Precote steel sheet coating composition

Abstract

This disclosure aims to provide a coating composition for pre-coated steel sheets that can achieve both energy efficiency during coating film formation and coating film properties (particularly processability and hardness). [Solution] A paint composition comprising a (meth)acrylate oligomer (A), a pigment (B), and a surface modifier (C), The (meth)acrylate oligomer comprises one or more selected from acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2). The surface tension of the aforementioned coating composition is 21.0 mN / m or more and 28.0 mN / m or less. The resulting coating film has a tensile strength of 5 MPa or more and 50 MPa or less. A coating composition for pre-coated steel sheets, wherein the resulting coating film has a breaking elongation of 1% or more and 20% or less.

Description

[Technical Field]

[0001] This disclosure relates to a coating composition for pre-coated steel sheets. [Background technology]

[0002] Painted steel sheets, which are made by applying paint to metal substrates such as cold-rolled steel sheets and plated steel sheets and then using them for forming processes, are also called pre-coated steel sheets (hereinafter also referred to as "PCM") and are used in a variety of applications, such as building components like shutters, lids, doors, roofs and siding; exterior materials for electrical equipment such as air conditioner outdoor units; and interior materials.

[0003] Patent Document 1 describes a coating composition for pre-coated metal sheets, comprising polyvinylidene fluoride resin, acrylic resin, polytetrafluoroethylene particles, wax, aggregate, and solvent, wherein the acrylic resin comprises at least one thermosetting acrylic resin, and the solvent comprises a solvent having a ketone structure and a boiling point of 180°C or higher. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-100740 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, from the perspective of energy conservation and reduction of carbon dioxide emissions, there has been a need to consider the painting process in the manufacturing of pre-coated steel sheets.

[0006] Typically, pre-coated steel sheets are coated with paint, heated (baked) for 30-60 seconds at a temperature that reaches a steel sheet temperature (also called "PMT") of 200-270°C to form a coating, and then processed into the required product. For the baking process, a hot air furnace using gas or the like is generally used. In this case, it is necessary to maintain a high ambient temperature of 250°C or higher at all times, and there is room for improvement from the perspective of environmental impact and energy costs.

[0007] In addition, since pre-coated steel sheets are processed into the required products after the coating is formed, the coating on the pre-coated steel sheets needs to have sufficient workability to prevent cracking or peeling during processing, and hardness to prevent scratches or dents.

[0008] However, conventional paint compositions for pre-coated steel sheets lack sufficient energy efficiency in the painting process, and attempting to increase energy sometimes resulted in a decrease in the workability and hardness of the resulting paint film.

[0009] This disclosure aims to provide a coating composition for pre-coated steel sheets that can achieve both energy efficiency during coating film formation and coating film properties (particularly processability and hardness). [Means for solving the problem]

[0010] This disclosure includes the following: [1] A paint composition comprising (meth)acrylate oligomer (A), pigment (B), and surface modifier (C), The (meth)acrylate oligomer comprises one or more selected from acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2). The surface tension of the aforementioned coating composition is 21.0 mN / m or more and 28.0 mN / m or less. The resulting coating film has a tensile strength of 5 MPa or more and 50 MPa or less. A coating composition for pre-coated steel sheets, wherein the resulting coating film has a breaking elongation of 1% or more and 20% or less. [2] The unsaturated bond equivalent of the (meth)acrylate-based oligomer (A) is 400 g / eq or more and 3,100 g / eq or less, and the paint composition for pre-coated steel sheets according to [1]. [3] The weight average molecular weight of the (meth)acrylate-based oligomer (A) is 900 or more and 50,000 or less, and the paint composition for pre-coated steel sheets according to [1] or [2]. [4] The surface tension of the acrylic (meth)acrylate-based oligomer (A1) is 29.0 mN / m or more and 35.0 mN / m or less, and the surface tension of the urethane (meth)acrylate-based oligomer (A2) is 29.0 mN / m or more and 45.0 mN / m or less, and the paint composition for pre-coated steel sheets according to any one of [1] to [3]. [5] The glass transition temperature of the coating film obtained from the acrylic (meth)acrylate-based oligomer (A1) is 50°C or more and 90°C or less, and the glass transition temperature of the coating film obtained from the urethane (meth)acrylate-based oligomer (A2) is 15°C or more and 60°C or less, and the paint composition for pre-coated steel sheets according to any one of [1] to [4]. [6] The paint composition for pre-coated steel sheets according to any one of [1] to [5], further comprising a (meth)acrylate-based monomer (D). [7] The mass ratio [(A)+(D):(B)] of the total amount of the (meth)acrylate-based oligomer (A) and the (meth)acrylate-based monomer (D) to the pigment (B) is 90:10 to 40:60, and the paint composition for pre-coated steel sheets according to [6]. [8] The total content of the active components of the (meth)acrylate-based oligomer (A), the pigment (B), the surface conditioner, and the (meth)acrylate-based monomer (D) in the paint composition is 70% by mass or more, and the paint composition for pre-coated steel sheets according to [6] or [7]. [9] A coating composition for pre-coated steel sheets, which is electron beam curable, as described in any one of [1] to [8].

[10] The system comprises a steel plate and a coating film disposed on the steel plate, A painted steel sheet, wherein the coating film is formed from a pre-coated steel sheet paint composition described in any one of [1] to [9].

[11] The system further comprises an undercoat coating disposed between the metal plate and the coating film, The thickness of the aforementioned undercoat film is 3 μm or more and 10 μm or less. The painted steel sheet according to

[10] , wherein the thickness of the coating film is 10 μm or more and 100 μm or less.

[12] A process of applying a paint composition to an object to be coated to obtain a painted film, and The process includes irradiating the aforementioned coating film with active energy rays to obtain a coating film, The aforementioned paint composition comprises the paint composition for pre-coated steel sheets described in any one of [1] to

[11] , A method for manufacturing a coating film, wherein the active energy ray is an electron beam.

[13] The aforementioned undercoat film comprises a polyester resin, as described in

[11] . [Effects of the Invention]

[0011] This disclosure may provide a coating composition for pre-coated steel sheets that can achieve both energy efficiency during coating film formation and coating film properties (particularly processability and hardness). [Modes for carrying out the invention]

[0012] The paint composition for pre-coated steel sheets of this disclosure is a paint composition comprising a (meth)acrylate oligomer (A), a pigment (B), and a surface modifier (C), The (meth)acrylate oligomer comprises one or more selected from acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2). The surface tension of the aforementioned coating composition is 21.0 mN / m or more and 28.0 mN / m or less. The resulting coating film has a tensile strength of 5 MPa or more and 50 MPa or less. The resulting coating film has a break elongation of 1% to 20%.

[0013] The coating composition for pre-coated steel sheets disclosed herein (hereinafter also simply referred to as the "coating composition") can achieve both energy efficiency during coating film formation and desirable coating film properties (particularly workability and hardness). While this disclosure should not be interpreted as being limited to any particular theory, the reasons why the coating composition of this disclosure can achieve such effects are thought to be as follows.

