Active energy ray curable coating composition for metal substrates, laminate, molded processing member, and method for manufacturing the same.

Abstract

The object of the present invention is to provide an active energy ray curable coating composition for metal substrates that exhibits good hardness, processability, and weather resistance of the cured coating film, as well as laminates and molded processed members using the same. Another object of the present invention is to provide an active energy ray curable coating composition for metal substrates that exhibits good coating film properties even when an ultraviolet absorber is used, and that does not cause precipitation of the ultraviolet absorber during storage, thus exhibiting good storage stability. [Solution] An active energy ray curable coating composition for a metal substrate comprising a binder component (A) and an ultraviolet absorber (B), wherein the binder component (A) comprises 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 a homopolymer glass transition temperature (Tg) of 20°C or higher, and a coated laminate using the same.

Description

Technical Field

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

Background Art

[0002] Generally, there are a post-coat method of coating after the metal substrate is formed into a product or part, and a pre-coat method of coating before the forming process. Here, a metal substrate coated by the pre-coat method is called PCM (pre-coated metal), and the paint used for this is called PCM paint.

[0003] Since the post-coat method is applied after the metal substrate is processed into a product or part, a coating system adapted to the shape and size of the object to be coated is required. On the other hand, for coating a plate-shaped metal substrate, the roll-coat method is widely adopted in the pre-coat method, and continuous operation at a very high speed is possible.

[0004] However, since PCM is processed after coating, not only the hardness and various resistances required for building materials and home appliances, which are the main applications, but also the processability that can withstand various forming processes carried out in the manufacturing process are required. Furthermore, excellent aesthetic properties are also required.

[0005] Conventional solvent drying type coating compositions are inferior in productivity because they require time for the solvent to dry, and there are problems of environmental load such as generation of VOC (volatile organic compounds) and CO2 emissions. Therefore, coating compositions cured by active energy rays such as electron beams and ultraviolet rays have come to be used. This active energy ray curable coating composition can generally be used without a solvent and can be cured with a small amount of energy in a short time, and thus has excellent characteristics from the viewpoints of productivity improvement and environmental load reduction.

[0006] Many PCMs require high weather resistance. In particular, when used in building materials, outdoor weather resistance of 10 years or more is often required. One known method to improve weather resistance is to incorporate additives such as UV absorbers and light stabilizers. Commonly used UV absorbers and light stabilizers absorb and / or reflect active energy rays such as ultraviolet rays. Therefore, they can reduce the curability of active energy ray curable coating compositions, and the physical properties of the coating film, such as water resistance, chemical resistance, and hardness, may decrease. In addition, since many of the above additives are poorly soluble in acrylate monomers, there is a risk of precipitation during storage in solvent-free active energy ray curable coating compositions, making it difficult to increase the amount of additive.

[0007] Patent Document 1 discloses an 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 1 or more (meth)acryloyl groups, and a photopolymerization initiator. Patent Document 2 discloses an active energy ray-curable coating composition for metal substrates containing a urethane (meth)acrylate with a weight-average molecular weight of 1,000 to 60,000, a compound having a hydrophilic group and one ethylenically unsaturated group, a compound having a cyclic hydrocarbon group and one ethylenically unsaturated group but lacking a hydrophilic group, and a compound having 2 or more (meth)acryloyl groups. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2022-131646 [Patent Document 2] Patent No. 5935668 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, while the active energy ray curing coating agent described in Patent Document 1 has good hardness and processability of the coating film, there is no description regarding weather resistance. There is a concern that adding UV absorbers to improve weather resistance may reduce the physical properties of the coating film after curing, or that UV absorbers may precipitate during storage. Furthermore, Patent Document 2 shows an active energy ray curing coating composition for metal substrates with good adhesion and solvent resistance, but there is no description regarding the physical properties of the coating film or weather resistance.

[0010] The object of the present invention is to provide an active energy ray curable coating composition for metal substrates that exhibits good hardness, processability, and weather resistance of the cured coating film, as well as laminates and molded processed members using the same. Another object of the present invention is to provide an active energy ray curable coating composition for metal substrates that exhibits good coating film properties even when an ultraviolet absorber is used, and has good storage stability because the ultraviolet absorber does not precipitate during storage.

