JP2013028509A - Method for producing alkaline earth metal carbonate, barium titanate and strontium titanate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an alkaline earth metal carbonate such as barium carbonate in which grain growth caused by heat is suppressed, and to provide uniform and fine barium titanate and strontium titanate.SOLUTION: The surface of an alkaline earth metal carbonate such as barium carbonate is treated by a titanium compound such as titanium hydroxide, to thereby produce an alkaline earth metal carbonate in which grain growth caused by heat is suppressed.

Description

  The present invention relates to a method for producing alkaline earth metal carbonates such as barium carbonate and strontium carbonate, and further relates to barium carbonate obtained by the method and barium titanate and strontium titanate produced from strontium carbonate as raw materials. The present invention relates to a method for producing an alkaline earth metal carbonate in which particle growth due to heat is suppressed, and to barium titanate and strontium titanate produced using barium carbonate and strontium carbonate obtained by the method as raw materials.

Alkaline earth metal carbonates, in particular barium carbonate and strontium carbonate, are useful as raw materials for dielectrics. For example, barium carbonate is barium titanate (BaTiO ₃ ) used for dielectric layers of ceramic ceramic capacitors. It is widely used as a starting material.

Barium titanate is generally produced by a solid-phase synthesis method. In this solid-phase synthesis method, barium carbonate (BaCO ₃ ) powder and titanium oxide (TiO ₂ ) powder are mixed in a wet manner, and after drying, the mixed powder is 900 It is fired at a temperature of about ˜1200 ° C. (see, for example, Patent Document 1).

JP 2008-222522 A

  In recent years, with the miniaturization and high performance of electronic components, there has been a demand for miniaturization of capacitors, and there has been a demand for thinner dielectric layers of capacitors. In order to realize this thinning, it is important how to make fine particles of the dielectric material barium titanate and the raw materials of both titanium oxide and barium carbonate.

  It is known that in the solid phase synthesis method, the mixed powder of barium carbonate powder and titanium oxide powder is used to grow particles of barium carbonate during the temperature rising process, and the barium carbonate particles during the temperature rising process. Due to the growth, the uniformity of mixing with fine titanium oxide decreases, and the number of contact points between barium carbonate and titanium oxide decreases, resulting in variations in the particle size and other characteristics of the barium titanate powder produced. As a result, there arises a problem that the characteristics of fine raw materials cannot be fully utilized.

  Therefore, in order to obtain uniform and fine barium titanate, it is necessary to suppress particle growth due to the heat of barium carbonate.

  Such a problem is not limited to barium carbonate but also applies to strontium carbonate.

  The present invention has been made in view of the above points, and provides a method for producing an alkaline earth metal carbonate in which particle growth due to heat is suppressed, and uniform and fine barium titanate and strontium titanate. With the goal.

  In order to achieve the above object, the present inventors have conducted intensive research, and as a result, by treating the surface of alkaline earth metal carbonate such as barium carbonate with a titanium compound, the alkaline earth metal carbonate particles are treated. The present inventors have found that particle growth due to heat can be suppressed and completed the present invention.

  That is, in the method for producing an alkaline earth metal carbonate of the present invention, the surface of the alkaline earth metal carbonate is treated with a titanium compound.

  The alkaline earth metal carbonate is preferably barium carbonate or strontium carbonate, and the titanium compound is preferably titanium hydroxide, but may be hydrous titanium oxide or titanium oxide.

  The treatment with the titanium compound is preferably a treatment in which, for example, titanium hydroxide is adsorbed on the surface of the alkaline earth metal carbonate.

  The titanium hydroxide which is a titanium compound is preferably produced by neutralizing an aqueous titanium tetrachloride solution with a basic substance such as ammonia.

  In another embodiment of the present invention, a step of adding an aqueous solution of titanium tetrachloride and an alkaline solution to the slurry of the alkaline earth metal carbonate is included.

  In still another embodiment of the present invention, the method further includes the step of separating the alkaline earth metal carbonate from the alkaline earth metal carbonate slurry to which the aqueous titanium tetrachloride solution and the alkaline solution are added in the adding step. It is a waste.

