JP4581619B2 - Magnetic fluid and manufacturing method thereof - Google Patents
Magnetic fluid and manufacturing method thereof Download PDFInfo
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本発明は、磁性流体に関し、更に詳しくは、発泡性が少なく、かつ、分散安定性に優れた磁性流体に関するものである。 The present invention relates to a magnetic fluid, and more particularly to a magnetic fluid that has low foaming properties and excellent dispersion stability.
一般的に磁性流体は、共沈法により製造された磁性微粒子を含有する水性サスペンジョンである。この水性サスペンジョンを乾燥して得られる磁性微粒子粉末は、親水性のために鉱物油、炭化水素、シリコーン油等の非水系溶剤には上手く分散できない。よって、これら磁性微粒子の表面に脂肪酸塩や界面活性剤等を吸着させることで親油性に変性することが必要である。これら磁性微粒子を非水系溶剤に分散した磁性流体は、磁気シールやクラッチやダンパ、アクチュエーター等への利用が種々検討されている。 In general, the magnetic fluid is an aqueous suspension containing magnetic fine particles produced by a coprecipitation method. The magnetic fine particle powder obtained by drying this aqueous suspension cannot be well dispersed in non-aqueous solvents such as mineral oil, hydrocarbon, silicone oil and the like due to its hydrophilicity. Therefore, it is necessary to modify the lipophilicity by adsorbing fatty acid salts, surfactants and the like on the surface of these magnetic fine particles. Magnetic fluids in which these magnetic fine particles are dispersed in a non-aqueous solvent have been studied for use in magnetic seals, clutches, dampers, actuators, and the like.
このように界面活性剤を吸着させた磁性微粒子は、一般に、ろ過した後、得られたケーキを減圧乾燥して脱水を行い、その後に鉱物油などの溶剤に分散させて製造される。この一旦乾燥した際に、磁性微粒子同士が凝集を起こしてしまい、本来の一次粒子としての分散状態ではないために、経時的な磁性微粒子の沈降等の安定性の問題が生じてしまい、実際に使用できるレベルのものではない。 In general, the magnetic fine particles having the surfactant adsorbed thereon are produced by filtering, drying the obtained cake under reduced pressure, dehydrating, and then dispersing in a solvent such as mineral oil. When this once dried, the magnetic fine particles are agglomerated with each other and are not in the original dispersed state as primary particles, resulting in stability problems such as sedimentation of the magnetic fine particles over time. It is not of a usable level.
従来では、マグネタイト粒子にＮ−ポリアルキルポリアミン置換アルケニルコハク酸イミドあるいはモノ−又はジ−オキシアルキレン置換基を有するリン酸エステル分散安定剤として低沸点炭化水素溶剤へ分散させたもの（特許文献１）やフェライト微粒子に４級アンモニウム塩を吸着し、さらにＮ−アルキルポリアミン置換アルケニルコハク酸イミドを吸着させ、低蒸気圧基油に分散させたものが示されている（特許文献２）。 Conventionally, N-polyalkylpolyamine-substituted alkenyl succinimide or phosphate ester dispersion stabilizer having mono- or di-oxyalkylene substituents dispersed in magnetite particles in a low-boiling hydrocarbon solvent (Patent Document 1) In addition, a quaternary ammonium salt is adsorbed on fine particles of ferrite and N-alkylpolyamine-substituted alkenyl succinimide is adsorbed and dispersed in a low vapor pressure base oil (Patent Document 2).
また、界面活性剤を被覆したフェライト類微粒子を、ハイドロキノンのモノアルキルエーテルまたは、モノ脂肪酸エステルあるいはこれらのアンモニウム塩または有機アミン塩の存在下にケロシン基油中または水性媒体中に分散（特許文献３）や磁性微粒子を脂肪酸で被覆し、スルホン酸塩系界面活性剤及び／または動物系ワックスを含有させた脂肪族炭化水素あるいは芳香族炭化水素中に分散させたものが記載されている（特許文献４）。 Further, ferrite fine particles coated with a surfactant are dispersed in a kerosene base oil or an aqueous medium in the presence of hydroquinone monoalkyl ether, mono fatty acid ester, ammonium salt or organic amine salt thereof (Patent Document 3). ) And magnetic fine particles coated with fatty acids and dispersed in aliphatic hydrocarbons or aromatic hydrocarbons containing sulfonate surfactants and / or animal waxes (Patent Documents) 4).
