JPS59102938A - Electrically conductive resin composition for shielding electromagnetic wave - Google Patents

Abstract

PURPOSE:To provide an electrically conductive resin composition having light weight and high electromagnetic wave shielding effect, at a low cost, by kneading a thermoplastic resin with a specific amount of aluminum flakes having specific ranges of size and thickness and coated with a specific coating. CONSTITUTION:A thermoplastic resin 1 (e.g. polypropylene, acrylonitrile-butadiene-styrene resin, nylon, etc.) is kneaded homogeneously with 10-30vol%, based on the resin, of aluminum flakes 2 (>=80% of the aluminum flake has a size of 0.3-4mm.<2> and a strength of >=0.5kg defined by the product of the tensile strength per unit area (kg/mm.<2>) at a width of 1mm. and the thickness (mm.), and the flake is coated with silane coupling agent or titanium coupling agent). USE:Manufacture of the housing of electronic device by injection molding, etc.

Description

[Detailed description of the invention] The present invention relates to a conductive resin composition for shielding electromagnetic waves.

2. Description of the Related Art Electronic devices generate interference radio waves that adversely affect peripheral devices such as televisions and radios, such as noise, and are therefore required to be shielded from them.

Synthetic resin housings are often used in such electronic devices, and since this material transmits the interference radio waves mentioned above, various methods have been devised to shield electromagnetic waves by turning it into metal. ing.

One method is to knead a conductive filler into a synthetic resin. Conventionally, brass fibers or aluminum fibers have been used as conductive fillers, but the former has a high weight when peeling. As the number of products increased, the cost increased, and even the latter ones were still difficult to manufacture, and the cost was a trade-off.

Therefore, this invention has low production cost, light weight,
Moreover, it is an object of the present invention to provide a conductive resin composition that has a good electromagnetic wave shielding effect.The present invention will be explained below with reference to the accompanying drawings.

The conductive resin composition of this invention is obtained by kneading thermo-iJ plastic resin 1 and aluminum flakes 2.

As the thermoplastic resins 1 and C, for example, polypropylene, polystyrene, acrylonitrile butadiene styrene resin, acrylonitrile styrene resin, polybutylene terephthalate, modified polyphenylene oxide, polycarbonate, nylon, polyacetal, etc. can be used.

The aluminum flakes 2 may be produced by cutting rolled aluminum foil, for example.

In addition, the thermoplastic resin 1 of the aluminum flakes 2
The filling meter, its size, strength, and properties are determined as follows, taking into consideration the conductivity, moldability, etc. of the conductive resin composition.

(1) Filling amount 10% to 30% by volume of aluminum flakes 2 are filled with respect to the thermoplastic resin 1.

If this is less than 10%, conductivity sufficient to shield electromagnetic waves cannot be obtained, but if it is more than 30%,
This is because the physical properties of the heat=J plastic resin 1 are poor and the moldability is impaired.

(3) The size of the surface is 0.3 marl to 4 marl,
Preferably, one having a value of 1 myi to 2 mId is used.

This is because if the size is less than 0.3 marl, the number of contact points with the aluminum flakes 2 increases significantly, resulting in increased contact resistance and poor conductivity; This is because when kneading it into a thermoplastic resin, uniform kneading cannot be achieved and the physical properties of the two-injection molded product are impaired.

Note that the aluminum flakes 2 have at least 80
It is fine if % is within the above range, and the remaining 2
0% may be 0.3 mare or less, and may include aluminum fibrous materials, or nickel, copper, iron, brass, and carbon fibers and flakes other than aluminum.

(3) Strength The strength of aluminum flake 2 is the tensile strength per unit area at 1 mm rl] K9/m,
+f) and the thickness (mm) should be 0.5 Kp or more. This relationship is expressed as follows.

Strength KSI) = tensile strength K per unit area
? /m+f) x Thickness (mm) This is to prevent this from happening.

Therefore, if the tensile strength per unit area of the aluminum flakes 2 is high, the thickness can be reduced, whereas if the tensile strength per unit area is low, the thickness must be increased.

