Silicone composition, silicone cured product, mechanical device, method for producing silicone composition, method for producing silicone paste, and method for producing silicone cured product

Abstract

Provided is a silicone composition comprising: (A) a magnetic fluid which comprises (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant and (A4) water; (B) a polyether-modified silicone oil which has an oxyalkylene structure having an EO ratio of 40% or more; and (C) a curable organopolysiloxane. In the silicone composition, the blending amount of the component (A4) is 0.1-40 parts by mass with respect to 100 parts by mass of the component (C).

Description

Silicone composition, cured silicone product, mechanical device, method for producing silicone composition, method for producing silicone paste, and method for producing cured silicone product

[0001] The present invention relates to a silicone composition, a cured silicone product, a mechanical device, a method for producing a silicone composition, a method for producing a silicone paste, and a method for producing a cured silicone product.

[0002] In recent years, magnetic fluids have been attracting attention as a hysteresis-free magnetic material that can be used in speakers, sensors, dampers, etc. (Patent Document 1). Magnetic fluids are simply liquids with no magnetic field when there is no magnetic field, but they are characterized by the fact that they become magnetized when an external magnetic field is applied and lose their magnetization when the external magnetic field is removed. Magnetic fluids are magnetic materials in which magnetic powders such as ferrite particles or magnetite particles with particle diameters ranging from 3 nm to 50 nm are dispersed in a dispersion medium such as isoparaffin or water.

[0003] Japanese Patent Application Laid-Open No. 2022-7758

[0004] However, because magnetic fluids are fluids, they have problems such as seeping into gaps between parts due to capillary action and scattering to areas where they should not adhere when a magnetic field is applied. In such cases, the amount of magnetic fluid actually required can be reduced, and the properties required of magnetic fluids may not be exhibited. For this reason, the industry has been looking for a silicone composition that can be formed by curing silicone rubber or silicone gel, which has good dispersibility of magnetic particles and does not scatter when a magnetic field is applied.

[0005] The present invention has been made in light of the above points, and aims to provide a silicone composition that has good dispersibility of magnetic particles and that, when cured, can form a rubber or gel that is effectively prevented from scattering when a magnetic field is applied, a cured silicone product, a mechanical device, a method for producing a silicone composition, a method for producing a silicone paste, and a method for producing a cured silicone product.

[0006] In order to solve the above-mentioned problems, the present invention is specified as follows (1) to (20): (1) A silicone composition comprising: (A) a magnetic fluid containing (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water; (B) a polyether-modified silicone oil having an oxyalkylene structure and an EO ratio of 40% or more; and (C) a curable organopolysiloxane, wherein the amount of component (A4) is in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C). (2) The silicone composition according to (1) above, wherein component (C) is at least one selected from the group consisting of (C-1) an organopolysiloxane having an alkenyl group, and (C-2) an organopolysiloxane having a silanol group or a silicon-bonded hydrolyzable group. (3) The silicone composition according to (1) or (2) above, wherein the component (A2) is at least one selected from the group consisting of sodium oleate, sodium dodecyl sulfate, dodecyl ammonium acetate, alkyl sulfosuccinates, n-acylamino acids and salts thereof, n-alkyltrimethylenediamine derivatives, polyoxyethylene alkyl ether phosphates, and alkyl phosphates. (4) The silicone composition according to any one of (1) to (3) above, wherein the component (A3) is at least one selected from the group consisting of anionic surfactants, nonionic surfactants, proteins, casein, albumin, and hemoglobin. (5) The silicone composition according to (2) above, wherein the component (C) is the component (C-1) above, and further comprises: (E) an organohydrogenpolysiloxane containing a hydrosilyl group; and (F) a platinum group metal catalyst. (6) The silicone composition according to (2) above, wherein the component (C) is the component (C-1) and the component (C-1) further contains a hydrosilyl group. (7) The silicone composition according to (2) above, wherein the component (C) is the component (C-1) and further contains (G) an organic peroxide. (8) The silicone composition according to (2) above, wherein the component (C) is the component (C-2) and further contains (H) a silane having at least three silicon-bonded hydrolyzable groups per molecule or a partial hydrolyzate thereof.(9) A silicone cured product obtained by curing the silicone composition described in any one of (5) to (8). (10) A mechanical device using the silicone cured product described in (9). (11) A method for producing a silicone composition by adding (A) a magnetic fluid containing (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water, (B) a polyether-modified silicone oil having an oxyalkylene structure and an EO ratio of 40% or more, and (C) a curable organopolysiloxane, wherein the amount of component (A4) is in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C), and component (B) is added first or second in the order of adding component (A), component (B), and component (C). (12) The method for producing a silicone composition according to (11) above, wherein component (C) is at least one selected from the group consisting of (C-1) an organopolysiloxane having an alkenyl group and (C-2) an organopolysiloxane having a silanol group or a silicon-bonded hydrolyzable group. (13) The method for producing a silicone composition according to (11) or (12) above, wherein component (A2) is at least one selected from the group consisting of sodium oleate, sodium dodecyl sulfate, dodecyl ammonium acetate, alkyl sulfosuccinates, n-acylamino acids and salts thereof, n-alkyl trimethylenediamine derivatives, polyoxyethylene alkyl ether phosphates, and alkyl phosphates. (14) The method for producing a silicone composition according to any of (11) to (13) above, wherein component (A3) is at least one selected from the group consisting of anionic surfactants, nonionic surfactants, proteins, casein, albumin, and hemoglobin. (15) The method for producing a silicone composition according to (12) above, wherein the component (C) is the component (C-1), and further comprises the step of adding: (E) an organohydrogenpolysiloxane containing a hydrosilyl group; and (F) a platinum group metal catalyst. (16) The method for producing a silicone composition according to (12) above, wherein the component (C) is the component (C-1), and the component (C-1) further contains a hydrosilyl group.(17) A method for producing a silicone composition according to (12) above, wherein the component (C) is the component (C-1) above, and further comprising the step of adding (G) an organic peroxide. (18) A method for producing a silicone composition according to (12) above, wherein the component (C) is the component (C-2) above, and further comprising the step of adding (H) a silane having at least three silicon-bonded hydrolyzable groups per molecule, or a partial hydrolyzate thereof. (19) A method for producing a silicone paste, comprising the step of obtaining a silicone paste by subjecting a silicone composition obtained by the method for producing a silicone composition according to any one of (11) to (18) above. (20) A method for producing a cured silicone product, comprising the step of curing the silicone composition obtained by the method for producing a silicone composition according to any one of (11) to (18) above.

[0007] According to an embodiment of the present invention, it is possible to provide a silicone composition that has good dispersibility of magnetic particles and that, when cured, can form a rubber or gel that is well-suppressed in scattering when a magnetic field is applied; a cured silicone product; a mechanical device; a method for producing a silicone composition; a method for producing a silicone paste; and a method for producing a cured silicone product.

[0008] FIG. 2 is a cross-sectional view of the operating mechanism of the speaker.

[0009] Below, we will explain the silicone composition, cured silicone product, mechanical device, method for producing a silicone composition, method for producing a silicone paste, and method for producing a cured silicone product of the present invention, but the present invention should not be interpreted as being limited to these embodiments, and various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art, as long as they do not deviate from the scope of the present invention.

[0010] In this specification, the term "to" representing a numerical range indicates a range that includes the numerical values ​​recited as the upper and lower limits. Furthermore, when a unit is recited for only the upper limit of a numerical range, this means that the lower limit is also expressed in the same unit as the upper limit. In the numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples. In this specification, when multiple substances corresponding to each component are present in the composition, the content or amount of each component in the composition refers to the total content or amount of the multiple substances present in the composition, unless otherwise specified.

[0011] <<Silicone Composition>> The silicone composition according to this embodiment comprises (A) a magnetic fluid containing (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water, (B) a polyether-modified silicone oil having an oxyalkylene structure and an EO ratio of 40% or more, and (C) a curable organopolysiloxane. Each component contained in the silicone composition according to this embodiment will be described below.

