Resin molded article and method for manufacturing the same

Abstract

To provide a sheet-like resin molded article with excellent flexibility and a method for manufacturing the same. [Solution] The resin molded article according to the present invention is a heat-cured resin molded article of a fiber-reinforced composite material comprising a reinforcing fiber material and a resin, and is a sheet-like resin molded article having a bendable portion, characterized in that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bendable portion. Preferably the thickness of the resin molded article is 70 μm to 500 μm. Preferably the reinforcing fiber material has one or more forms selected from the group consisting of a unidirectional material, a woven fabric, and a knitted fabric in which the reinforcing fibers are aligned in one direction.

Description

[Technical Field]

[0001] The present invention relates to a sheet-like resin molded article made of a heat-cured fiber-reinforced composite material containing a reinforcing fiber material and a resin, and to a method for producing the same. [Background technology]

[0002] Conventionally, sheet-like resin molded articles made of fiber-reinforced composite materials containing reinforcing fiber material and resin are known. For example, Patent Document 1 discloses that an optical sheet made by curing a fiber-reinforced composite material in which glass cloth is impregnated with (meth)acrylate resin has excellent smoothness and flexibility and can be suitably used as a resin substrate for display elements and the like.

[0003] In recent years, foldable smartphones and tablet devices have been proposed. Therefore, it is conceivable to manufacture the casings of such smartphones and tablet devices using fiber-reinforced composite materials containing reinforcing fiber material and resin.

[0004] However, sheet-like resin molded articles made from heat-cured fiber-reinforced composite materials containing reinforcing fiber material and resin have the disadvantage that repeated bending at the bends can easily cause fracture around the bend. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-180754 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a sheet-like resin molded article with excellent flexibility and a method for manufacturing the same. [Means for solving the problem]

[0007] The inventors of this invention have come to the present invention by discovering that in a sheet-like resin molded body made of a heat-cured fiber-reinforced composite material containing reinforcing fiber material and resin, and having a bendable portion, excellent bendability can be ensured when the orientation angle of the reinforcing fiber material with respect to the bendable portion is within a specific range.

[0008] In other words, the present invention has the following aspects.

[0009] (1) A resin molded body in the form of a sheet, comprising a heat-cured fiber-reinforced composite material containing reinforcing fiber material and resin, and having a bendable portion, characterized in that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bendable portion.

[0010] (2) The resin molded article according to (1), wherein the thickness of the resin molded article is 70 μm or more and 500 μm or less.

[0011] (3) The resin molded article according to (1) or (2) above, wherein the reinforcing fiber material has one or more forms selected from the group consisting of unidirectional materials, woven fabrics, and knitted fabrics in which the reinforcing fibers are aligned in one direction.

[0012] (4) The resin molded article according to any one of (1) to (3) above, wherein the reinforcing fiber material is one or more fibers selected from the group consisting of glass fibers and carbon fibers.

[0013] (5) A resin molded body according to any of (1) to (4) above, which is a smartphone casing, a tablet device casing, or a solar panel cover.

[0014] A method for manufacturing a sheet-shaped resin molded body made of a heat-cured body of a fiber-reinforced composite material containing a reinforcing fiber material and a resin, and having a bendable bending portion, the method comprising: a first step of obtaining a heat-cured body by heat-curing the fiber-reinforced composite material; and a second step of obtaining a resin molded body by cutting the heat-cured body into a predetermined dimension corresponding to the resin molded body, wherein in the second step, the heat-cured body is cut so that the reinforcing fiber material is oriented at an angle of 15° or more and 75° or less with respect to the bending portion.

[0015] (7) A method for manufacturing a sheet-shaped resin molded body made of a heat-cured body of a fiber-reinforced composite material containing a reinforcing fiber material and a resin, and having a bendable bending portion, the method comprising: an eleventh step of cutting the fiber-reinforced composite material into a predetermined dimension corresponding to the resin molded body; and a twelfth step of obtaining a resin molded body by heat-curing the fiber-reinforced composite material cut into the predetermined dimension, wherein in the twelfth step, the fiber-reinforced composite material is cut so that the reinforcing fiber material is oriented at an angle of 15° or more and 75° or less with respect to the bending portion.

[0016] (8) The method for manufacturing a resin molded body according to (6) or (7) above, wherein when the fiber-reinforced composite material is heat-cured, the number of laminations of the fiber-reinforced composite material is 1 or more and 3 or less. [Effect of the Invention]

[0017] According to the present invention, it is possible to provide a sheet-shaped resin molded body excellent in bendability and a method for manufacturing the same. [Brief Description of the Drawings]

[0018] [Figure 1] It is a schematic diagram showing an embodiment of the resin molded body according to the present invention. Fig. 1(a) is a perspective view, and Fig. 1(b) is a plan view. [Figure 2] It is a schematic diagram showing a conventional resin molded body. [Figure 3]It is a figure showing a method for a bending test of a resin molded body according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0019] <Resin molded body> Hereinafter, embodiments of the present invention will be described with reference to FIG. 1. A resin molded body 1 according to an embodiment of the present invention shown in FIGS. 1(a) and 1(b) is formed of a heat-cured body of a fiber-reinforced composite material including a reinforcing fiber material 2 and a resin (not shown), and is a sheet-shaped resin molded body provided with a bendable bending portion 3. The resin molded body 1 is characterized in that the reinforcing fiber material 2 is oriented at an angle θ of 15° or more and 75° or less with respect to the bending portion 3. From the viewpoints of workability, handling ease, etc., a prepreg is preferable as the fiber-reinforced composite material.

