JP7740265B2 - Unsaturated polyester resin composition and molded article - Google Patents

Description

The present invention relates to an unsaturated polyester resin composition and a molded article.

Unsaturated polyester resin compositions, which are made by blending unsaturated polyester resin with fiber reinforcing materials or inorganic fillers, have good resin fluidity during molding and produce cured products with excellent dimensional accuracy, heat resistance, and mechanical strength. Therefore, they are widely used in the manufacture of office equipment, business machine chassis, and lamp reflectors for automobile headlamps.

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

WO 2005/103152 International Publication No. 2016/035516

When manufacturing molded products, the unsaturated polyester resin composition flows into the gaps in the mold clearances and hardens, causing burrs to form on the molded product. Because the burrs must be removed in a removal process, the generation of large amounts of burrs poses a problem of increased manufacturing costs.

The present invention has been made to solve the above-mentioned problems, and aims to provide an unsaturated polyester resin composition that has good resin fluidity during molding, and can produce molded products with excellent molded product appearance, dimensional accuracy, and strength, and reduced burrs.

After extensive research, the inventors discovered that by setting the content of inorganic filler in an unsaturated polyester resin composition within a specific range and using inorganic fillers with three different average particle sizes in a specific ratio, it is possible to achieve an unsaturated polyester resin composition that has good resin fluidity during molding, and that can produce molded products with excellent molded product appearance, dimensional accuracy, and strength, and reduced burrs, thereby completing the present invention.

That is, the present invention includes the following aspects.
[Aspect 1]
An unsaturated polyester resin composition comprising (a) an unsaturated polyester resin, (b) an inorganic filler, (c) a metal soap, (d) a low-profile agent, (e) a fiber reinforcement material, and (f) a curing agent,
the content of the (b) inorganic filler is 250 to 600 parts by mass relative to 100 parts by mass of the (a) unsaturated polyester resin,
The (b) inorganic filler contains (b1) an inorganic filler having an average particle size of 0.5 to 5.0 μm, (b2) an inorganic filler having an average particle size of 6.0 to 50.0 μm, and (b3) an inorganic filler having an average particle size of 70.0 μm or more, in a ratio of (b1):(b2):(b3)=60-75:7-15:15-30 relative to 100% by mass of the total of the inorganic fillers (b1), (b2), and (b3),
Unsaturated polyester resin composition.
[Aspect 2]
The unsaturated polyester resin composition according to aspect 1, wherein the content of the (b) inorganic filler is 350 to 450 parts by mass per 100 parts by mass of the (a) unsaturated polyester resin.
[Aspect 3]
3. The unsaturated polyester resin composition according to claim 1, wherein the inorganic filler (b) comprises calcium carbonate.
[Aspect 4]
Aspect 4. The unsaturated polyester resin composition according to any one of Aspects 1 to 3, wherein the content of the (e) fiber reinforcing material is 70 to 120 parts by mass per 100 parts by mass of the (a) unsaturated polyester resin.
[Aspect 5]
A molded article comprising a cured product of the unsaturated polyester resin composition according to any one of Aspects 1 to 4.

The present invention provides an unsaturated polyester resin composition that exhibits good resin fluidity during molding, and can produce molded articles with excellent molded article appearance, dimensional accuracy, and strength, and reduced burrs. Furthermore, by curing the unsaturated polyester resin composition, it is possible to provide molded articles with excellent molded article appearance, dimensional accuracy, and strength, and reduced burrs.

The following describes in detail an embodiment of the present invention. However, the present invention is not limited to the embodiment described below.

In this disclosure, "ethylenically unsaturated bond" means a double bond formed between carbon atoms other than those forming an aromatic ring.

<Unsaturated polyester resin composition>
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 shrinkage reducing agent, (e) a fiber reinforcement material, and (f) a curing agent. Each component will be described below.

