JP4415361B2 - Adsorption method of surfactant on ferrite fine particles - Google Patents
Adsorption method of surfactant on ferrite fine particles Download PDFInfo
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- JP4415361B2 JP4415361B2 JP2000030312A JP2000030312A JP4415361B2 JP 4415361 B2 JP4415361 B2 JP 4415361B2 JP 2000030312 A JP2000030312 A JP 2000030312A JP 2000030312 A JP2000030312 A JP 2000030312A JP 4415361 B2 JP4415361 B2 JP 4415361B2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
- H01F1/445—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a compound, e.g. Fe3O4
Description
【０００１】
【発明の属する技術分野】
本発明は、フェライト類微粒子への界面活性剤の吸着方法に関する。更に詳しくは、水溶性界面活性剤の吸着量を増大せしめるフェライト類微粒子への界面活性剤の吸着方法に関する。
【０００２】
【従来の技術】
フェライト類微粒子を基油中に分散させて磁性流体を製造する際、まずフェライト類微粒子の水性サスペンションに水溶性界面活性剤を吸着せしめることが行われる。吸着された水溶性界面活性剤は、その反発力によりフェライト類微粒子を水またはメタノール水溶液、エタノール水溶液、アセトン水溶液等の水性媒体中に良好に分散せしめるという作用を有する。
【０００３】
一般に、水溶性界面活性剤は、フェライト類微粒子の水性サスペンションに対し約0.05〜3モル濃度で用いられ、約80〜95℃に約0.5〜2時間程度加熱することによって吸着処理が行われ、その後行われる低分子量基油等に対する分散を可能とさせる。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、フェライト類微粒子の水性サスペンションに水溶性界面活性剤を吸着させるに際し、その吸着量を増大せしめ、ひいては飽和磁化値を高めた磁性流体を形成させ得るフェライト類微粒子への界面活性剤の吸着方法を提供することにある。
【０００５】
【課題を解決するための手段】
かかる本発明の目的は、3〜40気圧(0.3〜4.05MPa)の加圧条件下および200〜300℃の加熱条件下で水溶性界面活性剤の吸着処理を行うことによって達成される。
【０００６】
【発明の実施の形態】
フェライト類微粒子としては、任意の方法によって製造されたものが用いられるものの、純度、粒径の制御、そして何よりも生産性の点において有利である共沈法によって製造された粒径約50〜300Å、好ましくは約70〜120Åのものが一般に用いられる。共沈法によってフェライト類微粒子を製造する場合、水または水性媒体中で微粒子が生成するため、フェライト類微粒子は水性サスペンションとして得られる。ここで、水性媒体として水溶液の形で用いられるメタノール、エタノール、アセトン等の水溶性有機溶媒は、界面活性剤の溶解度を高める働きをする。
【０００７】
フェライト類微粒子に吸着される水溶性界面活性剤としては、微粒子を炭化水素溶媒中に分散させる際に通常用いられている次のようなものが用いられ、好ましくは高級脂肪酸塩またはソルビタンエステルが用いられる。
オレイン酸ナトリウム、エルカ酸ナトリウムなどの高級脂肪酸塩
ポリオキシエチレンソルビタンエステルなどのソルビタンエステル
オレイン酸、ステアリン酸などの高級脂肪酸
エアロゾル-OTなどのジアルキルスルホこはく酸塩
ポリオキシエチレンノニルフェニルエーテルなどのポリオキシエチレンアルキルアリルエーテル
ポリオキシエチレンラウリルエーテルなどのポリオキシエチレンアルキルエーテル
ポリオキシエチレンアルキルエステル
ドデシル硫酸エステルなどのアルコール硫酸エステル
アルキルベンゼンスルホン酸
オレイルリン酸塩などのリン酸塩
ポリオキシエチレンアルキルアミン
