Thermosetting resin composition for electromagnetic wave 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 are excellent in fluidity, injection molding property, compression molding property, and in which a molded product excellent in electromagnetic wave shielding property can be obtained. The thermosetting resin composition for electromagnetic wave shielding is characterized by containing a thermosetting resin (A) containing an unsaturated polyester resin (a1) and a vinyl ester resin (a2), a low shrinkage agent (B), a thickening agent (C) containing acrylic resin particles (c1) and magnesium oxide (c2), a thermally conductive filler (D), and a reinforcing material (E).

Description

Technical Field

[0001] This invention relates to thermosetting resin compositions for electromagnetic wave shielding, bulk molding compounds, and molded articles thereof. Background Technology

[0002] Thermosetting resin compositions, made by adding low-shrinkage agents, inhibitors, curing agents, fillers, release agents, and reinforcing materials to thermosetting resins such as unsaturated polyester resins and vinyl ester resins and then mixing them using a mixing mill, possess advantages such as electrical insulation, heat resistance, flame retardancy, high rigidity, and dimensional stability. Therefore, they are widely used in electronic components related to home appliances, automobiles, and the energy sector. The aforementioned thermosetting resin compositions, when formed into clump-shaped molding compounds (hereinafter sometimes abbreviated as "BMC"), can be molded into finished products through molding methods such as compression molding, transfer molding, and injection molding.

[0003] On the other hand, from the perspective of preventing mutual interference between electrical and electronic devices caused by electromagnetic waves, electromagnetic wave shielding measures have become an important issue, and a method for manufacturing a battery casing with electromagnetic wave shielding effect has been proposed (for example, see Patent Document 1). However, this method for manufacturing a battery casing includes a step of heating and pressing a component containing a semi-cured resin fiber-reinforced composite intermediate material with metal foil, which requires a complex process. The aforementioned semi-cured resin fiber-reinforced composite intermediate material with metal foil is obtained by laminating and integrating at least two semi-cured resin sheets, fiber fabric or unidirectional fibers, and metal foil. Therefore, there is a need for a molding material that can easily impart electromagnetic wave shielding properties to the molded article.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 7466248 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The problem to be solved by the present invention is to provide a thermosetting resin composition for electromagnetic wave shielding, a bulk molding compound and the molded articles thereof, which have excellent flowability, injection molding properties, compression molding properties and can produce molded articles with excellent electromagnetic wave shielding properties.

[0009] Methods for solving problems

[0010] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that a thermosetting resin composition for electromagnetic wave shielding containing a specific thermosetting resin, a low-shrinkage agent, a specific thickener, a thermally conductive filler, and a reinforcing material solves the above-mentioned problems, thereby completing the present invention.

[0011] That is, the present invention provides a thermosetting resin composition for electromagnetic wave shielding, characterized in that it 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).

[0012] Invention Effects

[0013] The thermosetting resin composition for electromagnetic wave shielding of the present invention has excellent flowability, injection molding properties, and compression molding properties, and can produce molded articles with excellent electromagnetic wave shielding properties. Therefore, it is very useful for the frames of electrical and electronic components used in home appliances, personal computers, OA equipment, AV equipment, flat panel displays, mobile phones, medical devices, automotive parts, aircraft parts, etc. Detailed Implementation

[0014] The electromagnetic wave shielding thermosetting resin composition of the present invention contains a thermosetting resin (A), a low-shrinkage agent (B), a thickener (C), a thermally conductive filler (D), and a reinforcing material (E). 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).

[0015] The above-mentioned thermosetting resin (A) contains unsaturated polyester resin (a1) and vinyl ester resin (a2). From the perspective of further improving flowability and injection molding properties, the mass ratio (a1 / a2) of unsaturated polyester resin (a1) to vinyl ester resin (a2) is preferably 90 / 10 to 30 / 70, more preferably 70 / 30 to 50 / 50.

[0016] The thermosetting resin (A) mentioned above may also contain thermosetting resins other than unsaturated polyester resin (a1) and vinyl ester resin (a2).

[0017] The electromagnetic wave shielding thermosetting resin composition of the present invention contains a resin component consisting of a thermosetting resin (A) and a low-shrinkage agent (B) as essential components. From the perspective of balancing molding shrinkage and other physical properties, the mass ratio (A / B) of the thermosetting resin (A) to the low-shrinkage agent (B) is preferably 95 / 5 to 50 / 50, more preferably 90 / 10 to 70 / 30.

