Resin composition and molded article

Abstract

To provide a resin composition which can provide a molded article that is excellent in impact resistance, especially, a retention rate of the impact resistance when being retained, while achieving desired light-shielding property, and a molded article.SOLUTION: A resin composition contains, with respect to 100 pts.mass of a polycarbonate resin (A), 5.0-20.0 pts.mass of particles (B) containing a titanium oxide as a main component, and 0.11-5.0 pts.mass of diphenyl sulfone potassium sulfonate (C), where an equivalent circle diameter obtained by observing a molded article molded using the resin composition at a cylinder set temperature of 280°C for cycle time of 1 minute by an operation type electronic microscope, and calculation from the area of a region of the particles (B) containing the scattering titanium oxide as a main component using Expression (1) is 0.149 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to resin compositions and molded articles. [Background technology]

[0002] Conventionally, titanium dioxide has been added to polycarbonate resin for the purpose of improving the shielding properties and coloring of resin molded products (Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 172243 [Patent Document 2] Japanese Patent Publication No. 2019-123809 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] As described above, in order to improve the light-shielding properties of molded products formed from a resin composition containing polycarbonate resin, a large amount of titanium dioxide particles may be added to the resin composition. However, when a resin composition contains a large amount of titanium dioxide, the impact strength of the molded product obtained from such a resin composition tends to be inferior. In particular, when the resin composition is left in a cylinder during molding, the impact strength of the molded product tends to be inferior. The present invention aims to solve the above problems and to provide a resin composition and a molded article that can provide a molded article that achieves desired light shielding properties while having excellent impact resistance, particularly the retention rate of impact resistance when left in place. [Means for solving the problem]

[0005] Based on the above-mentioned problems, the inventors conducted research and found that the above-mentioned problems can be solved by combining polycarbonate resin and titanium dioxide particles with potassium diphenylsulfonate. Specifically, the above problem was solved by the following means. <1> A resin composition comprising 100 parts by mass of polycarbonate resin (A), 5.0 to 20.0 parts by mass of particles (B) mainly composed of titanium dioxide, and 0.11 to 5.0 parts by mass of potassium diphenylsulfonate (C), A resin composition in which a molded product formed using the above resin composition at a cylinder setting temperature of 280°C and a cycle time of 1 minute is observed with an operational electron microscope, and the equivalent circle diameter calculated using formula (1) from the area of ​​the region of scattered titanium oxide particles (B) is 0.149 μm or less.

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[0006] The present invention provides a resin composition and a molded article that can achieve desired light-shielding properties while also providing a molded article with excellent impact resistance, particularly in terms of retaining impact resistance when left in a state of retention. [Modes for carrying out the invention]

[0007] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). Note that the following embodiment is illustrative for explaining the present invention, and the present invention is not limited to this embodiment. In this specification, "~" is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In this specification, all physical properties and characteristic values ​​shall be those at 23°C unless otherwise specified. If the measurement methods, etc., described in the standards shown herein differ from year to year, unless otherwise specified, the standards as of January 1, 2022 shall apply.

[0008] The resin composition of the present embodiment is a resin composition containing 5 to 20 parts by mass of particles (B) mainly composed of titanium oxide (hereinafter sometimes referred to as "titanium oxide particles") and 0.11 to 5.0 parts by mass of potassium diphenylsulfone sulfonate (C) with respect to 100 parts by mass of a polycarbonate resin (A). Using the resin composition, a molded product molded at a cylinder set temperature of 280 °C and a cycle time of 1 minute is observed with an operating electron microscope, and the equivalent circle diameter calculated using the formula (1) from the area of the region of the particles (B) mainly composed of titanium oxide present is 0.149 μm or less. By reducing the equivalent circle diameter as described above, aggregation of the titanium oxide particles (B) can be suppressed. As a result, it becomes possible to provide a resin composition that can obtain a molded product excellent in impact resistance, particularly in the retention rate of impact resistance when retained, while achieving the desired light shielding property.

