JP7015533B2 - Magnetic materials and methods for manufacturing magnetic materials - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law 1. Publication of the proceedings by the website (1) Date of publication of the website September 26, 2017 (2) Address of the website https: // event. csj. jp / festa / program_list. php? entry = 2017 (3) Society name The Chemical Society of Japan Autumn Program 7th CSJ Chemistry Festa 2017 2. Presentation at the conference (1) Name of the conference Autumn project of the Chemical Society of Japan 7th CSJ Chemistry Festa 2017 (2) Date October 17-19, 2017

The present invention relates to a magnetic material and a method for producing a magnetic material.

Research on imparting magnetism to a material is generally carried out by compounding iron oxide magnetic particles such as Fe ₂ O ₃ and Fe ₃ O ₄ with the material, and is widely used in various fields. For example, Non-Patent Document 1 describes an example of use in the biocatalyst field, Non-Patent Documents 2 and 3 describe the field of diagnosis, and Non-Patent Document 4 describes examples of use in the field of information. It is a very useful material because it exhibits excellent magnetic field responsiveness, but since iron oxide magnetic particles are a dark brown material, they are used not only when using the magnetic particles themselves, but also in combination with other materials. Even in this case, there is a big problem that the target material is colored blackish brown. Therefore, in the conventional method, it is difficult to use the magnetic material as a color material such as a color display material or an optical material.

As a method of imparting magnetism to the target material without coloring, the surface of the material is modified by using a magnetic field-responsive surfactant. In Non-Patent Document 5, a magnetic field-responsive surfactant in which holmium, which is a kind of lanthanoid element, is combined with a general-purpose surfactant is synthesized, and when the surface of silica particles is coated, magnetism can be imparted without coloring to a magnet. It is stated that it will respond. Further, Non-Patent Document 6 describes that when the surface of polydopamine particles capable of structural color development is coated with a formium composite magnetic field responsive surfactant, the structural color is developed by applying a magnet and can be used as a coloring material. ..

M. Gijs, Chem. Rev., 2010, 110, 1518. H. Lee, Chem. Rev., 2015, 115, 10690. K. Ulbrich, Chem. Rev., 2016, 116, 5338. L. Wu, Chem. Rev., 2016, 116, 10473. G. N. Smith, J. Colloid Interface. Sci., 2014, 426, 252. A. Kawamura, Trans. Mat. Res. Soc. Jpn., 2016, 41, 301.

Conventional materials that combine iron oxide magnetic particles such as Fe ₂ O ₃ and Fe ₃ O ₄ respond to magnets in seconds to minutes. However, in the technique for modifying the surface of a material using a holmium composite magnetic field responsive surfactant shown in Non-Patent Documents 5 and 6, a system that achieves a response to a magnet over about 1 to 24 hours is disclosed. However, there remains a big problem in response speed.

Therefore, in view of the above problems, it is an object of the present invention to provide a colorless and colored magnetic field responsive magnetic material that responds to a magnet at high speed and a method for producing the same.

In order to solve the above problems, according to one aspect of the present invention, a magnetic material is provided with particles and a polymer having a β-diketone skeleton attached to the surface of the particles, and a paramagnetic lanthanoid element is added to the polymer. It was a composite.

Further, according to another aspect of the present invention, the magnetic material comprises particles and a polymer having a β-diketone skeleton attached to the surface of the particles, and the polymer is composited with holmium. Further, it is desirable that the content of holmium in the magnetic material is 0.03 mmol g ^-1 or more.

Further, according to another aspect of the present invention, the magnetic material comprises particles and a copolymer of a polymer having a β-diketone skeleton attached to the surface of the particles and a dye polymer, and a formium is compounded with the copolymer. I made it. Further, it is desirable that the particles contain silica, titania or alumina. Further, the particles may contain at least one organic compound selected from styrene-based or acrylic-based particles.

According to the present invention, it is possible to provide a colorless and colored magnetic field responsive magnetic material that responds to a magnet at high speed and a method for producing the same.

The left side of FIG. 1 shows particles having a magnetic field responsiveness complexed with holmium, and the right side of FIG. 1 shows the analysis results of TEM-EDS of the prepared particles. It is a figure which shows the problem of the conventional magnetic particle and the magnetic field responsiveness of the particle of this embodiment. It is a figure which shows the procedure of introducing holmium into a particle. It is a figure which shows the chemical formula of 2- (acetoacetyloxy) ethylmethacrilate (AAEM). It is a figure which shows the particle which has a holmium and the particle which has a polymer brush after holmium desorption. It is a figure which shows the magnetic field responsiveness of a particle by this Example.

Hereinafter, embodiments and examples of the present invention will be described, but the embodiments of the present invention are not limited to the embodiments and examples described below.

