Resin molded body and resin molding material

Abstract

To provide a resin molded body with excellent electromagnetic wave attenuation performance.SOLUTION: A resin molded body has an electromagnetic wave attenuation layer that contains a resin and a carbon fiber. The average length of the carbon fiber is 5 mm or less, and the content of the carbon fiber is 0.35 mass% or less on the basis of the total mass of the electromagnetic wave attenuation layer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin molding and a resin molding material. [Background technology]

[0002] As a measure against electromagnetic noise leaking from electronic devices such as personal computers, electronic devices have been shielded from electromagnetic waves using metal cases or metal-plated plastics. In particular, in recent years, it has become important to take measures against electromagnetic waves emitted by electronic components and high-frequency circuits that cause the electronic devices to malfunction (so-called auto-poisoning). In the field of automobiles, where electronic control is highly advanced, millimeter-wave radars are used for the purpose of autonomous driving and collision damage reduction, and it is necessary to prevent auto-poisoning of high-frequency circuits inside the radar device housing.

[0003] In response to this, for example, Patent Document 1 discloses a radio wave absorber that has high radio wave absorption regardless of the direction of radio wave incidence, is easy to handle, and can be manufactured at a manufacturing cost that allows it to be widely used as a general building material for offices, stores, logistics warehouses, public buildings, general housing, and condominiums, so as to be suitable for wireless communication systems such as wireless LANs and RFIDs that have a high degree of freedom in service areas. The radio wave absorber is characterized in that it is made by laminating a resistive film layer containing 0.4 to 3 mass % of conductive fibers with an average fiber length of 2 to 11 mm, a spacer, and a reflective material layer, and that at the frequency at which the maximum radio wave absorption is shown for perpendicular incidence, both the maximum radio wave absorption and the radio wave absorption in a measurement direction perpendicular to the measurement direction at which the maximum radio wave absorption is shown are 10 dB or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-39074 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a resin molding having excellent electromagnetic wave attenuation properties, and a resin molding material for use in said resin molding. [Means for solving the problem]

[0006] As a result of investigations aimed at solving the above-mentioned problems, the inventors have found that in a resin molded body and a resin molding material containing resin and carbon fiber, when the average length and content of the carbon fibers are within a specific range, superior electromagnetic wave attenuation properties are exhibited compared to when the average length and content are outside the range.

[0007] In some aspects, the present invention provides the following [1] to [8]. [1] A resin molded product having an electromagnetic wave attenuation layer containing resin and carbon fiber, wherein the average length of the carbon fiber is 5 mm or less, and the carbon fiber content is 0.35 mass% or less based on the total mass of the electromagnetic wave attenuation layer. [2] The resin molded body according to [1], wherein the electromagnetic wave attenuation layer further comprises an aggregate of fibers different from the carbon fibers. [3] The resin molded body according to [2], wherein the assembly is any one of a woven fabric, a nonwoven fabric, a cut fiber bundle mat, and a paper body. [4] The resin molded body according to [2] or [3], wherein the aggregate contains at least one fiber selected from the group consisting of glass fibers, ceramic fibers, fibers derived from natural stones, and organic fibers. [5] The resin molded article according to any one of [1] to [4], further comprising an electromagnetic wave reflective layer. [6] The resin molded body according to [5], wherein the electromagnetic wave reflective layer contains a resin and a carbon fiber. [7] The resin molding according to any one of [1] to [6], wherein the resin molding is an electromagnetic wave attenuation sheet or a housing for electronic equipment. [8] A resin molding material used for the resin molded body according to any one of [1] to [7], comprising a resin and carbon fibers, the carbon fibers having an average length of 5 mm or less, and a carbon fiber content of 0.35 mass% or less based on the total mass of the resin molding material. Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a resin molding having excellent electromagnetic wave attenuation properties, and a resin molding material used for the resin molding. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic cross-sectional view showing one embodiment of a resin molded body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described. One embodiment of the present invention is a resin molded body having an electromagnetic wave attenuation layer containing resin and carbon fiber. The resin molded body is obtained by molding a resin molding material (hereinafter also referred to as "resin molding material (1)") containing resin and carbon fiber for forming the electromagnetic wave attenuation layer. That is, another embodiment of the present invention is a resin molding material used for the resin molded body (more specifically, the electromagnetic wave attenuation layer), which is a resin molding material containing resin and carbon fiber.

[0011] The electromagnetic wave attenuation layer (hereinafter also simply referred to as "attenuation layer") is a layer capable of attenuating incident electromagnetic energy, and more specifically, may be a layer capable of attenuating electromagnetic waves of 30 GHz or more, 40 GHz or more, 50 GHz or more, or 60 GHz or more, or may be a layer capable of attenuating electromagnetic waves of 300 GHz or less, 200 GHz or less, 100 GHz or less, or 90 GHz or less.

[0012] The attenuation layer may be a layer that exhibits a peak of electromagnetic return loss of -5 dB or more, -10 dB or more, -15 dB or more, or -20 dB or more in the frequency range of 60 to 90 GHz when the electromagnetic return loss is measured according to the description in "Measurement of electromagnetic attenuation" in the Examples. The attenuation layer may be a layer that exhibits an electromagnetic transmission attenuation of -70 dB or more, -75 dB or more, -80 dB or more, or -85 dB or more over the entire frequency range of 60 to 90 GHz when the electromagnetic transmission attenuation is measured according to the description in "Measurement of electromagnetic attenuation" in the Examples.

[0013] In one embodiment of the present invention, the resin contained in the damping layer and the resin molding material (1) may be any commonly used resin, and is not particularly limited. In one embodiment, a curable resin may be used as the resin contained in the damping layer and the resin molding material (1). In this case, the damping layer and the resin molding material (1) provided in the resin molded body may be a cured product of a resin composition (described in detail below) containing the curable resin.

[0014] The resin composition is not particularly limited and can be arbitrarily selected depending on the desired physical properties of the molded product, the application, etc. Among them, the resin composition is preferably an epoxy resin composition or a vinyl ester resin composition, since a molded product with higher strength can be obtained. Hereinafter, the details of both resin compositions will be described.

[0015] The epoxy resin composition is a thermosetting resin composition containing an epoxy group-containing compound and a curing agent or a curing accelerator. The epoxy group-containing compound is not particularly limited in its specific structure as long as it has an epoxy group in its molecular structure, and a wide variety of compounds can be used, and one type may be used alone, or two or more types may be used in combination. Among them, the epoxy group-containing compound is preferably a compound having two or more epoxy groups in its molecular structure, since it becomes an epoxy resin composition having excellent curing reaction. The ratio of the compound having two or more epoxy groups in the molecular structure to the entire epoxy group-containing compound is preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0016] Examples of the epoxy group-containing compound include diglycidyloxybenzene, diglycidyloxynaphthalene, biphenol-type epoxy resins, bisphenol-type epoxy resins, polyglycidyl ethers of aliphatic polyols, 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, oxolidone-modified epoxy resins, brominated epoxy resins thereof, and epoxy resins obtained by extending these epoxy group-containing compounds with an extender.

