JPH10237313A - Resin composition containing conductive fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition useful for conductive materials improved in an electromagnetic wave-shielding property, dispersibility, rigidity and surface appearance, especially for electromagnetic wave-shielding members, by compounding a thermoplastic resin with metal fibers having a specific fiber length. SOLUTION: This resin composition comprises (A) 99-20wt.%, preferably 90-40wt.%, more preferably 85-50wt.%, of a thermoplastic resin such as polyethylene and (B) 1-80wt.% of metal fibers which are produced by a coil material- cutting method and which have each a triangular or square cross section, whose surfaces are roughened in an area of at least 10% among the longitudinal surfaces and which have a number-average fiber length of 0.1-5mm. The resin composition preferably further contains (C) 0.0001-5wt.% of a dispersant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material having improved electromagnetic wave shielding properties, dispersibility, rigidity and surface appearance, and more particularly to a resin composition useful for an electromagnetic wave shielding member.

[0002]

2. Description of the Related Art Electric circuits and ICs are used in various kinds of electric equipment, but may malfunction due to electromagnetic waves generated from outside and inside. In order to prevent this, the generation of electromagnetic waves has been reduced by changing the circuit design, but there is a limit, and they are covered with a material having electromagnetic wave shielding properties. For these materials, a method of forming a conductive film on a resin molded product by plating, painting, thermal spraying, or the like is employed, but a separate step is required and the cost is high.

[0003] Therefore, it has been practiced to give the resin itself shielding properties. As a method of imparting shielding properties to a resin, a method of kneading metal fibers, foils, particles, or carbon black, carbon fiber, ferrite, barium titanate, or the like is known. Among these,
The metal fiber method shows higher shielding properties in a smaller amount.

Conventionally, when these metal fibers are filled in a resin, the added metal fibers having a high aspect ratio exhibit a shielding effect more efficiently, and therefore, the length of the added fibers is preferably 3 to 3 μm. It was 5 mm or more. However, when long fibers are used, there is a problem that the fibers are entangled with each other, resulting in poor dispersion, failing to obtain a sufficient electromagnetic wave shielding effect, and lowering the mechanical strength of the molded product. In particular, when the surface of the fiber is rough or the fiber is curled, such as a metal fiber produced by using a coil material cutting method, the entanglement between the fibers is more remarkable. In order to improve the dispersibility of metal fibers,
A method of adding a dispersant such as a coupling agent has been used.

A method of providing a layer of a coupling agent on the surface of a metal fiber is described in, for example, JP-A-60-18314 and JP-A-60-18.
Although these are disclosed in JP-A-112854, metal fibers of 3 to 5 mm or more are used due to concerns about a decrease in aspect ratio, and fibers of the coil material cutting method are not used. The present inventors have tried to improve the dispersibility by adding a dispersant to fibers having a diameter of 5 mm or more using fibers obtained by the coil material cutting method, but they did not reach a sufficient level.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive material having improved electromagnetic wave shielding properties, dispersibility, rigidity and surface appearance, particularly a resin composition useful for an electromagnetic wave shielding member. .

[0007]

Under such circumstances, the present inventors have conducted intensive studies on an electromagnetic wave shielding material. As a result, surprisingly, by shortening the fiber, the dispersibility and the electromagnetic wave shielding material were reduced. It has been found that the properties are simultaneously satisfied, leading to the present invention. That is, the present invention is as follows. (1) (I) 99 to 20% by weight of a thermoplastic resin, and
(II) A resin composition comprising 1 to 80% by weight of a metal fiber having a number average fiber length of 0.1 mm or more and less than 5 mm. (2) (I) 98.9999 to 15% by weight of a thermoplastic resin, and (II) a number average fiber length of 0.1 mm or more and 5 m.
A resin composition comprising 1 to 80% by weight of a metal fiber having a particle size of less than m and 0.0001 to 5% by weight of a dispersant (III). (3) At least one of the longitudinal surfaces of the metal fibers
3. The resin composition according to the above item 1 or 2, wherein the surface in a range of 0% or more is rough. (4) The resin composition as described in (1), (2) or (3) above, wherein the cross-sectional shape of the metal fiber is triangular or square. (5) The resin composition as described in (1), (2), (3) or (4) above, wherein the metal fiber is formed by a coil material cutting method. (6) An electromagnetic wave shielding member formed from the resin composition described in the above item 1, 2, 3, 4 or 5. (7) A master pellet in which 10 to 99% by weight of a metal fiber bundle having a number average fiber length of 0.1 mm or more and less than 5 mm is coated with 90 to 1% by weight of a thermoplastic resin.

