JP6061878B2 - Method for producing coating composition and method for recovering coating film - Google Patents

Description

  The present invention relates to a coating composition and a method for producing the same, a coated article, and a method for recovering a coating film. Specifically, the present invention not only forms a coating film with excellent water repellency, but also easily recovers water repellency by heating even when the water repellency of the coating film is reduced by use. The present invention relates to a coating composition capable of forming a coating film capable of forming a coating film, a method for producing the same, a coated article having a coating film having the characteristics, and a method for recovering the coating film.

  Members used in various types of equipment such as air conditioning equipment, power transmission equipment, and communication equipment are manufactured using various materials such as glass, metal, and ceramic, but water, ice, frost, snow, etc. are on the surface of the parts. Adhesion may reduce the performance of the equipment. Therefore, as a method for suppressing the deterioration of the performance of these facilities, a method for preventing the adhesion of water, ice, frost, snow and the like by imparting water repellency to the surface of the member has been proposed.

  For example, Patent Document 1 discloses a method of forming a coating film using a coating composition in which hydrophobic fine particles having an average primary particle size of 100 nm or less are dispersed in an organic solvent containing 65% by mass or more of a hydrophobic solvent. Proposed. Patent Document 2 discloses a method for forming a base film on a base material using a base film forming composition containing carbonaceous fine particles having an average particle diameter of 1 to 1000 μm, a binder resin composition, and a volatile solvent. By forming a water-repellent finish film on the base film using a finish film composition containing hydrophobic fine particles having an average primary particle diameter of 5 to 500 nm, a binder resin composition and a volatile solvent, a two-layer structure A method for forming a coating film has been proposed. The coating films of the cited references 1 and 2 have improved water repellency due to the fine uneven structure formed on the surface due to the presence of hydrophobic fine particles.

JP 2010-155727 A JP2013-123660A

  However, although the coating films of Patent Documents 1 and 2 have good initial water repellency, there is a problem that the water repellency is lowered as a result of gradually flattening the fine uneven structure on the surface with use. . In order to restore the initial water repellency, it is necessary to form the coating film again after removing the coating film once.

The present invention has been made to solve the above-described problems. When the water repellency of the coating film is lowered, the water repellency can be easily recovered without forming the coating film again. An object of the present invention is to provide a coating composition capable of forming a coating film and a method for producing the same.
The present invention also provides a coated article that can easily recover the water repellency without re-forming the coating film when the water repellency of the coating film decreases with use, and a method for recovering the coating film The purpose is to do.

As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention incorporated a thermally expandable microcapsule into a coating composition containing hydrophobic fine particles in a predetermined method and a ratio, thereby coating the coating composition only by heating. It was found that a coating composition capable of easily recovering the water repellency of the film was obtained .

That is , the present invention is a method for producing a coating composition, in which hydrophobic fine particles are dispersed in a binder resin dissolved in a solvent using a high-pressure dispersing device, and then thermally expandable microcapsules are mixed and stirred. A method for producing a coating composition, wherein a mass ratio of the hydrophobic microparticles to 0.4 is 0.4 or more, and a mass ratio of the thermally expandable microcapsules to the binder resin is 0.05 or more. .
In addition , the present invention provides a coating composition by the method for manufacturing a coating composition, and forms a coating film by applying the coating composition to a substrate and drying, thereby reducing the water repellency of the coating film. In this case, the coating film recovering method is characterized in that the water repellency is recovered by heating the coating film.

ADVANTAGE OF THE INVENTION According to this invention, when the water repellency of a coating film falls, the coating composition which can form the coating film which can recover water repellency easily, without forming a coating film again, and its manufacture A method can be provided.
In addition, according to the present invention, when the water repellency of the coating film decreases with use, the coated article can easily recover the water repellency without forming the coating film again, and the coating film recovery method Can be provided.

It is an expanded sectional view of the coating article which has a coating film formed using the coating composition of this invention. A coated article having a coating film formed by using the coating composition of the present invention comprising a thermally expandable microcapsule and another thermally expandable microcapsule having a thermal expansion start temperature lower than that of the thermally expandable microcapsule. It is an expanded sectional view.

Embodiment 1 FIG.
Hereinafter, a coating composition of the present invention, a method for producing the same, a coated article, and a method for recovering a coating film will be described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view of a coated article having a coating film formed using the coating composition of the present invention. In FIG. 1, (a) is a coated article immediately after a coating film is formed, (b) is a coated article after the coating article of (a) has been used for a certain period, and (c) is a coated article of (b). It is an expanded sectional view of the coated article after performing the recovery method of a coating film.
As shown in FIG. 1, the coated article has a substrate 1 and a coating film 2 formed on the substrate 1. The coating film 2 is formed by applying the coating composition to the substrate 1 and drying it. As shown in FIG. 1A, the coating film 2 thus formed has a fine concavo-convex structure on the surface, and the water repellency of the coating film 2 is enhanced by this concavo-convex structure. .

