KR20120023490A - High modulus composite for emi shielding - Google Patents

Abstract

PURPOSE: A high modulus composite for EMI shielding is provided to be suitable for the EMI shielding by having high conductivity and low surface resistance. CONSTITUTION: A highly-rigid electromagnetic interference shielding composite comprises a thermoplastic resin(10) and a carbon fiber(20). The length of the carbon fiber is 8-20mm. The carbon fiber is 45-65 parts by weight of a whole composite. A thermoplastic resin is a crystallizable thermoplastic resin.

Description

High rigidity electromagnetic shielding composites {HIGH MODULUS COMPOSITE FOR EMI SHIELDING}

The present invention relates to a high rigidity electromagnetic shielding composite. More specifically, the present invention relates to a high-strength electromagnetic shielding composite having excellent mechanical strength and EMI shielding properties, thereby lowering the production cost by replacing an existing magnesium material and having excellent processability.

Electromagnetic wave is a noise phenomenon generated by electrostatic discharge, and it is known to not only cause noise and malfunction to surrounding components or devices, but also to have a harmful effect on the human body. Recently, the possibility of electromagnetic wave is rapidly increasing through high-efficiency, high power consumption, and highly integrated electric and electronic products, and the regulation of electromagnetic waves is strengthened not only in advanced countries but also in Korea.

Conventionally, there is a method using a metal material as a method for shielding electromagnetic waves. For example, IT brackets used in portable display products such as mobile phones, laptops, PDAs, and other mobile items protect LCDs, shield electromagnetic waves, and act as frames, requiring high rigidity and EMI shielding. . Recently, metals such as magnesium, aluminum and stainless steel are mainly used as materials for brackets and frames. By the way, in the case of such a metal material has an advantage that can effectively block the electromagnetic wave, it is produced by the die-casting method has a disadvantage of high production cost and high defective rate.

Accordingly, a method of replacing thermoplastics with ease of molding, excellent molding precision, and economical efficiency or productivity has been proposed.

Currently developed metal substitute resin modulus is less than FM 20GPa, electromagnetic shielding effect is about 30dB (@ 1GHz), there is a disadvantage that the rigidity and EMI shielding is significantly lower than the metal. In order to increase the modulus, a method of increasing the fiber content has been proposed, but in the case of a high fiber content, not only the impact strength is low, but also the fluidity is low and the processing is difficult, which makes it difficult to apply practically and the surface resistance is high. There is a problem that the conductivity is too low to use.

In addition, high filler loading is difficult at low flow bases. Recently, products having high modulus and electromagnetic shielding effect of more than 30dB using carbon-based fibers over 50% have been developed, but it is insufficient to replace metals, and there is difficulty in processing. Moreover, there is a problem that the conductivity is low to use such a material as the material of the electronic device. For example, problems such as deterioration of grounding performance and antenna performance have occurred when using a general mobile phone bracket.

In general high stiffness resin, the surface resistance is lowered by conducting plating in order to solve this problem, but it causes a price increase due to the plating process and the subsequent process, and has a disadvantage in that the surface is peeled off when used for a long time.

Therefore, there is a need for the development of a new material that can replace the existing magnesium material 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 shielding composite having excellent mechanical strength.

Another object of the present invention is to provide a high rigidity electromagnetic shielding composite suitable for EMI shielding having excellent conductivity and low surface resistance.

Still another object of the present invention is to provide a highly rigid electromagnetic shielding composite having excellent flowability and formability.

It is still another object of the present invention to provide a high rigidity electromagnetic shielding composite which requires no post-processing and which is economical and productive.

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

Still another object of the present invention is to provide a highly rigid electromagnetic shielding composite material that can replace the existing magnesium material.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the invention relates to a high rigidity electromagnetic shielding composite. The composite material (A) thermoplastic resin; And (B) a carbon fiber having a length of 8 to 20 mm, wherein the carbon fiber (B) is contained in 45 to 65% by weight of the total composite.

