JP2023089873A - Resin composition, pellet, molding, electromagnetic wave absorber, and method for producing resin composition - Google Patents

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 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.

Millimeter-wave radar emits radio waves in the millimeter-wave band with a wavelength of 1 to 10 mm with a frequency of 30 to 300 GHz, especially 60 to 90 GHz, and receives the reflected waves that collide with the target and return. It detects the presence of obstacles, the distance to an object, and the relative speed. Millimeter-wave radar is being considered for use in a wide range of fields, such as automobile collision prevention sensors, automatic driving systems, road information provision systems, security systems, and medical and nursing care devices.
As a resin composition for such millimeter wave radar, the one described in Patent Document 1 is known. Further, Patent Document 2 discloses a multifunctional resin composition that can be used for electromagnetic interference shielding or radio frequency interference shielding.

JP 2019-197048 A JP 2010-155993 A

Here, in the millimeter wave radar, transmitted electromagnetic waves are the biggest cause of malfunction. Therefore, there is a demand for a resin composition having a high absorbance of electromagnetic waves.
An object of the present invention is to solve such problems, and to provide a resin composition, a pellet, a molded article, an electromagnetic wave absorber, and a method for producing a resin composition having a high absorption rate of electromagnetic waves. With the goal.

（上記式（Ａ）中、Ｒはフリースペース法によって測定される反射減衰量を表し、Ｔはフリースペース法によって測定させる透過減衰量を表す。）
＜８＞前記樹脂組成物を２ｍｍ厚に成形したときの、周波数７６．５ＧＨｚにおける式（Ｂ）に従って求められる反射率が４０．０％以下である、＜１＞～＜７＞のいずれか１つに記載の樹脂組成物。
式（Ｂ）

（上記式（Ｂ）中、Ｒは、フリースペース法によって測定される反射減衰量を表す。）
＜９＞前記樹脂組成物を２ｍｍ厚に成形したときの、周波数７６．５ＧＨｚにおける式（Ｃ）に従って求められる透過率が４３．０％未満である、＜１＞～＜８＞のいずれか１つに記載の樹脂組成物。
式（Ｃ）

（上記式（Ｃ）中、Ｔはフリースペース法によって測定させる透過減衰量を表す。）
＜１０＞電磁波吸収体用である、＜１＞～＜９＞のいずれか１つに記載の樹脂組成物。
＜１１＞＜１＞～＜１０＞のいずれか１つに記載の樹脂組成物から形成されたペレット。
＜１２＞＜１＞～＜１０＞のいずれか１つに記載の樹脂組成物から形成された成形体。
＜１３＞＜１＞～＜１０＞のいずれか１つに記載の樹脂組成物から形成された電磁波吸収体。
＜１４＞固有粘度が０．８７～２．００ｄＬ／ｇのポリエステル樹脂と、ポリアミド樹脂でマスターバッチ化されたカーボンナノチューブを溶融混練することを含む、＜１＞～＜１０＞のいずれか１つに記載の樹脂組成物の製造方法。 Based on the above problems, the present inventors have investigated and found that a resin composition in which carbon nanotubes are blended with a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g, by blending a polyamide resin , the electromagnetic wave absorption rate of the resulting resin composition can be improved.
Specifically, the above problems have been solved by the following means.
<1> With respect to 100 parts by mass of a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g, 0.1 to 10.0 parts by mass of a polyamide resin,
A resin composition comprising a carbon nanotube.
<2> The resin composition according to <1>, wherein the carbon nanotubes are derived from carbon nanotubes masterbatched with a polyamide resin.
<3> The resin composition according to <2>, wherein the concentration of carbon nanotubes in the masterbatch is 1 to 50% by mass.
<4> The resin composition according to any one of <1> to <3>, wherein the polyester resin contains a polybutylene terephthalate resin.
<5> The resin composition according to any one of <1> to <4>, wherein the polyamide resin comprises an aliphatic polyamide resin.
<6> The resin composition according to any one of <1> to <5>, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10% by mass.
<7> Any one of <1> to <6>, wherein the absorptivity obtained according to the 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%. 1. The resin composition according to 1.
Formula (A)

(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.)
<8> Any one of <1> to <7>, wherein the reflectance obtained according to the 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. The resin composition according to 1.
Formula (B)

(In the above formula (B), R represents the return loss measured by the free space method.)
<9> Any one of <1> to <8>, wherein the transmittance obtained according to the formula (C) at a frequency of 76.5 GHz when the resin composition is molded to a thickness of 2 mm is less than 43.0%. The resin composition according to 1.
Formula (C)

(In the above formula (C), T represents the amount of transmission attenuation measured by the free space method.)
<10> The resin composition according to any one of <1> to <9>, which is used as an electromagnetic wave absorber.
<11> A pellet formed from the resin composition according to any one of <1> to <10>.
<12> A molded article formed from the resin composition according to any one of <1> to <10>.
<13> An electromagnetic wave absorber formed from the resin composition according to any one of <1> to <10>.
<14> Any one of <1> to <10>, including melt-kneading a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g and a carbon nanotube masterbatched with a polyamide resin. A method for producing the resin composition according to 1.