  The coating composition that provides the coating film 2 includes hydrophobic fine particles 3, thermally expandable microcapsules 4, a binder resin 5, and a solvent. A preferred coating composition in the present invention consists essentially of hydrophobic fine particles 3, thermally expandable microcapsules 4, a binder resin 5 and a solvent. Here, “essentially” in the present specification includes the hydrophobic fine particles 3, the thermally expandable microcapsule 4, the binder resin 5 and the solvent as essential components, and other than the essential components as long as the effects of the present invention are not impaired. It is meant that any component can be included. In the coating composition of the present invention, the hydrophobic fine particles 3 and the thermally expandable microcapsules 4 are dispersed in a binder resin 5 dissolved in a solvent.

The hydrophobic fine particles 3 are components that form a fine concavo-convex structure on the surface of the coating film 2 formed from the coating composition.
The hydrophobic fine particles 3 are not particularly limited, and those known in the technical field can be used. Examples of the hydrophobic fine particles 3 include fine particles formed from a hydrophobic resin such as silicone resin, acrylic resin, vinyl acetate resin, polyurethane resin, epoxy resin, melamine resin, alkylphenol resin, and rosin ester resin.
Further, as the hydrophobic fine particles 3, those obtained by subjecting the surfaces of various fine particles to a hydrophobic treatment can also be used. The method for hydrophobizing the surface of the fine particles is not particularly limited, and methods known in the technical field can be used. For example, the surface of the fine particle can be hydrophobized by introducing a hydrophobic group such as fluorine or an alkyl group into the surface of the fine particle. Specifically, the surface treatment of the fine particles may be performed using an organometallic compound such as a silylating agent, a silane coupling agent, or an alkylaluminum.

Preferred hydrophobic fine particles 3 in the present invention are silica fine particles whose surfaces have been hydrophobized. In this specification, “silica” generally means silicon dioxide (SiO ₂ ), but may contain silicon oxides other than SiO ₂ . By using silica fine particles having a hydrophobic surface as the hydrophobic fine particles 3, the water repellency of the coating film 2 tends to be improved.
The hydrophobic fine particles 3 can be used not only in a single kind but also in a combination of two or more kinds.

  The hydrophobic particles 3 having the above-described characteristics are also available as commercial products. For example, the trade name “Aerosil 200” (manufactured by Nippon Aerosil Co., Ltd.), the trade name “Aerosil 300” (Nippon Aerosil Co., Ltd.) Company name), product name “Aerosil 380” (manufactured by Nippon Aerosil Co., Ltd.), product name “Aerosil 90G” (manufactured by Nippon Aerosil Co., Ltd.), product name “Aerosil OX50” (manufactured by Nippon Aerosil Co., Ltd.), product name “Aerosil” "R972" (manufactured by Nippon Aerosil Co., Ltd.), trade name "Aerosil 972V" (manufactured by Nippon Aerosil Co., Ltd.), trade name "Aerosil R972CF" (manufactured by Nippon Aerosil Co., Ltd.), trade name "Aerosil R974" (manufactured by Nippon Aerosil Co., Ltd.) ), Product name "Aerosil R812" (manufactured by Nippon Aerosil Co., Ltd.), product name Aerosil R805 "(Nippon Aerosil Co., Ltd.), trade name" Aerosil RX200 "(Nippon Aerosil Co., Ltd.), trade name" Aerosil RX300 "(Nippon Aerosil Co., Ltd.), trade name" Aerosil RY200 "(Nippon Aerosil Co., Ltd.) Product name, “WACKER HDK H15” (Asahi Kasei Wacker Silicone), product name “WACKER HDK H15” (Asahi Kasei Wacker Silicone), product name “WACKER HDK H18” (Asahi Kasei Wacker Silicone), product name “WACKER HDK H20” (manufactured by Asahi Kasei Wacker Silicone), trade name “WACKER HDK H30” (manufactured by Asahi Kasei Wacker Silicone), trade name “Leolo Seal HM20S” (manufactured by Tokuyama Corporation), trade name “Leolo Seal HM3” “0S” (manufactured by Tokuyama Co., Ltd.), trade name “Leoroseal HM40S” (manufactured by Tokuyama Co., Ltd.), trade name “Leoroseal ZD30S” (manufactured by Tokuyama Co., Ltd.), trade name “Leoroseal DM30S” (manufactured by Tokuyama Co., Ltd.), etc. May be.

