JPH0226766B2 - - Google Patents
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- Publication number
- JPH0226766B2 JPH0226766B2 JP57214015A JP21401582A JPH0226766B2 JP H0226766 B2 JPH0226766 B2 JP H0226766B2 JP 57214015 A JP57214015 A JP 57214015A JP 21401582 A JP21401582 A JP 21401582A JP H0226766 B2 JPH0226766 B2 JP H0226766B2
- Authority
- JP
- Japan
- Prior art keywords
- fine particles
- surfactant
- oil
- organic solvent
- magnetic fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000002245 particle Substances 0.000 claims description 53
- 239000010419 fine particle Substances 0.000 claims description 52
- 230000005294 ferromagnetic effect Effects 0.000 claims description 48
- 239000004094 surface-active agent Substances 0.000 claims description 48
- 239000011553 magnetic fluid Substances 0.000 claims description 41
- 239000003960 organic solvent Substances 0.000 claims description 35
- 229920013639 polyalphaolefin Polymers 0.000 claims description 31
- 239000000203 mixture Substances 0.000 claims description 28
- 238000009835 boiling Methods 0.000 claims description 24
- 239000003963 antioxidant agent Substances 0.000 claims description 19
- 230000003078 antioxidant effect Effects 0.000 claims description 18
- 238000001704 evaporation Methods 0.000 claims description 12
- 125000004432 carbon atom Chemical group C* 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- -1 unsaturated fatty acid salt Chemical class 0.000 claims description 7
- 235000021122 unsaturated fatty acids Nutrition 0.000 claims description 7
- 150000004671 saturated fatty acids Chemical class 0.000 claims description 6
- 125000005471 saturated fatty acid group Chemical group 0.000 claims 1
- 239000003921 oil Substances 0.000 description 49
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 30
- 239000002609 medium Substances 0.000 description 23
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 22
- 238000000034 method Methods 0.000 description 22
- 230000005291 magnetic effect Effects 0.000 description 10
- 239000002612 dispersion medium Substances 0.000 description 9
- 230000008020 evaporation Effects 0.000 description 9
- 230000005415 magnetization Effects 0.000 description 8
- 239000000565 sealant Substances 0.000 description 7
- 238000001179 sorption measurement Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 239000006249 magnetic particle Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 239000000725 suspension Substances 0.000 description 6
- 150000004670 unsaturated fatty acids Chemical class 0.000 description 6
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 5
- 239000000084 colloidal system Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000314 lubricant Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- XDOFQFKRPWOURC-UHFFFAOYSA-N 16-methylheptadecanoic acid Chemical compound CC(C)CCCCCCCCCCCCCCC(O)=O XDOFQFKRPWOURC-UHFFFAOYSA-N 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 238000005119 centrifugation Methods 0.000 description 4
- 239000012530 fluid Substances 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 238000010298 pulverizing process Methods 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 description 3
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 description 3
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 description 3
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 description 3
- 239000005642 Oleic acid Substances 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000008346 aqueous phase Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 235000014113 dietary fatty acids Nutrition 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000000194 fatty acid Substances 0.000 description 3
- 229930195729 fatty acid Natural products 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- GJYCVCVHRSWLNY-UHFFFAOYSA-N 2-butylphenol Chemical compound CCCCC1=CC=CC=C1O GJYCVCVHRSWLNY-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 229940049918 linoleate Drugs 0.000 description 2
- 230000001050 lubricating effect Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000011859 microparticle Substances 0.000 description 2
- 239000002480 mineral oil Substances 0.000 description 2
- 235000010446 mineral oil Nutrition 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 235000003441 saturated fatty acids Nutrition 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000006228 supernatant Substances 0.000 description 2
- 239000004711 α-olefin Substances 0.000 description 2
- KVQVUCIQVFGPMS-UHFFFAOYSA-N 4-(octadecylamino)-4-oxo-2-sulfobutanoic acid Chemical compound CCCCCCCCCCCCCCCCCCNC(=O)CC(C(O)=O)S(O)(=O)=O KVQVUCIQVFGPMS-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910000531 Co alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerol Natural products OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- BCKXLBQYZLBQEK-KVVVOXFISA-M Sodium oleate Chemical compound [Na+].CCCCCCCC\C=C/CCCCCCCC([O-])=O BCKXLBQYZLBQEK-KVVVOXFISA-M 0.000 description 1
- RYYWUUFWQRZTIU-UHFFFAOYSA-N Thiophosphoric acid Chemical class OP(O)(S)=O RYYWUUFWQRZTIU-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 230000003064 anti-oxidating effect Effects 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- ZFMQKOWCDKKBIF-UHFFFAOYSA-N bis(3,5-difluorophenyl)phosphane Chemical compound FC1=CC(F)=CC(PC=2C=C(F)C=C(F)C=2)=C1 ZFMQKOWCDKKBIF-UHFFFAOYSA-N 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 1
- 239000003350 kerosene Substances 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 description 1
- 239000000693 micelle Substances 0.000 description 1
- NQNBVCBUOCNRFZ-UHFFFAOYSA-N nickel ferrite Chemical compound [Ni]=O.O=[Fe]O[Fe]=O NQNBVCBUOCNRFZ-UHFFFAOYSA-N 0.000 description 1
