Active energy ray-curable coating agent, and method for producing active energy ray-curable coating film

Abstract

To provide an active energy ray-curable coating agent capable of using also in an exterior use, without using an isocyanate compound, and having high weather resistance and scratch resistance.SOLUTION: A method for producing a coating film that includes a step (I) for forming active energy curable coating agent that contains urethane (meth)acrylate (A) and a compound (B) with a hydroxyl value of 50 mg KOH / g or higher, where the compound (B) is 10 mass% or less of the total mass calculated from the solid content of the urethane (meth)acrylate (A) and the compound (B), and does not contain isocyanate compounds, as well as a coating film of this active energy ray curable coating agent on a substrate, and a step (II) for irradiating an electron beam as an active energy ray irradiation on the coating film, in this order.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a coating agent using an active energy ray-curable composition and a method for producing an active energy ray-curable coating film.

Background Art

[0002] In the field of building interior decoration, from the viewpoints of the high designability and good processability of decorative sheets, cost reduction, and the ability to handle small lots, the replacement from painting to decorative sheets has been progressing from furniture to walls, ceilings, and floors. Even for interior use, weather resistance is required to prevent deterioration caused by sunlight, especially ultraviolet rays, entering through windows. In recent years, there has also been a demand for decorative sheets having high weather resistance and scratch resistance that can be used not only in the interior field but also in exterior applications.

[0003] As weathering agents used in decorative sheets, mainly organic triazine-based ultraviolet absorbers (UVA) and hindered amine-based light stabilizers (HALS) have been used. The triazine-based ultraviolet absorber (UVA) has a function of protecting the coating film by absorbing ultraviolet rays and converting them into thermal energy, and the hindered amine-based light stabilizer (HALS) has a function of capturing radicals generated by ultraviolet rays and preventing the deterioration of resins and coating films. By changing the types and contents of these additives, it is possible to efficiently prevent deterioration caused by ultraviolet rays. However, these weathering agents may bleed out over time, causing problems such as inhibiting the adhesion between layers of the decorative sheet or impairing the appearance of the surface layer of the decorative sheet.

[0004] As a decorative sheet having high scratch resistance, a decorative sheet having a surface protection layer containing an active energy ray-curable resin is known (see, for example, Patent Documents 1 to 3). However, when a weathering agent is used in combination with an active energy ray-curable resin composition, since the active energy ray-curable resin is cured by ultraviolet rays, curing inhibition may occur when the weathering agent is added at a high concentration in order to obtain high weather resistance.

[0005] In order to obtain high weather resistance and scratch resistance required in the field of exterior finishes, a method of incorporating an isocyanate compound into a surface protective layer containing an active energy ray-curable resin is also known (see, for example, Patent Documents 1 and 3). Further, a method is also known in which an isocyanate compound is incorporated into a lower layer of a surface protective layer containing an active energy ray-curable resin and the isocyanate compound is reacted between the surface protective layer and the lower layer (see, for example, Patent Document 2). However, in recent years, the toxicity of isocyanate compounds, which are raw materials of isocyanate compounds, has begun to be regarded as a problem, and a decorative sheet having high weather resistance and scratch resistance without using an isocyanate compound has been desired.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an active energy ray-curable coating agent for a decorative sheet having high weather resistance and scratch resistance, which can be used for exterior applications without using an isocyanate compound, and a method for producing an active energy ray-curable coating film.

[0008] The present inventors have found that an active energy ray-curable coating agent containing a urethane (meth) acrylate oligomer and a compound having a hydroxyl value in a specific range solves the above problems.

[0009] Generally, since an active energy ray-curable resin composition is instantaneously cured by energy rays, the resulting cured coating film is characterized by being firm and having high hardness while being brittle. In order to balance this firmness and brittleness, the inventors have found that the above problems can be solved by adding a specific amount of a compound having a hydroxyl value of 50 mgKOH / g or more and not reacting with the active energy ray-curable compound.

[0010] That is, the present invention provides an active energy ray-curable coating agent containing urethane (meth) acrylate (A) and a compound (B) having a hydroxyl value of 50 mgKOH / g or more, wherein the compound (B) is 10% by mass or less based on the total mass of the urethane (meth) acrylate (A) and the compound (B) in terms of solid content, and does not contain an isocyanate compound.

[0011] Further, the present invention provides a method for producing a coating film having, in this order, a step (I) of forming a coating film of an active energy ray-curable coating agent on a substrate and a step (II) of irradiating the coating film with active energy rays, wherein the active energy ray-curable coating agent is the active energy ray-curable coating agent according to any one of claims 1 to 4, and the active energy rays in the step (II) of irradiating the coating film with active energy rays are electron beams.

Effects of the Invention

[0012] According to the present invention, it is possible to provide an active energy ray-curable coating agent for a decorative sheet having high weather resistance and scratch resistance, which can also be used for exterior applications, and a method for producing an active energy ray-curable coating film.

Modes for Carrying Out the Invention

[0013] The active energy ray-curable coating agent of the present invention contains urethane (meth) acrylate (A) and a compound (B) having a hydroxyl value of 50 mgKOH / g or more, and (B) is 10% by mass or less based on the total mass in terms of solid content of (A) and (B), and is characterized by not containing an isocyanate compound.

