JPH0665171A - Production of oxamide - Google Patents

Abstract

PURPOSE:To obtain a granular oxamide useful as a slow-acting nitrogen fertilizer by reacting a mixture of an oxalic diester and an aliphatic alcohol with ammonia under a specific condition and granulating. CONSTITUTION:A mixture of an oxalic diester of the formula (COOR)2 (R is 1-6C alkyl) and an aliphatic alcohol is reacted with ammonia. After the reaction is completed, 5-40wt.% aliphatic alcohol is left in the reaction mixture and oxamide is granulated. Then the granulated oxamide is dried by heating and the aliphatic alcohol is evaporated and removed to form granular oxamide. Further the granulated material is mixed with 5-20wt.% water, humidified and dried by heating to give the objective granular oxamide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to granulation of oxamide produced after reacting oxalic acid diester with ammonia in the presence of an aliphatic alcohol, and then removing the aliphatic alcohol from the granulated product. By drying and further moistening the granulated product (preliminary granular oxamide) and then heating and drying, the water that retains the hardness and granularity of the oxamide granules in order to fully exert the effect as a slow-release nitrogen fertilizer The present invention relates to a method for producing granular oxamide, which has particularly excellent stability.

[0002]

2. Description of the Prior Art A method for producing oxamide is represented by the following formula. (In the formula, R represents a lower alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group.) Oxamide [(CONH ₂ ) ₂ obtained by the above-mentioned production method ] Is excellent as a slow-release fertilizer due to its low solubility in water, and has already been put to practical use.
However, when oxamide is used in powder form, loss due to runoff and scattering occurs, and the slow-release characteristics are not fully utilized. Therefore, it is desirable to limit the dispersibility in the form of granules or the like in order to fully exhibit the characteristics in any use situation. Also,
It is well known that the synthesized oxamide can exhibit its properties as a slow-release fertilizer if it is hard after granulation and the particles do not easily disintegrate in water and the shape is stable and stable.

However, oxamide (particularly oxamide fine powder) has very poor granulation property because it has no physical properties, especially solubility in a solvent such as water. for that reason,
In the known granulation method, for example, "JP-A-59-16952" is used.
7 ”, an expensive binder such as polyvinyl alcohol (PVA) and a large amount of energy are required, or“ JP-A-59-59 ”.
It was a very inefficient manufacturing method such as the compression granulation method under high pressure by a tableting machine shown in "-169527". Further, the production method of these granular oxamides has a problem that the operation and the apparatus are complicated and the production cost and the equipment cost are high.

[0004] The present inventors have found that in order to solve these problems, it is energy saving, moreover, as a simplified manufacturing process "method for producing a granular oxamide at once from oxalic acid diester", "oxalate A method for producing granular oxamide by granulating by allowing an aliphatic amide, which is a by-product of this reaction, to remain in the reaction mixture by degrading the diester to produce oxamide. Filed a patent application on July 10, 2010. However, although the granular oxamide can be easily obtained from the oxalic acid diester by the method of this earlier application, the crush hardness of the granular oxamide obtained by this method is 1 to 1.4 kg.
In some cases, the hardness of the granular oxamide is not sufficient to sufficiently exhibit the characteristics of oxamide as a slow-release fertilizer, as described above. Further, the granular oxamide obtained by the above-mentioned method has a powdery surface, and the oxamide fine powder adheres to the inner surface of the bag for packaging, or when it is handled manually, the handling of this granulated product Alternatively, dust may be generated during transportation, which is not preferable in terms of environmental hygiene.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to granulate an oxalic acid diester by subjecting it to an oxamide by decomposing the oxalic acid diester to leave an aliphatic alcohol, which is a by-product of the reaction, in the reaction mixture. The granular oxamide (preliminary granular oxamide) can be formed all at once by further heating the granulated oxamide after moistening and then heating and drying the granulated product to have a high hardness and to be stable in water. It is an object of the present invention to provide a completely new and industrial method for producing granular oxamide, which can obtain granular oxamide having no surface dusting at a high yield.

[0006]

The present invention is based on the general formula (COO
R) ₂ (wherein R represents 1 to 6 carbon atoms)
Is a lower alkyl group. ) In the method for producing oxamide by supplying ammonia to a mixture of oxalic acid diester and aliphatic alcohol to react with each other, after the completion of the reaction, 5 to 40% by weight of aliphatic alcohol remains in the reaction mixture to give oxamide. Is granulated, and the granulated product of the oxamide is dried by heating to evaporate the aliphatic alcohol (preferably up to 5% by weight) and removed to form a granular oxamide (preliminary granular oxamide). The present invention relates to a method for producing granular oxamide, which comprises adding 5 to 20% by weight of water to the granulated product to moisten it, and then heating and drying to obtain granular oxamide.

