Coating composition for in-mold coating and coated article

Abstract

To provide a coating composition for in-mold coating which is excellent in low-temperature curability and adhesion to a nonpolar resin substrate.SOLUTION: The coating composition for in-mold coating contains: a first compound (A) having an alicyclic skeleton and one reactive double bond; a second compound (B) having one reactive double bond copolymerizable with the first compound (A); a third compound (C) having two to six reactive double bonds; a styrene block copolymer (D) having a styrene block derived from styrene and an olefin block derived from a linear or branched olefin; and a polymerization initiator (E).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating composition for in-mold coating and to a coated article. [Background technology]

[0002] In recent years, resins have been proposed as an alternative to metals as materials for automobile parts. Patent Documents 1 to 3 disclose coating compositions for in-mold coating that are suitable for resin substrates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-249680 A [Patent Document 2] JP 2009-019073 A [Patent Document 3] JP 2022-100236 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a coating composition for in-mold coating which has excellent low-temperature curing properties and adhesion to non-polar resin substrates. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides the following aspects. [1] A first compound (A) having an alicyclic skeleton and one reactive double bond; A second compound (B) having one reactive double bond copolymerizable with the first compound (A); a third compound (C) having 2 to 6 reactive double bonds; A styrene block copolymer (D) having a styrene block derived from styrene and an olefin block derived from a linear or branched olefin; A coating composition for in-mold coating, comprising: [2] The coating composition for in-mold coating according to the above-mentioned [1], wherein the hydrocarbon group contained in the olefin block of the styrene block copolymer (D) is saturated. [3] With respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D), The coating composition for in-mold coating according to the above [1] or [2], wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less. [4] With respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D), The coating composition for in-mold coating according to the above [1] or [2], wherein the solid content of the styrene block copolymer (D) is from 1 part by mass to 30 parts by mass. [5] The coating composition for in-mold coating according to the above [1] or [2], wherein the alicyclic skeleton possessed by the first compound (A) is at least one selected from the group consisting of a cyclohexyl group, an isobornyl group, a dicyclopentenyl group, and a dicyclopentanyl group. [6] The coating composition for in-mold coating according to the above [1] or [2], wherein the olefin that is the raw material for the olefin block has a carbon number of 2 or more and 5 or less. [7] The coating composition for in-mold coating according to the above [1] or [2], wherein the styrene block copolymer (D) comprises at least one first styrene block copolymer (D1) selected from the group consisting of a styrene-ethylene-propylene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, and a styrene-ethylene-butylene-styrene block copolymer. [8] The coating composition for in-mold coating according to the above item [7], wherein the proportion of the first styrene block copolymer (D1) in the styrene block copolymer (D) is 55 mass % or more. [9] The coating composition for in-mold coating according to the above [1] or [2], further comprising an olefin resin (F).

[10] The coating composition for in-mold coating according to the above [1] or [2], further comprising at least one of a luster material and a colorant (G).

[11] A substrate including a non-polar resin; A coated article comprising: a coating film comprising a cured product of the coating composition for in-mold coating described in [1] or [2] above, disposed on the substrate. Effect of the Invention

[0006] According to the present invention, there is provided a coating composition for in-mold coating which has excellent low-temperature curing properties and adhesion to non-polar resin substrates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [In-mold coating paint composition] The coating composition for in-mold coating according to the present disclosure comprises: A first compound (A) having an alicyclic skeleton and one reactive double bond; a second compound (B) having one reactive double bond copolymerizable with the first compound (A); a third compound (C) having 2 to 6 reactive double bonds; A styrene block copolymer (D) having a styrene block derived from styrene and an olefin block derived from a linear or branched olefin; and a polymerization initiator (E).

