KR101397687B1 - High modulus composite for emi shielding - Google Patents

Abstract

The high rigidity electromagnetic wave shielding composite of the present invention comprises (A) a thermoplastic resin; And (B) a carbon fiber having a length of 8 to 20 mm, wherein the carbon fibers (B) are contained in an amount of 45 to 65% by weight of the total composite material and dispersed in a network form in the thermoplastic resin (A) .

Description

[0001] HIGH MODULUS COMPOSITE FOR EMI SHIELDING [0002]

The present invention relates to a high rigidity electromagnetic wave shielding composite material. More particularly, the present invention relates to a high-strength electromagnetic shielding composite material which is excellent in mechanical strength and EMI shielding property and which can reduce the production cost by replacing the existing magnesium material and has excellent processability.

Electromagnetic waves are known to cause noise and malfunctions in nearby parts or devices, and also have harmful effects on the human body due to noise caused by electrostatic discharge. In recent years, the possibility of generating electromagnetic waves has been rapidly increasing due to high efficiency, high power consumption, and highly integrated electric / electronic products. Regulation of electromagnetic waves has been strengthened not only in advanced countries but also in Korea.

Conventionally, there is a method of using a metallic material as a method for shielding electromagnetic waves. For example, IT brackets used in portable display products such as mobile phones, notebooks, PDAs and other mobile items require high rigidity and EMI shielding because they protect LCDs, shield electromagnetic waves, and serve as frames . In recent years, metals such as magnesium, aluminum, and stainless steel have been mainly used as materials for brackets and frames. However, such a metal material has an advantage that it can effectively block electromagnetic waves, but it is produced by a die-casting method and has a high production cost and a high defect rate.

Accordingly, a method of replacing the thermoplastic resin that is easy to mold, has excellent molding accuracy, and is excellent in economy and productivity compared to the metal materials has been proposed.

The modulus of currently developed metal substitute resin is below FM 20GPa and electromagnetic wave shielding effect is about 30dB (@ 1GHz), which has a disadvantage that rigidity and EMI shielding are remarkably lower than metal. A method of raising the fiber content to raise the modulus has been proposed. However, when the fiber content is high, the impact strength is low, the fluidity is low, and it is difficult to apply because of difficulty in practical application. There is a problem that the conductivity is too low to use.

In addition, high filler loading is difficult in low flow bases. In recent years, products having a high modulus and an electromagnetic shielding effect of 30 dB or more have been developed using carbon fibers of 50% or more, but they are insufficient to replace metals and have difficulty in processing. Furthermore, there is a problem in that the conductivity is low to use such a material as a material of an electronic device. For example, when a general mobile phone bracket is used, problems such as lowered grounding performance and antenna performance deteriorate.

In general high-stiffness resins, the surface resistance is lowered by conducting conductive plating in order to solve this problem. However, the cost is increased due to the plating process and the subsequent process, and the surface is peeled off during long-term use.

Therefore, it is necessary to develop new materials that can replace existing magnesium materials with excellent fluidity, impact strength and rigidity, excellent conductivity and shielding performance.

An object of the present invention is to provide a high rigidity electromagnetic wave shielding composite excellent in mechanical strength.

Another object of the present invention is to provide a highly rigid electromagnetic shielding composite suitable for EMI shielding because of its excellent conductivity and low surface resistance.

It is still another object of the present invention to provide a high-rigidity electromagnetic wave shielding composite excellent in fluidity and moldability.

Another object of the present invention is to provide a high-rigidity electromagnetic wave shielding composite which is free of post-processing and excellent in economy and productivity.

It is still another object of the present invention to provide a high rigidity electromagnetic wave shielding composite excellent in dimensional stability.

Another object of the present invention is to provide a high-strength electromagnetic wave shielding composite which can replace the existing magnesium material.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical subjects which are not mentioned can be understood by those skilled in the art from the following description.

One aspect of the present invention relates to a high rigidity electromagnetic wave shielding composite. The composite material comprises (A) a thermoplastic resin; And (B) carbon fibers having a length of 8 to 20 mm, wherein the carbon fibers (B) contain 45 to 65% by weight of the entire composite material.

In the specific example, the thermoplastic resin (A) may be at least one selected from the group consisting of a polyamide resin, a polyester resin, a polyacetal resin, a polycarbonate resin, a poly (meth) acrylate resin, a polyvinyl chloride resin, Polysulfide resins, polyimide resins, polysulfone resins, polyolefin resins, aromatic vinyl resins, and the like, but are not limited thereto. These may be used alone or in combination of two or more. Preferably, the thermoplastic resin (A) may be a crystalline thermoplastic resin.

In one embodiment, the composite material may further comprise metal coated graphite. The metal coated graphite may have particles, fibers, flakes, amorphous or a combination thereof.

The metal-coated graphite may have an average particle diameter of 10 to 200 mu m. In an embodiment, the metal may be aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt or the like.

The metal-coated graphite may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of (A) + (B).

In another embodiment, the composite material may further comprise carbon nanotubes. The carbon nanotubes may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of (A) + (B).

