JPH11138015A - Photocatalytic hydrophilic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic hydrophilic composition capable of keeping the surface of a glass product or a product made of a synthetic resin hydrophilic for a long duration by dissolving a photocatalytic metal oxide particle, a colloidal silica, and a cationic surfactant and/or an amphoteric surfactant in water. SOLUTION: This photocatalytic hydrophilic composition is produced by producing a stable aqueous dispersion containing a photocatalytic metal oxide particle, a colloidal silica, and a cationic surfactant and/or an amphoteric surfactant. The photocatalytic hydrophilic composition is preferably produced by adding from 0.01 wt.% to <=10 wt.% of the photocatalytic metal oxide particle, >=0.05 wt.% and <=20 wt.% of the colloidal silica, and >=0.0001 wt.% and <=0.1 wt.% of the cationic surfactant and/or the amphoteric surfactant. Anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, zinc oxide, etc., are examples of the photocatalytic metal oxide particle to be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalytic hydrophilic composition for maintaining the surface of a substance such as a synthetic resin product or a glass product hydrophilic for a long period of time.

[0002]

2. Description of the Related Art Many synthetic resins such as polyethylene, polystyrene, polyvinyl chloride, cellulose acetate, and polypropylene have a relatively small surface energy and exhibit hydrophobicity. For this reason, dew condensation and fogging occur on the surface. For this reason, physical means for imparting hydrophilicity by performing corona discharge treatment on the surface of the synthetic resin has been attempted, but satisfactory hydrophilicity has not been obtained.

[0003] Therefore, in general, hydrophilicity is exerted by the following means. (1) A method in which a hydrophilic substance such as a surfactant is kneaded in producing a molded article from a thermoplastic synthetic resin material. However, in this method, the hydrophilic substance is washed away by the water, and the antifogging property is lost in a short time. (2) A method of applying a water-soluble hydrophilic substance such as polyvinyl alcohol to the product surface (Japanese Patent Publication No. 46-13252). A method comprising applying a composition comprising a hydrophilic polymer mainly composed of hydroxyalkyl acrylate and a surfactant to the product surface (Japanese Patent Publication No. 50-6437). However, in these methods, the hydrophilic substance is easily hydrolyzed and has poor water resistance, so that a sufficient antifogging effect cannot be exhibited. (3) A method of insolubilizing a hydrophilic acrylic acid ester-based polymer having a hydroxy group with a cross-linking agent (Japanese Patent Publication No. Sho 56-3)
No. 4219). However, in this method, the antifogging property itself is reduced. (4) A composition obtained by adding a surfactant to an alumina sol is applied to the surface of a molded article (Japanese Patent Publication No. 49-32668). However, this composition has the disadvantage of lacking storage stability.

[0004]

SUMMARY OF THE INVENTION In order to improve the above-mentioned disadvantages of the prior art, Japanese Patent Publication No. 1-217173 discloses that
Colloidal silica is used as an aqueous solution for depositing colloidal silica particles on the surface of the synthetic resin molded article to prevent water droplets from adhering.
Hereinafter, an aqueous solution containing a cationic surfactant and / or an amphoteric surfactant in a ratio of 0.0001% by weight or more and 0.1% by weight or less and having a surface tension of 35 to 70 dynes / cm has been proposed.

However, in the composition according to this proposal, first, the degree of hydrophilicity is not more than about 10 ° in terms of the contact angle with water, and sufficient hydrophilicity cannot be exhibited. Secondly, since hydrophilicity is not exhibited unless the aqueous liquid is applied with a thickness of several tens of μm or more, if the aqueous liquid is applied with the thickness, white turbidity due to irregular reflection of light or color formation due to interference of light occurs. Third, even if a conventional aqueous liquid is applied and dried to impart hydrophilicity to the surface of the synthetic resin, it is difficult to maintain the hydrophilicity for a long time. Once the hydrophilicity is lost, unless it is applied again, Hydrophilicity is not restored.

