JPH06247783A - Production of granular delayingly effective nitrogenuous fertilizer - Google Patents

Abstract

PURPOSE:To easily obtain a product having desired degree of polymerization by granulating while adding specified urea/formaldehyde condensation reaction liq. to a condensation product of powdered and/or flaked urea.formaldehyde. CONSTITUTION:After mixing 30-45wt.% formaldehyde aqueous solution with urea so that the molar ratio of urea/formaldehyde is 2-5, an alkaline material is added to adjust pH at 7-9 so that it may arise addition reaction, and then an acidic material is added to adjust pH at 3-6 so that it may arise condensation reaction to obtain a condensation reaction liq. More than one kind of powdered and/or flaked or more than two kinds of polymers having various degrees of polymerization of urea.formaldehyde condensation products are granulated at 40-90 deg.C while adding 0.1-20wt.% the condensation reaction liq. based on the whole solid amt. and are dried.

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-release nitrogen fertilizer comprising a urea-formaldehyde condensate, and more particularly to a method for efficiently producing granular slow-release nitrogen fertilizer having excellent fertilizing properties. .

[0002]

2. Description of the Related Art A slow-release nitrogen fertilizer composed of a urea-formaldehyde condensate is usually a two-step reaction in which urea and formaldehyde solution are subjected to an addition reaction in an alkaline region and then an acidic substance is added to cause a condensation reaction. Is obtained by The urea-formaldehyde condensate produced through the two-step reaction is not a compound having a single degree of condensation irrespective of its production method, but a mixture of methylene ureas having various degrees of condensation. It is said that it is difficult to adjust the degree. That is, the urea / formaldehyde molar ratio (hereinafter referred to as U / F) used in the above reaction is generally 1 to 4, but the product obtained when the U / F is increased to cause the reaction is Since the amount of unreacted urea is high and the amount of low-condensate is high, the solubility in water is high and the low-condensate is easily decomposed. When such a substance is used in soil, for example, the organic nitrogen contained in urea has a high mineralization rate indicating the rate at which it is converted into inorganic nitrogen, which is an effective form for plants. Rather, it becomes a fertilizer with a fast-acting effect.

Therefore, in order to obtain the slow-acting condensate, U
/ F is made to react, but if U / F is made too small to react, the amount of unreacted urea will decrease, but the nitrogen content that is not soluble in hot water, that is, hot water-insoluble nitrogen Highly condensate containing (hereinafter referred to as HWIN) tends to increase. The highly condensed product does not decompose even in soil and therefore does not play a role as a fertilizer.

Thus, in order to obtain an agriculturally desirable slow-release nitrogen fertilizer composed of urea-formaldehyde condensate,
The important point is how to reduce the amount of unreacted urea and the amount of high-condensate that does not dissolve in hot water. Furthermore,
It is well known that the rate of mineralization of nitrogen in soil is smaller in granular products than in powdered products, and it is also easy to handle, so how to obtain granular products is also an important point. ing.

To solve these problems, JP-A-61-127690
In the publication, U / F is set to 1 to 2 for the purpose of obtaining a lot of active ingredients as a slow-release nitrogen fertilizer, an alkaline substance is added to cause an addition reaction, and then an acidic substance is added to cause a condensation reaction. There is disclosed a method in which the liquid in the condensation reaction zone is started and then granulated while conducting a condensation reaction with a part of the condensate in the circulation, which is granulated and dried. According to this method, unreacted urea nitrogen is about 4% by weight, HWI
It is possible to obtain a granular product of urea-formaldehyde condensate containing N of 5% by weight or less in a single step.

[0006]

However, according to the production method of the above-mentioned Japanese Patent Laid-Open No. 61-127690, on the other hand, a granular product containing a small amount of unreacted urea nitrogen is obtained, while the U / F of the liquid in the condensation reaction zone is obtained. The water content of HWIN is relatively high and the water solubility becomes small. Especially under the condition that U / F is 1.5 or less, a large amount of powdery product is also produced in the production process of granular product. However, it is impossible to efficiently produce a granular product having a desired degree of polymerization.

