Thermosetting resin composition and method for producing cured molded article using same

Abstract

To provide a thermosetting resin composition that is first put into a die and melt-processed and then can be cured without using any die.SOLUTION: According to one embodiment, a thermosetting resin composition contains (A) a thermosetting resin, (B) 1-15 wt.% of a microwave-sensitive agent, and (C) 0.1-30 wt.% of a crosslinker. The (A) thermosetting resin is solid at room temperature, the (B) microwave-sensitive agent has an average particle size of 1 nm-100 μm, and the (C) crosslinker is a polyfunctional organic compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermosetting resin composition and a method for producing a cured molded article using the same. [Background technology]

[0002] Generally, thermosetting resins require a mold to prevent deformation during hardening, and hardening takes time, so there is a limit to how many molded articles can be mass-produced in a short period of time.

[0003] Conventionally, a method of accelerating hardening by irradiating microwaves or high frequency waves has been known. For example, Patent Document 1 discloses a clay-like molding material that contains magnetite or ferrite and is subjected to a thermal crosslinking treatment by irradiating microwaves. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-184532 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors thought that if a thermosetting resin that can melt in an uncured state can be melt-molded using a mold and then cured after removal from the mold, it would be possible to dramatically improve the productivity (production efficiency) of a molded thermosetting resin body. For this purpose, it is necessary to complete the curing reaction faster than the time required for melt deformation after removal from the mold. However, the above-mentioned conventional techniques have not yet succeeded in suppressing melt deformation. In other words, the conventional techniques have room for improvement in terms of providing a thermosetting resin composition that can be melt-molded in a mold and then cured without using a mold.

[0006] An object of one aspect of the present invention is to provide a thermosetting resin composition that can be melt-molded in a mold and then cured without using a mold. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the present inventors have found that by using a microwave sensitizer and a crosslinking agent in combination, it is possible to realize a thermosetting resin composition that can be cured while retaining its shape after being removed from a mold. The present invention includes the following aspects. <1> A thermosetting resin composition comprising (A) a thermosetting resin, (B) 1 to 15% by weight of a microwave sensitizer, and (C) 0.1 to 30% by weight of a crosslinking agent, wherein (A) the thermosetting resin is solid at room temperature, (B) the microwave sensitizer has an average particle size of 1 nm to 100 μm, and (C) the crosslinking agent is a polyfunctional organic compound. <2> Further, (D) 0.001 to 15% by weight of a curing catalyst, <1> The thermosetting resin composition according to claim 1. <3> (A) The thermosetting resin is in an uncured state; <1> or <2> The thermosetting resin composition according to claim 1. <4> (A) the thermosetting resin is at least one selected from the group consisting of a phenolic resin, an epoxy resin, an imide resin, a benzoxazine resin, and a bismaleimide resin; <1> ~ <3> 13. The thermosetting resin composition according to claim 12. <5> (B) the microwave sensitizer is a carbon material; <1> ~ <4> 13. The thermosetting resin composition according to claim 12. <6> <1> ~ <5> 1. A method for producing a molded product of a thermosetting resin composition, comprising: a step of placing the thermosetting resin composition according to any one of claims 1 to 9 in a mold, and melt-molding the composition at a temperature at which the thermosetting resin composition is not completely cured, thereby obtaining a preformed product; and a step of removing the preformed product from the mold and curing it by irradiating it with microwaves, thereby obtaining a cured molded product. Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a thermosetting resin composition that can be once placed in a mold, melt-molded, and then cured without using a mold. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments of the present invention will be described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and larger than A) and B or less (including B and smaller than B)."

[0010] [1. Thermosetting resin composition] A thermosetting resin composition according to one embodiment of the present invention contains (A) a thermosetting resin, (B) 1 to 15% by weight of a microwave sensitizer, and (C) 0.1 to 30% by weight of a crosslinking agent, wherein (A) the thermosetting resin is solid at room temperature, (B) the microwave sensitizer has an average particle size of 1 nm to 100 μm, and (C) the crosslinking agent is a polyfunctional organic compound.