The production method of the present invention is roughly characterized in that oxalic acid diester is decomposed by decomposing to produce oxamide, and subsequently, the content of the aliphatic alcohol as a by-product of the decomposing reaction is 5-40% by weight. While the reaction mixture remains wet with the aliphatic alcohol as is, granulate (preferably under stirring of the mixture) a reaction mixture mainly containing the oxamide formed to form granular oxamide, and After removing the aliphatic alcohol from the granulated product and drying, 5 to 20% by weight of water is added to the granulated product to humidify it, and then the product is heated and dried to obtain granular oxamide. By this, it is a method of producing oxamide that has high hardness, is stable in water, and can produce “granular oxamide” without graininess on the grain surface with high yield. .

In the manufacturing method of the present invention, first, Japanese Patent Application No. 3-
By the method described in the specification of No. 128834 and the method described in the specification of the prior application (filing date: July 10, 1992), oxamide is produced from oxalic acid diester and ammonia, Then, the granulated product (preliminary granular oxamide) is formed all at once.

That is, in the present invention, first, a mixture (preferably a molten mixture) of oxalic acid diester represented by the above general formula (COOR) ₂ (R is as described above) and ammonia is added to ammonia. To produce an oxamide, and after the end of the reaction,
The reaction mixture is left to contain 5 to 40% by weight of an aliphatic alcohol, and if necessary, the oxamide is granulated while stirring the reaction mixture, and the granulated product of the oxamide is further dried by heating. It is preferred to form the pre-granular oxamide by evaporating and removing the aliphatic alcohol with.

In the formation of the above-mentioned preliminary granular oxamide, the oxalic acid diester is preferably 60 to 10.
0% by weight, and preferably 0% aliphatic alcohol
It is a mixture of about 40% by weight, and the mixture of both may be heated to a temperature equal to or higher than the melting point and used as a homogeneous molten solution for the reaction with ammonia.

In the formation of said pre-particulate oxamide, the reaction is initiated by supplying ammonia, preferably in the form of gas, with stirring of said melt, and with forced mixing of the reaction mixture in the reaction mixture. In the state where the content of the aliphatic alcohol of 5 to 40% by weight is maintained,
It is preferable to continuously supply gaseous ammonia to the reaction system to form a mixture of an oxamide and an aliphatic alcohol containing high-purity oxamide.

The ammonia used in the above reaction may be a mixed gas of ammonia, in which case the content of ammonia is preferably 50% by volume or more, particularly 60% by volume.
Any mixed gas of ammonia and an inert gas contained above may be used. Examples of the inert gas include nitrogen gas and argon gas.

As the aliphatic alcohol used in the above reaction, an aliphatic alcohol having an alkyl group having 1 to 6 carbon atoms is used, and as the aliphatic alcohol, methyl alcohol, ethyl alcohol, propyl alcohol,
Butyl alcohol, pentyl alcohol, and hexyl alcohol are preferable, and as the aliphatic alcohol used for the reaction, it is preferable to select and use an aliphatic alcohol having the same alkyl group as that of the oxalic acid diester used for the reaction. An aliphatic alcohol having the same alkyl group as the oxalic acid diester is preferable because the alcohol produced by the reaction and evaporated and separated and condensed can be recycled and reused in the above reaction. In addition, aliphatic alcohols having different alkyl groups may be used as long as they can be treated after separation of alcohols.

In the case of forming the above-mentioned preliminary granular oxamide, the state of the system in accordance with the progress of the above-mentioned reaction, along with the change of its composition, from the start of the reaction to the progress of the reaction,
It gradually changes from a liquid form to a slurry form, a paste form, and a powdery oxamide wet with an aliphatic alcohol. Next, after the completion of the reaction, the produced oxamide does not become a dry powdery oxamide, but shifts to a granulation operation while being sufficiently wet with the aliphatic alcohol as described above.

The composition of the reaction mixture has a large amount of unreacted oxalic acid diester at first, but as the reaction with ammonia progresses, the oxalic acid diester is consumed in the decomposition reaction with ammonia and the content ratio decreases. On the contrary, the reaction products (for example, oxalic acid monoester monoamide and oxamide) of the decomposition by addition increase. further,
The composition of the reaction product is such that, in the final stage of the reaction, the oxalic acid monoester monoamide is substantially eliminated by the additional decomposition reaction to give a highly pure oxamide.

[0016] In the formation of the above-mentioned preliminary granular oxamide, granulation and heating and drying from the above reaction can be carried out in one apparatus to obtain granular oxamide (preliminary granular oxamide) having uniform particle diameters at once. In order to perform such a series of operations, the reactor is a device having a stirring function and / or a granulating function from the reaction stage described above, and external heating / cooling having a structure capable of heating and cooling. It is preferable that the device is a jacketed device. In particular, it is desirable to use, for example, a stirring-type granulating dryer in a composite-type granulating device capable of performing sufficient stirring and mixing at each stage of the phase change accompanying the progress of the above-mentioned reaction.

