JP2000063733A - Precoated steel sheet with photocatalytic function - Google Patents

Abstract

(57) [Problem] To provide a pre-coated steel sheet having a photocatalytic function, being excellent in antibacterial, antifungal, anti-algae, low pollution, and also excellent in workability and durability. SOLUTION: This is a precoated steel sheet in which an undercoating film is formed on a base material made of a stainless steel sheet, and a topcoating film is further formed on the undercoating film, wherein the overcoating film contains vinylidene fluoride resin as a resin component. The photocatalyst function is characterized in that the photocatalyst function is characterized in that the photocatalyst is contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the resin component. Having pre-coated steel sheet.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoated steel sheet having a photocatalytic function. More specifically, the present invention relates to a precoated steel sheet having a photocatalytic function, having excellent antibacterial properties, antifungal properties, antialgal properties, and low pollution, and also having excellent workability and durability. 2. Description of the Related Art In recent years, awareness of problems with the living environment has rapidly increased. In particular, the control of the growth of various bacteria, molds, and algae that adversely affect the human body in the form of infectious diseases is an urgent problem. In urban living spaces, pollution of structures due to pollutants such as smoke from factories and automobiles has become a problem. From the viewpoint of maintaining the aesthetics of cities, low-contamination steel plates for buildings are desired. I have. In recent years, research on a photocatalytic reaction using a photocatalytic semiconductor represented by titanium oxide has been actively conducted. Photocatalytic semiconductors have the property of causing a photochemical reaction when irradiated with ultraviolet light and oxidatively decomposing water and organic substances, and have been applied in many fields. As the forming method, a method of firing titanium dioxide to be supported on cement or the like, a method of forming an inorganic coating film by a sol-gel method of a siloxane containing titanium dioxide, and the like are employed. It is also used in the field of coatings, and the surface of a substrate is coated with a coating composition containing the photocatalytic semiconductor and a binder. A coating using such a coating composition can remove organic substances by irradiating a photocatalytic semiconductor light source such as titanium dioxide with specific light such as artificial light, sunlight, or ultraviolet light. [0005] As a coating composition as described above, for example, JP-A-2-273514 discloses a remover and a method for removing oxidizable harmful substances by a clay former comprising an optical semiconductor and clay. Also, Japanese Patent Application Laid-Open No. 8-164334
Japanese Patent Application Publication No. JP-A-2002-209131 discloses a coating film-forming composition containing fine powder of titanium oxide having a photocatalytic function and a hydrolyzate of polysiloxane and capable of firmly coating and adhering to a substrate surface. However, since such a conventional coating composition uses a clay molding or an inorganic paint as a binder, sufficient workability cannot be obtained, and when the surface layer is processed after being formed, it is broken. There is a problem that it cannot be used for a precoated rigid plate. If an organic resin having sufficient processability is added to improve this point, the organic resin is decomposed by radicals generated from the photocatalyst and causes poor appearance. [0007] Since many precoated steel sheets are shipped in the form of sheets and are formed and processed at each factory, very strict workability is required for the surface layer formed at the time of shipment. No coating material satisfying both processability and durability was obtained from the coating composition containing the composition, and a precoated steel sheet containing a photocatalyst was not obtained. An object of the present invention is to provide a precoated steel sheet which has a photocatalytic function, is excellent in antibacterial, antifungal, antialgal, and low pollution, and is also excellent in workability and durability. Is to get. [0009] The present invention is a precoated steel sheet having a base coat made of a stainless steel sheet, an undercoat film formed thereon, and a topcoat film formed thereon.
The overcoating film contains 60% to 85% by weight of vinylidene fluoride resin and 40% of acrylic resin as resin components.
It is a precoated steel sheet having a photocatalytic function, wherein the precoated steel sheet contains 1 to 30 parts by weight of a photocatalyst as a pigment component based on 100 parts by weight of a resin component. DETAILED DESCRIPTION OF THE INVENTION The substrate used in the present invention is a stainless steel plate, that is, an alloy steel plate having high corrosion resistance.
For example, there are a single alloy of iron and chromium, a binary alloy of iron and nickel-chromium, and a material to which a small amount of other metal such as molybdenum and copper is added.
