JPS63156008A - Production of quickly dissolvable sulfamic acid - Google Patents

Abstract

PURPOSE:To easily produce quickly dissolvable sulfamic acid having high purity which is handled easily, by press-forming powdery sulfamic acid comprising dry crystal particles of sulfamic acid crystallized out of a solvent before the particles are caked and crushing coarsely the press-formed product thereafter. CONSTITUTION:Dry crystal particles of sulfamic acid crystallized out of a solvent are crushed finely to pref. <=500mu particle size. After press-forming the obtd. powdery sulfamic acid with a pelletizing machine or a compacting machine, etc. before the powdery sulfamic acid is caked, then the formed product is crushed coarsely. Thus, aimed granules of quickly dissolvable sulfamic acid are obtd. when the granules are thrown into water, water permeates easily into voids in the inside of the granules. Accordingly, the granules of sulfamic acid are dissolved quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing sulfamic acid granules that are rapidly soluble in water from highly pure sulfamic acid crystals obtained by crystallization.

Sulfamic acid is used in a variety of fields such as cleaning agents, nitrogen oxide removers, water glass hardening agents, and sulfonating agents, but because high purity is desired, it is made of wet-crystallized sulfamic acid crystal grains. Powder products are produced industrially. Sulfamic acid is often used in the form of an aqueous solution, but since the crystal grains of sulfamic acid dissolve at a low rate in water, a fast-dissolving solution is desired as an industrial product.

(Prior art) As methods for industrial production of sulfamic acid, there are two methods: the so-called dry method, in which urea and oleum are reacted directly, and the so-called wet method, in which urea and oleum are reacted in sulfuric acid (not known). The sulfamic acid produced by the dry method contains about 10% by weight of acidic ammonium sulfate, sulfuric acid, and other impurities.
In contrast, the wet method contains almost no impurities because it is obtained by crystallization.

It is also known that the dissolution rate of sulfamic acid crystal grains in water increases as the crystal grains become finer. Therefore, methods for producing highly pure and rapidly soluble sulfamic acid include a method of crystallizing fine crystals from a sulfamic acid crystallization mother liquor using a wet method and separating and recovering the crystals, or a method of crystallizing the crystals as relatively large particles. , a method of separating and recovering and then pulverizing.

In addition, as a method for producing rapidly soluble sulfamic acid, a method for directly obtaining a granular product by a dry method is disclosed in US Patent No. 2.
No. 408,492.

(Problems to be solved by the invention) Crystallizing fine crystals from the sulfamic acid crystallization mother liquor,
In the method of separating and recovering this, the separability in the centrifugation process used to separate it from the mother liquor is not good, and powder scattering etc. easily occur in the process of drying in an air stream after separation, so it is difficult to produce efficiently. It is difficult to do so. Furthermore, the sulfamic acid powder consisting of fine particles obtained by this method is prone to caking during storage. On the other hand, when relatively large particles are crystallized from the crystallization mother liquor, the above-mentioned problems are less likely in the centrifugation and drying steps, but the sulfamic acid powder after pulverization still causes caking during storage. easy.

As a method for preventing such caking, it is known to add about 0.1 to 1% of silica powder to fine sulfamic acid powder, but this addition reduces the purity of sulfamic acid or impairs the intended use. In some cases, this may cause problems such as the inability to use the device.

The granular product disclosed in the above-mentioned US Pat. No. 2,408,492 does not cause caking during storage and is rapidly soluble, but as described above, it has low purity and is still limited in terms of use. Therefore, in order to obtain highly pure sulfamic acid, it is necessary to purify the granules, and if this is carried out by the crystallization method, there are problems similar to those of the wet crystallized sulfamic acid described above.

The present invention aims to provide sulfamic acid as an industrial product that has high purity, does not cause caking during storage, and is rapidly soluble in water, and a method for producing the same.

(Means for Solving the Problems) The sulfamic acid of the present invention is in the form of granules, and the method for producing it comprises dry sulfamic acid crystal grains crystallized from a solvent, preferably a particle size of 500μ obtained by pulverization. It is characterized in that powdered sulfamic acid consisting of the following sulfamic acid crystal grains is pressure-molded before solidification and then coarsely crushed.

The sulfamic acid crystal grains are crystallized from a crystallization mother liquor in normal industrial production. This mother liquor often contains small amounts of unreacted raw materials, by-products, etc. in addition to water as a solvent.
The sulfamic acid crystals separated from the mother liquor are appropriately washed with water and then dried.

The size of the dried sulfamic acid crystal grains depends on the crystallization conditions described above. Usually, in order to facilitate separation from the mother liquor and drying, it contains particles of approximately 100 to 2000 microns, and most of the particles are crystallized as particles of 500 microns or more.

However, finer grains may be used when efficient separators and dryers are used. According to the invention, in order to obtain rapidly dissolving sulfamic acid granules, the size of the crystal grains is 5.
00μ or less, preferably 250μ or less. Therefore, in the case of a powder containing a large number of crystal grains with a size of 500 μm or more, the powder consisting of the dried sulfamic acid crystal grains is finely pulverized by a normal grinder, and the powder has a particle size of 500 μm or less, preferably 250 μm or less. It is used after being converted into something.

This sulfamic acid powder having crystal grains of 500 microns or less, preferably 250 microns or less, is then pressure-molded.

This pressure is 300 to 300 in the case of compression molding.
0kg/cal, preferably 600-1500kg/c!
Grade A is good, and in the case of roll forming, the linear pressure is 400 to 1600 kg/am, preferably 800 to 12
Approximately 00 kg/cIII is good. This pressure molding can be easily carried out using a conventional method such as a tablet press or compact machine.

