JP7788686B2 - Wood paints and wood exterior building materials - Google Patents

Description

The technical field of this specification relates to wood paints applied to wood (lumber), wood exterior building materials coated with wood paints, and wood exterior structures using wood exterior building materials.

Conventionally, wood paints that are applied to wood for use as exterior building materials have been known (for example, Patent Documents 1 and 2).

Patent No. 3524548 JP 2014-101504 A

However, conventional wood paints have the problem that when painted wood is used as an exterior material and the coating (paint film) formed on the wood deteriorates over time and partially peels off, the color tone of the peeled and unpeeled areas differs, making the change in appearance easily visible.

The problem that the technology of this specification aims to solve was conceived in light of the above points, and aims to provide a wood paint that, when painted wood is used as an exterior material, results in little visible change in appearance even if the coating formed on the wood peels off.

The wood paint according to the embodiment of the present specification is a wood paint using a synthetic resin as a binder,
The coating formed on wood is characterized by having a gloss retention rate of 5 to 50% after 500 hours of accelerated weather resistance testing (xenon lamp method).

According to the wood paints according to the embodiments of this specification, the coating formed by application to wood has poor accelerated weathering (light) resistance. Therefore, when wood coated with the wood paint is exposed to direct sunlight, wind, and rain in an outdoor environment, the synthetic resin binder quickly deteriorates due to ultraviolet light. As the synthetic resin binder deteriorates due to ultraviolet light, the coating becomes discontinuous and breaks into small coating pieces. Furthermore, as the synthetic resin becomes discontinuous, its adhesion to the wood weakens, and the coating gradually peels off in small coating pieces when exposed to direct sunlight, wind, and rain. Because the small coating pieces peel off gradually, the coating formed by application to wood shows little visible change in appearance, even when peeled off.

Here, the paint for wood contains ink,
The coating formed by application and having a thickness of 40 μm can have a light transmittance of 15 to 45% at wavelengths of 300 to 350 nm and 25 to 55% at wavelengths of 350 to 400 nm.

According to this, the coating formed by painting wood transmits ultraviolet rays. As a result, the surface of wood coated with wood paint deteriorates due to ultraviolet rays. When wood coated with wood paint is exposed to direct sunlight and wind and rain in an outdoor environment, the surface of the wood deteriorates due to ultraviolet rays and assumes a roughly gray color. Furthermore, because the wood paint contains ink, wood coated with the wood paint assumes a roughly gray color, a color similar to the color of the surface of wood deteriorated by ultraviolet rays. Because the color of the area coated with the wood paint and the surface of the deteriorated wood are similar, changes in appearance are difficult to see when small pieces of the coating gradually peel off.

Furthermore, in the above-mentioned wood paint, the synthetic resin may be a vinyl-modified epoxy ester resin.

This allows the coating formed when wood paint is applied to wood to be quickly degraded by ultraviolet rays.

Here, the wooden exterior building material according to the embodiment is a wooden exterior building material made of wood as a base material, which is coated with a coating film formed from a wood paint containing ink and a synthetic resin, and is intended for outdoor use where it is exposed to direct sunlight and wind and rain,
The coating is characterized by being transparent to ultraviolet rays and gradually peeling off when exposed to direct sunlight and wind and rain.

In the wood exterior building material according to this embodiment, the coating transmits ultraviolet rays, causing the surface of the wood to deteriorate due to ultraviolet rays. When wood coated with a wood paint is exposed to direct sunlight, wind, and rain in an outdoor environment, the surface of the wood deteriorates due to ultraviolet rays, becoming approximately gray. Furthermore, because the coating contains ink, the wood coated with the coating becomes approximately gray, a color similar to the color of the surface of wood that has deteriorated due to ultraviolet rays. Because the coating gradually peels off due to exposure to direct sunlight, wind, and rain, the wood exterior building material can be made so that even if the coating peels off, the change in appearance is difficult to see.

Furthermore, the wood exterior building materials according to the embodiment can be coated with a film formed from the above-mentioned wood paint.

By doing this, when exposed to direct sunlight and wind and rain, the small pieces of coating gradually peel off, making it difficult to visually detect any changes in appearance.

