JP7793359B2 - Water-based water-repellent coating composition and inorganic building material with cured coating film - Google Patents

Description

The present invention relates to an aqueous water-repellent coating composition, particularly an aqueous water-repellent coating composition for inorganic building materials. The present invention also relates to an inorganic building material with a cured coating film formed from the aqueous water-repellent coating composition on at least one surface of an inorganic substrate.

Conventionally, inorganic substrates such as asbestos cement boards and calcium silicate boards have been coated with paint and used as inorganic building materials because of their non-flammability and excellent durability. Inorganic building materials have been used, for example, as exterior walls (substrate: siding board) of houses, etc. From the viewpoint of contamination resistance, exterior walls of houses, etc., are often provided with a hydrophilic coating that can wash away dirt with rainwater, etc. To address these problems, a purifying coating composition has been proposed (see Patent Document 1), which contains as its main components: (a) 3 to 15 parts by weight of amine silicate in terms of _SiO2 ; (b) 0.5 to 8 parts by weight of a synthetic resin; (c) 0.002 to 2 parts by weight of at least one selected from the group consisting of silver, copper, and particulate titanium oxide in terms of silver or copper atoms or 3 to 25 parts by weight of titanium oxide; (d) 15 to 75 parts by weight of a water-insoluble inorganic filler having an average particle size or length of 0.01 to 50 μm (hereinafter also referred to as "(d) inorganic filler"); and (e) 15 to 75 parts by weight of water and/or a hydrophilic organic solvent (where (a) + (b) + (c) + (d) + (e) = 100 parts by weight). However, when a hydrophilic coating film is formed using the coating composition described in Patent Document 1, problems such as algae growth on the hydrophilic coating film occur in places with poor sunlight.

Furthermore, in coatings that have high water permeability but low moisture permeability resistance, moisture that penetrates into the base material of the siding board from edges and other areas remains inside the base material without being released, accelerating the deterioration of the siding board. Here, moisture includes both rainwater from the outside and indoor humidity from the inside. Therefore, in recent years, there has been a demand for coatings that have high water permeability resistance and high moisture permeability resistance. For example, a moisture-permeable waterproof coating composition has been proposed that contains a silicone resin emulsion and a synthetic resin emulsion other than a silicone resin emulsion (see Patent Document 2).

Japanese Patent Application Publication No. 10-298451 Japanese Patent Application Laid-Open No. 2003-55600

The coating films made from the coating compositions described in Patent Documents 1 and 2 have been evaluated for short- to medium-term weather resistance of approximately 2 to 5 years, but are thought to lack sufficient long-term (e.g., 10 years or more) weather resistance. However, in recent years, the warranty periods for exterior walls of houses and other buildings have been extended, making it necessary to maintain performance over the long term. Therefore, there is a demand for improvements in the long-term water repellency and long-term weather resistance of exterior walls.

The present invention was made in consideration of the above-mentioned background art, and its purpose is to provide an aqueous water-repellent coating composition that produces a cured coating film that has excellent long-term water repellency, water resistance, and long-term weather resistance.

The inventors conducted extensive research to solve the above-mentioned problems and discovered that the above-mentioned problems can be solved by adding specific titanium oxide, amorphous silica, and silicone resin to an aqueous water-repellent coating composition and adjusting the specific titanium oxide content, amorphous silica content, and pigment mass concentration (PWC). The present invention was completed based on this discovery.

That is, according to the present invention, the following inventions are provided.
[1] A water-based water-repellent coating composition comprising (A) titanium oxide, (B) amorphous silica, (C) a silicone resin, and water,
The median diameter of the titanium oxide (A) is 0.1 μm or more and 5 μm or less,
The aqueous water-repellent coating composition has a content of (A) titanium oxide of 30% by mass or more and 65% by mass or less, a content of (B) amorphous silica of 10% by mass or more and 55% by mass or less, and a pigment mass concentration (PWC) of 50% by mass or more and 80% by mass or less, based on 100% by mass of the aqueous water-repellent coating composition in terms of solid content.
[2] The aqueous water-repellent coating composition according to [1], wherein the (B) amorphous silica contains (b1) silica particles having a median diameter of 5 μm or more.
[3] The aqueous water-repellent coating composition according to [1] or [2], wherein the (B) amorphous silica contains (b2) diatomaceous earth having a median diameter of 1 μm or more.
[4] The aqueous water-repellent coating composition according to any one of [1] to [3], further comprising (D) a coating film-forming resin.
[5] The aqueous water-repellent coating composition according to any one of [1] to [4], which is used for coating inorganic building materials.
[6] A cured coating film formed from the aqueous water-repellent coating composition according to any one of [1] to [5].
[7] An inorganic building material with a cured coating film, comprising a cured coating film formed on at least one surface of the inorganic building material from the aqueous water-repellent coating composition according to any one of [1] to [5].
[8] A step of applying the aqueous water-repellent coating composition according to any one of [1] to [5] to at least a part of an inorganic building material;
and a step of drying and curing the coating film formed in the coating step.

