Paint composition

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a coating composition. More specifically, the present invention relates to a coating composition that can be suitably used as, for example, a coating material for a top coating, and can form a coating film capable of maintaining bactericidal and antibacterial properties for a long period of time.

【0002】

[Conventional technology]

As one of the methods for classifying paints, a method for classifying paints into undercoat paints and topcoat paints is known. A stable coating film having desired properties is formed by forming a coating film of the undercoat paint on the surface of the material and then further forming a coating film of the topcoat paint on the surface of the coating film of the undercoat paint to form a layered coating film. It is possible to form a surface. The performance required for such an undercoat paint is mainly good adhesion to both the material to which the undercoat paint is applied and the topcoat paint, while the topcoat paint is mainly required to have weather resistance.

【0003】

Conventionally, a coating composition containing titanium dioxide as a pigment has been used as a topcoat coating material. In such a composition, rutile-type titanium dioxide having a thermally stable crystal structure is used in order to prevent deterioration of the coating film due to exposure to ultraviolet rays. Further, in order to suppress the photocatalytic action of the rutile-type titanium dioxide itself, the titanium dioxide particles themselves are generally surface-treated. Therefore, the topcoat paints currently on the market are designed to reduce the photocatalytic action on the surface of the coating film as much as possible, and titanium dioxide having high photocatalytic activity is intentionally blended with the topcoat paint to provide a coating film having a photocatalytic action. The technical idea of forming a photocatalyst has not existed in the past.

【0004】

Further, as an antibacterial coating composition, one to which silver or copper ions or compounds or other antibacterial substances are added is known. The coating film formed by such a coating composition has an effective antibacterial action in a place where there are few pollutants, but the surface of the coating film is easily covered with dust such as organic substances, such as outdoors, a bathroom, or a food factory. In the harsh usage environment of, there is a problem that the antibacterial action is lost in a short period of time. Further, since the silver compound itself is expensive, there is a problem that an increase in manufacturing cost is unavoidable.

【0005】

On the other hand, as a means for evaluating the photocatalytic activity on the surface of the coating film, a method of evaluating from a quantitative value of a reaction product or a reaction product using a closed reactor, or a method of mixing a phenol-based radical trapping substance in a coating material is used. A method for measuring an electron spin resonance (ESR) spectrum (Japanese Patent Laid-Open No. 61-270640) is known. The former has a drawback that the operation is complicated and it takes a long time to evaluate, and the latter has a drawback that the photocatalytic activity inside the coating film is evaluated at the same time as the surface of the coating film.

【0006】

[Problems to be Solved by the Invention]

An object of the present invention is to provide a coating composition which can stably form a coating film surface having a bactericidal / antibacterial action and can be suitably used as, for example, a topcoat coating. Another object of the present invention is to provide a coating composition that forms a coating film surface that has sufficient weather resistance and can maintain a bactericidal / antibacterial action for a long period of time even in a harsh environment. Further, it is another subject of the present invention to provide a quick and simple method for evaluating the photocatalytic activity of the coating film surface.

【0007】

[Means for solving problems]

As a result of various studies to solve the above problems, the present inventors have found a coating composition containing titanium dioxide having high photocatalytic activity as a pigment and a fluororesin or polysiloxane resin as a coating film-forming resin. It has been found that a coating film having excellent weather resistance can be formed, and that the above composition can stably form a coating film having a bactericidal and antibacterial action for a long period of time even in a harsh environment. The present invention has been completed based on these findings.

【0008】

That is, the present invention provides a coating composition containing titanium dioxide and one or more coating film forming resins selected from fluororesins and polysiloxane resins to form a coating film surface having a photocatalytic action. is there. According to a preferred embodiment of the present invention, the above-mentioned coating composition in which titanium dioxide is fine particles having an impurity content of 5% or less and an average particle size of 1 μm or less; the above-mentioned coating composition in which titanium dioxide is an anatath type crystal type; Provided are the above-mentioned coating composition which is titanium dioxide fine particles having high photocatalytic activity; and the above-mentioned coating composition capable of forming a coating film in which a part of titanium dioxide is exposed from the surface of the coating film.

