Resin composition, pellets, molded body, electromagnetic wave absorber, and method for producing resin composition

Abstract

To provide a resin composition, a pellet, a molding, an electromagnetic wave absorber and a method for producing a resin composition, which have high electromagnetic wave absorption rates.SOLUTION: A resin composition contains, with respect to 100 pts.mass of a polyester resin having intrinsic viscosity of 0.87-2.00 dL / g, 0.1-10.0 pts.mass of a polyamide resin, and carbon nanotube.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a pellet, a molded article, an electromagnetic wave absorber, and a method for producing a resin composition. [Background technology]

[0002] Millimeter-wave radar emits millimeter-wave radio waves with wavelengths of 1 to 10 mm at frequencies between 30 and 300 GHz, particularly between 60 and 90 GHz, and detects the presence of obstacles as well as the distance and relative speed to the object by receiving the reflected waves that collide with the object. Millimeter-wave radar is being considered for use in a wide range of fields, including automobile collision prevention sensors, autonomous driving systems, road information systems, security systems, and medical and nursing care devices. Known resin compositions for such millimeter-wave radars are described in Patent Document 1. Patent Document 2 discloses a multifunctional resin composition that can be used for shielding electromagnetic interference or radio frequency interference. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-197048 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-155993 Summary of the Invention [Problem to be solved by the invention]

[0004] In millimeter-wave radar, the electromagnetic waves that pass through it are the biggest cause of malfunction, so there is a demand for resin compositions that have a high absorption rate of electromagnetic waves. The present invention aims to solve these problems and to provide a resin composition, pellets, molded body, electromagnetic wave absorber, and method for producing the resin composition, which have a high absorption rate of electromagnetic waves. [Means for solving the problem]

[0005] In light of the above-mentioned problems, the present inventors have conducted research and found that the electromagnetic wave absorption rate of a resin composition obtained by blending carbon nanotubes with a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g can be improved by blending a polyamide resin therewith. Specifically, the above problems were solved by the following means. <1> 0.1 to 10.0 parts by mass of a polyamide resin relative to 100 parts by mass of a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g; A resin composition comprising carbon nanotubes. <2> The carbon nanotubes are derived from carbon nanotubes masterbatched with a polyamide resin. <1> The resin composition according to claim 1. <3> The concentration of carbon nanotubes in the masterbatch is 1 to 50 mass%. <2> The resin composition according to claim 1. <4> The polyester resin includes a polybutylene terephthalate resin. <1> ~ <3> The resin composition according to any one of the above. <5> The polyamide resin includes an aliphatic polyamide resin. <1> ~ <4> The resin composition according to any one of the above. <6> The content of carbon nanotubes in the resin composition is 0.01 to 10% by mass. <1> ~ <5> The resin composition according to any one of the above. <7> When the resin composition is molded into a thickness of 2 mm, the absorption rate calculated according to formula (A) at a frequency of 76.5 GHz is 43.0 to 100%. <1> ~ <6> The resin composition according to any one of the above. Formula (A)

number

number

number

[0006] The present invention makes it possible to provide a resin composition, pellets, molded article, electromagnetic wave absorber, and a method for producing a resin composition, which have a high rate of electromagnetic wave absorption. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified. In this specification, the unit of return loss and transmission loss is "dB" (decibels). If the standards shown in this specification differ depending on the year and the measurement method, etc., they will be based on the standards as of January 1, 2021, unless otherwise stated.

[0008] The resin composition of this embodiment is characterized by containing 100 parts by mass of a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g (hereinafter sometimes referred to as "specific polyester resin"), 0.1 to 10.0 parts by mass of a polyamide resin, and carbon nanotubes. This configuration makes it possible to increase the electromagnetic wave absorption rate of a molded article formed from the resin composition. In particular, by masterbatching carbon nanotubes with a polyamide resin and blending the masterbatched carbon nanotubes with a specific polyester resin, a molded article with high electromagnetic wave absorption can be obtained. The reason for this is presumed to be as follows. Specifically, when carbon nanotubes masterbatched with a polyamide resin are blended with a polyester resin, the polyamide resin has many polar groups, which strongly interacts with the carbon nanotubes, making them difficult to disperse. Poor dispersibility of the carbon nanotubes leads to poor electromagnetic wave absorption. In this embodiment, by using a polyester resin with an intrinsic viscosity of 0.87 to 2.00 dL / g, the polyamide resin is strongly blended during melt blending, resulting in the polyamide resin containing aggregates of carbon nanotubes being finely dispersed in the polyester resin, presumably improving the dispersibility of the carbon nanotubes.

[0009] <Polyester resin with intrinsic viscosity of 0.87 to 2.00 dL / g> The resin composition of this embodiment contains a polyester resin (specific polyester resin) having an intrinsic viscosity of 0.87 to 2.00 dL / g. By containing such a specific polyester resin, when a resin composition containing a polyamide resin and carbon nanotubes, particularly carbon nanotubes masterbatched with a polyamide resin, is used, the carbon nanotubes can be effectively dispersed in the specific polyester resin.