[0006]

Means for Solving the Problems In order to solve the above problems, a photocatalytic hydrophilic composition according to the present invention is a composition for imparting hydrophilicity to the surface of a synthetic resin or the like, and comprises a photocatalytic metal oxide particle. , Colloidal silica, a cationic surfactant and / or an amphoteric surfactant are dispersed in water.

Here, as the photocatalytic metal oxide particles, for example, anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, zinc oxide, tin oxide,
Ferric oxide, bismuth trioxide, tungsten trioxide,
And strontium titanate.

The colloidal silica constituting the surface treating agent of the present invention includes (organo silica sol, IPA
-ST: Nissan Chemical), (Snowtex 40: Nissan Chemical), (Snowtex O: Nissan Chemical), (Snowtex C: Nissan Chemical), (Rudox HS-40:
DuPont).

In general, when a cationic surfactant or an amphoteric surfactant is added to silica sol, the charge of the silica is neutralized to cause precipitation or gelation, but the surfactant is added at a relatively low concentration. By doing so, it is possible to prevent precipitation. Examples of the cationic surfactant include an alkylamine salt, an alkylammonium salt, and an alkylpyridinium salt. Examples of the amphoteric surfactant include a petaine-type surfactant, a glycine-type surfactant, and a sulfate ester-type surfactant. , Sulfonic acid type, phosphoric acid ester type and the like. These surfactants do not prevent a combination of two or more.

Specific names of the cationic surfactant and the amphoteric surfactant include dodecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, dodecylpyridinium chloride, octylamine chloride, tridecyltrimethylammonium chloride, and Anone LG (Japan). And the like are suitable.

The photocatalytic metal oxide particles have a particle size of 0.01.
% By weight or more and 10% by weight or less;
The content of the cationic surfactant and / or the amphoteric surfactant is preferably from 0.0001% to 0.1% by weight.

When the proportion of the photocatalytic metal oxide particles is less than the above range, the hydrophilic effect of the photocatalyst becomes insufficient. Even if the proportion exceeds the above range, the effect is not improved by the addition. It will be lowered.
The amount of the photocatalytic metal oxide particles in the surface layer is 1 × 10 ⁻⁷ to 1 × 10 ⁻³ g / cm ² , preferably 5 × 10 ⁻³ g / cm ² .
× 10 ^{−7 to} 5 × 10 ⁻⁴ g / cm ² , more preferably 1 ×
It is 10 ^-6 to 1 × 10 ^-4 g / cm ² .

Further, the ratio of colloidal silica is 0.05
0.05% by weight or more when the content is from 20% by weight to 20% by weight.
If it is less than 2, silica particles hardly deposit on the member surface,
If the amount exceeds 0% by weight, the stability of the surface treatment agent deteriorates. The reason why the ratio of the surfactant is 0.0001% by weight or more and 0.1% by weight or less is less than 0.0001% by weight. If there is, silica particles hardly deposit on the member surface, and 0.1%
If the content is more than 30% by weight, aggregation occurs and storage stability deteriorates, and the surface tension of the surface treatment agent is 35 to 70 dynes / cm in consideration of ease of handling and deposition of silica particles.
Is appropriate. The surface tension is adjusted by the amount of the surfactant added.

Incidentally, the hydrophilization phenomenon according to the present invention is brought about by the following mechanism. That is, when light having energy equal to or greater than the energy gap between the upper end of the valence band and the lower end of the conduction band of the photocatalyst is irradiated on the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. I do. As a result, the surface is given a polarity (probably an electron-withdrawing property). As a result, an amount of water equal to or more than the equilibrium with the atmosphere is chemically adsorbed on the surface. Then, the surface free energy based on hydrogen bonding of the surface increases, and the amount of water molecules according to the increase in the surface free energy further physically adsorbs,
Fixed to the surface. By the way, substances having similar surface free energies are likely to adhere to each other, so that the surface on which water molecules are physically adsorbed is easily adapted to water. That is,
Such a surface will be hydrophilized.