[0008] In-mold coating is a method in which a coating composition is applied to a molded substrate in a mold and the coating is cured without exposure to the atmosphere (particularly oxygen). A coating composition for in-mold coating (hereinafter, sometimes simply referred to as a coating composition) is used for in-mold coating. The coating composition for in-mold coating is preferably used for, for example, injection molding, injection compression molding, injection press molding, compression molding, reaction injection molding, and RTM molding. In-mold coating reduces the amount of organic solvent and carbon dioxide emissions compared to spray coating. In-mold coating has been attracting attention in recent years because of its low environmental impact. In-mold coating is suitable as a method for coating a resin substrate.

[0009] Polypropylene is very light and highly processable, making it suitable as a material for automotive parts. On the other hand, polypropylene is said to have poor adhesion, and it is difficult to adhere a coating film to a polypropylene substrate. Therefore, in order to improve adhesion to a substrate containing a non-polar resin such as polypropylene (hereinafter, sometimes referred to as a non-polar substrate), a non-polar resin (e.g., olefin resin) having a similar structure has been conventionally blended into the coating composition. However, due to differences in polarity, etc., non-polar resins have low compatibility with other components of the coating composition (e.g., raw material monomers). Therefore, the stability of the coating composition decreases and the viscosity increases. In addition, the coating film may become turbid.

[0010] In the present disclosure, a first compound (A) and a styrene block copolymer (D) are used. The first compound (A) has an alicyclic skeleton and one reactive double bond. The reason why the adhesion is improved by the first compound (A) is not limited to a particular theory, but is believed to be as follows. The reactive double bond of the first compound (A) reacts with other polymerizable compounds (e.g., the second compound (B) and the third compound (C)) to form a coating film, while the alicyclic skeleton can penetrate into a non-polar substrate. Since the alicyclic skeleton is bulky, once it penetrates into a non-polar substrate, it is difficult to escape. This allows the coating film formed and the non-polar substrate to adhere to each other via the first compound (A). The penetration of the alicyclic skeleton into a non-polar substrate is likely to occur at high temperatures (e.g., above 120°C).

[0011] The styrene block copolymer (D) has an olefin block derived from a linear or branched olefin (i.e., a non-alicyclic olefin). The olefin block is easily permeated into a non-polar substrate. This permeation can occur even at low temperatures (e.g., 80°C or higher and 120°C or lower). However, the olefin block derived from the olefin has low compatibility with other components of the coating composition (particularly, the first compound (A)). In the present disclosure, styrene, which has excellent compatibility with other components of the coating composition, is blended into the coating composition as a block copolymer with an olefin. The styrene block derived from the styrene allows the non-polar portion (olefin block derived from the olefin) to be blended into the coating composition.

[0012] The first compound (A) also improves the compatibility between the third compound (C) and the styrene block copolymer (D). The third compound (C) and the styrene block copolymer (D) are difficult to dissolve in each other due to the difference in their structures, but the compatibility between them is improved by the first compound (A).

[0013] By using the first compound (A) in combination with the styrene block copolymer (D), the stability of the coating composition is maintained and the increase in viscosity is suppressed. Furthermore, even when the coating composition is cured at a low temperature (e.g., 80°C to 120°C, particularly 100°C to 120°C), the adhesion between the coating film and the non-polar substrate can be improved. Low-temperature curing suppresses deformation of the non-polar substrate.

[0014] The compatibility of the components (A) to (D) can be evaluated by the stability and viscosity of the coating composition, or the turbidity of the coating film. The adhesion of the coating film can be evaluated by initial adhesion, water-resistant adhesion, and flex resistance. According to the coating composition of the present disclosure, a coating film excellent in all of initial adhesion, water-resistant adhesion, and flex resistance can be obtained for a non-polar substrate.

[0015] ·First compound (A) The first compound (A) has an alicyclic skeleton and one reactive double bond. Since the alicyclic skeleton has low polarity, the first compound (A) improves the adhesion between the coating film and the non-polar substrate. Since the first compound (A) has only one reactive double bond, it easily penetrates the substrate and can contribute to improving the adhesion between the coating film and the non-polar substrate. The first compound (A) also improves the compatibility between the third compound (C) and the styrene block copolymer (D).

