HK1238274A1 - Magneto-rheological elastomer composition, method for producing same, and vibration absorbing device including same - Google Patents

Description

Magnetorheological elastomer composition, method for producing same, and vibration absorbing device incorporating same

Technical Field

The present invention relates to magnetorheological Elastomer (Magneto Rheological Elastomer) compositions. More specifically, the present invention relates to a magnetorheological elastomer composition having a high storage modulus (storage modulus) change when a magnetic force is applied, a method for producing the same, and a vibration absorbing device containing the same.

Background

A fluid whose rheological properties change by application of a magnetic field is called a magnetorheological fluid (MR fluid), and is known as a non-colloidal suspension in which magnetically active particles such as fine magnetic powder are uniformly dispersed in a liquid. The MR fluid can be used for clutches, dampers, shock absorbers, vibration damping support devices for various structures, vibration absorbers, and other devices for vehicles including shock absorption, power transmission, and attitude control, for muscle parts of assembled robots, valves for controlling liquid flow rates, various acoustic devices, medical and health care robot hands, nursing hands, and the like. However, the MR fluid is inconvenient in handling, and in recent years, an MR elastomer having excellent handling properties has been proposed.

Patent document 1 proposes a magnetic field responsive composition obtained by dispersing a magnetic filler such as permalloy (Fe — Ni alloy) in a viscoelastic resin material and performing rotational molding in a mold. Patent document 2 proposes that a magnetic filler is dispersed in a viscoelastic resin material and cured in a state where a magnetic field is applied. Patent document 3 proposes to orient the magnetic particles in the resin material, and patent document 4 proposes to not orient them.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-064441

Patent document 2: japanese patent laid-open publication No. 2013-181090

Patent document 3: japanese patent laid-open No. 2008-195826

Patent document 4: japanese patent laid-open No. 2008-013631

Disclosure of Invention

Problems to be solved by the invention

However, the conventional magnetorheological compositions have a problem that the change in storage modulus upon application of a magnetic force is still insufficient.

In order to solve the above-mentioned conventional problems, the present invention provides a magnetorheological elastomer composition having a high change in storage modulus when a magnetic force is applied, a method for producing the same, and a vibration absorbing device incorporating the same.

Means for solving the problems

The magnetorheological elastomer composition of the present invention is a magnetorheological elastomer composition comprising a matrix resin and a magnetic powder, wherein the magnetic powder is contained in an amount of 30 to 70% by volume based on 100% by volume of the composition, and the magnetorheological elastomer composition has an ASKER C hardness of 5 to 60 in accordance with the standard specification of the Japan rubber Association (SRIS 0101).

The method for producing a magnetorheological elastomer composition of the present invention is characterized by curing a mixture having the following composition to obtain the magnetorheological elastomer composition.

(A) Base polymer component: 1 a straight-chain organopolysiloxane containing an average of two or more alkenyl groups bonded to silicon atoms at both ends of a molecular chain in a molecule;

(B) crosslinking component: 1 an organohydrogenpolysiloxane containing an average of two or more silicon atom-bonded hydrogen atoms in a molecule, in an amount of less than 1 mole relative to 1 mole of the silicon atom-bonded alkenyl groups in the component a;

(C) platinum group metal catalyst: 0.01 to 1000ppm in terms of weight unit relative to the component A

(D) Magnetic powder: 20 to 80 vol% of organopolysiloxane (200 to 3000 parts by weight per 100 parts by weight of organopolysiloxane)

The vibration absorber of the present invention is a vibration absorber in which the magnetorheological elastomer composition is incorporated, wherein the magnetorheological elastomer composition is disposed in a vibrating portion, and the vibration of the vibrating portion is absorbed by a change in storage modulus when a magnetic force is applied.

Effects of the invention

The present invention can provide a magnetorheological elastomer composition having a high change in storage modulus upon application of a magnetic force. The high change in storage modulus means that the vibration absorption or vibration reduction effect is high.

