JP2894988B2 - Method for producing metallized plastic molded pellets for shielding electromagnetic interference - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metallized plastic molded pellet for shielding electromagnetic interference.

[0002]

2. Description of the Related Art Electromagnetic interference (EMI, electromagnetic int
Many methods have been proposed for shielding. However, metal shields are not suitable for the electronics industry because their form is cumbersome, heavy and complex. The metallization on the surface of the EMI shielding plastic article is easily stripped and partially loses shielding performance. The scraped pieces are electrically conductive and, when dropped on the printed wiring board of the electronic product, cause a short circuit and make the electronic product worse. On the other hand, metal coating or metal plating increases the problem of environmental protection.

[0003] Recently, various plastic molding methods have been disclosed in which metallic materials are incorporated into resin compositions to make EMI shields.

US Pat. No. 4,474,685, entitled "High Performance Molding Compounds for Shielding Electromagnetic Interference", discloses a molding composition comprising a thermosetting binder and an electrically conductive filler, comprising carbon black, graphite and particles of a conductive metal. In addition, there is disclosed one that has a shielding effect against electromagnetic interference.

[0005] However, when a resin and a particle filler are blended for molding by the method of manufacturing an EMI shielding material, such a particle filler easily flockes to disperse the electrically conductive filler in the resin matrix in a non-uniform manner. Affects the shielding effect of the product.

As described above, for other fillers such as a fiber filler and a flake filler, replacement with a particle filler can also be considered.

[0007] However, the method using a fiber filler is expensive and uneconomical in actual production.

When such flake fillers are used in the resin blending, pelletizing, and injection molding steps, they may break easily and reduce electrical conductivity and reduce the EMI shielding effect of the molded article.

[0009]

SUMMARY OF THE INVENTION The present inventors have developed EMI
The disadvantages of conventional methods of manufacturing shields have been found and effective EM
We have invented a method for producing homogeneous metallized plastic pellets for forming I-shields.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing metallized plastic molded pellets, comprising the following steps. Metallized plastic sheeting by first sandwiching an electrically conductive metal foil between two plastic films; secondly, slicing the metallized laminated plastic sheet into a plurality of metallized plastic strips.
thirdly, a plurality of radially arranged metallized plastic strips are wetted with a thermoplastic resin matrix, joined and formed by pultrusion to form a metallized plastic rod; and finally a pultruded metallization. The rod is cut to obtain a homogeneous metallized plastic pellet for the production of an effective EMI shield.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing metallized plastic molded pellets of the present invention comprises the following steps, as shown in FIGS. The electrically conductive metal foil M is sandwiched between the conductive films F, and the laminated plastic sheet is metallized to form a metallized laminated plastic sheet S.
Forming a plurality of metallized plastic strips S1 by slicing the metallized laminated plastic sheet S with a slicing means 2; R
Wetted, bonded, pultrusion and cooling by pultrusion means 3 to form a metallized plastic rod B;
A plurality of metallized plastic pellets P are obtained by cutting the pultruded metallized bar B by the cutting means 4.

The sheet metallizing means 1 includes a metal foil spool 11 for unwinding a metal foil M such as an aluminum foil, and both surfaces of the metal foil M for uniformly covering both surfaces of the metal foil M with the coupling agent A. A pair of drug applicators 12 provided on the sides, a pair of plastic film spools 13 for unwinding two plastic films F, where each plastic film is joined with a coupling agent A to form a metallized laminated plastic sheet S. The film guide roller 14 in contact with the metal foil M to sandwich the metal foil M between the two plastic films F
A pair of hot presses that effectively pulls and rotationally compresses a laminated plastic sheet S with a further metallized metal foil M stably sandwiched between two more metal films F guided by A roller 15 is provided.

[0013] The thermoplastic film F can be selected from acryloniloryl-butadiene-styrene (ABS) copolymer, polyethylene (PE) and other suitable thermoplastic materials. Film F
May be the same as or compatible with the resin matrix R.

The electrically conductive metal foil M can be selected from aluminum, copper, silver, nickel and other electrically conductive metals. Coupling agent A is a titanium coupling agent, a zirconium-aluminum coupling agent,
For example, one can choose from zircoaluminate and other suitable coupling agents.

