JP2000264887A - Production of glycoluril - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable glycoluril and a highly concentrated suspension thereof, effective as a controlled release fertilizer to be readily and extremely economically obtained by reacting glyoxal with urea. SOLUTION: A glyoxal aqueous solution is added dropwise to a urea-glyoxal mixed aqueous solution obtained by dissolving urea in a glyoxal aqueous solution so as to have a concentration from 50 wt.% to the saturated concentration in the presence of an acid catalyst, and the obtained mixture is reacted under the condition of the molar ratio of the urea to the glyoxal based on the whole reaction amount, regulated so as to be 2.01-2.3, and the temperature of 50-100 deg.C to produce the objective glycoluril.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing glycoluril. More specifically, the present invention relates to a method for producing glycoluril, which is also effective as a slow-release fertilizer, and a high-concentration suspension thereof.

[0002]

2. Description of the Related Art For example, US Pat. No. 3,061,423.
The glycoluril is represented by the following formula [1]

[0003]

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These compounds have the following structure: they are used as raw materials for anti-wrinkling agents and wet reinforcing agents for fibers, fabrics, papers, etc., and are the same as isobutylidene diurea (IB) and crotonylidene diurea (CDU), or It has extremely useful properties as a slow release fertilizer.

[0005]

However, glycoluril is expensive because (1) it is produced using expensive glyoxal as a raw material. (2) In most production methods, urea or an aqueous urea solution is added to an aqueous solution of glyoxal and reacted under acidic conditions. The yield of the reaction product is low, and the loss of raw materials is large. It is inevitable that it will be expensive. (3) In terms of yield, glycol monourein (4, 5
-Dihydroxy-2-imidazolidinone) in most cases, the reaction is carried out with the molar ratio of urea to glyoxal much higher than 2, and the cost of raw materials is relatively high. (4) When the reaction is performed in the presence of an acid catalyst and the reaction is a large reaction heat, and when an acid-resistant glass lining reactor or the like is used, a large cooling device is required to prevent damage due to thermal strain. , Equipment costs are high. In fact, glycoluril itself has been partially used for powder coatings, and has the disadvantage that it is too expensive to use in large quantities.

Regarding the method for producing glycoluril, for example,
If Soil Sci. PlantNutr. ,33
(2) 291-298, 1987 (Toshio Sh
imizu) on production conditions and yield.
Have been. According to the report, hydrochloric acid was used as a reaction catalyst.
Use the solution at a concentration of 5 to 10% based on the total volume of the reaction solution.
At a temperature of 60 to 80 ° C. and a reaction time of 1.5 to 3 hours,
Further, the filtrate is collected to recover unreacted glyoxal.
Is recycled six times, for a total yield of 91%
It is stated that.

[0007]

Means for Solving the Problems In view of the above facts, the present inventors have studied problems relating to the conventional production of glycoluril. That is, (1) reducing the yield of glycoluril by reducing by-products,
Can you lower the manufacturing cost? (2) Since an aqueous glyoxal solution is used, can the amount of water used be reduced as much as possible to increase the processing capacity and reduce the production cost? (3) Is the molar ratio of urea to glyoxal as close to the theoretical value as possible, and can the unreacted glyoxal be reduced to omit the recovery step and reduce the raw material cost and equipment cost? (4) Is there a method to remove the reaction heat efficiently and without affecting the production cost? Focusing on the points, etc., they conducted intensive research and examination. as a result,
The inventors have found that the above problem can be solved by combining the urea concentration, the reaction conditions, the raw material molar ratio, and the method of adding the catalyst, and have reached the present invention.

That is, the process for producing glycoluril according to the present invention is a process for producing glycoluril by reacting urea and glyoxal in an aqueous solution, wherein the urea / glyoxal mixture is prepared by dissolving urea in a glyoxal aqueous solution at a concentration of 50% by weight to a saturated concentration. In an aqueous solution, in the presence of an acid catalyst,
An aqueous glyoxal solution is added dropwise, and the reaction is performed under the conditions that the molar ratio of urea / glyoxal in all the reactants is 2.01 to 2.3 and the reaction temperature is 50 to 100 ° C. is there. According to the present invention, it is possible to obtain glycoluril effective as a slow-release fertilizer and a high-concentration suspension thereof by a very inexpensive, easy and safe operation.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, glyoxal, which is a raw material for producing glycoluril, has the following formula [2]

[0010]

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The compound is an easy-to-handle aldehyde that has no irritating odor and is less toxic than formalin and the like. This is industrially produced by a nitric acid oxidation method of acetaldehyde or an oxidative dehydrogenation method of ethylene glycol. Further, it is usually sold as an aqueous solution having a concentration of about 40% by weight, and its main uses are a soil stabilizer, a fiber treatment agent and the like. In the production of glycoluril, 1 mol of the above glyoxal and 2 mol of urea react as shown in the following formula [3] to produce 1 mol of glycoluril.