[0014] In other words, the paint composition for pre-coated steel sheets of this disclosure contains a (meth)acrylate oligomer (A) and can be cured by the action of active energy rays, thereby increasing the energy efficiency during film formation. Furthermore, by limiting the surface tension of the paint composition to a specific range, the wettability to the substrate is improved, and the adhesion to the substrate is enhanced. Additionally, by setting the tensile strength of the resulting film to a specific range, the durability against stress applied to the film during processing is improved. Moreover, by setting the elongation at break of the resulting film to a specific range, the film becomes less prone to tearing during processing, improving workability. It is believed that changing one of the surface tension, tensile strength, and elongation at break of the paint composition affects the other two, and only by balancing these can a paint composition be obtained that achieves high energy efficiency during film formation and simultaneously provides good workability and hardness in the resulting film.

[0015] The surface tension of the coating composition disclosed herein is 21.0 mN to 28.0 mN, preferably 22.0 mN to 27.0 mN, and more preferably 23.0 mN to 26.0 mN. This range is thought to improve wettability to the substrate and primer, thereby enhancing adhesion. As a result, the coating film is less likely to peel off the substrate during processing, and cracking is suppressed. In addition, the surface tension of the coating composition is thought to enhance adhesion to the substrate and primer even after the coating film has hardened. Furthermore, it is possible to reduce the amount of additives and organic solvents required. In this disclosure, surface tension can be measured in accordance with JIS K 6768.

[0016] The coating composition disclosed herein has a tensile strength of 5 MPa to 50 MPa, preferably 5 MPa to 45 MPa, and more preferably 6.5 MPa to 40 MPa. Being within this range can result in good hardness and processability of the coating. In this disclosure, tensile strength can be measured in accordance with JIS K 7161.

[0017] The coating composition of this disclosure has a break elongation of 1% to 20% of the resulting coating film, preferably 1% to 16%, and more preferably 3% to 16%. Being within this range can result in good hardness and processability of the coating film. In this disclosure, the elongation at break can be measured in accordance with JIS K 7161.

[0018] (A)(Meth)acrylate oligomers (Meth)acrylate oligomers mean oligomers obtained from monomer mixtures containing (meth)acrylic monomers as raw materials. In this disclosure, oligomers mean polymers having a weight-average molecular weight of, for example, 1,000 to 50,000. In this disclosure, the weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.

[0019] The (meth)acrylate oligomer (A) includes one or more selected from acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2). Acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2) may be used individually or in combination of two or more types.

[0020] (A1) Acrylic (meth)acrylate oligomer Acrylic (meth)acrylate oligomer (A1) (hereinafter also referred to as "component (A1)") can typically be a polymer obtained by modifying a (meth)acrylate polymer (a1) with an unsaturated oligomer (a2). In other words, as component (A1), a copolymer is preferred in which an (meth)acrylate polymer (a1) is used as the core polymer and an unsaturated oligomer (a2) is grafted onto it.

[0021] The (meth)acrylate polymer (a1) and the unsaturated oligomer (a2) each preferably have a group that can react with each other to form a crosslinked structure (hereinafter also referred to as a "crosslinkable functional group"). The crosslinkable functional group is not limited to one or more selected from epoxy groups, carboxyl groups, hydroxyl groups, and isocyanate groups.

[0022] The (meth)acrylate polymer (a1) may be a copolymer of a monomer mixture containing a (meth)acrylic monomer. The (meth)acrylic monomer preferably contains an acrylic monomer (a1-2) having a crosslinkable functional group, and more preferably contains a monomer (a1-1) without a crosslinkable functional group and a monomer (a1-2) having a crosslinkable functional group.

[0023] As for the possible combinations of crosslinkable functional groups that can be contained in the (meth)acrylate polymer (a1) and the unsaturated oligomer (a2), a combination in which one has an epoxy group or a hydroxyl group and the other has a carboxyl group or an isocyanate group is preferred. Specifically, combinations of epoxy group and carboxyl group, hydroxyl group and carboxyl group, and hydroxyl group and isocyanate group are more preferred.

[0024] Monomer (a1-1) is not limited as long as it does not have a crosslinking functional group. Examples of monomer (a1-1) include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate; isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclo Examples include alicyclic (meth)acrylates such as pentenyl (meth)acrylate; N-(meth)acryloylmorpholine; acrylamides such as (meth)acrylamide, N-methylolacrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide; acrylonitrile and methacronitrile; aromatic vinyl compounds such as styrene and substituted styrene; and vinyl ether compounds such as ethyl vinyl ether, butyl vinyl ether, and cyclohexyl vinyl ether.

[0025] Monomers (a1-2) are not limited as long as they are monomers having a crosslinkable functional group. Examples of monomers (a1-2) include monomers having epoxy groups such as glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; (meth)acrylic acid, monohydroxyethyl phthalate acrylate, ω-carboxy-polycaprolactone (n≒2) monoacrylate, (meth)acryloyloxyethyl succinate, (meth)acryloyloxyethyl hexahydrophthalate, (meth)acryloyloxyethyl phthalate, (meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and β-carboxyethyl acrylate. Examples include monomers having a carboxyl group, such as phthalic anhydride adduct of pentaerythritol triacrylate, succinic anhydride adduct of pentaerythritol triacrylate, succinic anhydride adduct of dipentaerythritol triacrylate, and phthalic anhydride adduct of dipentaerythritol triacrylate; monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ε-caprolactone adduct of 2-hydroxyethyl (meth)acrylate; and monomers having an isocyanate group, such as (meth)acryloxyethyl isocyanate. Commercially available products such as "Kalenz MOI" and "Kalenz AOI" (manufactured by Showa Denko Corporation) may be used as monomers having an isocyanate group.

[0026] The unsaturated oligomer (a2) may be an oligomer having an unsaturated group (typically an ethylenically unsaturated group). Examples of unsaturated groups include (meth)acryloyl groups and vinyl groups, more preferably (meth)acryloyl groups, and even more preferably acryloyl groups.

[0027] Examples of unsaturated oligomers (a2) include unsaturated oligomers having a carboxyl group; unsaturated oligomers having a carboxyl group such as (meth)acrylic acid and ε-caprolactone adducts of (meth)acrylic acid; ε-caprolactone adducts of hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and ε-caprolactone adducts of 2-hydroxyethyl (meth)acrylate, polypropylene glycol adducts of (meth)acrylic acid, polyethylene glycol adducts of (meth)acrylic acid, poly(3-hydroxybutyrate) adducts of 2-hydroxyethyl (meth)acrylate, and polytetramethylene glycol adducts of (meth)acrylic acid; unsaturated oligomers having an isocyanate group such as reaction products of diisocyanates and hydroxyl group-containing (meth)acrylates, and (meth)acryloxyethyl isocyanate; and the like.

[0028] Examples of the aforementioned diisocyanates include alicyclic diisocyanates such as isophorone diisocyanate; aliphatic diisocyanates such as hexamethylene diisocyanate; and urethane oligomers having an isocyanate group at the terminal end. Such urethane oligomers can be produced by reacting diisocyanates and diols in an organic solvent in the presence of a tin-based catalyst such as dioctyltin, in an amount that results in an excess of diisocyanates. Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl acrylate. Furthermore, product names such as "Kalenz MOI" and "Kalenz AOI" (manufactured by Showa Denko) may be used for (meth)acryloxyethyl isocyanate.

