KR100679486B1 - Manufacturing method of electromagnetic absorber - Google Patents

Abstract

A method for preparing an electromagnetic waves-absorbing body is provided to prevent the malfunction of articles due to radiation noise and to block electromagnetic waves which are harmful to the human. The method comprises (S1) preparing the magnetic material powder of a mixture consisting of one or at least two materials selected from ferrite, permalloy, sendust, conductive carbon black and graphite; (S2) mixing 10-50 parts by weight of the magnetic material powder with 100 parts by weight of a polymer consisting of one or at least two materials selected from synthetic rubber, elastomer, polyurethane and polyol which are placed at a temperature of 40-70 deg.C for 2hour or more; (S3) mixing 5-10 parts by weight of a foaming agent (based on 100 parts by weight of the polymer) with a mixture of the polymer and magnetic material powder; (S4) mixing 5-80 parts by weight of a curing agent (based on 100 parts by weight of the polymer) which are placed at a temperature of 40-60 deg.C for 1hour or more, with the mixture of (S3); and (S5) after foaming the mixture of (S4), being placed at 50-80 deg.C for 2 hour or more.

Description

 Manufacturing method of electromagnetic absorber

1 is a flowchart illustrating a method of manufacturing an electromagnetic wave absorber according to the present invention.

FIG. 2 is a flowchart for explaining the step (S1) of FIG. 1 in detail.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electromagnetic wave absorber, and more particularly, a material obtained by mixing a polymer material such as polyol and a magnetic material such as ferrite powder and then foaming and curing the same absorbs electromagnetic waves, in particular low-frequency electromagnetic waves. The present invention relates to a method for manufacturing an electromagnetic wave absorber capable of absorbing radiation noise that may be generated in a device.

At present, a lot of electronic products, such as electromagnetic waves are generated, the electromagnetic wave is harmful to the human body has been developed a lot of methods to block the electromagnetic waves. Among them, Japanese Patent Laid-Open No. 11-307361 introduces a technique in which a shielding performance is improved by applying a film containing metal, not a ferromagnetic material of a thick film of 2 µm or more, on the surface thereof to improve conductivity at the joint. This method prevents the penetration and emission of electromagnetic waves by using a material with high conductivity, and uses non-ferromagnetic materials such as zinc, gold, silver, and copper among metals.

On the other hand, European Patent No. 0,186,145 is a composite material of a metal-based and ceramic made of lead + zinc + niobium, lead + zinc + tantalum or lead + zinc + tungsten in the high frequency region (1 MHz-1 GHz) to increase the frequency shielding effect. Here's how. However, this method is difficult due to the mixing of metals and ceramics, and has a weak shielding performance. In addition, European Patent No. 0,107,863 relates to electromagnetic shielding by mixing a polymer material and a metal material such as palladium or nickel, and is known to have good electromagnetic shielding and absorption according to a frequency domain. There is a big difference in the shielding effect according to the particle size of the metal, there is a disadvantage in that the uniform distribution of the metal components difficult to shielding performance is reduced.

In addition, Japanese Patent No. 61-163231 introduces a method of shielding electromagnetic waves with a material produced by mixing a predetermined amount of elements such as copper, manganese, nickel, and iron with aluminum. However, this method has disadvantages in that the shielding ability is localized, the performance is weak, and the effect is low, especially in the low frequency (KHz region). In addition, Japanese Patent No. 2000-36419 improves shielding ability by making a steel sheet, but its manufacturing method is complicated and expensive. On the other hand, Japanese Patent Laid-Open No. 7-86788 discloses that the electromagnetic shielding performance is improved by modifying the surface of the steel sheet using a laser beam. However, this method has a disadvantage in that it is practically difficult to control the laser in a certain direction and thickness.

As described above, the development of a material aimed at shielding or absorbing electromagnetic waves has been steadily made in the related art, and the present invention has been devised under this technical background.

The technical problem to be achieved by the present invention on the basis of the above-mentioned conventional problems is to develop a material capable of effectively absorbing the electromagnetic wave in the low frequency band, and to provide a method for manufacturing an electromagnetic wave absorber that can achieve such a technical problem. There is an object of the present invention.

