In-mold coating composition and method for producing in-mold coated molded article

Abstract

To provide an in-mold coating composition that can form an in-mold coated molded article that has excellent solvent resistance and hot water resistance.SOLUTION: An in-mold coating composition includes: a scaly pigment (A); a bifunctional polymerizable compound (B) having a molecular weight of 180 to 600; a monofunctional polymerizable compound (C) having an alicyclic structure; a multifunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000; and a polymerization initiator (E).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an in-mold coating composition and a method for producing an in-mold coated molded article. [Background technology]

[0002] Molded products obtained from fiber-reinforced plastic moldings made of glass fiber, carbon fiber, organic fiber, mineral fiber, etc., with a thermosetting resin or thermoplastic resin matrix, such as sheet molding compound (SMC), bulk molding compound (BMC), and stampable sheet, are excellent in mechanical strength and moldability, and are lightweight. As such, they are widely used as alternative materials to metals in fields such as electrical equipment such as parabolic antennas, automobile exterior panels, and housing equipment parts.

[0003] However, these molded products have surface defects such as pinholes, voids, microcracks, and fiber patterns, and also have problems such as low gloss, poor appearance quality, poor weather resistance, water resistance, chemical resistance, and low hardness. In order to solve these problems, an in-mold coating method has been proposed.

[0004] For example, Patent Document 1 describes an in-mold coating composition for fiber-reinforced plastic moldings, which contains (A) a vehicle component consisting of (i) 10 to 70% by weight of a urethane acrylate or urethane methacrylate represented by general formula (I), (ii) 5 to 50% by weight of a thermoplastic polymer having a glass transition temperature of 30°C or higher, and (iii) 25 to 70% by weight of a radically polymerizable monomer, (B) a mold release agent, and (C) a polymerization initiator. Patent Document 2 describes an in-mold coating composition containing (A) at least one selected from a urethane oligomer, epoxy oligomer, polyester oligomer, polyether oligomer, or unsaturated polyester resin having a (meth)acryloyl group, (B) a monomer copolymerizable with the above (A), (C) an allyl ester oligomer, and (D) a polymerization initiator in specific ratios. Patent Document 3 describes an in-mold coating composition for fiber-reinforced plastic moldings, which comprises at least a urethane (meth)acrylate (A), a monofunctional ethylenically unsaturated monomer (B) having an alicyclic structure, at least one monofunctional ethylenically unsaturated monomer (C) copolymerizable with (A) and (B), a mold release agent (D), and an initiator (E), wherein at least one of the urethane (meth)acrylates (A) has a weight-average molecular weight of 600 or more and 7000 or less and further has a functionality of 2 or more and 4 or less. Patent Document 4 describes a thermosetting coating composition for plastic materials, which contains a urethane (meth)acrylate (A) having 2 to 4 polymerizable unsaturated groups and an aliphatic structure, a polymerizable unsaturated compound (B) having one polymerizable unsaturated group in one molecule, and a polymerization initiator (C). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-70712 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-51124 [Patent Document 3] Patent No. 6800392 [Patent Document 4] Patent No. 7370500 Summary of the Invention [Problem to be solved by the invention]

[0006] In some cases, an in-mold coating composition is required to have both solvent resistance and warm water resistance.

[0007] An object of one embodiment of the present disclosure is to provide an in-mold coating composition that can form an in-mold coated molded article that has excellent solvent resistance and hot water resistance. Another problem to be solved by another embodiment of the present disclosure is to provide a method for producing an in-mold coated molded article that has excellent solvent resistance and hot water resistance. [Means for solving the problem]

