JP2023138411A - Method of producing cobalt ferrite particles, and cobalt ferrite particles produced by the same - Google Patents
Method of producing cobalt ferrite particles, and cobalt ferrite particles produced by the same Download PDFInfo
- Publication number
- JP2023138411A JP2023138411A JP2023036445A JP2023036445A JP2023138411A JP 2023138411 A JP2023138411 A JP 2023138411A JP 2023036445 A JP2023036445 A JP 2023036445A JP 2023036445 A JP2023036445 A JP 2023036445A JP 2023138411 A JP2023138411 A JP 2023138411A
- Authority
- JP
- Japan
- Prior art keywords
- ferrite particles
- cobalt
- cobalt ferrite
- particles according
- producing
- 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.)
- Pending
Links
- 239000002245 particle Substances 0.000 title claims abstract description 182
- 229910000859 α-Fe Inorganic materials 0.000 title claims abstract description 139
- 239000010941 cobalt Substances 0.000 title claims abstract description 85
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 85
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title abstract description 23
- 239000007864 aqueous solution Substances 0.000 claims abstract description 39
- 239000002243 precursor Substances 0.000 claims abstract description 38
- 239000008139 complexing agent Substances 0.000 claims abstract description 23
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 150000002505 iron Chemical class 0.000 claims abstract description 22
- 150000001868 cobalt Chemical class 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims description 44
- 239000000843 powder Substances 0.000 claims description 40
- 239000007800 oxidant agent Substances 0.000 claims description 16
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 12
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 10
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000006174 pH buffer Substances 0.000 claims description 7
- 229910052709 silver Inorganic materials 0.000 claims description 7
- 239000004332 silver Substances 0.000 claims description 7
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 7
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 claims description 6
- 229910000335 cobalt(II) sulfate Inorganic materials 0.000 claims description 6
- 239000012530 fluid Substances 0.000 claims description 6
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims description 4
- 229910021580 Cobalt(II) chloride Inorganic materials 0.000 claims description 4
- 229910021577 Iron(II) chloride Inorganic materials 0.000 claims description 4
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 4
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 4
- 229940049920 malate Drugs 0.000 claims description 4
- BJEPYKJPYRNKOW-UHFFFAOYSA-N malic acid Chemical compound OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 4
- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 claims description 4
- 239000012670 alkaline solution Substances 0.000 claims description 3
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- 239000000243 solution Substances 0.000 abstract description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 39
- 238000006243 chemical reaction Methods 0.000 description 37
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 25
- 239000006249 magnetic particle Substances 0.000 description 23
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 22
- 239000002994 raw material Substances 0.000 description 15
- 238000010335 hydrothermal treatment Methods 0.000 description 11
- 229910052742 iron Inorganic materials 0.000 description 11
- 239000004317 sodium nitrate Substances 0.000 description 11
- 235000010344 sodium nitrate Nutrition 0.000 description 11
- 239000011734 sodium Substances 0.000 description 10
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 8
- 239000003513 alkali Substances 0.000 description 7
- GFHNAMRJFCEERV-UHFFFAOYSA-L cobalt chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Co+2] GFHNAMRJFCEERV-UHFFFAOYSA-L 0.000 description 7
- 238000009826 distribution Methods 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 238000001027 hydrothermal synthesis Methods 0.000 description 6
- 239000000976 ink Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000002087 whitening effect Effects 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- -1 iron salt Chemical class 0.000 description 4
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- 239000000725 suspension Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000000975 co-precipitation Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 239000011258 core-shell material Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000004627 transmission electron microscopy Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 238000009279 wet oxidation reaction Methods 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 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 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 2
- 230000000536 complexating effect Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000010612 desalination reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 150000004688 heptahydrates Chemical class 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 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 2
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 2
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 1
- 241001085205 Prenanthella exigua Species 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-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
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 125000005619 boric acid group Chemical group 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- MEYVLGVRTYSQHI-UHFFFAOYSA-L cobalt(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Co+2].[O-]S([O-])(=O)=O MEYVLGVRTYSQHI-UHFFFAOYSA-L 0.000 description 1
- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 description 1
- 150000004696 coordination complex Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007772 electroless plating Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 150000004687 hexahydrates Chemical class 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 1
- LNOZJRCUHSPCDZ-UHFFFAOYSA-L iron(ii) acetate Chemical compound [Fe+2].CC([O-])=O.CC([O-])=O LNOZJRCUHSPCDZ-UHFFFAOYSA-L 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 150000003608 titanium Chemical class 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
Abstract
Description
本発明は、コバルトフェライト粒子の製造方法、及びそれにより製造されたコバルトフェライト粒子に関するもので、特に平均粒子径が比較的大きく、さらに粒子径分布もそろったコバルトフェライト粒子を提供するものである。 The present invention relates to a method for producing cobalt ferrite particles and cobalt ferrite particles produced thereby, and in particular provides cobalt ferrite particles having a relatively large average particle size and a uniform particle size distribution.
フェライト粒子は、高透磁率材料や永久磁石材料として知られ、今日では磁性粉体はコピー用トナー、磁性インク、ＭＲ流体等の新たな素材に用いられるようになり、その品質や性能の向上が期待されている。
特にコバルトフェライトは、スピネル型フェライトの中でも結晶磁気異方性が大きく、保磁力の大きい磁性材料として知られている。また、コバルトは鉄と化学的な挙動が似ているため、その製造工程において各種制御が容易にできるという利点がある。
Ferrite particles are known as high magnetic permeability materials and permanent magnet materials, and today magnetic powders are being used in new materials such as copy toner, magnetic ink, and MR fluid, and their quality and performance are improving. It is expected.
In particular, cobalt ferrite is known as a magnetic material with a large crystal magnetic anisotropy and a large coercive force among spinel-type ferrites. Furthermore, since cobalt has similar chemical behavior to iron, it has the advantage that various controls can be easily controlled in the manufacturing process.
フェライト粒子の製造方法としては、共沈法、湿式酸化法、水熱法などの方法が知られている。
共沈法は、二種類以上のイオンを同時に沈殿させる反応で、コバルトフェライト粒子を製造する場合、Ｆｅ３＋とＣо２＋イオンを含む水溶液にアルカリを投入後、加熱することで反応を促進させてナノサイズのフェライト粒子を得る。この方法では、８０～１００℃の温度で反応をおこない、得られた粒子の平均粒子径は２０～５０ｎｍ程度で、比較的粒度分布の広い粒子しか得られない（特許文献１）。
As a method for producing ferrite particles, methods such as a coprecipitation method, a wet oxidation method, and a hydrothermal method are known.
The coprecipitation method is a reaction in which two or more types of ions are precipitated at the same time. When producing cobalt ferrite particles, an alkali is added to an aqueous solution containing Fe 3+ and Co 2+ ions, and then heated to accelerate the reaction. Obtain ferrite particles of size. In this method, the reaction is carried out at a temperature of 80 to 100° C., and the average particle diameter of the obtained particles is about 20 to 50 nm, and only particles with a relatively wide particle size distribution can be obtained (Patent Document 1).
湿式酸化法は、Ｆｅ２＋とＣо２＋イオンを含む原料水溶液に加熱しながら空気等の酸化剤を反応させる方法である。酸化剤として空気を使用した場合には、反応温度は６０～１００℃程度で、０．０５～０．３μｍ程度の粒子を得ている（特許文献２、特許文献３）。また、原料水溶液と酸化剤液との反応を連続的におこなう方法では、３０～１００℃の温度で反応をおこない、３～２０ｎｍのフェライト粒子を得ている（特許文献４）。 The wet oxidation method is a method in which an aqueous raw material solution containing Fe 2+ and Co 2+ ions is reacted with an oxidizing agent such as air while being heated. When air is used as the oxidizing agent, the reaction temperature is about 60 to 100° C., and particles of about 0.05 to 0.3 μm are obtained (Patent Document 2, Patent Document 3). Furthermore, in a method in which a raw material aqueous solution and an oxidizing agent solution are continuously reacted, the reaction is carried out at a temperature of 30 to 100° C. to obtain ferrite particles of 3 to 20 nm (Patent Document 4).
水熱法は、Ｆｅ２＋イオンを含む水溶液にＣо２＋イオンを含む水溶液を混合し、オートクレーブ中で水熱合成する方法で、１６０～３００℃という高温反応により、０．３～８μｍという比較的大きな粒子径のフェライト粒子を製造している（特許文献５）。 The hydrothermal method is a method in which an aqueous solution containing Fe 2+ ions is mixed with an aqueous solution containing Co 2+ ions, and hydrothermal synthesis is performed in an autoclave. Through a high temperature reaction of 160 to 300°C, relatively large particles of 0.3 to 8 μm are synthesized. Ferrite particles with a particle size are manufactured (Patent Document 5).