[0017] Examples of the biphenol type epoxy resin include biphenol compounds such as biphenol and tetramethylbiphenol, and polyglycidyl ethers of one or more alkylene oxide adducts of these biphenol compounds with epihalohydrin.

[0018] Examples of the bisphenol type epoxy resin include bisphenol compounds such as bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene, and polyglycidyl ethers of one or more alkylene oxide adducts of these bisphenol compounds with epihalohydrin.

[0019] Examples of the polyglycidyl ether of the aliphatic polyol include polyglycidyl ethers of one or more of various aliphatic polyol compounds and their alkylene oxide adducts with epihalohydrin. Examples of the aliphatic polyol compound 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, Examples of the diol compounds include aliphatic diol compounds such as 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and aliphatic polyol compounds with three or more functional groups such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0020] Examples of the novolac type epoxy resin include novolac resins made of one or more kinds of phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol, which are polyglycidyl etherified with epihalohydrin.

[0021] Examples of the alicyclic epoxy resin include those obtained by hydrogenating the biphenol compounds or bisphenol compounds, and those obtained by polyglycidyl etherifying one or more of the alkylene oxide adducts thereof with epihalohydrin, as well as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 1-epoxyethyl-3,4-epoxycyclohexane, and the like.

[0022] Examples of the glycidylamine type epoxy resin include N,N-diglycidylaniline, triglycidylaminophenol, tetraglycidylxylenediamine, and 4,4'-methylenebis[N,N-diglycidylaniline].

[0023] Examples of the heterocyclic epoxy resin include 1,3-diglycidyl-5,5-dimethylhydantoin and triglycidyl isocyanurate.

[0024] Examples of the glycidyl ester type epoxy resin include diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl-p-oxybenzoate, and glycidyl dimerate.

[0025] Examples of the extender for the epoxy resin include the above-mentioned various biphenol compounds and hydrogenated products thereof, the above-mentioned various bisphenol compounds and hydrogenated products thereof, dibasic acid compounds, and acid group-containing polyester resins.

[0026] Among these, the epoxy resin is preferably the bisphenol type epoxy resin, and more preferably a bisphenol type epoxy resin having an epoxy equivalent in the range of 160 to 260 g / equivalent, because it provides excellent strength and carbon fiber impregnation of the molded product. The proportion of the bisphenol type epoxy resin in the entire epoxy group-containing compound is preferably 40 mass% or more, more preferably 60 mass% or more, and particularly preferably 70 mass% or more. The proportion is preferably 95 mass% or less, and more preferably 90 mass% or less.

[0027] In terms of achieving even better carbon fiber impregnation, the epoxy resin is preferably a polyglycidyl ether of the aliphatic polyol, and more preferably a polyglycidyl ether of an aliphatic polyol having 2 to 6 carbon atoms. The proportion of the bisphenol-type epoxy resin in the entire epoxy group-containing compound is preferably 5% by mass or more, and more preferably 10% by mass or more. The proportion is preferably 50% by mass or less, and more preferably 35% by mass or less.

[0028] When the bisphenol type epoxy resin and the polyglycidyl ether of the aliphatic polyol are used in combination, the mass ratio of the two (bisphenol type epoxy resin) / (polyglycidyl ether of the aliphatic polyol) is preferably in the range of 60 / 40 to 95 / 5, and more preferably in the range of 70 / 30 to 85 / 15.

[0029] As the curing agent or curing accelerator, various compounds generally used as curing agents or curing accelerators for epoxy group-containing compounds can be used without any particular limitation. The curing agent or curing accelerator may be used alone or in combination of two or more kinds.

[0030] Examples of the curing agent or curing accelerator include amine compounds, amide compounds, acid anhydrides, phenolic hydroxyl group-containing compounds, phosphorus compounds, imidazole compounds, imidazoline compounds, urea compounds, organic acid metal salts, Lewis acids, and amine complex salts.

[0031] Examples of the amine compound include aliphatic amine compounds such as ethylenediamine, tetramethylethylenediamine, diethylenetriamine, hexamethylenediamine, triethylenetetramine, and guanidine derivatives; alicyclic and heterocyclic amine compounds such as piperidine, piperazine, isophoronediamine, and 1,8-diazabicyclo-[5.4.0]-undecene (DBU); aromatic amine compounds such as phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzylmethylamine, dimethylbenzylamine, xylylenediamine, and pyridine; and boron trifluoride amine complexes.

[0032] Examples of the amide compound include dicyandiamide and polyamidoamine. Examples of the polyamidoamine include those obtained by reacting an aliphatic dicarboxylic acid such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, or azelaic acid, or a carboxylic acid compound such as a fatty acid or a dimer acid, with an aliphatic polyamine or a polyamine having a polyoxyalkylene chain.

[0033] Examples of the acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0034] Examples of the phenolic hydroxyl group-containing resin include various novolak resins, dicyclopentadiene-phenol addition type resins, phenol or naphthol aralkyl resins, triphenolmethane resins, phenol or naphthol aralkyl resins, phenylene or naphthylene ether resins, and aminotriazine-modified phenol resins.

[0035] Examples of the phosphorus compound include alkyl phosphines such as ethylphosphine and butylphosphine, primary phosphines such as phenylphosphine, dialkyl phosphines such as dimethylphosphine and dipropylphosphine, secondary phosphines such as diphenylphosphine and methylethylphosphine, and tertiary phosphines such as trimethylphosphine, triethylphosphine and triphenylphosphine.

[0036] Examples of the imidazole compound include imidazole, 1-methylimidazole, 2-methylimidazole, 3-methylimidazole, 4-methylimidazole, 5-methylimidazole, 1-ethylimidazole, 2-ethylimidazole, 3-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 1-n-propylimidazole, 2-n-propylimidazole, 1-isopropylimidazole, 2 -Isopropylimidazole, 1-n-butylimidazole, 2-n-butylimidazole, 1-isobutylimidazole, 2-isobutylimidazole, 2-undecyl-1H-imidazole, 2-heptadecyl-1H-imidazole, 1,2-dimethylimidazole, 1,3-dimethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-phenylimidazole, 2-phenyl-1H- Imidazole, 4-methyl-2-phenyl-1H-imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole Examples of the isocyanuric acid adduct include isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, and 1-benzyl-2-phenylimidazole hydrochloride.

[0037] Examples of the imidazoline compound include 2-methylimidazoline and 2-phenylimidazoline.

[0038] Examples of the urea compound include p-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-N,N-dimethylurea, N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea, and 4,4'-methylenebisphenyldimethylurea.

[0039] Among these, the curing agent or curing accelerator is preferably an amine compound, an amide compound, an imidazole compound, or a urea compound, since it cures quickly and gives a cured product with excellent strength.