Drawings

FIG. 1 is a schematic cross-sectional view of a sheet of magnetorheological elastomer composition in an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method for measuring the storage modulus of a magnetorheological elastomer composition sheet according to an embodiment of the present invention.

Fig. 3 is an explanatory diagram of symbols for calculating the storage modulus.

FIG. 4 is a graph showing the measurement of storage modulus and frequency characteristics of the magnetorheological elastomer composition obtained in example 4 of the present invention.

Detailed Description

The present invention is a magnetorheological elastomer composition comprising a matrix resin and a magnetic powder. The magnetic powder includes a soft magnetic metal powder or an oxide magnetic powder (ferrite powder), and the soft magnetic metal powder includes an Fe-Si alloy, an Fe-Al alloy, an Fe-Si-Cr alloy, an Fe-Ni alloy (Permalloy), an Fe-Ni-Co alloy (Mumetal), an Fe-Ni-Mo alloy (Supermalloy), an Fe-Co alloy, an Fe-Si-Al-Cr alloy, an Fe-Si-B alloy, an Fe-Si-Co-B alloy or other iron-based alloy powder, or carbonyl iron powder, and the ferrite powder includes Mn-Zn ferrite, Mn-Mg-Zn ferrite, Mg-Cu-Zn ferrite, Ni-Zn ferrite, etc, Spinel-based ferrites such as Ni-Cu-Zn ferrite and Cu-Zn ferrite, and hexagonal ferrites such as W-type, Y-type, Z-type and M-type ferrites.

The carbonyl iron powder is known per se as a kind of soft magnetic iron powder and also as a powder industrial product. The carbonyl iron powder is prepared by reacting carbonyl iron (Fe (CO))₅) Gasifying and decomposing the mixture to remove CO. The average particle size of the carbonyl iron powder is preferably 2 to 10 μm, and more preferably 2 to 8 μm. Measurement of particle diameter 50 mass% particle diameter was measured by a laser diffraction light scattering method. The measuring instrument is exemplified by a laser diffraction/scattering type particle distribution measuring instrument LA-950S2 manufactured by horiba, Inc.

The magnetic powder is contained in an amount of 30 to 70 vol%, more preferably 35 to 70 vol%, based on 100 vol% of the composition. In the above range, the change in storage modulus when the magnetic force is applied is sufficiently high.

The matrix resin may be a thermosetting resin or a thermoplastic resin, and further includes rubber or an elastomer. Examples of the rubber include natural rubber (NR for short in ASTM), Isoprene Rubber (IR), Butadiene Rubber (BR), 1, 2-polybutadiene (1,2-BR), styrene-butadiene (SBR), Chloroprene Rubber (CR), nitrile rubber (NBR), butyl rubber (IIR), ethylene propylene rubber (EPM, EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO) polysulfide rubber (T), silicone rubber, fluorine rubber (FKM), and urethane rubber (U), but are not limited thereto. Thermoplastic elastomers (TPE) may also be suitable. Examples of the TPE include styrene-based TPE, olefin-based TPE, vinyl chloride-based TPE, urethane-based TPE, ester-based TPE, amide-based TPE, chlorinated polyethylene-based TPE, cis-1, 2-polybutadiene-based TPE, trans-1, 4-polyisoprene-based TPE, and fluorine-based TPE. In the above, the term "system" means a homopolymer, a copolymer or the like. The crosslinking of the silicone rubber may be an addition reaction or a peroxide reaction. The following is a description of crosslinking by addition reaction.

The base resin is preferably an organopolysiloxane. This is because organopolysiloxane has high heat resistance and good processability. The composition containing the organopolysiloxane as a base may be any of rubber, rubber sheet, putty, grease, and the like.

The magnetorheological elastomer composition has an ASKER C hardness of 5 to 60 in terms of the Japan rubber Association Standard Specification (SRIS0101), and more preferably 20 to 50 in terms of the ASKER C hardness. When the hardness is in the above range, the magnetorheological elastomer composition shows a high change in storage modulus when a magnetic force is applied. The magnetorheological elastomer composition of the present invention preferably has a storage modulus which changes by a factor of 5 or more, more preferably by a factor of 9 or more, when a magnetic force having a magnetic flux density of 0.2T is applied. The change in storage modulus described above is practical.

