JPS5825080B2 - Manufacturing method of fibrous calcium sulfate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing very elongated crystalline, so-called fibrous, stable calcium sulfate dihydrate (CaSO4.2H20) or insoluble anhydrous salt (■.Ca5O4).

The long and thin needle-shaped crystals of calcium sulfate that have been known include the fiber Ceracola (Satain Spar) (CaS04.2H20), which is produced as a natural mineral, and the reaction rate during neutralization or metathesis reaction is reduced by dogs. Acicular chemical Ceracola ('Ca S 04・2H20),
and acicular α produced by suspending Sansui Ceracola powder in water and heating it to about 110 to 140°C under the saturated water vapor pressure.
There are types such as Hanmizu Setsukou (α・Ca S 04・〆H20).

However, these known needle-like crystals of calcium sulfate are
Length L in the longitudinal direction (length in the C-axis direction in the crystal axis) with respect to width D of the single crystal (length in the a-axis or b-axis direction in the crystal axis)
In most cases, the ratio of L/D is about 10 to 15 (L/D) (e.g., acicular chemical ceracola), but in some cases where /D reaches 20 to 50, D is at least 50μ (e.g., fibers). ceracola), or unstable crystals of the type calcium sulfate hemihydrate, which can exist only as a metastable phase under all conditions (e.g., acicular alpha hemihydrate).

The present invention deals with Ca504-H2 in high concentration sulfuric acid solution.
When examining the equilibrium of the SO4-H2O system, CaSO4
・When precipitating calcium sulfate trihydrate (ceracola trihydrate) or anhydrous salt (insoluble anhydrous ceracola) from a sulfuric acid medium solution in which calcium sulfate is dissolved in a region where H2SO4 or CaSO4.3H2SOψS can generally stably exist, the width of the crystal This is based on the discovery that extremely elongated crystals with a diameter of 20μ or less and an L/D of 20 or more can be formed at a fast rate close to instantaneous.

In preparing the sulfuric acid medium containing calcium obligate sulfate used in the present invention, the sulfuric acid solution has a sulfuric acid content (H2SO4) of at least 60%.
It may be of a concentration containing % by weight, preferably a higher concentration.

Calcium sulfate, which serves as a solute, can be used in the form of its dihydrate (ceracola trihydrate), hemihydrate salt (ceracola hemihydrate), or anhydrous salt (ceracola anhydride), and can be produced naturally or as a byproduct through various chemical reactions. Calcium sulfate with any production history, such as raw, by-product, or anti-form, can be used.

Calcium compounds such as calcium carbonate, calcium hydroxide, and calcium chloride may also react with some sulfuric acid in the sulfuric acid solution used as a solvent to form calcium sulfate, thereby forming a calcium sulfate-dissolved sulfuric acid medium.

These are calcium sulfate hydrates or calcium compounds that are bound to components that do not react with a part of the sulfuric acid solution and cause vapors.

When using calcium sulfate, the sulfuric acid solution used as a solvent must be made to a higher concentration in advance so that the concentration of the sulfuric acid medium after dissolving as calcium sulfate is 60% by weight or more in terms of sulfuric acid content (H2S04), or the sulfuric acid medium must be It is necessary to concentrate until the concentration becomes 60% by weight or more.

The amount of calcium sulfate dissolved in a sulfuric acid medium containing calcium sulfate can take any value within the range of the saturated amount, since the saturated amount of calcium sulfate dissolved varies depending on the sulfuric acid concentration and temperature of the medium. Calcium (Ca S 0
4) at least 0.1% by weight based on the solvent sulfuric acid solution as min.
, preferably saturated.

In preparing the sulfuric acid medium solution containing calcium sulfate, it is desirable to stir and heat the solution in order to make the calcium sulfate a saturated or nearly saturated solution.

When crystallizing fibrous calcium sulfate, the conditions differ depending on whether the crystallized calcium sulfate is in the form of trihydrate or insoluble anhydrous salt.

Fibrous calcium sulfate dihydrate (Ca SO4・2H20
), the crystallization mother liquor should be a sulfuric acid solution or water with a concentration of about 40% by weight or less, while maintaining the concentration and temperature conditions in the region A in Figure 1. It is recommended to drop, inject, or inject calcium-dissolved sulfuric acid medium.

When crystallizing fibrous calcium sulfate anhydrous salt (■・Ca5O4), use a sulfuric acid solution having a concentration of about 40% by weight or more as the crystallization mother liquor and less than the sulfuric acid concentration of the calcium sulfate-dissolved sulfuric acid medium. It is preferable to drop, inject, or inject a calcium sulfate-dissolved sulfuric acid solution within approximately the same temperature range while maintaining the concentration/temperature gauge in the area B in the figure.