Furthermore, the wooden exterior structure according to the embodiment can include an insulating material installed on the outside of the exterior wall material of a building, a waterproof sheet installed on the outside of the insulating material, and the above-mentioned wooden exterior building material installed on the outside of the waterproof sheet.

This allows the exterior walls of a building to have a wooden exterior structure equipped with wooden exterior building materials that make changes to their appearance less visible.

According to the wood paint described in this specification, the coating formed by painting on wood gradually peels off in small pieces when exposed to direct sunlight, wind, and rain. Because the coating peels off gradually in small pieces, the coating formed by painting on wood can be made so that even if it peels off, the change in appearance is not easily noticeable.

1A is a diagram showing the configuration of a wooden exterior structure equipped with a wooden exterior building material coated with an embodiment of a wood paint, and FIG. 1B is a cross-sectional view taken along line IB-IB in FIG. 1A.

The following describes wood paints, wood exterior building materials, and wood exterior structures according to embodiments of this specification. The scope of the present invention is not limited to the scope disclosed in the embodiments. As shown in Figure 1, the wood exterior structure according to the embodiment comprises insulation 12 installed on the outside of the exterior wall material 11 of a building, a waterproof sheet 13 installed on the outside of the insulation, and wood exterior building materials 21 installed on the outside of the waterproof sheet 13 via furring strips 14. This allows the wood exterior structure to meet the fire prevention requirements of Article 2, Paragraph 8 of the Building Standards Act. The wood exterior building materials 21 are made by applying the wood paint according to the embodiment to wood, and forming a coating 22 made of the wood paint on the surface of the wood.

The color notations used in this specification are as follows:

Near gray refers to a color in which, when the color is expressed in CIELAB (L ^* a ^* b ^* ), the absolute values of a ^* and b ^* are each equal to or less than 50. In another embodiment, the absolute values of a ^* and b ^* can each be equal to or less than 30, and in yet another embodiment, the absolute values of a ^* and b ^* can each be equal to or less than 20.

An approximate color is a color that is approximate to a certain color, and when the colors are expressed in CIELAB (L ^* a ^* b ^* ), the color difference between the two colors (ΔE ^* = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 ) is 20 or less. In another embodiment, the color difference (ΔE ^* ) can be 10 or less, and in yet another embodiment, the color difference (ΔE ^* ) can be 5 or less.

In this specification, the gloss retention after 500 hours of accelerated weathering testing (xenon lamp method) refers to the gloss retention measured for 500 hours according to Method 1, Cycle A specified in JIS K 5600-7-7:2008 General Test Methods for Paints - Part 7: Long-Term Durability of Coating Films - Section 7: Accelerated Weathering and Accelerated Light Fastness (Xenon Lamp Method) under the conditions of relative humidity of 50±5%, irradiance of 300-400 nm of 60 W/ ^m2 , and black panel temperature of 63±2°C during the drying period (Method 1: Matching the spectral distribution of global radiation on a horizontal surface in the ultraviolet and visible ranges (used for weathering tests), Cycle A: Wetting time 18 minutes, Drying time 102 minutes, relative humidity of 40-60% during the drying period, and continuous irradiance).

Wood paint contains synthetic resin as a raw material, and may optionally contain ink, mica, silica, dispersants, antifoaming agents, preservatives, and antifreeze agents. Wood paint can be manufactured by mixing these raw materials using a mixer such as a dissolver mixer.

The synthetic resin used in the wood paint of this embodiment is a synthetic resin with poor weather resistance, forming a coating 22 on wood that has a gloss retention rate of 5-50% after 500 hours in an accelerated weathering test (xenon lamp method). Because the coating 22 formed on wood has poor weather resistance, wood coated with the wood paint is exposed to direct sunlight, wind, and rain in an outdoor environment, and the synthetic resin binder quickly degrades due to ultraviolet light, resulting in its degradation into smaller molecules. As the synthetic resin binder is degraded into smaller molecules, the coating 22 becomes discontinuous, breaking down into small pieces, weakening its adhesion to the wood. As the small pieces peel off gradually, the coating formed on wood shows little visible change in appearance, even when peeled off.

In embodiments, such synthetic resins may include acrylic resins with a weight-average molecular weight of 100,000 or less, vinyl-modified epoxy ester resins, polyvinyl alcohol, etc. The synthetic resins used in wood paints in embodiments may be used as is if they are liquid, or may be emulsified (synthetic resin emulsion), dispersed, or dissolved in water, or may be dispersed or dissolved in a solvent such as an organic solvent.