  The average particle diameter of the hydrophobic fine particles 3 is not particularly limited, but is preferably 100 nm or less, more preferably 5 nm to 100 nm, and most preferably 10 nm to 50 nm. Here, in the present specification, “hydrophobic fine particles 3” means primary particles or secondary particles of the hydrophobic fine particles 3, and “average particle diameter of the hydrophobic fine particles 3” means a dynamic light scattering method. Means the average value of the particle diameter of the hydrophobic fine particles 3 measured by Specifically, the “average particle diameter of the hydrophobic fine particles 3” means a particle diameter (D50) of cumulative 50% of the hydrophobic fine particles 3 measured by a dynamic light scattering method. If the average particle diameter of the hydrophobic fine particles 3 exceeds 100 nm, the uneven structure on the surface of the coating film 2 becomes too large, and the contact area of the liquid does not decrease, so that the desired water repellency may not be obtained. In addition, if the concavo-convex structure on the surface of the coating film 2 is large, the surface shape of the coating film 2 is likely to change due to external physical stimulation (for example, collision of foreign matter, friction, etc.), and water repellency is likely to be impaired. May be. Further, when the average particle size of the hydrophobic fine particles 3 is less than 5 nm, the hydrophobic fine particles 3 are likely to aggregate, so that the fluidity of the coating composition is lowered, and the coating composition can be uniformly applied to the substrate 1. It can be difficult.

Similarly, the heat-expandable microcapsule 4 is a component that forms a fine uneven structure on the surface of the coating film 2 formed from the coating composition. In addition, when the water repellency of the coating film 2 is lowered, the heat-expandable microcapsule 4 expands the heat-expandable microcapsule 4 by heating the coating film 2, thereby causing fine irregularities on the surface of the coating film 2. It is also a component that regenerates the structure and restores the water repellency of the coating film 2.
As shown in FIG. 1B, the coated article having the coating film 2 is accompanied by a decrease in the fine uneven structure on the surface of the coating film 2, resulting in a decrease in water repellency of the coating film 2. . Therefore, in the present invention, when the heat-expandable microcapsules 4 are introduced into the coating film 2 in advance, and the fine uneven structure on the surface of the coating film 2 is reduced, the coating film 2 is heated to be thermally expandable. By expanding the microcapsule 4, as shown in FIG. 1C, the fine concavo-convex structure on the surface of the coating film 2 is regenerated to restore the water repellency of the coating film 2.

  The thermally expandable microcapsule 4 is not particularly limited as long as it expands when heated. Examples of the thermal expansion microcapsule 4 include microspheres in which low-boiling hydrocarbons are encapsulated in a microcapsule with a thermoplastic polymer shell having a gas barrier property. Here, although it does not specifically limit as a low boiling point hydrocarbon, For example, a C1-C8 hydrocarbon, for example, isobutane, pentane, petroleum ether, hexane, octane, isooctane etc. can be used. The thermoplastic polymer used as the shell is not particularly limited, but vinylidene chloride copolymers, acrylonitrile copolymers, vinylindene chloride-acrylonitrile copolymers, and the like can be used.

The heat-expandable microcapsule 4 softens the thermoplastic polymer shell when heated, and the volume rapidly expands several times as the gas pressure in the shell increases. In the present invention, the fine concavo-convex structure on the surface of the coating film 2 is regenerated by utilizing this expansion force.
The volume expansion coefficient of the thermally expandable microcapsule 4 by heating is not particularly limited, but is preferably 1.1 to 10.0 times, more preferably, based on the volume of the thermally expandable microcapsule 4 before heating. Is 1.5 times or more and 9.0 times or less. When the volume expansion coefficient of the heat-expandable microcapsule 4 is less than 1.1 times, a fine uneven structure is not sufficiently formed on the surface, and as a result, the water repellency of the coating film 2 may not be sufficiently recovered. . On the other hand, if the volume expansion coefficient of the thermally expandable microcapsule 4 exceeds 10.0 times, the uneven structure on the surface of the coating film 2 becomes too large, and the contact area of the liquid does not decrease. It may not be obtained.

  The heat-expandable microcapsule 4 can be generally synthesized by emulsion polymerization. For example, a monomer of a polymer that forms a thermoplastic polymer shell, a polymerization initiator, and a foaming agent (low-boiling hydrocarbon) are added to water containing a dispersant, and the mixture is emulsified by stirring at high speed. Thereafter, the thermally expandable microcapsules 4 can be obtained by drying the water-dispersed fine particles obtained by the polymerization reaction.

