Method for manufacturing in-mold coated article

Abstract

According to the present invention, in in-mold coating using a molding machine provided with a fixed mold and a movable mold, a coating composition contains a first compound (A) having an alicyclic skeleton and one reactive double bond, a second compound (B) having one reactive double bond and copolymerizable with the first compound (A), a third compound (C) having between two and six reactive double bonds, inclusive, 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) having a 1 min half-life temperature between 110 °C and 155 °C, inclusive, wherein the temperature of the movable mold from the completion of the injection of the coating composition to the start of the opening of the mold is between 80 °C and 130 °C, inclusive, and the time from the completion of the injection of the coating composition to the start of the opening of the movable mold and the fixed mold is between 30 seconds and 10 minutes, inclusive.

Description

Manufacturing method for in-mold coated products

[0001] The present invention relates to a method for producing an in-mold coated article.

[0002] In recent years, resins have been proposed as a material for automobile parts instead of metals. Patent Documents 1 to 3 disclose coating compositions suitable for resin substrates.

[0003] JP 2002-249680 A JP 2009-019073 A JP 2022-100236 A

[0004] An object of the present invention is to provide a method for producing an in-mold coated article that has excellent curability at low temperature in a short time and excellent adhesion to non-polar resin substrates.

[0005] In order to solve the above problems, the present invention provides the following aspects: [1] An in-mold coating method using a molding machine equipped with a fixed mold and a movable mold, comprising: injecting a coating composition into a gap between the movable mold and a substrate containing a non-polar resin arranged on the surface of the fixed mold, curing the injected coating composition, and opening the movable mold and the fixed mold to remove an in-mold coated article comprising the substrate and a cured product of the coating composition, wherein the coating composition 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) having a half-life temperature within 1 minute of 110°C to 155°C, A method for producing an in-mold coated article, wherein the temperature of the movable mold from the completion of injection of the coating composition until the start of opening the movable mold and the fixed mold is 80°C or higher and 130°C or lower, and the time from the completion of injection of the coating composition until the start of opening the movable mold and the fixed mold is 30 seconds or higher and 10 minutes or lower. [2] A method for producing an in-mold coated article as described in [1] above, wherein the temperature of the substrate is 20°C or higher and 120°C or lower when injection of the coating composition is started. [3] A method for producing an in-mold coated article as described in [1] or [2] above, wherein the viscosity of the coating composition, measured using a Brookfield rotational viscometer at a temperature of 23°C and a rotation speed of 6 rpm, is 150 mPa·s or higher and 2000 mPa·s or lower. [4] A method for producing an in-mold coated article as described in [1] or [2] above, wherein the non-polar resin contained in the substrate is polypropylene. [5] A method for producing an in-mold coated article as described in [1] or [2] above, comprising placing a pre-molded substrate in the fixed mold before injection of the coating composition.[6] The method for producing an in-mold coated article according to [1] or [2] above, further comprising molding the non-polar resin in the molding machine before injecting the coating composition, wherein molding of the non-polar resin and injecting the coating composition are carried out continuously. [7] The method for producing an in-mold coated article according to [1] or [2] above, wherein the solid content of the polymerization initiator (E) is 1 part by mass or more and 5 parts by mass or less per 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). [8] The method for producing an in-mold coated article according to [1] or [2] above, wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less and the solid content of the styrene block copolymer (D) is 1 part by mass or more and 30 parts by mass or less per 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). [9] The method for producing an in-mold coated article according to the above [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.

[10] The method for producing an in-mold coated article according to the above [1] or [2], wherein the coating composition further comprises an olefin resin (F).

[11] The method for producing an in-mold coated article according to the above [1] or [2], wherein the coating composition further comprises at least one of a luster material and a colorant (G).

[0006] According to the present invention, there is provided a method for producing an in-mold coated article which has excellent curability at low temperature in a short time and excellent adhesion to non-polar resin substrates.

[0007] The method for manufacturing an in-mold coated article according to the present disclosure includes in-mold coating using a molding machine equipped with a fixed mold and a movable mold, injecting a coating composition into the gap between the movable mold and a substrate containing a non-polar resin arranged on the surface of the fixed mold, curing the injected coating composition, and opening the movable mold and fixed mold to remove the in-mold coated article comprising the substrate and the cured coating composition.