[0020] In the resin molded body 1 of the present embodiment, the bending portion 3 (the region indicated by the slashes in FIG. 1(a)) is provided at the center of the resin molded body 1, but the bending portion 3 can be provided at an arbitrary position. The resin molded body 1 is bent according to the configuration of a device such as a smartphone to which the resin molded body 1 is applied, and elastically deformed at the bending portion 3. The bending portion 3 is a region that elastically deforms, and may be provided with a slit at the center thereof for relaxing the stress load during bending. The slit may be provided, for example, at a position corresponding to the center line 3a of the bending portion 3, or a plurality of slits may be provided in parallel with the center line 3a.

[0021] The reinforcing fiber material 2 preferably has one or more forms selected from the group consisting of a unidirectional material in which reinforcing fibers are aligned in one direction, a woven fabric, and a knitted fabric. From the viewpoints of workability, handling ease, and strength, a woven fabric and a knitted fabric are preferable. From the viewpoint of flexibility, a knitted fabric is preferable. When the reinforcing fiber material 2 is a woven fabric, examples include a stitching sheet in which a sheet in which fiber bundles are aligned in one direction, such as plain weave, twill weave, satin weave, or non-crimp fabric, or a sheet laminated with an angle change is stitched so as not to come loose.

[0022] The orientation angle of the reinforcing fiber material 2 with respect to the bent portion 3 will now be described. The orientation angle can be defined, for example, by the orientation angle of the reinforcing fiber material 2 with respect to the center line 3a of the bent portion 3, or to the boundary line 5 between the non-bent portion 4, which is a region that does not elastically deform or undergoes only small elastic deformation when bent, and the bent portion 3. If the reinforcing fiber material 2 is a unidirectional material, the orientation angle θ is the smaller of the angles between the center line 3a or boundary line 5 of the bent portion 3 and the longitudinal direction of the unidirectional material. If the reinforcing fiber material 2 is a woven fabric, the orientation angle θ is the smaller of the angles between the center line 3a or boundary line 5 of the bent portion 3 and the warp or weft threads that make up the woven fabric. If the reinforcing fiber material 2 is a knitted fabric, the orientation angle θ is the smaller of the angles between the center line 3a or boundary line 5 of the bent portion 3 and the direction perpendicular to the direction in which the knitting yarn advances (the horizontal direction of the knitted fabric) or the knitting direction (the vertical direction of the knitted fabric, i.e., the row direction).

[0023] The orientation angle θ of the reinforcing fiber material 2 with respect to the bent portion 3 is 15° or more and 75° or less, but is preferably 30° or more and 60° or less, more preferably 35° or more and 55° or less, particularly preferably 40° or more and 50° or less, and most preferably approximately 45°.

[0024] Reinforcement fiber material 2 includes organic fibers such as carbon fiber, glass fiber, silicon carbide fiber, alumina fiber, boron fiber, metal fiber, aramid fiber, vinylon fiber, and tetron fiber. These may be used individually or in combination of two or more types. Among these, carbon fiber or glass fiber is preferred because it yields a higher-strength resin molded product. Glass fiber is also preferred because it yields a transparent or nearly transparent resin molded product. Transparent or nearly transparent resin molded products have excellent decorative properties and are therefore suitable for applications such as smartphone or tablet device casings and solar panel covers.

[0025] Reinforced fiber material 2 basis weight (fiber 1m 2The weight per unit area (basis weight) can be various without particular limitation. Also, the optimum value varies depending on the material of the reinforcing fiber material 2. Generally, since it is excellent in the balance between the fiber width uniformity of the reinforcing fiber material 2 and the resin impregnation property, it is preferably in the range of 30 to 650 g / m 2 Preferably, it is in the range of. When the reinforcing fiber material is glass fiber, it is preferably 50 g / m 2 or more, and preferably 100 g / m 2 or more. Also, it is preferably 600 g / m or less, and more preferably 350 g / m 2 or less. When the reinforcing fiber material 2 is carbon fiber, it is preferably 50 g / m 2 or more, and more preferably 80 g / m 2 or more. Also, it is preferably 300 g / m 2 or less, and more preferably 200 g / m 2 or less.

[0026] The resin constituting the fiber reinforced composite material can be impregnated into the reinforcing fiber material 2, and various resins can be used without particular limitation as long as the resulting fiber reinforced composite material can be molded by heating or the like. Among them, a thermosetting resin composition is preferably used from the viewpoint of ease of handling and the like. Details will be described later.

[0027] The thickness D of the resin molded body 1 can be arbitrarily set, but in consideration of the balance between strength and flexibility, it is preferably 70 μm or more and 500 μm or less. The thickness D of the resin molded body 1 can be adjusted by the number of laminated sheets of the fiber reinforced composite material when heat-curing, the amount of the resin composition in the fiber reinforced composite material, the height of the spacer disposed in the mold used for heat-curing, and the like.

[0028] In the resin molded body 1 of the present embodiment, the reinforcing fiber material 2 is oriented at an angle of 15° or more and 75° or less with respect to the bent portion 3. Thereby, the resin molded body 1 of the present embodiment can secure excellent flexibility and suppress breakage in the peripheral portion of the bent portion 3 when the bending at the bent portion 3 is repeated.​​

[0029] The resin molded body 1 of this embodiment can suppress fracture at the periphery of the bent portion 3 when repeatedly bent with a bending radius of 1 to 10 mm, depending on the thickness. In particular, when the thickness D is 70 μm or more and 200 μm or less, fracture at the periphery of the bent portion 3 can be suppressed even when bending with a small bending radius of 3 mm is repeated 100 times.