In order to achieve the technical problem to be achieved by the present invention, the composition for producing an electromagnetic wave absorber according to the present invention comprises a polymer material, electromagnetic shielding and absorber magnetic material powder, a curing agent and a foaming agent, the polymer material is synthetic rubber, elastomer, It is composed of one or a mixture of two or more of any one selected from polyurethane and polyol, the magnetic material powder is 10 to 50 parts by weight based on 100 parts by weight of the polymer material; 5 to 80 parts by weight of the curing agent; And 5 to 10 parts by weight of the blowing agent.

In relation to the magnetic material powder content, the electromagnetic wave absorption performance is lowered when the lower limit of the numerical limit is lowered, and when the upper limit of the numerical limit is exceeded, a product cannot be produced as a foam, which is not preferable. Can not do it. In addition, with respect to the content of the curing agent, when the lower limit of the numerical limit is less than the polymer material is not cured and exist in the liquid form, when the upper limit of the numerical limit is exceeded the product itself becomes too hard Cutting is difficult, which is undesirable. On the other hand, with respect to the foam content, when the lower limit of the numerical limit is not reached, the open cell of the polymer material itself is not formed, and the gap between the cells is so wide that the foam form is depressed and the product itself is too large. It is hardly hardened, making cutting work impossible, and ultimately, the absorption of electromagnetic waves is not effective, which is undesirable.

In this case, the magnetic material powder may be any one selected from ferrite powder, permalloy powder, sand dust, conductive carbon black, and graphite, or a mixture of two or more thereof, and the magnetic material powder may more preferably have a particle diameter of 100 mesh or more. .

In order to achieve the technical problem to be achieved by the present invention, the electromagnetic wave absorber manufacturing method according to the present invention, (S1) ferrite powder, permalloy powder, sand dust, conductive carbon black and graphite, any one selected from a single substance or a mixture of two or more magnetic Preparing a material powder; (S2) The magnetic material powder 10 with respect to 100 parts by weight of the polymer material which is a single substance or a mixture of two or more selected from synthetic rubber, elastomer, polyurethane, and polyol, which has been left for 2 hours or more at a temperature of 40 to 70 ° C. Mixing the polymer material with the magnetic material powder in an amount of 50 parts by weight, so as to maintain the temperature of the polymer material during the mixing process; (S3) mixing 5 to 10 parts by weight of the blowing agent with respect to 100 parts by weight of the polymer material in a mixture of the polymer material and the magnetic material powder; (S4) mixing the blowing agent having a quantity of 5 to 80 parts by weight based on 100 parts by weight of the polymer material in the mixture into which the blowing agent is added, and having undergone at least 1 hour at 40 to 60 ° C .; And (S5) after foaming the resultant of the step, the step of leaving for 2 hours at 50 to 80 ℃. At this time, the preparation of the magnetic material powder of the (S1) step, (S11) firing the magnetic material powder; (S12) step of slurrying by adding distilled water to the resultant; (S13) crushing the resultant; And (S14) after drying the resultant, selecting a magnetic material powder having a predetermined particle size condition. On the other hand, it is preferable to use the magnetic material powder having a particle size of 100 mesh or more.

If the temperature condition of the step (S2) is not met, it is not preferable because the mixed dispersion of the polymer material and the magnetic powder material is not sufficient. If the temperature condition of the step (S4) is not met, the curing agent is mixed. Because it is not effectively dispersed in, special care is required to maintain the temperature conditions.