[0011] In the technology described in Patent Document 1, when a spherical molded body with a diameter of 30 mm was subjected to a heat crosslinking treatment, it was deformed to a diameter of 26 mm even under the best conditions, and the shape retention characteristics were insufficient. In the thermosetting resin composition according to one embodiment of the present invention, the microwave sensitizer absorbs microwaves and rapidly generates heat, and the crosslinking agent acts to promote the curing reaction before the resin flows. This makes it possible to speed up the crosslinking reaction. Therefore, according to one embodiment of the present invention, after the thermosetting resin composition is once placed in a mold and melt-molded, it is possible to quickly cure the thermosetting resin composition without giving it time to lose its shape, even without using a mold.

[0012] In the manufacturing process of a molded article using a thermosetting resin composition, for example, when a high-throughput device such as an injection molding machine is used in the first melt molding process, the subsequent curing process becomes the rate-limiting step. Even in such a case, by using the thermosetting resin composition according to one embodiment of the present invention, it becomes possible to quickly cure the composition while maintaining its shape without using a mold. Therefore, the time and cost required for manufacturing the molded article can be reduced, and productivity can be improved.

[0013] In this specification, the thermosetting resin composition means a resin composition before curing. That is, the (A) thermosetting resin may be in an uncured state. The thermosetting resin composition is obtained by mixing each component described below.

[0014] <1-1. Thermosetting resin> The thermosetting resin according to one embodiment of the present invention is solid at room temperature (10°C to 35°C). Examples of the thermosetting resin include phenolic resin, epoxy resin, urea resin, imide resin, benzoxazine resin, and bismaleimide resin. These may be used alone or in combination of two or more. From the viewpoint of shortening the curing time by microwave irradiation, benzoxazine resin, phenolic resin, imide resin, and bismaleimide resin are preferred.

[0015] The benzoxazine resin may be polymerized with a diamine compound, a triamine compound, a polyamine compound, or the like. Examples of the diamine compound include 4,4'-diaminodiphenyl ether, hexamethylene diamine, paraphenylene diamine, ethylene diamine, metaphenylene diamine, diaminodiphenyl methane, and xylene diamine. Examples of the triamine compound include diethylene triamine, bis(hexamethylene) triamine, and trisaminomethylphenol. Examples of the polyamine compound include triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine. The solvent used in the polymerization reaction is not particularly limited, and examples thereof include 2-methoxyethanol, dioxane, and toluene.

[0016] <1-2. Microwave Sensitizer> In this specification, the microwave sensitizer means a substance that absorbs microwaves and generates heat. The microwave sensitizer efficiently absorbs microwaves and generates heat, thereby accelerating the thermosetting reaction.

[0017] The content of the microwave sensitizer in the thermosetting resin composition is 1 to 15% by weight, preferably 2 to 12% by weight, and more preferably 3 to 10% by weight. When the content of the microwave sensitizer is 1% by weight or more, the heat generation by microwaves and the curing associated therewith proceed sufficiently. When the content of the microwave sensitizer is 15% by weight or less, the microwaves reach the inside of the resin composition, and the curing of the inside of the resin composition also proceeds sufficiently. When the content of the microwave sensitizer is too much, a large amount of microwaves are absorbed on the surface of the resin composition, and there is a risk that the microwaves do not reach the inside of the resin composition.

[0018] The average particle size of the microwave sensitizer is 1 nm to 100 μm, preferably 10 nm to 50 μm, and more preferably 30 μm to 20 μm. A microwave sensitizer having an average particle size of 100 μm or less can enhance dispersibility in a resin, so that a small amount is sufficient, and has a large surface area, so that it has high thermal conductivity. Therefore, the thermosetting resin can be cured efficiently. In addition, if the average particle size of the microwave sensitizer is 1 nm or more, it can absorb microwaves and transmit the generated heat to the surroundings. In this specification, the average particle size means a value measured by a dynamic light scattering method, a laser diffraction method, a centrifugal sedimentation method, or the like.

