JP2007137688A - Method for manufacturing titanium oxide - Google Patents
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- JP2007137688A JP2007137688A JP2005330050A JP2005330050A JP2007137688A JP 2007137688 A JP2007137688 A JP 2007137688A JP 2005330050 A JP2005330050 A JP 2005330050A JP 2005330050 A JP2005330050 A JP 2005330050A JP 2007137688 A JP2007137688 A JP 2007137688A
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- titanium tetrachloride
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 89
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 title claims abstract description 87
- 238000004519 manufacturing process Methods 0.000 title claims description 26
- 238000000034 method Methods 0.000 title description 39
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 claims abstract description 58
- 239000007864 aqueous solution Substances 0.000 claims abstract description 55
- 239000000758 substrate Substances 0.000 claims abstract description 24
- 239000010936 titanium Substances 0.000 claims abstract description 16
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 239000002253 acid Substances 0.000 claims abstract description 7
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 26
- 239000000243 solution Substances 0.000 abstract description 11
- 239000010408 film Substances 0.000 description 54
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 29
- 239000000843 powder Substances 0.000 description 28
- 239000002245 particle Substances 0.000 description 25
- 239000000463 material Substances 0.000 description 14
- 238000000576 coating method Methods 0.000 description 12
- 239000010409 thin film Substances 0.000 description 11
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 10
- 239000011248 coating agent Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 239000013067 intermediate product Substances 0.000 description 9
- 238000001556 precipitation Methods 0.000 description 9
- 229910010413 TiO 2 Inorganic materials 0.000 description 8
- 238000006460 hydrolysis reaction Methods 0.000 description 8
- 230000006866 deterioration Effects 0.000 description 7
- 230000007062 hydrolysis Effects 0.000 description 7
- 239000011941 photocatalyst Substances 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000000354 decomposition reaction Methods 0.000 description 6
- 230000001699 photocatalysis Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 239000003595 mist Substances 0.000 description 4
- 239000007858 starting material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000010790 dilution Methods 0.000 description 3
- 239000012895 dilution Substances 0.000 description 3
- 239000003365 glass fiber Substances 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- GCUDAJWPHOSVPS-UHFFFAOYSA-M OC([Ti]O)=O Chemical compound OC([Ti]O)=O GCUDAJWPHOSVPS-UHFFFAOYSA-M 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000004744 fabric Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- RTBSTWCNYBMKBN-UHFFFAOYSA-J hydrogen carbonate titanium(4+) Chemical compound [Ti+4].OC([O-])=O.OC([O-])=O.OC([O-])=O.OC([O-])=O RTBSTWCNYBMKBN-UHFFFAOYSA-J 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000007590 electrostatic spraying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 239000002241 glass-ceramic Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- DKAGJZJALZXOOV-UHFFFAOYSA-N hydrate;hydrochloride Chemical compound O.Cl DKAGJZJALZXOOV-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- LLZRNZOLAXHGLL-UHFFFAOYSA-J titanic acid Chemical compound O[Ti](O)(O)O LLZRNZOLAXHGLL-UHFFFAOYSA-J 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
本発明は、出発物質として四塩化チタンを使用する酸化チタン製造方法に関し、より詳しくは、基材上における酸化チタン膜の形成、酸化チタンの微粉末の製造等に適した酸化チタン製造方法に関する。 The present invention relates to a titanium oxide manufacturing method using titanium tetrachloride as a starting material, and more particularly to a titanium oxide manufacturing method suitable for forming a titanium oxide film on a substrate, manufacturing a fine powder of titanium oxide, and the like.
酸化チタンは光触媒として注目されており、基材の表面に形成された薄膜の形態で使用されることが多い。酸化チタンの製造では、出発物質として四塩化チタン、より詳しくはその水溶液（チタン酸水溶液）が使用される。四塩化チタン水溶液の化学組成を化学式１に示す。 Titanium oxide has attracted attention as a photocatalyst and is often used in the form of a thin film formed on the surface of a substrate. In the production of titanium oxide, titanium tetrachloride, more specifically, an aqueous solution (titanic acid aqueous solution) is used as a starting material. The chemical composition of the aqueous titanium tetrachloride solution is shown in Chemical Formula 1.
化学式１から分かるように、四塩化チタン水溶液は塩酸を含む。また、この水溶液は四塩化チタン濃度により性質が変化し、Ｔｉ分が９重量％未満ではＴｉＯ2 を粒子状に析出し、９〜１７重量％の間で透明な水溶液となり、１７重量％超ではゲル化する特性をもつ。この特性のために、酸化チタンの製造においては、Ｔｉ分が９〜１７重量％の四塩化チタン水溶液が使用され、その塩酸濃度はおおよそ１５〜２０重量％である。 As can be seen from Chemical Formula 1, the titanium tetrachloride aqueous solution contains hydrochloric acid. The properties of this aqueous solution change depending on the concentration of titanium tetrachloride. When the Ti content is less than 9% by weight, TiO 2 is precipitated in the form of particles and becomes a transparent aqueous solution between 9 and 17% by weight. Has the property of gelling. Because of this characteristic, in the production of titanium oxide, an aqueous titanium tetrachloride solution having a Ti content of 9 to 17% by weight is used, and its hydrochloric acid concentration is approximately 15 to 20% by weight.
