Millimeter wave radome

Abstract

To provide a millimeter wave radome which has a low relative dielectric constant and dielectric loss tangent, and is excellent in radio wave transmission and heat resistance.SOLUTION: A millimeter wave radome uses a material containing a 3-methyl-1-butene-based polymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a millimeter wave radome. [Background technology]

[0002] As electric and electronic devices become more powerful and functional, vehicles such as cars and buses are equipped with radars such as LRR (Long Range Radar) and SRR (Short Range Radar). As a society realizes high-capacity, high-speed communications, the radars are required to detect radio waves in the high-frequency range exceeding 10 GHz, for example, millimeter waves (frequency band 30 GHz to 300 GHz). A radar usually consists of an antenna and a housing that encases the antenna (hereinafter referred to as a "radome.") The antenna and radome are made of low-dielectric materials in order to efficiently receive and transmit radio waves in the high-frequency range.

[0003] For example, Patent Document 1 discloses an exterior part for a vehicle that includes an exterior covering plate made of a radio wave-transmitting and transparent material, a metal film formed on the inner surface of the exterior covering plate, and a back covering plate made of a radio wave-transmitting material. The exterior covering plate is made of polycarbonate (PC) or polymethyl methacrylate (PMMA), and the back covering plate is made of syndiotactic polystyrene (SPS), polyphenylene ether (PPE), polyvinyl chloride (PVC), or acrylonitrile / butadiene / styrene copolymer (ABS). Patent Document 2 discloses an on-vehicle radar device that includes a housing for accommodating high-frequency circuits and the like, and a radome for protecting the transmitting and receiving antennas. The main material constituting the radome is polycarbonate (PC), syndiotactic polystyrene (SPS), polypropylene (PP), or ABS resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-135030 A [Patent Document 2] JP 2004-20514 A Summary of the Invention [Problem to be solved by the invention]

[0005] It has been difficult to obtain a sufficiently low dielectric constant and low dielectric loss tangent from PC, PMMA, ABS, and other materials that have traditionally been used as low-dielectric materials. Although PP, SPS, etc. have excellent dielectric properties, they lack the heat resistance required for the recent trend toward higher output and smaller size. Therefore, materials used for radomes are required to have better dielectric properties and heat resistance in the high frequency range.

[0006] In view of the above-mentioned circumstances, an object of the present invention is to provide a millimeter wave radome that has a low relative dielectric constant and dielectric loss tangent, as well as excellent radio wave transparency and heat resistance. [Means for solving the problem]

[0007] As a result of intensive research aimed at solving the above problems, the present inventors have conceived of the present invention described below and found that the problems can be solved. That is, the present invention is as follows.

[0008] [1] A millimeter wave radome made of a material containing a 3-methyl-1-butene polymer. [2] The millimeter wave radome according to [1] above, wherein the 3-methyl-1-butene polymer is at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene with ethylene or an α-olefin, and the α-olefin has 3 to 20 carbon atoms. [3] The millimeter wave radome according to [2] above, wherein the content of the structural units derived from the ethylene or α-olefin in the copolymer is more than 0 mol % and not more than 20 mol %. [4] The millimeter wave radome according to any one of the above [1] to [3], which has a water absorption rate of less than 0.05%. [5] The millimeter wave radome according to any one of the above [1] to [4], having a dielectric tangent of less than 0.00100 at 10 GHz to 300 GHz. [6] The millimeter wave radome according to any one of the above [1] to [5], wherein the material is a resin composition containing the above 3-methyl-1-butene polymer and an alkyl radical scavenger. [7] The millimeter wave radome according to the above [6], wherein the alkyl radical scavenger comprises at least one compound selected from the group consisting of an acrylphenol compound and a benzofuranone compound. Effect of the Invention

[0009] According to the present invention, it is possible to provide a millimeter wave radome that has a low relative dielectric constant and dielectric loss tangent, as well as excellent radio wave transparency and heat resistance. [Brief description of the drawings]

[0010] [Figure 1] 1A and 1B are a schematic perspective view and a schematic cross-sectional view showing a millimeter wave radome in a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present invention will be described based on an example of an embodiment. However, the embodiment shown below is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. In this specification, preferred embodiments are shown, but a combination of two or more of the individual preferred embodiments is also a preferred embodiment. When there are several numerical ranges for matters shown in numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is stated as "XX to YY", it means "not less than XX and not more than YY".

[0012] <Millimeter wave radome> The millimeter wave radome of this embodiment is a radome that can be suitably used for frequencies of 30 GHz to 300 GHz (i.e., millimeter waves). However, as long as the effects of the present invention are not impaired, the usable frequencies are not limited to millimeter waves. The millimeter wave radome of this embodiment is characterized in that it is made of a material containing a 3-methyl-1-butene-based polymer. When the material forming the millimeter-wave radome contains a 3-methyl-1-butene polymer, the millimeter-wave radome has a low relative dielectric constant and dielectric loss tangent, and is excellent in radio wave transparency and heat resistance. In addition, the material from which the millimeter-wave radome of this embodiment is made has excellent heat resistance and can be molded into any shape. Since the molded body of the above material is usually transparent, the millimeter-wave radome of this embodiment can be colored in any color. In addition, since the 3-methyl-1-butene polymer has low water absorption, the millimeter wave radome of this embodiment is expected to be less susceptible to the usage environment, exhibit stable physical properties, and be easy to store and manage. Furthermore, since the 3-methyl-1-butene polymer has a relatively low specific gravity, the millimeter wave radome of this embodiment can also contribute to weight reduction.

[0013] [material] The material used for the millimeter wave radome of this embodiment includes a 3-methyl-1-butene polymer. The material used for the millimeter wave radome of this embodiment may be a 3-methyl-1-butene polymer, or may be a resin composition containing a component other than the 3-methyl-1-butene polymer, as described later.

[0014] <3-Methyl-1-butene polymer> The 3-methyl-1-butene polymer may be a 3-methyl-1-butene homopolymer or a copolymer of 3-methyl-1-butene and an unsaturated hydrocarbon. The unsaturated hydrocarbon may be, for example, ethylene or an α-olefin, and from the viewpoint of good copolymerizability, preferably ethylene or an α-olefin having 3 to 20 carbon atoms. From the viewpoint of suitably exerting mechanical properties (adequate strength, flexibility, and impact resistance), the 3-methyl-1-butene polymer is preferably at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene with ethylene or an α-olefin having 3 to 20 carbon atoms, and more preferably a copolymer of 3-methyl-1-butene with ethylene or an α-olefin having 3 to 20 carbon atoms. The copolymer may be a random copolymer, a block copolymer, or an alternating copolymer. The method for producing the copolymer is not limited as long as it does not impair the effects of the present invention, and any known copolymerization method can be used.

