JP2010043188A - Photocatalytic film-forming paint, photocatalytic film, and layered product equipped with the photocatalytic film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paint for forming a photocatalytic film having good durability and moderate hardness, and excellent in chemical resistance, and to provide a coated photocatalytic film formed using the paint, and also a layered product equipped with a base material and the coated film. <P>SOLUTION: The paint for forming a photocatalytic film includes a photocatalytic particle, a silane coupling agent having a photopolymerizable functional group, and a photopolymerization initiator, and formation of the photocatalytic film is performed by coating the paint on a surface of a base material, then by irradiating ultraviolet ray so as to polymerize the photopolymerizable functional group contained in the film, and to construct a crosslinking structure in the film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating material used for forming a photocatalytic coating film on a substrate surface, a photocatalytic coating film formed using the coating material, and a laminate including the photocatalytic coating film. More specifically, the present invention relates to a coating material for forming a photocatalytic coating film that is excellent not only in weather resistance but also in durability, particularly chemical resistance and abrasion resistance.

  Conventionally, a molded article or film having a coating film with a so-called photocatalytic function, in which decomposition or oxidation of a substance occurs when light of a specific wavelength region is irradiated onto photocatalyst particles such as titanium oxide, has been proposed. Various techniques relating to coating liquids formed by mixing photocatalyst particles and other materials such as binder components have been proposed.

  In addition, photocatalyst particles such as titanium oxide are very cohesive and will aggregate in the coating solution if no surface treatment is applied, resulting in an aggregate of an inappropriate size for inclusion in the coating film. Therefore, in the development of a photocatalytic coating film and the development of a coating liquid for forming the coating film, various studies for dispersing titanium oxide particles in the coating liquid are combined. Has been done.

  For example, Patent Document 1 listed below includes one liquid having a coupling agent such as a silane coupling agent and photocatalyst particles, and two liquids composed of a solution obtained by dissolving an alkoxysilane and a photoacid generator in an organic solvent. A two-component photocatalytic coating is disclosed. By using such a paint, the dispersibility of the photocatalyst particles can be improved by the coupling agent in one liquid, and the hydrolysis and polycondensation by the acid generated from the photoacid generator in the alkoxysilane in the other one liquid. And the coating film is formed on the substrate.

  Similarly, Patent Document 2 below also discloses an invention of a resin composition in which an inorganic ultraviolet absorber such as titanium oxide is dispersed in a transparent thermoplastic resin, wherein the inorganic ultraviolet absorber is a specific silane coupling. An invention of a resin composition surface-treated with an agent is disclosed. Patent Document 2 describes that photocatalyst particles such as titanium oxide are very cohesive and that a silane coupling agent is used to disperse the photocatalyst particles in the composition.

  Patent Document 3 discloses an invention of a paint including a fluororesin powder, a binder, an additive of a substance whose surface free energy is smaller than the surface energy of the binder, and a titanium oxide powder having a photocatalytic action. Yes. In the above coating material, the composition of the fluororesin powder, the binder, and the additive are all made of fluorine, and the composition is not decomposed by the photocatalytic action of titanium oxide due to the strong binding force between fluorine and other elements. It is disclosed that the problem of choking due to binder decomposition is solved. Further, as the additive, by using an additive having a surface free energy intermediate between the fluororesin powder and the binder, the fluororesin powder is mixed with the additive or the binder, and the gaps between the individual fluororesin powders are filled, It has been described that deterioration of water repellency is prevented.

JP 11-323189 A JP 2006-77075 A Japanese Patent Laid-Open No. 10-88061

  However, the conventional technique using the photocatalyst particles described above has the following problems.

  That is, the photocatalyst particle-containing coating film formed by the method described in Patent Document 1 or 2 in which photocatalyst particles are dispersed using a silane coupling agent generally has good weather resistance, but on the other hand, frictional force, etc. In addition, they are brittle and inferior in chemical resistance, and have problems in wear resistance and chemical resistance. The problems of wear resistance and chemical resistance of the coating film were considered by the present inventors as follows.

  Silane coupling agents generally have four alkoxy groups and others have one functional functional group and three alkoxyl groups. And when the silane coupling agent is contained in the coating film having photocatalyst particles, one alkoxy group in the silane coupling agent molecule is bonded to the substrate surface or the photocatalyst particles. These two alkoxy groups are converted into silanols by hydrolysis, and then condensed with other silane coupling agent molecules having silanols to form siloxane bonds, thereby forming a coating film having excellent weather resistance. Is possible. However, the coating film formed by the silane coupling agent is likely to penetrate the organic solvent into the skeleton composed of the siloxane bond, and the presence of the organic solvent that has penetrated into the coating film causes the coating film to swell and dissolve. Since it was accelerated | stimulated, it was guessed that the chemical resistance of the coating film which consists of the said silane coupling agent was low.