The present invention provides an aqueous water-repellent coating composition that produces a cured coating film that exhibits excellent long-term water repellency, water resistance, and long-term weather resistance. The present invention also provides an inorganic building material that has a cured coating film that exhibits excellent long-term water repellency, water resistance, and long-term weather resistance.

The present invention will now be described in more detail.
In this specification, the term "solid content" refers to the amount of volatile components such as water removed from the aqueous water-repellent coating composition, and refers to the components that constitute the cured coating film when cured.
The "pigment mass concentration (PWC)" is the percentage of the total mass of the pigment components relative to the mass of the solid content of the aqueous water-repellent coating composition, and is expressed by the following formula:
The "pigment component" refers to the following solid particles: (A) titanium oxide, (B) amorphous silica, any other pigments, and additives.
PWC = [total mass of pigment components] / [mass of solids in water-based water-repellent coating composition] x 100 (%)

<Water-based water-repellent coating composition>
The aqueous water-repellent coating composition according to the present invention contains at least (A) titanium oxide, (B) amorphous silica, (C) a silicone resin, and water. The aqueous water-repellent coating composition according to the present invention may further contain (D) a film-forming resin and other components. A cured coating film formed from the aqueous water-repellent coating composition according to the present invention has excellent long-term water repellency, water resistance, and long-term weather resistance. Such a cured coating film can be suitably used for coating (top coat, back sealer) building materials requiring these properties, particularly inorganic building materials.

The water content of the aqueous water-repellent coating composition of the present invention is not particularly limited and can be adjusted as needed to achieve a viscosity suitable for coating. The water content of the aqueous water-repellent coating composition is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less.

The pigment mass concentration (PWC) of the aqueous water-repellent coating composition of the present invention is 50% by mass or more and 80% by mass or less, preferably 55% by mass or more and 80% by mass or less, and more preferably 60% by mass or more and 80% by mass or less. When the pigment mass concentration content is within the above range, a cured coating film with excellent long-term water repellency, water resistance, and long-term weather resistance can be obtained.

The following describes in detail each component of the water-based water-repellent coating composition according to the present invention.

((A) Titanium oxide)
The shape of (A) titanium oxide is not particularly limited, and any conventionally known titanium oxide can be used, as long as the median diameter is 0.1 μm or more and 5 μm or less. The median diameter of (A) titanium oxide is preferably 0.15 μm or more and 4.5 μm or less, more preferably 0.2 μm or more and 4 μm or less, and even more preferably 0.25 μm or more and 3.5 μm or less. If the median diameter of titanium oxide is within the above numerical range, the cured coating film can exhibit hiding power for the substrate (undercoat).
The median diameter of (A) titanium oxide can be calculated as the median value of the diameters of titanium oxide (fine particles) when the cured coating is observed using a scanning electron microscope or a transmission electron microscope.

(A) Titanium oxide may be of the rutile, anatase, or brookite type, with the rutile type being preferred due to its stability. (A) Titanium oxide can typically be used as a color pigment in the form of titanium dioxide. Titanium dioxide has photocatalytic reactivity and can cause paint film deterioration. Commercially available titanium dioxide for paint applications undergoes various surface treatments to suppress photocatalytic reactivity and to impart dispersion stability. Examples of surface treatment materials include silicon dioxide, aluminum oxide, zirconium dioxide, phosphate esters, selenium, and organic components (such as polyols).

(A) Commercially available titanium oxide products that can be used include, for example, TITONE R-5N (manufactured by Sakai Chemical Industry Co., Ltd.), TIPAQUE R-930, TIPAQUE PFC105, TIPAQUE Black SG-103, TIPAQUE Orange TY-200, and TIPAQUE Yellow TY-70 (all manufactured by Ishihara Sangyo Kaisha, Ltd.).

The content of (A) titanium oxide is 25% by mass or more and 65% by mass or less, preferably 30% by mass or more and 63% by mass or less, more preferably 32% by mass or more and 60% by mass or less, and even more preferably 35% by mass or more and 55% by mass or less, based on 100% by mass of the solids content of the aqueous water-repellent coating composition. If the titanium oxide content is within the above range, a cured coating film with excellent long-term water repellency, water resistance, and long-term weather resistance can be obtained.

((B) Amorphous Silica)
As the (B) amorphous silica, at least one of (b1) silica particles and (b2) diatomaceous earth can be used, and it is preferable to use (b2) diatomaceous earth.

