JP6556158B2 - Unsaturated polyester resin composition and encapsulated motor - Google Patents

Description

  The present invention relates to an unsaturated polyester resin composition and an encapsulated motor. Specifically, the present invention relates to an unsaturated polyester resin composition used for encapsulating electrical / electronic components, and an encapsulated motor.

  For the purpose of improving quietness and ease of incorporation in various apparatuses, it is performed to encapsulate and harden electric / electronic parts with an encapsulating material such as a resin composition. For example, an encapsulated motor in which motor components such as a coil, a rotor, a stator, and a bearing are encapsulated and cured with a resin composition is generally known. Enclosed motors are used in various applications such as electric vehicles, hybrid electric vehicles, air conditioners, and refrigerators.

  In recent years, encapsulated products such as encapsulated motors are required to be smaller and have higher output from the viewpoint of further efficiency in energy use. Due to these demands, the amount of heat generated by the encapsulated electrical / electronic components is increasing, and therefore encapsulating materials that give a cured product with excellent heat resistance are required. In addition, since the shape of electrical and electronic components has become complicated due to the miniaturization of encapsulated products, the encapsulating material has high fluidity during molding and the shrinkage rate during molding in order to securely enclose electrical and electronic components. Must be small.

As a conventional encapsulating material, an unsaturated polyester resin composition containing an unsaturated polyester resin, an inorganic filler, aluminum hydroxide, glass fiber, and a low shrinkage agent in a specific ratio has been proposed (patent) Reference 1).
On the other hand, as an unsaturated polyester resin composition that gives a cured product excellent in heat resistance, a crosslinking agent comprising an unsaturated polyester, a diallyl phthalate monomer or prepolymer, and a radically polymerizable unsaturated monomer other than diallyl phthalate monomer And a low-shrinkage agent composed of polystyrene, acrylic polymer, and styrene-diene block copolymer and / or a hydrogenated product or a modified product thereof in a specific ratio has been proposed (patent) Reference 2).

JP 2001-226573 A JP 2010-49918 A

However, although the unsaturated polyester resin composition of Patent Document 1 has high fluidity at the time of molding, it contains aluminum hydroxide, and thus cannot obtain a cured product having excellent heat resistance.
Moreover, since the unsaturated polyester resin composition of patent document 2 is used for manufacture of the base material for lamp reflectors, it does not have fluidity suitable for encapsulating materials for electric and electronic parts. In fact, when the unsaturated polyester resin composition of Patent Document 2 is used for encapsulating electric / electronic parts, the fluidity at the time of molding is not sufficient, so that the electric / electronic parts cannot be encapsulated reliably.
As described above, in the conventional unsaturated polyester resin composition, the fluidity during molding and the heat resistance of the cured product, both of which are required for encapsulating electric / electronic parts, are in reality.

  The present invention has been made in order to solve the above-described problems, and is an unsaturated polyester resin composition that provides a cured product having high flowability during molding, low molding shrinkage, and excellent heat resistance. The purpose is to provide. Another object of the present invention is to provide an encapsulated motor in which motor components are firmly encapsulated and cured with an unsaturated polyester resin composition having the above-described characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have identified an unsaturated polyester resin, an acrylic resin, a styrene-diene copolymer, a glass fiber having a fiber length of 5 mm or less, and an inorganic filler. It has been found that characteristics suitable for encapsulating materials for electric and electronic parts can be obtained by combining at a ratio of ## EQU2 ## and the present invention has been completed.

That is, the present invention includes the following [1] to [6].
[1] Unsaturation containing (a) unsaturated polyester resin, (b) acrylic resin, (c) styrene-diene copolymer, (d) glass fiber having a fiber length of 5 mm or less, and (e) inorganic filler. A polyester resin composition comprising:
(A) With respect to 100 parts by mass of the component, the total of the (b) component and the (c) component is 10 to 20 parts by mass, the (d) component is 30 to 55 parts by mass, and the (e) component is 300 mass parts-550 mass parts, and the mass ratio of (b) component and (c) component is 1: 2-2: 1, The unsaturated polyester resin composition characterized by the above-mentioned.