これらはいずれも、共沈法により作製した磁性微粒子を一旦乾燥し、続いて界面活性剤や分散剤等で溶剤に分散させる方法であり、乾燥工程を経ることにより粒子間の凝集を抑制することが困難である。よって、得られた磁性流体も経時的に安定なものとは言い難い。また、高濃度化するとその傾向はさらに強くなり、結果として高濃度化することが難しく、磁化値の低いものしか得ることができない。 All of these are methods in which the magnetic fine particles produced by the coprecipitation method are once dried and then dispersed in a solvent with a surfactant, a dispersant, etc., which suppresses aggregation between the particles through a drying process. Is difficult. Therefore, it is difficult to say that the obtained magnetic fluid is stable over time. In addition, when the concentration is increased, the tendency is further increased. As a result, it is difficult to increase the concentration, and only a low magnetization value can be obtained.
また上記以外の方法では、非イオン性界面活性剤を曇点以上の温度で磁性粒子に吸着させた後、有機溶媒を加えて陰イオン性界面活性剤あるいは陽イオン性界面活性剤を加えて水層から油層へ粒子を移行させることで溶媒中に分散させたものが示されている（特許文献５）。 In other methods than the above, a nonionic surfactant is adsorbed on the magnetic particles at a temperature higher than the cloud point, and then an organic solvent is added and an anionic surfactant or a cationic surfactant is added. The thing disperse | distributed in the solvent by moving particle | grains from a layer to an oil layer is shown (patent document 5).
この方法によると、一旦乾燥することなく油性媒体中に分散した磁性粒子を効率的に得ることができるが、磁性粒子に付着した非イオン性界面活性剤に対して、陰イオン性界面活性剤あるいは陽イオン性界面活性剤の親水性基を向けて、一方、疎水基を外側に向けて配向するために、必ずしも最外層の界面活性剤の磁性粒子への吸着性は強くなく、水層から油層への移行する際に、水−油界面の分離に問題を生じる。また、吸着できない界面活性剤が存在するために、発泡性が高いという問題が生じる。 According to this method, magnetic particles dispersed in an oily medium can be efficiently obtained without drying once. However, an anionic surfactant or a nonionic surfactant attached to the magnetic particles can be obtained. Since the hydrophilic group of the cationic surfactant is oriented and the hydrophobic group is oriented outward, the outermost surfactant is not necessarily strongly adsorbed to the magnetic particles, and the water layer to the oil layer When moving to, problems arise in the separation of the water-oil interface. In addition, since there is a surfactant that cannot be adsorbed, there is a problem that foamability is high.
本発明はかかる実情に鑑み、発泡性が少なく、かつ分散安定性に優れ、磁性微粒子の沈降のない磁性流体を提供することを目的とする。 In view of such circumstances, an object of the present invention is to provide a magnetic fluid that is less foamable, excellent in dispersion stability, and free from sedimentation of magnetic fine particles.
本発明者らは上記課題を解決するべく鋭意研究の結果、ロジンあるいはロジン誘導体を磁性微粒子に吸着させることにより、所期の目的が達成できることを見い出し、本発明に到達した。 As a result of intensive studies to solve the above problems, the present inventors have found that the intended purpose can be achieved by adsorbing rosin or a rosin derivative to magnetic fine particles, and have reached the present invention.
即ち、本発明の請求項１に係る発明は、磁性微粒子を炭化水素系溶剤、エステル系溶剤、グリコール系溶剤およびシリコーン系溶剤からなる分散媒中に分散してなる磁性流体において、分散剤としてロジンあるいはロジン誘導体を少なくとも含むことを特徴とする磁性流体である。 That is, the invention according to claim 1 of the present invention provides a rosin as a dispersant in a magnetic fluid in which magnetic fine particles are dispersed in a dispersion medium comprising a hydrocarbon solvent, an ester solvent, a glycol solvent, and a silicone solvent. Alternatively, the magnetic fluid includes at least a rosin derivative.