((b1) Silica particles)
The silica particles are not particularly limited in shape, etc., as long as they have a median diameter of 5 μm or more, and conventionally known amorphous silica can be used.The median diameter of the silica particles is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more and 70 μm or less, and even more preferably 20 μm or more and 50 μm or less.If the median diameter of the silica particles is within the above numerical range, the long-term water repellency and water repellency slip-off property of the cured coating film can be further improved.
The median diameter of the silica particles can be calculated as the median value of the diameters of the amorphous silica (fine particles) when the cured coating is observed using a scanning electron microscope or a transmission electron microscope.

Commercially available amorphous silica particles include, for example, Sylysia 370 and Sylysia 470 (both manufactured by Fuji Silysia Chemical Ltd.), Mizukasil P-78F (manufactured by Mizusawa Industrial Chemicals Ltd.), and OSC-BL6030 (manufactured by Oriental Silicas Co., Ltd.).

((b2) Diatomaceous earth)
Diatomaceous earth is a type of algae and is a sediment formed from fossilized diatom shells composed primarily of silicon dioxide. Such diatomaceous earth is porous. The shape of the diatomaceous earth is not particularly limited as long as it has a median diameter of 1 μm or more, and any conventionally known diatomaceous earth can be used. The median diameter of the diatomaceous earth is preferably 2 μm or more and 100 μm or less, more preferably 3 μm or more and 70 μm or less, and even more preferably 10 μm or more and 50 μm or less. If the median diameter of the diatomaceous earth is within the above numerical range, the long-term water repellency, water resistance, and long-term weather resistance of the cured coating film can be further improved.
The median diameter of diatomaceous earth can be calculated as the median value of the diameter of diatomaceous earth (fine particles) when the cured coating is observed using a scanning electron microscope or a transmission electron microscope.

Commercially available diatomaceous earth products that can be used include, for example, Celite Snow Floss (manufactured by Tokyo Diatomaceous Earth Industry Co., Ltd.), Radiolite F, Radiolite #100, Radiolite #300, Radiolite #700, and Radiolite #900 (all manufactured by Showa Chemical Industry Co., Ltd.).

The amorphous silica content (total content of (b1) silica particles and (b2) diatomaceous earth) is 10% by mass or more and 55% by mass or less, preferably 11% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the solids content of the aqueous water-repellent coating composition. When the amorphous silica content is within the above range, a cured coating film with excellent long-term water repellency, water resistance, and long-term weather resistance can be obtained.

((C) Silicone Resin)
As the silicone resin, any conventionally known silicone resin can be used without any particular limitation. From the viewpoint of coating workability, it is preferable to use, for example, a silicone resin emulsion or a silicone resin dispersion in which a polyorganosiloxane obtained by polycondensing an alkoxysilane compound or a condensate thereof is emulsified, dispersed, or dissolved in an aqueous medium.

Examples of alkoxysilane compounds that are components of polyorganosiloxane include silane compounds containing alkoxy groups having 1 to 6 carbon atoms, such as methoxy groups, ethoxy groups, n-propoxy groups, isopropoxy groups, n-butoxy groups, isobutoxy groups, tert-butoxy groups, pentyloxy groups, and hexyloxy groups. The alkoxy groups may be substituted with halogen atoms such as chlorine atoms or fluorine atoms.

The alkoxysilane compound may further contain an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkanol group, or an aralkyl group. Examples of the alkyl group include linear or branched alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, n-hexyl, n-heptyl, n-octyl, isooctyl, 2,2,4-trimethylpentyl, n-nonyl, n-decyl, and n-dodecyl. The alkyl group may be partially substituted with a halogen atom such as a chlorine atom or a fluorine atom, an acryloxy group, a methacryloxy group, a mercapto group, or an epoxycyclohexyl group.

Examples of cycloalkyl groups include cyclopentyl and cyclohexyl groups. The cycloalkyl group may be partially substituted with a lower alkyl group having 1 to 6 carbon atoms, and an example of the cycloalkyl group is 4-ethylcyclohexyl. Examples of alkenyl groups include vinyl, allyl, n-5-hexenyl, and 4-vinylcyclohexenyl groups. Examples of aryl groups include phenyl, biphenylyl, naphthyl, anthryl, and phenanthryl groups. Examples of alkanol groups include o-, m-, and p-tolyl, xylyl, and ethylphenyl groups. Examples of aralkyl groups include benzyl, α-, and β-phenylethyl groups.

Examples of alkoxysilane compounds having a substituent include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane. Examples of suitable silanes include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, di-i-propyldimethoxysilane, di-i-propyldiethoxysilane, divinyldimethoxysilane, divinyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane. These may be used alone or in any combination of two or more.