  In the method for producing an alkaline earth metal carbonate of the present invention, the detailed mechanism is unknown by surface treatment with a titanium compound such as titanium hydroxide, but titanium adsorbed on the surface of the alkaline earth metal carbonate particles. By the compound, the contact between the alkaline earth metal carbonate particles is inhibited, and the particle growth of the alkaline earth metal carbonate particles due to heat can be suppressed.

  The barium titanate of the present invention is produced using an alkaline earth metal carbonate produced by the production method of the present invention as a starting material, and the starting material is barium carbonate.

  The alkaline earth metal carbonate produced by the production method of the present invention, which is the starting material, is preferably a powder, but may be in a slurry state.

  The method for producing barium titanate is not particularly limited as long as it uses barium carbonate produced by the production method of the present invention as a starting material, and a known production method can be applied.

  Moreover, the strontium titanate of the present invention is produced using an alkaline earth metal carbonate produced by the production method of the present invention as a starting material, and the starting material is strontium carbonate.

  The method for producing strontium titanate is not particularly limited as long as strontium carbonate produced by the production method of the present invention is used as a starting material, and a known production method can be applied.

  According to the method for producing an alkaline earth metal carbonate of the present invention, an alkaline earth metal carbonate such as barium carbonate or strontium carbonate in which particle growth due to heat is suppressed can be obtained.

  Therefore, the barium titanate of the present invention produced using the barium carbonate obtained by the production method of the present invention as a starting material has the result that the particle growth due to the heat of the barium carbonate particles is suppressed during the temperature rising process during the production. In addition, the barium carbonate particles can be reacted in a state where they are uniformly mixed with the fine titanium oxide and fine particles. Barium titanate can be obtained.

  In addition, the strontium titanate of the present invention produced using strontium carbonate obtained by the production method of the present invention as a starting material is a result of suppressing the particle growth due to heat of the strontium carbonate particles during the temperature rising process during the production. , Strontium carbonate particles can be reacted in a finely mixed state with fine titanium oxide, reducing the variation in properties such as the particle size of the produced strontium titanate, and uniform and fine Barium titanate and strontium titanate can be obtained.

  According to the present invention, by treating the surface of an alkaline earth metal carbonate such as barium carbonate or strontium carbonate with a titanium compound such as titanium hydroxide, an alkaline earth metal carbonate in which particle growth due to heat is suppressed is obtained. Can do.

  Moreover, since barium titanate and strontium titanate are produced using such an alkaline earth metal carbonate as a starting material, barium titanate and strontium titanate having a uniform and fine particle size can be obtained.

2 is a SEM photograph showing the size and shape of particles of Example 1. FIG. 2 is a SEM photograph showing the size and shape of particles of Example 2. 4 is a SEM photograph showing the size and shape of particles of Comparative Example 1. It is a SEM photograph corresponding to FIG.3 (c) of lower magnification than FIG. It is the schematic which shows the structure of a reaction apparatus. 4 is a SEM photograph showing the size and shape of particles of Example 3. 4 is a SEM photograph showing the size and shape of particles of Example 4. 6 is a SEM photograph showing the size and shape of particles of Comparative Example 2. 6 is a SEM photograph showing the size and shape of particles in Example 5. 6 is a SEM photograph showing the size and shape of particles of Comparative Example 3. 6 is a SEM photograph showing the size and shape of particles of Example 6. 10 is a SEM photograph showing the size and shape of particles of Example 7. 6 is a SEM photograph showing the size and shape of particles of Comparative Example 4. 10 is a SEM photograph showing the size and shape of particles in Example 8. 6 is a SEM photograph showing the size and shape of particles of Comparative Example 5. 10 is a SEM photograph showing the size and shape of the particles of Example 9. 10 is a SEM photograph showing the size and shape of particles in Example 10. 10 is a SEM photograph showing the size and shape of particles in Comparative Example 6.

  Hereafter, the manufacturing method of the alkaline earth metal carbonate of this invention is demonstrated in detail.

  In the method for producing an alkaline earth metal carbonate of the present invention, the surface of the alkaline earth metal carbonate is treated with a titanium compound.

  As the alkaline earth metal carbonate, barium carbonate or strontium carbonate is preferable.

