JP5010966B2 - Water repellent paint and water repellent metal plate - Google Patents

Description

  The present invention relates to a water-repellent paint and a water-repellent metal plate, and in particular, a water-repellent paint that forms a water-repellent coating film excellent in water repellency (antifouling property, snow resistance, weather resistance) and the water-repellent paint. The applied water-repellent metal plate.

  Conventionally, in order to provide a metal plate excellent in antifouling property, snow resistance, weather resistance, etc., the metal plate is coated with a water-repellent paint such as fluorine resin or silicon resin on the surface of the metal plate. It has been practiced to impart water repellency. Here, for example, it is known that when a fluorine-based paint is applied to a flat aluminum alloy plate, water repellency with a water contact angle of about 100 to 110 ° is obtained. In addition, it is known that water repellency can be improved by forming irregularities on the surface of a coating film coated on a metal plate by mixing fine particles in the paint.

As described above, water repellent paint in which tetrafluoroethylene (PTFE) powder is mixed in a non-fluorine resin is used on a FRP (Fiber Reinforced Plastics) substrate to improve water repellency by mixing fine particles in the paint. A technique for providing water repellency with a water contact angle of about 150 ° by applying to the surface is disclosed (for example, see Patent Document 1). In addition, a technique has been disclosed in which a water repellent paint having a water contact angle of 170 ° at the maximum is obtained by applying a water repellent paint in which hydrophobic fine particles and a resin are mixed to an aluminum plate (see, for example, Patent Document 2). .
JP-A-8-3477 (paragraphs 0008 to 0013) JP-A-3-215570 (page 4, upper left column, line 10 to page 5, upper right column, line 20)

However, the above-described water-repellent paint has the following problems.
These water-repellent paints form irregularities on the surface of a coating film formed by applying paint to a metal plate by dispersing fine particles in the paint.
However, when fine particles are mixed in the paint, it is difficult to disperse the fine particles completely and uniformly, and the mixed fine particles are dispersed in a non-uniform state in the paint. Thus, if the fine particles are dispersed in a non-uniform state in the paint, the unevenness formed on the surface of the applied coating film becomes non-uniform when the paint is applied to the metal plate. Therefore, even if a coating film is formed on the metal plate, it is difficult to impart uniform water repellency to the entire surface of the metal plate, and there is a problem that a portion having poor water repellency is generated on the surface of the metal plate.

  The present invention has been made in view of the above problems, and the object thereof is excellent in water repellency, and due to this water repellency, it is excellent in antifouling property, snow resistance and weather resistance, and An object of the present invention is to provide a water-repellent paint that forms a coating film having uniform water repellency by uniformly forming irregularities on the surface of the coating film, and a water-repellent metal plate coated with this water-repellent paint.

As a result of intensive studies to solve the above problems, the present inventors have not formed the irregularities on the surface of the coating film of the metal plate only by dispersing fine particles, but spontaneous micron of the coating film itself. A water-repellent coating that forms a coating film with excellent water repellency (antifouling property, snow resistance, weather resistance) and uniform water repellency by forming unit irregularities uniformly on the entire surface of the coating film. And it came to complete the water-repellent metal plate which apply | coated this water-repellent coating.
That is, the water-repellent paint according to claim 1 is a water-repellent paint in which an acrylic resin is dissolved in an organic solvent and fine particles are mixed, and the average particle diameter of the fine particles is 5 to 1700 nm. The water-repellent paint contains ethylene glycol or polyethylene glycol as a structure control agent, and the organic solvent is one or more selected from toluene, benzene and xylene .

According to such a configuration, when the water-repellent paint is applied to the metal plate by containing fine particles and ethylene glycol or polyethylene glycol in the water-repellent paint, the coating film itself has a micron unit. Unevenness is uniformly formed on the entire surface of the coating film.
In addition, by mixing fine particles in an organic solvent and dispersing them in a water-repellent paint, functions (eg, photocatalytic function, strength, etc.) derived from the fine particles can be imparted to the coating film. These functions are improved in the metal plate coated with the paint.
Moreover, by using 1 or more types selected from toluene, benzene, and xylene as an organic solvent, melt | dissolution of an acrylic resin and ethylene glycol or polyethylene glycol becomes easy.

The water-repellent paint according to claim 2 contains fluorine in the main chain or side chain of the acrylic resin.

