JPS5922710A - Manufacture of electroconductive molding material - Google Patents

Abstract

PURPOSE:To obtain electroconductive molding material, which is favorably plasticized by uniformly dispersing carbon fiber filler and is excellent in shielding electromagnetic wave of electronic equipments, by a method wherein a bundle of carbon fiber filaments coated with metal film or the like are concentrically and uniformly covered with synthetic resin and then cut into pieces. CONSTITUTION:A bundle of carbon fiber filaments 3 (preferably the number of filaments is 3,000-30,000), the surface of each of which is coated with metal plating or metal depositing, are concentrically covered as electroconductive filler with synthetic resin 1 as matrix in the thickess, for example, 2-5 times the diameter of the bundle of carbon fiber filaments 3. Next, the resin-coated bundle is cut in uniform lengths, preferably in 3-10mm., so as to pelletize in order to obtain the objective molding material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a conductive molding material having an excellent electromagnetic wave shielding effect.

[Technical background of the invention and its problems]

BACKGROUND ART With the development of electronic devices, electronic devices may malfunction due to the influence of electromagnetic waves, and in order to prevent this, there is a demand for measures for shielding electromagnetic waves in the enclosures of these electronic devices. The current prevention methods, coating with conductive paint, film formation by metal spraying, adhesion of aluminum foil, metal coating processing by plating, etc. are the mainstream for spudder and FRC, and conductive materials are mixed into the molding material. There are not many examples of manufacturing enclosures using this method.

The method of mixing metal foils and foils according to molding requirements, which has been attempted since then, involves preparing pre-made metal fibers or metal foil powder to make it compatible with the resin, as shown in the first factor. After processing, it is mixed with a resin using a mixer, extruded using a granulator such as an extrusion machine or a kneader, and processed into pellets to be used as a molding material. In this case, the dispersion of the conductive filler and the resin serving as the matrix require a lot of time and a high degree of skill to uniformly mix the conductive filler due to the relationship between its original shape, size, and specific gravity.

The most preferable shape of the conductive filler to be mixed into the molding material is a nonwoven fabric with a large aspect ratio (the ratio of fiber strain to length), a dispersed layered conductive layer, and a spongy conductive layer. The purpose of this is to create a state in which electromagnetic waves are less permeable. Therefore, the development of molding materials is desired.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a molding material having an excellent electromagnetic wave shielding effect, in which carbon fiber filler is uniformly dispersed and plasticization is performed well.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention has been made as a result of intensive studies and has been made by using a conductive filler as a continuous bundle of filaments made of carbon fibers whose surfaces are coated with metal plating or metal vapor deposition. This method of producing a conductive molding material is characterized in that the conductive filler is uniformly coated with a synthetic resin serving as a matrix so that the conductive filler forms a central portion, and then the conductive molding material is cut into an arbitrary length.

The carbon fiber filament used as the conductive filler of the present invention is continuous and long and has a circular cross-sectional shape.
~10 μΦ, but the cross-sectional shape is not necessarily circular, and may be any other shape, and is not particularly limited to the shape.

As a filament bundle, the number of filaments is 3,000~
30,000 is desirable.

When the number of filaments is less than 3,000, the shielding effect is low;
Also 30. Exceeding OOO' is undesirable because the cost increases. Therefore, it is limited to the above range. The synthetic resin that covers the filament bundle in the center is often an easily moldable thermoplastic resin, but thermosetting resins such as epoxy resins and unsaturated polyester resins can also be used.

As a method for coating the carbon fiber filament bundle with resin, well-known methods such as extrusion and pultrusion, which are used for coating electric wires, etc., can be sufficiently employed.

By coating the synthetic resin and cutting it into arbitrary lengths, for example, 3 to 10 pieces, a conductive molding material pelletized efficiently and homogeneously can be obtained. At this time, the thickness of the synthetic resin coating is preferably about 2 to 5 times the diameter of the carbon fiber Neurament bundle.

[Embodiments of the invention]

The present invention will be specifically explained using drawings.

As shown in Figure 2, nickel-plated carbon fiber filler (filament diameter 7 p, number of filaments 12
,000 pieces) were extruded and coated with ABS resin as a conductive filler. Next, the pellets were uniformly cut into pellets of approximately 3φ×8 blades to obtain a molding material. In the cross section of this molding material, as shown in FIG. 3C, the carbon fiber filler was located approximately at the center of the pellet. This molding material was injection molded to form a sheet of 2001 x 200" x 3t, and the electromagnetic wave shielding effect was measured.
There was an effect of 30 to 65 dB in the MH7 region.

〔Effect of the invention〕

The molding material produced by the production method of the present invention has a uniform shape and a uniform pellet, and the carbon fiber filler is dispersed among the pieces.When a homogeneous pellet is plasticized by molding, it is uniformly unbundled and carbon fiber filaments are formed. The plasticization and dispersion of
It is an excellent product that has a sufficient electromagnetic wave shielding effect.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing a conventional manufacturing process for a conductive molding material, FIG. 2 is a flow sheet showing an example of the manufacturing method of the present invention, and FIG. 6 is a cross-sectional view of a pellet. A-B... Pele by conventional method, I-, C...
Berets according to the present invention, 1... resin, 2... scales 1
Granular, short fiber filler, 6...carbon fiber filler (filament bundle).

Claims (1)

[Claims] 1 Synthesis of filaments made of carbon fibers whose surfaces are coated with metal plating or metal vapor deposition, and in which a continuous bundle is used as a conductive filler, and the conductive filler is in the center to form a matrix or a matrix. 7. A method for producing a conductive molding material, which comprises uniformly coating the resin, and then cutting the material into a desired length.