In another embodiment, the composite material may include both metal coated graphite and carbon nanotubes. In an embodiment, the composite may include 0.1 to 3 parts by weight of graphite and 0.05 to 5 parts by weight of carbon nanotubes per 100 parts by weight of (A) + (B).

In an embodiment, the composite material may further comprise a metal filler. The metal filler may include at least one member selected from the group consisting of metal powder, metal beads, metal fibers, metal flakes, metal coated particles and metal coated fibers.

In another embodiment, the composite material may include both metal coated graphite, carbon nanotubes, and metal fillers.

In another embodiment, the composite material may include 0.1 to 3 parts by weight of graphite coated with metal, 0.1 to 5 parts by weight of carbon nanotubes and 1 to 20 parts by weight of metal filler per 100 parts by weight of (A) + (B) .

The composite material may further include additives such as a flame retardant, a plasticizer, a coupling agent, a heat stabilizer, a light stabilizer, a carbon filler, an inorganic filler, a releasing agent, a dispersant, a dripping inhibitor and a weathering stabilizer. These may be used alone or in combination of two or more.

In one embodiment, the composite material comprises carbon fibers having a length of 0.5 to 6 mm. The carbon fibers having the length of 0.5 to 6 mm may be 80% or more by weight of the whole carbon fibers in the molded product.

In another embodiment, the composite may have an average value of residual fiber length of at least 2 mm after 1 hour at 550 캜 for the molded article.

In one embodiment, the composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm according to ASTM D790, an Izod impact strength of at least 35 kgfcm / cm at a thickness of 3.2 mm according to ASTM D256, an EMI at a thickness of 1 GHz, The surface resistance by the 4-point probe method is 5.0 Ω · cm or less for a specimen having a thickness of 1 t, the residual fiber length measured after 550 ° C./1 hour for a molded article is 2.0 mm Or more.

In another embodiment, the composite has a flexural modulus of at least 37 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length of at least 200 mm at 300 < 0 > C, an EMI D257 specification at 1 GHz, The shielding effect is 44 dB or more, the surface resistance by the 4-point probe method is 4.2 Ω · cm or less for a specimen having a thickness of 1 t, and the residual fiber length measured after 550 ° C./1 hr for a molded article may be 2.5 mm or more.

In another embodiment, the composite has a flexural modulus of at least 40 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length of at least 250 mm at 300 < 0 > C, an EMI D257 specification at 1 GHz, , The surface resistance by a 4-point probe method is 1.0 Ω · cm or less for a specimen of 1 t thickness, and the residual fiber length measured after 550 ° C./1 hr for a molded article is 3.0 mm or more .

Another aspect of the present invention relates to a method of manufacturing a high-rigidity electromagnetic wave shielding composite.

In one embodiment, the method comprises: (A) feeding a thermoplastic resin into an extruder to melt; (B) carbon fiber is passed through the melt to impregnate it, followed by cutting to form a pellet; And molding the pellet.

In another embodiment, the method comprises the steps of (A) feeding a thermoplastic resin and (C) carbon nanotubes, metal-coated graphite, metal filler or a mixture of two or more thereof into an extruder and primary pelletizing, Pellets are prepared; Melting the composite resin pellets; (B) carbon fiber is passed through the composite resin pellet to impregnate the composite pellet, followed by cutting to form secondary pellets; And molding the secondary pellet impregnated with the carbon fibers; Step < / RTI >

Disclosed is a resin composition which is excellent in mechanical strength and conductivity, low in surface resistance, suitable for EMI shielding, excellent in fluidity and moldability, excellent in economical efficiency and productivity, no post processing is required, excellent in dimensional stability, The present invention has the effect of providing a high-rigidity electromagnetic wave shielding composite material.

FIG. 1 is a schematic diagram of a conventional composite material in which chopped carbon fibers are dispersed in a thermoplastic resin.
FIG. 2 is a schematic diagram showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to one embodiment of the present invention.
FIG. 3 is a schematic diagram showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention. FIG.
FIG. 4 is a schematic diagram in which carbon fibers are dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention.
FIG. 5 is a schematic diagram schematically showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention.

The high rigidity electromagnetic wave shielding composite of the present invention comprises (A) a thermoplastic resin; And (B) long carbon fibers having a length of 8 to 20 mm.

1 is a conventional composite material in which chopped carbon fibers are dispersed in a thermoplastic resin. Normally applied chopped carbon fibers are 3 mm or less in length. When such chopped carbon fibers contain 45% or more of such chopped carbon fibers, not only stiffness and impact strength may be lowered but also shielding performance is lowered . The present invention is characterized in that long carbon fibers having a length of 8 to 20 mm are applied instead of conventional chopped carbon fibers. 2 is a schematic diagram schematically showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to one embodiment of the present invention. As shown in Fig. 2, the molded article molded from the high-rigidity electromagnetic wave shielding composite of the present invention is characterized in that (A) the thermoplastic resin 10 and (B) the carbon fibers 20 are dispersed in a network shape. As described above, since the high-strength electromagnetic wave shielding composite material of the present invention has a high content of the long carbon fibers 20, a large number of contact points 20a formed between the fibers and the fibers are formed, Shielding property can be obtained.

