JP4681483B2 - Surface-treated metal - Google Patents

Description

  The present invention relates to a surface-treated metal having excellent contamination resistance by having a film showing photocatalytic activity on the surface. That is, the present invention relates to a surface-treated metal that has a photocatalytic activity and a weather resistance over a long period of time by having a film composed of particles having photocatalytic activity and a matrix resin that is less deteriorated by the photocatalyst.

  Metal materials typified by iron are often used for the purpose of improving durability or for the purpose of obtaining a beautiful appearance, and the painted metal is used for home appliances, automobiles, building materials, and outdoors. Widely used in the field of structures and the like. Among these, especially when used outdoors, it is required to have excellent contamination resistance in addition to corrosion resistance because it is exposed to rain, wind, dust and the like.

  Photocatalytic technology is a technology that decomposes and removes pollutants, mainly organic substances, by dispersing particles with excellent photocatalytic activity in the coating film on the surface. Although this technology is highly effective in decomposing surface pollutants, the resin-based coating film, which is an organic substance, gradually decomposes and deteriorates, so it can be used as it is for a long time. It is difficult to do. For this reason, various proposals have been made to minimize the deterioration of the coating film.

  For example, Patent Documents 1 and 2 disclose a method using an inorganic material as a matrix. Moreover, even if it is an organic type coating film, since the fluororesin is comparatively stable with respect to a photocatalyst, the method of using this as a matrix is disclosed (patent document 3). In particular, for pre-coated metals, high stability and processability with respect to photocatalysts are required. For this purpose, a technique using a silica-organosilane matrix as a matrix is used for acrylic resin, organoalkoxysilane, Patent Document 4 and Patent Document 5 disclose methods of using an alkyl silicate obtained by the polymerization reaction as a matrix. Further, Patent Document 6 discloses a method using a vinylidene fluoride resin and an acrylic resin.

JP-A-7-113272 JP-A-8-164334 JP-A-7-171408 JP-A-10-225658 JP 2000-317393 A JP 2000-63733 A

  However, the mechanism of decomposition / removal of contaminants is basically the same as the degradation / degradation mechanism of the coating film that constitutes the base. On the other hand, if it is unavoidable to suppress the deterioration of the coating film, a sufficient photocatalytic effect cannot be obtained, and it has been difficult to achieve both at a sufficiently satisfactory level.

  The present invention has been made in order to solve these problems. By exhibiting a sufficient photocatalytic effect, the present invention is excellent in stain resistance, while the resin component constituting the film and the organic resin coating as the base are coated. An object of the present invention is to provide a surface-treated metal in which film deterioration hardly occurs.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are mixtures of two or more kinds of particles having different components and particle size distributions, at least one of which contains particles having photocatalytic activity. to become inorganic - depending on the surface treatment metal having an organic composite coating, it found that the above problems can be solved, and completed the present invention. Specifically, it is as follows.

(1) A surface-treated metal having one or more coating layers on at least a part of a metal surface, wherein the coating layer is a tetraalkoxysilane, an alkoxysilane having an alkyl group having 1 to 12 carbon atoms, or an aryl group It is formed from a treatment liquid comprising, as a main component, at least one kind of alkoxysilane selected from the alkoxysilanes having the above or a hydrolyzate thereof, and containing particles having photocatalytic activity, a primary binding siloxane bond in the main skeleton, and includes one or more carbon atoms and 12 or less alkyl group, an aryl group, a carboxyl group, at least one organic group selected from the group consisting of amino group and a hydroxyl group, and, inorganic containing two or more particles of different ingredients - has an organic composite coating at least as the outermost layer, the total of two or more of the particles of the different components The content is in the range of 40 to 95% by volume with respect to the inorganic-organic composite film, and at least one of the particles has photocatalytic activity, and the other particles have photocatalytic activity. A surface-treated metal, characterized by not being particles.
(2) The surface-treated metal according to (1), wherein the particles having photocatalytic activity are titanium oxide containing an anatase structure.
(3) The surface-treated metal according to (1), wherein the two or more kinds of particles include at least particles having an average particle diameter of 100 nm or less and particles having an average particle diameter of 150 nm or more.
(4) The surface-treated metal according to (3), wherein the particles having an average particle diameter of 100 nm or less are titanium oxide containing an anatase structure.
( 5 ) The surface-treated metal according to any one of (1) to ( 4 ), wherein the metal is a metal plate.
( 6 ) The metal plate is plated on a steel plate, stainless steel plate, titanium plate, titanium alloy plate, aluminum plate, aluminum alloy plate, or steel plate, stainless steel plate, titanium plate, titanium alloy plate, aluminum plate, or aluminum alloy plate. The surface-treated metal according to ( 5 ), which is one kind selected from a treated plated metal plate.
( 7 ) Any one of (1) to ( 6 ), wherein the coating layer has a laminated structure having at least one organic coating film under the outermost inorganic-organic composite coating film. The surface-treated metal according to 1.

