Magnetic viscoelastic elastomer composition and method for producing magnetic viscoelastic elastomer composition

Abstract

The present invention addresses the problem of providing a magnetic viscoelastic elastomer composition which has a large change in storage elastic modulus before and after application of a magnetic field, while exhibiting excellent physical toughness. A means for solving the problem according to the present invention is a magnetic viscoelastic elastomer composition which contains a viscoelastic elastomer that contains a urethane resin and a magnetic powder that is dispersed in the viscoelastic elastomer, wherein: the urethane resin has a polyurethane skeleton which is composed of a reaction product of a polyol and a polyisocyanate; the polyurethane skeleton has an average molecular weight between crosslinks of 9,600 to 30,000 inclusive; and the urethane resin contains a slide-ring material that is bonded to the polyurethane skeleton.

Description

MAGNETORHEISTIC ELASTOMER COMPOSITION AND METHOD FOR PRODUCING MAGNETORHEISTIC ELASTOMER COMPOSITION

[0001] This patent application claims the benefit of Patent Application No. 2024-2816, filed in Japan on January 11, 2024, the contents of which are incorporated herein by reference. The present invention relates to a magnetorheological elastomer composition, and more particularly to a magnetorheological elastomer composition comprising a viscoelastic elastomer and a magnetic powder.

[0002] Magnetically responsive materials, which are made by dispersing magnetic material such as iron in a resin material such as an elastomer, are known as materials that can be used as vibration-proof / damping materials and energy-transmitting materials.

[0003] Patent Document 1 describes a polyurethane elastomer composition containing a reaction product of a polyol compound and a polyisocyanate compound, and magnetic particles, in which the polyol compound includes a propylene oxide adduct of bisphenol A, etc., and the polyisocyanate compound is a polyisocyanate compound having an aromatic ring. The magnetically responsive material in Patent Document 1 is described as a highly elastic, magnetic field-responsive soft material with a large change in elastic modulus.

[0004] Patent Document 2 describes a magnetorheological elastomer composition containing a matrix resin and magnetic powder, wherein the magnetic powder accounts for 30 to 70 volume percent of the composition taken as 100 volume percent, and the magnetorheological elastomer composition has an Asker C hardness of 5 to 60 according to the Society of Rubber Industry Standards (SRIS0101) of the Japan Rubber Industry Association. Specifically, the magnetorheological elastomer composition is a silicone rubber sheet prepared by mixing a two-component room-temperature curing silicone rubber matrix resin with permalloy and carbonyl iron powder that have been surface-treated with a silane coupling agent, followed by heating and curing. It also describes that by surface-treating the magnetic powder in this manner, it is possible to prevent curing inhibition in the case of silicone rubber.

[0005] Patent Document 3 describes a polyrotaxane in which blocking groups are arranged at both ends of a pseudo-polyrotaxane in which the openings of cyclic molecules are skewered and enclosed by linear molecules to prevent the cyclic molecules from detaching, the cyclic molecules having a hydroxyl-inert group and a hydroxyl group via a spacer group, and the hydroxyl value of the polyrotaxane is 10 to 65 mgKOH / g. Patent Document 3 also describes a method of obtaining a thermoset crosslinked product by mixing this polyrotaxane with a material that reacts with the hydroxyl groups of the polyrotaxane and hardens, and then reacting them by applying heat.

[0006] Specifically, the polyrotaxane is reacted with polycarbonate diisocyanate and polycarbonate diol to produce a thermosetting composition, and the elongation and breaking strength of the thermosetting composition are measured. The document describes that the thermosetting composition is flexible yet has high strength compared to a thermosetting composition that does not use polyrotaxane.

[0007] JP 2019-210311 A JP 2017-179338 A International Publication No. 2020 / 045325

[0008] Magnetically responsive materials are required to be highly elastic, magnetically responsive soft materials with large changes in elastic modulus, but also to have the physical toughness to withstand high loads, considering their application in vibration isolation / damping materials, energy transmission materials, tactile feedback devices, etc.

[0009] The present invention solves the above problems, and its object is to provide a magnetorheological elastomer composition that exhibits a large change in storage modulus before and after the application of a magnetic field and has excellent physical toughness.

[0010] The present invention provides a magnetorheological elastomer composition comprising a viscoelastic elastomer containing a slide-ring material and a urethane resin, and a magnetic powder dispersed in the viscoelastic elastomer.

[0011] According to the present invention, there is provided a magnetorheological elastomer composition that exhibits a large change in storage modulus before and after application of a magnetic field and has excellent physical toughness.

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values ​​are specified for a specific parameter, any upper and lower limit values ​​can be combined to form a suitable numerical range.

[0013] In this specification, a viscoelastic elastomer refers to a material that has both viscosity and elasticity, and can be distinguished based on the relaxation time of stress relaxation (change in stress over time) when a certain strain is applied. If the relaxation time is sufficiently short compared to the time scale of observation, it is considered to be a viscous material, if it is long, it is considered to be an elastic material, and if it is on the same scale, it is considered to be a viscoelastic material.

[0014] In this specification, the term "magnetorheological elastomer" refers to a viscoelastic elastomer containing magnetic particles, and preferably refers to a composite material in which magnetic particles are dispersed and fixed inside a viscoelastic elastomer. The magnetorheological elastomer reversibly changes its apparent elastic modulus and damping characteristics in response to an external magnetic field.

[0015] Among viscoelastic elastomers, thermosetting elastomers such as polyurethane elastomers are preferred from the viewpoint that the change in elastic modulus of the magnetically responsive material increases before and after application of a magnetic field.

[0016] [Polyurethane Elastomer] A polyurethane elastomer refers to an elastomer containing a urethane resin. Generally, the urethane resin corresponds to a component that forms the polymer skeleton of the polyurethane elastomer.

[0017] In this specification, the term "urethane resin" refers to a reaction product of a hydroxyl group-containing compound and an isocyanate group-containing compound. The hydroxyl group contained in the hydroxyl group-containing compound reacts with the isocyanate group contained in the isocyanate compound to form a urethane bond, thereby forming the urethane resin.

[0018] The urethane resin may be a reaction product of a hydroxyl group-containing compound and a polyisocyanate, and a chain extender and / or a terminal terminator, and these reaction products are included in the scope of the urethane resin. An example of a preferred urethane resin is the reaction product of a polyol compound and a polyisocyanate compound described in Patent Document 1.

[0019] Polyol refers to a hydroxyl-containing compound having two or more hydroxyl groups per molecule. In this specification, the term "polyol" refers to the hydroxyl-containing compound other than the slide-ring material. In addition, in this specification, the term "polyurethane skeleton" refers to a urethane resin composed of a polyol and a polyisocyanate, in which no slide-ring material is bonded.

[0020] A triol is a compound having three hydroxyl groups in one molecule. Each hydroxyl group in the triol reacts with an isocyanate group of a diisocyanate (described later) to form a urethane bond, and therefore the triol contains a branching point (crosslinking point) where three molecular chains are bonded to one atom.