また、本発明の請求項２に係る発明は、磁性微粒子が、鉄、コバルト、ニッケルの元素から選ばれる金属粒子若しくは合金粒子および強磁性を示すこれら金属化合物粒子から選ばれる少なくとも１種または２種以上の磁性粒子であることを特徴とする請求項１記載の磁性流体である。 In the invention according to claim 2 of the present invention, the magnetic fine particles are at least one or two selected from metal particles or alloy particles selected from elements of iron, cobalt and nickel, and from these metal compound particles exhibiting ferromagnetism. 2. The magnetic fluid according to claim 1, wherein the magnetic fluid is a magnetic particle as described above.
また、本発明の請求項３に係る発明は、分散剤が、ロジン誘導体と高級脂肪酸とを少なくとも含むことを特徴とする請求項１記載の磁性流体である。 The invention according to claim 3 of the present invention is the magnetic fluid according to claim 1, wherein the dispersant contains at least a rosin derivative and a higher fatty acid.
また、本発明の請求項４に係る発明は、磁性微粒子の懸濁液にロジンあるいはロジン誘導体を含有する水溶液を添加して分散処理を行った後、トルエンを添加し、ｐＨを調節することでロジン誘導体を少なくとも含む分散剤で表面処理された磁性微粒子を、水層からトルエン層へ転層を行いトルエン中に分散させることを特徴とする磁性流体の製造方法である。 In addition, the invention according to claim 4 of the present invention is to add a solution containing rosin or a rosin derivative to a suspension of magnetic fine particles and perform dispersion treatment, and then add toluene to adjust the pH. A magnetic fluid production method characterized in that magnetic fine particles surface-treated with a dispersant containing at least a rosin derivative are transferred from an aqueous layer to a toluene layer and dispersed in toluene.
また、本発明の請求項５に係る発明は、磁性微粒子の懸濁液にロジンあるいはロジン誘導体を含有する水溶液を添加して分散処理を行った後、トルエンを添加し、ｐＨを調節することでロジン誘導体を少なくとも含む分散剤で表面処理された磁性微粒子を、水層からトルエン層へ転層を行い、さらに、分散媒と該分散媒と相溶性に優れた分散剤を添加し、トルエンを除去することを特徴とする磁性流体の製造方法である。 Further, the invention according to claim 5 of the present invention is to add a solution containing rosin or a rosin derivative to a suspension of magnetic fine particles and perform dispersion treatment, and then add toluene to adjust the pH. The magnetic fine particles surface-treated with a dispersant containing at least a rosin derivative are transferred from an aqueous layer to a toluene layer, and a dispersion medium and a dispersant having excellent compatibility with the dispersion medium are added to remove toluene. A method for producing a magnetic fluid characterized by comprising:
本発明に係る磁性流体は、特定の分散剤を使用することにより、発泡性が少なく、長期にわたり、良好な分散安定性を維持することができる。 The magnetic fluid according to the present invention has a low foaming property and can maintain good dispersion stability over a long period of time by using a specific dispersant.
本発明の構成をより詳しく説明すれば、次の通りである。 The configuration of the present invention will be described in more detail as follows.
磁性微粒子としては、鉄、コバルト、ニッケルの元素から選ばれる金属粒子若しくは合金粒子、又は強磁性を示す前記金属の化合物粒子から選ばれる少なくとも１種または２種以上の磁性微粒子である。金属の化合物粒子としては、フェライト、マグネタイト、マグへマイト等であり、これらの粒子にＭｎ、Ｚｎ、Ｃｕ、Ｎｉ、Ｃｏ、Ｍｇ、Ｓｉ等の異種金属元素を含有してもよい。 The magnetic fine particles are metal particles or alloy particles selected from elements of iron, cobalt, and nickel, or at least one type or two or more types of magnetic fine particles selected from compound particles of the metal exhibiting ferromagnetism. The metal compound particles include ferrite, magnetite, maghemite, and the like, and these particles may contain different metal elements such as Mn, Zn, Cu, Ni, Co, Mg, and Si.
磁性微粒子の粒径は、５〜５０ｎｍが好ましく、より好ましくは５〜３０ｎｍである。粒径が５０ｎｍよりも大きくなると、沈降性が大きくなってしまう。一方、粒径が５ｎｍよりも小さいと、表面積が大きくなりすぎ、さらに分散剤を多く必要とするため粘度が高くなってしまう。 The particle size of the magnetic fine particles is preferably 5 to 50 nm, more preferably 5 to 30 nm. When the particle size is larger than 50 nm, the sedimentation property is increased. On the other hand, if the particle size is smaller than 5 nm, the surface area becomes too large, and a larger amount of dispersant is required, so that the viscosity becomes high.
