A surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, its preparation method, and coated fertilizer.
By using surfactant-assisted preparation of lignin-based coating materials modified with multi-element inorganic nano-minerals, the problems of poor density of lignin-based membranes and easy agglomeration of inorganic fillers are solved, achieving low-cost and high-efficiency fertilizer controlled-release performance, which is suitable for the green and sustainable development of modern agriculture.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA AGRICULTURAL UNIVERSITY
- Filing Date
- 2026-02-28
- Publication Date
- 2026-05-26
AI Technical Summary
Existing lignin-based membrane materials have poor density and inorganic fillers are prone to agglomeration, resulting in high costs, complex processes, and unstable controlled-release performance of traditional processes, making it difficult to meet the requirements for long-term sustained-release.
A method for preparing lignin-based coating materials modified by multi-element inorganic nano-minerals with surfactant assistance is proposed. The method involves liquefying lignin by mixing polyethylene glycol, polycaprolactone diol and glycerol, and adding hexadecyltrimethylammonium bromide, attapulgite and nano-silica to form a dense physical barrier network. The spatial complementarity is achieved by utilizing the difference in microstructure between attapulgite and nano-silica.
It improves the density and mechanical strength of the membrane material, reduces costs, achieves good controlled-release performance of single-layer coating, has a low initial nutrient release rate, and a cumulative release period of 28-56 days, which significantly improves fertilizer utilization.
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Figure CN122079686A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fertilizer technology, and in particular to a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material, its preparation method, and the coated fertilizer. Background Technology
[0002] Chemical fertilizers are crucial inputs for ensuring modern agricultural production and food security. However, traditional fertilizers such as urea and compound fertilizers dissolve rapidly after being applied to the soil, resulting in generally low nutrient utilization rates, typically less than 50%. The loss of large amounts of nutrients unabsorbed by crops not only causes enormous economic waste but also triggers increasingly serious environmental problems, such as eutrophication of water bodies, soil compaction and acidification, and greenhouse gas emissions, severely hindering the sustainable development of agriculture. Therefore, developing new fertilizers that can improve fertilizer utilization and reduce environmental pollution has become an urgent need in the field of agricultural science and technology.
[0003] Slow-release fertilizers, as an effective solution, slow down or control the release rate of nutrients by coating fertilizer granules, thus synchronizing nutrient supply with the crop's nutrient requirements throughout its growth cycle and significantly improving fertilizer utilization. Currently, the coating materials for commercially available slow-release fertilizers are mostly petroleum-based synthetic polymers such as polyolefins and polyurethanes. While these materials offer good controlled-release effects, their raw materials are derived from non-renewable petroleum resources, making them expensive. Furthermore, the coating materials are difficult to degrade after use, leaving residues in the soil over long-term, causing "white pollution," which contradicts the concept of green agricultural development.
[0004] To overcome the aforementioned drawbacks, the development of low-cost, renewable, and environmentally friendly coating materials has become a research hotspot in this field. Lignin is a natural organic polymer with reserves second only to cellulose in nature, and it is a major byproduct of agricultural and forestry wastes such as those from the paper industry. It has outstanding advantages such as wide availability, low price, complete biodegradability, and environmental friendliness. Its unique phenylpropane unit structure and the presence of active hydroxyl and carboxyl groups in its molecule make it an ideal biomass matrix for preparing controlled-release fertilizer coating materials, as it can replace petroleum-based polyols. However, coating materials prepared directly from lignin have inherent defects such as insufficient mechanical strength, poor toughness, and poor hydrophobicity, resulting in easy coating damage and unstable controlled-release performance, making it difficult to meet the practical application requirements of long-term controlled release.