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[0009] <Polycarbonate resin (A)> The resin composition of the present embodiment contains a polycarbonate resin (A). Specifically, the polycarbonate resin (A) is not particularly limited as long as it contains a -[O-R-OC(=O)]- unit (R is an organic group, preferably a hydrocarbon group, more preferably an aliphatic group, an aromatic group, or a group containing both an aliphatic group and an aromatic group, and further having a linear structure or a branched structure) containing a carbonate ester bond in the main chain of the molecule. In the present embodiment, the polycarbonate resin (A) is preferably an aromatic polycarbonate resin, and more preferably a polycarbonate resin having a bisphenol skeleton. By using such a polycarbonate resin, more excellent heat resistance and toughness are achieved. In the present embodiment, the polycarbonate resin having a bisphenol skeleton preferably has a constituent unit having a bisphenol skeleton in 90 mol% or more of all constituent units, and more preferably has a constituent unit derived from bisphenol A in 90 mol% or more of all constituent units.

[0010] Moreover, the viscosity average molecular weight (Mv) of the polycarbonate resin (A) is preferably 10,000 or more, more preferably 12,000 or more, and even more preferably 15,000 or more. By setting it to the above lower limit or more, the durability of the obtained molded product tends to be further improved. The upper limit of the viscosity average molecular weight (Mv) of the polycarbonate resin (A) is preferably 50,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. By setting it to the above upper limit or less, the molding processability of the molded product tends to be further improved. The viscosity average molecular weight (Mv) is obtained by using methylene chloride as a solvent and determining the intrinsic viscosity [η] (unit: dL / g) at a temperature of 25°C using an Ubbelohde viscometer, and using the Schnell viscosity formula, that is, η = 1.23×10 -4 ×Mv 0.83 、which means the value calculated from. When using two or more polycarbonate resins, it is the viscosity average molecular weight of the mixture.

[0011] The production method of the polycarbonate resin (A) is not particularly limited, and those produced by conventionally known phosgene method (interfacial polymerization method) or melting method (ester exchange method) can be used. Also, when using the melting method, a polycarbonate resin with the amount of terminal OH groups adjusted can be used.

[0012] The polycarbonate resin (A) used in this embodiment may be a recycled product of polycarbonate resin (including recycled products, material recycled products, chemical recycled products, etc.), defective products, or edge materials during thermoplastic resin molding.

[0013] In addition to the above, for the details of the polycarbonate resin (A), the descriptions in paragraphs 0013 to 0041 of JP-A-2021-084942 and paragraphs 0030 to 0035 of JP-A-2021-119211 can be referred to, and this content is incorporated herein.

[0014] The proportion of polycarbonate resin (A) in the resin composition of this embodiment is preferably 83% by mass or more, more preferably 85% by mass or more, and even more preferably 87% by mass or more. Setting it above the lower limit tends to further improve the impact resistance of the resulting molded product. Furthermore, the proportion of polycarbonate resin (A) in the resin composition of this embodiment is preferably 95% by mass or less, and more preferably 93% by mass or less. Setting it below the upper limit tends to further improve the light-shielding properties of the resulting molded product. The resin composition of this embodiment may contain only one type of polycarbonate resin (A), or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0015] <Particles mainly composed of titanium dioxide (B)> The resin composition of this embodiment contains titanium dioxide particles (titanium dioxide particles) (B) as the main component. By including titanium dioxide particles (B), the resulting molded product can achieve light-shielding properties. "Mainly composed of titanium dioxide" means that titanium dioxide is the most abundant component among the components contained in the titanium dioxide particles (B). Typically, the proportion of titanium dioxide (preferably titanium dioxide) in the titanium dioxide particles (B) is 85.0% by mass or more, and preferably 90.0% by mass or more. The titanium oxide particles (B) preferably contain TiO2: 90.0 to 98.0% by mass, Al2O3: 0.5 to 3.5% by mass, and SiO2: 0 to 6.0% by mass. Furthermore, in addition to the above components, the titanium oxide particles (B) may also contain SO3: 0 to 0.1% by mass, Na2O: 0 to 0.15% by mass, and Cl: 0 to 0.01% by mass. Moreover, the titanium oxide particles (B) may also contain other components, the total of which is 100% by mass.

