Excitation friction material, excitation brake pad, and excitation brake system

Abstract

To provide a magnetically operated braking device with superior braking force. [Solution] An excitation friction material comprising a magnetoviscoelastic elastomer composition containing a viscoelastic elastomer and magnetic powder dispersed in the viscoelastic elastomer.

Description

[Technical Field]

[0001] The present invention relates to a friction material comprising a magnetoviscoelastic elastomer composition, and more particularly to a friction material for an excitation brake. [Background technology]

[0002] Magnetic fluid brakes are known as braking devices that do not require force transmission by a mechanical mechanism and operate with a simple operation of applying a magnetic field. For example, Patent Document 1 describes a motor brake device in which a brake disc is mounted on the motor shaft of a motor, the brake disc is placed in a sealed space formed by a yoke member, magnetic fluid is filled into the sealed space, and a magnetic field is applied to the magnetic fluid to magnetize it and impart braking force to the brake disc. When a magnetic field is applied to a magnetorheological fluid, it changes to a high viscosity and becomes like a solid, thereby imparting braking force to the brake disc. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-281098 [Overview of the project] [Problems that the invention aims to solve]

[0004] On the other hand, magnetorheological fluids have a limited strength even when solidified, and magnetic fluid braking systems suffer from the problem of insufficient braking force.

[0005] The present invention solves the aforementioned problems, and its objective is to provide a magnetically operated excitation brake device with excellent braking force. [Means for solving the problem]

[0006] The present invention provides an excitation friction material containing a magneto-viscoelastic elastomer composition, an excitation brake pad using the friction material, and an excitation brake system using the brake pad. [Effects of the Invention]

[0007] By using the friction material of the present invention, a magnetically operated braking device with excellent braking force can be provided. The magnetoviscoelastic elastomer composition has stable properties, and the braking device of the present invention can exhibit excellent braking force over a long period of time. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view showing the external shape of an excitation brake pad, which is one embodiment of the present invention. [Figure 2] A cross-sectional view showing the structure of an excitation brake device, which is one embodiment of the present invention. [Figure 3] Figure 2 shows a magnified view of the dashed line portion of the braking device. [Figure 4] Figure 2 is a cross-sectional view showing the relationship between the brake rotor and brake pad when the brake system is released. [Figure 5] Figure 2 is a cross-sectional view showing the relationship between the brake rotor and brake pads in the operating state of the brake system. [Figure 6] A schematic diagram showing the configuration of the device used in the test to measure braking force. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below, 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 invention. Furthermore, if multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range.

[0010] In this specification, a viscoelastic elastomer refers to a material that possesses both viscosity and elasticity, and can be determined based on the relaxation time of stress relaxation (stress change over time) when a certain strain is applied. If the relaxation time is sufficiently short relative to the observed time scale, it is understood to be a viscous material; if it is long, it is understood to be an elastic material; and if it is on a similar scale, it is understood to be a viscoelastic material.

[0011] Furthermore, in this specification, a 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 apparent modulus and damping characteristics of the magnetorheological elastomer change reversibly in response to an external magnetic field.

[0012] <Excitation friction material> One embodiment of the excitation friction material of the present invention is a molded product of a magnetoviscoelastic elastomer composition. Friction materials generally have a shape having a friction surface and a support surface opposite the friction surface. Specific examples include layered, plate-shaped, disc-shaped, and donut-shaped with flat top and bottom surfaces. Excitation friction materials can be manufactured by molding a magnetoviscoelastic elastomer composition into a predetermined shape. Among viscoelastic elastomers, thermosetting elastomers such as polyurethane elastomers are preferred from the viewpoint of increasing the change in the elastic modulus of the magnetically responsive material before and after the application of a magnetic field.

[0013] In a magnetorheologically elastic elastomer composition, when a magnetic force is applied, the magnetic powder forms a chain structure along the magnetic field lines, increasing the hardness in the direction of the magnetic field lines. Therefore, it is preferable that the excitation friction material of the present invention be arranged so that the friction surface is approximately perpendicular to the direction of the magnetic field lines. In a magnetorheologically elastic elastomer composition, when a magnetic force is applied, the magnetic force can easily pass through the resin through the chain structure of the magnetic powder. As a result, the excitation friction material can produce a large friction force with a small magnetic force. The magnetic force applied to the excitation friction material is the magnetic force required to operate the excitation brake device.

[0014] [Polyurethane elastomer] A polyurethane elastomer refers to an elastomer containing a urethane resin. Generally, the urethane resin corresponds to the component forming the polymer backbone of the polyurethane elastomer.

[0015] In this specification, the urethane resin refers to the reaction product of a hydroxyl group-containing compound and an isocyanate group-containing compound. When the hydroxyl group contained in the hydroxyl group-containing compound reacts with the isocyanate group contained in the isocyanate group-containing compound, a urethane bond is formed and the urethane resin is formed.

[0016] The urethane resin may be a reaction product of a hydroxyl group-containing compound and a polyisocyanate, and a chain extender and / or a terminator, and these reaction products are included within the scope of the urethane resin. As an example of a preferred urethane resin, there may be mentioned the reaction product of a polyol compound and a polyisocyanate compound described in Patent Document 1.

[0017] A polyol means a hydroxyl group-containing compound having two or more hydroxyl groups in one molecule. In this specification, the term "polyol" means the above-mentioned hydroxyl group-containing compound other than the slide ring material. Further, in this specification, the term "polyurethane backbone" means a urethane resin composed of a polyol and a polyisocyanate and in a state where the slide ring material is not bonded.

[0018] A triol means a compound having three hydroxyl groups in one molecule. Each hydroxyl group contained in the triol reacts with the isocyanate group of the diisocyanate described later to form a urethane bond, so the triol includes a branching point (crosslinking point) to which three molecular chains are bonded to one atom.

[0019] The crosslinking point (branching point) in the triol can be introduced by a compound (initiator) having three or more active hydrogen atoms, and examples of such an initiator include glycerol, trimethylolethane, trimethylolpropane, trimellitic acid, diethylenetriamine, and the like.

[0020] 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. Having the number-average molecular weight of the triol within this range allows the molecular weight of the molecular chains bonded to the crosslinking points to be above a certain level. As a result, when the magnetic field strength is changed, the orientation of the magnetic powder can change without constraint, and the change in the elastic modulus of the magnetoviscoelastic elastomer composition is expected to increase.

