JP7110609B2 - Thermoplastic resin composition and molded article thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermoplastic resin composition containing an acrylic resin and carbon black, and more particularly to a thermoplastic resin composition in which the effect of carbon black for improving black color development and weather resistance is sufficiently exhibited. The present invention also relates to molded articles obtained by molding this thermoplastic resin composition.

Molded articles obtained by coloring acrylic resins such as polymethyl methacrylate black are used in a wide range of applications. In many cases, a black molded article containing an acrylic resin is required to exhibit a stronger blackness, that is, to exhibit a high black coloring property from the viewpoint of design.

Blending a black dye is known as a method for enhancing the black coloring property of a thermoplastic resin molded article. However, although black dyes are excellent in color development, they have the problem of low weather resistance.
Therefore, the use of carbon black as a black colorant has been studied to enhance the black color developability and weather resistance.

For example, in Patent Document 1, by blending an acrylic resin with carbon black having a number average particle size of 10 to 40 nm and a lubricant such as a fatty acid ester or fatty acid amide, the black color development and weather resistance of the molded product are improved. is stated to increase
Patent Document 2 describes that by blending carbon black coated with a fatty acid salt or fatty acid amide and a dye in a methacrylic resin, the black color development and weather resistance of the molded product are enhanced.

WO2011/152449 JP 2016-37518 A

However, as a result of studies by the present inventors, the molded article described in Patent Document 1 was insufficient in black color development, and the molded article described in Patent Document 2 was insufficient in weather resistance.

The present invention solves the above-mentioned problems of the prior art, and provides a thermoplastic resin composition which is excellent in both black coloring property and weather resistance, and which is excellent in weather resistance, coloring property, and molded appearance, and a molded article thereof. Make it an issue.

As a result of intensive studies to solve the above problems, the present inventors have found that by blending an acrylic resin with a specific viscosity and carbon black with a specific particle size, heat resistance, color development, and molding appearance can be improved. The inventors have found that a plastic resin composition and a molded article thereof can be obtained, and completed the present invention.

That is, the gist of the present invention is as follows.

[1] An acrylic resin (A) having a shear viscosity η satisfying η<3000 [Pa s] under conditions of a temperature of 240° C. and a shear rate of 10 [1/s], and an acrylic resin (A) having a primary particle number average particle diameter of 10 A thermoplastic resin composition containing carbon black (B) of up to 20 nm.

[2] The thermoplastic resin composition of [1], wherein the carbon black (B) has a pH of 6 or less.

[3] The thermoplastic resin composition of [1] or [2], wherein the carbon black (B) has a DBP absorption of 40 to 60 cm ³ /100 g.

[4] In any one of [1] to [3], the carbon black (B) is added to 0.00 parts per 100 parts by mass of the thermoplastic resin containing the acrylic resin (A) in the thermoplastic resin composition. A thermoplastic resin composition containing 1 to 5 parts by mass.

[5] A molded article obtained by molding the thermoplastic resin composition according to any one of [1] to [4].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a thermoplastic resin composition excellent in weather resistance, color developability and molded appearance, and a molded article thereof.

Embodiments of the present invention will be described in detail below.

In the present invention, the acrylic resin is one or more selected from the group consisting of acrylic monomers such as acrylic acid esters and methacrylic monomers such as methacrylic acid esters as monomers constituting the resin. It means an acrylic resin in a broad sense that is included as a main component, and therefore the acrylic resin in the present invention includes methacrylic resin.

[Effect]
In the thermoplastic resin composition of the present invention, carbon black (B) having a small primary particle size and a number average particle size of 10 to 20 nm is used as the black colorant. Although the carbon black (B) having a small particle size tends to enhance the black color development of the resulting molded product, it tends to aggregate and deteriorate the dispersibility in the resin, resulting in insufficient color development.
However, in the thermoplastic resin composition of the present invention, the dispersibility of carbon black (B) is improved by mixing acrylic resin (A) with low shear viscosity η together with carbon black (B) having a small particle size. can be made Therefore, it is possible to improve the black coloring property of the molded article obtained from the thermoplastic resin composition of the present invention.

