JP2008285503A - Stainproof coating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stainproof coating liquid exhibiting good hydrophilicity from just after coating, capable of being coated to a 3 μm thickness coating without causing crack and capable of providing a stainproof coated film. <P>SOLUTION: The stainproof coating liquid contains (A) a dispersion of inorganic oxide particles and (B) a bifunctional silane compound. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antifouling coating liquid, and more particularly to a coating liquid that forms a coating film that is excellent in stain resistance and can be applied to a thickness of several μm.

When the contact angle on the surface of the substrate is hydrophilic, the dirt adhering to the surface tends to flow with rain water and the like, and is difficult to get dirty. As such an antifouling coating film having hydrophilicity, a film designed around an inorganic oxide having high hydrophilicity can be mentioned.
For example, Patent Document 1 discloses an antifouling coating agent containing inorganic oxide fine particles dispersed in a volatile solvent and a surfactant. However, this coating film has good hydrophilicity due to the surface hydroxyl groups of the inorganic oxide particles, but has a problem in the flexibility of the coating film because it mainly contains inorganic components.
Further, Patent Document 2 discloses a graft composed of a polymer block having dimethylsiloxane as a repeating unit, a polymer block having a vinyl polymerizable monomer as a repeating unit, and a silicon-containing graft crossing unit copolymerized therewith. An aqueous coating composition containing an emulsion of a copolymer and a silicon oxide colloid (colloidal silica) surface-treated with a silane compound is disclosed. However, this coating film has a problem in hydrophilicity because an organic component exists on the surface of the coating film.

  As described above, it is difficult to satisfy both hydrophilicity and flexibility in these antifouling coating films. A coating film having insufficient hydrophilicity is poor in the ability to wash away dirt adhering to the surface, that is, the antifouling property. On the other hand, a coating film with insufficient flexibility tends to crack when applied thickly. That is, when it is applied to a substrate having surface irregularities of about submicron to several microns, cracks are likely to occur at portions where the coating is partially thick. Alternatively, when the coating is applied to a substrate having a smooth surface, if the coating film thickness is thin, there is a problem that interference fringes are generated due to the light interference action between the substrate and the coating film.

JP2003-206416 JP 10-168393 A

  An object of the present invention is to provide an antifouling coating solution that can form an antifouling coating film that exhibits good hydrophilicity immediately after application and that can be applied to a film thickness of 3 μm without causing cracks. .

As a result of intensive studies aimed at solving the above problems, the present inventors have reached the present invention. The present invention is as follows.
(1) An antifouling coating solution comprising an inorganic oxide particle (A) dispersion and a bifunctional silane compound (B).
(2) The antifouling coating liquid according to (1), wherein the inorganic oxide particle (A) dispersion comprises a silica dispersion dispersed in a volatile solvent.
(3) The bifunctional silane compound (B) is a bis (trialkoxysilyl) alkane having a methylene group or an ethylene group represented by the following general formula (1): Antifouling coating solution as described in 2).
X ₃ Si-A-SiX ₃ (1)
(In the formula, X represents a hydrolyzable group, and A represents a methylene group or an ethylene group.)
(4) The antifouling coating solution according to any one of (1) to (3), comprising a silane having a hydrolyzable group and / or a partially hydrolyzed condensate thereof (C).
(5) The antifouling coating solution according to any one of (1) to (4), which contains a functional metal oxide (D).

  The coating liquid of the present invention has a high antifouling property and has the effect of forming an antifouling coating film that can be applied to a thickness of 3 μm without causing cracks. In other words, when applied to a substrate with surface irregularities of submicron to several microns, it is possible to suppress the occurrence of cracks due to uneven thickness, while for a substrate with a smooth surface. It has the effect of forming an antifouling coating film capable of suppressing optical interference fringes by increasing the film thickness.