In specific embodiments, the thermoplastic resin (A) may be polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, poly (meth) acrylate resin, polyvinyl chloride resin, polyether resin, Polysulfide-based resins, polyimide-based resins, polysulfone-based resins, polyolefin-based resins, aromatic vinyl-based resins and the like can be used, but are not necessarily 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 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 ㎛. In embodiments, the metal may be aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt, and the like, and two or more alloys thereof may also be applied.

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

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

In yet another embodiment the composite may include both metal-coated graphite and carbon nanotubes. In embodiments, the composite material may be included in the range of 0.1 to 3 parts by weight of metal-coated graphite and 0.05 to 5 parts by weight of carbon nanotubes based on 100 parts by weight of (A) + (B).

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

In yet another embodiment the composite 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 metal-coated graphite, 0.1 to 5 parts by weight of carbon nanotubes, and 1 to 20 parts by weight of metal filler, based on 100 parts by weight of (A) + (B). .

The composite material may further include additives such as flame retardants, plasticizers, coupling agents, thermal stabilizers, light stabilizers, carbon fillers, inorganic fillers, mold release agents, dispersants, anti-dropping agents and weathering stabilizers. These may be used alone or in combination of two or more.

In one embodiment, the composite includes carbon fibers having a length of 0.5-6 mm when molded. The carbon fiber having a length of 0.5 to 6 mm may be 80 wt% or more of the total carbon fibers in the molded article.

In another embodiment, the composite material may have an average value of the residual fiber length of 2 mm or more after 1 hour at 550 ℃ 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 by ASTM D790, an Izod impact strength of at least 35 kgfcm / cm at a thickness of 3.2 mm by ASTM D256, EMI at 1 GHz, 1t thickness. The shielding effect according to D257 standard is 40 dB or more, the surface resistance by the 4-point probe method is less than 5.0 Ωcm for the 1t-thick specimen, and the residual fiber length measured after 550 ° C / 1hr for the molded product is 2.0 mm. It can be longer.

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

In another embodiment the composite has a flexural modulus of at least 40 GPa at a thickness of 3.2 mm by ASTM D790, a spiral flow length of at least 250 mm at 300 ° C., and conforms to EMI D257 specification at 1 GHz, 1t thickness. The shielding effect is 45 dB or more, the surface resistance by the 4-point probe method is less than 1.0 Ωcm for a 1t thick specimen, and the residual fiber length measured after 550 ° C./1hr for the molded article may be 3.0 mm or more. .

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

In one embodiment the method comprises (A) melting a thermoplastic resin by introducing it into an extruder; (B) impregnated by passing the carbon fiber through the melt and then cut and pelletized; And forming the pellets.

In another embodiment, the method comprises (A) a thermoplastic resin and (C) an additive comprising carbon nanotubes, metal-coated graphite, metal fillers, or a mixture of two or more thereof. Preparing pellets; Melting the composite resin pellets; (B) impregnated by passing the carbon fiber to the composite resin pellets and then cut into secondary pellets; And forming secondary pellets impregnated with the carbon fibers; It may comprise a step.

The present invention is suitable for EMI shielding due to its excellent mechanical strength and conductivity, and low surface resistance, excellent fluidity and formability, no post-processing, excellent economy and productivity, excellent dimensional stability, and can replace existing magnesium materials. It provides the effect of the invention to provide a highly rigid electromagnetic shielding composite.

