Magnetoviscoelastic elastomer composition and method for producing same

Abstract

The purpose of the present invention is to provide a magnetoviscoelastic elastomer composition in which the change in the storage elastic modulus when a magnetic field is applied is greater than the storage elastic modulus when the magnetic field is not applied. This magnetoviscoelastic elastomer composition contains a resin (A) and a magnetic powder (B), the resin (A) containing a polyurethane resin (A1), the polyurethane resin (A1) containing a reaction product of a polyol (x) and a polyisocyanate (y), and the polyol (x) containing a triol (x1) having a number average molecular weight of 4000 or more.

Description

Technical Field

[0001] The present disclosure relates to a magnetic viscoelastic elastomer composition. Background Art

[0002] As a material that can be used for a vibration-proofing / vibration-damping material or an energy transmission material, a magnetically responsive material in which a magnetic substance is dispersed in a resin material is known.

[0003] As the magnetically responsive material, Patent Document 1 describes a polyurethane elastomer composition including a reaction product of a polyol compound and a polyisocyanate compound and magnetic particles, and describes the use of a propylene oxide adduct of bisphenol A as the polyol compound.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-210311 Summary of the invention

[0007] In the polyurethane elastomer composition described in Patent Document 1, the change in the storage elastic modulus when a magnetic field is applied is not sufficiently satisfactory compared to the storage elastic modulus when no magnetic field is applied.

[0008] An object of the present disclosure is to provide a magnetic viscoelastic elastomer composition having a large change in storage elastic modulus when a magnetic field is applied relative to the storage elastic modulus when no magnetic field is applied.

[0009] The magnetic viscoelastic elastomer composition disclosed herein comprises a resin (A) and a magnetic powder (B),

[0010] The resin (A) comprises a polyurethane resin (A1),

[0011] The polyurethane resin (A1) comprises a reaction product of a polyol (x) and a polyisocyanate (y).

[0012] The polyol (x) includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0013] According to the present disclosure, it is possible to provide a magnetic viscoelastic elastomer composition having a large change in storage elastic modulus when a magnetic field is applied relative to the storage elastic modulus when no magnetic field is applied. DETAILED DESCRIPTION

[0014] The magnetic viscoelastic elastomer composition disclosed herein comprises a resin (A) and a magnetic powder (B),

[0015] The resin (A) comprises a polyurethane resin (A1),

[0016] The polyurethane resin (A1) comprises a reaction product of a polyol (x) and a polyisocyanate (y).

[0017] The polyol (x) includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0018] The change of the storage modulus of the magnetic viscoelastic elastomer composition of the present disclosure relative to the storage modulus of the storage modulus of the magnetic field under the condition of applying a magnetic field without applying a magnetic field is large. That is, for the magnetic viscoelastic elastomer composition of the present disclosure, the rate of change of the elastic modulus measured under the magnetic field relative to the condition of the magnetic field strength 0A / m (hereinafter, also referred to as "zero magnetic field") (hereinafter, also referred to as "elastic modulus change rate under magnetic field") is large. Although it should not be limited to a specific theory and explained, viscoelastic elastomers can be understood as materials with both elasticity and viscosity. Moreover, it is believed that elasticity can be derived from crosslinking points (branching points), and viscosity can be derived from the molecular chain between two adjacent crosslinking points. The magnetic viscoelastic elastomer composition of the present disclosure is due to the inclusion of a polyurethane resin (A1) using a triol (x1) with a number average molecular weight of more than a certain number as a raw material, so the crosslinking point is introduced into the magnetic viscoelastic elastomer composition by the above-mentioned triol (x1), and the molecular weight of the molecular chain bound to the crosslinking point is controlled to be more than a certain. Therefore, it is considered that when a magnetic field is applied, the magnetic powder (B) contained in the magnetic viscoelastic elastomer composition can change its orientation without restriction, and a good change in elastic modulus can be obtained.

[0019] In the present disclosure, viscoelastic elastomer refers to a material having both viscosity and elasticity, which can be distinguished according to the relaxation time of stress relaxation (temporal variation of stress) when a certain strain is given. If the relaxation time is short enough relative to the observation time range, it can be understood as a viscous body, if it is long enough, it can be understood as an elastomer, and if it is an equivalent range, it can be understood as a viscoelastic body.

[0020] In the present disclosure, a magnetic viscoelastic elastomer refers to a viscoelastic elastomer containing magnetic particles, preferably a composite material in which magnetic particles are dispersed and fixed inside the viscoelastic elastomer. The magnetic viscoelastic elastomer reversibly changes the apparent elastic modulus and damping characteristics in response to an external magnetic field.

[0021] In addition, in the present disclosure, a magnetic viscoelastic elastomer means a viscoelastic elastomer containing magnetic powder. When the storage elastic modulus measured at a magnetic field strength of 0 A / m is set to G'0, and the storage elastic modulus measured at a magnetic field strength greater than 0 A / m in a manner where the magnetic field direction is parallel to the rotation axis of the rotary viscoelasticity measuring device is set to G'1, the magnetic viscoelastic elastomer can be understood as a material whose G'1 is at least greater than G'0.

[0022] [Resin (A)]

[0023] The resin (A) contains a polyurethane resin (A1).