Carbon black has higher weather resistance as a material than dyes, but tends to have low compatibility with acrylic resins. Therefore, when a molded product containing an acrylic resin and carbon black is irradiated with ultraviolet rays for a long time, the carbon black may bleed out to the surface of the molded product and change the color tone of the surface of the molded product. A molded product whose color tone is likely to change due to ultraviolet irradiation has low weather resistance.
However, the acrylic resin (A) with a low shear viscosity η used in the thermoplastic resin composition of the present invention has good wettability with carbon black (B), and can improve compatibility with carbon black (B). can. Therefore, even if the molded article obtained from the thermoplastic resin composition of the present invention is irradiated with ultraviolet rays for a long time, the small-diameter carbon black (B) is unlikely to bleed out on the surface of the molded article, and the color tone of the molded article surface is improved. is difficult to change. Therefore, according to the thermoplastic resin composition of the present invention, weather resistance as a molded product can be improved.

As described above, according to the thermoplastic resin composition of the present invention, a molded article excellent in both black color development and weather resistance can be easily produced.
In addition, according to the thermoplastic resin composition of the present invention, it is possible to suppress the generation of aggregates of carbon black (B), so that a molded product having excellent appearance can be easily produced.

[Acrylic resin (A)]
The acrylic resin (A) contained in the thermoplastic resin composition of the present invention includes, for example, polymethyl methacrylate (methyl methacrylate homopolymer), methyl methacrylate and other acrylic monomers other than methyl methacrylate. and/or copolymers with methacrylic monomers, copolymers of methyl methacrylate with acrylic monomers and vinyl monomers other than methacrylic monomers (provided that the methyl methacrylate unit content is 50% by mass or more, preferably 60% by mass or more and less than 100% by mass). Among the acrylic resins (A), the effects of the present invention are more effectively exhibited when polymethyl methacrylate is used.

Examples of other acrylic monomers and methacrylic monomers include methacrylic acid esters other than methyl methacrylate, acrylic acid esters, methacrylic acid, and acrylic acid.
Examples of methacrylic acid esters other than methyl methacrylate include ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and 3-hydroxypropyl methacrylate.
Examples of acrylic esters include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate and the like.
One of these acrylic monomers and methacrylic monomers may be used alone, or two or more thereof may be used in combination.

Examples of other vinyl-based monomers include aromatic vinyls (eg, styrene, α-methylstyrene, etc.), vinyl cyanides (eg, acrylonitrile, methacrylonitrile, etc.), and vinyl esters (eg, vinyl acetate, etc.). be done. These may be used individually by 1 type, and may use 2 or more types together.

The acrylic resin (A) may also contain an N-substituted maleimide monomer unit. Examples of the N-substituted maleimide monomer include, but are not limited to, N-phenylmaleimide, N-substituted arylmaleimides such as No-chlorophenylmaleimide, N-substituted alkylmaleimides such as N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide and Nt-butylmaleimide, and N-substituted cycloalkylmaleimides such as N-cyclohexylmaleimide. Among these, N-phenylmaleimide is preferred because it has a high effect of improving heat resistance. Two or more of these N-substituted maleimide monomers can also be used in combination if necessary. It is preferably contained in an amount of 50% by mass or more, more preferably 50% by mass or more.

The acrylic resin (A) is an acrylic resin (A-1) or (A-2) obtained by copolymerizing methyl methacrylate, N-phenylmaleimide, and styrene used in Examples described later. In the case of a copolymerized acrylic resin of an acrylic monomer and/or methacrylic monomer, an aromatic vinyl, and an N-substituted maleimide monomer, 50 to 90 parts by mass of acrylic monomer and/or methacrylic monomer units, an aromatic It preferably contains 5 to 50 parts by mass of vinyl units and 2 to 30 parts by mass of N-phenylmaleimide units so that the total is 100 parts by mass.
Further, acrylic resins (A-3) and (A-4) obtained by copolymerizing methyl methacrylate, styrene, and acrylamide include acrylic monomers and/or methacrylic monomers, aromatic vinyl, and cyanide. In the case of a copolymerized acrylic resin with vinyl, 40 to 80 parts by mass of acrylic monomer and/or methacrylic monomer units, 10 to 40 parts by mass of aromatic vinyl units, and 10 to 40 parts by mass of vinyl cyanide units in total. It is preferable to contain 100 parts by mass.