[0019] Examples of the microwave sensitizer include carbon materials and metal oxides. Among them, carbon materials are preferred from the viewpoints of compatibility with resins and mechanical strength of the cured product. Examples of the carbon materials include graphite, graphene, carbon black, carbon nanotubes, and carbon fibers. Examples of the carbon black include acetylene black, furnace black, channel black, and thermal black. Examples of the metal oxides include iron oxide, zinc oxide, titanium oxide, copper oxide, cobalt oxide, barium titanate, and strontium titanate. Each of these may be used alone, or two or more of them may be used in combination.

[0020] <1-3. Crosslinking agent> The content of the crosslinking agent in the thermosetting resin composition is 0.1 to 30% by weight, preferably 0.5 to 20% by weight, and more preferably 1 to 15% by weight. If the content of the crosslinking agent is 0.1% by weight or more, the thermosetting resin can be cured efficiently. If the content of the crosslinking agent is 30% by weight or less, it is preferable from the viewpoint of the mechanical strength, particularly the toughness, of the cured product.

[0021] The crosslinking agent according to one embodiment of the present invention is a polyfunctional organic compound. In this specification, the polyfunctional organic compound means an organic compound having two or more reactive functional groups. Such reactive functional groups include epoxy groups, amino groups, hydroxyl groups, carboxyl groups, carbonyl groups, thiol groups, vinyl groups, etc.

[0022] Examples of polyfunctional organic compounds include polyfunctional epoxy compounds, polyfunctional amine compounds, polyfunctional phenol compounds, polyfunctional carboxylic acid compounds, polyfunctional carboxylic anhydrides, polyfunctional thiol compounds, polyfunctional vinyl compounds, polyfunctional alcohol compounds, polyfunctional isocyanate compounds, polyfunctional oxazoline compounds, etc. These may be used alone or in combination of two or more. Compounds having multiple different reactive functional groups, such as amino acids or hydroxycarboxylic acids, may also be used.

[0023] Examples of crosslinking agents that are preferably used in combination with phenolic resins include polyfunctional epoxy compounds, polyfunctional carboxylic acid compounds, and polyfunctional isocyanate compounds. In addition to polyfunctional organic compounds, hexamethylenetetramine or trioxane can also be used as a crosslinking agent for phenolic resins. Examples of crosslinking agents that are preferably used in combination with epoxy resins include polyfunctional amine compounds, polyfunctional carboxylic acid anhydrides, polyfunctional phenolic compounds, polyfunctional carboxylic acid compounds, and polyfunctional alcohol compounds. Examples of crosslinking agents that are preferably used in combination with urea resins include polyfunctional carboxylic acid compounds and polyfunctional amine compounds. Examples of crosslinking agents that are preferably used in combination with imide resins include polyfunctional carboxylic acid compounds, polyfunctional carboxylic acid anhydrides, and polyfunctional amine compounds. Examples of crosslinking agents that are preferably used in combination with benzoxazine resins include polyfunctional carboxylic acid compounds, polyfunctional epoxy compounds, polyfunctional carboxylic acid anhydrides, polyfunctional amine compounds, and polyfunctional oxazoline compounds. Examples of crosslinking agents that are preferably used in combination with bismaleimide resins include polyfunctional thiol compounds, polyfunctional vinyl compounds, and polyfunctional amine compounds.

[0024] Examples of the polyfunctional epoxy compound include bisphenol type epoxy compounds, novolac type epoxy compounds, glycidyl ester type epoxy compounds such as phthalic acid glycidyl ester, trisphenolmethane type epoxy compounds, tetrakisphenolethane type epoxy compounds, etc. Among them, examples of the polyfunctional epoxy compound that is preferably used in combination with a phenol resin or a benzoxazine resin include bisphenol type epoxy compounds, novolac type epoxy compounds, glycidyl ester type epoxy compounds, etc.

