Unsaturated polyester resin composition and molded body

Abstract

Provided is an unsaturated polyester resin composition for a molded product, which has good resin flowability at the time of molding, and which can achieve a molded product appearance, dimensional accuracy, and strength properties that are excellent, with reduced flash. In the unsaturated polyester resin composition, the content of an inorganic filler material is within a specific range, and as the inorganic filler material, a substance having three average particle diameters is used at a specific ratio.

Description

Technical Field

[0001] This invention relates to unsaturated polyester resin compositions and molded articles. Background Technology

[0002] Unsaturated polyester resin compositions, which incorporate fiber reinforcement materials and inorganic fillers, are widely used in the manufacture of OA equipment, office equipment racks, and automotive headlight reflectors due to their good resin flow during molding and the resulting cured products with excellent dimensional accuracy, heat resistance, and mechanical strength.

[0003] For example, Patent Document 1 and Patent Document 2 disclose unsaturated polyester resin compositions containing inorganic fillers, fiber reinforcing materials, hollow fillers, etc.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2005 / 103152

[0007] Patent Document 2: International Publication No. 2016 / 035516 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] During the manufacturing of the molded body, the unsaturated polyester resin composition flows into the gaps in the mold and solidifies, resulting in flash. Since flash needs to be removed through a removal process, a large amount of flash can increase manufacturing costs.

[0010] The present invention is proposed to solve the problems mentioned above, and its purpose is to provide an unsaturated polyester resin composition that provides good resin flow during molding, and can obtain molded articles with excellent appearance, dimensional accuracy and strength properties, and reduces flash.

[0011] Methods for solving problems

[0012] The inventors conducted in-depth research and found that if the content of inorganic filler material in the unsaturated polyester resin composition is within a specific range, and if a substance with three average particle sizes is used as the inorganic filler material in a specific ratio, good resin flowability during molding can be achieved, and the molded article can obtain an unsaturated polyester resin composition with excellent appearance, dimensional accuracy, and strength properties, and reduced flash. Thus, the present invention was completed.

[0013] That is, the present invention includes the following solutions.

[0014] [Option 1]

[0015] An unsaturated polyester resin composition comprising (a) an unsaturated polyester resin, (b) an inorganic filler, (c) a metallic soap, (d) a low-shrinkage agent, (e) a fiber reinforcement material, and (f) a curing agent.

[0016] The content of the inorganic filler material in (b) above is 250 to 600 parts by weight relative to 100 parts by weight of the unsaturated polyester resin in (a) above.

[0017] The inorganic filler material described above (b) comprises (b1), (b2), and (b3) in a ratio of (b1):(b2):(b3) = 60–75:7–15:15–30, relative to 100% by mass of the total inorganic filler material (b1) with an average particle size of 0.5–5.0 μm, inorganic filler material (b2) with an average particle size of 6.0–50.0 μm, and inorganic filler material (b3) with an average particle size of 70.0 μm or more.

[0018] [Option 2]

[0019] According to the unsaturated polyester resin composition of Scheme 1, the content of the inorganic filler material in (b) is 350 to 450 parts by mass relative to 100 parts by mass of the unsaturated polyester resin in (a).

[0020] [Option 3]

[0021] According to the unsaturated polyester resin composition of Scheme 1 or 2, the inorganic filler material of (b) above comprises calcium carbonate.

[0022] [Option 4]

[0023] According to the unsaturated polyester resin composition of any one of Schemes 1 to 3, the content of the fiber reinforcing material (e) is 70 to 120 parts by mass relative to 100 parts by mass of the unsaturated polyester resin (a).

[0024] [Option 5]

[0025] A molded article comprising a cured product of the unsaturated polyester resin composition described in any one of embodiments 1 to 4.

[0026] The effects of the invention

[0027] According to the present invention, an unsaturated polyester resin composition can be provided that provides good resin flowability during molding and yields molded articles with excellent appearance, dimensional accuracy, and strength properties, while reducing flash. Furthermore, by curing the above-mentioned unsaturated polyester resin composition, a molded article with excellent appearance, dimensional accuracy, and strength properties, and reduced flash, can be provided. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail. However, the present invention is not limited to the embodiments shown below.

[0029] In this disclosure, the term "olefinic unsaturated bond" refers to a double bond formed between carbon atoms other than the carbon atoms that form the aromatic ring.