- 239000002736 nonionic surfactant Substances 0.000 description 1
- 229940049964 oleate Drugs 0.000 description 1
- 239000012074 organic phase Substances 0.000 description 1
- AJCDFVKYMIUXCR-UHFFFAOYSA-N oxobarium;oxo(oxoferriooxy)iron Chemical compound [Ba]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O AJCDFVKYMIUXCR-UHFFFAOYSA-N 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 125000000020 sulfo group Chemical group O=S(=O)([*])O[H] 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000001238 wet grinding Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Description
この発明はコロイド粒子の大きさのマグネタイ
ト、フエライトなどの強磁性酸化物微粒子または
鉄、コバルト合金などの強磁性体微粒子を鉱油、
合成油など極性の小さな油類にきわめて安全に分
散させた磁性流体組成物とその製造方法、特に高
い磁化能力をもつた磁性流体組成物と、その効率
的な製造方法に関する。
磁性流体は液相中に上記微粒子をきわめて安定
に分散させたコロイド溶液であるから、磁力、重
力、遠心力などによつて磁性微粒子が凝集・沈澱
して液相と分離することがなく、磁場により見掛
け上液体自身が強い磁性を示す特性をもつたもの
である。
このため、近年、シーリング剤、ダンピング
剤、或いは接触部の潤滑剤その他各方面に、その
特異な性質を生かした用途が開拓され、注目され
ている。
磁性流体の液相としては種々の液体を用い得る
が、軸受潤滑剤、シーリング剤としての用途向け
には１潤滑性２耐熱性３低揮発性４化学的安定性
などが要求されるので、鉱油、合成油などの油類
が最も適している。
中でもポリアルフアオレフイン油は、ジオクチ
ルアジペートなどのエステル類に比べて、より低
揮発性で、水に対しても化学的に安定であり、同
じ蒸発速度をもつ鉱油に対しては低粘度であると
いう優れた性能をもつているので、磁気デイスク
向けのシーリング剤としては最適なものである。
このような油類を分散媒とした分散質の表面性
状は、分散媒とのぬれを良くするために親油性で
あることが必要となる。
シーリング剤に用いるときは、シール機構を構
成する磁石の磁速に拘束された磁性流体によりシ
ール作用がなされるから、磁性流体の強化は強い
ほど強固なシールが可能となる。軸受潤滑剤に用
いるときも、軸受機構を構成する磁石の磁力に拘
束された磁性流体が潤滑剤となるから、磁性流体
の磁化が強いほど大きな軸回転に伴う機械的撹拌
力に対抗可能となり、はねとばされて潤滑剤が損
耗したり、周辺を汚損したりする現象を防止でき
る。ところで磁性流体の磁化の強さは、流体中に
含まれる磁性粒子の濃度に左右される。したがつ
て、磁性粒子の濃度の高い磁性流体を得ることは
極めて重要な課題である。しかし、一般には、粒
子濃度を高めれば高める程、粒子同志の間隔が小
さくなるため、凝集し易くなるから、最適の分散
性を全ての粒子がもつようにしないと、高濃度の
磁性流体は得られない。流体中に凝集しやすい大
きい粒子や、界面活性剤の吸着が完全でない粒子
が多いと、濃度の向上には限界が生じてしまうこ
とになる。
これまで、磁性流体の製造方法としては、オレ
イン酸を含む有機相中でマグネタイトを粉砕する
方法が一般に知られている。
この方法は、磁性流体を製造するのに、特に吸
着工程において、長時間を要するという点に問題
があつた。
また、いわゆる共沈法で磁性コロイド粒子を形
成させる場合、反応条件を選択することにより粒
径50〜100Åに調整することも知られている。
本発明者らは、効率において粉砕法より優れた
湿式法において磁性粒子の濃度の高い安定した磁
性流体組成物およびその組成物を得る方法を開発
すべく研究を重ねた結果、磁性粒子は、粒径分布
をもつており高濃度の磁性流体を得るには、粒径
の大きな粒子を取り除く必要があること、使用目
的によつては、10年以上にわたつて安定性を要求
されるものがあり、界面活性剤の吸着力を高める
ため、吸着条件、吸着量を制御する必要があると
いう知見を得た。
すなわち、粒子の選別をすることが有効である
と共に吸着は、粒子の等電位点以下で行うことが
有効である。すなわち、等電位点以下で粒子は正
に帯電し、例えば不飽和脂肪酸など水溶液中で負
の電荷をもつ界面活性剤は吸着しやすく又吸着後
の固液分離も容易であるからである。そして、不
飽和脂肪酸等の界面活性剤が過剰にある場合は、
油状脂肪酸ができやすく、粒子の分散安定性に悪
影響を及ぼしやすいので、界面活性剤の量を制御
することが有効である。
本発明は、このような点に着目してなされたも
ので、特に強磁性体微粒子を高濃度にし、高い磁
化能力をもつ磁性流体を効率的に得る磁性流体組
成物およびその製造方法を提供することを目的と
している。
上記の目的を達成するためのこの発明の要旨と
するところは、炭素数が25以上45以下のものを主
成分とするポリアルフアオレフイン油と、粒径が
20〜500Aの粒子を体積比１〜20％の範囲で前記
油中に分散させた強磁性体微粒子と、この微粒子
に吸着する炭素数10以上の不飽和脂肪酸である第
１の界面活性剤及び炭素数18以上の飽和脂肪酸で
ある第２の界面活性剤と、前記油に対し重量比
0.1〜10％の範囲で含まれる酸化防止剤とからな
る磁性流体組成物である。又、強磁性体微粒子に
界面活性剤と低沸点有機溶媒とを加え、表面を界
面活性剤で被覆した強磁性体微粒子が低沸点有機
溶媒中に分散された中間媒体を得る工程と、該中
間媒体中の分散性の悪い微粒子を分離した後、ポ
リアルフアオレフイン油と炭素数18以上の飽和脂
肪酸と酸化防止剤とを中間媒体に加えて混合物と
する工程と、該混合物を加熱し、低沸点有機溶媒
を蒸発させる工程とを包含す前記磁性流体組成物
の製造方法である。
更に又、強磁性体微粒子に界面活性剤と低沸点
有機溶媒とを加え、表面を界面活性剤で被覆した
強磁性体微粒子が低沸点有機溶媒中に分散された
中間媒体を得る工程と、該中間媒体中の分散性の
悪い微粒子を分離した後、中間媒体を加熱し、低
沸点有機溶媒を蒸発させる工程と、該工程を経た
強磁性体微粒子にポリアルフアオレフイン油と炭
素数18以上の飽和脂肪酸と酸化防止剤とを加える
工程とを包含する前記磁性流体組成物の製造方法
である。
以下、この発明の磁性流体組成物とその製造方
法を説明する。
この発明の強磁性体微粒子の分散媒は、低揮発
性で、かつ低粘度のポリアルフアオレフイン油で
ある。
一般に、ポリアルフアオレフイン油は、低級ア
ルフアオレフインを原料として、重合度を制御す
ることによつて製造したオリゴマーで、その化学
式は例えば、次のようになる。
ポリアルフアオレフイン油は、種々の粘度グレ
ードの潤滑液が合成されているが、そのグレード
は、上記化学式のｎの違いによる。（通常ｎ量体
といる表現が使用されているが、これは、重合す
る前の低級アルフアオレフインのｎ倍を意味して
いる。）ポリアルフアオレフイン油のうち、潤滑
液としては、３〜６量体で構成されており、粘度
グレードは以下の表のとおり、数種類のｎ量体で
できている。
This invention uses fine particles of ferromagnetic oxides such as magnetite and ferrite, or fine particles of ferromagnetic substances such as iron and cobalt alloys, having the size of colloidal particles, in mineral oil,
The present invention relates to a magnetic fluid composition that is extremely safely dispersed in oils with low polarity such as synthetic oil and a method for producing the same, and particularly to a magnetic fluid composition with high magnetization ability and an efficient method for producing the same. Since magnetic fluid is a colloidal solution in which the above-mentioned fine particles are extremely stably dispersed in a liquid phase, the magnetic fine particles do not aggregate or precipitate due to magnetic force, gravity, centrifugal force, etc. and are not separated from the liquid phase. Due to this, the liquid itself apparently has the property of exhibiting strong magnetism. Therefore, in recent years, applications that take advantage of its unique properties have been developed and are attracting attention as sealants, damping agents, lubricants for contact parts, and other various fields. Various liquids can be used as the liquid phase of magnetic fluid, but for applications as bearing lubricants and sealants, the following properties are required: 1. Lubricity 2. Heat resistance 3. Low volatility 4. Chemical stability , synthetic oil and other oils are most suitable. Among them, polyalphaolefin oil has lower volatility than esters such as dioctyl adipate, is chemically stable in water, and has a lower viscosity than mineral oil, which has the same evaporation rate. Due to its excellent performance, it is ideal as a sealant for magnetic disks. The surface properties of a dispersoid using such an oil as a dispersion medium need to be lipophilic in order to improve wetting with the dispersion medium. When used as a sealant, the sealing action is performed by a magnetic fluid that is constrained by the magnetic velocity of the magnet that constitutes the sealing mechanism, so the stronger the reinforcement of the magnetic fluid, the stronger the seal. When used as a bearing lubricant, the lubricant is a magnetic fluid bound by the magnetic force of the magnets that make up the bearing mechanism, so the stronger the magnetization of the magnetic fluid, the more capable it is of resisting the mechanical