JPH09241420A - Leadless electroconductive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition, composition. comprising a thermoplastic resin, an electroconductive fiber and a specific low-melting metal in a specific proportion, capable of retaining electromagnetic wave shielding effects, excellent in long-term characteristics and environmental compatibility without eluting lead and useful as housings, etc., of various electronic devices. SOLUTION: This leadless electroconductive resin composition comprises (A) 30-98wt.% thermoplastic resin such as a polyphenylene ethereal resin, a polystyrene-based resin, an acrylonitrile-butadienestyrene resin, a polycarbonate resin or a blended material thereof, (B) 1-50wt.% electroconductive fiber such as a metallic fiber (e.g a copper fiber, a brass fiber, a stainless steel fiber, an aluminum fiber or a nickel fiber) and (C) 0.1-30wt.% low-melting metal without containing lead (e.g. an In-Sn alloy, an In-Bi alloy or an Sn-Ag alloy) and, as necessary, further (D) a flux in an amount of 0.1-10 pts.wt. based on 100 pts.wt. component C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive resin composition and a molded article thereof. More specifically, housings and internal parts of electronic devices such as microcomputers and mobile phones, housings and internal parts of home electric appliances such as televisions, videos, radios and air conditioners, light-electric devices such as housings and internal parts of liquid crystal display devices, electronic parts. The present invention relates to a conductive resin composition for devices and molded articles.

Particularly, it is optimally used as an electromagnetic wave shield material.

[0003]

2. Description of the Related Art Electromagnetic wave shielding materials have been used as internal parts and exterior parts of various electric and electronic devices, but for example, microcomputers have been remarkably popularized in recent years and are used in an increasingly wide field. Since the microcomputer has a built-in high-frequency oscillator for generating a clock signal and handles a pulsed wave, it contains a large amount of high-frequency components, which causes interference with peripheral electronic devices such as televisions and communication devices.

On the other hand, most of the microcomputers are portable and can be carried and installed anywhere, but depending on the installation conditions, strong pulsed radio waves (for example, generated by spark discharge) generated from peripheral devices or the like. The computer circuit is directly exposed to the computer system, which causes the computer to malfunction. In view of these circumstances, as a countermeasure against this, electric circuits have been taken into consideration, and measures have been taken to reduce the emission of unnecessary radio waves and reduce the influence of external pulses. An electromagnetic wave shielding effect is applied to the housing that surrounds the. Among them, as such a housing, those made of a thermoplastic resin are often used from the viewpoints of mass productivity, design freedom, economy, and lightweight.
Many measures have been taken to impart electromagnetic wave shielding properties to this. (1) A conductive electromagnetic wave shielding layer is provided on the inner and outer surfaces of the thermoplastic resin molded body by a method such as plating, painting, thermal spraying, and foil bonding. (2) A substance having an electromagnetic wave shielding effect, such as a wire net or a metal foil, is mounted in advance in a molding die and integrated by a molding operation of a thermoplastic resin to obtain an electromagnetic wave shielding molded body. (3) An electromagnetic wave shielding molded body is obtained by molding with a thermoplastic resin mixed with a conductive substance such as metal powder, carbon powder, metal foil, metal fiber, carbon fiber.

However, the method (1) of these measures requires the use of expensive materials and the introduction of expensive equipment in order to improve the adhesion strength between the thermoplastic resin molding and the electromagnetic wave shielding layer. I was there. Regarding the measure (2), in order to prevent the layer such as the wire mesh from moving, deforming or breaking due to the flow of the plasticized synthetic resin in the molding step, it is necessary to introduce expensive equipment.

On the other hand, it is a well-known fact that the measure (3) is particularly effective for improving the electromagnetic wave shielding effect by mixing metal, carbon fiber or flakes. However, it was necessary to further improve the reliability of long-term characteristics. In order to solve this, for example, Japanese Patent Publication No. 6-47254 discloses a pellet-shaped master pellet in which a surface of a conductive filler made of copper fiber and a low melting point metal is integrally formed with a thermoplastic resin layer. The invention of a conductive resin composition characterized by blending thermoplastic resin pellets is described.
According to the examples and comparative examples of the present invention, Sn 60%, P
b Add 40% low melting point metal to 80 ℃ × 3
The electromagnetic wave shielding effect after 000 hours has been improved. Further, Japanese Patent Laid-Open No. 60-189106 discloses a continuous fiber containing a thermoplastic resin and a long fiber conductive filler having a metal plating layer of nickel, tin, solder alloy or the like as a main component and having the metal plating layer. There is a description about a conductive molding material characterized in that the compounding amount of the conductive conductive filler is 5 to 40% by weight based on the thermoplastic resin. In addition, various proposals have been made regarding a low melting point metal containing lead as a component.