  According to such a structure, the water repellency in the metal plate which apply | coated the water-repellent coating material further improves by containing a fluorine in the principal chain or side chain of an acrylic resin.

The water-repellent paint according to claim 3 is characterized in that a part of the acrylic resin is a silicon-modified acrylic resin or a silicon-modified acrylic urethane resin.

The water-repellent paint according to claim 4 is characterized in that all of the acrylic resin is a silicon-modified acrylic resin or a silicon-modified acrylic urethane resin.

  According to the configuration like these, in addition to further improving the water repellency in the metal plate coated with the water-repellent paint, the adhesion between the fine particles in the coating film and the coating film component and the metal plate is improved, Durability when the water repellent coating film is exposed to physical contact is improved.

The water repellent metal plate according to claim 5 is characterized in that a water repellent coating film is formed on the metal plate by applying the water repellent paint described above to the metal plate.

  According to such a configuration, the entire surface of the metal plate is formed on the metal plate by forming a water-repellent coating film in which the unevenness of micron units of the coating film itself is uniformly formed on the entire surface of the coating film. A metal plate having uniform water repellency can be obtained.

The water-repellent metal plate according to claim 6 is characterized in that the metal plate is one selected from an aluminum plate, an aluminum alloy plate, a steel plate, a copper plate, and a titanium plate.

  According to such a configuration, the water repellent in which the unevenness of the micron unit of the coating film itself is uniformly formed on the entire surface of the coating film even in the aluminum plate, the aluminum alloy plate, the steel plate, the copper plate, and the titanium plate. By forming a coating film, uniform water repellency can be imparted to the entire surface of these metal plates.

According to the water-repellent paint according to claim 1 of the present invention, the water-repellent paint is applied to the metal plate, and the unevenness of the micron unit of the coating film itself is uniformly formed on the entire surface of the coating film. A water-repellent coating film having excellent water repellency (antifouling property, snow resistance, weather resistance) and uniform water repellency can be formed.
Further, the acrylic resin and ethylene glycol or polyethylene glycol can be easily dissolved.

According to the water-repellent paint according to claim 2 , the water repellency of the water-repellent coating film is improved, so that the water repellency of the metal plate coated with the water-repellent paint can be further improved.
According to the water-repellent paint according to claims 3 and 4 , the water repellency and adhesion of the water-repellent coating film are improved, so that the water repellency and physical contact durability of the metal plate coated with the water-repellent paint are improved. be able to. Such durability improvement of water-repellent coating is useful because it improves durability during use, and since coating damage during processing of coated metal sheets is suppressed, it is a major advantage in industry. Have

According to the water repellent metal plate according to claim 5 of the present invention, the water repellent coating film in which the irregularities of micron units of the coating film itself are uniformly formed on the entire surface of the coating film is formed on the metal plate. Thus, it is possible to obtain excellent water repellency (antifouling property, snow resistance, weather resistance) and uniform water repellency on the entire surface of the metal plate.
According to the water repellent metal plate according to claim 6 , excellent water repellency (antifouling property, snow resistance, weather resistance) is obtained even in an aluminum plate, an aluminum alloy plate, a steel plate, a copper plate, and a titanium plate. A uniform water repellency can be obtained over the entire surface of the metal plate.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
≪Water repellent paint≫
The water-repellent paint according to the present invention is one in which an acrylic resin is dissolved in an organic solvent and fine particles are mixed and dispersed in the water-repellent paint. As a structure control agent, ethylene glycol or polyethylene glycol is used. It contains.
Each configuration will be described below.

<Organic solvent>
The organic solvent dissolves acrylic resin and ethylene glycol or polyethylene glycol. Moreover, the fine particles are dispersed in the water-repellent paint by mixing the fine particles.
As an organic solvent to be used, an aromatic compound such as toluene, benzene, xylene (p-xylene, m-xylene, o-xylene) is preferably used, but an acrylic resin and an ethylene glycol or polyethylene glycol can be dissolved. If it is, it will not specifically limit. For example, ketone compounds such as acetone, cyclohexanone, and ethyl methyl ketone, ester compounds such as ethyl acetate, alcohol compounds such as pentanol, and the like can be used. In addition, these may be used independently and may mix and use 2 or more types.