従来技術によりフェライト粒子を製造する場合、共沈法や湿式酸化法によれば、比較的低い温度で製造することができるが、得られたフェライト粒子はｎｍオーダーの微細な粒子しか得られない。また、水熱法によればμｍオーダーの比較的大きな粒子を得ることができるが、高温高圧で水熱反応（シッコール反応）を行なわせる必要があり、設備やコストの面で問題があった。 When producing ferrite particles using conventional techniques, the coprecipitation method or the wet oxidation method allows production at relatively low temperatures, but the resulting ferrite particles are only nanometer-sized particles. Furthermore, although relatively large particles on the μm order can be obtained by the hydrothermal method, it is necessary to carry out a hydrothermal reaction (Sikkol reaction) at high temperature and high pressure, which poses problems in terms of equipment and cost.
本発明は、このような従来の技術の問題点を克服し、平均粒子径が従来のものよりも大きくかつ均一な粒子径を持つコバルトフェライト粒子を、より低いエネルギーで合成することができる製造方法及び、これにより製造された、丸みを帯びた形状を有し粒子径のそろったコバルトフェライト粒子を提供するものである。 The present invention overcomes the problems of the conventional technology and provides a manufacturing method that can synthesize cobalt ferrite particles having a larger average particle size and a more uniform particle size than the conventional method using lower energy. The present invention also provides cobalt ferrite particles having a rounded shape and a uniform particle size, produced thereby.
上記課題を解決するための手段として、本発明では、次の構成からなる手段を採用する。
(１) 錯化剤で安定化された二価鉄塩とコバルト塩を含む水溶液（フェライト前駆体）を加熱処理してなるコバルトフェライト粒子の製造方法。
(２) 加熱処理が、圧力容器中で１３０℃～２６０℃の温度範囲において、水熱条件で行なう（１）に記載のコバルトフェライト粒子の製造方法。
(３) 加熱処理が、圧力容器中で１９０℃～２４０℃の温度範囲において、水熱条件で行なう（２）に記載のコバルトフェライト粒子の製造方法。
(４) 水溶液（フェライト前駆体）に、さらに三価鉄塩を添加する（１）～（３）のいずれかに記載のコバルトフェライト粒子の製造方法。
(５) 水溶液（フェライト前駆体）に、さらにｐＨ緩衝剤を添加する（１）～（４）のいずれかに記載のコバルトフェライト粒子の製造方法。
(６) 二価鉄塩と前記コバルト塩が、塩化鉄（II）と塩化コバルト（II）である（１）～（５）のいずれかに記載のコバルトフェライト粒子の製造方法。
(７) 二価鉄塩と前記コバルト塩が、硫酸鉄（II）と硫酸コバルト（II）である（１）～（６）のいずれかに記載のコバルトフェライト粒子の製造方法。
(８) 錯化剤として、クエン酸塩、ニトリロ三酢酸塩、又はリンゴ酸塩から選択された1つを使用することからなる（１）～（７）のいずれかに記載のコバルトフェライト粒子の製造方法。
(９) 加熱処理を、錯化剤に加えてさらに酸化剤の存在下でおこなう（１）～（８）のいずれかに記載のコバルトフェライト粒子の製造方法。
(１０) 酸化剤が、硝酸塩であることからなる（９）に記載のコバルトフェライト粒子の製造方法。
(１１) 水溶液（フェライト前駆体）に、さらに種粒子を添加する（１）～（１０）のいずれかに記載のコバルトフェライト粒子の製造方法。
(１２) 種粒子が酸化鉄である（１１）に記載のコバルトフェライト粒子の製造方法。
(１３) 加熱処理の途中、あるいは終了後の圧力容器中に、アルカリ水溶液、またはフェライト前駆体を圧入し、さらに加熱処理をおこなう（１）～（１２）のいずれかに記載のコバルトフェライト粒子の製造方法。
(１４) 粒子径の変動係数であるＣＶ値が０．１～０．３であり、丸みを帯びた形状で、平均粒子径が５～５０μｍであるコバルトフェライト粒子。
（１５） 残留磁気モーメントが１０ｅｍｕ／ｇ以上であり、保磁力が１００～１０００Ｏｅである（１４）に記載のコバルトフェライト粒子。
(１６) （１５）に記載のコバルトフェライト粒子からなるコピー用トナー。
(１７) （１５）に記載のコバルトフェライト粒子からなる磁性インク。
(１８) （１５）に記載のコバルトフェライト粒子からなるＭＲ流体。
(１９) （１５）に記載のコバルトフェライト粒子の表面に、酸化チタン膜と金属銀膜とをこの順に有する白色粉体。
(２０) 明度Ｌ＊が７５以上である（１５）に記載の白色粉体。
As a means for solving the above problems, the present invention employs means having the following configuration.
(1) A method for producing cobalt ferrite particles by heat-treating an aqueous solution (ferrite precursor) containing a divalent iron salt and a cobalt salt stabilized with a complexing agent.
(2) The method for producing cobalt ferrite particles according to (1), wherein the heat treatment is performed in a pressure vessel under hydrothermal conditions in a temperature range of 130° C. to 260° C.
(3) The method for producing cobalt ferrite particles according to (2), wherein the heat treatment is performed in a pressure vessel under hydrothermal conditions in a temperature range of 190° C. to 240° C.
(4) The method for producing cobalt ferrite particles according to any one of (1) to (3), wherein a trivalent iron salt is further added to the aqueous solution (ferrite precursor).
(5) The method for producing cobalt ferrite particles according to any one of (1) to (4), further comprising adding a pH buffer to the aqueous solution (ferrite precursor).
(6) The method for producing cobalt ferrite particles according to any one of (1) to (5), wherein the divalent iron salt and the cobalt salt are iron (II) chloride and cobalt (II) chloride.
(7) The method for producing cobalt ferrite particles according to any one of (1) to (6), wherein the divalent iron salt and the cobalt salt are iron (II) sulfate and cobalt (II) sulfate.
(8) Cobalt ferrite particles according to any one of (1) to (7), which use one selected from citrate, nitrilotriacetate, or malate as a complexing agent. Production method.
(9) The method for producing cobalt ferrite particles according to any one of (1) to (8), wherein the heat treatment is performed in the presence of an oxidizing agent in addition to the complexing agent.
(10) The method for producing cobalt ferrite particles according to (9), wherein the oxidizing agent is a nitrate.
(11) The method for producing cobalt ferrite particles according to any one of (1) to (10), wherein seed particles are further added to the aqueous solution (ferrite precursor).
(12) The method for producing cobalt ferrite particles according to (11), wherein the seed particles are iron oxide.
(13) The cobalt ferrite particles according to any one of (1) to (12), wherein an aqueous alkaline solution or a ferrite precursor is pressurized into the pressure vessel during or after the heat treatment, and further heat treatment is performed. Production method.
(14) Cobalt ferrite particles having a CV value, which is a coefficient of variation of particle size, of 0.1 to 0.3, a rounded shape, and an average particle size of 5 to 50 μm.
(15) The cobalt ferrite particles according to (14), which have a residual magnetic moment of 10 emu/g or more and a coercive force of 100 to 1000 Oe.
(16) A toner for copying comprising the cobalt ferrite particles described in (15).
(17) A magnetic ink comprising the cobalt ferrite particles described in (15).
(18) An MR fluid comprising cobalt ferrite particles according to (15).
(19) A white powder having a titanium oxide film and a metal silver film in this order on the surface of the cobalt ferrite particles according to (15).
(20) The white powder according to (15), which has a lightness L* of 75 or more.
本発明の製造方法を採用することにより、従来方法で製造された磁性粒子と比較して、より低いエネルギーで、粒子径のそろったコバルトフェライトからなる磁性粒子を製造することができる。
本発明の製造方法で得られたコバルトフェライト粒子は、丸みをおびた形状で粒子径がそろっているので、コピー用トナー、磁性インク、ＭＲ流体としての用途が期待される。また、本発明のコバルトフェライト粒子は、公知の方法で白色化することにより、白色、あるいはさらに着色層を設けて、明度の高い白色粉体あるいは鮮やかな色に着色されたカラー粉体とすることができる。
By employing the production method of the present invention, magnetic particles made of cobalt ferrite with uniform particle diameters can be produced with lower energy than magnetic particles produced by conventional methods.
Since the cobalt ferrite particles obtained by the production method of the present invention have a rounded shape and uniform particle diameter, they are expected to be used as copying toners, magnetic inks, and MR fluids. In addition, the cobalt ferrite particles of the present invention can be whitened by a known method, or can be further provided with a colored layer to make a highly bright white powder or a brightly colored colored powder. I can do it.
本発明においては、二価鉄塩とコバルト塩からフェライト前駆体を形成し、フェライト前駆体を錯化剤の存在下で高温・高圧条件下で加熱処理をおこなうことに特徴がある。 The present invention is characterized in that a ferrite precursor is formed from a divalent iron salt and a cobalt salt, and the ferrite precursor is heat-treated under high temperature and high pressure conditions in the presence of a complexing agent.