[0030] The resin molded body 1 of this embodiment has excellent flexibility, making it suitable for applications such as smartphone and tablet device casings and solar panel covers, and is particularly suitable for foldable smartphone and tablet device casings.

[0031] In contrast, as shown in Figure 2, in a sheet-like resin molded body 11 made of a heat-cured fiber-reinforced composite material containing reinforcing fiber material 12 and resin, and having a bendable bendable portion 13, if the reinforcing fiber material 12 is oriented at an angle of 0° or 90° with respect to the bendable portion 13 (for example, the center line 13a of the bendable portion 13, or the boundary line 15 between the non-bendable portion 14 and the bendable portion 13), sufficient bendability cannot be ensured, and fracture will occur at the bendable portion when the bending at the bendable portion 13 is repeated. Also, although not shown, if the reinforcing fiber material 2 is a unidirectional material, and the longitudinal direction of the unidirectional material coincides with the short direction of the resin molded body 11 in Figure 2, and the reinforcing fiber material 12 is oriented at an angle of 0° with respect to the bendable portion 13, fracture will occur at the periphery of the bendable portion 13 when the bending at the bendable portion 13 is repeated. If the reinforcing fiber material 2 is a unidirectional material, and the longitudinal direction of the unidirectional material coincides with the longitudinal direction of the resin molded body 11 in Figure 2, and the reinforcing fiber material 12 is oriented at a 90° angle to the bend portion 13, then repeated bending at the bend portion 13 will cause fracture to occur around the bend portion 13.

[0032] <Method for manufacturing resin molded products> <<Manufacturing Method of the First Embodiment>> The resin molded body 1 of this embodiment described above can be manufactured, for example, as follows. That is, the method for manufacturing a resin molded body of the first embodiment according to the present invention is a method for manufacturing a sheet-like resin molded body having a bendable bend portion, comprising a first step of obtaining a heat-cured body by heat-curing the fiber-reinforced composite material, and a second step of obtaining a resin molded body by cutting the heat-cured body to a predetermined dimension corresponding to the resin molded body, wherein in the second step, the heat-cured body is cut such that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bend portion.

[0033] In this embodiment, the case in which the fiber-reinforced composite material is a prepreg is described, but the embodiment is not limited to this. The prepreg can be manufactured, for example, as follows. First, as the resin, in this embodiment, a thermosetting resin composition is prepared. Since the resulting resin molded article has strength, it is preferable that the resin composition contains urethane reaction components with isocyanate groups and hydroxyl groups, and that polymerizable unsaturated groups are present in the resin composition. Examples of such resin compositions include a resin composition (1) containing a polyisocyanate compound (r1) and a polyhydroxy(meth)acrylate compound (r2), and a resin composition (2) containing a polyisocyanate compound (r1), a monohydroxy(meth)acrylate compound (r3), and a polyhydroxy compound (r4).

[0034] Furthermore, a (meth)acrylate compound is a compound having one or both an acryloyl group and a methacryloyl group, a (meth)acryloyl group is one or both an acryloyl group and a methacryloyl group, and (meth)acrylic acid is one or both acrylic acid and methacrylic acid.

[0035] The polyisocyanate compound (r1) is, for example, an aliphatic diisocyanate compound such as butane diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate; an alicyclic diisocyanate compound such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate; tolylene diisocyanate, Examples include aromatic diisocyanate compounds such as xylylene diisocyanate, tetramethyl xylylene diisocyanate, lysine diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate; and modified forms of these isocyanate compounds, such as isocyanurate modified forms, biuret modified forms, allophanate modified forms, carbodiimide modified forms, urethaneimine modified forms, and polyol modified forms modified with polyols such as diethylene glycol and dipropylene glycol. These may be used individually or in combination of multiple types. Among these, aromatic diisocyanate compounds and their various modified forms are preferred because they yield resin molded articles with excellent heat resistance. When multiple types of polyisocyanate compounds (r1) are used in combination, the proportion of aromatic diisocyanate compounds and their various modified forms relative to the total mass of polyisocyanate compound (r) is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0036] Examples of the polyhydroxy(meth)acrylate compound (r2) include (meth)acrylate compounds that use epoxy resin and (meth)acrylic acid as reaction raw materials.

[0037] Examples of the epoxy resins include diglycidyloxybenzene, diglycidyloxynaphthalene, aliphatic epoxy resins, biphenol-type epoxy resins, bisphenol-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, glycidylamine-type epoxy resins, heterocyclic epoxy resins, glycidyl ester-type epoxy resins, triphenolmethane-type epoxy resins, phenol or naphthol aralkyl-type epoxy resins, phenylene or naphthylene ether-type epoxy resins, oxodoridone-modified epoxy resins, and epoxy resins obtained by brominating these. The epoxy resin may also be an epoxy resin obtained by stretching the above-mentioned specific examples with an elongating agent.

[0038] The aliphatic epoxy resins include, for example, various aliphatic polyol compounds and one or more alkylene oxide adducts thereof that have been polyglycidyl etherified with epihalohydrin. Examples of aliphatic polyol compounds include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methylpropanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1, Examples include aliphatic diol compounds such as 6-hexanediol, 1,4-bis(hydroxymethyl)cyclohesane, and 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and trifunctional or more aliphatic polyol compounds such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0039] Examples of the biphenol-type epoxy resin include biphenol compounds such as biphenol and tetramethylbiphenol, and one or more alkylene oxide adducts thereof, which are polyglycidyl etherified with epihalohydrin.