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

The high rigidity electromagnetic wave shielding composite material 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 in which chopped carbon fibers are dispersed in a thermoplastic resin. The chopped carbon fiber, which is generally applied, has a length of 3 mm or less, and when the chopped carbon fiber contains 45% or more of the chopped carbon fiber, not only the stiffness and impact strength can be lowered, but also the shielding performance is poor. . In the present invention, rather than applying conventional chopped carbon fiber, it is characterized by applying a long carbon fiber having a length of 8 to 20 mm. FIG. 2 is a schematic diagram of carbon fibers dispersed in a molded article molded from a high rigidity electromagnetic wave shielding composite according to an embodiment of the present invention. As shown in FIG. 2, the molded article molded from the high-strength electromagnetic wave shielding composite material of the present invention is characterized in that (B) the carbon fiber 20 is dispersed in a network shape in the (A) thermoplastic resin 10. As described above, since the high-strength electromagnetic wave shielding composite material has a high content of the long carbon fiber 20, a large number of contact points 20a formed in contact with each other are formed between the fibers and the fibers, thereby providing low surface resistance and excellent electromagnetic waves. The shielding property can be obtained.

Hereinafter, each said component is explained in full detail.

(A) thermoplastic resin

The thermoplastic resin that can be used in the present invention is not particularly limited. For example, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, poly (meth) acrylate resin, polyvinyl chloride resin, polyether resin, polysulfide resin, polyimide Resins, polysulfone resins, polyolefin resins, aromatic vinyl resins and the like may be used, but are not necessarily 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 resin or a polyester resin.

As the polyamide-based resin, both aliphatic polyamide resins, aromatic polyamide resins containing aromatic groups in the main chain, or copolymers or mixtures thereof can be used. Specific examples include NYLON 6, NYLON 66, NYLON 46, NYLON 610, NYLON 612, NYLON 66/6, NYLON 6 / 6T, NYLON 66 / 6I, NYLON 6T, NYLON 9T, NYLON 10T, NYLON MXD6, NYLON 6I / 6T, and the like. May be used, but is not necessarily limited thereto. An aromatic polyamide resin containing an aromatic group in the double main chain can be preferably used. As such, when the main chain contains an aromatic group, higher rigidity and strength can be given.

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 the balance of physical properties of excellent fluidity, rigidity and low moisture absorption in the above range.

In addition, 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. In the above range, both flowability and mechanical properties are excellent.

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

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

The polycarbonate-based resin may have a form such as a linear polycarbonate resin, a branched polycarbonate resin, or a polyester carbonate copolymer resin, and preferably a bisphenol A-based polycarbonate may be used.

As the poly (meth) acrylate resin, an aromatic (meth) acrylate polymer, an aliphatic (meth) acrylate polymer, a copolymer or a mixture thereof may be applied. In embodiments, homopolymers of methyl methacrylate may be used or copolymers of methyl methacrylate with other vinyl monomers may be used. The vinyl monomers include methacrylic acid esters including ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate and benzyl methacrylate; Acrylic esters including methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 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.

The polyolefin resin includes polyethylene, polypropylene, polybutylene, and the like, and copolymers or mixtures thereof may also be used. In addition, their atactic, 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 (A) thermoplastic resin forms a matrix and may be included in an amount of 35 to 55 wt% in the component (A) + (B). 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, when the content of the (A) thermoplastic resin is less than 35% by weight, moldability may be deteriorated.

(B) carbon fiber

Carbon fiber used in the present invention is already well known to those skilled in the art, it is easy to purchase commercially, it can be produced by conventional methods.

In specific embodiments, the carbon fiber may be one prepared from a PAN system or a pitch system.

The carbon fiber may have an average diameter of 1 to 30 μm, preferably 3 to 20 μm, and more preferably 5 to 15 μm. Excellent physical properties and conductivity can be obtained in the above range.

Carbon fiber used in the manufacture of the high rigidity electromagnetic wave shielding composite material of the present invention can be used in the form of a bundle. In a specific embodiment, the carbon fiber may be a long carbon fiber in a bundle form of 400 to 3000 TEX, preferably 800 to 2400 TEX, more preferably 800 to 1700 TEX. Impregnation can be good in the above range. The carbon fiber having a bundle form is impregnated in the melt of the polyamide resin (A) to bury the polyamide resin (A) on the surface, and then the carbon fiber in which the polyamide resin (A) is buried To 20 mm long and made into pellets 8-20 mm long. Since the length is cut along the length of the carbon fiber, the length of the pellet is the same as the length of the cut carbon fiber. That is, the pellet of 8-20 mm in length will contain 8-20 mm of carbon fiber as it is. The carbon fibers having the bundle form may be dispersed in a network shape in the polyamide resin (A) matrix in the final molded article dispersed in each other in the molding process.