The molded product obtained by this pressure molding is then roughly crushed to obtain the sulfamic acid granules of the present invention. This coarse crushing may also be carried out by a conventional method, for example, it can be easily carried out using a coarse crusher. The size of the granules is not particularly limited, but is preferably about 0.25 to 2.5 fins.

(Function) The sulfamic acid crystal grains crystallized from the mother liquor, separated and dried have high purity and are usually easily obtained with a content of 99% by weight or more. However, this dried sulfamic acid powder is prone to caking, and caking occurs when left at room temperature or during storage.

The strength of this solidified material is so high that it requires hammering with a hammer or the like. In addition, this solidified material or its coarsely crushed material does not exhibit rapid solubility even when put into water. This caking is probably due to the presence of moisture in the air or due to the welding of sulfamic acid crystal grains due to moisture absorption.

By press-molding the sulfamic acid powder consisting of dry sulfamic acid crystal grains before caking occurs, the above-mentioned welding can be avoided, and the welding can be performed by weak force or by forming a very small proportion of the sulfamic acid crystal grains together. It is thought that due to the welding of the granules, interparticle bonding occurs in the form of a large number of voids that allow water to easily enter the inside of the granules. Molding pressure is 300 kg/ci or less or linear pressure is 400 kg/ci
Below cn+, the obtained granules tend to disintegrate;
000 kg/cn1 or more or linear pressure 1600 kg/a
m or more, the obtained granules tend to become dense particles.

The water dissolution rate of the granules according to the invention also depends on the size of the dry sulfamic acid crystal grains used to make the granules;
The finer the particles, the faster the dissolution rate.

As mentioned above (the reason why granules put into water dissolve easily is because water enters the voids inside the granules, the finer the dried sulfamic acid crystal grains, the more the number of voids increases.
Increases the contact area of water.

When a press-molded product before being crushed is also put into water, water enters its internal voids and dissolves, but the granules obtained by coarse crushing exhibit a much higher dissolution rate. Further, by coarse crushing, granules can be made that are easy to measure and handle. In particular, it is surprising that the granules obtained by this coarse crushing maintain their original granule shape without caking even after long-term storage, but even if the granules come into contact, the contact area of the contact point is This is thought to be due to the fact that it is extremely small.

(Example) Example 1 When the particle size of dry sulfamic acid powder obtained by crystallization from the crystallization mother liquor in the wet method sulfupmic acid production process was measured, 85% was 105 to 1500μ and the average particle size was 550μ. there were.

88.7 g of this powder was added to a 300 ml beaker.
When the solution was poured into 3 g of 5° C. water and simultaneously stirred at a speed of 200 revolutions/minute using a three-blade stirrer to maintain the temperature at 5° C., the dissolution time was measured, and it was found that 30 minutes were required for complete dissolution. Separately, seal 20 kg of the above sulfamic acid powder in a paper bag,
When it was left in a room at room temperature, it solidified after three months.

However, when the above sulfamic acid powder was pulverized with a hammer type pulverizer, sulfamic acid fine powder with an average particle size of 70 μm was obtained. When the dissolution time of this fine powder was measured in the same manner as above, it was found that it took 4 minutes for complete dissolution. It was observed that the dissolution rate was significantly improved. Furthermore, when the storage caking property was examined in the same manner as above, caking occurred after 2 to 3 days, and the mass showed a caking strength of 0.5 kg/cJ after 1 month. Moreover, even before this standing, the powder fluidity is not good.

On the other hand, when the above-mentioned fine sulfamic acid powder having an average particle size of 70 μm was compression molded at 1100 kg/cffi using a roll granulator and coarsely crushed using a pulverizer, the sulfamic acid granules of the present invention having a particle size of 12 to 32 mesh were obtained. It was done. Regarding the granules, the dissolution time was measured in the same manner as above and was found to be 10 minutes. Further, when measured at a dissolution temperature of 20°C, the dissolution time was 4.5 minutes. Furthermore, this granule had good fluidity, and even after one year of storage, no caking occurred and maintained good fluidity. Furthermore, when this granule was observed under an electron microscope, it was found that there were grain boundaries due to the original particles with an average grain size of 70 μm, and that there were also many voids.

For comparison, 12 to 32 obtained by classifying with a sieve.
When the dissolution time was measured in the same manner as above for unpulverized powder consisting of sulfamic acid crystal grains of mesh,
It took 25-30 minutes.

Example 2 The sulfamic acid fine powder with an average particle size of 70μ obtained in Example 1 was compressed into tablets using a tablet press at a tableting pressure of 1000 kg/cnt, then coarsely crushed using a coarse crusher, and sieved to give 5.
Granules (A) with a size of 00 to 1000μ and granules (B) with a size of 250 to 500μ were obtained. Next, the dissolution time was measured in the same manner as in Example 1, and it was found that the granules (A) had a melting time of 6 at 5°C.
The dissolution time was 4 minutes at 20°C. For granules (B), 4 min at 5°C and 1 min at 20°C.
．． A dissolution time of 5 minutes was indicated. Furthermore, when these granules (A) and (B) were each stored for one year, no caking occurred.

(Effects of the Invention) According to the present invention, highly pure, non-caking, and rapidly soluble sulfamic acid can be obtained from a powder made of dry sulfamic acid crystal particles by a simple method. This product is in granular form, so it is easy to handle, and as usual,
It can be used in various fields.

Claims (2)

[Claims] (1) A method for producing rapidly soluble sulfamic acid, which comprises press-molding powdered sulfamic acid consisting of dry sulfamic acid crystal grains crystallized from a solvent before solidification, and then crushing the powder. (2) The method for producing rapidly soluble sulfamic acid according to claim (1), wherein the powdered sulfamic acid is composed of sulfamic acid crystal grains having a particle size of 500 μm or less obtained by pulverization.