[0011] The inventors of the present invention have conducted extensive research to solve the above problems and have found that the above problems can be solved by the following active energy ray curable coating composition for metal substrates, thereby completing the present invention.

[0012] In other words, the present invention is [1] An active energy ray curable coating composition for metal substrates comprising a binder component (A) and an ultraviolet absorber (B), The aforementioned binder component (A) is Urethane (meth)acrylate (A-1) and A radical polymerizable monofunctional monomer (A-2) having an alicyclic structure, A radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher, and A chemically active energy ray-curable coating composition for metal substrates, comprising the above.

[0013] [2] The active energy ray curable coating composition for metal substrates according to [1], wherein the content ratio (mass ratio) of the radical polymerizable monofunctional monomer (A-2) having an alicyclic structure and the radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher is 30 / 70 to 80 / 20.

[0014] [3] The active energy ray curable coating composition for metal substrates according to [1] or [2], wherein the content of the radical polymerizable monofunctional monomer (A-2) having an alicyclic structure is 15 to 45% by mass relative to the total amount of the binder component (A).

[0015] [4] The active energy ray curable coating composition for metal substrates according to any one of [1] to [3], wherein the content of the 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 binder component (A).

[0016] [5] The active energy ray curable coating composition for metal substrates according to any one of [1] to [4], wherein the content of the urethane (meth)acrylate (A-1) is 15 to 45% by mass relative to the total amount of the binder component (A).

[0017] [6] The active energy ray curable coating composition for metal substrates according to any one of [1] to [5], wherein the solvent content is 3% by mass or less of the entire active energy ray curable coating composition for metal substrates.

[0018] [7] The active energy ray curable coating composition for metal substrates according to any one of [1] to [6], wherein the content of the photopolymerization initiator is 0.5% by mass or less with respect to the entire active energy ray curable coating composition for metal substrates.

[0019] [8] An active energy ray curable coating composition for a metal substrate according to any of [1] to [7] above, for use with pre-coated metals.

[0020] [9]A laminate having a cured coating film of the active energy ray curable coating composition for a metal substrate according to any one of [1] to [8] on a metal substrate.

[0021]

[10] A molded product using the laminate according to [9].

[0022]

[11] A method for producing a laminate, comprising roll-coating the active energy ray curable coating composition for a metal substrate according to any one of [1] to [8] on a metal substrate and curing with active energy rays.

[0023]

[12] A method for producing a molded product, comprising roll-coating the active energy ray curable coating composition for a metal substrate according to any one of [1] to [8] on a metal substrate, curing with active energy rays, and performing molding.

Advantages of the Invention

[0024] According to the present invention, it is possible to provide an active energy ray curable coating composition for a metal substrate having good hardness, processability, and weather resistance of the cured coating film, as well as a laminate and a molded member using the same. Further, according to the present invention, it is possible to provide an active energy ray curable coating composition for a metal substrate having good coating film physical properties even when an ultraviolet absorber is used and having good storage stability without precipitation of the ultraviolet absorber during storage.

Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist thereof.

[0026] In the following description, (meth)acrylate, (meth)acryloyl, and (meth)acrylic each mean methacrylate and / or acrylate, methacryloyl and / or acryloyl, and methacrylic and / or acrylic, respectively.

[0027] In the following explanation, "number of functional groups" refers to the number of radically polymerizable functional groups, such as acryloyl groups, methacryloyl groups, vinyl groups, and other ethylenically unsaturated groups, that a resin or compound has in one molecule.

[0028] In this specification, binder component (A) refers to a coloring agent obtained by removing pigments, UV absorbers, light stabilizers, and other additives from a paint composition. Specifically, it refers to a mixture containing urethane (meth)acrylate (A-1), a radically polymerizable monofunctional monomer having an alicyclic structure (A-2), a radically polymerizable monofunctional monomer having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher (A-3), other compounds having radically polymerizable groups, and inert resins, etc.

[0029] In this specification, the homopolymer glass transition temperature (Tg) refers to the temperature at which a polymer composed of a single monomer changes from a glassy state to a rubbery state when heated, and is measured, for example, by a differential scanning calorimeter (DSC) or a thermomechanical analyzer (TMA).

