Active energy ray-curable coating composition for metal substrate, laminate, molded member, and method for producing same

Abstract

Provided are: an active energy ray-curable coating composition for a metal base material, the active energy ray-curable coating composition having a cured coating film with good hardness, workability, and weather resistance; a laminate and a molded member using the active energy ray-curable coating composition; and a method for producing the laminate and the molded member. The present invention addresses the problem of providing an active energy ray-curable coating composition for metal substrates, which has good coating film properties even when an ultraviolet absorber is used, does not precipitate during storage, and has good storage stability. An active energy ray-curable coating composition for a metal substrate, which contains a binder component (A) and an ultraviolet absorber (B), the adhesive component (A) contains a urethane (meth) acrylate (A-1), a radical polymerizable monofunctional monomer (A-2) having an alicyclic structure, and a radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and having a homopolymer glass transition temperature (Tg) of 20 DEG C or more.

Description

TECHNICAL FIELD

[0001] The present application relates to an active energy ray-curable coating composition for a metal substrate, a laminate, a molded processed member, and a method for producing the same. BACKGROUND

[0002] Generally, the coating method for a metal substrate has a post-coat method in which coating is performed after the molded processing of an article, and a pre-coat method in which coating is performed before the molded processing. Here, a metal substrate coated in the pre-coat method is referred to as a PCM (pre-coated metal), and a coating material used therein is referred to as a PCM coating material.

[0003] The post-coat method is a method in which coating is performed after a metal substrate is processed into an article or a member, and thus requires a coating system that matches the shape and size of the coated object. On the other hand, in the pre-coat method, a roll coating method is widely used in order to coat a plate-shaped metal substrate, and continuous operation can be performed at a very fast speed.

[0004] However, a PCM is processed after coating, and thus is required to have hardness and various resistances required for building materials and electric home appliances, which are main uses, and to have processability that can withstand various molded processes performed in a manufacturing process. Furthermore, excellent aesthetic properties are also required.

[0005] A conventional solvent-drying type coating composition requires time for drying of a solvent, and thus has poor productivity, and has problems of generation of VOC (volatile organic compound), environmental load of CO2 emission, and the like, and thus a coating composition that is cured using an active energy ray such as an electron beam or ultraviolet rays is used. The active energy ray-curable coating composition can generally be used without a solvent, and can be cured in a short time with a small amount of energy, and thus has excellent properties from the viewpoint of improving productivity and reducing environmental load.

[0006] A PCM is required to have high weather resistance in many cases. In particular, in the case of use for building material applications, outdoor weather resistance of more than ten years is required in many cases. As a method for improving weather resistance, it is known to incorporate an additive such as an ultraviolet absorber or a light stabilizer. An ultraviolet absorber or a light stabilizer that is generally used absorbs and / or reflects an active energy ray such as ultraviolet rays. Thus, the curability of an active energy ray-curable coating composition is sometimes reduced, and the coating film properties such as water resistance, chemical resistance, hardness, and the like are reduced. In addition, most of the above-described additives are difficult to dissolve in an acrylate monomer, and thus in a solvent-free active energy ray-curable coating composition, there is a possibility that the additives are precipitated during storage, and it is difficult to increase the amount of addition.

[0007] Patent Literature 1 discloses a active energy ray-curable resin composition comprising a (meth)acrylic polymer, a urethane (meth)acrylate having 1 to 4 (meth)acryloyl groups, a monomer having one or more (meth)acryloyl groups, and a photopolymerization initiator. Further, Patent Literature 2 discloses an active energy ray-curable coating composition for a metal substrate, which contains a urethane (meth)acrylate having a weight average molecular weight of 1,000 to 60,000, a compound having a hydrophilic group and one ethylenic unsaturated group, a compound having a cyclic hydrocarbon group and one ethylenic unsaturated group and not having a hydrophilic group, and a compound having two or more (meth)acryloyl groups.

[0008] Prior Art Documents

[0009] Patent Literature

[0010] Patent Literature 1: Japanese Patent Application Laid-Open No. 2022-131646

[0011] Patent Literature 2: Japanese Patent No. 5935668 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, in the active energy ray-curable coating agent described in the above Patent Literature 1, the hardness and processability of the coating film are good, but there is no description about weather resistance. In order to improve the weather resistance, by compounding an ultraviolet absorber or the like, it is possible that the coating film properties after curing decrease, or the ultraviolet absorber is precipitated in storage. Further, Patent Literature 2 shows an active energy ray-curable coating composition for a metal substrate which has good adhesion and solvent resistance, but there is no description about the coating film properties, weather resistance.

