Thermosetting resin composition for electromagnetic shielding, bulk molding compound, and molded article

Abstract

The present invention provides a thermosetting resin composition for electromagnetic wave shielding, a bulk molding compound, and a molded product thereof, which can be obtained that exhibits excellent fluidity, injection moldability, compression moldability, and superior electromagnetic wave shielding properties. [Solution] A thermosetting resin composition for electromagnetic shielding is used, comprising a thermosetting resin (A), a low-shrinkage agent (B), a thickener (C), a thermally conductive filler (D), and a reinforcing material (E), wherein the thermosetting resin (A) contains an unsaturated polyester resin (a1) and a vinyl ester resin (a2), and the thickener (C) contains acrylic resin particles (c1) and magnesium oxide (c2).

Description

Technical Field

[0001] The present invention relates to a thermosetting resin composition for electromagnetic shielding, a bulk molding compound, and a molded product thereof.

Background Art

[0002] Thermosetting resin compositions obtained by adding a low shrinkage agent, an inhibitor, a curing agent, a filler, a mold release agent, a reinforcing material, etc. to thermosetting resins such as unsaturated polyester resins and vinyl ester resins and kneading them with a kneader have advantages such as electrical insulation, heat resistance, flame retardancy, high rigidity, and dimensional stability. Therefore, they are widely applied to electronic components related to fields such as home appliances, automobiles, and energy. Among the above thermosetting resin compositions, a bulk molding compound in a bulk form (hereinafter sometimes abbreviated as "BMC") can be made into a molded product by molding methods such as compression molding, transfer molding, and injection molding.

[0003] On the other hand, from the viewpoint of preventing electromagnetic interference between electrical and electronic devices, etc., among the important issues is electromagnetic wave shielding measures. A manufacturing method of a battery case having an electromagnetic wave shielding effect has been proposed (for example, see Patent Document 1). However, this manufacturing method of the battery case includes a step of heating and press-molding a press molding member including a metal foil-containing semi-cured resin fiber reinforced composite material intermediate material in which at least two or more semi-cured resin sheets, a fiber fabric or unidirectional fibers, and a metal foil are laminated and integrated, and has a problem of requiring a complicated process. Therefore, there has been a demand for a molding material that can easily impart electromagnetic wave shielding properties to a molded product.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem that the present invention aims to solve is to provide a thermosetting resin composition for electromagnetic wave shielding, a bulk molding compound, and a molded article thereof that can be obtained with excellent fluidity, injection moldability, compression moldability, and electromagnetic wave shielding properties. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the present inventors have found that a thermosetting resin composition for electromagnetic wave shielding containing a specific thermosetting resin, a low-shrinkage agent, a specific thickening agent, a thermally conductive filler, and a reinforcing material solves the above problems, and have completed the present invention.

[0007] In other words, the present invention provides a thermosetting resin composition for electromagnetic wave shielding, comprising a thermosetting resin (A), a low-shrinkage agent (B), a thickener (C), a thermally conductive filler (D), and a reinforcing material (E), wherein the thermosetting resin (A) contains an unsaturated polyester resin (a1) and a vinyl ester resin (a2), and the thickener (C) contains acrylic resin particles (c1) and magnesium oxide (c2). [Effects of the Invention]

[0008] The thermosetting resin composition for electromagnetic shielding of the present invention is excellent in fluidity, injection moldability, and compression moldability, and can produce molded products with excellent electromagnetic shielding properties. Therefore, it is extremely useful for housings of electrical and electronic components used in home appliances, personal computers, office automation equipment, AV equipment, flat panel displays, mobile phones, medical devices, automobile parts, aircraft parts, and the like. [Modes for carrying out the invention]

[0009] The thermosetting resin composition for electromagnetic wave shielding of the present invention is a thermosetting resin composition for electromagnetic wave shielding that contains a thermosetting resin (A), a low shrinkage agent (B), a thickener (C), a thermally conductive filler (D), and a reinforcing material (E), wherein the thermosetting resin (A) contains an unsaturated polyester resin (a1) and a vinyl ester resin (a2), and the thickener (C) contains acrylic resin particles (c1) and magnesium oxide (c2).

[0010] The thermosetting resin (A) contains an unsaturated polyester resin (a1) and a vinyl ester resin (a2). However, to further improve fluidity and injection moldability, the mass ratio (a1 / a2) of the unsaturated polyester resin (a1) and vinyl ester resin (a2) is preferably 90 / 10 to 30 / 70, and more preferably 70 / 30 to 50 / 50.