このような四塩化チタン水溶液は、四塩化チタンの反応性が高いことに加え、強塩酸液でもあることから腐食性等が強く、加熱により多量の塩酸ガスを発生するなど、非常に扱い難い物質である。このため、実際の酸化チタンの製造では、多くの場合、四塩化チタン水溶液を中和処理したヒドラキシカルボキシラトチタンなどの取り扱いが容易な中間生成物から酸化チタンの粉末が製造されており、酸化チタンの薄膜は、製造された酸化チタンの粉末を基材の表面に焼結するとか、バインダーを用いて塗布するといった方法で形成されている。 Such titanium tetrachloride aqueous solution is highly difficult to handle, such as high reactivity of titanium tetrachloride and strong hydrochloric acid solution due to its strong corrosiveness and generation of a large amount of hydrochloric acid gas by heating. It is. For this reason, in the actual production of titanium oxide, in many cases, titanium oxide powder is produced from an intermediate product that is easy to handle, such as hydroxycarboxylate titanium obtained by neutralizing a titanium tetrachloride aqueous solution. The titanium thin film is formed by a method in which the manufactured titanium oxide powder is sintered on the surface of the base material or is applied using a binder.
このような酸化チタン粉末を使用する成膜方法に対し、酸化チタン粉末を使用しない簡易な酸化チタンの成膜方法がいくつか提案されている。その一つが、四塩化チタン水溶液を加水分解して酸化チタン含有ゾルを生成し、これを基材の表面に塗布して焼成することにより酸化チタン膜を形成する方法である（特許文献１）。また、別の方法としては、取り扱いが容易な中間生成物を基材の表面に塗布し、加熱してその表面上で加水分解を進行させながら焼成を行う方法も知られている（特許文献２）。 In contrast to such a film forming method using titanium oxide powder, several simple titanium oxide film forming methods not using titanium oxide powder have been proposed. One of them is a method of forming a titanium oxide film by hydrolyzing an aqueous solution of titanium tetrachloride to produce a titanium oxide-containing sol, applying this to the surface of a base material, and baking it (Patent Document 1). As another method, there is also known a method in which an intermediate product that is easy to handle is applied to the surface of a substrate, and baking is performed while heating to cause hydrolysis to proceed on the surface (Patent Document 2). ).
これらの簡易法は、酸化チタン粉末を取り扱わないので、工程的に有利であり、経済的である。また近年、光触媒としての酸化チタン膜では、薄膜化が追求されているが、粉末焼成の場合は薄膜の形成のためには酸化チタンの微粉末が必要となり、その微粉末の製造は容易でない。このような事情のため、酸化チタン粉末を使用しない簡易法は、薄膜の形成が容易な方法としても評価されている。なお、酸化チタンの微粉末の製造が困難な理由は後述する。 Since these simple methods do not handle titanium oxide powder, they are advantageous in terms of process and economical. In recent years, a titanium oxide film as a photocatalyst has been pursued to be thin. However, in the case of powder firing, a fine powder of titanium oxide is required for forming a thin film, and the production of the fine powder is not easy. Under such circumstances, the simple method that does not use titanium oxide powder has been evaluated as a method that facilitates the formation of a thin film. The reason why it is difficult to produce titanium oxide fine powder will be described later.
しかしながら、前者の簡易成膜方法は、四塩化チタン水溶液を加水分解して酸化チタン含有ゾルを生成する過程で、酸化チタン粒子が析出し、これを塗布するために、酸化チタン膜は酸化チタン粒子の集合体となり、均質な薄膜は得られない。但し、加水分解の工程で塩酸が除去されるので、塗布工程では塩酸は発生せず、これによる膜品質の悪化、環境悪化等は回避される。 However, in the former simple film formation method, titanium oxide particles are deposited in the process of hydrolyzing a titanium tetrachloride aqueous solution to produce a titanium oxide-containing sol. A homogeneous thin film cannot be obtained. However, since hydrochloric acid is removed in the hydrolysis step, hydrochloric acid is not generated in the coating step, and deterioration of film quality and environmental deterioration due to this are avoided.
一方、後者の簡易成膜方法は、取り扱いが容易な中間生成物を実質的な出発物質とするので、塗布工程での塩酸ガスの発生、これによる膜品質の悪化などの問題は、もとより生じない。しかし、中間生成物はコストが嵩む中和処理を経由しているので非常に高価であるため、その使用は経済性を悪化させる大きな要因になっている。 On the other hand, since the latter simple film formation method uses an intermediate product that is easy to handle as a substantial starting material, problems such as generation of hydrochloric acid gas in the coating process and deterioration of film quality due to this do not occur. . However, the intermediate product is very expensive because it goes through a costly neutralization treatment, and its use is a major factor that deteriorates the economy.
