Hydrophilic hardenable composition for building exterior and hydrophilicity imparting to building exterior surface

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a hydrophilic curable composition for building exteriors (curable composition for topcoat paints used for building exteriors) and a method for imparting hydrophilicity to the surface of building exteriors.

【0002】

[Problems to be solved by conventional techniques and inventions]

Conventionally, the surface of industrial products such as ceramic materials, steel frames, buildings and building materials has been coated with a composition containing an acrylic silicone resin. As a result, not only can a design effect be imparted to the industrial product, but also a high hardness film is formed on the surface, whereby physical properties such as weather resistance and corrosion resistance of the industrial product can be improved. It was.

【0003】

Furthermore, in today's society, it is socially required to impart hydrophilicity to the film surface for the following reasons. That is, for example, pollution of buildings has become a problem mainly in urban areas. However, by improving the wettability of the surface, the contaminants adhering to the surface can be washed away with rainwater or the like, and the stain resistance of the building can be improved.

【0004】

Although the imparting of hydrophilicity can be realized by adding a surfactant to the composition, it is not yet a satisfactory method due to problems such as a decrease in surface hardness and maintenance of hydrophilicity in long-term outdoor exposure. It was.

【0005】

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydrophilic curable composition having excellent surface hardness and capable of maintaining hydrophilicity even when exposed outdoors for a long period of time. Further, in order to make it easier for pollutants adhering to the surface of the building exterior to be washed away by rainwater or the like, it is an object of the present invention to provide a method of imparting hydrophilicity to the surface of the building exterior using the hydrophilic curable composition. ..

【0006】

[Means for solving problems]

The hydrophilic curable composition for building exterior of the present invention is (A) general formula; [Chemical 2]

<img file="JP2000136282A_D0001.tif" />(In the formula, R¹Is an alkyl group with 1 to 10 carbon atoms, R²Contains a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group and an alkoxy group, and a is a group represented by 0, 1 or 2). Consists of 100 parts by weight of an alkoxysilyl group-containing acrylic copolymer (hereinafter, simply referred to as "part"), (B) tetraalkyl silicate and / or a condensate thereof of 2 to 60 parts, (C) a curing catalyst, and a cured coating film. It is characterized in that the contact angle with water after 3 months of exposure is 52 degrees or less.

【0007】

Further, in the method for imparting hydrophilicity to the building exterior surface of the present invention, a cured coating film having a contact angle with water of 52 degrees or less after exposure for 3 months is formed on the building exterior surface to make the building exterior surface hydrophilic. It is a method of imparting and thereby facilitating washing away of pollutants adhering to the surface of the building exterior with rainwater or the like, and is characterized in that the above-mentioned hydrophilic curable composition for building exterior is applied to the surface of the building exterior. The method.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

An alkoxysilyl group-containing acrylic copolymer of the component (A), which is one component in the composition of the present invention (hereinafter, also referred to as "alkoxysilyl group-containing acrylic copolymer (A)" or simply "component (A)". ) Is a general formula; [Chemical 3]

<img file="JP2000136282A_D0002.tif" />It is a polymer having at least one, preferably two or more alkoxysilyl groups represented by. This alkoxysilyl group may be contained at the end of the main chain of the component (A), may be contained in the side chain, or may be contained in both.

【0009】

If the number of alkoxysilyl groups in one molecule of the component (A) is less than one, the solvent resistance of the cured product (for example, the coating film) obtained from the composition of the present invention tends to decrease.

【0010】

In the above formula, R¹Is an alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms. When the number of carbon atoms exceeds 10, the reactivity of the alkoxysilyl group decreases, and R¹When is a group other than an alkyl group, for example, a phenyl group or a benzyl group, the reactivity is lowered.

【0011】

R¹Specific examples of the above include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group and the like.

【0012】

In the above formula, R²Is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 alkyl groups, an aryl group, and an aralkyl group.

【0013】

R²As a specific example of the alkyl group, R¹Specific examples of the aryl group include, for example, a phenyl group, and specific examples of the aralkyl group include, for example, a benzyl group.

