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

Abstract

To provide an active energy ray-curable coating composition for a metal substrate which achieves all of high hardness, high processing and high weather resistance and a laminate and a molding processing member using the same and further to provide an active energy ray-curable coating composition for a metal substrate having good coating film properties and good storage stability even when an ultraviolet absorber is used.SOLUTION: There are provided: an active energy ray-curable coating composition for a metal substrate which comprises a urethane (meth)acrylate (A), a multifunctional (meth)acrylate monomer (B) having an isocyanurate skeleton, a radical polymerizable monofunctional monomer (C), an ultraviolet absorber (D) and a light stabilizing agent (E), in which the radical polymerizable monofunctional monomer (C) includes a radical polymerizable monofunctional monomer (C-1) having an alicyclic structure and a radical polymerizable monofunctional monomer (C-2) having a heterocyclic ring structure; and a laminate and a molding processing member using the same.SELECTED DRAWING: None

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 manufacturing the same.

Background Art

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

[0003] In the post-coat method, since the metal substrate is coated after being processed into a product or a part, a coating system adapted to the shape and size of the object to be coated is required. On the other hand, in the pre-coat method, since it is for coating a plate-shaped metal substrate, continuous operation at a very high speed is possible, and since the film thickness can be easily controlled, very uniform film formation is possible.

[0004] However, since PCM is processed after coating, not only the hardness and resistance 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 drying of the solvent, and there are problems of environmental load such as the generation of VOC (volatile organic compounds) and CO2 emissions. Therefore, coating compositions cured by active energy rays such as electron beams and ultraviolet rays are being 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. Therefore, it has excellent characteristics from the viewpoints of productivity improvement and environmental load reduction.

[0006] Many PCMs are required to have high weather resistance. Especially when used for building materials, outdoor weather resistance of ten years or more is often required. As a method for improving weather resistance, it is known to blend additives such as ultraviolet absorbers and light stabilizers. However, since many of the above additives are difficult to dissolve in acrylate monomers, there is a risk of precipitation during storage in a solvent-free coating composition, and it is difficult to increase the addition amount. In addition, ultraviolet absorbers and light stabilizers absorb and / or reflect active energy rays such as ultraviolet rays. Therefore, the curability of the active energy ray-curable coating composition may be reduced, and the coating film physical properties such as water resistance, chemical resistance, and hardness may be reduced.

[0007] Patent Document 1 proposes an active energy ray-curable resin composition containing 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, wherein the content of the solvent with respect to the total amount of the active energy ray-curable resin composition is 1% by mass or less. Further, Patent Document 2 proposes a coating film forming method in which a coating composition containing a urethane (meth)acrylate having a weight average molecular weight in the range of 550 or more and less than 10,000 and having 2 or more (meth)acryloyl groups in one molecule, a polymerizable unsaturated compound having a weight average molecular weight in the range of 200 or more and less than 550 and having 2 or more polymerizable unsaturated groups in one molecule, and a polymerization initiator is applied onto a substrate under conditions where the temperature reaches within the range of 28 to 70°C, and then cured.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, with the coating agent for precoated metal described in Patent Document 1 above, although both high hardness and high workability can be achieved, there is no description regarding weather resistance. In order to improve weather resistance, when an ultraviolet absorber or a light stabilizer is blended, there is a concern that the physical properties of the cured coating film may deteriorate, or that the ultraviolet absorber may precipitate during storage. Further, Patent Document 2 shows a method for forming a coating film using a coating composition having good adhesion and pencil hardness, but there is no description regarding the workability or weather resistance of the coating film, or the storage stability of the paint.

[0010] An object of the present invention is to provide an active energy ray-curable coating composition that achieves all of high hardness, high workability, and high weather resistance, as well as a coated article and a molded processing member using the same. Another object of the present invention is to provide an active energy ray-curable coating composition for a metal substrate that has good coating film physical properties even when an ultraviolet absorber is used, and that has good storage stability without precipitation of the ultraviolet absorber during storage.

[0011] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the active energy ray-curable coating composition for a metal substrate shown below, and have completed the present invention.

