JP6901257B2 - Arc resistance BMC - Google Patents

Description

The present invention relates to unsaturated polyester resin compositions with significantly improved arc resistance, particularly bulk molding compounds (BMCs) and electrical and electronic components obtained by curing them.

Fiber reinforced plastic in which glass fiber is dispersed in a binder resin as a dispersion reinforcing material is inexpensive and has excellent heat resistance, flame resistance, tracking resistance, etc., so it has been conventionally used for various structural materials and insulating materials. There is. In particular, bulk molding compound (BMC) using unsaturated polyester is used for various electrically insulating product members because it is excellent in moldability, electro-greenness, and arc resistance. Such an electrically insulating molded body can absorb the energy of the arc generated when the electrodes of an electric switch or the like are opened and closed, and has a function of protecting the electric device from the arc.

In recent years, with the miniaturization and weight reduction of electric devices, there is an increasing demand for miniaturization and high capacity of electric switches. As for the electrically insulating molded body, there is a demand for higher performance in terms of arc resistance, and various solutions have been proposed. For example, it is known that arc resistance is improved when a large amount of a flame-retardant filler that releases water or the like at a high temperature such as aluminum hydroxide is contained. Document 1 proposes to obtain an arc-resistant molded product by curing a sheet-like material composed of an inorganic sheet and an inorganic binder composition. Document 2 proposes to cure a prepreg using an epoxy resin composition containing aluminum oxide to obtain an arc-resistant electrically insulating molded product. Document 3 proposes to cure a prepreg containing a binder resin and a filler to obtain an arc-resistant electrically insulating molded product.

Japanese Unexamined Patent Publication No. 8-36938 Japanese Unexamined Patent Publication No. 9-207270 Japanese Unexamined Patent Publication No. 2005-89648

However, in these prior documents, since the amounts of the reinforcing fibers and the filler are large, the prepregs in which the fibers are impregnated with the resin composition have been limited in terms of handleability such as viscosity. In order to obtain a thick molded product, it is necessary to laminate a plurality of layers of the reinforcing fiber and the resin composition, which lowers the productivity. Further, the obtained molded product has a problem that anisotropy of mechanical strength occurs depending on the direction of the reinforcing fibers. Furthermore, prepregs containing a large amount of filler generally require a diluting solvent such as water or ketones in the manufacturing process, and the solvent needs to be removed in a subsequent step. On the other hand, the conventional BMC generally has a smaller amount of reinforcing fibers than the prepreg and a large amount of resin in the whole, so that there is a problem that the same level of arc resistance as the prepreg cannot be obtained. Therefore, it has been desired to invent an electric / electronic component having no anisotropy of strength, a simple molding operation, a uniform molded product, and an excellent arc resistance using BMC, which is a solvent-free kneaded product. ..
An object of the present invention is to provide a BMC that provides a molded product having excellent workability and moldability, good productivity, no anisotropy in strength, and excellent arc resistance.

As a result of diligent research to solve the above problems, the present inventors have obtained a BMC having high arc resistance and containing no diluting solvent by blending aluminum hydroxide and glass fiber in a certain ratio. We have found that it can be obtained and have completed the present invention.

That is, the present invention is the following [1] to [7].
[1] (a) unsaturated polyester, (b) monomer having one or more polymerizable carbon-carbon double bonds, (c) aluminum hydroxide, (d) chopped strand glass fiber, (e) low shrinkage agent, (F) A thermosetting resin composition containing a curing agent, wherein the content of (c) aluminum hydroxide is 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer. It is 300 to 590 parts by mass, and the content of the (d) chopped strand glass fiber is 10 to 200 parts by mass with respect to 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer. Characterized bulk molding compound (BMC).
[2] The BMC according to [1], wherein the BMC contains a compound having a (g) phosphate ester group.
[3] The content of the compound having the (g) phosphoric acid ester group is 0.2 to 30 parts by mass with respect to 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer. , [1] or [2].
[4] The BMC according to any one of [1] to [3], wherein the average particle size of (c) aluminum hydroxide is 15 μm or less.
[5] The BMC according to any one of [1] to [4], wherein the chopped strand glass fiber having a fiber length of 1 mm to 20 mm.
[6] The BMC according to any one of [1] to [5], wherein the unsaturated polyester (a) has a mass average molecular weight of 2,000 to 50,000.
[7] Of [1] to [6], the content of the (b) monomer is 25 to 70% by mass with respect to 100% by mass of the total of the (a) unsaturated polyester and the (b) monomer. BMC described in either.
[8] A cured product obtained by curing the BMC according to any one of [1] to [7].