[0025] Examples of the polyfunctional amine compound include 4,4'-diaminodiphenyl ether, hexamethylene diamine, paraphenylene diamine, melamine, etc. Among them, examples of the polyfunctional amine compound that is preferably used in combination with the epoxy resin or the imide resin include hexamethylene diamine, paraphenylene diamine, melamine, etc.

[0026] Examples of the polyfunctional oxazoline compound include 2,2'-bis(2-oxazoline), 1,3-bis(2-oxazolin-2-yl)benzene, and 1,4-bis(4,5-dihydro-2-oxazolyl)benzene.

[0027] Examples of the polyfunctional phenol compound include bisphenol A, hydroquinone, resorcinol, biphenol, naphthalenediol, and phenol resins.

[0028] Examples of the polyfunctional carboxylic acid compound include terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, maleic acid, fumaric acid, phthalic acid, biphenyltetracarboxylic acid, pyromellitic acid, trimesic acid, naphthalenetetracarboxylic acid, perylenetetracarboxylic acid, and esters thereof. Among them, examples of the polyfunctional carboxylic acid compound that is preferably used in combination with an epoxy resin or a benzoxazine resin include terephthalic acid, phthalic acid, biphenyltetracarboxylic acid, pyromellitic acid, trimesic acid, and esters thereof.

[0029] Examples of the polyfunctional carboxylic acid anhydride include phthalic anhydride, biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, maleic anhydride, naphthalene tetracarboxylic dianhydride, and perylene tetracarboxylic dianhydride. Among them, examples of the polyfunctional carboxylic acid anhydride that is preferably used in combination with an epoxy resin include phthalic anhydride, biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, and maleic anhydride. Examples of the polyfunctional carboxylic acid anhydride that is preferably used in combination with an imide resin include biphenyl tetracarboxylic dianhydride. Examples of the polyfunctional carboxylic acid anhydride that is preferably used in combination with a benzoxazine resin include phthalic anhydride, biphenyl tetracarboxylic dianhydride, and pyromellitic dianhydride.

[0030] Examples of the polyfunctional thiol compound include decanedithiol, trimethylolpropane tris(β-thiopropionate), and Karenz MT (registered trademark) manufactured by Showa Denko.

[0031] Examples of polyfunctional vinyl compounds include divinylbenzene, divinyl adipate, diallyl adipate, allyl ether, diisopropenylbenzene, diallyl maleate, diallyl urea, bisphenol A diallyl ether, diethylene glycol divinyl ether, allyl methacrylate, diallyl phthalate, trivinylbenzene, and triallyl isocyanurate.

[0032] Examples of the polyfunctional alcohol compound include ethylene glycol, glycerin, catechol, bisphenol A, hydroquinone, resorcinol, biphenol, naphthalenediol, and phenol resins.

[0033] Examples of the polyfunctional isocyanate compound include ethylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0034] <1-4.Curing catalyst> The thermosetting resin composition may contain a curing catalyst. The content of the curing catalyst in the thermosetting resin composition is preferably 0.001 to 15% by weight, more preferably 0.01 to 10% by weight, and further preferably 0.1 to 5% by weight. If the content of the curing catalyst is 0.001% by weight or more, the thermosetting resin can be cured efficiently. If the content of the curing catalyst is 15% by weight or less, it is preferable from the viewpoint of mechanical properties, heat resistance, and weather resistance of the cured product.