The polyorganosiloxanes used in the present invention include those composed of multiple different alkoxysilane compounds. It is also possible to use any combination of two or more different polyorganosiloxanes.

Emulsions containing polyorganosiloxanes, specifically polydimethylsiloxane, polydiphenylsiloxane, or polymethylphenylsiloxane, are particularly suitable for the aqueous water-repellent coating composition of the present invention. Specific commercially available products include, but are not limited to, "WACKER BS 45," "WACKER BS 1306," "WACKER BSR50," "WACKER 290," "WACKER SMK 1311," and "WACKER SMK 2101" (all manufactured by Wacker Asahi Kasei Silicones Co., Ltd.), "TEGO Phobé 1000S," "TEGO Phobé 1400," "TEGO Phobé 1500N 10," "TEGO Phobé 1600," and "TEGO Phobé 1650" (all manufactured by Evonik Degussa).

The silicone resin content is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 12% by mass or less, based on 100% by mass of the solids content of the aqueous water-repellent coating composition. If the silicone resin content is within the above range, the long-term water repellency, water resistance, and long-term weather resistance of the cured coating film can be further improved.

(D) Film-forming Resin The film-forming resin (D) is not particularly limited, and conventionally known resins can be used in addition to the silicone resin (C) described above. Examples of such film-forming resins (excluding silicone resins) include synthetic resins such as epoxy resins, (meth)acrylic resins, polyurethane resins, fluorine-containing resins, and polyester resins; and natural resins such as shellac resins, rosin resins, cellulose resins, rubber resins, and cashew resins. These film-forming resins may be appropriately selected according to the aqueous system (emulsified/dispersed system in water). These film-forming resins may be synthesized by conventionally known methods or may be commercially available products. Among these film-forming resins, (meth)acrylic resins are preferred.

The epoxy resin is not particularly limited, but examples include resins containing two or more epoxy groups in the molecule, and resins produced by the ring-opening reaction of these epoxy groups. Examples of such epoxy resins include glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, bisphenol epoxy resins, novolac epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, fatty acid-modified epoxy resins, and epoxidized oil-based epoxy resins.

The (meth)acrylic resin is not particularly limited as long as it is a resin other than the following fluorine-based resins, but examples thereof include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate; alicyclic, aromatic, and heterocyclic (meth)acrylic acid esters such as cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, glycidyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate; and vinyl group-containing (meth)acrylic acid esters such as allyl (meth)acrylate. Examples of suitable resins include resins obtained by (co)polymerizing one or more monomers selected from the following group of monomers: acrylic acid esters; hydroxy group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate; alkoxy group-containing (meth)acrylic acid esters such as 2-methoxyethyl (meth)acrylate; alkylamino group-containing (meth)acrylic acid esters such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; di- or tri(meth)acrylic acid esters such as ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate; and carboxy group-containing (meth)acrylic acid esters such as 2-(meth)acryloyloxyethyl phthalate. Here, for example, "(meth)acrylic acid" means acrylic acid or methacrylic acid, and similar terms have similar meanings.

The (meth)acrylic resin may be a resin obtained by copolymerizing, in addition to the above-mentioned monomer group, one or more selected from styrene, vinyl acetate, propionic acid, vinyl butyrate, vinyl benzoate, vinyl toluene, α-methylstyrene, crotonate esters, itaconic acid esters, etc. Furthermore, the (meth)acrylic resin may be a modified (meth)acrylic resin that has been modified, for example, by alkyd modification, silicone modification, urethane modification, or polyester modification, as necessary.

The polyurethane resin is not particularly limited as long as it is a resin other than the (meth)acrylic resin and has two or more urethane bonds in its molecule.

The polyurethane resin can be synthesized, for example, by reacting a compound having active hydrogen at both ends with a polyisocyanate compound. Examples of compounds having active hydrogen include polyalkylene glycols, polybutadiene glycols, polyalkylene adipates, polybutadiene glycols, polyalkylene carbonates, silicone polyols, polyester polyols, acrylic polyols, and other polyol compounds.

Examples of the polyisocyanate compound include aliphatic polyisocyanates, aromatic polyisocyanates, alicyclic polyisocyanates, and blocked polyisocyanates blocked with β-diketones, oximes, phenols, caprolactams, etc.

The fluorine-based resin is not particularly limited, but examples include resins having repeating units derived from fluorine-containing ethylene monomers. Specific examples include olefin compounds containing fluorine atoms, such as tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, and perfluoroalkyl vinyl ether; and resins obtained by homopolymerizing or copolymerizing compounds such as fluorine-containing (meth)acrylate compounds with other monomers. Examples of such other monomers include unsaturated carboxylic acid esters, unsaturated carboxylic acids, α,β-unsaturated nitriles, carbonyl group-containing compounds, conjugated dienes, aromatic vinyls, vinyl ethers, allyl ethers, and alkoxysilanes.