[0030] The following describes the components included in, or potentially included in, the active energy ray curable coating composition for metal substrates of this embodiment (hereinafter also simply referred to as "coating").

[0031] [Binder component (A)] <Urethane (meth)acrylate (A-1)> The urethane (meth)acrylate (A-1) is not particularly limited and any (meth)acrylate having a urethane bond is acceptable. By including urethane (meth)acrylate (A-1), the paint of the present invention has a good balance between film hardness and processability, and also good adhesion. Examples of urethane (meth)acrylate (A-1) include oligomers obtained by reacting polyvalent isocyanate compounds, polyol compounds, and hydroxyl group-containing (meth)acrylate; and oligomers obtained by reacting polyvalent isocyanate compounds and hydroxyl group-containing (meth)acrylate. Examples of commercially available products include EBECRYL4858 (2-function), EBECRYL8311 (3-function), EBECRYL8402 (2-function), EBECRYL8701 (3-function), EBECRYL9260 (3-function), EBECRYL8606 (4-function), and EBECRYL8301R (6-function) from Daicel Ornex, as well as CN8888NS (2-function), CN8898NS (2-function), CN8881NS (2-function), CN964NS (2-function), and CN9013NS (9-function) from Sartmar, and MiramerPU320 (3-function), MiramerPU340 (3-function), and MiramerPU5000 (6-function) from MIWON.

[0032] For urethane (meth)acrylate (A-1), aliphatic urethane (meth)acrylate is preferred. Aliphatic urethane (meth)acrylate refers to urethane (meth)acrylate in which both the polyol component and the isocyanate component are aliphatic and which does not have an aromatic ring in the molecule. Aliphatic urethane (meth)acrylate is preferred from the viewpoint of easily imparting adhesion, and having excellent processability and weather resistance.

[0033] The number of functional groups in urethane (meth)acrylate (A-1) is preferably 2 to 4, and more preferably 2 to 3. If the number of functional groups is above the lower limit, the hardness of the coating film increases, and if it is below the upper limit, the hardness of the coating film does not become too high, and the processability improves. Furthermore, the content of urethane (meth)acrylate (A-1) is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass, relative to the total amount of binder component (A). A good balance between the hardness and processability of the coating film is achieved when the content of urethane (meth)acrylate (A-1) is within the above range.

[0034] <Alicyclic structure-containing radical polymerizable monofunctional monomer (A-2)> In the radical polymerizable monofunctional monomer (A-2) having an alicyclic structure (hereinafter also referred to as "component (A-2)"), the alicyclic structure refers to a non-aromatic ring structure composed solely of carbon atoms. By containing the radical polymerizable monofunctional monomer (A-2) having an alicyclic structure, the paint of the present invention exhibits excellent weather resistance and readily dissolves ultraviolet absorbers.

[0035] The radical polymerizable monofunctional monomer (A-2) having an alicyclic structure is not particularly limited, and examples include 3,3,5-trimethylcyclohexyl (meth)acrylate, hexahydrophthalyloxyethyl (meth)acrylate, hexahydrophthalyloxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, etc. Component (A-2) is preferably homopolymer glass transition temperature (Tg) of 10°C or higher, more preferably 40°C or higher, and even more preferably 70°C or higher, from the viewpoint of good weather resistance and high hardness of the coating film.

[0036] Component (A-2) preferably has a condensed ring structure because it exhibits excellent solubility of the ultraviolet absorber. Specific examples of such components include isobornyl acrylate (Tg=97°C) and dicyclopentanyl acrylate (Tg=120°C).

[0037] The content of component (A-2) is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass, relative to the total amount of binder component (A). Having the content of component (A-2) within the above range provides a good balance between the solubility of the UV absorber and the hardness of the coating film.

[0038] <A radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher> In a radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher (hereinafter also referred to as "component (A-3)"), the heterocyclic structure refers to a ring structure composed of at least two different elements. By containing component (A-3), the paint of the present invention has high film hardness and excellent heat resistance.

[0039] The 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 includes, for example, glycerin carbonate acrylate, 4-cyclohexene-1,2-dicarboximide-N-ethyl acrylate, 2-(cyclohexane-1,2-dicarboximide)ethyl acrylate, acryloyl morpholine, cyclic trimethylolpropane formal acrylate, N-vinylcaprolactam, N-vinylpyrrolidone, and the like. Component (A-3) is more preferably homopolymer glass transition temperature (Tg) of 50°C or higher, and even more preferably 80°C or higher, from the viewpoint of good weather resistance and high hardness of the coating film.