【0009】

Further, as a more preferable embodiment, the above coating composition in which active oxygen is generated from oxygen molecules or water molecules existing on the surface of the coating film by irradiation with light having a wavelength of 400 nm or less; the active oxygen decomposes organic substances adhering to the surface of the coating film. The above-mentioned coating composition; the above-mentioned coating composition forming a bactericidal / antibacterial coating surface; one or 2 of the antibacterial / bactericidal compounds selected from the group consisting of silver ions, copper ions, silver compounds, and copper compounds. The above-mentioned coating composition containing seeds or more; and the above-mentioned coating composition to be used as a topcoat coating material are provided.

【0010】

BEST MODE FOR CARRYING OUT THE INVENTION

The coating composition of the present invention is characterized in that titanium dioxide having high photocatalytic activity is blended as a pigment. As the titanium dioxide having such properties, titanium dioxide having an anatas type crystal form defined in JIS K 5116 (pigment) and JIS K 1409 (for synthetic fibers) is suitable. For example, it is particularly preferable to use high-purity fine particles having an impurity content of less than 5%, preferably less than 2%, among titanium dioxide having an anatas-type crystal form. The particle size of titanium dioxide is, for example, 1 μm or less, preferably 0.3 μm or less on average by electron microscopy.

【0011】

The photocatalytic activity of the titanium dioxide fine particles themselves can be measured, for example, by irradiating the formic acid aqueous solution with ultraviolet rays in the presence of titanium dioxide and quantifying the production rate of carbon dioxide produced by the oxidative decomposition of formic acid. Titanium dioxide that has been surface-treated to enhance the photocatalytic action can also be used. Examples of such fine particles include titanium dioxide and Nb carrying Pt and the like.⁵⁺And Sb⁵⁺Titanium dioxide treated with such as is known. It is not preferable to use titanium dioxide fine particles that have been surface-treated in order to suppress the photocatalytic action, but the surface-treated titanium dioxide has high photocatalytic activity as described above. In some cases, it goes without saying that it is included in the scope of the present invention.

【0012】

The coating composition of the present invention is characterized by containing one or more selected from a fluororesin and a polysiloxane resin as a coating film-forming resin. In the composition of the present invention, these resins are components that act as main elements for forming a coating film. Among these coating film-forming resins, the property that a part of the pigment having a hydrophilic surface is exposed on the surface of the coating film without being deteriorated by active oxygen generated on the surface of the coating film due to the photocatalytic activity of titanium dioxide. Can be particularly preferably used. In order to expose titanium dioxide on the surface, the pigment concentration may be higher than that of a commonly used paint, or the pigment dispersion time may be shortened. Whether or not the coating film-forming resin has these properties can be easily determined by those skilled in the art according to the evaluation method described in the examples of the present specification, and the type and blending amount of titanium dioxide and the like can be easily determined. Needless to say, an appropriate type of coating film-forming resin can be selected according to the above.

【0013】

More specifically, the fluororesin formed by the coating film can be preferably a fluororesin produced by copolymerization of a fluoroolefin and a vinyl ether or a vinyl ester. As the crosslinkable reactive group of the fluorine copolymer, for example, a hydroxyl group, a carboxyl group, a glycidyl group or the like can be used. As a thermoplastic fluororesin, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), or PVF (polyvinyl fluoride) or the like may be used. These fluororesins are commercially available, for example, Lumiflon manufactured by Asahi Glass Co., Ltd., Zeffle manufactured by Daikin Industries, Ltd., Cefral Coat manufactured by Central Glass Co., Ltd., Zaffron manufactured by Toa Synthetic Co., Ltd., and Dainippon Ink Co., Ltd. Fluoronate, Kainer manufactured by Elf Atchem Co., Ltd., etc. can be used. Generally, thermosetting fluororesin (Mn = 4,000 ~ 10,000) or thermoplastic fluororesin (Mn = 10,000 ~ 50,000) Can be used.