[(a) Unsaturated polyester resin]
In this disclosure, (a) unsaturated polyester resin refers to a composition obtained by dissolving a condensation product (unsaturated polyester) obtained by esterifying a polyhydric alcohol with an unsaturated polybasic acid and, optionally, a saturated polybasic acid, in a crosslinking agent (also referred to as a "reactive diluent"). The unsaturated polybasic acid is a polybasic acid having a polymerizable ethylenically unsaturated bond, and the saturated polybasic acid is a polybasic acid having no polymerizable ethylenically unsaturated bond.

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

The polyhydric alcohol used as a raw material for the unsaturated polyester is not particularly limited, and any known polyhydric alcohol in the technical field of the present invention can be used. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol, hexanediol, neopentanediol, hydrogenated bisphenol A, bisphenol A, and glycerin. Polyhydric alcohols can be used alone or in combination.

Among these, at least one selected from the group consisting of propylene glycol, neopentanediol, bisphenol A, and hydrogenated bisphenol A is preferred from the viewpoint of excellent heat resistance, mechanical strength, and resin fluidity during molding.

The unsaturated polybasic acid used as a raw material for the unsaturated polyester is not particularly limited, and any known unsaturated polybasic acid in the technical field of the present invention can be used. Examples of unsaturated polybasic acids include maleic anhydride, fumaric acid, citraconic acid, itaconic acid, and HET acid. Unsaturated polybasic acids can be used alone or in combination.

Of these, maleic anhydride or fumaric acid is preferred from the standpoint of excellent heat resistance, mechanical strength, and resin fluidity during molding.

The saturated polybasic acid, which is an optional raw material for unsaturated polyesters, is not particularly limited, and known acids can be used. Examples of saturated polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, and tetrabromophthalic anhydride. Saturated polybasic acids can be used alone or in combination.

Unsaturated polyesters can be synthesized using known methods using the raw materials described above. The various conditions for synthesizing unsaturated polyesters can be set appropriately depending on the raw materials and their amounts used. A typical method involves esterification in a stream of inert gas such as nitrogen gas at a temperature of 140 to 230°C under increased or reduced pressure. An esterification catalyst can be used in the esterification reaction, if necessary. Examples of esterification catalysts include known catalysts such as manganese acetate, dibutyltin oxide, stannous oxalate, zinc acetate, and cobalt acetate. Esterification catalysts can be used alone or in combination.

The weight average molecular weight (MW) of the unsaturated polyester is not particularly limited. It is preferably 3,000 to 25,000, more preferably 5,000 to 20,000, and even more preferably 7,000 to 18,000. In the present disclosure, the term "weight average molecular weight" refers to a value measured using gel permeation chromatography (Shodex (registered trademark) GPC-101, Showa Denko K.K.) at room temperature (23°C) under the following conditions and determined using a standard polystyrene calibration curve.
Column: LF-804 (Showa Denko K.K.)
Column temperature: 40°C
Sample: 0.2% by mass solution of unsaturated polyester in tetrahydrofuran Flow rate: 1 mL/min Eluent: tetrahydrofuran Detector: RI-71S

The crosslinking agent (reactive diluent) that dissolves the unsaturated polyester is not particularly limited as long as it has an ethylenically unsaturated bond that can polymerize with the unsaturated polyester, and any agent known in the technical field of the present invention can be used. Examples of crosslinking agents include styrene monomer, diallyl phthalate monomer, diallyl phthalate prepolymer, methyl methacrylate, and triallyl isocyanurate. These may be used alone or in combination.

The content of crosslinking agent (reactive diluent) in the (a) unsaturated polyester resin is not particularly limited. From the standpoints of workability, polymerizability, shrinkage of molded bodies, and freedom in adjusting the amount, the content of crosslinking agent (reactive diluent) in the (a) 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, of the total of the unsaturated polyester and crosslinking agent.

(a) The unsaturated polyester resin may contain a polymerization inhibitor such as hydroquinone, if necessary.

[(b) Inorganic filler]
In one embodiment of the unsaturated polyester resin composition, the content of the inorganic filler is set within a specific range, and the inorganic filler contains fillers having three different average particle sizes in a specific ratio.