[0021] The crosslinking points (branching points) in the triol can be introduced by a compound (initiator) having three or more active hydrogen atoms, and examples of such initiators include glycerol, trimethylolethane, trimethylolpropane, trimellitic acid, and diethylenetriamine.

[0022] In one embodiment, the number-average molecular weight of the triol is, for example, 2,000 to 20,000, preferably 3,000 to 15,000, and more preferably 4,000 to 10,000. By having the number-average molecular weight of the triol within this range, the molecular weight of the molecular chains bonded to the crosslinking points can be maintained at a certain level or higher. As a result, when the magnetic field strength is changed, the orientation of the magnetic powder can be changed without restriction, which is thought to increase the change in the elastic modulus of the magnetorheological elastomer composition.

[0023] In the present invention, the number average molecular weight can be measured by gel permeation chromatography as a converted value using polystyrene as a standard sample.

[0024] The triol may be, for example, a polyether triol, a polyester triol, a polycarbonate triol, a polyolefin triol, a polyacrylic triol, or the like, and is preferably a polyether triol.

[0025] Polyether triol can typically be understood as a triol of a polymer having a unit containing an ether bond as a repeating unit, and the repeating unit preferably contains an oxyalkylene unit. Such units containing an ether bond include oxyalkylene units having from 2 to 4 carbon atoms, such as oxyethylene units, oxypropylene units, and oxytetramethylene units, and particularly include oxypropylene units and oxytetramethylene units. Polyether polyols may be homopolymers containing one type of oxyalkylene unit, or copolymers containing two or more types of oxyalkylene units. Examples of polyether polyols include polyethylene triol, polypropylene triol, polytetramethylene ether triol, and polyoxyethylene-polyoxypropylene triol.

[0026] The oxyalkylene units can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, and the like.

[0027] A polyester triol can be typically understood as a triol of a polymer having repeating units containing ester bonds. The units containing ester bonds can be formed by the reaction of a diol with a dicarboxylic acid or by ring-opening polymerization of a cyclic ester compound. A polyester polyol may be a homopolymer containing one type of repeating unit or a copolymer containing two or more types of repeating units.

[0028] The diol used as a raw material for the polyester triol may typically be a low-molecular-weight diol having a molecular weight of 50 or more and 300 or less, and specific examples thereof include linear or branched aliphatic diols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methylpentane-1,5-diol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; bisphenol compounds such as bisphenol A and bisphenol F; alkylene oxide adducts of these bisphenol compounds; and alicyclic diols such as cyclohexanedimethanol. The alkylene oxide adducts of bisphenol compounds can be formed by ring-opening polymerization of a cyclic ether with a bisphenol compound, and examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0029] Examples of dicarboxylic acids that are raw materials for polyester triols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid; anhydrides of the aliphatic dicarboxylic acids or aromatic dicarboxylic acids; and esters of aliphatic dicarboxylic acids or aromatic dicarboxylic acids. The esters of aliphatic dicarboxylic acids or aromatic dicarboxylic acids can be formed by reacting an aliphatic dicarboxylic acid or aromatic dicarboxylic acid with an alcohol, and examples of such alcohols include aliphatic alcohols having from 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and butanol.

[0030] Polycarbonate triol can be understood as a triol of a polymer having units containing carbonate bonds (-O-CO-O-) as repeating units. The units containing carbonate bonds (-O-CO-O-) can be formed by the reaction of a carbonate ester with a diol, or the reaction of phosgene with a diol, etc. Polycarbonate polyol may be a homopolymer containing one type of repeating unit, or a copolymer containing two or more types of repeating units.

[0031] Examples of carbonate esters that are raw materials for polycarbonate triol include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclohexyl carbonate, dicyclohexyl carbonate, and diphenyl carbonate.

[0032] As the diol that is a raw material for the polycarbonate triol, typically, a low molecular weight diol having a molecular weight of 50 or more and 300 or less, or a high molecular weight diol having a number average molecular weight of more than 300 may be used.

[0033] Examples of low-molecular-weight diols include linear or branched aliphatic diols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methylpentane-1,5-diol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; bisphenol compounds such as bisphenol A and bisphenol F; alkylene oxide adducts of the bisphenol compounds; and alicyclic diols such as cyclohexanedimethanol. The alkylene oxide adducts of bisphenol compounds can be formed by ring-opening polymerization of a bisphenol compound with a cyclic ether, and examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0034] Examples of high molecular weight diols include polyether diols such as polyethylene glycol and polypropylene glycol, polyester diols such as polyhexamethylene adipate, etc. The number average molecular weight of the high molecular weight diol is generally more than 300, preferably 400 to 5,000, more preferably 400 to 2,000.

[0035] Polyolefin triol can be understood as a triol of a polymer having a unit consisting of a divalent hydrocarbon group as a repeating unit. The unit consisting of a divalent hydrocarbon group can be formed by polymerization of an alkene or a diene. The polyolefin triol may be a homopolymer containing one type of repeating unit, or a copolymer containing two or more types of repeating units.

[0036] Examples of alkenes that are raw materials for polyolefin triols include ethylene, propylene, and isobutene, and examples of dienes that are raw materials for polyolefin triols include butadiene and isoprene.

[0037] Polyacrylic triol can be understood as a triol of a polymer having units derived from (meth)acrylic monomers as repeating units. The polyacrylic triol may be a homopolymer containing one type of repeating unit, or a copolymer containing two or more types of repeating units.

[0038] The (meth)acrylic monomer may include a (meth)acrylic monomer having a hydroxyl group, other (meth)acrylic monomers and / or other vinyl monomers.

[0039] Examples of the (meth)acrylic monomer having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0040] Other (meth)acrylic monomers include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, and itaconic acid; and (meth)acrylamide monomers such as unsubstituted (meth)acrylamide, dimethyl(meth)acrylamide, N,N-methylenebis(meth)acrylamide, and diacetone(meth)acrylamide.

[0041] Other vinyl monomers include styrene and methylstyrene.

[0042] The content of triol contained in the polyol is, for example, 5% by mass or more and 70% by mass or less, more preferably 5% by mass or more and 50% by mass or less, and even more preferably 15% by mass or more and 40% by mass or less.

[0043] The polyol preferably contains a diol. A diol refers to a compound having two hydroxyl groups in one molecule. By containing a diol as the polyol, it may be easier to control the molecular weight of the molecular chains bonded to the crosslinking points.

[0044] The diol may be a low molecular weight diol having a molecular weight of 50 or more and 300 or less, or may be a high molecular weight diol having a number average molecular weight of more than 300. In one embodiment, a high molecular weight diol is preferred, and a polyether diol is more preferred.

[0045] Examples of low-molecular-weight diols include linear or branched aliphatic diols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methylpentane-1,5-diol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; bisphenol compounds such as bisphenol A and bisphenol F; cyclic ether adducts of the bisphenol compounds; and alicyclic diols such as cyclohexanedimethanol. Alkylene oxide adducts of bisphenol compounds can be formed by ring-opening polymerization of a cyclic ether with a bisphenol compound, and examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0046] Examples of high molecular weight diols include polyether diols, polyester diols, polycarbonate diols, polyolefin diols, and polyacrylic diols.

