Patent Description:
With development of electric/electronic technology, there is a trend toward digitalization in various industrial fields. Also, in automobile and electrical/electronic fields, system digitalization is in progress to improve performance, stability, and convenience to meet the needs of users.

In recent years, it has been reported that electromagnetic waves generated from electronic devices adversely affect other devices or human bodies. Accordingly, research is being actively conducted to develop a material for shielding electromagnetic waves.

Metallic materials such as conductive materials are heavy and expensive. In consideration of these disadvantages, polymer resins, which are advantageous in terms of weight reduction, price, design, and the like, have mainly been used to manufacture electronic devices and automobile components.

However, since most polymer resins have a property of transmitting electromagnetic waves, it is difficult to effectively shield electromagnetic waves using a polymer.

Accordingly, a material for shielding electromagnetic waves needs to be developed, and in particular, there is increasing demand for a material capable of shielding electromagnetic waves while satisfying mechanical properties.

<CIT> discloses a high-rigidity electromagnetic shielding composition including: (A) about <NUM> to about <NUM> wt % of polyamide resin including an aromatic moiety in the backbone structure; (B) about <NUM> to about <NUM> wt % of carbon fiber; and (C) about <NUM> to about <NUM> wt % of metallic filler.

Therefore, the present invention has been made in view of the above problems, and it is one object of the present invention to provide a thermoplastic resin composition having excellent mechanical properties and electromagnetic wave shielding performance, the use of the thermoplastic resin composition, and a method of manufacturing a molded article using the thermoplastic resin composition.

The technical problems that are intended to be achieved in the present invention are not restricted to the above described problems, and other problems, which are not mentioned herein, could be clearly understood by those of ordinary skill in the art from details described below.

In accordance with one aspect of the present invention, provided is a thermoplastic resin composition including a thermoplastic resin, carbon fiber, carbon nanotube, plate-shaped graphite having an aspect ratio of <NUM> or more, and metal fiber, wherein, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber is contained in an amount of <NUM> parts by weight to <NUM> parts by weight, and wherein the carbon nanotube has a BET surface area of <NUM><NUM>/g to <NUM><NUM>/g as measured by BET analysis according to a nitrogen gas adsorption method.

In accordance with another aspect of the present invention, the thermoplastic resin composition according to the present invention is used in automobile components or electrical and electronic components requiring an electromagnetic wave shielding performance of <NUM> dB or more in MHz and GHz frequency range.

In accordance with a further aspect of the present invention, provided is a method of manufacturing a molded article, the method including forming a first kneaded product by kneading a thermoplastic resin, carbon nanotube, and plate-shaped graphite having an aspect ratio of <NUM> or more; forming a second kneaded product by adding carbon fiber to the first kneaded product and kneading; forming a thermoplastic resin composition according to the present invention by adding metal fiber to the second kneaded product and kneading; and manufacturing a molded article by molding the thermoplastic resin composition.

In accordance with yet another aspect of the present invention, provided is a molded article comprising the thermoplastic resin composition.

A thermoplastic resin composition according to one embodiment of the present invention can have excellent mechanical properties and electromagnetic wave shielding performance.

In addition, when a method of manufacturing a molded article according to one embodiment of the present invention is used, a molded article having excellent mechanical properties and electromagnetic wave shielding performance can be easily manufactured.

The effects of the present invention are not limited to the above-described effects, and effects not mentioned herein will be clearly understood by those skilled in the art from the present specification and the accompanying drawings.

<FIG> is a cross-sectional view of an extruder used to manufacture a molded article according to one embodiment of the present invention.

In the present invention, it is to be understood that, unless stated otherwise, when a part "comprises" any element, the part may include other elements without excluding other elements.

In the present invention, when a member is located "on" the other member, this includes not only the case where the member is in contact with the other member but also the case where another member is present between the two members.

In the present specification, "parts by weight" may mean a weight ratio between components.

Hereinafter, a thermoplastic resin composition and a method of manufacturing a molded article using the same according to the present invention will be described in detail.