[0010] The intrinsic viscosity of the specific polyester resin is 0.87 dL / g or more, preferably 0.90 dL / g or more, more preferably 0.95 dL / g or more, even more preferably 0.98 dL / g or more, even more preferably 1.00 dL / g or more, and even more preferably 1.05 dL / g or more. By making the intrinsic viscosity equal to or greater than the lower limit, the electromagnetic wave absorption property tends to be improved. The intrinsic viscosity is 2.00 dL / g or less, preferably 1.80 dL / g or less, more preferably 1.50 dL / g or less, even more preferably 1.40 dL / g or less, still more preferably 1.30 dL / g or less, and even more preferably 1.26 dL / g or less. By making the intrinsic viscosity 2.00 dL / g or less, the fluidity of the resin composition is further improved, and moldability tends to be improved. The intrinsic viscosity of the specific polyester resin is a value measured at 30° C. in a mixed solvent of tetrachloroethane and phenol in a 1:1 (mass ratio). When the resin composition of the present embodiment contains two or more polyester resins, the intrinsic viscosity is the intrinsic viscosity of the mixture.

[0011] As the specific polyester resin used in this embodiment, any known thermoplastic polyester resin can be used as long as it satisfies the above-mentioned intrinsic viscosity. Polyethylene terephthalate resin and polybutylene terephthalate resin are preferred, and it is more preferred that the specific polyester resin contains at least polybutylene terephthalate resin. The polybutylene terephthalate resin used in the resin composition of this embodiment is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded, and includes not only polybutylene terephthalate resin (homopolymer), but also polybutylene terephthalate copolymers containing other copolymerization components other than terephthalic acid units and 1,4-butanediol units, and mixtures of homopolymers and polybutylene terephthalate copolymers.

[0012] The polybutylene terephthalate resin may contain one or more dicarboxylic acid units other than terephthalic acid. Specific examples of other dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'-carboxyphenyl)methane, anthracenedicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 4,4'-dicyclohexyldicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dimer acid. In the polybutylene terephthalate resin used in this embodiment, terephthalic acid units preferably account for 80 mol% or more of all dicarboxylic acid units, more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 97 mol% or more, and even more preferably 99 mol% or more.

[0013] The diol unit may contain one or more other diol units in addition to 1,4-butanediol. Specific examples of other diol units include aliphatic or alicyclic diols having 2 to 20 carbon atoms, bisphenol derivatives, etc. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethanol, 4,4'-dicyclohexylhydroxymethane, 4,4'-dicyclohexylhydroxypropane, and ethylene oxide adduct diol of bisphenol A. In addition to the above-mentioned bifunctional monomers, small amounts of trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane can also be used in combination to introduce a branched structure, or monofunctional compounds such as fatty acids to adjust the molecular weight. In the polybutylene terephthalate resin used in the present embodiment, 1,4-butanediol units preferably account for 80 mol% or more of all diol units, more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 97 mol% or more, and even more preferably 99 mol% or more.

[0014] As described above, the polybutylene terephthalate resin is preferably a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. Alternatively, the polybutylene terephthalate copolymer may contain, as the carboxylic acid unit, one or more dicarboxylic acids other than the above-mentioned terephthalic acid and / or, as the diol unit, one or more diols other than the above-mentioned 1,4-butanediol. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers include polyester ether resins copolymerized with polyalkylene glycols, particularly polytetramethylene glycol, dimer acid-copolymerized polybutylene terephthalate resins, and isophthalic acid-copolymerized polybutylene terephthalate resins. Among these, polyester ether resins copolymerized with polytetramethylene glycol are preferred. These copolymers refer to those in which the copolymerization amount is 1 mol% or more and less than 50 mol% of all segments of the polybutylene terephthalate resin. In particular, the copolymerization amount is preferably 2 mol% or more and less than 50 mol%, more preferably 3 to 40 mol%, and even more preferably 5 to 20 mol%. By setting the copolymerization amount in this range, fluidity and toughness tend to be easily improved, which is preferable.

[0015] The amount of terminal carboxyl groups in the polybutylene terephthalate resin may be appropriately selected and determined, but is typically 60 eq / ton or less, preferably 50 eq / ton or less, and more preferably 30 eq / ton or less. By setting the amount below the upper limit, alkali resistance and hydrolysis resistance tend to be improved. The lower limit of the amount of terminal carboxyl groups is not particularly specified, but is typically 10 eq / ton or more, taking into account the productivity of polybutylene terephthalate resin production.

[0016] The amount of terminal carboxyl groups in the polybutylene terephthalate resin is determined by dissolving 0.5 g of the polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating the solution with a 0.01 mol / L benzyl alcohol solution of sodium hydroxide. The amount of terminal carboxyl groups can be adjusted by any conventional method, such as adjusting the polymerization conditions, such as the raw material charge ratio, polymerization temperature, and pressure reduction, or by reacting a terminal blocking agent.

