Polycarbonate resin composition

Abstract

To provide a polycarbonate resin composition excellent in millimeter wave absorption.SOLUTION: A polycarbonate resin composition comprising 0.05 to 0.4 parts by mass of a carbon nanotube (B) and 0.30 to 5.0 parts by mass of a polyethylene wax-based dispersant (C) with respect to 100 parts by mass of a polycarbonate resin (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polycarbonate resin composition, and more particularly to a polycarbonate resin composition having excellent millimeter wave absorption properties. [Background technology]

[0002] Millimeter-wave radar emits millimeter-wave radio waves with wavelengths of 1 to 10 mm at frequencies between 30 and 300 GHz, particularly between 60 and 90 GHz, and detects the presence of obstacles as well as the distance and relative speed of the object by receiving the reflected waves that collide with the object. Millimeter-wave radar is less affected by rain, fog, backlight, etc. than other methods of detecting obstacles (such as optical laser radar and cameras), making it effective at night or in bad weather when visibility is poor. It is therefore used in automobile collision prevention sensors, driver assistance systems, autonomous driving systems, road information systems, etc.

[0003] A millimeter-wave radar incorporates a transmitting and receiving antenna unit, and a millimeter-wave radar cover is attached to the front of the transmitting and receiving antenna to protect the antenna surface. The millimeter-wave radar cover is made of a material with excellent millimeter-wave transparency (for example, the polycarbonate resin material described in Patent Document 1), and it can detect targets and the like with high accuracy by receiving and transmitting millimeter waves emitted from the transmitting and receiving antenna and waves reflected from targets with high efficiency.

[0004] However, millimeter waves easily pass through plastic components, and millimeter waves that pass in directions other than the target object are scattered by the engine compartment or metal components. The scattered millimeter waves are then detected by the radar, causing ghosting and resulting in serious malfunctions. For this reason, absorbers are often attached to plastic components as needed. These absorbers are expensive and the manufacturing process is complicated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-197048 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a demand for the resin itself to absorb millimeter waves. The present invention has been made in view of the above circumstances, and an object (object) of the present invention is to provide a polycarbonate resin composition having high millimeter wave absorption properties. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the inventors discovered that the above object can be achieved by incorporating a polyethylene wax-based dispersant in combination with carbon nanotubes, and thus completed the present invention. The present invention relates to the following polycarbonate resin composition and molded article.

[0008] 1. A polycarbonate resin composition comprising 100 parts by mass of a polycarbonate resin (A), 0.05 to 0.4 parts by mass of carbon nanotubes (B), and 0.30 to 5.0 parts by mass of a polyethylene wax-based dispersant (C). 2. The polycarbonate resin composition according to the above item 1, wherein the polyethylene wax-based dispersant (C) is a polyethylene wax or a modified polyethylene wax. 3. The polycarbonate resin composition according to 2 above, wherein the modified polyethylene wax is one or more selected from polyethylene waxes modified with an unsaturated carboxylic acid monomer or an aromatic monomer, and oxidized polyethylene waxes. 4. Pellets of the polycarbonate resin composition according to any one of 1 to 3 above. 5. A molded article obtained by molding the polycarbonate resin composition according to any one of 1 to 3 above. 6. The molded article according to 5 above, which is a millimeter wave absorbing member. 7. A molded article obtained by molding the polycarbonate resin pellets described in 4 above. 8. The molded article according to the above item 7, which is a millimeter wave absorbing member. [Effects of the Invention]

[0009] The polycarbonate resin composition of the present invention has high millimeter wave absorption properties, low millimeter wave transmittance, and excellent mechanical strength by combining a polycarbonate resin with a small amount of carbon nanotubes and a polyethylene wax-based dispersant. The reason why the polycarbonate resin composition of the present invention exhibits such effects is thought to be as follows: When a cross section of a molded article is observed in the thickness direction, the carbon nanotubes are distributed in layers in the cross section direction, and moreover, are present in large numbers near the surface layer of the molded article, and it is therefore thought that by including a polyethylene wax-based dispersant, the carbon nanotubes are distributed in the above-mentioned layers due to the orientation that occurs during molding, and moreover, are present in large numbers near the surface layer of the molded article, resulting in an improved millimeter wave absorption rate. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below with reference to embodiments and examples. In this specification, unless otherwise specified, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0011] The polycarbonate resin composition of the present invention is characterized by containing 0.05 to 0.4 parts by mass of carbon nanotubes (B) and 0.30 to 5.0 parts by mass of a polyethylene wax-based dispersant (C) relative to 100 parts by mass of a polycarbonate resin (A).

