MAGNETIC VISCOSE LIQUID AND MECHANICAL DEVICE

Abstract

Magnetic viscous fluid comprising magnetic particles and a base oil, the base oil includes ester base oil and non-polar base oil, where the base oil has a nonpolarity index in the range of 10 to 45, and where the average particle diameter of the magnetic particles is in the range of 1 to 80 µm.

Description

AREA OF INVENTION

[0001] The present invention relates to a magnetic viscous fluid and a mechanical device. In particular, it relates to a magnetic viscous fluid for use in regulating frictional forces acting between objects in the mechanical device, and to a mechanical device comprising the magnetic viscous fluid. Examples of the mechanical device include, among others, brakes, clutches, and dampers of anti-vibration devices or vibration damping devices. BACKGROUND OF THE INVENTION

[0002] A magnetic viscous (magnetorheological (MR)) fluid is a liquid in which magnetic particles, which are magnetizable metal particles, are dispersed in a dispersion medium. When no magnetic field is applied to a magnetic viscous fluid, the magnetic particles are randomly suspended in the dispersion medium, and it behaves as a liquid. However, when a magnetic field is applied to the magnetic viscous fluid, the magnetic particles form numerous clusters and thicken, thereby increasing the internal stress.

[0003] Due to the aforementioned increase in internal stress, the magnetic viscous fluid behaves like a rigid body and exhibits hydrodynamic resistance to shear and pressure flows. Because of these characteristics, the magnetic viscous fluid is used in various mechanical devices to regulate the frictional force between objects, such as brakes, clutches, and dampers in anti-vibration or vibration damping systems.

[0004] Therefore, it is advantageous to exhibit a large hydrodynamic resistance force (hereinafter referred to as "hydrodynamic resistance force during excitation") against shear flow and pressure flow when a magnetic field is applied to the magnetically viscous fluid (during excitation). The hydrodynamic resistance force during excitation is evaluated by measuring the torque, viscosity, shear stress, and other quantities. In this description, the hydrodynamic resistance force during excitation is evaluated by measuring the viscosity during excitation.

[0005] The magnetic viscous fluid exhibits various properties, including the hydrodynamic resistance described above during excitation. In recent years, technologies have been developed to improve various properties of the magnetic viscous fluid by producing a dispersion medium for the magnetic viscous fluid. Patent literature 1 discloses such a magnetic viscous fluid composition comprising a monoester, magnetic particles, a dispersant, and a rheology control agent. With this composition, it is possible to provide a magnetic viscous fluid composition with low viscosity when the magnetic field is switched off, but with suppressed evaporation and excellent low-temperature flowability.

[0006] Patent literature 2 discloses a magnetic viscous fluid in which the relative density and kinematic viscosity of a dispersion medium are regulated within predetermined ranges, and the average primary particle diameter, density, and mass fraction of the magnetic particles are regulated within predetermined ranges. It is stated that according to such a configuration, it is possible to provide a magnetic viscous fluid in which the sedimentation of magnetic particles can be significantly suppressed without altering the kinematic viscosity of the dispersion medium.

[0007] Patent literature 3 discloses an oil-based magnetic ink with improved long-term storage stability.

[0008] Patent literature 4 discloses a magnetorheological fluid containing magnetic particles, a carrier fluid, an organic zinc compound and melamine(iso)cyanurate, and a magnetorheological fluid device containing this magnetorheological fluid. LITERATURE LIST Patent literature [Patent Literature 1] Publication of Japanese patent application no. JP 2017 - 92 119 A [Patent Literature 2] Publication of Japanese patent application no. JP 2021 - 163 969 A [Patent literature 3] US 2020 / 0 234 859 A1 [Patent literature 4] WO 2023 / 008 359 A1 SUMMARY OF THE INVENTION

[0009] Rubber is used as a sealing material for O-rings, oil seals, fillings, and other sealing materials in mechanical devices such as brakes, clutches, dampers, and anti-vibration or vibration damping devices that utilize magnetic viscous fluids. In this process, the rubber comes into contact with the magnetic viscous fluid, and the dispersion medium contained within the fluid can cause the rubber to deteriorate in the contact area. This deterioration of the rubber, used in sealing materials for O-rings, oil seals, and fillings, among other applications, leads to the failure of mechanical devices.

[0010] Therefore, the magnetic viscous fluid is required not only to improve hydrodynamic resistance during excitation but also to suppress rubber degradation (hereinafter referred to as "rubber-resistant characteristics"). However, no conventional technology exists that improves both hydrodynamic resistance during excitation and rubber-resistant characteristics.

[0011] The present invention was developed with regard to the above points. The purpose of the present invention is to provide a magnetic viscous fluid and a mechanical device with both improved hydrodynamic resistance during excitation and improved rubber-resistant properties.

[0012] The above problem is solved by the subject matter of claim 1. Optional embodiments are the subject matter of the dependent claims. Exemplary variants of the present publication are described in points (1) to (5) as follows: (1) Magnetic viscous fluid comprising a magnetic particle and a base oil, the base oil includes ester base oil and non-polar base oil, a nonpolarity index of the base oil in the range of 10 to 45, and where the average particle diameter of the magnetic particles is in the range of 1 to 80 µm. (2) The magnetic viscous fluid according to point (1), wherein the ester base oil is at least one selected from a hindered ester and a dibasic acid ester. (3) Magnetic viscous fluid according to point (1) or (2), further comprising an alkylbenzene having an alkyl group with 10 to 24 carbons and / or an alkylnaphthalene having an alkyl group with 10 to 24 carbons. (4) Magnetic viscous fluid according to any one of points (1) to (3), further comprising an inorganic cation exchanger with a siloxane bond and silicone oil. (5) Mechanical device comprising the magnetic viscous fluid according to any of points (1) to (4).

[0013] According to one embodiment of the present invention, it is possible to provide a magnetic viscous fluid and a mechanical device with both improved hydrodynamic resistance during excitation and improved rubber-resistant properties. BRIEF DESCRIPTION OF THE DRAWINGS Fig.Figure 1 shows the relationship between a nonpolarity index and a hardness change rate of NBR from examples 1 to 4, 7 to 14 and the comparison examples 1 to 3 from Tables 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following describes embodiments of a magnetic viscous fluid and a mechanical device according to the present invention.

[0015] In this description, the symbol “~” representing a range of numerical values ​​denotes a range that includes the numerical values ​​listed as the upper and lower limits of the range. If units are only specified for the upper limit of a numerical range, this means that the lower limit is also in the same units as the upper limit.

[0016] In the stepwise numerical value ranges described herein, the upper or lower limits described in one numerical value range can be replaced by the upper or lower limits of the other stepwise numerical value range.

[0017] In the numerical value ranges described herein, the upper or lower limits described in a particular numerical value range can be replaced by the values ​​given in the examples.