  The particle diameter of the alkaline earth metal carbonate whose surface is treated with the titanium compound, for example, the particle diameter of barium carbonate is preferably about 10 nm to 2000 nm, and 50 nm to 1000 nm, as measured by electron micrographs. Is more preferable. The particle diameter of strontium carbonate is preferably about 10 nm to 2000 nm, and more preferably 50 nm to 1000 nm. Barium carbonate and strontium carbonate are known to have a needle shape depending on the production method, and the major diameter corresponds to the particle diameter in that case.

  The titanium compound is preferably titanium hydroxide, but may be hydrous titanium oxide or titanium oxide.

  Barium carbonate and strontium carbonate may be produced by a conventionally known method, and the production method is not particularly limited.

  The treatment of the surface of the alkaline earth metal carbonate with the titanium compound is preferably performed by adsorbing titanium hydroxide on the surface of the alkaline earth metal carbonate.

  The adsorption amount of titanium hydroxide is preferably 0.3 wt% to 20 wt%, and more preferably 0.7 wt% to 15 wt%. If the adsorption amount of titanium hydroxide is less than 0.3 wt%, the effect of suppressing particle growth due to heat cannot be obtained, and conversely if it exceeds 20 wt%, the proportion of titanium oxide contained in barium carbonate increases. The influence on the properties of the finally obtained barium titanate is increased.

  Titanium hydroxide is preferably produced by a reaction between a water-soluble titanium compound and a basic substance. For example, titanium hydroxide is preferably produced by neutralizing an aqueous titanium tetrachloride solution with ammonia water or the like.

  The method for producing an alkaline earth metal carbonate according to the present invention preferably includes a step of adding an aqueous solution of titanium tetrachloride and an alkaline solution to the slurry of the alkaline earth metal carbonate. Further, in the step of adding, It is preferable to include a step of separating the alkaline earth metal carbonate from the aqueous titanium chloride solution and the alkaline earth metal carbonate slurry to which the alkaline solution is added.

  The slurry of the alkaline earth metal carbonate to which the titanium tetrachloride aqueous solution and the alkali solution are added in the adding step can be used as it is, for example, as a barium carbonate raw material of solid phase barium titanate.

  The order in which the titanium tetrachloride solution and the alkali solution are added to the alkaline earth metal carbonate slurry is not particularly limited. Ammonia water is added to the alkaline earth metal carbonate slurry, and then added to the mixed solution. Titanium chloride solution is added so that the pH is 6-11, more preferably 8-9. Alternatively, the titanium tetrachloride aqueous solution and the alkali solution are simultaneously added to the alkaline earth metal carbonate slurry while maintaining the pH of 6 to 10, and more preferably the titanium tetrachloride aqueous solution and the alkali solution are simultaneously added while maintaining the pH of 7 to 9.

  In the present invention, alkaline earth metal carbonate can be treated regardless of the concentration of alkaline earth metal carbonate in the slurry of alkaline earth metal carbonate, but when the viscosity, productivity, and workability of the slurry are taken into consideration. The concentration of the alkaline earth metal carbonate in the slurry is preferably 10 g / L to 400 g / L, more preferably 50 g / L to 200 g / L.

  The titanium tetrachloride aqueous solution added to the slurry preferably has a titanium concentration of 5 g / L to 200 g / L, and more preferably 15 g / L to 30 g / L. As the alkaline solution added to the slurry, for example, the concentration in the case of using an aqueous ammonia solution is preferably 1 wt% to 30 wt%, more preferably 5 wt% to 25 wt%.

  The treatment temperature when treating the surface of the alkaline earth metal carbonate by adding a titanium tetrachloride aqueous solution and an alkali solution to the slurry is preferably 5 ° C to 100 ° C, and preferably 10 ° C to 40 ° C. More preferably.

  Preferably, after the step of adding the titanium tetrachloride aqueous solution and the alkali solution to the slurry, a step of aging the slurry to which the both solutions are added is provided. In this step of aging, the slurry to which the both solutions are added is provided. Is preferably stirred.