ADVANTAGE OF THE INVENTION By this invention, it became possible to provide the manufacturing method of the resin composition, a pellet, a molded object, an electromagnetic wave absorber, and a resin composition with a high absorption rate of electromagnetic waves.

EMBODIMENT OF THE INVENTION Hereinafter, the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail. In addition, the present embodiment below is an example for explaining the present invention, and the present invention is not limited only to the present embodiment.
In this specification, the term "~" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.
In this specification, various physical property values and characteristic values are at 23° C. unless otherwise specified.
In this specification, the unit of return loss and transmission loss is "dB" (decibel).
If the standards shown in this specification differ from year to year in terms of measurement methods, etc., the standards as of January 1, 2021 shall be used unless otherwise specified.

The resin composition of the present embodiment is a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g (hereinafter sometimes referred to as "specific polyester resin") 100 parts by mass, polyamide resin 0.1 to 10.0 parts by mass and carbon nanotubes. With such a configuration, the electromagnetic wave absorptivity of the molded article formed from the resin composition can be increased.
In particular, by masterbatching carbon nanotubes with a polyamide resin and blending the masterbatch with a specific polyester resin, a molded article having a high electromagnetic wave absorption rate can be obtained. The reason for this is presumed to be as follows. That is, when the carbon nanotubes masterbatched with a polyamide resin are blended with the polyester resin, the polyamide resin has a large number of polar groups, so that the interaction with the carbon nanotubes is strong, making it difficult to disperse. Here, if the dispersibility of the carbon nanotubes is poor, the electromagnetic wave absorbability will be poor. In the present embodiment, by using a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g, the polyamide resin is strongly kneaded during melt kneading, so that the polyamide resin containing aggregates of carbon nanotubes is polyester. It was presumed that fine dispersion in the resin could improve the dispersibility of the carbon nanotubes.

<Polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL/g>
The resin composition of the present 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, in particular carbon nanotubes masterbatched with a polyamide resin, is used, the carbon nanotubes are effective in the specific polyester resin. can be distributed in

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, and 0.98 dL/g or more. more preferably 1.00 dL/g or more, and even more preferably 1.05 dL/g or more. By making it equal to or higher than the lower limit, (electromagnetic wave absorbability tends to improve.
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, and further preferably 1.40 dL/g or less. It is preferably 1.30 dL/g or less, even more preferably 1.26 dL/g or less. By making it 2.00 dL/g or less, the fluidity of the resin composition tends to be further improved, and the moldability tends to be improved.
The intrinsic viscosity of the specific polyester resin is a value measured at 30° C. in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.
When the resin composition of the present embodiment contains two or more polyester resins, the intrinsic viscosity of the mixture is used.

As the specific polyester resin used in the present embodiment, a known thermoplastic polyester resin can be used as long as the intrinsic viscosity is satisfied, and polyethylene terephthalate resin and polybutylene terephthalate resin are preferable, and at least polybutylene terephthalate resin may be included. more preferred.
The polybutylene terephthalate resin used in the resin composition of the present embodiment is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded, and in addition to the polybutylene terephthalate resin (homopolymer) , polybutylene terephthalate copolymers containing copolymer components other than terephthalic acid units and 1,4-butanediol units, and mixtures of homopolymers and polybutylene terephthalate copolymers.

The polybutylene terephthalate resin may contain one or more dicarboxylic acid units other than terephthalic acid.
Specific examples of other dicarboxylic acids include isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, Aromatic dicarboxylic acids such as biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'-carboxyphenyl)methane, anthracenedicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid , 1,4-cyclohexanedicarboxylic acid, 4,4'-dicyclohexyldicarboxylic acid and other alicyclic dicarboxylic acids, and adipic acid, sebacic acid, azelaic acid, dimer acid and other aliphatic dicarboxylic acids. .
In the polybutylene terephthalate resin used in the present embodiment, the terephthalic acid units preferably account for 80 mol% or more of the total dicarboxylic acid units, more preferably 90 mol% or more, and even more preferably 95 mol% or more. Preferably, it accounts for 97 mol % or more, and still more preferably 99 mol % or more.

The diol unit may contain one or more 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 and bisphenol derivatives. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethanol, 4,4′-dicyclohexylhydroxymethane, ,4'-dicyclohexylhydroxypropane, ethylene oxide-added diol of bisphenol A, and the like. In addition to the above bifunctional monomers, trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane for introducing a branched structure, and fatty acids for molecular weight adjustment. A small amount of monofunctional compound can also be used together.
In the polybutylene terephthalate resin used in the present embodiment, 1,4-butanediol units preferably account for 80 mol% or more, more preferably 90 mol% or more, and 95 mol% or more of the total diol units. More preferably, it accounts for 97 mol % or more, and even more preferably 99 mol % or more.

