Coating composition, coated substrate, method for producing coated substrate and method for producing in-mold coated molded body

Abstract

To provide a coating composition excellent in adhesiveness to a thermoplastic resin such as a polycarbonate resin and capable of forming a cured film excellent in chemical resistance.SOLUTION: A coating composition includes: a polymerizable compound (A) with a molecular weight of 180-400; a polymerizable compound (B) having 2-4 functional groups with a weight-average molecular weight of 500-3000; and a polymerization initiator (C). A ratio of the polymerizable compound (A) is 10-60 mass% based on a total content of the polymerizable compound (A) and the polymerizable compound (B). In the polymerizable compound (A), if T2 is a 60° glossiness value of a polycarbonate substrate after the polycarbonate substrate with 60° glossiness value T1 is immersed in the polymerizable compound (A) for 30 sec., a ratio of T2 to T1 is 70% or less. An application of the coating composition is also provided.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polycarbonate, which has excellent weather resistance, impact resistance, heat resistance, and non-flammability, is widely used as an engineering plastic suitable for transportation equipment such as automobiles and airplanes, medical equipment, optical equipment, etc. Polycarbonate substrates are often used after their surfaces are coated with paint for protection and decoration in order to improve scratch resistance and solvent resistance. Patent Documents 1 to 6 propose various paints suitable for polycarbonate substrates.

[0003] For example, Patent Document 1 describes a clear coating composition containing (A) a resin composition containing a hydroxyl group-containing fluororesin and an isocyanate-based curing agent, and further containing, per 100 parts by weight of the resin solid content, (B) 0.01 to 1.0 part by weight of a fluorosurfactant, (C) 1 to 15 parts by weight of an ultraviolet absorber, and (D) 1 to 30 parts by weight of an organosilicate compound. Patent Document 2 describes an ultraviolet-curable liquid composition containing a poly(meth)acrylate (A) having three or more (meth)acryloyl groups in the molecule, a urethane poly(meth)acrylate (B) having six or more (meth)acryloyl groups in the molecule obtained by reacting a compound (B1) having three or more isocyanate groups in the molecule with a compound (B2) having a hydroxyl group and two or more (meth)acryloyl groups in the molecule, an ultraviolet absorber (D), a light stabilizer (E), and a photopolymerization initiator (F) in specific proportions. Patent Document 3 describes an active energy ray-curable coating composition containing a specific silsesquioxane compound (a), a urethane (meth)acrylate (b) having two or more (meth)acryloyl groups in the molecule, a poly[(meth)acryloyloxyalkyl]isocyanurate (c), and a photopolymerization initiator (d). Patent Document 4 describes an in-mold coating composition containing (a) a urethane oligomer having at least two to eight (meth)acryloyl groups in at least one molecule, (b) at least one monomer having two ethylenic double bonds in one molecule, (c) at least one monomer having three or more ethylenic double bonds in one molecule, and (d) an organic peroxide polymerization initiator in specific ratios. Patent Document 5 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 6 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]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-217514 [Patent Document 2] Japanese Patent Application Publication No. 9-286809 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-219691 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-74896 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-51124 [Patent Document 6] Patent No. 7370500 Summary of the Invention [Problem to be solved by the invention]

[0005] BACKGROUND ART In coating compositions used for coating thermoplastic resins such as polycarbonate resins, there are cases where adhesion to the thermoplastic resin and chemical resistance of the cured film formed are required.

[0006] An object of one embodiment of the present disclosure is to provide a coating composition that is capable of forming a cured film that has excellent adhesion to thermoplastic resins such as polycarbonate resins and excellent chemical resistance. Another problem to be solved by another embodiment of the present disclosure is to provide a coated substrate having a cured film that has excellent adhesion to thermoplastic resins such as polycarbonate resins and excellent chemical resistance, a method for manufacturing a coated substrate, and a method for manufacturing an in-mold coated molded body. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. <1> a polymerizable compound (A) having a molecular weight of 180 to 400; a polymerizable compound (B) having 2 to 4 functional groups and a weight average molecular weight of 500 to 3,000; a polymerization initiator (C), the proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) is 10% by mass to 60% by mass; The coating composition is such that, when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds and the 60° gloss value of the polycarbonate substrate is defined as T2, the ratio of T2 to T1 is 70% or less. <2> The polymerizable compound (B) has a breaking elongation at 20°C of 25% or more. <1> The coating composition according to claim 1. <3> The polymerizable compound (A) is a bifunctional polymerizable compound. <1> The coating composition according to claim 1. <4> On a substrate containing a thermoplastic resin, <1> ~ <3> a step of applying the coating composition according to any one of the above to form a coating film; A method for producing a coated substrate, comprising a step of curing a coating film to form a cured film. <5> The substrate is heated to 80°C to 130°C and then the coating composition is applied. <4> 10. A method for producing a coated substrate according to claim 9. <6> The cure shrinkage rate of the cured film relative to the coating film is 3% to 11%. <4> 10. A method for producing a coated substrate according to claim 9. <7> a step of clamping a mold including a fixed mold portion and a movable mold portion; A step of molding a thermoplastic resin in a mold cavity to produce a resin molded body; into the mold cavity, <1> ~ <3> A step of injecting the 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 thermoplastic resin 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. <9> A substrate containing a thermoplastic resin and a cured film formed on the substrate, The cured film is a polymerizable compound (A) having a molecular weight of 180 to 400; a polymerizable compound (B) having 2 to 4 functional groups and a weight average molecular weight of 500 to 3,000; a polymerization initiator (C), the proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) is 10% by mass to 60% by mass; The polymerizable compound (A) is a coated substrate in which, when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds and the 60° gloss value of the polycarbonate substrate is defined as T2, the ratio of T2 to T1 is 70% or less. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, there is provided a coating composition that is capable of forming a cured film that has excellent adhesion to thermoplastic resins such as polycarbonate resins and excellent chemical resistance. According to other embodiments of the present disclosure, there are provided a coated substrate having a cured film that has excellent adhesion to thermoplastic resins such as polycarbonate resins and excellent chemical resistance, a method for manufacturing a coated substrate, and a method for manufacturing an in-mold coated molded body. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating a method for producing an in-mold coated molded body using an injection molding method. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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.

