Coating agent for transparent clay coating film, coated product, method for manufacturing the coating agent for transparent clay coating film and coated product

Abstract

To provide a coating agent for transparent clay coatings that can produce a transparent clay coating film, a coated object having a transparent clay coating film, and a method for manufacturing the coating agent for transparent clay coatings and the coated object. [Solution] A coating agent for transparent clay coatings having a water-swellable clay containing dimethyldialkylammonium between layers and an aromatic hydrocarbon organic solvent, wherein the alkyl chain of the dimethyldialkylammonium has 10 to 18 carbon atoms; a coated product characterized by having a transparent clay coating formed from this coating agent; a method for producing a coating agent for transparent clay coatings comprising the step of dispersing a dried water-swellable clay containing dimethyldialkylammonium having 10 to 18 carbon atoms in the alkyl chain between layers in an aromatic hydrocarbon organic solvent; and a method for producing a coated product coated and dried with the transparent clay coating agent.

Description

Technical Field

[0001] The present invention relates to a coating agent for a transparent clay film, an object coated with this coating agent, and a method for producing this coating agent for a transparent clay film and the object coated therewith.

Background Art

[0002] Smectite, which is a group of clay minerals, is composed of a layered structure in which sheets made of oxides are stacked and cations between the layers. Smectite in which the cations between the layers are sodium ions or lithium ions is known to easily allow water to enter between the oxide sheets and form a gel having thixotropic properties by swelling in water. It is known that this gel or a dispersion of clay can obtain a clay film by being applied and dried due to its thixotropic properties (Non-Patent Document 1). However, the obtained clay film has a problem in use in an environment where there is a risk of contact with water because it easily redisperses when it comes into contact with water.

[0003] Smectite into which a quaternary alkylammonium (QAA) is introduced as a cation between the layers is called an organic clay, and instead of being difficult to swell in water, it becomes swellable in an organic solvent. Organic clays are widely used as thickeners added to paints, cosmetics, medical products, etc., but due to insufficient dispersion and exfoliation in organic solvents, they have a cloudy appearance. Patent Document 1 describes a substance obtained by intercalating (c) an antibacterial substance into (a) a clay mineral using (b) a cationic surfactant which is either a primary to tertiary amine salt or a quaternary ammonium salt. This substance is used as an antibacterial filler to be mixed with a film-forming resin, and it is not described that it forms a clay film alone, and the quaternary ammonium is only used as a surfactant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] [Non-Patent Document 1] EA Hauser and DS Le Beau, J. Phys. Chem. 42, 961-969, (1938) [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a coating agent for transparent clay coatings that can produce a transparent clay coating film, a coated object having a transparent clay coating film, and a method for manufacturing the coating agent for transparent clay coatings and the coated object. [Means for solving the problem]

[0007] The means for solving the problems of the present invention are as follows. 1. A water-swellable clay containing dimethyldialkylammonium between the layers, Aromatic hydrocarbon organic solvents, It has, A coating agent for transparent clay coating films, characterized in that the alkyl chain of the dimethyldialkylammonium has 10 to 18 carbon atoms. 2. The coating agent for transparent clay coatings according to 1, characterized in that the water-swellable clay is synthetic smectite. 3. The transparent clay coating agent according to 1. or 2., characterized in that the alkyl chain of the dimethyldialkylammonium has 12 or more carbon atoms and 16 or less carbon atoms. 4. A coated object characterized by having a transparent clay coating film formed from a transparent clay coating agent described in any of 1. to 3. 5. A step of dispersing a dried product of water-swellable clay containing dimethyldialkylammonium, in which the alkyl chain has 10 to 18 carbon atoms, in an aromatic hydrocarbon organic solvent between the layers. A method for producing a coating agent for transparent clay coating films, characterized by having the following features. 6. A method for producing a coated product having a transparent clay coating, characterized by applying and drying a transparent clay coating agent described in any of 1 to 3. [Effects of the Invention]

