Sugar alcohol-containing fertilizer and preparation method thereof

Abstract

The invention discloses a sugar alcohol-containing fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The sugar alcohol-containing fertilizer comprises the following raw materials in parts by weight: 8-14 parts of activated sugar alcohol, 35-41 parts of a urea ammonium nitrate aqueous solution, 20-25 parts of urea, 20-25 parts of water, 5-8 parts of trace elements and 10-15 parts of a coating material. The preparation method comprises the following steps: heating water, and adding the activated sugar alcohol to obtain a first mixture; adding trace elements into the first mixture to obtain a second mixture; stopping heating the second mixture, and adding a urea ammonium nitrate aqueous solution and urea to obtain a third mixture: carrying out filter pressing and drying on the third mixture, and granulating by adopting a granulator to form a granular fertilizer; and placing the granular fertilizer in a drum coating machine, spraying a coating material on the surface of the granular fertilizer, and drying to obtain the sugar alcohol-containing fertilizer. The sugar alcohol-containing fertilizer prepared by the invention has good slow release performance and can promote crop growth.

Description

Technical Field

[0001] The invention relates to the field of fertilizers, and in particular to a fertilizer containing sugar alcohol and a preparation method thereof. Background Art

[0002] For a period of time, the effective way to increase crop yields in China's agriculture was to continuously increase the amount of nitrogen, phosphorus and potassium fertilizers. Under the background of long-term frequent and excessive use of macronutrient fertilizers (nitrogen, phosphorus and potassium), the growth trend of crop yields has gradually slowed down or even stagnated. According to the "minimum nutrient law" proposed by German chemist Liebig, the medium and trace elements that are gradually deficient in the soil but cannot be replenished in time are increasingly becoming the limiting factors affecting crop yields. On the other hand, the excessive use of chemical fertilizers has also caused problems such as deterioration of soil properties, decline in product quality and environmental pollution. Therefore, current agricultural planting pays more attention to coordinating the relationship between macronutrients and medium and trace element fertilizers, and by supplementing medium and trace element fertilizers, the nutrient supply of crops can be balanced to improve yield and quality.

[0003] However, even after applying medium and trace element fertilizers, it is impossible to fully utilize and exert its full fertilizer effect, because different medium and trace elements in fertilizers are easy to react chemically with many ions in the soil and are fixed, causing failure. An effective way to solve this problem is to use a chelating agent. Sugar alcohol is a natural wetting agent, mainly from the phloem of plants, and is a mixture of various hydroxy compounds. Because it is a small molecule penetrating substance, sugar alcohol has the characteristics of a chelating agent, and can stably combine trace elements (such as zinc, boron, manganese, copper, etc.) to form a stable chelate. This chelate has a small molecular weight and is easy to penetrate the cuticle of plant leaves, enter the plant body for transportation and absorption. When sugar alcohol is mixed with fertilizer, it can promote crop growth and nutrient absorption, and is often used as a fertilizer adjuvant in agriculture.

[0004] Patent CN105130683B provides a composite sugar alcohol liquid fertilizer containing high nitrogen and medium and trace elements and a preparation method thereof. The composite sugar alcohol liquid fertilizer obtained in the patent contains rich nitrogen sources and medium and trace elements, which makes it easier for crops to absorb under the action of composite sugar alcohols, thereby improving fertilizer utilization. However, the sugar alcohol fertilizer prepared in the patent does not have a slow-release property. After entering the soil, this type of fertilizer releases its nutrients in a short time, and it is difficult to meet the needs of crop growth for a long time. Summary of the invention

[0005] The invention provides a sugar alcohol-containing fertilizer and a preparation method thereof, which can solve the problem in the prior art that the sugar alcohol-containing fertilizer releases the nutrients contained therein in a short time after entering the soil, and it is difficult to meet the needs of crop growth in a long time.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a sugar alcohol-containing fertilizer, comprising the following raw materials in parts by weight: 8-14 parts of activated sugar alcohol, 35-41 parts of urea ammonium nitrate aqueous solution, 20-25 parts of urea, 20-25 parts of water, 5-8 parts of trace elements, and 10-15 parts of coating materials.

[0008] Furthermore, the activated sugar alcohol is prepared by the following steps:

[0009] Add polydopamine aqueous solution to sugar alcohol, heat to 40-50°C, stir to dissolve, and then cool to room temperature to obtain activated sugar alcohol.

[0010] The dosage ratio of sugar alcohol to polydopamine aqueous solution is 10 g:100 mL; the dosage ratio of polydopamine to deionized water in the polydopamine aqueous solution is 8-10 g:100 mL.