[0012] [Paint composition] The coating composition according to the present disclosure comprises a polymerizable compound (A) having a molecular weight of 180 to 400, a polymerizable compound (B) having 2 to 4 functional groups and a weight-average molecular weight of 500 to 3000, and a polymerization initiator (C), wherein the proportion of the polymerizable compound (A) in the total content of the polymerizable compounds (A) and (B) is 10% to 60% by mass, and when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds, and T2 is the 60° gloss value of the polycarbonate substrate, the ratio of T2 to T1 of the polymerizable compound (A) is 70% or less.

[0013] The coating composition according to the present disclosure can form a cured film that has excellent adhesion to thermoplastic resins such as polycarbonate resins and excellent chemical resistance. The reason for this effect is unclear, but is presumed to be as follows.

[0014] The coating composition according to the present disclosure contains a polymerizable compound (A) having a molecular weight of 180 to 400, and when the 60° gloss value of a polycarbonate substrate is T1 and the 60° gloss value after immersing the polycarbonate substrate in the polymerizable compound (A) for 30 seconds is T2, the ratio of T2 to T1 is 70% or less. This means that the polymerizable compound (A) has high permeability into the polycarbonate substrate. Because the polymerizable compound (A) has high permeability into the polycarbonate substrate, the coating composition according to the present disclosure has excellent adhesion to thermoplastic resins such as polycarbonate resins. The coating composition according to the present disclosure also contains a polymerizable compound (B) having 2 to 4 functional groups and a weight-average molecular weight of 500 to 3,000. By using a polymerizable compound (B) whose number of functional groups and weight-average molecular weight fall within specific ranges, cure shrinkage is reduced and internal stress is less likely to increase, resulting in the coating composition according to the present disclosure having excellent adhesion to thermoplastic resins such as polycarbonate resins. Furthermore, by using a polymerizable compound (B) whose number of functional groups and weight-average molecular weight fall within specific ranges, excellent curability is achieved, resulting in the cured film formed by the coating composition according to the present disclosure having excellent chemical resistance. Furthermore, by combining the polymerizable compound (A) and the polymerizable compound (B) in a specific ratio, it is possible to achieve both adhesion to thermoplastic resins and chemical resistance of the cured film.

[0015] Each component contained in the coating composition according to the present disclosure will be described below.

[0016] <Polymerizable compound (A)> The coating composition according to the present disclosure contains a polymerizable compound (A) having a molecular weight of 180-400. The coating composition may contain only one type of polymerizable compound (A), or two or more types.

[0017] The molecular weight of the polymerizable compound (A) is 180-400, preferably 180-300, and more preferably 180-250. The molecular weight of the polymerizable compound (A) is calculated based on the type and number of atoms constituting the polymerizable compound (A).

[0018] When the molecular weight of the polymerizable compound (A) is 180 or more, the solubility in the polycarbonate substrate and the interfacial curing property between the polycarbonate substrate and the coating composition are excellent. When the molecular weight of the polymerizable compound (A) is 400 or less, the compound is soluble in the polycarbonate substrate.

[0019] Furthermore, the polymerizable compound (A) satisfies the following requirements. If the 60° gloss value of the polycarbonate substrate is T1 and the 60° gloss value after immersing the polycarbonate substrate in polymerizable compound (A) for 30 seconds is T2, the ratio of T2 to T1 is 70% or less. The 60° gloss value T1 is 90 or more. Hereinafter, the ratio of T1 to T2 is also referred to as "gloss retention."

