JPS5823867B2 - Method for producing guanidine salts - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing guanidine salts.

There are the following industrial methods for producing guanidine salts.

(1) Reaction between dicyan and ammonia (CN)2+2NH3→(H2N) 2C: Bait HC
NThis method has the disadvantage that it must be carried out in a closed container and under high pressure because dicyanide is highly toxic.

(2) Reaction of urea and ammonium salts (NH2)2CO+NH4X→(H2N)2C:NE
←HX+H20 This method is inexpensive in terms of raw materials, but the yield is poor and the purity of the product is low, so purification is required, which makes it more costly than method (3).

However, an economical method for recovering guanidine carbonate, which is a by-product during urea production, has been considered.

(3) Reaction of dicyandiamide with ammonium salt This is a method commonly used at present.

Among guanidine salts, strong salts, i.e. hydrochloride, chlorate,
Sulfates, sulfanilates, nitrates, phosphates, etc. can be produced by heating and melting reactions of dicyandiamide and ammonium salts of these strong acids.

Salts of weak acids, such as carbonates, phosphates, and diphosphates, are produced by other methods because melt reactions have poor yields.

The present invention is an improved process for producing a guanidine salt of a strong acid by a heated melt reaction of dicyandiamide and an ammonium salt of a strong acid.

Now let the strong acid root be X, and if X is monovalent, then Also, if X is divalent The reaction proceeds according to the equation.

Here, examples of X are CI, Br, ■, ClO4,
There are SO4, 5O3NH2, PO4, and NO3.

Reference 1 [Yoshi Sugino Part 2 Journal of the Chemical Society of Japan, 267-364
According to [1938], this reaction usually takes 180 to 20
It proceeds at a temperature of 0°C, and is said to be a two-step reaction that involves a complicated process and uses a biguanide salt as an intermediate.

Therefore, in the conventional method, a highly pure reaction product cannot be obtained because various reaction intermediates and reaction by-products are mixed together.

Fields that do not require particularly pure products depending on their use,
For example, industrial chemicals such as synthetic detergents, flame retardants, antioxidants, and explosives may not necessarily require purified guanidine salts, but the goal should still be to obtain products with the highest possible purity. Probably.

For reference, the properties of typical pure guanidine salts are listed in the table below.

The purity of the product is ultimately determined by quantifying guanidine using the picrin manufacturing method, but it can also be estimated by measuring its melting point.

When producing guanidine salts by melt reaction, the present inventor first tried to follow the reaction conditions shown in the literature and conditions close to them, but could only obtain the purity level shown or a slightly higher degree.

Therefore, as a result of investigating ways to further increase the purity, they discovered that adding and blowing ammonia gas was effective.

Here, the production of guanidine hydrochloride will be explained as an example.

The reaction formula is.

For example, Document 2 [Sanno, Matsuda: Special Publication 36-16021]
According to dicyandiamide, 93% of the theoretically required amount of ammonium chloride was mixed and held at 180 to 210°C for about 30 minutes to produce 99.24% crude guanidine hydrochloride with a purity of 94.4%.
% yield.

In this follow-up test, the inventor investigated the effects of holding time and holding temperature on the purity of the product, and the results were as shown in FIG. 1A.

In contrast, Figure 1B shows 50m1/kg of content.
It is a graph obtained by determining the relationship between the holding time and holding temperature and the purity of the product when the reaction is carried out while adding min of ammonia gas.

In comparing both figures, in case of A, the highest point is 190°C to 75°C.
The purity is 94.6% at 200°C to 400°C for B.
The purity was 97.0% in 5 minutes, and it is clear that passing ammonia gas is an industrially advantageous condition because the relative purity is less likely to be high and the time is shorter.

In addition, Figure A shows that the reaction zone is unstable due to large variations.

In the literature, the blending ratio of ammonium chloride is lower than the theoretical value, but this is to prevent the hydrochloric acid gas generated during the reaction from contributing to the side decomposition of the product and corroding the reaction vessel.
On the other hand, by aerating ammonia gas, it is possible to suppress the decomposition of hydrochloric acid gas, so the amount of ammonium chloride blended can be close to the theoretical value, and the purity of the product can be further increased.

Next, the production of guanidine sulfur amino acid will be explained as an example.

The reaction formula is It is indicated by.

Document 3 CW, H, Hill: USP226594
2 (1941)) heated reaction equivalents of dicyandiamide and ammonium sulfaminate, starting at 150 to 1
They reported that they reacted at 75°C and held at 145-155°C for % time to obtain guanidine sulfamate with a purity of about 90%.

A follow-up test was conducted according to the method described in Reference 3, and the relationship between the holding time and temperature and the melting point of the reactant was determined, and the results were as shown in FIG. 2A.

Also, according to the method of the present invention, ammonia gas containing 1 kg
Figure 2B shows the results of reacting with Shirikawama-sama, which was added at 40 ml/min.

The melting point of pure guanidine sulfamate is 127° C., but the melting point of the reactant produced by melting reaction decreases as the purity decreases due to the presence of side reactants and other impurities.

