KR100496336B1 - The recrystallization of hexanitrostilbene using the methdo of direct contact cooling crystallization - Google Patents

Abstract

The present invention relates to a recrystallization method for controlling the shape and size of hexanitrostilbene crystals, which is different from conventional evaporation crystallization methods. Provided is a recrystallization method for controlling characteristics such as shape, particle size, packing density, etc. of HNS by a direct contact cooling crystallization method which is a direct addition method.

Description

Recrystallization method of hexanitrostilbene using direct contact cooling crystallization {THE RECRYSTALLIZATION OF HEXANITROSTILBENE USING THE METHDO OF DIRECT CONTACT COOLING CRYSTALLIZATION}

The present invention relates to a method of controlling the shape and size of hexanitrostilbene (2,2 ', 4,4', 6,6'-hexanitrostilbene, hereinafter HNS) crystals, more specifically in the recrystallization process A method of varying the shape and particle size of the final HNS using water as a nonsolvent.

HNS is a high performance desensitizer that is stable against radiation, static and heat, and has been widely used in space rockets, missiles, and the oil development industry since it was invented at the Naval Ordance Laboratory in the US in early 1970. However, the HNS crystals obtained in the synthesis process are fine plate aggregates, and these HNS crystals have a problem of low packing density, instability, and poor workability. For this reason, HNS recrystallization studies have been conducted by various researchers since the early 1970s in various ways.

However, HNS is very stable in molecular structure, so it has not only strong solubility in strong acid or some solvents, but also the growth behavior of HNS crystals makes needle crystals in most solvents except strong acid due to its molecular structure. There has been a problem.

Among the known recrystallization methods, NSWC / WOR TR 78-209 (1979) and USP 4,260,837 (1981) disclose a method of recrystallization of HNS using nitric acid as a solvent. Due to the presence of a small amount of acid in the thermal stability is low and there is a problem in long-term storage.

Confidentail NORTR 65-142 (1971), WS 5003F (1981), and USP 3,699,176 (1972) describe an evaporation crystallization process that results in the supersaturation of a solution by refluxing acetonitrile in an acetonitrile-toluene (or xylene) -HNS system. Methods of making HNS are known. The HNS produced by this evaporation crystallization method is polygonal (short to large axis ratio = 1 to 1 to 10) and has high filling density and purity. However, not only the solubility of HNS in acetonitrile is very low, but also azeotropes are formed between acetonitrile and toluene (or xylene), so that the solubility is further lowered. In particular, since the evaporation crystallization process controls the supersaturation state by using the difference in solubility due to the evaporation of the solvent, the operating conditions are not smooth and the operating variables, particularly the supersaturation control, on crystallization are very difficult.

On the other hand, in the recrystallization using the direct contact cooling crystallization method, the shape of the crystal is affected by the crystallization operation conditions such as the molecular structural properties of the crystalline material, the properties of the solvent, the properties of the nonsolvent, and the crystallization temperature, supersaturation, and cooling rate. The size and distribution of crystals, on the other hand, depend heavily on the initial supersaturation during crystallization. The initial degree of supersaturation can also be controlled by the rate of cooling as well as the rate of injection of the nonsolvent, the amount of injection, the crystallization temperature and the concentration of the solution.

An object of the present invention is to provide a method that can solve the problems caused by the recrystallization method and the evaporation crystallization method using nitric acid as described above by recrystallizing the HNS by the direct contact cooling crystallization method to improve the particle size and shape of the HNS To provide a way to control.

Another object of the present invention is to provide an HNS obtained by a method of controlling the particle size and shape of the HNS by recrystallizing the HNS by a direct contact cooling crystallization method.

The present invention

a) dissolving HNS in dimethylacetamide to prepare a solution;

b) adding water to the prepared solution to form crystal nuclei; And

c) cooling the solution in which the nuclei are formed.

It is made of a HNS recrystallization method comprising a, to provide a recrystallized crystal using this method.

In order to recrystallize HNS, HNS is first dissolved in dimethylacetamide. The solubility of HNS for dimethylacetamide has a characteristic sensitive to the temperature to 11% by weight at 25 ^o C 1 wt.%, At 115 ^o C. Thus the solution can be heated in a conventional manner to obtain sufficient solubility. By heating, the temperature of the solution is preferably maintained in the range of 30 ^° C. to 130 ^° C. The more preferred solution has a temperature of 50 ^o C to 120 ^o C and the most preferred solution has a temperature of 80 ^o C to 120 ^o C. If the temperature of the solution is lower than 30 ^o C, sufficient solubility cannot be obtained. If the temperature of the solution exceeds 130 ^o C, not only the problem of excessive process cost is caused, but also the decomposition of dimethylacetamide and HNS. May cause degeneration.

There is no particular limitation on the heating method.

In order to speed up dissolution of HNS in dimethylacetamide, those skilled in the art can add agitation using conventional methods known in the art. There is no particular limitation on the method of stirring.

