Styrene resin composition, radome, antenna, base station, and method for producing radome

Abstract

To provide a styrene-based resin composition capable of producing a radome excellent in low dielectric properties and strength under high temperature conditions.SOLUTION: According to the present invention, there is provided a styrene polymer composition, wherein the styrene polymer composition contains 30% by mass or more and 90% by mass or less of a styrene polymer and 10% by mass or more and 70% by mass or less of a polycarbonate polymer, the styrene polymer contains 85.0% by mass or more and 99.0% by mass or less of a styrene-derived repeating unit and 1.0% by mass or more and 15.0% by mass or less of a (meth) acrylic acid-derived repeating unit, and a molded article obtained by shaping the styrene polymer composition has a dielectric loss tangent of less than 0.0050 at a measuring frequency of 24GHz.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a styrene-based resin composition, a radome, an antenna, a base station, and a method for producing a radome. [Background technology]

[0002] In recent years, with the development of various mobile communication systems such as 5G, the installation and replacement of antennas for base stations has become increasingly common. Under these circumstances, there is a demand for low-dielectric materials, such as styrene-based resins, for components used in antennas, such as radomes, to accommodate increased capacity and speed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-140301 Summary of the Invention [Problem to be solved by the invention]

[0004] However, antenna components, which are sometimes installed outdoors, also require heat resistance, but this may not be sufficient depending on the installation conditions.

[0005] The present invention has been made in view of the above circumstances, and provides a styrene-based resin composition that can be used to fabricate a radome that has low dielectric properties and excellent strength under high-temperature conditions. [Means for solving the problem]

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a styrene-based resin composition containing a specific styrene-based resin and a polycarbonate resin has low dielectric properties and excellent strength under high-temperature conditions, and can solve the above-mentioned problems, thereby completing the present invention.

[0007] According to the present invention, the following inventions are provided. [1] A styrene-based resin composition, comprising 30% by mass or more and 90% by mass or less of a styrene-based resin and 10% by mass or more and 70% by mass or less of a polycarbonate-based resin, wherein the styrene-based resin has 85.0% by mass or more and 99.0% by mass or less of a repeating unit derived from styrene and 1.0% by mass or more and 15.0% by mass or less of a repeating unit derived from (meth)acrylic acid, and wherein a molded article obtained by molding the styrene-based resin composition has a dielectric loss tangent of less than 0.0050 at a measurement frequency of 24 GHz. [2] The styrene-based resin composition according to [1], which is used for a radome. [3] The styrene-based resin composition according to [1] or [2], which is used for a radome provided in a base station antenna. [4] A radome comprising the styrene resin composition according to any one of [1] to [3]. [5] An antenna comprising the radome described in [4]. [6] A base station comprising the antenna described in [5]. [7] A method for manufacturing the radome described in [4], comprising a step of molding the styrene-based resin composition. [Effects of the Invention]

[0008] The styrene-based resin composition of the present invention has excellent low dielectric properties and strength under high-temperature conditions, and can be used to produce radomes having excellent low dielectric properties and strength under high-temperature conditions, and can be used as a constituent material for radomes for base station antennas, etc. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

[0010] 1. Styrene-based resin composition A styrene-based resin composition according to one embodiment of the present invention contains 30 to 90% by mass of a styrene-based resin and 10 to 70% by mass of a polycarbonate-based resin, the styrene-based resin having 85 to 99% by mass of repeating units derived from styrene and 1 to 15% by mass of repeating units derived from (meth)acrylic acid. Such a styrene-based resin composition has low dielectric properties and excellent strength under high temperature conditions.

[0011] Styrenic resins have repeating units derived from styrene (hereinafter also referred to as "styrene units") and repeating units derived from (meth)acrylic acid (hereinafter also referred to as "(meth)acrylic acid units"). Styrenic resins are copolymers obtained by polymerizing raw material monomers including styrene and (meth)acrylic acid. Styrenic resins may also have repeating units derived from other monomers copolymerizable with styrene and (meth)acrylic acid (hereinafter also referred to as "other monomer units").

