JPS63162527A - Production of anhydrous magnesium chloride - Google Patents

Abstract

PURPOSE:To obtain anhydrous magnesium chloride excellent in safety and drying capacity, by allowing an organic soln. of water-contg. magnesium chloride to azeotropically distil with heating, dehydrating the distillate and refluxing the distillate to the original soln. CONSTITUTION:The organic solvent and a water are azeotropically distilled by heating the organic solvent soln. of water-contg. magnesium chloride and the water is removed from the distillate with a dehydrating treatment. Then, the anhydrous magnesium chloride contg. no free water is obtained by refluxing the dehydrated distillate to the original soln. or condensing and drying up the organic solvent soln. of the magnesium chloride contg. no free water. The solvent consisting of one or more kinds selected among >=4C monohydric alcohol and polyhydric alcohol as the principal component and if necessary, adding other component capable of forming an azeotrope with water, is preferable as the solvent to be used. Extremely the ethyl alcohol is preferable because of the application as the drying agent or the safety in operation for human being.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a practical method for producing anhydrous magnesium chloride, which is useful as a desiccant, food additive, and other industrial materials.

<Prior Art> Calcium chloride is commonly used as a desiccant. This desiccant is not only available at a low price, but also can easily achieve its purpose by applying intense heat to make it anhydrous, so it can certainly be said to be an excellent desiccant. However, in recent years, in various fields of increasingly sophisticated science and technology, drying capabilities that exceed the level of calcium chloride are sometimes required. Magnesium chloride is suitable as a desiccant to be applied in such cases. The inventor's study results revealed that magnesium chloride has superior drying ability than calcium chloride.

On the other hand, desiccant agents, especially magnesium chloride that can be used in highly pure medical applications, are not supplied as anhydrous. Magnesium chloride generally contains - 6 crystallized water in the molecule.
It is obtained as a so-called hexahydrate salt containing 6 hydrates, and it is almost never industrially converted into an anhydride. This is because, unlike calcium chloride, hydrated magnesium chloride decomposes and the desired anhydride cannot be obtained by simply igniting it. The following methods are known in the literature as methods for obtaining anhydrous magnesium chloride.

(1) Add carbon to magnesium oxide and react with chlorine gas in a chlorine furnace. Alternatively, heat and dehydrate while passing chlorine gas. Alternatively, ammonium chloride or potassium chloride is added and the mixture is heated and dehydrated.

(2) Actually, it is obtained by thermally decomposing magnesium ammonium chloride. However, applying these methods to actual production is impractical and extremely difficult due to contamination of raw materials such as chlorine gas.

<Problems to be solved by the invention> As a result of searching for a substance that is safer and has better drying ability than calcium chloride that has been conventionally used, the present inventor has developed magnesium chloride from which water has been substantially removed. found that it is suitable, and after conducting various studies on its practical manufacturing method, the present invention was completed.

Means for Solving the Problems> That is, the present invention heats an organic solvent solution of hydrated magnesium chloride to azeotropically distill the organic solvent and water, and dehydrates the distillate to remove water. , and then refluxing the dehydrated distillate back to the original solution. This is a method for producing anhydrous magnesium chloride that does not contain substantially water, which is characterized by concentrating and drying a solution of magnesium chloride in an organic solvent that does not contain substantially water.

In the present invention, first, hydrated magnesium chloride is dissolved in an aqueous solvent that can dissolve it, and the solution is heated to azeotropically distill off the organic solvent and water. According to the study results of the present inventors, the main constituent of such a solvent is one or more selected from monohydric alcohols and polyhydric alcohols having 4 or less carbon atoms, and if necessary, other azeotropic components with water. It is good to add In particular, ethyl alcohol is particularly preferred from the viewpoint of application as a desiccant to humans and operational safety.

If necessary, other third components may be added to ethyl alcohol to efficiently carry out azeotropy, but water can be effectively led out of the system even as it is.

Other azeotropic components with water include benzene.

One or more types of conventionally known materials such as toluene, dioxane, chloroform, and carbon tetrachloride can be used, but depending on the purpose,
It goes without saying that considerations such as safety should be taken into account.

In addition, the amount of these added molds depends on the required efficiency and care must be taken not to cause non-uniformity of the magnesium chloride solution, but in general, the amount of added mold is 50% by weight or less of the magnesium chloride solubilizing solvent used. Furthermore, 20% by weight or less is sufficient.

The distillate (water-containing solvent) distilled out of the system is led to a dehydration step and subjected to dehydration treatment. Specific methods for the dehydration process include: ■ Physical removal methods such as adsorbing water with molecular sieves, ■ Chemical removal methods that react with water such as calcium oxide or calcium hydride, and ■ A combination of these methods. There are methods etc. Method (2) is an excellent method in that a dehydrating agent such as a molecular sieve that has adsorbed water can be reused by desorbing water by a conventionally known method. Regardless of which method is used, the dehydrated solution 1s (dehydrated distillate) may be treated with suitable means to remove impurities from these dehydration steps, for example, by distilling the dehydrated distillate again. The magnesium chloride solution may be refluxed to the original magnesium chloride solution.

The magnesium chloride solution obtained in this manner is substantially free of water or contains only a small amount of water, usually having a water content of less than 1 mole, more preferably less than 0.5 mole, per mole of magnesium chloride.