Hereinafter, the present invention will be described in detail. The thermoplastic resin used in the present invention, low, medium, high-density polyethylene, polypropylene, polyvinyl chloride,
Polystyrene, acrylonitrile-styrene copolymer,
Acrylonitrile-butadiene-styrene copolymer (hereinafter abbreviated as ABS resin), polyamide, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether (hereinafter abbreviated as PPE), polymethyl methacrylate, polyetherimide And styrene-butadiene copolymers and hydrogenated compositions thereof, and polymer blends of combinations of two or more of these, such as polycarbonate and acrylonitrile-butadiene-styrene copolymer, polyphenylene ether and polystyrene. In particular, high impact polystyrene (hereinafter abbreviated as HIPS), acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyphenylene ether, polyamide and polycarbonate, and these resins alone and alloys thereof are preferable. Resins reinforced with glass fibers or carbon fibers can also be used. Further, a resin in which a dispersant such as a coupling agent is kneaded in advance in the above resin can be used. Further, a flame retardant may be used in combination.

In the present invention, the thermoplastic resin is 99 to 2
0% by weight, preferably 90 to 40% by weight, more preferably 85 to 50% by weight. If the amount of the thermoplastic resin is too large, the electromagnetic wave shielding properties decrease, and if the amount is too small, the fluidity of the resin during molding is hindered. The metal fibers used in the present invention are stainless steel, brass, copper, aluminum, iron, gold, silver, nickel, titanium, tin, lead, antimony, zinc, cadmium, magnesium, tungsten,
Platinum, lithium, molybdenum, beryllium and their two
An alloy of a combination of more than one kind, an alloy mainly composed of these, a compound of these with phosphorus, and the like can be given. Among these, stainless steel, brass, copper, aluminum, iron, gold, silver, nickel and titanium are preferred.

These metal fibers can be obtained by a method such as coil material cutting, wire drawing, melt spinning, and wire cutting. Further, these metal fibers may be surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent, or a surface treatment agent such as a triazine thiol compound. Among these metal fibers, the fiber produced by the coil material cutting method has a remarkable effect of the present invention.

[0011] The coil material cutting method is a method in which a metal foil plate is mounted in a coil material shape on a metal fiber manufacturing apparatus having a structure and a function substantially similar to a lathe, and the end surface thereof is cut to obtain metal fibers. Yes, for example, Electromagnetic Environment Engineering Information (EMC) 199
November 5, 2 <No. 55> pages 78 to 82. The coil material can be obtained by continuously winding a commercially available metal foil around a spindle drum. The metal foil to be used may be subjected to a surface treatment by applying or dipping a coupling agent such as a silane coupling agent or a titanate coupling agent, or a surface treatment agent such as a triazine thiol compound to the metal surface. What applied the resin containing an agent may be used.

In the metal fiber used in the present invention, the triangular shape and the quadrangular shape are shapes that have three or four sides and are regarded as substantially triangular or square, and the corners are slightly rounded. This includes a case where each side is not a perfect straight line. In the metal fiber used in the present invention, the rough surface refers to an infinite number of irregularities formed on the surface of the fiber in the longitudinal direction, and more specifically, irregularities in which the height difference between the concave portion and the convex portion is 1 μm or more are arbitrary. It means one or more in 10 μm square. More specifically, it is a streak-like unevenness that forms an angle within 45 degrees with a straight line perpendicular to the long axis direction of the fiber, and the unevenness with a height difference of 1 μm or more between the recess and the protrusion is 10 μm parallel to the long axis direction of the fiber. It means one or more present in an arbitrary straight line of length.
The roughness of the rough surface is measured by a surface shape measuring microscope (for example, VF7500 manufactured by Keyence Corporation), an atomic force microscope (AFM, for example, SPI370 manufactured by Seiko Electronics Co., Ltd.)
0), and can be measured by a scanning electron microscope (SEM) or the like. An example is a fiber created by a coil material cutting method. FIG. 1 shows a photograph of the fiber thus produced. The cross-sectional shape of the fiber obtained by the coil material cutting method is substantially rectangular, which is distinguished from the fact that the cross-sectional shape of the fiber manufactured by the conventional method of drawing and drawing is a fan shape or a polygonal shape. . The surface of the fiber obtained by the coil material cutting method has 4
At least one of the surfaces is rough. The chatter phenomenon is a phenomenon in which the cutting blade vibrates slightly during cutting, and as a result, streaky irregularities are generated on the cutting surface in a direction perpendicular to the cutting direction, that is, the major axis direction of the fiber, and this improves the surface roughness.