[0014] The active energy ray-curable coating agent of the present invention is characterized by not containing an isocyanate compound. As described above, the toxicity of the isocyanate monomer, which is the raw material of the isocyanate compound, has begun to be regarded as a problem, and legal regulations have also started in some countries. Furthermore, since the isocyanate compound has high reactivity, a coating agent added with the isocyanate compound has a pot life, and in some cases, aging for several days to about one week under appropriate temperature control is required until the coating film is completely cured, and the handling is somewhat inconvenient. In the present invention, even without using an isocyanate compound, it is possible to obtain weather resistance and scratch resistance that are equal to or higher than those of the prior art using an isocyanate compound. Furthermore, there is also a prior art in which weather resistance and scratch resistance are obtained by using an isocyanate compound in the lower layer of a surface protection layer containing an active energy ray-curable resin. However, in the present invention, even when the lower layer does not contain an isocyanate compound, sufficiently high weather resistance and scratch resistance can be obtained.

[0015] In the present invention, "not containing an isocyanate compound" means that the isocyanate compound is not intentionally added. An isocyanate compound is a compound having an isocyanate group as a free reactive group. Specifically, for example, aromatic isocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 1,5-naphthalene diisocyanate, n-isocyanatophenylsulfonyl isocyanate, o-isocyanatophenylsulfonyl isocyanate, p-isocyanatophenylsulfonyl isocyanate; aliphatic isocyanates such as 1,6-hexamethylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and adducts and multimers thereof. Compounds obtained by reacting an isocyanate group with another reactive group, such as urethane acrylate, etc., are not included in the isocyanate compound. Also, sometimes, there may be a trace amount of unreacted isocyanate compound remaining in commercially available products such as urethane acrylate (commercial products are also reactants), but this is an unintentionally contained compound and is excluded from "not intentionally adding an isocyanate compound" of the present invention.

[0016] In the present invention, "(meth)acrylate" means one or both of acrylate and methacrylate.

[0017] (urethane (meth)acrylate (A)) The urethane (meth)acrylate (A) used in the present invention has a (meth)acryloyl group and is, for example, obtained by reacting a diisocyanate with a (meth)acrylate having a hydroxyl group, or obtained by reacting an isocyanate group-containing urethane prepolymer formed by reacting a polyol and a polyisocyanate under conditions of an excess of isocyanate groups with a (meth)acrylate having a hydroxyl group. Alternatively, it can also be obtained by reacting a hydroxyl group-containing urethane prepolymer formed by reacting a polyol and a polyisocyanate under conditions of an excess of hydroxyl groups with a (meth)acrylate having an isocyanate group.

[0018] Specifically, for example, urethane (meth)acrylate, which is a reaction product of a hydroxyl group-containing (meth)acrylate, an isocyanate compound, and various polyols as needed, can be used.

[0019] Examples of the hydroxyl group-containing (meth)acrylate include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, glycidyl acrylate, glycidyl methacrylate, and the like.

[0020] Examples of the isocyanate compound include aromatic isocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 1,5-naphthalene diisocyanate, n-isocyanatophenylsulfonyl isocyanate, o-isocyanatophenylsulfonyl isocyanate, p-isocyanatophenylsulfonyl isocyanate; aliphatic isocyanates such as 1,6-hexamethylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and adducts and multimers thereof, which can be used alone or in combination of two or more.

[0021] Among them, from the viewpoint of weather resistance, it is preferably a caprolactone-based urethane (meth)acrylate having a caprolactone skeleton. Caprolactone-based urethane (meth)acrylate can usually be obtained by reacting a caprolactone-based polyol, an isocyanate compound, and a hydroxyl group-containing (meth)acrylate. As a synthesis method, it is preferable to react a polycaprolactone-based polyol and a diisocyanate compound to generate a polyurethane prepolymer containing -NCO groups (isocyanate groups) at both ends, and then react it with a hydroxyl group-containing (meth)acrylate. The reaction conditions and the like may follow conventional methods.

[0022] As the caprolactone-based polyol, commercially available ones can be used. Preferably, it has two hydroxyl groups, and the number average molecular weight is preferably 500 to 3000, more preferably 750 to 2000. In addition, polyols other than caprolactone-based polyols, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol and other polyols, can also be used by mixing one or more kinds in an arbitrary ratio.

[0023] In the present invention, when a caprolactone-based polyol is included, the caprolactone-based urethane (meth)acrylate is preferably a caprolactone diol-based urethane (meth)acrylate. The caprolactone diol-based urethane (meth)acrylate refers to a urethane (meth)acrylate in which the terminal of the caprolactone-based urethane (meth)acrylate is diethylene glycol. By using the caprolactone diol-based urethane (meth)acrylate, a cosmetic sheet that does not particularly crack or turn white can be obtained.

[0024] Other polyols that can be reacted include glycols such as 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol; aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, dimethylbutanediol, butylethylpropanediol, 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bis(hydroxyethoxy)benzene, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol;

[0025] ether glycols such as polyoxyethylene glycol and polyoxypropylene glycol; modified polyether diols obtained by ring-opening polymerization of aliphatic diols and various cyclic ether bond-containing compounds such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether;

[0026] bisphenols such as bisphenol A and bisphenol F; alkylene oxide adducts of bisphenols obtained by adding ethylene oxide, propylene oxide, etc. to bisphenols such as bisphenol A and bisphenol F; and polycarbonate polyols.