以下では、本発明のコバルトフェライト粒子の製造方法を、工程にそって説明する。
（フェライト前駆体の製造）
まず、二価鉄塩とコバルト塩を脱塩脱気水に溶解して原料水溶液を調製する。
本発明の方法において使用する二価鉄塩としては特に限定されず、硫酸鉄（II）、塩化鉄（II）、硝酸鉄（II）、酢酸鉄（II）等が例示でき、高炉や電炉の鉄洗廃液なども安価な原料として良い。また、コバルト塩についても特に限定されず、二価コバルト塩、例えば、硫酸コバルト（II）、塩化コバルト（II）、硝酸コバルト（II）、酢酸コバルト（II）等が例示できる。入手の容易性等から、二価鉄塩としては硫酸鉄（II）、または塩化鉄（II）、二価コバルト塩としては硫酸コバルト（II）、または塩化コバルト（II）が好ましい。
なお、後述の粒子径の調整の欄で説明するように、原料水溶液には、更に、三価鉄塩を添加してもよい。三価鉄塩としては特に限定されず、塩化鉄（III）、硫酸鉄（III）、硝酸鉄（III）等が例示できる。
ここで脱塩脱気水を使用するのは、溶液中に溶解した鉄等の金属イオンの電荷状態が、溶存している塩や酸素の影響を受けることを防ぐためである。例えば、反応系中に遊離酸素が存在すると二価鉄が三価鉄に酸化してしまい、目的としない粒子径の微粒子が発生してしまうことが知られている。
Below, the method for producing cobalt ferrite particles of the present invention will be explained step by step.
(Manufacture of ferrite precursor)
First, a raw material aqueous solution is prepared by dissolving a divalent iron salt and a cobalt salt in desalinated and degassed water.
The divalent iron salt used in the method of the present invention is not particularly limited, and examples include iron(II) sulfate, iron(II) chloride, iron(II) nitrate, iron(II) acetate, etc. Iron washing waste liquid can also be used as an inexpensive raw material. Further, the cobalt salt is not particularly limited, and examples include divalent cobalt salts such as cobalt (II) sulfate, cobalt (II) chloride, cobalt (II) nitrate, and cobalt (II) acetate. In view of ease of availability, the divalent iron salt is preferably iron (II) sulfate or iron (II) chloride, and the divalent cobalt salt is preferably cobalt (II) sulfate or cobalt (II) chloride.
Note that, as explained in the section on particle size adjustment below, a trivalent iron salt may be further added to the raw material aqueous solution. The trivalent iron salt is not particularly limited, and examples include iron (III) chloride, iron (III) sulfate, iron (III) nitrate, and the like.
The reason why desalinated and degassed water is used here is to prevent the charge state of metal ions such as iron dissolved in the solution from being affected by dissolved salts and oxygen. For example, it is known that when free oxygen exists in the reaction system, divalent iron is oxidized to trivalent iron, resulting in the generation of fine particles with an unintended particle size.
次に、アルカリと錯化剤を脱塩脱気水に溶解してアルカリ水溶液を調製する。その後に、原料水溶液とアルカリ水溶液を混合する。アルカリとしては、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、アンモニアなどの任意のアルカリが選ばれる。原料水溶液とアルカリ水溶液を混合することにより、フェライト前駆体となる原料の金属錯体を形成する。 Next, an alkali aqueous solution is prepared by dissolving an alkali and a complexing agent in demineralized and degassed water. After that, the raw material aqueous solution and the alkaline aqueous solution are mixed. As the alkali, any alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, etc. is selected. By mixing the raw material aqueous solution and the alkaline aqueous solution, a metal complex of the raw material that becomes the ferrite precursor is formed.
錯体を安定的に形成させるためには、上記した順番で混合することが好ましい。また、錯体が分解した後に良好な特性を持つフェライト粒子を合成するためには、混合液のｐＨは７～１３程度に調整することが好ましい。 In order to stably form a complex, it is preferable to mix in the above order. Further, in order to synthesize ferrite particles with good properties after the complex is decomposed, it is preferable to adjust the pH of the mixed solution to about 7 to 13.
（錯化剤）
本発明においては、前記したとおり、加熱処理を行う前に、錯化剤によりフェライト前駆体を錯体化させて酸化剤による酸化から保護することに特徴がある。
本発明における錯化剤としては、クエン酸塩、ニトリロ三酢酸塩、及びリンゴ酸塩等が使われる。
クエン酸塩を使用した場合には、平均粒子径が５～５０μｍ程度の大きな粒子径のコバルトフェライト粒子が得られる。ニトリロ三酢酸塩やリンゴ酸塩を使用した場合には、平均粒子径が１μｍ以下の微細な粒子が得られる。
(complexing agent)
As described above, the present invention is characterized in that, before heat treatment, the ferrite precursor is complexed with a complexing agent to protect it from oxidation by an oxidizing agent.
As the complexing agent in the present invention, citrate, nitrilotriacetate, malate, etc. are used.
When citrate is used, cobalt ferrite particles with a large average particle size of about 5 to 50 μm can be obtained. When nitrilotriacetate or malate is used, fine particles with an average particle size of 1 μm or less can be obtained.
本発明におけるフェライト生成反応は、次のとおり進行するものと考えられる。
水熱処理を開始する前の段階では、酸化剤による酸化反応は行なわれず、錯化剤の配位子による錯化作用によりフェライト前駆体は溶液中に安定的に存在する。これにより、酸化されやすく不安定な水酸化物の生成を防ぎ、前駆体を安定的に保護する。
次に、加熱が開始されるとフェライト前駆体を保護していた錯体が徐々に分解し、フェライト前駆体は酸化作用を受けやすくなる。この際に、フェライト形成のための酸化反応を均一に促進するために、硝酸ナトリウム等の酸化剤を添加してもよい。フェライト前駆体が酸化剤の環境下にあれば酸化剤の酸化作用を受け、酸化剤がない場合でも水熱環境の作用で酸化され、フェライトが形成される。
The ferrite production reaction in the present invention is considered to proceed as follows.
At a stage before starting the hydrothermal treatment, no oxidation reaction by the oxidizing agent is performed, and the ferrite precursor stably exists in the solution due to the complexing action by the ligand of the complexing agent. This prevents the formation of unstable hydroxides that are easily oxidized and stably protects the precursor.
Next, when heating is started, the complex protecting the ferrite precursor gradually decomposes, and the ferrite precursor becomes susceptible to oxidation. At this time, an oxidizing agent such as sodium nitrate may be added to uniformly promote the oxidation reaction for forming ferrite. If the ferrite precursor is in an oxidizing agent environment, it will be oxidized by the oxidizing agent, and even if there is no oxidizing agent, it will be oxidized by the action of a hydrothermal environment, forming ferrite.
本発明においては、錯化剤による錯化作用により、水熱条件下での熱処理においてフェライト前駆体の酸化反応の進行を遅らせることができる。これにより、合成されるフェライト粒子の粒子径を大きくすることができ、さらに粒子径がそろった粒子を製造することができる。 In the present invention, the progress of the oxidation reaction of the ferrite precursor can be delayed during heat treatment under hydrothermal conditions due to the complexing effect of the complexing agent. Thereby, the particle size of the ferrite particles to be synthesized can be increased, and particles with uniform particle sizes can be manufactured.
（熱処理）
本発明においては、圧力容器を用いた水熱法による熱処理がおこなわれる。
本発明で使用する圧力容器は、通常の高圧反応容器であれば良く、オートクレーブ、圧力釜、ボイラー等が例示できるが、汎用性等からオートクレーブが好ましい。
通常の高温シッコール法では２００℃以上の高温で反応が進められることが多いが、本発明では、錯化剤を選択することにより１３０～３００℃程度、好ましくは１３０～２８０℃程度、より好ましくは１３０～２６０℃、よりさらに好ましくは１３０～２４０℃程度の温度範囲でコバルトフェライトからなる磁性粒子を合成することができる。
熱処理の温度が高いほど反応が促進され、１９０℃よりも高い温度、例えば２００℃程度で熱処理した場合にコバルトフェライト粒子の反応率を９０％程度まで上げることができる。
高反応率が期待できる観点からは、熱処理の温度は、１９０℃よりも高く３００℃以下が好ましい。一方、反応温度が２７０℃を超えた辺りから不純物が入ってくる傾向がある。このことより、純度と反応率のバランスを図る観点からは、反応時温度は１９０～２７０℃が好ましく、１９０～２６０℃がより好ましい。
(Heat treatment)
In the present invention, heat treatment is performed by a hydrothermal method using a pressure vessel.
The pressure vessel used in the present invention may be any ordinary high-pressure reaction vessel, and examples thereof include an autoclave, a pressure cooker, and a boiler, but an autoclave is preferred from the viewpoint of versatility.
