JP2010222427A5 - - Google Patents

Description

Water-based coating agent, painted plate, and painting method

The present invention relates to an aqueous coating agent , a coated plate having a coating film formed therefrom , and a coating method .

  A building board for an outer wall usually has a clear coating film formed on the colored layer for the purpose of imparting weather resistance, antifouling property and the like on the colored layer to be colored. For example, it is also known to form an antifouling film by applying a clear coating composition containing silica fine particles.

  Specifically, Patent Document 1 discloses that a coating is formed on the surface of a plate material having a concavo-convex pattern to form a coating film on which silica fine particles, alcohol, water, and a surfactant are contained. A method for forming an antifouling layer characterized by applying a fouling treatment agent is described.

Japanese Patent No. 3964847

  However, when the coating film serving as a base is composed of a coating film containing a polymer having a structural unit having an alkoxysilane part (sometimes referred to as an alkoxysilane structural unit in the present specification), In order to provide functions such as excellent weather resistance and antifouling properties on the base coating film, an aqueous coating agent containing silica fine particles is used to form a coating film. In order to have water repellency, the aqueous coating agent may be repelled. In such a case, the aqueous coating agent cannot be uniformly applied in the form of the film, and the aesthetic appearance of the building board is impaired.

Therefore, in order to prevent such problems, the present invention is not repelled by the coating film even if the coating film contains a polymer having an alkoxysilane structural unit (that is, wetting to the coating film). An object of the present invention is to provide an aqueous coating agent containing silica fine particles , a coating plate having a coating film formed therefrom , and a coating method, which can be applied uniformly.

As a result of intensive studies, the present inventors have adjusted the pH of the aqueous coating agent containing silica fine particles to 3.0 to 6.5 so that the coating film contains a polymer having an alkoxysilane structural unit. Even so, the inventors have found that the wettability to the coating film is increased and uniform coating is possible, and as a result of further studies, the present invention has been completed.
That is, the present invention is described below in [1] to an aqueous coating agent of [8], there is provided a coating method, etc. [9] and coated plate [10], and [11] and [12].
[1]
A pH adjuster comprising a suspension of silica fine particles having a primary particle diameter of 3 to 50 nm and a pH 8.0 to 11.0 and an inorganic acid or an organic acid having a pKa value of 3.09 to 7.0;
Containing
pH is 3.0 to 6.5 der is,
It is applied on a clear coating film containing a polymer having an alkoxysilane structural unit.
An aqueous coating agent characterized by
[2]
The alkoxysilane structural unit is represented by the general formula (1)

（式中、Ｒはアルキル基である。）
で表される構成単位であること
を特徴とする前記［１］に記載の水性コーティング剤。
［３］
前記シリカ微粒子の含有量が、前記水性コーティング剤全体１００質量部に対して０．１〜１０質量部であること
を特徴とする前記［１］または前記［２］のいずれか１項に記載の水性コーティング剤。
［４］
更に酸化チタンを含有すること
を特徴とする前記［１］から前記［３］のいずれか１項に記載の水性コーティング剤。
［５］
前記酸化チタンが光触媒活性を有し、
前記酸化チタンの平均粒子径が３０ｎｍ〜１４０ｎｍであり、かつ
前記酸化チタンの含有量が水性コーティング剤全体１００質量部に対して０．００５〜２質量部であること
を特徴とする前記［４］に記載の水性コーティング剤。
［６］
更にノニオン系界面活性剤を含有すること
を特徴とする前記［１］から［５］のいずれか１項に記載の水性コーティング剤。
［７］
前記ノニオン系界面活性剤が、
アルキレンオキサイドユニットを有するもの、
アセチレンジオールユニットを有するもの、
アルキレンオキサイドユニットとアセチレンジオールユニットとを有するもの、
アクリル系ポリマー界面活性剤、
シリコーン系界面活性剤、および
フッ素系界面活性剤
から選ばれる少なくとも一つの界面活性剤であること
を特徴とする前記［６］に記載の水性コーティング剤。
［７］
前記ノニオン系界面活性剤の含有量が、前記水性コーティング剤全体１００質量部に対して、０．０２〜５質量部であること
を特徴とする前記［６］または前記［７］に記載の水性コーティング剤。
［９］
アルコキシシラン構成単位を有する重合体を含有する塗膜を有する塗装板であって、
前記塗膜上に前記［１］に記載の水性コーティング剤から形成されたコーティング層を有する、塗装板。
［１０］
前記アルコキシシラン構成単位が一般式（１）

