JPH05175031A - Magnetic composite material and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a material suitable for a magnetic shield material by arranging a plurality of linear aggregates of ferro-magnetic fine particles almost in the same direction within a polymer matrix. CONSTITUTION:Fine particles of magnetite having adsorbed a surface active agent and linolic acid are dispersed and dissolved in hexane. A radical polymer is added to the dispersed solution of hexane to remove hexane therefrom under the vacuum condition. Thereby a magnetic fluid including a radical-polymeric monomer as the base liquid can be obtained. Camphorquinone and p- dimethylaminobenzoic acid/ethyl ester are dissolved as a polymerization initiator into this magnetic fluid under the light shielded condition to obtain the raw material of magnetic composite material. Also under the light shielded condition, only a drop of raw material is applied on a slide glass and a cover glass is put thereon. The slide glass is provided so that the liquid surface becomes parallel with the direction of magnetic field. Thereafter, after the magnetic field is applied, the light is cast while the magnetic field is applied continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic composite material composed of ferromagnetic fine particles and a polymer, which is preferably used as a magnetic shield material.

[0002]

2. Description of the Related Art Conventionally, in the development of composite materials containing fine particles, the distribution of fine particles in the base material has always been a problem. Polymers with a large difference in specific gravity between the base material and the particles
It has been an important problem in systems such as metal fine particles, polymers / oxides, or systems using ferromagnetic fine particles in which agglomeration easily occurs between the fine particles. In these systems, uneven dispersion due to sedimentation and agglomeration of fine particles easily occurs, and it is very difficult to uniformly disperse the fine particles. When a polymer is used as a base material, the problem of uneven dispersion occurs regardless of whether it is contained during molding or during polymerization. In order to suppress dispersion unevenness, measures such as increasing the viscosity of the mother liquor during polymerization and molding and adding a dispersant have been taken, but this has not solved the fundamental cause. Further, as a method for obtaining a polymer having an antistatic property and an electromagnetic wave shielding effect, stainless steel, steel,
A master pellet method in which a pellet containing fine particles / fibers such as a metal such as aluminum or an oxide such as conductive titanium oxide is preliminarily molded is mainly used. It has been pointed out that this method has a problem in that pellets having different specific gravities are mixed together during pellet production. Molding using pellets having different specific gravities causes uneven dispersion in the product.

On the other hand, a polymer containing ferromagnetic fine particles has been proposed as a lightweight magnetic shield material. As fine particles, metals such as iron, nickel and cobalt or ferrites such as magnetite, Ba ferrite, Mn ferrite and Zn ferrite are used. The particle size of the particles used varies from 0.1 μm to several mm depending on the application. Usually, the fine particles that do not exhibit magnetism tend to reduce the difference in specific gravity between pellets by reducing the particle size, and to reduce the uneven dispersion of particles in the material. However, when ferromagnetic fine particles are used, even particles having a small particle diameter form an aggregate structure and behave as aggregates, so that dispersion unevenness in the polymer cannot be easily eliminated.
This phenomenon becomes more remarkable as ferromagnetic fine particles having a high magnetic permeability are used. It is considered that a magnetic shield material having uneven dispersion does not show a uniform magnetic shield effect. In addition, the weight of the molded product varies.

[0004]

Therefore, it has been desired to develop a polymer composite material in which ferromagnetic fine particles are uniformly dispersed in a state where there is no dispersion unevenness.

[0005]

The inventors of the present invention have conducted extensive research to develop a magnetic composite material having a high degree of dispersibility and alignment, and as a result, radical-polymerized ferromagnetic fine particles treated with a surfactant. The present invention has been completed by finding that the target magnetic composite material can be obtained by dispersing and mixing in a polymerizable monomer and polymerizing, especially by photopolymerization under application of a magnetic field. That is, the present invention is a magnetic composite material characterized in that a plurality of linear agglomerates of ferromagnetic fine particles are arranged in a polymer matrix in substantially the same direction.

Another invention is to disperse and mix ferromagnetic fine particles treated with a surfactant and a photopolymerization initiator in a radical-polymerizable monomer, and then polymerize by irradiating with light under application of a magnetic field. It is a method for producing the above magnetic composite material. Still another invention is a method for producing a magnetic composite material, characterized in that ferromagnetic fine particles treated with a surfactant are dispersed in a radical polymer monomer and then polymerized. As the ferromagnetic fine particles used in the present invention, known ones can be used without limitation. Specifically, Fe, Ni, Co or alloys thereof, magnetite, Ba ferrite, Mn
Examples of the ferrite include ferrites and Zn ferrites.

The particle size of these ferromagnetic fine particles is 50 in order to uniformly disperse them in the radical-polymerizable monomer described below.
It is preferably 0 nm or less, and particularly preferably 100 nm or less. If it exceeds 500 nm, irregularly shaped aggregates tend to be formed when dispersed in a radically polymerizable monomer. The content of the ferromagnetic fine particles is 0.1 to 50% by weight based on the total amount of the magnetic composite material. In the range less than this range, the ferromagnetic fine particle aggregates are not formed even when a magnetic field is applied, and in the range over this range, the ferromagnetic fine particles are not stably dispersed.

In the present invention, in order to uniformly disperse the ferromagnetic fine particles in the radical-polymerizable monomer without agglomerating, the ferromagnetic fine particles are preliminarily treated with the following surfactants. It is necessary. As this surfactant, an amphoteric surfactant, an anionic surfactant,
Among the cationic surfactants and nonionic surfactants, preferred ones may be selected and used according to the type of the ferromagnetic fine particles.