[0012] (A) Magnetic Fluid Comprising (A1) Magnetic Particles, (A2) First Surfactant, (A3) Second Surfactant, and (A4) Water. The magnetic fluid of component (A) contains components (A1) to (A4) and can be used without particular restrictions as long as it satisfies the relationship (hereinafter simply referred to as the "predetermined relationship") in which the content of (A4) water relative to the curable organopolysiloxane (C) described below is within a predetermined range. For example, such a magnetic fluid can be produced by the method described in JP-A-3-265693. Commercially available products can also be used. Alternatively, water may be removed from a magnetic fluid containing water as a dispersant to adjust it so that the predetermined relationship is satisfied. (Hereinafter, these magnetic fluids will be referred to as water-based magnetic fluids.) Furthermore, a magnetic fluid satisfying the predetermined relationship can be obtained by vacuum freeze-drying a water-based magnetic fluid or a magnetic fluid containing water as a dispersant (hereinafter, these will be referred to as water-based magnetic fluids, etc.) to remove the water as a dispersant, and then adding water to the resulting magnetic powder (hereinafter, this magnetic fluid will be referred to as a regenerated magnetic fluid). Water-based ferrofluid, regenerated ferrofluid and vacuum freeze-drying process are described below.

[0013] 1. Water-Based Magnetic Fluid The water-based magnetic fluid contains at least (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water.

[0014] (A1) Magnetic Particles Examples of magnetic particles contained in water-based magnetic fluids include ferromagnetic oxides, ferromagnetic metals, and metal nitrides. Examples of ferromagnetic oxides include magnetite (Fe3O4), γ-iron oxide, manganese ferrite, cobalt ferrite, or composite ferrites of these with zinc or nickel, and barium ferrite. Examples of ferromagnetic metals include iron, cobalt, and rare earth elements. Among these, magnetite is preferred as the magnetic particle from the viewpoint of mass production. The magnetic particles used in this embodiment are not particularly limited as long as they have an average particle size within the range in which they exhibit superparamagnetism, i.e., a critical particle size or smaller. For example, in the case of magnetite particles and γ-iron oxide particles, the average particle size is preferably 50 nm or smaller, and particularly preferably in the range of 10 nm to 40 nm. One type of magnetic particle may be used alone, or two or more types may be used in combination. The shape of the magnetic particles is preferably spherical or nearly spherical, as this facilitates dispersion.

[0015] The content of magnetic particles in the water-based magnetic fluid is preferably 50% by mass or more, more preferably in the range of 50 to 90% by mass, and particularly preferably in the range of 70 to 90% by mass. The magnetic particle content is calculated based on the mass of magnetic particles adhering to at least a portion of the surface of the first surfactant layer and the second surfactant layer relative to the total mass of the magnetic fluid. By ensuring that the magnetic particle content is 50% by mass or more relative to the total mass of the magnetic fluid, the amount of water added to the silicone composition can be reduced, thereby reducing the occurrence of air bubbles due to water evaporation during heat curing. Commercially available magnetic fluids using water as a dispersion medium can also be used. However, since commercially available magnetic fluids using water as a dispersion medium generally have a magnetic particle content in the range of 10 to 50% by mass in order to prevent aggregation of the magnetic particles, it is preferable to use a water-based magnetic fluid with a magnetic particle content of 50% by mass or more. A method for achieving a magnetic particle content of 50% by mass or more in a water-based magnetic fluid will be described later.

[0016] (A2) First Surfactant The water-based magnetic fluid contains a first surfactant. By including magnetic particles and the first surfactant in the magnetic fluid, at least a portion of the first surfactant adheres to the magnetic particles in the magnetic fluid. At least a portion of the surface of the magnetic particles is coated with the first surfactant. As the first surfactant, at least one selected from the group consisting of sodium oleate, sodium dodecyl sulfate, dodecyl ammonium acetate, alkyl sulfosuccinate, n-acylamino acid and its salt, n-alkyl trimethylenediamine derivative, polyoxyethylene alkyl ether phosphate, and alkyl phosphate is preferred. Among these, sodium oleate is particularly preferred from the viewpoints of low cost and easy availability. Only one type of first surfactant may be used, or two or more types may be used in combination.

[0017] (A3) Second Surfactant The water-based magnetic fluid contains a second surfactant. The second surfactant is preferably at least one selected from the group consisting of anionic surfactants, nonionic surfactants, proteins, casein, albumin, and hemoglobin. Examples of anionic surfactants include sodium dodecylbenzenesulfonate (SDBS), alkyl sulfate salts, and dialkyl sulfosuccinate salts. Examples of nonionic surfactants include polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. Only one type of second surfactant may be used, or two or more types may be used in combination.

[0018] (A4) Water: Used as a dispersion medium for water-based magnetic fluids. It is preferable to use pure water with few impurities, distilled water, ion-exchanged water, purified water, etc. The content of water as a dispersion medium is preferably less than 50% by mass, more preferably less than 30% by mass, and even more preferably less than 10% by mass, based on the total amount of the water-based magnetic fluid.

[0019] In a water-based magnetic fluid, the ratio of the total content of magnetic particles (inorganic components) to the total content of organic components such as the first surfactant and the second surfactant is not particularly limited as long as it is within a range that exhibits superparamagnetism. Generally, the mass ratio of the magnetic particles to the total amount of the first and second surfactants is preferably 60:40 to 90:10, and more preferably 70:30 to 85:15.

[0020] When magnetic particles, a first surfactant, and a second surfactant are added to water and stirred, the magnetic particles become colloidal particles having a structure in which the magnetic particles are coated with three layers (first surfactant layer / second surfactant layer / hydration fixing layer, in that order from the side closest to the particle). In a magnetic fluid, when the magnetic particles are magnetite or γ-iron oxide, the average particle size of the magnetic particles coated with the first surfactant layer, the second surfactant layer, and the hydration fixing layer is preferably 120 nm or less, particularly preferably 100 nm or less, and preferably 12 nm or more, taking into account the average particle size of the magnetic particles described above (preferably 50 nm or less, preferably 10 nm or more). The average particle size of the magnetic particles coated with the first surfactant layer, the second surfactant layer, and the hydration fixing layer is the average primary particle size measured by dynamic light scattering. For example, it can be measured using a nanoparticle analyzer (nano Partica SZ-100 series) manufactured by Horiba, Ltd.

[0021] 2. Vacuum Freeze-Drying Process Vacuum freeze-drying can be used to remove a portion of the water contained in a water-based magnetic fluid to satisfy a predetermined relationship. It can also be used to obtain magnetic powder for use in regenerated magnetic fluids. The following describes the vacuum freeze-drying process for obtaining magnetic powder for use in regenerated magnetic fluids. A water-based magnetic fluid is used as the drying material, and the material is subjected to vacuum freeze-drying to obtain magnetic powder. Magnetic powder is usually in a free-flowing powder form, but it may contain aggregates. Even if the magnetic powder is entirely in powder form, or even if some or all of the magnetic powder is aggregated, this is not a problem in this embodiment because the addition of water instantly breaks down the aggregates and disperses and mixes them. The water used can be the same as that described in (A4) above. The average particle size of each magnetic powder corresponds to the average particle size (described above) of the magnetic particles coated with the first surfactant layer, the second surfactant layer, and the hydrated fixing layer.

[0022] The vacuum freeze-drying performed on the material to be dried involves sublimating substantially all of the liquid component (polar liquid) from the material to be dried and separating and recovering magnetic particles at least part of whose surfaces are coated with the first surfactant and the second surfactant. The vacuum freeze-drying in this embodiment can be performed, for example, by a method including a pre-freezing step of freezing and solidifying the material to be dried, and a reduced-pressure drying step of sublimating and removing substantially all of the frozen polar liquid from the pre-frozen material to be dried.

[0023] Examples of the preliminary freezing step include an air blast method (air freezing), a liquid method (liquid freezing), a contact method (contact freezing), and a liquefied gas method, with the air blast method or the contact method being preferred.

[0024] In the preliminary freezing step, the material to be dried is frozen from room temperature (25°C) to, for example, -10°C to -80°C. The freezing temperature is preferably -20°C to -60°C. The freezing time varies depending on the concentration of the magnetic fluid and the freezing temperature, but can be, for example, 12 to 36 hours, preferably 20 to 30 hours. The container may be made of either metal or plastic.