[0005] To improve the overall performance of lignin-based membrane materials, researchers often use inorganic nanomaterials for filling and modification. However, existing research mostly focuses on using single inorganic minerals, and inorganic nanomaterials, due to their high surface energy, are prone to aggregation in organic matrices, making it difficult to form a uniform barrier layer, resulting in limited performance improvement. Therefore, there is an urgent need to provide a surfactant-assisted multi-element inorganic nanomineral modified lignin-based coating material, its preparation method, and a coated fertilizer to improve the membrane's density, mechanical strength, and water-blocking properties. Summary of the Invention
[0006] The purpose of this invention is to provide a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material, its preparation method, and coated fertilizer, addressing the shortcomings of existing technologies. This solves the problems of poor density of existing lignin-based membrane materials, easy agglomeration of inorganic fillers, and high cost and complex processes caused by the need for multi-layer coating in traditional processes.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating materials, comprising the following steps: 1) Polyethylene glycol, polycaprolactone glycol and glycerol are mixed to obtain a mixed liquefying agent; the mixed liquefying agent, lignin and acid catalyst are reacted to obtain liquefied lignin-based polyol; 2) Liquefy lignin-based polyol, hexadecyltrimethylammonium bromide, attapulgite and nano silica are mixed to obtain surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material.
[0008] Preferably, the polyethylene glycol comprises one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800; the polycaprolactone diol comprises one or more of polycaprolactone diol 530, polycaprolactone diol 830, and polycaprolactone diol 2000; the lignin is one or more of alkali lignin, lignin sulfonate, and organic solvent lignin; the particle size of the lignin is 60-120 mesh; and the acid catalyst is concentrated sulfuric acid and / or phosphoric acid.
[0009] Preferably, the mass ratio of polyethylene glycol, polycaprolactone diol, and glycerol is 6-10:1:1; the mass ratio of the mixed liquefying agent to lignin is 2-5:1; and the mass of the acid catalyst is 1-3% of the lignin mass.
[0010] Preferably, the mixing temperature in step 1) is 160~180℃, the mixing is carried out under stirring, the stirring speed is 300~400r / min, the reaction temperature is 160~180℃, and the reaction time is 0.5~1.5h.
[0011] Preferably, the mass of the hexadecyltrimethylammonium bromide is 0.5-5% of the mass of the liquefied lignin-based polyol, and the mass ratio of the hexadecyltrimethylammonium bromide, attapulgite, and nano-silica is 0.5-5:5-15:0.5-10. The attapulgite includes one or more of the following: high-quality attapulgite, opal attapulgite, dolomite attapulgite, and montmorillonite attapulgite.
[0012] Preferably, the mixing temperature in step 2) is 160~180℃, and the mixing time is 0.5~1.5h.
[0013] The present invention also provides a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material prepared by the above preparation method.
[0014] The present invention also provides a coated fertilizer prepared by the surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, wherein a mixture of surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, isocyanate compound and catalyst is sprayed onto the surface of preheated fertilizer particles and in-situ polymerization reaction is carried out to obtain surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coated fertilizer.
[0015] Preferably, the temperature of the preheated fertilizer granules is 75~85℃, the mass ratio of surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material to isocyanate compound is 1:0.5~1.5; the mass of catalyst is 0.1~0.3% of the mass of surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material; and the number of spraying times is 3~7.
[0016] Preferably, the isocyanate compound comprises one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, methylcyclohexyl diisocyanate, and tetramethylphenyldimethyl diisocyanate; the catalyst comprises one or more of dibutyltin dilaurate, stannous octoate, zinc naphthenate, zinc isooctanoate, bismuth carboxylate, bismuth isooctanoate, phenylmercuric propionate, and phenylmercuric acetate; and the fertilizer comprises one or more of urea, ammonium nitrate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, and potassium chloride.
[0017] The beneficial effects of this invention are: 1) This invention uses renewable biomass lignin and various natural minerals as the main raw materials, which are widely available and inexpensive. Furthermore, the coating material is biodegradable and environmentally friendly.
[0018] 2) By introducing the cationic surfactant hexadecyltrimethylammonium bromide, this invention improves the dispersibility and interfacial compatibility of inorganic nano-minerals in the organic phase, effectively reducing the aggregation of nanomaterials. On this basis, by utilizing the difference in microstructure between attapulgite and nano-silica, the spatial complementarity between rod-shaped and granular minerals enhances the compactness, hydrophobicity, and mechanical properties of lignin-based membrane materials.
