CN115959949B - Polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer and preparation method thereof - Google Patents
Polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer and preparation method thereof Download PDFInfo
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- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 61
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 61
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- 239000004368 Modified starch Substances 0.000 title claims abstract description 55
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- 238000002360 preparation method Methods 0.000 title claims abstract description 37
- 206010016807 Fluid retention Diseases 0.000 title claims abstract description 17
- 238000013270 controlled release Methods 0.000 title claims abstract description 16
- 238000013268 sustained release Methods 0.000 title claims abstract description 16
- 230000002459 sustained effect Effects 0.000 title claims abstract description 12
- 239000010410 layer Substances 0.000 claims abstract description 83
- 239000011248 coating agent Substances 0.000 claims abstract description 63
- 238000000576 coating method Methods 0.000 claims abstract description 63
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000000661 sodium alginate Substances 0.000 claims abstract description 44
- 235000010413 sodium alginate Nutrition 0.000 claims abstract description 44
- 229940005550 sodium alginate Drugs 0.000 claims abstract description 44
- 239000002356 single layer Substances 0.000 claims abstract description 38
- 239000002245 particle Substances 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 17
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- 239000000463 material Substances 0.000 claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 239000000843 powder Substances 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 79
- 239000000243 solution Substances 0.000 claims description 72
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 69
- 229920002472 Starch Polymers 0.000 claims description 43
- 238000003756 stirring Methods 0.000 claims description 36
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 35
- 239000008107 starch Substances 0.000 claims description 34
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- 238000005303 weighing Methods 0.000 claims description 28
- VBICKXHEKHSIBG-UHFFFAOYSA-N beta-monoglyceryl stearate Natural products CCCCCCCCCCCCCCCCCC(=O)OCC(O)CO VBICKXHEKHSIBG-UHFFFAOYSA-N 0.000 claims description 25
- 239000011259 mixed solution Substances 0.000 claims description 19
- 235000011187 glycerol Nutrition 0.000 claims description 14
- 239000012153 distilled water Substances 0.000 claims description 13
- 238000010907 mechanical stirring Methods 0.000 claims description 12
- 240000003183 Manihot esculenta Species 0.000 claims description 9
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- 229920001592 potato starch Polymers 0.000 claims description 9
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- YQEMORVAKMFKLG-UHFFFAOYSA-N glycerine monostearate Natural products CCCCCCCCCCCCCCCCCC(=O)OC(CO)CO YQEMORVAKMFKLG-UHFFFAOYSA-N 0.000 claims description 8
- SVUQHVRAGMNPLW-UHFFFAOYSA-N glycerol monostearate Natural products CCCCCCCCCCCCCCCCC(=O)OCC(O)CO SVUQHVRAGMNPLW-UHFFFAOYSA-N 0.000 claims description 8
- 238000001291 vacuum drying Methods 0.000 claims description 7
- 229920002261 Corn starch Polymers 0.000 claims description 6
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- 239000002689 soil Substances 0.000 description 9
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- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
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- 239000003814 drug Substances 0.000 description 1
- 238000009328 dry farming Methods 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
- Y02P60/20—Reduction of greenhouse gas [GHG] emissions in agriculture, e.g. CO2
- Y02P60/21—Dinitrogen oxide [N2O], e.g. using aquaponics, hydroponics or efficiency measures
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- Fertilizers (AREA)
Abstract
The preparation method of the polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer comprises the following steps: according to the mass parts, the polyvinyl alcohol and the gelatinized modified starch are blended to obtain a blending solution for standby; preparing sodium alginate solution with concentration of 2% for later use; step (3) uniformly spraying the blending solution in the step (1) on the surfaces of fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer; and (4) uniformly spraying the sodium alginate solution with the concentration of 2% prepared in advance on the outer layer of the single-layer coated fertilizer, uniformly coating the sodium alginate powder ground in advance on the outer layer of the single-layer coated fertilizer, and drying the fertilizer at room temperature for 24h to obtain the double-layer coated fertilizer. The coating used in the invention is a degradable material, adopts a double-layer coating mode, and can make up the defects of single-layer coating performance and difficult control. The invention has simple process, low cost, short process cycle and no waste.
Description
Technical Field
The invention relates to a preparation technology of a polyvinyl alcohol modified starch-based water-retaining double-layer sustained and controlled release fertilizer, belonging to the field of natural polymer materials.