 Hereinafter, the present invention will be described in detail with reference to examples, and detailed description will be made with reference to the accompanying drawings in order to help understanding of the present invention. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Example  One

Among magnetic material powders composed of hard ferrite (rare earth metal), soft ferrite powder, permalloy (MPP, 50Fe-50Ni), sandust (Fe-Al-Si), conductive carbon black, and graphite The selected nickel-zinc (Ni-Zn) ferrite powder was filled in an Attrition Mill with distilled water and wet milled for 5 to 12 hours. Thereafter, the wet milled slurry was completely dried at 105 ° C. The dried material is filled with a mesh of 60 mesh or more (250 μm or less), and then compared to a polyol using weight prepared from a polymer material group consisting of synthetic rubber, elastomer, elastomer, and polyol. After 30% by weight, the mixture was allowed to mix completely with the polyol. 8% by weight of blowing agent relative to the weight of the polyol used in the mixture was added and mixed, and then 65% by weight of curing agent was added to the mixture, followed by mixing, followed by a foaming process. after. The foamed product was placed in a drying furnace, and then dried for 2 to 6 hours at a temperature range of 50 to 80 ° C., and then the foamed product was sliced to a thickness of 4 mm. The electromagnetic wave absorber product manufactured according to the above is closely attached to the bottom of the general-purpose power supply (power supply) PCB, and then measured by a spectrum analyzer using a near field probe, and the low frequency band is between 20 MHz and 300 MHz. Attenuation effect of more than 5dB was obtained.

Example  2

Nickel-zinc (Ni-Zn) ferrite powder and metal powder for magnetic materials of more than 100 mesh (less than 150㎛), that is, magnetic material by selecting MPP, permalloy (50Fe-50Ni) and sand dust (Fe-Al-Si) A powder mixture was prepared, but an electromagnetic wave absorber was prepared by mixing a nickel-zinc (Ni-Zn) ferrite powder: metal powder with a mixing weight ratio of 7: 3 in a polyol as a polymer material. At this time, other components and contents other than the magnetic material powder mixture and the process progress conditions were performed under the same conditions as in Example 1. As a result, the same results were obtained by measuring in the same manner as in Example 1 described above.

Example  3

Ni-Zn ferrite powder, metal powder and conductive carbon black or graphite (magnetic) to prepare a magnetic material powder mixture, nickel-zinc (Ni-Zn) ferrite powder: metal powder: conductive carbon black Alternatively, an electromagnetic wave absorber was prepared by mixing a polyol, which is a polymer material, in a ratio of 7: 2: 1 by weight of graphite. At this time, other components and contents other than the magnetic material powder mixture and the process progress conditions were performed under the same conditions as in Example 1. As a result, the same results were obtained by measuring in the same manner as in Example 1 described above.

Example  4

Ni-Zn ferrite powder, metal powder and conductive carbon black or graphite is selected to prepare a magnetic material powder mixture, but nickel-zinc (Ni-Zn) ferrite powder: metal powder: conductive carbon black Alternatively, the electromagnetic wave absorber was prepared by mixing a polyol, which is a polymer material, in a ratio of 2: 7: 1 by weight of graphite. At this time, other components and contents other than the magnetic material powder mixture and the process progress conditions were performed under the same conditions as in Example 1. As a result, the electromagnetic wave was attenuated by about 5dB in the low frequency band, 20 ~ 300MHz band, it was confirmed that the electromagnetic wave is attenuated by 6 to 8dB when the thickness of the absorber is 8mm.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail the manufacturing method of the electromagnetic wave absorber according to the present invention.

1 is a flowchart illustrating a method of manufacturing an electromagnetic wave absorber according to the present invention, and FIG. 2 is a flowchart for explaining step (S1) of FIG. 1 in detail.

As shown in FIG. 1, a magnetic material powder of any one selected from ferrite powder, permalloy powder, sand dust, conductive carbon black, and graphite, or a mixture of two or more thereof is prepared (S1).

Subsequently, the magnetic material powder 10 to 100 parts by weight of a single material or a mixture of two or more of any one selected from synthetic rubber, elastomer, polyurethane, and polyol, which has been left to stand at a temperature of 40 to 70 ° C. for at least 2 hours. An appropriate amount of 50 parts by weight is mixed with the polymer material and the magnetic material powder, so that the temperature of the polymer material is maintained during the mixing process (S2). At this time, it is preferable to knead for 10 seconds or more at 1000rpm in order to facilitate the mixing and dispersing.