For example, when ferrite fine particles are used as the ferromagnetic fine particles, anionic surfactants, particularly unsaturated fatty acid-based compounds such as oleic acid, linoleic acid, and linolenic acid are preferable. 0.05 to 5 times by weight, preferably 0.1 to 3 times by weight. Although nonionic surfactants can be used, it is preferable to use them in combination with the above anionic surfactants rather than using them alone. The amount of the nonionic surfactant used is 0.5 to 0.5 with respect to the ferromagnetic fine particles.
The amount is 5 times by weight, preferably 0.5 to 3 times by weight. Specific examples of the nonionic surfactant include ether type such as polyoxyethylene nonylphenyl ether and polyoxyethylene stearyl ether; ether ester type such as polyoxyethylene glycerin monostearate and polyoxyethylene sorbitan monopalmitate. Examples thereof include ester types such as polyethylene glycol monolaurate, sorbitan monopalmitate, and sorbitan trioleate; and nitrogen-containing types such as polyoxyethylene stearic acid amide and polyoxyethylene oleylamine.

When the ferromagnetic fine particles are metal, an anionic surfactant, especially N-acyl sarcosine, N-acyl-
N-acyl amino acids such as N-methyl-β-alanine are preferred. Furthermore, lauryl dimethylamino acetic acid betaine,
Amphoteric surfactants such as 2-lauryl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, N-oleyltrimethylenediamine, stearyldimethylbenzylammonium chloride, 2-methyl-N-lauryl-N-methylimidazolium. A cationic surfactant such as chloride can also be preferably used. These anionic surfactant, cationic surfactant, and amphoteric surfactant are used in an amount of 0.05 to 5 times by weight, preferably 0.1 to 3 times by weight, the amount of ferromagnetic fine particles. ..

When the amount of the above-mentioned surfactant used is less than the range, it is difficult to stably disperse it in the radical-polymerizable monomer, and when it exceeds the range, curing due to polymerization becomes insufficient and it is practical. A cured product cannot be obtained. As a method for treating the ferromagnetic fine particles with the surfactant, a known treatment method in the manufacturing process of the magnetic fluid can be adopted. For example, when Fe, Ni, Co or an alloy thereof is used as the ferromagnetic fine particles, a method of thermally decomposing or photodecomposing the carbonyl complex of the metal in the presence of a surfactant can be mentioned. An example of a method for producing Fe fine particles treated with a surfactant by thermal decomposition is as follows. Fe ₂
A carbonyl complex of Fe such as (CO) ₉ or Fe ₃ (CO) ₁₂ , a surfactant, and a small amount of a solvent such as toluene are mixed in an atmosphere of an inert gas, and these mixed solutions are mixed at the decomposition temperature of the complex. Fe particles are obtained by heating above. The target product is obtained by evaporating and removing the by-product Fe (CO) ₅ and the solvent. An example of a method for producing Ni fine particles treated with a surfactant by photolysis is as follows. Using a container such as quartz that can transmit ultraviolet rays, mix Ni (CO) ₄ , a surfactant, and a small amount of a solvent such as toluene in an inert gas atmosphere, and irradiate these mixed solutions with ultraviolet rays. Thus, Ni fine particles are obtained. The target substance is obtained by evaporating and removing the raw material Ni (CO) ₄ and the solvent.

Magnetite, Ba as ferromagnetic fine particles
When ferrites such as ferrite, Mn ferrite, and Zn ferrite are used, a method in which a ferrite colloid is synthesized by a coprecipitation method in an aqueous solution and then treated with a surfactant, and ferrite particles having a large particle size are used in a ball mill together with the surfactant. A method of crushing may be used. The method for producing the magnetite fine particles treated with the surfactant by the coprecipitation method is as follows. Fine particles of magnetite are produced by reacting an aqueous solution containing a ferrous salt and a ferric salt with an alkaline aqueous solution such as sodium hydroxide. Then, a surfactant is added to the reaction solution and heat-treated to adsorb the surfactant on the surface of the fine particles. When an unsaturated fatty acid salt is used as the surfactant, the unsaturated fatty acid salt is changed to an unsaturated fatty acid by further adding an acid such as hydrochloric acid. The desired product is obtained by washing with water and drying. An example of the method for producing the magnetite fine particles treated with the surfactant by the pulverization method is as follows. Ferrite particles having a large particle size are ground in a ball mill together with a solvent such as unsaturated fatty acid as a surfactant and water for about 2 weeks. The target product is obtained by washing the resulting fine particles with water and drying. Furthermore, when a nonionic surfactant is added as a surfactant, it can be carried out by mixing magnetite fine particles treated with an unsaturated fatty acid into a radical-polymerizable monomer containing a nonionic surfactant. .

The radically polymerizable monomer used in the present invention is
Any known material can be used as long as it can uniformly disperse the ferromagnetic fine particles treated with the surfactant and exhibits a liquid state during polymerization. However, as shown in FIGS.
In order for the magnetic composite material of the present invention to contain a plurality of ferromagnetic fine particles in the form of linear aggregates arranged in substantially the same direction, the boiling point of the radical-polymerizable monomer is 80 ° C. or higher, if possible. It is preferably 100 ° C. or higher. When a radical-polymerizable monomer having a boiling point lower than 80 ° C. is used, evaporation occurs during the application of a magnetic field described below or during polymerization, which disturbs the alignment of the ferromagnetic fine particle aggregates and causes the ferromagnetic fine particles to be linearly aggregated. It becomes difficult to obtain the above-mentioned magnetic composite material that is aggregated and includes a plurality of magnetic composite materials in substantially the same direction. In the present invention, "almost the same direction" does not refer to a state in which the elements are arranged in exactly one direction geometrically strictly, but the one that is visually judged to be arranged in one direction with a microscope or the like. To call.