  The average particle size of the thermally expandable microcapsule 4 is not particularly limited, but is preferably 5 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less. Here, in this specification, “average particle diameter of the thermally expandable microcapsule 4” means an average value of the particle diameter of the thermally expandable microcapsule 4 measured by a dynamic light scattering method. Specifically, the “average particle diameter of the thermally expandable microcapsule 4” means a particle diameter (D50) of a cumulative 50% of the thermally expandable microcapsule 4 measured by a dynamic light scattering method. . By using the thermally expandable microcapsule 4 having an average particle diameter in this range, a fine uneven structure can be stably formed on the surface of the coating film 2. When the average particle diameter of the thermally expandable microcapsule 4 is less than 5 μm, the strength of the thermoplastic polymer shell becomes brittle after thermal expansion or the fine uneven structure is not sufficiently formed. It may not be able to fully recover. On the other hand, if the average particle diameter of the thermally expandable microcapsule 4 exceeds 50 μm, the uneven structure on the surface of the coating film 2 becomes too large, and the contact area of the liquid does not decrease, so that the desired water repellency cannot be obtained. Sometimes.

  The thermal expansion start temperature of the heat-expandable microcapsule 4 varies depending on the type and thickness of the thermoplastic polymer shell, the type of the low-boiling hydrocarbon to be included, and the like in the present invention, preferably 60 ° C. or higher. Preferably it is 70 to 140 degreeC. When the thermal expansion start temperature of the thermally expandable microcapsule 4 is less than 60 ° C., the temperature rises locally due to the influence of direct sunlight, etc. even at a normal outside air temperature, and unintended thermal expansion occurs. This is not preferable.

  The heat-expandable microcapsule 4 having the above-described characteristics is also available as a commercial product. For example, the trade name “ADVANCEL EML101” (manufactured by Sekisui Chemical Co., Ltd.), the trade name “ADVANCELL EML302” (Sekisui Chemical Co., Ltd.) Company name), trade name “Matsumoto Microsphere F-30” (Matsumoto Yushi Seiyaku Co., Ltd.), trade name “Matsumoto Microsphere F-36” (Matsumoto Yushi Seiyaku Co., Ltd.), trade name “Matsumoto Micros Co., Ltd.” Fair F-48 "(manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), trade name" Matsumoto Microsphere F-80GS "(manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and the like can be used.

A single type of thermally expandable microcapsule 4 can be used as the thermally expandable microcapsule 4, but two or more types of thermally expandable microcapsules 4 having different thermal expansion start temperatures may be used. By using a combination of two or more types of thermally expandable microcapsules 4, it is possible to stepwise regenerate the fine concavo-convex structure by heating, so that the water repellency of the coating film 2 can be recovered multiple times. it can.
FIG. 2 shows a coating film 2 formed using a coating composition including a thermally expandable microcapsule 4 and another thermally expandable microcapsule 6 having a lower thermal expansion start temperature than the thermally expandable microcapsule 4. It is an expanded sectional view of the coating article which has. In FIG. 2, (a) is a coated article immediately after the coating film 2 is formed, (b) is a coated article after performing the recovery method of the coating film 2 at the thermal expansion start temperature of the thermally expandable microcapsule 6, (C) is a coated article after using the coated article of (b) for a certain period, (D) is a coated article after performing the recovery method of the coating film 2 at the thermal expansion start temperature of the thermally expandable microcapsule 4. It is an expanded sectional view.

As shown in FIG. 2 (a), the coating film 2 formed using the coating composition containing two kinds of thermally expandable microcapsules 4 and 6 having different thermal expansion start temperatures has a fine concavo-convex structure on the surface. The water repellency of the coating film 2 is enhanced by this uneven structure.
However, as the coated article having the coating film 2 is used, the fine uneven structure on the surface of the coating film 2 gradually decreases, and as a result, the water repellency of the coating film 2 gradually decreases. Therefore, by recovering the coating film 2 at the thermal expansion start temperature of the thermally expandable microcapsule 6, as shown in FIG. 2B, the fine uneven structure on the surface of the coating film 2 is regenerated and coated. The water repellency of the film 2 is restored.

  As shown in FIG. 2 (c), the coated article having the coating film 2 whose water repellency has been recovered gradually reduces the fine uneven structure of the coating film 2 as shown in FIG. Drops again. Therefore, by recovering the coating film 2 at the thermal expansion start temperature of the thermally expandable microcapsule 4, as shown in FIG. 2 (d), the fine uneven structure on the surface of the coating film 2 is regenerated and coated. The water repellency of the film 2 is restored.

