KR20060104859A - Electrical isolation method for magnetized conductive powder - Google Patents

Abstract

Coating the surface of the magnetic conductor powder particles with a perhydropolysilazane solution, and oxidizing the resulting film at room temperature to form a silica film on the surface of the conductor particles. This is provided. The silica powder-coated conductor powder particles may be pressure molded after mixing with an organic binder and a silane coupling agent.

Magnetic Conductor Powder Particles, Perhydropolysilazane Solution

Description

Electrical isolation method for magnetized conductive powder

The present invention relates to a method of insulating the surface of magnetic conductor powder particles, and in particular to a method of electrically insulating the surface of magnetic conductor powder particles with silica (SiO ₂ ).

A number of methods are known for forming a thin silica film on the surface of the conductor powder particles to impart insulation and chemical resistance of the conductor powder particles. Various methods are known, such as a method of depositing a nonmetallic material to be coated by a physical or chemical method or converting it into a non-conductive material through reaction with a surface of a conductive powder particle by a chemical. However, considering the cost required among these conventional methods and the performance of the coated non-conductive film together, the silica coating method is most preferred, and in the silica coating process, an organic silicon compound containing a silica cation is used as a conductor (metal). The most common method is to coat the surface of the powder and then transfer it to an inorganic silica film through a suitable oxidation process. In the conventional method, a sol form in which the organic silicon compound such as tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) is mainly used as a starting material and partially hydrolyzed or completely hydrolyzed thereof. Although sol is mainly used, these sols must be oxidized to a high temperature, for example, 450 ° C. or higher, in order to completely remove organic matter and transfer it to a complete silica film. However, at such a high temperature, surface oxidation of the conductor powder cannot be prevented unless an atmosphere for preventing oxidation of the conductor powder itself is separately provided. Therefore, it is impossible to suppress the change of the properties of the conductor powder.

It is an object of the present invention to provide a method for solving such drawbacks of the prior art at once.

The object of the present invention is a combination of a process of coating the surface of the conductor powder particles with a solution of perhydropolysilazane (PHPS) and a process of oxidizing the resulting film at room temperature to form a silica film. It is achieved by the method of the invention, characterized in that. Another object of the present invention is to be achieved by the method of the present invention further comprising the step of mixing the conductive powder particles formed with the silica film with an organic binder and a silane coupling agent to obtain a press molded body of magnetic conductor powder particles. Can be.

라는 상품명으로 시판되고 있다. 이 제품은 주성분이 PHPS, 유기 용매, 미량의 촉매를 함유하는 제품이다. 유기 용매는 사용 목적에 따라 선택되는데, 케톤, 알콜 또는 에스테르 등과 같이 물에 용해되는 용매는 사용할 수 없고, 크실렌 등의 고비점 방향족 용매가 주로 사용된다. 또한, 촉매는 수분과의 반응을 촉진시킬 수 있는 것들이 선택되지만, 현재 시판 중인 것은 주로 아민계 촉매가 미량 첨가되어 있는 것이다. 주성분인 상기 PHPS는 불활성 분위기하에 고온 (약 450℃) 소성하면, 촉매 작용에 의하여 대기 중의 수분 및 산소와 반응하여 탈수소화 반응을 일으켜 치밀한 고순도의 비결정질 실리카를 형성할 수 있는 화합물이다. 이러한 성질 때문에, PHPS는 최근에 방오(防汚), 방식(防蝕), 내열 피막 재료 등으로 이용되고 있다. The perhydropolysilazane (PHPS) is a complete inorganic polymer containing "-(SiH ₂ NH)-" which is composed of only Si-H, NH, and Si-N, not containing carbon (C), and repeating units, AQUAMICA by Clariant Japan Kabushikaisha [Clariant (Japan) KK]