[0014] An object of the present application is to provide an active energy ray-curable coating composition for a metal substrate, in which the hardness, processability, and weather resistance of the cured coating film are good, and a laminate and a molded processed member using the same. Further, an object of the present application is to provide an active energy ray-curable coating composition for a metal substrate, in which the coating film properties are good even if an ultraviolet absorber is used, the ultraviolet absorber does not precipitate in storage, and the storage stability is good.

[0015] The present inventors have repeatedly conducted intensive research in order to solve the above problems, and as a result, have found that the above problems can be solved by the active energy ray-curable coating composition for a metal substrate shown below, thereby completing the present application.

[0016] That is, the present application is:

[0017] [1] A metal base active energy ray-curable coating composition comprising a binder component (A) and an ultraviolet absorber (B), the binder component (A) comprising a urethane (meth) acrylate (A-1), a free radical polymerizable monofunctional monomer having an alicyclic structure (A-2), and a free radical polymerizable monofunctional monomer having a heterocyclic structure and having a homopolymer glass transition temperature (Tg) of 20°C or higher (A-3).

[0018] [2] The metal base active energy ray-curable coating composition according to the above [1], wherein the contained ratio (mass ratio) of the free radical polymerizable monofunctional monomer having an alicyclic structure (A-2) to the free radical polymerizable monofunctional monomer having a heterocyclic structure and having a homopolymer glass transition temperature (Tg) of 20°C or higher (A-3) is 30 / 70 to 80 / 20.

[0019] [3] The metal base active energy ray-curable coating composition according to the above [1] or [2], wherein the content of the free radical polymerizable monofunctional monomer having an alicyclic structure (A-2) is 15 to 45 mass% relative to the total amount of the binder component (A).

[0020] [4] The metal base active energy ray-curable coating composition according to any one of the above [1] to [3], wherein the content of the free radical polymerizable monofunctional monomer having a heterocyclic structure and having a homopolymer glass transition temperature (Tg) of 20°C or higher (A-3) is 10 to 40 mass% relative to the total amount of the binder component (A).

[0021] [5] The metal base active energy ray-curable coating composition according to any one of the above [1] to [4], wherein the content of the urethane (meth) acrylate (A-1) is 15 to 45 mass% relative to the total amount of the binder component (A).

[0022] [6] The metal base active energy ray-curable coating composition according to any one of the above [1] to [5], wherein the content of a solvent is 3 mass% or less relative to the entire metal base active energy ray-curable coating composition.

[0023] [7] The metal base active energy ray-curable coating composition according to any one of the above [1] to [6], wherein the content of a photopolymerization initiator is 0.5 mass% or less relative to the entire metal base active energy ray-curable coating composition.

[0024] [8] The metal base active energy ray-curable coating composition according to any one of the above [1] to [7] for a pre-coated metal.

[0025] [9] A laminate having a cured coating film of the active energy ray-curable coating composition for a metal substrate described in any one of [1] to [8] on a metal substrate.

[0026]

[10] A molded processed product using the laminate described in [9] above.

[0027]

[11] A method for producing a laminate, wherein the active energy ray-curable coating composition for a metal substrate described in any one of [1] to [8] is applied to a metal substrate with a roll coater and cured with an active energy ray.

[0028]

[12] A method for producing a molded processed product, wherein the active energy ray-curable coating composition for a metal substrate described in any one of [1] to [8] is applied to a metal substrate with a roll coater, cured with an active energy ray, and subjected to a molding process.

[0029] Effects of the Invention

[0030] According to the present application, it is possible to provide an active energy ray-curable coating composition for a metal substrate, which is excellent in hardness, processability, and weather resistance of a cured coating film, and a laminate and a molded processed member using the same. In addition, according to the present application, it is possible to provide an active energy ray-curable coating composition for a metal substrate, which is excellent in coating film properties even if an ultraviolet absorber is used, does not cause precipitation of the ultraviolet absorber during storage, and is excellent in storage stability. DETAILED DESCRIPTION

[0031] Hereinafter, modes for carrying out the present application will be described in detail. It should be noted that the present application is not limited to the following embodiments, and can be carried out in various modifications within the scope of the gist thereof.