[0011] The amino and other functional groups of polydopamine can work synergistically with the hydroxyl groups of sugar alcohols to increase the binding sites of sugar alcohol molecules and trace elements, thereby improving the complexation efficiency. In addition, the adhesion of polydopamine also helps to stabilize the structure of the complex, making it more stable.

[0012] Furthermore, the sugar alcohol is any one of mannitol, sorbitol, xylitol and erythritol.

[0013] Furthermore, the coating material is made by the following steps:

[0014] A1: Add polyvinyl alcohol and deionized water into a beaker, stir for 2 hours at 90°C to obtain a polyvinyl alcohol aqueous solution; add chitosan and 2wt% acetic acid aqueous solution into a beaker, stir for 2-3 hours at 60°C to obtain a chitosan aqueous solution;

[0015] The dosage ratio of polyvinyl alcohol to deionized water is 2 g:18-20 mL; the dosage ratio of chitosan to acetic acid aqueous solution is 1 g:50 mL.

[0016] A2: The polyvinyl alcohol aqueous solution and the chitosan aqueous solution were mixed, stirred at 60°C for 2-3 hours, and allowed to stand for 24 hours to remove bubbles, and then 10wt% glutaraldehyde solution and 2-carboxyethyl disulfide aqueous solution were added, stirred at 70°C for 2 hours to obtain a polyvinyl alcohol / chitosan crosslinking solution, which was allowed to stand for 24 hours to remove bubbles;

[0017] Among them, the volume ratio of polyvinyl alcohol aqueous solution, chitosan aqueous solution, glutaraldehyde solution and 2-carboxyethyl disulfide aqueous solution is 20:50:(0.6-0.7):(0.1-0.2); the amount ratio of 2-carboxyethyl disulfide to deionized water in the 2-carboxyethyl disulfide aqueous solution is 10g:100mL.

[0018] In the above steps, glutaraldehyde and 2-carboxyethyl disulfide are used as cross-linking agents, and the two can jointly promote the cross-linking of polyvinyl alcohol and chitosan through synergistic action. Glutaraldehyde is used as a chemical cross-linking agent to cross-link polyvinyl alcohol and chitosan by forming chemical bonds. 2-carboxyethyl disulfide contains carboxyl groups, which can form hydrogen bonds with hydroxyl groups or amino groups on the surfaces of polyvinyl alcohol and chitosan, playing a role of auxiliary cross-linking and improving the degree of cross-linking between the two. In addition, 2-carboxyethyl disulfide contains disulfide bonds, and the bond energy of the disulfide bonds is relatively low, which can promote the slippage of molecular chains. This property can be used to repair the tearing of the membrane shell caused by the collision of fertilizer particles during the coating process in a timely manner, thereby ensuring the integrity of the coating and improving the sustained-release performance of the membrane material.

[0019] A3: Add modified nano-silica to the polyvinyl alcohol / chitosan cross-linked liquid, stir for 2-3 hours, add 10wt% glutaraldehyde solution and 2-carboxyethyl disulfide aqueous solution, stir thoroughly for 2 hours at 70°C, let stand for 24 hours to obtain the casting liquid, apply the casting liquid on the glass plate by the salivation method, heat the glass plate at 40°C for 24 hours to obtain the coating material.

[0020] Among them, the dosage ratio of polyvinyl alcohol / chitosan crosslinking liquid, modified nano-silica, glutaraldehyde solution, and 2-carboxyethyl disulfide aqueous solution is 70mL: 0.2-0.4g: 0.6-0.7mL: 0.1-0.2mL; the dosage ratio of 2-carboxyethyl disulfide to deionized water in the 2-carboxyethyl disulfide aqueous solution is 10g: 100mL.

[0021] Polyvinyl alcohol is a non-toxic, degradable, water-soluble polymer with good film-forming properties, hydrophilicity and biocompatibility. It has been widely studied and applied in the fields of industry, agriculture, and medicine. However, the strong hydrophilicity of polyvinyl alcohol limits its application as a coating material in polymer-coated fertilizers. Chitosan is a natural polymer with abundant sources and low prices. It has the advantages of being non-toxic, antibacterial, biocompatible and degradable, and has good film-forming properties. Compared with pure polyvinyl alcohol films, polyvinyl alcohol / chitosan films show lower oxygen permeability and higher water barrier properties. However, simply blending chitosan with polyvinyl alcohol has limited effect on reducing the hydrophilicity of polyvinyl alcohol films.

[0022] Nano-silica has a small size effect and a high specific surface area, which enable it to interact more effectively with the chitosan / polyvinyl alcohol matrix, thereby forming a denser structure in the membrane and blocking the penetration of water molecules. However, nano-silica itself is prone to agglomeration, which limits its water-blocking effect.

