JP5173143B2 - Electromagnetic wave shielding resin composition and molded product thereof - Google Patents

Description

  The present invention relates to a resin composition for electromagnetic wave shielding and a molded product thereof.

  Electronic devices such as mobile phones, notebook computers, and PDAs have electromagnetic shielding properties as their enclosures in order to prevent electromagnetic waves generated from the inside from leaking outside and adversely affecting surrounding electronic devices. The housing | casing which has is used.

  In recent years, high electromagnetic shielding properties in a high frequency region are required as various electronic devices have higher frequencies.

  Conventionally, in order to impart electromagnetic shielding properties to a casing, a casing is known in which conductivity is imparted by plating or vapor deposition of metal on the surface of a molded body made of a thermoplastic resin. The manufacturing process becomes complicated, and in the case of a molded body having a complicated shape, there is a problem that the processing becomes difficult.

  Therefore, in order to eliminate the complexity of such a processing step, an electromagnetic wave shielding property obtained by molding a resin composition containing a conductive material such as metal flakes, metal fibers, carbon fibers or metal-coated carbon fibers is provided. A molded product having the same and a manufacturing method thereof have been proposed.

  When manufacturing a plastic molded article having such electromagnetic wave shielding performance, a resin composition such as a pellet containing a thermoplastic resin and conductive fibers is used. The conductive fiber is impregnated with a thermoplastic resin in a state in which long fibers are aligned in one direction, and is evaluated as a material for an injection molded product having electromagnetic wave shielding performance. As such conductive fibers, fibers such as stainless steel fibers, carbon fibers, and metal coated carbon fibers are used. Of these, stainless steel fibers, carbon fibers, and metal coated fibers are most commonly used. Carbon fiber (see, for example, Patent Document 1-2).

  However, since the stainless fiber pellet usually contains 75-90% by weight of stainless fiber, the specific gravity of the pellet is about 2.5 to 4, and the specific gravity difference between this pellet and the thermoplastic resin pellet for molding is low. Therefore, the injection molding is performed in a state where each pellet is unevenly distributed without being uniformly mixed, which causes variations in electromagnetic shielding performance at the beginning and end of the molding shot.

  For this reason, the electric field and magnetic field performance of the electromagnetic wave shield does not exceed the specified level, and there is a risk that the electronic component incorporated in the molded product malfunctions and the electromagnetic wave shield performance is not exhibited and the appropriateness is lacking.

  In addition, in the case of carbon fiber, although measures such as increasing the fiber length, such as long fiber, have been devised, the electromagnetic wave shielding characteristics are low, it is limited to low level electromagnetic wave shielding, and it is not suitable for practical use at present is there.

  On the other hand, although the metal-coated carbon fiber has excellent electromagnetic wave shielding properties, in order to have the required electromagnetic wave shielding properties because the fiber is damaged in the molding process scene, 15 to 30 wt% is also necessary, and the addition amount increases, and mechanical characteristics may be lowered or moldability may be lowered.

  Therefore, in recent years, it has been proposed to impregnate metal-coated fibers with a thermoplastic resin into pellets, which are used as master batches. Specifically, for example, the surface of aramid fibers is made of a metal such as copper. It is coated, impregnated with resin, and used as a pellet having a length of 6 mm, thereby improving moldability and improving electromagnetic shielding characteristics (Patent Document 3).

However, even in this case, breakage of the metal-coated fiber as the conductive fiber is unavoidable, and the uniform dispersibility still has difficulty, and there has been a practical limitation in improving the electromagnetic shielding characteristics.
JP-A-9-235382 JP 2003-16073 A JP-A-2005-290086

  From the background as described above, the present invention eliminates the conventional problems associated with the production of electromagnetic shielding molded products by injection molding, and provides good electromagnetic shielding performance with good moldability and a small amount of conductive fibers. It is an object of the present invention to provide a new resin composition for electromagnetic wave shielding that can be stably realized by uniform dispersion and an electromagnetic wave shield molded product molded using the same.

  The resin composition for electromagnetic wave shielding and its molded product of the present invention are characterized by the following as a solution to the above problems.

