Urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer integrated preparation process and application

Abstract

The present invention belongs to the technical field of slow / controlled release fertilizers, and specifically relates to an integrated preparation process and application method of a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer. First, a hydroxymethyl urea solution is prepared, and then a part of the obtained hydroxymethyl urea solution is added to a reactor for preparing liquid fertilizer to finally obtain a polymer slow / controlled release liquid fertilizer; the remaining part of the obtained hydroxymethyl urea solution is injected into a reaction extrusion integrated machine, and a urea-formaldehyde polymer is extruded through a polycondensation reaction in a twin-screw reaction extruder of a reaction unit of the reaction extrusion integrated machine, and finally a polymer slow / controlled release solid granular fertilizer is obtained. The present invention realizes the simultaneous production of two different forms of urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release fertilizer, namely liquid and solid particles, on a set of equipment, and the process is simple and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of slow / controlled release fertilizers, and specifically relates to an integrated preparation process and application method of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer. Background Art

[0002] In order to solve the problem of low nutrient utilization rate of traditional chemical fertilizers, slow / controlled-release fertilizers have become a hot topic in fertilizer research and application. Among them, urea-formaldehyde slow-release nitrogen fertilizers are the first slow-release fertilizers to be successfully developed and commercialized, and are also the most promising slow / controlled-release fertilizer varieties at present. They have a very far-reaching significance for promoting the upgrading of the nitrogen fertilizer industry and alleviating energy and environmental pressures.

[0003] The commonly used methods for preparing urea-formaldehyde fertilizer are mainly dilute solution method and concentrated solution method. The so-called dilute solution method is to react urea and formaldehyde in the form of a dilute solution to generate a urea-formaldehyde suspension, separate the solid and liquid, and then dry and crush it to make a product, and the mother liquor is recycled. The characteristics of this method are good product quality, but the process is complicated, the cost is high, and it is difficult to achieve large-scale mass production. The concentrated solution method is to react urea and formaldehyde in the form of a concentrated solution, and the intermediate product obtained is not separated from the solid and liquid but directly added with a catalyst (curing agent) to solidify it into a product. This method has a simple process and low production cost, but the high-viscosity urea-formaldehyde fertilizer obtained is difficult to automatically discharge from the reaction device, so it can only stay in small batch production, or even in the laboratory stage. The difficulty in automatically discharging from the reaction device has become one of the main reasons that currently plague the urea-formaldehyde polymerization reaction and cannot achieve industrial amplification and continuous production. Therefore, how to automatically discharge high-viscosity urea-formaldehyde after the polymerization reaction is completed has become the technical key to the continuous production of urea-formaldehyde fertilizer.

[0004] Patents ZL 2023 1 1054388.9 and ZL 2023 1 0237417.9 have disclosed the use of reactive extrusion technology to realize the production and processing of urea-formaldehyde solid fertilizer particles, effectively solving the problem of continuous production of high-viscosity urea-formaldehyde. However, with the development of water-fertilizer integration technology, liquid fertilizers have been increasingly widely used due to their advantages such as fast absorption, flexible formula, environmental protection, convenient application and significant effect. In order to adapt to this trend, some scholars have developed urea-formaldehyde liquid fertilizers. At present, urea-formaldehyde liquid fertilizers are mainly divided into two categories. One is clear liquid urea-formaldehyde liquid fertilizer, which has a clear and transparent system and mainly contains soluble triazone compounds, hydroxymethyl urea and quick-acting nitrogen fertilizers. However, the nitrogen slow-release effect of clear liquid urea-formaldehyde liquid fertilizers is limited and the storage stability is poor. It has high requirements for ambient temperature and is easy to precipitate and deteriorate. The other is a suspended urea-formaldehyde liquid fertilizer, which is obtained by controlling the reaction of urea and formaldehyde to generate urea-formaldehyde polymers with relatively low molecular weight and adding a suspending agent to the system. The system is suspended and has a high viscosity. However, the existing suspended urea-formaldehyde liquid fertilizers are all obtained by repeatedly adjusting the pH of the urea-formaldehyde reaction system to control the degree of polymerization of urea-formaldehyde, resulting in a complicated preparation process and difficult to control product quality. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a process for preparing a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and a solid granular fertilizer in one piece, and an application method.