[0017] In this embodiment, the specific polyester resin may be a linear polymer or a branched polymer having a branched structure. In this embodiment, the specific polyester resin preferably has a small branched structure. For example, the specific polyester resin used in this embodiment preferably has a degree of branching (DB) of less than 10%, more preferably 5% or less, and even more preferably 3% or less. Here, the degree of branching is defined as DB(%) = 100 × (T + Z) / (T + Z + L), where T is the average number of terminally bonded monomer units, Z is the average number of branched monomer units, and L is the average number of linearly bonded monomer units (within the macromolecules of each substance).

[0018] Polybutylene terephthalate resin can be produced by batch or continuous melt polymerization of a dicarboxylic acid component containing terephthalic acid as the main component or an ester derivative thereof with a diol component containing 1,4-butanediol as the main component. Furthermore, after producing a low-molecular-weight polybutylene terephthalate resin by melt polymerization, the degree of polymerization (or molecular weight) can be increased to a desired value by further solid-state polymerization under a nitrogen gas flow or reduced pressure. The polybutylene terephthalate resin is preferably one obtained by a production method in which a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol are subjected to continuous melt polycondensation.

[0019] The catalyst used in carrying out the esterification reaction may be a conventionally known catalyst, such as a titanium compound, a tin compound, a magnesium compound, or a calcium compound. Among these, titanium compounds are particularly preferred. Specific examples of titanium compounds used as esterification catalysts include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[0020] In addition to the above, the specific polyester resin may be found in paragraphs 0013 to 0016 of JP-A No. 2010-174223, the contents of which are incorporated herein by reference.

[0021] The content of the specific polyester resin in the resin composition of this embodiment is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, when the total amount of the resin composition is 100% by mass. When the resin composition does not contain a reinforcing material, it is even more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. By making the content equal to or greater than the lower limit, the mechanical strength of the resin composition tends to be improved. Furthermore, the upper limit of the content of the specific polyester resin is preferably 99% by mass or less, when the total amount of the resin composition is 100% by mass. By making the content equal to or less than the upper limit, the stability of the resin during processing tends to be further improved.

[0022] Furthermore, the content of the specific polyester resin in the resin composition of this embodiment is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, when the total amount of resin components contained in the resin composition is 100% by mass. By making the content equal to or greater than the lower limit, the effect of suppressing the water absorption of the resin tends to be further improved. Furthermore, the upper limit of the content of the specific polyester resin is preferably such that, when the total amount of resin components contained in the resin composition is 100% by mass, all components other than the polyamide resin are the specific polyester resin. By making the content equal to or less than the upper limit, the electromagnetic wave absorption rate of the resulting molded product tends to be further improved. The resin composition of the present embodiment may contain only one type of specific polyester resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0023] <Polyamide resin> The resin composition of this embodiment contains 0.1 to 10.0 parts by mass of a polyamide resin relative to 100 parts by mass of a specific polyester resin. By blending the polyamide resin with the specific polyester resin and melt-kneading them, the dispersibility of the polyamide resin can be improved compared to when the intrinsic viscosity of the polyester resin is low, and the dispersibility of the carbon nanotubes can also be improved. The polyamide resin is a polymer having, as a constituent unit, an acid amide obtained by ring-opening polymerization of lactam, polycondensation of aminocarboxylic acid, or polycondensation of diamine and dibasic acid, and may be an aliphatic polyamide resin or a semi-aromatic polyamide resin, with an aliphatic polyamide resin being preferred. Specific examples include polyamide 6, 11, 12, 46, 66, 666, 610, 612, 6I, 6 / 66, 6T / 6I, 6 / 6T, 66 / 6T, 66 / 6T / 6I, 9T, 10T, polyamide resin (MXD6) synthesized from metaxylylenediamine and adipic acid, polyamide resin (MP10) synthesized from metaxylylenediamine, paraxylylenediamine, and sebacic acid, polyamide resin (MXD610) synthesized from metaxylylenediamine, adipic acid, and sebacic acid, polyamide resin (MXD10) synthesized from metaxylylenediamine and sebacic acid, polytrimethylhexamethylene terephthalamide, polybis(4-aminocyclohexyl)methanedodecamide, polybis(3-methyl-4-aminocyclohexyl)methanedodecamide, and polyundecamethylenehexahydroterephthalamide. The above "I" represents an isophthalic acid component, and "T" represents a terephthalic acid component. Regarding polyamide resins, the disclosure of paragraphs 0011 to 0013 of JP 2011-132550 A can be referred to, the contents of which are incorporated herein by reference.