By heating as described above, non-solvent water is added to induce supersaturation in a solution in which HNS is dissolved in dimethylacetamide to generate crystal nuclei. In this case, the concentration of HNS dissolved in dimethylacetamide is preferably 1-12% by weight. If the concentration of HNS in the solution is less than 1% by weight, the final production yield of HNS is lowered, which results in an increase in manufacturing cost. In addition, when the concentration of HNS exceeds 12% by weight, HNS solubility in dimethylacetamide is limited.

The amount of water added is preferably added to 2% by weight to 20% by weight of dimethylacetamide used in the preparation of the solution. If the amount of water to be added is less than 2% by weight, sufficient crystal nuclei are not formed. If the amount of water to be added is more than 20% by weight of dimethylacetamide as a solvent, the obtained HNS crystal has a predetermined polygonal shape. There is a problem that the shape of is not obtained. Water may be introduced into the solution through conventional methods used in the art. In order to prevent a sudden change in the process temperature due to the addition of water, it is preferable that the water is continuously added, and may be added in a small amount. The temperature of the water is used at room temperature, but when it is difficult to control the shape of the crystal formed by the rapid change of the process temperature, it may be added at the same or similar temperature as the solution.

In the process of adding water, the final shape of the particles is influenced by the non-solvent feed rate. The feed rate of water is preferably in the range of 10 ml / min-360 ml / min. If the input speed of water is out of the above range may cause a problem that the shape of the recrystallized HNS does not become a polygon.

Water is added to generate crystal nuclei, and crystal nuclei grow by cooling. Depending on the cooling rate, the final shape may be affected and the preferred cooling rate is from 0.1 ^o C / min to 20 ^o C / min. If the cooling rate is less than 0.1 ^o C / min, the cooling process may be a time-consuming step in the overall process, when the cooling rate exceeds 20 ^o C / min, it is impossible to obtain a polygonal crystal.

It is desirable to obtain polygonal crystals (short to long axis ratio of 1: 1 to 1 to 1 to 10) between 5 and 400 microns using a programmed chiller to keep the cooling rate within this range. In case of natural cooling, not only constant cooling rate can be maintained but also the cooling rate is slowed down, which lowers the process efficiency. On the other hand, it is preferable that such a process is made in a batch, a batch cooling crystallizer can be used.

The present invention will be described in detail with reference to the following examples, which are not intended to limit the present invention.

EXAMPLE

Example 1

160 g of HNS is mixed with 2000 ml of DMA and raised to 120 ^o C to form a saturated solution. 65 ml of water at 120 ^o C is injected at 10 ml per minute to nucleate and simultaneously cool down to 10 ^o C at a cooling rate of 0.5 ^o C per minute. The resulting crystals are filtered off and washed with 50 ml of acetone. The crystal obtained was polygonal in shape, and the average size of the crystal was 250 microns. The filling density of the crystallized HNS was 0.60 and the yield was about 85% by weight.

Recrystallization was carried out by the same method as in Example 1, with each cooling rate varied by 0.1 ^o C, 1 ^o C, 5 ^o C and 20 ^o C per minute. The results are shown in Table 1 below.

In the same manner as in Example 1, 80 g of HNS and 2000 ml of DMA were mixed and raised to 90 ^° C. to produce a saturated solution. Then, 90 ml of water at 90 ^° C. was injected into 10 ml / min and recrystallized. Table 2 shows.

In the recrystallization by the same method as in Example 1, the crystallization was recrystallized according to the injection rate of 65ml water to the saturated solution and the results are shown in Table 3.

According to the present invention there is provided a method of controlling the particle size and shape of HNS by recrystallizing HNS by a direct contact cooling crystallization method, and a method of controlling the particle size and shape of HNS by recrystallizing HNS by a direct contact cooling crystallization method. HNS obtained by is provided.

1 is a SEM photograph of the HNS according to the present invention

2 is a SEM photograph of the HNS by a conventional evaporation crystallization method

Claims (9)

In hexanitrostilbene recrystallization method, a) dissolving hexanitrostiben in dimethylacetamide to prepare a solution; b) adding water to the prepared solution to form crystal nuclei; And c) cooling the solution in which the nuclei are formed. Hexanitrostilbene recrystallization method comprising a. The method of claim 1 wherein the amount of hexanitrostilbene dissolved is 1-12% by weight of the solution. The method of claim 1, wherein the solution of the hexanitrostilbene is dissolved hexanitrostilbene recrystallization method characterized in that the temperature is 30 ^° C-130 ^° C. The method of claim 1, wherein the amount of water added is 2 to 20% by weight of the dimethylacetamide hexanitrostilbene recrystallization method. Claim 5 was abandoned upon payment of a set-up fee. The method of claim 1, wherein the water is added to the rate of 10 ml / min-360 ml / min hexanitrostilbene recrystallization method. The method of claim 1, wherein the cooling of the solution in which the nuclei are formed has a rate of 0.1-20 ^° C./min. Claim 7 was abandoned upon payment of a set-up fee. The method of claim 1, wherein the cooling of the solution in which the nuclei are formed is performed by a program control method. Claim 8 was abandoned when the registration fee was paid. 2. The method for hexanitrostilbene recrystallization according to claim 1, wherein the recrystallization is performed in a batch cooling crystallizer. delete