The use of a stirring-type granulating / drying device having the above-mentioned composite function means that the reaction operation by the stirring function is carried out by introducing ammonia gas into a mixture of liquid oxalic acid diester and aliphatic alcohol. It is advantageous for liquid contact reaction, and due to granulation function and heating / cooling function,
After the above-mentioned reaction operation, from the formation of the granulated product to the heat treatment for evaporating and removing the aliphatic alcohol in the granulated product, it is possible to carry out in the same apparatus, so that the homogeneous preparatory granules are finally obtained. Oxamide can be obtained all at once, which is preferable. By using this apparatus, the operation can be simplified and the equipment cost and manufacturing cost of the oxamide manufacturing apparatus can be significantly reduced. However, if the production volume increases, each operation can be performed by a separate device.

Each operation in the formation of the above-mentioned preliminary granular oxamide can be carried out batchwise as a matter of course.
Preparation of melt containing oxalic acid diester, supply of ammonia gas, mixing of reaction mixture, adjustment of content of aliphatic alcohol, granulation, heating, drying, cooling, etc., and granulation of high-purity oxamide It can be continuously carried out by continuously taking out the product (preliminary granular oxamide) in combination.

In the reaction for forming the above-mentioned preliminary granular oxamide, while the content of the aliphatic alcohol in the reaction mixture is maintained at 5 to 40% by weight, the gaseous ammonia is continuously supplied to the reaction system, Finally, it is of particular importance to obtain high purity oxamide, substantially free of oxalic acid monoester monoamide, which is a by-product that adversely affects plant growth. Further, by maintaining the content of the aliphatic alcohol in the range of 5 to 40% by weight, the content of the aliphatic alcohol after the end of the reaction can be adjusted to a concentration advantageous for the next granulation operation.

The reaction temperature in the reaction for forming the above-mentioned pre-particulate oxamide is at least a temperature at which the unreacted mixture of oxalic acid diester and aliphatic alcohol in the reaction mixture can be maintained in a molten state. It is preferable that the temperature is such that the content of the aliphatic alcohol in the reaction mixture can be maintained in the above range.
It is particularly advantageous that the temperature is around the boiling point of the aliphatic alcohol used (boiling point ± 30 ° C., especially boiling point ± 20 ° C.).

The reaction pressure in the above reaction is most preferably atmospheric pressure in the production process, but it may be under reduced pressure or under pressure,
It is preferably performed under a pressure condition of 10 torr to 10 kg / cm ² G. From the viewpoint of reaction rate, a higher one is advantageous, but an unnecessarily high pressure is disadvantageous in terms of equipment cost. A reduced pressure may be applied during granulation and drying. In particular, the drying is advantageous in reducing the pressure in terms of energy saving.

The reaction time in the above reaction may be any time until the high-purity oxamide can be produced from the oxalic acid diester in the decomposition reaction under the above reaction conditions, but is preferably 0.5. It is about 5 hours, particularly preferably 1 to 3 hours.

The concentration of the aliphatic alcohol at the time of granulation in the formation of the above-mentioned preliminary granular oxamide has a correlation with the average particle size of the finally obtained preliminary granular oxamide, and the desired average particle size can be adjusted by adjusting the concentration. Pre-particulate oxamide of diameter can be obtained. Therefore, the concentration of the aliphatic alcohol during granulation varies depending on the required particle size,
In order to produce the preliminary granular oxamide, it may be adjusted to an appropriate concentration within the range of 5 to 40% by weight depending on the set particle size. By maintaining a constant concentration of the aliphatic alcohol within this range, the particle size distribution of the granulated product can be controlled. When the amount of the aliphatic alcohol is less than 5% by weight, the amount of granules or fine powder having a particle size of 1 mm or less increases, and when the amount of the aliphatic alcohol exceeds 40% by weight, the granulation property is remarkably deteriorated. In order to obtain a fertilizer having a particle size of 2 to 4 mm, which is required for general fertilizer, with a good yield, it is preferably 10 to 30% by weight, particularly preferably 15 to 25% by weight.

During the reaction, the content of the aliphatic alcohol in the reaction mixture is maintained at 5 to 40% by weight,
When the reaction is complete, an aliphatic alcohol-moist powder oxamide is obtained. Next, when the granulation is started, the concentration of the aliphatic alcohol at the time of granulation is adjusted and set. The adjustment involves adjusting the temperature of the jacket while adjusting the concentration of the aliphatic alcohol in the system to obtain the corresponding set particle size. The concentration of the aliphatic alcohol at the time of granulation is set within a certain range of 5 to 40% by weight by evaporating or supplementing to reduce the concentration. In order to maintain the necessary set concentration of the aliphatic alcohol, fine analysis is performed by appropriately returning the distilled aliphatic alcohol into the system when the amount is small, while performing an appropriate analysis. When the amount is large, the concentration is adjusted by evaporating and removing the excess amount up to the set concentration of the aliphatic alcohol, and the concentration of the aliphatic alcohol is adjusted to start the granulation.

