JP5238998B2 - Method for imparting hydrophilicity to aluminum building materials - Google Patents

Description

The present invention relates to an aluminum building material such as a curtain wall or a sash that is installed in a building and used outdoors, and particularly relates to a method for imparting hydrophilicity to an aluminum building material that imparts a self-cleaning function to the thermosetting coating film.

  In order to impart a self-cleaning function to building materials, it is generally assumed that a photocatalytic semiconductor or a hydrophilizing agent is applied to the surface or a coating layer containing these is formed to impart hydrophilicity. Colloidal silica or the like is used as the chemical treatment agent, and titanium dioxide or the like is used as the photocatalytic semiconductor. On the other hand, for imparting hydrophilicity by ultraviolet irradiation treatment, for example, an inorganic resin having a siloxane bond is subjected to ultraviolet irradiation treatment as in the case where an alkoxysilane hydrolyzate is applied and polymerized, and OH is added to the side chain of Si. Those that form a functional group such as a group to impart hydrophilicity to the surface are known.

  However, photocatalytic semiconductors cannot be used for thermosetting coatings for decomposing organic substances, whereas hydrophilic treatment agents can be used for thermosetting coatings, even though they can be used for thermosetting coatings. It is difficult to ensure good adhesion with the film, and it is difficult to uniformly apply, and uneven coating is likely to cause poor appearance. In addition, when a hydrophilizing agent is added to an acrylic melamine-based paint for forming a thermosetting film, the paint is a water-soluble paint. Therefore, the hydrophilizing agent reacts with moisture in the paint to improve the stability of the paint. Therefore, none of these are suitable for imparting hydrophilicity to an aluminum building material provided with a thermosetting coating film such as an acrylic melamine type.

Therefore, the present inventors formed an acrylic melamine-based thermosetting coating film, and then subjected to ultraviolet irradiation treatment on the acrylic side chain in the thermosetting coating film in the same manner as described above. As a result of research intended to form a group imparting hydrophilicity, after performing ultraviolet ray irradiation processing integrated irradiation dose of 3,000 mJ / cm ² to 10,000 / cm ² in the thermosetting coating, When the thermosetting coating is applied to the thermosetting coating at 70 to 90 ° C., the short-term increase in the water contact angle, which is reduced to 60 degrees or less by ultraviolet irradiation, is prevented, and the performance of the thermosetting coating is maintained. However, it is possible to ensure good hydrophilicity over a long period of time and also to ensure good adhesion to sealing materials used between other aluminum building materials and building frames when installing this kind of aluminum building materials. UV irradiation The hydrophilicity imparting method of the aluminum building material of the following literature 1, and the aluminum building material of hydrophilic property of the following literature 1 which used the process and the hot-water contact process together, and provided hydrophilicity have been proposed.

JP 2008-194777 A

In this case, it is possible to impart a good water contact angle and hydrophilicity to the thermosetting coating film. However, UV irradiation to the thermosetting coating film may cause choking or deterioration due to bond bond breakage or dissociation energy. Therefore, it is preferable to reduce the UV irradiation amount as much as possible to eliminate the possibility of such damage to the thermosetting coating film. In order to ensure favorable hydrophilicity by contact with the hot water, it is generally necessary to perform the ultraviolet irradiation treatment with an integrated dose of 3,000 mJ / cm ² or more, which is less than 3,000 mJ / cm ² . When the UV irradiation treatment with the integrated irradiation amount is performed, the water contact angle is temporarily lowered, the maintenance period of the reduced water contact angle is relatively short, and the self-cleaning function as an aluminum building material is sufficiently achieved. It tends to cause a tendency that cannot be secured. Therefore, it is desirable to make it possible to further reduce the cumulative irradiation amount of ultraviolet irradiation to the thermosetting coating film and to maintain hydrophilicity for as long as possible.

The present invention has been made in view of such circumstances, and the solution to the problem is aluminum that imparts hydrophilicity to the aluminum building material by the ultraviolet irradiation treatment while eliminating the possibility of damage to the thermosetting coating film by ultraviolet irradiation. It is in providing the hydrophilicity imparting method of building materials .