[0008] The manufacturing method of an in-mold coated article according to the present disclosure is a so-called in-mold coating method. In-mold coating is a method in which a coating composition is injected into the gap between two molds (typically a core and a cavity) and cured without exposure to the atmosphere (particularly oxygen). Specific examples of in-mold coating methods include injection molding, injection compression molding, injection press molding, compression molding, reaction injection molding, and RTM molding. In-mold coating reduces organic solvent and carbon dioxide emissions compared to spray coating. In-mold coating has attracted attention in recent years due to its low environmental impact. In-mold coating is suitable as a method for coating resin substrates.

[0009] Polypropylene is very light and highly processable, making it suitable as a material for automotive components. However, polypropylene is known to have poor adhesion, making it difficult to adhere a coating to a polypropylene substrate. Therefore, to improve adhesion to substrates containing nonpolar resins, such as polypropylene (hereinafter sometimes referred to as nonpolar substrates), coating compositions have traditionally been formulated with structurally similar nonpolar resins (e.g., olefin resins). However, due to differences in polarity, nonpolar resins have low compatibility with other components of the coating composition (e.g., raw material monomers). This can result in reduced stability and increased viscosity of the coating composition. Furthermore, the resulting coating may become cloudy.

[0010] In the present disclosure, a coating composition containing a first compound (A) and a styrene block copolymer (D) is used for in-mold coating of a non-polar substrate. The first compound (A) has an alicyclic skeleton and one reactive double bond. The first compound (A) improves adhesion to the non-polar substrate. Without being bound by any particular theory, the reason for this is thought 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 the non-polar substrate. Because the alicyclic skeleton is bulky, once it penetrates into the non-polar substrate, it is difficult to remove. This allows the coating film formed to adhere to the non-polar substrate via the first compound (A).

[0011] 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 their different structures, but the first compound (A) improves the compatibility between them.

[0012] 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 easily penetrates non-polar substrates. This penetration can occur even at low temperatures (e.g., 80°C or higher and 120°C or lower). However, as described above, the olefin-derived olefin block 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-derived styrene block allows the non-polar portion (olefin-derived olefin block) to be blended into the coating composition.

[0013] In addition, a polymerization initiator (E) is used that has a half-life temperature in one minute of 110°C or more and 155°C or less. This allows the curing reaction of the coating composition to proceed quickly even at a low heating temperature of 80°C or more and 130°C or less, while suppressing the curing reaction during storage (typically, leaving the composition stationary at room temperature of about 25°C).

[0014] In other words, by using the first compound (A) and the styrene block copolymer (D) in combination, the stability of the coating composition is maintained, the increase in viscosity is suppressed, and the adhesion to non-polar substrates is improved. Furthermore, the polymerization initiator (E) enables a curing reaction at low temperature in a short time. This suppresses deformation of the non-polar substrate.

[0015] The adhesion refers to both the initial adhesion and the adhesion after an immersion test (water-resistant adhesion). The in-mold coated article obtained by the present disclosure has excellent initial adhesion and water-resistant adhesion even when cured under low-temperature, short-time conditions.

[0016] "Low temperature" means that the temperature of the movable mold from the completion of injection of the coating composition until the start of opening the movable mold and fixed mold is 80° C. or higher and 130° C. or lower. "Short time" means that the time from the completion of injection of the coating composition until the start of opening the movable mold and fixed mold is 30 seconds or higher and 10 minutes or lower.

[0017] [Paint Composition] First, the paint composition will be described. The paint composition 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) having a half-life temperature in 1 minute of 110°C to 155°C.

[0018] The coating composition may have a viscosity of 150 mPa·s or more and 2000 mPa·s or less, as measured using a Brookfield rotational viscometer at 23°C and 6 rpm. This facilitates uniform injection into a predetermined gap and helps prevent the coating composition from leaking from the molding machine. The viscosity may be 200 mPa·s or more, or 250 mPa·s or more. The viscosity may be 2000 mPa·s or less, 1500 mPa·s or less, 1000 mPa·s or less, or 700 mPa·s or less.

[0019] First Compound (A) The first compound (A) has an alicyclic skeleton and one reactive double bond. Because the alicyclic skeleton has low polarity, the first compound (A) improves the adhesion between the coating film and the non-polar substrate. Because the first compound (A) has only one reactive double bond, it easily penetrates into the non-polar substrate, which 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).

