JP7679615B2 - Water-based paint and article coated with said water-based paint - Google Patents

Description

The present invention relates to a water-based paint and an article coated with the water-based paint.

Traditionally, water-based paints have been used to protect the surfaces of various items and to improve their appearance and functionality, but in recent years, hygienic functions such as antibacterial and antiviral properties have also been desired, and there is a particular demand for water-based paints that can produce coatings with antiviral properties (virus inactivation properties) as a measure against infections such as new strains of influenza, SARS (Severe Acute Respiratory Syndrome), and norovirus.

Paints containing quaternary ammonium salts are known as paints that can impart antibacterial and antiviral properties to coating films (see, for example, Patent Document 1). However, these paints have low safety, and there has been a demand for materials that do not contain quaternary ammonium salts.

Patent No. 6603495

The problem that the present invention aims to solve is to provide a water-based paint that is highly safe and can impart excellent antiviral properties to various substrates, and to provide an article coated with the water-based paint.

As a result of intensive research into solving the above problems, the inventors discovered that the above problems could be solved by using a water-based paint containing a specific photocatalyst, resin, and aqueous medium, and thus completed the invention.

That is, the present invention relates to an aqueous paint that contains a visible light responsive photocatalyst (A), a resin (R), and an aqueous medium (W).

The aqueous coating material of the present invention can form a coating film with excellent antiviral properties, and therefore can be suitably used for metal products such as automobiles, railway vehicles, ships, machinery, furniture, cans, and building structures; plastic products such as automobile parts and home appliances; wood products such as furniture and building materials; and inorganic material products such as building materials and glass.

The water-based paint of the present invention contains a visible light responsive photocatalyst (A), a resin (R), and an aqueous medium (W).

The visible light responsive photocatalyst (A) may be, for example, a composition containing titanium oxide (a), and preferably a titanium oxide (a) carrying a metal compound, since this provides even more excellent antiviral properties.

As the titanium oxide (a), for example, rutile type titanium oxide (a1), anatase type titanium oxide, brookite type titanium oxide, etc. can be used. These titanium oxides may be used alone or in combination of two or more. Among these, it is preferable to include rutile type titanium oxide (a1) because it has excellent photocatalytic activity in the visible light region.

The content (rutilated rate) of the rutile-type titanium oxide (a1) is preferably 15 mol % or more, more preferably 50 mol % or more, and even more preferably 90 mol % or more, in order to obtain even better antiviral properties in bright and dark places, organic compound decomposition properties in bright places, and visible light responsiveness.

Generally, the liquid phase method and the gas phase method are known as methods for producing the titanium oxide (a). The liquid phase method is a method in which titanium oxide is obtained by hydrolyzing or neutralizing titanyl sulfate obtained from a liquid in which raw ore such as ilmenite ore is dissolved. The gas phase method is a method in which titanium oxide is obtained by a gas phase reaction between oxygen and titanium tetrachloride obtained by chlorinating raw ore such as rutile ore. In addition, a method for distinguishing between titanium oxides produced by both methods is to analyze the impurities. Titanium oxide produced by the liquid phase method contains zirconium, niobium, etc., which are derived from impurities in the ilmenite ore. In contrast, the gas phase method includes a process of purifying titanium tetrachloride and removing impurities, so that these impurities are hardly contained in the titanium oxide.

Although titanium oxide produced by the gas phase method has the advantage of being able to produce uniform particle diameters, it is thought that secondary aggregates are difficult to produce, and therefore the apparent specific surface area is high, which increases the viscosity of the mixed liquid during the reaction process. In contrast, titanium oxide (a) produced by the liquid phase method is thought to produce gentle secondary aggregates in the firing process, and has low cohesive force compared to the specific surface area (BET value) caused by the primary particles, making it possible to suppress the viscosity of the mixed liquid. For these reasons, titanium oxide (a) produced by the liquid phase method is preferable because it can further improve the productivity of water-based paints.

The BET specific surface area of the titanium oxide (a) is preferably in the range of 1 to 200 m ² /g, more preferably in the range of 3 to 100 m ² /g, more preferably in the range of 4 to 70 m ² /g, and even more preferably in the range of 8 to 50 m ² /g, from the viewpoint of obtaining even better antiviral properties and visible light responsiveness, and is preferably in the range of 7.5 to 9.5 m ² /g from the viewpoint of further increasing the productivity of the antiviral agent. The method for measuring the BET specific surface area of the rutile titanium oxide (a1) will be described in the Examples described later.

