Aqueous coating agent for building materials and decorative sheet

Abstract

To provide an aqueous coating agent for building materials which has good adhesion to a plastic substrate and has high durability and excellent scratch resistance.SOLUTION: There are provided: an aqueous coating agent for building materials which contains a (meth)acrylic emulsion, a curing agent, and a silane coupling agent and contains the silane coupling agent in an amount of 5-30 mass% based on the total solid content; and a decorative sheet using the aqueous coating agent for building materials. The aqueous coating agent for building materials preferably further contains a polar group-containing olefinic resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous coating agent for building materials and a decorative sheet using the same. [Background technology]

[0002] Generally, decorative sheets are used as materials that can impart an appearance (design) similar to that of natural materials by being attached to the surface of plywood or the like for furniture, residential interiors, vehicle interiors, etc. Such decorative sheets are required to have high durability, design, texture similar to that of real natural materials, and functionality, so in addition to a printed layer for imparting design, a coating layer that imparts high durability, texture, and functionality is provided on the plastic substrate.

[0003] Known coating agents for use in such coating layers for decorative sheets include aqueous coating agents containing an aqueous acrylic resin emulsion with a glass transition temperature of 80°C or higher and an acid value of 50 mgKOH / g or higher and a carbodiimide curing agent (see Patent Document 1), and an aqueous coating agent containing a polycarbonate-based urethane resin and a carbodiimide curing agent (see Patent Document 2). With the aim of achieving high durability, designability, and a texture similar to that of real natural materials, these coating agents use a carbodiimide curing agent to increase crosslink density, thereby imparting scratch resistance and stain resistance (see Patent Document 2, paragraph 0030), and add fillers such as silica to adjust gloss and impart scratch resistance (see Patent Document 2, paragraph 0035). However, poor adhesion sometimes occurred. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-144456 [Patent Document 2] Japanese Patent Application Publication No. 2023-122995 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an aqueous coating agent for building materials that has good adhesion to plastic substrates and is highly durable and scratch-resistant.

[0006] Performance degradation caused by poor adhesion in decorative sheets includes whitening after alkaline cleaning (which often occurs especially in decorative sheets used for flooring) and peeling of the coating layer on the surface of the decorative sheet after accelerated weathering tests. As a result of extensive research, the present inventors have found that an aqueous coating agent containing a (meth)acrylic emulsion, an epoxy-based curing agent or an aziridine-based curing agent, and a silane coupling agent can provide a coating layer that is less likely to cause adhesion defects, thereby achieving the above-mentioned object, and have thus completed the present invention.

[0007] That is, the present invention provides an aqueous coating agent for building materials, which contains a (meth)acrylic emulsion, a curing agent, and a silane coupling agent, and the silane coupling agent is contained in an amount of 5 to 30 mass % based on the total solid content.

[0008] The present invention also provides a decorative sheet having a coating layer of an aqueous coating agent on a plastic substrate whose coated surface has been subjected to corona treatment, wherein the aqueous coating agent is the aqueous coating agent described in claim 1. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an aqueous coating agent for building materials which is less likely to cause poor adhesion and has excellent durability and scratch resistance, and a decorative sheet using the same. DETAILED DESCRIPTION OF THE INVENTION

[0010] ((Meth)acrylic emulsion) The (meth)acrylic emulsion used in the present invention is not particularly limited, and any publicly known and available (meth)acrylic emulsion can be used.

[0011] ((Meth)acrylic resin) The (meth)acrylic resin contained in the aqueous (meth)acrylic emulsion is not particularly limited, and examples thereof include a homopolymer or copolymer of a (meth)acrylate, and a copolymer of a vinyl monomer copolymerizable with a (meth)acrylate. Furthermore, a copolymer having an acid value is preferred for the purpose of imparting water dispersibility, water solubility, and reactivity with epoxy-based curing agents and aziridine-based curing agents. In the present invention, "(meth)acrylate" refers to either or both of acrylate and methacrylate, and "(meth)acrylic" refers to either or both of acrylic and methacrylic.

[0012] Examples of (meth)acrylates and vinyl monomers copolymerizable with (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-pentafluoropropyl (meth)acrylate, acrylate, perfluorocyclohexyl (meth)acrylate, glycidyl (meth)acrylate, allyl glycidyl ether, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, (meth)acrylamide, N-monoalkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, 2-aziridinylethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, acrolein, diacetone (meth)acrylamide, acetoacetoxyethyl (meth)acrylate, etc. The (meth)acrylate may be used alone or in combination of two or more.

[0013] Examples of vinyl monomers include vinyl acetate, vinyl propionate, vinyl versatate, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, (meth)acrylonitrile, styrene, α-methylstyrene, divinylstyrene, isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone, etc. The polymerizable unsaturated group-containing compound may be used alone or in combination of two or more.