In the ordinary high-temperature Sikkol method, the reaction is often carried out at a high temperature of 200°C or higher, but in the present invention, by selecting a complexing agent, the reaction can be carried out at a temperature of about 130 to 300°C, preferably about 130 to 280°C, more preferably about 130 to 280°C. Magnetic particles made of cobalt ferrite can be synthesized in a temperature range of about 130 to 260°C, more preferably about 130 to 240°C.
The higher the heat treatment temperature is, the more the reaction is accelerated, and when the heat treatment is performed at a temperature higher than 190°C, for example about 200°C, the reaction rate of the cobalt ferrite particles can be increased to about 90%.
From the viewpoint that a high reaction rate can be expected, the temperature of the heat treatment is preferably higher than 190°C and equal to or lower than 300°C. On the other hand, impurities tend to enter when the reaction temperature exceeds 270°C. Therefore, from the viewpoint of achieving a balance between purity and reaction rate, the reaction temperature is preferably 190 to 270°C, more preferably 190 to 260°C.
（粒子径の調整１：三価鉄塩の添加）
本発明に係るコバルトフェライト粒子の製造方法では、その製造方法の各工程において、製造するコバルトフェライト粒子の粒子径を調整する手段を採用することができる。以下では、いくつかの粒子径調整手段を列記する。これらの手段は単独で、あるいは複数の手段を組み合わせて採用することができる。
原料水溶液（二価鉄塩とコバルト塩の水溶液）に三価鉄塩を添加することで、錯化剤で安定化された二価鉄塩とコバルト塩を含む水溶液に三価鉄塩を添加し、これにより、コバルトフェライト粒子の粒子径を調整することができる。これによれば、三価鉄塩の三価鉄イオンがフェライト粒子形成の核の作用をするので、酸化剤の有無に関わらずフェライト形成の反応が促進されるとともに、製造されるフェライト粒子の粒子径を調整することが可能である。
ここで使用する三価鉄塩としては特に限定されず、塩化鉄（III）、硫酸鉄(III)、硝酸鉄(III)等が例示でき、高炉や電炉の鉄洗廃液なども安価な原料として良い。
(Adjustment of particle size 1: Addition of trivalent iron salt)
In the method for producing cobalt ferrite particles according to the present invention, means for adjusting the particle size of the cobalt ferrite particles to be produced can be employed in each step of the production method. Below, some particle size adjustment means are listed. These means can be employed alone or in combination.
By adding trivalent iron salt to the raw material aqueous solution (aqueous solution of divalent iron salt and cobalt salt), trivalent iron salt is added to the aqueous solution containing divalent iron salt and cobalt salt stabilized with a complexing agent. , Thereby, the particle size of the cobalt ferrite particles can be adjusted. According to this, the trivalent iron ion of the trivalent iron salt acts as a nucleus for the formation of ferrite particles, so the reaction of ferrite formation is promoted regardless of the presence or absence of an oxidizing agent, and the particles of the ferrite particles produced are It is possible to adjust the diameter.
The trivalent iron salt used here is not particularly limited, and examples include iron (III) chloride, iron (III) sulfate, iron (III) nitrate, etc. Iron washing waste liquid from blast furnaces and electric furnaces can also be used as an inexpensive raw material. good.
（粒子径の調整２：ｐＨ緩衝剤の添加）
アルカリ水溶液（アルカリと錯化剤の水溶液）にｐＨ緩衝剤を添加することで、錯化剤で安定化された二価鉄塩とコバルト塩を含む水溶液にｐＨ緩衝液を添加し、これにより、コバルトフェライト粒子の粒子径を調整することができる。フェライト生成反応はｐＨ低下を伴う反応であり、ｐＨが低下するとフェライト前駆体の分解が抑えられてフェライト生成反応が抑制されてしまう。そこで、ｐＨの低下を抑制するためにｐＨ緩衝剤を添加することにより、フェライト粒子の成長を促進させることができる。
ここで使用するｐＨ緩衝剤としては、ホウ酸、炭酸ナトリウム/炭酸水素ナトリウムなどから選ばれる。
(Adjustment of particle size 2: Addition of pH buffer)
By adding a pH buffer to an aqueous alkaline solution (an aqueous solution of an alkali and a complexing agent), the pH buffer is added to an aqueous solution containing a divalent iron salt and a cobalt salt stabilized with a complexing agent, and thereby, The particle size of cobalt ferrite particles can be adjusted. The ferrite production reaction is a reaction accompanied by a decrease in pH, and when the pH decreases, decomposition of the ferrite precursor is suppressed and the ferrite production reaction is suppressed. Therefore, by adding a pH buffer to suppress the decrease in pH, the growth of ferrite particles can be promoted.
The pH buffer used here is selected from boric acid, sodium carbonate/sodium hydrogen carbonate, and the like.
（粒子径の調整３：種粒子の添加）
フェライト前駆体に種粒子を添加することで、コバルトフェライト粒子が析出する基体となる核を与えることができ、これにより、コバルトフェライト粒子の粒子径を調整することができる。ここで使用する種粒子としては特に限定されず、金属や合金、酸化物等の水に不溶な無機化合物等から選ばれる。特に、コバルトフェライトとの親和性から、酸化鉄が好ましい。酸化鉄としてはマグネタイトを用いることができる。
(Adjustment of particle size 3: Addition of seed particles)
By adding seed particles to the ferrite precursor, it is possible to provide a nucleus that serves as a base on which cobalt ferrite particles are precipitated, thereby making it possible to adjust the particle size of the cobalt ferrite particles. The seed particles used here are not particularly limited, and are selected from water-insoluble inorganic compounds such as metals, alloys, and oxides. In particular, iron oxide is preferred because of its affinity with cobalt ferrite. Magnetite can be used as iron oxide.
（粒子径の調整４：熱処理時にアルカリ水溶液、フェライト前駆体の圧入）
熱処理工程の途中あるいは終了後に、圧力容器中にアルカリ水溶液またはフェライト前駆体（錯体）を圧入し、その後も熱処理を継続することにより、コバルトフェライト粒子の粒子径を調整することができる。
アルカリ水溶液を圧入すると、反応容器中のｐＨが上昇することで未反応のフェライト前駆体の分解が進み、フェライト生成反応が促進される。これにより粒子成長（粗粒化）をはかることができる。アルカリ水溶液として特に限定されることはなく、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、アンモニア等から適宜選択することができる。
一方、フェライト前駆体（錯体）を圧入すると、フェライト形成原料が追加されることになり、フェライト粒子の粒子成長を促進することができる。フェライト前駆体の製造方法は前記したとおりである。
(Adjustment of particle size 4: Pressure injection of alkaline aqueous solution and ferrite precursor during heat treatment)
During or after the heat treatment step, the particle size of the cobalt ferrite particles can be adjusted by injecting an alkaline aqueous solution or a ferrite precursor (complex) into the pressure vessel and continuing the heat treatment thereafter.
When the alkaline aqueous solution is pressurized, the pH in the reaction vessel increases, which promotes the decomposition of unreacted ferrite precursors and accelerates the ferrite production reaction. This allows grain growth (grain coarsening) to be achieved. The alkaline aqueous solution is not particularly limited and can be appropriately selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, and the like.
On the other hand, when a ferrite precursor (complex) is press-injected, a ferrite-forming raw material is added, and the growth of ferrite particles can be promoted. The method for producing the ferrite precursor is as described above.
（コバルトフェライト粒子）
本発明で製造されたコバルトフェライト粒子は、平均粒子径が５～５０μｍにもなる比較的大きな粒子径の磁性粒子である。丸みをおびた形状で粒子径のそろった粒子となっている。粒子のアスペクト比はほぼ１である。
後述の図１３の説明にあるように、コバルトフェライト粒子の一態様として、コアシェル型構造を有する粒子が挙げられる。
本発明のコバルトフェライト粒子は、比較的粒子径が大きく、丸みをおび、粒子径の分布幅も狭いので、粒子相互間の凝集性が少なく、成形した場合に最密充填が可能なので成形体の磁性特性を向上することができる、あるいは嵩密度を大きくできるという特徴を有する。また、粒子表面に適度な凹凸があるため、表面が平滑な球形粒子と比較して、磁性インクとする場合に顔料が乗りやすくなる効果を有する。
このため、コピー用トナー、磁性インク、ＭＲ流体の用途に用いることで、その特性を充分に発揮することができる。
(Cobalt ferrite particles)
The cobalt ferrite particles produced according to the present invention are magnetic particles having a relatively large particle size with an average particle size of 5 to 50 μm. The particles have a rounded shape and uniform particle size. The aspect ratio of the particles is approximately 1.
As described below with reference to FIG. 13, one embodiment of cobalt ferrite particles includes particles having a core-shell structure.
