JP4851685B2 - Method for producing rutile type titanium oxide ultrafine particles - Google Patents

Description

The present invention relates to a method for producing rutile titanium oxide ultrafine particles having a high refractive index and an average particle diameter of 1 to 100 nm, which are excellent in transparency and dispersibility.

  Corresponding to the recent increase in the refractive index of plastic lenses, the hard coat film applied on the plastic lens has the disadvantage that a striped pattern occurs unless it has a high refractive index. Is required. Similarly, high refractive index ultrafine particles with excellent dispersion stability, scratch resistance, surface hardness, abrasion resistance, transparency, heat resistance, light resistance, weather resistance, UV shielding, etc., and the sol solution is an antireflection film , Plastic deterioration prevention additive, cosmetic additive, camera lens, automotive window glass, plasma display, liquid crystal display, EL display, optical filter and other optical members, metal materials, ceramic materials, glass materials, plastic materials, etc. There are also demands in the field of products such as electronic materials such as treatment agents, dielectric materials, and piezoelectric materials, photocatalysts, and water repellents. Since high dispersibility and transparency are required for use in such various applications, the inorganic oxide is desirably ultrafine particles.

  By the way, there are rutile type and anatase type as typical crystal types of titanium oxide, but so far, the material mainly composed of anatase type titanium oxide is used as the metal oxide ultrafine particle sol solution for high refractive index. It is used for. Rutile type titanium oxide is known to be superior in optical properties such as high refractive index and ultraviolet absorption as compared with anatase type, and a production method capable of industrial production is desired. However, conventionally, when producing rutile ultrafine particles, acicular rutile ultrafine particles having a large aspect ratio are produced, and they are aggregated to obtain a polycrystal having a large particle diameter, and the particle diameter is 1 It was difficult to obtain ultrafine particles of ˜100 nm. For example, rutile type nanocrystals can be obtained by peptization of an aqueous solution of titanium salt for a long time, but it has been reported that it becomes an aggregate of 200 to 400 nm due to secondary aggregation. (J. Phys. Chem. B, 101, 8052, 1997) In order to solve this problem, as described in Japanese Patent No. 2783417 (Patent Document 1), via hydrated titanium oxide, A method for producing rutile titanium oxide by adding a tin compound and aging with hydrogen peroxide at a relatively high temperature is known. However, this method inherently adds tin in order to prevent the formation of anatase-type titanium oxide, so that the amount of tin compound added is limited, and if it is too small, anatase-type titanium oxide crystals are produced, and if more, tin oxide crystals are produced. In addition to the fact that rutile-type titanium oxide cannot be obtained due to the formation of solid solution and the formation of a solid solution, there was a complicated process that required the use of expensive hydrogen peroxide and once produced hydrated titanium oxide. .

On the other hand, it is known that the growth of inorganic crystals is dependent on the direction of the crystal axis. In rutile titanium oxide crystals, the growth of microcrystals in the C-axis direction is remarkable, and crystals with an unusually large aspect ratio are obtained. It is done. (J. Am. Ceram. Soc., 82, 927, 1999) To solve this problem, methods of adding organic ligands such as citric acid have been reported, but satisfactory ones are still available. The fact is not. (J. Mater. Chem., 10, 2338, 2000)
Japanese Patent No. 2783417

  An object of the present invention is to provide an efficient production method of rutile titanium oxide having a high refractive index particle diameter of 1 to 100 nm excellent in transparency and dispersibility and excellent dispersibility as a sol liquid. It is in.

  The present inventors examined the formation process of rutile-type titanium oxide in solution from the viewpoint of research on the anisotropy of crystal growth, and the growth in the C-axis direction of rutile-type titanium oxide crystals was noticeable by the addition of tin metal salt. Thus, it was found that tin oxide was not produced, and as a result, an efficient method for producing rutile titanium oxide ultrafine particles having a particle diameter of 1 to 100 nm excellent in transparency and dispersibility was found.

  As a result of intensive investigations to solve the problems in the process of producing the rutile titanium oxide ultrafine particles described above, the present inventors coexisted with a tin compound under the conditions for synthesizing secondary agglomerates of rutile titanium oxide ultrafine particles. By effectively preventing crystal growth in the C-axis direction and preventing the formation of tin oxide, a synthesis method of rutile-type titanium oxide ultrafine particles having excellent dispersibility was found and the present invention was completed. .

That is, the present invention
In the presence of tin chloride having a tin to titanium molar ratio (Sn / Ti) of 0.001 to 2, a titanium compound solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of -0.2 to 1. It is related with the manufacturing method of the rutile type | mold titanium oxide ultrafine particle which has transparency characterized by making it make it let it be made.