According to one embodiment of the present invention, a thermoplastic resin composition including a thermoplastic resin; and a filler including carbon fiber, carbon nanotubes, plate-shaped graphite having an aspect ratio of <NUM> or more, and metal fiber, wherein, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber is contained in an amount of <NUM> parts by weight to <NUM> parts by weight, and wherein the carbon nanotube has a BET surface area of <NUM><NUM>/g to <NUM><NUM>/g as measured by BET analysis according to a nitrogen gas adsorption method, is provided.

The thermoplastic resin composition according to one embodiment of the present invention may have excellent mechanical properties and electromagnetic wave shielding performance.

According to one embodiment of the present invention, the thermoplastic resin may include at least one of a nylon resin, a polycarbonate resin, a polyalkylene terephthalate resin, and a maleic anhydride-modified polyolefin resin. In this case, when a thermoplastic resin composition including the thermoplastic resin is used, a molded article having excellent mechanical properties may be easily implemented.

According to one embodiment of the present invention, the thermoplastic resin may include at least one of a nylon resin, a polycarbonate resin, a polybutylene terephthalate resin, a polyethylene terephthalate resin, and a maleic anhydride-modified polyolefin resin. When a thermoplastic resin composition including at least one of a nylon resin, a polycarbonate resin, a polybutylene terephthalate resin, and a maleic anhydride-modified polyolefin resin is used, a molded article having excellent mechanical properties may be easily implemented.

According to one embodiment of the present invention, the maleic anhydride-modified polyolefin resin may be a polymer prepared by grafting maleic anhydride onto a polyolefin resin at a grafting degree of <NUM> % by weight to <NUM> % by weight. When a thermoplastic resin composition including a polyolefin resin onto which maleic anhydride is grafted at a grafting degree of <NUM> % by weight to <NUM> % by weight is used, a molded article having excellent mechanical properties such as tensile strength and impact strength may be provided.

In the present specification, grafting degree may be measured based on results obtained through acid-base titration of a modified polyolefin resin. As a specific example, <NUM> of a modified polyolefin resin is added to <NUM> of xylene saturated with water and refluxed for about <NUM> hours. Then, <NUM> % by weight of a thymol blue-dimethylformamide solution was added thereto in a small amount, and slight excess titration is performed using a <NUM> N sodium hydroxide-ethyl alcohol solution to obtain an ultramarine solution. An acid value is determined by performing back titration of this solution with a <NUM> N hydrochloric acid-isopropyl alcohol solution until the solution becomes yellowish. Thereby, the content (% by weight) of a compound, i.e., maleic anhydride, grafted onto a polyolefin resin may be calculated. In this case, the content of maleic anhydride included in a modified polyolefin resin corresponds to grafting degree.

The maleic anhydride-grafted polyolefin may be a polymer of monomer including an olefin having <NUM> to <NUM> carbon atoms. Specifically, in the present invention, polyethylene onto which maleic anhydride is grafted at a grafting degree of <NUM> % by weight to <NUM> % by weight may be used.

According to one embodiment of the present invention, the carbon fiber may have a diameter of <NUM> to <NUM>. Specifically, the carbon fiber may have a diameter of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. When a thermoplastic resin composition including carbon fiber having a diameter within this range is used, processability and moldability may be excellent and strength may be improved. In addition, when a thermoplastic resin composition includes the carbon fiber having a diameter within the above range, the electromagnetic wave shielding performance of the thermoplastic resin composition may be improved.

In the present specification, the diameter of carbon fiber may be measured using a scanning electron microscope (SEM). Specifically, <NUM> fiber strands are selected using a scanning electron microscope, and the diameter of each strand is measured using an icon bar for measuring diameter, and then an average diameter of the carbon fiber is calculated in arithmetic mean using the measured values.

According to the present invention, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber is contained in an amount of <NUM> parts by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber may be contained in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight. More specifically, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber may be contained in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the relative contents of the thermoplastic resin and the carbon fiber within the above-described range, the strength of the thermoplastic resin composition may be improved, and the appearance of a molded article manufactured using the thermoplastic resin composition may be excellent. In addition, when the carbon fiber is contained in an amount within the above-described range, the rigidity of a thermoplastic resin composition may be excellent, and a molded article having improved electromagnetic wave shielding efficiency may be easily implemented.