As described above, the polybutylene terephthalate resin is preferably a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. Also, a polybutylene terephthalate copolymer containing one or more dicarboxylic acids other than terephthalic acid as carboxylic acid units and/or one or more diols other than 1,4-butanediol as diol units. good. When the polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers thereof include polyester ether resins obtained by copolymerizing polyalkylene glycols, particularly polytetramethylene glycol, Examples include dimer acid-copolymerized polybutylene terephthalate resin and isophthalic acid-copolymerized polybutylene terephthalate resin. Among them, it is preferable to use a polyester ether resin obtained by copolymerizing polytetramethylene glycol.
In addition, these copolymers refer to those having a copolymerization amount of 1 mol % or more and less than 50 mol % in all segments of the polybutylene terephthalate resin. Among them, the copolymerization amount is preferably 2 mol % or more and less than 50 mol %, more preferably 3 to 40 mol %, still more preferably 5 to 20 mol %. By setting such a copolymerization ratio, fluidity and toughness tend to be improved, which is preferable.

The terminal carboxyl group content of the polybutylene terephthalate resin may be appropriately selected and determined. preferable. By adjusting the content to the above upper limit or less, the alkali resistance and hydrolysis resistance tend to be improved. Although the lower limit of the amount of terminal carboxyl groups is not particularly defined, it is usually 10 eq/ton or more in consideration of productivity in the production of polybutylene terephthalate resin.

The terminal carboxyl group content of polybutylene terephthalate resin is a value measured by dissolving 0.5 g of polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating with a 0.01 mol/L benzyl alcohol solution of sodium hydroxide. is. As a method for adjusting the amount of terminal carboxyl groups, any conventionally known method may be used, such as a method of adjusting polymerization conditions such as the raw material charge ratio during polymerization, the polymerization temperature, and a decompression method, or a method of reacting a terminal blocking agent. You can do it.

In this embodiment, the specific polyester resin may be a linear polymer or a branched polymer having a branched structure. In the present embodiment, the specific polyester resin preferably has few branched structures. For example, the specific polyester resin used in the present embodiment preferably has a degree of branching (DB) of less than 10%, more preferably 5% or less, and even more preferably 3% or less. The degree of branching is defined here as DB(%) = 100 x (T + Z)/(T + Z + L), where T is the average number of terminally linked monomer units and Z is the monomer forming the branch. is the average number of units and L is the average number of linearly linked monomeric units (within the macromolecule of each substance).

Polybutylene terephthalate resin is produced by melt-polymerizing a dicarboxylic acid component or an ester derivative thereof containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component in a batch or continuous process. be able to. Further, 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 solid-phase polymerization under a nitrogen stream or under reduced pressure.
The polybutylene terephthalate resin is preferably produced by continuous melt polycondensation of a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol.

Catalysts used in carrying out the esterification reaction may be those conventionally known, and examples thereof include titanium compounds, tin compounds, magnesium compounds, calcium compounds, and the like. Particularly suitable among these are titanium compounds. Specific examples of the titanium compound as the esterification catalyst include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

As for the specific polyester resin, in addition to the above, descriptions in paragraphs 0013 to 0016 of JP-A-2010-174223 can be referred to, the contents of which are incorporated herein.

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

Further, the content of the specific polyester resin in the resin composition of the present embodiment is preferably 85% by mass or more, and 90% by mass or more, when the total amount of the resin components contained in the resin composition is 100% by mass. and more preferably 95% by mass or more. By making it equal to or higher than the lower limit, the effect of suppressing the water absorption of the resin tends to be further improved. Further, the upper limit of the content of the specific polyester resin is preferably that all components other than the polyamide resin are the specific polyester resin when the total amount of the resin components contained in the resin composition is 100% by mass. When the content is equal to or less than the above upper limit, the electromagnetic wave absorptance of the obtained molded article 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 included, the total amount is preferably within the above range.