[0021] In this invention, the number-average molecular weight can be measured by gel permeation chromatography as a converted value using polystyrene as the standard sample.

[0022] The triol may be, for example, a polyether triol, a polyester triol, a polycarbonate triol, a polyolefin triol, a polyacrylic triol, etc., and a polyether triol is preferred.

[0023] Polyethertriols can typically be understood as triols of polymers having repeating units containing ether bonds, and these repeating units preferably contain oxyalkylene units. Examples of such ether-bonded units include oxyalkylene units having 2 to 4 carbon atoms, such as oxyethylene units, oxypropylene units, and oxytetramethylene units, with oxypropylene units and oxytetramethylene units being particularly noteworthy. 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 ethertriol, and polyoxyethylene-polyoxypropylene triol.

[0024] Oxyalkylene units can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran.

[0025] Polyester triols can typically be understood as triols of polymers having repeating units containing ester bonds. These ester-bonded units can be formed by the reaction of a diol with a dicarboxylic acid, or by ring-opening polymerization of cyclic ester compounds. Polyester polyols may be homopolymers containing one type of repeating unit, or copolymers containing two or more types of repeating units.

[0026] Typical diols used as raw materials for polyester triols include low molecular weight diols with a molecular weight of 50 to 300. Specifically, these 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. Alkylene oxide adducts of bisphenol compounds can be formed by ring-opening polymerization of a cyclic ether to a bisphenol compound. Examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0027] Examples of dicarboxylic acids used as 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 acid or aromatic dicarboxylic acid; and esters of the aliphatic dicarboxylic acid or aromatic dicarboxylic acid. The esters of the aliphatic dicarboxylic acid or aromatic dicarboxylic acid can be formed by reacting the aliphatic dicarboxylic acid or aromatic dicarboxylic acid with an alcohol, and examples of such alcohols include aliphatic alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, and butanol.

[0028] A polycarbonate triol can be understood as a triol of a polymer having repeating units containing a carbonate bond (-O-CO-O-). These units containing a carbonate bond (-O-CO-O-) can be formed by reactions such as those between a carbonate ester and a diol, or between a phosgene and a diol. A polycarbonate polyol may be a homopolymer containing one repeating unit, or a copolymer containing two or more repeating units.

[0029] Examples of carbonate esters used as raw materials for polycarbonate triols include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclohexyl carbonate, dicyclohexyl carbonate, and diphenyl carbonate.

[0030] Typical diols used as raw materials for polycarbonate triols include low-molecular-weight diols with a molecular weight of 50 to 300, or high-molecular-weight diols with a number-average molecular weight of over 300.

[0031] 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. Alkylene oxide adducts of bisphenol compounds can be formed by ring-opening polymerization of a cyclic ether to a bisphenol compound, and examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0032] Examples of high molecular weight diols include polyether diols such as polyethylene glycol and polypropylene glycol; and polyester diols such as polyhexamethylene adipate. The number-average molecular weight of high molecular weight diols is generally greater than 300, preferably between 400 and 5,000, and more preferably between 400 and 2,000.

[0033] A polyolefin triol can be understood as a polymer triol having repeating units consisting of divalent hydrocarbon groups. These divalent hydrocarbon units can be formed by the polymerization of alkenes and dienes. A polyolefin triol may be a homopolymer containing one type of repeating unit, or a copolymer containing two or more types of repeating units.

[0034] Examples of alkenes used as raw materials for polyolefin triols include ethylene, propylene, and isobutene, while examples of dienes used as raw materials for polyolefin triols include butadiene and isoprene.

[0035] A polyacrylic triol can be understood as a triol of a polymer having repeating units derived from (meth)acrylic monomers. A polyacrylic triol may be a homopolymer containing one type of repeating unit, or a copolymer containing two or more types of repeating units.

[0036] The (meth)acrylic monomer may include a (meth)acrylic monomer having a hydroxyl group, and other (meth)acrylic monomers and / or other vinyl monomers.

[0037] Examples of (meth)acrylic monomers having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0038] 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 (methacrylamide) monomers such as unsubstituted (meth)acrylamide, dimethyl(meth)acrylamide, N,N-methylenebis(meth)acrylamide, and diacetone(methacrylamide).

[0039] Other vinyl monomers include styrene and methylstyrene.

[0040] The triol content 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.

[0041] The polyol preferably contains a diol. A diol is a compound having two hydroxyl groups in one molecule. Including a diol as the polyol can make it easier to control the molecular weight of the molecular chains bonded to the crosslinking points.

[0042] The diol may be a low molecular weight diol with a molecular weight of 50 to 300, or a high molecular weight diol with 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.

[0043] 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 to a bisphenol compound, and examples of such cyclic ethers include ethylene oxide, propylene oxide, and tetrahydrofuran.

[0044] Examples of high molecular weight diols include polyether diols, polyester diols, polycarbonate diols, polyolefin diols, and polyacrylic diols.

[0045] Polyether diols can typically be understood as diols of polymers having repeating units containing ether bonds, and these repeating units preferably contain oxyalkylene units. Examples of such oxyalkylene units include oxyethylene units, oxypropylene units, oxytetramethylene units, and other oxyalkylene units having 2 to 4 carbon atoms, with oxypropylene units and oxytetramethylene units being particularly noteworthy. 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.

[0046] Oxyalkylene units can be formed by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, and tetrahydrofuran.

[0047] Polyester diols can typically be understood as polymer diols that have repeating units containing ester bonds.

[0048] Polycarbonate diols can typically be understood as diols of polymers that have repeating units containing carbonate bonds (-O-CO-O-).

[0049] Polyolefin diols can typically be understood as diols of polymers that have repeating units consisting of divalent hydrocarbon groups.

[0050] Polyacrylic diols can typically be understood as diols of polymers that have repeating units derived from (meth)acrylic monomers.

[0051] The number-average molecular weight of the high molecular weight diol is, for example, 500 to 50,000, preferably 1,500 to 20,000, and more preferably 3,000 to 10,000.

[0052] The diol content 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, per 100 parts by mass of triol.

[0053] In a preferred embodiment, the polyol comprises a triol and a diol. The total content of triols and diols in 100% by mass of 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.

[0054] The polyol may contain other polyols besides triols and diols. Such other polyols may include triols with a molecular weight of less than 4,000, triols having four or more hydroxyl groups in one molecule, and so on.

