JPH1135319A - Barium sulfate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the powder of precipitated barium sulfate having a small grain diameter and a narrow grain size distribution and excellent in dispersibility by solving the problems in the conventional process comprising allowing Glauber's salt or sulfuric acid to react with barium sulfide. SOLUTION: An ammonium sulfate soln. is used as the sulfate soln. to make to react with a barium sulfide soln., the barium sulfide soln. contains >=50 g/L barium and is kept at 30-60 deg.C, and 0.8-2.5 equivalents of ammonium sulfate, based on barium sulfide, is added to obtain the precipitate of barium sulfate. Sodium hydroxide is added to a slurry contg. the precipitated barium sulfate to regulate it to pH 11-13, and the slurry is aged at 60-90 deg.C and then filtered. The precipitated barium sulfate is washed with water, dried and disintegrated to obtain a barium sulfate powder. The powder contains, by weight, <=10 ppm sodium, the powder is kept in pH of 7.0-9.0 and almost neutral to weakly alkaline, the grain size distribution curve by laser-beam diffraction is shown in the figure, and the powder has a narrow grain size distribution and is excellent in dispersibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a precipitated barium sulfate having excellent dispersibility and a method for producing the same.

[0002]

2. Description of the Related Art There are two types of barium sulfate, elutriation (water arsenic) barium sulfate and sedimentation barium sulfate. In the former, barium sulfate (BaSO ₄ ) is selected and coarsely crushed and then wet-processed. The fine powder was collected by elutriation, a small amount of sulfuric acid was added to remove iron, washed with water, dried and ground. The latter precipitated barium sulfate is reacted with a barium sulfide leaching solution produced by reduction roasting of barite with a solution of borate (sodium sulfate) purified by iron removal with potassium permanganate, and the resulting precipitate is filtered and washed with water. And dried to produce the product. Further, sulfuric acid may be added in place of the sulfate aqueous solution, and the resulting white precipitate may be filtered and washed with water.

[0003] Precipitable barium sulfate is stable to air and heat and does not discolor, so it is called permanent white and is important as a white pigment, and is used as a filler for rubber, paper and insulating tape. In addition, since it has a high X-ray absorption power and low solubility and is harmless, it is used as an X-ray contrast agent in the examination of the digestive tract, and especially in art paper and barite paper which require gloss, the highest quality sedimentable barium sulfate is used. Used.

[0004]

However, the conventional precipitated barium sulfate has a large amount of sodium remaining in the product, and the dispersibility and the transparency are not always satisfactory. In addition, the sedimentable barium sulfate according to the conventional method, which is industrially obtained from the precipitation formed by the reaction between barium sulfide and bow nitrate or sulfuric acid, has a powder pH lower than 6.5, the whiteness is reduced, and the coating resin has a low pH. The mixing properties were poor.
Furthermore, the barium sulfide concentration of the barium sulfide solution as a raw material and the liquid temperature during the reaction affect the particle size and particle size distribution of the resulting white precipitate powder, and fine sedimentable barium sulfate with these characteristics stable cannot be obtained. There was a problem that. That is, the present inventors have improved the problems in the conventional method of reacting barium sulfide or sulfuric acid with barium sulfide, have a small particle size, and have a narrow particle size distribution. It was an object of the invention to obtain.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above-mentioned object, and in the conventional method of reacting a barium sulfide produced by reduction roasting of barite with a borate glass solution, the conventional method has been used. The dispersibility is not improved because of high sodium,
In addition, in view of the fact that the powder pH becomes less than 6.5 in the sulfuric acid method in which sulfuric acid is reacted, and there remains a problem in the mixing property with the paint, efforts were made to improve these drawbacks. By using ammonium sulfate solution instead of nitric acid or sulfuric acid solution, and by controlling the reaction conditions such as the concentration of barium sulfide, the amount of ammonium sulfate added and the liquid temperature, it is possible to suppress sodium, which has a detrimental effect on dispersibility, to 10 ppm or less, The present inventors have found that sedimentable barium sulfate having excellent dispersibility can be obtained, and have reached the present invention.