In another embodiment, the synthetic resin used in the wood paint can be a vinyl-modified epoxy ester resin. The coating 22 formed from a wood paint using a vinyl-modified epoxy ester resin as a binder has adhesive properties that allow it to maintain adhesion to the wood. Therefore, even if the coating breaks into small pieces, it does not immediately peel off, but rather has an excellent effect of gradually peeling them off. The adhesiveness of the coating 22 formed from the wood paint of this embodiment can be such that the scratch hardness (pencil method) (JIS K 5600-5-4:1999) is 2B or less. In another embodiment, the scratch hardness can be 4B or less, and in yet another embodiment, 6B or less. The weight-average molecular weight of the vinyl-modified epoxy ester resin of this embodiment can be 1,000 to 200,000. This is because it allows for early UV degradation of the coating 22 formed from the wood paint. In another embodiment, the weight-average molecular weight of the vinyl-modified epoxy ester resin can be 10,000 to 100,000.

Vinyl-modified epoxy ester resins can be obtained by polymerization of a mixture of vinyl compounds and a condensate obtained by an addition reaction between an epoxy resin and a fatty acid. Vinyl-modified epoxy ester resins can also be obtained by polymerization of a mixture of vinyl compounds and an unsaturated fatty acid-modified epoxy ester resin (A1), a compound represented by the following general formula (I):

(n is 1 to 10, and ^R1 is an alkylene group having 2 to 18 carbon atoms.)
and other vinyl monomers (a2), a basic compound, and water, to neutralize some or all of the carboxyl groups contained in the vinyl-modified epoxy ester resin (A2) with a basic compound (N,N-dimethylaminoethanol), and then disperse the neutralized vinyl-modified epoxy ester resin (A3) obtained by the neutralization in water.

Commercially available vinyl-modified epoxy ester resins can also be used. Examples of commercially available vinyl-modified epoxy ester resins that can be used include Modepics (manufactured by Arakawa Chemical Co., Ltd.), Lipoxy (manufactured by Showa Denko K.K.), Burnock (manufactured by DIC Corporation), and Haripol (manufactured by Harima Chemical Co., Ltd.).

The wood paint of this embodiment has a 40 μm-thick coating 22 that has a light transmittance of 15-45% at wavelengths of 300-350 nm and 25-55% at wavelengths of 350-400 nm. This allows ultraviolet light to pass through the coating 22 that is applied to wood. As a result, the surface of wood coated with the wood paint is subject to ultraviolet degradation. When wood coated with the wood paint is exposed to direct sunlight, wind, and rain in an outdoor environment, the surface of the wood deteriorates due to ultraviolet light and takes on a generally gray color.

The ink imparts a generally gray color to the coating 22 formed from the wood paint, simulating the ashed color of the wood until it turns to ashed. Therefore, even unashed solid wood can be used as the wood to which the wood paint is applied, and the generally gray color imparted to it approximates the ashed color. Because the coating 22 formed by painting on wood transmits ultraviolet light, the surface layer of wood coated with the wood paint gradually deteriorates (ashes) and gradually assumes a generally gray color, so that the color of the area coated with the wood paint and the color of the surface of the deteriorated wood are similar. In other words, the color difference before and after deterioration is small. Therefore, when small pieces of the coating 22 formed by painting on wood gradually peel off, the color of the remaining area of the coating 22 and the color of the peeled area are similar, making the change in appearance less noticeable.
In the embodiment, Japanese ink such as pine soot ink or lamp soot ink can be used. Japanese ink contains soot and glue.

Pine soot is made by burning pine trees and their resin. Using pine soot ink allows the soot particles to be non-uniform in size, creating a wide range of colors, from deep black to blue-gray. Lamp soot, on the other hand, is made by burning vegetable oil. Using lamp soot ink allows the soot particles to be fine and uniform, giving the color a gloss and depth, and also suppressing the aggregation of soot when using ink in the form of ink juice. In another embodiment, lamp soot ink can be used.

Nikawa (glue) is a gelatinous substance that forms a jelly-like substance when the skin and bones of animals such as cows and horses are boiled and cooled. The glue has the role of shaping the ink and giving the liquid the appropriate viscosity when the ink is grated. Japanese ink can be infused with fragrances such as borneol and musk, as these fragrances can help tone down the odor of the glue.

