JP2020164410A - Titanium oxide organic solvent dispersion - Google Patents
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 151
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 title claims abstract description 128
- 239000003960 organic solvent Substances 0.000 title claims abstract description 113
- 239000006185 dispersion Substances 0.000 title claims abstract description 102
- 239000002245 particle Substances 0.000 claims abstract description 125
- 239000011164 primary particle Substances 0.000 claims abstract description 20
- 230000001186 cumulative effect Effects 0.000 claims abstract description 15
- 230000008859 change Effects 0.000 abstract description 19
- 230000007774 longterm Effects 0.000 abstract description 8
- 238000003860 storage Methods 0.000 abstract description 8
- 239000002002 slurry Substances 0.000 description 57
- 238000000034 method Methods 0.000 description 33
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 32
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 23
- 239000000243 solution Substances 0.000 description 21
- 239000011362 coarse particle Substances 0.000 description 16
- 239000002904 solvent Substances 0.000 description 16
- 239000004065 semiconductor Substances 0.000 description 12
- 229910010413 TiO 2 Inorganic materials 0.000 description 10
- 238000002425 crystallisation Methods 0.000 description 10
- 230000008025 crystallization Effects 0.000 description 10
- 238000009826 distribution Methods 0.000 description 10
- 150000003609 titanium compounds Chemical class 0.000 description 10
- 235000010215 titanium dioxide Nutrition 0.000 description 10
- 230000002776 aggregation Effects 0.000 description 9
- 238000004220 aggregation Methods 0.000 description 8
- 239000003795 chemical substances by application Substances 0.000 description 8
- -1 nitrate ions Chemical class 0.000 description 8
- 239000004408 titanium dioxide Substances 0.000 description 8
- 239000002562 thickening agent Substances 0.000 description 7
- LLZRNZOLAXHGLL-UHFFFAOYSA-J titanic acid Chemical compound O[Ti](O)(O)O LLZRNZOLAXHGLL-UHFFFAOYSA-J 0.000 description 7
- 238000005119 centrifugation Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
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- 238000000576 coating method Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000000975 dye Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
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- 239000010936 titanium Substances 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 description 4
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 4
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000003125 aqueous solvent Substances 0.000 description 3
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- 150000002576 ketones Chemical class 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
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- 238000000733 zeta-potential measurement Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 239000001856 Ethyl cellulose Substances 0.000 description 2
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 150000007514 bases Chemical class 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000003995 emulsifying agent Substances 0.000 description 2
- 150000002170 ethers Chemical class 0.000 description 2
- 229920001249 ethyl cellulose Polymers 0.000 description 2
- 235000019325 ethyl cellulose Nutrition 0.000 description 2
- 150000002334 glycols Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000010335 hydrothermal treatment Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- UODXCYZDMHPIJE-UHFFFAOYSA-N menthanol Chemical compound CC1CCC(C(C)(C)O)CC1 UODXCYZDMHPIJE-UHFFFAOYSA-N 0.000 description 2
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 2
- 239000011941 photocatalyst Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000007650 screen-printing Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 2
- LNAZSHAWQACDHT-XIYTZBAFSA-N (2r,3r,4s,5r,6s)-4,5-dimethoxy-2-(methoxymethyl)-3-[(2s,3r,4s,5r,6r)-3,4,5-trimethoxy-6-(methoxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6r)-4,5,6-trimethoxy-2-(methoxymethyl)oxan-3-yl]oxyoxane Chemical compound CO[C@@H]1[C@@H](OC)[C@H](OC)[C@@H](COC)O[C@H]1O[C@H]1[C@H](OC)[C@@H](OC)[C@H](O[C@H]2[C@@H]([C@@H](OC)[C@H](OC)O[C@@H]2COC)OC)O[C@@H]1COC LNAZSHAWQACDHT-XIYTZBAFSA-N 0.000 description 1
- VXQBJTKSVGFQOL-UHFFFAOYSA-N 2-(2-butoxyethoxy)ethyl acetate Chemical compound CCCCOCCOCCOC(C)=O VXQBJTKSVGFQOL-UHFFFAOYSA-N 0.000 description 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229920002153 Hydroxypropyl cellulose Polymers 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000004640 Melamine resin Substances 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000010130 dispersion processing Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
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- 238000011156 evaluation Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000001863 hydroxypropyl cellulose Substances 0.000 description 1
- 235000010977 hydroxypropyl cellulose Nutrition 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
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- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
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- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
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- 229910052707 ruthenium Inorganic materials 0.000 description 1
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- 150000003608 titanium Chemical class 0.000 description 1
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 1
- 229910000348 titanium sulfate Inorganic materials 0.000 description 1
- 238000000108 ultra-filtration Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/542—Dye sensitized solar cells
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- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
Description
本発明は、酸化チタンの凝集粒子を含む有機溶媒分散体に関する。 The present invention relates to an organic solvent dispersion containing agglomerated particles of titanium oxide.
酸化チタンは、顔料、化粧料、光触媒として、幅広く使用されており、近年では、色素増感太陽電池にも使用されている。 Titanium oxide is widely used as pigments, cosmetics, and photocatalysts, and in recent years, it has also been used in dye-sensitized solar cells.
色素増感太陽電池は、有機色素を用いて光起電力を得る太陽電池の１種である。色素増感太陽電池は、従来の太陽電池と比べて構造がシンプルで、材料や製造プロセスが安く、形状のフレキシビリティが高いという特徴を有している。この色素増感太陽電池の構造は種々検討されている。例えば、ガラス板又は透明プラスチックシートの内側表面に、インジウム／スズ系の透明伝導層を有した構造がある。この構造では、透明伝導層に、ルテニウム系等の有機色素を吸着させた二酸化チタン等の微粒子を固定した電極と、白金や炭素等の対極とを有する。そして、両電極の間にヨウ素溶液等の酸化還元体を充填したものが知られている。また、これらの構造をより簡易的に作成するために、印刷法を用いることも検討されている。 A dye-sensitized solar cell is a type of solar cell that obtains photovoltaic power by using an organic dye. Dye-sensitized solar cells have the characteristics of being simpler in structure, cheaper in materials and manufacturing processes, and more flexible in shape than conventional solar cells. Various structures of this dye-sensitized solar cell have been studied. For example, there is a structure having an indium / tin-based transparent conductive layer on the inner surface of a glass plate or a transparent plastic sheet. In this structure, the transparent conductive layer has an electrode in which fine particles such as titanium dioxide adsorbed with an organic dye such as ruthenium are fixed, and a counter electrode such as platinum or carbon. Then, it is known that an oxidation-reduced substance such as an iodine solution is filled between both electrodes. In addition, in order to create these structures more easily, it is also considered to use a printing method.
色素増感太陽電池において広く用いられている二酸化チタンは、透明電極の表面に形成される多孔質半導体膜として用いられる。この二酸化チタンに吸着した色素が光エネルギーを吸収する。これよって励起された電子がこの多孔質半導体膜を通じて透明電極に移動することで、電気が発生する。したがって、色素増感太陽電池に用いられる二酸化チタンには、より多くの色素を吸着し得るように、多孔質で比表面積が大きいものが要望されていた。 Titanium dioxide, which is widely used in dye-sensitized solar cells, is used as a porous semiconductor film formed on the surface of a transparent electrode. The dye adsorbed on this titanium dioxide absorbs light energy. The electrons excited by this move to the transparent electrode through the porous semiconductor film, and electricity is generated. Therefore, titanium dioxide used in a dye-sensitized solar cell has been required to be porous and have a large specific surface area so that more dyes can be adsorbed.
このような色素増感太陽電池用の二酸化チタンは、これまで種々検討されている。例えば、特許文献１には、平均一次粒子径が２０ｎｍ以下の酸化チタンナノ粒子が集合した平均直径が３０〜５００ｎｍの集合体が記載されている。また、特許文献２には、平均粒子径が０．５〜１０μｍの範囲にあり、細孔容積が０．１〜０．８ｍＬ／ｇの範囲にある多孔質酸化チタン微粒子集合体と、平均粒子径が５〜４００ｎｍの範囲にある非集合体酸化チタン微粒子とを含んでなる半導体膜形成用の塗料が記載されている。このような色素増感太陽電池用の二酸化チタンの改良に伴い、色素増感太陽電池の性能は向上しつつある。 Various titanium dioxides for such dye-sensitized solar cells have been studied so far. For example, Patent Document 1 describes an aggregate having an average diameter of 30 to 500 nm, which is an aggregate of titanium oxide nanoparticles having an average primary particle diameter of 20 nm or less. Further, Patent Document 2 describes a porous titanium oxide fine particle aggregate having an average particle diameter in the range of 0.5 to 10 μm and a pore volume in the range of 0.1 to 0.8 mL / g, and average particles. A coating material for forming a semiconductor film containing non-aggregated titanium oxide fine particles having a diameter in the range of 5 to 400 nm is described. With the improvement of titanium dioxide for dye-sensitized solar cells, the performance of dye-sensitized solar cells is improving.