In particular, in the case of a silane coupling agent having one functional functional group, a functional group other than an alkoxy group exists on the surface of the coating film constituted by a siloxane bond as described above. In the presence of this functional group, the coating film has good flexibility, but the functional group is oxidized by the oxidizing action of the photocatalyst particles contained in the coating film, and silica is formed at an early stage after the coating film is formed. Or it becomes the state of silanol. As a result, while the coating film loses flexibility, the contact angle of the silane coupling agent with respect to the substrate surface is smaller than that immediately after the coating film formation and the wettability is increased, so that the coating film has desirable antifouling properties. it is conceivable that. However, the present inventors have inferred that the oxidation of functional groups other than the alkoxy group is involved in the brittleness of the coating film, resulting in deterioration of durability. Therefore, this deterioration in durability has been a problem particularly in application fields where durability is important.
On the other hand, by adding a crosslinking agent, the functional functional group can be crosslinked, for example, it is possible to react an aminopropyl group or the like with an isocyanate compound or an epoxy compound as a crosslinking agent. However, in such a case, it is extremely difficult to completely complete the reaction, and the storage stability in the solution state is also inferior.

  In addition, a silane coupling agent that is not a functional group but exhibits functionality by adjusting the flexibility, dimensional stability, curing speed, etc. of the coating film, such as methyltrimethoxysilane, methyltriethoxysilane, etc. When used in combination with tetraalkoxysilane, crystallization is hindered by the presence of a methyl group, and it is considered that a coating film having inferior denseness of the coating film and inferior surface strength and wear resistance is formed. This is because the methyl group is rapidly oxidatively decomposed by the photocatalytic action of titanium oxide, forming silica and forming a space in the coating film. This is supported by the fact that the oxidative degradation due to progresses to hydrophilicity as it progresses.

  On the other hand, the technique disclosed in Patent Document 3 is expected to provide flexibility to the coating film due to the presence of the fluororesin powder, and the photocatalytic coating with improved fragility and improved durability. It is expected that a film can be formed. However, since the density is increased, it is extremely difficult to stably disperse and hold the fluororesin powder in the paint, and the problem is that the chemical resistance and the adhesion to the substrate are extremely inferior. .

  The present invention has been made in view of the above problems, and has a good durability, an appropriate hardness, and a paint for forming a photocatalytic coating film excellent in chemical resistance, and the paint. The object is to provide a formed coating film, a substrate, and a laminate comprising the coating film.

  In order to solve the problem of the conventional photocatalytic coating film, the present inventors disperse photocatalyst particles with a specific silane coupling agent, and also use a specific silane coupling agent as a binder for coating film formation, It has been found that by realizing a structure in which functional groups other than alkoxy groups of the silane coupling agent are polymerized with each other, not only the weather resistance of the coating film but also durability, particularly chemical resistance and abrasion resistance can be improved. . Therefore, in the photocatalytic coating film-forming coating material, in addition to the photocatalyst particles and the silane coupling agent having an ultraviolet polymerizable functional group, a photopolymerization initiator film according to the present invention is contained. It was completed. Moreover, the coating film which has a structure which functional groups other than the alkoxy group of a silane coupling agent mutually superpose | polymerize was completed by apply | coating the coating material of this invention to a base-material surface, and then irradiating with an ultraviolet-ray.

That is, the present invention
(1) A paint for forming a photocatalytic coating film, comprising photocatalyst particles, a silane coupling agent having an ultraviolet polymerizable functional group, and a photopolymerization initiator,
(2) The coating composition for forming a photocatalytic coating film according to (1) above, wherein the ultraviolet polymerizable functional group is a vinyl group, or a vinyl group is provided in the ultraviolet polymerizable functional group,
(3) The photocatalytic coating film-forming paint as described in (1) or (2) above, wherein the photocatalyst particles are of a visible light responsive type,
(4) It is formed by applying the photocatalytic coating film-forming paint described in any one of (1) to (3) above on a substrate, and then irradiating with ultraviolet rays. Photocatalytic coating film,
(5) A laminate comprising a substrate and the photocatalytic coating film described in (4) above,
Is a summary.

  In the present invention, the term “silane coupling agent having an ultraviolet polymerizable functional group” means a silane coupling agent having a functional group capable of being polymerized between molecules when irradiated with ultraviolet rays. That is, “in the present invention, the“ silane coupling agent ”means a silane coupling agent having three alkoxy groups and one ultraviolet-polymerizable functional group in silicon (Si).

  Since the coating film formed by the photocatalytic coating film-forming coating material of the present invention contains photocatalyst particles, it can oxidize and decompose dirt such as organic substances adhering to the coating film surface. In addition, since the photocatalyst particles are well dispersed by the silane coupling agent present in the paint, a uniform and good photocatalytic action is exhibited in the coating film.

  In addition, the silane coupling agent has three alkoxy groups, and on the substrate surface, one alkoxy group adsorbs hydrogen bonding to the substrate surface to which the paint of the present invention is applied. The remaining two alkoxy groups undergo hydrolysis, and then undergo condensation polymerization between the silane coupling agents, so that the coating film aggregates on the surface of the substrate, thereby obtaining good weather resistance.

  Furthermore, the coating film formed by the photocatalytic coating film-forming coating used in the present invention is excellent not only in weather resistance but also in durability, particularly in friction resistance and chemical resistance. This is because the silane coupling agent used in the present invention has an ultraviolet polymerizable functional group, and the photopolymerization initiator is present in the paint, and therefore, when irradiated with ultraviolet rays, The inventors speculate that this is because the ultraviolet-polymerizable functional groups are polymerized to form a crosslinked structure of the ultraviolet-polymerizable functional groups in the coating film.

