JPH0725935B2 - Conductive plastic molding material - Google Patents

Description

The present invention relates to a novel conductive plastic molding material. More specifically, conductivity, especially EMI (Electro
Magnetic Interference) The present invention relates to a conductive plastic molding material having excellent shielding properties and low cost. Metal-coated carbon fiber is excellent in design effect due to conductivity and metallic luster of appearance in addition to various characteristics of carbon fiber, and uses a large number of antistatic materials, sheet heating elements, FRP molding dies, parabolic antennas, ICs, and LSIs. It is suitable for use as an EMI shield material, which is expected to increase in demand as digital electronics equipment has spread, and for sports leisure goods such as golf shafts, golf heads, face plates, tennis rackets, fishing rods, and acoustic parts such as speaker cones. It is a material that is used.

[Prior art and problems]

Conventionally, as a means of making plastic conductive, zinc spraying,
Conductive surface treatment such as conductive paint, electroless plating, vacuum deposition, etc. and various conductive fillers such as carbon black, aluminum flakes, metal fibers, carbon fibers, etc. are mixed into plastics, so-called conductive composite plastics, etc. However, each method has advantages and disadvantages.

In addition, the conductivity of the housing of a digital electronic device does not increase the added value of the product and cannot be reflected in the product price because of EMI shielding measures, and therefore, the lowest possible cost is required.

Among them, the use of conductive composite plastics is said to become the mainstream of EMI shielding measures in the future because it does not require secondary processing and does not cause the problem of conductive layer peeling, unlike conductive surface treatment. In general, when molding a housing using a conductive composite plastic, after a compound process for manufacturing a conductive composite pellet which is a molding material,
The housing is molded by injection molding. However, as described above, the material for the housing is required to have a cost as low as possible, and the cost increases due to the compounding process.

In addition, although the mixed filler undergoes shearing and breaks due to the compounding process and becomes short, the conductivity is lowered, and the desired conductivity cannot be obtained. In order to avoid this situation, it is necessary to mix a large amount of filler, resulting in an increase in cost.

Therefore, so-called direct molding, which does not go through the compounding process, can be considered. However, in direct molding, it is extremely difficult to disperse the filler, and the appearance of the molded product is impaired. In order to improve dispersibility, it is necessary to make the molding conditions harsh, such as increasing the screw rotation speed and increasing the back pressure, but if the molding conditions are made harsh, the filler will be sheared and damaged, shortening the conductivity. There is a problem of decrease.

[Object of the Invention]

The present invention intends to provide a conductive plastic molding material which has excellent conductivity, particularly excellent EMI shielding property, has a good appearance of a molded product, and is low in cost, which has solved the problems in the above-mentioned prior art. .

[Structure of Invention]

 The structure of the present invention is as follows.

(1) A conductive plastic molding material characterized in that metal-coated carbon fibers are bundled with a phosphate ester compound or / and a phthalate ester compound and a thermoplastic resin.

(2) The phosphoric acid ester compound and / or the phthalic acid ester compound are adhered to the inside of the metal-coated carbon fiber bundle and the thermoplastic resin is adhered to the outer periphery of the metal-coated carbon fiber bundle to be bundled. Conductive plastic molding material.

(3) The metal-coated carbon fiber has a metal film thickness of 0.1 to 1 μm,
The conductive plastic molding material according to claim 1, which has a fiber length of 1 to 10 mm.

(4) The conductive plastic molding material according to (1), wherein the amount of the phosphoric acid ester compound or / and the phthalic acid ester compound attached is 3 to 20% by weight.

According to such a conductive plastic molding material, it is possible to obtain a conductive plastic molded product having an excellent EMI shielding effect, a molded product having a good appearance, and a low cost.

The present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram schematically showing a cross section of a conductive plastic molding material according to the present invention. In the figure, 1 is a carbon fiber, 2 is a metal layer, 3 is a phosphoric acid ester compound or / and an ethyl phthalate compound, and 4 is a thermoplastic resin layer.

The carbon fiber 1 is covered with a metal layer. The carbon fibers are polyacrylonitrile-based, pitch-based, rayon-based carbonaceous and graphitic fibers which are usually composed of about 100 or more single fibers having a diameter of 4 to 10 μm.