According to the present invention, as a high refractive index agent, a light reflecting agent, an ultraviolet absorber, etc., a plastic lens, a film, a high refractive index hard coat film of a plastic molded product, an antireflection film, a plastic deterioration preventing additive, a cosmetic additive Agent, camera lens, automotive window glass, plasma display, liquid crystal display, EL display, optical member such as optical filter, surface treatment agent such as metal material, ceramic material, glass material, plastic material, dielectric material, piezoelectric body Provided is a method for producing ultrafine rutile titanium oxide particles having a high refractive index and an average particle diameter of 1 to 100 nm, which is effectively used for electronic materials such as materials, photocatalysts, and water repellents. be able to.

  Hereinafter, a method for producing rutile-type titanium oxide ultrafine particles according to the present invention will be described.

  The method for producing rutile-type titanium oxide ultrafine particles of the present invention is a titanium having a Ti concentration of 0.07 to 5 mol / l in the presence of a tin compound having a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2. The compound solution is reacted in a pH range of −1 to 3.

  The tin compound used in the present invention is not particularly limited, but specifically, for example, a tin salt compound such as tin chloride, tin nitrate, tin sulfate, stannate, or an oxide, hydroxide, metal Preferred examples include tin compounds selected from tin and the like.

  The titanium compound used in the present invention is not particularly limited. Specifically, for example, titanium chloride oxide, titanium sulfate, titanium nitrate, titanium alkoxide, hydrated titanium oxide (a titanium compound in advance under alkaline conditions). Preferred examples include titanium compounds selected from such as hydrolyzed ones).

  The reaction in the present invention will be described below.

  A tin compound selected from tin chloride compounds such as tin chloride, tin nitrate, tin sulfate, stannate or oxides, hydroxides, metal tin, etc. is added to the aqueous solution in the reaction vessel, and titanium chloride oxide is added thereto. A titanium compound selected from titanium sulfate, titanium nitrate, titanium alkoxide, hydrated titanium oxide (including those obtained by previously hydrolyzing a titanium compound under alkaline conditions), and the like are added. The tin compound and the titanium compound may be added at the same time, and either one may be first. Moreover, the form of a mixed compound may be sufficient.

In the present invention, the pH is set to be less than 4, preferably from -1 to 3, more preferably from -0.2 to 1. Adjust with hydrochloric acid or nitric acid as necessary. The reaction medium is preferably water, but may be an organic solvent such as alcohol or a mixed medium of water and an organic solvent.

  If the addition amount of the tin compound with respect to the titanium compound is within the range of 0.001 to 2 as Sn / Ti (molar ratio), rutile type titanium oxide ultrafine particles can be obtained. Preferably, it is 0.01 to 1, more preferably 0.01 to 0.1. If the amount of tin is less than the above range, rutile-type titanium oxide ultrafine particles are produced, but the particle size is increased, and therefore, the dispersibility may be deteriorated. In addition, it is possible to synthesize rutile-type titanium oxide ultrafine particles even if the amount is larger than the above range, but the reaction takes a long time. In this case, a large amount of tin adheres to the rutile-type titanium oxide ultrafine particles. There is a possibility that things will be obtained.

  In the present invention, the Ti concentration in the reaction solution is 0.07 mol / l to 5 mol / l, preferably 0.1 mol / l to 1 mol / l. When the Ti concentration is lower than the above range, there is a possibility that anatase-type and rutile-type mixed titanium oxide ultrafine particles may be produced even if a tin compound is added in the range of 0.01 to 0.03 as Sn / Ti (molar ratio). is there. Similarly, at a Ti concentration lower than the above range, if a tin compound is added in a range larger than 0.03 as Sn / Ti (molar ratio), there is a possibility that a titanium oxide-tin oxide mixed ultrafine particle having SnO2 rutile type is generated. is there.

  The reaction proceeds even at low temperatures, but the reaction rate increases with increasing temperature. Therefore, the reaction temperature is recommended from room temperature to 100 ° C., but can be varied as required. Although the reaction completion time is determined depending on the reaction temperature, it is usually carried out in 0.5 to 10 hours.