[0012] [Polycarbonate resin (A)] The polycarbonate resin (A) used in the present invention is not particularly limited, and various types can be used. Polycarbonate resins can be classified into aromatic polycarbonate resins in which the carbons directly bonded to the carbonate bonds are aromatic carbons, and aliphatic polycarbonate resins in which the carbons directly bonded to the carbonate bonds are aliphatic carbons, and either type can be used. Among these, aromatic polycarbonate resins are preferred as the polycarbonate resin (A) from the viewpoints of heat resistance, mechanical properties, electrical properties, etc.

[0013] Among the monomers that are raw materials for aromatic polycarbonate resins, examples of aromatic dihydroxy compounds include: dihydroxybenzenes such as 1,2-dihydroxybenzene, 1,3-dihydroxybenzene (i.e., resorcinol), and 1,4-dihydroxybenzene; dihydroxybiphenyls such as 2,5-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, and 4,4'-dihydroxybiphenyl;

[0014] dihydroxynaphthalenes such as 2,2'-dihydroxy-1,1'-binaphthyl, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene;

[0015] dihydroxydiaryl ethers such as 2,2'-dihydroxydiphenyl ether, 3,3'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, 1,4-bis(3-hydroxyphenoxy)benzene, and 1,3-bis(4-hydroxyphenoxy)benzene;

[0016] 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), 1,1-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane (i.e., bisphenol C), 2,2-bis(3-methoxy-4-hydroxyphenyl)propane, 2-(4-hydroxyphenyl)-2-(3-methoxy-4-hydroxyphenyl)propane, 1,1-bis(3-tert-butyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2-(4-hydroxyphenyl)-2-(3-cyclohexyl-4-hydroxyphenyl)propane, α,α'-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)cyclohexylmethane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)(4-propenylphenyl)methane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)naphthylmethane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-1-naphthylethane, 1,1-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)hexane, 2,2-bis(4-hydroxyphenyl)hexane, 1,1-bis(4-hydroxyphenyl)octane, 2,2-bis(4-hydroxyphenyl)octane, 4,4-bis(4-hydroxyphenyl)heptane, 2,2-bis(4-hydroxyphenyl)nonane, 1,1-bis(4-hydroxyphenyl)decane, 1,1-bis(4-hydroxyphenyl)dodecane, Bis(hydroxyaryl)alkanes such as;

[0017] 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,4-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,5-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxy-3,5-dimethylphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3-propyl-5-methylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3-tert-butyl-cyclohexane, 1,1-bis(4-hydroxyphenyl)-4-tert-butyl-cyclohexane, 1,1-bis(4-hydroxyphenyl)-3-phenylcyclohexane, 1,1-bis(4-hydroxyphenyl)-4-phenylcyclohexane, Bis(hydroxyaryl)cycloalkanes such as;

[0018] 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene Cardo structure-containing bisphenols such as;

[0019] 4,4'-dihydroxydiphenyl sulfide, Dihydroxydiaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; 4,4'-dihydroxydiphenyl sulfone, dihydroxydiarylsulfones such as 4,4'-dihydroxy-3,3'-dimethyldiphenylsulfone; etc.

[0020] Of these, bis(hydroxyaryl)alkanes are preferred, and bis(4-hydroxyphenyl)alkanes are particularly preferred. In particular, from the standpoints of impact resistance and heat resistance, 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A) and 2,2-bis(3-methyl-4-hydroxyphenyl)propane (i.e., bisphenol C) are preferred. The aromatic dihydroxy compounds may be used alone or in any combination of two or more in any ratio.

[0021] Among the monomers that serve as raw materials for polycarbonate resins, examples of carbonate precursors include carbonyl halides, carbonate esters, etc. The carbonate precursors may be used alone or in any combination and ratio of two or more.

[0022] Specific examples of carbonyl halides include phosgene; haloformates such as bischloroformates of dihydroxy compounds and monochloroformates of dihydroxy compounds; and the like.

[0023] Specific examples of carbonate esters include diaryl carbonates such as diphenyl carbonate and ditolyl carbonate; dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; biscarbonates of dihydroxy compounds, monocarbonates of dihydroxy compounds, and carbonates of dihydroxy compounds such as cyclic carbonates.