The binder resin 5 is the base of the coating film 2 and is a component that carries the hydrophobic fine particles 3 and the thermally expandable microcapsules 4.
The binder resin 5 is not particularly limited as long as it is soluble in a solvent and is hydrophobic, and those known in the technical field can be used. The binder resin 5 preferable in the present invention is a thermoplastic resin having a glass transition temperature lower than the thermal expansion start temperature of the thermally expandable microcapsule 4. In the case of the binder resin 5 having such characteristics, the binder resin 5 inhibits the expansion of the thermally expandable microcapsule 4 when the coating film 2 is recovered at the thermal expansion start temperature of the thermally expandable microcapsule 4. Therefore, the binder resin 5 can be easily deformed. On the other hand, if the glass transition temperature of the binder resin 5 is higher than the thermal expansion start temperature of the thermally expandable microcapsule 4, the expansion of the thermally expandable microcapsule 4 is inhibited and cracks are generated in the binder resin 5. There is.

Examples of the binder resin 5 include a fluororesin, a silicone resin, and a urethane resin. From the viewpoint of dispersibility of the hydrophobic fine particles 3 and the thermally expandable microcapsules 4, a fluororesin is preferable.
Examples of the fluororesin include polyvinylidene fluoride (PVDF) and a fluoroolefin copolymer. Examples of the monomer component that gives the fluoroolefin copolymer include chlorotrifluoroethylene, tetrafluoroethylene, and vinyl esters having various substituents.

  The binder resin 5 is also available as a commercial product. For example, the trade name “Fluonate (Dainippon Ink Co., Ltd.)”, the trade name “Zeffle (Daikin Industries Co., Ltd.)”, the trade name “Lumiflon ( Asahi Glass Co., Ltd.), trade name “Cefal Coat (Central Glass Co., Ltd.)” and the like can be used.

  It does not specifically limit as a solvent which melt | dissolves the binder resin 5, A well-known thing can be used in the said technical field. The solvent is generally a polar or nonpolar organic solvent. Examples of solvents include: fluorinated solvents; chlorinated solvents; aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents; ester solvents such as ethyl acetate and butyl acetate; methyl isobutyl ketone and acetone And ketone solvents; ether solvents and the like. These can be used alone or in combination of two or more.

  In the coating composition of the present invention, the mass ratio of the hydrophobic fine particles 3 to the binder resin 5 (that is, the mass of the hydrophobic fine particles 3 / the mass of the binder resin 5) is 0.4 or more, preferably 0.5 or more and 4 or less. More preferably, it is 1 or more and 3 or less. Within the range of the mass ratio, the presence of the hydrophobic fine particles 3 can sufficiently form a fine uneven structure on the surface of the coating film 2 and improve the water repellency of the coating film 2. If the mass ratio is less than 0.4, a fine uneven structure cannot be sufficiently formed on the surface of the coating film 2, and the coating film 2 having a desired water repellency cannot be obtained. On the other hand, if the mass ratio exceeds 4, the amount of the binder resin 5 is too small, the coating film 2 having a desired strength cannot be obtained, and the coating film 2 may be peeled off from the substrate 1. .

  In the coating composition of the present invention, the mass ratio of the thermally expandable microcapsule 4 to the binder resin 5 is 0.05 or more, preferably 0.1 or more and 1 or less. Within the range of the mass ratio, the presence of the thermally expandable microcapsule 4 can sufficiently form a fine concavo-convex structure on the surface of the coating film 2 and can improve the water repellency of the coating film 2. . If the mass ratio is less than 0.05, a fine uneven structure cannot be sufficiently formed on the surface of the coating film 2, and the coating film 2 having a desired water repellency cannot be obtained. On the other hand, when the mass ratio exceeds 1, the amount of the binder resin 5 is too small, the coating film 2 having a desired strength cannot be obtained, and the coating film 2 may be peeled off from the base material 1. .

  The coating composition of the present invention contains the hydrophobic fine particles 3, the heat-expandable microcapsules 4, the binder resin 5 and the solvent as essential components. However, the dispersant, leveling agent, and evaporation are within the range that does not impair the effects of the present invention. You may add well-known additives, such as an inhibitor and an adhesive improvement agent.

  The coating composition of the present invention can be produced by stirring and mixing the above components. However, while it is necessary for the coating composition of the present invention to uniformly disperse each component, the thermal expansible microcapsule 4 is destroyed when dispersed by applying a strong shearing force, and the effects of the present invention are sufficiently obtained. I can't get it. Therefore, from the viewpoint of preventing destruction of the thermally expandable microcapsules 4, the hydrophobic particles 3 are dispersed in the binder resin 5 dissolved in the solvent using a high-pressure dispersing device, and then the thermally expandable microcapsules 4 are mixed and stirred. There is a need.