[0012]

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Since the formed glycoluril has low solubility in water, it usually precipitates as white crystals from the reaction solution.

The above-mentioned glycoluril formation reaction is a two-stage reaction. First, 1 mole of urea is added to 1 mole of glyoxal, and glycoluril is formed by a dehydration reaction. At this time, it is well known that, when the urea concentration is low, glyoxal monourein is hydrolyzed to generate an intermediate product such as hydantoin. Therefore, in order to suppress the formation of intermediate products and to increase the yield of glycoluril alone, it is essential that the molar ratio of urea to glyoxal is 2 or more, while the excess urea is recovered. By doing so, it is possible to suppress the loss, but on the contrary, the cost of the recovery equipment is increased and the production cost is increased. In addition, if there is too much urea, there are problems such as an increase in the reactor volume and difficulty in purification and washing when glycoluril is separated by filtration.Therefore, it is necessary to minimize the molar ratio of urea to glyoxal as much as possible. Met. However, when glycoluril is used as a raw material for a liquid fertilizer as a suspension, the molar ratio of urea / glyoxal may be changed according to the conditions of use. Can be greatly suppressed, and as a result, a product having no problem can be obtained even if the reaction solution is directly used as a fertilizer.

In the reaction of the present invention, it is preferable to use glyoxal as an aqueous solution having a concentration of 30 to 45% by weight. In general, the lower the concentration of the aqueous glyoxal solution, the higher the conversion rate to glycoluril.However, in the present invention, when the concentration of the product is low, the treatment efficiency is reduced accordingly. preferable.

In the reaction of the present invention, urea has a concentration of 50.
It is used as a mixed aqueous solution with glyoxal at a concentration of from% by weight to a saturated concentration. Even if it is less than 50% by weight, the production of glycoluril is sufficiently possible, but since glyoxal is used as an aqueous solution, the treatment efficiency can be improved by reducing the amount of water. The molar ratio of urea to glyoxal is preferably as low as possible in the range from 2.0 to 2.3.

One specific example of the production of glycoluril is as follows: (1) First, a mixed aqueous solution of urea and glyoxal is prepared, a predetermined amount of acid is added as a catalyst, and then the temperature is raised to a predetermined temperature. (2) Next, a predetermined amount of glyoxal is added while stirring the above solution. (3) Aging is performed for a predetermined time while maintaining the temperature of the reaction solution to complete the reaction. (4) Next, neutralize by adding an alkali, and allow to cool,
A suspension containing the glycoluril reaction product is obtained.

In the present invention, the glycoluril-containing suspension obtained as described above can be used alone as a slow-release fertilizer by separating glycoluril by filtration, and is added for neutralization. If a compound having a fertilizing effect such as ammonia is used as the alkali, it can be used as a raw material of the liquid fertilizer as a suspension.

The reaction temperature between urea and glyoxal is usually in the range of 50 to 100 ° C. 50
Although the reaction proceeds even at a temperature lower than ℃, it is not efficient because it requires a long time. On the other hand, if the temperature exceeds 100 ° C., the hydrolysis reaction of urea remarkably occurs, which is not preferable.

In the reaction of the present invention, the generated reaction heat (20 kcal / mol) is advantageously obtained by a method of cooling, condensing and circulating the vapor generated from the reaction solution under reduced pressure, that is, by a reflux cooling method. Can be removed. Therefore, it is preferable to carry out the reaction at a reduced pressure in the range of 15 kPa to normal pressure. In general, as a method for removing the heat of reaction, various heat exchangers are brought into direct contact with the reaction solution to cool it.However, in the suspension of glycoluril, which is the reaction solution of this reaction, crystals adhere to the vessel wall. Direct cooling is disadvantageous because the heat exchange efficiency of the heat exchanger is reduced.

The reaction of the present invention can preferably proceed in the presence of an acid catalyst. Specific examples of the acid catalyst include mineral acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, or formic acid and acetic acid. Organic acids such as can be used. However, in the present invention, the reaction solution is neutralized after completion of the reaction,
And since it is assumed that it will be used as fertilizer, its neutralized form is harmless to plants,
Or rather, it is preferably in the form of a fertilizing component. From these aspects, it is preferable to use a mineral acid such as hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid as the acid catalyst used in the reaction in the present invention. The amount of the acid catalyst used also depends on the type of acid used, and suitable conditions are different. For example, when hydrochloric acid is used, it is usually 1 to 1 of the total weight of the raw materials (glyoxal solution + urea solution + hydrochloric acid solution).
An amount in the range of 0% by weight (as hydrochloric acid) is used.

