Resin having photocatalyst surface, resin coating material and its production

Description: TECHNICAL FIELD [Detailed description of the invention]

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INDUSTRIAL APPLICABILITY The present invention relates to a method for imparting photocatalytic property to a resin surface such as a resin material, a resin-coated metal material, and a resin coating material.

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[Conventional technology] Titanium oxide has excellent photocatalytic properties and exerts strong oxidizing power under irradiation with ultraviolet rays. Therefore, it prevents the adhesion of dirt, decomposes malodorous components, purifies water quality, prevents rust, and antibacterial. Attempts have been made to prevent the growth of algae and to decompose persistent waste.

When titanium oxide is used as a photocatalyst, it is necessary to fix the titanium oxide photocatalyst on the surface of various materials such as various metal materials, glass and ceramic materials, resin materials and resin coating materials, depending on the intended use.

Therefore, various titanium oxide paints and methods for producing the same have been proposed for the purpose of forming a titanium oxide film on the surface of the material.

The most common method for forming a titanium oxide film on the surface of metal or glass is the sol-gel method in which titanium alkoxide is hydrolyzed and applied, and then fired at 300 to 500 ° C. Similar techniques include, for example, a method of applying a composition obtained by adding amide or glycol to titanium alkoxide to JP-A-4-83537, or alcohol to titanium alkoxide as disclosed in JP-A-7-100378. A method of applying a composition to which amines are added is known.

However, in these conventional methods, since the photocatalyst cannot be applied unless the coating film is fired at a temperature of 300 to 500 ° C., it can be applied to glass, ceramics, and heat-resistant alloys, but it can be applied to resin materials and resin materials. It could not be applied to resin-coated materials at all.

As another method for coating titanium oxide, as disclosed in Japanese Patent Application Laid-Open No. 7-171408, crystalline titanium oxide particles are mixed with a binder such as water glass, colloidal silica, or a fluorine-based resin. And the method of applying is known.

However, in the method of directly applying the titanium oxide paint containing photocatalytic titanium oxide to the surface of a general hydrocarbon-based resin material or resin coating material, the titanium oxide particles come into direct contact with the base material, so that the base material is exposed to light. The resin itself gradually decomposed, causing deterioration and shedding of the film, which caused an important problem that it was not suitable for practical use.

On the other hand, if the photocatalytic titanium oxide content in the film or paint is lowered, deterioration of the resin on the surface of the base material can be prevented to some extent, but there is a problem that the photocatalytic property of the surface becomes insufficient.

Resin materials and resin coating materials have many potential applications due to their advantages of being lightweight and having excellent formability and decorativeness, but nevertheless, photocatalytic surfaces have been used so far. The reason why the practical use of the resin material and the resin coating material having the above is not advanced is due to the technical difficulty peculiar to such a resin material.

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PROBLEM TO BE SOLVED: To solve the above-mentioned problems of the prior art, the present invention is to irradiate the surface of a resin coating material such as a resin-coated product of various resins or metals with light or aging. A resin or resin coating material having a photocatalytic coating film that does not deteriorate the surface of the base material or the coating film, does not impair the decorativeness such as the color and luster of the surface of the base material, and has excellent transparency, and its coating material. It is intended to provide a manufacturing method.

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Means for Solving the Problems As a result of examining various methods for means for solving the above technical problems, the present inventors have formed a titanium oxide photocatalyst layer on a surface formed of a resin. In order to prevent deterioration or decomposition of the base material surface resin due to light, an intermediate layer having a specific composition is provided between the photocatalyst layer and the base material resin, and a titanium dioxide sol layer is formed on the intermediate layer. , The present invention has been completed by finding that the above problems can be solved.

The resin or resin coating material having a photocatalyst surface according to the present invention is a substrate made of a resin material or a resin coating material, and silica, alumina, or magnesia formed on the resin surface and having an average particle size of less than 120 nm. A first layer containing at least one oxide selected from, zirconia, and yttria, and a silane coupling agent, and a crystalline material formed on the first layer and having an average particle size of 20 to 120 nm. It is characterized by containing titanium dioxide particles and having a second layer having photocatalytic properties.