When the base resin is an organopolysiloxane, it is preferably obtained by curing a mixture of the following composition.

(A) Base polymer component: 1 a straight-chain organopolysiloxane containing an average of two or more alkenyl groups bonded to silicon atoms at both ends of a molecular chain in a molecule;

(B) crosslinking component: 1 an organohydrogenpolysiloxane containing an average of two or more silicon atom-bonded hydrogen atoms in a molecule, in an amount of less than 1 mole relative to 1 mole of the silicon atom-bonded alkenyl groups in the component A

(C) Platinum group metal catalyst: 0.01 to 1000ppm in terms of weight unit relative to the component A

(D) Magnetic powder: 20 to 80 vol% of organopolysiloxane (200 to 3000 parts by weight per 100 parts by weight of organopolysiloxane)

(E) Inorganic particle pigment: 0.1 to 10 parts by weight based on 100 parts by weight of the base resin

(1) Base Polymer component (A component)

The base polymer component (component a) is an organopolysiloxane containing two or more silicon atom-bonded alkenyl groups in one molecule, and the organopolysiloxane containing two alkenyl groups is the main agent (base polymer component) in the silicone rubber composition of the present invention. The organopolysiloxane has, as alkenyl groups, two silicon atom-bonded alkenyl groups having 2 to 8, particularly 2 to 6 carbon atoms such as vinyl groups and allyl groups in one molecule. The viscosity is preferably 10 to 1000000 mPas, particularly 100 to 100000 mPas at 25 ℃ from the viewpoints of handling property, curability and the like.

Specifically, an organopolysiloxane containing an average of two or more alkenyl groups bonded to silicon atoms at the molecular chain terminals in 1 molecule represented by the following general formula (chemical formula 1) is used. The side chain is straight-chain organopolysiloxane which is sealed by trisorganosilicon alkoxy. An organopolysiloxane having a viscosity of 10 to 1000000 mPas at 25 ℃ is preferred from the viewpoint of handling properties, curability, and the like. The linear organopolysiloxane may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain.

[ chemical formula 1]

In the formula, R¹Are identical or different kinds of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bond, R²Is an alkenyl group, and k is0 or a positive integer. Wherein, as R¹The monovalent hydrocarbon group having no aliphatic unsaturated bond(s) is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, and specifically includes methyl, ethyl, propyl, and isopropylAlkyl groups such as propyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl and decyl, aryl groups such as phenyl, tolyl, xylyl and naphthyl, aralkyl groups such as benzyl, phenylethyl and phenylpropyl, groups obtained by substituting a part or all of hydrogen atoms of these groups with halogen atoms such as fluorine, bromine and chlorine, cyano groups, halogenated alkyl groups such as chloromethyl, chloropropyl, bromoethyl and trifluoropropyl, and cyanoethyl groups. As R²The alkenyl group of (b) is preferably an alkenyl group having 2 to 6, particularly 2 to 3 carbon atoms, and specific examples thereof include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group, and a vinyl group is preferable. In the general formula (1), k is generally 0 or a positive integer satisfying 0. ltoreq. k.ltoreq.10000, preferably an integer satisfying 5. ltoreq. k.ltoreq.2000, more preferably an integer satisfying 10. ltoreq. k.ltoreq.1200.

The organopolysiloxane as component A may be a combination of organopolysiloxanes having in one molecule 3 or more, usually 3 to 30, preferably about 3 to 20, alkenyl groups bonded to silicon atoms, such as vinyl groups and allyl groups, having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms. The molecular structure may be any of linear, cyclic, branched, and three-dimensional network structures. Preferably, the organopolysiloxane has a main chain comprising repeating diorganosiloxane units and a viscosity at 25 ℃ of 10 to 1000000 mPas, particularly 100 to 100000 mPas, wherein both ends of the molecular chain are blocked with a triorganosiloxy group.