It is marketed under the brand name. This product contains PHPS, organic solvent and trace catalyst as main components. The organic solvent is selected according to the purpose of use, and solvents dissolved in water such as ketones, alcohols or esters cannot be used, and high boiling aromatic solvents such as xylene are mainly used. In addition, the catalyst is selected to be capable of promoting the reaction with water, but commercially available is mainly the addition of a small amount of the amine catalyst. The main component, PHPS, is a compound capable of forming dense, high-purity amorphous silica when calcined at high temperature (about 450 ° C.) under an inert atmosphere and reacting with moisture and oxygen in the air by catalytic action to cause dehydrogenation. Because of these properties, PHPS has recently been used as antifouling, anticorrosion, heat resistant coating materials and the like.

용액)을 자성 도전체 분말 입자에 피복함으로써, 피복 후 실리카로의 전이에 필요한 소성 온도를 획기적으로 낮출 수 있고, 이에 따라 도전체 분말 입자가 산화되는 등의 부작용을 예방할 수 있었다. In the present invention, the PHPS solution (AQUAMICA

By coating the magnetic conductor powder particles with the solution), the firing temperature required for transition to silica after coating can be drastically lowered, thereby preventing side effects such as oxidation of the conductor powder particles.

In general, in the case of, for example, a conventional Si-based organic compound (alkoxide) sol which is used to form a silica film on the surface of a conductor powder particle, as shown in Scheme 1 below, a hydroxide formed by a hydrolysis reaction ( From the silicon compound in the form of hydroxide), a silica film is formed through the reactions of Schemes 2a and 2b below depending on the environment in the sol.

In each said reaction formula, M is Si metal ion and R is an alkyl group.

In Schemes 2a and 2b, water and alcohol are produced as by-products with the formation of Si—O bonds, and these water and alcohols are completely removed in a gaseous state at a firing temperature of 450 ° C. or higher, so that the transition to a complete silica film is possible. .

On the other hand, the PHPS solution according to the present invention is oxidized by reaction with moisture and / or oxygen in air according to the following Reaction Scheme 3 at room temperature to form a silica film.

SiO ₂ + NH ₃ ↑ + 2H ₂ ↑ -(SiH ₂ NH)-+ 2H ₂ O (+ O ₂ )

SiO ₂ + NH ₃ ↑ + 2H ₂ ↑

If necessary, in order to increase the reaction rate of Scheme 3, the reaction system is heated to a low temperature of PHPS boiling point (boiling point of solvent xylene: about 137 to 144 占 폚), that is, about 150 to 450 占 폚. Also good.

When comparing the conventional method using the Si-alkoxide-based organometallic compound as the coating substrate and the method of the present invention using the inorganic polymer of the PHPS as the coating substrate, the biggest difference is the by-products involved in the production of Si-O bonds. This is a gas, not a liquid such as water and alcohol. Therefore, according to the method of the present invention, the formation rate of the silica film is very fast at the same temperature, and problems such as deterioration of the density of the silica film, which may be caused when the liquid by-products are vaporized and removed, do not occur. For this reason, according to the present invention, the insulation resistance of the magnetic conductor powder particles having the same thickness (for example, ˜500 kPa) and the magnetic conductor powder particles having the silica film formed by the conventional method in terms of stability at high temperature standstill are obtained. It is greatly increased compared with the molded body.

Hereinafter, the preparation and implementation steps of the method of the present invention will be described.

1) Compared with the metal powder from the specific surface area calculated from the average particle diameter of the magnetic conductor metal powder (average particle diameter 10 ^-1 to 10 ^-2 μm) or the specific measured surface area and silica film and thickness to be formed on the metal powder surface. Determine the weight ratio of the coating solution.

용액)을 혼합한다.2) metal powder and coating liquid according to the determined weight ratio (AUUAMICA)

Solution).

3) The solvent is evaporated while slowly stirring the mixture of the coating liquid and the metal powder below the boiling point of the coating liquid (room temperature ~ 50 ° C).

