JP2001157870A - Multi layer coating film for thermal shield - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve difficulties in selection of coatings for commodities, such as automobiles, of which the design (external appearance) is an important factor; such difficulties arise because thermal-shield coating compositions have been thought ineffective unless applied to the outermost surface of a material to be coated. SOLUTION: A multi layer coating film for thermal shield is formed in such a way that the coating film contains no carbon black and its light reflectance ratio is 20-90% in the region of the wavelength of 350-2500 nm based on JIS A 5759 as an electro-deposition layer of a substrate such as an automobile body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heat-shielding multilayer coating,
For example, the present invention relates to a heat-shielding multilayer coating film suitable for preventing a rise in temperature inside an automobile due to sunlight.

[0002]

2. Description of the Related Art When an automobile is left in the scorching sun, the temperature inside the automobile increases. If air conditioners are used to prevent this, gasoline usage will increase and CO ₂ gas emissions will also increase.
Such adverse effects of temperature rise due to sunlight, etc., and energy consumption for the purpose of suppressing temperature are not limited to automobiles,
For example, the same applies to ships such as warehouses, airplanes, and tankers.

In order to prevent the above-mentioned temperature rise, various thermal barrier paints have been proposed. For example, Japanese Patent Publication No. 59-31545 discloses a heat reflection enamel containing a pigment such as nickel oxide and antimony trioxide. Japanese Patent Application Publication No. JP-A-2005-115125 discloses a black solar heat shielding coating composition containing no heavy metal.

[0004]

However, due to its properties, it is considered that the above-mentioned heat-reflective enamel and solar heat-shielding coating composition have no effect unless they are applied to the outermost surface of a coated article exposed to sunlight. Therefore, especially for articles such as automobiles, in which the design (appearance) of a product is an important factor, paints that can be selected are limited, so that it has been difficult to apply them. Therefore, an object of the present invention is to provide a coating film that can exhibit a heat shielding effect without being formed on the outermost surface of the coating film.

[0005]

In order to solve the above-mentioned problems, a heat-shielding multilayer coating film according to the present invention is a multilayer coating film in which a primer layer, an intermediate coating layer and an overcoat layer are sequentially formed on a substrate surface. In the above, the primer layer does not contain carbon black and has a light reflectance of 20 in a wavelength region of 350 to 2500 nm in accordance with JIS A 5759.
~ 90%. Surprisingly, it has been found that by using a coating film having such specific properties as a primer layer, a sufficient heat shielding effect can be obtained without using a heat shielding paint in the outermost layer.

When the above-mentioned primer layer is formed on both sides of the substrate, the heat shielding effect is further improved. Further, the primer layer may be, for example, an electrodeposition coating film, and the heat shielding multilayer coating film of the present invention can be suitably used for an automobile body.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to FIG. FIG. 1 is a cross-sectional view showing one example of the heat shielding multilayer coating film of the present invention. The base material 1 is mainly a metal material, and examples thereof include steel materials such as galvanized steel and aluminum materials used for automobile bodies, roof materials, warehouse outer walls, and the like, and other plastics other than metals, tile materials, It can also be used for ceramics such as glass materials.

In the present invention, a primer layer 2 having a heat shielding effect is formed on a substrate 1. The primer layer 2 may be provided only on the front surface of the substrate 1, but the provision of the back primer layer 3 further increases the heat shielding effect.

On the primer layer 2, an intermediate coating layer 4,
Further, an overcoat layer 5 is formed thereon to form a heat shielding multilayer coating film. In addition, a top coat (not shown) may be further provided on the overcoat layer 5,
A heat insulating layer for improving the heat shielding function may be provided between the primer layer 2 and the intermediate coating layer 4.

The primer layer 2 (and the backside primer layer 3), which is a feature of the present invention, contains no carbon black and has a JI in a wavelength region of 350 to 2500 nm.
It has the property that the light reflectance according to SA5759 is 20 to 90%. A layer having such properties can be obtained by applying a paint containing a pigment that reflects light in the above wavelength range. As this pigment, a white pigment that reflects the entire wavelength range described above can be used. In addition, the pigments of cyanine, magenta, and yellow are appropriately combined, and the light reflectance can be secured by subtractive color mixture. In particular, a combination of a magenta pigment and a cyanine pigment is preferable because it significantly increases the light reflectance around the infrared region.

