JPS6213444A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To provide an electrically conductive resin compsn. which gives moldings having good surface conductivity and is suitable for use as an electromagnetic wave shielding molding material, by incorporating metallic fiber and carbon fiber as essential ingredients in a synthetic resin. CONSTITUTION:Metallic fiber (e.g. aluminum fiber or statinless fiber), carbon fiber and optionally, carbon black (e.g. acetylene black) and/or graphite are incorporated in a synthetic resin such as polybutylene terephthalate or nylon 6 to obtain the desired electrically conductive resin compsn. 20-60wt% metallic fiber, 5-20wt% carbon fiber, 5-30wt% carbon black and 3-15wt% graphite are added. The compsn. is suitable for use as an electromagnetic wave shielding molding material for a cable connector.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a conductive resin composition used as an electromagnetic shielding molding material for cable connectors, etc., and in particular, after molding, it has a good property on the surface of the molded product. The present invention relates to a conductive resin composition that imparts surface electrical conductivity.

[Prior art and its problems]

With the recent progress in OA or FA, digital devices such as computers and word processors have become widespread. With this trend, high frequency noise generated from inside these devices has become a problem, causing electromagnetic interference (EMI) to the device housing or cable connector.
Countermeasures have begun to be taken.

FIG. 1 is a perspective view of one embodiment of a conventional cable connector, designated by the designation number A.

This cable connector A is connector bin 1, l...l
an insulating member 2 into which is inserted, and an exterior member 3 that covers this
It is composed of. 4 is each connector pin 1, ■...
・It is a bundle of R wires connected to l.

As a countermeasure against electromagnetic interference with this type of cable connector A,
The exterior member 3 may be formed of a metal cover made by sheet metal processing, or
It has been put into practical use to intentionally improve the electrical conductivity of the surface of the exterior member 30, such as by applying metal plating to the exterior member 3 made of plastic. This is because it is necessary to ground the joint end surface of the connector exterior member 3 in order to prevent conduction noise generated from inside the digital device from leaking to the cable connected to the outside.

However, the sheet metal covered metal cover described above is difficult to handle for connectors with complex shapes, and metal plating requires chemical plating because the base material is plastic, which requires pretreatment and is expensive. It is also unfavorable from this point of view.

In order to improve these drawbacks, the exterior member 3 is made by injection molding using an EMI shielding compound containing a metal filler instead of the sheet metal-processed metal cover or metal-plated plastic described above. Measures are being considered, such as forming an insulating member and an exterior member using the aforementioned OEMI shielding compound into one piece by double molding.

As the above-mentioned EMI shielding compound, one filled with metal fibers is known, but with this, a skin layer is formed on the surface of the injection molded product, making it impossible to obtain surface electrical conductivity. It is not possible to ground from the ground.

[Purpose of the invention]

An object of the present invention is to provide a conductive resin composition used as an electromagnetic shielding molding material for cable connectors, etc., which imparts good surface electrical conductivity to the surface of the molded product after molding, and provides the above-mentioned The object of the present invention is to provide a conductive resin composition that improves the drawbacks of known techniques.

[Key points of the invention]

In order to achieve the above-mentioned object, according to the present invention, a synthetic resin contains metal fibers and carbon fibers, and further contains one or both of carbon black and graphite as necessary. It is characterized by imparting good surface electrical conductivity to the surface of the molded product after molding.

The above-mentioned synthetic resins according to the present invention include polybutylene terephthalate, nylon-6, and nylon-6, which have a high heat resistance temperature.
．． Any engineering plus material such as 6.6, nylon 12, polycarbonate, etc. may be used, and polybutylene terephthalate and nylon 6.6, which have a good balance of chemical resistance, strength, and heat distortion temperature, are particularly preferred.

Further, as the metal fiber, any fibers such as aluminum, cast iron, steel, stainless steel, brass, etc. obtained by the chatter vibration cutting method, or stainless steel fiber (SUS3161.5US304) obtained by the drawing method may be used. Fiber diameters of 6 μm to 70 μm can be used, but are preferably in the range of 8 μm to 50 μm. Furthermore, fiber lengths of 0.8 m to 9.0 m can be used, but preferably 1.0 m to 6.0 m. It is in the ON range.

