JP7740264B2 - Molding materials and molded products - Google Patents

Description

The present invention relates to a molding material and a molded article made using the molding material.

Conventionally, molding materials used as bulk molding compounds (BMC) or sheet molding compounds (SMC) have been widely used in applications such as chassis for office equipment and business machines, and lamp reflectors such as automobile headlamps, due to their excellent mechanical strength, rigidity, surface smoothness, dimensional accuracy, heat resistance, moldability, and other properties.

By blending inorganic fillers or fiber reinforcing materials, it is possible to impart the various properties mentioned above to molding materials, but this also increases the specific gravity of the molded product. Therefore, various efforts are being made to lower the specific gravity of molded products. For example, Patent Document 1 describes a resin composition containing hollow fillers.

JP 2013-216879 A

The need for lower specific gravity of molded products is growing year by year. As a result, research is being conducted into lowering the specific gravity of the inorganic filler used in molding materials and increasing the amount blended to lower the specific gravity of the molding material itself. However, increasing the amount of inorganic filler blended can cause the molding material to lose its integrity, making it difficult to mix properly using a kneader or other device. If the inorganic filler is made lower in specific gravity, it may be destroyed during mixing or molding, preventing the specific gravity of the molded product from being reduced.

The present invention was made to solve the above-mentioned problems, and aims to provide a molding material with a low specific gravity and good moldability. Another aim of the present invention is to provide a molded product with a low specific gravity that has excellent surface smoothness and heat resistance.

The present invention includes the following aspects.
[1]
(A) thermosetting resin,
(B) a reactive diluent;
(C) thermoplastic resin,
(D) hollow inorganic particles; and (E) a thermal polymerization initiator,
The (A) thermosetting resin contains at least an unsaturated polyester resin,
The content of the (C) thermoplastic resin is 5 to 15 mass %,
The true density of the hollow inorganic particles (D) is 0.3 to 0.7 g/cm ³ ,
The (D) hollow inorganic particles have a pressure resistance of 10 MPa or more,
The content of the (D) hollow inorganic particles is 35 to 70% by volume,
A molding material in which, when the theoretical specific gravity is a specific gravity calculated from the blending amount of the molding material, and the measured specific gravity is a specific gravity measured on a test piece obtained by molding a shrink disk specified in JIS K 6911:2006 by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes and cutting out the disk, the difference between the measured specific gravity and the theoretical specific gravity (measured specific gravity - theoretical specific gravity) is 0.03 or less.
[2]
The molding material according to [1], wherein the median diameter (d50) of the hollow inorganic particles (D) is 10 to 70 μm.
[3]
The molding material according to either [1] or [2], wherein the content of the (D) hollow inorganic particles is 20 to 50 mass%.
[4]
The molding material according to any one of [1] to [3], further comprising a fiber reinforcement (F), wherein the content of the fiber reinforcement (F) is 0.5 to 13 mass%.
[5]
A molded article comprising the molding material according to any one of [1] to [4] or a cured product thereof.
[6]
The molded article according to [5], having a specific gravity of 0.5 to 0.8.

The present invention can provide a molding material with a low specific gravity and good moldability. Furthermore, the present invention can provide a molded product with a low specific gravity and excellent surface smoothness and heat resistance.

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.

In this disclosure, "(meth)acrylic" means acrylic or methacrylic, "(meth)acrylate" means acrylate or methacrylate, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acryloxy" means acryloxy or methacryloxy.

<Molding material>
The molding material of one embodiment includes (A) a thermosetting resin, (B) a reactive diluent, (C) a thermoplastic resin, (D) hollow inorganic particles, and (E) a thermal polymerization initiator. The molding material may further include (F) a fiber reinforcing material, if necessary.

(A) Thermosetting Resin The (A) thermosetting resin contains at least an unsaturated polyester resin. The (A) thermosetting resin may contain, as necessary, a vinyl ester resin, a urethane (meth)acrylate resin, a diallyl phthalate resin, an epoxy resin, or a combination of two or more of these. In the present disclosure, each resin, such as the unsaturated polyester resin or the vinyl ester resin, does not contain the (B) reactive diluent described below.