However, when lead is discarded, it may be eluted by acid rain or the like to contaminate groundwater and the like. Therefore, in the Industrial Wastes Act, concrete that is blocked when 3 ppm or more of lead is detected in the dissolution test It is obligatory to dispose of it at the manufacturing site. Lead can be toxic if ingested and accumulated in the digestive and respiratory tracts. Moreover, the damage of acid rain is great in each country, and the damage has been reported recently in Japan, which is an alkaline soil.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive resin molding which has a high electromagnetic wave shielding effect, excellent long-term characteristics, and no lead elution, such as weak electric equipment and electronic equipment. is there.

[0009]

That is, according to the present invention, in the injection molding of a thermoplastic resin, the thermoplastic resin (A) 3 is used.
0-98% by weight, (B) conductive fiber 1-50% by weight,
(C) 0.1 to 30% by weight of a low melting point metal containing no lead,
And a molded body thereof.

The present invention will be described in detail below. Examples of the thermoplastic resin used in the present invention include polyphenylene ether resin, polystyrene resin, ABS resin, polycarbonate resin, polyamide resin, polyethylene resin,
Thermoplastic resins such as polypropylene resin and polyvinyl chloride resin can be mentioned.

Further, a blended product containing these resins as a main component can also be used in the present invention. For example, a polystyrene resin blended with polyphenylene ether, a blend of a polycarbonate resin and an ABS resin, and the like can be favorably used. Injection-molded products of these resins have a very good balance between performance and economy and are suitable for housings. Further, various reinforcing agents and various fillers can be added to these resins. For example, one kind or two or more kinds of glass fiber, glass flakes, glass beads, asbestos, calcium carbonate, wood powder and the like can be blended with the above resin.

It is more preferable that these resins contain a flame retardant, and examples thereof include organic phosphorus compounds, inorganic phosphorus compounds, magnesium hydroxide, aluminum hydroxide and halogen compounds. Examples of the organic phosphorus compound include phosphoric acid ester, phosphorous acid ester, phosphine, phosphine oxide, biphosphine, phosphonium salt, and phosphinic acid salt. Examples of inorganic phosphorus compounds include:
Examples thereof include inorganic phosphates represented by ammonium polyphosphate.

As the conductive filler mixed in the thermoplastic resin used in the present invention, metal fibers, metal foils, metal flakes, metal powders, carbon powders, carbon fibers, metal plating,
Examples thereof include metal vapor deposited or metal sprayed carbon fibers or glass fibers, metal plated mica, and organic fibers treated with a conductive substance. Metal fibers are preferred as the conductive filler.

Examples of metal fibers include copper fibers, brass fibers, stainless fibers, aluminum fibers, nickel fibers, and the like. These are drawn by wire drawing, melt spinning,
It can be obtained by a method such as a coil material cutting method, a chatter vibration cutting method, or a wire cutting method. Further, the metal fibers may be surface-treated with a titanate coupling agent or the like.

The content of these conductive fibers is 1 to 50.
%, Preferably 3 to 40% by weight, more preferably 5 to 35% by weight. It is added as needed according to the need of the conductive performance. The low-melting-point metal containing no lead used in the present invention refers to a metal simple substance having a melting point of 500 ° C. or lower, preferably 400 ° C. or lower, and more preferably 350 ° C. or lower, and a mixture. Among them, it means a substance that does not contain lead, and preferably does not contain lead, mercury, cadmium, thallium, or arsenic.

That is, it is an alloy represented by a simple substance of Sn, Bi, Zn, In, or an Sn-A-X-Y system or an In-A-X system. (Here, A is In, Bi, Ag, Cu, Sb,
Zn, Au, etc., and X and Y are not added or, if added, Ag, Cu, In, Bi, Sb, etc. ) As a specific example, Sn simple substance, Bi simple substance, Zn simple substance, Sn-
Bi-X system, Sn-In-X system, Sn-Ag-X system, S
n-Bi-X system, Sn-Zn-X system, Sn-Ag-X
System, Sn-Sb-X system, and the like. Here, X means addition of nothing or addition of another metal. Preferred among these metals are Sn-Bi.
-X system, Sn-In-X system, Sn-Ag-X system, Sn-
Bi-X system, Sn-Zn-X system, Sn-Ag-X system, S
It is an n-Sb-X system.