[0040] The amount of the curing agent or curing accelerator in the epoxy resin composition is preferably in the range of 0.5 to 1.2 moles of functional group or active hydrogen in the curing agent per mole of epoxy group in the epoxy group-containing compound when using a compound having a functional group that can react with an epoxy group, such as an amine compound, an amide compound, an acid anhydride, or a phenolic hydroxyl group-containing compound. Also, when using a phosphorus compound, an imidazole compound, an imidazoline compound, a urea-based compound, or the like, it is preferable to mix the curing agent or curing accelerator in a ratio of 0.5 to 20 parts by mass per 100 parts by mass of the epoxy group-containing compound.

[0041] The epoxy resin composition may contain other components other than the epoxy group-containing compound and the curing agent or curing accelerator. Examples of other components include curable compounds other than the epoxy group-containing compound, curing agent, or curing accelerator, curing catalysts, water absorbents, thermoplastic resins, inorganic fillers, low shrinkage agents, mold release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, ultraviolet stabilizers, reinforcing materials, etc. These other components are added appropriately depending on the desired performance and applications of the sheet molding compound, and the amount of addition is also arbitrary.

[0042] In particular, the epoxy resin composition preferably further contains a polyhydroxy compound and a polyisocyanate compound, since this results in a sheet molding compound that is excellent in handleability, such as peelability from the carrier film, etc. In this case, the total mass of the epoxy group-containing compound, the curing agent or curing accelerator, the polyhydroxy compound, and the polyisocyanate compound in the epoxy resin composition is preferably 80 mass% or more, and particularly preferably 90 mass% or more.

[0043] The polyhydroxy compound is not particularly limited in its specific structure, and a wide variety of compounds can be used as long as it has a plurality of hydroxyl groups in its molecular structure. The polyhydroxy compound may be used alone or in combination of two or more kinds. In this specification, the polyhydroxy compound having an epoxy group is treated as the epoxy group-containing compound.

[0044] Examples of the polyhydroxy compound include aliphatic polyol compounds, dihydroxybenzenes, dihydroxynaphthalenes, trihydroxybenzenes, trihydroxynaphthalenes, triphenol alkanes, biphenol compounds, bisphenol compounds, alicyclic polyol compounds, novolak resins, phenol or naphthol aralkyl resins, phenylene or naphthylene ether resins, and alkylene oxide adducts thereof.

[0045] Examples of the aliphatic polyol compound 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, and neopentyl glycol. aliphatic diol compounds such as 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and aliphatic polyol compounds with three or more functional groups such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0046] Examples of the biphenol compound include biphenol and tetramethylbiphenol.

[0047] Examples of the bisphenol compound include bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene.

[0048] Examples of the alicyclic polyol compound include cyclohexanediol and hydrogenated biphenol compounds and bisphenol compounds.

[0049] Examples of the novolak type resin include novolak resins made of one or more of various phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol.

[0050] Among them, it is preferable to use a polyhydroxy compound having a hydroxyl equivalent in the range of 125 to 600 g / equivalent, since it is a sheet molding compound having excellent handling properties such as peelability from a carrier film, and the ratio of polyhydroxy compounds having a hydroxyl equivalent in the range of 125 to 600 g / equivalent to the total polyhydroxy compounds is more preferably 70% by mass or more, and particularly preferably 80% by mass or more. In addition, the polyhydroxy compound is preferably one having a (poly)alkylene oxide structure in its molecular structure, more preferably an alkylene oxide adduct of the aliphatic polyol compound or the bisphenol compound, and more preferably an aliphatic polyol compound having 2 to 6 carbon atoms. In addition, it is more preferable that the hydroxyl equivalent is in the range of 150 to 400 g / equivalent.

[0051] In addition, the amount of the polyhydroxy compound is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, relative to 100 parts by mass of the epoxy group-containing compound, in order to provide a sheet molding compound having excellent handleability, such as strength of the molded product and peelability from the carrier film.

[0052] The polyisocyanate compound may have any of a wide variety of structures without any particular limitations, so long as it has a plurality of isocyanate groups in its molecular structure. The polyisocyanate compound may be used alone or in combination of two or more. Specific examples include aliphatic diisocyanate compounds such as butane diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and dimer acid diisocyanate; alicyclic diisocyanate compounds such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate; toluene diisocyanate, and xylylene diisocyanate. aromatic diisocyanate compounds such as tetramethylxylylene diisocyanate, tolidine diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate; modified products of these isocyanate compounds, such as isocyanurate modified products, biuret modified products, allophanate modified products, carbodiimide modified products, and urethane imine modified products, as well as polyol modified products modified with a polyol having a number average molecular weight of 1,000 or less, such as diethylene glycol or dipropylene glycol.

[0053] Among these, aromatic polyisocyanate compounds or various modified products thereof are preferred because they provide a sheet molding compound with excellent handling properties such as peelability from the carrier film, etc. The isocyanate group content is preferably 15% by mass or more, more preferably 20% by mass or more, and is preferably 40% by mass or less.

[0054] The amount of the polyisocyanate compound added is preferably 0.5 or more, more preferably 0.8 or more, in terms of the mole number of isocyanate groups in the polyisocyanate compound per mole of hydroxyl groups in the polyhydroxy compound, in order to obtain a sheet molding compound having excellent handling properties such as peelability from a carrier film, and is preferably 3.0 or less, more preferably 1.5 or less, and particularly preferably 1.2 or less.

[0055] When the epoxy resin composition contains the polyisocyanate compound or the polyol compound, a urethanization catalyst or a water absorbing agent may be added as necessary. The urethanization catalyst may be used alone or in combination of two or more. Examples of the urethanization catalyst include amine compounds such as triethylamine, dibutylamine, triethylenediamine, and pyridine; phosphorus compounds such as triphenylphosphine and triethylphosphine; organic tin compounds such as dibutyltin dilaurate, octyltin trilaurate, octyltin diacetate, dibutyltin diacetate, and tin octylate; organic zinc compounds such as zinc amine, zinc carboxylate, zinc stearate, and zinc octylate; organic bismuth compounds such as bismuth carboxylate; organic zirconium compounds such as zirconium acetylacetonate and zirconium tetraethanolate; organic aluminum compounds such as aluminum triethoxide; and organic titanium compounds such as titanium tetrabutylate and titanium ethylacetoacetate. Among them, organic zinc compounds and organic bismuth compounds are preferred because they are safer to living organisms and have better storage stability.

[0056] When the urethanization catalyst is used, the amount added is preferably in the range of 0.002 to 1 mass %, more preferably in the range of 0.01 to 0.8 mass %, based on the total mass of the epoxy group-containing compound, the curing agent or curing accelerator, the polyhydroxy compound, and the polyisocyanate compound.