  As a result of diligent examination along the above-mentioned problems, the present inventors found that after the ultraviolet curing treatment was applied to the thermosetting coating film, the ultraviolet curing treatment and the acidic treatment were performed such that the thermosetting coating film was further subjected to an acidic aqueous solution contact treatment. It has been found that, when used in combination with an aqueous solution contact treatment, good hydrophilicity can be maintained even if the cumulative dose of ultraviolet irradiation treatment is reduced as much as possible.

That is, the thermosetting paint used for forming the thermosetting coating generally contains an excessive thermosetting agent more than necessary for crosslinking of the coating, so that the surface layer of the thermosetting coating formed on the aluminum building material has When an excessive thermosetting agent self-condensation layer is present, by subjecting the thermosetting coating to ultraviolet irradiation, the surface layer is forcibly modified, that is, the self-condensation layer or the condensation of the cross-linked surface is broken. If the fractured surface layer is removed in the subsequent process to expose a cross-linked surface having a functional group such as an OH group on the surface of the thermosetting coating film, hydrophilicity can be imparted to the thermosetting coating film. It becomes possible. However, depending on the cumulative irradiation amount of ultraviolet irradiation, the condensation layer is not sufficiently broken, and as a result of leaving a residue when the surface layer is removed in a later step, the residue is considered to be a factor that impairs its maintenance or its maintenance. Contact with an acidic aqueous solution by immersing in or spraying an aqueous solution of an inorganic acid or organic acid having a pH of 2 or more and pH 5 or less after an ultraviolet irradiation treatment with an integrated irradiation amount of 1,500 mJ / cm ² or more and 3,000 mJ / cm ² or less. By performing the above-described washing treatment with hot water at 50 to 90 ° C., the acidic aqueous solution contact treatment further breaks the unbroken site including the residue of forced modification of the ultraviolet irradiation treatment, thereby It acts to complement forced modification by irradiation treatment , and the cleaning treatment removes the surface layer of the forced modification and forms a cross-linked surface having a functional group of OH group on the surface of the thermosetting coating film. The knowledge that hydrophilicity is ensured by exposing and a preferable self-cleaning function can be imparted to the aluminum building material was obtained.

The present invention has been made on the basis of such knowledge. That is, the invention according to claim 1 is an anodized film having a predetermined thickness on an aluminum substrate and an acrylic melamine-based heat having the same predetermined thickness on the anodized film. Using the aluminum building material provided with a cured coating film, after forming the acrylic melamine-based thermosetting coating film, the thermosetting coating film is subjected to ultraviolet irradiation treatment, acidic aqueous solution contact treatment, and subsequent cleaning treatment to perform the above thermosetting. A hydrophilicity imparting method for imparting hydrophilicity to a coating film, wherein the ultraviolet irradiation treatment is performed by ultraviolet irradiation with an integrated dose of 1,500 mJ / cm ² or more and 3,000 mJ / cm ² or less. The film is subjected to forced modification to break the condensation between the self-condensing layer of the film and the acrylic cross-linked surface, and the acidic aqueous solution contact treatment is immersed in an aqueous solution of an inorganic acid or an organic acid having a pH of 2 or more and a pH of 5 or less, or spraying of the aqueous solution As a result of this, the unrepaired part including the residue of the forced reforming, which constitutes a hindrance to maintaining hydrophilicity in the ultraviolet irradiation treatment, is further broken to supplement the forced reforming, and the cleaning treatment is performed 50 to An aluminum building material characterized by ensuring hydrophilicity by removing the surface layer of the above-mentioned forced modification and exposing a cross-linked surface having a functional group of OH group on the surface of the thermosetting coating as hot water washing at 90 ° C. This is a hydrophilicity imparting method.

In addition to the above, the invention described in claim 2 effectively performs forced reforming by setting the integrated irradiation amount of the ultraviolet irradiation treatment to 1,800 mJ / cm ² or more and 2,000 mJ / cm ² or less. Since it can be preferable in terms of securing and maintaining the water contact angle, the cumulative irradiation amount of the ultraviolet irradiation treatment should be set to 1,800 mJ / cm ² or more and 2,000 mJ / cm ² or less. The method for imparting hydrophilicity to an aluminum building material according to claim 1 .