<Polyamide resin>
The resin composition of the present embodiment contains 0.1 to 10.0 parts by mass of polyamide resin per 100 parts by mass of specific polyester resin. By blending the specific polyester resin with the polyamide resin and melt-kneading the mixture, the dispersibility of the polyamide resin can be enhanced and the dispersibility of the carbon nanotubes can be enhanced as compared with the case where the intrinsic viscosity of the polyester resin is low.
The polyamide resin is a polymer having an acid amide as a structural unit obtained by ring-opening polymerization of lactam, polycondensation of aminocarboxylic acid, or polycondensation of diamine and dibasic acid. Semi-aromatic polyamide resins may be used, and aliphatic polyamide resins are preferred.
Specifically, polyamides 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 meta-xylylenediamine and adipic acid Polyamide resin (MP10) synthesized from meta-xylylenediamine, para-xylylenediamine and sebacic acid, meta-xylylenediamine, adipic acid and sebacic acid Synthesized polyamide resin (MXD610), polyamide resin (MXD10) synthesized from metaxylylenediamine and sebacic acid, polytrimethylhexamethylene terephthalamide, polybis(4-aminocyclohexyl)methandodedecamide, polybis(3-methyl- 4-aminocyclohexyl)methandodecanamide, polyundecamethylenehexahydroterephthalamide and the like. Incidentally, the above "I" indicates an isophthalic acid component, and "T" indicates a terephthalic acid component. In addition, as the polyamide resin, the description in paragraphs 0011 to 0013 of JP-A-2011-132550 can be referred to, and the contents thereof are incorporated herein.

In the present embodiment, as described above, the polyamide resin is preferably an aliphatic polyamide resin, more preferably polyamide 6, 11, 12, 46, 66, 666, 610, 612, and more preferably polyamide 6, 66, 666. , polyamide 6 is more preferred.
Polyamide 6 here is a ring-opening polymer of caprolactam, but units derived from monomers other than caprolactam (dicarboxylic acid units, diamine units, aminocarboxylic acid units) and It is intended to include those containing terminal groups and the like. In the polyamide 6 used in the present embodiment, 99% by mass or more, excluding terminal groups, is preferably caprolactam-derived units. Other polyamide resins such as polyamide 66 are also considered in the same way.

The content of the polyamide resin in the resin composition of the present embodiment is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, relative to 100 parts by mass of the specific polyester resin, and 1.0 It is more preferably at least 1.5 parts by mass, even more preferably at least 2.0 parts by mass, and even more preferably at least 2.5 parts by mass. Further, 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, and 8.5 parts by mass or less with respect to 100 parts by mass of the specific polyester resin. 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. By making it equal to or less than the upper limit, the effect of suppressing the hygroscopicity 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 included, the total amount is preferably within the above range.

<Carbon nanotube>
The resin composition of this 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 include at least multi-walled carbon nanotubes. A carbon material partially having a carbon nanotube structure can also be used. In addition, the carbon nanotube is not limited to a cylindrical shape, and may have a coiled shape in which a spiral makes a round at a pitch of 1 μm or less.
Carbon nanotubes are commercially available, and examples thereof include carbon nanotubes available from Bayer Material Science, Nanosil, Showa Denko, and Hyperion Catalysis International. In addition to the name of carbon nanotube, it is sometimes called graphite fibril, carbon fibril, and the like.
The diameter (number average fiber diameter) of the carbon nanotube is preferably 0.5 to 100 nm, more preferably 1 to 30 nm. The aspect ratio of the carbon nanotubes is preferably 5 or more, more preferably 50 or more, from the viewpoint of imparting good electromagnetic wave absorbability. Although the upper limit is not particularly defined, it is, for example, 500 or less.

In the present embodiment, the carbon nanotubes are preferably derived from carbon nanotubes masterbatched with a polyamide resin. Such a structure tends to further improve the electromagnetic wave absorbability of the resulting resin composition or molded article.
As described above, the carbon nanotubes may be blended in a masterbatch. In this case, the concentration of the carbon nanotubes in the masterbatch is preferably 1% by mass or more, more preferably 5% by mass or more. Also, it is 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. When the content is in the range of 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.

The content of carbon nanotubes in the resin composition of the present embodiment is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and 0.1% by mass or more. is more preferable, and may be 0.2% by mass or more, and may be 0.4% by mass or more. By making it more than the said lower limit, electromagnetic wave absorptivity is exhibited effectively. In addition, the content of carbon nanotubes in the resin composition of the present embodiment is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, It is more preferably 4% by mass or less, even more preferably 3% by mass or less, may be 2% by mass or less, and may be 1% by mass or less. By making the content equal to or less than the above upper limit, the fluidity of the resin tends to be further improved.

The resin composition of the present embodiment also preferably contains 0.1 parts by mass or more of carbon nanotubes with respect to 100 parts by mass of the specific polyester resin. By making it more than the said lower limit, electromagnetic wave absorptivity is exhibited effectively. In addition, the resin composition of the present embodiment preferably contains 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, of carbon nanotubes with respect to 100 parts by mass of the specific polyester resin. 0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, further preferably 2.5 parts by mass or less, particularly may be 1.5 parts by mass or less. By making the content equal to or less than the above upper limit, the fluidity of the resin tends to be further improved.
The resin composition of the present embodiment may contain only one type of carbon nanotube, or may contain two or more types of carbon nanotubes. When two or more types are included, the total amount is preferably within the above range.