[0018] Where several substances corresponding to each component are present in the composition, in this description a content or amount of each component in a composition corresponds to the total content or amount of these several substances present in the composition, unless otherwise specified. (Magnetic viscous fluid)

[0019] The magnetic viscous fluid according to the present embodiment is a colloidal fluid containing a magnetic particle and a base oil, wherein the magnetic particles are dispersed in the base oil. The base oil contains ester base oil and nonpolar base oil. Prior to excitation, the magnetic particles in the magnetic viscous fluid are suspended in the base oil and form clusters along the magnetic field when a magnetic field is applied (excitation). The base oil acts as a resistor to cluster formation. Ester base oil is a synthetic oil and has a more uniform molecular structure than mineral oil and other oils. Therefore, when a magnetic field is applied, the physical resistance between the magnetic particles and the ester base oil decreases. This results in an ideal cluster and improves the magnetic properties.For the magnetic particles to be sedimented in a stable manner, the ester base oil must be polar, but most polar ester base oils tend to cause rubber to swell. In contrast, the magnetic viscous fluid according to the present embodiment has magnetic particles dispersed in the base oil, and the base oil contains both the ester base oil and the non-polar base oil, which has the property of shrinking rubber, thereby improving both the hydrodynamic resistance during excitation and the rubber's resistance characteristics.

[0020] The base oil contained in the magnetic viscous fluid according to the present embodiment comprises an ester base oil and a non-polar base oil. The ester base oil has the property of causing rubber to swell, while the non-polar base oil has the property of causing rubber to shrink. By mixing the ester base oil and the non-polar base oil, which have opposite properties, the non-polarity index, which is composed of the ester base oil and the non-polar base oil in the magnetic viscous fluid, can be adjusted to a predetermined range, thereby advantageously suppressing the decomposition of rubber upon contact with the magnetic viscous fluid.

[0021] The nonpolarity index is calculated according to the following formula (A). "Nonpolarity index"=[(Number of carbon atoms × molecular weight) / (Number of ester groups × 100)]×[(Ester base oil content) / (Ester base oil content + content of nonpolar base oil)] (In the above formula (A) “number of carbon atoms” represents the number of carbon atoms that make up the ester base oil, “molecular weight” represents the molecular weight of the ester base oil and “number of ester groups” represents the number of ester groups in an ester molecule).

[0022] In the present invention, "deterioration of the rubber" means that the absolute value of the rate of change in the rubber's hardness exceeds 5% after it has been in contact with the magnetic viscous fluid for a predetermined time. In the magnetic viscous fluid according to the present embodiment, the nonpolarity index is in the range of 10 to 45, preferably in the range of 15 to 40, and more preferably in the range of 20 to 40. A nonpolarity index of 45 or less can suppress deterioration of the rubber, and a nonpolarity index of 10 or more can improve the sedimentation suppression effect of magnetic particles as well as the hydrodynamic resistance during excitation. A method for calculating the rate of change in the rubber's hardness is described below.

[0023] Rubbers capable of suppressing degradation in the present invention are not limited to acrylonitrile butadiene rubber (hereinafter referred to as "NBR"), styrene butadiene rubber (SBR), chloroprene rubber (CR), silicone rubber, urethane rubber, and others. Of this group, NBR is particularly suitable as a sealing material for, among other things, O-rings, oil seals, and fillings in various mechanical devices such as brakes, clutches, dampers of anti-vibration devices, or vibration damping devices. The magnetic viscous fluid of the present invention exhibits particularly good rubber-resistant properties.

[0024] In the following, each component of the magnetic viscous fluid according to the present embodiment is described. 1. Magnetic particle

[0025] The magnetic particles encompassed by the magnetic viscous fluid according to the present embodiment can be selected according to the desired permeability. Examples include ferromagnetic oxides such as magnetite, carbonyl iron, gamma iron oxide, manganese ferrite, cobalt ferrite or compound ferrite with zinc or nickel, barium ferrite, and others; ferromagnetic metals such as iron, cobalt, and rare earth elements, and others; nitride metals; and various alloys such as Sendust (registered trademark), Permalloy (registered trademark), Super Permalloy (registered trademark), and others. Carbonyl iron is preferred from this group because it is a soft magnetic material with low retention and high permeability. Carbonyl iron is a high-purity metal particle produced by the thermal decomposition of pentacarbonyl iron (Fe(CO)₅).

[0026] Only one type of magnetic particle can be used, or two or more can be combined.

[0027] In the magnetic viscous fluid according to the present embodiment, the dispersed magnetic particles are aligned in the direction of the magnetic field when an external magnetic field is applied, forming chain-like clusters. This thickens the fluid and alters its flow properties and yield stress. The average particle diameter of the magnetic particles is determined to achieve this behavior. In particular, the range of 0.1 to 100 µm is preferred, 1 to 80 µm is more preferred, 5 to 60 µm is even more preferred, 10 to 50 µm is still more preferred, and 10 to 40 µm is most preferred. The shape of the magnetic particles is preferably spherical or nearly spherical to facilitate dispersion.

[0028] The average particle diameter of the magnetic particles is an average primary particle diameter measured using a laser diffraction / scattering particle size distribution analyzer.

[0029] The proportion of magnetic particles is preferably in the range of 30 to 90 percent by mass of the total amount of the magnetic viscous fluid according to the present embodiment. By adjusting the proportion of magnetic particles to this range, a necessary hydrodynamic resistance can be achieved when a magnetic field is applied, and dispersion of the magnetic particles can be maintained, allowing the magnetic viscous fluid to also function as a liquid. The proportion of magnetic particles is more preferably in the range of 40 to 85 percent by mass, even more preferably in the range of 45 to 80 percent by mass, and most preferably in the range of 50 to 75 percent by mass. 2. Base oil

[0030] The base oil contained in the magnetic viscous fluid according to the present embodiment comprises an ester base oil, a nonpolar base oil, and certain alkylbenzenes and alkylnaphthalenes, which are added as desired. The ester base oil, the nonpolar base oil, and certain alkylbenzenes and alkylnaphthalenes are described in detail below. 2-1. Ester base oil

[0031] The ester base oil contained in the magnetic viscous fluid according to the present embodiment is a polar base oil, and the ester base oil is a compound containing an ester group (-C(=O)-O-). Examples of ester base oils include, but are not limited to, monoesters, polyol esters, dibasic acid esters (diesters), and polyoxyalkylene glycol esters. One of these ester base oils can be used alone, or two or more can be combined.

[0032] Monoesters with 12 to 30 carbon atoms are preferred from this group, such as 2-ethylhexyl laurate, 2-ethylhexyl palmitate, n-butyl stearate, and others. Polyol esters are esters of polyhydric alcohols (polyols) and linear or branched-chain saturated or unsaturated fatty acids. Examples of polyol esters include hindered esters. 2-1-1. Hindered Ester

[0033] The ester base oil contained in the magnetic viscous liquid according to the present embodiment is explained in detail using the hindered ester as an example. The hindered ester is an ester of a hindered polyol having one or more quaternary carbons in the molecule and one to four methylol groups bonded to at least one of the quaternary carbons, and an aliphatic monocarboxylic acid.

[0034] Hindered polyols include, for example, trimethylolpropane (TMP), pentaerythritol (PE), dipentaerythritol (DPE), neopentyl glycol (NPG), 2-methyl-2-propyl-1,3-propanediol (MPPD) and others.