First: (a) Polyamide (PA) resin, polyethylene terephthalate (PET) resin, polycarbonate (PC) resin, and ABS resin are impregnated with at least one thermoplastic resin, and the pellet length is 1 to 3 mm. Metal-coated aramid fiber pellets;
(B) Polyamide (PA) resin, polybutylene terephthalate (PBT) resin, polycarbonate (PC) resin, and at least one thermoplastic resin of ABS resin, and the coated metal in the metal-coated aramid fiber is copper (Cu), iron (Fe), and nickel (Ni), at least one of which is a ratio of 1 to 10% by mass of the total amount of the metal-coated aramid fiber, and the metal-coated aramid The resin composition for electromagnetic wave shielding characterized by the ratio in the pellet of a fiber being in the range of 40-70 mass%.

Second : In any one of the above resin compositions, the electromagnetic wave further contains at least one of a metal powder of copper (Cu) powder, tin-copper (Sn-Cu) alloy powder, Ni powder and permalloy. Shielding resin composition.

Third : The above electromagnetic wave shielding resin composition, wherein the average particle size of the metal powder is in the range of 5 to 70 μm and in the range of 2 to 60% by mass of the total amount of the composition.

Fourth : An electromagnetic wave shield molded product which is an injection molded product of any of the above resin compositions.

Fifth : A cellular phone component or a vehicle-mounted component in which the electromagnetic wave shield molded product is at least a part of its configuration.

It is a composition comprising a resin-impregnated pellet of metal-coated aramid fiber as a specific conductive fiber having a specific pellet length of 1 to 3 mm impregnated with a specific thermoplastic resin, and a specific thermoplastic resin. According to the first aspect of the present invention, good electromagnetic shielding performance is achieved by uniformly dispersing the molded article with a small amount of the conductive fiber having good moldability without impairing the strength of the molded article in the injection molding. Can be realized stably.

Further, according to the second and third inventions in which Cu powder, Sn—Cu metal powder Ni powder and permalloy are further blended, the electromagnetic shielding performance is further improved.

And like the 4th and 5th invention , the molded article with favorable electromagnetic wave shielding performance is implement | achieved with said effect.

  The present invention has the features as described above, and an embodiment thereof will be described below.

  The resin-impregnated pellet of the above-mentioned (a) metal-coated aramid fiber blended as a conductive fiber in the resin composition for electromagnetic wave shielding of the present invention includes PA, PET, PC, and the like as the thermoplastic resin unique to the metal-coated aramid fiber. Although it is impregnated with at least one of the ABC resins, the aramid fiber here retains its shape even at the temperature during the impregnation step, and when the molded product is manufactured, From the viewpoint of preventing the organic fiber from being broken by physical force such as excessive kneading and preventing the electromagnetic wave shielding performance from being lowered, it is necessary that the shape be maintained even at the temperature during the molding process. There are no particular restrictions.

  The fiber surface may be subjected to physical treatment such as chemical treatment or electron beam irradiation. One or a combination of two or more of these may be used, and may be appropriately selected and used according to the required characteristics of the target molded product.

  From the viewpoint of imparting electromagnetic wave shielding properties, aramid fibers are preferred from the viewpoint of heat resistance because the fibers are not easily damaged. Typical examples of the aramid fiber in the present invention include a para type whose molecular skeleton is linear as a whole and a meta type whose molecular skeleton is zigzag.

  As the metal used for coating the aramid fiber, a metal that has good conductivity and is difficult to oxidize is preferable. Specific examples include copper, iron, nickel and the like from the viewpoint of conductivity. These 1 type or the combination of 2 or more types is possible. In particular, copper base nickel is preferable in terms of electromagnetic shielding properties.

  The method of metal coating on the aramid fiber is not particularly limited, but is generally electroless plating. In addition, methods such as vacuum deposition and sputtering are also possible. In the case of nickel, a nickel coating method in nickel carbonyl gas generated during nickel refining is also exemplified.

  The amount of metal coating is appropriately determined depending on the type of fiber used, the type of metal, and the required volume resistance, but a thickness of 0.1 to 1. It is preferable to coat with μm. The fiber diameter and number of the metal-coated aramid fibers used in the present invention are not particularly limited, but in the pellets of the present invention, the fiber diameter per fiber is 6 to 20 μm and one bundle from the viewpoint of the impregnation step and subsequent handling. The number per unit is preferably 2500 to 16000.