The types of metals forming the metal layer 2 are Au, Ag, Cu, Ni, and A.
Although any metal such as l, Cr, Zn, Sn, and Pb may be used, Ni is preferable in terms of conductivity, price, and corrosion resistance. The thickness of the metal film is preferably 0.1 to 1 μm, and if the thickness is less than 0.1 μm, the conductivity and the shielding effect are insufficient, and if it exceeds 1 μm, the specific gravity becomes large, and the lightness which is an advantage of plastic is lost. With weight, the capacity becomes small, the conductivity and the shielding effect are insufficient, and the reinforcing effect of the mechanical properties becomes small.

In the present invention, the phosphate compound is, for example, tricresyl phosphate, tributyl phosphate, triethyl phosphate and the like. In addition, the phthalate compound is, for example, dioctyl phthalate, butyl benzil phthalate, diheptyl phthalate, dibutyl phthalate, diisodecyl phthalate and the like.

The amount of the phosphoric acid ester compound or / and the phthalic acid ester compound adhered is preferably 3 to 20% by weight, and 3% by weight.
If it is less than the above range, the dispersion of the metal-coated carbon fiber is insufficient, and if it exceeds 20% by weight, the mechanical properties of the molded product deteriorate.

In the present invention, the thermoplastic resin is, for example, general-purpose engineering plastic such as polyamide, polyacetal, polycarbonate, polybutylene terephthalate, modified polyphenylene oxide (polyphenylene ether), and polyphenylene sulfide, polyarylate, polysulfone, polyether sulfone, polyether ether ketone. , Special engineering plastics such as polyetherketone, polyamideimide, polyetherimide, polyimide, liquid crystal polymer, various fluororesins (PTFE, PFA, FEP, ETFE, PVDF), and AB
It is a general-purpose resin such as S, polystyrene, polypropylene, and polyethylene. Practically, ABS, polystyrene, polycarbonate, modified polyphenylene oxide, polyamide, polybutylene terephthalate and the like are used for housings and chassis of electronic devices or various parts. The amount of these resins attached is usually 10 to 60% by weight.

The length of the molding material of the present invention is preferably 1 to 10 mm. If it is less than 1 mm, the conductivity and shielding effect are low with respect to the fiber content,
Moreover, the auxiliary effect of mechanical properties is small, and when it exceeds 10 mm, the fibers are easily entangled with each other at the time of molding, resulting in poor dispersion and impairing the appearance of the molded product, and low electrical conductivity and shielding effect, and reinforcement of mechanical properties The effect tends to be small.

Injection molding is usually employed to obtain a molded product using the molding material of the present invention. When additional resin is added during molding, the same or different resin as the resin applied to the molding material is used.

Preferred combinations when different resins are used are as follows, for example.

The molding material of the present invention is obtained, for example, as follows. A metal layer is formed on the carbon fiber, then a layer of a phosphoric acid ester compound and the like and a thermoplastic resin layer are formed, and if necessary,
Disconnect.

As the method for forming the metal layer, any method such as electroplating, chemical plating, physical vapor deposition, chemical vapor deposition, and spraying may be adopted,
It is preferable to use electroplating in which a uniform metal coating can be easily obtained on each single fiber, productivity is high, and cost is low. These methods are already well known.

The layer of the phosphoric acid ester compound or the like is generally formed by a dipping method in which the metal-coated carbon fiber is passed through a solvent in which the phosphoric acid ester compound or the like is dissolved, and may be formed by another method, for example, a spray method. .

The formation of the thermoplastic resin layer is performed in the same manner.

Inside the metal-coated carbon fiber, such as phosphate compounds,
In addition, it is important to attach the thermoplastic resin to the outer periphery of the metal-coated carbon fiber (to form a layered structure) and to bundle the fibers so that the intended effect of the present invention can be more significantly exhibited.

〔The invention's effect〕

When the conductive plastic material according to the present invention is used for molding, the thermoplastic resin adhered to the metal-coated carbon fiber is melted in the first half of the cylinder of the injection molding machine to be well compatible with the matrix resin, and subsequently, the action of the phosphate ester-based compound or the like. As a result, the metal-coated carbon fibers are uniformly dispersed, so that the content of the metal-coated carbon fibers can be small, and a product having a good appearance can be obtained at low cost.