[0029] The unsaturated bond equivalent of the acrylic (meth)acrylate oligomer (A1) is preferably 400 g / eq to 3,100 g / eq, more preferably 500 g / eq to 3,000 g / eq, and even more preferably 800 g / eq to 2,000 g / eq or 800 g / eq to 1,500 g / eq. Being within this range can result in good hardness and processability of the coating film of the paint composition.

[0030] The weight-average molecular weight of the acrylic (meth)acrylate oligomer (A1) is preferably 900 to 50,000, more preferably 1,000 to 40,000, and even more preferably 1,500 to 40,000. Being within this range can result in good hardness and processability of the coating film. Furthermore, it allows for a higher concentration of the active ingredients in the coating composition.

[0031] The surface tension of the acrylic (meth)acrylate oligomer (A1) is preferably 29.0 mN / m to 35.0 mN / m, more preferably 29.0 mN / m to 33.0 mN / m, and even more preferably 30.0 mN / m to 33.0 mN / m. Being within this range allows the paint composition to have good wettability to the substrate and improves substrate adhesion.

[0032] The glass transition temperature of the coating film obtained from the acrylic (meth)acrylate oligomer (A1) is preferably 50°C to 90°C, more preferably 60°C to 90°C, and even more preferably 60°C to 80°C. Being within this range can result in good hardness and processability of the coating film. In this disclosure, the glass transition temperature can be measured by differential thermal analysis. Furthermore, if two or more (meth)acrylate oligomers (A) are present, the glass transition temperature can also be calculated as the reciprocal of the sum of the quotients obtained by dividing the mass fraction of each material by its respective glass transition temperature (expressed in Kelvin).

[0033] Acrylic (meth)acrylate oligomers (A1) and their raw materials may be used individually or in combination of two or more types.

[0034] In the (meth)acrylate oligomer (A), the content of acrylic (meth)acrylate oligomer (A1) can be, in one embodiment, 0% to 100% by mass, 60% to 100% by mass, or 90% to 100% by mass, relative to 100% by mass of the total amount of (meth)acrylate oligomer (A). In another embodiment, it can be 0% to 100% by mass, 0% to 40% by mass, or 0% to 10% by mass. Being within these ranges can result in good hardness and processability of the resulting coating film.

[0035] (A2) Urethane (meth)acrylate oligomer Urethane (meth)acrylate oligomers (A2) are polymers that have urethane bonds and (meth)acrylate groups within their molecules. Examples of urethane (meth)acrylate oligomers (A2) include reaction products of polyols (a3), polyisocyanates (a4), and compounds (a5) having hydroxyl groups and (meth)acryloyl groups.

[0036] The polyol (a3) ​​is not particularly limited and includes, for example, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, dimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol, and their alkylene oxide (preferably C 2-3It may also be an alkylene oxide (alkylene oxide) adduct. Examples of alkylene oxide (alkylene oxide) adducts include glycerin with 3-12 moles of ethylene oxide, glycerin with 3-12 moles of propylene oxide, trimethylolpropane with 3-12 moles of ethylene oxide, trimethylolpropane with 3-12 moles of propylene oxide, ditrimethylolpropane with 4-16 moles of ethylene oxide, dimethylolpropane with 4-16 moles of propylene oxide, and pentaerythritol with 4-16 moles of ethylene oxide. Examples of adducts include pentaerythritol adducts with 4-16 moles of propylene oxide, dipentaerythritol adducts with 6-24 moles of ethylene oxide, dipentaerythritol adducts with 4-24 moles of propylene oxide, tripentaerythritol adducts with 8-32 moles of ethylene oxide, tripentaerythritol adducts with 8-32 moles of propylene oxide, isocyanuric acid adducts with 3-12 moles of ethylene oxide, and isocyanuric acid adducts with 3-12 moles of propylene oxide.

[0037] The polyisocyanate (a3) ​​may be any of the following: aliphatic, alicyclic, aromatic, and aromatic-aliphatic. Examples include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1,3-(isocyanate methyl)cyclohexane, isophorone diisocyanate. Socyanates, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, dianisidine diisocyanate, phenyl diisocyanate, halogenated phenyl diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene diisocyanate, octadecylene diisocyanate, 1,5-naphthalene diisocyanate, polymethylene polyphenyl diisocyanate, triphenylmethane triisocyanate, naphthylene diisocyanate, 3-phenyl-2-ethylene diisocyanate Anate, cumene-2,4-diisocyanate, 4-methoxy-1,3-phenylenediisocyanate, 4-ethoxy-1,3-phenylenediisocyanate, 2,4'-diisocyanate diphenyl ether, 5,6-dimethyl-1,3-phenylenediisocyanate, 4,4'-diisocyanate diphenyl ether, benzidine diisocyanate, 9,10-anthracene diisocyanate, 4,4'-diisocyanate dibenzyl, 3,3-dimethyl-4,4'-diisocyanate diphenyl, 2,6-dimethyl-4,4'-diisocyanate Examples include diisocyanates such as todiphenyl, 3,3-dimethoxy-4,4'-diisocyanate diphenyl, 1,4-anthracene diisocyanate, phenylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,10-decanemethylene diisocyanate, and 1,3-cyclohexylene diisocyanate; isocyanurates, biuretes, and adducts of these diisocyanates; and triisocyanates such as 2,4,6-tolurentriisocyanate and 2,4,4'-triisocyanate diphenyl ether.

[0038] From the viewpoint of weather resistance, aliphatic polyisocyanates and alicyclic polyisocyanates are preferred as polyisocyanates (a3).

[0039] Examples of compounds (a3) ​​having a hydroxyl group and a (meth)acryloyl group include poly(meth)acrylates such as pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, epoxy(meth)acrylate, 2-hydroxyethyl(meth)acrylate, and glycerol di(meth)acrylate; alkylene oxide adducts of the poly(meth)acrylates; and lactone-modified products of the poly(meth)acrylates. Examples of the alkylene oxides include ethylene oxide and propylene oxide, and examples of the lactones include ε-caprolactone and γ-butyrolactone. Compounds obtained by adding a polyisocyanate to these compounds may also be used as compound (a3).

[0040] The unsaturated bond equivalent of the urethane (meth)acrylate oligomer (A2) is preferably 400 g / eq to 3,100 g / eq, more preferably 500 g / eq to 3,000 g / eq, and even more preferably 800 g / eq to 2,000 g / eq or 800 g / eq to 1,500 g / eq. Being within this range can result in good hardness and processability of the coating film. Furthermore, it allows for a higher concentration of the active ingredients in the paint composition.

[0041] The weight-average molecular weight of the urethane (meth)acrylate oligomer (A2) is preferably 900 to 50,000, more preferably 1,000 to 40,000, and even more preferably 1,500 to 40,000. Being within this range can result in good hardness and processability of the coating film. Furthermore, it allows for a higher concentration of the active ingredients in the coating composition.

[0042] The surface tension of the urethane (meth)acrylate oligomer (A2) is preferably 29.0 mN / m to 45.0 mN / m, more preferably 29.0 mN / m to 40.0 mN / m, and even more preferably 32.0 mN / m to 40.0 mN / m. Being within this range allows the paint composition to have good wettability to the substrate, which can improve substrate adhesion.

