JP7549572B2 - Masterbatch for polycarbonate resin, polycarbonate resin composition, injection foam molded product, and method for producing same - Google Patents

Description

The present invention relates to a masterbatch for polycarbonate-based resins containing thermally expandable microcapsules capable of improving the appearance of injection foam molded articles of polycarbonate-based resin compositions, a polycarbonate-based resin composition, an injection foam molded article, and a method for producing the same.

In the injection foaming of resins, thermally decomposable chemical foaming agents such as sodium bicarbonate are often used. Thermally expandable microcapsules that expand and foam when heated are also used in the injection foaming of resins. In general, from the viewpoint of dispersibility in the base resin and workability, chemical foaming agents and thermally expandable microcapsules are often used in masterbatches containing 20 to 60% by weight of a thermoplastic resin or a thermoplastic elastomer. For example, Patent Document 1 describes a foaming agent masterbatch whose main components are an ethylene-α-olefin copolymer and a thermally decomposable foaming agent. Patent Document 2 describes a masterbatch containing thermally expandable microcapsules, a carrier resin containing an olefin polymer, and a lubricant.

There is also a method of physical foaming in which a supercritical fluid such as carbon dioxide or nitrogen is directly impregnated into the molten resin in the cylinder of an injection molding machine to cause foaming. For example, Patent Document 3 describes a method of producing a foamed molded article by melting and kneading a resin composition with a sea-island structure in which a resin (A) constituting the sea phase and a resin (B) constituting the island layer are kneaded in an injection molding machine, injecting a supercritical fluid into the molten resin composition, and injection molding it.

JP 2013-142146 A JP 2017-082244 A JP 2015-151461 A

However, when polycarbonate-based resin is foamed using a master batch of the foaming agent described in Patent Document 1, the thermal decomposition type foaming agent such as sodium bicarbonate generates moisture and metal components when gas is generated, which accelerates the hydrolysis of the polycarbonate-based resin, causing whitening due to low molecules generated by hydrolysis on the surface of the injection foamed product, resulting in a problem of poor appearance. When polycarbonate-based resin is foamed using a master batch of the thermally expandable microcapsules described in Patent Document 2, the carrier resin contains an olefin polymer, so whitening due to incompatible olefin components occurs on the surface of the injection foamed product, resulting in a problem of poor appearance. When polycarbonate-based resin is foamed by physical foaming as described in Patent Document 3, whitening due to impregnated gas occurs, resulting in a problem of poor appearance.

In order to solve the above-mentioned problems of the conventional art, the present invention provides a masterbatch for polycarbonate-based resins containing thermally expandable microcapsules that can produce injection foam molded products of polycarbonate-based resin compositions with suppressed whitening and good appearance, a polycarbonate-based resin composition, an injection foam molded product, and a method for producing the same.

The present invention relates to a master batch for polycarbonate-based resins (C) containing thermally expandable microcapsules (A) and a carrier resin composition (B), characterized in that the carrier resin composition (B) is a carrier resin composition (B1) containing a polystyrene-based resin having a weight-average molecular weight of 1,000 or more and less than 180,000 and being solid at 20°C, or the carrier resin composition (B) is a carrier resin composition (B2) containing a polystyrene-based resin that is solid at 20°C and an acrylic-based plasticizer having a weight-average molecular weight of 1,000 or more and 20,000 or less and being liquid at 20°C, or the carrier resin composition (B) is a carrier resin composition (B3) containing a polyester-based copolymer having a weight-average molecular weight of 1,000 or more and 10,000 or less and being solid at 20°C, and an acrylic-based plasticizer having a weight-average molecular weight of 1,000 or more and 20,000 or less and being liquid at 20°C.

The polystyrene resin preferably has a glass transition temperature of 25°C or higher and 130°C or lower.

The carrier resin composition (B1) may contain 0 parts by weight or more and less than 3 parts by weight of an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less per 100 parts by weight of polystyrene resin having a weight average molecular weight of 1,000 or more and less than 180,000.

In the carrier resin composition (B2), the weight average molecular weight of the polystyrene resin may be 1,000 or more and 450,000 or less.

The carrier resin composition (B) preferably has a shear viscosity at 130° C. of 1.0×10 ⁻⁴ Pa·s or more and 1.0×10 ⁶ Pa·s or less.

It is preferable that the carrier resin composition (B) is compatible with polycarbonate-based resins.

The thermally expandable microcapsule (A) has a core-shell structure and is composed of a core composed of one or more compounds having a boiling point of 10°C or more and 330°C or less, and a shell encapsulating the core. The shell may be composed of a resin having structural units derived from one or more monomers selected from the group consisting of nitrile-based monomers, (meth)acrylate-based monomers, aromatic vinyl-based monomers, diene-based monomers, vinyl-based monomers having a carboxyl group, and monomers having one or more reactive functional groups selected from the group consisting of methylol groups, hydroxyl groups, amino groups, epoxy groups, and isocyanate groups.

It is preferable that the thermally expandable microcapsule (A) has a maximum expansion temperature of 180°C or higher and 300°C or lower.

In the resin constituting the shell, it is preferable that the concentration of structural units derived from one or more monomers selected from the group consisting of monomers containing a carboxyl group and monomers containing an amino group is 12 mmol/g or less.

It is preferable that the average particle diameter of the thermally expandable microcapsules (A) is 0.5 μm or more and 50 μm or less.

The master batch (C) preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A) and 20% by weight or more and 70% by weight or less of the carrier resin composition (B).
When the master batch (C) contains the carrier resin composition (B1), it preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A) and 20% by weight or more and 70% by weight or less of the carrier resin composition (B1).
When the master batch (C) contains the carrier resin composition (B2), it preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 15% by weight or more and 40% by weight or less of the polystyrene-based resin, and 5% by weight or more and 30% by weight or less of the acrylic plasticizer.
When the master batch (C) contains the carrier resin composition (B3), it preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 15% by weight or more and 40% by weight or less of the polyester-based copolymer, and 5% by weight or more and 30% by weight or less of the acrylic plasticizer.

The present invention also relates to a polycarbonate-based resin composition containing 1% by weight or more and 5% by weight or less of the above-mentioned master batch, 30% by weight or more and 99% by weight or less of a polycarbonate-based resin, and 0% by weight or more and 55% by weight or less of one or more other thermoplastic resins selected from the group consisting of polyester-polyether copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-ethylene-propylene-diene-styrene copolymers, acrylate-styrene-acrylonitrile copolymers, acrylonitrile-styrene copolymers, polyarylate resins, polystyrene-based resins, and polyamide-based resins.

The polycarbonate-based resin composition may further contain an inorganic compound.

The present invention also relates to an injection foam molded article obtained by injection foam molding the above polycarbonate resin composition.
The specific gravity of the injection foamed article is preferably 0.3 g/cm ³ or more and 1.2 g/cm ³ or less.
The expansion ratio of the injection foamed product is preferably 1.1 times or more and 3.0 times or less.

The present invention also relates to an electrical appliance housing, a mobile phone housing, a personal computer housing, an automobile fender, an automobile door panel, an automobile back door panel, an automobile garnish, an automobile pillar, or an automobile spoiler, characterized by being formed by injection foam molding of the resin composition.

The present invention also relates to a method for producing an injection foam molded article by injection foam molding the above-mentioned polycarbonate-based resin composition.

The present invention also relates to a method for producing an injection foam molded article, which comprises supplying the polycarbonate resin composition to an injection molding machine, filling it to an initial filling thickness, and then pushing back the core of the mold.

According to the present invention, it is possible to provide a masterbatch for polycarbonate-based resin, a polycarbonate-based resin composition, and an injection foam molded product, which can provide an injection foam molded product of a polycarbonate-based resin composition in which the occurrence of whitening is suppressed and which has a good appearance. Also, according to the present invention, it is possible to provide an injection foam molded product of a polycarbonate-based resin composition in which the occurrence of whitening is suppressed and which has a good appearance.

FIG. 1 is an explanatory diagram of a cavity of a mold used when producing an injection foamed article.

The following describes an embodiment of the present invention. Note that the present invention is not limited to the embodiment described below.

<Thermal Expandable Microcapsules (A)>
The thermally expandable microcapsule (A) is a capsule-shaped foaming agent in which a liquid low-boiling point compound is wrapped in a shell of a thermoplastic polymer, and the capsule expands due to the pressure of the low-boiling point compound vaporized by heating in the cylinder of an injection molding machine and functions as a foaming agent. As the thermally expandable microcapsule (A), for example, those described in JP 2011-16884 A may be suitably used. Specifically, the thermally expandable microcapsule (A) has a core-shell structure, the core is composed of one or more compounds having a boiling point of 10°C or more and 330°C or less, and the shell contains the core and is composed of a thermoplastic resin.

The core may be composed of one or more compounds having a boiling point of 10°C or more and 330°C or more. The compounds constituting the core are not particularly limited, but examples thereof include hydrocarbons, alcohols, ketones, etc. The hydrocarbons are not particularly limited, but examples thereof include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, and structural isomers of these hydrocarbons. The compounds constituting the core are preferably one or more hydrocarbons having a boiling point of 10°C or more and 330°C or less, more preferably one or more hydrocarbons having a boiling point of 30°C or more and 280°C or less, and even more preferably one or more hydrocarbons having a boiling point of 30°C or more and 200°C or less. By using a compound having a boiling point of 10°C or more, it is easy to make a master batch of the thermally expandable microcapsules (A). Furthermore, by using a compound having a boiling point of 330° C. or less, the dispersibility during polymerization is improved, making it easier to produce thermally expandable microcapsules.