[0019] 3) The preparation process of this invention is simple, using solvent-free, one-step spraying and curing to form a film. It is easy to operate, has low energy consumption, and is easy to realize industrial continuous production. It has significant economic and environmental benefits, and provides important technical support and application value for improving the quality and efficiency of agricultural production and achieving green and sustainable development.
[0020] 4) The coated fertilizer prepared by this invention has excellent controlled-release performance. Its initial nutrient release rate is controlled below 2%, and the cumulative release period is as long as 28 to 56 days, which can effectively match the nutrient requirements of crops and improve fertilizer utilization.
[0021] 5) This invention develops a single-layer coated fertilizer that combines low cost, biodegradability and good controlled-release properties by synergistic modification of renewable biomass lignin, surfactants and multi-element natural inorganic nano-minerals. It effectively replaces traditional, difficult-to-degrade petroleum-based coating materials, and solves the problems of secondary soil pollution and resource waste caused by them from the source. Attached Figure Description
[0022] Figure 1 The cumulative nitrogen release of the surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizers prepared in Examples 1-5 is shown. Detailed Implementation
[0023] This invention provides a method for preparing surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating materials, comprising the following steps: 1) Polyethylene glycol, polycaprolactone glycol and glycerol are mixed to obtain a mixed liquefying agent; the mixed liquefying agent, lignin and acid catalyst are reacted to obtain liquefied lignin-based polyol; 2) Liquefy lignin-based polyol, hexadecyltrimethylammonium bromide, attapulgite and nano silica are mixed to obtain surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material.
[0024] In this invention, the polyethylene glycol preferably comprises one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800; the polycaprolactone diol preferably comprises one or more of polycaprolactone diol 530, polycaprolactone diol 830, and polycaprolactone diol 2000; the lignin preferably comprises one or more of alkali lignin, lignin sulfonate, and organic solvent lignin; the particle size of the lignin is preferably 60-120 mesh, more preferably 70-110 mesh, and even more preferably 80-90 mesh; the acid catalyst is preferably concentrated sulfuric acid and / or phosphoric acid.
[0025] In this invention, lignin sulfonate is preferably sodium lignin sulfonate or calcium lignin sulfonate; the organic solvent lignin is preferably ethanol lignin.
[0026] In this invention, the mass ratio of polyethylene glycol, polycaprolactone diol, and glycerol is preferably 6-10:1:1, more preferably 7-9:1:1, and even more preferably 8:1:1; the mass ratio of the mixed liquefying agent and lignin is preferably 2-5:1, more preferably 3-4:1, and even more preferably 3.5:1; the mass of the acid catalyst is preferably 1-3% of the lignin content, more preferably 1.5-2.5%, and even more preferably 2%.
[0027] In this invention, the mixing temperature in step 1) is preferably 160~180℃, more preferably 165~175℃, and even more preferably 170℃. The mixing is preferably carried out under stirring, and the stirring speed is preferably 300~400 r / min, more preferably 320~380 r / min, and even more preferably 350~360 r / min. The reaction temperature is preferably 160~180℃, more preferably 165~175℃, and even more preferably 170℃. The reaction time is preferably 0.5~1.5h, and even more preferably 1h.
[0028] In this invention, the mass of the hexadecyltrimethylammonium bromide is preferably 0.5-5% of the mass of the liquefied lignin-based polyol, more preferably 1-4%, and even more preferably 2-3%; the mass ratio of the hexadecyltrimethylammonium bromide, attapulgite, and nano-silica is preferably 0.5-5:5-15:0.5-10, more preferably 1-4:8-12:2-8, and even more preferably 2-3:9-10:4-6. The attapulgite preferably includes one or more of the following: high-quality attapulgite, opal attapulgite, dolomite attapulgite, and montmorillonite attapulgite.
[0029] In this invention, the high-quality attapulgite contains more than 85% attapulgite, and the main impurities are micron-sized detrital quartz and feldspar, as well as a small amount of authigenic opal and dolomite; hexadecyltrimethylammonium bromide is used as a surfactant, and attapulgite and nano-silica are used as multi-element inorganic nano-minerals.