[0024] The method for producing the polycarbonate resin (A) is not particularly limited, and any method can be used. Examples include interfacial polymerization, melt transesterification, ring-opening polymerization of a cyclic carbonate compound, and solid-phase transesterification of a prepolymer. Among these, the interfacial polymerization and melt transesterification methods are preferred because they have a greater effect of improving moist heat resistance, and the interfacial polymerization method is particularly preferred.

[0025] The molecular weight of the polycarbonate resin (A), expressed as a viscosity average molecular weight (Mv) calculated from the solution viscosity measured at 25°C using methylene chloride as a solvent, is preferably 10,000 to 50,000, more preferably 11,000 to 40,000, even more preferably 12,000 to 35,000, and particularly preferably 13,000 to 30,000. By setting the viscosity average molecular weight to at least the lower limit of the above range, the mechanical strength of the polycarbonate resin composition of the present invention can be further improved, and by setting the viscosity average molecular weight to at most the upper limit of the above range, the decrease in flowability of the polycarbonate resin composition of the present invention can be suppressed and improved, and molding processability can be improved, making molding process easier. Two or more polycarbonate resins having different viscosity average molecular weights may be mixed together, and in this case, polycarbonate resins having viscosity average molecular weights outside the above-mentioned preferred range may be mixed.

[0026] The viscosity average molecular weight [Mv] is calculated by using methylene chloride as a solvent and an Ubbelohde viscometer to determine the intrinsic viscosity [η] (unit: dl / g) at a temperature of 25°C, and then calculating it using the Schnell viscosity formula, i.e., η = 1.23 × 10 -4 Mv 0.83The intrinsic viscosity [η] is the specific viscosity [η] at each solution concentration [C] (g / dl). sp ] was measured and the value was calculated according to the following formula.

number

[0027] Furthermore, in order to improve the appearance and fluidity of molded articles, the polycarbonate resin (A) may contain a polycarbonate oligomer. The viscosity average molecular weight [Mv] of this polycarbonate oligomer is usually 1500 or more, preferably 2000 or more, and usually 9500 or less, preferably 9000 or less. Furthermore, the amount of the polycarbonate oligomer contained is preferably 30% by mass or less of the polycarbonate resin (including the polycarbonate oligomer).

[0028] Furthermore, the polycarbonate resin (A) may be not only virgin raw materials but also polycarbonate resin recycled from used products (so-called material-recycled polycarbonate resin), and it is also preferable to contain both virgin polycarbonate resin and recycled polycarbonate resin, or it may consist of recycled polycarbonate resin. When recycled polycarbonate resin is contained, the proportion of recycled polycarbonate resin in polycarbonate resin (A) is preferably 30% or more, 40% or more, 50% or more, 60% or more, or 80% or more, and it is also preferable that the recycled polycarbonate resin is 100%.

[0029] [Carbon nanotubes (B)] The polycarbonate resin composition of the present invention contains carbon nanotubes (B). The carbon nanotubes (B) may be either single-walled or multi-walled carbon nanotubes, and preferably contain at least multi-walled carbon nanotubes. Carbon materials partially having a carbon nanotube structure may also be used. The carbon nanotubes are not limited to a cylindrical shape, and may have a coiled shape with a spiral at a pitch of 1 μm or less.

[0030] There are various known methods for producing carbon nanotubes, and although there are no particular limitations, representative methods include arc discharge, laser evaporation, chemical vapor deposition (CVD), and catalytic chemical vapor deposition (CCVD). Carbon nanotubes are also commercially available.

[0031] The diameter (number average fiber diameter) of the carbon nanotubes (B) is preferably 0.5 to 100 nm, more preferably 1 to 30 nm. From the viewpoint of imparting good electromagnetic wave absorption, the aspect ratio of the carbon nanotubes is preferably 5 or more, more preferably 50 or more. There is no particular upper limit, but it is, for example, 500 or less. The average particle size of the carbon nanotubes (B), as determined by a laser scattering method (ISO13320:2009), is preferably 0.05 μm or more, more preferably 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, or 0.4 μm or more, and is preferably 10 μm or less, and even more preferably 8 μm or less, 6 μm or less, 4 μm or less, or 2 μm or less.