agitation force that accompanies large shaft rotations. This prevents the lubricant from being blown away, causing wear and tear, and contaminating the surrounding area. By the way, the strength of magnetization of a magnetic fluid depends on the concentration of magnetic particles contained in the fluid. Therefore, obtaining a magnetic fluid with a high concentration of magnetic particles is an extremely important issue. However, in general, the higher the particle concentration, the smaller the distance between particles, which makes them more likely to aggregate, so a highly concentrated magnetic fluid cannot be used unless all particles have optimal dispersibility. I can't. If there are many large particles that tend to aggregate in the fluid or particles that do not completely adsorb the surfactant, there will be a limit to the improvement of the concentration. Until now, as a method for producing magnetic fluids, a method of pulverizing magnetite in an organic phase containing oleic acid is generally known. This method has a problem in that it takes a long time to produce the magnetic fluid, especially in the adsorption step. It is also known that when magnetic colloid particles are formed by a so-called coprecipitation method, the particle size can be adjusted to 50 to 100 Å by selecting reaction conditions. The present inventors have conducted extensive research to develop a stable magnetic fluid composition with a high concentration of magnetic particles and a method for obtaining the composition using a wet method that is superior to the pulverization method in terms of efficiency. In order to obtain a highly concentrated magnetic fluid with a size distribution, it is necessary to remove large particles, and depending on the purpose of use, some fluids may require stability for more than 10 years. We obtained the knowledge that in order to increase the adsorption power of surfactants, it is necessary to control the adsorption conditions and adsorption amount. In other words, it is effective to sort out the particles, and it is also effective to perform the adsorption below the equipotential point of the particles. That is, particles are positively charged below the equipotential point, and surfactants that are negatively charged in an aqueous solution, such as unsaturated fatty acids, are easily adsorbed and solid-liquid separation after adsorption is also easy. If there is an excess of surfactants such as unsaturated fatty acids,
It is effective to control the amount of surfactant because oily fatty acids are likely to form and have a negative effect on the dispersion stability of the particles. The present invention has been made in view of these points, and provides a magnetic fluid composition and a method for producing the same, in which a magnetic fluid having high magnetization ability can be efficiently obtained by specifically increasing the concentration of fine ferromagnetic particles. The purpose is to The gist of this invention to achieve the above object is to use a polyalphaolefin oil whose main component is a carbon number of 25 to 45 and a particle size of
ferromagnetic fine particles in which particles of 20 to 500 A are dispersed in the oil at a volume ratio of 1 to 20%; a first surfactant that is an unsaturated fatty acid having a carbon number of 10 or more adsorbed to the fine particles; a second surfactant which is a saturated fatty acid having 18 or more carbon atoms and a weight ratio of the second surfactant to the oil;
and an antioxidant in the range of 0.1-10%. Further, a step of adding a surfactant and a low boiling point organic solvent to the ferromagnetic fine particles to obtain an intermediate medium in which the ferromagnetic fine particles whose surfaces are coated with the surfactant are dispersed in the low boiling point organic solvent; After separating fine particles with poor dispersibility in the medium, a step of adding polyalphaolefin oil, a saturated fatty acid having 18 or more carbon atoms, and an antioxidant to an intermediate medium to form a mixture, and heating the mixture to form a mixture with a low boiling point. and evaporating an organic solvent. Furthermore, a step of adding a surfactant and a low boiling point organic solvent to the ferromagnetic fine particles to obtain an intermediate medium in which the ferromagnetic fine particles whose surfaces are coated with the surfactant are dispersed in the low boiling point organic solvent; After separating fine particles with poor dispersibility in the intermediate medium, there is a step of heating the intermediate medium to evaporate the low-boiling point organic solvent, and adding polyalphaolefin oil and a saturated carbon number of 18 or more to the ferromagnetic fine particles that have undergone this step. and adding a fatty acid and an antioxidant. Hereinafter, the magnetic fluid composition of the present invention and its manufacturing method will be explained. The dispersion medium for the ferromagnetic fine particles of the present invention is a polyalphaolefin oil with low volatility and low viscosity. In general, polyalphaolefin oil is an oligomer produced by controlling the degree of polymerization using lower alphaolefin as a raw material, and its chemical formula is, for example, as follows. Lubricating liquids of various viscosity grades have been synthesized from polyalphaolefin oils, and the grades depend on the difference in n in the above chemical formula. (The expression "n-mer" is usually used, but this means n times the lower alpha-olefin before polymerization.) Among poly-alpha-olefin oils, as a lubricating liquid, 3 to 6 The viscosity grade is made up of several types of n-mers, as shown in the table below.