[0016] In this embodiment, the titanium dioxide particles (B) may be rutile-type titanium dioxide particles or anatase-type titanium dioxide particles. Furthermore, it is preferable that the surface of the titanium dioxide particles (B) is treated with a surface treatment agent. That is, it is preferable that the surface of the titanium dioxide particles (B) has a layer formed from the surface treatment agent (particularly an organic layer). With this configuration, the titanium dioxide is more easily dispersed in the polycarbonate resin (A), and a molded product with a better appearance can be obtained. Examples of surface treatment agents include polymers, siloxane compounds are preferred, and hydrogen methylsiloxane and dimethylsiloxane are particularly preferred. The surface treatment agent may be physically adsorbed on the titanium dioxide surface or chemically bonded to it. Titanium oxide is usually known as titanium dioxide.

[0017] In this embodiment, the resin composition contains 5.0 to 20.0 parts by mass of titanium oxide particles (B) per 100 parts by mass of polycarbonate resin (A). Setting the amount above the lower limit tends to improve shielding performance. Furthermore, setting the amount below the upper limit tends to provide higher impact resistance even during stagnant molding. In this embodiment, the content of titanium oxide particles (B) is preferably 6.0 parts by mass or more, more preferably 8.0 parts by mass or more, and even more preferably 9.0 parts by mass or more, per 100 parts by mass of polycarbonate resin (A). In this embodiment, the content of titanium oxide particles (B) is preferably 18.0 parts by mass or less, more preferably 16.0 parts by mass or less, even more preferably 14.0 parts by mass or less, and even more preferably 12.0 parts by mass or less, per 100 parts by mass of polycarbonate resin (A). The resin composition of this embodiment may contain only one type of titanium oxide particle (B), or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0018] <Potassium diphenylsulfonate (C)> The resin composition of this embodiment contains 0.11 to 5.0 parts by mass of potassium diphenylsulfonate (C) per 100 parts by mass of polycarbonate resin (A). By including potassium diphenylsulfonate (C), the aggregation of titanium oxide particles (B) can be effectively suppressed, and the impact resistance of the resulting molded product, in particular, the retention rate of impact resistance when left standing, can be improved. Potassium diphenylsulfonate (C) is a component commonly used as a flame retardant in polycarbonate resins. In this embodiment, by incorporating a higher amount of potassium diphenylsulfonate (C) than is typically used as a flame retardant, we succeeded in effectively dispersing titanium dioxide particles (B). Furthermore, while sodium p-toluenesulfonate is also known as a flame retardant for use in polycarbonate resins, the effect of the present invention is remarkable because even when sodium p-toluenesulfonate is added, the effect of promoting the dispersion of titanium dioxide particles (B) is small.

[0019] Potassium diphenylsulfonolate (C) is preferred over potassium diphenylsulfon-3-sulfonate. Commercially available potassium diphenylsulfonolate (C), such as Arichem's KSS-FR, can also be used.