[0043] The glass transition temperature of the coating film obtained from the urethane (meth)acrylate oligomer (A2) is preferably 15°C to 60°C, more preferably 40°C to 55°C, and even more preferably 40°C to 50°C. Being within this range can result in good hardness and processability of the coating film.

[0044] The urethane (meth)acrylate oligomer (A2) and its raw materials may be used individually, or two or more may be used in combination.

[0045] The unsaturated bond equivalent of the (meth)acrylate oligomer (A) is preferably 400 g / eq to 3,100 g / eq, more preferably 500 g / eq to 3,000 g / eq, and even more preferably 800 g / eq to 1,500 g / eq. Being within this range can result in good hardness and processability of the coating film of the paint composition.

[0046] The weight-average molecular weight of the (meth)acrylate oligomer (A) is preferably 900 to 50,000, more preferably 1,000 to 40,000, and even more preferably 1,500 to 40,000. Being within this range can result in good hardness and processability of the coating film. It also allows for a higher concentration of the active ingredients in the coating composition. If two or more (meth)acrylate oligomers (A) are included, the unsaturated bond equivalent and weight-average molecular weight may be calculated as weighted average values ​​that take into account the mass fraction of each material.

[0047] In the (meth)acrylate oligomer (A), the content of urethane (meth)acrylate oligomer (A2) can be, in one embodiment, 0% to 100% by mass, 60% to 100% by mass, or 90% to 100% by mass, relative to 100% by mass of the total amount of (meth)acrylate oligomer (A). In another embodiment, it can be 0% to 100% by mass, 0% to 40% by mass, or 0% to 10% by mass. Being within these ranges can result in good hardness and processability of the resulting coating film.

[0048] In the (meth)acrylate oligomer (A), the total content of acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2) is preferably 30% to 100% by mass, more preferably 40% to 100% by mass, and even more preferably 50% to 80% by mass, based on 100% by mass of the total amount of (meth)acrylate oligomer (A). Being within this range can result in good hardness and processability of the coating film.

[0049] The (meth)acrylate oligomer (A) may contain (meth)acrylate oligomers other than acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2).

[0050] The amount of (meth)acrylate oligomer (A) may be preferably 15 parts by mass or more and 100 parts by mass or less, more preferably 30 parts by mass or more and 100 parts by mass or less, and even more preferably 50 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the active ingredients of the paint composition excluding the pigment (B). In this disclosure, the active ingredients of a paint composition (specifically, components (A), (B), (C), and optionally component (D)) mean components that form a coating film (components that form a coating film after curing).

[0051] (B) Pigments As pigment (B), materials used as pigments in paint compositions can be used. Pigments not only impart the design, hardness, and scratch resistance required for PCM, but also have the effect of lowering the surface tension of the paint and improving wettability to the substrate in this application. Preferred pigments include coloring pigments, extender pigments, heat-shielding pigments, and gloss pigments, and it is preferable that they include coloring pigments and extender pigments.

[0052] Examples of extender pigments include calcium carbonate, barium sulfate, clay, talc, mica, and glass fiber. These may be used individually or in combination of two or more.

[0053] The amount of extender pigment is preferably 0 to 70 parts by mass, more preferably 0 to 30 parts by mass, based on 100 parts by mass of the total amount of active ingredients (meth)acrylate oligomer (A) and (meth)acrylate monomer (D). By having the amount of extender pigment within this range, the surface tension of the paint composition can be reduced, and the resulting coating film can have good scratch resistance.

[0054] Examples of coloring pigments include inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and cold dust; organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone, perylene, anthrapyrimidine, carbazole violet, anthrapyridine, azo orange, flavanthrone yellow, isoindoline yellow, azo yellow, induthrone blue, dibromanzathrone red, perylene red, azo red, and anthraquinone red; and aluminum powder, alumina powder, bronze powder, copper powder, tin powder, zinc powder, iron phosphide, and finely atomized titanium. These may be used individually or in combination of two or more.

[0055] The amount of coloring pigment is preferably 1 to 1500 parts by mass, more preferably 10 to 150 parts by mass, based on 100 parts by mass of the total amount of active ingredients of (meth)acrylate oligomer (A) and (meth)acrylate monomer (D). By having the amount of coloring pigment within this range, the surface tension of the paint composition can be reduced and the substrate can be sufficiently concealed.

[0056] The total amount of extender pigments and coloring pigments is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, of 100% by mass of the total amount of pigment (B).

[0057] A heat-shielding pigment refers to a pigment that does not absorb light in the near-infrared wavelength range (wavelength: 780nm to 2,500nm) or has a low absorption rate of light in the near-infrared wavelength range (wavelength: 780nm to 2,500nm). The heat-shielding pigment is not particularly limited, and the following inorganic and organic heat-shielding pigments can be used.

[0058] Examples of inorganic heat-shielding pigments include metal oxide pigments such as titanium dioxide, magnesium oxide, barium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, indium oxide, sodium titanate, silicon oxide, nickel oxide, manganese oxide, chromium oxide, iron oxide, copper oxide, cerium oxide, and aluminum oxide; iron oxide-manganese oxide, iron oxide-chromium oxide (for example, Dainichi Seika's Dipyroxide Color Black #9595, Asahi Kasei Kogyo's Black 6350), and iron oxide-cobalt oxide-chromium oxide (for example, Dainichi Seika's Dipyroxide Color Brown). Examples include composite oxide pigments such as #9290, dipyroxide color black #9590), copper oxide-magnesium oxide (e.g., dipyroxide color black #9598 from Dainichi Seika Co., Ltd.), manganese oxide-bismuth oxide (e.g., Black 6301 from Asahi Kasei Kogyo Co., Ltd.), and manganese oxide-yttrium oxide (e.g., Black 6303 from Asahi Kasei Kogyo Co., Ltd.); metallic pigments such as silicon, aluminum, iron, magnesium, manganese, nickel, titanium, chromium, and calcium; and alloy pigments such as iron-chromium, bismuth-manganese, iron-manganese, and manganese-yttrium. These may be used individually or in combination of two or more.

[0059] Examples of organic heat-shielding pigments include azo pigments, azomethine pigments, lake pigments, thioindigo pigments, anthraquinone pigments (anthanthrone pigment, diaminoanthraquinonyl pigment, indanthrone pigment, flavanthrone pigment, anthrapyrimidine pigment, etc.), perylene pigments, perinone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, phthalocyanine pigments, quiniphthalone pigments, quinacridone pigments, isoindoline pigments, isoindolinone pigments, etc. These may be used individually or in combination of two or more.

[0060] The amount of heat-shielding pigment is preferably 1 to 150 parts by mass, more preferably 10 to 150 parts by mass, based on 100 parts by mass of the total amount of active ingredients of (meth)acrylate oligomer (A) and (meth)acrylate monomer (D). By having the amount of heat-shielding pigment within this range, the resulting coating film can be imparted with heat-shielding properties.

[0061] Examples of luminous pigments include foil pigments such as aluminum foil, bronze foil, tin foil, gold foil, silver foil, titanium metal foil, stainless steel foil, nickel-copper alloy foil, and foil-like phthalocyanine blue. These may be used individually or in combination of two or more.