The present inventors have been diligently studying the above-mentioned problems, and found that the particulate material (see the left side of FIG. 1) coated with a polymer brush compounded with formium (Ho) is uncolored and can be magnetized. The present invention is completed by discovering that a particulate material coated with a polymer brush complexed with formium having a dye monomer introduced by copolymerization can be used as a colored magnetic material, which responds to a magnet at a higher speed than that of the above. It came to. The right side of FIG. 1 is an element mapping by TEM-EDS, and it was confirmed from the upper right figure of the right side of FIG. 1 that holmium was introduced into the produced particles. The holmium content in the magnetic material is preferably 0.03 mmol g ^-1 or more, and more preferably 0.30 mmol g ^-1 or more.

In the present embodiment, magnetism can be imparted to the material without coloring without impairing the optical characteristics of the target material. As shown in the upper part of FIG. 2, the conventional iron oxide magnetic particles are colored from brown to black, whereas the particles produced in the present embodiment are obtained when colorless silica particles are used as the base material. It can be seen that there is no coloring at all (the middle figure of FIG. 2), the particles respond to the magnet at high speed, and the particles can be recovered by the magnet in about 1 minute (equivalent to the conventional material). Further, when the red dye monomer is introduced by copolymerization, red colored magnetic particles can be produced (the lowermost figure of FIG. 2). By changing the type of dye monomer used, it is possible to add any color such as blue or green in addition to red. The size of the silica particles used in this system is about 100 nm. There has never been a magnetic particle that is submicron-sized and can be uncolored or colored in any color, and this technology can be applied to displays, simple sensors, optical devices, medical diagnostic materials, electronic paper development, and the like.

As described above, by using a holmium composite polymer material which has not been conventionally used, it is possible to provide a method for producing magnetic particles which can be colored without coloring and can be colored with any color and which responds to a magnet at high speed.

FIG. 3 shows a procedure for introducing holmium into transparent silica particles. First, a polymer brush is introduced into the silica particles by surface-initiated living polymerization. Then, holmium is introduced into the silica particles into which the polymer brush is introduced to impart magnetism.

FIG. 4 shows an example of a monomer that can be combined with a lanthanoid. FIG. 4 is 2- (acetoacetyloxy) ethylmethacrilate (2-acetoacetyloxy ethylmethacrylate, AAEM). It has a β-diketone skeleton.

The left side of FIG. 5 shows the particles having holmium, and the right side of FIG. 5 shows the particles having a polymer brush. Particles with holmium were stirred in dimethylformamide with acid. After repeated centrifugation, the supernatant (1st to 3rd) was collected and ICP-AES measurement was performed. As a result, 0.03 mmol g ^-1 to 0.30 mmol g ^-1 of holmium was introduced. It was confirmed.

FIG. 6 is a diagram showing the response behavior of the magnetic particles to a magnetic field. In 1 second the particles began to respond to the magnetic field and in 60 seconds the particles were attracted to the magnet. That is, it was found that it responds to the magnetic field in an extremely short time and at high speed.

The figure at the bottom of FIG. 2 is the result of an experiment on the magnetic field response to particles having an originally colorless polymer brush colored in red, and it was found that the particles respond to the magnetic field in a short time and at high speed.

The points of this embodiment are described below.

(1) Particles coated with a polymer having a β-diketone skeleton on the surface of silica particles were prepared by using surface-initiated living polymerization.

(2) Holmium was supported on the prepared polymer brush-coated particles.

(3) The produced magnetic field-responsive particles were uncolored.

(4) By copolymerizing the dye monomer and supporting holmium, colored magnetic field responsive particles of any color were produced.

(5) The produced uncolored magnetic field responsive particles could be accumulated in the magnet in 1 minute, and the colored magnetic field responsive particles could be accumulated in the magnet in 15 minutes, showing excellent magnetic responsiveness.

The present invention is industrially applicable as a magnetic material and a method for producing a magnetic material.

Claims (7)

A magnetic material comprising particles and a polymer having a β-diketone skeleton attached to the surface of the particles, in which a paramagnetic lanthanoid element is combined with the polymer. A magnetic material comprising particles and a polymer having a β-diketone skeleton attached to the surface of the particles, in which holmium is composited with the polymer. The magnetic material according to claim 2, wherein the holmium content of the magnetic material is 0.03 mmol g ^-1 or more. A magnetic material comprising particles and a copolymer of a polymer having a β-diketone skeleton attached to the surface of the particles and a dye polymer, in which formium is composited with the copolymer. The magnetic material according to claim 1 to 4, wherein the particles contain silica, titania or alumina. The magnetic material according to claim 1 to 5, wherein the particles contain at least one organic compound selected from styrene-based and acrylic-based. A method for producing a magnetic material, which comprises a procedure for introducing a polymer brush into particles and a procedure for introducing holmium into the polymer brush.

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