The cobalt ferrite particles of the present invention have a relatively large particle size, are rounded, and have a narrow particle size distribution width, so there is little agglomeration between particles, and when molded, close packing is possible, so that the molded product can be It has the characteristic that magnetic properties can be improved or bulk density can be increased. In addition, since the particles have appropriate irregularities on their surfaces, they have the effect of making it easier for pigments to adhere to them when used as magnetic ink, compared to spherical particles with smooth surfaces.
Therefore, by using it for copying toner, magnetic ink, and MR fluid, its characteristics can be fully exhibited.
（白色粉体）
本発明のコバルトフェライト粒子は、白色化して白色粉体としたり、白色化した後にさらに着色層を設けてカラー粉体とすることができる。
公知の方法で白色化できるが、例えば、本件出願人が特許権を有する白色化方法（特許第４１１３０４５号）によることが望ましい。
この白色化方法は、基体粒子と金属銀膜の間に酸化チタン膜を設けることによる粉体の白色化方法である。具体的には、チタンアルコキシドの加水分解（例えば、国際公開９６/２８２６９号）やチタン塩水溶液からの反応（例えば、特開平１１-１３１１０２号）等により、コバルトフェライト粒子の表面に酸化チタン膜を形成し、その後に、無電解メッキ法等の公知の方法により金属銀膜を形成することにより行うことができる。この方法により、本発明のコバルトフェライト粒子の表面に酸化チタン膜と金属銀膜とをこの順に有する白色粉体を製造することができ、その結果、コバルトフェライト粒子の明度Ｌ＊を７５以上に向上させることができる。
(white powder)
The cobalt ferrite particles of the present invention can be whitened to form a white powder, or can be whitened and then further provided with a colored layer to form a colored powder.
Although the whitening can be performed by a known method, for example, it is preferable to use a whitening method patented by the applicant (Japanese Patent No. 4113045).
This whitening method is a method for whitening powder by providing a titanium oxide film between the base particles and the metal silver film. Specifically, a titanium oxide film is formed on the surface of cobalt ferrite particles by hydrolysis of titanium alkoxide (for example, WO 96/28269) or reaction from a titanium salt aqueous solution (for example, JP 11-131102). This can be carried out by forming a metallic silver film by a known method such as electroless plating. By this method, it is possible to produce a white powder having a titanium oxide film and a metal silver film in this order on the surface of the cobalt ferrite particles of the present invention, and as a result, the lightness L* of the cobalt ferrite particles is improved to 75 or more. can be done.
以下に本発明について実施例を用いてさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。また、合成したフェライト粒子の平均粒子径と粒子径分布は、次の方法により測定した。 EXAMPLES The present invention will be described in more detail below using Examples, but the present invention is not limited to these Examples. Moreover, the average particle diameter and particle diameter distribution of the synthesized ferrite particles were measured by the following method.
（平均粒子径の測定）
粉体試料の走査型電子顕微鏡（ＳＥＭ）像上に縦線、横線を１６本ずつグリッド状に均等配置した画像を印刷し、縦線と横線の交点にある粒子あるいは交点に最も近い粒子計２５６個の直径をノギスで測定して平均値を求めた。また、ＳＥＭ像上のスケールバーの長さを測定し、その値を用いてｍｍ単位で測定した粒子径をμｍ単位に変換して平均粒子径とした。
(Measurement of average particle diameter)
A scanning electron microscope (SEM) image of a powder sample is printed with 16 vertical lines and 16 horizontal lines evenly arranged in a grid pattern, and the particles at the intersection of the vertical lines and horizontal lines or the particle counter 256 closest to the intersection are printed. The diameter of each piece was measured with a caliper and the average value was determined. Further, the length of the scale bar on the SEM image was measured, and using that value, the particle diameter measured in mm was converted to μm, which was defined as the average particle diameter.
（粒子径分布の測定）
本発明のコバルトフェライトの粒子径がそろっている点は、粒子径の変動係数であるＣＶ値により特定した。すなわち、統計学上はデータ分布のばらつきの1つの尺度として標準偏差が用いられるが、これをデータの算術平均値で割ることで規格化して、デー夕のばらつきを評価することが行なわれている。これが変動係数であるＣＶ値で、本発明でも、形成されたコバルトフェライト粒子の粒子径にばらつきが少ないことを、ＣＶ値を用いて評価することにした。ＣＶ値が小さいことが、粒子径分布にばらつきが少ないことを示しており、特にＣＶ値が０．１以下の粒子は単分散粒子であるとされ、その特性が注目されている。
(Measurement of particle size distribution)
The uniformity of the particle diameters of the cobalt ferrite of the present invention was determined by the CV value, which is the coefficient of variation of the particle diameters. In other words, standard deviation is used statistically as a measure of the dispersion of data distribution, but this is normalized by dividing it by the arithmetic mean value of the data to evaluate the dispersion of the data. . This is the CV value, which is a coefficient of variation, and in the present invention, it was decided to use the CV value to evaluate that there is little variation in the particle diameter of the cobalt ferrite particles formed. A small CV value indicates that there is little variation in particle size distribution, and in particular, particles with a CV value of 0.1 or less are said to be monodisperse particles, and their characteristics are attracting attention.
（磁気特性の測定）
本発明のコバルトフェライトの磁気特性は、振動試料型磁力計（ＶＳＭ）（玉川製作所製、型番「ＴＭ-ＶＳＭ１０１４８３Ｎ７-ＭＲＯ」）により評価した。最大磁界１０，０００Ｏｅでヒステリシス曲線または減磁曲線を取得し、飽和磁気モーメント、残留磁気モーメント、保磁力を測定した。
(Measurement of magnetic properties)
The magnetic properties of the cobalt ferrite of the present invention were evaluated using a vibrating sample magnetometer (VSM) (manufactured by Tamagawa Seisakusho, model number "TM-VSM101483N7-MRO"). A hysteresis curve or demagnetization curve was obtained at a maximum magnetic field of 10,000 Oe, and the saturation magnetic moment, residual magnetic moment, and coercive force were measured.
［実施例１］（コバルトフェライト粒子の製造）
（１） 脱塩脱気水の調製
脱塩水４８０ｇを２．５Ｌ/ｍｉｎのＮ２で３０分脱気し、脱塩脱気水を調製した。
（２） 原料水溶液の調製
塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）３２ｇ、塩化コバルト（II）六水和物（ＣоＣｌ２・６Ｈ２Ｏ）８ｇを脱塩脱気水１７２ｇに溶解し、原料水溶液を調製した。
（３） 錯化剤水溶液の調製
クエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）８６ｇ、硝酸ナトリウム(ＮａＮＯ３）５ｇを脱塩脱気水１６８ｇに溶解し、錯化剤水溶液を調製した。
（４） アルカリ水溶液の調製
水酸化ナトリウム（ＮａＯＨ）１０ｇを脱塩脱気水２５ｇに溶解し、アルカリ水溶液を調製した。
（５） 前駆体の調製
Ｎ２置換した容器の中で原料水溶液と錯化剤水溶液を混合した後、アルカリ水溶液を添加してｐＨ１０に調整することで前駆体を調製した。
（６） 前駆体の水熱処理による磁性粒子の調製
前駆体をＮ２置換したオートクレーブに入れ、攪拌しながら１９０℃で２０時間水熱処理を行い、磁性粒子を得た。
（７） 磁性粒子の洗浄
磁性粒子をろ過し、脱塩水で通水洗浄した。
（８） 磁性粒子の乾燥
洗浄後の磁性粒子を大気雰囲気の下１１０℃で２時間乾燥させた。
[Example 1] (Production of cobalt ferrite particles)
(1) Preparation of desalinated and degassed water 480 g of demineralized water was degassed with 2.5 L/min of N 2 for 30 minutes to prepare desalted and degassed water.
(2) Preparation of raw material aqueous solution 32 g of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O) and 8 g of cobalt (II) chloride hexahydrate (CоCl 2.6H 2 O) were added to desalted, degassed water. A raw material aqueous solution was prepared by dissolving in 172 g.
(3) Preparation of complexing agent aqueous solution 86 g of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) and 5 g of sodium nitrate (NaNO 3 ) were dissolved in 168 g of desalinated and degassed water. , an aqueous complexing agent solution was prepared.
(4) Preparation of alkaline aqueous solution 10 g of sodium hydroxide (NaOH) was dissolved in 25 g of demineralized and degassed water to prepare an alkaline aqueous solution.
(5) Preparation of Precursor After mixing the raw material aqueous solution and the complexing agent aqueous solution in a container purged with N2 , a precursor was prepared by adding an alkaline aqueous solution to adjust the pH to 10.
(6) Preparation of magnetic particles by hydrothermal treatment of precursor The precursor was placed in an autoclave purged with N 2 and hydrothermally treated at 190° C. for 20 hours with stirring to obtain magnetic particles.
(7) Washing of magnetic particles The magnetic particles were filtered and washed with demineralized water.
(8) Drying of magnetic particles The washed magnetic particles were dried at 110° C. for 2 hours in an air atmosphere.