[0012] The styrene resin contains 85.0% by mass or more and 99.0% by mass or less of styrene units, preferably 88.0% by mass or more and 97.0% by mass or less, based on 100% by mass of the styrene resin. The content of styrene units in the styrene resin is, for example, 85.0, 85.5, 86.0, 86.5, 87.0, 87.5, 88.0, 88.5, 89.0, 89.5, 90.0, 90.5, 91.0, 91.5, 92.0, 92.5, 93.0, 93.5, 94.0, 94.5, 95.0, 95.5, 96.0, 96.5, 97.0, 97.5, 98.0, 98.5, or 99.0% by mass, or may be within a range between any two of the values ​​exemplified here.

[0013] The (meth)acrylic acid unit is a repeating unit derived from acrylic acid or methacrylic acid (MAA), and from the viewpoint of heat resistance, methacrylic acid is preferred.

[0014] The styrene-based resin contains 1.0% by mass or more and 15.0% by mass or less of (meth)acrylic acid units, preferably 3.0% by mass or more and 12.0% by mass or less, based on 100% by mass of the styrene-based resin. By setting the content within this range, the resin has excellent low dielectric properties, such as a low dielectric loss tangent, and excellent heat resistance, particularly strength under high temperature conditions. The content of (meth)acrylic acid units in the styrene-based resin is, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0% by mass, and may be within a range between any two of the values ​​exemplified here.

[0015] Furthermore, the total content of (meth)acrylic acid units in the styrene-based resin composition is preferably 1.0% by mass or more and 10.0% by mass or less, based on 100% by mass of the total resin components. For example, when the styrene-based resin composition contains only a styrene-based resin containing (meth)acrylic acid units and a polycarbonate-based resin not containing (meth)acrylic acid units as resin components, the total content of (meth)acrylic acid units refers to the mass ratio of the (meth)acrylic acid units in the styrene-based resin, based on 100% by mass of the total content of the styrene-based resin and the polycarbonate-based resin. Specifically, the total content of (meth)acrylic acid units in the styrene-based resin composition, based on 100% by mass of the total resin components, may be, for example, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0% by mass, and may be within a range between any two of the values ​​exemplified here.

[0016] Examples of other monomer units include (meth)acrylic acid esters. The (meth)acrylic acid esters are acrylic acid esters or methacrylic acid esters. Examples of the (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, and 2-ethyl (meth)acrylate. Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters such as hexyl (meth)acrylate and lauryl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, tricyclodecanyl (meth)acrylate and adamantyl (meth)acrylate; (meth)acrylic acid glycidyl; and (meth)acrylic acid dicyclopentadienyl. These may be used alone or in combination of two or more. The (meth)acrylic acid ester is preferably a (meth)acrylic acid alkyl ester, more preferably a methacrylic acid alkyl ester, and even more preferably methyl methacrylate (MMA).

[0017] The content of other monomer units in the styrene-based resin is preferably 14% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the styrene-based resin. Specifically, the content of other monomer units is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14% by mass, and may be within a range between any two of the values ​​exemplified herein. The total content of styrene units and (meth)acrylic acid units in the styrene-based resin is preferably 86% by mass or more and 100% by mass or less, based on 100% by mass of the styrene-based resin. Specifically, the total content of styrene units and (meth)acrylic acid units in the styrene-based resin is, for example, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% by mass, and may be within a range between any two of the values ​​exemplified herein.

[0018] From the viewpoint of the balance between heat resistance and strength, the styrene-based resin preferably contains a random copolymer, and more preferably is a random copolymer.

[0019] The weight average molecular weight of the styrene resin (weight average molecular weight in terms of polystyrene when measured by GPC) is preferably 100,000 to 300,000, more preferably 150,000 to 250,000. Specific examples of the weight average molecular weight of the styrene resin are 100,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, and 300,000, and may be within a range between any two of the numerical values ​​exemplified here.