That is, the present invention firstly provides that a particle size distribution obtained by measurement with a laser diffraction type particle size distribution measuring device is as follows:
The cumulative 50% diameter D50 is 1 μm or less and the cumulative 90%
Barium sulfate, characterized by having a diameter D90 of 2 μm or less;
barium sulfate according to the above-mentioned 1, characterized in that it has a cumulative 50% diameter D50 of 0.6 μm or less and a cumulative 90% diameter D90 of 1 μm or less;
Barium sulfate according to any one of the first and second aspects, wherein the sodium content is not more than 10 ppm by weight. Barium sulfate according to any one of 1 to 3;
A method of producing barium sulfate by adding ammonium sulfate to a barium sulfide solution; and sixthly, aging after producing the barium sulfate precipitate. 7. The method for producing barium sulfate according to the fifth aspect, wherein the barium concentration of the barium sulfide solution is 50 g / l or more. Eighth, a method for producing barium powder; eighth, the temperature of the barium sulfide solution at the time of adding the ammonium sulfate is 30 to 60;
C., the method for producing barium sulfate according to any one of the fifth to seventh aspects, wherein the amount of the ammonium sulfate is at least 0.8 reaction equivalent to barium sulfide. The method for producing barium sulfate according to any one of the above fifth to eighth aspects; tenthly, in the aging of the barium sulfate, after adding ammonium sulfate to the barium sulfide solution to form a precipitate of barium sulfate. 10. The method for producing barium sulfate according to any one of the above items 6 to 9, wherein an alkali is added to the obtained slurry containing barium sulfate precipitate, and the pH is adjusted to 11 to 13 for aging. Eleventh, the temperature of the slurry during the aging is set to 60 to 90 ° C.
The method for producing barium sulfate according to any one of 10;
2, wherein the alkali added for adjusting the pH during the aging is sodium hydroxide;
12. A method for producing barium sulfate according to any one of items 11 to 11.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a barium sulfide concentration of 50 g / l or more is added to an aqueous solution of barium sulfide at a liquid temperature of 30 to 60.degree.
Ammonium sulfate is added in an amount equal to or greater than the reaction equivalent. Next, the pH is adjusted to 11 to 13 by adding an alkali to the obtained slurry containing barium sulfate precipitate. 60-90
After aging while stirring at a temperature of ℃ ° C., filtration, washing with water, drying and disintegration are performed to obtain barium sulfate powder. Here, aging is a treatment for a certain period of time at a constant temperature, and in particular, a characteristic required by stirring a liquid or slurry for a long period of time. Here, S component such as S, H ₂ S, etc. is dissolved as Na ₂ S. Means to obtain barium sulfate containing a small amount of S.

If the concentration of barium sulfide in the reaction solution is less than 50 g / l as barium, the particle diameter (D50) of the produced barium sulfate becomes larger than 1 μm, which is not preferable.
Further, the width of the particle size distribution is increased to D90> 2 μm, and the dispersibility of barium sulfate is lowered, which is not preferable.

If the temperature of the aqueous solution of barium sulfide during the reaction is lower than 30 ° C., the solubility of barium sulfide decreases, which is not industrially preferable. On the other hand, when the temperature becomes higher than 60 ° C., the particle diameter (D50) of barium sulfate obtained becomes 1
However, the width of the particle size distribution is undesirably widened to D90> 2 μm, and the dispersibility of barium sulfate is lowered.

The form of ammonium sulfate to be added may be either solid or aqueous solution. If the amount of ammonium sulfate to be added is less than 0.8 equivalent as a reaction equivalent to barium sulfide, unreacted barium sulfide is present, and the particle size of barium sulfate is undesirably too large. On the other hand, it is sufficient that the amount of ammonium sulfate to be added is 0.8 equivalent or more in terms of the reaction equivalent to barium sulfide, and there is no particular upper limit. This is not desirable from the viewpoint of raw material costs. During the reaction, an aqueous solution (or solid) of barium sulfide may be added to the aqueous solution of ammonium sulfate.

As the pH adjuster at the time of aging the slurry containing the precipitation of barium sulfate, an alkali such as sodium hydroxide or sodium sulfide can be used. However, since the S content can be dissolved as Na ₂ S to remove the S content, Sodium hydroxide is preferred. The form of sodium hydroxide to be added may be either solid or aqueous solution.