The carbon fiber has a length of 8 to 20 mm, preferably 10 to 15 mm. It has excellent physical balance of conductivity and mechanical strength in the above range.

Usually, most of the carbon fibers are cut after the molding, and when the long carbon fibers having a length of 8 to 20 mm are applied as in the present invention, most of the residual fibers have a length of 0.5 to 6 mm. Here, the length of the residual fiber refers to the length of the fiber after pelletizing and then forming. The molding process is a common general molding condition. For example, the injection conditions of the temperature of 280-320 degreeC, and the pressure of 170 Mpa-190 Mpa are common. Examples of the molding conditions are merely examples for reference, but are not necessarily limited thereto.

On the other hand, when the general chopped fiber is applied, there is a difference in physical properties because the length of the residual fiber is more than 0.5 mm in the molded article. In a specific embodiment, after molding the highly rigid electromagnetic wave shielding composite composition of the present invention, the carbon fiber having a length of 0.5 to 6 mm of residual fibers in the molded article is 80% by weight or more. In addition, after 1 hour at 550 ℃ for the molded article 100 residual fiber length is extracted to measure the length in the longitudinal direction may be an average value of 2mm or more.

In specific embodiments, the carbon fiber may be one having a surface treatment, and may be used in a bundle form.

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

Composites of the present invention may further comprise metal coated graphite. Figure 3 is a schematic diagram of the carbon fibers dispersed in the molded article formed from the high rigidity electromagnetic shielding composite material according to another embodiment of the present invention. When including the metal-coated graphite 30 as shown in Figure 3, it may be dispersed in the thermoplastic resin 10 which is a matrix. 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 may be formed together with the carbon fiber 20. When the metal-coated graphite is thus contained, the surface resistance is remarkably reduced, and it may have more excellent electromagnetic shielding performance and rigidity.

The metal-coated graphite may have an average particle diameter of 10 to 200 ㎛. In addition, when the metal-coated graphite has a fiber shape, it is preferable that the average diameter is 10 to 200 ㎛, the average length is 15 to 100 ㎛. While excellent in electrical conductivity in the above range, there is an advantage that the decrease in mechanical properties by addition.

In embodiments, the metal may be used as long as the metal is conductive. Preferably, aluminum, stainless steel, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt and the like may be used, and two or more kinds thereof may also be applied.

In addition, the metal coating may be formed of not only a single layer but also two or more layers.

In embodiments, 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 carbon nanotubes, wherein the content of the metal coated graphite may be applied in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of (A) + (B). It 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. Figure 4 is a schematic diagram of the dispersion of carbon fibers on a molded article molded from a high rigidity electromagnetic shielding composite material 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 that is a matrix. It may also be in contact with the carbon fiber (20). The carbon nanotubes may be used for any of single walls, double walls, and multiple walls, and a combination thereof may be applied. Preferably it is a multi-walled carbon nanotube. When the carbon nanotubes are contained, the surface resistance is significantly lowered, and thus the electromagnetic wave shielding performance and rigidity may be more excellent. The carbon nanotubes may be included in the range of 0.1 to 5 parts by weight based on 100 parts by weight of (A) + (B). It can have excellent fluidity and rigidity and electromagnetic shielding performance in the above range.

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

When the metal-coated graphite and carbon nanotubes are applied together, they have better electromagnetic shielding performance and stiffness even with a small amount. In embodiments, the composite material may be included in the range of 0.1 to 3 parts by weight of metal-coated graphite and 0.05 to 5 parts by weight of carbon nanotubes based on 100 parts by weight of (A) + (B). It can have excellent fluidity and rigidity and electromagnetic shielding performance in the above range.