[0015] When the 3-methyl-1-butene polymer is the above-mentioned copolymer, the content of structural units derived from ethylene or an α-olefin in the copolymer is preferably more than 0 mol % and 20 mol % or less. From the viewpoints of flexibility and impact resistance, the content of structural units derived from ethylene or an α-olefin in the copolymer is more preferably 0.1 mol % or more, and even more preferably 0.5 mol % or more. From the viewpoint of heat resistance, the content of structural units derived from ethylene or an α-olefin in the copolymer is more preferably 15 mol % or less, and even more preferably 10 mol % or less. From these viewpoints, the content of structural units derived from ethylene or an α-olefin in the copolymer is more preferably 0.1 to 15 mol %, and even more preferably 0.5 to 10 mol %. The content of structural units derived from ethylene or α-olefin in the copolymer can be determined by a Fourier transform infrared spectrophotometer (FT-IR). Specifically, it can be measured by the method described in the Examples.

[0016] When the 3-methyl-1-butene polymer is the above-mentioned copolymer, the content of structural units derived from 3-methyl-1-butene in the copolymer is preferably 80 mol % or more and less than 100 mol %. From the viewpoint of heat resistance, the content of structural units derived from 3-methyl-1-butene in the copolymer is more preferably 85 mol % or more, and further preferably 90 mol % or more. From the viewpoints of flexibility and impact resistance, the content of structural units derived from 3-methyl-1-butene in the copolymer is more preferably 99.9 mol % or less, and even more preferably 99.5 mol % or less. From these viewpoints, the content of structural units derived from 3-methyl-1-butene in the copolymer is more preferably 85 to 99.9 mol %, and further preferably 90 to 99.5 mol %.

[0017] From the viewpoint of favorably exerting the physical properties of the 3-methyl-1-butene polymer, the ethylene or the α-olefin having 3 to 20 carbon atoms is preferably an α-olefin having 4 to 16 carbon atoms, and more preferably an α-olefin having 4 to 12 carbon atoms. In addition, the α-olefin having 3 to 20 carbon atoms may be linear or branched.

[0018] Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, vinylcyclohexene, and vinylnorbornane. The ethylene or α-olefin having 3 to 20 carbon atoms may be used alone or in combination of two or more kinds.

[0019] The melting point of the 3-methyl-1-butene polymer is preferably 260 to 310° C. When the melting point of the 3-methyl-1-butene polymer is within the above range, the material used for the millimeter wave radome can be easily molded by injection molding or the like, and the heat resistance is improved. The melting point of the 3-methyl-1-butene polymer means the peak temperature measured by using a differential scanning calorimeter to raise the temperature of a test piece from 30° C. to 320° C. at a rate of 10° C. / min under a nitrogen flow rate (100 mL / min), hold the test piece at 320° C. for 5 minutes, lower the temperature to −70° C. at a rate of 10° C. / min, hold the test piece at −70° C. for 5 minutes, and then raise the temperature to 320° C. at a rate of 10° C. / min. Specifically, the melting point can be measured by the method described in the Examples. From the viewpoint of a balance between production efficiency and heat resistance, the melting point of the 3-methyl-1-butene polymer is more preferably 270 to 305°C, and further preferably 280 to 300°C.

[0020] The melt viscosity of the 3-methyl-1-butene polymer is preferably 10 to 1,000 Pa·s. When the melt viscosity of the 3-methyl-1-butene polymer is 10 Pa·s or more, the mechanical strength is further improved, and when it is 1,000 Pa·s or less, good flowability during molding is easily obtained. From the viewpoint of the balance between mechanical strength and fluidity during molding, the melt viscosity of the 3-methyl-1-butene polymer is more preferably from 30 to 500 Pa·s, and further preferably from 50 to 300 Pa·s. The melt viscosity of the 3-methyl-1-butene polymer is measured at a barrel temperature of 320°C and a shear rate of 1220 sec -1 It means a value measured under the conditions of (capillary: inner diameter 1.0 mm × length 10 mm, extrusion speed 10 mm / min), and specifically, it can be measured by the method described in the Examples.

[0021] From the viewpoint of heat resistance, the content of the 3-methyl-1-butene polymer in the material used for the millimeter wave radome is preferably 50.0 to 99.9 mass%, more preferably 60.0 to 99.9 mass%, and further preferably 65.0 to 99.9 mass%. Since 3-methyl-1-butene has a high melting point, increasing the content of 3-methyl-1-butene tends to improve the heat resistance of the millimeter wave radome.

[0022] 3-Methyl-1-butene polymers have a relatively low specific gravity and can contribute to weight reduction of millimeter wave radomes. In addition, 3-methyl-1-butene polymers do not generate harmful gases when incinerated. Furthermore, the decomposition products in an inert atmosphere are low molecular weight hydrocarbons, which are suitable for chemical recycling.

[0023] <Resin composition> <Alkyl radical scavengers> From the viewpoint of exerting better mechanical properties, the material used for the millimeter wave radome may be a resin composition containing the 3-methyl-1-butene polymer and an alkyl radical scavenger. In the present embodiment, the term "alkyl radical scavenger" refers to a compound that reacts with an alkyl radical derived from a 3-methyl-1-butene polymer and then has the function of stabilizing the radical, thereby suppressing a chain reaction of main chain scission initiated by the alkyl radical. From the viewpoint of exerting better mechanical properties, the alkyl radical scavenger preferably contains at least one selected from the group consisting of an acrylphenol compound and a benzofuranone compound. The alkyl radical scavengers may be used alone or in combination of two or more kinds.

[0024] (Acrylophenol compound) The acrylic phenol compound used in this embodiment can be represented, for example, by the following general formula (I).

[0025] [ka]

[0026] In general formula (I), R 1 represents a hydrogen atom or a methyl group, R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; R 3 ,R 4 ,R 5 and R 6 each independently represents an alkyl group having 1 to 9 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The alkyl group having 1 to 9 carbon atoms may be either linear or branched. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-nonyl group. R 1 is preferably a hydrogen atom. R 2 is preferably a hydrogen atom or a methyl group, more preferably a methyl group. R 3 ,R 4 ,R 5 and R 6 are each independently preferably an alkyl group having 3 to 8 carbon atoms, more preferably an alkyl group having 5 carbon atoms, and further preferably a 1,1-dimethylpropyl group.

[0027] Examples of the acrylic phenol compound represented by general formula (I) include 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, 2,4-di-t-butyl-6-[1-(3,5-di-t-butyl-2-hydroxyphenyl)ethyl]phenyl acrylate, and 2-t-butyl-6-[(3-t-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenyl acrylate. Commercially available alkyl radical scavengers may be used. Examples of the acrylic phenol compound represented by the general formula (I) include those available under the trade names "Sumilizer GS" and "Sumilizer GM" manufactured by Sumitomo Chemical Co., Ltd.

