JPH0821253B2 - Conductive filler and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive filler, and particularly to a conductive filler suitable for use as a conductive synthetic resin or synthetic paper used as an electromagnetic wave shielding material for electronic devices. And a manufacturing method thereof.

(Prior Art) In order to protect an electronic device from electromagnetic interference, a conductive filler is mixed with various materials such as a synthetic resin used for a housing of the electronic device.

This conductive filler is used for imparting conductivity to a synthetic resin or the like, and metal, carbon or the like is used, and there are fibrous, flake-like, granular, powdery, etc. shapes, which are compounded at the time of molding the synthetic resin.

Of these, aluminum-based, particularly aluminum fiber-based conductive fillers are promising because they are lightweight and inexpensive.

(Problems to be solved by the invention) When a metal-based, particularly aluminum-based conductive filler is blended with a synthetic resin and processed into a predetermined shape to be used as an electromagnetic wave shield, the initial conductivity is the elapsed usage time. At the same time, it could not be maintained and was found to deteriorate.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems, to provide a conductive filler having improved conductivity and excellent stability over time, and a method for producing the same.

(Means for Solving the Problems) The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, surface-treating aluminum short fibers with a thin film of a polymer or an oligomer, the conductivity is improved. It has been found that a conductive filler which is improved and has excellent stability over time can be obtained.

That is, the present invention provides a conductive filler comprising short aluminum fibers surface-treated with a thin film of a polymer or an oligomer.

The type of polymer or oligomer used for the surface treatment of the aluminum short fibers is not particularly limited as long as it forms a thin film on the surface of the aluminum short fibers when applied to the aluminum short fibers as a solution.

Preferred polymers are polyacrylonitrile, polystyrene, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene, ethylene vinyl acetate copolymer, styrene-butadiene diene copolymer and the like.

Further, as the oligomer, an oligomer of the above-mentioned polymer, a nylon oligomer or the like is used.

Further, the present invention provides (a) aluminum short fibers,
(B) A method for producing a conductive filler is provided, which comprises surface-treating the entire surface of the aluminum short fibers with a solution containing a polymer or an oligomer, and (c) drying the surface-treated aluminum short fibers. is there.

Here, the surface treatment with the solution containing the polymer or oligomer in the step (b) is performed by immersing the aluminum short fiber in the solution. The method of immersing in the solution is preferable because a more sufficient film can be formed on the surface of the filler.

The polymer or oligomer is applied to the aluminum short fibers in the form of a solution, and the combination of the polymer or oligomer and the solvent is polyacrylonitrile / dimethylformamide; polyvinyl alcohol / water; polyvinyl acetate / acetone; polystyrene / cyclohexane; polyvinyl chloride. / Tetrahydrofuran; chlorinated polyethylene [for example, Supercron 510 (trade name) (CH ₂ H ₄ -C
l _x ) _n ] / acetone; chlorinated polypropylene [eg, Supercron 106H (trade name) (C ₃ H _6x Cl _x ) _n ] / toluene; nylon oligomer [eg, diamide x 1874]
(Trade name) H [NH- (CH _{2) 11} -CO] _n OH / ethanol and the like.

The polymer or oligomer concentration of the solution can be used as long as it forms a thin and uniform film on the surface of the filler,
Usually, it is about 0.001% by weight to 2 to 3% by weight, particularly preferably about 0.1% by weight.

The treatment temperature may be 0 ° C. to a temperature lower than the boiling point of the solvent, but room temperature is preferable in practice.

The amount of the polymer or oligomer attached to the aluminum short fibers is 100 parts by volume of the aluminum short fibers,
For example, about 0.01 to 0.1 parts by volume, and the adhesion thickness of the polymer or oligomer to the aluminum short fibers is from a monomolecular film thickness to several microns.

The surface-treated conductive filler of the present invention is, for example,
It is mixed with various synthetic resins and used in various molded housings.

Examples of the synthetic resin to which the conductive filler of the present invention is added include polyethylene, polypropylene, ABS resin, polystyrene, polyamide, polyethylene terephthalate, polybutylene terephthalate, modified polyphenylene oxide, polyvinyl chloride, polychloroprene, polyacetal, and other thermoplastic resins. Or epoxy resin, phenolic resin,
Urea resin, melamine resin, diallyl phthalate resin,
Thermosetting polymers such as unsaturated polyester resin, silicone resin, polyurethane polyimide, polyamide imide are used, but not limited to these.

The composition ratio between the synthetic resin and the filler of the present invention is 98
The conductive filler is preferably 2 to 25% by volume with respect to ˜75% by volume. If the filler is less than 2% by volume, it is difficult to obtain a predetermined conductivity, while if it exceeds 25% by volume, the conductivity is good, but the strength of the molded part is lowered, which is a practical problem.