According to the present invention, when a granular slow-release nitrogen fertilizer comprising a urea-formaldehyde condensate is produced, the amount of powdery product produced is reduced and a product having any desired degree of polymerization is produced. It aims at providing the method of manufacturing efficiently.

[0008]

As described above, for example, U
Although it is difficult to efficiently produce a granular product of urea / formaldehyde condensate containing a large amount of active ingredients as a slow-release nitrogen fertilizer with a / F of 1.5 or less, powdery or flake-form urea / formaldehyde condensate It can be easily produced by a known method. The present inventors have used a granulator to produce these powdery and / or flaky urea-formaldehyde condensates, particularly U / F.
It was found that the powdery and / or flake-like condensate can be efficiently and easily granulated by adding a liquid during the condensation reaction in the range of 1) to complete the present invention.

That is, the present invention relates to a method for producing granular slow-release nitrogen fertilizer comprising urea / formaldehyde condensate by using a granulator, wherein powdery and / or flaky urea / formaldehyde condensation is used. U / F is 2 to 5
The method for producing a granular slow-release nitrogenous fertilizer, which comprises granulating while adding a liquid in a condensation reaction comprising

The present invention will be described in detail below. Urea-formaldehyde condensate powder used in the present invention and /
Or, to produce flaky products, for example, Japanese Patent Publication No. 4-7
The method described in Japanese Patent No. 4310 is possible, but in general, U
/ F is made relatively large to react, so that a high rate of mineralization of nitrogen, that is, a small degree of polymerization is obtained, and by making U / F relatively small, the mineralization of nitrogen is made. It is possible to obtain a polymer having a low rate, that is, a high degree of polymerization. In the present invention, powdery and / or flake-like ones are used, but powdery and / or flake-like 60 mesh passes are preferred.

In the present invention, one kind of the powdery and / or flake urea-formaldehyde condensate can be used, of course. Also, two or more kinds may be used, one having a high degree of polymerization and the other kind having a low degree of polymerization, the U / F of which is desired,
That is, the mixture is mixed in such a ratio that the desired degree of polymerization is obtained,
By adding a liquid in the condensation reaction having a U / F of 2 to 5 to this and producing it, it is possible to arbitrarily obtain a target granular product of urea-formaldehyde condensate having a mineralization rate of nitrogen. Become. For example, one is U / F 1.0 and the other is U / F 1.8 to obtain respective powdery and / or flake-form urea-formaldehyde condensates, and then granulate them as a 1: 1 mixture. U / F
A granular product consisting of a urea-formaldehyde condensate having a ratio of about 1.4 is obtained. To produce urea-formaldehyde condensates having different degrees of polymerization,
For example, as shown in Production Examples 1 to 3 and Table 1 described later, U
By changing / F and reaction conditions, it becomes possible to obtain different components of unreacted urea, low condensate, and high condensate constituting the condensate.

Next, in the present invention, the liquid in the condensation reaction having a U / F of 2 to 5 is an aqueous formaldehyde solution and urea, and an alkaline substance is added to the aqueous solution having a U / F of 2 to 5. To pH 7-9, preferably 7-8, and after stirring to carry out an addition reaction, an acidic substance is added thereto to adjust pH 3 to
It is a liquid in which the condensation reaction is started at 6, preferably 4 to 5. In the present invention, the U / F of the liquid during the condensation reaction is 2 to
It is preferably 5, and when it is less than 2, the liquid does not play a paste-like function and granulation becomes difficult, and
If it exceeds 5, the viscosity of the liquid becomes small and the granulated product easily becomes powdery, which is not preferable.

The concentration of the aqueous formaldehyde solution used above is usually 30 to 45% by weight, and urea may be a granular, powdery or highly concentrated slurry.
The alkaline substance used in the addition reaction is not particularly limited as long as it is a common alkali, and for example, an alkali metal hydroxide, an alkaline earth metal hydroxide or an amine can be used. The addition reaction is usually carried out at 50 to 100 ° C. and the reaction time is several minutes to 1 hour. Furthermore, the acidic substance that initiates the condensation reaction is not particularly limited as long as it is a general acid, and examples thereof include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, or citric acid, malic acid, phthalic acid, butyric acid. ,
Organic acids such as tartaric acid, propionic acid and acetic acid can be used.