The ink can be used in the form of ink juice, which is easy to handle. The ink juice can contain calcium chloride. The inclusion of calcium chloride stabilizes the soot colloid in the ink and also facilitates penetration of the soot into the wood grain when a wood coating is applied to the wood. Examples of commercially available lamp soot ink juices that can be used include Shogei Kuretake Shikon, Shogei Kuretake Pure Black, Shogei Kuretake Blue, Koinoku Shogei Kuretake, Choinoku Shogei Kuretake, and Shogei Kuretake Shikon Kyoku (all manufactured by Kuretake Co., Ltd.). Examples of commercially available pine soot ink juices that can be used include Jun Shoinku Masukui Shojun Kai (manufactured by Kuretake Co., Ltd.). The non-volatile content of the ink can be 15 to 35% by mass. The particle size of the ink can be 0.01 to 1 μm.

The mica in this embodiment is a thin-plate silicate mineral (mica) coated with a metal oxide such as titanium oxide, and is sometimes called a pearl pigment. When incorporated into wood paint, mica imparts a pearl-like luster to the wood paint coating 22 due to the interference of light, thereby enhancing the luster of the ink (thought to be due to the π bond of the ink's sp2 hybrid orbital).

Mica also has the effect of highlighting the wood grain. The water absorption of wood surfaces varies depending on the grain (annual rings), and when wood paint is applied to a wood surface, in areas with high water absorption, the synthetic resin in the wood paint is absorbed into the wood, causing the mica to emerge and align on the surface of the coating 22, enhancing the pearly luster. On the other hand, in areas with low water absorption, the mica is less oriented on the surface of the coating 22, resulting in a duller pearly luster.

The mica particle size can be 10 to 100 μm. This is because it can enhance the luster of the ink. If the mica particle size is less than 10 μm, the luster will be dull and the luster of the ink may not be enhanced. On the other hand, if it exceeds 100 μm, the luster will be too strong and may not be suitable for the luster of the ink. In another embodiment, the mica particle size can be 10 to 60 μm.

Silica is a raw material added to reduce the gloss of the coating 22 made of wood paint. In one embodiment, the particle size of the silica can be 1 to 10 μm. This is because it can effectively reduce the gloss of the coating 22. If the silica particle size is less than 1 μm, it may not be able to be uniformly dispersed in the wood paint. On the other hand, if it exceeds 10 μm, it may not be able to effectively reduce the gloss of the coating 22. In another embodiment, the particle size of the silica can be 2 to 5 μm. Note that silica with a hydrophilic surface can be used. This is because minute gaps form at the interface between the silica and synthetic resin in the coating 22, making the coating 22 more susceptible to water absorption. Repeated rainfall and drying causes the coating 22 to expand and contract repeatedly, which can gradually peel off from the wood surface.

Dispersants, antifoaming agents, preservatives, and antifreeze agents can be selected from commercially available products and added in appropriate amounts as needed.

Table 1 shows an example formulation of a wood paint according to an embodiment, and the preferred ranges (parts by mass) of other raw materials when the synthetic resin emulsion is taken as 100 parts by mass.

The wood paint of the embodiment can be applied using a roller, brush, etc. The amount of application is 30 to 50 g/ ^m2 in terms of non-volatile content, and the film thickness is 30 to 50 μm.

The wood to be coated with the wood paint of this embodiment is a thick flat plate, and the ratio of the flat plate's short-side length to its thickness (short-side length ÷ thickness) can be between 2 and 10. This is because it can prevent the wood from warping over the long term. In another embodiment, the ratio of the flat plate's short-side length to its thickness can be between 4 and 8.

The wooden exterior structure according to the embodiment comprises an insulating material 12 installed on the outside of the exterior wall material 11 of a building, a waterproof sheet 13 installed on the outside of the insulating material, and a wooden exterior building material 21 installed on the outside of the waterproof sheet 13 via furring strips 14. The wooden exterior building material 21 is made of wood that has been painted with the wood paint according to the embodiment, and has a coating 22 on its surface.

The exterior wall material 11 of this embodiment is not particularly limited, but examples that can be used include plywood, MDF (medium density fiberboard), OSB (oriented strand board), gypsum board, calcium silicate board, and particle board.