According to the present invention, it is possible to provide a BMC which is excellent in workability and moldability, can be manufactured with high productivity, has no anisotropy in strength, and gives a molded product having excellent arc resistance.

The BMC of the present invention comprises (a) unsaturated polyester, (b) a monomer having one or more polymerizable carbon-carbon double bonds, (c) aluminum hydroxide, (d) chopped strand glass fiber, and (e) low. It is a thermosetting resin composition containing a shrinkage agent and (f) a curing agent. Hereinafter, each component will be described.

[(A) Unsaturated polyester]
The unsaturated polyester (a) used in the present invention is not particularly limited, and known ones used as molding materials in the art can be used. (A) Unsaturated polyester is generally a compound obtained by polycondensing (esterifying) a polyhydric alcohol with an unsaturated polybasic acid or a saturated polybasic acid. As long as the effect of the present invention is not impaired, vinyl ester may be used as a part of (a) unsaturated polyester.

The mass average molecular weight (MW) of the unsaturated polyester is not particularly limited, but is preferably 2,000 to 50,000, more preferably 3,000 to 30,000, and even more preferably 5,000 to 20,000. .. When the mass average molecular weight is 2,000 or more, the strength after curing is good, and when it is 50,000 or less, the viscosity of the composition is preferable as BMC. In the present specification, the "mass average molecular weight" is measured by gel permeation chromatography (Shodex GPC-101 manufactured by Showa Denko KK) at room temperature under the following conditions, and is determined using a standard polystyrene calibration curve. Means the value.
Column: Showa Denko LF-804
Column temperature: 40 ° C
Sample: (a) 0.2 parts by mass tetrahydrofuran solution of unsaturated polyester Flow rate: 1 mL / min Eluent: tetrahydrofuran Detector: RI-71S

The polyhydric alcohol used for synthesizing the unsaturated polyester is not particularly limited, and known ones can be used. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol, hexanediol, neopentanediol, hydride bisphenol A, bisphenol A, and glycerin. Be done. These can be used alone or in combination of two or more.

The unsaturated polybasic acid used in the synthesis of the unsaturated polyester is not particularly limited, and known ones can be used. Examples of unsaturated polybasic acids include maleic anhydride, fumaric acid, citraconic acid, itaconic acid and the like. These can be used alone or in combination of two or more.

The saturated polybasic acid used for synthesizing the unsaturated polyester is not particularly limited, and known ones can be used. Examples of saturated polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, hetic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, endomethylenetetrahydrophthalic anhydride and the like. Can be mentioned. These can be used alone or in combination of two or more.

Unsaturated polyester can be synthesized by a known method using the above-mentioned raw materials. Various conditions in this synthesis need to be appropriately set according to the raw materials used and the amount thereof, but generally, they are pressurized or reduced in pressure at a temperature of 140 to 230 ° C. in an inert gas stream such as nitrogen. It may be esterified with. In this esterification reaction, an esterification catalyst can be used if necessary. Examples of catalysts include known catalysts such as manganese acetate, dibutyltin oxide, stannous oxalate, zinc acetate, and cobalt acetate. These can be used alone or in combination of two or more.

[(B) Monomer having one or more polymerizable carbon-carbon double bonds]
The monomer used in the present invention (b) having one or more polymerizable carbon-carbon double bonds is (a) a component that acts as a cross-linking agent for unsaturated polyester. (B) The monomer having one or more polymerizable carbon-carbon double bonds is particularly limited as long as it has one or more polymerizable carbon-carbon double bonds that can be polymerized with unsaturated polyester. There is nothing.

(B) Examples of the monomer having one or more polymerizable carbon-carbon double bonds include styrene, vinyltoluene, methylstyrene, and methyl methacrylate for the monofunctional monomer, and ethylene glycol di for the polyfunctional monomer. (Meta) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol # 200 (# 400, # 600) di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate ) Acrylate, 1,9-nonanediol di (meth) acrylate, trimethylpropantri (meth) acrylate, glycerindi (meth) acrylate, 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, triethylene glycol di Examples thereof include (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 1,10-decanediol di (meth) acrylate. .. These can be used alone or in combination of two or more. From the viewpoint of moldability of BMC, styrene, vinyltoluene and ethylene glycol di (meth) acrylate are preferable, and styrene is particularly preferable.
In addition, in this specification, "(meth) acrylate" means methacrylate or acrylate.

