JP6590338B2 - Bulk molding compound - Google Patents

Description

  The present invention relates to a bulk molding compound (hereinafter sometimes abbreviated as BMC), and more particularly to a bulk molding compound suitable for integrally fixing different parts such as metal and plastic. .

  Electrical parts such as home appliances are composed of many parts and have many production processes. Therefore, in recent years, packaging using a sealing resin that can improve productivity by integrating a plurality of parts and reducing processes has been adopted. The performance required for these sealing resins includes heat resistance, dimensional accuracy, corrosion resistance, mechanical strength, fluidity, etc., and radical polymerizable thermosetting as a resin that can satisfy these required performances. Resins, in particular unsaturated polyesters, are being used. However, sealing molding materials based on unsaturated polyesters have the problem of causing deformation and cracking of the molded product during heat cycling, and therefore there is a need for sealing molding materials with improved heat cycle resistance. It was. The cause of this problem is that the molding material for sealing based on unsaturated polyester generally tends to have a large coefficient of thermal expansion, and is largely based on the difference in coefficient of thermal expansion with the sealing component during the heat cycle. Since the stress is generated and molding materials used for sealing electrical parts such as home appliance parts are required to be capable of being sealed and molded at a low pressure, the amount and length of the fiber reinforcement is limited, and the strength of the material is reduced. It tends to be low and brittle, and cannot withstand the stress generated during the heat cycle.

  As a method for improving the toughness of the molding material for sealing, for example, there is a method using an unsaturated polyester having a high elongation rate using a long linear saturated dibasic acid such as adipic acid or sebacic acid as a raw material. However, such an unsaturated polyester has a problem that since the molecular weight is large, the flowability of the molding material is low, and low-pressure sealing molding is difficult.

  Technology to provide a sheet molding compound with excellent molding fluidity, good appearance of molded products, and excellent mechanical properties of molded products by using an unsaturated polyester resin composition containing urethane (meth) acrylate Is known (see, for example, Patent Document 1). However, since a large amount of fiber reinforcing material is blended in the sheet molding compound of Patent Document 1, a high pressure is required for molding, and it is difficult to use for sealing electrical parts such as home appliances. is there.

Japanese Patent No. 5379622

  Accordingly, an object of the present invention is to provide a bulk molding compound that can be sealed and molded at a low pressure and that is excellent in heat cycle resistance of the resulting molded product.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a specific urethane (meth) acrylate in a specific mass ratio in a bulk molding compound containing an unsaturated polyester, a reactive diluent and a fiber reinforcement. It discovered that the said subject could be solved by mix | blending, and came to complete this invention.

That is, the present invention is indicated by [1] to [2] below.
[1] A bulk molding compound containing unsaturated polyester, urethane (meth) acrylate, a crosslinking agent and a fiber reinforcing material, wherein the urethane (meth) acrylate has the following general formula

(In the formula, R ¹ is H or CH ₃ , R ² is a divalent hydrocarbon group, A is a structural unit derived from a polyester polyol having a weight average molecular weight of 500 to 4,000, R ³ is a divalent hydrocarbon group, and n, which is a repeating unit, is represented by 1-6),
The urethane (meth) acrylate is blended in an amount of 30 to 50 parts by mass with respect to 100 parts by mass of the unsaturated polyester, and the fiber reinforcement is 4 to 12% by mass in the bulk molding compound. Bulk molding compound characterized by being blended in the range of mass%.
[2] The bulk molding according to [1], further comprising an inorganic filler, wherein the inorganic filler is blended in the bulk molding compound in the range of 50% by mass to 70% by mass. compound.

  According to the present invention, it is possible to provide a bulk molding compound that can be sealed and molded at a low pressure and that is excellent in heat cycle resistance of the obtained molded product.

It is a schematic cross section of the mold for fluidity evaluation used for evaluating the thin wall fluidity of the bulk molding compound in the examples.

  The bulk molding compound of the present invention contains unsaturated polyester, urethane (meth) acrylate, a crosslinking agent and a fiber reinforcing material as essential components.

  In the present invention, “(meth) acrylate” means at least one selected from methacrylate and acrylate. The same applies to the “(meth) acryloyl group”.

  The unsaturated polyester used in the present invention is obtained by polycondensation of a polyhydric alcohol and an unsaturated polybasic acid, and the type thereof is not particularly limited as long as it is normally used as a molding material. Absent.

  Examples of the polyhydric alcohol used as the raw material for the unsaturated polyester include ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol, hexanediol, neopentanediol, hydrogenated bisphenol A, Bisphenol A, glycerol, etc. are mentioned. These polyhydric alcohols may be used alone or in combination of two or more.

