JP2003012945A - Conductive resin composition and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive resin composition which has high conductivity and an excellent shield effect of an electromagnetic wave, and is capable of forming a molding having good surface properties with small scattering physical properties, and particularly is suitably usable for a case part of an electrical apparatus, above all, as a case of a personal computer and a housing of information terminal of a portable phone or the like. SOLUTION: The conductive resin composition comprises a thermoplastic resin and a carbon fiber, per 100 pts.wt. of the composition, the proportion of the carbon fiber being 10-50 pts.wt., and in the carbon fiber, the proportion of a fiber length of >=500 μm being 10-50 wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive resin composition which can be formed into a molded product having high conductivity, excellent electromagnetic wave shielding effect, high rigidity, stable physical properties and good surface property, and more particularly to an electric resin composition. The present invention relates to a conductive resin composition that can be suitably used as a housing part of equipment, especially a housing of a personal computer or a housing of an information terminal such as a mobile phone.

[0002]

2. Description of the Related Art A resin composition used as a material for shielding electromagnetic waves such as a case or cover of a personal computer is required to have high conductivity in order to shield electromagnetic waves. As a material satisfying such requirements, a resin composition in which a conductive filler is dispersed in a thermoplastic resin matrix has been proposed.

As a filler to be mixed with a thermoplastic resin, carbon fiber is generally used because it has conductivity and also has an effect as a reinforcing agent. A molded article made of a resin composition in which a carbon fiber is mixed with a thermoplastic resin is excellent in rigidity and has conductivity, but in order to be used for the purpose of shielding electromagnetic waves, it is necessary to have higher conductivity. For that purpose, it is necessary to mix a large amount of carbon fibers with the thermoplastic resin.

However, when a resin composition containing a large amount of carbon fibers as described above is used as a molded article, not only the carbon fibers are oriented and warpage becomes large, but also the physical properties tend to decrease when the content is high. There is also the problem that the cost becomes high.

As a solution to such a problem, JP-A-3-181532 discloses, for example, polyester resin, polyethylene resin, polypropylene resin, polyamide resin, acrylonitrile-butadiene-styrene copolymer (hereinafter referred to as "ABS"). (Hereinafter referred to as)), a polyacetal resin, a modified polyphenylene oxide resin, a polycarbonate resin or the like, and a resin composition in which swollen graphite having a particle size of 20 μm or less is mixed at a ratio of 5 to 30% by weight has been proposed. A molded article composed of this resin composition,
Although the warp is small, it is inferior to the molded product containing the carbon fiber in terms of electrical conductivity.

On the other hand, the conductivity is greatly affected by the length of the carbon fiber, but when the thermoplastic resin and the carbon fiber are kneaded, the carbon fiber is broken and shortened, so that sufficient conductivity cannot be obtained. Therefore, long-fiber pellets having a pellet size = carbon fiber length are also used, but there is a problem that the physical properties become unstable because the blending ratio of the long fibers is large.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a molded article having high conductivity, excellent electromagnetic wave shielding properties, high rigidity, small variation in physical properties, and good surface properties. The present invention provides a conductive resin composition that can be used.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has shown in FIG. 1 the kneading operation after supplying the carbon fibers when kneading the thermoplastic resin and the carbon fibers. As shown in the order of carrying → kneading → carrying → weir → carrying, it is possible to reduce the rate at which the carbon fibers are broken, and as a result, the fiber length distribution of the carbon fibers becomes wide, so that the conductivity is high, The present inventors have found that a resin composition having a good surface property can be obtained, and have reached the present invention.

That is, according to the present invention, the ratio of the carbon fiber is 10 to 50 parts by weight to 100 parts by weight of the resin composition containing the thermoplastic resin and the carbon fiber, and the fiber length of the carbon fiber is 10 to 50 parts by weight. The ratio of particles of 500 μm or more is 10 to 50
The present invention relates to a conductive resin composition characterized in that the content is% by weight. Further, the present invention, the thermoplastic resin is supplied from the head of the kneading machine, when the carbon fiber is supplied from the middle of the kneading machine and melt-mixed, the kneading operation after the carbon fiber supply,
The present invention relates to the method for producing a conductive resin composition, which is carried out in the order of transportation → kneading → transportation → weir → transportation.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive resin composition of the present invention has a carbon fiber content of 10 to 50 parts by weight based on 100 parts by weight of a resin composition containing a thermoplastic resin and carbon fibers. The proportion of carbon fibers having a fiber length of 500 μm or more is 10 to 50% by weight.