[0006] The present invention is realized by the following technical scheme: a process for preparing a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled-release liquid fertilizer and a solid granular fertilizer in one body, comprising the following steps:

[0007] (1) Add a certain amount of urea, formaldehyde, catalyst and water into reactor A, react at 50-90°C for 0.5-3h to obtain hydroxymethyl urea solution; the molar ratio of urea to formaldehyde is 1.2-5:1; the amount of catalyst added is 0-5% of the total mass of urea and formaldehyde and is not 0; the water content of the raw materials in reactor A is 15-35% of the total mass of urea and formaldehyde;

[0008] (2) adding any part of the hydroxymethylurea solution obtained in step (1) into a reactor B containing an acidic suspension prepared from an acidic substance, water and a suspending agent at a temperature of T 1 Lower reaction time t 1 , obtaining a urea-formaldehyde thick liquid, and then adding the thick liquid to a mixed liquid prepared by an alkaline substance, a fertilizer system containing at least one nutrient element other than nitrogen, and a nutrient synergist, and mixing evenly to obtain a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer;

[0009] At the same time, the remaining portion of the hydroxymethyl urea solution obtained in step (1) and a mixture of a fertilizer system containing at least one nutrient element other than nitrogen are pumped into a twin-screw reaction extruder of a reaction extruder integrated reaction unit at a temperature T 2 and screw speed R 1 The reaction extrusion time t 2 In this process, hydroxymethyl urea is subjected to polycondensation reaction to generate urea-formaldehyde polymer; then the twin-screw reaction extruder conveys the reaction product to the twin-screw extruder of the extrusion unit of the reaction extruder integrated machine, and the reaction product is extruded at a temperature T 3 and screw speed R 2 Extrusion to obtain a strip, temperature T 4 After drying at room temperature, the mixture is pelletized to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer.

[0010] As a further improvement of the technical solution of the present invention, in step (1), the formaldehyde is at least one of formaldehyde aqueous solution, solid paraformaldehyde, and gaseous formaldehyde; and the catalyst is one of potassium carbonate and potassium hydroxide or a mixture of the two.

[0011] As a further improvement of the technical solution of the present invention, in step (2), any part of the hydroxymethyl urea solution is added to the acidic suspension by dripping, spraying or pouring; the acidic substance is an inorganic acid or an organic acid, selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid, and tartaric acid; the amount of the acidic substance added is 0 to 80 wt% of the amount of water added in step (2) and is not 0; the suspending agent is an inorganic suspending agent or an organic suspending agent, selected from at least one of attapulgite, bentonite, kaolin, lignin, humic acid, alginic acid, polyvinyl alcohol, colloidal protein, xanthan gum, cellulose, and starch; the amount of the suspending agent added is 0 to 5 wt% of the amount of water added in step (2) and is not 0.

[0012] As a further improvement of the technical solution of the present invention, in step (2), the temperature T 1 = room temperature ~ 90℃, reaction time t 1 =0.1~2h.

[0013] As a further improvement of the technical solution of the present invention, in step (2), the alkaline substance is an inorganic base, a strong base weak acid salt or an organic base, selected from at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium phosphate, and organic amine compounds; the amount of the alkaline substance added depends on the pH value required by different soils or liquid fertilizers.

[0014] As a further improvement of the technical solution of the present invention, in step (2), the temperature T 2 =50~130℃, screw speed R 1=5~150rpm, reaction extrusion time t 2 =1~30min, temperature T 3 =50~130℃, screw speed R 2 =5~150rpm, temperature T 4 =60~150℃.

[0015] As a further improvement of the technical solution of the present invention, in step (2), the fertilizer system containing at least one nutrient element other than nitrogen is selected from at least one of phosphates, potassium salts, and medium and trace element fertilizers; the phosphate is selected from at least one of hydroxyapatite, ammonium dihydrogen phosphate, superphosphate, and potassium dihydrogen phosphate; the potassium salt is selected from at least one of potassium sulfate, potassium chloride, potassium nitrate, and potassium carbonate; the medium and trace element fertilizer is selected from at least one of calcium sulfate, magnesium sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, boric acid, sodium silicate, and potassium silicate; and the nutrient enhancer is selected from at least one of humic acid, amino acids, seaweed extracts, gibberellins, and auxins.

[0016] As a further improvement of the technical solution of the present invention, in step (2), before the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder of the reaction unit of the reaction extruder, the die between the reaction unit and the extrusion unit of the reaction extruder is sealed; after the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder, the screws of the twin-screw reaction extruder are started, and the vacuum devolatilization device thereof is started to remove moisture from the reaction system; the die between the reaction unit and the extrusion unit of the reaction extruder is opened, and the twin-screw extruder of the extrusion unit of the reaction extruder is started, so that the twin-screw reaction extruder transports the reaction product to the twin-screw extruder.

[0017] The present invention also provides an application method of the urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer prepared above, including foliar spraying, seed soaking, root dipping, injection application, drench application, pouring application, sprinkler irrigation application or drip irrigation application; the application amount is 8-15 kg nitrogen / mu.

[0018] The present invention further provides a method for applying the above-prepared urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer, which uses a seed-fertilizer-seeding all-in-one machine to apply solid granular fertilizer while sowing or to apply solid granular fertilizer and spray liquid fertilizer while sowing; the application amount is 8-15 kg nitrogen / mu.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer produced by the process of the present invention has good fluidity and will not agglomerate when placed for a long time; it has good dispersibility and can be mixed evenly with irrigation water in any proportion; it has good stability and has a low sedimentation rate after being mixed with irrigation water and placed for a long time, and will not clog the irrigation system during use.

