JPS638459A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:An electrically conductive resin composition having uniform and good electrical conductivity and improved strength, showing white, obtained by blending a resin with electrically conductive tin oxide fibers having single fiber length of >= a specific ratio and the average of aspect ratio in a specific range. CONSTITUTION:(B) A resin is blended with (A) 5-50wt%, preferably 20-50wt% based on total amounts of the components A and B of electrically conductive tin oxide fibers which have >=3mum, preferably 3-100mum single fiber length, preferably <=2mum diameter and 10-10,000, preferably 50-1,000 average of aspect ratio and is obtained by blending tin oxide with copper, feeding the blend into an electric furnace, keeping the blend at high temperature while introducing a nitrogen gas to the furnace, melting the blend, successively sending evaporated tin oxide vapor to a low-temperature part in the furnace and precipitating fibrous tin oxide crystal and preferably further mixed with antimony.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a white conductive resin, particularly a resin composition for preventing static electricity.

<Prior art and problems> In recent years, electronic circuits have become smaller, more complex, and more precise. In order to protect ICs, LSIs, etc. from electrostatic damage and to eliminate dust as much as possible, conductive materials are being used to protect electronic circuits. surround the circuit,
Shielding is being done. Particularly when electronic circuits are surrounded by plastic materials, there is a problem in that the plastic becomes electrically charged due to its insulating properties, making it easy for dust to adhere to it. Therefore, in recent years, plastic materials have been made conductive to shield them. One method for making plastic materials electrically conductive is to mix a conductive filler with a resin. Conventionally, carbon, various metal powders, metal fibers, and the like are known as conductive fillers. However, most of the above-mentioned conductive fillers have a black or nearly black color tone, darken the resin, and have a large specific gravity.

Tin oxide-based fillers and zinc oxide-based fillers are known as conductive fillers that are white or have a color close to white, but conventional fillers are spherical powders of 0.2 to several gm that are contained in resin. However, there is a problem in that the content must be increased in order to provide sufficient conductivity. In other words, generally when the conductive filler is mixed into the resin, it is easier for the conductive fillers to come into contact with each other and a comparatively small amount of mixture is required. Therefore, a relatively large amount of mixing is required.

Conventionally, as a fibrous conductive filler, one in which the surface of potassium titanate fiber is coated with a tin oxide-based conductive material is known, but the conductive layer on the surface of this filler easily peels off, and Since the conductive layer is formed by adhering spherical tin oxide, it has poor compatibility with resin and has poor dispersibility.
It also has poor properties for reinforcing resins.

In addition, as another R-shaped conductive filler, tin oxide voice car (whisker-like single crystal) is known, but the m-fibers of tin oxide have a length of several cm and a diameter of about 20 μm, that is, the aspect ratio is 10,000 or more. However, when the aspect ratio is 10,000 or more, the dispersibility is poor and it is difficult to mix uniformly when mixed with resin.
Therefore, non-uniform conductivity is observed.

<Structure of the Invention> The present invention has been studied to solve the above problems, and as a result, the following knowledge has been obtained.

(1) When tin oxide fibers with an average aspect ratio within a specified range are included in resin, they have extremely good dispersibility, and even if the content is relatively small, they can provide sufficient conductivity and uniform conductivity. Demonstrate.

(2) The tin oxide fiber has a smooth surface and is compatible with the resin, thereby significantly improving the strength of the resin.

(3) The above-mentioned tin oxide fiber may be a single crystal or a twin crystal as long as the length of the single fiber is 3 Bm or more.
).

The present invention is based on the above findings, and according to the present invention, conductive tin oxide fibers having a single-m male length of 3 gm or more and an average aspect ratio of 10 to 10,000 are bonded to a resin. Further, there is provided a conductive resin composition characterized in that the content thereof is 5 to 50% by weight based on the total amount of the fiber and resin.

In a preferred embodiment, the length of the single fiber is 3 to 3.
100 gm, a diameter of 2 μm or less, an average aspect ratio of 50 to 1000, and a fiber content of 20 to 50% by weight based on the total amount of the fibers and resin.

The m-female crystal of tin oxide having the above aspect ratio is produced, for example, by the following method. That is, tin oxide and copper are mixed, the mixture is charged into an electric furnace in which atmospheric gas can be controlled, and nitrogen gas is flowed into the furnace to maintain the temperature at a high temperature to melt the mixture.

Subsequently, when the evaporated tin oxide vapor is led to a low temperature section in the furnace, ia fibrous tin oxide crystals are precipitated.

The tin oxide fibrous crystal has a length of 3 to 100 g, m,
Diameter: 2 gm or less is appropriate, and the average aspect ratio is 1.
0 to 10,000 is used.

Note that as long as the aspect ratio is within the above range, the length of the fibrous crystals may be 3 gm or more.

When the aspect ratio is 10 or less, the shape becomes close to spherical, so a large content is required to obtain a predetermined conductivity. Moreover, if the aspect ratio is 10,000 or more, the dispersibility of the fibrous crystals will be poor, and the conductivity of the resin will be non-uniform.