[0057] The water absorbing agent may be used alone or in combination of two or more kinds. Examples of the water absorbing agent include silica gel, activated alumina, and molecular sieves. Among these, molecular sieves are preferred because of their excellent water absorption efficiency. The pore size is preferably in the range of 0.1 to 0.5 nm, and more preferably in the range of 0.2 to 0.4 nm. The particle size is preferably 50 um or less, and more preferably 10 um or less. When the water absorbing agent is used, the amount of the water absorbing agent added is preferably in the range of 0.1 to 5 mass% based on the total mass of the epoxy group-containing compound, the curing agent or curing accelerator, the polyhydroxy compound, and the polyisocyanate compound.

[0058] In order to obtain excellent impregnation of carbon fibers, the viscosity of the epoxy resin composition at 25°C is preferably 100 mPa·s or more, more preferably 300 mPa·s or more, and is preferably 10,000 mPa·s or less, more preferably 6,000 mPa·s or less. In this specification, the viscosity of the epoxy resin composition is measured within 10 minutes after all the ingredients of the epoxy resin composition are mixed.

[0059] The vinyl ester resin composition is a thermosetting resin composition containing a vinyl ester resin. Examples of vinyl ester resins include those using an epoxy group-containing compound and (meth)acrylic acid as reaction raw materials. One type of vinyl ester resin may be used alone, or two or more types may be used in combination. In this specification, "(meth)acrylic acid" refers to either or both of acrylic acid and methacrylic acid, and "(meth)acrylate" refers to either or both of acrylate and methacrylate.

[0060] The epoxy group-containing compound that is the reaction raw material of the vinyl ester resin may be any of the various compounds exemplified above as those contained in the epoxy resin composition. Among them, the bisphenol type epoxy resin or the epoxy resin obtained by elongating the bisphenol type epoxy resin with an elongating agent is preferred because of its excellent strength and carbon fiber impregnation of the molded product. The epoxy equivalent of the bisphenol type epoxy resin or the epoxy resin obtained by elongating the bisphenol type epoxy resin with an elongating agent is preferably 160 g / equivalent or more, more preferably 170 g / equivalent or more, and is preferably 400 g / equivalent or less, more preferably 380 g / equivalent or less.

[0061] The reaction between the epoxy group-containing compound and (meth)acrylic acid can be carried out by heating at a temperature of about 60 to 140°C in the presence of any esterification catalyst. If necessary, a reaction solvent or a polymerization inhibitor may be added. In addition, the reaction ratio of the epoxy group-containing compound and (meth)acrylic acid is preferably such that the molar ratio of the functional groups of both [carboxy group / epoxy group] is in the range of 0.6 to 1.1 in order to obtain a vinyl ester resin with an excellent balance of performance such as impregnation ability into carbon fiber and curing ability. When multiple types of the vinyl ester resin are used in combination, multiple epoxy group-containing compounds may be (meth)acrylated together, or each may be (meth)acrylated separately and mixed.

[0062] The proportion of the vinyl ester resin using the bisphenol-type epoxy resin or the epoxy resin obtained by elongating the bisphenol-type epoxy resin with an elongator as a reaction raw material in the entire vinyl ester resin is preferably 70 mass % or more, more preferably 80 mass % or more, and particularly preferably 90 mass % or more.

[0063] The vinyl ester resin composition may contain other components other than the vinyl ester resin composition. Examples of other components include polymerizable unsaturated group-containing compounds other than the vinyl ester resin, polyisocyanate compounds, curing catalysts, water absorbents, thermoplastic resins, inorganic fillers, shrinkage reducing agents, release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, ultraviolet stabilizers, reinforcing materials, etc. These other components are added appropriately according to the desired performance and applications of the sheet molding compound, and the amount of addition is also arbitrary.

[0064] Among them, it is preferable to use a polymerizable unsaturated group-containing compound other than the vinyl ester resin, because it is excellent in strength of the molded product and carbon fiber impregnation. The polymerizable unsaturated group-containing compound may be used alone or in combination of two or more. When using a polymerizable unsaturated group-containing compound, the ratio of the vinyl ester compound to the total of both is preferably 30% by mass or more, more preferably 40% by mass or more, particularly preferably 50% by mass or more, and is preferably 85% by mass or less, more preferably 70% by mass or less.

[0065] Examples of the polymerizable unsaturated group-containing compound include 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, propylene glycol Aliphatic mono(meth)acrylate compounds such as chol(meth)acrylate alkyl ether; alicyclic mono(meth)acrylate compounds such as cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, adamantyl mono(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, dicyclopentanyl methacrylate; heterocyclic mono(meth)acrylate compounds such as glycidyl(meth)acrylate, tetrahydrofurfuryl acrylate; benzyl(meth)acrylate, phenyl(meth)acrylate, phenyl(meth)acrylate, aromatic ring-containing mono(meth)acrylate compounds such as phenylbenzyl (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, phenoxybenzyl (meth)acrylate, benzyl benzyl (meth)acrylate, and phenylphenoxyethyl (meth)acrylate; ) (poly)oxyalkylene-modified mono(meth)acrylate compounds having a polyoxyalkylene chain such as an oxytetramethylene chain introduced therein; lactone-modified mono(meth)acrylate compounds having a (poly)lactone structure introduced into the molecular structure of the various mono(meth)acrylate compounds mentioned above; 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, and neopentyl glycol di(meth)acrylate;Alicyclic di(meth)acrylate compounds such as 1,4-cyclohexanedimethanol di(meth)acrylate, norbornane di(meth)acrylate, norbornane dimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate; aromatic ring-containing di(meth)acrylate compounds such as biphenol di(meth)acrylate and bisphenol di(meth)acrylate; and compounds having (poly)oxyethylene in the molecular structure of the above di(meth)acrylate compounds. polyoxyalkylene-modified di(meth)acrylate compounds having a (poly)oxyalkylene chain such as a propylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain introduced therein; lactone-modified di(meth)acrylate compounds having a (poly)lactone structure introduced into the molecular structure of the above-mentioned various di(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 a (poly)oxyalkylene chain such as a (poly)oxyethylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain has been introduced into the aliphatic tri(meth)acrylate compound; lactone-modified tri(meth)acrylate compounds in which a (poly)lactone structure has been introduced into the molecular structure of the aliphatic tri(meth)acrylate compound; pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate aliphatic poly(meth)acrylate compounds having 4 or more functional groups, such as tetrafunctional or higher functional poly(meth)acrylates; (poly)oxyalkylene-modified poly(meth)acrylate compounds having 4 or more functional groups in which a (poly)oxyalkylene chain, such as a (poly)oxyethylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain, has been introduced into the molecular structure of the aliphatic poly(meth)acrylate compounds; and lactone-modified poly(meth)acrylate compounds having 4 or more functional groups in which a (poly)lactone structure has been introduced into the molecular structure of the aliphatic poly(meth)acrylate compounds.