The monomer component of the thermoplastic resin constituting the shell of the thermally expandable microcapsule (A) may be, for example, one or more monomers selected from the group consisting of nitrile-based monomers, (meth)acrylate-based monomers, aromatic vinyl-based monomers, diene-based monomers, vinyl-based monomers having a carboxyl group, and monomers having one or more reactive functional groups selected from the group consisting of methylol groups, hydroxyl groups, amino groups, epoxy groups, and isocyanate groups.

Examples of nitrile monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, etc.

Examples of (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, etc. In the present invention, "(meth)acrylate" may be either methacrylate or acrylate.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, p-nitrostyrene, and chloromethylstyrene.

Examples of diene monomers include butadiene, isoprene, chloroprene, etc.

Examples of vinyl monomers having a carboxyl group include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid; unsaturated dicarboxylic acids and their anhydrides such as maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid; and unsaturated dicarboxylic acid monoesters such as monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate.

Examples of monomers having one or more reactive functional groups selected from the group consisting of methylol groups, hydroxyl groups, amino groups, epoxy groups, and isocyanate groups (hereinafter also referred to simply as "monomers having reactive functional groups") include N-methylol (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, vinyl glycidyl ether, propenyl glycidyl ether, glycidyl (meth)acrylate, glycerin mono(meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, p-hydroxystyrene, blocked isocyanate, and the like. Examples of blocked isocyanates include blocked isocyanates of isocyanate compounds (diphenylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, etc.) with phenol, alcohol, dimethyl malonate, diethyl malonate, ethyl acetoacetate, oxime, dimethylpyrazole, methyl ethyl ketone oxime, caprolactam, etc. In the present invention, "(meth)acrylamide" may be methacrylamide or acrylamide.

From the viewpoint of suppressing the decomposition of the main chain of the resin component such as the polycarbonate resin by the shell of the thermally expandable microcapsule (A), it is preferable that the thermoplastic resin constituting the shell contains one or more selected from the group consisting of the above-mentioned nitrile monomers, (meth)acrylate monomers, aromatic vinyl monomers, and vinyl monomers having a carboxyl group. In addition, the thermoplastic resin constituting the shell may appropriately contain a chain transfer agent and a monomer having a reactive functional group.

The chain transfer agent is not particularly limited as long as it is one that is used in normal radical polymerization. Specifically, mercaptan compounds can be used. As mercaptan compounds, for example, alkyl mercaptans such as n-dodecyl mercaptan, n-octyl mercaptan, t-dodecyl mercaptan, and n-octadecyl mercaptan, 2-mercaptobenzothiazole, bromotrichloromethane, α-methylstyrene dimer, and 2-ethylhexyl thioglycolate can be suitably used.

From the viewpoint of improving the surface properties of the injection foamed molded product without causing decomposition of resin components such as polycarbonate resins, the concentration of structural units derived from one or more monomers selected from the group consisting of carboxyl group-containing monomers and amino group-containing monomers in the thermoplastic resin constituting the shell is preferably 12 mmol/g or less, more preferably 10 mmol/g or less, even more preferably 8 mmol/g or less, even more preferably 5 mmol/g or less, even more preferably 3 mmol/g or less, particularly preferably 1 mmol/g or less, and most preferably substantially free of carboxyl group-containing monomers and/or amino group-containing monomers. The lower limit of the carboxyl group concentration of the thermoplastic resin constituting the shell may be 0.001 mmol/g or more.

From the viewpoint of suppressing the decomposition of the main chain of resins such as polycarbonate-based resins, the concentration of the alkaline substance in the thermally expandable microcapsules (A) is preferably 2000 ppm or less, more preferably 1000 ppm or less, and even more preferably 800 ppm or less. If it exceeds 2000 ppm, the molecular weight of the polycarbonate-based resin may decrease, and the strength of the molded body may decrease. Examples of the alkaline substance include ion components derived from hydroxides (salts) of alkali metals and/or alkaline earth metals, and specifically, ion components derived from hydroxides (salts) of metals such as Li, Na, Mg, K, Ca, and Ba.

The pH of the thermally expandable microcapsule (A) is preferably near neutral. The thermally expandable microcapsule (A) can generally be produced by carrying out suspension polymerization in a mixture containing a polymerizable monomer and a low-boiling compound that forms a core in an aqueous dispersion medium, thereby encapsulating the low-boiling compound as a core component in a shell of a thermoplastic resin composed of monomers. The pH of the thermally expandable microcapsule (A) is preferably adjusted during such polymerization, and generally includes a method of adding a potassium hydrogen phosphate buffer. The preferred range of pH is 6.0 to 8.0, more preferably 6.0 to 7.5, and even more preferably 6.0 to 7.0. The glass electrode method can be used to measure pH. In the glass electrode method, two electrodes, a glass electrode and a reference electrode, are used to detect the potential difference generated between the electrodes and convert it into a pH value.

From the viewpoint of not causing a decrease in the molecular weight of the polycarbonate-based resin, it is preferable that the thermoplastic resin constituting the shell in the thermally expandable microcapsule (A) satisfies the following conditions. The temperature at which the 5% weight loss occurs by TG/DTA measurement of the pellet obtained by kneading 95 parts by weight of the polycarbonate-based resin and 5 parts by weight of the thermoplastic resin constituting the shell at 300°C in a φ30 mm single-screw extruder is preferably 200°C or higher, more preferably 220°C or higher, even more preferably 240°C or higher, and particularly preferably 260°C or higher. In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the pellet are preferably in the range of 60% or higher, more preferably 80% or higher, even more preferably 90% or higher, and particularly preferably 95% or higher, for the Mw and Mn of the polycarbonate-based resin.

The thermally expandable microcapsules (A) preferably have an average particle diameter (when unexpanded) of 0.5 μm or more and 50 μm or less, more preferably 0.7 μm or more and 50 μm or less, even more preferably 1.0 μm or more and 45 μm or less, even more preferably 1.0 μm or more and 40 μm or less, and particularly preferably 1.0 μm or more and 35 μm or less. The maximum particle diameter of the thermally expandable microcapsules (A) when heated is in the range of about 3 to 5 times the average particle diameter when unexpanded. If the average particle diameter when unexpanded is 0.5 μm or more and 50 μm or less, the particle diameter when expanded is about 1.5 μm or more and 250 μm or less, and the strength decrease of the Charpy impact strength and the surface impact strength when expanded can be greatly suppressed. The average particle diameter of the thermally expandable microcapsules (A) when unexpanded can be measured with a particle size distribution measuring device, specifically, the particle size distribution measuring device SALD-3000J manufactured by Shimadzu Corporation.

The maximum expansion temperature (also referred to as the maximum foaming temperature) of the thermally expandable microcapsule (A) is preferably 180°C or more and 300°C or less, more preferably 190°C or more and 290°C or less, even more preferably 200°C or more and 280°C or less, and particularly preferably 210°C or more and 270°C or less. In the present invention, the maximum expansion temperature of the thermally expandable microcapsule (A) can be measured by the measurement method described in Patent No. 5484673. Specifically, "TMA measurement" is performed using a TMA-7 model manufactured by Birkin Elmer. Approximately 0.25 mg of a sample is placed in a container, heated at a heating rate of 5°C/min, and the height displacement is continuously measured. The temperature at which the height displacement of the sample in the container becomes maximum is the maximum expansion temperature. If the maximum expansion temperature of the thermally expandable microcapsule (A) is in the above-mentioned range, it matches the molding temperature of the polycarbonate resin, making it easy to obtain an injection foam molding with low density and high strength.

<Carrier Resin Composition (B)>
The carrier resin composition (B) has a structure described below, so that it is substantially compatible with polycarbonate-based resins and has a shear viscosity at 130° C. that is easily 1.0×10 ⁻⁴ Pa·s or more and 1.0×10 ⁶ Pa·s or less. In particular, the carrier resin composition (B) has a structure described below, so that in a foamed resin molded product of a polycarbonate-based resin composition using a masterbatch of thermally expandable microcapsules (A) masterbatched with the carrier resin composition (B), whitening is suppressed and the appearance is improved. In the present invention, "substantially compatible with polycarbonate-based resins" specifically means that a mixture of the carrier resin composition (B) and the polycarbonate-based resin has one glass transition temperature peak in differential scanning calorimetry (DSC).

By having the shear viscosity of the carrier resin composition (B) at 130°C of 1.0 x ^10-4 Pa·s or more and 1.0 x ¹⁰⁶ Pa·s or less, it becomes easier to obtain a master batch in which the thermally expandable microcapsules (A) are uniformly dispersed in the carrier resin composition (B). Specifically, when the thermally expandable microcapsules (A) and the carrier resin composition (B) are kneaded at 130°C to prepare a master batch, the viscosity of the carrier resin composition (B) is in an appropriate range, so that the thermally expandable microcapsules (A) are not subjected to shear and can be pelletized without expanding the thermally expandable microcapsules (A). The shear viscosity of the carrier resin composition (B) at 130°C can be measured using a Shimadzu flow tester (model CFT-500C). Specifically, the measurement starting temperature is set to 50°C, and the carrier resin composition (B) is caused to flow through a capillary having a diameter of 1.0 mm and a length of 10 mm by applying a constant load of 30 kgf. The temperature is raised at a rate of 10°C/min, and the shear viscosity is measured when the measurement temperature reaches 130°C.