Hereinafter, the present invention will be described in detail.
The antifouling coating liquid of the present invention contains inorganic oxide particles (A) and a bifunctional silane compound (B).
In the bifunctional silane compound (B), an organic group is bonded between Si and Si, and the organic group is difficult to be exposed on the coating film surface. Therefore, the inorganic oxide particles (A) and / or the bifunctional silane compound (B ) Of the hydrolyzable group X occupies the coating film surface, and the hydrophilicity is improved. That is, it becomes possible to achieve both flexibility imparted by the organic group and good hydrophilicity.

  Examples of the inorganic oxide particles (A) that can be suitably used in the present invention include silicon oxide (silica), aluminum oxide, calcium silicate, magnesium oxide, antimony oxide, and composite oxides thereof. Among these, silicon oxide (silica) having a large surface hydroxyl group, aluminum oxide (alumina), antimony oxide, and complex oxides thereof are preferable, and a silicon oxide (silica) dispersion is more preferable. More preferably, a silicon oxide (silica) dispersion dispersed in a volatile solvent capable of improving the hydrolysis rate is used. Here, the dispersion is one in which particles are dispersed as primary particles and / or secondary particles in water and / or volatile solvent at 0.01 to 80% by mass, preferably 0.1 to 50% by mass. Examples of the volatile solvent include volatile organic solvents that are non-hydrophilic organic solvents such as alcohols, glycols, ketones, ethers, and esters. From the viewpoint of safety, manufacturing cost, and workability, alcohol Are preferred. As alcohol, methyl alcohol, ethyl alcohol, or isopropanol is used. The particle diameter of the inorganic oxide particles is preferably 1 to 100 nm which is excellent in transparency and strength, more preferably 5 to 50 nm, still more preferably 10 to 20 nm.

Examples of the bifunctional silane compound (B) that can be suitably used in the present invention include bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, bis (trimethoxysilyl) ethane, and bis (triethoxysilyl) ethane. 1,3-bis (trimethoxysilyl) propane, 1,3-bis (triethoxysilyl) propane, bis (trimethoxysilyl) hexane, bis (triethoxysilyl) octane, 1,2-bis (trimethoxysilyl) ) Decane, bis (3-triethoxysilylpropyl) amine, bis (3-triethoxysilylpropyl) disulfide, 1,4-bis (triethoxysilyl) benzene, bis (triethoxysilyl) ethylene, bis (m- ( 2-triethoxysilylethyl) tolyl) polysulfide, 2,2-bis (3-triethoxysilylpropoxymethyl) butanol, 1,3- (bis (3-triethoxysilylpropyl) poly Ethyleneethylene) -2-methylenepropane, bis (3-triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl) urea, 1,4-bis (trimethoxysilylethyl) benzene, p- Bis (trimethoxysilylmethyl) benzene, bis (trimethoxysilylmethyl) ethylene, bis (trimethoxysilylpropyl) amine, bis (3-trimethoxysilyl) propyl) ethylenediamine, N, N'-bis ((3-tri Methoxysilyl) propyl) ethylenediamine, bis (3-trimethoxysilylpropyl) -N-methylamine, 1,2,2-tris (triethoxysilyl) ethane and the like can be used. Among them, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, bis (trimethoxysilyl) ethane, bis (triethoxysilyl) ethane, which can form a coating film with good hydrophilicity, can be formed. 1,3-bis (trimethoxysilyl) propane and 1,3-bis (triethoxysilyl) propane are preferable, and bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, and bis (trimethoxy) are more preferable. Silyl) ethane and bis (triethoxysilyl) ethane are used.

In the present invention, hydrophilicity refers to a hydrophilic surface having a water contact angle of 20 ° or less at 20 ° C., and exhibits antifouling properties due to self-cleaning ability (self-cleaning) by water such as rain. From the viewpoint of more excellent stain resistance, the surface water contact angle is preferably 20 ° or less, more preferably 10 ° or less.
The range of the mass ratio (A) / (B) of the inorganic oxide particles (A) and the bifunctional silane compound (B) in terms of complete hydrolysis condensate is preferably 90/10 to 10/90, From the viewpoint of strength, 75/25 to 50/50 is more preferable. Here, the complete hydrolysis-condensation product refers to a product in which a hydrolyzable group of silane is hydrolyzed to 100% to become a SiOH group and further completely condensed to a siloxane structure.