The polyester resin is not particularly limited as long as it is a resin other than the (meth)acrylic resin and has two or more ester bonds in the molecule, and examples thereof include resins synthesized using a polybasic acid or anhydride thereof and a polyhydric alcohol.
Examples of the polybasic acid include phthalic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, isosebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, dimer acid, trimellitic acid, pyromellitic acid, pimelic acid, and azelaic acid.
Examples of the polyhydric alcohol include 1,6-hexanediol, diethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol.

From the perspective of ease of application, it is preferable to use a resin emulsion, resin dispersion, or a resin that is liquid at room temperature (25°C) as the film-forming resin. These emulsions and dispersions may contain conventional additives such as emulsifiers and surfactants, and can be obtained by polymerizing the monomers listed in the respective resin sections above using known methods such as emulsion polymerization.

The content of the film-forming resin is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, and even more preferably 3% by mass or more and 20% by mass or less, based on 100% by mass of the solids content of the aqueous water-repellent coating composition. If the content of the film-forming resin is within the above range, the long-term water repellency, water resistance, and long-term weather resistance of the cured coating can be further improved.

(Other ingredients)
The aqueous water-repellent coating composition of the present invention may contain other components in addition to the above components, provided that the object of the present invention is not impaired. These other components may include, as needed, a diluent (water), extender pigments and coloring pigments (excluding (A) titanium oxide and (B) amorphous silica), pH adjusters, thickeners, dispersants, film-forming aids, antifoaming agents, antifouling agents, non-reactive diluents, matting agents, anti-settling agents, leveling agents, heat stabilizers, ultraviolet absorbers, light stabilizers, adhesion improvers, preservatives, antibacterial agents, antifungal agents, antiviral agents, silane coupling agents, plasticizers, etc.

(Diluent (water))
The diluent (water) is not particularly limited, and may be tap water, ion-exchanged water, etc. The diluent (water) may be, for example, water derived from the (C) silicone resin and the (D) film-forming resin, but from the viewpoints of making it easier to prepare the aqueous water-repellent coating composition, adjusting the viscosity of the composition, and improving coating workability and penetration into inorganic building materials, it is preferable to further blend a diluent (water) into the composition.

The content of diluent (water) in the water-based water-repellent coating composition is not particularly limited, but is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, and even more preferably 30 to 80% by mass.

(Film-forming aid)
Examples of the coalescent include conventionally known alcohols, glycol ethers, and esters, such as alcohols having 1 to 3 carbon atoms, such as isopropyl alcohol, alcohols such as 2,2,4-trimethylpentanediol and 2,2,4-trimethylpentanediol monoisobutyrate, glycol ethers such as ethylene glycol diethyl ether, diethylene glycol diethyl ether, propylene glycol diethyl ether and dipropylene glycol diethyl ether, and esters such as 2,2,4-trimethylpentanediol diisobutyrate. One or more types of coalescent may be used.

The content of the coalescence aid in the water-based water-repellent coating composition may be determined taking into consideration the possibility of the water-based water-repellent coating composition freezing in winter due to the presence of water, and also the need to ensure appropriate coating workability as a water-based water-repellent coating composition. There are no particular restrictions on the content of the coalescence aid in the water-based water-repellent coating composition, but it is preferably 0.1 to 10% by mass.

<Method for preparing water-based water-repellent coating composition>
The aqueous water-repellent coating composition of the present invention can be obtained by mixing and stirring the above-mentioned components using a conventionally known device such as a mixer, disperser, or stirrer. Examples of such devices include a mixing/dispersing mill, a homodisper, a mortar mixer, a roll, a paint shaker, and a homogenizer. The aqueous water-repellent coating composition of the present invention is preferably prepared by thoroughly mixing and stirring the components other than the film-forming resin (D), and then finally mixing in the film-forming resin (D).

<Inorganic building materials with hardened coating>
The inorganic building material with a cured coating film according to the present invention comprises, on at least a portion of the inorganic building material, a cured coating film formed from the aqueous water-repellent coating composition. In the present invention, the inorganic building material with a cured coating film can be used, for example, as the surface of a building (such as a top coat on an exterior wall) or the back surface (such as a back sealer on a residential building). In particular, by providing a cured coating film on the wall material (surface) of a building, it is possible to maintain long-term water repellency, water resistance, long-term weather resistance, and other performance properties over a long period of time, and to prevent algae adhesion, etc.

Building materials refer to components used in the structure and finishing of buildings. Examples include windows, walls, ceilings, floors, roofs, fixtures, wallpaper, etc. Wall materials (top coats, back sheets) and flooring materials are particularly preferred.

