阅读说明：本技术 一种磷酸-氨基甲酸淀粉酯包覆尿素缓释型肥料的制备方法 (Preparation method of phosphoric acid-carbamate starch ester coated urea slow-release fertilizer ) 是由 张文治 牟忠华 董国华 吴昊 白丽明 隋丽丽 郎坤 郝丽娟 魏铭辉 于 2019-11-21 设计创作，主要内容包括：一种磷酸-氨基甲酸淀粉酯包覆尿素缓释型肥料的制备方法,它涉及一种缓释型肥料的制备方法。本发明的目的是要解决现有尿素的利用率低以及其他包覆材料包覆尿素价格高,工艺复杂,成本高,包覆材料污染环境的问题。方法：一、制备磷酸-氨基甲酸淀粉酯；二、制备纤维素分散液；三、制备纤维素粘结剂溶液；四、包覆,得到磷酸-氨基甲酸淀粉酯包覆尿素缓释型肥料。本发明工艺简单、可操作性强、低耗能、降低环境的污染、不需要昂贵仪器的生产条件,适合工业化生产和大型农田作物应用。本发明可获得一种磷酸-氨基甲酸淀粉酯包覆尿素缓释型肥料。(A preparation method of a phosphoric acid-carbamic acid starch ester coated urea slow-release fertilizer relates to a preparation method of a slow-release fertilizer. The invention aims to solve the problems of low utilization rate of the existing urea, high price of other coating materials for coating urea, complex process, high cost and environmental pollution caused by the coating materials. The method comprises the following steps: firstly, preparing phosphoric acid-carbamic acid starch ester; secondly, preparing cellulose dispersion liquid; thirdly, preparing a cellulose binder solution; and fourthly, coating to obtain the phosphoric acid-carbamate starch ester coated urea slow-release fertilizer. The invention has simple process, strong operability, low energy consumption, reduced environmental pollution, no need of expensive instruments and production conditions, and is suitable for industrial production and large-scale farmland crop application. The invention can obtain the slow-release fertilizer of urea coated by phosphoric acid-carbamic acid starch ester.)

1. A preparation method of a phosphoric acid-carbamate coated urea slow-release fertilizer is characterized in that the preparation method of the phosphoric acid-carbamate coated urea slow-release fertilizer is completed according to the following steps:

firstly, preparing phosphoric acid-carbamic acid starch ester:

①, uniformly mixing starch, phosphate and urea, grinding to obtain mixed powder, transferring the mixed powder into a reaction kettle, adding absolute ethyl alcohol and deionized water into the reaction kettle, and sealing the reaction kettle for esterification reaction to obtain a coarse product of the phosphoric acid-starch carbamate;

the mass ratio of the starch to the phosphate in the first step ① is (10.0-50.00): (9.0-45.0);

the mass ratio of the starch to the urea in the first step ① is (10.0-50.0): 7.0-35.0);

the volume ratio of the mass of the starch to the absolute ethyl alcohol in the first step ① is (10 g-50 g): 10 mL-50 mL;

the ratio of the mass of the starch to the volume of the deionized water in the first step ① is (10.0 g-50.0 g): 2 mL-10 mL;

②, firstly, washing a phosphoric acid-carbamic acid starch ester crude product by using absolute ethyl alcohol, then drying, grinding, and finally drying to obtain phosphoric acid-carbamic acid starch ester;

adding cellulose into distilled water, and stirring and reacting at the temperature of 50-120 ℃ to obtain cellulose dispersion liquid;

the mass ratio of the cellulose to the deionized water in the second step is (6.0 g-60 g): 10 mL-50 mL;

adding alcohol, aldehyde and alkali into the cellulose dispersion liquid, stirring and reacting at the temperature of 30-80 ℃, and cooling to room temperature to obtain a cellulose binder solution;

the volume ratio of the alcohol to the cellulose dispersion liquid in the third step is (2-20) to (10-50);

the volume ratio of the aldehyde to the cellulose dispersion liquid in the third step is (1-10) to (10-50);

the ratio of the mass of the alkali to the volume of the cellulose dispersion in the third step is (1 g-10 g): 10 mL-50 mL;

fourthly, coating:

①, soaking the urea in the cellulose binder solution for 10-60 min, and taking out to obtain urea with the surface containing the cellulose binder;

②, mixing urea with cellulose binder on the surface with phosphoric acid-starch carbamate, adding into a rotary evaporator, and distilling under reduced pressure at 30-70 deg.C and 0.01-0.1 MPa for 30-120 min;

the mass ratio of the urea with the cellulose binder on the surface to the phosphoric acid-starch carbamate in the step ② is (1-5) to (10-50);

③, repeating the step four ① - ② 2 times to 8 times to obtain the urea slow-release fertilizer coated by the phosphoric acid-carbamic acid starch ester.

2. The method for preparing a slow release fertilizer with urea coated with starch phosphate-carbamate according to claim 1, wherein the starch in the first step ① is corn starch, wheat starch or potato starch.

