JPH0666559B2 - Polyamide resin molding material for electromagnetic wave shielding - Google Patents

Description

The present invention relates to a polyamide resin molding material having a high electromagnetic wave shielding effect.

[Conventional technology]

2. Description of the Related Art Recently, with the development of electronic devices, problems relating to the electronic environment and the electromagnetic environment around the electronic device are emerging. These are due to the increase in the number of devices with built-in microcomputers, etc., due to the development of large-scale integrated circuit technology such as VLSI, and the electronic device housings having mass productivity, economical efficiency,
It is thought that this is because the electromagnetic environment in which electronic devices are placed has become diversified due to the fact that it is made of plastic from the viewpoint of light weight. These electronic devices (computers, office equipment, home appliances, etc.) have a low signal level due to high integration, and are therefore susceptible to noise.

On the other hand, since the elements and electronic circuits in these devices have an oscillation function by themselves, they emit noise to the outside and cause electromagnetic interference. As a measure against these problems, there is an improvement in an electronic circuit that is not affected by noise, but it is still necessary to give an electronic wave shielding effect to a casing portion surrounding these electronic devices. .

Therefore, many measures have been taken to impart electromagnetic wave shielding properties to the synthetic resin that is the material of the housing.

These measures can be broadly divided into plating, painting, thermal spraying, foil bonding, etc. on the surface of plastic molded products.
There are a method of coating a conductive film by post-processing and a method of forming a composite material by mixing a conductive filler in plastic.

However, in the former method, the conductive film may peel off or fall off due to drop impact, aging, heat shock, etc.
In addition to the deterioration of the electromagnetic wave shielding effect, the peeled pieces may fall onto the electronic circuit, causing damage to the equipment, electric shock, fire, or the like.

On the other hand, in the latter method, as the conductive filler, graphite, carbon black, carbon fiber, silver powder, copper powder, nickel powder, stainless powder, stainless fiber, aluminum flakes, aluminum ribbon, aluminum fiber,
Brass fiber, aluminum-coated glass fiber, nickel-coated glass fiber, etc. have been studied, but if the mixing ratio is increased until a sufficient electromagnetic wave shielding property is obtained, the mechanical strength of the molded product often decreases, and synthetic resin is also used. It is not easy to uniformly mix them with each other to have a sufficient electromagnetic wave shielding effect.

Therefore, recently, fibers such as stainless steel, brass, and copper, which are effective in a small amount, have been mainly studied, but those containing these metal fibers are not suitable for the dispersion of resistance value and the moldability due to the orientation of the fibers during molding. Bring about the deterioration of.

[Problems to be solved by the invention]

It is an object of the present invention to obtain a molding material having an electromagnetic wave shielding effect in a wide frequency band, which eliminates the drawbacks of the prior art.

[Means for solving problems]

As a result of intensive studies, the present inventors achieved the above object by mixing highly conductive glass fiber, carbon black and graphite into a linear aliphatic polyamide to form a composite.

Thus, the present invention comprises 30 to 150 parts by weight of highly conductive glass fiber, 5 to 20 parts by weight of carbon black, and 5 to 20 parts by weight of graphite with respect to 100 parts by weight of linear aliphatic polyamide. It is a polyamide resin molding material for electromagnetic wave shielding.

Examples of the linear aliphatic polyamide used in the present invention include nylon 66, nylon 6, nylon 12 and the like.

The highly conductive glass fiber used in the present invention, electroless plating on the glass fiber surface, copper by vapor deposition, aluminum,
Although it is coated with a simple substance such as nickel or a composite, if the blending amount exceeds the above range, the extrusion workability decreases, and if it is less than this range, sufficient electromagnetic wave shielding properties cannot be obtained.

The carbon black used in the present invention includes thermal black, channel black, acetylene black,
Ketjen black, furnace black and the like can be used, and furnace black is particularly preferable, but if the compounding amount exceeds the above range, the extrusion workability decreases, and if it is less than this range, sufficient electromagnetic wave shielding properties cannot be obtained.

The graphite used in the present invention may be either natural or artificial, and may be in the form of scales or lumps, and natural scale-like graphite is particularly preferable, but if the content exceeds the above range, the extrusion workability is If it falls below this range, sufficient electromagnetic wave shielding properties cannot be obtained.

Mixing of the components described above can be carried out by various methods, using an ordinary vent type extruder or a similar device, melt kneading at a temperature 5 to 50 ℃ higher than the melting point of the polyamide resin composition. The method of doing is suitable.

The polyamide resin molding material of the present invention is a conventional additive, for example, a stabilizer or an inhibitor against deterioration due to oxidation, heat, ultraviolet rays, etc., a nucleating agent, a plasticizer, a flame retardant, an antistatic agent,
Lubricants and the like can be added in one kind or in two or more kinds as long as the physical properties of the composition of the present invention are not adversely affected.

[Operation and effect of the invention]

The polyamide resin molding material of the present invention has mechanical properties such as tensile strength, tensile modulus, flexural modulus, etc., thermal properties such as heat deformation temperature, etc., and excellent chemical resistance. In addition, it has an electromagnetic wave shielding effect in a wide frequency band due to the synergistic action of the highly conductive glass fiber, carbon black and graphite. Therefore, the polyamide resin molding material of the present invention is extremely useful as a material for a casing portion surrounding an electronic device.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

In addition, "part" in an Example represents a weight part. Moreover, the physical property test
The procedure was as follows.

(1) Tensile strength: ASTM D638 (2) Tensile elongation: ASTM D638 (3) Tensile modulus: ASTM D638 (4) Bending strength: ASTM D790 (5) Bending modulus: ASTM D790 (6) Izod impact strength: ASTM D256 (7) Heat distortion temperature: ASTM D648 (8) Volume resistivity: ASTM D257 (9) Electromagnetic shielding property: Advantest method Example 1 Nylon 66 100 parts, fiber length 3 to 6 mm, specific resistance value 10 ^-3 to 10
^-5 Ω · cm metal-coated glass fiber (Asahi Fiber Glass Co., Ltd., Emitech) 106 parts, natural scaly graphite powder (Nippon Graphite Co., Ltd., special CP) 15 parts and highly conductive furnace black (Cabot Corporation) Manufactured by Vulcan XC-72) using a single-screw vent type extruder, melt kneading at a cylinder temperature of 270 ° C. and extruding into strands, cooling in a water bath, cutting into pellets, and drying to obtain polyamide resin. A composition was obtained.

This pellet is resin temperature 275 ℃, mold temperature 75 ℃, injection and holding time 5 seconds, cooling time 20 seconds, injection pressure 500-600kg /
A test piece was obtained by injection molding under the condition of cm ² , and was subjected to a physical property test.

The results are as shown in Table 1.

Examples 2 to 6 As described in Table 1, except that the types or mixing ratios of the constituents were changed (however, the resin temperature at the time of injection molding of the test pieces in Examples 4 to 6 was 240 ° C). Was carried out in the same manner as in Example 1.

The results were as shown in Table 1.

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Claims (1)

[Claims] 1. An electromagnetic wave shield comprising 100 parts by weight of a linear aliphatic polyamide and 30 to 150 parts by weight of highly conductive glass fiber, 5 to 20 parts by weight of carbon black and 5 to 20 parts by weight of graphite. Polyamide resin molding material.