[0008] The present disclosure includes the following aspects. <1> An in-mold coating composition comprising: a scaly pigment (A); a bifunctional polymerizable compound (B) having a molecular weight of 180 to 600; a monofunctional polymerizable compound (C) having an alicyclic structure; a polyfunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000; and a polymerization initiator (E). <2> For fiber reinforced plastics or thermosetting plastics, <1> The in-mold coating composition according to claim 1. <3> The content of the bifunctional polymerizable compound (B) is 1% by mass to 30% by mass based on the total amount of the in-mold coating composition. <1> or <2> The in-mold coating composition according to claim 1. <4> The polyfunctional polymerizable compound (D) is a difunctional to tetrafunctional urethane acrylate. <1> ~ <3> 10. The in-mold coating composition according to claim 9, wherein the in-mold coating composition is a coating composition for a mold. <5> The total content of all pigments contained in the in-mold coating composition is 15% by mass to 60% by mass based on the total amount of the in-mold coating composition. <1> ~ <4> 10. The in-mold coating composition according to claim 9, wherein the in-mold coating composition is a coating composition for a mold. <6> The ratio of the scaly pigment (A) to the pigments contained in the in-mold coating composition is 10 mass% or more. <1> ~ <5> 10. The in-mold coating composition according to claim 9, wherein the in-mold coating composition is a coating composition for a mold. <7> a step of clamping a mold including a fixed mold portion and a movable mold portion; A step of molding a fiber-reinforced plastic or a thermosetting plastic in a mold cavity to produce a resin molded body; into the mold cavity, <1> ~ <6> a step of injecting the in-mold coating composition according to any one of the above items to form a coating film on a resin molded body; a step of curing the coating film to form a cured film; and removing the resin molded article on which the cured film has been formed from the mold. <8> In the step of producing the resin molded body, a fiber reinforced plastic or a thermosetting plastic is molded using an injection molding method, an injection compression molding method, an injection press molding method, a compression molding method, or a reaction injection molding method. <7> 1. A method for producing the in-mold coated molded article according to claim 1. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, there is provided an in-mold coating composition capable of forming an in-mold coated molded article having excellent solvent resistance and hot water resistance. According to another embodiment of the present disclosure, there is provided a method for producing an in-mold coated molded article having excellent solvent resistance and hot water resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams illustrating a method for producing an in-mold coated molded body using a compression molding method. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in an example. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the present disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In the present disclosure, (meth)acrylate is a concept that encompasses both acrylate and methacrylate.

[0013] [In-mold coating composition] The in-mold coating composition according to the present disclosure comprises a scaly pigment (A), a bifunctional polymerizable compound (B) having a molecular weight of 180 to 600, a monofunctional polymerizable compound (C) having an alicyclic structure, a multifunctional polymerizable compound (D) having a weight average molecular weight of 1,000 to 20,000, and a polymerization initiator (E).

[0014] The in-mold coating composition according to the present disclosure can form an in-mold coated molded article that is excellent in solvent resistance and hot water resistance. The reason for this effect is not clear, but is presumed to be as follows.

[0015] It is believed that both solvent resistance and hot water resistance were achieved by combining the scaly pigment (A), the bifunctional polymerizable compound (B) having a molecular weight of 180 to 600, the monofunctional polymerizable compound (C) having an alicyclic structure, the multifunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000, and the polymerization initiator (E). In particular, while resistance to hot water is generally limited to about 40°C, the in-mold coating composition according to the present disclosure exhibits excellent resistance to hot water at higher temperatures (e.g., 65°C or higher).

[0016] Each component contained in the in-mold coating composition according to the present disclosure will be described below.

[0017] <Scaly pigment (A)> The in-mold coating composition according to the present disclosure contains a scaly pigment (A). The in-mold coating composition may contain only one type of scaly pigment (A), or may contain two or more types of scaly pigment (A).

[0018] The scaly pigment (A) is not particularly limited as long as it is a scaly pigment. In the present disclosure, "scale-like" means that the aspect ratio is 2 or greater.

[0019] The aspect ratio is the ratio of the long diameter to the short diameter of a particle. It is calculated by taking the average value of 100 particles in an electron microscope photograph.

[0020] Examples of the scaly pigment (A) include metal pigments such as zinc, nickel, chromium, tin, copper, silver, platinum, gold, and aluminum; glass flakes, talc, mica, kaolin clay, and micaceous iron oxide. Among these, from the viewpoint of warm water resistance, the scaly pigment (A) is preferably glass flake, talc, or mica, and more preferably mica.

[0021] The metal pigments also include pigments of alloys such as stainless steel, etc. For example, talc and mica may be surface-treated with a metal oxide such as titanium oxide.