[0024] In this embodiment, as described above, the polyamide resin is preferably an aliphatic polyamide resin, more preferably polyamide 6, 11, 12, 46, 66, 666, 610, 612, even more preferably polyamide 6, 66, 666, and most preferably polyamide 6. The polyamide 6 herein is a ring-opening polymer of caprolactam, but is intended to include those containing units derived from monomers other than caprolactam (dicarboxylic acid units, diamine units, aminocarboxylic acid units) and terminal groups, etc., within the scope of the present invention. The polyamide 6 used in this embodiment preferably contains 99% by mass or more of units derived from caprolactam, excluding terminal groups. The same applies to other polyamide resins such as polyamide 66.

[0025] The content of the polyamide resin in the resin composition of this embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more, per 100 parts by mass of the specific polyester resin. The upper limit of the content of the polyamide resin is 10.0 parts by mass or less, preferably 9.5 parts by mass or less, more preferably 8.5 parts by mass or less, even more preferably 6.5 parts by mass or less, even more preferably 6.2 parts by mass or less, and even more preferably 5.0 parts by mass or less, per 100 parts by mass of the specific polyester resin. By keeping the content below the upper limit, the effect of suppressing the moisture absorption of the resin composition tends to be further improved. The resin composition of the present embodiment may contain only one type of polyamide resin, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0026] <Carbon nanotubes> The resin composition of the present embodiment contains carbon nanotubes. By containing carbon nanotubes, a resin composition or molded article having a high electromagnetic wave absorption rate can be obtained. The carbon nanotubes used in this embodiment are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, and preferably contain at least multi-walled carbon nanotubes. Carbon materials partially having a carbon nanotube structure can also be used. The carbon nanotubes are not limited to a cylindrical shape, and may have a coiled shape with a spiral at a pitch of 1 μm or less. Carbon nanotubes are commercially available, and examples thereof include carbon nanotubes available from Bayer MaterialScience, Nanosil, Showa Denko K.K., and Hyperion Catalysis International, Inc. In addition to the name carbon nanotubes, they are also sometimes called graphite fibrils, carbon fibrils, etc. The diameter (number average fiber diameter) of the carbon nanotubes is preferably 0.5 to 100 nm, more preferably 1 to 30 nm. From the viewpoint of imparting good electromagnetic wave absorption properties, the aspect ratio of the carbon nanotubes is preferably 5 or more, more preferably 50 or more. There is no particular upper limit, but it is, for example, 500 or less.

[0027] In this embodiment, the carbon nanotubes are preferably derived from carbon nanotubes masterbatched with a polyamide resin, which tends to further improve the electromagnetic wave absorption properties of the resulting resin composition or molded article. As described above, the carbon nanotubes may be blended as a masterbatch, in which case the concentration of the carbon nanotubes in the masterbatch is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less. By adjusting the concentration within the above range to the upper limit or less and the lower limit or more, the dispersibility of the carbon nanotubes in the specific polyester resin tends to be further improved.

[0028] The content of carbon nanotubes in the resin composition of this embodiment is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and may be 0.2% by mass or more, or even 0.4% by mass or more. By making the content equal to or greater than the lower limit, electromagnetic wave absorption properties are effectively exhibited. Furthermore, the content of carbon nanotubes in the resin composition of this embodiment is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, even more preferably 4% by mass or less, even more preferably 3% by mass or less, may be 2% by mass or less, or even 1% by mass or less. By making the content equal to or less than the upper limit, the fluidity of the resin tends to be further improved.

[0029] The resin composition of this embodiment preferably contains 0.1 parts by mass or more of carbon nanotubes per 100 parts by mass of the specific polyester resin. By setting the content at or above the lower limit, electromagnetic wave absorption properties are effectively exhibited. The resin composition of this embodiment preferably contains 10.0 parts by mass or less of carbon nanotubes per 100 parts by mass of the specific polyester resin, more preferably 8.0 parts by mass or less, even more preferably 6.0 parts by mass or less, even more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and even 2.5 parts by mass or less, particularly 1.5 parts by mass or less. Setting the content at or below the upper limit tends to further improve the fluidity of the resin. The resin composition of the present embodiment may contain only one type of carbon nanotube, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0030] <Other ingredients> The resin composition of this embodiment may contain other components in addition to those described above, as necessary, as long as the desired physical properties are not significantly impaired. Examples of other components include thermoplastic resins other than the specific polyester resin and polyamide resin, reinforcing materials, various resin additives, etc. Note that one type of other component may be contained, or two or more types may be contained in any combination and ratio.

[0031] Preferred examples of the other thermoplastic resins include polycarbonate resins; polystyrene resins; polyolefin resins such as polyethylene resins, polypropylene resins, and cyclic cycloolefin resins; polyacetal resins; polyimide resins; polyetherimide resins; polyurethane resins; polyphenylene ether resins; polyphenylene sulfide resins; polysulfone resins; and polymethacrylate resins.

