JP2018142618A - Soft magnetic flat powder with high magnetic permeability and high weather resistance and soft magnetic resin composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic flat powder having high magnetic permeability and high weather resistance to be used for various electronic devices or the like and a soft magnetic resin composition such as a magnetic sheet containing the same.SOLUTION: The present invention relates to a soft magnetic flat powder which consists of an Fe-Si-Al based alloy and of which the C quantity/BET value existing on a surface of the flat powder is 0.01 or more and 1.00 or less, and a soft magnetic resin composition containing the soft magnetic flat powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a soft magnetic flat powder having high magnetic permeability and high weather resistance used for various electronic devices and the like, and a soft magnetic resin composition such as a magnetic sheet containing the same.

  Conventionally, various electronic devices such as smartphones, mobile phones, notebook personal computers, tablet personal computers have become widespread, electromagnetic interference due to their miniaturization has become a problem, and higher frequencies due to higher communication speeds, There is an increasing demand for soft magnetic resin compositions such as a magnetic sheet exhibiting a real part (hereinafter referred to as μ ′) having a high magnetic permeability at a high frequency. Among these electronic devices, soft magnetic resin compositions such as magnetic sheets are used for electromagnetic wave absorbers, RFID (Radio Frequency Identification) antennas, digitizer sheets, inductor members, and the like, and Fe-Si-Al alloys. A soft magnetic resin composition obtained by kneading a soft magnetic flat powder such as the above with rubber or resin to form a sheet is widely used.

  The soft magnetic resin composition referred to here is rubber or resin containing a soft magnetic filler, and can be used by being applied or molded into a sheet shape, a film shape, or a block shape. In order to realize a soft magnetic resin composition such as a magnetic sheet having a high μ ′, as shown in the so-called Ollendorf equation, a soft magnetic filler having a high aspect ratio and a high initial permeability is used. It is known to be advantageous to have a high filling with orientation in the direction of the external magnetic field.

  Also, in order to obtain a high aspect ratio powder, an alloy powder such as Fe-Si-Al based produced by a casting pulverization method or various atomizing methods can be used as a raw material powder and flattened by various ball mill methods. Are known. Furthermore, for flattening by the ball mill method, many proposals have been made to forcibly stir the raw material powder and the balls (grinding media) in various organic solvents.

  As described above, flattening by various ball mill methods is applied to the production of flat powder having a high aspect ratio, and various organic solvents are used for this processing. For example, JP-A-2006-72577 (Patent Document 1) describes that it is preferable to use an organic solvent for flattening, and industrial ethanol is used in the examples. In addition, JP 2009-266960 A (Patent Document 2) describes that it is preferable to use an organic solvent. In Examples, toluene, 2-propanol, ethanol, 1-propanol, 1-butanol, and isobutanol are used. Etc. are used. Furthermore, in Japanese Unexamined Patent Application Publication No. 2010-196123 (Patent Document 3), naphthesol is used in the examples.

  On the other hand, in these patent documents 1 to 3, there is no detailed description about separation of the organic solvent and the flat powder after the flat processing. In general, after flattening, the flat powder and the organic solvent are taken out and separated from the flat powder and the organic solvent by various filters and separators. It is used after being dried under conditions such as time. Here, the boiling point of the organic solvent is generally about 200 ° C. or less, and in the case of flat powder aiming at extremely high μ ′ as the object of the present invention, the strain introduced by the flat processing by the ball mill is increased to a high temperature ( In the examples of Patent Documents 1 to 3, it is essential to remove by a heat treatment of 700 ° C. or higher), and thus the low boiling point organic solvent of about 200 ° C. is completely evaporated in this high temperature heat treatment step. Has been.

JP-A-2006-72577 JP 2009-266960 A JP 2010-196123 A

  Such a soft magnetic resin composition, such as a magnetic sheet, has a problem that it may start up depending on the use environment, and high weather resistance may be required. In particular, in recent years, there is a strong demand for increasing the thickness and thickness of a magnetic sheet, and a magnetic sheet with a soft magnetic filler filling rate increased to the limit has come to be used. For this reason, it becomes difficult to add an additive that suppresses the occurrence of soft magnetic filler to the magnetic sheet, and conversely, the volume fraction of the resin must be reduced, and the entire soft magnetic filler is not necessarily surrounded by the resin. For the soft magnetic filler contained in the magnetic sheet, the sheet surface is exposed, a gap is formed at the interface between the resin and the soft magnetic filler, and the surface of the soft magnetic filler is easily exposed to an oxidizing atmosphere. It is becoming an easy-to-use environment.