[0025] In the reduced-pressure drying process, the atmospheric pressure and temperature around the frozen material to be dried are reduced to a pressure at which sublimation is possible, and are raised to a temperature at which sublimation is possible, so that the liquid component (polar liquid) in the frozen material to be dried is almost completely sublimated. For example, the frozen material to be dried is dried until the polar liquid content in the frozen material to be dried is preferably 2% by mass or less, more preferably 0.5% by mass or less. When reducing the atmospheric pressure around the frozen material to be dried, the frozen material to be dried may be placed in a freeze dryer and the atmospheric pressure may be reduced by reducing the pressure in the vacuum chamber. The pressure (degree of vacuum) during drying is preferably 200 Pa or less, more preferably 133 Pa or less, and particularly preferably 106 Pa or less. The drying temperature (shelf temperature) may be any temperature higher than the freezing point of the polar liquid and at which the surfactant does not degrade, for example, preferably 60°C or less, more preferably 50°C or less, and particularly preferably 40°C or less.

[0026] In this embodiment, both the pre-freezing step and the vacuum drying step may be performed using a freeze dryer, or the pre-freezing step and the vacuum drying step may be performed using separate means, such as a refrigerator and a freeze dryer. However, it is preferable to use a freeze dryer in order to reduce the size of the freeze drying device. Examples include the "RLEII" series and "RL-B" series freeze dryers manufactured by Kyowa Vacuum Engineering Co., Ltd. In the vacuum drying step, a heater or other configuration used in conventional freeze drying devices can be used to raise the ambient temperature around the frozen material to be dried from the temperature in the freezing step to the temperature in the vacuum drying step.

[0027] 3. Other Treatments In this embodiment, the magnetic powder can be used as it is as a magnetic material, but if the magnetic powder has aggregated, it can be subjected to a pulverization process or the like as necessary to be re-pulverized. In this embodiment, even if the magnetic powder has aggregated, adding it to water and stirring it will instantly disintegrate it and disperse and mix it, so re-pulverization is usually not required.

[0028] 4. Regenerated magnetic fluid The magnetic powder obtained by vacuum freeze-drying is mixed with water to obtain a regenerated magnetic fluid. When the polar solvent is removed from the water-based magnetic fluid by vacuum freeze-drying, magnetic powder is obtained that is exfoliated between the second surfactant layer and the hydrated fixing layer, as described below. When water is added to this magnetic powder, the magnetic powder can be dispersed in water without agglomeration, and a magnetic fluid can be obtained.

[0029] 5. Relationship Between Component (A1), Component (A2), and Component (A3) <State in Water-Based and Other Magnetic Fluids> Colloidal particles in water-based and other magnetic fluids have a structure in which the magnetic particles are coated with three layers (from the side closest to the magnetic particle: a lipophilic first coating layer, a hydrophilic second coating layer, and a hydrated fixing layer). (Non-patent document: Proceedings of the Joint Conference on Magnetic Fluids 2019-12 / Considerations on the Dispersion Stability and Aging Phenomenon of Polar Solvent-Based (Water-Based) Magnetic Fluids and Non-Polar Solvent-Based (Oil-Based) Magnetic Fluids / Published December 5, 2019). The lipophilic first coating layer corresponds to the layer made of the first surfactant (A2), and the hydrophilic second coating layer corresponds to the layer made of the second surfactant (A3).

[0030] <State of magnetic powder obtained by vacuum freeze-drying process from water-based or other magnetic fluid> By performing vacuum freeze-drying process from water-based or other magnetic fluid, magnetic particles coated with a first surfactant layer and a second surfactant layer can be obtained. It is assumed that the particle structure of the magnetic powder obtained by vacuum freeze-drying method is such that peeling occurs between the second surfactant layer and the hydrated fixing layer of the triple coating layer that covers the core magnetic particle. For this reason, it is assumed that the particle structure of the magnetic powder obtained by vacuum freeze-drying method has a hydrophilic surface.

[0031] <State of magnetic powder obtained by evaporation from water-based or other magnetic fluid> The particle structure of the magnetic powder obtained by evaporation of water from water-based or other magnetic fluid is presumed to be such that the triple coating layer covering the core magnetic particle has been peeled off between the first surfactant layer and the second surfactant layer, with the second surfactant layer and hydration fixing layer removed (i.e., the magnetic particle is coated only with the first surfactant layer). The surface of this particle structure is presumed to be lipophilic.

[0032] <State of colloid particles in recycled magnetic fluid> It is assumed that the colloid particles in recycled magnetic fluid have a structure similar to that of colloid particles in water-based magnetic fluids, etc. When water is removed from water-based magnetic fluids by vacuum freeze-drying to produce magnetic powder, and then water is added again, a hydrated fixed layer is formed on the second surfactant layer, forming a layer structure similar to that of colloid particles in water-based magnetic fluids, etc.

[0033] (B) Polyether-Modified Silicone Oil The silicone composition according to this embodiment contains a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more. The polyether-modified silicone oil serves to bridge the colloidal particles in the water-based magnetic fluid or the colloidal particles in the regenerated magnetic fluid with the component (C) described below, and is added to enable these colloidal particles to be uniformly dispersed in the component (C). The EO ratio will be described later. The oxyalkylene structure is preferably present in a side chain of the molecular chain. Hereinafter, a polyether-modified silicone oil having an oxyalkylene structure in a side chain of the molecular chain may be referred to as a side-chain polyether-modified silicone oil or simply as a "side-chain type."

[0034] The polyether structure contains a polyoxyalkylene structure (a repeating structure of oxyalkylene units) because it is easy to balance hydrophilicity and hydrophobicity. The terminal of the polyoxyalkylene structure is preferably a hydroxyl group. The terminal of the polyoxyalkylene structure may be capped with an alkyl group such as a methyl group, as long as the effect of this embodiment is not impaired.

[0035] The silicone composition according to this embodiment contains a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more, so that the magnetic particles whose surfaces are coated with a first surfactant layer and a second surfactant layer can form a complete crosslinked state with the curable organopolysiloxane (C) (hereinafter sometimes referred to as the silicone base) described below. This makes it possible to improve the dispersibility of the magnetic particles in the silicone composition. In this specification, the polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more will hereinafter sometimes be simply referred to as polyether-modified silicone oil.

[0036] The content of polyether-modified silicone oil in the silicone composition according to this embodiment is preferably in the range of 3 to 30% by mass, more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass. When the content of the polyether-modified silicone oil is 3% by mass or more, the magnetic particles can be more effectively bridged with the component (C), which will be described later. When the content of the polyether-modified silicone oil is 30% by mass or less, the potential costs can be reduced.

[0037] The EO ratio refers to the ratio of the total number of oxyethylene units to the total number of oxyalkylene units contained in the polyether-modified silicone oil. The silicone composition according to this embodiment has an EO ratio of 40% or more. When the ratio of the total number of oxyethylene units to the total number of oxyalkylene units contained in the polyether-modified silicone oil (EO ratio) is 40% or more, a good balance between hydrophilicity and hydrophobicity can be maintained. The EO ratio is more preferably 50% or more. The EO ratio is 100% or less.

[0038] The total number of oxyalkylene units refers to the number of moles of oxyalkylene units contained in one molecule of polyether-modified silicone oil. The total number of oxyethylene units refers to the number of moles of oxyethylene units contained in one molecule of polyether-modified silicone oil. Polyether-modified silicone oil containing only oxyethylene units as oxyalkylene units (EO ratio = 100%) may also be used.

[0039] Examples of polyether-modified silicone oils having the above EO ratios include TSF4440, TSF4441, TSF4445, TSF4450, and TSF4446 (number of moles of oxyethylene units / number of moles of oxypropylene units (=EO / PO) = 100 / 0 (EO ratio 100%)) and TSF4452 (number of moles of oxyethylene units / number of moles of oxypropylene units (=EO / PO) = 50 / 50 (EO ratio 50%)) manufactured by Momentive Performance Materials, Inc. All of these polyether-modified silicone oils are side chain types.

[0040] (C) Curable organopolysiloxane The (C) curable organopolysiloxane is the silicone base component in the silicone composition according to this embodiment. The form of component (C) may be a millable type or a liquid type. Component (C) may be linear or branched, or may be a mixture of linear and branched structures, but linear structures are preferred.

[0041] Component (C) may be at least one member selected from the group consisting of (C-1) organopolysiloxanes having alkenyl groups and (C-2) organopolysiloxanes having silanol groups or silicon-bonded hydrolyzable groups.