[0012] That is, the present invention relates to [1] An active energy ray-curable coating composition for a metal substrate, comprising urethane (meth)acrylate (A), a polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton (excluding the urethane (meth)acrylate (A)), a radically polymerizable monofunctional monomer (C) (excluding the urethane (meth)acrylate (A)), an ultraviolet absorber (D), and a light stabilizer (E), wherein the radically polymerizable monofunctional monomer (C) includes a radically polymerizable monofunctional monomer (C-1) having an alicyclic structure and a radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure.

[0013] Further, the present invention relates to [2] The present invention relates to the active energy ray-curable coating composition for a metal substrate according to [1] above, wherein the content ratio (mass ratio) of the radically polymerizable monofunctional monomer (C-1) having an alicyclic structure and the radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure is 20 / 80 to 70 / 30.

[0014] Further, the present invention relates to [3] The present invention relates to the active energy ray-curable coating composition for a metal substrate according to [1] or [2] above, wherein the solvent content is 3% by mass or less based on the total amount of the active energy ray-curable coating composition for a metal substrate.

[0015] Further, the present invention relates to [4] The present invention relates to the active energy ray-curable coating composition for a metal substrate according to any one of [1] to [3] above, wherein the content of the photopolymerization initiator is 0.5% by mass or less based on the total amount of the active energy ray-curable coating composition for a metal substrate.

[0016] Further, the present invention relates to [5] The present invention relates to the active energy ray-curable coating composition for a metal substrate according to any one of [1] to [4] above, which is for pre-coated metal.

[0017] Further, the present invention relates to [6] The present invention relates to a laminate having a cured layer of the active energy ray-curable coating composition for a metal substrate according to any one of [1] to [5] above on a metal substrate.

[0018] Further, the present invention relates to [7] The present invention relates to a method for producing a laminate, which comprises applying the active energy ray-curable coating composition for a metal substrate according to any one of [1] to [5] above to a metal substrate and curing it with active energy rays.

[0019] Further, the present invention relates to [8] The present invention relates to a molded member using the laminate according to [6] above.

[0020] Further, the present invention relates to [9]The present invention relates to a method for manufacturing a molded member, which comprises applying the active energy ray curable coating composition for a metal substrate according to any one of [1] to [5] to a metal substrate, curing with active energy rays, and performing a molding process.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide an active energy ray curable coating composition that achieves all of high hardness, high processability, and high weather resistance, 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 that has good coating film physical properties even when an ultraviolet absorber is used and has good storage stability without precipitation of the ultraviolet absorber during storage.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments for carrying out the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof.

[0023] In the following description, (meth)acrylate, (meth)acryloyl, and (meth)acrylic mean methacrylate and / or acrylate, methacryloyl and / or acryloyl, and methacrylic and / or acrylic, respectively.

[0024] In the following description, the "number of functional groups" refers to the number of radically polymerizable groups such as acryloyl groups, methacryloyl groups, and other reactive unsaturated groups that a resin or compound has in one molecule.

[0025] In this specification, the binder composition refers to the components constituting the binder, excluding the colorant, ultraviolet absorber, light stabilizer, and other additives from the coating material. Specifically, it refers to a mixture containing the urethane (meth)acrylate (A), the polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton, the radically polymerizable monofunctional monomer (C), other compounds having a radically polymerizable group, and an inert resin.

[0026] Hereinafter, components included in or that can be included in the active energy ray-curable coating composition of the present embodiment (hereinafter, also simply referred to as "coating") will be described.

[0027] <Urethane (meth) acrylate (A)> The urethane (meth) acrylate (A) contained in the active energy ray-curable coating composition of the present invention is not particularly limited as long as it is a (meth) acrylate having a urethane bond. By including the urethane (meth) acrylate (A), the coating of the present invention has a good balance between coating film hardness and processability, and also has good adhesion. As the urethane (meth) acrylate (A), for example, an oligomer obtained by reacting a polyvalent isocyanate-based compound, a polyol compound, and a hydroxyl group-containing (meth) acrylate; an oligomer obtained by reacting a polyvalent isocyanate-based compound and a hydroxyl group-containing (meth) acrylate, etc. can be mentioned. Commercially available products include, for example, EBECRYL4858 (bifunctional), EBECRYL8311, EBECRYL8402 (bifunctional), EBECRYL8701 (trifunctional), EBECRYL9260 (trifunctional), EBECRYL8606 (tetrafunctional), EBECRYL8301R (hexafunctional) manufactured by Daicel Ornex Co., Ltd., and CN8888NS (bifunctional), CN8898NS (bifunctional), CN8881NS (bifunctional), CN964NS (bifunctional), CN9013NS (nonafunctional) manufactured by Sartomer Co., Ltd.