3. The method for preparing a slow-release urea fertilizer coated with starch phosphate-carbamate according to claim 1, wherein the grinding time in the first step ① is 30min to 60 min.

4. The method of claim 1, wherein the phosphate in step one ① is one or a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate.

5. The method for preparing a slow-release urea fertilizer coated with starch phosphate-carbamate according to claim 1, wherein the esterification reaction temperature in the first step is 100 ℃ to 150 ℃ and the esterification reaction time is 5h to 13 h.

6. The method for preparing the starch phosphate-carbamate coated urea slow-release fertilizer according to claim 1, wherein the cleaning time in the first step ② is 2-5 times, the drying temperature in the first step ② is 30-70 ℃, the drying time is 30-180 min, and the grinding time in the first step ② is 30-60 min.

7. The method for preparing a slow release urea fertilizer coated with starch phosphate-carbamate according to claim 1, wherein the cellulose in the second step is ethyl cellulose.

8. The method for preparing a slow-release urea fertilizer coated with starch phosphate-carbamate according to claim 1, wherein the stirring reaction speed in the second step is 100-1000 r/min, and the stirring reaction time is 30-120 min.

9. The method for preparing a slow-release urea fertilizer coated with starch phosphate-carbamate according to claim 1, wherein the alcohol in step three is glycerol; the aldehyde is a formaldehyde solution with the mass fraction of 40%; the alkali is sodium hydroxide.

10. The preparation method of the starch phosphate-carbamate coated urea slow-release fertilizer as claimed in claim 1, wherein the stirring speed in the third step is 100r/min to 1000r/min, and the stirring time is 30min to 90 min.

Technical Field

The invention relates to a preparation method of a slow-release fertilizer.

Background

As a big agricultural country, China especially takes up a very important position in agricultural production. China is a large country for producing urea and a large country for using the urea, but the utilization rate of the urea after being applied to soil is not high, and the main reason is the volatilization and loss of nitrogen. Meanwhile, too much intake of the fertilizer not only causes loss of manpower and material resources, but also causes serious environmental damage, which is mainly characterized in that nutrient components which cannot be absorbed and utilized in the fertilizer destroy the quality of soil, the content of nitrate and nitrite in water is overproof due to gathering of the fertilizer nutrient components lost by permeation and showering on the surface layer and the underground water layer, the health of people is harmed, and meanwhile, part of nitrogen elements form nitric oxide through chemical action and are discharged into the atmosphere, acid rain is formed, and the ozone layer is destroyed to intensify the greenhouse effect.

With the improvement of living standard of people, people pay attention to environmental protection, and aiming at the problem of how to reasonably apply fertilizer to land, people have higher requirements, and the problems of high fertilizer utilization rate, yield increase, income increase, green and safe fertilizer and the like can be realized, so that the high attention of many countries in the world is also paid, therefore, in order to improve the utilization rate of urea, maintain the fertility of nitrogen in soil, reduce nitrogen loss and environmental pollution caused by nitrogen loss and increase the yield of crops, the use of slow-release urea is an important effective way for overcoming the defects. The coating material does not react with chemical fertilizers generally, different release performances can be obtained by selecting different coating materials, and the coating material is suitable for agricultural production in different environments. However, the performance of the coating material is improved by adding an organic polymer or an inorganic substance, but the strength of the coating material is reduced by adding the inorganic substance to the coating material, so that the coating material is relatively brittle and is easy to disintegrate in practical application, and is easy to damage in the production and transportation process, which brings economic loss, while the organic substance is added to the coating material, which is difficult to decompose in soil and brings harm to the environment and human body, and meanwhile, the organic solvents have high price, complex process and low efficiency, which brings cost improvement to industrial production.

Disclosure of Invention

The invention aims to solve the problems of low utilization rate of the existing urea, high price of other coating materials coated urea, complex process, high cost and environmental pollution caused by the coating materials, and provides a preparation method of a phosphoric acid-starch carbamate coated urea slow-release fertilizer.

A preparation method of a phosphoric acid-carbamate starch ester coated urea slow-release fertilizer comprises the following steps:

firstly, preparing phosphoric acid-carbamic acid starch ester:

①, uniformly mixing starch, phosphate and urea, grinding to obtain mixed powder, transferring the mixed powder into a reaction kettle, adding absolute ethyl alcohol and deionized water into the reaction kettle, and sealing the reaction kettle for esterification reaction to obtain a coarse product of the phosphoric acid-starch carbamate;

the mass ratio of the starch to the phosphate in the first step ① is (10.0-50.00): (9.0-45.0);

the mass ratio of the starch to the urea in the first step ① is (10.0-50.0): 7.0-35.0);

the volume ratio of the mass of the starch to the absolute ethyl alcohol in the first step ① is (10 g-50 g): 10 mL-50 mL;

the ratio of the mass of the starch to the volume of the deionized water in the first step ① is (10.0 g-50.0 g): 2 mL-10 mL;