[0028] (Benzofurano compounds) The benzofuranone compound used in this embodiment can be represented, for example, by the following general formula (II).

[0029] [ka]

[0030] In general formula (II), R 7 and R 8 each independently represents an alkyl group having 1 to 4 carbon atoms; R 9 and R 10 each independently represents an alkyl group having 1 to 9 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. The alkyl group having 1 to 9 carbon atoms may be linear or branched. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-nonyl group. R 7 and R 8 are each independently preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. R 9 and R 10 are each independently preferably an alkyl group having 1 to 4 carbon atoms, more preferably a t-butyl group.

[0031] Examples of the benzofuranone compound represented by the general formula (II) include 5,7-di-t-butyl-3-(3,4-di-methyl-phenyl)-3H-benzofuran-2-one, 5,7-di(t-butyl)-3-(3,4-di-propyl-phenyl)-3H-benzofuran-2-one, and 4-t-butyl-2-(5-t-butyl-2-oxo-3H-benzofuran-3-yl)phenyl-3,5-di-t-butyl-4-hydroxybenzoate. As the alkyl radical scavenger, commercially available products may be used. Examples of the benzofuranone compound represented by the general formula (II) include "Iragnox HP-136" (trade name) manufactured by BASF and "Revonox 501" (trade name) manufactured by Chitec.

[0032] (Alkyl radical scavenger content) The content of the alkyl radical scavenger in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is preferably 0.01 to 1.00 part by mass. When the content of the alkyl radical scavenger is 0.01 parts by mass or more, the physical properties of the resin composition can be more stably maintained during melt kneading of the resin composition, and molding defects caused by generation of decomposition gas during melt molding can be suppressed. In addition, when the content of the alkyl radical scavenger is 1.00 parts by mass or less, a millimeter wave radome having more excellent mechanical properties is easily obtained. In addition, the alkyl radical scavenger is prevented from bleeding out, or the physical properties required for the resin composition, such as deterioration of water absorption, are prevented from being impaired.

[0033] From the viewpoint of maintaining the physical properties of the resin composition more stably during melt kneading, the content of the alkyl radical scavenger in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.02 parts by mass or more, and even more preferably 0.05 parts by mass or more. From the viewpoint of a balance between maintaining the stability of the physical properties of the resin composition and economic efficiency, and from the viewpoint of obtaining a millimeter-wave radome having a lower dielectric constant and dielectric tangent, the content of the alkyl radical scavenger in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.80 parts by mass or less, and further preferably 0.70 parts by mass or less. From these viewpoints, the content of the alkyl radical scavenger in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.02 to 0.80 parts by mass, and further preferably 0.05 to 0.70 parts by mass. When two or more types of alkyl radical scavengers are contained, the content of the alkyl radical scavengers means the total content of the alkyl radical scavengers.

[0034] <Antioxidants> The resin composition may contain an antioxidant from the viewpoint of ensuring the stability of the polymer. The antioxidant preferably includes at least one selected from the group consisting of phenol-based antioxidants and phosphorus-based antioxidants. The antioxidants may be used alone or in combination of two or more.

[0035] (Phenol-based antioxidant) Examples of phenolic antioxidants include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-t-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and octaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]. Decyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, thiodiethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], 3,3',3'',5,5',5''-hexa-t-butyl-α,α',α''-(mesitylene-2,4,6-triyl)tri-p-cresol, ethylene bis (Oxyethylene)bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,6-di-t-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, 3,9-bis[2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl]-2, Examples of such compounds include 4,8,10-tetraoxaspiro(5,5)undecane, 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-t-butyl-m-cresol), 6,6'-di-t-butyl-4,4'-butylidene di-m-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, and benzenepropionic acid 3,5-bis-(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl ester.

[0036] As the phenol-based antioxidant, commercially available products may be used, for example, "ADEKA STAB AO series" manufactured by ADEKA Corporation, and "Irganox series" manufactured by BASF Japan Ltd. may be mentioned.

[0037] (Phosphorus-based antioxidant) Examples of phosphorus-based antioxidants include 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, tetrakis(2,4-di-t-butyl-phenyl)-4,4'-biphenylenephosphonite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, and tris(2,4-di-t-butylphenyl)phosphite. , bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, di-t-butyl-m-cresyl-phosphonite, diethyl[(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl]phosphonate, tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, 3,9-bis(octadecyoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, tetra-C12-15-alkyl (propane-2,2-diylbis(4,1-phenylene))bis(phosphite), 2-ethylhexyldiphenylphosphite, isodecyldiphenylphosphite, trisisodecylphosphite, triphenylphosphite, and 3,9-bis[2,4-bis(1-methyl-1-phenylethyl)phenoxy]-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0038] As the phosphorus-based antioxidant, commercially available products may be used, such as the "ADEKA STAB PEP series" and "ADEKA STAB HP series" manufactured by ADEKA Corporation, the "IRGAFOS series" manufactured by BASF Japan Ltd., and the trade name "HOSTANOX P-EPQ" manufactured by Clariant.

[0039] (Sulfur-based antioxidant) Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, laurylstearyl 3,3'-thiodipropionate, pentaerythritol-tetrakis-(β-lauryl-thio-propionate), 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and the like.

[0040] (Other antioxidants) The resin composition may contain an antioxidant other than the phenol-based antioxidant, the phosphorus-based antioxidant, and the sulfur-based antioxidant, as long as the effect of the present invention is not impaired. Examples of the antioxidant other than the phenol-based antioxidant, the phosphorus-based antioxidant, and the sulfur-based antioxidant include an amine-based antioxidant.

[0041] (Antioxidant content) The content of the antioxidant in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is preferably 0.01 parts by mass or more, more preferably 0.10 parts by mass or more, from the viewpoint of ensuring the stability of the 3-methyl-1-butene polymer, and is preferably 1.00 parts by mass or less, more preferably 0.80 parts by mass or less, from the viewpoint of the relative dielectric constant and the dielectric loss tangent, i.e., preferably 0.01 to 1.00 parts by mass, more preferably 0.10 to 0.80 parts by mass. When the resin composition contains two or more kinds of antioxidants, the content of the antioxidants means the total content of the antioxidants.

[0042] <Other additives> The resin composition may contain additives other than the alkyl radical scavenger and the antioxidant. Examples of other additives include antacids, fillers, light stabilizers, antistatic agents, flame retardants, pigments, polymerization inhibitors, heavy metal deactivators, ultraviolet absorbers, nucleating agents, clarifying agents, lubricants, fluorescent brightening agents, rust inhibitors, and sliding agents. The other additives may be used alone or in combination of two or more kinds.