The granulation of the preliminary granular oxamide is carried out after adjusting the concentration of the above-mentioned aliphatic alcohol and then at the boiling point of the aliphatic alcohol using the jacket temperature for maintaining the concentration, preferably 20 to 250 ° C. It is preferable to adjust The pressure in the system may be reduced pressure,
The pressure may be the same as during the reaction, preferably 10 torr
Granulation is performed under a pressure condition of 10 kg / cm ² G. Furthermore,
The stirring speed varies depending on the apparatus shape, apparatus capacity and stirring blade shape, but a range of 10 to 500 rpm is preferably selected, and the required granulation time for granulation is preferably 1 to 6
By carrying out in the range of 0 minute tube, the pre-granular oxamide of the set particle size is formed, and the homogenization of the particles is achieved.

After the granulation operation of the preliminary granular oxamide is completed, the preliminary granular oxamide is dried in the same apparatus where the reaction and the granulation operation were performed (preferably in the stirring type granulation apparatus). From the end of granulation, the stirring speed of the stirring blade is changed to a slow speed of preferably 1 to 200 rpm, and drying is carried out for preferably 0.5 to 2 hours under the condition that the preliminary granular oxamide formed into particles by granulation is not destroyed. The granulated product is dried so that the concentration of the aliphatic alcohol is 0 to 5% by weight. The aliphatic alcohol used at the time of granulation is prepared by heating the jacket temperature to a temperature equal to or higher than the boiling point of the aliphatic alcohol in the system to evaporate and remove the aliphatic alcohol in the system, thereby preserving the above-mentioned concentration range. This produces granular oxamide. The pressure for removing the aliphatic alcohol in the system may be under pressure or under reduced pressure, but is preferably 10
Drying is performed under a pressure condition of torr to 10 kg / cm ² G, but it is desirable to use reduced pressure in order to shorten the drying time.

In the granulated product (preliminary granular oxamide) after drying, it is desirable to completely evaporate and remove the aliphatic alcohol, but in some cases, the concentration of the aliphatic alcohol is 0.1 to 0.1. Part of the aliphatic alcohol may be about 5% by weight. This is because in the subsequent humidification operation with water, the aliphatic alcohol in the preliminary granular oxamide lowers the surface tension of water, which is convenient for efficiently introducing water into the pores of the particles, and the effect of the present invention is obtained. It can be exerted more effectively. However, making it higher than necessary is disadvantageous in that in the final drying step, the device for recovering the aliphatic alcohol becomes complicated or the wastewater treatment is expensive.

When the production amount is large, the above-mentioned operation for drying the preliminary granular oxamide can be carried out in an apparatus different from the reaction and granulation operations. In this case, a known dryer such as a conical dryer, a rotary dryer, an aeration band dryer, an aeration rotary dryer, a fluidized bed dryer, and a vibration fluidized dryer can be used as the drying device, but the evaporated and removed aliphatic In order to condense and collect alcohol, it is preferable to use an indirect heating system device rather than a direct heating system using hot air.

After the drying operation of the above-mentioned preliminary granular oxamide is completed, it is preferably 5 to 20% by weight with respect to the granulated product.
Of water is added (eg, water or steam is added or sprayed) and the granulation is moistened with water. When the amount of water added is less than 5% by weight, the effect of improving the hardness of the particles is small,
On the other hand, when the amount is more than 20% by weight, the effect is decreased, so that the range of the addition amount is particularly important.

In the operation of adding water to the above-mentioned pre-granular oxamide, in order to uniformly moisturize the granulated product, preferably the granulated product is tumbled, stirred or flowed while a single nozzle or a plurality of nozzles are used. Therefore, it is desirable to spray and add water or steam. The apparatus for performing the humidifying operation can be continuously performed in the apparatus in which the above-mentioned aliphatic alcohol is dried, or another container rotary type or stirring type mixer can be used. Alternatively, the granulated material can be humidified while being transferred in a feeder such as a belt conveyor or a screw feeder.

The pressure during the humidifying operation is most preferably normal pressure in the manufacturing operation, but it may be under reduced pressure or under increased pressure, preferably under a pressure condition of 10 torr to 10 kg / cm ² G. Reduced pressure is advantageous for efficiently introducing water into the pores of the particles. On the other hand, pressurizing is not particularly advantageous, but rather disadvantageous in terms of equipment cost.

The temperature at the time of humidification is not particularly limited, but is 5 to
It is performed at 180 ° C, preferably in the range of 20 to 90 ° C.
The temperature of water to be used is not particularly limited, but is 5 to 100.
C., preferably 10 to 90.degree. When steam is used, the steam pressure is preferably 0.
The use of saturated steam in the range 5-20 kg / cm ² G is desirable. The heating / drying operation in the final step may be performed immediately after the above-mentioned humidifying operation is completed.
When the moistened granulated product is aged for 60 minutes, preferably about 2 to 30 minutes, the added water can be sufficiently permeated into the inside of the granulated product, and finally a high quality granular oxamide is obtained with high hardness. It is particularly suitable because it can be done.

