Aqueous coating composition for wallpaper

Abstract

To provide a water-based coating composition for wallpaper which hardly drips, has good fixability, has a reduced VOC concentration, and has excellent antibacterial properties.SOLUTION: The aqueous coating composition for wallpapers comprises polyphenols, surfactants, and cellulose nanofibers having a mean fiber size of 1 to 1000nm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a water-based coating composition for wallpaper. [Background technology]

[0002] Many buildings have traditionally had wallpaper applied to their interior walls and ceilings. This wallpaper ranges from wallpapers made with a combination of resin materials such as vinyl chloride resin, wallpapers made from natural materials such as hemp, and paper wallpapers made from paper materials. Recently, wallpapers have been manufactured with low or no organic compound concentrations (e.g., low or zero formaldehyde), improving safety. However, organic compounds are sometimes used in the manufacturing process of furniture, electrical appliances, and other items brought in by residents. If these organic compounds remain in the products, they will volatilize when installed indoors. In particular, some buildings these days are highly airtight, and if volatilized organic compounds, i.e., volatile organic compounds (hereinafter also referred to as "VOCs"), fill the interior of a building and their concentrations increase, these VOCs can have adverse effects on humans (e.g., the onset of sick building syndrome).

[0003] Under these circumstances, there is a legal and social demand for a reduction in VOC concentration. For example, Patent Document 1 discloses a technology for reducing VOC concentration by providing a coating layer containing a VOC adsorption material on the surface of a substrate sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-233396 [Patent Document 2] Japanese Patent Application Publication No. 2018-145621 [Patent Document 3] Japanese Patent Application Publication No. 2023-143397 [Patent Document 4] Japanese Patent Application Publication No. 2023-137960 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to withstand changes in humidity within buildings and to prevent deformation of the wallpaper substrate, wallpaper is usually made using a water-repellent wallpaper substrate or a wallpaper substrate to which a coating layer with water-repellent properties (Patent Document 2) has been applied. When attempting to apply a coating layer to such a water-repellent wallpaper substrate, if the coating layer is water-based, it will be repelled by the wallpaper substrate, so oil-based coatings have often been used up to now. However, in order to apply such an oil-based coating layer to a wallpaper substrate, there is a problem in that the paint used to form the coating layer must be prevented from dripping as much as possible.

[0006] On the other hand, there is a technology that gives wallpaper antibacterial properties in addition to the function of reducing VOC concentration (Patent Document 3), but the problem of having to suppress dripping as much as possible remains in order to apply antibacterial paint to the wallpaper base material without causing dripping.

[0007] Therefore, the present invention aims to provide an aqueous wallpaper coating composition that is less likely to drip when applied to water-repellent wallpaper, has good adhesion, has a reduced VOC concentration, and has excellent antibacterial properties. [Means for solving the problem]

[0008] The above-mentioned problems are solved by the following aspects. (First aspect) It contains polyphenols, surfactants, and cellulose nanofibers with an average fiber diameter of 1 nm or more and 1000 nm or less. A water-based coating composition for wallpaper.

[0009] The aqueous wallpaper coating composition of this embodiment contains cellulose nanofibers, making it less likely to be repelled by water-repellent wallpaper, and also contains a surfactant along with polyphenols, which disperse the polyphenols in the composition in the form of oil droplets, making it less likely to be unevenly distributed. Furthermore, when the aqueous wallpaper coating composition is applied to wallpaper, the applied area is covered with cellulose nanofibers and the polyphenols are also dispersed, resulting in good adhesion and less dripping, as well as excellent antibacterial properties.

[0010] (Second aspect) Further comprising a thickener, A water-based wallpaper coating composition according to a first embodiment.

[0011] The inclusion of a thickener in the aqueous wallpaper coating composition of this embodiment makes the aqueous wallpaper coating composition excellent in adhesion to the wallpaper and less likely to drip.

[0012] (Third aspect) The surfactant is a naturally occurring surfactant. A water-based wallpaper coating composition according to a first embodiment.

[0013] The surfactant contained in the aqueous wallpaper coating composition of this embodiment is naturally derived, and therefore is highly safe for the human body.

[0014] (Fourth aspect) The polyphenol is a plant-derived polyphenol. A water-based wallpaper coating composition according to a first embodiment.

[0015] The surfactant contained in the aqueous wallpaper coating composition of this embodiment is naturally derived, and therefore is highly safe for the human body.

[0016] (Fifth aspect) Further having an antibacterial agent, A water-based wallpaper coating composition according to a first embodiment.

[0017] The aqueous wallpaper coating composition of this embodiment has better antibacterial properties.

[0018] (Sixth aspect) For the total amount of water-based wallpaper coating composition, The polyphenol 1 is contained in an amount of 1 to 10%, and the surfactant is contained in an amount of 0.1% or more and 0.5% or less. A water-based wallpaper coating composition according to a first embodiment.

[0019] When the polyphenol and surfactant are contained in the water-based paint composition in this ratio, the polyphenol is dispersed appropriately, resulting in a homogeneous paint composition.

[0020] (Seventh aspect) Adding water-repellent properties to wallpaper A water-based wallpaper coating composition according to a first embodiment.

[0021] When the aqueous wallpaper coating composition of the first embodiment is applied to wallpaper, the coated area is covered with cellulose nanofibers, but unlike water, cellulose nanofibers are not easily repelled even by water-repellent wallpaper, making it easy to apply evenly to wallpaper and less likely to drip after application.