In addition to the above, the invention described in claim 3 has a water contact angle of 60 after outdoor exposure to the thermosetting coating film so that the hydrophilicity of the thermosetting coating film is preferable. The method for imparting hydrophilicity to an aluminum building material according to claim 1 or 2, wherein hydrophilicity is imparted to less than 0 ° .

  The present invention uses each of these as the gist of the invention as means for solving the above problems.

Since the present invention is configured as described above, the invention according to claim 1 has a pH of 2 or more and a pH of 5 or less after the ultraviolet irradiation treatment in which the integrated irradiation amount is 1,500 mJ / cm ² or more and 3,000 mJ / cm ² or less. An acidic aqueous solution contact treatment by immersion in an inorganic acid or organic acid aqueous solution or spraying of the aqueous solution is performed, and further the washing treatment by hot water washing at 50 to 90 ° C. It acts to further break the unbroken part including the residue of forced modification of the irradiation treatment to supplement the forced modification by the ultraviolet irradiation treatment , and the cleaning treatment removes the surface layer of the forced reforming and heats it. By exposing the cross-linked surface with functional groups of OH groups on the surface of the cured coating, the least possible UV irradiation and the effect on the thermosetting coating can be minimized and as long as possible. Span It is possible to provide a method for imparting hydrophilicity to an aluminum building material that ensures hydrophilicity and imparts a preferable self-cleaning function to the aluminum building material.

In addition to the above, the invention described in claim 2 effectively performs forced reforming by setting the integrated irradiation amount of the ultraviolet irradiation treatment to 1,800 mJ / cm ² or more and 2,000 mJ / cm ² or less. From the aspect of securing and maintaining the water contact angle, it can be preferable.

In addition to the above, the invention described in claim 3 can also make the hydrophilicity of the thermosetting coating film preferable.

It is a bar graph which shows the initial contact angle of an Example and a comparative example. It is a line graph which shows a time-dependent change of the contact angle of an Example and a comparative example.

  The present invention will be described in more detail below. The aluminum building material has an acrylic melamine-based thermosetting coating film, and the thermosetting agent self-condensation layer on the surface of the thermosetting coating film that has been forcibly modified by ultraviolet irradiation is acidic. By removing it by contact with aqueous solution, the surface of the thermosetting coating is made hydrophilic by exposing an acrylic cross-linked surface having a functional group such as OH group in the side chain. It is as having.

That is, the aluminum building material is made of, for example, an aluminum substrate such as an aluminum panel, an aluminum extruded shape, and the like provided with an anodic oxide film having a predetermined film thickness and an acrylic melamine-based thermosetting film of the same film thickness on the anodic oxide film. In this example, the anodized film is a colored film that has been subjected to secondary electrolytic coloring, and the thermosetting coating film is an acrylic melamine-based film that uses melamine as a thermosetting agent. As a clear coating. On the surface of the thermosetting coating film, an acrylic cross-linked surface having the functional group is exposed so as to cover the entire surface thereof, whereby the water contact angle of the thermosetting coating film is 60 degrees or less, for example, on the order of 50 degrees. As the first half, it is assumed that it exhibits good hydrophilicity, while the hydrophilicity is to maintain its water contact angle constantly over a long period of several years or more when installed outdoors. At this time, the thermosetting coating film has not only the film thickness but also the coating properties such as weather resistance, corrosion resistance, hardness and the like, and a sealing agent that may be generated by imparting hydrophilicity to the thermosetting coating film, for example. As a result, it has a high degree of waterproofing performance at the same time with good sealing between other aluminum building materials and the wall of the building frame as an aluminum building material for outdoor use. It is as.

For imparting hydrophilicity to the aluminum building material, the hydrophilic property is obtained by subjecting the thermosetting coating film to ultraviolet irradiation treatment, acidic aqueous solution contact treatment, and subsequent washing treatment after the formation of the acrylic melamine-based thermosetting coating film . The above-described ultraviolet irradiation treatment is performed by an ultraviolet irradiation with an integrated irradiation amount of 1,500 mJ / cm ² or more and 3,000 mJ / cm ² or less. Forcibly modifying the condensation with the acrylic cross-linked surface, and the acidic aqueous solution contact treatment is performed by immersion in an aqueous solution of an inorganic acid or organic acid having a pH of 2 or more and a pH of 5 or less, or by spraying the aqueous solution. Further, the forced modification is supplemented by further rupturing the unbroken portion including the residue of the forced reforming, which is an inhibiting factor for maintaining the hydrophilicity in the treatment. As the water washing at 0 ° C., hydrophilicity is ensured by removing the surface layer of the forced modification and exposing a cross-linked surface having a functional group of OH group on the surface of the thermosetting coating film .