[0021] (2) At present, the granulation of urea-formaldehyde granular fertilizer is still generally carried out by a rough crushing granulation method, which has the disadvantages of large dust, environmental pollution, irregular particle shape, etc. The urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer produced by the process of the present invention has regular particle shape, no dust pollution in the production process, continuous production, and saves manpower and material investment.

[0022] (3) The urea-formaldehyde-based multi-nutrient biodegradable polymer slow / controlled-release liquid fertilizer and solid granular fertilizer produced by the process of the present invention can flexibly adjust the content of macro-, medium- and trace nutrients in the fertilizer according to the growth needs of crops, thereby meeting the needs of crops for macro-, medium- and trace nutrients throughout their growth cycle.

[0023] (4) The present invention realizes the production of urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer on a set of equipment. The process is simple and environmentally friendly, and it is easy to meet the needs of different regions for different fertilizer forms. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer prepared in Example 2 are 500-4000 cm -1 FTIR spectrum at .

[0027] Figure 2 This is the XRD spectrum of the urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer prepared in Example 2.

[0028] Figure 3 Thermogravimetric (a) and thermogravimetric differential graph (b) of the urea-formaldehyde based multi-nutrient biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer prepared in Example 2.

[0029] Figure 4 These are SEM photos of the urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer prepared in Example 2.

[0030] Figure 5 The static water release curves of the urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer prepared in Example 2.

[0031] The performance tests and characterizations of the present invention all adopt the following standards:

[0032] 1) Grind and crush the urea-formaldehyde-based multi-nutrient biodegradable polymer slow / controlled release liquid fertilizer after freeze-drying, and pass through a 0.25 mm sieve to obtain the liquid fertilizer sample powder to be tested. Grind and crush the prepared urea-formaldehyde-based multi-nutrient biodegradable polymer slow / controlled release solid granular fertilizer directly, and pass through a 0.25 mm sieve to obtain the solid fertilizer sample powder to be tested. Take a small amount of dry sample powder and press it into KBr tablets, and use an infrared spectrometer (Nicolet IS50) to test the infrared spectrum at room temperature, with a scanning range of 500~4000cm -1 ; X-ray diffractometer (HAOYUAN DX-2700B) was used to perform XRD analysis on the powder samples with a scanning range of 5~80°; under a nitrogen atmosphere, a thermogravimetric analyzer (TA Q50) was used to measure the thermal stability of the powder samples, with a set temperature range of 30~800℃, a temperature increase of 10℃ / min, and a nitrogen flow rate of 40mL / min; a scanning electron microscope (Hitachi SU8010) was used to observe the surface morphology of the fertilizer, and the liquid fertilizer suspension was diluted 100 times and then dropped onto a silicon wafer for testing and observation using a scanning electron microscope, and the prepared solid granular fertilizer was directly observed using a scanning electron microscope.

[0033] 2) Slow-release performance test: The nitrogen nutrient release performance and initial release rate were characterized by static water release test. 5 mL of urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer was directly added to a bottle containing 100 mL of deionized water, inverted three times, and cultured in a constant temperature water bath at 25°C. Samples were taken at 1, 3, 5, 7, 10, 14 and 28 days. When sampling, use a pipette to suck the upper clear liquid, filter it with filter paper, transfer 20mL of solution, digest the solution with sulfuric acid-hydrogen peroxide method, and determine the nitrogen content with Kjeldahl nitrogen determination method, calculate the cumulative nutrient release rate, and the test result on the first day is the initial release rate; take 5.00g of the prepared urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer, pack it in a 100-mesh nylon mesh bag and seal it, then put it in a bottle filled with 100mL of deionized water, culture it in a constant temperature water bath at 25℃, and sample it at 1, 3, 5, 7, 10, 14 and 28 days. When sampling, use tweezers to place the nylon mesh bag at the mouth of the bottle to drain the water, and put it in a new culture bottle filled with 100mL of deionized water to continue culturing after no water drops. Turn the original culture bottle upside down to ensure that the concentration of the internal solution is consistent. Take 20 mL of solution, digest the solution using sulfuric acid-hydrogen peroxide method, determine the nitrogen content using Kjeldahl method, calculate the cumulative nutrient release rate, and the test result on the first day is the initial release rate. DETAILED DESCRIPTION

[0034] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0036] The present invention provides a specific embodiment of a process for preparing a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled-release liquid fertilizer and a solid granular fertilizer in one body, comprising the following steps:

[0037] (1) Add a certain amount of urea, formaldehyde, catalyst and water into reactor A, react at 50-90°C for 0.5-3h to obtain hydroxymethyl urea solution; the molar ratio of urea to formaldehyde is 1.2-5:1; the amount of catalyst added is 0-5% of the total mass of urea and formaldehyde and is not 0; the water content of the raw materials in reactor A is 15-35% of the total mass of urea and formaldehyde;

[0038] (2) adding any part of the hydroxymethylurea solution obtained in step (1) into a reactor B containing an acidic suspension prepared from an acidic substance, water and a suspending agent at a temperature of T1 Lower reaction time t 1 , obtaining a urea-formaldehyde thick liquid, and then adding the thick liquid to a mixed liquid prepared by an alkaline substance, a fertilizer system containing at least one nutrient element other than nitrogen, and a nutrient synergist, and mixing evenly to obtain a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer;

[0039] At the same time, the remaining portion of the hydroxymethyl urea solution obtained in step (1) and a mixture of a fertilizer system containing at least one nutrient element other than nitrogen are pumped into a twin-screw reaction extruder of a reaction extruder integrated reaction unit at a temperature T 2 and screw speed R 1 The reaction extrusion time t 2 In this process, hydroxymethyl urea is subjected to polycondensation reaction to generate urea-formaldehyde polymer; then the twin-screw reaction extruder conveys the reaction product to the twin-screw extruder of the extrusion unit of the reaction extruder integrated machine, and the reaction product is extruded at a temperature T 3 and screw speed R 2 Extrusion to obtain a strip, temperature T 4 After drying at room temperature, the mixture is pelletized to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer.

[0040] In one embodiment provided by the present invention, in step (1), the formaldehyde is at least one of a formaldehyde aqueous solution, solid paraformaldehyde, and gaseous formaldehyde; and the catalyst is one of potassium carbonate and potassium hydroxide or a mixture of both.

[0041] In another embodiment provided by the present invention, in step (2), any part of the hydroxymethylurea solution is added to the acidic suspension by dripping, spraying or pouring; the acidic substance is an inorganic acid or an organic acid; the amount of the acidic substance added is 0-80 wt% of the amount of water added in step (2) and is not 0; the suspending agent is an inorganic suspending agent or an organic suspending agent; the amount of the suspending agent added is 0-5 wt% of the amount of water added in step (2) and is not 0. The acidic substance is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid, and tartaric acid. The suspending agent is selected from at least one of attapulgite, bentonite, kaolin, lignin, humic acid, alginic acid, polyvinyl alcohol, colloidal protein, xanthan gum, cellulose, and starch.

[0042] In one embodiment provided by the present invention, in step (2), the temperature T 1 = room temperature ~ 90℃, reaction time t 1 =0.1~2h.

[0043] In another embodiment provided by the present invention, in step (2), the alkaline substance is an inorganic base, a strong base weak acid salt or an organic base, and is selected from at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium phosphate, and organic amine compounds; the amount of the alkaline substance added depends on the pH value required by different soils or liquid fertilizers.

[0044] In one embodiment provided by the present invention, in step (2), the temperature T 2 = 50~130℃, screw speed R 1 =5~150rpm, reaction extrusion time t 2 =1~30min, temperature T 3 =50~130℃, screw speed R 2 =5~150rpm, temperature T 4 =60~150℃.

[0045] In another embodiment provided by the present invention, in step (2), the fertilizer system containing at least one nutrient element other than nitrogen is selected from at least one of phosphates, potassium salts, and medium and trace element fertilizers; the phosphate is selected from at least one of hydroxyapatite, ammonium dihydrogen phosphate, superphosphate, and potassium dihydrogen phosphate; the potassium salt is selected from at least one of potassium sulfate, potassium chloride, potassium nitrate, and potassium carbonate; the medium and trace element fertilizer is selected from at least one of calcium sulfate, magnesium sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, boric acid, sodium silicate, and potassium silicate; and the nutrient enhancer is selected from at least one of humic acid, amino acids, seaweed extracts, gibberellins, and auxins.

[0046] In one embodiment provided by the present invention, in step (2), before the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder of the reaction unit of the reaction extruder, the die between the reaction unit and the extrusion unit of the reaction extruder is sealed; after the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder, the screws of the twin-screw reaction extruder are started, and the vacuum devolatilization device thereof is started to remove moisture from the reaction system; the die between the reaction unit and the extrusion unit of the reaction extruder is opened, and the twin-screw extruder of the extrusion unit of the reaction extruder is started, so that the twin-screw reaction extruder conveys the reaction product to the twin-screw extruder.

[0047] The present invention further provides a method for applying the above-prepared urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer, including foliar spraying, seed soaking, root dipping, injection, drench application, pouring application, sprinkler irrigation or drip irrigation; the application amount is 8-15 kg nitrogen / mu.