[0022] (Eighth aspect) B-type viscosity is 20 to 1000 mPa·s. A water-based wallpaper coating composition according to a first embodiment.

[0023] If the water-based wallpaper coating composition has a Brookfield viscosity within this range, it is easy to apply to wallpaper and is less likely to cause peeling. [Effects of the Invention]

[0024] According to the present invention, an aqueous coating composition for wallpaper is obtained which is less likely to drip when applied to water-repellent wallpaper, has good adhesion, has a reduced VOC concentration, and has excellent antibacterial properties. [Brief explanation of the drawings]

[0025] [Figure 1] 1 shows the results of antiviral tests. [Figure 2] The results of the antibacterial test are shown. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The present embodiment is merely an example of the present invention. The scope of the present invention is not limited to the scope of the present embodiment.

[0027] The aqueous wallpaper coating composition according to this embodiment is characterized by containing polyphenols, surfactants, and cellulose nanofibers with an average fiber diameter of 1 to 1000 nm.

[0028] The polyphenols contained in the aqueous wallpaper coating composition according to this embodiment may be natural polyphenols, such as flavonoid polyphenols or phenolic acid polyphenols. Examples of flavonoid polyphenols include flavones such as luteolin, isoflavones such as genistein, catechins such as tannins, cocoa polyphenols, catechin, and epicatechin, flavonols such as rutin, quercetin, and myricetin, flavanones such as hesperetin, and anthocyanidins such as anthocyanins and cyanidins. Examples of phenolic acid polyphenols include gingerols, ferulic acids, hydroxybenzoic acids such as gallic acid and ellagic acid, hydroxycinnamic acids such as caffeic acid, diketones such as chlorogenic acid, neochlorogenic acid, and curcumin, and rosmarinic acid.

[0029] Among natural polyphenols, plant-derived polyphenols are preferred. Polyphenols obtained from extracts of persimmon leaves, Japanese knotweed, and mugwort are plant-derived, safe for the human body, and preferred for removing VOCs. Examples of polyphenols obtained from persimmon leaf extracts include tannins, catechins, and rutin. Examples of polyphenols obtained from Japanese knotweed extracts include flavonols such as neochlorogenic acid and rutin, and chlorogenic acid. Examples of polyphenols obtained from mugwort extracts include catechins. Polyphenols obtained from extracts of persimmon leaves, Japanese knotweed, and mugwort are plant-derived and safe for the human body, so they are preferably contained in aqueous wallpaper coating compositions. Plant-derived polyphenols can be obtained from hot water extracts of persimmon leaves, Japanese knotweed, or mugwort, as described, for example, in JP 2024-13172 A. On the other hand, among plant-derived polyphenols, those extracted from persimmon leaves, Japanese knotweed, and mugwort are particularly preferred because they exhibit a high VOC removal effect.

[0030] The mechanism by which VOCs are removed is, for example, a substitution reaction between VOCs and phenols. For example, in the case of formaldehyde and phenols, formaldehyde combines with the phenols, causing a substitution reaction, which results in VOCs being removed. This substitution reaction is known to proceed under both acidic and alkaline conditions.

[0031] On the other hand, polyphenols have bactericidal activity, which is due to the fact that they become negatively charged due to proton transfer from the phenolic hydroxyl group, and after binding to positively charged bacterial membrane components, they cause membrane damage.

[0032] Typical VOCs (volatile organic compounds) used in building materials include formaldehyde, acetaldehyde, toluene, xylene, styrene, ethylbenzene, and paradichlorobenzene, and formaldehyde, toluene, xylene, and paradichlorobenzene in particular are well known to have adverse effects on the human body.

[0033] (surfactant) Examples of surfactants contained in the aqueous wallpaper coating composition according to this embodiment include anionic surfactants, amine-type cationic surfactants, betaine-type amphoteric surfactants, nonionic surfactants, and naturally occurring surfactants. Examples of preferred anionic surfactants include alkyl sulfate ester salts, polyoxyethylene alkyl sulfate ester salts, alkylbenzene sulfonates, and α-olefin sulfonates. Examples of preferred amine-type cationic surfactants include alkoxydimethylamines, alkylamidodimethylamines, and alkyldimethylamines. Examples of preferred betaine-type amphoteric surfactants include alkyldimethylaminoacetic acid betaine and alkylamidodimethylaminoacetic acid betaine. Examples of preferred nonionic surfactants include glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, sorbitan fatty acid esters, and sorbitol fatty acid esters, as well as their alkylene glycol adducts, polyalkylene glycol fatty acid esters, sucrose fatty acid esters, polysorbate 20, polysorbate 60, polysorbate 80, polyoxyalkylene alkyl ethers, and polyoxyethylene alkylphenyl ethers.

[0034] Examples of naturally occurring surfactants include cyclic lipopeptide surfactants, which have a cyclic peptide and a long-chain hydrocarbon group. Examples of cyclic lipopeptide surfactants include surfactin, a salt of surfactin, iturin, a salt of iturin, arthrofactin, and a salt of arthrofactin. One or a combination of two or more selected from these is preferred, and surfactin or a salt of surfactin is particularly preferred.