[0043] (Antacids) From the viewpoint of suppressing deterioration due to acid components generated from residual metal components and the like during melt kneading, the resin composition preferably contains an antacid. Antacids include barium laurate, calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, zinc oleate, magnesium 12-hydroxystearate and the like. The antacids may be used alone or in combination of two or more.

[0044] The content of the antacid in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.01 to 200 parts by mass.

[0045] (Antistatic agent) Examples of the antistatic agent include sodium alkylsulfonate, phosphonium alkylsulfonate, and fatty acid ester hydroxyamine compounds such as glycerin ester of stearic acid.

[0046] The content of the antistatic agent in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 5 parts by mass or less.

[0047] (Filler) The resin composition may contain a filler from the viewpoint of further improving the mechanical properties of the millimeter wave radome. Examples of the filler include fibrous compounds such as glass fiber, alumina fiber, resin fiber, carbon fiber, and cellulose fiber; flat compounds such as mica, talc, montmorillonite, and flat aluminum; spherical compounds such as glass beads, shirasu balloons, and acrylic balloons; needle-shaped compounds such as needle-shaped metal titanate, wollastonite, needle-shaped silica, and tin oxide; powdered metal titanate, finely powdered wood chips, titanium oxide, calcium carbonate, silica, and alumina; and the like. These fillers may be surface-treated with, for example, a silane coupling agent. A compatibilizer may also be used to enhance the dispersibility of the filler. Among these, glass fiber is preferable from the viewpoint of further improving the mechanical properties of the millimeter wave radome. The fillers may be used alone or in combination of two or more.

[0048] The content of the filler in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.01 to 300 parts by mass or 0.1 to 100 parts by mass.

[0049] (UV absorber) Examples of the ultraviolet absorber include hindered amine ultraviolet absorbers such as 2,2,6,6-tetramethyl-4-piperidyl benzoate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, and 4-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)-1-(2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl)-2,2,6,6-tetramethylpiperidine. benzotriazole-based ultraviolet absorbers such as 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole; benzoate-based ultraviolet absorbers such as 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; and the like.

[0050] The content of the ultraviolet absorber in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.001 to 5 parts by mass, or 0.01 to 1 part by mass.

[0051] (lubricant) As the lubricant, inorganic fine particles are generally used. Here, examples of inorganic fine particles include oxides, hydroxides, sulfides, nitrides, halides, carbonates, sulfates, acetates, phosphates, phosphites, organic carboxylates, silicates, titanates, borates, and their hydrated compounds, composite compounds mainly composed of them, and natural minerals, etc., of elements of Groups 1, 2, 4, 6, 7, 8-10, 11, 12, 13, and 14 of the periodic table.

[0052] Examples of inorganic fine particles include Group 1 element compounds such as titanium fluoride and borax (sodium borate hydrate); Group 2 element compounds such as magnesium carbonate, magnesium phosphate, magnesium oxide (magnesium oxide), magnesium chloride, magnesium acetate, magnesium fluoride, magnesium titanate, magnesium silicate, magnesium silicate hydrate (talc), calcium carbonate, calcium phosphate, calcium phosphite, calcium sulfate (gypsum), calcium acetate, calcium terephthalate, calcium hydroxide, calcium silicate, calcium fluoride, calcium titanate, strontium titanate, barium titanate, zinc titanate, lanthanum titanate, bismuth titanate, lead titanate, barium carbonate, barium phosphate, barium sulfate, and barium phosphite; and titanium dioxide (titania ), titanium monoxide, titanium nitride, zirconium dioxide (zirconia), zirconium monoxide, and other group 4 element compounds; molybdenum dioxide, molybdenum trioxide, molybdenum sulfide, and other group 6 element compounds; manganese chloride, manganese acetate, and other group 7 element compounds; cobalt chloride, cobalt acetate, and other group 8 to 10 element compounds; cuprous iodide, and other group 11 element compounds; zinc oxide, zinc acetate, and other group 12 element compounds; aluminum oxide (alumina), aluminum hydroxide, aluminum fluoride, aluminosilicates (alumina silicate, kaolin, kaolinite), and other group 13 element compounds; silicon oxide (silica, silica gel), graphite, carbon, graphite, glass, and other group 14 element compounds; and natural mineral particles such as carnallite, kainite, mica, and byrrhotite. The average particle size of the inorganic particles is not particularly limited, but is preferably 0.01 to 3 μm.

[0053] The content of the lubricant in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, from 0.001 to 5 parts by mass, or from 0.005 to 3 parts by mass.

[0054] <Other resins> The resin composition may or may not contain a resin other than the 3-methyl-1-butene polymer. From the viewpoint of improving the dispersibility of additives containing polar groups, the resin composition may contain other resins such as vinyl acetate-ethylene copolymers and modified polyolefins partially modified with reactive functional groups such as oxidation or maleic acid. Examples of polyolefins constituting modified polyolefins modified with reactive functional groups include polyethylene, polypropylene, and polyolefins having α-olefins having 3 to 20 carbon atoms as structural units. Examples of α-olefins having 3 to 20 carbon atoms include those described in the above section on 3-methyl-1-butene polymers. These may be homopolymers or copolymers. In addition, these polyolefins may be high density or low density, and may be polymerized by a metallocene catalyst. Among these, at least one selected from the group consisting of polyethylene or polypropylene is preferred, at least one selected from the group consisting of modified polyethylene or modified polypropylene partially modified with reactive functional groups such as oxidation or maleic acid is more preferred, and at least one selected from the group consisting of maleic anhydride-modified polypropylene is even more preferred.

[0055] From the viewpoint of further exerting the effects of the present invention, the contents of the vinyl acetate-ethylene copolymer and the modified polyolefin partially modified with a reactive functional group such as oxidation or maleic acid in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer are preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0056] Examples of resins other than vinyl acetate-ethylene copolymers and modified polyolefins partially modified with reactive functional groups such as oxidation or maleic acid include polyolefins such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, very low-density polyethylene, polypropylene, syndiotactic polypropylene, polybutene, and polypentene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6 and nylon 66; ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers, polystyrene, syndiotactic polystyrene, polyphenylene sulfide, polyphenylene ether, polyamides, polyesters, polycarbonates, and thermoplastic elastomers. Examples of the thermoplastic elastomer include random or block copolymers of aromatic vinyl monomers and conjugated diene monomers, such as styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, and styrene-butadiene random copolymers; polyisoprene rubber; polyolefin rubbers, such as ethylene-propylene copolymers, ethylene-α-olefin copolymers, and propylene-α-olefin copolymers; diene copolymers, such as ethylene-propylene-diene copolymers, α-olefin-diene copolymers, diene copolymers, isobutylene-isoprene copolymers, and isobutylene-diene copolymers; norbornene rubber polymers, such as copolymers of norbornene monomers and ethylene or α-olefins, terpolymers of norbornene monomers, ethylene and α-olefins, and ring-opening polymers of norbornene monomers, or hydrogenated versions of these.