Since the hydrophobic fine particles 3 can be uniformly dispersed in the coating composition by previously dispersing the hydrophobic fine particles 3 in the binder resin 5 dissolved in the solvent using a high-pressure dispersing device, the homogeneous coating film 2 is formed. It becomes possible to form.
The high-pressure dispersion device is not particularly limited, and those known in the technical field can be used. Among these, a high-pressure dispersion device using the cavitation effect is preferable. Here, in this specification, “a high-pressure dispersion apparatus using a cavitation effect” means that particles are refined and / or refined by cavitation and shearing force when a liquid in which particles are dispersed is passed through a narrow tube at high pressure and high speed. It means a highly dispersed device. In addition, the “cavitation effect” means a phenomenon in which a low pressure portion is locally vaporized in a liquid flowing at high speed, bubbles are generated in a short time, and bubbles are crushed and disappear in a short time. Such a high-pressure dispersion apparatus is also available as a commercial product. For example, a high-pressure wet medialess atomization apparatus (Nanomizer Co., Ltd.), a wet cavitation mill atomization / nano-dispersion apparatus (Advanced Nano Technology Co., Ltd.) Etc. can be used.

The conditions for dispersing the hydrophobic fine particles 3 in the binder resin 5 dissolved in the solvent using a high-pressure dispersion device are not particularly limited, and may be set as appropriate according to the high-pressure dispersion device used.
When a general dispersing device such as a homogenizer is used, the dispersion of the hydrophobic fine particles 3 in the coating composition is not sufficient, and it is difficult to obtain a uniform coating film 2.

The thermally expandable microcapsules 4 are blended in the dispersion obtained as described above and mixed by stirring, whereby uniform dispersion is possible while preventing the thermally expandable microcapsules 4 from being broken. Moreover, although the thermally expansible microcapsule 4 may be mix | blended independently, you may mix | blend in the state added to the solvent.
The stirring and mixing method is not particularly limited as long as it does not give a strong shearing force. Examples of the stirring and mixing method include shaking and stirring using a shaker.

The coating composition produced as described above can be applied to the substrate 1 and dried to form the coating film 2.
The substrate 1 on which the coating film 2 can be formed is not particularly limited, and various materials can be used depending on the application. Examples of the substrate 1 include a metal substrate such as an aluminum substrate and a stainless steel substrate, a glass substrate, and a plastic substrate. Moreover, these may be a single substrate or two or more composite substrates.

The coating film 2 formed from the coating composition has a fine uneven structure on the surface due to the presence of the hydrophobic fine particles 3 and the thermally expandable microcapsules 4. This fine concavo-convex structure can improve the water repellency of the coating film 2 and can provide super water repellency with a water contact angle of 150 ° or more.
In the coated article on which the coating film 2 is formed, the fine concavo-convex structure on the surface decreases with use, and the water repellency of the coating film 2 decreases. However, when the water repellency of the coating film 2 is reduced, the coating film 2 is heated to expand the thermally expandable microcapsules 4, thereby re-forming a fine uneven structure on the surface of the coating film 2. The water repellency of the film 2 can be recovered.

When recovering the water repellency of the coating film 2, the heating temperature of the coating film 2 is not particularly limited as long as it is equal to or higher than the thermal expansion start temperature of the thermally expandable microcapsule 4. The heating temperature of the coating film 2 is generally 60 ° C. or higher, preferably 70 ° C. to 140 ° C.
It does not specifically limit as a heating method, A well-known method can be used in the said technical field. Examples of the heating method include a heater.

  According to the above method, it is not necessary to re-form the coating film 2 after removing the coating film 2 as in the prior art, and the water repellency of the coating film 2 can be easily recovered.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and various applications are possible without departing from the technical scope of the present invention. .
The following characteristics evaluation in Examples and Comparative Examples followed the following procedure.
(1) Initial water repellency evaluation of coating film Using a DM301 contact angle meter manufactured by Kyowa Interface Science, drop 2 μL of water droplets onto the coating film in the atmosphere (about 25 ° C.) to determine the static contact angle of the water droplets. It was measured. The water repellency was evaluated based on the following evaluation criteria.
○: Contact angle of water is 150 ° or more ×: Contact angle of water is less than 150 °