  The aging is preferably performed at a temperature of about 5 ° C to 100 ° C for about 5 minutes to 1 hour, more preferably at a temperature of 10 ° C to 40 ° C for about 10 minutes to 30 minutes.

  In the step of separating the alkaline earth metal carbonate from the slurry of the alkaline earth metal carbonate to which the titanium tetrachloride aqueous solution and the alkaline solution are added, the separation is performed using a suction filter, a pressure filter, a centrifuge, or the like. Is preferred.

  The barium titanate of the present invention is produced using barium carbonate produced by the production method of the present invention as a starting material, and the production method is not particularly limited, and a conventionally known method can be used.

  The strontium titanate of the present invention is produced using strontium carbonate produced by the production method of the present invention as a starting material, and is not particularly limited, and a conventionally known method can be used.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to these examples.

  Moreover, in the following description, about the barium carbonate, an Example and a comparative example are made to respond | correspond for every manufacturing method and product of barium carbonate before processing with the titanium hydroxide which is a titanium compound.

[Barium carbonate by the first production method]
Example 1
In Example 1, barium carbonate before the surface was treated with titanium hydroxide was produced as follows.

That is, barium chloride dihydrate was dissolved in pure water and adjusted to a concentration of 400 g / L. The liquid temperature at this time is adjusted to 60 ° C., and this barium chloride aqueous solution is used as the raw material A. Next, carbon dioxide gas was absorbed into the ammonia water to prepare a 44 g / L ammonium carbonate solution with a CO ₂ concentration. The liquid temperature at this time is adjusted to 30 ° C., and this ammonium carbonate solution is used as a raw material B.

  2 L of the raw material B was put in a 5 L glass beaker, and the mixture was stirred at a rotation speed of 300 rpm with a stirrer equipped with a Teflon (registered trademark) 2-mm blade stirring rod. Thereto, 850 ml of raw material A was dropped at a flow rate of 53 ml / min to obtain a barium carbonate slurry.

  The surface of barium carbonate dispersed in this slurry was treated with titanium hydroxide as follows.

That is, after adding 2 ml of 25 wt% ammonia water to the obtained barium carbonate slurry, a TiCl ₄ (titanium tetrachloride) aqueous solution adjusted to a Ti concentration of 18.8 g / L was added at a rate of 3 ml / min. 88 ml was added. The pH of the slurry after the addition was 8.6. After completion of the addition, the mixture was aged with stirring for 1 hour. The slurry after aging was separated by filtration using a 5C filter paper with Nutsche, and then washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake after washing with water was dried for 12 hours with a box dryer heated to 110 ° C. to obtain barium carbonate whose surface was treated with titanium hydroxide. The dried barium carbonate was crushed with a small pulverizer to prepare a sample.

(Example 2)
In Example 1, barium carbonate whose surface was treated with titanium hydroxide was produced in the same manner except that the amount of ammonia water added was 1 ml and the amount of TiCl ₄ added was 44 ml. Obtained.

(Comparative Example 1)
In Example 1, barium carbonate was produced by adding the aqueous ammonia and TiCl ₄ , but otherwise performing the same operation, that is, without treating the surface with titanium hydroxide. Obtained.

The thermal stability confirmation tests of Examples 1 and 2 and Comparative Example 1 were performed as follows.
That is, about 5 g of each sample is put in an alumina crucible, put in an electric furnace preheated to each set temperature, and ignited as it is for 30 minutes. After 30 minutes, the sample was taken out and allowed to cool, and the size and shape of the particles were confirmed with a scanning electron microscope (SEM). The ignition temperature was 500 ° C and 800 ° C.

  Further, the amount of titanium hydroxide adsorbed on the surface of barium carbonate in Examples 1 and 2 was calculated from the amount of titanium tetrachloride added.

  The adsorption amounts of titanium hydroxide in Examples 1 and 2 were 1.5 wt% and 0.7 wt%, respectively, with respect to Comparative Example 1 in which titanium hydroxide was not adsorbed.

  1 to 3 show SEM photographs of Examples 1 and 2 and Comparative Example 1 at a magnification of 10,000 times according to a thermal stability confirmation test, respectively. Further, in the SEM photograph of Comparative Example 1 ignited at 800 ° C. for 30 minutes, since the grown particles are large, a SEM photograph at a low magnification of 1,000 times is shown in FIG. 4 in addition to the magnification of 10,000. .

