JP7446127B2 - Resin composition and molded product made from the resin composition - Google Patents

Description

The present invention relates to a resin composition having electromagnetic shielding properties and a molded article made of the resin composition. The present invention relates to a resin composition having excellent electromagnetic shielding properties, particularly in the gigahertz band.

In recent years, electronic devices have been used in all fields. In particular, communication devices such as radios that use relatively long wavelength radio waves are increasing, and devices such as mobile phones, satellite broadcasting, and wireless LAN that use short wavelength radio waves are increasing, so electromagnetic shielding is important. It has become a technology.

Techniques for shielding electromagnetic waves to prevent malfunctions caused by electromagnetic waves include using a housing made of metal or the like, or using conductive fillers such as metal fibers, carbon fibers, metal-coated carbon fibers, or carbon nanotubes in resin housings. It is known to apply treatments such as adding conductive films, painting, and plating. (Patent Document 1)

Although metal casings have good performance, they are heavier and have less freedom in design, and methods such as applying film, painting, or plating to resin casings may peel off, so they are not suitable for use in products with long life cycles. It is said that it is not.

The combined use of carbon black and carbon fiber is known as a material that provides electromagnetic shielding properties without using metal (Patent Documents 2 and 3). These documents indicate shielding properties of about 1 GHz, and state that if the amount of carbon fiber is small, sufficient electromagnetic shielding properties cannot be obtained, and that high electromagnetic shielding properties can be obtained by imparting conductivity.

Japanese Patent Application Publication No. 2012-229345 Japanese Patent Application Publication No. 2010-31257 Japanese Patent Application Publication No. 2006-45385

Due to the development of electronic equipment, electromagnetic shielding properties against high frequency electromagnetic waves of 10 GHz or higher are required. Conventional conductive electromagnetic shielding materials are often combined with electrical insulating materials when used in electrical equipment parts that also require electrical insulation properties. It was necessary to use it.

An object of the present invention is to provide a resin composition that has shielding properties against high frequency electromagnetic waves of 10 GHz or higher and has excellent electrical insulation properties.

The objects of the invention were achieved by the following.
1. Contains at least 100 parts by mass of thermoplastic resin A, 2 to 6 parts by mass of carbon black B, and 0.3 to 4 parts by mass of carbon fiber C, and the total of the carbon black B and the carbon fiber C is 7 parts by mass. A resin composition having a volume resistivity of 1×10 ¹⁰ to 1×10 ¹⁷ Ω·cm, a transmission loss of -30 dB or less in a band of 75 to 110 GHz, and an electromagnetic wave absorption rate of 30 Ω/cm or less. % or more.
2. 1. The resin composition according to 1 above, wherein the carbon black B is Ketjenblack.
3. A molded article made of the resin composition described in 1 or 2 above.

According to the present invention, it is possible to provide a resin composition that has shielding properties against high-frequency electromagnetic waves and has excellent electrical insulation properties.

The resin composition of the present invention contains at least 100 parts by mass of thermoplastic resin A, 2 to 6 parts by mass of carbon black B, and 0.3 to 4 parts by mass of carbon fiber C, and the total of B and C is 7 parts by mass or less, a volume resistivity of 1 x 10 ¹⁰ to 1 x 10 ¹⁷ Ωcm, a transmission loss of -30 dB or less in a band of 75 to 110 GHz, and an electromagnetic wave absorption rate. is 30% or more.

<Thermoplastic resin A>
As the thermoplastic resin A of the present invention, a crystalline thermoplastic resin or an amorphous thermoplastic resin is suitably used. Examples of the crystalline thermoplastic resin include polyacetal resin (POM), polybutylene terephthalate resin (PBT), polyethylene terephthalate resin (PET), polyphenylene sulfide resin (PPS), polyamide resin (PA), and the like.

Examples of amorphous thermoplastic resins include polycarbonate resin (PC), acrylic resin, styrene resin, cyclic olefin (co)polymer (COP, COC), etc., but polycarbonate resin, cyclic Olefin (co)polymers are preferably used. Thermoplastic resin A of the present invention can be produced by a conventional method.