[0022] The aspect ratio of the scaly pigment (A) is preferably 2 to 120, more preferably 3 to 100, and even more preferably 5 to 100, from the viewpoint of improving adhesion. The average particle size of the scaly pigment (A) is preferably 0.5 μm to 50 μm, and more preferably 3 μm to 40 μm. The particle size refers to the longest diameter of a projected surface. The average value of 100 particles in an electron microscope photograph is used.

[0023] The content of the scaly pigment (A) is preferably 6% by mass to 60% by mass, and more preferably 10% by mass to 50% by mass, based on the total amount of the in-mold coating composition.

[0024] The in-mold coating composition according to the present disclosure may contain a pigment other than the scaly pigment (A). The type of other pigment is not particularly limited, and may be an extender pigment or a coloring pigment.

[0025] From the viewpoints of reducing cure shrinkage, preventing excessively high internal stress, and achieving excellent adhesion, the total content of all pigments contained in the in-mold coating composition is preferably 15% by mass to 60% by mass, and more preferably 25% by mass to 60% by mass, relative to the total amount of the in-mold coating composition.

[0026] From the viewpoint of improving water resistance, the proportion of the scaly pigment (A) in the pigment contained in the in-mold coating composition is preferably 10% by mass or more, and more preferably 20% by mass or more. The upper limit of the proportion of the scaly pigment (A) in the pigment is not particularly limited, and may be 100% by mass.

[0027] <Bifunctional polymerizable compound (B)> The in-mold coating composition according to the present disclosure contains a bifunctional polymerizable compound (B) having a molecular weight of 180-600. The bifunctional polymerizable compound (B) contained in the in-mold coating composition may be one type only, or may be two or more types.

[0028] The molecular weight of the bifunctional polymerizable compound (B) is 180-600, preferably 180-400, more preferably 180-300, and even more preferably 180-250. The molecular weight of the bifunctional polymerizable compound (B) is calculated based on the type and number of atoms constituting the bifunctional polymerizable compound (B).

[0029] When the molecular weight of the bifunctional polymerizable compound (B) is 180 or more, cure shrinkage is reduced, internal stress does not become too high, and adhesion is excellent. When the molecular weight of the bifunctional polymerizable compound (B) is 600 or less, the crosslinking density increases, and therefore the solvent resistance improves.

[0030] The bifunctional polymerizable compound (B) is a compound having a polymerizable group. The type of polymerizable group is not particularly limited, and the polymerizable group may be a cationically polymerizable group or a radically polymerizable group. From the viewpoint of curability, the polymerizable group is preferably a radically polymerizable group.

[0031] From the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group, more preferably a (meth)acryloyloxy group.

[0032] The bifunctional polymerizable compound (B) is a polymerizable compound having two polymerizable groups, and is preferably a bifunctional (meth)acrylate.

[0033] The structure of the bifunctional polymerizable compound (B) is not particularly limited, but it preferably contains at least one selected from the group consisting of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a cyclic ether group. The aliphatic hydrocarbon group is preferably a linear alkylene group or a branched alkylene group.

[0034] Examples of the bifunctional polymerizable compound (B) include 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate.

[0035] The content of the bifunctional polymerizable compound (B) is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, based on the total amount of the in-mold coating composition. When the content of the bifunctional polymerizable compound (B) is 1% by mass or more, the crosslink density increases, and therefore the solvent resistance improves. When the content of the bifunctional polymerizable compound (B) is 30% by mass or less, cure shrinkage is reduced, internal stress does not become too high, and adhesion is excellent.

[0036] <Monofunctional polymerizable compound having an alicyclic structure (C)> The in-mold coating composition according to the present disclosure contains a monofunctional polymerizable compound (C) having an alicyclic structure. The monofunctional polymerizable compound (C) having an alicyclic structure contained in the in-mold coating composition may be one type only, or two or more types.

[0037] The monofunctional polymerizable compound (C) is a compound having a polymerizable group. The type of polymerizable group is not particularly limited, and the polymerizable group may be a cationically polymerizable group or a radically polymerizable group. From the viewpoint of curability, the polymerizable group is preferably a radically polymerizable group. The radically polymerizable group may be a photo-radical polymerizable group or a thermally radical polymerizable group.