[0027] The urethane (meth)acrylate (A) is preferably contained in the range of 50 to 95% by mass, more preferably in the range of 60 to 90% by mass, based on the total solid content of the active energy ray-curable coating agent of the present invention.

[0028] (Compound (B) with a hydroxyl value of 50 mgKOH / g or more) In the compound (B) having a hydroxyl value of 50 mgKOH / g or more used in the present invention, the hydroxyl value is preferably 100 mgKOH / g or more, more preferably 500 mgKOH / g or more, because the weather resistance is further enhanced. On the other hand, as the upper limit of the hydroxyl value, less than 2000 mgKOH / g is preferable, less than 1500 mgKOH / g is more preferable, and less than 1000 mgKOH / g is most preferable.

[0029] In addition, since the compound (B) continues to be present in the coating film cured by the coating agent of the present invention, it is easy to obtain the effects of the invention. Therefore, it is preferably a non-volatile compound under normal temperature and pressure. The number average molecular weight of the compound (B) is preferably 10000 or less, more preferably 5000 or less, and most preferably 3000 or less. On the other hand, the upper limit is preferably 50 or more.

[0030] Specific examples of the compound (B) include glycols such as 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol; aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, dimethylbutanediol, butylethylpropanediol, 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bis(hydroxyethoxy)benzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, polycaprolactone diol, and polycarbonate diol; aliphatic triols such as 1,2,4-butanetriol, glycerin, trimethylolpropane, 1,3,5-cyclohexanetriol, polyoxypropylene triol, polycaprolactone triol, and polycarbonate triol; aliphatic tetraols such as 1,2,3,4-butanetetraol, 1,2,4,5-hexanetetraol, 1,2,4,5-cyclohexanetetraol, pentaerythritol, polycaprolactone tetraol, and polycarbonate tetraol; 1,2,3,4,5-pentanepentaol; polyethylene glycol; acrylic polyol; polyether polyol; polyester polyol; and the like.

[0031] The compound (B) is preferably contained in the range of 1 to 10% by mass, more preferably in the range of 1 to 6% by mass, based on the total solid content of the active energy ray-curable coating agent of the present invention.

[0032] (Other acrylates) In addition to the urethane (meth)acrylate (A) and the compound (B), the active energy ray-curable coating agent of the present invention may be used in combination with known (meth)acrylate resins, (meth)acrylate monomers, (meth)acrylate oligomers, etc. having a (meth)acryloyl group that can be cured by known active energy rays as necessary. (Hereinafter, it may be referred to as a compound (C) having a (meth)acryloyl group).

[0033] Examples of the (meth)acrylate monomer that can be used in combination include, as monofunctional (meth)acrylate, for example, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isoamyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, diethylaminoethyl (meth)acrylate, nonylphenoxyethyltetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenilyloxyethyl (meth)acrylate, ethoxyethoxyethanol acrylate polymer ester, etc.

[0034] Examples of the difunctional (meth)acrylate include di(meth)acrylates of dihydric alcohols such as 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate; di(meth)acrylates of polyethylene glycol, polypropylene glycol, and di(meth)acrylate of tris(2-hydroxyethyl)isocyanurate; di(meth)acrylates of diols obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol; di(meth)acrylates of diols obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A, and the like.

[0035] Examples of the (meth)acrylate having three or more functional groups include poly(meth)acrylates of polyhydric alcohols having trivalent or higher valences, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and poly(meth)acrylates of dipentaerythritol; tri(meth)acrylates of triols obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of glycerin; di- or tri(meth)acrylates of triols obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane; and poly(meth)acrylates of polyoxyalkylene polyols, such as di(meth)acrylates of diols obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of bisphenol A.

[0036] Furthermore, a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (which may be abbreviated as DPHA), which corresponds to a (meth)acrylate having two or more functional groups, ditrimethylolpropane tetraacrylate (which may be abbreviated as DTMPTA), trimethylolpropane ethylene oxide adduct tri(meth)acrylate, which is a tri(meth)acrylate of a triol obtained by adding 3 moles or more of ethylene oxide to 1 mole of trimethylolpropane, etc. may be used. Representative examples of the trimethylolpropane ethylene oxide adduct tri(meth)acrylate include trimethylolpropane ethylene oxide (hereinafter, ethylene oxide may be referred to as "EO") modified (n≈3) triacrylate. The total amount of the above-mentioned monofunctional (meth)acrylate and (meth)methacrylate having two or more functional groups is preferably in the range of 60 to 80% by mass, more preferably 65 to 75% by mass, of the total amount of the curing components in the coating agent.

[0037] Furthermore, a polymerizable oligomer may be used as necessary. Examples of the polymerizable oligomer include amine-modified acrylates such as amine-modified polyether acrylates, amine-modified epoxy arylates, amine-modified aliphatic acrylates, amine-modified polyester acrylates, and amino(meth)acrylates, polyacryl(meth)acrylates, polyester(meth)acrylates, polyether(meth)acrylates, polyolefin(meth)acrylates, polystyrene(meth)acrylates, and epoxy(meth)acrylates.