<Fine particles>
The fine particles are necessary for forming irregularities in micron units spontaneously on the coating film itself, and are dispersed in the water-repellent paint by mixing with an organic solvent.
The fine particles to be added are not particularly limited, and can be appropriately selected depending on the function to be further imparted to the water-repellent paint.
For example, when a photocatalytic function or an ultraviolet ray preventing function is imparted, titanium oxide can be added, and when strength is improved, silica can be added.

Examples of the titanium oxide include titanium oxide manufactured by Ishihara Sangyo Co., Ltd., such as ultrafine particle titanium oxide, titanium oxide for photocatalyst, white conductive titanium oxide, acicular conductive titanium oxide, and high-purity titanium oxide.
Examples of the silica include silica manufactured by Nippon Aerosil Co., Ltd., such as Aerosil 200 (registered trademark), Aerosil 300 (registered trademark), Aerosil R202 (registered trademark), Aerosil R972 (registered trademark), Aerosil R974 (registered trademark), and the like. Can be mentioned.

Here, the average particle diameter of the fine particles is 5 to 1700 nm. In addition, an average particle diameter here means the particle diameter of 50% volume when the particle | grains disperse | distributed to toluene with the Nikkiso Co., Ltd. Nanotrac particle size distribution measuring apparatus UPA-EX150 are measured.
When the average particle diameter of the fine particles is less than 5 nm, it is difficult to obtain the fine particles, and even when available, the fine particles are expensive, which is not preferable from the viewpoint of economy. On the other hand, when the thickness exceeds 1700 nm, when the paint is applied to the metal plate, the unevenness of the micron unit of the coating film itself is not formed on the surface of the coating film formed on the metal plate. The average particle size of the fine particles is preferably 5 to 500 nm, and more preferably 30 to 200 nm. When the average particle size of the fine particles is 5 to 500 nm, and further 30 to 200 nm, the particle sizes of the fine particles are close to each other, so that the fine particles are easily dispersed uniformly in the coating film. It tends to be uniform.
The surface of the fine particles may be either hydrophilic or hydrophobic.

<Acrylic resin>
The acrylic resin forms a water-repellent coating film on a metal plate by applying a water-repellent paint to the metal plate.
As the acrylic resin, polymers of acrylic esters such as methacrylic acid, acrylic acid, methyl acrylate and the like can be used, but are not limited thereto.

  Here, the main chain or side chain (ester group part) of the acrylic resin preferably contains fluorine. Therefore, it is preferable to use a compound containing fluorine in the main chain or side chain (ester group part) of the acrylic resin, whereby the water repellency of the coating film can be further improved.

  Examples of the compound containing fluorine include Asahi Guard AG-7600 (registered trademark), Asahi Guard AG-7160 (registered trademark), Asahi Guard AG-950 (registered trademark), Asahi Guard AG-7000 manufactured by Asahi Glass Co., Ltd. (Registered Trademark), Asahi Guard AG-1100 (Registered Trademark), Unidyne Series (Registered Trademark) manufactured by Daikin Industries, Ltd., and the like.

  Moreover, it is preferable that a part or all of the acrylic resin is a silicon-modified acrylic resin or a silicon-modified acrylic urethane resin. Thereby, in addition to the water repellency of the coating film, the durability against physical contact can be further improved.

  Examples of silicon-modified acrylic resins or silicon-modified acrylic urethane resins include Saimak US-270 (registered trademark), Saimak US-380 (registered trademark) manufactured by Toagosei Co., Ltd., and acrylics manufactured by Dainippon Ink & Chemicals, Inc. Dick A-9540 (registered trademark), Acridic A-9510 (registered trademark), Acridic A-9585 (registered trademark), Acridic BZ-1161 (registered trademark), Papyres (registered trademark) manufactured by NATCO, Isamu High Art # 3000 (registered trademark) manufactured by Paint Co., Ltd. can be used.

  There are no particular restrictions on the amount of acrylic resin, silicon-modified acrylic resin, and silicon-modified acrylic urethane resin, but from the viewpoint of the balance between water repellency and durability, the total resin mass relative to the total fine particle mass is The ratio is preferably 1.0 to 2.5 times.