Further, the method for producing a resin or a resin coating material having a photocatalyst surface of the present invention is from silica, alumina, magnesia, zirconia, and itria having an average particle size of less than 120 nm on the surface of the resin material or the resin coating material. A solution containing at least one selected oxide and a silane coupling agent is applied and dried to form a first layer, which has an average particle size of 20 to 120 nm. It is characterized in that a photocatalytic second layer is formed by applying a titanium dioxide sol solution containing crystalline titanium dioxide particles and drying the solution.

The material to be treated used in the present invention is a resin material or a resin coating material, and the base material or the base material thereof may be a resin material, or may be a metal, glass, ceramics, or the like. There are no particular restrictions on the type, but if it is a material other than a resin material, the surface of the base material or base material is a layer mainly composed of a resin material by coating, painting, joining, etc. Must be covered with.

The types of resins used for the material to be treated in the method of the present invention include thermoplastic resins such as ABS, polyvinyl chloride, polyacrylic, polystyrene, polyethylene, polypropylene, polycarbonate, PBT, PET, and nylon. , Epoxy, melamine, phenol, polyurethane, polyimide, polyamide, unsaturated polyester, diallyl phthalate, furan and other thermosetting resins, as well as elastomer rubber such as urethane rubber, butyl rubber and nitrile rubber. The method of the present invention can be applied in the same manner as described above when the surface of the material to be treated is coated with the above-mentioned resin-based paint, but a fluorine-based resin material such as PTFE has sufficient adhesion to it. It is not preferable to use it because it is difficult to have.

By applying the method of the present invention to the surface of the material to be treated, dust, dust and oil adhering to the surface of the material to be treated are removed to clean the surface prior to forming a photocatalytic film. When the material to be treated is a resin molded product, it is preferable to remove the release agent on the surface at the same time.

The surface of the material to be treated is preferably cleaned by appropriately using a water-based cleaning agent containing a surfactant, a quasi-water-based cleaning agent, an alcohol-based cleaning agent, a hydrocarbon-based cleaning agent, or the like. Depending on the type of material to be treated, it is also possible to obtain even better film adhesion by performing an etching treatment with an oxidizing agent such as chromic acid if necessary after cleaning.

First, a film of the first layer is formed on the surface of the cleaned material to be treated. The formation of this first layer film was cleaned of a solution containing a silane coupling agent and at least one oxide selected from silica, alumina, magnesia, zirconia, and yttria with an average particle size of less than 120 nm. This is done by applying it to the resin surface and drying it.

The coating step in each of the first and second steps can be performed by a dip method, but good results can also be obtained by a spray method, a mist spray method by ultrasonic atomization, or the like. It is also possible to obtain a thick film with few defects by further coating after drying.

The thickness of the film of the first layer is preferably 0.1 to 2 μm, and more preferably 0.2 to 1 μm. If this film thickness is less than 0.1 μm, a sufficient barrier effect on the resin surface of the obtained first layer cannot be obtained, and the resin surface may be photodecomposed. Further, it is not practical because the workability is poor because it requires several coatings in order to obtain a film thickness of 2 μm or more.

The oxide contained in the solution for forming the first layer film is at least one selected from silica, alumina, magnesia, zirconia, and yttria, and even if two or more of these are mixed and used. It doesn't matter. Of these, silica and alumina are particularly preferable. The pH of the solution is most preferably 3 to 7, but when magnesia is contained, the pH of the solution for forming the first layer is preferably 5 to 9.

Further, it is preferable that the oxide for the first layer is uniformly dispersed in the solution to form a sol state, and the average particle size of the oxide particles is less than 120 nm, and the preferable particle size is It is 5 to 70 nm. When the particle size is larger than 120 nm, the barrier effect when the upper layer titanium oxide sol solution is applied becomes insufficient, and the photocatalytic titanium oxide particles move from the gaps between the oxide particles to the surface of the base material via the second layer. , It is not preferable because it comes into direct contact with the resin. Further, the average particle size shown in the method of the present invention is the minimum size of the particles, that is, when the oxide particles used are greatly different in length and width, such as particles of chain silica sol and rod-shaped crystalline alumina sol. , Width (or minor axis) is used as the average particle size.