Any type of pigment may be used as long as it meets the above conditions.
Inorganic pigments such as iron oxide, lead oxide, strontium chromate, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chrome yellow, and aluminum flakes; and, for example, organic pigments such as phthalocyanine blue and synchasia red. . Of course, carbon black is not included in this. When the pigment content in the paint is expressed as a weight ratio of the pigment to the nonvolatile matter in the paint, the range of 0.05 to 1: 1 is preferable.

Examples of the vehicle used for dispersing the pigment include conventionally known acrylic resins, epoxy resins, polyamide resins, polyurethane resins, polyester resins, polybutadiene resins, and modified products of these resins. The coating form may be any of a solvent type, an aqueous dispersion type and an emulsion type. Further, as the coating method, any method such as spray coating, brush coating, dip coating, roll coating, and sink coating can be used.

However, when the heat-shielding multilayer coating film of the present invention is applied to an automobile, the primer layer 2 (and the back primer layer 3) are preferably formed of a cationic electrodeposition paint. In this case, the vehicle is preferably a cation-modified epoxy resin in terms of corrosion resistance and throwing power, and this resin is used as a water-soluble coating by neutralizing the resin with an acid.

The cation-modified epoxy resin is cationized by opening the epoxy ring of the epoxy resin with an amine such as a primary amine, secondary amine or tertiary amine.

Examples of the epoxy resin as a starting material include polyphenol polyglycidyl ether type epoxy resin which is a reaction product of a polycyclic phenol compound such as bisphenol A, bisphenol F, bisphenol S, phenol novolak, cresol novolac and epichlorohydrin. Resins. This resin can be used by extending the chain with a bifunctional polyester polyol, polyether polyol, bisphenols, dibasic carboxylic acid, or the like.

Before the ring-opening reaction of the epoxy ring with the amines, 2-epoxyhexanol, nonylphenol, 2-ethylhexanol, nonylphenol, A monohydroxy compound such as ethylene glycol mono-2-ethylhexyl ether and propylene glycol mono-2-ethylhexyl ether can be added for use.

Examples of amines that can be used to open the epoxy ring and introduce an amino group include butylamine,
Primary such as octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine, N, N-dimethylethanolamine,
Secondary or tertiary amines can be mentioned. In addition, 3
The secondary amine can also be used in the form of a salt with an acid used as a neutralizing agent.

Further, a secondary amine containing a ketimine block primary amino group such as aminoethylethanolamine methyl isobutyl ketimine can also be used. These amines need to be reacted in at least equal equivalents to the epoxy ring in order to open all epoxy rings.

The number average molecular weight of the cation-modified epoxy resin is preferably in the range of 1500 to 5000. When the number average molecular weight is less than 1500, physical properties such as solvent resistance and corrosion resistance of the cured coating film may be poor. On the contrary, 500
If it exceeds 0, not only the viscosity of the resin solution is difficult to control and the synthesis is difficult, but also the handling of the obtained resin may be difficult in terms of operation such as emulsification and dispersion. Further, the flow properties during heating and curing are poor, and the appearance of the coating film may be significantly impaired.

A pigment that reflects light in the above-mentioned wavelength region dispersed in a pigment dispersing resin such as an ammonium salt is added to a water-soluble vehicle composed of the cation-modified epoxy resin. In addition, extenders, rust preventive pigments, organic solvents, surfactants and the like may be added as necessary.

In the cationic electrodeposition coating, a known blocked polyisocyanate is used as a crosslinking agent. This blocked polyisocyanate is a blocking agent such as methanol, ethanol, diethanolamine, oxime, and ε-caprolactam that dissociates polyisocyanates such as tolylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate at a specific temperature, for example, 120 to 150 ° C. It's a block.

The vehicle of the coating material for forming the intermediate coating layer 4 is preferably an alkyd or polyester melamine resin system. Examples of the monomer constituting the resin include:
Examples include trimethylolpropane, neopentyl glycol, phthalic anhydride, isophthalic acid, hexahydrophthalic acid, adipic acid, and ε-caprolactone.