[0011] The thermosetting resin (A) may also contain thermosetting resins other than unsaturated polyester resin (a1) and vinyl ester resin (a2).

[0012] The thermosetting resin composition for electromagnetic wave shielding of the present invention contains a resin component comprising a thermosetting resin (A) and a low-shrinkage agent (B) as essential components. However, considering the balance between molding shrinkage rate and other physical properties, the mass ratio (A / B) of the thermosetting resin (A) and the low-shrinkage agent (B) is preferably 95 / 5 to 50 / 50, and more preferably 90 / 10 to 70 / 30.

[0013] The aforementioned shrinkage-reducing agent (B) is added to suppress the curing shrinkage of the thermosetting resin composition, and examples include polymethyl methacrylate, polystyrene, saturated polyester, styrene-butadiene rubber, and polyvinyl acetate. These shrinkage-reducing agents can be used individually or in combination of two or more.

[0014] The aforementioned thickener (C) contains acrylic resin particles (c1) and magnesium oxide (c2). By using these together, the fluidity of the BMC described later is improved, ensuring injection moldability (measurability) and injection moldability (fillability).

[0015] The acrylic resin particles (c1) are not particularly limited, but an average particle diameter of 0.1 to 8 μm is preferred, and 0.1 to 3 μm is more preferred, as this improves the fluidity of the BMC and further enhances injection moldability (metering) and injection moldability (filling). In this invention, the average particle diameter of the acrylic resin particles is measured by dynamic light scattering.

[0016] The acrylic resin particles (c1) are preferably in amounts of 1 to 20 parts by mass, and more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

[0017] The magnesium oxide (c2) is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

[0018] Examples of the thermally conductive filler (D) include metallic fillers such as silver, copper, aluminum, iron, and stainless steel; inorganic fillers such as alumina, magnesia, beryllia, silica, boron nitride, aluminum nitride, silicon carbide, boron carbide, and titanium carbide; and carbon-based fillers such as diamond, graphite, and carbon fiber. Among these, carbon-based fillers are preferred from the viewpoint of improving electromagnetic shielding and reducing weight, and graphite is more preferred. These thermally conductive fillers can be used individually or in combination of two or more types.

[0019] The thermal conductive filler (D) is preferably added in an amount of 150 to 550 parts by mass, more preferably 200 to 450 parts by mass, and even more preferably 290 to 400 parts by mass, based on 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B), as this improves the balance between fluidity, injection moldability, and electromagnetic shielding properties.

[0020] In addition, from the viewpoints of improving the fluidity of the thermosetting resin composition for electromagnetic wave shielding of the present invention and the electromagnetic wave shielding property of the molded product, the heat conductive filler (D) is preferably in a particulate form, and its average particle size is preferably 10 to 500 μm. However, it is more preferable to use a heat conductive filler (d1) having an average particle size of 100 μm or more and 500 μm or less and a heat conductive filler (d2) having an average particle size of 10 μm or more and less than 100 μm in combination.

[0021] Since the heat conductive filler (d1) can provide a thermosetting resin composition excellent in the balance between fluidity and injection moldability and electromagnetic wave shielding property, with respect to 100 parts by mass of the total amount of the thermosetting resin (A) and the shrinkage reducing agent (B), 150 to 400 parts by mass is preferable, and 200 to 350 parts by mass is more preferable.

[0022] As the heat conductive filler (d1), a filler having an average particle size of 100 μm or more and 500 μm or less can be used alone or in combination of two or more.

[0023] Since the heat conductive filler (d2) can further improve the balance between fluidity and injection moldability and electromagnetic wave shielding property, with respect to 100 parts by mass of the total amount of the thermosetting resin (A) and the shrinkage reducing agent (B), 20 to 130 parts by mass is preferable, and 30 to 120 parts by mass is more preferable.

[0024] As the heat conductive filler (d2), a filler having an average particle size of 10 μm or more and less than 100 μm can be used alone or in combination of two or more.

[0025] In addition, since the average particle size of the heat conductive filler (d2) can further improve the balance between fluidity and injection moldability and electromagnetic wave shielding property, 30 μm or more and less than 60 μm is more preferable.