The alkenyl group may be bonded to a certain portion of the molecule. For example, the alkenyl group may be bonded to a silicon atom at the molecular chain terminal or at the non-terminal (mid-molecular chain) of the molecular chain. Among them, a linear organopolysiloxane having 1 to 3 alkenyl groups (wherein, when the total of alkenyl groups bonded to silicon atoms at molecular chain terminals is less than 3 at both terminals, an organopolysiloxane having at least 1 alkenyl group bonded to silicon atoms at non-terminal ends (in the middle of the molecular chain) (for example, as a substituent in a diorganosiloxane unit)) on silicon atoms at both terminal ends of the molecular chain represented by the following general formula (chemical formula 2) and having a viscosity of 10 to 1,000,000mPa · s at 25 ℃ as described above is preferable from the viewpoints of handling properties, curability, and the like. The linear organopolysiloxane may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain.

[ chemical formula 2]

In the formula, R³Are unsubstituted or substituted monovalent hydrocarbon groups of the same or different kinds from each other, and at least 1 is an alkenyl group. R⁴Are identical or different kinds of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bond, R⁵Is alkenyl, l and m are 0 or positive integers. Wherein, as R³The monovalent hydrocarbon group(s) is preferably a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, and specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl and decyl, aryl groups such as phenyl, tolyl, xylyl and naphthyl, aralkyl groups such as benzyl, phenylethyl and phenylpropyl, alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl and octenyl, and groups obtained by substituting a part or all of the hydrogen atoms of these groups with halogen atoms such as fluorine, bromine and chlorine, cyano groups, and halogenated alkyl groups such as chloromethyl, chloropropyl, bromoethyl and trifluoropropyl, cyanoethyl, and the like.

Further, as R⁴The monovalent hydrocarbon group (b) is also preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, and the above R is exemplified¹The same monovalent hydrocarbon group is specifically exemplified, but an alkenyl group is not contained. As R⁵The alkenyl group of (2) is preferably an alkenyl group having 2 to 6 carbon atoms, particularly 2 to 3 carbon atoms, and specifically, an alkenyl group represented by the formula (chemical formula 1)R²The same alkenyl group is preferably vinyl.

l and m are generally 0 or a positive integer satisfying 0< l + m.ltoreq.10000, preferably 5. ltoreq. l + m.ltoreq.2000, more preferably 10. ltoreq. l + m.ltoreq.1200, and 0< l/(l + m). ltoreq.0.2, preferably 0.0011. ltoreq. l/(l + m). ltoreq.0.1.

(2) Crosslinking component (B component)

The organohydrogenpolysiloxane of component B of the present invention is a component that functions as a crosslinking agent, and is a component that forms a cured product by an addition reaction (hydrosilication) of the SiH groups in the component with the alkenyl groups in component a. The organohydrogenpolysiloxane may be any organohydrogenpolysiloxane as long as it has two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) in one molecule, and the molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but an organohydrogenpolysiloxane in which the number of silicon atoms in one molecule (i.e., the degree of polymerization) is 2 to 1000, particularly about 2 to 300, may be used.

The position of the silicon atom to which the hydrogen atom is bonded is not particularly limited, and may be a terminal of the molecular chain or a non-terminal (halfway). Examples of the organic group bonded to a silicon atom other than a hydrogen atom include the group R of the above general formula (chemical formula 1)¹The same unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond.

Examples of the organohydrogenpolysiloxane of component B include organohydrogenpolysiloxanes having the following structures.

[ chemical formula 3]

[ chemical formula 4]

[ chemical formula 5]

In the above formula, Ph is an organic group containing at least one of a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, and an alkoxy group. L is an integer of 0 to 1,000, particularly 0 to 300, and M is an integer of 1 to 200. )

(3) Catalyst component (C component)

The catalyst component of the component C is a component for accelerating the curing of the present composition. As the component C, a catalyst known as a catalyst for a hydrosilation reaction can be used. Examples thereof include platinum group metal catalysts such as platinum black, platinum chloride, platinic chloride, a reaction product of platinic chloride and a monohydric alcohol, a complex of platinic chloride and an olefin or a vinyl siloxane, a platinum group catalyst such as platinum bisacetoacetate, a palladium group catalyst, and a rhodium group catalyst. The amount of the component C to be blended may be an amount necessary for curing, and may be appropriately adjusted depending on a desired curing rate and the like. 0.01 to 1000ppm by weight of metal atom is added to the component A.