[0035] For example, a salt of surfactin can be represented by the following general formula (I): [ka] In the formula, X is an amino acid residue selected from leucine, isoleucine, and valine. X is an amino acid residue, and may be in the L- or D-configuration. R is a linear or monovalent branched saturated hydrocarbon group having 9 to 18 carbon atoms. Examples include n-nonyl, 6-methyloctyl, n-decyl, 8-methylnonyl, n-heptadecyl, and n-octadecyl. M + is an alkali metal ion, and is not particularly limited, but examples thereof include lithium ion, sodium ion, potassium ion, etc., with sodium ion being preferred.

[0036] The cyclic lipopeptide surfactant can be obtained by isolating it from a microorganism that produces the cyclic lipopeptide surfactant using a known method. For example, a strain of Bacillus subtilis can be used as a microorganism that produces surfactin. Alternatively, the cyclic lipopeptide surfactant can be obtained commercially.

[0037] Cyclic lipopeptide surfactants are particularly excellent surfactants for use in the aqueous wallpaper coating composition of this embodiment. While the exact mechanism is unknown, this is likely due to the carboxyl and hydroxyl groups of the cyclic lipopeptide surfactant in the cyclic peptide moiety. The cellulose nanofibers contained in the aqueous wallpaper coating composition have hydroxyl groups in the cellulose moiety and are thought to form a three-dimensional network structure with the cyclic lipopeptide surfactant. Because cyclic lipopeptide surfactants have excellent transparency, their inclusion in the aqueous wallpaper coating composition prevents the wallpaper from losing its color even after several hours of application and subsequent water loss. Furthermore, because cyclic lipopeptide surfactants have excellent emulsifying and dispersing properties and stability, the aqueous wallpaper coating composition of this embodiment containing cyclic lipopeptide surfactants allows the cellulose nanofibers and polyphenols to be uniformly dispersed in the composition and coating, maintaining the dispersed state.

[0038] The content of surfactant contained in the aqueous wallpaper coating composition according to this embodiment is, for example, preferably 0.1% or more, more preferably 0.2% or more, and optimally 0.3% of the total amount of the aqueous wallpaper coating composition. On the other hand, the upper limit of the content of surfactant contained in the aqueous wallpaper coating composition according to this embodiment is 0.5% or less. When the surfactant content is within this range, the aqueous wallpaper coating composition is less likely to be repelled by the wallpaper, can be applied evenly, and is less likely to produce uneven coating.

[0039] On the other hand, a water-based wallpaper coating composition containing a naturally-derived surfactant, a plant-derived polyphenol, and cellulose nanofibers is one preferred embodiment. This water-based wallpaper coating composition is particularly safe for the human body because the components are naturally-derived.

[0040] (Cellulose nanofiber) Cellulose nanofibers (also called "CNF") can be obtained by defibrating (refining) raw pulp, and can be produced by known processing methods such as chemical processing and mechanical processing.

[0041] The raw pulp for cellulose nanofibers can be one or more selected from the following: wood pulp made from hardwoods, softwoods, etc.; non-wood pulp made from straw, bagasse, cotton, hemp, bast fibers, etc.; and deionized paper pulp (DIP) made from waste brown paper, waste envelopes, waste magazines, waste flyers, waste cardboard, white waste paper, imitation waste paper, recycled waste paper, recovered waste paper, broke paper, etc. In recent years, there has been an increasing demand for products containing organic ingredients that take environmental impact into consideration, so wood pulp made from hardwoods or softwoods derived from plants other than waste paper is particularly suitable.

[0042] The wood pulp can be one or more selected from chemical pulps such as hardwood kraft pulp (LKP), softwood kraft pulp (NKP), sulfite pulp (SP), dissolving pulp (DP), etc., and mechanical pulp (TMP). In particular, chemical pulps such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), which are wood pulps that increase the cellulose content, are preferred, and bleached pulp (BKP) is also suitable.

[0043] As the mechanical pulp, for example, one or more types can be selected and used from stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi-ground pulp (CGP), thermo-ground pulp (TGP), ground pulp (GP), thermo-mechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), refiner mechanical pulp (RMP), bleached thermo-mechanical pulp (BTMP), etc.

[0044] From the viewpoint of producing cellulose nanofibers with a relatively small average fiber diameter, it is preferable to use kraft pulp, which is easy to defibrate and has high dispersibility.

[0045] The cellulose nanofibers may be subjected to pretreatment before being defibrated. For example, as a pretreatment, the raw material pulp may be mechanically pre-beaten or chemically modified. The method of pre-beating is not particularly limited, and known methods can be used.

[0046] Examples of chemical modification treatments of raw pulp include hydrolysis of polysaccharides with acids (e.g., sulfuric acid, etc.) (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), oxidation of polysaccharides with oxidizing agents (e.g., ozone, etc.) (oxidation treatment), reduction of polysaccharides with reducing agents (reduction treatment), oxidation with a TEMPO catalyst (oxidation treatment), anionization by phosphate esterification (anion treatment), and cationization (cation treatment).

