JP2001261975A - Electroconductive thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroconductive thermoplastic resin composition capable of providing a molded product excellent in electromagnetic wave shielding properties. SOLUTION: This electroconductive thermoplastic resin composition comprises (A) a thermoplastic resin, (B-1) electroconductive long fibers having 4-20 μm diameter and 4-30 mm length and (B-2) electroconductive staple fibers having 30-100 μm diameter and 1-5 mm length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive thermoplastic resin composition suitable for shielding electromagnetic waves.

[0002]

2. Description of the Related Art Electric circuits and ICs are used in various electric appliances, but may malfunction due to electromagnetic waves generated from outside and inside. To prevent this, the generation of electromagnetic waves has been reduced by changing the circuit design, but there is a limit, and it is necessary to cover them with a material having electromagnetic wave shielding properties.

As a method of imparting conductivity to a material and exhibiting electromagnetic wave shielding properties, a method of forming a thin metal film on the surface of a molded product by applying an electroless plating method or a zinc spraying process is known. However, there are problems such as low cost, poor mass productivity, and easy occurrence of environmental problems such as noise and air pollution.

Therefore, as a method of imparting conductivity to the resin itself, there is known a method of kneading metal fibers, foils, particles or carbon black, carbon fiber, ferrite, barium titanate, etc., and in particular, compounding metal fibers. The method is universal. However, when the metal fiber is blended in a large amount, the conductivity is improved, but the impact resistance, the moldability and the like are deteriorated. However, when the metal fiber is blended in a small amount, the conductive effect cannot be sufficiently exerted. In order to increase the conductivity, metal fibers having a large aspect ratio (fiber length / fiber diameter) may be used. However, in this case, there is a problem that a fiber ball is easily formed and uniform dispersion and blending becomes difficult.

[0005] Further, a resin composition having an electromagnetic wave shielding property by adding a conductive filler converged with a solvent-soluble polymer to a thermoplastic resin is known (Japanese Patent Application Laid-Open No. Sho 5).
8-129030). However, this composition has insufficient convergence and cannot solve the problem that it is particularly difficult to uniformly disperse and mix, and the dispersion state of the conductive filler is uneven. Lack.

Accordingly, in the present invention, by increasing the dispersibility of the fibers imparting conductivity, the extrudability and the injection processability are not deteriorated, and the mechanical strength and electromagnetic wave shielding properties are improved. It is an object of the present invention to provide a conductive thermoplastic resin composition mainly used for housings and internal parts of electronic devices and the like.

[0007]

The present inventor has conducted various studies to solve the above-mentioned problems. As a result, the combination of long fibers and short fibers of a specific size as the conductivity-imparting component greatly increases the dispersibility. It has been found that the dispersibility can be further improved by coating the surface of the long fiber with a thermoplastic resin, and the present invention has been completed.

The present invention relates to (A) a thermoplastic resin, and (B)
1) A conductive long fiber having a diameter of 4 to 20 μm and a length of 4 to 30 mm, and (B-2) a diameter of 30 to 100 μm and a length of 1 to 5 mm
And a method for producing the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic resin (A) used in the present invention is not particularly limited as long as it is used for applications requiring electromagnetic shielding properties. Vinyl resin and its copolymer resin, vinylidene chloride resin, polystyrene and its copolymer resin,
One or more selected from polyamide resins, polyacetals, polycarbonates, thermoplastic polyester resins, polysulfones, and the like.

Examples of the polyolefin resin include high density, medium density or low density polyethylene, polypropylene such as isotactic polypropylene and syndiotactic polypropylene, polybutene, and 4-methylpentene-1 resin. Copolymers with olefins such as ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and propylene-vinyl chloride copolymer can also be used.

Examples of the vinyl chloride copolymer resin include a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer resin, and a vinyl chloride-acrylonitrile copolymer resin.

Examples of the polystyrene copolymer resin include a rubber-containing or rubber-modified styrene resin and an AS resin.

Examples of the polyamide resin include nylon 6, nylon 11, nylon 66, nylon 610 and the like.

Examples of the polycarbonate include a polycarbonate obtained from bisphenol A and phosgene, a polycarbonate obtained from bisphenol A and diphenyl carbonate, and the like.

Examples of the thermoplastic polyester resin include polyethylene terephthalate and polypropylene terephthalate.

Among the thermoplastic resins (A), preferred are polystyrene and copolymer resins thereof, and more preferred are rubber-containing or rubber-modified styrene resins such as ABS resin, SBS resin and MBS resin. , N
It is polystyrene (so-called high-impact polystyrene) in which rubber-like component particles obtained by dissolving or mixing 2 to 20% by weight of a rubber such as an AS resin or polybutadiene in a styrene monomer and polymerizing the styrene monomer are dispersed.

The conductive long fiber of the component (B-1) used in the present invention has a diameter of 4 to 20 μm, preferably 6 to 15 μm.
The length is 4 to 30 mm, preferably 4 to 15 mm. When the diameter is 4 μm or more, the fiber is prevented from being cut at the time of processing and the electromagnetic wave shielding effect is prevented from being reduced.
m or less, high shielding properties can be obtained with a small amount of filling.

