JP2008195826A - Magnetic responsive material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic responsive material having variation characteristics of modulus of elasticity which is totally different from a conventional material. <P>SOLUTION: In the magnetic responsive material, non-spherical magnetic particles are dispersed in a viscous-elastic material, and the non-spherical magnetic particles are oriented in the viscous-elastic material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a magnetically responsive material and a manufacturing method thereof.

A material in which a magnetic material such as iron powder is uniformly dispersed in a rubber-like or gel-like polymer material is known to change its elastic modulus according to the strength of the magnetic field when a magnetic field is applied. Utilization of these properties is expected for applications as anti-vibration / damping materials and energy transmission materials. And the mechanism by which the elastic modulus changes with such a material is explained as follows.

When a magnetic field is applied to a material in which a magnetic material is uniformly dispersed, the dispersed particles are magnetically polarized because the magnetic moment existing in the dispersed particles (magnetic particles) is directed in a certain direction along the direction of the lines of magnetic force. A magnetic coupling is formed between them, and this coupling force increases the elastic modulus of the entire material. On the contrary, when the magnetic field is removed, the magnetic coupling between the dispersed particles is canceled, and the elastic modulus of the entire material is lowered to the original state. Moreover, even if a magnetic field is continuously applied, the elastic modulus corresponding to the strength of the magnetic field is constant (for example, Patent Document 1).

While it has been possible to obtain the above-described characteristics by using such a material, it has also been desired to provide a material that exhibits completely different characteristics (such as a change characteristic of elastic modulus).
JP-A-4-266970

The present invention has been made in view of the above situation, and an object of the present invention is to provide a magnetic response material having a change characteristic of elastic modulus completely different from that of a conventional material.

The present invention relates to a magnetic response material in which non-spherical magnetic particles are dispersed in a viscoelastic material, wherein the non-spherical magnetic particles are oriented in the viscoelastic material. Material.

When the magnetic responsive material magnetizes magnetic particles by applying a magnetic field to the magnetic responsive material, the elastic modulus E ₁ (MPa) before application of the magnetic responsive material and the elastic modulus E ₂ ( MPa) is the following formula (1);
_{E 1 -E 2> 0 (MPa} ) (1)
It is preferable to satisfy | fill the relationship represented by these.

The magnetically responsive material preferably includes non-spherical magnetic particles in which part of the surface of the particles is in contact with the surface of another non-spherical magnetic particle.
The magnetically responsive material preferably includes nonspherical magnetic particles having an acute angle formed by the orientation directions of the nonspherical magnetic particles.
The content of the non-spherical magnetic particles is preferably 1 to 45% by mass.
The viscoelastic material is preferably a polyurethane elastomer.

The present invention is also a method for producing the above-described magnetically responsive material, wherein a raw material composition containing a viscoelastic material and non-spherical magnetic particles is molded while applying a magnetic field, It is also a method for producing a magnetically responsive material, comprising a step of dispersing and orienting non-spherical magnetic particles.
Hereinafter, the present invention will be described in detail.

[Magnetic Responsive Material of the Present Invention]
As will be described below, the magnetically responsive material of the present invention has completely different properties from those conventionally known.
The magnetically responsive material of the present invention, when a predetermined magnetic field is applied to the material for a predetermined time to magnetize non-spherical magnetic particles in the material, the elastic modulus of the material before the magnetic field is applied, and after the application When the elastic modulus of each of the materials is measured, the elastic modulus is greatly reduced after application compared to before application.

On the other hand, in a conventionally known material, when the elastic modulus before and after application of a magnetic field is measured in the same manner, it has substantially the same elastic modulus before and after application.
Thus, the magnetically responsive material of the present invention and the conventional material have completely different properties in that the elastic modulus changes before and after the application of the magnetic field. Therefore, it is clear that both materials have their elastic modulus varied by a fundamentally different mechanism, and have completely different properties.

The mechanism by which the magnetically responsive material of the present invention lowers its elastic modulus by applying a magnetic field is not clear, but the magnetic particles formed in the magnetically responsive material have a dominant influence on the elastic modulus. It can be inferred that the relatively rigid aggregate structure consisting of physical contact causes distortion due to magnetization and changes the physical contact state of the magnetic particles.

In other words, since the viscoelastic material in which magnetic particles are dispersed exhibits the Pain effect (a phenomenon in which the elastic modulus suddenly decreases nonlinearly with an increase in strain), a small amount of strain is applied to the magnetically responsive material by applying a magnetic field. In contrast to the high modulus of elasticity due to the formation of structures with many physical contacts of non-spherical magnetic particles in the material before the application of a magnetic field It is surmised that after application, the elastic modulus was greatly reduced due to the reduced contact.

In the magnetically responsive material of the present invention, the non-spherical magnetic particles are oriented and dispersed in the viscoelastic material. For this reason, the magnetically responsive material not only has the above-described property (the property that the elastic modulus is greatly reduced after application of a magnetic field), but this property is very efficient as described below. It is a material to be demonstrated.