For example, the tensile strength per unit area is 249/yru
In the case of aluminum flake 2 with a thickness of 0.03 mm at rff, the strength at 1 mm width is 0.72 Kp.
Therefore, the above conditions are satisfied.

Moreover, the thickness of the aluminum flake 2 is 10μ to 80μ
Make it.

This is because if a material with a thickness of 10μ or less is used, the flakes will bend when kneaded with resin, resulting in poor continuity and connectivity between flakes and impairing conductivity. If a resin with a thickness of
This is because sufficient conductivity cannot be obtained.

(4) Surface properties The surface of the aluminum flakes 2 is coated with a silane coupling agent or a titanium coupling agent to improve adhesion to the resin.

The silane coupling agents include r-glycidoxypropyltrimethoxysilane, r-aminopropyltrimethoxysilane, r-aminopropyltriethoxysilane, N-β(aminoethyl)raminopropyltrimethoxysilane, and- Meta-acrylopropyltrimethoxysolane, r-mercaptopropyltrimethoxysilane, and the like can be used. In addition, examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tridecyl benzene sulfonyl titanate, inpropyl tris(dioctylpyrophosphate) titanate, and tetra(2.2 sialyloxymethyl-1-butyl)bis(di- tridecyl) phosphite titanate, bis(dioctylpyrophosphate)
Oxyacetate titanate, bis(dioctylpyrophosphate-1.)ethylene ditanate, and the like can be used. These silane coupling agents and titanium coupling agents may be used alone or in combination. In this way, when the surface of the aluminum flakes 2 is subjected to silane treatment or titanium treatment, when a mixture of resin and flakes is injection molded, the flakes tend to be arranged in parallel as shown in the drawing. This is because the adhesion between the resin and the flakes is improved, so that the flakes tend to flow along with the flow of the resin during molding and melting.

The conductive resin composition of the present invention is prepared by kneading a thermoplastic resin and aluminum flakes, and changing the filling appearance, size, strength, and surface properties of the aluminum flakes to the following. It is easy to maintain the continuity and connectivity between flakes, and it is designed so that the physical properties of the resin are hardly impaired, so it has an excellent electromagnetic shielding effect, has good moldability, and is suitable for injection molding. A housing for an electronic device can be easily produced and produced by the above method.

Furthermore, since aluminum flakes are used, the molded product is lightweight and has the advantage of being low in product cost.

Examples and comparative examples of the present invention under various conditions are shown in Table 1 below.

The samples in Table 1 were prepared by pelletizing a mixture of thermoplastic resin and aluminum flakes, and then using an injection molding machine for 30 minutes.
It is molded into a 10o+ square plate with a thickness of mm,
For this sample, volume resistivity (Ω・cm), 5 Q
The transmission loss (clB) at QMHy, was measured to measure the electromagnetic wave shielding effect. Measurement of excess loss is as follows:
A cubic box was formed using the above plates, a 500 MF11 oscillation source was placed in the box in a sealed state, an antenna was provided outside, and the field strength was measured using an electric field strength meter. This measurement location is a so-called anechoic chamber.

In Table 1 above, ABS: Acrylonitrile styrene PP: Polypropylene P B r: Polybutylene terephthalate KBM603
° Silane coupling agent A187 manufactured by Shin-Etsu Chemical Co., Ltd. A172. Al100: A silane coupling agent manufactured by Nippon Unicar Co., Ltd.

[Brief explanation of the drawing]

The drawing is an enlarged cross-sectional view of the tsukuji fat composition according to the present invention. 1°°°Thermoplastic resin・2...Aluminum flake supplier i person bundle (4-aluminum 4;, 1. 2 meeting; Kamide Qn agent Fumi Ni

Claims (1)

[Claims] Thermoplastic resin and 10 in volume for this thermoplastic resin
% ~ 30% aluminum flakes are uniformly kneaded, and the above aluminum flakes have a size of 0.3 mare ~ 4 m, +rl.
, and the tensile strength per unit area (K11l/m+t) and thickness (rILm
) A conductive resin composition for shielding electromagnetic waves, which has a strength of 0.5 K9 or more, and has a surface coated with a silane coupling agent or a titanium coupling agent.