(4) Magnetic powder (D component)

The magnetic powder is preferably surface-treated with an alkoxysilane or an alkyl titanate. When this surface treatment is performed, in the case of silicone rubber, curing inhibition can be prevented. The above alkoxysilane is preferably R (CH)₃)_aSi(OR’)_3-a(R is an alkyl group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is0 or 1), or a partial hydrolysate thereof. R (CH)₃)_aSi(OR’)_3-a(R is an alkyl group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is0 or 1) as an example, a silyl group compound (hereinafter, simply referred to as "silane") represented bySilane compounds such as methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadodecyltrimethoxysilane, hexadodecyltriethoxysilane, octadecyltrimethoxysilane and octadecyltriethoxysilane. The silane compound may be used alone or in combination of two or more. The surface treatment agent may be an alkoxysilane in combination with a single-terminal silanol siloxane. The surface treatment here includes not only covalent bonding but also adsorption.

(5) Other component (E component)

The composition of the present invention may contain other components than those described above as necessary. For example, an inorganic pigment such as red iron oxide, an alkyltrialkoxysilane added for the purpose of surface treatment of a filler, or the like may be added. As a material added for the purpose of filler surface treatment or the like, an alkoxy group-containing silicone may also be added.

The vibration absorber of the present invention is a vibration absorber in which the magnetorheological elastomer composition is incorporated, and the vibration absorber is a device in which the magnetorheological elastomer composition is disposed in a vibrating portion and the vibration of the vibrating portion is absorbed by a change in storage modulus when a magnetic force is applied. The vibration part is preferably at least one vibration part selected from the group consisting of an impact part, a power transmission part, an attitude control part, a clutch of a vehicle, a damper of a vehicle, a shock absorber of a vehicle, a vibration damping support device for a building, a muscle part of an assembly robot, a valve for controlling a liquid flow rate, an acoustic device, a medical/health care robot hand, and a nursing hand. Specific devices are illustrated in fig. 2-3.

The following description is made with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a sheet of magnetorheological elastomer composition in an embodiment of the present invention. The magnetorheological elastomer composition sheet 10 has magnetic powder 11 dispersed in a matrix resin 12.

The method for measuring the storage modulus will be described with reference to fig. 2. The storage modulus measuring apparatus 20 includes a dc stabilization power supply 21 for generating a current to be applied to the coil portion 22, a magnetic coil 22 for generating a magnetic field and forming a closed magnetic path in the cores 23 and 24 and the MREs 25a and 25b, and an upper core 23 as a circulating path of a magnetic induction line inserted at right angles to the cross sections of the MREs 25a and 25 b. The upper core 23 also serves as a mass of a 1-degree-of-freedom vibration system in the viscoelasticity evaluation formula. The lower side cores 24 and 23 are the same as the magnetic flux lines. MREs 25a and 25b are MREs (measurement samples) as viscoelastic elements in the 1-degree-of-freedom vibration system, and their viscoelasticity is evaluated on the assumption of deformation in the direction accompanying relative displacement of the upper-side core 23 and the lower-side core 24 in the left-right direction (shear direction) of the figure. The accelerometer 26a measures the acceleration in the horizontal direction generated in the upper core 23. The accelerometer 26b measures an acceleration (vibration input acceleration) in the horizontal direction generated in the lower core 24. The horizontal vibration table 27 is coupled to the lower core 24, and vibrates the core in the horizontal direction by restricting vertical displacement of the core. An electromagnetic exciter 28 is coupled to the horizontal stage 27 to move the stage in a horizontal direction. The power amplifier 29 supplies electric power to the electromagnetic exciter 28. The signal analyzer 30 subjects the acceleration signals detected in the accelerometers 26a, 26b to transfer function processing over the frequency region. The signal amplifier 31 amplifies the voltage signals from the accelerometers 26a, 26 b.