By simply having the above properties, a sufficient change in elastic modulus cannot be obtained unless a relatively large amount of non-spherical magnetic particles having a large specific gravity are dispersed in a viscoelastic material. And there is a problem that the weight increases. In addition, since the dispersion amount (blending amount) of the magnetic particles in the raw material solution or melt is large before molding, the viscosity of the solution or melt increases, making it difficult to disperse the magnetic particles or evenly mix the blending materials. Thus, there is a problem that the moldability and productivity of the magnetically responsive material are lowered. Furthermore, since the magnetic particles are simply dispersed in the viscoelastic material, the magnetic particles are not in contact with each other, and there are a large number of magnetic particles dispersed alone (magnetic particles that do not contribute to a decrease in elastic modulus). There is also a problem.

The magnetically responsive material of the present invention is formed by orienting non-spherical magnetic particles in a viscoelastic material by molding a raw material composition constituting the material and applying a magnetic field thereto to magnetize the magnetic particles. It is dispersed. For this reason, it is speculated that the magnetically responsive material is in a state in which many magnetic particles are in contact with each other (a state in which the magnetic particles are in contact with each other at least one point).

That is, in the present invention, the dispersed magnetic particles are positively oriented to bring the magnetic particles into contact with each other more efficiently, and the amount of magnetic particles that do not contribute to a decrease in elastic modulus is reduced. Even if the amount of dispersion (blending amount) is small, the elastic modulus can be greatly reduced. In addition, since the amount of magnetic particles can be reduced, the increase in viscosity of the solution or melt before molding can be suppressed, contributing to improvement in moldability and productivity of magnetically responsive materials. Can do.

As described above, the magnetically responsive material of the present invention has the property that it responds at a high speed to the application of a magnetic field and greatly reduces the elastic modulus extremely efficiently, and has also been reduced without continuing to apply a magnetic field. The elastic modulus can be maintained. In addition, since a large current is not required as a drive source, a safe device with low energy consumption can be constructed. Furthermore, the shape design is easy and the durability is excellent. Therefore, it can be expected to be applied to energy absorption / transmission devices, anti-vibration / isolation devices, camera shake correction devices for digital cameras, switches, sensors, actuators and the like.

The magnetically responsive material of the present invention is obtained by dispersing nonspherical magnetic particles in a viscoelastic material, and the nonspherical magnetic particles are oriented in the viscoelastic material. By dispersing and orienting the above-mentioned non-spherical magnetic particles in a viscoelastic material, even if the amount of magnetic particles is small, the elastic modulus of the material decreases well before and after applying a magnetic field. Can be made. In the magnetically responsive material, the magnetic particles are in contact with each other and dispersed before magnetization, whereas after the magnetization, the contact state of the particles changes and is dispersed (the contact is dispersed). Therefore, it is assumed that the elastic modulus is greatly reduced.

In the present invention, non-spherical magnetic particles are oriented in the viscoelastic material when the non-spherical magnetic particles are aligned in substantially the same direction in the viscoelastic material and arranged over the entire sample. Means. Thereby, the property mentioned above can be exhibited efficiently. The orientation of the non-spherical magnetic particles is preferably by applying a magnetic field.

As the magnetic responsive material of the present invention, as a non-spherical magnetic particle in the viscoelastic material, a part of the surface of the particle (the surface of the non-spherical magnetic particle) is the surface of the other non-spherical magnetic particle (the relevant Those including those in contact with the surface of nonspherical magnetic particles other than nonspherical magnetic particles are preferred. When such contact exists, the above-described properties can be satisfactorily exhibited even when the amount of non-spherical magnetic particles is small. In the viscoelastic material, when a part (one point or more) of the surface of each non-spherical magnetic particle is in contact with the surface of another non-spherical magnetic particle, it contacts at two or more sites (two points). More preferably. In particular, it is preferable that contact is made in the vicinity of both end portions on the surface of the non-spherical magnetic particles. In this case, the above-described properties can be obtained more efficiently.

The magnetically responsive material of the present invention preferably includes a non-spherical magnetic particle having an acute angle formed by the orientation direction of each non-spherical magnetic particle in the viscoelastic material. Thereby, even when the amount of non-spherical magnetic particles is small, the above-described properties can be exhibited well. Here, the angle formed by the orientation directions of the non-spherical magnetic particles refers to the direction in which a certain non-spherical magnetic particle in the viscoelastic material is oriented and the other non-spherical magnetic particles are oriented. It means the angle made with the direction. The angle is more preferably 30 ° or less, still more preferably 10 ° or less, and most preferably 0 ° (all magnetic particles are oriented in the same direction). In this case, the above-described properties can be obtained more efficiently.

Hereinafter, the magnetically responsive material of the present invention in which non-spherical magnetic particles are dispersed and oriented in a viscoelastic material will be described more specifically with reference to the drawings.
FIG. 1 shows an example of a schematic diagram of a magnetically responsive material 1, in which each particle of non-spherical magnetic particles 3 is randomly dispersed in a viscoelastic material 2. . In the magnetically responsive material 1, the nonspherical magnetic particles 3 are not in contact with each other. Thus, since the non-spherical magnetic particles are randomly dispersed and the particles are not in contact with each other, the above-described properties cannot be efficiently exhibited when the amount of the magnetic particles is small.