The radical polymerizable monomer used in the present invention will be specifically shown below. Generally, the radically polymerizable monomer that is preferably used is a (meth) acrylate compound having the following acrylic group and / or methacrylic group. (A) Monofunctional monomer Methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, isoamyl acrylate, acrylic acid Hexyl, cyclohexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, decyl acrylate, isodecyl acrylate, dodecyl acrylate, tridecyl acrylate, benzyl acrylate, methoxydiethylene glycol acrylate, acrylic 2-hydroxyethyl acid, tetrahydrofurfuryl acrylate, glycidyl acrylate, or methacrylic acid esters thereof. (B) Bifunctional monomer

2,2-bis (acryloxyphenyl) propane, 2,2-bis [4- (3-acryloxy) -2
-Hydroxypropoxyphenyl] propane, 2,2-
Bis (4-acryloxyethoxyphenyl) propane,
2,2-bis (4-acryloxydiethoxyphenyl)
Propane, 2,2-bis (4-acryloxytetraethoxyphenyl) propane, 2,2-bis (4-acryloxypentaethoxyphenyl) propane, 2,2-bis (4-acryloxypolyethoxyphenyl) propane,
2,2-bis (4-acryloxydipropoxyphenyl) propane, 2 (4-acryloxyethoxyphenyl) -2 (4-acryloxydiethoxyphenyl) propane, 2 (4-acryloxydiethoxyphenyl) -2
(4-acryloxytriethoxyphenyl) propane,
2 (4-acryloxydipropoxyphenyl) -2 (4
-Acryloxytriethoxyphenyl) propane, 2,
2-bis (4-acryloxypropoxyphenyl) propane, 2,2-bis (4-acryloxyisopropoxyphenyl) propane, or methacrylic acid esters thereof.

1,3-butanediol diacrylate,
1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate, diethylene glycol Diacrylate, triethylene glycol diacrylate, propylene glycol diacrylate, butyl glycol diacrylate, glycerin diacrylate, or their methacrylic acid esters. (C) Trifunctional or tetrafunctional monomer Trimethylolpropane triacrylate, trimethylolethane triacrylate, pentaerythritol triacrylate, trimethylolmethane triacrylate, pentaerythritol tetraacrylate, or methacrylic acid ester thereof.

Radical polymerizable monomers other than the above (meth) acrylate compounds include vinyl esters such as vinyl propionate; vinyl ethers such as butyl vinyl ether and isobutyl vinyl ether; styrene, vinyltoluene, α-methylstyrene, chloro. Alkenylbenzenes such as methylstyrene, divinylbenzene and stilbene can also be preferably used. These radical-polymerizable monomers may be used alone or in combination.
For example, when the radical polymerizable monomer has an extremely high viscosity at room temperature or is a solid, it is preferably used in combination with a low viscosity monomer. This combination is not limited to two types and may be three or more types. Further, since a polymer composed of only a monofunctional radically polymerizable monomer does not have a crosslinked structure, the mechanical strength of the polymer generally tends to be poor. Therefore, when using a monofunctional radically polymerizable monomer, it is preferable to use it together with a polyfunctional radically polymerizable monomer.

The ferromagnetic fine particles treated with the surfactant and the radically polymerizable monomer are uniformly dispersed and mixed to prepare a liquid substance called a magnetic fluid. As a typical dispersion and mixing method of both components, ferromagnetic fine particles are directly added to a radical-polymerizable monomer, and then dispersed by stirring, homogenizer, ultrasonic irradiation, vibrating ball mill, etc., and then centrifugal separation. The method of preparing by removing particles with poor dispersibility by first, first, add ferromagnetic fine particles to a low boiling point solvent such as hexane or chloroorm, and mix by stirring, homogenizer, ultrasonic irradiation, vibrating ball mill, etc. .. After removing particles with poor dispersibility by centrifugation, this liquid is added to the radical-polymerizable monomer and the solvent is removed by evaporation or the like to obtain a magnetic fluid in which ferromagnetic fine particles are dispersed. There are ways. The obtained magnetic fluid is centrifuged or left for a long time to confirm that no precipitate is formed. The dispersibility may be examined by microscopic observation. Put a magnetic fluid between the slide glass and the cover glass, and objective lens 40 times, eyepiece 1
It can be used in the present invention as long as no aggregate is found by observing at a magnification of about 0.
It is possible to visually confirm the presence or absence of precipitation, but
Magnetic fluids with high particle concentration are very dark black and are difficult to confirm.

Polymerization is carried out after dissolving a thermal polymerization initiator, a redox type polymerization initiator, a photopolymerization initiator, etc. in the magnetic fluid. Usually, a method in which these initiators are added and dissolved after the magnetic fluid is prepared is preferably adopted, but if the conditions are such that the progress of polymerization can be suppressed, these initiators are previously added to the radical-polymerizable monomer. It is also possible to employ a method in which the above is contained and dispersed and mixed with the ferromagnetic fine particles treated with a surfactant. The magnetic fluid in which the polymerization initiator is dissolved is polymerized at room temperature under heating or light irradiation to obtain a magnetic composite material in which ferromagnetic fine particles are uniformly dispersed in the polymer matrix without agglomeration. Be done.

It can be confirmed by observation with a transmission electron microscope that the ferromagnetic fine particles are uniformly dispersed in the polymer matrix without agglomeration. The magnetic fluid containing the thermal polymerization initiator is heated to 50 to 200 ° C. under normal pressure or pressure to be polymerized and cured. The polymerization time may be 10 minutes to several hours. The heat polymerization is preferably carried out in an inert gas such as nitrogen, helium or argon. When a redox type polymerization initiator is used, a method of mixing both the magnetic fluid of the present invention to which an organic peroxide is added and the one to which a tertiary amine is added, and polymerizing and curing is generally adopted. It is preferable to carry out the polymerization in a closed container that is not in contact with air or in an inert gas such as nitrogen, helium or argon.