That is, the hydrophilicity is imparted by forming the thermosetting coating film, and then performing the ultraviolet irradiation treatment , the acidic aqueous solution contact treatment, and the washing treatment of the thermosetting coating film by water washing or hot water washing by a series of processes or by a batch process. It is supposed to give.

The ultraviolet irradiation treatment is performed by ultraviolet irradiation at an integrated dose of 1,500 mJ / cm ^{2 to} 3,000 mJ / cm ² and the acidic aqueous solution contact treatment is performed with an inorganic acid having a pH of 2 or more and pH 5 or less. It is performed by immersion in an organic acid aqueous solution or spraying of the aqueous solution, in this example, immersion. In this example, the hot water washing is performed by immersing in hot water or hot water at 50 ° C. or higher, for example, about 90 ° C.

For example, the ultraviolet irradiation treatment may be performed by passing the aluminum building material through a line in which a UV lamp such as a high-pressure mercury lamp is installed, or by irradiating the aluminum building material suspended and supported in the space in which the UV lamp is installed. When the amount is less than 1,500 mJ / cm ² , the forced modification of the thermosetting coating film by the ultraviolet irradiation treatment becomes insufficient, and even if an acidic aqueous solution contact treatment is performed thereafter, the hydrophilic water contact angle can be maintained. This shortens the period and makes it impossible to ensure hydrophilicity over a long period of time. Therefore, the lower limit of the cumulative irradiation amount of the ultraviolet irradiation treatment is preferably set to 1,500 mJ / cm ² . In this case, the amount of ultraviolet irradiation is preferably 1,800 mJ / cm ² or more, particularly about 2,000 mJ / cm ² from the viewpoint of securing and maintaining a water contact angle by effectively performing forced reforming. On the other hand, if the integrated irradiation amount is large, it leads to pulverization and deterioration factors of the thermosetting coating film, and the coating performance of the thermosetting coating film is reduced. However, in the ultraviolet ray, that is, the ultraviolet ray having a wavelength of 280 to 400 nm, In the integrated irradiation amount of up to about 10,000 to 12,000 mJ / cm ^2, it can be used without damaging the thermosetting coating film, but the above-mentioned up to 3,000 mJ / cm ² . From the standpoint of suppressing the influence on the thermosetting coating as much as possible while the forced modification of the thermosetting coating can be sufficiently achieved with the integrated irradiation, the upper limit of the integrated irradiation is generally the above 3, 000 mJ / cm ² is preferable.

  On the other hand, the acidic aqueous solution contact treatment can use various inorganic acids or organic acids such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, phosphoric acid, formic acid, citric acid, oxalic acid, etc. The difference in hydrophilization is relatively small, but when the aqueous solution is below pH 2, the hydrogen ion concentration is too high. This will damage the thermosetting coating film. Accordingly, the lower limit of the hydrogen ion concentration in the acidic aqueous solution contact treatment is preferably set to pH 2. On the other hand, if the pH is higher than 5, the hydrogen ion concentration is too low. As a result, the removal of the forcedly reformed surface layer becomes insufficient, and the forced reforming by the ultraviolet irradiation treatment cannot be supplemented. Therefore, the upper limit of the hydrogen ion concentration in the acidic aqueous solution contact treatment is preferably set to pH 5. The acidic aqueous solution contact treatment may be performed, for example, by immersing the aluminum building material in an aqueous solution of the above inorganic acid or organic acid for about 1 to 2 minutes or spraying the aqueous solution.

