Thermosetting resin composition, bulk molding compound and molded article thereof

Abstract

To provide: a thermosetting resin composition that offers excellent mixability and storage stability, exhibits low shrinkage during molding, and yields a molded article with superior flame retardancy and thermal conductivity as well as a low specific gravity; a bulk molding compound; and a molded article thereof.SOLUTION: A thermosetting resin composition contains an unsaturated polyester resin (A), a shrinkage reducer (B), aluminum hydroxide (C), magnesium oxide (D), and a hollow filler (E).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermosetting resin composition, a bulk molding compound, and a molded article thereof. [Background technology]

[0002] Thermosetting resin compositions, which are prepared by adding low-shrinkage agents, inhibitors, curing agents, fillers, release agents, reinforcing materials, etc. to thermosetting resins such as unsaturated polyester resins and vinyl ester resins and kneading them in a kneader, have advantages such as electrical insulation, heat resistance, flame retardancy, high rigidity, and dimensional stability, and are therefore widely used in electronic parts related to home appliances, automobiles, the energy field, etc. Among the thermosetting resin compositions, bulk molding compounds (hereinafter sometimes abbreviated as "BMC") can be made into molded articles by molding methods such as compression molding, transfer molding, and injection molding.

[0003] In recent years, electronic components have become increasingly powerful (high density) and compact (lightweight), making them more susceptible to internal heat buildup, posing a risk of fire or the spread of fire after it has started.

[0004] In this situation, BMC is required to have excellent flame retardancy, thermal conductivity, and weight reduction, and a flame-retardant, low-specific-gravity unsaturated polyester resin composition containing unsaturated polyester, a crosslinking agent, aluminum hydroxide, and a hollow filler has been proposed (see, for example, Patent Document 1). However, molded articles using this resin composition have the problem of insufficient thermal conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-261954 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a thermosetting resin composition, a bulk molding compound, and a molded article thereof, which have excellent kneadability and storage stability, have a low shrinkage rate during molding, and are capable of producing a molded article having a low specific gravity and excellent flame retardancy and thermal conductivity. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a thermosetting resin composition containing an unsaturated polyester resin, a polymerizable monomer, a low-profile agent, aluminum hydroxide, magnesium oxide, and a hollow filler solves the above-mentioned problems, and have completed the present invention.

[0008] That is, the present invention provides a thermosetting resin composition comprising an unsaturated polyester resin (A), a low-profile agent (B), aluminum hydroxide (C), magnesium oxide (D), and a hollow filler (E). [Effects of the Invention]

[0009] The thermosetting resin composition of the present invention has excellent kneadability and storage stability, exhibits low shrinkage during molding, and can give molded articles with low specific gravity and excellent flame retardancy and thermal conductivity. Therefore, the composition is suitable for use as supports for various electric and electronic parts, sealing materials, battery holders for electric vehicles, etc. DETAILED DESCRIPTION OF THE INVENTION

[0010] The thermosetting resin composition of the present invention contains an unsaturated polyester resin (A), a low-profile agent (B), aluminum hydroxide (C), magnesium oxide (D), and a hollow filler (E).

[0011] The thermosetting resin composition of the present invention contains resin components having the unsaturated polyester resin (A) and the low-profile agent (B) as essential components. In view of the balance between molding shrinkage rate and other physical properties, the mass ratio (A / B) of the unsaturated polyester resin (A) to the low-profile agent (B) is preferably 90 / 10 to 40 / 60, more preferably 80 / 20 to 50 / 50.

[0012] Examples of the low shrinkage agent (B) include styrene solutions of acrylic resins and polystyrene resins, and from the viewpoint of improving the thermal conductivity of the resulting molded article, styrene solutions of polystyrene resins are preferred.

[0013] The thermosetting resin composition of the present invention has excellent flame retardancy due to the inclusion of the aluminum hydroxide (C). In order to further improve the balance between thermal conductivity and low specific gravity, the amount of the aluminum hydroxide (C) is preferably 200 to 350 parts by mass, more preferably 220 to 320 parts by mass, per 100 parts by mass of the total of the unsaturated polyester resin (A) and the low profile agent (B).

[0014] The aluminum hydroxide (C) preferably has an average particle size of 1 to 100 μm, more preferably 2 to 60 μm, from the viewpoint of improving the kneadability, fluidity, and flame retardancy of the molded article of the thermosetting resin composition of the present invention.

[0015] The thermosetting resin composition of the present invention is excellent in thermal conductivity by containing the magnesium oxide (D). In order to obtain a better balance between flame retardancy and low specific gravity, the content of the magnesium oxide (D) is preferably 10 to 100 parts by mass, more preferably 15 to 80 parts by mass, per 100 parts by mass of the total of the unsaturated polyester resin (A) and the low profile agent (B).

