KR20030014479A - The method for fabricating a pad as an absorber of broadband radio waves - Google Patents

Abstract

PURPOSE: A method for fabricating a sheet for a broadband electromagnetic wave absorber is provided to improve flexibility and elasticity by fabricating sendust of a metal alloy as a flat shape and blending the flat shape of sendust with polyolefin resin. CONSTITUTION: Polyolefin resin of 100 weight percent is processed to a state of sheet by a using kneader or a banbury mixer or a roll. Flat sendust of 300 to 1000 weight percent is used as a metal alloy. Aluminium hydroxide or magnesium hydroxide of 60 to 150 weight percent is used as an inorganic flame retardant. Phosphor 0.5 to 5 weight percent is used as a flame retardant. A non-woven fabric or a rubber pad is formed by blending the flat sendust of 300 to 1000 weight, the aluminium hydroxide or magnesium hydroxide of 60 to 150 weight percent, and the phosphor of 0.5 to 5 weight percent. A multi-layer is formed by laminating the non-woven fabrics or the rubber pads on an upper portion and a lower portion of the sheet.

Description

The method for fabricating a pad as an absorber of broadband radio waves

The present invention relates to a nonwoven fabric or pad for electromagnetic wave absorbers that not only has high absorption efficiency in the broadband frequency region, but also has excellent flexibility and stretchability. More specifically, the present invention relates to a nonwoven fabric or rubber pad containing a flat metal sander, which is a metal alloy. The present invention relates to a method for producing a pad for electromagnetic wave absorbers having excellent flexibility and stretchability by forming a layer or by forming a nonwoven fabric or rubber pad containing a flat sandblasted magnetic material or a metal layer into a multi-layered layer, and branding it with a functional polar polyolefin resin.

The development of scientific civilization is rapidly increasing the use of electrical, electronic and communication-related devices, and these civilizations provide a lot of convenience to human life, but there is also a downside. For example, the radiation of electromagnetic waves in the radio frequency domain generates noise due to radio wave interference between transmitting and receiving equipment, and reduces the efficiency and lifespan of internal electronic products by high voltage generators of automobiles, and between electronic equipment. And mutual disturbances. Therefore, serious problems have been raised in relation to the disturbance of electromagnetic waves, and the development of electromagnetic wave absorbers has become an important task.

The principle of the electromagnetic wave absorber is to use magnetic losses (imaginary part of complex permeability) for the purpose of absorption or reflection suppression of radio waves, and to absorb electromagnetic waves and convert them into heat so that reflected waves do not occur. In particular, ferrite is recognized as an absorber that efficiently absorbs microwaves by using the loss caused by the magnetic resonance between the magnetic field component of the electromagnetic wave and the atomic spin system of the ferrite.

It is desirable to absorb 99% electric propagation energy at the absorption rate of ≧ 20 to 30 dB and the absorption rate as a technical problem of the electromagnetic wave absorbing material which avoids the detection of radio waves in an invisible airplane. Moreover, since the direction of the radar wave is not determined, it must have a characteristic that it is sufficient to be incident on a broadband and any blind spot.

The characteristics of the electromagnetic wave absorber are to be absorbed at a thickness of 0.1 mm in the VHF-TV, and to develop an absorber having a large attenuation, light weight and thinness at a wideband frequency.

There are three kinds of material constants that cause electromagnetic wave loss: conductivity σ, dielectric loss ε ″ and magnetic loss μ ″. The loss due to the conductivity σ is called the conductivity loss or ohm loss, and corresponds to the resistance caused by the free charge in the material moving in an electric field and in phase. Dielectric loss ε ″ is caused by a late change in the dipole's temporal change that leads to heredity, caused by a bond electron bound to the atom, not a free electron. Magnetic loss μ ″ occurs because the spin motion that causes magnetism follows the external magnetic field change.

Conventionally, the conductive loss material is widely used in the radio wave absorber is carbon (ca-rbon), the magnetic material is a metal magnetic material and an oxide magnetic material, the dielectric material is using a barium titanate (BaTiO ₃ ) or This setting uses a mixture.

However, absorbers using only these materials are not only difficult to process but also result in expensive losses due to waste of external energy during processing, and they are easily broken or worn due to lack of flexibility and elongation as absorbent materials. There is difficulty.