グリセリンエステル
アミノアルコールエステル
【０００８】
これらの水溶性界面活性剤のフェライト類微粒子への吸着は、フェライト類微粒子の水性サスペンションに約0.05〜1M濃度の水溶性界面活性剤水溶液を添加し、3〜40気圧(0.3〜4.05MPa)、好ましくは3〜30気圧(0.3〜3.04MPa)の加圧条件下および200〜300℃、好ましくは200〜250℃の温度条件下で、攪拌しながら約0.5〜4時間程度加熱することによって行われる。これ以上の温度および圧力が用いられると、界面活性剤の分解および微粒子の凝集が発生するようになる。
【０００９】
このような条件下での水溶性界面活性剤の吸着処理は、吸着量を増大させることにより、微粒子間凝集に対抗する反発力を高めることができ、その結果として微粒子分散濃度の増大、換言すれば最終的に得られる磁性流体の飽和磁化値を高めることができる。
【００１０】
このようにして吸着処理された後、塩酸等を用いてpHを4〜7に調整し、そこにアセトン、メタノール等の凝集溶媒を加えると、ケーキ状の微粒子が凝集してくる。このケーキ状の微粒子は、例えばアセトン-トルエン(1：1)混合溶液で洗浄するなどの操作をくり返して適用することにより、余分の水溶性界面活性剤の除去が行われる。
【００１１】
得られた水溶性界面活性剤吸着フェライト類微粒子を低分子量基油中に分散させる場合には、例えばテトラリン、ケロシン、デカリン、n-デカン、メシチレン、石油エーテル、リグロイン、ナフサ等の分子量が約100〜300程度の炭化水素系有機溶媒中に、超音波照射やホモジナイザ等を用いる方法などによって分散処理することが行われる。これらの低分子量基油は、最終的に得られる磁性流体中のフェライト類微粒子の分散濃度が約10〜50重量%となるような割合で用いられる。
【００１２】
また、水溶性界面活性剤吸着フェライト類微粒子を低蒸気圧基油中に分散させる場合には、一旦低分子量炭化水素系溶媒(上記低分子量基油)中へ分散処理した後、そこに高沸点(沸点約150〜350℃)の炭化水素溶媒、例えばドデシルベンゼン、テトラリン等に、約0.01〜0.5M、好ましくは約0.1〜0.5Mの濃度で溶解させたN-ポリアルキレンポリアミン置換アルケニルコハク酸イミドの溶液が添加される。その添加割合は、微粒子の低分子量溶媒溶液に対し、一般に容積比で約0.5〜5倍、好ましくは約1〜2倍であり、両者の混合はそこに超音波照射を約0.5〜2時間程度適用することにより行われる。
【００１３】
また、低蒸気圧基油中に溶解させて用いられるN-ポリアルキレンポリアミン置換アルケニルコハク酸イミドとしては、次のようなものが用いられる。
分子量約300〜2000のポリブテニル基
R´：炭素数1〜6のアルキレン基
R´が2個以上くり返されるとき互いに同一または異なり得る
【００１４】
その後、ロータリエバポレータなどを用いて低分子量溶媒の除去が行われ、残渣の高沸点炭化水素溶媒溶液について、不活性ガス中、約150〜350℃、好ましくは約200〜300℃に約0.5〜5時間程度加熱することにより、N-ポリアルキレンポリアミン置換アルケニルコハク酸イミドの吸着処理が行われる。
【００１５】
次いで、アセトンまたはトルエン-アセトン、トルエン-メタノール、n-ヘキサン-アセトン、イソオクタン-アセトンの各等量混合溶液等を添加して余分のN-ポリアルキレンポリアミン置換アルケニルコハク酸イミドを除去した後、低分子量溶媒の添加による溶媒の置換が行われる。このようにして得られるN-ポリアルキレンポリアミン置換アルケニルコハク酸イミド吸着フェライト類微粒子の低分子量溶媒溶液に低蒸気圧基油を加え、超音波による分散処理を行った後、低分子量溶媒を減圧留去することにより、磁性流体が製造される。ここで一旦低分子量溶媒溶液とするのは、粘度を低下させ、分散処理を効率良く行うためである。
【００１６】
低蒸気圧基油としては、25℃において0.1mmHg以下、好ましくは0.01mmHg以下の蒸気圧を有する液体、例えば天然油であるホワイトオイル(流動パラフィン)、鉱油、スピンドル油など、あるいは合成油である高級アルキルベンゼン、高級アルキルナフタレン、ポリブテン(分子量約300〜2000)、ジカルボン酸ジエステル(ジオクチルアゼレート、ジオクチルアジペート、ジオクチルセバケート、ジブチルフタレート、ジヘキシルマレエートなど)、ポリオールと炭素数6〜10のカルボン酸とのポリオールポリエステル(トリメチロールプロパントリn-ヘプチルエステル、ペンタエリスリトールテトラn-ヘキシルエステル、ペンタエリスリトールテトラ2-エチルヘキシルエステルなど)、リン酸トリエステル(リン酸トリブチルエステル、リン酸トリ2-エチルヘキシルエステル、リン酸トリクレジルエステルなど)、更に酸化防止剤、耐摩耗剤、油性剤、清浄分散剤などのいわゆる潤滑添加剤を含んだ潤滑油等が、最終的に得られる磁性流体中のフェライト類微粒子の分散濃度が約10〜50重量%となるような割合で用いられる。