The blending amount of the component (b) in the BMC of the present invention is preferably 25 to 70% by mass, more preferably 30 to 65% by mass, based on 100% by mass of the total amount of the component (a) and the component (b). More preferably, it is 35 to 65% by mass. When the blending amount of the cross-linking agent is 25% by mass or more, the resin viscosity is appropriate and sufficient workability can be obtained. On the other hand, when the blending amount of the component (b) is 70% by mass or less, sufficient strength can be obtained as BMC.

[(C) Aluminum hydroxide]
Aluminum hydroxide is used as an inorganic filler. From the viewpoint of arc resistance, the content of aluminum hydroxide is preferably 300 to 590 parts by mass and 320 to 580 parts by mass with respect to 100 parts by mass of the total amount of the components (a) and (b). Is more preferable, and 350 to 550 parts by mass is particularly preferable. If it is 300 parts by mass or more, the arc resistance is good, and if it is 590 parts by mass or less, the kneading property is good, which is preferable.

The aluminum hydroxide (c) has an average particle size of at least 0.5 μm or more. The average particle size is the median diameter measured by a laser diffraction / scattering type particle size distribution measuring device (manufactured by Microtrac Bell, FRA). If it is 0.5 μm or more, the viscosity is appropriate, and a moldable resin can be obtained. From the viewpoint of moldability, the average particle size of aluminum hydroxide is more preferably 0.7 μm or more, and further preferably 1.8 μm or more. On the other hand, the average particle size is preferably 15 μm or less, more preferably 12 μm or less, still more preferably 10 μm or less, from the viewpoint of surface smoothness and mechanical properties of the molded product. If it is 15 μm or less, the surface smoothness and mechanical strength of the molded product are good, the fluidity of the material is appropriate, and the moldability is excellent.

[(D) Chopped strand glass fiber]
The chopped strand glass fiber used in the present invention is not particularly limited, and known ones used as molding materials in the art can be used. Chopped strand glass fiber can be obtained by bundling glass fiber with a converging agent and cutting it. (D) The fiber length of the chopped strand glass fiber is preferably 1 mm to 20 mm, more preferably 1.5 mm to 15 mm, and particularly preferably 1.5 mm to 13 mm. If the fiber length is 20 mm or less, the fluidity in the mold of BMC is appropriate, and if it is 1 mm or more, the viscosity is excellent in handleability, which is preferable. The fiber length is a number average value of 100 fibers randomly collected with a caliper or a micrometer of an optical microscope.

The blending amount of the component (d) in the BMC of the present invention is not particularly limited, but is preferably 10 to 200 parts by mass, more preferably 20 to 200 parts by mass with respect to a total of 100 parts by mass of the components (a) and (b). It is 180 parts by mass, particularly preferably 25 to 160 parts by mass. If the blending amount of the component (d) is 10 parts by mass or more, the mechanical strength of the cured product is good, and if the blending amount of the component (d) is 200 parts by mass or less, each component is produced when BMC is produced. Is easy to mix.

[(E) Hypo-shrinkant]
The (e) low shrinkage agent used in the present invention is not particularly limited, and those known in the art can be used. Examples of the low shrinkage agent (e) include thermoplastic polymers generally used as low shrinkage agents such as polystyrene, polymethylmethacrylate, polyvinyl acetate, saturated polyester, and styrene-butadiene rubber. These can be used alone or in combination of two or more. Further, as the (e) low shrinkage agent, polystyrene is preferably used from the viewpoint of low shrinkage.

The amount of the (e) low shrinkage agent to be blended in the BMC of the present invention is not particularly limited, but is preferably 3 to 70 parts by mass, more preferably 3 to 70 parts by mass, based on 100 parts by mass of the total of the components (a) and (b). It is 10 to 60 parts by mass, particularly preferably 15 to 50 parts by mass. When the blending amount of the low shrinkage agent is 3 parts by mass or more, the molding shrinkage of the cured product can be suppressed. When the blending amount of the low shrinkage agent is 70 parts by mass or less, the fluidity in the mold of BMC is appropriate, and defects such as unfilling and damage to insert parts can be suppressed.

