JPS59217690A - Manufacture of super slow release nitrogen fertilizer of urea-formaldehyde condensate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention releases nitrogen over a long period of time after being applied to the soil.
The present invention relates to a method for producing an ultra-slow-release nitrogen fertilizer based on urea-formaldehyde condensate, which allows good cultivation of plants.

Conventionally, methods of using a condensate of urea and formaldehyde as nitrogen fertilizer have been known, for example,
No. 1166 discloses that urea-formaldehyde resin is foamed using a foaming agent in an appropriate foaming device, and the resulting foamy cured product is crushed into particles with a particle size of 0.1 to 20 rm using a cutting machine. A method has been proposed in which the mixture is then mixed with water to form a slurry, mulch, plant seeds, etc., and then applied to the soil.

Also, in Japanese Patent Publication No. 57-565.17.

Urea and formalin urea:formaldehyde (molar ratio)
= 1:2 to 2.5 to produce methylolated urea or a substantially water-soluble urea-formaldehyde initial condensate, and then the resulting reaction solution was adjusted to pH 3.
~7, and then spray-dried at a temperature of 200-400''C to produce urea resin micro hollow spheres with specific partial water solubility, and the thus obtained micro hollow spheres were It has been proposed to use it as a fertilizer.

However, conventional urea-
Formaldehyde condensate-based slow-release fertilizer 1
The manufacturing method is often complicated, and in terms of fertilizer effect, the rate of mineralization is fast, and the phenomenon of inhibiting germination occurs, making it suitable as a slow-release fertilizer or a super-slow-release fertilizer. I can't find anything.

For these reasons, the present inventors conducted various studies in an attempt to produce ultra-slow-release fertilizer based on urinary compound-formaldehyde condensate using a method that was easier than conventional methods. It has been reached in the present invention of Chita 2 that that objective is achieved.

That is, the present invention provides (a) urea and formalin reacted in a ratio of urea:formaldehyde (molar ratio) = 1:2.0 to 2.5 to produce urea having a degree of condensation that is substantially soluble in water. - preparing an aqueous solution of formaldehyde precondensate;

(b) Next, add urea to the reaction solution in an amount that satisfies the following relational expression, and allow the reaction to occur until the solution becomes cloudy.

(tt'+μ) : F, :1 : 0.9~1.2
However, μ′: Amount of urea used in the step (mol) μ: Amount of urea used in step (a) (mol) F: Amount of formaldehyde used in step (a) (mol) (C) In this way A curing agent was added to the obtained reaction solution, and the reaction was carried out while kneading and dehydrating, so that the total methylol amount was 0.1 to 1.0 weight (based on water content), and the hot water elution rate [temperature A urea-formaldehyde condensate-based super-effective nitrogen product that produces a hydrated cured product with a dissolution rate of 10% by weight or less (based on anhydride) when immersed in water at 80°C for 30 minutes. This relates to the method of manufacturing fertilizer.

8 The present invention will be explained below. 9 In the present invention, first, in step (a), urea and formalin are reacted in a ratio of urea:formaldehyde (molar ratio) = 1:2.0 to 2.5. An aqueous solution of a urea-formaldehyde precondensate having a degree of condensation at a water-soluble level is prepared.

As the formalin used for this removal, commercially available formalin having a formaldehyde concentration of 35 to 40% by weight, particularly one having a formaldehyde concentration of about 37% by weight, is preferably used.

For the reaction of urea and formalin in this step, conditions conventionally used in the production of this type of condensate can be selected.

To illustrate typical manufacturing conditions in this step, urea:formaldehyde (molar ratio) = 1:2.0~
A mixture of 2.5 parts urea and 37 formalin is adjusted to a slightly alkaline state, preferably pH 7 to 8, using an alkaline substance such as caustic soda, and then heated to a pH of 1 to 3 at a temperature of 20 to 95°C.
React for 0 hours.

The reaction product is mainly dimethylol urea.

By adding small amounts of monomethylol urea and trimethylol urea to this, an aqueous solution containing a small amount of free formaldehyde is obtained.