The acrylic resin (A) is obtained by polymerizing a mixture of acrylic monomers and/or methacrylic monomers and optionally other vinyl monomers. The polymerization method is not particularly limited, and includes known polymerization methods (emulsion polymerization method, suspension polymerization method, solution polymerization method, etc.).

As a method for producing the acrylic resin (A) by an emulsion polymerization method, for example, a vinyl monomer mixture, an emulsifier, a polymerization initiator, and a chain transfer agent are charged in a reactor, heated and polymerized, and the produced acrylic resin A method of recovering the acrylic resin (A) from an aqueous dispersion containing the resin (A) by a precipitation method can be mentioned.

Examples of the emulsifier include common emulsifiers for emulsion polymerization (potassium rosinate, sodium alkylbenzenesulfonate, etc.).

Polymerization initiators include organic and inorganic peroxide-based initiators.

Chain transfer agents include mercaptans, α-methylstyrene dimers, terpenes and the like.

As a method for producing the acrylic resin (A) by suspension polymerization, for example, a vinyl monomer mixture, a suspending agent, a suspending aid, a polymerization initiator, and a chain transfer agent are charged into a reactor and heated. and the slurry is dehydrated and dried to recover the acrylic resin (A).

Suspending agents include, for example, anionic water-soluble polymers, nonionic water-soluble polymers, and sparingly water-soluble inorganic salts.

Examples of anionic water-soluble polymers include polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polymethacrylic acid, sodium polymethacrylate, potassium polymethacrylate, sodium methacrylate-alkyl methacrylate copolymer. etc. 1 type, or 2 or more types are mentioned. Among them, sodium polyacrylate and sodium polymethacrylate are preferred.

Examples of nonionic water-soluble polymers include polyvinyl alcohol, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyvinylpyrrolidone, hydroxypropylmethylcellulose, polyalkylene oxides such as polyethylene oxide, and polyoxyethylene-polyoxypropylene block copolymers. , polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol fatty acid ester, polyoxyethylene laurylamine, and the like. Polyvinyl alcohol and polyoxyethylene-polyoxypropylene copolymers are preferred, and polyoxyethylene-polyoxypropylene block copolymers are more preferred.

Examples of sparingly water-soluble inorganic salts include one or more of barium sulfate, tribasic calcium phosphate, magnesium carbonate, and the like. Tribasic calcium phosphate is preferred.

It is preferable to use 0.1 to 3 parts by mass of the suspending agent with respect to 100 parts by mass of the obtained acrylic resin (A).

Suspension aids include carboxylates (e.g., sodium sarcosinate, fatty acid potassium, fatty acid sodium, potassium alkenyl succinate, dipotassium alkenyl succinate, rosin acid soap, etc.), alkyl sulfate salts, sodium alkylbenzene sulfonate, alkyl One or more dibasic acids having an alkyl group and/or an alkenyl group such as sodium sulfosuccinate, sodium polyoxyethylene nonylphenyl ether sulfate, or salts thereof may be used.

As the suspension aid, it is preferable to use potassium alkenyl succinate from the viewpoints of stability during production and color development of the obtained acrylic resin (A).

It is preferable to use 0.0001 to 1 part by mass of the suspension aid per 100 parts by mass of the obtained acrylic resin (A).

Polymerization initiators include organic peroxides. It is preferable to use 0.01 to 1.0 parts by mass of the polymerization initiator with respect to 100 parts by mass of the obtained acrylic resin (A).

Chain transfer agents include one or more of mercaptans, α-methylstyrene dimers, terpenes and the like. It is preferable to use 0.05 to 1.0 parts by mass of the chain transfer agent per 100 parts by mass of the obtained acrylic resin (A).