(b) The type of inorganic filler is not particularly limited, and any filler known in the technical field of the present invention can be used. Examples of (b) inorganic fillers include calcium carbonate, silica, alumina, aluminum hydroxide, barium sulfate, wollastonite, clay, talc, mica, gypsum, silicic anhydride, and glass powder. These can be used alone or in combination. Of these, it is preferable to use at least calcium carbonate from the standpoints of surface smoothness of the resulting molded product, cost reduction, and ease of availability.

(b) The shape of the inorganic filler is not particularly limited, and examples include approximately spherical, ellipsoidal, scaly, and amorphous.

(b) The true specific gravity of the inorganic filler is not particularly limited, but is preferably 1 to 10 g/cm ³ , more preferably 1.5 to 8 g/cm ³ , and even more preferably 2 to 5 g/cm ³ .

When the true specific gravity of the inorganic filler is 1 g/cm3 or ^more , the mechanical properties of the obtained molded article become better, and when the true specific gravity of the inorganic filler is 10 g/ ^cm3 or less, the kneadability of the unsaturated polyester resin composition becomes better.

The amount of (b) inorganic filler to be blended is 250 to 600 parts by mass, more preferably 300 to 550 parts by mass, and even more preferably 350 to 450 parts by mass per 100 parts by mass of (a) unsaturated polyester resin.

If the blending amount of (b) inorganic filler is 250 parts by mass or more, the mechanical properties of the resulting molded body will be better. Furthermore, if the blending amount of (b) inorganic filler is 600 parts by mass or less, the (b) inorganic filler will be more uniformly dispersed in the unsaturated polyester resin composition, making it possible to produce a homogeneous molded body.

The (b) inorganic filler is a combination of at least three types: (b1) an inorganic filler having an average particle size of 0.5 to 5.0 μm (hereinafter also referred to as "(b1) inorganic filler"), (b2) an inorganic filler having an average particle size of 6.0 to 50.0 μm (hereinafter also referred to as "(b2) inorganic filler"), and (b3) an inorganic filler having an average particle size of 70.0 μm or more (hereinafter also referred to as "(b3) inorganic filler").

By using at least three types of inorganic fillers (b1) to (b3) with different average particle sizes in combination, the fluidity of the unsaturated polyester resin composition during molding can be improved, resulting in molded articles with excellent appearance, dimensional accuracy, and strength properties, and burrs on the molded articles can be reduced.

In the present disclosure, the "average particle size" of the inorganic filler (b) means the particle size calculated from the specific surface area determined by the air permeability method according to the following formula:
Average particle diameter [μm] = (6×10000)/(true specific gravity [g/cm ³ ]×specific surface area [cm ² /g])

(b1) The average particle size of the inorganic filler is preferably 0.7 μm or more, and more preferably 1.0 μm or more. (b1) The average particle size of the inorganic filler is preferably 4.0 μm or less, and more preferably 3.0 μm or less. (b1) By using the inorganic filler, it is possible to obtain a molded product with excellent appearance and strength.

(b2) The average particle size of the inorganic filler is preferably 6.5 μm or more, and more preferably 7.0 μm or more. (b2) The average particle size of the inorganic filler is preferably 40.0 μm or less, and more preferably 30.0 μm or less. (b2) By using an inorganic filler, it is possible to obtain a molded product that has excellent appearance and strength properties while reducing burrs.

(b3) The average particle diameter of the inorganic filler is preferably 100 μm or more, more preferably 200 μm or more. (b3) The average particle diameter of the inorganic filler is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 360 μm or less. (b3) By using an inorganic filler, a molded product with reduced burrs can be obtained.

The inorganic fillers (b1) to (b3) are contained in a ratio of (b1):(b2):(b3) of 60-75:7-15:15-30, based on a total of 100% by mass of the inorganic fillers (b1), (b2), and (b3). To further reduce burrs in the resulting molded body and to ensure excellent surface smoothness and mechanical strength, the ratio is preferably 60-70:10-15:20-25.