As described above, the hydrophilicity according to the present invention is considered to be due to the photocatalytic hydrophilicity rather than to the aqueous liquid containing colloidal silica and a cationic surfactant and / or an amphoteric surfactant. Can be This means that in order to exhibit hydrophilicity with an aqueous liquid containing colloidal silica and a cationic surfactant and / or an amphoteric surfactant, it was necessary to apply a coating having a thickness of several tens of μm or more. In the case of the composition according to the above, it can be confirmed that the composition exhibits hydrophilicity even at 0.4 μm or less. Here, 0.
When the thickness is 4 μm or less, white turbidity due to irregular reflection of light can be prevented, and when the thickness is 0.2 μm or less, coloring of a surface phase due to light interference can be prevented.

[0016]

(Example 1) 2.0% by weight of colloidal silica, 0.02% by weight of dodecyltrimethylammonium chloride and 10% by weight of anatase type titania were mixed, and the mixture was further mixed at 30% by weight. Was mixed with water to prepare a photocatalytic hydrophilic composition liquid (A). In the same manner, a photocatalytic hydrophilic composition liquid (B) in which rutile-type titania was dispersed instead of anatase-type titania and a photocatalytic hydrophilic composition liquid (C) in which brookite-type titania were dispersed were prepared. After applying these photocatalytic hydrophilic composition liquids (A to C) to the surface of the synthetic resin product by wiping with a sponge, the photocatalytic layer was cured by drying at 20 ° C. for 20 minutes to obtain a sample. After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 1) A composition liquid was prepared by removing crystalline titania from Example 1 above, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

Example 2 Photocatalytic hydrophilicity containing 2.0% by weight of colloidal silica, 0.05% by weight of dodecyltrimethylammonium chloride, 1% by weight of anatase type titania and a surface tension of 35 dynes / cm A composition liquid (A) was prepared. In the same manner, a photocatalytic hydrophilic composition liquid (B) in which rutile-type titania was dispersed instead of anatase-type titania and a photocatalytic hydrophilic composition liquid (C) in which brookite-type titania were dispersed were prepared. After applying these photocatalytic hydrophilic composition liquids (A to C) to the surface of the synthetic resin product by wiping with a sponge, the photocatalytic layer was cured by drying at 20 ° C. for 20 minutes to obtain a sample. After the photocatalytic layer was formed, the sample was exposed to sunlight for 3 hours, so that the sample was irradiated with ultraviolet rays.
When water was sprayed, water droplets were not formed, and it was observed that the water spread evenly. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 2) A composition liquid prepared by removing crystalline titania from Example 2 was prepared, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

Example 3 A photocatalytic composition containing 2.0% by weight of colloidal silica, 0.001% by weight of octadecyltrimethylammonium bromide and 0.1% by weight of anatase type titania and having a surface tension of 68 dynes / cm. A hydrophilic composition liquid (A) was prepared. In the same manner, a photocatalytic hydrophilic composition liquid (B) in which rutile-type titania was dispersed instead of anatase-type titania and a photocatalytic hydrophilic composition liquid (C) in which brookite-type titania were dispersed were prepared. After applying these photocatalytic hydrophilic composition liquids (A to C) to the surface of the synthetic resin product by wiping with a sponge,
By drying for 20 minutes at, the photocatalyst layer was cured to obtain a sample. After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 3) A composition liquid prepared by removing crystalline titania from Example 3 was prepared, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

Example 4 Photocatalytic hydrophilic containing 2.0% by weight of colloidal silica, 0.05% by weight of dodecylpyridinium chloride, 0.01% by weight of anatase titania and having a surface tension of 43 dynes / cm. A liquid composition (A) was prepared. In the same manner, a photocatalytic hydrophilic composition liquid (B) in which rutile-type titania was dispersed instead of anatase-type titania and a photocatalytic hydrophilic composition liquid (C) in which brookite-type titania were dispersed were prepared. After applying these photocatalytic hydrophilic composition liquids (A to C) to the surface of the synthetic resin product by wiping with a sponge, the photocatalytic layer was cured by drying at 20 ° C. for 20 minutes to obtain a sample.
After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 4) A composition liquid prepared by removing crystalline titania from Example 4 was prepared, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