[0032] Examples of various resin additives include stabilizers, mold release agents, flame retardants, reactive compounds, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, etc. The resin composition of the present embodiment preferably contains at least one of stabilizers and mold release agents. The resin composition of this embodiment is prepared so that the total of the specific polyester resin, polyamide resin, carbon nanotubes, and other optional components is 100% by mass. In one example of the resin composition of this embodiment, the total of the specific polyester resin, polyamide resin, and reinforcing material (preferably glass fiber) accounts for 95% by mass or more of the resin composition. In another example of the resin composition of this embodiment, the total of the specific polyester resin, polyamide resin, carbon nanotubes, stabilizer, and release agent accounts for 99% by mass or more of the resin composition. In yet another example of the resin composition of this embodiment, the total of the specific polyester resin, polyamide resin, carbon nanotubes, reinforcing material (preferably glass fiber), stabilizer, and release agent accounts for 99% by mass or more of the resin composition.

[0033] <<Stabilizer>> The resin composition of this embodiment may contain a stabilizer. Examples of stabilizers include hindered phenol compounds, hindered amine compounds, phosphorus compounds, and sulfur-based stabilizers. Among these, hindered phenol compounds are preferred. It is also preferred to use a hindered phenol compound and a phosphorus compound in combination. As the stabilizer, specifically, the descriptions in paragraphs 0046 to 0057 of JP 2018-070722 A, the descriptions in paragraphs 0030 to 0037 of JP 2019-056035 A, and the descriptions in paragraphs 0066 to 0078 of WO 2017 / 038949 A can be referred to, the contents of which are incorporated herein by reference.

[0034] The resin composition of this embodiment preferably contains 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more of the stabilizer relative to 100 parts by mass of the specific polyester resin. The upper limit of the amount of the stabilizer is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the specific polyester resin. The resin composition of the present embodiment may contain only one stabilizer, or may contain two or more stabilizers. When two or more stabilizers are contained, the total amount is preferably in the above range.

[0035] <<Release Agent>> The resin composition of the present embodiment preferably contains a release agent. As the release agent, a wide variety of known release agents can be used, and preferred are esters of aliphatic carboxylic acids, paraffin wax, polystyrene wax, and polyolefin wax, with polyethylene wax being more preferred. For details of the release agent, please refer to the descriptions in paragraphs 0115 to 0120 of JP-A No. 2013-007058, paragraphs 0063 to 0077 of JP-A No. 2018-070722, and paragraphs 0090 to 0098 of JP-A No. 2019-123809, the contents of which are incorporated herein by reference.

[0036] The resin composition of this embodiment preferably contains 0.01 parts by mass or more of the release agent relative to 100 parts by mass of the specific polyester resin, more preferably 0.08 parts by mass or more, and even more preferably 0.2 parts by mass or more. The upper limit of the amount of the release agent contained relative to 100 parts by mass of the specific polyester resin is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and even more preferably 0.8 parts by mass or less. The resin composition may contain only one type of release agent, or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0037] <<Reinforcement material>> The resin composition of the present embodiment may or may not contain a reinforcing material. By containing a reinforcing material, the mechanical strength of the resulting molded article can be improved. The reinforcing material that can be used in this embodiment is not particularly limited in terms of type, and may be any of fibers, fillers, beads, etc., with fibers being preferred.

[0038] When the reinforcing material is a fiber, it may be a short fiber or a long fiber. When the reinforcing material is short fibers, fillers, beads, or the like, the resin composition of this embodiment may be in the form of pellets, powdered pellets, or a film formed from the pellets. When the reinforcing material is a long fiber, examples of the reinforcing material include so-called long fiber for unidirectional (UD) materials, sheet-like long fiber such as woven fabric and knitted fabric, etc. When using these long fibers, the components other than the reinforcing material of the resin composition of the present embodiment can be impregnated into the sheet-like long fiber reinforcing material to form a sheet-like resin composition (for example, a prepreg).

[0039] The raw materials for the reinforcing material include inorganic materials such as glass, carbon (carbon fiber, etc.), alumina, boron, ceramics, and metals (steel, etc.), and organic materials such as plants (including kenaf, bamboo, etc.), aramid, polyoxymethylene, aromatic polyamide, polyparaphenylene benzobisoxazole, and ultra-high molecular weight polyethylene, with glass being preferred.