【0014】

Specific examples of the alkoxysilyl group represented by the general formula [Chemical Formula 3] include groups contained in the alkoxysilyl group-containing monomer described later.

【0015】

Since the main chain of the alkoxysilyl group-containing acrylic copolymer (A) is substantially composed of an acrylic copolymer chain, the cured product is excellent in weather resistance, chemical resistance, water resistance and the like. Further, in the component (A), if the alkoxysilyl group is bonded to the carbon atom, the water resistance of the obtained cured product will be further excellent, and the alkali resistance, acid resistance and the like will also be excellent.

【0016】

The number average molecular weight of the alkoxysilyl group-containing acrylic copolymer (A) is preferably 1,000 to 30,000, more preferably 3,000 to 25,000, from the viewpoint of physical properties such as durability of the cured product obtained from the composition of the present invention.

【0017】

The component (A) can be obtained by copolymerizing an acrylic monomer such as acrylic acid, methacrylic acid, or a derivative thereof with an alkoxysilyl group-containing monomer.

【0018】

The acrylic monomer is not particularly limited, and specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, and benzyl (meth). Meta) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth) acrylonitrile, glycidyl (meth) acrylate, dimethylaminoethyl (meth) ) Acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethylacrylamide, N-methylacrylamide, acryloylmorpholine, 2-hydroxy Ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N-methylol (meth) acrylamide, Aronix M-5700 manufactured by Toa Synthetic Chemical Industry Co., Ltd., macromonomer manufactured by Toa Synthetic Chemical Industry Co., Ltd. AS-6, AN-6, AA-6, AB-6, AK-5, Placcel FA-1, Placcel FA-4, Placcel FM-1, Placcel FM-4, (Meta) manufactured by Daicel Chemical Industry Co., Ltd. ) A phosphoric acid ester group-containing vinyl compound, urethane bond, which is a condensation product of α, β-ethylenic unsaturated carboxylic acid hydroxyalkyl esters such as acrylic acid hydroxyalkyl esters and phosphoric acid or phosphoric acid esters. And (meth) acrylate containing a siloxane bond.

【0019】

The alkoxysilyl group-containing monomer is not particularly limited except that it has a polymerizable double bond, and specific examples thereof include, for example. [Chemical 4]

<img file="JP2000136282A_D0003.tif" />[Chemical 5]

<img file="JP2000136282A_D0004.tif" />However, (meth) acrylate having an alkoxysilyl group at the terminal via a urethane bond or a siloxane bond is also included.

【0020】

The proportion of the alkoxysilyl group-containing monomer in the component (A) is preferably 5 to 90%, more preferably 10 to 70% from the viewpoint of curability of the composition and durability of the coating film.

【0021】

The component (A) may contain a segment formed by a urethane bond or a siloxane bond in the main chain within a range not exceeding 50%, and a segment derived from a monomer other than the (meth) acrylic acid derivative may be contained. It may be included. This monomer is not limited, and specific examples thereof include aromatic hydrocarbon-based vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, styrenesulfonic acid, 4-hydroxystyrene, and vinyltoluene; maleic acid and fumal. Unsaturated carboxylic acids such as acids and itaconic acids, their salts (alkali metal salts, ammonium salts, amine salts, etc.), their acid anhydrides (maleic anhydride, etc.), or their direct 1 to 20 carbon atoms. Estel of unsaturated carboxylic acid such as diester or half ester with chain or branched alcohol; vinyl ester or allyl compound such as vinyl acetate, vinyl propionate, diallyl phthalate; amino group containing vinyl such as vinyl pyridine, aminoethyl vinyl ether Compounds; Amide group-containing vinyl compounds such as itaconic acid diamide, crotonamide, maleic acid diamide, fumaric acid diamide, N-vinylpyrrolidone; 2-hydroxyethylvinyl ether, methylvinyl ether, cyclohexylvinyl ether, vinyl chloride, vinylidene chloride, chloroprene, Other vinyl compounds such as propylene, butadiene, isoprene, fluoroolefin maleimide, N-vinylimidazole, vinyl sulfonic acid and the like can be mentioned.