【0014】

The polysiloxane resin has the following general formula: R¹-Si (OR²) (OR³)-[-O-Si (OR)⁴) (OR⁵)-]_n-OR⁶The polysiloxane resin represented by is preferably used. In the formula, R¹Or R⁶Are independently hydrogen atoms; linear or branched alkyl groups such as methyl, ethyl, n-propyl, or isopropyl groups, preferably C._1-6It represents an alkyl group; or an aryl group such as a phenyl group or a naphthyl group, which may be the same or different from each other. n indicates an integer from 1 to 100. More specifically, polyhydroxysiloxane, polymethoxysiloxane, polyethoxysiloxane, polybutoxysiloxane and the like can be mentioned.

【0015】

The blending ratio of titanium dioxide and the coating film-forming resin in the coating composition of the present invention is not particularly limited. For example, when a thermosetting fluororesin having a reactive group is used, the resin and, if necessary, the resin are used. Titanium dioxide should be used in a proportion of 50 to 140 parts by weight, preferably 80 to 120 parts by weight, based on a total of 100 parts by weight (solid content) of the curing agent (for example, isocyanate). Further, for example, when a resin composition containing a fluororesin (for example, vinylidene fluoride resin) or a polysiloxane resin in a proportion of 50 parts by weight (solid content) or more in 100 parts by weight (solid content) of the composition is used. It is also preferable to add titanium dioxide in a proportion of 50 to 140 parts by weight, preferably 80 to 120 parts by weight, based on 100 parts by weight of the resin composition.

【0016】

In the coating composition of the present invention, in addition to one or more coating film-forming resins selected from fluororesins and polysiloxane resins, those known in the art as coating film-forming components may be used in combination. Good. Examples of such coating film-forming components include oils such as flaxseed oil and soybean oil; synthetic resins such as polyester resin, acrylic resin, phenol resin, urea resin, melamine resin, phthalic acid resin, and vinyl resin; nitrocellulose. Such as cellulose derivatives; rubber derivatives such as rubber chloride; water-soluble compounds such as polyvinyl alcohol can be used. The blending amount of these coating film-forming components is not particularly limited, but the blending amount should be appropriately selected and blended so that the performance of the coating film is not deteriorated by the photocatalytic action of titanium dioxide. In addition, the coating composition of the present invention may contain additives for drying, curing, or improving various physical properties of the coating film. For example, a desiccant, a curing agent, a plasticizer, a dispersant, an emulsifier and the like can be blended as needed. The types and amounts of such additives are well known to those skilled in the art and can be easily selected as needed.

【0017】

The coating composition of the present invention can generally be produced by dispersing or dissolving the above-mentioned non-volatile component in a solvent or a diluent according to a method well known to those skilled in the art. The type of solvent or diluent is not particularly limited as long as it easily evaporates during the drying process and does not remain in the coating film, but is generally an alcohol such as ethyl alcohol or butyl alcohol; petroleum spirit, kerosene. Hydrocarbons such as xylene and sorbesso; esters such as ethyl acetate; ketones such as acetone, ethylmethylketone and cyclohexanone; ethers such as diethylene glycol and cellosolve, and halogenated aliphatic hydrocarbons such as trichloroethylene and methylene chloride. Etc. can be used alone or in combination of two or more.

【0018】

Without being bound by any particular theory, a portion of titanium dioxide is exposed on the surface of the coating film formed by applying the coating composition of the present invention. When this titanium dioxide is irradiated with light having an energy equal to or higher than the band gap energy (wavelength 400 nm or less), electron-hole pairs are generated, but when oxygen molecules or water molecules react with these electron-hole pairs, it is high. Active oxygen such as superoxide ion, hydrogen peroxide, and hydroxyl radical, which have oxidizing power and can decompose organic substances, are generated (Noda, H., et al., Bull. Chem. Soc. Jpn., 85. , 2505, 1992; ibid, 66, 455, 1993; ibid, 66, 3542, 1993; ibid, 67, 2031, 1994).

【0019】

For example, when the surface of the coating film formed by the coating composition of the present invention is covered with dust containing organic substances such as soot, dirt, tar, microorganisms, and viruses, the organic substances on the coating film are produced by the photocatalytic action of titanium dioxide. Is oxidized and decomposed, so that organic substances do not accumulate on the surface of the coating film. Since organic substances such as microorganisms and viruses are easily oxidatively necrotic, a long-lasting bactericidal and antibacterial action can be expected on the coating film surface. In general, sterilization means killing microorganisms such as yeast, bacteria, fungi, and viruses, and antibacterial means a state in which the growth of these microorganisms is suppressed. -The term antibacterial should be interpreted in the broadest sense, including these concepts.