After the above humidification operation is completed (and if necessary, after the aging after the above humidification operation is completed), the granulated product is heated to 100 ° C. or higher, particularly 100 to 350 ° C., and more preferably 120 to 250. After heating to ℃ and drying, water is evaporated to substantially (in the granule, preferably about 2.0% by weight or less, particularly preferably 1.0% by weight or less, further preferably 0.5% by weight). It is preferable to remove (up to the following water content) to produce the target granular oxamide. The heating and drying operation is performed for 3 minutes or longer, preferably 10 minutes or longer, particularly preferably 20 to 60 minutes. If the drying is performed for a time shorter than 3 minutes, the effect of improving the hardness of the particles becomes small, which is not desirable. In the present invention, the granulated product shrinks and is consolidated in the course of this heating / drying operation, and as a result, the hardness of the granule is improved, which is a particularly important operation.
The operating pressure in heating and drying is preferably atmospheric pressure in view of the manufacturing operation conditions. In some cases, it can be carried out under pressure, but this is disadvantageous in terms of device cost.

In the drying of the humidified granulated product, the removal rate of water evaporated and removed from the granulated product per unit weight of the granulated product per unit time is about 0.5 to 3.
It is preferably 0 g / kg / min, particularly about 1.0 to 15 g / kg / min. That is, if the removal rate by evaporation of water from the humidified granules becomes too fast,
It may not be possible to obtain granular oxamide having a high crushing strength, which is not preferable.

The heating and drying operation of the granulated product moistened with water may be carried out batchwise by using the same device as the above-mentioned device for drying the aliphatic alcohol, but when the production amount is large. It is desirable to carry out continuously with another device. As the device for performing the heating and drying, a device of a direct heating system using hot air or superheated steam, for example, a rotary dryer, an aeration rotary dryer, a fluidized bed dryer, a vibrating fluidized bed dryer, an aerated band dryer, or a heat medium or It is possible to use an indirect heating type device having a structure such as a jacket, which can use steam, for example, a conical dryer, a rotary dryer, a stirring dryer, a vibration dryer and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0037]

【Example】

Example 1 As a device, a stirring type granulator with a jacket (effective volume of 50 liters) was used. The inside of the apparatus was replaced with nitrogen gas while passing a 64 ° C. heating medium through the jacket, and 30 kg of dimethyl oxalate and 18 kg of methanol were charged and heated / melted to prepare a molten liquid. Rotating speed of stirring blade for molten liquid 1
Ammonia gas was added to 20.5 while stirring at 60 rpm.
It was introduced into the apparatus with Nm ³ / Hr to start the decomposition reaction with an ammonium chloride. During the reaction, the inside of the apparatus was kept at 0.3 Kg / cm ² G, and the heating medium temperature of the jacket was kept at 70 ° C. Reaction heat is generated with the progress of the reaction, and a corresponding amount of methanol is evaporated by the reaction heat and is carried along with the unreacted ammonia gas and discharged outside the apparatus through a pipe. The derived distillate of methanol and ammonia gas was cooled in a condenser, and methanol was condensed and separated. In order to complete the reaction, the introduction of ammonia gas was continuously performed at the above-described rate for 66 minutes, and then the introduction of ammonia gas was stopped. Granulation of the oxamide produced by the reaction was carried out at a rotation speed of the stirring blade of 120
Granulation was started at pm and completed in 5 minutes. The methanol concentration of the obtained granule was 21.3% by weight.

Next, drying was subsequently carried out in order to substantially remove the methanol. The drying was carried out by lowering the rotation speed of the stirring blade to 10 rpm, raising the temperature of the heating medium in the jacket to 120 ° C., and maintaining the internal pressure of the system at 550 Torr for 40 minutes to obtain 22 kg of highly pure preliminary granular oxamide. Substantially no methanol was detected in the dried granules. Granulated product after methanol drying (preliminary granular oxamide)
The crush hardness was measured with a Kiya type hardness meter. Particle size is 3.3
The crushing hardness of the particles was measured for 30 pre-granular oxamides of 5 to 4.0 mm, and the average value was 1.1 kg / particle.

Next, the internal pressure of the system was set to normal pressure, the temperature of the heating medium in the jacket was lowered to 80 ° C., and the granulated product (preliminary granular oxamide) was stirred at a rotating speed of the stirring blade of 10 rpm for 15 minutes.
2.2 kg of water at 10 ° C. (10% by weight with respect to the granulated product) was added by spraying, and the granulated product was uniformly moistened with water. Then, the temperature of the heating medium of the jacket was raised to 150 ° C., and the stirring blade was heated and dried at 40 rpm for 40 minutes to obtain the target granular oxamide. The water content in the granulated product after heating and drying (target granular oxamide) was 0.1% by weight or less. The average particle size of the granular oxamide is 3.44 m.
The average value of the hardness of the granular oxamide measured for 30 granular oxamides having a particle size of 3.3 to 4.0 mm was 2.7 kg / grain.