The slicing means 2 includes a sheet metalizing means 1
At least one slicing guide roller 21 for guiding the metallized laminated plastic sheet S from above to the feed opening 22 of the slicing means 2 and for discharging a plurality of metallized plastic strips S1 which are generally arranged linearly from the side. There is an outlet 23 formed downstream of the slicing means 2.

A plurality of plastic strips S1 from a feed (feed) roller 31 are branched and unfolded in the drawing forming means 3 so as to form a rectangular cross section, generally rectangular or Co. A stretching roller set 3 comprising at least four stretching rollers rotatably mounted on a frame (not shown) made in a quadrilateral shape
Feed roller 31 with a feed roller shaft 311 generally perpendicular to the plurality of metallized plastic strips S1 guided from the slicing means 2 to guide the plastic strips S1 in parallel towards the feed roller 2; To guide the plurality of plastic strips S1 having a rectangular shape Co (cross section) convergently and to form the first conical core member C1, grooves are radially formed in the first guide mold so as to specify the circular area A1. A plurality of first radial apertures 3 attached
First guide mold having a first conical core member C
In order to make the second conical core member C2 smaller than 1, a second guide mold 34 having a second radial aperture 341 for specifying a circular area A2 smaller than the area A1 of the first mold 33 is provided with a radial hole. A second guide mold 34 located in parallel after the first guide mold 33 to continuously converge the plurality of plastic strips S1 through the opened second radial apertures 341; both ends of the drawing forming means 35 The first and second guide dies 3 are provided by a pultrusion molding means 35 having an inlet die 351 and an outlet die 352 provided in the
Since the centers 330 and 340 of the third die 34 and the third die 34 are straight, and a plurality of slits (not shown) are formed radially in the entrance die 351, the second conical core member C <b> 2 from the second die 34 can be removed. Convergent and capable of forming the columnar core member C in the drawing forming means 35;
The cylindrical core member C is heated by the heater 353 provided in the pultrusion molding means 35 so as to be convergently guided by the inlet die 351 and discharged from the outlet die 352 to form the metallized plastic rod B. Moistening and melting the resin matrix R from the resin feed 36 provided in the pultrusion molding means 35 to keep the temperature of the pultrusion molding means constant; discharged from the central opening of the exit die 352 of the pultrusion molding means 35 Cooling means 37 for cooling and hardening the metallized plastic rod B; and a pair of tension rollers 38 located downstream of the cooling means 37 for extending and pulling the metallized plastic rod B in the direction of the cutting means 4. Is provided.

In the cutting means 4, a cutter 41 and an anvil roller 42 are provided on both sides of the metallized plastic bar B, and the bar B is cut and, as shown in FIG.
A plurality of metallized pellets of a predetermined length can be formed.

Each guide mold 33, 34 is made of Teflon or other suitable material.

The pultrusion molding means 35 is linear along the longitudinal axis X of the columnar core member C passing through the pultrusion molding means 35, and is further provided with first and second guide dies 33,3.
4 has a die center of an entrance die 351 and an exit die 352 that coincide with the centers 330 and 340, respectively.

The resin feed 36 includes a screw extruder 36
A hopper 361 surrounded by a preheater for charging and preheating the resin matrix R added to the cooling medium 37;
The cylindrical core member C, which is composed of a plurality of metallized plastic strips arranged in a radial direction so as to be discharged from the exit die 352, is wetted, bonded, and heated in the pultrusion molding means. Resin applicator 3 receiving resin from extruder 360 for transporting resin R1
63 are included.

The cooling means 37 includes a rubber pulling roller 3.
When pulled at 8, a plurality of spray nozzles for spraying cooling water onto the metallized plastic rod B are included.

[0022]

The preferred embodiment for carrying out the method of the present invention is described below.