[0035] From the group of these hindered polyols, trimethylolpropane, pentaerythritol, and dipentaerythritol are preferred because of the higher flash point of the resulting hindered ester. Trimethylolpropane is preferred because of the lower flow point of the resulting hindered ester.

[0036] Aliphatic monocarboxylic acids with 5-15 carbon atoms are preferred. The acyl groups of these monocarboxylic acids can be linear or branched. Examples of aliphatic monocarboxylic acids include valeric acid, caproic acid, caprylic acid, enanthate, perargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, undecylenic acid, linderic acid, stannic acid, fizetellic acid, myristoleic acid, sorbic acid, sabic acid, and others. One of these aliphatic monocarboxylic acids can be used alone or in combination with two or more of them in the esterification. The carbon number of the aliphatic monocarboxylic acid is more preferably in the range of 5 to 12. A carbon number of 5 or more is more preferred because the flash point of a resulting hindered ester is higher.The number of carbon atoms in the aliphatic monocarboxylic acid is more preferably 15 or less to achieve an improved solubility parameter of the resulting hindered ester. Even more preferably, the number of carbon atoms in the aliphatic monocarboxylic acid is in the range of 6 to 10, and most preferably in the range of 7 to 9.

[0037] The carbon number of the above fatty acid includes the carbon atom of the carboxyl group (-COOH) that the fatty acid possesses. 2-1-2. Dibasic acid ester

[0038] The ester base oil contained in the magnetic viscous liquid according to the present embodiment is explained in detail using the example of the dibasic acid ester.

[0039] The dibasic acid esters include esters of dicarboxylic acids with 2 to 10 carbon atoms and of alcohols with 1 to 10 carbon atoms.

[0040] Dicarboxylic acids with 2 to 10 carbon atoms include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, cortic acid, azelaic acid and sebacic acid and others, as well as aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid and others.

[0041] Alcohols with 1 to 10 carbon atoms include, among others, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, hexanol, octanol, 2-ethylhexanol, isononyl alcohol, decyl alcohol, and isodecyl alcohol. Among dibasic acid esters, esters of dicarboxylic acids with 6 to 10 carbon atoms, such as diisobutyl adipate, di(2-ethylhexyl) adipate (DOA), diisodecyl adipate (DIDA), diisononyl adipate (DINA), bis(2-ethylhexyl)azelaic acid (DOZ), and di(2-ethylhexyl) sebacate (DOS), as well as alcohols with 4 to 10 carbon atoms, are preferred. In esterification, one of these dicarboxylic acids and alcohols can be used alone or in combination with two or more of them.

[0042] Unless otherwise specified, the carbon number of the aliphatic dicarboxylic acid in the present invention comprises the carbon atom of the carboxyl group (-COOH) of the aliphatic dicarboxylic acid. One of these dibasic acid esters can be used alone or in combination with two or more of them.

[0043] The ester base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a kinematic viscosity of 50.0 mm at 40°C. 2 / s or less, preferably in the range of 10.0 to 50.0 mm 2 / s and most strongly preferred in the range of 10.0 to 4.0 mm 2 / s. It is preferred that the kinematic viscosity of the ester base oil at 40°C is 50.0 mm. 2 / s or less to facilitate the dispersion of the magnetic particles.

[0044] Kinematic viscosity is a kinematic viscosity measured according to JIS K2283:2000 (Method for testing kinematic viscosity).

[0045] The ester base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a flash point of 200°C or higher, and more preferably 250°C or higher.

[0046] If the flash point of the base oil is 200°C or higher, the base oil composition is reclassified from Class 3 to Class 4 petroleum according to fire service regulations. This is preferable because it allows for an increase in the quantity of hazardous materials handled (declared quantity). The flash point is measured according to JIS K2265-4:2007 (Cleveland Open-Circuit (COC) method).

[0047] The ester base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a melting point of -10°C or less, more preferably -20°C or less, particularly preferably -30°C or less, and most preferably -50°C or less. A melting point of -10°C or less is preferred because of its excellent flowability at low temperatures. The melting point is a melting point measured according to JIS K2269:1987.

[0048] The solubility parameter of the ester base oil is preferably in the range of 8.5 to 12.0 (cal / cm³). 3 ) 1 / 2 (17,386.8 J 1 / 2 m 3 / 2 up to 24,546.0 J 1 / 2 m 3 / 2 ), more preferably in the range of 8.8 to 11.0 (cal / cm³) 3 ) 1 / 2 (18,000.4 J 1 / 2 m 3 / 2 up to 22,500.5 years 1 / 2 m 3 / 2 ), and most strongly preferred in the range of 9.0 to 10.0 (cal / cm²). 3 ) 1 / 2 (18,408.5 J 1 / 2 m3 / 2 up to 20,455.0 J 1 / 2 m 3 / 2 A solubility parameter of 8.5 (cal / cm³) 3 ) 1 / 2 (17,386.8 J 1 / 2 m 3 / 2 A solubility parameter of 12.0 (cal / cm³) or higher is preferred, as it renders the ester base oil incompatible with the silicone oil described below. 3 ) 1 / 2 (24,546.0 J 1 / 2 m 3 / 2 ) or less is preferred because it improves the heat resistance of the ester base oil.

[0049] The solubility parameter (SP value) can be calculated according to the method proposed by Fedors et al. (see “Polymer Engineering and Science, 14, 147-154 (1974)”), i.e. it can be calculated using the following formula (B): SP value δ=(∑Δe / ∑Δv)1 / 2

[0050] (In the above formula (B), Δe is the vaporization energy of each atom or group of atoms at 25°C and Δv is the molar volume of each atom or group of atoms at the same temperature). 2-2. Nonpolar base oil

[0051] The nonpolar base oil contained in the magnetic viscous fluid according to the present embodiment is a nonpolar oil material consisting only of carbon and hydrogen. Examples of nonpolar base oils include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, polyalphaolefin (PAO), alphaolefin, synthetic naphthenic oils, polybutene oils, and others. From this group, polyalphaolefin is preferred because of its excellent heat resistance and high viscosity index. One of these nonpolar base oils can be used alone, or two or more can be combined.

[0052] From this group, compounds with rings consisting of cyclohexane ring, bicycloheptane ring and bicyclooctane ring are preferred as naphthenic mineral oils.

[0053] Polyalphaolefin is a polyalphaolefin or a hydride thereof obtained by polymerization of at least one type of alphaolefin at a degree of polymerization of 2 to 10.

[0054] The polyalphaolefin can be an alpha olefin monopolymer, a copolymer of two or more alpha olefins, or a hydride thereof.

[0055] The alpha olefin used as a raw material can be linear or branched, with the linear form being preferred. There are no particular restrictions on the number of carbon atoms in the alpha olefin, but numbers from 8 to 12 are preferred, and 10 is even more preferred. Linear alpha olefins with 8 to 12 carbon atoms include 1-octene (8 carbon atoms), 1-nonene (9 carbon atoms), 1-decene (10 carbon atoms), 1-undecene (11 carbon atoms), and 1-dodecene (carbon number: 12). When the carbon number of the raw material, the alpha olefin, is between 8 and 12, the flash point of the resulting polyalpha olefin is higher, which is desirable because of its excellent low-temperature flowability.