  According to the present invention, it is possible to easily obtain a surface-treated metal that has excellent contamination resistance due to the photocatalytic effect and hardly causes deterioration of the resin component constituting the film and the organic resin coating film that is the base. In addition, a photocatalyst film that has been mainly used in the post-coating method can be easily obtained by the pre-coating method. That is, it is possible to easily obtain a surface-treated metal that has excellent weather resistance and stain resistance and can be bent, drawn, and the like.

  The target of the present invention is as follows.

  First, the outermost surface coating (outermost surface layer, photocatalytic coating) contains particles of two or more different compounds, and the coating contains particles of two or more different components at a high filling rate. is there. By using two or more kinds of particles at the same time, it becomes possible to contain these two or more kinds of particles at a high filling rate in the film, especially when these particles have different particle size distributions. , The effect of realizing a high filling rate becomes even more remarkable. Here, by making one or more of the two or more types of particles into particles having a photocatalytic effect (photocatalyst particles), the outermost surface layer contains photocatalyst particles at a predetermined ratio, and the surface is contaminated. The effect of removal is manifested. On the other hand, since particles are present in the outermost surface layer at a high filling rate, light transmission is hindered, and ultraviolet rays hardly reach the vicinity of the interface between the photocatalyst layer and the lower layer film. As a result, it is possible to form a photocatalytic film directly on the surface of an organic coating without using a protective layer, even when a protective layer is provided for the purpose of protecting the underlying organic film. It becomes.

  Second, even if the transmission of ultraviolet rays is suppressed by the above-mentioned concept, if the constituent material of the film other than the photocatalyst, particularly the resin constituting the matrix is decomposed by the photocatalyst, the degradation of the outermost surface layer results. Will occur and will not function as a photocatalytic film. In this respect, the matrix of the photocatalyst film, which is the outermost layer used in the present invention, is an inorganic-organic composite film that has been studied by the inventors so far. A good appearance and antifouling effect due to the photocatalyst.

  The present invention is described in detail below.

  The 1st aspect about the particle | grains contained in the outermost surface layer (photocatalyst membrane | film | coat) of this invention contains the particle | grains of 2 or more types of different compounds. At least one of these has a photocatalytic effect. Examples of particles having a photocatalytic effect include titanium oxide, zinc oxide, cerium oxide, tin oxide, bismuth oxide, indium oxide, zirconium oxide, tungsten oxide, chromium oxide, molybdenum oxide, iron oxide, nickel oxide, ruthenium oxide, and oxide. Cobalt, copper oxide, manganese oxide, germanium oxide, lead oxide, cadmium oxide, vanadium oxide, niobium oxide, tantalum oxide, rhodium oxide, rhenium oxide, barium titanate, strontium titanate, iron titanate and the like are preferably used. Among these, titanium oxide, zinc oxide, tin oxide, zirconium oxide, tungsten oxide, iron oxide, and niobium oxide are preferably used because they exhibit high activity even when treated at a low temperature of 100 ° C. or lower. Among these, titanium oxide containing an anatase structure is particularly preferably used because of its high activity as a photocatalyst.

  On the other hand, particles having no photocatalytic effect can be selected from a wide range of inorganic particles such as oxides, nitrides, carbides, borides, and metal fine particles, and silicon oxide, aluminum oxide, magnesium oxide, calcium oxide. , Oxides including strontium oxide and yttrium oxide, nitrides such as boron nitride, silicon nitride, and aluminum nitride, carbides such as silicon carbide, silicon, zinc, aluminum powder, and the like.