  Therefore, the coating film formed by the photocatalytic coating film-forming paint exhibits excellent weather resistance and photocatalytic action, and has moderate hardness, excellent durability, particularly friction resistance and chemical resistance, so that the surface is Even if it is difficult to get dirty, the surface of the coating film can be cleaned with a cleaning tool such as a cloth, and the destruction of the coating film can be satisfactorily prevented even if it is wiped off firmly. It also has excellent resistance against organic solvents such as methanol, petroleum thinner, sodium hypochlorite, etc., which have been thought to swell or dissolve photocatalytic coatings. It is possible.

  In particular, in the present invention in which the photocatalyst particles are of a visible light responsive type, photocatalysis can be achieved only with visible light from an artificial light source such as indoors even in places where sunlight (ultraviolet rays) is insufficient or where sunlight does not reach. It is possible to provide a coating film capable of exhibiting. Therefore, a coating film formed from the coating material of the present invention containing visible light responsive photocatalyst particles or a decorative plate provided with the coating film is very useful as a decorative sheet or decorative plate used indoors.

Photocatalytic coating film coating:
BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described first for each component of the photocatalytic coating film-forming paint of the present invention (hereinafter sometimes simply referred to as “the paint of the present invention”).

[Photocatalyst particles]
The photocatalyst particles used in the present invention generally exist in the form of aggregates, and those having an average particle diameter of 10 nm or more and 150 nm or less are preferably used, and the average particle diameter is 10 nm or more and 100 nm or less. More preferably, it is 30 nm or more and 100 nm or less. If the average particle diameter of the aggregate of photocatalyst particles exceeds 150 nm, the coating film tends to become opaque. If it is desirable that the color or pattern of the substrate is appropriately visually recognized through the coating film, the average particle It is desirable to use photocatalyst particles that are aggregates having a diameter of 150 nm or less, more preferably 100 nm or less. Further, from the viewpoint of maintaining the surface strength of the coating film in a favorable range, the average particle size is desirably 150 nm or less, preferably 100 nm or less. Further, although it varies depending on the kind of particles forming the aggregate, when the average particle size is less than 10 nm or less than 30 nm, the size becomes close to the primary particle size of the photocatalyst particles, and the dispersion work is difficult. There is a possibility that the photocatalyst particles are completely buried in the coating film, and the oxidizing action is not suitably exhibited on the coating film surface.

  Known photocatalyst particles include titanium oxide and tungsten oxide. Titanium oxide is roughly divided into anatase type, rutile type, and brookite type according to its crystal structure. In the present invention, it is preferable to use anatase type or brookite type photocatalyst particles, or these 2 A mixture of the above may also be used. These photocatalyst particles are generally UV-responsive and exhibit photocatalytic action when irradiated with UV light. In particular, anatase-type titanium oxide has high photocatalytic performance and is easy to handle, and is preferably used in the present invention. Photocatalytic particles other than titanium oxide such as tungsten oxide may be used, and tungsten oxide can exhibit a photocatalytic action in the visible light region. Hereinafter, as a photocatalyst particle used in the present invention, titanium oxide will be mainly described as an example. However, the photocatalyst particles in the present invention are not limited to titanium oxide, and other substances capable of exhibiting photocatalytic action may be used, or other photocatalytic particles and titanium oxide may be mixed and used.

  The ultraviolet responsive photocatalyst particles can be used after being processed into a visible light responsive type by a conventionally known method. In particular, when the coating film formed using the photocatalytic coating film-forming coating material of the present invention is used in a place where the amount of sunlight irradiation is small or in a place where sunlight does not reach, such as indoors, a visible light response type It is desirable to use the photocatalyst particles.

As a technique for making titanium oxide responsive to visible light from an ultraviolet responsive type, for example, by ion implantation, other metal ions are implanted into the ultraviolet responsive type titanium oxide molecule, ^Examples include a method of replacing titanium ions (Ti ⁴⁺ ) or oxygen ions (O ²⁻ ) with external ions. More specifically, examples of ions that can cause an absorption shift to the visible light region by substitution with the titanium ions include chromium ions, vanadium ions, manganese ions, and iron ions. Examples of ions that can cause an absorption shift to the visible light region by substitution with the oxygen ions include nitrogen ions, sulfur ions, and carbon ions. In particular, nitrogen-doped photocatalyst particles in which nitrogen and oxygen are substituted have a very low degree of secondary aggregation compared to other visible light responsive type particles, and in a dispersion solvent when added to a paint. Since it can exist in a very small aggregate size, it can be preferably used in the paint of the present application.

  The amount to be replaced varies depending on the crystal structure of the photocatalyst particles used, ions to be implanted, and the like. For example, when oxygen and nitrogen ions in the titanium oxide crystal are replaced, 8% of the total oxygen ions. By substituting about -10% with nitrogen ions, a significant shift in absorption up to the visible light region can be realized.

[Silane coupling agent]
Next, the silane coupling agent used in the present invention will be described. The silane coupling agent used in the present invention is represented by the following formula 1,
_{R-Si (OR ') 3} ( Equation 1)
R is an ultraviolet polysynthetic functional group, and R ′ is a methyl group or an ethyl group (that is, OR ′ is an alkoxy group).