On the other hand, FIG. 2 shows an example of a schematic diagram of the magnetically responsive material of the present invention. In the magnetically responsive material 11, it is shown that the nonspherical magnetic particles 13 are dispersed in the viscoelastic material 12 and are oriented in substantially the same direction (arrow direction). Further, a state in which a part of the surface of each particle of the non-spherical magnetic particle 13 is in contact with the surface of another non-spherical magnetic particle 13 is shown (in FIG. 2, one point or two on the particle surface). Point touch).

3 is an enlarged view of the non-spherical magnetic particles 13a and 13b existing in the viscoelastic material 12 of FIG. 2, and is a schematic diagram showing an angle 14 formed by the orientation directions of the respective particles 13a and 13b. It is an example. FIG. 3 shows that the orientation direction of both particles forms an acute angle. In the present invention, as shown in FIGS. 2 and 3, the non-spherical magnetic particles 13 are dispersed and oriented in the viscoelastic material 12 (preferably a part of the surface of each particle is other). Even when the amount of non-spherical magnetic particles is small, it is possible to satisfactorily exhibit the property that the elastic modulus is greatly reduced after application of a magnetic field.

The primary particle shape of the magnetic particles contained in the magnetically responsive material of the present invention is a non-spherical shape. When spherical magnetic particles are used, a large change in elastic modulus before and after application of a magnetic field cannot be expressed. This is presumably because the magnetic particles in the viscoelastic material become weakly caught. The primary particle shape of the magnetic particles can be confirmed, for example, by observation with a scanning electron microscope (SEM) or an upright microscope.

In the present invention, the non-spherical particles are particles having a shape other than a true spherical shape, and are polygonal shapes such as three to hexagonal shapes, needle shapes, columnar shapes, beaded shapes, rod shapes, plate shapes, massive shapes, fibrous shapes, spindles , Cubic shapes, rectangular shapes, scaly shapes, irregular shapes, whisker-like particles and the like can be used. In addition, dry powders of magnetic particles that are actively non-sphericalized by crushing, pulverizing, cutting, or the like on the magnetic particles, or sludges of the magnetic particles can be used. Among these, as the non-spherical particles, it is preferable to use magnetic particles with many irregularities or magnetic particles with a high aspect ratio from the viewpoint that the elastic modulus of the material is effectively lowered before and after the application of the magnetic field. It is also preferable to use needle-like, columnar, rod-like, fibrous, rectangular, or whisker-like particles.

The non-spherical magnetic particles are preferably particles having an aspect ratio of 1.10 or more, more preferably 1.5 or more. If it is 1.10 or more, the property of lowering the elastic modulus can be obtained by applying a magnetic field, but the effect of orientation due to the magnetic field is fully expressed, the amount of magnetic particles is reduced, and the magnetic energy required for orientation For the purpose of reducing and improving the degree of orientation, it is more preferably 1.5 or more. In the present specification, the aspect ratio is the ratio (DS / DL) of the minimum diameter (DS) to the maximum diameter (DL) of the particles, for example, a scanning electron microscope (SEM), an upright microscope, a flow type particle. As a result of observation by the image analyzer, it can be calculated by the ratio of the minimum diameter to the maximum diameter observed.

The major axis diameter (maximum diameter, DL) of the non-spherical magnetic particles is preferably 1000 μm or less, and those treated as normal fine particles in the range of 0.001 to 1000 μm can be used. If it exceeds 1000 μm, the moment of inertia when orienting the magnetic particles becomes too large, and not only a large energy is required for the orientation but also the degree of orientation may be lowered. In addition, since the mass of the magnetic particles themselves increases, the magnetic particles settle in the viscoelastic material, and it may be difficult to uniformly disperse and orient them. The major axis diameter is preferably from 0.01 to 100 μm, particularly preferably from 0.5 to 20 μm.

In this specification, the major axis diameter of non-spherical magnetic particles is taken by SEM photography, the major axis diameter (maximum diameter) of any number of particles (5) is measured, and this arithmetic average value is used. This is the value obtained.

The magnetic particles are not particularly limited as long as they are magnetic substances. For example, ferrites such as barium ferrite, strontium ferrite, magnesium ferrite, sodium ferrite; iron, iron nitride, iron carbide, carbonyl iron, carbon steel, nickel Magnetic iron oxides such as chromium oxide, iron oxide, γ-iron oxide, cobalt-containing magnetic iron oxide; aluminum-containing iron alloy, silicon-containing iron alloy, cobalt-containing iron alloy, nickel-containing iron alloy, vanadium-containing iron alloy Iron alloys such as molybdenum-containing iron alloys, chromium-containing iron alloys, tungsten-containing iron alloys, manganese-containing iron alloys, and copper-containing iron alloys; rare earth magnets such as alnico magnets, samarium magnets, and neodymium magnets; gadolinium and gadolinium organic derivatives; , Carbon nanotube, carbon nanoho It can be given to the hematite, magnetite, goethite, paramagnetic such as carbon fiber, superparamagnetic or ferromagnetic compound particles; emissions, carbon nano coils, carbon nanofiber. These magnetic particles may be used alone or in combination of two or more.

Among the above magnetic particles, ferrites and magnetic iron oxides that tend to have an agglomerated structure in the viscoelastic material are preferable from the viewpoint that the elastic modulus of the material can be efficiently reduced before and after the application of the magnetic field. Barium ferrite, strontium Ferrite and γ-iron oxide are particularly preferred.