In this storage modulus measuring apparatus 20, the mass in which the coil 22 and the upper core 23 are combined, among the coil 22, the upper core 23, the lower core 24, and the MREs (measurement samples) 25a and 25b placed on the horizontal vibration table 27, is regarded as a mass, the MREs (measurement samples: elastic bodies) 25a and 25b are regarded as 2 parallel spring elements, and a 1-degree-of-freedom vibration system constituted by these mass and spring elements is subjected to displacement vibration in the base portion (horizontal vibration table 27) and vibrates in the horizontal direction. The displacement vibration is generated by an electromagnetic vibrator 28 connected to a horizontal vibration table 27. The acceleration of the accelerometer 26b attached to the base and the acceleration of the accelerometer 26a attached to the mass are measured at the same time, and the acceleration transfer functions of both are obtained in the frequency domain by the calculation function of the signal analyzer 30. The complex spring constant is used as an index of viscoelasticity, and the obtained transfer function is used to calculate the complex spring constant according to the following theory. Let m be the mass, x be the absolute displacement of the mass, u be the displacement of the horizontal excitation stage, and k be the complex spring constant of the MRE. The equation of motion of the system that vibrates by being subjected to displacement excitation is expressed by the following equation (equation 1).

[ mathematical formula 1]

Here, the complex spring constant k is defined as the following equation (equation 2) in consideration of the frequency dependence.

[ mathematical formula 2]

k^*(ω)＝k'(ω){1+jη(ω)} (2)

In equation (2), k' (ω) is a spring constant, η (ω) is a loss coefficient, and ω is an angular vibration frequency. In addition, j represents an imaginary unit. Next, when the following expression (1) is laplace-transformed to obtain a transfer function g(s) of the response displacement X(s) to the displacement input U(s) which is X/U, the following expression (expression 3) is obtained.

[ mathematical formula 3]

Further, when the equation (3) is substituted by s ═ j ω and the equation (2) for defining the complex spring constant is substituted, the transfer function G (j ω) in the frequency region is obtained as follows.

[ mathematical formula 4]

Wherein, the real part and the imaginary part of the acceleration transfer function obtained as the actual measurement value are respectively set as G_R、G_IThe transfer function may be, for example, G (j ω) ═ G_R+jG_IThat is shown. Consider G_R、G_IThe spring constant k' (ω) and the loss coefficient η (ω) are calculated from the actual measurement values by equating the real part and the imaginary part of equation (4) with each other, using the following equations (equations 5 to 6).

[ math figure 5]

[ mathematical formula 6]

Next, referring to fig. 3, a method of calculating the storage modulus E '(ω) from the spring constant k' (ω) is shown. Now, the viscoelastic body has a rectangular parallelepiped shape, and its thickness is t, width is b, and length is a. In the viscoelastic body, the lower surface is constrained, and the upper surface is subjected to an external force F to be displaced by d in the horizontal direction.

First, the following relationship is established between the load F and the deformation amount d.

[ math figure 7]

F＝k'd (7)

Note that ω indicating the frequency dependence is not denoted by the symbol. Next, the relationship of the formula (7) is converted into a relationship between the shear stress τ and the shear strain γ generated in the elastomer. The storage modulus E' is used to establish the following relationship between τ and γ.

[ mathematical formula 8]

τ＝E'γ (8)

Here, τ and γ are represented as follows using the symbols in fig. 3.

[ mathematical formula 9]

[ mathematical formula 10]

γ＝d/t (10)

By substituting formula (7) into formula (9) to eliminate F, and further substituting formulae (9) and (10) into formula (8), E' is written as follows.

[ mathematical formula 11]

Further, the loss elastic modulus E ″ can be calculated as follows using the storage modulus E' and the loss coefficient η.