[0047] Among the modification treatments using chemical methods, oxidation using a TEMPO catalyst can be carried out by known methods (for example, the method disclosed in Japanese Patent Application Laid-Open No. 2023-40759), but it can also be carried out by the following method. TEMPO-catalyzed oxidation is a treatment using TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) as a catalyst. When cellulose fibers are oxidized using a TEMPO catalyst, the primary hydroxyl groups of the cellulose fibers are regioselectively oxidized to carboxyl groups, and then the C6 position is substituted with a carboxylate salt by alkali treatment. In TEMPO-catalyzed oxidation, cellulose fibers are produced in which the C6 position is substituted with a carboxylate salt by reacting with hypochlorous acid in the presence of TEMPO or sodium bromide while maintaining a predetermined pH.

[0048] In the method of anionizing cellulose fibers by phosphoric acid esterification, anionic functional groups are introduced into the cellulose fibers. Examples of cellulose nanofibers into which anionic functional groups have been introduced include cellulose nanofibers into which phosphorus oxoacid ester groups have been introduced and cellulose nanofibers in which the hydroxyl groups of the pyranose rings have been directly oxidized to carboxyl groups. Esterification with phosphorus oxoacid can be carried out, for example, by the method described in JP 2019-199671 A.

[0049] Cellulose nanofibers modified by the introduction of anionic functional groups have relatively high dispersibility. This is presumably because the anionic functional groups cause localized charge bias, many of the defibrated cellulose nanofibers have relatively small fiber diameters, reducing the variation in fiber diameter, and the anionic functional groups easily form hydrogen bonds with water and organic solvents in the dispersion.

[0050] When cellulose fibers are subjected to esterification with phosphorus oxoacid, which is an example of anionization, the fiber raw material can be refined, and the resulting cellulose nanofibers have a large aspect ratio, excellent strength, high light transmittance, and high viscosity.

[0051] On the other hand, sodium carboxymethylcellulose, a polysaccharide having a structure in which a carboxymethyl group is ether-bonded to the hydroxyl group of cellulose, is also preferred as a cellulose nanofiber that has been modified by a chemical method.

[0052] Defibration of cellulose fibers can be carried out by known methods, including, for example, the following defibration devices and methods. Defibration can be carried out using one or more of the following: homogenizers, such as high-pressure homogenizers and high-pressure homogenizers; grinders, grinders, millstone-type friction machines, such as conical refiners and disc refiners; refiners, such as conical refiners and disc refiners; and various bacteria. However, defibration of cellulose fibers is preferably carried out using devices and methods that use a water flow, particularly a high-pressure water flow, to refine the fibers. This device and method results in cellulose nanofibers with extremely uniform size and dispersion. In contrast, using a grinder that grinds the fibers between rotating grindstones, for example, makes it difficult to uniformly refine the cellulose fibers, and in some cases, there is a risk that some undisintegrated fiber clumps may remain.

[0053] An example of a grinder used to defibrate cellulose fibers is the Masscolloider manufactured by Masuko Sangyo Co., Ltd. Furthermore, examples of devices that use high-pressure water flow to pulverize the fibers include the Starburst (registered trademark) manufactured by Sugino Machine Co., Ltd. and the Nanovater (registered trademark) manufactured by Yoshida Kikai Kogyo Co., Ltd. Furthermore, an example of a high-speed rotary homogenizer used to defibrate cellulose fibers is the Clearmix-11S manufactured by M Technique Co., Ltd.

[0054] Cellulose nanofibers obtained by defibrating cellulose fibers through chemical modification treatment can be called chemically modified cellulose nanofibers, while cellulose nanofibers obtained by defibrating without chemical modification treatment can be called unmodified cellulose nanofibers.

[0055] The cellulose nanofibers contained in the aqueous wallpaper coating composition according to this embodiment may consist of only unmodified cellulose nanofibers, or may consist of only chemically modified cellulose nanofibers, or may contain both unmodified and chemically modified cellulose nanofibers.

[0056] The raw material pulp is preferably defibrated so that the physical properties of the resulting cellulose nanofibers have the desired values ​​or evaluations shown below.

[0057] (average fiber diameter) The upper limit of the average fiber diameter (average fiber width; average diameter of a single fiber) of cellulose nanofibers is 1000 nm, preferably 500 nm or less, more preferably 100 nm or less, and particularly preferably 50 nm or less. When the average fiber diameter of cellulose nanofibers is 1000 nm or less, the cellulose nanofibers attached to the wallpaper to which the aqueous wallpaper coating composition according to this embodiment has been applied are inconspicuous, and are less likely to detract from the design of the wallpaper itself, which is preferable. On the other hand, the lower limit of the average fiber diameter of cellulose nanofibers is preferably 1 nm. If the average fiber diameter is below this lower limit, the cellulose nanofibers will be more easily dissolved in the coating composition, causing a decrease in the viscosity of the aqueous wallpaper coating composition.

[0058] The average fiber diameter of cellulose nanofibers can be adjusted, for example, by selecting raw material pulp, pre-treating it, defibrating it, etc.

[0059] The method for measuring the average fiber diameter of cellulose nanofibers is as follows. First, 100 ml of an aqueous dispersion of cellulose nanofibers with a solid content of 0.01 to 0.1% by mass was filtered through a Teflon® membrane filter and solvent-substituted once with 100 ml of ethanol and three times with 20 ml of t-butanol. The sample was then freeze-dried and osmium-coated to obtain a sample. This sample was then observed using an SEM electron microscope at a magnification of 3,000x to 30,000x, depending on the width of the fibers. Specifically, two diagonal lines were drawn on the observed image, and three straight lines were arbitrarily drawn passing through the intersections of the diagonal lines. The widths of a total of 100 fibers intersecting these three straight lines were then visually measured. The median diameter of the measured values ​​was then taken as the average fiber diameter.

