Ferrite particle powder for absorbing electromagnetic waves, method for producing same, resin composition using same, and electromagnetic wave absorbing material

Abstract

Provided is a ferrite particle powder for absorbing electromagnetic waves, which is capable of maintaining the flexibility and uniformity of physical properties of a sheet even when the sheet is highly filled, and which has excellent electromagnetic wave absorption performance in the GHz band. A ferrite particle powder for absorbing electromagnetic waves, which is composed of a magnetoplumbite ferrite represented by the chemical formula: AxFe (12-y) (TizMn (1-z)) yO19, where A is at least one element selected from the group consisting of Ba, Sr, Ca and Pb, x is 0.9-1.1, y is 5.0 or less, and z is 0.35-0.65, has a compressive density of 3.00 g / cm3 or more, and has a D10 of 0.8 [mu] m or less and a D90 of 8.6 [mu] m or less as determined by a laser diffraction method.

Description

Technical Field

[0001] The present disclosure relates to ferrite particle powder for electromagnetic wave absorption, a method for producing the ferrite particle powder for electromagnetic wave absorption, and a resin composition and an electromagnetic wave absorbing material using the ferrite particle powder for electromagnetic wave absorption. Background Art

[0002] As information communication has advanced, 5G communication, which has become popular in recent years, is expected to be used in many electronic devices. This 5G communication uses radio waves with a frequency in the GHz band that can transmit a large amount of information at high speed, with low latency, and in a simultaneous connection.

[0003] In addition, as electronic devices become smaller, the density of electronic components continues to increase. If current flows through the densely packed electronic components, some of the energy may become electromagnetic waves and radiate to other electronic components.

[0004] Furthermore, the radiated electromagnetic waves may be reflected in the housing of the electronic device. As a result, the radiated or reflected electromagnetic waves may cause malfunction of the electronic device. In order to suppress the electromagnetic wave noise that causes such malfunction, an electromagnetic wave absorbing material may be used.

[0005] Electromagnetic wave absorbing materials are often used for subsequent countermeasures. Therefore, the electromagnetic wave absorbing materials used are often attached to uneven surfaces such as electronic components. Therefore, the electromagnetic wave absorbing materials are required to have good flexibility. At the same time, the electromagnetic wave absorbing materials are often used in electronic housings where electronic components are densely arranged and there is almost no empty space. Therefore, the electromagnetic wave absorbing materials are required to have a thin sheet shape and high electromagnetic wave absorbing performance.

[0006] Electromagnetic wave absorbing materials are materials that convert absorbed electromagnetic wave energy into heat energy. That is, the amount of energy loss becomes the electromagnetic wave absorption performance. Theoretically, for example, energy is lost due to magnetic loss, dielectric loss or conductive loss. Magneto-plumbite ferrite (hereinafter sometimes referred to as M-type ferrite) has high crystal magnetic anisotropy. As a result, M-type ferrite exhibits magnetic resonance in the GHz band, at which frequency, the imaginary part μ" of the complex magnetic permeability that obtains magnetic loss is displayed. Therefore, M-type ferrite is expected to be used as a high-frequency absorbing material.

[0007] For example, it is known that M-type barium ferrite has a resonance frequency around 50 GHz. However, due to its large coercive force, M-type barium ferrite can hardly be said to be soft magnetic. However, by replacing part of the iron with, for example, titanium, manganese, zinc, cobalt, nickel, copper, tin or zirconium, the soft magnetic property is promoted. As a result, the crystal magnetic anisotropy and saturation magnetization change. Therefore, the resonance frequency can be controlled. In this way, an electromagnetic wave absorbing ferrite that can correspond to various high-frequency bands such as the 5G communication band can be obtained.

[0008] The absorption performance of the electromagnetic wave absorbing material obtained from the resin composition containing M-type ferrite and resin varies greatly depending on the filling amount of ferrite in the resin composition. In order to improve the electromagnetic wave absorption performance, it is necessary to increase the filling amount of ferrite. On the other hand, if the filling amount of ferrite is increased, the electromagnetic wave absorbing material required as the flexibility of the sheet becomes hard and brittle. That is, if the filling amount of ferrite is too much, the sheet production itself becomes difficult.

[0009] In addition, when ferrite and resin are kneaded, the resin is melted by heating. At this time, for the resin composition with a high filling amount of ferrite, the viscosity when melted becomes high. As a result, the components in the resin composition are difficult to mix evenly when kneading, so microdispersion becomes difficult. Especially when the additive that shows its effect in a trace amount cannot be microscopically microdispersed, the effect of the additive cannot be fully exerted.