  And it is preferable that the pellet length is 5 mm or less. The range of 1 to 4 mm is more preferable. Here, the pellet length refers to the length of the longest dimension in a cylinder, a prism, or various pellet shapes such as blocks and spheres.

  When it exceeds 5 mm, sufficient effects cannot be obtained in terms of moldability and conductivity.

  The content of the metal-coated aramid pellets of the present invention is preferably in the range of 45 to 70% by mass from the viewpoint of pellet moldability and sufficient conductivity effect.

  The resin-impregnated metal-coated aramid fiber in the present invention is kneaded with (b) a thermoplastic resin as a pellet having a pellet length of 5 mm or less and used for injection molding. In this case, the pellet is a metal as described above. The coated aramid fiber is formed by impregnating a specific thermoplastic resin such as PA, PET, PC, and ABS.

  As a condition for satisfactorily impregnating the metal-coated aramid fiber with these resins, the melt viscosity value measured by the method defined in JIS K 6862 under the temperature condition at the time of impregnation is 4000 mPs · s or less. Preferably there is.

  A known method can be used for the impregnation method of the thermoplastic resin without any particular limitation.

  In the present invention, the metal-coated aramid fiber makes the fiber bundle compact and easy to handle by a specific thermoplastic resin impregnation step, and the fiber dispersion in the molded product is improved. If the fiber is in a disjointed state, it becomes bulky, a uniform resin composition for electromagnetic wave shielding cannot be obtained, and if the resin is not impregnated, the fiber is not wet with the resin, so air is contained in the fiber However, when a molded product is manufactured using the fibers in this state, bubbles enter the molded product, resulting in poor mechanical properties and appearance. However, in the present invention, such inconvenience does not occur.

  The molded product of the present invention can be obtained by putting a mixture obtained by uniformly stirring and mixing the above (a) pellets and (b) resin into an injection molding machine and molding.

  PA, PET, PC, and ABS resins impregnated in metal-coated aramid fibers, and (b) PA, PBT, PC, and ABS resins used during molding are required for performance requirements of molded products such as heat resistance. Accordingly, it can be appropriately selected from commercially available products and synthetic products.

  During the production of a molded product, the resin portion in the resin composition for electromagnetic wave shielding is melted, the bundles of metal-coated aramid fibers are separated, and the metal-coated aramid fibers are uniformly dispersed in the thermoplastic resin for molding. In the molded product thus formed, the metal-coated aramid fibers come into contact with each other and are in a dispersed state, thereby having an electromagnetic shielding performance through the metal on the fiber surface.

  In order to obtain the electromagnetic shielding performance as described above, the content of the (a) metal-coated aramid fiber in the molded product is preferably in the range of 1 to 10% by mass in the total amount of the composition.

  In the present invention, at least one of Cu powder and Sn—Cu alloy powder may be further added to the electromagnetic shielding resin composition as described above. By doing so, the electromagnetic shielding performance is further remarkably improved. For such powders, the average particle diameter is preferably in the range of 5 to 70 μm, and the additive content is preferably considered to be in the range of 2 to 60% by mass of the total amount of the composition. .

  When the average particle size is less than 5 μm and the content is less than 2% by mass, the contribution to the improvement of the electromagnetic shielding performance is small. On the other hand, when the average particle size exceeds 70 μm and the content exceeds 60% by mass, a molded product is obtained. It tends to decrease the mechanical strength and formability of the.

  The mixing of components (a) and (b) in the resin composition of the present invention and the injection molding with a kneaded product should be appropriately selected in consideration of conventionally known methods and conditions, and the performance and shape of the molded product. Can do.

  Examples of the molded product of the present invention include a mobile phone functional component, an in-vehicle functional component, and the like. More specifically, examples include housing applications such as OA equipment, AV equipment, measurement equipment, transportation equipment, and communication equipment, and connections.

  The electromagnetic wave shielding resin composition and molded product of the present invention are provided with a heat stabilizer, anti-glare agent, lubricant, slip agent, flame retardant, nucleating agent, pigment, dye, etc. within a range not inhibiting the effects of the present invention. Can be blended.

  In addition, since the metal-coated aramid fiber is not damaged during the molding process and the fiber length can be maintained, a dispersant may be added to improve the metal-coated aramid fiber dispersibility in the molded product.