[0055] An isocyanate compound is defined as a compound having two or more isocyanate groups in one molecule. The number of isocyanate groups in one molecule of an isocyanate compound is typically between two and four, and more specifically, between two and three.

[0056] Examples of isocyanate compounds include aliphatic isocyanates, aromatic isocyanates, and alicyclic isocyanates.

[0057] Examples of aliphatic isocyanates include tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0058] Aromatic isocyanates include 1,3- and 1,4-phenylenediisocyanate, 1-methyl-2,4-phenylenediisocyanate, 1-methyl-2,6-phenylenediisocyanate, 1-methyl-2,5-phenylenediisocyanate, 1-methyl-2,6-phenylenediisocyanate, 1-methyl-3,5-phenylenediisocyanate, 1-ethyl-2,4-phenylenediisocyanate, 1-isopropyl-2,4-phenylenediisocyanate, 1,3-dimethyl-2,4-phenylenediisocyanate, 1,3-dimethyl-4,6-phenylenediisocyanate, 1,4-dimethyl-2,5-phenylenediisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, 3 -Methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methylnaphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-di Examples include socyanates, 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.

[0059] Examples of alicyclic isocyanates 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.

[0060] When manufacturing urethane resin, the molar ratio [NCO / OH] of isocyanate groups in the isocyanate compound to hydroxyl groups in the polyol may be, for example, 0.1 to 5, preferably 0.3 to 3, and more preferably 0.4 to 1.5.

[0061] Chain extenders are compounds containing two or more active hydrogen atoms in a single molecule, and are typically used to further react the reaction product of a polyol and a polyisocyanate. By further reacting the reaction product of a polyol and a polyisocyanate with a chain extender, it becomes easy to obtain high molecular weight urethane resins.

[0062] Examples of chain extenders include chain extenders having an amino group and chain extenders having a hydroxyl group.

[0063] Examples of chain extenders containing 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.

[0064] Examples of chain extenders containing hydroxyl groups include aliphatic polyols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, saccharose, 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.

[0065] When a chain extender is included, the molar ratio [NCO / (H+OH)] of the isocyanate groups in the polyisocyanate to the total of the hydroxyl groups in the polyol and the active hydrogen atoms in the chain extender may be, for example, 0.1 to 5, preferably 0.3 to 3, and more preferably 0.4 to 1.

[0066] End-terminating agents are compounds that contain one active hydrogen atom per molecule and are typically used to further react the reaction product of a polyol, a polyisocyanate, and a chain extender, if necessary.

[0067] Examples of end-stopping agents include alcohols such as hexanol, heptanol, octanol, nonanol, and undecanol; and amines such as dibutylamine.

[0068] The end-terminating agent may be preferably 0.01 parts by mass or more and 20 parts by mass, more preferably 0.1 parts by mass or more and 10 parts by mass, per 100 parts by mass of the reaction product of the polyol and polyisocyanate.

[0069] The average inter-crosslink molecular weight of the polyurethane skeleton is, for example, 1,000 to 30,000, preferably 3,000 to 20,000, and more preferably 5,000 to 15,000. The average inter-crosslink molecular weight can be understood as the average value of the molecular weights of the molecular chains between two adjacent crosslink points (branching points). Although it should not be interpreted in a way that is limited to a specific theory, it is thought that when a magnetic field is applied, the magnetic powder can undergo unrestricted orientation changes, and the change in elastic modulus increases, because the inter-crosslink molecular weight in the urethane resin is within this range.

[0070] If the average inter-crosslinking molecular weight of the polyurethane skeleton is less than 1000, the elastic modulus of the magneto-viscoelastic elastomer composition increases, making it easier for the braking force to decrease. If it exceeds 30000, the fracture strain rate of the magneto-viscoelastic elastomer composition decreases, making it easier for the braking force to decay over time.

[0071] The average molecular weight between crosslinking points can be controlled by the number-average molecular weight of the triol, the number-average molecular weight of the diol (if a diol is used), and the amounts of triol and diol used.

[0072] In one embodiment, the average molecular weight between crosslinking points is M, where M is the number-average molecular weight of the i-functional polyol contained in the polyol. i Let C be the mole fraction of the i-functional polyol in the total amount of polyols. i In that case, it can be calculated based on the following formula.

[0073]

number

[0074] In other words, if we assume 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 in the polyol is the number of functional groups of the polyol minus 2, then the above formula is equivalent to dividing the total length of the polyol by the total number of crosslinking points.

[0075] According to classical rubber theory, in crosslinked rubber free of impurities, the molecular weight between crosslinking points is thought to correlate with the elastic modulus of the crosslinked rubber. That is, Mc is the molecular weight between crosslinking points of the crosslinked rubber, μ is the Poisson's ratio of the crosslinked rubber, and ρ is the density of the crosslinked rubber (g / m³). 3 Given that the gas constant is R(J / (K·mol)) and the temperature is T(K), the modulus of elasticity E(Pa) of the crosslinked rubber is expressed by the following formula.

[0076]

number

[0077] In other words, in crosslinked rubber that does not contain impurities, the larger the molecular weight between crosslinking points, the smaller the elastic modulus of the crosslinked rubber.

[0078] Urethane resins can be produced by reacting a hydroxyl group-containing compound, a polyisocyanate, and, if necessary, a chain extender and a end-terminating agent. Such reactions can be carried out without a solvent or in the presence of a reaction solvent. The reaction temperature may be between 50°C and 150°C. Examples of reaction solvents include ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; acetic acid ester solvents such as ethyl acetate and butyl acetate; nitrile solvents such as acetonitrile; and amide solvents such as dimethylformamide and N-methylpyrrolidone.

[0079] The polyurethane elastomer contains urethane resin, preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass.

[0080] [Slide Ring Material] As the slide ring material, a polyrotaxane is preferably used, which is a pseudo-polyrotaxane in which the opening of a cyclic molecule is skewered and enclosed by a linear molecule, and sealing groups are placed at both ends (both ends of the linear molecule). The cyclic molecule has a hydroxyl group inert group and a hydroxyl group via a spacer group.

[0081] (Spacer base) The spacer group is not particularly limited as long as it is a group that connects the cyclic molecule of the polyrotaxane to a hydroxyl group. By having a hydroxyl group via it, the spacer group can enhance the compatibility of the polyrotaxane with other materials, enhance the solubility of the polyrotaxane in solvents, or enhance 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. Alternatively, the spacer group may preferably have a group derived from hydroxypropyl.