S G4303, G4304, G4305, G430
6, G4307, G4308, G4313, and the like. [0011] The precoated steel sheet of the present invention is obtained by forming an undercoat film on such a base material made of stainless steel and forming an overcoat film having a vinylidene fluoride resin, an acrylic resin, and a photocatalyst thereon. , Thereby maintaining the same workability as the conventional pre-coated steel sheet,
It is a precoated steel sheet having a photocatalytic action. The undercoating film in the present invention is for bonding the stainless steel base material and the topcoating film, and preferably has excellent adhesion to both and excellent workability. As a coating material for forming such an undercoat film, any material capable of forming a film having the above characteristics may be used.For example, an epoxy resin type, a polyester resin type, a linear polyester resin type, an acrylic resin type or An undercoat paint obtained by mixing a plurality of types of resin systems is preferred, and any commercially available undercoat paint generally used for improving the adhesion and appearance of the above resin systems can be used. The overcoating film in the present invention is a coating film containing a vinylidene fluoride resin and an acrylic resin as resin components and a photocatalyst as a pigment component. Here, the vinylidene fluoride resin is a homo- or copolymer containing vinylidene fluoride as a main structural unit, and a commercially available product can be used. The acrylic resin is a homo- or copolymer containing an acrylate or methacrylate as a main structural unit, and a commercially available product can be used. The photocatalyst used for the top coat in the present invention is a substance having a function of causing a photochemical reaction when irradiated with light of a specific wavelength, and includes a valence band filled with electrons, an empty conduction band, and Semiconductors having an energy structure represented by a forbidden band that separates them are preferable. As such a photocatalyst, a semiconductor having a band gap of 0.5 to 5 eV, preferably 1 to 3 eV is preferable. Examples of such a semiconductor include metal oxides such as tin dioxide, zinc oxide, tungsten trioxide, titanium oxide, cerium oxide, barium titanate, ferric oxide and bismuth oxide; zinc sulfide and cadmium sulfide. Metal chalcogenides such as lead, sulfide, zinc selenide and cadmium selenide; Group IV elements such as silicon and germanium;
II of gallium phosphide, gallium arsenide, indium phosphide, etc.
Group IV compound semiconductor; organic semiconductors such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polyvinylcarbazole. Among these, metal oxides such as zinc oxide, tungsten trioxide, titanium oxide, cerium oxide, ferric oxide, tin dioxide, bismuth oxide, and barium titanate are preferred. It is preferable because it has versatility. Examples of the titanium oxide include hydrous titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide, and the like, in addition to titanium dioxide. The crystal type includes a rutile type and an anatase type, and an anatase type is preferable. The method for producing titanium oxide and the surface treatment are not limited at all. The above photocatalysts can be used alone or in combination of two or more. The photocatalyst is preferably in the form of particles, and the particle diameter is preferably from 1 nm to 200 μm by electron microscopy. The above-mentioned photocatalyst can be used in the same manner as that doped with impurities such as arsenic, phosphorus, aluminum, boron, sodium, and halogen. By supporting a noble metal such as platinum on the surface, a catalytic effect can be obtained. It can be improved. The overcoating film having a photocatalytic function in the present invention has a vinylidene fluoride resin as a resin component of 60 to 85% by weight and an acrylic resin of 40 to 15% by weight.
% Of a photocatalyst as a pigment component
It is contained in an amount of 1 part by weight to 30 parts by weight with respect to 00 parts by weight, but may further contain a resin well known to those skilled in the art, an additive, and various paint additives such as metal pigments and organic pigments. If the amount of the photocatalyst is less than 10 parts by weight, sufficient photocatalytic activity cannot be obtained, and if it exceeds 30 parts by weight, it becomes difficult to maintain and process the form of the film. The top coat for forming the above top coat is generally prepared by dispersing or dissolving the above-mentioned non-volatile components in a solvent or diluent according to a method well known to those skilled in the art. Can be. in this case,
A surfactant such as a silane coupling agent or a fluorine compound may be added in addition to the nonvolatile components to improve the dispersibility of the coating solution, coating workability, and leveling property. The types and amounts of such additives are well known to those skilled in the art, and can be easily selected as needed. The solvent or diluent is not particularly limited as long as it easily evaporates during the drying step and does not remain in the coating film. Generally, alcohols such as ethyl alcohol and butyl alcohol: petroleum spirit, Hydrocarbons such as kerosene, xylene and solvesso; esters such as ethyl acetate; ketones such as acetone and ethyl methyl ketone;