In the present invention, one kind of powdery and / or flake type urea-formaldehyde condensate or a mixture of two or more kinds having different degrees of polymerization is supplied to a granulator and the mixture is subjected to the above-mentioned condensation reaction. This is a method of granulating while adding a liquid. When continuously granulating, after drying the urea-formaldehyde condensate discharged from the granulator,
By circulating 1/2 to 19/20 of the condensate to the granulator, it is possible to efficiently produce a granular product, which is preferable. The circulating amount at this time is the temperature and water content of the liquid during the condensation reaction of urea and formaldehyde, the temperature and water content of the circulating material circulating to the granulator, and the powder and / or flake form to be supplied. The amount of urea / formaldehyde condensate varies depending on the conditions such as temperature and the like, so it can be selected appropriately. However, when the circulation amount is less than 1/2,
The amount of liquid in the granulator becomes relatively large, and the generated particles tend to adhere to each other.If it is more than 19/20, the inside of the granulator will be too dry, and both will be granulated. The efficiency is extremely low.

The addition of the liquid during the condensation reaction in the granulator in the present invention is carried out in the form of liquid droplets or spray, and the addition amount is
0.1 to 20 based on total solids fed and circulated to the granulator
% By weight, preferably 1 to 5% by weight. If it exceeds 20% by weight, the estimation of the product composition obtained tends to be unclear, and if it is less than 0.1% by weight, granulation becomes difficult. The condensation reaction and granulation in the granulator are usually preferably carried out at 40 to 90 ° C, and if it is less than 40 ° C, it takes a long time to react and solidify, and 90 ° C. Even if it exceeds the above range, granulation is possible, but heat loss becomes large, which is not preferable.

The granulation in the present invention can be carried out by fluidized bed granulation or spouted bed granulation, but generally, a rotary drum type granulator is used, and a urea-formaldehyde condensate One or two or more powdery and / or flake-like products are continuously supplied and granulation is performed while the condensation reaction is proceeding while continuously adding the liquid in the condensation reaction. It is also possible to granulate using a granulator.

In the case of continuously granulating, the condensate discharged from the granulator is dehydrated by a dryer and then sieved to be divided into a product, a fine grain product and a coarse grain product. Drying is usually performed using a hot air dryer or the like, and the temperature of the material to be dried is 50 to 100.
It is performed in the range of about ℃. The coarse-grained product is crushed and then circulated to the granulator together with the fine-grained product as a circulating product.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the following,% is on a weight basis unless otherwise specified, U / F is a urea / formaldehyde molar ratio,
TN is total nitrogen (%), UN is urea nitrogen (%) in total nitrogen, WN is cold water soluble nitrogen (%) in total nitrogen, WI
N represents cold water-insoluble nitrogen (%) in total nitrogen, and HWIN represents hot water-insoluble nitrogen (%) in total nitrogen. AI is an activity coefficient (%) of nitrogen and is a numerical value calculated by the following formula. AI (%) = (WIN-HWIN) / WIN × 100

The mineralization rate showing the rate at which organic nitrogen becomes effective inorganic nitrogen for plants in soil was determined as follows. Into a 50 ml Erlenmeyer flask, add 19.12 g of sandy loam and 10 mg of sample (as nitrogen), mix well, and then add water corresponding to 60% of the maximum water capacity of the soil. Doubly cover the mouth of the flask with an aluminum wheel and incubate at 30 ° C. After a predetermined period of time, ammonia nitrogen and nitrate nitrogen are analyzed and added together, and the amount per 10 mg of sample is taken as the mineralization rate (%).

Production Example 1 883 g of urea and 596 g of 37% aqueous formaldehyde solution were placed in a beaker, heated to 60 ° C. and dissolved with stirring. Then, 1.6 g of 80% aqueous triethanolamine solution was added to adjust pH to 7.86. After adding 0.6 g of 98% sulfuric acid, the reaction product was poured into a stainless steel container (43 cm × 50 cm × height 6 cm × thickness 1 mm) and solidified. After drying this, crush it into powder
950 g were obtained.