The inorganic building material is not particularly limited as long as it is a commonly used inorganic substrate. Examples of inorganic substrates include asbestos cement board, asbestos perlite board, calcium silicate board, asbestos cement calcium silicate board, gypsum board, mortar board, pulp cement board, wood chip cement board, GRC (glass fiber reinforced cement) board, CFRC (carbon fiber reinforced cement) board, SFRC (steel fiber reinforced cement) board, and rock wool inorganic molded bodies.

The thickness of the building material is not particularly limited, but is preferably 0.1 to 30 mm, and more preferably 1 to 20 mm.

<Method for manufacturing inorganic building materials with cured coating film>
The inorganic building material with a cured coating film according to the present invention comprises a step of applying the above-mentioned aqueous water-repellent coating composition to at least a part of the inorganic building material (coating step), and a step of drying and curing the coating film formed in the coating step (curing step).

(painting process)
The coating process is a process of coating at least one side of an inorganic building material with the aqueous water-repellent coating composition by a conventionally known method. For example, a sponge roll coater, a natural roll coater, a reverse roll coater, a curtain flow coater, a knife coater, a die coater, an air spray, an airless spray, a roller, a brush coating, immersion, etc. can be used, and can be appropriately selected. Among these, the use of a spray, a flow coater, or a sponge roll coater is preferred because it allows a larger amount of coating to be applied to the substrate and improves coating film performance such as water resistance.

The coating amount of the aqueous water-repellent coating composition is preferably 1 to 300 g/ ^m2 , more preferably 10 to 200 g/ ^m2 . If the coating amount is equal to or greater than the lower limit, the adhesion between the cured coating film and the substrate (building material) is improved, and if the coating amount is equal to or less than the upper limit, the cured coating film has excellent drying properties and workability is improved. The aqueous water-repellent coating composition may also be applied multiple times.

The coating thickness, measured after curing and drying, is preferably 0.5 to 150 μm. From the standpoint of drying and curing properties, a more preferred upper limit is 100 μm, and from the standpoint of long-term water repellency, water resistance, and long-term weather resistance, a more preferred lower limit is 5 μm.

(Curing process)
The curing step is a step in which the coated surface of the building material is dried to cure the applied aqueous water-repellent coating composition and form a cured coating film. Examples of drying methods include hot air drying (using a dryer, etc.). The drying temperature is preferably 10 to 200°C, with a more preferred upper limit of 150°C from the viewpoint of the smoothness and appearance of the coating film, and a more preferred lower limit of 30°C from the viewpoint of drying speed.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples.

[Examples 1 to 18, Comparative Examples 1 to 15]
<Preparation of Water-Based Water-Repellent Coating Composition>
First, the following raw materials were prepared for preparing the water-based water-repellent coating composition.
Titanium oxide 1: white, median diameter 0.5 μm, manufactured by Sakai Chemical Industry Co., Ltd., product name: TITONE R-5N
Titanium oxide 2: white, median diameter 0.28 μm, manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Typaque PFC105 (ultra-high weather resistance)
Titanium oxide 3: black, median diameter 1.2 μm, manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Typaque Black SG-103 (black heat-shielding)
Titanium oxide 4: orange, median diameter 0.7 μm, manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Typaque Orange TY-200 (high weather resistance)
Titanium oxide 5: yellow, median diameter 0.7 μm, manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Typaque Yellow TY-70 (high weather resistance)
Silica particles 1: median diameter 6.4 μm, Fuji Silysia Chemical Ltd., product name: Sylysia 370
Silica particles 2: median diameter 14 μm, Fuji Silysia Chemical Ltd., product name: Silica 470 (14 μm)
Silica particles 3: median diameter 18 μm, Mizusawa Industrial Chemicals, Ltd., product name: Mizukasil P-78F
Silica particles 4: median diameter 20 to 50 μm, manufactured by Oriental Silicas Co., Ltd., product name: OSC-BL6030
Diatomaceous earth 1: median diameter 1-2 μm, manufactured by Tokyo Diatomaceous Earth Industry Co., Ltd., product name: Celite Snow Floss Diatomaceous earth 2: median diameter 4.3 μm, manufactured by Showa Chemical Industry Co., Ltd., product name: Radiolite F
Diatomaceous earth 3: median diameter 13 μm, manufactured by Showa Chemical Industry Co., Ltd., trade name: Radiolite #100
Diatomaceous earth 4: median diameter 15 μm, manufactured by Showa Chemical Industry Co., Ltd., trade name: Radiolite #300
Diatomaceous earth 5: median diameter 30 μm, manufactured by Showa Chemical Industry Co., Ltd., trade name: Radiolite #700
Diatomaceous earth 6: median diameter 40 μm, manufactured by Showa Chemical Industry Co., Ltd., trade name: Radiolite #900
Silicone resin 1: Wacker Chemicals Co., Ltd., product name: BS45
Silicone resin 2: water-dilutable, manufactured by Wacker Chemicals Co., Ltd., product name: BS1306
Carbon black: Carbon black FW200 manufactured by Orion Engineered Carbons GmbH
Iron oxide 1: Yellow iron oxide, manufactured by Toda Kogyo Co., Ltd., product name: Yellow iron oxide TSY-1
Iron oxide 2: Bengalese red, manufactured by Toda Pigment Co., Ltd., product name: Moonlight BB
Calcium carbonate 1: median diameter 5 μm, manufactured by Maruo Calcium Co., Ltd., product name: Tankal Super SS
Calcium carbonate 2: median diameter 12 μm, manufactured by Maruo Calcium Co., Ltd., product name: Heavy calcium carbonate Calcium carbonate 3: median diameter 20 μm, manufactured by Maruo Calcium Co., Ltd., product name: R Heavy carbon Mica 1: median diameter 42 μm, manufactured by Yamaguchi Mica Co., Ltd., product name: SYA-41R
Mica 2: Median diameter 16 μm, manufactured by Lingshou Huajing Mica Co., Ltd., trade name: Mica Powder 325 mesh Mica 3: Median diameter 2.4 μm, manufactured by Yamaguchi Mica Co., Ltd., trade name: Mica Powder A-11
Acrylic emulsion: manufactured by Ohtake Meishin Chemical Co., Ltd., product name: WSR325
pH adjuster: Wacker Chemicals Co., Ltd., product name: BS198
Thickener: FUJI CHEMI HEC SW-25F, manufactured by Sumitomo Seika Chemicals Co., Ltd.
・Preservative: Manufactured by Osaka Gas Chemicals Co., Ltd., product name: Deltop
Dispersant: Rohm & Haas Company, trade name: 25% Orothane 731 aqueous solution Coalescence agent: JNC Corporation, trade name: Texanol (A) CS-12
Defoaming agent: BASF Japan Ltd., trade name: Foamaster MO 2111 NC