[0056] The upper and lower limits of the proportion of nonpolar base oil contained in the magnetic viscous fluid according to the present embodiment are regulated such that the nonpolarity index of the base oil is in the range of 10 to 45. The proportion of nonpolar base oil can generally be set to 3 to 20% by mass, preferably 4 to 15% by mass, and more preferably 4 to 10% by mass.

[0057] The nonpolar base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a kinematic viscosity of 50.0 mm at 40°C. 2 / s or less, preferably in the range of 10.0 to 50.0 mm 2 / s and most strongly preferred in the range of 10.0 to 4.0 mm 2 / s. It is preferred that the kinematic viscosity of the ester base oil at 40°C is 50.0 mm. 2 / s or less to facilitate the dispersion of the magnetic particles.

[0058] Kinematic viscosity is a kinematic viscosity that is measured using the same procedure as for the ester base oil.

[0059] The nonpolar base oil contained in the magnetic viscous fluid according to the present embodiment has a flash point of 200°C or higher, and more preferably 250°C or higher.

[0060] If the flash point of the base oil is 200°C or higher, the composition of the base oil is reclassified from Class 3 to Class 4 petroleum according to fire service regulations. This is preferable because it allows for an increase in the quantity of hazardous materials handled (declared quantity). The flash point is measured using the same procedure as for ester base oil.

[0061] The nonpolar base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a melting point of -10°C or less, more preferably -20°C or less, particularly preferably -30°C or less, and most preferably -50°C or less. A melting point of -10°C or less is preferred because of its excellent flowability at low temperatures. The melting point is measured using the same method as for the ester base oil.

[0062] The magnetic viscous fluid of the present invention may contain, in addition to the ester base oil and the nonpolar base oil, a further base oil, up to an amount that does not impair the effect of the present invention. Base oils other than the ester base oil and the nonpolar base oil include higher fatty acids, higher alcohols, polyhydric alcohols, ether base oil, and others. 2-3. Alkylbenzene, having alkyl groups with 10 and 24 carbons; alkylnaphthalene, having alkyl groups with 10 and 24 carbons

[0063] The magnetic viscous fluid according to the present embodiment preferably contains alkylbenzene having alkyl groups with 10 to 24 carbon atoms, and / or alkylnaphthalene having alkyl groups with 10 to 24 carbon atoms. The alkylbenzene and the alkylnaphthalene can be used alone or in combination. The alkylbenzene and the alkylnaphthalene each act as lubricating agents, improving the lubricity of the magnetic viscous fluids. The alkylbenzene and the alkylnaphthalene, as well as the ester base oil, are polar and compatible with each other.

[0064] Alkylbenzene with an alkyl group of 10 to 24 carbons is an aromatic hydrocarbon containing an alkyl group of 10 to 24 carbons bonded to a benzene ring. The alkyl group can be linear or branched. The alkyl group can be bonded singly or multiply to the benzene ring. Alkylbenzenes include monoalkylbenzenes, dialkylbenzenes, trialkylbenzenes, tetraalkylbenzenes, and others. In the alkyl groups of alkylbenzenes, 10 to 20 carbons are preferred, 12 to 18 carbons are more preferred, and 13 to 18 carbons are even more preferred.

[0065] The alkylbenzenes preferably have 1 to 4 alkyl groups bonded to the benzene ring. The alkylbenzenes preferably have a total of 10 to 40 carbon atoms in alkyl groups bonded to the benzene ring, more preferably 10 to 30 total carbon atoms in alkyl groups, and even more preferably 10 to 20 total carbon atoms in alkyl groups bonded to the benzene ring.

[0066] The alkyl groups include, among others, decyl, undecyl, dodecyl, tridecyl, tetradecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tricosyl and tetracosyl groups.

[0067] An alkylbenzene having an alkyl group with 10 to 24 carbons can be used alone, or two or more can be used in combination.

[0068] As long as they function, for example, as lubricating aids as described above, specific examples of alkylbenzenes with alkyl groups having 10 and 24 carbon atoms for use in the magnetic viscous fluid according to the present embodiment are not limited to decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, hexadecylbenzene, heptadecylbenzene, octadecylbenzene, nonadecylbenzene, icosylbenzene, henicosylbenzene, docosylbenzene, tricosylbenzene, tetracosylbenzene and others.

[0069] Alkylnaphthalene with an alkyl group of 10 to 24 carbon atoms is an aromatic hydrocarbon with an alkyl group bonded to a naphthalene ring. The alkyl group may be the same as the alkyl group bonded to the preceding alkylbenzene. The alkyl group with 10 to 24 carbon atoms may be bonded to one or more naphthalene rings.

[0070] The alkyl groups of the alkylnaphthalene preferably have 10 to 24 carbons, more preferably 12 to 18 carbons, and even more preferably 13 to 18 carbons. One to four alkyl groups with 10 to 24 carbons bonded to the naphthalene ring are preferred for the alkylnaphthalene.

[0071] An alkylnaphthalene having an alkyl group with 10 to 24 carbon atoms can be used alone, or two or more can be used in combination.

[0072] As long as it functions as the lubricating agent as described above, specific examples of alkylnaphthalene for use in the magnetic viscous fluid according to the present embodiment are not limited to, for example, decylnaphthalene, undecylnaphthalene, dodecylnaphthalene, tridecylnaphthalene, tetradecylnaphthalene, heptadecylnaphthalene, hexadecylnaphthalene, octadecylnaphthalene, nonadecylnaphthalene, icosylnaphthalene, henicosylnaphthalene, docosylnaphthalene, tricosylnaphthalene, tetracosylnaphthalene and others.

[0073] If alkylbenzene with an alkyl group having 10 to 24 carbon atoms or alkylnaphthalene with an alkyl group having 10 to 24 carbon atoms is present alone, the lower limit of the proportion of such a component, or if both alkylbenzene and alkylnaphthalene are present, is preferably 5% by mass or more, more preferably 5% to 25% by mass or more, even more preferably 10% to 25% by mass or more, and most preferably 10% to 20% by mass or more, of the total amount of the base oil of the magnetic viscous fluid according to the present embodiment. By adjusting the proportion to 5% by mass or more, the lubricity of the magnetic viscous fluid can be further improved, and the polarity of the magnetic viscous fluid can be further improved.By adjusting the content to 25% by mass or less, it can be prevented that the relative content of the ester base oil decreases too much, and it can be prevented that the sedimentation suppression effect of the magnetic particles decreases.

[0074] The ester base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a kinematic viscosity of 50.0 mm at 40°C. 2 / s or less, preferably in the range of 10.0 to 40.0 mm 2 / s. It is preferred that the kinematic viscosity of the base oil at 40°C is 50.0 mm. 2 / s or less to facilitate the dispersion of the magnetic particles.

[0075] Kinematic viscosity is a kinematic viscosity that is measured using the same procedure as for the ester base oil.

[0076] The base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a flash point of 200°C or higher, more preferably of 250°C or higher.