The ratio of carbon fiber in the resin composition is 10
When the amount is less than the weight part, the conductivity is not stably expressed and the rigidity when formed into a molded product is poor, and when the mixing ratio exceeds 50 parts by weight, the mechanical properties start to deteriorate and the carbon fiber is oriented and molded. The warp of the product increases, resulting in poor appearance.

If the proportion of carbon fibers having a fiber length of 500 μm or more is less than 10% by weight, sufficient conductivity cannot be obtained, and if the proportion exceeds 50% by weight, the physical properties vary greatly. And the surface of the molded product becomes rough, resulting in poor appearance.

Further, in the present invention, 3 to 12 parts by weight of the carbon fibers having a fiber length of 50 μm or less,
It is preferable that the amount of particles exceeding 50 μm is 7 to 38 parts by weight. If the fiber length is less than 50 μm and is less than 3 parts by weight, the surface of the molded product becomes rough, resulting in poor appearance. If it exceeds 12 parts by weight, sufficient conductivity cannot be obtained.
On the other hand, if the fiber length is more than 50 μm less than 7 parts by weight, sufficient conductivity cannot be obtained, and if it exceeds 38 parts by weight, the surface of the molded product becomes rough, resulting in poor appearance.

Examples of the thermoplastic resin which is the main component of the conductive resin composition include polyamide resins such as nylon 6, nylon 66 and nylon 12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins and polyarylate. Resin, vinyl chloride resin, polyethylene resin, chlorinated polyethylene resin, chlorinated polypropylene resin, polypropylene resin, polystyrene resin, acrylonitrile-styrene resin, ABS resin, vinylidene chloride resin, vinyl acetate resin, thermoplastic polyimide resin, butadiene resin, Polyacetal resin, ionomer resin, ethylene-vinyl chloride copolymer resin, ethylene-vinyl acetate copolymer resin, polyphenylene oxide resin, modified polyphenylene oxide resin, Risaruhon resin, acrylic resin,
Examples thereof include methacrylic resin, phenoxy resin, polyvinyl formal resin, polyvinyl butyral resin, and the like, and also a mixture of two or more of these resins. Among them, polyamide resin, polyester resin, polycarbonate resin, polycarbonate ABS resin (ABS resin blended with polycarbonate), and polyarylate resin are preferable, and among them, polyamide resin is particularly preferable because it has good affinity with carbon fiber.

The polyamide resin includes homopolyamide and copolyamide obtained by polymerizing monomers such as lactam, aminocarboxylic acid and / or diamine and dicarboxylic acid, and a mixture thereof. That is, polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon) 612), polyundecamethylene adipamide (nylon 116), polybis (4-aminocyclohexyl) methandodecamide (nylon PACM1)
2), polybis (3-methyl-4aminocyclohexyl) methandodecamide (nylon dimethyl PACM1
2), Polynonamethylene terephthalamide (nylon 9
T), polyundecamethylene terephthalamide (nylon 11T), polyundecamethylene hexahydroterephthalamide (nylon 11T (H)), polyundecamide (nylon 11), polydodecamide (nylon 1)
2), polytrimethylhexamethylene terephthalamide (nylon TMDT), polyhexamethylene terephthalamide (nylon 6T), polyhexamethylene isophthalamide (nylon 6I), polymethaxylylene adipamide (nylon MXD6) and copolymers thereof. , A mixture, etc., among them, nylon 6, nylon 66,
Nylon 12, copolymerized polyamides or mixed polyamides thereof are particularly preferable.

In the present invention, when an amorphous polyamide is blended with the crystalline polyamide resin, a resin composition having excellent appearance can be obtained. Examples of the amorphous polyamide resin include polycondensates of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane, terephthalic acid / 2,
2,4-trimethylhexamethylenediamine / 2,4,
4-trimethylhexamethylenediamine polycondensate, isophthalic acid / bis (3-methyl-4-aminocyclohexyl) methane / ω-laurolactam polycondensate, isophthalic acid / terephthalic acid / hexamethylenediamine polycondensate, Isophthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine polycondensate, isophthalic acid / terephthalic acid /
2,2,4-trimethylhexamethylenediamine / 2,
Examples thereof include polycondensates of 4,4-trimethylhexamethylenediamine and polyphthalates of isophthalic acid / bis (3-methyl-4-aminocyclohexyl) methane / ω-laurolactam. In addition, the terephthalic acid component and / or the isophthalic acid component constituting these polycondensates may have the benzene ring substituted with an alkyl group or a halogen atom. Furthermore, these amorphous polyamides can be used in combination of two or more kinds. Preferably, a polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane, or terephthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4 Polycondensate of trimethylhexamethylenediamine, or polycondensate of isophthalic acid / terephthalic acid / hexamethylenediamine / bis (3-methyl-4-aminocyclohexyl) methane and terephthalic acid /
2,2,4-trimethylhexamethylenediamine / 2,
A mixture with a polycondensate of 4,4-trimethylhexamethylenediamine is used.

