JPH06305869A - Production of slow-release nitrogen fertilizer - Google Patents

Abstract

PURPOSE:To obtain a fertilizer having excellent slow-releasing property and suitable for agriculture in a short time in high efficiency by mixing a liquid comprising urea and formaldehyde with a liquid mixture of an acidic substance and formaldehyde in a specific state. CONSTITUTION:A slow-release nitrogen fertilizer composed of a ureaformaldehyde condensate is produced by the following procedures. An aqueous solution of urea and formaldehyde having a urea/formaldehyde molar ratio of 1-10 is adjusted to pH 7-10 with an alkaline substance to start the methylolation reaction and obtain a liquid A. Separately, a liquid consisting of an acidic substance or its aqueous solution is mixed with an aqueous solution of formaldehyde to obtain a liquid B. The liquid A is mixed with the liquid B in a line mixer to a urea/formaldehyde molar ratio of 1-3 and a pH of 3.5-4.5 and the methylenation reaction is started to obtain the objective slow-release nitrogen fertilizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a slow-acting nitrogen fertilizer comprising a urea-formaldehyde condensate.

[0002]

2. Description of the Related Art Slow-release nitrogen fertilizers contain urea-formaldehyde condensate as an active ingredient and are usually produced by the following method. That is, an alkaline substance such as sodium hydroxide is added to a solution of urea and an aqueous formaldehyde solution to cause a methylolation reaction at pH 7 to 10, and then an acidic substance such as sulfuric acid is added to the resulting methylol urea solution to adjust the pH. After the methyleneation reaction is carried out at a ratio of 4 or less, the product is solidified, dried and pulverized. Usually, in the methylolation reaction in the above, the urea / formaldehyde molar ratio (hereinafter referred to as U / F) is in the range of 1 to 3, and the reaction temperature is 40 to 80.
The reaction time is 30 to 60 minutes at ℃. As described above, the methyleneation reaction is started by adding an acidic substance to the solution in which the methylolation reaction has been completed, so that the reaction temperature is approximately the same as that during the methylolation reaction.
Then, after the addition of the acidic substance, methylolurea condenses to methyleneurea, which usually solidifies in 30 minutes or less.

The urea-formaldehyde condensate thus obtained is composed of methylene urea represented by the following general formula (1) (formula 1) and unreacted urea.

## STR1 ## _{H (NHCONHCH 2) n -NHCONH 2} (1) Since the methylene reaction is a遂時competitive reaction, methylene urea urea-formaldehyde condensate obtained is regardless of the method, The above general formula (1)
It is a mixture of the compounds of Chemical Formula 1 in which the number of n has various values. Then, in the above, when U / F is decreased and the reaction is carried out, a product having a large ratio of n is obtained, and conversely, when U / F is increased and reacted. Although the number of n having a large number is decreased, that of unreacted urea or the one having a small number of n is increased.
Here, as will be described later, it is well known that it is preferable that the number of n is 2 to 3 as the methylene urea showing a slow-acting effect as a nitrogen fertilizer.

Further, as a measure showing the difficulty of water solubility of nitrogen in slow-release nitrogen fertilizers containing urea-formaldehyde condensate as an active ingredient, the nitrogen is water-soluble nitrogen (hereinafter referred to as WN). , Water-insoluble nitrogen (hereinafter referred to as WIN), hot-water-soluble nitrogen (hereinafter referred to as HWN), and hot-water-insoluble nitrogen (hereinafter referred to as HWIN). The above classification is A. O. A. C (Methods of Analysis of the
According to the above analytical method, WN (nitrogen soluble in water at 25 ± 2 ° C.) is unreacted urea and the above-mentioned general formula (1) (Chemical Formula 1). The nitrogen contained in the methyleneurea of n = 1 in) corresponds to this, and the WIN (nitrogen insoluble in water at 25 ± 2 ° C.) has almost the same nitrogen contained in the methyleneurea of n ≧ 2. This is the case with HWN (nitrogen soluble in a buffer at 100 ° C., pH 7.5), which is almost the same as nitrogen contained in n ≦ 3 methylene urea, and HWIN (insoluble in the above buffer). The nitrogen contained in the methylene urea with n ≧ 4 corresponds to this. In the following, the total nitrogen in the slow-release nitrogen fertilizer containing the urea-formaldehyde condensate as an active ingredient is abbreviated as TN, and urea nitrogen is abbreviated as UN.