The magnetic particles may be those obtained by subjecting the surface of these magnetic particles to a surface treatment. Examples of the magnetic particles (surface-treated magnetic particles) having a surface treated on the surface include those obtained by treating the surface of the magnetic particles with a silane coupling agent.

Examples of the surface-treated magnetic particles include those obtained by treating the surface of magnetic particles with a silane coupling agent containing an epoxy group or an amino group. The silane coupling agent containing an epoxy group or amino group is not particularly limited as long as it is a silane coupling agent containing at least one epoxy group or amino group in one molecule, but is represented by the following formula (2). The compound to be used is preferably used.

X- (Y) -SiR _3-b L _b (2)
In the formula, X represents an epoxy group, a cyclic epoxy group or an amino group. Y represents (CH ₂ ) _k or a hydrocarbon group containing an ether bond, an ester bond or a ketone bond. k represents an integer of 1 to 4. R represents an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group. L represents an alkoxyl group such as a halogen atom, a hydroxyl group, a methoxyl group, an ethoxyl group, a propoxyl group, or a butoxyl group, or an acyloxyl group such as a formyl group, an acetoxyl group, a propionyloxyl group, or a butyryloxyl group. b represents an integer of 1 to 3.

As a method for treating the surface of the magnetic particles with a silane coupling agent containing an epoxy group or an amino group, for example, a solution in which the silane coupling agent containing the epoxy group or amino group is dissolved in a solvent such as alcohol In addition, the magnetic particles may be immersed, or the silane coupling agent solution may be sprayed onto the magnetic particles and then the solvent is volatilized. Furthermore, after volatilizing the solvent, heat treatment may be performed at 40 to 150 ° C. for 5 minutes to 24 hours.

In the magnetically responsive material of the present invention, the amount of magnetic particles to be blended depends on its size and shape, aspect ratio, magnetization characteristics, ease of orientation in a magnetic field, and how it aggregates in a viscoelastic material. Since it greatly depends, it is possible to set an appropriate amount as appropriate. This is presumably because the elastic modulus change in the magnetically responsive material is based on the change in the contact state between the magnetic particles before and after the application of the magnetic field.

Thus, in the magnetic responsive material of the present invention, the content of the magnetic particles is not particularly limited, but is preferably 1% by mass or more in 100% by mass of the magnetic responsive material. Thereby, since the magnetic particles are dispersed and oriented in the viscoelastic material and the magnetic particles are sufficiently in contact with each other, the above-described properties can be obtained satisfactorily. It is more preferably 1 to 45% by mass, and further preferably 5 to 30% by mass.

As described above, the magnetically responsive material of the present invention is obtained by dispersing non-spherical magnetic particles in a viscoelastic material. Thereby, the characteristic that the elasticity modulus of a material falls efficiently before and after the application of a magnetic field can be acquired.

The viscoelastic material is a material having both properties of viscosity and elasticity.Generally, when deformed by applying an external force, the viscoelastic material exhibits properties as a viscous body in a time region where the observation time is long, In the time region where the observation time is short, the property as an elastic body is shown. The viscoelastic material used in the present invention is a solid material. In the present specification, a gel material containing a liquid medium such as water or an organic solvent is also included in the solid material.

The viscoelastic material is not particularly limited as long as the material has the above properties, and examples thereof include rubber materials, gel materials, thermoplastic elastomers, thermoplastic resins, and thermosetting elastomers such as polyurethane elastomers. .

The rubber material is not particularly limited. For example, natural rubber (NR), modified natural rubber, graft natural rubber, cyclized natural rubber, chlorinated natural rubber, synthetic natural rubber (IR); styrene-butadiene rubber (SBR) , Diene synthetic rubbers such as butadiene rubber (BR), chloroprene rubber (CR), nitrile rubber (NBR), carboxylated nitrile rubber; a mixture of nitrile rubber and vinyl chloride resin, a mixture of nitrile rubber and EPDM rubber; butyl rubber (IIR) ), Brominated butyl rubber, chlorinated butyl rubber, ethylene-vinyl acetate rubber, acrylic rubber, ethylene-acrylic rubber, chlorosulfonated polyethylene, chlorinated polyethylene (CM), epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, methyl silicone rubber, vinyl-methylsilyl Non-diene synthetic rubbers such as polyethylene rubber, phenyl-methyl silicone rubber, fluorinated silicone rubber, ethylene propylene rubber (EPM, EPDM), urethane rubber, silicone rubber, chlorosulfonated polyethylene (CSM), fluorine rubber, etc. it can. The rubber material may be in any state of vulcanized / unvulcanized and may contain liquid substances such as oil, plasticizer, softener and the like.

The gel material is not particularly limited. For example, water-based gel obtained by gelling water using a gelling agent derived from a natural product such as gelatin, pectin, agar, carrageenan, gellan gum; water, polyvinyl alcohol, N- Aqueous gel composed of a combination with a synthetic polymer such as isopropylacrylamide, polyacrylic acid, polyacrylic acid soda, polymethacrylic acid, hydroxymethylcellulose; 12-hydroxystearic acid or 1,3: 2,4-bis-O— ( An organogel obtained by gelling an oily liquid with an oil gelling agent such as phenylmethylene) -D-glycitol; a non-volatile gel made of a mixture of an ionic liquid and carbon black.

