JPH06306201A - Electromagnetic wave shielding resin composition - Google Patents

Abstract

PURPOSE:To prevent shielding effects of an electromagnetic wave shielding resin composition from being deteriorated even in a cold-heat shock environment of repetitive high and low temperatures by blending a thermoplastic resin with carbon back and stainless steel fiber. CONSTITUTION:The electromagnetic wave shielding resin composition comprises 100 pts.wt. thermoplastic resin blended with 1-80 pts.wt. carbon black and 1-40 pts.wt. stainless steel fiber. The shielding effects thereof are not deteriorated even in a cold-heat shock environment of repetitive high and low temperatures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding resin composition having a small decrease in shielding property even when used in an outdoor environment where high and low temperatures are repeated.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, a large number of products equipped with ICs and LSIs have been used in office automation machines, FA control equipment, AV equipment, communication equipment, home appliances, etc. There is a growing concern about malfunctions caused by electromagnetic waves emitted from these devices, and obstacles such as effects on the human body. As a method of preventing the generation of unnecessary electromagnetic waves, measures have been taken to reduce the intensity of electromagnetic waves generated from the circuit itself such as noise filters, ferrite cores, and pass capacitors. However, if such circuit measures are taken, digital signals for high-speed processing may be affected, and shield measures other than circuit measures are often required.

In addition to circuit measures, as a method of preventing electromagnetic interference, the housing of electronic equipment may be plated, zinc sprayed, vacuum deposited, sputtered, conductive coated, or the like to impart the function of blocking electromagnetic waves, or to form a housing. There is a method in which a conductive filler is filled in the resin to block electromagnetic waves. Metal fibers, metal flakes, carbon fibers, metal-plated glass fibers and the like are known as conductive fillers to be mixed in the thermoplastic resin, but among them, stainless fibers having a diameter of about 8 μm are excellent in stretchability. Only a few weight% (approximately 0.2-2% by volume) due to the ability to process very fine fibers of a few microns and excellent corrosion resistance
It is a material superior to other conductive fillers in that it has a shielding effect for practical use.

Attempts have been made to make an electromagnetic wave shielding material by taking advantage of the advantages of the thermoplastic resin and the stainless fiber, but it has been found that there are the following problems. That is, especially when used as a housing for equipment used outdoors,
When exposed to severe operating temperature environments such as repeated low and high temperature environments, the thermal deformation of the thermoplastic resin itself causes the stainless steel fibers to weaken contact, weakening the electrical conductivity and reducing the electromagnetic wave shielding effect. . This tendency is remarkable especially when it is attempted to maintain the electromagnetic wave shielding property while keeping the weight and cost down.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, an electromagnetic wave shielding resin composition obtained by blending a thermoplastic resin with stainless fiber has a shielding effect even under a high temperature and low temperature repeated thermal shock environment. It is intended to maintain excellent mechanical properties without deteriorating.

[0006]

The electromagnetic wave shielding resin composition according to the present invention comprises (A) 100 parts by weight of a thermoplastic resin, (B) 1 to 80 parts by weight of carbon black and (C) 1 to 40 parts by weight. Part of the stainless fiber is mixed. In addition, various inorganic fillers can be blended with the thermoplastic resin composition of the present invention. As the inorganic filler to be blended, glass fiber, fibrous inorganic filler such as carbon fiber, silicate compound such as graphite, mica, talc, powder of barium sulfate, calcium carbonate, potassium titanate, magnesium oxide, zinc oxide, etc. There is a body-shaped inorganic filler. The fibrous inorganic filler has an equivalent diameter of 4 to 1
It is preferably 5 μm and D / L is 0.0004 to 0.02. The powdery inorganic filler has an average particle size of 0.5 to 20 μm.
m is preferable.

When the inorganic filler is compounded, the compounding amount thereof is 10 to 90 parts by weight, preferably 20 to 60 parts by weight, relative to 100 parts by weight of the thermoplastic resin, and the compounding amount of the inorganic filler is 20. If it is less than 10 parts by weight, the mechanical properties such as flexural modulus and tensile strength will be deteriorated, which is not preferable, and conversely 60 parts by weight, especially 9 parts by weight.
If the amount is more than 0 parts by weight, the specific gravity becomes too large, and the impact strength deteriorates sharply, which is not preferable. The carbon black used in the present invention does not have to be a conductive carbon black, but is a rubber carbon black, an acetylene carbon black, a channel carbon black,
Furnace carbon black, thermal carbon black, lamp black and the like can be used. In particular,
A nitrogen adsorption specific surface area of 20 to 300 is advantageous in terms of cost and is preferable because the reduction of the shielding effect in a cold shock environment is reduced.