[0077] If the flash point of the base oil is 200 °C or higher, the base oil composition is reclassified from Class 3 to Class 4 petroleum according to fire service regulations. This is preferable because it allows for an increase in the quantity of hazardous materials handled (specified quantity). The flash point is measured using the same procedure as for the ester base oil.

[0078] The base oil contained in the magnetic viscous fluid according to the present embodiment comprises an ester base oil, a nonpolar base oil, and certain alkylbenzenes and alkylnaphthalenes, which are added as desired. In this case, the flash point refers to a flash point calculated using the Flash Point Blending Index (FPI). This is what is meant when "flash point" is simply mentioned below.

[0079] The flash point mixing index for calculating the flash point is obtained from the flash point mixing index table in Hydrocarbon Processing & Petroleum Refiner, June 1963, Vol. 42, No. 6. For example, the flash point of a mixture of oil A, with a flash point of 190°F (87.8°C), and oil B, with a flash point of 330°F (165.6°C), in a volume ratio of 30:70, is calculated as follows. Based on the flash point mixing index table in the aforementioned literature, the FPI of oil A is 30 and the FPI of oil B is 1.0. Calculating the FPI of the mixture by dividing it by the FPI of the individual oils yields "Mixture FPI = (30 / 100) × (30) + (70 / 100) × (1.0) = 9.7". Applying this FPI of 9.7 to the flash point of the mixture, the flash point corresponding to FPI 9.7 can be estimated to be approximately 110°C (230°F).

[0080] The base oil contained in the magnetic viscous fluid according to the present embodiment preferably has a melting point of -10°C or less, more preferably -20°C or less, particularly preferably -30°C or less, and most preferably -50°C or less. A melting point of -10°C or less is preferred because of its excellent flowability at low temperatures. The melting point is measured using the same method as for the ester base oil.

[0081] The proportion of base oil in the magnetic viscous fluid according to the present embodiment is preferably 10% by mass or more, more preferably 10 to 70% by mass, even more preferably 20 to 70% by mass, and most preferably 20 to 60% by mass, based on the total amount of the magnetic viscous fluid according to the present embodiment. A base oil proportion of 10% by mass or more can disperse the magnetic particles and improve flowability. A base oil proportion of 70% by mass or less is more preferred, as it can improve the magnetic properties during excitation. 3. Inorganic cation exchanger with siloxane bonding, silicone oil

[0082] The magnetic viscous fluid according to the present embodiment further preferably comprises an inorganic cation exchanger with a siloxane bond and a silicone oil. According to such a configuration, the hydrodynamic resistance of the magnetic viscous fluid during excitation is further improved.

[0083] More precisely, the magnetic particles are dispersed in the base oil. Since the magnetic particles exhibit cationic properties, they adsorb inorganic cation exchangers with siloxane bonds. Furthermore, the silicone oil is dispersed in the ester base oil, which has a low surface energy and a high solubility parameter, without dissolving within it. Moreover, the inorganic cation exchanger with siloxane bonds and the silicone oil exhibit a high affinity, as both contain silicon, and it is assumed that the silicone oil exists in a state surrounding the magnetic particles, which are then adsorbed by the inorganic cation exchanger with siloxane bonds.

[0084] When a magnetic field is applied in this state, the magnetic particles surrounded by silicone oil quickly bond together and form clusters. The presence of silicone oil around the magnetic particles prevents excessive aggregation. Therefore, when the hydrodynamic resistance (viscosity) is measured by applying a magnetic field, a shear force is generated, but the clusters do not break apart, and the hydrodynamic resistance is considered stable. <Anorganischer Kationentauscher mit Siloxanbindung>

[0085] Inorganic cation exchangers with siloxane bonding include, for example, zeolite, silica, phyllosilicate, and others. Zeolite is preferred from this group due to its wear resistance. A single type of inorganic cation exchanger with siloxane bonding can be used alone or in combination with two or more other types. Both natural and synthetic products can be used.

[0086] Zeolite consists of a crystalline, porous aluminum silicate framework with anionic properties and a cationic metal element M adsorbed onto the framework. More precisely, the basic structural unit consists of SiO₄ and AlO₄, which have a tetrahedral structure and are three-dimensionally bonded to form a crystal with pores (cavities) in which water of crystallization and the cationic metal element M are adsorbed. The crystal structure of zeolite is not limited, in particular not to zeolite type A, zeolite type X, zeolite type Y, zeolite type L, beta-zeolite, ZSM-5, ZSM-11, silicalite, ferrierite, mordenite, clinoptilolite, porringite, and others.

[0087] A layered silicate is a silicate compound with a crystal structure consisting of layers formed by ionic bonds and other factors, which are weakly bonded to one another and arranged in layers. Layered silicates often carry a negative charge in all layers, and large cations move between the layers to neutralize this negative charge. Due to the small layer charge, these cations are exchangeable with cations in solution and exhibit cation-exchange properties.The layered silicate group includes, for example, the smectite group (bentonite, montmorillonite, bidelite, nontronite, saponite, hectorite, and stevensite), vermiculite, the kaolin group (kaolinite, halloysite, chrysotile, and amesite), the mica group (muscovite, biotite, ferric mica, phlogopite, albite, soda mica, siderophyllite, Hefezite, polylithiotite, trilithiotite, lithi mica, Chinwald mica, margarite, illite, and Seestein), talc, parigorskite, sepiolite, magadiite, kanemite, kenyite, synthetic fluorinated mica, and others. Of this group, the smectite group, vermiculite, and synthetic fluorinated mica are favored with respect to ion exchange capacity.

[0088] The cation exchange capacity of the inorganic cation exchanger with siloxane bonding is preferably 30 meq / 100 g or more, more preferably in the range of 30 to 400 meq / 100 g, even more preferably in the range of 60 to 350 meq / 100 g, even more preferably in the range of 60 to 300 meq / 100 g and most preferably in the range of 60 to 150 meq / 100 g.

[0089] The cation exchange capacity of inorganic cation exchangers with siloxane bonding is 260 meq / 100 g for mordenite, 120 meq / 100 g for synthetic fluorite, 60 to 150 meq / 100 g for the smectite group, 80 to 150 meq / 100 g for montmorillonite, and 100 to 150 meq / 100 g for vermiculite. (1 meq / 100 g = 1 cmol / kg)

[0090] The proportion of the inorganic cation exchanger with siloxane bonding is preferably 0.8% by mass or more, more preferably in the range of 0.8 to 4.0% by mass, even more preferably in the range of 1.0 to 3.5% by mass, and most preferably in the range of 1.3 to 3.0% by mass, of the total magnetic viscous fluid according to the present embodiment. A proportion of 0.8% by mass or more is more preferred because it can suppress the agglomeration of the magnetic particles in a state where no magnetic field is applied. A proportion of 4.0% by mass or less is more preferred because clusters of the magnetic particles can form appropriately when a magnetic field is applied. <Silikonöl>

[0091] Silicone oil can be used without restriction as long as it is incompatible with the ester base oil. Silicone oil can be broadly divided into pure silicone oil and modified silicone oil. Pure silicone oil includes dimethyl silicone oil, methylphenyl silicone oil, and methyl hydrogen silicone oil. Modified silicone oil includes reactive and non-reactive silicone oil. Reactive silicone oil includes, for example, amino-modified, epoxy-modified, carboxy-modified, carbinol-modified, methacryl-modified, mercapto-modified, phenol-modified, and other types of silicone oil. Non-reactive silicone oil includes polyether-modified, methyl styryl-modified, alkyl-modified, higher fatty acid ester-modified, hydrophilic specially modified, higher fatty acid-containing, fluorine-modified, and others.From this group, dimethyl silicone oil and fluoromodified silicone oil are preferred because of their low surface energy, with dimethyl silicone oil being preferred because of its easy availability.