Example 2 The same operation as in Example 1 was carried out except that the rotation speed of the stirring blade during the reaction was changed to 120 rpm, and the concentration of methanol was 23.
A 1% by weight granulated product was obtained. Drying of methanol was performed using a 20 liter rotary evaporator.
That is, with a jacketed stirring type granulator, the reaction to the granulation operation were carried out in the same manner as in Example 1, and 8 kg per batch of the obtained granulated product was charged in a rotary evaporator, and the rotation speed was 10 rpm and the bath temperature was 120. 60 ° C under normal pressure
After drying for a minute, 22 kg of highly pure preliminary granular oxamide was obtained. Methanol was not detected in the dried granulated product (preliminary granular oxamide). The hardness of the preliminary granular oxamide was 1.3 kg / grain.

Next, 150 g of the granulated product (preliminary granular oxamide) after drying with methanol was charged into a 500 ml rotary evaporator equipped with two scraping plates on the inner surface and rotated at a rotation speed of 10 rpm to form the granulated product. While rolling, 7.5 g of water (5% by weight based on the granules) at 15 ° C. was added by spraying. Water was sprayed at room temperature under normal pressure.

Immediately after the humidifying operation of the preliminary granular oxamide was completed, the rotary evaporator was immediately heated to a temperature of 150 ° C.
The resulting granular product was heated and dried for 30 minutes under atmospheric pressure while rolling the granulated product at 30 rpm while rotating the granulated product in the oil bath. The heat-dried granulated product (target granular oxamide) had an average particle diameter substantially similar to that in Example 1, and the water content in the granular oxamide was 0.1% by weight or less. The hardness of the granular oxamide is
Improved to 1.9 kg / grain.

Example 3 The amount of water added during the humidifying operation of the preliminary granular oxamide was 15 g.
The target granular oxamide was obtained by performing the same operation as in Example 2 except that (10% by weight based on the granulated product) and the heating and drying time after humidification was changed to 60 minutes. The granulated product (objective granular oxamide) after humidification and heat drying of the preliminary granular oxamide had an average particle diameter substantially similar to that in Example 1, and the water content in the granular oxamide was 0.1% by weight. % Or less. The hardness of the granular oxamide is 2.
It was 2 kg / grain.

Example 4 The amount of water added during the humidifying operation of the preliminary granular oxamide was set to 22.
The target granular oxamide was obtained by performing the same operation as in Example 2 except that the amount was 5 g (15% by weight based on the granulated product) and the heating and drying time was changed to 70 minutes. The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide had the same average particle size as in Example 1, and the water content in the granular oxamide was 0.1% by weight or less. . Also,
The hardness of the granular oxamide was 2.3 kg / grain.

Example 5 The amount of water added during the humidifying operation of the preliminary granular oxamide was 30 g.
(20% by weight with respect to the granulated product), and heat drying time to 7
The same operation as in Example 2 was carried out except that the time was changed to 0 minutes to obtain the desired granular oxamide. Granules after humidification and heat drying of preliminary granular oxamide (target granular oxamide)
Had the same average particle size as in Example 1, and the water content in the granular oxamide was 0.1% by weight. The hardness of the granular oxamide was 1.7 kg / grain.

Example 6 The target granular oxamide was obtained by the same procedure as in Example 3 except that the bath temperature during heating and drying after humidification of the preliminary granular oxamide was changed to 120 ° C. and the heating and drying time was changed to 75 minutes. It was The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide had almost the same average particle size as in Example 1, and the water content in the granular oxamide was 0.1% by weight or less. It was The hardness of the granular oxamide was 1.8 kg / grain.

Example 7 In the humidifying operation of the preliminary granular oxamide, the same operation as in Example 3 was carried out except that water was added, the container was closed, and the mixture was aged at 80 ° C. for the desired granular oxamide. It was The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide had almost the same average particle size as in Example 1, and the water content in the granular oxamide was 0.1% by weight or less. It was The hardness of the granular oxamide was 2.9 kg / grain.

Example 8 Preliminary granular oxamide was obtained by performing methanol drying in the same manner as in Example 2 except that the drying time in forming the preliminary granular oxamide was changed to 13 minutes. The methanol concentration in the granulated product (preliminary granular oxamide) was 1.53% by weight, and the hardness of the preliminary granular oxamide was 0.5 kg / grain. The target granular oxamide was obtained in the same manner as in Example 3 except that the preliminary granular oxamide obtained as described above was used and the humidifying operation and the heat drying operation of water were performed. The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide has almost the same average particle diameter as in Example 1, and the water content in the granular oxamide is 0.1.
It was less than weight%. The hardness of granular oxamide is 3.
It was 0 kg / grain.