[0035] Examples of the curing catalyst that is preferably used in combination with the phenolic resin include acid catalysts (oxalic acid, acetic acid, sulfonic acid, phosphoric acid, organic phosphonic acid), basic catalysts (sodium hydroxide, potassium hydroxide, calcium hydroxide, amines), etc. Examples of the organic phosphonic acid include 1,4-butylene phosphonic acid, hexyl phosphonic acid, 4-phosphonobenzoic acid, propyl phosphonic acid, paraxylene diphosphonic acid, 4-hydroxybenzyl phosphonic acid, ethyl phosphonic acid, etc. Examples of the amine include triethylamine, etc.

[0036] Examples of the curing catalyst that is preferably used in combination with the epoxy resin include triphenylphosphine, tertiary amine, dicyandiamide, diazabicycloundecene, morpholine, imidazole compound, BF3 complex, phenol compound, etc. Examples of the tertiary amine include triethylamine, triphenylamine, tetramethylphenylenediamine, etc. Examples of the imidazole compound include phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, etc. Examples of the BF3 complex include BF3 methanol complex, BF3 butyl ether complex, BF3 ethyl ether complex, etc. Examples of the phenol compound include bisphenol A, hydroquinone, resorcinol, biphenol, etc.

[0037] Examples of curing catalysts that are preferably used in combination with urea resins include sodium hydroxide, ammonium carbonate, hexamethylenetetramine, sulfuric acid, formic acid, acetic acid, oxalic acid, phthalic acid, amine hydrochlorides, etc. Examples of amine hydrochlorides include hexamethylenediamine dihydrochloride, paraphenylenediamine dihydrochloride, melamine noradamantanamine hydrochloride, ethylenediamine dihydrochloride, benzylhydroxylamine hydrochloride, tetramethylphenylenediamine dihydrochloride, diisobutylamine hydrochloride, etc.

[0038] Examples of the curing catalyst that is preferably used in combination with the imide resin include amine compounds, carboxylic acid anhydrides, etc. Examples of the amine compounds include pyridine, triethylamine, diazabicyclooctane, diazabicycloundecene, hexamethylenediamine, paraphenylenediamine, melamine, etc. Examples of the carboxylic acid anhydrides include acetic anhydride, trifluoroacetic anhydride, etc.

[0039] Examples of the curing catalyst that is preferably used in combination with the benzoxazine resin include a carboxylic acid compound, a phenolic compound, a sulfonic acid, a Lewis acid, and triphenyl phosphite. Examples of the carboxylic acid compound include terephthalic acid, pyromellitic acid, trimesic acid, acetic acid, trifluoroacetic acid, and benzoic acid. Examples of the phenolic compound include phenol, hydroquinone, and catechol. Examples of the Lewis acid include titanium tetrachloride, aluminum chloride, and phosphorus pentachloride.

[0040] Examples of the curing catalyst that is preferably used in combination with the bismaleimide resin include imidazole, peroxide, etc. Examples of the peroxide include sodium peroxide, barium peroxide, magnesium peroxide, lithium peroxide, zinc peroxide, benzoyl peroxide, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxyester, perbenzoic acid, etc.

[0041] These may be used alone or in combination of two or more. Among the crosslinking agents and curing catalysts, there are compounds that function as both crosslinking agents and curing catalysts, such as terephthalic acid, phthalic acid, pyromellitic acid, trimesic acid, bisphenol A, hydroquinone, resorcinol, biphenol, hexamethylenediamine, paraphenylenediamine, and melamine.

[0042] <1-6. Other ingredients> The thermosetting resin composition may contain various additives such as flame retardants, nucleating agents, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, flame retardant assistants, antistatic agents, antifogging agents, fillers, softeners, plasticizers, and colorants. These may be used alone or in combination of two or more. The content of the additives in the thermosetting resin composition is not limited and may be, for example, 0 to 20% by weight, 0 to 10% by weight, 0 to 5% by weight, or 0 to 1% by weight.