[0040] The resin composition of the present embodiment preferably contains glass fibers as a reinforcing material. The glass fiber is selected from glass compositions such as A-glass, C-glass, E-glass, R-glass, D-glass, M-glass, and S-glass, with E-glass (alkali-free glass) being particularly preferred. Glass fiber refers to a fibrous material whose cross section, cut perpendicular to the longitudinal direction, is circular or polygonal. The number-average fiber diameter of the single fiber of the glass fiber is usually 1 to 25 μm, preferably 5 to 17 μm. By making the number-average fiber diameter 1 μm or more, the molding processability of the resin composition tends to be further improved. By making the number-average fiber diameter 25 μm or less, the appearance of the obtained molded article tends to be improved, and the reinforcing effect also tends to be improved. The glass fiber may be a single fiber or a plurality of single fibers twisted together. The glass fiber may be in the form of a glass roving obtained by continuously winding a single fiber or a plurality of twisted fibers, a chopped strand cut to a length of 1 to 10 mm (i.e., glass fiber having a number average fiber length of 1 to 10 mm), or a milled fiber pulverized to a length of about 10 to 500 μm (i.e., glass fiber having a number average fiber length of 10 to 500 μm), but chopped strand cut to a length of 1 to 10 mm is preferred. Glass fibers of different forms can also be used in combination. Glass fibers having an irregular cross-sectional shape are also preferred. The irregular cross-sectional shape has an oblateness, which is the ratio of the major axis to the minor axis of the cross section perpendicular to the longitudinal direction of the fiber, of, for example, 1.5 to 10, preferably 2.5 to 10, more preferably 2.5 to 8, and even more preferably 2.5 to 5.

[0041] The glass fiber may be surface-treated with, for example, a silane-based compound, an epoxy-based compound, a urethane-based compound, or the like, or may be oxidized, in order to improve its affinity with the resin component, as long as the properties of the resin composition of this embodiment are not significantly impaired.

[0042] When the resin composition of this embodiment contains a reinforcing material (preferably glass fiber), the content thereof is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, relative to 100 parts by mass of the specific polyester resin. By setting the content at or above the lower limit, the mechanical strength of the obtained molded article tends to be further increased. Furthermore, the content of the reinforcing material (preferably glass fiber) is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less, relative to 100 parts by mass of the specific polyester resin. By setting the content at or below the upper limit, the appearance of the molded article tends to be improved, and the flowability of the resin composition tends to be further improved.

[0043] The content of the reinforcing material (preferably glass fiber) in the resin composition of this embodiment is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more in the resin composition. The content of the reinforcing material (preferably glass fiber) in the resin composition is more preferably 50% by mass or less, even more preferably 45% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less. By setting the content at or above the lower limit, mechanical strength tends to be further increased. By setting the content at or below the upper limit, the appearance of the molded article tends to be improved, and the fluidity of the resin composition when melted tends to be further improved. The resin composition of the present embodiment may contain only one type of reinforcing material (preferably glass fiber), or may contain two or more types. When two or more types are contained, the total amount is preferably in the above range.

[0044] <Physical properties of resin composition> The resin composition of this embodiment preferably has a high absorption rate of electromagnetic waves. Specifically, the resin composition of this embodiment preferably has an absorption rate of 43.0 to 100% at a frequency of 76.5 GHz calculated according to formula (A) when molded into a 2 mm thickness (preferably, 100 mm × 100 mm × 2 mm thickness). Formula (A)

number

[0045] The absorbency is preferably 45.0% or more, more preferably 47.0% or more, even more preferably 49.0% or more, and even more preferably 50.0% or more. The upper limit is ideally 100%, but even if it is 90.0% or less, the required performance is sufficiently met.

[0046] The resin composition of this embodiment preferably has low reflectance of electromagnetic waves. Specifically, the resin composition of this embodiment preferably has a reflectance of 40.0% or less at a frequency of 76.5 GHz, as calculated according to formula (B), when molded to a thickness of 2 mm (preferably, 100 mm x 100 mm x 2 mm). Formula (B)

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[0047] The reflectance is preferably 35.0% or less, more preferably 30.0% or less, even more preferably 26.0% or less, even more preferably 22.0% or less, and even more preferably 18.5% or less. The lower limit is ideally 0%, but even if it is 1.0% or more, or even 5.0% or more, the required performance is sufficiently met.

[0048] The resin composition of the present embodiment preferably has low transmittance. The resin composition of this embodiment preferably has a transmittance of less than 43.0% at a frequency of 76.5 GHz as determined according to formula (C) when molded into a 2 mm thickness (preferably 100 mm x 100 mm x 2 mm thickness). Formula (C)

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[0049] The transmittance is preferably 42.0% or less, and more preferably 40.0% or less. The lower limit is ideally 0%, but even if it is 5.0% or more, the required performance is sufficiently met.

[0050] The resin composition of the present embodiment preferably satisfies all of the absorptance calculated according to the above formula (A), the reflectance calculated according to the above formula (B), and the transmittance calculated according to the above formula (C).

[0051] The resin composition of the present embodiment also has a surface resistance of 1.0×10 when molded into a thickness of 2 mm (preferably, 100 mm×100 mm×2 mm) according to IEC 60093. 8 Ω or more is preferable, and 1.0×10 9 Ω or more is more preferable, and 1.0×10 10 It is more preferable that the resistance is 1.0×10 Ω or more. 11 Ω or more is more preferable, and 1.0×10 12Ω or more is more preferable, and 1.0×10 13 It is even more preferable that the resistance is 1.0×10 Ω or more. 14 It is particularly preferable that the resistance is 1.0×10 Ω or more. 16 Ω or less is preferable, and 1.0×10 15 It is more preferable that the hardness is Ω or less. By setting the hardness in this range, the electromagnetic wave absorption rate of the obtained molded article tends to be higher. The surface resistance is a value obtained by measuring the surface resistance (unit: Ω) in accordance with IEC60093 using a test piece of 100 mm×100 mm×2 mm thick formed from the resin composition.