【表】
化したものの値である。
この発明にあつては、例えば、磁気デイスク用
シーリング剤の磁性流体の性能を考慮すると、上
記の粘度６のものが優れていることを見出した。
これは、粘度４、５のものは蒸発量が多く、粘度
38〜43のものはトルクが大きく、温度上昇が起こ
るからである。
この粘度６のものは、炭素数にすると、C30、
C40が主成分である。従つて、この発明のポリア
ルフアオレフイン油の炭素数の主成分の範囲は
C25〜C45であり、望ましくは４量体（C40）が多
い分子量分布を構成するものである。
この発明の強磁性体微粒子としては、既に述べ
た湿式法によつて得られるマグネタイトコロイド
を用い得る。また、水もしくは有機溶媒中でマグ
ネタイト粉末をボールミル粉砕するいわゆる湿式
粉砕法で得られるものでもよい。
湿式粉砕法を利用する場合、研削液として水以
外のものすなわち後述する有機溶媒を用いるとき
は、所望の強磁性体粉末とその粒子表面に単分子
層を形成できる量の界面活性剤を加えたうえでボ
ールミル中で数時間以上粉砕しても良い。この有
機溶媒をベースとした磁性流体では、過剰の界面
活性剤により形成される油状物のため、生成する
コロイド状微粒子の分留りが悪くなることはな
い。また、マグネタイト以外のマンガンフエライ
ト、ニツケルフエライト、コバルトフエライトも
しくはこれらと亜鉛の複合フエライトやバリウム
フエライトなどの強磁性酸化物を用いることもで
きる。
更にまた、強磁性体微粒子として、上記湿式法
或いは湿式粉砕法によるもののほか、乾式法で得
たものを用いてもよい。
この発明の強磁性体微粒子の粒径は20〜500A
の間にある。例えばマグネタイトは格子定数約
8Aの単位格子で逆スピネル構造をとり、結晶は
単位格子が数個以上でなりたつから、少くとも
20A以上の粒子径が必要となる。一方粒子径の上
限については、磁性微粒子の懸濁液としての磁性
流体の安定性の見地からみると、λ＝Ms2V2／
d3kTで表わされるパラメータλの値が重要とな
る。（ここにMs：飽和磁化、Ｖ：粒子の体積、
ｄ：粒子の直径ｋ：ボルツマン定数、Ｔ：絶対温
度）。一般に、粒子表面に吸着形成された界面活
性剤層の反撥力によつて、粒子間引力及び磁性粒
子のもつ磁気双極子間引力に抗して、凝集を防止
できる限界値はλ＝103とされる。そこで、今安
全を見積もりλ＝102とし、かつ飽和磁化Ms＝
400Gとすると、上式より、求める粒子径ｄの上
限は500Aである。もつとも、望ましい粒径は
100A前後である。
この場合には上式に於けるMs＝400Gのときλ
＝１となり、分散磁性微粒子は長時間静置して
も、沈降するおそれはない。
この発明の強磁性体微粒子の含有量は、体積比
１〜20％の範囲であり、望ましくは２〜10％であ
る。ケロシンにオレイン酸をベースとする界面活
性剤層を形成したマグネタイト粒子を分散させて
なる最も単純な系としての磁性流体に於て、その
粘度は、粒子濃度0.5ｇ／mlの付近を過ぎると急
激に上昇することが知られている。
上記濃度は粒子表面を被覆しているオレイン酸
の長さを考慮すると、体積濃度で約20％であり、
更に複雑な系にあつては、粘度の大巾な上昇をも
たらさないためには、粒子濃度は体積比20％以下
とする必要がある。
一方、上記系に於て磁性流体が磁化を示すに
は、粒子濃度0.05ｇ／ml以上必要とすることも知
られており、これは体積濃度にして約１％以上と
なる。ただし、ポリアルフアオレフイン油をベー
スとした磁性流体をシーリング剤の用途に供する
に際しては、実用上求められる耐圧性能を考慮す
れば、その最も望ましい粒子濃度は体積比で２〜
10％の範囲となる。
この発明の工程は、上述の強磁性体微粒子に第
１の界面活性剤と低沸点有機溶媒とを加え、表面
を界面活性剤で被覆した強磁性体微粒子が低沸点
有機溶媒中に分散された中間媒体を得る工程を包
含する。
上記の第１の界面活性剤としては、カルボキシ
ル基（−COOH）、ヒドロキシ基（−OH）、スル
ホ基（−SO3H）などの極性基を少なくとも１個
以上有し、炭素数が10以上のものであればよい。
炭素数10以下のものは微粒子の分散状態が良好に
ならないからである。このような界面活性剤は、
オレイン酸イオン、リノール酸イオン、リノレイ
ン酸イオン、エルカ酸イオンなどの不飽和脂肪酸
のナトリウム塩やカリウム塩もしくはＮ−（１、
２ジカルボキシエチル）、Ｎ−ステアリルスルホ
サクシナメートなどがある。この種の不飽和脂肪
酸は不飽和部分の極性により臨界ミセル濃度（C.
M.C）が高いので、強磁性体微粒子である酸化鉄
に対する吸着性が良い。
この第１の界面活性剤を加えるに際して、例え
ば強磁性体微粒子が、既に述べた湿式法を利用し
て得たものである場合には、懸濁液に酸を加えて
PHをコロイド粒子の等電位点以下となるように調
整する。
コロイド粒子が鉄酸化物の場合はPH７以下が好
ましい。これによりコロイド粒子の表面は正電荷
となり、界面活性剤イオンが吸着され易くなる。
加える界面活性剤の量はコロイド状の強磁性体
微粒子表面に単分子層を形成することのできる量
とし、過剰添加による油状物の生成ないし２分子
層形成による親水性コロイドの生成を防止するの
が良い。界面活性剤イオンを単分子層吸着して疎
水性（すなわち親油性）とした微粒子の懸濁液中
に有機溶媒を加えることにより、水相中の微粒子
を有機溶媒相に移行せしめて、有機溶媒中に強磁
性体微粒子が分散した状態の中間媒体を得る。な
お層別した水相は分液して除去するが、多少有機
溶媒中に残る水分は加熱蒸発で除去できる。また
この時、水相の懸濁液の状態で、有機溶媒を加え
る必要は必ずしもない。すなわち、水懸濁液をい
つたん洗浄・乾燥して、疎水性強磁性体微粒子を
得たのち、有機溶媒を加えて、分散させてもよ
い。
この発明の中間媒体を得る手順は、必ずしも上
記に限定されるものではない。すなわち、強磁性
体微粒子に低沸点有機溶媒を加えて懸濁液とし、
その後に界面活性剤を加えて中間媒体を得てもよ
く、もしくは界面活性剤と低沸点有機溶媒との混
合液を加えて中間媒体を得てもよい。
この発明の工程は、前記中間媒体中の分散性の
悪い微粒子を例えば5000〜8000Gで遠心分離して
除去した後、ポリアルフアオレフイン油と第２の
界面活性剤と酸化防止剤を加えて十分に撹拌し混
合物とするものである。
前記中間媒体の状態で強磁性体微粒子は分散性
のよいものと悪いものとが選別される。一度目の
選別は有機溶媒に分散させる時に行われ、二度目
の選別は、さらにその中から遠心力によつて選別
される。
このように選別をくり返すことにより、中間媒
体中の強磁性体微粒子の濃度はかなり減少する
が、中間媒体は容易に揮発させ得るので、ポリア
ルフアオレフイン油にくり返し加えることによつ
て、多量の強磁性体微粒子を磁性流体中に分散さ
せることができる。
もし、このような中間媒体を用いず、直接分散
媒であるポリアルフアオレフイン油を加えた場
合、分散媒はその用途から低揮発性を要求される
ので、もともと加熱による蒸溜濃縮は困難であ
る。
又、最初にポリアルフアオレフイン油の量を少
な目に調整して強磁性体微粒子の含有率を高めよ
うとしても、必ず、分散性が余りよくない強磁性
体微粒子も一緒にいつたん油中にとりこまれ、こ
のため、分散性のよい強磁性体微粒子の含有率は
制限され、もともと少なくなつてしまう。
しかも、これら分散性が不十分な強磁性体微粒
子は遠心分離の際にそれら自身が分離沈降するの
みならず、隣接して浮遊していた分散性のよい強
磁性体微粒子と一緒に沈降してしまうために、非
常に多くの沈澱物を生じ、油中の強磁性体微粒子
は著しく減少し、性能上必要な強磁性体微粒子濃
度を得ることは困難である。
前記第２の界面活性剤としては、ポリアルフア
オレフイン油と乳化または可溶性で、炭素数が18
以上の飽和脂肪酸を用いる。ポリアルフアオレフ
イン油を分散媒とする磁性流体の場合は、界面活
性剤として非イオン系の例えばポリ脂肪酸グリセ
リンエステルを用いるより、脂肪酸カルボン酸を
用いた方が磁粉の濃度があがり、その結果表−１
の如く飽和磁化が高くなる。[Table] These are the converted values.