Next, components (A) through (C) and all other components except component (D) were thoroughly mixed and stirred using a Homodisper according to the formulations shown in Tables 1 through 4. After that, component (D) was added and mixed and stirred using a Homodisper to obtain a water-based water-repellent coating composition.

<Production of inorganic building materials with cured coating film>
The aqueous water-repellent coating compositions obtained in Examples 1 to 18 and Comparative Examples 1 to 15 were diluted with 40 parts by weight of water per 100 parts by weight of composition and then applied to inorganic building boards (calcium silicate boards) using an air sprayer at a coating amount of 140 g/ ^m2 . The coated surfaces of the inorganic building boards were then dried in a hot air dryer at 100°C for 20 minutes to cure the coating film, yielding inorganic building materials with a cured coating film. The thickness of the cured coating film was 40 to 50 μm.

<Evaluation of inorganic building materials with cured coating>
The inorganic building materials with cured coating films produced in Examples 1 to 18 and Comparative Examples 1 to 15 were subjected to the following evaluation tests.

[Water repellency evaluation]
(Contact angle measurement test)
To evaluate the water repellency of the inorganic building materials with cured coating films, the contact angle of water was measured. Specifically, using an automatic contact angle meter ("Drop Master DM500", manufactured by Kyowa Interface Science Co., Ltd.), 1 μl of pure water was dropped onto the cured coating surface of a test panel (10 cm × 10 cm) of the inorganic building material with cured coating film, and the contact angle with water was measured 10 seconds after the drop landed, and evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 4.
[Evaluation criteria]
5 points: The contact angle was 130 degrees or more.
4 points: The contact angle was 120 degrees or more and less than 130 degrees.
3 points: The contact angle was 110 degrees or more and less than 120 degrees.
2 points: The contact angle was 100 degrees or more and less than 110 degrees.
1 point: The contact angle was less than 100 degrees.

(Slip-off test)
To evaluate the water repellency of the inorganic building material with a cured coating film, the water sliding property was measured. Specifically, a test plate (10 cm x 10 cm) of the inorganic building material with a cured coating film was tilted 30 degrees relative to a horizontal table, with the cured coating film surface facing upward. Next, one drop of water (approximately 0.05 mL) was dropped onto the upper end of the test plate from a height of 5 cm above using a dropper, and the sliding property was evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 4.
[Evaluation criteria]
5 points: The water droplets rolled off the test plate.
4 points: The water droplet rolled but stopped halfway down the test plate.
3 points: The water droplet stopped immediately after rolling.
・2 points: Water droplets formed but did not roll.
・1 point: The water spread out without forming droplets.