［実施例２］
実施例１で酸化剤として添加した硝酸ナトリウムを使用しなかった以外は実施例１と同じ条件で、磁性粒子を製造した。
[Example 2]
Magnetic particles were produced under the same conditions as in Example 1, except that sodium nitrate, which was added as an oxidizing agent in Example 1, was not used.
［実施例３］
実施例１から（５）のアルカリ水溶液の添加により１０に調整したｐＨを８とし、（６）の水熱処理時間を４０時間に代えた以外は実施例１と同じ条件で磁性粒子を製造した。
[Example 3]
Magnetic particles were produced under the same conditions as in Example 1, except that the pH of Examples 1 to (5) was adjusted to 10 by adding an aqueous alkali solution to 8, and the hydrothermal treatment time in (6) was changed to 40 hours.
［実施例４］
実施例１から（２）の塩化鉄（II）四水和物(ＦｅＣｌ２・４Ｈ２Ｏ）の量を２５．７ｇへ、塩化コバル卜（II）六水和物(ＣоＣｌ２・６Ｈ２Ｏ）の量を１５．４ｇへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を５９．９ｇへ、硝酸ナトリウム(ＮａＮＯ３）の量を１．７ｇへ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 4]
The amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O) in Examples 1 to (2) was reduced to 25.7 g, and the amount of cobalt (II) chloride hexahydrate (CoCl 2.6H 2 O) was changed to 25.7 g. ) to 15.4 g, the amount of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) in (3) to 59.9 g, and the amount of sodium nitrate (NaNO 3 ) to 59.9 g. Magnetic particles were produced under the same conditions as in Example 1 except that the amount was changed to 1.7 g.
［実施例５］
実施例１から（１）の脱塩水の量を２３００．０ｇへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）の量を３３７．３ｇへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）の量を８０．７ｇへ、脱塩脱気水の量を８２７．５ｇへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を６０４．７ｇへ、硝酸ナトリウム(ＮａＮＯ３）の量を１７．３ｇへ、脱塩脱気水の量を８０７．８ｇへ、（４）の水酸化ナトリウム（ＮａＯＨ）を８６．４ｇへ、脱塩脱気水の量を９３．６ｇへ、（６）の水熱処理を２００℃で１６時間へ、（８）の乾燥を２５０℃で１時間へ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 5]
From Example 1, the amount of demineralized water in (1) was reduced to 2300.0 g, the amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O) in (2) was reduced to 337.3 g, and cobalt chloride ( II) The amount of hexahydrate (CoCl 2.6H 2 O) was reduced to 80.7 g, the amount of demineralized degassed water was reduced to 827.5 g, and the amount of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) amount to 604.7 g, sodium nitrate (NaNO 3 ) amount to 17.3 g, desalted degassed water amount to 807.8 g, (4). Sodium hydroxide (NaOH) was reduced to 86.4g, the amount of demineralized and degassed water was reduced to 93.6g, the hydrothermal treatment of (6) was increased to 200°C for 16 hours, and the drying of (8) was increased to 250°C for 1 hour. Magnetic particles were manufactured under the same conditions as in Example 1, except that the conditions were changed to .
［実施例６］
実施例１から（１）の脱塩水の量を１３，０００.０gへ、Ｎ２の流量を１０Ｌ/ｍｉｎへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）３２ｇを硫酸鉄（II）七水和物（ＦｅＳＯ４・７Ｈ２Ｏ）２，６９０．０gへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）８ｇを硫酸コバルト（II）七水和物（ＣｏＳＯ４・７Ｈ２Ｏ）５４４．０gへ、脱塩脱気水の量を４７１８．７gへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を３，４４８.０gへ、硝酸ナトリウム（ＮａＮＯ３）の量を９９．０gへ、脱塩脱気水の量を４６０６．３gへ、（４）の水酸化ナトリウム（ＮａＯＨ）の量を４８０．０ｇへ、脱塩脱気水の量を５２０．０gへ、（５）のｐＨを９ヘ、（６）の水熱処理を２４０℃で0時間（２４０℃へ到達後直ちに冷却）へ、（８）の乾燥を２５０℃で１時間へ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 6]
From Example 1, the amount of demineralized water in (1) was changed to 13,000.0 g, the flow rate of N 2 was changed to 10 L/min, and the amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O in (2) was changed to 13,000.0 g. ) to 2,690.0 g of iron (II) sulfate heptahydrate (FeSO 4.7H 2 O), and 8 g of cobalt (II) chloride hexahydrate (CoCl 2.6H 2 O) to cobalt (II) sulfate (FeSO 4.7H 2 O). ) Heptahydrate ( CoSO 4.7H 2 O) to 544.0 g, the amount of demineralized degassed water to 4718.7 g, trisodium citrate dihydrate (C 6 H 5 Na 3) of (3) O 7.2H 2 O) amount to 3,448.0g, sodium nitrate (NaNO 3 ) amount to 99.0g, desalted degassed water amount to 4606.3g, hydroxide of (4) The amount of sodium (NaOH) was changed to 480.0 g, the amount of demineralized and degassed water was changed to 520.0 g, the pH of (5) was changed to 9, and the hydrothermal treatment of (6) was performed at 240°C for 0 hours (to 240°C). Magnetic particles were produced under the same conditions as in Example 1, except that (8) the drying time was changed to 250° C. for 1 hour.
［実施例７］
実施例１から（１）の脱塩水の量を１２，０００.０gへ、Ｎ２の流量を１０Ｌ/ｍｉｎへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）の量を１,９２３．０gへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）の量を４６０．０g、脱塩脱気水の量を４４３６．３gへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を３，４４８.０gへ、硝酸ナトリウム（ＮａＮＯ３）の量を９９．０gへ、脱塩脱気水の量を４３３０．７gへ、（４）の水酸化ナトリウム（ＮａＯＨ）の量を４８０．０gへ、脱塩脱気水の量を５２０．０gへ、（５）のｐＨを9ヘ、（６）の水熱処理を２６０℃で0時間（２６０℃へ到達後直ちに冷却）へ、（８）の乾燥を２５０℃で１時間へ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 7]
From Example 1, the amount of demineralized water in (1) was changed to 12,000.0 g, the flow rate of N 2 was changed to 10 L/min, and the amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O in (2) was changed to 12,000.0 g. ) amount to 1,923.0 g, the amount of cobalt(II) chloride hexahydrate (CoCl 2.6H 2 O) to 460.0 g, the amount of desalted degassed water to 4436.3 g, (3 ) of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) to 3,448.0 g, sodium nitrate (NaNO 3 ) to 99.0 g, desalination The amount of degassed water was changed to 4330.7g, the amount of sodium hydroxide (NaOH) in (4) was changed to 480.0g, the amount of demineralized degassed water was changed to 520.0g, and the pH of (5) was changed to 9. , Magnetic particles were prepared under the same conditions as in Example 1, except that the hydrothermal treatment in (6) was changed to 260°C for 0 hours (cooled immediately after reaching 260°C), and the drying in (8) was changed to 250°C for 1 hour. was manufactured.
［実施例８］
実施例１から、（１）の脱塩水の量を７５０．０ｇへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）３２ｇを硫酸鉄（II）七水和物（ＦｅＳＯ４・７Ｈ２Ｏ）１２５．８ｇへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）８ｇを硫酸コバルト（II）七水和物（ＣｏＳＯ４・７Ｈ２Ｏ）６３．６ｇへ、脱塩脱気水の量を１４２．７ｇへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を２０５．６ｇへ、硝酸ナトリウム（ＮａＮＯ３）の量を５．８ｇへ、脱塩脱気水の量を３９４．０ｇへ、（４）の水酸化ナトリウム（ＮａＯＨ）の量を３５．０ｇへ、脱塩脱気水の量を３７．９ｇへ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 8]
From Example 1, the amount of demineralized water in (1) was reduced to 750.0 g, and 32 g of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O) in (2) was reduced to iron (II) sulfate heptahydrate. 8 g of cobalt( II ) chloride hexahydrate (CoCl 2.6H 2 O) was added to 125.8 g of cobalt(II) sulfate heptahydrate (CoSO 4.7H 2 O). 63.6g, the amount of desalted degassed water to 142.7g, and the amount of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) in (3) to 205.6 g. , the amount of sodium nitrate (NaNO 3 ) was changed to 5.8 g, the amount of demineralized degassed water was changed to 394.0 g, the amount of sodium hydroxide (NaOH) in (4) was changed to 35.0 g, and the amount of desalted degassed water was changed to 35.0 g. Magnetic particles were produced under the same conditions as in Example 1 except that the amount of air and water was changed to 37.9 g.