  Examples of the unsaturated polybasic acid used as the raw material for the unsaturated polyester include maleic acid, maleic anhydride, fumaric acid, citraconic acid, itaconic acid and the like. Examples of the saturated polybasic acid include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, hetic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, endomethylenetetrahydro And phthalic anhydride. These unsaturated polybasic acids may be used alone or in combination of two or more.

  The urethane (meth) acrylate used in the present invention has the following general formula:

(In the formula, R ¹ is H or CH ₃ , R ² is a divalent hydrocarbon group, and is a residue derived from a hydroxyl group-containing (meth) acrylate that is one of the raw materials of urethane (meth) acrylate. R ² may have a substituent and is preferably an alkylene group having 2 to 4 carbon atoms, and examples of the substituent include a phenyl group, a phenoxy group, etc. A has a weight average molecular weight of 500 to 500. 4,000 is a structural unit derived from polyester polyol, R ³ is a divalent hydrocarbon group, and is a residue derived from a diisocyanate compound (repeating unit n is 1 to 6). It has a structure in which a (meth) acryloyl group is bonded to a base polyester polyol via a urethane bond. It is important that the value of n in the above general formula is in the range of 1-6. When the value of n exceeds 6, the viscosity of urethane (meth) acrylate increases, and workability decreases. The method for obtaining n as a repeating unit was obtained by calculating the weight average molecular weight by the GPC method. As an outline of the measurement, 1.0 to 2.0 mg of urethane (meth) acrylate is precisely weighed in a sample tube and dissolved in 2.5 ml of tetrahydrofuran (THF). Subsequently, the weight average molecular weight of the solution filtered through the membrane filter is determined using Shodex (trademark) GPC-101 manufactured by Showa Denko K.K. The number of repetitions is determined from the measured weight average molecular weight.

  Diisocyanate compounds used as raw materials for urethane (meth) acrylates include isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated. Examples include xylylene diisocyanate. These diisocyanate compounds may be used alone or in combination of two or more.

  The hydroxyl group-containing (meth) acrylate used as a raw material for urethane (meth) acrylate is hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate. Phenoxyhydroxypropyl acrylate, phenoxyhydroxypropyl methacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, dipropylene glycol monoacrylate, dipropylene glycol monomethacrylate and the like. These hydroxyl group-containing (meth) acrylates may be used alone or in combination of two or more.

  Polyester polyols used as raw materials for urethane (meth) acrylates include aliphatic glycols such as ethylene glycol, propylene glycol, dipropylene glycol, and hexanediol, and fats such as oxalic acid, fumaric acid, succinic acid, adipic acid, and sebacic acid. It is obtained by a condensation reaction with a group 2 dibasic acid. When a non-aliphatic glycol or a non-aliphatic dibasic acid is used, the elongation of urethane (meth) acrylate is reduced, and the effect of improving the toughness of the resulting molded product may not be obtained. It is important that the weight average molecular weight of the polyester polyol is 500 to 4,000. It is preferably 1,000 to 3,000, and more preferably 1,300 to 2,000. If the weight average molecular weight of the polyester polyol is less than 500, the elongation of the urethane (meth) acrylate becomes small, and the effect of improving the toughness of the resulting molded product cannot be obtained. On the other hand, when the weight average molecular weight of the polyester polyol exceeds 4,000, the elongation of the urethane (meth) acrylate increases, but the strength decreases and the effect of improving the toughness of the resulting molded product cannot be obtained.

  In the bulk molding compound of the present invention, the compounding amount of the urethane (meth) acrylate described above needs to be 30 parts by mass to 50 parts by mass with respect to 100 parts by mass of the unsaturated polyester, and 35 parts by mass to 45 parts by mass. It is preferable that it is a mass part. The effect which improves the toughness of the molded article obtained as the compounding quantity of urethane (meth) acrylate is less than 30 mass parts is not acquired. On the other hand, when the compounding amount of the urethane (meth) acrylate exceeds 50 parts by mass, the reactivity decreases, and the unreacted urethane (meth) acrylate is separated at the time of molding, and the surface of the obtained molded product is contaminated.

  In the present invention, the aforementioned unsaturated polyester and urethane (meth) acrylate are dissolved in a reactive diluent and used. Such a reactive diluent may be a liquid compound having at least one polymerizable double bond polymerizable with unsaturated polyester and urethane (meth) acrylate. Examples thereof include styrene, diallyl phthalate, diallyl phthalate prepolymer, methyl methacrylate, triallyl isocyanurate and the like.