[0024] [Polyurethane resin (A1)]

[0025] The polyurethane resin (A1) includes a reaction product of a polyol (x) and a polyisocyanate (y). The hydroxyl group contained in the polyol (x) reacts with the isocyanate group contained in the polyisocyanate (y) to form a urethane bond, thereby obtaining a polyurethane resin. The polyurethane resin (A1) may be a reaction product of a polyol (x) and a polyisocyanate (y), and a reaction product with a chain extender (z1) and / or a terminal stopper (z2), and all of these reaction products are included in the technical scope of the polyurethane resin (A1).

[0026] The polyol (x) is a compound having two or more hydroxyl groups in one molecule, and includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0027] The triol (x1) has three hydroxyl groups in one molecule. Each hydroxyl group contained in the triol (x1) reacts with an isocyanate group of a diisocyanate (y) described later to form a urethane bond, so the triol (x1) contains branching points (crosslinking points) in which three molecular chains are bonded to one atom.

[0028] The crosslinking points (branching points) in the triol (x1) can be introduced by a compound (initiator) having three or more active hydrogen atoms. Examples of the initiator include glycerin, trimethylolethane, trimethylolpropane, trimellitic acid, and diethylenetriamine.

[0029] The number average molecular weight of the triol (x1) is 4000 or more, preferably 4000 to 15000, more preferably 4000 to 10000, and further preferably 4000 to 8000. By making the number average molecular weight of the triol (x1) within the above range, the molecular weight of the molecular chain bonded to the crosslinking point can be made to be above a certain level. As a result, it is believed that when the magnetic field strength is changed, the orientation of the magnetic powder (B) can be changed without restriction, and the elastic modulus of the magnetic viscoelastic elastomer composition changes well.

[0030] In the present disclosure, the number average molecular weight can be measured by gel permeation chromatography as a converted value using polystyrene as a standard sample.

[0031] The triol (x1) may be, for example, a polyether triol, a polyester triol, a polycarbonate triol, a polyolefin triol, a polyacrylic acid triol, etc., and is preferably a polyether triol.

[0032] The above-mentioned polyether triol can be representatively 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. As the above-mentioned unit containing an ether bond, oxyalkylene units having 2 to 4 carbon atoms such as ethylene oxide units, propylene oxide units, and butylene oxide units can be cited, and propylene oxide units and butylene oxide units can be cited in particular. The above-mentioned polyether polyol can be a homopolymer containing one oxyalkylene unit, or a copolymer containing two or more oxyalkylene units. As the above-mentioned polyether polyol, polyethylene triol, polypropylene triol, polytetramethylene ether triol, polyethylene oxide-polypropylene oxide triol, etc. can be cited.

[0033] The oxyalkylene unit can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran.

[0034] The polyester triol can be representatively understood as a triol of a polymer having a unit containing an ester bond as a repeating unit. The unit containing an ester bond can be formed by the reaction of a diol with a dicarboxylic acid, or by the ring-opening polymerization of a cyclic ester compound. The polyester polyol can be a homopolymer containing one repeating unit, or a copolymer containing two or more repeating units.

[0035] As the diol as the raw material of the polyester triol, a low molecular weight diol having a molecular weight of 50 to 300 can be used representatively, and specifically, 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 can be mentioned; bisphenol compounds such as bisphenol A and bisphenol F; alkylene oxide adducts of the bisphenol compounds; alicyclic diols such as cyclohexanedimethanol, etc. The alkylene oxide adducts of the bisphenol compounds can be formed by ring-opening polymerization of cyclic ethers and bisphenol compounds, and examples of the cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0036] Examples of the dicarboxylic acid as a raw material of the polyester triol 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 naphthalene dicarboxylic acid; anhydrides of the aliphatic dicarboxylic acids or aromatic dicarboxylic acids; esters of aliphatic dicarboxylic acids or aromatic dicarboxylic acids, etc. 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 the alcohol include aliphatic alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, and butanol.

[0037] The polycarbonate triol can be understood as a triol of a polymer having a unit containing a carbonate bond (-O-CO-O-) as a repeating unit. The unit containing a carbonate bond (-O-CO-O-) can be formed by a reaction between a carbonate and a diol, a reaction between phosgene and a diol, etc. The polycarbonate polyol can be a homopolymer containing one repeating unit, or a copolymer containing two or more repeating units.

[0038] Examples of carbonates as a raw material of the polycarbonate triol include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclohexyl carbonate, dicyclohexyl carbonate, and diphenyl carbonate.

[0039] As the diol as a raw material of the polycarbonate triol, a low molecular weight diol having a molecular weight of 50 to 300 or a high molecular weight diol having a number average molecular weight exceeding 300 can be typically used.

[0040] Examples of the 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; alicyclic diols such as cyclohexanedimethanol, etc. The alkylene oxide adducts of the bisphenol compounds can be formed by ring-opening polymerization of the bisphenol compounds and cyclic ethers, and examples of the cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0041] Examples of the high molecular weight diol 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 more than 300, preferably 400 to 5000, and more preferably 400 to 2000.

[0042] The 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 the divalent hydrocarbon group can be formed by polymerization of olefins and dienes. The polyolefin triol can be a homopolymer containing one repeating unit or a copolymer containing two or more repeating units.