  Conventionally, as a method for improving the weather resistance of metal powders regardless of spherical or flat shape, mainly using a metal powder having a high weather resistance as an alloy composition, or Ni plating on the powder surface In general, a method of forming a highly weather-resistant film is employed. However, in flat powders and soft magnetic resin compositions requiring extremely high μ ′ targeted by the present invention, μ ′ is not sufficient in a high weather resistance alloy such as so-called electromagnetic stainless steel, while permalloy or the like Fe-Ni alloys with high weather resistance are difficult to apply because of the high raw material costs. In addition, the conventional plating method for forming a highly weather-resistant film is remarkably expensive and significantly reduces μ ′ due to the effect of strain introduction accompanying the film formation. It is difficult to apply to flat powders and soft magnetic resin compositions.

  Thus, for the purpose of suppressing the generation of magnetic sheets, which has not been a problem in the past, in the present invention, the flat powder of Fe-Si-Al alloy showing a high initial permeability is extremely inexpensive, In addition, a soft magnetic flat powder having a surface film effective for improving weather resistance and having both high μ ′ and weather resistance and a soft magnetic resin composition containing the same were studied.

  As described above, the heat treatment temperature is significantly higher than the boiling point, and it is not considered that the residue of the organic solvent remains after the heat treatment. Conventionally, the separation of the flat powder and the organic solvent after flattening in the organic solvent is large. In general, sufficient filtration and separation are performed in order to reduce the drying time after separation without attention. However, in earnest studies by the inventors, it has been found that C, which is the main component of the organic solvent, is detected from the surface of the flat powder even after the flat powder after flat processing, filtration, and drying is sufficiently heat-treated. It is found that the amount of C increases with the remaining amount of the organic solvent before the drying step, and further, a film that is considered to be formed of C detected from the surface of the flat powder has a weather resistance. As a result, the present invention has been found.

  Conventionally, such a series of knowledge has not been known, and therefore, an example in which the remaining amount of the organic solvent after the filtration and separation process of the flat powder and the organic solvent was actually examined, and further, the remaining amount and the flatness were examined. There have been no examples in which the relationship between the powder and the weather resistance of the soft magnetic resin composition has been studied. In addition, regarding the occurrence of the magnetic sheet that is considered as a problem in the present invention, it is due to the recent demand for a significantly high μ ′, thinning of the magnetic sheet, which has not been a problem in the past. Therefore, as described above, the fact is that sufficient attention was not paid to the filtration and separation processes of the flat powder from the organic solvent.

  On the other hand, monitoring the “C amount / BET value existing on the surface of the flat powder”, which is the most important parameter in the present invention, is the weather resistance of each lot of the flat powder produced in the actual mass production process. In order to grasp it, it can be a very important method, and can also be used as a management method for stable weather-resistant flat powder.

The gist of the invention is that
(1) A soft magnetic flat powder comprising an Fe-Si-Al alloy and having a C amount / BET value existing on the surface of the flat powder of 0.01 or more and 1.00 or less.
(2) A soft magnetic resin composition containing the soft magnetic flat powder described in (1).

  As described above, according to the present invention, it is possible to provide a soft magnetic resin composition such as a soft magnetic flat powder having high magnetic permeability and high weather resistance and a magnetic sheet containing the same, which is used in various electronic devices.

It is a conceptual explanatory drawing which shows the characteristic which concerns on this invention.

Hereinafter, the reason for the restriction of the present invention will be described.
C amount / BET value present on the surface of the flat powder is 0.01 or more and 1.00 or less. In the present invention, the C amount / BET value existing on the surface of the flat powder is the C per unit surface area of the flat powder. Is a numerical value that affects the amount of the weather-resistant film containing, and if it is less than 0.01, the effect of improving the weather resistance is not sufficient, and if it exceeds 1.00, the volume of the Fe-Si-Al alloy part having high μ ′ Will decrease μ ′ of the flat powder. Preferably, it is more than 0.05 and less than 0.75, more preferably more than 0.07 and less than 0.50. The amount of C present on the surface of the flat powder can be calculated by subtracting the amount of C in the raw material powder before flattening with an organic solvent from the amount of C in the entire flat powder. The C amount is mass%, the BET value is a specific surface area, and the unit is m ² / g.

  Here, in the present invention, as shown in FIG. 1, the C concentrated film 2 can be formed on the surface of the Fe—Si—Al alloy flat powder 1. Thus, even after the heat treatment at a temperature sufficiently higher than the boiling point of the organic solvent, details about the cause of C remaining on the surface of the flat powder are unknown, but the following is presumed. Due to the flat processing by the ball mill, the raw material powder undergoes remarkably large processing. At this time, a part of the organic solvent present on the powder surface may react with the powder surface or may enter the crystal grain boundary of the powder and change in quality. Furthermore, at the time of drying, there is a possibility that the layer of the deteriorated product is promoted to increase in the further deteriorated layer by increasing the temperature while being in contact with the remaining organic solvent.