ちなみに、酸化チタンの微粉末の製造が困難な理由は次のとおりである。生成する酸化チタンの一次粒径は数ｎｍ〜数十ｎｍと小さいものが得られるが、後の乾燥工程や焼成工程で強固に凝集し、得られる粉末の粒径は数十μｍ以上の粗大なものになる。このため、一般的には更に粉砕する工程が必要であるが、粒径が１０μｍ以下の微細粉末を製造することが困難であることには変わりない。 Incidentally, the reason why it is difficult to produce titanium oxide fine powder is as follows. The primary particle size of the titanium oxide to be produced can be as small as several nanometers to several tens of nanometers, but it is strongly agglomerated in the subsequent drying step or firing step, and the resulting powder has a coarse particle size of several tens of μm or more. Become a thing. For this reason, in general, a further pulverization step is required, but it is still difficult to produce a fine powder having a particle size of 10 μm or less.
本発明の目的は、基材の表面に均質な酸化チタン膜を経済的に形成できる酸化チタン製造方法を提供することにある。本発明の別の目的は、酸化チタンの微粉末を経済的に製造できる酸化チタン製造方法を提供することにある。 The objective of this invention is providing the titanium oxide manufacturing method which can form a homogeneous titanium oxide film | membrane economically on the surface of a base material. Another object of the present invention is to provide a titanium oxide production method capable of economically producing titanium oxide fine powder.
上記目的を達成するために、本発明者らは高価な中間生成物を使わずに、四塩化チタンを出発物質として酸化チタン膜を形成する技術に着目し、その技術の膜品質上の問題点である加水分解過程での酸化チタンの粒状析出、これによる薄膜の不均質化を解消する方法について鋭意検討した。 In order to achieve the above object, the present inventors paid attention to a technique for forming a titanium oxide film using titanium tetrachloride as a starting material without using an expensive intermediate product, and problems in film quality of the technique. The inventors studied diligently about the method of eliminating the granular precipitation of titanium oxide during the hydrolysis process and the resulting inhomogeneity of the thin film.
すなわち、四塩化チタンを出発点とする従来の酸化チタン成膜方法では、加水分解、基材への塗布、焼成の各工程を経て基材上に酸化チタン膜が形成されるが、加水分解の工程で酸化チタンが粒子状に析出するため、粒子によって膜が形成されることになり、その均質化が困難なことは前述したとおりである。この問題を解決するために、本発明者らは四塩化チタンの水溶液を直接基材の表面に塗布し焼成することを企画し、種々実験を繰り返した。その結果、次のような新事実が判明した。 That is, in the conventional titanium oxide film formation method starting from titanium tetrachloride, a titanium oxide film is formed on the substrate through the hydrolysis, application to the substrate, and firing steps. Since titanium oxide precipitates in the form of particles in the process, a film is formed by the particles, and the homogenization thereof is difficult as described above. In order to solve this problem, the present inventors planned to apply an aqueous solution of titanium tetrachloride directly to the surface of the substrate and baked, and repeated various experiments. As a result, the following new facts were found.
直接塗布は、特許文献２に記載されているように、中和処理を終え塩酸を消滅させてヒドラキシカルボキシラトチタンなどの中間生成物では公知であるが、四塩化チタン水溶液については試みられていない。 As described in Patent Document 2, direct coating is known for intermediate products such as hydroxycarboxylatotitanium after the neutralization treatment is completed and hydrochloric acid is extinguished. However, an aqueous solution of titanium tetrachloride has been attempted. Absent.
四塩化チタン水溶液は、中間生成物とは異なり塩酸を多量に含む強酸水溶液であるため、これを基材の表面に直接塗布し焼成する場合は、焼成のための加熱により液膜中から塩酸ガスが多量に発生し、膜品質を維持できないおそれがあるが、四塩化チタン水溶液の塗布厚を薄く管理するならば、塩酸ガスの発生による膜品質の低下を防止することができる。 Unlike the intermediate product, the titanium tetrachloride aqueous solution is a strong acid aqueous solution containing a large amount of hydrochloric acid. Therefore, when this is directly applied to the surface of the substrate and baked, the hydrochloric acid gas is heated from the liquid film by heating for baking. However, if the coating thickness of the titanium tetrachloride aqueous solution is controlled thinly, deterioration of the film quality due to generation of hydrochloric acid gas can be prevented.
四塩化チタン水溶液の直接塗布では、塗布後の焼成加熱工程で加水分解反応が進み、酸化チタンの粒子が析出する懸念のあるところ、四塩化チタン水溶液の初期濃度を管理すれば、酸化チタンの粒子状の析出現象も回避され、酸化チタン粒子が混在も存在もしない均質な酸化チタン膜が基材上に形成することができる。 In direct application of titanium tetrachloride aqueous solution, there is a concern that the hydrolysis reaction proceeds in the baking and heating process after application and titanium oxide particles precipitate, so if the initial concentration of titanium tetrachloride aqueous solution is controlled, titanium oxide particles Thus, a uniform titanium oxide film in which titanium oxide particles are neither mixed nor present can be formed on the substrate.