[0043] Examples of the olefin as a raw material of the polyolefin triol include ethylene, propylene, isobutylene, and the like, and examples of the diene as a raw material of the polyolefin triol include butadiene, isoprene, and the like.

[0044] The polyacrylic acid triol can be understood as a triol of a polymer having a unit derived from a (meth)acrylic acid monomer as a repeating unit. The polyacrylic acid triol may be a homopolymer containing one type of repeating unit or a copolymer containing two or more types of repeating units.

[0045] The (meth)acrylic monomer may include a (meth)acrylic monomer having a hydroxyl group, other (meth)acrylic monomers, and / or other vinyl monomers.

[0046] Examples of the (meth)acrylic acid monomer having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0047] Examples of the other (meth)acrylic acid 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.

[0048] Examples of the other vinyl monomers include styrene and methylstyrene.

[0049] The content of the triol (x1) contained in the polyol (x) is, for example, 3 mass % or more, preferably 3 mass % to 70 mass %, more preferably 5 mass % to 60 mass %, further preferably 7 mass % to 55 mass %.

[0050] The polyol (x) preferably includes a diol (x2). A diol (x2) is a compound having two hydroxyl groups in one molecule. By including a diol as the polyol (x), the molecular weight of the molecular chain bonded to the crosslinking point can be more easily controlled.

[0051] The diol (x2) may be a low molecular weight diol having a molecular weight of 50 to 300 or a high molecular weight diol having a number average molecular weight exceeding 300. In one embodiment, a high molecular weight diol is preferred, and a polyether diol is more preferred.

[0052] Examples of the 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; alicyclic diols such as cyclohexanedimethanol, etc. The alkylene oxide adducts of the bisphenol compounds can be formed by ring-opening polymerization of the bisphenol compounds and cyclic ethers, and examples of the cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0053] Examples of the high molecular weight diol include polyether diol, polyester diol, polycarbonate diol, polyolefin diol, and polyacrylic acid diol.

[0054] The above-mentioned polyether diol can be representatively understood as a diol of a polymer having the above-mentioned unit containing an ether bond as a repeating unit, and the repeating unit preferably contains an oxyalkylene unit. As the above-mentioned oxyalkylene unit, oxyalkylene units having 2 to 4 carbon atoms such as ethylene oxide units, propylene oxide units, and butylene oxide units can be mentioned, and propylene oxide units and butylene oxide units can be mentioned in particular. The above-mentioned polyether polyol can be a homopolymer containing one oxyalkylene unit, or a copolymer containing two or more oxyalkylene units. As the above-mentioned polyether polyol, polyethylene triol, polypropylene triol, polytetramethylene ether triol, polyethylene oxide-polypropylene oxide triol, etc. can be mentioned.

[0055] The oxyalkylene unit can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran.

[0056] The polyester diol can be typically understood as a diol of a polymer having the above-mentioned unit containing an ester bond as a repeating unit.

[0057] The polycarbonate diol can be representatively understood as a diol of a polymer having a repeating unit of the unit containing a carbonate bond (—O—CO—O—).

[0058] The polyolefin diol mentioned above can be typically understood as a diol of a polymer having a unit composed of the above-mentioned divalent hydrocarbon group as a repeating unit.

[0059] The polyacrylic acid diol mentioned above can be typically understood as a diol of a polymer having a unit derived from the above-mentioned (meth)acrylic acid monomer as a repeating unit.

[0060] The number average molecular weight of the high molecular weight diol is more than 300, preferably 400 to 5,000, and more preferably 400 to 3,000.

[0061] The content of the diol (x2) is preferably 50 to 2,000 parts by mass, more preferably 60 to 1,500 parts by mass, and even more preferably 70 to 1,200 parts by mass, based on 100 parts by mass of the triol (x1).

[0062] In a preferred embodiment, the polyol (x) comprises a triol (x1) and a diol (x2). In 100% by mass of the polyol (x), the total content of the triol (x1) and the diol (x2) is, for example, 80% by mass to 100% by mass, preferably 90% by mass to 100% by mass, and more preferably 95% by mass to 100% by mass.

[0063] The polyol (x) may contain other polyols (x3) in addition to the triol (x1) and the diol (x2). The other polyols (x3) may contain triols having a molecular weight of less than 4000, triols having 4 or more hydroxyl groups in one molecule, and the like.

[0064] The polyisocyanate (y) is a compound having two or more isocyanate groups in one molecule. The number of isocyanate groups contained in one molecule of the polyisocyanate (y) is typically 2 to 4, particularly 2 to 3.

[0065] Examples of the polyisocyanate (y) include aliphatic polyisocyanates, aromatic polyisocyanates, and alicyclic polyisocyanates.

[0066] Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0067] Examples of the aromatic polyisocyanate 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, diethylphenylene diisocyanate, diisopropylphenylene diisocyanate, 1-methyl-3,5-diethylphenylene diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, 1,4-naphthalene-diisocyanate, 1,5-naphthalene-diisocyanate, 1-methyl-1,5-naphthalene-diisocyanate, 2,6-naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-diisocyanate, 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, xylene diisocyanate, etc.

[0068] Examples of the alicyclic polyisocyanate include 1,3-cyclopentylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, 1,4-bis(isocyanatemethyl)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.