[0032] In the following description, (meth)acrylate, (meth)acryloyl, and (meth)acrylic acid each mean methacrylate and / or acrylate, methacryloyl and / or acryloyl, and methacrylic acid and / or acrylic acid.

[0033] In the following description, the "number of functional groups" means the number of radical-polymerizable functional groups such as acryloyl groups, methacryloyl groups, vinyl groups, and other olefinic unsaturated groups, which a resin or a compound has in one molecule.

[0034] In the present specification, the binder component (A) refers to a vehicle excluding pigments, ultraviolet absorbers, light stabilizers, other additives from the coating composition. Specifically, it refers to a mixture of urethane (meth) acrylate (A-1), a free radical polymerizable monofunctional monomer having a alicyclic structure (A-2), a free radical polymerizable monofunctional monomer having a heterocyclic structure and having a homopolymer glass transition temperature (Tg) of 20°C or higher (A-3), other compounds having a free radical polymerizable group, and an inert resin, and the like.

[0035] In the present specification, the homopolymer glass transition temperature (Tg) refers to the temperature at which the state changes from glass to rubber when a polymer composed of only a monomer is heated, and is measured by, for example, a differential scanning calorimeter (DSC), a thermal mechanical analyzer (TMA).

[0036] Hereinafter, the components included or that can be included in the active energy ray-curable coating composition for metal substrates (hereinafter also simply referred to as "coating") of the present embodiment will be described.

[0037] [Binder component (A)]

[0038] [Urethane (meth) acrylate (A-1)]

[0039] The urethane (meth) acrylate (A-1) is not particularly limited as long as it is a (meth) acrylate having a urethane bond. By containing the urethane (meth) acrylate (A-1), the balance between the film hardness and the processability of the coating of the present application is good, and the adhesion is good. As the urethane (meth) acrylate (A-1), if one example is given, an oligomer obtained by reacting a polyvalent isocyanate-based compound, a polyol compound, and a (meth) acrylate containing a hydroxyl group, an oligomer obtained by reacting a polyvalent isocyanate-based compound and a (meth) acrylate containing a hydroxyl group, and the like can be given. As a commercial product, for example, EBECRYL 4858 (2 functional), EBECRYL 8311 (3 functional), EBECRYL 8402 (2 functional), EBECRYL 8701 (3 functional), EBECRYL 9260 (3 functional), EBECRYL 8606 (4 functional), EBECRYL 8301R (6 functional) manufactured by DAICEL-ALLNEX Co., Ltd., CN8888NS (2 functional), CN8898NS (2 functional), CN8881NS (2 functional), CN964NS (2 functional), CN9013NS (9 functional) manufactured by Sartomer Co., Ltd., Miramer PU320 (3 functional), Miramer PU340 (3 functional), Miramer PU5000 (6 functional) manufactured by MIWON Co., Ltd., and the like can be given.

[0040] The urethane (meth)acrylate (A-1) is preferably an aliphatic urethane (meth)acrylate. An aliphatic urethane (meth)acrylate refers to an urethane (meth)acrylate in which the polyol component and isocyanate component are both aliphatic and do not possess an aromatic ring within the molecule. From the viewpoint of easily imparting excellent adhesion, processability, and weather resistance, aliphatic urethane (meth)acrylates are preferred.

[0041] The number of functional groups in urethane (meth)acrylate (A-1) is preferably 2 to 4, more preferably 2 to 3. When the number of functional groups is above the lower limit mentioned above, the hardness of the coating film increases; if it is below the upper limit mentioned above, the hardness of the coating film will not become too high, and the processability will be improved. In addition, the content of urethane (meth)acrylate (A-1) relative to the total amount of binder component (A) is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass. By keeping the content of urethane (meth)acrylate (A-1) within the above range, a good balance between the hardness and processability of the coating film is achieved.