<Other ingredients>
The resin composition of the present embodiment may optionally contain other components in addition to those mentioned above, as long as the desired physical properties are not significantly impaired. Examples of other components include thermoplastic resins other than specific polyester resins and polyamide resins, reinforcing materials, and various resin additives. In addition, 1 type may be contained and 2 or more types may contain other components by arbitrary combinations and a ratio.

Polystyrene resins; polyolefin resins such as polyethylene resins, polypropylene resins, and cyclic cycloolefin resins; polyacetal resins; polyimide resins; polyetherimide resins; polyurethane resins; Sulfide resin; polysulfone resin; polymethacrylate resin; and the like are preferably exemplified.

Various resin additives include stabilizers, release agents, flame retardants, reactive compounds, pigments, dyes, UV absorbers, antistatic agents, antifogging agents, antiblocking agents, fluidity improvers, plasticizers, dispersants agents, antibacterial agents, and the like. The resin composition of this embodiment preferably contains at least one of a stabilizer and a release agent.
The resin composition of the present embodiment is adjusted so that the total amount of the specific polyester resin, polyamide resin, carbon nanotubes, and other selectively blended components is 100% by mass. An example of the resin composition of the present embodiment is that the total of the specific polyester resin, the polyamide resin, and the reinforcing material (preferably glass fiber) accounts for 95% by mass or more of the resin composition. Another example of the resin composition of the present embodiment is that the total of the specific polyester resin, the polyamide resin, the carbon nanotubes, the stabilizer, and the release agent accounts for 99% by mass or more of the resin composition. Furthermore, another example of the resin composition of the present embodiment has a specific polyester resin, a polyamide resin, carbon nanotubes, a reinforcing material (preferably glass fiber), a stabilizer, and a total of 99% of the resin composition. It is to occupy more than mass %.

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

The resin composition of the present embodiment preferably contains 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and 0.08 parts by mass or more of the stabilizer with respect to 100 parts by mass of the specific polyester resin. More preferably, it contains In addition, the upper limit of the content of the stabilizer is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and 1 part by mass or less with respect to 100 parts by mass of the specific polyester resin. is more preferred.
The resin composition of the present embodiment may contain only one stabilizer or may contain two or more stabilizers. When two or more types are included, the total amount is preferably within the above range.

<< Release agent >>
The resin composition of the present embodiment preferably contains a release agent.
A wide range of known mold release agents can be used as the mold release agent, and esters of aliphatic carboxylic acids, paraffin wax, polystyrene wax, and polyolefin wax are preferable, and polyethylene wax is more preferable.
As the release agent, specifically, the description of paragraphs 0115 to 0120 of JP-A-2013-007058, the description of paragraphs 0063-0077 of JP-A-2018-070722, and the paragraph of JP-A-2019-123809 0090 to 0098 can be referred to, and the contents thereof are incorporated herein.

The resin composition of the present embodiment preferably contains 0.01 parts by mass or more, more preferably 0.08 parts by mass or more, and 0.2 parts by mass of the release agent with respect to 100 parts by mass of the specific polyester resin. It is more preferable to include the above. In addition, the upper limit of the content of the release agent is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and 1 part by mass or less with respect to 100 parts by mass of the specific polyester resin. is more preferable, and 0.8 parts by mass or less is even more preferable.
The resin composition may contain only one release agent, or may contain two or more release agents. When two or more types are included, the total amount is preferably within the above range.

<<Reinforcing material>>
The resin composition of the present embodiment may or may not contain a reinforcing material. By including the reinforcing material, the mechanical strength of the resulting molded article can be improved.
The reinforcing material that can be used in the present embodiment is not particularly limited in terms of its type and the like, and may be any of fibers, fillers, beads, etc., but fibers are preferred.

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 the present embodiment is exemplified by pellets, pulverized pellets, films formed from the pellets, and the like.
When the reinforcing material is long fibers, examples of the reinforcing material include long fibers for so-called UD materials (Uni-Directional), sheet-like long fibers such as woven and knitted fabrics, and the like. When these filaments are used, components other than the reinforcing material of the resin composition of the present embodiment are impregnated into the sheet-like filament reinforcing material to form a sheet-like resin composition (eg, prepreg). can do.

Raw materials for reinforcing materials include glass, carbon (carbon fiber, etc.), alumina, boron, ceramics, metals (steel, etc.) and other inorganic substances, and plants (including Kenaf, bamboo, etc.), aramid, polyoxymethylene. , aromatic polyamide, polyparaphenylenebenzobisoxazole, and organic substances such as ultra-high-molecular-weight polyethylene, and glass is preferable.