これらの二酸化チタンは、水や有機溶媒に分散した分散体として、塗布やスクリーン印刷等の方法に用いられ、多孔質半導体膜に成形される。このとき、均質な多孔質半導体膜を形成するためには、塗料の粘度が非常に重要なファクターである。しかし、これらの分散体には、長期間保存すると粒子の沈降等が発生して二酸化チタンの凝集状態に変化が生じ、長期間保存した後の粘度の変化が大きくなるという課題があった。 These titanium dioxides are used as a dispersion dispersed in water or an organic solvent in methods such as coating and screen printing, and are formed into a porous semiconductor film. At this time, in order to form a homogeneous porous semiconductor film, the viscosity of the coating material is a very important factor. However, these dispersions have a problem that when they are stored for a long period of time, particles settle down and the aggregated state of titanium dioxide changes, and the change in viscosity after long-term storage becomes large.
本発明では、酸化チタンを含む有機溶媒分散体であって、長期間保存しても粘度の変化が小さいものを提供することを目的とする。 An object of the present invention is to provide an organic solvent dispersion containing titanium oxide, which has a small change in viscosity even after long-term storage.
本発明者らは、有機溶媒分散体中に含まれる酸化チタンの凝集粒子径に着目し、この凝集粒子径を特定の範囲に制御したうえでそのばらつきを小さくした。これによって、長期間保存しても粘度の変化が生じ難くなり、前記有機溶媒分散体の長期保存が可能になることを見出した。 The present inventors focused on the aggregated particle size of titanium oxide contained in the organic solvent dispersion, controlled the aggregated particle size within a specific range, and reduced the variation. It has been found that this makes it difficult for the viscosity to change even after long-term storage, and enables long-term storage of the organic solvent dispersion.
すなわち、本発明は、酸化チタンの凝集粒子が有機溶媒に分散した分散体であって、酸化チタン粒子の一次粒子径が５ｎｍ以上２５ｎｍ以下の範囲にあり、前記凝集粒子の凝集粒子径（Ｄ５０）が１５０ｎｍ以下であり、前記凝集粒子の９０％累積径と１０％累積径の差分（Ｄ９０−Ｄ１０）が１７０ｎｍ以下である、有機溶媒分散体（以下、本発明の有機溶媒分散体ともいう。）である。 That is, the present invention is a dispersion in which aggregated particles of titanium oxide are dispersed in an organic solvent, and the primary particle diameter of the titanium oxide particles is in the range of 5 nm or more and 25 nm or less, and the aggregated particle diameter (D 50) of the aggregated particles. ) Is 150 nm or less, and the difference between the 90% cumulative diameter and the 10% cumulative diameter (D 90 − D 10 ) of the agglomerated particles is 170 nm or less (hereinafter, also referred to as the organic solvent dispersion of the present invention). It says.).
本発明によれば、長期間保存しても粘度の変化が小さい、酸化チタンを含む有機溶媒分散体を提供できる。 According to the present invention, it is possible to provide an organic solvent dispersion containing titanium oxide, which has a small change in viscosity even when stored for a long period of time.
［本発明の有機溶媒分散体の概要］
本発明の有機溶媒分散体は、酸化チタン粒子の凝集粒子径を特定の範囲に制御したうえで、そのばらつきを小さくしたものである。したがって、本発明の有機溶媒分散体は、極端に大きい又は小さい凝集粒子を可能な限り含まない。凝集粒子は、有機溶媒中において、特定の表面電位を有して分散している。この凝集粒子の大きさがばらつくと、その表面電位もばらつき、有機溶媒中において電荷が不均衡な状態になる。有機溶媒分散体がこのような状態にあると、凝集粒子の凝集状態が変化しやすくなる。このため、有機溶媒分散体の粘度も変化しやすくなる。そこで、例えば、図１に示される方法を用いて、酸化チタン粒子の凝集粒子径を特定の範囲に制御したうえで、そのばらつきを小さくする。そして、この凝集粒子を有機溶媒に分散させることで、長期間保存しても粘度の変化が小さい有機溶媒分散体が得られる。
[Overview of Organic Solvent Dispersion of the Present Invention]
In the organic solvent dispersion of the present invention, the aggregated particle size of the titanium oxide particles is controlled within a specific range, and the variation is reduced. Therefore, the organic solvent dispersions of the present invention do not contain extremely large or small aggregated particles as much as possible. The agglomerated particles are dispersed in an organic solvent with a specific surface potential. When the size of the agglomerated particles varies, the surface potential of the aggregated particles also varies, resulting in an imbalanced charge in the organic solvent. When the organic solvent dispersion is in such a state, the agglomerated state of the agglomerated particles is likely to change. Therefore, the viscosity of the organic solvent dispersion also tends to change. Therefore, for example, by using the method shown in FIG. 1, the aggregated particle diameter of the titanium oxide particles is controlled within a specific range, and the variation thereof is reduced. Then, by dispersing the aggregated particles in an organic solvent, an organic solvent dispersion having a small change in viscosity can be obtained even if it is stored for a long period of time.
本発明では、酸化チタン粒子の凝集粒子径及びそのばらつきを、ゼータ電位測定法によりえられる粒度分布から算出した。具体的には、前記粒度分布において５０％累積径（Ｄ５０）を凝集粒子径とし、１０％累積径（Ｄ１０）と９０％累積径（Ｄ９０）の差分を凝集粒子のばらつき（Ｄ９０−Ｄ１０）とした。 In the present invention, the aggregated particle size of the titanium oxide particles and the variation thereof were calculated from the particle size distribution obtained by the zeta potential measurement method. Specifically, the particle size of 50% cumulative diameter in the distribution of (D 50) and aggregated particle diameter, the difference of the variation in aggregated particles of 10% cumulative diameter (D 10) 90% cumulative diameter (D 90) (D 90 -D 10 ).
［先行技術との対比］
本発明の有機溶媒分散体は、特許文献１〜２と比較し、「前記凝集粒子径（Ｄ５０）が１５０ｎｍ以下であり、前記凝集粒子の９０％累積径と１０％累積径の差分（Ｄ９０−Ｄ１０）が１７０ｎｍ以下である」との点で少なくとも相違する。特に、有機溶媒分散体中に含まれる酸化チタンの凝集粒子径を特定の範囲に制御したうえで、そのばらつきを小さくするという思想は、前記特許文献に記載されていない。
[Comparison with prior art]
Compared with Patent Documents 1 and 2, the organic solvent dispersion of the present invention has "the aggregated particle diameter (D 50 ) of 150 nm or less, and the difference between the 90% cumulative diameter and the 10% cumulative diameter of the aggregated particles (D). 90- D 10 ) is 170 nm or less ”, which is at least different. In particular, the idea of controlling the diameter of the aggregated particles of titanium oxide contained in the organic solvent dispersion to a specific range and reducing the variation thereof is not described in the above patent documents.
［本発明の有機溶媒分散体］
以下、本発明の有機溶媒分散体について、詳述する。
[Organic solvent dispersion of the present invention]
Hereinafter, the organic solvent dispersion of the present invention will be described in detail.
［酸化チタン］
本発明の有機溶媒分散体は、酸化チタン粒子を含む。本発明において、酸化チタンとは、二酸化チタンのみを指すものではなく、二酸化チタンの酸素が一部欠損した組成のものも含む。また、これらの酸化チタン粒子の表面は、通常末端ＯＨ基を含むが、有機官能基で修飾されていてもよい。
[Titanium oxide]
The organic solvent dispersion of the present invention contains titanium oxide particles. In the present invention, titanium oxide does not mean only titanium dioxide, but also includes those having a composition in which titanium dioxide is partially deprived of oxygen. The surface of these titanium oxide particles usually contains a terminal OH group, but may be modified with an organic functional group.
［酸化チタン粒子の一次粒子径およびアスペクト比］
本発明の有機溶媒分散体は、有機溶媒を分散媒にした酸化チタン凝集粒子の分散体であって、前記凝集粒子を構成する前記酸化チタンの一次粒子の大きさ（以下、「一次粒子径」ともいう。）は、５ｎｍ以上２５ｎｍ以下の範囲にある。この一次粒子径は、５ｎｍ以上２０ｎｍ以下の範囲にあることが好ましい。この一次粒子径が小さいほど、酸化チタン粒子の比表面積が大きくなる。例えば、本発明の有機溶媒分散体を用い、色素増感太陽電池用の多孔質半導体膜を形成した場合、酸化チタン粒子の比表面積が大きくなる。このため、前記多孔質半導体膜の色素吸着量が多くなるので好ましい。なお、この一次粒子径は、前述の有機溶媒分散体から抽出した酸化チタン粒子を電子顕微鏡観察する方法で算出される。また、例えば、有機溶媒分散体は、図１のような酸化チタンスラリーを調製した後で、水を有機溶媒に溶媒置換する方法で得ることができる。この有機溶媒分散体は、有機溶媒置換前の酸化チタンスラリーに含まれる酸化チタン粒子を電子顕微鏡観察することによっても、酸化チタン一次粒子径を算出することができる。この算出方法は、後述の実施例にて詳述する。
また、前記酸化チタン粒子のアスペクト比（長径／短径）は、１以上３以下の範囲にあることが好ましい。このようにアスペクト比が１に近い酸化チタン粒子を含む有機溶媒分散体を用いて酸化チタンの層を形成すると、層の密度が高くなりやすい。
[Primary particle size and aspect ratio of titanium oxide particles]
The organic solvent dispersion of the present invention is a dispersion of titanium oxide agglomerated particles using an organic solvent as a dispersion medium, and the size of the titanium oxide primary particles constituting the agglomerated particles (hereinafter, “primary particle diameter””. Also referred to as) is in the range of 5 nm or more and 25 nm or less. The primary particle diameter is preferably in the range of 5 nm or more and 20 nm or less. The smaller the primary particle diameter, the larger the specific surface area of the titanium oxide particles. For example, when the porous semiconductor film for a dye-sensitized solar cell is formed using the organic solvent dispersion of the present invention, the specific surface area of the titanium oxide particles becomes large. Therefore, the amount of dye adsorbed on the porous semiconductor film is large, which is preferable. The primary particle diameter is calculated by observing the titanium oxide particles extracted from the organic solvent dispersion described above with an electron microscope. Further, for example, the organic solvent dispersion can be obtained by a method of preparing a titanium oxide slurry as shown in FIG. 1 and then substituting water with an organic solvent. With this organic solvent dispersion, the titanium oxide primary particle size can also be calculated by observing the titanium oxide particles contained in the titanium oxide slurry before replacement with the organic solvent with an electron microscope. This calculation method will be described in detail in Examples described later.