［実施例９］
実施例１から（３）の硝酸ナトリウム（ＮａＮＯ３）の量を１．７ｇ、へ変更し、（６）で前駆体と共に酸化鉄の一種であるマグネタイト（Ｆｅ３Ｏ４）０．８ｇを種粒子としてオートクレーブへ入れた以外は、実施例１と同じ条件で磁性粒子を製造した。
[Example 9]
From Example 1 to (3), the amount of sodium nitrate (NaNO 3 ) was changed to 1.7 g, and in (6), 0.8 g of magnetite (Fe 3 O 4 ), a type of iron oxide, was added as a seed along with the precursor. Magnetic particles were produced under the same conditions as in Example 1, except that the particles were placed in an autoclave.
［参考例１］
実施例１から（１）の脱塩水の量を１２，０００.０ｇへ、Ｎ２の流量を１０Ｌ/ｍｉｎへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）の量を１，９２３．０gへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）の量を４６０．０ｇ、脱塩脱気水の量を４４３６．３gへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を３，４４８.０gへ、硝酸ナトリウム（ＮａＮＯ３）の量を９９．０gへ、脱塩脱気水の量を４３３０．７gへ、（４）の水酸化ナトリウム（ＮａＯＨ）の量を４８０．０gへ、脱塩脱気水の量を５２０．０gへ、（５）のｐＨを９ヘ、（６）の水熱処理を３００℃で０．５時間へ、（８）の乾燥を２５０℃で１時間へ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Reference example 1]
From Example 1, the amount of demineralized water in (1) was changed to 12,000.0 g, the flow rate of N 2 was changed to 10 L/min, and the amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O in (2) was changed to 12,000.0 g. ) amount to 1,923.0 g, the amount of cobalt(II) chloride hexahydrate (CoCl 2.6H 2 O) to 460.0 g, the amount of desalted degassed water to 4436.3 g, (3 ) of trisodium citrate dihydrate (C 6 H 5 Na 3 O 7.2H 2 O) to 3,448.0 g, sodium nitrate (NaNO 3 ) to 99.0 g, desalination The amount of degassed water was changed to 4330.7 g, the amount of sodium hydroxide (NaOH) in (4) was changed to 480.0 g, the amount of desalted degassed water was changed to 520.0 g, and the pH of (5) was changed to 9. Magnetic particles were produced under the same conditions as in Example 1, except that the hydrothermal treatment in (6) was changed to 300° C. for 0.5 hours, and the drying in (8) was changed to 250° C. for 1 hour.
［参考例２］
実施例１から（１）の脱塩水の量を１３，０００.０gへ、Ｎ２の流量を１０Ｌ/ｍｉｎへ、（２）の塩化鉄（II）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）３２ｇを硫酸鉄（II）七水和物（ＦｅＳＯ４・７Ｈ２Ｏ）２，６９０．０gへ、塩化コバルト（II）六水和物（ＣｏＣｌ２・６Ｈ２Ｏ）８ｇを硫酸コバルト（II）七水和物（ＣｏＳＯ４・７Ｈ２Ｏ）５４４．０gへ、脱塩脱気水の量を４７１８．７ｇへ、（３）のクエン酸三ナトリウム二水和物（Ｃ６Ｈ５Ｎａ３Ｏ７・２Ｈ２Ｏ）の量を３，４４８.０gへ、硝酸ナトリウム（ＮａＮＯ３）の量を９９．０gへ、脱塩脱気水の量を４６０６．３gへ、（４）の水酸化ナトリウム（ＮａＯＨ）の量を４８０．０gへ、脱塩脱気水の量を５２０．０gへ、（５）のｐＨを９ヘ、（６）の水熱処理を３００℃で０．５時間へ、（８）の乾燥を２５０℃で１時間へ変更した以外は、実施例１と同じ条件で磁性粒子を製造した。
[Reference example 2]
From Example 1, the amount of demineralized water in (1) was changed to 13,000.0 g, the flow rate of N 2 was changed to 10 L/min, and the amount of iron (II) chloride tetrahydrate (FeCl 2.4H 2 O in (2) was changed to 13,000.0 g. ) to 2,690.0 g of iron (II) sulfate heptahydrate (FeSO 4.7H 2 O), and 8 g of cobalt (II) chloride hexahydrate (CoCl 2.6H 2 O) to cobalt (II) sulfate (FeSO 4.7H 2 O). ) Heptahydrate ( CoSO 4.7H 2 O) to 544.0 g, the amount of demineralized degassed water to 4718.7 g, trisodium citrate dihydrate (C 6 H 5 Na 3) of (3) O 7.2H 2 O) amount to 3,448.0g, sodium nitrate (NaNO 3 ) amount to 99.0g, desalted degassed water amount to 4606.3g, hydroxide of (4) The amount of sodium (NaOH) was changed to 480.0 g, the amount of demineralized and degassed water was changed to 520.0 g, the pH of (5) was changed to 9, the hydrothermal treatment of (6) was changed to 300°C for 0.5 hours, Magnetic particles were produced under the same conditions as in Example 1, except that the drying time in (8) was changed to 250° C. for 1 hour.
［比較例１］
実施例１で錯化剤と酸化剤を使用しなかった以外は実施例1と同じ条件で、磁性粒子を製造した。
[Comparative example 1]
Magnetic particles were produced under the same conditions as in Example 1 except that the complexing agent and oxidizing agent were not used in Example 1.
磁性粒子の各種特性を整理すると次のとおりとなる。
表中の反応率は、基本的に下記式Ａに従い算出し、実施例６、７、参考例１、２については、加温中のオートクレーブから部分的に内容物を取り出すことで磁性粒子を得たため、前駆体の全量が完全に反応した際のコバルトフェライト収量を分母とする式Ａでは不適切である、という理由より式Ｂに従って算出した。
式Ａ：フェライト前駆体の水熱処理によって実際に得られた粉体の質量/{仕込んだ原料中の鉄およびコバルトが全て反応した場合に得られるコバルトフェライト(ＣｏｘＦｅ(３-ｘ)Ｏ４)の理論的な質量}×１００
式Ｂ：{1-(水熱処理終了後の水溶液中に溶存する鉄およびコバルトの質量濃度)/(水熱処理前のフェライト前駆体中の鉄およびコバルトの理論的な質量濃度)}×１００
The reaction rates in the table are basically calculated according to the following formula A, and for Examples 6 and 7 and Reference Examples 1 and 2, magnetic particles were obtained by partially removing the contents from the autoclave during heating. Therefore, formula A, which uses the cobalt ferrite yield when the entire amount of the precursor is completely reacted, as the denominator, is inappropriate, and therefore, formula B was used for calculation.
Formula A: Mass of powder actually obtained by hydrothermal treatment of ferrite precursor/{Cobalt ferrite obtained when all iron and cobalt in the charged raw materials react (C x Fe (3-x) O 4 ) Theoretical mass of )}×100
Formula B: {1-(mass concentration of iron and cobalt dissolved in the aqueous solution after hydrothermal treatment)/(theoretical mass concentration of iron and cobalt in the ferrite precursor before hydrothermal treatment)}×100
実施例１～９は、いずれも錯化剤で安定化されたフェライト前駆体を加熱処理してフェライト粒子を形成しており、得られた粒子は平均粒子径が大きく、粒子径のばらつきの少ないフェライト粒子であった。ＣＶ値が０．１５、０．１７、０．１６、０．２１、０．２３、０．２４、０．２２、０．２０、０．２０であるので、単分散粒子に近い粒子であった。一方、比較例１の条件で製造した場合には、平均粒子径が小さくばらつきの大きな粒子しか得られなかった。 In Examples 1 to 9, ferrite particles were formed by heat-treating a ferrite precursor stabilized with a complexing agent, and the obtained particles had a large average particle size and little variation in particle size. They were ferrite particles. Since the CV values are 0.15, 0.17, 0.16, 0.21, 0.23, 0.24, 0.22, 0.20, and 0.20, the particles are close to monodisperse particles. Ta. On the other hand, when produced under the conditions of Comparative Example 1, only particles with a small average particle diameter and large variations were obtained.
図１～９は実施例１～９の粉体試料のＳＥＭ写真であり、図１０，１１は参考例１、２の粉体試料のＳＥＭ写真であり、図１２は比較例１の粉体試料のＳＥＭ写真である。製造したフェライト粒子の形状のＳＥＭ観察より、実施例１～７のフェライト粒子は丸みをおびている点で、図１２の比較例１のフェライト粒子とは異なることが示された。 Figures 1 to 9 are SEM photographs of powder samples of Examples 1 to 9, Figures 10 and 11 are SEM photographs of powder samples of Reference Examples 1 and 2, and Figure 12 is SEM photographs of powder samples of Comparative Example 1. This is an SEM photo of. SEM observation of the shapes of the produced ferrite particles showed that the ferrite particles of Examples 1 to 7 were different from the ferrite particles of Comparative Example 1 in FIG. 12 in that they were rounded.