[0048] The present invention further provides a method for applying the above-prepared urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer, using a seed-fertilizer-seeding all-in-one machine, applying solid granular fertilizer while sowing, or applying solid granular fertilizer and spraying liquid fertilizer while sowing; the application amount is 8-15 kg nitrogen / mu.

[0049] The specific embodiments of the present invention are described in detail below. Example 1

[0050] A process for preparing a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and a solid granular fertilizer in one piece, comprising the following steps:

[0051] (1) Add a certain amount of urea, a 37 wt% formaldehyde aqueous solution, a catalyst potassium hydroxide and water into a reactor A, wherein the molar ratio of urea to formaldehyde contained in the formaldehyde aqueous solution is 1.5:1, and the amount of the catalyst potassium hydroxide added is 0.5% of the total mass of urea and formaldehyde. The reaction is carried out at 80° C. for 2 h to obtain a hydroxymethyl urea solution; the water content of the entire system is 35% of the total mass of urea and formaldehyde;

[0052] (2) pouring half of the hydroxymethylurea solution obtained in step (1) into a reactor B containing an acidic suspension prepared by sulfuric acid, water and attapulgite as a suspending agent, wherein the sulfuric acid solute accounts for 20% of the mass of the added water, and the amount of attapulgite added is 1% of the mass of the water; the temperature T 1 = reaction time at room temperature t 1 =0.5h, to obtain a urea-formaldehyde thick liquid, which is then added to a mixed liquid prepared from sodium hydroxide, ammonium dihydrogen phosphate and nutrient enhancer humic acid, wherein the molar ratio of sodium hydroxide to sulfuric acid added to the acidic suspension is 2:1, the mass ratio of ammonium dihydrogen phosphate to urea in step (1) is 1:2, and the mass ratio of humic acid to urea in step (1) is 0.1:1, and the mixture is fully mixed to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer;

[0053] The other half of the hydroxymethyl urea solution obtained in step (1) and the mixture of ammonium dihydrogen phosphate in a urea mass ratio of 1:2 in step (1) are injected into the twin-screw reaction extruder of the reaction extruder integrated machine with a die seal between the reaction unit and the extrusion unit, the screws of the twin-screw reaction extruder are turned on, and the vacuum devolatilization device is started to remove the moisture in the reaction system, and the temperature is T 2 =80℃ and screw speed R 1 = reaction extrusion time t at 50 rpm 2= 30min, during which hydroxymethyl urea generates urea-formaldehyde polymer through polycondensation reaction; then open the die between the reaction unit and the extrusion unit of the reaction extruder, start the twin-screw extruder of the extrusion unit of the reaction extruder, and make the twin-screw reaction extruder convey the reaction product to the twin-screw extruder, at temperature T 3 =60℃ and screw speed R 2 =50rpm, and the strips are obtained at a temperature of T 4 =80°C and then granulated to obtain urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer.

[0054] The prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer has a nutrient element N content of 18.8 g / L and P 2 O 5 The content is 11.5 g / L, and the initial nitrogen nutrient release rate is 26.3%. When planting corn, the liquid fertilizer sprayer applies fertilizer at a rate of 80 L / mu.

[0055] The prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer has a nutrient element N content of 30.2 wt%, P 2 O 5 The content is 18.5 wt%, and the initial nitrogen nutrient release rate is 22.8%. When planting corn, use a seed and fertilizer machine to apply fertilizer at a rate of 50 kg / mu. Example 2

[0056] A process for preparing a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and a solid granular fertilizer in one piece, comprising the following steps:

[0057] (1) A certain amount of urea, solid paraformaldehyde, catalyst potassium hydroxide and water were added to reactor A, wherein the molar ratio of urea to the formaldehyde structural unit contained in paraformaldehyde was 1.5:1, and the amount of catalyst potassium hydroxide added was 0.1% of the total mass of urea and paraformaldehyde. The reaction was carried out at 70°C for 2 hours to obtain a hydroxymethyl urea solution. The water content of the whole system was 30% of the total mass of urea and paraformaldehyde.

[0058] (2) Pour half of the hydroxymethylurea solution obtained in step (1) into a reactor B containing an acidic suspension prepared by sulfuric acid, water and suspending agent xanthan gum, wherein the sulfuric acid solute accounts for 20% of the mass of the added water, and the amount of xanthan gum added is 0.3% of the mass of the water; the temperature T 1 = reaction time t at 60°C 1=0.3h, to obtain a urea-formaldehyde thick liquid, which is then added to a mixed liquid prepared from potassium hydroxide, ammonium dihydrogen phosphate, potassium sulfate and a nutrient synergist amino acid, wherein the molar ratio of potassium hydroxide to the sulfuric acid added to the acidic suspension is 3:1, the mass ratio of ammonium dihydrogen phosphate to the urea in step (1) is 1:5, the mass ratio of potassium sulfate to ammonium dihydrogen phosphate is 1:3, and the mass ratio of amino acid to the urea in step (1) is 0.5:1, and the mixture is fully mixed to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer;