[0008] The present invention makes it possible to obtain a transparent clay coating. The transparent clay coating obtained by the present invention possesses antibacterial, antifungal, and anti-wood-decaying fungal properties derived from dimethyldialkylammonium. The transparent clay coating obtained by the present invention has excellent water resistance, does not easily swell when in contact with water, and does not redisperse even when submerged in water for several days. Because the clay coating of the present invention is transparent, it can form a transparent protective film on the substrate surface that has antibacterial, antifungal, and anti-wood-decaying fungal properties without impairing the color or pattern of the substrate, thereby preventing mold growth on the substrate. In particular, because the transparent clay coating of the present invention has anti-wood-decaying fungal properties, it can be suitably applied to wood-based materials. [Brief explanation of the drawing]

[0009] [Figure 1] X-ray diffraction patterns of the clay coating obtained in Example 1 and the coating made solely from hectorite, its raw material. [Figure 2] FT-IR spectra of the clay coating obtained in Example 1, the quaternary alkylammonium powder which is the raw material for this clay coating, and a coating prepared solely from hectorite. [Figure 3] Transmission spectra of the clay coating film (6 μm, C12) obtained in Example 1 and the substrate Tempax glass (1.1 mm). [Figure 4] Transmission spectra of the clay coating film (6 μm, C10) obtained in Example 5 and the substrate Tempax glass (1.1 mm). [Figure 5] Transmission spectra of the clay coating film (6 μm, C12, fluorine-substituted hectorite) obtained in Comparative Example 1 and the substrate Tempax glass (1.1 mm). [Figure 6]Transmission spectra of the clay coating film (6 μm, C18, unheated gel) obtained in Comparative Example 6 and the substrate, Tempax glass (1.1 mm). [Figure 7] Transmission spectra of the clay coating film (6 μm, C18, heated gel) obtained in Example 6 and the substrate, Tempax glass (1.1 mm). [Figure 8] Figure showing the state of the test piece after the anti-wood decay fungus test.

Embodiments for Carrying Out the Invention

[0010] "Coating Agent for Transparent Clay Coating Film" The coating agent for a transparent clay coating film of the present invention has a water-swellable clay containing dimethyldialkylammonium between layers and an aromatic hydrocarbon-based organic solvent, and the alkyl chain of dimethyldialkylammonium has 10 to 18 carbon atoms. In the present invention, when the clay coating film is transparent, it means that the visible light transmittance of a laminate formed by forming a clay coating film with a thickness of 5 μm or more and 10 μm or less on a Tempax glass substrate with a thickness of 1.1 mm is 70% or more in the wavelength range of 380 nm to 780 nm. The definition of visible light transmittance is based on JIS R3106:2019. This visible light transmittance is preferably 74% or more, more preferably 78% or more, further preferably 82% or more, and even more preferably 86% or more.

[0011] · Water-swellable clay The present invention uses a water-swellable clay. By using a water-swellable clay, a clay coating film with high transparency can be formed. The water-swellable clay used in the present invention is not particularly limited as long as the transparent clay coating film of the present invention can be obtained, and any of natural clay, purified natural clay, and synthetic clay can be used, but synthetic clay is preferred. Natural clay or purified natural clay tends to have lower transparency compared to when synthetic clay is used, probably because of its lower purity. Examples of the water-swelling synthetic clay include synthetic smectite, synthetic vermiculite, etc., and synthetic smectite is preferred. Examples of smectite include hectorite, saponite, stibnite, montmorillonite, beidellite, nontronite, sauconite, etc., and one or more of them can be mixed and used. Among these, hectorite, saponite, and stibnite are more preferred.

[0012] The type of interlayer cation of the water-swelling clay before substituting the interlayer cation is not particularly limited, but sodium or lithium is preferred because they are excellent in swelling property in water and water dispersibility. From the viewpoint of improving the swelling property during dispersion, the cation exchange capacity (CEC: Cation Exchange Capacity) of the water-swelling clay is preferably 15 meq (milliequivalent) / 100 g or more, more preferably 20 meq / 100 g or more, and even more preferably 25 meq / 100 g or more. In addition, the upper limit of the cation exchange capacity of smectite is generally about 250 meq / 100 g or less.