The thermoplastic elastomer material is not particularly limited, and for example, a polystyrene-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic Examples include elastomers, vinyl chloride thermoplastic elastomers, fluororubber thermoplastic elastomers, chlorinated polyethylene elastomers, and nitrile thermoplastic elastomers.

The thermoplastic resin is not particularly limited. For example, polyvinyl chloride, chlorinated polypropylene, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl fluoride, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, styrene.・ Acrylic nitrile copolymer, acrylonitrile / butadiene / styrene terpolymer, vinyl chloride / vinyl acetate copolymer, acrylic / vinyl chloride graft copolymer, ethylene / vinyl chloride copolymer, ethylene / vinyl alcohol, A chlorinated vinyl chloride etc. can be mentioned. The said viscoelastic material may be used independently and may use 2 or more types together.

Among the above viscoelastic materials, thermosetting elastomers such as polyurethane elastomers and gelling agents derived from natural products can be obtained from the point that the elastic modulus of the material is effectively reduced before and after application of a magnetic field. A water-based gel obtained by gelling is preferably used, and a polyurethane elastomer is more preferable. As the gelling agent derived from the natural product, carrageenan is preferable.

Examples of the polyurethane elastomer include those obtained by reacting a polyol and a polyisocyanate. For example, the polyurethane elastomer further crosslinks a prepolymer obtained by reacting a polyol and a polyisocyanate. It can be obtained by a method of reacting an agent.

The polyol is not particularly limited, and examples thereof include polyether polyols such as polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, and polybutylene glycol; polycarbonate diol, neopentyl glycol, polyethylene adipate ester, polyethylene butylene adipate Mention may be made of polyester polyols such as esters, polybutylene adipate esters, caprolactone ester diols and the like. These may be used alone or in combination of two or more.

It does not specifically limit as said polyisocyanate, A conventionally well-known thing can be used, For example, aliphatic isocyanate, alicyclic isocyanate, aromatic isocyanate etc. can be mentioned. As said aliphatic isocyanate, a C6-C10 aliphatic diisocyanate etc. are mentioned, for example. Specific examples include 1,6-hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like. Moreover, the isocyanurate body of hexamethylene diisocyanate and isophorone diisocyanate, the biuret body, the modified body of an adduct body, etc. can be mentioned. Examples of the alicyclic isocyanate include alicyclic diisocyanates such as isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate (NBDI), and the like. Examples of the aromatic isocyanate include tolylene diisocyanate (TDI), phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate (XDI), carbodiimide-modified MDI, and the like. Can be mentioned. These may be used alone or in combination of two or more.

The crosslinking agent is not particularly limited, and examples thereof include low molecular diols such as ethylene glycol, 1,4-butanediol, diethylene glycol, trimethylolpropane, 1,6-hexanediol, and neopentyl glycol; ethylenediamine, hexamethylenediamine, Examples include diamines such as isophorone diamine. These may be used alone or in combination of two or more.

Among the polyurethane elastomers, those obtained by reacting a castor oil-based polyol with a polyisocyanate are preferable. Thereby, the characteristic that the elasticity modulus of a material falls efficiently before and after the application of a magnetic field can be acquired favorably.

The castor oil-based polyol means a broad meaning made of castor oil or a castor oil derivative.
Examples of the castor oil-based polyol include castor oil, dehydrated castor oil, modified products thereof; polyol obtained by transesterification or esterification of ricinoleic acid, which is a castor oil fatty acid, with a low molecular polyol, a polyether polyol, and a polyester polyol. be able to.

The low molecular polyol is preferably a polyol having a molecular weight of 60 to 500. Examples of the low molecular polyol include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, trimethylolpropane, and the like. Can be mentioned. The polyether polyol is preferably a polyether polyol having a molecular weight of 500 to 30,000. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The polyester polyol is preferably a polyester polyol having a molecular weight of 500 to 30,000. Examples of the polyester polyol include linear or branched polyester polyols obtained from carboxylic acids and polyols, polycaprolactone polyols obtained by ring-opening polymerization of caprolactone, and the like.

Other castor oil-based polyols include partially dehydrated castor oil, partially acylated castor oil (partially acetylated castor oil, etc.), castor oil alkylene oxide adduct, castor oil epoxide, castor oil halide, and bisphenol alkylene oxide adduct. Castor oil fatty acid mono- or diester, esterified product of dimer acid and castor oil-based polyol, transesterified product of polymerized castor oil and caprolactone, condensate of dimer or more of castor oil fatty acid or condensate thereof and polyhydric alcohol Examples of the ester may also be mentioned. Also, hydrogenated products of castor oil or castor oil derivatives such as hydrogenated castor oil can be used.

It does not specifically limit as said polyisocyanate, For example, the thing similar to what was mentioned above can be used.
In the castor oil-based polyol and the polyisocyanate, the ratio of the OH group of the castor oil-based polyol to the NCO group of the polyisocyanate (NCO group / OH group, also referred to as NCO Index) is in the range of 0.65 to 1.30. What was made to react by is preferable. By setting it within this range, a predetermined mechanical strength can be secured as polyurethane. If it is less than 0.65, excessive permanent strain, high tackiness, and fluidity may be exhibited, and the wet heat characteristics may be significantly deteriorated. If it exceeds 1.30, the free isocyanate group reacts with the active hydrogen of the urethane bond to form an allophanate bond, which may adversely affect the flexibility and tackiness of the polyurethane elastomer, as well as the heat aging characteristics.