[0010] For example, when using NBR (acrylonitrile butadiene rubber) of thermosetting resin to make sheet, in addition to resin and ferrite, also add additive. Then, after these components are kneaded, appropriate elasticity and flexibility are given to sheet by vulcanization. At this time, owing to high filling of ferrite, therefore under the condition of high viscosity during melt kneading of this resin combination, additive is not microscopically micro-dispersed. As a result, the subsequent vulcanization is carried out unevenly, so the physical property such as sheet that becomes hard and poor in flexibility is reduced.

[0011] Patent document 1 discloses an electromagnetic wave absorbing sheet having an electromagnetic wave absorbing layer, wherein the electromagnetic wave absorbing layer contains an electromagnetic wave absorbing material that performs magnetic resonance in a frequency band above the millimeter wave band, namely, magnetic iron oxide, and a rubber adhesive. The maximum elongation of the elastic region in one direction within the plane of the electromagnetic wave absorbing sheet is 20% to 200%. The content of the magnetic iron oxide in the electromagnetic wave absorbing layer is 30% by volume or more. As the magnetic iron oxide, ε iron oxide or strontium ferrite can be used.

[0012] Patent document 2 discloses a method of using AFe (12－X) (B1 0.5 (Co (1－y) Zn y ) 0.5 ) x O 19 A magnetoplumbite type hexagonal ferrite suitable for an electromagnetic wave absorber for GHz bands represented by a composition formula of . Here, A is one or two of Ba and Sr. B1 is one or two of Ti and Zr. x is 0.1 to 2.0. y is 0.2 to 0.8.

[0013] Prior art literature

[0014] Patent Literature

[0015] Patent Document 1: Japanese Patent Application Publication No. 2019-75571

[0016] Patent Document 2: Japanese Patent Application Publication No. 2010-260766 Summary of the invention

[0017] Electromagnetic wave absorbing sheets are required to have flexibility and high electromagnetic wave absorbing performance. In order to improve the electromagnetic wave absorbing performance of an electromagnetic wave absorbing sheet using M-type ferrite having electromagnetic wave absorbing performance in the GHz band, it is necessary to highly fill the sheet with ferrite powder. However, generally speaking, if the filling amount of powder is increased, the flexibility of the sheet is significantly reduced. As a result, if the filling amount of powder is excessively increased, sheeting itself becomes difficult.

[0018] In addition, if the filling amount of the powder is increased, the viscosity of the resin composition during melt kneading becomes higher. Therefore, the microdispersion of each component in the resin composition is relatively difficult. As a result, the softness of the sheet and the uniformity of the physical properties are significantly reduced. In particular, the effect of the additive is manifested by a trace amount of the additive. Therefore, there is the following problem: in the case of not realizing the microscopic microdispersion of the additive, the processability and physical properties of the sheet are greatly affected.

[0019] The electromagnetic wave absorbing resin sheet containing magnetic iron oxide such as ferrite in the resin described in Patent Document 1 can be installed in a location where the shape of the installation location is not flat because the elongation of the sheet is controlled. However, the document does not describe the purpose of improving the following problem by controlling the powder of magnetic iron oxide such as ferrite: when a resin composition highly filled with fillers is kneaded, the microscopic dispersion of each component is deteriorated because the resin composition in a molten state has a high viscosity, thereby deteriorating the sheet properties.

[0020] The magnetoplumbite hexagonal ferrite suitable for the electromagnetic wave absorber for GHz band described in Patent Document 2 can suppress the frequency fluctuation caused by the thickness fluctuation of the electromagnetic wave absorbing resin sheet containing ferrite. However, in this document, when the resin composition containing a large amount of filler is kneaded, the viscosity of the resin composition in the molten state becomes high. Therefore, with the kneading, the microscopic microdispersion of each component becomes worse. Moreover, the physical properties of the sheet also become worse. There is no record in previous documents about the purpose of improving such a subject by controlling the powder of magnetic iron oxide such as ferrite.

[0021] The present disclosure is an invention for coping with the above-mentioned problems. That is, the subject of the present disclosure is to provide a ferrite particle powder for electromagnetic wave absorption which can maintain the softness and uniformity of the physical properties of the sheet even if the sheet is highly filled and has excellent electromagnetic wave absorption performance in the GHz band, a resin composition containing the ferrite particle powder for electromagnetic wave absorption, and an electromagnetic wave absorbing material using the resin composition.

[0022] In order to solve the above-mentioned problems, researchers have conducted intensive studies and found that the above-mentioned problems can be solved by optimizing the powder properties of the M-type ferrite powder that should be paid attention to to predetermined properties.