4) After evaporation of the solvent, heat-treat at 100 ~ 250 ℃ for 10 ~ 60 minutes to transfer the coated film to silica.

5) A metal powder coated with silica is mixed with a modified phenol / epoxy binder of 1-7% by weight of the metal powder and a coupling agent of 0.1-1% by weight of the metal powder. The binder is used as a liquid dissolved in an acetone / butanol mixed solvent in order to facilitate uniform mixing with the metal powder.

6) The solvent is evaporated off while stirring the mixture of the metal powder, the binder solution, and the coupling agent coated with silica slowly below the boiling point of the binder solution (at room temperature to 50 ° C).

7) After evaporation removal of the solvent, heat treatment at 100 ~ 250 ℃ for 10 to 60 minutes to completely remove the organic solvent remaining in the binder solution.

8) The binder mixture prepared in the above manner is sieved to form granules having a particle diameter of 50 to 150 μm. The granulating operation helps to improve the flow of the powder in the mold during press molding, which helps to uniform the density of the molded body.

9) Put the appropriate amount of powder into the appropriate mold, press molding at 1.0 ~ 2.0 GPa, remove it from the mold and cure for 20 to 60 minutes at the temperature of 120 ~ 180 ℃ to complete the molded body.

The process of 1) to 4) can be collectively processed using a spray drying furnace in the mass treatment at the time of mass production, and the process of 5) to 7) can be collectively processed using the spray drying furnace in the mass powder treatment at the time of mass production.

In the practice of the present invention, the amount of PHPS used should be appropriately adjusted according to the type, particle size, purpose of use, etc. of the magnetic conductor powder particles to be coated, but in general, 0.5 to 0.5 unit weight of the magnetic conductor powder particles. An amount of 1.5% is appropriate. If it is less than 0.5%, the insulating film formed on the surface of the powder is so thin that it is difficult to form uniformly, so that the function as an insulating film is weakened, and if it exceeds 1.5%, the magnetic properties of the powder itself are greatly deteriorated.

In the present invention, a known organic binder solution and an epoxy functional silane (eg, 3-glycidoxypropyltriethoxysilane) or an amino functional silane (eg, N-2 (aminoethyl) ) By mixing a known appropriate coupling agent alone or a mixture of 3-aminopropyltrimethoxysilane) and pressure molding in a predetermined mold, so that each conductive powder particle is electrically changed without altering its electrical and magnetic properties. A molded article that is an insulator can be obtained. In the present invention, usable organic binders include thermosetting resins such as phenol resins, epoxy resins, urethane resins, polyimide resins, and the like. Among them, phenol resins and epoxy resins can be easily used, bonding strength, and price. It is advantageous in the back. The amount of the organic binder used is 0.5 to 5% per unit weight of the conductor powder particles. As the coupling agent useful in the present invention described above, a silane coupling agent such as 3-glycidoxypropyltriethoxysilane or N-2 (aminoethyl) 3-aminopropyltrimethoxysilane may be used for the type of organic binder to be used. Can be selected accordingly. This coupling agent can be used in the ratio of 0.1 to 1% with respect to the unit weight of conductor powder particle. In this way, the coated magnetic conductor powder compact has excellent magnetic properties but has a low electric resistance, thereby greatly expanding the application range of the magnetic metal.