このように、四塩化チタン水溶液の直接塗布、焼成によれば、独立した加水分解工程の省略により工数、コストが大幅に節減できるのみならず、四塩化チタン水溶液の使用で問題となる塩酸ガスの発生による膜品質の低下も、酸化チタン粒子の析出も共に回避でき、高品質な薄膜を低コストで形成できることが、本発明者による実験、調査、検討から知見された。 Thus, direct application and baking of titanium tetrachloride aqueous solution not only saves man-hours and costs significantly by omitting an independent hydrolysis step, but also eliminates the problem of hydrochloric acid gas, which is a problem with the use of titanium tetrachloride aqueous solution. It has been found from experiments, investigations and examinations by the present inventors that both the deterioration of film quality due to generation and the precipitation of titanium oxide particles can be avoided, and a high-quality thin film can be formed at low cost.
また同時に、粒子析出による酸化チタン粉末の製造方法では、粒径が１０μｍ以下の微細粉末を製造することは困難であるが、四塩化チタン水溶液を微細な液滴に噴霧し、これを液滴状態のまま加熱し焼成すれば、塩酸ガスの発生による品質低下の見られない高品質な酸化チタンの微粉末が非常に簡単に製造できることも合わせて知見された。ちなみに、四塩化チタン水溶液を微細な液滴にすることは、超音波等を利用すれば容易である。 At the same time, it is difficult to produce a fine powder with a particle size of 10 μm or less by the production method of titanium oxide powder by particle precipitation. It was also found that if heated and fired as it is, fine powder of high-quality titanium oxide that does not show any deterioration in quality due to generation of hydrochloric acid gas can be produced very easily. Incidentally, it is easy to make the aqueous solution of titanium tetrachloride into fine droplets using ultrasonic waves or the like.
本発明の酸化チタン製造方法は、かかる知見を基礎として完成されたものであり、四塩化チタン水溶液を加熱して当該水溶液中のＨ2 Ｏ及びＨＣＬを揮発させることにより酸化チタンを製造するものであり、より具体的には、製造すべき酸化チタンの形態に対応する形態に四塩化チタン水溶液を処理し、その処理形態のまま当該四塩化チタン水溶液を加熱する、四塩化チタンからの直接製造方法である。 The titanium oxide production method of the present invention has been completed on the basis of such knowledge, and produces titanium oxide by heating a titanium tetrachloride aqueous solution to volatilize H 2 O and HCL in the aqueous solution. More specifically, a direct production method from titanium tetrachloride, in which a titanium tetrachloride aqueous solution is treated in a form corresponding to the form of titanium oxide to be produced, and the titanium tetrachloride aqueous solution is heated in the treated form. It is.
そして、製造すべき酸化チタンの形態が薄膜の場合は、耐酸性及び耐熱性を有する基材の表面に四塩化チタン水溶液を膜状に付着させ、液膜状態のまま加熱して液膜中のＨ2 Ｏ及びＨＣＬを揮発させることにより基材の表面に酸化チタン膜を形成する。また酸化チタンの形態が粉末の場合は、四塩化チタン水溶液を加熱雰囲気中に直接噴霧すればよい。 When the form of titanium oxide to be manufactured is a thin film, an aqueous solution of titanium tetrachloride is attached to the surface of the base material having acid resistance and heat resistance, and heated in the liquid film state to heat the liquid in the liquid film. A titanium oxide film is formed on the surface of the substrate by volatilizing H 2 O and HCL. When the form of titanium oxide is powder, an aqueous solution of titanium tetrachloride may be sprayed directly into a heated atmosphere.
本発明の酸化チタン製造方法で重要な条件は、膜製造の場合は四塩化チタン水溶液の濃度、付着膜厚、加熱温度及び基材の材質等である。四塩化チタン水溶液の濃度についてはＴｉ分で表して０．１〜１７重量％が好ましく、９〜１７重量％がより好ましい。９〜１７重量％の濃度範囲内で四塩化チタン水溶液は無色透明な液体となり、扱いやすい上に、この状態から加熱を開始することにより、加熱に伴う濃度上昇により酸化チタンの析出領域（Ｔｉ分９重量％未満）を経由せずにゲル化領域（Ｔｉ分１７重量％超）に至り、粒子状組織が存在しない均質度の高い酸化チタン膜が形成される。 The important conditions in the titanium oxide production method of the present invention are the concentration of the titanium tetrachloride aqueous solution, the deposited film thickness, the heating temperature, the material of the substrate, etc. in the case of film production. The concentration of the titanium tetrachloride aqueous solution is preferably 0.1 to 17% by weight, more preferably 9 to 17% by weight in terms of Ti content. Within the concentration range of 9 to 17% by weight, the aqueous solution of titanium tetrachloride becomes a colorless and transparent liquid, and it is easy to handle. In addition, when heating is started from this state, the titanium oxide precipitation region (Ti The titanium oxide film having a high degree of homogeneity that does not have a particulate structure is formed by reaching the gelation region (more than 17% by weight of Ti) without passing through (less than 9% by weight).
