JP2006045370A - Super hydrophilic coating composition and coating and super hydrophilic colored steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a super hydrophilic coating composition having a soil removal effect equal to that of photocatalytic coating which requires barrier coats without using them. <P>SOLUTION: The super hydrophilic coating composition contains, as the main ingredient, a graft polymer comprising a tetrafluoroethylene polymer having perfluorosulfonic acid groups expressed by the formula in the side chains (Dupont Company Nafion (R)). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a super-hydrophilic coating composition and a coating containing the coating composition, and more specifically, a coating composition having a super-hydrophilic property over a long period of time when applied to an object, The present invention relates to a super hydrophilic color steel plate.

  If the surface of an object such as a window glass, lens, or building wall is made hydrophilic, effects such as 1) making it less susceptible to environmental pollution due to rainfall, 2) preventing condensation, and 3) eliminating static electricity can be expected. . In order to apply such hydrophilicity to the surface of an object, conventionally, it is common to apply a photocatalytic substance that changes its hydrophilicity by applying a substance rich in hydrophilicity or irradiating light. However, due to the lack of water resistance, there is currently no treatment method that has a short life, and therefore is easy to construct and exhibits hydrophilicity for a long time.

On the other hand, with respect to a hydrophilic coating composition for forming a coating film capable of maintaining a hydrophilic surface such as a building or window glass, for example, a coating film made of siloxane that forms a silicone resin film when cured. There has been proposed a photocatalytic hydrophilic coating composition containing a forming element and a photocatalytic titanium oxide dispersed in the coating film forming element and hydrophilizing the surface of the film in response to photoexcitation (for example, Patent Document 1). This hydrophilic coating composition is based on the discovery that when the photocatalyst is photoexcited, the surface of the member is highly hydrophilized. When the photocatalyst is irradiated to the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes, and the action of either or both imparts polarity to the surface, thereby Water is chemically adsorbed on the surface, and a physical adsorbed water layer is formed and increased on the surface, so that the surface exhibits a high degree of hydrophilicity with a water wetting angle of 10 ° or less.
Japanese Patent No. 3348613

  However, the above-described conventional coating composition is a kind of so-called photocatalyst coating material containing a photocatalyst called titanium oxide as a main component. Since the photocatalyst paint decomposes dirt by a chemical reaction, there is a risk of causing a chemical reaction with an object to be coated. Therefore, a barrier coating operation for previously applying an inorganic silica or the like to the coating surface of the paint is necessary.

  Furthermore, the colored steel plate is manufactured by being baked at a high speed (for example, about 60 seconds) through an oven while coloring the surface of a plain steel plate wound up in a roll shape. For this reason, since a photocatalyst coating requires several days for drying, a hydrophilic colored steel sheet could not be produced.

  The present invention is intended to provide a superhydrophilic coating composition, a coating material, and a superhydrophilic color steel plate that have the same effect of removing dirt without using a photocatalytic coating that requires a barrier coating operation.

  In order to achieve the above object, the superhydrophilic coating composition according to the present invention comprises:

Graft polymer comprising a repeating unit of polymer tetrafluoroethylene (Nafion (registered trademark of DuPont)) having a perfluorosulfonic acid group (R _f , the same _applies hereinafter) represented by the above chemical formula in the side chain. Is the main component.

  According to the super-hydrophilic coating composition of the present invention having the above-described configuration, the coating composition is dissolved in alcohol, for example, diluted, applied in a liquid state, for example, on the outer wall surface of the building, and then applied to the outer wall surface. Ions are immobilized and super hydrophilicity is exhibited over a long period of time. Thereby, even if dirt etc. adhere to an outer wall surface, dirt etc. fall easily with rain water or shower water. In addition, since superhydrophilicity is exhibited by ionization rather than chemical reaction, the barrier coating treatment that is necessary for the photocatalyst coating is not required, and the coating operation becomes easier.

  By the way, the above-mentioned polymer polymer of tetrafluoroethylene, which constitutes the main component of the coating composition of the present invention, is an organic substance (resin material) generally used as a solid electrolyte of a polymer solid fuel cell. The coating composition can be dissolved with alcohol (methylene or ethylene) and diluted with water. Since the inventor normally uses water for the electrolyte (liquid), water is used for the polymer tetrafluoroethylene graft polymer as the main component of the present coating composition used for the solid electrolyte of the fuel cell. I thought that there might be a property similar to or a property that attracts water. And it melt | dissolved with alcohol, it apply | coated to the surface of a tent place with water repellency, for example, and it was confirmed that it has hydrophilicity by applying the colored water to the application surface, and this is the trigger of this invention.

  Furthermore, according to the coating composition of the present invention, since the conventional photocatalyst coating requires two days to several days for drying after application, a curing period after application is necessary, but the drying time is extremely short. There is no need for curing.

  In order to achieve the above object, a superhydrophilic paint according to the present invention comprises a graft polymer (Nafion) comprising a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the following chemical formula in the side chain. (Nafion) (a registered trademark of DuPont).