[0028] The urethane (meth) acrylate (A) is preferably an aliphatic urethane (meth) acrylate. The aliphatic urethane (meth) acrylate refers to a urethane (meth) acrylate in which each of the polyol component and the isocyanate component constituting it is aliphatic and does not have an aromatic ring in the molecule. The aliphatic urethane (meth) acrylate is preferable from the viewpoints of being easy to impart adhesion, excellent processability and weather resistance, etc.

[0029] The functionality number of the urethane (meth)acrylate (A) is preferably from 2 to 4, more preferably from 2 to 3. If the functionality number is at least the above lower limit, the hardness of the coating film increases, and if it is at most the above upper limit, the hardness of the coating film does not become too high and the processability is improved. Further, the content of the urethane (meth)acrylate (A) is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, still more preferably 15 to 30% by mass based on the total amount of the binder composition. When the content of the urethane (meth)acrylate (A) is within the above range, the balance between the hardness and processability of the coating film becomes good.

[0030] <Polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton> The polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton is a (meth)acrylate other than the urethane (meth)acrylate (A) and has an isocyanurate group and a (meth)acryloyl group. By including the monomer (B), the paint of the present invention ensures good processability while achieving good coating film hardness. For example, bis((meth)acryloxymethyl)hydroxymethyl isocyanurate, bis((meth)acryloxyethyl)hydroxyethyl isocyanurate, tris((meth)acryloxymethyl) isocyanurate, tris((meth)acryloxyethyl) isocyanurate, methoxylated triacrylate isocyanurate, ethoxylated triacrylate isocyanurate, caprolactone-modified di((meth)acryloxymethyl) isocyanurate, caprolactone-modified tris((meth)acryloxyethyl) isocyanurate, etc. can be mentioned. Among these, the monomer (B) preferably has a structure modified with polylactone from the viewpoint of excellent processability of the coated article obtained using the coating composition. Specific examples of such are caprolactone-modified di((meth)acryloxymethyl) isocyanurate and caprolactone-modified tris((meth)acryloxyethyl) isocyanurate. Examples of commercially available products include Aronix M-313, Aronix M-315, Aronix M-327 (manufactured by Toagosei Co., Ltd.), A-9300, A-9300-1CL (manufactured by Shin-Nakamura Chemical Co., Ltd.), SR368 (manufactured by Sartomer Co., Ltd.), and the like. These acrylate monomers can be used alone or in combination of two or more.

[0031] The content of the polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and still more preferably 10 to 20% by mass with respect to the total amount of the binder composition. When the content of the polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton is 5% by mass or more, a coating film having a more suitable hardness for PCM applications can be obtained for the coated article obtained using the coating composition. Further, when the content of the polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton is 30% by mass or less, the coated article obtained using the coating composition has good processability.

[0032] <Radical polymerizable monofunctional monomer (C)> The coating composition of the present invention contains a radical polymerizable monofunctional monomer (C). The radical polymerizable monofunctional monomer (C) is a radical polymerizable monomer other than the urethane (meth)acrylate (A), has only one radical polymerizable group, and polymerizes by irradiation with active energy rays. The radical polymerizable monofunctional monomer (C) has the effect of significantly reducing the viscosity of the coating composition and improving the adhesion and smoothness of the cured coating film.

[0033] The radically polymerizable monofunctional monomer (C) includes a radically polymerizable monofunctional monomer (C-1) having an alicyclic structure and a radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure. The radically polymerizable monofunctional monomer (C-1) having an alicyclic structure is a radically polymerizable monofunctional monomer having a ring structure composed only of carbon in the compound, is easy to dissolve an ultraviolet absorber, and has good storage stability of the paint. The radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure is a radically polymerizable monofunctional monomer having a ring structure composed of at least two or more different elements, and has higher coating film hardness, heat resistance, etc. The present invention improves the weather resistance due to the synergistic effect of the monomer (C-1) and the monomer (C-2), and can be compatible with coating film hardness, processability, and storage stability.