(In the formula, R is an alkyl group.)
Must be a structural unit
The aqueous coating agent as described in [1] above,
[ 3 ]
The content of the silica fine particles is 0.1 to 10 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent , according to any one of the above [1] or [2] . Water-based coating agent.
[ 4 ]
The aqueous coating agent according to any one of [1] to [3], further comprising titanium oxide.
[ 5 ]
The titanium oxide has photocatalytic activity;
The titanium oxide has an average particle size of 30 nm to 140 nm, and
Content of the said titanium oxide is 0.005-2 mass part with respect to 100 mass parts of the whole aqueous coating agent, The aqueous coating agent as described in said [ 4 ] characterized by the above-mentioned.
[ 6 ]
The aqueous coating agent according to any one of [1] to [5] , further comprising a nonionic surfactant.
[ 7 ]
The nonionic surfactant is
Having an alkylene oxide unit,
Having an acetylene range all unit,
Having an alkylene oxide unit and an acetylenic diol unit,
Acrylic polymer surfactant,
The aqueous coating agent as described in [ 6 ] above, which is at least one surfactant selected from silicone surfactants and fluorine surfactants.
[ 7 ]
Content of the said nonionic surfactant is 0.02-5 mass parts with respect to 100 mass parts of said whole aqueous coating agents, The said aqueous solution as described in said [ 6 ] or the said [ 7 ] characterized by the above-mentioned. Coating agent.
[ 9 ]
A coated plate having a coating film containing a polymer having an alkoxysilane structural unit,
The coating board which has a coating layer formed from the aqueous coating agent as described in said [1] on the said coating film.
[ 10 ]
The alkoxysilane structural unit is represented by the general formula (1)

（式中、Ｒはアルキル基である。）
で表される構成単位であること
を特徴とする前記［９］に記載の塗装板。
［１１］
アルコキシシラン構成単位を有する重合体を含有する塗膜を用意する工程と、
前記塗膜上に請求項１に記載の水性コーティング剤を塗布してコーティング層を形成する工程と、
を備える塗装方法。
［１２］
前記アルコキシシラン構成単位が一般式（１）

(In the formula, R is an alkyl group.)
The coated plate according to [ 9 ], wherein the coated plate is a structural unit represented by
[11]
Preparing a coating film containing a polymer having an alkoxysilane structural unit;
Applying the aqueous coating agent according to claim 1 on the coating film to form a coating layer;
A painting method comprising:
[12]
The alkoxysilane structural unit is represented by the general formula (1)

(In the formula, R is an alkyl group.)
Must be a structural unit
The coating method according to [11] above, wherein

  According to the present invention, an aqueous coating containing silica fine particles that has high wettability to the coating film and can be uniformly applied even when the coating film contains a polymer having an alkoxysilane structural unit. An agent is provided.

  The invention of the present application is a coated plate having a coating film containing a polymer containing an alkoxysilane part as a constituent unit as a base, and has a coating layer formed from the aqueous coating agent on the coating film, Provided is an unprecedented coated plate with an excellent self-cleaning function.

[Water-based coating agent]
Below, the aqueous coating agent of this invention is demonstrated in detail.

The aqueous coating agent of the present invention is
A pH adjuster comprising silica fine particles having a primary particle diameter of 3 to 50 nm and an inorganic acid or organic acid having a pKa value of 3.09 to 7.0;
Containing
The pH is 3.0 to 6.5.

  The aqueous coating agent of the present invention has a pH of 3.0 to 6.5.

  Even when the pH is less than 3.0 or the pH exceeds 6.5, when the object of coating is a coating film containing a polymer having an alkoxysilane structural unit, wettability to the coating film May be low.

The method for adjusting the pH will be described later.
[Silica fine particles]
The aqueous coating agent of the present invention contains fine silica particles having a primary particle size of 3 to 50 nm.