Specific examples of the thermal polymerization initiator include benzoyl peroxide, di-t-butyl peroxide and t.
-Organic peroxides such as butyl perbenzoate, 2,2 '
-Azobisisobutyronitrile, 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2,4-
Dimethylvaleronitrile), 2,2'-azobis (4-
Methoxy-2,4-dimethylvaleronitrile), 1,
1'-azobis (cyclohexane-1-carbonitrile), dimethyl 2,2'-azobisisobutyrate, 2,2 '
-Azobis (2-methylpropionic acid) 2,2'-azobis (2-cyclobutylpropionic acid) 2,2'-azobis [2- (3-hydroxyphenyl) butyric acid], 2,
Azo compounds such as 2'-azobis (4-nitrovaleric acid) 2,2'-azobis (4-chlorovaleric acid) are preferably used. As the redox-based polymerization initiator, the above-mentioned organic peroxide and a tertiary amine system described later can be preferably used. As an example of a typical redox-based polymerization initiator,
Benzoyl peroxide and N, N-dihydroxyethyl-p-toluidine or benzoyl peroxide and N, N-dimethyl-p-toluidine.

In order to produce a magnetic composite material having a specific structure containing fine ferromagnetic particles as linear aggregates as shown in FIGS. 1 to 8, a photopolymerization initiator is used to produce a magnetic field. It is essential to photopolymerize under the application of. For example, a system in which the initiation of polymerization occurs simultaneously with the mixing of the polymerization initiator and the polymerizable monomer is not suitable because the curing proceeds before the formation of a regular linear aggregate structure. Such systems include anionic polymerization,
Examples include cationic polymerization and radical polymerization using a redox initiator. Polymerization is not started when the polymerization initiator and the polymerizable monomer are mixed, and the system in which the polymerization is started with heating,
At the same time as heating, the thermal motion of the dispersion medium becomes violent and the alignment of the linear aggregate structure is disturbed, which is not suitable. Examples of such a system include radical polymerization using a thermally decomposable peroxide.

As the photopolymerization initiator, known ones can be used without limitation, but the boiling point is 80 ° C. or higher, preferably 100.
C. or higher is preferable. With a photopolymerization initiator having a boiling point lower than 80 ° C., evaporation occurs during application of a magnetic field or during curing, which tends to disturb the alignment of ferromagnetic fine particle aggregates. Further, those which are excited by visible light irradiation to initiate polymerization are particularly suitable. The photopolymerization initiator is generally used in combination with a photosensitizer and a photopolymerization accelerator. Examples of suitable photosensitizers include benzyl, camphorquinone, α
-Naphthyl, acetonaphthene, p, p'-dimethoxybenzyl, p, p'-dichlorobenzyldiacetyl, pentanedione, 1,2-phenathrenelenquinone, 1,4-
Α-diketones such as phenanthrenequinone, 3,4-phenanthrenequinone, 9,10-phenanthrenequinone and naphthoquinone. These photosensitizers may be used alone or in combination of two or more. Camphor quinone is most preferably used.

As the photopolymerization accelerator, N, N, -dimethylaniline, N, N, -diethylaniline, N, N, -di-n-butylaniline, N, N, -dibenzylaniline, N, N, -Dimethyl-p-toluidine, N, N,-
Diethyl-p-toluidine, N, N, -dimethyl-m-
Toluidine, p-bromo-N, N, -dimethylaniline, m-chloro-N, N, -dimethylaniline, p-dimethylaminobenzaldehyde, p-dimethylaminoacetophenone, p-dimethylaminobenzoic acid, p-dimethylamino. Benzoic acid ethyl ester, p-dimethylamino benzoic acid amino ester, N, N, -dimethylanthranilic acid methyl ester, N, N, -dihydroxyethylaniline, N, N, -dihydroxyethyl-p-toluidine, p-dimethylaminophenethyl alcohol, p-dimethylaminostilbene, N, N, -dimethyl-3,5
-Xylidine, 4-dimethylaminopyridine, N, N,
-Dimethyl-α-naphthylamine, N, N, -dimethyl-β-naphthylamine, tributylamine, tripropylamine, triethylamine, N-methyldiethanolamine, N-ethyldiethanolamine, N, N, -dimethylhexylamine, N, N, -Dimethyldodecylamine, N, N, -dimethylstearylamine, N, N,
-Dimethylaminoethyl methacrylate, N, N, -diethylaminoethyl methacrylate, 2,2 '-(n-
Butylimino) diethanol and other tertiary amines;
Typical examples are barbituric acids such as butyl barbituric acid and 1-benzyl-5-phenyl barbituric acid.

When a tertiary amine is used as a promoter, N, in which the nitrogen atom is directly substituted on the aromatic group,
N, -dihydroxyethyl-p-toluidine, N, N,
-A tertiary amine such as dimethyl-p-toluidine is more preferably used. Furthermore, in order to improve the ability to promote photopolymerization, in addition to tertiary amines, citric acid, malic acid, tartaric acid, glycolic acid, glycolic acid, α-oxyisobutyric acid,
It is effective to add oxycarboxylic acids such as 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid and dimethylolpropionic acid. These polymerization initiators are contained in the magnetic fluid in an amount of 0.001 to 5% by weight, preferably 0.01 to 5% by weight.
It may be dissolved in the range of 3% by weight. Further, an ultraviolet absorber such as 2-hydroxy-4-methylbenzophenone, a polymerization inhibitor component such as hydroquinone, hydroquinone monomethyl ether, and 2,5-di-t-butyl-4-methylphenol are added as necessary. it can. A typical method of applying a magnetic field to a magnetic fluid containing a photopolymerization initiator will be described below.