[0043] It is preferable that the thermosetting resin composition does not substantially contain any substance having a boiling point of 120° C. or lower and any compound that decomposes to generate a gas or liquid at a temperature of 120° C. or lower. For example, the content of such substances and compounds in the thermosetting resin composition may be 0 to 5% by weight, or may be 0 to 3% by weight.

[0044] 2. Method for producing molded article from thermosetting resin composition The method for producing a cured molded body according to one embodiment of the present invention includes the steps of putting the above-mentioned thermosetting resin composition into a mold, melt-molding the composition at a temperature at which the thermosetting resin composition does not completely cure, to obtain a preformed body, and irradiating the preformed body with microwaves in a state where the preformed body is removed from the mold to cure the preformed body. In this specification, the term "preformed body" refers to a molded body obtained by melt-molding the thermosetting resin composition put into a mold. In addition, the term "cured molded body" refers to a molded body obtained by irradiating microwaves in a state where the preformed body is removed from the mold to cure the preformed body.

[0045] Examples of the material of the mold include metal, clay, stone, glass, and resin. The temperature at which the thermosetting resin composition does not completely cure is, for example, the temperature at which the degree of cure of the preform obtained by melt molding does not reach 50% when the degree of cure of the preform is measured by the same method as the degree of cure of the cured molded body described in the Examples below. The temperature can be appropriately set depending on the type and amount of the thermosetting resin, crosslinking agent, curing catalyst, etc.

[0046] The microwave wavelength is preferably 0.3 to 30 GHz, and more preferably 1 to 20 GHz. When the microwave wavelength is in the above range, the thermosetting resin composition can be efficiently heated. The heating temperature by microwave is preferably such that the temperature of the uncured resin composition is 150 to 250°C, and more preferably 170 to 200°C.

[0047] The microwave irradiation time is preferably 1 to 10 minutes, more preferably 1 to 5 minutes, and even more preferably 1 to 3 minutes. The above-mentioned thermosetting resin composition efficiently absorbs microwaves, so that it can be cured in such a short time.

[0048] The thickness of the obtained cured resin may be 0.1 to 300 mm, or may be 10 to 100 mm. The thickness of the thermosetting resin composition to which microwaves are irradiated may be set to the above-mentioned thickness. Since the above-mentioned thermosetting resin composition efficiently absorbs microwaves, a cured product having a certain thickness can be efficiently obtained by the above-mentioned production method. Note that the "thickness" referred to here means the maximum thickness of the obtained cured resin or the thermosetting resin composition used as a material.

[0049] The thermosetting resin composition may be impregnated into a sheet made of, for example, carbon fiber and then cured.

[0050] 3. Uses of the thermosetting resin composition Applications of the thermosetting resin composition include, for example, films, sheets, containers, housings, building materials, dolls, and structural materials.

[0051] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. EXAMPLES

[0052] Examples and comparative examples are presented below to explain one embodiment of the present invention, but the present invention is not limited thereto.

[0053] [Method of measuring degree of cure] The cured molded body obtained in the Examples, Comparative Examples, and Reference Examples described later was crushed uniformly. 3 to 10 mg of the crushed cured molded body was collected, and the area of ​​the exothermic peak of the curing reaction was determined by DSC analysis. In addition, the area of ​​the exothermic peak of the curing reaction was similarly determined by DSC analysis using the resin composition before curing in each of the Examples, Comparative Examples, and Reference Examples. The degree of curing was estimated from the ratio of the area of ​​the exothermic peak of the curing reaction of the cured molded body to the area of ​​the exothermic peak of the curing reaction of the resin composition before curing.