[0026] Examples of the reinforcing material (E) include fibrous materials such as glass fibers, vinylon fibers, phenolic fibers, carbon fibers, and polyester fibers. Among these, glass fibers are preferred from the viewpoint of availability, BMC fluidity, and improvement of the strength and physical properties of the molded product. Any type of glass fiber can be used, such as glass chopped strands or milled glass. Fibers with a length of 1.5 to 12 mm are preferred, and those with a length of 1.5 to 9 mm are more preferred, as they improve the fluidity of the BMC and further improve injection moldability (metering), injection moldability (filling), and the physical properties of the BMC molded product.

[0027] The amount of the reinforcing material is preferably 10 to 80 parts by mass, and more preferably 15 to 50 parts by mass, based on 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

[0028] In addition to the above components (A) to (E), the thermosetting resin composition for electromagnetic wave shielding of the present invention may also contain thermoplastic resins, polymerization inhibitors, curing agents, curing accelerators, dispersants, mold release agents, pigments, colorants, defoaming agents, etc., to the extent that they do not impair the effects of the present invention.

[0029] Examples of polymerization inhibitors include toluhydroquinone, hydroquinone, hydroquinone monomethyl ether, 1,4-naphthoquinone, parabenzoquinone, pt-butylcatechol, and 2,6-t-butyl-4-methylphenol. When incorporating a polymerization inhibitor into the thermosetting resin composition for electromagnetic shielding of the present invention, the amount incorporated is preferably in the range of 10 to 1500 ppm in the thermosetting resin composition for electromagnetic shielding of the present invention.

[0030] The curing agent is preferably an organic peroxide, such as diacyl peroxide, peroxyester, hydroperoxide, dialkyl peroxide, ketone peroxide, peroxyketal, alkyl perester, or parkerborne. These curing agents can be used individually or in combination of two or more.

[0031] The amount of curing agent is preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, based on 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

[0032] The aforementioned mold release agent is intended to facilitate the removal of the molded product from the mold after the thermosetting resin composition for electromagnetic wave shielding of the present invention has been molded using a mold. Examples of the mold release agent include unsaturated fatty acid amide mold release agents, polyethylene wax mold release agents, metal soap mold release agents, silicone mold release agents, and fluorine mold release agents. Examples of the metal soap mold release agents include zinc lauryl stearate, calcium laurate, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zinc myristate, calcium montanoate, zinc montanoate, aluminum montanoate, calcium behenate, magnesium behenate, and zinc behenate. These mold release agents can be used individually or in combination of two or more types.

[0033] The amount of the mold release agent is preferably 1 to 10 parts by mass, and more preferably 3 to 8 parts by mass, based on 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

[0034] The thermosetting resin composition for electromagnetic wave shielding of the present invention can be manufactured by kneading the above-mentioned components using a kneader or other mixing machine. Furthermore, by adjusting the blending composition so that the resulting resin composition becomes bulk, it can be made into a bulk molding compound (BMC).

[0035] By using BMC as the thermosetting resin composition for electromagnetic wave shielding according to the present invention, molded products can be easily produced by molding methods such as compression molding, transfer molding, and injection molding. [Examples]

[0036] The present invention will be described in more detail below with reference to examples. The acid value of the resin was measured in accordance with JIS K6901.

[0037] (Manufacturing Example 1: Synthesis of unsaturated polyester resin (a1-1)) In a 2L glass flask equipped with a nitrogen gas inlet tube, thermometer, reflux condenser, and stirrer, 206 parts by mass of neopentyl glycol, 53 parts by mass of propylene glycol, 266 parts by mass of hydrogenated bisphenol A, and 288 parts by mass of isophthalic acid were charged, and heating was started under a nitrogen stream. At an internal temperature of 215°C, a dehydration condensation reaction was carried out by a conventional method, and when the solid content acid value reached 6 (mgKOH / g), it was cooled to 190°C. Next, 198 parts by mass of maleic acid was added and the dehydration condensation reaction was continued, and when the solid content acid value reached 28 (mgKOH / g), 0.4 parts by mass of toluhydroquinone was added. The mixture was dissolved in styrene monomer to obtain an unsaturated polyester resin (a1-1) with an unsaturated polyester concentration of 65% by mass.