When compounding the conductive filler of the present invention with a synthetic resin,
If necessary, a proper amount of additives such as pigments and antioxidants are added.

(Function) As described above, the conductive resin composition using the aluminum short fibers surface-treated with the thin film of the polymer or the oligomer has a conductivity higher than that of the untreated aluminum short fibers. It has improved stability and little deterioration over time.

This is because surface-treated short aluminum fibers have better dispersibility in synthetic resin than untreated ones, and the thin coating formed during surface treatment prevents deterioration of short aluminum fibers due to oxidation. It is thought to be to do.

(Example) Hereinafter, the Example of this invention is described in detail, referring drawings.

[1] Preparation of Sample (1) Preparation of Conductive Filler of the Present Invention and Sample Blended with It The aluminum short fiber (l = 3 mm, φ = 60 μm) 10.9 g
It was immersed in 200 ml of a 0.1 wt% PAN (polyacrylonitrile) / DMA (dimethylformamide) solution, and stirred at room temperature for 10 minutes.

Then, the aluminum short fibers were taken out and dried under reduced pressure to obtain the conductive filler of the present invention.

Next, dry-blend 10.9 g (15% by volume) of this conductive filler and 23.4 g (85% by volume) of nylon 12 powder,
It was compression molded in air at a temperature of 200 ° C. under a pressure of 200 kg / cm ² . Then, this was cooled and the sample (sample A) which mix | blended the electroconductive filler of this invention was prepared.

Similarly, a sample containing a conductive filler obtained by treating with polystyrene / cyclohexane (Sample B), a sample containing a conductive filler obtained by treating with polyvinyl alcohol / water (Sample C), polyvinyl acetate / Sample containing a conductive filler obtained by treatment with acetone (Sample D), sample containing a conductive filler obtained by treatment with polyvinyl chloride / tetrahydrofuran (Sample E), chlorinated polyethylene [Super Clone 106H (Trade name) / Sample containing conductive filler obtained by treatment with toluene (Sample F), sample containing conductive filler obtained by treatment with chlorinated polypropylene (Super Clone 510 (trade name)] acetone (Sample G), a nylon oligomer [Diamidome 1874 (trademark) / a sample containing a conductive filler obtained by treatment with ethanol (test sample) H) was adjusted.

(2) Preparation of conductive filler and sample containing it for comparison Untreated short aluminum fibers (φ = 60 μm, l = 3 m
m) of 10.9 g (15% by volume) and commercially available powdered nylon 12
Dry-blend with 23.4g (85% by volume), 200 in air
A sample (untreated sample) having a thickness of 2 mm was prepared by compression forming at 200 ° C. and 200 kg / cm ² .

Also, two types of silane coupling agents cr-aluminopropyltriethoxysilane: TSL 8331 and r-glycidoxypropyltrimethoxysilane: TSL 8350) were surface-treated with a 1% solution dissolved in isopropyl alcohol. A sample was prepared in the same manner from the fiber and commercially available powdered nylon 12.

[2] Heat treatment The sample was heated in an oven at 80 ° C in air.

[3] Measurement The specific resistance was measured with a double bridge and the shielding effect was measured with a shield box.

FIG. 1 shows the specific resistance with respect to the heating time when each sample was heat-treated in air at 80 ° C. Although not shown in the figure, as a result of conducting a test for a heating time of about 1000 hours, each sample according to the present invention was able to obtain a value substantially similar to the value at a heating time of 600 hours.

Fig. 2 shows the shielding effect of magnetic field waves at 250MHz at a heating time of about 600 hours when each sample was heated in air at 80 ° C, and Fig. 3 shows the shielding effect of magnetic field waves at 1200MHz under the same conditions. It is shown. Although not shown, as a result of conducting a test for heating time of about 1000 hours, each sample according to the present invention has a heating time of 60 hours.
A value similar to the value at 0 hours could be obtained.

FIG. 4 is a diagram showing the shielding effect of the magnetic field wave between the sample A and the untreated sample under the same conditions as those in FIGS. 2 and 3 for a heating time of about 2500 hours.

FIG. 5 shows the shielding effect of electric field waves at 1200 MHz for a heating time of about 600 hours when each sample was heated at 80 ° C. in air. Although not shown in the drawings, as a result of conducting a test for a heating time of about 1000 hours, it was possible to obtain a value substantially the same as the value at a heating time of 600 hours for each sample according to the present invention.

FIG. 6 shows the effect of shielding the magnetic field waves between the sample A and the untreated sample under the same heating time as that of FIG.
It is the figure shown over 2500 hours.

[4] Consideration (1) From FIG. 1, Sample A containing aluminum short fibers surface-treated with a thin film of a polymer or an oligomer is mixed.
It can be seen that the specific resistance of H is smaller than that of the sample containing untreated short aluminum fibers, and only slightly increases even after heating for about 600 hours.