  When the two or more kinds of particles having different components have different average particle diameters, the ultraviolet transmission suppression effect intended in the present invention is further remarkable. This is due to an increase in the packing rate of the particles, and the particles having a relatively small average particle diameter are efficiently introduced into the voids of the skeleton formed by the particles having a relatively large average particle diameter. It can be explained by filling. Here, as the average particle diameter of each particle, the average particle diameter of the smaller particles is preferably 1 nm or more and 100 nm or less, and the average particle diameter of the larger particles is preferably 150 nm or more and less than 2000 nm, more preferably. The average particle size of the smaller particles is 3 nm or more and 80 nm or less, the average particle size of the larger particles is 200 nm or more and less than 1500 nm, more preferably the average particle size of the smaller particles is 5 nm or more and 50 nm or less, The average particle diameter of the larger particles is 300 nm or more and less than 1000 nm.

  If the average particle diameter of the particles is too small beyond the above range, aggregates are likely to be formed, or the particle diameter is too small, and handling as particles becomes extremely difficult. On the other hand, when the average particle diameter is too large exceeding the above range, the particle diameter is too large with respect to the thickness of the coating layer. In addition, when the relatively small particle diameter is more than 100 nm, a high filling rate may not be obtained because the particle diameter becomes too large. When the relatively large particle diameter is less than 200 nm However, there is a possibility that a high filling rate cannot be realized because the particle size becomes too small. Moreover, as a whole, the particle size of the relatively larger particle and the particle size of the smaller particle are too close to each other, so that a high filling rate may not be obtained. Here, the average particle size is, in principle, the value obtained by measuring the particle size of each particle and averaging the values.

  One of the methods for measuring the average particle size is a method for measuring the particle size of powder particles used as a raw material. That is, the average particle size of the particles contained in the film can be substituted by the particle size of the powder particles used as the raw material. For this, a light scattering method using laser light or the like is preferably used. However, with this method, if aggregated particles are present, care must be taken because the size of the aggregated particles may be measured. When aggregated particles are present, it is preferable to combine them with a direct observation method using a microscope.

  Another method for calculating the average particle size is to observe the cross section of the film with a microscope and calculate from the observed particle size. The microscope used should be selected according to the particle to be observed. In other words, it is desirable to use an optical microscope when observing relatively large particles, and a transmission electron microscope when observing fine particles, and more efficiently using a scanning electron microscope together. can do.

  In order to determine the average particle size of the particles contained in the film, it is necessary to determine the particle size of all the particles, but this is extremely difficult and is impossible in practice. Therefore, it is possible to represent the whole by measuring some particles extracted by a non-artificial method. According to the results of studies conducted by the inventors on particles with a known average particle size, the average particle size can be determined with little error by observing and measuring the particle size of 500 or more, preferably 1000 or more particles. I know it is required. However, measuring the particle size of 500 to 1000 is a very difficult task. When particles containing different components are contained, after classifying them into two or more components, image processing, etc. It is possible to use a method such as automatically measuring the particle diameter by the above method.

  Here, of the two or more different types of particles, one component is a particle having a photocatalytic effect. The average particle size of the photocatalyst particle is either a particle having a large average particle size or a particle having a small average particle size. There is no problem. However, the effect of the present invention can be further enhanced by using photocatalyst particles having a smaller average particle size, that is, using photocatalyst particles having a smaller average particle size. This is because the photocatalyst particles having a small average particle diameter have a higher photocatalytic activity, and therefore an excellent anti-contamination effect can be obtained. The average particle size of the photocatalyst used is more preferably 30 nm or less, and even more preferably 20 nm or less.

  The content of the entire particle composed of two or more different components in the film must be present at a filling ratio of 40% or more by volume from the viewpoint of suppressing the transmission of ultraviolet rays in the film. Here, in order to obtain a sufficient ultraviolet light transmission inhibiting effect, it is preferably present at a content ratio of 50% or more by volume ratio, more preferably at a filling ratio of 60% or more by volume ratio. . On the other hand, it is desirable that the packing ratio of the particles be as high as possible. However, if the packing ratio is too high, the content of the matrix other than the packing particles is small and it is difficult to obtain a stable film. In order to obtain a more stable film, the volume ratio is preferably 90% or less.