[0023] That is, the first embodiment of the present disclosure is an electromagnetic wave absorbing ferrite particle powder having a chemical formula: x Fe (12-y) (Ti z Mn (1-z) ) y O 19 The magnetoplumbite ferrite represented by the present invention is composed of at least one selected from Ba, Sr, Ca and Pb, x is 0.9 to 1.1, y is 5.0 or less, z is 0.35 to 0.65, and the electromagnetic wave absorbing ferrite particle powder has a particle size of 3.00 g / cm 3 The above compressed density has D10 of 0.8 μm or less and D90 of 8.6 μm or less determined by laser diffraction.

[0024] The second embodiment of the present disclosure is a method for manufacturing ferrite particle powder for electromagnetic wave absorption of the first embodiment, characterized in that iron raw materials, titanium raw materials, manganese raw materials and compound raw materials of element A are mixed, molded and calcined to generate magnetoplumbite ferrite, which is then crushed and annealed.

[0025] A third embodiment of the present invention is a resin composition comprising the electromagnetic wave absorbing ferrite particle powder of the first embodiment and a resin.

[0026] A fourth embodiment of the present invention is an electromagnetic wave absorbing material comprising the electromagnetic wave absorbing ferrite particle powder of the first embodiment and a resin.

[0027] According to the electromagnetic wave absorbing ferrite particle powder and the resin composition using the same of this embodiment, the electromagnetic wave absorbing material (electromagnetic wave absorbing sheet) highly filled with ferrite particle powder can also maintain its flexibility and uniformity of physical properties. In addition, the electromagnetic wave absorbing material of this embodiment has excellent electromagnetic wave absorption performance in the GHz band. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a conceptual diagram of a vulcanization curve created using a vulcanizer. DETAILED DESCRIPTION

[0029] Hereinafter, this embodiment will be described in detail. The electromagnetic wave absorbing ferrite particle powder of this embodiment comprises a material having a chemical formula: x Fe (12－y) (Ti z Mn (1－z) ) y O 19 Here, A is at least one element selected from Ba, Sr, Ca and Pb. Preferred elements are Ba and Sr.

[0030] x is 0.9 to 1.1, preferably 0.94 to 1.06, and more preferably 0.97 to 1.03. y is 5.0 or less, preferably 0.02 to 4.20, more preferably 0.05 to 3.30, and more preferably 0.08 to 2.40. z is 0.35 to 0.65, preferably 0.38 to 0.63, and more preferably 0.40 to 0.60. That is, the magnetoplumbite ferrite of the present embodiment contains Ti and Mn at a ratio within a specific range.

[0031] When x is less than 0.9 or exceeds 1.1, it is difficult to obtain a single-phase magnetoplumbite ferrite. Therefore, x less than 0.9 or exceeding 1.1 is not preferred. When y exceeds 5.0, since the saturation magnetization becomes too low, the following problems arise: the imaginary part μ" of the complex magnetic permeability that obtains magnetic loss also becomes low; a part of the added elements is not dissolved in the ferrite but precipitates as impurities; or since the sintered body becomes significantly hard during reaction calcination, the crushing efficiency is reduced. Therefore, y exceeding 5.0 is not preferred. When z is less than 0.35 or exceeds 0.65, electrical neutrality cannot be maintained, resulting in impurities precipitation. Therefore, z less than 0.35 or exceeding 0.65 is not preferred.

[0032] The compressed density of the electromagnetic wave absorbing ferrite particles powder of this embodiment is 3.00 g / cm 3 As a result, the viscosity of the resin composition during melt kneading can be reduced. The compressed density is less than 3.00 g / cm 3 When the viscosity of the resin composition is reduced, it is difficult to reduce the viscosity of the resin composition during melt kneading. The compressed density is preferably 3.06 g / cm 3 More preferably, 3.10 g / cm 3 The upper limit of the compression density is, for example, 3.60 g / cm 3 The compressed density is measured by the method described in the examples below.

[0033] The ferrite particle powder for electromagnetic wave absorption of the present embodiment has a D10 of less than 0.8μm and a D90 of less than 8.6μm obtained by a laser diffraction method. When D10 exceeds 0.8μm, the viscosity of the resin composition during kneading increases. Therefore, due to insufficient dispersion of the components of the resin composition, the flexibility of the electromagnetic wave absorbing material (electromagnetic wave absorbing sheet) obtained from the resin composition is impaired. When D90 exceeds 8.6μm, the viscosity of the resin composition during kneading also rises. Therefore, due to insufficient dispersion of the components of the resin composition, the flexibility of the electromagnetic wave absorbing sheet is impaired. D10 is preferably less than 0.75μm, more preferably less than 0.65μm. D90 is preferably less than 8.5μm, more preferably less than 7.0μm, and further preferably less than 6.0μm. The lower limit of D10 is about 0.4μm. The lower limit of D90 is about 2.0μm.