Further, the aspect ratio (major axis / minor axis) of the titanium oxide particles is preferably in the range of 1 or more and 3 or less. When the titanium oxide layer is formed by using the organic solvent dispersion containing the titanium oxide particles having an aspect ratio close to 1, the density of the layer tends to be high.
［凝集粒子径：Ｄ５０］
本発明の有機溶媒分散体に含まれる酸化チタン粒子は、有機溶媒分散体中において凝集粒子として存在する。本発明では、前記凝集粒子の大きさは、ゼータ電位測定して得られる粒度分布から算出される５０％累積径で表される。ここで、本発明の有機溶媒分散体に含まれる前記凝集粒子径は、前記凝集粒子が溶媒中に分散した状態で測定することが重要である。これは、溶媒中における凝集粒子の状態が分散体の長期保存性に大きく影響をあたえるからである。溶媒中から前記凝集粒子を取り出し、電子顕微鏡で観察する測定方法では、溶媒を除去する際に凝集粒子同士がさらに凝集する。このような状態では凝集粒子の境界がわかりにくくなるので、本発明の有機溶媒分散体の凝集粒子径を測定する方法としては適切ではない。なお、本発明で用いるゼータ電位測定は、溶媒中に存在する粒子の粒度分布を測定する従来知られた測定方法のひとつである。ただし、この測定方法は、有機溶媒中であっても水系溶媒であっても実施できるが、水系溶媒中の方がより精度が高い。そこで、本発明では、有機溶媒分散体中の前記凝集粒子が成長しない条件で取り出した後、特定の条件で水系溶媒に再分散させて測定する。また、図１のような酸化チタンスラリーを調製した後で、水を有機溶媒に溶媒置換する方法で得られた有機溶媒分散体は、溶媒置換前の酸化チタンスラリーの測定値を有機溶媒分散体の測定値とみなすこともできる。
[Agglomerated particle size: D 50 ]
The titanium oxide particles contained in the organic solvent dispersion of the present invention exist as aggregated particles in the organic solvent dispersion. In the present invention, the size of the agglomerated particles is represented by a 50% cumulative diameter calculated from the particle size distribution obtained by measuring the zeta potential. Here, it is important to measure the diameter of the agglomerated particles contained in the organic solvent dispersion of the present invention in a state where the agglomerated particles are dispersed in the solvent. This is because the state of the agglomerated particles in the solvent has a great influence on the long-term storage stability of the dispersion. In the measurement method in which the agglomerated particles are taken out from the solvent and observed with an electron microscope, the agglomerated particles are further agglomerated when the solvent is removed. In such a state, the boundary of the agglomerated particles becomes difficult to understand, so that it is not suitable as a method for measuring the agglomerated particle diameter of the organic solvent dispersion of the present invention. The zeta potential measurement used in the present invention is one of the conventionally known measuring methods for measuring the particle size distribution of particles existing in a solvent. However, although this measurement method can be carried out in an organic solvent or an aqueous solvent, the accuracy is higher in the aqueous solvent. Therefore, in the present invention, the aggregated particles in the organic solvent dispersion are taken out under the condition that they do not grow, and then redispersed in the aqueous solvent under the specific conditions for measurement. Further, in the organic solvent dispersion obtained by the method of solvent-substituting water with an organic solvent after preparing the titanium oxide slurry as shown in FIG. 1, the measured value of the titanium oxide slurry before the solvent replacement is the organic solvent dispersion. It can also be regarded as a measured value of.
本発明においてこの前記凝集粒子径（Ｄ５０）は、１５０ｎｍ以下であり、５０ｎｍ以上１５０ｎｍ以下の範囲にあることが好ましく、７５ｎｍ以上１２５ｎｍ以下の範囲にあることがより好ましく、８０ｎｍ以上１００ｎｍ以下の範囲にあることが特に好ましい。前記凝集粒子径がこの範囲にある本発明の有機溶媒分散体は、長期間保存しても粘度の変化や粒子の沈降が起こりにくい。 In the present invention, the aggregated particle diameter (D 50 ) is 150 nm or less, preferably in the range of 50 nm or more and 150 nm or less, more preferably in the range of 75 nm or more and 125 nm or less, and in the range of 80 nm or more and 100 nm or less. It is particularly preferable to be in. The organic solvent dispersion of the present invention having the agglomerated particle size in this range is unlikely to change in viscosity or settle even when stored for a long period of time.
［凝集粒子径：Ｄ９０−Ｄ１０］
本発明の有機溶媒分散体に含まれる前記凝集粒子の大きさのばらつきは、可能な限り小さくすることが好ましい。本発明では、前記凝集粒子の大きさのばらつきを表す指標として、前記有機溶媒分散体をゼータ電位測定して得られる粒度分布の１０％累積径（Ｄ１０）と９０％累積径（Ｄ９０）の差分（Ｄ９０−Ｄ１０）を用いた。この差分が小さい本発明の有機溶媒分散体は、長期間保存しても粘度の変化が起きにくい。具体的には、本発明の有機溶媒分散体は、この差分が１７０ｎｍ以下であり、１６０ｎｍ以下であることが好ましく、１５０ｎｍ以下であることが特に好ましい。なお、前記凝集粒子径（Ｄ５０）が小さい場合は、凝集粒子の分散状態が変化しやすくなり、有機溶媒分散体の粘度も変化しやすくなる。そこで、前記凝集粒子径（Ｄ５０）が５０ｎｍ以下の場合は、この差分（Ｄ９０−Ｄ１０）が５０ｎｍ以下であることが好ましい。
[Agglomerated particle size: D 90- D 10 ]
It is preferable that the variation in the size of the aggregated particles contained in the organic solvent dispersion of the present invention is as small as possible. In the present invention, 10% cumulative diameter (D 10 ) and 90% cumulative diameter (D 90 ) of the particle size distribution obtained by measuring the zeta potential of the organic solvent dispersion as an index showing the variation in the size of the aggregated particles. Difference (D 90- D 10 ) was used. The organic solvent dispersion of the present invention having a small difference is unlikely to change in viscosity even when stored for a long period of time. Specifically, in the organic solvent dispersion of the present invention, this difference is 170 nm or less, preferably 160 nm or less, and particularly preferably 150 nm or less. When the agglomerated particle diameter (D 50 ) is small, the dispersed state of the agglomerated particles is likely to change, and the viscosity of the organic solvent dispersion is also likely to change. Therefore, when the aggregated particle diameter (D 50 ) is 50 nm or less, the difference (D 90- D 10 ) is preferably 50 nm or less.
［凝集粒子径：Ｄ１００］
本発明の有機溶媒分散体には、可能な限り粗大粒子が含まれていないことが好ましい。具体的には、前述のゼータ電位測定法を用いて測定された粒度分布の１００％累積径（Ｄ１００）が１μｍ以下であることが好ましく、０．５μｍ以下であることがより好ましい。本発明の有機溶媒分散体にこのような粗大粒子が含まれていると、有機溶媒分散体中の電荷がより不均一になる。
[Agglomerated particle size: D 100 ]
It is preferable that the organic solvent dispersion of the present invention does not contain coarse particles as much as possible. Specifically, the 100% cumulative diameter (D 100 ) of the particle size distribution measured by the above-mentioned zeta potential measurement method is preferably 1 μm or less, and more preferably 0.5 μm or less. When such coarse particles are contained in the organic solvent dispersion of the present invention, the charge in the organic solvent dispersion becomes more non-uniform.
［酸化チタン粒子の結晶構造］
本発明の有機溶媒分散体に含まれる酸化チタン粒子の結晶構造は、アナターゼ型、ブルッカイト型、ルチル型といった従来公知の結晶構造をとることができる。これらの結晶構造は、酸化チタン粒子の用途によって好ましい構造が異なる。例えば、光触媒用又は色素増感太陽電池用に含まれる半導体層用の酸化チタン粒子であれば、バンドギャップの大きいアナターゼ型が好ましい。また、リチウムイオン二次電池の負極として用いる場合は、ブルッカイト型が好ましい。なお、これらの結晶構造の有無は、Ｘ線回折測定により判断することができる。
[Crystal structure of titanium oxide particles]
The crystal structure of the titanium oxide particles contained in the organic solvent dispersion of the present invention can be a conventionally known crystal structure such as anatase type, brookite type, or rutile type. The preferable structure of these crystal structures differs depending on the use of the titanium oxide particles. For example, in the case of titanium oxide particles for a semiconductor layer contained for a photocatalyst or a dye-sensitized solar cell, an anatase type having a large bandgap is preferable. Further, when used as a negative electrode of a lithium ion secondary battery, a brookite type is preferable. The presence or absence of these crystal structures can be determined by X-ray diffraction measurement.