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

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

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 another embodiment, a low melting point 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, zinc and combinations thereof Metals can be used. When the low melting point metal is used as described above, the filler-to-pillar network can be easily formed to further improve the electromagnetic shielding efficiency. Such a low melting point metal preferably has a solidus temperature (Solidus temp .: temperature at which solidification ends) lower than the composite process process temperature of the thermoplastic resin (A). Preferably, the solidus temperature of the low melting point metal is 20 ° C or more lower than the process temperature of the thermoplastic resin (A) in terms of the composite manufacturing process and the network formation between the fillers, and 100 ° C or more higher than the environment for the composite material in terms of stability. good. Preferably, tin / copper (97/3 weight ratio) and tin / copper / silver (92/6/2 weight ratio) may be used as the melting point of 300 ° C. or less.

The metal filler may be formed of metal powder, metal beads, metal fibers, metal flakes, metal coated particles, metal coated fibers, and the like, but are not limited thereto. These may be used alone or in combination of two or more.

When using the form of the metal filler in the form of metal powder or metal beads, the average particle diameter may be 30 to 300 ㎛. There is an advantage that feeding is good when extrusion in the above range.

When using the form of the metal filler 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 ㎛. In addition, the metal fiber has a density of 0.7? 6.0 g / ml may be used. It is possible to maintain proper feeding during the extrusion process in the above range.

When using the form of the metal filler in the form of a metal flake, the average size may be 50 to 500 ㎛. There is an advantage in maintaining the proper feeding during the extrusion processing in the above range.

The metal powder, metal beads, metal fibers, etc. may be a single metal or an alloy of two or more kinds, and may have a multilayer structure.

The metal-coated particles and the metal-coated fibers form a core of a resin, ceramic, metal, carbon, and the like, and the core is coated with 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 diameter of 30 to 300 μm. There is an advantage that feeding is good when extrusion in the above range. In addition, the metal-coated fibers may have an average diameter of 10 to 100 ㎛, and a length of 50 to 500 mm. There is an advantage in maintaining the proper feeding during the extrusion processing in the above range.

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). Within this range, it is possible to obtain a balance of conductivity and fluidity, impact strength and flexural modulus.

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

The composite material may further include additives such as flame retardants, plasticizers, coupling agents, thermal stabilizers, light stabilizers, carbon fillers, inorganic fillers, mold release agents, dispersants, anti-dropping agents and weathering stabilizers. These may be used alone or in combination of two or more.

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

In addition, the inorganic filler may be applied to the above-described metal filler, metal oxide filler, metal salt filler and the like. Among these, metal fillers are preferable.

In another embodiment, after the molding using the composite material, the length of the carbon fiber residual fiber in the molded article may be 80 wt% or more.

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

In another embodiment, the composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm by ASTM D790, a spiral flow length of at least 200 mm at 300 ° C., and is in accordance with EMI D257 specification at 1 GHz, 1t thickness. The shielding effect is 44 dB or more, the surface resistance by the 4-point probe method is less than 4.2 Ωcm for a 1t thick specimen, and the residual fiber length measured after 550 ° C./1hr may be 2.5 mm or more.

In another embodiment the composite has a flexural modulus of at least 40 GPa at a thickness of 3.2 mm by ASTM D790, a spiral flow length of at least 250 mm at 300 ° C., and conforms to EMI D257 specification at 1 GHz, 1t thickness. The shielding effect is 45 dB or more, the surface resistance by the four-point probe method for a 1t thick specimen is 1.0 시 ~ cm or less, the residual fiber length measured after 550 ℃ / 1hr may be more than 3.0 mm.

Another aspect of the invention relates to a method for producing the high rigidity electromagnetic shielding composite. The method comprises (A) injecting a thermoplastic resin into an extruder to melt it; (B) impregnated by passing the carbon fiber through the melt and then cut and pelletized; And it may be prepared including the step of molding the pellets. In embodiments, the pelletization may be pelletized by cutting the impregnated carbon fibers.