[0038] From the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group, more preferably a (meth)acryloyloxy group.

[0039] The monofunctional polymerizable compound (C) is a polymerizable compound having one polymerizable group, and is preferably a monofunctional (meth)acrylate.

[0040] The monofunctional polymerizable compound (C) has an alicyclic structure. Examples of the alicyclic structure include a tricyclodecane ring structure, a cyclohexane ring structure, a norbornene ring structure, and an adamantane ring structure.

[0041] Examples of the monofunctional polymerizable compound (C) include (meth)acrylates having a tricyclodecane ring structure, such as dicyclopentanyl (meth)acrylate and dicyclopentanyloxyethyl (meth)acrylate; (meth)acrylates having a cyclohexane ring structure, such as cyclohexyl (meth)acrylate; (meth)acrylates having a norbornene ring structure, such as isobornyl (meth)acrylate; and (meth)acrylates having an adamantane ring structure, such as 1-adamantyl (meth)acrylate.

[0042] The content of the monofunctional polymerizable compound (C) is preferably 10% by mass to 35% by mass, and more preferably 15% by mass to 30% by mass, based on the total amount of the in-mold coating composition.

[0043] <Polyfunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000> The in-mold coating composition according to the present disclosure contains a polyfunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000. The polyfunctional polymerizable compound (D) having an alicyclic structure contained in the in-mold coating composition may be one type only, or two or more types.

[0044] The weight average molecular weight of the polyfunctional polymerizable compound (D) is 1,000 to 20,000, preferably 1,500 to 20,000, and more preferably 2,000 to 15,000. When the weight average molecular weight of the polyfunctional polymerizable compound (D) is 1,000 or more, cure shrinkage is reduced, internal stress does not become too high, and adhesion is excellent. When the weight average molecular weight of the polyfunctional polymerizable compound (D) is 20,000 or less, the curing rate is sufficient, and the adhesiveness and solvent resistance are excellent.

[0045] In this disclosure, the weight average molecular weight is measured by size exclusion chromatography using polystyrene as the standard.

[0046] The polyfunctional polymerizable compound (D) is a compound having a polymerizable group. The type of polymerizable group is not particularly limited, and the polymerizable group may be a cationically polymerizable group or a radically polymerizable group.

[0047] From the viewpoint of curability, the polymerizable group is preferably a radically polymerizable group.

[0048] From the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group, more preferably a (meth)acryloyloxy group.

[0049] The polyfunctional polymerizable compound (D) is a polymerizable compound having two or more polymerizable groups. The number of polymerizable groups in the polyfunctional polymerizable compound (D) is preferably 2 to 4, and more preferably 2 or 3.

[0050] By having 2 to 4 polymerizable groups, cure shrinkage is reduced, internal stress does not become too high, and adhesion is excellent.

[0051] The structure of the polyfunctional polymerizable compound (D) is not particularly limited, but the polyfunctional polymerizable compound (D) is preferably at least one selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate.

[0052] Among these, from the viewpoints of elongation, hardness, and solvent resistance, the polyfunctional polymerizable compound (D) is preferably a urethane (meth)acrylate, and more preferably a difunctional to tetrafunctional urethane acrylate.

[0053] Urethane (meth)acrylates can be obtained, for example, by reacting an isocyanate compound, a polyol compound, and a hydroxyl group-containing (meth)acrylate. Examples of isocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of polyol compounds include an adduct of hydrogenated bisphenol A and ethylene oxide, hydrogenated bisphenol A, neopentyl glycol, 1,6-hexanediol, and trimethylolpropane. Examples of hydroxyl group-containing (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0054] Among these, from the viewpoint of weather resistance, the urethane (meth)acrylate is preferably an aliphatic urethane (meth)acrylate, which can be obtained, for example, by reacting an aliphatic isocyanate, an aliphatic polyol, and a hydroxy group-containing (meth)acrylate.

[0055] The epoxy (meth)acrylate can be obtained, for example, by adding (meth)acrylic acid to an epoxy resin (preferably an alicyclic epoxy resin).