Example 1 By using the method and the apparatus of the present invention as described above, a metallized plastic molded pellet was prepared by using titanium coupling agent, 1.2 phf (parts per one hundred part
s of resin)

[0024]

Embedded image

Neoalkoxy tri (dioctylpyrophosphato) titanate (Kearich Petrochemi)
cals Inc, USA (Lica38)) on both sides of an aluminum foil (20 μm thick);
The aluminum foil is rotationally compressed and sandwiched between two ABS plastic films (40 μm thick) to form a metallized plastic laminated sheet; such laminated sheet is made up of 16 metallized plastic strips, where each strip is The 16 strips are sliced into two guide molds 33, to form a core member having a radially arranged metallized strip in the core member, the width being 1 mm.
The core member is wetted and bonded with a molten ABS resin matrix at 220-230 ° C. in a pultrusion molding means, and the temperature of the pultrusion molding means is maintained at 230 ° C. in a pultrusion molding means. Plasticized rod; withdrawing such plastic rod through the central opening of a 3 mm diameter exit die 352;
The drawn plastic rod is cooled and hardened with 25 ° C. water sprayed from the nozzle of the above;
It is obtained by cutting into a cylindrical pellet P having a length of 5 mm according to 1. The metallized plastic strip substantially comprises a plurality of metal flakes Mf radially oriented about the longitudinal direction of each pellet P in a resin matrix.

The pellets thus obtained can be provided for molding electronic or computer products by a plastic molding method for shielding electromagnetic interference.

Example 2 The pellets obtained from Example 1 are provided to test samples by a plastic molding method for testing the electromagnetic shielding effect. A test was conducted on the shielding effect of the molded article of the present invention by the two-chamber test method of ASTM ES7-83, and as shown in FIG. SE) 0-1000 compared to a reference test by measuring
For a frequency (Fr) of MHz, the shielding effect between the two curves is obtained in decibels, as shown in FIG.

The various settings and test data are summarized as follows: 1. Distance between antenna and test sample: 5 mm 2. Spectrum analyzer: Frequency range: 30 MHz to 1.5 GHz BW = 300 KHz 3. Tracking generator: 0 dBm to 10 dBm; 30 MHz to 1.5 GHz Amplifier: 100 KHz to 1.3 GHz Gain 226 dB 5. TEM cell: DC-200 MHz 6. Dummy load: 50 ohm, 500W Close Field Probe Pmax = 0.5 W Rdc = 18.97 ohm.

As shown in FIG. 5, the unmetallized ABS plastic product has substantially no shielding effect.

In comparison, the metallized molded product of the present invention has a
It shows an average dB attenuation of about 30-35 dB at a frequency of 1000 MHz (FIG. 6).

Thus, the present invention can provide a shielding effect for metallized plastic products for electromagnetic interference.

The electrically conductive metal flakes Mf are firmly and radially provided on each pellet P, and such metal flakes are homogeneously dispersed in the resin matrix during the molding process without hardening or breaking. According to the present invention, a molded article can be provided with an excellent shielding effect.

As shown in FIG. 4, the length of each metal piece Mf, the density or the number of metal pieces oriented in the resin matrix R are changed based on actual requirements such as the commercial reliability of the EMI shielding effect. Or you can adjust.

The present invention can be modified without departing from the spirit or scope of the present invention.

[0035]

As described above, the pellet obtained according to the present invention substantially comprises a plurality of metal flakes radially oriented around the longitudinal direction of the pellet in the resin matrix. Is homogeneously dispersed in the resin matrix during the molding process without hardening or breaking, so that an excellent shielding effect can be given to the molded product.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing the method of the present invention.

FIG. 2 is a perspective view of a first guide mold of the present invention.

FIG. 3 is a perspective view of a second guide mold of the present invention.

FIG. 4 is a schematic view showing a pultruded pellet according to the present invention.

FIG. 5: ABS without metallization against frequency (Fr)
2 is a graph showing two curves that determine the shielding efficiency (SE) of a plastic material.