[0023] Furthermore, the modified nano silicon dioxide is prepared by the following steps:

[0024] Add nano-silica to an ethanol aqueous solution, then add triethoxysilyl undecanal, stir at 60° C. for 12-24 hours, cool to room temperature, centrifuge, wash, and dry to obtain modified nano-silica.

[0025] The dosage ratio of nano-silicon dioxide, ethanol aqueous solution and triethoxysilyl undecanedialdehyde is 10 g:100 mL:0.5-0.7 g; the volume ratio of deionized water and anhydrous ethanol in the ethanol aqueous solution is (1-2):(8-9).

[0026] In the above reaction steps, triethoxysilyl undecylaldehyde undergoes condensation reaction with the silanol groups on the surface of nano-silicon dioxide to generate silicon oxygen bonds (SiOSi), thereby connecting triethoxysilyl undecylaldehyde to the surface of nano-silicon dioxide, increasing the spatial distance between particles, and this spatial steric hindrance effect helps prevent nanoparticles from approaching and agglomerating each other during the dispersion process, thereby improving the dispersibility of nano-silicon dioxide, thereby improving the water barrier properties of nano-silicon dioxide, improving the stability of the film material, and enhancing the sustained release performance. And triethoxysilyl undecylaldehyde contains hydrophobic long chains and aldehyde groups, and the hydrophobic long chains can further improve the sustained release performance of the material. The aldehyde groups can participate in the cross-linking of polyvinyl alcohol and chitosan together with the above-mentioned glutaraldehyde and 2-carboxylethyl disulfide cross-linking agent, which is conducive to forming a more uniform cross-linking network, further improving the sustained release performance of the material. Nano-silicon dioxide also contains silicon, which can promote the growth of crops.

[0027] Furthermore, the trace elements are zinc sulfate monohydrate, magnesium sulfate monohydrate and sodium polyborate in a mass ratio of 2:(2.5-4):(0.5-2).

[0028] In a second aspect, the present invention provides a method for preparing a fertilizer containing sugar alcohol, comprising the following steps:

[0029] S1: Heat water to 70-80°C, add activated sugar alcohol, keep the temperature constant, stir for 30-45 minutes, until fully dissolved, to obtain a first mixture; add trace elements to the first mixture, keep the temperature constant, stir until fully dissolved, react for 3-4 hours, to obtain a second mixture; stop heating the second mixture, and add urea ammonium nitrate aqueous solution and urea, stir until fully dissolved, to obtain a third mixture: filter the third mixture after pressure drying, and use a granulator to granulate it to form a granular fertilizer;

[0030] S2: placing the granular fertilizer in a drum coating machine, spraying the coating material on the surface of the granular fertilizer, and drying to obtain the fertilizer containing sugar alcohol.

[0031] Beneficial effects of the present invention:

[0032] 1. The present invention uses polydopamine to activate sugar alcohol chelating trace elements, which can improve the utilization rate of trace elements. Polydopamine also contains a large amount of nitrogen, which can be used as a nitrogen source together with urea to synergistically promote crop growth.

[0033] 2. The present invention adds 2-carboxyethyl disulfide and modified nano-silica to the coating material. 2-carboxyethyl disulfide can improve the compactness of the coating material, and the disulfide bond contained in the substance can improve the sustained release performance of the coating material. The modified nano-silica has good dispersibility and contains hydrophobic long chains and aldehyde groups, which can participate in cross-linking and improve the sustained release performance of the material. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0035] Example 1

[0036] The present embodiment provides a fertilizer containing sugar alcohol, comprising the following raw materials in parts by weight: 8 parts of activated sugar alcohol, 35 parts of urea ammonium nitrate aqueous solution, 20 parts of urea, 20 parts of water, 2 parts of zinc sulfate monohydrate, 2.5 parts of magnesium sulfate monohydrate, 0.5 parts of polysodium borate, and 10 parts of coating material.

[0037] Activated sugar alcohols are made by the following steps:

[0038] 100 mL of polydopamine aqueous solution (the ratio of polydopamine to deionized water in the polydopamine aqueous solution is 8 g:100 mL) was added to 10 g of mannitol, heated to 40° C., stirred and dissolved, and then cooled to room temperature to obtain activated sugar alcohol.