磁性流体中の磁性微粒子の含有量は、１５〜４０重量％が好ましく、より好ましくは２０〜３５重量％である。磁性粒子の含有量が４０重量％よりも多くなると、磁性流体としての粘度が高くなりすぎ、流動性において問題となることがある。一方、１５重量％よりも少なくなると、磁気力が不十分である。 The content of magnetic fine particles in the magnetic fluid is preferably 15 to 40% by weight, more preferably 20 to 35% by weight. If the content of the magnetic particles exceeds 40% by weight, the viscosity as a magnetic fluid becomes too high, which may cause a problem in fluidity. On the other hand, if it is less than 15% by weight, the magnetic force is insufficient.
本発明におけるロジンあるいはロジン誘導体の含有量は、固形分として磁性微粒子に対して５〜３５重量％が好ましく、より好ましくは１０〜３０重量％である。ロジンあるいはロジン誘導体の含有量が５重量％未満の場合には、水層からトルエン層への転層が上手くできないことがある。３５重量％を越える場合には、磁性流体としての粘性が高くなりすぎて、流動性が悪くなってしまうことがある。 The content of the rosin or rosin derivative in the present invention is preferably 5 to 35% by weight, more preferably 10 to 30% by weight, based on the magnetic fine particles as a solid content. If the content of rosin or rosin derivative is less than 5% by weight, the phase transfer from the aqueous layer to the toluene layer may not be successful. If it exceeds 35% by weight, the viscosity as a magnetic fluid may become too high, resulting in poor fluidity.
ロジンあるいはロジン誘導体のアルカリ水溶液としては、サイズパインＥ５０、サイズパインＧ−Ｆ、マルキード３２−３０ＷＳ（いずれも荒川化学製）等が用いられる。また、ロジンあるいはロジン誘導体の固形物を苛性ソーダ等でアルカリ水溶液としてもかまわない。 As the alkaline aqueous solution of rosin or rosin derivative, Size Pine E50, Size Pine GF, Marquide 32-30WS (all manufactured by Arakawa Chemical Co., Ltd.) or the like is used. Further, the solid matter of rosin or rosin derivative may be used as an alkaline aqueous solution with caustic soda or the like.
本発明において、分散剤としての高級脂肪酸としては、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、オレイン酸、ベヘニン酸又はこれらの塩等が使用できる。これらの添加量は、磁性微粒子に対して１〜２０重量％が好ましく、より好ましくは２〜１５重量％である。１重量％未満の場合には、分散媒中での磁性微粒子の沈降が生じる場合がある。一方、２０重量％を越える場合には、粘度が高くなりすぎてしまい流動性が悪化することがある。 In the present invention, as the higher fatty acid as the dispersant, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid or a salt thereof can be used. The amount of addition is preferably 1 to 20% by weight, more preferably 2 to 15% by weight, based on the magnetic fine particles. If it is less than 1% by weight, the magnetic fine particles may settle in the dispersion medium. On the other hand, if it exceeds 20% by weight, the viscosity becomes too high and the fluidity may deteriorate.
さらに分散剤として、陰イオン性界面活性剤や陽イオン性界面活性剤あるいは非イオン性の界面活性剤を添加してもかまわない。これらの添加量は、磁性微粒子に対して０〜２０重量％が好ましく、より好ましくは０〜１０重量％である。 Furthermore, an anionic surfactant, a cationic surfactant, or a nonionic surfactant may be added as a dispersant. The amount of addition is preferably 0 to 20% by weight, more preferably 0 to 10% by weight, based on the magnetic fine particles.
また、分散媒としては、炭化水素系溶剤、エステル系溶剤、グリコール系溶剤およびシリコーン系溶剤を用いることができ、これらは単独で、又は必要に応じ、２種以上組み合わせて用いられる。 Moreover, as a dispersion medium, a hydrocarbon solvent, an ester solvent, a glycol solvent, and a silicone solvent can be used, and these are used alone or in combination of two or more as required.
本発明に係る磁性流体の粘度は、１０ｍＰａ〜４００ｍＰａが好ましく、より好ましくは１０ｍＰａ〜２００ｍＰａである。 The viscosity of the magnetic fluid according to the present invention is preferably 10 mPa to 400 mPa, more preferably 10 mPa to 200 mPa.