<Ethylene glycol or polyethylene glycol>
Ethylene glycol or polyethylene glycol as a structure control agent is a substance that plays a major role in forming irregularities in units of microns on the surface of a coating film formed on a metal plate.
By adding ethylene glycol or polyethylene glycol together with the fine particles, the unevenness of micron units of the coating itself, which is different from the unevenness formed only by dispersing the fine particles, is uniformly formed on the entire surface of the coating film. Is done. The concavo-convex structure formed on the surface of the coating film improves the water repellency because it works in the direction of enhancing (enlarging) the contact angle by increasing the surface area of the coating film.

  Ethylene glycol or polyethylene glycol is soluble in an organic solvent, but it is considered that it is in a state where phase separation is likely to occur in an organic solvent because of its high water solubility. For this reason, ethylene glycol or polyethylene glycol dissolved in an organic solvent is considered to cause phase separation when the organic solvent is dried after application of the paint. By causing this phase separation, it is considered that pores are formed on the surface of the coating film due to a synergistic effect with the added fine particles, thereby forming an uneven structure.

In addition, the unevenness | corrugation of a micron unit specifically points out the location which has a part with a hole with a diameter of 0.5-500 micrometers in width, and a flat part. Many of these irregularities are formed by forming a recess in a flat portion, and even smaller irregularities are formed in the formed concave portion.
Further, the hole width is preferably 1 to 10 μm in diameter, and more preferably 1 to 3 μm in diameter. When the diameter is 1 to 10 μm, and further 1 to 3 μm, the unevenness in units of microns is more uniformly formed, so that the water repellency on the surface of the metal plate tends to be more uniform.

Here, the content of ethylene glycol or polyethylene glycol is preferably in the range of 0.1 to 20% by mass in the water-repellent coating. When the content of ethylene glycol or polyethylene glycol is less than 0.1% by mass, the content is too small, so that an uneven structure is hardly formed on the surface of the coating film. On the other hand, when the amount exceeds 20% by mass, the viscosity of the water-repellent coating is increased, so that the case where it cannot be applied to the metal plate is likely to occur, and the uneven structure may not be formed on the surface of the coating film.
The molecular weight of ethylene glycol or polyethylene glycol is preferably 2000 or less. This is because when the molecular weight exceeds 2000, the solubility in an organic solvent is greatly reduced, and it becomes difficult to add the minimum mass% (0.1 mass%) shown above.

Next, the water repellent metal plate coated with the above water repellent paint will be described.
≪Water repellent metal plate≫
The water-repellent metal plate according to the present invention is obtained by applying a water-repellent paint as described above to form a water-repellent coating on the metal plate.
Such a water-repellent coating film can be formed on the surface of the metal plate by applying a water-repellent coating to the metal plate, heating to remove the organic solvent, washing with water, and drying by heating again.
As the metal plate to which the water repellent paint is applied, an aluminum plate, an aluminum alloy plate, a steel plate, a copper plate, a titanium plate, or the like can be used, but is not limited thereto.
In addition, in order to improve adhesiveness with a water-repellent coating film, you may give a surface treatment to these metal plates. In addition, in order to improve the adhesion between the water-repellent coating and the metal plate, or to ensure the coating property of the paint, the surface conditioner, coupling agent, thixotropic agent, lubricant, curing agent, etc. May be added.

As described above, according to the water-repellent paint according to the present invention, the coating film itself has irregularities on the micron scale by coating the water-repellent paint with fine particles and ethylene glycol or polyethylene glycol. A water repellent coating film that is uniformly formed on the entire surface of the film can be formed. Therefore, it is possible to obtain a metal plate on which a water repellent coating film having excellent water repellency (antifouling property, snow resistance, weather resistance) and a uniform water repellency is formed.
According to the water-repellent metal plate according to the present invention, the metal plate is excellent by forming a water-repellent coating film in which the irregularities in micron units of the coating film itself are uniformly formed on the entire surface of the coating film. It is possible to obtain water repellency (antifouling property, snow resistance, weather resistance) and uniform water repellency on the entire surface of the metal plate.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and can be modified without departing from the scope of the present invention.
For example, the substrate to which the water-repellent paint according to the present invention is applied is not limited to a metal plate, but may be applied to plastic, ceramics, wood, glass, and the like, and may be applied to other substrates as appropriate. Good.