[0020] The gloss retention was calculated as follows. First, a polycarbonate substrate having a 60° gloss value T1 of 90 or more is selected, and the 60° gloss value T1 is measured. The polycarbonate substrate is immersed in the polymerizable compound adjusted to 23°C. After 30 seconds of immersion, the polycarbonate substrate is removed and washed with isopropyl alcohol. After drying the washed polycarbonate substrate, the 60° gloss value T2 is measured. The gloss retention is calculated based on the following formula. Gloss retention rate = {(60° gloss value T2) / (60° gloss value T1)} x 100 The 60° gloss value is measured using a gloss meter, such as the "Micro Trigloss" product manufactured by BYK.

[0021] From the viewpoint of adhesion to thermoplastic resins, the gloss retention is preferably 70% or less, more preferably 40% or less. The lower limit of the gloss retention is not particularly limited, but is, for example, 3%.

[0022] The polymerizable compound (A) has a solubility parameter (SP value) of 17.3 (MPa) in order to enhance the permeability to the thermoplastic resin. 1 / 2 ~21.5(MPa) 1 / 2 It is preferable that the pressure is 17.3 (MPa) 1 / 2 ~20.5(MPa) 1 / 2 More preferably, it is 18.3 (MPa) 1 / 2 ~20.5(MPa) 1 / 2 It is more preferable that:

[0023] In the present disclosure, the SP value is calculated in the following manner. The SP value is a value inherent to a resin composition and serves as a guideline for determining compatibility, and there are various calculation and measurement methods. In this disclosure, the SP value refers to a value calculated in accordance with the method described in K. L. Hoy, J. Paint Technology, 42,

[0541] , 76 (1970) using the molecular attraction constant obtained using the SP value by the vapor pressure method proposed by Hoy.

[0024] From the viewpoint of hardness, the polymerizable compound (A) preferably has a glass transition temperature of -30°C to 300°C, more preferably 50°C to 200°C when made into a homopolymer.

[0025] In the present disclosure, the glass transition temperature of the polymerizable compound (A) when made into a homopolymer is measured by the following method.

[0026] Polymerization of the polymerizable compound (A) is carried out by a general solution polymerization method. Specifically, 5% by mass of azobisisobutyronitrile as a polymerization initiator is added to a 10% by mass toluene solution of the polymerizable compound (A), and the mixture is stirred at 60°C for 6 hours to synthesize and isolate a homopolymer having a weight-average molecular weight of 10,000 to 50,000. The glass transition temperature of the resulting homopolymer is determined using a DSC120U manufactured by Seiko Instruments in accordance with JIS K 7121:2012. If the weight average molecular weight of the homopolymer is in the range of 10,000 to 50,000, the fluctuation in the glass transition temperature is small.

[0027] The polymerizable compound (A) 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 photoradical polymerizable group or a thermally radical polymerizable group.

[0028] From the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group, more preferably a (meth)acryloyloxy group.

[0029] The polymerizable compound (A) may be a monofunctional polymerizable compound having one polymerizable group, or may be a polyfunctional polymerizable compound having two or more polymerizable groups.

[0030] From the viewpoint of chemical resistance and adhesion, the polymerizable compound (A) is preferably a polyfunctional polymerizable compound, and more preferably a bifunctional polymerizable compound.

[0031] The structure of the polymerizable compound (A) 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.

[0032] The gloss retention rates of various polymerizable compounds are shown below. 1,6-Hexanediol diacrylate: 6% Neopentyl glycol diacrylate: 7% 3-Methyl-1,5-pentanediol diacrylate: 8% Butanediol dimethacrylate: 9% Phenoxyethyl acrylate: 61% Isobornyl acrylate: 105% Lauryl acrylate: 102% Tricyclodecane dimethanol diacrylate: 101% Trimethylolpropane triacrylate: 103% Pentaerythritol tetraacrylate: 102% Pentaerythritol triacrylate: 100% Cyclic trimethylolpropane formal acrylate: 60% 2-(2-vinyloxyethoxy)ethyl methacrylate: 9% 2-(2-vinyloxyethoxy)ethyl acrylate: 8%

[0033] Among the polymerizable compounds, a polymerizable compound having a molecular weight of 180 to 400 and a gloss retention rate of 70% or less is the polymerizable compound (A).

[0034] Examples of the polymerizable compound (A) include 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 3-methyl-1,5-pentanediol diacrylate, butanediol dimethacrylate, phenoxyethyl acrylate, cyclic trimethylolpropane formal acrylate, 2-(2-vinyloxyethoxy)ethyl methacrylate, and 2-(2-vinyloxyethoxy)ethyl acrylate.

[0035] If the permeability of the polymerizable compound (A) into the substrate is too high, the permeated polymerizable compound (A) may cause cohesive failure at the interface between the substrate and the cured film. The polymerizable compound (A) is particularly preferably 1,6-hexanediol diacrylate, since it has an appropriate degree of permeability to thermoplastic resins.

[0036] The proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and a polymerizable compound (B) described below is 10 to 60% by mass, and preferably 10 to 40% by mass. When the proportion of the polymerizable compound (A) is 10% by mass or more, sufficient permeability into the polycarbonate substrate can be obtained. When the proportion of the polymerizable compound (A) is 60% by mass or less, it is possible to achieve both permeability into the polycarbonate substrate and chemical resistance.