[0013] · Dimethyldialkylammonium The present invention uses dimethyldialkylammonium having 10 to 18 carbon atoms in the alkyl chain. The dimethyldialkylammonium used in the present invention is known as a cationic surfactant, and it is also known that it acts on cell membranes to exhibit antibacterial and antifungal properties. By using a water-swelling clay having this specific dimethyldialkylammonium as an interlayer cation, a transparent coating agent and a transparent clay coating film can be obtained. Although the detailed mechanism is unclear, the inventors of the present invention推测 that dimethyldialkylammonium having 10 to 18 carbon atoms in the alkyl chain is excellent in the dispersibility of the water-swelling clay and is difficult to have its arrangement disordered during drying.

[0014] The alkyl chain of the dimethyldialkylammonium used in this invention has 10 to 18 carbon atoms. The coating agent of this invention is a transparent gel having thixotropy, and from the viewpoint of gelation, the number of carbon atoms is preferably 12 or more. The gelation ability is almost constant for carbon atoms between 12 and 18, but as described later, it is possible to easily obtain a transparent gel for obtaining a transparent clay coating film, so a carbon atom number of 16 or less is preferred. Furthermore, from the viewpoint of antibacterial properties, a carbon atom number of 10 to 14 is preferred, and 10 to 12 is more preferred.

[0015] The coating agent for transparent clay coatings of the present invention contains an aromatic hydrocarbon organic solvent. By using an aromatic hydrocarbon organic solvent, a transparent clay coating can be obtained. Examples of aromatic hydrocarbon organic solvents include toluene, xylene, phenol, chlorobenzene, nitrobenzene, etc., and a mixture of two or more miscible types is also acceptable. Among these, toluene and xylene are preferred from the viewpoint of drying properties, etc. The coating agent of the present invention may also contain a non-aromatic organic solvent that is miscible with the aromatic hydrocarbon organic solvent used, as long as a transparent coating can be obtained. However, the ratio of the aromatic hydrocarbon organic solvent to the total organic solvent is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more.

[0016] The transparent clay coating agent of the present invention may contain additives such as dispersants, binder resins, crosslinking agents, curing agents, colorants, pigments, and ultraviolet absorbers, which are used in coating agents containing organic clay, within the range in which a transparent clay coating film can be formed.

[0017] "Method for manufacturing a coating agent for transparent clay coating films" A method for producing a coating agent for transparent clay coatings comprises the step of dispersing a dried product of water-swellable clay containing dimethyldialkylammonium having an alkyl chain with 10 to 18 carbon atoms in an aromatic hydrocarbon organic solvent. Water-swellable clay containing dimethyldialkylammonium having 10 to 18 carbon atoms in its alkyl chain can be obtained by ion exchange of the water-swellable clay in water. In this process, dimethyldialkylammonium is added in excess of the ions to be exchanged. That is, the amount of dimethyldialkylammonium added must be more than 1 times the cation exchange capacity of the water-swellable clay, preferably 1.01 times or more, more preferably 1.05 times or more, even more preferably 1.1 times or more, and even more preferably 1.2 times or more. There is no particular upper limit to the amount of dimethyldialkylammonium, but if the amount added is too large, dimethylammonium that does not substitute or surface adsorb will be produced, resulting in high costs, so it is preferable to keep it at around 5 times or less.

[0018] Water-swellable clay containing dimethyldialkylammonium, in which the alkyl chain has 10 to 18 carbon atoms after ion exchange, is dispersed in water and is a white gel. A dried product can be obtained by washing and drying this clay. The moisture content of the dried water-swellable clay is preferably 3% by mass or less, and more preferably 2% by mass or less. On the other hand, excessive removal of moisture tends to reduce dispersibility in aromatic hydrocarbon organic solvents. In this specification, the moisture content of the clay is determined from the weight change rate before and after drying at 105°C for 24 hours.