Any unsaturated polyester resin known in the art can be used. Unsaturated polyesters are generally compounds obtained by polycondensation (esterification) of a polyhydric alcohol, an unsaturated polybasic acid, and, if necessary, a saturated polybasic acid. They can be appropriately selected and used depending on the desired properties. Unsaturated polyester resins may be used alone or in combination.

The polyhydric alcohol used in the synthesis of the unsaturated polyester resin is not particularly limited, and known polyhydric alcohols can be used. Examples of polyhydric alcohols include alkanediols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, and neopentanediol; (poly)oxyalkylene polyols such as diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; glycerin; and bisphenol compounds such as hydrogenated bisphenol A, bisphenol A, and bisphenol F. Among these, from the standpoints of heat resistance and moldability, alkanediols and bisphenol compounds are preferred. It is more preferable to use two or more selected from the group consisting of alkanediols and bisphenol compounds in combination, and it is even more preferable to use two or more selected from the group consisting of propylene glycol, neopentanediol, bisphenol A, and hydrogenated bisphenol A in combination. These polyhydric alcohols can be used alone or in combination.

The unsaturated polybasic acid used in the synthesis of the unsaturated polyester resin is not particularly limited, and any known polybasic acid having an ethylenically unsaturated bond can be used. Examples of unsaturated polybasic acids include maleic acid, maleic anhydride, fumaric acid, citraconic acid, and itaconic acid. Among these, maleic acid, maleic anhydride, and fumaric acid are preferred from the standpoints of heat resistance and moldability. These unsaturated polybasic acids can be used alone or in combination.

The saturated polybasic acid used in the synthesis of the unsaturated polyester resin is not particularly limited, and any known polybasic acid can be used, as long as it does not contain an ethylenically unsaturated bond. Examples of saturated polybasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrachlorophthalic anhydride, and tetrabromophthalic anhydride. These saturated polybasic acids can be used alone or in combination.

The content of unsaturated polyester resin in (A) thermosetting resin is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass. If the content of unsaturated polyester resin is 60% by mass or more, good curability and moldability are achieved.

The weight-average molecular weight of the unsaturated polyester resin is preferably 6,000 to 35,000, more preferably 7,000 to 20,000, and even more preferably 8,000 to 15,000. If the weight-average molecular weight is 6,000 to 35,000, the moldability of the molding material will be even better.

In the present disclosure, the term "weight average molecular weight" refers to a value measured at room temperature (23°C) using gel permeation chromatography (hereinafter also referred to as "GPC") under the following conditions and determined using a standard polystyrene calibration curve.
Apparatus: Shodex (registered trademark) GPC-101 manufactured by Showa Denko K.K.
Column: LF-804 manufactured by Showa Denko K.K.
Column temperature: 40°C
Sample: 0.2% by mass solution of sample in tetrahydrofuran Flow rate: 1 mL/min Eluent: tetrahydrofuran Detector: RI-71S

The degree of unsaturation of the unsaturated polyester resin is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, and even more preferably 70 to 100 mol%. When the degree of unsaturation is within the above range, the moldability of the molding material is better. The degree of unsaturation of the unsaturated polyester resin can be calculated using the following formula using the number of moles of the unsaturated polybasic acid and saturated polybasic acid used as raw materials.
Degree of unsaturation (mol %)={(number of moles of unsaturated polybasic acid×number of ethylenically unsaturated bonds per molecule of unsaturated polybasic acid)/(number of moles of unsaturated polybasic acid+number of moles of saturated polybasic acid)}×100

Vinyl ester resins known in the art can be used. Vinyl ester resins are generally compounds containing ethylenically unsaturated bonds obtained by a ring-opening reaction between an epoxy group in an epoxy compound containing two or more epoxy groups and a carboxy group in an unsaturated monobasic acid containing an ethylenically unsaturated bond and a carboxy group. Such vinyl ester resins are described, for example, in the Polyester Resin Handbook (published by Nikkan Kogyo Shimbun, 1988). Vinyl ester resins may be used alone or in combination.

