JPH062582B2 - Crystalline ceric oxide sol and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crystalline cerium oxide sol and a method for producing the same.

Cerium oxide is used for abrasives, catalysts, masking agents for IC substrates, ultraviolet absorbers, glass decolorizers, electron beam absorbers, ceramic dielectrics and the like. The present invention provides an excellent ultraviolet absorbing material which can be applied to improving the weather resistance of ultraviolet absorbing glass, ultraviolet absorbing polymer film, plastics, synthetic fibers and the like among these fields of application.

(Prior Art) In recent years, development of ultraviolet absorbing glass and film having excellent translucency has been carried out. Conventionally, the method for obtaining such glass has been manufactured by melting a metal oxide having an ultraviolet absorbing ability together with a glass component.

Further, a coating method for depositing a metal oxide on the glass surface by a chemical vapor deposition method (CVD method) has also been developed.

However, in the chemical vapor deposition method, as a result of generally using anhydrous metal chloride as a raw material, corrosive chlorine gas is generated during vapor deposition, or vapor deposition is performed at high temperature in a closed furnace. However, it was difficult to obtain a uniform thin film. Further, there is a drawback that the apparatus used in this case becomes large in size and the manufacturing cost becomes high.

Further, according to the physical vapor deposition method (PVD method) of metal, a thin film of metal that absorbs visible light is formed on the glass surface.
The light-transmitting property of the glass is remarkably lowered, resulting in a dark glass having poor light-transmitting property, so that the use of this method is limited.

On the other hand, recently, there has been a strong demand for glass for automobiles to have an ultraviolet absorbing ability, a surface treatment technology for large glass is required more than ever, and the vapor deposition method tends to be more difficult and costly.

Therefore, in place of the CVD method and the PVD method, there is a demand for the development of an inexpensive method capable of forming a uniform thin film even on a large product.

In addition, regarding films for food packaging and the like, there is a growing demand for non-harmful substitutes for organic UV absorbers in order to prevent photooxidative deterioration of plastics due to UV rays or to prevent deterioration of foods.

(Problems to be Solved by the Invention) In view of these circumstances, the inventors of the present invention have excellent translucency and ultraviolet absorptivity, and further are excellent in various properties such as dispersibility during use and coating properties. As a result of earnest research on a crystalline sol to obtain an absorbing material, it was found that the novel sol of the present invention consisting of crystalline ceric oxide is excellent as an ultraviolet absorbing material, and the present invention was completed based on such findings. It is a thing.

(Means for Solving Problems) That is, the present invention relates to a crystalline cerium oxide sol and a method for producing the same. The first invention is a cerium oxide sol having a particle diameter of 300 Å or less, and The invention of 1) is a method for producing a crystalline cerium oxide sol characterized by reacting a cerium salt compound with an alkali metal hydroxide or ammonia to form a gel, and then hydrothermally treating the gel.

(Operation) First, the crystalline cerium oxide sol of the present invention will be described in detail below.

Heretofore, no crystalline cerium oxide sol has been known.

When the water-soluble cerium salt compound is neutralized with an alkaline agent, the solution may become a sol. However, this is a sol because a small amount of neutralized precipitates temporarily became colloidal-sized, and this was a sol composed of amorphous or hydroxide particles. It is a thing.

Therefore, when the neutralization reaction proceeds, this precipitate grows largely and becomes a precipitate, and the solution changes from sol to gel.

Further, by removing the acid radicals of the cerium salt compound with an ion exchange resin, or by dissolving the gel obtained by neutralizing the cerium salt compound in an acid below equivalent (for example, in the case of hydrochloric acid, the composition is Ce (OH ) ones represented by _m Cl _4-m can be obtained), it is possible to obtain a basic salt solution or a gel product.

However, the sol obtained by such a method is all amorphous and unstable.

On the other hand, the cerium oxide sol of the present invention is crystalline, and it is an extremely fine colloidal particle of 300 Å or less, and it is stable in an aqueous solution state, and it sediments even when left for several months. There is no.

Such a sol has never been known so far, and will create a new application in the field of application of the cerium oxide-based composite material.

The characteristics of the crystalline cerium oxide sol of the present invention will be further described below.

First, the sol of the present invention can be obtained in a solution state as a cerium oxide having a high concentration of 40% or more.

An amorphous sol is generally highly viscous, but since the sol of the present invention is a low-viscosity, high-concentration sol, it can be used as a UV absorber, an electron beam absorber, a masking agent for IC substrates, etc. A coating film having a desired film thickness can be prepared by a single coating operation, and a coating film with excellent performance can be obtained.