[0034] The specific surface area of ​​the electromagnetic wave absorbing ferrite particles of the present embodiment is preferably 0.50 to 4.0 m 2 / g. Specific surface area is less than 0.50m 2 When the specific surface area exceeds 4.0 m / g, the resin space between the ferrite particle powders becomes larger, so the electromagnetic wave absorbing sheet becomes brittle. As a result, the flexibility of the sheet is impaired. 2 / g, the wettability of the ferrite particle powder surface with the resin decreases, so the flexibility of the sheet is impaired. The specific surface area is more preferably 1.00 to 3.80 m 2 / g, more preferably 1.40 to 3.60 m 2 / g, more preferably 1.80 to 3.50 m 2 / g.

[0035] The average particle size (Ps-b) of the ferrite particle powder for electromagnetic wave absorption of the present embodiment obtained by the air permeation method (Blaine method) is preferably 0.50 to 3.0 μm. When the average particle size (Ps-b) is less than 0.50 μm, the wettability of the surface of the ferrite particle powder with the resin is reduced. Therefore, the flexibility of the sheet may be impaired. When the average particle size (Ps-b) exceeds 3.0 μm, the resin space between the ferrite particle powders becomes larger. As a result, the electromagnetic wave absorbing sheet may become brittle. In this case, the flexibility of the sheet is impaired. The average particle size (Ps-b) is more preferably 0.65 to 2.50 μm, and further preferably 0.80 to 2.00 μm.

[0036] Next, a method for producing the electromagnetic wave absorbing ferrite particle powder according to the present embodiment will be described.

[0037] In the method for producing electromagnetic wave absorbing ferrite particles and powders of this embodiment, iron raw materials, titanium raw materials, manganese raw materials and compound raw materials of element A are mixed, molded and calcined to generate magnetoplumbite ferrite. The generated magnetoplumbite ferrite is crushed and then annealed to obtain the target electromagnetic wave absorbing ferrite particles and powders.

[0038] As the iron raw material, iron oxide such as α-Fe2O3 can be preferably used. As the titanium raw material, titanium oxide such as TiO2 can be preferably used. As the manganese raw material, manganese oxide such as Mn2O3 or Mn3O4 can be preferably used. Preferred examples of the raw material of element A include oxides, hydroxides and carbonates of Ba, Sr, Ca and Pb.

[0039] First, the chemical formula: A x Fe (12－y) (Ti z Mn (1－z) ) y O 19 The iron raw material, titanium raw material, manganese raw material and compound raw material of element A are mixed in a ratio corresponding to x, y and z. These raw materials can be mixed using, for example, a wet grinder, a homomixer or a high-speed mixer. The obtained raw material mixture is crushed and then granulated using an extruder or the like.

[0040] When the raw material mixture is pulverized or granulated, a flux is preferably added. Then, the obtained molded body is calcined. Preferred examples of the flux include BaCl 8.4 H2O, SrCl2·6H2O, CaCl 8.4 H2O, KCl, MgCl2, NaCl, Na2B4O7. The amount of flux added is preferably 0.1 to 10.0 wt%, more preferably 0.1 to 8.0 wt%, relative to the raw material mixture obtained above.

[0041] Alternatively, Bi2O3 as a reaction accelerator may be added to the raw material mixed powder or the pulverized powder after calcination and mixed.

[0042] The obtained molded body is calcined to generate a magnetoplumbite ferrite. The calcination temperature is preferably 1000-1400°C, more preferably 1050-1350°C. When the calcination temperature is lower than 1000°C, the ferritization reaction sometimes cannot proceed sufficiently. Therefore, sometimes a single phase cannot be obtained, or the theoretical saturation magnetization value (σs) under the composition cannot be obtained. When the calcination temperature is higher than 1400°C, the particles are fused to each other by sintering, which places a burden on the manufacturing process such as pulverization to control the particle size to a specified value. Therefore, a calcination temperature higher than 1400°C is not preferred.

[0043] The obtained calcined product is pulverized. The pulverization can be performed at room temperature. The pulverization is performed using, for example, a hammer mill, a wet mill, etc. When the pulverization is performed using a wet mill, the pulverized product is then washed with water, filtered, and dried.

[0044] Next, the obtained pulverized product is annealed in the air, preferably at 600 to 1100°C, more preferably at 650 to 1050°C. When the annealing temperature is higher than 1100°C, the particles are fused to each other by sintering, and a powder with good dispersibility cannot be obtained, which is not preferred. It should be noted that the annealing treatment is carried out at a temperature lower than the calcination temperature. In the present invention, the annealing treatment carried out in this temperature range is more important for achieving the powder properties of the magnetoplumbite type ferrite particle powder specified in the present invention.