[(F) Hardener]
The (f) curing agent used in the present invention is not particularly limited, and a radical polymerization initiator known in the art can be selected. As the radical polymerization initiator, an organic peroxide, an azo-based initiator, a redox initiator and the like can be used. Above all, from the viewpoint of reaction efficiency, it is preferable to use an organic peroxide. Examples of organic peroxides are t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2. -Ethylhexanate, benzoyl peroxide, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-hexylperoxycyclohexane, 1,1-di-t-butylperoxy-3,3 , 5-trimethylcyclohexane, t-butylperoxyisopropyl carbonate, t-hexylperoxyisopropylcarbonate, t-butylperoxybenzoate, t-hexylperoxybenzoate, 1,6-bis (t-butylperoxycarbonyloxy) ) Organic peroxides such as hexane, dicumyl peroxide, and di-t-butyl peroxide. These can be used alone or in combination of two or more.

The blending amount of the component (f) in the BMC of the present invention is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the total of the components (a) and (b). , Particularly preferably 2 to 6 parts by mass. When the blending amount of the component (f) is 0.1 part by mass or more, curing failure can be suppressed. When the blending amount of the component (f) is 15 parts by mass or less, the storage stability is good.

The thermosetting resin composition of the present invention contains the above-mentioned components (a) to (f) as essential components, but other components can be blended from the viewpoint of enhancing desired physical properties. The other components are not particularly limited, and components generally used in thermosetting resin compositions can be blended. For example, as other components, (g) a compound having a phosphoric acid ester group, (h) a mold release agent, (i) a polymerization inhibitor, (j) a thickener, (k) a colorant, and (l) hydroxide. Examples include inorganic fillers other than aluminum.

[(G) Compound having a phosphate ester group]
In the present invention, it is preferable to add a compound having a phosphoric acid ester group. The compound having a phosphoric acid ester group can (c) be adsorbed on the surface of aluminum hydroxide to improve the wettability of the surface of aluminum hydroxide particles and the dispersion stability of the particles, and can enhance the filling property. .. The compound having a phosphoric acid ester group is not particularly limited, and examples thereof include a copolymer of a saturated polyester having a phosphoric acid ester bond, and the trade names of BYK-W985, W995, W996, and W9010 (BYK Chemie). It is also possible to use a commercially available product sold by (manufactured by the company).

The content of the compound (g) having a phosphoric acid ester group is 0.2 to 30 parts by mass, more preferably 0.5, based on 100 parts by mass of the total amount of the components (a) and (b). It is ~ 20 parts by mass, and particularly preferably 1 to 15 parts by mass.

When the content of the component (g) is 0.5 parts by mass or more with respect to 100 parts by mass of the total amount of the components (a) and (b), the filling property of (c) aluminum hydroxide is improved (heat). (C) Increasing the content of aluminum hydroxide in the curable resin composition) is possible. On the other hand, when the content of the component (g) is 30 parts by mass or less, the arc resistance of the cured product of the present invention is sufficiently maintained.

The types of inorganic fillers other than (h) mold release agent, (i) polymerization inhibitor, (j) thickener, (k) colorant and (l) aluminum hydroxide are not particularly limited. Those known in the art can be used.

(H) Examples of the release agent include stearic acid, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, carnauba wax and the like. The amount of the release agent (h) to be blended is 0.2 to 50 parts by mass, more preferably 1 to 40 parts by mass with respect to 100 parts by mass of the total amount of the components (a) and (b). , Particularly preferably 3 to 30 parts by mass. Sufficient releasability can be obtained when the blending amount of the component (h) is 0.2 or more. If the blending amount of the component (h) is 50 parts by mass or more, the moldability may be inferior.

The (i) polymerization inhibitor used in the present invention is not particularly limited, and those known in the art can be used. For example, quinones such as parabenzoquinone, toluquinone, naphthoquinone, phenanthraquinone, and 2,5 diphenylparabenzoquinone; toluhydroquinone, hydroquinone, tarshalibutylcatechol, monotershalibutylhydroquinone, and 2,5 ditershalibutylhydroquinone. Hydroquinones such as; and hydroquinone monomethyl ethers, and monophenols such as 2,6-di-t-butyl-p-cresol. These can be used alone or in combination of two or more. Among these, it is preferable to use quinones from the viewpoint of suppressing gelation.