[0039] The coating material is made by the following steps:

[0040] A1: Add 2g of polyvinyl alcohol and 18mL of deionized water into a beaker, stir thoroughly at 90°C for 2h to obtain a polyvinyl alcohol aqueous solution; add 1g of chitosan and 50mL of a 2wt% acetic acid aqueous solution into a beaker, stir at 60°C for 2h to obtain a chitosan aqueous solution;

[0041] A2: 20 mL of polyvinyl alcohol aqueous solution and 50 mL of chitosan aqueous solution were mixed, stirred at 60°C for 2 h, and allowed to stand for 24 h to remove bubbles, followed by adding 0.7 mL of 10 wt% glutaraldehyde solution and 0.1 mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water was 10 g: 100 mL), stirred at 70°C for 2 h to obtain a polyvinyl alcohol / chitosan crosslinked solution, which was allowed to stand for 24 h to remove bubbles;

[0042] A3: Add 0.2g of modified nano-silica to 70mL of polyvinyl alcohol / chitosan cross-linked liquid, stir for 2h, add 0.7mL of 10wt% glutaraldehyde solution and 0.1mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water is 10g:100mL), stir well at 70℃ for 2h, let stand for 24h to obtain casting liquid, coat the casting liquid on a glass plate by salivation method, heat the glass plate at 40℃ for 24h to obtain the coating material.

[0043] Modified nano-silica is made by the following steps:

[0044] 10 g of nano-silica was added to 100 mL of ethanol aqueous solution (the volume ratio of deionized water to anhydrous ethanol was 1:9), and then 0.5 g of triethoxysilyl undecane was added, stirred at 60° C. for 12 h, cooled to room temperature, centrifuged, washed, and dried to obtain modified nano-silica.

[0045] The preparation method comprises the following steps:

[0046] S1: Heat water to 70°C, add activated sugar alcohol, keep the temperature constant, stir for 30 minutes until fully dissolved, and obtain a first mixture; then add zinc sulfate monohydrate, magnesium sulfate monohydrate, and polysodium borate to the first mixture, keep the temperature constant, stir until fully dissolved, and react for 3 hours to obtain a second mixture; stop heating the second mixture, and add urea ammonium nitrate aqueous solution and urea, stir until fully dissolved, and obtain a third mixture: filter the third mixture after pressure drying, and then use a granulator to granulate it to form a granular fertilizer;

[0047] S2: placing the granular fertilizer in a drum coating machine, spraying the coating material on the surface of the granular fertilizer, and drying to obtain the fertilizer containing sugar alcohol.

[0048] Example 2

[0049] The present embodiment provides a fertilizer containing sugar alcohol, comprising the following raw materials in parts by weight: 8 parts of activated sugar alcohol, 35 parts of urea ammonium nitrate aqueous solution, 20 parts of urea, 20 parts of water, 2 parts of zinc sulfate monohydrate, 2.5 parts of magnesium sulfate monohydrate, 0.5 parts of polysodium borate, and 10 parts of coating material.

[0050] Activated sugar alcohols are made by the following steps:

[0051] 100 mL of polydopamine aqueous solution (the ratio of polydopamine to deionized water in the polydopamine aqueous solution is 9 g:100 mL) was added to 10 g of mannitol, heated to 45° C., stirred and dissolved, and then cooled to room temperature to obtain activated sugar alcohol.

[0052] The coating material is made by the following steps:

[0053] A1: Add 2g of polyvinyl alcohol and 20mL of deionized water into a beaker, stir thoroughly at 90°C for 2h to obtain a polyvinyl alcohol aqueous solution; add 1g of chitosan and 50mL of a 2wt% acetic acid aqueous solution into a beaker, stir at 60°C for 3h to obtain a chitosan aqueous solution;

[0054] A2: 20 mL of polyvinyl alcohol aqueous solution and 50 mL of chitosan aqueous solution were mixed, stirred at 60°C for 2 h, and allowed to stand for 24 h to remove bubbles, followed by adding 0.6 mL of 10 wt% glutaraldehyde solution and 0.2 mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water was 10 g: 100 mL), stirred at 70°C for 2 h to obtain a polyvinyl alcohol / chitosan crosslinked liquid, which was allowed to stand for 24 h to remove bubbles;

[0055] A3: Add 0.3g of modified nano-silica to 70mL of polyvinyl alcohol / chitosan cross-linked liquid, stir for 3h, add 0.6mL of 10wt% glutaraldehyde solution and 0.2mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water is 10g:100mL), stir well at 70℃ for 2h, let stand for 24h to obtain casting liquid, coat the casting liquid on a glass plate by salivation method, heat the glass plate at 40℃ for 24h to obtain the coating material.

[0056] Modified nano-silica is made by the following steps:

[0057] 10 g of nano-silica was added to 100 mL of ethanol aqueous solution (the volume ratio of deionized water to anhydrous ethanol was 1:9), and then 0.6 g of triethoxysilyl undecane was added, stirred at 60° C. for 12-24 h, cooled to room temperature, centrifuged, washed, and dried to obtain modified nano-silica.