The acid catalyst may be added to the urea / glyoxal mixed aqueous solution first, or the acid catalyst may be added to both the urea / glyoxal mixed aqueous solution and the glyoxal solution added dropwise. A reaction may be performed. In any case, the amount of the acid catalyst used is 1 to 1 of the total weight of the raw materials (glyoxal solution + urea solution + hydrochloric acid solution).
The reaction is carried out within a range of 0% by weight (as hydrochloric acid).

The time required for the reaction between urea and glyoxal varies depending on the reaction conditions, but is usually in the range of 30 minutes to 9 hours. The conversion of glycoluril is determined by the time required for the reaction between urea and glyoxal to be 1-3.
By adding an acid catalyst to the urea-glyoxal mixed aqueous solution within a time range, about 70 to 90% of glyoxal can be converted to glycoluril. When the time is in the range of 3 to 9 hours, the hydrolysis of urea is suppressed by adding an acid catalyst to both the urea-glyoxal mixed aqueous solution and the glyoxal aqueous solution, and the yield of glycoluril is reduced to about 70 to 90%. Can be enhanced.

In the present invention, the acid catalyst used in the reaction between urea and glyoxal is neutralized with an alkali after the reaction. The alkali used at this time is, as in the case of the acid catalyst described above, from the viewpoint that it may be used as a fertilizer after neutralization, is the form after neutralization a form that does not harm plants? Rather, it is preferably the effectiveness of the fertilizer. In this sense, it is preferable to use ammonia or potassium hydroxide as the alkali used for neutralization in the present invention. The preferred range of the neutralization reaction varies depending on the form of use of the neutralized product solution, but usually an alkali is added so that the pH of the product solution is about 4 to 7. .

The raw material glyoxal in the present invention is generally produced by oxidizing monoethylene glycol with molecular oxygen or nitric acid of acetaldehyde. Since a very small amount of nitric acid as an oxidizing agent remains in glyoxal produced by nitric acid oxidation of acetaldehyde, the reaction of the present invention produces a small amount of a nitrated organic compound by an acid catalyst. In addition, the product contains a large amount of high molecular weight compounds, and the yield of glycoluril is significantly reduced. The reason for this cannot be specified, but since the purity is the same, it is considered that trace impurities in the raw materials due to differences in the production methods have some adverse effect. Therefore, in the production of glycoluril, it is preferable to use glyoxal obtained by oxidizing monoethylene glycol with molecular oxygen in order to obtain glycoluril in high yield while ensuring safety during production.

[0026]

EXAMPLES Hereinafter, the method for producing glycoluril of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The percentages in the following examples are based on weight.

Example 1 A 40% aqueous glyoxal solution synthesized by oxidizing monoethylene glycol with molecular oxygen was used, and a 40% aqueous glyoxal solution was placed in a 4-liter separable flask.
Then, 00 g, 900 g of urea, and 100.5 g of 35% hydrochloric acid are added, and dissolved by heating to 80 ° C. in a water bath. When the temperature reaches 80 ° C., 500 g of a 40% aqueous glyoxal solution is added to about 1 g.
It is dropped in over time and allowed to react. The reaction molar ratio of urea to glyoxal is 2.175. The temperature of the reaction solution is controlled so as not to exceed 85 ° C. The reaction solution was heated to a temperature of 8
While keeping the temperature at 5 ° C., the reaction is left for 3 hours to complete the reaction. This is left to cool, and 25.5 g of 25% aqueous ammonia is added to adjust the pH of the reaction solution to 6.0. The amount of cake formed by filtering the reaction solution was measured to be 935 g, and the suspension concentration was 44.6%. The purity of glycoluril in the cake was determined by liquid chromatography to be 98.0%, and the yield of glycoluril based on glyoxal was 93.4%.

Example 2 A 40% aqueous glyoxal solution synthesized by oxidizing monoethylene glycol with molecular oxygen was used, and a 40% aqueous glyoxal solution was placed in a 2-liter separable flask.
Then, 00 g, 380 g of urea, and 56 g of 35% hydrochloric acid are added, and the mixture is heated and dissolved in a water bath up to 80 ° C. When the temperature reaches 80 ° C., 200 g of a 40% aqueous glyoxal solution is dropped in over 40 minutes to cause a reaction. The reaction molar ratio of urea to glyoxal is 2.3. The temperature of the reaction solution is controlled so as not to exceed 90 ° C. The reaction solution is left for 3 hours while maintaining the temperature at 90 ° C. to complete the reaction. This is left to cool, and 28.8 g of 25% aqueous ammonia is added to adjust the pH of the reaction solution to 6.1. The reaction solution was filtered, and the amount of the formed cake was measured to be 370 g.
It was 5.2%. When the glycoluril purity in the cake was measured by liquid chromatography, it was 98.1%.
And the yield of glycoluril based on glyoxal was 91.8%.