The primary particle diameter of the titanium oxide (a) is preferably in the range of 0.01 to 0.5 μm, more preferably in the range of 0.06 to 0.35 μm, in order to obtain even better antiviral properties and visible light responsiveness. The primary particle diameter of the titanium oxide (a) is measured by a method in which a transmission electron microscope (TEM) is used to directly measure the size of the primary particles from an electron microscope photograph. Specifically, the minor axis diameter and major axis diameter of each primary particle of titanium oxide are measured, and the average is taken as the particle diameter of the primary particle. Next, the volume (weight) of each particle is calculated for 100 or more titanium oxide particles by approximating it to the cube of the calculated particle diameter, and the volume average particle diameter is taken as the average primary particle diameter.

In addition, as the visible light responsive photocatalyst, it is preferable to use a metal compound supported on titanium oxide (a) because this further improves the photocatalytic activity in the visible light region and is likely to exhibit appropriate activity to decompose dirt components under practical indoor lighting.

As the metal compound, for example, a copper compound, an iron compound, a tungsten compound, etc. can be used. Among these, a copper compound is preferred, and a divalent copper compound is more preferred, in that it provides even more excellent antibacterial and antiviral properties. A known method can be used to support the metal compound on the titanium oxide (a).

Next, we will explain the most preferred method of supporting a divalent copper compound on titanium oxide (a).

As an example of a method for supporting a divalent copper compound on the titanium oxide (a), there can be mentioned a method having a mixing step (i) of titanium oxide (a) including rutile-type titanium oxide (a1), a divalent copper compound raw material (b), water (c), and an alkaline substance (d).

The concentration of the titanium oxide (a) in the mixing step (i) is preferably in the range of 3 to 40% by mass. In the present invention, when titanium oxide (a) produced by a liquid phase method is used, the mixing step can be carried out with good handling even if the concentration of titanium oxide (a) is increased. Specifically, the mixing step can be carried out well even if the concentration of titanium oxide (a) is in the range of more than 25% by mass to 40% by mass or less.

As the divalent copper compound raw material (b), for example, a divalent copper inorganic compound, a divalent copper organic compound, etc. can be used.

Examples of the divalent copper inorganic compound that can be used include inorganic acid salts of divalent copper such as copper sulfate, copper nitrate, copper iodate, copper perchlorate, copper oxalate, copper tetraborate, ammonium copper sulfate, copper amidosulfate, ammonium copper chloride, copper pyrophosphate, and copper carbonate; divalent copper halides such as copper chloride, copper fluoride, and copper bromide; copper oxide, copper sulfide, azurite, malachite, and copper azide. These compounds may be used alone or in combination of two or more.

Examples of the divalent copper organic compounds include copper formate, copper acetate, copper propionate, copper butyrate, copper valerate, copper caproate, copper enanthate, copper caprylate, copper pelargonate, copper caprate, copper myristic acid, copper palmitate, copper margarate, copper stearate, copper oleate, copper lactate, copper malate, copper citrate, copper benzoate, copper phthalate, copper isophthalate, copper terephthalate, copper salicylate, copper mellitic acid, copper oxalate, copper malonate, copper succinate, copper glutarate, copper adipic acid, copper fumarate, and glycol. Examples of compounds that can be used include copper glycerate, copper gluconate, copper tartrate, copper acetylacetonate, copper ethylacetoacetate, copper isovalerate, copper β-resorcylate, copper diacetoacetate, copper formylsuccinate, copper salicylamine, copper bis(2-ethylhexanoate), copper sebacate, copper naphthenate, copper oxine, copper acetylacetonate, copper ethylacetoacetate, copper trifluoromethanesulfonate, copper phthalocyanine, copper ethoxide, copper isopropoxide, copper methoxide, and copper dimethyldithiocarbamate. These compounds may be used alone or in combination of two or more.

As the divalent copper compound raw material (b), among those mentioned above, it is preferable to use one represented by the following general formula (1).
_CuX2 (1)
(In formula (1), X represents a halogen atom, CH ₃ COO, NO ₃ , or (SO ₄ ) _1/2 .)

In the formula (1), X is more preferably a halogen atom, and even more preferably a chlorine atom.

The amount of the divalent copper compound raw material (b) used in the mixing step (i) is preferably in the range of 0.01 to 20 parts by mass, more preferably in the range of 0.1 to 15 parts by mass, and even more preferably in the range of 0.3 to 10 parts by mass, per 100 parts by mass of the titanium oxide (a).

