JP2002069049A - Method for producing hydrazodicarbonamide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing hydrazodicarbonamide in high yield. SOLUTION: This method for producing hydrazodicarbonamide is characterized in that a ketazine or a hydrazone is reacted with urea in the presence of soluble salts under a reduced pressure condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing hydrazodicarbonamide useful as an intermediate for synthesizing azodicarbonamide which is a pyrolytic foaming agent for rubber or resin applications.

[0002]

2. Description of the Related Art As a method for producing hydrazodicarbonamide, for example, (1) a method in which hydrazine hydrate or a salt thereof is reacted with urea in the presence of a non-oxidizing mineral acid, and (2) a method in which ketazine and urea are aqueous A method in which ketone and by-produced by-product and ammonia are taken out of the system under normal pressure conditions in the medium and heated and reacted is exemplified.

[0003] However, the method (1) requires not only a non-oxidizing mineral acid in an amount equal to or more than the by-equivalent ammonia equivalent, but also requires a high-level formulation to treat the residual liquid as wastewater. There are drawbacks. In the method (2), in order to remove the by-product ketone out of the system, the reaction must be performed at a relatively high temperature. As a result, the generation of impurities due to thermal decomposition of excess urea is promoted, and the impurities are removed. However, there is a drawback in that the quality of the target product is deteriorated, the usable time of the reaction solution is reduced, and the ammonia and ketone recovery lines are blocked due to precipitation of ammonium carbonate.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a method for producing hydrazodicarbonamide of high quality with a low yield of urea, low yield and high yield. Is to do.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have conducted a reaction under reduced pressure, and forcibly taken out by-product ketone and ammonia out of the system to obtain a high yield even at a low temperature. And found a method for producing hydrazodicarbonamide which can suppress the thermal decomposition of urea, and reached the present invention.

That is, the present invention relates to a method for producing hydrazodicarbonamide, comprising reacting a compound represented by the general formula (1) with urea under reduced pressure in the presence of a soluble salt.

[0007]

Embedded image 中 In the formula, R ₁ and R _{2 each} represent an alkyl group. These may be bonded to each other. A- is

Embedded image (In the formula, R ₁ and R ₃ represent an alkyl group. These may be bonded to each other.)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the compound represented by the general formula (1) include hydrazone and ketazine. Examples of ketazine include acetone azine and methyl ethyl azine. These can be used alone or as a mixture.

In the present invention, it is preferable to continuously add the compound of the general formula (1) to a mixture of urea, soluble salts and an aqueous solvent, and the addition rate may not be constant. Further, the compound of the general formula (1) and urea may be added at the same time. The amount of urea is 2 to 1 based on the compound of the general formula (1).
It is 5 moles, preferably 2.5 to 6.0 moles.

As soluble salts, they have no oxidizing ability,
Known compounds can be used as long as they are metal salts or ammonium salts having a solubility in water of 0.1% by weight or more. Specific examples include ammonium sulfate, ammonium nitrate, and sodium formate. These can be used either alone or as a mixture. The amount of the soluble salts to be used is 0.1 to the compound of the general formula (1).
The molar amount is from 01 to 3.0 times, preferably from 0.1 to 2.0 times.

The aqueous medium used in the present invention is water or water-soluble alcohols such as methanol and ethylene glycol. These can be used either alone or as a mixture.

In the present invention, by carrying out the reaction under reduced pressure, the by-product ketone and ammonia are forcibly removed from the system. It is desirable to carry out the reaction after attaching a sufficient fractionation pipe which requires a separating ability for volatile by-products, and the pressure in the system is 66500 to 99750 Pa, preferably 66500 to 86450 Pa. Reaction temperature is 60 ~
The temperature is 150C, preferably 60 to 105C. It may be changed depending on the degree of reaction progress.

[0013]

The present invention will be described in more detail with reference to the following examples.

Example 1 330 g (5.5 mol) of urea, ammonium sulfate 13
2 g (1.0 mol) and 272 g of water were added to a 11-neck four-necked flask equipped with a stirrer, a thermometer, a vacuum fractionator having a sufficient capacity, and a heating bath. The mixture was heated with stirring, and when the temperature of the mixture reached 102 ° C., 95% methyl ethyl ketazine 14 was supplied from a dropping pump provided in the four-necked flask.
7 g (1.0 mol) was constantly added dropwise over 3 hours. After the completion of the dropwise addition, the reaction was further performed for 1 hour. The reaction was carried out under reduced pressure using an aspirator in order to forcibly remove by-produced ketone and ammonia, and the degree of reduced pressure was appropriately adjusted to about 79800 Pa so that ketazine was not distilled off. The temperature of the reaction solution was 102 to 103 ° C.

After the completion of the reaction, the liquid temperature was cooled to 60 ° C., and the formed white crystals of hydrazodicarbonamide were filtered off, and then sufficiently washed with water. This white crystal is
Dry weighing at 10 ° C. yielded 108.3 g. This was 91.7% based on the amount of ketazine dropped. The selectivity of hydrazodicarbonamide based on urea was 98.4%, and no precipitation of ammonium carbonate was observed in a fractionating apparatus, a distillation line, or the like.

Comparative Example 1 The procedure of Example 1 was repeated, except that methyl by-product ketone and ammonia were extracted out of the system under normal pressure. The obtained hydrazodicarbonamide white crystals are 4
9 g. This is 4 to the dropped ketazine.
1.6%.

COMPARATIVE EXAMPLE 2 By-product methyl ethyl ketone and ammonia were taken out of the system under normal pressure, and the reaction temperature was set at 106 to 108 ° C.
The procedure was performed in the same manner as in Example 1, except that The amount of white crystals of the obtained hydrazodicarbonamide was 108.5 g. This was 91.9% based on the dropped ketazine. The hydrazodicarbonamide selectivity based on urea was 93.6%, and a large amount of ammonium carbonate was precipitated in a fractionating apparatus, a distillation line, and the like.

[0018]

According to the method of the present invention, hydrazodicarbonamide can be obtained in a high yield. Further, generation of impurities due to thermal decomposition of urea is also suppressed.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Isamu Masumoto F-term (reference) 4Y006 AA02 AB84 AC13 AC57 BA02 BA34 BA36 in Yokkaichi Plant, 2-4-1-16 Hinagahigashi, Yokkaichi City, Mie Prefecture BB14 BB31 BC10 BC11 4H039 CA73 CD10 CD90

Claims (5)

[Claims] 1. A method for producing hydrazodicarbonamide, comprising reacting a compound represented by the general formula (1) with urea under reduced pressure in the presence of a soluble salt. Embedded image 中 In the formula, R ₁ and R _{2 each} represent an alkyl group. These may be bonded to each other. A- is represented by the following: (In the formula, R ₁ and R ₃ represent an alkyl group. These may be bonded to each other.) 2. The method for producing hydrazodicarbonamide according to claim 1, wherein the reaction is carried out at 66500 to 99750 Pa. 3. The method for producing hydrazodicarbonamide according to claim 1, wherein the reaction is carried out while forcibly removing ketone and ammonia as by-products. 4. The method for producing hydrazodicarbonamide according to claim 1, wherein the reaction is carried out at 60 to 105 ° C. 5. The method for producing a hydrazodicarbonamide according to claim 1, wherein the compound represented by the general formula (1) is continuously introduced into the reaction system.