[0037] The content of the polymerizable compound (A) is preferably 5% by mass to 55% by mass relative to the total amount of the coating composition.

[0038] <Polymerizable compound (B)> The coating composition according to the present disclosure contains a polymerizable compound (B) having 2 to 4 functional groups and a weight average molecular weight of 500 to 3,000. The coating composition may contain only one type of polymerizable compound (B), or two or more types.

[0039] The weight average molecular weight of the polymerizable compound (B) is 500 to 3,000, preferably 500 to 2,000, and more preferably 800 to 1,200. When the weight average molecular weight of the polymerizable compound (B) is 500 or more, cure shrinkage is reduced, internal stress does not become too high, and adhesion to thermoplastic resins is excellent. When the weight average molecular weight of the polymerizable compound (B) is 3,000 or less, the curing rate is sufficient, adhesion to thermoplastic resins is excellent, and the cured film has excellent chemical resistance.

[0040] In this disclosure, the weight average molecular weight is measured by size exclusion chromatography using polystyrene as the standard.

[0041] The number of functional groups of the polymerizable compound (B) is 2 to 4, and preferably 2 or 3. When the number of functional groups is 2 to 4, cure shrinkage is reduced, internal stress does not become too high, and adhesion to thermoplastic resins is excellent.

[0042] The polymerizable compound (B) preferably has a breaking elongation of 25% or more, more preferably 30% or more, at 20° C. The upper limit of the breaking elongation is not particularly limited, but is, for example, 200%.

[0043] When the polymerizable compound (B) has a breaking elongation at 20° C. of 25% or more, it has excellent conformability to the substrate and can prevent cracking of the cured film.

[0044] In the present disclosure, the breaking elongation is measured by the following method. The polymerizable compound (B) is cured to obtain a cured product (length 7 cm, width 1 cm, thickness 100 μm). The breaking elongation of the obtained cured product is measured at a chuck distance of 2 cm and a tensile speed of 200 mm / min.

[0045] From the viewpoint of elongation and hardness, the polymerizable compound (B) preferably has a glass transition temperature of -20°C to 100°C when made into a homopolymer, more preferably 0°C to 80°C, and even more preferably 10°C to 50°C.

[0046] In the present disclosure, the glass transition temperature when the polymerizable compound (B) is made into a homopolymer is measured in the same manner as the glass transition temperature when the polymerizable compound (B) is made into a homopolymer.

[0047] The 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. The radically polymerizable group may be a photoradical polymerizable group or a thermally radical 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 structure of the polymerizable compound (B) is not particularly limited, but the polymerizable compound (B) is preferably at least one selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate. Among these, from the viewpoints of elongation, hardness, and chemical resistance, the polymerizable compound (B) is preferably a urethane (meth)acrylate.

[0050] 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.

[0051] 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.

[0052] The epoxy (meth)acrylate can be obtained, for example, by adding (meth)acrylic acid to an epoxy resin (preferably an alicyclic epoxy resin).

[0053] 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.

[0054] The content of the polymerizable compound (B) is preferably 35% by mass to 80% by mass relative to the total amount of the coating composition.

[0055] <Polymerization initiator (C)> The coating composition according to the present disclosure contains a polymerization initiator (C). The polymerization initiator (C) is not particularly limited as long as it is a compound capable of promoting the polymerization reaction of the polymerizable compound (A) and the polymerizable compound (B). Examples of the polymerization initiator (C) 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.

[0056] The content of the polymerization initiator (C) is preferably 0.4 to 4.0% by mass relative to the total amount of the coating composition.

[0057] The coating composition according to the present disclosure may contain components other than the polymerizable compound (A), the polymerizable compound (B), and the polymerization initiator (C).

[0058] Examples of other components include colorants, dispersants, antifoaming agents, ultraviolet absorbers, light stabilizers, polymerization inhibitors, and mold release agents.

[0059] The proportion of the film-forming components in the coating composition according to the present disclosure is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. In this disclosure, the term "film-forming component" refers to a component in a coating composition that becomes a coating film. The proportion of the film-forming component is calculated based on the following formula, assuming that Xg of the coating composition has a coating mass of Yg after curing. Film-forming component ratio (%) = {(Y) / (X)} x 100 On the other hand, components that do not form a coating film are called volatile components, and examples of volatile components include water and organic solvents.

[0060] [Method of manufacturing coated substrate] The method for producing a coated substrate according to the present disclosure preferably includes the steps of applying the coating composition to a substrate containing a thermoplastic resin to form a coating film, and curing the coating film to form a cured film. Here, the term "coating film" refers to a film before the polymerizable compound contained in the coating composition is cured, specifically, a film in a state where the volatile components in the coating composition have been removed. The term "cured film" refers to a film after the polymerizable compound contained in the coating composition has been cured.

[0061] By using the coating composition of the present disclosure to form a cured film on a substrate containing a thermoplastic resin, a cured film that has excellent adhesion to the substrate and excellent chemical resistance can be obtained.