[0030] <Unsaturated polyester resin composition>

[0031] One embodiment of the present invention is an unsaturated polyester resin composition comprising (a) an unsaturated polyester resin, (b) an inorganic filler, (c) a metal soap, (d) a low-shrinkage agent, (e) a fiber reinforcement material, and (f) a curing agent. The components are described below.

[0032] [(a) Unsaturated polyester resin]

[0033] In this disclosure, (a) an unsaturated polyester resin refers to a composition obtained by dissolving a condensation product (unsaturated polyester) obtained by esterification of a polyol, an unsaturated polyacid, and an optional saturated polyacid in a crosslinking agent (also called a "reactive diluent"). An unsaturated polyacid is a polyacid having polymerizable olefinic unsaturated bonds, while a saturated polyacid is a polyacid not having polymerizable olefinic unsaturated bonds.

[0034] Such unsaturated polyester resins are generally known in the technical field of this invention, for example, as described in "Polyester Resin Handbook" (Nikkan Kogyo Shimbun, published in 1988) and "Coating Terminology Dictionary" (edited by the Color Materials Association, published in 1993), etc.

[0035] The polyols used as raw materials for unsaturated polyesters are not particularly limited, and substances known in the technical field of this invention can be used. Examples of polyols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, pentylene glycol, hexanediol, neopentylene glycol, hydrogenated bisphenol A, bisphenol A, and glycerol. Multiple polyols can be used alone or in combination.

[0036] Among them, from the viewpoint of excellent heat resistance, mechanical strength and resin flowability during molding, at least one of propylene glycol, neopentyl glycol, bisphenol A and hydrogenated bisphenol A is preferred.

[0037] The unsaturated polyacids used as raw materials for unsaturated polyesters are not particularly limited, and substances known in the technical field of this invention can be used. Examples of unsaturated polyacids include maleic anhydride, fumaric acid, citraconic acid, itaconic acid, and chlorobridged acid. Multiple unsaturated polyacids can be used alone or in combination.

[0038] Among them, maleic anhydride or fumaric acid are preferred from the viewpoint of superior heat resistance, mechanical strength, and resin flowability during molding.

[0039] There are no particular limitations on the saturated polyacids that can be used as optional raw materials for unsaturated polyesters; any known substances can be used. Examples of saturated polyacids include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, and tetrabromophthalic anhydride. Multiple saturated polyacids can be used alone or in combination.

[0040] Unsaturated polyesters can be synthesized using the aforementioned raw materials through known methods. The various conditions in the synthesis of unsaturated polyesters can be appropriately set according to the raw materials used and their quantities. Generally, an example is esterification under pressure or reduced pressure at a temperature of 140–230°C in an inert gas stream such as nitrogen. An esterification catalyst can be used as needed for the esterification reaction. Examples of known esterification catalysts include manganese acetate, dibutyltin oxide, stannous oxalate, zinc acetate, and cobalt acetate. Esterification catalysts can be used alone or in combination.

[0041] The weight-average molecular weight (MW) of the unsaturated polyester is not particularly limited. Preferably, it is 3,000 to 25,000; more preferably, 5,000 to 20,000; and even more preferably, 7,000 to 18,000. It should be noted that, in this disclosure, "weight-average molecular weight" refers to the value obtained by measuring using gel permeation chromatography (Shodex GPC-101, Showa Denko Corporation) at room temperature (23°C) under the following conditions, using a standard polystyrene standard curve.

[0042] Column: LF-804 (Showa Denko Co., Ltd.)

[0043] Column temperature: 40℃

[0044] Sample: 0.2% by mass tetrahydrofuran solution of unsaturated polyester

[0045] Flow rate: 1 mL / min

[0046] Eluent: Tetrahydrofuran

[0047] Detector: RI-71S

[0048] As a crosslinking agent (reactive diluent) for dissolving unsaturated polyesters, there are no particular limitations as long as the substance has an olefinic unsaturated bond capable of polymerizing with the unsaturated polyester; substances known in the technical field of this invention can be used. Examples of crosslinking agents include styrene monomer, diallyl phthalate monomer, diallyl phthalate prepolymer, methyl methacrylate, and triallyl isocyanurate. These can be used alone or in combination.

[0049] (a) The content of the crosslinking agent (reactive diluent) in the unsaturated polyester resin is not particularly limited. (a) From the viewpoint of workability, polymerizability, shrinkage of the molded article, and freedom of quantity adjustment, the content of the crosslinking agent (reactive diluent) in the unsaturated polyester resin is preferably 25 to 70% by mass, more preferably 30 to 68% by mass, and even more preferably 35 to 65% by mass, relative to the total of the unsaturated polyester and the crosslinking agent.