[0019] A dried water-swellable clay containing dimethyldialkylammonium with an alkyl chain having 10 to 18 carbon atoms is dispersed in an aromatic hydrocarbon organic solvent. When water is used as the dispersion medium, it is a white gel. However, when water-swellable clay containing dimethyldialkylammonium with an alkyl chain having 10 to 16 carbon atoms is dispersed in an aromatic hydrocarbon organic solvent, it becomes a transparent gel. On the other hand, water-swellable clay containing dimethyldialkylammonium with an alkyl chain having 18 carbon atoms remains a white gel even when an aromatic hydrocarbon organic solvent is used as the dispersion medium. However, this white gel becomes a transparent gel when heated to approximately 40°C or higher. The mechanism by which the white gel becomes a transparent gel upon heating is presumed to be that heating improves the mobility of dimethyldialkylammonium, thereby improving its dispersibility. The upper limit of the heating temperature for obtaining a transparent gel is as long as it is below the boiling point (Tb) of the aromatic hydrocarbon organic solvent used. From a safety standpoint, Tb-20°C or lower is preferred, Tb-30°C or lower is more preferred, and Tb-40°C or lower is even more preferred. Furthermore, this transparent gel exhibits thixotropy, and its viscosity decreases and it becomes liquid when shear stress is applied, so it can be applied as a coating agent for transparent clay coatings according to the present invention.

[0020] "Coated products" By applying and drying the transparent clay coating agent of the present invention, a coated object having a transparent clay coating can be obtained. The object to which the transparent clay coating agent of the present invention is applied is not particularly limited as long as it does not dissolve in the aromatic hydrocarbon organic solvent contained in the coating agent, and examples include wood materials such as wood, plywood, and laminated wood, ceramics, metals, and plastics. Among these, wood materials that are prone to mold growth are preferred because the resulting transparent clay coating has antibacterial, antifungal, and anti-wood-rotting fungal properties derived from dimethyldialkylammonium. [Examples]

[0021] "Example 1" Synthetic hectorite (Laponite RD, BYK) was added at a concentration of 2 wt% to deionized water and shaken at 40°C for 4 hours. The temperature was raised to 70°C, and then an aqueous solution of didodecyldimethylammonium chloride (alkyl chain with 12 carbon atoms) also at 70°C was added. The mixture was shaken at 70°C for 2 hours to perform ion exchange. The total amount of didodecyldimethylammonium chloride added was twice the ion exchange equivalent of the synthetic hectorite. After shaking, the resulting white gel-like substance was separated into solid and liquid phases using a centrifuge, washed with deionized water, and then centrifuged again. The washed white gel-like substance was dried at 80°C for 12 hours to obtain solid organic clay. After grinding the obtained organic clay in a mortar, xylene was added in an amount equal to twice the amount of organic clay (w / w), and the mixture was mixed while grinding until it became a transparent gel. The resulting transparent gel was applied to a substrate (1.1 mm thick Tempax glass) using an applicator and dried at room temperature to obtain a transparent clay coating with a thickness of approximately 6 μm after drying.

[0022] Example 2 A clay coating film was obtained in the same manner as in Example 1, except that toluene was used as the organic solvent. The obtained clay coating film had the same transparency as that of Example 1. "Example 3" A clay coating film was obtained in the same manner as in Example 1, except that synthetic saponite (Smecton SA, manufactured by Kunimine Industries Co., Ltd.) was used. The obtained clay coating film had the same transparency as that of Example 1.

[0023] "Example 4" A clay coating film was obtained in the same manner as in Example 1, except that synthetic stivunsite (Smecton SA, manufactured by Kunimine Industries Co., Ltd.) was used. The obtained clay coating film had the same transparency as in Example 1. "Example 5" A clay coating film was obtained in the same manner as in Example 1, except that didecyldimethylammonium chloride (with 10 carbon atoms in the alkyl chain) was used. The obtained clay coating film had transparency, although it was slightly inferior to that of Example 1.