[0014] Furthermore, for the purpose of introducing one or more acidic groups selected from the group consisting of carboxyl groups and carboxylate groups in which the carboxyl group has been neutralized with a basic compound, a copolymer having an acid value can be obtained by copolymerizing a (meth)acrylic monomer having a carboxyl group, such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, β-(meth)acryloyloxyethyl hydrogen succinate, or β-(meth)acryloyloxyethyl hydrogen phthalate. When an acidic group is introduced, it is preferable to appropriately adjust the amount of the monomer so that the acid value falls within a desired range, as will be described in detail later.

[0015] The (meth)acrylic resin may also be reacted with a self-crosslinking component. That is, the (meth)acrylic resin may be a self-crosslinking type. Examples of the self-crosslinking component include an isocyanate compound, an epoxy compound, an amine compound, a melamine compound, a hydrazine compound, an aldehyde compound, and an oxazoline compound.

[0016] (Meth)acrylic resins can be produced, for example, by polymerizing various monomers in the presence of a polymerization initiator at a temperature range of 50°C to 180°C, more preferably 80°C to 150°C. Examples of polymerization methods include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Furthermore, when the (meth)acrylic resin is a copolymer, it may be a random copolymer, block copolymer, graft copolymer, or the like, depending on the polymerization mode. When obtained by the bulk polymerization or solution polymerization method, the (meth)acrylic resin having an acidic group introduced therein can be neutralized with a neutralizing agent such as an alkali after polymerization, and the solvent can be replaced with an aqueous medium to form an aqueous emulsion.

[0017] The (meth)acrylic resin may preferably be a core-shell emulsion. The core-shell emulsion refers to a state in which a first polymer is dispersed in an aqueous medium by a second polymer, and usually, the second polymer is present at the outermost part of the resin particles to form a shell portion, and a part or all of the first polymer forms a core portion.

[0018] The aqueous (meth)acrylic emulsion is characterized by a glass transition temperature (Tg) of 0 to 110°C. This range is preferred because it maximizes the effects of the present invention. The glass transition temperature (Tg) is more preferably 20°C or higher, even more preferably 30°C or higher, even more preferably 40°C or higher, and more preferably 100°C or lower.

[0019] In the present invention, the glass transition temperature (Tg) refers to the so-called calculated glass transition temperature, which is a value calculated by the following method. (Formula 1) 1 / Tg(K)=(W1 / T1)+(W2 / T2)+...(Wn / Tn) (Equation 2) Tg(°C)=Tg(K)-273 In Equation 1, W1, W2, ..., Wn represent the mass percentage of each monomer relative to the total mass of the monomers used in producing the polymer, and T1, T2, ..., Tn represent the glass transition temperature (K) of the homopolymer of each monomer. The values ​​of T1, T2, ..., Tn are those listed in the Polymer Handbook (Fourth Edition, edited by J. Brandrup, E.H. Immergut, and E.A. Grulke). For the homopolymers of monomers whose glass transition temperatures are not listed in the Polymer Handbook, the glass transition temperatures were measured using a differential scanning calorimeter "DSCQ-100" (manufactured by TA Instrument) according to JIS K7121. Specifically, the polymer was vacuum-suctioned to completely remove the solvent, and the heat change was measured in the range of -100°C to +200°C at a temperature increase rate of 20°C / min. The glass transition temperature was determined as the point where a line equidistant in the vertical direction from the extended line of each baseline intersected with the curve of the stepwise change portion of the glass transition.

[0020] The acid value (also referred to as "AV") of the (meth)acrylic resin used in the (meth)acrylic emulsion is preferably 10 mgKOH / g or more, and most preferably 20 mgKOH / g or more. An acid value of 10 mgKOH / g or more allows the resin to be strongly crosslinked, which is preferable because it maximizes the effects of the present invention. In the present invention, the acid value refers to the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g of resin.

[0021] The glass transition temperature (also referred to as "Tg") of the (meth)acrylic resin used in the (meth)acrylic emulsion is preferably 0 to 110° C., and most preferably 10 to 100° C. This range is preferred because it allows the effects of the present invention to be maximized.

[0022] The minimum film-forming temperature (also referred to as "MFT") of the (meth)acrylic emulsion is preferably from -20 to 80°C, and most preferably not more than 70°C. This range is preferred because it allows the effects of the present invention to be maximized.

[0023] In the present invention, the (meth)acrylic resin (A) is preferably an acrylic resin (i.e., a resin obtained by polymerizing substantially only (meth)acrylic acid ester monomers) or a styrene-acrylic resin (i.e., a resin obtained by copolymerizing a styrene monomer and a (meth)acrylic acid ester monomer).