  The ultraviolet polymerizable functional group may be any functional group that does not inhibit the dispersibility of the photocatalyst particles in the paint and can undergo a polymerization reaction between molecules when irradiated with ultraviolet rays after forming the coating film. A vinyl group is mentioned as a typical example of the said functional group. Or what has a vinyl group in the said ultraviolet polymerizable functional group, for example, an acryloxy group, a methacryloxy group, a styryl group, etc. may be sufficient.

  The alkoxy group is hydrolyzed by contact with water to generate a silanol group. The silanol groups are condensation polymerized to form a coating film.

  Specific examples of the silane coupling agent used in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylethyldimethoxysilane, and 3-methacryloxypropyltrimethoxy. Examples thereof include silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane. A particularly preferred silane coupling agent is 3-methacryloxypropyltriethoxysilane.

  The amount of the silane coupling agent blended in the paint of the present invention varies depending on the type of silane coupling agent, the photocatalyst particles constituting the paint, the type of solvent, etc., so that the photocatalyst particles can be sufficiently dispersed. In addition, the amount is appropriately determined in consideration of an amount capable of sufficiently constructing a crosslinked structure by polymerization of ultraviolet polymerizable functional groups in the formed coating film. That is, the amount of the silane coupling agent as a binder in the coating film is insufficient only with the minimum amount of the silane coupling agent for dispersing the photocatalyst particles, and there is a possibility that the photocatalyst-containing coating film cannot be formed. Therefore, it is desirable that the silane coupling agent having an ultraviolet polymerizable functional group used in the present invention is blended in the paint in an amount sufficient to carry out both the photocatalyst particle dispersion effect and the binder effect in the coating film.

  In consideration of the above circumstances, the amount of the silane coupling agent having an ultraviolet polymerizable functional group in the present invention is 3 to 100 parts by weight, more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the photocatalyst particles. Use at 70 parts by weight is preferable because the dispersion effect of the photocatalyst particles and the binder effect in the coating film are satisfactorily exhibited. If the addition amount of the silane coupling agent exceeds 100 parts by weight, the photocatalyst particles are completely buried, and the photocatalytic function may be impaired. Moreover, when the addition amount of the silane coupling agent is less than 3 parts by weight, the dispersion effect of the photocatalyst particles and the binder effect may not be desirably exhibited.

[Photopolymerization initiator]
The photopolymerization initiator used in the present invention starts a polymerization reaction between the ultraviolet polymerizable functional groups when the coating film containing the silane coupling agent having the ultraviolet polymerizable functional group is irradiated with ultraviolet rays. As long as it can be used, it can be appropriately selected and used. For example, radicals are generated by irradiation of ultraviolet rays, and the radicals trigger polymerization, such as benzoin derivatives and the like. In particular, benzyl dimethyl ketal (BDK such as Ciba Specialty) that is an alkylphenone photopolymerization initiator. (Irgacure 651 manufactured by Tea Chemicals) and α-hydroxyalkylphenone (for example, Irgacure 184, 907, 369, 379 manufactured by Ciba Specialty Chemicals) can be suitably used. In addition, a photoacid generator that generates a cation (acid) when irradiated with ultraviolet rays, a photobase generator that generates an anion (base) when irradiated with ultraviolet rays, and the like can also be used. Moreover, it is also possible to use said 3 types of photoinitiators individually or in combination.

  In the present invention, since the polymerization of the polymerizable functional group of the silane coupling agent is carried out particularly by ultraviolet rays, the polymerization reaction can proceed even at room temperature. Therefore, even if the base material for forming the coating film of the present invention is a molded product or sheet made of a material having low heat resistance such as polyester or styrene, problems such as discoloration or deformation of the base material may occur. A coating film can be formed without any problem. In addition, in the case of polymerizing with ultraviolet rays, the curing time is shorter than that in thermal polymerization, so it is possible to suppress the load on the material and the substrate in the coating film during the polymerization reaction, and to improve the production efficiency. Can be improved.

  The amount of the photopolymerization initiator added to the paint is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the silane coupling agent having the ultraviolet polymerizable functional group. 0.3 parts by weight to 10 parts by weight is more preferable, and 0.5 parts by weight to 5 parts by weight is further preferable. By using the photopolymerization initiator in the above preferred range, the molecules of the silane coupling agent bonded by the siloxane bond constituting the coating film can be favorably crosslinked.

[Optional ingredients]
The coating composition for forming a photocatalytic coating film of the present invention may contain at least the photopolymerization initiator, the silane coupling agent, and the photopolymerization initiator described above, but within a range not departing from the gist of the present invention. Any other ingredients can be further added. For example, optional components include auxiliary binder components, silica, alumina, zirconia, zinc oxide, flame retardants, antioxidants, fillers, and the like.

  The auxiliary binder is a component that may be added to the coating composition for forming a photocatalytic coating film in order to prevent the base material from being oxidized and deteriorated by the oxidizing action of the photocatalyst particles contained in the coating film. It is. More specifically, as in the case of the silane coupling agent in the present invention, an auxiliary for forming a coating film by intermolecular bonding by hydrolysis / condensation reaction of functional groups or photopolymerization by ultraviolet irradiation. Binder. Due to the presence of such an auxiliary binder, an oxidizing action is exhibited by the photocatalyst on the surface of the coating film, but the influence of the oxidizing action is prevented or suppressed on the substrate side supporting the coating film.