[0038] Of the compounds (C) having a (meth)acryloyl group, preferred are phenol EO modified acrylate, EO modified 1,6-hexanediol diacrylate, EO modified bisphenol A diacrylate, EO modified trimethylolpropane triacrylate, pentaerythritol alkoxytetraacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane tri(meth)acrylate, DPHA, acrylic (meth)acrylate, epoxy (meth)acrylate, amine modified polyether acrylate, amine modified epoxy acrylate, amine modified aliphatic acrylate, amine modified polyester acrylate, amine modified acrylate such as amino (meth)acrylate, polyacrylic (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polyolefin (meth)acrylate, polystyrene (meth)acrylate, and the like. Among these, epoxy (meth)acrylate and polyacrylic (meth)acrylate are more preferred since they have a viscosity suitable for coating, low gloss, stain resistance, and scratch resistance.

[0039] The molecular weight of the compound (C) having a (meth)acryloyl group is preferably in the range of 150 to 100,000, more preferably 200 to 10,000, in terms of number average molecular weight.

[0040] The addition amount of the compound (C) having the (meth)acryloyl group may be added within a range that does not impair the effects of the present invention. Specifically, it is preferably contained in an amount of 1 to 20% by mass based on the total mass of the active energy ray-curable compound. By containing 1% by mass or more of the compound (C) having the (meth)acryloyl group with respect to the total mass of the active energy ray-curable compound, the scratch resistance tends to be maintained, and if it is 20% by mass or less, the viscosity that can be applied as a coating agent tends to be maintained.

[0041] (Weather resistance additive) In order to obtain higher weather resistance, it is preferable to add weather resistance additives such as ultraviolet absorbers, light stabilizers, and antioxidants to the active energy ray-curable coating agent of the present invention. Among the weather resistance additives, hydroxy phenyl triazine-based ultraviolet absorbers, hindered amine-based light stabilizers, and hindered phenol-based antioxidants are preferable in terms of obtaining higher weather resistance. In addition, weather resistance additives having reactive functional groups such as hydroxyl groups and (meth)acrylate groups are also preferable in terms of obtaining higher weather resistance. Weather resistance additives having no reactive functional groups can move freely in the active energy ray-curable coating film, and weather resistance additives having reactive functional groups can be fixed in the active energy ray-curable coating film to exhibit functions for a longer period. Therefore, it is most preferable to use both of them in combination.

[0042] The weather resistance additive is preferably contained in an amount of 0.5 to 15% by mass, more preferably 1 to 10% by mass, based on the total solid mass of the active energy ray-curable coating agent. When the weather resistance additive is an ultraviolet absorber, it is preferably contained in an amount of 0.5 to 10% by mass, more preferably 1 to 5% by mass, based on the total solid mass of the active energy ray-curable coating agent. When the weather resistance additive is a light stabilizer, it is preferably contained in an amount of 0.5 to 15% by mass, more preferably 1 to 10% by mass, based on the total solid mass of the active energy ray-curable coating agent. When the weather resistance additive is an antioxidant, it is preferably contained in an amount of 0.5 to 10% by mass, more preferably 1 to 5% by mass, based on the total mass of the solid content of the active energy ray-curable coating agent.

[0043] (Matting agent) When a matte appearance is required, the active energy ray-curable coating agent of the present invention can use a matting agent as needed. As the matting agent, any known organic and / or inorganic agents can be used without particular limitation, either alone or in combination. Specifically, for example, 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. In order to expect a high matting effect, silica, aluminosilicate beads, etc. as inorganic fine particles, acrylic resin beads, urethane resin beads, etc. as organic fine particles, and silicone beads are preferred.

[0044] The volume average particle diameter of the matting agent is not particularly limited, but is generally 0.5 to 25 μm, more preferably 1 to 15 μm, and even more preferably 3 to 10 μm. When the volume average particle diameter of the matting agent is 0.5 μm or more, it is preferable from the viewpoint of the matting effect. Here, the volume average particle diameter refers to the particle diameter at 50% of the integrated value in the particle size distribution determined by the laser diffraction-scattering method. The addition amount of the matting agent is preferably 0.5 to 50% by mass, more preferably 5 to 30% by mass, based on the total mass of the solid content of the active energy ray-curable coating agent.

[0045] (Wax) It is preferable to add wax to the active energy ray-curable coating agent of the present invention in order to obtain scratch resistance. As the wax, for example, polyolefin wax can be used. Among them, polyethylene wax is preferable in that higher scratch resistance can be obtained. The addition amount of the wax is preferably 0.5 to 5% by mass, more preferably 1 to 3% by mass, based on the total mass of the solid content of the active energy ray-curable coating agent.

[0046] (Non-reactive resin) The active energy ray-curable coating agent of the present invention can also be used in combination with a non-reactive binder resin that does not cure with active energy rays. For example, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl isobutyl ether copolymer resin, acrylic resin, rosin-based resin, polyurethane resin, polyamide-based resin, chlorinated polypropylene resin, ethylene-vinyl acetate copolymer resin, vinyl acetate resin, vinyl chloride-based resins such as polyvinyl chloride resin, polyester resin, alkyd resin, ketone resin, cyclized rubber, chlorinated rubber, butyral, petroleum resin, and the like can be mentioned.