[0047] Polyether diols can typically be understood as polymer diols having units containing ether bonds as repeating units, and the repeating units preferably contain oxyalkylene units. Such oxyalkylene units include oxyalkylene units having from 2 to 4 carbon atoms, such as oxyethylene units, oxypropylene units, and oxytetramethylene units, and particularly include oxypropylene units and oxytetramethylene units. Polyether polyols may be homopolymers containing one type of oxyalkylene unit, or copolymers containing two or more types of oxyalkylene units. Examples of polyether polyols include polyethylene triol, polypropylene triol, polytetramethylene ether triol, and polyoxyethylene-polyoxypropylene triol.

[0048] The oxyalkylene units can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, and the like.

[0049] A polyester diol can typically be understood as a polymer diol having a unit containing an ester bond as a repeating unit.

[0050] Polycarbonate diol can be typically understood as a polymer diol having units containing carbonate bonds (—O—CO—O—) as repeating units.

[0051] Polyolefin diols can be typically understood as polymeric diols having units consisting of divalent hydrocarbon groups as repeating units.

[0052] Polyacrylic diol can be typically understood as a polymeric diol having units derived from (meth)acrylic monomers as repeating units.

[0053] The number average molecular weight of the high molecular weight diol is, for example, 500 or more and 50,000 or less, preferably 1,500 or more and 20,000 or less, and more preferably 3,000 or more and 10,000 or less.

[0054] The content of the diol is preferably 50 parts by mass or more and 1,000 parts by mass or less, more preferably 100 parts by mass or more and 700 parts by mass or less, and even more preferably 150 parts by mass or more and 550 parts by mass or less, relative to 100 parts by mass of the triol.

[0055] In a preferred embodiment, the polyol includes a triol and a diol. The total content of the triol and the diol in 100% by mass of the polyol is, for example, 80% by mass or more and 100% by mass or less, preferably 90% by mass or more and 100% by mass or less, and more preferably 95% by mass or more and 100% by mass or less.

[0056] The polyol may contain other polyols in addition to the triol and diol, such as a triol having a molecular weight of less than 4,000 or a triol having four or more hydroxyl groups per molecule.

[0057] The isocyanate compound refers to a compound having two or more isocyanate groups in one molecule. The number of isocyanate groups contained in one molecule of the isocyanate compound is typically 2 to 4, and particularly 2 to 3.

[0058] Examples of the isocyanate compound include aliphatic isocyanates, aromatic isocyanates, and alicyclic isocyanates.

[0059] Examples of the aliphatic isocyanate include tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0060] Aromatic isocyanates include 1,3- and 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-2,5-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1-isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, 1,3-dimethyl-4,6-phenylene diisocyanate, 1,4-dimethyl-2,5-phenylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, 3-methyl-4,6-phenylene diisocyanate, 3-methyl-5,5-diisocyanate, 5-methyl-6,6-diisocyanate, 5-methyl-7,6-diisocyanate, 5-methyl-8,6-diisocyanate, 5-methyl-9,6-diisocyanate, 5-methyl-10,10-diisocyanate, 1-methyl-11,12-diisocyanate, 1-methyl-12,13-diisocyanate, 1-methyl-13,14-diisocyanate, 1-methyl-14,15-diisocyanate, 1-methyl-15,16-diisocyanate, 1-methyl-15,17-diisocyanate, 1-methyl-16,18-diisocyanate, 1-methyl-17,19-diisocyanate, 1-methyl-18,19-diisocyanate, 1-methyl-19, -methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methyl-naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-diisocyanate isocyanate, biphenyl-2,4'-diisocyanate, biphenyl-4,4'-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4-diisocyanate, toluene diisocyanate, xylylene diisocyanate, and the like.

[0061] Examples of alicyclic isocyanates include 1,3-cyclopentylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate.

[0062] When producing the urethane resin, the molar ratio [NCO / OH] of the isocyanate groups contained in the isocyanate compound to the hydroxyl groups contained in the polyol can be, for example, 0.1 or more and 5 or less, preferably 0.3 or more and 3 or less, and more preferably 0.4 or more and 1.5 or less.

[0063] A chain extender is a compound having two or more active hydrogen atoms in one molecule, and is typically used to further react with a reaction product of a polyol and a polyisocyanate. By further reacting a chain extender with the reaction product of a polyol and a polyisocyanate, it becomes easy to obtain a high-molecular-weight urethane resin.

[0064] Examples of the chain extender include a chain extender having an amino group and a chain extender having a hydroxyl group.

[0065] Examples of chain extenders having an amino group include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,2-cyclohexanediamine, 1,4-cyclohexanediamine, aminoethylethanolamine, hydrazine, diethylenetriamine, and triethylenetetramine.

[0066] Examples of chain extenders having a hydroxyl group include aliphatic polyols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, sucrose, methylene glycol, glycerin, and sorbitol; aromatic polyols such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone; and water.

[0067] When a chain extender is contained, the molar ratio [NCO / (H+OH)] of the isocyanate groups contained in the polyisocyanate to the sum of the hydroxyl groups contained in the polyol and the active hydrogen atoms contained in the chain extender may be, for example, 0.1 or more and 5 or less, preferably 0.3 or more and 3 or less, and more preferably 0.4 or more and 1 or less.

[0068] The terminal terminator is a compound having one active hydrogen atom per molecule, and is typically used to further react the reaction product of the polyol, the polyisocyanate, and the chain extender used as needed.

[0069] Examples of the end terminator include alcohols such as hexanol, heptanol, octanol, nonanol, and undecanol; and amines such as dibutylamine.

[0070] The amount of the terminal terminator may be preferably 0.01 parts by mass or more and 20 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, per 100 parts by mass of the reaction product of the polyol and the polyisocyanate.

[0071] The average molecular weight between crosslinks of the polyurethane skeleton is preferably 9,600 or more and 30,000 or less, more preferably 12,000 or more and 28,000 or less, and even more preferably 15,000 or more and 27,000 or less. The average molecular weight between crosslinks can be understood as the average value of the molecular weight of the molecular chain between two adjacent crosslinks (branch points). Although not limited to a particular theory, it is believed that when the molecular weight between crosslinks of the urethane resin is in this range, the magnetic powder can change its orientation without restriction when a magnetic field is applied, thereby increasing the change in elastic modulus.

[0072] If the average molecular weight between crosslink points of the polyurethane skeleton is less than 9,600, the initial modulus of elasticity of the magnetorheological elastomer composition increases and the change in modulus of elasticity tends to decrease, whereas if it exceeds 30,000, the initial modulus of elasticity of the magnetorheological elastomer composition decreases and the toughness tends to decrease.

[0073] The average molecular weight between crosslinking points can be controlled by the number average molecular weight of the triol, or when a diol is used, the number average molecular weight of the diol, the amounts of the triol and diol used, and the like.