[0042] (C-1) Organopolysiloxane Having Alkenyl Groups The alkenyl groups of component (C-1) are not particularly limited, but examples include those having 2 to 8 carbon atoms, such as vinyl groups, aryl groups, butenyl groups, pentenyl groups, hexenyl groups, heptenyl groups, and octenyl groups. Of these, vinyl groups are preferred from the standpoints of ease of synthesis and reactivity. Furthermore, the alkenyl group is preferably an alkenyl group directly bonded to a silicon atom.

[0043] The alkenyl groups may be contained either at the terminals or in the side chains of the molecular chain of the polysiloxane structure of component (C-1), or may be contained at both the terminals and the side chains. However, it is preferable to contain them at least at the terminals, more preferably at both terminals of the molecular chain, and even more preferably at both terminals only.

[0044] The number of alkenyl groups in one molecule of component (C-1) is preferably 2 or more, more preferably 2 to 8, even more preferably 2 to 4, and particularly preferably 2.

[0045] Examples of residual groups bonded to silicon atoms other than alkenyl groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl, aryl groups such as phenyl, and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl, as well as substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, methyl is preferred from the standpoint of ease of synthesis.

[0046] Commercially available products such as "YE5822A Liquid" and "TSE3062A Liquid" manufactured by Momentive Performance Materials Japan, LLC can also be used as component (C-1).

[0047] (C-2) Organopolysiloxane Having Silanol Groups or Silicon Atom-Bonded Hydrolyzable Groups The silanol groups or silicon atom-bonded hydrolyzable groups of component (C-2) may be contained at either the terminals or side chains of the molecular chain of the polysiloxane structure of component (C-2), or may be contained at both the terminals and the side chains. However, it is preferable to contain them at least at the terminals, more preferably at both terminals of the molecular chain, and even more preferably at both terminals only.

[0048] The number of silanol groups or silicon-bonded hydrolyzable groups per molecule of component (C-2) is preferably 2 or more, more preferably 2 to 8, even more preferably 2 to 4, and particularly preferably 2.

[0049] Examples of silicon-bonded hydrolyzable groups in component (C-2) include alkoxy groups, alkoxyalkoxy groups, acyloxy groups, ketoxime groups, alkenoxy groups, amino groups, aminoxy groups, and amide groups. In addition to the above hydrolyzable groups, the silicon atom in the silane may also be bonded with, for example, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a halogenated alkyl group.

[0050] Examples of residual groups bonded to silicon atoms other than silanol groups and silicon-bonded hydrolyzable groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl, aryl groups such as phenyl, and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl, as well as substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, methyl groups are preferred from the standpoint of ease of synthesis.

[0051] <Amount of Component (A4) Relative to Component (C) in Silicone Composition> In the silicone composition according to this embodiment, the amount of component (A4) is in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C). When the amount of component (A4) is 0.1 part by mass or more, the magnetic particles can be dispersed. When the amount of component (A4) is 40 parts by mass or less, the aggregation of the magnetic particles can be suppressed. In the silicone composition according to this embodiment, the amount of component (A4) is preferably in the range of 0.2 to 35 parts by mass, more preferably 0.2 to 33 parts by mass, and particularly preferably 0.3 to 31 parts by mass per 100 parts by mass of component (C).

[0052] <Contents of Components (A) to (C) in the Silicone Composition> The total amount of components (A1), (A2), and (A3) can be adjusted taking into account the hardness and magnetic properties of the gel / rubber produced when the silicone composition is cured. Generally, when the silicone composition is cured to form a gel, it is contained in the cured silicone product in an amount ranging from 10 to 50% by mass. When the silicone composition is cured to form a rubber, it is contained in the cured silicone product in an amount ranging from 10 to 60% by mass. The blending amount of component (B) is preferably in the range of 25 to 300% by mass relative to the total amount of components (A1), (A2), and (A3). A range of 30 to 150% by mass is more preferred, and a range of 40 to 120% by mass is even more preferred. By maintaining a content in the range of 25 to 300% by mass, the effect of bridging the colloidal particles of the magnetic fluid and component (C) can be fully exerted, thereby preventing separation even when a magnetic field is applied.

[0053] <Addition reaction-curable silicone composition, organic peroxide-curable silicone composition, condensation reaction-curable silicone composition> By further adding an appropriate curing agent and catalyst to the silicone composition of this embodiment, an addition reaction-curable silicone composition, an organic peroxide-curable silicone composition, or a condensation reaction-curable silicone composition can be obtained. Each of these silicone compositions is described below.

[0054] <Addition Reaction Curable Silicone Composition> When the component (C) in the silicone composition of this embodiment is the component (C-1), it may further contain (E) an organohydrogenpolysiloxane having a hydrosilyl group, and (F) a platinum group metal catalyst.

[0055] (E) Organohydrogenpolysiloxane having hydrosilyl groups Component (E) functions as a curing agent for component (C-1), and component (E) undergoes an addition reaction with component (C-1) in the presence of component (F) to form a cured product with appropriate hardness.

[0056] Component (E) may be linear or branched, or may be a mixture of linear and branched structures, but is preferably linear. In component (E), the hydrosilyl groups may be contained either at the terminals of the molecular chain of the polysiloxane structure or along the molecular chain, or may be contained at both the terminals and along the molecular chain, but it is preferable to contain them at least at the terminals, and it is even more preferable to contain hydrosilyl groups at both terminals of the molecular chain of the polysiloxane structure. The number of hydrosilyl groups per molecule of component (E) is not particularly limited, as long as it is one or more, but it is preferably two or more, more preferably 2 to 25, and even more preferably 2 to 20.

[0057] In component (E), examples of residual groups bonded to silicon atoms other than hydrosilyl groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl, aryl groups such as phenyl, and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl, as well as substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl.The organohydrogenpolysiloxanes of component (E) may use either a single type or a combination of two or more types.

[0058] (F) Platinum Group Metal Catalyst By including the component (F) in the silicone composition of this embodiment, the addition reaction between the component (C-1) and the component (E) is promoted, allowing the silicone composition to be properly cured.

[0059] The component (F) can be appropriately selected from conventionally known addition reaction catalysts such as platinum-based, palladium-based, and rhodium-based catalysts. Examples of platinum-based catalysts include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, complexes of chloroplatinic acid and vinylsiloxanes, and platinum bisacetoacetate. These catalysts may be used alone or in combination of two or more.

[0060] The blending amount of component (F) is preferably 0.1 to 500 ppm, more preferably 0.5 to 100 ppm, in terms of platinum group metal, by mass relative to the combined amount of components (C) and (E).

[0061] In the silicone composition of this embodiment, when the component (C) is the component (C-1), the component (C-1) may further contain a hydrosilyl group per molecule. By containing a hydrosilyl group per molecule of the component (C-1), an addition reaction can proceed without the need for the curing agent (E), as described below, to form a silicone rubber.

[0062] <Organic Peroxide-Curable Silicone Composition> When the silicone composition of this embodiment is the component (C-1) as the component (C), it may further contain an organic peroxide (G). By containing an organic peroxide and curing the composition, an organic peroxide-curable silicone cured product can be obtained.

[0063] (G) Organic Peroxides Examples of organic peroxides that can be used in the silicone composition of this embodiment include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis(2,5-t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,1-bis(t-butylperoxycarboxy)hexane, etc. These organic peroxides may be used alone or in combination of two or more.

[0064] <Condensation Reaction Curable Silicone Composition> When the silicone composition of this embodiment is component (C-2) as component (C), it may further contain (H) a silane having at least three silicon-bonded hydrolyzable groups per molecule or a partial hydrolyzate thereof. A two-component curing, condensation reaction curable silicone cured product can be obtained by mixing and curing a silane having at least three silicon-bonded hydrolyzable groups per molecule or a partial hydrolyzate thereof.

[0065] (H) Silane or partial hydrolyzate thereof having at least three silicon-bonded hydrolyzable groups per molecule. Component (H) functions as a curing agent. Examples of the silicon-bonded hydrolyzable groups in the silane include alkoxy groups, alkoxyalkoxy groups, acyloxy groups, ketoxime groups, alkenoxy groups, amino groups, aminoxy groups, and amide groups. Examples include tetramethoxysilane, tetraethoxysilane, and tetra-n-propoxysilane. In addition to the hydrolyzable groups described above, the silicon atoms in the silane may be bonded with, for example, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a halogenated alkyl group. Examples of such silanes or partial hydrolyzates thereof include methyltriethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and ethylorthosilicate.