Next, the water-repellent paint and the water-repellent metal plate according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.
[Example 1]
The following test was performed about the water repellency of the metal plate surface in which the coating film was formed.
First, each substance shown in Table 1 was mixed and stirred for 1 hour to prepare a water-repellent paint. Next, this water-repellent paint was applied on a 1000 series aluminum plate or an iron metal plate (EG steel plate) to form a coating film having a coating thickness of 25 μm. Thereafter, it was dried at 37 ° C. for 15 minutes, washed with water, and further dried at 150 ° C. for 30 minutes. And the static contact angle of the water at that time was measured using FACE-CA-A (made by Kyowa Interface Chemical Co., Ltd.). The results are shown in the “Contact angle” column of Table 1.

In addition, the contact angle increased by 10 ° or more on the basis of the contact angle (82 ° of No. 11 as a comparative example) of a coating film formed using a paint not containing ethylene glycol or polyethylene glycol. The water repellency was good when the water repellency was good and the contact angle did not increase by 10 ° or more. That is, water repellency was good when the contact angle was 92 ° or more and poor water repellency when the contact angle was less than 92 °.
In Table 1, those that do not contain components are indicated by "-".

  As shown in Table 1, the example No. Since 1 to 9 satisfied the scope of the present invention, the water repellency was good. In particular, no. No. 6 uses a fluorine-containing compound as an acrylic resin, so that the value of the contact angle was higher than that of the other examples.

On the other hand, no. No. 10 does not contain fine particles, ethylene glycol or polyethylene glycol, and an organic solvent, and the coating film is formed only with an acrylic resin. It was not formed uniformly and the water repellency was poor.
No. No. 11 is mixed with fine particles but does not contain ethylene glycol or polyethylene glycol. Therefore, spontaneous micron irregularities of the coating film itself are not uniformly formed on the entire surface of the coating film, resulting in poor water repellency. Met.

No. In No. 12, since the average particle diameter of titanium oxide, which is a fine particle, exceeds the upper limit, spontaneous irregularities in micron units of the coating film itself were not uniformly formed on the entire surface of the coating film, resulting in poor water repellency.
In addition, No. which is an Example. In No. 1, when the content of polyethylene glycol (PEG 600) was 50% by mass, the viscosity of the water-repellent coating became high and could not be applied.

[Example 2]
The following tests were conducted on the water repellency of the metal plate surface on which the coating film was formed and the durability of the coated metal plate.
First, each substance shown in Table 2 was mixed and stirred for 1 hour to prepare a water-repellent paint. Next, this water-repellent coating was applied onto a 1000 series aluminum plate to form a coating having a coating thickness of 25 μm. Thereafter, it was dried at 37 ° C. for 15 minutes, washed with water, and further dried at 150 ° C. for 30 minutes. And the static contact angle of the water at that time was measured using FACE-CA-A (made by Kyowa Interface Chemical Co., Ltd.). The results are shown in the “Contact angle” column of Table 2.

The durability of the painted metal plate is the same as the test material after rubbing Kimwipe S-200 (manufactured by Nippon Paper Crecia) in four, and rubbing it once at a speed of about 5 cm / sec while applying a load of 3 kg. Evaluation was made by visual observation. The case where there was no change in the appearance of the coating film was marked as ◎, the case where the appearance slightly changed was marked as ◯, and the case where the metal background was partially exposed was marked as △. The results are shown in Table 2.
The evaluation criteria for water repellency are the same as in Example 1. Moreover, Cymel 350 (registered trademark) manufactured by Cytec Co., Ltd. in Table 2 is a curing agent.

As shown in Table 2, the example No. Since Nos. 13 to 19 satisfied the range of the present invention, the water repellency was good. In particular, since they contain silicon-modified acrylic resin or silicon-modified acrylic urethane resin, they have high durability in addition to water repellency. No. as an example. Since No. 20 satisfied the range of the present invention, the water repellency was good. However, the durability was somewhat low because it did not contain silicon-modified acrylic resin or silicon-modified acrylic urethane resin.
No. Nos. 21 to 24 had low water repellency because a resin outside the range of the present invention was applied.

[Example 3]
The following tests were conducted on the surface state of a metal plate coated with a paint containing ethylene glycol or polyethylene glycol and a metal plate coated with a paint not containing ethylene glycol or polyethylene glycol.