本発明に係る磁性流体のチキソトロピー性は、後述する評価法において、２〜２０が好ましく、より好ましくは２〜１５である。 The thixotropy of the magnetic fluid according to the present invention is preferably 2 to 20, more preferably 2 to 15, in the evaluation method described later.
本発明に係る磁性流体の飽和磁化値は、１０ｍＴ以上が好ましく、より好ましくは２０ｍＴ以上である。 The saturation magnetization value of the magnetic fluid according to the present invention is preferably 10 mT or more, more preferably 20 mT or more.
本発明に係る磁性流体の製造方法について述べる。 A method for producing a magnetic fluid according to the present invention will be described.
本発明においては、共沈法で得られた磁性微粒子を含有する水懸濁液に、ロジン又はロジン誘導体を含有する水溶液を添加することによって、一度も乾燥工程を経ることなく磁性微粒子を水層からトルエン層へ転層し、有機溶媒に磁性微粒子が分散した磁性流体とするものである。 In the present invention, an aqueous solution containing rosin or a rosin derivative is added to an aqueous suspension containing magnetic fine particles obtained by the coprecipitation method. To a toluene layer and a magnetic fluid in which magnetic fine particles are dispersed in an organic solvent.
本発明に係る磁性流体の調製方法は、例えば、アルカリ性水溶液で共沈反応によって得られる磁性粒子の懸濁液に、ロジンのアルカリ水溶液および必要により分散剤を加え、所定時間攪拌した後、トルエンを加え、さらに硫酸などの酸でｐＨを酸性領域まで調整することで、水層にあった磁性微粒子がトルエン層へ転層してくる。得られた磁性微粒子が分散したトルエン溶液からトルエンをエバポレートすることで目的の濃度に調整することができる。
また、トルエン以外の溶剤で分散させる場合には、水層と分離して得られた磁性微粒子を含有するトルエン溶液に目的の溶剤を所定量添加した後、トルエンをエバポレートすることで目的の溶剤に磁性微粒子が分散した磁性流体を得ることができる。
The method for preparing a magnetic fluid according to the present invention includes, for example, adding an alkaline aqueous solution of rosin and, if necessary, a dispersing agent to a suspension of magnetic particles obtained by a coprecipitation reaction with an alkaline aqueous solution, stirring for a predetermined time, and then adding toluene. In addition, by adjusting the pH to an acidic range with an acid such as sulfuric acid, the magnetic fine particles in the aqueous layer are transferred to the toluene layer. The target concentration can be adjusted by evaporating toluene from a toluene solution in which the obtained magnetic fine particles are dispersed.
In addition, in the case of dispersing with a solvent other than toluene, a predetermined amount of a target solvent is added to a toluene solution containing magnetic fine particles obtained by separation from an aqueous layer, and then toluene is evaporated to make the target solvent. A magnetic fluid in which magnetic fine particles are dispersed can be obtained.
本発明に係る磁性流体は、トルエン溶液の状態又は他の溶媒を添加した後に、ホモジナイザー、ホモミキサー、ボールミル、メカニカルミキサー等の高せん断力が与えられる処理機によって分散処理を施すことが好ましい。これら処理機によって、十分に分散させることで、分散剤が有効に働き、分散安定な磁性流体を調製することが可能となる。 The magnetic fluid according to the present invention is preferably subjected to a dispersion treatment by a processing machine to which a high shear force is applied, such as a homogenizer, a homomixer, a ball mill, a mechanical mixer, etc. after adding a toluene solution or other solvent. By sufficiently dispersing with these processors, the dispersant works effectively, and a dispersion-stable magnetic fluid can be prepared.
以下、本発明を実施例及び比較例に基づいて、更に詳細に説明するが、本発明はこれらにより何ら制限されるものではない。
尚、以下の記載において、「％」は特に断らない限り「重量％」を表す。
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not restrict | limited at all by these.
In the following description, “%” represents “% by weight” unless otherwise specified.
粘度は、Ｅ型粘度計（ＴＶ−３０；東機産業（株）製）を用いて２５℃で測定した。 The viscosity was measured at 25 ° C. using an E-type viscometer (TV-30; manufactured by Toki Sangyo Co., Ltd.).