[0082] Examples of cyclic molecules having hydroxyl groups via spacer groups include, but are not limited to, hydroxyl groups via spacer groups of alkylene groups such as 1-hydroxypropyl, 2-hydroxypropyl, and hydroxybutyl groups; and hydroxyl groups via spacer groups such as polyethylene glycol, polypropylene glycol, polycaprolactone, and polylactide. The spacer group is preferably polyethylene glycol, polypropylene glycol, polycaprolactone, or polylactide.

[0083] When manufacturing urethane resin, the slide ring material described above can be used as a hydroxyl group-containing compound to bond the slide ring material to the polyurethane skeleton. The amount of slide ring material used is, for example, 0.3% to 20% by mass, preferably 0.5% to 15% by mass, more preferably 0.6% to 14% by mass, and even more preferably 0.7% to 13% by mass, based on the total amount of polyol and slide ring material.

[0084] If the amount of slide ring material used, based on the total amount of polyol and slide ring material, is less than 0.3 mass%, the fracture strain rate of the magneto-viscoelastic elastomer composition decreases, making it easier for the braking force to decrease over time. If it exceeds 20 mass%, the elastic modulus of the magneto-viscoelastic elastomer composition increases, making it easier for the braking force to decrease.

[0085] (Hydroxyl value) The slide ring material preferably has a hydroxyl value of more than 60 mg KOH / g and 200 mg KOH / g or less, more preferably 61 mg KOH / g and 200 mg KOH / g or less, even more preferably 65 mg KOH / g and 150 mg KOH / g or less, even more preferably 70 mg KOH / g and 100 mg KOH / g or less, and particularly preferably 75 mg KOH / g and 90 mg KOH / g or less.

[0086] 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 spacer groups are the active hydroxyl groups.

[0087] Generally, a high hydroxyl value results in a high crosslink density in crosslinked materials, which significantly affects their mechanical properties. A high crosslink density generally improves the strength and modulus of the crosslinked material, but reduces its elongation. Conversely, a low hydroxyl value generally results in a low crosslink density, increasing the elongation, but decreasing the modulus of elasticity and fracture strength. Furthermore, in applications requiring particularly hydrophobic properties, such as electrical and electronic components and engineering, excess hydroxyl groups not used in crosslinking can cause moisture absorption, so having fewer hydroxyl groups than necessary can suppress these effects.

[0088] To achieve excellent mechanical properties, such as elongation, modulus of elasticity, and fracture strength, in a crosslinked body using slide ring material, it is preferable to keep the values ​​within the above range. By using slide ring material, a tough material can be created by achieving a high elongation while simultaneously achieving a relatively low modulus of elasticity and high strength (a large ratio of strength to modulus of elasticity).

[0089] If the hydroxyl value of the slide ring material is 60 mgKOH / g or less, the initial modulus of the magneto-viscoelastic elastomer composition decreases, making it more prone to reduced toughness. If it exceeds 200 mgKOH / g, the initial modulus of the magneto-viscoelastic elastomer composition increases, making it more prone to reduced modulus change.

[0090] (Hydroxyactive group) The slide ring material preferably has hydroxyl-inactive groups in which the hydroxyl groups of the cyclic molecule are inactivated. The hydroxyl-inactive groups suppress the excessive presence of active hydroxyl groups in the slide ring material and, by maintaining the aforementioned hydroxyl value, have the effect of molecularly designing the properties of the slide ring material. The hydroxyl-inactive groups depend on the manufacturing method of the slide ring material of this application, but are preferably provided on the cyclic molecule in the following forms i) to iv).

[0091] i) When an active hydroxyl group is directly bonded to a cyclic molecule, a portion of the hydroxyl group is deactivated to obtain the product.

[0092] ii) A cyclic molecule to which a first spacer group is bonded, and in the case where an active hydroxyl group is present at the terminal end of the first spacer group, a portion of the hydroxyl group is deactivated to obtain the result.

[0093] iii) In the case where a first spacer group and a second spacer group are bonded to a cyclic molecule in the order of the first spacer group followed by the second spacer group from the cyclic molecule, and an active hydroxyl group is present at the end of the second spacer group, a portion of which is deactivated to obtain the result.

[0094] iv) Any combination of the forms described in i) to iii) above.

[0095] The hydroxyl group inactivating group is not particularly limited as long as it is a group that has the effect of inactivating active hydroxyl groups. Examples of hydroxyl group inactivating groups include, but are not limited to, alkyl ester groups, alkyl carbamoyl groups, and alkyl ether groups (each alkyl group is independently a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms, preferably 2 to 10, more preferably 4 to 8 carbon atoms).

[0096] Specifically, examples include acetyl groups, propionyl groups, butyl esters, octyl esters, cyclohexyl carboxyl groups, butyl carbamoyl groups, cyclopentyl carbamoyl groups, cyclohexyl carbamoyl groups, hexyl carbamoyl groups, dodecyl carbamoyl groups, ethylhexyl carbamoyl groups, butyloxy groups, and hexyloxy groups. The hydroxyl group inactive group is preferably an alkyl ester group, an alkyl carbamoyl group, and more preferably an alkyl carbamoyl. Specifically, the hydroxyl group inactive group is preferably butyl carbamoyl, cyclohexyl carbamoyl, ethylhexyl carbamoyl, dodecyl carbamoyl, and more preferably butyl carbamoyl and cyclohexyl carbamoyl.

[0097] (Cyclic molecule) The cyclic molecules of the rideing material are not particularly limited, as long as they are cyclic, have an opening, and are encapsulated in a skewer-like manner by linear molecules. The cyclic molecules have hydroxyl groups via the spacer groups described above. It is also preferable that they have the hydroxyl group inert groups described above. The cyclic molecules may have groups other than those described above. For example, other groups include, but are not limited to, phenyl groups, benzylcarbamoyl groups, phenylethylcarbamoyl groups, benzyl ester groups, and butylbenzyl ester groups.

[0098] The cyclic molecule should preferably be selected from the group consisting of, for example, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. For example, some of the -OH groups of α-cyclodextrin, etc., may be substituted with the above-mentioned spacer group and / or the above-mentioned hydroxyl group inert group, or they may be substituted with groups other than those mentioned above.