[0074] In one embodiment, the average molecular weight between crosslink points is determined by calculating the number average molecular weight of the i-functional polyol contained in the polyol as M ｉ The molar fraction of the polyol having the i-functionality in the total amount of polyol is C ｉ can be calculated based on the following formula:

[0075]

[0076] That is, assuming that the length of one polyol molecule is twice the number obtained by dividing the number average molecular weight of the polyol by the number of functional groups of the polyol, and that the number of crosslinking points contained in the polyol is the number obtained by subtracting 2 from the number of functional groups of the polyol, the above formula means that the total length of the polyol is divided by the total number of crosslinking points.

[0077] According to classical rubber theory, in crosslinked rubber that does not contain impurities, the molecular weight between crosslinking points of the crosslinked rubber is considered to correlate with the elastic modulus of the crosslinked rubber. That is, the molecular weight between crosslinking points of the crosslinked rubber is defined as Mc, the Poisson's ratio of the crosslinked rubber is defined as μ, and the density of the crosslinked rubber is defined as ρ (g / m ３, the gas constant is R (J / (K·mol)), and the temperature is T (K), the elastic modulus E (Pa) of the crosslinked rubber is expressed by the following formula:

[0078]

[0079] That is, in a crosslinked rubber that does not contain impurities, the larger the molecular weight between crosslinks, the smaller the elastic modulus of the crosslinked rubber.

[0080] The urethane resin can be produced by reacting a hydroxyl group-containing compound, a polyisocyanate, and optionally a chain extender and a terminal terminator. This reaction can be carried out without a solvent or in the presence of a reaction solvent. The reaction temperature can be 50°C or higher and 150°C or lower. Examples of reaction solvents include ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; acetate ester solvents such as ethyl acetate and butyl acetate; nitrile solvents such as acetonitrile; and amide solvents such as dimethylformamide and N-methylpyrrolidone.

[0081] The content of the urethane resin contained in the polyurethane elastomer is preferably 80% by mass or more and 100% by mass, more preferably 90% by mass or more and 100% by mass, and even more preferably 95% by mass or more and 100% by mass.

[0082] [Slide-Ring Material] A suitable slide-ring material is a polyrotaxane in which blocking groups are placed at both ends of a pseudo-polyrotaxane in which the openings of cyclic molecules are skewered and enclosed by linear molecules (both ends of the linear molecules). The cyclic molecules have hydroxyl-inert groups and hydroxyl groups via spacer groups.

[0083] (Spacer Group) The spacer group is not particularly limited as long as it is a group that connects the cyclic molecules of the polyrotaxane with the hydroxyl groups. The spacer group has a hydroxyl group therebetween, which can enhance the compatibility of the polyrotaxane with other materials, enhance the solubility of the polyrotaxane in solvents, or enhance the compatibility with various solvents, and the hydroxyl group via the spacer group can act as a crosslinking point. The spacer group preferably has a group derived from polycaprolactone. The spacer group preferably has a group derived from hydroxypropyl.

[0084] Specific examples of the cyclic molecule having a hydroxyl group via a spacer group include, but are not limited to, a hydroxyl group via a spacer group of an alkylene group such as 1-hydroxypropyl, 2-hydroxypropyl, or hydroxybutyl; a hydroxyl group via a spacer group such as polyethylene glycol, polypropylene glycol, polycaprolactone, or polylactide; etc. The spacer group is preferably polyethylene glycol, polypropylene glycol, polycaprolactone, or polylactide.

[0085] When producing a urethane resin, the slide-ring material can be used as a hydroxyl group-containing compound to bond the slide-ring material to the polyurethane skeleton. The amount of the slide-ring material used is, for example, 0.1% by mass to 15% by mass, preferably 0.1% by mass to less than 15% by mass, more preferably 0.5% by mass to 14% by mass, even more preferably 1% by mass to 13% by mass, and even more preferably 3% by mass to 12% by mass, based on the total amount of the polyol and the slide-ring material.

[0086] If the amount of the slide-ring material used is less than 0.1% by mass based on the total amount of the polyol and the slide-ring material, the initial modulus of elasticity of the magnetorheological elastomer composition decreases, and the toughness tends to decrease. If the amount of the slide-ring material used is more than 15% by mass, the initial modulus of elasticity of the magnetorheological elastomer composition increases, and the change in modulus of elasticity tends to decrease.

[0087] (Hydroxyl value) The slide-ring material preferably has a hydroxyl value of more than 60 mgKOH / g and not more than 200 mgKOH / g, more preferably from 61 mgKOH / g to 200 mgKOH / g, even more preferably from 65 mgKOH / g to 150 mgKOH / g, still more preferably from 70 mgKOH / g to 100 mgKOH / g, and particularly preferably from 75 mgKOH / g to 90 mgKOH / g.

[0088] Here, the hydroxyl value represents the amount of active hydroxyl groups measured in accordance with JIS K00701, and its unit is "mgKOH / g" unless otherwise specified in this application. In the slide-ring material, the hydroxyl groups provided via the spacer groups are active hydroxyl groups.

[0089] Generally, when a hydroxyl value is high, a crosslinked body obtained using a raw material with a high hydroxyl value has a high crosslink density, which significantly affects its mechanical properties. A high crosslink density generally improves the strength and elastic modulus of the crosslinked body, but reduces the elongation percentage. On the other hand, a low hydroxyl value generally reduces the crosslink density of the crosslinked body, increasing the elongation percentage, but reducing the elastic modulus and breaking strength of the crosslinked body. Furthermore, in applications such as electrical and electronic components and engineering that require hydrophobic properties, excess hydroxyl groups not used for crosslinking can cause moisture absorption, etc., so the absence of unnecessary hydroxyl groups can suppress the effects of moisture absorption, etc.

[0090] The above ranges are desirable because a crosslinked body using a slide-ring material will have excellent mechanical properties, such as elongation, elastic modulus, and breaking strength. By using a slide-ring material, a tough material can be created by realizing a high elongation, a relatively low elastic modulus, and high strength (a large ratio of strength to elastic modulus).

[0091] If the hydroxyl value of the slide-ring material is 60 mgKOH / g or less, the initial modulus of elasticity of the magnetorheological elastomer composition decreases, and the toughness tends to decrease. If the hydroxyl value exceeds 200 mgKOH / g, the initial modulus of elasticity of the magnetorheological elastomer composition increases, and the change in modulus of elasticity tends to decrease.

[0092] (Hydroxyl-inert groups) The slide-ring material preferably comprises hydroxyl-inert groups in which hydroxyl groups in the cyclic molecules have been inactivated. The hydroxyl-inert groups suppress the presence of excessive active hydroxyl groups in the slide-ring material, achieving the above-mentioned hydroxyl value, thereby achieving molecular design of the properties of the slide-ring material. The hydroxyl-inert groups depend on the production method of the slide-ring material of the present application, but are preferably provided on the cyclic molecules in the following forms i) to iv).

[0093] i) When an active hydroxyl group is directly bonded to a cyclic molecule, one obtained by deactivating a portion of the hydroxyl group. ii) When a first spacer group is bonded to a cyclic molecule and an active hydroxyl group is present at the end of the first spacer group, one obtained by deactivating a portion of the hydroxyl group. iii) When a first spacer group and a second spacer group are bonded to a cyclic molecule in the order of the first spacer group and the second spacer group from the cyclic molecule, and an active hydroxyl group is present at the end of the second spacer group, one obtained by deactivating a portion of the hydroxyl group. iv) Any combination of the above forms i) to iii).