The coating liquid of the present invention can be heated for the purpose of promoting condensation after coating. As the film formation temperature, room temperature to 150 ° C. is suitable, but cracking may occur during drying depending on the coefficient of thermal expansion of the substrate, adhesion to the substrate, and coating film thickness. It is necessary to make a comprehensive decision including gender.
The coating agent of the present invention is preferably applied to a film thickness of 0.5 to 10.0 μm. If transparency is required, the film thickness may be reduced. If a light interference fringe is formed on the surface of the coating film, the film thickness can be suppressed by increasing the thickness. Therefore, a film thickness of 2.0 to 3.0 μm is more preferable.

The coating liquid of the present invention may contain a silane having a hydrolyzable group and / or a partial hydrolysis condensate (C) thereof for the purpose of improving strength. Examples of the silane having a hydrolyzable group include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, and tetra-n-butoxysilane; methyltrimethoxysilane, Methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, n-butyltrimethoxysilane, n-butyltri Ethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysila , Cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyl Trimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3- Sodium propyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloyloxypropyltri Trialkoxysilanes such as n-propoxysilane, 3- (meth) acryloyloxypropyltriisopropoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldi Toxisilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, Di-n-pentyldimethoxysilane, di-n-pentyldiethoxysilane, di-n-hexyldimethoxysilane, di-n-hexyldiethoxysilane, di-n-heptyldimethoxysilane, di-n-heptyldiethoxysilane Dialkoxysilanes such as di-n-octyldimethoxysilane, di-n-octyldiethoxysilane, di-n-cyclohexyldimethoxysilane, di-n-cyclohexyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; Trimethylmethoxysilane, trimethylethoxysilane, etc. Mono alkoxysilanes or the like is used. These silicon alkoxides and silane coupling agents can be used alone or in admixture of two or more. Among the hydrolyzable group-containing silanes, tetramethoxysilane and tetraethoxysilane are preferable.
The range of the mass ratio (A) / (C) in terms of complete hydrolysis condensate of the inorganic oxide particles (A) and the hydrolyzable group-containing silane and / or its partial hydrolysis condensate (C) is 90/10. ~ 10/90 is preferable, and 75/25 to 50/50 is more preferable from the viewpoint of flexibility and film strength.

  By containing the functional metal oxide (D) in the coating liquid of the present invention, a functional coating film can be formed. Examples of the functional metal oxide include titanium oxide, strontium oxide, barium oxide, zinc oxide, tungsten oxide, nickel oxide, iron oxide, indium oxide, tin oxide, zirconium oxide, antimony oxide, lead oxide, niobium oxide, and Those composite oxides can be mentioned. Among them, titanium oxide, strontium titanate, barium titanate, zinc oxide, tungsten oxide, iron oxide known as photocatalysts, ITO (tin doped indium oxide) known as conductive metal oxides, ATO (antimony doped oxidation) Indium), tin oxide, and zinc oxide are preferred. Among photocatalysts, titanium oxide is more preferred because it has photoinduced superhydrophilicity, is harmless and has excellent chemical stability. As the titanium oxide, any crystal of anatase, rutile, brookite can be used.

Here, the photocatalyst refers to a substance that causes an oxidation or reduction reaction by light irradiation. That is, when light (excitation light) with energy larger than the energy gap between the conduction band and the valence band is irradiated, excitation (photoexcitation) of electrons in the valence band occurs, and conduction electrons and holes are It is a substance that can be generated, and is a catalyst that utilizes the reducing power of electrons generated in the conduction band and / or the oxidizing power of holes generated in the valence band.
The photocatalytic activity means that an oxidation or reduction reaction is caused by light irradiation. These photocatalytic activities can be evaluated, for example, by measuring the decomposability of organic substances such as pigments when the film surface is irradiated with light. On the surface having photocatalytic activity, it is possible to decompose contaminating organic substances.