Background
Throughout the world, the grain yield reduction caused by drought stress may exceed the sum of yield losses caused by other factors. The dry land area of China accounts for 52.5% of the total land area of China, and drought is an important factor for restricting sustainable development of agriculture in China. In recent 10 years, the agricultural water consumption of China is more than 60% of the total water consumption of China, and along with the continuous aggravation of the agricultural water crisis of China, the agriculture is developed towards high yield and stable yield, and the water-saving and water-retaining technology of dry farmland is greatly developed so as to fully utilize limited rainfall resources and ensure the sustainable development of agricultural production. The application of the water-retaining agent is an effective measure, can achieve the aims of soil improvement, water saving and yield increase, and is particularly suitable for popularization in dry farming agriculture areas in northern China. The water-retaining agent is a high polymer material with strong water absorption capacity, is known as a miniature reservoir, can absorb hundreds or thousands of times of water, can repeatedly absorb water and slowly release the water for plant absorption and utilization, and has the characteristics that the water-retaining agent can play a role in drought and relieve drought. The water-preserving agent can absorb liquid by molecular bonding and swelling, and simultaneously nutrient ions in the solution enter the molecular structure of the water-preserving agent to be wrapped and held, and then the water-preserving agent is slowly released along with the release of moisture and the relaxation of the molecular network structure, so that the slow release effect of the nutrient ions is achieved. Meanwhile, the physical properties of soil can be improved, seed germination is promoted, the survival rate is improved, and irrigation requirements are reduced.
The existing synthetic water-retaining material has the problems of high production cost, difficult degradation of residues and the like. With the introduction of various polymer materials into the life of people, some polymer materials which are renewable, easy to biodegrade, recyclable in waste, environment-friendly and the like are attracting great attention, and the research of preparing green and biodegradable composite materials by using natural polymer materials is most prominent. Starch is a hot spot for scientific research due to its abundant natural resources, low cost, renewable and biodegradability. In the past decades, starch and its composites have found widespread use in numerous technical fields, such as modern agriculture, medicine, cosmetics, textile and paper industry. As a natural polymer-based water-retaining agent, starch, cellulose and the like are widely applied due to good water absorption and water retention, however, the application of the starch is limited to a certain extent because the chemical structure of the starch has inherent defects, such as low strength of hydrogel bodies, poor agglomeration force, easy loose loss, poor salt resistance and stability, too short decay and decomposition time and difficult long-term soil moisture and water retention. The starch molecules are chemically modified by different polymers, so that the comprehensive application performance of the starch-based composite material is improved to be a new research direction.
Based on the above, the polyvinyl alcohol, the starch and the sodium alginate are introduced into a sustained and controlled release fertilizer system by a coating technology, so that the polyvinyl alcohol modified starch-based double-layer water-retention sustained and controlled release fertilizer is developed, and Chinese agriculture enters into a high-efficiency and high-quality development line.
Disclosure of Invention
The invention aims to prolong the degradation period and improve the water and fertilizer retention performance.
The invention relates to a polyvinyl alcohol modified starch-based water-retaining double-layer sustained and controlled release fertilizer and a preparation method thereof, wherein the modified starch of the polyvinyl alcohol modified starch-based water-retaining double-layer sustained and controlled release fertilizer consists of 10-15g of corn starch, 100ml of distilled water and 0.25-1.0g of citric acid; the inner layer coating material consists of polyvinyl alcohol, modified starch, distilled water, glycerin and glycerin monostearate, wherein the components of the inner layer coating material are 1-8g of polyvinyl alcohol, 2g of modified starch, 20-100ml of distilled water, 2g of glycerin and 0.1g of glycerin monostearate; the outer layer coating material consists of sodium alginate and distilled water, wherein the composition of the outer layer coating material is 1g of sodium alginate and 50ml of distilled water.