[0042] <A free radical polymerizable monofunctional monomer with an alicyclic structure (A-2)>

[0043] In the free radical polymerizable monofunctional monomer (A-2) with an alicyclic structure (hereinafter also referred to as "component (A-2)"), the alicyclic structure refers to a non-aromatic ring structure consisting only of carbon. By including the free radical polymerizable monofunctional monomer (A-2) with an alicyclic structure, the coatings of the present invention exhibit excellent weather resistance and readily dissolve ultraviolet absorbers.

[0044] The free radical polymerizable monofunctional monomer (A-2) with an alicyclic structure is not particularly limited. Examples include 3,3,5-trimethylcyclohexyl (meth)acrylate, hexahydrophthalo-dimethoxyethyl (meth)acrylate, hexahydrophthalo-dimethoxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and isobornyl (meth)acrylate. From the viewpoint of good weather resistance and high hardness of the coating film, the glass transition temperature (Tg) of the homopolymer of component (A-2) is preferably 10°C or higher, more preferably 40°C or higher, and even more preferably 70°C or higher.

[0045] From the perspective of excellent solubility of the ultraviolet absorber, component (A-2) preferably has a fused ring structure. Specific examples of this include isobornyl acrylate (Tg=97℃) and dicyclopentyl acrylate (Tg=120℃).

[0046] The content of component (A-2) relative to the total amount of adhesive component (A) is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass. When the content of component (A-2) is within the above range, a good balance is achieved between the solubility of the ultraviolet absorber and the hardness of the coating film.

[0047] <A-3 is a free radical polymerizable monofunctional monomer with a heterocyclic structure and a homopolymer glass transition temperature (Tg) above 20°C>

[0048] In the free radical polymerizable monofunctional monomer (A-3) (hereinafter also referred to as "component (A-3)") having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher, the heterocyclic structure refers to a ring structure composed of at least two different elements. By including component (A-3), the coating of the present invention has high film hardness and excellent heat resistance.

[0049] The free radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher is not particularly limited, and examples include glyceryl carbonate acrylate, 4-cyclohexene-1,2-dicarboximide-N-ethyl acrylate, 2-(cyclohexane-1,2-dicarboximide)ethyl acrylate, acrylmorpholine, cyclic trimethylolpropane-formaldehyde acrylate, N-vinylcaprolactam, and N-vinylpyrrolidone. From the viewpoint of good weather resistance and high hardness of the coating film, the homopolymer glass transition temperature (Tg) of component (A-3) is more preferably 50°C or higher, and even more preferably 80°C or higher.

[0050] From the viewpoint of excellent coating hardness, component (A-3) is preferably nitrogen-containing in the heterocyclic ring. Specific examples of this include acryloylmorpholine (Tg=145℃) and N-vinylcaprolactam (Tg=90℃).

[0051] The content of component (A-3) relative to the total amount of adhesive component (A) is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, and even more preferably 20 to 30% by mass. With the content of component (A-3) within the above range, a good balance between weather resistance and coating hardness is achieved.

[0052] The preferred mass ratio of component (A-2) to component (A-3) is 30 / 70 to 80 / 20, more preferably 40 / 60 to 70 / 30, and even more preferably 45 / 55 to 65 / 35. By keeping the mass ratio of component (A-2) to component (A-3) within the above range, good coating hardness can be maintained while ensuring the solubility of the ultraviolet absorber.

[0053] In addition to (A-1), (A-2), and (A-3) mentioned above, adhesive component (A) may also contain other free radical polymerizable monomers and / or oligomers. The amount of other free radical polymerizable monomers and / or oligomers is not particularly limited, but is preferably 40% by mass or less relative to the total amount of adhesive component (A). Adhesive component (A) may also contain inert resins, etc.

[0054] [additive]

[0055] <UV Absorber (B)>

[0056] Examples of UV absorbers (B) include organic UV absorbers such as salicylic acid-based, benzophenone-based, benzotriazole-based, triazine-based, and cyanoacrylate-based UV absorbers, as well as inorganic UV absorbers composed of zinc oxide, titanium oxide, or cerium oxide particles. Among these, benzotriazole-based or triazine-based UV absorbers with high UV absorption capacity and low degradation for high-energy UV light are preferred.