<Carbon black B>
Carbon black B of the present invention is a carbon black having a primary particle size of 5 to 40 nm and a nitrogen adsorption specific surface area of 100 m ² /g or more. The carbon black can be contained in an amount of 2 to 6 parts by mass based on 100 parts by mass of the thermoplastic resin A.

The primary particle diameter in the present invention is determined by adding carbon black into a solvent, dispersing it with ultrasonic vibration, fixing the dispersed sample on a support membrane, and photographing it with a transmission electron microscope (TEM). The particle size was measured from the diameter. (1000 or more) The primary particle diameter can be determined by the arithmetic average of these values.

As the carbon black B, furnace black, acetylene black, Ketjen black, etc. can be used, and Ketjen black is preferable from the viewpoint of the balance between transmission loss and electromagnetic wave absorption rate.

<Carbon fiber C>
The carbon fiber C of the present invention is a PAN-based, pitch-based, rayon-based carbon fiber, or the like. Further, metal-coated carbon fibers, which are carbon fibers coated with metals such as nickel and copper, can also be used in the present invention. Carbon fiber has a high effect of reflecting electromagnetic waves, but the reflected electromagnetic waves can cause electronic devices to malfunction, so the amount of carbon fiber C added is 0.3 to 4 parts by mass per 100 parts by mass of thermoplastic resin A. , preferably 0.5 to 3 parts by weight, more preferably 1 to 2 parts by weight.

The carbon fiber of the present invention preferably has a tensile elongation at break of at least 1.5%. In order to impart high mechanical properties, the tensile elongation at break is 1.5% or more, more preferably the tensile elongation at break is 1.7% or more, and even more preferably the tensile elongation at break is 1.9% or more. It is better to use carbon fiber. There is no upper limit to the tensile elongation at break of the carbon fibers used in the present invention, but it is generally less than 5%. The diameter of the carbon fiber is preferably 4 to 20 μm, more preferably 5 to 10 μm.

More preferably, the carbon fiber is a PAN-based carbon fiber, which has an excellent balance between strength and elastic modulus. The tensile modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Further, the tensile strength is 2000 MPa to 10000 MPa, preferably 3000 to 8000 MPa.

In addition, these carbon fibers may be surface-treated with silane coupling agents, aluminate coupling agents, titanate coupling agents, etc., or treated with urethane resins, epoxy resins, polyester resins, styrene resins, olefin resins, etc. It may be subjected to a focusing treatment with an amide resin, an acrylic resin, a phenolic polymer, a liquid crystal resin, an alcohol, a water-soluble resin, or the like.

<Inorganic filler>
The molded article of the present invention preferably contains an inorganic filler in order to improve heat resistance and mechanical strength. The type of inorganic filler is not particularly limited as long as it does not impede the effects of the present application, but it is better to avoid conductive substances such as metal fibers and carbon nanotubes as they reduce insulation.For example, glass fibers, glass flakes, Glass beads, silica, talc, mica, etc. are preferred, and glass fiber is particularly preferred. The length of the glass fiber (before being prepared into a composition by melt-kneading or the like) is preferably 1 to 10 mm, and the diameter of the glass fiber is preferably 5 to 20 μm.

In the present invention, the inorganic filler preferably contains 20 to 150 parts by mass, more preferably 30 to 100 parts by mass, based on 100 parts by mass of thermoplastic resin A, from the viewpoint of improving heat resistance and mechanical strength.

<Other ingredients>
In the present invention, in addition to the above-mentioned components, known additives generally added to thermoplastic resins and thermosetting resins, such as burr inhibitors, mold release agents, lubricants, etc. Agents, plasticizers, flame retardants, coloring agents such as dyes and pigments, crystallization promoters, crystal nucleating agents, various antioxidants, heat stabilizers, weathering stabilizers, corrosion inhibitors, etc. may be added.

<Properties of resin composition>
The resin composition of the present invention has a volume resistivity of 1×10 ¹⁰ to 1×10 ¹⁷ Ω·cm, a transmission loss of -30 dB or less in the band of 75 to 110 GHz, and an electromagnetic wave absorption rate of 30% or more. be. These properties can be achieved by adjusting the amounts of carbon black B and carbon fiber C added.