In addition, the above-mentioned materials are used in various forms such as absorbent materials such as paints and sheets by branding the materials with functional polymers.However, in the case of blends using functional polymers, there is a problem of storing for a long time with respect to the dispersibility problem as the absorber material, Difficulties in industrialization and absorption efficiency tend to be lowered due to the difference in specific gravity. In addition, when a large amount of absorbent material is added to increase the absorption efficiency, it is difficult to industrialize because it has a big problem such as easily broken or cracked and worn due to poor flexibility and elongation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pad for electromagnetic wave absorbers excellent in flexibility and elongation by producing a metal alloy sendust in a planar shape and blending with a polar polyolefin-based resin.

In addition, by using a pad containing a flat sender as a multilayer or by manufacturing a multi-layer pad consisting of a flat sender, a magnetic material, and one selected from a metal, the pad is composed of upper, middle, and lower layers. In addition, the present invention provides a material for absorbing electromagnetic waves having high absorption efficiency in a wide band.

1 is a multi-layered structure of a sendust-sendust-sendust layer as an embodiment of the present invention.

Cross section of pad for electromagnetic wave absorber.

FIG. 2 is a view illustrating another embodiment of the sender (or magnetic body) -sender dust-magnetic layer.

Sectional drawing of the pad for electromagnetic wave absorbers which has a multilayered structure.

3 is a cross-sectional view of a pad for an electromagnetic wave absorber having a multilayer structure of a sendust (or magnetic) -magnetic- sender (or magnetic) layer as another embodiment of the present invention.

4 is a cross-sectional view of a pad for an electromagnetic wave absorber having a multilayer structure of a sendust (or magnetic material) -magnetic material-sender (or magnetic material) layer as another embodiment of the present invention.

5 is another embodiment of the present invention sendend (or magnetic material)-metal-sendust

Sectional drawing of the pad for electromagnetic wave absorbers which has a multilayer structure of a (or magnetic substance) layer.

6 is a multi-layer structure of a sendust-sendust-sendust layer according to an embodiment of the present invention.

It is a graph which shows the reflection coefficient of the pad for electromagnetic wave absorbers which it has.

FIG. 7 is a graph showing reflection coefficients of pads for electromagnetic wave absorbers having a multilayer structure of a sendust-sendust-ferrite layer in an embodiment of the present invention; FIG.

8 shows a multilayer structure of sendust-ferrite-sendust-ferrite in an embodiment of the present invention.

Graph showing reflection coefficient of pad for electromagnetic wave absorber.

9 is an embodiment according to the present invention, having a multilayer structure of sendust-ferrite-silver layers.

It is a graph which shows the reflection coefficient of the pad for electromagnetic wave absorbers.

The present invention relates to a method for manufacturing a pad for electromagnetic wave absorbers having not only high absorption efficiency in the broadband frequency range but also flexibility and stretchability, by using a planar sendust and a polar polyolefin resin newly prepared according to the present invention. By manufacturing a non-woven fabric or rubber pad for a multi-layer electromagnetic wave absorber having flexibility and stretchability, it is possible to produce a material for the electromagnetic wave absorber having a high absorption efficiency in a wide band while supplementing the disadvantages of the conventional commercialized electromagnetic wave absorber material.

Carbon, magnetic materials, metal magnetic materials, oxide magnetic materials, and dielectric materials widely used in existing electromagnetic wave absorbers. In the case of the absorber material using only these materials, not only the processing is difficult but also a high price loss due to external energy waste during processing, and there is a great difficulty in industrialization, such as being easily broken or worn due to lack of flexibility and elongation.

In addition, a method of blending the material with a functional polyolefin-based resin and using it as an absorbent material in various forms such as a paint and a sheet is known. However, in the case of a blend through a functional polymer, the problem and the specific gravity of the storage for a long time due to the dispersibility of the absorber material In addition to the difficulties of industrialization due to the difference, there was a defect that the absorption efficiency is low. Therefore, when a large amount of absorbent material is added to increase the absorption efficiency, there is a problem in that it is difficult to industrialize applications because it has a problem of being easily broken, cracked and worn down due to its flexibility and elongation.