Ｔｉ分が０．１重量％以上、９重量％未満の四塩化チタン水溶液については、従来は前述したとおり、ＴｉＯ2 が粒子状に析出し、酸化チタンの製造に不向きと考えられていた。しかし、本発明者らによる調査によると、９〜１７重量％の透明な水溶液を一時的に希釈して使用するならばＴｉＯ2 析出は致命的な問題にならないことが判明した。すなわち、９〜１７重量％の透明な水溶液を希釈して使用するならば、希釈後に放置するとＴｉＯ2 析出の問題が発生するが、希釈から長時間を経過しなければ（希釈後、短期間で使用すれば）、ＴｉＯ2 析出の問題を生じることなく使用できることが判明した。希釈した低濃度の四塩化チタン水溶液は粘度が低く、付着厚を薄くできるので、薄膜の製造に適する利点がある。ＴｉＯ2 膜は薄くし過ぎると光触媒作用は低下するが、所定厚さ以上（波長に依存する）であれば、その厚さまでは薄くしても光触媒作用は低下しない特性があり、薄膜化は原料コストを低減できるのである。また、基材がフレキシブルな場合は耐剥離性を向上させることができる。 Conventionally, titanium tetrachloride aqueous solutions having a Ti content of 0.1% by weight or more and less than 9% by weight have been considered unsuitable for the production of titanium oxide because TiO 2 is precipitated in the form of particles as described above. However, according to a study by the present inventors, it was found that TiO 2 precipitation is not a fatal problem if a 9 to 17% by weight transparent aqueous solution is temporarily diluted and used. That is, if a transparent aqueous solution of 9 to 17% by weight is used after being diluted, if it is allowed to stand after dilution, a problem of TiO 2 precipitation occurs, but if a long time has not passed since the dilution (after dilution, in a short period of time). It has been found that it can be used without causing TiO 2 precipitation problems. The diluted low-concentration titanium tetrachloride aqueous solution has an advantage suitable for the production of a thin film because the viscosity is low and the adhesion thickness can be reduced. If the TiO 2 film is too thin, the photocatalytic action will decrease, but if the thickness is greater than the specified thickness (depending on the wavelength), the photocatalytic action will not decrease even if the thickness is reduced. Cost can be reduced. Moreover, when a base material is flexible, peeling resistance can be improved.
四塩化チタン水溶液の付着膜厚については、これが厚いと加熱過程での塩酸ガスの発生に伴い気泡等が膜中に残り、膜品質が低下する。このために塗布厚は薄い方がよく、加熱後の製品膜厚で表して１ｍｍ以下が好ましく、１００μｍ以下が特に好ましい。光触媒としての酸化チタン膜はその触媒作用が厚みに影響されない。このため薄くして材料コストを節減するのが有利であり、薄くすることにより柔軟性が生じるので、この点からも膜厚は小さい方が好ましい。一方、製品膜厚の下限については、光触媒作用を効果的に発揮させるために０．１μｍ以上が好ましく、０．５μｍ以上が特に好ましい。 When the thickness of the titanium tetrachloride aqueous solution is thick, bubbles and the like remain in the film due to the generation of hydrochloric acid gas during the heating process, and the film quality deteriorates. For this reason, it is better that the coating thickness is thin, and it is preferably 1 mm or less, particularly preferably 100 μm or less, in terms of the product film thickness after heating. The titanium oxide film as a photocatalyst is not affected by the thickness of its catalytic action. For this reason, it is advantageous to reduce the material cost by reducing the thickness, and since flexibility is obtained by reducing the thickness, it is preferable that the film thickness is small also in this respect. On the other hand, the lower limit of the product film thickness is preferably 0.1 μm or more and particularly preferably 0.5 μm or more in order to effectively exhibit the photocatalytic action.
焼成のための加熱温度は３００〜６００℃が好ましい。加熱温度が低いと膜中のＣｌが完全に飛散できず残留してしまう。また、生成する酸化チタンの結晶化が不十分となる。これらのために高い光触媒活性がえられない。逆に高すぎる場合は結晶粒径の粗大化が起こり、これもまた光触媒活性の低下の原因となる。 The heating temperature for firing is preferably 300 to 600 ° C. When the heating temperature is low, Cl in the film cannot be completely scattered and remains. Moreover, the crystallization of the titanium oxide produced becomes insufficient. For these reasons, high photocatalytic activity cannot be obtained. On the other hand, if it is too high, the crystal grain size becomes coarse, which also causes a decrease in photocatalytic activity.
基材の材質については用途によって決定されるが、特定の条件を満足する必要がある。第１の条件は耐酸性を有することである。強塩酸液である四塩化チタン水溶液が塗布されるので、これに浸食されない材質であることが必要である。第２の条件は耐熱性を有することである。四塩化チタン水溶液の塗布後の焼成のための加熱を受けるので、この加熱に耐える材質であることが必要である。これらの条件を満足する材質としてはガラス繊維やセラミックス部材が挙げられる。 The material of the substrate is determined by the application, but it is necessary to satisfy specific conditions. The first condition is to have acid resistance. Since a titanium tetrachloride aqueous solution, which is a strong hydrochloric acid solution, is applied, it is necessary that the material does not corrode. The second condition is to have heat resistance. Since it is heated for baking after the application of the titanium tetrachloride aqueous solution, it must be made of a material that can withstand this heating. Examples of materials that satisfy these conditions include glass fibers and ceramic members.