[0057] Examples of benzotriazole-based UV absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-pentylphenyl)benzotriazole, and 3-[3-(benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate of polyethylene glycol. Examples of triazine-based UV absorbers include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, 1,3,5-triazin-2,4,6(1H,3H,5H)-trione, and 1,3,5-tris[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]. In addition, commercially available products include ADEKA's "ADK STAB LA-F70" and "ADK STAB LA-40", and BASF Japan's "Tinuvin 405" and "Tinuvin 479".

[0058] The ultraviolet absorber (B) can be added to the coating in any amount, but from the perspective of the solubility of the coating and the strength of the coating film, it is preferably 3 to 15% by mass relative to the total amount of the binder component (A), more preferably 5 to 10% by mass.

[0059] In addition to the ultraviolet absorber (B), the active energy ray curable coating composition for metal substrates of the present invention may appropriately contain substances known as additives. Examples include light stabilizers, pigments, dyes, sensitizers, polymerization initiators, fluorescent whitening agents, curing agents, coupling agents, plasticizers, surface conditioners, defoamers, substrate wetting agents, antistatic agents, extender pigments, and pigment dispersants.

[0060] Examples of light stabilizers include hindered amine light stabilizers (HALS), phenolic antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. Among these, HALS are preferred due to their high thermal stability and excellent free radical scavenging ability. Specifically, examples of HALS include bis(1,2,2,6,6-pentamethyl-4-piperidinyl)2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2'-n-butylmalonic acid bis(1,2,2,6,6-pentamethyl-4-piperidinyl), bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and methyl(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate. 2,4-Bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidinyl-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, tetra(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, etc.

[0061] In addition, commercially available products include ADEKA's "ADK STAB LA-72" and "ADK STAB LA-82", and BASF Japan's "Tinuvin 123" and "Tinuvin 249".

[0062] The content of light stabilizer is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total amount of adhesive component (A).

[0063] As a pigment, there are no particular restrictions; any known pigment can be used, and either inorganic or organic pigments can be used. A single pigment can be used alone, or two or more pigments can be used in combination.

[0064] Examples of inorganic pigments mentioned above include ultramarine, titanium dioxide, iron oxides, composite oxide pigments, and carbon black.

[0065] Examples of organic pigments mentioned above include phthalocyanine pigments, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, and quinophthalone pigments.

[0066] The pigment content is adjusted appropriately according to the type and purpose. For example, the pigment content is preferably 3% by mass or more relative to the total amount of the coating composition. Furthermore, the pigment content is preferably 60% by mass or less relative to the total amount of the coating composition. By keeping the pigment content within the above range, the coating composition can achieve sufficient concealment and also ensure dispersion stability.

[0067] [Photopolymerization initiator]

[0068] There are no particular limitations on the photopolymerization initiator; any known photopolymerization initiator may be used appropriately. When the metal substrate of the present invention is cured by ultraviolet light using an active energy ray curable coating composition, it is necessary to include a photopolymerization initiator.

[0069] When the metal substrate-based active energy ray-curable coating composition of the present invention is cured by electron beams, it is preferable that it does not contain a photopolymerization initiator. As an example, the content of the photopolymerization initiator relative to the total amount of the coating composition is preferably 0.5% by mass or less, more preferably 0.1% or less.

[0070] [solvent]

[0071] The active energy ray-curable coating composition for metal substrates of the present invention preferably contains substantially no organic solvents or water. "Substantially no organic solvents" means that the total amount of the active energy ray-curable coating composition for metal substrates is 3% or less, more preferably 1% or less. Because it is solvent-free, a heating drying process is unnecessary, resulting in excellent productivity. Furthermore, it has the advantage of reducing environmental impact such as VOC generation and CO2 emissions.

[0072] [Viscosity]

[0073] The viscosity of the active energy radiation-curable coating composition for metal substrates of the present invention is not particularly limited and can be appropriately set according to the coating method. For example, when coating using a roller coater suitable for PCM manufacturing, the viscosity at 25°C is preferably 100-2000 mPa·s, more preferably 200-1000 mPa·s, and most preferably 200-500 mPa·s. If the viscosity at 25°C is within the above range, coating and printing adaptability are excellent. Regarding viscosity, for example, it was measured using a viscoelasticity measuring device (Discovery HR-2, manufactured by TA Instruments, Japan), with a cone diameter of 20 mm, a cone angle of 1 degree, and a temperature of 25°C, with a shear rate starting from 0.1 sec... -1 The rate increases at a certain rate, reaching a shear rate of 100 sec after 60 seconds. -1 At that time, based on the shear rate of 100 seconds -1 The measured value was obtained at that time.