Production Example 2 938 kg of urea and 792 kg of 37% aqueous formaldehyde solution were charged into a reaction vessel equipped with a heater and a stirrer, 0.7 kg of 80% aqueous triethanolamine solution was added thereto, and the mixture was reacted at 60 ° C. for 30 minutes, then 98%. 1.1 kg of sulfuric acid was added, and this was poured onto a rotating endless belt conveyor and solidified. Then, it was dried with a band dryer and then crushed. This operation was repeated in the same manner to obtain 30 tons of powdery product.

Production Example 3 900 kg of urea and 913 kg of 37% aqueous formaldehyde solution were charged in the same reaction vessel as in Production Example 2, 0.8 kg of 80% triethanolamine aqueous solution was added thereto, and the mixture was reacted at 60 ° C. for 30 minutes, then 98 1.2 kg of% sulfuric acid was added, and this was flown out onto a rotating endless belt conveyor and solidified. Then, it was dried with a band dryer and then crushed. This operation was repeated in the same manner to obtain 30 tons of powdery product.

The analysis results of the urea-formaldehyde condensates obtained in the above Production Examples 1 to 3 are shown in Table 1.
Moreover, the result of having measured those mineralization rates is shown in FIG.

[Table 1]

Example 1 460 g each of the powdery products of the urea-formaldehyde condensate obtained in Production Example 1 and Production Example 3 were placed in a plate type granulator having a diameter of 50 cm, and preheated to 50 ° C. while rolling. did. Next, as a liquid to be added to the powdery product, urea was added to 37% formaldehyde aqueous solution to make U / F 3 and 80% triethanolamine aqueous solution was added to this to carry out an addition reaction at pH 7.5, Furthermore, a liquid with 20% sulfuric acid aqueous solution added to bring the pH to 5
110 g were heated to 90 ° C. and added to the above mixture as a spray over 5 minutes. After the addition was completed, it was dried to obtain 1 kg of granular product. The particle size distribution of the obtained product is shown in Table 2.

[0025]

[Table 2] The result of measuring the mineralization rate of the obtained product, and
Estimated value obtained from Production Examples 1 and 3 (numerical value obtained by averaging both)
Are shown in FIG. 2, respectively. In this example, although the liquid in the condensation reaction of urea / formaldehyde with U / F = 3 was added, Production Example 1 (U / F = 2.0) and Production Example 3
It can be seen that it agrees well with the calculated value obtained by averaging the mineralization rate of (U / F = 1.33).

Example 2 The powdery products of the urea-formaldehyde condensate obtained in Production Example 2 and Production Example 3 were continuously fed to a rotary drum type granulator at a feed rate of 1000 kg / H. Next, as a liquid to be added to the powdered product, urea was added to a 37% formaldehyde aqueous solution to make U / F 2 and 80% triethanolamine aqueous solution was added to this to carry out an addition reaction at pH 7.5, Furthermore, add a 20% aqueous sulfuric acid solution to adjust the pH to 4.5.
300 kg / H was continuously added to the above mixture in the form of a spray in a granulator. The residence time in the granulator was about 5 minutes, and the outlet temperature was about 80 ° C. The discharge from the granulator is dried with a drum type dryer, then sieved, and a product with a particle size of 2 to 4 mm is continuously extracted at about 2100 kg / H to obtain a product, and a coarse particle product is crushed. , With fine grain 20000
It was circulated in the granulator at kg / H. The results of measuring the mineralization rate of 2000 kg of the product collected 30 hours after the start of granulation and the estimated values (numerical values obtained by averaging both) obtained from Production Examples 2 and 3 are shown in FIG. Also in this example, it can be seen that the calculated values obtained by averaging the mineralization rates of Production Examples 2 and 3 are in good agreement.