[0059] (2) injecting the other half of the hydroxymethyl urea solution obtained in step (1) into a mixture of ammonium dihydrogen phosphate (with a mass ratio of 1:5 to the urea in step (1)) and potassium sulfate (with a mass ratio of 1:3 to the ammonium dihydrogen phosphate) into a twin-screw reaction extruder of the reaction extruder integrated machine with a die seal between the reaction unit and the extrusion unit, starting the screws of the twin-screw reaction extruder and simultaneously starting its vacuum devolatilization device to remove moisture from the reaction system, and heating the reaction system at a temperature T 2 =100℃ and screw speed R 1 = reaction extrusion time t at 60 rpm 2 = 30min, during which hydroxymethyl urea generates urea-formaldehyde polymer through polycondensation reaction; then open the die between the reaction unit and the extrusion unit of the reaction extruder, start the twin-screw extruder of the extrusion unit of the reaction extruder, and make the twin-screw reaction extruder convey the reaction product to the twin-screw extruder, at temperature T 3 =50℃ and screw speed R 2 = 60rpm to obtain a strip, temperature T 4 =100°C and then granulated to obtain urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer.

[0060] The prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer has a nutrient element N content of 18.05 g / L, P 2 O 5 The content is 10.9 g / L, K 2 O content was 12.9 g / L; the initial nitrogen nutrient release rate was 27.05%. When planting corn, the liquid fertilizer sprayer applied fertilizer at a rate of 85 L / mu.

[0061] The content of nutrient element N in the prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer is 35.22 wt%, P 2 O 5 The content is 12.58 wt%, K 2 O content is 8.45 g / L; the initial nitrogen nutrient release rate is 23.65%. When planting corn, use a seed-fertilizer-seeding machine to apply fertilizer at a rate of 42.5 kg / mu.

[0062] Figure 1 In the present embodiment, the liquid fertilizer and solid fertilizer prepared in 3327cm -1 There is a strong -NH- stretching vibration absorption peak at all locations, which belongs to the characteristic -NHCONH-CH 2 -chain segment, indicating that urea-formaldehyde molecular chains exist in both liquid fertilizer and solid fertilizer; in addition, liquid fertilizer and solid fertilizer have -1 Characteristic absorption peaks appeared, which belong to -NH-CH 2 -NH-methylene bridge asymmetric stretching vibration, at 1023cm -1 -CH appeared 2 -O-CH 2 -Methylene ether bond stretching vibration absorption peak, by comparison, it can be found that the characteristic absorption peak intensity ratio of liquid fertilizer is A 1023 / A 1132 The results are significantly larger than those of solid fertilizer, indicating that under the catalysis of strong acid, the hydroxymethyl urea in liquid fertilizer forms more methylene ether bonds through polycondensation reaction, that is, more cross-linked structures are formed, while solid fertilizer forms more linear structures. The FTIR spectrum shows that the product has the above structure.

[0063] Figure 2 In the embodiment, the liquid fertilizer prepared in this example has an obvious urea characteristic diffraction peak at 22.01°, but this peak is not significant in the spectrum of solid fertilizer, indicating that the residual amount of raw material urea in the solid fertilizer is significantly reduced; in addition, the liquid fertilizer and the solid fertilizer both have characteristic diffraction peaks of urea formaldehyde at 22.64° and 24.95°, and the crystallinity (X C =32.45%) is lower than solid fertilizer (X C =48.37%), indicating that more cross-linked structures in the liquid fertilizer inhibit the regular arrangement of urea-formaldehyde molecular chains. The XRD spectrum shows that the product has the above structure.

[0064] Figure 3 In the embodiment, the overall thermal stability of the liquid fertilizer prepared in this embodiment is lower than that of the solid fertilizer because the liquid fertilizer contains more unreacted small molecule urea or urea-formaldehyde oligomers. It can also be seen from the thermogravimetric differential diagram that the thermal weight loss peak of the liquid fertilizer at 100-250°C is significantly higher than that of the solid fertilizer, indicating that the liquid fertilizer contains more urea or urea-formaldehyde oligomers. At 250-350°C, the thermal weight loss peak of the liquid fertilizer is significantly lower than that of the solid fertilizer, indicating that the content of high-polymerization urea-formaldehyde in the liquid fertilizer is lower than that of the solid fertilizer. The reason is that during the preparation process, the solid fertilizer undergoes a high-temperature curing process, so the polymerization degree of the urea-formaldehyde molecular chain is higher. The thermogravimetric and thermogravimetric differential diagrams show that the product has the structure.

[0065] Figure 4In the embodiment, the liquid fertilizer prepared in this embodiment is a uniform flower-shaped particle with an average particle size of 4.76 μm. The smaller particle size gives the liquid fertilizer dispersion stability in the suspension; the solid fertilizer is formed by extruding, stacking and bonding urea-formaldehyde particles, and there are a large number of fine cracks and holes on the surface, which enhances its biodegradation rate. The SEM photo shows that the product has the structure.