Since the WN in the above is methyleneurea nitrogen and UN in which the number of n in the general formula (1) (formula 1) is 1, it is mineralized in soil in a short time. It is more like a fast-acting rather than a slow-acting. On the other hand, HWIN has a large number of n, condensation is too advanced, and mineralization rate is very slow in soil,
It has virtually no fertilizer effect. In contrast, n
Methylene urea (WIN to HW
Excluding IN. Hereinafter referred to as WIN-HWIN)
Since it gradually becomes mineralized in soil, it exhibits a fertilizer effect for a long time. That is, this WIN-HWIN is an active ingredient as a slow-release nitrogen fertilizer.

[0006] Further, as an index showing the magnitude of the slow-release effect of nitrogen fertilizer, the activity coefficient of nitrogen (Activity-Index, hereinafter referred to as AI) represented by the following formula (Formula 1) is usually used.

[Formula 1] AI (%) = ((WIN-HWIN) / WIN) × 100 And, as a preferable slow-release nitrogen fertilizer, this AI is large, the content of UN and HWIN is small, and WIN is small.
-A lot of HWIN.

[0007]

As described above, the methyleneation reaction is carried out on the solution after completion of the methylolation reaction.
The method is carried out by adding an acidic substance to start the reaction. However, since the amount of the acidic substance relative to the amount of the methylolurea aqueous solution is very small and the methyleneation reaction proceeds in a relatively short time, the conventional production method allows the entire reaction liquid to be uniformly methylated. It was very difficult to get the reaction going. That is, the obtained product has a problem that its composition tends to be non-uniform, and can be obtained by sufficiently reducing unreacted urea or one having n of 4 or more in the general formula (1) (formula 1). In that respect, I was still not satisfied. With respect to such problems, the present invention provides a method for efficiently obtaining a slow-release nitrogen fertilizer having a low content of UN and HWIN and a large value of AI and WIN-HWIN. Is the purpose.

[0008]

In order to achieve the above-mentioned object, the present inventors first examined the time required for the methylolation reaction of urea and formaldehyde before the methyleneation reaction. That is, in the conventional production method, the methylolation reaction takes 30 to 60 minutes, and then the methyleneation reaction is started.However, using the reaction vessel with a stirrer that is generally used, the above-mentioned preferable reaction is carried out. When obtaining an effective nitrogen fertilizer, the amount of time required for the methylolation reaction was investigated by experiments. As a result, in the methylolation reaction, it is no longer necessary that the urea is in a dissolved state after the start of the reaction, and even if it takes more time, the quality of the obtained product hardly changes. I got the knowledge. Regarding the time required for this methylolation reaction, the experimental contents are shown in Experimental Example 1 and the results are shown in Table 1.

[0009] Further, the inventors of the present invention, when producing slow-release nitrogen fertilizer, in order to make the content of UN and HWIN in the product as small as possible and to make it as uniform as possible, a general reaction vessel equipped with a stirrer. Is more effective than the method of initiating the methyleneation reaction by using the method of mixing the liquid and the acidic substance in the methylolation reaction in the line mixer to initiate the methyleneation reaction, and is more efficient in a short time. It was clarified that a slow-release nitrogen fertilizer was obtained well, and the present invention was completed.

That is, the present invention provides a slow-release nitrogen fertilizer comprising a urea-formaldehyde condensate,
A solution of urea and formaldehyde solution in which U / F is in the range of 1 to 10 and a methylolation reaction is started by adjusting the pH to 7 to 10 with an alkaline substance is a solution of A, an acidic substance or an aqueous solution thereof, and a formaldehyde aqueous solution. When the solution obtained by mixing is the solution B, both solutions A and B are mixed by a line mixer, the U / F is 1 to 3, and the pH is 3.5.
It is a method for producing a slow-release nitrogenous fertilizer characterized by starting the methyleneation reaction within a range of up to 4.5.