[0062] The preferred embodiments of the coating composition are as described above.

[0063] Examples of thermoplastic resins contained in the substrate include polyamide, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polystyrene, polycarbonate, polyethylene ether, ABS resin, etc. In particular, by using the coating composition of the present disclosure, a cured film with excellent adhesion can be formed on a substrate containing polycarbonate.

[0064] The method for applying the coating composition is not particularly limited, and examples thereof include brush coating, spray coating, immersion, flow coating, roll coating, curtain coating, spin coating, knife coating, etc. By applying the coating composition and then drying it, a coating film can be formed on the substrate. The drying may be natural drying or heat drying.

[0065] When applying the coating composition, it is preferable to apply the coating composition after heating the substrate to 80 to 130°C. Specifically, the temperature of the surface of the substrate on which the coating composition is to be applied is preferably 80 to 130°C. Preheating the substrate improves adhesion to the substrate and the cure rate.

[0066] The method for heating the substrate is not particularly limited, and examples thereof include a method in which the substrate is heated from at least one of the front and back surfaces using a commonly known heating device.

[0067] The method for curing the coating film formed on the substrate is not particularly limited, and may be heat curing or photocuring.

[0068] In the case of thermal curing, the heating temperature is, for example, 80° C. to 130° C., and the heating time is, for example, 0.5 minutes to 3 minutes.

[0069] The cure shrinkage rate of the cured film relative to the coating film is preferably 3% to 11%. The coating composition according to the present disclosure contains the polymerizable compound (A) and the polymerizable compound (B) in a specific ratio, and therefore can reduce the shrinkage rate of the cured film relative to the coating film.

[0070] When the cure shrinkage rate of the cured film relative to the coating film is 3% to 11%, a coated substrate having a cured film with excellent adhesion to thermoplastic resins can be obtained.

[0071] The cure shrinkage rate of the cured film relative to the coating film is measured by the following method.

[0072] The specific gravity of the coating film and the specific gravity of the cured film are measured using an electronic balance (product name "ATX224R", manufactured by Shimadzu Corporation) equipped with a specific gravity measurement kit under an environment of 23°C and 50% relative humidity. The cure shrinkage is calculated based on the following formula: Cure shrinkage rate (%) = {(specific gravity of cured film) - (specific gravity of coating film)} / (specific gravity of cured film) x 100

[0073] [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 thermoplastic resin in the mold cavity to produce a resin molded body, injecting the 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.

[0074] 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.

[0075] FIG. 1 is a diagram illustrating a method for producing an in-mold coated molded article using injection molding. In Figure 1, reference numeral 1 denotes a fixed platen of a mold clamping device of an injection molding machine, and reference numeral 2 denotes a movable platen, each of which is provided with a fixed mold portion 3 and a movable mold portion 4, which are opposing molding die members. The movable platen 2 is configured to be moved forward and backward by a mold clamping cylinder 5. A cavity 6 of a predetermined shape is formed in the mating portion of the fixed mold portion 3 and the movable mold portion 4. A thermoplastic resin in a molten or softened state is injected into this cavity 6, filled, and solidified. Thermoplastic resin can be injected into the cavity 6 from an injection cylinder 7 having a screw through a nozzle 8 and a sprue 9 . The coating composition injection means includes an injector 10 equipped with a shut-off pin 10A, a measuring cylinder 11 for supplying a predetermined amount of coating composition to the injector 10, and a supply pump 13 for supplying the coating composition from a storage section 12 to the measuring cylinder 11. The measuring cylinder 11 is equipped with a plunger regulator 11A for injecting the coating composition. During molding, first, the clamping cylinder 5 is operated to close the fixed mold portion 3 and the movable mold portion 4, and clamping pressure is applied. The clamping pressure must be able to withstand the injection pressure of the thermoplastic resin. Typically, the injection pressure at the nozzle 8 is 40 MPa to 250 MPa. During this process, the supply pump 13 operates to supply the required amount of coating composition to the metering cylinder 11. Next, a thermoplastic resin in a molten or softened state is injected into the cavity 6 from the injection cylinder 7 via the nozzle 8 and the sprue 9. When the thermoplastic resin has solidified in the mold to an extent that it can withstand the injection pressure and flow pressure of the coating composition, the clamping pressure is reduced, or the movable mold member 4 is retracted a distance (preferably 0.2 mm to 5 mm) that is greater than the desired thickness of the cured film but does not cause the fixed mold member 3 and the movable mold member 4 to break away from each other. Next, the shutoff pin 10A is operated to open the injection port of the injector 10. Next, the plunger regulator 11A for injecting the coating composition of the measuring cylinder 11 is operated to inject an amount of coating composition sufficient to obtain the desired film thickness (preferably a cured film of 20 μm to 1,000 μm) between the cavity 6, i.e., the inner wall of the fixed mold portion 3, and the surface of the resin molded body to be coated inside the mold. After the coating composition is injected, the injection port is closed again with the shut-off pin 10A. If necessary, the mold clamping cylinder 5 is operated to perform the mold clamping operation. The coating composition is spread within the mold and coated onto the surface of the resin molded body. This forms a coating film on the resin molded body. The coating film is semi-cured or fully cured by heat in the cavity 6 to the extent that it can be demolded. Next, the mold clamping cylinder 5 is operated to separate the fixed mold part 3 and the movable mold part 4, and the in-mold coated molded body on which the semi-cured or completely cured cured film has been formed is removed from the mold.