[0092] The lower limit of the silicone oil content is preferably 0.5% by mass or more, more preferably 0.5 to 3.0% by mass, and most preferably 1.0 to 2.5% by mass, based on the total amount of the magnetic viscous fluid according to the present embodiment. A content of 0.5% by mass or more is preferred because it can surround the magnetic particles to which the inorganic cation exchanger with siloxane bonding is attached. A content of 3.0% by mass or less is preferred because it can prevent a decrease in the dispersion of the magnetic particles.

[0093] The mixing ratio of the inorganic cation exchanger with siloxane bond and silicone oil is preferably in the range of 2:8 to 8:2 by mass, more preferably 3:7 to 7:3.

[0094] A mixing ratio in the range of 2:8 to 8:2 by mass is preferable, as it improves the aging resistance of the hydrodynamic resistance during excitation.

[0095] An absolute value of the difference in solubility parameters between the ester base oil and the silicone oil is preferably 1.3 (cal / cm³). 3 ) 1 / 2 (2,659.2 J 1 / 2 m 3 / 2 ) or more, preferably 1.5 (cal / cm²) 3 ) 1 / 2 (3,068.3 J 1 / 2 m 3 / 2 ) or more, and especially preferably 1.8 (cal / cm²) 3 ) 1 / 2 (3,681.9 J 1 / 2 m 3 / 2 ) or more. If the absolute value of the difference in the solubility parameters between the ester base oil and the silicone oil is 1.3 (cal / cm³). 3 ) 1 / 2(2,659.2 J 1 / 2 m 3 / 2 ) or more, it is more preferred to improve the incompatibility between the ester base oil and the silicone oil. <Andere Komponenten >

[0096] In addition to the aforementioned components, the magnetic viscous fluid according to the present embodiment can be combined with various other components depending on the intended use, as long as the effect of the present invention is not impaired.

[0097] Other components include, for example, anti-wear agents, dispersants, surfactants, viscosity regulators, flow improvers, sedimentation inhibitors, flow point reducers, high pressure agents, rust inhibitors, oxidation inhibitors, corrosion inhibitors, metal inactivators, defoamers and others.

[0098] Anti-wear agents include, for example, sulfur compounds such as sulfides, sulfoxides, sulfones, thiophosphinates and others, halogenated compounds such as chlorinated hydrocarbons and others, organometallic compounds such as molybdenum dithiophosphate (MoDTP), molybdenum dithiocarbamate (MoDTC), tricresyl phosphate and others.

[0099] One type of wear protection agent can be used alone or in combination with two or more.

[0100] Dispersants are added to improve the dispersibility of the magnetic particles in the base oil and include well-known low molecular weight dispersants, high molecular weight dispersants, and others. One type of dispersant can be used alone, or two or more can be combined.

[0101] Examples of viscosity regulators include castor oil, hydrogenated castor oil, fatty acid amides, beeswax, carnauba wax, benzylidene sorbitol, metal soap, polyethylene oxide, anionic sulfate activator, polyolefin, (meth)acrylic acid esters, polyisobutylene, ethylene-propylene copolymer, polyalkylene styrene and others.

[0102] One type of viscosity regulator can be used alone, or two or more can be used in combination.

[0103] Flow improvers include modified silicone oil. For example, pure silicone oils are modified with alkyl, aralkyl, polyether, and higher fatty acid esters, as well as amino, epoxy, carboxyl, and alcohols. The modified silicone oil must be compatible with the ester base oil. One type of flow improver can be used alone, or two or more can be used in combination. <Viskosität der magnetischen viskosen Flüssigkeit>

[0104] The viscosity of the magnetic viscous fluid according to the present embodiment before excitation is preferably in the range of 0.02 to 1.0 Pa·s at 40 °C, more preferably in the range of 0.03 to 0.6 Pa·s. The measurement conditions for the viscosity before excitation are as follows.

[0105] 3 ml of the magnetic viscous liquid are injected into a test plate of a TA Instruments Rheometer DHR-2, which is equipped with the possibility for magnetic measurements, and the viscosity (Pa · s) is measured at 20 revolutions of a 100 µm wide gap in an atmosphere of 40°C. <Magnetische Eigenschaften von magnetischen viskosen Flüssigkeiten >

[0106] As described above, the magnetic viscous fluid according to the present embodiment exhibits the characteristic of high hydrodynamic resistance during excitation. High hydrodynamic resistance during excitation means that the maximum viscosity of the magnetic viscous fluid of the present invention during excitation is 230 Pa·s or more under the following conditions, when the proportion of magnetic particles in the total amount of the magnetic viscous fluid is 64 to 67 percent by mass. The maximum viscosity during excitation is preferably 230 Pa·s or more, and more preferably 240 Pa·s or more.

[0107] As described above, excellent aging resistance of the hydrodynamic resistance during excitation (viscosity aging resistance) can be achieved by further comprising the inorganic cation exchanger with siloxane bonding and silicone oil. Excellent aging resistance of the hydrodynamic resistance during excitation (viscosity aging stability) means that a stabilization ratio B, as described below, is 80% or more. A stabilization ratio A is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

[0108] The viscosity during excitation is the viscosity during 210 seconds in which the magnetic field is applied, using the same measuring device with which the viscosity was measured before excitation, and under the same temperature atmosphere, wherein a magnetic field of 0.8 T DC is applied 5 seconds after the start of the measurement and the application of this magnetic field is terminated 215 seconds after the start of the measurement.

[0109] The stabilization ratio A (%) is calculated according to the following formula. Stabilization rate A (%) = (Stabilization time A / Total duration of application) × 100

[0110] The stabilization time A is the application time that corresponds to 95 to 100% of the maximum viscosity value during excitation.