The above-mentioned tin oxide fibrous crystals may be single crystals or twin crystals, and the shape of the fibers may be flat fibrous or columnar FR.
Various shapes can be used, such as a filamentous ring or one in which the R male is further branched.

Usually, the above-mentioned tin oxide crystal has an electrical resistance of 100 to 2000 ΩCm, but the crystal further contains 0.5 to 2000 ΩCm of antimony.
When the content is 10% by weight, it exhibits a low resistance of 0.1 to 1 Ωcm and is more suitable as a conductive filler.

The above-mentioned tin oxide fibers may be mixed with the resin by a conventional method. For example, the resin and the tin oxide fibers may be kneaded using two rolls. In addition, a conductive film can be formed by dispersing or dissolving a resin in a solvent, dispersing Fa male tin oxide therein, and then coating the resin on a substrate.

The mixing ratio of the tin oxide fiber and the resin is preferably such that the amount of the fiber is 5 to 50% by weight based on the total amount of the resin and the fiber.

If the amount of fiber is less than 5% by weight, the surface resistance of the resin will be 10 ILΩ/mouth or more, and the purpose of preventing static electricity cannot be achieved, and if the amount is more than 50% by weight, the resin will become brittle, which is not preferable.

When mixing the above-mentioned fibers with a resin, the resin may be dissolved and mixed with a solvent, and the resin containing the fibers may also be used as a paint component. In this case, the above amount of fibers is within the above mixing amount based on the total amount of the resin and the m fibers excluding the solvent or other components in the paint, such as pigments, solvents, additives, etc. good.

The type of resin is not particularly limited, and examples include phenol formaldehyde resin, urea formaldehyde resin, melamine formaldehyde resin, vinyl acetate resin, vinyl chloride resin, vinyl acetate vinyl chloride resin, styrene resin, acrylic resin, polyethylene resin, polypropylene resin, alkyd. Various resins such as resin, silicone resin, and fluororesin can be used.

<Effects of the Invention> The resin containing the m-male crystals of tin oxide in the above mixing amount has a surface resistance of 104 to 1011 Ω/mouth, and the mixing amount can be significantly reduced compared to conventional ones. .

Further, the resin according to the present invention has more uniform conductivity than a conventional resin having a fibrous conductive filler.

Furthermore, the strength of the resin is significantly improved compared to conventional spherical conductive fillers. Incidentally, the strength of the resin mixed with a predetermined amount of the above-mentioned fibrous tin oxide is increased by approximately 30% to 2 times. Conventional spherical conductive fillers do not show such an improvement in strength.

<Examples and Comparative Examples> A mixture of raw materials shown in Table 1 of Examples was charged into an electric furnace in which atmospheric gas could be controlled, and nitrogen gas was flowed into the furnace to heat the mixture to 1250°C.
The mixture was melted at a temperature of
A tin oxide fiber containing 0.7% by weight of antimony and having a diameter of 50 m and a length of 50 m was obtained.

Table 1: Using two rolls (manufactured by Monsando Kasei Co., Ltd.), 145°
The mixture was uniformly kneaded for 10 minutes at a temperature of C, and then molded into a sheet at a temperature of 170C.

Table 2 shows the surface resistance and strength of the above resin.

As is clear from Table 2, the resins according to the present invention (No.
It can be seen that samples 1 to 5) contain a small amount of conductive filler mixed. In addition, a comparative example (No.
, 6 to 8) are also shown in Table 2.

Furthermore, when measuring various parts of the surface of the resins of the present invention according to Examples (Nos. 1 to 5) above at 5 mm intervals using a needle electrode, the surface resistances were all within one digit, indicating that the surface was uniform. had resistance.

The aspect ratio of the comparative fiber is thicker than 105, for example, the length is 3.
A long-R male with a diameter of ~4 cm and a diameter of 0.2 gmφ was kneaded into vinyl chloride resin under the same conditions as in the example.

In this case, Fa males were intertwined with each other and difficult to mix, making it impossible to obtain a homogeneous mixture.

The average surface resistance of the above resin surface was 3X 10'Ω/hole, but when we measured each part of the surface at 5 mm intervals using a needle electrode, the surface resistance per unit was as shown in Table 3. The resistance was different in the range of 10 13 to 10 6 Ω/mouth at each measurement part, and was extremely nonuniform.

Table 2 Table 3

Claims (2)

[Claims] (1) Conductive tin oxide fibers with a single fiber length of 3 μm or more and an average aspect ratio of 10 to 10,000 are added to the resin, with an average aspect ratio of 5 to 50 μm based on the total amount of the fibers and resin.
% by weight of a conductive resin composition. (2) The single fiber length is 3 to 100 μm, the diameter is 2 μm or less, the average aspect ratio is 50 to 1000, and the fiber content is 20 to 50% by weight based on the total amount of the fiber and resin. The composition of claim 1.