[0030] In this invention, the mixing temperature in step 2) is preferably 160~180℃, more preferably 165~175℃, and even more preferably 170℃, and the mixing time is preferably 0.5~1.5h, and even more preferably 1h.
[0031] The present invention also provides a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material prepared by the above preparation method.
[0032] The present invention also provides a coated fertilizer prepared by the surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, wherein a mixture of surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, isocyanate compound and catalyst is sprayed onto the preheated fertilizer surface and in-situ polymerization reaction is carried out to obtain surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coated fertilizer.
[0033] In this invention, the temperature of the preheated fertilizer granules is preferably 75~85℃, more preferably 78~82℃, and even more preferably 80℃; the mass ratio of the surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material to the isocyanate compound is preferably 1:0.5~1.5, more preferably 1:0.8~1.2, and even more preferably 1:1; the mass of the catalyst is preferably 0.1~0.3% of the mass of the surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material, more preferably 0.15~0.25%, and even more preferably 0.2%.
[0034] In this invention, the number of spraying operations is preferably 3 to 7 times, more preferably 4 to 5 times; the spraying rate is preferably 4 to 5 g / min, more preferably 4.5 g / min; the total mass of surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material and isocyanate compounds is preferably 3 to 7% of the fertilizer mass, more preferably 4 to 6%, and more preferably 5%.
[0035] In this invention, the isocyanate compound preferably comprises one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, methylcyclohexyl diisocyanate, and tetramethylphenyldimethyl diisocyanate; the catalyst preferably comprises one or more of dibutyltin dilaurate, stannous octoate, zinc naphthenate, zinc isooctanoate, bismuth carboxylate, bismuth isooctanoate, phenylmercuric propionate, and phenylmercuric acetate; and the fertilizer preferably comprises one or more of urea, ammonium nitrate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, and potassium chloride.
[0036] In this invention, the temperature of the in-situ polymerization reaction is preferably 75~85℃, more preferably 80℃, and the time of the in-situ polymerization reaction is preferably 25~35min, more preferably 30min.
[0037] This invention employs a surfactant-assisted synergistic modification strategy for multiple inorganic nano-minerals. By introducing hexadecyltrimethylammonium bromide as a dispersant and interface modifier, the dispersibility and compatibility of inorganic minerals in a lignin matrix are effectively improved. Furthermore, by combining at least two minerals with different structures and morphologies (e.g., minerals with rod-like structures and minerals with nanoparticle structures), a denser physical barrier network can be constructed within the lignin matrix. Specifically, the rod-like minerals dispersed by hexadecyltrimethylammonium bromide form a stable supporting framework, while the particulate minerals effectively fill the micropores between the framework. This deep complementarity in structure and function significantly enhances the density, mechanical strength, and water-blocking properties of the composite membrane, achieving results far superior to single-mineral or traditional physical mixing modification.
[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0039] In the examples and comparative examples, alkali lignin, sodium lignin sulfonate and ethanol lignin were purchased from Shandong Xinglong Paper (Group) Co., Ltd., urea was purchased from Shaanxi Shanhua Coal Chemical Group Co., Ltd., diphenylmethane diisocyanate (MDI) was purchased from Guangzhou Baichuan Chemical Co., Ltd., and hexadecyltrimethylammonium bromide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; the mass fraction of concentrated sulfuric acid was 98%.
[0040] Example 1
[0041] Polyethylene glycol 400, polycaprolactone diol 530, and glycerol were mixed in a mass ratio of 8:1:1 and placed in a reactor equipped with a stirrer, heating device, and condenser. The mixture was heated to 160°C and stirred at 350 r / min to obtain a homogeneous mixed liquefying agent. Subsequently, 40 g of alkali lignin that had passed through a 100-mesh sieve was added to 100 g of the mixed liquefying agent, and concentrated sulfuric acid at 2% of the mass of the alkali lignin was added as a catalyst. The mixture was reacted at 160°C and atmospheric pressure for 1 h to obtain liquefied lignin-based polyol.