[0058] The preparation method comprises the following steps:

[0059] S1: Heat water to 80°C, add activated sugar alcohol, keep the temperature constant, stir for 45 minutes until fully dissolved, and obtain a first mixture; then add zinc sulfate monohydrate, magnesium sulfate monohydrate, and polysodium borate to the first mixture, keep the temperature constant, stir until fully dissolved, and react for 4 hours to obtain a second mixture; stop heating the second mixture, and add urea ammonium nitrate aqueous solution and urea, stir until fully dissolved, and obtain a third mixture: filter the third mixture after pressure drying, and then use a granulator to granulate it to form a granular fertilizer;

[0060] S2: placing the granular fertilizer in a drum coating machine, spraying the coating material on the surface of the granular fertilizer, and drying to obtain the fertilizer containing sugar alcohol.

[0061] Example 3

[0062] The present embodiment provides a fertilizer containing sugar alcohol, comprising the following raw materials in parts by weight: 8 parts of activated sugar alcohol, 35 parts of urea ammonium nitrate aqueous solution, 20 parts of urea, 20 parts of water, 2 parts of zinc sulfate monohydrate, 2.5 parts of magnesium sulfate monohydrate, 0.5 parts of polysodium borate, and 10 parts of coating material.

[0063] Activated sugar alcohols are made by the following steps:

[0064] Add 100 mL of polydopamine aqueous solution (the ratio of polydopamine to deionized water in the polydopamine aqueous solution is 10 g:100 mL) to 10 g of mannitol, heat to 50° C., stir to dissolve, and then cool to room temperature to obtain activated sugar alcohol.

[0065] The coating material is made by the following steps:

[0066] A1: Add 2g of polyvinyl alcohol and 20mL of deionized water into a beaker, stir thoroughly at 90°C for 2h to obtain a polyvinyl alcohol aqueous solution; add 1g of chitosan and 50mL of a 2wt% acetic acid aqueous solution into a beaker, stir at 60°C for 3h to obtain a chitosan aqueous solution;

[0067] A2: 20 mL of polyvinyl alcohol aqueous solution and 50 mL of chitosan aqueous solution were mixed, stirred at 60°C for 2 h, and allowed to stand for 24 h to remove bubbles, followed by adding 0.6 mL of 10 wt% glutaraldehyde solution and 0.2 mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water was 10 g: 100 mL), stirred at 70°C for 2 h to obtain a polyvinyl alcohol / chitosan crosslinked liquid, which was allowed to stand for 24 h to remove bubbles;

[0068] A3: Add 0.4g of modified nano-silica to 70mL of polyvinyl alcohol / chitosan cross-linked liquid, stir for 3h, add 0.6mL of 10wt% glutaraldehyde solution and 0.2mL of 2-carboxyethyl disulfide aqueous solution (the ratio of 2-carboxyethyl disulfide to deionized water is 10g:100mL), stir well at 70℃ for 2h, let stand for 24h to obtain casting liquid, coat the casting liquid on a glass plate by salivation method, heat the glass plate at 40℃ for 24h to obtain the coating material.

[0069] Modified nano-silica is made by the following steps:

[0070] 10 g of nano-silica was added to 100 mL of ethanol aqueous solution (the volume ratio of deionized water to anhydrous ethanol was 1:9), and then 0.7 g of triethoxysilyl undecane was added, stirred at 60° C. for 12-24 h, cooled to room temperature, centrifuged, washed, and dried to obtain modified nano-silica.

[0071] The preparation method comprises the following steps:

[0072] S1: Heat water to 80°C, add activated sugar alcohol, keep the temperature constant, stir for 45 minutes until fully dissolved, and obtain a first mixture; then add zinc sulfate monohydrate, magnesium sulfate monohydrate, and polysodium borate to the first mixture, keep the temperature constant, stir until fully dissolved, and react for 4 hours to obtain a second mixture; stop heating the second mixture, and add urea ammonium nitrate aqueous solution and urea, stir until fully dissolved, and obtain a third mixture: filter the third mixture after pressure drying, and then use a granulator to granulate it to form a granular fertilizer;

[0073] S2: placing the granular fertilizer in a drum coating machine, spraying the coating material on the surface of the granular fertilizer, and drying to obtain the fertilizer containing sugar alcohol.

[0074] Example 4

[0075] Compared with Example 3, this embodiment is different in that:

[0076] A fertilizer containing sugar alcohol comprises the following raw materials in parts by weight: 11 parts of activated sugar alcohol, 38 parts of urea ammonium nitrate aqueous solution, 22.5 parts of urea, 22.5 parts of water, 2 parts of zinc sulfate monohydrate, 3.5 parts of magnesium sulfate monohydrate, 1 part of polysodium borate, and 12 parts of coating material.