四塩化チタン水溶液の付着法は特に問わない。基材の表面に液を均等な厚みに付着させることができる方法であればよく、どぶ漬けと呼ばれる浸漬法でもよいし、静電噴霧法等のスプレー法でもよく、更には超音波ミストによる方法でもよい。膜厚低減の観点からはスプレー法、超音波ミストによる方法が好ましい。 The method of attaching the titanium tetrachloride aqueous solution is not particularly limited. Any method can be used as long as the liquid can be attached to the surface of the base material with a uniform thickness. The dipping method may be a soaking method, a spraying method such as an electrostatic spraying method, or a method using ultrasonic mist. But you can. From the viewpoint of reducing the film thickness, a spray method or a method using ultrasonic mist is preferable.
以上は酸化チタン膜を製造する場合であるが、酸化チタンの微粉末を製造する場合も、同じ理由から、使用する四塩化チタン水溶液の濃度はＴｉ分で表して０．１〜１７重量％が好ましく、９〜１７重量％が特に好ましい。また加熱温度は３００〜６００℃が好ましい。液滴径は塗布厚に対応しており、塩酸ガスの発生による品質低下を防ぐためにも、また製造される粒子の径が小さいほど製品価値が高いことからも小さいほどよく、１０μｍ以下が好ましい。液滴径の下限については、より微細な酸化チタン粒子を製造するためには小さければ小さいほどよいため、特に制限はない。 The above is the case of manufacturing a titanium oxide film, but also when manufacturing a fine powder of titanium oxide, for the same reason, the concentration of the titanium tetrachloride aqueous solution used is 0.1 to 17% by weight expressed in terms of Ti content. Preferably, 9 to 17% by weight is particularly preferable. The heating temperature is preferably 300 to 600 ° C. The droplet diameter corresponds to the coating thickness. In order to prevent deterioration in quality due to the generation of hydrochloric acid gas, the smaller the particle diameter, the higher the product value. The lower limit of the droplet diameter is not particularly limited because the smaller the better in order to produce finer titanium oxide particles, the better.
本発明の酸化チタン製造方法は、四塩化チタン水溶液から直接的に酸化チタンの薄膜や微粉末を製造するので、非常に経済的である。また、強塩酸である四塩化チタン水溶液を使用し、しかも簡易な製造法を採用するにもかかわらず、製品に高品質を与えることができる。したがって、高品質な酸化チタンを低価格で市場に提供でき、その工業的、産業的価値は非常に大きい。 The titanium oxide production method of the present invention is very economical because a titanium oxide thin film or fine powder is produced directly from an aqueous solution of titanium tetrachloride. Moreover, despite using a titanium tetrachloride aqueous solution, which is strong hydrochloric acid, and adopting a simple manufacturing method, high quality can be imparted to the product. Therefore, high quality titanium oxide can be provided to the market at a low price, and its industrial and industrial value is very large.
以下に本発明の実施形態を説明する。 Embodiments of the present invention will be described below.
本実施形態では、セラミックなどの耐酸性及び耐熱性を有する基材の表面に四塩化チタン水溶液を塗布する。塗布法は例えば超音波ミスト法であり、その場合の塗布液の膜厚は例えば３００μｍ以下である。基材に要求される耐酸性とは、使用する四塩化チタン水溶液と反応しないという意味である。四塩化チタン水溶液の濃度は、Ｔｉ分で表して０．１〜１７重量％であり、より好ましくは、透明な液体状態を維持する９〜１７重量％である。 In this embodiment, an aqueous solution of titanium tetrachloride is applied to the surface of a substrate having acid resistance and heat resistance such as ceramic. The coating method is, for example, an ultrasonic mist method, and the thickness of the coating liquid in that case is, for example, 300 μm or less. The acid resistance required for the substrate means that it does not react with the aqueous titanium tetrachloride solution used. The concentration of the titanium tetrachloride aqueous solution is 0.1 to 17% by weight in terms of Ti content, and more preferably 9 to 17% by weight maintaining a transparent liquid state.
基材への四塩化チタン水溶液の塗布が終わると、その基材を加熱炉に挿入し、３００℃以上、好ましくは４５０℃以上で加熱する。加熱の工程で塗布膜から塩酸ガス、水分が蒸発し、四塩化チタン水溶液の濃度が上昇し、この過程で加水分解が起こることにより、最終的には固体の酸化チタン膜が基材の表面上に形成される。このときの化学反応を化学式２に示す。 When the application of the aqueous titanium tetrachloride solution to the substrate is completed, the substrate is inserted into a heating furnace and heated at 300 ° C. or higher, preferably 450 ° C. or higher. During the heating process, hydrochloric acid gas and moisture evaporate from the coating film, and the concentration of the titanium tetrachloride aqueous solution increases. In this process, hydrolysis occurs, so that the solid titanium oxide film eventually becomes on the surface of the substrate. Formed. The chemical reaction at this time is shown in Chemical Formula 2.