Comparative Example 1 Among products obtained by the same operation as in Example 1, 1000 g of granular urea-formaldehyde condensate having a particle diameter of 2 to 4 mm (9 to 5 mesh) was granulated into a dish type granule having a diameter of 50 cm. It was put in a machine and preheated to 50 ° C while rolling. Next, as a liquid to be added to the above-mentioned granular products, urea was added to 37% formaldehyde aqueous solution to make U / F 1.5, and 80% triethanolamine aqueous solution was added to this to adjust the pH to 7.5 at 60 ° C for addition reaction. , And then add 20% sulfuric acid to adjust the pH to 4.5 3
00 g (this corresponds to 160 g when converted to a dried urea-formaldehyde condensate) was heated to 90 ° C., and this was added to the above granules in a spray state over 5 minutes. During the granulation, there was dust that did not adhere to the particles and scattered, but was not collected. After addition is complete, dry
00 g of product was obtained. Table 3 shows the particle size distribution of the obtained product.

In this case, it is well understood that most of the supplied urea-formaldehyde condensate becomes fine-grained products or powdery products having a particle size smaller than 9 mesh. Furthermore, if there is no scattering as dust, 1160 g of the product should be obtained, but about 60 g has been scattered as dust. Table 4 shows the results of analyzing the composition of each of the granular products thus obtained, which were mixed with 12 mesh on to 32 mesh pass. From this table, it can be seen that in this comparative example, a very large amount of highly condensate was produced.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

In the method for producing a granular urea-formaldehyde condensate according to the present invention, a powdery product and / or a flake-like product having a desired degree of polymerization is obtained in advance, and the product is easily and efficiently granulated. Is possible. Furthermore, by setting the mixing ratio of powdery and / or flaky products of two or more urea / formaldehyde condensates having different degrees of polymerization, a granular urea / formaldehyde condensate having a desired degree of polymerization can be obtained. It can be easily obtained.

That is, in Examples 1 and 2 according to the present invention, the degree of polymerization of the obtained products can be easily estimated from the raw materials from the production examples and the mixing ratio thereof, and from Table 2, it can be seen that they are powdery. It turns out that there are very few. On the other hand, in Comparative Example 1 which is outside the present invention, as is clear from Tables 3 and 4, most of the added liquid is not a granular substance but scatters, and also in terms of composition. U / F =
It has a composition with a large amount of HWIN (less active ingredient as a slow-release fertilizer) for 1.5. Therefore, the method for producing a granular slow-release nitrogen fertilizer comprising a urea-formaldehyde condensate according to the present invention can easily and efficiently produce a product having a desired degree of polymerization.

[Brief description of drawings]

FIG. 1 is a graph showing the results of measuring the mineralization rate of urea-formaldehyde condensates obtained in Production Examples 1 to 3.

FIG. 2 shows the mineralization rate of the granular slow-release nitrogen fertilizer obtained in Example 1, which is an example of the present invention, and the estimated value obtained from the average of the mineralization rates of Production Example 1 and Production Example 3. It is a graph shown.

FIG. 3 shows the mineralization rate of the granular slow-release nitrogen fertilizer obtained in Example 2 which is another example of the present invention, the mineralization rate of Production Examples 2 and 3, and the production rate of Production Example 2 and Production Example 3. It is a graph which shows the estimated value calculated from the average of the mineralization rate.

 ─────────────────────────────────────────────────── ─── 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 (3)

[Claims] 1. A method for producing a granular slow-release nitrogen fertilizer comprising a urea-formaldehyde condensate using a granulator, wherein the powdery and / or flake urea-formaldehyde condensate is converted into urea. A method for producing a granular slow-release nitrogen fertilizer, which comprises granulating while adding a liquid in a condensation reaction having a molar ratio of / formaldehyde of 2 to 5. 2. The method for producing granular slow-release nitrogenous fertilizer according to claim 1, wherein the powdery and / or flakeous urea / formaldehyde condensate is two or more kinds of urea / formaldehyde condensates having different degrees of polymerization. . 3. The urea / formaldehyde condensate discharged from the granulator is dried, and then 1/2 to 19/20 of the condensate is circulated to the granulator. A method for producing granular slow-release nitrogen fertilizer.