  The silica fine particles used in the aqueous coating agent of the present invention have a primary particle size of 3 to 50 nm. Silica fine particles having a primary particle diameter of less than 3 nm have a high affinity with water and are coated on a coating layer containing silica fine particles obtained by coating on a coating film containing a polymer having the alkoxysilane structural unit. If water is applied, only the coating layer containing silica fine particles will flow down, and the antifouling effect of such a coating film may be insufficient, and if it exceeds 50 nm, the unevenness of the coating layer containing silica fine particles becomes too large. As a result, the appearance of the coating film may be deteriorated. A preferable primary particle diameter of the silica fine particles is 10 to 25 nm. The measurement of the primary particle diameter of the silica fine particles can be obtained by a well-known measurement method such as observation with an electron microscope.

  0.1-10 mass parts is preferable with respect to 100 mass parts of the whole aqueous coating agent, and, as for the content rate of the silica fine particle in the aqueous coating agent of this invention, 0.5-5 mass parts is more preferable. If the amount is less than 0.1 parts by mass, a sufficient antifouling effect may not be obtained in the coating film containing the alkoxysilane part. If the amount exceeds 10 parts by mass, the unevenness of the coating layer containing silica fine particles becomes too large, and The film appearance may be deteriorated.

  As the silica fine particles used in the present invention, for example, silica fine particles that exhibit basicity by having a sodium salt portion or an ammonium salt portion are preferably used. This is for the reason explained below.

  In general, silica fine particles can be obtained as a suspension of silica fine particles. Therefore, the silica fine particles used in the present invention are usually derived from a suspension of silica fine particles.

  The silica fine particle suspension (also referred to as colloidal silica) is commercially available in the basic region and in the acidic region, but the silica fine particles stabilized in the acidic region In many cases, when mixed with an organic solvent or other components, the dispersion stability is impaired, making it difficult to use in preparing a composition. In addition, when silica fine particles stabilized in the acidic region are used, a coating film appearance defect may occur immediately after coating or after an exposure test due to the presence of aggregated silica fine particles that impair dispersion stability.

  For this reason, in order to ensure the dispersion stability of the suspension of the silica fine particles, silica fine particles showing basicity are preferable. However, it is known that the polymerization reaction of the alkoxysilane moiety proceeds even under strongly basic conditions.

  Many commercially available silica fine particle suspensions are neutralized with a strong basic compound and stabilized in the basic region. However, under the condition in which a strong basic compound is present, the polymerization reaction of the alkoxysilane part serving as a base may proceed. In such a case, an unpredictable problem may occur. For this reason, it is preferable to use the silica fine particle suspension stabilized in the basic region without using the strongly basic compound as the suspension of the silica fine particles.

  Specifically, the pH of the silica fine particle suspension is preferably 8.0 to 11.0, and more preferably 8.5 to 10.5. A suspension of silica fine particles having a pH outside the above-described preferred range may cause the above-mentioned problems.

  Such silica fine particles (or suspensions of silica fine particles) can be easily obtained as commercial products. More specifically, the following products can be used in the present invention.

Adelite AT-20, 30, 50, 20A, 30A manufactured by ADEKA Corporation
Snowtex SS, Snowtex XS, Snowtex S, Snowtex N, Snowtex 20, Snowtex 30, Snowtex 40, Snowtex C, manufactured by Nissan Chemical Industries, Ltd.
Cataloid 350, 20H, 30, 30H, 40, 50, SA manufactured by Catalyst Chemical Industry Co., Ltd.
Silica Doll 20, 30, 40 manufactured by Nippon Chemical Industry Co., Ltd.
Mitsubishi Monsanto Saiton X-30, D-30, T-40
DuPont Ludox SM-30, L, HS-30, HS-40, TM, AM
Nalco Nalcoag 1115, 1130, 1030, 1140, 1050, 2327
As described above, the aqueous coating agent of the present invention has a pH of 3.0 to 6.5.

The pH of the aqueous coating agent is adjusted by adding an acid having a pKa value of 3.09 to 7.0, preferably a pKa value of 3.5 to 7.0.