The amount of the metal fibers added is 20 to 60% by weight for those obtained by the chatter vibration cutting method, but is preferably in the range of 25 to 45% by weight. 5 to 30% by weight for stainless steel fibers obtained by the pultrusion method
However, it is preferably in the range of 5 to 15 severe.

Furthermore, the carbon fibers may be either bread yarn or pinch yarn (and their properties may be either bound or non-bound. The fiber diameter is preferably 5 to 30 μm, but preferably 5 to 15 μm. The fiber length is in the range of 9.2 mm to 9.0 mm, preferably 0.2 to 1.5 am in the case of non-bound fibers, and 3 to 9.0 mm in the case of bundled fibers.

As for the pitch yarn, it is preferable that the fiber surface be graphitized by firing at about 2000° C. after spinning. The amount added is 5 to 20% by weight, preferably 5 to 15% by weight.

The present invention comprises the above-mentioned synthetic resin containing the above-mentioned metal fibers and carbon fibers, and if necessary, one or both of carbon black and graphite may be added to further improve the effects of the present invention. be able to. Examples of the carbon black mentioned above include furnace black, acetylene black, channel black, etc., and the amount thereof in the composition is 5 to 30% by weight, preferably 5 to 20% by weight. In addition, the graphite may be either naturally produced or artificial, and its particle size may be 0.5 to 80 μm, and its content is 3 to 15% by weight in the composition, but preferably It ranges from 3 to 10% by weight.

In the present invention, after blending the above-mentioned components in a desired ratio, they are kneaded, extruded, and granulated using an extruder to form pellets with a diameter of 4 cm and a length of about 31 mm, which are then processed using an injection molding machine to form pellets into desired proportions. It is used after being molded into a shape. The obtained molded product has good surface conductivity and is used as an electromagnetic shielding molding material, for example, as a molding material for the exterior member 3 of the cable connector A as shown in the first figure.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained with reference to Examples.

Blend each sample with the blending ratio shown in Table 1 using a 201 super mixer, then knead, extrude, and granulate each compound using a 30Φ Tsuru bent type extruder to form round pellets with a diameter of 4 m and a length of 3 ms. . Using the obtained pellets, 3.5
50x25x at a temperature of 270℃ by ounce injection molding machine
2. Form into a (fi) plate.

The surface resistance of the molded product is measured by checking the conductivity of the molded product surface using a tester, and the volume resistance is measured by scraping the end surface of the molded plate with a knife to expose the metal fibers in the molded product. Silver paste was applied to form an electrode, and the volume resistivity was measured by calculating the resistance value between the electrodes, taking into account the dimensions of the molded product. For impact strength, a 10x60x2 (am) test piece was cut out from the molded product and a predetermined notch was cut to prepare a test piece for an impact tester. Impact strength was measured using this test piece. The results are shown in Table-■.

From Table I, samples 1ml to 5 (invention) have better surface conductivity than samples 6 to 9 (comparative examples), and their volume resistivity is at a level that can be expected to have an EM shielding effect. It can be seen that it has sufficient performance for connectors in terms of impact strength as well.

〔Effect of the invention〕

As described above, the conductive resin composition according to the present invention is made by making a synthetic resin contain metal fibers and carbon fibers, and further containing one or both of carbon fibers, silica, and graphite as necessary. Therefore, after molding, good surface conductivity is imparted to the surface of the molded product, and the composition is suitable as an electromagnetic shielding molding material for cable connectors and the like.

[Brief explanation of drawings]

FIG. 1 shows a perspective view of an example of an integrated cable connector to which the composition of the present invention is applied. A... Cable connector, 1... Connector pin 2... Insulating member, 3... Exterior member, 4... Bundle of conducting wires Patent applicant: Dainichiseika Kogyo Co., Ltd. June 6, 1961, Michibe Uga, Commissioner of the Patent Office1, Indication of the case, Patent Application No. 152638 of 19852, Name of the invention, Conductive resin composition 3, Relationship with the person making the amendment Patent application Person Address: 7-6, Nihonbashi Bakuro-cho, Chuo-ku, Tokyo Name (282) Dainichiseika Kogyo Co., Ltd. 4, Agent

Claims (1)

[Claims] The synthetic resin contains metal fibers and carbon fibers, and if necessary, one or both of carbon black and graphite is added to the synthetic resin, thereby ensuring good surface electrical conductivity on the surface of the molded product after molding. A conductive resin composition used as an electromagnetic shield molding material, which is characterized by imparting properties.