Ethers such as diethylene glycol and cellosolve;
One or more kinds of halogenated aliphatic hydrocarbons such as trichloroethylene and methylene chloride can be used as needed. The precoated steel sheet of the present invention is produced by applying the above-mentioned undercoat paint and topcoat paint to a stainless steel sheet as a substrate and forming a film. In this case, there may be a step of subjecting the base material to a surface treatment prior to the application of the undercoat paint, or applying an intermediate paint between the undercoat paint and the overcoat paint. As a method for applying each of the above paints, a coating method used for PCM is possible, and specifically, generally used roll coating is preferable, but other methods may be used. The applied coating film is baked and cured as necessary, but in this case, each coating film may be baked,
Further, baking may be performed after all the coating films are formed. The precoated steel sheet produced in this way is used as it is or as a final product by a forming process such as roll forming or drawing forming for environmental facilities and other uses. Since the top coat and the undercoat of the precoated steel sheet of the present invention are excellent in adhesion and workability, peeling and cracking of each coat by processing do not occur, and a processed product excellent in coatability and appearance is obtained. can get. When the above-mentioned precoated steel sheet or its processed product is used as an environmental material or the like, it is possible to decompose harmful substances such as odors, toxic gases, bacteria, molds, algae, and organic substances by being irradiated with natural light or artificial light. Can be. When the semiconductor is used as a photocatalyst, when light having energy equal to or higher than the forbidden band is absorbed, electrons in the valence band are excited to the conduction band, and holes remain in the valence band due to the photoexcitation. The excited electrons and holes generated on the semiconductor surface act on oxygen and moisture in the film to generate oxygen radicals. Harmful substances are removed by utilizing the redox reaction of oxygen radicals. When the above-mentioned pre-coated steel sheet or its processed product is used for general purposes other than environmental materials, the above-mentioned phenomenon occurs, thereby purifying the use environment, and also erasing bacteria, fungi, algae and the like. Adhesion and proliferation are suppressed, and the contamination is improved. The precoated steel sheet of the present invention has an undercoating film and an overcoating film having a specific photocatalytic activity on a stainless steel base material, so that it has a photocatalytic function, A precoated steel sheet which is excellent in mold resistance, anti-algae, low pollution, and excellent in workability and durability can be obtained. The present invention will be described below with reference to examples and comparative examples. In each case, parts are% by weight. Examples 1 to 4 Each component having the composition shown in Table 1 was dispersed in a paint shaker for 30 minutes to produce an undercoat P. [Table 1] * 1: Trade mark made by Sakai Chemical Co., Ltd. * 2: Trade mark made by Toyobo Co., Ltd. * 3: Trade mark made by Sumitomo Chemical Co., Ltd. * 4: Trade mark made by Wako Pure Chemical Co., Ltd. * 5: Trade mark made by Honshu Chemical Co., Ltd. In the same manner, overcoats A to D were produced with the compositions shown in Table 2. [Table 2] * 6: Polyvinylidene fluoride resin (solid content 100%) manufactured by Elphatochem Co., Ltd. * 7: 2,4,6-vinylidene fluoride copolymer (solid content 100%) manufactured by Elphatochem Co., Ltd. * 8: Teika Corporation Titanium dioxide JA-3 (average particle size 0.18 μm, purity 98% or more) * 9: Talox LLXLO (trademark) * 10: Mitsubishi Rayon Co., Ltd., Dianal BR-64 (trademark) The undercoat P was dried on a stainless steel plate (JIS G4303, thickness 0.3 mm) with a dry coating thickness of 5 μm.
And baked at 260 ° C. for 40 seconds. Further, the top coatings A (Example 1), B (Example 2),
C (Example 3) and D (Example 4) were each coated to a dry film thickness of 20 μm and baked at 260 ° C. for 60 seconds to produce precoated steel sheets T1 to T4. Comparative Examples 1 to 4 In Examples 1 to 4, the top coats A (Comparative Example 1), B (Comparative Example 2), C
(Comparative Example 3) and D (Comparative Example 4) were
By baking for 0 seconds, precoated steel sheets S1 to S4 were manufactured. Comparative Example 5 In Example 1, the undercoat paint P was applied so as to have a dry film thickness of 5 μm, baked at 260 ° C. for 40 seconds, and was further coated with a pre-color N, a fluororesin paint for pre-coated steel sheets.