[0062] The amount of the lustrous pigment is preferably 1 to 20 parts by mass, more preferably 10 to 20 parts by mass, based on 100 parts by mass of the total amount of the active ingredients of the (meth)acrylate oligomer (A) and (meth)acrylate monomer (D). By having the amount of the lustrous pigment within this range, the resulting coating film can be made to have a design with the desired metallic feel.

[0063] The mass ratio [(A)+(D):(B)] of the total amount of the (meth)acrylate oligomer (A) and the (meth)acrylate monomer (D) to the pigment (B) is preferably 90:10 to 40:60, more preferably 90:10 to 50:50, and even more preferably 80:20 to 50:50.

[0064] (C) Surface modifier The surface modifier can be any material that adjusts the surface tension of the paint composition, and preferably a material that lowers the surface tension of the paint composition. By including a surface modifier, the surface tension of the paint composition can be adjusted, which can improve the wettability to the substrate.

[0065] The surface conditioner (C) can typically be a polymer having a hydrophilic portion and / or a hydrophobic portion. Examples of the surface conditioner include a silicone-based surface conditioner, an acrylic-based surface conditioner, an acetylene glycol-based surface conditioner, and a fluorine-based surface conditioner. The fluorine-based surface conditioner preferably has a perfluoroalkyl group and / or a perfluoroalkenyl group.

[0066] The weight average molecular weight of the surface conditioner (C) is preferably 5,000 or more and 1,000,000 or less, more preferably 10,000 or more and 150,000 or less, and still more preferably 10,000 or more and 130,000 or less. When the weight molecular weight is within the above range, the compatibility with the (meth)acrylate-based oligomer (A) and / or the (meth)acrylate-based monomer (D) is adjusted to an appropriate range, and the appearance of the resulting coating film can be improved.

[0067] The solubility parameter (SP value) of the surface conditioner (C) is preferably 7 (cal / cm 3 ) 1 / 2 or more and 10 (cal / cm 3 ) 1 / 2 or less, more preferably 7 (cal / cm 3 ) 1 / 2 or more and 9 (cal / cm 3 ) 1 / 2 or less, and still more preferably 8 (cal / cm 3 ) 1 / 2 or more and 9 (cal / cm 3 ) 1 / 2 or less. When the solubility parameter is within the above range, the compatibility with the (meth)acrylate-based oligomer (A) and / or the (meth)acrylate-based monomer (D) is adjusted to an appropriate range, and the appearance of the resulting coating film can be improved.

[0068] The SP value is an abbreviation of solubility parameter and is a measure of solubility. The SP value indicates that the higher the numerical value, the higher the polarity, and conversely, the lower the numerical value, the lower the polarity.

[0069] SP values ​​can be measured by, for example, the following method [Reference: SUH, CLARKE, JPSA-1, 5, 1671~1681 (1967)].

[0070] As a sample, 0.5 g of the sample to be measured is weighed into a 100 mL beaker, 10 mL of acetone is added using a volumetric pipette, and the mixture is dissolved using a magnetic stirrer. A poor solvent is added dropwise to this sample using a 50 mL burette at a measurement temperature of 20°C, and the point at which turbidity occurs is recorded as the volume added. Deionized water is used as the high SP poor solvent, and n-hexane is used as the low SP poor solvent, and turbidity is measured for each. In this disclosure, the SP value of the sample to be measured is δ[(cal / cm²)]. 3 ) 1 / 2 ] is given by the following formula. δ=(V ml 1 / 2 δ ml +V mh 1 / 2 δ mh ) / (V ml 1 / 2 +V mh 1 / 2 ) V m =V1V2 / (φ1V2+φ2V1) δ m =φ1δ1+φ2δ2 V i : Molecular volume of solvent (ml / mol) φ i : Volume fraction of each solvent at the turbidity point δ i : SP value of the solvent m l : Low SP poor solvent mixed system m h : High SP poor solvent mixed system

[0071] The content of the surface modifier (C) is preferably 0.05 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, and even more preferably 0.5 parts by mass or more and 2 parts by mass or less, based on 100 parts by mass of the total active ingredients of the (meth)acrylate oligomer (A) and the pigment (B). Having the content within this range can improve the appearance of the resulting coating film.

[0072] (D)(meth)acrylate monomer The coating composition of this disclosure preferably further comprises a (meth)acrylate monomer (D) in addition to a (meth)acrylate oligomer (A), a pigment (B), and a surface modifier (C). The inclusion of the (meth)acrylate monomer (D) suppresses shrinkage during curing and improves adhesion to the substrate. Furthermore, it is believed that the glass transition temperature of the coating film may be increased, thereby improving its tensile strength. The (meth)acrylate monomer (D) may be a compound with a molecular weight of less than 1,000.

[0073] (Meth)acrylate monomers (D) are typically compounds having one or more (meth)acryloyl groups in one molecule.

[0074] Compounds having one (meth)acryloyl group in one molecule include cyclic (meth)acrylate compounds such as cyclohexyl (meth)acrylate, isobolonyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 3,3,5-trimethylcyclohexanol acrylate, and cyclic trimethylolpropane formal acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; (meth)acrylate compounds of alkoxyoxide adducts of phenols such as phenoxyethyl (meth)acrylate; mono(meth)acrylates of glycols such as ethylene glycol mono(meth)acrylate, methoxyethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, and tripropylene glycol mono(meth)acrylate; and vinyl compounds such as N-vinylpydrilon and N-vinylcaprolactam.

[0075] Examples of compounds having two (meth)acryloyl groups in one molecule include di(meth)acrylates of aliphatic diols such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate and nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate; di(meth)acrylates of alicyclic diols such as tricyclodecanedimethylol di(meth)acrylate; and di(meth)acrylates of alkylene oxide adducts of isocyanuric acid. Epoxy di(meth)acrylate obtained by reacting epoxy resin with (meth)acrylic acid; Di(meth)acrylates of alkylene oxide adducts of bisphenol A and di(meth)acrylates of alkylene oxide adducts of bisphenol F, etc. (Examples of alkylene oxide adducts include ethylene oxide adducts, propylene oxide adducts, and ethylene oxide and propylene oxide adducts, etc.); These are some examples.

[0076] Examples of compounds having three or more (meth)acryloyl groups in one molecule include glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tri(meth)acrylate of trimethylolpropane ethylene oxide adducts, tri(meth)acrylate of trimethylolpropane propylene oxide adducts, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acrylate of isocyanurate ethylene oxide adducts, and polyfunctional urethane(meth)acrylates which are reaction products of hydroxyl group-containing poly(meth)acrylates such as pentaerythritol tri(meth)acrylate with polyisocyanates.

[0077] Commercially available compounds containing two or more (meth)acryloyl groups in one molecule may be used. Examples of commercially available compounds containing two or more (meth)acryloyl groups in one molecule include Aronics M-208, M-211B, M-215, M-220, M-240, M-309, M-310, M-321, M-350, M-360, M-315, M-305, M-450, M-408, M-400, M-402, M-460, etc. (all manufactured by Toagosei Co., Ltd.). Examples include DPGDA, HDDA, TPGDA, EBECRYL145, EBECRYL150, IRR214-K, EBECRYL130, PEG400DA-D, EBECRYL11, HPNDA, EBECRYL210, EBECRYL230, EBECRYL280, PETIA, PETRA, TMPTA, TMPEOTA, EBECRYL135, OTA480, EBECRYL40, EBECRYL140, EBECRYL1142, PETA, DPHA, EBECRYL1290, EBECRYL4265, etc. (all manufactured by Daicel Ornex Corporation).