[0056] Polyester (meth)acrylates can be obtained, for example, by reacting a hydroxyl-containing polyester synthesized from a polybasic acid or its acid anhydride and a polyhydric alcohol with (meth)acrylic acid. Examples of polybasic acids include phthalic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, isosebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, dimer acid, trimellitic acid, pyromellitic acid, pimelic acid, and azelaic acid. Examples of polyhydric alcohols include 1,6-hexanediol, diethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol.

[0057] The content of the polyfunctional polymerizable compound (D) is preferably 10% by mass to 35% by mass, and more preferably 15% by mass to 30% by mass, based on the total amount of the in-mold coating composition.

[0058] <Polymerization initiator (E)> The in-mold coating composition according to the present disclosure contains a polymerization initiator (E). The polymerization initiator (E) is not particularly limited as long as it is a compound capable of promoting the polymerization reaction of the bifunctional polymerizable compound (B), the monofunctional polymerizable compound (C), and the polyfunctional polymerizable compound (D). The polymerization initiator (E) may be either a thermal polymerization initiator or a photopolymerization initiator, but is preferably a thermal polymerization initiator from the viewpoint of improving the polymerization rate. Examples of the polymerization initiator (E) include organic peroxides such as di-(4-t-butylcyclohexyl)peroxydicarbonate, t-butylperoxybenzoate, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisopropyl carbonate, lauroyl peroxide, t-butyloxylaurate, and 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane; and azo compounds such as azobisisobutyronitrile.

[0059] The content of the polymerization initiator (E) is preferably 0.4% by mass to 4.0% by mass based on the total amount of the in-mold coating composition.

[0060] The in-mold coating composition according to the present disclosure may contain components other than the scaly pigment (A), the bifunctional polymerizable compound (B), the monofunctional polymerizable compound (C), the polyfunctional polymerizable compound (D), and the polymerization initiator (E).

[0061] Examples of other components include colorants, dispersants, antifoaming agents, ultraviolet absorbers, light stabilizers, polymerization inhibitors, curing accelerators, and mold release agents.

[0062] <Application> The in-mold coating composition according to the present disclosure is useful for fiber-reinforced plastics or thermosetting plastics. That is, the in-mold coating composition according to the present disclosure is suitable for in-mold coating of fiber-reinforced plastics or thermosetting plastics.

[0063] Examples of fiber reinforced plastics include sheet molding compounds (SMC), bulk molding compounds (BMC), fiber reinforced thermoplastics (FRTP), stampable sheets, and the like. The resin used in the fiber reinforced plastic may be a thermosetting resin or a thermoplastic resin.

[0064] Examples of thermosetting resins include unsaturated polyester resins, epoxy acrylate resins, phenolic resins, and epoxy resins. Examples of thermoplastic resins include polyolefin, polystyrene, and polycarbonate. Examples of fibers used in fiber reinforced plastics include glass fibers, carbon fibers, organic fibers, and mineral fibers.

[0065] Thermosetting plastic means a thermosetting resin that is not fiber reinforced.

[0066] [Method of manufacturing in-mold coated molded body] The method for producing an in-mold coated molded body according to the present disclosure preferably includes the steps of clamping a mold consisting of a fixed mold part and a movable mold part, molding a fiber-reinforced plastic or a thermosetting plastic in the mold cavity to produce a resin molded body, injecting the in-mold coating composition into the mold cavity to form a coating film on the resin molded body, curing the coating film to form a cured film, and removing the resin molded body with the cured film formed thereon from the mold.

[0067] Below, the configuration of the molding machine, the molding mold, and the coating composition injection device for the manufacturing method of the in-mold coated molded body according to the present disclosure will be specifically explained with reference to the drawings, but the present disclosure is not limited to this specific embodiment.

[0068] FIG. 1 is a diagram illustrating a method for producing an in-mold coated molded article using compression molding.

[0069] An example of a manufacturing apparatus for manufacturing an in-mold coated molded article using compression molding is shown in Figure 1. As the molding material, for example, a glass fiber reinforced thermosetting plastic material is used. As a molding method, any conventional method of molding in a mold can be used without any particular limitation, but preferably the method described in Japanese Patent Publication No. 55-9291 or Japanese Patent Application Laid-Open No. 61-273921 can be used.