Examples of the fiber reinforcing material used in the present invention include glass fiber, carbon fiber, organic fiber (for example, aramid fiber) and the like. These may be used alone or in combination of two or more. These fiber reinforcing materials are unsaturated polyester resins containing unsaturated polyester, urethane (meth) acrylate and reactive diluent, which are cut to a fiber length of about 3.0 to 12.5 mm in the same manner as ordinary bulk molding compounds. Used by impregnating the composition.
The fiber reinforcing material needs to be blended in the bulk molding compound in the range of 4% by mass to 12% by mass, and preferably in the range of 6% by mass to 10% by mass. The intensity | strength of the molded product obtained that the compounding quantity of a fiber reinforcement is less than 4 mass% falls. On the other hand, when the blending amount of the fiber reinforcing material exceeds 12% by mass, the unsaturated polyester resin composition does not sufficiently impregnate the fiber reinforcing material, and the fluidity at the time of molding decreases.

  In the bulk molding compound of the present invention, a curing agent, a low shrinkage agent, an inorganic filler, an internal mold release agent, a thickener, a polymerization inhibitor, a colorant and the like are used as necessary in addition to the above-described components. be able to. When these components are used, each component can be blended in the unsaturated polyester resin composition of the present invention within a range not impeding the effects of the present invention according to the respective purposes.

  Examples of the curing agent include t-butyl peroxy octoate, benzoyl peroxide, 1,1 di-t-butyl peroxy 3,3,5 trimethylcyclohexane, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate. , Peroxides such as dicumyl peroxide and di-t-butyl peroxide. These curing agents may be used alone or in combination of two or more. A hardening | curing agent can be added in 0.5 mass part-3.5 mass parts with respect to a total of 100 mass parts of unsaturated polyester, urethane (meth) acrylate, and a reactive diluent.

  As the low shrinkage agent, those generally used in bulk molding compounds can be used, and examples thereof include polystyrene, polyethylene, polymethyl methacrylate, polyvinyl acetate, saturated polyester, and polycaprolactone. These low shrinkage agents may be used alone or in combination of two or more. The low shrinkage agent can be added in the range of 10 to 30 parts by mass with respect to 100 parts by mass in total of the unsaturated polyester, urethane (meth) acrylate and crosslinking agent.

  Examples of the inorganic filler include inorganic powders such as silica, alumina, mica, aluminum hydroxide, calcium carbonate, gypsum, barium sulfate, clay, and talc. These inorganic fillers may be used alone or in combination of two or more. An inorganic filler can be added in the range of 50 mass%-70 mass% in a bulk molding compound. If the blending amount of the inorganic filler exceeds 70% by mass, the fluidity and moldability may be deteriorated. On the other hand, if the blending amount of the inorganic filler is less than 50% by mass, there is a case where the inorganic filler is not settled and may not be formed into a bulk molding compound.

  Examples of the internal release agent include stearic acid, oleic acid, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, stearic acid amide, oleic acid amide, silicone oil, synthetic wax and the like. These internal mold release agents may be used independently and may use 2 or more types together. An internal mold release agent can be added in 10 mass parts-20 mass parts with respect to a total of 100 mass parts of unsaturated polyester, urethane (meth) acrylate, and a crosslinking agent.

  Examples of the thickener include metal oxides such as magnesium oxide, magnesium hydroxide, calcium hydroxide, calcium oxide, and isocyanate compounds. These thickeners may be used alone or in combination of two or more. Note that the thickener is not necessarily used.

  Examples of the polymerization inhibitor include hydroquinone, trimethylhydroquinone, P-benzoquinone, naphthoquinone, t-butylhydroquinone, catechol, pt-butylcatechol, 2,6-di-t-butyl-4-methylphenol, and the like. It is done. These may be used alone or in combination of two or more. The polymerization inhibitor can be added in the range of 0.01 parts by mass to 1.0 part by mass with respect to 100 parts by mass in total of the unsaturated polyester, urethane (meth) acrylate, and crosslinking agent.

  The colorant is used when it is necessary to color a molded article, and various inorganic pigments and organic pigments that are usually used in bulk molding compounds can be used. What is necessary is just to adjust the usage-amount of a coloring agent suitably according to the coloring degree of a molded article.

  The bulk molding compound of the present invention constituted by the components as described above can be obtained by kneading using a commonly performed method such as a kneader.