First, the magnetic fluid is inserted into a closed container so as not to come into contact with air. The material of the closed container is required to allow the light irradiation surface to transmit light used for photopolymerization. Quartz is most suitable when the light used in the photopolymerization is ultraviolet light, and glass or transparent plastic is most suitable when it is visible light. Good results can be obtained even if the material of the portion other than the light irradiation surface is a metal as long as it is not a ferromagnetic material. Before and during the application of the magnetic field, it is desirable that the closed container is not irradiated with light capable of photopolymerization. It is particularly desirable to operate in the dark.
Incidentally, it is desirable to install the electromagnet in a place where there is no vibration, and it is particularly desirable to use a vibration isolation table. This container is placed between the magnetic poles of an electromagnet capable of forming a parallel magnetic field. After the magnetic fluid in the container is left to stand, a magnetic field is applied to form linear aggregates of ferromagnetic fine particles. The strength of the applied magnetic field depends on the dispersion state of the fine particles. That is, fine particles that are stably dispersed do not form aggregates unless a strong magnetic field is applied, whereas particles that are unstable and dispersible, such as containing precipitates, form aggregates even with a slight magnetic field. . Therefore, the magnetic field strength cannot be determined unconditionally, but it is preferable to use the optimum magnetic field strength within the range of 10 Oersted to 5,000 Oersted. In order to improve the arrayability of aggregates,
It is important to use particles that are stably dispersed. In addition, the following can be mentioned as general tendencies in the relationship between the magnetic field and the formation of aggregates. The diameter of aggregates produced by the strength of the applied magnetic field does not change so much, but the line length and number of aggregates change significantly. The line length becomes longer and the number tends to increase as the strength of the magnetic field becomes stronger. The application time of the magnetic field varies depending on the magnetic field strength, the viscosity of the magnetic fluid, etc., but it is usually preferable to select the optimum application time within the range of 1 second to several tens of minutes. Aggregates are formed in a shorter time as the magnetic field becomes stronger and the viscosity becomes lower.

Next, the magnetic fluid in which the linear aggregated structure is formed is irradiated with light to polymerize and cure. Application of a magnetic field is essential at the start of light irradiation. It is desirable to continue during the light irradiation, but the application of the magnetic field may be stopped if the curing progresses moderately. The magnetic fluid containing the photopolymerization initiator exemplified above is 390 to 700 nm, preferably 4
It can be polymerized and cured by irradiating with light in the range of 00 to 600 nm. Examples of light sources in this wavelength range include halogen lamps, xenon lamps, lasers, fluorescent lamps, and the sun, but it is important that the temperature rise of the magnetic fluid due to light irradiation is small. This is because the heat generation of the magnetic fluid by the infrared rays radiated from the light source causes the alignment of the linear ferromagnetic fine particle aggregates formed by the application of the magnetic field to be disturbed. It is preferable to use light that has passed through an optical fiber or an infrared filter rather than direct light from a light source. The irradiation time varies depending on the type of the radical-polymerizable monomer used and the intensity of irradiation light, but it is generally preferable to select the optimum irradiation time within the range of 10 seconds to several hours. After the hardening of the magnetic fluid is completed, the application of the magnetic field is released to obtain the desired magnetic composite material.

A typical structure of a magnetic composite material of the present invention, which comprises a plurality of linear agglomerates of ferromagnetic fine particles arranged in substantially the same direction in a polymer matrix, is shown in FIG. Figure 8
It is illustrated in. As detailed in the section on how to apply a magnetic field,
The line length and the number of the agglomerates change largely depending on the strength of the applied magnetic field. For example, as shown in FIG. 1, a composite material containing linear aggregates having a line length that is almost completely continuous from one end to the other end of the magnetic composite material is obtained, while the kind of the radical-polymerizable monomer and the applied magnetic field are obtained. In the magnetic composite material of FIG. 5 obtained by changing the strength of the composite material, although the line length of the linear aggregate is relatively short and not completely continuous from one end to the other end of the composite material, they are almost all It is contained by being arranged in one direction and substantially in parallel.

[0029]

EXAMPLES Examples will be given below to describe the present invention more specifically, but the present invention is not limited to these examples. Example 1 FeSO ₄ .7H ₂ O and Fe ₂ (S
50 ml of a 1 molar aqueous solution of O ₄ ) ₃ · nH ₂ O was mixed with each other, and a 6N NaOH aqueous solution was added thereto with stirring until the pH reached 11.5. Heat this to 60 ℃, 1
The mixture was stirred for 0 minutes to sufficiently generate magnetite colloid. On the other hand, 7.3 g of linoleic acid was weighed in another container under nitrogen, 8.8 ml of 3N NaOH aqueous solution was added thereto, 50 ml of water was added with stirring, and the mixture was heated to 60 ° C.
After the resulting white precipitate of sodium linoleate had dissolved, the total amount was added to the previously prepared magnetite suspension and kept at 80 ° C. for 30 minutes while stirring. After cooling this, 1N
HCI aqueous solution was added to adjust the pH to 5.5, and the suspension was aggregated. Aggregates are removed by repeating washing with water,
Finally, the solid content obtained by vacuum filtration was dried at 90 ° C. under vacuum overnight. After allowing to cool to room temperature, it was taken out from the dryer.
The obtained black clay-like crude product was 14.8 g.

