JPH05155616A - Transparent yttria sol and its production - Google Patents

Abstract

PURPOSE:To obtain a transparent yttria sol having a small average grain diameter and a high grain concn. and excellent in economical stability by allowing yttrium acetate to react with an alkaline substance, cleaning the produced yttria sol with an ultrafilter membrane and then concentrating the sol. CONSTITUTION:An aq. soln. of yttrium acetate is heated and agitated, and an alkaline substance is gradually added to allow the yttrium acetate to react with the alkaline substance. The produced yttria sol is cleaned by an ultrafilter membrane and then concentrated to obtain the desired transparent yttria sol contg. the grains having 10-80Angstrom average diameter. Although the concn. of the yttrium acetate in the soln. to be used is relatively low since the solubility of the yttrium acetate in pure water is low, the concn. can be increased to 0.4mol/l by heating the soln.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent yttriasol and a method for producing the same, and more specifically, a transparent yttriasol having a small average particle size, a high particle concentration and excellent stability over time, and a method for producing the same. Regarding

[0002]

2. Description of the Related Art As yttriasol, JP-A-62-1
Japanese Patent No. 143864 discloses a transparent yttria sol having a particle diameter of 100 angstroms in a sol and a particle concentration of 14% by weight, and a refractory composition using this sol as a binder is proposed. But in general,
In order for the sol to exhibit high strength as an inorganic binder, it is necessary that the concentration of particles such as inorganic oxides in the sol is high, so the particle concentration exceeds 14% by weight.
There is a need for yttriasols with even higher particle concentrations. The above publication does not describe a specific method for preparing yttriasol.

Japanese Unexamined Patent Publication (Kokai) No. 59-213620 relates to the production of yttrium oxide in the form of fine powder, not yttria sol as in the present invention. A method of producing a precipitate of a basic salt of yttrium by adding it little by little and roasting the precipitate to produce fine powdery yttrium oxide is described.

Japanese Patent Publication No. 2-38577 discloses that
There is described a basic yttrium acetate aqueous solution which is substantially composed of only yttrium ions and acetate ions and has an acetic acid / yttrium (CH ₃ COOH / Y) molar ratio in a specific range. Since this aqueous solution has a high concentration, it is useful as a high-concentration yttria source material, but it is not a yttria sol as in the present invention, but an yttrium acetate aqueous solution.

[0005]

An object of the present invention is to exhibit a high-strength binder effect, and particularly useful as an inorganic binder or coating agent, having a small average particle size and a high particle concentration, Further, it is to provide a transparent yttria sol excellent in stability over time.

Another object of the present invention is to provide a method for efficiently producing the above transparent yttria sol.

[0007]

The present invention relates to a transparent yttria sol containing particles in which the average particle size of the particles in the sol is in the range of 10 to 80 angstroms.

Further, in the present invention, an yttrium acetate aqueous solution is heated and stirred, and an alkaline substance is gradually added to this to react the yttrium acetate with the alkaline substance, and the produced yttria sol is used with an ultrafiltration membrane. The present invention relates to a method for producing the transparent yttria sol, which comprises:

The present invention will be described in detail below.

The transparent yttrium sol of the present invention is obtained by reacting an aqueous yttrium acetate solution with an alkaline substance. The yttrium acetate aqueous solution used is either yttrium acetate dissolved in pure water or yttrium oxide in pure water. It can be prepared by dispersing the powder and then adding acetic acid thereto to dissolve the yttrium oxide. Incidentally, when the transparent yttriasol of the present invention is used as, for example, an inorganic binder, it may be good in performance even if it contains a rare earth element other than yttrium.In such a case, yttrium is oxidized. A mixed yttrium acetate aqueous solution can be prepared by using a mixed rare earth acetate or mixed rare earth oxide having a content of at least 65% by weight calculated as yttrium.

The concentration of the yttrium acetate aqueous solution is usually relatively low because the solubility of yttrium acetate in pure water is low, but it is 0.4 mol / liter (hereinafter, (Displayed with L) can be used.

There is no particular limitation on the alkaline substance used in the reaction with the aqueous solution of yttrium acetate, and ammonia gas, aqueous ammonia, sodium hydroxide, potassium hydroxide, etc. can be used. Ammonia water is preferably used from the standpoint of avoiding contamination with other substances. Therefore, the present invention will be described below by taking the case of using aqueous ammonia as the alkaline substance as an example.