Specific examples of the auxiliary binder include tetraethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, ethyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, Examples thereof include diethyldimethoxysilane and hydrolysates or condensates thereof. These auxiliary binders form a crosslinked structure by hydrolyzing at least a part of functional groups and then performing a condensation reaction. In addition, as said condensate, the thing about a 2-30 mer is used suitably, for example, the Colcoat Co., Ltd. methyl silicate 51, the methyl silicate 53A, the ethyl silicate 40, the ethyl silicate 48, HAS-1, HAS-6, Commercial products such as HAS-10, Colcoat P, Colcoat N103X and the like can be used.

  Another example of the auxiliary binder is a vinyl group-containing silicone compound as a type that can be cross-linked by ultraviolet irradiation. As a commercially available product of the vinyl group-containing silicone compound, both terminal methacryl-modified silicone oil X-22-164 manufactured by Shin-Etsu Chemical Co., Ltd. or one terminal methacryl-modified silicone oil X-22-2475 can be suitably used. . Other examples of the vinyl group-containing silicone compound include vinyltrimethoxysilane (KBM1003), vinyltriethoxysilane (KBE1003), p-styryltrimethoxysilane (KBM1403), 3-methacryloxypropylmethyldimethoxysilane ( KBM502), 3-methacryloxypropyltolylmethoxysilane (KBM503), 3-methacryloxypropylmethyldiethoxysilane (KBE502), 3-methacryloxypropyltriethoxysilane (KBE503), 3-acryloxypropyltrimethoxysilane (KBM5103) ) Etc. (all manufactured by Shin-Etsu Chemical Co., Ltd.) can be used.

  Still other examples of auxiliary binders include vinyl group-containing compounds other than those described above. Examples of the vinyl group-containing compound include a commercially available UV curable hard coat agent (for example, Defender FH-8000ME manufactured by Dainippon Ink and the like). When a vinyl group-containing compound is used as an auxiliary binder in the present invention, a photocatalyst particle pretreated with a silane coupling agent having an ultraviolet crosslinkable functional group, which is an essential component of the present invention, is added to a solvent. Then, a vinyl group-containing compound is added to the above solvent, or a photocatalyst particle pretreated with a silane coupling agent having an ultraviolet crosslinkable functional group is added to the solvent, and this is made into one solution to contain a vinyl group. The present invention can be carried out by adding the compound to another solvent to make it another one liquid and as a two-pack type paint.

[solvent]
As each of the above components in the present invention, a solvent appropriately selected from various solvents generally used for producing a paint can be used. For example, alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, and pentanol can be used alone or in any combination as a solvent for the coating material of the present invention. The solvent is preferably adjusted so that the weight (concentration) of the photocatalyst particles is 5 to 20% by weight when the total weight of the solvent and solute is 100 in the produced paint. It is more preferable to adjust to be in the range of%.

  As a method of dispersing the photocatalyst particles with a silane coupling agent in an arbitrary solvent, the photocatalyst particles and the silane coupling agent are added to an arbitrary solvent, and in addition to this, a dispersing agent such as beads is further added. You may disperse | distribute with a bead mill. Similarly, methods such as a ball mill and a sand mill may be employed. Alternatively, the photocatalyst particles in the paint can be well dispersed by adjusting the paint by mixing the photocatalyst particles, the silane coupling agent and the solvent using various blenders such as a ribbon blender and a tumbler. Similarly, a mixer such as a Henschel mixer may be used.

[Combination ratio]
The amounts of the components and the solvent used in the coating described above are as described in each item, and can be appropriately adjusted according to the purpose and application. Examples of preferable blending of the paint include 40 to 90 parts by weight of the photocatalyst particles, 5 to 30 parts by weight of the silane coupling agent, and in the case of using an auxiliary binder, it is adjusted within the range of 9 to 30 parts by weight, It is preferable to adjust the photocatalyst particles to 0.5 to 3% by weight with respect to the total solid content in the paint. In consideration of the applicability to the substrate surface, the total solid content in the coating is preferably adjusted to about 1 to 15%, more preferably 3 to 10%, based on the total amount of the coating.

  The coating composition for forming a photocatalytic coating film of the present invention described above can be used as a one-pack type in which all additive components are mixed. In particular, since the paint of the present invention contains a silane coupling agent having a UV-polymerizable functional group and a photopolymerization initiator as essential components, photopolymerization may start in the paint, thus preventing polymerization. Therefore, it is desirable to use a light-shielding container as a container for storing the one-pack type paint of the present invention. Further, by shielding the paint from light, the oxidizing action of the photocatalyst particles in the paint can be satisfactorily suppressed. When it is desired to strictly prevent photopolymerization in the paint, the air in the container for storing the paint may be replaced with an inert gas. Alternatively, in the one-pack type paint of the present invention, polymerization in the paint can be prevented by adding a photopolymerization initiator afterwards. In such a case, it is desirable to add a photopolymerization initiator immediately before the coating material is applied to the substrate surface.