Hereinafter, each of the above components will be described in detail.

(A) a thermoplastic resin

The thermoplastic resin that can be used in the present invention is not particularly limited. Examples of the resin include polyamide resins, polyester resins, polyacetal resins, polycarbonate resins, poly (meth) acrylate resins, polyvinyl chloride resins, polyether resins, polysulfide resins, polyimide resins A resin, a polysulfone resin, a polyolefin resin, an aromatic vinyl resin, and the like may be used, but are not limited thereto. These may be used alone or in combination of two or more.

Preferably, the thermoplastic resin is a crystalline thermoplastic resin, more preferably a polyamide-based resin or a polyester-based resin.

As the polyamide-based resin, an aliphatic polyamide resin, an aromatic polyamide resin containing an aromatic group in the main chain, or a copolymer or a mixture thereof may be used. In a specific example, NYLON 6, NYLON 66, NYLON 46, NYLON 610, NYLON 612, NYLON 66/6, NYLON 6/6 T, NYLON 66/6 I, NYLON 6T, NYLON 9T, NYLON 10T, NYLON MXD 6, NYLON 6I / May be used, but are not necessarily limited thereto. An aromatic polyamide resin containing an aromatic group in its double main chain can be preferably used. When the aromatic group is contained in the main chain in this manner, higher rigidity and strength can be imparted.

In one embodiment, the polyamide resin may have a glass transition temperature (Tg) of 60 to 120 ° C, preferably 80 to 100 ° C. It is possible to obtain excellent balance of fluidity, rigidity and low moisture absorptivity in the above range.

The polyamide resin may have a number average molecular weight of 10,000 to 200,000 g / mol, preferably 30,000 to 100,000 g / mol. There is an advantage in that both the flowability and the mechanical properties are excellent in the above range.

As the polyester resin, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or the like may be used, but not always limited thereto.

As the polyacetal-based resin, a polyoxymethylene-based resin may be used, but the present invention is not limited thereto.

The polycarbonate resin may be in the form of a linear polycarbonate resin, a branched polycarbonate resin or a polyester carbonate copolymer resin, and preferably a bisphenol A polycarbonate may be used.

As the poly (meth) acrylate-based resin, an aromatic (meth) acrylate polymer, an aliphatic (meth) acrylate polymer, a copolymer or a mixture thereof may be applied. In a specific example, a homopolymer of methyl methacrylate is used, or a copolymer of methyl methacrylate and another vinyl monomer may be used. Examples of the vinyl monomer include methacrylic acid esters including ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate and benzyl methacrylate; Acrylate esters including methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, and 2-ethylhexyl acrylate; Unsaturated carboxylic acids including acrylic acid and methacrylic acid; Acid anhydrides including maleic anhydride; Esters containing hydroxy groups including 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and monoglycerol acrylate, and the like.

Examples of the polyolefin-based resin include polyethylene, polypropylene, polybutylene, and the like. Copolymers or mixtures thereof may also be used. In addition, their adducttic, isotactic, and syndiotactic structures can all be applied.

As the aromatic vinyl resin, polystyrene, HIPS, ABS, SAN, ASA, MABS, or a combination thereof may be used.

In the present invention, the thermoplastic resin (A) forms a matrix and may be contained in an amount of 35 to 55% by weight in the (A) + (B) component. If (A) the thermoplastic resin exceeds 55% by weight, the modulus and strength are lowered, the volume resistance is increased, and the EMI shielding performance is lowered. On the other hand, if the content of the thermoplastic resin (A) is less than 35% by weight, the moldability may be deteriorated.

(B) carbon fiber

The carbon fibers used in the present invention are well known to those skilled in the art and are commercially available and can be prepared by conventional methods.

In the specific examples, the carbon fibers produced from the PAN system or the pitch system may be used.

The average diameter of the carbon fibers may be 1 to 30 탆, preferably 3 to 20 탆, more preferably 5 to 15 탆. Excellent physical properties and conductivity can be obtained within the above range.

The carbon fiber used in the production of the high rigidity electromagnetic wave shielding composite material of the present invention may be of a bundle type. In the specific example, the carbon fibers may be bundled long carbon fibers having a length of 400 to 3000 TEX, preferably 800 to 2400 TEX, more preferably 800 to 1700 TEX. Impregnation can be performed well in the above range. The carbon fiber having the bundle shape is impregnated with the melt of the polyamide resin (A), the polyamide resin (A) is applied to the surface, and the carbon fiber having the polyamide resin (A) To 20 mm long and made of pellets of length 8-20 mm. The length of the pellet is the same as the length of the cut carbon fiber since it is cut along the carbon fiber length. That is, a pellet having a length of 8 to 20 mm will contain carbon fibers having a length of 8 to 20 mm. The carbon fibers having the bundle shape may be dispersed in the form of a network in a polyamide resin (A) matrix in a final molded article dispersed in the molding process.