[0099] (linear molecule) The linear molecules of the slide ring material are not particularly limited as long as they can be skewered and enclosed in the opening of the cyclic molecule used. For example, the linear molecules include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, cellulosic resins (carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, etc.), polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc. and / or copolymers thereof, polyolefin resins such as polyethylene, polypropylene, and copolymer resins with other olefin monomers, polyester resins, polyvinyl chloride resins, polystyrene resins such as polystyrene and acrylonitrile-styrene copolymer resins, polymethyl methacrylate and (meth)acrylic acid. It is preferable to select from the group consisting of acrylic resins such as acrylic acid ester copolymers and acrylonitrile-methyl acrylate copolymer resins, polycarbonate resins, urethane resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, etc., and their derivatives or modified forms, polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymer (ABS resin), polyamides such as nylon, polyimides, polyisoprene, polydienes such as polybutadiene, polysiloxanes such as polydimethylsiloxane, polysulfones, polyimines, polyacetic anhydride, polyureas, polysulfides, polyphosphozenes, polyketones, polyphenylenes, polyhaloolefins, and their derivatives. For example, it is preferable to select from the group consisting of polyethylene glycol, polyisoprene, polyisobutylene, polybutadiene, polypropylene glycol, polytetrahydrofuran, polydimethylsiloxane, polyethylene, polypropylene, polyvinyl alcohol, and polyvinyl methyl ether. Polyethylene glycol is particularly preferable.

[0100] The slide ring material has a number-average molecular weight (i.e., Mn) of, for example, 50,000 to 400,000, preferably 100,000 to 300,000, and more preferably 150,000 to 200,000.

[0101] (blocking group) The chokeholding group of the slide ring material is not particularly limited, as long as it is positioned at both ends of the pseudopolyrotaxane and acts to prevent the cyclic molecule used from being eliminated. For example, the chokeholding group is preferably selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, pyrenes, substituted benzenes (substituents may include, but are not limited to, alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, and phenyl; one or more substituents may be present), substituted polynuclear aromatics (substituents may include, but are not limited to, the same as above; one or more substituents may be present), and steroids.

[0102] Furthermore, it is preferable to select from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, and pyrenes, and more preferably adamantane groups or cyclodextrins.

[0103] [Other resins] The polyurethane elastomer may further contain resins other than urethane resin. Examples of such resins include acrylic resin, polyester resin, polyamide resin, polycarbonate resin, and silicone resin.

[0104] [Plasticizer] Polyurethane elastomers may contain plasticizers in addition to urethane resin. Examples of plasticizers include aromatic dicarboxylic acid plasticizers, alicyclic dicarboxylic acid plasticizers, aliphatic dicarboxylic acid plasticizers, phosphate plasticizers, trimellitic acid plasticizers, and the like.

[0105] 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.

[0106] Examples of alicyclic dicarboxylic acid plasticizers include bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylic acid, di2-ethylhexyl 4,5-epoxycyclohexane-1,2-dicarboxylic acid, di(9,10-epoxystearyl) 4,5-epoxycyclohexane-1,2-dicarboxylic acid, and diisononyl 1,2-cyclohexanedicarboxylic acid.

[0107] Examples of aliphatic dicarboxylic acid plasticizers include adipic acid diesters such as dioctyl adipic acid, di-2-ethylhexyl adipic acid, isononyl adipic acid, and diisodecyl adipic acid; and sebacate acid diesters such as dioctyl sebacate, di-2-ethylhexyl sebacate, and diisononyl sebacate.

[0108] Examples of phosphate-based plasticizers include phosphate esters such as trioctyl phosphate, tri-2-ethylhexyl phosphate, and tricresyl phosphate.

[0109] Examples of trimellitic acid-based plasticizers include trimellitic acid triesters such as trioctyl trimellitic acid and tri-2-ethylhexyl trimellitic acid; and pyromellitic acid tetraesters such as tetraoctyl pyromellitic acid and tetra-2-ethylhexyl pyromellitic acid.

[0110] The plasticizer preferably comprises an aromatic dicarboxylic acid plasticizer or an alicyclic dicarboxylic acid plasticizer, and more preferably comprises 4-cyclohexene-1,2-dicarboxylic acid bis(2-ethylhexyl).

[0111] The plasticizer content is 60% by mass or less, preferably 5% to 40% by mass, and more preferably 10% to 30% by mass, based on the entire composition. Having the plasticizer content within this range allows the magnetorheologically viscoelastic elastomer composition to have appropriate viscosity, making it easier for the orientation of the magnetic powder to change in response to changes in the magnetic field.

[0112] [Additives] Polyurethane elastomers may contain additives in addition to urethane resin and plasticizers. Examples of such additives include urethane catalysts, antioxidants, light stabilizers, impact stabilizers, antistatic agents, flame retardants, preservatives, ultraviolet absorbers, viscosity modifiers, and colorants.

[0113] Urethane catalysts are used in the reactions of polyols and polyisocyanates and include tin-based compounds such as tin octylate, dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate; titanium-based compounds such as dibutyltitanium dichloride, tetrabutyltitanate, 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.

[0114] The content of the urethane catalyst may be 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of urethane resin.

[0115] [Magnetic powder] Magnetic powder refers to a powder made of a magnetic material whose magnetic moment direction or magnitude can change in response to changes in an external magnetic field. The magnetic material is typically a ferromagnetic material, and preferably a soft magnetic material.

[0116] 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.

[0117] Examples of 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 alloy, FeCo alloy, FeSi alloy, FeSiCr alloy, FeSiAl alloy, and FeSiBCr alloy. Among these, the most preferred magnetic materials are Fe, iron oxide, FeCo alloy, and FeSiCr alloy.

[0118] The coercivity of the magnetic material is preferably 100 A / m or less, and the lower limit may be 0 A / m or more.

[0119] The saturation magnetic flux density of the magnetic material may preferably be 0.1T or more and 3T or less, more preferably 0.5T or more and 2.5T or less, and even more preferably 0.7T or more and 2.3T or less.

[0120] The magnetic permeability of the magnetic material measured under a magnetic field of 0.002T is 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.

[0121] The coercivity, saturation magnetic flux density, and permeability of a magnetic material represent the coercivity, saturation magnetic flux density, and permeability measured as bulk material, and can typically be measured using a sample vibration magnetometer.

[0122] The magnetic powder may be surface-treated. Examples of surface treatment agents for the magnetic powder include silane compounds and silane coupling agents.

[0123] Average particle size of magnetic powder (D 50 From the viewpoint of improving the toughness of the magneto-viscoelastic elastomer composition, the thickness is, for example, 0.3 μm to 30 μm, preferably 0.5 μm to 15 μm, and more preferably 0.8 μm to 10 μm.