[2] The defect according to [1], wherein (c) the styrene-diene copolymer is at least one selected from the group consisting of SBS thermoplastic elastomers and SIS thermoplastic elastomers. Saturated polyester resin composition.
[3] The unsaturated polyester resin composition according to [1] or [2], wherein the (e) inorganic filler is calcium carbonate.
[4] The unsaturated polyester resin composition according to any one of [1] to [3], wherein the unsaturated polyester resin composition is used for enclosing electric / electronic parts.
[5] The unsaturated polyester resin composition according to [4], wherein the electric / electronic component is a motor component.
[6] An encapsulated motor obtained by encapsulating and curing a motor component with the unsaturated polyester resin composition according to any one of [1] to [5].

  According to the present invention, it is possible to provide an unsaturated polyester resin composition that provides a cured product having high fluidity during molding, a small molding shrinkage ratio, and excellent heat resistance. In addition, according to the present invention, it is possible to provide an encapsulated motor in which motor component parts are firmly encapsulated and cured with an unsaturated polyester resin composition having the above characteristics.

  The unsaturated polyester resin composition of the present invention comprises (a) an unsaturated polyester resin, (b) an acrylic resin, (c) a styrene-diene copolymer, (d) a glass fiber having a fiber length of 5 mm or less, and (e ) Contains inorganic filler. The unsaturated polyester resin composition preferred in the present invention consists essentially of the components (a) to (e). Here, “essentially” in the present specification includes the components (a) to (e) as essential components and includes optional components other than the essential components within a range not inhibiting the effects of the present invention. Means you can.

  The (a) unsaturated polyester resin used in the unsaturated polyester resin composition of the present invention is not particularly limited, and those known in the technical field can be used. (A) An unsaturated polyester resin generally comprises a condensation product (unsaturated polyester) obtained by an esterification reaction of a polyhydric alcohol, an unsaturated polybasic acid and an arbitrary saturated polybasic acid with a crosslinking agent (“reactive dilution”). It is also referred to as “agent”. Such unsaturated polyester resins are generally known in the art, and include, for example, “Polyester Resin Handbook” (Nikkan Kogyo Shimbun, published in 1988), “Paint Glossary of Terms” (edited by Color Material Association, published in 1993). ) Etc.

  The polyhydric alcohol used for the synthesis of the unsaturated polyester is not particularly limited, and those known in the technical field can be used. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (also referred to as “neopentyl glycol”). 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,4-butanediol, 1,5-pentanediol 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2 , 5-hexanediol, 1,2-octanediol, 1,2-nonanediol, 1,4-cyclohexanedioe 1,8-octanediol, 1,9-nonanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, bisphenol S, 2, Examples include 2-di (4-hydroxycyclohexyl) propane (also referred to as “hydrogenated bisphenol A”), polyethylene glycol, polypropylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like. These components can be used alone or in combination of two or more components.

  It does not specifically limit as unsaturated polybasic acid used for the synthesis | combination of unsaturated polyester, A well-known thing can be used in the said technical field. Examples of unsaturated polybasic acids include α, β-unsaturated polycarboxylic acids and derivatives thereof. Examples of the α, β-unsaturated polyvalent carboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid and the like. Examples of α, β-unsaturated polyvalent carboxylic acid derivatives include acid anhydrides such as maleic anhydride, itaconic anhydride and chloromaleic anhydride, and lower alkyl esters of the above unsaturated polyvalent carboxylic acids. Can be mentioned. These components can be used alone or in combination of two or more components.

  It does not specifically limit as a saturated polybasic acid used for the synthesis | combination of unsaturated polyester, A well-known thing can be used in the said technical field. Examples of saturated polybasic acids include succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, hexahydrophthalic acid (eg, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid , 1,4-cyclohexanedicarboxylic acid, etc.), orthophthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid, chlorendic acid, het acid, tetrabromophthalic acid, phthalic anhydride, tetrahydro Phthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, succinic anhydride, chlorendic anhydride, trimellitic anhydride, pyromellitic anhydride, dimethyl orthophthalate, dimethyl isophthalate, dimethyl terephthalate And the like. These components can be used alone or in combination of two or more components.

  Unsaturated polyester is compoundable by a well-known method using the above raw materials. Various conditions in this synthesis need to be set as appropriate according to the raw materials to be used and the amount thereof, but are generally pressurized or heated at a temperature of 140 ° C. to 230 ° C. in an inert gas stream such as nitrogen gas. What is necessary is just to esterify under reduced pressure. In this esterification reaction, an esterification catalyst can be used as needed. Examples of the catalyst include known catalysts such as manganese acetate, dibutyltin oxide, stannous oxalate, zinc acetate, and cobalt acetate. These catalysts can be used alone or in combination of two or more components.