The length of the carbon fibers includes 8 to 20 mm, preferably 10 to 15 mm. And has excellent physical properties balance of conductivity and mechanical strength within the above range.

Usually, after carbon fiber is cut, most of the carbon fibers are cut. When long carbon fibers having a length of 8 to 20 mm are applied as in the present invention, the length of the residual fibers in molded products is generally 0.5 to 6 mm. Here, the length of the residual fiber refers to the fiber length after pelletization and subsequent molding. The molding process is a typical molding condition. For example, injection conditions of a temperature of 280 to 320 DEG C and a pressure of 170 MPa to 190 MPa are common. Examples of the molding conditions are merely examples for reference and are not necessarily limited thereto.

On the other hand, when the ordinary chopped fiber is applied, the residual fiber length of the molded article is not more than 0.5 mm, so the physical properties are different. In a specific example, the carbon fiber having a residual fiber length of 0.5 to 6 mm in the molded article after molding the high-rigidity electromagnetic wave shielding composite composition of the present invention is 80% by weight or more. Further, after 100 hours at 550 ° C for the molded product, the residual fiber length may be extracted, and the length may be measured in the longitudinal direction, and the average value may be 2 mm or more.

In the specific examples, the carbon fibers may be subjected to a surface treatment and may be used in the form of a bundle.

The carbon fibers may be used in an amount of 45 to 65% by weight, preferably 50 to 60% by weight, of the components (A) + (B). If the carbon fiber (B) is less than 45% by weight, the modulus and flexural modulus are lowered, the volume resistance and moisture absorption rate are increased, and the EMI shielding performance is lowered. On the other hand, when the content of the carbon fibers (B) exceeds 65% by weight, the fluidity may be lowered and the impact strength and flexural modulus may be lowered.

The composite material of the present invention may further comprise metal coated graphite. 3 is a schematic diagram schematically showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention. 3, it may be dispersed in the thermoplastic resin 10, which is a matrix, when the metal-coated graphite 30 is included. The metal coated graphite may have particles, fibers, flakes, amorphous or a combination thereof. When the metal-coated graphite has a fiber shape, a network structure can be formed together with the carbon fibers 20. [ When such a metal-coated graphite is contained, the surface resistance is remarkably lowered, and the electromagnetic wave shielding performance and rigidity can be further improved.

The metal-coated graphite may have an average particle diameter of 10 to 200 mu m. When the metal-coated graphite has a fiber shape, it is preferable that the average diameter is 10 to 200 mu m and the average length is 15 to 100 mu m. There is an advantage in that the electrical conductivity is excellent in the above range, but the mechanical properties are not lowered by the addition.

In an embodiment, the metal may be any metal having conductivity. Preferably, aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt and the like may be used.

The metal coating may be formed of not only a single layer but also a plurality of layers of two or more.

In an embodiment, the metal-coated graphite may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of (A) + (B).

In another embodiment, the metal-coated graphite may be applied together with the carbon nanotubes. The content of the graphite coated with the metal may be 0.1 to 3 parts by weight based on 100 parts by weight of (A) + (B). And can have excellent fluidity and rigidity and electromagnetic shielding performance in the above range.

The composite material of the present invention may further include carbon nanotubes. 4 is a schematic diagram schematically showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention. As shown in FIG. 4, when the carbon nanotubes 40 are included, the carbon nanotubes 40 may be dispersed in the thermoplastic resin 10 as a matrix. And may also be in contact with the carbon fibers 20 as well. The carbon nanotube may be a single wall, a double wall, or a multiple wall, or a combination thereof may be used. Walled carbon nanotubes. When the carbon nanotubes are contained, the surface resistance is remarkably lowered and the electromagnetic wave shielding performance and rigidity can be further improved. The carbon nanotubes may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of (A) + (B). And can have excellent fluidity and rigidity and electromagnetic shielding performance in the above range.

In another embodiment, the composite material may include both metal coated graphite and carbon nanotubes. 5 is a schematic diagram schematically showing carbon fibers dispersed on a molded article formed from a high-rigidity electromagnetic wave shielding composite according to another embodiment of the present invention. 5, carbon fibers 20, metal-coated graphite 30, and carbon nanotubes 40 are dispersed in a matrix of a thermoplastic resin 10, and these carbon fibers 20, metal The coated graphite 30 and the carbon nanotubes 40 may be in contact with each other.

When the metal-coated graphite and the carbon nanotube are applied together, they have better electromagnetic wave shielding performance and rigidity even with a small content. In an embodiment, the composite may include 0.1 to 3 parts by weight of graphite and 0.05 to 5 parts by weight of carbon nanotubes per 100 parts by weight of (A) + (B). And can have excellent fluidity and rigidity and electromagnetic shielding performance in the above range.

In yet another embodiment, the composite material may further comprise a metal filler.

The metal filler used in the present invention can be used without limitation as long as it is a conductive filler. In the specific examples, aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt and alloys of two or more thereof may be used. These may be used alone or in combination of two or more. In one embodiment, it may be an iron-chromium-nickel alloy.