[0034] Examples of the radically polymerizable monofunctional monomer (C-1) having an alicyclic structure include 3,3,5-trimethylcyclohexyl acrylate, hexahydrophthalanyloxyethyl (meth)acrylate, hexahydrophthalanyloxypropyl (meth)acrylate, cyclohexyl acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentenyl oxyethyl (meth)acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, isobornyl acrylate, vinylcyclohexane and the like. Among them, it preferably has a condensed ring structure from the viewpoint of excellent solubility of the ultraviolet absorber. As such specific examples, isobornyl acrylate and dicyclopentanyl acrylate are preferable.

[0035] Examples of the radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure include tetramethylpiperidyl methacrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, (cyclohexane spiro-2-(1,3-dioxolan-4-yl))methyl acrylate, acryloylmorpholine, cyclic trimethylolpropane formal acrylate, tetrahydrofurfuryl acrylate, a large amount of acrylate ester of tetrahydrofurfuryl alcohol, N-vinylcaprolactam, N-vinylpyrrolidone, and the like. Among them, those having a glass transition point (Tg) of 0°C or higher are preferred. Specific examples thereof include acryloylmorpholine (Tg = 145°C), cyclic trimethylolpropane formal acrylate (Tg = 27°C), and the like. The glass transition point of component (C-2) can be measured using a differential scanning calorimeter (DSC).

[0036] The content of the radically polymerizable monofunctional monomer (C-1) having an alicyclic structure is preferably 10 to 45% by mass, more preferably 20 to 40% by mass, based on the total amount of the binder composition. When the content of component (C-1) is within the above range, the balance between the solubility of the ultraviolet absorber and the coating film hardness becomes good. The content of the radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure is preferably 25 to 40% by mass, more preferably 15 to 30% by mass, based on the total amount of the binder composition. When the content of component (C-2) is within the above range, the balance between the weather resistance and the coating film hardness becomes good.

[0037] The content ratio (mass ratio) of the radically polymerizable monofunctional monomer (C-1) having an alicyclic structure to the radically polymerizable monofunctional monomer (C-2) having a heterocyclic structure is preferably 20 / 80 to 70 / 30, more preferably 25 / 75 to 60 / 40. When the content ratio of component (C-1) to component (C-2) is within the above range, good coating film hardness and weather resistance can be maintained while ensuring the solubility of the ultraviolet absorber.

[0038] <Ultraviolet absorber (D)> Examples of the ultraviolet absorber (D) include organic ultraviolet absorbers such as salicylic acid-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers, or inorganic ultraviolet absorbers composed of fine particles of zinc oxide, titanium oxide, and cerium oxide. Among them, benzotriazole-based ultraviolet absorbers or triazine-based ultraviolet absorbers, which have high ultraviolet absorption ability and are less likely to deteriorate against high energy such as ultraviolet rays, are more preferable.

[0039] Specific examples of the benzotriazole-based ultraviolet absorber include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, and polyethylene glycol 3-[3-(benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate. Specific examples of the triazine-based ultraviolet absorber include 2-(4,6-diphenyl-1,3,5-triazin-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]. Commercially available products include "ADEKA STAB LA-F70", "ADEKA STAB LA-40" from ADEKA Corporation, and "Tinuvin 405", "Tinuvin 479" manufactured by BASF Japan Ltd.

[0040] <Light stabilizer (E)> Examples of the light stabilizer (E) include hindered amine light stabilizers (HALS), phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, HALS is more preferable because of its high thermal stability and excellent radical scavenging ability. Specific examples of HALS include bis(1,2,2,6,6-pentamethyl-4-piperidyl) 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2'-n-butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, methyl (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamino)-1,3,5-triazine), tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, and the like. Examples of commercially available products include "ADEKA STAB LA-72" and "ADEKA STAB LA-82" from ADEKA Corporation, and "Tinuvin 123" and "Tinuvin 249" manufactured by BASF Japan Ltd.