Although the weight average molecular weight (MW) of unsaturated polyester is not specifically limited, Preferably it is 3,000-50,000, More preferably, it is 5,000-30,000. In this specification, the “weight average molecular weight” is measured at normal temperature (23 ° C.) under the following conditions using gel permeation chromatography (Shodex GPC-101, Showa Denko KK), and is a standard polystyrene calibration curve. It means the value obtained using.
Column: Showa Denko LF-804
Column temperature: 40 ° C
Sample: 0.2% by mass tetrahydrofuran solution of copolymer Flow rate: 1 mL / min Eluent: Tetrahydrofuran Detector: RI-71S

(A) The crosslinking agent used in the unsaturated polyester resin is not particularly limited as long as it has an ethylenic double bond polymerizable with the unsaturated polyester, and those known in the technical field are used. be able to. Examples of the crosslinking agent include styrene monomer, diallyl phthalate monomer, diallyl phthalate prepolymer, methyl methacrylate, triallyl isocyanurate and the like. A single component or a combination of two or more components can be used.
(A) Although the compounding quantity of the crosslinking agent in unsaturated polyester resin is not specifically limited, From a viewpoint of workability | operativity, polymerizability, the shrinkability of a molded object, and the freedom degree of quantity adjustment, Preferably it is 25 mass%-85 mass%. More preferably, it is 30 mass%-80 mass%, Most preferably, it is 40 mass%-70 mass%.
In addition, from the viewpoint of imparting specific characteristics to the unsaturated polyester resin composition of the present invention, a part of the unsaturated polyester resin (a) may be a vinyl ester resin as long as the effects of the present invention are not impaired.

  The (b) acrylic resin used in the unsaturated polyester resin composition of the present invention is not particularly limited, and those known in the technical field can be used. Among them, the (b) acrylic resin preferable in the present invention is a homopolymer or copolymer having an acrylic monomer as a main component. Examples of acrylic monomers include acrylic acid esters such as methyl acrylate, n-butyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethyl-hexyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl And methacrylates such as methacrylate.

(B) The acrylic resin can be produced by polymerizing an acrylic monomer. The polymerization conditions are not particularly limited, and may be set as appropriate according to the type and amount of the acrylic monomer used.
Moreover, a commercial item can also be used as (b) acrylic resin. Examples of commercially available products include “ARUFON (trademark) series” manufactured by Toagosei Co., Ltd., “Dianar (trademark) series” manufactured by Mitsubishi Rayon Co., Ltd., and “Delpet (trademark) series” manufactured by Asahi Kasei Chemicals Corporation. Etc. Specifically, ARUFON (trademark) UH-3910, UC-3920, manufactured by Toagosei Co., Ltd., Dialnal (trademark) BR-50, BR-52, BR-60, BR-73, manufactured by Mitsubishi Rayon Co., Ltd., BR-77, BR-83, BR-96, BR-113, MB-2389, MB-7033, BR-2389, Techno Polymer MB manufactured by Sekisui Chemical Co., Ltd., F320 manufactured by Nippon Zeon Co., Ltd., Asahi Kasei Chemicals Corporation Delpet (trademark) 560F, 60N, and 80NB manufactured by the company can be used.

(B) Although the weight average molecular weight (MW) of an acrylic resin is not specifically limited, Preferably it is 3,000-1,000,000, More preferably, it is 10,000-500,000.
Moreover, (b) acrylic resin can be used combining a single component or 2 or more types of components.

The (c) styrene-diene copolymer used in the unsaturated polyester resin composition of the present invention is not particularly limited, and those known in the technical field can be used. Among them, the (c) styrene-diene copolymer preferable in the present invention is an SBS thermoplastic elastomer having polystyrene as a hard segment and polybutadiene as a soft segment, or polystyrene and a soft segment as a hard segment, from the viewpoint of molding shrinkage. It is a SIS thermoplastic elastomer having polyisoprene.
(C) The arrangement pattern of the repeating units (polystyrene part and diene polymer part) constituting the styrene-diene copolymer is not particularly limited, and may be either a linear type or a radial type.
(C) Although the ratio of the polystyrene part and diene polymer part in a styrene-diene copolymer is not specifically limited, It is preferable that a polystyrene part is 10 mass%-50 mass% of the whole. When the ratio of the polystyrene part is less than 10% by mass or more than 50% by mass, a cured product having a desired molding shrinkage rate may not be obtained.