〔Example〕

 Example 1 Ni-coated carbon fiber [Besfight manufactured by Toho Rayon Co., Ltd.
-MC ] As a phosphate compound in the filament
Triethyl phosphate (TEP) dissolved in acetone
8% by weight, and further used as a thermoplastic matrix.
ABS resin dissolved in chill ethyl ketone (Sumitomo Nogata
22% by weight of Clastic SHF]
Then, cut it to 6 mm and cut it into "Vesfight-MC" chopped fat
Got iver. This chopped fiber and ABS resin
[Clarastic AN450 manufactured by Sumitomo Nogatac Co., Ltd.]
Dry so that "Bethfight-MC" is 10% by weight.
Blended and injection molded 150 mm x 150 mm x 3 mm flat plate
Was molded and the conductivity and EMI shielding effect were measured.

Comparative Example 1 Similarly to "Besphite-MC" filament, 28 wt% of a mixture of triethyl phosphate dissolved in acetone and ABS resin dissolved in methyl ethyl ketone was adhered and cut into 6 mm to obtain chopped fiber.

As in Example 1, dry blending was performed so that the content of "Vesphite-MC" was 10% by weight, and injection molding was performed to obtain 15
A 0 mm × 150 mm × 3 mm flat plate was molded and the volume resistivity (conductivity) and EMI shielding effect were measured.

The above measurement results are shown in the table below.

Example 2 The Ni film thicknesses of "Vesphite-MC" were 0.05 μm and 0.1 μm, respectively.
Ni was coated so as to have a thickness of 3 μm and 1.2 μm, triethyl phosphate and ABS resin were adhered in the same manner as in Example 1, and cut into 6 mm to obtain chopped fiber.

"Bethfight-MC" was dry blended with ABS resin so as to be 10% by weight, injection molding was performed, and tensile strength, volume resistivity (conductivity), and EMI shielding effect were measured. The measurement results were as follows.

Example 3 Ni-coated carbon fiber [Besfight manufactured by Toho Rayon Co., Ltd.
-MC ] As a phthalate compound in the filament
Dioctyl phthalate (DOP) dissolved in acetone
5% by weight is attached, and then methyl chloride is used as a thermoplastic resin.
Modified polyphenylene oxide resin [Nori]
Resin, N731J Engineering Plastics Co., Ltd.
18% by weight, and cut into 6 mm
-MC "chopped fiber was obtained. This chopped
Fiber and Noryl resin N190J [Engineering Plus
Chick Co., Ltd.] "Besfight-MC" 10% by weight
150mm x 1 by dry blending and injection molding
50mm x 3mm flat plate is molded, volume resistivity (conductivity), EMI
The shield effect was measured.

Comparative Example 2 Similarly, pelletization was performed by compounding so that the content of "Vesphite-MC" was 10% by weight, and a 150 mm x 150 mm x 3 mm flat plate was formed by injection molding to obtain a volume resistivity (conductivity), The EMI shielding effect was measured.

The above measurement results are shown in the table below.

Example 4 "Vesphite-MC" prepared in the same manner as in Example 3 was used.
Cut into 0.5mm, 3mm, and 15mm respectively, and
It was dry-blended with Noryl resin so that "MC" was 10% by weight, injection-molded, and measured for volume resistivity (conductivity) and EMI shielding effect.

The measurement results were as follows.

[Brief description of drawings]

FIG. 1 is a conceptual diagram schematically showing a cross section of a conductive plastic molding material according to the present invention. 1: Carbon fiber, 2: Metal layer, 3: Phosphate compound or / and phthalate compound, 4: Thermoplastic resin layer

Claims (4)

[Claims] 1. A conductive plastic molding material characterized in that metal-coated carbon fibers are bundled with a phosphoric acid ester compound and / or a phthalic acid ester compound and a thermoplastic resin. 2. A phosphorous ester compound and / or a phthalic acid ester compound are adhered to the inside of the metal-coated carbon fiber bundle and a thermoplastic resin is adhered to the outer periphery of the metal-coated carbon fiber bundle to form a bundle. ) The conductive plastic molding material as described above. 3. The metal-coated carbon fiber has a metal film thickness of 0.1 to 1.
The conductive plastic molding material according to claim 1, which has a fiber length of 1 to 10 mm. 4. The conductive plastic molding raw material according to claim 1, wherein the amount of the phosphoric acid ester compound and / or the phthalic acid ester compound attached is 3 to 20% by weight.