[0070] In the apparatus shown in Figure 1, the upper and lower halves 1 and 2 of the split mold are opposing molding components. The upper and lower halves 1 and 2 are fixed to the movable and fixed plates 3 and 4 of the clamping device, respectively. The movable platen 3 is moved back and forth by a clamping cylinder 5. The upper and lower halves 1 and 2 form a split mold cavity 6 of a predetermined shape. The movement of the upper and lower halves 1 allows the cavity to expand toward the surface to be coated in the in-mold coated molded body. The surface to be coated in the in-mold may be one surface or two or more surfaces. Therefore, the cavity expansion toward the surface to be coated in the in-mold may be one direction or two or more directions. A molding material is placed between the upper and lower halves 1 and 2, and the clamping cylinder 5 is operated to bring the upper and lower halves 1 and 2 closer together to form the molding material into the shape of the cavity. The molding material is then hardened by applying clamping pressure.

[0071] 1 also includes an injector 7 equipped with a shut-off pin 7A as a means for injecting the in-mold coating composition, a measuring cylinder 8 for supplying a predetermined amount of the in-mold coating composition to the injector 7, and a supply pump 9 for supplying the in-mold coating composition from a storage section 10 to the metering cylinder 8. The metering cylinder 8 is equipped with a plunger regulator 8A for injecting the in-mold coating composition.

[0072] The molding method will be described below. First, the clamping cylinder 5 is operated to separate the upper mold 1 from the lower mold 2, and the molding material is placed on the lower mold 2. Thereafter, the clamping cylinder 5 is operated to bring the upper mold 1 and the lower mold 2 closer together, molding the molding material into the shape of the cavity, and clamping pressure is applied. The clamping pressure is usually 4 MPa to 15 MPa. The molding temperature is set as desired depending on the molding time, type of molding material, etc. A molding temperature of 120 to 180°C is usually appropriate, and it is desirable to set the mold to the molding temperature before adding the molding material and maintain the molding temperature until a cured coating, as described below, is obtained.

[0073] Next, when the molded body in the cavity has hardened to the extent that it can withstand the injection pressure and flow pressure of the in-mold coating composition, the mold clamping pressure is maintained as is, or reduced, or the upper mold 1 is moved away from the surface of the molded body to a distance (preferably 0.2 mm to 5 mm) that is greater than the desired thickness of the cured coating but does not cause the upper mold 1 and lower mold 2 to separate from each other. Thereafter, an amount of the in-mold coating composition sufficient to obtain a cured coating of the desired thickness (preferably 20 μm to 1,000 μm) is injected from injector 7 between the inner wall of upper mold 1 and the surface of the molded article to be coated in the in-mold.

[0074] After the in-mold coating composition has been injected, the injection port is closed with the shut-off pin 7A. If necessary, the mold clamping cylinder 5 is operated to perform the mold clamping operation. The in-mold coating composition is cured on the surface of the molded body in the cavity 6. A pressure of approximately 1 MPa to 10 MPa is typically applied so that the in-mold coating composition uniformly coats the surface of the molded body. This pressure is typically maintained for approximately 10 seconds to 300 seconds until a cured coating is formed. After a cured coating has been formed on the surface of the molded body, the mold clamping cylinder 5 is operated to separate the upper mold 1 and lower mold 2, and the in-mold coated molded body is removed from the mold.

[0075] In the above embodiment, an example of manufacturing an in-mold coated molded body using a compression molding method is shown, but in the process of producing a resin molded body, fiber reinforced plastic or thermosetting plastic may also be molded using injection molding, injection compression molding, injection press molding, or reaction injection molding, in addition to compression molding. [Example]

[0076] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0077] <Preparation of composition for coating inside mold> The components shown in Tables 1 to 3 were mixed in the amounts (parts by mass) shown in Tables 1 to 3 to prepare compositions for coating inside the mold. Details of each component are as follows:

[0078] (Flake pigment (A)) Talc (product name: Micro Ace P-2, manufactured by Nippon Talc Co., Ltd.) Mica (product name "Takaramica 35", manufactured by Shiraishi Kogyo Co., Ltd.) Glass flakes (product name: Glass flakes RCF-140N, manufactured by Nippon Sheet Glass Co., Ltd.)