EXAMPLE

1. Preparation of Sample

25 g of dry carbonyl iron powder having an average particle size of 0.5 to 10 μm was immersed in 4 g of a PHPS solution (solvent: m -xalene), and then 30 minutes at a temperature below the boiling point (140 ° C.) of the solution. After the above drying was carried out to remove the solvent, the mixture was further maintained at a temperature of 200 ° C. for at least 30 minutes to obtain 25.2 g of carbonyl iron coated with a silica film. Subsequently, 1.3 g of a 40% dilution solution of a mixed binder of a phenyl resin and an epoxy resin (solvent = acetone + methanol) as an organic binder and 0.1 g of an epoxy silane and an amino silane mixture (1: 1) were added as a coupling agent and sufficiently mixed. The solvent was then removed at 80 ° C. and then held at 130 ° C. for 20 minutes to partially cure the organic binder coated on the metal powder surface. Subsequently, the resultant was sifted into granules having a particle size of ˜100 μm, press-molded under molding conditions of 2.0 Gpa, removed from the mold, and cured at a temperature of 160 ° C. for 40 minutes to obtain 1 g of a molded product sample (sample 1). For control purposes, 1 g of a molded article was obtained in the same process using 5.2 g of TMOS sol (5% solids) instead of the above PHPS solution (Sample 2). The molding conditions of each of these molded bodies are summarized in Table 1 below. In Samples 1 and 2, the weight increase of the metal powder was calculated from the theoretical density of silica in terms of the silica film weight. As a result, the thickness (silica) of each sample was about 500 kPa on average.

Conductor powder Coating liquid bookbinder Molding pressure Curing conditions Sample size Sample 1 Carbonyl iron PHPS solution ^* Phenolic Resin or Epoxy Resin 0.5 ~ 1.5 Gpa 120 ~ 180 ℃ 15 ~ 60 minutes 8.5 Φ t = 1.3 mm Sample 2 TMOS Sol

용액* AQUAMICA

solution

2. Measurement of the characteristics of the sample

In each sample of Table 1, molding densities and resistance values of (Table 2) and (Table 3) when the organic binder and the silane coupling agent were not used were measured, respectively. The density was calculated by measuring the weight and volume, and the resistance was measured by using an LCR meter after forming an electrode by coating and curing Ag paste to a predetermined width on both sides of the sample.

sample Molding density Resistance immediately after molding Resistance after completion of curing Resistance after 100 hours of high temperature One ~ 6.2 g / cc 300 mm / mm 250 mm / mm 10 mm / mm 2 ~ 6.2 g / cc 6 mm / mm 4.5 mm / mm 0.1 mm / mm

sample Molding density Resistance immediately after molding Resistance after completion of curing Resistance after 100 hours of high temperature 3 ~ 6.2 g / cc 1.5 GΩ / mm 1.3 GΩ / mm 1.3 mm / mm 4 ~ 6.2 g / cc 75 mm / mm 55 mm 1.5 mm / mm

As can be seen from Tables 2 and 3, the samples 1 and 2 exhibiting the same molding density shows that there is no difference in the compactness of the film of the microstructure according to the difference in the coating liquid. However, in the resistance value after long time (100 hours) high temperature standing closely related to not only resistance but also high temperature reliability upon application to electronic products immediately after molding and curing, Sample 1 shows a remarkable improvement over Sample 2. From these data, it can be seen that the silica film formed by the PHPS solution used in the method of the present invention exhibits very good insulating properties compared to the conventional one.

In addition, from the data in Table 3, when the organic binder and the silane coupling agent are mixed and molded under the conductor powder particles having a silica film coated on the surface by using a PHPS solution as the coating material, the insulating properties of the conductor powder particles are further reduced. It can be seen that the increase.

The press-molded article according to the present invention has the effect of obtaining magnetic conductor powder particles which are electrically non-conducting while maintaining the electrical and magnetic properties thereof. Therefore, according to the present invention, it is possible to significantly widen the application range of the magnetic metal, which is excellent in magnetic properties but low in electrical resistance and has been restricted in its use range.

Claims (3)

A magnetic method characterized by combining the process of coating the surface of the magnetic conductor powder with a perhydropolysilazane solution, and consequently oxidizing the film formed on the surface of the conductor powder particles at room temperature to form a silica film. Electrically insulating method of conductive powder particles. The method of claim 1, further comprising a step of mixing the silica powder-coated conductor powder particles with an organic binder and a coupling agent followed by pressure molding. The method of claim 2, wherein the organic binder is a phenol resin and an epoxy resin and the coupling agent is a silane coupling agent.