[0066] <Other Components> In addition to the above-described components, the silicone composition according to this embodiment may further contain various other components depending on the purpose, as long as the effects of this embodiment are not impaired. Examples of other components include polyether-modified silicone oils other than those of component (B), viscosity index improvers, anti-wear agents, surfactants, viscosity modifiers, anti-settling agents, pour point depressants, extreme pressure agents, rust inhibitors, antioxidants, corrosion inhibitors, metal deactivators, antifoaming agents, inorganic fillers, polar solvents (excluding water), etc.

[0067] As the polyether-modified silicone oil that does not fall under the category of component (B), commercially available products can be used, such as TSF4460 (EO ratio 0%) manufactured by Momentive Performance Materials, Inc. The content of polyether-modified silicone oil that does not fall under the category of component (B) is preferably 15 mass% or less of the total polyether-modified silicone oil.

[0068] Examples of anti-wear agents include sulfur-based compounds such as sulfides, sulfoxides, sulfones, and thiophosphinates; halogen-based compounds such as chlorinated hydrocarbons; organometallic compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC); and phosphate esters. Examples of phosphate esters include phosphate triesters such as trioctyl phosphate and tricresyl phosphate, monooctyl phosphate, and dioctyl phosphate. One type of anti-wear agent may be used alone, or two or more types may be used in combination.

[0069] Examples of viscosity modifiers include castor oil, hydrogenated castor oil, fatty acid amides, beeswax, carnauba wax, benzylidene sorbitol, metal soaps, polyethylene oxide, sulfate ester-based anionic surfactants, acrylic acid esters, methacrylic acid esters, polyisobutylene, polyalkylstyrene, etc. One type of viscosity modifier may be used alone, or two or more types may be used in combination.

[0070] Examples of inorganic fillers include alumina, calcium carbonate, silica, and boron nitride. In this specification, the term "inorganic filler" also includes the magnetically responsive composite material defined in Japanese Patent No. 7240436. One type of inorganic filler may be used alone, or two or more types may be used in combination. The shape of the inorganic filler is preferably spherical.

[0071] Examples of polar solvents (excluding water) include methanol and ethanol.

[0072] <Dispersibility of Silicone Composition> The dispersibility of the silicone composition according to this embodiment can be evaluated by preparing a silicone composition by mixing the above-described components, placing the composition in a beaker, and leaving it at room temperature (25°C) for a predetermined time, and then visually observing whether the component (A1) and the component (C) separate. In the silicone composition according to this embodiment, the component (A1) and the component (C) remain in a state where they are not separated (a well-dispersed state) even after being left at room temperature for a predetermined time. On the other hand, examples of the state in which the component (A1) and the component (C) are separated include a state in which the component (A1) and the component (C) are phase-separated into an upper layer and a lower layer, a state in which the component (A1) is separated into particles, and a state in which the component (A1) is separated into a solid component and a liquid component.

[0073] <<Cured Silicone Product>> Examples of the cured silicone product according to this embodiment include silicone rubber and silicone gel. In this specification, silicone rubber refers to a material having a rubber hardness (i.e., hardness measured by a durometer A hardness scale as defined in JIS K 6253-3) of 1 or greater, exhibiting a valid rubber hardness value. Silicone gel refers to a material having a rubber hardness of less than 1, exhibiting a low hardness (softness) that does not exhibit a valid rubber hardness value. The curable polysiloxane used in the silicone rubber is selected according to the intended use, and either a liquid type or a millable type can be used. Furthermore, a curing mechanism can be selected according to the type of curable organopolysiloxane. Examples of the curing mechanism of the silicone rubber include an addition (hydrosilylation) reaction curing type, an organic peroxide curing type, and a condensation reaction curing type. Furthermore, both one-component curing types and two-component curing types can be used for the addition (hydrosilylation) reaction curing type silicone rubber and the condensation reaction curing type silicone rubber. Silicone rubber and silicone gel are described below.

[0074] 1. Silicone Rubber 1-1. Addition (Hydrosilylation) Reaction-Curing Silicone Rubber - One-component curing type: When the component (C-1) contained in the silicone composition described above further contains a hydrosilyl group per molecule, an addition reaction proceeds to form silicone rubber without the need for the curing agent (E), described below. Furthermore, one-component curing type silicone rubber can be produced by heat-curing a silicone composition consisting of components (A), (B), (C-1), (E), and (F). - Two-component curing type: The two-component curing type is cured by mixing component A, which is a mixture containing components (A) and (B) further mixed with component (C-1), and component B, which contains component (E), immediately before use. Either component A or component B contains a platinum group metal catalyst (F). In both one-component curing and two-component curing types, water evaporates during the process of forming the silicone cured product, leaving it substantially absent from the cured silicone product. The blend amount of component (E) is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of component (C-1). As mentioned above, in this specification, silicone rubber refers to a material having a hardness of 1 or more as measured by a durometer A hardness scale, with a hardness in the range of 10 to 90 being preferred, and a hardness in the range of 20 to 80 being more preferred.

[0075] In order to suppress the progress of the addition reaction, a reaction inhibitor may be added to either the one-component curing type or the two-component curing type. Examples of the reaction inhibitor include acetylene compounds such as acetylene alcohols (e.g., ethynylmethyldecylcarbinol, 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organic phosphorus compounds such as triphenylphosphine, oxime compounds, and organic chloro compounds.

[0076] The amount of the reaction inhibitor to be added is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2 parts by mass, per 100 parts by mass of component (E).

[0077] 1-2. Organic Peroxide-Cured Silicone Rubber The organic peroxide-cured silicone rubber is a silicone cured product obtained by heat-curing a silicone composition comprising the aforementioned components (A), (B), (C-1), and (G). The blending amount of component (G) is 0.01 to 10 parts by mass per 100 parts by mass of component (C-1). When the blending amount of component (G) is 0.01 part by mass or more per 100 parts by mass of component (C-1), the silicone composition can be sufficiently cured. Furthermore, when the blending amount of component (G) is 10 parts by mass or less per 100 parts by mass of component (C-1), the generation of voids can be suppressed while the curing rate of the silicone composition is significantly improved. Furthermore, the organic peroxide-curable silicone rubber may contain other optional components, as long as they do not impair the objectives of the present invention. For example, fillers such as fumed silica, precipitated silica, and fumed titanium oxide; fillers whose surfaces have been hydrophobized with an organosilicon compound; adhesion promoters such as 3-glycidoxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; pigments, dyes, fluorescent dyes, heat-resistant additives, flame retardants such as triazole compounds, and plasticizers. Furthermore, a thermally conductive filler may also be blended within the range that does not impair the effects of the present invention. Examples of such thermally conductive fillers include aluminum powder, copper powder, silver powder, nickel powder, gold powder, zinc oxide powder, boron nitride powder, aluminum nitride powder, diamond powder, and carbon powder.

[0078] 1-3. Condensation Reaction Curing Silicone Rubber - One-component Curing Type This type cures upon contact with moisture in the air by the component (C-2) contained in the silicone composition described above. - Two-component Curing Type The two-component curing type is a cured silicone product obtained by curing a silicone composition comprising the aforementioned components (A), (B), (C-2), and (H). The amount of component (H) is the amount necessary to cure the silicone composition according to this embodiment. Specifically, it is preferably in the range of 0.01 to 20 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of component (C-2). When the content of component (H) is 0.01 parts by mass or more per 100 parts by mass of component (C-2), the storage stability of the resulting cured silicone product is improved. Furthermore, when the content is 20 parts by mass or less per 100 parts by mass of component (C-2), a significant delay in the curing of the silicone composition can be suppressed.