チキソトロピー指数は、上記Ｅ型粘度計を用いてせん断速度が３８．３Ｓ−１の時の粘度に対する３．８３Ｓ−１時の粘度の比率によって表した。 The thixotropy index was represented by the ratio of the viscosity at 3.83 S −1 to the viscosity at a shear rate of 38.3 S −1 using the E-type viscometer.
沈降性は、次の方法で測定した。
１００ｍｌのメスシリンダーに磁性流体を５０ｍｌ入れ、６０℃で１ヶ月間放置し、１ヶ月後の上澄み層の容量を測定した。
The sedimentation property was measured by the following method.
50 ml of ferrofluid was placed in a 100 ml graduated cylinder and allowed to stand at 60 ° C. for 1 month, and the volume of the supernatant layer after 1 month was measured.
磁気特性は、ＶＳＭ（東栄工業製）で外部磁場（１０Ｋ／４π）Ａｍ２／ｋｇで測定した。 The magnetic properties were measured with an external magnetic field (10K / 4π) Am 2 / kg using VSM (manufactured by Toei Kogyo).
粒子径は、透過型電子顕微鏡観察により求めた。 The particle diameter was determined by observation with a transmission electron microscope.
実施例１
８０℃に調節した３．２７ＮのＮａＯＨ水溶液２８０ｍｌ中に、１．４ＭのＦｅＳＯ４を６２ｍｌと２．８ＭＦｅＣｌ３を６２ｍｌとを予め混合した溶液を攪拌しながら滴下し、その後、８０℃で１時間熟成させて、マグネタイト微粒子の水懸濁液を得た。次に、サイズパインＥ−５０（商品名：荒川化学工業（株）製）１０ｍｌを添加し、同温度で１時間攪拌させる。ここにトルエン２００ｍｌを添加し、１０％Ｈ２ＳＯ４水溶液を滴下してｐＨを調整することで、それまで水層に存在したマグネタイト粒子が、トルエン層へ転層した。そのときの水溶液のｐＨは５．０であった。次に、分液ロートを用いて水層を除去した後、パラフィン系オイル（スーパーオイルＭ１０；商品名 新日本石油株式会社製）８０ｇを加え、ホモミキサーで５分間混合させ、さらに、トルエンをエバポレーターを用いて除去することで、粒径１０ｎｍで、マグネタイト濃度が２０重量％の油系微粒磁性ペーストからなる磁性流体（Ａ）を得た。
得られた磁性流体（Ａ）は、飽和磁化３２ｍＴ、粘度７５ｍＰａ、チキソトロピー指数６．７であった。沈降性は０ｍＬであった。さらに、得られた磁性流体を手で振っても発泡はほとんど見られなかった。
Example 1
A solution prepared by previously mixing 62 ml of 1.4 M FeSO 4 and 62 ml of 2.8 M FeCl 3 was added dropwise to 280 ml of a 3.27N NaOH aqueous solution adjusted to 80 ° C. with stirring, and then at 80 ° C. for 1 hour. After aging, an aqueous suspension of magnetite fine particles was obtained. Next, 10 ml of size pine E-50 (trade name: manufactured by Arakawa Chemical Industries, Ltd.) is added and stirred at the same temperature for 1 hour. 200 ml of toluene was added thereto, and 10% H 2 SO 4 aqueous solution was added dropwise to adjust the pH, whereby the magnetite particles that had existed in the aqueous layer until then were transferred to the toluene layer. The pH of the aqueous solution at that time was 5.0. Next, after removing the aqueous layer using a separatory funnel, 80 g of paraffinic oil (Super Oil M10; trade name: Shin Nippon Oil Co., Ltd.) is added and mixed with a homomixer for 5 minutes, and toluene is further evaporated. The magnetic fluid (A) made of an oil-based fine magnetic paste having a particle size of 10 nm and a magnetite concentration of 20% by weight was obtained.
The obtained magnetic fluid (A) had a saturation magnetization of 32 mT, a viscosity of 75 mPa, and a thixotropy index of 6.7. The sedimentation property was 0 mL. Furthermore, foaming was hardly observed even when the obtained magnetic fluid was shaken by hand.