[0045] Next, the resin composition of the present embodiment and the electromagnetic wave absorbing material (electromagnetic wave absorbing sheet) of the present embodiment will be described.

[0046] The resin composition of the present embodiment is composed of ferrite particle powder for electromagnetic wave absorption and resin. As examples of resins, hydrogenated styrene-based thermoplastic elastomer (SEBS), vinyl chloride resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, PPS resin, polyamide (nylon) resin, polyamide elastomer, polymerized fatty acid polyamide, acrylonitrile butadiene rubber (NBR), natural rubber (NR), isoprene rubber (IR), ethylene-propylene rubber (EPDM), acrylic rubber (ACM) and silicone rubber (Q) can be cited. In addition, the mixing ratio of ferrite particle powder for electromagnetic wave absorption is preferably 20 to 75 volume %.

[0047] In order to improve the compatibility and dispersibility of the electromagnetic wave absorbing ferrite particles in the resin, it is preferred to preliminarily treat the electromagnetic wave absorbing ferrite particle powder with a surface treatment agent. Examples of surface treatment agents that can be added include silane coupling agents and titanate coupling agents. Furthermore, examples of additives that can be added as needed include plasticizers, reinforcing agents, heat resistance enhancers, thermal conductivity fillers, adhesives, antioxidants, light stabilizers, antistatic agents, and colorants.

[0048] When various coupling agents are used, coupling agents having any of vinyl, epoxy, amino, methacryloyl, mercapto, phosphoryl and sulfo groups and alkoxy groups such as methoxy and ethoxy groups as functional groups can be used.

[0049] The electromagnetic wave absorbing ferrite particle powder (which may be surface treated as needed), resin and various additives as needed are mixed to produce a resin composition. The shape of the resin composition is not particularly limited, but by crushing or cutting into granular or particle shapes, it can be suitable for use as a molding material for electromagnetic wave absorbing materials. Then, the obtained resin composition is molded and rolled into a desired thickness and shape by a known method. In this way, an electromagnetic wave absorbing material (electromagnetic wave absorbing sheet) is manufactured.

[0050] When rubber is used as the resin, the resin can be vulcanized by the following method. First, an additive such as a vulcanizing agent (sulfur), a vulcanization accelerator (such as 2-mercaptobenzothiazole (MBT) or N-cyclohexyl-2-benzothiazolesulfonamide (CBS)) or a vulcanization accelerator (such as stearic acid or zinc oxide) is added to the resin composition. Then, the components of the resin composition are kneaded, molded, and rolled at a temperature lower than the temperature at which the vulcanization reaction occurs (such as 60 to 100°C) to produce an unvulcanized sheet. Then, the unvulcanized sheet is hot pressed at a temperature at which the vulcanization reaction occurs (such as 120 to 200°C). In this way, a vulcanized electromagnetic wave absorbing sheet is obtained.

[0051] Although the details of the reason why the ferrite particle powder for electromagnetic wave absorption of the present embodiment is suitable as a material for electromagnetic wave absorption material is not yet clear, it is speculated as follows. In order to improve the electromagnetic wave absorption performance of the ferrite particle powder itself, it is important to achieve the theoretical amount of saturation magnetization value (σs) under the composition and to microscopically disperse the elements constituting the composition. In the present embodiment, by optimizing the preparation method of ferrite, a ferrite particle powder that satisfies the above two points can be obtained. Thus, high electromagnetic wave absorption performance is achieved.

[0052] In addition, the compression density was controlled to 3.0 g / cm 3 Furthermore, D10 is controlled to be less than 0.8 μm and D90 is controlled to be less than 8.6 μm. As a result, the viscosity of the resin composition during melt kneading is reduced, so that the constituent elements of the resin composition can be microscopically dispersed. In addition, the ferrite particle powder has an excellent effect of enhancing the physical properties of the electromagnetic wave absorbing sheet. As a result, an electromagnetic wave absorbing sheet with excellent flexibility can be achieved.

[0053] The higher the compression density of the ferrite particle powder, the lower the viscosity of the resin composition during melt kneading. Therefore, the additive can be microscopically dispersed. As a result, the effect can be exhibited by a trace amount of the additive.

[0054] Example

[0055] Representative embodiments of the present disclosure are as follows: First, the measurement method and the evaluation method are described.