The resin composition of the present embodiment preferably contains glass fiber 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, and E glass (alkali-free glass) is particularly preferred.
Glass fiber refers to a fibrous material having a perfect circular or polygonal cross-sectional shape when cut perpendicularly to the length direction. The glass fiber has a single fiber number average fiber diameter of usually 1 to 25 μm, preferably 5 to 17 μm. By setting the number average fiber diameter to 1 μm or more, the moldability of the resin composition tends to be further improved. By setting the number average fiber diameter to 25 μm or less, there is a tendency that the appearance of the obtained molded article is improved and the reinforcing effect is also improved. The glass fiber may be a single fiber or a plurality of twisted single fibers.
The forms of glass fibers include glass rovings obtained by continuously winding a single fiber or a plurality of twisted fibers, chopped strands cut to a length of 1 to 10 mm (that is, glass fibers with a number average fiber length of 1 to 10 mm), Any milled fiber (that is, glass fiber having a number average fiber length of 10 to 500 μm) that has been pulverized to a length of about 10 to 500 μm may be used, but chopped strands cut to a length of 1 to 10 mm are preferred. Glass fibers having different forms can be used together.
As the glass fiber, one having a modified cross-sectional shape is also preferable. This irregular cross-sectional shape means that the oblateness indicated by the length/breadth ratio of the cross section perpendicular to the length direction of the fiber is, for example, 1.5 to 10, especially 2.5 to 10, and more preferably 2.5 to 10. 5 to 8, particularly preferably 2.5 to 5.

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

When the resin composition of the present embodiment contains a reinforcing material (preferably glass fiber), the content thereof is preferably 10 parts by mass or more, and 20 parts by mass or more with respect to 100 parts by mass of the specific polyester resin. is more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more. By making it equal to or higher than the above lower limit, the mechanical strength of the molded article to be obtained tends to be further increased. Further, 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, and 85 parts by mass with respect to 100 parts by mass of the specific polyester resin. It is more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less. By adjusting the content to the above upper limit or less, there is a tendency that the appearance of the molded article is improved and the fluidity of the resin composition is further improved.

The content of the reinforcing material (preferably glass fiber) in the resin composition of the present embodiment is preferably 10% by mass or more, more preferably 15% by mass or more, and 20% by mass in the resin composition. It is more preferably 25% by mass or more, and even more preferably 25% by mass or more. In addition, the content of the reinforcing material (preferably glass fiber) is more preferably 50% by mass or less, further preferably 45% by mass or less, and 40% by mass or less in the resin composition. is more preferable, and 35% by mass or less is even more preferable. By making it more than the said lower limit, there exists a tendency for mechanical strength to raise more. In addition, when the content is equal to or less than the above upper limit, there is a tendency that the appearance of the molded article is improved and the fluidity of the resin composition when melted is 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 included, the total amount is preferably within the above range.

（上記式（Ａ）中、Ｒはフリースペース法によって測定される反射減衰量を表し、Ｔはフリースペース法によって測定させる透過減衰量を表す。） <Physical properties of the resin composition>
The resin composition of the present embodiment preferably has a high absorbance of electromagnetic waves.
Specifically, the resin composition of the present embodiment has an absorptance of 43 at a frequency of 76.5 GHz when molded to a thickness of 2 mm (preferably, a thickness of 100 mm × 100 mm × 2 mm). 0 to 100% is preferred.
Formula (A)

(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.)

The absorption rate 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. preferable. The upper limit is ideally 100%, but even if it is 90.0% or less, the required performance is sufficiently satisfied.

（上記式（Ｂ）中、Ｒは、フリースペース法によって測定される反射減衰量を表す。） The resin composition of the present embodiment preferably has a low electromagnetic wave reflectance.
Specifically, the resin composition of the present embodiment has a reflectance of 40 at a frequency of 76.5 GHz when molded to a thickness of 2 mm (preferably 100 mm × 100 mm × 2 mm), which is obtained according to the formula (B). It is preferably 0% or less.
Formula (B)

(In the above formula (B), R represents the return loss measured by the free space method.)

The reflectance is preferably 35.0% or less, more preferably 30.0% or less, even more preferably 26.0% or less, and even more preferably 22.0% or less. It is preferably 18.5% or less, and 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 satisfied.

（上記式（Ｃ）中、Ｔはフリースペース法によって測定させる透過減衰量を表す。） The resin composition of the present embodiment preferably has low transmittance.
The resin composition of the present embodiment has a transmittance of less than 43.0% when molded to a thickness of 2 mm (preferably 100 mm × 100 mm × 2 mm thickness) at a frequency of 76.5 GHz, which is obtained according to formula (C). Preferably.
Formula (C)

(In the above formula (C), T represents the amount of transmission attenuation measured by the free space method.)

The transmittance is preferably 42.0% or less, 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 satisfied.

The resin composition of the present embodiment satisfies all of the absorptance determined according to the above formula (A), the reflectance determined according to the above formula (B), and the transmittance determined according to the above formula (C). preferable.