[0020] Examples of the alicyclic skeleton include 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.

[0021] The first compound (A) may be an alicyclic (meth)acrylate. (Meth)acrylate refers to acrylate and methacrylate. Examples of alicyclic (meth)acrylates 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.

[0022] The content of the first compound (A) is preferably 5 parts by mass or more and 70 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). 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.

[0023] 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. The inclusion of the second compound (B) prevents the relative content of the third compound (C) from becoming too high, making it difficult for the flexibility of the coating film to be impaired. Unlike the first compound (A), the second compound (B) does not have an alicyclic skeleton.

[0024] 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.

[0025] The content of the second compound (B) may be 2 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). 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.

[0026] Third Compound (C) The third compound (C) has 2 to 6 reactive double bonds. The third compound (C) forms a three-dimensional crosslinked structure, imparting toughness and appropriate hardness to the coating film.

[0027] 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, and may be, for example, urethane-modified, amine-modified, caprolactone-modified, alkyl-modified, silicone-modified, or polyoxyalkylene-modified.

[0028] The content of the third compound (C) is preferably 10 parts by weight or more and 40 parts by weight or less, relative to 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 likely to be obtained. When the content of the third compound (C) is 40 parts by weight or less, adhesion can be further improved. 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.

[0029] 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 of the coating film to a non-polar substrate, even in the case of low-temperature curing.

[0030] 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.

[0031] From the viewpoint of adhesiveness, the hydrocarbon group contained in the olefin block is preferably saturated, and the hydrocarbon group can be saturated by adding a hydrogen atom to the double bond (hydrogenation).

[0032] The hydrocarbon group contained in the olefin block has a C-C single bond as the main chain. The main chain may contain an unsaturated bond, but is preferably saturated from the viewpoint of adhesiveness. 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 side chain being a hydrocarbon group can further improve adhesiveness. From the viewpoint of adhesiveness, it is preferable that the hydrocarbon group in the side chain is also saturated.

[0033] The styrene block copolymer (D) preferably contains at least one first styrene block copolymer (D1) selected from the group consisting of a styrene-ethylene-propylene block copolymer (SEP), a styrene-ethylene-propylene-styrene block copolymer (SEPS), and a styrene-ethylene-butylene-styrene block copolymer (SEBS). The order of the olefin blocks contained in the first styrene block copolymer (D1) is arbitrary.

[0034] 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, 60% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0035] The content of the styrene block copolymer (D) may be 1 part by mass or more and 30 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). When the content of the styrene block copolymer (D) is 1 part by mass or more, adhesion can be further improved. When the content of the styrene block copolymer (D) is 30 parts by mass or less, it is easy to adjust the viscosity to a level 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, even more preferably 15 parts by mass or less.

[0036] The solid content of the first compound (A) may be 5 parts by mass or more and 70 parts by mass or less, and the solid content of the styrene block copolymer (D) may be 1 part by mass or more and 30 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). This can particularly improve initial adhesion.

[0037] Polymerization Initiator (E) The polymerization initiator (E) generates free radicals and initiates a polymerization reaction of the first compound (A), the second compound (B), and the third compound (C).

[0038] The polymerization initiator is usually selected taking into consideration the curing conditions (temperature and time). In the present disclosure, a polymerization initiator (E) having a one-minute half-life temperature of 110°C or higher and 155°C or lower is used. When the one-minute half-life temperature of the polymerization initiator is 110°C or higher, the curing reaction of the coating composition during storage (typically, when left stationary at room temperature of about 25°C) is suppressed. When the half-life temperature is 155°C or lower, the curing reaction of the coating composition proceeds even if the temperature of the movable mold during the curing process is 130°C or lower. When the half-life temperature is 110°C or higher and 155°C or lower, the curing reaction can be completed in 30 seconds to 10 minutes when the temperature of the movable mold during the curing process is 80°C or higher and 130°C or lower.

[0039] The half-life temperature in one minute is the temperature at which the concentration of the polymerization initiator is reduced to half in one minute. Since the decrease in the concentration of the polymerization initiator occurs due to a decomposition reaction, the half-life temperature indicates the ease of radical generation, i.e., the ease of the curing reaction.

[0040] The half-life temperature of the polymerization initiator (E) in one minute may be 120° C. or higher or 125° C. or higher from the viewpoint of handleability. The half-life temperature may be 140° C. or lower or 135° C. or lower from the viewpoint of curability and suppressing unreacted polymerization initiator.