[0056] The amount of each element (Ti, Mn, Zn, Ba and Fe) contained in the ferrite particle powder was measured by a fluorescent X-ray spectrometer "ZSX PrimusII" (manufactured by Rigaku Corporation). The obtained amounts of Ti, Mn, Zn, Ba and Fe were converted into moles to calculate the composition ratios x, y and z.

[0057] As the compressed density of the ferrite particle powder, a hydraulic press was used to measure the compressed density of the ferrite particle powder at 1 t / cm 2 The pressure is the density of the particle powder when compressed.

[0058] The D10 and D90 of the ferrite particle powder were measured using a "laser diffraction particle size distribution measuring device HELOS & RODOS (measurement unit form HELOS / BF-M, airflow dry dispersion unit RODOS / M)" (manufactured by Sympatec GmbH). Specifically, in RODOS / M, the sample dispersed at a dispersion pressure of 5 bar was measured with HELOS / BF-M under the conditions of measurement range 1 (0.1 / 0.18 to 35 μm). The 10% particle size in the cumulative particle size distribution is expressed as D10, and the 90% particle size is expressed as D90.

[0059] The specific surface area of ​​the ferrite particle powder was measured using a "specific surface area measuring device Macsorb" (manufactured by Mountech Co., Ltd.) Specifically, the specific surface area was measured based on the principle of the BET one-point method utilizing the adsorption and desorption characteristics of nitrogen gas on a sample.

[0060] The average particle size (Ps-b) of the ferrite particle powder obtained by the air permeation method (Blaine method) was measured by a "constant pressure air-through type rapid standard universal powder specific surface area measuring device" (manufactured by Shimadzu Corporation).

[0061] As the electromagnetic wave absorption characteristics of the electromagnetic wave absorption sheet produced using the ferrite particle powder, the absorption peak frequency and the transmission attenuation (S) were measured using a “network analyzer E8361A” (manufactured by Agilent Technologies). 21 ).

[0062] The tensile modulus is measured by the following method according to the JIS K6251 standard. First, a block rubber composition is prepared using "LaboPlasto Mill 4C150" (manufactured by Toyo Seiki Co., Ltd.). Then, an unvulcanized rubber sheet is prepared using "Benchtop Test Mixing Roller 191-TM" (manufactured by Yasuda Seiki Co., Ltd.). Next, a vulcanized rubber sheet is prepared using a "hot press" (manufactured by Tester Industries, Ltd.). Furthermore, a dumbbell test piece (total length 115 mm, width 25.0 mm, thickness 2.0 mm ± 0.2 mm) is obtained using a test piece punching blade No. 5. Then, the tensile modulus is measured using a "computer measurement controlled precision universal testing machine AG-1" (manufactured by Shimadzu Corporation).

[0063] Using a vulcanizer, a vulcanization curve is obtained according to the JIS K6300-2 standard (die vulcanization test method A). The maximum torque MH and 10% vulcanization time Tc (10) are obtained from the vulcanization curve. The block rubber composition is made using "Labo Plasto Mill 4C150" (manufactured by Toyo Seiki Co., Ltd.). Then, an unvulcanized rubber sheet (thickness 3.2±0.2mm) is made using "Benchtop Test Mixing Roller 191-TM" (manufactured by Yasuda Seiki Co., Ltd.). A circular resin sheet with a diameter of 45mm is punched out from the sheet. Then, a vulcanization curve is obtained using "Vulcanizer 7" (manufactured by JSR Trading Co., Ltd.). In this measurement method, the resin sheet punched into a circle is vulcanized while being heated and a torsional torque is applied. The vulcanization characteristics are obtained based on a curve representing the torque change from before the start of vulcanization to the end of vulcanization.

[0064] Figure 1 This is a conceptual diagram of a vulcanization curve obtained using a vulcanizer. Based on the vulcanization curve, information related to the physical properties of the resin sheet including the minimum torque value ML before vulcanization and the maximum torque value MH after vulcanization can be obtained. Furthermore, information related to the vulcanization speed can be obtained, including the 10% vulcanization time Tc(10) (the time from the start of vulcanization until the 10% change in the torque change from ML to MH is completed).

[0065] The maximum torque MH after vulcanization is an index showing how much elasticity the vulcanized sheet has. The higher the value, the harder the sheet is. The lower the value, the softer the sheet is.

[0066] In addition, the 10% vulcanization time Tc(10) is the time required for initial vulcanization. The smaller the value, the faster the vulcanization progresses. If the sheet state when vulcanization progresses quickly is considered, when the time required for initial vulcanization is short (Tc(10) is small), it is difficult to say that the microdispersion of components such as additives can be fully achieved. As a result, it is expected that uneven vulcanization will occur. In addition, when the initial vulcanization progresses slowly (Tc(10) is large), it is considered that uniform vulcanization occurs.