(1) As a case where a paint containing polyethylene glycol was applied, No. 1 as an example of Table 1. The surface state of the aluminum plate 1 was observed. Specifically, in toluene, which is an organic solvent, as fine particles, titanium oxide (TTO-55 (S) (registered trademark) manufactured by Ishihara Sangyo Co., Ltd.) and silica (R972 manufactured by Nippon Aerosil Co., Ltd.), polymethacryl as the acrylic resin PEG 600 (manufactured by Sanyo Chemical Industries) was mixed as methyl acid (code number: 138-02375 manufactured by Wako Pure Chemical Industries, Ltd.) and polyethylene glycol, and stirred for 1 hour to contain each of these substances. A water repellent paint was prepared. Next, this water-repellent coating was applied onto a 1000 series aluminum plate to form a coating having a coating thickness of 25 μm. Thereafter, it was dried at 37 ° C. for 15 minutes, washed with water, and further dried at 150 ° C. for 30 minutes. The surface of the aluminum plate was observed with a 500-fold SEM (using Nikon ESEM-2700). This SEM photograph is shown in FIG.

(2) As a case where a paint not containing ethylene glycol or polyethylene glycol was applied, No. 1 as a comparative example in Table 1. The surface state of 11 aluminum plates was observed. Specifically, in toluene, which is an organic solvent, as fine particles, titanium oxide (TTO-55 (S) (registered trademark) manufactured by Ishihara Sangyo Co., Ltd.) and silica (R972 manufactured by Nippon Aerosil Co., Ltd.), polymethacryl as the acrylic resin Methyl acid (Wako Pure Chemical Industries, Ltd. code number: 138-02375) was mixed and stirred for 1 hour to prepare a water-repellent paint containing these substances. Next, this water-repellent coating was applied onto a 1000 series aluminum plate to form a coating having a coating thickness of 25 μm. Thereafter, it was dried at 37 ° C. for 15 minutes, washed with water, and further dried at 150 ° C. for 30 minutes. The surface of the aluminum plate was observed with a 500-fold SEM (using Nikon ESEM-2700). This SEM photograph is shown in FIG.

  From FIG. 1 and FIG. 2, in the case of the coating material containing polyethylene glycol, the unevenness | corrugation of the micron unit of coating film itself is uniformly formed in the whole surface of the aluminum plate. On the other hand, in the case of paints that do not contain ethylene glycol or polyethylene glycol, there is no spontaneous micron irregularity of the coating film itself, and it has a surface where fine particles are unevenly dispersed in some places. I understand.

From these results, polyethylene glycol (or ethylene glycol) plays a major role in the formation of unevenness in micron units, and differs from the unevenness formed only by dispersing fine particles by adding polyethylene glycol (or ethylene glycol). It can be seen that the unevenness of micron units of the coating film itself is uniformly formed on the entire surface of the coating film.
In addition, it can be seen that the water repellency is improved when the irregularities of micron units of the coating film itself are uniformly formed on the entire surface of the coating film.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be widely changed and modified within the scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

It is a SEM photograph of the aluminum plate surface which applied the water repellent paint containing polyethyleneglycol in the paint. It is a SEM photograph of the aluminum plate surface which applied the water repellent paint which does not contain ethylene glycol or polyethylene glycol in paint.

Claims (6)

A water-repellent paint in which an acrylic resin is dissolved in an organic solvent and fine particles are mixed,
The fine particles have an average particle diameter of 5 to 1700 nm,
In the water-repellent paint, as a structure control agent, contains ethylene glycol or polyethylene glycol ,
The water-repellent paint , wherein the organic solvent is at least one selected from toluene, benzene and xylene . The water repellent paint according to claim 1, wherein fluorine is contained in a main chain or a side chain of the acrylic resin. The water-repellent paint according to claim 1 or 2 , wherein a part of the acrylic resin is a silicon-modified acrylic resin or a silicon-modified acrylic urethane resin. 2. The water-repellent paint according to claim 1, wherein all of the acrylic resin is a silicon-modified acrylic resin or a silicon-modified acrylic urethane resin. A water-repellent metal plate, wherein a water-repellent coating film is formed on the metal plate by applying the water-repellent paint according to any one of claims 1 to 4 to the metal plate. The water repellent metal plate according to claim 5 , wherein the metal plate is one selected from an aluminum plate, an aluminum alloy plate, a steel plate, a copper plate, and a titanium plate.