  Among these, an acid having a pKa value of 3.5 to 5.0 is preferable from the viewpoint of obtaining high wettability.

  When a strong acid that is lower than the lower limit of the pKa value or a basic compound that is higher than the upper limit of the pKa value is used as the pH adjusting agent, the pH adjustment of the aqueous coating agent is applied to the lower layer to which the aqueous coating agent of the present invention is applied. There is a possibility that the polymerization reaction of the alkoxysilane part contained in the coating film containing the polymer having a certain alkoxysilane structural unit proceeds rapidly.

  When the polymerization reaction of the alkoxysilane portion proceeds rapidly, the water repellency of the coating film surface containing the polymer having an alkoxysilane structural unit may become too high. Even if an aqueous coating agent is applied, it cannot be applied uniformly, and a phenomenon called repelling may occur in some cases.

  Examples of acids having such a pKa value include acetic acid (pKa4.76), glycolic acid (pKa3.82), malic acid (pKa3.40), glutaric acid (pKa4.34), and adipic acid (pKa4.42). ), Succinic acid (pKa 4.21), lactic acid (pKa 3.86), citric acid (pKa 3.09), and formic acid (pKa 3.77). Of these acids, those having a pKa value of 3.5 to 5.0 are particularly preferred, and two or more acids may be used in combination.

  What is necessary is just to determine the addition amount of the said pH adjuster in the aqueous coating agent of this invention so that pH of the aqueous coating agent of this invention may be 3.0-6.5.

  The aqueous coating agent of the present invention preferably further contains titanium oxide (titanium dioxide).

  In particular, the titanium oxide used in the aqueous coating agent of the present invention preferably has photocatalytic activity.

By this photocatalytic action, it is possible to add a soil decomposition function to the antifouling layer formed from the aqueous coating agent of the present invention and to enhance hydrophilicity. In particular, anatase-type titanium oxide generates excited electrons and holes by the energy of irradiated light (ultraviolet light), and the presence of oxygen and moisture on the titanium oxide surface by the generated excited electrons and holes. Under the reaction, reactive oxygen species such as O ₂ ⁻ , O ⁻ , • OH (• indicates an unpaired electron and means a radical species) are generated. Thus, it is considered that the active oxygen species generated on the surface of titanium oxide can be used to add a function of decomposing dirt and enhance hydrophilicity.

  The titanium oxide used in the aqueous coating agent of the present invention is preferably a particle having an average particle size of 30 nm to 140 nm, more preferably a particle having a particle size of 50 nm to 120 nm. The average particle diameter can be measured by a scattering method using a laser. With particles having an average particle diameter of less than 30 nm, the transparency of the coating film is high, but cracking is likely to occur during film formation, and it is difficult to increase the film thickness. On the other hand, when the average particle diameter is larger than 140 nm, since titanium oxide is originally a white pigment, it has a high concealing property and causes the coating film to become cloudy, which is not preferable when a coating film having transparency is desired. Further, depending on the composition of the coating solution, it is not preferable because a precipitate, particularly a hard cake that cannot be redispersed, may be generated during storage.

  The content of the photocatalytically active titanium in the aqueous coating agent of the present invention is preferably 0.005 to 2 parts by mass and more preferably 0.025 to 0.5 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent. When the content of the photocatalytically active titanium is less than the preferred lower limit, the antifouling effect due to the photocatalytic activity cannot be expected.

  STS-21 (trade name, manufactured by Ishihara Sangyo Co., Ltd.) and STS-01 (trade name, manufactured by Ishihara Sangyo Co., Ltd.) and STS-100 (trade name, Ishihara Sangyo Co., Ltd.) as titanium oxide satisfying the above requirements. Manufactured).

  The aqueous coating agent of the present invention preferably further contains a surfactant.

  By the surfactant, the wettability of the aqueous coating agent of the present invention to the coating film can be further increased.

  The surfactant used in the aqueous coating agent of the present invention is preferably a nonionic surfactant from the viewpoint of the stability of the aqueous coating agent. Examples of the nonionic surfactant include those having an alkylene oxide unit, those having an acetylene diol unit, those having an alkylene oxide unit and an acetylene diol unit, an acrylic polymer surfactant, and a silicone interface. An activator, a fluorine-type surfactant, etc. are mentioned. These surfactants may be used alone or in combination of two or more.