[0094] The hydroxyl-inert group is not particularly limited as long as it has the function of inactivating an active hydroxyl group. Examples of the hydroxyl-inert group include, but are not limited to, alkyl ester groups, alkylcarbamoyl groups, and alkyl ether groups (the alkyl groups in each group are each independently a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms, preferably 2 to 10, and more preferably 4 to 8 carbon atoms).

[0095] Specific examples include acetyl, propionyl, butyl ester, octyl ester, cyclohexylcarboxyl, butylcarbamoyl, cyclopentylcarbamoyl, cyclohexylcarbamoyl, hexylcarbamoyl, dodecylcarbamoyl, ethylhexylcarbamoyl, butyloxy, and hexyloxy groups. The hydroxyl-inert group is preferably an alkyl ester group or an alkylcarbamoyl group, more preferably an alkylcarbamoyl. Specifically, the hydroxyl-inert group is preferably butylcarbamoyl, cyclohexylcarbamoyl, ethylhexylcarbamoyl, or dodecylcarbamoyl, more preferably butylcarbamoyl or cyclohexylcarbamoyl.

[0096] (Cyclic Molecule) The cyclic molecule of the cyclic ring material is not particularly limited as long as it is cyclic, has an opening, and is skewered and enclosed by the linear molecule. The cyclic molecule has a hydroxyl group via the spacer group described above. It is also preferable that it has the hydroxyl-inert group described above. The cyclic molecule may have a group other than those described above. For example, examples of groups other than those described above include, but are not limited to, a phenyl group, a benzylcarbamoyl group, a phenylethylcarbamoyl group, a benzyl ester group, and a butylbenzyl ester group.

[0097] The cyclic molecule may be selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. For example, some of the —OH groups of α-cyclodextrin may be substituted with the spacer group and / or the hydroxyl-inert group, or with groups other than those mentioned above.

[0098] (Linear molecule) The linear molecule of the slide-ring material is not particularly limited as long as it can be included in the opening of the cyclic molecule used in a skewered manner. For example, linear molecules include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, cellulose-based resins (carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal-based resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc. and / or copolymers thereof, polyolefin-based resins such as polyethylene, polypropylene, and copolymer resins with other olefin-based monomers, polyester resins, polyvinyl chloride resins, polystyrene-based resins such as polystyrene and acrylonitrile-styrene copolymer resins, polymethyl methacrylate and (meth)acrylic acid. p) The resin may be selected from the group consisting of acrylic resins such as acrylic ester copolymers and acrylonitrile-methyl acrylate copolymers, polycarbonate resins, urethane resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, and derivatives or modifications thereof, polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymers (ABS resins), polyamides such as nylon, polyimides, polydienes such as polyisoprene and polybutadiene, polysiloxanes such as polydimethylsiloxane, polysulfones, polyimines, polyacetic anhydrides, polyureas, polysulfides, polyphosphazenes, polyketones, polyphenylenes, polyhaloolefins, and derivatives thereof, such as polyethylene glycol, polyisoprene, polyisobutylene, polybutadiene, polypropylene glycol, polytetrahydrofuran, polydimethylsiloxane, polyethylene, polypropylene, polyvinyl alcohol, and polyvinyl methyl ether. In particular, polyethylene glycol is preferable.

[0099] The slide-ring material has a number average molecular weight (ie, Mn) of, for example, 50,000 or more and 400,000 or less, preferably 100,000 or more and 300,000 or less, and more preferably 150,000 or more and 200,000 or less.

[0100] (Blocking Group) The blocking groups of the slide-ring material are not particularly limited as long as they are arranged at both ends of the pseudopolyrotaxane and act to prevent the cyclic molecules used from detaching. For example, the blocking group may be selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, pyrenes, substituted benzenes (substituents include, but are not limited to, alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, phenyl, etc., and one or more substituents may be present), optionally substituted polynuclear aromatics (substituents include, but are not limited to, the same as those described above, and one or more substituents may be present), and steroids.

[0101] Preferably, the group is selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, and pyrenes, and more preferably, the group is an adamantane group or a cyclodextrin.

[0102] [Other Resins] The polyurethane elastomer may further contain a resin other than the urethane resin, such as an acrylic resin, a polyester resin, a polyamide resin, a polycarbonate resin, or a silicone resin.

[0103] [Plasticizer] The polyurethane elastomer may contain a plasticizer in addition to the urethane resin. Examples of the plasticizer include aromatic dicarboxylic acid plasticizers, alicyclic dicarboxylic acid plasticizers, aliphatic dicarboxylic acid plasticizers, phosphoric acid plasticizers, and trimellitic acid plasticizers.

[0104] Examples of aromatic dicarboxylic acid plasticizers include phthalate diesters such as dibutyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, and ditridecyl phthalate; isophthalate diesters such as dioctyl isophthalate and di-2-ethylhexyl isophthalate; and terephthalate diesters such as dioctyl terephthalate and di-2-ethylhexyl terephthalate.

[0105] Examples of the alicyclic dicarboxylic acid plasticizer include bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate, di-2-ethylhexyl 4,5-epoxycyclohexane-1,2-dicarboxylate, di(9,10-epoxystearyl) 4,5-epoxycyclohexane-1,2-dicarboxylate, and diisononyl 1,2-cyclohexanedicarboxylate.

[0106] Examples of the aliphatic dicarboxylic acid plasticizer include adipic acid diesters such as dioctyl adipate, di-2-ethylhexyl adipate, isononyl adipate, and diisodecyl adipate; and sebacate diesters such as dioctyl sebacate, di-2-ethylhexyl sebacate, and diisononyl sebacate.

[0107] Examples of the phosphoric acid plasticizer include phosphate esters such as trioctyl phosphate, tri-2-ethylhexyl phosphate, and tricresyl phosphate.

[0108] Examples of trimellitic acid plasticizers include trimellitic acid triesters such as trioctyl trimellitate and tri-2-ethylhexyl trimellitate; and pyromellitic acid tetraesters such as tetraoctyl pyromellitate and tetra-2-ethylhexyl pyromellitate.

[0109] The plasticizer preferably includes an aromatic dicarboxylic acid plasticizer or an alicyclic dicarboxylic acid plasticizer, and more preferably includes bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate.

[0110] The content of the plasticizer is 60% by mass or less, preferably 5% by mass to 40% by mass, and more preferably 10% by mass to 30% by mass, based on the total mass of the composition. When the content of the plasticizer is within this range, the magnetorheological elastomer composition has an appropriate viscosity, and the orientation of the magnetic powder is likely to change in response to changes in the magnetic field.

[0111] [Additives] The polyurethane elastomer may contain additives in addition to the urethane resin and plasticizer. Examples of such additives include urethane catalysts, antioxidants, light stabilizers, impact resistance agents, antistatic agents, flame retardants, preservatives, UV absorbers, viscosity modifiers, and colorants.