Further, a coating of a low-concentration and high-viscosity material such as an amorphous sol is likely to cause cracks during drying. Therefore, it has to be diluted and coated many times, but the phenomenon of returning to the second and subsequent times occurs at a degree of drying.

Therefore, after each coating, it has to be fired to obtain a ceric oxide material and then coated again, which is an industrially complicated operation.

Secondly, the sol of the present invention dried after coating is only CeO ₂ and a stabilizer, and since it contains almost no water, there is little weight loss even if it is baked, and as a result, it is robust. A coating film is obtained.

In this case, when a cerium salt aqueous solution is used instead of the sol of the present invention, many acid radicals and water of crystallization still remain even after drying, so that the film is porous and crystallizes on the substrate, resulting in a robust coating. No film can be obtained.

Thirdly, the sol of the present invention has excellent characteristics as an abrasive.

Cerium oxide generally has an excellent polishing power as compared with zirconium oxide and valve stems, and thus has a great demand as an abrasive in the field of application.

Due to recent technological advances, the demands on the surface accuracy of optical glass, single crystals and translucent ceramics have become strict, and finer abrasive grains have been demanded as the abrasive. The sol of the present invention has a small particle size, is uniform, and has a high polishing power because it is crystalline, and its crystal particle size can be adjusted to a desired value, and the performance required as these abrasives is satisfied. It is a thing.

In the present invention, the colloidal particle size was measured by electron microscope observation, but in the sol of the present invention, substantially all colloidal particles had a particle size of 300 Å or less.

Next, the method for producing a crystalline ceric oxide sol, which is the second invention, will be described in detail.

The second invention relates to a method for producing a crystalline cerium oxide sol characterized by reacting a cerium salt compound with a hydroxide of an alkali metal or ammonia to form a gel, and then hydrothermally treating the gel. .

Examples of the cerium salt compound used in the present invention include ceric sulfate, ceric ammonium nitrate, ceric ammonium sulfate, ceric acetate, ceric chloride, ceric ammonium nitrate, ceric nitrate and ceric nitrate. Examples include cerium and the like.

Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

In the present invention, first, the cerium salt compound is reacted with an alkali metal hydroxide or ammonia to form a gel.

Regarding the conditions for producing this gel, the temperature during the reaction between the two is approximately 10 to 90 ° C.

Regarding the use ratio of these, the equivalent ratio of the alkali metal hydroxide or ammonia (A) and the acid radical (B) derived from the cerium salt compound is about 0.9 to A / B.
Use each to give a range of 1.3.

When cerium / ammonium double salt is used, the amount of vinegar roots derived from the ammonium salt is calculated by the amount removed from the above (B).

The order of addition is not particularly limited, and either one of the cerium salt compound and the alkali metal hydroxide or ammonia may be added first, or both may be added and reacted simultaneously.

When the first cerium salt is used, after the gel is formed, the first cerium is gradually oxidized to the second cerium, but the oxidation time is long and the oxidation rate is low. It is preferable to use an agent together.

The gel thus obtained is then filtered and washed to remove impurities in the gel.

This residual impurity needs to be reduced in terms of the production of the ceric oxide sol and in terms of application. For example, if the above filtration and washing operation is not performed at all, the obtained sol will be unstable, and I can't get a sol.

The filtration and washing means are not particularly limited, and any commonly used means such as a water filter such as a filter press or centrifugal filtration, a repulp-centrifugal separation method, or the like can be used.

An acid is then added to the gel after filtration and washing, and the gel is subjected to hydrothermal treatment. The types of acids to be added include hydrochloric acid, nitric acid, acetic acid,
Examples thereof include formic acid, lactic acid, glycolic acid and the like. The amount of acid added is in the range of 0.01 to 1.00 mol with respect to 1 mol of CeO ₂ in the gel. In this case, if the addition amount of the acid deviates from this range, the sol having excellent dispersibility of the present invention cannot be obtained.

The acid may be added after the hydrothermal treatment, and the order of the acid addition and the hydrothermal treatment is not particularly limited.

Regarding hydrothermal treatment conditions, the temperature is 100 ° C or higher,
Generally, the higher the processing temperature and the longer the processing time, the better the development of the crystal form, and the colloidal particles having a large particle size can be obtained.

