JP2014145027A - Coating material composition excellent in heat shield - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material composition capable of forming a coating film for effectively suppressing a flow of thermal energy from the outside, such as sunlight, into the inside of a coated object in the coated object.SOLUTION: Movement of thermal energy received from sunlight into the inside of the coating layer of a top layer formed by drying a coating material is effectively suppressed by coating a coating material composition having resin based hollow particles dispersed in the coating layer and having 0.6-1.2 μm of an average diameter of hollow parts and 10-35% of the total volume of the hollow parts to the total volume of the coating film.

Description

The present invention relates to a coating material capable of forming a coating film aiming at suppressing the movement of heat energy received from sunlight to the inside.

The roofs and exterior walls of buildings that are constantly exposed to sunlight rise in temperature due to the heat energy of sunlight. Particularly in the summer, from the viewpoint of energy saving, a paint having a heat shielding effect is used when it is desired to suppress the temperature rise.

As these thermal barrier paints, for example, as disclosed in Japanese Patent No. 3794837, Japanese Patent Application Laid-Open No. 2002-320912, Japanese Patent Application Laid-Open No. 2009-286862, etc., pigments having excellent reflectivity in the infrared region having a wavelength longer than that of visible light It is widely applied to use solar reflective paints using

Most of the pigments with excellent reflectivity in the infrared region are supported by selecting a material. However, in Patent No. 4546834, by controlling the particle size of titanium oxide, which is a typical white pigment, Technologies that effectively reflect infrared radiation have been presented.

Further, as disclosed in, for example, JP-A No. 2001-64544, a method for reducing the thermal conductivity of the coating layer by using various hollow particles and suppressing the movement of heat to the inside by a heat insulating effect is practical. It has become.

Generally speaking, as described above, there are a method for improving the reflectivity in sunlight, particularly in the infrared region, and a method for improving the heat insulation property, which have been put into practical use either individually or in combination. . It is an object of the present invention to provide a coating composition that can be applied to these methods and can form a coating layer that more effectively suppresses heat from moving inside.

Since the hollow particles having the heat insulation performance described above cannot make the coating layer so thick by a general coating method, the heat shielding effect by heat insulation is also very limited. On the other hand, since the hollow particles are in a gas phase such as air, the refractive index is very low compared to the resin or inorganic material constituting the coating layer. Therefore, there is a large difference in the refractive index at the boundary between the hollow particles dispersed in the coating layer. Therefore, the incident sunlight is scattered and reflected at the boundary between the hollow particles, so that the hollow particles themselves are white pigments. In addition to having a function, it has the ability to reflect sunlight, that is, heat shielding properties.

The dispersed hollow particles most efficiently scatter light with a wavelength of 0.8 to 3 μm, which is the infrared region of sunlight, in the case of Mie scattering as the light scattering form by the dispersed particles. It is considered to be a phenomenon of strong scattering when equal to 1/2. When the spectral reflectance of the coating film in which the hollow particles were actually dispersed was measured, it was found that the light in the infrared region was efficiently reflected when the average diameter of the hollow portion was in the range of 0.6 to 1.2 μm. .

Furthermore, in the case of hollow particles, the heat capacity per volume is small compared to resins and pigments that form a coating film. In particular, the resin-based hollow particles have a smaller heat capacity than the hollow particles in which the outer shell is formed of ceramics, and thus the characteristics are remarkable. Titanium oxide, which is a common white pigment, has a higher heat capacity per volume than the resin component, which is the main component of the coating film. Therefore, by using hollow particles as white pigment and lowering the titanium oxide content, A coating film having a low heat capacity per unit volume can be formed. In the case of a coating film with a low heat capacity, the temperature easily rises with the heat energy absorbed from sunlight, and as the temperature rises on the surface, the temperature difference from the surroundings increases, heat dissipation is promoted, and heat energy is transferred to the inside. It is suppressed accordingly.

  Based on the above idea, the coating composition of the present invention obtained by repeating the coating composition confirmation test, the average layer diameter of the hollow portion in the uppermost coating layer obtained by drying the coating is 0.6 ~ Resin-based hollow particles having a range of 1.2 μm are dispersed, and the total volume of the hollow portions is in the range of 10 to 35% with respect to the total volume of the coating film. Here, if the total volume of the hollow portions is less than 10% with respect to the total volume of the coating film, no significant effect appears, and if it exceeds 35%, sufficient color concealment with respect to the background cannot be ensured. In addition, the reflectivity of infrared rays also decreases particularly in white and pale colors.

In the coating composition of the present invention, the resin used is not particularly limited, and a suitable resin is selected from the application, required quality and the like. Preferable examples include water-soluble resins and / or water-dispersed resins, and types thereof include ethylene resins, vinyl acetate resins, polyester resins, alkyd resins, vinyl chloride resins, epoxy resins, acrylic resins, acrylic silicone resins, A urethane resin, a silicone resin, a fluororesin, etc., or a mixed system, modified or copolymerized system, or the like can be given.