[0040] Examples of the bisphenol-type epoxy resin include bisphenol compounds such as bisphenol A, tetrabromobisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene, and one or more alkylene oxide adducts thereof, which are polyglycidyl etherified with epihalohydrin.

[0041] Examples of the novolac-type epoxy resin include those obtained by polyglycidyl etherifying a novolac resin, which consists of one or more phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol, with an epihalohydrin.

[0042] Examples of alicyclic epoxy resins include those obtained by hydrogenating the biphenol compounds or bisphenol compounds, or by polyglycidyl etherifying one or more alkylene oxide adducts thereof with epihalohydrin, as well as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 1-eposyethyl-3,4-epoxycyclohexane, and the like.

[0043] Examples of the glycidylamine-type epoxy resins include N,N-diglycidylaniline, triglycidylaminophenol, tetraglycidylxylenediamine, and 4,4'-methylenebis[N,N-diglycidylaniline].

[0044] Examples of the heterocyclic epoxy resins include 1,3-diglycidyl-5,5-dimethylhydantoin and triglycidyl isocyanurate.

[0045] Examples of the glycidyl ester type epoxy resin include diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl-p-oxybenzoic acid, and glycidyl dimer acid.

[0046] Examples of epoxy resin extenders include the various biphenol compounds and their hydrogenated derivatives, the various bisphenol compounds and their hydrogenated derivatives, dibasic acid compounds, and acid group-containing polyester resins.

[0047] Among these, the bisphenol-type epoxy resin is preferred because it exhibits excellent impregnation properties into the reinforcing fiber material and superior strength of the resulting resin molded article. In this case, the epoxy equivalent of the epoxy resin is preferably in the range of 150 to 600 g / equivalent, and more preferably in the range of 200 to 450 g / equivalent.

[0048] The reaction between epoxy resin and (meth)acrylic acid can be carried out by heating at a temperature of approximately 60 to 140°C in the presence of any esterification catalyst. A reaction solvent or polymerization inhibitor may be added as needed. Furthermore, the reaction ratio of epoxy resin to (meth)acrylic acid is preferably such that the molar ratio of the functional groups [carboxyl groups / epoxy groups] is in the range of 0.6 to 1.1.

[0049] When the bisphenol-type epoxy resin is used as the epoxy resin, the hydroxyl value of the resulting (meth)acrylate compound is preferably 50 to 200 mg / KOH. Furthermore, the (meth)acryloyl group equivalent is preferably in the range of 300 to 600 g / equivalent.

[0050] The polyhydroxy(meth)acrylate compound (r2) may be used alone or in combination of multiple types. When multiple types of polyhydroxy(meth)acrylate compounds (r2) are used in combination, the ratio of the bisphenol-type epoxy resin (meth)acrylate compound to the total mass of the polyhydroxy(meth)acrylate compound (r2) is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0051] Examples of the monohydroxy(meth)acrylate compound (r3) include hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, trimethylolpropanedi(meth)acrylate, glycerindi(meth)acrylate, pentaerythritoltri(meth)acrylate, ditrimethylolpropanetri(meth)acrylate, dipentaerythritolpenta(meth)acrylate, (poly)oxyalkylene(meth)acrylate compounds in which (poly)oxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains are introduced into the molecular structure of these compounds, and lactone-modified(meth)acrylate compounds in which a (poly)lactone structure is introduced into the molecular structure of these compounds. These may be used individually or in combination of multiple types.

[0052] Among these, monohydroxymono(meth)acrylate compounds are preferred, and hydroxyethyl(meth)acrylate is more preferred, due to their excellent balance between impregnation into the reinforcing fiber material and the strength of the resulting resin molded article. When multiple types of monohydroxy(meth)acrylate compounds (r3) are used in combination, the ratio of hydroxyethyl(meth)acrylate to the total mass of the monohydroxy(meth)acrylate compounds (r3) is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0053] Examples of the polyhydroxy compound (r4) include dihydroxybenzene, dihydroxynaphthalene, the various aliphatic polyols mentioned above, biphenol compounds, bisphenol compounds, alkylene oxide adducts thereof, and lactone-modified compounds. These may be used individually or in combination of multiple types. Among these, alkylene oxide adducts of bisphenol compounds are preferred because they offer an excellent balance between impregnation into the reinforcing fiber material and the strength of the resulting resin molded article. Furthermore, the average number of added moles of alkylene oxide is preferably in the range of 2 to 10 moles.

[0054] When multiple types of polyhydroxy compounds (r4) are used in combination, it is preferable that the ratio of the alkylene oxide adduct of the bisphenol compound to the total mass of the polyhydroxy compound (r4) is 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0055] In the resin composition (1), the molar ratio (NCO / OH) of isocyanate groups contained in the polyisocyanate compound (r1) to hydroxyl groups contained in the polyhydroxy(meth)acrylate compound (r2) is preferably in the range of 0.3 to 1.2, more preferably in the range of 0.4 to 1.1, and particularly preferably in the range of 0.5 to 1.0, as this provides excellent handling and moldability of the prepreg.