The resin composition of the present embodiment preferably has a surface resistance of 1.0×10 ⁸ Ω or more according to IEC60093 when molded into a thickness of 2 mm (preferably 100 mm×100 mm×2 mm thickness). , more preferably 1.0×10 ⁹ Ω or more, still more preferably 1.0×10 ¹⁰ Ω or more, even more preferably 1.0×10 ¹¹ Ω or more, and 1.0× It is more preferably 10 ¹² Ω or more, even more preferably 1.0×10 ¹³ Ω or more, and particularly preferably 1.0×10 ¹⁴ Ω or more, and 1.0× It is preferably 10 ¹⁶ Ω or less, more preferably 1.0×10 ¹⁵ Ω or less. By setting it as such a range, the electromagnetic wave absorptivity of the molded article obtained tends to become higher.
The surface resistance is a value obtained by measuring the surface resistance (unit: Ω) according to IEC60093 using a test piece of 100 mm×100 mm×2 mm thickness formed from the resin composition.

The resin composition of the present embodiment has a dielectric constant of 4.00 or more, preferably 4.20 or more, more preferably 4.45 or more, and 4.60 or more at a frequency of 76.5 GHz. is more preferably 4.70 or more, and even more preferably 5.10 or more. By making it equal to or higher than the above lower limit, there is a tendency that the electromagnetic wave absorptance of the resulting molded article becomes higher. Further, the upper limit value of the dielectric constant is preferably 8.00 or less, more preferably 6.00 or less, further preferably 5.50 or less, and 5.30 or less. is more preferable, and 5.20 or less is even more preferable. When the content is equal to or less than the above upper limit, there is a tendency that the electromagnetic wave reflectance of the resulting molded article can be further lowered.
The resin composition of the present 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 it equal to or higher than the above lower limit, there is a tendency that the electromagnetic wave absorptance of the resulting molded article becomes higher. Moreover, the lower limit value of the dielectric loss tangent is not particularly defined, but is, for example, 0.50 or less, and may be 0.40 or less.

<Method for producing 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 a polyamide resin). More specifically, a specific polyester resin, carbon nanotubes masterbatched with a polyamide resin, and other components (glass fiber, etc.) blended as necessary are put into an extruder and melt-kneaded to manufacture. be done. One form formed from such a resin composition is a pellet.
Each component may be premixed and supplied to the extruder at once, or each component may be premixed without premixing, or only a part thereof may be premixed and supplied to the extruder using a feeder. good too. The extruder may be a single screw extruder or a twin screw extruder.
Further, when a reinforcing material such as glass fiber is blended, it is preferable to supply it from a side feeder in the middle of the cylinder of the extruder.
The heating temperature for melt-kneading can usually be appropriately selected from the range of 170 to 350°C.

<Method for manufacturing molded body>
A molded article, particularly an electromagnetic wave absorber, is formed from the resin composition of the present embodiment.
The method for producing the molded article in the present embodiment is not particularly limited, and any molding method generally employed for resin compositions containing thermoplastic resins can be employed. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, hollow molding such as gas assist, molding using heat insulating molds, and rapid heating molds. Molding method, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding) molding method, extrusion molding method, sheet molding method, thermoforming method, rotational molding method, laminate molding method, press molding method, A blow molding method and the like can be mentioned, and among them, an injection molding method is preferable.

<Application>
The electromagnetic wave absorber of this embodiment is formed from the resin composition of this embodiment. That is, the resin composition of the present embodiment is preferably for an electromagnetic wave absorber (also referred to as an electromagnetic wave absorbing member), more preferably for an electromagnetic wave absorber with a frequency of at least 60 to 90 GHz, and at least a frequency of 70 to More preferably, it is for an 80 GHz electromagnetic wave absorber. Such electromagnetic wave absorbers are preferably used for radar applications. Specifically, it is used for housings, covers, etc. for millimeter wave radars.
The electromagnetic wave absorber of this embodiment includes an automatic brake control device, an inter-vehicle distance control device, a steering device for reducing pedestrian accidents, an erroneous transmission suppression control device, an acceleration suppression device for pedal misapplication, an approaching vehicle warning device, and a lane keeping support device. , rear-end collision prevention warning device, parking support device, vehicle surrounding obstacle warning device, etc. Platform monitoring / railroad crossing obstacle detection device, content transmission device in train, streetcar / railroad collision prevention device Millimeter-wave radars for railroads and aviation used for detecting foreign objects on runways, etc.; millimeter-wave radars for traffic infrastructure such as intersection monitoring devices and elevator monitoring devices; millimeter-wave radars for various security devices; monitoring systems for children and the elderly, etc. medical and nursing care millimeter wave radar; millimeter wave radar for transmitting various information contents; and the like.

EXAMPLES The present invention will be described more specifically with reference to examples below. The materials, usage amounts, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Accordingly, the scope of the present invention is not limited to the specific examples shown below.
If the measuring instruments and the like used in the examples are discontinued and difficult to obtain, other instruments having equivalent performance can be used for measurement.