Example 3 Using a 40% aqueous glyoxal solution synthesized by oxidizing monoethylene glycol with molecular oxygen, 300 g of a 40% aqueous glyoxal solution, 515.1 g of urea and 35% of 35% were placed in a 3-liter decompressible separable flask. 60 g of hydrochloric acid is added and dissolved by heating to 70 ° C. in a water bath. The temperature is 70 ° C
, While adjusting the pressure to a reduced pressure of 32 kPa,
300 g of a 0% glyoxal aqueous solution is added dropwise over 40 minutes to cause a reaction. The reaction molar ratio of urea to glyoxal is 2.075. The temperature of the reaction solution is controlled to 70 ° C. by circulating the generated steam by a reflux condenser. While maintaining the reaction solution at a temperature of 70 ° C., the reaction is left for 1 hour to complete the reaction. After the pressure was returned to normal pressure, the mixture was allowed to cool, and 13.8 g of 25% aqueous ammonia was added to adjust the pH of the reaction solution to 6.4. The amount of cake formed by filtering the reaction solution was 547.5 g, and the concentration of the suspension was 46.0%. The purity of glycoluril in the cake was measured by liquid chromatography.
The yield of glycoluril based on glyoxal was 91.1%.

Example 4 A 40% aqueous glyoxal solution synthesized by oxidizing monoethylene glycol with molecular oxygen was used. In a 1-liter decompressible separable flask, 80 g of a 40% aqueous glyoxal solution, 186.2 g of urea, and 35% Add 14 g of hydrochloric acid and heat and dissolve in a water bath up to 80 ° C. When the temperature reaches 80 ° C., while adjusting the pressure to a reduced pressure of 56 kPa,
A mixed solution of 14 g of 14% hydrochloric acid and 120 g of a 40% aqueous glyoxal solution is dropped and reacted over 30 minutes. The reaction molar ratio of urea to glyoxal is 2.25.
The reaction solution cools the steam generated by the reflux cooler and circulates to control the temperature to 90 ° C. While keeping the temperature of the reaction solution at 90 ° C., it is left for another 1.5 hours to complete the reaction. After the pressure was returned to normal pressure, the mixture was allowed to cool, and 14.4 g of 25% aqueous ammonia was added to adjust the pH of the reaction solution to 6.1. The amount of cake formed by filtering the reaction solution was measured to be 189 g, and the concentration of the suspension was 44.7%. The purity of glycoluril in the cake was determined by liquid chromatography to be 98.1%, and the yield of glycoluril based on glyoxal was 92.5%.

Comparative Example 1 A reaction was carried out in exactly the same manner as in Example 1 except that a 40% aqueous glyoxal solution synthesized by nitric acid oxidation of acetaldehyde was used, and the reaction was left to complete. This is 2
5.7 g of 5% aqueous ammonia is added to adjust the pH of the reaction solution to 6.3. After allowing to cool, the reaction liquid was filtered to form a partially viscous cake.
g and the suspension concentration was 38.4%. The purity of glycoluril in the cake was determined by liquid chromatography to be 71.2%, and the yield of glycoluril based on glyoxal was 63.4%.

[0032]

According to the method of the present invention, glyoxal and urea are reacted to produce glycoluril, which is effective as a slow-release fertilizer by a simple and safe operation, and a high-concentration suspension thereof in a very high yield and extremely economical. It is possible to obtain it.

Claims (4)

[Claims] 1. A method for producing glycoluril by reacting urea and glyoxal in an aqueous solution, wherein a urea / glyoxal mixed aqueous solution in which urea is dissolved in an aqueous glyoxal solution at a concentration of 50% by weight to a saturated concentration is added to an aqueous solution of urea / glyoxal in the presence of an acid catalyst. Glyoxal aqueous solution is added dropwise, and the urea / glyoxal molar ratio in all the reactants is 2.01 to 2.3, and the reaction is carried out under the conditions of a reaction temperature of 50 to 100 ° C. Manufacturing method. 2. The process for producing glycoluril according to claim 1, wherein the acid catalyst is hydrochloric acid and the concentration of the catalyst in all the reactants is 1 to 10% by weight. 3. The process for producing glycoluril according to claim 1, wherein glyoxal obtained by oxidizing ethylene glycol with molecular oxygen is used. 4. The process for producing glycoluril according to claim 1, wherein the reaction is carried out under reduced pressure.