[0040] Component (A-3) preferably contains nitrogen in its heterocycle from the viewpoint of having excellent coating hardness. Specific examples of such components include acryloylmorpholine (Tg=145°C) and N-vinylcaprolactam (Tg=90°C).

[0041] The content of component (A-3) is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, and even more preferably 20 to 30% by mass, relative to the total amount of binder component (A). A good balance between weather resistance and coating hardness is achieved when the content of component (A-3) is within the above range.

[0042] The content ratio (mass ratio) of component (A-2) to component (A-3) is preferably 30 / 70 to 80 / 20, more preferably 40 / 60 to 70 / 30, and even more preferably 45 / 55 to 65 / 35. By having the content ratio of component (A-2) to component (A-3) within the above range, it is possible to maintain good coating hardness while ensuring the solubility of the ultraviolet absorber.

[0043] In addition to (A-1), (A-2), and (A-3) above, the binder component (A) may also contain other radical polymerizable monomers and / or oligomers. The amount of other radical polymerizable monomers and / or oligomers is not particularly limited, but it is preferably 40% by mass or less of the total amount of binder component (A). The binder component (A) may also contain inert resins, etc.

[0044] [Additives] <UV absorber (B)> Examples of UV absorbers (B) include organic UV absorbers such as salicylic acid-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, triazine-based UV absorbers, and cyanoacrylate-based UV absorbers, or inorganic UV absorbers consisting of fine particles of zinc oxide, titanium dioxide, and cerium oxide. Among these, benzotriazole-based UV absorbers or triazine-based UV absorbers are more preferred because they have high UV absorption capacity and are less prone to degradation even under high energy conditions such as ultraviolet light.

[0045] Examples of benzotriazole-based UV absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, and polyethylene glycol 3-[3-(benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionic acid. Examples of triazine-based UV absorbers include 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]phenol, 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3,5-tri[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]. Other commercially available products include ADEKA's "ADEKA Stub LA-F70" and "ADEKA Stub LA-40," and BASF Japan's "Tinuvin 405" and "Tinuvin 479."

[0046] The ultraviolet absorber (B) may be added to the paint in any amount, but from the viewpoint of solubility in the paint and film strength, it is preferably 3 to 15% by mass, and more preferably 5 to 10% by mass, relative to the total amount of binder component (A).

[0047] The active energy ray curable coating composition for metal substrates of the present invention may contain, in addition to the ultraviolet absorber (B), known additives as appropriate. Examples include light stabilizers, pigments, dyes, sensitizers, polymerization initiators, fluorescent whitening agents, curing agents, coupling agents, plasticizers, surface modifiers, defoaming agents, substrate wetting agents, antistatic agents, extender pigments, pigment dispersants, and the like.

[0048] Examples of light stabilizers include hindered amine light stabilizers (HALS), phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants. Among these, HALS are more preferred due to their high thermal stability and excellent radical scavenging ability. Specifically, HALS include 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2'-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidyl), bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and methyl(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate. Examples include cate, 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine), tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, and 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate. Other commercially available products include ADEKA's "ADEKA Stab LA-72" and "ADEKA Stab LA-82," and BASF Japan's "Tinuvin 123" and "Tinuvin 249."

[0049] The content of the 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, based on the total amount of binder component (A).

[0050] There are no particular restrictions on the pigments used; known pigments can be used, and either inorganic or organic pigments can be used. A single pigment may be used, or two or more pigments may be used in combination.

[0051] Examples of the inorganic pigments mentioned above include ultramarine, titanium dioxide, iron oxides, complex oxide pigments, and carbon blacks.

[0052] Examples of the above-mentioned organic pigments include phthalocyanine pigments, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, and quinophthalone pigments.

[0053] The pigment content is adjusted as appropriate depending on the type and purpose. For example, the pigment content is preferably 3% by mass or more of the total amount of the paint composition. Alternatively, the pigment content is preferably 60% by mass or less of the total amount of the paint composition. By keeping the pigment content within the above range, the paint composition can exhibit sufficient opacity while also ensuring dispersion stability.