[0020] A polycarbonate resin is a resin in which the bond between monomer units is formed by a carbonate group (-O-(C=O)-O-), and commercially available general products can be used. There are no restrictions on the specific type of polycarbonate resin, and it may be, for example, a polycarbonate polymer obtained by reacting a dihydroxy compound with a carbonate precursor. The polycarbonate polymer may be linear or branched. The polycarbonate resin may be a polymer consisting of one type of repeating unit, or a copolymer having two or more types of repeating units.

[0021] The polycarbonate resin may be, for example, an aromatic polycarbonate resin in which the carbon atoms directly bonded to the carbonate bonds are aromatic carbon atoms, or an aliphatic polycarbonate resin in which the carbon atoms directly bonded to the carbonate bonds are aliphatic carbon atoms. From the viewpoints of heat resistance and strength, aromatic polycarbonate resins are preferred.

[0022] The styrene-based resin composition contains 30% to 90% by mass of a styrene-based resin and 10% to 70% by mass of a polycarbonate-based resin, preferably 40% to 60% by mass of a styrene-based resin and 40% to 60% by mass of a polycarbonate-based resin, based on 100% by mass of the styrene-based resin composition. The content of the styrene-based resin in the styrene-based resin composition is, for example, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% by mass, or may be within a range between any two of the values ​​exemplified herein. The content of the polycarbonate-based resin in the styrene-based resin composition is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70% by mass, or may be within a range between any two of the values ​​exemplified herein.

[0023] The styrene-based resin composition may contain other resins in addition to the styrene-based resin and the polycarbonate-based resin as resin components. Examples of the other resins include elastomers containing a rubber component. Examples of the elastomers include thermosetting elastomers and thermoplastic elastomers. The content of the other resins in the styrene-based resin composition is, for example, 20% by mass or less, preferably 10% by mass or less, and more preferably 1% by mass or less, based on 100% by mass of the styrene-based resin composition. Specifically, the content of the other resins in the styrene-based resin composition may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20% by mass, and may be within a range between any two of the values ​​exemplified here.

[0024] The total content of the styrene resin and the polycarbonate resin in the styrene resin composition is, for example, 40% by mass or more and 100% by mass or less, and preferably 80% by mass or more and 100% by mass or less, based on 100% by mass of the styrene resin composition. Specifically, the total content of the styrene resin and the polycarbonate resin in the styrene resin composition is, for example, 40, 50, 60, 70, 80, 85, 90, 95, 99, or 100% by mass, and may be within a range between any two of the values ​​exemplified here.

[0025] The styrene-based resin composition may contain additives to the extent that the effects of the present invention are not impaired. Examples of additives include flame retardants, flame retardant aids, antioxidants, antiaging agents, impact modifiers, release agents, UV absorbers, antistatic agents, antifogging agents, lubricants / antiblocking agents, flow improvers, compatibilizers, plasticizers, dispersants, and antibacterial agents. Common additives commonly used in styrene-based resin compositions can be blended. The content of these additives is, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less, based on 100% by mass of the styrene-based resin composition. The content of other resins in the styrene-based resin composition may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10% by mass, and may be within a range between any two of the values ​​exemplified herein.

[0026] <Characteristics of styrene-based resin compositions> The dielectric loss tangent at a measurement frequency of 24 GHz of a molded article (40 mm long x 30 mm wide x 0.15 mm thick) obtained by molding the styrene-based resin composition is less than 0.0050, preferably less than 0.0045, and more preferably less than 0.0040. When it is within this range, it can be expected that the propagation loss of radio waves from a radome or the like will be small. The dielectric loss tangent does not need to have a lower limit, but is, for example, 0.0001 or more, or 0.0010 or more. The dielectric tangent may be, for example, 0.0001, 0.0005, 0.0010, 0.0015, 0.0020, 0.0025, 0.0030, 0.0035, 0.0036, 0.0037, 0.0038, 0.0039, 0.0040, 0.0045, or 0.0049, and may be within a range between any two of the values ​​exemplified here.