On the other hand, in the samples containing the short silane coupling-treated aluminum fibers even with the same surface treatment, the specific resistance of both samples increased with heating time as compared with the sample containing untreated short aluminum fibers.

(2) From FIG. 2 to FIG. 4, it can be seen that the magnetic field wave shielding effect of the sample in which the aluminum short fiber surface-treated with the thin film of the polymer or the oligomer is blended is hardly decreased even by the heat treatment for a long time.

(3) From FIGS. 5 and 6, it can be seen that the electric field wave shielding effect of the sample in which the aluminum short fiber surface-treated with the thin film of the polymer or the oligomer is blended is hardly reduced even by the heat treatment for a long time.

(4) From the above, it can be understood that the deterioration of the shielding effect with time when the aluminum short fibers are mixed with the synthetic resin or the like can be prevented by the surface treatment with a polymer such as polyacrylonitrile. In addition, the surface treatment with a polymer reduces the specific resistance, that is, the conductivity is improved, so by adding a smaller amount of aluminum short fibers than before, a molded product such as a synthetic resin having a large conductivity and electromagnetic wave shielding effect can be obtained. To be

Although the aluminum short fibers according to the present invention have been described as being used as molded articles of synthetic resin in the above-mentioned examples, the invention can be applied as follows in addition to them.

(I) This aluminum short fiber can be made into an article as an electromagnetic wave shielding paper or a thin body similar to this by dissolving a raw material such as paper in water and adding it to a thin sheet spread on a cage.

(Ii) The aluminum short fibers can be formulated as a paint and applied to the housing of electronic equipment.

(Iii) In addition, it is possible to provide an electric wire having an electromagnetic wave shielding function by forming a layered product obtained by adding the aluminum short fibers to the electric wire coating.

(Iv) Furthermore, it is possible to provide a semiconductor device having an electromagnetic wave shielding function by forming, on the passivation film on the surface of the semiconductor device or the like, the aluminum short fibers added thereto as an extremely thin layer.

The present invention is not limited to the above-mentioned embodiment, and various modifications can be made based on the spirit of the present invention.
They are not excluded from the scope of the present invention.

(Effects of the Invention) As described in detail above, according to the present invention, the following effects can be achieved.

(1) It is possible to provide a stable shielding material that does not deteriorate in conductivity and electromagnetic wave shielding function over time.

(2) Since the electroconductivity is improved as compared with untreated short aluminum fibers, a shielding material having high electroconductivity and electromagnetic wave shielding effect can be obtained by adding a smaller amount of short aluminum fibers than before.

(3) The conductive filler of the present invention is easy to manufacture, and
It is possible to obtain various articles which are inexpensive and have an electromagnetic wave shielding function in combination with, for example, plastic molding processing, paper manufacturing processing, paint, electric wires and semiconductor device manufacturing.

As described above, its application field is very wide, and the effect brought by the present invention is remarkable.

[Brief description of drawings]

FIG. 1 is a diagram showing the specific resistance of a conductive composite material containing the conductive filler of the present invention with respect to a heat treatment time, and FIGS. 2 to 4 are graphs showing the conductive composite material containing the conductive filler of the present invention. The figure showing the shielding effect of the magnetic field wave with respect to the heat treatment time, and FIGS. 5 and 6 are the diagrams showing the shielding effect of the electric field wave with respect to the heat treatment time of the conductive composite material containing the conductive filler of the present invention. is there.

Claims (10)

[Claims] 1. A conductive filler in which the entire surface of aluminum short fibers is surface-treated with a thin film of a polymer or an oligomer. 2. The polymer used for the surface treatment is polyacrylonitrile, polystyrene, polyvinyl alcohol,
The conductive filler according to claim 1, which is selected from the group consisting of polyvinyl acetate, polyvinyl chloride, chlorinated polyethylene and chlorinated polypropylene. 3. The conductive filler according to claim 1, wherein the oligomer used for the surface treatment is a nylon oligomer. 4. The conductive filler according to claim 1, which is used in a resin composition for electromagnetic wave shielding. 5. The conductive filler according to claim 1, which is used for electromagnetic wave shielding paper. 6. The conductive filler according to claim 1, which is used as a paint for electromagnetic wave shielding. 7. The conductive filler according to claim 1, which is used for an electric wire for electromagnetic wave shielding. 8. The conductive filler according to claim 1, which is used for a semiconductor device for electromagnetic wave shielding. 9. (a) Prepare aluminum short fibers, (b) surface-treat the entire surface of the aluminum short fibers with a solution containing a polymer or oligomer, and (c) dry the surface-treated aluminum short fibers. A method of manufacturing a conductive filler comprising: 10. The method for producing a conductive filler according to claim 9, wherein the surface treatment in the step (b) is performed by immersing the aluminum short fibers in a solution containing a polymer or an oligomer.