Also, the treatment at a temperature below 100 ° C does not crystallize the colloidal particles even if it is carried out for a long time, and the crystallinity of the colloidal particles is remarkably low even if a part thereof is crystallized. Due to the inability to obtain, the object of the present invention cannot be achieved.

According to the method of the present invention, the hydrothermal treatment condition can be selected according to each application of the sol of the present invention to obtain a sol having a desired particle size, and the control can be performed by selecting the hydrothermal treatment condition. This is a major feature of the present invention.

Then, the sol obtained by hydrothermal treatment is subjected to a drying step.

As a drying method, any means such as heat drying, vacuum drying and freeze drying can be used.

In the case of heat drying, the drying condition needs to be lower than the temperature at which the added acid evaporates or deteriorates.

By removing only the water content in the sol solution by drying and pulverizing the solution, the sol solution when re-dissolved becomes extremely stable.

In the previous step, if the acid is added before the hydrothermal treatment and the addition amount of the acid is 0.2 mol or more relative to 1 mol of CeO ₂ in the gel, this drying operation is not necessary. The sol of the present invention can be obtained. That is, this drying step is not particularly necessary depending on the selection of the production conditions for the sol of the present invention.

Further, the sol powder obtained by drying can be adjusted to a desired sol solution concentration, and can be further dispersed in a solvent other than water to form an organ nozzle, which means that the crystalline ceric oxide sol of the present invention can be prepared. The purpose of use is further expanded.

(Example) Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto. All percentages are by weight unless otherwise specified.

Example 1 1028 g of aqueous ammonia (NH ₃ 4.0%) was added to 1000 g of an aqueous cerium sulfate solution (CeO ₂ 8.0%) with stirring to form a gel.

This was thoroughly washed with water until SO ₄ ²⁻ ions were not observed in the filtrate, and a gel of CeO ₂ 21.0% was obtained.

Nitric acid was added to 200 g of this gel so that the HNO ₃ / CeO ₂ molar ratio would be 0.1.
2.5 g of (HNO ₃ 61%) and 322 g of water were added, and this was placed in an autoclave and subjected to hydrothermal treatment at 150 ° C. for 15 hours.

After the hydrothermal treatment, this slurry was dried at 100 ° C. until a constant weight was obtained to obtain a powder of the sol of the present invention.

When this sol powder was analyzed, CeO ₂ 92.5%, NO
₂ 3.3% SO ₄₀ %.

Moreover, when this sol powder was dispersed in water to prepare a sol containing 1.0% of CeO ₂ and allowed to stand, the dispersion ratio after one month was 99.5%.

Furthermore, as a result of measuring the colloidal particle diameter by observation with a transmission electron microscope, the average particle diameter was 90Å.

Further, the sol of the present invention was subjected to X-ray diffraction measurement, and the diffraction diagram is shown in FIG.

As is clear from FIG. 1, the diffraction peak is broad because the crystalline cerium oxide sol of the present invention has a particle size of 90Å, which is considerably small, as can be understood from the Scherrer equation. It is a thing.

Incidentally, in the measurement of X-ray diffraction, an RAD-Ia type manufactured by Rigaku Corporation was used as an X-ray diffraction apparatus, and the measurement was performed using a Cu tube under the conditions of 3 OKV and 20 mA.

Example 2 1.8 g of glacial acetic acid and 320 g of water were added to 100 g of the gel obtained by the reaction between cerium cerium sulfate and aqueous ammonia in Example 1 so that the molar ratio of CH ₃ COOH / CeO _{2 was} 0.25. It was placed in an autoclave and subjected to hydrothermal treatment at 200 ° C. for 24 hours to obtain a sol of the present invention.

When this sol solution was analyzed, it was found that CeO ₂ 5.0% and SO ₄₀
% And CH ₃ COOH 0.4%.

Further, this sol was dried at 80 ° C. to a constant weight, and the dried product was subjected to measurement of X-ray diffraction in the same manner as in Example 1, and the diffraction diagram thereof is shown in FIG.

Further, as a result of measuring the colloidal particle diameter by observation with a transmission electron microscope, the average particle diameter was 170Å.

In addition, the d (Å) values in X-ray diffraction were 3.12, 1.91, and 1.63, which are JCPDS cards (Joint Co
mmittee on Powder Diffraction Standard) 1986 version, identified as ceric oxide crystals (Cerianite).