The concentration of oxide particles in the solution for forming the first layer is preferably controlled so that the total concentration of these oxides is 2 to 35% by weight, and a more preferable concentration is 4 to 20. It is a weight percent. If this concentration is less than 2% by weight, a sufficient film thickness may not be obtained as a barrier film, and if it exceeds 35% by weight, cracks are likely to occur when the film is dried, which is not preferable.

0025 Further, it is necessary that the solution for forming the first layer contains a silane coupling agent in addition to the oxide particles. The type of silane coupling agent that can be used in the present invention is preferably methoxysilane having an organic reactive group such as a vinyl group, an epoxy group, an amino group, a methacryl group, or a mercapto group, or ethoxysilane. For example, vinyl triethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltri. Such as methoxysilane. The type of preferred silane coupling agent varies depending on the type of resin on the surface of the base material, but when the resin is ABS, polystyrene, polypropylene, polystyrene, unsaturated polyester, etc., γ-methacryloxypropylmethyldimethoxysilane, γ-methacry Most preferably, loxypropyltrimethoxysilane, γ-methacrystyrenetriethoxysilane, or the like is used. When the resin is polyvinyl chloride, nylon, acrylic, furan or the like, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane or γ -It is most preferable to use aminopropyltrimethoxysilane or the like.

The preferable concentration of the silane coupling agent in the solution for forming the first layer is 2 to 60 g / liter, and the more preferable concentration is 5 to 30 g / liter. If this concentration is less than 2 g / liter, the adhesion between the resin and the obtained film and the wettability when applied are not sufficient, and it is uneconomical and not preferable to exceed 60 g / liter.

The coating solution forming the first layer is preferably an aqueous solution, but when a sol solution is used as the oxide raw material to be used, it can be mixed with water such as alcohol, ketone, glycol and the like. It is preferable to include the organic solvent in a small amount of less than several tens of percent from the viewpoint of improving wettability, and an oxide sol dispersed in an organic solvent compatible with these waters can also be used.

If the wettability of the first layer forming solution is insufficient depending on the type of resin used, the problem can be solved by adding a small amount of a surfactant to the solution.

It is necessary to dry the coating liquid layer formed from the solution for forming the first layer, and the drying temperature thereof is not particularly limited, but is generally preferably 60 to 110 ° C., for example, temperature. It is preferable to select a method using wind or hot air. When the base material or substrate to be treated is a thermoplastic resin, it is necessary to select a drying temperature that does not cause deformation or the like.

The drying time of the first layer coating liquid layer is not particularly limited, but the temperature of the surface of the material to be treated does not become too high when the second layer is applied, so that the temperature does not rise to the inside of the material. It is preferable to finish the drying within 180 seconds from the viewpoint of workability, and the preferable drying time is 60 to 180 seconds.

After the formation of the first layer is completed, a titanium dioxide photocatalyst layer is then formed on the first layer as a second layer.

In the present invention, in order to form the second layer containing the titanium dioxide photocatalyst, a titanium dioxide sol solution containing crystalline titanium dioxide particles having an average particle size of 20 to 120 nm is applied onto the surface of the first layer. ,dry. The titanium dioxide used to form the second layer needs to contain crystalline particles, and the crystal type thereof is most preferably anatase type, and then preferably rutile type. Amorphous titanium oxide is not preferable because it exhibits almost no photocatalytic property unless it is heated to 300 ° C. or higher. The crystal form of titanium dioxide can be qualitatively confirmed by thin film X-ray diffraction of the second layer titanium dioxide film after coating and drying.

Further, the size of the titanium dioxide crystal used for forming the second layer needs to have an average particle size in the range of 20 to 120 nm. If this size is less than 20 nm, the photocatalytic particles may permeate into the barrier layer (first layer) and reach the resin surface, which is not preferable, and if it exceeds 120 nm, the first layer and the second layer It is not preferable because the adhesion between the layers is reduced. The most preferable average particle size of crystalline titanium dioxide is 30 to 80 nm.