[0077] The remaining materials and steps are the same as in Example 3.

[0078] Example 5

[0079] Compared with Example 3, this embodiment is different in that:

[0080] A fertilizer containing sugar alcohol comprises the following raw materials in parts by weight: 14 parts of activated sugar alcohol, 41 parts of urea ammonium nitrate aqueous solution, 25 parts of urea, 25 parts of water, 2 parts of zinc sulfate monohydrate, 4 parts of magnesium sulfate monohydrate, 2 parts of polysodium borate and 15 parts of coating material.

[0081] The remaining materials and steps are the same as in Example 3.

[0082] Comparative Example 1

[0083] Compared with Example 1, this comparative example is different in that:

[0084] The sugar alcohol was not activated by polydopamine, and mannitol was directly added. The other raw materials and steps were the same as those in Example 1.

[0085] Comparative Example 2

[0086] Compared with Example 1, this comparative example is different in that:

[0087] The coating material is made by the following steps:

[0088] A1: Add 2g of polyvinyl alcohol and 18mL of deionized water into a beaker, stir thoroughly at 90°C for 2h to obtain a polyvinyl alcohol aqueous solution; add 1g of chitosan and 50mL of a 2wt% acetic acid aqueous solution into a beaker, stir at 60°C for 2h to obtain a chitosan aqueous solution;

[0089] A2: 20 mL of polyvinyl alcohol aqueous solution and 50 mL of chitosan aqueous solution were mixed, stirred at 60°C for 2 h, and allowed to stand for 24 h to remove bubbles, then 0.8 mL of 10 wt% glutaraldehyde solution was added, stirred at 70°C for 2 h to obtain a polyvinyl alcohol / chitosan crosslinked liquid, and allowed to stand for 24 h to remove bubbles;

[0090] A3: Add 0.2g of modified nano-silica to 70mL of polyvinyl alcohol / chitosan cross-linked liquid, stir for 2h, add 0.8mL of 10wt% glutaraldehyde solution, stir thoroughly at 70℃ for 2h, let stand for 24h to obtain casting liquid, coat the casting liquid on a glass plate by salivation method, heat the glass plate at 40℃ for 24h to obtain the coating material.

[0091] Modified nano-silica is made by the following steps:

[0092] 10 g of nano-silica was added to 100 mL of ethanol aqueous solution (the volume ratio of deionized water to anhydrous ethanol was 1:9), and then 0.5 g of triethoxysilyl undecane was added, stirred at 60° C. for 12 h, cooled to room temperature, centrifuged, washed, and dried to obtain modified nano-silica.

[0093] The remaining materials and steps are the same as in Example 1.

[0094] Comparative Example 3

[0095] Compared with Example 1, this comparative example is different in that:

[0096] The coating material is made by the following steps:

[0097] A1: Add 2g of polyvinyl alcohol and 18mL of deionized water into a beaker, stir thoroughly at 90°C for 2h to obtain a polyvinyl alcohol aqueous solution; add 1g of chitosan and 50mL of a 2wt% acetic acid aqueous solution into a beaker, stir at 60°C for 2h to obtain a chitosan aqueous solution;

[0098] A2: 20 mL of polyvinyl alcohol aqueous solution and 50 mL of chitosan aqueous solution were mixed, stirred at 60°C for 2 h, and allowed to stand for 24 h to remove bubbles, then 0.8 mL of 10 wt% glutaraldehyde solution was added, stirred at 70°C for 2 h to obtain a polyvinyl alcohol / chitosan crosslinked liquid, and allowed to stand for 24 h to remove bubbles;

[0099] A3: Add 0.2g of nano-silica to 70mL of polyvinyl alcohol / chitosan cross-linked liquid, stir for 2h, add 0.8mL of 10wt% glutaraldehyde solution, stir thoroughly at 70℃ for 2h, let stand for 24h to obtain casting liquid, coat the casting liquid on a glass plate by salivation method, heat the glass plate at 40℃ for 24h to obtain the coating material.

[0100] The remaining materials and steps are the same as in Example 1.

[0101] The performance tests of the sugar alcohol-containing fertilizers obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were performed, and the test items were as follows:

[0102] 1. Slow-release performance test: According to the national standard of slow-release fertilizer (GB / T 23348-2009), the water dissolution rate method was used for determination; about 10 g of the fertilizer sample was weighed and put into a small bag made of 100-mesh nylon mesh, the small bag was put into a 250 mL glass bottle, 200 mL of water was added, the bottle was sealed with a cover, and placed in a 25°C biochemical constant temperature incubator. Samples were taken every day, and the nitrogen release was tested by an automatic analyzer. The cumulative nitrogen release rate was calculated. The calculation formula is as follows: v=Wn / W, where Wn is the mass fraction of the nitrogen release measured on the nth day, and W is the mass fraction of the total nitrogen. The test results are shown in Table 1.