[0079] (Other pigments (AX)) Other pigments (AX) are pigments that do not fall under the category of flake pigments (A). Titanium dioxide (product name "R62N", manufactured by Sakai Chemical Industry Co., Ltd.)

[0080] (Bifunctional polymerizable compound (B)) 1,6-Hexanediol dimethacrylate 1,6-Hexanediol diacrylate

[0081] (Monofunctional polymerizable compound (C)) Isobornyl acrylate Dicyclopentanyl acrylate

[0082] (Polyfunctional polymerizable compound (D)) Urethane acrylate 1: Product name "EBECRYL8402", manufactured by Daicel Allnex Co., Ltd. Urethane acrylate 2: Product name "CN9001NS", manufactured by Sartomer Urethane acrylate 3: Product name "CN8881", manufactured by Sartomer Urethane acrylate 4: Product name "CN989", manufactured by Sartomer

[0083] (Other polymerizable compounds) The other polymerizable compounds are polymerizable compounds that do not fall under any of the bifunctional polymerizable compounds (B), the monofunctional polymerizable compounds (C), and the polyfunctional polymerizable compounds (D). Dipentaerythritol hexaacrylate Polyethylene glycol diacrylate: Product name: Light Acrylate 14EG-A, manufactured by Kyoeisha Chemical Co., Ltd. Hydroxypropyl methacrylate ·styrene Urethane acrylate 5: Product name "EBECRYL4738", manufactured by Daicel Allnex Co., Ltd.

[0084] (Polymerization initiator (E)) Thermal polymerization initiator: t-butyl peroxybenzoate, product name "Perbutyl Z", manufactured by NOF Corporation

[0085] (dispersant) Product name: DISPERBYK-110, manufactured by BYK

[0086] (mold release agent) Zinc stearate (product name "ZNS-P", manufactured by ADEKA)

[0087] <Preparation of in-mold coated molded body> A chrome-plated box-shaped test mold was used, with a cavity for obtaining a box-shaped resin molded article measuring 250 mm in length, 150 mm in width, 20 mm in height, and 5 mm in thickness. The molding temperatures were set at 145°C for the upper mold and 140°C for the lower mold. First, 350 g of an SMC material, an unsaturated polyester-based thermosetting glass fiber-reinforced plastic molding material (glass fiber content: 30%), was placed on the lower mold and molded under a molding pressure of 9 MPa and a molding time of 90 seconds. After the molding pressure was reduced, 8 mL of each in-mold coating composition was injected between the upper mold and the molded article, and the molding pressure was increased to 7 MPa and maintained for 90 seconds. The mold was then opened, and the molded article was removed. As a result, an in-mold coated molded article coated with a coating film (approximately 200 μm thick) composed of the in-mold coating composition was obtained. The obtained in-mold coated molded article was evaluated for warm water resistance, solvent resistance, and adhesion.

[0088] <Hot water resistance> The obtained in-mold coated molded articles were subjected to a liquid resistance test (water immersion method: test conditions: 65±1°C, total immersion, test time: 600 hours) in accordance with JIS K 5600-6-2:2016. After leaving the molded articles to stand for 24 hours indoors, the appearance of the coating film was visually observed. The warm water resistance was evaluated based on the degree of defects in the coating film, such as wrinkles, blisters, cracks, and peeling. A: The coating film has no wrinkles, bulges, cracks, or peeling. B: The coating film has 1 to 3 wrinkles, swelling, cracks, peeling, etc. C: The coating film has many wrinkles, bulges, cracks, peeling, etc.

[0089] <Solvent resistance> The obtained in-mold coated molded articles were subjected to a solvent rubbing test to evaluate their solvent resistance. In the solvent rubbing test, a gauze soaked in methyl ethyl ketone was applied with a load of 500 g and rubbed back and forth against the surface of each in-mold coated molded article five times, and the solvent resistance was evaluated based on whether or not there were any dissolved or swollen areas in the coating film. A: There are no dissolved or swollen areas in the coating film. B: There are no dissolved areas in the coating film, but there are swollen areas. C: The coating film has dissolved and swollen areas.