[0047] (Photoinitiator) The active energy ray-curable coating agent of the present invention may use a photoinitiator as necessary. As the photoinitiator used at this time, known ones may be used. Among them, radical polymerization type photoinitiators are preferred, and α-hydroxyalkyl ketone-based photoinitiators that do not cause coloring of the solution when dissolving the active energy ray curable compound and have little yellowing over time can be mentioned. Examples of the α-hydroxyalkyl ketone-based photoinitiator include 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-i-propylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, etc. Further, phenylglyoxylate-based photoinitiators are also preferred. Examples of the phenylglyoxylate-based photoinitiator include methyl benzoylformate. Among them, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0048] In addition, as other radical polymerization type photoinitiators, monoacylphosphine oxide-based photoinitiators having an absorption wavelength in the long wavelength region among ultraviolet rays may be appropriately combined and used. As the monoacylphosphine oxide-based photoinitiator, bisacylphosphine oxides that color when dissolved in the active energy ray curable compound are excluded, and monoacylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,6-dimethoxybenzoyl-diphenylphosphine oxide, 2,6-dichlorobenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-phenylphosphinic acid methyl ester, 2-methylbenzoyl-diphenylphosphine oxide, pivaloyl phenylphosphinic acid isopropyl ester, etc. can be mentioned. In particular, among these, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide has a UV absorption wavelength that matches the emission wavelength region of UV-LEDs having emission wavelengths of 385 nm or 395 nm, so a suitable curable type can be obtained, and it is more preferable in that the yellowing of the cured film is less.

[0049] The above-mentioned photoinitiators may be used alone or in combination of two or more. The total addition amount of the photoinitiator is preferably in the range of 0% by mass to 30% by mass based on the total mass of the solid content of the coating agent. More preferably, it is in the range of 1% by mass to 25% by mass based on the total amount of the coating agent.

[0050] (Organic solvent) In the active energy ray-curable coating agent of the present invention, an organic solvent can be added as a diluent if necessary. As the organic solvent, any solvent that can dissolve the compound having a (meth)acryloyl group to be used can be used. For example, aromatic hydrocarbons such as toluene and xylene, aliphatic or alicyclic hydrocarbons such as n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane, esters such as ethyl acetate, butyl acetate, and propyl acetate, alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alkylene glycol monoalkyl ethers such as ethylene glycol monoethyl ether and propylene glycol monomethyl ether, ether esters such as propylene glycol monomethyl ether acetate, etc. can be mentioned, and these may be used in combination. However, for the purpose of environmental protection, when thoroughly reducing the evaporation amount of the organic solvent into the atmosphere, that is, reducing volatile organic compounds (VOCs), it is more preferable not to contain the above organic solvents.

[0051] From the viewpoint of coatability, the active energy ray-curable coating agent of the present invention is preferably adjusted to a viscosity that can be coated in the method for producing the active energy ray-curable coating film of the present invention described below. The viscosity is preferably adjusted to 30 to 3000 mPa·s. In particular, when a high molecular weight and high viscosity polymer is used in combination, the viscosity can be adjusted by diluting or heating with an organic solvent if necessary.

[0052] (Other additives) The active energy ray-curable coating agent of the present invention may further contain a polymerization inhibitor, a leveling agent, a thixotropic agent, a desiccant, a thickening agent, an anti-dripping agent, a plasticizer, a dispersant, an anti-settling agent, an antifoaming agent, an ultraviolet absorber, a light stabilizer, and the like.

[0053] (Substrate) The substrate used in the present invention can be used without particular limitation. For example, in the case of a decorative sheet for building materials, a general-purpose substrate sheet used for a decorative sheet can be used as the substrate. There is no particular limitation on the substrate sheet, and a sheet formed of a general-purpose thermoplastic resin (sometimes referred to as a film) or paper used for a general decorative sheet is used. Examples of the sheet (film) formed of a thermoplastic resin include polyolefin resins such as polyethylene, ethylene-α-olefin copolymer, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate copolymer, polyvinyl chloride, polyethylene terephthalate (PET), polybutylene terephthalate, polyamide, polycarbonate, polyethylene naphthalate, ionomer, acrylate polymer, methacrylate polymer, and the like. The substrate sheet may be formed by using these resins alone or in combination of two or more.

[0054] The substrate sheet may be colored, and may contain various additives such as a filler, a matting agent, a foaming agent, a flame retardant, a lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, and a light stabilizer as required. The thickness of the substrate sheet can be appropriately set according to the use and usage method of the final product, but generally 20 to 300 μm is preferable.

[0055] On one or both sides of the base material sheet, surface treatments such as corona discharge treatment, ozone treatment, plasma treatment, ionizing radiation treatment, dichromic acid treatment, etc. may be performed as necessary. For example, when performing corona discharge treatment, the surface tension of the base material sheet surface may be set to 30 dyne or more, preferably 40 dyne or more. The surface treatment may be performed according to the conventional methods of each treatment.

[0056] Examples of the types of paper base materials for decorative sheets include paper sheets such as tissue paper, ordinary paper, reinforced paper, resin-impregnated paper, titanium paper, etc.

[0057] Also, a wood veneer board or the like widely used for decorative boards may be used as the base material. Examples of the wood base material of the wood veneer board include known ones such as plywood, particle board, hard board, MDF, etc. that have been conventionally used as wood base materials for decorative boards, furniture, building members, etc. Also, it does not matter how these known base materials are obtained by what manufacturing method. Furthermore, examples of non-combustible materials that can be used as the base material include perforated board building materials made of gypsum board, gypsum panel, calcium silicate board, etc., ceramic plates such as pottery, porcelain, stoneware, earthenware, glass, enamel, etc., and metal plates such as iron plate, galvanized steel plate, polyvinyl chloride sol-coated steel plate, aluminum plate, copper plate, etc.

