JP2006008963A - Coating material and solution for dispersing photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a coating film having ultralong life without causing chalking even when a substrate surface is directly coated with a coating material. <P>SOLUTION: An emulsion prepared by dispersing an alkali-solubilized type hydrophilic polymeric material in a solution consisting essentially of water is used as a dispersion medium. A photocatalyst such as titanium dioxide is dispersed therein. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is a coating material having antibacterial, antifouling, deodorizing, air purification, and other coating materials applied to a surface of a building exterior or interior material, various molded products, or animals and plants, etc. The present invention relates to a photocatalyst dispersion liquid.

It has been conventionally known that the photocatalyst typified by titanium dioxide has antibacterial, antifouling and deodorizing actions, and recently various materials utilizing these actions have been researched and developed.

Specifically, when titanium dioxide is irradiated with ultraviolet rays, water and oxygen contained in the air are decomposed to generate active oxygen (OH ⁻ , O ²⁻ ) on the surface. And by the action of this active oxygen, it is possible to oxidize and decompose pollutants in the atmosphere, to decompose odor components and deodorize them, or to kill bacteria.

However, since the photocatalytic function of titanium dioxide is extremely strong, not only the contaminants that touch the coating film are oxidatively decomposed, but also the substrate coated with the coating material is oxidatively decomposed, and the substrate becomes chalky and worn out. Cause so-called choking.

For this reason, when used as a coating material, conventionally, titanium dioxide is mixed with a resin paint containing a resin that is difficult to be decomposed by the action of a photocatalyst as a coating film forming element, and the surface of the substrate is coated using this resin paint. Alternatively, there may be mentioned a method in which a resin paint is applied to the surface of the substrate and then titanium dioxide is applied on the resin paint before the resin paint is cured.

However, in these methods, the resin paint becomes cloudy or titanium dioxide is buried in the film, and it does not show sufficient activity, or the process is complicated, and a uniform and transparent coating film can be obtained. There are no drawbacks. Furthermore, when an organic base material such as a plastic molded body, a film, or an organic coating film is used as a base material for immobilizing the photocatalyst, the photocatalyst film obtained by the above-described conventional technique oxidatively decomposes the organic base material by photocatalytic action. However, when the organic base material surface portion is decomposed, both the intermediate layer and the photocatalyst layer present on the organic base material lose their scaffolds and fall off. In addition, not only the intended function (antifouling property, antibacterial property, deodorizing property, etc.) using photocatalysis is lost, but also the original appearance characteristics such as surface gloss is lowered and powder is blown. And design will be lost. In the painting process, there is a problem that not only the material cost increases, but also labor and time that are twice as much as those of ordinary painting, and special techniques are required.

Moreover, even if it apply | coated in this way, since the lifetime of the coating film was short and it will peel in 1 to 2 years, there also existed a problem that it had to repaint frequently.

As a result of the inventor's research on the defects of the coating film, it was found that the emulsion in which the photocatalyst is dispersed is oxidized because the photocatalyst particles themselves are not subjected to non-choking treatment.

Therefore, the present invention has a technical problem that a coating film having a very long life can be formed without causing choking even when directly applied to a substrate.

In order to solve this problem, the coating material according to the present invention uses, as a dispersion medium, an emulsion in which an alkaline desolvation type hydrophilic polymer material is dispersed in a water-based solution, and a photocatalyst is dispersed in the emulsion. It is characterized by that. In this specification, the photocatalyst refers to a substance that causes a reaction of generating active oxygen from water or oxygen in the air by light absorption and oxidatively decomposing other substances by the active oxygen.

When the coating material of the present invention is applied to a substrate and dried, an alkali-dissolving hydrophilic polymer film having acid resistance is interposed between the photocatalyst and the substrate, so that the surface of the article is oxidized. Further, the coating film itself is not oxidized and the coating film lasts for a very long time.

When the coating material according to the present invention is applied to the surface of the substrate, first, a coating layer is formed in which the photocatalyst is dispersed in the emulsion, and the coating layer is on the surface side as the water contained in the emulsion evaporates. A coating film is formed in which the photocatalyst is exposed on the surface layer.

When air touches the exposed surface of the photocatalyst, active oxygen is generated from the water and oxygen contained in the air under light irradiation, and contaminants adhering thereto are oxidized by the oxidizing action of active oxygen. Disassembled and washed away with rainwater. Further, when an odor component contained in the air is touched, it is decomposed by oxidization and deodorized, and even if bacteria adhere, it is sterilized by the oxidizing action of active oxygen.

In addition, when the coating material of the present invention was used, no chalking of the base material occurred. Therefore, it is considered that a film of an alkali-dissolving hydrophilic polymer material is formed between the photocatalyst and the base material surface. It is done. That is, since the individual photocatalyst particles do not directly contact the substrate surface, active oxygen is not generated on the substrate surface, and chalking of the substrate surface is prevented.