[0018] The aforementioned low-shrinkage agent (B) is a substance formulated to inhibit the curing shrinkage of thermosetting resin compositions. Examples include polymethyl methacrylate, polystyrene, saturated polyester, styrene-butadiene rubber, and polyvinyl acetate. One or more of these low-shrinkage agents may be used.

[0019] The thickener (C) mentioned above contains acrylic resin particles (C1) and magnesium oxide (C2). By using them together, the flowability of the BMC described later is improved, which can ensure injection molding properties (measurement) and injection molding properties (filling).

[0020] The acrylic resin particles (c1) mentioned above are not particularly limited. From the perspective of improving the flowability of BMC and further enhancing its injection molding properties (measurement) and injection molding properties (filling properties), the average particle size is preferably 0.1 to 8 μm, more preferably 0.1 to 3 μm. It should be noted that in this invention, the average particle size of the acrylic resin particles is determined by dynamic light scattering method.

[0021] Relative to the total of 100 parts by mass of the above-mentioned thermosetting resin (A) and the above-mentioned low-shrinkage agent (B), the above-mentioned acrylic resin particles (c1) are preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass.

[0022] Relative to the total of 100 parts by mass of the above-mentioned thermosetting resin (A) and the above-mentioned low-shrinkage agent (B), the above-mentioned magnesium oxide (C2) is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass.

[0023] Examples of thermally conductive fillers (D) include metallic fillers such as silver, copper, aluminum, iron, and stainless steel; inorganic fillers such as alumina, magnesium oxide, beryllium oxide, silicon dioxide, boron nitride, aluminum nitride, silicon carbide, boron carbide, and titanium carbide; and carbon-based fillers such as diamond, lead, graphite, and carbon fiber. Among these, carbon-based fillers are preferred from the viewpoint of improved electromagnetic shielding and weight reduction, and lead is more preferred. These thermally conductive fillers can be used alone or in combination of two or more.

[0024] From the perspective of further improving the balance between fluidity, injection molding properties and electromagnetic wave shielding, the thermally conductive filler (D) is preferably 150 to 550 parts by mass, more preferably 200 to 450 parts by mass, and even more preferably 290 to 400 parts by mass, relative to a total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B).

[0025] Furthermore, from the viewpoint of improving the flowability of the thermosetting resin composition for electromagnetic wave shielding of the present invention and the electromagnetic wave shielding performance of the molded article, the above-mentioned thermally conductive filler (D) is preferably granular, and its average particle size is preferably 10 to 500 μm. More preferably, a thermally conductive filler (d1) with an average particle size of 100 μm or more and 500 μm or less and a thermally conductive filler (d2) with an average particle size of 10 μm or more and less than 100 μm are used together.

[0026] From the perspective of obtaining a thermosetting resin composition that achieves an excellent balance between flowability, injection molding properties, and electromagnetic wave shielding properties, the thermally conductive filler (d1) is preferably 150 to 400 parts by mass, more preferably 200 to 350 parts by mass, relative to 100 parts by mass of the total amount of the thermosetting resin (A) and the low-shrinkage agent (B).

[0027] As the aforementioned thermally conductive filler (d1), fillers with an average particle size of 100 μm or more and 500 μm or less can be used alone, or two or more can be used together.

[0028] From the perspective of further improving the balance between fluidity, injection molding properties and electromagnetic wave shielding, the thermally conductive filler (d2) is preferably 20 to 130 parts by mass, more preferably 30 to 120 parts by mass, relative to 100 parts by mass of the total amount of the thermosetting resin (A) and the low-shrinkage agent (B).

[0029] As the aforementioned thermally conductive filler (d2), fillers with an average particle size of 10 μm or more and less than 100 μm can be used alone, or two or more can be used together.

[0030] Furthermore, from the perspective of further improving the balance between flowability, injection molding properties and electromagnetic wave shielding, the average particle size of the above-mentioned thermally conductive filler (d2) is more preferably 30 μm or more and less than 60 μm.

[0031] Examples of fibrous materials such as glass fiber, vinylon fiber, phenolic fiber, carbon fiber, and polyester fiber can be used as the reinforcing material (E). Among these, glass fiber is preferred from the viewpoints of ease of acquisition, flowability of BMC, and improved strength properties of molded articles. The glass fiber can be any of chopped glass filaments or ground glass. From the perspectives of improving the flowability of BMC, further enhancing injection molding properties (measurement), injection molding properties (filling properties), and the physical properties of BMC molded articles, materials with fiber lengths of 1.5 to 12 mm are preferred, and materials with fiber lengths of 1.5 to 9 mm are more preferred.