In other embodiments, metal oxides or metal carbides such as tin oxide, indium oxide, silicon carbide, zirconium carbide, titanium carbide and the like may also be used.

In still another embodiment, a low melting point material comprising a main component selected from the group consisting of tin, lead and combinations thereof and a subcomponent selected from the group consisting of copper, aluminum, nickel, silver, germanium, indium, Metal may be used. When such a low-melting-point metal is used, the formation of a network between pillars is facilitated, and the electromagnetic wave shielding efficiency can be further improved. The low melting point metal preferably has a solidus temperature (a temperature at which solidification ends) lower than the composite process temperature of the thermoplastic resin (A). Preferably, the solidus temperature of the low melting point metal is lower than the process temperature of the thermoplastic resin (A) by 20 DEG C or more in terms of network formation between the composite material manufacturing process and the filler, good. Tin / copper (97/3 by weight) and tin / copper / silver (92/6/2 by weight) may be used, preferably having a melting point of 300 占 폚 or less.

The shape of the metal filler may be a metal powder, a metal bead, a metal fiber, a metal flake, a metal coated particle, and a metal coated fiber, but is not limited thereto. These may be used alone or in combination of two or more.

When the metal filler is used in the form of metal powder or metal beads, the average particle diameter may be 30 to 300 mu m. In the above range, feeding is advantageous when extruded.

When the metal filler is used in the form of a metal fiber, it may have a length of 50 to 500 mm and a diameter range of 10 to 100 탆. The metal fibers may have a density of 0.7 to 6.0 g / ml. Proper feeding can be maintained during extrusion processing in the above range.

When the shape of the metal filler is used in the form of a metal flake, the average size may be 50 to 500 mu m. In this range, proper feeding can be maintained during extrusion processing.

The metal powder, the metal bead, the metal fiber and the like may be a single metal or two or more kinds of alloys, and may have a multilayer structure.

The metal coated particles and the metal coated fibers are in the form of a resin, a ceramic, a metal, a carbon, or the like as a core, and the core is coated with a metal. For example, the resin-based fine particles or fibers may be coated with a metal such as nickel or nickel-copper, and the metal coating may be a single layer or a multilayer.

In embodiments, the metal coated particles may have an average particle size of from 30 to 300 microns. In the above range, feeding is advantageous when extruded. The metal coated fibers may have an average diameter of 10 to 100 占 퐉 and a length of 50 to 500 mm. In this range, proper feeding can be maintained during extrusion processing.

In the present invention, the metal filler may be used in an amount of 1 to 20 parts by weight, preferably 3 to 15 parts by weight based on 100 parts by weight of (A) + (B). In the above range, conductivity and flowability, impact strength and balance of flexural modulus can be obtained.

In one embodiment, the ratio between the carbon fiber and the metal filler may be carbon fiber: metal filler = 6 to 20: 1. Excellent physical property balance can be obtained in the above range.

The composite material may further include additives such as a flame retardant, a plasticizer, a coupling agent, a heat stabilizer, a light stabilizer, a carbon filler, an inorganic filler, a releasing agent, a dispersant, a dripping inhibitor and a weathering stabilizer. These may be used alone or in combination of two or more.

As the carbon filler, various carbon fillers other than the carbon fibers (B) may be applied. Specific examples include graphite, carbon nanotubes, carbon black, and the like, and metal coatings thereof may also be included. For example, the above-described metal-coated graphite may also be included. These may be used alone or in combination of two or more.

As the inorganic filler, the metal filler, metal oxide filler, metal salt filler, and the like described above can be applied. Of these, metal fillers are preferred.

In another embodiment, the length of the carbon fiber remaining fibers in the molded product after molding using the composite material may be 80 wt% or more, which is 0.5 to 6 mm in length.

In one embodiment, the composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm according to ASTM D790, an Izod impact strength of at least 35 kgfcm / cm at a thickness of 3.2 mm according to ASTM D256, an EMI at a thickness of 1 GHz, The surface resistance by the 4-point probe method is 5.0 Ω · cm or less and the residual fiber length measured after 550 ° C / 1 hr is 2.0 mm or more for a specimen of 1 t thickness with a shielding effect of D257 specification of 40 dB or more have.

In another embodiment, the composite has a flexural modulus of at least 37 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length of at least 200 mm at 300 < 0 > C, an EMI D257 specification at 1 GHz, The shielding effect is 44 dB or more, the surface resistance by the 4-point probe method is 4.2 Ω · cm or less, and the residual fiber length after 550 ° C. / 1 hour is 2.5 mm or more for a 1-ton thick test piece.

In another embodiment, the composite has a flexural modulus of at least 40 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length of at least 250 mm at 300 < 0 > C, an EMI D257 specification at 1 GHz, The shielding effect by the 4-point probe method is less than 1.0 Ω · cm and the residual fiber length measured after 550 ° C / 1 hr is more than 3.0 mm.

Another aspect of the present invention relates to a method of manufacturing the high-rigidity electromagnetic wave shielding composite material. The method comprises: (A) feeding a thermoplastic resin into an extruder to melt; (B) carbon fiber is passed through the melt to impregnate it, followed by cutting to form a pellet; And molding the pellet. In embodiments, the pelletization may be pelletized by cutting the impregnated carbon fibers.