[0016] The alicyclic skeleton may be, for example, at least one selected from the group consisting of a cyclohexyl group, an isobornyl group, a dicyclopentenyl group, and a dicyclopentanyl group. Among these, from the viewpoint of adhesion, the alicyclic skeleton is preferably a dicyclopentanyl group.

[0017] The first compound (A) may be an alicyclic (meth)acrylate. (Meth)acrylate refers to acrylate and methacrylate. Examples of the alicyclic (meth)acrylate include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

[0018] The content of the first compound (A) is preferably 5 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D). From the viewpoint of adhesion, the content of the first compound (A) may be 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more. From the viewpoint of flexibility of the coating film, the content of the first compound (A) may be 60 parts by mass or less, 55 parts by mass or less, or 50 parts by mass or less.

[0019] ·Second compound (B) The second compound (B) has one reactive double bond copolymerizable with the first compound (A). The second compound (B) imparts various properties to the coating composition or coating film. By blending the second compound (B), the relative content of the third compound (C) is prevented from becoming too high, so that the flexibility of the coating film is less likely to be impaired. Unlike the first compound (A), the second compound (B) does not have an alicyclic skeleton.

[0020] Examples of the second compound (B) include (meth)acrylic acid; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, and t-butyl (meth)acrylate; monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 18 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; allyl alcohol; vinyl aromatic compounds such as styrene, α-methylstyrene, and vinyltoluene; polymerizable amide compounds such as acrylamide and methacrylamide; polymerizable aromatic compounds, polymerizable nitriles, polymerizable alkylene oxide compounds, polymerizable amine compounds, α-olefins, dienes, polymerizable carbonyl compounds, and polymerizable alkoxysilyl compounds. These may be used alone or in combination of two or more. They may be, for example, urethane-modified, amine-modified, caprolactone-modified, alkyl-modified, silicone-modified, or polyoxyalkylene-modified. (Meth)acrylic acid refers to acrylic acid and methacrylic acid.

[0021] The content of the second compound (B) may be 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D). The content of the second compound (B) may be 5 parts by mass or more. The content of the second compound (B) may be 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less. The content of the second compound (B) is appropriately set within a range that does not interfere with the adhesion improving effect of the first compound (A) and the styrene block copolymer (D) and can impart the desired performance to the coating composition or coating film.

[0022] ·Third compound (C) The third compound (C) has 2 to 6 reactive double bonds. A three-dimensional crosslinked structure is formed by the third compound (C), and the coating film is provided with toughness and an appropriate hardness.

[0023] Examples of polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, glycerin di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, trifunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate, trimethylolethane tri(meth)acrylate, and trimethylolpropane tri(meth)acrylate; tetrafunctional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, tripentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate; pentafunctional (meth)acrylates such as dipentaerythritol penta(meth)acrylate and tripentaerythritol penta(meth)acrylate; hexafunctional (meth)acrylates such as dipentaerythritol hexa(meth)acrylate and tripentaerythritol hexa(meth)acrylate, polyfunctional urethane (meth)acrylates, polyfunctional epoxy (meth)acrylates, and polyfunctional polyester (meth)acrylates. These may be used alone or in combination of two or more. They may be, for example, urethane-modified, amine-modified, caprolactone-modified, alkyl-modified, silicone-modified, or polyoxyalkylene-modified.

[0024] The content of the third compound (C) is preferably 10 parts by weight or more and 40 parts by weight or less, based on 100 parts by weight of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D). When the content of the third compound (C) is 10 parts by weight or more, good chemical resistance and weather resistance are easily obtained. When the content of the third compound (C) is 40 parts by weight or less, the adhesion can be further improved. It may be. The content of the third compound (C) is more preferably 15 parts by weight or more. The content of the third compound (C) is more preferably 30 parts by weight or less.