From the viewpoint of improving the low-temperature processability of the masterbatch, the carrier resin composition (B) preferably has a shear viscosity of 1.0×10 ^-4 Pa·s or more and 1.0×10 ⁶ Pa·s or less at any temperature in the temperature range of 40° C. or more and 100° C. or less.

The carrier resin composition (B) is a carrier resin composition (B1) containing a polystyrene resin having a weight average molecular weight of 1,000 or more and less than 180,000 and being solid at 20°C, or the carrier resin composition (B) is a carrier resin composition (B2) containing a polystyrene resin that is solid at 20°C and an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less and being liquid at 20°C, or the carrier resin composition (B) is a carrier resin composition (B3) containing a polyester copolymer having a weight average molecular weight of 1,000 or more and 10,000 or less and being solid at 20°C and an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less and being liquid at 20°C. In one or more embodiments of the present invention, the weight average molecular weight of the resin is measured by GPC (gel permeation chromatography).

Carrier Resin Composition (B1)
The carrier resin composition (B1) contains a polystyrene-based resin having a weight average molecular weight of 1,000 or more and less than 180,000, and being solid at 20° C. This makes it easier for the carrier resin composition (B1) to have a shear viscosity at 130° C. in the range of 1.0×10 ² Pa·s or more and 1.0×10 ⁶ Pa·s or less. From the viewpoint of improving the processability of the master batch, the shear viscosity of the carrier resin composition (B1) at 130°C is preferably ^1.0x103 Pa·s or more and ^1.0x106 Pa·s or less, more preferably ^2.0x103 Pa·s or more and ^1.0x106 Pa·s or less, even more preferably ^3.0x103 Pa·s or more and ^9.0x105 Pa·s or less, and even more preferably ^5.0x103 Pa·s or more and ^9.0x105 Pa·s or less. The carrier resin composition (B1) preferably has a weight average molecular weight of 1,000 or more and 20,000 or less, and is substantially free of an acrylic plasticizer that is liquid at 20°C. Here, "substantially free" means that the carrier resin composition (B1) contains 0 part by weight or more and less than 3 parts by weight of an acrylic plasticizer that has a weight average molecular weight of 1,000 or more and 20,000 or less and is liquid at 20°C, relative to 100 parts by weight of the polystyrene resin, and preferably contains 0 part by weight or more and less than 1 part by weight.

In the carrier resin composition (B1), the polystyrene resin may have a weight average molecular weight of 1,000 or more and less than 180,000, but is not particularly limited. The polystyrene resin may be a homopolymer of one type of styrene monomer, or a copolymer of two or more types of styrene monomers. It may also be a copolymer of another monomer copolymerizable with the styrene monomer, in which case the repeating units derived from the styrene monomer may be contained in an amount of 50% by weight or more of the total repeating units, and preferably 80% by weight or more.

Examples of the styrene monomer include styrene and styrene derivatives. Examples of the styrene derivatives include methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and trichlorostyrene. Of these, styrene is preferred.

Examples of the other copolymerizable monomers include polyfunctional vinyl compounds such as divinylbenzene; (meth)acrylic compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, and acrylonitrile; diene compounds and derivatives thereof such as butadiene; and unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride. These can be used alone or in combination of two or more.

From the standpoint of processability, it is preferable that the polystyrene-based resin is a homopolymer of styrene.

In the carrier resin composition (B1), from the viewpoint of improving compatibility with the polycarbonate-based resin, the weight average molecular weight of the polystyrene-based resin is preferably 150,000 or less, more preferably 130,000 or less, even more preferably 100,000 or less, even more preferably 80,000 or less, and particularly preferably 40,000 or less. In addition, from the viewpoint of improving the processability of the master batch, the weight average molecular weight of the polystyrene-based resin is preferably 2,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more.

The polystyrene resin is not particularly limited as long as it is solid at 20°C, but it is preferable that the glass transition temperature is 25°C or higher and 130°C or lower. If the glass transition temperature of the polystyrene resin is 25°C or higher, it is easy to control the temperature of the extruder when preparing the master batch, and the processability is good. In addition, if the glass transition temperature of the polystyrene resin is 130°C or lower, the carrier resin composition (B1) is likely to have an appropriate viscosity when preparing the master batch, so that the thermally expandable microcapsules (A) do not break and the processability is good.

<<Carrier resin composition (B2)>>
The carrier resin composition (B2) contains a polystyrene-based resin that is solid at 20° C., and an acrylic-based plasticizer that has a weight average molecular weight of 1,000 or more and 20,000 or less and is liquid at 20° C. This makes it easier for the carrier resin composition (B2) to have a shear viscosity at 130° C. that is in the range of 1.0×10 ² Pa·s or more and 1.0×10 ⁶ Pa·s or less. From the viewpoint of improving the processability of the master batch, the shear viscosity of the carrier resin composition (B2) at 130°C is preferably 1.0 x 10 ³ Pa·s or more and 1.0 x 10 ⁶ Pa·s or less, more preferably 2.0 x 10 ³ Pa·s or more and 1.0 x 10 ⁶ Pa·s or less, even more preferably 3.0 x 10 ³ Pa·s or more and 9.0 x 10 ⁵ Pa·s or less, and even more preferably 5.0 x 10 ³ Pa·s or more and 9.0 x 10 ⁵ Pa·s or less.

In the carrier resin composition (B2), the polystyrene resin is not particularly limited as long as it is solid at 20°C, but it is preferable that the glass transition temperature is 25°C or higher and 130°C or lower. If the glass transition temperature of the polystyrene resin is 25°C or higher, it is easy to control the temperature of the extruder when preparing the master batch, and the processability is good. In addition, if the glass transition temperature of the polystyrene resin is 130°C or lower, the carrier resin composition (B2) is likely to have an appropriate viscosity when preparing the master batch, so that the thermally expandable microcapsules (A) do not break and the processability is good.

In the carrier resin composition (B2), the polystyrene resin is not particularly limited and may be a homopolymer of one type of styrene monomer or a copolymer of two or more types of styrene monomer. It may also be a copolymer of another monomer copolymerizable with the styrene monomer. In that case, it is sufficient that the repeating units derived from styrene account for 50% by weight or more of the total repeating units, and preferably 80% by weight or more.

Examples of the styrene monomer include styrene and styrene derivatives. Examples of the styrene derivatives include methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and trichlorostyrene. Of these, styrene is preferred.

Examples of the other copolymerizable monomers include polyfunctional vinyl compounds such as divinylbenzene; (meth)acrylic compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, and acrylonitrile; diene compounds and derivatives thereof such as butadiene; and unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride. These can be used alone or in combination of two or more.

From the standpoint of processability, it is preferable that the polystyrene-based resin is a homopolymer of styrene.

In the carrier resin composition (B2), the weight average molecular weight of the polystyrene resin is not particularly limited, but is preferably 1,000 to 450,000, more preferably 1,000 to 400,000, even more preferably 1,000 to 350,000, particularly preferably 2,000 to 200,000, and most preferably 2,500 to 180,000, since the amount of acrylic plasticizer to be blended can be reduced. From the viewpoint of availability and use in combination with acrylic plasticizer, the weight average molecular weight of the polystyrene resin in the carrier resin composition (B2) is preferably 100,000 to 190,000. In addition, when the weight average molecular weight of the polystyrene resin is less than 180,000, and when the composition contains less than 3 parts by weight of an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less per 100 parts by weight of the polystyrene resin, it corresponds to carrier resin composition (B1), and when the composition contains 3 parts by weight or more of an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less per 100 parts by weight of the polystyrene resin, it corresponds to carrier resin composition (B2).

[Acrylic plasticizers]
The acrylic plasticizer has a weight average molecular weight of 1,000 or more and 20,000 or less. This allows for a carrier resin composition (B2) having a shear viscosity of 1.0×10 ² Pa·s or more and 1.0×10 ⁶ Pa·s or less at 130° C. to be obtained when used in combination with a polystyrene resin, particularly a polystyrene resin having a weight average molecular weight of 180,000 or more. The weight average molecular weight of the acrylic plasticizer is preferably 1,000 or more and 18,000 or less, more preferably 1,000 or more and 15,000 or less, and even more preferably 1,000 or more and 13,000 or less.

The acrylic plasticizer is not particularly limited as long as it is liquid at 20°C, but the viscosity at 25°C is preferably 300 mPa·s or more and 100,000 mPa·s or less, more preferably 350 mPa·s or more and 90,000 mPa·s or less, and even more preferably 400 mPa·s or more and 80,000 mPa·s or less. When the viscosity of the acrylic plasticizer at 25°C is in the above-mentioned range, it becomes easy to obtain a carrier resin composition (B2) having a shear viscosity at 130°C of 1.0×10 ² Pa·s or more and 1.0×10 ⁶ Pa·s or less. The acrylic plasticizer is preferably liquid at room temperature (20±5°C). The viscosity of the acrylic plasticizer at 25°C can be measured using an E-type viscometer in accordance with JIS Z 8803-1991.

The acrylic plasticizer may be any of those generally known as acrylic plasticizers, and it is preferable to use a non-functional acrylic plasticizer. Examples of acrylic plasticizers include (meth)acrylic acid ester polymers and (meth)acrylic acid ester-aromatic vinyl monomer copolymers, and (meth)acrylic acid ester polymers are preferred. The acrylic plasticizer preferably contains 50% by weight or more, and more preferably 70% by weight or more, of repeating units derived from (meth)acrylic acid esters in the total repeating units.