In the reaction between the yttrium acetate and the alkaline substance, if the reaction is continued while adding an appropriate amount of ammonia water to the yttrium acetate aqueous solution, the reaction proceeds while the transparency of the reaction solution is maintained. However, if the amount of ammonia water added increases, a white precipitate will appear. In the present invention, in order to obtain a transparent yttriasol, ammonia water is added within a range where precipitation does not occur, but in order to obtain a transparent yttriasol having a high concentration and excellent stability over time, the above reaction In the above, it is necessary to continuously supply ammonia water little by little while heating and stirring the reaction solution. In addition, the pH of the reaction solution at the time when the same amount of ammonia water is supplied varies depending on the supply rate of the ammonia water continuously supplied during the reaction, and the slower the supply rate, the lower the pH value of the reaction solution. Become. In the present invention, it is important to slow the supply rate of the ammonia water to lower the pH value during the reaction and at the time when the supply is stopped, and the ammonia water is rapidly supplied without using a metering pump or the like. When the reaction is carried out by supplying it to an aqueous solution of yttrium acetate, the yttria sol obtained has a high viscosity even at a low concentration, and the yttrium acetate concentration is from 2 to 2.
Even if it is as low as 3% by weight, it may gelate when left overnight. The effect obtained by carrying out the reaction by slowing the supply rate of the ammonia water is also affected by the reaction temperature of the reaction solution during the reaction, and in order to obtain the transparent yttriasol of the present invention, the reaction temperature is 30-100
It is preferable to set the temperature in the range of 40 ° C., preferably 40 to 70 ° C. to carry out the above reaction. When the reaction temperature is lower than 30 ° C, the stability of the obtained transparent yttria sol with time is poor, and 1
Even when the temperature exceeds 00 ° C, a transparent yttria sol having excellent stability over time cannot be obtained.

The details of the reaction mechanism, reaction rate, etc. in the reaction of yttrium acetate with ammonia are not clear, but when the reaction is carried out by adding aqueous ammonia to the aqueous solution of yttrium acetate, the supply of aqueous ammonia does not react. The yttrium acetate aqueous solution is heated and stirred so as to be the rate-determining step of, while maintaining a particularly high stirring state, in which the supply of ammonia water is quantitatively and the supply rate is slowed in the reaction system. The transparent yttria sol of the present invention can be obtained by carrying out the reaction so that the ammonia concentration becomes uniform.

Specifically, for example, while maintaining the reaction solution at a temperature of 30 ° C. or higher under high agitation, this is treated with ammonia water for 40 minutes or longer, preferably 60 minutes or longer, more preferably 180 minutes or longer. By adding and reacting, a transparent yttria sol excellent in stability over time can be obtained.

The amount of ammonia water added is 0.9 to 1 mol of yttrium acetate.
It is preferable to add it in a range of 1.5 mol.
Ammonia / yttrium acetate (molar ratio) exceeds 1.5, adding a large amount of ammonia water causes the reaction solution to thicken and yttrium hydroxide to precipitate to obtain the target transparent yttrium sol. I can't. Further, if it is less than 0.9, the reaction rate of yttrium becomes low, which is not preferable.

As the reactor used in the present invention, a reactor equipped with a heating device and a stirring device is used. As the stirring device, a homomixer, in order to ensure a high stirring state,
It is preferable to use a device having a large mixing and stirring ability such as a colloid mill or a triaxial mixer. Further, it is preferable to attach a reflux device to the reactor in order to prevent scattering of water vapor and gases generated during the heating reaction.

The transparent yttria sol obtained by the above reaction contains impurities such as ammonium ions, acetate ions and unreacted yttrium ions, and these impurities have the action of promoting thickening and gelation of the sol. In the present invention, the transparent yttria sol is washed with an ultrafiltration membrane to remove these impurities.

Generally, as a method of washing the sol, a method of diffusion by a semipermeable membrane, a method of dialysis or electrodialysis, or a method of using an ion exchange resin is known, but these methods require a long time for washing. However, there is a drawback that the washing operation is complicated, and the use of an ultrafiltration membrane is advantageous for industrially washing the sol. As the ultrafiltration membrane used in the present invention, it is necessary to select a membrane having a permeation pore structure that does not allow passage of sol particles but only impurity ions, but the shape of the membrane is not limited, and is a flat membrane. , Tubular membranes, spiral membranes and the like can be used.
It is desirable for the filtration device to employ a circulation system in which the above ultrafiltration membrane is set.The solvent containing impurity ions is discharged to the outside of the system, and the solvent is added to the concentrated sol for continuous washing. To do.

In cleaning the sol of the present invention, deionized water is used, and the cleaning is preferably performed so that the conductivity of the sol after cleaning is about 1/20 or less of the conductivity of the sol before cleaning. .. The unreacted yttrium ions in the waste water can be easily recovered and reused.

By washing with the ultrafiltration membrane, a transparent yttria sol having a particle concentration in the sol of Y ₂ O ₃ of about 15% by weight can be obtained. This transparent yttria sol can be used as it is, but when it is used as an inorganic binder, for example, it is necessary to increase the concentration of the sol in order to exert a high-strength binder effect. The sol after washing is further concentrated. The concentration is 90 ° C. with stirring under vacuum by the usual heating and evaporation operation.
Hereafter, it can be carried out at a temperature of preferably 60 ° C. or lower. The degree of concentration depends on the viscosity of the obtained sol, but the particle concentration in the sol can be up to 35% by weight as Y ₂ O ₃ .

The thus obtained transparent yttria sol having a particle concentration in the sol of 15 to 35% by weight as Y ₂ O ₃ was observed by an electron microscope, and the average particle diameter was 10 to 80 angstroms. Range, usually 2
It is 0 to 50 angstroms. Further, according to the electrophoresis method, the charge of the particles in this transparent yttriasol is positive (positive).