[0025] Styrene block copolymer (D) The styrene block copolymer (D) has a styrene block derived from styrene and an olefin block derived from a linear or branched olefin. The styrene block copolymer (D) improves the adhesion between the coating film and a non-polar substrate even in the case of low temperature curing.

[0026] The olefin used as the raw material for the olefin block may be linear or branched. The number of carbon atoms in the olefin used as the raw material for the olefin block is, for example, 2 or more and 5 or less.

[0027] From the viewpoint of adhesion, it is preferable that the hydrocarbon group contained in the olefin block is saturated. The hydrocarbon group can be saturated by adding a hydrogen atom to the double bond (hydrogenation).

[0028] The hydrocarbon group contained in the olefin block has a CC single bond as the main chain. The main chain may contain an unsaturated bond, and is preferably saturated from the viewpoint of adhesion. The hydrocarbon group contained in the olefin block may also have a hydrocarbon group (e.g., having 1 to 3 carbon atoms) as a side chain. The adhesion can be further improved by the side chain being a hydrocarbon group. From the viewpoint of adhesion, it is preferable that the side chain also has a hydrocarbon group.

[0029] The styrene block copolymer (D) preferably contains at least one first styrene block copolymer (D1) selected from the group consisting of styrene-ethylene-propylene block copolymer (SEP), styrene-ethylene-propylene-styrene block copolymer (SEPS) and styrene-ethylene-butylene-styrene block copolymer (SEBS). The order of the olefin blocks contained in the first styrene block copolymer (D1) is arbitrary.

[0030] From the viewpoint of adhesion, the proportion of the first styrene block copolymer (D1) in the styrene block copolymer (D) may be 55% by mass or more. The proportion of the first styrene block copolymer (D1) may be 60% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0031] The content of the styrene block copolymer (D) may be 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D). When the content of the styrene block copolymer (D) is 1 part by mass or more, the adhesion can be further improved. When the content of the styrene block copolymer (D) is 30 parts by mass or less, the viscosity is easily adjusted to be suitable for in-mold coating. The content of the styrene block copolymer (D) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more. The content of the styrene block copolymer (D) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less.

[0032] Polymerization initiator (E) The polymerization initiator (E) generates free radicals and initiates polymerization of the first compound (A), the second compound (B) and the third compound (C).

[0033] Examples of the polymerization initiator (E) include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; peroxyketals such as 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide; 1,3-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, diisopropylbenzene peroxide, and t-butyl Examples of the organic peroxides include dialkyl peroxides such as lucumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; peroxycarbonates such as bis(t-butylcyclohexyl)peroxydicarbonate; peroxyesters such as t-butylperoxy-2-ethylhexanate, t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; and azo compounds such as 2,2'-azobisisobutyronitrile, 1,1-azobis(cyclohexane-1-carbonitrile), azocumene 2,2'-azobismethylvaleronitrile, and 4,4'-azobis(4-cyanovaleric acid).

[0034] Olefin resin (F) The coating composition may contain an olefin resin (F). Since the olefin resin has low polarity or is non-polar, it has a high affinity with non-polar substrates. Therefore, it is expected that the adhesion between the coating composition and the non-polar substrate will be further improved. Furthermore, the styrene block copolymer (D) may function as a compatibilizer for the olefin resin (F). Therefore, when the olefin resin (F) is blended into the coating composition in the presence of the styrene block copolymer (D), the decrease in stability and the increase in viscosity of the coating composition can be suppressed.

[0035] Examples of the olefin resin (F) include a polymer of an olefin monomer (e.g., at least one selected from the group consisting of ethylene, propylene, butene, 3-methyl-1-butene, and 3-methyl-1-heptene). The olefin resin (F) may be a copolymer of an olefin monomer with vinyl acetate, butadiene, an acrylic acid ester, a methacrylic acid ester, or the like.