As a urethane (meth)acrylate resin, for example, a resin obtained by introducing (meth)acryloyl groups into the hydroxyl groups or isocyanato groups at both ends of a polyurethane obtained by reacting a polyisocyanate with a polyhydric alcohol can be used.

As polyhydric alcohols, the compounds described as raw materials for the unsaturated polyester resins above can be used without any particular restrictions.

Examples of polyisocyanates include aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, and trimethylhexane diisocyanate; cyclic aliphatic polyisocyanates such as hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6)-diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,3-(isocyanatomethyl)cyclohexane; aromatic polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate; and adducts, isocyanurates, and biurets of these polyisocyanates. Polyisocyanates may be used alone or in combination.

When introducing a (meth)acryloyl group, for example, a method can be used in which a terminal isocyanato group is reacted with a hydroxyl group-containing (meth)acrylic compound, or a method can be used in which a terminal hydroxyl group is reacted with an isocyanato group-containing (meth)acrylic compound such as 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, or 1,1-bis(acryloyloxymethyl)ethyl isocyanate. Examples of hydroxyl group-containing (meth)acrylic compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, tris(hydroxyethyl)isocyanuric acid di(meth)acrylate, pentaerythritol tri(meth)acrylate, glycerin mono(meth)acrylate, and hydroxyethyl acrylamide, with 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, and hydroxyethyl acrylamide being preferred. The isocyanato group-containing (meth)acrylic compounds and hydroxyl group-containing (meth)acrylic compounds may each be used alone or in combination of two or more.

Diallyl phthalate resins known in the art can be used. Diallyl phthalate resins may be used alone or in combination of two or more types.

There are no particular restrictions on the epoxy resin, as long as it is a compound having two or more epoxy groups. Preferably, it is at least one selected from the group consisting of bisphenol-type epoxy compounds and novolac phenol-type epoxy compounds, and more preferably, it is a bisphenol-type epoxy compound. Epoxy resins may be used alone or in combination of two or more types.

Examples of bisphenol-type epoxy compounds include those obtained by reacting a bisphenol compound such as bisphenol A, bisphenol F, bisphenol S, or tetrabromobisphenol A with epichlorohydrin and/or methylepichlorohydrin; and those obtained by reacting a condensate of a compound obtained by glycidyl etherifying one or more of the above bisphenol compounds with one or more of the above bisphenol compounds with epichlorohydrin and/or methylepichlorohydrin. Among these, from the standpoint of durability, reaction products of bisphenol compounds with epichlorohydrin are preferred, and reaction products of bisphenol A with epichlorohydrin are more preferred.

Novolak phenol-type epoxy compounds include, for example, those obtained by reacting phenol novolak or cresol novolak with epichlorohydrin and/or methyl epichlorohydrin.

The content of (A) thermosetting resin is preferably 30 to 75% by mass, and more preferably 35 to 65% by mass, based on the total mass of (A) thermosetting resin and (B) reactive diluent. When the content of (A) thermosetting resin is 30% by mass or more, the workability of the molding material and the dimensional accuracy of the molded product are good. When the content of (A) thermosetting resin is 75% by mass or less, the curability of the molding material is good.

(B) Reactive Diluent The (B) reactive diluent is a compound having at least one polymerizable ethylenically unsaturated bond as a polymerizable functional group in the molecule. The (B) reactive diluent may be a monofunctional monomer or a polyfunctional monomer. By using a molding material containing the (B) reactive diluent, it is easy to adjust the viscosity.

(B) Examples of monofunctional monomers used as reactive diluents include (meth)acrylamide compounds such as (meth)acrylamide, N-methylol (meth)acrylamide, methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, and butoxymethoxymethyl (meth)acrylamide; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Examples of the monofunctional monomer include (meth)acrylate compounds such as 2-(meth)acryloyloxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxyethyl phthalate, glycerin mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, and half (meth)acrylates of phthalic acid derivatives; aromatic vinyl compounds such as styrene, α-methylstyrene, α-chloromethylstyrene, and vinyltoluene; and carboxylic acid esters such as vinyl acetate and vinyl propionate. The monofunctional monomers may be used alone or in combination of two or more.