[0020] The content of potassium diphenylsulfonates (C) in the resin composition of this embodiment is 0.11 parts by mass or more, preferably 0.13 parts by mass or more, more preferably 0.15 parts by mass or more, even more preferably 0.2 parts by mass or more, even more preferably 0.24 parts by mass or more, and even more preferably 0.26 parts by mass or more, per 100 parts by mass of polycarbonate resin (A). Setting the content above the lower limit tends to further improve impact resistance, particularly the retention rate of impact resistance when the resin is left standing. The upper limit of the content of potassium diphenylsulfonates (C) is 5.0 parts by mass or less, preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, even more preferably 0.8 parts by mass or less, and even more preferably 0.5 parts by mass or less, per 100 parts by mass of polycarbonate resin (A). By setting the value above the aforementioned lower limit, the impact resistance, particularly the retention rate of impact resistance when the material is left in a stagnant state, tends to improve further. The resin composition of this embodiment may contain only one type of potassium (C) diphenylsulfonsulfonate, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0021] The resin composition of this embodiment may or may not contain alkali metal salts other than potassium diphenylsulfonsulfonate (C). For alkali metal salts other than potassium diphenylsulfonsulfonate (C), refer to paragraphs 0069 to 0078 of Japanese Patent Application Publication No. 2015-117298, the contents of which are incorporated herein by reference. The resin composition of this embodiment preferably contains substantially no alkali metal salts other than potassium diphenylsulfonulfonate (C). Substantially free means that the content of alkali metal salts other than potassium diphenylsulfonulfonate (C) is 10% by mass or less of the content of potassium diphenylsulfonulfonate (C) contained in the resin composition, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0022] <Other ingredients> The resin composition of this embodiment may further contain other components not listed above. Examples of other components include reinforcing agents, mold release agents, colorants other than titanium dioxide (e.g., carbon black), stabilizers (heat stabilizers, antioxidants, etc.), flame retardants other than alkali metal salts, flame retardant additives, anti-dripping agents, ultraviolet absorbers, fluorescent whitening agents, impact resistance modifiers, epoxy compounds, anti-fogging agents, fluidity modifiers, plasticizers, dispersants, antibacterial agents, antiviral agents, and the like. Details of these components can be found in paragraphs 0107 to 0115 of Japanese Patent Application Publication No. 2014-136710, paragraphs 0106 to 0128 of Japanese Patent Application Publication No. 2015-117298, and paragraphs 0055 to 0061 of Japanese Patent Application Publication No. 2018-095706, the contents of which are incorporated herein by reference. The content of the other components mentioned above, if present, is, for example, 0.001% by mass or more, and for example, 5.0% by mass or less, preferably 3.0% by mass or less, and more preferably 1.0% by mass or less, based on the mass of the resin composition.

[0023] In this embodiment, it is preferable that the resin composition contains less than 0.1 parts by mass of polyolefin wax per 100 parts by mass of polycarbonate resin (A). This configuration allows for more effective suppression of the aggregation of titanium dioxide particles (B). In other words, polyolefin wax tends to attract hydroxyl groups on the surface of titanium dioxide particles (B), making them prone to aggregation. However, in this embodiment, the resin composition contains a larger amount of potassium diphenylsulfonulfonate (C) to improve the dispersibility of titanium dioxide particles (B). In this embodiment, the polyolefin wax content in the resin composition is more preferably less than 0.05 parts by mass, even more preferably less than 0.01 parts by mass, and even more preferably less than 0.005 parts by mass, per 100 parts by mass of polycarbonate resin (A). The lower limit of the polyolefin wax content in the resin composition may be 0 parts by mass or more per 100 parts by mass of polycarbonate resin (A).

[0024] <Physical properties of resin compositions> The resin composition of this embodiment effectively suppresses the aggregation of titanium oxide particles (B) in the molded product. Specifically, when a molded product formed using the resin composition of this embodiment at a cylinder setting temperature of 280°C and a cycle time of 1 minute was observed with an operational electron microscope, the equivalent circle diameter calculated using formula (1) from the area of ​​the region of scattered titanium dioxide particles (B) was 0.149 μm or less. Here, π is the ratio of a circle's circumference to its diameter. Such a small equivalent circle diameter can be achieved by adjusting the amount of titanium dioxide particles (B) blended, blending potassium diphenylsulfonate (C), adjusting the amount of potassium diphenylsulfonate (C), and reducing the content of components that tend to aggregate titanium dioxide particles (B), such as polyolefin wax described later.

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[0025] In this embodiment, the equivalent circle diameter means that the smaller it is, the less the aggregation of titanium oxide particles (B) in the molded product. The equivalent circle diameter is preferably 0.148 μm or less, more preferably 0.147 μm or less, still more preferably 0.146 μm or less, and even more preferably 0.145 μm or less. The lower limit of the equivalent circle diameter is not particularly defined, but 0.050 μm or more is practical. The equivalent circle diameter in this embodiment is measured according to the description in the examples described later.