  The bulk molding compound of the present invention thus obtained can be used for various molding means. For example, a wide range of molded products can be obtained by compression molding, transfer molding, or injection molding. The bulk molding compound of the present invention is capable of sealing and molding at a low pressure as compared with conventional bulk molding compounds, and the shape of the molded product is limited because of the excellent heat cycle resistance and toughness of the resulting molded product. Therefore, it is suitable for integrally fixing parts made of different materials such as metal, magnet and plastic. Also, the appearance of the molded product is comparable to that of conventional bulk molding compounds. Electrical parts such as home appliances obtained by integrally fixing different material parts using the bulk molding compound of the present invention have excellent heat cycle resistance.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples. Of course, the present invention is not limited by the following examples as long as the gist thereof is not exceeded.

Using a double-arm kneader, the components shown in Tables 1 and 2 were kneaded under the temperature condition of 30 ° C. to obtain BMCs of Examples 1 to 6. Similarly, each component was knead | mixed with the compounding composition shown to Table 3 and 4, and BMC of Comparative Examples 1-6 was obtained.
The BMC raw materials used here are as follows.

<Preparation of unsaturated polyester A>
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 100 mol of fumaric acid, 80 mol of propylene glycol and 20 mol of hydrogenated bisphenol A, and heated to 210 ° C. while stirring under a nitrogen stream. The esterification reaction was carried out by a conventional procedure. The degree of unsaturation of this unsaturated polyester was 100 mol%, and the weight average molecular weight was 10,000.
Next, 0.015 part by mass of hydroquinone was added to this unsaturated polyester, and this was dissolved in styrene to prepare unsaturated polyester A having an unsaturated polyester solid content of 60% by mass.

<Preparation of urethane acrylate A>
Into a 1 L four-necked flask equipped with a stirrer, a reflux condenser, a gas inlet tube and a thermometer, 466 g of a polyester polyol having a weight average molecular weight of 1,500 obtained from the condensation reaction of adipic acid and ethylene glycol, and 566 g of styrene Then, 0.17 g of hydroquinone was charged, and the mixture was heated to 80 ° C. Subsequently, 80 g of isophorone diisocyanate was added dropwise over 1.5 hours and stirred to form a terminal isocyanate-containing prepolymer. Next, 20 g of 2-hydroxyethyl acrylate was added dropwise over 0.5 hour, and then reacted until the absorption peak of the isocyanato group disappeared in the infrared absorption spectrum to obtain urethane acrylate A having a urethane acrylate solid content of 50% by mass. . N of this urethane acrylate calculated | required from the weight average molecular weight was 3.4.

<Preparation of urethane acrylate B>
In a 1 L four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction tube and a thermometer, 342 g of a polyester polyol having a weight average molecular weight of 400 obtained from the condensation reaction of adipic acid and ethylene glycol, 589 g of a styrene monomer, 0.17 g of hydroquinone was charged, and the mixture was heated to 80 ° C. Next, 212 g of isophorone diisocyanate was stirred while being dropped over 1.5 hours to produce a prepolymer containing terminal isocyanate. Subsequently, 35 g of 2-hydroxyethyl acrylate was added dropwise over 0.5 hours, and then reacted until the absorption peak of the isocyanato group disappeared in the infrared absorption spectrum to obtain urethane acrylate B having a urethane acrylate solid content of 50% by mass. . N of this urethane acrylate calculated | required from the weight average molecular weight was 5.7.

<Preparation of urethane acrylate C>
Into a 1 L four-necked flask equipped with a stirrer, reflux condenser, gas inlet tube and thermometer, 551 g of a polyester polyol having a weight average molecular weight of 5,000 obtained from the condensation reaction of adipic acid and ethylene glycol, styrene monomer 597 g and hydroquinone 0.17 g were charged, and the mixture was heated to 80 ° C. Next, 34 g of isophorone diisocyanate was stirred while being dropped over 1.5 hours to produce a terminal isocyanate-containing prepolymer. Next, 12 g of 2-hydroxyethyl acrylate was dropped over 0.5 hour, and then reacted until the absorption peak of the isocyanate group disappeared in the infrared absorption spectrum to obtain urethane acrylate C having a urethane acrylate solid content of 50% by mass. . N of this urethane acrylate calculated | required from the weight average molecular weight was 2.2.

<Reactive diluent>
styrene.

<Fiber reinforcement>
Chopped strand glass cut to about 9 mm.

<Curing agent>
t-Butyl peroxybenzoate.

<Low shrinkage agent>
Polystyrene having a styrene content of 20% by mass.

<Inorganic filler>
Calcium carbonate.

<Internal release agent>
Calcium stearate.

  About these BMC, the linear expansion coefficient, bending strength, bending elastic modulus, tensile strength, heat cycle resistance, and thin-wall fluidity | liquidity were evaluated in accordance with the following method. The evaluation results are shown in Tables 1 to 4.