(B) Examples of polyfunctional monomers used as reactive diluents include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, ethylene glycol diglycidyl Ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, glycerin triacrylate, glycerin polyglycidyl ether poly(meth)acrylate, urethane (meth)acrylate (for example, a polyisocyanate such as tolylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, etc., and a hydroxy group-containing (meth)acrylate such as 2-hydroxyethyl (meth)acrylate, Examples of the polyfunctional monomer include (meth)acrylate compounds such as tris(hydroxyethyl)isocyanurate, tri(meth)acrylate, and the like; aromatic vinyl compounds such as divinylbenzene, diallyl phthalate, and diallyl benzene phosphonate; dicarboxylic acid esters such as divinyl adipate; triallyl cyanurate; and (meth)acrylamide compounds such as methylene bis(meth)acrylamide, (meth)acrylamide methylene ether, and condensates of polyhydric alcohols and N-methylol (meth)acrylamide. The polyfunctional monomers may be used alone or in combination of two or more.

Among these, styrene monomer is preferred as the (B) reactive diluent from the standpoint of availability and cost.

The total content of (A) thermosetting resin and (B) reactive diluent in the molding material is preferably 25 to 80% by mass, more preferably 30 to 65% by mass, and even more preferably 35 to 50% by mass. When the total content of (A) thermosetting resin and (B) reactive diluent is 25% by mass or more, kneadability or fluidity during molding is good. When the total content of (A) thermosetting resin and (B) reactive diluent is 80% by mass or less, the dimensional accuracy of the molded product or the moldability of the molding material is good.

(C) Thermoplastic Resin The thermoplastic resin (C) is not particularly limited as long as it exhibits thermal plasticity, and any resin known in the art can be used. The use of the thermoplastic resin (C) improves the integrity of the molding material, allowing the content of the hollow inorganic particles (D) to be increased while maintaining good moldability, thereby reducing the specific gravity of the molding material.

(C) Examples of thermoplastic resins include polystyrene, polymethyl methacrylate, polyvinyl acetate, saturated polyester, and styrene-butadiene rubber. These thermoplastic resins may be used alone or in combination of two or more. Among these, polystyrene and styrene-butadiene rubber are preferred from the standpoint of dimensional accuracy and color unevenness of the molded product.

The content of (C) thermoplastic resin in the molding material is 5 to 15% by mass, and preferably 7 to 13% by mass. When the content of (C) thermoplastic resin is 5% by mass or more, the dimensional stability of the molded product or the kneadability of the molding material is good. When the content of (C) thermoplastic resin is 15% by mass or less, the curability of the molding material is good.

(D) Hollow Inorganic Particles Examples of (D) hollow inorganic particles include glass balloons, silica balloons, and alumina balloons. Among these, glass balloons are preferred from the viewpoint of pressure resistance. These hollow inorganic particles may be used alone or in combination of two or more. By using (D) hollow inorganic particles, the specific gravity of the molding material can be reduced, and the molding material can be molded to obtain a molded product with a low specific gravity.

The true density of the (D) hollow inorganic particles is 0.3 to 0.7 g/ ^cm3 , preferably 0.3 to 0.5 g/ ^cm3 , and more preferably 0.38 to 0.45 g/ ^cm3 . If the true density of the (D) hollow inorganic particles is less than 0.3 g/ ^cm3 , the pressure resistance strength of the (D) hollow inorganic particles themselves will be insufficient, and the (D) hollow inorganic particles will be damaged during production of the molding material or molding. If the true density of the (D) hollow inorganic particles is greater than 0.7 g/ ^cm3 , the specific gravity of the (D) hollow inorganic particles will be high. In either case, the desired low specific gravity as a molding material cannot be achieved, which is undesirable.