There is no particular limitation on the pigment, but the use of a paint containing a pigment that reflects light in the above-mentioned wavelength range can further enhance the heat shielding effect.

As the vehicle of the paint for forming the overcoat layer 5, alkyd and polyester melamine resins for solid colors and acrylic melamine resins for metallic colors or clear can be suitably used. Further, since there is no limitation on the pigment used for both solid color and metallic color, it is possible to express a free design.

As an example of the procedure for forming the heat-shielding multilayer coating film of the present invention, the substrate 1 is degreased / washed, subjected to a chemical conversion treatment, and then immersed in an electrodeposition tank to form the primer layer 2 (and the backside primer layer 3). After coating, washing and baking at 120-150 ° C. Next, the middle coat layer 4 and the top coat layer 5 are sequentially applied by spray coating. The baking can be performed separately for each layer, but it is preferable to use a two-coat one-bake method in which the overcoat layer 5 and the clear coat layer are simultaneously baked.

Further, the number of layers may be increased or decreased as necessary, for example, by providing a heat insulating layer between the primer layer 2 and the intermediate coating layer 4 for the purpose of further improving the heat shielding property.

Primer layer 2 and backside primer layer 3
Has a dry film thickness of at least 1 to maintain the heat shielding effect.
0 μm, preferably 10 to 30 μm, more preferably 15 to 20 μm. The dry film thicknesses of the intermediate coat layer 4 and the top coat layer 5 are each 20 to 50 μm, preferably 30 to 40 μm.

[0028]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition,% in each example represents weight%.

[0029]Example 1  30cm x 40cm x with degreasing and chemical conversion treatment
Heat insulation of the following composition on a 0.8 mm thick iron test piece
The pigment-containing electrodeposition paint was applied and baked at 150 ° C.

The dry film thickness of the electrodeposition coating film (primer layer) is 2
The three-point average light reflectance in the region of 0 μm and 350 to 2500 nm was 22%. The measurement of the light reflectance was performed in accordance with JIS A 5759 using a near-infrared spectrum measuring device (U-3500 type self-recording spectrophotometer, using a WI lamp (iodine tungsten), manufactured by Hitachi, Ltd.).

[0031]Electrodeposition paint composition containing thermal barrier pigment  Amino-modified epoxy resin (number average molecular weight 2200) 15.0% Infrared reflective pigment 0.4% (mixture of benzimidazolone-based, phthalocyanine-based and quinacridone-based pigments) Titanium white 3.3% Extender pigment (Si-Al-based) 1.0% Rust prevention pigment (Pb-Si type) 0.3% Additive (neutralizing agent etc.) 0.6% Solvent (cellosolve type) 1.8% Pure water 77.6%

Next, Olga P-28 was coated on the electrodeposition coating film.
101 (manufactured by Nippon Paint Co., Ltd., middle coating) is spray-coated, and Olga P-2-1 202B (manufactured by Nippon Paint Co., Ltd., top coating) is spray-coated thereon.
Simultaneous baking was performed at 0 ° C. The dry film thickness of both the intermediate coating film and the top coating film was 40 μm.

The test piece on which the heat-shielding multilayer coating film completed as described above was formed was set in a test box for temperature measurement shown in FIG. 2 and tested, and the results are shown in Table 1 below.

This box comprises a main body 6 made of a heat insulating foam (polystyrene foam) and a lid 7 of the same material.

To perform the temperature measurement test, first, the test piece 8 is placed on the main body 6 and fixed with the frame 7. Further, a thermocouple 9 for measuring the surface temperature is provided on the outer surface of the test piece 8, a thermocouple 10 for measuring the back surface temperature is provided on the back surface, and a thermocouple 11 for measuring the center temperature of the box is provided at the center of the main body 6. Is measured with a thermometer 12 (HR2500E, manufactured by Yokogawa Electric Corporation). A 100 V, 200 W infrared lamp 13 (Toshiba Ref Lamp RF, manufactured by Toshiba Corporation) was placed at a position 15 cm above the center of the test piece 8 and irradiated with heat rays, and each temperature was measured after one hour.