Furthermore, there is no restriction | limiting in particular also about the pigment and filler to be used, A suitable pigment or filler is selected according to a desired color and a required physical property. However, it is better to avoid those that have high infrared absorption such as carbon black, which is a black pigment.Preferred examples include various pigments and fillers marketed as infrared reflective pigments, aluminum flakes, titanium oxide, Barium sulfate, zinc oxide, calcium carbonate, silicon oxide, magnesium oxide, zirconium oxide, indium oxide, alumina, perylene pigment, azo pigment, yellow lead, petal, titanium red, cadmium red, quinacridone red, isoindolinone, benzimidazo Ron, phthalocyanine green, phthalocyanine blue, cobalt blue, indanthrene blue, ultramarine blue, and bitumen.

In the coating composition of the present invention, that is, the uppermost coating layer formed by drying the coating, resin-based hollow particles having an average hollow portion diameter in the range of 0.6 to 1.2 μm are dispersed, and the volume of the hollow portion In addition to efficiently reflecting the wavelength in the infrared region of sunlight, paints using paint compositions characterized by the sum of Since the coating film having a small heat capacity is formed, the accumulated heat is easily radiated. In other words, the coated object with the coating composition according to the present invention can effectively suppress the transfer of heat energy received from sunlight to the inside, and as a result, the temperature rise on the indoor side is suppressed and the thickness of the heat insulating layer is reduced. It can be used as a structural member that can contribute to energy saving effects.

EXAMPLES Hereinafter, although this invention is demonstrated in a specific Example, this invention is not limited to a following example.

[Create test plate]
As a base material, a molten 55% Al-Zn alloy-plated steel sheet with a thickness of 0.5 mm is used, and the surface is surface-treated with a coating-type chromate treatment agent, and a weak solvent type two-component epoxy resin paint is used as an undercoat. The film was painted and dried so that the dry coating thickness was 5 ± 1 μm.

  The top coating is based on an acrylic emulsion resin, and the color is white as shown in Example 1 and Example 2 in Table 1 as a white pigment in order to make the color the most heat-insulating and difficult to show differences in paint composition. A paint was prepared by blending hollow particles having a rutile type titanium oxide and a styrene-acrylic copolymer as an outer shell. The paint was applied and dried so that the dry coating thickness was 25 ± 3 μm, and used as a test material.

As comparative examples, samples having four compositions shown in Table 1 were prepared, and coated and dried in the same manner as in Examples to obtain test materials. The features of the comparative example are as follows.
(Comparative Example 1) Corresponds to the composition of a general white paint (Comparative Example 2) Composition when the average diameter of the hollow part of the hollow particle is smaller than the claims (Comparative Example 3) Volume of the hollow part of the hollow particle In the case where the sum of the above is larger than the claims (Comparative Example 4) Composition using infrared reflective titanium oxide according to Japanese Patent No. 454634

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[Confirmation of heat insulation 1]
Using a spectrophotometer, spectral reflectance in the wavelength range of 300 to 2500 nm was measured. The measurement results are shown in FIGS. Moreover, from the integration of the spectral reflectance obtained at each wavelength and the weight coefficient described in JIS K 5602, the reflectance in the entire wavelength range (300 to 2500 nm), the ultraviolet to visible light range (300 to 780 nm). The reflectance and the reflectance in the infrared region (780 to 2500 nm) were calculated and are shown in Table 1.
(Figure 1)

(Figure 2)

(Figure 3)

(Fig. 4)

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(Fig. 6)

[Confirmation of heat insulation 2]
At an atmospheric temperature of 25 ° C., the temperature change on the back side of the test plate was measured over time while the tip of a 100 W reflex lamp was placed 5 cm directly above the painted surface of the test plate and irradiated with light. The temperature became almost constant in about 12 to 18 minutes, and the temperature at that time is shown in the column of “Lamp Test” in Table 1.

From the description so far and the results of Table 1, the coated product with the coating composition according to the present invention has a high reflectance in the infrared region, and in the lamp test compared to Comparative Example 4 in Table 1 using infrared reflective titanium oxide. It is considered that the heat dissipation from the painted surface is good also from the fact that the temperature rise of the film is suppressed.

Claims (2)

In the uppermost coating layer formed by drying the paint, resin-based hollow particles having an average hollow portion diameter of 0.6 to 1.2 μm are dispersed, and the total volume of the hollow portion is the total coating volume. A coating composition characterized by being in the range of 10 to 35%. The aqueous coating composition according to claim 1, wherein the resin-based hollow particles have a styrene-acrylic copolymer as an outer shell.