  (C) Styrene-diene copolymers having the above-described characteristics are commercially available. Examples of commercially available products include “Tufprene (trademark) series” and “Asaprene (trademark) series” manufactured by Asahi Kasei Chemicals Corporation, “JSR SIS series” manufactured by JSR Corporation, and “Nipol (trademark) manufactured by Nippon Zeon Corporation. ) Series ”. Specifically, TUFPRENE (trademark) A, 125, 126S, T-411, T-432, T-437, T-438, T-439 manufactured by Asahi Kasei Chemicals Corporation, JSR SIS5002, SIS5200 manufactured by JSR Corporation. , SIS5250, SIS5405, SIS5505, Nipol (trademark) 1502, 1723 and 1739 manufactured by ZEON CORPORATION can be used.

(C) Although the weight average molecular weight (MW) of a styrene-diene copolymer is not specifically limited, Preferably it is 10,000-1,000,000, More preferably, it is 100,000-800,000.
Moreover, (c) a styrene-diene copolymer can be used in combination of a single component or two or more components.

  The blending ratio of (b) acrylic resin and (c) styrene-diene copolymer in the unsaturated polyester resin composition of the present invention is (b) acrylic resin and 100 parts by mass of unsaturated polyester resin. (C) The total of the styrene-diene copolymer is 10 to 20 parts by mass, preferably 11 to 19 parts by mass, more preferably 12 to 18 parts by mass. When the total of (b) the acrylic resin and (c) the styrene-diene copolymer is less than 10 parts by mass, the molding shrinkage decreases. On the other hand, when the sum total of (b) acrylic resin and (c) styrene-diene copolymer exceeds 20 mass parts, the fluidity | liquidity at the time of shaping | molding and the heat resistance of hardened | cured material will fall.

  The ratio of (b) acrylic resin and (c) styrene-diene copolymer in the unsaturated polyester resin composition of the present invention is 1: 2 to 2: 1, preferably 1: 1.8 to 1.8: 1, more preferably 1: 1.5 to 1.5: 1. (C) When the ratio of the (b) acrylic resin with respect to the styrene-diene copolymer is too high, the fluidity and molding shrinkage during molding are lowered. On the other hand, if the ratio of (c) styrene-diene copolymer to (b) acrylic resin is too high, the heat resistance of the cured product is lowered.

  The glass fiber having a fiber length of 5 mm or less used in the unsaturated polyester resin composition of the present invention is not particularly limited, and those known in the technical field can be used. Examples of glass fibers include glass chopped strands and milled glass fibers. When the fiber length of glass fiber exceeds 5 mm, the fluidity at the time of shaping | molding will fall. The fiber length of the glass fiber is preferably 3 mm or less, more preferably 1.5 mm or less. The fiber diameter of the glass fiber is preferably 3 μm to 25 μm.

  In the unsaturated polyester resin composition of the present invention, the blending ratio of (d) glass fiber having a fiber length of 5 mm or less is 30 to 55 parts by mass, preferably 32 to 100 parts by mass of (a) unsaturated polyester resin. It is 35 mass parts-53 mass parts, More preferably, it is 35 mass parts-50 mass parts. (D) The heat resistance of hardened | cured material falls that the mixture ratio of glass fiber whose fiber length is 5 mm or less is less than 30 mass parts. On the other hand, d) When the blending ratio of the glass fiber having a fiber length of 5 mm or less exceeds 55 parts by mass, the fluidity at the time of molding is lowered.

  The inorganic filler (e) used in the unsaturated polyester resin composition of the present invention is not particularly limited, and those known in the technical field can be used. In the present invention, the preferred (e) inorganic filler is an inorganic filler other than aluminum hydroxide that causes a decrease in heat resistance. (E) Examples of inorganic fillers include calcium carbonate, spherical or amorphous alumina, magnesium oxide, beryllium oxide, aluminum nitride, boron nitride, titanium nitride, boron carbide, titanium carbide, titanium boride, clay, mica, etc. Can be mentioned. These can be used alone or in combination of two or more components. Of these, calcium carbonate is preferred from the viewpoint of fluidity during molding and heat resistance of the cured product.