Example 5 Colloidal silica (2.0% by weight), octylamine chloride (0.01% by weight), a mixture of anatase-type titania, rutile-type titania and brookite-type titania (10% by weight) were contained. A 51 dyne / cm photocatalytic hydrophilic composition solution was prepared. The photocatalytic hydrophilic composition liquid was applied to the surface of the synthetic resin product by wiping with a sponge, and then dried at 20 ° C. for 20 minutes to cure the photocatalytic layer, thereby obtaining a sample. After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 5) A liquid composition was prepared by removing crystalline titania from Example 5 above, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

(Example 6) 2.0% by weight of colloidal silica, 0.01% by weight of Anon LG (manufactured by NOF CORPORATION),
It contains 10% by weight of a mixture of anatase-type titania, rutile-type titania and brookite-type titania, and has a surface tension of 4%.
A photocatalytic hydrophilic composition solution of 5 dynes / cm was prepared.
The photocatalytic hydrophilic composition liquid was applied to the surface of the synthetic resin product by wiping with a sponge, and then dried at 20 ° C. for 20 minutes to cure the photocatalytic layer, thereby obtaining a sample. After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. When left in a dark place and then irradiated again with ultraviolet rays, the water returned to a state where it spread uniformly.

(Comparative Example 6) A composition liquid was prepared by removing crystalline titania from Example 6 above, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

Example 7 2.0% by weight of colloidal silica, 0.01% by weight of tridecyltrimethylammonium chloride, and 0.0% of Anone LG (manufactured by NOF Corporation)
A photocatalytic hydrophilic composition solution containing 1% by weight, 10% by weight of a mixture of anatase type titania, rutile type titania and brookite type titania and having a surface tension of 43 dynes / cm was prepared. After applying this photocatalytic hydrophilic composition liquid to the surface of the synthetic resin product by wiping with a sponge,
The sample was obtained by curing the photocatalyst layer by drying for a minute. After the photocatalyst layer was formed, the sample was exposed to sunlight for 3 hours after being irradiated with ultraviolet light, and then sprayed with water. As a result, it was observed that no water droplets were formed and the water spread evenly. Was. Also, after leaving in a dark place,
Irradiation of ultraviolet light again returned to a state where water spread evenly.

(Comparative Example 7) A composition liquid prepared by removing crystalline titania from Example 7 was prepared, applied to the surface of a synthetic resin product, and dried at 20 ° C for 20 minutes.
The sample was obtained by curing the photocatalyst layer. As a result, the hydrophilicity of the surface of the synthetic resin product is approximately 10 ° in terms of the contact angle with water.
Became. When the product was left for one month, the contact angle with water became about 50 °. Irradiation with ultraviolet light did not change the contact angle with water.

[0030]

As described above, according to the present invention, photocatalytic metal oxide particles, colloidal silica, a cationic surfactant and / or an amphoteric surfactant are dispersed in water to form a photocatalytic hydrophilic substance. Since the composition is composed of a hydrophilic composition, it is possible to form a uniform and thin photocatalytic hydrophilic film without being repelled by the surface of the object to be coated such as a synthetic resin product at the time of application. The photocatalytic hydrophilic coating can maintain a highly hydrophilic surface for a long period of time and can reduce the thickness of the coating, so that there is no problem such as cloudiness or coloring. Furthermore, since it is an aqueous composition, there is no solvent odor,
Excellent handleability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08J 7/06 C08J 7/06

Claims (2)

[Claims] 1. A composition for imparting hydrophilicity to the surface of a synthetic resin or the like, comprising a photocatalytic metal oxide particle, colloidal silica, a cationic surfactant and / or
Or a photocatalytic hydrophilic composition comprising a stable aqueous dispersion containing an amphoteric surfactant. 2. The photocatalytic hydrophilic composition according to claim 1, wherein the composition comprises photocatalytic metal oxide particles in an amount of from 0.1 to 10.
01 wt% to 10 wt%, colloidal silica of 0.05 wt% to 20 wt%, cationic surfactant and / or amphoteric surfactant of 0.0001 wt% to 0.1 wt%. A photocatalytic hydrophilic composition, which is contained in a proportion.