As is clear from FIGS. 2A and 2B, it can be seen that according to the method of the present invention, in which the reaction is carried out while ammonia gas is aerated, a product with a higher melting point, that is, a product with higher purity, can be obtained than in the case of the conventional method.

That is, the method of the present invention in which the reaction is carried out while ammonia gas is aerated can improve the purity of the product.

2. The product's pH does not depend on the acidic side.

3. Reaction time can be shortened.

4. It is possible to prevent corrosion of the material of the reaction container (steroy, SUH, etc.).

5. Therefore, whitening of the product can be improved.

6. Variations between lots of reactions are reduced.

7. When the product is dissolved in water, there are few insoluble clusters.

There are advantages such as

A paper describing the reaction of dicyandiamide and ammonium salt at high pressure in the presence of liquid ammonia, J, H9Paden: Ind, Eng, Chem.

39 952 (1947).

According to this report, a product with a purity of 91-92% was obtained at a yield of 91-93% by sealing it in an autoclave with liquid ammonia and carrying out the process at 160° C. and 2000 psi.

However, reacting under such high pressure requires extremely expensive equipment, requires safety precautions, and is economically difficult to produce in large quantities.

The present invention is applied only to melting reactions under normal pressure, and continuous operation is also possible in the case of mass production.

In some cases, the ammonia to be fed is liquid ammonia contained in a cylinder, so this part is under high pressure, but it is then vaporized into a gas and introduced into the reaction layer.

The reaction vessel is equipped with a sealed lid, and the lid is equipped with a stirrer, a thermometer, a sight glass, a sample collection port, a raw material inlet, and an ammonia and other gas overflow port.

Since the gas overflow port is at normal pressure, the ammonia gas pressure introduced is sufficient to cause bubbles to bubble out from the tip of the lance immersed in the molten layer.

Comparing the four purity levels of the product obtained by the method of the present invention and the product obtained by the high-pressure method according to the method described in the Examples, the quality is actually higher as shown below.

High pressure method Ordinary pressure conventional method Invention method Nitrate 94.0% 941% 97.4% Hydrochloride
93.7% 90.7% 95.1% In carrying out the method of the invention, ammonia gas can be introduced at room temperature or at elevated temperature through a lance inserted into the melt bed.

At this time, ammonia gas may be mixed with air or other gas to be diluted and added.

It is desirable to thoroughly dehumidify this gas before passing it through, so that the moisture in the raw material that has absorbed moisture can be removed.

Example 1 27.0 kg of dicyandiamide and 73.0 kg of ammonium sulfaminate and 9 were thoroughly mixed, 10 kg of the mixture was put into an enameled container equipped with an external heater, and then carefully heated to 145°C. Melted.

□Ammonia gas 5 g/min and dry air 5 g/min
The temperature was gradually raised to 180° C. at a rate of 180° C./min.

Next, add 90k of the remaining mixture while passing ammonia gas through it.
g was added while maintaining the temperature of the molten layer between 175 and 185°C.

After adding the entire amount, the temperature was raised to 185°C, and 30 minutes later, the molten contents were poured into a stainless steel vat, and cooled to obtain 99.8 kg of crystallized guanidine sulfamino acid (
A).

98.6 kg of guanidine sulfamino acid (B
), and the product inspection i results are as follows.

Purity MP PH Solubility (A) 94.73% 108-112℃ 7
．． 82 Transparent (B) 92.86% 9
0 to 102°C 6,65 or cloudy Example 2 Dicyandiamide 679z and ammonium nitrate 3212 were mixed, passed through ammonia gas IQQ ml/min, and melted by heating at 200°C for 20 minutes in a Hastelloy container. Guanidine nitrate (5) was obtained by the method of the present invention.

Separately, a product (B) that does not allow ammonia gas to pass through was obtained in the same manner, and the comparison between the two was as follows.

Yield Product purity Color tone (A) 97.4% 97.3% Spinning wheel
White (13) 96.2% 94.1% Slightly yellowish In this way, when the method of the present invention is used, a guanidine salt with high product purity can be obtained.

Although the mechanism is not clear, it is speculated that it is probably to suppress the acid content generated by thermal dissociation of the ammonium salt.

In this sense, the addition of ammonium carbonate or ammonium carbamate may be considered, or the moisture generated by their decomposition may have an adverse effect.

Note that when the method of the present invention is carried out, the pH becomes neutral or alkaline, so it is possible to indirectly know whether or not the method of the present invention has been carried out.

[Brief explanation of drawings]

FIG. 1A is a graph showing the relationship between the holding time and temperature and product purity in the production of guanidine hydrochloride by the conventional method, and FIG. Figure A is a graph showing the relationship between the holding time and temperature and product purity in the production of guanidine sulfamate by the conventional method, and Figure 2B is a graph similarly obtained by the method of the present invention.

Claims (1)

[Claims] 1. A method for producing guanidine salts, which is characterized in that when dicyandiamide and ammonium salt are mixed and heated and melted to produce guanidine salts, ammonia gas is passed through the heated melt under normal pressure and the reaction is also carried out.