In the present invention, for example, when considering the performance of the magnetic fluid used as a sealant for magnetic disks, it has been found that a sealant having a viscosity of 6 is excellent.
This is because those with a viscosity of 4 or 5 have a large amount of evaporation, and the viscosity
This is because those with numbers 38 to 43 have a large torque and cause a rise in temperature. This one with a viscosity of 6 has a carbon number of C 30 ,
C40 is the main component. Therefore, the range of the main component of the carbon number of the polyalphaolefin oil of this invention is
It is C25 to C45 , and preferably constitutes a molecular weight distribution with a large amount of tetramer ( C40 ). As the ferromagnetic fine particles of the present invention, magnetite colloid obtained by the wet method described above can be used. Alternatively, it may be obtained by a so-called wet pulverization method in which magnetite powder is pulverized in a ball mill in water or an organic solvent. When using the wet grinding method, when using something other than water as the grinding fluid, that is, an organic solvent described below, add the desired ferromagnetic powder and an amount of surfactant that can form a monomolecular layer on the particle surface. Then, it may be ground in a ball mill for several hours or more. In this organic solvent-based magnetic fluid, the fractionation of colloidal fine particles produced does not deteriorate due to oily substances formed by excess surfactant. Furthermore, ferromagnetic oxides other than magnetite such as manganese ferrite, nickel ferrite, cobalt ferrite, composite ferrite of these and zinc, and barium ferrite can also be used. Furthermore, as the ferromagnetic fine particles, in addition to those obtained by the above-mentioned wet method or wet pulverization method, those obtained by a dry method may be used. The particle size of the ferromagnetic fine particles of this invention is 20 to 500A.
It's between. For example, magnetite has a lattice constant of approximately
It has an inverse spinel structure with a unit cell of 8A, and since the crystal consists of several or more unit cells, at least
A particle size of 20A or more is required. On the other hand, regarding the upper limit of the particle size, from the viewpoint of the stability of the magnetic fluid as a suspension of magnetic fine particles, λ=Ms 2 V 2 /
The value of the parameter λ, expressed as d 3 kT, is important. (where Ms: saturation magnetization, V: volume of particle,
d: particle diameter, k: Boltzmann constant, T: absolute temperature). In general, the limit value at which agglomeration can be prevented by resisting interparticle attraction and magnetic dipole attraction of magnetic particles due to the repulsive force of a surfactant layer adsorbed and formed on the particle surface is λ = 10 3 . be done. Therefore, we now estimate safety by setting λ = 10 2 and saturation magnetization Ms =
Assuming 400G, the upper limit of the particle diameter d to be determined is 500A from the above equation. However, the desirable particle size is
It is around 100A. In this case, when Ms=400G in the above equation, λ
= 1, and there is no fear that the dispersed magnetic fine particles will settle even if they are left standing for a long time. The content of the ferromagnetic fine particles of the present invention is in a volume ratio of 1 to 20%, preferably 2 to 10%. In the simplest magnetic fluid system, which is made by dispersing magnetite particles with an oleic acid-based surfactant layer in kerosene, the viscosity decreases rapidly when the particle concentration exceeds 0.5 g/ml. It is known to rise to The above concentration is approximately 20% by volume, considering the length of oleic acid coating the particle surface.
In more complex systems, the particle concentration needs to be 20% or less by volume in order to avoid a significant increase in viscosity. On the other hand, it is also known that in order for the magnetic fluid to exhibit magnetization in the above system, a particle concentration of 0.05 g/ml or more is required, which is about 1% or more in terms of volume concentration. However, when using a magnetic fluid based on polyalphaolefin oil as a sealant, the most desirable particle concentration in terms of volume ratio is 2 to
The range is 10%. In the process of this invention, a first surfactant and a low boiling point organic solvent are added to the above-mentioned ferromagnetic fine particles, and the ferromagnetic fine particles whose surfaces are coated with the surfactant are dispersed in the low boiling point organic solvent. The method includes a step of obtaining an intermediate medium. The above-mentioned first surfactant has at least one polar group such as a carboxyl group (-COOH), a hydroxyl group (-OH), or a sulfo group (-SO 3 H), and has 10 or more carbon atoms. It is fine as long as it is from .
This is because if the carbon number is less than 10, the fine particles will not be well dispersed. Such surfactants are
Sodium or potassium salts of unsaturated fatty acids such as oleate ion, linoleate ion, linoleate ion, erucate ion, or N-(1,
2dicarboxyethyl), N-stearyl sulfosuccinamate, and the like. This type of unsaturated fatty acid has a critical micelle concentration (C) due to the polarity of the unsaturated moiety.
Since it has a high MC), it has good adsorption to iron oxide, which is a ferromagnetic fine particle. When adding this first surfactant, for example, if the ferromagnetic fine particles are obtained using the wet method described above, an acid is added to the suspension.
Adjust the pH so that it is below the equipotential point of the colloidal particles. When the colloidal particles are iron oxide, the pH is preferably 7 or less. This makes the surface of the colloid particles positively charged, making it easier for surfactant ions to be adsorbed. The amount of surfactant to be added is such that it can form a monomolecular layer on the surface of the colloidal ferromagnetic fine particles, and should be sufficient to prevent the formation of an oily substance due to excessive addition or the formation of a hydrophilic colloid due to the formation of a bimolecular layer. is good. By adding an organic solvent to a suspension of microparticles made hydrophobic (i.e. lipophilic) by adsorbing a monomolecular layer of surfactant ions, the microparticles in the aqueous phase are transferred to the organic solvent phase, and the organic solvent An intermediate medium having ferromagnetic fine particles dispersed therein is obtained. Note that the stratified aqueous phase is removed by separation, but some water remaining in the organic solvent can be removed by heating and evaporation. Further, at this time, it is not necessarily necessary to add an organic solvent to the aqueous phase in a suspension state. That is, after the aqueous suspension is washed and dried to obtain hydrophobic ferromagnetic fine particles, an organic solvent may be added and dispersed. The procedure for obtaining the intermediate medium of this invention is not necessarily limited to the above. That is, a low boiling point organic solvent is added to ferromagnetic fine particles to form a suspension,
Thereafter, a surfactant may be added to obtain an intermediate medium, or a mixture of a surfactant and a low-boiling organic solvent may be added to obtain an intermediate medium. In the process of this invention, fine particles with poor dispersibility in the intermediate medium are removed by centrifugation at, for example, 5,000 to 8,000 G, and then polyalphaolefin oil, a second surfactant, and an antioxidant are added to sufficiently Stir to form a mixture. In the state of the intermediate medium, ferromagnetic fine particles are sorted into those with good dispersibility and those with poor dispersibility. The first sorting is performed when dispersing in an organic solvent, and the second sorting is carried out by centrifugal force. By repeating the sorting in this way, the concentration of ferromagnetic fine particles in the intermediate medium is considerably reduced, but since the intermediate medium can be easily volatilized, a large amount of ferromagnetic particles can be obtained by repeatedly adding it to polyalphaolefin oil. Ferromagnetic particles can be dispersed in a magnetic fluid. If polyalphaolefin oil, which is a dispersion medium, is directly added without using such an intermediate medium, the dispersion medium is required to have low volatility due to its intended use, so distillation and concentration by heating is originally difficult. Furthermore, even if you initially try to increase the content of ferromagnetic particles by adjusting the amount of polyalphaolefin oil to a small amount, the ferromagnetic particles, which do not have very good dispersibility, will always be absorbed into the oil. Therefore, the content of ferromagnetic fine particles with good dispersibility is limited and is originally small. Moreover, these ferromagnetic particles with insufficient dispersibility not only separate and settle themselves during centrifugation, but also settle together with the ferromagnetic particles with good dispersibility that were floating adjacent to them. As a result, a large amount of precipitate is generated and the ferromagnetic particles in the oil are significantly reduced, making it difficult to obtain the concentration of ferromagnetic particles required for performance. The second surfactant is emulsifiable or soluble with polyalphaolefin oil and has 18 carbon atoms.