  In FIG. 3 (c) showing the particles of Comparative Example 1 having the same magnification as compared to FIGS. 1 (c) and 2 (c) showing the particles of Examples 1 and 2 ignited at 800 ° C. for 30 minutes, It shows a state in which small particles are attached to the surface of large particles that are too large to fit on the screen because the particle diameter is too large. As shown in FIG. 4 in which the magnification in FIG. 3C is 1/10, in Comparative Example 1, even if the magnification is 1/10, the particles are larger than those in Examples 1 and 2. I understand that.

  That is, in Examples 1 and 2, it can be seen that the particle growth due to heat is suppressed as compared with Comparative Example 1.

[About barium carbonate by the second manufacturing method]
(Example 3)
In Example 3, barium carbonate before the surface was treated with titanium hydroxide was produced as follows.

  That is, barium hydroxide octahydrate was dissolved in pure water, and 50 L of a barium hydroxide aqueous solution having a concentration of 75 g / L was prepared. The liquid temperature at this time is adjusted to 40 ° C., and this barium hydroxide aqueous solution is used as the raw material C.

  This raw material C was mixed with carbon dioxide using the reactor 1 shown in FIG. 5 to synthesize barium carbonate. In FIG. 5, P1, P2, and P3 are pumps of the first stage, the second stage, and the third stage, and the configurations of the pumps P1 and P2 of each stage are as follows.

(A) First stage pump P1: centrifugal pump (manufactured by Lhasa Corporation), suction port diameter 1.5 inches, discharge port diameter 1 inch, discharge amount 170 L / min, impeller rotation speed 2080 rpm
(B) Second stage pump P2: Centrifugal pump (manufactured by Rasa Shoji Co., Ltd.), suction port diameter 1 inch, discharge port diameter 3/4 inch, discharge rate 30 L / min, impeller rotation speed 1420 rpm
(C) Third stage pump P3: centrifugal pump (manufactured by Taiheiyo Metal Co., Ltd.), suction port diameter 1 inch, discharge port diameter 3/4 inch, discharge rate 30 L / min, impeller rotation speed 1420 rpm
A specific method for synthesizing barium carbonate is to feed the raw material C and carbon dioxide into the first-stage pump P1 using a double pipe. At this time, the flow rate of the raw material C is 12 L / min, and the flow rate of carbon dioxide gas is 300 L / min. Simultaneously with the reaction, the citric acid solution adjusted to a concentration of 25 g / L is continuously added to the third stage pump P3 from the citric acid charging point in FIG. 5 using a double pipe at a flow rate of 1.2 L / min. Thus, a barium carbonate slurry was obtained.

  Next, the surface of barium carbonate dispersed in the slurry was treated with titanium hydroxide as follows.

That is, 324 ml of TiCl ₄ aqueous solution adjusted to a Ti concentration of 18.8 g / L was added to 22 L of barium carbonate slurry in the slurry receiver 2 of FIG. 5 over 30 minutes. Simultaneously with the addition of TiCl ₄ , ammonia water having a concentration of 25 wt% was added to the slurry, and the pH of the slurry was adjusted to 8.5 ± 0.2. During the addition, stirring was continued at a stirring speed of 300 rpm using a stirrer equipped with stainless steel 10 mmφ six stirring blades. After completion of the addition, stirring was continued for 30 minutes, and aging was performed. After aging, the slurry was separated by filtration using 5C filter paper with Nutsche, and subsequently washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake after washing with water was dried for 12 hours with a box dryer heated to 110 ° C. to obtain barium carbonate whose surface was treated with titanium hydroxide. The dried barium carbonate was crushed with a small pulverizer to prepare a sample.

Example 4
In Example 3, barium carbonate whose surface was treated with titanium hydroxide was manufactured in the same manner except that the amount of TiCl ₄ added was changed to 810 ml, and a sample was obtained.

(Comparative Example 2)
In Example 3, barium carbonate was produced by adding the aqueous ammonia and TiCl ₄ , but otherwise performing the same operation, that is, without treating the surface with titanium hydroxide. Obtained.