The preparation method of the polyvinyl alcohol modified starch-based water-retention controlled-release fertilizer comprises the following steps:
step (1) preparation of citric acid modified starch: weighing 10g of starch and citric acid proportional to the starch, namely 0.25g, 0.5g, 0.75g and 1.00g, adding the starch and the citric acid into 100mL of deionized water, adding the mixed solution into a three-necked flask, fixing the three-necked flask into a constant-temperature water bath kettle with the temperature of 75 ℃ by using an iron stand, starting mechanical stirring, setting the speed to 200r/min, stopping the reaction after stirring for 2 hours, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven, drying at the temperature of 90 ℃ for 24 hours, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified corn starch;
step (2) comparing the starch with the modified starch obtained in step (1);
and (3) preparing an inner layer coating solution: firstly weighing 8g of polyvinyl alcohol, then weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath at 90 ℃, weighing 2g of modified starch, dispersing the modified starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, stirring for 30min in the water bath at 90 ℃ at 250r/min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified starch, mixing and stirring for 15min, then adding 2g of glycerol and 0.1g of glyceryl monostearate, then continuing stirring for 2h to obtain white uniform inner-layer coating solution, and preparing the single-layer coated fertilizer in the ultrasonic step (4) after taking out: firstly, placing fertilizer particles into a coating machine for rotation, then uniformly spraying an inner layer blending solution on the surfaces of the fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer;
step (5) preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2%;
and (6) preparing a double-layer coated fertilizer: firstly, placing single-layer coated fertilizer particles into a coating machine for rotation, uniformly spraying sodium alginate solution on the surfaces of the fertilizer particles, uniformly coating sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
The beneficial effects of the invention are as follows: 1. compared with the existing single-layer water-retention slow-release fertilizer, the invention can make up the defects of single performance, short slow-release time and difficult control of the single-layer coated fertilizer. 2. The step (4) of the invention is coated on the surface of the fertilizer particles to form an inner layer coating, so that the surface of the fertilizer becomes smooth and compact to prevent water from entering, thereby reducing the release rate of fertilizer nutrients and improving the utilization rate of the fertilizer; 3. the coating layer prepared in the step (6) is an outer coating layer, so that the water absorption and water retention capacity of soil can be improved, and the fertilizer can be slowly released according to the water content of the soil by cooperation of the inner coating layer, so that the release rate of the fertilizer can be controlled. 4. The method is applicable to the preparation of various water-soluble slow-release fertilizers, the materials used for the inner and outer coating are natural degradable materials, the soil environment is not polluted, the green sustainable development of the future agriculture can be promoted, and compared with the existing synthetic polymer, the method can make up the defect that the synthetic polymer is not degradable. 5. The invention has the advantages of simple process, clear thought, simple and convenient operation, low cost, short process period, no waste, natural degradation of the coating material, and accordance with the economical and environment-friendly concept of green water and Qingshan, thereby being beneficial to increasing the production and income.
Drawings
FIG. 1 is a technical roadmap of the invention; FIG. 2 is an infrared spectrum of modified starch, wherein a is pure starch, b is 2.5% citric acid modified starch, c is 5.0% citric acid modified starch, and d is 7.5% citric acid modified starch; FIG. 3 is a digital photograph of fertilizer granules; FIG. 4 is a surface topography of non-coated fertilizer particles; FIG. 5 is a surface topography of a single layer coated fertilizer particle;
FIG. 6 is a surface topography of inner layer coated fertilizer granules; FIGS. 7, 8 and 9 are cross-sectional morphology diagrams of single-layer coated fertilizer granules; FIGS. 10, 11 and 12 are cross-sectional morphology diagrams of single-layer coated fertilizer granules; FIG. 13 is a digital photograph of a single layer coated and double layer coated fertilizer after swelling; FIG. 14 is a graph of the swelling ratio of a citric acid modified starch blended polyvinyl alcohol film; FIG. 15 is a graph of water retention of double-layer coated fertilizers, wherein the abscissas 0, 1, 2, 3, 4 represent soil samples with 0g, 1g, 2g, 3g, 4g of double-layer coated slow-release fertilizer added to 200g of dry soil, respectively; FIG. 16 is a graph of water retention of double-layer coated fertilizers, respectively representing the addition of 0g, 1g, 2g, 3g and 4g of double-layer coated slow-release fertilizers to 200g of dry soil; FIG. 17 is a graph showing the dissolution rate of fertilizer in water, wherein a is urea, b is single-layer coated fertilizer, and c is double-layer coated fertilizer; FIG. 18 is a graph of mechanical properties of a citric acid modified starch blended polyvinyl alcohol film;
FIG. 19 is a graph showing experiments on potted plants of ryegrass plants without fertilizer groups, with single-layer coating, and with double-layer coating, respectively; FIG. 20 is a ryegrass plant, wherein A, B, C, D is the highest ryegrass plant of the non-fertilizer group, non-coated fertilizer group, single-layer coated fertilizer group, double-layer coated fertilizer group, respectively; fig. 21 shows ryegrass leaves, wherein a, b, c, d is the highest leaf of ryegrass plants in the non-fertilizer group, non-coated fertilizer group, single-layer coated fertilizer group, and double-layer coated fertilizer group, respectively.