[0069] When producing the polyurethane resin (A1), the molar ratio [NCO / OH] of the isocyanate group contained in the polyisocyanate (y) to the hydroxyl group contained in the polyol (x) may be, for example, 0.1 to 5, preferably 0.3 to 3, and more preferably 0.4 to 1.5.

[0070] The chain extender (z1) is a compound having two or more active hydrogen atoms in one molecule, and is typically used to further react with the reaction product of the polyol (x) and the polyisocyanate (y). By further reacting the reaction product of the polyol (x) and the polyisocyanate (y) with the chain extender (z1), a high molecular weight polyurethane resin can be easily obtained.

[0071] Examples of the chain extender (z1) include a chain extender having an amino group and a chain extender having a hydroxyl group.

[0072] Examples of the chain extender having an amino group include ethylenediamine, 1,2-propylenediamine, 1,6-hexamethylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,2-cyclohexyldiamine, 1,4-cyclohexyldiamine, aminoethylethanolamine, hydrazine, diethylenetriamine, and triethylenetetramine.

[0073] Examples of the chain extender 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, glycerol, 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.

[0074] When the chain extender (z1) is contained, the molar ratio [NCO / (H+OH)] of the isocyanate groups contained in the polyisocyanate (y) to the total of the hydroxyl groups contained in the polyol (x) and the active hydrogen atoms contained in the chain extender (z1) may be, for example, 0.1 to 5, preferably 0.3 to 3, and more preferably 0.4 to 1.

[0075] The terminal terminator (z2) is a compound having one active hydrogen atom in one molecule, and is typically used to further react the reaction product of the polyol (x) and the polyisocyanate (y) and, if necessary, the chain extender (z1).

[0076] Examples of the terminal blocking agent include alcohols such as hexanol, heptanol, octanol, nonanol, and undecanol; and amines such as dibutylamine.

[0077] The amount of the blocking agent (z1) is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the reactant of the polyol (x) and the polyisocyanate (y).

[0078] The average molecular weight between crosslinking points of the polyurethane resin (A1) may preferably be 9300 to 30000, more preferably 9500 to 27000, further preferably 9500 to 20000, and further preferably 9500 to 12000. The average molecular weight between crosslinking points may be understood as the average value of the molecular weight of the molecular chain between two adjacent crosslinking points (branching points). Although the explanation should not be limited to a specific theory, it is believed that by making the molecular weight between crosslinking points in the polyurethane resin (A1) within the above range, the magnetic powder (B) can change its orientation without restriction when a magnetic field is applied, thereby obtaining a good change in elastic modulus.

[0079] The average molecular weight between crosslinking points is the number average molecular weight of the triol (x1). When the diol (x2) is used, it is the number average molecular weight of the diol (x2), and can be controlled by the amounts of the triol (x1) and the diol (x2) used.

[0080] In one embodiment, the average molecular weight between crosslinking points is denoted by M, where the number average molecular weight of the i-functional polyol contained in the polyol (x) is denoted by i The molar fraction of the i-functional polyol in all polyols (x) is C i When , it can be calculated according to the following formula (1).

[0081]

[0082] That is, when the value obtained by dividing the number average molecular weight of the polyol by the number of functional groups of the polyol by twice the value is assumed to be the length of one polyol molecule, and the value obtained by subtracting 2 from the number of functional groups of the polyol is assumed to be the number of crosslinking points contained in the polyol, the above formula (1) becomes the total length of the polyol divided by the total number of crosslinking points.

[0083] According to the classical rubber theory, it is believed that the molecular weight between crosslinking points of the crosslinked rubber in a crosslinked rubber without impurities is related to the elastic modulus of the crosslinked rubber. That is, the molecular weight between crosslinking points of the crosslinked rubber is Mc, the Poisson's ratio of the crosslinked rubber is μ, and the density of the crosslinked rubber is 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 cross-linked rubber is expressed by the following formula.

[0084]

[0085] That is, in a cross-linked rubber containing no impurities, the larger the molecular weight between cross-linking points, the smaller the elastic modulus of the cross-linked rubber.

[0086] The magnetic viscoelastic elastomer composition disclosed in the present invention contains magnetic powder (B) in addition to the polyurethane resin (A1). It is believed that the relationship between the average molecular weight between cross-linking points of the above-mentioned polyurethane resin (A1) and the elastic modulus of the magnetic viscoelastic elastomer composition does not necessarily conform to the above formula. However, in the present disclosure, it is confirmed that a good elastic modulus change can be obtained by making the number average molecular weight of the triol (x1) used in the manufacture of the polyurethane resin (A1) be greater than 4000, which is worthy of attention.

[0087] The polyurethane resin (A1) can be produced by reacting the polyol (x), polyisocyanate (y), and, if necessary, a chain extender (z1) and a terminal blocking agent (z2). The reaction can be carried out without a solvent or in the presence of a reaction solvent. The reaction temperature can be 50 to 150°C. Examples of the reaction solvent include ketone solvents such as acetone and methyl ethyl ketone; tetrahydrofuran, dihydrofuran, and the like; Ether solvents such as oxane; acetate solvents such as ethyl acetate and butyl acetate; nitrile solvents such as acetonitrile; amide solvents such as dimethylformamide and N-methylpyrrolidone, etc.

[0088] The content of the polyurethane resin (A1) contained in the resin (A) is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and further preferably 95 to 100% by mass.