The carbon fiber may have a bundle form.

In another embodiment, the composite material is (A) thermoplastic resin and (C) carbon nanotubes, metal-coated graphite, metal filler or a variety of additives including two or more thereof in an extruder and pelletized first Preparing a composite resin pellet; Melting the composite resin pellets; (B) impregnated by passing the carbon fiber to the composite resin pellets and then cut into secondary pellets; And it may be prepared including the step of molding the carbon pellet impregnated secondary pellets.

The impregnated carbon fibers may be cut to a certain size and pelletized. In embodiments it may be pelletized by cutting to a length of 8 to 20 mm, preferably 10 to 15 mm. The shape of the carbon fiber of the long fiber is maintained in the above range can be obtained excellent shielding properties and strength.

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

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

The carbon fiber may be partially cut after the molding. In embodiments, carbon fibers having a length of 0.5 to 6 mm of residual fibers in the molded article may be dispersed in a network shape. In addition, after 1 hour at 550 ℃ for the molded article 100 residual fiber length is extracted to measure the length in the longitudinal direction may be an average value of 2mm or more.

Molded articles made of the composite material of the present invention has excellent electromagnetic shielding properties, conductivity, mechanical properties, moldability and can be preferably applied to the LCD protective bracket of portable display products.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

Example

The specifications of each component used in the following Examples and Comparative Examples are as follows:

(A) thermoplastic resin

(A1): As a PA66 product, Dupont's ZYTEL 101 F was used.

(A2): Hyosung's 1031 BRT was used as a PA6 product.

(A3): Toyobo T-600 was used as PAA (metalxylenediamineadipamide (MXD6, polyarylamide)).

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

(A5): Shinite K001 from ShinKong was used as a PBT product.

(B) carbon fiber

(B1) Toray TORAYCA T700S 50C, 1650TEX manufactured by Toray having an average diameter of 20 μm and long carbon fibers were used.

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

(B3) Glass fiber: TufRov 4588 from PPG, which had an average diameter of 20 µm and a long glass fiber, was used.

(C1) Carbon Nano Tube: NC7000 (multi-wall CNT) manufactured by Nanocyl 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 ° C. or less: 97C (97% Sn, 2.5% Cu as powder type tin-copper alloys) manufactured by Warton Metals Limited was used.

(D) Thermal stabilizer and lubricant: IRGANOX1010 of CIBA chemical was used as a thermal stabilizer, and PE-Wax was mixed 1: 1 as a lubricant.

Example  1-12 and Comparative example  2, 5-7

The components were mixed in a conventional mixer in the content shown in Table 1 and extruded using a twin screw extruder having L / D = 35 and Φ = 45 mm, and then the extrudate was prepared in pellet form, which was 100 ° C. for 4 hours. After drying in a hot air dryer, the carbon fiber was impregnated with a pultrusion method and cut into 12 mm long pellets to prepare a carbon fiber having a length of 12 mm. The pellets were prepared at the injection temperature of 270 ° C. using a long fiber injection machine for specimens for measuring properties and evaluating applications such as EMI resistance. After the specimens were allowed to stand for 48 hours at 23 ° C. and 50% relative humidity, the physical properties were evaluated by the following method, and the results are shown in Table 1.

Assessment Methods:

(1) Flexural modulus: evaluated at 1.27 mm / min by ASTM D790, and the unit is GPa.

(2) Izod impact strength (unnotched): evaluated at 3.2 mm thickness by ASTM D256 at 23 ° C., unit is kgfcm / cm.

(3) Spiral flow: 6oz injection machine is injected into a spiral mold with a thickness of 2mm under constant conditions of molding temperature 250 ℃, mold temperature 60 ℃, injection pressure 50%, injection speed 70% mm) was measured.

(4) EMI shieldability (dB): After leaving the sample for 48 hours at 23 ° C., 50% relative humidity, the electromagnetic shielding performance of the 1t-thick sample (6 × 6) at 1 GHz was measured according to EMI D257.