Detailed Description
The invention relates to a polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer and a preparation method thereof, wherein the modified starch of the polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer consists of 10-15g of corn starch, 100ml of distilled water and 0.25-1.0g of citric acid; the inner layer coating material consists of polyvinyl alcohol, modified starch, distilled water, glycerin and glycerin monostearate, wherein the components of the inner layer coating material are 1-8g of polyvinyl alcohol, 2g of modified starch, 20-100ml of distilled water, 2g of glycerin and 0.1g of glycerin monostearate; the outer layer coating material consists of sodium alginate and distilled water, wherein the composition of the outer layer coating material is 1g of sodium alginate and 50ml of distilled water.
The preparation method of the polyvinyl alcohol modified starch-based water-retention controlled-release fertilizer comprises the following steps:
step (1) preparation of citric acid modified starch: weighing 10g of starch and citric acid (0.25 g, 0.5g, 0.75g and 1.00 g) in proportion to the starch, adding the mixed solution into 100mL of deionized water, adding the mixed solution into a three-necked flask, mechanically stirring for 2 hours, stopping the reaction, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven for drying at 90 ℃ for 24 hours, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally finishing the pulverizing to obtain modified starch;
step (2) comparing the starch with the modified starch obtained in step (1);
and (3) preparing an inner layer coating solution: firstly weighing 8g of polyvinyl alcohol, then weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath, weighing 2g of modified starch, dispersing the modified starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, mechanically stirring the solution in the water bath at 90 ℃ for 30min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified starch, mixing and stirring the solution for 15min, then adding 2g of glycerol and 0.1g of glycerol monostearate, then continuing stirring for 2h, obtaining inner-layer coating solution, and taking out the inner-layer coating solution for ultrasonic defoaming;
and (4) preparing a single-layer coated fertilizer: firstly, placing fertilizer particles into a coating machine for rotation, then uniformly spraying an inner layer blending solution on the surfaces of the fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer;
step (5) preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2%;
and (6) preparing a double-layer coated fertilizer: firstly, placing single-layer coated fertilizer particles into a coating machine for rotation, uniformly spraying sodium alginate solution on the surfaces of the fertilizer particles, uniformly coating sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
The preparation method of the polyvinyl alcohol modified starch-based water-retaining double-layer sustained-release fertilizer is characterized in that the stirring speed of the mixed solution in the step (1) is 200r/min, the stirring temperature is 75 ℃, the starch is successfully modified after stirring for 2 hours, and the modified starch is obtained after drying and crushing.
The preparation method of the polyvinyl alcohol modified starch-based water-retaining double-layer controlled release fertilizer is characterized in that the starch in the step (1) and the step (2) is one of corn starch, potato starch, tapioca starch or wheat starch; the starch has an amylose content of 22% -26%.
The preparation method of the polyvinyl alcohol modified starch-based water-retention double-layer sustained-release fertilizer is characterized in that the polyvinyl alcohol in the step (3) is completely dissolved and then added into gelatinized modified starch, the stirring speed is adjusted to 250r/min, and then glycerol and glycerol monostearate are added for reaction in a water bath to obtain the white uniform and good-fluidity inner layer coating solution.
The preparation method of the polyvinyl alcohol modified starch-based water-retention double-layer sustained-release fertilizer is characterized in that the dissolution condition of the polyvinyl alcohol in the step (3) is that the polyvinyl alcohol is mechanically stirred for 2 hours at 280r/min in a water bath at 90 ℃.
0016 the preparation method of the polyvinyl alcohol modified starch-based water-retaining double-layer controlled release fertilizer is characterized in that the ultrasonic frequency in the step (3) is 80Hz.