The film thickness of the second layer is not particularly limited, but is preferably 0.05 to 2 μm, more preferably 0.1 to 1 μm. If this film thickness is less than 0.05 μm, the resulting second layer may not exhibit a sufficient photocatalytic effect, and it requires several coats to obtain a film thickness of 2 μm or more. Workability is poor and it is not practical because it may be done.

The titanium dioxide sol solution used for forming the titanium dioxide film layer of the second layer uses a titanium salt aqueous solution such as titanium tetrachloride, titanium sulfate, titanium oxysulfate, titanium oxychloride as a raw material, and the aqueous solution is used as a raw material. After heat treatment at a temperature of 50 ° C. or higher and lower than 100 ° C. for several minutes to several hours, preferably, an alkali metal hydroxide or ammonia is further added to generate a precipitate, and titanium dioxide particles or titanium acid in the solution are microfiltered. It can be produced by a method of preparing by filtering and washing with titanium dioxide particles collected by filtration and redispersing them in water. However, the titanium dioxide particles collected by filtration have a drawback that they are difficult to redisperse. In this case, a peroxide compound such as hydrogen peracid is added at the time of dispersion to remove all or part of the titanium acid. , Peroxytitanic acid is preferable. Further, as a more preferable method, a method of heat-treating a titanium salt aqueous solution in the same manner as described above and then dialyzing through a semipermeable membrane such as an anion exchange membrane, a method of electrodialysis via an ion exchange membrane, or an ion exchange. It is more preferable to produce a titanium dioxide sol solution by removing contaminant ions by a method of treating with a resin or the like.

The drying step after coating the second layer has the effect of further advancing the reaction between the silane coupling agent in the first layer and the resin surface, and further strengthening the adhesion force. It is preferable to carry out the drying treatment at a temperature of 70 to 150 ° C. for several minutes. The preferred drying temperature is 80-120 ° C. It is not preferable that the drying temperature exceeds the heat resistant temperature of the resin, and it should be less than 250 ° C. at the maximum, preferably 150 ° C. or lower, more preferably 120 ° C. or lower.

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[Action] The resin or resin coating material having a photocatalytic surface of the present invention and the method for producing the same can provide various performances such as good adhesion, translucency, and photocatalytic property on the resin surface. In addition, problems such as deterioration of the resin surface and peeling of the film due to light irradiation and aging do not occur or are extremely few.

In the method of the present invention, a surface having excellent photocatalytic activity is formed by performing a step of providing a barrier layer on the resin surface with a special coating solution before the step of forming the titanium dioxide film layer. It is possible to prevent deterioration of the resin surface due to light irradiation, aging, etc., deterioration of the adhesion of the titanium dioxide film, and deterioration such as peeling phenomenon.

In the coating solution for forming the first layer containing the oxide colloidal particles having a specific particle size and the silane coupling agent, the methoxy group and the ethoxy group of the silane coupling agent are bonded to the surface of the oxide particles. On the other hand, in the process of coating and drying, functional groups such as vinyl group, epoxy group, methacryloxy group, and / or amino group of the silane coupling agent react and bond with the resin surface to form a resin surface. It is possible to form a strong adhesion with the first layer (barrier layer).

Further, since the silane coupling agent bonded to the resin surface by the method of the present invention directly coats and protects the outermost surface of the resin with a Si atom chain, even if the photocatalyst particles come into contact with the resin surface, It has the effect of preventing the decomposition reaction of the resin. Further, the decomposition preventing effect of this resin exhibits an excellent barrier effect that cannot be obtained by the conventional method.

Further, in the method of the present invention, in order to achieve both good adhesion between the first layer (barrier layer) and the second layer (titanium oxide layer) and excellent photocatalytic property of the second layer, the first layer is used. The lower limit of the particle size of the titanium oxide particles contained in the second layer is 20 nm, and the upper limit of the oxide particle size contained in the first layer (barrier layer) is 6 times the diameter of the titanium dioxide particles in the second layer. The reason for limiting the particle size to 120 nm is as follows. That is, this is to prevent the photocatalytic titanium oxide particles of the second layer from diffusing through the oxide particles of the first layer (barrier layer) at the time of coating and not reaching the resin surface. For this purpose, the relationship between the particle size of the oxide in the coating solution for forming the first layer and the particle size of titanium dioxide in the coating solution for forming the second layer is important. In particular, when the oxide particles constituting the first layer are spherical and have a hexagonal fine structure, the titanium dioxide particles are formed by controlling the particle size to less than about 6 times the titanium dioxide particle size contained in the second layer. It is possible to prevent invasion into one layer (barrier layer).