[0078] The (meth)acrylate monomer (D) is preferably 0 to 240 parts by mass, more preferably 0 to 160 parts by mass, and even more preferably 0 to 120 parts by mass, per 100 parts by mass of (meth)acrylate oligomer (A). Being within this range allows for a higher amount of active ingredients in the coating composition and can result in a coating film with good hardness and processability.

[0079] The aforementioned paint composition may optionally contain an organic solvent as a diluent. The organic solvent is not particularly limited and includes, for example, hydrocarbon solvents such as toluene and xylene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as ethyl acetate, butyl acetate, and ethylene glycol monoethyl ether acetate; alcohol solvents such as methanol, ethanol, and isopropanol; ether alcohol solvents such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether; amide solvents such as dimethylformamide, diethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; and cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve. These solvents may be used individually or in combination of two or more.

[0080] (Other materials) The aforementioned paint composition may further contain other additives as needed. Examples of such other additives include: photopolymerization initiators; photopolymerization initiators; polymerization inhibitors; colorants such as dyes; aggregates (resin particles, silica particles, etc.); waxes; solvents other than those mentioned above; ultraviolet absorbers (benzophenone-based ultraviolet absorbers, etc.); antioxidants (phenol-based, sulfoid-based, hindered amine-based antioxidants, etc.); light stabilizers; plasticizers; coupling agents (silane-based, titanium-based, zirconium-based coupling agents, etc.); anti-sagging agents; viscosity modifiers; pigment dispersants; pigment wetting agents; leveling agents; defoamers; color separation inhibitors; sedimentation inhibitors; settling inhibitors; defoamers; surfactants; antifreeze agents; emulsifiers; rust inhibitors; preservatives; fungicides; lubricants; antibacterial agents; stabilizers; antistatic agents, etc. These additives may be used individually or in combination of two or more.

[0081] Furthermore, while there are UV-curable paint compositions that harden quickly when irradiated with ultraviolet light, as a method for solving the problems described in this disclosure, namely a method for improving energy efficiency during coating film formation, they cannot contain ultraviolet absorbers (UVA) because UV irradiation is required for curing. Therefore, UV-curable paint films have limited applications (unsuitable for outdoor use), whereas the paint compositions described in this disclosure have the advantage of not having such restrictions.

[0082] The total content of the active ingredients (meth)acrylate oligomer (A), pigment (B), surface modifier and (meth)acrylate monomer (D) in the paint composition is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, and even more preferably 95% to 100% by mass, based on 100% by mass of the total amount of the paint composition.

[0083] The viscosity of the paint composition is preferably 80 seconds or less using the Ford Cup No. 4 during application, but is not limited to this. For example, a higher viscosity may be used when applying while heating.

[0084] The coating compositions of this disclosure are preferably curable by active energy rays, and more preferably by electron beams. Examples of active energy rays include near-infrared light, visible light, ultraviolet light, extreme ultraviolet light, and electron beams, and electron beams are preferred from the viewpoint of weather resistance of the resulting coating film.

[0085] <Method for preparing paint composition> The method for preparing the paint composition of this disclosure is not particularly limited and can be prepared by mixing each component. For example, it can be mixed using a roller mill, ball mill, bead mill, pebble mill, sand grind mill, pot mill, paint shaker, or disperser, or a kneader. The coating film formed from the aforementioned coating composition and the method for producing the coating film are also included within the technical scope of the present invention.

[0086] <Object to be coated> Examples of substrates to be coated with the paint composition include galvanized steel sheets, zinc-aluminum alloy coated steel sheets, aluminum alloy coated steel sheets, hot-dip zinc-aluminum-magnesium alloy coated steel sheets, stainless steel sheets, and cold-rolled steel sheets, all manufactured by methods such as melting or electrolysis. In addition to these steel sheets or coated steel sheets, metal sheets such as aluminum sheets (including aluminum alloy sheets) can also be coated.

[0087] The workpiece to be coated is preferably surface-treated. Specifically, the workpiece to be coated is preferably subjected to a chemical conversion treatment after undergoing pretreatment such as alkaline degreasing, hot water washing, or water washing. The chemical conversion treatment may be carried out by known methods, and includes, for example, non-chromate treatments such as chromate treatment and zinc phosphate treatment. The surface treatment can be appropriately selected depending on the steel sheet used, but treatments that do not contain heavy metals are preferred. By applying the paint composition of the present invention onto the workpiece that has undergone such chemical conversion treatment, the adhesion of the coating film to the metal sheet surface is improved, as is the corrosion resistance. Alternatively, an undercoat coating film (primer coating film) can be formed on the metal sheet surface that has undergone chemical conversion treatment, and the paint can be applied on top of it. The film thickness of the undercoat coating film is preferably 3 to 15 μm, more preferably 5 to 10 μm.

[0088] The surface tension of the paint composition obtained is 21 mN or more and 28 mN or less, preferably 22 mN or more and 27 mN or less, and more preferably 23 mN or more and 26 mN or less. Being within this range allows the paint composition to have good wettability to the substrate and improves the adhesion to the substrate.

[0089] The elongation at break of the coating film obtained from the aforementioned coating composition is 1% to 20%, preferably 1% to 16%, and more preferably 3% to 16%. Being within this range can result in good hardness and processability of the coating film.

[0090] The tensile strength of the coating film obtained from the aforementioned coating composition is 5 MPa to 50 MPa, preferably 5 MPa to 45 MPa, and more preferably 6.5 MPa to 40 MPa. Being within this range can result in good hardness and processability of the coating film.

[0091] <Method for manufacturing coating film> The method for manufacturing a coating film according to the present disclosure includes the steps of applying the coating composition according to the present disclosure to an object to be coated to form a coating film, and irradiating the coating film with active energy rays to cure it and obtain a coating film.

[0092] The method for applying the coating composition of this disclosure to an object to be coated is not particularly limited, but conventionally known methods such as the roll coater method, airless spray method, electrostatic spray method, and curtain flow coater method can be used. Preferably, the roll coater method and the curtain flow coater method are mentioned, and more preferably the roll coater method.

[0093] Examples of active energy rays include near-infrared light, visible light, ultraviolet light, extreme ultraviolet light, and electron beams, with electron beams being preferable from the viewpoint of the weather resistance of the resulting coating film.

[0094] If the active energy ray curing coating composition contains a solvent, the process may include a step of preheating the coating film before irradiation with active energy rays. Preheating can be performed, for example, by heating at 60 to 150°C for 10 to 900 seconds.

[0095] The film thickness of the coating after drying and / or curing (dry film thickness) is preferably 1 to 30 μm, more preferably 5 to 25 μm.

[0096] A laminate having the aforementioned object to be coated and the coating film formed on the object to be coated is also included within the technical scope of the present invention. If the object to be coated has the coating film on one surface, it may also have a coating film on the other surface formed from a known coating composition, such as a coating composition containing polyester resin or epoxy resin.