Considering the relaxation of the crystallinity of the polyamide resin, the heat of fusion of this amorphous polyamide resin is 1 cal when measured with a differential scanning calorimeter at a temperature rising rate of 16 ° C./min in a nitrogen atmosphere. / G or less is preferable.

The mixing ratio of the crystalline polyamide and the amorphous polyamide is not particularly limited, but (crystalline polyamide) / (amorphous polyamide) = 50/50 to 98
It is preferably / 2 (weight ratio). If the amount of the amorphous polyamide is less than 2% by weight, the surface smoothness, that is, the glossiness tends to be lost when the carbon fiber is mixed in a high concentration, and if the amount of the amorphous polyamide is more than 50% by weight, the high concentration is obtained. When carbon fiber is blended with, amorphous polyamide generally has a high melt viscosity, so a smooth surface cannot be obtained unless it is molded with a high temperature mold, and the crystallinity is low, so injection molding etc. The molding cycle is extended and the productivity deteriorates.

The relative viscosity of the polyamide resin used in the present invention is not particularly limited, but the relative viscosity measured by using 96 wt% concentrated sulfuric acid as a solvent at a temperature of 25 ° C. and a concentration of 1 g / dl is 1. It is preferably in the range of 4 to 4.0. If the relative viscosity is less than 1.4, the viscosity is low,
After the melt-kneading, the take-up property becomes difficult, and it becomes difficult to obtain desired physical properties in the composition. On the other hand, when it is more than 4.0, the fluidity at the time of molding is poor due to the high viscosity, and a sufficient injection pressure is not applied, which makes it difficult to form a molded product.

In the present invention, examples of the carbon fibers which serve as a conductive agent and a reinforcing agent include polyacrylonitrile-based (PAN-based) and pitch-based carbon fibers having high strength and high conductivity. Specific examples of the PAN-based carbon fiber include Bethfight chopped fiber and Bethfight milled fiber manufactured by Toho Rayon Co., Ltd., Toraysha's trading card chopped fiber and trading card milled fiber, Mitsubishi Rayon Pyrofil, Fort
Examples of the pitch-based carbon fiber include Donacarbo chopped fiber and Donacarbo milled fiber manufactured by Osaka Gas Co., Ltd., and Creca Chopped Fiber manufactured by Kureha Chemical Co., Ltd. Examples include creca and milled fiber.

The carbon fiber has a fiber length of 0.1 to 1 before kneading.
2 mm is preferable, and 1-8 mm is particularly preferable. The fiber diameter is preferably in the range of 5 to 15 μm.

The conductive resin composition having the above-mentioned composition contains a brominated flame retardant or a phosphorus flame retardant in an amount of 50 parts by weight or less, preferably 20 parts by weight, based on 100 parts by weight of the resin composition.
It is preferable that the proportion is ˜40 parts by weight because the flame retardancy can be further improved in addition to the above characteristics. If the blending ratio exceeds 50 parts by weight, the mechanical strength of the molded product tends to be impaired.

The brominated flame retardant used in the present invention preferably has a bromine content of 50 to 90% by weight. When the bromine content is less than 50% by weight, the flame retardant effect is poor and it is necessary to add a large amount of flame retardant, which impairs the mechanical strength. Further, when the bromine content exceeds 90% by weight, bromine is likely to be liberated during molding, so that the effect of the present invention cannot be sufficiently exhibited. Specifically, for example, brominated polystyrene, brominated crosslinked aromatic polymer, brominated styrene / maleic anhydride copolymer, brominated polyphenylene ether, brominated epoxy resin, brominated phenoxy resin, etc. Particularly, brominated polystyrene can be preferably used.