(I) The amount of the polymerization inhibitor blended is preferably 0.005 to 0.2 parts by mass, more preferably 0.01 to 0, based on 100 parts by mass of the total of the components (a) and (b). .1 part by mass. When the blending amount of the component (i) is 0.005 part by mass or more with respect to the total of 100 parts by mass of the component (a) and the component (b), a BMC having desired in-mold fluidity can be obtained. On the other hand, when the blending amount of the component (i) is 0.2 parts by mass or less, the curing time and the curing after a certain period of time are sufficient.

Examples of the thickener (j) include metal oxides such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium oxide, and isocyanate compounds. These components may be used alone or in combination of two or more.

(K) The colorant is used when it is necessary to color the molded product, and various inorganic pigments and organic pigments usually used in bulk molding compounds can be used. The amount of the colorant used may be appropriately adjusted according to the degree of coloring of the molded product.

(L) As the inorganic filler other than aluminum hydroxide, powdered materials such as alumina, wallastonite, clay, talc, mica, and silicic anhydride can be used as needed. Above all, calcium carbonate is preferable from the viewpoint of surface smoothness and heat resistance of the resin composition.
(L) The blending amount of the inorganic filler other than aluminum hydroxide is preferably 1 to 500 parts by mass, preferably 1 to 300 parts by mass with respect to 100 parts by mass of the total amount of the components (a) and (b). Is more preferable, and 1 to 200 parts by mass is particularly preferable. When the blending amount is 500 parts by mass or less, the kneading property is good.

The blending amounts of the optional component (h), component (i), component (j) and component (k) are not particularly limited as long as they do not impair the effects of the present invention.

The BMC of the present invention can be produced by blending and kneading a predetermined amount of each component as described above by a known method. For example, BMC can be obtained by adding a predetermined amount of each component to a kneader or the like and mixing them.

Since the BMC of the present invention thus obtained can improve curability without impairing storage stability, it is possible to improve workability and productivity when producing a cured product having a desired shape. It becomes.

Since the BMC of the present invention provides a cured product having high arc resistance and mechanical strength, it can be used as a highly reliable material for electrical and electronic parts. When BMC is used for electrical and electronic components, the arc resistance according to JIS-K6911 (1995) is preferably 185 seconds or longer, more preferably 188 seconds or longer, and particularly preferably 190 seconds or longer. Further, as the mechanical strength when BMC is used for electrical and electronic parts, the tensile strength according to JIS-K7113 (1995) is preferably 30 MPa or more, more preferably 35 MPa or more, and particularly preferably 37 MPa or more.

The molding method of the electric / electronic part is not particularly limited, and the electric / electronic part is formed by molding the BMC of the present invention by a molding means such as compression molding, transfer molding, or injection molding and then curing it. can get. Specifically, the BMC of the present invention may be placed in a mold by various means and then cured by heating and pressurizing to a predetermined temperature.
The curing conditions may be appropriately set according to the raw material used for the BMC of the present invention, but generally, the curing temperature is 120 to 160 ° C. and the curing time is 1 minute to 30 minutes.

Since the BMC of the present invention gives a cured product having high arc resistance, it is most suitable for use as a material for electrical and electronic parts that require a high degree of arc resistance. That is, the electric / electronic component formed by molding the BMC of the present invention is excellent in arc resistance, and can be manufactured with good workability and productivity.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Examples 1 to 6, Comparative Examples 1 to 6)
(Synthesis of unsaturated polyester resin)
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen gas introduction tube and a thermometer, 100 mol of propylene glycol, 30 mol of phthalic anhydride and 70 mol of maleic anhydride were charged, and the acid value was 20 mgKOH / at 210 ° C. according to a conventional method. It was reacted until it reached g. Next, 0.015 parts by mass of hydroquinone was added to 100 parts by mass of the reaction product and cooled to 160 ° C., and then a styrene monomer was further added to obtain an unsaturated polyester resin. Here, the styrene monomer was added so as to be 30 parts by mass in the unsaturated polyester resin. The weight average molecular weight (MW) of the unsaturated polyester was measured under the above conditions and found to be 15,000.