[0057] From the viewpoint of further improving the flexibility, bendability, and impact resistance of the millimeter-wave radome, the resin composition may contain a thermoplastic elastomer. When the resin composition contains a thermoplastic elastomer, the millimeter-wave radome is less susceptible to distortion and impact, and the occurrence of cracks can be suppressed.

[0058] From the viewpoint of impact resistance, the thermoplastic elastomer preferably has a glass transition temperature (Tg) of 40°C or less. Some block copolymers have two or more Tg points, but as long as one of the Tg points is 40°C or less, it can be preferably used. The number average molecular weight is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, and preferably 200,000 or less. If the number average molecular weight is 10,000 or more, the mechanical properties are more excellent, and if it is 200,000 or less, the production becomes easier. In addition, from the viewpoint of compatibility with 3-methyl-1-butene polymers, non-polar ones, that is, ones composed only of carbon and hydrogen, are preferable.

[0059] From the viewpoint of obtaining a millimeter wave radome having a low relative dielectric constant and dielectric loss tangent, it is preferable that the resin composition has a reduced amount of metal elements. Therefore, from the viewpoint of easily reducing the amount of metal elements, the thermoplastic elastomer is preferably a copolymer of an aromatic vinyl monomer and a conjugated diene monomer, and more preferably a block copolymer thereof. From the viewpoint of improving weather resistance, hydrogenated products thereof are more preferred.

[0060] The content of other resins other than the thermoplastic elastomer, vinyl acetate-ethylene copolymer, and modified polyolefin partially modified with reactive functional groups such as oxidized or maleic acid in the resin composition is preferably 1 to 100 parts by mass, more preferably 2 to 50 parts by mass, and further preferably 3 to 30 parts by mass, based on 100 parts by mass of the 3-methyl-1-butene polymer. When in the above range, the excellent physical properties of the 3-methyl-1-butene polymer, such as heat resistance and chemical resistance, are easily exhibited.

[0061] <Dielectric tangent> The dielectric loss tangent of the millimeter-wave radome of this embodiment in the range of 10 GHz to 300 GHz is preferably 0.00001 or more, more preferably 0.00005 or more, and even more preferably 0.00010 or more. From the viewpoint of reducing transmission loss, the dielectric loss tangent of the millimeter-wave radome is preferably less than 0.00100, more preferably 0.00080 or less, and even more preferably 0.00070 or less. That is, the dielectric loss tangent of the millimeter-wave radome in the range of 10 GHz to 300 GHz is preferably 0.00001 or more and less than 0.00100, more preferably 0.00005 to 0.00080, and even more preferably 0.00010 to 0.00070. The dielectric loss tangent of the millimeter wave radome at 10 GHz to 300 GHz means a value measured by a general method such as a capacitance method, a resonance method, a frequency change method, etc. Specifically, the dielectric loss tangent can be measured by the method described in the examples. When the measurement wavelength is 10 GHz or more and 50 GHz or less, it is preferable to perform the measurement by the resonance method, and when the measurement wavelength is more than 50 GHz and 300 GHz or less, it is preferable to perform the measurement by the frequency change method.

[0062] <Dielectric constant> The relative dielectric constant of the millimeter-wave radome of this embodiment in the range of 10 GHz to 300 GHz is preferably 0.5 or more, more preferably 1.5 or more, and further preferably 2.0 or more. From the viewpoint of reducing transmission loss, the relative dielectric constant of the millimeter-wave radome is preferably 5.0 or less, more preferably 4.0 or less, and further preferably 3.5 or less. That is, the relative dielectric constant of the millimeter-wave radome in the range of 10 GHz to 300 GHz is preferably 0.5 to 5.0, more preferably 1.5 to 4.0, and further preferably 2.0 to 3.5. The dielectric constant of the material used in the millimeter-wave radome at 10 GHz to 300 GHz means a value measured by a common method such as a capacitance method, a resonance method, or a frequency change method. The dielectric constant means the dielectric constant of a molded body obtained by molding the material used in the millimeter-wave radome. Specifically, the dielectric constant can be measured by the method described in the examples. When the measurement wavelength is 10 GHz or more and 50 GHz or less, it is preferable to perform the measurement by the resonance method, and when the measurement wavelength is more than 50 GHz and 300 GHz or less, it is preferable to perform the measurement by the frequency change method.

[0063] <Water absorption rate> The water absorption rate of the millimeter wave radome of this embodiment is preferably less than 0.05 mass %, more preferably less than 0.03 mass %, and further preferably less than 0.01 mass %. If the water absorption rate of the millimeter wave radome is within the above range, the radio wave transmittance becomes more stable even in a humid environment, and storage and management becomes easier. The water absorption rate of the material used in the millimeter-wave radome means a value measured on a molded body made of the material used in the millimeter-wave radome in accordance with Method A of JIS K 7209:2000, and specifically, it can be measured by the method described in the examples.

[0064] <Deflection temperature under load> From the viewpoint of even better heat resistance, the deflection temperature under load of the millimeter-wave radome of this embodiment is preferably 250° C. or more, more preferably 260° C. or more, and even more preferably 270° C. or more. The deflection temperature under load is preferably 320° C. or less, more preferably 310° C. or less, and even more preferably 300° C. or less. That is, the deflection temperature under load is preferably 250 to 320° C., more preferably 260 to 310° C., and even more preferably 270 to 300° C. If the deflection temperature under load of the millimeter wave radome is within the above range, it becomes easier to prevent the radome from being deformed by heat without being affected by the usage environment. The deflection temperature under load of the millimeter-wave radome means a value measured on a molded body made of a material used in the millimeter-wave radome in accordance with Method A of JIS K 7191-1:2015, and specifically, it can be measured by the method described in the examples.

[0065] <Manufacturing method of millimeter wave radome> The method for manufacturing the millimeter wave radome of this embodiment can employ a known method and is not particularly limited. The method for producing the millimeter-wave radome of the present embodiment preferably includes a step of obtaining a 3-methyl-1-butene polymer and a step of obtaining the millimeter-wave radome. In addition, when a resin composition is obtained by blending other components such as an alkyl radical scavenger, an antioxidant, and other additives in addition to the 3-methyl-1-butene polymer, it is preferable to go through a step of obtaining a resin composition described later.

[0066] [Step for obtaining 3-methyl-1-butene polymer] In this embodiment, the method for obtaining the 3-methyl-1-butene polymer is not particularly limited, and the polymer can be produced using a known catalyst such as a Ziegler-Natta catalyst, a metallocene catalyst, etc. As a method for obtaining the 3-methyl-1-butene polymer, for example, as described in JP-A-61-103910, the polymer can be obtained as a powder by homopolymerizing 3-methyl-1-butene in the presence of a catalyst, or copolymerizing 3-methyl-1-butene with ethylene or the above-mentioned α-olefin. The stereoregularity of the 3-methyl-1-butene polymer may be isotactic or syndiotactic.