[0036] The content of the olefin resin (F) is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D). From the viewpoint of adhesion, the content of the olefin resin (F) is preferably 1 part by mass or more, and more preferably 3 parts by mass or more. From the viewpoint of compatibility, the content of the olefin resin (F) is preferably 10 parts by mass or less, and more preferably 7 parts by mass or less.

[0037] · Luster material / colorant (G) The coating composition may contain at least one of a luster material and a colorant (hereinafter, sometimes referred to as luster material / colorant) (G), which improves the design.

[0038] The colorant may be a color pigment or a dye. The color pigment may be an inorganic pigment or an organic pigment. The color pigment may be achromatic or achromatic. Examples of organic color pigments include azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments. Examples of inorganic color pigments include yellow lead, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. These may be used alone or in combination of two or more.

[0039] Examples of the dye include azo dyes, triphenylmethane dyes, chromium complexes, and cobalt complexes. These may be used alone or in combination of two or more.

[0040] Examples of the luster pigment include mica pigments such as interference mica, white mica, and colored mica; graphite pigments; glass flake pigments; and metal pigments such as aluminum, copper, zinc, iron, nickel, tin, aluminum oxide, chromium oxide, and alloys containing these. These may be used alone or in combination of two or more. The luster pigment may be colored.

[0041] The content of the lustrous material / colorant (G) may be 0.5 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D).

[0042] ·others The coating composition may contain other components such as other pigments (for example, extender pigments), defoamers, ultraviolet absorbers, light stabilizers, polymerization inhibitors, surface conditioners, film-forming assistants, rust inhibitors, and release agents.

[0043] The coating composition is obtained by mixing the above components. The mixing is performed, for example, by using a disperser (a stirrer). Examples of the disperser include low-speed stirrers such as a propeller mixer, a paddle mixer, and an anchor mixer; and high-speed stirrers such as a homomixer, a disperser mixer, and an ultra mixer.

[0044] [Painted items] The coated article according to the present disclosure comprises a non-polar substrate and a coating film (hereinafter sometimes referred to as a cured coating film) comprising a cured product of the above-mentioned coating composition disposed on the non-polar substrate.

[0045] ·Non-polar base material The non-polar substrate includes a non-polar resin. The non-polar resin may be disposed at least on the surface of the substrate. The entire non-polar substrate may be formed of the non-polar resin.

[0046] Non-polar resins have a surface tension of 32 dyne / cm or less. Such resins have no polarity or only a very small polarity.

[0047] Examples of non-polar resins include aliphatic polyolefin resins such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE) copolymerized with α-olefin and ethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE), isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), polypropylene copolymer, and polypropylene block copolymer; cyclic olefin copolymer; polystyrene; fluorinated resin; silicone resin; epoxy silicone resin; and silicone elastomer. Among them, various polypropylenes may be used. The coating composition according to the present disclosure exhibits high adhesion to substrates containing polypropylene in particular.

[0048] ·Cured coating film The cured coating film includes a cured product of the above-mentioned coating composition. The thickness of the cured coating film may be, for example, 20 μm or more and 1 mm or less.

[0049] A cured product is obtained by heating the coating composition. The heating temperature is preferably 80°C or higher (particularly 100°C or higher) and 120°C or lower. When the heating temperature is within the above range, the shape of the non-polar substrate is easily maintained. The cured product of the coating composition according to the present disclosure has high adhesion to the non-polar substrate even when cured at a low temperature of 80°C or higher (particularly 100°C or higher) and 120°C or lower. The heating time is appropriately set according to the heating temperature. The heating time may be, for example, 2 minutes or more and 10 minutes or less.

[0050] The coated article may have another coating (eg, a clear coat) disposed on the cured coating.

[0051] [Manufacturing method of coated articles] The coated article is produced by in-mold coating, which comprises, for example, placing a non-polar substrate in a fixed mold, injecting a coating composition into the gap between the fixed mold and a movable mold, and then heating the coating composition.