The weight average molecular weight of the acrylic resin (A) used in the present invention is not particularly limited, but is preferably in the range of 10,000 to 300,000, more preferably in the range of 70,000 to 100,000. . If the mass-average molecular weight of the acrylic resin (A) is within the above range, the thermoplastic resin composition of the present invention will be excellent in color developability, weather resistance and molding appearance.

Here, the mass average molecular weight of the acrylic resin (A) is measured by dissolving in tetrahydrofuran (THF) using gel permeation chromatography (GPC), and shown in terms of standard polystyrene (PS).

The acrylic resin (A) of the present invention has a shear viscosity η satisfying η<3000 [Pa s] under conditions of a temperature of 240° C. and a shear rate of 10 [1/s], preferably η<2000 [Pa · s], more preferably η<1500 [Pa·s]. The lower the shear viscosity η, the higher the wettability between the acrylic resin (A) and the carbon black (B), and the resulting thermoplastic resin composition has excellent color developability, weather resistance, and molding appearance. .
However, the shear viscosity η is usually 500 [Pa·s] or more from the viewpoint of productivity.
The shear viscosity η of the acrylic resin (A) in the present invention under conditions of a temperature of 240° C. and a shear rate of 10 [1/s] is measured by the following method.

<Measurement of shear viscosity η of acrylic resin (A)>
Using a capillary rheometer (Capilograph Model 1C manufactured by Toyo Seiki Co., Ltd.), the temperature is set to 240°C, and the resin viscosity η [Pa s] is measured under the conditions of a shear rate of 10 [1/s]. do.

The thermoplastic resin composition of the present invention may contain one type of such acrylic resin (A) alone, or may contain two or more types having different physical properties and monomer compositions. good too.

[Carbon black (B)]
The carbon black (B) contained in the thermoplastic resin composition of the present invention is carbon black having a small particle size in which the number average particle size of the primary particles is in the range of 10 to 20 nm, and functions as a black colorant. Fulfill. The number average particle diameter of primary particles of carbon black (B) is preferably 10 to 15 nm.
When the number average particle size of the primary particles of carbon black (B) is at least the above lower limit, bleeding out of carbon black (B) can be suppressed and weather resistance can be improved. When the number average particle size of the primary particles of the carbon black (B) is equal to or less than the above upper limit value, the black coloring property of the molded article can be improved.

The number average particle size of primary particles of carbon black (B) in the present invention is a value determined as follows.

<Measurement of number average particle size of primary particles of carbon black (B)>
Observe the carbon black using a transmission electron microscope (TEM) and measure the diameter of the contoured, inseparable particles. The diameters of 10 or more particles are measured, and the number average particle diameter is obtained from the formula Σ(nd)/Σn (where n is the number of particles and d is the diameter of the particles).

In addition, carbon black is known to have a structure structure in which primary particles are aggregated, and each particle constituting this structure is also measured as a primary particle (Reference Latest Carbon Black Encyclopedia P213).

Further, the dispersed state of the carbon black (B) is preferably primary dispersion from the viewpoint of developing a black color. Here, primary dispersion refers to a state in which carbon black particles are primary particles, that is, unit particles are dispersed without aggregating with other particles. The dispersed state of carbon black (B) can be confirmed by TEM observation.

The carbon black (B) used in the present invention preferably has a pH of 6 or less, more preferably 5 or less, for example 2-5. When the pH of the carbon black (B) is equal to or less than the above upper limit, the dispersibility is excellent, which is preferable from the viewpoint of color developability and weather resistance.

Further, the DBP absorption of carbon black (B) is preferably 40 to 60 cm ³ /100 g. Carbon black (B) having a DBP absorption within this range is preferable because it is excellent in color development.

Here, the DBP absorption of carbon black (B) is ASTM
Values measured according to D-3493-88. pH is a value measured according to ASTM D-1512-84.