[0067] [Step of obtaining resin composition] The step of obtaining a resin composition is a step of blending and mixing a 3-methyl-1-butene polymer and other components to obtain a resin composition. The blending method is not particularly limited, and a method of melt-kneading using a twin-screw kneading extruder or the like can be used. When no other components are blended besides the 3-methyl-1-butene polymer, there is no need to go through the step of obtaining a resin composition. Examples of other components include those similar to those described in the above [Resin composition], such as alkyl radical scavengers, antioxidants, antacids, fillers, light stabilizers, antistatic agents, flame retardants, pigments, polymerization inhibitors, heavy metal deactivators, ultraviolet absorbers, nucleating agents, clarifying agents, lubricants, fluorescent brightening agents, rust inhibitors, and sliding agents.

[0068] <Melting and kneading conditions> The melt kneading conditions are not particularly limited, but it is preferable to perform melt kneading by injecting an inert gas into the inside of a melt kneader, or by degassing the inside of the melt kneader under reduced pressure. In order to suppress deterioration of the physical properties of the resin composition due to oxygen and to produce a millimeter wave radome having better mechanical properties, it is preferable to melt and knead the resin composition in an inert atmosphere or in a low-oxygen state. Here, in this embodiment, the "low oxygen state" refers to a state in which the oxygen concentration is lower than that before the degassing by depressurizing the inside of the melt kneader. In the "low oxygen state", the oxygen concentration inside the melt kneader is preferably 5% or less, more preferably 2% or less, and even more preferably 1% or less. The oxygen concentration is measured using an oxygen concentration meter such as a diaphragm-type galvanic type.

[0069] The method of injecting an inert gas into the melt kneader to melt and knead may be, for example, to feed each component while injecting an inert gas into the melt kneader to perform melt kneading, or to feed each component into the melt kneader and then inject an inert gas to perform melt kneading. Also, the inert gas may be continuously injected into the melt kneader during melt kneading. The method of injecting the inert gas can be carried out depending on the equipment provided in each melt kneader. For example, the inert gas may be injected from a gas supply section for an inert gas or the like provided in the melt kneader, from a supply section for each component provided in the melt kneader, or from a gas vent vent provided in the melt kneader. There is no limitation on the injection method as long as the inert gas can be injected throughout the entire area from the inert gas supply section to the heating section where melting and kneading is performed, and melting and kneading can be performed. Examples of the inert gas include nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and carbon dioxide gas. From the viewpoints of availability and versatility, nitrogen gas is preferred.

[0070] The method of degassing the inside of the melt kneader under reduced pressure and melt kneading may be, for example, to feed each component into the melt kneader, and then degass the inside of the melt kneader under reduced pressure and melt kneading. During melt kneading, degassing the inside of the melt kneader under reduced pressure may be performed intermittently or continuously. The method of degassing the inside of the melt kneader under reduced pressure can be carried out according to the equipment provided in each melt kneader, and may be carried out through a vacuum vent, for example. When degassing under reduced pressure, the inside of the melt kneader can be in a vacuum state of, for example, 0.1 kPa or more and 50 kPa or less.

[0071] The melt kneader may be a single-screw extruder, a multi-screw extruder, a kneader, a Banbury mixer, or the like, which is equipped with equipment capable of melt-kneading by injecting an inert gas into the inside of the melt kneader, or equipment capable of melt-kneading by degassing the inside of the melt kneader under reduced pressure.

[0072] The melt kneading temperature is preferably 300 to 380°C. When the melt kneading temperature is 300° C. or higher, the 3-methyl-1-butene polymer can be sufficiently melted, and additives can be easily dispersed. When the melt kneading temperature is 380° C. or lower, thermal decomposition of the 3-methyl-1-butene polymer and additives can be suppressed. From the viewpoint of thoroughly dispersing the additives throughout the 3-methyl-1-butene polymer, the melt kneading temperature is more preferably 300° C. or higher, and further preferably 310° C. or higher. From the viewpoint of suppressing significant decomposition of the raw materials, the melt kneading temperature is more preferably 380° C. or lower, and further preferably 360° C. or lower.

[0073] The melt-kneading time can be adjusted depending on the size of the kneading device. For example, it may be 1 to 15 minutes, but is not limited to the numerical range of the melt-kneading time. In the present embodiment, the "melt-kneading time" refers to the time during which the mixer rotates in a batch kneader, and refers to the residence time of the raw materials in the device in the case of a continuous extrusion kneader.

[0074] The mixer rotation speed during melt kneading may be 80 rpm or more or 100 rpm or more, and may be 300 ppm or less or 250 ppm or less. After the melt-kneading, the resin composition is removed from the melt-kneader and cooled.

[0075] [Process for obtaining the millimeter wave radome] In this embodiment, the process of obtaining a millimeter-wave radome is a process of forming a material to be used for the millimeter-wave radome to obtain the millimeter-wave radome. Methods for forming a millimeter-wave radome from the above-mentioned materials include, for example, injection molding, extrusion molding, pressure molding, and heat press molding. The shape of the millimeter-wave radome is not particularly limited as long as it can cover the antenna and other components of the radar, and it may have curved surfaces or corners, and any known shape may be adopted. The shape of the millimeter-wave radome may be, for example, a hemispherical or rectangular parallelepiped shape, may have the same thickness throughout the millimeter-wave radome, and may have a partition inside the millimeter-wave radome.

[0076] <Uses of millimeter wave radome> The millimeter-wave radome of this embodiment has a low relative dielectric constant and dielectric loss tangent, and is excellent in radio wave transparency and heat resistance, so that transmission loss is unlikely to occur even when used in the band of several tens of GHz. Therefore, the millimeter-wave radome of this embodiment can be used for short-distance wireless communication applications, vehicle-mounted radar applications for automobiles, mobile phones, PHS, smartphones, tablets (tablet computers), mobile computers (mobile PCs), personal digital assistants (PDAs), and the like. EXAMPLES

[0077] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0078] <Measurement and evaluation methods> Various physical properties were measured or evaluated by the following methods.

[0079] [Content of structural units derived from comonomers] The content ratio of structural units derived from α-olefins (comonomers) other than 3-methyl-1-butene in the copolymers (3-methyl-1-butene polymers) obtained in Production Examples 1 and 2 was determined by IR measurement using an FT-IR (manufactured by Ailent Technologies, device name "cary 600 series FTIR spectrometer") as an analytical device by the ATR method, as follows. Bending vibration originating from the main chain methylene group of 3-methyl-1-butene homopolymer: 1,461 cm -1 and the bending vibration of 727 cm originating from the side chain methylene group of the homopolymer of α-olefin. -1 A calibration curve was created from the ratio of the peak area of ​​the copolymer (A) obtained in Production Example 1 and the copolymer (B) obtained in Production Example 2, and the content of structural units derived from α-olefins other than 3-methyl-1-butene was calculated by inserting the measured values ​​into the calibration curve.