[0060] (average fiber length) The average fiber length of the cellulose nanofibers (average length of single fibers) is, for example, preferably 0.01 to 1000 μm, more preferably 0.03 to 500 μm. If the average fiber length is within this range, the cellulose nanofibers are less likely to entangle with each other and therefore less likely to aggregate, resulting in an aqueous wallpaper coating composition in which the dispersed state is maintained.

[0061] The average fiber length can be adjusted as desired by, for example, selecting the raw pulp, pre-treating it, defibrating it, and the like.

[0062] The average fiber length of cellulose nanofibers is measured in the same manner as for the average fiber diameter, by visually measuring the length of each fiber. The median length of the measured values ​​is taken as the average fiber length.

[0063] (Axle ratio) The axial ratio of the cellulose nanofibers (average fiber length / average fiber width) is preferably 10 to 1,000,000, more preferably 30 to 500,000, and particularly preferably 50 to 100,000. When the axial ratio of the cellulose nanofibers is within this range, the degree of entanglement between the fibers is small, and the cellulose nanofibers are in a sufficiently dispersed state in the resulting aqueous wallpaper coating composition.

[0064] (crystallinity) The lower limit of the crystallinity of the cellulose nanofibers is preferably 50 or more, more preferably 60 or more, and particularly preferably 70 or more, and the upper limit is preferably 100 or less, more preferably 95 or less, and particularly preferably 90 or less. If the crystallinity is less than 50, the entanglement of the fibers will be weakened due to the influence of temperature changes during drying, and the ability to retain other substances will be weakened, making it difficult to form cellulose particles with the desired particle size.

[0065] The crystallinity is a value measured by X-ray diffraction in accordance with JIS-K0131 (1996) "General rules for X-ray diffraction analysis." Cellulose nanofibers have amorphous and crystalline portions, and the crystallinity refers to the proportion of crystalline portions in the entire cellulose nanofiber.

[0066] (Water retention) The water retention of the cellulose nanofibers is not particularly limited, but for example, for unmodified cellulose nanofibers, it is 500% or less, more preferably 100 to 500%. If the water retention is within this range, the cellulose nanofibers are less likely to dry out, wallpaper coated with an aqueous wallpaper coating composition is maintained at a predetermined humidity or higher, and the wallpaper is less likely to deform due to drying.

[0067] The water retention of cellulose nanofibers can be adjusted as desired by, for example, selecting the raw pulp, pre-treating it, defibrating it, etc.

[0068] The water retention of cellulose nanofibers is a value measured in accordance with JAPAN TAPPI No. 26 (2000).

[0069] The aqueous wallpaper coating composition according to this embodiment may contain, for example, 1 to 10% polyphenols and preferably 0.04 to 2%, more preferably 0.05 to 1%, and even more preferably 0.1 to 0.5% cellulose nanofibers based on the solids content of the total aqueous wallpaper coating composition. It is believed that the cellulose nanofibers form a three-dimensional network structure in the aqueous wallpaper coating composition, and even a small amount of cellulose nanofibers can provide sufficient viscosity for the aqueous wallpaper coating composition. When the aqueous wallpaper coating composition contains cellulose nanofibers within the above range, sufficient viscosity is achieved, and the thixotropic properties allow for good spreadability during application, making it easy to apply.

[0070] (Antibacterial agent) An antibacterial agent can be added to the aqueous wallpaper coating composition according to this embodiment. Examples of antibacterial agents include sodium benzoate, alkyldiamine ethylglycine hydrochloride, sodium dehydroacetate, chlorhexidine gluconate, alkylisoquinonylium bromide, sodium lauryldiaminoethylglycine, chloroxylenol, thymol, piroctone olamine polyaminopropyl biguanide, chlorhexidine chloride, and quaternary ammonium salts. Examples of quaternary ammonium salts include alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, benzalkonium chloride, didecyldimethylammonium chloride, cetyltrimethylammonium chloride, and cetylpyridinium chloride. Quaternary ammonium salts are particularly preferred, with benzalkonium chloride being particularly preferred due to its excellent antibacterial properties and low cost. Even small amounts provide excellent antibacterial properties. These antibacterial agents exhibit antibacterial properties in small amounts and are highly safe for human skin, making them suitable for use in aqueous wallpaper coating compositions.

[0071] The content of the antibacterial agent in the aqueous wallpaper coating composition according to this embodiment is, for example, preferably 0.03% or less, more preferably 0.02% or less, even more preferably 0.01% or less, and optimally 0.005%, relative to the total amount of the aqueous wallpaper coating composition. When the content of the antibacterial agent is within the above range, the antibacterial agent is dispersed together with the cellulose nanofibers in the aqueous wallpaper coating composition, and by applying the aqueous wallpaper coating composition to wallpaper, the coated wallpaper preferably remains antibacterial.

[0072] (thickener) Cellulose nanofibers are formed by cellulose that contains many hydroxyl groups (OH groups). The presence of many hydroxyl groups is believed to allow hydrogen bonds to form between the cellulose nanofibers, forming a three-dimensional network structure between the cellulose nanofibers. Due to these characteristics, a liquid in which cellulose nanofibers are dispersed has a relatively high viscosity, as the cellulose nanofibers are less likely to move freely individually. Furthermore, a liquid in which cellulose nanofibers are dispersed has both viscosity and thixotropy.