[0097] The coating composition disclosed herein can produce a coating film with high curability and good coating film properties (adhesion, crack resistance, and other workability, scratch resistance) even when cured under conditions that are lower in temperature and shorter in duration than those typically used for coating metal substrates (e.g., PMT 200-250°C, drying / curing time 20-60 seconds). Furthermore, it can significantly reduce carbon dioxide emissions from the coating process.

[0098] The coating composition disclosed herein can achieve both energy efficiency during film formation and desirable coating properties (particularly processability and hardness). Therefore, the coating composition disclosed herein is preferably used in a variety of applications, particularly in pre-coated steel sheet applications, especially in building components such as shutters, awnings, doors, roofs, and siding; exterior materials for electrical equipment such as air conditioner outdoor units; and interior materials. [Examples]

[0099] The present invention will be further described in detail by the following examples, but the present invention is not limited thereto.

[0100] (Preparation Example 1) <Examples of preparation of coating-forming resins (A1-4)> In a 1,500 mL reactor equipped with a heating device, a stirring device, and a dropping device, 737 parts by mass of butyl acetate were charged, and the temperature was maintained at 110°C. Next, a monomer mixture consisting of 369 parts by mass of methyl methacrylate, 540 parts by mass of ethyl acrylate, 131 parts by mass of glycidyl methacrylate, and 0.2 parts by mass of t-butyl peroxyhexanoate as a polymerization initiator was added dropwise to the reactor from the dropping device over 3 hours to obtain an epoxy group-containing (meth)acrylate polymer. Next, 2 parts by mass of dibutylhydroxytoluene and 66 parts by mass of acrylic acid were added to the same reaction vessel as polymerization inhibitors, and then 16 parts by mass of triphenylphosphine was added as a reaction catalyst. The mixture was stirred for 12 hours while maintaining a temperature of 95°C to obtain acrylic (meth)acrylate oligomers (A1-4).

[0101] (Example 1) Preparation of paint composition 1 In a 200 ml metal container, 33.3 parts by mass of DR-A820 as an acrylic (meth)acrylate oligomer (A1-1), 50.0 parts by mass of Typake CR-97 as a pigment (B-1), 15.0 parts by mass of isobornyl acrylate as a (meth)acrylate monomer (D-1), and 15.0 parts by mass of tripropylene glycol diacrylate as (D-8) were measured out and stirred in a disperser for 10 minutes. Then, the pigment was dispersed using glass beads in an SG mill until the maximum particle size of the pigment was 10 μm or less. After dispersing, the glass beads were removed from the solution, 0.5 parts by mass of BYK-333 as a surface modifier (C-1) was added, and the mixture was further stirred in a disperser at 2,000 rpm for 10 minutes to obtain paint composition 1.

[0102] Preparation of test plates After alkaline degreasing of an aluminum-zinc plated steel sheet (29.7 x 21.0 x 0.4 mm), Surfcoat EC2310 (phosphate-based surface treatment agent: manufactured by Nippon Paint Surf Chemicals Co., Ltd.) was applied to both the front and back surfaces of the steel sheet as a surface treatment agent, and then dried.

[0103] N Supercoat 5620NC (polyester-based primer: manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was applied to the surface of the treated steel plate to a dry film thickness of 7 μm, and the plate was baked in a conveyor oven at PMT 220°C for 30 seconds to obtain a primer-coated plate.

[0104] On the aforementioned undercoated board, the paint composition 1 obtained above was applied using a bar coater to a dry film thickness of 15 μm, dried at 80°C for 3 minutes to allow the solvent components to evaporate, and then irradiated with an electron beam using an electron beam irradiation device EC250 (manufactured by Iwasaki Electric Co., Ltd.) under conditions of irradiation dose of 50 kGy and acceleration voltage of 100 keV to form a cured paint film and obtain a test board.

[0105] (Examples 2-23, Comparative Examples 1-15) A paint composition and a cured coating film were obtained in the same manner as in Example 1, except that the composition before dispersion was changed to the materials and proportions shown in Tables 3 to 5. Note that the proportions in the tables refer to parts by mass of the material as is, including volatile components. However, in Example 4 and Comparative Example 14, (A2-1) ※1 The column indicates the amount of urethane acrylate contained in (A2-1), and (D-1) ※2 The column shows the total amount, including the amount of isobornyl acrylate contained in (A2-1).

[0106] Details of the (meth)acrylate oligomer (A) used in the examples and comparative examples are as follows. However, (A2-1) JE101 (manufactured by Nagase Industrial Materials Co., Ltd.) is a mixture of urethane acrylate and isobornyl acrylate, with a content ratio (urethane acrylate:isobornyl acrylate) of 75:25 by mass. In Table 2, the unsaturated bond group equivalent and weight-average molecular weight shown in the (A2-1) column represent the values ​​for the urethane acrylate contained in (A2-1), while the glass transition temperature, surface tension, and active ingredient amount represent the values ​​for the mixture of urethane acrylate and isobornyl acrylate.

[0107] [Table 1]

[0108] The details of each component used in the examples and comparative examples, as shown in the table below, are as follows. Pigment (B) (B-1) Typeque CR-97; Titanium dioxide, manufactured by Ishihara Sangyo Co., Ltd. (B-2) Bayferrox 140M; Iron oxide, manufactured by Lanxess. (B-3) Alpaste FZ-U75C; Aluminum pigment, manufactured by Toyo Aluminum Co., Ltd.: Aluminum pigment concentration: 42% by mass Surface modifier (C) (C-1)BYK-333; Silicone-based surface modifier, manufactured by Bic Chemie, active ingredient content: 100% by mass (C-2)BYK-361N; Acrylic surface modifier, manufactured by Bic Chemie, active ingredient content: 100% by mass others • Pigment dispersant: BYK-111; acrylic pigment dispersant, manufactured by Bic Chemie, active ingredient content: 95% by mass • Organic solvent: Butyl acetate, manufactured by Daicel Chemical Industries, Ltd.

[0109] Details of the (meth)acrylate monomer (D) used in the examples and comparative examples are as follows.

[0110] [Table 2]

[0111] (3) Evaluation items 1) Surface tension of the paint composition The measurement was performed using a dynometer (manufactured by Big Gardner GmbH, Germany) and the platinum ring method. The measurement temperature was 25°C.

[0112] 2) Tensile strength and elongation of the coating film After forming the cured coating of the example or comparative example on a 0.1 mm thick polyethylene film with a smooth surface using the same method as described above, test specimens for measuring elongation and tensile strength were prepared by punching them out using a dumbbell No. 2 shape as specified in JIS K 6251. For measuring elongation and tensile strength, two gauge marks were placed 10 mm from the center of the long axis of the test specimen (20 mm between the gauge marks). The marked test specimens were then gripped and mounted on a universal tensile testing machine with a 50 mm gap between them. The specimens were then pulled at a tensile speed of 50 mm / min at room temperature, and the maximum load and gauge mark distance at which the coating of the test specimen broke were measured. The elongation (ratio of the distance between the chucks before pulling to the distance between the chucks before pulling (%)) was calculated using the following formula (1), and the tensile strength (tensile strength) was calculated using the following formula (2). Elongation (%) = (Length between gauge marks at break (mm) - 20) ÷ 20 × 100 ... (1) Tensile strength (MPa=N / mm 2 ) = Maximum load (N) ÷ Cross-sectional area of ​​the test specimen (mm²)2 )··(2)

[0113] In this case, a higher elongation rate indicates greater elongation before fracture, while a higher tensile strength indicates greater force required for fracture. The higher both values, the higher the coating strength and toughness.