In order to increase the yield of fibrous calcium sulfate, when crystallizing its trihydrate salt, the crystallization mother liquor is always mixed with technical water Ceracola (
When crystallizing its anhydrous salt with CaSO4・H2O), always use anhydrous ceracola (■・Ca5O4) as the crystallization mother liquor.
It is desirable to keep it saturated.

In addition, there is no particular restriction on whether or not to stir the mother liquor during crystallization, but excessive stirring may lead to breakage of the fibrous crystals, so it should be performed statically, especially when crystallizing long fibers. This is desirable.

The present invention will be specifically explained below by way of Examples.

Parts and percentages are by weight.

Example 1 10 parts of finely pulverized Moroccan natural sulfuric acid (CaSO4.2H 20 minutes 93%) was added to 300 parts of a 95% sulfuric acid solution, and the mixture was heated at 120°C with stirring.
After heating for an hour, it was allowed to cool.

A sulfuric acid medium solution containing calcium sulfate was prepared with a small amount of hexagonal plate-shaped Ca S 04 .3H 2 SO 4 crystals formed at the bottom of the solution.

This medium was mixed with 30% sulfuric acid solution prepared separately.
Add 1 part of the same natural Sansui Setsuko powder to 30°C.
One drop is approximately 0.31 rll in the crystallization mother liquor maintained at a temperature of
It dripped in small amounts.

At this time, in order to suppress the rise in the temperature of the crystallization mother liquor and the increase in sulfuric acid concentration due to the heat of dilution due to the dropwise addition of the concentrated medium, water at about 25° C. saturated with Ceracola trihydrate was added along with the dropwise addition of the medium.

During the crystallization period, the upper mother liquor was gently stirred at a rate of 6 revolutions per minute in the upper part of the crystallization mother liquor tank.

The temperature change of the mother liquor during the crystallization period was 29.5-31.8℃,
The concentration change was 29-32%.

The smallest single crystal of industrial water ceracola obtained is 3 (width)
The fibers were extremely long and slender, with a maximum length of 20 x 400 microns (length) x 100 microns, which were intertwined and formed at the bottom of the mother liquor tank, and were able to be fixed as neutral felt-like Ceracola cotton by filtering and washing with water.

The purity of Sansui Ceracola was 99.1%.

Example 2 Sansui Setsuko powder (CaSO, 2
H20 min 86%, Ca COa 11%) 18 parts to 97
．． Add to 300 parts of 5% sulfuric acid solution and add 1 part while stirring.
Heat at 80℃ for 1 hour, then heat to about 25℃ while stirring continuously.
A calcium sulfate dissolving medium solution was prepared.

This medium was added dropwise to a crystallization mother liquor prepared by adding 0.02 parts of natural anhydrous Ceracola powder to 300 parts of a 60% sulfuric acid solution and maintaining the temperature at 25° C., so that each drop was about 0.311 Ll.

During the dropping period, the temperature and concentration of the crystallization mother liquor were maintained at 20°C.
A 40% strength sulfuric acid solution saturated with anhydrous ceracola at .degree. C. was added, and the upper part of the mother liquor was gently stirred as in Example 1.

The temperature change of the mother liquor during the crystallization period was 23.5-27.8℃,
The concentration change was 58-62%.

The single crystals of anhydrous Ceracola (■.CaSO4) obtained were extremely long and slender, measuring approximately 1 (width) x 50 (length) microns at the smallest size and 10 x 200 microns at the largest, and had a purity of 99.3%.

Reference Example The results obtained when the crystallization conditions were changed in Example 2 described above are shown.

100 parts of the calcium sulfate-dissolved sulfuric acid medium prepared in Example 2 was mixed with a sulfuric acid concentration of 20 parts saturated with industrial water Ceracola.
While maintaining the liquid temperature in the range of ~25% in the range of 20 to 30°C, the crystallization mother liquid tank was adjusted to a retention volume of 500 parts and a circulation rate of 100 parts per minute, and a fine hole nozzle was applied at a rate of 50 parts per minute. It was injected continuously.

The obtained trihydric ceracola crystals have a width of 5 to 10 μm and a length of approximately 12 crr1, which corresponds to the retention depth of the mother liquor in the mother liquor tank.
It was in the form of long fibers and had a purity of 99.4%.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the stability region of crystallized calcium sulfate in the method of the present invention.

Claims (1)

[Claims] 1. Calcium sulfate is dissolved in a sulfuric acid solution with a concentration of at least 60% by weight, and this medium is dissolved in a sulfuric acid solution or water with a concentration of about 40% by weight or less, or in a range of about 40% by weight or more and below the sulfuric acid concentration of the medium. A method for producing fibrous calcium sulfate, which is characterized by dropping, injecting, or injecting the calcium sulfate into a concentrated sulfuric acid solution.