JPS6286053A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. having excellent electrical conductivity and electromagnetic wave shielding properties and suitable for use in the production of housings for electrical and electronic appliance, by cutting specified long metallic fibers and blending it with a thermoplastic resin. CONSTITUTION:A metallic wire having a diameter of 1-20mm. obtd. by cold- drawing at least one member selected from among iron, cobalt, nickel, copper and aluminum is cut into a long metallic fiber having a fiber diameter of 10-150mu, which is then cut into a metallic fiber (B) having a fiber length of 15mm or below. 100pts.wt. thermoplastic resin (A) such as a polyamide, a polyes ter, a polyolefin, a polyacetal, an ABS resin, etc. is premixed with 100-500pts. wt. metallic fiber (B) and the mixture is meet-kneaded with a single- or twin- screw extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conductive resin composition having excellent electromagnetic shielding properties suitable for electrical appliances, housings of electronic devices, and the like.

(Prior Art) With the rapid spread of office automation equipment in recent years, problems such as malfunctions and loss of magnetically recorded information due to unnecessary magnetic waves emitted from these equipment are becoming a problem.

As a countermeasure for this, is there a metal plate on the casing of the extractor? Electromagnetic wave shielding is performed using conductive resin that imparts conductivity to the tree's eyebrows themselves. In particular, conductive resins have excellent moldability, so conventionally those blended with metal powder, primary carbon, or metal fibers are used.In particular, those blended with metal fibers are Many types of metal fibers are used because they can provide excellent electromagnetic shielding properties with a relatively small amount of fiber, and there is little deterioration in mechanical properties, unlike when metal powder or carbon powder is mixed. .

For example, in JP-A-55-152743 ``Conductive resin composition'', a conductive substance such as metal is attached several μm around a low hardness copper wire, aluminum wire, or fiber such as glass. are listed as the best. In addition, in JP-A-58-150203 ``Plastic products with conductive fibers'', ultra-fine metal fibers produced by wire drawing are cited as a suitable material, and JP-A-58-784
In Publication No. 99 "Resin material for electromagnetic shielding",
No. 4-161911 discloses the use of short metal fibers by the so-called chatter vibration cutting method, which is proposed as a "method for manufacturing short metal fibers."

(Problems to be Solved by the Invention) These metal fiber composite materials that have been conventionally used as conductive fillers for thermoplastic resins are pl? : When blended with plastic resin, breakage during melt-kneading or molding is significant, and injection molding processing methods in particular have the disadvantage that sufficient electromagnetic shielding effects cannot be obtained; It is desirable to reuse the sprues, runners, etc. that are generated.

In this case as well, it was difficult because the electromagnetic shielding effect deteriorated due to the breakage of the metal fibers.

(Means for Solving the Problems) The present inventors have completed the present invention as a result of intensive research to improve the drawbacks of conventional techniques.

That is, the present invention is a conductive resin composition prepared by cutting long metal fibers obtained by cutting a metal wire and then blending the fibers into a thermoplastic resin.

The metal wire used in the present invention is a metal material that has a circular cross section and is continuous in the longitudinal direction.

Wires with a diameter of 1 to 20 m are used, and those processed into materials by cold working are particularly preferred.

The material of the metal wire is not particularly limited as long as it has conductivity, but it preferably contains at least one of iron, cobalt, nickel, copper, and aluminum, and particularly preferably contains iron. 1 for cutting metal wire
For example, it is sufficient to continuously feed the metal wire in the longitudinal direction while pressing the cutting blade against the metal wire. At this time, if a roll is used to feed the metal wire, long metal fibers can be produced more efficiently.

The fiber diameter of the metal long fiber obtained by cutting is usually 200 μm or less, particularly preferably 10 to 150 μm.
Use the one.

The long metal fibers may be cut with a cutter having a cutting blade, or may be crushed and shredded with a mixer having high-speed rotary blades such as a Henschel mixer, a hammer mill, or the like. The fiber length after cutting is as follows when blended with thermoplastic resin:
As long as it has a shape that allows for uniform dispersion and fluidity that allows injection molding, there are no particular restrictions, but it is usually 15 m or less, preferably
Use one with a size of 1 to 10M5.