Types of carbon black (B) include, for example, channel black, furnace black, lamp black, thermal black, ketjen black, naphthalene black, etc., and any of them can be used in the present invention.

Moreover, the carbon black (B) may be surface-treated. Examples of the surface treatment include oxidation treatment for imparting functional groups to the surface, heat treatment in an inert atmosphere for graphitization, steam treatment, carbon dioxide gas treatment, and the like.

Oxidation treatment includes treatment with ozone, nitric acid, nitrous acid, sodium hypochlorite, or hydrogen peroxide. Such an oxidation treatment can generate acidic functional groups such as carboxy groups and phenolic hydroxyl groups on the surface of the carbon black. As a result, the wettability of the surface of the carbon black is enhanced, so that the dispersibility of the carbon black (B) in the acrylic resin (A) is enhanced.

The thermoplastic resin composition of the present invention may contain one type of carbon black (B) alone, or may contain two or more types having different types and physical properties.
Further, if carbon black (B) having a primary particle number average particle size in the range of 10 to 20 nm is included, a small amount of carbon black having a primary particle size outside the above range (for example, thermoplastic 3 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin containing the acrylic resin (A) in the resin composition).

[Other ingredients]
The thermoplastic resin composition of the present invention may contain additives other than the carbon black (B).
Examples of additives include antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, lubricants, fillers, flame retardants, plasticizers, and silicone oils.
Moreover, the thermoplastic resin composition of the present invention may contain a dye in a small amount.

Moreover, the thermoplastic resin composition of the present invention may contain other thermoplastic resins than the acrylic resin (A) described above.
Thermoplastic resins other than the acrylic resin (A) described above include, for example, acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-styrene-alkyl (meth)acrylate copolymer (ASA resin), Acrylonitrile-ethylene-propylene-diene-styrene copolymer (AES resin), polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-α-methylstyrene copolymer, styrene-maleic anhydride copolymer, acrylonitrile-styrene-N -substituted maleimide terpolymers, styrene-maleic anhydride-N-substituted maleimide terpolymers, methyl methacrylate-styrene copolymers, acrylonitrile-styrene-methyl methacrylate copolymers, polyvinyl chloride, polyolefins ( polyethylene, polypropylene, etc.), ethylene-vinyl acetate copolymer, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polyether sulfone, polyether ether ketone, polyarylate, liquid crystal polyester, polyamide, Styrene-based elastomers (styrene-butadiene-styrene (SBS), styrene-butadiene (SBR), hydrogenated SBS, styrene-isoprene-styrene (SIS), etc.), various olefin-based elastomers, various polyester-based elastomers, etc. . Other thermoplastic resins may be used singly or in combination of two or more.

[Content ratio of each component]
The content of the carbon black (B) in the thermoplastic resin composition of the present invention is 100 parts by mass of the thermoplastic resin containing the acrylic resin (A) (when the thermoplastic resin contains only the acrylic resin (A), 100 parts by mass of the acrylic resin (A), and 100 parts by mass of the total when the acrylic resin (A) and another thermoplastic resin are included as the thermoplastic resin). 0.1 to 5 parts by mass. is preferred, and 0.3 to 3 parts by mass is more preferred. If the content of carbon black (B) is at least the above lower limit, the black coloration of the molded article will be further enhanced. If the content of carbon black (B) is equal to or less than the above upper limit, the weather resistance of the molded article will be higher.

When the thermoplastic resin composition of the present invention contains the above additives, the content of each additive is 0.1 to 5 parts by mass with respect to 100 parts by mass of the thermoplastic resin containing the acrylic resin (A). preferably 0.3 to 2 parts by mass. If the content of each additive is at least the above lower limit, the effect of adding each additive can be sufficiently exhibited. If the content of each additive is equal to or less than the above upper limit, the amount of additive that is wasted is reduced, which is economical.
In addition, the total content of all additives is 0 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin containing the acrylic resin (A) in order to prevent deterioration of the mechanical properties of the molded product. It is preferably 0 mass parts or more and 3 mass parts or less.