The water (c) is a solvent in the mixing step (i), and although water alone is preferred, other solvents may be included as necessary. Examples of the other solvents that can be used include alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; dimethylformamide, tetrahydrofuran, and the like. These solvents may be used alone or in combination of two or more.

Examples of the alkaline substance (d) that can be used include sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, triethylamine, trimethylamine, ammonia, and basic surfactants, and it is preferable to use sodium hydroxide.

The alkaline substance (d) is preferably added as a solution in order to facilitate control of the reaction, and the concentration of the alkaline solution added is preferably in the range of 0.1 to 5 mol/L, more preferably in the range of 0.3 to 4 mol/L, and even more preferably in the range of 0.5 to 3 mol/L.

In the mixing step (i), the titanium oxide (a), the divalent copper compound raw material (b), the water (c), and the alkaline substance (d) may be mixed. For example, the titanium oxide (a) may be mixed with the water (c) and stirred as necessary, the divalent copper compound raw material (b) may then be mixed and stirred, and the alkaline substance (d) may then be added and stirred. By this mixing step (i), the divalent copper compound derived from the divalent copper compound raw material (b) is supported on the titanium oxide (a).

The total stirring time in the mixing step (i) is, for example, 5 to 120 minutes, and preferably 10 to 60 minutes. The temperature during the mixing step (i) is, for example, in the range of room temperature to 70°C.

In order to ensure good support of the divalent copper compound on the titanium oxide (a), the titanium oxide (a), the divalent copper compound raw material (b), and water (c) are mixed and stirred, and then the alkaline substance (d) is mixed and stirred to produce a mixture having a pH value preferably in the range of 8 to 11, and more preferably in the range of 9.0 to 10.5.

After the mixing step (i) is completed, the mixture can be separated as a solid content. Examples of methods for the separation include filtration, sedimentation, centrifugation, and evaporation and drying, with filtration being preferred. The separated solid content may then be washed with water, crushed, classified, etc., as necessary.

After obtaining the solid content, it is preferable to heat treat the solid content in order to more firmly bond the divalent copper compound derived from the divalent copper compound raw material (b) supported on the titanium oxide (a). The heat treatment temperature is preferably in the range of 150 to 600°C, more preferably in the range of 250 to 450°C. The heat treatment time is preferably 1 to 10 hours, more preferably 2 to 5 hours.

By the above method, a titanium oxide composition containing titanium oxide in which a divalent copper compound is supported on titanium oxide (a) can be obtained. From the viewpoint of photocatalytic activity including antiviral activity, it is preferable that the amount of the divalent copper compound supported on the titanium oxide (a) is in the range of 0.01 to 20 parts by mass per 100 parts by mass of titanium oxide (a). The amount of the divalent copper compound supported can be adjusted by the amount of the divalent copper compound raw material (b) used in the mixing step (i).

The resin (R) is not particularly limited as long as it is one that is generally used as a resin for paints, but examples thereof include acrylic resin, polyester resin, epoxy ester resin, alkyd resin, urethane resin, and epoxy resin.

It is preferable that the resin (R) has a hydrophilic group, since this improves the solubility and dispersibility in the aqueous medium (W).

Examples of the hydrophilic group include anionic groups, cationic groups, and nonionic groups.

In addition, by introducing a crosslinkable functional group into the resin (R), the water-based paint of the present invention can be used as a two-component paint.

Examples of the aqueous medium (W) include water, hydrophilic organic solvents, and mixtures thereof. As the hydrophilic organic solvent, a water-miscible organic solvent that is miscible with water without separating is preferred, and among these, an organic solvent having a solubility in water (the number of grams of organic solvent that dissolves in 100 g of water) of 3 g or more at 25°C is preferred. Examples of these water-miscible organic solvents include alcohol-based solvents such as methanol, ethanol, propanol, butanol, 3-methoxybutanol, and 3-methyl-3-methoxybutanol; ketone-based solvents such as acetone and methyl ethyl ketone; and glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol dimethyl ether. These water-miscible organic solvents may be used alone or in combination of two or more.

The content of the visible light responsive photocatalyst (A) in the aqueous coating material of the present invention is preferably 1 to 20% by mass, since this provides better antiviral properties and storage stability.

The content of the resin (R) in the aqueous paint of the present invention is preferably 25 to 50% by mass, since this provides better antiviral properties and storage stability.

The content of the aqueous medium (W) in the aqueous paint of the present invention is preferably 40 to 70 mass % because this provides better antiviral properties and storage stability.