  That is, an acrylic melamine-based paint forms a thermosetting coating film by, for example, crosslinking acrylic with melamine as a thermosetting agent (crosslinking agent) in the baking step after electrodeposition coating. Since excessive melamine is added excessively to the surface, the melamine self-condensation layer is formed on the surface of the thermosetting coating by the self-condensation of excess melamine in the baking process and floating on the surface side. It is common. The ultraviolet irradiation treatment is carried out by forced modification to break the condensation between the melamine self-condensed layer or the acrylic cross-linked surface, while the acidic aqueous solution contact treatment used in combination with the ultraviolet irradiation treatment causes unbreakage in the ultraviolet irradiation treatment. The part is further broken to supplement the forced modification by the ultraviolet irradiation treatment, and the surface layer subjected to the forced modification is removed by the contact treatment, or further washed by water or hot water, and in this example, further washed by hot water. As a result of removing the surface layer and exposing the cross-linked surface having a functional group such as OH group on the surface of the thermosetting coating film, the water contact angle of the thermosetting coating film is reduced, and the hydrophilicity is ensured. When the ultraviolet irradiation amount is below the lower limit, forced reforming by ultraviolet irradiation treatment is performed, and when the hydrogen ion concentration of the acidic aqueous solution exceeds the upper limit, the compulsory reforming is insufficient. Contact angle That difficult without 60 degrees or less and a water contact angle that long-term maintenance. Therefore, in order to make the thermosetting coating hydrophilic without damaging the thermosetting coating, it is necessary to pay attention to the lower limit of the cumulative irradiation amount in the ultraviolet irradiation amount and the upper limit of the hydrogen ion concentration in the acidic aqueous solution.

  The washing treatment of the thermosetting coating after the acidic aqueous solution contact treatment is performed by washing with water or hot water by immersion washing or running water washing, etc., and the melamine adhering to the thermosetting coating without being removed by the acidic aqueous solution contact treatment. The self-condensation layer and the residue thereof may be removed, and the acidic aqueous solution attached to the thermosetting coating film may be removed. When hot water washing is performed, for example, at about 50 to 90 ° C. for about 1 to 2 minutes, the self-condensation layer and the acidic aqueous solution can be reliably removed.

Using a JIS6063 aluminum plate in which an acrylic melamine thermosetting coating film using melamine as a thermosetting agent is formed on a colored coating film subjected to secondary electrolytic coloring according to a conventional method, the output is 120 W and the distance between lamps is 10 cm. , 2,000 mJ / cm ² of UV irradiation treatment with an integrated dose, followed by acid aqueous solution contact treatment immersed in a pH 2 sulfuric acid aqueous solution for 1 minute, followed by water washing at room temperature for 1 minute and hot water washing at 78 ° C. for 1 minute. A specimen subjected to the cleaning treatment was prepared, and the initial contact angle was measured with a contact angle meter CA-X150 type (manufactured by Kyowa Interface Science Co., Ltd.). The results are shown in FIG. Thereafter, the test specimens were exposed to the outdoors, and the contact angles after 1 week, 2 weeks and 30 days were measured in the same manner, and changes in the contact angles with time were observed. The result is shown in FIG. Furthermore, the acid resistance test (48 hours with 5% H2SO4, 72 hours, 48 hours with 5% HCl), alkali resistance test (48 hours, 0.5 hours with 0.5% NaOH), CASS test (72 hours, 144 hours) Time) and boiling water test (appearance after 5 hours, pencil hardness and cross-cut adhesion test) were performed. The results are shown in Table 1.

The same procedure as in Example 1 was conducted except that the test body was made with an integrated dose of ultraviolet irradiation treatment of 3,000 mJ / cm ² . Similarly, the results are shown in Table 1, FIG. 1 and FIG.

Comparative Example 1

  The acidic aqueous solution contact treatment after the ultraviolet irradiation treatment was omitted, a washing treatment by washing with water at room temperature for 1 minute was performed to obtain a test body, and the same as Example 1 except that each test was omitted. Similarly, the results are shown in FIGS.

Comparative Example 2

  The same procedure as in Example 2 was conducted except that the acidic aqueous solution contact treatment after the ultraviolet irradiation treatment was omitted, and a test treatment was performed by washing with water at room temperature for 1 minute. Similarly, the results are shown in FIGS.

Comparative Example 3

  It replaced with the acidic aqueous solution contact process after an ultraviolet irradiation process, and it was the same as that of Example 2 except having performed the washing process (hot water contact process) by hot water washing at 78 degreeC for 1 minute. Similarly, the results of the initial contact angle and the change with time of the contact angle are shown in FIGS.