[0054] Example 1 Pd-type benzoxazine (10 g) manufactured by Shikoku Kasei Kogyo Co., Ltd. and 4,4'-diaminodiphenyl ether (3.5 g) were reacted by stirring in 2-methoxyethanol (100 mL) at 50°C for 5 days. The resulting precipitate was filtered to obtain an uncured thermosetting resin. The uncured thermosetting resin obtained by this reaction is hereinafter referred to as PDDA. This PDDA was found to be an oligomer with a number average molecular weight of 1600 and a weight average molecular weight of 9200 by GPC analysis using N-methylpyrrolidone as an eluent. This thermosetting resin PDDA (426.5 mg), acetylene black (AB) (26.1 mg, 5.2 wt%) as a microwave sensitizer, and terephthalic acid (TPA) (51.3 mg, 10.2 wt%) as a curing catalyst and crosslinking agent were placed in an agate mortar and ground and mixed for 12 minutes. The average particle size of the ground AB was 35 nm.

[0055] The obtained thermosetting resin composition (73.1 mg) was placed in a cylindrical mold and heated in an electric furnace at 120 ° C for 5 minutes to melt mold. The obtained preform was removed from the mold and measured for size Φ5.70 mm × H5.10 mm. The preform removed from the mold was irradiated with microwaves at 150 ° C and 1 minute (2.45 GHz) using Anton Paar's Monowave300. Since no exothermic peak was observed during curing in the DSC analysis, the molded product was determined to be completely cured (100% cured). The size of this cured molded product was Φ5.85 mm × H4.95 mm, which was the same as the preformed product before curing.

[0056] Comparative Example 1 Pd-type benzoxazine (950.0 mg) was used as an uncured thermosetting resin instead of PDDA, and TPA (50.4 mg, 5.0 wt%) was used as a curing catalyst and crosslinking agent, and they were ground and mixed in an agate mortar for 10 minutes. The obtained thermosetting resin composition (134.2 mg) was placed in a cylindrical mold and heated in an electric furnace at 100°C for 5 minutes to be melt-molded. The size of the obtained preformed body measured after being removed from the mold was Φ6.10 mm x H5.20 mm. The preformed body removed from the mold was irradiated with microwaves in a microwave oven under the conditions of 200 W, 15 minutes → 500 W, 15 minutes. As a result, the obtained cured molded body was melted and deformed. The size of the cured molded body was Φ8.20 mm x H2.75 mm. The degree of curing of the obtained cured molded body was 41%.

[0057] Comparative Example 2 PDDA (990.4 mg) described in Example 1 as a thermosetting resin and single-walled carbon nanotubes (CNTs) (10.2 mg, 10.2 wt%) as a microwave sensitizer were ground and mixed in an agate mortar for 30 minutes. The obtained thermosetting resin composition (88.3 mg) was placed in a cylindrical mold and heated in an electric furnace at 120 ° C for 5 minutes to be melt-molded. The size of the obtained preformed body measured after being removed from the mold was Φ4.80 mm × H4.90 mm. The preformed body removed from the mold was irradiated with microwaves in a microwave oven under the conditions of 500 W, 15 minutes → 700 W, 45 minutes. The degree of curing of the obtained cured molded body was 26%, and curing did not progress.

[0058] [Reference example 1] The same thermosetting resin composition (22.6 mg) as in Example 1 was placed in a cylindrical mold in the same manner as in Example 1, and melt-molded by heating in an electric furnace at 120°C for 5 minutes. The obtained preform was removed from the mold and measured for size Φ4.60mm×H1.80mm. This preform was heated in an electric furnace at 200°C for 2 hours to be cured. As a result, the obtained cured molded product was melt-deformed. The size of the cured molded product was Φ5.10mm×H1.35mm. The degree of curing of the cured molded product was 100%.

[0059] Example 2 Pd-type benzoxazine (Pd) (594 mg) manufactured by Shikoku Chemical Industry Co., Ltd., acetylene black (AB) (99.9 mg, 10.0 wt%) as a microwave sensitizer, 1,3-bis(2-oxazolin-2-yl)benzene (BPO) (295.3 mg, 29.5 wt%) as a crosslinker, and triphenyl phosphite (TPP) (10.3 mg, 1.0 wt%) as a curing catalyst were placed in an agate mortar and ground and mixed for 12 minutes. The average particle size of the ground AB was 35 nm.