[0027] The relative permittivity at a measurement frequency of 24 GHz of a molded article (40 mm length × 30 mm width × 0.15 mm thickness) obtained by molding the styrene-based resin composition is preferably 3.0 or less, more preferably 2.7 or less. When it is in this range, it can be expected that the propagation loss of radio waves from a radome or the like will be small. The relative permittivity does not need to have a lower limit, but it may be, for example, 1.0 or more, or 2.0 or more. Specific examples of the relative permittivity are 1.0, 1.5, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, and 3.5, and may be within a range between any two of the values ​​exemplified here.

[0028] The method for measuring the relative dielectric constant and the dielectric loss tangent will be described in detail later.

[0029] The deflection temperature under load of a molded article (A-type test piece (dumbbell) according to JIS K 7139) obtained by molding the styrene resin composition, measured in accordance with JIS K 7197 using the flatwise method under conditions of a stress of 1.8 MPa, is preferably 100°C or higher, more preferably 105°C or higher. When the deflection temperature is within this range, the heat resistance of the radome or the like can be expected to be excellent, and the strength, particularly under high temperature conditions, can be expected to be high. The upper limit of the deflection temperature under load does not need to be particularly limited, but it is, for example, 125°C or lower. The deflection temperature under load is, for example, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, or 125°C, and may be within a range between any two of the values ​​exemplified here.

[0030] The bending stress of a molded article (type A test piece (dumbbell) according to JIS K 7139) obtained by molding the styrene resin composition, measured in accordance with JIS K 7171 at a test speed of 2 mm / min, is preferably 85 MPa or more, more preferably 90 MPa or more. The upper limit of the bending stress is not particularly limited, but is, for example, 105 MPa or less. Specific examples of the bending stress are 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, and 105 MPa, and may be within a range between any two of the values ​​exemplified here.

[0031] The flexural modulus of a molded article (type A test piece (dumbbell) according to JIS K 7139) obtained by molding the styrene resin composition, measured in accordance with JIS K 7171 at a test speed of 2 mm / min, is preferably 2.00 GPa or more, more preferably 2.50 GPa or more. The upper limit of the flexural modulus is not particularly limited, but is, for example, 3.50 GPa or less. Specific examples of the flexural modulus are 2.00, 2.25, 2.50, 2.75, 3.00, 3.25, and 3.50 GPa, and may be within a range between any two of the values ​​exemplified here.

[0032] <Method of producing styrene-based resin composition> A method for producing a styrene-based resin composition according to one embodiment of the present invention includes a styrene-based resin synthesis step of preparing a styrene-based resin and a mixing step of mixing a styrene-based resin with a polycarbonate-based resin. The styrene-based resin synthesis step includes a polymerization step of polymerizing raw material monomers including styrene and (meth)acrylic acid to produce a styrene-based resin. The polymerization step can be carried out by a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. From the viewpoints of quality and productivity, bulk polymerization and solution polymerization are preferred, and continuous polymerization is preferable. Examples of solvents that can be used include alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene; ketones such as acetone and methyl ethyl ketone; and aliphatic hydrocarbons such as hexane and cyclohexane.

[0033] Known polymerization conditions can be adopted as the polymerization conditions, but in particular the content of each monomer unit in the resulting polymer can be controlled by various conditions such as the ratio and concentration of each monomer in the raw material monomers, the addition rate, etc.

[0034] During polymerization of the styrene-based resin, polymerization aids such as a polymerization initiator, a chain transfer agent, a crosslinking agent, and other polymerization aids may be used as needed. The polymerization initiator is preferably a radical polymerization initiator, and examples of the polymerization initiator include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide, alkyl peroxides such as t-amylperoxyisononanoate, and dialkyl peroxides such as t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide. Examples of the peroxides include peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxycarbonates such as t-butylperoxyisopropyl carbonate and polyether tetrakis(t-butylperoxycarbonate); N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]; and these can be used alone or in combination of two or more. Examples of chain transfer agents include aliphatic mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, aromatic mercaptans, thiocarboxylic acids such as thioglycolic acid and mercaptopropionic acid, polyfunctional mercaptans in which the hydroxyl group of a polyhydric alcohol such as ethylene glycol, tetraethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, or sorbitol is esterified with thioglycolic acid or mercaptopropionic acid, pentaphenylethane, α-methylstyrene dimer, and terpinolene. Among these, aliphatic mercaptans, aromatic mercaptans, thiocarboxylic acids, and polyfunctional mercaptans are preferred because of their ease of molecular weight adjustment.