The range of the mass ratio (A) / (D) between the inorganic oxide particles (A) and the metal oxide (D) having photocatalytic activity is preferably 50/50 to 99/1. From the standpoint of performance development and film formability, it is more preferably 80/20 to 97/3, and still more preferably 85/15 to 95/5.
In addition, depending on the application and method of use, components that are usually added to paints and molding resins, such as thickeners, leveling agents, thixotropic agents, antifoaming agents, freeze stabilizers, matting agents, Cross-linking reaction catalyst, pigment, curing catalyst, cross-linking agent, filler, anti-skinning agent, dispersant, wetting agent, light stabilizer, antioxidant, ultraviolet absorber, rheology control agent, antifoaming agent, film-forming aid Select a rust preventive, dye, plasticizer, lubricant, reducing agent, antiseptic, antifungal agent, deodorant, yellowing preventive, antistatic agent, charge control agent, etc. according to their purpose, It can mix | blend in combination.

  Examples of the application of the coating agent of the present invention to the antifouling technology field include, for example, building materials, building exteriors, building interiors, window frames, window glass, structural members, housing and other building equipment, particularly toilets, bathtubs, washstands, and lighting fixtures. , Lighting covers, kitchen utensils, dishes, dishwashers, dish dryers, sinks, cooking ranges, kitchen hoods, ventilation fans, etc. The coating agent of the present invention can also be used for the exterior and painting of vehicles, depending on the application, and the interior thereof, such as covers for vehicle lighting, window glass, instruments, display panels, etc. Dust cover and painting, display equipment, its covers, traffic signs, various display devices, display objects such as advertising towers, sound insulation walls for roads and railways, bridges, guardrail exterior and painting, tunnel interior and painting, insulators, sun It can also be used for exteriors such as battery covers, solar water heater heat collection covers such as externally used electronic and electrical equipment exteriors, greenhouses and greenhouses.

  The coating agent containing the photocatalytic metal oxide of the present invention can be applied to the antibacterial and antifungal technical fields by photocatalytic action. For example, building materials, building exteriors, building interiors, window frames, structural members, housing and other building equipment, especially toilets, bathtubs, washstands, lighting fixtures, lighting covers, kitchenware, tableware, dishwashers, dish dryers, sinks, Cooking ranges, kitchen hoods, ventilation fans, cupboards, display cabinets, bathroom and washroom walls, ceilings, doorknobs, medical and public facilities, such as hospital parts, ambulance parts, food and pharmaceutical factories, schools・ For hygiene management in public facilities such as gymnasiums / stations, public baths, public toilets, inns, hotels, etc., mention the use of walls, floors and ceilings, fixtures, fixtures, doorknobs, etc. it can. In particular, it can be widely used as a hospital infection prevention method for members in hospitals. Examples of the members in the hospital include floors, walls, ceilings, handrails, door handles, water faucets, etc. in places where an unspecified number of things come into contact, such as hospital rooms, examination rooms, corridors, stairs, elevators, waiting rooms, and washrooms. Examples include various medical equipment. In addition, the antibacterial and antifungal properties can be effectively imparted not only to the hospital but also to various members in places requiring hygiene such as an ambulance, a food storage room, and a food cooking room.

The present invention will be specifically described by the following examples and comparative examples, but these do not limit the scope of the present invention.
An antifouling coating solution having the following composition was applied to a PET film substrate, and the contact angle of water and the film thickness limit were evaluated. Here, the limit film thickness refers to a limit coating film thickness that enables film formation without causing cracks.
The contact angle of water with respect to the coating film surface was measured using a CA-X150 contact angle meter manufactured by Kyowa Interface Science after placing a drop of deionized water on the surface of the film and leaving it at 20 ° C. for 1 minute. The lower the contact angle of the coating film, the better the hydrophilicity of the coating film surface.
The limit film thickness of the coating film was evaluated by bar coating the coating solution to various thicknesses, and measuring the limit film thickness at which cracks do not occur with a film thickness meter. Thickness Viewer ver.1.26.4 manufactured by Spectra Corp. was used as the software for the film thickness meter, and MHF-D100LR light source device manufactured by Moritex Co., Ltd. was used as the light source.