  The mixing ratio of the photocatalyst particles and the particles having no photocatalytic effect is preferably selected as appropriate according to the activity of the photocatalyst particles. When the activity of the photocatalyst particles is high, a small amount may be used. However, when using photocatalyst particles with a low activity, the content can be increased. The addition amount of the photocatalyst is preferably selected from the addition amount of about 5% to 30%. For example, the composition of the film containing 40% of the whole particle is 5-30% of photocatalyst particles, 10-35% of particles having no photocatalytic effect, and 60% of matrix resin constituting the film. Filling rate. For example, the composition of the film containing 60% of the whole particle is 5 to 30% of photocatalyst particles, 30 to 55% of particles having no photocatalytic effect, and 40% of matrix resin constituting the film. The filling rate becomes.

  Here, the surface-treated metal of the present invention has a great feature also in the matrix resin constituting the surface film. That is, even when the photocatalyst is used at the same time, decomposition and degradation by the photocatalyst are extremely small. This will be described in detail below.

First, the resin structure has an inorganic skeleton developed into a three-dimensional network structure as a main skeleton, and the main skeleton is composed of an inorganic siloxane bond represented by ≡Si—O—Si≡ as a main bond. By including at least one selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group, a carboxyl group, an amino group, and a hydroxyl group in the structure mainly composed of siloxane bonds, it has excellent stability to photocatalysts. In addition to weather resistance, for example, it can have workability required for a precoat film. The reason for this is that the main component is an inorganic siloxane bond, which ensures stability to the photocatalyst and weather resistance. In addition to controlling the crosslink density of the resin, the organic component can be used to make the film flexible. It is considered that excellent workability is secured. Here, as an alkyl group having 1 to 12 carbon atoms, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a 2-ethylhexyl group, a dodecyl group, etc., and as an aryl group, a phenyl group, a tolyl group, A xylyl group, a naphthyl group, etc. are mentioned. Further, the carboxyl group -COOH, amino group -NH _2, hydroxyl points to each -OH.

  Two or more kinds of organic components used in the present invention can be used at the same time. Of these, the main organic group, that is, the organic group having the largest content is an alkyl group having 5 to 12 carbon atoms. It is preferable to use a group or an aryl group, more preferably an alkyl group or aryl group having 6 to 12 carbon atoms, and still more preferably an alkyl group or aryl group having 6 to 10 carbon atoms. . Among these, the phenyl group is most preferably used as the organic group of the present invention. By combining with a siloxane bond that forms the main skeleton using only the phenyl group, stability against photocatalyst, weather resistance and processability, In addition, a film having excellent adhesion during processing can be obtained. These organic components may be present in the main skeleton or in the side chain. The presence of these components in the film expresses the excellent characteristics of the film used in the present invention.

Examples of the bond other than the siloxane bond include an ether bond such as —CH ₂ —CH (CH ₂ ) —O—CH ₂ — or an amino bond that becomes a secondary or tertiary amine. Among these, when one or both of an ether bond and an amino bond are present in the main skeleton or side chain in the film structure, or both, a film excellent in stability to photocatalyst and processability can be obtained.

  In the film, particles such as a photocatalyst can achieve a high filling rate by being uniformly dispersed, but it is not always necessary to be uniform. For example, as described above, when the agglomerate is formed, or when the concentration of particles is different between the outermost surface and the inside, or when the concentration is inclined, a better anti-staining effect is obtained. Of course, it may be obtained, and in those cases, it is not necessarily required to be uniformly dispersed. Here, the filling rate of the particles used in the present invention is a case where the entire coating is measured, and there is no problem even if the above-mentioned local non-uniformity or the gradient of the filling rate of the particles exists.

  The thickness of the film having photocatalytic activity used in the present invention varies depending on required properties or applications, but is preferably 0.05 μm or more and 25 μm or less, more preferably 0.1 μm or more and 20 μm or less, More preferably, they are 0.1 micrometer or more and 10 micrometers or less. When the film thickness is too thin, the film has a uniform film that has excellent anti-contamination properties and prevents the deterioration of the resin components that make up the film and the organic resin film that is the base. On the other hand, when the film is too thick beyond the above range, molding processability is often insufficient or adhesion during processing is often insufficient. . In addition, due to the nature of the matrix film, it is not preferable to form a thick coating film by a single operation because it causes cracking and peeling. In the case of forming a film having a predetermined thickness or more, it is preferable to repeatedly perform a coating-drying (solidification) operation described later.