[0090] <Adhesion> The obtained in-mold coated molded articles were subjected to an adhesion test in accordance with JIS K 5600-5-6:1999 (Adhesion (cross-cut method)). The cut interval was 2 mm, and the appearance of 100 grids was evaluated visually using a Cellotape (registered trademark) peel test. The adhesion of the coating film was evaluated based on the classification of test results described in JIS K 5600-5-6. The evaluation was performed at five locations each, and the average value was used. A: The remaining rate of the coating film is 95% or more. B: The remaining rate of the coating film is 65% or more and less than 95%. C: The remaining rate of the coating film is less than 65%.

[0091] The evaluation results are shown in Tables 1 to 3.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] As shown in Tables 1 to 3, Examples 1 to 14 contain a scaly pigment (A), a bifunctional polymerizable compound (B) having a molecular weight of 180 to 600, a monofunctional polymerizable compound (C) having an alicyclic structure, a multifunctional polymerizable compound (D) having a weight average molecular weight of 1000 to 20000, and a polymerization initiator (E), and were found to have excellent hot water resistance and solvent resistance.

[0096] On the other hand, in Comparative Examples 1 to 3, the scaly pigment (A) was not contained, and it was found that the warm water resistance was poor. In Comparative Examples 4 to 6, the bifunctional polymerizable compound (B) was not contained, and it was found that the warm water resistance or solvent resistance was poor. In Comparative Example 7, the monofunctional polymerizable compound (C) was not contained, and it was found that the warm water resistance was poor. In Comparative Example 8, the polyfunctional polymerizable compound (D) was not contained, and it was found that the warm water resistance was poor. [Explanation of symbols]

[0097] 1 Upper mold 2 Lower mold 3 Movable platen of mold clamping device 4. Fixed platen of mold clamping device 5 Mold clamping cylinder 6 cavities 7 Injectors 7A shutoff pin 8 Measuring Cylinder 8A Plunger Regulator 9. Supply Pump 10 Storage Unit

Claims

1. An in-mold coating composition comprising: a scaly pigment (A); a bifunctional polymerizable compound (B) having a molecular weight of 180 to 600; a monofunctional polymerizable compound (C) having an alicyclic structure; a multifunctional polymerizable compound (D) having a weight-average molecular weight of 1,000 to 20,000; and a polymerization initiator (E).

2. The in-mold coating composition according to claim 1, which is for fiber-reinforced plastics or thermosetting plastics.

3. 3. The in-mold coating composition according to claim 1, wherein the content of the bifunctional polymerizable compound (B) is 1% by mass to 30% by mass based on the total amount of the in-mold coating composition.

4. 3. The in-mold coating composition according to claim 1, wherein the polyfunctional polymerizable compound (D) is a difunctional to tetrafunctional urethane acrylate.

5. 3. The in-mold coating composition according to claim 1, wherein a total content of all pigments contained in the in-mold coating composition is 15% by mass to 60% by mass, based on the total amount of the in-mold coating composition.

6. 3. The in-mold coating composition according to claim 1, wherein the ratio of the scaly pigment (A) to the pigments contained in the in-mold coating composition is 10% by mass or more.

7. a step of clamping a mold including a fixed mold portion and a movable mold portion; A step of molding a fiber-reinforced plastic or a thermosetting plastic in a mold cavity to produce a resin molded body; A step of injecting the in-mold coating composition according to claim 1 or 2 into the mold cavity to form a coating film on the resin molded body; a step of curing the coating film to form a cured film; removing the resin molded body on which the cured film has been formed from the mold; A method for producing an in-mold coated molded article, comprising:

8. 8. The method for producing an in-mold coated molded body according to claim 7, wherein in the step of producing the resin molded body, the fiber reinforced plastic or thermosetting plastic is molded using injection molding, injection compression molding, injection press molding, compression molding, or reaction injection molding.

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