[ mathematical formula 12]

E″＝ηE' (12)

In order to examine the magnetic field dependence of MRE viscoelasticity, the current applied to the coil 22 from the dc stabilization power supply 21 was varied in stages at 0 to 2A (equivalent to 0 to 200mT in terms of magnetic flux density), while measuring the acceleration transfer function at the time of random displacement excitation, and the spring constant and the loss coefficient were calculated for each constant current value using equations (5) and (6).

[ examples ]

The following examples are used for illustration. The present invention is not limited to the examples.

< hardness >

The hardness of ASKER C specified in the standard specification of the Japan rubber society (SRIS0101) was measured.

< storage modulus >

The storage modulus was measured and calculated as shown in fig. 2 and 3 and the description using fig. 2 and 3. Fig. 2 and 3 and the description using fig. 2 and 3 described above are not only the measurement of the storage modulus, but also an embodiment of the vibration absorbing device of the present invention.

(examples 1 to 4)

1. Material composition

(1) Silicone component

As the silicone component, a two-part room temperature curing silicone rubber was used. In addition, the base polymer component (component A), the crosslinking component (component B) and the platinum group metal catalyst (component C) are previously added to the two-component RTV.

(2) Magnetic powder

Example 1: permalloy (50Fe-50Ni) having an average particle size of 10.5 μm after silane treatment described below was added in a proportion of 50 vol%, and uniformly mixed.

Example 2: the same procedure as in example 1 was repeated, except that a carbonyl iron powder having an average particle size of 3.9 to 5.0 μm was used in place of the permalloy.

Comparative example 1: the same procedure as in example 1 was repeated, except that a ferrite (Mn-Zn based iron) having an average particle size of 10.8 μm was used in place of the permalloy.

Comparative example 2: the procedure of example 1 was repeated, except that a ferrite (Ni-Zn-based iron) having an average particle size of 30.1 μm was used in place of the permalloy.

(3) Silane treatment

A silane coupling agent was added to the magnetic powder at a ratio of 1 mass%, and the mixture was stirred until the mixture became homogeneous. The stirred magnetic powder was uniformly spread on a tray or the like, and dried at 100 ℃ for 2 hours.

2. Sheet forming method

A metal frame having a thickness of 3mm was placed on the polyester film subjected to the mold release treatment, and the mixture was poured, and another polyester film subjected to the mold release treatment was placed thereon. The mixture was cured at 120 ℃ for 10 minutes under a pressure of 5MPa to form a silicone rubber sheet having a thickness of 3.0 mm. The physical properties of the obtained silicone rubber sheet are collectively shown in table 1.

[ Table 1]

As can be seen from table 1, the viscoelastic change of carbonyl iron was the greatest.

(examples 3 to 6 and comparative examples 3 to 4)

As the magnetic powder, carbonyl iron powder having an average particle size of 3.9 to 5.0 μm was used, and experiments were conducted by changing the amount of addition as shown in Table 2. Other conditions were the same as in example 1. The results are also shown collectively in Table 2.

[ Table 2]

It is presumed from table 2 that the change in storage modulus depends on the hardness and the content of carbonyl iron powder. When the carbonyl iron powder is 60 vol%, the hardness increases and the change in storage modulus decreases. When the carbonyl iron content is 80 vol%, the flowability during molding is poor and the molding cannot be performed.

FIG. 4 is a graph showing the frequency characteristics of the storage modulus of the magnetorheological elastomer composition obtained in example 4.

(examples 7 to 11, comparative example 5)

An experiment was carried out in the same manner as in example 1 except that carbonyl iron powder having an average particle diameter of 3.9 to 5.0 μm was used as the magnetic powder and the rubber hardness was changed by changing the amount of the vulcanizing agent added. The conditions and results are shown collectively in table 3.

[ Table 3]

As can be seen from Table 3, when the carbonyl iron content is 50% by volume and the ASKER C hardness is 10-52, the change in storage modulus is more than 5 times when a magnetic field is applied. When the ASKER C hardness is 69, the change in storage modulus is less than 5 times when a magnetic field is applied.