[0076] The degree of semi-curing or complete curing varies depending on the surface temperatures of the fixed mold part and the movable mold part, the time from when the thermoplastic resin is injected into the mold to when the coating composition is poured, the type of coating composition, the retention time in the mold after pouring the coating composition, etc. For example, the surface temperatures of the fixed mold part and the movable mold part are 90°C, the time from when the thermoplastic resin is injected into the mold to when the coating composition is poured is about 30 seconds, and the retention time in the mold after pouring the coating composition is about 30 seconds.

[0077] The removed in-mold coated molded article may be irradiated with active energy rays such as ultraviolet rays using a UV irradiator such as a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, or a carbon arc lamp to completely cure the semi-cured cured film. The ultraviolet irradiation conditions are not particularly limited, and it is preferable to irradiate ultraviolet rays having a wavelength of 150 nm to 450 nm in air or in an inert gas atmosphere such as nitrogen or argon. The ultraviolet irradiation dose is 50 mJ / cm. 2 ~2000mJ / cm 2 is preferred, and 200 mJ / cm 2 ~1200mJ / cm 2 is more preferred.

[0078] In the above embodiment, an example of manufacturing an in-mold coated molded body using injection molding has been shown, but in the process of producing a resin molded body, the thermoplastic resin may be molded using injection compression molding, injection press molding, compression molding, or reaction injection molding, in addition to injection molding.

[0079] [Coated substrate] The coated substrate according to the present disclosure includes a substrate containing a thermoplastic resin and a cured film formed on the substrate, the cured film being a cured product of the coating composition.

[0080] By using the coating composition of the present disclosure to form a cured film on a substrate containing a thermoplastic resin, a cured film that has excellent adhesion to the substrate and excellent chemical resistance can be obtained.

[0081] Preferred embodiments of the substrate containing a thermoplastic resin and the coating composition are as described above. [Example]

[0082] 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.

[0083] <Preparation of Coating Composition> The components shown in Tables 1 to 4 were mixed to prepare coating compositions. Details of each component are as follows:

[0084] (Polymerizable compound (A)) 1,6-Hexanediol diacrylate Neopentyl glycol diacrylate 3-Methyl-1,5-pentanediol diacrylate Butanediol dimethacrylate Phenoxyethyl acrylate

[0085] (Polymerizable compound (AX)) The polymerizable compound (AX) is a polymerizable compound having a molecular weight of 180 to 400, which does not fall under the category of the polymerizable compound (A). Isobornyl acrylate Lauryl acrylate Tricyclodecane dimethanol diacrylate ·Trimethylolpropane triacrete

[0086] (Polymerizable compound (B)) Urethane acrylate 1: Product name "EBECRYL8402", manufactured by Daicel Allnex Co., Ltd. Urethane acrylate 2: Product name "EBECRYL8409", manufactured by Daicel Allnex Co., Ltd. Urethane acrylate 3: Product name "EBECRYL4513", manufactured by Daicel Allnex Co., Ltd. Epoxy acrylate 1: Product name "EBECRYL3500", manufactured by Daicel Allnex Co., Ltd.

[0087] (Polymerizable compound (BX)) The polymerizable compound (BX) is a polymerizable compound having a weight average molecular weight of 500 to 3,000, which does not fall under the category of the polymerizable compound (B). Urethane acrylate 4: Product name "EBECRYL4858", manufactured by Daicel Allnex Co., Ltd. Urethane acrylate 5: Product name "EBECRYL230", manufactured by Daicel Allnex Co., Ltd. Urethane acrylate 6: Product name "EBECRYL1290", manufactured by Daicel Allnex Co., Ltd.

[0088] (coloring agent) Black pigment: Carbon black, product name "MA100", manufactured by Mitsubishi Chemical Corporation White pigment: Titanium dioxide, product name "CR97", manufactured by Ishihara Sangyo Kaisha Yellow pigment: hydrated iron oxide ochre, product name "XLO", manufactured by Titan Kogyo Co., Ltd. Blue pigment: Cobalt blue, product name "DPC9410", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. Red pigment: DPP Red, product name "L3670HD", manufactured by DIC Corporation

[0089] (dispersant) Dispersant 1: Product name "DISPERBYK-168", manufactured by BYK Dispersant 3: Product name "DISPERBYK-111", manufactured by BYK

[0090] (Antifoaming agent) Product name: AC326F, manufactured by Kyoeisha Chemical Co., Ltd.

[0091] (ultraviolet absorber) Triazine-based UV absorber: Product name "Tinuvin 400", manufactured by BASF Japan Ltd.