  (E) Although the average particle diameter of an inorganic filler is not specifically limited, From a fluid viewpoint at the time of shaping | molding, Preferably it is 0.5 micrometer-30 micrometers, More preferably, it is 1 micrometer-20 micrometers. Here, the “average particle diameter” in this specification means an average particle diameter measured by a laser diffraction / scattering method, a Coulter counter method, etc., but is an average particle diameter measured by a laser diffraction / scattering method. Preferably there is. The average particle size measured by the laser diffraction / scattering method, the Coulter counter method, or the like means the particle size at an integrated value of 50% in the particle size distribution (number distribution) obtained by these methods.

The blending ratio of the (e) inorganic filler in the unsaturated polyester resin composition of the present invention is (a) 100 parts by weight of the unsaturated polyester resin from the viewpoint of achieving both the fluidity during molding and the heat resistance of the cured product. On the other hand, it is 300 to 550 parts by mass, preferably 330 to 420 parts by mass, more preferably 350 to 450 parts by mass. (E) If the proportion of the inorganic filler is less than 3 0 0 parts by weight, heat resistance of the cured product is reduced. On the other hand, if the blending ratio of (e) the inorganic filler exceeds 550 parts by mass, the fluidity at the time of molding is lowered.

From the viewpoint of improving various physical properties, the unsaturated polyester resin composition of the present invention contains optional components such as a curing agent, a mold release agent, a thickener, and a pigment as necessary. Can be contained.
It does not specifically limit as a hardening | curing agent, A well-known thermal polymerization initiator can be used in the said technical field. Examples of curing agents include t-butyl peroxy octoate, benzoyl peroxide, 1,1, -di-t-butyl peroxy-3,3,5-trimethylcyclohexane, t-butyl peroxyisopropyl carbonate, t -Peroxides such as butyl peroxybenzoate, dicumyl peroxide, and di-t-butyl peroxide. These components can be used alone or in combination of two or more components.

  The blending ratio of the curing agent in the unsaturated polyester resin composition of the present invention is not particularly limited, but (a) is preferably 0.1 parts by mass to 10 parts by mass, more preferably 100 parts by mass of the unsaturated polyester resin. 2 parts by mass to 6 parts by mass. When the blending amount of the curing agent is less than 0.1 parts by mass, the curing time may be long or may not be sufficiently cured. On the other hand, when the compounding quantity of a hardening | curing agent exceeds 10 mass parts, storage stability may fall.

The release agent is not particularly limited, and those known in the technical field can be used. Examples of the mold release agent include stearic acid, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, carnauba wax and the like. These components can be used alone or in combination of two or more components.
The blending ratio of the release agent in the unsaturated polyester resin composition of the present invention is not particularly limited, and may be appropriately adjusted within a range that does not impair the effects of the present invention, depending on the type of the release agent used.

The thickener is not particularly limited, and those known in the technical field can be used. Examples of thickeners include magnesium hydroxide, calcium hydroxide, calcium oxide, isocyanate compounds and the like. These components can be used alone or in combination of two or more components.
The blending ratio of the thickener in the unsaturated polyester resin composition of the present invention is not particularly limited, and may be appropriately adjusted within a range that does not impair the effects of the present invention, depending on the type of the thickener used.

The unsaturated polyester resin composition of the present invention can be produced by blending and kneading the above-mentioned predetermined amounts of each component by a conventional method. For example, an unsaturated polyester resin composition can be obtained by adding a predetermined amount of each component to a kneader and mixing them. Moreover, from the viewpoint of producing a homogeneous unsaturated polyester resin composition, (d) after kneading each component excluding glass fibers having a fiber length of 5 mm or less with a double-type kneader, (d) the fiber length is It is preferable to add a glass fiber of 5 mm or less and further knead.
The unsaturated polyester resin composition of the present invention obtained as described above has high fluidity at the time of molding, and can give a cured product having a small molding shrinkage ratio and excellent heat resistance. Can be used. Among them, the unsaturated polyester resin composition of the present invention is most suitable as an encapsulating material for electric / electronic parts, particularly motor components such as coils, rotors, stators and bearings. By encapsulating and curing the motor component with the unsaturated polyester resin composition of the present invention, it is possible to obtain an encapsulated motor that is firmly encapsulated and cured.