【００１７】
【発明の効果】
フェライト類微粒子の水性サスペンションに水溶性界面活性剤を吸着させるに際し、加圧加熱条件下で吸着処理を行うことにより、水溶性界面活性剤の吸着量の増大が図られ、これにより微粒子間の凝集が抑制され、微粒子分散濃度を高めることができ、ひいては飽和磁化値を高めた磁性流体を得ることができる。
【００１８】
【実施例】
次に、実施例について本発明を説明する。
【００１９】
実施例
FeCl 2 ・4H 2 O 184gおよびFeCl 3 ・6H 2 O 500gを溶解させた水溶液1850ml中に、撹拌しながら6N NaOH水溶液をpHが11になる迄滴下し、その後80℃で30分間熟成、冷却し、塩をデカンテーションで除去して、マグネタイトの水性サスペンション(マグネタイト濃度10重量%)を得た。
【００２０】
この水性サスペンション2Lに、0.1モル濃度のオレイン酸ナトリウム水溶液500mlを添加し、5気圧、200℃の条件下で、600rpmの回転数で攪拌しながら、2時間加熱して吸着処理を行った。冷却後、1N塩酸をpHが6になる迄添加して、pHを調整した。そこにアセトンを加えて微粒子を凝集させ、ケーキ状の微粒子を得た。
【００２１】
得られたケーキ状の微粒子を、アセトン-トルエン(容積比1:1)混合溶液で洗浄する操作を3回行ない、余分の界面活性剤を除去した後、一昼夜減圧乾燥を行って、アセトンおよびトルエンを完全に蒸発させた。乾燥後の微粒子の熱分析から界面活性剤の吸着量を求めると、界面活性剤を含む全重量に対し25%であった。
【００２２】
この乾燥後の微粒子10gを、低分子量基油であるケロシン100g中に加え、ホモジナイザで1時間分散処理した後、遠心分離(15000G、30分間)して沈降物を除去し、ケロシン分散液が流動性を失わない範囲内でケロシンを減圧除去し、ケロシンを基油とする飽和磁化530Gの磁性流体(分散濃度12重量%)を得た。
【００２３】
また、上記遠心分離後のケロシン分散液50mlに、ポリブテニルコハク酸イミドテトラエチレンペンタミン
10gをドデシルベンゼン50mlに溶解させた溶液を添加し、超音波照射後減圧下でケロシンを完全に除去した。
【００２４】
これを250℃で1時間加熱した後、アセトンを加えて微粒子を凝集させ、ケーキ状の微粒子を得た。このケーキ状微粒子を、アセトン-トルエン(容積比1:1)混合溶液で3回洗浄して、余分なポリブテニルコハク酸イミドテトラエチレンペンタミンを除去した後、ホモジナイザを用いて再びケロシン中に分散させた。
【００２５】
そこに高級アルキルナフタレン4gを加えた後、遠心分離して沈降物を除去し、減圧下でケロシンを完全に除去して、高級アルキルナフタレンを基油とする飽和磁化500Gの磁性流体(分散濃度11重量%)を得た。
【００２６】
比較例
実施例において、オレイン酸ナトリウムの吸着処理を大気圧下、80℃の条件下で2時間攪拌しながら行ないケーキ状の微粒子を得、同様に洗浄および減圧乾燥を行った。乾燥後の微粒子の熱分析から、界面活性剤の吸着量はそれを含む全重量の15%であった。
【００２７】
また、この乾燥後の微粒子を用い、実施例と同様にしてケロシンまたは高級アルキルナフタレンを基油とする磁性流体を調製すると、これらの飽和磁化はそれぞれ400Gおよび380Gであった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for adsorbing a surfactant on ferrite fine particles. More specifically, the present invention relates to a method for adsorbing a surfactant onto fine ferrite particles that increases the amount of adsorption of a water-soluble surfactant.