[0074] [Substrate]

[0075] As the substrate for applying the coating of the present invention, a metal substrate is particularly preferred. Specifically, examples of metal substrates include aluminized zinc-coated steel sheets, aluminum sheets, tin-free steel (TFS) sheets, tin-plated iron sheets, corrugated sheets, stainless steel sheets, copper sheets, and brass sheets. Alternatively, metal substrates on which a primer layer or base coat is formed are preferred. Furthermore, a resin film lamination process can also be used. For example, in applications involving building materials, where hardness and weather resistance are particularly important, steel sheet substrates such as aluminized zinc-coated steel sheets and galvanized steel sheets are more preferred.

[0076] [Coating Method]

[0077] The coating method for the active energy ray curable coating composition for metal substrates of the present invention can employ known methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roller coating, reverse roller coating, curtain coating, coincidence coating, dip coating, screen coating, rod coating, flow coating, and comma coating. Among these, coating methods that require sufficient hardness and processability after coating and curing are particularly suitable for pre-coating methods. From the perspective of high productivity, roller coating and reverse roller coating are more preferred.

[0078] [Curing Method]

[0079] The method for curing the active energy ray-curable coating composition for metal substrates of the present invention is not particularly limited, and known methods can be used. For example, curing can be carried out by irradiation with alpha rays, gamma rays, electron rays, X-rays, ultraviolet rays, visible light, or infrared rays. Among these, ultraviolet rays and electron rays are preferred, and electron rays are more preferred.

[0080] Even when cured by ultraviolet light, the coating composition of the present invention exhibits the effects of improving the hardness, processability, and weather resistance of the coating film.

[0081] When the coating composition of the present invention is cured by electron beams, it is not hindered by the blocking of ultraviolet rays or the like that associated with high pigment concentrations and ultraviolet absorbers. Furthermore, since no initiator is required, the usable time of the coating is shortened, and the coating film properties are not degraded after curing due to initiator decomposition products. Therefore, the effects of the present invention, such as improved coating film hardness, processability, and weather resistance, can be maximized.

[0082] Electron beam curing is preferably performed by irradiation with electron beams at an accelerating voltage of 10-500 kV, particularly 30-200 kV. When curing is performed with electron beams at an accelerating voltage of 30-200 kV, the effects of this invention, such as improving the hardness and processability of the coating film, can be maximized. If the accelerating voltage is too high, it is difficult to achieve a balance between the hardness and processability of the resulting coating film. A preferred irradiation dose is approximately 10 kGy to 200 kGy, more preferably 30 kGy to 200 kGy. If the irradiation dose is too low, curing is insufficient; conversely, if it is too high, the processability of the coating film decreases.

[0083] [Layered Body]

[0084] After the metal substrate is coated with the active energy ray-curable coating composition of the present invention, it is cured by irradiation with active energy rays, thereby obtaining a laminate having a cured coating film on the metal substrate. The film thickness when coating the metal substrate with the active energy ray-curable coating composition is generally preferably 1 to 50 μm, more preferably 10 to 20 μm. The laminate can be suitable for use as a pre-coated metal.

[0085] [Molded and processed components]

[0086] The laminate of the present invention has excellent processability and the processing method is not particularly limited. For example, as a molded component that has undergone molding processing, it can be used in building materials, home appliances, etc.

[0087] Example

[0088] The present invention will be described in detail below with examples, but the following examples do not limit the scope of the present invention in any way.

[0089] [Preparation of Active Energy Ray Curable Coating Composition for Metal Substrates: Example 1]

[0090] Following the formulation described in Table 1, the raw materials were dispersed and stirred at room temperature (3000 rpm) to prepare an active energy radiation-curable coating composition for metal substrates. The resulting coating composition was evaluated for its storage stability, processability, film hardness, and weather resistance using the following methods. The results are shown in Table 1.

[0091] [Preparation of Active Energy Ray Curable Coating Compositions for Metal Substrates: Examples 2-26, Comparative Examples 1-7]

[0092] Except for changes to the raw materials and quantities listed in Table 1, Examples 2-26 and Comparative Examples 1-7 were obtained using the same method as Example 1. It should be noted that the numbers in Tables 1 and 2 represent the amount of each compound (mass %).