  The film matrix of the present invention contains Si as a metal component, but as other elements, one or more metals selected from B, Al, Ge, Ti, Y, Zr, Nb, Ta and the like are used. Elements can be added. Among them, Al, Ti, Nb, and Ta show a catalytic action for completing the solidification of the film at a low temperature or in a short time when an acid is added to the system as a catalyst. When these metal alkoxides are added using an acid as a catalyst, the ring-opening speed of the epoxy is increased, and the film can be cured at a low temperature in a short time. In particular, Ti is often used, and Ti alkoxides such as Ti-ethoxide and Ti-isopropoxide are used as raw materials. In addition, since the alkali resistance of the film is remarkably improved in the system to which Zr is added, it is preferably used in applications that require alkali resistance.

  The metal used as the base material of the surface-treated metal of the present invention is not limited in any way, including the material, shape, presence / absence of processing, and final product (shape), and any material is preferably used. can do. For example, steel, stainless steel, titanium, aluminum, aluminum alloys, or those plated with these materials are suitable, and molded products such as thick plates, thin plates, tubes (pipes), and shaped steel, rods, wires, etc. are suitable. Can be used.

  Among these, particularly preferable metals include steel plates, stainless steel plates, titanium plates, aluminum plates, aluminum alloy plates, plated metal plates obtained by plating them, or coated steel plates on which organic coatings are formed. Plated steel sheets include galvanized steel sheets, zinc-iron alloy plated steel sheets, zinc-nickel alloy plated steel sheets, zinc-chromium alloy plated steel sheets, zinc-aluminum alloy plated steel sheets, aluminum-plated steel sheets, zinc-aluminum-magnesium alloy-plated steel sheets, Examples include zinc-aluminum-magnesium-silicon alloy-plated steel sheets, aluminum-silicon alloy-plated steel sheets, galvanized stainless steel sheets, and aluminum-plated stainless steel sheets.

  Examples of the stainless steel plate include a ferritic stainless steel plate, a martensitic stainless steel plate, and an austenitic stainless steel plate. The thickness of the stainless steel plate ranges from a thickness of about several tens of mm to a so-called stainless steel foil that is thinned to about 10 μm by rolling. The surface of the stainless steel plate and the stainless steel foil may be subjected to a surface treatment such as bright annealing or buffing.

  Aluminum alloy sheets include JIS 1000 series (pure Al series), JIS 2000 series (Al-Cu series), JIS 3000 series (Al-Mn series), JIS 4000 series (Al-Si series), JIS 5000 series (Al -Mg system), JIS6000 system (Al-Mg-Si system), JIS7000 system (Al-Zn system), and the like.

  In the above embodiment, when a coating is formed on a base metal other than a coated steel plate, it is of course possible to form directly on the base metal, but other pre-treatment coatings are formed on the base metal, There is no problem even if it is in a state of being made. For example, a film having a photocatalytic activity used in the present invention is formed on a metal surface subjected to a chromate treatment, or a metal surface subjected to a known surface treatment other than chromate (for example, phosphate treatment). The case where it is done is mentioned.

  The film used in the present invention can be directly formed, for example, even on the surface of a resin coating film. As described repeatedly, since ultraviolet rays hardly pass through the photocatalyst film, even if photocatalyst particles are present at the interface with the lower layer film (resin-based film), the organic resin is hardly deteriorated. Because. Therefore, even a coated metal plate having an organic coating film, which has been considered difficult so far, can be directly formed on the surface thereof. This can be said to be a preferable mode because one painting step can be omitted. On the other hand, when it is desired to completely prevent the lower layer film from being deteriorated by the photocatalyst, an intermediate layer (protective layer) can be provided between the lower layer film and the photocatalyst film. Since this intermediate layer hardly deteriorates, it is not particularly limited and any material can be used. However, the above-mentioned inorganic-organic composite, that is, the matrix used in the outermost photocatalytic film is used. It is considered preferable to use the resin without mixing the photocatalyst.

  The surface-treated metal of the present invention can be used as a material, but can be suitably used even in a state of being processed into parts. There are no particular restrictions on the parts, and it is suitable for building materials applications, such as exterior walls of houses, sizing, etc., and home appliances for outdoor use, such as air conditioner outdoor units, water heater housings (outer plates), etc. Can be used.

  The treatment liquid for forming the outermost layer for suitably producing the surface-treated metal of the present invention is selected from tetraalkoxysilane, alkoxysilane having an alkyl group having 1 to 12 carbon atoms, and alkoxysilane having an aryl group. It is a liquid comprising, as a main component, one or more kinds of one or more alkoxysilanes or hydrolysates thereof, and particles having photocatalytic activity.

  Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Examples of the alkoxysilane having an alkyl group having 1 to 12 carbon atoms include methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane. , Decyltriethoxysilane and the like. Examples of the alkoxysilane having an aryl group include phenyltrimethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane, and diphenyldiethoxysilane.

  The treatment liquid contains, as a main component, the above-mentioned silane compound or a hydrolyzate thereof or a polymer obtained by polymerization or condensation reaction thereof. By using these components, the main bond of the main skeleton used in the present invention is a siloxane bond, and at least one selected from an alkyl group having 1 to 12 carbon atoms, an aryl group, a carboxyl group, an amino group, or a hydroxyl group. An inorganic-organic composite film containing various organic groups can be easily obtained. In addition, by using the above components, the ratio of the inorganic component / organic component in the composite film can be easily changed, and the kind and amount of the organic component introduced into the film can be easily controlled. it can. That is, the inorganic component can be increased according to the properties required for the film, or conversely, the organic component can be increased, and the kind of the organic component to be added is also appropriately selected according to the required properties. can do.

  In addition, as an example only, when the coating of the present invention is used as a thin intermediate layer, it is not necessary to consider the workability, so that it can be a component mainly composed of an inorganic component with little deterioration against the photocatalyst. Is possible. On the other hand, when an organic component is added to some extent, it is possible to design the film component while taking into consideration the balance between processability, flexibility, and deterioration of the film due to the photocatalyst.

  The treatment liquid used in the present invention can further contain an alkoxysilane having an epoxy group and an alkoxysilane having an amino group. Examples of the alkoxysilane having an epoxy group include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, 3 , 4-epoxycyclohexylmethyltrimethoxysilane, 3,4-epoxycyclohexylmethyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane Are preferably used, and γ-glycidoxypropyltriethoxysilane is particularly preferably used in terms of easy handling and reactivity.

  Examples of the alkoxysilane having an amino group include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, (β-aminoethyl) -β-aminopropyltrimethoxysilane, and (β-aminoethyl) -β-aminopropylmethyl. Dimethoxysilane, (β-aminoethyl) -γ-aminopropyltrimethoxysilane and the like are preferably used, and aminopropyltriethoxysilane is particularly preferably used from the viewpoint of ease of handling.

  These alkoxysilanes, like the alkoxysilanes described above, may be polymerized in the treatment liquid in which all or part of the alkoxy groups are hydrolyzed, or they undergo polymerization and condensation reactions. The merit of blending these alkoxysilanes having an epoxy group and alkoxysilanes having an amino group is that adhesion to a metal serving as a base material and stability to a photocatalyst are improved. Although the details of this reason have not been clarified, it is estimated that the addition of an epoxy group or amino group forms a strong bond that contributes to adhesion with the base metal. .

  Moreover, the alkoxide of metal components other than tetraalkoxysilane can also be used as an additive in the treatment liquid of the present invention as required. In particular, when at least one metal alkoxide selected from Ti, Al, Ta, and Nb is added and acetic acid is used as an acid catalyst, the ring opening speed of the epoxy group is increased, and the effect of low temperature and short time curing is particularly effective. growing. In the metal alkoxide other than alkoxysilane, all or part of the alkoxy group may be hydrolyzed. In addition, the treatment liquid of the present invention can contain at least one of a zirconium compound, for example, a zirconium alkoxide, a hydrolyzate thereof, or a zirconium oxide (zirconia) sol, if necessary. This component is a component that improves the alkali chemical resistance of the treatment liquid mainly composed of silica used as the coating liquid of the present invention. The mechanism by which alkali resistance is improved by the addition of this component has not yet been clarified, but Zr is substituted at the position of Si constituting the siloxane bond, focusing on silica and zirconium. This is because a network is formed and stabilized against alkali.