[0035] In the case of continuous polymerization, the styrene-based resin synthesis process may include a polymerization step, a devolatilization step, and a granulation step.

[0036] In the polymerization step, a known complete mixing tank type stirring tank or tower type reactor is used, and the polymerization reaction can be controlled by adjusting the polymerization temperature or the like so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate.

[0037] The polymer solution containing the polymer that has left the polymerization process is transferred to the devolatilization process, where unreacted monomers and polymerization solvent are removed. The devolatilization process is composed of a vacuum devolatilization tank equipped with a heater or a devolatilization extruder equipped with a vent. The molten polymer that has left the devolatilization process is transferred to the granulation process. In the granulation process, the molten resin is extruded in the form of strands through a multi-hole die and processed into pellets using the cold cut method, the in-air hot cut method, or the underwater hot cut method.

[0038] In the mixing step, the styrene resin obtained in the styrene resin synthesis step and the polycarbonate resin are mixed to a predetermined ratio. The mixing is carried out by melt kneading using, for example, a single-screw extruder, a twin-screw extruder, or a kneader, and the resins may be mixed in advance using a tumbler or a Henschel mixer.

[0039] In the method for producing a styrene-based resin composition, the additives may be added to a raw material solution before polymerization of the styrene-based resin, or the additives may be mixed in an extruder or static mixer installed after polymerization of the styrene-based resin and before granulation. Alternatively, the styrene-based resin may be dry-blended with pellets obtained by granulation and the additives, followed by melt-kneading to produce the composition. Alternatively, the polycarbonate-based resin may be dry-blended with the additives, followed by melt-kneading to produce the composition. Alternatively, the additives may be melt-kneaded in advance with a small amount of either or both of the styrene-based resin and the polycarbonate resin to produce a pellet-like masterbatch, which is then dry-blended with the remaining styrene-based resin and the polycarbonate resin, followed by melt-kneading to prepare the composition.

[0040] 2.Radomes, antennas, base stations The styrene-based resin composition can be preferably used for a radome, and more specifically, for a radome provided in a base station antenna.

[0041] A radome according to one embodiment of the present invention includes a styrene-based resin composition, and more specifically, includes a component made of the styrene-based resin composition. When the radome includes a multilayer body made of multiple layers, at least one of the multiple layers can be made of the styrene-based resin composition.

[0042] The method for manufacturing a radome includes a step of molding a styrene-based resin composition. A general molding method can be used to mold the styrene-based resin composition, such as injection molding, extrusion molding, or insert molding. The method for manufacturing a radome can also include a step of combining the molded body (member) of the styrene-based resin composition obtained by molding with another member.

[0043] An antenna according to an embodiment of the present invention includes the above-described radome.A base station according to an embodiment of the present invention includes the antenna. [Example]

[0044] The present invention will be described in more detail below with reference to examples, but these examples are merely illustrative and are not intended to limit the scope of the present invention.