In addition, the film of the alkaline desolubilized hydrophilic polymer material formed by evaporation of the water contained in the emulsion has acid resistance and is not oxidized by active oxygen generated by the photocatalyst. Long-lasting without easily peeling off. In particular, when an organic substance is contained as an alkali-dissolving hydrophilic polymer material, a strong resin film is formed when moisture evaporates, so that it does not dissolve even when exposed to wind and rain thereafter. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing a coating material according to the present invention, and FIG. 2 is an explanatory view showing another embodiment.

The coating material 1 of this example uses, as a dispersion medium, an emulsion 4 in which an alkali-dissolving hydrophilic polymer material 3 is dispersed in a hot metal 2 containing water as a main component, and a powder or liquid dioxide that serves as a photocatalyst. Titanium 5 is dispersed at a concentration of about 10%.

The solution 2 used for the emulsion 4 may be a case where water is the main component and only water is used, or an aqueous solution in which a water-soluble additive or the like is dissolved may be used.

The alkali-dissolving hydrophilic polymer material 3 dispersed in the solution 2 is either one of the alkali-dissolving hydrophilic organic polymer material 3A and the alkali-dissolving hydrophilic inorganic polymer material 3B or Both are used.

As the alkaline desolubilizing hydrophilic organic polymer material 3A, water-based aqueous polyester resin, which is made water-based by introducing hydrophilic groups such as carboxyl groups, and any organic polymer material such as acrylic resin and urethane resin can be made water-based. Can be used.

Further, as the alkali desolubilizing hydrophilic inorganic polymer material 3B, in addition to natural polymers such as seaweed extract, substances generally used as stabilizers such as natural polymer derivatives and synthetic polymers can be used. .

The natural polymers include plant-based, microbial-based and animal-based ones. Plant systems include seaweed extracts such as agar, carrageenan, fercelan, alginic acid, seed mucilage such as locust bean gum, guar gum, tamarind gum, resinous mucilage such as gum arabic, tragacanth gum, karaya gum, pectin, arabi Plant mucilage (fruit) such as nogalactan, plant protein such as soybean protein and wheat protein, starch such as raw starch, and lipid such as soybean lecithin can be used.

In addition, xanthan gum, pullulan, dextran can be used as the microorganism system, and animal proteins such as gelatin, casein, and albumin, and lipids such as egg yolk lecithin can be used as the animal system.

Furthermore, as the natural polymer derivative, starch systems such as phosphosan starch and carboxymethylated starch, and cellulose systems such as microcellulose, hydroxyethylcellulose, and carboxymethylcellulose can be used.

Furthermore, as the synthetic polymer, polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acid, polyethylene oxide, polyethylene glycol, or the like can be used.

Table 1 shows a composition example of the emulsion 4 that is a liquid material for dispersing the photooxidation catalyst used for the coating material 1 (1A to 1C).

Emulsion 4 of coating material 1A is obtained by adding alkaline solution to solution 2 in which 59% water is mixed with 10% ethylene glycol monotertiary butyl ether (CH ₃ C (CH ₃ ) ₂ O.CH ₂ CH ₂ OH) as an additive. 30% water-based polyester resin, which is the desolubilized hydrophilic organic polymer material 3A, and 1% carrageenan, which is the alkali desolubilized hydrophilic inorganic polymer material 3B, were dispersed.

Emulsion 4 of coating material 1B is obtained by adding alkali 2 to solution 2 in which 10% ethylene glycol monotertiary butyl ether (CH ₃ C (CH ₃ ) ₂ O.CH ₂ CH ₂ OH) is mixed as an additive with 60% water. A 30% aqueous polyester resin, which is the dissolution type hydrophilic organic polymer material 3A, was dispersed.

In the emulsion 4 of the coating material 1C, 2% carrageenan, which is the alkali desolubilized hydrophilic inorganic polymer material 3B, was dispersed in 98% of water used as the solution 2.

And each coating material 1A-1C should just disperse | distribute about 10% of powder or liquid titanium dioxide 5 as a dispersoid by making these emulsion 4 into a dispersion medium, fully stirring.

The above is a configuration example of the coating material according to the present invention and the photooxidation catalyst solution used therefor, and the operation thereof will be described next. First, a description will be given of a coating material 1A that uses both an alkali-dissolving hydrophilic organic polymer material 3A and an alkali-dissolving hydrophilic inorganic polymer material 3B as the alkali-dissolving hydrophilic polymer material 3.

As shown in FIG. 1A, the coating material 1 </ b> A is covered with an alkali-dissolving hydrophilic inorganic polymer material 3 </ b> B around the titanium dioxide 5. It is considered that the hydrocolloid particles 6 are formed by being covered in two layers with the molecular material 3A, and the hydrocolloid particles 6 are dispersed in the solution 2.

When this coating material 1A is applied to the base material 7 of the building, a coating layer 8 in which particles of titanium dioxide 5 are dispersed in the emulsion 4 is formed in an undried state. Then, as time passes, the water contained in the emulsion 4 gradually evaporates, and at the same time, the alkali-dissolving hydrophilic polymer material 3 is solidified and the coating layer 8 is thinned. As shown in (b), a film in which the particles of titanium dioxide 5 are exposed on the surface layer of the coating layer 8 is formed.