  When the unsaturated polyester resin composition of the present invention is used as an encapsulating material for electric / electronic parts, the method for enclosing the electric / electronic parts is not particularly limited, and methods known in the art can be used. For example, after the electrical / electronic component is encapsulated with the unsaturated polyester resin composition of the present invention, the unsaturated polyester resin composition of the present invention may be cured. Encapsulation molding may be performed by introducing the unsaturated polyester resin composition of the present invention into a mold containing electrical / electronic components by various molding methods such as compression molding, transfer molding, and injection molding. Moreover, hardening of the unsaturated polyester resin composition of this invention can be performed by heating to predetermined temperature. Curing conditions may be appropriately set according to the type of components used in the unsaturated polyester resin composition of the present invention, but generally, the curing temperature is 110 ° C. to 180 ° C., the curing time is 1 minute to 30 minutes, The molding pressure is 2 MPa to 10 MPa.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited by these.
Various physical properties of the unsaturated polyester resin composition and its cured product prepared in the following examples and comparative examples were evaluated as follows.

(1) Molding Shrinkage A shrinkage disk defined in JIS K6911 was produced by compression molding at a molding temperature of 150 ° C., a molding pressure of 10 MPa, and a molding time of 3 minutes, and the molding shrinkage was calculated according to JIS K6911. .
Here, it is desirable that the molding shrinkage is in the range of -0.03% to 0.03% in consideration of the shape of the electric / electronic component and use under a harsh environment.

(2) Heat resistance The heat resistance was evaluated by the retention rate of the bending strength of the cured product after the heat treatment relative to the bending strength of the cured product before the heat treatment (hereinafter abbreviated as “strength retention rate”).
For the bending strength, a test piece (80 mm × 10 mm × 4 mm) was produced by compression molding at a molding temperature of 140 ° C., a molding pressure of 10 MPa, and a molding time of 3 minutes, and the bending strength was measured according to JIS K6911.
The heat treatment of the test piece was performed by heating at 210 ° C. for 1000 hours in a dryer.
Here, the strength retention is desirably 70% or more in consideration of use in a harsh environment.

(3) Fluidity A spiral flow test mold provided with a spiral curved groove having a trapezoidal cross section (groove width: upper base 6 mm, lower base 8 mm, thickness 2 mm, length 120 cm) is attached to a 70 t transfer molding machine. The unsaturated polyester resin composition was injected under the conditions of molding temperature (mold temperature) 140 ° C., injection pressure 5 MPa, curing time 130 seconds, injection amount 50 g, and the spiral flow length (SF value) was measured.
Here, the SF value is desirably 70 cm or more in consideration of the shape of the electric / electronic component.

(4) Comprehensive evaluation In evaluation of said (1)-(3), what achieved said evaluation criteria was represented as (circle), and what failed to achieve any evaluation criteria was represented as x.

<Synthesis of (a) unsaturated polyester resin>
In a four-necked flask equipped with a thermometer, stirrer, nitrogen gas inlet tube and reflux condenser, 100 moles of fumaric acid, 80 moles of propylene glycol and 20 moles of hydrogenated bisphenol A are placed and heated and stirred under a nitrogen stream. While raising the temperature to 200 ° C., an unsaturated polyester was obtained by carrying out an esterification reaction according to a conventional method. Thereafter, a styrene monomer was added to the unsaturated polyester to obtain an unsaturated polyester resin. Here, the styrene monomer was added so that it might become 50 mass% in unsaturated polyester resin. Moreover, it was 12,000 when the weight average molecular weight (MW) of unsaturated polyester was measured on said conditions.

<Other ingredients>
(B) Dianal (trademark) BR-77 (MW: 65,000) manufactured by Mitsubishi Rayon Co., Ltd. was used as the acrylic resin.
(C) The styrene-diene copolymer includes an SBS thermoplastic elastomer having polystyrene as a hard segment and polybutadiene as a soft segment (Asaprene (trademark) T-411 manufactured by Asahi Kasei Chemicals Corporation, MW: 430,000, SBS system). The proportion of polystyrene part in the thermoplastic elastomer was 30% by mass).
(D) A glass chopped strand having a fiber diameter of 13 μm and a fiber length of 3 mm, 6 mm, or 9 mm was used as the glass fiber.
(E) As the inorganic filler, calcium carbonate (average particle size 1.9 μm) or alumina (average particle size 0.9 μm) was used.

<Preparation of unsaturated polyester resin compositions of Examples 1 to 6 and Comparative Examples 1 to 12>
Each of the above components was charged at a blending ratio shown in Table 1, and kneaded using a double-type kneader to obtain an unsaturated polyester resin composition. In addition, the unit of the mixture ratio of Table 1 is a mass part. Moreover, content of the styrene monomer in the used unsaturated polyester resin is 50 mass%.
The unsaturated polyester resin composition thus obtained was evaluated in the above (1) to (4). The results are shown in Tables 1 and 2.