According to the present invention, the carbon nanotubes have a BET surface area of <NUM><NUM>/g to <NUM><NUM>/g. Specifically, the carbon nanotubes may have a BET surface area of <NUM><NUM>/g to <NUM><NUM>/g, <NUM><NUM>/g to <NUM><NUM>/g, <NUM><NUM>/g to <NUM><NUM>/g, <NUM><NUM>/g to <NUM><NUM>/g, or <NUM><NUM>/g to <NUM><NUM>/g. A thermoplastic resin composition including the carbon nanotubes having a BET surface area within this range may have improved conductivity and electromagnetic wave shielding efficiency.

In the present specification, a BET surface area may be measured using BET analysis equipment (surface area and porosity analyzer ASAP <NUM>, Micromeritics Co. ) according to a nitrogen gas adsorption method.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the carbon nanotubes may be contained in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the carbon nanotubes may be contained in an amount of <NUM> part by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the relative contents of the thermoplastic resin and the carbon nanotubes within the above-described range, the conductivity and electromagnetic wave shielding efficiency of a thermoplastic resin composition may be effectively improved. In addition, when the carbon nanotubes are contained in an amount within the above-described range, deterioration in the mechanical properties of a thermoplastic resin composition may be prevented.

According to the present invention, the thermoplastic resin composition includes plate-shaped graphite having an aspect ratio of <NUM> or more. By using plate-shaped graphite, the electromagnetic wave shielding efficiency of the thermoplastic resin composition may be further improved.

Plate-shaped graphite commonly used in the art to which the present invention pertains may be used in the present invention without particular limitation. Such plate-shaped graphite may have a high aspect ratio, and may be naturally plate-shaped or chemically or physically separated from a layered structure to have a plate shape. As a specific example, plate-shaped graphite having an aspect ratio of <NUM> or more, <NUM> or more, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> may be used, without being limited thereto.

In the present specification, aspect ratio measurement methods commonly used in the art to which the present invention pertains may be used without particular limitation.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the plate-shaped graphite may be contained in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the plate-shaped graphite may be contained in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the content of the plate-shaped graphite included in the thermoplastic resin composition within the above-described range, the electromagnetic wave shielding efficiency of the thermoplastic resin composition may be further improved. In addition, by adjusting the relative contents of the thermoplastic resin and the plate-shaped graphite within the above-described range, deterioration in the mechanical properties of the thermoplastic resin composition may be prevented, and a molded article having excellent appearance may be implemented.

According to one embodiment of the present invention, the metal fiber may have a diameter of <NUM> to <NUM>. Specifically, the metal fiber may have a diameter of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. When the metal fiber has a diameter within this range, the electromagnetic wave shielding performance of a thermoplastic resin composition may be further improved.

In the present specification, the diameter of metal fiber may be measured using a scanning electron microscope (SEM). Specifically, <NUM> fiber strands are selected using a scanning electron microscope, and the diameter of each strand is measured using an icon bar for measuring diameter, and then an average diameter of the metal fiber is calculated in arithmetic mean using the measured values.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the metal fiber may be contained in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the metal fiber may be contained in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the content of the metal fiber within the above-described range, the rigidity and electromagnetic wave shielding performance of a thermoplastic resin composition may be further improved.

In addition, when the relative contents of the thermoplastic resin and the metal fiber are adjusted within the above-described range, when a thermoplastic resin composition including the thermoplastic resin and the metal fiber is used, a molded article having excellent appearance may be manufactured.

The thermoplastic resin composition of the present invention preferably has a tensile strength of <NUM> MPa or more, more preferably <NUM> MPa or more, still more preferably <NUM> MPa or more as measured according to ASTM D638. As a specific example, the thermoplastic resin composition preferably has a tensile strength of <NUM> to <NUM> MPa, more preferably <NUM> to <NUM> MPa, still more preferably <NUM> to <NUM> MPa. Within this range, tensile strength and physical property balance may be excellent.