[0093] [How to create a layered object]

[0094] The obtained metal substrate was coated with an active energy radiation-curable coating composition using a reverse roller coater to a galvanized steel sheet (registered trademark) (manufactured by Yodogawa Steel Works, Yodo GLEco-Green, thickness 0.27 mm) with a film thickness of 20 μm. Then, the coating composition was cured by irradiating it with electron beams using an electron beam irradiation device Eye·Compact EB (manufactured by Iwasaki Electric Co., Ltd., accelerating voltage 90 kV, radiation dose 100 kGy) to produce a laminate.

[0095] [Maintain stability]

[0096] The storage stability is evaluated by visually confirming whether any precipitates are produced in the coating after it has been left to stand at room temperature for one week following preparation, as described below.

[0097] 〔evaluate〕

[0098] A: No precipitate.

[0099] B: Only trace amounts of precipitate were detected.

[0100] C: Only trace amounts of precipitate were detected.

[0101] D: Obvious precipitates were observed.

[0102] It should be noted that the practical evaluation is A, B, and C.

[0103] [Processability]

[0104] Regarding processability, bending resistance was evaluated using a 180° bending test. The side with the cured coating was designated as the outer side, and the bent portion as the inner side. For a test piece sandwiched between 10 overlapping substrate steel plates, a 1kg load was dropped from a height of 50cm, thereby bending the coated sheet 180° to obtain the processed product. The bent portion of the processed product was visually evaluated for cracks.

[0105] 〔evaluate〕

[0106] A: No crack was detected.

[0107] B: Only a very small amount of cracks were detected.

[0108] C: Only a trace amount of cracks were detected.

[0109] D: Large cracks were observed.

[0110] It should be noted that the practical evaluation is A, B, and C.

[0111] [Coating Hardness]

[0112] For the evaluation of coating hardness, pencil hardness was determined according to JIS K5600-5-4. Pencils of various hardnesses were placed at a 45° angle on the surface of the cured coating, and a scratch test was performed with a load of 750g. The hardness of the hardest pencil without damage was evaluated.

[0113] 〔evaluate〕

[0114] A: No damage was detected at hardness H.

[0115] B: No damage was detected at hardness F.

[0116] C: Hardness HB - No damage confirmed.

[0117] D: Hardness HB confirms damage.

[0118] It should be noted that the practical evaluation is A, B, and C.

[0119] [Weather resistance]

[0120] For the evaluation of weather resistance, a xenon weathering tester (product name "Q-SUN Xe-1", manufactured by Q-Lab) was used, and repeated tests were conducted at 120W / m. 2 The surface condition of the test piece was evaluated after 700 hours by irradiating it with ultraviolet light for 102 minutes under the condition of 63°C blackboard temperature and spraying it with water for 18 minutes while irradiating it with ultraviolet light.

[0121] 〔evaluate〕

[0122] A: No abnormalities.

[0123] B: A very small amount of surface anomaly occurred.

[0124] C: Minor surface abnormalities have occurred.

[0125] D: Numerous surface anomalies occurred.

[0126] It should be noted that the practical evaluation is A, B, and C.

[0127] [Table 1]

[0128]

[0129] [Table 2]

[0130]

[0131] The information for each raw material in Tables 1 and 2 is as follows.

[0132] • EBECRYL 8402: Difunctional aliphatic urethane acrylate (DAICEL-ALLNEX)

[0133] • EBECRYL 8701: 3-functional aliphatic urethane acrylate (DAICEL-ALLNEX)

[0134] • MIRAMER PU5000: 6-functional aliphatic urethane acrylate (MIWON Corporation)

[0135] • IBXA: Isobornyl Acrylate (Osaka Organic Chemicals Co., Ltd.)

[0136] • Viscoat 196: 3,3,5-Trimethylcyclohexyl acrylate (Osaka Organic Chemicals Co., Ltd.)

[0137] • Viscoat 155: Cyclohexyl acrylate (Osaka Organic Chemicals Co., Ltd.)