The carbon fibers may have a bundle shape.

In another embodiment, the composite material is obtained by extruding an extruder, which comprises (A) a thermoplastic resin and (C) a carbon nanotube, a metal-coated graphite, a metal filler or a mixture of two or more thereof, Preparing composite resin pellets; Melting the composite resin pellets; (B) carbon fiber is passed through the composite resin pellet to impregnate the composite pellet, followed by cutting to form secondary pellets; And molding the secondary pellet impregnated with the carbon fibers.

The impregnated carbon fibers may be cut into a predetermined size and then pelletized. In embodiments, it may be cut to a length of 8 to 20 mm, preferably 10 to 15 mm and pelletized. In this range, the shape of the long fiber carbon fibers is maintained, and excellent shielding property and strength can be obtained.

The prepared pellets can be manufactured in various forms through injection molding, compression molding, casting, and the like.

Through this molding process, the carbon fibers having a bundle shape may be dispersed to each other so that the fibers are dispersed in a network shape in the final molded product. Here, the network shape means that the fibers form a plurality of contact points and are connected to each other between the fibers.

The carbon fibers can be partially cut after molding. In an embodiment, the carbon fibers having a length of residual fibers of 0.5 to 6 mm may be dispersed in a network shape in the molded article. Further, after 100 hours at 550 ° C for the molded product, the residual fiber length may be extracted, and the length may be measured in the longitudinal direction, and the average value may be 2 mm or more.

The molded article made of the composite material of the present invention has excellent electromagnetic wave shielding properties, conductivity, mechanical properties, and moldability, and therefore can be preferably applied to an LCD protective bracket of a portable display product.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example

The specifications of each component used in the following examples and comparative examples are as follows:

(A) a thermoplastic resin

(A1): ZYTEL 101 F from Dupont was used as PA66 product.

(A2): 1031 BRT of Hyosung Co. was used as PA6 product.

(A3): Toyobo T-600 was used as a product of PAA (MXX6, polyarylamide).

(A4): Anychem A1100 product was used as PET product.

(A5): shinite K001 from SHINKONG was used as a PBT product.

(B) carbon fiber

(B1) Toray TORAYCA T700S 50C, 1650 TEX manufactured by Toray, which has an average diameter of 20 탆 and long carbon fiber, was used.

(B2) Carbon fiber: PANEX PX35CA0250-65 manufactured by Zoltek, chopped carbon fiber having an average diameter of 20 탆 and a length of 10 mm, was used.

(B3) Glass fiber: TufRov 4588 manufactured by PPG, which has an average diameter of 20 탆 and is long glass fiber, was used.

(C1) Carbon Nano Tube: Nanocyl's NC7000 (multi-wall CNT) was used.

(C2) Ni-coated graphite: Sulzer 2805 (Ni: 75 wt%, graphite: 25 wt%) was used.

(C3) Metal powder having a low melting point of 300 占 폚 or less: 97C (97% Sn, manufactured by Warton metals Limited, Powder type tin-copper alloy as 2.5% Cu) was used.

(D) Heat stabilizer and lubricant: IRGANOX1010 of CIBA chemical as a heat stabilizer and PE-Wax as a lubricant were mixed at a ratio of 1: 1.

Example  1 to 12 and Comparative Example  2, 5 ~ 7

The above components were mixed in the usual mixer in the contents shown in the following Table 1 and extruded by using a twin screw extruder having L / D = 35 and Φ = 45 mm. The extrudate was then pelletized, After drying in a hot air drier, carbon fibers were impregnated by a pultrusion method and cut into long pellets having a length of 12 mm to prepare carbon fibers having a length of 12 mm. The pellets were manufactured at an injection temperature of 270 ° C. using a long fiber injection machine for evaluation of properties and evaluation of EMI and resistance. These specimens were allowed to stand at 23 ° C and 50% relative humidity for 48 hours, and then their physical properties were evaluated by the following methods. The results are shown in Table 1.

Assessment Methods:

(1) Flexural modulus: Evaluated according to ASTM D790 at a rate of 1.27 mm / min. The unit is GPa.

(2) Izod impact strength (unnotched): Evaluated at 23 캜 according to ASTM D256 at a thickness of 3.2 mm, and the unit is kgfcm / cm.

(3) Spiral flow: 6oz Injection into a spiral mold having a thickness of 2 mm at a molding temperature of 250 DEG C, a mold temperature of 60 DEG C, an injection pressure of 50% and an injection speed of 70% mm) was measured.

(4) EMI shielding (dB): The sample was allowed to stand for 48 hours under a condition of 23 deg. C and a relative humidity of 50%, and electromagnetic wave shielding performance was measured for a sample (6X6) having a thickness of 1t at 1 GHz according to EMI257.

(5) Surface resistivity: The injection specimen of 1 t thickness was evaluated by the 4 point probe method (Ω · cm).