The pressure resistance strength of the (D) hollow inorganic particles is 10 MPa or more, and preferably 20 MPa or more. If the pressure resistance strength of the (D) hollow inorganic particles is less than 10 MPa, the (D) hollow inorganic particles will be destroyed during the production of the molding material or during molding, making it impossible to achieve the desired low specific gravity of the molded product, which is undesirable. There is no particular upper limit for the pressure resistance strength of the (D) hollow inorganic particles, but it is generally 200 MPa or less.

In this disclosure, the pressure resistance strength of (D) hollow inorganic particles is the pressure value at which 10 volume percent of the (D) hollow inorganic particles are broken when pressure is applied to (D) hollow inorganic particles dispersed in glycerol in accordance with ASTM D3102-78 (1982) "Practice for Determination of Isostatic Collapse Strength of Hollow Glass Microspheres."

The median diameter (d50) of the (D) hollow inorganic particles is preferably 10 to 70 μm, more preferably 15 to 60 μm, and even more preferably 20 to 50 μm. When the median diameter (d50) of the (D) hollow inorganic particles is 10 μm or more, the viscosity as a molding material can be kept within an appropriate range. When the median diameter (d50) of the (D) hollow inorganic particles is 70 μm or less, the (D) hollow inorganic particles are not destroyed during the production of the molding material or during molding, and the (D) hollow inorganic particles do not become highly dense, resulting in good surface smoothness and specific gravity of the molded product.

In the present disclosure, the median diameter (d50) of (D) hollow inorganic particles is determined by laser diffraction/scattering method.

The content of (D) hollow inorganic particles in the molding material is 35 to 70 volume %, preferably 50 to 65 volume %, and more preferably 55 to 65 volume %. If the content of (D) hollow inorganic particles is less than 35 volume %, the specific gravity of the molded product will be high, which is undesirable. If the content of (D) hollow inorganic particles is more than 70 volume %, the molding material will not be able to achieve integrity and will not be able to be sufficiently kneaded. This will result in poor moldability of the molding material and a significant decrease in surface smoothness of the molded product. In this disclosure, the content (vol %) of (D) hollow inorganic particles is the content at a temperature condition of 23°C, and is the theoretical volume % calculated by dividing the amount of each raw material used by its specific gravity to determine the theoretical volume of each, and then dividing the theoretical volume of (D) hollow inorganic particles by the sum of the theoretical volumes of each raw material determined above.

(D) The content of hollow inorganic particles in the molding material is preferably 20 to 50 mass%, more preferably 30 to 50 mass%, and even more preferably 35 to 45 mass%.

Since the kneadability and moldability of the molding material are greatly affected by the content (volume %) of (D) hollow inorganic particles, it is preferable to control the content of (D) hollow inorganic particles by volume rather than by mass.

(E) Thermal Polymerization Initiator As the (E) thermal polymerization initiator, peroxides known in the technical field can be used. Examples of the (E) thermal polymerization initiator include 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. These thermal polymerization initiators may be used alone or in combination of two or more.

The content of (E) the thermal polymerization initiator in the molding material is preferably 0.1 to 5% by mass, more preferably 0.5 to 4% by mass, and even more preferably 0.8 to 3% by mass. If the content of (E) the thermal polymerization initiator is within the above range, good curing properties can be obtained as a molding material.

(F) Fiber Reinforcement The molding material may further contain (F) a fiber reinforcement. The (F) fiber reinforcement is a fibrous substance with an aspect ratio of 3 or more. The aspect ratio can be measured by the microscopic method described in JIS Z 8900-1:2008, "Particles for Calibration of Particle Diameter Measuring Devices." Examples of the (F) fiber reinforcement include organic and inorganic fibers such as glass fiber, pulp fiber, Tetron (registered trademark) fiber, vinylon fiber, carbon fiber, aramid fiber, and wollastonite. Examples of the form of the (F) fiber reinforcement include a sheet-like material using continuous or discontinuous fibers, roving, and chopped strands. The (F) fiber reinforcement may be used alone or in combination of two or more types. Among these, glass fiber is preferred from the standpoints of cost and dispersibility, and chopped strand glass is more preferred.