[0032] The amount of the reinforcing material is preferably 10 to 80 parts by mass relative to the total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B), and more preferably 15 to 50 parts by mass.

[0033] In addition to the components (A) to (E) mentioned above, the thermosetting resin composition for electromagnetic wave shielding of the present invention may also contain thermoplastic resin, polymerization inhibitor, curing agent, curing accelerator, dispersant, release agent, pigment, colorant, defoamer, etc., without impairing the effect of the present invention.

[0034] Examples of polymerization inhibitors include methylhydroquinone, hydroquinone, hydroquinone monomethyl ether, 1,4-naphthoquinone, p-benzoquinone, p-tert-butylcatechol, and 2,6-tert-butyl-4-methylphenol. Regarding the amount of polymerization inhibitor incorporated into the thermosetting resin composition for electromagnetic wave shielding of the present invention, it is preferably in the range of 10 to 1500 ppm.

[0035] As the curing agent mentioned above, organic peroxides are preferred, such as acyl peroxide-based organic peroxides, peroxide-based organic peroxides, hydroperoxide-based organic peroxides, dialkyl peroxide-based organic peroxides, ketone peroxide-based organic peroxides, peroxide ketal-based organic peroxides, alkyl perester-based organic peroxides, and percarbonate-based organic peroxides. It should be noted that these curing agents can be used alone or in combination of two or more.

[0036] The amount of curing agent is preferably 0.5 to 5 parts by mass relative to the total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B), and more preferably 1 to 3 parts by mass.

[0037] The aforementioned mold release agent facilitates the removal of the molded article from the mold after the thermosetting resin composition for electromagnetic wave shielding of the present invention has been molded using a mold. Examples of such mold release agents include unsaturated fatty acid amide-based mold release agents, polyethylene wax-based mold release agents, metal soap-based mold release agents, silicone-based mold release agents, and fluorine-based mold release agents. Furthermore, examples of such metal soap-based mold release agents include zinc laurate, calcium laurate, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zinc myristate, calcium lignite, zinc lignite, aluminum lignite, calcium behenate, magnesium behenate, and zinc behenate. It should be noted that these mold release agents can be used alone or in combination of two or more.

[0038] The amount of the release agent is preferably 1 to 10 parts by mass relative to the total of 100 parts by mass of the thermosetting resin (A) and the low-shrinkage agent (B), and more preferably 3 to 8 parts by mass.

[0039] The thermosetting resin composition for electromagnetic wave shielding of the present invention can be manufactured by mixing the above-mentioned components using a mixing machine such as a kneader. Furthermore, by adjusting the formulation to make the obtained resin composition into a clump, a bulk molding compound (BMC) can be produced.

[0040] By forming BMC from the thermosetting resin composition for electromagnetic wave shielding of the present invention, molded articles can be easily manufactured using molding methods such as compression molding, transfer molding, and injection molding.

[0041] [Example]

[0042] The present invention will be described in more detail below through examples. It should be noted that the acid value of the resin was determined according to JIS K6901.

[0043] (Manufacturing Example 1: Synthesis of Unsaturated Polyester Resin (a1-1))

[0044] In a 2L glass flask equipped with a nitrogen 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 added, and heating was initiated under a nitrogen flow. The dehydration condensation reaction was carried out at an internal temperature of 215°C using conventional methods, and the temperature was cooled to 190°C when the solid component acid value reached 6 (mgKOH / g). Next, 198 parts by mass of maleic acid were added, and the dehydration condensation reaction continued. When the solid component acid value reached 28 (mgKOH / g), 0.4 parts by mass of methylhydroquinone were added. The solution was dissolved in styrene monomer to achieve an unsaturated polyester concentration of 65% by mass, yielding an unsaturated polyester resin (a1-1).

[0045] (Manufacturing Example 2: Synthesis of Vinyl Ester Resin (a2-1))

[0046] In a 2L flask equipped with a nitrogen inlet tube, thermometer, and stirrer, 246 parts by weight of epoxy resin (DIC Corporation's "EPICLON 860-C", bisphenol A type epoxy resin, epoxy equivalent 240), 730 parts by weight of epoxy resin (DIC Corporation's "EPICLON 1050", bisphenol A type epoxy resin, epoxy equivalent 470), 215 parts by weight of methacrylic acid, and 0.45 parts by weight of dibutylhydroxytoluene were added. The mixture was heated to 100°C under a 1:1 mixture of nitrogen and air. 0.96 parts by weight of 2-methylimidazole were then added, and the temperature was raised to 110°C to proceed with the reaction. When the solid component acid value reached below 6 (mgKOH / g), 0.46 parts by weight of methylhydroquinone were added and dissolved in styrene monomer to achieve a vinyl ester concentration of 70% by weight, yielding vinyl ester resin (a2-1).