The content of the visible light responsive photocatalyst (A) in the solid content of the aqueous paint of the present invention is preferably 5 to 20 mass%, and more preferably 5 to 15 mass%, because this provides a better balance between antiviral properties and other coating film properties.

The aqueous paint of the present invention contains the visible light responsive photocatalyst (A), the resin (R), and the aqueous medium (W), and it is preferable that the visible light responsive photocatalyst (A) and the resin (R) are dissolved or dispersed in the aqueous medium (W).

In addition, various additives such as inorganic pigments, organic pigments, extender pigments, waxes, surfactants, stabilizers, flow regulators, dyes, leveling agents, rheology control agents, UV absorbers, antioxidants, plasticizers, antistatic agents, defoamers, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, pigment dispersants, thermosetting resins, and thermoplastic resins can be used in the water-based paint of the present invention as needed.

The aqueous paint of the present invention can be prepared, for example, by adding the visible light responsive photocatalyst (A) and a pigment to an aqueous resin composition in which the resin (R) is dispersed in the aqueous medium (W), and preparing the paint using a mixer such as a sand mill or a disperser. If necessary, a curing agent can be further added to prepare a two-component paint.

Examples of methods for applying the water-based paint of the present invention include methods using a gravure coater, roll coater, comma coater, knife coater, air knife coater, curtain coater, kiss coater, shower coater, wheeler coater, spin coater, dipping, screen printing, spraying, applicator, bar coater, brush, etc.

The water-based paint of the present invention can provide a cured coating film with excellent antiviral properties to the surfaces of various articles.

The water-based paint of the present invention may be applied directly to the object to be coated, or a primer coating material suitable for the object to be coated may be applied first, and then the water-based paint of the present invention may be applied. In addition, after applying the water-based paint of the present invention, a top coat may be applied over it.

Materials of the article to be coated include various metals such as steel plate, iron, copper, zinc, aluminum, magnesium, etc. and their alloys; plastic substrates such as polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), PC-ABS polymer alloy, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyamide (PA), polypropylene (PP), fiberglass, carbon fiber, etc., and fiber-reinforced plastic (FRP) containing fillers; glass, etc.

Examples of articles having a coating film of the water-based paint of the present invention include metal products such as automobiles, railway vehicles, ships, machinery, furniture, cans, and building structures; plastic products such as automobile parts and home appliances; wood products such as furniture and building materials; and inorganic material products such as building materials and glass.

The present invention will be explained in more detail below with specific examples.

(Preparation Example 1: Preparation of visible light responsive photocatalyst (A-1))
(1) Titanium oxide a) Crystalline rutile titanium oxide b) Manufacturing method: Liquid phase method (sulfuric acid method)
c) Physical properties: BET specific surface area: 9.0 m ² /g
- Rutile rate: 95.4%
・Primary particle size: 0.18μm

(2) Manufacturing process a) Mixing process (reaction process)
600 parts by mass of the titanium oxide, 8 parts by mass of copper(II) chloride dihydrate, and 900 parts by mass of water were mixed in a stainless steel container. The mixture was then stirred with a stirrer ("Robomix" manufactured by Tokushu Kika Kogyo Co., Ltd.), and 1 mol/L of aqueous sodium hydroxide solution was added dropwise until the pH of the mixture reached 10.
b) Dehydration step The mixture was filtered under reduced pressure using qualitative filter paper (5C) to separate the solid matter from the mixture, and then washed with ion-exchanged water. The washed solid matter was then dried at 120°C for 12 hours to remove moisture. After drying, a powdered titanium oxide composition was obtained using a mill (Iwatani Sangyo Co., Ltd.'s "Miller").
c) Heat Treatment Step Heat treatment was performed for 3 hours at 450°C in the presence of oxygen using a precision incubator ("DH650" manufactured by Yamato Scientific Co., Ltd.) to obtain a visible light responsive photocatalyst (A-1) containing titanium oxide carrying a divalent copper compound.

(Example 1: Production of Water-Based Paint (1))
To 100 parts by mass of an aqueous acrylic resin (DIC Corporation's "Burnoc WD-551", containing hydroxyl groups), 11.2 parts by mass of the visible light responsive photocatalyst (A-1) obtained above, 33.7 parts by mass of a titanium oxide pigment (Chemours's "Ti-Pure R-706"), and 19.9 parts by mass of ion-exchanged water were added and kneaded for 30 minutes with a sand mill to obtain a pigment dispersion. To the obtained pigment dispersion, 29.3 parts by mass of a polyisocyanate resin (DIC Corporation's "Burnoc DNW-5500") was added as a curing agent, and the mixture was stirred with a disper for 5 minutes to obtain an aqueous coating material (1).