The thermoplastic resin composition of the present invention preferably has an impact strength of <NUM> J/m or more, more preferably <NUM> J/m or more, still more preferably <NUM> J/m or more as measured according to ISO 180A. As a specific example, the thermoplastic resin composition preferably has an impact strength of <NUM> to <NUM> J/m, more preferably <NUM> to <NUM> J/m, still more preferably <NUM> to <NUM> J/m. Within this range, impact strength and physical property balance may be excellent.

The thermoplastic resin composition of the present invention preferably has a flexural modulus of <NUM>,<NUM> MPa or more, more preferably <NUM>,<NUM> MPa or more, still more preferably <NUM>,<NUM> MPa as measured according to ASTM D790. As a specific example, the thermoplastic resin composition preferably has a flexural modulus of <NUM>,<NUM> to <NUM>,<NUM> MPa, more preferably <NUM>,<NUM> to <NUM>,<NUM> MPa, still more preferably <NUM>,<NUM> to <NUM>,<NUM> MPa. Within this range, flexural modulus and physical property balance may be excellent.

The thermoplastic resin composition of the present invention preferably has an electromagnetic wave shielding ability of <NUM> dB or more, more preferably <NUM> dB or more, still more preferably <NUM> dB or more as measured under a condition of <NUM> using EM2107A manufactured by Electro-Metrics Corporation. As a specific example, the thermoplastic resin composition preferably has an electromagnetic wave shielding ability of <NUM> to <NUM> dB, more preferably <NUM> to <NUM> dB, still more preferably <NUM> to <NUM> dB. Within this range, electromagnetic wave shielding performance and mechanical property balance may be excellent.

The thermoplastic resin composition of the present invention is preferably used in automobile components or electrical and electronic components, more preferably automobile components or electrical and electronic components requiring an electromagnetic wave shielding performance of <NUM> dB or more in MHz and GHz frequency regions, still more preferably substitutes for automobile metal components or electrical and electronic metal components, still more preferably electric automobile components or hybrid electric automobile components. In this case, the automobile components or the electrical and electronic components may be defined as products including the thermoplastic resin composition of the present invention or products manufactured using the thermoplastic resin composition of the present invention.

In one embodiment of the present invention, a method of manufacturing a molded article including a step of forming a first kneaded product by kneading a thermoplastic resin, carbon nanotubes, and plate-shaped graphite having an aspect ratio of <NUM> or more; a step of forming a second kneaded product by adding carbon fiber to the first kneaded product and performing kneading; a step of forming a thermoplastic resin composition according to the invention by adding metal fiber to the second kneaded product and performing kneading; and a step of forming a molded article by molding the thermoplastic resin composition may be provided.

When the method of manufacturing a molded article according to one embodiment of the present invention is used, a molded article having excellent mechanical properties and electromagnetic wave shielding performance may be easily manufactured.

The method of manufacturing a molded article according to one embodiment of the present invention may be a method of manufacturing a molded article using the thermoplastic resin composition according to one embodiment described above.

Specifically, a thermoplastic resin, carbon fiber, carbon nanotubes, plate-shaped graphite, and metal fiber used in the method of manufacturing a molded article according to one embodiment of the present invention may be the same as those included in the above-described thermoplastic resin composition.

According to the method of manufacturing a molded article according to one embodiment of the present invention, by controlling the order in which a thermoplastic resin, carbon fiber, carbon nanotubes, plate-shaped graphite, and metal fiber are kneaded, a molded article having excellent mechanical properties and electromagnetic wave shielding performance may be more efficiently manufactured.

<FIG> is a cross-sectional view of an extruder used to manufacture a molded article according to one embodiment of the present invention. Referring to <FIG>, an extruder <NUM> may include first, second, and third inlets <NUM>, <NUM>, and <NUM> and first, second, and third kneading blocks <NUM>, <NUM>, and <NUM>. With this configuration, a material put in a first direction DR1 may be kneaded and discharged. Specifically, materials put into the first inlet <NUM> may be kneaded in the process of being moved to the first kneading block <NUM> to form a first kneaded product in the first kneading block <NUM>. Materials put into the second inlet <NUM> may be mixed with the first kneaded product, and may be kneaded in the process of being moved to the second kneading block <NUM> to form a second kneaded product in the second kneading block <NUM>. In addition, materials put into the third inlet <NUM> may be mixed with the second kneaded product, and may be kneaded in the process of being moved to the third kneading block <NUM> to form a final product in the third kneading block <NUM>.