[0050] (a) Unsaturated polyester resins may contain polymerization inhibitors such as hydroquinone as required.

[0051] [(b) Inorganic filler materials]

[0052] One embodiment of the unsaturated polyester resin composition uses an inorganic filler material with an inorganic filler material content within a specific range, and uses a substance having three average particle sizes in a specific ratio as the inorganic filler material.

[0053] The type of inorganic filler material (b) is not particularly limited, and any substance known in the technical field of this invention may be used. Examples of inorganic filler materials (b) include calcium carbonate, silica, alumina, aluminum hydroxide, barium sulfate, wollastonite, clay, talc, mica, gypsum, anhydrous ketoacid, and glass powder. These can be used individually or in combination. From the viewpoint of surface smoothness of the resulting molded article, cost reduction, and ease of acquisition, it is preferable to use at least calcium carbonate.

[0054] The shape of (b) inorganic filler material is not particularly limited, and examples include approximately spheres, ellipsoids, scaly shapes, and amorphous shapes.

[0055] (b) The true specific gravity of the inorganic filler material is not particularly limited, but is preferably 1 to 10 g / cm³. 3 More preferably, it is 1.5–8 g / cm³. 3 Further preferably 2-5 g / cm³ 3 .

[0056] If the true specific gravity of the inorganic filler material is 1 g / cm³ 3 The resulting molded body exhibits better mechanical properties if the true specific gravity of the inorganic filler material is 10 g / cm³.3 The following results in better composability of the unsaturated polyester resin composition.

[0057] (b) The amount of inorganic filler material mixed relative to 100 parts by weight of (a) unsaturated polyester resin is 250 to 600 parts by weight, more preferably 300 to 550 parts by weight, and even more preferably 350 to 450 parts by weight.

[0058] If the amount of inorganic filler in (b) is 250 parts by mass or more, the mechanical properties of the resulting molded article become better. Furthermore, if the amount of inorganic filler in (b) is 600 parts by mass or less, the inorganic filler in (b) is more uniformly dispersed in the unsaturated polyester resin composition, thus allowing the manufacture of a homogeneous molded article.

[0059] (b) An inorganic filler material in combination with at least three of the following: (b1) an inorganic filler material with an average particle size of 0.5 to 5.0 μm (hereinafter also referred to as "(b1) inorganic filler material"); (b2) an inorganic filler material with an average particle size of 6.0 to 50.0 μm (hereinafter also referred to as "(b2) inorganic filler material"); and (b3) an inorganic filler material with an average particle size of 70.0 μm or more (hereinafter also referred to as "(b3) inorganic filler material").

[0060] By using at least three inorganic filler materials with different average particle sizes (b1) to (b3), the unsaturated polyester resin composition can be made to have good flowability during molding, resulting in excellent appearance, dimensional accuracy, and strength properties of the molded body, and reducing flash of the molded body.

[0061] In this disclosure, the so-called "average particle size" of the inorganic filler material (b) refers to the particle size calculated from the specific surface area obtained by the air permeation method according to the following formula.

[0062] Average particle size [μm] = (6 × 10000) / (true specific gravity [g / cm³]) 3 ] × Specific surface area [cm 2 / g])

[0063] (b1) The average particle size of the inorganic filler material is preferably 0.7 μm or more, more preferably 1.0 μm or more. (b1) The average particle size of the inorganic filler material is preferably 4.0 μm or less, more preferably 3.0 μm or less. By using the (b1) inorganic filler material, a molded article with excellent appearance and strength properties can be obtained.

[0064] (b2) The average particle size of the inorganic filler material is preferably 6.5 μm or more, more preferably 7.0 μm or more. (b2) The average particle size of the inorganic filler material is preferably 40.0 μm or less, more preferably 30.0 μm or less. By using the inorganic filler material (b2), a molded article with excellent appearance, strength properties, and reduced flash can be obtained.

[0065] (b3) The average particle size of the inorganic filler material is preferably 100 μm or more, more preferably 200 μm or more. (b3) The average particle size of the inorganic filler material is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 360 μm or less. By using the inorganic filler material (b3), a molded article with reduced flash can be obtained.

[0066] The inorganic filler materials (b1) to (b3) are contained in a ratio of 60–75:7–15:15–30, relative to a total of 100% by mass of the inorganic filler materials (b1), (b2), and (b3). From the perspective of further reducing flash in the resulting molded article and providing excellent surface smoothness and mechanical strength, a ratio of 60–70:10–15:20–25 is preferred.