［酸化チタン粒子の濃度］
本発明の有機溶媒分散体に含まれる酸化チタン粒子の濃度は、ＴｉＯ２換算で、５質量％以上２５質量％以下の範囲にあることが好ましく、１０質量％以上２０質量％以下の範囲にあることがより好ましい。この酸化チタン粒子の濃度が高すぎると長期間保存した際に粒子の沈降が起きやすくなる。
[Concentration of titanium oxide particles]
The concentration of titanium oxide particles contained in the organic solvent dispersion of the present invention is preferably in the range of 5% by mass or more and 25% by mass or less in terms of TiO 2 , and is in the range of 10% by mass or more and 20% by mass or less. Is more preferable. If the concentration of the titanium oxide particles is too high, the particles are likely to settle when stored for a long period of time.
［有機溶媒］
本発明の有機溶媒分散体に含まれる有機溶媒は、特に限定されない。有機溶媒としては、アルコール類、ケトン類、グリコール類、エーテル類、及びテレピン類等が好ましい。これらは、１種単独又は２種以上混合して使用することができる。アルコール類としては、例えば、メタノール、エタノール、イソプロピルアルコール、及びブタノール等が好ましい。ケトン類としては、例えば、アセトン等が好ましい。グリコール類としては、例えば、エチレングリコール、及びプロピレングリコール等が好ましい。エーテル類としては、例えば、ブチルカルビトール、及びブチルカルビトールアセテート等が好ましい。テレピン類としては、例えば、ターピネオール、ジヒドロターピネオール、及びターピノーレン等が好ましい。特に、ブチルカルビトール、又はターピネオールが好ましい。本発明の有機溶媒分散体に含まれる有機溶媒の濃度は、その他の成分の濃度によっても変わるが、概ね５０質量％以上の範囲にあることが好ましく、５０質量％以上９５質量％以下の範囲にあることがより好ましい。
[Organic solvent]
The organic solvent contained in the organic solvent dispersion of the present invention is not particularly limited. As the organic solvent, alcohols, ketones, glycols, ethers, terepine and the like are preferable. These can be used alone or in combination of two or more. As the alcohols, for example, methanol, ethanol, isopropyl alcohol, butanol and the like are preferable. As the ketones, for example, acetone and the like are preferable. As the glycols, for example, ethylene glycol, propylene glycol and the like are preferable. As the ethers, for example, butyl carbitol, butyl carbitol acetate and the like are preferable. As the terpines, for example, tarpineol, dihydroterpineol, tarpinolene and the like are preferable. In particular, butyl carbitol or turpineol is preferable. The concentration of the organic solvent contained in the organic solvent dispersion of the present invention varies depending on the concentration of other components, but is preferably in the range of about 50% by mass or more, and in the range of 50% by mass or more and 95% by mass or less. More preferably.
［増粘剤］
本発明の有機溶媒分散体は、必要によって増粘剤を含んでいてもよい。増粘剤としては、例えば、ポリエチレングリコール、ポリビニルピロリドン、ヒドロキシプロピルセルロース、ポリアクリル酸、エチルセルロース、メチルセルロース、カルボキシメチルセルロース、ポリビニルアルコール、アクリル樹脂、ケトン樹脂、及びメラミン樹脂等の化合物を含んでいてもよい。本発明の塗料に含まれる増粘剤の濃度は、目標とする粘度によっても変わるが、概ね１質量％以上４０質量％以下の範囲にあってもよく、４質量％以上１０質量％以下の範囲にあってもよい。
[Thickener]
The organic solvent dispersion of the present invention may contain a thickener if necessary. The thickener may contain, for example, compounds such as polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl cellulose, polyacrylic acid, ethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylic resin, ketone resin, and melamine resin. .. The concentration of the thickener contained in the coating material of the present invention varies depending on the target viscosity, but may be in the range of approximately 1% by mass or more and 40% by mass or less, and is in the range of 4% by mass or more and 10% by mass or less. May be.
［粘度］
本発明の有機溶媒分散体の粘度は、０．５×１０５ｍＰａ・ｓ以上２．０×１０５ｍＰａ・ｓ以下の範囲にあることが好ましい。また、本発明の有機溶媒分散体を色素増感太陽電池の半導体層を形成するために用いる場合は、その粘度が１．０×１０５ｍＰａ・ｓ以上２．０×１０５ｍＰａ・ｓ以下の範囲にあることがより好ましい。この粘度が前述の範囲にある場合、スクリーン印刷等で多孔質半導体層を形成しやすくなる。
[viscosity]
The viscosity of the organic solvent dispersion of the present invention is preferably in the range of 0.5 × 10 5 mPa · s or more and 2.0 × 10 5 mPa · s or less. When the organic solvent dispersion of the present invention is used to form a semiconductor layer of a dye-sensitized solar cell, its viscosity is 1.0 × 10 5 mPa · s or more and 2.0 × 10 5 mPa · s or less. It is more preferable that it is in the range of. When this viscosity is in the above range, it becomes easy to form a porous semiconductor layer by screen printing or the like.
［硝酸イオン濃度］
本発明の有機溶媒分散体を色素増感太陽電池の多孔質半導体層を形成するために用いる場合、本発明の塗料には硝酸イオンが含まれていることが好ましい。このように酸化チタン粒子と硝酸イオンが共存した有機溶媒分散体を用いて多孔質半導体層を形成すると、酸化チタンのバンドギャップに変化が生じる。このようなバンドギャップの変化は、吸収できる光の波長範囲を広げるので、好ましい。バンドギャップの変化は、加熱処理に伴う硝酸イオンによる酸化チタン表面の還元に起因するものと発明者は推測する。この推測は、本発明を限定するものではない。特に、本発明の有機溶媒分散体に含まれる酸化チタン粒子の全質量に対して、１質量％以上１０質量％以下の範囲で硝酸イオンが含まれることが好ましい。
[Nitrate ion concentration]
When the organic solvent dispersion of the present invention is used to form a porous semiconductor layer of a dye-sensitized solar cell, the coating material of the present invention preferably contains nitrate ions. When the porous semiconductor layer is formed by using the organic solvent dispersion in which titanium oxide particles and nitrate ions coexist in this way, the band gap of titanium oxide changes. Such a change in bandgap is preferable because it widens the wavelength range of light that can be absorbed. The inventor speculates that the change in the bandgap is due to the reduction of the titanium oxide surface by nitrate ions during the heat treatment. This speculation does not limit the present invention. In particular, it is preferable that nitrate ions are contained in the range of 1% by mass or more and 10% by mass or less with respect to the total mass of the titanium oxide particles contained in the organic solvent dispersion of the present invention.
［水の含有量］
本発明の有機溶媒分散体に極性の有機溶媒又は増粘剤が含まれる場合、本発明の有機溶媒分散体にごく微量の水分が含まれることが好ましい。このような微量の水分は、原料に含まれる水分と、製造する過程で一定量の水分を含むよう調湿する工程を経て導入されたものである。このようにごく少量の水分を本発明の有機溶媒分散体に含ませておくことで、有機溶媒中において酸化チタン粒子の凝集粒子の分散性が良好になる。これにより、長期間保存しても粘度の変化や粒子の沈降が起きにくくなる。発明者は、微量の水分が存在することで極性の有機溶媒又は増粘剤が酸化チタン凝集粒子に配位しやすくなったためと推測する。この推測は、本発明を限定するものではない。
[Water content]
When the organic solvent dispersion of the present invention contains a polar organic solvent or a thickener, it is preferable that the organic solvent dispersion of the present invention contains a very small amount of water. Such a small amount of water is introduced through a step of adjusting the water content in the raw material and the water content so as to contain a certain amount of water in the manufacturing process. By including a very small amount of water in the organic solvent dispersion of the present invention in this way, the dispersibility of the aggregated particles of the titanium oxide particles in the organic solvent is improved. As a result, changes in viscosity and sedimentation of particles are less likely to occur even after long-term storage. The inventor presumes that the presence of a small amount of water facilitates the coordination of the polar organic solvent or thickener to the titanium oxide agglomerated particles. This speculation does not limit the present invention.
［本発明の有機溶媒分散体の製造方法］
本発明の分散体は、例えば、下記（Ａ）〜（Ｄ）の工程を含む製造方法によって製造することができる。
（Ａ）酸化チタンスラリー生成工程
（Ｂ）粗粒除去工程
（Ｃ）凝集状態調整工程
（Ｄ）溶媒置換工程
[Method for Producing Organic Solvent Dispersion of the Present Invention]
The dispersion of the present invention can be produced, for example, by a production method including the following steps (A) to (D).