  These Examples 3 and 4 and Comparative Example 2 were subjected to the same thermal stability confirmation test as described above. The ignition temperature was 800 ° C.

  Moreover, the adsorption amount of titanium hydroxide of Examples 3 and 4 calculated in the same manner as in Examples 1 and 2 was 1.4 wt% and 3.6 wt%, respectively.

  6 to 8 show SEM photographs of Examples 3 and 4 and Comparative Example 2 at a magnification of 10,000 times according to the thermal stability test.

  6 (b) and FIG. 7 (b) showing the particles of Examples 3 and 4 heated at 800 ° C. for 30 minutes, respectively, FIG. 8 (B) showing the particles of Comparative Example 2 similarly heated at 800 ° C. for 30 minutes. It can be seen that, compared with b), the particle size is clearly small and particle growth due to heat is suppressed.

[Barium carbonate by the third manufacturing method]
(Example 5)
In Example 5, barium carbonate before the surface was treated with titanium hydroxide was produced as follows.

  That is, 3.7 kg of a 50 wt% gluconic acid solution, 6 kg of barium hydroxide octahydrate and pure water are mixed to prepare a 50 L barium hydroxide aqueous solution. The temperature of the aqueous solution at this time is adjusted to 40 ° C., and this barium hydroxide aqueous solution is used as the raw material D. This raw material D and carbon dioxide gas are fed into the first stage pump P1 of the reactor 1 of FIG. 5 using a double pipe. At this time, the flow rate of the raw material D is 12 L / min, and the flow rate of the carbon dioxide gas is 300 L / min. Simultaneously with the reaction, the citric acid solution whose concentration was adjusted to 12.5 g / L was continuously added to the third stage pump P3 using a double pipe from the citric acid charging point in the figure at a rate of 1.2 L / min. A slurry of barium carbonate was obtained.

  The barium carbonate slurry was filtered and separated with a Nutsche using 5C filter paper, and then washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake washed with water was repulped into pure water to prepare 22 L of a 67.5 g / L slurry as a solid content of barium carbonate.

  Next, the surface of the barium carbonate of this slurry was treated with titanium hydroxide as follows.

That is, 324 ml of a TiCl ₄ aqueous solution adjusted to a Ti concentration of 18.8 g / L was added to this slurry over 30 minutes. Simultaneously with the addition of TiCl ₄ , ammonia water having a concentration of 25 wt% was added to the slurry, and the pH of the slurry was adjusted to 8.5 ± 0.2. During the addition, stirring was continued at a stirring speed of 300 rpm using a stirrer equipped with a stainless steel 10 mmφ 6-blade stirring blade. After completion of the addition, stirring was continued for 30 minutes, and aging was performed.

  After aging, the slurry was separated by filtration using 5C filter paper with Nutsche, and subsequently washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake after washing with water was dried for 12 hours with a box dryer heated to 110 ° C. to obtain barium carbonate whose surface was treated with titanium hydroxide. The dried barium carbonate was crushed with a small pulverizer to prepare a sample.

(Comparative Example 3)
In Example 5, barium carbonate was produced by performing the same operation without adding ammonia water and TiCl ₄ , that is, without treating the surface with titanium hydroxide, and obtaining a sample thereof. It was.

  These Example 5 and Comparative Example 3 were subjected to the same thermal stability confirmation test as described above. The ignition temperature was 550 ° C and 800 ° C.

  Moreover, the adsorption amount of the titanium hydroxide of Example 5 was 1.0 wt%.

  FIG. 9 and FIG. 10 show SEM photographs of Example 5 and Comparative Example 3, respectively, at a magnification of 10,000 times in the thermal stability confirmation test.

  9 (c) showing the particles of Example 5 ignited at 800 ° C. for 30 minutes, clearly compared to FIG. 10 (c) showing the particles of Comparative Example 3 similarly ignited at 800 ° C. for 30 minutes. It can be seen that the size is small and particle growth due to heat is suppressed.