  The reaction product may be used as it is as a rutile-type titanium oxide sol solution or may be subjected to a desired post-treatment. That is, it can be purified by a known method such as vacuum concentration using an evaporator or ultrafiltration, and concentrated to an appropriate concentration. Centrifugation can yield a white precipitate that can be redispersed in water or other desired media. The aqueous sol solution in which the rutile titanium oxide ultrafine particles are dispersed is replaced with an organic solvent such as alcohols such as methanol and cellosolves such as 2-methoxyethanol, and the sol solution of organic solvent-dispersed rutile titanium oxide ultrafine particles. It can also be used as (organic sol).

  The surface of the rutile titanium oxide ultrafine particles obtained by the present invention is modified with a silane coupling agent such as carboxylic acid such as acrylic acid or glycolic acid, hydroxycarboxylic acid, amine, or γ-glycidoxypropyltrimethoxysilane. Thus, it can be used as a sol solution of surface-modified rutile-type titanium oxide ultrafine particles. Further, by adding a zirconium salt, zinc salt, tin salt or other metal salt or an alkoxy compound, and covering the surface with an inorganic layer, it is possible to treat where dispersibility or light resistance is desired.

  In the present invention, the Ti concentration and the pH of the synthesis reaction solution are particularly important. If it is reacted at a low concentration Ti or pH exceeding the desired range described, it is highly likely that it will become anatase type titanium oxide as it is, and in order to avoid this, when trying to obtain a rutile structure by adding a tin compound, There is a possibility that a foreign substance that is not a rutile type titanium oxide such as tin oxide may be generated.

  Although the reaction mechanism for obtaining rutile-type ultrafine particle titanium oxide by the method of the present invention is not sufficiently clear at present, tin ions or tin ions can be added by adding a tin compound in a molar ratio of 0.001 or more with respect to Ti. Highly dispersed rutile type titanium oxide in order for the compound to coordinate to the plane perpendicular to the C axis direction of the rutile type titanium oxide seed crystal and inhibit growth in the C axis direction in the formation of conventional rutile type titanium oxide crystals. Presumably, ultrafine particles are formed. Or it may be coordinated to a titanium ion or a titanium oxide seed crystal to promote the formation of a precursor-like rutile crystal. Moreover, it is thought that making it react at low pH has played the effect of suppressing the production | generation of a tin oxide crystal | crystallization together.

  The production method according to the present invention is presumed to have a completely different precursor and reaction mechanism from the case where the hydrated titanium oxide sol is reacted with hydrogen peroxide at a temperature limited to a relatively high temperature as has been conventionally performed. The (According to the description in Patent Document 1, if the Sn content is small such that Sn / Ti (molar ratio) is 0.03, anatase-type titanium oxide is formed, or Sn / Ti (molar ratio) is 0.5. (For example, if the Sn content is large, tin oxide is generated. However, in the present invention, this does not occur.)

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

0.09 g of tin tetrachloride pentahydrate was charged into a 100 cc eggplant type flask, dissolved in 50 ml of ion-exchanged water, and 5 ml of a hydrochloric acid aqueous solution of titanium oxide chloride (containing Ti 15 wt%) was added. The pH of the solution was -0.1. (Ti concentration = 0.45, Sn / Ti molar ratio = 0.01) The mixture was stirred with a magnetic stirrer and heated at 50 ° C. for 1 hour to obtain a white precipitate. Centrifugation was performed, and the white precipitate was collected and redispersed in ion-exchanged water. Ultrafiltration was performed to obtain a sol solution having a solid content of 3 wt%. This solid was subjected to powder X-ray diffraction measurement and electron microscope observation. Powder X-ray diffraction was measured after hot air drying at 120 ° C. for 2 hours. The observation with an electron microscope was performed using a transmission electron microscope, and a thin sol solution dropped onto a mesh was observed at a magnification of 200,000 times and 2 million times. As a result, it was a rutile type titanium oxide having a primary particle diameter of 5 nm in the short axis, 8 nm in the long axis (c axis), 15 nm in the short axis of the polycrystalline particles, and 75 nm in the long axis. The elemental molar ratio of Sn / Ti by inductively coupled plasma analysis was 0.01. 1 g of 3 wt% sol solution of the above solid content was added, 30 mg of polyvinylpyrrolidone was added, and 1 g of water was further spin-coated on a quartz substrate, dried at 120 ° C., and immediately measured for refractive index with an ellipsometer. The refractive index (n) of the solid content was evaluated from the volume fraction of the solid content contained, and n = 2.75 was obtained.

The same operation as in Example 1 was carried out except that 0.27 g of tin tetrachloride pentahydrate was used in Example 1. (Ti concentration: 0.45, Sn / Ti = 0.03) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result, the primary particle size was 5 nm short axis and 8 nm long axis (c axis). The particle was a rutile type titanium oxide having a minor axis of 10 nm and a major axis of 35 nm. The element molar ratio of Sn / Ti was 0.02. The refractive index of the solid content was evaluated in the same manner as in Example 1 to obtain n = 2.72.