[0067] Embodiments 1 to 7:

[0068] <Manufacturing of ferrite particle powder>

[0069] Various powder raw materials (α-Fe2O3, TiO2, Mn3O4, BaCO3) weighed in such a way that the composition of the final processed product becomes the composition formula shown in Table 1 are mixed in a wet mill for 15 minutes. Then, the obtained mixture is filtered and dried. BaCl is added to the obtained raw material mixed powder. 8.4 H2O, and then the mixture is extruded. At this time, BaCl 8.4 The amount of H2O added was 3.0 wt%. The obtained granules were calcined at 1280°C in the air. The obtained calcined product was coarsely crushed and then crushed with a wet mill. The obtained crushed product was washed with water, filtered and dried. Next, the obtained crushed product was annealed at 600°C in the air. The manufacturing conditions at this time are shown in Table 1, and the various properties of the obtained ferrite particle powder are shown in Table 2.

[0070] Comparative Example 1:

[0071] Ferrite particle powder was produced in the same manner as in Example 1 except that the composition of the ferrite particle powder was changed (Zn was added) and annealing was not performed. The production conditions at this time are shown in Table 1, and various properties of the obtained ferrite particle powder are shown in Table 2.

[0072] [Table 1]

[0073]

[0074] [Table 2]

[0075]

[0076] Embodiments 8 to 13:

[0077] <Production of electromagnetic wave absorbing sheets>

[0078] 60.0% by volume of each ferrite particle powder obtained in Examples 1 to 6, 39.0% by volume of hydrogenated styrene-based thermoplastic elastomer (SEBS) resin, and 1.0% by volume of a titanate coupling agent (Plenact TTS, manufactured by Ajinomoto Fine Science Co., Ltd.) were roll-kneaded at 160°C. Then, the obtained kneaded product (resin composition) was molded and rolled to produce an electromagnetic wave absorbing sheet. During the molding and rolling process, the thickness of the produced electromagnetic absorbing sheet was adjusted to 1 mm.

[0079] The absorption peak frequency and transmission attenuation (S) of the obtained electromagnetic wave absorption sheet were measured using a “network analyzer E8361A” (manufactured by Agilent Technologies). 21 ). The electromagnetic wave absorption characteristics at this time are shown in Table 3.

[0080] [Table 3]

[0081]

[0082] Comparative Example 2:

[0083] 60.0% by volume of each ferrite particle powder obtained in Comparative Example 1, 39.0% by volume of hydrogenated styrene-based thermoplastic elastomer (SEBS) resin, and 1.0% by volume of a titanate coupling agent (Plenact TTS, manufactured by Ajinomoto Fine Science Co., Ltd.) were roll-kneaded at 160°C. However, a lump-shaped resin kneaded product was obtained in the middle of kneading. In addition, the kneaded product did not bite into the forming roll. Therefore, the use of SEBS resin to make electromagnetic wave absorbing sheets was abandoned.

[0084] Comparative Example 3:

[0085] NBR was used as a substitute resin for the SEBS resin used in the sheet production in Comparative Example 2 to produce a sheet. 60.0% by volume of each ferrite particle powder obtained in Comparative Example 1 and 35.0% by volume of NBR (N239SV manufactured by JSR Corporation) and 0.69% by volume of stearic acid, 0.26% by volume of zinc oxide, 0.25% by volume of sulfur, 0.55% by volume of N-cyclohexyl-2-benzothiazolesulfonamide (CBS) and 3.3% by volume of Polycizer W320 (manufactured by DIC Corporation) as additives were kneaded at 80°C. Then, an unvulcanized sheet was produced by molding and rolling the obtained kneaded product (resin composition) at 60°C. During the molding and rolling process, the thickness of the produced unvulcanized sheet was adjusted to 1.0 mm. Next, the unvulcanized sheet was heated at 150°C using a hot press. Then, a vulcanized electromagnetic wave absorbing sheet was produced by applying a pressure of 3 MPa for 10 minutes. The electromagnetic wave absorption measurement of the obtained electromagnetic wave absorbing sheet was carried out in the same manner as in Examples 8 to 13 above.