[0038] (Manufacturing Example 2: Synthesis of vinyl ester resin (a2-1)) In a 2L flask equipped with a nitrogen inlet tube, thermometer, and stirrer, 246 parts by mass of epoxy resin (DIC Corporation's "Epiclon 860-C," bisphenol A type epoxy resin, epoxy equivalent 240), 730 parts by mass of epoxy resin (DIC Corporation's "Epiclon 1050," bisphenol A type epoxy resin, epoxy equivalent 470), 215 parts by mass of methacrylic acid, and 0.45 parts by mass of dibutylhydroxytoluene were added. The mixture was then heated to 100°C under a gas flow of nitrogen and air in a 1:1 ratio. 0.96 parts by mass of 2-methylimidazole was then added, and the mixture was heated to 110°C to carry out the reaction. When the solid content acid value fell below 6 (mgKOH / g), 0.46 parts by mass of toluhydroquinone was added and dissolved in styrene monomer to obtain vinyl ester resin (a2-1) at a vinyl ester concentration of 70% by mass.

[0039] (Manufacturing Example 3: Manufacturing of a low-shrinkage agent (B-1)) In a 2L flask equipped with a nitrogen inlet tube, thermometer, and stirrer, 900 parts by mass of styrene monomer, 600 parts by mass of polystyrene (DIC Corporation's "DIC Styrene CR-3500"), and 0.25 parts by mass of toluhydroquinone were added, and the mixture was heated to 50°C under a flow of nitrogen gas. The mixture was stirred until the thermoplastic polystyrene was completely melted, and then the temperature was lowered to below 40°C to obtain a low-shrinkage agent (B-1) with a polystyrene concentration of 40% by mass.

[0040] (Example 1: Preparation of thermosetting resin composition (1) for electromagnetic wave shielding) 50 parts by mass of unsaturated polyester resin (a1-1) obtained in Production Example 1, 30 parts by mass of vinyl ester resin (a2-1) obtained in Production Example 2, 20 parts by mass of low shrinkage agent (B-1) obtained in Production Example 3, 4 parts by mass of acrylic resin particles (c1-1) (Zephyr F303 manufactured by Aica Kogyo Co., Ltd.; average particle size 2 μm), 0.15 parts by mass of magnesium oxide (c2-1) (Kyowa Mag 40 manufactured by Kyowa Chemical Industry Co., Ltd.), 0.6 parts by mass of curing agent (1) (Perbutyl O manufactured by NOF Corporation; peroxyester organic peroxide), 1.2 parts by mass of curing agent (2) (Perbutyl Z manufactured by NOF Corporation; peroxyester organic peroxide), 4 parts by mass of mold release agent ( 2) 1.2 parts by mass of calcium stearate (manufactured by NOF Corporation), 50 parts by mass of thermal conductive filler (d1-1) (AGB-32, manufactured by Ito Graphite Industry Co., Ltd.; graphite powder, average particle size 200-300 μm), 200 parts by mass of thermal conductive filler (d1-2) (AGB-100, manufactured by Ito Graphite Industry Co., Ltd.; graphite powder, average particle size 110 μm), and 100 parts by mass of thermal conductive filler (d2-1) (AGB-604, manufactured by Ito Graphite Industry Co., Ltd.; graphite powder, average particle size 55 μm) were kneaded for 9 minutes using a planetary mixer. Then, 33 parts by mass of reinforcing material (E-1) (glass fiber / chopped strand; ECS404-6, manufactured by Chongqing International Composite Materials Co., Ltd.; fiber length 6 mm) were added and kneaded for a further 6 minutes to obtain a bulk material. The obtained bulk material was packaged in an aluminum vapor-deposited film and left in a 40°C constant temperature bath for 12 hours to obtain a thermosetting resin composition (1) for electromagnetic wave shielding as BMC.

[0041] (Examples 2-7) Thermosetting resin compositions (2) to (7) for electromagnetic wave shielding were obtained as BMC in the same manner as in Example 1, except that the compounding composition was changed as shown in Tables 1 and 2.

[0042] (Comparative Examples 1-3) Thermosetting resin compositions (R1) to (R3) for electromagnetic wave shielding were obtained as BMC in the same manner as in Example 1, except that the compounding composition was changed as shown in Table 2.

[0043] The thermosetting resin compositions (1) to (7) and (R1) to (R3) for electromagnetic shielding obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated as follows.