【0020】

Since the light of the above wavelength is sufficiently contained in the light of sunlight and fluorescent lamps, the surface of the coating film formed by the coating composition of the present invention has sufficient bactericidal and antibacterial effects both indoors and outdoors. There is. However, in order to form a coating film having a higher bactericidal / antibacterial effect, or to form a coating film having a bactericidal / antibacterial effect even in a dark place, silver ion, copper ion, or a compound of silver or copper ( (Silver oxide, copper oxide, cuprous oxide, etc.) can be blended as a bactericidal / antibacterial compound. According to such an aspect, a coating film having very excellent bactericidal / antibacterial properties can be formed by blending an extremely small amount of the bactericidal / antibacterial compound, which is preferable from the viewpoint of manufacturing cost. Further, since it is not necessary to add a large amount of bactericidal / antibacterial compounds in order to enhance the bactericidal / antibacterial property of the coating film surface, the weather resistance and stability of the coating film are not impaired.

【0021】

According to another aspect of the present invention, there is a method for measuring the photocatalytic activity of a thin film surface formed by a thin film-forming composition containing a substance having photocatalytic activity, wherein the following steps: (a) Photoexcited thin film surface. Step of reacting titanium dioxide with water or oxygen: (b) Step of spin-trapping hydroxyl radicals generated on the surface of the coating film by the reaction; and (c) Electron spin resonance of the signal intensity of the obtained spin adduct. A method is provided that includes a step of measuring by device;

【0022】

In the above invention, for example, a coating composition, a floor polish composition, or the like can be used as the thin film-forming composition, and examples of the substance having photocatalytic activity include titanium dioxide, preferably titanium dioxide high-purity fine particles and the like. Can be mentioned. For example, a coating film having a photocatalytic action formed by the above-mentioned coating composition of the present invention is a suitable target of this measuring method. A spin trap agent can be used as the spin trap, and for example, 5,5-dimethyl-2H-pyrrole-1-oxide (DMPO) or the like can be preferably used. According to this method, the photocatalytic activity of the thin film surface can be easily and quickly evaluated using the signal intensity measured in the third step as an index. The details of the above method are described in the following examples, but the method of the present invention is not limited to any details of the method of the examples.

【0023】

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples. Example 1 A coating composition having the composition shown in Table 1 below was produced. In the table, 1) is CTFE ((chlorotrifluoroethylene) / vinyl ether) resin (solid content 50%) manufactured by Asahi Glass Co., Ltd., and 2) is HDI (hexaethylene diisocyanate) trimer (solid content) manufactured by Bayer Corporation. 75%), and 3) is titanium dioxide JA3 manufactured by TAYCA Corporation (average particle size 0.18 μm, purity 98% or more). The formulations of a to d were dispersed in a paint shaker for 30 minutes to obtain a paint composition. The obtained coating composition was spray-coated on a concrete wall and left for a whole day and night to obtain a dry coating film of 40 μm.

【0024】

[table 1]

Paint composition abcdlmno Lumiflon LF200¹⁾ 100 100 100 100 100 100 100 100 Death module N²⁾ 10 10 10 10 10 10 10 10 Anatas type titanium dioxide³⁾ 75 75 30 30 57.5 28.75 5.75 2.88 Carbon Black 2-1 ---- ---- ---- Dissolving agent 100 100 100 100 50 50 50 50 [0025]

Example 2 A coating composition having the composition shown in Table 2 below was produced. In the table, 1) is PVdF resin (100% solid content) manufactured by Elf Atchem Co., Ltd., and 2) is 2,4,6-vinylidene fluoride copolymer (100% solid content) manufactured by Elf Atchem Co., Ltd., 3 ) Is Titanium Dioxide A-100 manufactured by Ishihara Sangyo Co., Ltd. (average particle size 0.15 μm, purity 98% or more), 4) is Titanium LLXLO manufactured by Titanium Industry Co., Ltd., and 5) is Dianal manufactured by Mitsubishi Rayon Co., Ltd. BR-64. The formulations of e to h were dispersed in a paint shaker for 30 minutes to obtain a paint composition. The iron plate was coated with the coating compositions of e and f, and the coating film was baked at 200 ° C. for 30 minutes to form a dry coating film of 40 μm. In addition, after painting the wall material with the paint compositions of g and h, it was left for a whole day and night to form a dry coating film of 80 μm.