[0066] Figure 5 In the 0-7 days, the nitrogen release rate of the liquid fertilizer prepared by the present embodiment is higher than that of the solid fertilizer, which again shows that the content of unreacted urea or urea-formaldehyde oligomer in the liquid fertilizer is higher than that of the solid fertilizer. After 7 days, the nitrogen release rate of the liquid fertilizer is lower than that of the solid fertilizer, which again shows that the cross-linking degree of the liquid fertilizer is higher. Within 28 days, the nitrogen cumulative release rate of the liquid fertilizer and the solid fertilizer is lower than 80%, indicating that the slow-release effect is good and is suitable for cash crops or field crops. Example 3

[0067] A process for preparing a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and a solid granular fertilizer in one piece, comprising the following steps:

[0068] (1) A certain amount of urea, solid paraformaldehyde, catalyst potassium carbonate and water were added to reactor A, wherein the molar ratio of urea to the formaldehyde structural unit contained in paraformaldehyde was 2.1:1, and the amount of catalyst added was 0.05% of the total mass of urea and paraformaldehyde. The reaction was carried out at 70°C for 1.5 hours to obtain a hydroxymethyl urea solution; the water content of the whole system was 25% of the total mass of urea and paraformaldehyde;

[0069] (2) adding half of the hydroxymethylurea solution obtained in step (1) dropwise into a reactor B containing an acidic suspension prepared from phosphoric acid, water and a suspending agent, bentonite, wherein the phosphoric acid solute accounts for 10% of the mass of the added water and the amount of bentonite added is 1% of the mass of the water; the temperature T 1 = reaction time t at 30°C 1 = 1h, to obtain a urea-formaldehyde thick liquid, which is then added to a mixed liquid prepared from potassium hydroxide, ammonium dihydrogen phosphate and a nutrient synergist gibberellin, wherein the molar ratio of potassium hydroxide to the phosphoric acid added to the acidic suspension is 3:1, the mass ratio of ammonium dihydrogen phosphate to the urea in step (1) is 1:4, and the mass ratio of gibberellin to the urea in step (1) is 0.05:1, and the mixture is fully mixed to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer;

[0070] The other half of the hydroxymethyl urea solution obtained in step (1) and a mixture of ammonium dihydrogen phosphate (with a mass ratio of 1:4 to the urea in step (1)) are pumped into a twin-screw reaction extruder of the reaction extruder integrated machine with a die seal between the reaction unit and the extrusion unit, the screws of the twin-screw reaction extruder are turned on, and the vacuum devolatilization device is started to remove moisture from the reaction system.2 =110℃ and screw speed R 1 = reaction extrusion time t at 70 rpm 2 = 10min, during which hydroxymethyl urea generates urea-formaldehyde polymer through polycondensation reaction; then open the die between the reaction unit and the extrusion unit of the reaction extruder, start the twin-screw extruder of the extrusion unit of the reaction extruder, and make the twin-screw reaction extruder convey the reaction product to the twin-screw extruder at temperature T 3 =60℃ and screw speed R 2 =20rpm, and the strips are obtained at a temperature of T 4 = The product is dried at 120°C and then pelletized to obtain a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer.

[0071] The prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer has a nutrient element N content of 19.3 g / L and P 2 O 5 The content is 9.7 g / L, K 2 O content is 7.3g / L; the initial nitrogen nutrient release rate is 28.3%. When planting corn, the liquid fertilizer sprayer applies fertilizer at a rate of 78 L / mu.

[0072] The prepared urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer has a nutrient element N content of 35.2 wt%, P 2 O 5 The content is 15.2wt%, K 2 O content is 0.85g / L; the initial nitrogen nutrient release rate is 24.0%. When planting corn, use a seed and fertilizer machine to apply fertilizer at a rate of 43 kg / mu.