[0026] The resin composition of this embodiment can provide a molded product with high shielding properties. In particular, when the resin composition of this embodiment is molded to a thickness of 1.0 mm, the total light transmittance is preferably 0.04% or less, more preferably less than 0.02%, and still more preferably 0.015% or less. The lower limit of the total light transmittance may be 0%, but 0.001% or more also sufficiently satisfies the required performance. The total light transmittance is measured according to the description in the examples described later.

[0027] Also, the resin composition of this embodiment can provide a molded product with excellent impact resistance. In particular, using the resin composition, a test piece with a thickness of 3 mm is molded at a cylinder temperature of 280 °C and a cycle time of 1 minute, and the notched Charpy impact strength measured based on ISO179-1 is 40 kJ / m 2 or more, preferably 42 kJ / m 2 or more, more preferably 44 kJ / m 2 or more, still more preferably 46 kJ / m 2 or more, even more preferably 49 kJ / m 2 or more, and more preferably 49 kJ / m 2 or more. The upper limit of the notched Charpy impact strength is not particularly defined, but 70 kJ / m The resin composition of this embodiment can achieve high impact resistance even when it is retained in the cylinder during molding. Specifically, using the resin composition of this embodiment, a 3 mm thick test piece was molded at a cylinder temperature of 310°C and a residence time of 7 minutes in the cylinder, and the notched Charpy impact strength measured according to ISO 179-1 was 30 kJ / m². 2 Preferably, it is 32 kJ / m³ or more. 2 It is more preferable that the value be greater than or equal to 34 kJ / m³ 2 It is even more preferable that the value be 36 kJ / m³ or higher. 2 It is even more preferable that the value be 39 kJ / m³ 2 It is more preferable that the above is true. There is no upper limit to the notched Charpy impact strength, but it is 60 kJ / m 2 The following is practical.

[0028] The resin composition of this embodiment can maintain high impact resistance even when it is retained in the cylinder during molding. Specifically, when a 3 mm thick test piece is molded using the resin composition at a cylinder setting temperature of 310°C and a residence time of 7 minutes in the cylinder, and the notched Charpy impact strength measured according to ISO 179-1 is preferably 70% or more, more preferably 73% or more, even more preferably 76% or more, even more preferably 80% or more, and even more preferably 83% or more, the impact strength retention rate is 70% or more compared to the notched Charpy impact strength measured by the same method when the resin composition is molded at a cylinder setting temperature of 280°C and a cycle time of 1 minute. There is no particular upper limit for the impact strength retention rate, but 95% or less is practical. The notched Charpy impact strength is measured according to the example described below.

[0029] <Manufacturing of resin compositions> There are no limitations on the manufacturing method of the resin composition of this embodiment, and a wide range of known methods for manufacturing resin compositions can be used. For example, a method may be used in which polycarbonate resin (A), titanium dioxide particles (B), potassium diphenylsulfonate (C), and other components that may be added as needed are pre-mixed using various mixers such as a tumbler or Henschel mixer, and then melt-kneaded using a mixer such as a Banbury mixer, roll, braver, single-screw extruder, twin-screw extruder, or kneader. The melt-kneading temperature is not particularly limited, but is usually in the range of 240 to 320°C.

[0030] The resin composition of this embodiment is molded into various molded articles. That is, the molded article of this embodiment is a molded article formed from the resin composition of this embodiment. There is no particular method for molding the molded article, but examples include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using a heat-insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, etc., with injection molding being preferred among them.

[0031] Furthermore, there are no particular restrictions on the shape of the molded product in this embodiment, and it can be appropriately selected according to the application and purpose of the molded product. Examples include plate-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, annular, circular, elliptical, polygonal, irregularly shaped, hollow, frame-shaped, box-shaped, panel-shaped, and other special shapes.

[0032] The molded articles of this embodiment are preferably used as structural members, portable electronic device components, vehicle and medical device components, other electronic components including electrical circuits, food and pharmaceutical containers, and composite materials for forming these. In particular, the molded product of this embodiment is preferably used as an in-vehicle component, specifically as a headlamp, and especially as a light guide base. [Examples]

[0033] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0034] 1.Raw materials The raw materials used were those listed in the table below.