The above saturated fatty acids are used. In the case of a magnetic fluid using polyalphaolefin oil as a dispersion medium, the concentration of magnetic particles is higher when a fatty acid carboxylic acid is used as a surfactant than when a nonionic surfactant such as a polyfatty acid glycerin ester is used. 1
The saturation magnetization increases as shown in FIG.
【表】
この第２の界面活性剤は、そのカルボキシル基
が強磁性体微粒子に強く吸着する性質をもつてい
るので、強磁性体微粒子のうち、第１の界面活性
剤が十分に吸着していない粒子があると、その表
面にカルボキシル基が吸着して油とのぬれ性を高
める効果を示す。分散媒であるポリアルフアオレ
フイン油は既に述べたように、その主成分の炭素
数の範囲が25以上45以下であるから、用いる界面
活性剤の炭素数も多い方がよく、炭素数18以上が
好ましい。また飽和脂肪酸は不飽和脂肪酸と異な
り二重結合がないから熱的安定性の点でより優利
である。
酸化防止剤としては、炭化水素の酸化防止用に
一般的に用いられているもの、例えばフエノール
類、アミン類その他チオりん酸塩等を用いてよ
い。また相乗効果を得るために数種類の酸化防止
剤を併用することもあり得る。酸化防止剤の添加
量は、油に対し重量比で0.1〜10％の範囲であれ
ばよい（第２図参図。但し、油はパオール60、酸
化防止剤は４−4′メチレンビス−２、６−ジタル
ト（tert）−ブチルフエノールで、温度は80℃の
場合につき、油の酸化の度合いを油の蒸発量によ
り表示してある。上記範囲の上限を越えると、酸
化防止剤自身が炭化水素酸化反応に寄与し始める
などして、効果はかえつて減少することとなる。
この発明の工程は、以上のようにして得られた
混合物を大気中または真空中で加熱し、低沸点の
有機溶媒を蒸発させるものである。この蒸発過程
において、有機溶媒相中に分散していた強磁性体
微粒子は油の中に移行し、最終的に所望の油を液
相とする磁性流体が得られる。
油と有機溶媒との極性は比較的近いものにして
あるから、蒸発に伴う磁性体微粒子の移行は極め
て自然に円滑に行われ、油中に分散する粒子濃度
が濃い場合も安定分散を保つことができる。
この発明の工程は、前記中間媒体中の分散性の
悪い微粒子を分離した後は、上述とは異なり、そ
の中間媒体を加熱することにより、先に低沸点有
機溶媒を蒸発させるものとしてもよい。その場合
には、この低沸点有機溶媒蒸発工程の後に、強磁
性体微粒子にポリアルフアオレフイン油と第２の
界面活性剤と酸化防止剤とを加える工程が続くこ
ととなる。
このようにして得たポリアルフアオレフイン油
を媒体とする磁性流体を、更に5000〜8000Gで遠
心分離した後、別の新たな低沸点有機溶媒を媒体
とする磁性流体（すなわち新たな工程で得る中間
媒体）と再び混合する工程と、この混合物から低
沸点有機溶媒を蒸発させる工程とを繰り返すこと
により、分散性の高い微粒子をさらに付加せしめ
て、微粒子濃度の極めて高い磁性流体を得ること
ができる。
この発明によれば、強磁性体微粒子を新油性と
したのち、一旦低沸点の有機溶媒を媒体とする中
間媒体とし、次いでこれに極性の近いポリアルフ
アオレフイン油と第２の界面活性剤と酸化防止剤
とを加えて得た混合物を蒸溜することにより、或
いは先に中間媒体を加熱し、次いでポリアルフア
オレフイン油と第２の界面活性剤と酸化防止剤と
を加えるようにして、中間媒体中の低沸点分を除
去し濃縮するようにしたため、油中に強磁性体微
粒子を高濃度に安定して分散すると共に耐酸化防
止能力をも備えた磁性流体組成物を、効率よく、
経済的に製造することができるという効果が得ら
れる。
以下に、この発明の実施例を説明する。
実施例 １
ポリアルフアオレフイン油（Bray Oil社、Ｐ
−60）を分散媒とし、第２の界面活性剤としてイ
ソステアリン酸を用い、マグネタイトを分散質と
した磁性流体組成物の作成。
まず、硫酸第一鉄と硫酸第二鉄の各１モル／
の水溶液１に6NのNaOH水溶液をPHが11以上
になるまで加えた後、60℃で30分間熟成して、マ
グネタイトコロイドを得た。その後、60℃に保つ
たままこのマグネタイト懸濁液に3NのHCl溶液
を加えてPH４〜５の間に調整した後、第１の界面
活性剤としてオレイン酸ナトリウムを20ｇ添加
し、30分間撹拌する。静置し、マグネタイト粒子
を凝集させた後、上澄を拾てて水を加え、その水
を拾てるという水洗を繰り返して電解質を除く。
この際、PHが上昇して分散状態になつた時は、更
に少量のHClを加える。その後、この液をろ過
し、マグネタイト粒子を脱水する。このマグネタ
イト粒子に低沸点有機溶媒としてヘキサンを加え
よく混合した液を4000Gの遠心力下に20分間遠心
分離する。その上部の上澄液を取りろ過した後、
分液ろうとに移す。静置して水とヘキサンを分離
し、マグネタイトが分散したヘキサンを取り出
す。このヘキサン溶液を90℃に保ち、ロータリエ
バポレータでヘキサンを蒸発させる。蒸発後エバ
ポレータのフラスコ内に残つたマグネタイト粒子
を取り出し、真空恒温乾燥器内に入れる。100℃
で１時間保ち、マグネタイト粒子を完全に乾燥さ
せる。
乾燥後、マグネタイト粒子を２ｇ取り、ヘキサ
ンに再分散させた後、ポリアルフアオレフイン油
（Ｐ−60）を５c.c.、第２の界面活性剤としてイソ
ステアリン酸0.03c.c.、および酸化防止剤として
４，4′メチレンビス−２，６−ジ・タルト（tert）
−ブチルフエノール0.05ｇを加え、よく混合す
る。混合後、ロータリエバポレータでヘキサンを
蒸発させる。蒸発後、マグネタイトはポリアルフ
アオレフイン油（Ｐ−60）に分散させる。これを
8000Gの遠心分離下で60分間分離する。この操作
によつて非分散固形物は取り除かれたが、その上
部のコロイド溶液は極めて安定な磁性流体であつ
た。
実施例 ２
ポリアルフアオレフイン油（Bray Oil社、Ｐ
−60）を分散媒とし、第２の界面活性剤としてメ
リシン酸を用い、マグネタイトを分散質とした磁
性流体組成物の作成。
マグネタイトの作成法およびヘキサンに分散さ
せる方法および乾燥法は実施例１と同様である。
乾燥後、マグネタイト粒子を２ｇ取り、ヘキサ
ンに再分散させた後、ポリアルフアオレフイン油
（Ｐ−60）を５c.c.、メリシン酸0.03ｇ、実施例１
と同じ酸化防止剤0.05ｇを加え、よく混合する。
混合後、ロータリエバポレータでヘキサンを蒸発
させる。蒸発後、マグネタイトはポリアルフアオ
レフイン油（Ｐ−60）に分散させる。これを
8000Gの遠心分離下で60分間分離する。この操作
によつて非分散固形物は取り除かれたが、その上
部コロイド溶液は極めて安定な磁性流体であつ
た。[Table] This second surfactant has a property that its carboxyl group strongly adsorbs to the ferromagnetic fine particles, so the first surfactant is not sufficiently adsorbed to the ferromagnetic fine particles. If there are particles that do not have carboxyl groups on their surfaces, carboxyl groups will be adsorbed on their surfaces, which will have the effect of increasing their wettability with oil. As mentioned above, the polyalphaolefin oil used as a dispersion medium has a carbon number range of 25 or more and 45 or less as its main component, so it is better to use a surfactant with a larger number of carbon atoms. preferable. Also, unlike unsaturated fatty acids, saturated fatty acids do not have double bonds, so they are more advantageous in terms of thermal stability. As the antioxidant, those commonly used for preventing the oxidation of hydrocarbons, such as phenols, amines, and thiophosphates, may be used. It is also possible to use several types of antioxidants in combination to obtain a synergistic effect. The amount of antioxidant to be added may be in the range of 0.1 to 10% by weight based on the oil (see Figure 2. However, the oil should be Paol 60, the antioxidant should be 4-4' methylene bis-2, The degree of oxidation of the oil is indicated by the amount of evaporation of the oil using 6-ditart(tert)-butylphenol at a temperature of 80°C.If the upper limit of the above range is exceeded, the antioxidant itself becomes hydrocarbon. The effect will actually decrease as it starts to contribute to oxidation reactions, etc. In the process of this invention, the mixture obtained as described above is heated in the air or in vacuum, and a low boiling point organic solvent is heated. In this evaporation process, the ferromagnetic fine