  In the treatment liquid used in the present invention, for the purpose of improving the design properties, corrosion resistance, abrasion resistance, catalytic function, etc. of the coating film, further, coloring pigments, moisture resistant pigments, catalysts, anticorrosive pigments, metal powders, high frequency It is also possible to add a loss agent, aggregate, etc. Examples of the pigment include oxides such as Ti and Al, composite oxides, metal powders such as Zn powder, and Al powder in addition to the above-described compounds. As the rust preventive pigment, it is preferable to use non-chromic pigments such as calcium molybdate, calcium phosphomolybdate, and aluminum phosphomolybdate that do not contain environmental pollutants. Moreover, Zn-Ni ferrite is mentioned as a high frequency loss agent, and potassium titanate fiber etc. are mentioned as an aggregate.

  Moreover, an acid catalyst can be added to the treatment liquid used in the present invention as necessary. Examples of the acid catalyst include organic acids such as formic acid, maleic acid, and benzoic acid, and inorganic acids such as hydrochloric acid and nitric acid. Acetic acid is particularly preferably used. By using an acid as a catalyst, the alkoxysilane used as a raw material takes a polymerization state suitable for film formation, and when acetic acid is used as a catalyst, the ring opening of the epoxy group is promoted, and the curing is performed at a low temperature for a short time This is because the effect of.

  Further, as an additive, a leveling effect agent, an antioxidant, an ultraviolet absorber, a stabilizer, a plasticizer, a wax, an additive type ultraviolet stabilizer and the like can be mixed and used. In addition, if necessary, a resin-based paint such as a fluororesin, a polyester resin, or a urethane resin may be included as long as the heat resistance of the film is not impaired or the deterioration due to the photocatalyst does not occur. These additives may be used alone or in combination of two or more.

The present invention will be specifically described by the following experimental examples.
(Experimental example 1)
(Example 1 to Example 9)
100 parts by mass of γ-glycidoxypropyltriethoxysilane (GPTES), 8.2 parts by mass of titanium tetraethoxide (TE), 144 parts by mass of phenyltriethoxysilane (PhTES), 87 parts by mass of tetraethoxysilane (TEOS) After sufficiently stirring, hydrolysis was performed under acidic conditions using distilled water diluted with ethanol. Here, 39.7 parts by mass of aminopropyltriethoxysilane (APTES) was added, and further hydrolysis was carried out using a distilled water / ethanol mixed solution to prepare a coating solution containing an inorganic-organic composite as a main component.

A sufficient amount of water was added to the hydrolysis, and the treatment liquid was adjusted to a solid content concentration of 10% by mass when dried at 150 ° C. To this treatment liquid, photocatalyst particles and second component particles having no photocatalytic activity were added to prepare a coating liquid for coating. The photocatalyst particles used have a particle diameter of about 60 nm for ZnO, about 10 nm for TiO ₂ , and 100 nm for Nb ₂ O ₅ and Ta ₂ O ₅ .

  The steel plate on which the contamination resistance test was performed was a pre-coated steel plate having a zinc-coated steel plate as a base material and a melamine-crosslinked polyester film coated on the outermost surface with a thickness of about 15 μm. The coating solution prepared above is applied to a steel plate with a bar coater, dried and baked at a maximum temperature of 250 ° C. using a temperature rising condition such that the plate temperature becomes 250 ° C. after 50 seconds, and a film containing photocatalyst particles is formed. A surface-treated steel sheet was obtained. The thicknesses of the formed films were all about 5 μm.

(Comparative Examples 1 to 8)
Moreover, the following three types of steel plates were prepared as comparative examples. First, a steel plate (Comparative Examples 1 to 3) coated on the surface with an inorganic-organic composite film in which only anatase-type TiO ₂ particles are added to the pre-coated steel plate. A steel plate (Comparative Examples 4 to 6) and a tetraethoxysilane (TEOS) formed with a film added with TiO ₂ particles and Al ₂ O ₃ particles as second component particles were hydrolyzed with sufficient water under acetic acid acidic conditions. the matrix obtained is anatase type TiO ₂ particles and _Al 2 _{O 3} grains to form the added coating the steel sheet (Comparative examples 7 and 8). The thickness of the formed film was about 5 μm as in the example.

  A sample was prepared from the photocatalyst film on the surface-treated steel sheet and the particle filling rate was determined by observation with an electron microscope. The results shown in Table 1 were obtained. All the obtained values were the target filling rate and the accuracy within 1%.