Next, the pH of the two reaction solutions was adjusted to 3.5-7, and the pH was adjusted to 80-98.
Let the reaction take place at a temperature of ℃ for several hours or more.

The end point of the reaction is preferably a point at which the liquid becomes slightly cloudy when the two reaction liquids are cooled to 20°C,
There is a risk that the reaction will proceed further.

After the reaction is completed, the pH of the two reaction solutions is adjusted to 7 to 9 using an alkaline substance, if necessary, in order to improve the storage stability of the reaction solution.

Next, in the present invention, in step (b).

Urea is added to the above reaction solution for further reaction, and the amount of urea used at this time is set so as to satisfy the following relational expression.

(μ′ 10 μ): F, , 1; 0.9 to 1.2 However, μ′
; Amount of urea used in step (b) (moles) μ: Amount of urea used in step (a) (moles) F; Amount of formaldehyde used in step (a) (moles) The amount of urea used in this step is If the amount is less than the range specified in the invention, the cured product of the urea-formaldehyde condensate produced in the subsequent step (C) may become too strong, making it difficult to obtain the desired product. However, the product obtained in this case has the disadvantage that the germination of the seeds is suppressed, the fertilizing effect is rapid, and the fertilizing effect of red fertilizing does not last for a long period of time.

On the other hand, if the amount of urea used in this step is greater than the range specified in the present invention, the desired product can be easily manufactured, but the product obtained in this case is different from that when the amount of urea used is small. Similarly, it has the disadvantage that the fertilizer effect that suppresses seed germination develops too quickly.

The reaction solution obtained in step (a) with urea is usually 2.

Within the temperature range of 20 to 95° C. for 2 hours and 0.5 to 24 hours, the reaction time is shortened when the temperature is raised, and the time is lengthened when the temperature is lowered. For example, when the reaction temperature in 9 is set to 80° C., the reaction is completed in about 1 hour.

The end point of the reaction does not need to be critically determined in view of the further reaction in step (c), and it is usually appropriate to set it at the point when the reaction solution becomes cloudy.

Next, in step (C) of the present invention, a curing agent is added to the reaction solution obtained in step (b), and the reaction solution is kneaded, summed, and dehydrated in an appropriate device to form an initial supply of urea-formaldehyde. A final product (ultra slow-release fertilizer) consisting of a hydrated hardened metal product is produced.

The curing agent used in this case may be any agent as long as it can harden the urea-formaldehyde initial charge, but acidic substances are usually used, and preferred examples include sodium hydrogen sulfate and potassium hydrogen sulfate.

Examples include monosodium hydrogen phosphate, monopotassium hydrogen phosphate, phosphoric acid, acetic acid, citric acid, and tartaric acid.

These curing agents can be used not only alone, but also as a mixture of two or more.

The amount of curing agent used is 1. Usually 5. The pH of the reaction solution is slightly acidic (pH
-3 to 5), for example, when concentrated sulfuric acid is used.

It is added in an amount of 0.5 to 5% by weight based on the reaction solution.

In addition, the equipment used for processing in this process changes the state of the material to be treated from an aqueous solution to a sushi-like and paste-like stage, and finally to a granular or powdered form. Any shape or structure may be used as long as it can continuously stir and mix the objects in various states and homogenize them. Preferred examples include various types of kneaders and Ben mixers. An example of this is the Nanekka crosstalk machine.

In the present invention, a step (b) is added to such a crosstalk machine.
) After charging the reaction solution obtained in step 2 and the curing agent, the contents are slowly kneaded at a temperature of usually 60 to 80°C, and if the amount of ice water in the reaction solution is too small, the mixture will become large in the shape of dumplings. ,
In any case, don't do any post-processing such as (iil etc.)
.

It is difficult to obtain the optimal form of fertilizer.

It is desirable that the amount of water removed in this step is such that the final product usually contains 35 to 45% by weight of water, preferably around 40% by weight. A final product with good fertilization properties is obtained with a particle size in the range 045-5fi.