[0080] [Melting point] The copolymers or homopolymers (3-methyl-1-butene polymers) obtained in Production Examples 1 to 3 were heated from 30° C. to 320° C. at 10° C. / min under a nitrogen flow rate (100 mL / min) using a differential scanning calorimeter (TA Instruments, “DSC25”), held at 320° C. for 5 minutes, and then cooled to −70° C. at 10° C. / min. The peak temperature was measured when the temperature was raised to 320° C. at 10° C. / min after holding at −70° C. for 5 minutes, and the temperature was taken as the melting point.

[0081] [Melt Viscosity] The melt viscosity (Pa s) of the copolymers or homopolymers (3-methyl-1-butene polymers) obtained in Production Examples 1 to 3 was measured using a capillary rheometer ("Capillography 1C" manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a barrel temperature of 320°C and a shear rate of 1220 sec -1 The measurements were performed under the following conditions: (capillary: inner diameter 1.0 mm × length 10 mm, extrusion speed 10 mm / min).

[0082] [specific gravity] The resin compositions obtained in Examples 1 to 3 and the resins used in Comparative Examples 1 to 3 were press molded to prepare test pieces (length: 40 mm, width: 10 mm, thickness: 4 mm). The specific gravity of the test pieces was measured in accordance with JIS K 7112:1999, Method A.

[0083] [Water absorption rate] The resin compositions obtained in Examples 1 to 3 and the resins used in Comparative Examples 1 to 3 were press-molded to prepare test pieces (length: 60 mm, width: 60 mm, thickness: 1 mm). The test pieces were used to measure water absorption in accordance with JIS K 7209:2000, Method A.

[0084] [Deflection temperature under load] The resin compositions obtained in Examples 1 to 3 and the resins used in Comparative Examples 1 to 3 were injection molded under the conditions described in Examples 1 to 3 and Comparative Examples 1 to 3 below to prepare test pieces (length: 80 mm, width: 10 mm, thickness: 4 mm). The test pieces were used to perform a deflection temperature test under load using a load deflection temperature tester ("HDT Tester S3M" manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K 7191-1:2015 Method A under conditions of a load of 1.80 MPa and a heating rate of 120°C / h, and were evaluated according to the following criteria. ○: Heat deflection temperature is 250℃ or higher ×: Heat deflection temperature is less than 250℃

[0085] [Dielectric constant and dielectric loss tangent] The resin compositions obtained in Examples 1 to 3 and the resins used in Comparative Examples 1 to 3 were injection molded under the conditions described below in Examples 1 to 3 and Comparative Examples 1 to 3, respectively, to prepare test pieces (length: 30 mm, width: 30 mm, thickness: 1 mm). The above test pieces were used to measure the relative dielectric constant and the dielectric loss tangent at a measurement frequency of 100 GHz by a frequency change method using a millimeter wave module (WR10 67 GHz-115 GHz, manufactured by Virginia Diodes Inc.).

[0086] [Catalyst adjustment] Preparation of titanium catalyst components 47.6g (500mmol) of anhydrous magnesium chloride, 250mL of decane and 234mL (1.5mol) of 2-ethylhexyl alcohol were heated at 130℃ for 2 hours to obtain a homogeneous solution. The homogeneous solution obtained was cooled to room temperature (23℃) and then dropped into 2L (18mol) of titanium tetrachloride kept at -20℃ over 1 hour. After the dropwise addition, the temperature of the mixture was raised to 90℃ over 2 hours, and when it reached 90℃, 11.4mL (80mmol) of ethyl benzoate was added and kept at the same temperature for 2 hours while stirring. After the reaction for 2 hours was completed, the mixture was left to stand and the supernatant was removed. Decane and hexane were added to this, and the solid components were washed three times, then resuspended in 2L of titanium tetrachloride and heated again at 90℃ for 2 hours. After the reaction was completed, the mixture was left to stand again using decane and hexane, the supernatant was removed repeatedly, and the mixture was thoroughly washed until no free titanium compounds were detected in the washings. The resulting suspension was dried under reduced pressure at room temperature for 6 hours to obtain a titanium catalyst component. The composition of the obtained titanium catalyst component was 4.0 mass % titanium, 56.0 mass % chlorine, 17.0 mass % magnesium, 10.4 mass % ethyl benzoate, and 12.6 mass % of the hydrocarbon solvent consisting of decane and hexane.

[0087] [Production Example 1] Preparation of copolymer (A) In a 20L stainless steel autoclave, 8.0kg of 3-methyl-1-butene, 0.6kg of 1-decene, 50g of triethylaluminum diluted with hexane to a concentration of 1mol / L, and 4g of the titanium catalyst component prepared in the above [Preparation of catalyst] were added, and the polymerization reaction was carried out at 70°C for 4 hours. During the polymerization reaction, hydrogen was continuously fed at a rate of 40mL / min. After 4 hours, 200g of 3-methyl-1-butanol was injected to stop the reaction and expel excess unreacted monomers. Next, 2kg of normal heptane was introduced, and the mixture was stirred at 60°C for 30 minutes, after which the solids were filtered off with a pressure filter. This operation was repeated twice, and then the solvent was changed from 2kg of normal heptane to 3kg of 2-propanol, and the same operation was repeated twice. 7.7 kg of the obtained crude polymer was placed in a 50 L container equipped with a stirrer, and then 8 kg of 1 mol / L hydrochloric acid and 16 kg of 2-propanol were added and stirred for 1 hour. The suspension was filtered by vacuum filtration and washed with 10 kg of 2-propanol. The crude polymer was placed in a 50 L container equipped with a stirrer, and then 20 kg of 2-propanol was added and stirred for 1 hour. The suspension was filtered by vacuum filtration and washed with 10 kg of 2-propanol. The washed polymer obtained was dried under reduced pressure at 80 ° C for 2 days to obtain 3.2 kg of copolymer (A), which is a copolymer of 3-methyl-1-butene and 1-decene. The obtained copolymer (A) was subjected to the above-mentioned measurements, and the melting point was 286°C, the melt viscosity was 104 Pa s, and the content of structural units derived from the comonomer 1-decene in the copolymer (A) was 1.1 mol%.

[0088] [Production Example 2] Preparation of copolymer (B) The same operation as in Production Example 1 was carried out except that 0.6 kg of 1-decene was changed to 3.6 kg of 1-decene, thereby obtaining 2.8 kg of a copolymer (B) which is a copolymer of 3-methyl-1-butene and 1-decene. The obtained copolymer (B) was subjected to the above-mentioned measurements, and the melting point was 281°C, the melt viscosity was 99 Pa s, and the content of structural units derived from the comonomer 1-decene in the copolymer (B) was 6.4 mol%.