  In the case of producing the one-pack type paint of the present invention, necessary components can be simultaneously added to an appropriate solvent, but the components can be mixed and dispersed or dissolved in any order. For example, as the first mixing step, an amount of silane coupling agent necessary for dispersing the photocatalyst particles is separated, mixed with the photocatalyst particles, and the photocatalyst particles are preliminarily treated to be in a dispersed state, and then the second mixing. As the process, a method of adding the remaining silane coupling agent is preferable. Depending on the amount of ultraviolet rays that the paint is exposed to, when the photocatalyst particles and the silane coupling agent having an ultraviolet polymerizable functional group are present in the paint, the action of the photocatalytic particles causes the ultraviolet polymerizable functional group to polymerize. However, in the method of adding the silane coupling agent in two steps as described above, it is expected to significantly suppress the polymerization of functional groups due to the action of the photocatalyst particles contained in the paint. preferable. Incidentally, the photopolymerization initiator can be arbitrarily determined whether it is added at the same time as the above-mentioned remaining silane coupling agent or further added in a later step, from the viewpoint of preventing the start of photopolymerization in the paint. It is desirable to add the photopolymerization initiator last.

  Moreover, the coating material of this invention can also be made into a 2 liquid type. In the case of producing as a two-component type, the above-described components and the blending ratio thereof are understood as the components and ratios contained as a whole when the two components are mixed. One component may be added in two liquids. For example, in the first liquid, among the total amount of photocatalyst particles and the total amount of silane coupling agent having an ultraviolet polymerizable functional group, a silane having an ultraviolet polymerizable functional group in an amount necessary for dispersing the photocatalytic particles. The second liquid can be prepared so as to include other materials including the silane coupling agent having the remaining ultraviolet polymerizable functional group, and a two-pack type paint can be obtained. In such a case, the photopolymerization initiator may be added to either the first liquid or the second paint liquid, and when mixing the two liquids, a photopolymerization initiator is added together. May be.

  Below, the photocatalytic coating film of this invention and a laminated body provided with this photocatalytic coating film are demonstrated.

Photocatalytic coating:
The photocatalytic coating film of the present invention can be obtained by applying the above-described coating material of the present invention to a substrate to form a coating film. As a method for applying the coating material of the present invention to a substrate, any of conventionally known methods can be appropriately selected and employed. Specific examples include a method of applying a paint to a substrate surface using a wire bar, a method of spraying a paint on a substrate surface, a gravure coating method, a roll coating method, a dipping method (dip coating method). In various printing methods such as the above, a method of forming a coating film on the substrate surface using the coating material of the present invention instead of ink, and the like can be mentioned.

  In addition, as for application | coating of the said coating material, it is desirable to apply | coat an appropriate amount so that the thickness of the coating film after drying may be 0.05-10 micrometers. If the thickness of the resulting coating film after drying exceeds 10 μm, the photocatalyst particles may be completely buried in the coating film, and effective photocatalytic action may not be exhibited by the ultraviolet rays irradiated to the coating film surface. is there.

  In general, the substrate on which the paint is applied is subsequently dried. By the drying treatment, the solvent in the coating film is removed, the silane coupling agent is hydrolyzed, and the silica formation reaction by silanol group dehydration condensation reaction is promoted to form a cured coating film.

  Further, by irradiating the surface of the cured coating film with ultraviolet rays, the UV-polymerizable functional group of the silane coupling agent located mainly on the coating film surface side is polymerized to complete the photocatalytic coating film of the present invention. .

[Base material]
As a base material for supporting the coating film of this invention, any of an organic base material and an inorganic base material may be sufficient. As specific examples of the organic base material, various materials such as plastic film, plastic molded body, plywood, decorative board, artificial marble, paper, leather, synthetic leather, and cloth can be used as the base material. On the other hand, specific examples of the inorganic material include glass, metal, tile, concrete, ceramic, cement, and the like. Among them, a plastic film or the surface of a plastic molded body is used as the organic substrate, and glass is used as the inorganic substrate. The coating property of the present invention is good, and a photocatalytic coating can be easily formed. It is desirable because the durability of the coating film is also excellent.

Laminate:
The laminate of the present invention is formed from a base material and the photocatalytic coating film of the present invention. It may be composed of two layers of a base material and a photocatalytic coating film, or may be a laminate of three or more layers provided with further arbitrary layers without departing from the gist of the present invention. As a laminated body of three or more layers, an arbitrary layer may be present between the substrate and a photocatalytic coating film in which the substrate is formed of a plurality of layers.

  The laminate of the present invention has a photocatalytic coating film on the surface thereof, and is installed, used or stored in a place where ultraviolet rays or visible rays can be irradiated. Is preferably used on the surface of what is expected. For example, the laminate of the present invention is used on a window glass, a mirror, an outer wall of a building, a decorative sheet that is an interior material of a building, or an article itself such as a decorative board, furniture, play equipment, clothing, tableware, or the surface of the article. be able to.

  Examples of the variable color sheet of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
In order to prepare the coating material of this invention, the photocatalyst dispersion liquid was obtained as follows as a 1st mixing process. First, as a photocatalyst particle, as a silane coupling agent having a nitrogen-doped visible light responsive photocatalyst (manufactured by Toyota Tsusho Co., Ltd., VCT02, primary particle diameter 7 nm) and an ultraviolet polymerizable functional group for dispersing the photocatalyst particle. 100 g of 3-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM503), 4400 g of isopropyl alcohol as a solvent, and 150 g of zirconia beads (Nikkato Co., Ltd., particle size 30 μm) are set in a bead mill MSC100 manufactured by Mitsui Mining Co., Ltd. Then, a photocatalyst dispersion liquid in which aggregates of photocatalyst particles having an average particle diameter of 50 nm were dispersed was obtained by pulverization for 3 hours at a peripheral speed of 10 m / sec, a circulation rate of 0.8 L / min, and a liquid temperature of 32 ° C. In addition, the average particle diameter of the said photocatalyst particle | grain was measured using Nikkiso Co., Ltd. Microtrac UPA-EX150 as a particle diameter measuring apparatus.