The insulation material 12 in this embodiment is not particularly limited, but mineral fiber insulation, wood fiber insulation, and foam plastic insulation can be used. These can be commercially available products selected as appropriate. In another embodiment, foam plastic insulation, which has excellent thermal insulation properties, can be used, and in yet another embodiment, phenol foam insulation, which is a foam plastic insulation, can be used. The thickness of the phenol foam insulation can be 50 to 200 mm. This is because a wooden exterior structure can be considered a fire-resistant structure as defined in Article 2, Paragraph 8 of the Building Standards Act.

The waterproof sheet 13 of this embodiment is not particularly limited, but a moisture-permeable waterproof sheet can be used. This is because moisture permeability can help prevent condensation on the wooden exterior structure. The waterproof sheet 13 can contain an ultraviolet absorber to improve its weather resistance. The waterproof sheet 13 can also be painted with a moisture-permeable paint.

The moisture-permeable paint contains synthetic resin emulsion, colloidal silica, and, as necessary, color pigment, extender pigment, wetting agent, pH adjuster, and thickener as raw materials. Table 2 shows an example of a moisture-permeable paint formulation and the preferred ranges (parts by mass) of other raw materials when the synthetic resin emulsion is taken as 100 parts by mass.

Synthetic resin emulsion is the binder for moisture-permeable paint, and the resin composition can be urethane resin, acrylic resin, styrene-butadiene copolymer resin, or silicone resin. These can be used alone, in combination with two or more other materials, or copolymerized with different monomers. Colloidal silica is a raw material that increases the moisture permeability of the coating formed from moisture-permeable paint. Coloring pigments are raw materials that impart color to the coating, and examples of such materials include titanium oxide, carbon black, and iron oxide. Extender pigments form a coating together with the binder, and examples of such materials include calcium carbonate, silica sand, talc, and barium sulfate.

In one embodiment, the moisture-permeable paint is applied at a thickness that provides a hiding rate (hiding power (for light color paints) (JIS K 5600-4-1:1999)) of 80% or more. This is because the moisture-permeable paint can improve weather resistance even without containing a UV absorber, and does not significantly reduce the moisture permeability of the waterproof sheet 13. In another embodiment, the hiding rate can be 90% or more, and in yet another embodiment, 95% or more.

The breathable paint of this embodiment can be applied to a thickness that provides a hiding rate of 80% or more, thereby enhancing waterproofing. The enhanced waterproofing of the coating formed from the breathable paint allows the wooden exterior structure to omit the waterproof sheet 13. This is because waterproofing is ensured by the coating formed from the breathable paint. Since the breathable paint is applied directly to the insulation 12, the pH of the breathable paint is adjusted to 6-8. This is because hydrolysis of the insulation 12 (phenolic foam insulation) can be suppressed.

The wooden exterior building material 21 is installed via furring strips 14 on the insulation material 12, which has a waterproof sheet 13 attached and a moisture-permeable paint applied to it.

The furring strips 14 are not particularly limited, but may be made of metal, wood, or plastic. Provided the base (the coating made of breathable paint) is flat (with minimal unevenness), the furring strips 14 may be omitted.

Next, we will describe the construction method for the wooden exterior structure of this embodiment. The wood paint of this embodiment consists of the following steps: a first step of attaching insulation material 12 to the exterior wall material 11; a second step of attaching a waterproof sheet 13 to the insulation material 12; a third step of applying a breathable paint to the waterproof sheet 13; a fourth step of placing furring strips 14 on the waterproof sheet 13 to which the breathable paint has been applied; and a fifth step of fixing the wooden exterior building material 21 to the furring strips 14.

The first step, attaching the insulation material 12 to the exterior wall material 11, is to use nails, screws, adhesives, etc. to attach the insulation material 12 to the exterior wall material 11. General-purpose waterproof tape is applied to the joints of the insulation material 12 to ensure airtightness. The second step, attaching the waterproof sheet 13 to the insulation material 12, is to use pin tackers, nails, etc. to attach the waterproof sheet 13 to the insulation material 12.