[0079] A catalyst may also be used in the above-mentioned condensation reaction. The catalyst is an optional component and is not essential, for example, when a silane having a hydrolyzable group such as an aminoxy group, an amino group, or a ketoxime group is used as the curing agent. Examples of such condensation reaction catalysts include organic titanate esters such as tetrabutyl titanate and tetraisopropyl titanate; organic titanium chelate compounds such as diisopropoxybis(acetylacetate)titanium and diisopropoxybis(ethylacetoacetate)titanium; organic aluminum compounds such as aluminum tris(acetylacetonate) and aluminum tris(ethylacetoacetate); organic zirconium compounds such as zirconium tetra(acetylacetonate) and zirconium tetrabutylate; dibutyltin dioctoate and dibutyltin dilaurate. Examples of suitable condensation reaction catalysts include organotin compounds such as tin acrylate, butyltin-2-ethylhexoate, and dibutyltin diacetate; metal salts of organic carboxylic acids such as tin naphthenate, tin oleate, tin butyrate, cobalt naphthenate, and zinc stearate; amine compounds and salts thereof such as hexylamine and dodecylamine phosphate; quaternary ammonium salts such as benzyltriethylammonium acetate; lower fatty acid salts of alkali metals such as potassium acetate and lithium nitrate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; and guanidyl group-containing organosilicon compounds. When the above-mentioned condensation reaction catalyst is incorporated, its amount need only be the amount necessary for curing the silicone composition. Specifically, it is preferably incorporated in the range of 0.01 to 20 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of component (C-2). When a condensation reaction catalyst is used, the silicone composition can be sufficiently cured if the amount of this catalyst is 0.01 parts by mass or more per 100 parts by mass of component (C-2).The storage stability of the silicone cured product is improved if the amount of condensation reaction catalyst is 20 parts by mass or less per 100 parts by mass of component (C-2).

[0080] 2. Silicone Gel In this specification, silicone gel refers to a material having a hardness of less than 1 measured on a durometer A hardness scale, and the amount of component (E) blended may be adjusted to achieve this hardness. The silicone gel according to this embodiment is obtained by curing a silicone composition containing components (A), (B), (C-1), (E), and (F), and either a one-component curing type or a two-component curing type may be used. Furthermore, the reaction inhibitor described above may be included as necessary.

[0081] (Mechanical Devices Using Cured Silicone Products) The silicone gel and silicone rubber used in the cured silicone products of this embodiment undergo rapid and reversible changes in elastic modulus and shape when a magnetic field is applied. This allows them to be safely used in energy transmission and absorption components such as automobile clutches and dampers, and actuators such as artificial muscles.

[0082] The silicone gel and silicone rubber according to this embodiment are semi-solid or solid magnetic materials in which the magnetic particles in the silicone gel and silicone rubber are well dispersed without aggregation, similar to the magnetic particles contained in a magnetic fluid, and exhibit superparamagnetic properties without observing magnetic hysteresis.Because of these characteristics, the silicone gel and silicone rubber according to this embodiment can be suitably used in mechanical devices such as speakers and vibration motors, which will be described later.

[0083] A speaker using a silicone gel according to this embodiment will now be described. FIG. 1 shows a cross-sectional schematic diagram of the speaker's operating mechanism. The operating mechanism includes a cylindrical center pole 12 as its main body, a yoke 11 surrounding the lower and sides of the center pole 12, and a magnet 13 positioned between the lower part of the center pole 12 and the yoke 11. A voice coil 15, which serves as a vibrating unit, is disposed along the outer periphery of the center pole 12. As described above, the speaker 10 is provided with a voice coil (vibrating unit) 15. The voice coil 15 is generally suspended by a suspension. This voice coil 15 must be positioned appropriately in the speaker 10 with appropriate tension. Therefore, providing the silicone gel 14 according to this embodiment around the voice coil 15 enables centering of the voice coil 15 and application of appropriate tension. Furthermore, the silicone gel 14 also functions as a heat dissipation unit, dissipating heat from the voice coil 15 to the outside. Furthermore, while liquid magnetic fluids may be scattered inside the speaker 10 due to vibrations of the voice coil 15 when the speaker 10 is in use, the silicone gel 14 of this embodiment is a gel-like magnetic fluid with an appropriate viscosity, so even if it is placed around the voice coil 15, there is no risk of it being scattered due to vibrations when the speaker 10 is in use.Furthermore, unlike liquid magnetic fluids, it does not need to be placed around the entire circumference of the voice coil 15, and it is sufficient to place it in only a few places around the periphery.

[0084] Another example of a mechanical device using the silicone gel according to this embodiment is a vibration motor built into a smartphone or the like. Because the vibration motor vibrates violently within the device, a damper is provided between the vibration motor and the surrounding case to prevent it from colliding with the case and causing damage. The silicone gel according to this embodiment can be suitably used as this damper, is useful as a heat dissipation part for the vibration motor, and is not likely to be scattered by the vibration of the vibration motor. Furthermore, unlike liquid magnetic fluid, it does not need to be provided around the entire circumference of the vibration motor, but only in a few places around the periphery.

[0085] <<Method for Producing a Silicone Composition>> In the method for producing a silicone composition according to this embodiment, a magnetic fluid containing magnetic particles, a first surfactant, a second surfactant, and water, a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more, and a curable organopolysiloxane are added and mixed, with the polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more being added first or second. The blending ratios of water and curable organopolysiloxane have a predetermined relationship. In this way, a silicone composition is produced in which magnetic particles are dispersed in the main component of the silicone composition. It is believed that the polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more bridges the magnetic particles and the silicone main component, thereby preventing the magnetic particles from separating from the silicone main component. Therefore, by mixing the magnetic fluid with the polyether-modified silicone oil and then adding it to the silicone main component, a silicone composition in which the magnetic particles are well dispersed without agglomeration can be obtained. The method of adding the curable organopolysiloxane can be selected according to the shape of the curable organopolysiloxane. When the curable organopolysiloxane is millable, it is preferable to produce the curable organopolysiloxane using an apparatus capable of uniformly kneading the predetermined amounts of the above-mentioned components (A) to (C), and, if necessary, the above-mentioned components (E) to (H). There are no particular limitations on the apparatus capable of uniformly kneading the components, but specific examples include a kneader, a Banbury mixer, and a roll mill. When the curable polysiloxane is liquid, the method of mixing the components (A) to (C), and, if necessary, the components (E) to (H), can be any conventionally known method, but is not particularly limited. Typically, a uniform mixture is obtained by simple stirring. Alternatively, a vibration mixer, a dissolver, a kneader, a roll mill, or the like can be used.

[0086] <<Silicone Paste Manufacturing Method>> The curable organopolysiloxane of component (C) according to this embodiment is a liquid type, and the silicone paste according to this embodiment can be obtained by subjecting an addition reaction curable silicone composition to a heat treatment. The heat treatment is preferably a heat treatment at 80 to 120°C for 20 minutes to 1 hour. Heat treatment is preferable because it evaporates water, thereby increasing the content of magnetic particles.

[0087] <<Method for Producing a Cured Silicone Product>> An addition reaction-curable silicone gel or silicone rubber according to this embodiment can be obtained by adding a hydrosilyl group-containing organohydrogenpolysiloxane as a curing agent and a platinum group metal catalyst to a silicone composition according to this embodiment in which the curable organopolysiloxane is an organopolysiloxane having alkenyl groups, and then performing a heat treatment. An organic peroxide-curable silicone rubber according to this embodiment can be obtained by adding an organic peroxide as a curing agent and performing a heat treatment. Furthermore, a one-component condensation reaction-curable silicone rubber can be obtained by using moisture to cure a silicone composition according to this embodiment in which the curable organopolysiloxane is an organopolysiloxane having silanol groups or silicon-bonded hydrolyzable groups. Furthermore, by adding a silane or a partial hydrolyzate thereof having at least three silicon-bonded hydrolyzable groups per molecule as a curing agent to the silicone composition according to this embodiment, in which the curable organopolysiloxane is an organopolysiloxane having silanol groups or silicon-bonded hydrolyzable groups, and then heat-curing the composition, a two-component curing, condensation-curable silicone cured product according to this embodiment can be obtained. The curing conditions are not particularly limited and can be appropriately selected depending on the curing mechanism (addition reaction, condensation reaction, or organic peroxide curing) and the intended use. Curing conditions are generally 25 to 300°C, particularly 80 to 250°C, for several seconds to several days, and particularly 5 seconds to 1 hour. Secondary curing may also be performed if necessary. Secondary curing is typically performed at 180 to 250°C for approximately 1 to 10 hours. The silicone cured product can be molded according to the desired application (molded product). Specific examples include compression molding, injection molding, and transfer molding.

[0088] Examples of the present invention are given below, but these examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0089] Silicone compositions in which the curable organopolysiloxane is in the form of a liquid at room temperature <Examples 1 to 5, 8 to 17, 20 to 22, Comparative Examples 1 to 14> The components shown in Tables 1 to 3 were placed in a beaker in the mass ratios shown therein, and stirred at 40 Hz at room temperature for 5 minutes using a Seiko Advance Corporation universal vibration mixer AD-MIX to produce silicone compositions. Note that components (A), (B), and (C) were added in the following order: component (A), component (B), component (C). The raw materials for each component shown in Tables 1 to 3 are listed below.