(1) Linear expansion coefficient The linear expansion coefficient of the molded product was measured based on the TMA method. Molding conditions were as follows: mold temperature: 140 to 160 ° C., curing time: 180 seconds, press pressure: 15 MPa, mold size: 200 mm × 150 mm.

(2) Bending strength and bending elastic modulus Test pieces were prepared according to JIS K 6911-1995, and bending strength and bending elastic modulus were measured. Molding conditions were as follows: mold temperature: 140 to 160 ° C., curing time: 180 seconds, press pressure: 15 MPa, mold size: 200 mm × 150 mm.

(3) Tensile strength A test piece was prepared according to JIS K 6911-1995, and the tensile strength was measured. Molding conditions were as follows: mold temperature: 140 to 160 ° C., curing time: 180 seconds, press pressure: 15 MPa, mold size: 200 mm × 150 mm.

(4) Heat cycle resistance evaluation A heat cycle test was performed using a test piece in which a magnet was sealed. Using a thermostat with a temperature program function, holding at 120 ° C. for 60 minutes and then holding at −40 ° C. for 60 minutes was taken as one cycle, and this was performed for 10 cycles. Molding conditions were as follows: mold temperature: 140 to 160 ° C., curing time: 180 seconds, press pressure: 5 MPa, mold size: 200 mm × 200 mm. After the test, the surface of the molded article was visually checked for cracks and evaluated as follows.
○: No crack ×: Crack

(5) Thin-wall fluidity Using the mold for fluidity evaluation shown in FIG. 1, the molding temperature of 140 to 160 ° C., filling pressure: 10 MPa, and holding pressure: 3 MPa. The flow distance was measured, and the thin wall fluidity was evaluated according to the following criteria. It can be said that the longer the flow distance of BMC that has flowed to the gate portion, the better the moldability at low pressure. As shown in FIG. 1, the fluidity evaluation mold includes a movable mold part 2 provided with a sprue 1 and a fixed mold part 3. When the movable mold part 2 and the fixed mold part 3 are clamped, the runner part 4 and the gate part 5 are formed. The runner portion 4 has a rectangular parallelepiped shape having a length of 80 mm, a thickness of 3 mm, and a width of 30 mm, and is connected to the gate portion 5 at an end portion in the length direction. The gate portion 5 has a rectangular parallelepiped shape having a length of 100 mm, a thickness of 100 μm, and a width of 10 mm. The sprue portion 1 has a truncated cone shape having a height of 90 mm, and is configured to expand from the diameter of 5 mm (upper bottom diameter) to 10 mm (lower base diameter) toward the runner portion 4. In the fluidity evaluation mold configured as described above, the melted BMC is filled from the sprue portion 1 and flows to the gate portion 5 through the runner portion 4.
○: Flow distance to the gate part is 80 mm or more and 100 mm or less Δ: Flow distance to the gate part is 50 mm or more and less than 80 mm ×: Flow distance to the gate part is less than 50 mm

  As is clear from the results in Tables 1 and 2, the BMCs of the examples had good heat cycle resistance and thin wall fluidity. As is clear from the results of Tables 3 and 4, the BMC of the comparative example had poor heat cycle resistance and / or thin wall fluidity.

  From the above, it is clear that the BMC of the present invention is excellent in moldability at low pressure, unlike the conventional one, and the obtained molded product is excellent in heat cycle resistance. Therefore, the BMC of the present invention is extremely useful in the field of electrical parts such as home appliances that require heat resistance, dimensional accuracy, corrosion resistance, mechanical strength, fluidity, and the like, and can be used in a wide range. .

  1 sprue part, 2 movable mold part, 3 fixed mold part, 4 runner part, 5 gate part.

Claims (2)

A bulk molding compound containing unsaturated polyester, urethane (meth) acrylate, a reactive diluent and a fiber reinforcement, wherein the urethane (meth) acrylate has the following general formula:

(In the formula, R ¹ is H or CH ₃ , R ² is a divalent hydrocarbon group, A is a structural unit derived from a polyester polyol having a weight average molecular weight of 500 to 4,000, R ³ is a divalent hydrocarbon group, and n, which is a repeating unit, is represented by 1-6),
The urethane (meth) acrylate is blended in an amount of 30 to 50 parts by mass with respect to 100 parts by mass of the unsaturated polyester, and the fiber reinforcement is 4 to 12% by mass in the bulk molding compound. Bulk molding compound characterized by being blended in the range of mass%.   The bulk molding compound according to claim 1, further comprising an inorganic filler, wherein the inorganic filler is blended in the bulk molding compound in the range of 50% by mass to 70% by mass.

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