According to one embodiment of the present invention, by kneading a thermoplastic resin, carbon nanotubes, and plate-shaped graphite, a first kneaded product may be formed. Referring to <FIG>, by putting the thermoplastic resin, the carbon nanotubes, and the plate-shaped graphite into the first inlet <NUM> and performing kneading, the first kneaded product may be formed in the first kneading block <NUM>.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the carbon nanotubes may be fed in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the carbon nanotubes may be fed in an amount of <NUM> part by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the relative input amounts of the thermoplastic resin and the carbon nanotubes within the above-described range, the conductivity and electromagnetic wave shielding efficiency of a molded article to be manufactured may be effectively improved. In addition, when the carbon nanotubes are fed within the above-described range, deterioration in the mechanical properties of the molded article may be prevented.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the plate-shaped graphite may be fed in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the plate-shaped graphite may be fed in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the input amount of the plate-shaped graphite within the above-described range, the electromagnetic wave shielding efficiency of a molded article may be further improved. In addition, when the relative input amounts of the thermoplastic resin and the plate-shaped graphite are within the above-described ranges, deterioration in the mechanical properties of a molded article may be prevented, and a molded article having excellent appearance may be implemented.

According to one embodiment of the present invention, by adding the carbon fiber to the first kneaded product and performing kneading, a second kneaded product may be formed. Referring to <FIG>, by putting the carbon fiber into the second inlet <NUM> and kneading the carbon fiber and the first kneaded product, the second kneaded product may be formed in the second kneading block <NUM>.

According to the present invention, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber is fed in an amount of <NUM> parts by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber may be fed in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the relative input amounts of the thermoplastic resin and the carbon fiber within the above-described range, a molded article having improved strength and excellent appearance may be manufactured. In addition, when the carbon fiber is fed in an amount within the above-described range, a molded article having excellent rigidity and improved electromagnetic wave shielding efficiency may be easily implemented.

According to one embodiment of the present invention, by adding the metal fiber to the second kneaded product and performing kneading, a thermoplastic resin composition may be formed. Referring to <FIG>, by putting the metal fiber into the third inlet <NUM> and kneading the metal fiber and the second kneaded product, the thermoplastic resin composition may be formed in the third kneading block <NUM>.

According to one embodiment of the present invention, based on <NUM> parts by weight of the thermoplastic resin, the metal fiber may be fed in an amount of <NUM> part by weight to <NUM> parts by weight. Specifically, based on <NUM> parts by weight of the thermoplastic resin, the metal fiber may be fed in an amount of <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, <NUM> part by weight to <NUM> parts by weight, <NUM> parts by weight to <NUM> parts by weight, or <NUM> parts by weight to <NUM> parts by weight.

By adjusting the input amount of the metal fiber within the above-described range, the rigidity and electromagnetic wave shielding performance of a molded article may be further improved. In addition, when the relative input amounts of the thermoplastic resin and the metal fiber are within the above-described range, a molded article having excellent appearance may be provided.

According to one embodiment of the present invention, in the step of molding a thermoplastic resin composition, the thermoplastic resin composition may be extrusion-molded or injection-molded to manufacture a molded article. That is, the molded article may be formed by injection-molding or extrusion-molding the thermoplastic resin composition. Any extrusion molding method or injection molding method commonly used in the art to which the present invention pertains may be used without particular limitation.

For example, the molded article may be formed by kneading and extruding the thermoplastic resin composition. Kneading and extrusion may be performed using a conventional extruder. As a preferred example, a single-screw extruder, a twin-screw extruder, or the like may be used.

The molded article of the present invention includes the thermoplastic resin composition of the present invention.

The molded article preferably includes automobile components or electrical and electronic components, more preferably automobile components or electrical and electronic components requiring an electromagnetic wave shielding performance of <NUM> dB or more in MHz and GHz frequency range, still more preferably substitutes for automobile metal components or electrical and electronic metal components, still more preferably electric automobile components or hybrid electric automobile components.