②, firstly, washing a phosphoric acid-carbamic acid starch ester crude product by using absolute ethyl alcohol, then drying, grinding, and finally drying to obtain phosphoric acid-carbamic acid starch ester;

adding cellulose into distilled water, and stirring and reacting at the temperature of 50-120 ℃ to obtain cellulose dispersion liquid;

the mass ratio of the cellulose to the deionized water in the second step is (6.0 g-60 g): 10 mL-50 mL;

adding alcohol, aldehyde and alkali into the cellulose dispersion liquid, stirring and reacting at the temperature of 30-80 ℃, and cooling to room temperature to obtain a cellulose binder solution;

the volume ratio of the alcohol to the cellulose dispersion liquid in the third step is (2-20) to (10-50);

the volume ratio of the aldehyde to the cellulose dispersion liquid in the third step is (1-10) to (10-50);

the ratio of the mass of the alkali to the volume of the cellulose dispersion in the third step is (1 g-10 g): 10 mL-50 mL;

fourthly, coating:

①, soaking the urea in the cellulose binder solution for 10-60 min, and taking out to obtain urea with the surface containing the cellulose binder;

②, mixing urea with cellulose binder on the surface with phosphoric acid-starch carbamate, adding into a rotary evaporator, and distilling under reduced pressure at 30-70 deg.C and 0.01-0.1 MPa for 30-120 min;

the mass ratio of the urea with the cellulose binder on the surface to the phosphoric acid-starch carbamate in the step ② is (1-5) to (10-50);

③, repeating the step four ① - ② 2 times to 8 times to obtain the urea slow-release fertilizer coated by the phosphoric acid-carbamic acid starch ester.

The principle and the advantages of the invention are as follows:

the phosphate-carbamate starch ester as amphoteric starch has excellent physical and chemical properties, such as high viscosity, low gelatinization temperature, strong ion adsorption capacity and the like. The phosphate carbamate is applied to the coating material, so that the starch can be naturally degraded and does not pollute the environment, and phosphate fertilizer and nitrogen fertilizer can be provided for soil after the starch is degraded, so that the utilization rate of the phosphate carbamate as the coating material is maximized;

the phosphoric acid-carbamate starch ester is used for coating the urea, so that the utilization rate of the urea and the soil fertility are improved, the cost is reduced, the fertilization times are reduced, the pollution to the environment is reduced, and the comprehensive development of resource utilization and environment optimization is realized;

thirdly, the preparation method of the phosphate-carbamate coated urea slow-release fertilizer provided by the invention is that the ethyl cellulose binder and the phosphate-carbamate are sprayed on the surface of urea, and the phosphate-carbamate coated urea slow-release fertilizer with different release rates in water or soil is obtained by controlling the concentration of the phosphate-carbamate, the quality of the phosphate-carbamate and the thickness of a layer coated for many times, so that the release time of the urea can be prolonged, the pollution of the urea to the environment can be improved, and the starch derivative can be degraded under natural conditions to form nutrients, so that the secondary pollution of the coated material can be avoided;

the phosphoric acid-carbamate starch ester used in the invention can be degraded under natural conditions, can form nutrients, improve the fertility and avoid secondary pollution of the coating material;

the method has the advantages of simple process, strong operability, low energy consumption, reduction of environmental pollution, no need of expensive instruments, and suitability for industrial production and large-scale farmland crop application;

sixthly, the release rate of the phosphoric acid-carbamic acid starch ester coated urea slow-release fertilizer prepared by the invention in the soil within 24 hours at the initial stage is less than 11%.

The invention can obtain the slow-release fertilizer of urea coated by phosphoric acid-carbamic acid starch ester.

Drawings

FIG. 1 is a flow chart of urea coated with a phosphoric acid carbamate;

FIG. 2 is an infrared spectrum in which 1 is an infrared spectrum curve of corn starch and 2 is an infrared spectrum curve of starch phosphate-carbamate prepared in one step one of the example;

FIG. 3 is a graph of starch viscosity, where 1 is the corn starch viscosity and 2 is the viscosity of the starch phosphate carbamate prepared in one step one of the example;

FIG. 4 is a graph of starch gelatinization temperature, where 1 is the gelatinization temperature of corn starch and 2 is the gelatinization temperature of starch phosphate prepared in step one of the examples;

FIG. 5 is a graph showing the release profile of urea in water, in which 1 is the release profile of normal urea in water, 2 is the release profile of a corn starch-coated urea slow-release type fertilizer prepared in comparative example in water, and 3 is the release profile of a phosphoric acid-starch carbamate-coated urea slow-release type fertilizer prepared in example one in water;

FIG. 6 is a graph showing the release profile of urea in soil, in which 1 is the release profile of normal urea in soil and 2 is the release profile of a starch phosphate-carbamate coated urea slow-release fertilizer prepared in example one;

FIG. 7 is a photographic image of corn starch;

FIG. 8 is a photographic image of a starch phosphate-carbamate prepared in one step one of the example;

FIG. 9 is a photograph of a starch phosphate-carbamate coated urea slow release fertilizer prepared in example one;

FIG. 10 is a comparison between before and after urea coating, in which 1 is urea and 2 is a phosphate-urethane coated urea slow-release fertilizer prepared in example one.

Detailed Description