[0054] [Photopolymerization initiator] The photopolymerization initiator is not particularly limited, and known photopolymerization initiators can be used as appropriate. When the active energy ray curable coating composition for metal substrates of the present invention is cured by ultraviolet light, it is necessary to include a photopolymerization initiator. When curing the active energy ray curable coating composition for metal substrates of the present invention with an electron beam, it is preferable that it does not contain a photopolymerization initiator. For example, the content of the photopolymerization initiator is preferably 0.5% by mass or less, and more preferably 0.1% or less, based on the total amount of the coating composition.

[0055] [solvent] The active energy ray-curable coating composition for metal substrates of the present invention preferably contains substantially no organic solvents or water. "Substantially no" means that these substances constitute 3% or less, more preferably 1% or less, of the total amount of the active energy ray-curable coating composition for metal substrates. The absence of solvents eliminates the need for a heating drying process, resulting in superior productivity. Furthermore, it offers the advantage of reducing environmental impact, such as the generation of VOCs and CO2 emissions.

[0056] [viscosity] The viscosity of the active energy ray curable coating composition for metal substrates of the present invention is not particularly limited and can be appropriately set depending on the coating method. For example, in the case of coating by a roll coater, which is suitably used in the production of PCM, the viscosity at 25°C is preferably 100 to 2000 mPa·s, more preferably 200 to 1000 mPa·s, and most preferably 200 to 500 mPa·s. When the viscosity at 25°C is within the above range, the coating and printing suitability is excellent. Viscosity is measured, for example, by a viscoelasticity measuring device (DiscoveryHR-2, manufactured by T.A. Instruments Japan Co., Ltd.) with a cone diameter of 20 mm, a cone angle of 1 degree, a temperature of 25°C, and a shear rate of 0.1 sec. -1 The temperature is increased at a constant rate, and after 60 seconds the shear rate is set to 100 sec. -1 When it reaches this point, the shear rate is 100 sec. -1 It can be determined from the measured values ​​at that time.

[0057] [Base material] As a substrate to which the coating of the present invention is applied, a metal substrate is particularly preferred. Specific examples of metal substrates include galvalume steel sheets, aluminum sheets, tin-free steel (TFS) sheets, tinplate sheets, corrugated iron sheets, stainless steel sheets, copper sheets, brass sheets, and the like. Alternatively, a metal substrate on which a base coat layer, primer layer, etc., is formed is preferred. It may also be laminated with a resin film. For example, when used in building materials, hardness and weather resistance are particularly required, and a steel sheet substrate such as galvalume steel sheet or galvanized steel sheet is more preferred.

[0058] [Coating method] Known methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, curtain coating, kiss coating, dip coating, silkscreen coating, bar coating, flow coating, and comma coating can be applied as coating methods for the active energy ray curable coating composition for metal substrates of the present invention. Among these, roll coating and reverse roll coating are more preferred in terms of their high productivity, as they are particularly suitable for pre-coating methods that require sufficient hardness and workability after coating and curing.

[0059] [Curing method] 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, it can be cured by irradiation with alpha rays, gamma rays, electron beams, X-rays, ultraviolet rays, visible light, or infrared rays. Among these, ultraviolet rays and electron beams are preferred, and electron beams are more preferred.

[0060] The paint composition of the present invention exhibits the effects of the present invention, such as improving the hardness, processability, and weather resistance of the paint film, even when cured by ultraviolet light. The paint composition of the present invention, when cured by electron beam, is not inhibited from curing by shielding from ultraviolet rays due to high pigment concentration or the inclusion of UV absorbers. Furthermore, since it does not require an initiator, the paint's pot life is not shortened, and the paint film performance does not deteriorate after curing due to initiator decomposition products. Therefore, the effects of the present invention, which improve the hardness, processability, and weather resistance of the paint film, can be maximized.

[0061] Electron beam curing is preferably performed by irradiating with an electron beam with an acceleration voltage of 10 to 500 kV, particularly 30 to 200 kV. When curing is performed with an electron beam with an acceleration voltage of 30 to 200 kV, the effects of the present invention, which improve the hardness and processability of the coating film, can be maximized. If the acceleration voltage is too high, it becomes difficult to balance the hardness and processability of the resulting coating film. The preferred irradiation dose is about 10 kGy to 200 kGy, and more preferably 30 kGy to 200 kGy. If the irradiation dose is too low, curing will be insufficient, and if it is too high, the processability of the coating film will decrease.