The conductive filaments of the component (B-1) are preferably bundles of 500 to 20,000 fibers, more preferably
It is preferable to use 000 to 10,000 bundles in order to increase dispersibility and maintain high productivity. When the component (B-1) is bundled as described above, polyethylene glycol, mineral oil, terpene resin, or the like can be used as a tackifier.

The surface of the conductive long fiber of the component (B-1) is preferably coated with a thermoplastic resin in order to enhance dispersibility. The thermoplastic resin used in this case is preferably the same as the thermoplastic resin as the component (A) contained in the composition. When the conductive long fiber of the component (B-1) is coated with a thermoplastic resin, the conductive long fiber of the component (B-1) is coated on the fiber surface with the thermoplastic resin of the component (A) shown above. Cut the unified coating into pellets,
Master pellets containing conductive long fibers (master batch)
Is preferable.

The length of the pellet is preferably 4 to 20 m
m, more preferably 6 to 15 mm. If it is 4 mm or more, high shielding properties can be obtained with a small amount of filling, and if it is 20 mm or less, entanglement between the pellets will be prevented and poor dispersion will be prevented, so that the electromagnetic wave shielding properties of the molded product will be reduced. In addition, a reduction in mechanical strength is prevented.

In the case of pellets, the mixing ratio of the thermoplastic resin for coating and the conductive long fibers is preferably 97 to 10% by volume, more preferably 95 to 20% by volume of the thermoplastic resin. The fibers are preferably 3 to 90% by volume,
More preferably, it is 5 to 80% by volume. When the blending ratio of the conductive long fibers is within the above range, a decrease in the melting rate of the coated thermoplastic resin is prevented, so that the dispersibility of the component (B-1) formed into a master pellet is improved.

The amount of the component (B-1) is preferably 0.1 to 3% by volume, more preferably 0.2 to 1.5% by volume. In addition, since the said compounding quantity is a compounding quantity as an electroconductive long fiber, what was made into a master pellet (B
When used as the component -1), the amount of the component (B-1) is adjusted so that the conductive long fibers have the above amount. When the compounding amount of the component (B-1) is 0.1% by volume or more, a sufficient electromagnetic wave shielding effect is obtained, and when it is 3% by volume or less, a decrease in workability is prevented.

The conductive short fiber of the component (B-2) used in the present invention has a diameter of 30 to 100 μm, preferably 30 to 60 μm.
μm and a length of 1 to 5 mm, preferably 2 to 4 mm. When the diameter is 30 mm or more, it is difficult to cut during processing, the electromagnetic wave shielding effect is enhanced, and the diameter is 100 μm.
When it is less than the above, a decrease in workability is prevented.

The amount of component (B-2) is preferably 3
-15% by volume, more preferably 4-12% by volume.
When the content is 3% by volume or more, a sufficient electromagnetic wave shielding effect is obtained, and when the content is 15% by volume or less, a decrease in workability is prevented, and an increase in the weight of a molded product due to an increase in specific gravity is also prevented.

The total amount of the components (B-1) and (B-2) is preferably 3.1 to 18% by volume, more preferably 5 to 15% by volume. When the total content is 3.1% by volume or more, a sufficient electromagnetic wave shielding effect is obtained, and when the total content is 18% by volume or less, a decrease in workability is prevented.

The mixing ratio of the component (B-1) and the component (B-2) depends on the electromagnetic wave shielding effect required by the application, the strength of the mechanical strength, etc., the type of the thermoplastic resin, and other components. The amount of the component (B-1), (B-2)
It can be appropriately selected within the range of the compounding amounts of the components and the total compounding amounts thereof.

The conductive long fiber (B-1) and the conductive short fiber (B-2) are as follows:
It is preferably selected from (b-3).

(B-1): stainless steel, copper, brass, iron,
Fiber consisting of one kind selected from nickel, aluminum, gold, silver, titanium, tin, lead, antimony, and zinc; (b-2): alloy consisting of a combination of two or more kinds selected from the metals of (b-1) (B-3): glass fiber and / or carbon fiber whose surface is plated or coated with at least one selected from gold, silver, copper, lead and nickel.

The components (B-1) and (B-2) are preferably the fibers of (b-1) among the above, and stainless steel fibers are particularly preferable. As the stainless steel which is the material of the stainless steel fiber, for example, chromium-based stainless steel and nickel-chromium-based stainless steel can be used.

The composition of the present invention may contain, if necessary, conventional additives, for example, as long as the object of the present invention is not impaired.
Stabilizers (antioxidants, UV absorbers, heat stabilizers, etc.), flame retardants, lubricants (zinc stearate, calcium stearate, ethylene bisstearylamide, etc.), release agents, antistatic agents, fillers, plasticizers ( Dibutyl phthalate, butyl benzyl phthalate, dioctyl adipate, etc.). By adding a lubricant or a plasticizer among these, the moldability of the electromagnetic wave shielding molding material can be improved.