The amount of carbon black compounded is 1 to 80 parts by weight, preferably 2 to 50 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the blending amount of carbon black is less than 2 parts by weight, particularly less than 1 part by weight, the electromagnetic wave shielding property is deteriorated in a repeated environment of low temperature and high temperature, which is not preferable. It is not preferable because the strength decreases. .
The stainless fiber used in the present invention has a D / L of 0.
0005 to 0.008 and an equivalent diameter of 2 to 15 μm are preferable from the viewpoint of fiber dispersibility and shielding properties. The blending amount of the stainless fiber is 1 to 40 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the thermoplastic resin. Furthermore, the total blending amount of carbon black and stainless fiber with respect to 100 parts by weight of the thermoplastic resin is 10
It is preferably 0 parts by weight or less.

The resin composition of the present invention can be manufactured by any method. For example, it is possible to prepare pellets of a thermoplastic resin containing an inorganic filler and carbon black and a masterbatch of stainless fibers, mix them in a predetermined amount, and form a molded product by injection molding, extrusion molding, or the like. it can. The master batch of stainless fibers is made by bundling 1000 to 35,000 stainless fibers and impregnating the bundle with a thermoplastic resin such as thermoplastic polyester.
Further, the periphery of the fiber bundle is coated with a thermoplastic resin such as thermoplastic polyester or polyethylene wax, and the weight ratio of stainless fiber / thermoplastic resin is 95/5 to 60/4.
0 strands can be formed and cut into 2 to 6 mm to be supplied as a columnar member.

Further, a pellet-like mixture prepared by preliminarily blending a high concentration of carbon black in a thermoplastic resin (so-called color masterbatch) and a predetermined amount of both of the thermoplastic resins, and melt-mixing with an extruder. It is also possible to mix the master batch of the stainless fiber and to form a molded product by injection molding, extrusion molding or the like. You may add additives, such as a stabilizer, an antioxidant, a copper damage inhibitor, a flame retardant, a mold release agent, a dye, and a crystallization inhibitor, to the resin composition of this invention.

[0011]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 100 parts by weight of PET resin (Mitsui Pet Resin Co., Ltd., trade name Mitsuipet J120) was added to carbon black (Mitsubishi Kasei Co., Ltd., trade name Mitsubishi Carbon 30).
33 parts by weight was previously stirred for 10 minutes using a Henschel mixer. The obtained mixture was extruded (screw diameter 5
0 mm, L / D = 32, resin temperature = 260 ° C.) was melt-mixed, pelletized and used as a carbon black masterbatch.

Glass fiber and mineral reinforced PE
T resin (manufactured by DuPont Japan Limited, trade name Rinite R935-glass fiber addition amount 15% by weight,
The amount of mica added is 20% by weight), 12.6 parts by weight of the above carbon black masterbatch, and 12000 stainless steel fibers having a diameter of 8 μm and a convergent number of 12000 (Bekaert NVSA, trade name Beki). -Sh
(Yellow BU) 75% by weight and thermoplastic resin 25% by weight (manufactured by Toyo Ink Mfg. Co., Ltd., trade name Rio Conduct EMI-SGR-30)
13.5 parts by weight of 434) and add 10 by tumbler.
Dry blended for minutes.

Using the pellet-shaped blend thus obtained, a test piece having a thickness of 3 mm and a length of 150 mm was prepared at a resin temperature of 260 ° C. using a 7 ounce injection molding machine (IS80A) manufactured by Toshiba Machine. The shield effect of the obtained test piece was measured by Advantest Corp. Spectrum Analyzer T
R4172 and shield measuring jig TR17301A
Was measured using. Further, the volume resistivity was measured using Wheatstone Bridge TYPE2759 manufactured by Yokogawa Electric Corporation. Next, the measured test piece was placed in Tabai Espec's thermal shock tester TSR-103 at −30 ° C. (30 minutes), +12.
After repeatedly standing for 10 cycles in an environment of 0 ° C. (30 minutes), the shield effect and the volume resistivity were measured in the same manner.

Further, subsequently, 90 cycles (total of 100
(Cycle) The same measurement was carried out after leaving in the thermal shock tester. Continuing further, 400 cycles (total 500
(Cycle) The same measurement was carried out after leaving in the thermal shock tester. Further on, 500 cycles (total 100
(0 cycle) After leaving in the thermal shock tester, the same measurement was performed. Table 1 shows the measurement results. Examples 2 to 6 The contents of the composition of Example 1 were changed as shown in Table 1, and test pieces were prepared and measured in the same manner. Table 1 shows the measurement results.