The fiber diameter of the metal fiber used in the present invention in terms of a circle is 1 μm to 500 μm, preferably 3 μm to 500 μm.
00 μm, more preferably 5 to 60 μm. The number average fiber length is 0.1 mm or more and less than 5 mm, preferably 0.1 mm or more and 3 mm or less, and more preferably 0.1 mm or more.
5 mm or more and 3 mm or less. If the number average fiber length is too short, the electromagnetic wave shielding effect is not sufficiently obtained, and if it is too long, the fibers are entangled, causing poor dispersion, causing a problem at the time of molding, or the electromagnetic wave shielding effect is not sufficiently obtained. .

As the fiber bundle, the number of the above fibers is 10 to 10.
It is good to be bundled 100,000, more preferably 50 to 30,000, further preferably 100 to 100
It is desirable that the bundle is zero. In the present invention, the metal fiber is used in an amount of 1 to 80% by weight, preferably 10 to 60% by weight, and more preferably 15 to 50% by weight. If the amount of the metal fiber is too small, the electromagnetic wave shielding property is insufficient, and if it is too large, the fluidity of the resin at the time of molding is hindered.

[0015] The fiber obtained by the coil material cutting method is produced as a continuous long fiber. The method for introducing the fiber into the thermoplastic resin is not particularly limited, and examples thereof include the following method. A method in which a sizing agent is added, cut into a certain fiber length, blended with a resin, kneaded and extruded. A method in which a fiber having a high-speed rotor is mixed with a small piece of resin while cutting the fiber into short pieces. A method in which a resin is extruded while feeding fibers continuously or in the middle of an extruder. A method of coating a metal fiber as it is or after applying a sizing agent, coating it with a resin, cutting it into a certain fiber length to obtain a master pellet, blending the master pellet with a resin, and molding. A method in which a metal fiber is formed into a flat plate and then sandwiched between sheets to form a sheet or compression.

[0016] Among these, the method of using a master pellet formed by coating a metal fiber with a thermoplastic resin and cutting it into a certain fiber length maintains the fiber aspect ratio,
This is preferable as a method for efficiently exhibiting the electromagnetic wave shielding effect. The master pellet contains 90 to 1% by weight of a thermoplastic resin and 10 to 99% by weight of a metal fiber. The amount of the metal fiber is preferably 30 to 99% by weight, more preferably 50 to 99% by weight. If the amount of the metal fibers is too small, the melting rate of the coating resin decreases, and the dispersibility of the metal fibers decreases. The cross-sectional shape of the master pellet is not particularly limited, but it is more preferable that the thermoplastic resin is present between metal fibers from the viewpoint of dispersibility.

In the resin composition of the present invention, a dispersant can be further used. In that case, 98.9999 to 15% by weight of the thermoplastic resin, 1 to 80% by weight of the metal fiber, and 0.0001 to 5% by weight of the dispersant. The amount of the dispersant is preferably 0.0001 to 3% by weight, more preferably 0.0001 to 2% by weight. If the amount of the dispersant is too large, conduction between the metal fibers is hindered, and the electromagnetic wave shielding effect may be reduced.

The dispersing agent used in the present invention includes a coupling agent such as a titanate coupling agent, a silane coupling agent, an aluminate coupling agent, a zirconia aluminate coupling agent, and a triazine thiol compound. Can be used. Of these, titanate-based coupling agents and silane-based coupling agents are particularly preferred.