[0124] Average particle size of magnetic powder (D 50 The particle size distribution of magnetic powder can be measured and calculated using the laser diffraction-scattering method based on Mie scattering theory. Specifically, the particle size distribution of magnetic powder is created on a volume basis using a laser diffraction-scattering particle size distribution analyzer, and the 50% particle size (average particle size) (D 50 The particle size distribution can be calculated. Preferably, the measurement sample is magnetic powder dispersed in pure water using ultrasound. Suitable laser diffraction scattering particle size distribution analyzers include the "MT3000II" from Microtrac Bell, the "LA-960" from Horiba, Ltd., and the "SALD-2200" from Shimadzu Corporation.

[0125] Unless otherwise specified, the particle size of magnetic powder as used herein refers to the average particle size (D 50 ) means.

[0126] Magnetic powders are known to have, for example, spherical three-dimensional shapes and non-spherical three-dimensional shapes. Non-spherical magnetic powders are magnetic powders that have three-dimensional shapes other than spherical. Examples of non-spherical magnetic powders include magnetic powders having three-dimensional shapes such as flattened, flattened spherical, plate-like, flaky, needle-like, columnar, polygonal, and polyhedral shapes. The magnetic powder may be spherical magnetic powder, or it may be a mixture of spherical magnetic powder and non-spherical magnetic powder. In one preferred embodiment, the magnetic powder is a mixture of spherical magnetic powder and flattened magnetic powder, or a mixture of spherical magnetic powder and polyhedral magnetic powder.

[0127] 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, with a lower limit of, for example, 1.

[0128] The aspect ratio of the flattened magnetic powder is preferably 7 to 15, more preferably 10 to 13, and even more preferably 10 to 11.

[0129] In this specification, the aspect ratio of magnetic powder 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 may be, for example, the number average obtained by measuring the major axis lengths of, for example, 50 magnetic powders based on scanning electron microscope images. 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 particles that have the longest distance between them.

[0130] If 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).

[0131] A polyhedron is a three-dimensional shape having four or more planes, face angles greater than 0° and less than 180°, and edge angles greater than 0° and less than 180°. Specific examples of polyhedra include tetrahedrons, hexahedrons, octahedrons, decahedrons, dodecahedrons, and 14-hedrons. Among these, the hexahedron and octahedron are preferred. A specific example of a hexahedron is a hexahedron with face angles of approximately 90° and edge angles of approximately 90°. A specific example of an octahedron is an octahedron with face angles of approximately 109° and edge angles of approximately 60°.

[0132] If the connection between the faces of the aforementioned polyhedron is composed of a curved surface, the angle between the faces can be the angle of the intersection of the lines extrapolated from both planes. In one form, there may be a part of the polyhedron that has a depression, and the angle between the faces that form a convex shape below it is greater than 180°, which is x°. In such a case, to identify the shape of the polyhedron as the overall outline that includes the convex shape below, the angle between the faces may be set to (360-x)°.

[0133] It is believed that when a magnetic field is applied to a magnetorheological viscoelastic elastomer composition, the magnetic powder in the viscoelastic elastomer aligns along the magnetic field lines and stacks up in a chain-like manner, forming numerous pillars of magnetic powder, thereby increasing the hardness in the direction of the magnetic field lines.

[0134] In the magneto-viscoelastic elastomer composition of the present invention, the magnetic powder content is, for example, 15% to 60% by volume, preferably 20% to less than 50% by volume, and more preferably 30% to 45% by volume, based on the magneto-viscoelastic elastomer composition as a volume fraction. Having the magnetic powder content within this range allows for good changes in the elastic modulus in response to changes in the magnetic field.

[0135] The magnetic powder content can be determined by applying heat (500°C or higher) to the magnetoviscoelastic elastomer to remove organic components and then measuring the weight of the remaining magnetic powder.

[0136] [Method for producing the composition] The magnetorheological viscoelastic elastomer composition of the present invention can be produced by mixing a viscoelastic elastomer and magnetic powder. The mixing of the viscoelastic elastomer and magnetic powder may include, for example, directly mixing the viscoelastic elastomer and magnetic powder, or it may include mixing the raw materials for the viscoelastic elastomer with the magnetic powder and then reacting the raw materials to form a viscoelastic elastomer. When mixing the viscoelastic elastomer and magnetic powder, catalysts, plasticizers, and additives may be appropriately included as needed.

[0137] When polyurethane elastomers are used as viscoelastic elastomers, magnetoviscoelastic elastomer compositions can be produced by mixing a polyol, polyisocyanate, and magnetic powder, and then heating the mixture to obtain a reaction product between the polyol and polyisocyanate. The heating temperature may be between 50°C and 150°C, and the heating time may be between 30 minutes and 20 hours. The heating may be carried out without a solvent or in the presence of a reaction solvent. Examples of such reaction solvents include toluene, acetone, and n-methylpyrrolidone.

[0138] The mixing order of 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 first, and then the mixture may be mixed with the polyisocyanate. When mixing the polyol, polyisocyanate, and magnetic powder, urethane catalysts, resins, plasticizers, and additives may be added as needed.

[0139] [Characteristics of the composition] The magnetoviscoelastic elastomer composition has viscosity and elasticity.

[0140] The magneto-viscoelastic elastomer composition of the present invention exhibits excellent toughness and a high fracture strain rate. The fracture strain rate refers to the percentage of elongation before the material fractures. The magneto-viscoelastic elastomer composition of the present invention exhibits a fracture strain rate of, for example, 1200% or more, preferably 1350% or more, and more preferably 1400% or more.

[0141] The magnetoviscoelastic elastomer composition of the present invention has a storage modulus G'0 measured under zero magnetic field conditions of, for example, 15 kPa or less, preferably 10 kPa or less, and more preferably 6 kPa or less.

[0142] The magnetoviscoelastic 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'1 when a magnetic field of 150 mT is applied is, for example, 300 kPa or more, preferably 500 kPa or more, and more preferably 600 kPa or more.

[0143] When the rate of change of the storage modulus due to the application of a magnetic field (hereinafter also simply referred to as the "rate of change of storage modulus due to magnetic field") is G'1 / G'0, the change in the storage modulus of the magnetoviscoelastic 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.