[0024] (water-based solvent) The aqueous solvent used in the present invention includes water and water-soluble organic solvents that dissolve in water. As the water, pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, or ultrapure water can be used. Furthermore, it is preferable to use water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide. Examples of water or aqueous solvents that serve as a medium include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, and hexanediol; glycol esters such as propylene glycol laurate; diethylene glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl, and carbitol; glycol ethers such as cellosolves containing propylene glycol ether, dipropylene glycol ether, and triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; lactones such as sulfolane, esters, ketones, and γ-butyrolactone; lactams such as N-(2-hydroxyethyl)pyrrolidone; and various other solvents known as aqueous organic solvents, such as glycerin and its polyalkylene oxide adducts. These aqueous organic solvents can be used alone or in combination. Of these, water is most preferred.

[0025] Examples of commercially available (meth)acrylic emulsions include the Burnock series manufactured by DIC Corporation, the Hi-Loss series manufactured by Seiko PMC Corporation, Joncryl manufactured by BASF Japan Ltd., and NeoCryl manufactured by Covestro Japan Ltd.

[0026] (hardening agent) The curing agent used in the present invention includes at least one of an isocyanate-based curing agent, an epoxy-based curing agent, a metal chelate-based curing agent, an aziridine-based curing agent, and a carbodiimide-based curing agent. As the curing agent, it is preferable to use one or more of these. Among them, an epoxy-based curing agent or an aziridine-based curing agent is preferable.

[0027] (epoxy curing agent) The epoxy-based curing agent used in the present invention is not particularly limited, and any publicly known and available epoxy-based curing agent can be used. Specific examples include phenol (ethylene glycol-modified) glycidyl ether, lauryl alcohol (ethylene glycol-modified) glycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and epoxy cresol novolac. Among these, polyglycerol polyglycidyl ether and sorbitol polyglycidyl ether are preferred, and sorbitol polyglycidyl ether is most preferred.

[0028] The epoxy equivalent of the epoxy curing agent used in the present invention is preferably 120 g / eq. or more, more preferably 140 g / eq. or more. The epoxy equivalent is measured in accordance with JIS K 7236. The epoxy-based curing agent is preferably contained in an amount of 5 to 30 mass % relative to the total solid content of the aqueous coating agent of the present invention, and more preferably 10 to 20 mass %.

[0029] Examples of the aziridine curing agent used in the present invention include N,N'-(4,4'-methylenediphenyl)bis(aziridine-1-carboxamide), 1,1'-isophthaloylbis(2-methylaziridine), tris(1-aziridinyl)phosphine oxide, 1,1'-hexamethylenebis(iminocarbonyl)bisaziridine, trimethylolpropane-tris(2-aziridinylpropionate), 2,4,6-tris(1-aziridinyl)-1,3,5-triazine, and 2,2-bis(hydroxymethyl)butanol tris[3-(1-aziridinyl)propionate].

[0030] The curing agent is preferably used in an amount of 5 to 30% by mass, more preferably 10 to 20% by mass, based on the total solid content of the aqueous coating agent for building materials of the present invention.

[0031] (Silane coupling agent) The silane coupling agent used in the present invention is not particularly limited, and any publicly known and available silane coupling agent can be used. Specific examples include epoxysilanes, aminosilanes, chlorosilanes, vinylsilanes, and isocyanatosilanes. Examples of epoxysilanes include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Examples of aminosilanes include N-2-(aminoethyl)-3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. Examples of chlorosilanes include vinyltrichlorosilane. Examples of vinylsilanes include vinyltriethoxysilane. Examples of isocyanatosilanes include 3-isocyanatopropyltrimethoxysilane. These can be used alone or in combination of two or more. Among these, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 8-glycidoxyoctyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane are preferred, and 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane are most preferred.

[0032] The silane coupling agent is preferably contained in an amount of 5 to 30% by mass, more preferably 10 to 20% by mass, based on the total solid content of the aqueous coating agent of the present invention. By including 5% or more of a silane coupling agent, improved adhesion to the substrate and improved alkali resistance can be expected, while by including 30% or less, the carboxyl groups of the resin remain, ensuring reaction points with the epoxy curing agent, which is expected to improve the crosslink density of the coating film.

[0033] The present invention is characterized in that the ratio of the curing agent to the silane coupling agent is 4:1 to 1:2. Within this range, the effects of the present invention can be maximized. The ratio is preferably 3:1 to 1:2, and most preferably 2:1 to 1:2. In particular, it is preferable to use an epoxy-based curing agent or an aziridine curing agent as the curing agent.

[0034] (Polar group-containing olefin resin) In the present invention, in addition to containing the (meth)acrylic emulsion, the curing agent, and the silane coupling agent, the use of a polar group-containing olefin resin in combination can particularly improve adhesion to plastic substrates. The aqueous coating agent in combination with the polar group-containing olefin resin is particularly useful for preventing whitening caused by lifting of the coating layer on the surface of the decorative sheet due to weathering deterioration, and is therefore also useful as, for example, an undercoat layer (sealant layer) that comes into direct contact with the plastic substrate.