[0073] As described above, the aqueous wallpaper coating composition according to this embodiment contains cellulose nanofibers, and therefore has a predetermined viscosity. However, if further improvement in adhesion to wallpaper is desired, a thickener can be added to the aqueous wallpaper coating composition. Examples of thickeners include gum arabic, starch, sodium alginate, pectin, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, and hydroxypropyl methyl cellulose (HPMC). Sodium alginate is particularly preferred because it produces a thickening effect even in small amounts. When a thickener is added to the aqueous wallpaper coating composition according to this embodiment, for example, the amount is preferably 0.3% or less, more preferably 0.2% or less, and even more preferably 0.1% or less, based on the total amount of the aqueous wallpaper coating composition. If the thickener is contained within the above range, the aqueous wallpaper coating composition applied to wallpaper will be less likely to drip. However, if a large amount of thickener is added to the aqueous wallpaper coating composition, the viscosity will be too high, making application difficult. Note that when a thickener is added to the aqueous wallpaper coating composition, the lower limit should be greater than 0%.

[0074] The aqueous wallpaper coating composition according to this embodiment can be applied with good adhesion to both water-repellent (hydrophobic) and hydrophilic wallpaper, but is particularly suitable for application to water-repellent wallpaper. Conventional aqueous coatings tend to repel water-repellent wallpaper, forming droplets, making it difficult to achieve a uniform coating. However, the aqueous wallpaper coating composition according to this embodiment is less likely to be repelled by water-repellent wallpaper. While the exact reason why the aqueous wallpaper coating composition according to this embodiment is less likely to be repelled is unclear, it is likely due to the action of cellulose nanofibers. When an aqueous coating composition or coating containing cellulose nanofibers is applied to water-repellent wallpaper, the applied area is covered with numerous cellulose nanofibers and water. Because the cellulose nanofibers are hydrogen-bonded to each other and their free movement is restricted, the cellulose nanofibers likely inhibit the free deformation of the water contained in the aqueous coating composition or coating (e.g., the formation of droplets due to surface tension), thereby maintaining a non-repelling form. It is also believed that the free movement of polyphenols contained in the aqueous wallpaper coating composition within the composition or coating is restricted by the three-dimensional network structure of the cellulose nanofibers, maintaining them in a dispersed state. Furthermore, it is presumed that the inclusion of a surfactant in the aqueous wallpaper coating composition makes it difficult for polyphenols to separate from water, maintaining the polyphenols in a well-dispersed state in the aqueous coating composition or water-based coating. This means that even poorly water-soluble polyphenols, which are difficult to dissolve in water, are prevented from free movement by the network structure of the cellulose nanofibers, and are maintained in a dispersed state in the aqueous wallpaper coating composition according to this embodiment.

[0075] Wallpaper, which is the target of application of the aqueous wallpaper coating composition according to this embodiment, is a sheet made of cloth, paper, or vinyl used as an interior finishing material for walls and ceilings in buildings, and is applied for purposes such as protecting the substrate of walls and ceilings or for decorative purposes. Examples of wallpaper include, but are not limited to, fiber-based wallpaper, vinyl chloride resin-based wallpaper, and plastic-based wallpaper. Examples of fiber-based wallpaper include those primarily made of vegetable fibers or cellulose-based recycled fibers such as rayon (including synthetic fibers), and those primarily made of synthetic fibers (acrylic, polyester, etc.). Examples of vinyl chloride resin-based wallpaper include those primarily made of vinyl chloride resin and those whose base surface is covered with vinyl chloride resin. Examples of plastic-based wallpaper include those primarily made of plastics other than vinyl chloride resin and those whose base surface is covered with the aforementioned plastics. Other examples include wallpaper containing synthetic fibers made of polyester or acrylic resin as disclosed in Patent Document 2, wallpaper coated with a water-repellent coating composition characterized by containing copolymer particles of an ethylenically unsaturated monomer, wax particles containing a hydrocarbon compound having 8 to 60 carbon atoms and a functional group, and a dispersion medium as disclosed in Patent Document 4, and wallpaper with a fluorine-treated surface.

[0076] There are no particular limitations on water-repellent wallpaper as long as it repels water, but water-repellent wallpaper refers to wallpaper that has the property of repelling water, and when a drop of water is placed on the wallpaper, the contact angle between the wallpaper and the water is preferably 40° or more and less than 180°, more preferably 90° or more and less than 180°.

[0077] The aqueous wallpaper coating composition according to this embodiment has a Brookfield viscosity at 6 rpm of 20 to 1,000 mPa·s, preferably 30 to 500 mPa·s. The aqueous wallpaper coating composition according to this embodiment has a Brookfield viscosity at 60 rpm of 5 to 200 mPa·s, preferably 10 to 150 mPa·s, and more preferably 10 to 100 mPa·s. The thixotropy index (Ti value) of the aqueous wallpaper coating composition according to this embodiment is 1 to 10, preferably 1 to 8, and more preferably 1 to 5. The thixotropy index (Ti value) is calculated by dividing the Brookfield viscosity at 6 rpm by the Brookfield viscosity at 60 rpm. When the Brookfield viscosity and thixotropy index are within the above ranges, the composition is less likely to drip or peel when applied to wallpaper with a brush, brush roller, or the like, and can be applied with good spreadability.