[0041] The solid content of the polymerization initiator (E) is preferably 1 part by mass or more and 5 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). From the viewpoint of adhesion, the content of the polymerization initiator (E) is preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more. From the viewpoint of reducing the influence of unreacted polymerization initiator (E), the content of the polymerization initiator (E) is preferably 4 parts by mass or less, more preferably 3 parts by mass or less.

[0042] 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 diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; peroxycarbonates such as bis(t-butylcyclohexyl)peroxydicarbonate; organic peroxides such as 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).

[0043] Olefin Resin (F) The coating composition may contain an olefin resin (F). Because olefin resins are either non-polar or have low polarity, they have a high affinity with non-polar substrates. This is expected to further improve adhesion between the coating composition and non-polar substrates. 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 a coating composition in the presence of the styrene block copolymer (D), a decrease in stability and an increase in viscosity of the coating composition can be suppressed.

[0044] 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.

[0045] The solid content of the olefin resin (F) is preferably 1 part by mass or more and 10 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). From the viewpoint of adhesion, the content of the olefin resin (F) is preferably 1 part by mass or more, 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, more preferably 7 parts by mass or less.

[0046] - Luster material / colorant (G) The coating composition may contain at least one of a lustrous material and a colorant (hereinafter sometimes referred to as a lustrous material / colorant) (G), which improves the design properties.

[0047] 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 chromatic 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.

[0048] Examples of dyes include azo dyes, triphenylmethane dyes, chromium complexes, and cobalt complexes, which may be used alone or in combination of two or more.

[0049] 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.

[0050] 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).

[0051] Others The coating composition may contain other components such as other pigments (e.g., extender pigments), antifoaming agents, ultraviolet absorbers, light stabilizers, polymerization inhibitors, surface conditioners, film-forming aids, rust inhibitors, and mold release agents.

[0052] The coating composition can be obtained by mixing the above components. Mixing can be carried out, for example, using a disperser (a mixer). Examples of dispersers include low-speed mixers such as a propeller mixer, a paddle mixer, and an anchor mixer; and high-speed mixers such as a homomixer, a disperser mixer, and an ultra mixer.

[0053] [In-mold coated article] The in-mold coated article comprises a non-polar substrate and a cured product of the coating composition described above disposed on the non-polar substrate. The thickness of the cured product is, for example, 20 μm or more and 1 mm or less.

[0054] Non-polar substrate 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 from the non-polar resin.

[0055] A non-polar resin has a surface tension of 32 dyne / cm or less. Such a resin has no polarity or only a very small polarity.

[0056] 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 copolymers, and polypropylene block copolymers; cyclic olefin copolymers; polystyrene; fluorinated resins; silicone resins; epoxy silicone resins; and silicone elastomers. Among these, various polypropylenes may be used. The coating composition used in the present disclosure exhibits high adhesion, particularly to substrates containing polypropylene.

[0057] On the cured product of the in-mold coating, another coating film (for example, a clear coating film) can be further formed. The other coating film can be formed, for example, by spray coating.

[0058] [Method for manufacturing an in-mold coated article] The method for manufacturing an in-mold coated article according to the present disclosure involves in-mold coating using a molding machine equipped with a fixed mold and a movable mold, injecting the above-mentioned coating composition into a gap between the movable mold and a non-polar substrate arranged on the surface of the fixed mold, curing the injected coating composition, and opening the movable mold and the fixed mold to remove the in-mold coated article comprising the non-polar substrate and a cured product of the coating composition. The curing is carried out in a state where the atmosphere is blocked.

[0059] The temperature of the movable mold when the injection of the coating composition begins is 80° C. or higher and 130° C. or lower. The time from the completion of the injection of the coating composition until the start of opening the movable mold and fixed mold is 30 seconds or higher and 10 minutes or lower. In the present disclosure, a curing reaction can be performed at a low temperature in a short time.

[0060] (1) Preparation of Non-Polar Substrate A non-polar substrate is prepared. The non-polar substrate may be pre-molded into a predetermined shape. That is, the method for producing an in-mold coated article according to the present disclosure may include placing the pre-molded non-polar substrate on the surface of a fixed mold before injecting the coating composition.