As the “surfactant having an alkylene oxide unit”, for example,
New Call 2302, 2303, 2305, 2307, 2308, 2308HE, 2310, 2312, 1204, 1210, 1305, 1310, 2502-A, 3504-C, 2303-Y, 2304-YM, 2304-Y, NT-3, NT-5, NT-7, NT-9 (trade name, Nippon Emulsifier Co., Ltd.);
NAROACTY N-40, ID-40, EMALMIN 40, 50, 60, Cedran FF-180, 200, 210, Cedran SF-506, Ionette DL-200, MO-200, Sanmorin 11 (trade name, Sanyo Chemical Co., Ltd. ); And SN wet 366, 980, 984 (trade name, San Nopco)
Is mentioned.

As the “surfactant having acetylenic diol”, for example,
Surfynol 104, 420, 440, 465, MD20, PSA-336, 2502, Dinol 604, 607 (trade name, Air Products Japan Co., Ltd.) may be mentioned.

As the “acrylic polymer surfactant”, for example,
Polyflow WS, WS-30, WS-314 (trade name, Kyoeisha Chemical Co., Ltd.); and BYK-380N, BYK-381 (trade name, Big Chemie Japan Co., Ltd.)
Is mentioned.

As the “silicone surfactant”, for example,
Granol 100, 400, 440, Polyflow KL-245, KL-270, KL-280, KL-600 (trade name, Kyoeisha Chemical Co., Ltd.);
BYK-307, 333, 345, 346, 348, 375, 378 (trade name, Big Chemie Japan Co., Ltd.); and SN wet 125, 126 (trade name, San Nopco Corporation)
Is mentioned.

As the “fluorine surfactant”, for example,
Footage 250, 251, 222F, 208G (trade name, Neos Co., Ltd.);
Megafuck F-443, F-444, F-445, F-470, F-471, F-475, F-477, F-479 (trade name, DIC Corporation);
NOVEC FC-4430, 4432 (trade names, 3M);
Unidyne DS-401, 403 (trade name, Nisshinsei, Daikin); and F-top EF-121, EF-122A, EF-128B, EF-122C (trade name, Gemco).

  From the viewpoint of obtaining the effect of the surfactant, the content of the surfactant in the aqueous coating agent of the present invention is preferably 0.02 to 5 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent. Preferably, it is 0.1-1 mass part.

  The aqueous coating agent of the present invention may further contain an antibacterial complex composed of an antialgae or antifungal agent. The antibacterial complex has a function of suppressing the generation of algae and mold. The antibacterial complex is fixed to minute irregularities on the surface of the colloidal silica, and the colloidal silica is fixed to the coating film on the surface of the substrate through hydrogen bonding.

  As the component of the antibacterial complex, one containing at least one organic antibacterial agent and an inorganic antibacterial agent can be used. Examples of organic antibacterial agents include pyrithione antibacterial agents, nitrile antibacterial agents, pyridine antibacterial agents, haloalkylthio antibacterial agents, organic iodine antibacterial agents, thiazole antibacterial agents, benzimidazole antibacterial agents, and imidazole antibacterial agents. is there. Inorganic antibacterial agents include crystalline silver aluminosilicate and sodium (silver-substituted zeolite), silver / zinc zeolite, silver / zeolite, zirconium phosphate, silver oxide zirconium phosphate, silver oxide, silver supported zirconium phosphate, zinc oxide , Titanium phosphate, zinc oxide and titanium oxide gel mixture, silver phosphate silver supported gel and zinc oxide mixture, silver supported silicon dioxide, silver oxide, ammonium triphosphate and sodium phosphate mixture, silver chloride, silver, copper There is a hydrophilic amino silicone polymer containing a copper compound tetraamine copper ion phosphate glass metal oxide.

  The aqueous coating agent of the present invention contains water.