[0032] The surfaces and ends of carbon nanotubes may be modified with functional groups to enhance their affinity with polycarbonate resins, for example, by functionalizing them with hydroxyl, carboxyl, or amino groups using an acid or alkali. Furthermore, carbon nanotubes may be pretreated with a coupling agent, such as an isocyanate compound, an organic silane compound, an organic titanate compound, or an epoxy compound.

[0033] The carbon nanotubes are preferably masterbatched with a thermoplastic resin, which tends to further improve the millimeter wave absorption of the resulting polycarbonate resin composition or molded article. Various thermoplastic resins can be used as the thermoplastic resin for the masterbatch, but styrene-based resins or polycarbonate resins are particularly preferred. The concentration of the carbon nanotubes (B) in the masterbatch is preferably 1% by mass or more, more preferably 5% by mass or more, and is preferably 95% by mass or less, more preferably 92% by mass or less.

[0034] The content of carbon nanotubes (B) is 0.05 to 0.4 parts by mass per 100 parts by mass of polycarbonate resin (A), and by combining such a small content with polyethylene wax-based dispersant (C), millimeter wave absorption is improved. If the content is less than the lower limit, millimeter wave absorption is insufficient, and even if the content is increased to exceed the upper limit, no improvement in millimeter wave transmittance can be expected, the millimeter wave reflectance increases, and the millimeter wave absorption is Since absorptance (%) = 100 - transmittance - reflectance, no improvement in absorptance can be expected. The content of carbon nanotubes (B) is preferably 0.06 parts by mass or more, more preferably 0.07 parts by mass or more, 0.08 parts by mass or more, 0.09 parts by mass or more, and particularly preferably 0.10 parts by mass or more, per 100 parts by mass of polycarbonate resin (A), and is preferably 0.35 parts by mass or less, more preferably 0.30 parts by mass or less, 0.25 parts by mass or less, and particularly preferably 0.20 parts by mass or less.

[0035] [Polyethylene wax-based dispersant (C)] The polycarbonate resin composition of the present invention contains a polyethylene wax-based dispersant (C). The polyethylene wax-based dispersant (C) contains polyethylene wax (hereinafter also referred to as "unmodified polyethylene wax") or a modified polyethylene wax (hereinafter also referred to as "modified polyethylene wax").

[0036] The unmodified polyethylene wax is an ethylene homopolymer or a copolymer of ethylene and at least one α-olefin preferably selected from α-olefins having 3 to 12 carbon atoms. Examples of α-olefins having 3 to 12 carbon atoms that can be copolymerized with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and more preferably propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. α-olefins having 3 to 8 carbon atoms are even more preferred, and more preferably propylene and 1-butene. Regarding the copolymerization ratio of the ethylene and α-olefin copolymer, when the sum of the amount of ethylene-derived structural units and the amount of α-olefin-derived structural units is taken as 100 mol%, the amount of ethylene-derived structural units is preferably 91.0 to 99.9 mol%, more preferably 93.0 to 99.9 mol%, 95.0 to 99.9 mol%, and particularly preferably 95.0 to 99.0 mol%, while the amount of structural units derived from α-olefins having 3 or more carbon atoms is preferably 0.1 to 9.0 mol%, more preferably 0.1 to 7.0 mol%, 0.1 to 5.0 mol%, and particularly preferably 1.0 to 5.0 mol%.

[0037] Preferred examples of the modified polyethylene wax include polyethylene wax obtained by modifying the above-mentioned unmodified polyethylene wax with an unsaturated carboxylic acid monomer or an aromatic monomer, and oxidized polyethylene wax. The modified polyethylene wax may be a graft-modified product of the above-mentioned polyethylene wax, for example, a modified product grafted with an unsaturated carboxylic acid or a derivative thereof, or a modified product grafted with an aromatic monomer.