Therefore, contaminants adhering to the surface layer of the coating layer 8 are oxidatively decomposed by active oxygen having a high oxidizing ability, and exhibit antibacterial, antifouling, deodorizing, and air purification effects.

At this time, a film of the alkali desolubilizing hydrophilic polymer material 3 is formed on the back side of each titanium dioxide 5 dispersed in the coating layer 8, and the titanium dioxide 5 is directly applied to the substrate 7. Since there is no contact, active oxygen is not generated in the base material 7. Accordingly, chalking is prevented without applying an antioxidant to the base material 7.

Further, the film of the alkali desolubilized hydrophilic polymer material 3 formed by evaporating the water contained in the emulsion 4 has acid resistance and is not oxidized by the active oxygen generated by the photocatalyst. The coating film lasts for 1-2 years without being easily peeled off. In particular, when the alkali-dissolving hydrophilic organic polymer material 3A is included, after the moisture evaporates and a strong resin film is formed, it does not melt even if exposed to wind and rain. It can be used as an outdoor coating material.

Next, coating materials 1B and 1C using either the alkali desolubilized hydrophilic organic polymer material 3A or the alkali desolubilized hydrophilic inorganic polymer material 3B as the alkali desolubilized hydrophilic polymer material 3 explain.

As shown in FIG. 2 (a), the coating materials 1B and 1C are covered with an alkali-dissolving hydrophilic organic polymer material 3A or an alkali-dissolving hydrophilic inorganic polymer material 3B. It is considered that hydrocolloid particles are formed and the hydrocolloid particles are dispersed in the solution 2.

When the coating materials 1B and 1C are applied to the substrate 7, a coating layer 8 in which particles of titanium dioxide 5 are dispersed in the emulsion 4 is formed in an undried state. Then, as time passes, the water contained in the emulsion 4 gradually evaporates, and at the same time, the alkali-dissolving hydrophilic polymer material 3 is solidified and the coating layer 8 is thinned. As shown in (b), a film in which the particles of titanium dioxide 5 are exposed on the surface layer of the coating layer 8 is formed.

Due to the photocatalytic function of the titanium dioxide 5, active oxygen OH ⁻ and O ₂ ⁻ are generated from moisture H ₂ O and oxygen O ₂ contained in the air, and pollutants and odors in the air adhering to the surface layer of the coating layer 8. The point of having a self-cleaning action of oxidatively decomposing components and sterilizing bacteria is the same as described above.

Also in this example, a film of the alkali-dissolving hydrophilic polymer material 3 is formed on the back side of the individual titanium dioxide 5 dispersed in the coating layer 8, and the titanium dioxide 5 is directly applied to the substrate 7. Since they are not in contact with each other, active oxygen is not generated in the base material 7, and thus chalking is prevented without applying an antioxidant to the base material 7.

In addition, since the film of the alkali-dissolving hydrophilic polymer material 3A or 3B formed by evaporation of water contained in the emulsion 4 has acid resistance, it is not oxidized by the active oxygen generated by the photocatalyst. . In particular, the film of the organic polymer material 3A is strong and does not melt even when exposed to wind and rain, so it can be used as an outdoor coating material.

The photocatalyst is not limited to titanium dioxide, and any substance can be applied as long as it can generate active oxygen from water or oxygen under irradiation of sunlight or illumination light.

Explanatory drawing which shows the coating material concerning this invention Explanatory drawing which shows other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coating material 2 Solution 3 Alkali desolubilization type hydrophilic polymer material 3A Alkali desolubilization type hydrophilic organic polymer material 3B Alkali desolubilization type hydrophilic inorganic polymer material 4 Emulsion 5 Titanium dioxide (photocatalyst)
6 Colloidal particles 7 Base material 8 Coating layer

Claims (5)

  A coating material characterized in that an emulsion in which an alkali-dissolving hydrophilic polymer material is dispersed in a solution containing water as a main component is used as a dispersion medium, and a photocatalyst is dispersed therein.   The coating according to claim 1, wherein one or both of an alkali-dissolving hydrophilic organic polymer material and an alkali-dissolving hydrophilic inorganic polymer material is used as the alkali-dissolving hydrophilic polymer material. Wood.   The coating material according to claim 1 or 2, wherein the photocatalyst is titanium dioxide.   A photocatalyst dispersion liquid used as a dispersion medium for dispersing a photocatalyst, wherein the photocatalyst dispersion is composed of an emulsion in which an alkali-dissolving hydrophilic polymer material is dispersed in a water-based solution Solution.   5. The photocatalyst according to claim 4, wherein one or both of an alkali-dissolving hydrophilic organic polymer material and an alkali-dissolving hydrophilic inorganic polymer material is used as the alkali-dissolving hydrophilic polymer material. Dispersing liquid.

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