[0061] The non-polar substrate may be molded in the molding machine. That is, the method for producing an in-mold coated article according to the present disclosure may include molding a substrate from a non-polar resin in the molding machine before injecting the coating composition. For example, a non-polar resin melted by heating is injected into the gap between the fixed mold and the movable mold and then cooled. This results in a non-polar substrate molded into a predetermined shape.

[0062] The molding of the non-polar resin may be carried out continuously with the injection of the coating composition described below. This increases productivity. "The molding of the non-polar resin and the injection of the coating composition are carried out continuously" means, for example, that the coating composition is injected into the gap between the non-polar substrate placed on the surface of the fixed mold and the movable mold without removing the molded non-polar substrate from the mold. In continuous processing, the movable mold used for molding the non-polar substrate and the movable mold used for injecting the coating composition may be the same or different.

[0063] (2) Injection of the coating composition The molded non-polar substrate is placed on the surface of the fixed mold. Next, the fixed mold and the movable mold are opened and placed in a predetermined position, and the coating composition is injected into the gap between the non-polar substrate and the movable mold.

[0064] When injection of the coating composition begins, the temperature of the movable mold may be 80°C or higher and 130°C or lower. When the temperature of the movable mold is 80°C or higher, curing of the coating composition begins quickly, improving productivity. In addition, the curing reaction proceeds appropriately, improving adhesion. When the temperature of the movable mold is 130°C or lower, deformation of the non-polar substrate is suppressed. The temperature of the movable mold may be 100°C or higher, or may be 110°C or higher. The temperature of the movable mold may be 120°C or lower.

[0065] The temperature of the movable mold may be the actual temperature of the movable mold surface measured by a contact or non-contact thermometer. The surface temperature is measured at any location of the movable mold (for example, an end or center). The surface temperature at any one location of the movable mold may be 80°C or higher and 130°C or lower, and the surface temperatures at other locations may be outside this range. The temperature of the movable mold may also be the heating temperature set in the molding machine.

[0066] When the injection of the coating composition is started, the temperature of the non-polar substrate may be 20° C. or higher and 120° C. or lower. That is, when the injection of the coating composition is started, the non-polar substrate may be heated or may not be heated. The non-polar substrate can be heated by heating the fixed mold.

[0067] When the temperature of the non-polar substrate is 20°C or higher, the curing reaction proceeds more easily, and adhesion can be further improved. When the temperature of the non-polar substrate is 120°C or lower, deformation of the non-polar substrate is easily suppressed. The temperature of the non-polar substrate may be 60°C or higher, or may be 100°C or higher. The temperature of the non-polar substrate may be 110°C or lower.

[0068] The temperature of the non-polar substrate may be an actual measured value of the temperature of the surface of the non-polar substrate measured with a contact or non-contact thermometer. The surface temperature is measured at any location (for example, an end or a center) of the non-polar substrate. The surface temperature at any one location of the non-polar substrate may be 20°C or higher and 120°C or lower, and the surface temperatures at other locations may be outside this range. The temperature of the non-polar substrate may also be a predicted value predicted from the heating temperature and heating time.

[0069] (3) Hardening of the coating composition After the coating composition has been poured, the movable mold is moved as necessary to close the mold. The interior of the mold may be degassed using a vacuum pump or the like. The interior of the mold may also be pressurized.

[0070] Hereinafter, the time from the completion of injection of the coating composition to the start of opening the movable mold and the fixed mold will be referred to as the curing time. The process from the completion of injection of the coating composition to the start of opening the movable mold and the fixed mold will be referred to as the curing process.

[0071] The temperature of the movable mold in the curing step is 80°C or higher and 130°C or lower. When the temperature of the movable mold is 80°C or higher, excellent adhesion is obtained. When the temperature of the movable mold is 130°C or lower, deformation of the non-polar substrate is suppressed. The temperature of the movable mold may be 100°C or higher, or may be 110°C or higher. The temperature of the movable mold may be 120°C or lower. The curing reaction of the coating composition used in the present disclosure proceeds at such low temperatures.

[0072] In the curing step, the temperature of the movable mold is allowed to fluctuate, as long as the average temperature of the movable mold in the curing step (hereinafter also referred to as the curing temperature) is 80°C or higher and 130°C or lower.

[0073] The curing time is 30 seconds to 10 minutes, and the curing reaction of the coating composition used in the present disclosure is completed in such a short time.