[0112] The urethanization catalyst is used in the reaction of polyol and polyisocyanate, and examples thereof include tin-based compounds such as tin octoate, dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate; titanium-based compounds such as dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; zinc-based compounds such as zinc naphthenate and zinc 2-ethylhexanoate; and tertiary amines such as triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undecene-7.

[0113] The content of the urethanization catalyst may be 0.01 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the urethane resin.

[0114] [Magnetic Powder] The magnetic powder refers to a powder of a magnetic material whose magnetic moment can change in direction or magnitude in response to a change in an external magnetic field. The magnetic material may typically be a ferromagnetic material, and preferably a soft magnetic material.

[0115] The magnetic material may be, for example, Fe, or an alloy or oxide containing Fe; preferably, Fe, or an alloy or oxide containing Fe and at least one selected from the group consisting of B, C, N, O, Na, Mg, Al, Si, P, S, Cl, K, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Zr, Nb, Mo, Pd, Sn, Ba, La, Ta, and Bi; more preferably, Fe, or an alloy containing Fe and at least one selected from the group consisting of B, Al, Si, Cr, Co, and Ni.

[0116] Such magnetic materials include Fe, iron oxide, soft ferrites such as manganese zinc ferrite, nickel zinc ferrite, copper zinc ferrite, and sodium ferrite, and alloys such as FeNi alloys, FeCo alloys, FeSi alloys, FeSiCr alloys, FeSiAl alloys, and FeSiBCr alloys. Of these, preferred magnetic materials are Fe, iron oxide, FeCo alloys, and FeSiCr alloys.

[0117] The coercive force of the magnetic material is preferably 100 A / m or less, and the lower limit can be 0 A / m or more.

[0118] The saturation magnetic flux density of the magnetic material may be preferably 0.1 T or more and 3 T or less, more preferably 0.5 T or more and 2.5 T or less, and even more preferably 0.7 T or more and 2.3 T or less.

[0119] The magnetic permeability of the magnetic material measured under a magnetic field of 0.002 T may be preferably 0.0001 H / m or more and 1 H / m or less, more preferably 0.0005 H / m or more and 0.1 H / m or less, and even more preferably 0.001 H / m or more and 0.01 H / m or less.

[0120] The coercive force, saturation magnetic flux density and magnetic permeability of a magnetic material refer to the coercive force, saturation magnetic flux density and magnetic permeability measured in bulk, and can typically be measured by a vibrating sample magnetometer.

[0121] The magnetic powder may be surface-treated. Examples of the surface treatment agent used to treat the surface of the magnetic powder include a silane compound and a silane coupling agent.

[0122] Average particle size of magnetic powder (D ５０From the viewpoint of improving the toughness of the magnetorheological elastomer composition, the thickness of the magnetorheological elastomer composition is, for example, 0.3 μm or more and 30 μm or less, preferably 0.5 μm or more and 15 μm or less, and more preferably 0.8 μm or more and 10 μm or less.

[0123] Average particle size of magnetic powder (D ５０ ) can be measured and calculated by a laser diffraction / scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the magnetic powder is created on a volume basis using a laser diffraction / scattering particle size distribution measuring device, and the 50% particle size (average particle size) (D ５０ ) can be calculated. A measurement sample that can be preferably used is one in which magnetic powder is dispersed in pure water using ultrasonic waves. As a laser diffraction scattering type particle size distribution measuring device, "MT3000II" manufactured by Microtrackbell, "LA-960" manufactured by Horiba, Ltd., "SALD-2200" manufactured by Shimadzu Corporation, etc. can be used.

[0124] Unless otherwise specified, the particle size of the magnetic powder in this specification is the average particle size (D ５０ ) means

[0125] Known magnetic powders include those having spherical three-dimensional shapes and those having non-spherical three-dimensional shapes. Non-spherical magnetic powders are magnetic powders having a three-dimensional shape other than spherical. Examples of non-spherical magnetic powders include magnetic powders having three-dimensional shapes such as flat, flat spherical, plate-like, scale-like, needle-like, columnar, polygonal, and polyhedral. The magnetic powder may be spherical magnetic powder, or may be a mixture of spherical and non-spherical magnetic powders. In a preferred embodiment, the magnetic powder is a mixture of spherical magnetic powder and flat magnetic powder, or a mixture of spherical magnetic powder and polyhedral magnetic powder.

[0126] The aspect ratio of the spherical magnetic powder is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.2 or less. The lower limit can be 1, for example.

[0127] The aspect ratio of the flat magnetic powder is preferably 7 or more and 15 or less, more preferably 10 or more and 13 or less, and even more preferably 10 or more and 11 or less.

[0128] The aspect ratio of the magnetic powder referred to in this specification is the value (a / b) calculated by dividing the "average major axis length a (μm) of the magnetic powder" by the "average thickness b (μm) of the magnetic powder." The average major axis length of the magnetic powder is the average value of the major axis lengths of the magnetic powder. The average value of the major axis length of the magnetic powder can be, for example, the number average when the major axis lengths of, for example, 50 magnetic powder particles are measured based on a scanning electron microscope image. The major axis length of the magnetic powder refers to the length of the line segment connecting any two points on the outer surface of the magnetic powder particle that are the longest distance apart.

[0129] When the shape of the magnetic powder is spherical or flattened spherical, the aspect ratio of the magnetic powder is the value (a / b) calculated by dividing the "average radial length a (μm) of the magnetic powder" by the "average thickness b (μm) of the magnetic powder."

[0130] A polyhedron refers to a three-dimensional shape having four or more flat faces, a face-to-face angle greater than 0° but less than 180°, and an edge-to-edge angle greater than 0° but less than 180°. Specific examples of polyhedra include tetrahedrons, hexahedrons, octahedrons, decahedrons, dodecahedrons, and tetradecahedrons. Among these, preferred polyhedra are hexahedrons and octahedrons. Specific examples of hexahedrons include hexahedrons having face-to-face angles of approximately 90° and edge-to-edge angles of approximately 90°. Specific examples of octahedrons include octahedrons having face-to-face angles of approximately 109° and edge-to-edge angles of approximately 60°.

[0131] When the connecting portions between the faces of the polyhedron are formed by curved surfaces, the angle between the faces can be the angle of the intersection of straight lines extrapolated from both planes. In one embodiment, there may be a case where a depression exists in a part of the polyhedron, and the angle between the faces constituting the downward convex shape is x degrees, which is greater than 180 degrees. In such a case, the angle between the faces may be set to (360-x) degrees in order to specify the polyhedron shape as the overall outline supplementing the downward convex shape.

[0132] It is believed that when a magnetic field is applied to a magnetorheological elastomer composition, the magnetic powder in the viscoelastic elastomer aligns along the magnetic field lines and stacks up in chains, forming numerous magnetic powder pillars, thereby increasing the hardness in the direction of the magnetic field lines.