[0066] Among these, the aromatic ring-containing (meth)acrylate compounds are preferred, and aromatic ring-containing mono(meth)acrylates are more preferred, because they provide excellent strength of molded articles and carbon fiber impregnation properties.

[0067] In addition, the vinyl ester resin composition preferably contains a polyisocyanate compound, since it becomes a sheet molding compound with excellent handling properties such as peelability from a carrier film. The polyisocyanate compound may be used alone or in combination of two or more. The amount of the polyisocyanate compound added is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the vinyl ester resin and the polymerizable unsaturated group-containing compound.

[0068] The polyisocyanate compound may be any of the various compounds exemplified as those that may be contained in the epoxy resin composition. Among them, aromatic polyisocyanate compounds or various modified compounds thereof are preferred because they provide a sheet molding compound with excellent handling properties such as peelability from a carrier film. The isocyanate group content is preferably 15% by mass or more, more preferably 20% by mass or more, and is preferably 40% by mass or less.

[0069] The vinyl ester resin composition may contain a polymerization initiator. The polymerization initiator may be a general one without any particular limitation, but is preferably an organic peroxide. Examples of the organic peroxide include diacyl peroxide compounds, peroxyester compounds, hydroperoxide compounds, ketone peroxide compounds, alkyl perester compounds, percarbonate compounds, and peroxyketals. These polymerization initiators may be used alone or in combination of two or more. From the viewpoint of the balance between storage stability and curability, the amount of the polymerization initiator added is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and more preferably 3% by mass or less, and more preferably 2% by mass or less, based on the total mass of the vinyl ester resin and the polymerizable unsaturated group-containing compound.

[0070] The vinyl ester resin composition may contain a polymerization inhibitor. Examples of the polymerization inhibitor include hydroquinone, trimethylhydroquinone, pt-butylcatechol, t-butylhydroquinone, toluhydroquinone, p-benzoquinone, naphthoquinone, hydroquinone monomethyl ether, phenothiazine, copper naphthenate, and copper chloride. These may be used alone or in combination of two or more. The amount of the polymerization inhibitor added is preferably in the range of 0.01 to 3 mass% based on the total mass of the vinyl ester resin and the polymerizable unsaturated group-containing compound.

[0071] In order to provide excellent impregnation of carbon fibers, the viscosity of the vinyl ester resin composition at 25°C is preferably 100 mPa·s or more, more preferably 300 mPa·s or more, and is preferably 10,000 mPa·s or less, more preferably 6,000 mPa·s or less. In this specification, the viscosity of the vinyl ester resin composition is measured within 10 minutes after all the ingredients of the vinyl ester resin composition are mixed.

[0072] Thermoplastic resins may be used as the resins contained in the damping layer and the resin molding material (1). Examples of thermoplastic resins include polyamide resins, polyacetal resins, aromatic polyester resins such as polyethylene terephthalate resins, polybutylene terephthalate resins, and polycarbonate resins, polyurethane resins, polyolefin resins such as polypropylene resins and polyethylene resins, polystyrene resins, acrylic resins, polyarylene sulfide resins, and resins modified by copolymerization or the like. These may be used alone or in combination of two or more.

[0073] In order to obtain excellent electromagnetic wave attenuation properties, the carbon fibers contained in the attenuation layer and the resin molding material (1) have an average length of 5 mm or less. The average length of the carbon fibers may be preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more.

[0074] The average length of the carbon fibers is measured by the following method. Approximately 20 mg of carbon fiber is weighed into a polyethylene cup and rubbed against the cup wall with a metal spatula to defibrate it. The carbon fiber attached to the cup wall is pressed onto one side of a weak adhesive double-sided tape to attach it to the tape. The other side of the double-sided tape to which the carbon fiber has been attached is attached flatly to a white plastic sheet to create a sheet for microscopic observation. This sheet for microscopic observation is observed with the following optical microscope device, and optical images are obtained. Carbon fibers of 1 to 5 mm in length could be observed as being almost straight, so the distance obtained using the two-point distance measurement tool of the following image analysis software was used as the length of the fiber. 100 carbon fibers are randomly selected, their lengths are measured and recorded, and the number average length is calculated. As the optical microscope device, for example, a digital microscope VR-3200 manufactured by KEYENCE Corporation can be used, and the magnification of the microscope can be, for example, 12 to 40 times depending on the length of the carbon fiber. As the analysis software, for example, software VR-3000 G2 observation application Ver2.4.0.115 (plane measurement-two-point distance measurement tool) manufactured by KEYENCE Corporation can be used.

[0075] In addition, when measuring the average length of the carbon fibers, if it is necessary to separate and recover the carbon fibers from the resin molding (damping layer) or the resin molding material (1), the carbon fibers are separated and recovered by the following method. The resin molding (damping layer) or resin molding material (1) containing carbon fiber is placed in a magnetic crucible and heated in air in a muffle furnace set at 150°C for 1 hour, then heated to 550°C and heated for an additional 2.5 hours. After cooling, the carbon fiber can be separated and recovered from the residue in the crucible.

[0076] The carbon fiber used in the attenuation layer may be a monofilament or a carbon fiber bundle, and is preferably a monofilament since it has better electromagnetic wave attenuation properties.

[0077] From the viewpoint of obtaining excellent electromagnetic wave attenuation properties, the carbon fiber content may be 0.35 mass % or less, preferably 0.3 mass % or less, more preferably 0.25 mass % or less, even more preferably 0.2 mass % or less, particularly preferably 0.15 mass % or less, or most preferably 0.1 mass % or less, based on the total mass of the attenuation layer (resin molding material (1)). Also, it may be 0.01 mass % or more, preferably 0.02 mass % or more, more preferably 0.03 mass % or more, even more preferably 0.04 mass % or more, or most preferably 0.05 mass % or more.

[0078] In one embodiment of the present invention, the damping layer and the resin molding material (1) may further include an aggregate of fibers other than carbon fibers (hereinafter also referred to as a "fiber aggregate") from the viewpoint of easily ensuring the thickness and strength of the damping layer. In this case, the fiber aggregate may be in a state of being impregnated with the above-mentioned resin (resin composition). Examples of the fiber aggregate include woven fabric, nonwoven fabric, cut fiber bundle mat, and paper body. The fiber aggregate may include at least one fiber selected from the group consisting of glass fiber, ceramic fiber, fiber derived from natural stone, and organic fiber. Examples of the fiber aggregate containing glass fiber include chopped glass fiber mat, glass fiber woven fabric, and glass fiber nonwoven fabric. Examples of the ceramic fiber include alumina fiber, zirconia fiber, and boron fiber. Examples of the fiber derived from natural stone include basalt fiber. Examples of the organic fiber include polyester fiber, polypropylene fiber, polyamide fiber, polyarylene sulfide fiber, and natural organic fiber.