[0067] By making the mass ratio of inorganic filler materials (b1) to (b3) within the above range, the resulting molded article can have both excellent appearance and strength properties and reduced flash. If the mass ratio is outside the above range, any of the properties of the molded article, such as appearance, strength properties and reduction of flash, will be compromised.

[0068] [(c) Metallic soap]

[0069] (c) Metallic soap is a component generally used as a release agent in the technical field of this invention. There is no particular limitation on (c) metallic soap; any substance known in the technical field of this invention may be used. Examples of (c) metallic soap include calcium stearate, zinc stearate, aluminum stearate, and magnesium stearate. Various (c) metallic soaps may be used alone or in combination.

[0070] (c) The amount of metal soap mixed is not particularly limited, but is preferably 1 to 15 parts by weight relative to 100 parts by weight of (a) unsaturated polyester resin, more preferably 2 to 10 parts by weight.

[0071] If the amount of (c) metal soap is 1 part by mass or more, the molded article has better release properties. On the other hand, if the amount of (c) metal soap is 15 parts by mass or less, it can prevent (c) metal soap from seeping onto the surface of the molded article, thus obtaining a molded article with satisfactory atomization and coatability of the primer.

[0072] (d) Low shrinkage agent

[0073] As for (d) the low-shrinkage agent, there is no particular limitation, and any substance known in the technical field of this invention may be used. Examples of low-shrinkage agents include thermoplastic polymers commonly used as low-shrinkage agents, such as polystyrene, polymethyl methacrylate, polyvinyl acetate, saturated polyester, and styrene-butadiene rubber. (d) Low-shrinkage agents may be used alone or in combination of two or more.

[0074] (d) The content of the low-shrinkage agent is preferably 10 to 40 parts by mass relative to 100 parts by mass of the unsaturated polyester resin in (a), more preferably 20 to 35 parts by mass. If the amount of the low-shrinkage agent in (d) is 10 parts by mass or more, the shrinkage rate of the molded article is reduced, and the desired dimensional accuracy can be obtained. On the other hand, if the amount of the low-shrinkage agent in (d) is 40 parts by mass or less, the mechanical properties of the molded article become better.

[0075] [(e) Fiber-reinforced materials]

[0076] (e) The fiber-reinforced material is a material with an aspect ratio of 3 or greater. The aspect ratio can be determined by microscopy as described in Japanese Industrial Standard JIS Z8900-1:2008 "Particles for testing particle size measuring devices (particles for testing particle size measuring devices)".

[0077] As for the fiber reinforcement material (e), there is no particular limitation, and any material known in the technical field of this invention can be used. Examples of fiber reinforcement materials (e) include various organic and inorganic fibers such as glass fiber, pulp, polyethylene terephthalate fiber, vinylon fiber, carbon fiber, aramid fiber, and wollastonite. Among these, glass fiber is preferred, and chopped glass fibers cut into short filaments with a fiber length of about 1.5 to 25 mm are more preferred.

[0078] (e) The content of the fiber reinforcing material is preferably 70 to 120 parts by weight, more preferably 75 to 100 parts by weight, relative to 100 parts by weight of the unsaturated polyester resin in (a). If the amount of (e) fiber reinforcing material is 70 parts by weight or more, the mechanical properties of the molded article become better. On the other hand, if the amount of (e) fiber reinforcing material is 120 parts by weight or less, the (e) fiber reinforcing material is more uniformly dispersed in the unsaturated polyester resin composition, and a homogeneous molded article can be produced.

[0079] [(f) Curing agent]

[0080] As the curing agent (f), there is no particular limitation as long as it is a free radical polymerization initiator capable of polymerizing olefinic unsaturated bonds, and any substance known in the technical field of this invention can be used. Examples of curing agents (f) include tert-butyl peroxyoctanoate, benzoyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, dicumyl peroxide, di-tert-butyl peroxide, and other organic peroxides. Two or more curing agents (f) can be used alone or in combination.

[0081] (f) The content of the curing agent can be set appropriately according to the raw materials used, and there is no particular limitation. (f) The content of the curing agent relative to 100 parts by weight of (a) unsaturated polyester resin is preferably 1 to 10 parts by weight, more preferably 1 to 8 parts by weight, and even more preferably 1 to 5 parts by weight.

[0082] [Other ingredients]

[0083] In addition to the above-mentioned components, the unsaturated polyester resin composition of the present invention may also include thickeners, pigments, anti-tack agents, and other components known in the technical field of the present invention, within a range that does not impair the effects of the present invention.