By setting the volume resistivity to 1×10 ¹⁰ to 1×10 ¹⁷ Ω·cm, insulation properties when used in electronic equipment can be obtained. Since the transmission loss is −30 dB or less in the band of 75 to 110 GHz and the electromagnetic wave absorption rate is 30% or more, excellent electromagnetic shielding properties can be obtained.

<Molded product>
A molded article can be produced from the resin composition of the present invention, and the method thereof is not particularly limited, and any known method can be employed. For example, it can be produced by charging a resin composition into an extruder, melting and kneading it into pellets, charging the pellets into an injection molding machine equipped with a predetermined mold, and performing injection molding. The molded article of the present invention is useful for electronic devices and the like.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

<Materials>
A Thermoplastic resin polybutylene terephthalate resin (PBT) manufactured by Polyplastics B1 Carbon black (Ketjen black): ECX manufactured by Lion Specialty Chemicals
B2 Carbon black (furnace black): Mitsubishi Chemical #750B
B3 Carbon black (acetylene black): Denka black granular C manufactured by Denka Corporation Carbon fiber: HTC432 manufactured by Toho Tenax Corporation
Antioxidant: Irganox 1010 manufactured by BASF Japan
Glass fiber: Nippon Electric Glass ECS03T-187

<Preparation of resin composition test piece>
The above materials were dry-blended in the proportions shown in Table 1 below (unit: parts by mass), fed from a hopper to a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) with a 30 mmφ screw, and melted at 250°C. A thermoplastic resin composition in the form of pellets was obtained by kneading, and a test piece was produced by injection molding.

<Evaluation>
The evaluation was performed as follows. The results are shown in Table 1. Note that unless otherwise specified, measurements were performed at 23° C. and in a 50% RH atmosphere.
≪Volume resistivity (Ω・cm)≫
The measurement was carried out in accordance with IEC60093 using an ultra-high resistance meter R8340 (manufactured by Advantest) at an applied voltage of 500V. The test piece was 100 mm x 100 mm x 3 mm.

≪Transmission loss (dB)≫
Measurements were made using the following equipment, measurement method, and frequency. The test piece was 100 mm x 100 mm x 3 mm.
·measuring device:
Horn antenna: FSS-05 (manufactured by HVS)
Dielectric lens: FSS-06 (manufactured by HVS)
Network analyzer: N5227A (manufactured by Keysight Technologies)
Millimeter wave controller: N5261A (manufactured by Keysight Technologies)
・Measurement method: Free space method ・Frequency: 75-110GHz

≪Electromagnetic wave absorption rate≫
It was calculated using the following formula.
Reflection loss | S11 | = reflected wave electromagnetic wave intensity / incident wave electromagnetic wave intensity (amplitude ratio of incident wave and reflected wave)
S11 (dB) = 20log | S11 |
Transmission loss | S21 | = transmitted electromagnetic wave intensity / incident wave electromagnetic wave intensity (amplitude ratio of incident wave and transmitted wave)
S21 (dB) = 20log | S21 |
Electromagnetic wave absorption rate (%) = (1-(|S11|＾ ² + |S21｜＾ ² ))×100
<Evaluation results>

As shown in Table 1, it can be seen that the present invention has excellent electromagnetic shielding properties at high frequencies and high volume resistivity.

Claims (3)

It contains at least 100 parts by mass of thermoplastic resin A, 2 to 6 parts by mass of carbon black B, and 0.3 to 4 parts by mass of carbon fiber C, and the total of the carbon black B and the carbon fiber C is 3. 6 to 7 parts by mass of a resin composition,
The thermoplastic resin A is polybutylene terephthalate resin,
A resin composition having a volume resistivity of 1×10 ¹⁰ to 1×10 ¹⁷ Ω·cm, a transmission loss of -30 dB or less in a band of 75 to 110 GHz, and an electromagnetic wave absorption rate of 30% or more. 2. The resin composition according to claim 1, wherein the carbon black B is Ketjen black. A molded article comprising the resin composition according to claim 1 or 2.