  What is necessary is just to prepare the content rate of the water in the water-based coating agent of this invention so that painting workability | operativity can be ensured. For example, when spraying a paint, the solid content concentration may be adjusted so that the viscosity of the range in which the paint is discharged from the coating machine and the appropriate fluidity of the paint after coating can be secured. Moreover, what is necessary is just to prepare so that it may become a viscosity suitable for brush coating also when painting with a brush.

[Method for producing aqueous coating agent of the present invention]
The aqueous coating agent of this invention can be manufactured by mixing the component demonstrated above using the method conventionally used in the said technical field.

The manufacturing method is
To a suspension of silica fine particles having a primary particle diameter of 3 to 50 nm, pH 8 to 11,
a step of adjusting the pH to 3.0 to 6.5 by adding a pH adjuster comprising an inorganic acid or an organic acid having a pKa value of 3.09 to 7.0.

  Here, the suspension of silica fine particles having a primary particle diameter of 3 to 50 nm and having a pH of 8 to 11 may be present alone or in a state of being mixed with other components.

  As will be apparent to those skilled in the art, when a suspension of silica fine particles having a primary particle diameter of 3 to 50 nm and a pH of 8 to 11 is mixed with other components, the pH of the mixed solution is not necessarily limited to pH 8. It may not be -11, and it is within the range of the manufacturing method of this invention also in that case.

  The aqueous coating agent of the present invention can be preferably applied to a coating film containing a polymer having an alkoxysilane structural unit, and can be uniformly applied without being repelled by the coating film.

  Examples of the “polymer having an alkoxysilane structural unit” include a polymer of a silicate compound such as tetraethoxysilane.

  Examples of the alkoxysilane part include a methoxysilane part, an ethoxysilane part, a propoxysilane part, and an isopropoxysilane part.

  Specifically, as the alkoxysilane structural unit, the general formula (1)

（式中、Ｒはアルキル基である。）
で表される構成単位が挙げられる。

(In the formula, R is an alkyl group.)
The structural unit represented by these is mentioned.

  Examples of the alkyl group represented by R include a methyl group, an ethyl group, a purpyl group, and an isopropyl group.

  Examples of the coating film containing such a polymer include a clear coating film and an enamel coating film.

  The coating layer is formed by applying the aqueous coating agent of the present invention to the surface of the coating film as described above and drying it.

  As a method for applying the aqueous coating agent of the present invention to the surface of the coating film, a conventional method used for water-based paints may be used. Examples thereof include a brush, a roller, a spray, or an airless spray. The method of apply | coating is mentioned.

  The drying after the application may be performed at room temperature, or may be performed by heating in order to shorten the drying time.

  The coating film to which the aqueous coating agent of the present invention is applied is preferably a coating film formed on the surface of an article (eg, ceramic building material) that is used outdoors for a long time.

  The building board of the outer wall material having the coating layer formed as described above is also one embodiment of the present invention.

  Furthermore, in order to ensure the workability at the time of painting, various thickeners commonly used by those skilled in the art (also referred to as “viscosity modifiers”) such as clay minerals, alkali swellable thickeners, urethane associative thickeners, etc. Needless to say, it may be further added.

  The coating layer obtained by applying and drying the aqueous coating agent of the present invention preferably has a film thickness of 0.1 to 2.0 μm, and if it falls below the lower limit of the preferable film thickness, an antifouling effect can be obtained. On the other hand, if it exceeds the preferable upper limit, cracking may occur in the coating film over time, which is not preferable. The coating amount of the aqueous coating agent is determined by the relationship between the solid content concentration and the film thickness after drying.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Examples 1-3 and Comparative Examples 1-3 (correlation test between pH and wettability)]
The following 1. ~ 5. The coated siding boards of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured by the coating process. The 1. ~ 5. The coating process was performed continuously.

1. Paint substrate A commercially available sealer-coated siding board UB board 12 flat 2 grooves (trade name, manufactured by Ube Board Co., Ltd.) was used.

2. Application of base enamel Odetite 390 (dark blue) (trade name, Nippon Paint) is applied with air spray at a coating amount of 100 g / m ^{2 and then} applied to a jet dryer (100 ° C. × 10 m × 3 minutes, 10 m / s). Dried.