[0052] The other coating is applied, for example by spray painting, after the coated article is removed from the mold. EXAMPLES

[0053] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0054] [Example 1] (1) Preparation of coating composition A vessel equipped with a stirring blade, a thermometer, a temperature control rod, and a cooling tube was charged with 10 parts by weight of a first compound (A-1) (dicyclopentanyl acrylate), 30 parts by weight of a second compound (B-2) (t-butyl methacrylate), 20 parts by weight of a second compound (B-3) (lauryl acrylate), and 10 parts by weight of a styrene block copolymer (D1-1) (product name "Tuftec H1517", manufactured by Asahi Kasei Corporation, SEBS), and the mixture was left at room temperature for 12 hours to allow the styrene block copolymer (D1-1) to swell.

[0055] The mixture was then heated to 90°C while stirring, and the styrene block copolymer (D1-1) was dissolved over 4 hours. While maintaining the temperature at 90°C, 15 parts by weight of the third compound (C-1) (dimethylol-tricyclodecane diacrylate) and 15 parts by weight of the third compound (C-3) (trade name "Ebecryl 8402", manufactured by Daicel Allnex Corporation) were added and stirred until homogenous. After cooling to room temperature, 2 parts by weight of the polymerization initiator (E) (t-butylperoxy-2-ethylhexanate) were added and stirred to obtain a coating composition.

[0056] (2) Preparation of painted items A 200mm x 200mm polypropylene (PP) substrate was degreased with isopropyl alcohol. A 200μm thick tape was then attached to the surface of the PP substrate to create a frame. The PP substrate was then placed on a 300mm x 300mm x 10mm metal plate and placed in a dryer set to a specified temperature (100℃, 110℃, or 120℃).

[0057] After confirming that the PP substrate had reached the specified temperature, about 10 g of the coating composition was dropped into the frame of the PP substrate. The substrate was covered with a 300 mm x 300 mm x 10 mm metal plate that had been heated to a specified temperature separately to block air, and heated at the specified temperature for a specified time (3 or 5 minutes) to obtain a coated article.

[0058] [Examples 2 to 15, Comparative Examples 1 to 4] Coating compositions were prepared and coated articles were produced in the same manner as in Example 1, except that the types or amounts of the components used to prepare the coating compositions were changed as shown in Table 1. The symbols in Table 1 are explained below.

[0059] ·First compound (A) A-1: Dicyclopentanyl acrylate A-2: Cyclohexyl methacrylate A-3: Isobornyl acrylate

[0060] ·Second compound (B) B-1: Styrene B-2: t-butyl methacrylate B-3: Lauryl acrylate B-4: Hydroxypropyl methacrylate

[0061] ·Third compound (C) C-1: Dimethylol-tricyclodecane diacrylate C-2: Dipentaerythritol hexaacrylate C-3: Product name "Ebecryl 8402", manufactured by Daicel Allnex Corporation, bifunctional aliphatic urethane acrylate

[0062] Styrene block copolymer (D) (First styrene block copolymer (D1)) D1-1: Product name "Tuftec H1517", manufactured by Asahi Kasei Corporation, SEBS block copolymer, styrene content 43% by mass D1-2: Product name "Tuftec H1043", manufactured by Asahi Kasei Corporation, SEBS block copolymer, styrene content 67% by mass D1-3: Product name "Tuftec M1943", manufactured by Asahi Kasei Corporation, SEBS block copolymer, styrene content 20% by mass D1-4: Product name "Septon 1020", manufactured by Kuraray Co., Ltd., SEP block copolymer, styrene content 36% by mass D1-5: Product name "Septon 2063", manufactured by Kuraray Co., Ltd., SEPS block copolymer, styrene content 13% by mass (Other styrene block copolymers (D2)) D2: Product name "Tufprene A", manufactured by Asahi Kasei Corporation, SBS block copolymer, styrene content 40% by mass

[0063] Polymerization initiator (E) E-1: t-Butylperoxy-2-ethylhexanate

[0064] [evaluation] The coating compositions and coated articles of the Examples and Comparative Examples were subjected to the following evaluations.