[0035] Specific examples of the polar group contained in the polar group-containing olefin resin include halogen groups such as chlorine, bromine, and iodine groups, hydroxyl groups, and carboxyl groups. Of these, chlorine and carboxyl groups are preferred.

[0036] (Chlorine-containing olefin resin) The olefin-based resin (also referred to as chlorinated polyolefin) containing a chlorine group as a polar group used in the present invention is not particularly limited, and known chlorinated polyolefins can be used. Specific examples of chlorinated polyolefins include chlorinated polypropylene resin and chlorinated polyethylene resin. Examples of the olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, butadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. The chlorinated polyolefin may also be a modified product. The modified product is not particularly limited. For example, a modified chlorinated polyolefin may be a chlorinated polyolefin graft-polymerized with a polymerizable acrylic compound (e.g., acrylic acid, methacrylic acid, or an alkyl ester thereof) or an unsaturated polycarboxylic acid (e.g., maleic acid, maleic anhydride, itaconic acid, itaconic anhydride), or a chlorinated polyolefin graft-polymerized with the unsaturated polycarboxylic acid.

[0037] The chlorine content of the chlorinated polyolefin is not particularly limited. For example, the chlorine content is preferably 1% by mass or more, more preferably 10% by mass or more, based on the total mass of the resin. The chlorine content is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the resin.

[0038] When a chlorinated polyolefin is used in combination, the content of the chlorinated polyolefin is preferably 5 to 30 mass %, more preferably 10 to 20 mass %, based on the total solid content of the aqueous coating agent of the present invention.

[0039] (Carboxyl group-containing olefin resin) The olefin-based resin (also referred to as an olefin-α,β-unsaturated carboxylic acid copolymer) used in the present invention, which contains a carboxyl group as a polar group, may be a copolymer of an olefin with at least one monomer selected from the group consisting of an α,β-unsaturated carboxylic acid, a metal salt of an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid ester. Specific examples include copolymers of an α,β-unsaturated carboxylic acid, a metal salt of an α,β-unsaturated carboxylic acid, or an α,β-unsaturated carboxylic acid ester with an olefin, such as an olefin-α,β-unsaturated carboxylic acid copolymer, an ethylene-acrylic acid ester copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methacrylic acid ester copolymer, an ethylene-acrylic acid-maleic anhydride copolymer, an ethylene-acrylic acid ester-maleic anhydride copolymer, an ethylene-methacrylic acid-maleic anhydride copolymer, an ethylene-methacrylic acid ester-maleic anhydride copolymer, and metal salts thereof. These copolymers may be used alone or in combination. Among these, olefin-α,β-unsaturated carboxylic acid copolymers are preferred. Examples of the olefin-α,β-unsaturated carboxylic acid copolymer include random copolymers or block copolymers of ethylene and α,β-unsaturated carboxylic acid. Examples of the olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, butadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, etc. Among these, ethylene is preferred. Examples of the α,β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Among these, acrylic acid and methacrylic acid are preferred. These α,β-unsaturated carboxylic acids may be used alone or in combination.

[0040] The α,β-unsaturated carboxylic acid ester can be any known alkyl ester, hydroxyalkyl ester, alkoxyalkyl ester, or the like of acrylic acid or methacrylic acid, without any particular limitation. Specific examples include acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, 2-hydroxyethyl acrylate, and 2-methoxyethyl acrylate, and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-ethoxyethyl methacrylate. These can be used alone or in combination of two or more.

[0041] (Water dispersion of polar group-containing olefin resin) The polar group-containing olefin resin is used as an aqueous dispersion dispersed in an aqueous solvent. The method for dispersing in an aqueous solvent is not particularly limited and may be any known method. For example, a method of emulsifying with a surfactant and dispersing in an aqueous solvent, or (particularly when the polar group is a carboxyl group) a method of neutralizing the polar group with a basic compound or the like and then dispersing in an aqueous solvent, etc., may be mentioned.

[0042] As the surfactant used in the emulsification, various known anionic, cationic, and nonionic surfactants, or various water-soluble polymers can be used in combination as appropriate.

[0043] Examples of basic compounds used to neutralize the carboxyl groups of the carboxyl group-containing olefin resin include organic amines such as ammonia, methylamine, ethylamine, diethylamine, dimethylethanolamine, diethanolamine, and triethanolamine, and alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. These basic compounds may be used alone or in combination of two or more. The degree of neutralization by the basic compound may be, for example, 30 to 100 mol % of the carboxyl groups, and more preferably 40 to 90 mol %.

[0044] The dispersion method can be a known method, for example, a media-based dispersion device such as a paint shaker, ball mill, attritor, basket mill, sand mill, sand grinder, Dyno Mill, Dispermat, SC mill, spike mill, or agitator mill, or a media-free dispersion device such as an ultrasonic homogenizer, high-pressure homogenizer, Nanomizer, Dissolver, Disper, or high-speed impeller disperser.