[Water resistance evaluation]
(Water resistance test)
To evaluate the water resistance of the cured coating films, a hot water resistance test was conducted. Specifically, each test piece (10 mm × 10 mm) with a cured coating film was immersed in hot water at 60°C for 240 hours. The test piece was then removed from the hot water, and the coating surface was lightly wiped. A cross-cut adhesion test was conducted based on JIS K5400 to evaluate the adhesion of the cured coating film to inorganic building materials.
[Evaluation criteria (adhesion after 240 hours of water resistance test/cross-cut test)]
・5 points: There are 25 remaining squares.
・4 points: The number of remaining squares was 23 or more but less than 25.
・3 points: The number of remaining squares was 21 or more but less than 23.
・2 points: The number of remaining squares was 19 or more but less than 21.
・1 point: The number of remaining squares was 17 or more but less than 19.
・0 points: The number of remaining squares was less than 17.

Next, contact angle measurement tests and slide-off tests were conducted in the same manner as the water repellency evaluation described above, except that the test plates used were those that had undergone the water resistance test. The evaluation results are shown in Tables 1 to 4.

[Weather resistance evaluation]
(Weather resistance test)
To evaluate the weather resistance of the inorganic building materials with cured coating films, weather resistance tests were conducted. Specifically, an accelerated weather resistance test was conducted using an Eye Super UV Tester on the cured coating surface of test panels (5 cm x 5 cm) of each inorganic building material with cured coating film to evaluate the weather resistance of the coating film. Specifically, the weather resistance test was conducted under the following conditions.
Testing machine: Eye Super UV Tester (manufactured by Iwasaki Electric Co., Ltd., filter: WJ100-SUV, irradiance on test piece surface: 75 mW/cm ² , wavelength range: 295 to 450 nm)
Test time: 1000 hours Test cycle: 4 hours of irradiation → 4 hours of condensation (30-second shower before and after condensation)
Average humidity: 50% when irradiated, 98% when condensed,
Black panel temperature: 63°C during irradiation, 30°C during condensation

Subsequently, the gloss of the cured coating surface of the test plate after the weather resistance test was measured using a gloss meter ("GLOSSMETER", manufactured by Murakami Color Research Laboratory Co., Ltd.). The gloss of the cured coating surface of the test plate before the weather resistance test was measured in advance using the same method, and the gloss retention was calculated using the following formula. The evaluation results are shown in Tables 1 to 4.
Gloss retention (%) = gloss of the cured coating surface of the test panel after weather resistance test / gloss of the cured coating surface of the test panel before weather resistance test × 100
[Evaluation criteria]
5 points: Gloss retention was 90% or more.
4 points: Gloss retention was 80% or more and less than 90%.
3 points: Gloss retention was 70% or more and less than 80%.
2 points: Gloss retention was 60% or more and less than 70%.
1 point: Gloss retention was less than 60%.

In addition, contact angle measurement tests and slide-off tests were conducted in the same manner as the water repellency evaluation described above, except that test panels after the weather resistance test were used. The evaluation results are shown in Tables 1 to 4.

Claims (8)

A water-based water-repellent coating composition comprising (A) titanium oxide, (B) amorphous silica, and (C) a silicone resin,
The median diameter of the titanium oxide (A) is 0.1 μm or more and 5 μm or less,
The (B) amorphous silica is (b2) diatomaceous earth having a median diameter of 1 μm or more,
The aqueous water-repellent coating composition has a content of (A) titanium oxide of 30% by mass or more and 65% by mass or less, a content of (B) amorphous silica of 10% by mass or more and 30.8 % by mass or less, and a pigment mass concentration (PWC) of 50% by mass or more and 80% by mass or less, based on 100% by mass of the aqueous water-repellent coating composition in terms of solid content. 2. The aqueous water-repellent coating composition according to claim 1 , wherein the median diameter of the diatomaceous earth ( b2) is 10 μm or more and 50 μm or less. 3. The aqueous water-repellent coating composition according to claim 1, wherein the content of the silicone resin (C) is 1% by mass or more and 20% by mass or less, based on 100% by mass of the aqueous water-repellent coating composition in terms of solid content. The aqueous water-repellent coating composition according to any one of claims 1 to 3, further comprising (D) a film-forming resin. The aqueous water-repellent coating composition according to any one of claims 1 to 4, which is used for coating inorganic building materials. A cured coating film formed from the aqueous water-repellent coating composition described in any one of claims 1 to 5. An inorganic building material with a cured coating film, comprising a cured coating film formed from the aqueous water-repellent coating composition described in any one of claims 1 to 5 on at least one surface of the inorganic building material. A step of applying the aqueous water-repellent coating composition according to any one of claims 1 to 5 to at least a part of an inorganic building material;
and a step of drying and curing the coating film formed in the coating step.