[0056] In the resin composition (2), the molar ratio (NCO / OH) of the isocyanate groups contained in the polyisocyanate compound (r1) to the total hydroxyl groups contained in the monohydroxy(meth)acrylate compound (r3) and the polyhydroxy compound (r4) is preferably in the range of 0.7 to 1.3, more preferably in the range of 0.8 to 1.1, and particularly preferably in the range of 0.8 to 1.0, as this provides excellent handling and moldability of the prepreg. Furthermore, the molar ratio (r3 / r4) of the monohydroxy(meth)acrylate compound (r3) to the polyhydroxy compound (r4) is preferably in the range of 40 / 60 to 80 / 20, and more preferably in the range of 50 / 50 to 70 / 30, as this improves heat resistance and curability.

[0057] The resin compositions (1) and (2) may also contain other polymerizable unsaturated group-containing compounds other than the polyhydroxy(meth)acrylate compound (r2) and the monohydroxy(meth)acrylate compound (r3). Specific examples include, for instance, aliphatic mono(meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, isotridecyl (meth)acrylate, n-stearyl (meth)acrylate, ethylene glycol (meth)acrylate alkyl ether, and propylene glycol (meth)acrylate alkyl ether; alicyclic mono(meth)acrylate compounds such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl mono(meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl methacrylate; and glycidyl (meth)acrylate and tetrahydrofurfuryl acrylate. Mono(meth)acrylate compounds containing heterocyclic rings such as benzyl(meth)acrylate, phenyl(meth)acrylate, phenylbenzyl(meth)acrylate, phenoxy(meth)acrylate, phenoxyethyl(meth)acrylate, phenoxyethoxyethyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, phenoxybenzyl(meth)acrylate, benzylbenzyl(meth)acrylate, phenylphenoxyethyl(meth)acrylate, etc.; Mono(meth)acrylate compounds containing aromatic rings such as phenoxybenzyl(meth)acrylate, phenoxybenzyl(meth)acrylate, etc.; (poly)oxyalkylene-modified mono(meth)acrylate compounds obtained by introducing polyoxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains into the molecular structure of the above-mentioned mono(meth)acrylate monomers; Lactone-modified mono(meth)acrylate compounds obtained by introducing a (poly)lactone structure into the molecular structure of the above-mentioned mono(meth)acrylate compounds;Aliphatic di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate; 1,4-cyclohexanedimethanol di(meth)acrylate, norbornane di(meth)acrylate, norbornane dimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate Alicyclic di(meth)acrylate compounds such as; aromatic ring-containing di(meth)acrylate compounds such as biphenol di(meth)acrylate and bisphenol di(meth)acrylate; polyoxyalkylene-modified di(meth)acrylate compounds in which (poly)oxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains are introduced into the molecular structure of the above-mentioned di(meth)acrylate compounds; lactone-modified di(meth)acrylate compounds in which a (poly)lactone structure is introduced into the molecular structure of the above-mentioned di(meth)acrylate compounds. Meth)acrylate compounds; aliphatic tri(meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate and glycerin tri(meth)acrylate; (poly)oxyalkylene-modified tri(meth)acrylate compounds in which (poly)oxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains are introduced into the molecular structure of the aliphatic tri(meth)acrylate compounds; lactone-modified tri(meth)acrylate compounds in which a (poly)lactone structure is introduced into the molecular structure of the aliphatic tri(meth)acrylate compounds. Tri(meth)acrylate compounds; tetrafunctional or more aliphatic poly(meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; tetrafunctional or more (poly)oxyalkylene-modified poly(meth)acrylate compounds obtained by introducing (poly)oxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains into the molecular structure of the aliphatic poly(meth)acrylate compounds;Examples include lactone-modified poly(meth)acrylate compounds with four or more functions, in which a (poly)lactone structure is introduced into the molecular structure of the aforementioned aliphatic poly(meth)acrylate compound. These may be used individually or in combination of multiple types.

[0058] In particular, (meth)acrylate compounds with a molecular weight in the range of 150 to 600 are preferred because they offer an excellent balance between their impregnation properties into the reinforcing fiber material and the strength of the resulting resin molded article. When multiple types of other polymerizable unsaturated group-containing compounds are used in combination, the proportion of the (meth)acrylate compounds with a molecular weight in the range of 150 to 600 with a molecular weight in the range of 150 to 600 to the total mass of the other polymerizable unsaturated group-containing compounds is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0059] In the resin composition (1) described above, when other polymerizable unsaturated group-containing compounds are used, the amount of these compounds is preferably 40% by mass or less, and more preferably 30% by mass or less, relative to the total mass of the polyisocyanate compound (r1) and the polyhydroxy(meth)acrylate compound (r2), as this provides an excellent balance between impregnation into the reinforcing fiber material and the strength of the resulting resin molded article. Furthermore, when other polymerizable unsaturated group-containing compounds are used in the resin composition (2) described above, the amount of these compounds is preferably 40% by mass or less, and more preferably 30% by mass or less, relative to the total mass of the polyisocyanate compound (r1), the monohydroxy(meth)acrylate compound (r3), and the polyhydroxy compound (r4).