Examples of the brominated polystyrene used here include those obtained by adding bromine to polystyrene, those obtained by polymerizing a styrene monomer to which bromine has been added, or a mixture of both of these. In particular, bromine has been added. PDBS manufactured by Great Lakes Co., which is obtained by polymerizing a styrene monomer, and Pyrocheck 68PB manufactured by Ferro Co., which is obtained by adding bromine to polystyrene, is preferable in terms of color tone, fluidity and heat resistance.

As the phosphorus-based flame retardant, various allotrope species of inorganic phosphorus (red, purple or black phosphorus) sold under the name of phosphorus and organic phosphorus-based flame retardants such as organic phosphates are used. it can. Red phosphorus and melamine phosphate are preferred for engineering plastic resins such as polyamides that have high processing temperatures. The shape of red phosphorus when blended in the thermoplastic resin is not particularly limited, but in consideration of dispersibility in the resin composition, it is generally a finely divided shape, for example, a particle diameter of 200 μm or less. It is desirable to use red phosphorus in divided form, preferably in the form of particles having an average particle size in the range of 1-100 μm.

The red phosphorus may be used only as the red phosphorus, but a red heat-resistant type having a shape in which the surface of the red phosphorus particles is coated with a polymer film or an inorganic coating material is preferable. As the polymer for coating the surface of the red phosphorus particles, an epoxy resin, a polymer having maleic acid, fumaric acid or an allyl unsaturated bond, a melting point of 50 to 90 ° C. and 10,000
Unsaturated polyesters having the following molecular weights, novolac type thermoplastic phenol-formaldehyde polycondensation products and thermoplastic phenol-isobutyraldehyde polycondensation products are mentioned, among them thermoplastic phenol-isobutyraldehyde polycondensation products. It can be preferably used. The blending amount of these polymers is not particularly limited, but is at most 90% by weight with respect to the total weight of the mixture of red phosphorus and the coating polymer, and generally 2 to 50%.
It is preferably in the weight%.

The resin composition of the present invention may contain a flame retardant aid in addition to the above flame retardant for the purpose of bringing out the effect of the flame retardant sufficiently. Examples of the flame retardant aid used with the brominated flame retardant include antimony trioxide, sodium antimonate, tin oxide (IV), iron oxide (III), zinc oxide, zinc borate, etc., and red phosphorus flame retardant. Examples of the flame retardant auxiliary used together include melamine polyphosphate, melamine cyanurate, and magnesium hydroxide. The blending ratio of the flame retardant aid to the flame retardant is, in the case of a brominated flame retardant in a weight ratio, flame retardant: flame retardant aid = 5: 1 to 1:
1. In the case of red phosphorus, it is preferable that the ratio of flame retardant: flame retardant aid = 1: 2 to 1: 7.

In addition to the conductive resin composition of the present invention, a releasing agent, a heat stabilizer, an antioxidant, a light stabilizer, a lubricant, a pigment, a plasticizer, a cross-linking agent, and a resistance to Various additives such as impact modifiers, inorganic substances and dyes, and carbon-based or metal-based conductive aids may be added, and these are added when the resin composition is melt-kneaded or melt-molded.

The conductive resin composition of the present invention is produced by melting and kneading a thermoplastic resin, carbon fiber, a flame retardant and various additives optionally blended with a kneader and pelletizing. At that time, the thermoplastic resin is supplied from the top of the kneading machine, the carbon fiber is supplied from the middle of the kneading machine, and the kneading operation after the carbon fiber is supplied is carried out as shown in FIG. It can be manufactured by carrying out in the order of → weir → transfer.

Conventionally, when the thermoplastic resin and the carbon fiber are kneaded by a kneader, the kneading operation after the carbon fiber is fed is as shown in FIG.
As shown in Figure 3, the process was carried out in the order of transfer → kneading → weir → transfer. This is because in order to sufficiently mix the thermoplastic resin and the carbon fiber, it was considered necessary to carry out the kneading with the weir once stopping the transportation. However, in this method, the carbon fibers are broken during mixing, and for example, what was 3 mm before kneading is shortened to about 300 μm, so that sufficient conductivity cannot be obtained.

On the other hand, in the present invention, the kneading operation after supplying the carbon fibers is carried out in the order of transportation → kneading → transportation → weir → transportation as shown in FIG. Since a resin having a fiber length of 500 μm or more remains in an amount of 5 to 50% by weight, a resin composition having high conductivity and good surface property can be obtained.