[0133] The content of the magnetic powder in the magnetorheological elastomer composition of the present invention, expressed as a volume fraction based on the magnetorheological elastomer composition, is, for example, 15 to 60 volume %, preferably 20 to less than 60 volume %, and more preferably 40 to 55 volume %. When the content of the magnetic powder is within this range, a good change in the elastic modulus in response to a change in the magnetic field can be achieved.

[0134] The content of the magnetic powder can be determined by applying heat (500° C. or higher) to the magnetorheological elastomer to remove the organic components, and then measuring the weight of the remaining magnetic powder.

[0135] [Method for Producing the Composition] The magnetorheological elastomer composition of the present invention can be produced by mixing a viscoelastic elastomer and a magnetic powder. Mixing the viscoelastic elastomer and the magnetic powder can include, for example, directly mixing the viscoelastic elastomer and the magnetic powder, or mixing the raw materials for the viscoelastic elastomer with the magnetic powder and then reacting the raw materials to form the viscoelastic elastomer. When mixing the viscoelastic elastomer and the magnetic powder, catalysts, plasticizers, and additives may be used as needed.

[0136] When a polyurethane elastomer is used as the viscoelastic elastomer, the magnetorheological elastomer composition can be produced by mixing a polyol, a polyisocyanate, and a magnetic powder, followed by heating to obtain a reaction product of the polyol and the polyisocyanate. The heating temperature can be 50°C or higher and 150°C or lower, and the heating time can be 30 minutes or higher and 20 hours or lower. The heating can be carried out without a solvent or in the presence of a reaction solvent. Examples of such a reaction solvent include toluene, acetone, and n-methylpyrrolidone.

[0137] The order of mixing the polyol, polyisocyanate, and magnetic powder is not particularly limited. For example, the polyol, polyisocyanate, and magnetic powder may be mixed simultaneously, or the polyol and magnetic powder may be mixed together and then the mixture may be mixed with the polyisocyanate. When mixing the polyol, polyisocyanate, and magnetic powder, a urethane catalyst, resin, plasticizer, and additives, which are used as needed, may be present as appropriate.

[0138] [Characteristics of the Composition] The magnetorheological elastomer composition has viscosity and elasticity.

[0139] The magnetorheological elastomer composition of the present invention has excellent toughness and exhibits a high breaking strain rate. The breaking strain rate refers to the percentage of elongation a material undergoes before breaking. The magnetorheological elastomer composition of the present invention exhibits a breaking strain rate of, for example, 1000% or more, preferably 1350% or more, more preferably 1480% or more, and even more preferably 1500% or more.

[0140] The magnetorheological elastomer composition of the present invention has a storage modulus G' measured under zero magnetic field. ０ However, the pressure is, for example, 15 kPa or less, preferably 10 kPa or less, and more preferably 6 kPa or less.

[0141] The magnetorheological elastomer composition of the present invention exhibits an increased storage modulus when a magnetic field is applied compared to when no magnetic field is applied. Specifically, the storage modulus G' when a magnetic field of 150 mT is applied １ is, for example, 300 kPa or more, preferably 500 kPa or more, and more preferably 600 kPa or more.

[0142] The rate of change in storage modulus due to application of a magnetic field (hereinafter simply referred to as "rate of change in storage modulus due to a magnetic field") is defined as G' １ / G' ０ In this case, the change in storage modulus of the magnetorheological elastomer composition of the present invention due to a magnetic field is, for example, 80 times or more, preferably 120 times or more, and more preferably 125 times or more.

[0143] The magnetorheological elastomer composition of the present invention is preferably used to deflect sound waves or ultrasonic waves, and is particularly suitable for use in acoustic devices such as speakers and ultrasonic devices such as ultrasonic sensors. The magnetorheological elastomer composition of the present invention can also be used in tactile feedback devices that utilize changes in elastic modulus.

[0144] The present invention provides the following aspects: [1] A magnetorheological elastomer composition comprising a viscoelastic elastomer containing a urethane resin and a magnetic powder dispersed in the viscoelastic elastomer, wherein the urethane resin has a polyurethane skeleton formed from a reaction product of a polyol and a polyisocyanate, the polyurethane skeleton having an average molecular weight between crosslink points of 9,600 or more and 30,000 or less, preferably 12,000 or more and 28,000 or less, and more preferably 15,000 or more and 27,000 or less, and the urethane resin contains a slide-ring material bonded to the polyurethane skeleton.

[0145] [2] The magnetorheological elastomer composition of aspect 1, wherein the slide-ring material is contained in an amount of 0.1% by mass or more and 15% by mass or less, preferably 0.1% by mass or more and less than 15% by mass, more preferably 0.5% by mass or more and 14% by mass or less, even more preferably 1% by mass or more and 13% by mass or less, and even more preferably 3% by mass or more and 12% by mass or less, based on the total amount of the polyol and the slide-ring material.

[0146] [3] The magnetorheological elastomer composition of aspect 1 or 2, wherein the slide-ring material is a polyrotaxane formed by arranging blocking groups at both ends of a pseudo-polyrotaxane in which the openings of cyclic molecules are skewered and enclosed by linear molecules to prevent the cyclic molecules from detaching, and the cyclic molecules include a polyrotaxane having a hydroxyl-inert group and a hydroxyl group via a spacer group.

[0147] [4] The magnetorheological elastomer composition of any one of Aspects 1 to 3, wherein the slide-ring material has a number average molecular weight of 50,000 to 400,000, preferably 100,000 to 300,000, and more preferably 150,000 to 200,000, and a hydroxyl value of more than 60 mgKOH / g to 200 mgKOH / g, preferably 61 mgKOH / g to 200 mgKOH / g, more preferably 65 mgKOH / g to 150 mgKOH / g, even more preferably 70 mgKOH / g to 100 mgKOH / g, and particularly preferably 75 mgKOH / g to 90 mgKOH / g.

[0148] [5] The magnetorheological elastomer composition of any one of Aspects 1 to 4, wherein the magnetic powder is contained in an amount of 15 vol% or more and 60 vol% or less, preferably 20 vol% or more and less than 60 vol%, and more preferably 40 vol% or more and 55 vol% or less.

[0149] [6] The magnetorheological elastomer composition of any one of Aspects 1 to 5, wherein the magnetic powder has an average particle size of 0.3 μm or more and 30 μm or less, preferably 0.5 μm or more and 15 μm or less, and more preferably 0.8 μm or more and 10 μm or less.

[0150] [7] The magnetorheological elastomer composition of any one of Aspects 1 to 6, further comprising, as a plasticizer, at least one selected from the group consisting of an aromatic dicarboxylic acid plasticizer and an alicyclic dicarboxylic acid plasticizer.

[0151] [8] The magnetorheological elastomer composition of any one of Aspects 1 to 7, wherein the polyol comprises a triol having a number average molecular weight of 2,000 or more and 20,000 or less, preferably 3,000 or more and 15,000 or less, and more preferably 4,000 or more and 10,000 or less.