[0078] The B-type viscosity of the aqueous wallpaper coating composition according to this embodiment can be adjusted by mixing an aqueous solvent, such as water, into the aqueous wallpaper coating composition. When the aqueous wallpaper coating composition according to this embodiment is actually applied to wallpaper, the aqueous wallpaper coating composition will have an excellent VOC reduction effect if it contains preferably 1 to 10%, more preferably 3 to 9%, and even more preferably 4 to 8% of polyphenols relative to the total amount of the aqueous wallpaper coating composition.

[0079] On the other hand, the aqueous wallpaper coating composition according to this embodiment can be applied to wallpaper in the form of an oil-in-water emulsion, and can be applied evenly even to water-repellent wallpaper.

[0080] The aqueous wallpaper coating composition according to this embodiment preferably has a film thickness of 0.1 to 5 μm, more preferably 1 to 3 μm, on the wallpaper.

[0081] The aqueous wallpaper coating composition according to this embodiment can be applied to wallpaper installed on the walls or ceilings of buildings. As long as people do not inappropriately touch the wallpaper to which the composition has been applied, the effects of applying the aqueous wallpaper coating composition according to this embodiment will last for a long period of time, for example, one year or more. [Example]

[0082] (Preparation of Test Examples) A test example is described below. Polyphenols, cellulose nanofibers, surfactants, sodium alginate, and benzalkonium chloride were added to a beaker containing an appropriate amount of water while stirring, and further water was added to make a 200 mL solution. The test sample was prepared using the formulations shown in Table 1. The polyphenols used were "Bansei" manufactured by Nature Grace Co., Ltd. The cellulose nanofibers used were "ELLEX®-S" (hereinafter referred to as "CNF1") manufactured by Daio Paper Corporation, with an average fiber diameter of 50 nm, "ELLEX®-☆ (Star)" (hereinafter referred to as "CNF2") manufactured by Daio Paper Corporation, with an average fiber diameter of 3 nm, and "Carboxymethylcellulose Sodium" (hereinafter referred to as "CNF3") manufactured by Nippon Paper Industries Co., Ltd. The surfactants used were "Kaneka Surfactin Sodium" manufactured by Kaneka Corporation (referred to as "Surfactant 1") and "Polyflow KL-100" manufactured by Kyoeisha Chemical Co., Ltd. (referred to as "Surfactant 2"). For sodium alginate, we used "Sodium Alginate" manufactured by Matsuba Pharmaceutical Co., Ltd. For benzalkonium chloride, we used "Benzalkonium Chloride Solution Osban S (10 w / v%)" manufactured by Nippon Pharmaceutical Co., Ltd. The amounts of polyphenols, CNF1, CNF2, CNF3, and benzalkonium chloride in Table 1 are calculated as solid content.

[0083] [Table 1]

[0084] The test example was applied to a water-repellent wallpaper ("airrefre LW-4350" product manufactured by Lilycolor Co., Ltd.) with a brush roller so that the film thickness of the test example was 2 μm. The test example or the wallpaper to which the test example was applied was subjected to an antibacterial evaluation test (Lumitester test), a liquid contact angle test, B-type viscosity measurement, evaluation of coating unevenness, and evaluation of fixation.

[0085] (Antibacterial evaluation test) Antibacterial properties were evaluated using a Lumitester. The Lumitester uses the firefly luciferase enzyme to measure the amount of ATP (adenosine triphosphate) light emitted by the substance that energizes all living organisms, as an indicator of microorganisms and dirt. Each test sample was applied to wallpaper and left for 10 minutes. A tissue was then placed over the wallpaper to ensure that no moisture had penetrated the tissue. The wallpaper was then wiped with the cotton swab provided with the Lucifer AT100 ATP measurement kit manufactured by Kikkoman Biochemifa Corporation. The cotton swab was then inserted into the Lumitester C-110 luminometer manufactured by the same company to generate light, and the amount of ATP light emitted was measured.

[0086] (Liquid contact angle test) The liquid contact angle of the test sample surface was measured. The measurement device used was the "DMs-401" device manufactured by Kyowa Interface Science Co., Ltd. The liquid contact angle test was conducted in accordance with JIS-R3257 (1999), with a liquid droplet (test sample) placed on the test piece. The test result was calculated by averaging three values ​​obtained by performing the test three times for each test sample. The liquid contact angle test was conducted using a flat glass plate measuring 50 mm x 100 mm and 1.6 mm thick as the test piece, in an environment with a temperature of 23.5 ± 1°C and a relative humidity of 65 ± 1%.

[0087] (B type viscosity, etc.) For the test examples, Brookfield viscosity at 6 rpm and Brookfield viscosity at 60 rpm were measured, and the thixotropy index (Ti value) was calculated. The Ti value was calculated using the following formula: (Ti value) = (B-type viscosity at 6 rpm) / (B-type viscosity at 60 rpm)

[0088] (Uneven paint) The wallpaper coated with the test sample was left to stand for 60 minutes after application, and then checked for unevenness in the coating according to the following evaluation criteria. ⊚: When the entire coated area was visually inspected, no coating unevenness was observed. ○: When the entire coated area was visually inspected, no coating unevenness was observed. △: When the entire coated area was visually inspected, uneven coating was observed that may cause problems in the future. ×: When the entire coated area was visually inspected, uneven coating was observed that is likely to cause problems in the future.