(F) The fiber length of the fiber reinforcing material is not particularly limited, but is preferably 1 mm to 25 mm, more preferably 1.5 mm to 15 mm, and even more preferably 1.5 mm to 13 mm. A fiber length of 1 to 25 mm will result in good kneadability with the resin and good fluidity during molding. The fiber length is the number average value measured using a vernier caliper or a micrometer on an optical microscope for 100 randomly selected fibers.

When (F) fiber reinforcement is used, the content of (F) fiber reinforcement in the molding material is preferably 0.5 to 13% by mass, more preferably 3 to 13% by mass, and even more preferably 4 to 13% by mass. When the content of (F) fiber reinforcement is 0.5% by mass or more, the molding material has good moldability. When the content of (F) fiber reinforcement is 13% by mass or less, the content of (D) hollow inorganic particles can be relatively increased, allowing the molded product to have a desired low specific gravity. When the content of (F) fiber reinforcement is 13% by mass or less, it is possible to prevent the (F) fiber reinforcement from destroying the (D) hollow inorganic particles during molding, which also contributes to achieving the desired low specific gravity.

(G) Optional Components In addition to the above components, the molding material of one embodiment may optionally contain inorganic fillers, release agents, thickeners, viscosity reducers, pigments, etc. When these components are used, each component may be used in an amount typically used depending on the respective purpose.

Examples of inorganic fillers include powdered materials such as calcium carbonate, aluminum hydroxide, wollastonite, clay, talc, mica, and silicic anhydride.

Examples of release agents that can be used include stearic acid, zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, or carnauba wax in appropriate proportions.

Examples of thickeners include metal oxides such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and calcium oxide, and isocyanate compounds.

<Method of manufacturing molding material>
The form of the molding material is not particularly limited, but it is preferable that the molding material be a thermosetting resin molding material such as a bulk molding compound (hereinafter referred to as "BMC") or a sheet molding compound (hereinafter referred to as "SMC"), from the viewpoint of diversifying the shape of the cured product and providing excellent productivity.

The BMC molding material can be produced using the same method as in conventional BMC production, for example, by kneading under the following conditions using a kneader. The components except for (F) the fiber reinforcement are added to a double-arm kneader with the jacket temperature set to a range of 20-50°C, the lid is closed, and the mixture is kneaded for 20-60 minutes until the components are sufficiently dispersed and form a putty. After the resin mixture has formed into a putty, the lid is opened, and the (F) fiber reinforcement is gradually added over 1-2 minutes while kneading. After the specified amount has been added, the lid is closed and the mixture is kneaded for 5-60 minutes until the (F) fiber reinforcement is uniformly dispersed. After kneading is complete, the resulting BMC is packaged in a laminate film of polyethylene film and polyethylene terephthalate film, vinylon film, or the like.

SMC molding materials can be manufactured using a standard SMC manufacturing equipment using the following method. First, all components except for (F) the fiber reinforcement are mixed using a mixer or other device to obtain a resin mixture. While there are no particular restrictions on the order in which the raw materials are mixed or the type of mixer, a mixing temperature of 20 to 45°C is preferred. Next, the resin mixture is applied to a uniform thickness on carrier films installed above and below the SMC manufacturing equipment. There are no particular restrictions on the carrier films as long as they are commonly used, but polyethylene film, polypropylene film, etc. can be used. Next, (F) the fiber reinforcement, cut to a predetermined length (e.g., 12 to 25 mm), is sprayed onto the lower carrier film coated with the resin mixture. The resulting sheet is then sandwiched between the upper and lower carrier films and passed through impregnation rolls while applying pressure to the entire surface to form a sheet, which is then wound into a roll or packaged in a zigzag fold. The resulting sheet is preferably aged at room temperature to 60°C for 1 to 240 hours. By aging the film at room temperature to 60° C. for 1 to 240 hours, the carrier film can be easily peeled off, and there is little stickiness when the carrier film is peeled off, resulting in a sheet with good workability.