More specifically, examples of these low melting point metals are 48Sn-52In (melting point 117 ° C.), 43
Sn-57Bi (melting point 139 ° C), Sn-Ag, for example, Senju Metal Industry Co., Ltd. product No. 220 (96.5Sn-3.5).
Ag) (melting point 221 ° C), Sn-Cu, for example Senju Metal Industry Co., Ltd. product number 230 (melting point 227 ° C), Sn-Ag-
Cu For example, Senju Metal Industry Co., Ltd. product number 7027 (melting point 2
16-220 ℃) Senju Metal Industry Co., Ltd. Product No. 7047
(Melting point 216 to 323 ° C.) Sn-Ag- (Bi, S
b), Sn-Sb-Cu, for example, Senju Metal Industry Co., Ltd. product number 9028 (232 to 321 ° C), 97In-3Ag.
(Melting point 143 ° C), Sn-In- (Ag, Cu), Sn
-Bi- (Ag, Cu, In) such as Sn-Ag-Bi
-Cu Senju Metal Industry Co., Ltd. Product No. 7046, Sn-Zn
-(In, Bi, Ag), Sn-Ag- (Bi, Sb,
Cu), 50Sn-50Sb (melting point 235-240)
C.), 20Sn-80Au (280.degree. C.) and the like. These metals and alloys may be used alone or in combination of two or more. Furthermore, other metals may be included as a trace component of 5% or less. These are merely examples, and low-melting-point metals that do not contain lead are within the scope of the present application. Therefore, it is clear that the scope of the present invention also includes those with the addition of trace components other than lead based on these substances. The shape of these low melting point metals may be any of granular, linear, powder and rod shapes.

The amount of the low melting point metal added is 0.1
-30% by weight, preferably 0.5-20% by weight, more preferably 1-10% by weight. If it is added in excess of 30% by weight, the low melting point metal is liberated and the physical properties and appearance of the resin are impaired, which is not preferable. Examples of the flux used in the present invention include commonly used organic acid-based stearic acid, lactic acid, oleic acid, glutamic acid, lauric acid and resin-based rosin, active rosin, vegetable pine resin, fats and oils. Flux containing halogen is not preferable because it causes mold corrosion and the like. In the present invention, flack is an optional component. When sflux is added, it is added in an amount of 0.1 to 10 parts by weight, preferably 1 to 8 parts by weight, based on 100 parts by weight of the low melting point metal.

Various stabilizers, plasticizers, lubricants, flame retardants other than those exemplified, pigments, inorganic fillers, etc. are appropriately added to the resin composition of the present invention within a range not impairing the characteristics thereof according to known methods. Can be used. When the conductive material of the present invention is used as an electromagnetic wave shielding material, the electromagnetic wave shielding effect must be at least 10 dB or more, preferably 20 dB or more, more preferably 30 d.
Must be B or higher.

Specific examples of the use of the conductive material of the present invention include televisions, mobile phones, personal computers, NES, game machines, air conditioners, copying machines, microwave ovens, housings for medical equipment having electronic circuits, and the like. It is suitable as a material for covering internal parts, circuits, etc., or as a material for covering automobile electronic devices. The method of molding the electromagnetic wave shielding member from the resin composition of the present invention is not particularly limited, and molding by an injection molding machine which is usually performed, or a method by melt pressing, vacuum molding, sheet molding including multilayer molding Etc. are used. The raw materials may be the ones according to the present invention at the stage of molding, and the thermoplastic resin, the conductive fiber, and the low melting point metal may be simply mixed and used.
The conductive fiber and the low melting point metal may be mixed and used, or the conductive fiber / the low melting point metal and the thermoplastic fiber may be mixed and used, and the thermoplastic resin / the conductive fiber and the thermoplastic resin / the low melting point metal may be used. It may be mixed and used, or may be used by mixing thermoplastic resin / conductive fiber / low melting point metal and thermoplastic resin,
You may mix and use thermoplastic resin / electroconductive fiber / low melting point metal and thermoplastic resin / electroconductive fiber and thermoplastic resin.
At this time, as an example of the method for producing thermoplastic resin / conductive fiber, thermoplastic resin / low melting point metal, thermoplastic fiber / conductive fiber / low melting point metal, etc. It can be granulated by cutting after coating the fibers and / or low melting metal fibers, and a method of mixing this with pellets of a thermoplastic resin, bundling conductive fibers with a low melting metal and cutting this And a method of mixing with thermoplastic resin pellets and the like.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The measuring method used in the examples will be described. [1] Measurement of electromagnetic wave shield effect Anritsu Corporation spectroanalyzer MS623
A measuring instrument and a tracking generator MH628A were used to measure a 100 × 100 × 2 mm flat plate test piece in an anechoic box in the frequency range of 100 to 1000 MHz, and the attenuation value was 500 MHz. [2] Measurement of long-term characteristics Put the molded product in a thermo-hygrostat at a temperature of 70 ° C and a humidity of 70% 1
After exposure for 00 days, the electromagnetic wave shielding property is dB
And the retention rate. [3] Dissolution test A molded product was crushed into chips of 1 mm to 2 mm, mixed with an eluate at a ratio of 10% by weight, and shaken continuously for 6 hours with a shaker, and the amount of eluted lead was measured. Measure by absorption method. The eluent is 0.1 mol acetic acid and 0.0643 mol
A solution obtained by dissolving the sodium hydroxide in 1000 ml of pure water was used.