実施例２
実施例１と同様にして共沈反応を行い、サイズパインＥ−５０；８ｍｌと１０％オレイン酸ナトリウム水溶液を２６ｇを添加し、さらにトルエン２００ｍｌを加え、実施例１と同様に処理することで、粒径１０ｎｍでマグネタイト濃度が２０重量％のトルエン油系微粒磁性ペーストからなる磁性流体（Ｂ）を得た。
得られた磁性流体（Ｂ）は、飽和磁化３１ｍＴ、粘度８８ｍＰａ、チキソトロピー指数８．５であった。沈降性は０ｍＬであった。
Example 2
Co-precipitation reaction was performed in the same manner as in Example 1, and size pine E-50; 8 ml and 26 g of 10% sodium oleate aqueous solution were added, and 200 ml of toluene was further added, and the same treatment as in Example 1 was performed. A magnetic fluid (B) made of a toluene oil-based fine magnetic paste having a particle size of 10 nm and a magnetite concentration of 20% by weight was obtained.
The obtained magnetic fluid (B) had a saturation magnetization of 31 mT, a viscosity of 88 mPa, and a thixotropy index of 8.5. The sedimentation property was 0 mL.
実施例３
実施例１と同様にしてＭｎ−Ｚｎフェライト粒子の共沈反応を行い、サイズパインＥ−５０；８ｍｌとドデシルベンゼンスルホン酸ナトリウム（１０％溶液）２３ｍｌを添加した以外は、実施例１と同様に処理することで、粒径２３ｎｍで磁性粉濃度が２０重量％の油系微粒磁性ペースト（Ｃ）を得た。
得られた磁性流体（Ｃ）は、飽和磁化２７ｍＴ、粘度７７ｍＰａ、チキソトロピー指数９．２であった。沈降性は０ｍＬであった。
Example 3
Similar to Example 1, Mn—Zn ferrite particles were co-precipitated, and Size Pine E-50; 8 ml and sodium dodecylbenzenesulfonate (10% solution) 23 ml were added. By the treatment, an oil-based fine magnetic paste (C) having a particle size of 23 nm and a magnetic powder concentration of 20% by weight was obtained.
The obtained magnetic fluid (C) had a saturation magnetization of 27 mT, a viscosity of 77 mPa, and a thixotropy index of 9.2. The sedimentation property was 0 mL.
比較例
実施例１と同様にしてマグネタイトの共沈反応を行い、２％ポリエチレングリコール−Ｐ−ノニルフェニルエーテル；２０ｍｌとドデシルベンゼンスルホン酸ナトリウム（１０％溶液）；２４ｍｌを添加した以外は、実施例１と同様に処理を行ったが、マグネタイトが水層からトルエン層へ移行しなかった。
Comparative Example A magnetite coprecipitation reaction was carried out in the same manner as in Example 1 except that 2% polyethylene glycol-P-nonylphenyl ether; 20 ml and sodium dodecylbenzenesulfonate (10% solution); 24 ml were added. Treatment was performed in the same manner as in Example 1, but magnetite did not migrate from the aqueous layer to the toluene layer.
本発明に係る磁性流体は、飽和磁化値が高く、かつ分散安定性に優れ、磁性微粒子の沈降がないため、クラッチやダンパ、アクチュエーター等において有用である。
The magnetic fluid according to the present invention is useful in clutches, dampers, actuators and the like because it has a high saturation magnetization value, excellent dispersion stability, and no sedimentation of magnetic fine particles.
Claims (5)
Magnetic dispersion surface-treated with a dispersing agent containing at least a rosin derivative by adding toluene to a suspension of magnetic fine particles and then performing dispersion treatment by adding an aqueous solution containing rosin or a rosin derivative and then adjusting the pH. A method for producing a magnetic fluid, comprising transferring particles from an aqueous layer to a toluene layer, adding a dispersion medium and a dispersant excellent in compatibility with the dispersion medium, and removing toluene.
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| JPS5889802A (en) * | 1981-11-24 | 1983-05-28 | Matsumoto Yushi Seiyaku Kk | Manufacture of magnetic fluid |
| JPH0481498A (en) * | 1990-07-25 | 1992-03-16 | Nok Corp | Production of magnetic fluid |
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| JPS5889802A (en) * | 1981-11-24 | 1983-05-28 | Matsumoto Yushi Seiyaku Kk | Manufacture of magnetic fluid |
| JPH0481498A (en) * | 1990-07-25 | 1992-03-16 | Nok Corp | Production of magnetic fluid |
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