[0103] 2. Fertilizer was applied to peanuts as a base fertilizer before sowing, 30 kg / mu. The test results after harvest are shown in Table 2.

[0104] Table 1

[0105] project 1d dissolution rate 15d dissolution rate 30d dissolution rate 45d dissolution rate 65d dissolution rate Example 1 1.07％ 10.32％ 31.24％ 72.28％ 90.45％ Example 2 1.06％ 10.31％ 31.15％ 72.25％ 90.42％ Example 3 1.04％ 10.28％ 31.08％ 72.23％ 90.39％ Example 4 1.02％ 10.14％ 30.72％ 72.17％ 90.27％ Example 5 0.99％ 10.03％ 30.56％ 72.09％ 89.94％ Comparative Example 1 1.14％ 10.38％ 31.29％ 72.34％ 90.51％ Comparative Example 2 1.63％ 11.96％ 34.27％ 73.89％ 92.14％ Comparative Example 3 5.86％ 23.79％ 67.48％ / /

[0106] Note: “ / ” represents the dissolution rate is 100%.

[0107] As can be seen from Table 1, the slow-release performance of the fertilizers prepared in Examples 1 and 5 is better than that of the fertilizers prepared in Comparative Examples 1 to 3. Comparative Example 2 does not add 2-carboxyethyl disulfide, and its slow-release performance is lower than that of Example 1, indicating that 2-carboxyethyl disulfide contains carboxyl groups, which can form hydrogen bonds with hydroxyl groups or amino groups on the surface of polyvinyl alcohol and chitosan, play a role in auxiliary cross-linking, and improve the degree of cross-linking of the two. In addition, 2-carboxyethyl disulfide contains disulfide bonds, and the bond energy of the disulfide bonds is relatively low, which can promote the slippage of the molecular chain. By utilizing this property, the tearing of the membrane shell caused by the collision of fertilizer particles during the coating process can be repaired in time, thereby ensuring the integrity of the coating and improving the slow-release performance of the membrane material. In Comparative Example 3, 2-carboxyethyl disulfide was not added, and the nano-silicon dioxide was not modified, and its sustained release performance was reduced compared with Example 1, indicating that triethoxysilyl undecanedialdehyde was connected to the surface of nano-silicon dioxide, increasing the spatial distance between particles. This steric hindrance effect helps to prevent the nanoparticles from approaching and agglomerating each other during the dispersion process, thereby improving the dispersibility of nano-silicon dioxide, thereby improving the water-blocking performance of nano-silicon dioxide, improving the stability of the film material, and enhancing the sustained release performance. In addition, triethoxysilyl undecanedialdehyde contains a hydrophobic long chain and an aldehyde group, which can further improve the sustained release performance of the material. The aldehyde group can participate in the cross-linking of polyvinyl alcohol and chitosan together with the above-mentioned glutaraldehyde and 2-carboxyethyl disulfide cross-linking agent, which is conducive to forming a more uniform cross-linked network, further improving the sustained release performance of the material.

[0108] Table 2

[0109]

[0110]

[0111] As can be seen from Table 1, the fertilizers prepared in Example 1 and Example 5 are more conducive to the growth of crops. Comparative Example 1 does not contain polydopamine, and the growth of its crops has decreased, indicating that polydopamine activates sugar alcohols to chelate trace elements, which can improve the utilization rate of trace elements, and polydopamine also contains a large amount of nitrogen, which can be used as a nitrogen source together with urea to synergistically promote crop growth. Comparative Example 2 does not contain 2-carboxyethyl disulfide, and the growth of crops has decreased, indicating that the slow-release performance of Example 1 is better, and the slow-release fertilizer can continuously provide the required nutrients for crops, avoiding the problem of nutrient loss and uneven crop growth caused by the one-time release of too much nutrients in traditional fertilizers. Comparative Example 3 did not add 2-carboxyethyl disulfide, and the nano-silicon dioxide was not modified, and the growth of crops also decreased.

[0112] The above disclosures are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A fertilizer containing sugar alcohol, characterized in that: The invention comprises the following raw materials in parts by weight: 8-14 parts of activated sugar alcohol, 35-41 parts of urea ammonium nitrate aqueous solution, 20-25 parts of urea, 20-25 parts of water, 5-8 parts of trace elements and 10-15 parts of coating materials.

