JPH0665610B2 - Method for producing zirconia sol - Google Patents

Description

TECHNICAL FIELD The present invention relates to a zirconia sol and a method for producing the same,
More specifically, it relates to a zirconia sol stable in a wide pH range, particularly in a neutral to alkaline region, and a method for producing the same.

The zirconia sol of the present invention is used as a coating agent, an inorganic binder, or a composite material of an organic or inorganic compound and zirconia. Particularly, it is suitably used for a ceramic material containing a basic substance, and is used as a binder for a refractory molded article or a casting mold.

(Prior Art) Conventionally, as a method of producing a zirconia sol from a zirconium salt aqueous solution, a method of peptizing a precipitate obtained by reacting the zirconium salt aqueous solution with a basic substance with an acid or a basic substance to the zirconium salt aqueous solution is used. A method is known in which sol is generated by injecting and mixing to a pH at which precipitation does not occur. Further, a method of obtaining a zirconia-based colloid sol by heating an aqueous solution containing a zirconium salt under normal pressure or under pressure to hydrolyze is also known.

However, all of the zirconia sols produced by the above-mentioned conventional methods are stable only in the acidic region of pH, the viscosity is increased in the neutral or alkaline region, or gelled and cannot be used as a sol. For example, by mixing calcium oxide, magnesium oxide, other basic powders, composite powders containing these as composition components, or powders containing these as impurities and a conventional zirconia sol stable only in the acidic region. It is not possible to prepare a slurry that is stable or has a low viscosity over time. Further, when the above-mentioned conventional zirconia sol is applied to a metallic material as a coating agent or the like, there is a problem of corrosion due to acid in the sol, which is difficult to use, and a zirconia sol stable in a neutral or alkaline region is desired.

On the other hand, when a zirconium component is required in the alkaline region, an alkaline zirconium salt such as zirconyl ammonium carbonate or potassium zirconyl carbonate is used. Among them, the zirconyl ammonium carbonate aqueous solution itself or the aqueous solution obtained by hydrolyzing the zirconyl ammonium carbonate aqueous solution by heating or addition of an acidic substance has a function as a zirconia sol to some extent, and thus is used as an inorganic binder or the like. Has been done.
However, this sol, which should also be referred to as zirconyl ammonium carbonate sol, contains a large amount of ammonium ions and carbonate ions, or a sol produced by heating and hydrolyzing an aqueous zirconyl ammonium carbonate solution causes gelation of the sol during heating. Since only a low concentration sol can be obtained, it has weaknesses as an inorganic binder and a coating agent, and has a large shrinkage rate after heat treatment.

(Problems to be Solved by the Invention) The object of the present invention is to overcome the drawbacks of the above-mentioned aqueous zirconyl ammonium carbonate solution or this sol, and to prevent the use of a conventional zirconia sol which is stable only in an acidic range, in a pH range, particularly in a neutral range. Or to provide a zirconia sol which is stable even in an alkaline region.

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

(Means for Solving the Problems) In the present invention, an aqueous zirconyl ammonium carbonate solution and a chelating agent are mixed, zirconyl ammonium carbonate is once made into a zirconium chelate compound, and then the chelate compound is heated and hydrolyzed, and then if necessary. The present invention was completed based on the finding that the desired zirconia sol can be obtained by using an ultrafiltration membrane and washing.

That is, the present invention relates to zirconyl ammonium carbonate and oxyphenols in an aqueous medium; amino alcohols; oxy acids, polycarboxylic acids and their esters;
Oxyaldehydes; amino acids; β-diketones; and a reaction product obtained by reacting with at least one chelating agent selected from α-, β-, γ-ketone acids and their esters. Provided is a method for producing a zirconia sol, which comprises heating and hydrolyzing at a temperature in the range of 60 to 300 ° C in the presence of an amount of an aqueous medium required for formation.

Furthermore, the present invention provides a method for producing a zirconia sol, which comprises heating and hydrolyzing a reaction product of zirconyl ammonium carbonate and a chelating agent.

Hereinafter, the present invention will be described in detail.

Zirconyl ammonium carbonate is usually obtained by reacting zirconyl carbonate with an alkali carbonate such as ammonium carbonate or ammonium hydrogen carbonate.

2ZrOCO ₃・ 8H ₂ O + 4NH ₄ HCO ₃ + (NH ₄ ) ₂ CO ₃ → 2 (NH ₄ ) ₃ ZrOH (CO ₃ ) ₃・ 2H ₂ O + 5H ₂ O Dissolve this zirconyl ammonium carbonate in pure water. An aqueous solution of zirconyl ammonium carbonate is used.However, an excessive amount of alkali carbonate is used in the above reaction, the structure of zirconyl ammonium carbonate is complicated, and there are many unclear points about the behavior of zirconyl ammonium carbonate in an aqueous solution. Although it is difficult to uniquely define the zirconyl ammonium aqueous solution, in the present invention, it is a commonly called zirconyl ammonium carbonate aqueous solution, and a commercially available zirconium ammonium carbonate aqueous solution is preferably used.