[0079] When the fiber assembly is a woven fabric, a nonwoven fabric, a cut fiber bundle mat, or a paper body, the thickness of the fiber assembly may be appropriately set and selected so that the thickness of the attenuation layer, which is a wavelength control factor of the electromagnetic wave to be attenuated, is the desired thickness. The thickness of the fiber assembly may be, for example, 0.1 mm or more, 1 mm or more, or 2 mm or more, and may be 2 mm or less, 1.5 mm or less, or 1 mm or less. The basis weight of the fiber assembly is 300 g / m 2 More than 350g / m 2 or more than 400g / m 2 or more, and 2 Below 550g / m 2 or less than 500g / m 2 It may be the following:

[0080] In one embodiment of the present invention, the damping layer and the resin molding material (1) may further contain other components, such as fillers (excluding the above-mentioned carbon fibers and fiber aggregates), low-shrinkage agents, release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, UV stabilizers, reinforcing materials, and photocuring agents.

[0081] The thickness of the attenuation layer may be appropriately set depending on the wavelength of the electromagnetic wave to be attenuated and the dielectric constant of the attenuation layer, and may be, for example, 0.1 mm or more, 0.2 mm or more, or 0.4 mm or more, or 3 mm or less, 2 mm or less, or 1 mm or less.

[0082] The resin molded body may include only the electromagnetic wave attenuation layer (may be a single layer), or may further include a layer other than the electromagnetic wave attenuation layer. In one embodiment, the resin molded body may include the electromagnetic wave attenuation layer and the electromagnetic wave reflecting layer.

[0083] Fig. 1 is a schematic cross-sectional view showing one embodiment of a resin molded body. As shown in Fig. 1, a resin molded body 1 according to one embodiment includes an electromagnetic wave attenuation layer 2 and an electromagnetic wave reflecting layer 3 laminated on the electromagnetic wave attenuation layer 2. In this embodiment, the electromagnetic wave reflecting layer 3 is disposed directly (without any other layer) on the electromagnetic wave attenuation layer 2. In another embodiment, another layer (for example, a spacer) may be provided between the electromagnetic wave attenuation layer and the electromagnetic wave reflecting layer.

[0084] The electromagnetic wave reflection layer (hereinafter, simply referred to as the "reflection layer") is a layer capable of reflecting electromagnetic waves. The semi-reflection layer may be formed of a material having a characteristic impedance different from the characteristic impedance (expressed by the dielectric constant and the magnetic permeability) of the attenuation layer, for example, may be formed of a resin, and is more preferably formed of a material rich in free electrons, which can greatly change the characteristic impedance of the reflection layer, since higher reflection characteristics can be obtained. In this case, the resin molding is particularly suitable for use in applications in which external electromagnetic waves are shielded by the electromagnetic wave reflection layer.

[0085] In one embodiment, the reflective layer may contain a metal, or may contain a compound or fiber with a graphite structure. Examples of metals include aluminum, iron, nickel, copper, silver, and alloys thereof. The reflective layer containing a metal may be, for example, a plate, foil, film containing fine particles, plated film, net, perforated plate, or a box such as a casting made of the metal or alloy.

[0086] In another embodiment, the reflective layer may contain resin and carbon fiber. That is, the resin molded body may have a reflective layer containing resin and carbon fiber. In this case, the resin molded body is obtained by molding a resin molding material (hereinafter also referred to as "resin molding material (2)") containing resin and carbon fiber for forming the reflective layer. The resin contained in the resin molding material (2) may be the resin (including the resin composition) described as the resin contained in the attenuation layer and the resin molding material (1). In one embodiment, the resin composition in the attenuation layer and the resin molding material (1) and the resin composition in the reflective layer and the resin molding material (2) may be the same as each other except for the average length and the content of the carbon fibers.

[0087] In another embodiment, the resin composition in the attenuation layer and the resin molding material (1) and the resin composition in the reflective layer and the resin molding material (2) may be the same except for the average length and content of carbon fibers and the content of polymerization initiator when the resin in the resin composition is a vinyl ester resin. In this embodiment, since warping of the resin molded body can be suppressed, the content of polymerization initiator in the resin composition in the attenuation layer and the resin molding material (1) may be less than the content of polymerization initiator in the resin composition in the reflective layer and the resin molding material (2), preferably 20 to 40 mass % less.

[0088] The carbon fibers used in the reflective layer and the resin molding material (2) may be monofilaments or may be in the form of a carbon fiber bundle. When the carbon fibers are in the form of a carbon fiber bundle, the carbon fiber bundle may be, for example, monofilaments bound together with a bundling agent (sizing agent). The number of filaments in the carbon fiber bundle may be, for example, 1,000 or more and 60,000 or less.

[0089] The average length of the carbon fibers contained in the reflective layer and the resin molding material (2) may be 1 mm or more, 3 mm or more, or 5 mm or more, and may be 50 mm or less, 25 mm or less, or 15 mm or less. The average length of the carbon fibers contained in the reflective layer and the resin molding material (2) is measured in the same manner as the average length of the carbon fibers contained in the attenuation layer and the resin molding material (1).

[0090] The carbon fiber content may be 1 mass% or more, 5 mass% or more, or 10 mass% or more, and may be 55 mass% or less, 50 mass% or less, or 45 mass% or less, based on the total mass of the reflective layer (resin molding material (2)).

[0091] The thickness of the reflective layer (resin molding material (2)) can be appropriately set depending on the desired shape and strength, and may be, for example, 0.5 mm or more, 1 mm or more, or 2 mm or more, and may be 5 mm or less, 3 mm or less, or 2.5 mm or less.

[0092] The shape of the resin molding may be any shape, and may be a sheet-like shape or a three-dimensional shape such as a box. In one embodiment, the attenuation layer may be produced by curing a sheet-like resin molding material (1). In one embodiment, the reflective layer may be produced by curing a sheet-like resin molding material (2). From the viewpoint of excellent formability and ease of forming into a box such as a housing of a millimeter wave radar, it is preferable that the attenuation layer and the reflective layer are produced from the sheet-like resin molding material (1) and the sheet-like resin molding material (2), respectively.

[0093] The resin molded body of this embodiment can be obtained, for example, by a manufacturing method including a manufacturing step of a resin molding material (B) and a manufacturing step of a resin molded body (C). The carbon fiber used in the manufacturing step of the resin molding material (B) may be a commercially available carbon fiber, may be a carbon fiber contained in a recycled material, or may be a carbon fiber obtained by a manufacturing method including the following (A) carbon fiber cutting step.

[0094] The recycled material may be a molded article recovered during the manufacturing process (before it is used as a product), or may be a molded article recovered after it has been used as a product. It is preferable that the recycled molded article is one that has been crushed to such an extent that the average length of the carbon fibers contained in the molded article falls within the range of the average length of the carbon fibers contained in the damping layer described above.