【0022】

The alkoxysilyl group-containing acrylic copolymer (A) can be produced, for example, by the methods shown in JP-A-54-36395, JP-A-57-36109, and JP-A-58-157810. From the viewpoint of ease of synthesis, it is most preferable to produce by a solution polymerization method using an azo radical initiator such as azobisisobutyronitrile.

【0023】

Also in this case, if necessary, n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ- Mercaptopropylmethyldiethoxysilane, (CH₃O)₃Si-SS-Si (OCH₃)₃The molecular weight can be adjusted by using a chain transfer agent such as. In particular, it is preferable to use a chain transfer agent having an alkoxysilyl group in the molecule, for example, γ-mercaptopropyltrimethoxysilane because an alkoxysilyl group can be introduced into the terminal of the silyl group-containing acrylic copolymer.

【0024】

The polymerization solvent used in the solution polymerization method is hydrocarbons (toluene, xylene, n-hexane, cyclohexane, etc.), acetate esters (ethyl acetate, butyl acetate, etc.), ethers (ethyl cellosolve, butyl cellosolve, cellosolve, etc.). There is no particular limitation as long as it is a non-reactive solvent such as (acetate, etc.) and ketones (methyl ethyl ketone, ethyl acetoacetate, acetyl acetone, methyl isobutyl ketone, acetone, etc.).

【0025】

As such an alkoxysilyl group-containing polymer (A), one type may be used, or two or more types may be used in combination.

【0026】

Further, from the viewpoint of compatibility with the tetraalkyl silicate of the component (B) and / or a condensate thereof, it is desirable to introduce 20 to 50 parts of n-butyl methacrylate as the copolymerization monomer in the component (A).

【0027】

The tetraalkyl silicate and / or condensate thereof of the component (B) used in the present invention improves the hydrophilicity and hardness of the cured coating film obtained by coating the composition, or the adhesion between the coating film and the substrate. Improve sex.

【0028】

Examples of the tetraalkyl silicate include tetramethyl silicate, tetraethyl silicate, tetra-n-propyl silicate, tetra-i-propyl silicate, and tetra-n-butyl silicate.

【0029】

The tetraalkyl silicate condensate can be produced by a known production method obtained by condensing the tetraalkyl silicate under hydrolysis conditions. That is, it can be carried out by adding water to the tetraalkyl silicate and condensing it. Further, as the tetraalkyl silicate condensate, a commercially available product can also be used. Examples of such a condensate include MSI51, ESI28, ESI40 (all manufactured by Corcote Co., Ltd.) and the like.

【0030】

The tetraalkyl silicate and / or a condensate thereof may be mixed with the component (A), and when the component (A) is synthesized, that is, when the alkoxysilyl group-containing monomer and the acrylic monomer are copolymerized, ( B) The component can be pre-existed in the reaction vessel. The latter method improves compatibility and hydrophilicity.

【0031】

The blending ratio of the tetraalkyl silicate is 2 to 60 parts, preferably 5 to 40 parts, based on 100 parts of the resin content of the component (A). If it is less than 2 parts, the hydrophilicity of the obtained cured product is not sufficient, and if it exceeds 60 parts, there is a problem that the appearance of the cured product is deteriorated and cracks are likely to occur.

【0032】

Specific examples of the curing catalyst (hereinafter, also referred to as curing catalyst (C) or simply component (C)) which is the component (C) used in the present invention include dibutyltin dilaurate, dibutylsummarate, and dioctylstinlaurate. , Dioctyl tinmalate, organotin compounds such as tin octylate, phosphate, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, di. Phosphate esters such as decyl phosphate; propylene oxide, butylene oxide, cyclohexene oxide, glycidyl methacrylate, glycidol, acrylic glycidyl ether, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycid Xypropylmethyldimethoxysilane, [Chemical 6]

<img file="JP2000136282A_D0005.tif" />Addition reaction products of epoxy compounds such as Cardura E manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 828 and Epicoat 1001 manufactured by Yuka Shell Epoxy Co., Ltd. and phosphoric acid and / or monoacidic phosphate ester, maleic acid, Acidic compounds such as adipic acid, azelaic acid, sebacic acid, itaconic acid, citric acid, succinic acid, phthalic acid, trimellitic acid, pyromellitic acid, their acid anhydrides, paratoluenesulfonic acid and dodecylbenzenesulfonic acid are listed. Be done. Also included are mixtures or reactants of these acidic catalysts with amines. For example, amines such as hexylamine, N, N-dimethyldodecylamine and dodecylamine can be mentioned.