[0092] (light stabilizer) Hindered amine light stabilizer: Product name "Tinuvin 123", manufactured by BASF Japan Ltd.

[0093] (polymerization inhibitor) BHT (dibutylhydroxytoluene)

[0094] (Polymerization initiator (C)) Thermal polymerization initiator: bis(tert-butylcyclohexyl) peroxydicarbonate, product name "Perkadox 16", manufactured by Nouryon Chemical Co., Ltd.

[0095] (mold release agent) Non-neutralizing phosphate alcohol (product name "ZELEC-UN", manufactured by Stepan)

[0096] -Gloss retention rate of polycarbonate substrate- The gloss retention of the polycarbonate substrate was calculated for the polymerizable compound (A) and the polymerizable compound (AX). First, the 60° gloss value T1 of a polycarbonate substrate (product name "White Polycarbonate Plate", manufactured by TP Giken Co., Ltd.) was measured. A polycarbonate substrate was immersed in polymerizable compound (A) or polymerizable compound (AX) adjusted to 23°C. After 30 seconds of immersion, the polycarbonate substrate was removed and washed with isopropyl alcohol. The washed polycarbonate substrate was dried, and then the 60° gloss value T2 was measured. The gloss retention was calculated based on the following formula. Gloss retention rate = {(60° gloss value T2) / (60° gloss value T1)} x 100 The 60° gloss value was measured using a gloss meter (product name "Micro Trigloss", manufactured by BYK). In Tables 1 to 4, "PC gloss retention" indicates the ratio of T2 to T1, where T2 is the 60° gloss value after immersing a polycarbonate substrate in polymerizable compound (A) or polymerizable compound (AX) for 30 seconds.

[0097] -Breaking elongation- The elongation at break of the polymerizable compound (B) and the polymerizable compound (BX) was measured. The polymerizable compound (B) and the polymerizable compound (BX) were cured to obtain a cured product (length 7 cm, width 1 cm, thickness 100 μm). The breaking elongation of the obtained cured product was measured at a chuck distance of 2 cm and a tensile speed of 200 mm / min.

[0098] <Preparation of in-mold coated molded body> Using a mold having a cavity for obtaining a box-shaped resin molded body with a length of 300 mm, a width of 200 mm, a height of 10 mm, and a thickness of 2.5 mm, the resin molded body was coated using the device shown in Figure 1. The fixed mold part 3 was set to 100°C, the movable mold part 4 was set to 100°C, and the barrel temperature was heated to 280°C. First, polycarbonate (product name "Iupilon ML300", manufactured by Mitsubishi Engineering Plastics Corporation) was heated and melted in the injection cylinder 7, injected into a mold clamped at a clamping pressure of 100 MPa over approximately 1 second, and cooled for 40 seconds. The resin molded body was solidified to a degree that could withstand the injection and flow pressure of the coating composition. Next, the movable mold part 4 was separated by approximately 0.5 mm, and 7 mL of the coating composition was injected between the mold surface and the surface of the resin molded body over approximately 0.7 seconds. After injection was completed, the mold clamping pressure was increased to 3 MPa over 1 second and held for 60 seconds to cure the coating composition until it could be demolded, and then the in-mold coated molded body was removed from the mold. The thickness of the cured film formed on the resin molded body was approximately 100 μm. The obtained in-mold coated molded articles were evaluated for adhesion, chemical resistance, and appearance of the coating film, and the cure shrinkage was also measured.

[0099] <Adhesion> The in-mold coated molded article was 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 the cured film was evaluated visually by a tape peel test on 100 grid squares. The adhesion was evaluated on a six-level scale of 0 to 5 based on the classification of test results described in JIS K 5600-5-6. Category 0: The edges of the cut are completely smooth and there is no peeling on any of the grids. Category 1: The remaining rate of the cured film is 95% to 99%. Category 2: The remaining rate of the cured film is 85% or more but less than 95%. Category 3: The remaining rate of the cured film is 65% or more but less than 85%. Category 4: The remaining rate of the cured film is 0% or more but less than 65%. Category 5: Peeling that cannot be classified as Category 4.

[0100] <Chemical resistance> Using the in-mold coated molded product, an acid resistance test was conducted in accordance with Method 2 (absorption medium method) of JIS K 5600-6-1:2016. However, the test liquid was a 0.1N aqueous sulfuric acid solution, and after leaving it under standard conditions (temperature 25±2°C, relative humidity 50±5% RH) for 24 hours, the test plate was rinsed with water and wiped, and the condition of the coated surface of the test area was visually observed. The evaluation criteria are as follows. A: No change on the surface of the cured film. B: Decreased gloss and discoloration were observed on the surface of the cured film.

[0101] <Appearance> The in-mold coated molded article was left to stand in a room for 2 hours, and then the surface of the cured film was visually inspected to check for cracks. The evaluation criteria were as follows: A: Cracks are observed. B: No cracks are observed.