[0090] - Silicone composition in which the shape of the curable organopolysiloxane is millable at room temperature Example 6 20 parts by mass of TSE221-3U described below was masticated using a twin roll mill, and 5 parts by mass of polyether-modified silicone oil 2 having an EO ratio of 40% or more described below was added and kneaded. Furthermore, 15 parts by mass of recycled magnetic fluid 1 described below was added, and kneaded at 25°C to obtain a silicone composition. Example 7 20 parts by mass of KE-551U described below was masticated using a twin roll mill, and 5 parts by mass of polyether-modified silicone oil 2 having an EO ratio of 40% or more described below was added, and kneaded. Furthermore, 15 parts by mass of recycled magnetic fluid 1 described below was added, and kneaded at 25°C to obtain a silicone composition.

[0091] Silicone Paste The silicone composition of Example 2 was heated at 100°C for 60 minutes to evaporate the water, yielding a silicone paste. The magnetic particles in the resulting silicone paste did not aggregate, and the magnetic particles and the curable polysiloxane did not separate, resulting in a separability rating of "A."

[0092] (A) Component - Water-based magnetic fluid (magnetic particles: magnetite, first surfactant: sodium oleate, second surfactant: sodium dodecylbenzenesulfonate, dispersion medium: water, magnetic particle content: 50% by mass, primary average particle diameter: 40 nm) - Regenerated magnetic fluid 1 (a magnetic fluid obtained by adding 5 g of ion-exchanged water to 10 g of the recovered material 1 described below) - Method for producing recovered material 1 (vacuum freeze-drying method): 2 liters of water-based magnetic fluid 1 was dispensed into an aluminum container and placed on a shelf in a freeze-dryer (RLEII-103 model, manufactured by Kyowa Vacuum Engineering Co., Ltd.). Next, vacuum drying at -56°C under 133 Pa (shelf temperature: 40°C) was performed for 24 hours. Thereafter, the container was removed from the freeze-dryer to obtain recovered material 1. Regenerated magnetic fluid 2 (10 g of the recovered material 1 was mixed with 5 g of the following standard water / methanol to prepare a magnetic fluid) Standard water / methanol: Karl Fischer water content determination reagent (titer 10 mg HO / mL), manufactured by Hayashi Pure Chemical Industries, Ltd.

[0093] Magnetic fluids not corresponding to component (A) Oil-based magnetic fluid: (product name: DS50, manufactured by Sigma High Chemical Co., Ltd., magnetic particles: magnetite, first surfactant: sodium oleate, dispersion medium: isoparaffin, magnetic particle content: 60% by mass, average primary particle diameter: 15 nm) Magnetic fluid (magnetic fluid obtained by adding 5 g of ion-exchanged water to 10 g of recovered material 2 described below) Manufacturing method for recovered material 2 (evaporation method): 100 ml of water-based magnetic fluid was placed in a beaker and dried at a drying temperature of 80°C under atmospheric pressure for 8 hours, thereby obtaining recovered material 2.

[0094] Component (B) Polyether-modified silicone oil 1 having an EO ratio of 40% or more (EO ratio: 100%, product name: TSF4440, manufactured by Momentive) Polyether-modified silicone oil 2 having an EO ratio of 40% or more (EO ratio: 50%, product name: TSF4452, manufactured by Momentive)

[0095] Silicone oils that do not fall under component (B) Polyether-modified silicone oil (EO ratio: 0%, product name: TSF4460, manufactured by Momentive Corporation) Higher fatty acid ester-modified silicone oil (product name: X-22-715, manufactured by Shin-Etsu Chemical Co., Ltd.) Amino-modified silicone oil (product name: TSF4700, manufactured by Momentive Corporation)

[0096] Component (C) (C-1) Organopolysiloxanes Having Alkenyl Groups - Vinyl group-containing polydimethylsiloxane (product name: TSE3062A, containing platinum catalyst, manufactured by Momentive Corporation, form before curing: liquid, form after curing: gel, reaction mechanism: two-part addition reaction cure type) - Vinyl group-containing polyorganosiloxane (product name: KE-106F, containing platinum catalyst, manufactured by Shin-Etsu Chemical Co., Ltd., form before curing: liquid, form after curing: rubber, reaction mechanism: two-part addition reaction cure type) - Vinyl group-containing polydimethylsiloxane (product name: KE-551U, manufactured by Shin-Etsu Chemical Co., Ltd., form before curing: Millable, form after curing: rubber, reaction mechanism: two-part addition reaction cure type) (C-2) Organopolysiloxanes Having Silanol Groups or Silicon Atom-Bonded Hydrolyzable Groups・Polydimethylsiloxane with silanol groups at both ends (product name: TSE382, manufactured by Momentive Corporation; form before curing: liquid; form after curing: rubber; reaction mechanism: one-component condensation reaction cure type) ・Polydimethylsiloxane with silanol groups at both ends (product name: TSE3663A, manufactured by Momentive Corporation; form before curing: liquid; form after curing: rubber; reaction mechanism: two-component condensation reaction cure type) ・Vinyl-containing polydimethylsiloxane (product name: TSE221-3U, manufactured by Momentive Corporation; form before curing: Millable; form after curing: rubber; reaction mechanism: organic peroxide cure type)

[0097] Polar solvents other than water: Methanol, Propylene glycol

[0098] Curing agents: Organohydrogenpolysiloxane 1 having hydrosilyl groups (product name: TSE3062B, manufactured by Momentive, form after curing: gel, reaction mechanism: two-component addition reaction cure type) Organohydrogenpolysiloxane 2 having hydrosilyl groups (product name: CAT-106F, manufactured by Shin-Etsu Chemical Co., Ltd., form after curing: rubber, reaction mechanism: two-component addition reaction cure type) Organohydrogenpolysiloxane 3 having hydrosilyl groups (product name: C-25B, manufactured by Shin-Etsu Chemical Co., Ltd., form after curing: rubber, reaction mechanism: two-component addition reaction cure type) Tetraethoxysilane (product name: TSE3663B, containing dibutyltin diacetate catalyst, manufactured by Momentive, form before curing: liquid, form after curing: rubber, reaction mechanism: two-component condensation reaction cure type) 2,5-dimethyl-2,5-ditertiarybutylperoxyhexane (product name: TC-8, manufactured by Momentive, form after curing: rubber, reaction mechanism: organic peroxide curing type)

[0099] <Evaluation of Separation> In Examples 1 to 17, 20 to 22 and Comparative Examples 1 to 14, the formulations were mixed and then left to stand at room temperature for 4 hours, and the state of the magnetic particles in each silicone composition was observed visually and rated according to the following criteria. The evaluation results are shown in Tables 1 to 3. In Examples 18 and 19, the formulations were kneaded and then left to stand at room temperature for 4 hours, and the state of the magnetic particles in each silicone composition was observed visually and rated according to the following criteria. The evaluation results are shown in Table 3. The method for producing the silicone compositions of Examples 18 and 19 will be described later. "A": Good (no separation or aggregation of the magnetic particles in the silicone composition) "B": Poor (the magnetic particles and the curable organopolysiloxane in the silicone composition separated, or the magnetic particles aggregated)

[0100] <Method for producing a cured product when the curable organopolysiloxane is liquid> For Examples 14 to 16 and 20 to 22, which were rated "A" for separability, curing was performed at 80°C for 30 minutes to obtain a cured product (molded product). For Examples 4 and 17, curing was performed at 25°C for 1 day to obtain a cured product (molded product).

[0101] <Method for producing a silicone composition in which the curable organopolysiloxane is millable and a cured product thereof> 0.12 parts by mass of TC-8 was added to the silicone composition of Example 6 and kneaded at 25°C to produce a silicone compound, resulting in the silicone composition of Example 18. This silicone compound was placed in a mold and compression molded at 170°C for 10 minutes, followed by secondary curing in an oven at 200°C for 4 hours to produce a cured silicone product (molded product). 0.4 parts by mass of C-25B was added to the silicone composition of Example 7 and kneaded at 25°C to produce a silicone compound, resulting in the silicone composition of Example 19. This silicone compound was placed in a mold and compression molded at 120°C for 10 minutes, followed by secondary curing in an oven at 200°C for 4 hours to produce a cured silicone product (molded product).