In the present invention, conventionally known methods can be used for the reaction of the castor oil-based polyol and the polyisocyanate.
The reaction between the castor oil-based polyol and the polyisocyanate may be performed in the presence of a catalyst. By using the catalyst, the urethane reaction can be controlled. Examples of the catalyst include amines such as tertiary amines such as 1,2-dimethylimidazole and triethylenediamine; organic compounds such as tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, and tin 2-ethylhexanoate. Examples thereof include metal compounds; alkali metal hydroxides; fatty acid salts; triphenylphosphine.

The magnetic responsive material of the present invention is a component other than the above components (dispersant, preservative, antioxidant, anti-aging agent, ultraviolet absorber, stabilizer, etc.) within a range that does not inhibit the contact state between magnetic particles. Liquids such as viscosity modifiers, reinforcing fillers, bulking agents, softeners, tackifiers, scorch inhibitors, vulcanization accelerators, lubricants, flame retardants, antistatic agents, internal mold release agents, modifiers, colorants, etc. Or a solid material).

When the magnetic responsive material of the present invention magnetizes magnetic particles by applying a magnetic field to the magnetic responsive material, the elastic modulus E ₁ (MPa) before application of the magnetic responsive material and elasticity after application. It is preferable that the rate E ₂ (MPa) satisfies the relationship represented by the above formula (1) [E ₁ −E ₂ > 0 (MPa)]. In this case, the above-described characteristics can be obtained satisfactorily. It is more preferable to satisfy the relationship represented by E ₁ −E ₂ ≧ 0.3.

When the magnetic responsive material of the present invention magnetizes magnetic particles by applying a magnetic field to the magnetic responsive material, the elastic modulus E ₁ (MPa) before application of the magnetic responsive material and elasticity after application. It is preferable that the rate E ₂ (MPa) satisfies the relationship represented by the following formula (3).
(E ₂ / E ₁ ) × 100 <100 (%) (3)
In this case, the above-described characteristics can be obtained satisfactorily. It is more preferable to satisfy the relationship represented by (E ₂ / E ₁ ) × 100 ≦ 85 (%), and the relationship represented by (E ₂ / E ₁ ) × 100 ≦ 75 (%) is satisfied. More preferably.

The elastic modulus of the magnetically responsive material before and after the application of the magnetic field is a value obtained by measuring in a compression mode using dynamic viscoelasticity measurement at room temperature (25 ° C.). The elastic modulus is measured in a state where no magnetic field is applied to the magnetically responsive material.
The dynamic viscoelasticity measurement to be used is “Rheospectra-DVE-V4” (manufactured by Rheology), and the measurement conditions are as follows.
(Measurement condition)
Frequency: 0.1-100Hz
Dynamic strain: 1 × 10 ^{−5 to} 9 × 10 ⁻³
Initial strain: 3%

In the measurement of the elastic modulus of the magnetically responsive material before and after the application of the magnetic field, the magnetic field is applied by placing the magnetically responsive material (10 × 10 × 10 mm sample) in a magnetic field having a magnetic flux density of 1 T for 30 seconds.
The apparatus used is “electromagnet TM-YSV8110C-152SD” (manufactured by Tamagawa Seisakusho Co., Ltd.), and the magnetic field strength was measured using a Tessler meter TM-601 (manufactured by Kanetech Co., Ltd.).

[Method of manufacturing magnetically responsive material]
The method for producing the magnetically responsive material is not particularly limited as long as it is a method capable of dispersing and orienting non-spherical magnetic particles in the viscoelastic material, but contains a viscoelastic material and non-spherical magnetic particles. It is preferable that the raw material composition is molded while applying a magnetic field, and the non-spherical magnetic particles are dispersed and oriented in the viscoelastic material. Thereby, the characteristic that the elasticity modulus of a material falls efficiently before and after the application of a magnetic field can be acquired favorably. Such a manufacturing method is also one aspect of the present invention.

The viscoelastic material and non-spherical magnetic particles used in the above process are the same as those described above. The said raw material composition is a composition containing the component which comprises a magnetic responsive material, and contains the component mentioned above as needed other than the said viscoelastic material and a non-spherical magnetic particle.

In the above process, molding while applying a magnetic field, and dispersing and orienting non-spherical magnetic particles in the viscoelastic material can be obtained by mixing the raw materials constituting the magnetically responsive material by a conventionally known method. While the raw material composition is molded using a conventionally known molding means (cured as necessary), a magnetic field is applied to the material to be molded using a conventionally known magnetic field applying means, This can be done by orienting spherical magnetic particles along the lines of magnetic force.

The molding means is not particularly limited. For example, casting, extrusion molding, injection molding, reaction injection molding (RIM), calendar molding, blow molding, compression molding, transfer molding, insert molding, rotational molding, spinning, etc. are used. Can be mentioned.