The following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1: the preparation method comprises the following steps: 1) Preparation of citric acid modified corn starch: weighing 10g of corn starch and citric acid (0.25 g, 0.5g, 0.75g and 1.00 g) in proportion to the corn starch according to the mass parts, adding the mixed solution into 100mL of deionized water, adding the mixed solution into a three-necked flask, fixing the three-necked flask into a constant-temperature water bath kettle with the temperature of 75 ℃ by using an iron stand, starting mechanical stirring, setting the speed to be 200r/min, stopping the reaction after stirring for 2 hours, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven for drying at the temperature of 90 ℃ for 24 hours, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified corn starch for later use; 2) Preparation of inner layer coating solution: weighing 8g of polyvinyl alcohol, weighing deionized water, adding into a three-neck flask, carrying out high-speed mechanical stirring in a water bath at 90 ℃ to obtain 10% polyvinyl alcohol solution, weighing 2g of modified corn starch, dispersing in 20mL of deionized water uniformly, rapidly pouring into the three-neck flask, stirring for 30min in a water bath at 90 ℃ at 250r/min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified corn starch, mixing and stirring for 15min, adding 2g of glycerol and 0.1g of glycerol monostearate, continuing stirring for 2h to obtain white uniform inner-layer coating solution, taking out, and carrying out ultrasonic defoaming for later use; 3) Preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2% for later use; 4) Uniformly spraying the inner layer coating solution obtained in the step 2) on the surfaces of fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer; 5) Uniformly spraying the sodium alginate solution obtained in the step 3) on the surface of the single-layer coated fertilizer particles obtained in the step 4), uniformly coating the sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
Example 2: the preparation method comprises the following steps: 1) Preparation of citric acid modified potato starch: weighing 10g of potato starch and citric acid (0.25 g, 0.5g, 0.75g and 1.00 g) in proportion to the potato starch according to the mass parts, adding the mixed solution into 100mL of deionized water, adding the mixture into a three-necked flask, fixing the three-necked flask into a constant-temperature water bath kettle with the temperature of 75 ℃ by using an iron stand table, starting mechanical stirring, setting the speed to be 200r/min, stopping the reaction after stirring for 2 hours, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven for drying at the temperature of 90 ℃ for 24 hours, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified potato starch for later use; 2) Preparation of inner layer coating solution: weighing 8g of polyvinyl alcohol, weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath at 90 ℃, weighing 2g of modified potato starch, dispersing the modified potato starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, stirring for 30min in the water bath at 90 ℃ at 250r/min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified potato starch, mixing and stirring for 15min, adding 2g of glycerol and 0.1g of glycerol monostearate, continuing stirring for 2h to obtain white uniform inner-layer coating solution, taking out and performing ultrasonic defoaming for later use; 3) Preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2% for later use; 4) Uniformly spraying the inner layer coating solution obtained in the step 2) on the surfaces of fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer; 5) Uniformly spraying the sodium alginate solution obtained in the step 3) on the surface of the single-layer coated fertilizer particles obtained in the step 4), uniformly coating the sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
Example 3: the preparation method comprises the following steps: 1) Preparing citric acid modified tapioca starch: weighing 10g of tapioca starch and citric acid (0.25 g, 0.5g, 0.75g and 1.00 g) which are proportional to the tapioca starch according to the mass parts, adding the mixed solution into 100mL of deionized water, adding the three-necked flask into a constant-temperature water bath kettle with the temperature of 75 ℃ by using an iron stand table, starting mechanical stirring, setting the speed to 200r/min, stopping the reaction after stirring for 2 hours, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven for drying for 24 hours at the temperature of 90 ℃, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified tapioca starch for later use; 2) Preparation of inner layer coating solution: weighing 8g of polyvinyl alcohol, weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath at 90 ℃, weighing 2g of modified tapioca starch, dispersing the modified tapioca starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, stirring for 30min in the water bath at 90 ℃ at 250r/min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified tapioca starch, mixing and stirring for 15min, adding 2g of glycerol and 0.1g of glycerol monostearate, continuing stirring for 2h to obtain white uniform inner-layer coating solution, taking out and performing ultrasonic defoaming for later use; 3) Preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2% for later use; 4) Uniformly spraying the inner layer coating solution obtained in the step 2) on the surfaces of fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer; 5) Uniformly spraying the sodium alginate solution obtained in the step 3) on the surface of the single-layer coated fertilizer particles obtained in the step 4), uniformly coating the sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
Example 4: the preparation method comprises the following steps: 1) Preparation of citric acid modified wheat starch: weighing 10g of wheat starch and citric acid (0.25 g, 0.5g, 0.75g and 1.00 g) in proportion to the wheat starch according to the mass parts, adding the mixed solution into 100mL of deionized water, adding the mixed solution into a three-necked flask, fixing the three-necked flask into a constant-temperature water bath kettle with the temperature of 75 ℃ by using an iron stand table, starting mechanical stirring, setting the speed to 200r/min, stopping the reaction after stirring for 2 hours, pouring the mixed solution into a culture dish, then placing the culture dish into a vacuum drying oven for drying at the temperature of 90 ℃ for 24 hours, placing the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified wheat starch for later use; 2) Preparation of inner layer coating solution: weighing 8g of polyvinyl alcohol, weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath at 90 ℃, weighing 2g of modified wheat starch, dispersing the modified wheat starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, stirring for 30min in the water bath at 90 ℃ at 250r/min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified wheat starch, mixing and stirring for 15min, adding 2g of glycerol and 0.1g of glycerol monostearate, continuing stirring for 2h to obtain white uniform inner-layer coating solution, taking out, and performing ultrasonic defoaming for later use; 3) Preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2% for later use; 4) Uniformly spraying the inner layer coating solution obtained in the step 2) on the surfaces of fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer; 5) Uniformly spraying the sodium alginate solution obtained in the step 3) on the surface of the single-layer coated fertilizer particles obtained in the step 4), uniformly coating the sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer.
