JPS61278565A - Electromagnetic wave-shielding electrically conductive composition - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic wave-shielding product which has a sufficient strength and is electrically conductive and inexpensive, by blending a metallic fiber or metallic powder treated with sulfonic acid, with a thermoplastic resin. CONSTITUTION:A metallic fiber and/or metallic powder treated with an aq. soln. contg. 2-acrylamido-2-methylpropenesulfonic acid are/is blended with a thermoplastic resin. Pref. 2-acrylamido-2-methylpropanesulfonic acid is used in a quantity of 0.1-5vol% based on that of water. The treatment of the metal lic fiber or powder is carried out by immersing it in said aq. soln. or spraying the aq. soln. thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive resin composition used for shielding electromagnetic waves, and more particularly to a conductive resin composition for shielding electromagnetic waves, which is obtained by kneading metal fibers or metal powder into a thermoplastic resin. be.

In Western countries, housings of electronic devices such as computers, word processors, etc. are often It is mandatory to use equipment that has been treated to shield electromagnetic waves emitted by the equipment.

Electromagnetic wave shielding in electronic equipment as described above is becoming mandatory in Japan as well, and various electromagnetic wave shielding methods are being considered.

Shielding of electromagnetic waves as mentioned above can basically be achieved by imparting appropriate conductivity to the housing that encloses the electronic device. Conventionally, zinc is sprayed onto the inner wall of the housing to form a zinc coating. , a method of imparting electrical conductivity to the housing, and a method of imparting electrical conductivity to the housing by applying a conductive paint to the inside of the housing are well known.

Furthermore, it is also known that metal fibers or metal powder are introduced into the thermoplastic resin that forms the main body of the housing to make the housing itself conductive.

However, in the method of zinc spraying or applying conductive paint to the inner wall of the housing as described above, the manufacturing time is reduced because zinc is sprayed or the conductive paint is applied to the inner wall of the housing that has been formed in advance. In addition, especially in the case of conductive paints, the conductive paint itself is expensive, so there is a drawback that the cost must be high.

In addition, if a housing made of metal fibers or metal powder mixed with thermoplastic resin is intended to maintain its electrical conductivity at a volume resistivity of 1o-1 to 10-3ΩG, which has an electromagnetic wave shielding effect, gold H fibers or metal powder may be mixed in. The drawback was that the amount had to be increased. Mixing a large amount of metal fibers or metal powder in this manner causes deterioration of various physical properties of the housing, reducing the durability of the housing.

The present invention has been made in view of the above points, and an object thereof is to provide a conductive composition for shielding electromagnetic waves that has sufficient strength and conductivity and can be used to manufacture inexpensive products for shielding electromagnetic waves. do.

Therefore, the conductive composition for shielding electromagnetic waves according to the present invention is characterized by containing metal fibers and/or metal powder treated in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid in a thermoplastic resin. It is something to do.

According to the present invention, metal fibers or metal powders can be treated with an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid to improve their compatibility with thermoplastic resins. This has the advantage that products for shielding electromagnetic waves can be manufactured without deteriorating physical properties.

The present invention will be explained in more detail.

The conductive substance used in the present invention is metal fiber or metal powder treated with an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid as described above.

The general formula of 2-acrylamido-2-methylpropanesulfonic acid is shown below.

2-Acrylamido-2-methylpropane H3 A specific example of such 2-acrylamido-2-methylpropanesulfonic acid is AMPS (manufactured by Tokyo Kasei, trade name).

By treating with the above-mentioned aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid, a film of the above-mentioned compound is formed on the metal fiber or metal powder. At this time, an ionic bond is formed between the sulfonic acid group and the metal, and on the other hand, compatibility with the thermoplastic resin can be improved at the unsaturated double bond portion.

Therefore, when metal fibers and metal powder treated with such an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid are kneaded into a thermoplastic resin, the metal fibers or metal powder are uniformly dispersed in the resin. Become,
It has been found that by kneading a smaller amount into a thermoplastic resin than before, it is possible to change the conductivity to a predetermined value. That is, it is possible to maintain sufficient strength and physical properties without reducing conductivity.

The above-mentioned 2-acrylamido-2-methylpropanesulfonic acid is preferably added in an amount of 0.1 to 5% by volume relative to water. If it is less than 0.1% by volume, the ionic binding effect and dispersion effect will not be exhibited, and if it exceeds 5% by volume, the amount of 2-acrylamido-2-methylpropanesulfonic acid attached to the metal will increase, This is because a film may be formed on the metal surface, which may impede electrical conductivity.

The metal fibers or metal powders treated with the aqueous solution as described above are not fundamentally limited in the present invention. That is, any material may be used as long as it forms an ionic bond with the above-mentioned compound. For example, one or more of copper, copper alloy, aluminum, aluminum alloy, iron, and iron alloy such as stainless steel can be used.

The method of treatment with the aqueous solution is not fundamentally limited in the present invention. For example, it may be immersed in an aqueous solution or applied by spraying or the like.

Furthermore, the thermoplastic resin into which the metal fibers and metal powder treated in this manner are mixed is not fundamentally limited in the present invention, and resins conventionally used for the housings of electronic devices of this type can be used. It can be used for.

For example, polypropylene resin, ABS resin, modified PP
oResin, polyamide resin, polycarbonate resin, PP
It can be one or more types such as S resin.

The composition ratio of such thermoplastic resin and metal fibers or metal powder is preferably 1 to 25% by volume of metal fibers or metal powder to 99 to 75% by volume of thermoplastic resin. If the amount of metal fiber or metal powder is less than 1% by volume, it is difficult to obtain the desired conductivity, and if it exceeds 25% by volume,
Although the conductivity is good, the strength of the molded product decreases, which may cause problems in practical use.

Next, examples of the present invention will be described.

Example 2 - Brass fibers with a diameter of 60 μm and a length of 2.5 mm were immersed in a 2.5% aqueous solution of acrylamide-2-methylpropanesulfonic acid for 7 minutes, and after sufficient dehydration and drying, 90 volumes of ABS resin melt was added. % by volume and kneaded.

Test pieces were prepared from the conductive resin composition thus produced using an injection machine, and subjected to bending and impact tests, as well as measuring volume resistivity and shielding effect.

Comparative Example A conductive composition was prepared by adding and kneading 10% by volume of brass fibers similar to those in the example which were not treated with the above-mentioned compound and 90% by volume of ABS resin. Using this composition, a test piece was prepared. We fabricated and conducted bending and impact tests, as well as measuring the volume resistivity and shielding effect.

The results are shown in the table below.

As is clear from the table above, the test specimens manufactured using the electromagnetic shielding composition according to the present invention have improved physical and electrical properties compared to conventional ones, and also have a higher volume resistivity than conventional ones. , it got better.

Claims (1)

[Claims] (1) A conductive composition for shielding electromagnetic waves, characterized in that a thermoplastic resin contains metal fibers and/or metal powder treated in an aqueous solution containing 2-acrylamido-2-methylpropanesulfonic acid.