[0144] <Brake pads> Applications of the excitation friction material of the present invention include excitation brake pads. Figure 1 is a perspective view showing the external shape of an excitation brake pad, which is one embodiment of the present invention. The excitation brake pad 10 of the present invention has a support 11 and an excitation friction material layer 12 formed on the surface of the support 11. The support 11 is preferably made of a magnetic material such as a rope suitable for transmitting magnetic fields. The excitation friction material layer 12 may be formed on one side of the support 11 or on both sides.

[0145] The excitation brake pad 10 can be manufactured in the same manner as conventional brake pads using resin friction material, except that the excitation friction material of the present invention is used. For example, a support 11 can be prepared in advance, a pre-molded body of a magnetoviscoelastic elastomer composition can be placed in contact with the surface of the support 11, the pre-molded body can be thermoformed using a thermoforming die to form an excitation friction material layer 12, and the support 11 and the excitation friction material layer 12 can be fixed together.

[0146] <Excitation Brake System> Another application of the excitation friction material of the present invention is an excitation brake device. The excitation brake device is not particularly limited, and an example is the excitation-operated electromagnetic brake described in Figure 4 of Japanese Patent Application Publication No. 2002-340059. This excitation-operated electromagnetic brake has a structure consisting of an electromagnetic brake body 3, which is mounted on a case 2a integrated with the stator of an electric motor 2 and consists of a yoke member 5 having an excitation coil winding 4, and an armature 6 as a brake movable member fixed to the motor rotation shaft 2b by a fixing member 7 via a leaf spring 8. The armature 6 is capable of axial movement only by the deflection of the leaf spring 8. The armature 6 corresponds to the excitation friction material, and by changing it to the excitation friction material or excitation brake pad of the present invention, the excitation brake device of the present invention can be constructed.

[0147] In the excitation brake device of the present invention, by using the excitation friction material or excitation brake pad of the present invention instead of the armature, noise during friction by the brake pad can be suppressed, and the properties of the magneto-viscoelastic elastomer composition when a magnetic force is applied allow for greater braking force with a smaller magnetic force.

[0148] Figure 2 is a cross-sectional view showing the structure of an excitation brake device, which is one embodiment of the present invention. The excitation brake device 20 of this embodiment comprises a braking unit 21 and a rotating unit 22. The rotating unit 22 is located at the end of the braking unit 21. The rotating unit 22 rotates around a central rotation axis (not shown), while the braking unit 21 is fixed and stationary. The rotating unit 22 has a rotating cylinder 23 and a brake rotor 24 connected to the rotating cylinder 23 and rotating together with the rotating cylinder 23. The brake rotor 24 is made of a magnetic material such as a rope suitable for transmitting a magnetic field. The braking unit 21 has a magnetic field generator 25, a yoke 26, and a brake pad 10 connected to the yoke 26. For example, an electromagnet can be used as the magnetic field generator 25. The connection between the yoke 26 and the brake pad 10 is such that the brake pad 10 can move in the direction of the brake rotor 24.

[0149] Figure 3 is an enlarged view of the dashed line portion of the brake device shown in Figure 2, and is a cross-sectional view showing the structure of the brake rotor 24 and brake pad 10. Three brake rotors 24 are provided. Six brake pads 10 are provided, one above and one below each brake rotor 24. The excitation friction material layer 12 of the brake pads 10 is formed facing the surface of the brake rotor 24. The two brake pads 10 that sandwich the brake rotor 24 are movable toward the brake rotor 24, but a spacer 27 made of an elastic material is provided between them, and in the released state, a space is formed between the surface of the brake rotor 24 and the excitation friction material layer 12 of the brake pads 10.

[0150] Figure 4 is a cross-sectional view showing the relationship between the brake rotor 24 and the brake pad 10 in the released state of the brake device shown in Figure 2. The magnetic field generator of the brake device is not operating, and a space is formed between the surface of the brake rotor 24 and the excitation friction material layer 12 of the brake pad 10 due to the elastic force of the spacer 27. As a result, the rotating part 22 can rotate.

[0151] In one preferred embodiment, the distance between the brake pad and the brake rotor is 0.1 mm or more and 5.0 mm or less, preferably 0.3 mm or more and 3 mm or less, and more preferably 0.5 mm or more and 2.0 mm or less. If the distance is less than 0.1 mm, the brake pad and brake rotor will come into contact in the released state, which will easily restrict the rotation of the rotating part, and if it exceeds 5.0 mm, the contact between the brake pad and brake rotor will be insufficient, which will easily reduce the braking force.

[0152] Figure 5 is a cross-sectional view showing the relationship between the brake rotor 24 and the brake pad 10 in the operating state of the brake device shown in Figure 2. The magnetic field generator of the brake device is operating, and the excitation friction material layer 12 is magnetized, attracting the brake rotor 24 and causing it to be adsorbed onto its surface. As a result, the rotating part 22 is braked and unable to rotate.

[0153] The present invention provides the following embodiments. [1] An excitation friction material comprising a magnetoviscoelastic elastomer composition comprising a viscoelastic elastomer and magnetic powder dispersed in the viscoelastic elastomer.

[0154] [2] The magneto-viscoelastic elastomer composition contains magnetic powder in an amount of 15% to 60% by volume, preferably 20% to 50% by volume, and more preferably 30% to 45% by volume, according to embodiment 1.

[0155] [3] The excitation friction material according to embodiment 1 or 2, wherein the viscoelastic elastomer includes a urethane resin composed of a polyol and an isocyanate.

[0156] [4] The excitation friction material of embodiment 3, wherein the urethane resin has an average inter-crosslinking molecular weight of 1,000 to 30,000, preferably 3,000 to 20,000, more preferably 5,000 to 15,000, and contains slide ring material in an amount of 0.3% to 20% by mass, preferably 0.5% to 15% by mass, more preferably 0.6% to 14% by mass, and even more preferably 0.7% to 13% by mass, based on the total amount of polyol and slide ring material.

[0157] [5] An excitation brake pad having a support and a friction material layer fixed on the support, wherein the friction material layer is made of the excitation friction material described in any of embodiments 1 to 4.

[0158] [6] An excitation brake device comprising a brake pad having a support and a friction material layer fixed on the support, and a brake rotor disposed with a space above the surface of the friction material layer, wherein the friction material layer is made of an excitation friction material according to any of embodiments 1 to 4, and the brake rotor is made of a magnetic material.

[0159] [7] An excitation brake device according to embodiment 6, comprising a magnetic field generating device for applying a magnetic field to the excitation friction material.