(A) Titanium oxide slurry generation step (B) Coarse grain removal step (C) Aggregation state adjustment step (D) Solvent replacement step
［（Ａ）酸化チタンスラリー生成工程］
この工程は、酸化チタンスラリーを生成する工程である。なお、本発明におけるスラリーは、液体に粒子が混ざった懸濁体であって、ゾルやゲルも含まれる。酸化チタンスラリーは、例えば、チタン化合物を加水分解して無定形のオルソチタン酸を生成し、これに結晶化剤を添加した後、水熱処理する方法で得ることができる。
[(A) Titanium oxide slurry generation step]
This step is a step of producing a titanium oxide slurry. The slurry in the present invention is a suspension in which particles are mixed with a liquid, and includes a sol and a gel. The titanium oxide slurry can be obtained, for example, by hydrolyzing a titanium compound to produce amorphous orthotitanic acid, adding a crystallization agent to the hydrolyzed titanium compound, and then hydrothermally treating the slurry.
チタン化合物としては、チタンハロゲン化物（四塩化チタン等）、チタン塩（硫酸チタン、及び硫酸チタニル等）及びチタンアルコキシド（チタンテトラメトキシド、チタンテトラエトキシド、及びチタンテトライソプロポキシド等）を用いることもできる。これらのチタン化合物を溶液として用いることが好ましい。チタン化合物の溶液における溶媒は、水、有機溶媒、又はこれらの混合物であってもよい。また、チタン化合物の溶液には、必要によって、酸やアルカリといった加水分解を促進させる成分が予め含まれていてもよい。このとき、チタン化合物の濃度は、ＴｉＯ２換算で、１質量％以上２０質量％以下の範囲にあることが好ましく、１質量％以上１０質量％以下の範囲にあることがより好ましい。チタン化合物の濃度がこの範囲にあると、均一な一次粒子径を有する酸化チタン粒子を得ることができる。 As the titanium compound, titanium halides (titanium tetrachloride, etc.), titanium salts (titanium sulfate, titanyl sulfate, etc.) and titanium alkoxides (titanium tetramethoxydo, titanium tetraethoxydo, titanium tetraisopropoxide, etc.) are used. You can also do it. It is preferable to use these titanium compounds as a solution. The solvent in the solution of the titanium compound may be water, an organic solvent, or a mixture thereof. Further, the solution of the titanium compound may contain, if necessary, a component that promotes hydrolysis, such as an acid or an alkali. At this time, the concentration of the titanium compound is preferably in the range of 1% by mass or more and 20% by mass or less, and more preferably in the range of 1% by mass or more and 10% by mass or less in terms of TiO 2 . When the concentration of the titanium compound is in this range, titanium oxide particles having a uniform primary particle size can be obtained.
これらのチタン化合物の溶液を水の存在下で加水分解する場合、この溶液を撹拌しつつ、酸又はアルカリを徐々に添加し、最終的なｐＨを７以上１３以下の範囲にすることが好ましい。このとき、最終的なｐＨは８以上１０以下の範囲にあることがより好ましい。また、酸又はアルカリは、少なくとも１時間以上かけて前述のｐＨの範囲になるように添加することが好ましい。このように、チタン化合物の溶液のｐＨを徐々に変化させ、前述の範囲にすることで、最終的に得られる酸化チタンの一次粒子径のばらつきが小さくなる。酸化チタンの一次粒子径のばらつきが小さくなれば、酸化チタンの凝集粒子径のばらつきも小さくなりやすい。なお、この溶液の温度は、０℃以上６０℃以下の範囲にあることが好ましく、３０℃以上５０℃以下の範囲にあることがより好ましい。前述の温度の範囲で加水分解を行うことで、酸化チタン粒子の一次粒子径及びそのばらつきがさらに小さくなる。発明者は、上記の条件で加水分解することで微細で大きさが整った無定形のオルソチタン酸が生成すると推測する。そして、これが後述の水熱処理によって結晶化して酸化チタン粒子になると発明者は推測する。これらの推測は、本発明を限定するものではない。 When a solution of these titanium compounds is hydrolyzed in the presence of water, it is preferable to gradually add an acid or an alkali while stirring the solution to bring the final pH to the range of 7 or more and 13 or less. At this time, the final pH is more preferably in the range of 8 or more and 10 or less. Further, it is preferable to add the acid or alkali so as to be in the above-mentioned pH range over at least 1 hour. By gradually changing the pH of the solution of the titanium compound to the above-mentioned range in this way, the variation in the primary particle size of the titanium oxide finally obtained becomes small. If the variation in the primary particle size of titanium oxide is small, the variation in the aggregated particle size of titanium oxide tends to be small. The temperature of this solution is preferably in the range of 0 ° C. or higher and 60 ° C. or lower, and more preferably in the range of 30 ° C. or higher and 50 ° C. or lower. By performing hydrolysis in the above-mentioned temperature range, the primary particle size of the titanium oxide particles and the variation thereof are further reduced. The inventor presumes that hydrolysis under the above conditions produces fine, well-sized amorphous orthotitanic acid. Then, the inventor presumes that this is crystallized by the hydrothermal treatment described later to become titanium oxide particles. These speculations do not limit the invention.
前述の加水分解を行って得られた無定形のオルソチタン酸を含む溶液を水熱処理して酸化チタンスラリーを得ることができる。この場合、この溶液をオートクレーブ中で１００℃以上２５０℃以下の温度の範囲で水熱処理することが好ましい。更に、前述の温度範囲で保持する時間は、２時間以上４８時間以下の範囲にあることが好ましい。この保持時間が短すぎると酸化チタン粒子が十分に生成しないことがある。この保持時間が長すぎても経済性の観点から好ましくない。 A titanium oxide slurry can be obtained by hydrothermally treating a solution containing amorphous orthotitanic acid obtained by performing the above-mentioned hydrolysis. In this case, it is preferable to hydrothermally treat this solution in an autoclave in a temperature range of 100 ° C. or higher and 250 ° C. or lower. Further, the holding time in the above-mentioned temperature range is preferably in the range of 2 hours or more and 48 hours or less. If this holding time is too short, titanium oxide particles may not be sufficiently produced. If this holding time is too long, it is not preferable from the viewpoint of economy.
無定形のオルソチタン酸を含む溶液には、必要によって結晶化剤を加えてもよい。結晶化剤としては、ＮａＯＨ、ＫＯＨ等のアルカリ金属水酸化物、第４級アンモニウムハイドロオキサイド、アルコールアミン等の有機塩基性化合物を用いることができる。本発明では、有機塩基性化合物を用いることが好ましい。また、結晶化剤は、結晶化剤のモル数（ＭＣ）と無定形のオルソチタン酸のＴｉＯ2換算モル数（ＭＴ）との比（ＭＣ／ＭＴ）が、０．０００１以上０．１以下の範囲となるように前記溶液に添加されることが好ましい。０．００１以上０．０１以下の範囲となるように添加されることがより好ましい。結晶化剤は酸化チタン粒子の結晶化を促進する働きがある。このため、その添加量が少なすぎると結晶化が不十分になることがある。また、水熱処理後の酸化チタンスラリーに含まれる結晶化剤は、必要によってイオン交換法や限外ろ過法等を用いて除去することができる。 A crystallization agent may be added to the solution containing amorphous orthotitanic acid, if necessary. As the crystallization agent, an alkali metal hydroxide such as NaOH or KOH, an organic basic compound such as a quaternary ammonium hydroxide or an alcohol amine can be used. In the present invention, it is preferable to use an organic basic compound. Further, the crystallization agent, the ratio of the moles of crystallization agent (M C) and in terms of TiO 2 moles of ortho titanate amorphous (M T) (M C / M T) is 0.0001 or more It is preferably added to the solution so as to be in the range of 0.1 or less. It is more preferable that the mixture is added so as to be in the range of 0.001 or more and 0.01 or less. The crystallization agent has a function of promoting the crystallization of titanium oxide particles. Therefore, if the amount added is too small, crystallization may be insufficient. Further, the crystallization agent contained in the titanium oxide slurry after the hydrothermal treatment can be removed by an ion exchange method, an ultrafiltration method or the like, if necessary.
この工程で得られた酸化チタンスラリーは、ｐＨが２以下の範囲にあることが好ましい。酸化チタンはｐＨが１付近にあると凝集を始めるので、この段階でｐＨを上記の範囲に調整し、酸化チタンの凝集粒子を作成する。このように、一度酸化チタンの凝集粒子を作成しておき、後述の工程で粗粒を除去した後、この凝集粒子を解膠、再凝集する。このことによって、大きさのばらつきが小さい酸化チタンの凝集粒子を得ることができる。ｐＨ調整剤としては、硝酸が好ましい。 The titanium oxide slurry obtained in this step preferably has a pH in the range of 2 or less. Titanium oxide begins to aggregate when the pH is around 1, so at this stage the pH is adjusted to the above range to create aggregated particles of titanium oxide. In this way, agglomerated particles of titanium oxide are once prepared, coarse particles are removed in a step described later, and then the agglomerated particles are unglued and reaggregated. This makes it possible to obtain agglomerated particles of titanium oxide having a small variation in size. Nitric acid is preferable as the pH adjuster.