[0074] The temperature of the non-polar substrate in the curing step is not particularly limited. The temperature of the non-polar substrate in the curing step may be higher than 20°C. The temperature of the non-polar substrate in the curing step may be similar to the temperature of the movable mold. From the viewpoint of suppressing deformation, the temperature of the non-polar substrate in the curing step may be 120°C or less.

[0075] The curing time can be adjusted by the curing temperature. For example, as follows: (Aspect 1) When the curing temperature is 80°C or higher and 100°C or lower, the curing time may be 5 minutes or higher and 10 minutes or lower. (Aspect 2) When the curing temperature is higher than 100°C and lower than 120°C, the curing time may be 1 minute or higher and 5 minutes or lower. (Aspect 3) When the curing temperature is 120°C or higher and 130°C or lower, the curing time may be 30 seconds or higher and 3 minutes or lower.

[0076] In the embodiments 1 to 3, the temperature of the non-polar substrate during the curing step is not particularly limited. In the present disclosure, all of the above embodiments 1 to 3 are satisfied.

[0077] (4) Removal of In-Mold Coated Product The movable mold and the fixed mold are opened to remove the in-mold coated product comprising the non-polar substrate and the cured product of the coating composition. This gives an in-mold coated product.

[0078] The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0079] 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) (trade name "Tuftec H1517", manufactured by Asahi Kasei Corporation, SEBS), and the mixture was left to stand at room temperature for 12 hours to swell the styrene block copolymer (D1-1).

[0080] The mixture was then heated to 90°C with 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 a third compound (C-1) (dimethylol-tricyclodecane diacrylate) and 15 parts by weight of a third compound (C-3) (trade name "Ebecryl 8402", manufactured by Daicel Allnex Corporation) were added and stirred until uniform. After cooling to room temperature, 2 parts by weight of a polymerization initiator (E) (t-butylperoxy-2-ethylhexanate) was added and stirred to obtain a coating composition.

[0081] (2) Preparation of in-mold coated object A 200 mm x 200 mm polypropylene (PP) substrate was surface degreased with isopropyl alcohol. A 200 μm thick tape was then attached to the surface of the PP substrate to create a frame. The PP substrate was then placed on a 300 mm x 300 mm x 10 mm metal plate (fixed mold) and placed in a dryer set to a predetermined temperature (23 ° C, 50 ° C, or 80 ° C).

[0082] After confirming with a contact thermometer that the PP substrate was at the specified temperature, approximately 10 g of the coating composition was dropped into the frame of the PP substrate. A 300 mm × 300 mm × 10 mm metal plate (movable mold) separately heated to a specified temperature (100°C, 110°C, or 120°C) was placed over the PP substrate to shut out air, and the mold was heated at the specified temperature for a specified time (1 minute, 3 minutes, or 5 minutes) to obtain an in-mold coated product.

[0083] [Examples 2 to 14, Comparative Examples 1 to 5] Coating compositions were prepared and in-mold coated articles were produced using the same procedure as in Example 1, except that the types or amounts of components used to prepare the coating compositions were changed as shown in Table 1. The "temperature of the movable mold" listed in Table 1 is the average temperature of the actual measurements on the surface at the center of the movable mold from the start of injection of the coating composition to the end of the curing process. The "temperature of the non-polar substrate" listed in Table 1 is the average temperature of the actual measurements on the surface at the center of the non-polar substrate from the start of injection of the coating composition to the end of the curing process. The symbols in Table 1 are explained below.

[0084] First Compound (A) A-1: ​​dicyclopentanyl acrylate A-2: cyclohexyl methacrylate A-3: isobornyl acrylate

[0085] Second Compound (B) B-1: Styrene B-2: t-butyl methacrylate B-3: Lauryl acrylate B-4: Hydroxypropyl methacrylate

[0086] Third Compound (C) C-1: Dimethylol-tricyclodecane diacrylate C-2: Dipentaerythritol hexaacrylate C-3: Trade name "Ebecryl 8402", manufactured by Daicel Allnex Corporation, bifunctional aliphatic urethane acrylate

[0087] Styrene block copolymer (D) (First styrene block copolymer (D1)) D1-1: Trade name "Tuftec H1517", manufactured by Asahi Kasei Corporation, SEBS block copolymer, styrene content 43% by mass D1-2: Trade name "Septon 1020", manufactured by Kuraray Co., Ltd., SEP block copolymer, styrene content 36% by mass