[0160] [8] An excitation brake device according to embodiment 6 or 7, wherein the distance between the brake pad and the brake rotor is 0.1 mm or more and 5.0 mm or less, preferably 0.3 mm or more and 3 mm or less, more preferably 0.5 mm or more and 2.0 mm or less. [Examples]

[0161] The present invention will be further described by the following examples, but the present invention is not limited thereto. Unless otherwise specified, the amounts of ingredients in the examples refer to parts by mass.

[0162] The raw materials, manufacturing method, and evaluation method for the magnetoviscoelastic elastomer composition are described below.

[0163] <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) (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) (y) Tolylene-2,4-diisocyanate (product name: "Tolylene-2,4-diisocyanate" manufactured by Tokyo Chemical Industry Co., Ltd.)

[0164] (A2) Polyrotaxane ASM's "SH1300P" (product name), hydroxyl value 85 mg KOH / mol, Mn = 180,000 ASM's "SH2400P" (product name), hydroxyl value 76 mg KOH / mol, Mn = 400,000

[0165] B.Magnetic powder Iron-silicon-chromium alloy powder (JFEM Co., Ltd. "FeSiCr" (product name), particle size 0.8 μm) Iron silicon chromium alloy powder (manufactured by Seiko Instruments Inc., "EA-SMP-10 PF-20F" (product name), particle size 10 μm) Iron silicon chromium alloy powder (manufactured by Seiko Instruments Inc., "EA-SMP-10 -325mesh" (product name), particle size 30 μm)

[0166] C. Plasticizer Dioctyl phthalate Bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate

[0167] D. Urethane-forming catalyst Tin octylate

[0168] <Manufacturing method> The reaction vessel was filled with the above raw materials in the blending amounts shown in Tables 1 and 2. Using a defoaming stirrer, the filler was uniformly mixed to obtain a paste. Using a hot plate, the obtained paste was heated at 75 °C for 2 hours and thermally cured to produce a magnetorheological elastomer composition.

[0169] [Measurement of elongation at break] The elongation at break of the magnetorheological elastomer composition was measured. The elongation at break is an index indicating the toughness of the material. When the length after break is L f and the initial length is L0, the elongation at break δ is expressed by the following formula.

[0170] δ (%) = {(L f - L0) / L0} × 100

[0171] The magnetorheological elastomer composition was formed into a rod shape (5 mm × 20 mm × thickness 1 mm) to obtain a sample. Next, the sample was set in a dynamic viscoelasticity measuring device (manufactured by TA Instruments, model: RSA-G2), and the elongation until the sample broke was measured to measure the elongation at break. The results are shown in Tables 1 and 2.

[0172] (Measurement conditions for elongation at break) Measurement temperature: 25 °C Tensile speed: 0.2 mm / s

[0173] (Evaluation criteria for fracture strain rate) A (Excellent): 1350% or higher B (Inferior): Less than 1350%

[0174] [Brake pad creation] The magneto-viscoelastic elastomer composition paste (before heat curing) obtained in each example was applied to a support made of an iron disc (outer diameter 47 mm, inner diameter 26 mm, thickness 0.7 mm), and heated and molded at 75°C for 2 hours to produce a brake pad equipped with a friction material layer made of MRE (outer diameter 46 mm × inner diameter 36 mm × thickness 1 mm).

[0175] Using the fabricated brake pads, a brake device with the structure shown in Figure 2 was manufactured. The dimensions of the component parts are shown below.

[0176] [Table 1]

[0177] The braking force of the brake pads was measured by a test in accordance with "JIS B1404-2:2005, Section 5.4.1.1, a) Measurement using a torque measuring arm". Figure 6 is a schematic diagram showing the configuration of the apparatus used for the brake force measurement test. The torque measuring arm length l was set to 0.2m, and the tension measuring instrument used was the "FGJN-20" (product name) manufactured by NIDEK Drive Technology Co., Ltd.

[0178] A voltage of 20W and a current of 2A (equivalent to a magnetic force of 300mT) was applied to the brake under test. When the tension measuring device shown in Figure 6 was pulled in the direction of the arrow, the arm moved (i.e., the braking force and the force pulling the measuring device became equal), and the value at which the displayed tension became constant (P) × arm length (l) = braking force (N·m) was recorded.

[0179] (Evaluation criteria for braking force) A(Excellent): 6Nm or more B (poor): less than 6Nm

[0180] (Evaluation criteria for brake force damping rate) A (Excellent): Less than 10% B (poor): 10% or more

[0181] [Table 2]

[0182] [Table 3] [Explanation of Symbols]

[0183] 10 Brake Pads 11 Support 12 Friction material layer 20. Excitation Brake System 21 Braking part 22 Rotating part 23 Rotating cylinder 24 Brake rotors 25 Magnetic field generator 26 York 27 Spacers a Core diameter b. Coil outer diameter c. Distance from the outer diameter of the coil to the friction material layer d Friction material layer width e Electromagnet height P Load Value l Arm length

Claims

1. An excitation friction material comprising a magnetoviscoelastic elastomer composition containing a viscoelastic elastomer and magnetic powder dispersed in the viscoelastic elastomer.

2. The magneto-viscoelastic elastomer composition contains magnetic powder in an amount of 15% by volume or more and 60% by volume or less, as described in claim 1, for the excitation friction material.

3. The excitation friction material according to claim 1, wherein the viscoelastic elastomer comprises a urethane resin composed of a polyol and an isocyanate.

4. The excitation friction material according to claim 3, wherein the urethane resin has an average inter-crosslinking molecular weight of 1,000 or more and 30,000 or less, and contains slide ring material in an amount of 0.3% by mass or more and 20% by mass or less based on the total amount of polyol and slide ring material.

5. An excitation brake pad having a support and a friction material layer fixed on the support, wherein the friction material layer is made of the excitation friction material described in any one of claims 1 to 4.

6. An excitation brake device comprising a brake pad having a support and a friction material layer fixed on the support, and a brake rotor disposed with a space above the surface of the friction material layer, wherein the friction material layer is made of an excitation friction material according to any one of claims 1 to 4, and the brake rotor is made of a magnetic material.

7. The excitation brake device according to claim 6, further comprising a magnetic field generating device for applying a magnetic field to the excitation friction material.

8. The excitation brake device according to claim 6, wherein the distance between the brake pad and the brake rotor is 0.1 mm or more and 5.0 mm or less.

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