[0036]Examples 2 to 4 and Comparative Examples 1 to 4  Coating used for top coat, middle coat, electrodeposition layer, back electrodeposition layer
Change of charge, change of type of test box for temperature measurement, and
Add a heat insulating layer, etc.
A test piece was prepared and a temperature measurement test was performed. In addition,
The insulation layer used in some examples was
It is a layer provided between the layer and the coating composition is as follows
It is.

[0037]Insulation layer paint composition  Polyester resin 29.8% (number average molecular weight 2500, acid value 6, OH value 100) Melamine resin (butylated melamine, number average molecular weight 1200) 10.0% Epoxy resin 4.0% (epichlorohydrin-bisphenol type, number average) Hollow beads (made of ceramic) 1.0% Surfactant (non-silicon type) 0.2% Solvent 45.0% (mixture of aromatic hydrocarbon type, ester type and alcohol type)

The composition of Power Top V6 (manufactured by Nippon Paint Co., Ltd.), which is a paint for forming an electrodeposition layer, used in Comparative Examples is as follows.

[0039]Comparative electrodeposition coating composition  Amino-modified epoxy resin (number average molecular weight 2200) 15.0% carbon black 0.1% titanium white 3.6% extender pigment (Si-Al type) 1.0% rust preventive pigment (Pb-Si type) 0.3 % Additive (neutralizing agent, etc.) 0.6% Solvent (cellosolve type) 1.8% Pure water 77.6% In the region of 350 to 2500 nm of the electrodeposition coating film of the comparative example
The average three-point light reflectance was 12.0%. Each implementation
Tables 1 and 2 show the specifications and test results of the examples and comparative examples.
did.

As is clear from the results of the above Examples and Comparative Examples, it was found that the center temperature of the box can be sufficiently reduced without using a heat-shielding paint for the overcoat layer.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

As described above, according to the present invention, at least the primer layer of the heat-shielding multilayer coating does not contain carbon black and has a light reflectance in the wavelength range of 350 to 2500 nm in accordance with JIS A 5759. Is 20
Since the paint of 90% is used, a sufficient heat shielding effect is exhibited. Even without using a heat-shielding paint for the outermost layer, the sunlight passes through the upper layer coating film and reaches the primer layer, and the primer layer reflects the sunlight, thereby providing a shielding effect.

The outermost layer does not need to use a heat-shielding paint, so that it does not affect the appearance, and is therefore particularly useful for articles such as automobiles, where design is an important factor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of a heat-shielding multilayer coating film of the present invention.

FIG. 2 is a sectional view of a test box for temperature measurement according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Primer layer 3 Back primer layer 4 Intermediate coating layer 5 Top coating layer 6 Main body 7 Frame 8 Test piece 9, 10, 11 Thermocouple 12 Thermometer 13 Infrared lamp

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shin Moriyama 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Inside Japan Paint Co., Ltd. (72) Inventor Yasuo Sato 4-1-15-1 Minamishinagawa, Shinagawa-ku, Tokyo Nippon Paint Co., Ltd. (72) Inventor Goro Nagao 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Nippon Paint Co., Ltd. (72) Inventor Takamitsu Sawamura No address at Taura Port Town, Yokosuka City, Kanagawa Prefecture Kanto Motor Industry Co., Ltd. (72) Inventor Hiroyuki Shioda No-address in Taura Port Town, Yokosuka City, Kanagawa Prefecture Within Kanto Automobile Industry Co., Ltd. (72) Inventor Kiyoshi Nomura 476 Fueda, Kamakura City, Kanagawa Prefecture 809-4 F-term (reference) 4D075 AE19 BB89Y CA17 DA06 DB02 DC12 EA60

Claims (4)

[Claims] 1. A multi-layer coating film comprising a primer layer, an intermediate coating layer, and an overcoat layer formed on a substrate surface in order,
The primer layer contains no carbon black and has a JIS A in a wavelength region of 350 to 2500 nm.
A heat-shielding multilayer coating film having a light reflectance according to 5759 of 20 to 90%. 2. The heat-shielding multilayer coating film according to claim 1, wherein the primer layer is formed on both surfaces of the substrate. 3. The heat-shielding multilayer coating film according to claim 1, wherein the primer layer is an electrodeposition coating film. 4. The vehicle according to claim 1, wherein said base material is an automobile body.
The heat-shielding multilayer coating film according to any one of claims 1 to 3.