[0016] The magnesium oxide (D) is hard-burned magnesium oxide, and from the viewpoint of improving the thermal conductivity of the molded article of the thermosetting resin composition of the present invention, it is preferably in the form of particles, and its average particle size is preferably 10 to 100 μm, more preferably 30 to 70 μm.

[0017] The thermosetting resin composition of the present invention can have a low specific gravity by containing the hollow filler (E). In order to obtain a better balance between thermal conductivity and low specific gravity, the amount of the hollow filler (E) is preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the total of the unsaturated polyester resin (A) and the low shrinkage agent (B).

[0018] Examples of the hollow filler (E) include glass balloons, silica balloons, and alumina balloons. From the overall viewpoints of pressure resistance, low density, and hardness, glass balloons are preferred. Furthermore, since they can be used in molding methods such as injection molding and compression molding, hollow fillers with a pressure resistance of 20 MPa or more are preferred. Furthermore, from the viewpoint of the kneadability of the thermosetting resin composition of the present invention, the particle size of the hollow filler is preferably 20 to 60 μm, more preferably 20 to 45 μm.

[0019] The thermosetting resin composition of the present invention may contain inorganic fillers other than the aluminum hydroxide (C), the magnesium oxide (D), and the hollow filler (E) within the range that does not impair the effects of the present invention. Examples of the inorganic fillers include boron nitride, aluminum nitride, aluminum oxide (alumina), and magnesium carbonate.

[0020] In addition to the above components (A) to (E), the thermosetting resin composition of the present invention may contain other resins besides the unsaturated polyester resin, polymerization inhibitors, curing accelerators, dispersants, release agents, thickeners, curing agents, reinforcing materials, pigments, colorants, antifoaming agents, and the like, within the scope of not impairing the effects of the present invention.

[0021] Examples of the polymerization inhibitor include toluhydroquinone, hydroquinone, hydroquinone monomethyl ether, 1,4-naphthoquinone, parabenzoquinone, toluhydronone, pt-butylcatechol, 2,6-t-butyl-4-methylphenol, etc. When a polymerization inhibitor is blended into the thermosetting resin composition of the present invention, the blending amount is preferably in the range of 10 to 1500 ppm in the thermosetting resin composition of the present invention.

[0022] The release agent is used to facilitate removal of the molded article obtained from the mold after molding the thermosetting resin composition of the present invention using a mold. Examples of the release agent include unsaturated fatty acid amide-based release agents, polyethylene wax-based release agents, metal soap-based release agents, silicone-based release agents, and fluorine-based release agents. Examples of the metal soap-based release agents include zinc laurate, calcium laurate, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zinc myristate, calcium montanate, zinc montanate, aluminum montanate, calcium behenate, magnesium behenate, and zinc behenate.

[0023] Examples of the thickener include metal oxides and hydroxides such as light-burned magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, and isocyanate compounds, and can be selected appropriately depending on the handleability of the heat-compression molding material of the present invention. These thickeners can be used alone or in combination of two or more. Among these, light-burned magnesium oxide is preferred.

[0024] Examples of the reinforcing material include fibrous materials such as glass fiber, vinylon fiber, phenol fiber, carbon fiber, and polyester fiber. Among these, glass fiber is preferred from the viewpoint of availability. Any of chopped glass, milled glass, and roving glass can be used as the glass fiber.

[0025] The thermosetting resin composition of the present invention can be produced by kneading the above-mentioned components using a kneader or other kneading machine. In addition, by adjusting the blending composition so that the resulting resin composition is in a bulk state, it can be made into a bulk molding compound (BMC).

[0026] By using the thermosetting resin composition of the present invention as a BMC, it can be easily formed into a molded article by molding methods such as compression molding, transfer molding, and injection molding. [Example]

[0027] The present invention will be explained in more detail below with reference to examples.

[0028] (Example 1: Preparation of thermosetting resin composition (1)) 65 parts by mass of unsaturated polyester resin ("PS-361" manufactured by DIM Corporation; a mixture of 65% by mass of unsaturated polyester and 35% by mass of styrene), 35 parts by mass of low-profile additive ("PB-964" manufactured by DIM Corporation; a mixture of 42% by mass of polystyrene and 58% by mass of styrene), 0.12 parts by mass of polymerization inhibitor (10% parabenzoquinone), 7 parts by mass of hollow filler ("S32HS" manufactured by 3M Japan Ltd.; average particle size 25 μm), 20 parts by mass of magnesium oxide ("RF-50-SC" manufactured by Ube Material Industries, Ltd.; average particle size 50 μm), 200 parts by mass of aluminum hydroxide ("B103" manufactured by Nikkeikin Co., Ltd.; average particle size 7 μm), 90 parts by mass of aluminum (2) ("B53" manufactured by Nikkeikin Co., Ltd.; average particle size 55 μm), 4 parts by mass of a release agent (zinc stearate; "SZ-2000" manufactured by Sakai Chemical Industry Co., Ltd.), 0.3 parts by mass of a thickener (light-burned magnesium oxide; "MgO-40" manufactured by Kyowa Chemical Industry Co., Ltd.), and 1.8 parts by mass of a curing agent (organic peroxide; "Perbutyl O" manufactured by NOF Corporation; 0.6 parts by mass and "Perbutyl Z" 1.2 parts by mass) were kneaded using a planetary mixer for 12 minutes, and then 36 parts by mass of a reinforcing material (glass fiber / chopped strand; "ECS404-6" manufactured by Chongqing International Composite Materials Co., Ltd.; fiber length 6 mm) was added, and the mixture was kneaded for an additional 6 minutes to obtain a thermosetting resin composition (1).