[0062] [Laminated structure] By coating a metal substrate with the active energy ray-curable coating composition of the present invention, and then curing it by irradiation with active energy rays, a laminate having a cured coating film on a metal substrate is obtained. The film thickness when coating with the active energy ray-curable coating composition for metal substrates is usually preferably 1 to 50 μm, and more preferably 10 to 20 μm. The laminate can be suitably used as a pre-coated metal.

[0063] [Molded parts] The laminate of the present invention has excellent processability, and although the processing method is not particularly limited, it can be suitably used as a molded component in building materials, home appliances, and the like. [Examples]

[0064] The present invention will be described in detail below with reference to examples, but the following examples do not limit the scope of the rights of the present invention in any way.

[0065] [Preparation of Active Energy Ray Curable Coating Composition for Metal Substrates: Example 1] According to the formulations listed in Table 1, each raw material was mixed at room temperature by disperser stirring (3000 rpm) to prepare an active energy ray curable coating composition for metal substrates. The obtained coating composition was evaluated for storage stability, processability, coating hardness, and weather resistance using the following evaluation methods. The results are shown in Table 1.

[0066] [Preparation of active energy ray curable coating compositions for metal substrates: Examples 2-26, Comparative Examples 1-7] Examples 2-26 and Comparative Examples 1-7 were obtained using the same method as in Example 1, except that the raw materials and quantities listed in Table 1 were changed. The numbers in Tables 1 and 2 indicate the blending amount (mass %).

[0067] [Method for fabricating laminates] A base material, galvalume steel sheet (registered trademark) (manufactured by Yodogawa Steel Works, Yodo GL Eco Green, thickness 0.27 mm), was coated with the obtained active energy ray curable coating composition for metal substrates using a reverse roll coater to a coating thickness of 20 μm. Subsequently, the coating composition was cured by irradiating it with an electron beam using an electron beam irradiation device i-Compact EB (manufactured by Iwasaki Electric Co., Ltd., acceleration voltage 90 kV, irradiation dose 100 kGy) to produce a laminate.

[0068] [Storage stability] The storage stability of the paint was evaluated as follows by visually checking for the formation of precipitates in the paint after it had been left to stand at room temperature for one week after preparation. 〔evaluation〕 A: No precipitates. B: Only trace amounts of precipitate were observed. C: Only trace amounts of precipitate were observed. D: Clear precipitates were observed. The ratings for practical use are A, B, and C.

[0069] [Workability] Processability was evaluated by a 180° bending test to assess bending resistance. A test specimen was prepared by placing the hardened coating side outward and sandwiching 10 base steel plates inside the bending portion. A 1 kg load was dropped from a height of 50 cm to bend the coated specimen 180° and obtain a processed product. The presence or absence of cracks in the bent portion of the processed product was visually evaluated. 〔evaluation〕 A: No cracks were found. B: Only extremely small cracks were observed. C: Only minor cracks were observed. D: A large crack was observed. The ratings for practical use are A, B, and C.

[0070] [Coating film hardness] The hardness of the coating film was evaluated by measuring pencil hardness according to JIS K5600-5-4. Pencils of various hardness levels were placed on the surface of the hardened coating film at a 45° angle, and a scratch test was performed by applying a load of 750g. The hardness of the pencil that did not scratch the surface was evaluated. 〔evaluation〕 A: No scratches were found in the hardness H. B: No scratches were found in the hardness F. C: No scratches were found at a hardness of HB. D: Scratches were found in a hardness HB sample. The ratings for practical use are A, B, and C.

[0071] [Weather resistance] Weather resistance was evaluated using a xenon weathering tester (product name "Q-SUN Xe-1", manufactured by Q-Lab) at 120 W / m². 2 The experiment involved repeatedly irradiating the specimens with ultraviolet light for 102 minutes under irradiation conditions of a black panel temperature of 63°C, and then spraying them with water for 18 minutes while irradiating them with ultraviolet light under the same irradiation conditions. The surface condition of the specimens was evaluated after 700 hours. 〔evaluation〕 A: No abnormalities B: A very small amount of surface abnormality occurs. C: Minor surface abnormalities occur. D: A large number of surface abnormalities occurred. The ratings for practical use are A, B, and C.