[0102] <Cure shrinkage rate> A fluororesin film (product name "Nitoflon Film No. 900", manufactured by Nitto Denko Corporation) was inserted into the mold beforehand, and an in-mold coated molded article was produced in the same manner as in the production of the in-mold coated molded article described above. Next, the cured film was peeled off from the fluororesin film to obtain an isolated cured film. The specific gravity of the coating film and the specific gravity of the cured film were measured using an electronic balance (product name "ATX224R", manufactured by Shimadzu Corporation) equipped with a specific gravity measurement kit under an environment of 23°C and 50% relative humidity. The cure shrinkage was calculated based on the following formula. Cure shrinkage rate (%) = {(specific gravity of cured film) - (specific gravity of coating film)} / (specific gravity of cured film) x 100

[0103] The evaluation results are shown in Tables 1 to 4. In Tables 1 to 4, "proportion of polymerizable compound (A)" means the proportion of polymerizable compound (A) in the total content of polymerizable compound (A) and polymerizable compound (B).

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

[0107] [Table 4]

[0108] As shown in Tables 1 to 4, Examples 1 to 14 contain a polymerizable compound (A) having a molecular weight of 180 to 400, a polymerizable compound (B) having 2 to 4 functional groups and a weight-average molecular weight of 500 to 3,000, and a polymerization initiator (C), where the proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) is 10% by mass to 60% by mass. The polymerizable compound (A) is a coating composition in which, when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds and the 60° gloss value of the polycarbonate substrate is defined as T2, the ratio of T2 to T1 is 70% or less. It was found that these coating compositions formed cured films with excellent adhesion to thermoplastic resins and excellent chemical resistance.

[0109] On the other hand, Comparative Example 1 did not contain a polymerizable compound having a weight-average molecular weight of 500 or more, and was found to be inferior in adhesion and chemical resistance. In Comparative Example 2, a polymerizable compound having a weight-average molecular weight of 3000 or less was not contained, and it was found that the chemical resistance was poor. Comparative Example 3 contained a polymerizable compound with a weight average molecular weight of 500 to 3000, but had six functional groups, and was found to be inferior in adhesion and chemical resistance. In Comparative Examples 4 to 7, a polymerizable compound having a molecular weight of 180 to 400 was contained, but the gloss retention was over 70%, and it was found that the adhesion and chemical resistance were poor. In Comparative Example 8, the proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) was less than 10 mass%, and it was found that the adhesion and chemical resistance were poor. In Comparative Example 9, the proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) was more than 60 mass %, and it was found that the chemical resistance was poor. [Explanation of symbols]

[0110] 1 Fixed plate 2 Movable plate 3 Fixed mold section 4 Movable mold section 5 Mold clamping cylinder 6 cavities 7 Injection Cylinder 8 nozzles 9 sprues 10 Injector 10A shutoff pin 11 Measuring cylinder 11A plunger regulator 12 Storage Unit 13 Supply pump

Claims

1. a polymerizable compound (A) having a molecular weight of 180 to 400; a polymerizable compound (B) having 2 to 4 functional groups and a weight average molecular weight of 500 to 3,000; a polymerization initiator (C), a proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) is 10% by mass to 60% by mass, The polymerizable compound (A) is a coating composition in which, when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds and the 60° gloss value of the polycarbonate substrate is defined as T2, the ratio of T2 to T1 is 70% or less.

2. 2. The coating composition according to claim 1, wherein the polymerizable compound (B) has a breaking elongation at 20°C of 25% or more.

3. The coating composition according to claim 1, wherein the polymerizable compound (A) is a bifunctional polymerizable compound.

4. A step of applying the coating composition according to any one of claims 1 to 3 onto a substrate containing a thermoplastic resin to form a coating film; A method for producing a coated substrate, comprising the step of curing the coating film to form a cured film.

5. The method for producing a coated substrate according to claim 4, wherein the substrate is heated to 80°C to 130°C and then the coating composition is applied.

6. The method for producing a coated substrate according to claim 4, wherein the cure shrinkage rate of the cured film relative to the coating film is 3% to 11%.

7. a step of clamping a mold including a fixed mold portion and a movable mold portion; A step of molding a thermoplastic resin in a mold cavity to produce a resin molded body; A step of injecting the coating composition according to any one of claims 1 to 3 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; and removing the resin molded article on which the cured film has been formed from the mold.

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 thermoplastic resin 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.

9. A substrate containing a thermoplastic resin and a cured film formed on the substrate, The cured film is a polymerizable compound (A) having a molecular weight of 180 to 400; a polymerizable compound (B) having 2 to 4 functional groups and a weight average molecular weight of 500 to 3,000; a polymerization initiator (C), a proportion of the polymerizable compound (A) in the total content of the polymerizable compound (A) and the polymerizable compound (B) is 10% by mass to 60% by mass, The coated substrate is a cured product of a coating composition in which, when a polycarbonate substrate having a 60° gloss value T1 is immersed in the polymerizable compound (A) for 30 seconds and the 60° gloss value of the polycarbonate substrate is defined as T2, the ratio of T2 to T1 is 70% or less.

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