The (meth)acrylic acid ester is not particularly limited, but examples thereof include alkyl acrylates having an alkyl group with 10 or less carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; and alkyl methacrylates having an alkyl group with 10 or less carbon atoms, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. These may be used alone or in combination of two or more. Among these, it is preferable to use one or more selected from the group consisting of methyl methacrylate, butyl methacrylate, ethyl acrylate, and butyl acrylate.

The aromatic vinyl monomer is not particularly limited, but examples thereof include styrene, α-methylstyrene, monochlorostyrene, dichlorostyrene, etc.

The (meth)acrylic acid ester polymer includes a homopolymer of an alkyl acrylate, a homopolymer of an alkyl methacrylate, a copolymer of alkyl acrylates, a copolymer of alkyl methacrylates, and a copolymer of an alkyl acrylate and an alkyl methacrylate.

The acrylic plasticizer is not particularly limited, but specifically, commercially available non-functional acrylic plasticizers such as those manufactured by Toagosei Co., Ltd. under the product names "UP-1000," "UP-1010," "UP-1020," "UP-1021," and "UP-1061" can be used.

<<Carrier Resin Composition (B3)>>
The carrier resin composition (B3) contains a polyester copolymer having a weight average molecular weight of 1,000 or more and 10,000 or less and which is solid at 20° C., and an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less and which is liquid at 20° C. This makes it easier for the carrier resin composition (B3) to have a shear viscosity at 130° C. in the range of 1.0×10 ^-4 Pa·s or more and 1.0×10 ⁶ Pa·s or less. From the viewpoint of improving the processability of the master batch, the shear viscosity of the carrier resin composition (B3) at 130°C is preferably ^1.0x10-4 Pa.s or more and ^9.0x105 Pa.s or less, more preferably ^3.0x10-4 Pa.s or more and ^8.0x105 Pa.s or less, even more preferably ^6.0x10-4 Pa.s or more and ^3.0x105 Pa.s or less, and even more preferably ^8.0x10-4 Pa.s or more and ^1.5x105 Pa.s or less.

The polyester copolymer is not particularly limited as long as it has a weight average molecular weight of 1,000 or more and 10,000 or less and is solid at 20°C. For example, a polyester compound having a structure in which the ends are blocked with a monohydric alcohol, as described in JP 2007-262290 A, can be used.

The polyester compound can be produced, for example, by reacting a polyester having a carboxyl group at the end, which is obtained by esterifying a polycarboxylic acid with a polyhydric alcohol by a known method, with a monohydric alcohol.

The esterification reaction can be accelerated by, for example, an acid catalyst such as paratoluenesulfonic acid or phosphoric acid, or a metal catalyst such as tetraisopropyl titanate, tetrabutyl titanate, dibutyltin oxide or zinc chloride. In particular, it is preferable to use the metal catalyst during the esterification reaction. In addition, it is preferable to carry out the esterification reaction under heating at 130 to 270°C.

As the polyvalent carboxylic acid, preferably, an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an aromatic tricarboxylic acid can be used. Among them, from the viewpoint of improving compatibility with the polycarbonate resin (a) and the heat resistance of the resulting polycarbonate resin composition, it is preferable to use an aromatic dicarboxylic acid having 8 to 18 carbon atoms.

As the aromatic dicarboxylic acid, preferably, terephthalic acid, isophthalic acid, phthalic acid, naphthalene 2,6-dicarboxylic acid, α,β-(4-carboxyphenoxy)ethane, 4,4'-dicarboxydiphenyl, 5-sodium sulfoisophthalic acid, or ester derivatives thereof can be used.

As the polyhydric alcohol, preferably, an aliphatic diol, an aliphatic triol, or a dihydric phenol can be used. Among them, it is preferable to use a diol from the viewpoint of reducing the melt viscosity of the polycarbonate resin (a), and it is more preferable to use an aliphatic diol having 2 to 25 carbon atoms.

Preferably, the diol used may be ethylene glycol, propylene glycol, 1,4-butanediol, 3-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanediol, cyclohexanedimethanol, etc.

The monohydric alcohol is preferably one having an aliphatic or alicyclic hydrocarbon group having 4 to 18 carbon atoms, and specific examples include butanol, hexanol, isohexanol, heptanol, octanol, isooctanol, 2-ethylhexanol, nonanol, isononanol, 2-methyloctanol, decanol, isodecanol, undecanol, dodecanol, tridecanol, tetradecanol, hexadecanol, and cyclohexanol. These can be used alone or as a mixture of two or more. In particular, it is more preferable to use 2-ethylhexanol in terms of the balance between mechanical strength and fluidity.

It is preferable to use the polyester compound having a weight average molecular weight in the range of 1000 to 8000, and more preferably a weight average molecular weight in the range of 2000 to 6000. Using a polyester compound having a weight average molecular weight in this range can improve the fluidity of the polycarbonate resin.

The melting point of the polyester compound is preferably in the range of 140 to 220°C, and more preferably in the range of 150 to 180°C. If the melting point is in the above range, blocking under the hopper of the extruder can be prevented when compounding the polycarbonate resin composition, making it easy to handle and easily improving the fluidity of the polycarbonate resin used.

The acid value of the polyester compound is preferably 2 or less, and the hydroxyl value of the polyester compound is preferably 15 or less. If a polyester compound having an acid value or hydroxyl value within the above range is used, the molecular weight of the polycarbonate resin is not reduced when melt-mixed with the polycarbonate resin, the mechanical strength and impact resistance of the resulting molded product are maintained, and coloring, etc. does not occur. More preferably, the acid value is 1 or less, and the hydroxyl value is 5 or less.

Specific examples of the polyester copolymer that can be used include aromatic polyesters such as those described in Table 5 of Patent No. 6,397,787.

<Masterbatch (C)>
The master batch (C) contains the thermally expandable microcapsules (A) and the carrier resin composition (B). In the master batch (C), the carrier resin composition (B) has the above-mentioned configuration, so that the shear viscosity at 130 ° C. of the carrier resin composition (B) mixed with the thermally expandable microcapsules (A) is likely to be 1.0 × 10 ^-4 Pa · s or more and 1.0 × 10 ⁶ Pa · s or less, and therefore, using the carrier resin composition (B), it is possible to obtain a master batch in which the thermally expandable microcapsules (A) are uniformly dispersed without impairing the foaming power. In addition, since the carrier resin composition (B) has the above-mentioned configuration, the carrier resin composition (B) is substantially compatible with the polycarbonate resin, and therefore, when the master batch (C) is used, whitening is suppressed and an injection foam molded product with good appearance can be obtained. That is, in the injection foam molding using the master batch (C) of the thermally expandable microcapsules (A) obtained above, a molded product with good appearance can be obtained without impairing the foaming power.

From the standpoints of handleability, storage stability, dispersibility in the base resin, etc., the masterbatch (C) preferably contains 30% by weight or more and 80% by weight or less of thermally expandable microcapsules (A), more preferably 30% by weight or more and 70% by weight or less, and even more preferably 30% by weight or more and 60% by weight or less.

From the viewpoints of compatibility with polycarbonate-based resins and processability, the masterbatch (C) preferably contains 20% by weight or more and 70% by weight or less of the carrier resin composition (B), more preferably 30% by weight or more and 70% by weight or less, and even more preferably 40% by weight or more and 70% by weight or less.

When the master batch (C) contains the carrier resin composition (B1), from the viewpoints of compatibility with polycarbonate-based resins, shear viscosity at 130°C, as well as handleability, storage stability, and dispersibility in the base resin, it is preferable that the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A) and 20% by weight or more and 70% by weight or less of the carrier resin composition (B1), more preferable that the master batch (C) contains 30% by weight or more and 70% by weight or less of the thermally expandable microcapsules (A) and 30% by weight or more and 70% by weight or less of the carrier resin composition (B1), and even more preferable that the master batch (C) contains 30% by weight or more and 60% by weight or less of the thermally expandable microcapsules (A) and 40% by weight or more and 70% by weight or less of the carrier resin composition (B1).

When the master batch (C) contains the carrier resin composition (B2), it preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 15% by weight or more and 40% by weight or less of the polystyrene resin, and 5% by weight or more and 30% by weight or less of the acrylic plasticizer. When the amount of the acrylic plasticizer is 5% by weight or more, the low shear effect is easily exhibited when the master batch (C) is prepared, and the capsules can be prevented from breaking. Also, when the amount of the acrylic plasticizer is 30% by weight or less, the increase in the amount of thermal decomposition of the plasticizer relative to the temperature during foam molding is suppressed, and adverse effects on the appearance are prevented. More preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 45% by weight or less of the polystyrene resin, and 8% by weight or more and 25% by weight or less of the acrylic plasticizer. More preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 50% by weight or less of the polystyrene resin, and 8% by weight or more and 20% by weight or less of the acrylic plasticizer. Particularly preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 55% by weight or less of the polystyrene resin, and 8% by weight or more and 15% by weight or less of the acrylic plasticizer.