【0026】

[Table 2]

<img file="JPH09100437A_D0001.tif" />【0027】

Example 3 A coating composition having the composition shown in Table 3 below was produced. In the table, 1) is a polysiloxane-based clear paint (solid content 40%) manufactured by Showa Technocoat Co., Ltd., and 2) is titanium dioxide KA-20 manufactured by Titan Kogyo Co., Ltd. (average particle size 0.2 μm, purity 98% or more). ). A paint composition was produced by dispersing the formulations i to k using a paint shaker. These compositions were brushed onto an iron plate and the coating was baked at 170 ° C for 20 minutes to form a 30 μm dry coating.

[Table 3]

<img file="JPH09100437A_D0002.tif" />【0028】

Example 4 Using the coating film-forming resin of Example 1, coating compositions l to o (Table 1) in which the blending ratio of anatas-type titanium dioxide was changed were prepared. Using these compositions, a 200 × 300 mm test piece (thickness 40 μm) was prepared, and a 4 × 30 mm strip-shaped sample piece was cut out. This sample piece was set in an ESR measurement cell (Labotech's tissue cell) and 900 mmol dm.^-310 to 30 μl of the spin trapping agent (5,5-dimethyl-2H-pyrrole-1-oxide: DMPO) was dropped onto the surface of the sample piece, covered with a quartz cover, and then set in an ESR measuring device. The ESR spectrum was measured after irradiating the test piece with light for 1 minute with a xenon lamp equipped with a filter capable of cutting wavelengths of 350 nm or less.

【0029】

FIG. 1 is an example of the ESR spectrum obtained by the above measurement. The four lines of 1: 2: 2: 1 are spin adduct signals generated by trapping hydroxyl radicals generated by reacting with water or oxygen by a spin trapping agent. The intensity of the obtained ESR signal is Mn, which is a standard sample.²⁺Normalized by the signal strength of (a / I).

【0030】

Figure 2 shows the relationship between the P / B and the normalized ESR signal intensity (average value of three measurements). From the results shown in this figure, it can be seen that the signal intensity increases as the blending ratio of the titanium dioxide fine particles increases. Therefore, the increase in signal intensity observed on the ESR spectrum is clearly due to the titanium dioxide fine particles, and it is possible to evaluate the photocatalytic activity of the coating film surface using this signal intensity as an index. The time required for measurement including the set of samples is 3 minutes / sample, and it is possible to quickly evaluate the photocatalytic activity of a large number of samples.

【0031】

Example 5 Using the coating compositions prepared in Examples 1 to 4, an antibacterial property test was conducted under room light irradiation according to the following method. Ten⁵Pieces / cm²After applying Escherichia coli on the surface of the coating film, the sample was placed under room light irradiation, and the number of Escherichia coli present on the sample surface was measured 1 hour later. As a result, bacterial growth was observed in the control group using the sample coated with only the coating film-forming resin, whereas bacterial growth was not observed at all in the coating material of the present invention.

【0032】

[Effect of the invention]

The coating film formed by the coating composition of the present invention has excellent weather resistance and can maintain a stable coating film for a long period of time. In addition, organic substances (dust, microorganisms, etc.) adhering to the coating film surface are decomposed by active oxygen generated in the presence of light, so the coating film surface is always kept fresh, and the bactericidal and antibacterial action of the coating film surface. Is characterized by being maintained for a long period of time. Further, according to the method of the present invention, there is a feature that the photocatalytic action on the surface of a coating film or the like can be measured easily and quickly.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the ESR spectrum of the spin adduct which trapped the hydroxyl radical generated when the coating composition of this invention was irradiated with light.

[Figure 2]

It is a figure which shows the relationship between the ESR signal intensity and P / B of the coating composition of this invention.