In the present invention, among the carbon fibers,
Fiber having a fiber length of 50 μm or less, 3 to 12 parts by weight, 50 μ
The conductive resin composition having 7 to 38 parts by weight of more than m supplies thermoplastic resin and 3 to 12 parts by weight of carbon fiber from the head of the kneader, and 7 to 38 parts by weight of carbon fiber. It can be produced by supplying from the middle of the step and mixing by the same kneading operation as described above.

As described above, by supplying the carbon fibers separately in two places, the carbon fibers initially supplied are strongly kneaded in the shear melting zone of the resin at the time of kneading, so that the carbon fibers are cut into fine particles of 50 μm or less. Since the carbon fiber supplied later does not pass through the above kneading zone, it is 50 μm.
It will be a very long length. As a result, a resin composition having high conductivity and good surface property can be obtained.

In order to obtain a molded product from the resin composition thus obtained, the resin composition may be injection-molded using an injection molding machine or press-molded using a press molding machine. . A molded article composed of the conductive resin composition configured as described above has a high conductivity and an excellent electromagnetic wave shielding effect, a high rigidity, and a good surface property with little variation in physical properties can be obtained. Fuel system parts, electric / electronic parts and electric equipment housings, such as PC housings and covers, mechanical bearings, mechanical packing sealants, fuel tubes, fuel connectors, clean room equipment, printers and copier parts. Can be suitably used as.

[0035]

EXAMPLES The present invention will now be specifically described based on examples, but the present invention is not limited to these examples. The measurement of various physical properties in the following examples and comparative examples was carried out by the following methods.

[Measurement of Fiber Length Distribution of Carbon Fiber] A pellet of a thermoplastic resin containing carbon fiber was dissolved in sulfuric acid having a concentration of 96% or more, and the carbon fiber was taken from this solution and an enlarged photograph was taken with a microscope. The fiber length of the carbon fiber in the photograph was measured, and the weight fraction of less than 50 μm, 50 μm or more and less than 500 μm, or 500 μm or more was calculated from the distribution of the fiber length.

[Conductivity] Metal terminals are heated and press-fitted into ASTM No. 1 pieces molded by injection molding using NESTAL SG75 manufactured by Sumitomo Heavy Industries, Ltd. at a 150 mm interval shown in FIG. Was embedded, and the resistance between the terminals was measured with a tester of MODEL3010 manufactured by HIOKI.

[Flexural Modulus] According to ASTM D790, it was measured using ASTM No. 1 piece molded by injection molding using Nestal SG75 manufactured by Sumitomo Heavy Industries, Ltd.

[Surface property] In accordance with JIS B0601, Sumitomo Heavy Industries, Ltd. Nestal SG75 injection molded using ASTM No. 1 piece, Tokyo Seimitsu Co., Ltd.
Centerline parallel roughness (Ra) was measured using Handy Surf E-30A.

[Flame retardancy] The flame retardancy was measured according to UL94 V-0.

Example 1 Polyamide A (UBE Nylon 1011FB manufactured by Ube Industries)
Carbon fiber A (Mitsubishi Rayon) as shown in FIG. 1 is placed in the place where the resin is in a molten state (resin temperature 280 ° C.) when 80 wt% is charged into an extruder (Tem35B manufactured by Toshiba Machine Co., Ltd.) having the screw configuration shown in FIG. Pyrofil TR06NEB3E) was added so as to be 20 wt%, kneaded and pelletized, and the distribution length of carbon fiber was measured. Further, using the obtained pellets, ASTM No. 1 pieces were injection-molded by NESTAL SG75 manufactured by Sumitomo Heavy Industries, Ltd. at a resin temperature of 280 ° C. and a mold temperature of 80 ° C., and the conductivity, bending elastic modulus and surface property were measured. The results obtained are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that the screw structure was changed to that shown in FIG.
Flexural modulus and surface properties were measured. The results obtained are shown in Table 1.

Example 2 Polyamide A (UBE Nylon 1011FB made by Ube Industries)
90 wt% was put into an extruder (Tem35B manufactured by Toshiba Machine Co., Ltd.) having the screw configuration shown in FIG. 1, and when the resin was in a molten state (resin temperature 280 ° C.), carbon fiber B (Fortafil Fiber) as shown in FIG. Inc. Fortafil 243) is 10
The carbon fiber was added so as to be wt%, kneaded and pelletized, and the distribution length of the carbon fiber was measured. Also, using the pellets obtained, ASTM No. 1 pieces were put together by Sumitomo Heavy Industries, Ltd. Nestal SG
The resin was injection molded at a resin temperature of 280 ° C. and a mold temperature of 80 ° C. at 75, and the conductivity, bending elastic modulus and surface property were measured. The results obtained are shown in Table 1.