(Examples 2 to 5: Production of Water-Based Coatings (2) to (5))
Water-based paints (2) to (5) were obtained in the same manner as in Example 1, except that the raw materials used were changed to those shown in Table 1.

(Comparative Examples 1 to 5: Production of Water-Based Paints (R1) to (R5))
Water-based paints (R1) to (R5) were obtained in the same manner as in Example 1, except that the raw materials used were changed to those shown in Table 1.

[Preparation of coating film for evaluation]
Each of the water-based paints obtained above was sprayed onto a chromate-treated aluminum plate to a film thickness of 15 μm, and then dried at 23° C. for 7 days to obtain a test plate having a coating film for evaluation.

[Evaluation of antiviral activity]
An anti-phage virus test (see JIS R1756:2020) was carried out on the test plates on which the coating films for evaluation obtained in the Examples and Comparative Examples were formed.

1) The light irradiation conditions were as follows: white fluorescent light was filtered out with an N113 filter to block ultraviolet rays, and the illuminance was set to 500 lux.
2) 100 μL of a Qβ phage solution with a known concentration was dropped onto a 5 cm×5 cm test plate obtained in the Examples and Comparative Examples, and then a 4 cm×4 cm adhesive film was placed over the plate to prepare a sample for evaluation.
3) The sample irradiated for 8 hours was collected in SCDLP solution, appropriately diluted, infected with Escherichia coli, spread on an agar medium, and evaluated by counting the number of colonies after cultivation. The antiviral activity was evaluated based on the degree of inactivation of Qβ phage according to the following criteria.
◎: Inactivation degree is -3 or less ◯: Inactivation degree is greater than -3 and less than -2 ×: Inactivation degree is greater than -2

The compositions and evaluation results of the water-based paints (1) to (5) and (R1) to (R5) obtained above are shown in Tables 1 and 2.

The raw materials in the table are as follows:
"Burnoc WD-551": DIC Corporation, aqueous acrylic resin (hydroxyl value: 100 mg KOH/g, resin content: 44% by mass, aqueous medium: water, diethylene glycol dimethyl ether)
"Burnoc WE-306": DIC Corporation, water-based acrylic resin (hydroxyl value: 100 mg KOH/g, resin content: 45% by mass, aqueous medium: water)
"WATERSOL CD-520P": Water-based polyester resin manufactured by DIC Corporation (resin content: 39% by mass, aqueous medium: water, ethylene glycol monopropyl ether)
"WATERSOL EFD-5580": Water-based epoxy ester resin manufactured by DIC Corporation (resin content: 40% by mass, aqueous medium: water, propylene glycol monobutyl ether, propylene glycol monopropyl ether)
"HYDRAN AP-20": Water-based urethane resin manufactured by DIC Corporation (resin content: 30% by mass, aqueous medium: water)
"Burnoc DNW-5500": water-dispersible polyisocyanate resin manufactured by DIC Corporation (isocyanate group content (NCO%): 13.5% by mass, resin content: 80% by mass, solvent: propylene glycol monomethyl ether acetate)
"DICNATE 3111TL": Cobalt-based metal soap manufactured by DIC Corporation

The coating films obtained from Examples 1 to 5, which are the aqueous resin compositions of the present invention, were confirmed to have excellent antiviral properties.

On the other hand, Comparative Examples 1 to 5 are examples that do not contain the visible light responsive photocatalyst (A), which is an essential component of the present invention, and it was confirmed that the resulting coating film had inferior antiviral properties.

Claims (3)

A method for producing an aqueous paint containing a visible light responsive photocatalyst (A), a resin (R), and an aqueous medium (W), wherein the visible light responsive photocatalyst (A) is a titanium oxide (a) containing rutile type titanium oxide (a1) carrying a divalent copper compound, the titanium oxide (a) is produced by a liquid phase method, the visible light responsive photocatalyst (A) is produced by a method having a mixing step (i) of the titanium oxide (a), a divalent copper compound raw material (b), water (c), and an alkaline substance (d), and the concentration of the titanium oxide (a) in the mixing step (i) is in the range of more than 25% by mass to 40% by mass or less. The method for producing a water-based paint according to claim 1, wherein the resin (R) contains one or more resins selected from the group consisting of acrylic resins, polyester resins, epoxy ester resins, alkyd resins, urethane resins, and epoxy resins. The method for producing the water-based paint according to claim 1 or 2, which is a two-component curing type.