Examples of the titanate-based coupling agent include isopropyl triisostearoyl titanate, isopropyl octanoyl titanate, isopropyl dimethacryl isostearyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri (dioctyl phosphate). ) Titanate, isopropyl rimyl phenyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (n-aminoethyl-aminoethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) Titanate, tetra (2,2-diallyloxymethyl-1) Heptyl) bis (ditridecyl) phosphite titanate, dicumyl phenyloxy acetate titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, diisostearoyl ethylene titanate, bis (dioctyl pyrophosphate) ethylene titanate.

Among them, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (n-aminoethyl-aminoethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate , Tetraoctylbis (ditridecylphosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, bis (dioctylpyrophosphate) Ethylene titanate is preferred.

Examples of the silane coupling agent include vinyl trimethoxysilane, vinyl triethoxy silane, vinyl trichlorosilane, vinyl tris (β-methoxyethoxy) silane, and amino-based N- ( 2-aminoethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl)
3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltriethoxysilane,
3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, epoxy-based compounds such as 3-glycidoxypropyltrimethoxysilane,
-Glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,
4-epoxycyclohexyl) ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane as chloro-based, 3-methacryloxypropyltrimethoxysilane, 3-methacrylic as methacryloxy-based Roxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, mercapto-type, 3-mercaptopropyltrimethoxysilane, cationic-type N- (2- (Vinylbenzylamino) ethyl) -3-aminopropyltrimethoxysilane.hydrochloride.

Examples of the aluminate coupling agent include acetoalkoxyaluminum diisopropylate. Examples of the zirconia aluminate-based coupling agent include alcohol-based and glycol-based coupling agents. To the resin composition of the present invention, various stabilizers, plasticizers, flame retardants, pigments, inorganic fillers and the like can be appropriately added according to a known method as long as the characteristics are not impaired. In particular, when used as an electromagnetic wave shielding member, it is more preferable to use a flame retardant in combination.

In the present invention, the electromagnetic wave shielding member is
It is necessary that the electromagnetic wave shielding effect is 10 dB or more,
It is preferably 20 dB or more, and more preferably 30 dB or more. Specific examples of the use of materials include televisions, mobile phones, personal computers, NES, game machines, air conditioners, copiers, housings such as microwave ovens, internal components, members for covering circuits, medical devices, and electronic devices for automobiles. Used for covering materials, building materials used for walls, floors, etc.

The method for molding an electromagnetic wave shielding member from the resin composition of the present invention is not particularly limited, and may be a method generally used for molding by an injection molding machine, a method using a melt press, vacuum molding, or multilayer molding. Sheet molding or the like is used.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In addition, each measurement and the materials used are as follows. Electromagnetic wave shielding effect: 100 × in an anechoic box using a spectrum analyzer MS623A measuring device and tracking generator MH628A manufactured by Anritsu Corporation.
A test piece having a thickness of 100 × 1 mm was measured at a frequency of 100 to 1
It is measured in the range of 000 MHz and expressed as an attenuation value of 500 MHz. Flexural modulus; measured in accordance with ASTM D790. Dispersibility: Soft X-ray inspection device (Softex, SV-
At 100A), the state of dispersion of the metal fibers in the injection-molded article was observed. Surface appearance: The state of the surface of the injection-molded article was visually observed, and a good product was evaluated as ○, a better product as ◎, and a slightly poor product as Δ,
Defective objects are represented by x. [Used resin, etc.] The following substances are used.

High impact polystyrene resin (HIP
S) is manufactured by Asahi Kasei Kogyo Co., Ltd .; Styron H9405
And acrylonitrile-butadiene-styrene copolymer resin (ABS) manufactured by Asahi Kasei Corporation; Styrac A
BS / VA51 was replaced with a polyphenylene ether-based resin (P
PE) is manufactured by Asahi Chemical Industry Co., Ltd .;
And nylon 66 resin (PA66) manufactured by Asahi Kasei Kogyo Co., Ltd .;
6) Made by Ube Industries, Ltd .; UBE nylon 6.101
3B, and a blend of polycarbonate resin and ABS resin (PC / ABS) manufactured by Ube Sykon Co., Ltd .; [Production of Metal Fiber by Coil Material Cutting Method] As in Reference Example 1 below.

