 23° C. The wet film thickness of the mid-coat paint was 220 μm, and the wet film thickness of the top-coat paint was 180 μm.

[0051] (5) Comparative Example 2 A thermal barrier paint having the following composition was applied to a galvalume steel plate test piece of 150 mm x 70 mm x 0.8 mm and dried for 1 hour. The wet film thickness of the thermal barrier paint was 140 μm.

[0052] Heat-insulating coating composition Acrylic emulsion resin (non-volatile content 50%) 50.0% Infrared reflective pigment 1.5% (Benzimidazolone, Phthalocyanine, Quinacridone) Titanium dioxide 8.0% Extender pigment (talc) 5.0% Extender pigment (precipitated barium sulfate) 5.0% Additive (neutralizer) 0.5% Pure water 30.0% Total 100.0%

[0053] Next, an acrylic urethane paint (commercially available) was applied onto the heat-shielding paint film using a 22 mm long-pile roller, and after drying for 8 hours, an acrylic urethane paint (commercially available) was applied again using a 22 mm long-pile roller and dried for 8 hours at room temperature of 23° C. The wet film thickness of the undercoat paint was 220 μm, and the wet film thickness of the topcoat paint was 180 μm.

[0054] (6) Comparative Example 3 The test was performed on unpainted galvalume steel sheet test pieces measuring 150 mm x 70 mm x 0.8 mm. (7) Evaluation method The test pieces of Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following methods. The results are shown in Tables 1 and 2.

[0055] (7-1)Surface temperature The test pieces were exposed outdoors for a short period of time under clear skies in mid-June, and the surface temperatures of the test pieces were measured using a thermography camera TVS-200EX (manufactured by Nippon Avionics Co., Ltd.).

[0056] To examine the thermal barrier performance of the exposed plate over time, the test pieces were exposed outdoors for three months, and the thermal barrier performance was measured using the above-mentioned method for measuring the surface temperature.

[0057] (7-2) Color difference The test piece was placed on a flat surface at an angle of 15 degrees and left for three months, after which the degree of surface contamination was measured with a color difference ΔE meter. Measurements were performed by comparing an unexposed standard plate with an exposed plate. The larger the color difference ΔE value, the more the coating is contaminated and dissociated from the standard plate.

[0058] (7-3) Surface condition of the coating To check for ultraviolet degradation of the coating, the test pieces were placed in a Super UV tester (Iwasaki Electric's iSuper UV Tester) and subjected to an accelerated weather resistance test for 1600 hours, after which the surface condition of the coating was observed.

[0059] [Table 1]

[0060] [Table 2]

[0061] In Comparative Example 1, the surface temperature of the test piece was high because the primer layer contained carbon black. In Comparative Example 2, the top coat layer and the intermediate coat layer were formed using an acrylic urethane resin paint, so the color difference ΔE value increased after three months of outdoor exposure, and the coating surface was whitened and chalked. In Examples 1 to 3, the increase in surface temperature was suppressed at the beginning of outdoor exposure and after three months, the color difference ΔE was small, and no change was observed on the coating surface. [Explanation of symbols]

[0062] 1 Base material 2. Thermal barrier layer 3 Protective layer 1 4 Protective layer 2

Claims

1. A multi-layer coating film comprising a substrate, a thermal barrier layer, and a protective layer in this order.

2. The multi-layer coating according to claim 1 , wherein the thermal barrier layer is substantially free of ultraviolet absorbing materials.

3. The multilayer coating film according to claim 1 or 2, wherein the protective layer is made of a polyurea resin.

4. The multilayer coating film according to claim 1 or 2, wherein the substrate is made of a metal.

5. forming a thermal barrier layer on the substrate; and forming a protective layer on the thermal barrier layer; A method for producing the multi-layer coating film according to claim 1 or 2.

6. In the step of forming a protective layer on the heat shielding layer, a coating composition for forming a polyurea resin is applied onto the heat shielding layer and cured to form a protective layer made of a polyurea resin. A method for producing the multi-layer coating film according to claim 5.

7. The method for producing a multi-layer coating film according to claim 6, wherein the coating composition for forming a polyurea is a one-component type.

Images