(5) Surface resistance: 1-t thick injection specimens were evaluated by 4 point probe method (Ω? Cm).

(6) Residual fiber length (mm) after ignition loss: 100 residual fiber lengths were extracted after 550 ° C / 1hr for the molded article, the length was measured in the longitudinal direction, and the arithmetic mean value was determined.

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 Flexural 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, Example 1-12 has a flexural modulus of 35 GPa or more, it can be seen that the shielding effect by the EMI D257 standard at 1 GHz, 1t thickness is more than 40 dB. In addition, it was confirmed that Examples 1 to 7 to which the crystalline thermoplastic resin was applied had higher flexural modulus and spiral than those of Example 11 to which the amorphous thermoplastic resin was applied, and the residual fiber length was longer after the ignition of the injection. In addition, when the CNT and / or Ni-caoted graphite is added as in Examples 8 to 10 and 12 it can be seen that the surface resistance is significantly lower than 2.0 Ω · cm or less.

Comparative Examples 1 and 3 to 4

Each component was mixed in a conventional mixer in the content shown in Table 2, and extruded using a twin screw extruder having L / D = 35 and Φ = 45 mm, and then an extrudate was prepared in pellet form. The prepared pellets were dried in a hot air dryer for 4 hours at 100 ° C., and then specimens for measuring physical properties at the injection temperature of 270 ° C. and for evaluating applications such as EMI resistance were prepared using a long fiber injection machine. After the specimens were allowed to stand for 48 hours at 23 ° C. and 50% relative humidity, the physical properties were evaluated by the following method, and the results are shown in Table 2.

Comparative Example 2 and 5 to 7

Except that each component was added to the content shown in Table 2 was carried out in the same manner as in Example 1.

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 Flexural 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 stiffness (FM) is lowered and the impact strength (IZOD) is lowered, the surface resistance is increased, and the residual fiber length is shortened after the ignition. There is a problem.

As shown in Comparative Examples 2, 5 and 6, the use of long glass fibers instead of carbon fibers was found to reduce surface resistance and EMI shielding properties. In addition, as in Comparative Example 7, the spiral was reduced when the long carbon fiber is excessively applied.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention belongs may have the technical idea of the present invention. However, it will be understood that other specific forms may be practiced without changing the essential features. 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: metal coated graphite 40: carbon nanotube

Claims (22)

(A) thermoplastic resin; And
(B) carbon fiber having a length of 8 to 20 mm; It includes, wherein the carbon fiber (B) is a high-strength electromagnetic shielding composite containing 45 to 65% by weight of the total composite.