[0088] Polymerization initiators (E) E-1: t-butylperoxy-2-ethylhexanate, trade name: Luperox 26, manufactured by Arkema Yoshitomi Co., Ltd., 1-minute half-life temperature: 127°C E-2: t-amylperoxyisononanoate, trade name: Luperox 570, manufactured by Arkema Yoshitomi Co., Ltd., 1-minute half-life temperature: 152°C E-3: t-amylperoxy-oxypivalate (70%), trade name: Perbutyl PV, manufactured by NOF Corporation, 1-minute half-life temperature: 110°C

[0089] Polymerization initiator e-1: di-t-hexyl peroxide, trade name: Perhexyl D, manufactured by NOF Corporation, 1-minute half-life temperature: 177°C

[0090] [Evaluation] The in-mold coated articles of the Examples and Comparative Examples were evaluated as follows.

[0091] (1) Initial Adhesion Using a cutter, the coating film of the in-mold coated object 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 taking care not to trap air bubbles, and then pressed down, after which the cellophane tape was quickly peeled off. The number of squares that peeled off together with the cellophane tape was counted. A rating of C or higher can be evaluated as having good adhesion. A: No peeling B: Not completely peeled off, but some chipping was observed in the grid C: 1 to 5 squares peeled off D: 6 or more squares peeled off

[0092] (2) Water-resistant adhesion The coated molded object was immersed in warm water at 40°C for 240 hours, then removed and dried for 10 minutes. The coating film was then cross-cut in the same manner as above to evaluate adhesion. A rating of C or higher was considered to have water-resistant adhesion.

[0093] (3) Bending resistance A test piece measuring 150 mm in length and 15 mm in width was cut out from the in-mold coated product. The test piece was bent 90° near the center in the longitudinal direction over one second. The condition of the coating film around the bent part was evaluated visually according to the following criteria. A rating of C or higher can be evaluated as having bending resistance. A: No abnormalities B: Slight wrinkles C: Wrinkles D: Cracks

[0094]

[0095] The coating films of Examples 1 to 14 exhibited good initial adhesion and water-resistant adhesion even when the temperature of the movable mold in the curing step (curing temperature) was 100°C.

[0096] The coating composition of Comparative Example 1 had a half-life temperature of over 155°C in 1 minute. Therefore, the adhesion was low even at a curing temperature of 120°C. This is thought to be because even at 120°C, the amount of radicals generated was small, resulting in insufficient crosslinking, and in addition, the unreacted compounds and polymerization initiator acted like a plasticizer in the coating film.

[0097] The coating composition of Comparative Example 2 does not contain a styrene block copolymer (D). As a result, the initial adhesion was poor at a curing temperature of 100°C, and the water-resistant adhesion was low at all curing temperatures. The coating composition of Comparative Example 3 does not contain a first compound (A). As a result, the initial adhesion was poor at a curing temperature of 100°C, and the water-resistant adhesion was low at all curing temperatures. In addition, the compatibility of the coating composition was also low. The coating composition of Comparative Example 4 does not contain a second compound (B). As a result, the water-resistant adhesion was low at all curing temperatures, and the flex resistance was also poor. The coating composition of Comparative Example 5 does not contain a third compound (C). As a result, the resulting coating film had poor film-forming performance, and the adhesion and flex resistance could not be evaluated.

[0098] The present disclosure includes the following aspects: [1] An in-mold coating method using a molding machine equipped with a fixed mold and a movable mold, comprising: injecting a coating composition into a gap between the movable mold and a substrate containing a non-polar resin arranged on the surface of the fixed mold, curing the injected coating composition, and opening the movable mold and the fixed mold to remove an in-mold coated article comprising the substrate and a cured product of the coating composition, wherein the coating composition 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) having a half-life temperature within 1 minute of 110°C to 155°C,