6.80 g of this crude product was weighed and 50 ml of hexane was added. After mixing well with an emulsifier, 800
Centrifugation was carried out for 20 minutes under 0 G of centrifugal force. The supernatant was taken and hexane was further added to adjust the volume to 50 ml. The weight of the precipitate after vacuum drying was 4.11 g.
The precipitate is magnetite fine particles adsorbed with a surfactant that cannot be dispersed in hexane. Precipitation occurs when 100 ml of isopropyl alcohol is added to the dispersion obtained by the same procedure. Centrifuge for 5 minutes under 2000 G centrifugal force,
Separate into precipitate and supernatant. The weight of the precipitate after vacuum drying was 1.13 g, and 1.56 g of a viscous liquid was obtained by removing isopropyl alcohol and hexane from the supernatant. The precipitate obtained by this operation is magnetite fine particles in which a surfactant dispersible in hexane is adsorbed.
The amount of the adsorbing surfactant determined from the carbon content by elemental analysis was 12 parts by weight. The particle size was about 10 nm when observed with a transmission electron microscope. The viscous liquid is linoleic acid dissolved in hexane. Therefore, 1.13 g of magnetite fine particles adsorbed with 12 parts by weight of a surfactant and 1.56 g of linoleic acid are dispersed and dissolved in 50 ml of hexane.

0.93 g of each radical-polymerizable monomer shown in Table 1 was added to 0.93 ml of this hexane dispersion, and hexane was removed under vacuum to use the radical-polymerizable monomer as a base liquid. A magnetic fluid was obtained. In these radical-polymerizable monomers, the magnetite particles adsorbed by the surfactant were stably dispersed, and no aggregates were observed even when observed under a microscope. Similarly, from 3.72 ml of the hexane dispersion and 0.30 g of the radical-polymerizable monomer, a magnetic fluid based on the stably dispersed monomer could be obtained. Under light shielding, 0.02 g of camphorquinone as a polymerization initiator and 0.02 g of p-dimethylaminobenzoic acid ethyl ester were dissolved in the former magnetic fluid to prepare a raw material for the magnetic composite material.

Under the light-shielding condition, one drop of the above raw material was dropped on a slide glass, and a cover glass was placed on it. Install this slide glass between the magnetic poles of an electromagnet equipped with an anti-vibration table.
Let stand for a minute. The slide glass was installed so that the liquid surface was parallel to the magnetic field direction. Then, after applying the magnetic field shown in Table 1 for 10 minutes, light irradiation was performed while continuing the application of the magnetic field. Using an optical fiber type cold light illuminator, light with an illuminance of 50,000 lx on the surface of a slide glass is mixed with a monofunctional radical-polymerizable monomer and divinylbenzene for 1 hour, and monofunctional and difunctional mixed radical polymerization is performed. The polymerizable monomer was irradiated for 10 minutes. After the irradiation was completed, the magnetic field application was released. The transmission optical microscope observation photographs of the obtained magnetic composite materials are shown in FIGS. From these photographs, it is recognized that linear ferromagnetic fine particle agglomerates are formed in the magnetic composite material, and each agglomerate is arranged and arranged in a certain direction. Further, even if the obtained magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates. This was also observed in the magnetic composite material obtained from any of the radically polymerizable monomers.

[0033]

[Table 1]

Example 2 MnSO ₄ .4-5H ₂ O, ZnSO ₄ under nitrogen
・ 7H ₂ O, 1 molar aqueous solution of Fe ₂ (SO ₄ ) ₃ .nH ₂ O was added to Mn ²⁺ : Zn ²⁺ : Fe ³⁺ = 0.5: 0.5: 2,
Preparatively mix so that the total volume becomes 100 ml.
Aqueous NaOH solution was added with stirring until the pH reached 10. This was heated to 80 ° C. and stirred for 10 minutes to generate a manganese zinc ferrite colloid. On the other hand, 7.3 g of linoleic acid was weighed in another container under nitrogen, 8.8 ml of 3N NaOH aqueous solution was added thereto, 50 ml of water was added with stirring, and the mixture was heated to 60 ° C. After the resulting white precipitate of sodium linoleate had dissolved, this total amount was added to the previously prepared manganese zinc ferrite suspension and kept at 80 ° C. for 30 minutes while stirring. After cooling this, 1N HCl aqueous solution was added to adjust the pH to 5.5, and the suspension was aggregated. The agglomerate was washed with water repeatedly to remove the electrolyte, and finally the solid content obtained by vacuum filtration was dried at 90 ° C. under vacuum overnight. After allowing to cool to room temperature, it was taken out from the dryer. The obtained black clay-like crude product was 15.5 g.

A magnetic fluid using the monomer as a base liquid was prepared in the same manner as in Example 1 except that the crude product and various radically polymerizable monomers shown in Table 2 were used. When ferrite fine particles were mixed in the radical-polymerizable monomer so as to be 5% by weight, no agglomerate was observed even when observed with a microscope. Similarly, when ferrite fine particles were mixed in an amount of 40% by weight, a magnetic fluid containing a stably dispersed monomer as a base liquid could be obtained. Under the light-shielding condition, the former magnetic fluid, camphorquinone 0.
02 g and p-dimethylaminobenzoic acid ethyl ester 0.02 g were dissolved to prepare a raw material for the magnetic composite material. One drop of the above-mentioned raw material was dropped on a slide glass under a light shield, and a cover glass was placed on it. Place this slide glass between the magnetic poles of an electromagnet equipped with a vibration isolation table.
Let stand for 0 minutes. The slide glass was installed so that the liquid surface was parallel to the magnetic field direction. Then, after applying a magnetic field of 200 oersted for 10 minutes, light irradiation was performed while continuing the application of the magnetic field. The illuminance on the slide glass surface is 50,000 using the optical fiber type cold light illuminator.
The monofunctional radical-polymerizable monomer and dibilylbenzene were irradiated with lx light for 1 hour, and the monofunctional and polyfunctional mixed radical-polymerizable monomer was irradiated for 10 minutes. After the irradiation was completed, the magnetic field application was released. The results of the transmission optical microscope observation of the obtained magnetic composite material are summarized in Table 2. Similar to Example 1, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0036]