[0024] "Comparative Example 1" The procedure was the same as in Example 2, except that a synthetic hectorite (Laponite XL21, manufactured by BYK) in which some of the OH groups were substituted with fluorine was used. The resulting gel had the same transparency as that of Examples 1-5, but the prepared clay coating film was more cloudy than the clay coating films obtained in Examples 1-5. "Comparative Example 2" The procedure was the same as in Example 1, except that purified bentonite (Kunipia-F, manufactured by Kunimine Industries Co., Ltd.) was used. The resulting gel was cloudy, and a cloudy clay coating was obtained. The resulting clay coating was more cloudy than that of Comparative Example 1.

[0025] "Comparative Example 3" The procedure was the same as in Example 1, except that dodecyltrimethylammonium chloride was used. The resulting gel was cloudy white, and when this gel was coated and dried, it failed to form a film and turned into a powder. "Comparative Example 4" The procedure was the same as in Example 1, except that dimethylformamide was used as the organic solvent. The resulting gel was cloudy, and a cloudy clay coating was obtained. The resulting clay coating was more cloudy than that of Comparative Example 1.

[0026] "Comparative Example 5" The procedure was the same as in Example 1, except that dioctyldimethylammonium chloride (with 8 carbon atoms in the alkyl chain) was used. The resulting gel was transparent, but the degree of gelation was less than in Example 1. When this gel was coated and dried, it failed to form a film and turned into a powder. "Comparative Example 6" The procedure was the same as in Example 1, except that dioctadecyldimethylammonium chloride (with 18 carbon atoms in the alkyl chain) was used. The resulting gel was cloudy, and a cloudy clay coating was obtained. The resulting clay coating was more transparent than Comparative Example 1, but more cloudy than Examples 1 to 5.

[0027] "Example 6" The procedure was the same as in Comparative Example 6, except that the mixture was heated to 70°C when adding xylene and grinding it. The gel obtained by heating during preparation was transparent. The clay coating obtained by applying this transparent gel while it was still warm retained the same transparency as in Example 1 even after drying and cooling. The gel before application became cloudy when it cooled to room temperature, but it became transparent again after heating and mixing. The clay coating obtained by applying this transparent gel while it was still warm was also transparent, and the gel that had cooled and become cloudy could be reused by heating it to make it transparent again.

[0028] "Other comparative examples" The procedure was the same as in Example 1, except that lower alcohols (methanol, ethanol, isopropyl alcohol, butanol, cyclohexanol), linear hydrocarbons (hexane, decane), ketones (acetone, ethyl methyl ketone), and esters (ethyl acetate) were used as organic solvents. None of them gelled.

[0029] • Evaluation method (X-ray diffraction) The X-ray diffraction pattern of the clay coating film fabricated on the Tempax glass substrate (1.1 mm) obtained in Example 1 was measured using a Cu-based X-ray diffractometer (fully automated horizontal multi-purpose X-ray diffractometer SmartLab, Rigaku Corporation). The X-ray output was 30 kV and 40 mA, and the sample was irradiated with X-rays transmitted through a kβ filter. The measurement range was from 2° to 90°, and a semiconductor detector was used. The X-ray diffraction pattern is shown in Figure 1.

[0030] (FT-IR) The infrared absorption spectrum of the clay coating film fabricated on the Tempax glass substrate (1.1 mm) obtained in Example 1 was measured using a Fourier transform infrared spectrophotometer (FT / IR-6100, JASCO Corporation). The measurement was performed using the ATR method with a diamond prism. The FT-IR spectrum is shown in Figure 2.

[0031] (transmittance) For the clay coatings prepared on Tempax glass substrates (1.1 mm) obtained in Examples 1 and 5, Comparative Examples 1 and 6, and Example 6, the transmittance from 380 to 780 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (V-670, JASCO). From the obtained spectra, the visible light transmittance as shown in JIS R3126:2019 was calculated. The visible transmission spectra are shown in Figures 3-6 and 7.