Example 9 Preliminary granular oxamide was obtained by performing methanol drying in the same manner as in Example 2 except that the drying time in forming the preliminary granular oxamide was changed to 23 minutes. The concentration of methanol in the granulated product (preliminary granular oxamide) was 0.78% by weight, and the hardness of the granule was 0.9 kg / grain. Other than using the pre-particulate oxamide obtained as described above,
The operation of humidifying water and the operation of heating and drying were carried out in the same manner as in Example 3 to obtain the target granular oxamide. The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide had almost the same average particle size as in Example 1, and the water content in the granular oxamide was 0.1% by weight. . The hardness of the granular oxamide was 2.8 kg / grain.

Example 10 The system internal pressure in the formation of preliminary granular oxamide was 200 To.
Preliminary granular oxamide was obtained by performing methanol drying in the same manner as in Example 2 except that rr was changed. No methanol was detected in the granulated product. The hardness of the preliminary granular oxamide was 1.0 kg / grain. The target granular oxamide was obtained by the same procedure as in Example 3 except that the preliminary granular oxamide obtained as described above was used, and the water humidifying operation and the heat drying operation were performed. The moisture content of the granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide was 0.1% by weight or less. The hardness of the granular oxamide was 2.3 kg / grain.

Example 11 In the humidifying operation of the preliminary granular oxamide, the addition of water was adjusted to 2
The target granular oxamide was obtained in the same manner as in Example 10 except that the pressure was reduced to 0 torr. The granulated product (target granular oxamide) after humidification and heat drying of the preliminary granular oxamide had almost the same average particle size as in Example 1, and the water content in the granular oxamide was 0.
It was 1% by weight or less. The hardness of the granular oxamide was 2.6 kg / grain.

Example 12 The charged amounts of dimethyl oxalate and methanol were each 3
0 kg and 17.1 kg, and under the reaction conditions of dimethyl oxalate and ammonia, the system internal pressure is 0.4 kg / cm ^2.
G, the number of revolutions of the stirring blade was changed to 120 rpm, and the reaction time was changed to 61 minutes. The same operation as in Example 1 was carried out to obtain a granulated product having a methanol concentration of 22.2% by weight. Drying of methanol in the granules was performed in the same manner as in Example 2 to obtain preliminary granular oxamide. No methanol was detected in the preliminary granular oxamide, and the hardness of the preliminary granular oxamide was 1.1 kg / grain.

Next, 150 g of the preliminary granular oxamide obtained as described above was placed in a wire mesh container and 4 kg / cm.
² G of saturated steam was sprayed for 20 minutes for humidification. The water content in the granulated product after humidification was 7.6% by weight (based on the wet amount). Immediately after the humidification of the preliminary granular oxamide, the granulated product was transferred to a 500-ml rotary evaporator, and heat-dried at a bath temperature of 150 ° C. and a rotation speed of 30 rpm for 60 minutes under normal pressure to obtain the target granular oxamide. The granulated product (target granular oxamide) after heating and drying is
The average particle diameter was almost the same as in Example 1, and the water content in the granular oxamide was 0.1% by weight or less. Also,
The hardness of the granular oxamide was 2.8 kg / grain.

Example 13 The amounts of dimethyl oxalate and methanol charged were each 2
4 kg and 14 kg, and under the reaction conditions of dimethyl oxalate and ammonia, the heating medium temperature of the jacket is 73
The same operation as in Example 1 was carried out except that the temperature was changed to 120 ° C., the stirring blade was rotated at 120 rpm, and the reaction time was changed to 43 minutes to obtain a granulated product having a methanol concentration of 20.5 wt%. Drying of methanol in the granulated product is performed by an indirect heating type groove-type stirring dryer (effective volume 50 liters, heat transfer area 1.9
m ² ). This dryer is jacketed and heated with steam. In addition, the horizontal stirring shaft and the ten disks attached to it are hollow and heated. 22.2 kg of the above-mentioned granulated product containing 20.5% by weight of methanol was charged into the above-mentioned indirect heating type groove-type stirring dryer, and a jacket and a rotating disk were set at 1.9 k.
It was kept at 120 ° C. with steam of g / cm ² G, and dried at normal pressure for 60 minutes while stirring at a disk rotation speed of 20 rpm to obtain preliminary granular oxamide. The methanol concentration in the preliminary granular oxamide was 1.1% by weight, and the hardness of the preliminary granular oxamide was 1.3 kg / grain.

The preliminary granular oxamide obtained as described above was sprayed on and added with 1.8 kg of water at 20 ° C. (10% by weight based on the preliminary granular oxamide). After spraying water, jacket and rotating disk 5kg / cm
Maintained at 150 ° C with ² G steam, rotation speed 20 rpm
While stirring with, the product was dried under normal pressure for 45 minutes to obtain the target granular oxamide. The average particle size of the granulated product (granular oxamide) after drying by heating was almost the same as in Example 1,
The water content in the granular oxamide was 0.7% by weight, and the hardness of the granular oxamide was 3.2 kg / grain.