[0058] (Method for manufacturing an active energy ray curable coating agent) The active energy ray-curable coating agent of the present invention can be produced by mixing and kneading / dispersing urethane (meth)acrylate (A), a compound (B) having a hydroxyl value of 50 mgKOH / g or more, a (meth)acrylate compound (C) as required, a weathering additive, a photopolymerization initiator, a matting agent, an organic solvent, and various other additives. It is possible to appropriately adjust the size of the grinding media, the filling rate of the grinding media, the dispersion treatment time, etc. by using a commonly used dispersing machine, for example, a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, etc. When the coating agent contains bubbles or unexpectedly coarse particles, etc., it is preferable to remove them by filtration or the like in order to reduce the quality of the coated article. A conventionally known filter can be used.

[0059] (Method for forming a coating film) The active energy ray-curable coating agent of the present invention can form a coating film by a known coating / printing method. As specific coating methods, for example, a roll coater, a gravure coater, a gravure offset coater, a flexo coater, an air doctor coater, a blade coater, an air knife coater, a squeeze coater, an impregnation coater, a transfer roll coater, a kiss coater, a curtain coater, a cast coater, a spray coater, a die coater, an offset printing machine, a screen printing machine, etc. can be appropriately adopted.

[0060] (Step (I) of forming a coating film) When the coating agent used contains an organic solvent, the coating film formed by the above forming method is dried in a drying furnace or the like, and then cured with an electron beam or ultraviolet rays to obtain a cured coating film.

[0061] (Step (II) of irradiating with active energy rays) Next, the coating film is irradiated with active energy rays. The active energy rays may be ultraviolet rays or electron beams. Ultraviolet irradiation can be performed by known methods. For example, irradiation with ultraviolet light using a germicidal lamp, a fluorescent lamp for ultraviolet rays, an ultraviolet light-emitting diode (UV-LED), a carbon arc, a metal halide lamp, a xenon lamp, a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp for copying, a medium-pressure or high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an electrodeless lamp, a metal halide lamp, natural light, etc. as a light source. The integrated light quantity of ultraviolet rays is preferably in the range of 20 to 1000 mJ / cm 2 so that the effects of the present invention can be maximally exerted. Among them, it is still more preferable that the integrated light quantity is in the range of 40 to 800 mJ / cm 2 . If it is 20 mJ / cm 2 or more, the curing efficiency is good, and if it is 1000 mJ / cm 2 or less, damage to the base material due to heat generation can be prevented. On the other hand, when using an electron beam, an electron beam irradiation device is used. The acceleration voltage is preferably 200 kV or less. The irradiation dose is preferably about 10 to 230 kGy, and more preferably about 10 to 100 kGy. For the atmosphere in the case of electron beam irradiation, the oxygen concentration is preferably 2% or less. In the present invention, it is preferable to use an electron beam.

[0062] The film thickness of the coating film thus obtained is preferably in the range of 0.1 to 100 μm, and most preferably in the range of 0.5 to 50 μm. By being in this film thickness range, the effects of the present invention can be maximally exerted.

[0063] In addition, the production method of the present invention can be widely applied not only to building material applications such as the aforementioned decorative sheets, but also to surface coating applications of furniture, musical instruments, office supplies, sports goods, toys, etc.

[0064] Hereinafter, the present invention will be described in more detail with reference to examples. In the following examples, "parts" and "parts by mass" represent mass%.

[0065] In the present invention, the weight average molecular weight and the number average molecular weight are the values measured by the following method. Measuring device: HLC-8220 manufactured by Tosoh Corporation Column; Guard column HXL-H manufactured by Tosoh Corporation + TSKgel G5000HXL manufactured by Tosoh Corporation + TSKgel G4000HXL manufactured by Tosoh Corporation + TSKgel G3000HXL manufactured by Tosoh Corporation + TSKgel G2000HXL manufactured by Tosoh Corporation Detector; RI (Differential Refractometer) Data processing: SC-8010 manufactured by Tosoh Corporation Measurement conditions: Column temperature 40 °C Solvent: Tetrahydrofuran Flow rate 1.0 ml / min Standard; Polystyrene Sample; A 0.4 mass% tetrahydrofuran solution in terms of resin solid content filtered through a microfilter (100 μl)

[0066] In addition, the hydroxyl value of each raw material is the amount of hydroxyl groups in 1 g of the compound calculated by back-titrating the remaining acid with an alkali when the hydroxyl groups in the compound are acetylated with an excess of acetyl reagent, and is expressed in mg of potassium hydroxide (KOH), and is in accordance with JIS K0070. In addition, the average particle diameter of the silica was measured using a nanoparticle size distribution analyzer Nanotrac UPA EX-150 manufactured by Nikkiso Co., Ltd.