[0041] These ultraviolet absorbers (D) and light stabilizers (E) may be added in any amount in the composition, but from the viewpoint of solubility in the paint, it is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less in total based on the total amount of the binder composition. Further, the content of the ultraviolet absorber (D) is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less based on the total amount of the binder composition. The content of the light stabilizer (E) is preferably 7% by mass or less, more preferably 5% by mass or less, and still more preferably 3% by mass or less based on the total amount of the binder composition. By the content of the ultraviolet absorber (D) and the light stabilizer (E) being within the above ranges, good weather resistance can be exhibited while ensuring the coating film hardness and the storage stability of the paint.

[0042] In addition to the above urethane (meth)acrylate (A), polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton, radical polymerizable monofunctional monomer (C), ultraviolet absorber (D), and light stabilizer (E), other radical polymerizable monomers / oligomers and inert resins may be included. The amount of other radical polymerizable monomers / oligomers and inert resins is not particularly limited, but it is preferably 30% by mass or less of the binder composition.

[0043] [Additives] The active energy ray-curable coating composition of the present invention can appropriately contain known additives. For example, colorants, sensitizers, polymerization initiators, fluorescent brighteners, curing agents, coupling agents, plasticizers, leveling agents, surface modifiers, defoamers, substrate wetting agents, antistatic agents, extender pigments, pigment dispersants, etc. can be mentioned.

[0044] [Colorant] As the colorant, at least one of a pigment and a dye can be used. From the viewpoint of weather resistance, a pigment is preferred. There is no particular limitation on the pigment, and known pigments can be used. The pigment can be either an inorganic pigment or an organic pigment. The pigment may be used alone or in combination of two or more.

[0045] Examples of the inorganic pigment include ultramarine, titanium dioxide, iron oxides, composite oxides, carbon blacks, and the like.

[0046] Examples of the organic pigment include phthalocyanine-based pigments, azo-based pigments, quinacridone-based pigments, diketopyrrolopyrrole-based pigments, quinophthalone-based pigments, and the like.

[0047] The content of the pigment is appropriately adjusted depending on the type and purpose. For example, the content of the pigment is preferably 3% by mass or more in the coating composition. Also, the content of the pigment is preferably 60% by mass or less in the coating composition. When the content of the pigment is within the above range, the coating composition can exhibit sufficient hiding power and ensure dispersion stability.

[0048] [Solvent] The active energy ray-curable coating composition of the present invention preferably does not substantially contain an organic solvent or water. "Not substantially contain" means 3% or less, more preferably 1% or less, based on the total mass of the active energy ray-curable coating composition. By not containing a solvent, a drying step by heating becomes unnecessary, resulting in excellent productivity. Also, there is an advantage that environmental loads such as generation of VOC and CO2 emissions can be reduced.

[0049] [Photoinitiator] The photoinitiator is not particularly limited, and known photoinitiators can be appropriately used. When the active energy ray-curable coating composition for a metal substrate of the present invention is cured by ultraviolet rays, it is necessary to contain a photoinitiator. The content of the photoinitiator is not particularly limited. For example, the content of the photoinitiator is preferably 2 to 15% by mass, more preferably 3 to 10% by mass in the coating composition. When the content of the photoinitiator is within the above range, the coating composition can be sufficiently cured even when cured by ultraviolet rays. When the active energy ray-curable coating composition for a metal substrate of the present invention is cured by electron beams, it is preferably free of a photoinitiator. For example, the content of the photoinitiator is preferably 0.5% by mass or less, more preferably 0.1% or less based on the total amount of the coating composition.

[0050] [Viscosity] The viscosity of the active energy ray-curable coating composition of the present invention is not particularly limited and can be appropriately set according to the coating method. For example, in the case of coating with a roll coater, 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 applicability is excellent. The viscosity refers to the measurement value at a shear rate of 100 sec when using a viscoelasticity measuring device (Discovery HR-2, manufactured by TA Instruments Japan Co., Ltd.), with a cone diameter of 20 mm, a cone angle of 1 degree, a temperature of 25°C, and the shear rate is increased at a certain rate from 0.1 sec -1 and reaches 100 sec after 60 seconds -1 when reaching -1 100 sec.