In the third step of applying the moisture-permeable paint to the waterproof sheet 13, the moisture-permeable paint is applied to the waterproof sheet 13 using a roller, brush, or the like. The amount of paint applied is 100 to 150 g/ ^m2 in terms of non-volatile content. In the fourth step of placing the furring strips 14 on the waterproof sheet 13 coated with the moisture-permeable paint, the furring strips 14 are fixed using screws or nails to the insulation material 12 to which the waterproof sheet 13 coated with the moisture-permeable paint is attached.

The fifth step, which involves fixing the wooden exterior building material 21 to the furring strips 14, is to fix the wooden exterior building material 21 to the furring strips 14 using screws, nails, or adhesive. The wooden exterior building material 21 can be positioned (fixed) using either a lattice joint or a butt joint, and when butting, a tongue and groove joint can also be used. The wooden exterior building material 21 can be positioned so that the grain of the wood that makes up the wooden exterior building material 21 runs horizontally. This is because it is possible to reduce water absorption from the wood's ducts.

A wooden exterior structure constructed in this way can be used as a wooden exterior structure with wooden exterior building materials 21 on the exterior walls of a building, and can be a fire-resistant structure as defined in Article 2, Paragraph 8 of the Building Standards Act.

Wood exterior building materials 21 equipped with a coating 22 formed from wood paint peel off gradually in small pieces, so even if the coating peels off, the change in appearance is difficult to see.

The wood paints of the present embodiment, each with a different formulation, were applied to the surface of a 105 mm wide x 300 mm long x 12 mm thick cedar lumber piece at a coating weight of 150 g/ ^m2 (wet state), and then dried to prepare test specimens, which were then evaluated (tested) as described below. The paint compositions of the examples and comparative examples, as well as the test results, are shown in Table 3.

Changes in appearance Changes in appearance were evaluated by exposing the test specimen outdoors for one year and comparing its appearance with that of a spare specimen (a specimen not exposed outdoors).The test specimen and the spare specimen were then evaluated as follows: ○: those in which there was almost no difference between them; △: those in which a difference was visible when placed side by side but not when observed from a distance; ×: those in which a difference was visible even when observed from a distance.

Similarity of appearance to unpainted wood after deterioration The similarity of appearance to unpainted wood after deterioration was evaluated by exposing test specimens outdoors for one year and comparing their appearance with that of unpainted cedar lumber exposed under the same conditions. Exposed test specimens and unpainted wood that looked similar in appearance were evaluated as ◎, differences were visible when placed side by side but there was no difference when observed from a distance, △, and those that looked very different in appearance were evaluated as ×.

Details of the ingredients are listed below.

Synthetic resin A
Vinyl-modified epoxy ester resin Weight average molecular weight: approx. 50,000 Non-volatile content: 60% by mass
Pencil hardness <6B
Synthetic resin B
Urethane-acrylic copolymer resin Weight average molecular weight: approx. 1 million Non-volatile content: 50% by mass
Pencil hardness 2H
Metal oxide coated mica particle size 30 μm
Composition: Mica 70wt%, Titanium dioxide 29.5wt%, Silica 0.5wt%
Silica particle size 3.4 μm
India ink A
Type Oil smoke ink Non-volatile content 19.5% by mass
Ink particle size: 0.1 μm
India ink B
Type: Pine soot ink Non-volatile content: 27.8% by mass
Ink particle size: 0.1 μm
The dispersant, antifoaming agent, preservative and antifreeze agent were selected from commercially available products.

Example 1
Example 1, which represents the best mode, used synthetic resin A, a vinyl-modified epoxy ester resin, as the binder, India ink A, and added metal oxide-coated mica and silica. Because the coating 22 of the outdoor-exposed specimens was transparent to ultraviolet light, the surface of the wood coated with the wood paint deteriorated (ashed) by ultraviolet light and turned approximately gray, while the coating 22 turned approximately gray due to the ink. The coating 22 of the outdoor-exposed specimens had poor weather resistance and peeled off in small pieces. However, because the coating pieces were small and the coating 22 and the wood surface (the areas where the coating 22 had peeled off) were similar in color (ΔE ^* = 5.0), the peeled areas were difficult to see from the outside and appeared as a roughly uniform color. Therefore, when comparing the appearance of the outdoor-exposed specimens with the spare specimens, there was little difference. Furthermore, the outdoor-exposed specimens had an appearance similar to that of unpainted cedar lumber exposed under the same conditions, with the metal oxide-coated mica enhancing the gloss of the ink and the silica reducing the gloss of the coating 22.