[0052] The resin composition of this embodiment has a relative dielectric constant at a frequency of 76.5 GHz of 4.00 or more, preferably 4.20 or more, more preferably 4.45 or more, even more preferably 4.60 or more, even more preferably 4.70 or more, and even more preferably 5.10 or more. By setting the relative dielectric constant at or above the lower limit, the electromagnetic wave absorption rate of the obtained molded article tends to be higher. Furthermore, the upper limit of the relative dielectric constant is preferably 8.00 or less, more preferably 6.00 or less, even more preferably 5.50 or less, even more preferably 5.30 or less, and even more preferably 5.20 or less. By setting the relative dielectric constant at or below the upper limit, the electromagnetic wave reflectivity of the obtained molded article tends to be lower. The resin composition of this embodiment preferably has a dielectric loss tangent of 0.05 or more, more preferably 0.10 or more, at a frequency of 76.5 GHz. By making the dielectric loss tangent equal to or greater than the lower limit, the electromagnetic wave absorption rate of the resulting molded article tends to be higher. The lower limit of the dielectric loss tangent is not particularly limited, but may be, for example, 0.50 or less, or even 0.40 or less.

[0053] <Method of manufacturing resin composition> The resin composition of this embodiment can be produced by a conventional method for producing a resin composition containing a thermoplastic resin. For example, it can be obtained by melt-kneading a specific polyester resin, a polyamide resin, and carbon nanotubes (preferably carbon nanotubes masterbatched with polyamide resin). More specifically, it is produced by feeding the specific polyester resin, the carbon nanotubes masterbatched with polyamide resin, and other components (glass fibers, etc.) that are blended as needed into an extruder and melt-kneading them. One form formed from such a resin composition is pellets. The components may be mixed in advance and fed all at once to the extruder, or the components may be mixed in advance without mixing, or only a portion of the components may be mixed in advance, and then fed to the extruder using a feeder. The extruder may be a single-screw extruder or a twin-screw extruder. When a reinforcing material such as glass fiber is compounded, it is preferable to feed it from a side feeder midway through the cylinder of the extruder. The heating temperature during melt-kneading can usually be appropriately selected from the range of 170 to 350°C.

[0054] <Method of manufacturing molded body> A molded article, particularly an electromagnetic wave absorber, is formed from the resin composition of this embodiment. The method for producing the molded article in this embodiment is not particularly limited, and any molding method generally used for resin compositions containing thermoplastic resins can be used. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, gas-assisted hollow molding, molding using a heat-insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding), extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, blow molding, etc., and among these, injection molding is preferred.

[0055] <Application> The electromagnetic wave absorber of this embodiment is formed from the resin composition of this embodiment. That is, the resin composition of this embodiment is preferably used for an electromagnetic wave absorber (also referred to as an electromagnetic wave absorbing member), more preferably for an electromagnetic wave absorber having a frequency of at least 60 to 90 GHz, and even more preferably for an electromagnetic wave absorber having a frequency of at least 70 to 80 GHz. Such an electromagnetic wave absorber is preferably used for radar applications. Specifically, it is used for housings, covers, etc. for millimeter-wave radar. The electromagnetic wave absorber of this embodiment can be suitably used for in-vehicle millimeter-wave radars used in automatic brake control devices, inter-vehicle distance control devices, pedestrian accident reduction steering devices, erroneous transmission suppression control devices, devices for suppressing acceleration when pedal misapplication occurs, devices for warning of approaching vehicles, lane keeping assist devices, rear-end collision prevention warning devices, parking assist devices, devices for warning of obstacles around the vehicle, etc.; railway and aviation millimeter-wave radars used in platform monitoring / railroad crossing obstacle detection devices, in-train content transmission devices, tram / railroad collision prevention devices, foreign object detection devices in runways, etc.; millimeter-wave radars for transportation infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radars for various security devices; millimeter-wave radars for medical and nursing care such as systems for watching over children and the elderly; millimeter-wave radars for transmitting various information content; etc. [Example]

[0056] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be performed using other instruments with equivalent performance.

[0057] raw material The following raw materials were used: In Table 1 below, PBT stands for polybutylene terephthalate resin, and CNT stands for carbon nanotubes (the same applies to Table 2).