  The sulfuric acid aqueous solution in the acidic aqueous solution treatment was added to pH 2 to adjust pH 4 and pH 5 and was the same as Example 1 except that the initial contact angle was measured. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution processing, and was carried out similarly to Example 3 except having used the hydrochloric acid aqueous solution. The results are shown in Table 2.

  Example 3 was repeated except that an aqueous nitric acid solution was used instead of the aqueous sulfuric acid solution in the acidic aqueous solution treatment. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution processing, and was carried out similarly to Example 3 except having used the acetic acid aqueous solution. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution process, and was carried out similarly to Example 3 except having used the phosphoric acid aqueous solution. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution processing, and was carried out similarly to Example 3 except having used the formic acid aqueous solution. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution processing, and was carried out similarly to Example 3 except having used the citric acid aqueous solution. The results are shown in Table 2.

  It replaced with the sulfuric acid aqueous solution in acidic aqueous solution process, and was carried out similarly to Example 3 except having used the oxalic acid aqueous solution. The results are shown in Table 2.

  According to Table 1, no difference was observed between Examples and Comparative Examples in each acid resistance test, boiling water test, alkali resistance test, and boiling water test, and no difference was also observed in the CASS test.

  According to FIG. 1, the initial contact angle is less than 60 degrees for both the example and the comparative example, but the first example is 46 degrees, the first comparative example is 59 degrees, the second example is 40 degrees, the second comparative example is 57 degrees, Comparative Example 3 is 46 degrees, so that the acidic aqueous solution contact treatment after the ultraviolet irradiation treatment greatly reduces the water contact angle of the thermosetting coating, and Example 1 is the same result as Comparative Example 3. Therefore, it can be seen that the acidic aqueous solution contact treatment is effective in reducing the ultraviolet irradiation amount.

  According to FIG. 2, the initial contact angle increases over a period of about 2 weeks, but after that, stable hydrophilicity is exhibited. In particular, Example 2 maintains a contact angle in the first half of the 50 degree range, It turns out that preferable hydrophilicity is exhibited.

  According to Table 2, the contact angle is lowered to 60 degrees or less, which is generally considered to have a self-cleaning function, by subjecting the thermosetting coating film subjected to ultraviolet irradiation treatment to an acidic aqueous solution contact treatment, and the type of acid is not limited. It can be seen that the thermosetting coating film is made hydrophilic.

Claims (3)

Using an aluminum building material provided with an anodic oxide film having a predetermined film thickness and an acrylic melamine-based thermosetting film of the same predetermined thickness on the anodized film on the aluminum substrate, after the acrylic melamine-based thermosetting film formation, A hydrophilicity imparting method for imparting hydrophilicity to the thermosetting coating film by subjecting the thermosetting coating film to ultraviolet irradiation treatment, acidic aqueous solution contact treatment, and subsequent cleaning treatment , wherein the ultraviolet irradiation treatment is performed by 1 , as by ultraviolet irradiation of 500 mJ / cm ² or more 3,000 mJ / cm ² or less of the total irradiation amount, to force modification breaking the condensation of self Chijimigoso to this and acrylic crosslinked surface of the heat cured coating film, The acidic aqueous solution contact treatment is performed by immersion in an inorganic acid or organic acid aqueous solution having a pH of 2 or more and a pH of 5 or less, or by spraying the aqueous solution, thereby inhibiting hydrophilicity maintenance in the ultraviolet irradiation treatment. The unbreaked portion including the forced reforming residue is further broken to supplement the forced reforming, and the cleaning process is performed as hot water washing at 50 to 90 ° C. to remove the surface layer of the forced reforming and heat. A method for imparting hydrophilicity to an aluminum building material, wherein hydrophilicity is ensured by exposing a cross-linked surface having an OH functional group to the surface of a cured coating film . The integrated irradiation amount of the ultraviolet irradiation treatment is 1,800 mJ / cm. ² More than 2,000mJ / cm ² The method for imparting hydrophilicity to an aluminum building material according to claim 1, wherein: 3. The method for imparting hydrophilicity to an aluminum building material according to claim 1, wherein the thermosetting coating film is imparted with hydrophilicity such that a water contact angle after 30 days of outdoor exposure is less than 60 °.

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