[0072] [Table 1]

[0073] [Table 2]

[0074] The information for each ingredient in Tables 1 and 2 is as follows: EBECRYL8402: Bifunctional aliphatic urethane acrylate (Daicel Ornex Co., Ltd.) EBECRYL8701: Trifunctional aliphatic urethane acrylate (Daicel Ornex Co., Ltd.) • MIRAMER PU5000: Heterofunctional aliphatic urethane acrylate (MIWON Co.) IBXA: Isobornyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) • Viscoat 196: 3,3,5-trimethylcyclohexyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) • Viscoat 155: Cyclohexyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) • ACMO: Acryloylmorpholine (KJ Chemicals) • Arronix M-140: N-Acryloyloxyethylhexahydrophthalimide (Toagosei Co., Ltd.) • Viscoat 200: Cyclic trimethylolpropaneform acrylate (Osaka Organic Chemical Industry Co., Ltd.) • Yupimer UV SA1002: Tricyclodecanedimethanol diacrylate (Mitsubishi Chemical Corporation) • Light acrylate HPP-A: Neopentyl glycol diacrylate hydroxypivalate (Kyoeisha Chemical Co., Ltd.) • Viscoat 150: Tetrahydrofurfuryl acrylate (Osaka Organic Chemical Industry Co., Ltd.) • ADEKA LA-46: 2-ethylhexanoic acid = 2-[3-hydroxy-4-(4,6-diphenyl-1,3,5-triazine-2-yl)phenoxy]ethyl (ADEKA Corporation) • Tinuvin479: Structure not disclosed. Hydroxyphenyltriazine-based UV absorber (BYK Corporation). RUVA-93: 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole (Otsuka Chemical Co., Ltd.) • ADEKA LA-72: Bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (ADEKA Corporation) • Typeque CR-90: Rutile-type titanium dioxide (Ishihara Sangyo Co., Ltd.) • DisperBYK111: Copolymer containing acid groups (BYK Corporation)

[0075] As is clear from the results in Tables 1 and 2, in Examples 1 to 26 using the active energy ray curable coating composition for metal substrates of the present invention, the resulting cured coating films exhibited good hardness, processability, and weather resistance, and the coating composition also showed good storage stability. On the other hand, in Comparative Examples 1 to 7, one or more of the hardness, processability, weather resistance, and storage stability were insufficient.

Claims

1. A metal substrate active energy ray curable coating composition comprising a binder component (A) and an ultraviolet absorber (B), The aforementioned binder component (A) Urethane (meth)acrylate (A-1) and A radical polymerizable monofunctional monomer (A-2) having an alicyclic structure, A radical polymerizable monofunctional monomer (A-3) having a heterocyclic structure and a homopolymer glass transition temperature (Tg) of 20°C or higher, and A chemically active energy ray-curable coating composition for metal substrates, comprising the above.

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

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

4. The active energy ray curable coating composition for metal substrates according to claim 1, wherein the content of the radical polymerizable monofunctional monomer (A-3) having the 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 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 binder component (A).

6. The active energy ray curable coating composition for a metal substrate according to claim 1, wherein the solvent content is 3% by mass or less of the total active energy ray curable coating composition for a metal substrate.

7. The active energy ray curable coating composition for a metal substrate according to claim 1, wherein the content of the photopolymerization initiator is 0.5% by mass or less of the total active energy ray curable coating composition for a metal substrate.

8. The active energy ray curable coating composition for metal substrates according to claim 1, which is for use with pre-coated metals.

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

10. A molded processing member using the laminate described in claim 9.

11. A method for manufacturing a laminate, comprising applying an active energy ray-curable coating composition for a metal substrate according to any one of claims 1 to 8 to a metal substrate using a roll coater and curing it with active energy rays.

12. A method for manufacturing a molded member, comprising applying an active energy ray-curable coating composition for a metal substrate according to any one of claims 1 to 8 to a metal substrate using a roll coater, curing it with active energy rays, and then molding it.

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