The high stiffness electromagnetic shielding composite according to claim 1, wherein the thermoplastic resin (A) is a crystalline thermoplastic resin.
The method of claim 1, wherein the thermoplastic resin (A) is a polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, poly (meth) acrylate resin, polyvinyl chloride resin, polyether A high rigid electromagnetic shielding composite material comprising at least one resin selected from the group consisting of resins, polysulfide resins, polyimide resins, polysulfone resins, polyolefin resins and aromatic vinyl resins.
The high stiffness shielding composite according to claim 1, wherein the composite further comprises metal-coated graphite.
5. The high rigidity electromagnetic shielding composite of claim 4, wherein the metal-coated graphite has particles, fibers, flakes, amorphous, or a combination thereof.
The highly rigid electromagnetic shielding composite of claim 5, wherein the metal-coated graphite has an average particle diameter of 10 to 200 μm.
The method of claim 4, wherein the metal is at least one selected from the group consisting of aluminum, stainless, iron, chromium, nickel, black nickel, copper, silver, gold, platinum, palladium, tin, cobalt and two or more alloys thereof. High-strength electromagnetic shielding composite material, characterized in that.
The highly rigid electromagnetic shielding composite according to claim 4, wherein the metal-coated graphite is included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of (A) + (B).
The high stiffness electromagnetic shielding composite of claim 1, wherein the composite further comprises carbon nanotubes.
The highly rigid electromagnetic shielding composite according to claim 9, wherein the carbon nanotubes are included in the range of 0.1 to 5 parts by weight based on 100 parts by weight of (A) + (B).
According to claim 1, The composite material (A) + (B) High rigidity electromagnetic waves, characterized in that it comprises a metal coated graphite in the range of 0.1 to 3 parts by weight and carbon nanotubes 0.1 to 5 parts by weight Shielding composites.
The high stiffness shielding composite according to claim 1, wherein the composite further comprises a metal filler.
13. The highly rigid electromagnetic shielding composite of claim 12, wherein the metal filler comprises at least one 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 includes 0.1 to 3 parts by weight of metal-coated graphite, 0.1 to 5 parts by weight of carbon nanotubes, and 1 to 20 parts by weight of metal filler, based on 100 parts by weight of (A) + (B). High-strength electromagnetic shielding composite material.
The method of claim 1, wherein the composite material further comprises one or more additives selected from the group consisting of carbon fillers, flame retardants, plasticizers, coupling agents, thermal stabilizers, light stabilizers, inorganic fillers, mold release agents, dispersants, anti-dropping agents and weathering stabilizers High-strength electromagnetic shielding composite material.
According to claim 1, The composite material is a highly rigid electromagnetic shielding composite, characterized in that the carbon fiber having a length of 0.5 to 6mm of the residual fiber in the molded article after molding, more than 80% by weight of the total carbon fiber.
The high stiffness electromagnetic shielding composite according to claim 1, wherein the composite has an average value of at least 2 mm of residual fiber length after 1 hour at 550 ° C.
The composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm by ASTM D790, an Izod impact strength of at least 35 kgfcm / cm at a thickness of 3.2 mm by ASTM D256, and a thickness of 1 GHz, 1t. The shielding effect according to the EMI D257 standard is 40 dB or more, the surface resistance by the four-point probe method is less than 5.0 Ωcm for the 1t-thick specimen, and the residual fiber length measured after 550 ° C / 1hr for the molded product is 2.0 High-strength electromagnetic shielding composite material, characterized in that more than mm.
The composite has a flexural modulus of at least 37 GPa at a thickness of 3.2 mm by ASTM D790, a spiral flow length of at least 200 mm at 300 ° C., and an EMI D257 standard at 1 GHz, 1t. The shielding effect by is more than 44 dB, the surface resistance by the 4-point probe method is less than 4.2 Ωcm for the 1t-thick specimen, and the residual fiber length measured after 550 ℃ / 1hr for the molded product is 2.5 mm or more. High-strength electromagnetic shielding composite material.
The composite has a flexural modulus of at least 40 GPa at a thickness of 3.2 mm according to ASTM D790, a spiral flow length of at least 250 mm at 300 ° C., and an EMI D257 standard at 1 GHz, 1t thickness. The shielding effect of the specimen was 45 dB or more, the surface resistance by the four-point probe method was less than 1.0 Ωcm for the 1t-thick specimen, and the residual fiber length measured after 550 ° C / 1hr for the molded product was 3.0 mm or more. High-strength electromagnetic shielding composite material.
(A) pouring a thermoplastic resin into an extruder and melting it;
(B) impregnated by passing the carbon fiber through the melt and then cut and pelletized; And
Forming the pellets;
Method for producing a high rigidity electromagnetic shielding composite comprising a step.
(A) a thermoplastic resin and (C) an additive comprising carbon nanotubes, metal coated graphite, metal fillers, or a mixture of two or more thereof, are introduced into an extruder and first pelletized to produce a composite resin pellet;
Melting the composite resin pellets;
(B) impregnated by passing the carbon fiber to the composite resin pellets and then cut into secondary pellets; And
Forming secondary pellets impregnated with the carbon fibers;
Method for producing a high rigidity electromagnetic shielding composite comprising a step.

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