[0152] [9] A method for producing a magnetorheological elastomer composition containing a viscoelastic elastomer containing a urethane resin and a magnetic powder dispersed in the viscoelastic elastomer, the method comprising: forming a polyurethane skeleton consisting of a polyol and a polyisocyanate; adjusting the average molecular weight between crosslink points of the polyurethane skeleton to 9,600 or more and 30,000 or less, preferably 12,000 or more and 28,000 or less, more preferably 15,000 or more and 27,000 or less; and bonding a slide-ring material to the polyurethane skeleton.

[0153] The present invention will be described in more detail with reference to the following examples, but is not limited thereto. The amounts blended in the examples are in parts by mass unless otherwise specified.

[0154] The raw materials, manufacturing method, and evaluation method of the magnetorheological elastomer composition are described below. <Raw Materials> A. Resin (A1) Raw materials for urethane resin (x1) Triol Polypropylene glycol, triol type (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (polypropylene glycol, triol type, average molecular weight 4,000), Mn = 4,000) Polypropylene glycol, triol type (manufactured by Murata Manufacturing Co., Ltd., Mn = 10,000)

[0155] (x2) Diol Polypropylene glycol, diol type (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (polypropylene glycol, diol type, average molecular weight 3,000), Mn=3,000) Polypropylene glycol, diol type (manufactured by Murata Manufacturing Co., Ltd., Mn=4,000) Polypropylene glycol, diol type (manufactured by Murata Manufacturing Co., Ltd., Mn=10,000)

[0156] (y) Tolylene diisocyanate ("Tolylene-2,4-diisocyanate" (trade name) manufactured by Tokyo Chemical Industry Co., Ltd.)

[0157] (A2) Polyrotaxane "SH1300P" (trade name) manufactured by ASM Corporation, hydroxyl value 85 mg KOH / mol, Mn = 180,000 "SH2400P" (trade name) manufactured by ASM Corporation, hydroxyl value 76 mg KOH / mol, Mn = 400,000

[0158] B. Magnetic Powders Iron silicon chromium alloy powder ("FeSiCr" (trade name), manufactured by JFEM Corporation, particle size 0.8 μm) Iron silicon chromium alloy powder ("EA-SMP-10 PF-20F" (trade name), manufactured by Epson Atmix Corporation, particle size 10 μm) Iron silicon chromium alloy powder ("EA-SMP-10 -325mesh" (trade name), manufactured by Epson Atmix Corporation, particle size 30 μm)

[0159] C. Plasticizer Dioctyl phthalate 4-cyclohexene-1,2-dicarboxylate bis(2-ethylhexyl)

[0160] D. Urethane catalyst: stannous octoate

[0161] <Production Method> The raw materials were charged into a reaction vessel in the amounts shown in Tables 1 and 2. The charged materials were uniformly mixed using a degassing mixer to obtain a paste. The obtained paste was heated at 75°C for 2 hours using a hot plate to be thermally cured, thereby producing a magnetorheological elastomer composition.

[0162] [Measurement of Breaking Strain Rate] The breaking strain rate of the magnetorheological elastomer composition was measured. The breaking strain rate is an index showing the toughness of the material. The length after breaking is defined as L ｆ , initial length is L ０ Then, the breaking strain rate δ is expressed by the following formula: δ (%) = {(L ｆ -L ０ ) / L ０} x 100

[0163] The magnetorheological elastomer composition was molded into a rod (5 mm x 20 mm x 1 mm thick) to prepare a sample. The sample was then placed in a dynamic viscoelasticity measuring device (TA Instruments, model: RSA-G2) and the strain until the sample broke was measured to determine the breaking strain rate. The results are shown in Tables 1 and 2.

[0164] (Measurement conditions for fracture strain rate) Measurement temperature: 25°C Tensile speed: 0.2 mm / s

[0165] (Evaluation criteria for breaking strain rate) A (Excellent): 1350% or more B (Poor): Less than 1350%

[0166] [Measurement of storage modulus] The magnetorheological elastomer composition was molded into a disk shape with a diameter of 2 cm and a thickness of 1 mm to prepare a sample. The sample was then placed in a viscoelasticity measuring device (manufactured by Anton Paar, model: MCR301), and the storage modulus was measured before and after application of a magnetic field using a magnetic field generator (manufactured by Anton Paar, model: PS-MRD). The measurement was performed with the rotation axis of the viscoelasticity measuring device parallel to the direction of the magnetic field. The results are shown in Tables 1 and 2.

[0167] (Conditions for viscoelasticity measurement) Measurement temperature: 25°C Load applied to sample from terminal: 0.3 N Frequency: 1 Hz Strain: 0.01% Magnetic field strength when applying magnetic field: 150 mT

[0168] (Evaluation criteria for change in elastic modulus) A (Excellent): 100 times or more B (Poor): Less than 100 times

[0169]

[0170]

Claims

1. A magnetorheological elastomer composition comprising a viscoelastic elastomer containing a urethane resin and magnetic powder dispersed in the viscoelastic elastomer, wherein the urethane resin has a polyurethane skeleton composed of a reaction product of a polyol and a polyisocyanate, the polyurethane skeleton has an average crosslinking point molecular weight of 9,600 or more and 30,000 or less, and the urethane resin contains a slide ring material bonded to the polyurethane skeleton.

2. The magnetorheological elastomer composition according to claim 1, wherein the slide ring material is contained in an amount of 0.1% by mass or more and 15% by mass or less based on the total amount of the polyol and the slide ring material.

3. The slide ring material is a polyrotaxane in which a blocking group is arranged at both ends of a pseudo-polyrotaxane in which an opening of a cyclic molecule is included in a skewered manner by a linear molecule so that the cyclic molecule does not desorb, and the cyclic molecule includes a polyrotaxane having a hydroxyl group-inactive group and a hydroxyl group via a spacer group. The magnetorheological elastomer composition according to claim 1 or 2.

4. The magnetorheological elastomer composition according to any one of claims 1 to 3, wherein the slide ring material has a number average molecular weight of 50,000 or more and 400,000 or less and a hydroxyl value of more than 60 mg KOH / g and 200 mg KOH / g or less.

5. The magnetorheological elastomer composition according to any one of claims 1 to 4, wherein the magnetic powder is contained in an amount of 15% by volume or more and 60% by volume or less.

6. The magnetorheological elastomer composition according to any one of claims 1 to 5, wherein the magnetic powder has an average particle diameter of 0.3 µm or more and 30 µm or less.

7. The magnetorheological elastomer composition according to any one of claims 1 to 6, further comprising at least one selected from the group consisting of an aromatic dicarboxylic acid plasticizer and a cyclic non-aromatic dicarboxylic acid plasticizer as a plasticizer.

8. The magnetorheological elastomer composition according to any one of claims 1 to 7, wherein the polyol contains a triol having a number average molecular weight of 2,000 or more and 20,000 or less.

9. A method for producing a magnetorheological elastomer composition comprising a magnetorheological elastomer containing a urethane resin and magnetic powder dispersed in the magnetorheological elastomer, the method comprising: forming a polyurethane skeleton composed of a polyol and a polyisocyanate; adjusting the average molecular weight between crosslinking points of the polyurethane skeleton to be 9,600 or more and 30,000 or less; and bonding a sliding ring material to the polyurethane skeleton.

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