By setting the mass ratio of inorganic fillers (b1) to (b3) within the above range, it is possible to achieve excellent appearance and strength properties of the resulting molded body while also reducing burrs. If the mass ratio is outside the above range, any one of the following characteristics will be impaired: appearance, strength properties, or reduced burrs of the molded body.

[(c) Metal soap]
(c) Metal soap is a component generally used as a mold release agent in the technical field of the present invention. There are no particular limitations on the (c) metal soap, and any known metal soap in the technical field of the present invention can be used. Examples of (c) metal soap include calcium stearate, zinc stearate, aluminum stearate, and magnesium stearate. (c) Metal soaps can be used alone or in combination.

The amount of (c) metal soap is not particularly limited, but is preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of (a) unsaturated polyester resin.

If the blending amount of (c) metal soap is 1 part by mass or more, the resulting molded article will have better demolding properties. On the other hand, if the blending amount of (c) metal soap is 15 parts by mass or less, bleeding of (c) metal soap onto the surface of the molded article can be prevented, resulting in a molded article that satisfies the desired fogging properties and paintability of the undercoat agent.

[(d) Low-Profile Agent]
The (d) low shrinkage agent is not particularly limited, and any agent known in the technical field of the present invention can be used. Examples of low shrinkage agents include thermoplastic polymers that are commonly used as low shrinkage agents, such as polystyrene, polymethyl methacrylate, polyvinyl acetate, saturated polyester, and styrene-butadiene rubber. The (d) low shrinkage agent can be used alone or in combination of two or more types.

The content of (d) low shrinkage agent is preferably 10 to 40 parts by mass, and more preferably 20 to 35 parts by mass, per 100 parts by mass of (a) unsaturated polyester resin. If the amount of (d) low shrinkage agent is 10 parts by mass or more, the shrinkage rate of the molded body will be small, and the desired dimensional accuracy can be achieved. On the other hand, if the amount of (d) low shrinkage agent is 40 parts by mass or less, the mechanical properties of the molded body will be better.

[(e) Fiber reinforcement]
(e) The fiber reinforcement is a material having an aspect ratio of at least 3. The aspect ratio can be measured by the microscopic method described in Japanese Industrial Standard JIS Z 8900-1:2008 "Particles for Calibration of Particle Size Measuring Devices."

(e) The fiber reinforcing material is not particularly limited, and any material known in the technical field of the present invention can be used. (e) Examples of the fiber reinforcing material include various organic and inorganic fibers such as glass fiber, pulp, polyethylene terephthalate fiber, vinylon fiber, carbon fiber, aramid fiber, and wollastonite. Of these, glass fiber is preferred, and chopped strand glass cut to a fiber length of approximately 1.5 to 25 mm is more preferred.

The content of (e) fiber reinforcing material is preferably 70 to 120 parts by mass, and more preferably 75 to 100 parts by mass, per 100 parts by mass of (a) unsaturated polyester resin. If the blending amount of (e) fiber reinforcing material is 70 parts by mass or more, the mechanical properties of the molded body will be better. On the other hand, if the blending amount of (e) fiber reinforcing material is 120 parts by mass or less, the (e) fiber reinforcing material will be more uniformly dispersed in the unsaturated polyester resin composition, making it possible to produce a homogeneous molded body.

[(f) Curing Agent]
The (f) curing agent is not particularly limited as long as it is a radical polymerization initiator capable of polymerizing ethylenically unsaturated bonds, and those known in the technical field of the present invention can be used. Examples of the (f) curing agent include organic peroxides such as t-butyl peroxyoctoate, benzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylperoxyisopropyl carbonate, t-butyl peroxybenzoate, dicumyl peroxide, and di-t-butyl peroxide. The (f) curing agents can be used alone or in combination of two or more.

The content of the (f) curing agent is not particularly limited and can be set appropriately depending on the raw materials used. The content of the (f) curing agent is preferably 1 to 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 1 to 5 parts by mass per 100 parts by mass of the (a) unsaturated polyester resin.