[0047] (Manufacturing Example 3: Manufacturing of Low Shrinkage Agent (B-1))

[0048] In a 2L flask equipped with a nitrogen inlet tube, thermometer, and stirrer, 900 parts by weight of styrene monomer, 600 parts by weight of polystyrene (DIC Corporation's "DICSTYRENE CR-3500"), and 0.25 parts by weight of methylhydroquinone were added. The mixture was heated to 50°C under nitrogen atmosphere. The thermoplastic resin polystyrene was stirred until completely melted, and then cooled to below 40°C to obtain a low-shrinkage agent (B-1) with a polystyrene concentration of 40% by weight.

[0049] (Example 1: Preparation of thermosetting resin composition (1) for electromagnetic wave shielding)

[0050] Using a planetary mixer, 50 parts by weight of the unsaturated polyester resin (a1-1) obtained in Manufacturing Example 1, 30 parts by weight of the vinyl ester resin (a2-1) obtained in Manufacturing Example 2, 20 parts by weight of the low-shrinkage agent (B-1) obtained in Manufacturing Example 3, 4 parts by weight of acrylic resin particles (c1-1) (AICA Kogyo Co., Ltd. "ZEFIAC F303"; average particle size 2 μm), 0.15 parts by weight of magnesium oxide (c2-1) (Kyowa Chemical Industry Co., Ltd. "Kyowamag40"), 0.6 parts by weight of curing agent (1) (Nippon Yu Co., Ltd. "Perbutyl O"; peroxide ester-based organic peroxide), 1.2 parts by weight of curing agent (2) (Nippon Yu Co., Ltd. "Perbutyl Z"; peroxide ester-based organic peroxide), and 1 part by weight of release agent (1) (Sakai Chemical Industry Co., Ltd. "ZINC STEARATE") were mixed. SZ-2000” 4 parts by weight, release agent (2) (CALCIUM STEARATE manufactured by Nippon Oil Co., Ltd.) 1.2 parts by weight, thermally conductive filler (d1-1) (AGB-32 manufactured by Ito Black Lead Industry Co., Ltd.; black lead powder, average particle size 200-300 μm) 50 parts by weight, thermally conductive filler (d1-2) (AGB-100 manufactured by Ito Black Lead Industry Co., Ltd.; black lead powder, average particle size 110 μm) 200 parts by weight, and thermally conductive filler (d2-1) (AGB-604 manufactured by Ito Black Lead Industry Co., Ltd.; black lead powder, average particle size 55 μm) 100 parts by weight are mixed for 9 minutes. Then, reinforcing material (E-1) (glass fiber / chopped strand; ECS404-6 manufactured by Chongqing International Composite Materials Co., Ltd.; fiber length 6 33 parts by weight of (mm) were further mixed for 6 minutes to obtain lumps. The obtained lumps were wrapped with aluminum vapor deposition film and placed in a constant temperature bath at 40°C for 12 hours to obtain a thermosetting resin composition for electromagnetic wave shielding (1) in the form of BMC.

[0051] (Examples 2-7)

[0052] Except for changing the formulation composition to that shown in Tables 1 and 2, the same procedure as in Example 1 was followed to obtain thermosetting resin compositions (2) to (7) for electromagnetic wave shielding in the form of BMC.

[0053] (Comparative Examples 1-3)

[0054] Except for changing the formulation composition as shown in Table 2, the same procedure as in Example 1 was followed to obtain thermosetting resin compositions (R1) to (R3) for electromagnetic wave shielding in the form of BMC.

[0055] Thermosetting resin compositions (1) to (7) for electromagnetic wave shielding and thermosetting resin compositions (R1) to (R3) for electromagnetic wave shielding obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated as follows.

[0056] [Liquidity Assessment]

[0057] The initial viscosity of the thermosetting resin composition for electromagnetic wave shielding obtained above was determined. Viscosity determination was performed using a capillary viscometer (thin-tube rheometer) under the following conditions: resin composition input (sample amount): 75 g; measurement temperature: 50°C; extrusion speed: 50 mm / min; nozzle diameter: 6 mm; nozzle length: 10 mm.