When the master batch (C) contains the carrier resin composition (B3), it preferably contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 15% by weight or more and 40% by weight or less of the polyester copolymer, and 5% by weight or more and 30% by weight or less of the acrylic plasticizer. When the amount of the acrylic plasticizer is 5% by weight or more, the low shear effect is easily exhibited during the preparation of the master batch (C), and the capsules can be prevented from breaking. In addition, when the amount of the acrylic plasticizer is 30% by weight or less, the increase in the amount of thermal decomposition of the plasticizer relative to the temperature during foam molding is suppressed, and adverse effects on the appearance are prevented. More preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 45% by weight or less of the polyester copolymer, and 8% by weight or more and 25% by weight or less of the acrylic plasticizer. More preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 50% by weight or less of the polyester copolymer, and 8% by weight or more and 20% by weight or less of the acrylic plasticizer. Particularly preferably, the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A), 12% by weight or more and 55% by weight or less of the polyester copolymer, and 8% by weight or more and 15% by weight or less of the acrylic plasticizer.

<Polycarbonate Resin Composition>
The polycarbonate-based resin composition is a resin composition containing a polycarbonate-based resin (G) and a master batch (C) and containing a polycarbonate-based resin as a main component. Here, the term "main component" means that the content of the polycarbonate-based resin is the largest among all the components contained in the polycarbonate-based resin composition. In the polycarbonate-based resin composition, the components other than the master batch (C) are also referred to as base components.

In the polycarbonate-based resin composition, the content of the master batch (C) may be appropriately set depending on the foaming ratio of the final product, the type of foaming agent, the resin temperature during molding, etc. The content of the master batch (C) in the polycarbonate-based resin composition is preferably 1% by weight or more and 20% by weight or less, more preferably 2% by weight or more and 15% by weight or less, and particularly preferably 3% by weight or more and 10% by weight or less. By using the master batch (C) in this range, it is easy to economically obtain a foamed molded product with a foaming ratio of 1.1 times or more and uniform fine bubbles.

<Polycarbonate resin (G)>
The polycarbonate-based resin (G) is a polycarbonate-based resin derived from a compound having two phenolic hydroxyl groups (hereinafter referred to as a dihydric phenol), and is usually a resin obtained by reacting a dihydric phenol with phosgene, or a dihydric phenol with a carbonate diester.

Examples of the dihydric phenol include biphenol, methylene bisphenol (bisphenol F), bis(4-hydroxyphenyl)sulfone (bisphenol S), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), etc. Among these, bisphenol A is preferred, but is not limited thereto.

From the viewpoints of impact resistance, chemical resistance, moldability, etc., the polycarbonate-based resin (G) preferably has a number average molecular weight of 10,000 to 60,000, more preferably 10,000 to 30,000. The content of the polycarbonate-based resin (G) in the polycarbonate-based resin composition is preferably 30% by weight to 99% by weight, more preferably 30% by weight to 80% by weight, and even more preferably 30% by weight to 70% by weight. In one or more embodiments of the present invention, the number average molecular weight of the resin is measured by GPC (gel permeation chromatography).

The polycarbonate-based resin composition may further contain one or more other thermoplastic resins selected from the group consisting of polyester-based resins, polyester-polyether copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-ethylene-propylene-diene-styrene copolymers, acrylate-styrene-acrylonitrile copolymers, acrylonitrile-styrene copolymers, polyarylate resins, polystyrene-based resins, and polyamide-based resins.

<Polyester Resin (H1)>
Examples of the polyester resin (H1) that can be used include amorphous thermoplastic polyester resins such as amorphous aliphatic polyesters, amorphous semi-aromatic polyesters, and amorphous wholly aromatic polyesters; crystalline thermoplastic polyester resins such as crystalline aliphatic polyesters, crystalline semi-aromatic polyesters, and crystalline wholly aromatic polyesters; and liquid crystalline thermoplastic polyester resins such as liquid crystalline aliphatic polyesters, liquid crystalline semi-aromatic polyesters, and liquid crystalline wholly aromatic polyesters.

Specific examples of crystalline thermoplastic polyesters include crystalline copolymer polyesters such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polybutylene naphthalate, poly 1,4-cyclohexylene dimethylene terephthalate, polyethylene-1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, polyethylene isophthalate/terephthalate, polybutylene terephthalate/isophthalate, polybutylene terephthalate/decane dicarboxylate, and polycyclohexane dimethylene terephthalate/isophthalate. Among these, it is preferable to use polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polybutylene naphthalate, and poly 1,4-cyclohexylene dimethylene terephthalate. The content of the polyester resin (H1) in the polycarbonate resin composition is preferably 0 to 40% by weight from the viewpoint of improving the appearance of the injection foam molded article.

<Polyester-polyether copolymer (H2)>
The polyester-polyether copolymer (H2) preferably contains an aromatic polyester unit and a polyether unit. Examples of the polyether unit include those represented by the following general formula (1), general formula (2), general formula (3), general formula (4), general formula (5), and general formula (6). Among these, the one represented by the following general formula (6) is preferred.

In the general formula (1), -A- is -O-, -S-, -SO-, -SO ₂ -, -CO-, an alkylene group having 1 to 20 carbon atoms, or an alkylidene group having 6 to 20 carbon atoms. R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are each a hydrogen atom, a halogen atom, or a monovalent hydrocarbon group having 1 to 5 carbon atoms. R ⁹ and R ¹⁰ are each a divalent hydrocarbon group having 1 to 5 carbon atoms. m and n represent the number of repeating units of the oxyalkylene unit, and m and n are each an integer of 0 to 70, and 10≦m+n≦70. m and n are each preferably an integer of 0 to 50. m is more preferably an integer of 2 to 70.

In the general formula (2), R ¹ , R ² , R ³ , and R ⁴ are each a hydrogen atom, a halogen atom, or a monovalent hydrocarbon group having 1 to 5 carbon atoms. R ⁹ and R ¹⁰ are each a divalent hydrocarbon group having 1 to 5 carbon atoms. m and n represent the number of repeating oxyalkylene units, and m and n are each an integer of 0 to 70, and 10≦m+n≦70. m and n are each preferably an integer of 0 to 50. m is more preferably an integer of 2 to 70.

In the general formula (3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each a hydrogen atom, a halogen atom, or a monovalent hydrocarbon group having 1 to 5 carbon atoms. R ⁹ and R ¹⁰ are each a divalent hydrocarbon group having 1 to 5 carbon atoms. m and n represent the number of repeating oxyalkylene units, and m and n are each an integer of 0 to 70, and 10≦m+n≦70. m and n are each preferably an integer of 0 to 50. m is more preferably an integer of 2 to 70.

In the general formula (4), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are each a hydrogen atom, a halogen atom, or a monovalent hydrocarbon group having 1 to 5 carbon atoms. R ⁹ and R ¹⁰ are each a divalent hydrocarbon group having 1 to 5 carbon atoms. m and n represent the number of repeating oxyalkylene units, and m and n are each an integer of 0 to 70, with 10≦m+n≦70. m and n are each preferably an integer of 0 to 50. m is more preferably an integer of 2 to 70.

In the general formula (5), R ⁹ is a divalent hydrocarbon group having 1 to 5 carbon atoms, and m is the number of repeating oxyalkylene units, and m is an integer of 2 to 70.

In the general formula (6), m and n indicate the number of repeating oxyalkylene units, and m and n are each an integer from 0 to 50, with 10≦m+n≦50.

The aromatic polyester unit is an alternating polycondensation product composed of an aromatic dicarboxylic acid or an aromatic dicarboxylic acid ester and a diol. Examples of the aromatic polyester unit include polyalkylene terephthalate units such as polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate; and polyalkylene naphthalate units such as polyethylene naphthalate, polypropylene naphthalate, and polybutylene naphthalate. Among these, polyalkylene terephthalate units are preferred, and polyethylene terephthalate units are more preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyl dicarboxylic acid, and diphenoxyethane dicarboxylic acid. Among these, terephthalic acid is preferred. Examples of the aromatic dicarboxylic acid ester include dialkyl esters of the aromatic dicarboxylic acids. In addition to the aromatic dicarboxylic acid, other aromatic oxycarboxylic acids such as oxybenzoic acid, and aliphatic or alicyclic dicarboxylic acids such as adipic acid, sebacic acid, and cyclohexane 1,4-dicarboxylic acid may be used in combination. The diol is, for example, a glycol having 2 to 10 carbon atoms, such as ethylene glycol, trimethylene glycol, tetramethylene glycol, hexanediol, decanediol, cyclohexanedimethanol, etc. From the viewpoint of impact resistance, chemical resistance and molding processability of the resulting molded article, the solution viscosity of the aromatic polyester is preferably an inherent viscosity (IV value) of 0.3 to 1.0 at a concentration of 0.5 g/dl at 25° C. in a phenol/tetrachloroethane=1/1 (weight ratio) mixed solvent.

Methods for producing polyester-polyether copolymers are not particularly limited, but include (1) a direct esterification method in which an aromatic dicarboxylic acid, a diol, and a polyether are reacted; (2) an ester exchange method in which an aromatic dicarboxylic acid dialkyl ester, a diol, and a polyether are reacted; (3) a method in which a modified polyether is added during or after the ester exchange of an aromatic dicarboxylic acid dialkyl ester and a diol, followed by polycondensation; and (4) a method in which a high molecular weight aromatic polyester is used, mixed with a polyether, and then ester exchange is carried out under reduced pressure in the melt.

The content of polyester-polyether copolymer (H2) in the polycarbonate resin composition is preferably 0 to 40% by weight from the viewpoint of improving the appearance of the injection foam molded article.

<Acrylonitrile-butadiene-styrene copolymer (H3)>
From the viewpoint of improving the appearance and maintaining heat resistance, the acrylonitrile-butadiene-styrene copolymer is preferably contained in an amount of 0 to 40% by weight, more preferably 0 to 30% by weight, based on 100% by weight of the polycarbonate resin composition.