[0067] (Preparation of active energy ray curable coating agent) [Example 1] 66.0 parts by mass of caprolactone-based urethane acrylate, 3.0 parts by mass of 1,6-hexanediol (hydroxyl value 950 mg KOH / g), 1.5 parts by mass of a hydroxyphenyltriazine-based ultraviolet absorber, 1.0 part by mass of a hindered amine-based light stabilizer, 5.0 parts by mass of a reactive hindered amine-based light stabilizer, 1.0 part by mass of a hindered phenol-based antioxidant, 20.0 parts by mass of wet silica "Silica 350" (manufactured by Fuji Silysia Chemical Ltd.) as a matting agent, 2.0 parts by mass of polyethylene wax, 0.5 part by mass of a polymer type anionic dispersant, and a mixed solvent such as ethyl acetate were added to make a total of 150.0 parts by mass, and the mixture was thoroughly stirred with a stirrer to prepare an active energy ray curable coating agent (1).

[0068] [Examples 2 to 10, Comparative Examples 1 to 6] According to the formulations shown in Table 1, Table 2, and Table 3, each active energy ray curable coating agent was prepared in the same procedure as in Example 1.

[0069] [Formation of Coating Film by Step (I)] On the substrate, the active energy ray curable coating agent prepared in the above Example or Comparative Example was coated using a bar coater (#4) to a film thickness of about 5 μm to form a coating film. As the substrates, the following two types of substrates were used. PET film: Polyester film (A4100, film thickness 50 μm, manufactured by Toyobo Co., Ltd.) Olefin sheet: A sheet having a printed ink layer, an adhesive layer, a polypropylene sheet, and a primer layer provided in this order on a polypropylene sheet (film thickness 150 μm)

[0070] [Irradiation with Active Energy Rays by Step (II)] The coating film formed in the above Step (I) was irradiated with electron beams at an acceleration voltage of 125 kV and an irradiation dose of 50 kGy using a curtain type electron beam irradiation apparatus ("Electro Curtain EC250 / 15 / 180L" manufactured by Iwasaki Electric Co., Ltd.) to cure the coating film.

[0071] Regarding the prepared active energy ray-curable coating film, for the one with a PET film as the base material, evaluations of "weather resistance (gloss retention rate)" and "weather resistance (color difference)" were conducted. Also, for the one with an olefin sheet as the base material, evaluations of "weather resistance (gloss retention rate)", "weather resistance (durability time)", "scratch resistance", "stain resistance", and "solvent resistance" were conducted.

[0072] (Evaluation Item 1: Weather Resistance (Gloss Retention Rate)) For the prepared coating film, using a super UV weather resistance accelerator tester (Eye Super UV Tester SUV-W261 manufactured by Iwasaki Electric Co., Ltd.), ultraviolet rays were irradiated under the settings of illuminance 60 mW, irradiation temperature 63 °C, rest temperature 50 °C, irradiation humidity 50%, rest humidity 50%, irradiation time 20 hours, dew condensation time 4 hours, rest time 6 minutes, and shower 10 seconds. For the one with a polyester film as the base material, the evaluation was conducted when the total test time reached 240 hours, and for the one with an olefin sheet as the base material, the evaluation was conducted when the total test time reached 1440 hours. Regarding the cured coating film before and after the test, in order to measure the specular gloss value in accordance with JIS Z8741, the gloss value (glossiness) was measured using a gloss meter ("MULTI GLOSS 268A" manufactured by Konica Minolta). The measurement conditions of the gloss value were an incident angle of 60° and a reflection angle of 60°. The gloss retention rate was calculated by formula (1), and the pass / fail judgment was made according to the values shown in the table.

[0073] Gloss Retention Rate (%) = (Gloss Value after Test / Gloss Value before Test) × 100 Formula (1)

[0074] (Evaluation Item 2: Weather Resistance (Color Difference)) For the prepared coating film, using a super UV weather resistance accelerator tester (Eye Super UV Tester SUV-W261 manufactured by Iwasaki Electric Co., Ltd.), ultraviolet rays were irradiated under the settings of illuminance 60 mW, irradiation temperature 63 °C, rest temperature 50 °C, irradiation humidity 50%, rest humidity 50%, irradiation time 20 hours, dew condensation time 4 hours, rest time 6 minutes, and shower 10 seconds. The evaluation was conducted when the total test time reached 240 hours. For the cured coating film before and after the test, the ultraviolet shielding property of the coating film was evaluated by tracking the color difference (ΔE) before and after ultraviolet irradiation using a spectrophotometer CM-700d manufactured by Konica Minolta, Inc. The smaller the numerical value of the color difference, the better the weather resistance. The pass / fail judgment was made according to the values shown in the table.

[0075] (Evaluation Item 3: Weather Resistance (Durability Time)) The prepared coating film was irradiated with ultraviolet rays using a super UV weather resistance accelerator tester (Eye Super UV Tester SUV-W261 manufactured by Iwasaki Electric Co., Ltd.) under the settings of illuminance 60 mW, irradiation temperature 63°C, rest temperature 50°C, irradiation humidity 50%, rest humidity 50%, irradiation time 20 hours, dew condensation time 4 hours, rest time 6 minutes, and shower 10 seconds. The test time was confirmed when a part of the test piece peeled off and the coating film disintegrated, and the pass / fail judgment was made according to the values shown in the table.