[0035] [Table 1] The above titanium oxide particles contain TiO2: 90.0-98.0% by mass, Al2O3: 0.5-3.5% by mass, and SiO2: 0-6.0% by mass. In addition, 0.1% by mass of Riken Vitamin S-100A and 0.3% by mass of Emery Oleo VPG861 were added as release agents to all samples examined in the examples and comparative examples, and 0.03% by mass of Adeka Stab 2112 manufactured by Adeka Industries was added as a stabilizer. Furthermore, in Tables 2 and 3, "Polycarbonate resin (A1) / (A2)" refers to polycarbonate resin (A1) and polycarbonate resin (A2) with a melt volume rate (MVR, 300℃, 1.2kgf) of 17.5cm³. 3 A sample adjusted to have a time of 10 minutes was used. The mass ratio of polycarbonate resin (A1) to polycarbonate resin (A2) in "polycarbonate resin (A1) / (A2)" is approximately 77:13.

[0036] 2. Examples 1-5, Comparative Examples 1-7 <Preparation of resin pellets> Each component listed in Table 1 was blended in the proportions shown in Table 2 or Table 3 (each component is in parts by mass), and the mixture was uniformly mixed in a tumbler mixer to prepare a mixture. This mixture was supplied to a twin-screw extruder (TEX25αIII manufactured by Japan Steel Works, Ltd.), kneaded under the conditions of screw rotation of 700 rpm, discharge rate of 20 kg / hour, and barrel temperature of 260°C, and extruded in a strand shape from the nozzle tip. The extruded material was rapidly cooled in a water bath and cut into pellets using a pelletizer to obtain pellets of the resin composition.

[0037] <Mold Deposit> The pellets obtained as described above were dried at 120°C for 5 hours. Then, 200 shots were molded using an injection molding machine (Sumitomo Heavy Industries, SE7M-C12) under the following conditions: cylinder temperature 280°C, mold temperature 40°C, screw rotation speed 300 rpm, and injection speed 4 mm / s. The mold contamination status was evaluated based on the following criteria. Five experts reviewed the results and made a decision by majority vote. A: The degree of mold contamination is the same as that of products without metal salts. B: The degree of mold contamination is worse than in products without metal salts.

[0038] <Total light transmittance (1.0mm thickness)> After drying the pellets obtained by the above method at 120°C for 5 hours, test specimens with a thickness of 1.0 mm were manufactured using an injection molding machine (Shibaura Machine Co., Ltd. "EC75") under the following conditions: cylinder temperature 280°C, mold temperature 80°C, screw rotation speed 100 rpm, and injection speed 30 mm / s. The total light transmittance (in %) of the obtained test specimens was measured using a haze meter. A haze meter, model NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd., was used.

[0039] <Equivalent diameter of a circle (μm)> The obtained pellets were dried at 120°C for 5 hours, and then injection molded using an injection molding machine (Shibaura Machine Co., Ltd. "EC75") under the following conditions: cylinder temperature 280°C, mold temperature 80°C, screw rotation speed 80 rpm, and injection speed 30 mm / s to produce ISO multipurpose test specimens (3.0 mm thick). The obtained test specimens were ultrasonically cleaned with methanol for 5 minutes, and the surface of the central part of the dumbbell was observed using an operational electron microscope (SEM) S-4800 (Hitachi High-Technologies Corporation) with an acceleration voltage of 3.0 kV, a current of 10 μA, and 3000x magnification. The obtained images were subjected to a Gaussian 3x3 filter and automatic binarization processing was performed to obtain a 0.001 μm 2 The areas displayed below were removed as noise. The diameter equivalent to a circle was calculated from the area of ​​each titanium dioxide scattered on the obtained image data using the following formula, and the average value was taken as the equivalent circle diameter (unit: μm) of this sample.