The composition of the present invention comprises the component (A), (B-
It can be produced by a method of mixing the component (1) and the component (B-2) with a mixer such as a Henschel mixer, or a method of melt-kneading with a Banbury mixer, a roll mill, a screw extruder, or the like. In the production method of the present invention, a method in which the component (B-1) is coated in advance with a thermoplastic resin to form a master pellet, and then mixed or melt-kneaded with the component (B-2) and the component (A). preferable.

The composition of the present invention can be prepared by injection molding, casting,
It is molded into various molded products by various molding methods such as extrusion molding and press molding, and this molded product is used for housings and internal parts such as light electric equipment and electronic equipment, etc., which require electromagnetic shielding properties. It is suitable for.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In addition, each measurement test method is as follows. (1) Electromagnetic wave shielding property A 120 mm x 120 mm x 2 mm test piece was subjected to a frequency of 1 MHz using the ELECTRO-MAGNETIC CHARASTICS TESTER MA8602B.
The measurement was performed in the range of z to 1 GHz, and the evaluation was made based on the attenuation value at 300 MHz. (2) Izod impact strength Evaluated according to ASTM D256 (notched). (3) Volume specific resistance Measured according to the Japan Rubber Association Standard SRIS2301.

Examples 1 to 5 and Comparative Examples 1 to 4 After blending (A) a thermoplastic resin, (B-1) a master pellet containing conductive long fibers, and (B-2) conductive short fibers shown in Table 1 The mixture was extruded and pelletized using a single screw extruder with a cylinder temperature of 220 ° C. However, the compounding amount of the component (B-1) is the compounding amount of the conductive long fiber. Next, the obtained pellet was dried at 80 ° C. for 8 hours, and then a test piece was formed using a screw-type injection molding machine adjusted to a cylinder temperature of 220 ° C. and a mold temperature of 50 ° C. Table 1 shows the results.

[0035]

[Table 1]

As is clear from Table 1, Examples 1 to 5
Is a combination of long fibers and short fibers of a specific size, and the long fibers are coated with a thermoplastic resin, so that the dispersibility of the long fibers and short fibers is enhanced, resulting in the mechanical strength and electromagnetic wave Excellent shielding properties. On the other hand, Comparative Examples 1 and 2 in which only long fibers were blended were inferior in all test items, and Comparative Examples 3 and 4 in which only short fibers were blended had high impact resistance, but other tests Item was inferior.

[0037]

Industrial Applicability The composition of the present invention has good dispersibility of conductive long fibers and short fibers, does not impair molding processability, and has excellent mechanical strength and electromagnetic wave shielding properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 7/14 C08K 7/14 9/02 9/02 9/04 9/04 H01B 1/22 H01B 1 / 22 Z 1/24 1/24 Z F term (reference) 4F070 AA18 AB08 AC04 AC07 AC28 AD02 AE06 FA03 FA15 FA17 FC05 4J002 BB031 BB061 BB121 BB141 BB151 BB171 BD051 BD081 BN141 BN151 BN161 CF051 CF061 CG011 CL011 FB071 GQ00 5G301 DA02 DA03 DA04 DA05 DA06 DA07 DA10 DA13 DA15 DA20 DA29 DA42 DD06 DD08 DD10 DE01

Claims (6)

[Claims] 1. A thermoplastic resin, (B-1) a conductive filament having a diameter of 4 to 20 μm and a length of 4 to 30 mm, and (B-2) a conductive filament having a diameter of 30 to 100 μm and a length of 1 to 5 mm. A conductive thermoplastic resin composition containing conductive short fibers. 2. (B-1) a conductive long fiber and (B-2)
The conductive thermoplastic resin composition according to claim 1, wherein the conductive short fibers are selected from the following (b-1) to (b-3). (B-1): a fiber composed of one selected from stainless steel, copper, brass, iron, nickel, aluminum, gold, silver, titanium, tin, lead, antimony, and zinc; (b-2): (b-1) (B): a glass fiber whose surface is plated or coated with one or more selected from gold, silver, copper, lead and nickel; and And / or carbon fiber. 3. The composition according to claim 1, wherein the content of the component (B-1) is 0.1 to 3% by volume and the content of the component (B-2) is 3%.
The conductive thermoplastic resin composition according to claim 1, wherein the content is from 15 to 15% by volume. 4. The composition according to claim 1, wherein the component (B-1) is 500 to 20,000.
4. The conductive thermoplastic resin composition according to claim 1, wherein the composition is a book bundle. 5. The conductive thermoplastic resin composition according to claim 1, wherein the conductive long fiber of the component (B-1) is coated with a thermoplastic resin. 6. The method for producing a conductive thermoplastic resin composition according to claim 1, wherein the conductive long fibers of the component (B-1) are coated with a thermoplastic resin to form a master pellet. A method for producing a conductive thermoplastic resin composition, comprising mixing or melt-kneading the mixture with the conductive short fibers of the component (B-2) and the thermoplastic resin of the component (A).