When the thermoplastic resin composition of the present invention contains a dye, it is preferable that the content of the dye is small from the viewpoint of preventing deterioration of the weather resistance of the molded article. Specifically, the content of the dye in the thermoplastic resin composition is preferably 1.0 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin containing the acrylic resin (A), and 0.5 parts by mass. It is more preferably 0.1 parts by mass or less, and particularly preferably 0 parts by mass.

When the thermoplastic resin composition of the present invention contains a thermoplastic resin other than the acrylic resin (A), the content of the other thermoplastic resin should be small from the viewpoint of preventing deterioration of the weather resistance of the molded product. is preferred. Specifically, the content of the other thermoplastic resin in the thermoplastic resin composition is 50% by mass or less with respect to the total 100% by mass of the other thermoplastic resin and the acrylic resin (A). It is preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass.

[Method for producing thermoplastic resin composition]
The thermoplastic resin composition of the present invention is obtained by adding carbon black (B) and, if necessary, other additives and other thermoplastic resins to acrylic resin (A). After adding carbon black (B) and optionally other additives and other thermoplastic resins to the acrylic resin (A), the mixture is sufficiently mixed using a mixer to prepare a mixture. It is preferable to melt-knead using a kneader.
As the mixer, for example, a Henschel mixer, a V-type blender, a tumbler mixer, or the like can be used.
Examples of kneaders that can be used include single-screw extruders, twin-screw extruders, Banbury mixers, pressure kneaders, and mixing rolls.
After the melt-kneading, the obtained melt-kneaded product is preferably cooled and then pelletized using a pelletizer.

Further, when producing the thermoplastic resin composition of the present invention, a carbon black mixture (so-called masterbatch) in which carbon black (B) is mixed with a diluent resin is used, and the carbon black mixture is an acrylic resin (A ). When the carbon black mixture is mixed with the acrylic resin (A), the dispersibility of the carbon black (B) in the acrylic resin (A) is further increased, and the black color development and weather resistance of the molded product are further increased. be able to.

As the diluent resin contained in the carbon black mixture, resins similar to the acrylic resin (A) and other thermoplastic resins can be used. The resin for dilution may be the same resin as the acrylic resin (A), or may be a different resin. When the diluent resin is different from the acrylic resin (A), at least one of the above other thermoplastic resins can be used as the diluent resin.
For example, when the acrylic resin (A) is polymethyl methacrylate, the diluent resin may be polymethyl methacrylate, or a resin other than polymethyl methacrylate (for example, a styrene-acrylonitrile copolymer, etc.). There may be.

The carbon black mixture may contain a lubricant for further improving the dispersibility of the carbon black (B). Any known lubricant can be used without limitation. Specific examples of lubricants include fatty acid esters and fatty acid amides. The lubricant may be added together with the carbon black (B) even when the carbon black (B) is directly mixed with the acrylic resin (A) without being mixed with the carbon black (B).

The content of carbon black (B) in the carbon black mixture is preferably 20 to 70% by mass when the total of carbon black (B) and diluent resin is 100% by mass, and 30 to 60% by mass. is more preferable. If the content of carbon black (B) is within the above range, it is possible to sufficiently improve the black color developability and weather resistance of the resulting molded article.

The carbon black mixture is preferably melt-kneaded. Moreover, the carbon black mixture is preferably pelletized after melt-kneading.

[Molding]
The molded article of the present invention is obtained by molding the thermoplastic resin composition of the present invention by a known molding method.
Examples of molding methods include injection molding, press molding, extrusion molding, vacuum molding, and blow molding.

Since the molded article of the present invention contains the thermoplastic resin composition of the present invention, it is excellent in black coloring and weather resistance. Such a molded product of the present invention is suitable for automobile interior and exterior materials, office equipment parts, household appliance parts, medical equipment parts, electronic equipment parts, building materials, daily necessities, and the like.

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.
"Parts" in the following examples means "mass parts" unless otherwise specified.

[Acrylic resin (A) and other thermoplastic resins]
The acrylic resin (A) and other thermoplastic resins used in the following examples and comparative examples were produced as follows.