[0089] The content of the polyurethane resin (A1) in the magnetic viscoelastic elastomer composition may be, for example, 1 to 50% by mass, preferably 2 to 30% by mass, and more preferably 3 to 20% by mass in the magnetic viscoelastic elastomer composition.

[0090] [Other resins (A2)]

[0091] The resin (A) may further contain other resins (A2) in addition to the polyurethane resin (A1). Examples of the resin (A2) include acrylic resins, polyester resins, polyamide resins, polycarbonate resins, and silicone resins.

[0092] [Magnetic powder (B)]

[0093] The magnetic powder (B) is a powder of a magnetic substance that can change the direction or magnitude of its magnetic moment in response to changes in an external magnetic field. The magnetic substance is typically a ferromagnetic substance, and is preferably a soft magnetic substance.

[0094] The magnetic body may be, for example, Fe or an alloy or oxide containing Fe; preferably, it may be Fe, or an alloy or oxide containing Fe and at least one selected from 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, it may be Fe, or an alloy containing Fe and at least one selected from B, Al, Si, Cr, Co and Ni.

[0095] Examples of the magnetic body include Fe; 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.

[0096] The coercive force of the magnetic body is preferably 100 A / m or less, and the lower limit may be 0 A / m or more.

[0097] The saturation magnetic flux density of the magnetic body may be preferably 0.1T to 3T, more preferably 0.5T to 2.5T, and even more preferably 0.7T to 2.3T.

[0098] The magnetic permeability of the magnetic substance measured in a magnetic field of 0.002 T is preferably 0.0001 H / m to 1 H / m, more preferably 0.0005 H / m to 0.1 H / m, and even more preferably 0.001 H / m to 0.01 H / m.

[0099] The coercive force, saturation magnetic flux density, and magnetic permeability of the magnetic body described above refer to the coercive force, saturation magnetic flux density, and magnetic permeability measured as a whole, and can be measured typically using a vibrating sample magnetometer.

[0100] The shape of the magnetic powder (B) may be, for example, spherical, flat, or needle-like, and typically, spherical.

[0101] The magnetic powder (B) may be a powder having an insulating film on its surface. Examples of the insulating film include inorganic glass films, organic polymer films, organic-inorganic hybrid films, and inorganic insulating films formed by a sol-gel reaction of metal alkoxides.

[0102] The content of the magnetic powder (B) in the magnetic viscoelastic elastomer composition disclosed herein is preferably 25% to 55% by volume, more preferably 35% to 50% by volume, and further preferably 40% to 45% by volume in 100% by volume of the total of the resin (A) and the magnetic powder (B). By setting the content of the magnetic powder (B) within the above range, the change in elastic modulus in response to the change in the magnetic field can be improved.

[0103] The content of the magnetic powder (B) can be measured by applying heat (500° C. or higher) to the magnetic viscoelastic elastomer to remove the organic components and measuring the weight of the remaining magnetic powder.

[0104] The total content of the resin (A) and the magnetic powder (B) in the magnetic viscoelastic elastomer composition of the present disclosure is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 75 to 100% by mass.

[0105] [Plasticizer (C)]

[0106] The magnetic viscoelastic elastomer composition of the present disclosure may further contain a plasticizer (C) in addition to the resin (A) and the magnetic powder (B).

[0107] Examples of the plasticizer (C) include aromatic dicarboxylic acid plasticizers, aliphatic dicarboxylic acid plasticizers, phosphoric acid plasticizers, trimellitic acid plasticizers, and the like.

[0108] Examples of the aromatic dicarboxylic acid plasticizer include phthalic acid diesters such as dibutyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, and ditridecyl phthalate; isophthalic acid diesters such as dioctyl isophthalate and di-2-ethylhexyl isophthalate; and terephthalic acid diesters such as dioctyl terephthalate and di-2-ethylhexyl terephthalate.

[0109] 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 sebacic acid diesters such as dioctyl sebacate, di-2-ethylhexyl sebacate, and diisononyl sebacate.

[0110] Examples of the phosphoric acid-based plasticizer include phosphoric acid esters such as trioctyl phosphate, tri(2-ethylhexyl) phosphate, and tricresyl phosphate.

[0111] Examples of the trimellitic acid plasticizer 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.

[0112] The plasticizer (C) preferably contains an aromatic dicarboxylic acid plasticizer, more preferably contains a phthalic acid diester, and particularly preferably contains dioctyl phthalate or di(2-ethylhexyl) phthalate.

[0113] The content of the plasticizer (C) in the magnetic viscoelastic elastomer composition disclosed herein is preferably 0 to 40 parts by mass, more preferably 5 to 35 parts by mass, and further preferably 10 to 33 parts by mass, relative to 100 parts by mass of the total of the resin (A) and the magnetic powder (B). By making the content of the plasticizer (C) within the above range, the magnetic viscoelastic elastomer composition has appropriate viscosity, and the orientation change of the magnetic powder (B) in response to the change in the magnetic field can be improved.

[0114] The total content of the resin (A), the magnetic powder (B), and the plasticizer (C) in the magnetic viscoelastic elastomer composition of the present disclosure is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass.