particles dispersed in the organic solvent phase migrate into the oil, and finally a magnetic fluid having the desired oil as a liquid phase is obtained. Since the polarity of the oil and the organic solvent are relatively close, the transfer of the magnetic particles due to evaporation occurs very naturally and smoothly, and stable dispersion can be maintained even when the concentration of particles dispersed in the oil is high. In the process of this invention, after separating the fine particles with poor dispersibility in the intermediate medium, unlike the above, the low boiling point organic solvent is first evaporated by heating the intermediate medium. In that case, this low-boiling organic solvent evaporation step is followed by a step of adding polyalphaolefin oil, a second surfactant, and an antioxidant to the ferromagnetic fine particles. After further centrifuging at 5000 to 8000G, the magnetic fluid using polyalphaolefin oil as a medium obtained in step 1 is further centrifuged to produce a magnetic fluid using another new low-boiling organic solvent as a medium (i.e., an intermediate medium obtained in a new process). By repeating the step of mixing again with the mixture and the step of evaporating the low boiling point organic solvent from this mixture, highly dispersible fine particles can be further added and a magnetic fluid with an extremely high concentration of fine particles can be obtained.This invention According to , after ferromagnetic fine particles are made into a new oil, they are first made into an intermediate medium using an organic solvent with a low boiling point, and then a polyalphaolefin oil of similar polarity, a second surfactant, and an antioxidant are added. or by first heating the intermediate medium and then adding the polyalphaolefin oil, the second surfactant, and the antioxidant. By removing boiling point components and concentrating, we can efficiently create a magnetic fluid composition that stably disperses ferromagnetic particles in oil at a high concentration and also has anti-oxidation ability.
The effect is that it can be manufactured economically. Examples of the present invention will be described below. Example 1 Polyalphaolefin oil (Bray Oil Company, P
-60) as a dispersion medium, isostearic acid as a second surfactant, and creation of a magnetic fluid composition with magnetite as a dispersoid. First, 1 mol each of ferrous sulfate and ferric sulfate/
A 6N NaOH aqueous solution was added to the aqueous solution 1 until the pH became 11 or more, and then aged at 60°C for 30 minutes to obtain a magnetite colloid. Then, while keeping the temperature at 60°C, add 3N HCl solution to this magnetite suspension to adjust the pH to between 4 and 5, then add 20g of sodium oleate as the first surfactant and stir for 30 minutes. . After standing still to allow the magnetite particles to coagulate, the supernatant is collected, water is added, and the water is repeatedly washed to remove the electrolyte.
At this time, if the pH rises and the mixture becomes dispersed, add a small amount of HCl. This liquid is then filtered to dehydrate the magnetite particles. Hexane is added as a low-boiling organic solvent to the magnetite particles, and the mixture is thoroughly mixed and centrifuged for 20 minutes under a centrifugal force of 4000 G. After removing the upper supernatant and filtering it,
Transfer to a separatory funnel. Leave it to stand to separate water and hexane, and take out the hexane in which magnetite is dispersed. This hexane solution is kept at 90°C and the hexane is evaporated using a rotary evaporator. After evaporation, the magnetite particles remaining in the evaporator flask are taken out and placed in a vacuum constant temperature dryer. 100℃
to completely dry the magnetite particles. After drying, 2 g of magnetite particles were taken and redispersed in hexane, followed by 5 c.c. of polyalphaolefin oil (P-60), 0.03 cc of isostearic acid as a second surfactant, and 4 cc as an antioxidant. ,4'methylenebis-2,6-di-tart (tert)
- Add 0.05 g of butylphenol and mix well. After mixing, evaporate the hexane on a rotary evaporator. After evaporation, the magnetite is dispersed in polyalphaolefin oil (P-60). this
Separate for 60 min under centrifugation at 8000G. Although this operation removed undispersed solids, the colloidal solution above was an extremely stable magnetic fluid. Example 2 Polyalphaolefin oil (Bray Oil Co., Ltd., P
-60) as a dispersion medium, melisic acid as a second surfactant, and creation of a magnetic fluid composition with magnetite as a dispersoid. The method for producing magnetite, the method for dispersing it in hexane, and the drying method are the same as in Example 1. After drying, 2 g of magnetite particles were taken and redispersed in hexane, followed by 5 c.c. of polyalphaolefin oil (P-60), 0.03 g of melisic acid, and Example 1.