As a general method for hydrolyzing zirconyl ammonium carbonate, there is a method of heating the above aqueous solution at 60 ° C. or higher, a method of adding an acid to the above aqueous solution, and the like. In the above-mentioned thermal hydrolysis method, zirconyl ammonium carbonate is hydrolyzed to form hydrous zirconia while generating gases such as ammonia and carbon dioxide, and this reaction solution has an alkaline pH and exhibits a sol property. However, if the reaction is continued, the viscosity of the reaction solution increases and gelation occurs in a relatively short time, and only a small amount of zirconyl ammonium carbonate can be hydrolyzed. Further, the sol obtained by the hydrolysis method with acids needs to remove the ions in the sol, and therefore, an ultrafiltration membrane is used, but the sol becomes unstable as the cleaning of the sol progresses, and the sol becomes It causes thickening and gelation, making it difficult to wash the sol. Therefore, there is also a method of washing the sol by using a chelating agent as a stabilizer of the sol, but this method has a drawback that it takes a long time for washing because the sol contains a large amount of ions. is there.

In the above-mentioned heating hydrolysis method, the present inventors have paid attention to the fact that unnecessary ions can be gasified by the reaction and removed to the outside of the system, and as a result of diligent studies on a method for stably continuing the hydrolysis reaction of zirconyl ammonium carbonate. Came to That is, in the present invention, an aqueous zirconyl ammonium carbonate solution and a chelating agent are mixed to form a reaction product of the zirconyl ammonium carbonate and the chelating agent in advance, and then the aqueous solution containing the product is heated to 60 ° C. or higher. This is a method of obtaining a zirconia sol by performing a hydrolysis reaction. Specifically, when an aqueous zirconyl ammonium carbonate solution is placed in a stirred tank reactor and the chelating agent is added with stirring, the zirconyl ammonium carbonate and the chelating agent react rapidly at room temperature.

After the reaction, when the reaction solution is heated to 60 ° C. or higher, the hydrolysis reaction of the reaction product of the zirconyl ammonium carbonate and the chelating agent proceeds while generating a gas mainly containing carbon dioxide and ammonia. The reaction liquid does not thicken during the reaction, and the reaction can be completed while maintaining the transparency of the reaction liquid. The pH of the reaction solution after the reaction is weakly alkaline to neutral, and even if an alkaline substance is added to the reaction solution, thickening and gelation of the reaction solution does not occur, and the reaction solution is in a neutral region or an alkaline region. Also used as a stable zirconia sol.

It should be noted that minute amounts of unreacted substances, carbonate ions, ammonium ions, etc. remaining in the reaction solution can be efficiently passed and washed in a short time by using an ultrafiltration membrane, and further heating and ultrafiltration membrane can be performed. A high-purity and high-concentration zirconia sol can be obtained by concentrating with.

In the present invention, the concentration of zirconyl ammonium carbonate is not particularly limited and a higher concentration can be produced more economically, but in consideration of the stability of the aqueous zirconyl ammonium carbonate solution over time, 10 to 25% by weight as ZrO ₂ is used. desirable.

Examples of the chelating agent used in the present invention include oxyphenols such as catechol and pyrogallol; amino alcohols such as diethanolamine and triethanolamine; glycolic acid, citric acid, tartaric acid, lactic acid, mandelic acid, malic acid, and hydroxyacryl. Oxyacids such as acids and their esters such as methyl, ethyl and hydroxyethyl, oxyaldehydes such as glycolaldehyde; polycarboxylic acids such as oxalic acid and malonic acid; amino acids such as glycine and alanine; acetylacetone, benzoylacetone , Stearoyl acetone,
Β-diketones such as stearoylbenzoylmethane and dibenzoylmethane, and β-ketone acids such as acetoacetic acid, propionylacetic acid and benzoylacetic acid, and their methyl, ethyl, n-propyl, isopropyl, n
One or two of esters such as -butyl and t-butyl
Combinations of more than one species can be used. Of these, oxy acids such as glycolic acid, citric acid, tartaric acid, lactic acid, mandelic acid, malic acid and hydroxyacrylic acid, and β-diketones such as acetylacetone are preferably used. More preferably, α, β, and γ-
The oxyacids are α-, β-, γ-ketone acids or their esters each having a functional group having an oxygen atom on the α, β, γ carbon atoms.

The amount of chelating agent used depends on the type of chelating agent used, but chelating agent (mol number) / zirconia (mol number) is 0.02 / 1 to 4/1, preferably 0.1 / 1.
˜3 / 1, more preferably 0.5 / 1 to 2/1.

When the amount of the chelating agent used is too small, certain organic zirconium salts produced by the reaction of the chelating agent and zirconyl ammonium carbonate are hydrolyzed by the method of the present invention, and the zirconyl ammonium carbonate alone is used. The same behavior is exhibited, the hydrolysis reaction cannot be continued, and the effect of using a chelating agent is ineffective. On the other hand, even if it is used in a ratio exceeding 4/1, no special effect is obtained and it is not economical. .