(2) Evaluation of water repellency after recovery of the coating film After the coating film was subjected to deterioration treatment by a wear test (load 80 g, 10 reciprocations), it was heated using a heater at the thermal expansion start temperature of the thermally expandable microcapsule for 5 minutes. A recovery process was performed. Next, using a DM301 contact angle meter manufactured by Kyowa Interface Science, 2 μL of water droplets were dropped on the coating film after the recovery treatment in the atmosphere (about 25 ° C.), and the static contact angle of the water droplets was measured. The water repellency was evaluated based on the following evaluation criteria.
○: Contact angle of water is 150 ° or more ×: Contact angle of water is less than 150 °

Example 1
Dissolve 3.0 parts by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 12 nm in 92.5 parts by mass of butyl acetate (solvent) Binder resin (trade name “Lumiflon LF-200”, glass transition temperature 35 ° C., manufactured by Asahi Glass Co., Ltd.) is added to 3.0 parts by mass, and wet atomization equipment (Nanovaita C-ES, manufactured by Yoshida Kikai Co., Ltd.) After performing the mixing and dispersion treatment using a thermal expansion microcapsule A having an average particle size of 10 μm (trade name “Matsumoto Microsphere F-36”, thermal expansion start temperature 70 ° C., volume expansion coefficient 9 times, 1.5 parts by mass (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) was further added and the mixture was shaken and stirred to obtain a coating composition. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Example 2)
As the thermally expandable microcapsule, 0.75 part by mass of thermally expandable microcapsule A and thermally expandable microcapsule B having an average particle diameter of 10 μm (trade name “Matsumoto Microsphere FN-100S”, thermal expansion start temperature 125 ° C., A coating composition was obtained in the same manner as in Example 1 except that 0.75 parts by mass of a volume expansion ratio of 5 times (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) was used. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

Example 3
As the thermally expandable microcapsules, 0.5 parts by mass of thermally expandable microcapsules A, 0.5 parts by mass of thermally expandable microcapsules B, and thermally expandable microcapsules C having an average particle diameter of 30 μm (trade name “ADVANCELELL EHM401”, heat A coating composition was obtained in the same manner as in Example 1 except that 0.5 parts by mass of expansion start temperature 140 ° C., volume expansion coefficient 5 times, Sekisui Chemical Co., Ltd. was used. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

Example 4
1.5 parts by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 12 nm, and butyl acetate (solvent) A coating composition was obtained in the same manner as in Example 1 except that was changed to 94 parts by mass. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Example 5)
12 parts by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 12 nm and 83 parts by mass of butyl acetate (solvent) A coating composition was obtained in the same manner as in Example 1 except that the content was changed to 5 parts by mass. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Example 6)
A coating composition was obtained in the same manner as in Example 1 except that the amount of butyl acetate (solvent) was changed to 93.7 parts by mass and the amount of thermally expandable microcapsule A was changed to 0.3 parts by mass. . Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Example 7)
A coating composition was obtained in the same manner as in Example 1 except that the amount of butyl acetate (solvent) was changed to 91 parts by mass and the amount of thermally expandable microcapsule A was changed to 3 parts by mass. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 1)
In Comparative Example 1, a coating composition containing no thermally expandable microcapsules was prepared. That is, 3.0 parts by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle diameter of about 12 nm is dissolved in 94 parts by mass of butyl acetate (solvent). Binder resin (trade name “Lumiflon LF-200”, glass transition temperature 35 ° C., manufactured by Asahi Glass Co., Ltd.) is added to 3.0 parts by mass, and wet atomization equipment (Nanovaita C-ES, manufactured by Yoshida Kikai Co., Ltd.) A coating composition was obtained by mixing and dispersing using Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 2)
In Comparative Example 2, a coating composition was prepared without using a wet atomizer. That is, a coating composition was obtained in the same manner as in Example 1 except that the stirring was performed using a shaker instead of the wet atomizer. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 3)
In Comparative Example 3, after mixing all the components, a coating composition was prepared by performing a dispersion treatment using a wet atomizer. That is, 3.0 parts by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle diameter of about 12 nm, and 1.5 parts by mass of thermally expandable microcapsules A Is added to 3.0 parts by mass of a binder resin (trade name “Lumiflon LF-200”, glass transition temperature 35 ° C., manufactured by Asahi Glass Co., Ltd.) dissolved in 92.5 parts by mass of butyl acetate (solvent). A coating composition was obtained by performing mixing and dispersion treatment using an apparatus (Nanovaita C-ES, manufactured by Yoshida Kikai Kogyo Co., Ltd.). Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 4)
In Comparative Example 4, a coating composition was prepared by mixing all components and then performing a dispersion treatment using a shaker. That is, a coating composition was obtained in the same manner as in Comparative Example 3 except that a shaker was used instead of the wet atomizer. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 5)
In Comparative Example 5, a coating composition having a mass ratio of hydrophobic fine particles (hydrophobic silica) to binder resin of less than 0.4 was prepared. That is, 1.0 part by mass of hydrophobic silica (hydrophobic fine particles, trade name “Aerosil RX200”, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of about 12 nm and butyl acetate (solvent) A coating composition was obtained in the same manner as in Example 1 except that the amount was changed to 94.5 parts by mass. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