The unsaturated polyester resin obtained above and each component shown in Table 1 were kneaded at a ratio shown in Tables 2 and 3 at 25 ° C. for 30 minutes using a twin bowl type kneader to obtain BMC. In Tables 2 and 3, the styrene monomer is the total amount of the amount added at the time of producing the unsaturated polyester resin and the amount added at the time of kneading. (A) Unsaturated polyester does not contain styrene monomer.
In the blending of Comparative Example 1 and Comparative Example 2, the composition did not come together at the time of kneading, and a uniform kneaded product could not be obtained. In Tables 2 and 3, the unit of the blending amount of each component is a mass part.

Next, the moldability, arc resistance, and tensile strength of the obtained BMC and its cured product were evaluated as follows. The results are shown in Tables 2 and 3.

(Evaluation of moldability)
The obtained BMCs of Examples 1 to 6 and Comparative Examples 3 to 6 were molded into a flat plate of 100 mm × 100 mm × thickness 3 mm by injection molding at a molding temperature of 150 ° C., a molding pressure of 100 MPa, and a molding time of 3 minutes. The presence or absence of molding defects was visually confirmed by appearance. The case where a crack was formed was confirmed as a defect.

(Evaluation of arc resistance)
The obtained BMCs of Examples 1 to 6 and Comparative Examples 3 to 6 were molded into a flat plate of 100 mm × 100 mm × thickness 3 mm by injection molding at a molding temperature of 150 ° C., a molding pressure of 100 MPa, and a molding time of 3 minutes. It was cut into a circle with a diameter of 100 mm and subjected to an arc resistance test of JIS-K6911 (1995) standard.

(Evaluation of tensile strength)
A dumbbell type test piece of JIS-K7113 (1995) was prepared by injection molding the obtained BMCs of Examples 1 to 6 and Comparative Examples 3 to 6 at a molding temperature of 150 ° C., a molding pressure of 100 MPa, and a molding time of 3 minutes. -K7113 (1995) standard tensile strength test was performed.

As shown in Tables 2 and 3, the BMCs of Examples 1 to 6 had good moldability, and a molded product in which the shape of the mold was transferred could be easily obtained. Further, the BMCs of Examples 1 to 6 had an arc resistance of 190 seconds or more, and were excellent in arc resistance. Further, the BMCs of Examples 1 to 6 had a tensile strength of 38 MPa or more, and had a strength suitable for use in electrical and electronic parts. On the other hand, since the compositions of Comparative Example 1 and Comparative Example 2 contained too much powder or chopped strand glass fiber, the materials were not organized at the time of kneading, and BMC having a uniform composition could not be obtained. The BMCs of Comparative Examples 3 to 5 had an arc resistance of 175 seconds or less, and were inferior in arc resistance. The BMC of Comparative Example 6 had a tensile strength of 25 MPa and was inferior in strength.

As can be seen from the above results, according to the present invention, a BMC having good and general-purpose moldability can be produced with good workability and productivity, and a cured product having excellent arc resistance can be obtained. By using the cured product, it is possible to provide an electric / electronic component having excellent arc resistance.

Claims (6)

(A) unsaturated polyester, (b) monomer having one or more polymerizable carbon-carbon double bonds, (c) aluminum hydroxide, (d) chopped strand glass fiber, (e) low shrinkage agent, (f) A thermosetting resin composition containing a curing agent and (g) a compound having a phosphoric acid ester group , wherein the (a) unsaturated polyester has a mass average molecular weight of 2,000 to 50,000. The content of (c) aluminum hydroxide is 300 to 590 parts by mass with respect to 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer, and the content of the (d) chopped strand glass fiber. Is a bulk molding compound (BMC), which is 10 to 200 parts by mass with respect to 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer. The claim that the content of the compound having the (g) phosphoric acid ester group is 0.2 to 30 parts by mass with respect to 100 parts by mass of the total amount of the (a) unsaturated polyester and the (b) monomer. BMC according to 1. The BMC according to claim 1 or 2, wherein the average particle size of (c) aluminum hydroxide is 15 μm or less. (D) The BMC according to any one of claims 1 to 3 , wherein the chopped strand glass fiber has a fiber length of 1 mm to 20 mm. The invention according to any one of claims 1 to 4 , wherein the content of the (b) monomer is 25 to 70% by mass with respect to 100% by mass of the total of the (a) unsaturated polyester and the (b) monomer. BMC. A cured product obtained by curing the BMC according to any one of claims 1 to 5.