[0060] The obtained thermosetting resin composition (74.3 mg) was placed in a cylindrical mold and heated in an electric furnace at 120°C for 5 minutes to perform melt molding. The obtained preform was removed from the mold and measured for size Φ5.10 mm x H4.35 mm. The preform removed from the mold was irradiated with microwaves at 700 W for 3 minutes (2.45 GHz) using a microwave oven. The degree of cure determined from the heat generation peak during curing in DSC analysis was 91%. The size of this cured molded product was Φ5.05 mm x H4.20 mm, which was the same as the preform before curing.

[0061] Example 3 Ba-type benzoxazine (Ba) (797.5 mg) manufactured by JFE Chemical Corporation, acetylene black (AB) (101.3 mg, 10.2 wt%) as a microwave sensitizer, and terephthalic acid (TPA) (97.4 mg, 9.8 wt%) as a crosslinking agent and curing catalyst were placed in an agate mortar and ground and mixed for 12 minutes. The average particle size of the ground AB was 35 nm.

[0062] The obtained thermosetting resin composition (74.3 mg) was placed in a cylindrical mold and heated in an electric furnace at 120°C for 5 minutes to melt mold. The obtained preform was removed from the mold and measured for size Φ5.65 mm x H4.60 mm. The preform removed from the mold was irradiated with microwaves using a microwave oven under the conditions of 500 W, 1 minute + 700 W, 1 minute (2.45 GHz). The degree of cure determined from the heat generation peak during curing in DSC analysis was 98%. The size of this cured molded product was Φ5.70 mm x H4.45 mm, which was equivalent to the preform before curing.

[0063] Example 4 A similar experiment was carried out using carbon nanotubes (CNT) instead of AB in Example 2. The size of the preform was Φ5.25 mm×H4.50 mm, while the size of the cured molded body was Φ5.40 mm×H4.40 mm, and the degree of curing was 90%.

[0064] 〔summary〕 In Examples 1 to 4, in which a specific microwave sensitizer and a crosslinking agent were used in combination, it was possible to obtain a cured molded product that retained its shape after being removed from the mold. On the other hand, in Comparative Example 1, in which no microwave sensitizer was used, melt deformation occurred. In addition, in Comparative Example 2, in which no crosslinking agent was used, curing was insufficient.

[0065] It is possible to cure the composition by heating in an electric furnace without irradiating microwaves as in Reference Example 1, but the curing took longer than in Example 1. In addition, deformation due to melting also occurred. [Industrial Applicability]

[0066] The present invention can be used in fields where thermosetting resins are used.

Claims

1. (A) a thermosetting resin, (B) 1 to 15% by weight of a microwave sensitizer, and (C) 0.1 to 30% by weight of a crosslinking agent; (A) the thermosetting resin is a solid at room temperature; (A) the thermosetting resin is a benzoxazine resin; (B) the microwave sensitizer has an average particle size of 1 nm to 100 μm; (C) the crosslinking agent is a polyfunctional organic compound; (C) A thermosetting resin composition, wherein the crosslinking agent is a polyfunctional carboxylic acid compound or a polyfunctional oxazoline compound.

2. The thermosetting resin composition according to claim 1, further comprising: (D) 0.001 to 15% by weight of a curing catalyst.

3. The thermosetting resin composition according to claim 1 or 2, wherein the thermosetting resin (A) is in an uncured state.

4. The thermosetting resin composition according to any one of claims 1 to 3, wherein the microwave sensitizer (B) is a carbon material.

5. A step of putting the thermosetting resin composition according to any one of claims 1 to 4 into a mold and melt-molding the thermosetting resin composition at a temperature at which the thermosetting resin composition is not completely cured to obtain a preform; and curing the preform by irradiating the preform with microwaves while the preform is removed from the mold to obtain a cured molded body.