In order to solve the above problems, the present invention provides a rubber pad for electromagnetic wave absorber having not only a high shielding efficiency in the broadband range but also forming a sender in a planar shape and blending it with a newly designed polar polyolefin resin to have flexibility and stretchability. To manufacture.

The nonwoven fabric or rubber pad for the electromagnetic wave absorber having flexibility and stretchability manufactured according to the present invention has long-term storage problem due to the dispersibility of the polymer and the absorber, which is a problem of the existing electromagnetic wave absorber, and the difficulty of industrialization and absorption efficiency due to the specific gravity difference. When a large amount of the material of the absorber is added for the increase, it does not have flexibility and elongation, so that problems such as being easily broken, cracked and worn can be completely solved.

In addition, while the conventional commercialized electromagnetic wave absorber shows low absorption efficiency in a narrow region, the nonwoven fabric or rubber pad for the electromagnetic wave absorber having the flexibility and stretchability produced in the present invention is high electromagnetic wave in the broadband (frequency range below 5GHz) Absorption efficiency (reflection coefficient; -40 dB) was shown.

Looking at the electromagnetic wave absorption efficiency according to the structural change of the pad for the electromagnetic wave absorber having flexibility and stretchability produced in accordance with the present invention, the brand of the planar sendust prepared by the present invention and the polar polyolefin resin newly prepared by the present invention The absorption efficiency from 3MHz to 6GHz frequency range of pad, which is a non-woven fabric or rubber pad layer of Sendust formed by upper, middle and lower layers, is -20dB reflection coefficient and wide range of 3MHz to 4GHz frequency range. It can be seen that the absorption efficiency at.

In addition, the nonwoven fabric or rubber pad layer of the sender through the blend of the planar sendust and the newly prepared polar polyolefin resin according to the present invention is made into the upper layer and the lower layer, and the silver is a metal and the polar polyolefin resin newly prepared by the present invention. The absorption efficiency from 3MHz to 6GHz frequency band of the pad, which is an electromagnetic wave absorber consisting of a middle layer of silver rubber pad layer through the blend, shows a reflection coefficient of 12dB and absorption efficiency in a wide range from 3MHz to 4GHz frequency range. Absorption efficiency of the pad, which is an electromagnetic wave absorber having a nonwoven fabric or a rubber pad layer as an upper layer and a middle layer, and a rubber pad layer with a silver as a metal through the blend of silver and a newly prepared polar polyolefin resin according to the present invention It shows a reflection coefficient of -22dB and absorption efficiency over a wide range from 3MHz to 4GHz. Able to know.

Absorption of a rubber pad, which is an electromagnetic wave absorber composed of a middle layer, of a nonwoven fabric or rubber pad layer of planar sendust as an upper layer and a lower layer, and a ferrite pad layer formed of a magnetic layer and a blend of a polar polyolefin-based resin newly prepared according to the present invention. In terms of the efficiency, it can be seen that the reflection coefficient of -24dB and the absorption efficiency in the wide range of 4.5GHz frequency range from 3MHz are shown, and the upper and middle layers of the rubber pad layer of planar nonwoven fabric or sendust are ferrite and bone The absorption efficiency of the rubber pad, which is an electromagnetic wave absorber composed of a ferrite pad layer through a blend of a newly prepared polar polyolefin resin, is -25 dB reflection coefficient and absorption efficiency in a wide range of 4.5 GHz at 3 MHz. It can be seen that.

According to the absorption efficiency of the pad, which is an electromagnetic wave absorber having the nonwoven fabric or rubber pad layer of the planar sender fabric prepared according to the present invention as the upper layer and the third layer and the pad layer of the ferrite as the magnetic layer, the second layer and the lower layer, In the case of the pad, which is an electromagnetic wave absorber having the upper pad layer of the sender as the middle layer and the pad layer of the ferrite as the magnetic layer, and the lower pad layer of the silver as the metal, the absorption efficiency is -40 dB in the reflection coefficient and the frequency range of 4.5 GHz at 3 MHz. It shows the absorption efficiency in a wide range of fields, which can be used not only for industrialization but also for military use.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1