[Example 1]
Methanol-dispersed colloidal silica (trade name: MA-ST-S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-1) with bis (triethoxysilyl) ethane (B-1) and tetraethoxysilane After mixing (C-1) so that the ratio of (A-1) / (B-1) / (C-1) is 50/25/25 in terms of mass ratio in terms of complete hydrolysis condensate, magnetic Stir with a stirrer for 1 hour. The above coating solution was bar-coated on a 20 cm × 30 cm PET film and then dried at 70 ° C. for 10 minutes to obtain a coating film sample.
The resulting coating film had a water contact angle of 9.0 ° and a limit film thickness of 5.5 μm. The evaluation results are shown in Table 1.

[Example 2]
In Example 1, methanol-dispersed colloidal silica (trade name: MA-ST-S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-1) was mixed with isopropanol-dispersed colloidal silica (trade name: IPA-ST -S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-2) The evaluation results of the obtained coating film are shown in Table 1.

[Example 3]
In Example 1, solvent-dispersed titania sol (trade name: TKS-251, manufactured by Teika Co., Ltd., titanium oxide solid content 19.6%) (D-1) was mixed with methanol-dispersed colloidal silica (trade name: MA-ST-S, (A-1) / (D-1) is 50/3 in the solid content mass ratio with respect to the solid content of silica (25%) (A-1) manufactured by Nissan Chemical Industries, Ltd. The same operation as in Example 1 was conducted except that it was added in a split manner. The evaluation results of the obtained coating film are shown in Table 1.

[Comparative Example 1]
Methanol-dispersed colloidal silica (trade name: MA-ST-S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-1) and tetraethoxysilane (C-1) in terms of complete hydrolysis condensate After mixing so that the mass ratio (A-1) / (C-1) was 50/50, the mixture was stirred with a magnetic stirrer for 1 hour. The above coating solution was bar-coated on a 20 cm × 30 cm PET film, and then dried at 70 ° C. for 10 minutes to obtain a coating film sample. The evaluation results of the obtained coating film are shown in Table 1. It can be seen that the limit film thickness is inferior compared to the examples.

[Comparative Example 2]
In Comparative Example 1, methanol-dispersed colloidal silica (trade name: MA-ST-S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-1) was mixed with isopropanol-dispersed colloidal silica (trade name: IPA-ST -S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-2) The evaluation results of the obtained coating film are shown in Table 1. It can be seen that the limit film thickness is inferior compared to the examples.

[Comparative Example 3]
Methanol-dispersed colloidal silica (trade name: MA-ST-S, manufactured by Nissan Chemical Industries, Ltd., silica solid content 25%) (A-1) with methyltrimethoxysilane (C-2) and tetraethoxysilane (C- After mixing 1) so that the ratio of (A-1) / (C-2) / (C-1) is 50/25/25 in terms of mass ratio in terms of complete hydrolysis condensate, 1 Stir for hours. The above coating solution was bar-coated on a 20 cm × 30 cm PET film, and then dried at 70 ° C. for 10 minutes to obtain a coating film sample. The evaluation results of the obtained coating film are shown in Table 1. It can be seen that the contact angle is inferior compared to the examples.

  The coating liquid of the present invention can be suitably used in fields such as architectural exteriors, exterior display applications, and automobiles.

Claims (5)

  An antifouling coating solution comprising an inorganic oxide particle (A) dispersion and a bifunctional silane compound (B).   2. The antifouling coating solution according to claim 1, wherein the inorganic oxide particle (A) dispersion comprises a silica dispersion dispersed in a volatile solvent. 3. The bifunctional silane compound (B) is a bis (trialkoxysilyl) alkane having a methylene group or an ethylene group represented by the following general formula (1): Antifouling coating solution.
X ₃ Si-A-SiX ₃ (1)
(In the formula, X represents a hydrolyzable group, and A represents a methylene group or an ethylene group.)   The antifouling coating solution according to any one of claims 1 to 3, comprising a silane having a hydrolyzable group and / or a partially hydrolyzed condensate (C) thereof.   The antifouling coating solution according to any one of claims 1 to 4, which contains a functional metal oxide (D).