  The photocatalytic effect was verified by the following method. First, (1) an outdoor steel plate exposure test was conducted to evaluate rain pollution and dust contamination. (2) In the exposure test, it may take a long time before the effect appears, so as a simple evaluation method, apply a contaminant (black magic, red magic) to the surface of the coated steel sheet. The irradiation time of ultraviolet rays and the state of removing contaminants were measured. The degree of contaminant removal was determined by measuring the surface color. (3) The deterioration (damage) of the photocatalyst coating film was measured by measuring the color and gloss of the surface. The degradation of the lower polyester film was evaluated by observing the interface state between the photocatalyst film and the polyester film. The evaluation of the test results was made in four stages: ◎ → ○ → △ → ×. In addition, only the deterioration state of the coating film was evaluated on a 5-grade scale by adding ◎◎, which is the highest rank, in order to clarify each difference. The criteria for each evaluation are shown in Table 2.

  The results are shown in Table 3 below. It can be seen that all the steel plates tested in Experimental Example 1 have excellent contamination resistance. Although not shown in the table, the 2T bending test was conducted to test the bending workability. As a result, neither cracking nor peeling of the film was observed, and the bending workability was excellent. The deterioration of the film was greatly different between each example and the comparative example. In the steel plate of this example, neither the photocatalyst film nor the lower layer film was noticeably deteriorated. That is, in the steel plate using an organic-inorganic composite film as the matrix of the outermost photocatalyst film and adding the second component particles together with the photocatalyst particles to suppress light transmission, both the photocatalyst film and the lower layer film hardly deteriorate. It became clear. On the other hand, among the comparative examples, in the steel sheets of Comparative Examples 1 to 3 using an inorganic-organic composite film as a matrix and not adding the second component particles, the photocatalyst film is hardly deteriorated, but the lower layer film is remarkably deteriorated. You can see that Further, in Comparative Examples 4 to 6 using a polyester film as a matrix, although an excellent antifouling effect was obtained, remarkable deterioration of the coating film occurred particularly in the outermost photocatalyst film. In addition, a coating in which two different kinds of particles are dispersed in an inorganic matrix obtained by hydrolyzing TEOS provides excellent anti-contamination effect and little deterioration of the coating, but it is the most outer layer coating in 4T bending test. Remarkable peeling was observed. By comprehensively evaluating the above results, it can be seen that the surface-treated metal of the present invention is excellent in stain resistance and that the deterioration of the photocatalytic film and the lower layer coating film is remarkably suppressed.

As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

Claims (7)

A surface-treated metal having one or more coating layers on at least a part of a metal surface,
The coating layer is mainly composed of one or more kinds of tetraalkoxysilane, one or more alkoxysilanes selected from tetraalkoxysilane, alkoxysilane having an alkyl group having 1 to 12 carbon atoms, and alkoxysilane having an aryl group, or a hydrolyzate thereof. And formed from a treatment liquid containing particles having photocatalytic activity, wherein the main bond of the main skeleton is a siloxane bond, and an alkyl group or aryl group having 1 to 12 carbon atoms. comprises at least one organic group selected from the group consisting of carboxyl group, an amino group and a hydroxyl group, and an inorganic containing two or more particles of different ingredients - it has an organic composite coating at least as the outermost layer The total content of two or more particles of the different components is in the range of 40 to 95% by volume with respect to the inorganic-organic composite film. , At least one of said particles have a photocatalytic activity, and wherein the other particles are particles having no photocatalytic activity, surface-treated metal.   2. The surface-treated metal according to claim 1, wherein the particles having photocatalytic activity are titanium oxide containing an anatase structure.   The surface-treated metal according to claim 1, wherein the two or more kinds of particles include at least particles having an average particle size of 100 nm or less and particles having an average particle size of 150 nm or more.   The surface-treated metal according to claim 3, wherein the particles having an average particle size of 100 nm or less are titanium oxide containing an anatase structure. The metal is characterized by a metal plate, surface-treated metal according to any one of claims 1-4. The metal plate is a steel plate, stainless steel plate, titanium plate, titanium alloy plate, aluminum plate, aluminum alloy plate, or steel plate, stainless steel plate, titanium plate, titanium alloy plate, aluminum plate, or aluminum alloy plate plated The surface-treated metal according to claim 5 , wherein the surface-treated metal is one selected from metal plates. The said coating layer is a laminated structure which has at least 1 layer of organic coating film between the said metal surface and the inorganic-organic composite film of the outermost layer, The any one of Claims 1-6 characterized by the above-mentioned. The surface-treated metal according to claim 1.