[0115] [Additives (D)]

[0116] The magnetic viscoelastic elastomer composition disclosed in the present invention may contain other additives (D) in addition to the above-mentioned resin (A), magnetic powder (B) and plasticizer (C) used as needed. Examples of the above-mentioned additives (D) include polyurethane catalysts, antioxidants, light stabilizers, impact resistance agents, antistatic agents, flame retardants, preservatives, ultraviolet absorbers, viscosity modifiers, colorants, etc.

[0117] The above-mentioned polyurethane catalyst is used for the reaction of polyol (x) and polyisocyanate (y), and examples thereof include tin compounds such as tin octoate, dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate; titanium compounds such as dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; zinc compounds such as zinc cyclohexaneate and zinc 2-ethylhexanoate; tertiary amines such as triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undec-7-ene, and the like.

[0118] The amount of the urethanization catalyst may be 1 to 10 parts by mass based on 100 parts by mass of the urethane resin (A1).

[0119] [Method for producing composition]

[0120] The magnetic viscoelastic elastomer composition disclosed herein can be manufactured by mixing a resin (A) and a magnetic powder (B). The mixing of the resin (A) and the magnetic powder (B) may, for example, include directly mixing the resin (A) and the magnetic powder (B), or may include mixing the raw material of the resin (A) with the magnetic powder and reacting the raw material of the resin (A) to form the resin (A). When the resin (A) and the magnetic powder (B) are mixed, a polyurethane catalyst, a plasticizer (C) and an additive (D) used as needed may coexist appropriately.

[0121] Representatively, the magnetic viscoelastic elastomer composition disclosed herein can be prepared by mixing the above-mentioned polyol (x), polyisocyanate (y) and magnetic powder (B) and heating to obtain a reaction product of polyol (x) and polyisocyanate (y). The heating temperature can be 50 to 150° C., and the heating time can be 30 minutes to 20 hours. In addition, the above-mentioned heating can be carried out in the absence of a solvent or in the presence of a reaction solvent. As the above-mentioned reaction solvent, toluene, acetone, N-methylpyrrolidone, etc. can be mentioned.

[0122] The order of mixing the polyol (x), the polyisocyanate (y) and the magnetic powder (B) is not particularly limited. For example, the polyol (x), the polyisocyanate (y) and the magnetic powder (B) may be mixed simultaneously, or the polyol (x) and the magnetic powder (B) may be mixed and then the mixture may be mixed with the polyisocyanate (y). When the polyol (x), the polyisocyanate (y) and the magnetic powder (B) are mixed, a polyurethane catalyst, a resin (A2), a plasticizer (C) and an additive (D) may be appropriately coexisted as needed.

[0123] In a preferred embodiment, the method for producing a magnetic viscoelastic elastomer composition of the present invention comprises the following steps: reacting a polyol (x) with a polyisocyanate (y) in the presence of a magnetic powder (B) to obtain a magnetic viscoelastic elastomer composition;

[0124] The reaction of the polyol (x) and the polyisocyanate (y) is carried out under a magnetic field having a magnetic field intensity exceeding 0 mT, and the polyol (x) contains a triol (x1) having a number average molecular weight of 4,000 or more.

[0125] According to the above-mentioned manufacturing method, since a magnetic field is applied when the resin (A) is formed by the reaction of the polyol (x) and the polyisocyanate (y), the magnetic powder (B) can be arranged along the magnetic field lines of the applied magnetic field in the obtained magnetic viscoelastic elastomer composition. Even if the magnetic field is released after the magnetic viscoelastic elastomer composition is formed, the orientation of the magnetic powder (B) can be maintained. Moreover, it is believed that if a magnetic field is applied again along the arrangement direction of the magnetic powder (B), the interaction of the magnetic powder (B) can be further enhanced compared to the case where the magnetic powder (B) is not arranged, and a higher elastic modulus can be obtained. On the other hand, in the absence of a magnetic field, the interaction between the magnetic powder (B) is generally not generated, so the softness as an elastomer can be maintained. As a result, in the magnetic viscoelastic elastomer composition in which the magnetic powder (B) is oriented, the change in the storage elastic modulus when a magnetic field is applied can be further increased compared to the storage elastic modulus when a magnetic field is not applied.

[0126] The magnetic field intensity when the polyol (x) and the polyisocyanate (y) are reacted may be preferably 10 mT or more, more preferably 10 mT to 400 mT, further preferably 20 mT to 350 mT, and further preferably 100 mT to 350 mT.

[0127] [Characteristics of the composition]

[0128] The magnetic viscoelastic elastomer composition has viscosity and elasticity.

[0129] The storage modulus G'0 of the magnetic viscoelastic elastomer composition measured under zero magnetic field is preferably 1000 Pa to 20000 Pa, more preferably 1000 Pa to 10000 Pa, and further preferably 1000 Pa to 5000 Pa. When the storage modulus of the magnetic viscoelastic elastomer composition is within the above range, the change in elastic modulus when a magnetic field is applied can be improved.