[0084] There are no particular limitations on thickeners, and examples include, for instance, metal oxides other than (b) inorganic fillers, such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium oxide, as well as isocyanate compounds. Thickeners can be used alone or in combination of two or more.

[0085] [Method for manufacturing unsaturated polyester resin composition]

[0086] Unsaturated polyester resin compositions can be manufactured by methods typically performed in the technical field of this invention, such as mixing the components using a kneader or the like.

[0087] [Method for manufacturing molded articles of unsaturated polyester resin compositions]

[0088] Molded articles can be manufactured by molding an unsaturated polyester resin composition into a desired shape and then curing it. There are no particular limitations on the molding and curing methods; methods commonly practiced in the field of this invention can be cited, such as compression molding, transfer molding, and injection molding.

[0089] Example

[0090] The present invention will now be described in detail with reference to examples and comparative examples, but the present invention is not limited thereto.

[0091] <(a) Preparation of unsaturated polyester resin>

[0092] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux cooler, 0.93 kg (9.5 mol) of maleic anhydride, 0.07 kg (0.5 mol) of phthalic anhydride, and 0.76 kg (10 mol) of propylene glycol were added. Then, an esterification reaction was carried out by heating and stirring under a nitrogen atmosphere until the temperature reached 200°C, thereby obtaining an unsaturated polyester. The resulting unsaturated polyester had an unsaturation degree of 95 mol%, a weight-average molecular weight of 8,000. Next, styrene monomer was added to the obtained unsaturated polyester in a manner that made the total amount of the unsaturated polyester and styrene monomer 30% by mass, to obtain (a) an unsaturated polyester resin.

[0093] <Examples 1-2, Comparative Examples 1-7>

[0094] The unsaturated polyester resin composition was obtained by adding the materials constituting the unsaturated polyester resin composition to the mixture shown in Table 1 and kneading it at 25°C for 30 minutes using a double-wrist kneader. It should be noted that the unsaturated polyester resin shown in Table 1(a) is the substance obtained by the above method, containing 30% by mass of styrene monomer.

[0095] <Materials>

[0096] The materials used in the embodiments and comparative examples are described below.

[0097] (b) Inorganic filler materials

[0098] (b1) Calcium carbonate (S-1200BM, Bikita Powdered Chemical Industry Co., Ltd., average particle size: 1.8μm, true specific gravity: 2.7g / cm³) 3 )

[0099] (b2) Calcium carbonate (Tancal R Heavy Carbonate, Maruo Calsim Co., Ltd., average particle size: 7.4μm, true specific gravity: 2.7g / cm³) 3 )

[0100] (b3) Calcium carbonate (KD-70, Calfin Co., Ltd., average particle size: 300μm, true specific gravity: 2.7g / cm³) 3 )

[0101] (c) Metallic soaps

[0102] Calcium stearate (Dannan Chemical Industry Co., Ltd.)

[0103] (d) Low shrinkage agent

[0104] Polystyrene (weight average molecular weight 200,000, Sekisui Chemicals Co., Ltd.)

[0105] (e) Fiber-reinforced materials

[0106] Chopped strand glass (fiber length: 9mm, Nippon Electric Glass Co., Ltd.)

[0107] (f) Curing agent

[0108] tert-butyl peroxide benzoate (Nippon Yu Co., Ltd.)

[0109] <Evaluation>

[0110] Regarding the unsaturated polyester resin compositions of the obtained examples and comparative examples, the compounding properties, in-mold flowability of the resin composition, surface smoothness of the molded article, molding shrinkage, strength properties (flexural strength and flexural modulus), and flowability using thin-walled flow molds as a confirmation of low flash were measured or evaluated. The measurement and evaluation methods are described below. The results are shown in Table 1.

[0111] (1) Mixing properties

[0112] During the preparation of the unsaturated polyester resin composition (using a double-wrist kneader at 25°C for 30 minutes), the uniformity of the unsaturated polyester resin composition without poor dispersion was visually evaluated. The evaluation criteria are shown below.

[0113] Good: The unsaturated polyester resin composition is uniform.

[0114] Defect: The unsaturated polyester resin composition exhibits poor dispersion.