(6) Residual fiber length after ignition loss (mm): After the residual fiber length was measured at 550 ° C / 1 hour for the molded article, the length was measured in the longitudinal direction to obtain the arithmetic average value for the length.

Example One 2 3 4 5 6 7 8 9 10 11 12 A1 50 - - - - - - - - - - - A2 - 50 - - - - - - - - - - A3 - - 50 - - 40 - 50 50 50 50 50 A4 - - - 50 - - 20 - - - - - A5 - - - - 50 - 20 - - - - - A6 - - - - - - - - - - - - B1 50 50 50 50 50 60 60 50 50 50 50 50 B2 - - - - - - - - - - - - B3 - - - - - - - - - - - - C1 - - - - - - - 0.3 - 0.1 - - C2 - - - - - - - - 3 One - - C3 - - - - - - - - 5 10 D 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Bending modulus 41 38 43 44 42 47 44 43 44 43 44 45 Shock
burglar 22 24 26 19 21 28 20 26 22 23 18 16 spiral 280 290 300 300 310 260 270 300 280 290 270 260 EMI
Shielding 45 44 44 46 44 61 60 47 49 48 53 59 surface
resistance 4.0 4.1 4.1 3.9 3.8 2.7 2.8 0.7 0.3 0.4 0.2 0.1 Pellet length 12 12 12 12 12 12 12 12 12 12 12 12 Residual fiber length 3.1 3.2 3.5 2.8 3.0 2.7 2.4 3.4 3.1 3.2 2.3 2.1

As shown in Table 1, in Examples 1-12, the flexural modulus is 35 GPa or more, and the shielding effect according to the EMI D257 standard is superior to 40 dB or more at 1 GHz and 1 t thickness. In Examples 1 to 7, in which the crystalline thermoplastic resin was applied, it was confirmed that the flexural modulus and spiral were higher and the residual fiber length after the ignition of the injection product was longer than that of Example 11 in which the amorphous thermoplastic resin was applied. In addition, when CNT and / or Ni-caoted graphite is added as in Examples 8 to 10 and 12, the surface resistance is remarkably lowered to 2.0 Ω · cm or less.

Comparative Examples 1 and 3 to 4

The above components were mixed in the usual mixer at the contents shown in the following Table 2 and extruded by using a twin-screw extruder having L / D = 35 and Φ = 45 mm, and then extrudates were prepared in the form of pellets. The prepared pellets were dried at 100 ℃ for 4 hours in a hot air drier, and the specimens for application evaluation such as measurement of property and EMI / resistance at an injection temperature of 270 ℃ were prepared by using a long fiber injection machine. These specimens were allowed to stand for 48 hours at 23 ° C and 50% relative humidity, and then their physical properties were evaluated by the following methods. The results are shown in Table 2.

Comparative Examples 2 and 5 to 7

The procedure of Example 1 was repeated except that each of the above components was added in the amounts shown in Table 2 below.

Comparative Example One 2 3 4 5 6 7 A1 50 50 50 50 50 50 20 A2 - - - - - - - A3 - - - - - - - A4 - - - - - - - A5 - - - - - - - A6 - - - - - - - B1 - - - - - - 80 B2 50 - 50 50 - - - B3 - 50 - - 50 50 - C1 - - 0.1 - 0.1 - - C2 - - - 3 - 3 - D 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Bending modulus 30 15 30 31 15 16 48 Impact strength 8 25 8 6 25 22 42 spiral 300 270 300 290 270 250 180 EMI Shielding 32 One 35 36 One 3 60 Surface resistance 18 10 ¹⁰ 12 9 10 ⁹ 10 ⁹ 2.1 Pellet length 3 12 3 3 12 12 12 Residual fiber length 0.3 2.7 0.4 0.2 2.7 2.5 1.8

As shown in Table 2, in Comparative Examples 1, 3 and 4 using chopped carbon fibers, the rigidity (FM) was lowered, the impact strength (IZOD) was lowered, the surface resistance was increased, There is a problem.

As shown in Comparative Examples 2, 5 and 6, when the long glass fiber was used instead of the carbon fiber, the surface resistance and the EMI shielding property were found to be inferior. Also, as in Comparative Example 7, when the long carbon fiber was excessively applied, the spiral was degraded.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are in all respects illustrative and not restrictive.

1: thermoplastic resin 2: chopped carbon fiber
10: thermoplastic resin 20: carbon fiber
30: Metallic coated graphite 40: Carbon nanotubes

Claims (22)

(A) a thermoplastic resin; And
(B) carbon fibers having a length of 8 to 20 mm; Wherein the carbon fiber (B) contains 45 to 65% by weight of the entire composite material,
Wherein the carbon fibers (B) are dispersed in a network form in the thermoplastic resin (A) and have contact points formed by contact between the fibers and the fibers.