<Molded product>
A molded article according to one embodiment can be obtained by molding the molding material. By using the molding material, a molded article having a low specific gravity and excellent physical properties such as surface smoothness, rigidity, and heat resistance can be obtained. By heating the molding material after molding as necessary, a molded article containing a cured product of the molding material can also be obtained.

The specific gravity of the molded product is preferably 0.5 to 0.8, and more preferably 0.6 to 0.8. A specific gravity of 0.5 or higher results in good moldability. A specific gravity of 0.8 or lower achieves a sufficiently low specific gravity. The specific gravity of the molded product in this disclosure is the numerical value of the specific gravity of the compression-molded product measured in accordance with JIS K 6911:2006.

The difference (measured specific gravity - theoretical specific gravity) between the specific gravity obtained by actually measuring the molded product (measured specific gravity) and the specific gravity calculated from the blending amount of the molding material (theoretical specific gravity) is 0.03 or less, and preferably 0.02 or less. When the difference between the measured specific gravity and the theoretical specific gravity is 0.03 or less, it is possible to obtain a molded product with the desired low specific gravity, in which the shape of the (D) hollow inorganic particles is sufficiently maintained during molding. The measured specific gravity in this disclosure is the value measured at 23°C on a test specimen obtained by molding and cutting out a shrink disk as specified in JIS K 6911:2006 by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes.

<Method of manufacturing molded products>
Molded articles can be produced by subjecting the above-mentioned molding materials to various molding methods, such as compression molding, transfer molding, and injection molding.

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

[Preparation of molding material]
Example 1
Using a double-arm kneader with the jacket temperature set at 40° C., the components in the composition shown in Table 1 were kneaded for 30 minutes to obtain a molding material of Example 1.

(Examples 2 to 5)
Molding materials of Examples 2 to 5 were obtained in the same manner as in Example 1, except that the compositions shown in Table 1 were used.

(Comparative Examples 1 to 9)
Molding materials of Comparative Examples 1 to 9 were obtained in the same manner as in Example 1, except that the compositions shown in Table 2 were used.

[Raw materials]
The following raw materials were used:

(A) Thermosetting resin/unsaturated polyester resin: a resin obtained by polycondensation of maleic acid (100 mol), propylene glycol (50 mol), and neopentanediol (50 mol) (weight average molecular weight 11,000, specific gravity 1.1)

(B) Reactive diluent: styrene monomer (manufactured by Asahi Kasei Corporation, specific gravity 0.91)

(C) Thermoplastic resin/polystyrene (manufactured by Sekisui Plastics Co., Ltd., weight average molecular weight 200,000, specific gravity 1.05)
Styrene-butadiene rubber (product name: Asaprene (trademark) T-411, manufactured by Asahi Kasei Corporation, styrene/butadiene ratio = 30/70, specific gravity 0.95)

(D) Hollow inorganic particles/glass balloons (product name: K25, manufactured by 3M Japan Ltd., pressure resistance strength 5 MPa, true density 0.25 g/cm ³ , median diameter (d50) 55 μm)
Glass balloon (product name: VS5500, manufactured by 3M Japan Ltd., pressure resistance 38 MPa, true density 0.38 g/cm ³ , median diameter (d50) 44 μm)
Glass balloon (product name: K46, manufactured by 3M Japan Ltd., pressure resistance 41 MPa, true density 0.46 g/cm ³ , median diameter (d50) 40 μm)

(E) Thermal polymerization initiator: t-butyl peroxybenzoate (manufactured by NOF Corporation)

(F) Fiber reinforcement material: glass chop (manufactured by Nitto Boseki Co., Ltd., fiber length 3.0 mm)

(G) Optional component (mold release agent)
Calcium stearate (NOF Corporation)

[Evaluation method]
The molding materials were evaluated for the following items.
(1) (D) Content of hollow inorganic particles (volume %)
The calculation was made using the theoretical volume calculated from the specific gravity and blending amount of each raw material.