[About Barium Carbonate BW-KHR (trade name)]
(Example 6)
In Example 6, high purity barium carbonate BW-KHR manufactured by Sakai Chemical Industry Co., Ltd. was used as the barium carbonate before the surface was treated with titanium hydroxide.

  The surface of this barium carbonate BW-KHR was treated with titanium hydroxide as follows.

That is, barium carbonate BW-KHR was mixed with pure water and stirred at a rotation speed of 300 rpm using a stirrer equipped with a 75 mm Teflon (registered trademark) stirring blade to prepare 5 L of a slurry having a concentration of 10 g / liter. To the slurry, 12.8 ml of an aqueous TiCl ₄ solution adjusted to a Ti concentration of 18.8 g / L was added over 30 minutes. Ammonia water having a concentration of 25 wt% was continuously added so that the slurry pH during the addition of the aqueous TiCl ₄ solution was 8.5 ± 0.2.

TiCl ₄ and the mixture was stirred at the end of the addition after 30 minutes of intact state. All reactions were performed at room temperature. After 5 minutes, the slurry was filtered and separated with Nutsche using 5C filter paper, and then washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake after washing with water was dried for 12 hours with a box dryer heated to 110 ° C. to obtain barium carbonate whose surface was treated with titanium hydroxide. The dried barium carbonate was crushed with a small pulverizer to prepare a sample.

(Example 7)
In Example 6, the same operation was performed except that the addition amount of the TiCl ₄ aqueous solution having a concentration of 18.8 g / L added to the barium carbonate slurry was increased to 25.6 ml. Barium was produced and a sample was obtained.

(Comparative Example 4)
As a comparative sample in which the surface treatment with titanium hydroxide was not performed, high purity barium carbonate BW-KHR manufactured by Sakai Chemical Industry Co., Ltd. was used as Comparative Example 4.

  About these Example 6, Example 7, and Comparative Example 4, the same thermal stability confirmation test as the above-mentioned was done. The ignition temperature was 800 ° C.

  Moreover, the adsorption amount of the titanium hydroxide of Example 6 and Example 7 was 1.2 wt% and 2.3 wt%, respectively.

  11, 12, and 13 show SEM photographs of Example 6, Example 7, and Comparative Example 4 at a magnification of 10,000 times in the thermal stability confirmation test, respectively.

  FIGS. 11 (b) and 12 (b) show the particles of Examples 6 and 7 ignited at 800 ° C. for 30 minutes, respectively. FIG. 13 (13) shows the particles of Comparative Example 4 similarly ignited at 800 ° C. for 30 minutes. It can be seen that the particle size is small compared to b), and particle growth due to heat is suppressed.

[About barium carbonate BW-KH30 (trade name)]
(Example 8)
In Example 6, except that the barium carbonate used was changed to Sakai Chemical Industry Co., Ltd. high purity barium carbonate BW-KH30, all the same operations were performed to produce barium carbonate whose surface was treated with titanium hydroxide. And got that sample.

(Comparative Example 5)
As a comparative sample in which the surface treatment with titanium hydroxide was not performed, high purity barium carbonate BW-KH30 manufactured by Sakai Chemical Industry Co., Ltd. was used as Comparative Example 5.

  These Example 8 and Comparative Example 5 were subjected to the same thermal stability confirmation test as described above. The ignition temperature was 800 ° C.

  The adsorption amount of titanium hydroxide of Example 8 was 1.2 wt%.

  14 and 15 show SEM photographs of Example 8 and Comparative Example 5, respectively, at a magnification of 10,000 times in the thermal stability confirmation test.

  In FIG. 14 (b) showing the particles of Example 8 ignited at 800 ° C. for 30 minutes, the particle size is similar to FIG. 15 (b) showing the particles of Comparative Example 5 similarly ignited at 800 ° C. for 30 minutes. It can be seen that the particle growth due to heat is obviously suppressed.

[About strontium carbonate]
Example 9
In Example 9, strontium carbonate before the surface was treated with titanium hydroxide was produced as follows.