[0002]
[Prior art]
When producing a magnetic fluid by dispersing ferrite fine particles in a base oil, first, a water-soluble surfactant is adsorbed on an aqueous suspension of ferrite fine particles. The adsorbed water-soluble surfactant has an action of dispersing fine ferrite particles in water or an aqueous medium such as an aqueous methanol solution, an aqueous ethanol solution or an aqueous acetone solution by its repulsive force.
[0003]
In general, a water-soluble surfactant is used in an aqueous suspension of ferrite fine particles at a concentration of about 0.05 to 3 mol, and is adsorbed by heating to about 80 to 95 ° C. for about 0.5 to 2 hours. Dispersion in the low molecular weight base oil or the like to be performed is enabled.
[0004]
[Problems to be solved by the invention]
It is an object of the present invention to increase the amount of adsorption of a water-soluble surfactant on an aqueous suspension of ferrite fine particles, thereby increasing the amount of adsorption, and thus forming a magnetic fluid having an increased saturation magnetization value. It is to provide a method for adsorbing an agent.
[0005]
[Means for Solving the Problems]
The object of the present invention is achieved by carrying out an adsorption treatment of a water-soluble surfactant under a pressure condition of 3 to 40 atmospheres ( 0.3 to 4.05 MPa) and a heating condition of 200 to 300 ° C.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
As the ferrite fine particles, those produced by any method are used, but the particle size of about 50 to 300 mm produced by the coprecipitation method, which is advantageous in terms of purity, control of the particle size, and above all, productivity. In general, those having a diameter of about 70 to 120 mm are generally used. When ferrite fine particles are produced by the coprecipitation method, fine particles are formed in water or an aqueous medium, so that the ferrite fine particles are obtained as an aqueous suspension. Here, a water-soluble organic solvent such as methanol, ethanol, or acetone used as an aqueous medium in the form of an aqueous solution serves to increase the solubility of the surfactant.
[0007]
As the water-soluble surfactant adsorbed on the ferrite fine particles, the following ones usually used when dispersing the fine particles in a hydrocarbon solvent are used, preferably higher fatty acid salts or sorbitan esters are used. It is done.
Higher fatty acid salts such as sodium oleate and sodium erucate, sorbitan esters such as polyoxyethylene sorbitan ester, higher fatty acid aerosols such as oleic acid and stearic acid-polyoxyethylene nonylphenyl ether such as dialkylsulfosuccinate polyoxyethylene nonylphenyl ether Polyoxyethylene alkyl ethers Polyoxyethylene alkyl ethers Polyoxyethylene alkyl ethers Polyoxyethylene alkyl ethers Polyoxyethylene alkyl ethers Polyoxyethylene alkyl esters Polyoxyethylene alkyl esters Dodecyl sulfates Alcohol sulfates Alkyl benzene sulfonates Oleyl phosphates Polyphosphates Polyoxyethylene alkylamines Glycerin esters Esters [0008]
Adsorption of these water-soluble surfactants to ferrite fine particles can be achieved by adding an aqueous water-soluble surfactant solution having a concentration of about 0.05 to 1M to an aqueous suspension of ferrite fine particles, and 3 to 40 atmospheres ( 0.3 to 4.05 MPa). Preferably, it is carried out by heating for about 0.5 to 4 hours with stirring under a pressurized condition of 3 to 30 atm (0.3 to 3.04 MPa) and a temperature of 200 to 300 ° C, preferably 200 to 250 ° C. . When temperatures and pressures higher than this are used, the surfactant is decomposed and the fine particles are aggregated.