[0089] [Production Example 3] Preparation of homopolymer (C) The same operation as in Production Example 1 was carried out except that 0.6 kg of 1-decene was not added, to obtain 3.3 kg of homopolymer (C), which is a homopolymer of 3-methyl-1-butene. The homopolymer (C) thus obtained was subjected to the above-mentioned measurements, and it was found that the melting point was 305° C. and the melt viscosity was 126 Pa·s.

[0090] [Example 1] (1) Production of resin composition To 100 parts by mass of the copolymer (A) obtained in Production Example 1, 0.2 parts by mass of pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] ("AO-60", manufactured by ADEKA Corporation), 0.2 parts by mass of 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane ("PEP-36", manufactured by ADEKA Corporation), 0.1 parts by mass of 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate ("Sumilizer GS", manufactured by Sumitomo Chemical Co., Ltd.), 0.25 parts by mass of zinc stearate (antacid), glass fiber ("ECS 03 30 parts by mass of "T-480H" manufactured by Nippon Electric Glass Co., Ltd.) and 5 parts by mass of maleic anhydride modified polypropylene ("PMA H1000P" manufactured by Toyobo Co., Ltd.) were dry blended, and then melt-kneaded at a cylinder temperature of 320°C using a twin-screw kneading extruder "KZW15-45" (manufactured by Technovel Corporation) to obtain a pellet-shaped resin composition (M1).

[0091] (2) Manufacturing of millimeter wave radomes The obtained pellet-like resin composition (M1) was melt-kneaded under a nitrogen atmosphere at 40 rpm and a cylinder temperature of 310°C using a Sumitomo electric injection molding machine "SE18DU" (manufactured by SUMITOMO Heavy Industries, Ltd.), and injection-molded under conditions of an injection pressure of 45 MPa, a retention time in the mold of 33 seconds, and a mold temperature of 160°C, to obtain a millimeter-wave radome having a shape (length L: 80 mm, width W: 130 mm, height H: 40 mm, thickness T: 10 mm) shown in the schematic oblique view and schematic cross-sectional view in Figure 1. In Example 1, the results of evaluation according to the above-mentioned evaluation method are shown in Table 1.

[0092] [Example 2] A resin composition (M2) and a millimeter wave radome were produced in the same manner as in Example 1, except that the copolymer (B) obtained in Production Example 2 was used instead of the copolymer (A) in Example 1. In Example 2, the results of evaluation according to the above-mentioned evaluation method are shown in Table 1.

[0093] [Example 3] A resin composition (M3) and a millimeter wave radome were produced in the same manner as in Example 1, except that the homopolymer (C) obtained in Production Example 3 was used instead of the copolymer (A) in Example 1. In Example 3, the results of evaluation according to the above-mentioned evaluation method are shown in Table 1.

[0094] [Comparative Example 1] A millimeter wave radome was produced in the same manner as in Example 1, except that in Example 1, syndiotactic polystyrene (SPS) "XAREC (registered trademark) C132" (manufactured by Idemitsu Kosan Co., Ltd.) was used instead of the resin composition (M1), and the cylinder temperature during melt kneading and injection molding was changed to 280°C and the mold temperature was changed to 80°C. In Comparative Example 1, the results of evaluation according to the above-mentioned evaluation method are shown in Table 1.

[0095] [Comparative Example 2] A millimeter wave radome was produced in the same manner as in Example 1, except that polymethylpentene (TPX) "T730" (manufactured by Mitsui Fine Chemicals, Inc.) was used instead of the resin composition (M1) in Example 1, and the cylinder temperature during melt kneading and injection molding was changed to 260°C and the mold temperature was changed to 70°C. In Comparative Example 2, the results of evaluation performed according to the above-mentioned evaluation method are shown in Table 1.

[0096] [Comparative Example 3] A millimeter-wave radome was produced in the same manner as in Example 1, except that polybutylene terephthalate (PBT) "DURANEX (registered trademark) PBT 3300" (manufactured by Polyplastics Co., Ltd.) was used instead of the resin composition (M1) in Example 1, and the cylinder temperature during melt-kneading and injection molding was changed to 260°C, and the mold temperature was changed to 80°C. In Comparative Example 3, the results of evaluation according to the above-mentioned evaluation method are shown in Table 1.

[0097] [Table 1]

[0098] Examples 1 to 3 show low relative dielectric constant and dielectric loss tangent, and are excellent in radio wave transmission, and also have high deflection temperature under load, which indicates excellent heat resistance. On the other hand, Comparative Example 1 has high deflection temperature under load and is excellent in heat resistance, but has high dielectric loss tangent and is poor in radio wave transmission. Comparative Example 2 has low dielectric loss tangent and is excellent in radio wave transmission, but has low deflection temperature under load and is poor in heat resistance. Comparative Example 3 is poor in both heat resistance and radio wave transmission. As can be seen from Table 1, the millimeter-wave radome of this embodiment has a low relative dielectric constant and dielectric loss tangent, and is excellent in radio wave transmission and heat resistance. In particular, since it has excellent heat resistance, it can be made smaller. Furthermore, as can be seen from the evaluation of specific gravity and water absorption rate in Table 1, Examples 1 to 3 are lightweight and have low water absorption. Therefore, it is considered that the millimeter-wave radome of this embodiment is lightweight, is not affected by external factors such as rain, and can exhibit stable radio wave transmission. [Explanation of symbols]

[0099] L:Length W: Width H: Height T: Thickness

Claims

1. A millimeter-wave radome made of a material containing a 3-methyl-1-butene polymer.

2. The millimeter-wave radome according to Claim 1, wherein the 3-methyl-1-butene polymer is at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene and ethylene or an α-olefin, and the α-olefin has 3 to 20 carbon atoms.

3. The millimeter-wave radome according to Claim 2, wherein the content ratio of the structural unit derived from ethylene or the α-olefin in the copolymer is more than 0 mol% and 20 mol% or less.

4. The millimeter-wave radome according to any one of Claims 1 to 3, having a water absorption rate of less than 0.05%.

5. The millimeter-wave radome according to any one of Claims 1 to 3, having a dielectric loss tangent of less than 0.00100 at 10 GHz to 300 GHz.

6. The millimeter-wave radome according to any one of Claims 1 to 3, wherein the material is a resin composition containing the 3-methyl-1-butene polymer and an alkyl radical scavenger.

7. The millimeter-wave radome according to Claim 6, wherein the alkyl radical scavenger contains at least one selected from the group consisting of an acrylic phenol compound and a benzofuranone compound.

Images