  In addition, the C concentration layer thickness detected when Auger analysis of the flat powder after the high-temperature heat treatment in Examples described later was in the range of more than 0.1 nm and less than 5 nm. Although the detailed structure and components are unknown, it is considered that this C concentrated layer suppresses the contact between the Fe—Si—Al alloy flat powder and the outside air or corrosive liquid, thereby contributing to improvement in weather resistance.

  Since the present invention can improve the weather resistance while maintaining the high μ ′ in the conventionally proposed Fe—Si—Al-based alloy flat powder having a high μ ′, the physical properties of the surface of the flat powder are “ As for the physical property values related to the flat powder itself other than the “C amount / BET value present on the surface of the flat powder”, those of the conventional example can be applied, but each physical property preferable for obtaining high μ ′ The range is as follows.

  In the composition of the Fe-Si-Al based alloy, Si is more than 6.5% and less than 11%, more preferably more than 7% and less than 9.5%, still more preferably more than 7.5% and less than 8%. Al is more than 4% and less than 10%, more preferably more than 5.5% and less than 9.5%, still more preferably more than 7% and less than 9%.

Moreover, an average particle diameter is 20-100 micrometers, More preferably, it is 35-80 micrometers, More preferably, it is 50-70 micrometers. The tap density is 0.50 to 1.50 Mg / m ³ , more preferably 0.55 to 1.00 Mg / m ³ , and still more preferably 0.60 to 0.80 Mg / m ³ . The coercive force measured by applying in the longitudinal direction is 24 to 800 A / m, more preferably 32 to 240 A / m, and still more preferably 40 to 120 A / m.

  The coercive force measured by applying in the thickness direction is 48 to 2000 A / m, more preferably 64 to 1000 A / m, and still more preferably 80 to 320 A / m. Coercivity measured by applying in the thickness direction / coercivity measured by applying in the longitudinal direction is 1.5 to 4.0, more preferably 2.0 to 3.5, and even more preferably 2.3 to 3. .3. The amount of oxygen is 1.5% or less, more preferably 1.0% or less, and still more preferably 0.7% or less. The amount of nitrogen is 0.50% or less, more preferably 0.10% or less, and still more preferably 0.03% or less.

The average aspect ratio is 5 or more, more preferably 15 or more, and further preferably 30 or more. The BET value is 0.5 to 1.5 m ² / g, more preferably 0.6 to 1.3 m ² / g, and still more preferably 0.8 to 1.2 m ² / g. As for the additive element, it is possible to add an element in a range that does not greatly affect the Fe—Si—Al alloy showing high initial permeability. For example, any one or more of Mn, Cr, Ni, and Cu Is preferably 5% or less, more preferably 3% or less, and even more preferably no addition. However, the scope of the present invention should not be construed as being limited by the range of these various physical property values.

Hereinafter, the present invention will be specifically described with reference to examples.
Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

(Production of flat powder)
Powders of predetermined components were prepared and classified to 150 μm or less by any of the water atomizing method, gas atomizing method, disk atomizing method, or pulverization method after alloying by casting (casting pulverization method). Various atomizations can be performed by a conventionally proposed general method. An alumina crucible is used for melting, a molten alloy is discharged from a nozzle having a diameter of 2 mm under the crucible, and high pressure water is sprayed on the molten metal to divide the molten metal. It was carried out by spraying high-pressure gas (argon or nitrogen) and dividing the molten metal, or by dividing the molten metal by centrifugal force using a rotating disk. Some of these powders were heat-treated before the subsequent flattening. The flattening process was carried out using these as raw material powders. Flattening can be performed by a conventionally proposed general method, using attritor processing, using a ball of 4.8 mm in diameter made by SUJ2, and putting it into a stirring container together with 100 g of raw material powder and various organic solvents, The number of rotations was 300 rpm.

The addition amount of the organic solvent was 100 parts by mass with respect to 100 parts by mass of the raw material powder. Although the tap density decreases with the flattening time, a small amount of powder was sampled during the flattening process, and the flattening process was completed when a predetermined tap density was obtained. After flattening, the flat powder and the organic solvent are taken out into a beaker, the supernatant liquid is discarded, and then taken out on a paper cloth laid on a classification mesh with an opening of 1000 μm and left at room temperature and normal pressure for a predetermined time. The solvent was filtered (up to 1 hour filtration). In some powders (filtered for 1 hour and the excess organic solvent was sufficiently removed), a predetermined weight of the organic solvent was added again after filtration, and the powder was also included.
With the organic solvent remaining as described above, these were transferred to a stainless steel dish and dried at 80 ° C. for 24 hours. Further, the flat powder thus obtained was heat-treated in vacuum, argon or nitrogen and used for various evaluations.