Furthermore, by concentrating and drying the dehydrated magnesium chloride solution described above, the obtained magnesium chloride can also have a similar water content ω, which is highly useful industrially. This concentration to dryness may be carried out using a separate device or process from the refluxing of the solvent as described above, but more practically, it is carried out using the same device, following the refluxing, or during the refluxing. This can also be carried out by controlling the amount of reflux of the solvent gradually. Finally, in obtaining magnesium chloride as a solid, it is an effective and preferred embodiment to reduce the pressure in order to reduce the amount of residual solvent. It is also useful to intensify the heating, but if the heating becomes severe, the magnesium chloride will be decomposed, so careful consideration is required. When magnesium chloride decomposes, it becomes an aqueous solution and can be judged by the presence of an insolubilized portion, but compounds that can adjust the solution to an acidic range when dissolved in water together with magnesium chloride, such as j! ! By adding compounds such as l-arginine, cysteine, nicotinamide, citric acid, and glycine, it is possible to suppress the generation of insolubilized substances and improve the solubilization of magnesium chloride, which may be useful depending on the application. be.

Such additives may be used alone or in combination of two or more, and the appropriate amount (m) to be added is about 0.1 to 10 parts, preferably about 0.2 to 5 parts, based on 1 part of magnesium chloride. The anhydrous magnesium chloride thus obtained exhibits a drying effect superior to that of calcium chloride, and is industrially useful.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

<Example> Example-1 Magnesium chloride hexahydrate 60.6! J for ethanol 60
Dissolved in 0d. At this time, the concentration of magnesium chloride in the ethanol solution was about 4.7%, and the concentration of water was about 5.6%. This solution was boiled and the distillate was condensed and then introduced into a column packed with about 500 g of zeolite beads.

The dehydrated ethanol obtained by passing through this column was distilled again and returned to the above magnesium chloride-ethanol solution. After operating the circulation system for about 12 hours, the magnesium chloride-ethanol solution was quantified and found to have a magnesium chloride concentration of about 4.8% and a water concentration of about 0.1%.

This solution was filtered through a 0.45 μm non-aqueous membrane filter under a dry atmosphere, and then dispensed into a vial so that magnesium chloride reached a predetermined amount, and the ethanol was distilled off and dried. The dried product was a white crystal, and most of it was at the bottom of the vial. The moisture concentration in the dry matter at this time was 169%, which is 0.10% of magnesium chloride.
Equivalent to water salt.

Example-2 The substantially water-free magnesium chloride-ethanol solution prepared in Example-1 was mixed with 50q of magnesium chloride.
The solution was dispensed into vials and heated under reduced pressure to distill off the ethanol. The heating temperature was 50 to 120° C., and the pH and solubility of the dried product dissolved as it was in 10 d of water and that dissolved in 10 d of water together with various additives were observed. The results are shown in Table 1.

Table 1 <Effects of the Invention> According to the method of the present invention, substantially anhydrous A solution of magnesium chloride in ethanol or the like can be obtained. If necessary, this is subjected to operations such as filtration, and then dispensed into, for example, injection containers, and the solvent, such as ethanol, is distilled off, so that the container contains substantially no or very little water. It is possible to leave behind magnesium chloride, which contains water. Of course, the steps described above should be carried out in a dry atmosphere and care should be taken to minimize moisture introduced from this step. Also, at this time, consideration must be given to bacterial contamination.

Furthermore, as shown below, the anhydrous magnesium chloride obtained by the present invention has a drying power greater than that of calcium chloride.

(1) The hygroscopicity of magnesium chloride and calcium chloride in powder form was compared.

Anhydrous magnesium chloride was pulverized in a dry atmosphere, and the known ω was spread in a petri dish to a uniform thickness. For comparison, anhydrous calcium chloride was pulverized in the same manner, and the known ω was spread in a petri dish to a uniform thickness. These petri dishes were left open indoors under the conditions of room temperature and 60 to 63% RH, and the adsorbed water concentration (water content/anhydrous weight %) was measured over time. The results are shown in Table 2 and Figure 1.

From these results, it can be seen that anhydrous magnesium chloride is superior in terms of moisture absorption rate.

Table 2 (2 Comparison of hygroscopic power of magnesium chloride and calcium chloride in ethanol solution state).

Anhydrous magnesium chloride and anhydrous calcium chloride powders were each made into 2.5% ethanol (EtOH) solutions. These were left open indoors under the conditions of room temperature and 60 to 63% RH, and the adsorbed water concentration (water base = weight j%) was measured over time by the Karl Fischer method. The results are shown in Table 3 and Figure 2. From these results, it can be seen that anhydrous magnesium chloride is superior in moisture absorption rate even in the solution state.

Table 3 (2,5% Et OH?mfffl (7) Moisture 1
i: help%)

[Brief explanation of the drawing]

Figure 1 shows the adsorbed moisture concentration (water content/anhydride content) in the fine powder state of anhydrous magnesium chloride, which is a desiccant according to the present invention, and anhydrous calcium chloride, which is a conventionally used desiccant. Figure 2 shows the adsorbed water concentration (moisture R2) of these desiccants in a 2.5% ethanol solution state.
% by weight) over time. Patent applicant: Teijin Ltd. 1234t6 [For 13j]

Claims (1)

[Claims] 1. Heating a solution of hydrated magnesium chloride in an organic solvent to azeotropically distill the organic solvent and water, dehydrating the distillate to remove water, and then dehydrating the distillate. A method for producing anhydrous magnesium chloride substantially free of water, the method comprising refluxing the effluent back to the original solution. 2. Heat an organic solvent solution of hydrated magnesium chloride to azeotropically distill the organic solvent and water, dehydrate the distillate to remove water, and return the dehydrated distillate to the original solution. 1. A method for producing anhydrous magnesium chloride substantially free of water, which comprises refluxing to obtain a solution of magnesium chloride in an organic solvent substantially free of water, and then concentrating the solution to dryness.