Preparation method for electromagnetic wave shield composite material using copper- and nickel-plated carbon fiber prepared by electroless and electrolytic continuous processes, and electromagnetic wave shield composite material
The present invention relates to a preparation method for an electromagnetic wave shield composite material and the electromagnetic wave shield composite material prepared by the method. The present invention uses a highly conductive carbon fiber prepared by electroless and electrolytic continuous processes, and thus is suitable for an EMI shield due to having an excellent conductivity and low surface resistance, and is capable of providing the electromagnetic wave shield composite material having an excellent productivity and economic value. Furthermore, the electromagnetic wave shield composite material of the present invention can be used for blocking electromagnetic waves by being inserted into a cell phone cover and a cell phone pouch, and can also be applied to a bracket for protecting an LCD of a portable display product.
1. A method for preparing an electromagnetic shielding composite comprising:
(a) copper plating a carbon fiber by passing said carbon fiber through an electroless plating liquid,
wherein the electroless plating liquid contains 2.5-5.5 g/l Cu ions, 20-55 g/l EDTA, 2.5-4.5 g/l formalin, 2-6 g/l triethanolamine (TEA), 8-12 ml/l 25% NaOH, and 0.008-0.15 g/l 2,2′-bipiridine on the basis of the volume of pure water,
wherein the electroless plating liquid has pH 12-13 and a temperature of 36-45° C.;
(b) nickel plating the copper-plated carbon fiber by passing the copper-plated carbon fiber through an electrolytic plating liquid,
wherein the electrolytic plating liquid contains 280-320 g/l Ni(NH 2 SO 3 ) 2 , 15-25 g/l NiCl 2 , and 35-45 g/l H 3 BO 3 ,
wherein the electrolytic plating liquid has pH 4.0-4.2 and a temperature of 50-60° C.;
(c) mixing 50-90 wt % of a thermoplastic resin and 10-50wt % of copper- and nickel-plated carbon fibers;
(d) preparing compounding pellets from the product in step (c) by performing extrusion in conditions of a temperature of 230-255° C. and a speed of 70-150 rpm; and
(e) performing injection or extrusion molding on the product in step (c) to obtain an electromagnetic shielding composite,
wherein the copper- and nickel-plated carbon fiber in step (c) has a chopped shape with a length of 3 mm to 500 mm.
2. The method of claim 1 , wherein the thermoplastic resin is at least one thermoplastic resin selected from the group consisting of polycarbonate-based resins, polystyrene-based resins, polyether-based resins, polysulfone-based resins, polyolefin-based resins, polyimide-based resins, fluorine-based resins, poly(meth)acrylate-based resins, polyacetal-based resins, polyamide-based resins, aromatic vinyl-based resins, acrylic-butadiene-styrene copolymer resins, and polyvinylchloride-based resins.
3. The method of claim 1 , wherein the product in step (c) further comprises a conductive material selected from the group consisting of ferrite, graphite, and metal-plated graphite.
4. The method of claim 3 , wherein the product in step (c) comprises 40-89.5 wt % of the thermoplastic resin, 10-50 wt % of the copper- and nickel-plated carbon fibers, and 0.5-10 wt % of the conductive material.
5. The method of claim 3 , wherein a metal of the metal-plated graphite is at least one metal selected from the group consisting of aluminum, iron, chromium, stainless, copper, nickel, black nickel, silver, gold, platinum, palladium, tin, cobalt, and an alloy of two or more thereof.
6. The method of claim 1 , wherein the injection molding in step (e) fill is performed in an extruder in conditions of a temperature of 215-275° C., a speed of 40-70 rpm, a pressure of 40-80 bars and a mold cooling time of 4-12 seconds.
7. The method of claim 1 , wherein the extrusion molding in step (e) is performed in an extruder in conditions of a temperature of 230-265° C. and a speed of 30-60 rpm.
8. The method of claim 1 , wherein the mixing in step (c) is performed by mixing with the thermoplastic resin and the copper- and nickel-plated carbon fibers 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 dispersing agent, an anti-dropping agent and a weathering stabilizer.