[0045] (filler) When the aqueous coating agent of the present invention is used as a matte coating agent, it is preferable to add a filler. There are no particular limitations on the filler, but fine particles with an average particle size of 0.3 to 20 μm are often used. These fine particles may be organic and / or inorganic, and may be used alone or in combination, as long as they are well known. Specifically, inorganic particles such as silica, titanium oxide, alumina particles (aluminum oxide), calcium carbonate, barium sulfate, and glass, or organic particles such as acrylic resin, urethane resin, polycarbonate resin, silicone resin, and polystyrene resin, and silicone beads can be used. To achieve a higher matte effect, preferred inorganic particles include silica and aluminosilicate beads, and preferred organic particles include acrylic resin beads, urethane resin beads, and silicone beads. Silica and resin beads are particularly preferred.

[0046] (silica) Specifically, amorphous silica is more preferred as the silica used in the present invention. Examples of the amorphous silica include diatomaceous earth and activated clay. Among the amorphous silicas, synthetic amorphous silicas such as dry silica, wet silica, and silica gel can be used. Among them, wet silica produced by neutralizing and decomposing an aqueous solution of sodium silicate with an acid or an alkali metal salt is preferred. Surface-treated wet silica can also be used. The method for surface-treating the silica particles is not particularly limited, and any known method can be used. Examples include surface-treated wet silica with wax or a silane coupling agent. A mixture of the above-mentioned surface-treated and untreated wet silicas may be used.

[0047] The filler content is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, calculated as the solid content of the total amount of the aqueous coating agent. If the content is less than 1% by mass, a sufficient matting effect is not obtained, and if it exceeds 30% by mass, the filler tends to easily fall off from the coating surface, which is not preferable. The average particle size is preferably in the range of 1 to 10 μm, more preferably 2 to 8 μm.

[0048] (Other additives) The coating agent used in the present invention may also contain various additives, such as inorganic pigments, organic pigments, extender pigments, clay minerals, waxes, release agents, surfactants, antibacterial agents, stabilizers, flow adjusters, dyes, leveling agents, rheology control agents, ultraviolet absorbers, antioxidants, or plasticizers, as required.

[0049] If necessary, ultraviolet absorbers and light stabilizers may be added as weather resistance agents. Examples of ultraviolet absorbers include benzotriazoles, benzoates, benzophenones, and triazines, and examples of light stabilizers include hindered amines. These are generally added in any combination. The content of the ultraviolet absorber is not particularly limited, but is preferably in the range of 1% to 30% by mass, more preferably 2% to 20% by mass, based on the total solid content of the coating agent used in the present invention. The content of the light stabilizer is also not particularly limited, but is preferably in the range of 1% to 20% by mass, more preferably 2% to 10% by mass, based on the total solid content of the coating agent used in the present invention.

[0050] (Coating method) Specific examples of the application / printing method of the coating agent used in the present invention include a roll coater, gravure coater, flexo coater, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, curtain coater, cast coater, spray coater, die coater, offset printing machine, screen printing machine, etc., which can be appropriately used as the coating method.

[0051] (Coating film formation method) The coating layer is formed by drying and curing the coating film layer formed by applying and printing the coating agent used in the present invention. The temperature and time for drying and curing can be set appropriately within a range that does not cause deformation of the substrate layer, for example, a temperature of 25 to 140°C and a time of 1 minute to 72 hours. Specific drying methods include using hot air or a drying oven (dryer) in a known coating machine.

[0052] (Coating thickness) There are no particular restrictions on the thickness of the coating layer of the coating agent of the present invention, but it is preferably 0.1 to 100 μm, more preferably 0.3 to 50 μm, and particularly preferably 0.3 to 30 μm.

[0053] (decorative sheet) The decorative sheet of the present invention has a coating layer of the aqueous coating agent of the present invention on a plastic substrate. An example of a specific embodiment of the configuration envisioned for the decorative sheet of the present invention is shown below. Of course, this is not limited to this in the present invention. The "coating layer of the aqueous coating agent" referred to here is a coating layer of the aqueous coating agent of the present invention. The "coating layer of the aqueous coating agent" may be one layer or multiple layers superimposed. When multiple layers are superimposed, all of the multiple layers may be solid printed layers, or may be printed layers printed using a cut plate. As described above, the aqueous coating agent containing a (meth)acrylic emulsion, a curing agent, a silane coupling agent, and a polar group-containing olefin resin has excellent adhesion to plastic substrates. Therefore, in applications requiring better adhesion, it is preferable to coat the coating agent directly onto the plastic substrate to form a coating layer.

[0054] In a specific embodiment, coating layer 1 is a coating layer of the aqueous coating agent of the present invention containing a (meth)acrylic emulsion, a curing agent, a silane coupling agent, and a polar group-containing olefin resin, and coating layer 2 is a coating layer of the aqueous coating agent of the present invention containing a (meth)acrylic emulsion, a curing agent, and a silane coupling agent, but not containing a polar group-containing olefin resin.