Example 14 The charged amounts of dimethyl oxalate and methanol were each 3
0 kg and 13.5 kg, and under the reaction conditions of dimethyl oxalate and ammonia and the granulation conditions, the system internal pressure was set to 0.
Granules having a methanol concentration of 18.7% by weight were prepared in the same manner as in Example 1 except that 5 kg / cm ² G, the rotation speed of the stirring blade was changed to 120 rpm, and the reaction time was changed to 53 minutes. The granulated product was dried with methanol at a bath temperature of 90 ° C., a system pressure of 350 torr, and a drying time of 90.
Preliminary granular oxamide was obtained in the same manner as in Example 2 except that the time was changed. In the preliminary granular oxamide,
No methanol was detected and the hardness of the preliminary granular oxamide was 1.2 kg / grain.

The operation of humidifying the preliminary granular oxamide with water was performed while supplying the preliminary granular oxamide to the rotary dryer for heating and drying with a screw feeder. While supplying the granulated product at 130 kg / Hr, water at 20 ° C. was sprayed and added from a nozzle attached in the middle of the screw feeder. The water content in the granulated product after humidification was in the range of 9 to 11% by weight (wet amount basis).

The humidified granulated product was continuously supplied to a rotary dryer with a screw feeder and heated and dried. The rotary dryer used has a diameter of 0.5.
It is a hot-air heating type dryer having a length of m, a length of 2.8 m, and a scraping plate attached to the inner surface. The number of rotations of the drum is 8
Hot air at 630 ° C. was sent in parallel with the granulated product at rpm, and the granulated product was dried so that the average residence time was 11 minutes to obtain the target granular oxamide. The average particle diameter of the granulated product (granular oxamide) after heating and drying was almost the same as in Example 1, and the water content in the granular oxamide was 0.2% by weight.
The hardness of the granular oxamide was 2.8 kg / grain.

COMPARATIVE EXAMPLE 1 Except that no water was added to the preliminary granular oxamide.
The same operation as in Example 3 was performed to obtain a dried granular oxamide. The hardness of the granulated product after heating was 1.4 kg / grain, and the effect of improving the hardness of the grain was not recognized.

[Evaluation as a slow-release fertilizer] Examples 1 to 1
Each of the granules obtained in Example 4 and Comparative Example 1 was evaluated as a slow-release fertilizer by testing each item of grain hardness, grain surface dusting, and underwater shape stability. These test methods are as follows. [Grain hardness] Measured using a Kiya type hardness meter. Particle size is 3.3
It measured about 30 particles of 5-4 mm, and showed the average value as hardness. [Powdering on the grain surface] The granulated product was touched by hand and evaluated by whether or not the powder adhered to the hand. [Shape stability in water] 100 granules were put into 500 cc of water and left at room temperature for 2 weeks to observe whether or not the shape collapsed. The evaluation results of the obtained granular oxamide are shown in Tables 1 and 2.

[0061]

According to the production method of the present invention, oxalic acid diester is subjected to decomposition to synthesize oxamide, and an aliphatic alcohol, which is a by-product of this reaction, is left in the reaction mixture for granulation. In the method for producing granular oxamide carried out, after drying in order to adjust the concentration of the aliphatic alcohol in the obtained granulated product, water is further added to this granulated product or humidification is performed by spraying steam. It is a completely new and industrial method for producing granular oxamide, which is capable of obtaining granular oxamide which has high hardness, is stable in water, and has no dusting on the grain surface by heating and drying thereafter.

The granular oxamide obtained by the production method of the present invention has a very high hardness, does not easily disintegrate even in water, and retains the morphology of the granules and is stable. Therefore, it is suitably used as a slow-release fertilizer. can do.

[Table 1]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Noguchi 10 1978, Koujigushi, Ube City, Yamaguchi Prefecture 10 1978, Ube Kosan Co., Ltd. Ube Integrated Works (72) Inventor, Shiji Funatsu 10 10 1978, Kogushi, Ube, Yamaguchi Prefecture Ube Kosan Co., Ltd.

Claims (1)

[Claims] 1. Ammonia is supplied to a mixture of an oxalic acid diester and an aliphatic alcohol represented by the general formula (COOR) ₂ (wherein R represents a lower alkyl group having 1 to 6 carbon atoms). In the method for producing an oxamide by reacting, after the completion of the reaction, 5
Granules of oxamide are carried out with 40% by weight of aliphatic alcohol remaining, and granules of the oxamide are dried by heating to evaporate and remove the aliphatic alcohol to form granular oxamide. 5 to 2 for this granulation
A method for producing granular oxamide, which comprises adding 0% by weight of water to moisturize, and then heating and drying to obtain granular oxamide.