[0014] A method for producing an in-mold coated article, wherein the temperature of the movable mold from the completion of injection of the coating composition until the start of opening the movable mold and the fixed mold is 80°C or higher and 130°C or lower, and the time from the completion of injection of the coating composition until the start of opening the movable mold and the fixed mold is 30 seconds or higher and 10 minutes or lower. [2] A method for producing an in-mold coated article as described in [1] above, wherein the temperature of the substrate is 20°C or higher and 120°C or lower when injection of the coating composition is started. [3] A method for producing an in-mold coated article as described in [1] or [2] above, wherein the viscosity of the coating composition, measured using a Brookfield rotational viscometer at a temperature of 23°C and a rotation speed of 6 rpm, is 150 mPa·s or higher and 2000 mPa·s or lower. [4] A method for producing an in-mold coated article as described in any of [1] to [3] above, wherein the non-polar resin contained in the substrate is polypropylene. [5] A method for producing an in-mold coated product according to any one of [1] to [4] above, which comprises placing a pre-molded substrate in the fixed mold before injecting the coating composition. [6] A method for producing an in-mold coated product according to any one of [1] to [4] above, which further comprises molding the non-polar resin in the molding machine before injecting the coating composition, and which comprises molding the non-polar resin and injecting the coating composition continuously.[7] The method for producing an in-mold coated article according to any one of [1] to [6] above, wherein the solid content of the polymerization initiator (E) is 1 part by mass or more and 5 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). [8] The method for producing an in-mold coated article according to any one of [1] to [7] above, wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less, and the solid content of the styrene block copolymer (D) is 1 part by mass or more and 30 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). [9] The method for producing an in-mold coated article according to any one of the above [1] to [8], 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.

[10] The method for producing an in-mold coated article according to any one of the above [1] to [9], wherein the coating composition further comprises an olefin resin (F).

[11] The method for producing an in-mold coated article according to any one of the above [1] to

[10] , wherein the coating composition further comprises at least one of a luster material and a colorant (G).

[0099] The production method of the present invention is suitable for producing in-mold coated articles on non-polar resin substrates at low temperatures in a short time.

[0100] This application claims priority based on Japanese Patent Application No. 2023-218342, filed on December 25, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. In in-mold coating using a molding machine including a fixed mold and a movable mold, injecting a coating composition into a gap between a base material containing a nonpolar resin disposed on the surface of the fixed mold and the movable mold, curing the injected coating composition, and opening the movable mold and the fixed mold to take out an in-mold coating including the base material and a cured product of the coating composition, wherein the coating composition includes: 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 or more and six or less 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) having a half-life temperature of 110°C or higher and 155°C or lower in one minute, and the temperature of the movable mold from when the injection of the coating composition is completed until the movable mold and the fixed mold start to open is 80°C or higher and 130°C or lower, and the time from when the injection of the coating composition is completed until the movable mold and the fixed mold start to open is 30 seconds or longer and 10 minutes or shorter. A method for manufacturing an in-mold coating.

2. The method for manufacturing an in-mold coating according to claim 1, wherein the temperature of the base material is 20°C or higher and 120°C or lower when the injection of the coating composition is started.

3. The method for manufacturing an in-mold coating according to claim 1 or 2, wherein the coating composition has a viscosity of 150 mPa·s or higher and 2000 mPa·s or lower as measured using a Brookfield rotational viscometer at a temperature of 23°C and a rotation speed of 6 rpm.

4. The method for manufacturing an in-mold coating according to any one of claims 1 to 3, wherein the nonpolar resin contained in the base material is polypropylene.

5. The method for manufacturing an in-mold coating according to any one of claims 1 to 4, further comprising installing the pre-molded base material on the fixed mold before injecting the coating composition.

6. The method for manufacturing an in-mold coating according to any one of claims 1 to 4, further comprising molding the nonpolar resin in the molding machine before injecting the coating composition, and the molding of the nonpolar resin and the injection of the coating composition are performed continuously.

7. The method for producing an in-mold coating according to any one of claims 1 to 6, wherein the solid content of the polymerization initiator (E) is 1 part by mass or more and 5 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).

8. The method for producing an in-mold coating according to any one of claims 1 to 7, wherein the solid content of the first compound (A) is 5 parts by mass or more and 70 parts by mass or less, and the solid content of the styrene block copolymer (D) is 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).

9. The method for producing an in-mold coating according to any one of claims 1 to 8, 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.

10. The method for producing an in-mold coating according to any one of claims 1 to 9, wherein the coating composition further contains an olefin resin (F).

11. The method for producing an in-mold coating according to any one of claims 1 to 10, wherein the coating composition further contains at least one of a brightening agent and a colorant (G).

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