As shown in Table 1, the unsaturated polyester resin compositions of Examples 1 to 6 had a small molding shrinkage ratio and a large strength retention and SF value, and were able to obtain a good comprehensive evaluation.
On the other hand, as shown in Table 2, the unsaturated polyester resin composition of Comparative Example 1 had a large molding shrinkage because the total amount of the component (b) and the component (c) was too small. It was. Since the unsaturated polyester resin composition of Comparative Example 2 contained too much component (d), the SF value was small. The unsaturated polyester resin composition of Comparative Example 3 had a large molding shrinkage because the mass ratio of the component (b) to the component (c) was not within a predetermined range. The unsaturated polyester resin composition of Comparative Example 4 had a low strength retention because the content of the component (d) was too small. In the unsaturated polyester resin composition of Comparative Example 5, since the content of the component (e) was too small, the molding shrinkage ratio increased and the strength retention ratio decreased. In the unsaturated polyester resin composition of Comparative Example 6, since the total amount of the component (b) and the component (c) was too much, the molding shrinkage ratio was increased and the strength retention ratio and the SF value were decreased. In the unsaturated polyester resin composition of Comparative Example 7, the total amount of the component (b) and the component (c) was too large, and the mass ratio of the component (b) to the component (c) was not within a predetermined range. As the molding shrinkage ratio increased, the strength retention ratio and SF value decreased. In the unsaturated polyester resin composition of Comparative Example 8, since the mass ratio of the component (b) and the component (c) was not within a predetermined range, the molding shrinkage ratio increased and the strength retention ratio decreased. In the unsaturated polyester resin compositions of Comparative Examples 9 and 10, the SF value was small because the fiber length of the component (d) was too long. In the unsaturated polyester resin composition of Comparative Example 11, since the mass ratio of the component (b) and the component (c) is not within a predetermined range, and the fiber length of the component (d) is too long, the SF value becomes small. It was. Since the unsaturated polyester resin composition of Comparative Example 12 contained too much component (e), the SF value was small.

  As can be seen from the above results, according to the present invention, it is possible to provide an unsaturated polyester resin composition that gives a cured product that has high fluidity during molding, a small molding shrinkage ratio, and excellent heat resistance. . Further, by encapsulating and curing the motor component with the unsaturated polyester resin composition having such characteristics, it is possible to provide an encapsulated motor in which the motor component is firmly encapsulated.

  Note that this international application claims priority based on Japanese Patent Application No. 2014-213739 filed on October 20, 2014, and the entire contents of this Japanese patent application are incorporated herein by reference. To do.

Claims (6)

(A) unsaturated polyester resin, (b) acrylic resin, (c) styrene-diene copolymer, (d) glass fiber having a fiber length of 5 mm or less, and (e) an unsaturated polyester resin composition containing an inorganic filler A thing,
(A) With respect to 100 parts by mass of the component, the total of the (b) component and the (c) component is 10 to 20 parts by mass, the (d) component is 30 to 55 parts by mass, and the (e) component is a 300 parts by weight to 550 parts by weight, and (b) weight ratio of the component and the component (c) is 1: 2 to 2: Ri 1 der,
The (a) unsaturated polyester resin contains an unsaturated polyester and a crosslinking agent, and the amount of the crosslinking agent in the (a) unsaturated polyester resin is 25% by mass to 85% by mass,
The unsaturated polyester resin composition according to (e), wherein the inorganic filler has an average particle size of 0.5 m to 30 m .   2. The unsaturated polyester resin according to claim 1, wherein the (c) styrene-diene copolymer is at least one selected from the group consisting of SBS-based thermoplastic elastomers and SIS-based thermoplastic elastomers. Composition.   The unsaturated polyester resin composition according to claim 1 or 2, wherein the inorganic filler (e) is calcium carbonate.   The unsaturated polyester resin composition according to any one of claims 1 to 3, wherein the unsaturated polyester resin composition is used for enclosing electric / electronic parts.   The unsaturated polyester resin composition according to claim 4, wherein the electric / electronic component is a motor component.   An encapsulated motor obtained by encapsulating and curing a motor component with the unsaturated polyester resin composition according to any one of claims 1 to 5.