[0060] The resin compositions (1) and (2) described above may contain a polymerization initiator. While any common polymerization initiator can be used without particular limitation, organic peroxides are particularly preferred. Examples of organic peroxides include diacyl peroxide compounds, peroxyester compounds, hydroperoxide compounds, ketone peroxide compounds, alkyl perester compounds, parkerized compounds, and peroxyketals. These may be used individually or in combination. Among these, those with a temperature of 60°C or higher to achieve a 10-hour half-life are preferred, as this shortens the molding time. Furthermore, when manufacturing a laminate by the manufacturing methods 1 and 3 described later, and especially when the core layer (a) or core layer (A) is polystyrene foam, a 10-hour half-life temperature of 90°C or lower is preferred, more preferably 80°C or lower, and particularly preferred 70°C or lower, in order to avoid molding defects due to swelling of the polystyrene foam. Examples of such polymerization initiators include 1,6-bis(t-butylperoxycarbonyloxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-amylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, t-butylperoxydiethyl acetate, t-butylperoxyisopropyl carbonate, t-butylperoxy2-ethylhexyl carbonate, t-amylperoxyisopropyl carbonate, and t-amylperoxy2-ethylhexyl Examples include t-hexyl peroxyisopropyl carbonate, di-tert-butyl peroxyhexahydroterephthalate, t-amyl peroxytrimethylhexanoate, t-amyl peroxyisononaate, t-hexyl peroxy-2-ethylhexanoate, n-butyl 4,4-di(t-butyl peroxy)valerate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, and t-butyl peroxybivalate. The amount of polymerization initiator added is preferably in the range of 0.5 to 3% by mass relative to the total mass of polymerizable unsaturated group-containing compounds in the resin composition.

[0061] The resin compositions (1) and (2) may contain other components in addition to the various compounds mentioned above. Examples of other components include thermoplastic resins, polymerization inhibitors, curing accelerators, fillers, low-shrinkage agents, mold release agents, thickeners, devisers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, UV stabilizers, reinforcing materials, and photocuring agents.

[0062] Examples of the thermoplastic resins include polyamide resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polycarbonate resins, urethane resins, polypropylene resins, polyethylene resins, polystyrene resins, acrylic resins, polybutadiene resins, polyisoprene resins, and those modified by copolymerization or the like. These may be used individually or in combination of two or more types.

[0063] Examples of polymerization inhibitors include hydroquinone, trimethylhydroquinone, pt-butylcatechol, t-butylhydroquinone, toluhydroquinone, p-benzoquinone, naphthoquinone, hydroquinone monomethyl ether, phenothiazine, copper naphthenate, and copper chloride. These may be used individually or in combination of two or more.

[0064] Examples of the curing accelerators include metal soaps such as cobalt naphthenate, cobalt octenoate, vanadyl octenoate, copper naphthenate, and barium naphthenate, and metal chelate compounds such as vanadyl acetyl acetate, cobalt acetyl acetate, and iron acetylacetonate. Examples of amines include N,N-dimethylamino-p-benzaldehyde, N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N-ethyl-m-toluidine, triethanolamine, m-toluidine, diethylenetriamine, pyridine, phenylmorpholine, piperidine, and diethanolaniline. These may be used individually or in combination of two or more.

[0065] The aforementioned fillers can be broadly classified into inorganic compounds and organic compounds. Fillers are primarily added to molded products to adjust their physical properties, such as strength, elastic modulus, impact strength, and fatigue durability.

[0066] Examples of the inorganic compounds include calcium carbonate, magnesium carbonate, barium sulfate, mica, talc, kaolin, clay, Celite, asbestos, Perlite, baryta, silica, silica sand, dolomite limestone, gypsum, aluminum powder, hollow balloons, alumina, glass powder, aluminum hydroxide, granite, zirconium oxide, antimony trioxide, titanium oxide, molybdenum dioxide, and iron powder. Examples of organic compounds include natural polysaccharide powders such as cellulose and chitin, and synthetic resin powders. Examples of synthetic resin powders include powders of organic materials composed of hard resins, soft rubbers, elastomers, or polymers (copolymers), and particles having a multilayer structure such as a core-shell type. Specific examples of synthetic resin powders include particles made of butadiene rubber, acrylic rubber, urethane rubber, silicone rubber, polyimide resin powder, fluororesin powder, and phenolic resin powder. These may be used individually or in combination of two or more types.

[0067] Examples of the mold release agent include zinc stearate, calcium stearate, paraffin wax, polyethylene wax, and carnauba wax. Preferably, paraffin wax, polyethylene wax, and carnauba wax are used. These may be used individually or in combination of two or more types.

[0068] Examples of the thickening agents include metal oxides and metal hydroxides such as magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, as well as acrylic resin-based fine particles. These thickening agents can be used individually or in combination of two or more types.

[0069] Examples of the aforementioned flame retardants include phosphorus-containing compounds, halogen-containing compounds, nitrogen-containing compounds, hydrated metal compounds, borates, metal oxides, and silicone compounds. These flame retardants can be used individually or in combination of two or more types.

[0070] The method for producing the prepreg is not particularly limited, but examples include mixing the components of the matrix resin (r) using a known mixer such as a static mixer, power mixer, planetary mixer, or kneader, impregnating the reinforcing fiber material with the mixture, sandwiching the material between release films, and rolling it with a rolling mill. When impregnating the reinforcing fiber material with the matrix resin (r), heating may be applied as appropriate.

[0071] When using the resin compositions (1) and (2) as the matrix resin (r), the rolled sheet can be left to stand at room temperature to 50°C to allow the isocyanate groups and hydroxyl groups in the resin composition to undergo a urethane reaction, thereby producing a prepreg with excellent storage properties and handling capabilities. Alternatively, when using the resin compositions (1) and (2) as the matrix resin (r), a resin composition in which the urethane reaction has partially progressed during the preparation process may be used.