3. Clear coating W-3108F (trade name, Kaneka; inorganic organic hybrid resin containing a polymer having an alkoxysilane constituent unit) 100 parts by weight, QC # 006C (trade name, Kaneka) 12.5 mass as a curing agent The part added was coated with an air spray at a coating amount of 70 g / m ² and then dried with a jet dryer (100 ° C. × 10 m × 1 minute, 10 m / s).

4). Preparation of aqueous coating agent An aqueous coating agent having the following composition was prepared (Example 1).

As silica fine particles (average particle diameter: 10 to 20 nm), an equivalent amount contained in 15 parts by mass of ADEKA's trade name Adelite AT-20 (SiO ₂ ratio is 20 to 21 wt%) Acetic acid: 0.075 parts by mass Nonionic Surfactant (trade name: FC-4430, 3M): 0.1 part by mass For Examples 2-3 and Comparative Examples 1-3, aqueous coating agents were prepared using the pH adjusters shown in Table 1, respectively. did.

5. Application of aqueous coating agent A coating amount of 40 g / m ² was applied to the aqueous coating agent by air spray.

  The aqueous coating agent was dried by the residual heat of the building material heated by the jet dryer used in the clear coating process.

  The pH of the aqueous coating agent was adjusted to the value shown in Table 1 using the pH adjuster shown in Table 1, respectively.

実施例１〜３および比較例１〜３の塗装されたサイディングボードの製造時の、水性コーディング剤の濡れ性を以下の基準によって評価したところ、前掲の表１の結果が得られた。

When the wettability of the water-based coating agent during the production of the coated siding boards of Examples 1 to 3 and Comparative Examples 1 to 3 was evaluated according to the following criteria, the results shown in Table 1 above were obtained.

(Wettability evaluation criteria)
5 points: Uniform and very good wettability 4 points: Although some repelling spots are seen, almost uniform and good wettability 3 points: Overall, a slight repelling tendency is observed 2 points: Partially good Although the wettability is obtained, it repels as a whole. 1 point: The state where the entire coating film is repelled. As is clear from this, the pH of the aqueous coating agent is adjusted to 3.0 to 6.5. In addition, good wettability was obtained.
[Examples 4 to 9 and Comparative Example 4 (correlation test between pKa and wettability)]
Examples 4 to 9, and Examples 1 to 3 and Comparative Examples 1 to 3, except that the pH adjustment was performed by adding the acid in the following table as a pH adjusting agent to the aqueous coating agent. A painted siding board of Comparative Example 4 was produced.

Note that the pH of each aqueous coating agent was adjusted to about 4.5. When the wettability was evaluated according to the above criteria, the results shown in Table 2 were obtained. As is clear from this, when an acid having a pKa value of 3.09 to 7.0 was used, good wettability could be obtained.

［実施例１０〜１１、および比較例５（コロイダルシリカの粒径と性能の相関）］
水性コーティング剤に、コロイダルシリカとして次表の１次粒子径のコロイダルシリカを使用して、実施例１〜３および比較例１〜３と同様にして、実施例１０〜１１、および比較例５の、塗装されたサイディングボードを製造した。

[Examples 10 to 11 and Comparative Example 5 (correlation between particle size and performance of colloidal silica)]
In the aqueous coating agent, colloidal silica having the primary particle size shown in the following table was used as colloidal silica, and in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, Examples 10 to 11 and Comparative Example 5 Manufactured a painted siding board.

The pH of the aqueous coating agent was adjusted to about 4.5 using acetic acid.
(Evaluation)
The water contact angle (initial contact angle) of the coating film was determined as the angle formed between the tangent of the droplet and the solid surface by dropping 4 μL of pure water onto the coating film surface. The contact angle was measured by the θ / 2 method.