The curing reaction of the urea-formaldehyde initial condensate with acid proceeds more quickly as the pH of the reaction system is lower, and as the reaction temperature is higher and the reaction time is longer.2 As the reaction progresses, the total amount of methylol in the product decreases. As it decreases, the hot water dissolution rate of the cured product also decreases.

In the present invention, in this step, the above reaction conditions are appropriately selected and combined to give a total methylol content of 0.1 to 1% by weight (based on water content) and a hot water dissolution rate [temperature 80°C].
A final product is produced which has a dissolution rate of the cured product (based on anhydrous material) of 10 liters or less when immersed in water for 30 minutes.

If the total methylol content and hot water dissolution rate in the final product are outside the ranges defined by the present invention, seed germination will be inhibited when the final product is applied to soil. Undesirable problems such as long-term ridges and inability to sustain the fertilizing effect occur.

Next, the effects of the present invention will be explained. Firstly, in the conventional method for producing this type of urea-formaldehyde metal condensate fertilizer, the final reaction solution is completely dehydrated, and the resulting hardened product is pulverized. , many methods require separate dehydration and pulverization processes;

However, it cannot be said to be technically advantageous since there are many steps involved.

In the present invention, as mentioned above, it is not necessary to completely dehydrate the reaction solution, and the dehydration of the reaction solution and the granulation of the dehydrated material are performed in the same process (simultaneously), so the process is simplified compared to the conventional method. It is advantageous.

Second, nitrogen is normally released over a long period of time, e.g., up to three years, without adversely affecting the ultra-slow-release properties produced in accordance with the present invention. ,
Compared to coating fertilizers, etc., the fertilizer effect lasts longer, and because of this, there is no need to add additional nitrogen source.

Furthermore, although conventional fertilizers of this type often solidify due to moisture absorption,9 the super slow-release fertilizer produced by the present invention remains hydrated even if stored for a long time. There is no solidification.

Next, one embodiment of the present invention will be explained based on an example.

Example (1) Production of ultra-slow release nitrogen fertilizer (a) Step A mixture of urea and 37-thiformin in a ratio of urea:formaldehyde (molar ratio) = 1:2.3 was adjusted to pH 7.8 using a caustic soda aqueous solution. The temperature was adjusted and raised at a constant rate from 20°C to 95°C over about 65 minutes while stirring.

After the contents reached 95° C., the reaction was continued for about 30 minutes.

The pH of the reaction mixture was then adjusted using an aqueous potassium sulfate solution.
was adjusted to 4, and the reaction was carried out at a temperature of 90 to 95°C for 3 hours.

As a result, an aqueous solution of urea-formaldehyde initial condensate having a nonvolatile content of about 38% by weight was obtained.

(BL step (ATL step) A predetermined amount of urea was added to the obtained aqueous solution of the urea-formaldehyde initial condensate, and the mixture was reacted at a predetermined temperature for a predetermined time.

The μ'/μ/F molar ratio, reaction temperature, reaction time, etc. used in this step were as shown in Table 1.

(c) Step (b) Charge the reaction product obtained in the step into a kneader,
After bringing the temperature of the contents to 70 to 80°C while stirring,
1.5% phosphoric acid was added by volume.

Next, the contents were kept at the above temperature and reacted for a predetermined time while gradually dehydrating while kneading, to produce a hydrous cured product (final product).

At this time, the contents of the kneader changed from an initial liquid state to a slurry, a paste, a dumpling, a granule, and a powder as the water evaporated.

The reaction time in this step, the properties of the final product, the moisture content, etc. are as shown in Table 1.

Performance test of hydrous cured product Regarding the hydrous cured product obtained in step (c), total methylol amount, hot water elution rate, bulk density 1 germination rate.

Tests were conducted on items such as the residual rate of nitrogen in the soil and the growth status of grass.

The results obtained are as shown in Table 1.The test methods for each of the above items are as follows.

1) Total amount of methylol Total amount of methylol in a hydrated cured product (based on hydrated material) by the iodine method. In the presence of an alkali, formaldehyde is oxidized with iodine and then acidified to liberate unreacted iodine.

It is back titrated with sodium thiosulfate.