Add 0.05g of the same antioxidant and mix well.
After mixing, evaporate the hexane on a rotary evaporator. After evaporation, the magnetite is dispersed in polyalphaolefin oil (P-60). this
Separate for 60 min under centrifugation at 8000G. Although this operation removed undispersed solids, the top colloidal solution was a very stable magnetic fluid.
第１図はポリアルフアオレフイン油のグレード
別の分子量分布を示すグラフ、第２図はこの発明
に係る酸化防止剤の添加の効果を示すグラフであ
る。
FIG. 1 is a graph showing the molecular weight distribution of different grades of polyalphaolefin oil, and FIG. 2 is a graph showing the effect of adding an antioxidant according to the present invention.
Claims (1)
とするポリアルフアオレフイン油と、該油中に分
散した強磁性体微粒子と、該微粒子に吸着する第
１の界面活性剤および第２の界面活性剤と、酸化
防止剤とからなる磁性流体組成物。 ２ 強磁性体微粒子の粒径が20〜500Aである特
許請求の範囲第１項記載の磁性流体組成物。 ３ 強磁性体微粒子が体積比１〜20％の範囲で前
記油中に分散している特許請求の範囲第１項又は
第２項記載の磁性流体組成物。 ４ 第１の界面活性剤が炭素数10以上の不飽和脂
肪酸塩である特許請求の範囲第１項ないし第３項
のいずれかの項記載の磁性流体組成物。 ５ 第２の界面活性剤が炭素数18以上の飽和脂肪
酸である特許請求の範囲第１項ないし第４項のい
ずれかの項記載の磁性流体組成物。 ６ 酸化防止剤が前記油に対し重量比0.1〜10％
の範囲で含まれる特許請求の範囲第１項ないし第
５項いずれかの項記載の磁性流体組成物。 ７ 強磁性体微粒子に第１の界面活性剤と低沸点
有機溶媒とを加え、表面を前記第１の界面活性剤
で被覆した強磁性体微粒子が低沸点有機溶媒中に
分散された中間媒体を得る工程と、該中間媒体中
の分散性の悪い微粒子を分離した後、ポリアルフ
アオレフイン油と炭素数18以上の飽和脂肪酸と酸
化防止剤とを中間媒体に加えて混合物とする工程
と、該混合物を加熱し低沸点有機溶媒を蒸発させ
る工程とを包含する磁性流体組成物の製造方法。 ８ 強磁性体微粒子に第１の界面活性剤と低沸点
有機溶媒とを加え、表面を前記第１の界面活性剤
で被覆した強磁性体微粒子が低沸点有機溶媒中に
分散された中間媒体を得る工程と、該中間媒体中
の分散性の悪い微粒子を分離した後、中間媒体を
加熱し低沸点有機溶媒を蒸発させる工程と、該工
程を経た強磁性体微粒子にポリアルフアオレフイ
ン油と第２の界面活性剤である炭素数18以上の飽
和脂肪酸と酸化防止剤とを加える工程とを包含す
る磁性流体組成物の製造方法。[Scope of Claims] 1. A polyalphaolefin oil whose main component is an oligomer having 25 to 45 carbon atoms, ferromagnetic fine particles dispersed in the oil, and a first surfactant adsorbed to the fine particles. and a second surfactant and an antioxidant. 2. The magnetic fluid composition according to claim 1, wherein the ferromagnetic fine particles have a particle size of 20 to 500A. 3. The magnetic fluid composition according to claim 1 or 2, wherein ferromagnetic fine particles are dispersed in the oil in a volume ratio of 1 to 20%. 4. The magnetic fluid composition according to any one of claims 1 to 3, wherein the first surfactant is an unsaturated fatty acid salt having 10 or more carbon atoms. 5. The magnetic fluid composition according to any one of claims 1 to 4, wherein the second surfactant is a saturated fatty acid having 18 or more carbon atoms. 6 Antioxidant is 0.1 to 10% by weight of the oil
A magnetic fluid composition according to any one of claims 1 to 5 falling within the scope of the present invention. 7 A first surfactant and a low boiling point organic solvent are added to ferromagnetic fine particles, and an intermediate medium in which the ferromagnetic fine particles whose surfaces are coated with the first surfactant are dispersed in the low boiling point organic solvent is prepared. After separating the fine particles with poor dispersibility in the intermediate medium, a step of adding polyalphaolefin oil, a saturated fatty acid having 18 or more carbon atoms, and an antioxidant to the intermediate medium to form a mixture; and evaporating a low boiling point organic solvent. 8 Adding a first surfactant and a low boiling point organic solvent to ferromagnetic fine particles, and creating an intermediate medium in which the ferromagnetic fine particles whose surfaces are coated with the first surfactant are dispersed in the low boiling point organic solvent. After separating fine particles with poor dispersibility in the intermediate medium, heating the intermediate medium to evaporate the low boiling point organic solvent; and adding polyalphaolefin oil and a second A method for producing a magnetic fluid composition comprising the step of adding a saturated fatty acid having 18 or more carbon atoms as a surfactant and an antioxidant.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57214015A JPS59105093A (en) | 1982-12-08 | 1982-12-08 | Magnetic fluid composition and its preparation |
| US06/478,876 US4485024A (en) | 1982-04-07 | 1983-03-25 | Process for producing a ferrofluid, and a composition thereof |
| DE19833312565 DE3312565A1 (en) | 1982-04-07 | 1983-04-07 | METHOD FOR PRODUCING A FERROFLUID AND FERROFLUID COMPOSITION |
| US06/920,226 USRE32573E (en) | 1982-04-07 | 1986-10-16 | Process for producing a ferrofluid, and a composition thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57214015A JPS59105093A (en) | 1982-12-08 | 1982-12-08 | Magnetic fluid composition and its preparation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59105093A JPS59105093A (en) | 1984-06-18 |
| JPH0226766B2 true JPH0226766B2 (en) | 1990-06-12 |
Family
ID=16648856
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP57214015A Granted JPS59105093A (en) | 1982-04-07 | 1982-12-08 | Magnetic fluid composition and its preparation |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59105093A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH061728B2 (en) * | 1986-02-25 | 1994-01-05 | 住友セメント株式会社 | Magnetic fluid manufacturing method |
| JP2689251B2 (en) * | 1987-10-20 | 1997-12-10 | 昇 一ノ瀬 | Magnetic fluid manufacturing method |
| JP2725015B2 (en) * | 1988-03-11 | 1998-03-09 | エヌオーケー株式会社 | Manufacturing method of magnetic fluid |
| JP2009188426A (en) * | 2009-05-20 | 2009-08-20 | Inst Nuclear Energy Research Rocaec | Preparation method of oily magnetic fluid |
-
1982
- 1982-12-08 JP JP57214015A patent/JPS59105093A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59105093A (en) | 1984-06-18 |
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