[0130] The magnetic viscoelastic elastomer composition disclosed herein has an increased storage elastic modulus when a magnetic field is applied compared to when a magnetic field is not applied. Specifically, in one embodiment, under the condition of a magnetic field strength of 120000A / m, the storage elastic modulus G'1 measured in a manner parallel to the rotation axis of the rotary viscoelasticity measuring device in the direction of the magnetic field can be preferably 400000Pa or more, more preferably 800000Pa or more, and further preferably 1000000Pa or more. In another embodiment, under the condition of a magnetic field strength of 120000A / m, the storage elastic modulus G'1 measured in a manner parallel to the rotation axis of the rotary viscoelasticity measuring device in the direction of the magnetic field can be preferably 40000Pa or more, more preferably 80000Pa or more, and further preferably 100000Pa or more. By applying a magnetic field, the storage elastic modulus in the above range can increase the propagation speed of compression waves, especially sound waves and ultrasonic waves passing through the magnetic viscoelastic elastomer composition.

[0131] When the rate of change of the storage modulus due to the application of a magnetic field (hereinafter, also referred to as "the rate of change of the storage modulus based on the magnetic field") is set to G'1 / G'0, the rate of change of the storage modulus based on the magnetic field of the magnetic viscoelastic elastomer composition disclosed in the present invention is preferably 5 or more, more preferably 20 or more, and further preferably 40 or more, for example, it can be 300 or less, and further 200 or less or 150 or less. By having the rate of change of the storage modulus based on the magnetic field in the above range, the compression waves, especially sound waves and ultrasonic waves passing through the magnetic viscoelastic elastomer composition can be highly deflected. In addition, by having the storage modulus of the magnetic viscoelastic elastomer composition in the above range and the rate of change of the storage modulus based on the magnetic field in the above range, it is possible to reproduce an elastic modulus in a wider range than the strength of the applied magnetic field, change the sound wave or ultrasonic wave, and thus it can be preferably used.

[0132] The magnetic viscoelastic elastomer composition disclosed in the present invention can be preferably used because it can increase the storage elastic modulus by applying a magnetic field, thereby changing the propagation direction of compression waves such as sound waves, ultrasonic waves, and vibration waves (deflecting the compression waves). The propagation speed c (m / s) of the compression wave is proportional to the square root of the elastic modulus of the propagation medium. Specifically, the density is set to ρ (kg / M 3 ), when the bulk elastic modulus is set to κ (Pa), it is expressed by the following formula (2).

[0133]

[0134] Therefore, when the elastic modulus is high, the propagation speed of the compression wave is fast, and when the elastic modulus is low, the propagation speed of the compression wave is slow. Although it should not be limited to a specific theory for interpretation, it is believed that when a magnetic field is applied to the magnetic viscoelastic elastomer composition disclosed in the present invention, the increase in the storage elastic modulus is related to the direction of the magnetic field, and representatively, the storage elastic modulus in the direction parallel to the direction of the magnetic field increases. Therefore, by applying a magnetic field, the storage elastic modulus is anisotropic, and as a result, the propagation direction of the compression wave changes.

[0135] The magnetic viscoelastic elastomer composition disclosed herein is preferably used to deflect sound waves or ultrasonic waves, and is particularly suitable for use in acoustic devices such as speakers; ultrasonic devices such as ultrasonic sensors. In addition, the magnetic viscoelastic elastomer composition disclosed herein can be used in tactile feedback devices that utilize changes in elastic modulus.

[0136] The present disclosure includes the following aspects.

[0137] [1] A magnetic viscoelastic elastomer composition comprising a resin (A) and a magnetic powder (B),

[0138] The resin (A) comprises a polyurethane resin (A1),

[0139] The polyurethane resin (A1) comprises a reaction product of a polyol (x) and a polyisocyanate (y).

[0140] The polyol (x) includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0141] [2] The magnetic viscoelastic elastomer composition according to [1], wherein the average molecular weight between crosslinking points of the polyurethane resin (A1) is 9,500 to 27,000.

[0142] [3] The magnetic viscoelastic elastomer composition according to [1] or [2], wherein the content of the magnetic powder (B) is 25% to 55% by volume in 100% by volume of the total of the resin (A) and the magnetic powder (B).

[0143] [4] The magnetic viscoelastic elastomer composition according to any one of [1] to [3], further comprising a plasticizer (C), wherein the plasticizer (C) comprises an aromatic dicarboxylic acid plasticizer.

[0144] [5] A method for producing a magnetic viscoelastic elastomer composition, comprising the steps of: reacting a polyol (x) with a polyisocyanate (y) in the presence of a magnetic powder (B) to obtain a magnetic viscoelastic elastomer composition;

[0145] The reaction of the polyol (x) and the polyisocyanate (y) is carried out under a magnetic field having a magnetic field strength exceeding 0 mT.

[0146] The polyol (x) includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0147] [6] A magnetic viscoelastic elastomer composition obtained by reacting a polyol (x) and a polyisocyanate (y) in the presence of a magnetic powder (B),

[0148] The reaction of the polyol (x) and the polyisocyanate (y) is carried out under a magnetic field having a magnetic field strength exceeding 0 mT.

[0149] The polyol (x) includes a triol (x1) having a number average molecular weight of 4,000 or more.

[0150] Example

[0151] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0152] (Experimental Example 1)

[0153] 1.64 parts by mass of polypropylene triol with a number average molecular weight of 3000, 3.39 parts by mass of polypropylene glycol with a number average molecular weight of 3000, 0.45 parts by mass of toluene diisocyanate as polyisocyanate (y), 70.9 parts by mass of FeSiCr powder with a particle size of 3 μm as magnetic powder (B), and 22.8 parts by mass of dioctyl phthalate as plasticizer (C) were added to the reaction container and mixed. Next, 0.4 parts by mass of tin octylate was added to the mixture as a polyurethane catalyst, and after further mixing, a degassing mixer was used to stir at 2000 rpm for 390 seconds to obtain a paste. Using a hot plate, the obtained paste was heated at 75°C for 2 hours for thermal curing to obtain a magnetic viscoelastic elastomer (MRE) composition.