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[Example] The present invention will be described in more detail with reference to the following examples. Examples 1 to 15 and Comparative Examples 1 to 6 In Examples 1 to 15 and Comparative Examples 1 to 6, a photocatalyst layer was formed by using the following materials to be treated and by the following steps, and the test was evaluated by the following method.

Material to be Treated (Substrate) In each of Examples 1 to 15 and Comparative Examples 1 to 6, various resin plates or resin-coated metal plates (10 × 10 cm) shown in Table 1 were used as substrates.

Pretreatment (Surface Cleaning) The surface of the substrate was wiped with gauze to which isopropyl alcohol or methyl isobutyl ketone was attached to clean the surface.

Formation of First Layer and Second Layer The surface-cleaned substrate was immersed in a coating solution for forming the first layer, slowly pulled up after 30 seconds, and quickly dried with warm air at 80 ° C. This was further immersed in a coating solution for forming a second layer, slowly pulled up, dried with warm air at 80 ° C., and then dried at 100 ° C. for 5 minutes in a drying oven.

The total concentration of oxides contained in the coating solution for forming the first layer was controlled to 3 to 30% by weight, and the concentration of the silane coupling agent was controlled to 1 to 3% by weight. The oxide particle sol in the solution used for forming the first layer (barrier layer) was a commercially available product or synthesized from a raw material as shown below.

(Oxide sol used for the coating solution of the first layer) [Silica] Average particle size 5 nm: Snowtex XS average particle size 15 nm manufactured by Nissan Chemical Industry Co., Ltd .: Snowtex O average particle size 45 nm manufactured by Nissan Chemical Industry Co., Ltd .: Snowtex OL average particle size 40nm (minor diameter): Snowtex ST-UP (chain) average particle size 115nm: Nihon Kagaku Kogyo Co., Ltd. Silica Doll 30G-100 [Alumina] Average particle size (width) ) 15 nm: Aluminasol-520 manufactured by Nissan Chemical Industry Co., Ltd. Average particle size (width) 10 nm: Aluminasol-100 manufactured by Nissan Chemical Industry Co., Ltd. [Magnesia] Average particle size 100 nm: Add sodium hydroxide solution to magnesium chloride solution and heat at 95 ° C. The resulting precipitate was filtered, washed with water, dried, fired at 600 ° C., crushed with a ball mill, and redispersed with water. [Zirconia] Average particle size 62 nm: Zirconia sol NZS-30A manufactured by Nissan Chemical Industry Co., Ltd. Average particle size 150 nm: Zirconyl sulfate aqueous solution is heated at 100 ° C., and the resulting precipitate is filtered, washed with water, dried and then redispersed with water. I let you. [Itria] Average particle size 80 nm: A solution of yttrium oxide dissolved in hydrochloric acid was heated at 95 ° C., and the resulting precipitate was filtered, washed with water, dried, and then a trace amount of surfactant was added and redispersed with water.

Table 1 shows the materials (bases) to be treated used.

[Table 1] <img file="000002.tif" id="000002" he="080" wi="098" img-format="tif" img-content="drawing" />

Table 2 shows the types of silane coupling agents used to form the first layer and their chemical structures.

[Table 2] <img file="000003.tif" id="000003" he="110" wi="098" img-format="tif" img-content="drawing" />

The components of the solution used to form the first layer and the second layer and the coating thickness are shown in Tables 3 and 4.