[0089] (adhesion) The fixation of the wallpaper coated with the test sample was checked according to the following evaluation criteria after leaving it to stand for 60 minutes after application. ⊚: When the test sample was applied, there was no repelling and the adhesion was excellent. ◯: When the test sample was applied, there was generally no repelling and the adhesion was good. △: When the test sample was applied, it repelled, and there was a slight problem with fixation. ×: When the test sample was applied, repelling occurred, and there was a major problem with fixation.

[0090] The results are shown in Table 2. [Table 2]

[0091] Furthermore, Test Example 1 was subjected to a VOC concentration test, an antiviral test, and an antibacterial test as follows.

[0092] (VOC concentration test) The formaldehyde concentration was measured using the sampling bag method (ISO / IEC-17025). The test procedure was as follows: A 125 mm diameter filter paper coated with Test Example 1 was used as the test specimen. The test specimen was placed in a Tedlar bag with the bottom end cut off, and after removing as much air as possible from the bag, the bag was sealed with a sealing band. 3 L of formaldehyde gas adjusted to a specified concentration using paraformaldehyde was sealed in the bag. The bag containing formaldehyde was left standing in a dark place, and a blank test was performed using an empty bag left standing in a dark place. The test results are shown in Table 3.

[0093] [Table 3]

[0094] (Antiviral test) The antiviral test was conducted in accordance with ISO 21702. The viruses used in the test were influenza A virus (H3N2 type) and feline calicivirus (a norovirus surrogate virus). The test procedure was as follows.

[0095] Test Example 1 was applied to polyethylene plate 1 and polyethylene plate 2 (each 3 cm × 3 cm) to a film thickness of 2 μm. An uncoated polyethylene plate 3 (blank) was prepared as a comparative example (blank). A liquid containing the virus was dropped onto the coated surfaces of polyethylene plate 1 and polyethylene plate 2 with Test Example 1, and onto one side of polyethylene plate 3, and the liquid was covered with a film and pressed. Polyethylene plate 1 (Test Example 1) and polyethylene plate 3 (blank) were left for 24 hours at 25°C and 90% humidity. After 24 hours, the liquid was recovered and inoculated onto cells. The number of holes formed in the cells due to virus infection was counted using the plaque method, and the number of remaining viruses was measured. Furthermore, for polyethylene plate 2 (Test Example 1), the liquid containing the virus was dropped, and the liquid was covered with a film and pressed, after which the liquid was immediately recovered and inoculated onto cells. The number of holes formed in the cells due to virus infection was counted using the plaque method, and the number of remaining viruses was measured. The results are shown in Figure 1. Comparing the results after 24 hours, the viral infectivity titer of polyethylene plate 1 coated with Test Example 1 was significantly lower than that of polyethylene plate 3, which was the blank.

[0096] On the other hand, the antiviral activity value of the polyethylene plate coated with Test Example 1 was 4.3, which was significantly higher than the judgment standard value of 2.0 or more. This result demonstrated that the polyethylene plate coated with Test Example 1 has high antiviral activity against influenza virus A (H3N2 type, enveloped virus).

[0097] (Antibacterial test) A polyethylene plate 11 coated with Test Example 1 and a blank polyethylene plate 12 were prepared, and an antibacterial test was conducted in accordance with JIS-Z-2801. The results are shown in Figure 2. The antibacterial activity value of the polyethylene plate 11 coated with Test Example 1 was 3.9, which exceeded the judgment standard value of 2.0 and demonstrated antibacterial effect against Escherichia coli.

[0098] (others) The B-type viscosity of water-based wallpaper coating compositions is a value measured at 25°C in accordance with JIS-Z8803 (2011) "Method for measuring viscosity of liquids." B-type viscosity is the resistance torque when stirring the dispersion; the higher the viscosity, the more energy is required for stirring. Unless otherwise specified, the JIS, TAPPI and other tests and measurement methods shown in the above specification are performed at room temperature, particularly 25°C, and at atmospheric pressure, particularly 1 atm. [Industrial Applicability]

[0099] The present invention can be used for wallpaper installed in buildings.

Claims

1. A cellulose nanofiber having a polyphenol, a surfactant, and an average fiber diameter of 1 nm or more and 1000 nm or less. A water-based coating composition for wallpaper.

2. Further comprising a thickener, The water-based wallpaper coating composition according to claim 1.

3. The surfactant is a naturally occurring surfactant. The water-based wallpaper coating composition according to claim 1.

4. The polyphenol is a plant-derived polyphenol. The water-based wallpaper coating composition according to claim 1.

5. Further having an antibacterial agent, The water-based wallpaper coating composition according to claim 1.

6. For the total amount of water-based wallpaper coating composition, The polyphenol is contained in an amount of 1 to 10%, and the surfactant is contained in an amount of 0.1% or more and 0.5% or less. The water-based wallpaper coating composition according to claim 1.

7. Adding water-repellent properties to wallpaper The water-based paint composition according to claim 1.

8. Brookfield viscosity at 6 rpm is 20 to 1000 mPa s; The water-based wallpaper coating composition according to claim 1.

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