[0058] [Evaluation of Injection Molding Performance (Dosage)]

[0059] The specified amount (75 cm) of the thermosetting resin composition for electromagnetic wave shielding obtained above. 3 The amount of material that can be moved from the material magazine (feed hopper) to the barrel by the screw within a specified time (30 seconds) is measured, and the injection molding performance (metrics) is evaluated according to the following criteria.

[0060] Test conditions: Infeed pressure 5 MPa, screw speed 20 rpm, feed hopper and barrel temperature 35℃

[0061] ○: 75 cm when less than 30 seconds 3

[0062] △: 40–75 cm at 30 seconds 3

[0063] ×: Less than 40 cm at 30 seconds 3

[0064] [Evaluation of Injection Molding Properties (Filling Properties)]

[0065] For the thermosetting resin composition for electromagnetic wave shielding with a measurement evaluation result of ○, injection molding was performed using a flowability evaluation mold, and the appearance of the molded article was visually observed. The injection molding performance (filling performance) was evaluated according to the following criteria.

[0066] Molding conditions: mold temperature 160℃, clamping force 750 kN, injection speed 70 mm / s, curing time 55 seconds.

[0067] ○: No underfilling, no voids on the surface of the molded part.

[0068] △: No underfilling, but gaps are present on the surface of the molded part.

[0069] ×: Insufficient filling, gaps appear on the surface of the molded part.

[0070] [Evaluation of Compression Formability]

[0071] The thermosetting resin composition for electromagnetic wave shielding obtained above was compressed and molded, and its compressibility was evaluated according to the following criteria.

[0072] Molding conditions: Molding temperature 145℃, pressure 10 MPa, pressing time 300 seconds, mold 220 mm × 220 mm

[0073] ○: No underfilling was observed in molded parts with thicknesses of 3 mm, 4 mm, and 10 mm.

[0074] △: Insufficient filling was observed in molded parts with a thickness of 3 mm, but not in molded parts with a thickness of 4 mm and 10 mm.

[0075] ×: Insufficient filling occurred in molded parts with a thickness of 3 mm and 4 mm, but not in molded parts with a thickness of 10 mm.

[0076] [Evaluation of Electromagnetic Wave Shielding Performance]

[0077] The thermosetting resin composition for electromagnetic wave shielding obtained above was compressed and molded at a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding holding time of 300 seconds to produce a plate with a thickness of 3 mm and a diameter of 220 mm. The electromagnetic wave shielding level was measured using the KEC method, and the electromagnetic wave shielding performance was evaluated according to the following criteria. The electromagnetic wave measurement frequency range was 0.1–1000 MHz. It should be noted that the values ​​in parentheses in the evaluation results of the examples and comparative examples in the electromagnetic wave shielding performance items in Tables 1 and 2 are measured values ​​at a frequency of 500 MHz.

[0078] [Radio Waves]

[0079] ○: Shielding level is above 80 dB

[0080] ×: Shielding level less than 80 dB

[0081] [Magnetic Waves]

[0082] ○: Shielding level is above 20 dB

[0083] ×: Shielding level less than 20 dB

[0084] The composition and evaluation results of the thermosetting resin composition for electromagnetic wave shielding obtained above are shown in Tables 1 and 2.

[0085] [Table 1]

[0086]

[0087] [Table 2]

[0088]

[0089] The following has been confirmed: the thermosetting resin compositions for electromagnetic wave shielding of the present invention in Examples 1 to 7 have excellent flowability, injection molding properties, and compression molding properties, and can produce molded articles with excellent electromagnetic wave shielding properties.

[0090] On the other hand, Comparative Examples 1 to 3, which do not contain thermally conductive filler (D), confirmed that the electromagnetic wave shielding was insufficient.

Claims

1. A thermosetting resin composition for electromagnetic wave shielding, characterized in that, It contains thermosetting resin A, low-shrinkage agent B, thickener C, thermally conductive filler D, and reinforcing material E. The thermosetting resin A contains unsaturated polyester resin a1 and 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, Relative to a total of 100 parts by mass of the thermosetting resin A and the low-shrinkage agent B, the acrylic resin particles c1 are 1 to 20 parts by mass, and the magnesium oxide c2 is 0.05 to 5 parts by mass.

3. The thermosetting resin composition for electromagnetic wave shielding according to claim 1, wherein, The thermally conductive filler D is 150 to 550 parts by mass relative to a total of 100 parts by mass 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 relative 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 in that, It comprises the thermosetting resin composition for electromagnetic wave shielding as described in any one of claims 1 to 4.

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

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