[0009]
The adsorption treatment of the water-soluble surfactant under such conditions can increase the repulsive force against the aggregation between the fine particles by increasing the adsorption amount, and as a result, the fine particle dispersion concentration is increased, in other words, For example, the saturation magnetization value of the finally obtained magnetic fluid can be increased.
[0010]
After the adsorption treatment in this way, the pH is adjusted to 4 to 7 using hydrochloric acid or the like, and cake particles are aggregated when an aggregating solvent such as acetone or methanol is added thereto. The cake-like fine particles are subjected to repeated operations such as washing with an acetone-toluene (1: 1) mixed solution, for example, to remove excess water-soluble surfactant.
[0011]
When the obtained water-soluble surfactant-adsorbed ferrite fine particles are dispersed in a low molecular weight base oil, for example, tetralin, kerosene, decalin, n-decane, mesitylene, petroleum ether, ligroin, naphtha and the like have a molecular weight of about 100. Dispersion treatment is performed in about ~ 300 hydrocarbon organic solvent by a method using ultrasonic irradiation, a homogenizer or the like. These low molecular weight base oils are used in a proportion such that the final dispersion concentration of ferrite fine particles in the magnetic fluid is about 10 to 50% by weight.
[0012]
When water-soluble surfactant-adsorbed ferrite fine particles are dispersed in a low vapor pressure base oil, the dispersion is once dispersed in a low molecular weight hydrocarbon solvent (the above low molecular weight base oil) and then has a high boiling point. N-polyalkylene polyamine substituted alkenyl succinimide dissolved in a hydrocarbon solvent (boiling point about 150-350 ° C.) such as dodecylbenzene, tetralin, etc. at a concentration of about 0.01-0.5M, preferably about 0.1-0.5M Of solution is added. The addition ratio is generally about 0.5 to 5 times, preferably about 1 to 2 times in volume ratio with respect to the low molecular weight solvent solution of fine particles, and both are mixed by ultrasonic irradiation for about 0.5 to 2 hours. It is done by applying.
[0013]
Further, as the N-polyalkylene polyamine-substituted alkenyl succinimide used by being dissolved in a low vapor pressure base oil, the following can be used.
R ′: an alkylene group having 1 to 6 carbon atoms
When two or more R ′ are repeated, they may be the same or different from each other.
Thereafter, the low molecular weight solvent is removed using a rotary evaporator or the like, and the residual high boiling point hydrocarbon solvent solution is about 0.5 to 5 to about 150 to 350 ° C., preferably about 200 to 300 ° C. in an inert gas. The N-polyalkylene polyamine-substituted alkenyl succinimide is adsorbed by heating for about an hour.
[0015]
Next, acetone or toluene-acetone, toluene-methanol, n-hexane-acetone, isooctane-acetone mixed solution of equal amounts, etc. are added to remove excess N-polyalkylene polyamine-substituted alkenyl succinimide. Replacement of the solvent by addition of a molecular weight solvent is performed. A low vapor pressure base oil is added to the low molecular weight solvent solution of the N-polyalkylene polyamine substituted alkenyl succinimide adsorbed fine particles thus obtained, and after ultrasonic dispersion treatment, the low molecular weight solvent is distilled under reduced pressure. By leaving, a magnetic fluid is produced. Here, the reason why the low molecular weight solvent solution is once used is to reduce the viscosity and efficiently perform the dispersion treatment.