[0115] (2) In-mold flowability of the resin composition

[0116] A spiral flow mold (cross-sectional shape: trapezoidal with a top edge of 6mm, a bottom edge of 8mm, and a height of 2mm) was installed on a transfer molding machine (Teknomarschich Co., Ltd.). A spiral flow test was conducted at a mold temperature of 150°C and an injection pressure of 10MPa, and the flow length (cm) was measured. The measurement results and evaluation results are shown in Table 1. If the flow length is 30cm or more, the resin composition exhibits good in-mold flowability.

[0117] (3) Surface smoothness of molded products

[0118] Using a transfer molding machine (Technomarschia Co., Ltd.), a transfer-molded body (φ117mm, thickness 3mm) was produced under the conditions of molding temperature 150°C, injection pressure 20MPa, and molding time 1 minute. The appearance of the obtained transfer-molded body was visually confirmed, and it was evaluated according to the following evaluation criteria.

[0119] Good: Overall glossy and free of shrinkage marks.

[0120] Defective: Lack of luster, either entirely or partially, or presence of shrinkage marks, either entirely or partially.

[0121] (4) Molding Shrinkage

[0122] Using a compression molding machine (compression molding machine, Techno-Marushichi Co., Ltd.), shrinkage disks (φ90mm×11mm) specified in JIS K-6911 5.7 were produced by compression molding under the conditions of a molding temperature of 160°C, a molding pressure of 10MPa, and a molding time of 3 minutes. The molding shrinkage (%) was calculated in accordance with JIS K-6911 5.7. The results are shown in Table 1.

[0123] (5) Strength Physical Properties (Flexural Strength and Flexural Modulus)

[0124] Using a compression molding machine (compression molding machine, Techno-Marushichi Co., Ltd.), test pieces for flexural modulus (90mm×10mm×4mm) specified in JIS K-6911 5.17 were produced by compression molding under the conditions of a molding temperature of 150°C, a molding pressure of 10MPa, and a molding time of 3 minutes. The flexural strength (MPa) and flexural modulus (MPa) were measured in accordance with JIS K-6911 5.17, and evaluated based on the following evaluation criteria. The measurement results and the evaluation results of strength physical properties are shown in Table 1.

[0125] Good: Flexural strength is 130MPa or more, and flexural modulus is 13GPa or more; Poor: Flexural strength is less than 130MPa, or flexural modulus is less than 13GPa

[0126] (6) Thin-Wall Fluidity (Flash Evaluation)

[0127] As an evaluation of flash property, a transfer molding machine (Techno-Marushichi Co., Ltd.) was used to produce a transfer molded body under the conditions of a molding temperature of 150°C, an injection pressure of 20MPa, and a molding time of 1 minute. The length (mm) of flash generated on the obtained transfer molded body was measured, and evaluated based on the following evaluation criteria. The measurement results and the flash evaluation results are shown in Table 1.

[0128] Good: No flash of 20mm or more is generated in the 140μm gap of the mold.

[0129] Poor: Flash of 20mm or more is generated in the 140μm gap of the mold.

[0130] [Table 1]

[0131]

[0132] Industrial Applicability

[0133] According to the present invention, an unsaturated polyester resin composition can be provided that provides good resin flowability during molding and can obtain molded articles with excellent appearance, dimensional accuracy and strength properties, and reduces flash.

Claims

1. An unsaturated polyester resin composition comprising (a) an unsaturated polyester resin, (b) an inorganic filler, (c) a metallic soap, (d) a low-shrinkage agent, (e) a fiber reinforcement material, and (f) a curing agent. The content of the inorganic filler material in (b) is 250 to 600 parts by weight relative to 100 parts by weight of the unsaturated polyester resin in (a). The inorganic filler material (b) comprises (b1), (b2), and (b3) in a ratio of (b1):(b2):(b3) = 60–75:7–15:15–30, representing 100% by mass of the total inorganic filler material (b1) with an average particle size of 0.5–5.0 μm, inorganic filler material (b2) with an average particle size of 6.0–50.0 μm, and inorganic filler material (b3) with an average particle size of 100 μm or more. The content of the fiber-reinforcing material in (e) is 70 to 120 parts by mass relative to 100 parts by mass of the unsaturated polyester resin in (a).

2. The unsaturated polyester resin composition according to claim 1, wherein the content of the inorganic filler material in (b) is 350 to 450 parts by weight relative to 100 parts by weight of the unsaturated polyester resin in (a).

3. The unsaturated polyester resin composition according to claim 1 or 2, wherein the inorganic filler (b) comprises calcium carbonate.

4. A molded article comprising a cured product of the unsaturated polyester resin composition according to any one of claims 1 to 3.

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