[0095] (A) Carbon fiber cutting process This step (A) is a step of cutting carbon fibers, which are continuous fibers made of reinforcing fibers, to produce chopped carbon fibers. In order to improve productivity, it is preferable to simultaneously cut a plurality of continuous fibers that have been split in advance to form a plurality of fibers along the longitudinal direction of the fibers. As a method for cutting chopped carbon fibers, for example, the continuous fibers can be cut by inserting them into a rotary cutter such as a guillotine cutter or a roving cutter. The chopped carbon fibers after cutting can also be adjusted by a distributor so that the chopped carbon fibers are substantially randomly oriented. When the chopped carbon fibers come into contact with the distributor, the chopped carbon fibers can also be split into a plurality of chopped carbon fibers along the longitudinal direction of the fibers.

[0096] (B) Manufacturing process of resin molding material In this step (B), for example, the aggregate of chopped carbon fibers obtained in the step (A) or an aggregate of commercially available carbon fibers is sandwiched between the sheet-like resin (matrix resin) from both sides to integrate the aggregate of carbon fibers with the matrix resin. The aggregate of carbon fibers is impregnated with the matrix resin by means of pressure or the like to obtain, for example, a sheet-like resin molding material (1). The resin molding material (1) thus obtained is called an SMC sheet in the case of a thermosetting resin, or a stampable sheet in the case of a thermoplastic resin.

[0097] (C) Manufacturing process of resin molded products In this step (C), the resin molding material (1) obtained in step (B) is hardened to form a resin molded body. More specifically, the resin molding material (1) is placed in the cavity in a state smaller than the projected area of ​​the cavity of the mold and thicker than the cavity thickness. Next, the mold is clamped to pressurize the resin molding material (1) to fill the cavity with the resin molding material (1) and then mold it. There are no particular limitations on the molding means. For example, if the matrix resin is a thermosetting resin, the thermosetting resin is crosslinked by heating and pressing using a heated press machine to obtain a resin molded body. Also, for example, if the matrix resin is a thermoplastic resin, the resin molding material (1) is heated to a melting point of the resin or higher, and then cooled and pressed using a press machine adjusted to a predetermined temperature, whereby the thermoplastic resin that has flowed due to softening or melting is solidified by cooling, and a resin molded body is obtained.

[0098] In the following, as a more specific example of a method for manufacturing a resin molded body, a manufacturing method will be described in which an attenuation layer and a reflective layer are molded by laminating sheet-shaped resin molding material (1) and resin molding material (2).

[0099] In this manufacturing method, the carbon fiber for the damping layer is first mixed with a resin composition, and the resulting mixture is applied to each side of two process films. Next, a fiber aggregate is placed on one of the two process films, and the other of the two process films is placed on top of it to obtain a laminate. At this time, the process films are placed so that the coated side of each film is in contact with the fiber aggregate.

[0100] Next, the obtained laminate is pressed to impregnate the fiber aggregate with the resin composition. The laminate after pressing may be left to stand at room temperature (e.g., 25°C) for, for example, 10 hours or more to be aged. This produces a sheet-shaped resin molding material (1).

[0101] Next, a sheet-shaped resin molding material (2) is laminated on the obtained sheet-shaped resin molding material (1). The sheet-shaped resin molding material (2) may be one obtained by a known method or a commercially available product. In this way, a laminated compound sheet is obtained.

[0102] Next, the laminated compound sheet is placed in a mold, and pressurized and heated to obtain a resin molded body. If necessary, the obtained resin molded body may be adjusted to a desired thickness. The resin molded body thus produced is a molded body in which the electromagnetic wave attenuation layer and the electromagnetic wave reflection layer are obtained by laminating and molding sheet-shaped resin molding materials. The electromagnetic wave attenuation layer is a resin molded body obtained by molding a resin molding material (1), the electromagnetic wave reflection layer is a resin molded body obtained by molding a resin molding material (2), and the resin molded body is a resin molded body obtained by laminating and molding the resin molding material (1) and the resin molding material (2).

[0103] The resin molded body of the present embodiment is used in various applications that require attenuation (absorption) of electromagnetic waves. In this case, the resin molded body is molded into a sheet (electromagnetic wave attenuation sheet, electromagnetic wave absorbing sheet) or a housing (housing for electronic devices) and can be used as an electromagnetic wave attenuator (electromagnetic wave absorber). The resin molded body can be used as an electromagnetic wave attenuator (electromagnetic wave absorber) for, for example, electronic devices such as smartphones, tablet terminals, and personal computers, millimeter wave radar devices, building materials such as building materials walls and window glass, vehicles, ships, and aircraft, etc., in which electromagnetic waves need to be absorbed. In addition, the resin molded body can also be used as an electromagnetic wave attenuator (electromagnetic wave absorber) by joining it to a flexible printed wiring board, a rigid printed wiring board, a COF, a TAB, a flexible connector, a liquid crystal display, a touch panel, etc. In addition, the resin molded body can also be used as an electromagnetic wave attenuator (electromagnetic wave absorber) for use in an electronic toll collection system (ETC) on a highway and installed on the roof of a toll booth or between ETC lanes. EXAMPLES

[0104] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0105] Example 1 <Preparation of vinyl ester resin paste> 9.60 g of phenoxyethyl methacrylate was added to 90.40 g of bisphenol A type vinyl ester resin (Exdoma (registered trademark) manufactured by DIC Materials Corporation), and the mixture was thoroughly stirred and mixed at room temperature to obtain a vinyl ester resin paste.

[0106] <Preparation of Resin Composition for Damping Layer> 13.08g of polyisocyanate was added to 60.40g of the obtained vinyl ester resin paste, mixed well at room temperature, and 0.07g of carbon fiber bundle (YS-CFCH-1, manufactured by Yoshino Co., Ltd., average length: 1mm) was added and mixed further. By mixing well, the added carbon fiber became monofilament-like. 0.58g of polymerization initiator (Trigonox 117, manufactured by Kayaku Akzo Co., Ltd.) was added to this, and stirred well at room temperature to obtain a resin composition for a damping layer.

[0107] <Preparation of resin molding material (1)> The obtained resin composition for the damping layer was divided into approximately half and half, and one half was applied to a square area of ​​27 cm square on a polypropylene casting film. On the top of the applied area, a chopped glass fiber mat (MC450A-030SC manufactured by Nitto Boseki Co., Ltd., thickness: approximately 0.7 mm, basis weight: 450 g / m) cut into a square of 27 cm square was placed. 2 ) was layered on top of each other. Half of the remaining resin composition for the damping layer was similarly applied to a 27 cm square area of ​​a polypropylene casting film, and the coated surface was layered on top of the chopped glass fiber mat to form a laminate. The laminate was pressed together with the casting film with a hand roller to thoroughly impregnate the chopped glass fiber mat with the resin composition for the damping layer, and the mixture was aged at room temperature for 24 hours or more to obtain a damping layer (resin molding material (1)) which is a molding compound. The carbon fiber content based on the total mass of the damping layer (resin molding material (1)) was 0.1 mass%.