[0016]
The low vapor pressure base oil is a liquid having a vapor pressure of 0.1 mmHg or less, preferably 0.01 mmHg or less at 25 ° C., such as white oil (liquid paraffin) which is a natural oil, mineral oil, spindle oil, or synthetic oil. Higher alkylbenzene, higher alkylnaphthalene, polybutene (molecular weight about 300-2000), dicarboxylic acid diester (dioctyl azelate, dioctyl adipate, dioctyl sebacate, dibutyl phthalate, dihexyl maleate, etc.), polyol and carboxylic acid having 6 to 10 carbon atoms Polyol polyester (trimethylolpropane tri n-heptyl ester, pentaerythritol tetra n-hexyl ester, pentaerythritol tetra 2-ethylhexyl ester, etc.), phosphoric acid triester (tributyl ester phosphate, tri-2-ethylhexyl phosphate) Ferrites in magnetic fluids that are finally obtained from lubricating oils containing so-called lubricating additives such as antioxidants, antiwear agents, oiliness agents, detergent dispersants, etc. The fine particles are used in such a ratio that the dispersion concentration is about 10 to 50% by weight.
[0017]
【The invention's effect】
When adsorbing a water-soluble surfactant to an aqueous suspension of ferrite fine particles, the adsorption amount of the water-soluble surfactant is increased by performing an adsorption treatment under pressure and heating conditions, thereby aggregating between the fine particles. Is suppressed, the fine particle dispersion concentration can be increased, and as a result, a magnetic fluid having an increased saturation magnetization value can be obtained.
[0018]
【Example】
Next, the present invention will be described with reference to examples.
[0019]
Example
To 1850 ml of an aqueous solution in which 184 g of FeCl 2 · 4H 2 O and 500 g of FeCl 3 · 6H 2 O were dissolved, 6N NaOH aqueous solution was added dropwise with stirring until the pH reached 11, then aging at 80 ° C. for 30 minutes and cooling. The salt was removed by decantation to obtain an aqueous suspension of magnetite (magnetite concentration 10% by weight).
[0020]
To 2 L of this aqueous suspension, 500 ml of a 0.1 molar sodium oleate aqueous solution was added, and adsorption treatment was performed by heating for 2 hours while stirring at 5 rpm and 200 ° C. at a rotation speed of 600 rpm. After cooling, 1N hydrochloric acid was added until the pH reached 6 to adjust the pH. Acetone was added thereto to agglomerate the fine particles to obtain cake-like fine particles.
[0021]
The cake-like fine particles obtained were washed with an acetone-toluene (volume ratio 1: 1) mixed solution three times to remove excess surfactant, and then dried under reduced pressure overnight to obtain acetone and toluene. Was completely evaporated. The amount of the surfactant adsorbed was determined from the thermal analysis of the fine particles after drying and found to be 25% with respect to the total weight including the surfactant.
[0022]
Add 10g of the dried fine particles into 100g of kerosene, which is a low molecular weight base oil. Kerosene was removed under reduced pressure within a range not losing properties, and a ferrofluid (dispersion concentration: 12% by weight) having a saturation magnetization of 530G using kerosene as a base oil was obtained.
[0023]
In addition, the polybutenyl succinimide tetraethylenepentamine was added to 50 ml of the kerosene dispersion after centrifugation.
A solution prepared by dissolving 10 g in 50 ml of dodecylbenzene was added, and kerosene was completely removed under reduced pressure after ultrasonic irradiation.
[0024]
After heating this at 250 ° C. for 1 hour, acetone was added to agglomerate the fine particles to obtain cake-like fine particles. The cake-like fine particles were washed three times with an acetone-toluene (volume ratio 1: 1) mixed solution to remove excess polybutenyl succinimide tetraethylenepentamine, and then again put into kerosene using a homogenizer. Dispersed.
[0025]
After adding 4 g of higher alkylnaphthalene, the precipitate was removed by centrifugation, kerosene was completely removed under reduced pressure, and a ferrofluid with a saturation magnetization of 500 G (dispersion concentration 11 % By weight) was obtained.
[0026]
In Comparative Example, sodium oleate adsorption treatment was performed with stirring at 80 ° C. for 2 hours under atmospheric pressure to obtain cake-like fine particles, which were similarly washed and dried under reduced pressure. From the thermal analysis of the fine particles after drying, the adsorption amount of the surfactant was 15% of the total weight including the surfactant.
[0027]
Further, when the magnetic fluid using kerosene or higher alkylnaphthalene as a base oil was prepared in the same manner as in Examples using the dried fine particles, the saturation magnetizations thereof were 400 G and 380 G, respectively.
Claims (3)
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