In the composition of the present invention, 100 parts by weight of a functional polar polyolefin resin is first processed into a sheet form in a knead-er, a banbury mixer or a roll, and 300 to 1000 parts by weight of a planar sender which is a metal alloy. 60 to 150 parts by weight of aluminum hydroxide (or magnesium hydroxide) as an inorganic flame retardant, and 0.5 to 5 parts by weight of an additive as a flame retardant, are compounded in a kneader, a Benbury mixer, a busneder or an open roll mill, or a Henschel mixer, In the ribbon blender, V blender, etc., the mixture is first mixed sufficiently, and then compounded in a kneader, a Benbury mixer, a bus kneader, a single extruder, a twin extruder, etc. The compound may be in the form of a continuous ribbon or pellet. . The method of laminating the compound into sheets typically includes a carpenter method and a T-die extrusion method. In the present invention, in order to orient and laminate metal flakes in a direction parallel to the sheet, the die is extruded after calendering, as well as two rolls. It is preferable to perform the above calendaring. The calender should be at least 3 rolls of 12-20 inches, preferably at least 4 rolls.

In the above-described method, a rubber pad for electromagnetic wave absorber having flexibility and stretchability is produced.

The method for producing the functional polar polyolefin resin used herein is as follows.

20 to 80% by weight of polyolefin resin, 20 to 100% by weight of a monomer having a carboxyl group or a derivative thereof and a copolymer of ethylene, and 5 to 80% by weight of a polyolefin resin graft-modified with an unsaturated carboxylic acid or a derivative thereof. The above resins are resins alone or blended and mixed with 100 parts by weight of the resin.

The ethylene copolymer used in the present invention is a copolymer of ethylene and a monomer having a carboxyl group or a derivative thereof. For example, ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene methyl acryl Elate (EMA), ethylene butyl acrylate (EBA), ethylene methyl methacrylate (EMMA), ethylene acrylic acid (EAA), or ethylene methacrylic acid copolymer (EMAA) may be used alone or in combination, preferably Ethylene ethyl acrylate, ethylene methyl acrylate or ethylene vinyl acetate.

The content of the carboxyl group of the ethylene copolymer is preferably in the range of 5 to 50% by weight. If the content of the carboxyl group is less than 5% by weight, the flexibility is poor when mixed with the polyolefin resin and the metal flake, It is difficult to fill and the mechanical strength is lowered. If the content of the carboxyl group exceeds 50% by weight, the compatibility with other polyolefin resins is reduced, the sheet appearance and physical properties are deteriorated, and the adhesiveness is increased, resulting in poor workability of the calendar. .

Post reactor modification (grafting) of various types of reactive monomers to the polyolefin backbone by a specific method of graft modification by reactive monomers

As a modification method, special functions (adhesiveness, reactivity, polarity) are given while maintaining the properties of the polyolefin resin, which is a base resin. The graft-modified polyolefin resin used in the present invention is reacted and extruded by adding 0.5 to 4% by weight of an unsaturated carboxylic acid or a derivative thereof to a polyolefin-based resin in the presence of an organic peroxide. It is a mixture with.

The polyolefin resin may be a copolymer of ethylene and α-olefin, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, vinyl acetate or a copolymer of ethylene and octane-1, and the like. Acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid or anhydrides thereof may be used as the derivative, and maleic anhydride is particularly preferable.

In the present invention, the flakes are grafted to the polymer resin by strongly chemically bonding the -OH group attached to the surface of the metal flakes (such as sender) and the anhydride of unsaturated carboxylic acid.

The manufacturing method of the planar sendust used above is as follows.

A metal softener, a reaction promoter, and a dispersant were added to the aluminum-iron-silicon mixture [mixed at 5 to 15 parts by weight versus 75 to 90 parts by weight to 10 to 20 parts by weight], and then mixed using a 3 roll mill and melted. The sender made of the melt-synthesized aluminum-iron-silicon mixture had a specific gravity of 2 and a particle size of about 5 micro.

After the above-mentioned raw dust was milled and washed with water, a metal antioxidant and a dispersant were added. The sender was added to the metal antioxidant and dispersant second milling, washed again with water, filtered, and then dried and ground to prepare a flat sender.

The planar sendust had a specific gravity of 1 or less and a particle size of about 20 microns.