[0051] [Substrate] As the substrate to which the paint of the present invention is applied, a metal substrate is particularly preferred. Specific examples of the metal substrate include galvanized steel sheets, aluminum plates, tin-free steel (TFS) plates, iron plates, galvanized iron plates, stainless steel plates, copper plates, brass plates, and the like. Alternatively, a metal substrate having a base coat layer, a primer layer, or the like formed on these metal plates is preferred. Further, it may be laminated with a resin film. For example, when used for building materials, steel plate substrates such as galvanized steel sheets (registered trademark) and stainless steel plates are more preferred because hardness and weather resistance are particularly required.

[0052] [Coating method] As the coating method of the active energy ray curable paint composition of the present invention, known means such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, curtain coating, kiss coating, dip coating, silk screen coating, wire bar coating, flow coating, comma coating, etc. can be applied. Among these, it is particularly suitable for precoat type coating that requires sufficient hardness and workability after coating and curing, and roll coating and reverse roll coating are more preferred in terms of high productivity.

[0053] [Curing method] The method for curing the active energy ray curable paint composition of the present invention is not particularly limited, and known methods can be used. For example, it can be cured by irradiating with α-rays, γ-rays, electron beams, X-rays, ultraviolet rays, visible light, infrared rays, or the like. Among them, ultraviolet rays and electron beams are preferred, and electron beams are more preferred.

[0054] When cured by an electron beam, it is not affected by curing inhibition due to shielding of ultraviolet rays or the like associated with a high pigment concentration or the addition of an ultraviolet absorber. Further, since an initiator is not required, the pot life of the paint does not become short, and the performance of the coating film is not deteriorated by the initiator decomposition product after curing, and the effects of the present invention of improving the hardness, workability, and weather resistance of the coating film can be maximally exerted.

[0055] Curing by electron beam is preferably carried out by irradiating an electron beam with an accelerating voltage of 10 to 500 kV, particularly 30 to 200 kV. When cured with an electron beam having an accelerating voltage of 30 to 200 kV, the effects of the present invention of improving the hardness and processability of the coating film can be maximally exerted. If the accelerating voltage is too high, it becomes difficult to balance the hardness and processability of the resulting coating film. The preferable irradiation dose is about 10 kGy to 200 kGy, more preferably 30 kGy to 200 kGy. If the irradiation dose is too low, curing is insufficient, and if it is too high, the processability of the coating film is impaired.

[0056] [Laminate] After applying the active energy ray curable coating composition of the present invention onto a substrate and irradiating it with active energy rays for curing, a laminate is obtained. The film thickness when applying the active energy ray curable coating composition is preferably usually 1 to 50 μm, more preferably 10 to 20 μm. The laminate can be suitably used as a pre-coated metal.

[0057] [Molded processing member] The laminate of the present invention is excellent in processability, and the processing method is not particularly limited. For example, it can be suitably used for building materials, home appliances, etc. as a molded processing member obtained by molding. [Examples]

[0058] Hereinafter, the present invention will be described in detail with reference to examples, but the following examples do not limit the scope of the present invention in any way.

[0059] [Preparation of active energy ray curable coating composition: Example 1] According to the formulation described in Table 1, each raw material was mixed by dispersing and stirring (3000 rpm) at room temperature to prepare an active energy ray curable coating composition. For the obtained coating composition, processability, coating film hardness, weather resistance, long-term weather resistance, and storage stability were evaluated by the following evaluation methods. The results are shown in Table 1.

[0060] [Preparation of Active Energy Ray-Curable Coating Composition: Examples 2 to 32, Comparative Examples 1 to 6] Examples 2 to 32 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1, except that the raw materials and amounts described in Tables 1 and 2 were changed. The numbers in Tables 1 and 2 indicate the blending amounts (mass %).