(Comparative Example 6)
In Comparative Example 6, a coating composition having a mass ratio of thermally expandable microcapsules to binder resin of less than 0.05 was prepared. That is, the coating composition was prepared in the same manner as in Example 1 except that the amount of butyl acetate (solvent) was changed to 93.9 parts by mass and the amount of thermally expandable microcapsule A was changed to 0.1 parts by mass. Obtained. Next, the obtained coating composition was applied onto a substrate (slide glass) and dried to form a coating film.

  Table 1 shows the results of evaluating the characteristics of the above (1) and (2) for the above Examples and Comparative Examples.

As shown in the results of Table 1, the coating films formed using the coating compositions of Examples 1 to 7 were not in contact with water not only in the initial stage but also after the recovery treatment after the wear test. Super water repellency with an angle of 150 ° or more was exhibited.
On the other hand, although the coating film formed from the coating composition of Comparative Example 1 initially exhibited super water repellency of 150 ° or more, it does not contain a thermally expandable microcapsule, and therefore water repellency after a wear test. Did not recover. Since the coating compositions of Comparative Examples 2 and 4 were prepared without using a wet atomization apparatus, the hydrophobic fine particles were not sufficiently dispersed, and a coating film exhibiting a desired water repellency could not be formed. The coating composition of Comparative Example 3 was blended with thermally expandable microcapsules and then subjected to a dispersion treatment using a wet atomizer, so that the thermally expandable microcapsules were destroyed at that time, and the water repellency was not improved after the abrasion test. It did not recover. The coating composition of Comparative Example 5 was unable to form a coating film exhibiting the desired water repellency because the proportion of hydrophobic fine particles was too small. Although the coating composition of Comparative Example 6 initially exhibited super water repellency of 150 ° or more, the water repellency did not recover after the abrasion test because the proportion of the thermally expandable microcapsules was too small.

  As can be seen from the above results, according to the present invention, when the water repellency of the coating film decreases, it is possible to form a coating film that can easily recover the water repellency without forming the coating film again. Possible coating compositions and methods for their production can be provided. In addition, according to the present invention, when the water repellency of the coating film decreases with use, the coated article can easily recover the water repellency without forming the coating film again, and the coating film recovery method Can be provided.

  DESCRIPTION OF SYMBOLS 1 Base material, 2 Coating film, 3 Hydrophobic microparticle, 4 Thermal expansion microcapsule, 5 Binder resin, 6 Another thermal expansion microcapsule.

Claims (9)

A method for producing a coating composition in which hydrophobic fine particles are dispersed in a binder resin dissolved in a solvent using a high-pressure dispersing device, and then thermally expandable microcapsules are mixed and stirred.
Production of a coating composition, wherein a mass ratio of the hydrophobic fine particles to the binder resin is 0.4 or more, and a mass ratio of the thermally expandable microcapsules to the binder resin is 0.05 or more. Method. The method for producing a coating composition according to claim 1, wherein the thermally expandable microcapsules are two or more kinds of thermally expandable microcapsules having different thermal expansion start temperatures. The method for producing a coating composition according to claim 1 or 2, wherein a mass ratio of the hydrophobic fine particles to the binder resin is 0.5 or more and 4 or less. The method for producing a coating composition according to any one of claims 1 to 3, wherein a mass ratio of the thermally expandable microcapsule to the binder resin is 0.1 or more and 1 or less. The method for producing a coating composition according to any one of claims 1 to 4, wherein the thermally expandable microcapsule has an average particle size of 5 µm or more and 50 µm or less. The method for producing a coating composition according to any one of claims 1 to 5, wherein the thermally expandable microcapsule has a volume expansion ratio of 1.1 times to 10.0 times. The said hydrophobic fine particle has an average particle diameter of 5 nm or more and 100 nm or less, The manufacturing method of the coating composition as described in any one of Claims 1-6 characterized by the above-mentioned. The method for producing a coating composition according to any one of claims 1 to 7, wherein a glass transition temperature of the binder resin is lower than a thermal expansion start temperature of the thermally expandable microcapsules. A coating composition is produced by the method for producing a coating composition according to any one of claims 1 to 8, and a coating film is formed by applying the coating composition to a substrate and drying the coating composition. A method for recovering a coating film, comprising recovering the water repellency by heating the coating film when the water repellency of the film is lowered.

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