The thermoplastic resin used in the present invention may be one that is generally subjected to injection molding, but particularly preferred ones include polyamide, polyester, polyolefin, polyphenylene oxide, polyaceter,
Mention may be made of polycarbonate and AB8 resin.

The amount of metal fibers in the conductive resin composition according to the present invention is not particularly limited as long as it maintains melt fluidity that allows injection molding and sufficient electromagnetic shielding properties, but it is preferred. is 10 parts by weight for 100 parts by weight of thermoplastic resin
The amount is 0 to 500 parts by weight.

The blending of metal fibers into the thermoplastic resin may be carried out at any stage up to the final molded product. For example, after premixing the thermoplastic resin and the metal fibers at a predetermined ratio, uniaxial or The mixture may be melt-kneaded using a multi-screw extruder and then subjected to molding, or a premixed mixture may be directly subjected to molding.

(Effects of the Invention) Is the conductive resin composition according to the present invention blended with conventional metal fibers after melt-kneading and molding? It has excellent conductivity and electromagnetic shielding properties that cannot be obtained with five-conductor resin compositions, and even if unnecessary parts such as sprues and runners that are generated during molding are remolded and used, the conductivity and electromagnetic shielding properties are maintained. It has the advantage that there is little deterioration in sexual performance.

A more detailed explanation will be given below using examples.

Examples 1 to 5 Low carbon steel (JIS standard 812C) was drawn at room temperature to produce a wire with a wire diameter of 2.9 fl, and this wire was further cut to obtain a metal long fiber rule with a wire diameter of 50 μm. Ta. Next, this metal long fiber was cut into an average fiber length of 3 cm.

The obtained metal fibers were blended with nylon 6 resin pellets in the proportions shown in Table 1, premixed using a Henschel mixer, and then melted and kneaded using a twin-screw extruder to ensure uniformity of the resin and metal fibers. A mixed pellet was obtained. Next, this pellet was injection molded and various physical properties were measured. The results are also shown in Table-1.

Table-1 value for the surface boundary component used.

Comparative examples 1 to 5 Uses low carbon steel (JIS standard 512c).

This method is disclosed in Japanese Patent Application Laid-open No. 54-161911 entitled "Method for manufacturing short metal fibers." A metal fiber having a fiber diameter of 50 ttyn and a fiber length of 3B is obtained by the vibration cutting method.

Hereinafter, melt kneading and injection molding are performed under the same blending ratio and conditions as shown in Examples 1 to 5, and various physical properties are measured. The results are shown in Table 2ic.

Table 2 Examples 6 and 7 and Comparative Examples 6 and 7 The sprues and runners generated in Example 3 and Comparative Example 3 were reused in the molding of Example 3 and Comparative Example 3 in the proportions shown in Table 3. Molded. The measurement results of various physical properties of the obtained molded product are also listed in Table-3.

Table-3

Claims (8)

[Claims] (1) A conductive resin composition prepared by cutting long metal fibers obtained by cutting a metal wire and then blending the fibers into a thermoplastic resin. (2) The resin composition according to claim 1, wherein the metal wire is cold-drawn. (3) The resin composition according to claim 1, wherein the metal wire contains at least one of iron, cobalt, nickel, copper, and aluminum. (4) The resin composition according to claim 1, wherein the metal wire contains iron. (5) The resin composition according to claim 1, wherein the long metal fibers have a fiber diameter of 10 to 150 μm. (6) The fiber length after cutting the metal long fiber is 1 to 10 mm.
The resin composition according to claim 1. (7) The resin composition according to claim 1, wherein the thermoplastic resin is polyamide, polyester, polyolefin, polyphenylene oxide, polyacetal, polycarbonate, or ABS resin. (8) The resin composition according to claim 1, wherein the metal fiber is blended in an amount of 100 to 500 parts by weight based on 100 parts by weight of the thermoplastic resin.