The present invention will be described in detail below. The urea used in the present invention is preferably a granular and / or powdery one, but a high-concentration aqueous solution or slurry is also possible. In addition, as for formaldehyde, for example, commercially available formalin or the like can be used, and the concentration thereof is not particularly limited, but in consideration of the post-process drying treatment and the like, 37% by weight
Those having a degree of at least the above are preferable.

The line mixer in the present invention is a continuous stirring device preferably used when continuously mixing and / or emulsifying a plurality of fluids. For example, a static mixer (manufactured by Noritake Co. Ltd.) ), Pipeline mixer (manufactured by Mizuho Industry Co., Ltd.),
Motionless mixer, TK homojetter (or more,
Tokushu Kika Kogyo Co., Ltd., and the like.

Of these, in the present invention, it is preferable to use a static mixer which has no moving parts and has a small conduit resistance. Here, the static mixer
For example, it is described in Japanese Patent Publication No. 1-31928, and a right-handed twist baffle plate and a left-handed twist baffle plate are alternately arranged at a certain angle inside a pipe-shaped housing. That is, the plurality of fluids introduced into the static mixer are vigorously agitated while undergoing a spiral motion and a rotational motion while being divided by the baffle plate, and further divided by the next baffle plate, and then, this time. By receiving spiral motion and rotary motion in the opposite direction and repeating these motions, the mixing / stirring operation can be efficiently performed.

In the present invention, a line mixer such as the static mixer mentioned above as an example is used, and a solution A which is undergoing a methylolation reaction in the mixer and a mixed solution of an acidic substance or an aqueous solution thereof and an aqueous formaldehyde solution are used. This is a method of mixing two liquids with a certain liquid B to start the methyleneation reaction. The solution A used in the above is a solution in which urea and formaldehyde aqueous solution have U / F in the range of 1 to 10 and pH 7 to 10 by an alkaline substance to start the methylolation reaction, and as the solution B. Is a solution obtained by mixing a solution containing an acidic substance or an aqueous solution thereof with an aqueous formaldehyde solution. Then, both liquids A and B had U / F of 1 to 3 and pH of 3.5 at the outlet of the line mixer.
It is a method of supplying to the mixer so that the range becomes to 4.5.

However, in the present invention, even if the U / F of the above-mentioned liquid A is set within the range of 1 to 3 from the beginning and the pH is adjusted to 7 to 10 with an alkaline substance, the object of the present invention is sufficiently achieved. It is possible to achieve. In this case,
The liquid B may be an acidic substance or an aqueous solution thereof. The pH of both solutions A and B at the outlet of the line mixer
It is also possible to supply to the mixer so that the ratio is in the range of 3.5 to 4.5.

The alkaline substance for initiating the methylolation reaction in the present invention is not particularly limited as long as it is a general alkali, and examples thereof include alkali metal hydroxides, alkaline earth metal hydroxides or amines. It can be used. The acidic substance that initiates the methyleneation reaction is not particularly limited as long as it is a general acid, and examples thereof include sulfuric acid, hydrochloric acid, nitric acid, mineral acids such as phosphoric acid, citric acid, malic acid, phthalic acid, butyric acid, Organic acids such as tartaric acid, propionic acid and acetic acid can be used.

As the solution A in the present invention, a solution in which the U / F of the mixed solution of urea and formaldehyde is in the range of 1 to 10 and the methylolation reaction is initiated by adding an alkaline substance is used. Preferably, when this is carried out with U / F of less than 1, H in the product obtained is
It is easy to become a product containing a lot of WIN. Further, if it exceeds 10, depending on the temperature of the solution, urea is generally likely to precipitate, and urea that does not participate in the reaction tends to remain in the product, resulting in a product containing a large amount of UN, which is not preferable. .