[0044] [Assessment of liquidity] The initial viscosity of the thermosetting resin composition for electromagnetic shielding obtained above was measured. Viscosity measurement was performed using a capillary viscometer (capillary rheometer) under the following conditions: Resin composition input amount (sample amount): 75 g, Measurement temperature: 50°C, Extrusion speed: 50 mm / min, Nozzle diameter: 6 mm, Nozzle length: 10 mm

[0045] [Evaluation of injection moldability (measurability)] A predetermined amount (75 cm³) of the thermosetting resin composition for electromagnetic shielding obtained above. 3 For each of these, the amount that could be moved from the material storage (push hopper) to the cylinder by the screw within a predetermined time (30 seconds) was measured, and the injection moldability (measurability) was evaluated according to the following criteria. Measurement conditions: Push pressure 5 MPa, screw rotation speed 20 rpm, push hopper and cylinder temperature 35°C ○: 75cm in less than 30 seconds 3 △: 40-75cm in 30 seconds 3 ×: 40cm in 30 seconds 3 less than

[0046] [Evaluation of injection moldability (fillability)] For the thermosetting resin compositions for electromagnetic wave shielding that received a "○" in the above quantitative evaluation results, injection molding was performed using a mold for fluidity evaluation, and the appearance of the molded products was visually observed to evaluate the injection moldability (fillability) according to the following criteria. Molding conditions: Mold temperature 160°C, clamping force 750kN, injection speed 70mm / sec, curing time 55 seconds ○: No shorts, no voids on the molded product surface. △: No shorts, voids present on the surface of the molded product. ×: Shortened parts present, voids present on the surface of the molded product.

[0047] [Evaluation of compression moldability] The thermosetting resin compositions for electromagnetic shielding obtained above were subjected to compression molding, and their compressibility was evaluated according to the following criteria. Molding conditions: Molding temperature 145℃, pressure 10MPa, pressurization time 300 seconds, mold 220mm x 220mm ○: No shorting in any of the molded parts with thicknesses of 3mm, 4mm, and 10mm. △: Shortness present in 3mm thick molded parts, but not present in 4mm and 10mm thick molded parts. ×: Shorting occurs in molded parts with a thickness of 3mm and 4mm, but not in molded parts with a thickness of 10mm.

[0048] [Evaluation of electromagnetic shielding performance] The thermosetting resin composition for electromagnetic shielding obtained above was compression molded under the conditions of a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding holding pressure time of 300 seconds to produce a flat plate measuring 220 mm × 220 mm × 3 mm thick. The electromagnetic shielding level was measured using the KEC method, and the electromagnetic shielding performance was evaluated according to the following criteria. The electromagnetic wave measurement frequency range was 0.1 to 1000 MHz. Note that the values ​​in parentheses in the evaluation results of the examples and comparative examples in the electromagnetic shielding performance items in Tables 1 and 2 are the measured values ​​at a frequency of 500 MHz. [Radio waves] ○: Shield level 80dB or higher ×: Shield level less than 80dB [Magnetic wave] ○: Shield level 20dB or higher ×: Shield level less than 20dB

[0049] The composition and evaluation results of the thermosetting resin composition for electromagnetic shielding obtained above are shown in Tables 1 and 2.

[0050] [Table 1]

[0051] [Table 2]

[0052] The thermosetting resin compositions for electromagnetic shielding of the present invention described in Examples 1 to 7 were found to have excellent fluidity, injection moldability, and compression moldability, and it was confirmed that molded articles with excellent electromagnetic shielding properties could be obtained.

[0053] On the other hand, Comparative Examples 1-3, which do not contain the thermally conductive filler (D), were found to have insufficient electromagnetic shielding properties.

Claims

1. A thermosetting resin composition for electromagnetic shielding comprising a thermosetting resin (A), a low-shrinkage agent (B), a thickener (C), a thermally conductive filler (D), and a reinforcing material (E), wherein the thermosetting resin (A) contains an unsaturated polyester resin (a1) and a vinyl ester resin (a2), and the thickener (C) contains acrylic resin particles (c1) and magnesium oxide (c2).

2. The thermosetting resin composition for electromagnetic wave shielding according to claim 1, wherein the amount of acrylic resin particles (c1) is 1 to 20 parts by mass and the amount of magnesium oxide (c2) is 0.05 to 5 parts by mass, based on a total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B).

3. The thermosetting resin composition for electromagnetic wave shielding according to claim 1, wherein the amount of the thermally conductive filler (D) is 150 to 550 parts by mass per 100 parts by mass of the total of the thermosetting resin (A) and the low-shrinkage agent (B).

4. The thermosetting resin composition for electromagnetic wave shielding according to claim 1, wherein the reinforcing material (E) is 10 to 80 parts by mass with respect to a total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B).

5. A bulk molding compound characterized by comprising the thermosetting resin composition for electromagnetic wave shielding described in any one of claims 1 to 4.

6. A molded article obtained using the bulk molding compound described in claim 5.

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