[0038] Examples of unsaturated carboxylic acids or derivatives thereof used for graft modification include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, sec-butyl acrylate, isobutyl acrylate, propyl acrylate, isopropyl acrylate, 2-octyl acrylate, dodecyl acrylate, stearyl acrylate, hexyl acrylate, isohexyl acrylate, phenyl acrylate, 2-chlorophenyl acrylate, diethylaminoethyl acrylate, 3-methoxybutyl acrylate, diethylene glycol ethoxylate acrylate, and 2,2,2-trifluoroethyl acrylate; and methyl methacrylate, ethyl methacrylate, butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, isopropyl methacrylate, and 2-octyl methacrylate. methacrylic acid esters such as dodecyl methacrylate, stearyl methacrylate, stearyl methacrylate, hexyl methacrylate, decyl methacrylate, phenyl methacrylate, 2-chlorohexyl methacrylate, diethylaminoethyl methacrylate, 2-hexylethyl methacrylate, and 2,2,2-trifluoroethyl methacrylate; maleic acid esters such as ethyl maleate, propyl maleate, butyl maleate, diethyl maleate, dipropyl maleate, and dibutyl maleate; fumaric acid esters such as ethyl fumarate, butyl fumarate, and dibutyl fumarate; dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, crotonic acid, nadic acid, and methylhexahydrophthalic acid; and anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic anhydride, glutaconic anhydride, and nadic anhydride. Among these, maleic anhydride is particularly preferred.

[0039] Furthermore, when the polyethylene wax is graft-modified with an aromatic monomer, examples of the aromatic monomer include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene, p-chloromethylstyrene, 4-vinylpyridine, 2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine, 2-isopropenylpyridine, and the like. Of these, styrene is particularly preferred.

[0040] Various known methods can be used to graft the unsaturated carboxylic acid or its derivative monomer and the aromatic monomer onto the polyethylene wax. For example, the polyethylene wax may be directly melted or dissolved in a solvent, and the unsaturated carboxylic acid or its derivative monomer and the aromatic monomer may be added with or without the use of a radical initiator to carry out grafting.

[0041] Oxidized polyethylene wax is obtained by oxidizing polyethylene wax to introduce polar groups, such as oxygen-containing groups such as carboxyl groups, ester groups, carbonyl groups, and hydroxyl groups, into the polyethylene wax. Oxidized polyethylene wax is usually produced by melting raw polyethylene wax and introducing oxygen or an oxygen-containing gas into the melt to cause an oxidation reaction.

[0042] The content of the polyethylene wax-based dispersant (C) is 0.30 to 5.0 parts by mass per 100 parts by mass of the polycarbonate resin (A). By combining the carbon nanotubes (B) in such an amount, the carbon nanotubes (B) are distributed in layers in the flow direction in the molded article due to the orientation that occurs during molding, and more of them are present near the surface of the molded article, resulting in a high millimeter wave absorption rate. The content of the polyethylene wax-based dispersant (C) is preferably 0.35 parts by mass or more, more preferably 0.40 parts by mass or more, and even more preferably 0.45 parts by mass or more, per 100 parts by mass of the polycarbonate resin (A), and is also preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less.

[0043] [Additives, etc.] The polycarbonate resin composition of the present invention may contain additives other than those described above, such as stabilizers, fillers, ultraviolet absorbers, fluorescent brighteners, pigments, dyes, mold release agents, etc. These additives may be contained alone or in combination of two or more.

[0044] Furthermore, the polycarbonate resin (A) may contain other resins. Examples of other resins include thermoplastic polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate; styrene-based resins such as polystyrene resin, high impact polystyrene resin (HIPS), acrylonitrile-styrene copolymer (AS resin), and acrylonitrile-butadiene-styrene copolymer (ABS resin); polyolefin resins such as polyethylene resin and polypropylene resin; polyamide resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene ether resin; polyphenylene sulfide resin; polysulfone resin; and polymethacrylate resin. When a resin other than the polycarbonate resin (A) is contained, the content thereof is preferably 45 parts by mass or less per 100 parts by mass of the polycarbonate resin (A), and particularly preferably 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, and particularly preferably 1 part by mass or less.

[0045] [Polycarbonate resin composition] The polycarbonate resin composition of the present invention has high millimeter wave absorption, and can achieve a millimeter wave absorption rate of preferably 45% or more, particularly 47% or more, 49% or more, 50% or more, 52% or more, 53% or more, 55% or more, 58% or more, 60% or more, 62% or more, 64% or more, and particularly 65% ​​or more, at 76.5 GHz using a 2.0 mm thick test piece. The reflectance is preferably less than 20%.

[0046] The polycarbonate resin composition of the present invention can be molded into a molded article. The molding method for producing a molded article can be any molding method commonly used for polycarbonate resin compositions. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, gas-assisted hollow molding, molding using an insulated mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding), extrusion molding, sheet molding, thermoforming, rotational molding, laminate molding, press molding, and blow molding. Molding methods using a hot runner system can also be used. Among these, injection molding methods such as injection molding, ultra-high speed injection molding, and injection compression molding are preferred.