[0055] Substrate 1 / pattern layer / adhesive layer / substrate 2 / water-based coating agent 1 coating layer Substrate 1 / pattern layer / adhesive layer / substrate 2 / water-based coating agent 2 coating layer Substrate 1 / pattern layer / adhesive layer / substrate 2 / water-based coating agent 1 coating layer / water-based coating agent 2 coating layer Substrate 1 / pattern layer / adhesive layer / substrate 2 / coating layer of aqueous coating agent 1 / coating layer of aqueous coating agent 1 Base material 1 / pattern layer / water-based coating layer 1 Base material 1 / pattern layer / water-based coating agent 2 coating layer Substrate 1 / pattern layer / water-based coating agent 1 coating layer / water-based coating agent 2 coating layer Substrate 1 / Pattern layer / Water-based coating agent 1 coating layer / Water-based coating agent 1 coating layer Substrate 1 / water-based coating layer 1 Substrate 1 / water-based coating layer 2 Substrate 1 / coating layer of water-based coating agent 1 / coating layer of water-based coating agent 2 Substrate 1 / coating layer of water-based coating agent 1 / coating layer of water-based coating agent 1 In particular, a decorative sheet having a coating layer 1 of aqueous coating agent 1 and a coating layer 2 of aqueous coating agent 1 or aqueous coating agent 2 on a plastic substrate is preferred.

[0056] (base material) The substrate used in the present invention is not particularly limited as long as it is a plastic substrate, and a substrate suitable for the desired purpose can be used appropriately. Examples include film or sheet-like substrates made of polyolefin resins such as polyethylene (LLDPE: low-density polyethylene, HDPE: high-density polyethylene, MDOPE: uniaxially oriented polyethylene, OPE: biaxially oriented polyethylene), polypropylene (CPP: unoriented polypropylene film, OPP: biaxially oriented polypropylene film), polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene-butene copolymer, and polyolefin thermoplastic elastomer. Other examples include film or sheet-like substrates made of polyethylene terephthalate (PET), polystyrene, polyamide, polyacrylonitrile, ethylene vinyl alcohol copolymer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and the like. These substrates may be single-layered or may be multi-layered substrates.

[0057] To produce a film or sheet-like substrate, for example, methods such as calendaring, inflation, T-die extrusion, etc. The thickness of these is not particularly limited and can be set depending on the product characteristics, but is usually about 40 to 150 μm, and preferably about 50 to 100 μm.

[0058] The base material may contain additives as needed. Examples of additives include fillers such as calcium carbonate and clay, flame retardants such as magnesium hydroxide, antioxidants, lubricants, foaming agents, colorants, etc. The amount of additives to be added can be appropriately determined depending on the product characteristics.

[0059] One or both surfaces of the substrate are preferably subjected to a surface treatment such as corona discharge treatment, ozone treatment, plasma treatment, ionizing radiation treatment, dichromate treatment, etc. In particular, a plastic substrate having a corona treatment applied to the coating surface is preferred. The aqueous coating agent for building materials of the present invention contains a specific amount of silane coupling agent, which is presumed to react with functional groups (e.g., hydroxyl groups and carboxyl groups) presumably generated on the corona discharge-treated plastic substrate, thereby improving adhesion.

[0060] When the corona discharge treatment is carried out, the surface tension of the substrate surface should be 30 dyne or more, preferably 40 dyne or more. The surface treatment may be carried out according to a conventional method for each treatment.

[0061] (Picture layer) The substrate used in the present invention may have a design layer. The design layer is usually provided by printing. The design layer may be a single layer, or multiple layers may be laminated. Furthermore, the design layer may be solid printed, or may be a design layer printed only on a portion of the substrate. A printed design layer may also be called a printed layer. The design layer can be printed on the substrate by a known coating or printing method, such as roll coating, gravure coating, or spray coating, or gravure printing, offset printing, letterpress printing, screen printing, or inkjet printing. The pattern to be imparted to the design layer may be freely determined, and examples include patterns imitating the surface of rock such as wood grain and marble, fabric patterns imitating the grain of fabric or patterns on fabric, tile patterns, etc., floral patterns consisting of flowers or bunches of flowers arranged at equal intervals, letters, etc. In addition, to make the pattern stand out, a solid print layer such as a white background may be provided under the pattern print layer.

[0062] The ink constituting the design layer may be any known ink, such as an oil-based ink, a water-based ink, or an active energy ray-curable ink. Alternatively, the ink may be selected from liquid printing inks such as flexographic printing inks and gravure printing inks, lithographic offset printing inks, inkjet inks, etc., depending on the printing method.