［（Ｂ）粗粒除去工程］
この工程は、前述の酸化チタンスラリー生成工程で得られた酸化チタンスラリーから、粗粒を除去する工程である。この粗粒は、酸化チタンスラリーに含まれる過度に成長した酸化チタン粒子や、大きい凝集粒子等で構成される。この粗粒は、本発明の有機溶媒分散体を長期間保存する際に悪影響を及ぼす。そこで、この工程では、酸化チタンスラリーのゼータ電位を測定して得られる粒度分布において、Ｄ１００が１μｍ以下になるまで従来公知の方法を用いてこの粗粒を除去する。
[(B) Coarse grain removing step]
This step is a step of removing coarse particles from the titanium oxide slurry obtained in the above-mentioned titanium oxide slurry generation step. These coarse particles are composed of overgrown titanium oxide particles contained in the titanium oxide slurry, large aggregated particles, and the like. These coarse particles have an adverse effect on long-term storage of the organic solvent dispersion of the present invention. Therefore, in this step, in the particle size distribution obtained by measuring the zeta potential of the titanium oxide slurry, the coarse particles are removed by a conventionally known method until D 100 becomes 1 μm or less.
この工程では、粗粒を除去する従来公知の方法として、特定の目開きを有する篩やメッシュを通過させる方法、遠心分離法等を用いることができる。特に大きい粗粒に対しては、篩やメッシュを通過させる方法が有効である。これ以外の粗粒に対しては、遠心分離法が有効である。前述の粒度分布の程度によって、これらの方法を適切に使い分ければよい。また、１回で除去しきれない場合は、この工程を複数回繰り返してもよい。 In this step, as a conventionally known method for removing coarse particles, a method of passing through a sieve or a mesh having a specific opening, a centrifugation method, or the like can be used. Especially for large coarse particles, a method of passing through a sieve or a mesh is effective. Centrifugation is effective for other coarse particles. These methods may be appropriately used depending on the degree of particle size distribution described above. Further, if it cannot be completely removed at one time, this step may be repeated a plurality of times.
［（Ｃ）凝集状態調整工程］
この工程は、前述の粗粒除去工程で粗粒が除去された酸化チタンスラリーに含まれる酸化チタンの凝集粒子を解膠し、再凝集させる。これによって、酸化チタンの凝集粒子の大きさを整える工程である。
[(C) Aggregation state adjustment step]
In this step, the aggregated particles of titanium oxide contained in the titanium oxide slurry from which the coarse particles have been removed in the above-mentioned coarse particle removing step are deglutinized and reaggregated. This is a step of adjusting the size of the aggregated particles of titanium oxide.
この工程では、酸化チタンスラリーに含まれる酸化チタンの凝集粒子を解膠する方法として、酸化チタンスラリーのｐＨを０．５以上２以下の範囲、及びゼータ電位を４０ｍＶ以上の範囲に調整する。その後、超音波処理等の分散処理を行う方法を用いることができる。酸化チタンのｐＨ及びゼータ電位を前述の範囲に調整することで、まず酸化チタン粒子が分散しやすい環境を作る。次に、このように酸化チタン粒子が分散しやすい環境下で酸化チタン粒子を分散処理して、凝集した酸化チタン粒子を解膠する。分散処理の方法としては、ホモジナイザーやビーズミル等を用いる方法がある。例えば、高圧ホモジナイザー又は超音波ホモジナイザーを用いることができる。 In this step, the pH of the titanium oxide slurry is adjusted to a range of 0.5 or more and 2 or less, and the zeta potential is adjusted to a range of 40 mV or more as a method of defibrating the aggregated particles of titanium oxide contained in the titanium oxide slurry. After that, a method of performing dispersion processing such as ultrasonic processing can be used. By adjusting the pH and zeta potential of titanium oxide within the above ranges, first, an environment in which titanium oxide particles are easily dispersed is created. Next, in such an environment where the titanium oxide particles are easily dispersed, the titanium oxide particles are dispersed and the aggregated titanium oxide particles are deglued. As a method of dispersion treatment, there is a method using a homogenizer, a bead mill or the like. For example, a high pressure homogenizer or an ultrasonic homogenizer can be used.
この工程では、前述の分散処理を行ったのち、解膠した酸化チタン粒子を再凝集させ、一定の大きさの凝集粒子に整える。このとき、酸化チタンスラリーのｐＨ及びゼータ電位を前述の範囲より低くすることで、解膠した酸化チタン粒子を再凝集させることができる。 In this step, after performing the above-mentioned dispersion treatment, the deflated titanium oxide particles are reaggregated to prepare the aggregated particles having a certain size. At this time, by lowering the pH and zeta potential of the titanium oxide slurry below the above ranges, the deflated titanium oxide particles can be reaggregated.
［（Ｄ）溶媒置換工程］
この工程では、前述の凝集状態調整工程を経て得られた酸化チタンスラリー中に含まれる水を有機溶媒に置換する工程である。
[(D) Solvent replacement step]
In this step, water contained in the titanium oxide slurry obtained through the above-mentioned aggregation state adjusting step is replaced with an organic solvent.
酸化チタンスラリー中に含まれる水を有機溶媒に置換する方法は、従来公知の方法を用いることができる。例えば、酸化チタンスラリーを遠心分離して、発生した上澄み液を除いた後に、所定の有機溶媒を加えるという方法を用いることができる。また、このような操作を繰り返すことで、有機溶媒分散体中の有機溶媒の純度をより高めることができる。別の方法として、エタノール等の極性の有機溶媒で置換した後に、所定の有機溶媒を加え、その後ロータリーエバポレーターや真空乳化器を用いて極性の有機溶媒を除去する方法を用いることができる。また、このような方法を用いれば、有機溶媒の純度をさらに高めることができる。なお、増粘剤を添加する場合は、有機溶媒中で置換した後に添加することが好ましい。また、各方法で有機溶媒に置換した後は、超音波処理やホモジナイザー処理といった分散処理を行うことが好ましい。ただし、この分散処理は、凝集粒子を有機溶媒中に分散させる程度の強度で行う。このような溶媒置換処理を経て、有機溶媒分散体が得られる。 As a method for substituting the water contained in the titanium oxide slurry with an organic solvent, a conventionally known method can be used. For example, a method of centrifuging the titanium oxide slurry to remove the generated supernatant and then adding a predetermined organic solvent can be used. Further, by repeating such an operation, the purity of the organic solvent in the organic solvent dispersion can be further increased. As another method, a method can be used in which the polar organic solvent is replaced with a polar organic solvent such as ethanol, a predetermined organic solvent is added, and then the polar organic solvent is removed using a rotary evaporator or a vacuum emulsifier. Further, by using such a method, the purity of the organic solvent can be further increased. When the thickener is added, it is preferable to add it after replacing it in an organic solvent. Further, after replacement with an organic solvent by each method, it is preferable to perform dispersion treatment such as ultrasonic treatment or homogenizer treatment. However, this dispersion treatment is performed with such an intensity that the agglomerated particles are dispersed in an organic solvent. Through such a solvent substitution treatment, an organic solvent dispersion is obtained.
前述の工程を経て得られた有機溶媒分散体に、ごく微量の水分を加えることで、有機溶媒分散体を長期間保存した際の粘度の変化をさらに抑制することができる。これは、単に有機溶媒分散体に水滴を添加したり、霧吹きを用いて水分を噴霧する方法ではなく、大気中の水分を利用して吸湿させる方法を用いる。大気中の水分を利用する方法は、ごく微量の水分を有機溶媒分散体に添加できる。このような方法を用いることで、有機溶媒分散体中に均一に水分を分散させることができる。具体的には、恒温恒湿槽において、有機溶媒分散体を露出した状態で混練する。このとき、槽内の湿度がどれだけ低下したかで、有機溶媒分散体に吸収された水分量をコントロールする。なお、前述の霧吹きを用いる方法等では、有機溶媒分散体中で水が偏析する。このため、有機溶媒分散体を長期間保存した際に粘度の変化が大きくなる。 By adding a very small amount of water to the organic solvent dispersion obtained through the above steps, it is possible to further suppress the change in viscosity when the organic solvent dispersion is stored for a long period of time. This is not a method of simply adding water droplets to the organic solvent dispersion or spraying water by spraying, but a method of absorbing moisture by using the moisture in the atmosphere. In the method of utilizing the moisture in the atmosphere, a very small amount of moisture can be added to the organic solvent dispersion. By using such a method, water can be uniformly dispersed in the organic solvent dispersion. Specifically, the organic solvent dispersion is kneaded in an exposed state in a constant temperature and humidity chamber. At this time, the amount of water absorbed by the organic solvent dispersion is controlled by how much the humidity in the tank is lowered. In the above-mentioned method using a sprayer or the like, water segregates in the organic solvent dispersion. Therefore, when the organic solvent dispersion is stored for a long period of time, the change in viscosity becomes large.
以下、実施例によって本発明を更に詳細に説明するが、本発明はこれらの実施範囲に限定されるものではない。 Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these embodiments.