Hereinafter, the present invention will be described in detail by describing exemplary embodiments of the invention. These embodiments are provided to more fully describe the present invention to those skilled in the art.

Materials used in Examples and Comparative Examples below are as follows.

To prepare a thermoplastic resin composition and manufacture a molded article, an extruder was manufactured as shown in <FIG>. The temperature of the extruder was set to about <NUM> to <NUM>, and the rate of rotation was set to <NUM> revolutions/minute.

In the extruder <NUM>, a nylon <NUM> resin as a thermoplastic resin, carbon nanotubes, and plate-shaped graphite were fed into the first inlet <NUM> and kneaded to form a first kneaded product. In this case, based on <NUM> parts by weight of the thermoplastic resin, the carbon nanotubes were fed in an amount of <NUM> part by weight, and the plate-shaped graphite was fed in an amount of <NUM> parts by weight.

Thereafter, carbon fiber was fed into the second inlet <NUM> and kneaded to form a second kneaded product. In this case, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber was fed in an amount of <NUM> parts by weight.

Thereafter, metal fiber was fed into the third inlet <NUM> and kneaded to form a thermoplastic resin composition. In this case, based on <NUM> parts by weight of the thermoplastic resin, the metal fiber was fed in an amount of <NUM> parts by weight.

Thereafter, the thermoplastic resin composition was molded into pellets through the extruder to manufacture a molded article.

Thermoplastic resin compositions were prepared and molded articles were manufactured in the same manner as in Example <NUM>, except that components and contents of the compositions fed into the extruder were adjusted according to Table <NUM> below.

The molded articles manufactured in Examples <NUM> to <NUM>, Reference Example <NUM> and Comparative Examples <NUM> to <NUM> were molded into specimens for measuring physical properties using an injection machine (<NUM> tons, Engel Co.

The physical properties of the specimens were measured according to the following methods, and the results are shown in Tables <NUM> and <NUM>.

* Tensile strength: Tensile strength was measured using a specimen having a thickness of <NUM> at a measurement rate of <NUM>/min according to ASTM D638. * Impact strength: Notched Izod impact strength was measured using a specimen having a thickness of <NUM> according to ISO 180A. Specifically, impact strength was measured at room temperature (<NUM>) after the specimen was notched. * Flexural modulus: Flexural modulus was measured using a specimen having a thickness of <NUM> at a measurement rate of <NUM>/min according to ASTM D790. * Electromagnetic wave shielding ability: Electromagnetic wave shielding ability was measured at <NUM> and <NUM> using EM2107A manufactured by Electro-Metrics Corporation. * Appearance: The appearance of an injection-molded specimen was visually evaluated. When moldability and appearance were excellent, it was marked with "⊚". When moldability and appearance were good, it was marked with "○". When appearance was excellent, it was marked with "△". When appearance was deteriorated, it was marked with "X". When appearance was very poor, it was marked with "XX".

Referring to Tables <NUM> to <NUM>, it can be confirmed that, compared to Comparative Examples <NUM> to <NUM>, the molded articles according to Examples <NUM> to <NUM> and <NUM> to <NUM> of the present invention have excellent mechanical properties and electromagnetic wave shielding performance. In particular, it can be seen that the molded articles according to Examples <NUM> to <NUM> and <NUM> to <NUM> of the present invention exhibit an electromagnetic wave shielding ability of <NUM> dB or more at <NUM> and an electromagnetic wave shielding ability of <NUM> dB or more at <NUM>.

Claim 1:
A thermoplastic resin composition, comprising a thermoplastic resin, carbon fiber, carbon nanotube, plate-shaped graphite having an aspect ratio of <NUM> or more, and metal fiber,
wherein, based on <NUM> parts by weight of the thermoplastic resin, the carbon fiber is contained in an amount of <NUM> parts by weight to <NUM> parts by weight, and
wherein the carbon nanotube has a BET surface area of <NUM><NUM>/g to <NUM><NUM>/g as measured by BET analysis according to a nitrogen gas adsorption method.