[0111] The stabilization ratio B (%) is calculated according to the following formula. Stabilization rate B (%) = (Stabilization time B / Total duration of application) × 100

[0112] The stabilization time B is the application time that corresponds to 90 to 100% of the maximum viscosity value during excitation. (Method for producing a magnetic viscous fluid)

[0113] A process for producing the magnetic viscous fluid according to the present embodiment is not subject to any particular limitations. For example, magnetic particles, ester base oil, nonpolar base oil, if required, alkylnaphthalene, inorganic cation exchanger with siloxane bonding, silicone oil, and, if desired, other components are mixed in varying quantities using a homogenizer, a bead mill, a mechanical mixer, or another high-shear processing machine. The ester base oil and the nonpolar base oil are mixed such that the nonpolarity index, which is the sum of the ester base oil and the nonpolar base oil, is within the specified range. The mixture can be heated or cooled as required during the production of the magnetic viscous fluid. (Mechanical device comprising a magnetic viscous fluid)

[0114] The magnetic viscous fluid according to the present embodiment can be used in various mechanical devices, such as brakes for regulating the frictional force between objects, couplings, and dampers of anti-vibration or vibration damping devices. In such a configuration within these various mechanical devices, the magnetic viscous fluid exhibits good hydrodynamic resistance during excitation, and the deterioration of the rubber in contact with the magnetic viscous fluid can be effectively suppressed. EXAMPLES

[0115] The following examples according to the present invention are provided for a better understanding of the present invention and its advantages and are not intended to limit the invention. <Beispiele 1 bis 14, Vergleichsbeispiele 1 bis 3>

[0116] Each of the components listed in Tables 1 to 3 was added to a beaker in the mass ratios specified therein and stirred at 40 Hz for 5 minutes at room temperature using a Seiko Advance Inc. AD-MIX universal vibrating stirrer to produce a magnetic viscous liquid. The raw materials for each component from Tables 1-3 are listed below. (A) Magnetic particle (a1) Carbonyl iron (average particle size D50 = 6.0 µm) (B) Ester base oil <Gehinderter Ester>

[0117] (b1) Trimethylolpropane trioctanoate (SP value: 9.1 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 40°C: 16.0 mm 2 / s, Flash point 260°C, Flow point -57°C) <Zweibasiger Säureester>

[0118] (b2) Di(2-ethylhexyl) sebacate (SP value: 8.9 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 40°C: 11.3 mm 2 / s, Flash point: 228°C, Flow point: -66°C)

[0119] (b3) Di(2-ethylhexyl) adipate (SP value: 8.9 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 40°C: 7.8 mm 2 / s, Flash point: 205°C, Temperature difference: -68°C)

[0120] (b4) Diisodecyl adipate (SP value: 8.9 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 40°C: 14.2 mm 2 / s, Flash point: 232°C, Flow point: -63°C) (C) Nonpolar base oil (c1) Polyalphaolefin (Trimer of 1-Decene, kinematic viscosity at 40°C: 17.2 mm) 2 / s, flash point 222°C, melting point -68°C) (D) Alkylnaphthalene (d1) Monoalkylnaphthalene with alkyl groups having 16 to 18 carbons (kinematic viscosity at 40°C: 37.0 mm) 2 / s, flash point 221°C, melting point -25°C or less) (E) Inorganic cation exchanger with siloxane bonding (e1) Zeolite (crystal structure: mordenite type, cation exchange capacity: 160 to 190 meq / 100g) (F) Silicone oil (f1) Dimethyl silicone oil (SP value: 7.2 (cal / cm 3 ) 1 / 2 , kinematic viscosity at 40°C: 37.8 mm 2 / s) <Bewertung der gummibeständigen Merkmale>

[0121] Solutions of the magnetic viscous liquids from Examples 1 to 14 and Comparison Examples 1 to 3, without magnetic particles, were prepared to evaluate their rubber-resistant properties. 300 ml of each solution were placed in a 500 cc beaker. Additionally, AS-ONE NBR was separately cut into strips measuring 10 mm × 60 mm × 5 mm (width × length × thickness).

[0122] The solutions were then placed in a convection oven (Advantest® DRF633TA) heated to 100 °C and left for 24 hours to assess the rubber-resistant properties. Afterwards, the NBR strips were placed in the beaker and used as test samples.

[0123] 480 hours after the sample was placed in the convection oven, the beaker was removed, the NBR immersed in the magnetic viscous liquid was taken out, and the oil on the NBR surface was removed using Kimwipes (registered trademark) S200, manufactured by Nippon Paper Crecia Co. The hardness (hardness after heating) of the NBR was then measured according to the procedure described below. The hardness (initial hardness) of NBR strips before placement in the beaker was also measured in the same manner.

[0124] - Hardness measurement: DUROMETER: The hardness was measured using the DUROMETER ADM-E manufactured by Niigata Seiki in accordance with JIS K 6253.

[0125] For examples 1 to 14 and comparison examples 1 to 3, three samples each were produced, and the rubber-resistant properties described above were evaluated under the same conditions. The average of the hardness test results for NBR in these three samples was calculated. The calculation results are presented in Tables 1 and 2.

[0126] The rate of hardness change was then calculated using the formula described below. The calculation results are shown in Tables 1 and 2.

[0127] - Hardness change rate = [(Hardness after heating - Initial hardness) / Initial hardness] × 100(%) It should be noted that “-” in the hardness change rate listed in Tables 1 and 2 indicates expansion and contraction, while “+” means swelling. <Bewertung der Viskosität vor und während der Anregung>

[0128] Three milliliters of the magnetic viscous liquids from Examples 1 to 7 and Comparison Examples 1 to 2 were injected into the test plate of a TA Instruments DHR-2 rheometer equipped for magnetic measurements, and the viscosity (Pa·s) before excitation was measured at 20 revolutions per 100 µm gap under an atmosphere of 40°C. The viscosity during excitation was also measured using the same measuring device under the following conditions at 40°C.

[0129] Magnetic field excitation conditions: A magnetic field of 0.8 T DC was applied 5 seconds after the start of the measurement, and the application of the magnetic field was stopped 215 seconds after the start of the measurement.

[0130] Three samples of the magnetic viscous fluid for Examples 1 to 7 and Comparison Examples 1 to 2 were prepared as described above, and the viscosities before and during excitation were evaluated under the same conditions. The average of the measured viscosity of NBR before and during excitation in these three samples was calculated. The results of the calculations are shown in Table 3.

[0131] Aging resistance was assessed based on the stabilization rate A (%) and the stabilization rate B (%), calculated using the following formulas. The calculation results are shown in Table 3. Stabilization rate A (%) = (Stabilization time A / Total duration of application) × 100

[0132] The stabilization time A is the application time that corresponds to 95 to 100% of the maximum viscosity value during excitation. Stabilization rate B (%) = (Stabilization time B / Total duration of application) × 100