[0032] (Antifungal) The base material was a test piece of cedar wood dried at 70 degrees Celsius and sanded with sandpaper equivalent to 180 grit. Three types of samples were prepared, three of each: (1) unpainted, (2) coated with a 5 wt% hectorite dispersion that was gelled by adding water and shaking at 40 degrees Celsius for 4 hours, and (3) coated with a transparent gel obtained in Example 2, which was prepared to a concentration of approximately 30 wt%, and were dried overnight at 70 degrees Celsius before being used for testing. The test conditions conformed to JIS Z 2911:2023 Mold Resistance Test Methods, Section 7, Testing of General Industrial Products (Measuring Instruments and Wood / Bamboo Products), and the products were evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) 0: No mycelial growth was observed in the inoculated area of ​​the sample or test piece. 1: The area of ​​mycelial growth observed in the inoculated portion of the sample or test piece is: It does not exceed one-third of the total area. 2: The area of ​​mycelial growth observed in the inoculated portion of the sample or test piece is: It accounts for more than one-third of the total area.

[0033] [Table 1]

[0034] (Anti-wood rotting fungi) The base material was a test piece of cedar wood dried at 70 degrees Celsius and sanded with sandpaper equivalent to 180 grit. Five types of samples were prepared: (1) unpainted, (2) coated with a 4 wt% hectorite dispersion gel prepared by adding water and shaking at 40°C for 4 hours, (3) coated with a transparent gel obtained in Example 5, prepared to approximately 30 wt%, (4) coated with a transparent gel obtained in Example 1, prepared to approximately 30 wt%, and (5) coated with a transparent gel obtained in Example 6, prepared to approximately 30 wt%, and then used in the tests after 85 hours of gamma ray sterilization (cesium-137, 250 Gy / h).

[0035] On identical potato dextrose agar (PDA) plates, the sample was placed in the center, and a small piece of PDA medium in which the test fungus had been grown was placed at the edge. The plates were incubated at 26°C for 3 weeks. The number of repetitions (n) was 3. Every week, the surface of the sample (top and sides) was observed with the naked eye to determine whether or not the test fungus had grown. Trametes versicolor MAFF 420002 was used as the test fungus. Figure 8 shows the condition of each test specimen after 1 week and 3 weeks of culture.

[0036] ·result Figures 1 and 2 confirm that dimethyldialkylammonium is present between layers of water-swellable clay. As shown in Figures 3 and 4, the transmittances of the clay coating obtained in Example 1 (C12) and Example 5 (C10) were 89% and 80%, respectively, indicating transparency. In contrast, as shown in Figure 5, the transmittance of the clay coating obtained in Comparative Example 1 (fluorine-substituted hectorite) was 50-51%, indicating it was not transparent. As shown in Figures 6 and 7, the transmittance of the clay coating obtained in Comparative Example 6 (C18), where the gel was not heated, was 63%, indicating it was not transparent. However, the transmittance of the clay coating obtained in Example 6 (C18), where the gel was heated to make it transparent, was 91%, indicating it was transparent. As shown in Table 1, the clay coating obtained in Example 2 had antibacterial and antifungal properties. As shown in Figure 8, the clay coatings obtained in Examples 5, 1, and 6 exhibited anti-wood-rotting fungal properties. In particular, in Example 5, which had 10 carbon atoms, a clear growth inhibition zone was observed around the wood chips.

Claims

1. A water-swellable clay containing dimethyldialkylammonium is present between the layers, Aromatic hydrocarbon organic solvents, It has, A coating agent for transparent clay coating films, characterized in that the alkyl chain of the dimethyldialkylammonium has 10 to 18 carbon atoms.

2. The coating agent for transparent clay coatings according to claim 1, characterized in that the water-swellable clay is synthetic smectite.

3. The coating agent for transparent clay coating film according to claim 1, characterized in that the alkyl chain of the dimethyldialkylammonium has 12 or more carbon atoms and 16 or less.

4. A coated object characterized by having a transparent clay coating film formed from a transparent clay coating agent according to any one of claims 1 to 3.

5. A step of dispersing a dried water-swellable clay containing dimethyldialkylammonium, in which the alkyl chain has 10 to 18 carbon atoms, in an aromatic hydrocarbon organic solvent between the layers. A method for producing a coating agent for transparent clay coating films, characterized by having the following features.

6. A method for producing a coated product having a transparent clay coating film, characterized by applying and drying a coating agent for transparent clay coating films described in any one of claims 1 to 3.

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