(Titanium dioxide sol for forming the second layer) In each of Examples 1 to 11, the titanium dioxide sol used for forming the second layer was obtained by diluting an aqueous solution of titanium tetrachloride (20% by weight) with water. A sodium hydroxide solution is added to adjust the pH to 1-2, heat treatment is performed at a temperature of 40 to 95 ° C., water cooling is performed, and this solution is diffusely dialyzed with deionized running water via a semipermeable membrane. At that time, titanium dioxide sol having various average particle sizes was prepared by changing the pH of the aqueous titanium solution and the heat treatment conditions. An evaluation test was conducted on the titanium solution after dialysis.

Further, in each of Examples 12 to 15, the titanium dioxide sol used for forming the second layer was prepared by adjusting the pH of the titanium tetrachloride solution and heat-treating it in the same manner as in Examples 1 to 11. Further, the pH was adjusted to 7 with a sodium hydroxide solution, and an evaluation test was conducted using a solution obtained by filtering the generated precipitate and dispersing it in water containing hydrogen peroxide.

Regarding the crystallinity of the titanium dioxide sol, a titanium dioxide solution was applied to a glass plate, dried, and the presence or absence of crystallinity was examined by thin film X-ray diffraction. As a result, it was confirmed that only the liquid used in Comparative Example 5 was amorphous, and the titanium dioxide in the other sol was anatase-type crystalline material.

Evaluation of Coating Film Performance Specimens were collected from the photocatalytic material obtained by completing the coating of the first and second layers, and the adhesion of the coating film immediately after coating was applied to the specimens. And the transparency, the photocatalytic property of the coating film, and the deterioration resistance of the film and the surface of the test material after being irradiated with light for a long time were evaluated and tested. (1) Adhesion of coating film For the adhesion of the coating film of the test piece, a cellophane tape was attached to the surface of the coating film of the test material, and the cellophane tape was further peeled off to check whether or not the coating film was peeled off. (2) Transparency of coating film The transparency of the coating film of the specimen was visually judged according to the following criteria. : The coating film is transparent and uniform without turbidity : The coating film is turbid ×: The coating film is opaque

(3) Photocatalytic property For photocatalytic property, tristearic acid is applied as a test oil to the surface of a specimen of 25 mm × 75 mm, and ultraviolet rays are irradiated for 72 hours with a UV lamp (15 W), and the coating oil before and after that is applied. Decomposition amount (g / m)²) Was obtained from the weight difference before and after ultraviolet irradiation. (4) Deterioration resistance The test piece is irradiated with ultraviolet rays for 200 hours using a weather resistance tester (manufactured by Suga Test Instruments Co., Ltd.), and then cellophane tape is attached to the surface of the test piece. Deterioration resistance was judged by the degree of peeling and peeling of the coating film after peeling. : The coating film or resin did not peel off or fall off : Part of the coating film peeled off or dropped off ×: Most of the coating film peeled off or dropped off

Tables 3 and 4 show the test results.

[Table 3] <img file="000004.tif" id="000004" he="175" wi="128" img-format="tif" img-content="drawing" />

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[Table 4] <img file="000005.tif" id="000005" he="175" wi="061" img-format="tif" img-content="drawing" />

As can be seen from Table 3, the resin or resin coating material having a photocatalytic surface according to Examples 1 to 15 produced by the method of the present invention has excellent photocatalytic properties and at the same time deteriorates due to light irradiation. There was almost no loss, and its performance and appearance were not impaired for a long period of time.

On the other hand, in the resin or resin coating material surface-treated under the conditions outside the scope of the present invention shown in Comparative Examples 1 to 6 in Table 4, none of these performances was satisfied.

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[Effects of the Invention] The resin or resin coating material having a photocatalytic surface of the present invention has good transparency and adhesion of a coating film, does not impair the decorativeness of these surfaces, and imparts excellent photocatalytic properties. A material having a resin surface having such photocatalytic properties, which can be obtained and has a performance that has not been obtained in the past such that these performances are not lost for a long period of time, can be obtained by the method of the present invention. It can be manufactured efficiently.

Therefore, the resin or resin coating material having a photocatalyst surface of the present invention is used for antibacterial treatment of various resin products and resin coated products, prevention of adhesion of stains, decomposition of malodorous components, purification of air and water, and the like. It can be used, has a wide range of applications, and has high industrial utility value.