Yttria is thermodynamically stable at high temperatures,
Since it has the property of low reactivity with molten metal,
By utilizing such characteristics, the transparent yttriasol of the present invention can be used in various fields. In particular, the transparent yttriasol of the present invention can be effectively used as an inorganic binder or coating agent. When the transparent yttria sol of the present invention is used as an inorganic binder, the particle concentration in the sol is usually 20 to 30 wt% as Y ₂ O ₃ , the viscosity is 10 to 60 cps, and the pH is
Is used in the range of 7.2 to 8.7, but the transparent yttriasol having such properties is 3
Even if stored for more than a month, no increase in viscosity is observed and it is stable over time. When the transparent yttria sol of the present invention is used as a coating agent, it is usually diluted with pure water or an organic solvent so that the concentration of particles in the sol is 10% by weight or less as Y ₂ O _3. A transparent coating film can be formed by applying it to the material.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 1208 g (4 mol) of yttrium nitrate was charged into a 20 L polyethylene container and dissolved in 1450 g of deionized water. While this solution was heated to 50 ° C. and stirred with an ultra disperser, ammonia water was quantitatively introduced directly into the stirrer stirring section. This ammonia water is 1 mol / k
Diluted to a concentration of g, 4400 g (4.4 mol) was used in total. Ammonia water was introduced at a rate of 16 g / min (0.016 mol / min) on average using a tube pump. The reaction process was monitored using a pH meter and a conductivity meter, and changes in pH and conductivity with addition of aqueous ammonia are shown in FIG.

After the reaction was completed, the reaction solution was returned to 25 ° C., and the pH of the reaction solution was 8.9. The conductivity was about 60 mS / cm. The reaction solution was washed with an ultrafiltration membrane and then concentrated under reduced pressure to obtain a transparent yttria sol having a particle concentration of Y ₂ O ₃ of 35% by weight.

Since this sol was slightly viscous, it was diluted with deionized water to 25% by weight. The pH of the sol thus obtained by dilution was 8, and the conductivity was 4 mS / cm.
Met. The sol was stored in a polyethylene container for 3 months, but no particular thickening was observed. When the sol was observed with a transmission electron microscope, the average particle size was about 20 Å.

The sol had a good film-forming property, and when this sol was diluted to 5% by weight and dip-coated on a glass substrate, a uniform and transparent coating film was obtained.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 35 ° C. The pH change during the reaction was almost the same as in Example 1.

After the reaction was completed, the temperature of the reaction solution was returned to 25 ° C., and the pH was 8.9. The conductivity is about 60m.
It was S / cm. The reaction solution is washed with an ultrafiltration membrane and then concentrated under reduced pressure to obtain a sol having a particle concentration of Y.
_{As a 2} O ₃ , 32% by weight of a transparent yttria sol was obtained.
Since this sol was slightly viscous, it was diluted with deionized water to a concentration of 25% by weight. When this sol was stored in a polyethylene container, it was stable for 2 months or more. The average particle size of this sol was about 30 Å.

Example 3 In Example 1, the feed rate of ammonia water was 25 g /
The reaction was carried out in the same manner as in Example 1 except that the amount was changed to 0.025 mol / min. The pH change during the reaction was about 0.1 higher than that in Example 1.

After the reaction was completed, the reaction solution was returned to 25 ° C., the pH of the reaction solution was 8.9, and the conductivity was about 60 m.
It was S / cm. When this reaction solution was washed with an ultrafiltration membrane, it was concentrated under reduced pressure to obtain a particle concentration in the sol of Y ₂
A 32% by weight transparent yttria sol as O ₃ was obtained.
Since this sol is slightly viscous, it was diluted with deionized water to a concentration of 25% by weight. When this sol was stored in a polyethylene container, it was stable for 2 months or more. The average particle size of this sol was about 40 Å.

[0033]

[Effect] The transparent yttria sol of the present invention has a small average particle size of 10 to 80 angstroms in the sol and a high particle concentration of Y ₂ O ₃ of 15 to 35% by weight. When used as a binder, a high-strength binder effect can be exhibited.

The transparent yttriasol of the present invention is excellent in stability over time, and does not thicken or gel even after long-term storage.

[Brief description of drawings]

FIG. 1 is a graph showing changes in pH and conductivity during a reaction in Example 1.

Claims (3)

[Claims] 1. The average particle size of the particles in the sol is from 10 to 80.
A transparent yttriasol comprising particles in the Angstrom range. 2. The concentration of particles in the sol is 15 to 15 as Y ₂ O _3.
The transparent yttria sol according to claim 1, which is 35% by weight. 3. An yttrium acetate aqueous solution is heated and stirred, and an alkaline substance is gradually added thereto to cause a reaction between the yttrium acetate and the alkaline substance, and the produced yttria sol is washed with an ultrafiltration membrane. , The average particle size of the particles in the sol is 10
A method for producing a transparent yttria sol, which comprises particles in the range of -80 angstroms.