[0015]

[Table 1]

Comparative Examples 1 to 4 When the blending amount of carbon black, the blending amount of stainless fiber, etc., exceeds the scope of the claims, a mixture having the blending contents shown in Table 2 was prepared in the same manner as in Example 1, Each measurement was performed. The measurement results are shown in Table 2.

[0017]

[Table 2]

Example 7 95% by weight of glass fiber reinforced PBT resin (manufactured by DuPont Japan Ltd., trade name: Rinite RE7003-glass fiber addition amount: 30% by weight), carbon black (manufactured by Mitsubishi Kasei Co., Ltd., trade name) 5.0% by weight of Mitsubishi Carbon 30) was previously stirred for 10 minutes using a Henschel mixer. The obtained mixture is an extruder (screw diameter 50 mm, L / D = 32, resin temperature = 2
50 ° C.) was melt mixed and pelletized. With respect to 100 parts by weight of the pellet-like mixture, stainless fibers having a diameter of 8 μm and a convergent number of 12,000 (Bekaert NV
S. 12.0 A stainless steel masterbatch (manufactured by Toyo Ink Mfg. Co., Ltd., trade name Rio Conduct EMI-SGR-30434) consisting of 75% by weight of Company A, trade name Beki-shield BU) and 25% by weight of thermoplastic resin.
Parts by weight were added and dry blended for 10 minutes with a tumbler. Using the pellet-shaped blend thus obtained, a test piece having a thickness of 3 mm and a length of 150 mm was prepared at a resin temperature of 250 ° C. using a 7 ounce injection molding machine (IS80A) manufactured by Toshiba Machine.

The shield effect of the obtained test piece was measured by ADVANTEST CORPORATION spectrum analyzer TR417.
2 and shield measurement jig TR17301A. Further, the volume resistivity was measured using Wheatstone Bridge TYPE2759 manufactured by Yokogawa Electric Corporation. Next, the measured test piece is used as a thermal shock tester T manufactured by Tabai Espec.
-30 ° C (30 minutes), + 120 ° C (3
After repeatedly standing for 10 cycles in an environment of 0 minutes), the shield effect and the volume resistivity were measured in the same manner. Further, subsequently, after leaving it in the thermal shock tester for 90 cycles (100 cycles in total), the same measurement was performed.

Further, subsequently, 400 cycles (50 in total)
(0 cycle) After leaving in the thermal shock tester, the same measurement was performed. Continuing further, 500 cycles (total 10
(00 cycle) After leaving it in the thermal shock tester, the same measurement was performed. Table 3 shows the measurement results. Examples 8 to 11 The content of Example 7 was changed as shown in Table 3, and test pieces were prepared and measured in the same manner. Table 3 shows the measurement results. In addition, in Examples 10 and 11, the test piece after the initial measurement was used as a thermal shock tester TS manufactured by Tabai Espec.
-30 ° C (30 minutes), + 80 ° C (30 minutes in R-103
After repeatedly leaving it for a predetermined number of times in the environment of (1), the shield effect and the volume resistance value were measured in the same manner. Table 3 shows the measurement results.

[0021]

[Table 3]

Comparative Examples 5 to 9 When the blending amount of carbon black, the blending amount of stainless fiber, etc. exceeds the scope of the claims, a mixture having the blending content as shown in Table 4 was prepared in the same manner as in Example 7, Each measurement was performed. The measurement results are shown in Table 4.

[0023]

[Table 4]

[0024]

The electromagnetic wave shielding resin composition of the present invention has a high electromagnetic wave shielding effect of 42 dB or more in the initial value with respect to electromagnetic waves in the range of several kHz to 2 GHz.
Moreover, this shielding effect is from -30 ° C to 120 ° C (AB
In the case of the S-based resin, the retention rate of the shielding effect is greatly improved when the low temperature and high temperature heat cycles of -30 ° C. to + 80 ° C.) are repeated, as compared with the case where the carbon black is not added, and the electromagnetic wave shielding resin of the present invention Even if the composition is used in an outdoor environment, the electromagnetic wave shielding effect can be maintained for a long time.

Further, since the stainless fiber content is small, not only can the weight be reduced, but also because the molten resin has a good fluidity, the moldability is good, and a molded product having a complicated shape can be manufactured.

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Claims (1)

[Claims] 1. A blend of 100 parts by weight of a thermoplastic resin (A) with 1 to 80 parts by weight of carbon black and (C) 1 to 40 parts by weight of a stainless fiber. Electromagnetic wave shielding resin composition.