[0065] (1) Compatibility (1-1) Paint composition 50 g of the coating composition was placed in a 100 ml screw tube and left at room temperature (about 23°C) for 24 hours. After that, the condition of the coating composition was visually evaluated according to the following criteria. If the evaluation was B or higher, it can be evaluated that the components are compatible with each other. A: It is colorless and transparent, and when the screw tube is turned upside down, the entire content falls out in less than 5 seconds. B: The screw tube does not fall when turned upside down, or it takes more than 5 seconds for it to fall C: Cloudy or layer separated

[0066] (1-2) Coating The coating composition was cured by heating at 120°C for 3 minutes in an airtight state to prepare a 200μ film. The cloudiness of the film was evaluated visually according to the following criteria. A rating of B or higher indicates that the components are compatible with each other. A: Colorless and transparent B: Slightly cloudy C: Clear turbidity (whitening)

[0067] (2) Adhesion (2-1) Initial adhesion Using a cutter, the coating film of the coated article was cross-cut into a grid of 100 squares, each 2 mm on a side. Cellophane tape (registered trademark "Cellotape", manufactured by Nichiban Co., Ltd.) was applied to the cross-cut coating film while being careful not to include air bubbles, and then the cellophane tape was quickly peeled off. The number of squares that were peeled off together with the cellophane tape was counted. A rating of C or higher was considered to be good adhesion. A: No peeling B: The plate did not peel off completely, but some of the grid patterns were chipped. C: 1 to 5 squares peeled off D: 6 or more squares peeled off

[0068] (2-2) Water-resistant adhesion The coated article was immersed in 40°C warm water for 240 hours, then removed and dried for 10 minutes. The coating was then cross-cut in the same manner as above to evaluate adhesion. A rating of C or higher indicates water-resistant adhesion.

[0069] (2-3) Flexibility A test piece measuring 150 mm in length and 15 mm in width was cut out from the coated article. The test piece was bent 90 degrees near the center in the longitudinal direction over one second. The condition of the coating around the bent part was visually evaluated according to the following criteria. A rating of C or higher was considered to have bending resistance. A: No abnormalities B: Slightly wrinkled C: Wrinkled D: Cracked

[0070] [Table 1]

[0071] The coating films of Examples 1 to 15 showed good adhesion even when cured at 100°C. The coating composition of Comparative Example 1 did not contain a styrene block copolymer (D). Therefore, the initial adhesion and water-resistant adhesion when cured at 100°C were poor. The coating composition of Comparative Example 2 did not contain a first compound (A). Therefore, the compatibility and the initial adhesion and water-resistant adhesion when cured at 100°C were poor. The coating composition of Comparative Example 3 did not contain a second compound (B). Therefore, the water-resistant adhesion and flex resistance were poor. The coating composition of Comparative Example 4 did not contain a third compound (C). Therefore, the obtained coating film had poor film-forming performance, and each adhesion could not be evaluated.