Then, 5 to 10 parts by weight of the blowing agent is mixed with respect to 100 parts by weight of the polymer material and the mixture of the polymer material and the magnetic material powder (S3).

Subsequently, the blowing agent is mixed with a curing agent having an amount of 5 to 80 parts by weight based on 100 parts by weight of the polymer material and subjected to at least 1 hour at 40 to 60 ℃ (S4). At this time, in order to facilitate mixing of the curing agent, it is preferable to knead for 10 to 30 seconds at 1500 rpm or more.

Finally, after foaming the resultant of the above step, the preparation of the electromagnetic wave absorber is completed by standing at 50 to 80 ℃ for 2 hours. At this time, if the conditions do not meet the above conditions, the electromagnetic wave absorber product may not be cured properly, the powder may be buried, when using the product in the field, the electromagnetic wave absorption performance is lowered, it is repeated that does not meet the purpose As it has been confirmed through the experiments, special care is required to maintain the standing conditions of the product after the completion of foaming.

In this case, when the temperature condition of the step (S2) is not met, it is not preferable because the mixed dispersion of the polymer material and the magnetic powder material is not sufficient, and the curing agent does not meet the temperature condition of the step (S4). Since is not effectively dispersed in the mixture, special attention is paid to the maintenance of temperature conditions.

Meanwhile, the preparing of the magnetic material (S1) will be described with reference to FIG. 2. That is, in preparation of the magnetic material powder (S1), the magnetic material powder is calcined (S11), and the resultant is slurried by adding distilled water (S12), and then the slurry is subjected to, for example, an Attrition Mill. To grind for 12 hours (S13). Finally, after the pulverized product is sufficiently dried, a powder material having a fine particle size passed through a mesh of 100 mesh or more (150 μm or less) is prepared.

Optimal embodiments of the present invention described above have been disclosed. Although specific terms have been used herein, these are merely used for the purpose of describing the present invention in detail to those skilled in the art, and are not intended to limit the scope of the present invention as defined in the claims or the claims.

According to the present invention, the performance of the electromagnetic wave absorption is improved compared to the conventional products, in particular, it is possible to effectively absorb the electromagnetic waves even in the low frequency band (20 to 300 MHz), radiation noise (Radiation Noise) generated in various electronic devices Due to the malfunction between the products, as well as has the advantage of eliminating the source of electromagnetic waves that are harmful to the human body.

Claims (6)

(S1) preparing a magnetic material powder of any one or a mixture of two or more selected from ferrite powder, permalloy powder, sand dust, conductive carbon black, and graphite; (S2) The magnetic material powder 10 with respect to 100 parts by weight of the polymer material which is a single substance or a mixture of two or more selected from synthetic rubber, elastomer, polyurethane, and polyol, which has been left for 2 hours or more at a temperature of 40 to 70 ° C. Mixing the polymer material with the magnetic material powder by appropriate amount of 50 parts by weight to maintain the temperature of the polymer material during the mixing process; (S3) mixing 5 to 10 parts by weight of the blowing agent with respect to 100 parts by weight of the polymer material in a mixture of the polymer material and the magnetic material powder; (S4) mixing the blowing agent having a quantity of 5 to 80 parts by weight based on 100 parts by weight of the polymer material in the mixture into which the blowing agent is added, and having undergone at least 1 hour at 40 to 60 ° C .; And (S5) after the foaming of the result of the step, the step of leaving for 2 hours at 50 to 80 ℃; electromagnetic wave absorber manufacturing method comprising the. According to claim 1, wherein the preparation of the magnetic material powder of the step (S1), (S11) firing the magnetic material powder; (S12) step of slurrying by adding distilled water to the resultant; (S13) crushing the resultant; And (S14) after drying the resultant, selecting a magnetic material powder having a predetermined particle size conditions; manufacturing method of the electromagnetic wave absorber comprising the. The method according to claim 1 or 2, The magnetic material powder has a particle diameter of 100 mesh or more manufacturing method of the electromagnetic wave absorber. delete delete delete

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