[0061] [Method for Producing Laminate] The obtained active energy ray-curable coating composition was applied to a galvanized steel sheet (registered trademark) (manufactured by Yodogawa Steel Works, Ltd., Yodo GL Eco Green, thickness 0.27 mm) as a substrate using a bar coater #14 (coating film thickness: approximately 20 μm). Subsequently, an electron beam was irradiated using an electron beam irradiation device, Eye Compact EB (manufactured by Iwasaki Electric Co., Ltd., acceleration voltage 90 kV, irradiation dose 100 kGy) to cure the coating composition and produce a laminate.

[0062] [Workability] Workability was evaluated for flexural resistance by a 180° bending test using a DuPont impact tester. With the surface on which the cured coating film was formed facing outward, a test piece with 10 substrate steel sheets stacked and sandwiched inside the bent portion was dropped with a 1 kg load from a height of 50 cm to bend the coated piece 180° to obtain a processed product. Workability was evaluated as follows by visually checking for cracks in the bent portion of the processed product. [Evaluation] A: No cracks were confirmed. B: Only extremely minute cracks were confirmed. C: Only minute cracks were confirmed. D: Large cracks were observed. Note that the evaluations of being practical are A, B, and C.

[0063] [Coating Film Hardness] The coating film hardness was evaluated for pencil hardness in accordance with JIS K5600-5-4. Pencils of various hardnesses were applied to the surface of the cured coating film at an angle of 45°, a load of 750 g was applied, and a scratching test was performed. The hardness of the hardest pencil that did not cause scratches was evaluated. [Evaluation] A: No scratches were confirmed with a hardness of H. B: No scratches were confirmed at hardness F. C: No scratches were confirmed at hardness HB. D: Scratches were confirmed at hardness HB. Note that the evaluations for practical usability are A, B, and C.

[0064] [Weather resistance] For the evaluation of weather resistance, using a xenon lamp (product name "Q-SUN Xe-1", manufactured by Q-Lab), under irradiation conditions of 120 W / m 2 , with a black panel temperature of 63°C, an irradiation process of irradiating with ultraviolet rays for 102 minutes and a shower process of spraying water for 18 minutes while irradiating with ultraviolet rays under the same irradiation conditions were repeated, and the surface state of the test piece after 700 hours was evaluated. [Evaluation] A: No abnormality B: Very little surface abnormality occurred C: A small amount of surface abnormality occurred D: A large amount of surface abnormality occurred Note that the evaluations for practical usability are A, B, and C.

[0065] [Long-term weather resistance] For the evaluation of long-term weather resistance, using a xenon lamp (product name "Q-SUN Xe-1", manufactured by Q-Lab), under irradiation conditions of 120 W / m 2 , with a black panel temperature of 63°C, an irradiation process of irradiating with ultraviolet rays for 102 minutes and a shower process of spraying water for 18 minutes while irradiating with ultraviolet rays under the same irradiation conditions were repeated, and the surface state of the test piece after 2100 hours was evaluated. [Evaluation] A: No abnormality B: Very little surface abnormality occurred C: A small amount of surface abnormality occurred D: A large amount of surface abnormality occurred Note that the evaluations for practical usability are A, B, and C.

[0066] [Storage stability] The storage stability was evaluated as follows by visually checking whether precipitates occurred in the paint after standing at room temperature for one week after preparing the paint. [Evaluation] A: No precipitate. B: Only a very small amount of precipitate was confirmed. C: Only a small amount of precipitate was confirmed. D: Obvious precipitate was observed. Note that the evaluations of being practical are A, B, and C.

[0067]

Table 1

[0068]