Further, when the methylolation reaction in the above is initiated, the addition of an alkaline substance makes it necessary to adjust the pH of the solution.
Is 7 to 10, preferably 7.4 to 8. pH
When the value is less than 7, the methyleneation reaction is started in the liquid A, the liquid is likely to be solidified in the line mixer, and the products obtained have a large amount of UN and WN. Further, if it exceeds 10, a large amount of an acidic substance is required for the methyleneation reaction, which is not preferable.

Further, after mixing with a line mixer, U
It is preferable that / F is in the range of 1 to 3 and pH is in the range of 3.5 to 4.5. If the U / F after mixing exceeds 3, the obtained product tends to be a urea-formaldehyde condensate containing a large amount of UN and WN. Also, the pH after mixing is 3.5
If it is less than 5, it will contain a large amount of HWIN, and further 4.5
If it exceeds the range, a product containing a large amount of UN and WN is likely to be formed.

The temperature of both liquids before mixing in the line mixer in the present invention is 40 to 70 ° C, preferably 40 to 65 ° C for liquid A.
Is the range. If the temperature is lower than 40 ° C, urea may be precipitated, and the product obtained tends to be a product containing a large amount of UN and WN.
Tends to be a product containing a large amount of. The other liquid, B
The liquid is not particularly limited, and it can be sufficiently used at room temperature.

In the present invention, both liquids A and B described above are mixed using a line mixer to start the methyleneation reaction. The method of supplying the liquids to the line mixer is to control the flow rate of both liquids. The pH after mixing is 3.5-4.5, and U
It is preferable to supply each at a constant flow rate so that / F is in the range of 1 to 3. For this purpose, for example, a metering pump such as a diaphragm pump can be used to supply the line mixer at a constant flow rate.

The liquid which has been mixed and started the methyleneation reaction by a line mixer is usually received in a stirring tank equipped with a general stirrer, stirred until the liquid is solidified, and then crushed to a water content of 3% by weight. The product of the slow-release nitrogen fertilizer can be obtained by drying until the following. In addition, as an industrially preferable method, the liquid from the line mixer is supplied onto an endless rotating belt as described in, for example, Japanese Patent Publication No. 4-74310, and after solidifying on the endless rotating belt, roughening is performed. It is also possible to continuously obtain a slow-release nitrogen fertilizer by going through the crushing and drying steps.

[0023]

EXAMPLES The present invention will be described in more detail with reference to experimental examples and examples. In the following, "%" is based on weight, and the type of nitrogen is the same as the above-mentioned A. O. A. The method described in C was used as the value.

Experimental Example 1 In order to obtain a preferable slow-release nitrogen fertilizer, a reaction tank equipped with an ordinary stirring device and heating equipment is used, and what time is required for the methylolation reaction Whether or not it was good was examined by the following experiment. First, 80% triethanolamine was added to 1194 g of 37% formaldehyde aqueous solution to adjust the pH to 7.5, and urea was added to adjust U / F to 1.5.
26 g was added and heated to 60 ° C. to dissolve. Immediately after the complete dissolution of urea and keeping it at 60 ℃ for 1, 5, 15, 3
After 0, 45, 60, 75, 90 and 120 minutes, 200 g of each solution was sampled, 0.6 g of 20% sulfuric acid aqueous solution was immediately added, and the mixture was stirred for 10 minutes to cause a methylene reaction. The product obtained is 80
After drying at 5 ° C. for 5 hours, the components of each nitrogen component were analyzed. The results of those analyzes are shown in Table 1.

[0025]

[Table 1] It can be seen from Table 1 that the time required for the methylolation reaction is sufficient immediately after the urea is completely dissolved, and that even if it takes more time, the quality of the obtained product hardly changes. I understand.