[0027]

[Reference Example 1] Electromagnetic Environmental Engineering Information (EMC) 1992/1
January 5 <No. 55> A metal fiber of stainless steel, brass, copper, or aluminum was produced based on the method described on pages 78 to 82. That is, using a device shown in FIG. 2, a 5% aqueous solution of polyvinyl alcohol is continuously applied on both sides of a 30 μm-thick metal sheet by a coating roll, and dried to a coating thickness of about 20 μm with a coating drying heater. (This coating operation was omitted for brass). As shown in FIG. 3, a thin metal plate was wound 500 times around a turning spindle drum of a metal fiber manufacturing apparatus having the same structure and function as a lathe, and the end face was tool-feeded at 15 μm.
Metal fibers are obtained by cutting with a cutting blade at a speed of / rev. One side of the obtained fiber cross section corresponds to the thickness of the coil material, and the other side has a rectangular shape determined by the feed amount of the tool.

The cross-sectional area of the fiber is measured from a photograph of the cross section of the fiber. The converted diameter converted to the diameter of the circular cross section is 30 μ on average. The ratio of the rough surface measured by a scanning electron microscope observation and a surface shape measurement microscope (VF7500, manufactured by Keyence Corporation) was 21%, and an arbitrary straight line parallel to the long axis direction, 10 μm, measured at any 10 points. There are four average irregularities of 1 μm or more that intersect with the straight line.

[0029]

Examples 1 to 7 Cutting was performed by the method of Reference Example 1, and the surface of a metal fiber of the type shown in Table 1 was extruded and coated with the coating resin shown in Table 1, and an extruded product containing the metal fiber was 3 mm. And cut into pellets to obtain master pellets.
The master pellet is dry-blended with natural pellets of the base resin shown in Table 1 so that the amount of the metal fiber after blending becomes 25 wt%, and injection molding is performed. Table 1 shows the results.

[0030]

Example 8 Example 1 is carried out in the same manner as in Example 1 except that 3% by weight of a titanate coupling agent (manufactured by Ajinomoto Co .; Prenact KR38S) is used as the coating resin for the metal fibers. Table 1 shows the results.

[0031]

Comparative Examples 1 to 7 The same procedure as in Examples 1 to 7 was carried out except that the cutting length of the master pellet was changed to 5 mm. Table 2 shows the results.

[0032]

Comparative Example 8 The same operation as in Example 8 was carried out except that the cut length of the master pellet was changed to 5 mm.
Table 2 shows the results. As can be seen from Tables 1 and 2, Examples 1 to 7 are excellent in flexural modulus and dispersibility as compared with Comparative Examples 1 to 7, respectively, and have poor surface appearance due to undispersed fibers. can not see. In addition, despite having the same amount of metal fibers, it has excellent electromagnetic wave shielding properties.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

The composition of the present invention has excellent electromagnetic wave shielding properties, and has good dispersibility, surface appearance and rigidity.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a brass fiber produced by a coil material cutting method.

FIG. 2 is a schematic diagram of a step of applying a metal-soluble plastic to a coil material cutting metal fiber and winding a thin metal sheet in Reference Example 1.

FIG. 3 is a schematic diagram of a cutting process of a metal fiber manufacturing apparatus in which a thin metal coil is wound around a turning spindle drum in Reference Example 1.

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[Procedure amendment]

[Submission date] February 28, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (7)

[Claims] (I) 99 to 20% by weight of a thermoplastic resin,
And (II) a resin composition comprising 1 to 80% by weight of metal fibers having a number average fiber length of 0.1 mm or more and less than 5 mm. (I) a thermoplastic resin 98.9999-1
5% by weight and (II) 1 to 80% by weight of metal fibers having a number average fiber length of 0.1 mm or more and less than 5 mm, and (II)
I) A resin composition comprising 0.0001 to 5% by weight of a dispersant. 3. The resin composition according to claim 1, wherein at least 10% or more of the surfaces of the metal fibers in the major axis direction are rough. 4. A metal fiber having a triangular or quadrangular cross section.
The resin composition as described in the above. 5. The resin composition according to claim 1, wherein the metal fiber is prepared by a coil material cutting method. 6. An electromagnetic wave shielding member formed of the resin composition according to claim 1, 2, 3, 4, or 5. 7. A thermoplastic resin is contained in 10 to 99% by weight of a metal fiber bundle having a number average fiber length of 0.1 mm or more and less than 5 mm.
~ 1% by weight coated master pellets.