Example 2

Ferrite, nickel, zinc, manganese mixed with one or two or more kinds of ferrite, nickel, zinc, and manganese in a functional polar polyolefin resin prepared in the same manner as the pad manufacturing method of Example 1 from the group selected from the group selected from silver, iron and iron , Iron-nickel mixture [model name; 120 HF (55.58 to 44.42, 54.25 to 45.75 weight ratio), HF120 (54.29 to 45.71 weight ratio), 120 MMP (20.70 to 79.93 weight ratio), MMP120 (29.88 to 70.12 weight ratio)], Iron-silicon mixture

[Model name: 80FS120 (92.37 to 7.63 weight ratio) 120FS (93.29 to 6.71 weight ratio)], aluminum

Iron-silicon mixture [Model name: 200SDST325 (6.59 to 81.34 to 12.06 weight ratio), 325SDST

(6.99 to 81.77 to 11.24 weight ratio)] from 300 to 1000 parts by weight of one species selected from the group selected from aluminum hydroxide (or magnesium hydroxide) 60 to 150 parts by weight as an inorganic flame retardant, 0.5 to 5 parts by weight as a flame retardant aid Compounding in kneader, bentbury mixer, booth kneader or open roll mill or mixing the mixture in Henschel mixer, ribbon blender, V blender, etc. There is a method. The compound may be in the form of a continuous ribbon or pellet. The method of laminating the compound into a sheet typically includes a calender method and a Ti-die extrusion method. In the present invention, in order to orient and laminate the metal flakes in a direction parallel to the sheet, two or more rolls may be used after the die-casting as well as the calender. It is characterized by calendaring. The calender should be at least three rolls of 12-20 inches and preferably at least four rolls. In the above method, a rubber pad for electromagnetic wave absorber having flexibility and stretchability can be produced.

Example 3

Pads containing a planar sendust, which is a metal alloy prepared in Example 1, and a functional polyolefin-based resin, are used as the upper and middle layers, and the magnetic materials (ferrite, nickel, zinc, manganese) prepared in Example 2 are one to two or more. A multilayer rubber pad for electromagnetic wave absorbers having flexibility and stretchability was prepared in the same manner as in Example 1 using a rubber pad including one of the mixed ferrite mixtures selected from the group selected) as a lower layer.

Example 4

A nonwoven fabric for an electromagnetic wave absorber was manufactured by branding with a planar sendust, which is a metal alloy prepared in Example 1, and a functional polyolefin resin, and using the nonwoven fabric as an upper and a lower layer, and using the magnetic material prepared in Example 2 (ferrite, nickel, zinc). , A multi-layered rubber for electromagnetic wave absorber having flexibility and stretchability in the same manner as in Example 1 with a rubber pad containing a manganese one selected from the group selected from the group consisting of one or two or more ferrite mixtures) The pad was prepared

Example 5

A nonwoven fabric for absorbing electromagnetic waves was produced by branding with the planar sender and functional polyolefin resin prepared in Example 1, using the nonwoven fabric as a middle layer, and the magnetic material prepared in Example 2 (ferrite, nickel, zinc, manganese 1). Multi-layered rubber pad for electromagnetic wave absorber having flexibility and stretchability in the same manner as in Example 1, with the rubber pad including one or more species selected from the group selected from the group consisting of two or more species of ferrite mixture Prepared.

Example 6

A nonwoven fabric for absorbing electromagnetic waves was made by branding with the planar sender and functional polyolefin resin prepared in Example 1, and the magnetic material (ferrite, nickel, zinc) prepared in Example 2 using a rubber pad containing the nonwoven fabric as an upper layer. , A manganese rubber pad containing one or two or more selected from the group selected from the ferrite mixture mixed two or more layers, the metal prepared in Example 2 (silver, iron, iron-nickel mixture, iron-silicon mixture In the same manner as in Example 1, a rubber pad containing a rubber pad containing one kind from the group selected from the group consisting of aluminum-iron-silicon mixtures was prepared.

Example 7

Rubber pads containing the magnetic material prepared in Example 2 (ferrite, nickel, zinc, manganese one to two or more selected from the group selected from the group selected from the group) is made of upper and middle layers, and in Example 2 Flexibility and lead in the same manner as in Example 1 with a rubber pad containing a metal (silver, iron, iron-nickel mixture, iron-silicon mixture, aluminum-iron-silicon mixture selected from the group selected) The multilayer rubber pad for electromagnetic wave absorber which has the novel was manufactured.