That is, dissolved strontium chloride (SrCl ₂ · 1H ₂ O) of pure water and adjusted to a concentration of 200 g / L. The liquid temperature at this time is adjusted to 60 ° C., and this strontium chloride aqueous solution is used as the raw material E. Next, carbon dioxide gas was absorbed into the ammonia water to prepare a 44 g / L ammonium carbonate solution as the CO ₂ concentration. The liquid temperature at this time is adjusted to 30 ° C., and this ammonium carbonate solution is used as the raw material F.

  2 L of the raw material F was placed in a 5 L stainless steel tank, and the mixture was stirred at a rotational speed of 300 rpm with a stirrer equipped with a 75 mm Teflon (registered trademark) two-blade stirring blade. Thereto, 1 L of raw material E was dropped at a flow rate of 188 ml / min to obtain a slurry of strontium carbonate.

  The surface of strontium carbonate dispersed in this slurry was treated with titanium hydroxide as follows.

That is, 72 ml of a TiCl ₄ aqueous solution adjusted to a Ti concentration of 18.8 g / L was added to the obtained strontium carbonate slurry at a constant flow rate over 30 minutes. Simultaneously with the addition of TiCl ₄ , ammonia water having a concentration of 25 wt% was added to the slurry, and the pH of the slurry was adjusted to 8.5 ± 0.2. After completion of the addition of TiCl _{4, the} mixture was stirred and aged for 30 minutes.

  After aging, the slurry was separated by filtration using 5C filter paper with Nutsche, and subsequently washed with pure water. The washing was performed until the conductivity of the washing water became 100 μs or less. The cake after washing with water was dried for 12 hours in a box-type dryer heated to 110 ° C. to obtain strontium carbonate whose surface was treated with titanium hydroxide. The dried strontium carbonate was pulverized with a small pulverizer to prepare a sample.

(Example 10)
In Example 9, except that the addition amount of TiCl ₄ was changed to 180 ml, the same operation was carried out to produce strontium carbonate whose surface was treated with titanium oxide, and a sample was obtained.

(Comparative Example 6)
In Example 9, strontium carbonate was produced by performing the same operation except that TiCl ₄ and aqueous ammonia were not added, that is, without treating the surface with titanium hydroxide, and a sample thereof was obtained. It was.

  These Examples 9 and 10 and Comparative Example 6 were subjected to the same thermal stability confirmation test as described above. The ignition temperature was 800 ° C.

  Moreover, the adsorption amounts of titanium hydroxide in Examples 9 and 10 were 2.0 wt% and 4.9 wt%, respectively.

  FIGS. 16 to 18 show SEM photographs of Examples 9 and 10 and Comparative Example 6 at a magnification of 10,000 times in the thermal stability confirmation test, respectively.

  In each of the above-described embodiments, the surface of an alkaline earth metal carbonate such as barium carbonate is treated with titanium hydroxide, but the surface may be treated with zirconium hydroxide.

1 reactor 2 slurry receiver

Claims (7)

Treating the surface of the alkaline earth metal carbonate with a titanium compound;
A method for producing an alkaline earth metal carbonate. The alkaline earth metal carbonate is barium carbonate or strontium carbonate;
The titanium compound is titanium hydroxide;
The method for producing an alkaline earth metal carbonate according to claim 1. The treatment is a treatment of adsorbing the titanium hydroxide on the surface of the alkaline earth metal carbonate.
The manufacturing method of the alkaline-earth metal carbonate of Claim 2. Adding a titanium tetrachloride aqueous solution and an alkali solution to the slurry of the alkaline earth metal carbonate,
The method for producing an alkaline earth metal carbonate according to claim 2 or 3. Further comprising the step of separating the alkaline earth metal carbonate from the slurry of the alkaline earth metal carbonate to which the titanium tetrachloride aqueous solution and the alkaline solution have been added in the adding step.
The manufacturing method of the alkaline-earth metal carbonate of Claim 4. The alkaline earth metal carbonate produced by the method for producing an alkaline earth metal carbonate according to any one of claims 1 to 5 is used as a starting material, and the starting material is barium carbonate.
Barium titanate characterized in that. The alkaline earth metal carbonate produced by the method for producing an alkaline earth metal carbonate according to any one of claims 1 to 5 is used as a starting material, and the starting material is strontium carbonate.
Strontium titanate characterized by that.