[0086] Examples 14 to 16, Comparative Example 4:

[0087] <Manufacturing of dumbbell test pieces for tensile testing>

[0088] 60.0 volume % of each ferrite particle powder obtained in Examples 1, 3, 5 and Comparative Example 1, 35.0 volume % of NBR (N239SV manufactured by JSR Corporation), 0.69 volume % of stearic acid, 0.26 volume % of zinc oxide, 0.25 volume % of sulfur, 0.55 volume % of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and 3.3 volume % of Polycizer W320 (manufactured by DIC Corporation) as additives such as vulcanizers and vulcanization accelerators were kneaded at 80°C. Then, an unvulcanized sheet was prepared by molding and rolling the obtained kneaded product (resin composition) at 60°C. During the molding and rolling process, the thickness of the unvulcanized sheet was adjusted to 2.0 mm. Next, the unvulcanized sheet was heated at 180°C for 25 minutes using a hot press. Then, a vulcanized electromagnetic wave absorbing sheet was prepared by applying a pressure of 3 MPa for 5 minutes. Then, a dumbbell test piece was punched out from the sheet using a test piece punching blade No. 5. Table 4 shows the tensile elastic modulus of the test piece molded body.

[0089] <Preparation of test pieces for vulcanization curve measurement>

[0090] 60.0 volume % of the ferrite particle powder obtained in Examples 1, 3, 5 and Comparative Example 1, 35.0 volume % of NBR (N239SV manufactured by JSR Corporation), 0.69 volume % of stearic acid, 0.26 volume % of zinc oxide, 0.25 volume % of sulfur, 0.55 volume % of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and 3.3 volume % of Polycizer W320 (manufactured by DIC Corporation) as additives such as vulcanizers and vulcanization accelerators were kneaded at 80°C. Then, an unvulcanized sheet was prepared by molding and rolling the obtained kneaded product (resin composition) with a 60°C roll to a thickness of 3.2 mm. During the molding and rolling process, the thickness of the obtained unvulcanized sheet was adjusted to 3.2 mm. Next, a circular test piece was punched out from the sheet using a circular punching blade (diameter 45 mm).

[0091] Table 4 shows the maximum value MH of the torque and the 10% vulcanization time Tc(10) obtained from the vulcanization curve of the test piece molded body at 180°C.

[0092] [Table 4]

[0093]

[0094] As can be seen from Table 4, the tensile modulus of Examples 14, 15, and 16 is a low value of 21 to 34 MPa. In contrast, Comparative Example 4 shows a high value of 40 MPa or more. This shows that by using the ferrite of the Examples, a sheet that is easily elongated and flexible can be produced.

[0095] Next, MH of Examples 14, 15, and 16 is a low value of 15 to 19 kgf·cm. In contrast, Comparative Example 4 shows a high value of 20 kgf·cm or more. This shows that a soft sheet can be produced by using the ferrite of the Examples.

[0096] In addition, it was confirmed that the Tc(10) of Examples 14, 15, and 16 was 1.0 minutes or more. In contrast, it was confirmed that the Tc(10) of Comparative Example 4 was a short time of 0.7 minutes or less. Thus, uniform vulcanization was achieved in the ferrite of the Examples. That is, since the viscosity of the resin composition during melt kneading was low, it is considered that the components contained in the resin composition were finely dispersed.

[0097] Industrial Applicability

[0098] The electromagnetic wave absorbing ferrite particle powder of this embodiment can maintain the flexibility and uniformity of the sheet even when the sheet is highly filled, and has excellent electromagnetic wave absorption performance in the GHz band. Therefore, the electromagnetic wave absorbing ferrite particle powder of this embodiment can be preferably used as an electromagnetic wave absorbing material.

Claims

1. A ferrite particle powder for electromagnetic wave absorption, having a chemical formula: A x Fe (12-y) (Ti z Mn (1-z) ) y O 19 The magnetoplumbite ferrite represented by the invention is composed of: A is at least one selected from Ba, Sr, Ca, and Pb; x is 0.9 to 1.1; y is 5.0 or less; and z is 0.35 to 0.

65. The electromagnetic wave absorbing ferrite particle powder has a particle size of 3.00 g / cm 3 The above compressed density has D10 of 0.8 μm or less and D90 of 8.6 μm or less determined by laser diffraction.

2. The electromagnetic wave absorbing ferrite particle powder according to claim 1, wherein With 0.50~4.0m 2 / g specific surface area.

3. A method for producing the electromagnetic wave absorbing ferrite particle powder according to claim 1, comprising: The iron raw material, the titanium raw material, the manganese raw material and the compound raw material of the element A are mixed, molded and calcined to generate the magnetoplumbite type ferrite. crushing the magnetoplumbite ferrite, and The pulverized magnetoplumbite ferrite is subjected to annealing treatment.

4. A resin composition comprising the electromagnetic wave absorbing ferrite particle powder according to claim 1 and a resin.

5. An electromagnetic wave absorbing material, comprising the electromagnetic wave absorbing ferrite particle powder according to claim 1 and a resin.

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