[0072] The aforementioned prepreg is easy to handle and has excellent moldability, so it is preferably 0.02 mm or more in thickness, more preferably 0.05 mm or more. Furthermore, it is preferably 2.0 mm or less in thickness, more preferably 1.0 mm or less, and particularly preferably 0.5 mm or less.

[0073] The prepreg can be obtained, for example, by applying the obtained resin composition to carrier films placed above and below to a uniform thickness, sandwiching the reinforcing fiber material between the resin composition on the carrier films, then passing the entire structure between impregnation rolls and applying pressure to impregnate the reinforcing fiber material with the resin composition, and finally winding it into a roll or folding it in a zigzag pattern. Furthermore, it is preferable to mature the prepreg at a temperature of 10 to 60°C for 2 to 48 hours after this.

[0074] As the carrier film, polyethylene film, polypropylene film, polyethylene and polypropylene laminate film, polyethylene terephthalate, nylon, etc. can be used.

[0075] In this embodiment, in the first step, a heat-cured body is obtained by heat-curing the prepreg from which the carrier film has been peeled off the obtained carrier film-attached prepreg. It is preferable to perform heat compression molding as the heat curing method.

[0076] As for the aforementioned heat compression molding, for example, a manufacturing method is used in which a predetermined amount of prepreg is weighed, placed into a flat plate press, mold, etc., that has been preheated to 110 to 180°C, the mold is clamped in a compression molding machine to form the prepreg, the prepreg is hardened by maintaining a molding pressure of 0.1 to 30 MPa, and then the molded product is removed from the mold to obtain the molded product. In order to adjust the thickness, strength, etc. of the obtained resin molded product, it is preferable that the number of layers of prepreg placed into the flat plate press, etc., be 1 to 3. The thickness of the resin molded product may also be adjusted by the height of the spacers placed in the mold. As for specific molding conditions, it is preferable to maintain a molding pressure of 1 to 15 MPa for 1 to 5 minutes at a temperature of 100 to 160°C in a flat plate press, and more preferably, a molding condition of maintaining a molding pressure of 1 to 15 MPa for 1 to 3 minutes at a temperature of 140 to 160°C is preferred because it further improves productivity.

[0077] Next, in the second step, a resin molded body is obtained by cutting the obtained heat-cured body to a predetermined size corresponding to the resin molded body. At this time, the heat-cured body is cut so that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bent portion (center line or boundary line of the bent portion) of the obtained resin molded body.

[0078] By performing the first and second steps described above in order, a resin molded body 1 can be obtained, as shown in Figure 1, in which the reinforcing fiber material 2 is oriented at an angle of 15° to 75° with respect to the bending portion 3.

[0079] <<Manufacturing method according to the second embodiment>> The resin molded body 1 of the above-described embodiment can also be manufactured as follows. That is, the method for manufacturing a resin molded body of the second embodiment according to the present invention is a method for manufacturing a sheet-like resin molded body having a bendable bend portion, comprising: an eleventh step of cutting the fiber-reinforced composite material to a predetermined dimension corresponding to the resin molded body; and a twelfth step of obtaining a resin molded body by heat curing the fiber-reinforced composite material cut to the predetermined dimension, wherein in the twelfth step, the fiber-reinforced composite material is cut such that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bend portion.

[0080] In this embodiment, in the 11th step, the obtained carrier film-attached prepreg is cut to a predetermined size corresponding to the resin molded article. At this time, the carrier film-attached prepreg is cut such that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bend portion (center line or boundary line of the bend portion) of the resulting resin molded article. Instead of cutting the carrier film-attached prepreg, the prepreg from which the carrier film has been peeled off may be cut in the same manner.

[0081] Next, in the 12th step, a resin molded body is obtained by heat curing the prepreg, which has been cut to predetermined dimensions, using a flat plate press, a mold, etc. During or after heat curing, a slit parallel to the center line of the bend may be formed. Furthermore, after heat curing, burrs formed on the peripheral edge of the resin molded body may be removed as needed.

[0082] By performing the 11th and 12th steps described above in order, a resin molded body 1 can be obtained, as shown in Figure 1, in which the reinforcing fiber material 2 is oriented at an angle of 15° to 75° with respect to the bending portion 3. [Examples]

[0083] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0084] <Preparation of thermosetting resin composition> In a 2L flask equipped with a thermometer, nitrogen inlet tube, and stirrer, 725 parts by mass of epoxy resin (DIC Corporation's "Epiclon 840," bisphenol A type epoxy resin, epoxy equivalent 186), 335 parts by mass of methacrylic acid, and 0.28 parts by mass of t-butylhydroquinone were charged. The mixture was heated to 90°C under a gas flow of nitrogen and air in a 1:1 ratio. 0.60 parts by mass of 2-methylimidazole was added, and the temperature was raised to 110°C for 10 hours. The reaction was terminated when the acid value fell to 6 or less. After cooling to around 60°C, the mixture was removed from the reaction vessel to obtain vinyl ester resin (A) with a hydroxyl value of 217 mgKOH / g. The hydroxyl value was determined by measuring the amount of potassium hydroxide (mgKOH / g) required to neutralize the acetic acid produced when 1 g of the resin sample was reacted with an acetylating agent at a specified temperature and time according to the method specified in JIS K-0070.