(2) Theoretical specific gravity: Calculated from the blending amount of molding material.

(3) Molded product specific gravity (measured specific gravity)
A shrink disk as specified in JIS K 6911:2006 was molded by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes, and then a test piece was cut out and its specific gravity (23°C) was measured in accordance with JIS K 6911:2006.

(4) Moldability: A disk for measuring appearance after heating according to JIS K 6911:2006 was obtained by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes. The mold releasability and filling property of the disk for measuring appearance were evaluated visually. The evaluation criteria were A: very good, B: good, C: slightly poor, and D: poor.

(5) Surface Appearance: A disk for measuring appearance after heating according to JIS K 6911:2006 was obtained by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes. The surface appearance of the disk for measuring appearance was evaluated visually. The evaluation criteria were A: very good, B: good, C: slightly poor, and D: poor.

(6) Glossiness A disk for measuring appearance after heating as specified in JIS K 6911:2006 was obtained by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes. The glossiness of the disk for measuring appearance was measured using a HANDY GLOSSMETER PG-1M manufactured by Nippon Denshoku Industries Co., Ltd., based on Method 3 of JIS Z 8741:1997 "Specular Glossiness - Measurement Method."

(7) Heat resistance (appearance after heating)
Disks for measuring appearance after heating, as specified in JIS K 6911:2006, were obtained by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes. The appearance change at 180°C was evaluated based on JIS K 6911:2006 "Appearance after heating." The evaluation criteria were A: no change, B: blistering, and C: cracking.

The compositions and evaluation results of the molding materials for Examples 1 to 5 are shown in Table 1, and the compositions and evaluation results of the molding materials for Comparative Examples 1 to 9 are shown in Table 2. The molding materials for Comparative Examples 1, 2, 6, and 7 could not be manufactured in an integrated form, so their properties were not evaluated.

The molding materials and molded articles of the present invention can be widely used in applications such as chassis for office equipment or business machines, and lamp reflectors such as automotive headlamps.

Claims (5)

(A) thermosetting resin,
(B) a reactive diluent;
(C) thermoplastic resin,
(D) hollow inorganic particles; and (E) a thermal polymerization initiator,
The (A) thermosetting resin contains at least an unsaturated polyester resin,
the reactive diluent (B) is a compound having at least one polymerizable ethylenically unsaturated bond,
The content of the (C) thermoplastic resin is 5 to 15 mass %,
The true density of the hollow inorganic particles (D) is 0.3 to 0.7 g/cm ³ ,
the (D) hollow inorganic particles have a pressure resistance strength of 10 MPa or more, and the pressure resistance strength is a pressure value measured when 10% by volume of the (D) hollow inorganic particles are broken when pressure is applied to the (D) hollow inorganic particles dispersed in glycerol in accordance with ASTM D3102-78 (1982) "Practice for Determination of Isostatic Collapse Strength of Hollow Glass Microspheres";
The content of the (D) hollow inorganic particles is 35 to 70% by volume,
The content of the (D) hollow inorganic particles is 30 to 50 mass %,
A molding material in which, when the theoretical specific gravity is a specific gravity calculated from the blending amount of the molding material, and the measured specific gravity is a specific gravity measured on a test piece obtained by molding a shrink disk specified in JIS K 6911:2006 by compression molding at a molding temperature of 150°C, a molding pressure of 2 MPa, and a molding time of 3 minutes and cutting out the disk, the difference between the measured specific gravity and the theoretical specific gravity (measured specific gravity - theoretical specific gravity) is 0.03 or less. The molding material according to claim 1, wherein the median diameter (d50) of the hollow inorganic particles (D) is 10 to 70 μm. The molding material according to claim 1 or 2 , further comprising a fiber reinforcement (F), wherein the content of the fiber reinforcement (F) is 0.5 to 13 mass %. A molded article comprising the molding material according to any one of claims 1 to 3 or a cured product thereof. 5. The molded article according to claim 4 , having a specific gravity of 0.5 to 0.8.