<Method for producing acrylic resin (A-1)>
74 parts of methyl methacrylate, 10 parts of N-phenylmaleimide, 16 parts of styrene, 0.1 part of Perbutyl PV (manufactured by NOF Corporation), 0.1 part of Perbutyl O (manufactured by NOF Corporation) were placed in a 20-liter pressure-resistant reactor equipped with a stirrer. 05 parts, 0.05 parts of Perhexa HC (manufactured by NOF Corporation), 0.6 parts of t-dodecylmercaptan, and 0.2 parts of α-methylstyrene dimer were added and mixed. Next, a mixed solution of 200 parts of pure water, 0.5 parts of tribasic calcium phosphate and 0.003 parts of potassium alkenyl succinate was charged into the 20-liter pressure-resistant reactor and mixed with stirring. Thereafter, the temperature was raised to 40° C. while stirring to initiate polymerization. During the polymerization reaction, the temperature is raised at a rate of 5 to 10° C./hr for 9 hours. After the polymerization is completed at 120° C., the acrylic resin, which is a bead polymer, is passed through cooling, washing, filtering, and drying steps. (A-1) was obtained. The acrylic resin (A-1) had a shear viscosity η of 2500 [Pa·s] measured under conditions of 240° C. and a shear rate of 10 [1/s].

<Production of acrylic resins (A-2) to (A-6) and acrylonitrile-styrene copolymer resin (X-1)>
Acrylic resins (A-2) to (A-6) and acrylonitrile-styrene copolymer resin (AS resin) in the same manner as acrylic resin (A-1), except that the monomer formulation was the formulation shown in Table 1. (X-1) was produced.
Table 1 shows the shear viscosities η of the obtained acrylic resins (A-2) to (A-6) and AS resin (X-1).

[Distributed state]
The specifications of carbon black (B) used in the following examples and comparative examples are as follows.

(B-1) "#2900B" manufactured by Mitsubishi Chemical Corporation
Number average particle size of primary particles: 15 nm
DBP absorption: 59cm ³ /100g
pH: 2.5
(B-2) "#2600B" manufactured by Mitsubishi Chemical Corporation
Number average particle size of primary particles: 13 nm
DBP absorption: 77cm ³ /100g
pH: 6.5
(B-3) "#750B" manufactured by Mitsubishi Chemical Corporation
Number average particle size of primary particles: 22 nm
DBP absorption: 116cm ³ /100g
pH: 7.5

[dye]
The following dyes were used.
C-1: "Plast Black DA-423" manufactured by Arimoto Chemical Industry Co., Ltd.

[Evaluation of thermoplastic resin molded product]
Methods for evaluating thermoplastic resin molded articles obtained in Examples and Comparative Examples are as follows.

<Evaluation of Gloss (Appearance)>
Using a digital variable angle gloss meter ("UGV-5D" manufactured by Suga Test Instruments Co., Ltd.), the glossiness (Gs) of the surface of the molded product was measured at an incident angle of 60° as defined in JIS Z8741. The higher the glossiness, the better the appearance of the molded product.

<Evaluation of color tone (black color development)>
Using an SCE colorimeter (“CM-508D” manufactured by Konica Minolta Japan, Inc.), the color tone (L ^* ) of the molded product was measured. The smaller the value of L ^* , the darker the blackness of the molded product, and the better the black coloring property.

<Weather resistance evaluation>
Using a "Sunshine Super Long Life Weather Meter WEL-SUN-DCH Type" manufactured by Suga Test Instruments Co., Ltd., the molded product was exposed to an environment of 63°C and cycle conditions of 60 minutes (rainfall: 12 minutes) for 2000 hours. Then, a weather resistance test was performed. The degree of discoloration (ΔE) of the molded product before and after the weather resistance test was measured using the SCE colorimeter. The smaller the value of ΔE, the better the weather resistance.