[0102] <Evaluation of Magnetic Properties of Cured Products> In order to evaluate the dispersibility of the magnetic particles contained in the cured products obtained by curing the silicone compositions of Examples 4 and 14 to 22, the relationship between magnetic flux density (B) and magnetic field (H) of the obtained molded products was examined using a vibrating sample magnetometer (VSM) to observe the presence or absence of magnetic hysteresis. The evaluation results are shown in Table 3. For all of the molded products of Examples 4 and 14 to 22, no magnetic hysteresis was observed, and it was found that they possessed superparamagnetism and had excellent magnetic properties.

[0103] <Evaluation of Hardness of Cured Products> The hardness of the cured products obtained by curing the silicone compositions of Examples 4 and 14 to 22 was measured using Durometer A in accordance with JIS K 6253-3. The evaluation results are shown in Table 3.

[0104]

[0105]

[0106]

[0107] <Discussion> The silicone compositions of Examples 1 to 22 contained a magnetic fluid containing (A) (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water; (B) a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more; and (C) a curable organopolysiloxane. Since the amount of component (A4) was in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C), all of these compositions exhibited good magnetic particle dispersibility. Furthermore, the silicone compositions of Examples 4 and 14 to 22 formed rubber or gel upon curing that effectively prevented scattering when a magnetic field was applied. It is believed that the silicone compositions of Examples 1 to 3 and 5 to 13 also formed rubber or gel in the same manner as the silicone compositions of Examples 4 and 14 to 22 by adding a curing agent. The silicone compositions of Comparative Examples 1 to 3 and 8 to 10 did not contain component (A4), and therefore all of these compositions exhibited poor magnetic particle dispersibility. Comparative Examples 4 to 7 and 13 did not contain component (B), and therefore all of them exhibited poor dispersibility of the magnetic particles. Comparative Examples 11 and 12 used magnetic powder obtained by drying a water-based magnetic fluid by evaporation, and therefore exhibited poor dispersibility of the magnetic particles. Comparative Example 14 exhibited poor dispersibility of the magnetic particles because the content of component (A4) per 100 parts by mass of component (C) exceeded the upper limit.

[0108] <Evaluation of Separation Properties Depending on the Addition Order of Components (A) to (C)> The silicone composition of Example 23 was obtained in the same manner as in Example 2, except that the components (A), (B), and (C) were added in the following order: component (B), component (A), and component (C). The silicone composition of Example 24 was obtained in the same manner as in Example 2, except that the components (A), (B), and (C) were added in the following order: component (C), component (B), and component (A). The sample of Comparative Example 15 was obtained in the same manner as in Example 2, except that the components (A), (B), and (C) were added in the following order: component (A), component (C), and component (B). The silicone composition of Comparative Example 16 was obtained in the same manner as in Example 3, except that the components (A), (B), and (C) were added in the following order: component (A), component (C), and component (B). The silicone composition of Comparative Example 17 was obtained in the same manner as in Example 8, except that components (A), (B), and (C) were added in the following order: component (A), component (C), and component (B). The state of the magnetic particles in each of these samples was evaluated using the same criteria as for evaluating separability.

[0109] The silicone compositions of Examples 23 and 24 were evaluated for separability in the same manner as in Examples 1 to 22, and all of them were evaluated as "A": good (no separation or aggregation of the magnetic particles in the silicone composition). On the other hand, the silicone compositions of Comparative Examples 15 to 17 were evaluated for separability in the same manner as in Examples 1 to 22, and all of them were evaluated as "B": poor (the magnetic particles and the curable organopolysiloxane in the silicone composition were separated, or the magnetic particles were aggregated). These results demonstrate that, in order to obtain a silicone composition in which separation and aggregation of the magnetic particles is suppressed, the order in which component (B) is added in the method for producing the silicone composition must be either first or second in the order in which component (A), component (B), and component (C) are added.

[0110] 10 Speaker 11 Yoke 12 Center pole 13 Magnet 14 Silicone gel 15 Voice coil (vibration part)

Claims

1. A silicone composition comprising: (A) a magnetic fluid containing (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water; (B) a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more; and (C) a curable organopolysiloxane; wherein the amount of component (A4) blended is in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C).

2. The silicone composition according to claim 1, wherein component (C) is at least one member selected from the group consisting of (C-1) organopolysiloxanes having alkenyl groups and (C-2) organopolysiloxanes having silanol groups or silicon-bonded hydrolyzable groups.

3. The silicone composition according to claim 1, wherein component (A2) is at least one member selected from the group consisting of sodium oleate, sodium dodecyl sulfate, dodecyl ammonium acetate, alkyl sulfosuccinates, n-acylamino acids and salts thereof, n-alkyltrimethylenediamine derivatives, polyoxyethylene alkyl ether phosphates, and alkyl phosphates.

4. The silicone composition according to claim 1, wherein component (A3) is at least one selected from the group consisting of anionic surfactants, nonionic surfactants, proteins, casein, albumin, and hemoglobin.

5. The silicone composition according to claim 2, wherein the component (C) is the component (C-1), and further comprises: (E) an organohydrogenpolysiloxane containing a hydrosilyl group; and (F) a platinum group metal catalyst.

6. The silicone composition according to claim 2, wherein the component (C) is the component (C-1), and the component (C-1) further contains a hydrosilyl group.

7. The silicone composition according to claim 2, wherein the component (C) is the component (C-1), and further comprises an organic peroxide (G).

8. The silicone composition according to claim 2, wherein component (C) is component (C-2) and further comprises (H) a silane or partial hydrolyzate thereof having at least three silicon-bonded hydrolyzable groups per molecule.

9. A silicone cured product obtained by curing the silicone composition according to any one of claims 5 to 8.

10. A mechanical device using the silicone cured product according to claim 9.

11. A method for producing a silicone composition comprising adding (A) a magnetic fluid containing (A1) magnetic particles, (A2) a first surfactant, (A3) a second surfactant, and (A4) water, (B) a polyether-modified silicone oil having an oxyalkylene structure with an EO ratio of 40% or more, and (C) a curable organopolysiloxane, wherein the amount of component (A4) is in the range of 0.1 to 40 parts by mass per 100 parts by mass of component (C), and component (B) is added first or second in the order of adding components (A), (B), and (C).

12. The method for producing a silicone composition according to claim 11, wherein component (C) is at least one member selected from the group consisting of (C-1) an organopolysiloxane having an alkenyl group and (C-2) an organopolysiloxane having a silanol group or a silicon-bonded hydrolyzable group.

13. The method for producing a silicone composition according to claim 11, wherein component (A2) is at least one member selected from the group consisting of sodium oleate, sodium dodecyl sulfate, dodecylammonium acetate, alkyl sulfosuccinates, n-acylamino acids and salts thereof, n-alkyltrimethylenediamine derivatives, polyoxyethylene alkyl ether phosphates, and alkyl phosphates.

14. The method for producing a silicone composition according to claim 11, wherein the component (A3) is at least one selected from the group consisting of anionic surfactants, nonionic surfactants, proteins, casein, albumin, and hemoglobin.

15. The method for producing a silicone composition according to claim 12, wherein the component (C) is the component (C-1), and further comprising the step of adding: (E) an organohydrogenpolysiloxane containing a hydrosilyl group; and (F) a platinum group metal catalyst.

16. The method for producing a silicone composition according to claim 12, wherein the component (C) is the component (C-1), and the component (C-1) further contains a hydrosilyl group.

17. The method for producing a silicone composition according to claim 12, wherein the component (C) is the component (C-1), and further comprising the step of adding an organic peroxide (G).

18. The method for producing a silicone composition according to claim 12, wherein component (C) is component (C-2), and further comprising the step of adding (H) a silane or partial hydrolyzate thereof having at least three silicon-bonded hydrolyzable groups per molecule.

19. A method for producing a silicone paste, comprising the step of subjecting a silicone composition obtained by the method for producing a silicone composition according to any one of claims 11 to 18 to a heat treatment to obtain a silicone paste.

20. A method for producing a cured silicone product, comprising a step of curing a silicone composition obtained by the method for producing a silicone composition according to any one of claims 11 to 18.

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