[0029] (Examples 2 and 3) The same procedure as in Example 1 was carried out except that the blending compositions were changed as shown in Table 1, and thermosetting resin compositions (2) and (3) were obtained.

[0030] (Comparative Examples 1 and 2) The same procedure as in Example 1 was carried out except that the blending compositions were changed to those shown in Table 1, and thermosetting resin compositions (R1) to (R2) were obtained.

[0031] The thermosetting resin compositions (1) to (3) and (R1) to (R2) obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated as follows.

[0032] [Evaluation of kneadability] The appearance of the thermosetting resin composition obtained above was visually observed, and the kneadability was evaluated according to the following criteria. ◎: Bulky and excellent dispersion of reinforcing material ○: Bulky and well-dispersed reinforcing material ×: Not bulky and poorly dispersed reinforcing material

[0033] [Evaluation of storage stability] The thermosetting resin composition obtained above was stored at 25°C, and the number of days during which the viscosity increase rate could be maintained at 20% or less was measured. The viscosity measurement was carried out using a capillary viscometer (narrow tube rheometer) under the following conditions: resin composition input amount (sample amount): 75 g, measurement temperature conditions: 50°C, extrusion speed: 50 mm / min, nozzle diameter: 6 mm, nozzle length: 10 mm

[0034] [Measurement of molding shrinkage rate] A shrink disk was prepared as a test piece for measurement by compression molding under conditions of a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding pressure holding time of 300 seconds, and the molding shrinkage rate was calculated based on JIS K6911.

[0035] [Measurement of thermal conductivity] The material was compression molded under the conditions of a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding pressure holding time of 300 seconds to prepare a flat plate measuring 220 mm x 220 mm x 10 mm thick, and its thermal conductivity was measured using the QTM method.

[0036] [Oxygen index measurement] Compression molding was performed under conditions of a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding pressure holding time of 300 seconds to prepare a flat plate of 220 mm x 220 mm x 3 mm thickness. Test specimens (length: 130 mm, width: 6.5 mm, thickness: 3 mm) were cut out based on JIS K7201, and the oxygen index was measured.

[0037] [Measurement of specific gravity] Compression molding was performed under conditions of a molding temperature of 145°C, a molding pressure of 10 MPa, and a molding pressure holding time of 300 seconds to prepare a flat plate of 220 mm x 220 mm x 3 mm thick. Test specimens for measurement were cut out based on JIS K6911, and the specific gravity was measured.

[0038] The composition and evaluation results of the thermosetting resin compositions prepared above are shown in Table 1.

[0039] [Table 1]

[0040] It was confirmed that the thermosetting resin compositions of the present invention in Examples 1 to 3 have excellent kneadability and storage stability, have a low shrinkage rate during molding, and can give molded articles with low specific gravity that are excellent in flame retardancy, thermal conductivity, and mechanical properties such as bending strength.

[0041] On the other hand, Comparative Example 1 is an example that does not contain magnesium oxide, but it was confirmed that the thermal conductivity was insufficient.

[0042] Comparative Example 2 is an example in which no hollow filler was contained, but it was confirmed that the specific gravity was not sufficiently reduced.

Claims

1. 1. A thermosetting resin composition comprising an unsaturated polyester resin (A), a low-profile agent (B), aluminum hydroxide (C), magnesium oxide (D), and a hollow filler (E), wherein the magnesium oxide (D) is dead-burned magnesium oxide, the mass ratio (A / B) of the unsaturated polyester resin (A) to the low-profile agent (B) is 90 / 10 to 40 / 60, and the amount of the aluminum hydroxide (C) is 200 to 350 parts by mass, the amount of the magnesium oxide (D) is 10 to 100 parts by mass, and the amount of the hollow filler (E) is 3 to 30 parts by mass per 100 parts by mass of the total of the unsaturated polyester resin (A) and the low-profile agent (B).

2. A bulk molding compound comprising the thermosetting resin composition of claim 1.

3. A molded article obtained by using the bulk molding compound according to claim 2.

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