[0076] (Evaluation Item 4: Scratch Resistance) On the surface of the prepared coating film, steel wool (「BON STAR No.0000」manufactured by Nippon Steel Wool Co., Ltd.) was reciprocated 10 times with a load of 1.5 Kg, and the way of scratching the coating film was evaluated based on three levels of criteria. Pass is defined as ○ or above. (Evaluation Criteria) ◎: There are no scratches at all, or there is a slight change in gloss, but there are no linear scratches. ○: The linear scratches are within an area less than half of the friction surface. ×: The linear scratches cover almost the entire friction surface and the coating film turns white.

[0077] (Evaluation Item 4: Stain Resistance) In accordance with the stain A test, which is a JAS special plywood standard, contaminants were applied to the surface of the prepared coating film. After 4 hours, the remaining condition of the contaminants was visually observed after wiping the surface with a cloth containing alcohol. As contaminants, commercially available office black magic, blue ink, red crayon, shoe polish, a mixture of commercially available curry powder and tap water in a ratio of 1:4 (curry), and mercurochrome were used. The staining state was evaluated according to the following three-level criteria. Pass is defined as 〇 or above. (Evaluation Criteria) ◎: No residue of contaminants ○: There is residue of contaminants, but it is slight and there is no practical problem ×: Considerable residue of contaminants

[0078] (Evaluation item 5: Solvent resistance) A gauze moistened with an organic solvent was applied with a load of 1.5 Kg to the surface of the prepared coating film and reciprocated 50 times, and the durability of the coating film was evaluated according to three criteria. As the organic solvents, industrial ethanol, ethyl acetate, and methyl ethyl ketone were used. Passing is defined as ○ or above. (Evaluation criteria) ◎: No change at all, or slight change in gloss appears ○: Gloss changes, but there is no peeling of the coating film ×: Gloss changes significantly and peeling of the coating film occurs

[0079] The compositions of each active energy ray-curable coating agent are shown in Tables 1 to 3, and the evaluation results of the prepared coating films are shown in Tables 4 to 6. Note that all the numerical values in the tables are in parts by mass or mass %, and the blanks indicate non-formulation. Also, all values other than the organic solvents are in terms of solid content conversion.

[0080]

Table 1

[0081]

Table 2

[0082]

Table 3

[0083]

Table 4

[0084]

Table 5

[0085]

Table 6

[0086] · 1,6 - hexanediol (number - average molecular weight 118, hydroxyl value 950 KOHmg / g, manufactured by Genry Chemical Group Co., Ltd.) · Placcel 303 (polycaprolactone triol, number - average molecular weight 310, hydroxyl value 541.3 KOHmg / g, manufactured by Daicel Corporation) · Placcel 410 (polycaprolactone tetraol, number - average molecular weight 1030, hydroxyl value 217.8 KOHmg / g, manufactured by Daicel Corporation) · Cyclohexanedimethanol (number - average molecular weight 144, hydroxyl value 779.3 KOHmg / g, manufactured by EASTMAN) · PK - 400GD (polypropylene glycol, number - average molecular weight 400, hydroxyl value 280 KOHmg / g, manufactured by Sannopco) · PP - 1000GD (polypropylene glycol, number - average molecular weight 1000, hydroxyl value 112.2 KOHmg / g, manufactured by Sannopco) · T5651 (polycarbonate diol, number - average molecular weight 1000, hydroxyl value 100 - 120 KOHmg / g, manufactured by Asahi Kasei Corporation) · Placcel 220 (polycaprolactone diol, number - average molecular weight 2000, hydroxyl value 56.7 KOHmg / g, manufactured by Daicel Corporation) · Acrit 6CV - 102 (acrylic polyol, number - average molecular weight 40000, hydroxyl value 44 KOHmg / g, solid content 40%, manufactured by Daiso Fine Chemical Co., Ltd.) · Placcel 240 (polycaprolactone diol, number - average molecular weight 4000, hydroxyl value 28.5 KOHmg / g, manufactured by Daicel Corporation) · Acrit 6KW-700 (acrylic polyol, number average molecular weight 65,000, hydroxyl value 10 KOH mg / g, solid content 36.5%, manufactured by Dainippon Fine Chemical Co., Ltd.) · Silicia 350 (matting agent colloidal silica, manufactured by Fuji Silysia Chemical Ltd.)

Claims

1. An active energy ray-curable coating agent, which contains urethane (meth) acrylate (A) and a compound (B) having a hydroxyl value of 50 mgKOH / g or more, wherein the compound (B) is 10% by mass or less based on the total mass of the urethane (meth) acrylate (A) and the compound (B) in terms of solid content, and does not contain an isocyanate compound.

2. The active energy ray-curable coating agent according to Claim 1, wherein the active energy ray is an electron beam.

3. The active energy ray-curable coating agent according to Claim 1, wherein the urethane (meth) acrylate (A) is a caprolactone-based urethane (meth) acrylate.

4. The active energy ray-curable coating agent according to Claim 1, which contains a weather resistance additive in an amount of 0.5 to 15% by mass based on the total amount of the active energy ray-curable coating agent.

5. A method for producing a coating film, which comprises a step (I) of forming a coating film of an active energy ray-curable coating agent on a substrate, and a step (II) of irradiating the coating film with active energy rays, in this order, wherein the active energy ray-curable coating agent is the active energy ray-curable coating agent according to any one of Claims 1 to 4, and the active energy ray in the step (II) of irradiating the coating film with active energy rays is an electron beam. ​

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