Examples of the magnetic field applying means include means for generating a known magnetic force such as a permanent magnet such as a plastic magnet, a processed magnet, a ferrite magnet, and a rare earth magnet, and an electromagnet. Specifically, a magnetic field can be applied using the above-mentioned device “electromagnet TM-YSV8110C-152SD”.

The non-spherical magnetic particles can be oriented by applying a magnetic field in a certain direction using the magnetic field applying means, so that the magnetic particles can be oriented along the direction of the lines of magnetic force. For example, in the example shown in FIG. 2, by applying a magnetic field in the direction of the arrow, the non-spherical magnetic particles 13 are oriented in the viscoelastic material 12 along the direction of the arrow (direction of the lines of magnetic force).

The application condition of the magnetic field is not particularly limited as long as non-spherical magnetic particles are oriented. However, a magnetic field having a magnetic flux density of 0.1 to 200 mT is applied for 1 second to 2 hours (more preferably 1 second to 20 minutes). It is preferable to apply. In the case of the above conditions, the non-spherical magnetic particles can be oriented well along the lines of magnetic force. In addition, the surface of the non-spherical magnetic particle can be efficiently brought into contact with the surface of another non-spherical magnetic particle, and the angle formed by the orientation direction of each non-spherical magnetic particle can be made acute. is there. For this reason, the characteristic that the elasticity modulus of a material falls efficiently before and after the application of a magnetic field can be acquired favorably.

For example, when using an aqueous gel in which water is gelled using a natural product-derived gelling agent as a viscoelastic material, an aqueous solution obtained by adding and dissolving a natural product-derived gelling agent in water After magnetic particles are added to and stirred and dispersed, the obtained magnetic particle-dispersed aqueous solution is poured into a mold for molding and gelled while applying a predetermined uniform magnetic field, so that the magnetic particles are aligned along the direction of the lines of magnetic force. Magnetically responsive material can be manufactured. When polyurethane elastomer is used as the viscoelastic material, magnetic particles (adding a catalyst if necessary) are added to the polyol and mixed and dispersed, and then the polyisocyanate is added and stirred and mixed. The magnetic responsive material in which the magnetic particles are similarly oriented can be produced by pouring into a mold and curing and molding while applying a predetermined uniform magnetic field (further crosslinking if necessary).

Since the magnetic responsive material of the present invention is obtained by dispersing and orienting non-spherical magnetic particles in a viscoelastic material, when a magnetic field is applied to the material to magnetize the non-spherical magnetic particles, It has a property that the elastic modulus is greatly reduced as compared with that before application. Therefore, it is a material having completely different properties from a conventionally known material that exhibits substantially the same elastic modulus before and after application. In addition, even if the amount of magnetic particles dispersed is small, the above properties can be sufficiently exerted, so that it can be manufactured at a light weight and at a low price, and moldability and productivity can be improved.

In addition, the magnetically responsive material of the present invention can maintain a reduced elastic modulus without continuing to apply a magnetic field. Furthermore, the energy consumption is small, a safe device can be constructed, the shape design is easy, and the durability is excellent.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.

Example 1
Pure water was added to the carrageenan powder and stirred at 90 ° C. for about 1 hour to obtain a 3 mass% carrageenan aqueous solution. Here, γ-iron oxide, which is a non-spherical magnetic particle, was added so that the amount of γ-iron oxide in the entire sample (magnetic responsive material) was 15% by mass, and the mixture was stirred and dispersed. This γ-iron oxide-dispersed carrageenan aqueous solution was poured into a glass mold equipped with an electromagnet and gelled over 20 minutes while applying a uniform magnetic field of 50 mT to obtain a 10 × 10 × 10 mm sample.

Example 2
The same amount of the same magnetic particles as in Example 1 was added to the castor oil-based polyol, and a very small amount of organotin-based urethanization catalyst was added and mixed and dispersed with a mechanical stirring device. Diphenylmethane diisocyanate was added thereto as diisocyanate so that NCO INDEX was 1.05, and the mixture was stirred and mixed with a mechanical stirring device. This viscous liquid was poured into the mold of Example 1 previously heated to 120 ° C. and cured at the same temperature for 1.5 hours while applying a uniform magnetic field of 100 mT. Here, the magnetic field was applied for 30 minutes from the end of pouring into the mold. Thereafter, the sample molded from the mold was taken out and post-crosslinked in an oven at 100 ° C. for 12 hours to obtain a 10 × 10 × 10 mm sample.

Example 3
A sample was obtained in the same manner as in Example 1 except that the amount of γ-iron oxide in the entire sample was 10% by mass.

Example 4
A sample was obtained in the same manner as in Example 1 except that the amount of γ-iron oxide in the entire sample was 5% by mass.

Example 5
A sample was obtained in the same manner as in Example 1 except that the amount of γ-iron oxide in the entire sample was 30% by mass.

Comparative Example 1
A sample was obtained in the same manner as in Example 1 except that gelation was performed without applying a magnetic field.
Comparative Example 2
A sample was obtained in the same manner as in Example 2 except that curing was performed without applying a magnetic field.

Comparative Example 3
A sample was obtained in the same manner as in Example 1 except that the amount of γ-iron oxide in the entire sample was 75% by mass and gelled without applying a magnetic field.