  The superhydrophilic paint of the present invention having the above-described configuration basically exhibits the same effects as the superhydrophilic paint composition according to claim 1. This paint exhibits the above-described effects when the paint composition is contained in an amount of about 40% by weight or more. For example, a thinner as a solvent or a pigment may be mixed to be colored. it can.

  In order to achieve the above object, a super hydrophilic color steel sheet according to the present invention comprises a fluorine-based graft comprising repeating units of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the following chemical formula in the side chain. A coating material containing a polymer ((Nafion (registered trademark of DuPont)) is applied to the surface of a rolled steel sheet, and is baked at a high speed and wound into a roll.

  The super-hydrophilic color steel sheet of the present invention having the above-described configuration basically exhibits the above-described effects of the super-hydrophilic paint composition according to claim 1, and the paint used is different from the photocatalyst paint. Since the drying time after coating is as short as several tens of seconds at room temperature, it is possible to cope with high-speed baking of colored steel sheets, making it possible to produce super hydrophilic colored steel sheets.

  The super-hydrophilic coating composition and super-hydrophilic coating of the present invention include a graft polymer (Nafion) (registered trademark of DuPont) comprising a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group in the side chain. )) As a main component, so that it is dissolved in alcohol and diluted to a liquid state and applied to the outer wall surface of the building. Even if it adheres to the outer wall surface, it is possible to easily remove dirt by rain or shower water jet. Moreover, since it exhibits superhydrophilicity by ionization rather than chemical reaction, the barrier coating treatment (undercoating) required for the photocatalyst coating is unnecessary, and the coating operation is further simplified. Further, the super-hydrophilic color steel sheet of the present invention also has super-hydrophilicity and exhibits the same effects as described above.

  Hereinafter, embodiments of the superhydrophilic paint composition, superhydrophilic paint and superhydrophilic color steel sheet according to the present invention will be described.

  The super-hydrophilic property in the present invention refers to a state exhibiting a water wettability of 5 ° or less in terms of a contact angle with water.

  The fluorine-based graft polymer (Nafion) (registered trademark of DuPont) comprising a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group as a main component of the coating composition of the present invention or a main chain of the coating composition. ), Hereinafter also simply referred to as Nafion), is represented by the following chemical formula, sold by DuPont, and is generally used as a solid electrolyte for polymer solid fuel cells. This paint composition is mainly composed of the same fluorine-based graphite resin, and this paint is a transparent paint prepared by dissolving the fluorine graphite resin in methanol and diluting it, or mixing it as it is with further water. is there.

Here, in order to confirm the super hydrophilicity of the present coating composition or the present coating, the contact angle with water was compared with various familiar polymers. The comparison data is shown in Table 1 below. The various polymers were in a solid state, and the contact angles with respect to water on their surfaces were determined. As for Nafion, which is the main component of the present coating composition or the present coating, 100 g of a solution obtained by diluting solid Nafion with ethanol until the nonvolatile content becomes 0.4% is added to the surface of the vinyl chloride resin plate. The film was applied at a rate of / m ² and dried at room temperature for about 10 minutes. And the contact angle with respect to water is calculated | required.

  As shown in the above table, the contact angle of Nafion is 4 °, and the hydrophilicity is so high that it is less than 5 °. This is called “superhydrophilicity”. It has only been achieved. Nafion is a graft polymer in which a sulfonic acid group is substituted on the perfluoro main chain, but since the main chain and side chain have fluorine, it looks like a hydrophobic polymer that repels water. However, sulfonic acid is hydrophilic with water. For this reason, when water contacts, it will be estimated that water gathers in the part of sulfonic acid and exhibits super hydrophilicity.

Examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.
Example 1

  100 parts by weight of a fluorine-based graft polymer “Nafion (registered trademark)” (DuPont) consisting of repeating units of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the above chemical formula in the side chain with ethanol (100 %) Was mixed at a weight ratio of 2: 8 and stirred to obtain a transparent solution as a coating composition of this example. The coating composition was directly applied to the wall surface of the building and allowed to dry naturally to form a super hydrophilic wall surface.

  A thinner was added to the coating composition at a weight ratio of 1: 9, and further diluted by adding twice as much water to obtain a coating material of this example. The surface of the colored paint coated with this paint when a colored paint (for example, Evagrad 5000 (Kansai Paint Co., Ltd.) is applied to the surface of the plain steel sheet rolled and rolled up and baked at high speed in an oven. And superbaked colored steel sheet was obtained by baking at high speed (for example, 60 seconds).

Claims (3)

A superhydrophilic coating composition comprising a graft polymer composed of a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the above chemical formula in a side chain as a main component.

A paint comprising a graft polymer composed of a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the above chemical formula in a side chain.

A paint containing a graft polymer composed of a repeating unit of polymer tetrafluoroethylene having a perfluorosulfonic acid group represented by the above chemical formula in its side chain is applied to the surface of a rolled plain steel sheet together with a colored paint. Super hydrophilic color steel sheet, characterized by high-speed baking.