[0138] • ACMO: Acryloylmorpholine (KJ Chemicals)

[0139] • ARONIX M-140: N-Acryloyloxyethyl hexahydrophthalimide (Dong-A Synthetic Co., Ltd.)

[0140] • Viscoat 200: Cyclic Trimethylolpropane Formaldehyde Acrylate (Osaka Organic Chemicals Co., Ltd.)

[0141] • Yupimer UV SA1002: Tricyclodecanedimethyl diacrylate (Mitsubishi Chemical Corporation)

[0142] • Light Acrylate HPP-A: Neopentyl Glycol Diacrylate Hydroxypentanoic Acid (Kyoei Chemical Co., Ltd.)

[0143] • Viscoat 150: Tetrahydrofurfuryl acrylate (Osaka Organic Chemicals Co., Ltd.)

[0144] • ADK STAB LA-46: 2-Ethylhexanoic acid = 2-[3-hydroxy-4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]ethyl ester (ADEKA)

[0145] • Tinuvin 479: A structurally undisclosed hydroxyphenyl triazine-based ultraviolet absorber (BYK Corporation)

[0146] • RUVA-93: 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole (Otsuka Chemical Co., Ltd.)

[0147] • ADK STAB LA-72: Bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (ADEKA)

[0148] • TIPAQUE CR-90: Rutile titanium dioxide (Ishihara Sangyo Co., Ltd.)

[0149] • DisperBYK 111: A copolymer containing acid groups (BYK Corporation)

[0150] As can be seen from the results in Tables 1 and 2, the cured coatings obtained in Examples 1 to 26 using the active energy ray curable coating composition for metal substrates of the present invention exhibited good hardness, processability, and weather resistance, and the coating compositions showed good storage stability. On the other hand, any one or more of the hardness, processability, weather resistance, and storage stability of Comparative Examples 1 to 7 were insufficient.

Claims

1. A coating composition for metal substrates that is cured by active energy radiation, comprising a binder component (A) and an ultraviolet absorber (B), The adhesive component (A) comprises urethane (meth)acrylate (A-1), a free radical polymerizable monofunctional monomer with an alicyclic structure (A-2), and a free radical polymerizable monofunctional monomer with a heterocyclic structure and a homopolymer glass transition temperature Tg of 20°C or higher (A-3).

2. The active energy ray-curable coating composition for metal substrates according to claim 1, wherein, The mass ratio of the free radical polymerizable monofunctional monomer (A-2) with an alicyclic structure to the free radical polymerizable monofunctional monomer (A-3) with a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher is 30 / 70 to 80 / 20.

3. The active energy radiation-curable coating composition for metal substrates according to claim 1, wherein, The content of the free radical polymerizable monofunctional monomer (A-2) with an alicyclic structure is 15 to 45% by mass relative to the total amount of the binder component (A).

4. The active energy radiation-curable coating composition for metal substrates according to claim 1, wherein, The content of the free radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature Tg of 20°C or higher is 10 to 40% by mass relative to the total amount of the binder component (A).

5. The active energy ray-curable coating composition for metal substrates according to claim 1, wherein, The content of the urethane (meth)acrylate (A-1) is 15 to 45% by mass relative to the total amount of the adhesive component (A).

6. The active energy ray-curable coating composition for metal substrates according to any one of claims 1 to 5, wherein, The solvent content is less than 3% by mass relative to the total active energy ray curable coating composition for the metal substrate.

7. The active energy ray-curable coating composition for metal substrates according to any one of claims 1 to 5, wherein, The content of the photopolymerization initiator is less than 0.5% by mass relative to the total active energy ray curable coating composition for the metal substrate.

8. The active energy ray curable coating composition for metal substrates according to any one of claims 1 to 5, used for pre-coating metals.

9. A laminate having a cured coating film on a metal substrate of the active energy ray curable coating composition for metal substrates according to any one of claims 1 to 8.

10. A molded component that uses the laminate as described in claim 9.

11. A method for manufacturing a laminated body, wherein, The active energy ray curable coating composition for metal substrates according to any one of claims 1 to 8 is applied to the metal substrate using a roller coater and cured using active energy rays.

12. A method for manufacturing a shaped component, wherein, The active energy ray curable coating composition for metal substrates according to any one of claims 1 to 8 is applied to the metal substrate using a roller coater, cured using active energy rays, and then formed.

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