[Example 1]
Acrylic resin (A-1) 100 parts by mass, carbon black (B-1) 1.0 parts, ethylene bisstearylamide (manufactured by Kao Corporation) 0.4 parts, antioxidant (manufactured by ADEKA Co., Ltd. "ADEKA STAB AO -60") and 0.4 part of a light stabilizer ("ADEKA STAB LA-57" manufactured by ADEKA Co., Ltd.) were mixed using a Henschel mixer. The resulting mixture was melt-kneaded at 250° C. using a screw extruder (“TEX-30α type twin-screw extruder” manufactured by The Japan Steel Works, Ltd.). After cooling the melt-kneaded product thus obtained, it was pelletized using a pelletizer to obtain a pellet-like thermoplastic resin composition.
Using the obtained pellet-shaped thermoplastic resin composition, molding was performed using an injection molding machine (manufactured by The Japan Steel Works, Ltd.) to prepare a test piece (molded product) having a size of 100 mm square and a thickness of 3 mm.
The obtained molded article was evaluated for gloss, color tone, and weather resistance as described above, and the results are shown in Table 2.

[Examples 2 to 7 and Comparative Examples 1 to 5]
As shown in Tables 2 and 3, a pellet-shaped thermoplastic resin composition was obtained in the same manner as in Example 1 except that the blending of the thermoplastic resin composition was changed, and the molded product was evaluated in the same manner. , the results are shown in Tables 2 and 3.

[Discussion]
As shown in Table 2, according to the thermoplastic resin composition of each example, molded articles with high glossiness, small L ^* , and small ΔE before and after the weather resistance test were obtained. Therefore, according to the thermoplastic resin composition of each example, it can be seen that molded articles excellent in all of appearance, black color development and weather resistance could be obtained.

On the other hand, as shown in Table 3, the molded articles obtained from the thermoplastic resin compositions of the respective comparative examples are insufficient in either or both of the black coloring property and the weather resistance.
Specifically, in Comparative Examples 1 and 2, since the shear viscosity η of the acrylic resin used was high, the color developability and weather resistance of the molded product were inferior.
In Comparative Example 3, the weather resistance was poor because no acrylic resin was used.
In Comparative Example 4, the number-average particle size of the primary particles of the carbon black used exceeded 20 nm, so the molded article was inferior in black color development.
In Comparative Example 5, the weather resistance was poor because only the dye was used as the coloring agent.

Claims (5)

A thermoplastic resin containing an acrylic resin (A) and carbon black (B) having a primary particle number average particle size of 10 to 20 nm,
The acrylic resin (A) is an acrylic resin (A) having a shear viscosity η satisfying η<3000 [Pa s] under conditions of a temperature of 240° C. and a shear rate of 10 [1/s],
The acrylic resin (A) is
Acrylic resin containing 50 to 90 parts by mass of acrylic monomer and/or methacrylic monomer units, 16 to 50 parts by mass of aromatic vinyl units, and 2 to 30 parts by mass of N-phenylmaleimide units in total of 100 parts by mass,
or
Acrylic resin containing 100 parts by mass in total of 40 to 80 parts by mass of acrylic monomer and/or methacrylic monomer units, 10 to 40 parts by mass of aromatic vinyl units, and 10 to 40 parts by mass of vinyl cyanide units,
When the thermoplastic resin contains a thermoplastic resin other than the acrylic resin (A), the content of the other thermoplastic resin is the total of the other thermoplastic resin and the acrylic resin (A) A thermoplastic resin composition having a content of 10% by mass or less based on 100% by mass. 2. The thermoplastic resin composition according to claim 1, wherein the carbon black (B) has a pH of 6 or less. 3. The thermoplastic resin composition according to claim 1, wherein the carbon black (B) has a DBP absorption of 40 to 60 cm ³ /100 g. 4. In any one of claims 1 to 3, the carbon black (B) is 0.1 to 5 parts per 100 parts by mass of the thermoplastic resin containing the acrylic resin (A) in the thermoplastic resin composition. A thermoplastic resin composition containing parts by mass. A molded article obtained by molding the thermoplastic resin composition according to any one of claims 1 to 4.