The hydrolysis reaction in the present invention is carried out at a temperature in the range of 60 to 300 ° C., but a reaction in a pressurized atmosphere is also desirable in order to accelerate the reaction.

After the hydrolysis reaction, the reaction solution has a transparent appearance and its pH
Is about 7 and is used as the zirconia sol of the present invention. To obtain a high-purity zirconia sol by removing a trace amount of unreacted substances and impurities such as ammonium ion and carbonate ion remaining in the sol. This is achieved by further filtering and washing the sol after the reaction with an ultrafiltration membrane.
The above impurities in the sol are discharged out of the system together with water, and continuous washing is performed while adding pure water to the sol, but since the sol is stabilized, it is possible to wash at a high concentration and efficiently. The sol can be washed, and the sol can be washed substantially without loss of the sol particles by appropriately selecting the ultrafiltration membrane. Although the concentration of the sol by ultrafiltration filtration membrane can as ZrO ₂ up to 35 wt%, to the even higher concentrations, ZrO ₂ can be easily performed by heating concentrated
Can produce up to 45% by weight of sol.

(Effect of the invention) The zirconia sol thus obtained has a long-term stability and pH
It does not cause gelation even when used in the range of 6 to 14, and is suitable for use as a neutral or basic type inorganic binder and coating agent, and also for basic agents such as calcium oxide, calcium carbonate and magnesium oxide. A stable slurry can be obtained by mixing with a powder or a powder containing these, and it is also used as a binder for a mold, an inorganic paint, and the like.

Example 1 A flask of 10 was charged with 13000 g of a commercially available aqueous zirconyl ammonium carbonate solution containing 13% by weight of ZrO ₂ . To this, 1040 g of glycolic acid was gradually added with stirring. At this time, odorless gas was generated. Then, the flask was heated by a mantle heater to carry out a hydrolysis reaction. Ammonia odorous gas begins to be generated from the reaction solution temperature of 50 to 60 ° C., and foams violently as the temperature rises, while discharging gases generated from unnecessary ions in the sol such as ammonia and carbon dioxide gas to the outside of the system. The reaction proceeded. Foaming subsides by reacting for about 3 hours at a reaction liquid temperature of about 100 ° C., heating is continued for another 12 hours while appropriately adding pure water to the flask, and the concentration as ZrO ₂ is 35% by weight.
A zirconia sol having a pH of 7 was obtained. The sol was stable for a long period of time.

Example 2 A ZrO ₂ concentration of 3 was obtained by the same method as in Example 1 except that 840 g of tartaric acid was added instead of glycolic acid.
0% by weight of zirconia sol was obtained. Then, the sol was introduced into an ultrafiltration device with an ultrafiltration membrane having a total excess area of about 4,000 cm ² , and while adding pure water to the sol, the liquid passing through the membrane was continuously discharged while being discharged from the system. And then washed. After washing, the ZrO ₂ was adjusted to 30% by weight to obtain a high-purity sol having a stable pH of 6.9 for a long period of time.

[Example 3] To 1 part by weight of the zirconia sol prepared in Example 1, 2 parts by weight of 200-mesh calcium carbonate was added with stirring to prepare a slurry. The slurry was kept at room temperature under stirring to examine the stability of the slurry with time.
The slurry was extremely stable without thickening for more than a month.

Comparative Example

30 kg of 18 wt% zirconium nitrate aqueous solution as ZrO ₂
And 3 kg of urea were added to 200 pure water. Next, this aqueous solution was heated to obtain a transparent zirconia sol. After cooling this sol, it was introduced into an ultrafiltration device and concentrated to 10 weight as ZrO ₂ . Further, the sol was heated and concentrated under vacuum at 50 ° C. or lower to obtain a transparent zirconia sol having a concentration of 25% by weight. The pH of this zirconia sol was 1.5 and was stable for a long period of time.

1 part by weight of this sol contains 1 part of 200 mesh calcium carbonate
A slurry was prepared by adding 1 part by weight with stirring. This slurry was completely gelated after 10 minutes and could not be used as a slurry.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Teruyuki Honmoto, Inventor, Teruyuki 1 992, Nishioki, Nishihama, Aboshi-ku, Himeji-shi, Hyogo, Japan Toshiko Nakata, Examiner, Catalysis Laboratory, Nippon Catalysis Chemical Co., Ltd. (56) Reference JP-A-63-25205 (JP, A)

Claims (1)

[Claims] 1. Zirconyl ammonium carbonate and oxyphenols in an aqueous medium; amino alcohols; oxy acids, polycarboxylic acids and their esters; oxy aldehydes; amino acids; β-diketones; and α
At least one chelating agent selected from-, β-, γ-ketone acids and their esters, and the resulting reaction product is added in an amount of 60 to 60% in the presence of an aqueous medium required for sol formation. A method for producing a zirconia sol, which comprises heating and hydrolyzing at a temperature in the range of 300 ° C.