2. The fertilizer containing sugar alcohol according to claim 1, characterized in that: The activated sugar alcohol is prepared by the following steps: Add polydopamine aqueous solution to sugar alcohol, heat to 40-50°C, stir to dissolve, and then cool to room temperature to obtain activated sugar alcohol.

3. A fertilizer containing sugar alcohol according to claim 2, characterized in that: The dosage ratio of sugar alcohol to polydopamine aqueous solution is 10g:100mL; the dosage ratio of polydopamine to deionized water in the polydopamine aqueous solution is 8-10g:100mL.

4. The fertilizer containing sugar alcohol according to claim 2, characterized in that: The sugar alcohol is any one of mannitol, sorbitol, xylitol and erythritol.

5. The fertilizer containing sugar alcohol according to claim 1, characterized in that: The coating material is made by the following steps: A1: Add polyvinyl alcohol and deionized water into a beaker, stir for 2 hours at 90°C to obtain a polyvinyl alcohol aqueous solution; add chitosan and 2wt% acetic acid aqueous solution into a beaker, stir for 2-3 hours at 60°C to obtain a chitosan aqueous solution; A2: The polyvinyl alcohol aqueous solution and the chitosan aqueous solution were mixed, stirred at 60°C for 2-3 hours, and allowed to stand for 24 hours, then a 10wt% glutaraldehyde solution and a 2-carboxyethyl disulfide aqueous solution were added, stirred at 70°C for 2 hours to obtain a polyvinyl alcohol / chitosan crosslinking solution, and allowed to stand for 24 hours; A3: Add modified nano-silica to the polyvinyl alcohol / chitosan cross-linked liquid, stir for 2-3 hours, add 10wt% glutaraldehyde solution and 2-carboxyethyl disulfide aqueous solution, stir at 70°C for 2 hours, let stand for 24 hours to obtain a casting liquid, and coat the casting liquid on a glass plate by a salivation method. The glass plate is heated at 40°C for 24 hours to obtain a coating material.

6. The fertilizer containing sugar alcohol according to claim 5, characterized in that: In step A1, the ratio of polyvinyl alcohol to deionized water is 2 g:18-20 mL; the ratio of chitosan to acetic acid aqueous solution is 1 g:50 mL.

7. The fertilizer containing sugar alcohol according to claim 5, characterized in that: In step A2, the volume ratio of the polyvinyl alcohol aqueous solution, the chitosan aqueous solution, the glutaraldehyde solution, and the 2-carboxyethyl disulfide aqueous solution is 20:50:(0.6-0.7):(0.1-0.2); the amount ratio of 2-carboxyethyl disulfide to deionized water in the 2-carboxyethyl disulfide aqueous solution is 10 g:100 mL.

8. The fertilizer containing sugar alcohol according to claim 5, characterized in that: In step A3, the amount ratio of polyvinyl alcohol / chitosan crosslinking liquid, modified nano-silica, glutaraldehyde solution, and 2-carboxyethyl disulfide aqueous solution is 70 mL: 0.2-0.4 g: 0.6-0.7 mL: 0.1-0.2 mL; and the amount ratio of 2-carboxyethyl disulfide to deionized water in the 2-carboxyethyl disulfide aqueous solution is 10 g: 100 mL.

9. The fertilizer containing sugar alcohol according to claim 5, characterized in that: The modified nano silicon dioxide is prepared by the following steps: Adding nano-silica to an ethanol aqueous solution, and then adding triethoxysilyl undecanedialdehyde, stirring at 60° C. for 12-24 hours, cooling to room temperature, centrifuging, washing, and drying to obtain modified nano-silica; The dosage ratio of nano-silicon dioxide, ethanol aqueous solution and triethoxysilyl undecanedialdehyde is 10 g:100 mL:0.5-0.7 g; the volume ratio of deionized water and anhydrous ethanol in the ethanol aqueous solution is (1-2):(8-9).

10. The method for preparing a fertilizer containing sugar alcohol according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Heat water to 70-80°C, add activated sugar alcohol, keep the temperature constant, stir for 30-45 minutes, until fully dissolved, to obtain a first mixture; add trace elements to the first mixture, keep the temperature constant, stir until fully dissolved, react for 3-4 hours, to obtain a second mixture; stop heating the second mixture, and add urea ammonium nitrate aqueous solution and urea, stir until fully dissolved, to obtain a third mixture: filter the third mixture after pressure drying, and use a granulator to granulate it to form a granular fertilizer; S2: placing the granular fertilizer in a drum coating machine, spraying the coating material on the surface of the granular fertilizer, and drying to obtain the fertilizer containing sugar alcohol.

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