(Examples 2 and 3)
Example 2 is an example in which the amount of metal oxide-coated mica was increased from Example 1. Example 3 is an example in which the amount of metal oxide-coated mica was reduced and the amount of silica was increased from Example 1. When comparing the appearance of each outdoor-exposed test specimen with that of the spare test specimen, there was almost no difference, and the appearance was similar to that of unpainted cedar lumber exposed under the same conditions.

(Examples 4 to 6)
Example 4 is Example 1, except that the metal oxide-coated mica is omitted and the amount of silica is increased. Example 5 is Example 1, except that the silica is omitted and the amount of metal oxide-coated mica is increased. Example 6 is Example 1, except that the metal oxide-coated mica and silica are omitted. When comparing the appearance of each outdoor-exposed test specimen with that of the spare test specimen, there was almost no difference, but when compared with unpainted cedar lumber exposed under the same conditions, Example 4 lacked the ink gloss, Example 5 had a strong ink gloss, and Example 6 had a resin gloss, and although there was no sense of incongruity when they were separated from each other, the differences were noticeable when placed side by side.

Example 7
In Example 7, the amount of synthetic resin was reduced, the blending amounts of metal oxide-coated mica and silica were adjusted, and a dispersant and an antifoaming agent were added compared to Example 1. The test specimens exposed outdoors showed almost no difference in appearance when compared with the spare test specimens, and were similar in appearance to unpainted cedar lumber exposed under the same conditions.

(Example 8)
Example 8 was the same as Example 1 except that the amount of synthetic resin was increased, the ink was changed to India ink B, and the blending amounts of metal oxide-coated mica and silica were adjusted. The outdoor-exposed test specimen showed almost no difference in appearance when compared with the spare test specimen, and was closer in appearance to unpainted cedar lumber exposed under the same conditions.

(Comparative Example 1)
In Comparative Example 1, the synthetic resin used in Example 1 was changed to Synthetic Resin B, a urethane-acrylic copolymer resin with excellent weather resistance, and the ink was eliminated. The outdoor-exposed specimens showed little resin degradation, and although a wet color was visible, there was almost no UV degradation (ashing) of the wood surface, and they were in a state similar to that of unpainted boards. There was little difference from the test specimens, and while the difference was noticeable when placed side by side, it was imperceptible when separated. However, when compared to unpainted cedar lumber exposed under the same conditions, the unpainted cedar lumber showed UV degradation (ashing), resulting in a completely different appearance.

(Comparative Example 2)
Comparative Example 2 is Comparative Example 1 with ink added. The outdoor-exposed test specimen showed little resin degradation, and although a wet color was visible, there was almost no UV degradation (ashing) of the wood surface, and it was in a state similar to that of an unpainted board, with only a small difference from the counter specimen; when placed side by side, the difference was noticeable, but when separated, the difference was imperceptible. Compared to unpainted cedar lumber exposed under the same conditions, UV degradation (ashing) was observed in the unpainted cedar lumber, and the outdoor-exposed test specimen of Comparative Example 2, to which ink was added, showed a nearly gray color, and when placed side by side, the difference was noticeable, but when separated, there was no sense of incongruity.

11...exterior wall material, 12...insulating material, 13...waterproof sheet, 14...furring strip, 21...wood exterior building material, 22...coating.

Claims (5)

The composition contains, in terms of nonvolatile content, 40 parts by mass of vinyl-modified epoxy ester resin, 1 to 2 parts by mass of India ink, and 1 to 5 parts by mass of metal oxide-coated mica.
The metal oxide-coated mica has a particle size of 10 to 100 μm . The composition contains, in terms of nonvolatile content, 3 to 15 parts by mass of silica relative to 40 parts by mass of the vinyl-modified epoxy ester resin,
2. The wood paint according to claim 1, wherein the particle size of the silica is 1 to 10 μm . 3. The wood coating material according to claim 1, wherein the weight-average molecular weight of the vinyl-modified epoxy ester resin is 10,000 to 100,000 . 4. The wood paint according to claim 1, wherein the ink is lamp black ink. 5. A wooden exterior building material coated with a coating film formed from the wood paint according to any one of claims 1 to 4 .