The types of raw materials used in the examples and the manufacturing method are shown below. Modified polyphenylene ether resin Asahi Kasei Corporation, Zylon 240Z, PP in Table 1
Abbreviated as E / PS. PC / ABS (blend of polycarbonate resin and ABS resin) Psycoloy C280 manufactured by Ube Saikon Corporation, abbreviated as PC / ABS in Table 1. HIPS (Rubber Reinforced Polystyrene Resin) Flame-retardant polystyrene VS40 manufactured by Asahi Kasei Corporation, abbreviated as HIPS in Table 1. Preparation of Metal Fiber Master Pellets Used in this Example EMC 1992.11.5. <No. 55> p7
The method described in Nos. 8 to 82, that is, the coil material cutting method, was used to cut into a circle-converted diameter of 30 μm.

Metal fibers 50 of each material shown in Table 1
The surface of zero metal and linear low melting point metal (including rosin-based flux in some cases shown in Table 1) is coated with a thermoplastic resin through a die of an extruder. This is cut into a length of 5 mm in the fiber direction with a pelletizer to obtain metal fiber master pellets. The low melting point metals shown in Table 1 are as follows.・ # 7046: Senju Metal Industry Co., Ltd. product number 7046
(Sn-Ag-Bi-Cu system; melting temperature 189 to 214
℃) ・ # 220: Senju Metal Industry Co., Ltd. product number 220 (S
n-Ag system; melting temperature 221 ° C.) # 7027: Senju Metal Industry Co., Ltd. product number 7027
(Sn-Ag-Cu system; melting temperature 216-220 ° C) # 230: Senju Metal Industry Co., Ltd. product number 220 (S
n-Cu system; melting temperature 227 ° C.) Sn / Pb: Normal Sn63% -Pb37% solder.

[0024]

Examples 1 to 10 The metal fiber master pellets are shown in Table 1.
The mixture was mixed with each thermoplastic resin in the compounding ratio shown therein, and the cylinder temperature was PPE / PS of 270 ° C. and PC / PC using an injection molding machine (Autoshot 50B manufactured by FANUC).
ABS is set to 250 ℃, HIPS is set to 240 ℃,
The mold temperature is set to 50 ° C. and a flat plate test piece of 100 × 100 × 2 mm is molded. This molded product is used for various tests.

[0025]

[Comparative Examples 1 to 3] The same procedure as in Examples was carried out except that a low melting point metal of Sn / Pb was used. Comparative Example 1 corresponds to Example 1, Comparative Example 2 to Example 9 and Comparative Example 3 to Example 10.

[0026]

[Table 1]

[0027]

The conductive resin composition and molded product of the present invention retain the electromagnetic wave shielding effect, have excellent long-term characteristics, do not elute lead, and are better to the environment than the conventional ones.

Claims (7)

[Claims] 1. A thermoplastic resin of 30 to 98% by weight,
(B) 1 to 50% by weight of conductive fibers and (C) 0.1 to 30% by weight of a low-melting point metal containing no lead (C), a conductive resin composition. 2. The conductive resin composition according to claim 1, and (D) flux 0.1 to 10 parts by weight (low melting point metal 10).
(Based on 0 parts by weight). 3. The conductive resin composition according to claim 1, wherein the conductive fiber is a metal fiber. 4. The conductive resin composition according to claim 1, wherein the thermoplastic resin comprises a polyphenylene ether resin, a polystyrene resin, an ABS resin, a polycarbonate resin and a blend thereof. Stuff. 5. The conductive resin composition according to claim 1, which comprises a flame retardant. 6. A molded article comprising the conductive resin composition according to claim 1, 2, 3, 4, or 5. 7. A conductive resin molded body, wherein the conductive resin molded body according to claim 6 is a housing.