[0133] The stabilization time B is the application time that corresponds to 90 to 100% of the maximum viscosity value during excitation. composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 (Mass%) Recipe magnetic particles / total amount of magnetic viscous fluid 66,66 66,66 66,29 66,29 64,17 66,67 66,29 66,64 Synthetic ester base oil / (synthetic ester base oil + non-polar base oil) 0,5 0,5 0,7 0,7 0,7 0,7 0,8 0,26 (A) Magnetic particle (a1)Carbonyl iron 200 200 200 200 200 200 200 200 (B)Ester base oil Hindered Ester (b1)Trimethylolpropane trioctanoate 44,2 0 63,0 0 63,0 70 72,0 22,7 Dibasic acid ester (b2)Di(2-ethylhexyl) sebacate 0 44,2 0 63,0 0 0 0 0 (b3)Di(2-ethylhexyl) adipate 0 0 0 0 0 0 0 0 (b4)Diisodecyl adipate 0 0 0 0 0 0 0 0 (C) Non-polar base oil Polyalphaolefin (c1)Trimer of 1-decene 44,2 44,2 27,0 27,0 27,0 30 18,0 65,7 (D)Alkylnaphthalene (d1)Monoalkylnaphthalene with alkyl groups having 16 to 18 carbons 11,7 11,7 11,7 11,7 11,7 0 11,7 11,7 (E) Inorganic cation exchanger with siloxane bonding (e1)Zeolite 0 0 0 0 5 0 0 0 (F)Silicone oil (f1)Dimethyl silicone oil 0 0 0 0 5 0 0 0 Test results Nonpolarity Index (NPI) 25,6 27,7 35,8 38,8 35,8 35,8 35,8 14,4 Hardness of NBR in the rubber resistance test Before the experiment 82 82 82 82 82 82 82 82 After the experiment 81 81 82 85 82 84 85 80 Hardness change rate (%) -1,2 -1,2 0,0 3,7 0,0 2,4 3,7 -2,4 A "-" in the rate of change in hardness indicates expansion and contraction, while a "+" indicates swelling. composition See 1 See 2 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 See 3 (Mass%) Recipe magnetic particles / total amount of magnetic viscous fluid 64,16 64,17 66,65 66,65 66,29 66,65 66,65 66,29 64,17 Synthetic ester base oil / (synthetic ester base oil + non-polar base oil) 1,0 1,0 0,26 0,5 0,7 0,26 0,5 0,7 1,0 (A) Magnetic particle (a1)Carbonyl iron 200 200 200 200 200 200 200 200 200 (B)Ester base oil Hindered Ester (b1)Trimethylolpropane trioctanoate 100 0 0 0 0 0 0 0 0 Dibasic acid ester (b2)Di(2-ethylhexyl) sebacate 0 100 0 0 0 0 0 0 0 (b3)Di(2-ethylhexyl) adipate 0 0 22,7 44,2 63,0 0 0 0 0 (b4)Diisodecyl adipate 0 0 0 0 0 22,7 44,2 63,0 100 (C) Non-polar base oil Polyalphaolefin (c1)Trimer of 1-decene 0 0 65,7 44,2 27,0 65,7 44,2 27,0 0 (D)Alkylnaphthalene (d1)Monoalkylnaphthalene with alkyl groups having 16 to 18 carbons 11,7 11,7 11,7 11,7 11,7 11,7 11,7 11,7 11,7 (E) Inorganic cation exchanger with siloxane bonding (e1)Zeolite 0 0 0 0 0 0 0 0 0 (F)Silicone oil (f1)Dimethyl silicone oil 0 0 0 0 0 0 0 0 0 Test results Nonpolarity Index (NPI) 51,2 55,4 10,6 20,4 28,5 14,4 27,7 38,8 55,4 Hardness of NBR in the rubber resistance test Before the experiment 82 82 82 82 82 82 82 82 82 After the experiment 91 90 80,7 82,3 83 81 82,3 85 90 Hardness change rate (%) 11,0 9,8 -1,6 0,4 1,2 -1,2 0,4 3,7 9,8 A "-" in the rate of change in hardness indicates expansion and contraction, while a "+" indicates swelling. composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 See 1 See 2 (Mass%) Recipe magnetic particles / total amount of magnetic viscous fluid 66,66 66,66 66,29 66,29 64,17 66,67 66,29 64,16 64,17 Synthetic ester base oil / (synthetic ester base oil + non-polar base oil) 0,5 0,5 0,7 0,7 0,7 0,7 0,8 1,0 1,0 (A) Magnetic particle (a1)Carbonyl iron 200 200 200 200 200 200 200 200 200 (B)Ester base oil Hindered Ester (b1)Trimethylolpropane trioctanoate 44,2 0 63,0 0 63,0 70 72,0 100 0 Dibasic acid ester (b2)Di(2-ethylhexyl) sebacate 0 44,2 0 63,0 0 0 0 0 100 (C) Non-polar base oil Polyalphaolefin (c1)Trimer of 1-decene 44,2 44,2 27,0 27,0 27,0 30 18,0 0 0 (D)Alkylnaphthalene (d1)Monoalkylnaphthalene with alkyl groups having 16 to 18 carbons 11,7 11,7 11,7 11,7 11,7 0 11,7 11,7 11,7 (E) Inorganic cation exchanger with siloxane bonding (e1)Zeolite 0 0 0 0 5 0 0 0 0 (F)Silicone oil (f1)Dimethyl silicone oil 0 0 0 0 5 0 0 0 0 Test results Viscosity at excitation (0.8T, 400 °C, Pa · s) Max 259,3 253,0 275,8 275,5 264,7 285,0 282,9 260,8 262,9 stabilization ratio Stabilisation ratio A(%) 86,7 74,3 74,8 67,1 99,0 81,9 79,5 85,2 78,1 Stabilisation ratio B(%) 97,6 88,1 91,4 88,1 99,0 92,9 89,5 96,2 90,5 Viscosity before excitation (0.8T, 40 °C, Pa · s) 0,03 0,05 0,09 0,37 0,31 0,09 0,03 0,23 0,19

[0134] All examples 1 to 14 are magnetic viscous fluids containing magnetic particles and a base oil, where the base oil comprises ester base oil and nonpolar base oil, and the nonpolarity index of the base oil ranges from 10 to 45. Therefore, in examples 1 to 7, the maximum viscosity during excitation was 230 Pa·s or more, indicating good hydrodynamic resistance during excitation. Furthermore, the absolute values ​​of the hardness change rate for NBR in examples 1 to 14 were all below 5%, indicating good rubber-resistant properties.

[0135] Furthermore, in examples 1 to 7, the stabilization ratio B was 80% or more, which indicates good aging resistance of the hydrodynamic resistance during excitation.

[0136] On the other hand, the magnetic viscous fluid in comparison examples 1 to 3 did not contain a non-polar base oil, which resulted in a hardness change rate of 9% or more for NBR, and the rubber-resistant characteristics were poor. Fig. Figure 1 shows the relationship between the nonpolarity indices and the hardness change rate of NBR for examples 1 to 4, 7 to 14, and the comparison examples 1 to 3 in Tables 1 and 2. The diagram in Fig. Figure 1 shows that the rate of hardness change is 5% or less when the nonpolarity index of the base oil is in the range of 10 to 45, which indicates good rubber-resistant characteristics.

Claims

[1] Magnetic viscous fluid comprising magnetic particles and a base oil, the base oil includes ester base oil and non-polar base oil, where the base oil has a nonpolarity index in the range of 10 to 45, and where the average particle diameter of the magnetic particles is in the range of 1 to 80 µm. [2] Magnetic viscous fluid according to claim 1, wherein the ester base oil is at least one selected from a hindered ester and a dibasic acid ester. [3] Magnetic viscous fluid according to claim 1, further comprising an alkylbenzene having an alkyl group with 10 to 24 carbons and / or an alkylnaphthalene having an alkyl group with 10 to 24 carbons. [4] Magnetic viscous fluid according to claim 1, further comprising an inorganic cation exchanger with a siloxane bond and silicone oil. [5] Mechanical device comprising the magnetic viscous fluid according to any one of claims 1 to 4.

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