Commercial products and equipment used are as follows.
Carrageenan powder: “CS-530” (manufactured by Saneigen FFI Co., Ltd.)
Castor oil-based polyol; “HS3G-500B” (manufactured by Toyokuni Oil Co., Ltd.), hydroxyl value 54 (KOHmg / g)
γ-iron oxide; γ-Fe ₂ O ₃ (manufactured by Titanium Industry Co., Ltd.), primary particle shape, needle shape, aspect ratio 8, major axis diameter 2.56 μm
Electromagnet: “TM-YSV8110C-152SD” (manufactured by Tamagawa Seisakusho)
The method for observing the primary particle shape of the magnetic particles and the method for measuring the aspect ratio and the major axis diameter are as described above.
Samples of Examples and Comparative Examples were produced by the method shown in the schematic diagram of FIG. 4 (molding while applying a magnetic field) (FIG. 4 is Examples 1 and 3 to 5).

(Measurement of elastic modulus)
About the elasticity modulus under room temperature (25 degreeC) of the sample obtained by the Example and the comparative example, it measured by the compression mode using the dynamic viscoelasticity measuring apparatus (before magnetic field application). Next, the sample was placed in a magnetic field having a magnetic flux density of 1 T for 30 seconds. Thereafter, the elastic modulus was measured again (after application of the magnetic field), and the change in elastic modulus (MPa) before and after magnetization was evaluated. In the measurement of the elastic modulus in the compression mode, the orientation direction (major axis direction) of the magnetic particles was set to the compression direction. Moreover, it measured with the apparatus mentioned above and measurement conditions. The results are shown in Table 1.

[Observation of orientation and contact state of each magnetic particle]
Using a light microscope (Axio Imager M1m, manufactured by Carl Zeiss), bright field observation was performed in a transmission mode. In addition, the same observation could be performed using an electron microscope. As representative examples of the micrographs of bright-field observation with an optical microscope, photographs of the samples obtained in Example 4 and Comparative Example 2 are shown in FIG.

In the viscoelastic material, the magnetically responsive material of the example is oriented in substantially the same direction along the direction in which the magnetic field is applied (direction of magnetic force), and the surface of the magnetic particles is in many places. I was in contact. Moreover, although the compounding quantity of the magnetic particle was a small amount (5-30 mass%), the elasticity modulus fell greatly before and after magnetization. On the other hand, the amount of magnetic particles was small (15% by mass), and the materials of Comparative Examples 1 and 2 that were not oriented showed no change in elastic modulus before and after magnetization. Therefore, it became clear that the material of an Example and the material of Comparative Examples 1-2 have a completely different property. Further, from the result of Comparative Example 3, it was revealed that when the magnetic particles are not oriented, a large amount (75% by mass) is necessary to exert the above-described properties.

The magnetically responsive material of the present invention is applied to energy absorption / transmission devices such as clutches, dampers, shock absorbers, engine mounts, anti-vibration / isolation devices, camera shake correction devices for digital cameras, switches, sensors, actuators, etc. be able to.

An example of the schematic diagram of the magnetic-responsive material in which each particle | grain of the nonspherical magnetic particle is disperse | distributing at random in a viscoelastic material. 1 is an example of a schematic diagram of a magnetically responsive material of the present invention in which non-spherical magnetic particles are dispersed and oriented in substantially the same direction in a viscoelastic material. FIG. 3 is an example of a schematic diagram illustrating angles formed by orientation directions of non-spherical magnetic particles present in the viscoelastic material of FIG. 2. An example of the schematic which showed preparation of the sample of an Example and a comparative example. An example of the microscope picture of the bright field observation of the optical microscope of the sample obtained in Example 4 and the comparative example 2. FIG.

Explanation of symbols

1, 11 Magnetic responsive material 2, 12 Viscoelastic material 3, 13, 13a, 13b Non-spherical magnetic particle 14 Angle formed by the orientation direction of particles 13a and 13b

Claims (7)

A magnetically responsive material in which non-spherical magnetic particles are dispersed in a viscoelastic material,
The non-spherical magnetic particles are oriented in the viscoelastic material. When the magnetic particles are magnetized by applying a magnetic field to the magnetic responsive material, the elastic modulus E ₁ (MPa) before application of the magnetic responsive material and the elastic modulus E ₂ (MPa) after application are expressed by the following formula ( 1);
_{E 1 -E 2> 0 (MPa} ) (1)
The magnetically responsive material according to claim 1, which satisfies the relationship represented by: 3. The magnetically responsive material according to claim 1, wherein a part of the surface of the particle contains non-spherical magnetic particles in contact with the surface of another non-spherical magnetic particle. The magnetically responsive material according to claim 1, 2 or 3, comprising nonspherical magnetic particles having an acute angle formed by the orientation directions of the nonspherical magnetic particles. The magnetically responsive material according to claim 1, 2, 3 or 4, wherein the content of non-spherical magnetic particles is 1 to 45 mass%. The magnetically responsive material according to claim 1, 2, 3, 4, or 5, wherein the viscoelastic material is a polyurethane elastomer. A method for producing a magnetically responsive material according to claim 1, 2, 3, 4, 5 or 6,
A raw material composition containing a viscoelastic material and non-spherical magnetic particles is molded while applying a magnetic field, and the non-spherical magnetic particles are dispersed and oriented in the viscoelastic material. Manufacturing method of magnetically responsive material.