[0063] (Transparent resin layer) The transparent resin layer is preferably made of polyolefin, such as polypropylene, polyethylene, polybutene, or various α-olefin copolymers (copolymers of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc.). The transparent resin layer may contain various additives, such as an ultraviolet absorber, a heat stabilizer, a light stabilizer, an antiblocking agent, a catalyst scavenger, a colorant, a light scattering agent, and a gloss adjuster, as needed. The method for forming the transparent resin layer is not particularly limited, and a conventional method such as calender film formation or extrusion film formation can be used. The transparent resin layer may be provided with surface irregularities to impart design properties. Examples of methods for providing the irregularities include a method of subjecting the transparent resin layer to hot embossing after extrusion molding, and a method of subjecting the extrusion layer to embossing simultaneously with extrusion molding using a cooling roll provided with irregularities during extrusion molding.

[0064] (decorative materials) A decorative material can be obtained by laminating the decorative sheet of the present invention to wood, plywood, fiberboard, metal plate, etc. The decorative sheet of the present invention can also be used for residential interior materials, furniture, home appliances, office supplies, toys, vehicle interior materials, etc., which require weather resistance and scratch resistance, and is particularly ideal for use in residential interior materials, furniture, and home appliances. [Example]

[0065] The present invention will be described in more detail below with reference to examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass".

[0066] (Preparation of aqueous coating agent) Example 1 A total of 100 parts of the following solids were mixed: 48 parts of acrylic emulsion resin A (glass transition temperature 82°C, acid value 25, solid content 43%), 16 parts of acrylic emulsion resin B (glass transition temperature 21°C, acid value 31, solid content 43%), 7 parts of PP resin A (chlorinated polyolefin resin, maleic acid / polypropylene ratio = 0.2), 6.0 parts of ultraviolet absorber (Tinuvin 1130, manufactured by BASF Japan Ltd.), 2.6 parts of light stabilizer (Tinuvin 292, manufactured by BASF Japan Ltd.), 11 parts of epoxy curing agent A (epoxy equivalent 167 g / eq.), and 11 parts of silane coupling agent A (3-glycidoxypropyltriethoxysilane). The mixture was thoroughly stirred for 15 minutes using a stirrer to prepare the aqueous coating agent of Example 1. The maleic acid / polypropylene ratio of the polar group-containing olefin resin was measured using an infrared spectrophotometer (FT / IR-460Plus, manufactured by JASCO Corporation) by measuring the sum of the maleic acid peaks (1710 cm -1 +1740cm -1 +1780cm -1 ) to the polypropylene peak (1460 cm ―1 This is the value obtained by dividing by

[0067] Examples 2 to 14 According to the formulations shown in the table below, aqueous coating agents of Examples 2 to 16 were prepared in the same manner as in Example 1.

[0068] (Creating decorative sheets) A polyethylene sheet with opacity was used as the base layer, and a wood grain pattern layer was applied using acrylic ink. A dry laminating adhesive was then applied to the pattern layer, and a polypropylene sheet was laminated on top of this as a transparent resin layer to create a plastic base material. The surface of the plastic substrate laminated with the polypropylene layer was subjected to a corona discharge treatment so that the surface tension of the substrate sheet surface was 40 dyne or more. Using a bar coater, 5 g / m of the aqueous coating agent of Example 1 was applied to the corona discharge-treated surface laminated with the polypropylene layer. 3 After application, the coating was dried in a dryer and aged at 40°C for 3 days.

[0069] [Evaluation method] The evaluation methods for the decorative sheet and coating layer of the present invention are as follows, and the evaluation results are shown in the table below.

[0070] [Adhesion test] The adhesion of the coating layer to the substrate was evaluated according to JIS K 5600-5-6 using the following five-point scale. The test was conducted after the coating layer was formed (initial adhesion) and after 10 cycles of weather resistance testing (weather-resistant adhesion). (Evaluation criteria) A: No delamination in any of the lattices. B: There is very slight peeling at the corners of the grid. C: Some peeling occurs, but no practical problems occur. D: Peeling occurs over 1 / 3 or 1 / 2 of the test area. E: Peeling occurs over half or more of the test area. In this evaluation, a grade of "C" or higher was considered a pass.

[0071] The weather resistance test was carried out under the following conditions: 10 cycles of 20 hours of irradiation, 4 hours of condensation, and 15 seconds of showering before and after irradiation. (Weather resistance test conditions) Testing equipment: Eye Super UV Tester SUV-W261 <When irradiated> Black panel temperature: 63℃ ·Irradiance: 60mW / cm 2 ·Battle humidity: 50%RH Duration: 20 hours <When condensation occurs> ·Illuminance: 0mW / cm 2 ·Battle humidity: 98%RH Duration: 4 hours

[0072] (Creating evaluation samples) The surface of the resulting decorative sheet that did not have a coating layer was completely coated with a mixture of the adhesive "Rikabond BA-10L" and the isocyanate-based curing agent "BA-11B" (manufactured by Japan Coating Resins), and then the sheet was attached to plywood "MDF" (manufactured by Benichu) and aged at room temperature to obtain a sample for evaluation.