Example 3 5000 g of ceric ammonium nitrate aqueous solution (Ceo ₂ 2.0%)
And sodium hydroxide aqueous solution (Na1.5%) 3380% water 1000g beforehand
Was added simultaneously with stirring to the reaction tank in which the above was added by separate metering pumps for about 1 hour. At this time, the reaction liquid temperature was 21 ° C.

After the reaction, the gel was filtered and washed with water, CeO ₂ 17.33%, NO ₃ 0.3%, N
A wet cake containing 20 ppm or less of NH ₃ and NH ₃ was obtained.

Water (145 g) was added to this wet cake (200 g) to form a uniform slurry, which was placed in an autoclave and subjected to hydrothermal treatment at 180 ° C. for 15 hours.

After the hydrothermal treatment, 5.2 g of nitric acid (HNO ₃ 61%) was added and mixed uniformly.

This slurry was dried at 100 ° C. until a constant weight was obtained to obtain the sol of the present invention.

This sol powder dispersed in water to have CeO _{2 of} 35% had excellent fluidity despite its high concentration.

Then, a sol prepared by adjusting this to CeO ₂ 6% was coated on quartz glass.

The coating device is Spinner 1H-0 manufactured by Mikasa Co., Ltd.
Type 2 was used.

After coating the sol on the glass, dry it,
Next, firing was performed at 500 ° C. for 1 hour.

In order to observe the absorption of the coating glass after firing in the ultraviolet to visible region, a spectrophotometer (UV-260 manufactured by Shimadzu Corporation) was used to measure the light transmittance in the wavelength range of 190 to 900 nm.

The results are shown in Table 2.

For comparison, a titanium oxide sol is produced by the following method, and similarly the light transmittance in the ultraviolet region to the visible region is measured,
The results are shown in Fig. 2. (Comparative Example 1) (Production method of titanium oxide sol) Ammonia water (NH ₃ ) was added to 600 g of titanium tetrachloride aqueous solution (TiO ₂ 3.0%).
2.0%) 812 g was added to the mixture under stirring for about 1 hour to give a gel.

After the generated gel was filtered off, water injection filtration washing was performed until no chlorine ion was found in the gel. 100g of this gel
Ammonia water (NH ₃ 2.0%) 16 g and water 24 g were added to, and the mixture was transferred to an autoclave and subjected to hydrothermal treatment at 120 ° C. for 10 hours to obtain a TiO ₂ 6% titanium oxide sol of Comparative Example.

As is clear from FIG. 2, it is understood that the examples of the present invention have a higher ultraviolet absorption ability than the titanium oxide of the comparative example.

Example 4 1000 g of a ceric ammonium sulfate solution (CeO ₂ 2.5%) was added to 260 g of ammonia water (NH ₃ 4.2%) at room temperature with stirring,
A gel was produced.

After the generated gel was separated by filtration, the gel was washed until SO ₄ ions were not observed in the gel.

As a result of analyzing this gel, NH ₃ ions were not detected in CeO ₂ 23.5%.

CH ₃ COOH / CeO ₂ molar ratio 0.4 to 100 g of this gel,
3.3 g of acetic acid and 130 g of water were added, and this was placed in an autoclave, subjected to hydrothermal treatment at 130 ° C. for 15 hours, and then this slurry was freeze-dried until a constant weight was obtained to obtain the sol of the present invention.

Water was added to this sol powder to make a sol containing 15% CeO ₂ and polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., NL-0
5) was mixed to prepare a solution having a CeO ₂ / polyvinyl alcohol weight ratio of 0.05.

This solution was poured into a mold of 100 × 100 mm and dried at 40 ° C. for about 70 hours to obtain a film having a thickness of 100 × 100 mm × 0.2 mm.

The light transmittance from the visible region to the ultraviolet region of this film was measured, and the results are shown in FIG.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the crystalline ceric oxide sol of the present invention obtained in Examples 1 and 2. FIG. 2 is a diagram showing the light transmittance in the ultraviolet to visible region of the crystalline cerium oxide sol of the present invention obtained in Example 3 and the titanium oxide sol obtained by glass coating. FIG. 3 is a diagram showing the light transmittance in the ultraviolet to visible region of the polyvinyl alcohol film containing the crystalline cerium oxide sol of the present invention obtained in Example 4.

Claims (2)

[Claims] 1. A crystalline cerium oxide sol having a particle size of 300 Å or less. 2. A cerium salt compound is reacted with an alkali metal hydroxide or ammonia to form a gel,
A method for producing a crystalline cerium oxide sol, which comprises subjecting this to a hydrothermal treatment.