The high rigidity electromagnetic wave shielding composite material according to claim 1, wherein the thermoplastic resin (A) is a crystalline thermoplastic resin.
The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin (A) is at least one selected from the group consisting of a polyamide resin, a polyester resin, a polyacetal resin, a polycarbonate resin, a poly (meth) acrylate resin, a polyvinyl chloride resin, Wherein the resin composition contains at least one resin selected from the group consisting of a polyolefin resin, a polyamide resin, a polyamide resin, a polysulfone resin, a polyolefin resin, and an aromatic vinyl resin.
The high rigidity electromagnetic wave shielding composite material according to claim 1, wherein the composite material further comprises a metal-coated graphite.
The high strength electromagnetic wave shielding composite material according to claim 4, wherein the metal coated graphite has particles, fibers, flakes, amorphous or a combination thereof.
6. The high rigidity electromagnetic wave shielding composite according to claim 5, wherein the metal-coated graphite has an average particle diameter of 10 to 200 mu m.
The method of claim 4, wherein the metal is at least one selected from the group consisting of aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt, Wherein the electromagnetic wave shielding composite material is a high strength electromagnetic wave shielding composite material.
5. The high rigidity electromagnetic wave shielding composite material according to claim 4, wherein the metal-coated graphite is contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of (A) + (B).
The high strength electromagnetic wave shielding composite material according to claim 1, wherein the composite material further comprises carbon nanotubes.
The high strength electromagnetic wave shielding composite material according to claim 9, wherein the carbon nanotube is contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of (A) + (B).
The composite material according to claim 1, wherein the composite material comprises 0.1 to 3 parts by weight of graphite coated with metal and 100 to 5 parts by weight of carbon nanotubes with respect to 100 parts by weight of (A) + (B) Shielding composite.
The high rigidity electromagnetic wave shielding composite material according to claim 1, wherein the composite material further comprises a metal filler.
The high strength electromagnetic wave shielding composite material according to claim 12, wherein the metal filler comprises at least one member selected from the group consisting of metal powder, metal beads, metal fibers, metal flakes, metal coated particles and metal coated fibers.
The composite material according to claim 1, wherein the composite material comprises 0.1 to 3 parts by weight of graphite coated with metal, 0.1 to 5 parts by weight of carbon nanotubes and 1 to 20 parts by weight of a metal filler per 100 parts by weight of (A) + (B) High strength electromagnetic wave shielding composite material.
The composite material according to claim 1, wherein the composite material further comprises at least one additive selected from the group consisting of a carbon filler, a flame retardant, a plasticizer, a coupling agent, a heat stabilizer, a light stabilizer, an inorganic filler, a releasing agent, a dispersant, High strength electromagnetic wave shielding composite material.
The high rigidity electromagnetic wave shielding composite material according to claim 1, wherein the composite material has a residual carbon fiber length of 0.5 to 6 mm in the molded product after molding is at least 80% by weight of the total carbon fibers.
The high strength electromagnetic wave shielding composite material according to claim 1, wherein the composite material has an average value of residual fiber lengths of at least 2 mm after 1 hour at 550 ° C.
The composite according to claim 1, wherein the composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm according to ASTM D790, an Izod impact strength of at least 35 kgfcm / cm at a thickness of 3.2 mm according to ASTM D256, The shielding effect according to the EMI D257 standard is 40 dB or more, the surface resistance by the 4-point probe method is 5.0 Ω · cm or less for a specimen of 1 t thickness, and the residual fiber length measured after 550 ° C./1 hour for a molded article is 2.0 mm < / RTI > or higher.
The composite material of claim 1, wherein the composite has a flexural modulus of at least 37 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length at 300 DEG C of at least 200 mm, an EMI D257 specification at 1 GHz, Shielding effect of 44 dB or more and a surface resistance of 4.2 Ω · cm or less by the 4-point probe method for a specimen of 1 t thickness and a residual fiber length of 2.5 mm or more measured after 550 ° C./1 hour for the molded article High strength electromagnetic wave shielding composite material.
The composite material according to claim 1, wherein the composite has a flexural modulus of at least 40 GPa at 3.2 mm thickness according to ASTM D790, a spiral flow length of at least 250 mm at 300 占 폚, an EMI D257 specification Having a shielding effect of 45 dB or more and a surface resistance of 1.0 Ω · cm or less by the 4-point probe method with respect to a specimen of 1 t thickness and a residual fiber length of 3.0 mm or more measured after 550 ° C./1 hr of the molded product High strength electromagnetic wave shielding composite material.
(A) feeding a thermoplastic resin into an extruder to melt it;
(B) carbon fibers are passed through the molten thermoplastic resin to impregnate them, followed by cutting to form pellets; And
Molding said pellet;
Wherein the electromagnetic wave shielding composite material has a thickness of 10 to 100 angstroms.
(A) a thermoplastic resin and (C) an additive comprising a carbon nanotube, a metal-coated graphite, a metal filler, or a mixture of two or more thereof, into an extruder and firstly pelletizing to produce a composite resin pellet;
Melting the composite resin pellets;
(B) carbon fiber is passed through the composite resin pellet to impregnate the composite pellet, followed by cutting to form secondary pellets; And
Molding the secondary pellet impregnated with the carbon fibers;
Wherein the electromagnetic wave shielding composite material has a thickness of 10 to 100 angstroms.

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