Raw Materials The following raw materials were used. In Table 1 below, PBT means polybutylene terephthalate resin and CNT means carbon nanotube (the same applies to Table 2).

Example 1, Comparative Example 1
<Production of resin composition (pellets)>
As shown in Table 2, each component shown in Table 1 was placed in a stainless steel tumbler and mixed with stirring for 1 hour. The resulting mixture was supplied to an intermeshing co-rotating twin-screw extruder (“TEX-30α” manufactured by The Japan Steel Works, Ltd., screw diameter 32 mm, L/D=42) from the main feed port. Set the barrel temperature of the first kneading section to 250° C., melt-knead under the conditions of a discharge rate of 40 kg/h and a screw rotation speed of 200 rpm, and a nozzle number of 4 holes (circular (φ4 mm), length 1.5 cm). Extruded as strands. The extruded strand was introduced into a water tank, cooled, inserted into a pelletizer, and cut to obtain a resin composition (pellets).

（上記式（Ａ）中、Ｒはフリースペース法によって測定される反射減衰量を表し、Ｔはフリースペース法によって測定させる透過減衰量を表す。） <76.5 GHz electromagnetic wave absorption rate, reflectance, transmittance>
Using the pellets obtained above, injection molding was performed using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder setting temperature of 260 ° C. and a mold temperature of 80 ° C., and a test piece of 100 mm × 100 mm × 2 mm thickness. got Using the obtained test piece, the absorptance determined according to formula (A), the reflectance determined according to formula (B), and the transmittance determined according to formula (C) at a frequency of 76.5 GHz are as follows. It was measured.
A network analyzer "N5252A" manufactured by Keysight Corporation was used for the measurement.
The TD (transverse direction) direction of the injection molded product was measured by placing the test piece in a direction parallel to the direction of the electric field.
Formula (A)

(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.)

（上記式（Ｂ）中、Ｒは、フリースペース法によって測定される反射減衰量を表す。） Formula (B)

(In the above formula (B), R represents the return loss measured by the free space method.)

（上記式（Ｃ）中、Ｔはフリースペース法によって測定させる透過減衰量を表す。） Formula (C)

(In the above formula (C), T represents the amount of transmission attenuation measured by the free space method.)

<Relative permittivity and dielectric loss tangent>
Using the pellets obtained above, injection molding was performed using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.) at a cylinder setting temperature of 260 ° C. and a mold temperature of 80 ° C., and a test piece of 100 mm × 100 mm × 2 mm thickness. got
Using the obtained test piece, the relative dielectric constant and dielectric loss tangent at a frequency of 76.5 GHz were determined. The TD (transverse direction) direction of the injection molded product was measured by placing the test piece in a direction parallel to the direction of the electric field.
Measurement was performed using a network analyzer "N5252A" manufactured by Keysight Corporation, and the values of dielectric constant and dielectric loss tangent were estimated using "N1500A material measurement suite" manufactured by Keysight Corporation, and using the calculation model "NIST Precision Each value was calculated by

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. Furthermore, the electromagnetic wave transmittance and reflectance were low.

Claims (14)

0.1 to 10.0 parts by mass of a polyamide resin with respect 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 a carbon nanotube. 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 carbon nanotubes in the masterbatch is 1 to 50% by mass. The resin composition according to any one of claims 1 to 3, wherein the polyester resin comprises a polybutylene terephthalate resin. The resin composition according to any one of claims 1 to 4, wherein the polyamide resin comprises an aliphatic polyamide resin. The resin composition according to any one of claims 1 to 5, wherein the content of carbon nanotubes in the resin composition is 0.01 to 10% by mass. 7. The method according to any one of claims 1 to 6, wherein, when the resin composition is molded to have a thickness of 2 mm, the absorptance calculated according to the formula (A) at a frequency of 76.5 GHz is 43.0 to 100%. Resin composition.
Formula (A)

(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.) The resin according to any one of claims 1 to 7, wherein the reflectance obtained according to the 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. Composition.
Formula (B)

(In the above formula (B), R represents the return loss measured by the free space method.) The resin according to any one of claims 1 to 8, wherein the transmittance obtained according to formula (C) at a frequency of 76.5 GHz when the resin composition is molded to a thickness of 2 mm is less than 43.0%. Composition.
Formula (C)

(In the above formula (C), T represents the amount of transmission attenuation measured by the free space method.) The resin composition according to any one of claims 1 to 9, which is used as an electromagnetic wave absorber. A pellet formed from the resin composition according to any one of claims 1 to 10. A molded article formed from the resin composition according to any one of claims 1 to 10. An electromagnetic wave absorber formed from the resin composition according to any one of claims 1 to 10. The resin composition according to any one of claims 1 to 10, comprising melt-kneading a polyester resin having an intrinsic viscosity of 0.87 to 2.00 dL / g and a carbon nanotube masterbatched with a polyamide resin. A method of making things.