[0058] [Table 1]

[0059] Example 1, Comparative Example 1 <Production of Resin Composition (Pellets)> As shown in Table 2, the components listed in Table 1 were placed in a stainless steel tumbler and mixed under stirring for 1 hour. The resulting mixture was fed into an intermeshing co-rotating twin-screw extruder ("TEX-30α" manufactured by The Japan Steel Works, Ltd., screw diameter 32 mm, L / D = 42) through the main feed port. The barrel temperature of the first kneading section was set to 250°C, and the mixture was melt-kneaded at a discharge rate of 40 kg / h and a screw rotation speed of 200 rpm. The mixture was then extruded as a strand using a four-hole nozzle (circular (φ4 mm), length 1.5 cm). The extruded strand was introduced into a water bath for cooling, then inserted into a pelletizer and cut to obtain a resin composition (pellets).

[0060] <76.5GHz electromagnetic wave absorption rate, reflectance, transmittance> The pellets obtained above were injection molded in an injection molding machine ("NEX80" manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder temperature of 260°C and a mold temperature of 80°C to obtain test pieces measuring 100 mm x 100 mm x 2 mm thick. Using the test pieces obtained, the absorptance calculated according to formula (A), the reflectance calculated according to formula (B), and the transmittance calculated according to formula (C) at a frequency of 76.5 GHz were measured as follows. For the measurements, a Keysight network analyzer "N5252A" was used. The measurement was performed by placing the test piece so that the TD (transverse direction) direction of the injection molded article was parallel to the direction of the electric field. Formula (A)

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[0061] Formula (B)

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[0062] Formula (C)

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[0063] <Relative permittivity and dielectric loss tangent> The pellets obtained above were injection molded in an injection molding machine (NEX80 manufactured by Nissei Plastic Industrial Co., Ltd.) at a cylinder temperature of 260°C and a mold temperature of 80°C to obtain test pieces measuring 100 mm x 100 mm x 2 mm thick. The dielectric constant and dielectric loss tangent at a frequency of 76.5 GHz were determined using the obtained test specimen. The test specimen was placed so that the TD (transverse direction) direction of the injection-molded article was parallel to the electric field direction. The measurements were performed using a Keysight network analyzer "N5252A," and the values ​​of the relative permittivity and dielectric loss tangent were estimated using Keysight's "N1500A Materials Measurement Suite," with each value calculated using the "NIST Precision" calculation model.

[0064] [Table 2]

[0065] In Table 2 above, the CNT content indicates the content of carbon nanotubes in the resin composition. As is clear from the above results, the resin composition of the present invention had a high electromagnetic wave absorption rate, and further had low electromagnetic wave transmittance and reflectance.

Claims

1. 0.1 to 10.0 parts by mass of a polyamide resin relative to 100 parts by mass of a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g; and carbon nanotubes, the polyester resin comprises a polybutylene terephthalate resin, the content of carbon nanotubes in the resin composition is 0.01 to 10% by mass, A resin composition, wherein the polyamide resin comprises at least one of polyamide 6, polyamide 66, and polyamide 6 / 66.

2. The resin composition according to claim 1 , wherein the carbon nanotubes are derived from carbon nanotubes masterbatched with a polyamide resin.

3. The resin composition according to claim 2, wherein the concentration of the carbon nanotubes in the masterbatch is 1 to 50 mass %.

4. The resin composition according to any one of claims 1 to 3, wherein the absorption rate calculated according to formula (A) at a frequency of 76.5 GHz when the resin composition is molded to a thickness of 2 mm is 43.0 to 100%. Formula (A) [Equation 1] (In the above formula (A), R represents the return loss measured by the free space method, and T represents the transmission loss measured by the free space method.)

5. The resin composition according to any one of claims 1 to 4, wherein the reflectance calculated according to formula (B) at a frequency of 76.5 GHz when the resin composition is molded to a thickness of 2 mm is 40.0% or less. Formula (B) [Equation 2] (In the above formula (B), R represents the return loss measured by the free space method.)

6. The resin composition according to any one of claims 1 to 5, wherein the transmittance calculated according to formula (C) at a frequency of 76.5 GHz when molded to a thickness of 2 mm is less than 43.0%. Formula (C) [Equation 3] (In the above formula (C), T represents the transmission attenuation measured by the free space method.)

7. The resin composition according to any one of claims 1 to 6, which is used for an electromagnetic wave absorber.

8. A pellet formed from the resin composition according to any one of claims 1 to 6.

9. A molded article formed from the resin composition according to any one of claims 1 to 6.

10. An electromagnetic wave absorber formed from the resin composition according to any one of claims 1 to 6.

11. A method for producing the resin composition according to any one of claims 1 to 7, comprising melt-kneading a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g and carbon nanotubes masterbatched with a polyamide resin, the polyester resin comprises a polybutylene terephthalate resin, the content of carbon nanotubes in the resin composition is 0.01 to 10% by mass, The method for producing a resin composition, wherein the polyamide resin comprises at least one of polyamide 6, polyamide 66, and polyamide 66 / 6.

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