［実施例１］
［（Ａ）酸化チタンスラリー生成工程］
純水を限外ろ過してＵＦ水を得た。このＵＦ水は、反応容器において、４０℃に加熱した。この加熱したＵＦ水に四塩化チタン水溶液（大阪チタニウムテクノロジーズ製、ＴｉＯ２換算濃度：２８．２質量％）を添加し、ＴｉＯ２換算濃度が約４質量％の四塩化チタン水溶液を得た。この四塩化チタン水溶液に、最終的に得られる無定形のオルソチタン酸を含む水溶液のｐＨが８．６となるようにアンモニア水溶液（ＮＨ３濃度１５質量％）を一定の速度で１時間かけて添加し、その後１時間撹拌し、無定形のオルソチタン酸を含む溶液を得た。この溶液を遠心分離して得られたケーキを、５０℃に加熱したＵＦ水で洗浄した。この洗浄したケーキにＵＦ水を添加し、ＴｉＯ２換算濃度が７質量％の無定形のオルソチタン酸を含む溶液を得た。この溶液に、水酸化テトラメチルアンモニウム（多摩化学社製、濃度：２５質量％）を添加し、この溶液に含まれる無定形オルソチタン酸のＴｉＯ２換算モル数（ＭＴ）と結晶化剤のモル数（ＭＣ）とのモル比（ＭＣ／ＭＴ）が０．００２である溶液を得た。この溶液を、オートクレーブを用いて、１５０℃で１５時間加熱し、続けて１９０℃で２時間加熱し、酸化チタンスラリーを得た。この酸化チタンスラリーにＵＦ水を添加し、ＴｉＯ２換算濃度が２．５６質量％の酸化チタンスラリーを得た。この酸化チタンスラリーに硝酸（濃度：６１質量％）を加え、ｐＨが１．５の酸化チタンスラリーを得た。このスラリーをイオン交換して、水酸化テトラメチルアンモニウムを除去した。このスラリーは、ＴｉＯ２換算濃度が２１質量％となるまで、限外濃縮法を用いて濃縮した。このときに発生した濾水は、後述の粗粒除去工程で濃度調整用の溶液として、保存した。
[Example 1]
[(A) Titanium oxide slurry generation step]
Pure water was ultrafiltered to obtain UF water. The UF water was heated to 40 ° C. in the reaction vessel. A titanium tetrachloride aqueous solution (manufactured by Osaka Titanium Technologies, TiO 2 equivalent concentration: 28.2% by mass) was added to the heated UF water to obtain a titanium tetrachloride aqueous solution having a TiO 2 equivalent concentration of about 4% by mass. This aqueous titanium tetrachloride solution and an aqueous ammonia solution so that the pH of the aqueous solution containing the ortho titanate of the finally obtained amorphous becomes 8.6 (NH 3 concentration of 15 wt%) over a period of 1 hour at a constant speed The mixture was added and then stirred for 1 hour to obtain a solution containing amorphous orthotitanic acid. The cake obtained by centrifuging this solution was washed with UF water heated to 50 ° C. UF water was added to the washed cake to obtain a solution containing amorphous orthotitanic acid having a TiO 2 conversion concentration of 7% by mass. To this solution, tetramethylammonium hydroxide (Tama Chemicals Co., concentration: 25 wt%) was added and the amorphous orthotitanic acid contained in the solution in terms of TiO 2 moles (M T) and the crystallization agent moles (M C) and the molar ratio of (M C / M T) to obtain a solution which is 0.002. This solution was heated at 150 ° C. for 15 hours using an autoclave, followed by heating at 190 ° C. for 2 hours to obtain a titanium oxide slurry. UF water was added to this titanium oxide slurry to obtain a titanium oxide slurry having a TiO 2 conversion concentration of 2.56% by mass. Nitric acid (concentration: 61% by mass) was added to this titanium oxide slurry to obtain a titanium oxide slurry having a pH of 1.5. The slurry was ion-exchanged to remove tetramethylammonium hydroxide. This slurry was concentrated using an extraconcentration method until the TiO 2 equivalent concentration was 21% by mass. The filtered water generated at this time was stored as a solution for adjusting the concentration in the coarse grain removing step described later.
［（Ｂ）粗粒除去工程］
前述の酸化チタンスラリー調製工程で得た酸化チタンスラリーを２８００ｒｐｍで１０分間遠心分離した。このスラリーから遠心分離により発生したケーキを除去し、残った上澄みにＴｉＯ２換算濃度が２０質量％となるまで前述の濾水を添加した。更に、このスラリーを６５００ｒｐｍで１０分間遠心分離した。このスラリーから遠心分離により発生したケーキを除去した。この操作によって酸化チタンスラリーから粗粒を除去した。
[(B) Coarse grain removing step]
The titanium oxide slurry obtained in the above-mentioned titanium oxide slurry preparation step was centrifuged at 2800 rpm for 10 minutes. The cake generated by centrifugation was removed from this slurry, and the above-mentioned filtered water was added to the remaining supernatant until the TiO 2 conversion concentration became 20% by mass. Further, the slurry was centrifuged at 6500 rpm for 10 minutes. The cake generated by centrifugation was removed from this slurry. Coarse particles were removed from the titanium oxide slurry by this operation.
［（Ｃ）凝集状態調整工程］
前述の粗粒除去工程で得た酸化チタンスラリーに塩酸（濃度：１５質量％）を添加した。このとき、このスラリーのｐＨは１．１であり、そのゼータ電位は４２ｍＶであった。このスラリーを出力（３００Ｗ、１９．５ｋＨｚ）で５分間超音波処理した。この超音波処理したスラリーに、硝酸（濃度：６１質量％）を添加した。このとき、スラリーのｐＨは１．０であった。このスラリーは出力（３００Ｗ、１９．５ｋＨｚ）で５分間超音波処理した。この工程を経て得られた酸化チタンスラリーのｐＨは１．０であり、そのゼータ電位は３４ｍＶであった。
[(C) Aggregation state adjustment step]
Hydrochloric acid (concentration: 15% by mass) was added to the titanium oxide slurry obtained in the above-mentioned coarse grain removing step. At this time, the pH of this slurry was 1.1, and its zeta potential was 42 mV. This slurry was sonicated at output (300 W, 19.5 kHz) for 5 minutes. Nitric acid (concentration: 61% by mass) was added to the sonicated slurry. At this time, the pH of the slurry was 1.0. This slurry was sonicated at power (300 W, 19.5 kHz) for 5 minutes. The pH of the titanium oxide slurry obtained through this step was 1.0, and its zeta potential was 34 mV.
［（Ｄ）溶媒置換工程］
前述の凝集状態調整工程を経て得た酸化チタンスラリーにエタノールを添加した。このエタノールを添加した酸化チタンスラリーを、３０００ｒｐｍで１０分間遠心分離した。このとき遠心分離により発生した上澄みを除去し、残ったケーキにエタノールを添加した。その後、これを出力（３００Ｗ、１９．５ｋＨｚ）で１０分間超音波処理した。さらにこの工程（遠心分離、エタノール添加、超音波処理）を２回繰り返した。これを１００００ｒｐｍで３分間ホモミキサ―処理し、エタノール分散体を得た。このエタノール分散体に、エチルセルロース（シグマアルドリッチ社製）、ターピネオール（ヤスハラケミカル社製）及びブチルカルビトール（関東化学社製、製品名：２−（２−ｎ−ブトキシエトキシ）エタノール）を添加した。更に、この分散体を、１００００ｒｐｍで３分間ホモミキサ―処理し、その後、出力（３００Ｗ、１９．５ｋＨｚ）で１０分間超音波処理した。このホモミキサ―処理及び超音波処理を合計３回繰り返した。この分散体は、エバポレーター及び真空乳化器によってエタノールを除去し、酸化チタンを含むペーストを得た。２５℃、湿度５７％の恒温恒湿槽内において、この酸化チタンを含むペーストを３本ロール上で３０分間以上混練した。このとき、恒温恒湿槽内の湿度は３５％まで低下し、酸化チタンを含むペーストに一定量の水分が添加され、最終的に有機溶媒分散体を得た。
[(D) Solvent replacement step]
Ethanol was added to the titanium oxide slurry obtained through the above-mentioned aggregation state adjusting step. This ethanol-added titanium oxide slurry was centrifuged at 3000 rpm for 10 minutes. At this time, the supernatant generated by centrifugation was removed, and ethanol was added to the remaining cake. Then, this was ultrasonically treated at an output (300 W, 19.5 kHz) for 10 minutes. Further, this step (centrifugation, addition of ethanol, ultrasonic treatment) was repeated twice. This was homomixer-treated at 10000 rpm for 3 minutes to obtain an ethanol dispersion. Ethyl cellulose (manufactured by Sigma-Aldrich), tarpineol (manufactured by Yasuhara Chemical Co., Ltd.) and butyl carbitol (manufactured by Kanto Chemical Co., Inc., product name: 2- (2-n-butoxyethoxy) ethanol) were added to this ethanol dispersion. Further, the dispersion was homomixed at 10000 rpm for 3 minutes and then sonicated at an output (300 W, 19.5 kHz) for 10 minutes. This homomixer treatment and ultrasonic treatment were repeated a total of 3 times. Ethanol was removed from this dispersion by an evaporator and a vacuum emulsifier to obtain a paste containing titanium oxide. The paste containing titanium oxide was kneaded on three rolls for 30 minutes or more in a constant temperature and humidity chamber at 25 ° C. and 57% humidity. At this time, the humidity in the constant temperature and humidity chamber was lowered to 35%, and a certain amount of water was added to the paste containing titanium oxide to finally obtain an organic solvent dispersion.
［実施例２］
粗粒除去工程において酸化チタンスラリーを１３０００ｒｐｍで１０分間遠心分離したこと、以外は実施例１と同様の方法で有機溶媒分散体を得た。この有機溶媒分散体の性状は、表１に示される。
[Example 2]
An organic solvent dispersion was obtained in the same manner as in Example 1 except that the titanium oxide slurry was centrifuged at 13000 rpm for 10 minutes in the coarse particle removing step. The properties of this organic solvent dispersion are shown in Table 1.