Table 2

[0069] The information of each raw material in Table 1 is as follows. · EBECRYL8402: Aliphatic urethane acrylate (bifunctional), manufactured by Daicel Ornex Co., Ltd. · EBECRYL8701: Aliphatic urethane acrylate (trifunctional), manufactured by Daicel Ornex Co., Ltd. · EBECRYL8301R: Aliphatic urethane acrylate (hexafunctional), manufactured by Daicel Ornex Co., Ltd. · Miramer M370: Tris 2-hydroxyethyl isocyanurate triacrylate, manufactured by MIWON Co., Ltd. · Aronix M327: ε-Caprolactone-modified tris 2-hydroxyethyl isocyanurate triacrylate, manufactured by Toagosei Co., Ltd. · IBXA: Isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. · FA513AS: Dicyclopentanyl acrylate, manufactured by Resona Co., Ltd. · Biscoat 196: 3,3,5-Trimethylcyclohexyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. · ACMO: Acryloylmorpholine, manufactured by KJ Chemicals Co., Ltd. · Biscoat 200: Cyclic trimethylolpropane formal acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. · Biscote 150: Tetrahydrofurfuryl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. · Light Acrylate HPP-A: Neopentyl glycol diacrylate hydroxy pivalate, manufactured by Kyoeisha Chemical Co., Ltd. · Light Acrylate L-A: Lauryl acrylate, manufactured by Kyoeisha Chemical Co., Ltd. · Adeka Stab LA-F70: 6,6’,6’’-(1,3,5-Triazine-2,4,6-triyl)tris[3-(hexyloxy)-2-methylphenol], manufactured by ADEKA Corporation · Adeka Stab LA-46: 2-Ethylhexanoic acid = 2-[3-hydroxy-4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]ethyl, manufactured by ADEKA Corporation · Tinuvin 479: Hydroxyphenyltriazine-based ultraviolet absorber, manufactured by BYK · MT-700HD: Fine particle titanium oxide (average primary particle size 50 nm), manufactured by Teika Corporation · Tinuvin 400: 2-[4,6-Bis(2,4-dimethylphenyl)-s-triazin-2-yl]5-[2-hydroxy-3-(dodecyloxy)propoxy]phenol, manufactured by BYK · RUVA-93: 2-[2-Hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, manufactured by Otsuka Chemical Co., Ltd. · Adeka Stab LA-72: Bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, manufactured by ADEKA Corporation · Tinuvin 292: Bis(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate, manufactured by BYK · Adeka Stab AO-20: Tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, manufactured by ADEKA Corporation · CR58-2: Titanium oxide, manufactured by Ishihara Sangyo Co., Ltd. · DisperBYK 111: Copolymer containing acid groups, manufactured by BYK

[0070] As is clear from the results in Tables 1 and 2, in Examples 1 to 32 using the active energy ray-curable coating composition of the present invention, the obtained cured coating films achieved all of high hardness, high processability, and high weather resistance, and the storage stability of the coating composition was good. On the other hand, in Comparative Examples 1 to 6, any one or more of the coating film hardness, processability, weather resistance, long-term weather resistance, and storage stability were insufficient.

Claims

1. An active energy ray-curable coating composition for metal substrates, comprising a urethane (meth)acrylate (A), a polyfunctional (meth)acrylate monomer (B) having an isocyanurate skeleton (excluding the urethane (meth)acrylate (A)), a radical polymerizable monofunctional monomer (C) (excluding the urethane (meth)acrylate (A)), an ultraviolet absorber (D), and a light stabilizer (E), wherein the radical polymerizable monofunctional monomer (C) comprises a radical polymerizable monofunctional monomer (C-1) having an alicyclic structure and a radical polymerizable monofunctional monomer (C-2) having a heterocyclic structure.

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 (C-1) having an alicyclic structure and the radical polymerizable monofunctional monomer (C-2) having a heterocyclic structure is 20 / 80 to 70 / 30.

3. 2. The active energy ray-curable coating composition for metal substrates according to claim 1, wherein the content of the solvent is 3 mass % or less based on the entire active energy ray-curable coating composition for metal substrates.

4. 2. The active energy ray-curable coating composition for metal substrates according to claim 1, wherein the content of the photopolymerization initiator is 0.5 mass % or less based on the entire active energy ray-curable coating composition for metal substrates.

5. The active energy ray-curable coating composition for metal substrates according to claim 1, which is for use in precoating metals.

6. A laminate having a cured layer of the active energy ray-curable coating composition according to any one of claims 1 to 5 on a metal substrate.

7. A method for producing a laminate, comprising coating a metal substrate with the active energy ray-curable coating composition according to any one of claims 1 to 5, and curing the coating composition with active energy rays.

8. A molded member using the laminate according to claim 6.

9. A method for producing a molded member, comprising coating a metal substrate with the active energy ray-curable coating composition according to any one of claims 1 to 5, curing the coating composition with active energy rays, and molding the coated metal substrate.

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