  Also, an excellent molded product can be obtained by molding after kneaded with an extruder in advance.

  Hereinafter, the present invention will be specifically described with reference to examples.

  Of course, the invention is not limited by the following examples.

<1> Metal-Coated Aramid Fiber Resin Pellets The surface of aramid fibers having a fiber diameter of 8 to 12 μm per one is made to have a thickness of 0.4 to 0.7 μm by electroless plating with Cu, Fe or Ni. Coated. 4000 to 4300 pieces of the metal-coated aramid fibers were made into one bundle, and this was impregnated with a resin at a temperature at which the melt viscosity value (JIS K 6862) was 2800 to 3200 mPa · s to obtain pellets.

  The length of the pellets was in the range of 3 to 10 mm. Moreover, the ratio of the metal-coated aramid fiber in the pellets was in the range of 50 to 60% by mass.

  The resin used is as follows.

ABS Nippon A & L Clarastic (trade name) GA-501
PC Sumitomo Dow Caliber (trade name) 301-22
PBT Wintech Polymer Geranex (trade name) 2000
PA Ube Industries UBE nylon (trade name) 1013B
<2> Injection molding In the above, different types of impregnating resins and different pellet lengths are used and mixed with a thermoplastic resin so that the ratio of metal-coated aramid fibers is 5% by mass or 1% by mass. Molded.

Nissin Resin “ES600” was used as the molding machine, and the cylinder temperature was 240 ° C., the mold temperature was 60 ° C., and the screw rotation speed was 80 rpm.
<Evaluation>
The moldability in injection molding and the electromagnetic shielding performance of the molded product were evaluated by the following methods.
(Electromagnetic wave shielding KEC method electric field)
100 sheets of molded φ50 were molded and evaluated with 1, 100, 250, and 500 shots.

An evaluation value “70” or more at an electric field of 800 MHz was determined to be good.
(Electromagnetic shielding KEC magnetic field)
100 sheets of molded φ50 were molded and evaluated with 1, 100, 250, and 500 shots.

An evaluation value “50” or more at an electric field of 800 MHz was determined to be good.
(Formability)
100 sheets of thin-wall formability (0.2 mm * 100 * 50 mm) were molded and the fillability was evaluated.

  A defect number of “5” or less was determined to be good.

  The results are shown in Table 1 (Example 1-13), Table 2 (Example 14-23), and Table 3 (Comparative Example 1-5). In Examples 14-23 in Table 1, Sn—Cu alloy powder (Fukuda Metal Foil: average particle size 25 μm, melting point 230 ° C.), Cu powder (average particle size 35 μm) and Ni powder (average particle size 30 μm) ) Is also shown.

  As is apparent from the results of Tables 1, 2 and 3, it was confirmed that the moldability and electromagnetic wave shielding performance were excellent in the examples of the present invention.

Claims (5)

(A) Metal-coated aramid impregnated with at least one thermoplastic resin among polyamide (PA) resin, polyethylene terephthalate (PET) resin, polycarbonate (PC) resin, and ABS resin, and having a pellet length of 1 to 3 mm Fiber pellets,
(B) Polyamide (PA) resin, polybutylene terephthalate (PBT) resin, polycarbonate (PC) resin, and at least one thermoplastic resin of ABS resin, and the coated metal in the metal-coated aramid fiber is copper (Cu), iron (Fe), and nickel (Ni), at least one of which is a ratio of 1 to 10% by mass of the total amount of the metal-coated aramid fiber, and the metal-coated aramid The resin composition for electromagnetic wave shielding characterized by the ratio in the pellet of a fiber being in the range of 40-70 mass%.   2. The electromagnetic wave shield according to claim 1, further comprising at least one metal powder of copper (Cu) powder, tin-copper (Sn—Cu) alloy powder, Ni powder, and permalloy. Resin composition.   3. The resin composition for electromagnetic wave shielding according to claim 2, wherein the average particle diameter of the metal powder is in the range of 5 to 70 [mu] m and in the range of 2 to 60% by mass of the total amount of the composition.   An electromagnetic wave shield molded article, which is an injection molded article of the resin composition according to any one of claims 1 to 3.   5. A cellular phone part or a vehicle-mounted part, wherein the electromagnetic wave shield molded article according to claim 4 is at least a part of its configuration.