Example 1 First, an aqueous solution was prepared by adding 2 mol of urea to 1 mol of formaldehyde and adjusting the pH to 7.5 with an alkaline substance.
It was confirmed that in order to add pH to 3.7 by adding hydrochloric acid, hydrochloric acid should be added so that the concentration of hydrogen chloride in the aqueous solution becomes 0.0324 mol / Lit. Next, to a solution of 25% sodium hydroxide aqueous solution added to 1688 g of 37% formaldehyde aqueous solution to adjust the pH to 7.5, 3952 g of urea was added and heated to 60 ° C. to be dissolved to obtain a solution A. As the solution B, 847 g of 37% aqueous formaldehyde solution and 17.51 g of 35% aqueous hydrochloric acid solution were added and stirred to adjust. For each of the two liquids prepared above, a static mixer, T4-21R-2PT type (trade name; manufactured by Noritake Co., Ltd.), was used with a diaphragm pump, and 32640 g / h of liquid A and 5187 of liquid B were used.
It was supplied at a flow rate of g / h. Incidentally, the pH at the outlet of the mixer was 3.7. After passing through the mixer, the mixed liquid was received in a stirring tank equipped with a stirrer, stirred for 10 minutes, and then the solidified product was dried at 80 ° C. for 3 hours using a constant temperature dryer to obtain a product. The nitrogen analysis values of the product are shown in Table 2.

Example 2 First, an aqueous solution was prepared by adding 2 mol of urea to 1 mol of formaldehyde and adjusting the pH to 7.5 with an alkaline substance.
It was confirmed that in order to add pH to 3.7 by adding sulfuric acid, sulfuric acid should be added so that the concentration of sulfuric acid in the aqueous solution becomes 0.0162 mol / Lit. Next, a solution prepared by adding 80% triethanolamine aqueous solution to 1688 g of 37% aqueous formaldehyde solution to adjust the pH to 7.5, and adding 3752 g of urea and heating to 60 ° C. to dissolve it was used as solution A. Further, as the solution B, 847 g of a 37% aqueous solution of formaldehyde and 8.42 g of a 98% aqueous solution of sulfuric acid were added and agitated. 2 adjusted above
Using a diaphragm pump for each of the liquids, 32640 g / h of liquid A and 51 of liquid B were added to the same static mixer as in Example 1.
It was supplied at a flow rate of 33 g / h. Incidentally, the pH at the outlet of the mixer was 3.7. The liquid passed through the mixer was stirred and dried in the same manner as in Example 1, and then the obtained product was analyzed for nitrogen. The results are shown in Table 2.

Example 3 To a solution of 37% formaldehyde aqueous solution (2535 g) and 80% triethanolamine aqueous solution (pH = 7.5) was added 3752 g of urea, which was heated to 60 ° C. and dissolved to obtain solution A. . The solution B was prepared as a 10% sulfuric acid aqueous solution at room temperature. Next, these two solutions were passed through the same static mixer as in Example 1 with solution A at a flow rate of 37722 g / h, and
Liquid B was also supplied using a diaphragm pump so that the pH at the outlet of the mixer was in the range of 4.0 to 4.5. Incidentally, the flow rate of the liquid B was 495 g / h. The liquid that passed through the mixer was stirred and dried in the same manner as in Example 1, and then the obtained product was analyzed for nitrogen. The results are shown in Table 2.

Comparative Example 1 A reaction vessel equipped with a stirrer and a heater was charged with 2535 g of 37% formaldehyde aqueous solution, and 80% triethanolamine aqueous solution was added to adjust the pH to 7.5. This solution was heated to 60 ° C., and then 3752 g of urea was added and dissolved, and then a methylolation reaction was carried out for 30 minutes. Next, add 98% sulfuric acid aqueous solution to 8.
42 g was added and the pH of the solution was adjusted to 3.7 to start the methyleneation reaction. After 10 minutes from the start of the reaction, the mixed solution was solidified and then dried in the same manner as in Example 1 to obtain a product. The nitrogen analysis of the resulting product is shown in Table 2.