Since this method completely reacts with unreacted formaldehyde and methylol groups in the reaction system of urea and formaldehyde, the sum of both can be determined.

(Calculation formula) A: Consumption amount of sodium thiosulfate in blank test (+n
1) B; Consumption amount of sodium thiosulfate in the sample (ml) f; 4/10 Sodium thiosulfate factor 0.
0015;N/110Na252Q11 =0.001
5g HOHIll) Hot water elution rate Hot water elution rate in hydrated cured product (anhydrous basis).

Approximately 41 samples were placed in 80ml of water and heated at a temperature of 80℃ for 30 minutes.
After stirring occasionally for a minute, the solution is passed through the solution, and the percentage of the cured product dissolved in the P solution relative to the original sample (anhydride equivalent) is determined.

111) Germination rate Test size: 3 consecutive fibrepots in 1 section Test soil: Yonegawa alluvial soil (moisture 2.91%).

4001 as dry soil with a maximum water capacity of 64%) Test plant: Komatsuna, 20 grains/10 holes/1 pot Location: Nigarasu greenhouse, temperature 25°C iv) Nitrogen residual rate test scale in soil: Bot 1 area test Soil: Alluvial soil for Tone NH, -N, 0.75■7100ψ; NOs -N,, 0.71mg7100? The amount of sample added is O in terms of nitrogen to soil IQOKy/m”.
``'''L soil moisture was adjusted to 60±5% of the maximum soil water capacity.

The test location was in a glass greenhouse, the temperature was 25±5℃, and the method for measuring the survival rate was ■) Grass growth status Test size: 10 m" 71 sections Test soil: 6:4 ratio of alluvial soil and sand for Tone mixture of proportions.

Test turf: Addition amount of high leprosy test sample: 0.37/soil 1.0051 - Test location: Outdoor sowing started in March of the first year, growth status after 1 year was 9 after the 6th month Average value ratio from March to November (dry weight?/m”・may).

The growth status after 3 years will be 30 to 35 months. Average value (dry weight 1/m゛・@ay).

Cultivation overview 1st year: Green creation in March, top dressing in October Second year: February, April, May, September.

Top dressing in October, soil in May and September 3rd year; top dressing in February, April, May, and September Relationship with the case of Kazuo Wakasugi, Director-General of the Agency, and the case of a person amending the name of the patent application No. 90792 filed in 1982 Patent applicant No. 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo 100 Subject of amendment 2 of the specification Detailed Description of the Invention Column 5゜Contents of Amendment (1) “...” stated on page 5, line 10 of the specification
"Super-mobility nitrogen fertilizer" is replaced by "super-slow-release nitrogen fertilizer"
and correct it.

(2) Page 16 of the specification, line 2 from the bottom (2) “4/
10...--" is corrected to "1/10...".

(3) r stated in the rightmost column of Table 1 on page 20 of the specification
#/77I! aayl as “9-/trt ・day
Correct it with J.

that's all

Claims (1)

[Claims] (a) Urea and formalin are reacted in a ratio of urea:polmaldehyde (molar ratio) = 1:2.0 to 2.5 to form a substantially water-soluble stage. An aqueous solution of a urea-formaldehyde initial condensate having a degree of condensation is prepared. (1)) Next, an amount of urea that satisfies the following relational expression is added to the reaction solution, and the reaction is allowed to occur until cloudiness occurs in the solution. (/lZ' 10μ): p=l: 0.9 to 1.2 However, μ': Amount of urea used in the step (mol) 71'; Amount of urea used in the step (al) (mol) F; Amount of formaldehyde used in step (a) (Mo/I/) (C) A curing agent is added to the reaction solution obtained in this way, and the reaction is carried out while kneading and dehydrating, until the total amount of methylol is reduced. At 0.1 to 1.0% by weight (based on water content), the hot water elution rate [elution rate of the cured product when immersed in water at a temperature of 80°C for 30 minutes (based on anhydrous content)] is 10. 1. A method for producing a urea-formaldehyde condensate-based ultra-slow-release nitrogen fertilizer, which comprises producing a cured product containing water at % by weight or less.