[0154] (Experimental Examples 2 to 9)

[0155] A magnetic viscoelastic elastomer composition was obtained in the same manner as in Experimental Example 1 except that the number average molecular weight (Mn) and the amount used of the triol and diol, and the amount used of the magnetic powder (B) and the plasticizer (C) were changed as shown in Tables 1 and 2.

[0156] (Experimental Examples 10 to 14)

[0157] 2.07 parts by mass of polypropylene triol with a number average molecular weight of 4000, 3.63 parts by mass of polypropylene glycol with a number average molecular weight of 3000, 0.45 parts by mass of toluene diisocyanate as polyisocyanate (y), 70.9 parts by mass of FeSiCr powder with a particle size of 3 μm as magnetic powder (B), and 22.8 parts by mass of dioctyl phthalate as plasticizer (C) were added to a reaction container and mixed. Next, 0.4 parts by mass of tin octylate was added to the mixture as a polyurethane catalyst, and after further mixing, a degassing stirrer was used to stir at 2000 rpm for 390 seconds to obtain a paste. Using a hot plate, a magnetic field was applied under the conditions shown in Table 2, and the obtained paste was heated at 75°C for 2 hours to perform thermal curing to obtain a magnetic viscoelastic elastomer (MRE) composition.

[0158] The magnetic viscoelastic elastomer compositions of Experimental Examples 1 to 14 were subjected to the following measurements.

[0159] [Measurement method of storage elastic modulus]

[0160] The magnetic viscoelastic elastomer composition was molded into a disk shape with a diameter of 2 cm and a thickness of 1 mm as a sample. Next, the sample was placed in a viscoelasticity measuring device (manufactured by Anton Paar, model: MCR301), and a magnetic field generator (manufactured by Anton Paar, model: PS-MRD) was used to measure the storage elastic modulus when no magnetic field was applied and when a magnetic field was applied. The rotation axis of the viscoelasticity measuring device was set parallel to the magnetic field to perform the measurement.

[0161] (Conditions for viscoelasticity measurement)

[0162] Measurement temperature: 25℃

[0163] Load applied to the sample from the terminal: 0.3N

[0164] Frequency: 1Hz

[0165] Strain: 0.01%

[0166] Magnetic field strength when magnetic field is applied: 150mT

[0167] The results are shown in Tables 1 and 2. In Experimental Examples 1 to 17 in Tables 1 and 2, examples corresponding to comparative examples of the present invention are indicated by a symbol "*", and other examples correspond to examples of the present invention.

[0168] [Table 1]

[0169]

[0170] Experimental Examples 2 to 6 and 8 to 9 are examples of the present disclosure, and the change in the storage elastic modulus when a magnetic field is applied is larger than that when no magnetic field is applied.

[0171] Experimental Examples 1 and 7 are examples in which a triol having a number average molecular weight of 4,000 or more is not contained, and the change in the storage elastic modulus when a magnetic field is applied is not sufficiently satisfactory.

[0172] [Table 2]

[0173]

[0174] Examples 10 to 14 are examples of implementing the reaction of polyol (x) and polyisocyanate (y) under a magnetic field with a magnetic field strength of 20 to 500 mT. The storage modulus of the obtained magnetic viscoelastic elastomer composition when the magnetic field is applied is high, and the elastic modulus change is good. The storage modulus of the resin (A) monomer is 3.0 kPa. It is believed that since the magnetic viscoelastic elastomer composition disclosed in the present invention contains the above-mentioned highly flexible resin (A), the arrangement change of the magnetic powder (B) is not easily hindered, and a high elastic modulus change is obtained.

Claims

1. A magnetic viscoelastic elastomer composition comprising resin A and magnetic powder B, The resin A comprises a polyurethane resin A1, The polyurethane resin A1 comprises a reactant of polyol x and polyisocyanate y, The polyol x includes a triol x1 having a number average molecular weight of 4000 or more.

2. The magnetic viscoelastic elastomer composition according to claim 1, wherein The average molecular weight between crosslinking points of the polyurethane resin A1 is 9500 to 27000.

3. The magnetic viscoelastic elastomer composition according to claim 1 or 2, wherein: The content of the magnetic powder B is 25 volume % to 55 volume % in the total of the resin A and the magnetic powder B (100 volume %).

4. The magnetic viscoelastic elastomer composition according to any one of claims 1 to 3, wherein The plasticizer C further comprises an aromatic dicarboxylic acid plasticizer.

5. A method for producing a magnetic viscoelastic elastomer composition, comprising the steps of: reacting a polyol x with a polyisocyanate y in the presence of a magnetic powder B to obtain a magnetic viscoelastic elastomer composition, The reaction of the polyol x and the polyisocyanate y is carried out in a magnetic field having a magnetic field strength exceeding 0 mT, The polyol x includes a triol x1 having a number average molecular weight of 4000 or more.

Images