[0073] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A process for preparing a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer in one, characterized in that: The following steps are involved: (1) Add a certain amount of urea, formaldehyde, catalyst and water into reactor A, react at 50-90° C. for 0.5-3 h to obtain a hydroxymethyl urea solution; the molar ratio of urea to formaldehyde is 1.2-5:1; the amount of catalyst added is 0-5% of the total mass of urea and formaldehyde and is not 0; the water content of the raw materials in reactor A is 15-35% of the total mass of urea and formaldehyde; (2) adding any part of the hydroxymethyl urea solution obtained in step (1) to a reactor B containing an acidic suspension prepared by an acidic substance, water and a suspending agent, reacting at a temperature of T1 for a time of t1 to obtain a urea-formaldehyde viscous liquid, and then adding the urea-formaldehyde viscous liquid to a mixed liquid prepared by an alkaline substance, a fertilizer system containing at least one nutrient element other than nitrogen, and a nutrient synergist, and mixing them evenly to obtain a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer; the acidic substance is an inorganic acid or an organic acid, the alkaline substance is an inorganic base, a strong base and a weak base acid salt or an organic base, and the suspending agent is an inorganic suspending agent or an organic suspending agent; the temperature T1 is room temperature to 90°C, and the reaction time t1 is 0.1 to 2h; the fertilizer system containing at least one nutrient element other than nitrogen is selected from at least one of phosphates, potassium salts, and medium and trace element fertilizers; the nutrient synergist is selected from at least one of humic acid, amino acids, seaweed extracts, gibberellins, and auxins; At the same time, the remaining part of the hydroxymethyl urea solution obtained in step (1) and the mixture of the fertilizer system containing at least one nutrient element other than nitrogen are introduced into the twin-screw reaction extruder of the reaction unit of the reaction extruder, and the reaction extrusion time is t2 at the temperature T2 and the screw speed R1. During this process, the hydroxymethyl urea generates a urea-formaldehyde polymer through a polycondensation reaction; then the twin-screw reaction extruder conveys the reaction product to the twin-screw extruder of the extrusion unit of the reaction extruder, and extrudes it at the temperature T3 and the screw speed R2 to obtain a strip, which is dried at the temperature T4 and then pelletized to obtain a urea-formaldehyde-based multi-nutrient element biodegradable polymer slow / controlled release solid granular fertilizer; the temperature T2 is 50-130°C, the screw speed R1 is 5-150rpm, the reaction extrusion time t2 is 1-30min, the temperature T3 is 50-130°C, the screw speed R2 is 5-150rpm, and the temperature T4 is 60-150°C.

2. The integrated preparation process of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer according to claim 1, characterized in that: In step (1), the formaldehyde is at least one of a formaldehyde aqueous solution, solid paraformaldehyde, and gaseous formaldehyde; and the catalyst is one of potassium carbonate and potassium hydroxide, or a mixture of the two.

3. The integrated preparation process of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer according to claim 1, characterized in that: In step (2), any part of the hydroxymethyl urea solution is added to the acidic suspension by dripping, spraying or pouring; the inorganic acid or organic acid is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid and tartaric acid; the amount of the acidic substance added is 0-80 wt% of the amount of water added in step (2) and is not 0; the inorganic suspending agent or organic suspending agent is selected from at least one of attapulgite, bentonite, kaolin, lignin, humic acid, alginic acid, polyvinyl alcohol, colloidal protein, xanthan gum, cellulose and starch; the amount of the suspending agent added is 0-5 wt% of the amount of water added in step (2) and is not 0.

4. The integrated preparation process of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer according to claim 1, characterized in that: In step (2), the inorganic base, strong base weak acid salt or organic base is selected from at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, potassium phosphate and organic amine compounds; the amount of the alkaline substance added depends on the pH value required by different soils or liquid fertilizers.

5. The integrated preparation process of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer according to claim 1, characterized in that: In step (2), the phosphate is selected from at least one of hydroxyapatite, diammonium phosphate, superphosphate and potassium dihydrogen phosphate; the potassium salt is selected from at least one of potassium sulfate, potassium chloride, potassium nitrate and potassium carbonate; the trace element fertilizer is selected from at least one of calcium sulfate, magnesium sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, boric acid, sodium silicate and potassium silicate.

6. The integrated preparation process of a urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer and solid granular fertilizer according to claim 1, characterized in that: In step (2), before the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder of the reaction unit of the reaction extruder, the die between the reaction unit and the extrusion unit of the reaction extruder is sealed; after the hydroxymethyl urea solution obtained in step (1) is injected into the twin-screw reaction extruder, the screws of the twin-screw reaction extruder are started, and the vacuum devolatilization device thereof is started to remove moisture from the reaction system; the die between the reaction unit and the extrusion unit of the reaction extruder is opened, and the twin-screw extruder of the extrusion unit of the reaction extruder is started, so that the twin-screw reaction extruder conveys the reaction product to the twin-screw extruder.

7. The method for applying the urea-formaldehyde based multi-nutrient element biodegradable polymer slow / controlled release liquid fertilizer prepared as claimed in claim 1, characterized in that: It includes foliar spraying, seed soaking, root dipping, injection, sprinkling, pouring, sprinkler irrigation or drip irrigation; the application amount is 8~15 kg nitrogen / mu.

8. The method for applying the urea-formaldehyde based multi-nutrient biodegradable polymer slow / controlled release solid granular fertilizer prepared as claimed in claim 1, characterized in that: Use a seed-fertilizer-seeding machine to apply solid granular fertilizer at the same time as sowing, or apply solid granular fertilizer and spray liquid fertilizer at the same time as sowing; the application amount is 8~15 kg nitrogen / mu.

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