加熱途中で発生する塩酸ガス、水分は、塗布液の膜厚が薄いために内部に残留しない。また、四塩化チタン水溶液の濃度がＴｉ分で９〜１７重量％の場合は、加熱途中に粒子析出領域を経ない。これらのために、最終的に形成される薄膜は、粒子も気泡も存在しない均質な酸化チタン膜となる。最終的な酸化チタン膜の膜厚は、塗布液の膜厚の１／３〜１／６となる。塗布液の膜厚を３００μｍ以下に制限しているので、酸化チタン膜の膜厚は１００μｍ以下となる。 Hydrochloric acid gas and water generated during heating do not remain inside because the coating solution is thin. Further, when the concentration of the titanium tetrachloride aqueous solution is 9 to 17% by weight in terms of Ti, the particle precipitation region does not pass through the heating. For these reasons, the thin film finally formed is a homogeneous titanium oxide film having no particles or bubbles. The final thickness of the titanium oxide film is 1/3 to 1/6 of the thickness of the coating solution. Since the film thickness of the coating solution is limited to 300 μm or less, the thickness of the titanium oxide film is 100 μm or less.
かくして、基材の表面に高品質の酸化チタン膜が、高価なヒドラキシカルボキシラトチタンなどの中間生成物、酸化チタン粒子を使用することなく、しかも簡単な工程で極めて経済的に形成される。 Thus, a high-quality titanium oxide film can be formed on the surface of the base material very economically by a simple process without using expensive intermediate products such as hydroxycarboxylate titanium and titanium oxide particles.
酸化チタンの微粉末を製造する場合は、四塩化チタン水溶液を噴霧する。より詳しくは炉内を３００℃以上、好ましくは４５０℃以上に加熱した加熱炉内に、四塩化チタン水溶液を噴霧する。超音波を使用したミスト発生器を使用すれば、粒径が１０μｍ以下の微細な液滴を形成できる。この液滴が加熱炉内を浮遊する過程で加熱されることにより塩素ガス、水分が除去され、加水分解が進むことにより、酸化チタンの微粉末が製造される。 When producing a fine powder of titanium oxide, an aqueous solution of titanium tetrachloride is sprayed. More specifically, an aqueous titanium tetrachloride solution is sprayed into a heating furnace heated to 300 ° C. or higher, preferably 450 ° C. or higher. If a mist generator using ultrasonic waves is used, fine droplets having a particle size of 10 μm or less can be formed. When the droplets are heated in the process of floating in the heating furnace, chlorine gas and moisture are removed, and hydrolysis proceeds to produce fine titanium oxide powder.
加熱途中で発生する塩酸ガス、水分は、液滴が小径のために内部に残留しない。また、四塩化チタン水溶液の濃度がＴｉ分で９〜１７重量％の場合は、加熱途中に粒子析出領域を経ない。これらのために、最終的に形成される粉末は、粒状組織も気泡も存在しない均質な酸化チタン粒となる。最終的な酸化チタン粒の粒径は、噴霧時の粒径の０．３４〜０．４２倍となる。噴霧時の液滴径を１０μｍ以下に制限した場合、製造される酸化チタン粒は粒径が５μｍ以下の微粒子となる。 Hydrochloric acid gas and moisture generated during heating do not remain inside because the droplets are small in diameter. Further, when the concentration of the titanium tetrachloride aqueous solution is 9 to 17% by weight in terms of Ti, the particle precipitation region does not pass through the heating. For these reasons, the finally formed powder becomes homogeneous titanium oxide grains having no granular structure or bubbles. The final particle size of the titanium oxide particles is 0.34 to 0.42 times the particle size at the time of spraying. When the droplet diameter at the time of spraying is limited to 10 μm or less, the manufactured titanium oxide particles are fine particles having a particle diameter of 5 μm or less.
かくして、高価なヒドラキシカルボキシラトチタンなどの中間生成物等を使用することなく、また大がかりな反応容器を使用することなく、更には粉砕工程や篩分けなどの選別工程を経ない簡単な工程により、高品質の酸化チタンの微粉末が極めて経済的に形成される。 Thus, without using an intermediate product such as expensive hydroxycarboxylato titanium, without using a large reaction vessel, and by a simple process that does not go through a sorting process such as a pulverization process or sieving. High quality titanium oxide fine powder is formed very economically.