[0108] Example 2 A damping layer (resin molding material (1)) was obtained in the same manner as in Example 1, except that the amounts of each component in the preparation of the resin composition for the damping layer were changed to 60.57 g of vinyl ester resin paste, 13.12 g of polyisocyanate, 0.037 g of carbon fiber bundles (average length: 1 mm), and 0.41 g of polymerization initiator. The content of carbon fiber based on the total mass of the damping layer (resin molding material (1)) was 0.05 mass%.

[0109] Comparative Example 1 A damping layer (resin molding material (1)) was obtained in the same manner as in Example 1, except that the amounts of each component in the preparation of the resin composition for the damping layer were changed to 60.15 g of vinyl ester resin paste, 13.03 g of polyisocyanate, 0.37 g of carbon fiber bundles (average length: 1 mm), and 0.58 g of polymerization initiator. The content of carbon fiber based on the total mass of the damping layer (resin molding material) was 0.5 mass%.

[0110] Example 3 A carbon fiber bundle (average length: 5 mm) was used instead of the carbon fiber bundle (YS-CFCH-1 manufactured by Yoshino Co., Ltd., average length: 1 mm), and the amounts of each component in the preparation of the resin composition for the damping layer were changed to 60.40 g of vinyl ester resin paste, 13.08 g of polyisocyanate, 0.07 g of carbon fiber bundle (average length: 5 mm), and 0.58 g of polymerization initiator. The damping layer (resin molding material (1)) was obtained in the same manner as in Example 1. The carbon fiber content based on the total mass of the damping layer (resin molding material (1)) was 1.0 mass%.

[0111] Example 4 The amounts of each component in the preparation of the resin composition for the damping layer were changed to 41.46 g of vinyl ester resin paste, 8.98 g of polyisocyanate, 0.05 g of carbon fiber bundles (average length: 1 mm), and 0.40 g of polymerization initiator, and a glass fiber woven fabric (WE181 100BA manufactured by Nittobo Co., Ltd., thickness: about 0.25 mm) cut into a square of 27 cm was used instead of the chopped glass fiber mat. The damping layer (resin molding material (1)) was obtained in the same manner as in Example 1. The carbon fiber content based on the total mass of the damping layer (resin molding material (1)) was 0.1 mass%.

[0112] Comparative Example 2 A resin molding was obtained in the same manner as in Example 3, except that the amounts of each component in the preparation of the resin composition for the damping layer were changed to 60.16 g of vinyl ester resin paste, 13.03 g of polyisocyanate, 0.37 g of carbon fiber bundles (average length: 5 mm), and 0.58 g of polymerization initiator. The content of the carbon fiber bundles based on the total mass of the damping layer (resin molding material) was 0.5 mass%.

[0113] Comparative Example 3 In preparing the composition for the damping layer, a damping layer (resin molding material) was obtained in the same manner as in Example 1, except that no carbon fiber bundles were used and the amounts of each component were changed to 60.46 g of vinyl ester resin paste, 13.09 g of polyisocyanate, and 0.58 g of polymerization initiator.

[0114] <Measurement of electromagnetic wave attenuation> As the reflective layer, a sheet-shaped carbon fiber / resin molding material (DICARBO (registered trademark) CF manufactured by DIC Corporation, basis weight 2 kg / m 2, vinyl ester resin composition system, carbon fiber content 45 mass%, polymerization initiator content 0.8 mass% were used. The sheet-like carbon fiber / resin molding material was cut into a square of 27 cm square with a rolling cutter, and the process film on the surface was removed. The attenuation layers (resin molding materials) obtained in the above examples and comparative examples were overlaid on this reflective layer with the process film removed, and placed in the center of a 30 cm square concave mold with the reflective layer facing down. The mold was closed and pressed for 10 minutes under conditions of mold temperatures of 140 ° C (convex mold), 150 ° C (concave mold), and 92t to obtain a 30 cm square resin molded body in which the attenuation layer and the reflective layer were laminated. A 15 cm square area was cut out from the center of each obtained resin molded body to obtain a test piece. The obtained test piece was a flat plate without warping and did not interfere with the measurement of electromagnetic wave attenuation.

[0115] The electromagnetic wave attenuation (electromagnetic wave reflection attenuation and electromagnetic wave transmission attenuation) was measured by measuring S parameters by the free space method using the following device configuration. The electromagnetic wave was incident on the test piece perpendicularly to the attenuation layer side of the test piece. The frequency of the electromagnetic wave was 60 to 90 GHz. The device was adjusted by placing a reference metal plate (2 mm aluminum plate) on the sample stand and adjusting the angle of the horn antenna to the angle at which the reception level was maximized. In addition, the reception level when the reference metal plate was placed on the sample stand was recorded, and the reflection amount was calculated by subtracting it from the reception level from the sample. The measured electromagnetic wave reflection attenuation is shown in Table 1. Meanwhile, with regard to the electromagnetic wave transmission attenuation, all of the examples and comparative examples showed attenuation of -85 dB or more. RF measuring instrument: Keysight Technologies Vector Network Analyzer N5290A Measurement fixture: S-parameter method measuring fixture FS110 (EM Lab's horn antenna with dielectric lens (for E band) and sample stand) Measurement software: Keysight Technologies N1500A

[0116] [Table 1] [Explanation of symbols]

[0117] 1...resin molding, 2...electromagnetic wave attenuation layer, 3...electromagnetic wave reflecting layer.

Claims

1. A resin molded body having an electromagnetic wave attenuation layer containing resin and carbon fiber, The carbon fibers have an average length of 5 mm or less, A resin molded article, wherein the carbon fiber content is 0.35 mass % or less based on the total mass of the electromagnetic wave attenuation layer.

2. The resin molding according to claim 1 , wherein the electromagnetic wave attenuation layer further comprises an aggregate of fibers different from the carbon fibers.

3. The resin molded article according to claim 2 , wherein the assembly is any one of a woven fabric, a nonwoven fabric, a cut fiber bundle mat, and a paper body.

4. The resin molded article according to claim 2 , wherein the aggregate comprises at least one fiber selected from the group consisting of glass fibers, ceramic fibers, fibers derived from natural stones, and organic fibers.

5. The resin molded article according to claim 1 , further comprising an electromagnetic wave reflective layer.

6. The resin molded article according to claim 5 , wherein the electromagnetic wave reflective layer contains a resin and a carbon fiber.

7. The resin molding according to claim 5, which is used as an electromagnetic wave attenuation sheet or a housing for electronic equipment.

8. A resin molding material for use in the resin molded article according to any one of claims 1 to 7, Contains resin and carbon fiber, The carbon fibers have an average length of 5 mm or less, The resin molding material has a carbon fiber content of 0.35 mass% or less based on the total mass of the resin molding material.

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