表３から明らかなように、シリカ微粒子の１次粒子径が５０ｎｍよりも大きいと、塗装外観不良が発生する上、初期の接触角も大きくなった。また、初期接触角が１０度の実施例１０〜１１のものは、優れたセルフクリーニング機能を有するが、初期接触角が４０度の比較例４のものは、セルフクリーニング機能を有していない。
［実施例１２（光触媒酸化チタンを配合した場合）］
実施例１０に使用したオーデナノガードに、光触媒酸化チタン（石原産業製、ＳＴＳ−２１）を、無機成分１００質量部に対し、ＳＴＳ−２１の光触媒チタン量が２質量部になるように配合し、実施例１〜３および比較例１〜３と同様にして、実施例１２、比較例の塗装されたサイディングボードを製造した。なお水性コーティング剤のｐＨは、酢酸を使用し、約４．５に調整した。

As is apparent from Table 3, when the primary particle diameter of the silica fine particles is larger than 50 nm, the appearance of the coating is poor and the initial contact angle is also increased. In addition, Examples 10 to 11 having an initial contact angle of 10 degrees have an excellent self-cleaning function, but Comparative Example 4 having an initial contact angle of 40 degrees does not have a self-cleaning function.
[Example 12 (when photocatalytic titanium oxide is blended)]
To the Ode nano guard used in Example 10, photocatalytic titanium oxide (Ishihara Sangyo Co., Ltd., STS-21) is blended so that the amount of the photocatalytic titanium of STS-21 is 2 parts by mass with respect to 100 parts by mass of the inorganic component. The coated siding boards of Example 12 and Comparative Example were manufactured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3. The pH of the aqueous coating agent was adjusted to about 4.5 using acetic acid.

The coated plate was irradiated with 1 mW / cm ² of ultraviolet light for 24 hours, and the contact angle was measured.

  Compared with the coating plate (Example 10) which does not mix | blend photocatalytic titanium oxide, the coating plate of Example 12 fell the contact angle after ultraviolet irradiation. That is, it became clear that the low pollution function is enhanced.

The aqueous coating agent containing silica fine particles of the present invention has high wettability to a coating film containing a polymer having an alkoxysilane structural unit, and can be uniformly applied.

Claims (12)

A pH adjuster comprising a suspension of silica fine particles having a primary particle diameter of 3 to 50 nm and a pH 8.0 to 11.0 and an inorganic acid or an organic acid having a pKa value of 3.09 to 7.0;
Containing
pH is 3.0 to 6.5 der is,
It is applied on a clear coating film containing a polymer having an alkoxysilane structural unit.
An aqueous coating agent characterized by The alkoxysilane structural unit is represented by the general formula (1)

(In the formula, R is an alkyl group.)
Must be a structural unit
The aqueous coating agent according to claim 1. The aqueous coating agent according to claim 1 or 2 , wherein the content of the silica fine particles is 0.1 to 10 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent. The aqueous coating agent according to any one of claims 1 to 3, further comprising titanium oxide. The titanium oxide has photocatalytic activity;
The titanium oxide has an average particle size of 30 nm to 140 nm, and
5. The aqueous coating agent according to claim 4 , wherein the titanium oxide content is 0.005 to 2 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent. The aqueous coating agent according to any one of claims 1 to 5 , further comprising a nonionic surfactant. The nonionic surfactant is
Having an alkylene oxide unit,
Having an acetylene range all unit,
Having an alkylene oxide unit and an acetylenic diol unit,
Acrylic polymer surfactant,
The aqueous coating agent according to claim 6 , which is at least one surfactant selected from a silicone-based surfactant and a fluorine-based surfactant. The aqueous coating agent according to claim 6 or 7 , wherein the content of the nonionic surfactant is 0.02 to 5 parts by mass with respect to 100 parts by mass of the entire aqueous coating agent. A coated plate having a coating film containing a polymer having an alkoxysilane structural unit,
Wherein on the coated film having a coating layer formed from the aqueous coating agent according to claim 1, coated plate. The alkoxysilane structural unit is represented by the general formula (1)

(In the formula, R is an alkyl group.)
The coated plate according to claim 9 , wherein the painted plate is a structural unit represented by: Preparing a coating film containing a polymer having an alkoxysilane structural unit;
Applying the aqueous coating agent according to claim 1 on the coating film to form a coating layer;
A painting method comprising: The alkoxysilane structural unit is represented by the general formula (1)

(In the formula, R is an alkyl group.)
Must be a structural unit
The coating method according to claim 11.