[0114] 4) Hardness of the coating The pencil hardness of the coating film was measured using the coated steel sheets obtained in the examples and comparative examples, in accordance with JIS K 5600-5-4. A hardness of H or higher was considered acceptable. Specifically, a pencil (manufactured by Mitsubishi Pencil Co., Ltd.: used for scratch hardness testing by the Japan Paint Inspection Association) was pressed against the surface of the hardened electrodeposited coating at a 45° scratching angle and moved, and the presence or absence of scratches from the pencil lead was visually observed. For example, in a test using an H pencil, if no marks were observed, it was judged as H or higher. If a slight indentation was visible in one of the five tests, it was judged as H. If indentations were observed in two or more of the five tests, it was judged as less than H, and the evaluation was similarly lowered by one level.

[0115] 5) Processability (crack resistance) Each painted steel sheet obtained in the examples and comparative examples was cut to 5cm x 3cm and pre-bent using a seam folding machine (manufactured by Ueshima Seisakusho Co., Ltd.) so that the painted surface was facing outwards. N sheets of steel sheet of the same thickness (0.4mm) were placed between the test pieces and folded using a press machine (manufactured by Kyōritsu Kogyo Co., Ltd.). The number of steel sheets (n) was increased until no cracks were observed in the processed area, and the minimum number of sheets at which no cracks were observed was defined as nT to evaluate crack resistance. A value of 9T or less (9 or fewer steel sheets) was considered acceptable. The test conditions were a temperature of 23°C and a humidity of 60RH%, and the processed area was observed with a 15x magnifying glass.

[0116] [Table 3]

[0117] [Table 4]

[0118] [Table 5]

[0119] Examples 1 to 23 are embodiments of the present invention, demonstrating that a coating film can be formed by electron beam irradiation, and that the resulting coating film has both good processability and hardness.

[0120] Comparative Example 1 is an example where the resulting coating film had a tensile strength exceeding 50 MPa, and its processability was poor. Comparative Examples 2 and 11 were examples where the resulting coating film had a tensile strength of less than 5 MPa and exhibited inferior hardness. Comparative Example 3 is an example where the elongation of the resulting coating film exceeded 20%, and the hardness was inferior. Comparative Example 4 is an example in which the surface tension of the resulting coating composition exceeded 28.0 mN / m and the elongation of the resulting coating film was less than 1%, resulting in poor processability of the coating film. Comparative Examples 5 and 12 were examples in which the surface tension of the resulting coating composition exceeded 28.0 mN / m, and the processability and / or hardness of the resulting coating film were poor. Comparative Example 6 is an example in which the surface tension of the resulting coating composition was less than 21.0 mN / m. During the preparation of the test plate, repellency occurred in the coating film on the coated steel plate, and a uniform coating film could not be obtained. Comparative Example 7 is an example where the elongation rate of the resulting coating film exceeded 20%, resulting in poor processability. Comparative Examples 8, 9, and 10 were examples in which the elongation of the resulting coating film was less than 1% and the tensile strength exceeded 50 MPa, indicating poor processability. Comparative Example 13 was a system that did not contain (meth)acrylate oligomer (A), and the resulting coating film had inferior processability and hardness. Comparative Example 14 was an example that did not include pigment (B), and the resulting coating film had inferior hardness. Comparative Example 15 was an example that did not include the surface modifier (C), and when the test plate was prepared, the coating did not wet and spread uniformly, resulting in an ununiform coating. [Industrial applicability]

[0121] The coating composition disclosed herein can achieve both energy efficiency during film formation and desirable coating properties (particularly processability and hardness). Therefore, the coating composition disclosed herein is preferably used in a variety of applications, particularly in pre-coated steel sheet applications, especially in building components such as shutters, awnings, doors, roofs, and siding; exterior materials for electrical equipment such as air conditioner outdoor units; and interior materials.

Claims

1. A paint composition comprising (meth)acrylate oligomer (A), pigment (B), surface modifier (C), and (meth)acrylate monomer (D), The (meth)acrylate oligomer comprises one or more selected from acrylic (meth)acrylate oligomer (A1) and urethane (meth)acrylate oligomer (A2). The unsaturated bond equivalent of the (meth)acrylate oligomer (A) is 400 g / eq or more and 3,100 g / eq or less. The weight-average molecular weight of the (meth)acrylate oligomer (A) is 900 or more and 50,000 or less. The total amount of the (meth)acrylate oligomer (A) and the (meth)acrylate monomer (D) to the pigment (B) is the mass ratio [(A) + (D):(B)] which is 85:15 to 50:

50. The surface tension of the aforementioned paint composition is 21.0 mN / m or more and 28.0 mN / m or less. The resulting coating has a tensile strength of 5 MPa or more and 50 MPa or less. A coating composition for pre-coated steel sheets, wherein the resulting coating film has a breaking elongation of 1% or more and 20% or less.

2. The surface tension of the acrylic (meth)acrylate oligomer (A1) is 29.0 mN / m or more and 35.0 mN / m or less. The aforementioned urethane (meth)acrylate oligomer (A2) The paint composition for pre-coated steel sheets according to claim 1, wherein the surface tension is 29.0 mN / m or more and 45.0 mN / m or less.

3. The glass transition temperature of the coating film obtained from the acrylic (meth)acrylate oligomer (A1) is 50°C or higher and 90°C or lower. The paint composition for pre-coated steel sheets according to claim 1, wherein the glass transition temperature of the coating film obtained from the urethane (meth)acrylate oligomer (A2) is 15°C or more and 60°C or less.

4. The paint composition for pre-coated steel sheets according to claim 1, wherein the total content of the active ingredients (meth)acrylate oligomer (A), pigment (B), surface modifier and (meth)acrylate monomer (D) in the paint composition is 70% by mass or more.

5. The coating composition for pre-coated steel sheets according to claim 1, which is electron beam curable.

6. The system comprises a steel plate and a coating film disposed on the steel plate, The coating film is formed from a pre-coated steel sheet paint composition according to any one of claims 1 to 5, wherein the coating film is a painted steel sheet.

7. The system further comprises an undercoat coating disposed between the steel plate and the coating film, The thickness of the aforementioned undercoat film is 3 μm or more and 10 μm or less. The painted steel sheet according to claim 6, wherein the thickness of the coating film is 10 μm or more and 100 μm or less.

8. A process of applying a paint composition to an object to be coated to obtain a painted film, and The process includes irradiating the aforementioned coating film with active energy rays to obtain a coating film, The aforementioned paint composition comprises the paint composition for pre-coated steel sheets described in any one of claims 1 to 5, A method for manufacturing a coating film, wherein the active energy ray is an electron beam.

9. The painted steel sheet according to claim 7, wherein the undercoat film comprises a polyester resin.

Images