If the adjusted pH of the slurry containing the barium sulfate precipitate during aging is less than 11, the S content tends to remain, which is not preferable. On the other hand, if the pH exceeds 13, the washing time for removing alkali is required to be long, which is not preferable.

If the liquid temperature during aging is lower than 60 ° C., there is no problem for the purpose of aging, but if it is lower than 60 ° C., the aging time for removing S components is undesirably extended. on the other hand,
The temperature during aging is sufficient if it is 60 ° C. or higher, and there is no particular upper limit. However, considering the heat resistance of the apparatus and the boiling point of the aqueous solution, it is appropriate to set the temperature to 90 ° C.

The method of separating the sediment from the solution after aging and washing with water are not particularly limited, and a general method can be applied, such as decantation, natural filtration or suction filtration using a Nutsche or Buchner funnel, a filter press,
Alternatively, a centrifugal separation method or the like can be applied, but other devices and methods may be applied. The washing time is based on the NaO
It is performed appropriately so that H and N ₂ S disappear and the pH becomes 9 or less.

The drying method is not particularly limited, and a general method can be applied. Atmospheric pressure drying, reduced pressure drying, vacuum drying and the like can be applied, but other devices and methods may be applied. The disintegration method is not particularly limited, and a general method can be applied.

Various measurements were performed on the obtained barium sulfate and compared with conventional barium sulfate. The sodium content was measured by the atomic absorption method. The S content was analyzed as a sulfide by a titration method. Next, the powder pH was measured according to JIS K51.
Measured according to 01B. The particle size distribution was measured with a laser diffraction type particle size distribution analyzer manufactured by Shimadzu Corporation, and the cumulative 10
% Diameter D10, cumulative 50% diameter D50, cumulative 90% diameter D90
Was measured. Bet is MONO made by Yuasa Ionics
Measured by SORB. In the grain test to check the surface condition and unevenness when applied, kneaded with oil and then simmered in JIS
It was measured by K5400 (Method A, Method B). Whiteness is
It was measured by a color difference meter manufactured by Minolta.

The precipitated barium sulphate obtained by the process according to the invention has a very low sodium content and is always 100%.
Ppm by weight or less, and can be easily reduced to 10 ppm by weight or less if necessary. And the powder pH is 7.0 to 7.0
Approximately neutral to slightly alkaline of 9.0. Further, the particle size distribution by laser diffraction method is such that the cumulative 50% diameter (D50) is 1 μm.
m and the cumulative 90% diameter (D90) is 2 μm or less. If desired, products having a cumulative 10% diameter (D10) of 0.4 μm or less, a cumulative 50% diameter (D50) of 0.6 μm or less, and a cumulative 90% diameter (D90) of 1 μm or less can be easily manufactured. it can. The working example shows an example of the production.

High sodium content, for example 100 p
If it exceeds pm, the dispersibility of barium sulfate decreases, and the width of the particle size distribution becomes unfavorable, and the transparency of barium sulfate undesirably decreases. Therefore, it is necessary to control the sodium content to be 100 ppm or less, more preferably 10 ppm or less. However, in the method of the present invention, the sodium content can be easily made 100 ppm or less, and if desired, 10 ppm or less. You can also. The S content as sulfide is preferably <0.01%.
If ≧ 0.01%, S is oxidized to SO ₄ etc.
H tends to decrease, which is not preferable.

If the pH of the powder is less than 7.0, as in the case of using sulfuric acid instead of bowing nitrate, the whiteness of barium sulfate decreases, and the miscibility with the resin coating is poor, which is not preferable.

On the other hand, although the powder pH can be used even if it is 9.0, if it exceeds 9.0, the resin paint tends to deteriorate after mixing, which is not preferable.

If the cumulative 50% diameter in the particle size distribution in the laser diffraction method exceeds 1 μm and the cumulative 90% diameter exceeds 2 μm, it takes a long time to knead with the resin or the surface after coating becomes non-uniform. Absent.