The butadiene content in the acrylonitrile-butadiene-styrene copolymer may be 10 to 30% by weight.

As the acrylonitrile-butadiene-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer in which part of the styrene is replaced with α-methylstyrene and thus has improved heat resistance compared to ordinary acrylonitrile-butadiene-styrene copolymers may be used, and it is also possible to appropriately use acrylonitrile-butadiene-styrene copolymers modified with phenylmaleimide, which have further improved heat resistance.

From the viewpoint of effectively suppressing whitening of the surface of the injection foam molded article and improving the appearance, it is preferable that the polycarbonate-based resin composition contains 1 to 15 weight % of master batch (C), 30 to 99 weight % of polycarbonate-based resin (G), and 0 to 55 weight % of one or more thermoplastic resins selected from the group consisting of polyester-based resins, polyester-polyether copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-ethylene-propylene-diene-styrene copolymers, acrylate-styrene-acrylonitrile copolymers, acrylonitrile-styrene copolymers, polyarylate resins, polystyrene-based resins, and polyamide-based resins.

<Inorganic compound (J)>
In order to improve the bending rigidity and dimensional stability of the injection foamed article, the polycarbonate resin composition may further contain an inorganic compound (J). Examples of the inorganic compound include mica, talc, montmorillonite, sericite, It is preferable to use at least one selected from the group consisting of kaolin, glass flakes, plate-like alumina, synthetic hydrotalcite, wollastonite, hollow glass balloons, carbon fibers, aramid fibers, and whiskers, which have the effect of improving bending rigidity and polycarbonate resin. From the viewpoint of dispersibility in water, one or more selected from the group consisting of mica, talc, montmorillonite, sericite, kaolin, glass flakes, hollow glass beads, and carbon fibers are more preferred. From the viewpoint of a balanced appearance, one or more selected from the group consisting of mica, talc, glass flakes, and wollastonite is more preferable.

From the viewpoints of impact resistance, heat resistance, rigidity, moldability, etc., the inorganic compound (J) is preferably contained in the polycarbonate resin composition in an amount of 5% by weight or more and 45% by weight or less, more preferably 5% by weight or more and 35% by weight or less, and even more preferably 5% by weight or more and 25% by weight or less.

<Impact resistance modifier (K)>
In order to further improve the impact resistance of the injection foamed article, the polycarbonate resin composition may further contain an impact modifier, which is preferably at least one selected from the group consisting of multi-stage graft polymers, polyolefin polymers, olefin-unsaturated carboxylic acid ester copolymers, and thermoplastic polyester elastomers.

The multi-stage graft polymer is a rubber-like polymer grafted with a vinyl monomer. The rubber-like polymer preferably has a glass transition temperature of 0°C or less, more preferably -40°C or less. Specific examples of such rubber-like polymers include diene-based rubbers such as polybutadiene, butadiene-styrene copolymer, butadiene-acrylic acid ester copolymer, and butadiene-acrylonitrile copolymer; acrylic rubbers such as polybutyl acrylate, poly2-ethylhexyl acrylate, dimethylsiloxane-butyl acrylate rubber, and silicone/butyl acrylate composite rubber; olefin-based rubbers such as ethylene-propylene copolymer and ethylene-propylene-diene copolymer; polydimethylsiloxane-based rubber; and dimethylsiloxane-diphenylsiloxane copolymer-based rubber. Examples of butadiene-acrylic acid ester copolymers include butadiene-butyl acrylate copolymer and butadiene-2-ethylhexyl acrylate copolymer. From the viewpoint of impact resistance, polybutadiene, butadiene-styrene copolymer, and butadiene-butyl acrylate copolymer are preferably used. Among butadiene-butyl acrylate copolymers, a copolymer containing 50 to 70% by weight of butyl acrylate and 30 to 50% by weight of butadiene is preferred from the viewpoint of weather resistance and impact resistance. There is no particular limitation on the average particle size of the rubber-like polymer, but it is preferably in the range of 0.05 μm to 2.00 μm, more preferably 0.1 μm to 0.4 μm. There is also no particular limitation on the gel content, but it is preferably in the range of 10% by weight to 99% by weight, and further preferably 80% by weight to 96% by weight.

Examples of vinyl monomers used in the production of the multi-stage graft polymer include aromatic vinyl monomers, vinyl cyanide monomers, (meth)acrylic acid esters, etc. These may be used alone or in combination of two or more. As the aromatic vinyl monomers and (meth)acrylic acid esters, those listed in the explanation of the acrylic plasticizers can be used as appropriate. As the vinyl cyanide monomers, for example, acrylonitrile, methacrylonitrile, etc. can be used.

Specifically, the multi-stage graft polymer is preferably composed of 10 to 90% by weight of one or more rubber-like polymers selected from the group consisting of polybutadiene, butadiene-styrene copolymer, butadiene-acrylic acid ester copolymer, and polyorganosiloxane, and 10 to 90% by weight of a graft component composed of a polymer obtained by polymerizing, in the presence of the rubber-like polymer, one or more vinyl-based monomers selected from the group consisting of aromatic vinyl monomers, vinyl cyanide monomers, and (meth)acrylic acid ester compounds. It is particularly preferable to use a multi-stage graft polymer produced using an organic phosphorus-based emulsifier.

When preparing a core/shell graft polymer as the multi-stage graft polymer, it is preferable that the rubber polymer is 10% by weight to 90% by weight and the vinyl monomer is 10% by weight to 90% by weight, and more preferably that the rubber polymer is 30% by weight to 85% by weight and the vinyl monomer is 15% by weight to 70% by weight, assuming that the total amount of the rubber polymer and the vinyl monomer is 100% by weight. If the proportion of the rubber polymer is less than 10% by weight, the impact resistance is likely to decrease, while if it exceeds 90% by weight, the heat resistance tends to decrease.

From the standpoints of impact resistance, heat resistance, rigidity, moldability, etc., the amount of impact modifier in the polycarbonate resin composition is preferably 0 to 20% by weight, more preferably 0 to 15% by weight, and even more preferably 0 to 10% by weight.

<Injection foam molded article>
By injecting and foaming the polycarbonate-based resin composition, whitening is suppressed, and an injection foam molded product with good appearance is obtained. Specifically, the injection foam molded product can be produced by a method of foaming the polycarbonate-based resin composition in a mold. The method of foaming in a mold is not particularly limited, but examples include a core-back method, a short shot method, and a full-filling method. Among them, a so-called core-back method (Moving Cavity method) is preferred, in which a mold consisting of a fixed mold (also called a cavity) and a movable mold (also called a core) that can advance and retreat to any position is used, and after the resin composition is injected to the initial filling thickness, the movable mold is retreated to foam the resin composition. According to the core-back method, a non-foamed layer is formed on the surface, which smooths out the unevenness of the appearance on the order of several μm to several tens of μm, and the foamed layer inside is likely to become uniform fine bubbles, and it is easy to obtain an injection foam molded product with excellent lightness.

In the core-back method, the retraction of the movable mold may be performed in one step or in multiple steps of two or more steps, and the retraction speed may be appropriately adjusted. For example, it is preferable to include a step of injecting and filling into a mold that is composed of a fixed mold and a movable mold that can advance and retreat to any position and has an initial cavity clearance t ₀ (initial filling thickness) of 1.5 mm to 2.7 mm, and a step of retracting the movable mold to foam after completion of injection filling up to the initial filling thickness so that the cavity clearance t _f after core-back is 2.0 mm to 6.0 mm.

In the core-back method, other molding conditions may be, for example, a resin temperature of 240°C or higher and 280°C or lower, a mold temperature of 60°C or higher and 90°C or lower, a molding cycle of 1 second or higher and 60 seconds or lower, an injection speed of 10 mm/sec or higher and 400 mm/sec or lower, an injection pressure of 10 MPa or higher and 200 MPa or lower, a back pressure of 5 MPa or higher and 40 MPa or lower, and a screw rotation speed of 10 rpm or higher and 200 rpm or lower.

The injection foam molded products can be suitably used for applications such as electrical appliances such as mobile phones and computer housings; and vehicle components (exterior/outer panels) such as automobile fenders, door panels, tailgate panels, garnishes, pillars, and spoilers.

The specific gravity of the injection foam molded product is preferably 0.3 g/cm ³ or more and 1.2 g/cm ³ or less from the viewpoint of weight reduction and impact strength of the molded product. If the specific gravity of the injection foam molded product is less than 0.3 g/cm ³ , the number of coarse bubbles exceeding 1.5 mm increases and the impact strength tends to decrease, and if it exceeds 1.2 g/cm ³ , it is difficult to achieve weight reduction. The specific gravity can be calculated by the underwater displacement method in accordance with JIS K 7112:1999. From the viewpoint of weight reduction and impact strength, the expansion ratio of the injection foam molded product is preferably 1.1 times or more and 3.0 times or less, more preferably 1.1 times or more and 2.5 times or less, and even more preferably 1.1 times or more and 2.0 times or less. If the expansion ratio is less than 1.1 times, it tends to be difficult to obtain light weight, and if it exceeds 3.0 times, the decrease in surface impact strength tends to be significant. In this specification, the expansion ratio is a value obtained by dividing the thickness of the injection foamed molded article (cavity clearance after core-back t _f ) by the initial cavity clearance t ₀ .

The present invention will be described below based on specific examples and comparative examples, but the present invention is not limited to the following examples. In the following, unless otherwise specified, "parts" means parts by weight and "%" means % by weight.