[0072] The present disclosure includes the following aspects. [1] A first compound (A) having an alicyclic skeleton and one reactive double bond; A second compound (B) having one reactive double bond copolymerizable with the first compound (A); a third compound (C) having 2 to 6 reactive double bonds; A styrene block copolymer (D) having a styrene block derived from styrene and an olefin block derived from a linear or branched olefin; A coating composition for in-mold coating, comprising: [2] The coating composition for in-mold coating according to the above-mentioned [1], wherein the hydrocarbon group contained in the olefin block of the styrene block copolymer (D) is saturated. [3] With respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D), The coating composition for in-mold coating according to the above [1] or [2], wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less. [4] With respect to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C) and the styrene block copolymer (D), The coating composition for coating inside a mold according to any one of the above [1] to [3], wherein the solid content of the styrene block copolymer (D) is from 1 part by mass to 30 parts by mass. [5] The coating composition for coating inside a mold according to any one of the above [1] to [4], wherein the alicyclic skeleton in the first compound (A) is at least one selected from the group consisting of a cyclohexyl group, an isobornyl group, a dicyclopentenyl group, and a dicyclopentanyl group. [6] The coating composition for in-mold coating according to any one of the above [1] to [5], wherein the olefin that is the raw material of the olefin block has 2 or more and 5 or less carbon atoms. [7] The coating composition for coating inside a mold according to any one of the above [1] to [6], wherein the styrene block copolymer (D) comprises at least one first styrene block copolymer (D1) selected from the group consisting of a styrene-ethylene-propylene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, and a styrene-ethylene-butylene-styrene block copolymer. [8] The coating composition for in-mold coating according to the above item [7], wherein the proportion of the first styrene block copolymer (D1) in the styrene block copolymer (D) is 55 mass % or more. [9] The coating composition for coating inside a mold according to any one of the above [1] to [8], further comprising an olefin resin (F).

[10] The coating composition for coating inside a mold according to any one of the above [1] to [9], further comprising at least one (G) of a luster material and a colorant.

[11] A substrate including a non-polar resin; A coated article comprising: a coating film comprising a cured product of the coating composition for in-mold coating according to any one of the above [1] to

[10] , disposed on the substrate. [Industrial Applicability]

[0073] The coating composition for in-mold coating of the present invention has excellent low-temperature curing properties and adhesion to non-polar resin substrates, and therefore can be used for in-mold coating of non-polar resin substrates.

Claims

1. A first compound (A) having an alicyclic skeleton and one reactive double bond; A second compound (B) having one reactive double bond copolymerizable with the first compound (A); a third compound (C) having 2 to 6 reactive double bonds; A styrene block copolymer (D) having a styrene block derived from styrene and an olefin block derived from a linear or branched olefin; A polymerization initiator (E), Relative to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C), and the styrene block copolymer (D), A thermosetting coating composition for inside-mold coating, wherein the solid content of the styrene block copolymer (D) is 1 part by mass or more and 30 parts by mass or less.

2. 2. The thermosetting coating composition for in-mold coating according to claim 1, wherein the hydrocarbon group contained in the olefin block of the styrene block copolymer (D) is saturated.

3. Relative to 100 parts by mass of the total solid content of the first compound (A), the second compound (B), the third compound (C), and the styrene block copolymer (D), 3. The thermosetting coating composition for in-mold coating according to claim 1 or 2, wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less.

4. The thermosetting coating composition for in-mold coating according to claim 1 or 2, wherein the alicyclic skeleton of the first compound (A) is at least one selected from the group consisting of a cyclohexyl group, an isobornyl group, a dicyclopentenyl group and a dicyclopentanyl group.

5. 3. The thermosetting coating composition for in-mold coating according to claim 1, wherein the olefin used as the raw material for the olefin block has a carbon number of 2 or more and 5 or less.

6. The thermosetting coating composition for in-mold coating according to claim 1 or 2, wherein the styrene block copolymer (D) comprises at least one first styrene block copolymer (D1) selected from the group consisting of a styrene-ethylene-propylene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, and a styrene-ethylene-butylene-styrene block copolymer.

7. 7. The thermosetting coating composition for in-mold coating according to claim 6, wherein the proportion of the first styrene block copolymer (D1) in the styrene block copolymer (D) is 55 mass% or more.

8. The thermosetting coating composition for inside-mold coating according to claim 1 or 2, further comprising an olefin resin (F).

9. 3. The thermosetting coating composition for in-mold coating according to claim 1 or 2, further comprising at least one of a luster material and a colorant (G).

10. A substrate including a non-polar resin; A coated article comprising: a coating film comprising a cured product of the thermosetting coating composition for in-mold coating according to claim 1 or 2, disposed on the substrate.

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