The higher the BET, the better. However, if the BET is too high, secondary agglomeration proceeds and it takes time to disperse the resin.
m ² / g is preferred.

The lower the particle size obtained in the particle test, the better.
The thickness is preferably 30 μm or less in the method B, and 20 μm or less in the method B.

As for the whiteness, it is better that W and L are higher.
Should be closer to 0.

The barium sulfate of the present invention satisfies all the above requirements and can be used for a wide range of applications as the highest quality precipitated barium sulfate.

When the barium sulfate of the present invention was used as a filler for art paper and barite paper, D50 ≦
1 μm, D90 ≦ 2 μm, good dispersibility, powder pH 7.0-9.0, high whiteness, good kneading,
Hardly deteriorated, Na ≦ 10 wt ppm, good dispersibility, high transparency, grain test A method ≦ 30 μm, B method ≦ 20
μm, good mixing properties, good conformability, little unevenness on the surface, and uniform and good art paper and barite paper were obtained. Furthermore, similar good results were obtained when used as a pigment for paints.

[0027]

EXAMPLE The concentration of barium sulfide (BaS) was 100 g /
2 (equivalent to 81 g / l of Ba) at 40 ° C. was reacted with 2 equivalents of ammonium sulfate [(NH ₄ ) ₂ SO ₄ ] aqueous solution.
H was adjusted to 12 and aged while stirring for 2 hours, then N
o. The mixture was filtered through a Nutsche lined with 5C filter paper, washed with water for about 1 hour, dried and crushed to obtain a barium sulfate powder.

With respect to the obtained barium sulfate, the sodium content and various physical properties were measured by the methods described in the embodiments.

When the sodium content in the barium sulfate was examined, it was less than 10 ppm by weight, and the S content was 0.0
At less than 1% by weight, the powder pH was 8.1. Laser diffraction particle size distribution has a cumulative 10% diameter of 0.37 μm, a cumulative 5%
The 0% diameter was 0.51 μm, and the cumulative 90% diameter was 0.70 μm. The particle size distribution curve 1 is shown in FIG.

The BET was 5.7 m ² / g, and the grain test was 25 μm for Method A and 14 μm for Method B. The whiteness was W 98.5, L 99.0, a-0.45, b
0.22.

When the barium sulfate of the present invention was used as a filler for art paper and barite paper, D50 ≦
1 μm, D90 ≦ 2 μm, good dispersibility, powder pH 7.0-9.0, high whiteness, good kneading,
Hardly deteriorated, Na ≦ 10 wt ppm, good dispersibility, high transparency, grain test A method ≦ 30 μm, B method ≦ 20
μm, good mixing properties, good conformability, little unevenness on the surface, and uniform and good art paper and barite paper were obtained. Furthermore, similar good results were obtained when used as a pigment for paints.

[0032]

Comparative Example 1 Barium sulfide having a concentration of 100 g / l was prepared in the same manner as in the example, sulfuric acid was added thereto, and the solution was adjusted to pH 3 at a liquid temperature of 4
After the temperature was adjusted to 0 ° C., aging was performed in the same manner as in the example to obtain barium sulfate. The sodium content was 10 ppm by weight, the S content was 0.01% by weight, and the powder pH was 6.5. Laser diffraction particle size distribution has a cumulative 10% diameter of 0.56.
μm, the cumulative 50% diameter was 0.80 μm, and the cumulative 90% diameter was 4.34 μm. The particle size distribution curve 2 is shown in FIG.

The BET was 6.5 m ² / g, and the grain test was 40 μm in Method A and 25 μm in Method B. The whiteness was W 97.4, L 98.0, a-0.24, b
2.11.

The above barium sulfate was used as a filler for art paper and barite paper and as a pigment for paints.
No good results were obtained.

[0035]

Comparative Example 2 A powder was obtained in the same manner as described above by reacting barium sulfide at a concentration of 100 g / l with boric acid.

When the sodium content is 100 ppm by weight,
The S content was less than 0.01% by weight, and the powder pH was 9.5. In the particle size distribution by the laser diffraction method, the cumulative 10% diameter is 0.1%.
75 μm, the cumulative 50% diameter was 2.69 μm, and the cumulative 90% diameter was 3.81 μm. The particle size distribution curve 3 is shown in FIG.