Comparative Example 2 The same procedure as in Example 2 was carried out except that the screw structure in Example 2 was changed to that shown in FIG.
Flexural modulus and surface properties were measured. The results obtained are shown in Table 1.

Example 3 Polyamide A (UBE Nylon 1011FB manufactured by Ube Industries)
47 wt%, polyamide B (manufactured by EMS-CHEIE)
Extrusion having 5% by weight of grivory 21), 7% by weight of antimony oxide (antimony trioxide No. 0 of Mikuni Smelting Co., Ltd.) and 21% by weight of flame retardant (GLC PDBS-80 by Great Lakes Chemical Corporation) with the screw configuration shown in FIG. Machine (Toshiba Machinery Co., Ltd. tem35B)
The carbon fiber A (Mitsubishi Rayon) as shown in Fig. 1 is placed in the place where the resin is in a molten state (resin temperature 280 ° C).
Pyrofil TR06NEB3E) was added so as to be 20 wt%, kneaded and pelletized, and the distribution length of carbon fiber was measured. Also, using the obtained pellets, ASTM No. 1 pieces were subjected to resin temperature 2 at Nestal SG75 manufactured by Sumitomo Heavy Industries, Ltd.
Injection molding was performed at a mold temperature of 80 ° C., and the conductivity, flexural modulus, surface property, and flame retardancy were measured. The results obtained are shown in Table 1.

Example 4 Polyamide A (UBE Nylon 1011FB made by Ube Industries)
46 wt%, polyamide B (manufactured by EMS-CHEIE)
Grivory 21) 2 wt%, antimony oxide (Mikuni Smelting Co., Ltd. antimony trioxide No. 0) 7 wt%, flame retardant (G made by Great Lakes Chemical Corporation G
LC PDBS-80) 20 wt% and carbon fiber B
(Fortafil Fiber Inc. Fortafil 243) 5wt% Figure 2
Extruder with screw configuration (Toshiba Machinery Co., Ltd.
35B) and the resin is in a molten state (resin temperature 28
Carbon fiber A from Fig. 2 at the temperature of 0 ° C)
(Mitsubishi Rayon Pyrofil TR06NEB3E) 20wt%
Was additionally charged, kneaded and pelletized, and the distribution length of carbon fiber was measured. In addition, using the obtained pellet, ASTM1
The piece was injection-molded by Nestal SG75 manufactured by Sumitomo Heavy Industries, Ltd. at a resin temperature of 280 ° C. and a mold temperature of 80 ° C., and the conductivity, flexural modulus, surface property, and flame retardancy were measured. The results obtained are shown in Table 1.

Example 5 Polycarbonate ABS (Uberoi CX5 manufactured by Ube Saikon Co., Ltd.)
5B) 80 wt% was charged into an extruder (Tem35B manufactured by Toshiba Machine Co., Ltd.) having the screw structure shown in FIG. 1, and carbon fiber B (resin temperature 280 ° C.) was applied to the resin in a molten state (resin temperature 280 ° C.) as shown in FIG. Fortafil Fiber Inc. Fortafil24
3) was added so as to be 20 wt%, kneaded and pelletized, and the distribution length of carbon fiber was measured. Further, using the obtained pellets, ASTM No. 1 pieces were injection-molded by NESTAL SG75 manufactured by Sumitomo Heavy Industries, Ltd. at a resin temperature of 280 ° C. and a mold temperature of 80 ° C., and the conductivity, bending elastic modulus and surface property were measured. The results obtained are shown in Table 1.

Example 6 Polyamide A (UBE Nylon 1011FB made by Ube Industries)
Carbon fiber C (Nippon Polymer Co., Ltd.) as shown in FIG. 1 is put in the place where the resin is in a molten state (resin temperature 280 ° C.) when 70 wt% is put into an extruder (Tem35B manufactured by Toshiba Machine Co., Ltd.) having the screw configuration shown in FIG. Sangyo Co., Ltd. CFPA-LC
3) was added so as to be 30 wt%, kneaded and pelletized, and the distribution length of carbon fiber was measured. Further, using the obtained pellets, ASTM No. 1 pieces were injection-molded by NESTAL SG75 manufactured by Sumitomo Heavy Industries, Ltd. at a resin temperature of 280 ° C. and a mold temperature of 80 ° C., and the conductivity, bending elastic modulus and surface property were measured. The obtained results are shown in Table 2.