Various measurement and evaluation methods are shown below.

(1) Glass Transition Temperature The glass transition temperature was measured using a differential scanning calorimeter (DSC220C, manufactured by Seiko Instruments Inc.) at a temperature increase rate of 5° C./min.
(2) Weight-average molecular weight The weight-average molecular weight of the resin was measured by GPC (gel permeation chromatography). Specifically, the measurement was performed using a Tosoh HLC-8220 system, Tosoh TSKgel Super HZM-H (x2 columns), and THF solvent, and the weight-average molecular weight was calculated in terms of polystyrene.
(3) Average Particle Diameter The average particle diameter of the thermally expandable microcapsules (unexpanded) was measured using a particle size distribution analyzer SALD-3000J manufactured by Shimadzu Corporation.
(4) Compatibility with Polycarbonate Resin (PC) Differential scanning calorimetry (DSC) was carried out on a mixture of the carrier resin composition (B) and a polycarbonate resin, and the compatibility with PC was judged according to the following criteria.
Compatible: one glass transition temperature peak in DSC Non-compatible: two glass transition temperature peaks in DSC (5) Shear Viscosity The shear viscosity of the carrier resin composition (B) at 130°C was measured using a flow tester "Model CFT-500C" manufactured by Shimadzu Corporation. Specifically, the measurement start temperature was set to 50°C, and the carrier resin composition (B) was made to flow in a capillary having a diameter of 1.0 mm and a length of 10 mm under a constant load of 30 kgf, and the temperature was raised at a rate of 10°C/min, and the shear viscosity was measured when the measurement temperature reached 130°C.
(6) Viscosity The viscosity of the acrylic plasticizer at 25° C. was measured using an E-type viscometer in accordance with JIS Z 8803-1991.
(7) Maximum Expansion Temperature "TMA measurement" was performed using a TMA-7 model manufactured by Birkin Elmer Co., Ltd. Approximately 0.25 mg of a sample was placed in a container, and the temperature was increased at a rate of 5°C/min. The change in height was continuously measured, and the temperature at which the change in the height of the sample in the container reached a maximum was taken as the maximum expansion temperature.
(8) Processability of Masterbatch The cross section of the masterbatch pellet was observed with a scanning electron microscope (SEM, manufactured by JEOL Ltd., model "JSM-6060LA"), and the processability of the masterbatch was evaluated based on the state of the thermally expandable microcapsules.
A: No foaming of the thermally expandable microcapsules and good dispersion. B: No foaming of the thermally expandable microcapsules but poor dispersion. C: Foaming of the thermally expandable microcapsules and poor dispersion or broken capsules. (9) Evaluation of foaming ratio of injection foam molded products. A: The thickness of the injection foam molded product is 1.9 mm or more. B: The thickness of the injection foam molded product is 1.7 mm or more and less than 1.9 mm. C: The thickness of the injection foam molded product is less than 1.7 mm. (10) Appearance of injection foam molded products. The surface of the flat injection foam molded products was visually observed and the appearance was evaluated.
A: No whitening and no white spots, very good appearance. B: No whitening, some white spots, good appearance. C: No whitening, many white spots, poor appearance.

<Production Example 1 of Polyester-Polyether Copolymer>
A reactor equipped with an agitator and a gas exhaust outlet was charged with polyethylene terephthalate (IV = 0.65) produced using a germanium catalyst, bisphenol A 30 mole ethylene oxide adduct (manufactured by Toho Chemical Industry Co., Ltd., "Bisol 30EN", which corresponds to a polyether unit represented by the general formula (6), where n + m is 30), and 400 ppm of germanium dioxide and a stabilizer (Ciba Spektrum, Inc.) based on the total amount of polyethylene terephthalate and bisphenol A 30 mole ethylene oxide adduct. The mixture was charged with 2000 ppm of Irganox 1010 (manufactured by Charity Chemicals) and held at 270°C for 2 hours, then depressurized with a vacuum pump and polycondensation was carried out at 1 torr. When a predetermined degree of polymerization was reached, the depressurization was terminated to stop the reaction and the product was taken out, and the strands cooled in a water bath were simultaneously post-crystallized and dried in a hot air dryer set at 100°C, and then fed into a pulverizer to pelletize, thereby obtaining polyester-polyether copolymer (H2) in a pellet state. The polyether content of the obtained polyester-polyether copolymer (H2) was 30% by weight, and the IV value was 0.45. The IV values of polyethylene terephthalate and polyester-polyether copolymer were calculated from the inherent viscosity at 25°C and 0.5 g/dl in a mixed solvent of tetrachloroethane/phenol = 50/50 (weight ratio).

The polystyrene resin, polyester copolymer, acrylic plasticizer and thermally expandable microcapsules used in the examples and comparative examples are as follows.
(1) Polystyrene resin 1: homopolymer of styrene, weight average molecular weight (Mw): 10,000, number average molecular weight (Mn): 5,000, Mw/Mn: 2.0, solid at 20°C, glass transition temperature (Tg): 68°C
(2) Polystyrene resin 2: homopolymer of styrene, weight average molecular weight (Mw): 20,000, number average molecular weight (Mn): 8,000, Mw/Mn: 2.5, solid at 20°C, glass transition temperature (Tg): 86°C
(3) Polystyrene resin 3: Styrene homopolymer (manufactured by PS Japan Co., Ltd., grade name: 680), weight average molecular weight (Mw): 180,000, solid at 20° C., glass transition temperature (Tg): 102° C.
(4) Polystyrene resin 4: Styrene homopolymer (manufactured by Toyo Styrene Co., Ltd.), weight average molecular weight (Mw): 150,000, solid at 20° C., glass transition temperature (Tg): 100.4° C.
(5) Polyester-based copolymer 1: A polyester compound having a structure in which the ends are blocked with a monohydric alcohol, as described in JP 2007-262290 A, solid at 20° C., melting point: 199° C., weight average molecular weight: 1,300, Mw/Mn: 2.7
(6) Polyester-based copolymer 2: A polyester compound having a structure in which the ends are blocked with monohydric alcohol, as described in JP 2007-262290 A, solid at 20° C., melting point: 212° C., weight average molecular weight: 2400, Mw/Mn: 2.7
(7) Acrylic plasticizer: "Alphon UP1020" manufactured by Toa Gosei Co., Ltd., weight average molecular weight 2000, liquid at 20°C, viscosity at 25°C 500 mPa·s, all acrylic, no functional groups (8) Thermally expandable microcapsule: "Microsphere S2640D" manufactured by Kureha Corporation, average particle size 21 μm, maximum expansion temperature 249°C

Example 1
<Preparation of Masterbatch of Thermally Expandable Microcapsules>
Polystyrene resin 1 and thermally expandable microcapsules were mixed in the weight ratio shown in Table 1 below, then set in a gravimetric feeder and fed to a co-rotating intermeshing twin-screw extruder (Technovel, 25 mm extruder), melt-kneaded at 130°C, and the strands were water-cooled and cut with a pelletizer to obtain a pellet-shaped thermally expandable microcapsule master batch (C-1).

<Preparation of polycarbonate resin composition>
50 parts of polycarbonate resin (Mitsubishi Chemical Corporation "S-2000", number average molecular weight 23,000), 15 parts of thermoplastic polyester resin (Bell Polyester Products Co., Ltd. "Bellpet EFG70", polyethylene terephthalate), 15 parts of the polyester-polyether copolymer (H2) obtained above, 15 parts of inorganic compound (mica, Yamaguchi Mica Co., Ltd. "YM-21S", number average particle size 27 μm) were fed to a co-directional intermeshing twin screw extruder (Japan Steel Works, TEX44), melt-kneaded at 280 ° C., and the strands were water-cooled and cut with a pelletizer to obtain a polycarbonate resin composition that becomes a pellet-shaped base component. 95 parts of the obtained polycarbonate resin composition of the base component and 5 parts of the master batch (C-1) of the thermally expandable microcapsules (A) obtained above were hand-blended to obtain a polycarbonate resin composition (I-1).

<Preparation of injection foamed article>
The polycarbonate-based resin composition obtained above was injection-foam molded to produce an injection foam molded article. Specifically, the polycarbonate-based resin composition (I-1) was supplied to an electric injection molding machine (manufactured by Toyo Machinery & Metals Co., Ltd.) having a core-back function and a shut-off nozzle with a clamping force of 180 t, melt-kneaded at a cylinder temperature of 270°C and a back pressure of 10 MPa, and then injected and filled at an injection speed of 100 mm/sec into a mold consisting of a fixed mold set at 60°C and a movable mold capable of forward and backward movement, and having a flat plate-shaped cavity (having an initial cavity clearance t ₀ =1.5 mm and a direct gate of φ8 mm at the center position of the bottom surface) having a length of 160 mm x width of 160 mm as shown in FIG. 1. After injection filling was completed up to the initial filling thickness (initial cavity clearance _t0 ), the movable mold was retreated so that the bottom part had the desired thickness (so that the clearance after core back was 2.0 mm, i.e., the cavity clearance _tf ) and the polycarbonate-based resin composition in the cavity was foamed. After foaming was completed, the injection foam molded article was cooled for 40 seconds and then removed.

Example 2
A master batch (C-2) of thermally expandable microcapsules, a polycarbonate-based resin composition (I-2), and an injection foam molded article were prepared in the same manner as in Example 1, except that polystyrene-based resin 2 was used instead of polystyrene-based resin 1.