Example 4 First, 1.5 mol of urea was added to 1 mol of formaldehyde, and an aqueous solution whose pH was adjusted to 7.5 with an alkaline substance was added with sulfuric acid to have a pH of 3.9. It was confirmed that sulfuric acid should be added so that the concentration becomes 0.0074 mol / Lit. Next, to a solution of 2253 g of 37% formaldehyde aqueous solution, 80% triethanolamine aqueous solution was added to adjust the pH to 7.5, and 3952 g of urea was added.
The solution which was heated to 0 ° C. and dissolved was designated as solution A. As the solution B, 1126 g of 37% aqueous formaldehyde solution and 4.34 g of 98% aqueous sulfuric acid solution were added and stirred to adjust. Each of the two liquids prepared above was supplied to the same static mixer as in Example 1 at a flow rate of 36030 g / h and B liquid of 6782 g / h using a diaphragm pump. Incidentally, the pH at the mixer outlet was 3.9. The liquid that passed through the mixer was stirred and dried in the same manner as in Example 1, and then the obtained product was analyzed for nitrogen. The results are shown in Table 2.

Comparative Example 2 A reaction tank equipped with a stirrer and a heater was charged with 1194 g of 37% formaldehyde aqueous solution, and 80% triethanolamine aqueous solution was added to adjust the pH to 7.5. This solution was heated to 60 ° C., 1326 g of urea was added and dissolved, and then a methylolation reaction was carried out for 30 minutes. Then, a 20% sulfuric acid aqueous solution was added to adjust the pH of the solution to 3.9, and a methyleneation reaction was carried out for 10 minutes. After drying the obtained product in the same manner as in Example 1,
The product was analyzed for nitrogen. The results are shown in Table 2.

[0032]

[Table 2]

[0033]

INDUSTRIAL APPLICABILITY In the method for producing a slow-release nitrogen fertilizer according to the present invention, it is possible to promote the methyleneation reaction evenly throughout the reaction solution in a short time, and the obtained product is
UN and HWIN values are relatively low, and AI and WIN-
High HWIN value. That is, in Examples 1 to 3 according to the manufacturing method of the present invention performed so that U / F was 2, all were UN 7.2% or less and HWIN 0.8% or less, and WIN-HWIN was 8.1%. As mentioned above, it is possible to achieve 92% in AI.

On the other hand, in Comparative Example 1 which was carried out by the conventional manufacturing method so as to obtain the same molar ratio, UN was 12
%, HWIN is as high as 1.5%, and WIN-HW
IN is only about 7% and AI is only 82%. Also, U / F
In Example 4 in which the value of 1.5 was 1.5, UN and HWIN were all low values, and WIN-HWIN and AI were all high values, as compared with Comparative Example 2 performed as a conventional manufacturing method. . Therefore, according to the method for producing a slow-release nitrogen fertilizer according to the present invention, it is possible to efficiently obtain a fertilizer with excellent slow-release and which is extremely agriculturally suitable in a short time.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Go Watanabe 1900 Togo, Mobara-shi, Chiba Mitsui Toatsu Fertilizer Co., Ltd. Chiba factory (72) Inventor Kiyokata Chimasa, Shinkai-cho, Omuta-shi, Fukuoka Mitsui Toatsu Fertilizer Co., Ltd. Omuta factory

Claims (2)

[Claims] 1. When producing a slow-release nitrogen fertilizer comprising a urea-formaldehyde condensate, urea and formaldehyde solution are mixed at a urea / formaldehyde molar ratio of 1.
In the range of 10 to 10, and when the liquid in which the methylolation reaction is started by adjusting the pH to 7 to 10 with the alkaline substance is the liquid A, and the mixture of the liquid containing the acidic substance or its aqueous solution and the aqueous formaldehyde solution is the liquid B, Both liquids A and B were mixed by a line mixer to give a urea / formaldehyde molar ratio of 1 to 3 and a pH of 3.5 to 4.5.
A method for producing a slow-release nitrogenous fertilizer, which comprises initiating a methyleneation reaction. 2. The liquid A has a urea / formaldehyde molar ratio in the range of 1 to 3 and a pH of 7 due to an alkaline substance.
Is a liquid which has initiated the methylolation reaction as ~ 10, and B
The method according to claim 1, wherein the liquid is an acidic substance or an aqueous solution thereof.