  Next, the coating material was prepared using the compound and solvent of the following contents as a 2nd mixing process. 2.3 parts by weight of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM503) to form a skeleton by a siloxane bond on the surface of the substrate with respect to 100 parts by weight of the photocatalyst dispersion liquid, Mix 0.43 parts by weight of Irgacure 184 as a photopolymerization initiator, 4.3 parts by weight of ion-exchanged water as condensation water, and 179 parts by weight of isobutanol as a diluent solvent, and stir with a homogenizer at 5000 rpm for 10 minutes. Thus, a photocatalytic coating film-forming coating material was prepared and used as the coating material 1 of the present invention.

As a base material, the coating 1 is applied to one surface of a 50 μm thick highly weather-resistant PET film (manufactured by Teijin DuPont) with a wire bar to a thickness of 5 g / m ² (Wet), and then in a drying oven The substrate was placed on and dried by heating at 80 ° C. for 15 minutes. Next, after taking out from the drying oven and returning to room temperature, an ultraviolet curing device with a conveyor made by Iwasaki Electric (use lamp: 6 kW × 1 lamp, 160 W / cm ² , irradiator: aluminum mirror condensing type, conveyor speed: 2 To 20 m / min, irradiation distance: 120 to 170 mm), and the coating film surface was irradiated with ultraviolet rays to obtain a laminate composed of a substrate and a coating film, which was referred to as Example 1. In addition, the said ultraviolet irradiation was implemented on the conditions of conveyor speed 2.5m / min and irradiation distance 150mm.

(Example 2)
Except that 0.043 parts by weight of Irgacure 651 was used as a photopolymerization initiator, a paint for forming a photocatalytic coating film was prepared in the same manner as paint 1, and this was used as paint 2 of the present invention. Then, a laminate was produced in the same manner as in Example 1 except that the paint 2 was used, and was used as Example 2.

(Comparative Example 1)
A paint for forming a photocatalytic coating film was prepared in the same manner as paint 1 except that Irgacure 184 was not blended (no photopolymerization initiator was used), and this was used as paint 3 as a comparative example. A laminate was prepared in the same manner as in Example 1 except that the coating material 3 was used, and it was designated as Comparative Example 1.

(Comparative Example 2)
Instead of 2.3 parts by weight of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM503) blended later, HAS10 (manufactured by Colcoat Co., Ltd.) which is an ethyl silicate hydrolyzate having no vinyl group ) Was used in the same manner as paint 1 except that 23 parts by weight was used, and this was used as paint 4 as a comparative example. A laminate was prepared in the same manner as in Example 1 except that the coating material 4 was used, and it was designated as Comparative Example 2.

(Comparative Example 3)
A laminate was prepared in the same manner as in Example 1 except that the coating material 1 described in Example 1 was used and ultraviolet irradiation treatment by an ultraviolet curing device was not performed.

(Comparative Example 4)
A laminate was prepared in the same manner as in Example 2 except that the coating material 2 described in Example 2 was used and ultraviolet irradiation treatment by an ultraviolet curing device was not performed.

(Chemical resistance evaluation)
A cotton cloth soaked with methanol was prepared, and the coating film surfaces of Example 1, Example 2 and Comparative Examples 1 to 4 were manually reciprocated 100 times to wipe the coating film surface. Then, the coating film surface was observed with the naked eye and evaluated as follows. The evaluation results are summarized in Table 1. Similarly, evaluation results to be described later are collectively shown in Table 1.

No scratches were observed on the coating surface ...
Clear scratches were observed on the coating surface.

(Pencil hardness test)
According to JIS K5400, a pencil scratch coating film hardness tester (Toyo Seiki Seisakusho Co., Ltd.) using a pencil of each hardness on the coating surfaces of Examples 1, 2 and Comparative Examples 1 to 4 at a load of 500 g. When the surface of the coating film was scratched at 5 locations and scratches were confirmed at two or more locations, the hardness of the coating film was measured as one hardness lower than the pencil hardness.

(Evaluation of photocatalytic performance)
The surface of the coating film of Example 1, Example 2 and Comparative Examples 1 to 6 was irradiated with black light (FL20S / BLB, manufactured by Toshiba Lighting & Technology Corp.) (10 mW / cm ² , irradiation distance 18 cm) for 16 hours, and then ion-exchanged water. After washing at room temperature and drying at room temperature, pretreatment for photocatalytic performance evaluation was performed.