[Other ingredients]
In addition to the above components, the unsaturated polyester resin composition of the present invention may contain components known in the technical field of the present invention, such as thickeners, pigments, and viscosity reducers, to the extent that the effects of the present invention are not impaired.

Thickeners are not particularly limited, but examples include metal oxides other than (b) inorganic fillers, such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium oxide, and isocyanate compounds. Thickeners can be used alone or in combination of two or more.

[Method of producing unsaturated polyester resin composition]
The unsaturated polyester resin composition can be produced by a method commonly used in the technical field of the present invention, for example, by kneading the components using a kneader or the like.

[Method for producing molded article of unsaturated polyester resin composition]
The unsaturated polyester resin composition can be molded into a desired shape and cured to produce a molded article. The molding and curing methods are not particularly limited, and include methods commonly used in the technical field of the present invention, such as compression molding, transfer molding, and injection molding.

The present invention will be explained in detail below using examples and comparative examples, but the present invention is not limited by these.

<(a) Preparation of Unsaturated Polyester Resin>
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 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. Subsequently, the temperature was raised to 200°C while heating and stirring under a nitrogen gas flow, and an esterification reaction was carried out to obtain an unsaturated polyester. The obtained unsaturated polyester had an unsaturation degree of 95 mol% and a weight-average molecular weight of 8,000. Subsequently, styrene monomer was added to the obtained unsaturated polyester in an amount of 30% by mass relative to the total of the unsaturated polyester and the styrene monomer, to obtain (a) an unsaturated polyester resin.

<Examples 1 and 2, Comparative Examples 1 to 7>
The materials constituting the unsaturated polyester resin composition were charged according to the formulation shown in Table 1 and kneaded for 30 minutes at 25° C. using a double-arm kneader to obtain an unsaturated polyester resin composition. The unsaturated polyester resin (a) shown in Table 1 was obtained by the above method and contains 30% by mass of styrene monomer.

<Materials>
The materials used in the examples and comparative examples are as follows.
(b) Inorganic filler (b1) Calcium carbonate (S-1200BM, Bihoku Funka Kogyo Co., Ltd., average particle size: 1.8 μm, true specific gravity: 2.7 g/cm ³ )
(b2) Calcium carbonate (Tankal R heavy carbon, Maruo Calcium Co., Ltd., average particle size: 7.4 μm, true specific gravity: 2.7 g/cm ³ )
(b3) Calcium carbonate (Kansuiseki KD-70, Calfine Co., Ltd., average particle size: 300 μm, true specific gravity: 2.7 g/cm ³ )
(c) Metal soap
Calcium stearate (Tannan Chemical Industry Co., Ltd.)
(d) Low-shrinkage agent
Polystyrene (weight average molecular weight 200,000, Sekisui Plastics Co., Ltd.)
(e) Fiber reinforcement
Chopped strand glass (fiber length: 9 mm, Nippon Electric Glass Co., Ltd.)
(f) hardener
t-Butyl peroxybenzoate (NOF Corporation)

<Evaluation>
The unsaturated polyester resin compositions obtained in the Examples and Comparative Examples were measured or evaluated for kneadability, in-mold flowability of the resin composition, surface smoothness of the molded product, molding shrinkage, strength properties (flexural strength and flexural modulus), and flowability using a thin-walled flow mold to confirm low flash. The measurement and evaluation methods were as follows. The results are shown in Table 1.

(1) Kneadability When preparing an unsaturated polyester resin composition (kneading for 30 minutes at 25°C using a double-arm kneader), whether or not a uniform unsaturated polyester resin composition without poor dispersion was obtained was visually evaluated. The evaluation criteria are shown below.
Good: The unsaturated polyester resin composition is uniform.
Poor: The unsaturated polyester resin composition is poorly dispersed.

(2) In-mold fluidity of resin composition A spiral flow mold (cross-sectional shape: trapezoidal with an upper side of 6 mm, a base of 8 mm, and a height of 2 mm) was attached to a transfer molding machine (Technomarushi Co., Ltd.), and a spiral flow test was performed under conditions of a mold temperature of 150°C and an injection pressure of 10 MPa to measure the flow length (cm). The measurement results and evaluation results are shown in Table 1. A flow length of 30 cm or more indicates good in-mold fluidity of the resin composition.