The same operation as in Example 1 was carried out except that 0.9 g of tin tetrachloride pentahydrate was used in Example 1. (Ti concentration = 0.45, Sn / Ti = 0.1)) When the solid content of the obtained sol solution was analyzed in the same manner as in Example 1, the primary particle diameter was 5 nm for the short axis and 8 nm for the long axis (c axis). The crystal grain was a rutile type titanium oxide having a minor axis of 10 nm and a major axis of 30 nm. The element molar ratio of Sn / Ti was 0.06. The refractive index of the solid content was evaluated in the same manner as in Example 1 to obtain n = 2.65.

The same procedure as in Example 1 was performed except that 4.3 g of tin tetrachloride pentahydrate was used in Example 1. (Ti concentration: 0.45, Sn / Ti = 0.5) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result, the primary particle diameter was 4 nm for the short axis and 6 nm for the long axis (c axis). The particle was a rutile type titanium oxide having a minor axis of 10 nm and a major axis of 20 nm. The element molar ratio of Sn / Ti was 0.18. The refractive index of the solid content was evaluated in the same manner as in Example 1 to obtain n = 2.47.

The same operation as in Example 1 was carried out except that 8.6 g of tin tetrachloride pentahydrate was used in Example 1. (Ti concentration = 0.45, Sn / Ti = 1) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result, the primary particle size was 5 nm short axis and 6 nm long axis (c axis) was polycrystalline. The particle was a rutile type titanium oxide having a minor axis of 10 nm and a major axis of 20 nm. The element molar ratio of Sn / Ti was 0.18.

  The same operation as in Example 1 was carried out except that the reaction temperature was set to 100 ° C. in Example 1. (Ti concentration = 0.45, Sn / Ti = 1) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result, the primary particle size was 6 nm short axis and 9 nm long axis (c axis). .

[Comparative Example 1]
The same procedure as in Example 1 was performed except that tin tetrachloride pentahydrate was not added in Example 1. (Ti concentration = 0.45, Sn / Ti = 0) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result, the primary particle size was 7 nm short axis and 9 nm long axis (c axis) was polycrystalline. It was a rutile type titanium oxide having particles of 200 nm or more.

[Comparative Example 2]
The same procedure as in Example 5 was performed except that the amount of ion-exchanged water added in Example 5 was changed to 500 ml. (Ti concentration = 0.05, Sn / Ti = 1) The solid content of the obtained sol solution was analyzed in the same manner as in Example 1. As a result of the powder X-ray diffraction measurement, a rutile crystal of tin oxide was produced. A rutile type titanium oxide was not obtained.

[Comparative Example 3]
The same procedure as in Example 1 was conducted except that ammonia water was added to the aqueous solution of tin tetrachloride pentahydrate and titanium chloride oxide in Example 1 to react with the solution adjusted to pH = 4. The reaction solution was turbid, and no rutile titanium oxide was produced.

The rutile-type titanium oxide ultrafine particles obtained by the present invention are used as a high refractive index agent, a light reflector, an ultraviolet absorber, etc., as a plastic lens, a film, a high refractive index hard coat film of a plastic molded product, an antireflection film, a plastic. Anti-degradation additive, cosmetic additive, camera lens, automotive window glass, plasma display, liquid crystal display, EL display, optical member such as optical filter, surface treatment agent such as metal material, ceramic material, glass material, plastic material It is used for electronic materials such as dielectric materials and piezoelectric materials, photocatalysts, water repellents and the like.

The powder X-ray-diffraction result of Example 1 is shown. The powder X-ray-diffraction result of Example 2 is shown. The powder X-ray-diffraction result of Example 3 is shown. The powder X-ray-diffraction result of Example 4 is shown. The powder X-ray-diffraction result of Example 5 is shown. The powder X-ray-diffraction result of the comparative example 2 is shown.

Claims (2)

In the presence of tin chloride having a tin to titanium molar ratio (Sn / Ti) of 0.001 to 2, a titanium compound solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of -0.2 to 1. A method for producing rutile-type titanium oxide ultrafine particles having transparency, characterized in that: In the manufacturing method of the rutile type titanium oxide ultrafine particles having transparency according to claim 1,
A method for producing transparent rutile-type titanium oxide ultrafine particles, wherein the molar ratio of tin to titanium (Sn / Ti) is 0.01 to 0.1 .

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