直径が１０μｍのグラスファイバーからなる厚みが約１ｍｍのガラスクロス基材の表面に、Ｔｉ分が９．３重量％の四塩化チタン水溶液を浸漬法により平均厚みが５μｍとなるように付着させた。付着乾燥後、直ちに基材を加熱炉内に装入し、４００℃に１時間加熱した。基材の表面に平均膜厚が約０．２μｍの酸化チタン膜（ＴｉＯ2 膜）が形成された。形成された酸化チタン膜の組織は緻密な膜状形態を示した。また、光触媒としての適性を調査した結果は次のとおりである。 A titanium tetrachloride aqueous solution having a Ti content of 9.3% by weight was attached to the surface of a glass cloth substrate made of glass fibers having a diameter of 10 μm and having a thickness of about 1 mm by an immersion method so that the average thickness becomes 5 μm. Immediately after the adhesion drying, the substrate was placed in a heating furnace and heated to 400 ° C. for 1 hour. A titanium oxide film (TiO 2 film) having an average film thickness of about 0.2 μm was formed on the surface of the substrate. The structure of the formed titanium oxide film showed a dense film form. Moreover, the result of having investigated the suitability as a photocatalyst is as follows.
光学窓を備えた容量３．５リットルの容器中に４０ｍｍ角の試料を置き、アセトアルデヒド初期注入量２５０ｐｐｍとして紫外線強度４ｍＷ／ｃｍ2 の光を照射してアセトアルデヒド分解試験を実施した。分解生成物であるＣＯ2 の発生速度は１１ｐｐｍ／分であり、非常に優れた光触媒作用を示すものであった。 A 40 mm square sample was placed in a 3.5 liter container equipped with an optical window, and an acetaldehyde decomposition test was carried out by irradiating light with an ultraviolet intensity of 4 mW / cm 2 with an initial acetaldehyde injection amount of 250 ppm. The generation rate of CO 2 as a decomposition product was 11 ppm / min, indicating a very excellent photocatalytic action.
付着法を浸漬法からスプレー法に変更し、付着膜厚を平均２．５μｍ、製品膜厚を平均０．１μｍにした。形成された酸化チタン膜の組織は緻密な膜状形態を示した。また、光触媒としての適性を同じアセトアルデヒド分解試験法により調査した結果は、分解生成物であるＣＯ2 の発生速度が５．２ｐｐｍ／分というものであった。 The adhesion method was changed from the dipping method to the spray method, and the adhesion film thickness was 2.5 μm on average and the product film thickness was 0.1 μm on average. The structure of the formed titanium oxide film showed a dense film form. The result of investigating the suitability as a photocatalyst by the same acetaldehyde decomposition test method was that the generation rate of CO 2 as a decomposition product was 5.2 ppm / min.
比較例として、Ｔｉ分が９．３重量％の四塩化チタン水溶液を８０℃の加熱により加水分解し酸化チタン含有ゾルを生成した。これを直径が１０μｍのグラスファイバーからなる厚みが約１ｍｍのガラスクロス基材の表面に浸漬法により平均５μｍの厚みに塗布し、加熱炉にて４００℃×１時間の条件で焼成した。基材の表面に形成された酸化チタン膜（ＴｉＯ2 膜）の組織は、粒状の集合体がまだらに付着した様相を呈し、取り扱いの際に容易に欠落するものであった。また、形成された酸化チタン膜の膜厚は不均一で０〜０．３μｍであった。更に、光触媒としての適性を同じアセトアルデヒド分解試験法により調査した結果は、ＣＯ2 の発生速度が３．１ｐｐｍ／分という低レベルなものであった。 As a comparative example, a titanium tetrachloride aqueous solution having a Ti content of 9.3% by weight was hydrolyzed by heating at 80 ° C. to produce a titanium oxide-containing sol. This was applied to the surface of a glass cloth substrate made of glass fiber having a diameter of 10 μm and having a thickness of about 1 mm by an immersion method to an average thickness of 5 μm, and fired in a heating furnace at 400 ° C. for 1 hour. The structure of the titanium oxide film (TiO 2 film) formed on the surface of the base material had a state in which granular aggregates adhered to the mottle and were easily lost during handling. The formed titanium oxide film had a nonuniform thickness of 0 to 0.3 μm. Further, as a result of investigating the suitability as a photocatalyst by the same acetaldehyde decomposition test method, the CO 2 generation rate was a low level of 3.1 ppm / min.
Ｔｉ分が９．３重量％の四塩化チタン水溶液を超音波法により約２０μｍの液滴にして、４００℃に加熱された雰囲気中に噴霧した。粒径が約７μｍの酸化チタン（ＴｉＯ2 ）の微粉末が製造された。製造された酸化チタンの微粉末はアナターゼの結晶構造を有し、０．３ｇの粉末を４０ｍｍ角に引き伸ばしたものを試料として、同じアセトアルデヒド分解試験法により光触媒としての適性を調査した結果は、ＣＯ2 の発生速度が８．５ｐｐｍ／分という高レベルなものであった。 A titanium tetrachloride aqueous solution having a Ti content of 9.3% by weight was made into droplets of about 20 μm by an ultrasonic method and sprayed in an atmosphere heated to 400 ° C. A fine powder of titanium oxide (TiO 2 ) having a particle size of about 7 μm was produced. The produced fine powder of titanium oxide has a crystal structure of anatase, and the result of investigating the suitability as a photocatalyst by the same acetaldehyde decomposition test method using a sample obtained by stretching 0.3 g of powder to 40 mm square is The generation rate of 2 was a high level of 8.5 ppm / min.
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