Example 3
A master batch (C-3) of thermally expandable microcapsules, a polycarbonate-based resin composition (I-3), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polystyrene-based resin 3, the acrylic plasticizer, and the thermally expandable microcapsules were mixed in the weight ratios shown in Table 1 below.

Example 4
A master batch of thermally expandable microcapsules (C-4), a polycarbonate-based resin composition (I-4), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polystyrene-based resin 4 and the thermally expandable microcapsules were mixed in the weight ratio shown in Table 1 below.

Example 5
A master batch of thermally expandable microcapsules (C-5), a polycarbonate-based resin composition (I-5), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polystyrene-based resin 4, the acrylic plasticizer, and the thermally expandable microcapsules were mixed in the weight ratios shown in Table 1 below.

Example 6
A master batch (C-6) of thermally expandable microcapsules, a polycarbonate resin composition (I-6), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polyester copolymer 1, the acrylic plasticizer, and the thermally expandable microcapsules were mixed in the weight ratios shown in Table 2 below.

(Example 7)
A master batch (C-7) of thermally expandable microcapsules, a polycarbonate resin composition (I-7), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polyester copolymer 2, the acrylic plasticizer, and the thermally expandable microcapsules were mixed in the weight ratios shown in Table 2 below.

(Comparative Example 1)
A master batch of thermally expandable microcapsules (C-8), a polycarbonate-based resin composition (I-8), and an injection foam molded article were prepared in the same manner as in Example 1, except that the polystyrene-based resin 3 and the thermally expandable microcapsules were mixed in the weight ratio shown in Table 1 below.

(Comparative Example 2)
An attempt was made to prepare a master batch of thermally expandable microcapsules in the same manner as in Example 1, except that the polyester copolymer 1 and the thermally expandable microcapsules were mixed in the weight ratio shown in Table 2 below. Although the mixture passed through the extruder, a master batch in the form of pellets could not be obtained. In Comparative Example 2, the melting point of the polyester copolymer 1 was high and no acrylic plasticizer was included, so the shear viscosity of the carrier resin composition at 130°C could not be measured, and therefore a master batch in the form of pellets could not be obtained.

(Comparative Example 3)
An attempt was made to prepare a master batch of thermally expandable microcapsules in the same manner as in Example 1, except that polyester copolymer 2 and thermally expandable microcapsules were mixed in the weight ratio shown in Table 2 below. Although the mixture passed through the extruder, it did not take the shape of a master batch pellet. In Comparative Example 3, since polyester copolymer 2 had a high melting point and did not contain an acrylic plasticizer, the shear viscosity of the carrier resin composition at 130°C could not be measured, and therefore a master batch in the shape of a pellet could not be obtained.

The processability of the masterbatches in the Examples and Comparative Examples was evaluated as described above, and the results are shown in Tables 1 and 2 below. The appearance of the injection foamed molded articles in the Examples and Comparative Examples was evaluated as described above, and the results are shown in Tables 1 and 2 below, in which the expansion ratios are also shown.

As can be seen from Table 1 above, in Examples 1 to 5 using carrier resin composition (B1) or carrier resin composition (B2) containing a polystyrene resin having a weight average molecular weight of 1,000 or more and less than 180,000, or containing a polystyrene resin and an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less, which is substantially compatible with the polycarbonate resin, and has a shear viscosity at 130°C of 1.0 x ¹⁰² Pa·s or more and 1.0 ^{x 106} Pa·s or less, the processability of the master batch of thermally expandable microcapsules was good, and the injection foam molded body obtained by injection foam molding the polycarbonate resin composition using the master batch did not have any whitening or white bumps on the surface, and had a very good appearance.

On the other hand, as can be seen from Table 1, in Comparative Example 1 in which the carrier resin composition (B) did not contain an acrylic plasticizer and contained a polystyrene-based resin having a weight-average molecular weight of more than 180,000, the processability of the master batch of expandable microcapsules was poor, and the injection foam molded body obtained by injection foam molding of the polycarbonate-based resin composition using the master batch had many white particles on the surface, resulting in a poor appearance.

As can be seen from Table 2, in Examples 6 and 7 using a carrier resin composition (B3) containing a polyester copolymer having a weight average molecular weight of 1,000 to 10,000 and an acrylic plasticizer having a weight average molecular weight of 1,000 to 20,000, which is substantially compatible with the polycarbonate resin and has a shear viscosity of 1.0×10 ⁻⁴ Pa·s to 1.0×10 ⁶ Pa·s at 130° C., no whitening occurred on the surface of the injection foam molded product obtained by injection foam molding the polycarbonate resin composition, and the appearance was good. In particular, in Example 7, the processability of the master batch of the thermally expandable microcapsules was also good.

On the other hand, as can be seen from Table 2, in Comparative Examples 2 and 3 in which the carrier resin composition (B) did not contain an acrylic plasticizer and contained a polyester copolymer having a weight average molecular weight of 1,000 or more and 10,000 or less, the mixture passed through the extruder, but did not take the shape of a masterbatch pellet because the melting point of the polyester copolymer was high and no acrylic plasticizer was contained.

Claims (16)

A master batch (C) for a polycarbonate-based resin, comprising a thermally expandable microcapsule (A) and a carrier resin composition (B),
The carrier resin composition (B) is a carrier resin composition (B1) containing a polystyrene-based resin having a weight average molecular weight of 1,000 or more and less than 180,000 and being solid at 20° C.,
The carrier resin composition (B) is a carrier resin composition (B2) containing a polystyrene-based resin that is solid at 20° C. and an acrylic-based plasticizer that has a weight average molecular weight of 1,000 to 20,000 and is liquid at 20° C., or
The carrier resin composition (B) is a carrier resin composition (B3) containing a polyester copolymer having a weight average molecular weight of 1,000 or more and 10,000 or less and being a solid at 20°C, and an acrylic plasticizer having a weight average molecular weight of 1,000 or more and 20,000 or less and being a liquid at 20°C. The polycarbonate-based resin masterbatch according to claim 1, wherein the polystyrene-based resin has a glass transition temperature of 25°C or higher and 130°C or lower. The master batch for polycarbonate-based resin according to claim 1 or 2, wherein the carrier resin composition (B1) contains 0 parts by weight or more and less than 3 parts by weight of an acrylic-based plasticizer having a weight-average molecular weight of 1,000 or more and 20,000 or less per 100 parts by weight of a polystyrene-based resin having a weight-average molecular weight of 1,000 or more and less than 180,000. The master batch for polycarbonate-based resin according to claim 1 or 2, wherein the weight average molecular weight of the polystyrene-based resin in the carrier resin composition (B2) is 1,000 or more and 450,000 or less. 5. The master batch for polycarbonate resins according to claim 1, wherein the carrier resin composition (B) has a shear viscosity at 130° C. of 1.0×10 ⁻⁴ Pa·s or more and 1.0×10 ⁶ Pa·s or less. The masterbatch for polycarbonate-based resins according to any one of claims 1 to 5, wherein the carrier resin composition (B) is compatible with polycarbonate-based resins. The thermally expandable microcapsule (A) has a core-shell structure and is composed of a core made of one or more compounds having a boiling point of 10° C. or more and 330° C. or less, and a shell encapsulating the core,
The master batch for polycarbonate-based resins according to any one of claims 1 to 6, wherein the shell is composed of a resin having a structural unit derived from one or more monomers selected from the group consisting of a nitrile-based monomer, a (meth)acrylate-based monomer, an aromatic vinyl-based monomer, a diene-based monomer, a vinyl-based monomer having a carboxyl group, and a monomer having one or more reactive functional groups selected from the group consisting of a methylol group, a hydroxyl group, an amino group, an epoxy group, and an isocyanate group. The masterbatch for polycarbonate-based resin according to any one of claims 1 to 7, wherein the thermally expandable microcapsules (A) have a maximum expansion temperature of 180°C or more and 300°C or less. 8. The master batch for polycarbonate-based resin according to claim 7, wherein in the resin constituting the shell, a concentration of structural units derived from one or more monomers selected from the group consisting of a monomer containing a carboxyl group and a monomer containing an amino group is 12 mmol/g or less. The masterbatch for polycarbonate-based resins according to any one of claims 1 to 9, wherein the average particle size of the thermally expandable microcapsules (A) is 0.5 μm or more and 50 μm or less. The master batch for polycarbonate resin according to any one of claims 1 to 10, wherein the master batch (C) contains 30% by weight or more and 80% by weight or less of the thermally expandable microcapsules (A) and 20% by weight or more and 70% by weight or less of the carrier resin composition (B). A polycarbonate-based resin composition containing 1 to 15% by weight of the masterbatch for polycarbonate-based resin according to any one of claims 1 to 11, 30 to 99% by weight of a polycarbonate-based resin, and 0 to 55% by weight of one or more other thermoplastic resins selected from the group consisting of polyester-based resins, polyester-polyether copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-ethylene-propylene-diene-styrene copolymers, acrylate-styrene-acrylonitrile copolymers, acrylonitrile-styrene copolymers, polyarylate resins, polystyrene-based resins, and polyamide-based resins. The polycarbonate resin composition according to claim 12, further comprising an inorganic compound. An injection foam molded product obtained by injection foam molding the polycarbonate resin composition according to claim 12 or 13. A method for producing an injection foam molded article by injection foam molding the polycarbonate resin composition according to claim 12 or 13. The method for producing an injection foam molded article according to claim 15, characterized in that the polycarbonate resin composition is supplied to an injection molding machine, filled to an initial filling thickness, and then the core of the mold is pushed back.

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