Claims (1)
1. The polyvinyl alcohol modified starch-based water-retaining double-layer sustained and controlled release fertilizer is characterized in that modified starch consists of starch, distilled water and citric acid; the inner layer coating material consists of polyvinyl alcohol, modified starch, distilled water, glycerol and glycerol monostearate; the outer layer coating material consists of sodium alginate and distilled water;
the preparation method of the polyvinyl alcohol modified starch-based water-retention double-layer sustained and controlled release fertilizer comprises the following steps:
step (1) preparation of citric acid modified starch: weighing 10g of starch and adding 0.5g of citric acid into 100mL of deionized water, adding the mixed solution into a three-necked flask, mechanically stirring for 2 hours, stopping the reaction, pouring the mixed solution into a culture dish, putting the culture dish into a vacuum drying oven for drying at 90 ℃ for 24 hours, putting the dried content into a pulverizer, continuously pulverizing for 5 minutes, pulverizing again according to the pulverizing condition, and finally pulverizing to obtain modified starch;
step (2) comparing the starch with the modified starch obtained in step (1);
and (3) preparing an inner layer coating solution: firstly weighing 8g of polyvinyl alcohol, then weighing deionized water, adding the polyvinyl alcohol into a three-necked flask, preparing 10% polyvinyl alcohol solution by high-speed mechanical stirring in a water bath, weighing 2g of modified starch, dispersing the modified starch into 20mL of deionized water uniformly, rapidly pouring the solution into the three-necked flask, mechanically stirring the solution in the water bath at 90 ℃ for 30min, directly adding the obtained polyvinyl alcohol solution into gelatinized modified starch, mixing and stirring the solution for 15min, then adding 2g of glycerol and 0.1g of glycerol monostearate, then continuing stirring for 2h, obtaining inner-layer coating solution, and taking out the inner-layer coating solution for ultrasonic defoaming;
and (4) preparing a single-layer coated fertilizer: firstly, placing fertilizer particles into a coating machine for rotation, then uniformly spraying an inner layer blending solution on the surfaces of the fertilizer particles, and repeating coating for a plurality of times to obtain a single-layer coated fertilizer;
step (5) preparation of sodium alginate solution: 1g of sodium alginate is weighed, put into a three-necked flask, added with 50mL of deionized water, and stirred for 2 hours at room temperature at 250r/min to prepare sodium alginate solution with concentration of 2%;
and (6) preparing a double-layer coated fertilizer: firstly, placing single-layer coated fertilizer particles into a coating machine for rotation, uniformly spraying sodium alginate solution on the surfaces of the fertilizer particles, uniformly coating sodium alginate powder which is ground in advance on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at room temperature for 24 hours to obtain the double-layer coated fertilizer;
the preparation method of the polyvinyl alcohol modified starch-based water-retaining double-layer sustained-release fertilizer comprises the steps that the stirring speed of the mixed solution in the step (1) is 200r/min, the stirring temperature is 75 ℃, starch is successfully modified after stirring for 2 hours, and modified starch is obtained after drying and crushing;
the starch in the step (1) and the step (2) is one of corn starch, potato starch, tapioca starch or wheat starch; the starch has an amylose content of 22% -26%;
the polyvinyl alcohol in the step (3) is completely dissolved and then added into gelatinized modified starch, the stirring speed is adjusted to 250r/min, then glycerin and glycerin monostearate are added, and the mixture reacts in a water bath to obtain white uniform inner-layer coating solution with good fluidity;
the dissolution condition of the polyvinyl alcohol in the step (3) is that the polyvinyl alcohol is mechanically stirred for 2 hours at 280r/min in a water bath at 90 ℃;
the ultrasonic frequency in the step (3) is 80Hz.
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