(Evaluation of flat powder)
The average particle diameter, tap density, coercive force (longitudinal direction and thickness direction), oxygen value, nitrogen value, BET value, and C concentrated layer thickness by Auger analysis were measured for the obtained flat powder after heat treatment. Average particle size is laser diffraction method, tap density is about 20g of flat powder packed in a cylinder of 100cm ³ capacity, drop height is 10mm, packing density when the number of taps is 200 times, coercive force is a commercially available coercive force meter. It was evaluated with. In addition, the C amount of the obtained flat powder after heat treatment and the raw material powder before flat processing was also evaluated, and the difference was calculated as the C amount existing on the surface of the flat powder.

(Production of magnetic sheet and evaluation of average aspect ratio and μ ')
As a configuration of the magnetic sheet other than the flat powder, a conventionally proposed general configuration can be applied, and a magnetic sheet can be manufactured by a conventionally proposed general method. Chlorinated polyethylene was dissolved in toluene, and the resulting flat powder was mixed and dispersed. This dispersion was applied to a polyester resin to a thickness of about 100 μm and dried at normal temperature and humidity. Then, it pressed at 130 degreeC and the pressure of 15 Mpa, and obtained the magnetic sheet. The size of the magnetic sheet is 150 mm × 150 mm and the thickness is 50 μm. The volume filling rate of the flat powder in the magnetic sheet was about 50%.

  Next, this magnetic sheet was cut into a donut shape having an outer diameter of 7 mm and an inner diameter of 3 mm, and the frequency characteristic of the impedance characteristic was measured at room temperature with an impedance measuring instrument, and μ ′ was calculated from the result. Here, an average value of 1 to 5 MHz was used for evaluating μ ′. Further, a resin-embedded polished sample in which the thickness direction of the obtained magnetic sheet can be observed was prepared, and the average thickness and average aspect ratio were calculated from image analysis for 50 powders randomly selected by SEM observation. The aspect ratio is “the length of the flat powder in the longitudinal direction / the thickness of the flat powder”.

(Evaluation of weather resistance of magnetic sheet)
The obtained magnetic sheet was cut out to 20 × 20 mm, immersed in a 20% NaCl aqueous solution at 60 ° C. for 100 hours, and the subsequent wrinkling state was observed. The magnetic sheet was evaluated as A where no wrinkles were observed, B as partly spot-like brownish brown discoloration, and C as the whole surface discolored brownish.

As shown in Tables 1 to 20, Tables 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 are production conditions for each raw material powder alloy composition. Tables 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 show characteristics and performance of the flat powder based on the manufacturing conditions.

  Comparative Example No. 2 shown in Table 2 No. 1 has a high surface C amount / BET value, and the value of μ ′ lacks the target value of the present invention. Comparative Example No. No. 6 has poor weather resistance because the surface C amount / BET value is 0. Similarly, the comparative example Nos. Shown in Table 4, Table 6, Table 8, Table 10, Table 12, and Table 14 were used. 7, 13, 19, 25, 31, 37 have a high surface C amount / BET value, and the value of μ ′ is lacking the target value of the present invention. Comparative Example No. Nos. 12, 18, 24, 30, 36, and 42 have poor weather resistance because the surface C amount / BET value is 0.

  In addition, Comparative Example Nos. Shown in Table 16, Table 18, and Table 20 were used. Nos. 43, 49 and 55 have poor weather resistance since the surface C amount / BET value is 0. Comparative Example No. Nos. 48, 54 and 60 have a high surface C amount / BET value, and the value of μ ′ is lacking the target value of the present invention. On the other hand, the present invention example No. 2-5, 8-11, 14-17, 20-23, 26-29, 32-35, 38-41, 44-47, 50-53, 56-59 all satisfy the conditions of the present invention. Thus, it can be seen that the high μ ′ and the high weather resistance are excellent.

  As described above, the surface of the flat powder is made of an Fe-Si-Al-based alloy, and is dried with an appropriate amount of the organic solvent remaining in the flattening treatment in the organic solvent and the subsequent filtering step of the organic solvent. C-enriched layer can be produced in this way, and this makes it possible to improve the weather resistance at low cost while maintaining the magnetic permeability (μ ′) inherent to this Fe—Si—Al alloy powder. It is effective.

1 Fe-Si-Al alloy flat powder 2 C concentrated film


Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (2)

A soft magnetic flat powder comprising an Fe-Si-Al alloy and having a C amount / BET value present on the surface of the flat powder of 0.01 or more and 1.00 or less. A soft magnetic resin composition comprising the soft magnetic flat powder according to claim 1.