[0073] [MEK rubbing resistance] The evaluation sample was placed horizontally, and a gauze moistened with MEK (methyl ethyl ketone) was attached to the tip of a 400g / cm2 weight, and a rubbing test was performed on the decorative sheet surface. After the test, the coating condition was visually checked, and the number of rubs required to remove 50% of the surface area was evaluated using the following five-point scale. (Evaluation criteria) A: 50 or more round trips B: 40 or more round trips but less than 50 round trips C: 30 or more round trips but less than 40 round trips D: 20 or more round trips but less than 30 round trips E: Less than 20 round trips In this evaluation, a grade of "C" or higher was considered a pass.

[0074] [Alkali resistance] A 2% sodium hydroxide solution was dropped onto the surface of a horizontally placed sample for evaluation, and the sample was left to stand for 24 hours after being covered with a watch glass. The surface was then wiped clean with a damp cloth. The condition of the coating was visually inspected after the test and rated on the following five-point scale. (Evaluation criteria) A: No change in the coating B: Swelling of the coating film and slight changes in gloss are observed. C: Slight swelling of the coating film and slight changes in gloss are observed, but this does not pose a problem for practical use. D: There is a clear change in the coating film's swelling or gloss. E: Paint film swelling and significant change in gloss are observed. In this evaluation, a grade of "C" or higher was considered a pass.

[0075] [Scratch resistance] The evaluation sample was placed horizontally and a scratch test was carried out using a Hoffman scratch hardness tester (manufactured by BYK instruments). The heaviest load that did not cause major scratches on the surface of the decorative sheet was measured and rated on a five-point scale as follows: A: The coating surface peels off when the load is 1000g or more. B: The load at which the coating surface peels off is between 800g and 1000g C: The load at which the coating surface peels off is between 600g and 800g D: The load at which the coating surface peels off is between 400g and 600g E: The load required for the coating surface to peel off is less than 400g In this evaluation, a grade of "C" or higher was considered a pass.

[0076] The results are shown in the table below, where blank spaces indicate no blending.

[0077] [Table 1]

[0078] [Table 2]

[0079] The abbreviations in the table are as follows: Acrylic emulsion A: Tg 82°C, acid value 25, solids 43% Acrylic emulsion B: Tg 21°C, acid value 31, solids 43% UV absorber: Tinuvin 1130 Light stabilizer: Tinuvin 292 Epoxy hardener A: Epoxy equivalent weight 167 g / eq. Epoxy hardener B: Epoxy equivalent 141 g / eq. Aziridine-based hardener: Aziridine content 6.0 mmol / g PP resin A: Chlorinated polyolefin resin, maleic acid / polypropylene ratio = 0.2 PP resin B: Chlorinated polyolefin resin, maleic acid / polypropylene ratio = 0.3 PP resin C: Chlorinated polyolefin resin, maleic acid / polypropylene ratio = 0.3 PP resin D: Maleic acid modified polyolefin resin, maleic acid / polypropylene ratio = 0.45 PP resin E: Maleic acid modified polyolefin resin, maleic acid / polypropylene ratio = 0.16 Silica: Colloidal silica, average particle size 3.9 μm, oil absorption 320 ml / 100 g Silane coupling agent A: 3-glycidoxypropyltriethoxysilane Silane coupling agent B: 8-glycidoxyoctyltrimethoxysilane

[0080] The decorative sheets of Examples 1 to 16 of the present invention had excellent adhesion to plastic substrates and were highly durable, scratch-resistant, solvent-resistant, and alkali-resistant. On the other hand, the decorative sheets of the comparative examples had poor adhesion to plastic substrates and were therefore inferior in weather-resistant adhesion and alkali resistance.

Claims

1. An aqueous coating agent for building materials, comprising a (meth)acrylic emulsion, a curing agent, and a silane coupling agent, the silane coupling agent being contained in an amount of 5 to 30 mass % based on the total solid content.

2. 2. The aqueous coating agent for building materials according to claim 1, which contains a polar group-containing olefin resin.

3. 2. The aqueous coating agent for building materials according to claim 1, wherein the curing agent is an epoxy-based curing agent or an aziridine-based curing agent.

4. A decorative sheet having a coating layer of an aqueous coating agent on a plastic substrate whose coated surface has been subjected to corona treatment, wherein the aqueous coating agent is the aqueous coating agent described in claim 1.

5. A decorative sheet having a coating layer 1 of an aqueous coating agent 1 and a coating layer 2 of an aqueous coating agent 2 on a plastic substrate, wherein the aqueous coating agent 1 is an aqueous coating agent containing the aqueous coating agent of claim 1 and a polar group-containing olefin resin, and the aqueous coating agent 2 is the aqueous coating agent of claim 1.

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