Comparative Example 3 The procedure of Example 6 was repeated except that the screw structure was changed to that shown in FIG.
Flexural modulus and surface properties were measured. The obtained results are shown in Table 2.

Comparative Example 4 The procedure of Example 6 was repeated except that the screw structure was changed to that shown in FIG.
Flexural modulus and surface properties were measured. The obtained results are shown in Table 2.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

According to the present invention, by blending a thermoplastic resin with carbon fibers having a wide fiber length distribution in a predetermined ratio, it is possible to obtain conductivity which can be used for electromagnetic wave shielding, and A resin composition having high rigidity and good surface property can be obtained. Therefore, it is possible to provide a conductive resin composition that can be suitably used as an electromagnetic wave shield that requires conductivity and rigidity, and can be suitably used as a casing or cover of electric equipment, particularly a personal computer.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a kneading operation of a thermoplastic resin and a carbon fiber by a kneader in Example 1 of the present invention.

FIG. 2 is a diagram showing an outline of a kneading operation of a thermoplastic resin and carbon fibers by a kneading machine in Example 4 of the present invention.

FIG. 3 is a diagram showing an outline of a kneading operation of a thermoplastic resin and carbon fibers by a kneader in Comparative Example 1 of the present invention.

FIG. 4 is a diagram showing an outline of a kneading operation of a thermoplastic resin and carbon fibers by a kneader in Comparative Example 4 of the present invention.

FIG. 5 is a schematic diagram showing a method for measuring conductivity.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01B 1/18 H01B 1/18 5/00 5/00 H 13/00 13/00 Z // B29K 105: 06 B29K 105: 06 F-term (reference) 4F071 AA02 AA12X AA22X AA34X AA43 AA48 AA50 AA54 AB03 AD01 AF37 AH05 AH12 AH16 4F201 AA29 AB11 AB18 AB25 AD16 AE03 AH33 AR12 BA01 BD06 BK02 BK13 BK38 BK49 BK63 BK66 BK69 BQ07 BQ50 4J002 BN15X CG00W CL001 CL002 DA016 FA046 FD116 GG01 GN00 GQ00 5G301 DA20 DA42 DA51 DD10 DE01 DE02 5G307 AA08

Claims (6)

[Claims] 1. The ratio of carbon fiber is 10 to 5 relative to 100 parts by weight of a resin composition containing a thermoplastic resin and carbon fiber.
0 parts by weight of the carbon fibers having a fiber length of 500
A conductive resin composition, characterized in that the proportion of particles having a thickness of μm or more is 10 to 50% by weight. 2. The proportion of carbon fibers is 10 to 5 relative to 100 parts by weight of a resin composition containing a thermoplastic resin and carbon fibers.
0 parts by weight of the carbon fibers having a fiber length of 500
The proportion of the carbon fibers having a fiber length of 50 μm or more is 10 to 50% by weight, and the carbon fibers having a fiber length of 50 μm or less are 3 to 12 parts by weight, and those having a fiber length of more than 50 μm are 7 to 38 parts by weight. A characteristic conductive resin composition. 3. The conductive resin composition according to claim 1, wherein the thermoplastic resin is a polyamide resin. 4. When the thermoplastic resin is supplied from the head of the kneading machine and the carbon fibers are supplied from the middle of the kneading machine to be melt-mixed, the kneading operation after the carbon fiber supply is carried out → kneading → carrying → weir → The method for producing a conductive resin composition according to claim 1, wherein the steps are performed in the order of transportation. 5. When the thermoplastic resin and the carbon fibers are melt-mixed by a kneader, the thermoplastic resin and 3 to 12 parts by weight of the carbon fibers are supplied from the top of the kneader, and then the carbon fibers 7 to 3 are added.
The method for producing a conductive resin composition according to claim 2, wherein 8 parts by weight are supplied from the middle of the kneading machine, and the kneading operation is carried out in the order of transportation → kneading → transportation → weir → transportation. 6. A molded product obtained by molding the conductive resin composition according to claim 1.