実施例５の結果より、反応温度を２００℃にすることにより、粉体試料の反応率が９１．４％になることが示された。このことより、反応温度を１９０℃よりも高くすることにより、粉体試料の反応率が向上することが示された。 The results of Example 5 showed that by setting the reaction temperature to 200°C, the reaction rate of the powder sample was 91.4%. This indicates that the reaction rate of the powder sample is improved by increasing the reaction temperature higher than 190°C.
参考例１，２の結果より、反応温度を３００℃にすることにより、粉体試料の反応率が９９．９％になることが示された。このことより、粉体試料の反応率を高めるには反応温度を３００℃にすることが好ましいことが示された。一方、反応温度を３００℃にすることにより、不純物が入ってくることが示された。これらより、純度と反応率のバランスを図る観点からは、反応温度は３００℃未満であることが好ましいことが示された。また実施例７と参考例１の対比より、反応時間は２６０℃以下がより好ましいことが示された。 The results of Reference Examples 1 and 2 showed that by setting the reaction temperature to 300°C, the reaction rate of the powder sample became 99.9%. This indicates that it is preferable to set the reaction temperature to 300° C. in order to increase the reaction rate of the powder sample. On the other hand, it was shown that impurities were introduced by increasing the reaction temperature to 300°C. From these results, it was shown that the reaction temperature is preferably less than 300° C. from the viewpoint of achieving a balance between purity and reaction rate. Further, a comparison between Example 7 and Reference Example 1 showed that the reaction time was more preferably 260°C or less.
得られた粒子の断面構造を確認するために透過型電子顕微鏡（ＴＥＭ）観察を行った。そして、種粒子なし粒子の代表例として、図１３Ａに実施例６の粉体の断面概念図を示し、種粒子ありの代用例として図１３Ｂに実施例９の粉体の断面概念図を示す。
図１３Ａに示すように、粒子は、複数のナノ粒子からなるコア部と、表面に丸みを帯びた突部が連なるシェル部とを備えるコアシェル構造を有することが確認された。
図１３Ｂに示すように、種粒子を用いて粒子を作製した場合、コア部は、複数のナノ粒子からなる海に複数の種粒子が浮かぶ、いわゆる海島構造を有することが確認された。
本明細書において、単に「粒子径」という場合は、図１３Ａの矢印Ａで示されるように、コアシェル構造粒子の最外殻の直径を指すものとする。
Transmission electron microscopy (TEM) observation was performed to confirm the cross-sectional structure of the obtained particles. As a representative example of particles without seed particles, FIG. 13A shows a conceptual cross-sectional view of the powder of Example 6, and FIG. 13B shows a conceptual cross-sectional view of the powder of Example 9 as a substitute example with seed particles.
As shown in FIG. 13A, it was confirmed that the particles had a core-shell structure including a core portion made of a plurality of nanoparticles and a shell portion having a series of rounded protrusions on the surface.
As shown in FIG. 13B, when particles were produced using seed particles, it was confirmed that the core part had a so-called sea-island structure in which a plurality of seed particles floated in a sea made up of a plurality of nanoparticles.
In this specification, the term "particle diameter" refers to the diameter of the outermost shell of a core-shell structure particle, as shown by arrow A in FIG. 13A.
［実施例１０]（コバルトフェライト粒子の白色化）
脱イオン水１９．８ｇに４塩化チタン溶液（１６．０～１７．０％ａｓＴｉ）２．２ｍＬ、アンモニア水５．８４ｇ、過酸化水素水１０．０ｇを混合して黄色透明のペルオキソチタン酸溶液を作成した。脱イオン水５３５．８１ｇに無水ホウ酸９．９２ｇ、塩化カリウ厶１１．７２ｇ、水酸化ナトリウム２．５５ｇを溶解し、実施例４で得られたフェライ卜粒子１６．７５ｇを懸濁した。懸濁液を撹拌しながらペルオキソチタン酸溶液を滴下混合し、その後に懸濁物の乾燥を行うことで、酸化チタン被覆粉末を得た。
脱イオン水２６．５６ｇにブドウ糖１．２ｇ、酒石酸０．１２ｇ、エタノール２．１２ｇを溶解して還元液を調製した。脱イオン水９０ｇに水酸化ナトリウム１．２５ｇ、硝酸銀１．７５ｇ、アンモニア水３ｇを混合して銀アンミン錯体溶液を調製し、これに酸化チタン被覆粉末６．３ｇを懸濁した。懸濁液に超音波照射を行いながら還元液を混合し、懸濁物を乾燥して銀膜被覆粉体を得た。得られた白色粉体は、明度Ｌ＊が７９．９８であった。
[Example 10] (Whitening of cobalt ferrite particles)
Mix 19.8 g of deionized water with 2.2 mL of titanium tetrachloride solution (16.0-17.0% asTi), 5.84 g of ammonia water, and 10.0 g of hydrogen peroxide solution to make a transparent yellow peroxotitanic acid solution. It was created. 9.92 g of boric anhydride, 11.72 g of potassium chloride, and 2.55 g of sodium hydroxide were dissolved in 535.81 g of deionized water, and 16.75 g of the ferrite particles obtained in Example 4 were suspended. A peroxotitanic acid solution was added dropwise to the suspension while stirring, and the suspension was then dried to obtain a titanium oxide-coated powder.
A reducing solution was prepared by dissolving 1.2 g of glucose, 0.12 g of tartaric acid, and 2.12 g of ethanol in 26.56 g of deionized water. A silver ammine complex solution was prepared by mixing 90 g of deionized water with 1.25 g of sodium hydroxide, 1.75 g of silver nitrate, and 3 g of aqueous ammonia, and 6.3 g of titanium oxide coated powder was suspended in this solution. A reducing solution was mixed with the suspension while irradiating it with ultrasonic waves, and the suspension was dried to obtain a silver film-coated powder. The obtained white powder had a lightness L* of 79.98.
本発明の製造方法で得られたコバルトフェライト粒子は、丸みをおびた形状で粒子径がそろっているので、コピー用トナー、磁性インク、ＭＲ流体としての用途が期待される。 Since the cobalt ferrite particles obtained by the production method of the present invention have a rounded shape and uniform particle diameter, they are expected to be used as copying toners, magnetic inks, and MR fluids.
Claims (20)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2023/010313 WO2023176926A1 (en) | 2022-03-17 | 2023-03-16 | Method for producing cobalt ferrite particles and cobalt ferrite particles produced by same |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022042172 | 2022-03-17 | ||
| JP2022042172 | 2022-03-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2023138411A true JP2023138411A (en) | 2023-10-02 |
Family
ID=88197441
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2023036445A Pending JP2023138411A (en) | 2022-03-17 | 2023-03-09 | Method of producing cobalt ferrite particles, and cobalt ferrite particles produced by the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2023138411A (en) |
-
2023
- 2023-03-09 JP JP2023036445A patent/JP2023138411A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP7454425B2 (en) | Method for producing cobalt ferrite particles and cobalt ferrite particles produced thereby | |
| WO2020217982A1 (en) | Method for producing cobalt ferrite particles and cobalt ferrite particles produced by same | |
| WO2023176926A1 (en) | Method for producing cobalt ferrite particles and cobalt ferrite particles produced by same | |
| JP2023138411A (en) | Method of producing cobalt ferrite particles, and cobalt ferrite particles produced by the same | |
| JPH0368923B2 (en) | ||
| US20230381861A1 (en) | METHOD FOR MANUFACTURING IRON (Fe)-NICKEL (Ni) ALLOY POWDER | |
| CN114496442A (en) | Nano magnetic particle, preparation method thereof and magnetic liquid | |
| WO2016199937A1 (en) | Epsilon iron oxide and method for producing same, magnetic paint, and magnetic recording medium | |
| JP4780856B2 (en) | Granular magnetite particles and method for producing the same | |
| JPH10226520A (en) | Hydrate iron oxide and production of ferromagnetic iron oxide | |
| JP3884860B2 (en) | Method for producing magnetic powder | |
| JP3087778B2 (en) | Method for producing acicular goethite particle powder | |
| JPS5877505A (en) | Production of metallic magnetic powder | |
| JPS6334608B2 (en) | ||
| JP3087777B2 (en) | Method for producing acicular goethite particle powder | |
| JP3087780B2 (en) | Method for producing acicular goethite particle powder | |
| Fouad | Growth of nickel nanostructured beads and thin films | |
| JPS63105901A (en) | Magnetic particle powder essentially consisting of iron alloy exhibiting spherical shape and its production | |
| JPH061618A (en) | Production of acicular goethite powdery particle | |
| JPH0518766B2 (en) | ||
| JPH0616426A (en) | Production of spindle-shaped goethite granular powder | |
| JPS61140110A (en) | Manufacture of acicular alpha-feooh for magnetic recording material | |
| JPH09188520A (en) | Production of fusiform goethite | |
| JPS62128926A (en) | Production of magnetic iron oxide grain powder having spindle type | |
| JPH06104575B2 (en) | Method for producing tabular Ba ferrite fine particle powder |