o. 4600 (manufactured by NOF CORPORATION, registered trademark) was applied to a dry film thickness of 25 μm,
After baking for 2 seconds, a precoated steel sheet, S5, was manufactured. Comparative Examples 6 to 9 Each component having the composition shown in Table 3 was dispersed in a paint shaker for 30 minutes to produce overcoats E to H. [Table 3] * 6: Polyvinylidene fluoride resin (solid content 100%) manufactured by Elphatochem Co., Ltd. * 7: 2,4,6-vinylidene fluoride copolymer (solid content 100%) manufactured by Elphatochem Co., Ltd. * 8: Teika Corporation Titanium dioxide JA-3 (average particle size 0.18 μm, purity 98% or more) * 9: Talox LLXLO (trademark) * 10: Mitsubishi Rayon Co., Ltd., Dianal BR-64 (trademark) In Examples 1 to 4, overcoats A to D
Instead of the above, the top coats E (Comparative Example 6), F (Comparative Example 7), G (Comparative Example 8), and H (Comparative Example 9) were applied so that the dry coating film thickness became 20 μm. Prebaked steel sheets S6 to S9 were manufactured by baking for 60 seconds. Test Example 1 Adhesion Test Using the precoated steel sheets T1 to T4 obtained in Examples 1 to 4 and the precoated steel sheets S1 to S4 obtained in Comparative Examples 1 to 4, peeling of the coating film based on JIS K5400. Was determined, and the results are shown in Table 4. From Table 4, it was confirmed that the samples subjected to the two-layer coating of Examples 1 to 4 had excellent adhesion and did not cause peeling. [Table 4] Test Example 2 Flexibility test A test on JIS K54008 coating film resistance using the precoated steel sheets T1 to T4 obtained in Examples 1 to 4 and the precoated steel sheets S1 to S5 obtained in Comparative Examples 1 to 5. A bending test is performed on a 0.3 mm plate based on the 8.1 bending resistance during the method. That is, the sample plate was folded in two, and the presence or absence of cracks in the coating film on the bent and bent surface was determined by means of a vice with a 0.3 mm plate interposed therebetween. The results are shown in Table 5. From Table 5, it was confirmed that the samples of the examples were remarkably excellent in workability as compared with the comparative examples, and that the workability was improved by the presence of the undercoat film. [Table 5] Test Example 3 Antibacterial Test Using the precoated steel sheets T1 to T4 obtained in Examples 1 to 4 and the precoated steel sheets S6 to S9 obtained in Comparative Examples 6 to 9, antimicrobial treatment under UV light irradiation was carried out according to the following method. The test was performed. After applying 10 ⁵ cells / cm ² of E. coli to the surface of the member, the sample is placed under irradiation of 120 μW / cm ² of UV light, and the number of Escherichia coli present on the surface of the sample 24 hours later is determined by a film adhesion method. The number of viable bacteria was measured, and the results are shown in Table 6. From Table 6, in the presence of light, bacterial growth was observed in the samples of Comparative Examples 6 to 9 containing no photocatalyst, whereas the samples of Examples 1 to 4 were confirmed to have excellent antibacterial properties. . [Table 6] * ... Plastic petri dish Test Example 4 Chlamydomonas reinhard using the pre-coated steel sheets T1 to T4 obtained in Examples 1-4 and the pre-coated steel sheets S6-S9 obtained in Comparative Examples 6-9.
tii, Euglena gracilis, Chlo
rella sp. The growth of the algae was observed for 4 weeks at 23 ° C. by irradiation with a white light by the sticking method using the three kinds of mixed algae. The results are shown in Table 7. From Table 7, in the presence of light, the growth of algae was observed in the samples of Comparative Examples 6 to 9 containing no photocatalyst, whereas the samples of Examples 1 to 3 were confirmed to have excellent algal protection. Was. [Table 7] -: No growth of algae was observed on the sample surface at all ±: Very little growth of algae was observed on the sample surface +: Algae growth was observed on 1/3 or less of the sample surface ++: 2/3 of the sample surface The growth of algae is observed below. +++: The growth of algae is observed on 2/3 or more of the sample surface. Test Example 5 Rain streak contamination test Precoated steel sheets T1 to T4 obtained in Examples 1 to 4 and comparison Using the precoated steel sheets S6 to S9 obtained in Examples 6 to 9, tests were conducted in accordance with the Japanese Industrial Standard (draft) outdoor exposure test method for the contamination of building exterior materials, and the results are shown in Table 8. . From Table 8, it was confirmed that the samples of Examples 1 to 4 erased the rain streaks in 2 to 3 weeks and maintained the appearance. [Table 8] -: No trace of rain streak is observed on the sample surface. +: Trace of rain streak is observed on the sample surface. ++: Trace of rain streak is observed considerably densely on the sample surface. Has a photocatalytic function as compared with the comparative example, and has antibacterial, antifungal, antialgal,
It can be seen that a precoated steel sheet having excellent low-contamination properties and excellent workability and durability can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat (Reference) C09D 13:00) (72) Inventor Masahiro Sasaki 1-30 Oyamacho, Sagamihara-shi, Kanagawa Nippon Kinzoku Kogyo Co., Ltd. Company Sagamihara Works (72) Inventor Satoshi Ichihara 1-30 Oyamacho, Sagamihara City, Kanagawa Prefecture F Term in Sagamihara Works, Nippon Metal Industry Co., Ltd. 4J038 CD111 CG142 CH032 CK022 CN002 HA066 HA216 HA246 HA356 JA02 JA03 JA07 JA19 JA25 JA55 KA04 KA06 MA07 MA09 NA05 PA07 PC02

Claims (1)

Claims: 1. A precoated steel sheet having a base coat made of a stainless steel plate, a base coat formed thereon, and a top coat formed thereon, wherein the top coat is formed of a resin component. 60% to 85% by weight of vinylidene fluoride resin and 40% of acrylic resin
A precoated steel sheet having a photocatalytic function, comprising from 1 to 30% by weight of a photocatalyst as a pigment component based on 100 parts by weight of a resin component.