[0045] [Preparation of Resin Composition] First, the styrene polymers (styrene resins) used in each resin composition were synthesized. For the styrene polymers 1 to 3, the following first to third reactors were connected in series to constitute a polymerization process. First reactor: 39 L volume complete mixing reactor with agitator Second reactor: 39 L volume complete mixing reactor with agitator Third reactor: 16 L volume plug flow reactor with static mixer

[0046] <Styrene-based polymer 1> A raw material solution consisting of 75.4 parts by mass of styrene monomer, 6.9 parts by mass of methacrylic acid monomer, 15.0 parts by mass of ethylbenzene, 2.5 parts by mass of 1-octanol, 0.14 parts by mass of polyoxyethylene lauryl ether (Emulgen 109P manufactured by Kao Corporation), and 0.020 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane (Perhexa C manufactured by NOF Corporation) was continuously fed to the first reactor at a feed rate of 14 L / hr, and polymerization was carried out at a temperature of 125 ° C in the first reactor, 132 ° C in the second reactor, and 132 to 136 ° C in the third reactor. The resulting polymerization solution was introduced into a vacuum devolatilizer tank equipped with a preheater, consisting of two stages in series. Unreacted styrene, methacrylic acid, and ethylbenzene were separated, extruded into strands, cooled, and then cut into pellets. The resin temperature in the first devolatilization tank was set to 160°C, the pressure in the vacuum devolatilization tank was 65 kPa, the resin temperature in the second devolatilization tank was set to 230°C, and the pressure in the vacuum devolatilization tank was 0.7 kPa. The styrene polymer had a methacrylic acid content of 9.7% by mass and a weight-average molecular weight of 180,000.

[0047] <Styrene-based polymer 2> A raw material solution consisting of 80.1 parts by mass of styrene monomer, 2.8 parts by mass of methacrylic acid monomer, 15.0 parts by mass of ethylbenzene, 2.0 parts by mass of 1-octanol, 0.060 parts by mass of polyoxyethylene lauryl ether (Emulgen 109P manufactured by Kao Corporation), and 0.020 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane (Perhexa C manufactured by NOF Corporation) was continuously fed to the first reactor at a feed rate of 14 L / hr, and polymerization was carried out at a temperature of 125 ° C in the first reactor, 132 ° C in the second reactor, and 132 to 136 ° C in the third reactor. The resulting polymerization solution was introduced into a two-stage preheater-equipped vacuum devolatilizer tank in series, and after separating unreacted styrene, methacrylic acid, and ethylbenzene, it was extruded into a strand shape, cooled, and then cut into pellets. The resin temperature in the first devolatilization tank was set to 160°C, the pressure in the vacuum devolatilization tank was 65 kPa, the resin temperature in the second devolatilization tank was set to 230°C, and the pressure in the vacuum devolatilization tank was 0.7 kPa. The methacrylic acid content of the styrene polymer was 3.9% by mass, and the weight-average molecular weight was 280,000.

[0048] <Styrene-based polymer 3 (GPPS)> A raw material solution consisting of 94.0 parts by mass of styrene monomer and 6.0 parts by mass of ethylbenzene was continuously fed to the first reactor at a feed rate of 20 L / hr. Polymerization was carried out at a temperature of 150°C in the first reactor, 155°C in the second reactor, and 155-160°C in the third reactor. The resulting polymerization solution was introduced into a two-stage preheater-equipped vacuum devolatilizer tank in series. Unreacted styrene and ethylbenzene were separated, and the resulting polymer was extruded into a strand, cooled, and then cut into pellets. The resin temperature in the first devolatilizer tank was set to 160°C, the pressure in the vacuum devolatilizer tank was 65 kPa, and the resin temperature in the second devolatilizer tank was set to 230°C, the pressure in the vacuum devolatilizer tank was 0.7 kPa. The methacrylic acid content of the styrene-based polymer was 0% by mass, and the weight-average molecular weight was 200,000.

[0049] <Polycarbonate> Mitsubishi Engineering Plastics Corporation, Iupilon HL-4000

[0050] [Examples 1 to 4 and Comparative Examples 1 to 4] Pellets of the styrene polymer obtained as described above and polycarbonate were heated and dried at 80°C for 3 hours to obtain the formulations of the resin compositions shown in Table 1. The components were premixed in a Henschel mixer (Mitsui Miike Chemical Co., Ltd., FM20B) in the amounts shown in Table 1. The mixture was fed into a twin-screw extruder (Toshiba Machine Co., Ltd., TEM26SS) and extruded at a cylinder temperature of 200°C and a feed rate of 25 kg / h. The extruded mixture was then water-cooled and pelletized in a pelletizer. The resulting pellets were molded into type A test pieces (dumbbells) according to JIS K 7139 using an injection molding machine (Japan Steel Works, Ltd., "J100E-P"). The cylinder temperature was 240°C and the mold temperature was 45°C.