[0085] To 100 parts by mass of the obtained vinyl ester resin (A), 1 part by mass of an organic peroxide (manufactured by Kayaku Akzo Co., Ltd., Trigonox® 117) as a thermosetting agent (C) and 0.9 parts by mass of DBSA (dodecylbenzenesulfonic acid) as a foaming inhibitor (D) were added, and the mixture was then stirred to homogenize it. Furthermore, 20 parts by mass of m-xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., Takenate® 500) as an isocyanate (B) were added and the mixture was stirred. At this time, the NCO / OH ratio, which is the ratio of OH groups of the vinyl ester resin to NCO groups of the polyisocyanate, was 0.55. Furthermore, this mixture was aged at 60°C for 20 hours to prepare a thermosetting resin composition (hereinafter referred to as "resin composition (1)").

[0086] <Prepreg fabrication> The obtained resin composition (1) is melted at a temperature of 90°C and applied to one side of a release PET film with a coating width of 1 m and a weight per unit area of ​​53 g / m². 2 Two sheets were prepared, uniformly coated in the following manner. Next, the resin-coated surfaces of these two sheets were coated with glass cloth (E10T (manufactured by Unitika), 1,060 mm wide, 106 g / m²) as a fiber-reinforced material. 2 The materials were bonded together so that they were in contact with each other. Then, degassing was performed by applying temperature and pressure with an impregnation roll, and the resin composition (1) was impregnated into the glass cloth to produce a prepreg with a release film as a reinforced fiber composite material. The unit weight of the prepreg was 212 g / m². 2 The Resin Content (RC), which represents the weight ratio of the resin composition (1) to the glass cloth, was 50%.

[0087] <Fabrication of resin molded products> The release film was peeled off the obtained prepreg with release film, and the prepreg was fed into a flatbed press. The prepreg was laminated appropriately according to the thickness of the resin molded body to be obtained. The flatbed press was closed, the temperature of the upper plate was set to 140°C and the temperature of the lower plate to 150°C, and the press was applied at a pressure of 3 MPa for 5 minutes to obtain a resin cured body with a thickness D as shown in Table 1. Next, the obtained resin cured body was cut to dimensions of 150 mm in length and 70 mm in width, with the reinforcing fiber material contained in the resin cured body oriented at the angle shown in Table 1 with respect to the center line of the bend of the resulting resin molded body. The resin molded bodies of Examples 1 to 3 and Comparative Examples 1 to 2 were thus produced.

[0088] <Evaluation of resin molded products> The resin molded bodies obtained from the examples and comparative examples were used as test specimens. At a temperature of 25°C, the test specimens were placed horizontally on a flat surface and straightened. The specimens were then bent 180° at the bent portion so that the bending radius R was the value shown in Table 1, and then straightened again. This process was repeated 100 times. When the test specimens were bent, the distance L between both ends of the specimen was 6 mm. Based on the following evaluation criteria, the number of bends until a crack appeared in the test specimen was used as an indicator of bending durability. The results are shown in Table 1. <<Rating>> ○: No cracks appeared in the test specimen after 100 bending operations. ×: After performing the bending motion five times, cracks appeared in the test specimen.

[0089] [Table 1]

[0090] Table 1 shows that the orientation angle θ of the reinforcing fiber material in the resin molded article with respect to the center line of the bend affects the bendability. Furthermore, it is clear that the resin molded articles of Examples 1 to 3 have superior bendability compared to the resin molded articles of Comparative Examples 1 and 2. [Explanation of symbols]

[0091] 1... Resin molded body, 2... Reinforced fiber material, 3... Bending part.

Claims

1. A sheet-like resin molded body made of a heat-cured fiber-reinforced composite material containing reinforcing fiber material and resin, having a bendable portion, A resin molded article characterized in that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bending portion.

2. The resin molded article according to claim 1, wherein the thickness of the resin molded article is 70 μm or more and 500 μm or less.

3. The resin molded article according to claim 1 or claim 2, wherein the reinforcing fiber material has one or more forms selected from the group consisting of unidirectional materials, woven fabrics, and knitted fabrics in which reinforcing fibers are aligned in one direction.

4. The resin molded article according to claim 1 or claim 2, wherein the reinforcing fiber material is one or more fibers selected from the group consisting of glass fibers and carbon fibers.

5. A resin molded article according to claim 1 or claim 2, which is a smartphone casing, a tablet device casing, or a solar panel cover.

6. A method for manufacturing a sheet-like resin molded body comprising a heat-cured fiber-reinforced composite material containing reinforcing fiber material and resin, and having a bendable portion, A first step is to obtain a heat-cured body by heat-curing the fiber-reinforced composite material, The process includes a second step of obtaining a resin molded body by cutting the heat-cured body to a predetermined size corresponding to the resin molded body, A method for manufacturing a resin molded article, characterized in that, in the second step, the heat-cured article is cut such that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bent portion.

7. A method for manufacturing a sheet-like resin molded body comprising a heat-cured fiber-reinforced composite material containing reinforcing fiber material and resin, and having a bendable portion, An eleventh step of cutting the fiber-reinforced composite material to a predetermined size corresponding to the resin molded body, The process includes a 12th step of obtaining a resin molded body by heat curing the fiber-reinforced composite material that has been cut to predetermined dimensions, A method for manufacturing a resin molded article, characterized in that, in the 12th step, the fiber-reinforced composite material is cut such that the reinforcing fiber material is oriented at an angle of 15° to 75° with respect to the bending portion.

8. The method for manufacturing a resin molded article according to claim 6 or claim 7, wherein when the fiber-reinforced composite material is heat-cured, the number of layers of the fiber-reinforced composite material is 1 or more and 3 or less.

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