FIG. 6 is a graph showing two curves that determine the shielding efficiency (SE) of the shield of the present invention versus frequency (Fr).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sheet metallization means 2 ... Slicing means 3 ... Pultrusion molding means 4 ... Cutting means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29B 7/00-17/02

Claims (8)

(57) [Claims] 1. A method comprising: a. Sandwiching an electrically conductive metal foil between two thermoplastic films to form a metallized laminated plastic sheet by sheet metallization means; b. Slicing said metallized laminated plastic sheet by slicing means into a plurality of metallized plastic strips; c. In the pultrusion means, each of said metallized plastic strips is arranged radially, moistened with a thermoplastic resin matrix and joined to form a metallized plastic rod, and further said metallized plastic drawn from said pultrusion means. Cool rod; d. Cutting the metallized plastic rod by a cutting means to obtain a plurality of metallized plastic pellets, each pellet having a plurality of metal flakes arranged radially around its long axis; Of manufacturing plasticized plastic molded pellets. 2. A metal foil spool for unwinding a pre-wound metal foil, a pair of drug applicators provided on both sides of the metal foil to uniformly cover both sides of the metal foil. A pair of plastic film spools for unwinding two plastic films, wherein said metal foil is sandwiched between two plastic films and joined with a coupling agent to produce a metallized laminated plastic sheet, and such plastic film Is a pair of hot press rollers that are guided by a film guide roller adjacent to the metal foil and that tension and rotationally compress a laminated plastic sheet having a metal foil that is stably sandwiched and metallized between two plastic films. The method of claim 1, comprising: 3. The slicing means comprises: at least one slicing guide roller for guiding the metallized laminated plastic sheet from the sheet metallizing means to the entrance of the slicing means, in a generally line-wise arrangement when viewed from the side. 2. The method according to claim 1, including a discharge port formed downstream of the slicing means for discharging a plurality of metallized plastic strips. 4. The pultrusion means comprises a feed roller having a feed roller axis generally perpendicular to the plurality of metallized plastic strips derived from the slicing means, wherein the plurality of plastic strips from the feed roller are provided. Towards a stretching roller set consisting of at least four stretching rollers rotatably mounted in a frame, generally rectangular or parallelogram, so as to be branched and unfolded to produce a generally rectangular cross section. Guiding plastic strips in parallel; a first conical core member for concentrically guiding a plurality of rectangular plastic strips from the stretching roller set to define a circular area. A first guide mold having a plurality of first radial apertures formed by radially grooved one guide mold; a first conical core member A plurality of second radially perforated second guide molds having a second radial aperture that specifies a circular area smaller than the area of the first mold to produce a smaller second conical core member; A second guide mold positioned in parallel after the first guide mold to continuously converge a plurality of plastic strips through the aperture; a pultrusion molding means having an inlet die and an outlet die provided at both ends; Pultruding means for converging the second conical core member from the second mold since the centers of the first and second guide molds are straight and the entrance die has a plurality of radially formed slits. A heater provided on the pultrusion means for heating the die, which is convergently guided by the inlet die and discharged from the outlet die to form a metallized core member. Wet the columnar core member to form a plastic rod,
Melting the resin matrix from the resin feed provided in the pultrusion molding means and keeping the temperature of the pultrusion molding means constant; metallized plastic when released from the central opening of the exit die of the pultrusion molding means 2. The method according to claim 1, comprising cooling means for cooling and hardening the rod; and a pair of tension rollers located downstream of the cooling means for extending and pulling the metallized plastic rod in the direction of the cutting means. 5. The cutting means comprises: a cutter, an anvil provided rotatably provided on both sides of the metallized plastic rod for cutting the plastic rod into a plurality of metallized pellets each pellet having a predetermined length. The method of claim 1, comprising a roller. 6. The pultrusion molding means is linear with the longitudinal axis of the cylindrical core member passing through the pultrusion molding means, and further has an entrance die and an exit die which coincide with respective centers of the first and second guide dies. The method of claim 4 having a die center. 7. The resin feeder according to claim 1, wherein the resin extruder is filled with a resin matrix in a screw extruder, and a hopper provided with a pre-heater around the extruder for receiving and preheating the resin matrix. The resin is heated in the pultrusion molding means,
As it is melted, the cylindrical core member comprising a plurality of radially arranged metallized plastic strips is wetted and bonded to form a metallized plastic rod exiting the exit die, wherein the metallized plastic rod is cooled by the cooling means. By cooling,
5. The method of claim 4, comprising curing. 8. The method according to claim 7, wherein said cooling means includes a plurality of spray nozzles for spraying cooling water onto the metallized plastic rod.