【0033】

Of these curing catalysts (C), an acidic curing catalyst is preferable, and an acidic phosphoric acid ester, a mixture or a reaction product of an acidic phosphoric acid ester and an amine is particularly active, and hydrophilicity is also preferable. The curing catalyst (C) may be used alone or in combination of two or more.

【0034】

The amount of the component (C) used is not particularly limited, but is usually preferably 0.1 to 20 parts, more preferably 0.1 to 10 parts, based on 100 parts of the resin solid content of the components (A) and (B). When the amount of the component (C) used is less than 0.1 parts, the curability tends to decrease, and when it exceeds 20 parts, the appearance of the coating film tends to decrease.

【0035】

It is preferable to use a dehydrating agent and an alkyl alcohol in order to ensure storage stability that does not cause any problem even after repeated use over a long period of time.

【0036】

Specific examples of the dehydrating agent include, for example, methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, methyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, methylsilicate, ethylsilicate and the like. Examples of the hydrolyzable ester compound of. Examples of alkyl alcohols include low molecular weight alcohols such as methanol and ethanol. The dehydrating agent and the alkyl alcohol may be added before the polymerization of the alkoxysilyl group-containing polymer (A), after the polymerization, or during the polymerization.

【0037】

The amount of the dehydrating agent and the alkyl alcohol used is not particularly limited, but 0.5 to 20 parts and 2 to 10 parts are more preferable with respect to 100 parts of the resin solid content of the component (A) and the component (B).

【0038】

The combined use of a dehydrating agent and an alkyl alcohol has a significant effect on storage stability.

【0039】

The compositions of the present invention include additives such as diluents, pigments (including extender pigments), ultraviolet absorbers, light stabilizers, antisettling agents, leveling agents, etc., depending on the application; nitrocellulose, cellulose acetate butyrate, etc. Fiber elements; resins such as epoxy resin, melamine resin, vinyl chloride resin, chlorinated polypropylene, rubber chloride, polyvinyl butyral; fillers and the like may be added.

【0040】

After applying the above composition to the object to be coated by various coatings, especially dipping, spraying, brush coating, etc., it is usually cured at 30 ° C or higher to adhere to the surface of the object to be coated and to have durability. It is possible to form an excellent coating film.

【0041】

[Example]

Hereinafter, the hydrophilic curable composition for building exterior of the present invention will be described in more detail based on Examples.

【0042】

Synthesis example 1 A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introduction tube and a dropping funnel is charged with 40.4 parts of xylene, the temperature is raised to 110 ° C while introducing nitrogen gas, and then a mixture having the following composition (a). ) Was dropped at a constant velocity over 5 hours using a dropping funnel. Mixture (a) Methyl methacrylate 28.4 parts Methacrylic acid n buty 47. 1 part Butyl acrylate 11.8 parts 11.8 parts of γ-methacryloxypropyltrimethoxysilane 0.9 parts of acrylamide Xylene 17.9 copies 2,2-azobisisobutyronitrile 1.0 part.

【0043】

After completion of dropping the mixture (a), 0.5 part of 2,2-azobisisobutyronitrile and 8.1 parts of toluene were added dropwise at a constant velocity over 1 hour. After completion of the dropping, the mixture was aged at 110 ° C. for 2 hours and then cooled, and xylene was added to the resin solution to adjust the solid content concentration to 50%. The number average molecular weight of the obtained resin was 15,000.