[0040] <Charpy impact strength (molding temperature 280℃, 1 minute cycle)> The obtained pellets were dried at 120°C for 5 hours, and then injection molded using an injection molding machine (Shibaura Machine Co., Ltd. "EC75") under the following conditions: cylinder temperature 280°C, mold temperature 80°C, screw rotation speed 80 rpm, and injection speed 30 mm / s (cycle time 1 minute) to produce ISO multipurpose test specimens (3.0 mm thick). Using the obtained ISO multipurpose test specimen (3.0 mm thick), the notched Charpy impact strength (unit: kJ / m²) was measured at 23°C according to ISO standard 179-1. 2 ) was measured.

[0041] <Charpy impact strength (molding temperature 310℃, 7 minutes retention)> The obtained pellets were dried at 120°C for 5 hours, and then weighed using an injection molding machine (Shibaura Machine Co., Ltd. "EC75") with a cylinder temperature of 310°C, a mold temperature of 80°C, and a screw rotation speed of 80 rpm. After being held in the cylinder for 7 minutes, the pellets were injection molded at an injection speed of 30 mm / s to produce ISO multipurpose test specimens (3.0 mm thick). Using the obtained ISO multipurpose test specimen (3.0 mm thick), the notched Charpy impact strength (unit: kJ / m²) was measured at 23°C according to ISO standard 179-1. 2 ) was measured.

[0042] <Impact strength retention rate (%)> From the above Charpy impact strength (molding temperature 310°C, 7 minutes retention) and Charpy impact strength (molding temperature 280°C, 1 minute cycle) values, the impact strength retention rate, [Charpy impact strength (molding temperature 310°C, 7 minutes retention) / Charpy impact strength (molding temperature 280°C, 1 minute cycle)] × 100 (unit: %), was calculated.

[0043] [Table 2] [Table 3]

[0044] As is clear from the above results, the molded articles obtained from the resin composition of this embodiment achieved the desired light-shielding properties while exhibiting excellent impact resistance, particularly in terms of retaining impact resistance when left standing.

Claims

1. A resin composition comprising 100 parts by mass of polycarbonate resin (A) in which 90 mol% or more of the total constituent units are derived from bisphenol A, 8.0 to 12.0 parts by mass of titanium dioxide-based particles (B), and 0.11 to 0.3 parts by mass of potassium diphenylsulfonsulfonate (C), wherein the content of other components not mentioned above is 1.0% by mass or less based on the mass of the resin composition. A resin composition in which a molded product formed using the above resin composition at a cylinder setting temperature of 280°C and a cycle time of 1 minute is observed with a scanning electron microscope, and the equivalent circle diameter calculated using formula (1) from the area of ​​the region of scattered titanium oxide particles (B) is 0.149 μm or less. [Math 1]

2. The resin composition according to claim 1, wherein the content of polyolefin wax in the resin composition is less than 0.1 parts by mass per 100 parts by mass of polycarbonate resin (A).

3. Using the aforementioned resin composition, a 3 mm thick test specimen was molded at a cylinder temperature of 280°C and a cycle time of 1 minute. The notched Charpy impact strength measured according to ISO 179-1 was 40 kJ / m². ２ The resin composition according to claim 1 or 2, as described above.

4. Using the aforementioned resin composition, a 3 mm thick test specimen was molded at a cylinder temperature of 310°C and a residence time of 7 minutes in the cylinder. The notched Charpy impact strength, measured according to ISO 179-1, was 30 kJ / m². ２ The resin composition according to claim 1 or 2, as described above.

5. The resin composition according to claim 1 or 2, wherein when a 3 mm thick test piece is molded using the resin composition at a cylinder setting temperature of 310°C and a residence time of 7 minutes in the cylinder, the notched Charpy impact strength measured in accordance with ISO 179-1 is 70% or more compared to the notched Charpy impact strength measured by the same method when the resin composition is molded at a cylinder setting temperature of 280°C and a cycle time of 1 minute.

6. The aforementioned particles (B) mainly composed of titanium dioxide are TiO ２ :90.0 to 98.0% by mass, Al ２ O ３ : 0.5 to 3.5 mass%, and SiO ２ A resin composition according to claim 1 or 2, comprising 0 to 6.0% by mass.

7. A molded article formed from the resin composition according to claim 1 or 2.

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