(Methylene blue fading test)
Next, a methylene blue (MB) fading test was performed as follows. First, on the surface of the coating film that has been pretreated as described above, two drops of ion-exchanged water are dropped with a dropper, and a 3 cm square OHP film is placed on the water droplet so that air does not enter the interface with the coating surface. L, a, and b (0) were measured with a color difference meter (CR-200B manufactured by Minolta Camera Co., Ltd.) to measure the color of the sample.
Next, 2 drops of 0.1 mmol / L methylene blue aqueous solution was dropped onto the sample with a dropper, and a 3 cm square OHP film was placed on the water drop so as not to enter air, and a color difference meter (Minolta Camera Co., Ltd.). L, a, b (1) was measured by CR-200B), and the color difference ΔE was calculated from the difference between L, a, b (0) and L, a, b (1) as follows. Was the initial value ΔE (0) before methylene blue decomposition.
The sample was irradiated with a photocatalytic activity photocatalyst evaluation checker PCC-2 black light (0.26 mW / cm ² , 100 LUX, irradiation distance 2.5 cm) manufactured by ULVAC-RIKO Co., Ltd. for 3 hours, and a color difference meter for 3 hours. L, a, b (3) after irradiation was measured, and the color difference ΔE was calculated as follows from the difference between L, a, b (0) and L, a, b (3). The color difference ΔE (3) was used.
ΔE (0) = ((L ₀ −L ₁ ) ² + (a ₀ −a ₁ ) ² + (b ₀ −b ₁ ) ² ) ^0.5
ΔE (3) = ((L ₀ −L ₃ ) ² + (a ₀ −a ₃ ) ² + (b ₀ −b ₃ ) ² ) ^0.5

The results of the methylene blue fading test were evaluated as follows.
ΔE (3) was less than half of ΔE (0)
ΔE (3) exceeded half of ΔE (0)

(Acetaldehyde (AA) degradation test)
In addition, as an evaluation with different photocatalytic properties, Examples 1 and 2 and Comparative Examples 1 to 6, which are base materials provided with a coating film pretreated in the same manner as described above, were cut into A4 size, and the back surface of the base material (coating A specimen was prepared by coating the side with a non-significant film and a side with aluminum tape. Each test specimen was placed in a 5 L transparent tedra bag, and 25 ppm of acetaldehyde (AA) was sealed in the tedra bag. Thereafter, a white fluorescent lamp (manufactured by Toshiba Corporation, FL20SS W / 18, two, 6000 lux, irradiation distance to the coating surface of 18 cm) was irradiated, and the concentration of acetaldehyde in the tedra bag was measured and evaluated as follows.

The concentration of acetaldehyde was 5 ppm or less.
The concentration of acetaldehyde exceeded 5ppm ...

The contents of the abbreviations used in Table 1 are as follows.
KBM503: manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane IRGA184: manufactured by Ciba Specialty Chemicals, 1-hydroxy-cyclohexyl-phenylketone, IRGACURE184
IRGA651: Ciba Specialty Chemicals, 2,2-dimethoxy-1,2-diphenylethane-1-one, IRGACURE651
HAS10: Colcoat Co., Ltd., ethyl silicate hydrolyzate, solid content 10%
VCT: VCT-02 manufactured by Toyota Tsusho Corporation, 2 parts by weight of KBM503 and 88 parts by weight of IPA per 10 parts by weight, and a photocatalyst dispersion liquid dispersed in a bead mill

  As shown in Table 1, each of the examples and comparative examples uses a nitrogen-doped visible light responsive photocatalyst VCT-02, so that the acetaldehyde decomposition test is also performed by irradiation with black light in a methylene blue fading test. It was confirmed that a good photocatalytic function was exhibited even by irradiation with a white fluorescent lamp.

  Examples 1 and 2 were confirmed to have desirable chemical resistance in the chemical resistance test, and the hardness of the coating film was also confirmed to have moderate hardness with HB. . Further, in the chemical resistance test, it was confirmed that the film was excellent in friction resistance and toughness of the coating film because it was not damaged even after 100 reciprocal wiping with a cotton cloth.

  On the other hand, it was confirmed that all of the comparative examples had low chemical resistance and the pencil hardness was 2B, which was very brittle.

  In Examples 1 and 2 in which good photocatalytic properties were shown, it is not clear why the chemical resistance and the coating film hardness were both excellent, but Examples 1 and 2 and Comparative Examples After comparing the contents, the present inventors infer as follows. That is, in this example, 3-methacryloxypropyltrimethoxysilane, which is a silane coupling agent having an ultraviolet polymerizable functional group, blended in the second mixing step is irradiated with ultraviolet rays in the presence of a photopolymerization initiator. By polymerizing between the UV-polymerizable functional groups in the coating film, and thereby building a crosslinked structure in the coating film, it is excellent in coating film hardness, coating film chemical resistance, and friction resistance. It was inferred that a laminate was obtained. It was also confirmed that the photocatalytic function was maintained well even under such a crosslinked structure.

Claims (5)

A paint for forming a photocatalytic coating film, comprising photocatalyst particles, a silane coupling agent having an ultraviolet polymerizable functional group, and a photopolymerization initiator. 2. The paint for forming a photocatalytic coating film according to claim 1, wherein the ultraviolet polymerizable functional group is a vinyl group, or a vinyl group is provided in the ultraviolet polymerizable functional group. 3. The coating composition for forming a photocatalytic coating film according to claim 1 or 2, wherein the photocatalyst particles are of a visible light responsive type. A photocatalytic coating film formed by applying the photocatalytic coating film-forming coating material according to any one of claims 1 to 3 on a substrate and then irradiating with ultraviolet rays. A laminate comprising a base material and the photocatalytic coating film according to claim 4.