(3) Surface Smoothness of Molded Articles Using a transfer molding machine (Technomarushi Co., Ltd.), transfer molded articles (φ117 mm, thickness 3 mm) were produced under the conditions of a molding temperature of 150°C, an injection pressure of 20 MPa, and a molding time of 1 minute. The appearance of the obtained transfer molded articles was visually inspected and evaluated according to the following criteria.
Good: The entire surface is glossy and has no sink marks.
Poor: The surface is entirely or partially lacking in gloss, or has sink marks entirely or partially.

(4) Mold shrinkage Using a compression molding machine (compression molding machine, Technomaru City Co., Ltd.), a shrink disk (φ90 mm × 11 mm) specified in JIS K-6911 5.7 was produced by compression molding under conditions of a molding temperature of 160 ° C, a molding pressure of 10 MPa, and a molding time of 3 minutes, and the mold shrinkage (%) was calculated in accordance with JIS K-6911 5.7. The results are shown in Table 1.

(5) Strength properties (flexural strength and flexural modulus)
Using a compression molding machine (compression molding machine, Technomarusichi Co., Ltd.), a flexural modulus test piece (90 mm x 10 mm x 4 mm) specified in JIS K-6911 5.17 was prepared by compression molding under conditions of a molding temperature of 150 ° C, a molding pressure of 10 MPa, 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 according to the following evaluation criteria. The measurement results and strength property evaluation results are shown in Table 1.
Good: Flexural strength of 130 MPa or more and flexural modulus of 13 MPa or more. Poor: Flexural strength less than 130 MPa or flexural modulus less than 13 MPa.

(6) Thin-wall fluidity (burr evaluation)
To evaluate flashing, a transfer molding machine (Technomarushi Co., Ltd.) was used to produce a transfer molding product under conditions of a molding temperature of 150°C, an injection pressure of 20 MPa, and a molding time of 1 minute. The length (mm) of flashing generated on the resulting transfer molding product was measured and evaluated according to the following criteria. The measurement results and flash evaluation results are shown in Table 1.
Good: No burrs of 20 mm or more were generated in the 140 μm gap of the mold.
Poor: A burr of 20 mm or more was generated in the 140 μm gap of the mold.

The present invention provides an unsaturated polyester resin composition that has good resin fluidity during molding, and can produce molded articles with excellent molded product appearance, dimensional accuracy, and strength, and reduced burrs.

Claims (4)

An unsaturated polyester resin composition comprising (a) an unsaturated polyester resin, (b) an inorganic filler, (c) a metal soap, (d) a low-profile agent, (e) a fiber reinforcement material, and (f) a curing agent,
the content of the (b) inorganic filler is 250 to 600 parts by mass relative to 100 parts by mass of the (a) unsaturated polyester resin,
The (b) inorganic filler comprises (b1) an inorganic filler having an average particle size of 0.5 to 5.0 μm, (b2) an inorganic filler having an average particle size of 6.0 to 50.0 μm, and (b3) an inorganic filler having an average particle size of 70.0 μm or more and 360 μm or less , in a ratio of (b1):(b2):(b3)=60 to 75:7 to 15:15 to 30, relative to 100% by mass of the total of the inorganic fillers (b1), (b2), and (b3);
The content of the (e) fiber reinforcing material is 70 to 120 parts by mass per 100 parts by mass of the (a) unsaturated polyester resin.
Unsaturated polyester resin composition. The unsaturated polyester resin composition according to claim 1, wherein the content of the (b) inorganic filler is 350 to 450 parts by mass per 100 parts by mass of the (a) unsaturated polyester resin. The unsaturated polyester resin composition according to claim 1 or 2, wherein the inorganic filler (b) includes calcium carbonate. A molded article comprising a cured product of the unsaturated polyester resin composition described in any one of claims 1 to 3.