The BET was 3.5 m ² / g, and the grain test was 40 μm in Method A and 30 μm in Method B. The whiteness was W 97.4, L 97.8, a-0.51, b
0.40.

The above barium sulfate was used as a filler for art paper and barite paper and as a pigment for paints.
No good results were obtained.

[0039]

As described above, according to the method of the present invention, in contrast to the conventional method of reacting boat nitrate or sulfuric acid,
0.8 to 2.5 equivalents of ammonium sulfate are added to and reacted with barium sulfide to form a precipitate, and the concentration of barium sulfide, the liquid temperature, and the pH of the slurry after the generation of the precipitate are adjusted. 10 weight pp
m or less, and it is possible to obtain precipitated barium sulfate having an appropriate powder particle size distribution and excellent dispersibility.
The barium sulfate of the present invention has an extremely sharp particle size distribution as compared with conventional barium sulfate, and this property can be used for identifying the product of the present invention. FIG. 4 shows the particle size distribution curve 1 of the product of the present invention obtained in the example on the same coordinates as the particle size distribution curves 2 and 3 of the conventional product obtained in Comparative Examples 1 and 2. Also, the physical property values of each product are shown in comparison with Table 1.

[0040]

[Table 1]

As is clear from this table, the barium sulfate of the present invention has high whiteness and excellent dispersibility, and thus is suitably used as a filler for art paper, barite paper, and the like, or as a pigment for paints. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a particle size distribution curve 1 obtained by a laser diffraction method for barium sulfate of the present invention obtained by the method described in Example 1.

FIG. 2 is a graph showing a particle size distribution curve 2 obtained by a laser diffraction method with respect to the conventional barium sulfate obtained by the method described in Comparative Example 1.

FIG. 3 is a graph showing a particle size distribution curve 2 obtained by a laser diffraction method for a conventional barium sulfate obtained by the method described in Comparative Example 2.

FIG. 4 shows the particle size distribution curves 1, 2, and 3 on the same coordinates for comparison.

Claims (12)

[Claims] 1. The particle size distribution obtained by measuring with a laser diffraction type particle size distribution measuring device is such that the cumulative 50% diameter D50 is 1 μm.
m and a cumulative 90% diameter D90 of 2 μm or less. 2. The particle size distribution in which the cumulative 10% diameter D10 is 0.1%.
2. The barium sulfate according to claim 1, wherein the cumulative 50% diameter D50 is 4 μm or less, the cumulative 50% diameter D50 is 0.6 μm or less, and the cumulative 90% diameter D90 is 1 μm or less. 3. The barium sulfate according to claim 1, wherein the powder has a pH of 7.0 to 9.0. 4. The barium sulfate according to claim 1, wherein the sodium content is 10 ppm by weight or less. 5. A method for producing barium sulfate, comprising a step of adding ammonium sulfate to a barium sulfide solution to form a precipitate of barium sulfate. 6. The method for producing barium sulfate according to claim 5, wherein the barium sulfate is matured after the precipitation. 7. The method for producing barium sulfate according to claim 5, wherein the barium sulfide solution has a barium concentration of 50 g / l or more. 8. The method for producing barium sulfate according to claim 5, wherein the temperature of the barium sulfide solution at the time of adding the ammonium sulfate is 30 to 60 ° C. 9. The method for producing barium sulfate according to claim 5, wherein the amount of said ammonium sulfate added is 0.8 reaction equivalent or more with respect to barium sulfide. 10. The aging of the barium sulfate,
After adding ammonium sulfate to the barium sulfide solution to generate a barium sulfate precipitate, an alkali is added to the obtained slurry containing the barium sulfate precipitate to adjust the pH to 11 to 11.
13. Aged by adjusting to 13
The method for producing barium sulfate according to any one of the above. 11. The temperature of the slurry at the time of aging is 60 to
The method for producing barium sulfate according to any one of claims 6 to 10, wherein the temperature is set to 90 ° C. 12. The method for producing barium sulfate according to claim 6, wherein the alkali added for adjusting the pH during aging is sodium hydroxide.