[Table 2]

Example 3 35.0 g of Fe ₂ (CO) _{9 was} weighed out in a 3 L eggplant type flask equipped with a reflux condenser under an argon atmosphere. 10.7 g of N-acyl-sarcosine and 100 ml of toluene were further added to this container. Heating was continued for 3 hours at a bath temperature of 130 ° C. using an oil bath. After cooling, distillation under reduced pressure was performed to remove toluene and by-product Fe (CO) ₅ . By-products were completely removed by adding toluene and repeating vacuum distillation. 19.9 g of crude product was obtained. 10.0 g of this crude product and 100 ml of chloroform were thoroughly mixed in an emulsifier. It was centrifuged under a centrifugal force of 8,000 G for 20 minutes. Take the supernatant,
Chloroform was further added to adjust the volume to 100 ml. The weight of the precipitate after vacuum drying was 2.6 g. A magnetic fluid having a monomer as a base liquid was prepared in the same manner as in Example 1 using a chloroform dispersion liquid in which iron particles were dispersed and various radically polymerizable monomers shown in Table 3.

When iron fine particles were mixed in the radical-polymerizable monomer in an amount of 5% by weight, no aggregate was observed even under a microscope. Similarly, when the iron fine particles were mixed in an amount of 40% by weight, a magnetic fluid containing a stably dispersed monomer as a base liquid could be obtained. Under light shielding, 0.02 g of camphorquinone as a polymerization initiator and 0.02 g of p-dimethylaminobenzoic acid ethyl ester were dissolved in the former magnetic fluid to prepare a raw material for the magnetic composite material. One drop of the above-mentioned raw material was dropped on a slide glass under a light shield, and a cover glass was placed on it. The slide glass was allowed to stand for 10 minutes between the magnetic poles of an electromagnet equipped with a vibration isolation table. The slide glass was installed so that the liquid surface was parallel to the magnetic field direction. Then 50
After applying a magnetic field of 0 oersted for 10 minutes, light irradiation was performed while continuing the application of the magnetic field. The illuminance on the slide glass surface is 5 with the optical fiber type cold light illuminator.
The monofunctional radical-polymerizable monomer and dibilylbenzene were irradiated with light of 10,000 lx for 1 hour, and the polyfunctional mixed radical-polymerizable monomer was irradiated for 1 minute. After the irradiation was completed, the magnetic field application was released. The results of the transmission optical microscope observation of the obtained magnetic composite material are summarized in Table 3. Example 1
Similarly to the above, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state of being arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0039]

[Table 3]

Example 4 Example 4 was repeated except that the surfactants shown in Table 4 were used. The amounts of oleic acid and linolenic acid used were the same as those of the linoleic acid used in Example 1. When oleic acid and polyoxyethylenonyl phenyl ether were used, the amount of oleic acid used was 3.6 g and the amount of polyoxyethylenonyl phenyl ether used was 3.4 g. The polyoxyethylenonyl phenyl ether, hexane and the crude product were mixed with them during mixing. The radical-polymerizable monomer used was a mixed monomer composed of 80% by weight of 2-ethylhexyl acrylate and 20% by weight of 1,9-nonanediol dimethacrylate. A magnetic field of 200 Oersted was applied for 10 minutes, and 50,000 lx of light was applied for 10 minutes while continuing to apply the magnetic field. After the irradiation was completed, the magnetic field application was released. The results of the transmission optical microscope observation of the obtained magnetic composite material are summarized in Table 4. Similar to Example 1, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state of being arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0041]

[Table 4]

Example 5 The procedure of Example 3 was repeated except that the various radically polymerizable monomers shown in Table 5 were used. 1 magnetic field of 500 Oersted
Apply for 0 minutes, 50,000l while continuing to apply magnetic field
The light of x was irradiated. The monofunctional radical-polymerizable monomer was irradiated for 1 hour, and the polyfunctional radical-polymerizable monomer or a mixture thereof was irradiated for 1 minute. After the irradiation was completed, the magnetic field application was released. The results of microscopic observation of the obtained composite material are summarized in Table 5. Similar to Example 1, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state of being arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0043]

[Table 5]

Example 6 The procedure of Example 1 was repeated except that the various photosensitizers shown in Table 6 were used. The monomer used was a mixed monomer consisting of 80% by weight of 2-ethylhexyl acrylate and 20% by weight of 1,9-nonanediol dimethacrylate. A magnetic field of 200 Oersted was applied for 10 minutes, and 50,000 lx of light was applied for 10 minutes while continuing to apply the magnetic field. After the irradiation was completed, the magnetic field application was released. The results of the transmission optical microscope observation of the obtained magnetic composite material are summarized in Table 6. Similar to Example 1, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state of being arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0045]

[Table 6]

Example 7 Example 7 was repeated except that the photopolymerization accelerator shown in Table 7 was used. The radical polymerizable monomer used was acrylic acid-
It is a mixed monomer composed of 80% by weight of 2-ethylhexyl and 20% by weight of 1,9-nonanediol dimethacrylate. A magnetic field of 200 Oersted was applied for 10 minutes, and 50,000 lx of light was applied for 10 minutes while continuing to apply the magnetic field. After the irradiation was completed, the magnetic field application was released. The results of the transmission optical microscope observation of the obtained magnetic composite material are summarized in Table 7. Similar to Example 1, linear ferromagnetic fine particle agglomerates were formed, and the agglomerates were contained in a state of being arranged in a certain direction. Further, even if this magnetic composite material was left for a long time in the absence of a magnetic field, no change was observed in the arrangement of aggregates.