［実施例３］
粗粒除去工程において酸化チタンスラリーを１３０００ｒｐｍで１００分間遠心分離したこと、以外は実施例１と同様の方法で有機溶媒分散体を得た。この有機溶媒分散体の性状は、表１に示される。
[Example 3]
An organic solvent dispersion was obtained in the same manner as in Example 1 except that the titanium oxide slurry was centrifuged at 13000 rpm for 100 minutes in the coarse particle removing step. The properties of this organic solvent dispersion are shown in Table 1.
［実施例４］
粗粒除去工程において酸化チタンスラリーを１３０００ｒｐｍで１８０分間遠心分離したこと、以外は実施例１と同様の方法で有機溶媒分散体を得た。この有機溶媒分散体の性状は、表１に示される。
[Example 4]
An organic solvent dispersion was obtained in the same manner as in Example 1 except that the titanium oxide slurry was centrifuged at 13000 rpm for 180 minutes in the coarse grain removing step. The properties of this organic solvent dispersion are shown in Table 1.
［実施例５］
粗粒除去工程において酸化チタンスラリーを１３０００ｒｐｍで２４０分間遠心分離したこと、以外は実施例１と同様の方法で有機溶媒分散体を得た。この有機溶媒分散体の性状は、表１に示される。
[Example 5]
An organic solvent dispersion was obtained in the same manner as in Example 1 except that the titanium oxide slurry was centrifuged at 13000 rpm for 240 minutes in the coarse particle removing step. The properties of this organic solvent dispersion are shown in Table 1.
［比較例１］
凝集状態調整工程において酸化チタンスラリーに塩酸（濃度：１５質量％）を添加しなかったこと、溶媒置換工程において恒温恒湿槽を用いなかったこと、以外は実施例１と同様の方法で有機溶媒分散体を得た。この有機溶媒分散体の性状は、表１に示される。
[Comparative Example 1]
The organic solvent was prepared in the same manner as in Example 1 except that hydrochloric acid (concentration: 15% by mass) was not added to the titanium oxide slurry in the aggregation state adjusting step and a constant temperature and humidity chamber was not used in the solvent replacement step. A dispersion was obtained. The properties of this organic solvent dispersion are shown in Table 1.
［酸化チタンの一次粒子径・アスペクト比測定］
前述の凝集状態調整工程を経て得られた酸化チタンスラリーを用いて、酸化チタンの一次粒子を測定した。酸化チタンスラリーは、凝集状態調整工程後、溶媒置換工程のエタノール添加前に、２０ｍＬスポイトを用いて、容器中央部のスラリー表面から液体とともに１０ｍＬを吸い取って１回採取した。これをエタノール２０ｍＬに分散させた。攪拌しながら別の５ｍＬスポイトを用いて、２ｍＬ採取し、透過型電子顕微鏡の試料台に滴下し、溶媒を自然蒸発させた。その後、透過型電子顕微鏡（日本電子社製、ＪＥＭ１４００）を用いて、酸化チタンの一次粒子を観察できる倍率で、試料の中央部を撮影した。そして、画像中央部にある３００個の酸化チタンの一次粒子について、すべての長径と短径を定規で測定した。測定したすべての長径・短径を合計した値を３００で除し、酸化チタンの一次粒子径を決定した。また、酸化チタンのアスペクト比（長径／短径）を決定した。
[Measurement of primary particle size and aspect ratio of titanium oxide]
The primary particles of titanium oxide were measured using the titanium oxide slurry obtained through the above-mentioned aggregation state adjusting step. The titanium oxide slurry was collected once by sucking 10 mL together with the liquid from the slurry surface in the center of the container using a 20 mL dropper after the aggregation state adjusting step and before adding ethanol in the solvent replacement step. This was dispersed in 20 mL of ethanol. While stirring, 2 mL was collected using another 5 mL dropper and dropped onto a sample table of a transmission electron microscope to allow the solvent to evaporate spontaneously. Then, using a transmission electron microscope (JEM1400, manufactured by JEOL Ltd.), the central part of the sample was photographed at a magnification at which the primary particles of titanium oxide could be observed. Then, all the major and minor diameters of the 300 titanium oxide primary particles in the center of the image were measured with a ruler. The total value of all the measured major and minor diameters was divided by 300 to determine the primary particle diameter of titanium oxide. In addition, the aspect ratio (major axis / minor axis) of titanium oxide was determined.
［凝集粒子径の測定］
前述の凝集状態調整工程を経て得られ、溶媒置換工程におけるエタノール添加前の酸化チタンスラリーを用いて、凝集粒子径の測定を行った。具体的には、酸化チタンスラリー中の酸化チタンの濃度が２０質量％、ゼータ電位を４０ｍＶ以上４５ｍＶ以下の範囲に調整した状態で、ゼータ電位測定装置（大塚電子社製、ＥＬＳＺ−２０００）を用いて、その粒度分布（体積基準）を測定した。この粒度分布から、１０％頻度の粒子径（Ｄ１０）、５０％頻度の粒子径（Ｄ５０）、９０％頻度の粒子径（Ｄ９０）を算出した。その結果を表１に示した。なお、有機溶媒分散体から酸化チタン粒子を取り出した後、これを水に再分散させる方法でも測定することができる。このとき、酸化チタンの濃度が１０質量％、ゼータ電位が４０ｍＶ以上４５ｍＶ以下の範囲になるように溶媒を調整する。
[Measurement of aggregated particle size]
The agglomerated particle size was measured using the titanium oxide slurry obtained through the above-mentioned agglomeration state adjusting step and before the addition of ethanol in the solvent replacement step. Specifically, a zeta potential measuring device (manufactured by Otsuka Electronics Co., Ltd., ELSZ-2000) was used with the concentration of titanium oxide in the titanium oxide slurry adjusted to 20% by mass and the zeta potential adjusted to a range of 40 mV or more and 45 mV or less. Then, the particle size distribution (volume basis) was measured. From this particle size distribution, the particle size of 10% frequency (D 10 ), the particle size of 50% frequency (D 50 ), and the particle size of 90% frequency (D 90 ) were calculated. The results are shown in Table 1. It should be noted that the measurement can also be carried out by a method in which titanium oxide particles are taken out from the organic solvent dispersion and then redispersed in water. At this time, the solvent is adjusted so that the concentration of titanium oxide is in the range of 10% by mass and the zeta potential is in the range of 40 mV or more and 45 mV or less.
［粘度測定］
有機溶媒分散体の粘度（初日）を以下の条件で測定した。なお、この粘度は、有機溶媒分散体の調製が完了してから１日以内に測定した。
粘度計：型式ＲｈｅｏＳｔｒｅｓｓ３０００
ローター：型式Ｃ３５／１Ｔｉ
恒温槽温度：３０±１℃
サンプル量：１ｇ
せん断速度：０〜１００（１／ｓ）で変化させる
粘度 ：せん断速度が４．２の時のせん断応力から算出。
[Viscosity measurement]
The viscosity (first day) of the organic solvent dispersion was measured under the following conditions. This viscosity was measured within 1 day after the preparation of the organic solvent dispersion was completed.
Viscometer: Model RheoStress3000
Rotor: Model C35 / 1Ti
Constant temperature bath temperature: 30 ± 1 ° C
Sample amount: 1g
Shear velocity: Change from 0 to 100 (1 / s) Viscosity: Calculated from the shear stress when the shear rate is 4.2.
［粘度の経時変化評価］
有機溶媒分散体を、冷暗所（１０℃）で９０日間保管した。その後、前述の条件で有機溶媒分散体の粘度（９０日後）を測定した。前述の粘度測定で得られた粘度（初日）および粘度（９０日後）の値を用い、次の式から粘度の変化率を算出した。
粘度の変化率［％］＝|粘度（初日）−粘度（９０日後）|／粘度（初日）×１００
[Evaluation of changes in viscosity over time]
The organic solvent dispersion was stored in a cool dark place (10 ° C.) for 90 days. Then, the viscosity of the organic solvent dispersion (after 90 days) was measured under the above-mentioned conditions. Using the values of viscosity (first day) and viscosity (after 90 days) obtained in the above-mentioned viscosity measurement, the rate of change in viscosity was calculated from the following formula.
Viscosity change rate [%] = | Viscosity (first day) -Viscosity (90 days later) | / Viscosity (first day) x 100
Claims (1)
酸化チタン粒子の一次粒子径が５ｎｍ以上２５ｎｍ以下の範囲にあり、
前記凝集粒子の凝集粒子径（Ｄ５０）が１５０ｎｍ以下であり、
前記凝集粒子の９０％累積径と１０％累積径の差分（Ｄ９０−Ｄ１０）が１７０ｎｍ以下である、
有機溶媒分散体。 A dispersion in which agglomerated particles of titanium oxide are dispersed in an organic solvent.
The primary particle size of the titanium oxide particles is in the range of 5 nm or more and 25 nm or less.
The agglomerated particle diameter (D 50 ) of the agglomerated particles is 150 nm or less.
The difference (D 90 − D 10 ) between the 90% cumulative diameter and the 10% cumulative diameter of the agglomerated particles is 170 nm or less.
Organic solvent dispersion.
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