Example 8

Rubber pads containing the planar sender and functional polyolefin resins prepared in Example 1 were used as upper and middle layers, and the metals prepared in Example 2 (silver, iron, iron-nickel mixture, iron-silicon mixture, aluminum- 1) from the group selected from the group selected from the iron-silicon mixture, the rubber pad containing a metal pad prepared in Example 2 as a lower layer having flexibility and stretchability in the same manner as in Example 1 A multilayer rubber pad was prepared for the electromagnetic wave absorber.

As described above, the present invention relates to the manufacture of a nonwoven fabric or rubber pad for electromagnetic wave absorbers having flexibility and stretchability by manufacturing the sender according to the present invention in a planar shape and blending with a polymer. Multi-layer pads are prepared by using as a top, middle and bottom layer of nonwoven fabric or rubber pad including flat sender, magnetic material, metal, etc. as well as excellent flexibility and elongation as well as high absorption efficiency in broadband. By providing the material, it has excellent flexibility, high working environment, economical efficiency, mechanical properties and uniform dispersion compared to the existing electromagnetic wave absorber material, so it has excellent absorption efficiency of electromagnetic wave. The nonwoven fabric or rubber pad for the electromagnetic wave absorber having flexibility and stretchability can be widely used as an electromagnetic wave absorber material for electronic semiconductors, information and communication devices, mobile phones and mobile communication device cases.

Claims (9)

100 parts by weight of a functional polar polyolefin-based resin is processed in a mixer or roll into a sheet, and a nonwoven fabric or rubber branded with 300 to 1000 parts by weight of planar sendust, which is a metal or metal alloy, and / or 300 to 1000 parts by weight of a magnetic material and a metal mixture. A method for producing a pad for broadband electromagnetic wave absorbers excellent in flexibility and stretchability, characterized by laminating pads up and down to form multiple layers. The pad of claim 1, wherein the upper layer and the middle layer are formed of a nonwoven fabric or rubber pad containing planar sendust, and the lower layer is formed of a nonwoven fabric or rubber pad containing a magnetic material. Manufacturing method. The broadband electromagnetic wave absorber having excellent flexibility and stretchability according to claim 1, wherein an upper layer and a lower layer are formed of a nonwoven fabric or rubber pad containing planar sendust, and a middle layer is formed of a nonwoven fabric or rubber pad containing a magnetic material. Method for producing a pad. The method of claim 1, wherein the upper layer and the lower layer are formed of a nonwoven fabric or rubber pad containing a magnetic substance, and the middle layer is formed of a nonwoven fabric or rubber pad containing a flat sender. Method for producing a pad. The method of claim 1, wherein the upper layer is formed of a nonwoven fabric or rubber pad containing a flat sender, the middle layer is composed of a nonwoven fabric or rubber pad containing a magnetic material, the lower layer is formed of a nonwoven fabric or rubber pad containing a metal The manufacturing method of the pad for broadband electromagnetic wave absorbers excellent in flexibility and stretchability. The method of claim 1, wherein the upper layer and the middle layer are formed of a nonwoven fabric or rubber pad containing a magnetic material, and the lower layer is formed of a nonwoven fabric or rubber pad containing a metal. Manufacturing method. The pad of claim 1, wherein the upper layer and the middle layer are formed of a nonwoven fabric or rubber pad containing planar sendust, and the lower layer is formed of a nonwoven fabric or rubber pad containing a metal. Manufacturing method. The method according to any one of claims 1 to 7, wherein the magnetic material is selected from a ferrite mixture mixed with one or two or more of ferrite, nickel, zinc and manganese for flexible and stretchable broadband electromagnetic wave absorber Method for producing a pad. The method of claim 1 or 5 to 7, wherein the metal or metal alloy is flexible and extensible, characterized in that one selected from silver, iron, iron-nickel mixture, iron-silicon mixture, aluminum-iron-silicon mixture The manufacturing method of this outstanding pad for wideband electromagnetic wave absorbers.