[0047] [Molded products] Molded articles of the polycarbonate resin composition of the present invention are particularly suitable for use as components for millimeter wave radars. [Example]

[0048] The present invention will be explained in more detail below by showing examples, but the present invention should not be construed as being limited to the following examples. The components used in the examples and comparative examples are as shown in Table 1 below.

[0049] [Table 1]

[0050] [Examples 1 to 6, Comparative Examples 1 to 6] <Production of Resin Composition (Pellets)> The components listed in Table 1 were placed in a stainless steel tumbler so that the carbon nanotubes were blended in the amounts listed in Table 2 below, and the mixture was stirred and mixed for 1 hour. The resulting mixture was fed through the main feed port of an intermeshing co-rotating twin-screw extruder ("TEX-30α" manufactured by The Japan Steel Works, Ltd.). The barrel temperature of the first kneading section was set to 270°C, and the mixture was melt-kneaded at a discharge rate of 30 kg / h and a screw rotation speed of 200 rpm. The mixture was extruded as a strand, introduced into a water tank for cooling, and then cut into pellets of the resin composition by being inserted into a pelletizer.

[0051] <Millimeter wave absorption rate, reflectance, transmittance> The pellets obtained above were injection molded in an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder temperature of 270°C and a mold temperature of 80°C to obtain test pieces measuring 100 mm x 100 mm x 2 mm thick. Using the obtained test pieces, the absorptance calculated according to the following formula (1), the reflectance calculated according to the formula (2), and the transmittance calculated according to the formula (3) at a frequency of 76.5 GHz were measured as follows. For the measurements, a Keysight network analyzer "N5252A" was used. The measurement was performed by placing the test piece so that the TD direction (direction perpendicular to the flow direction) of the injection molded article was parallel to the direction of the electric field.

[0052]

number

[0053] The results are shown in Tables 2 and 3 below. In the table, Actual n is Example n, and Relative n is Comparative Example n.

[0054] [Table 2]

[0055] From the results of Examples 1 to 4 and Comparative Example 1 above, it can be seen that by adding polyethylene wax as a dispersant to the composition of Comparative Example 1, the absorption rate of Examples 1 to 4 is improved, and that the same effect can be obtained with any polyethylene wax, whether it is polystyrene graft-modified polyethylene wax, maleic anhydride-modified polyethylene wax, or unmodified polyethylene wax.

[0056] [Table 3]

[0057] Comparing Example 5 with Comparative Example 2, and Example 6 with Comparative Example 3 in Table 3 above, it can be seen that the absorption rate of the Examples is improved by adding polyethylene wax as a dispersant to the composition of the Comparative Examples. Furthermore, the results of Comparative Examples 4-6 show that when polyethylene wax is added to the composition of Comparative Example 4 in which the amount of carbon nanotubes added exceeds 0.4 parts, the absorbency does not improve. Preferably, the reflectance is less than 20%. [Industrial Applicability]

[0058] The polycarbonate resin composition of the present invention has excellent millimeter wave absorption properties and can therefore be suitably used for components for millimeter wave radars, etc.

Claims

1. A polycarbonate resin composition comprising 0.05 to 0.4 parts by mass of carbon nanotubes (B) and 0.30 to 5.0 parts by mass of a polyethylene wax-based dispersant (C) per 100 parts by mass of a polycarbonate resin (A).

2. 2. The polycarbonate resin composition according to claim 1, wherein the polyethylene wax-based dispersant (C) is a polyethylene wax or a modified polyethylene wax.

3. 3. The polycarbonate resin composition according to claim 2, wherein the modified polyethylene wax is one or more selected from the group consisting of polyethylene waxes modified with an unsaturated carboxylic acid monomer or an aromatic monomer, and oxidized polyethylene waxes.

4. Pellets of the polycarbonate resin composition according to any one of claims 1 to 3.

5. A molded article obtained by molding the polycarbonate resin composition according to any one of claims 1 to 3.

6. The molded article according to claim 5, which is a millimeter wave absorbing member.

7. A molded article obtained by molding the polycarbonate resin pellets according to claim 4.

8. The molded article according to claim 7, which is a millimeter wave absorbing member.

Images