[0051] Table 1 shows the formulations and properties of resin compositions P-1 to P-8 used in the injection molding.

[0052] <Deflection temperature under load> The deflection temperature under load of the resin composition was measured using an A-type test piece by the flatwise method under a stress of 1.8 MPa in accordance with JIS K 7197. The deflection temperature under load was evaluated according to the following criteria. ◎: Heat deflection temperature is 105℃ or higher ○: The deflection temperature under load is 100℃ or higher and less than 105℃ ×: Deflection temperature under load is less than 100°C

[0053] <Bending stress / bending modulus> The bending stress and bending modulus of the resin composition were measured using an A-type test piece at a test speed of 2 mm / min in accordance with JIS K 7171. The bending stress was evaluated according to the following criteria. ◎: Bending stress is 85 MPa or more ○: Bending stress is 75 MPa or more and less than 85 MPa ×: Bending stress is less than 75 MPa The flexural modulus was evaluated according to the following criteria. ◎: Flexural modulus is 2.50 GPa or more ◯: Flexural modulus is 2.00 GPa or more and less than 2.50 GPa ×: Flexural modulus is less than 2.00 GPa

[0054] <Dielectric properties> The dielectric constant and dielectric loss tangent of the resin compositions were measured using the following method. Pellets of each resin composition were dried at 80°C for 2 hours and then molded using a heat press at 250°C and 15 MPa to produce test specimens measuring 40 mm long, 30 mm wide, and 0.15 mm thick. The resulting test specimens were then left to stand for 24 hours at 25°C and 50% humidity. The dielectric constant and dielectric loss tangent at 24 GHz were then measured using a network analyzer (Keysight Technologies, Inc., N5222B) and a split cylinder resonator for 24 GHz (Kanto Electronics Application Development Co., Ltd., CR724). The dielectric loss tangent was evaluated according to the following criteria. ◎: Dielectric tangent is less than 0.0040 ○: Dielectric tangent is 0.0040 or more and less than 0.0050 ×: Dielectric tangent is 0.0050 or more The relative dielectric constant was evaluated according to the following criteria. ○: The relative dielectric constant is 3.0 or less ×: The relative dielectric constant is greater than 3.0

[0055] As shown in Table 1, the dielectric loss tangent and the deflection temperature under load were excellent in Examples 1 to 4. On the other hand, the dielectric loss tangent and the deflection temperature under load were insufficient in Comparative Examples 1 to 4.

[0056] [Table 1]

Claims

1. A styrene-based resin composition, The styrene-based resin composition contains 30% by mass or more and 90% by mass or less of a styrene-based resin and 10% by mass or more and 70% by mass or less of a polycarbonate-based resin, the styrene-based resin contains 85.0% by mass or more and 99.0% by mass or less of repeating units derived from styrene and 1.0% by mass or more and 15.0% by mass or less of repeating units derived from (meth)acrylic acid, A styrene-based resin composition, wherein a molded product obtained by molding the styrene-based resin composition has a dielectric loss tangent of less than 0.0050 at a measurement frequency of 24 GHz.

2. The styrene-based resin composition according to claim 1, which is used for a radome.

3. The styrene-based resin composition according to claim 1, which is used for a radome provided in a base station antenna.

4. A radome comprising the styrene-based resin composition according to any one of claims 1 to 3.

5. An antenna comprising the radome according to claim 4.

6. A base station comprising an antenna according to claim 5.

7. 5. A method for manufacturing the radome according to claim 4, comprising a step of molding the styrene-based resin composition.

Images