Industrial applicability

The magnetorheological elastomer composition of the present invention can be applied to various types of products such as sheets, rods, extrusion molded products, mold molded products, putty materials and composite products thereof.

Description of the symbols

10 magnetorheological elastomer composition sheet

11 magnetic powder

12 matrix resin

20 storage modulus measuring device

21 DC stabilized power supply

22 magnetic coil

23 upper side core

24 lower side core

25a, 25b MRE (measurement sample)

26a, 26b accelerometer

27 horizontal vibration exciting table

28 electromagnetic exciter

29 power amplifier

30 signal analyzer

31 signal amplifier

Claims (10)

1. A magnetorheological elastomer composition comprising a matrix resin and a magnetic powder,

the magnetic powder comprises 30-70 vol% when the composition is 100 vol%,

the magnetorheological elastomer composition has an ASKER C hardness of 5-60 according to the standard specification of the Japan rubber Association, namely SRIS 0101.

2. The magnetorheological elastomer composition according to claim 1, wherein the magnetic powder is at least one of iron-based alloy powders selected from carbonyl iron powder, Fe-Si alloy, Fe-Al alloy, Fe-Si-Al alloy, sendust alloy, Fe-Si-Cr alloy, Fe-Ni alloy, permalloy alloy, Fe-Ni-Co alloy, nife-Mo alloy, nimodi alloy, Fe-Co alloy, Fe-Si-Al-Cr alloy, Fe-Si-B alloy, and Fe-Si-Co-B alloy.

3. The magnetorheological elastomer composition of claim 1, wherein the magnetic powder is surface treated with an alkoxysilane or an alkyltitanate.

4. The magnetorheological elastomer composition of claim 3, wherein the alkoxysilane is R (CH)₃)_aSi(OR’)_3-aThe silane compound or a partial hydrolysate thereof is disclosed, wherein R is an alkyl group having 1-20 carbon atoms, R' is an alkyl group having 1-4 carbon atoms, and a is0 or 1.

5. The magnetorheological elastomer composition of claim 1, wherein the matrix resin is an organopolysiloxane.

6. The magnetorheological elastomer composition of claim 1, wherein the magnetorheological elastomer composition has a storage modulus that changes by a factor of 5 or more when subjected to a magnetic force having a flux density of 200 mT.

7. The magnetorheological elastomer composition of claim 1, wherein the magnetorheological elastomer composition is in the form of a sheet.

8. The method of any of claims 1 to 7, wherein the magnetorheological elastomer composition is obtained by curing a mixture of the following constituents,

(A) base polymer component: a linear organopolysiloxane containing an average of two or more alkenyl groups bonded to silicon atoms at both ends of a molecular chain in 1 molecule;

(B) crosslinking component: an organohydrogenpolysiloxane containing an average of two or more silicon atom-bonded hydrogen atoms in 1 molecule in an amount of less than 1 mole relative to 1 mole of the silicon atom-bonded alkenyl groups in the component a;

(C) platinum group metal catalyst: 0.01 to 1000ppm in terms of weight unit relative to the component A;

(D) magnetic powder: when the amount of the organopolysiloxane is 20 to 80% by volume, the amount is 20 to 80% by volume, that is, 200 to 3000 parts by weight per 100 parts by weight of the organopolysiloxane.

9. A vibration absorber comprising the magnetorheological elastomer composition according to any one of claims 1 to 7,

the magnetorheological elastomer composition is arranged in a vibration part, and the vibration of the vibration part is absorbed by utilizing the change of the storage modulus when magnetic force is applied.

10. The vibration absorbing apparatus according to claim 9, wherein the vibrating portion is a vibrating portion selected from at least one of an impact portion, a power transmitting portion, an attitude control portion, a clutch of a vehicle, a damper of a vehicle, a shock absorber of a vehicle, a vibration reduction supporting device for a building, a muscle portion of a fitting robot, a valve for liquid flow control, an acoustic device, a medical/health robot hand, and a nursing hand.