[0047]

[Table 7]

Application Example 1 In accordance with Example 3, a raw material for a magnetic composite material containing 40% by weight of iron fine particles was obtained by using neopentyl glycol dimethacrylate as a base liquid. 3 cm in diameter and 2 m in depth under shade
The above raw materials were filled in a split mold made of aluminum having a hole of m and pressed with a polypropylene film. This split mold was allowed to stand for 10 minutes between the magnetic poles of an electromagnet equipped with a vibration isolation table.
The split mold was installed so that the pressure contact surface was parallel to the magnetic field direction. Then, a magnetic field of 500 Oersted was applied for 10 minutes. Irradiation of light was performed while continuing to apply the magnetic field. Using an optical fiber type cold light illuminator, light having an illuminance on the slide glass surface of 50,000 lx was irradiated for 1 hour.
After the irradiation was completed, the magnetic field application was released. Then, the cured product was removed from the split mold and washed with methanol to obtain a target composite material. The magnetic shield effect was examined by using the device shown in FIG. 9, which was composed of an electromagnet and a Gauss meter. The current value of the electromagnet was adjusted so that the Gauss meter value was 100 Gauss. When the above magnetic composite material is inserted between the probe and the electromagnet, the Gauss meter value is 50 Gauss.
Decreased to. It was set so that the line connecting the probe and the electrode was perpendicular to the plane of the magnetic composite material.

Example 8 0.93 ml of a hexane dispersion of magnetite treated with the surfactant obtained in Example 1 was mixed with acrylic acid-2-
0.95 g of ethylhexyl was added, and a magnetic fluid in which magnetite fine particles were stably dispersed was obtained in the same manner as in Example 1. In this magnetic fluid, camphorquinone 0.02g and p-
Dimethylaminobenzoic acid ethyl ester (0.02 g) was dissolved to prepare a magnetic composite material. One drop of the above raw material was dropped on a slide glass, and a cover glass was placed thereon. The slide glass was heated to 50 ° C. and irradiated with light having an illuminance of 50,000 lx on the surface of the slide glass for 1 hour using an optical fiber type cold light illumination device. Observation of the fracture surface of the obtained magnetic composite material with a transmission electron microscope revealed that only fine particles having a particle size of about 10 nm were dispersed in the base material, no aggregates were observed, and the fine particles retained the dispersed state. Was there.

Example 9 0.95 g of dodecyl acrylate was added to 0.93 ml of the hexane dispersion of magnetite treated with the surfactant obtained in Example 1 to remove hexane under vacuum. A magnetic fluid was obtained using the polymer as a base liquid. In the monomer, the magnetite fine particles adsorbed by the surfactant were stably dispersed, and no aggregate was observed even under the observation under a microscope.
Under the light shielding, 0.02 g of azobisisobutyronitrile which is a thermal polymerization initiator was dissolved in this magnetic fluid to prepare a raw material for the magnetic composite material. All of the above raw materials were added to a glass ampoule having a content of about 3 ml, the atmosphere was replaced with nitrogen, and the ampoule was sealed. This was heated at 80 ° C. for 5 hours. Then, the composite material was obtained by cooling and opening, and breaking an ampoule. Observation of the fracture surface of the obtained composite material with a transmission electron microscope revealed that only fine particles having a particle size of about 10 nm were dispersed in the base material, no aggregates were observed, and the fine particles retained the dispersed state. It was

[0051]

The magnetic composite material obtained by the present invention is
It is a material containing ferromagnetic fine particles highly dispersed or further arranged linearly in substantially the same direction, and can be a material suitable as a magnetic shield material or the like.

[Brief description of drawings]

FIG. 1 is a transmission optical microscope photograph showing an aggregated state of ferromagnetic fine particles in a magnetic composite material of Example 1 No. 1.

FIG. 2 is a transmission optical microscope photograph of the magnetic composite material of Example 1 No. 2 as well.

FIG. 3 is a transmission optical microscope photograph of the magnetic composite material of Example 1 No. 3 similarly.

FIG. 4 is a transmission optical microscope photograph of the magnetic composite material of Example 1 No. 4 as well.

FIG. 5 is a transmission optical micrograph of the magnetic composite material of Example 1 No. 5 as well.

FIG. 6 is a transmission optical microscope photograph of the magnetic composite material of Example 1 No. 6 similarly.

FIG. 7 is a transmission optical micrograph of the magnetic composite material of Example 1 No. 7 as well.

FIG. 8 is a transmission optical microscope photograph of the magnetic composite of Example 1 No8.

FIG. 9 is a schematic diagram showing a situation in which magnetic flux density is measured.

[Explanation of symbols]

 1 N pole of electromagnet 2 S pole of electromagnet 3 Gauss meter probe 4 Magnetic composite material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08K 3/22 KAE 7167-4J H01F 1/04 H05K 9/00 H 7128-4E // C01G 49 / 00 B 9151-4G 49/08 A 9151-4G

Claims (3)

[Claims] 1. A magnetic composite material comprising a plurality of linear agglomerates of ferromagnetic fine particles arranged in substantially the same direction in a polymer matrix. 2. Ferromagnetic fine particles treated with a surfactant and a photopolymerization initiator are dispersed and mixed in a radically polymerizable monomer,
Next, the method for producing a magnetic composite material according to claim 1, characterized in that light irradiation is carried out under application of a magnetic field to cause polymerization. 3. A method for producing a magnetic composite material, which comprises dispersing the ferromagnetic fine particles treated with a surfactant in a radical polymer monomer and then polymerizing the dispersion.