【0044】

Synthesis example 2 A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introduction tube and a dropping funnel was charged with 40.4 parts of xylene, and the temperature was raised to 110 ° C while introducing nitrogen gas, and then a mixture having the following composition (b). ) Was dropped at a constant velocity over 5 hours using a dropping funnel. Mixture (b) Methyl methacrylate 56.6 parts Butyl acrylate 30.7 parts 11.8 parts of γ-methacryloxypropyltrimethoxysilane 0.9 parts of acrylamide Xylene 17.9 copies 2,2-azobisisobutyronitrile 1.0 part.

【0045】

After completion of dropping the mixture (b), 0.5 part of 2,2-azobisisobutyronitrile and 8.1 parts of toluene were added dropwise at a constant velocity over 1 hour. After completion of the dropping, the mixture was aged at 110 ° C. for 2 hours and then cooled, and xylene was added to the resin solution to adjust the solid content concentration to 50%. The number average molecular weight of the obtained resin was 15,000.

【0046】

Synthesis example 3 30 parts of ESI40 (*) and 10.4 parts of xylene were placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen gas introduction tube and dropping funnel, and the temperature was raised to 110 ° C while introducing nitrogen gas. Then, the mixture (c) having the following composition was added dropwise at a constant velocity over 5 hours using a dropping funnel. (* Commercially available tetraethyl silicate condensate manufactured by Corcote Co., Ltd.).

【0047】

Mixture (c) Methyl methacrylate 56.6 parts Butyl acrylate 30.7 parts 11.8 parts of γ-methacryloxypropyltrimethoxysilane 0.9 parts of acrylamide Xylene 17.9 copies 2,2-azobisisobutyronitrile 1.0 part.

【0048】

After completion of dropping the mixture (c), 0.5 part of 2,2-azobisisobutyronitrile and 8.1 parts of toluene were added dropwise at a constant velocity over 1 hour. After completion of the dropping, the mixture was aged at 110 ° C. for 2 hours and then cooled, and xylene was added to the resin solution to adjust the solid content concentration to 50%. The number average molecular weight of the obtained resin was 15,000.

【0049】

Example 1 30 parts of MSI51 (manufactured by Corcote Co., Ltd.), which is the component (B), was added to 100 parts of the resin shown in Synthesis Example 1. Using this resin solution, titanium oxide (CR-90 manufactured by Ishihara Sangyo Co., Ltd.) was dispersed so that PWC (ratio of pigment to total solid content) was 40% and paint solid concentration was 60%, and white enamel was adjusted. .. Dispersion was carried out using glass beads in a paint conditioner for 2 hours. Dioctyl phosphate and dodecylamine were added to the white enamel as curing catalysts in an amount of 0.25 parts each based on 100 parts of the resin solid content, and diluted with thinner to a solid content concentration of 45%.

【0050】

This paint was applied to an aluminum plate (A5052P) with an air spray so that the dry film thickness was about 30 μm. After that, the coated plate was cured at 23 ° C. for 7 days to form a coating film on the surface of the aluminum plate. The glossiness, perozos hardness, contact angle with water, and contact angle with water after exposure for 3 months were measured in the coating film, respectively.

Described in [Table 2].

【0051】

Example 2 to Example 6 and Comparative Example 1 to Comparative Example 3 The compounding composition shown in [Table 1] was prepared into a paint by adjusting white enamel under the same conditions as described above.

The curing catalyst shown in [Table 1] was added, and the mixture was diluted with thinner to a solid content concentration of 45%.

【0052】

This paint was applied to an aluminum plate (A5052P) with an air spray so that the dry film thickness was about 30 μm. After that, the glossiness, perozos hardness, contact angle with water, and contact angle with water after three months of exposure were measured in the coating film formed by curing the coated plate under the curing conditions shown in [Table 1].

It is also shown in [Table 2].

【0053】

[table 1]

<img file="JP2000136282A_D0006.tif" />[Table 2]

<img file="JP2000136282A_D0007.tif" />【0054】

[Effect of the invention]

By the hydrophilic curable composition for building exterior and the method for imparting hydrophilicity to the surface of building exterior of the present invention, a coating film having excellent surface hardness and capable of maintaining hydrophilicity even when exposed outdoors for a long period of time is applied to the surface of building exterior. Can be formed. As a result, the pollutants adhering to the surface of the building exterior are easily washed away by rainwater or the like.