[0042] Add 0.8% (by mass) of hexadecyltrimethylammonium bromide to liquefied lignin-based polyol. After stirring and dispersing evenly at 160°C, add montmorillonite and nano-silica (mass ratio of hexadecyltrimethylammonium bromide, montmorillonite, and nano-silica is 0.8:5:2). Continue stirring and mixing at 160°C for 45 minutes until the mixture is evenly dispersed to obtain a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material.
[0043] 1000g of urea granules with a particle size of 2-4mm were placed in a rotary drum coating machine and preheated at 80℃ for 15min. The coating process was carried out in three stages. Each stage involved spraying a mixture of 4.445g of coating material, 5.555g of diphenylmethane diisocyanate, and 0.2% (by mass) of stannous octoate catalyst onto the surface of the preheated urea granules at a rate of 4.5g / min. After spraying, the mixture was further subjected to in-situ polymerization at 80℃ for 30min to allow the film to fully solidify. After the reaction, the mixture was allowed to cool naturally to obtain a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer.
[0044] Example 2
[0045] Polyethylene glycol 600, polycaprolactone diol 530, and glycerol were mixed in a mass ratio of 6:1:1 and placed in a reactor equipped with a stirrer, heating device, and condenser. The mixture was heated to 180°C and stirred at 350 r / min to obtain a homogeneous mixed liquefying agent. Subsequently, 50 g of sodium lignosulfonate that had passed through an 80-mesh sieve was added to 100 g of the mixed liquefying agent, and concentrated sulfuric acid at 1% of the mass of sodium lignosulfonate was added as a catalyst. The mixture was reacted at 180°C and atmospheric pressure for 0.5 h to obtain liquefied lignin-based polyol.
[0046] Add 1.5% (by mass) of hexadecyltrimethylammonium bromide to liquefied lignin-based polyol. After stirring and dispersing evenly at 180°C, add opal attapulgite and nano-silica (mass ratio of hexadecyltrimethylammonium bromide, opal attapulgite, and nano-silica is 1.5:5:1). Continue stirring and mixing at 180°C for 30 minutes until the mixture is evenly dispersed to obtain a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material.
[0047] 1000g of urea granules with a particle size of 2-4mm were placed in a rotary drum coating machine and preheated at 85℃ for 15 minutes. The coating process was carried out in three stages. Each stage involved spraying a mixture of 5g of coating material, 5g of diphenylmethane diisocyanate, and 0.2% (by mass) of stannous octoate catalyst onto the surface of the preheated urea granules at a rate of 4g / min. After spraying, an in-situ polymerization reaction was carried out at 85℃ for 30 minutes to allow the film to fully solidify. After the reaction, the mixture was allowed to cool naturally to obtain a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer.
[0048] Example 3
[0049] Polyethylene glycol 400, polycaprolactone diol 530, and glycerol were mixed in a mass ratio of 10:1:1 and placed in a reactor equipped with a stirrer, heating device, and condenser. The mixture was heated to 170°C and stirred at 350 r / min to obtain a homogeneous mixed liquefying agent. Subsequently, 50 g of alkali lignin that had passed through a 100-mesh sieve was added to 100 g of the mixed liquefying agent, and concentrated sulfuric acid at 3% of the mass of the alkali lignin was added as a catalyst. The mixture was reacted at 170°C and atmospheric pressure for 1.5 h to obtain liquefied lignin-based polyol.
[0050] Add 2.5% (by mass) of hexadecyltrimethylammonium bromide to liquefied lignin-based polyol. After stirring and dispersing evenly at 170°C, add dolomite attapulgite and nano-silica (mass ratio of hexadecyltrimethylammonium bromide, dolomite attapulgite, and nano-silica is 2.5:8:5). Continue stirring and mixing at 170°C for 1 hour until the mixture is evenly dispersed to obtain a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material.
[0051] 1000g of urea granules with a particle size of 2-4mm were placed in a rotary drum coating machine and preheated at 75℃ for 15min. The coating process was carried out in 5 stages. Each coating stage involved spraying a mixture of 4.444g of coating material, 5.556g of diphenylmethane diisocyanate, and 0.2% (by mass) of stannous octoate catalyst onto the surface of the preheated urea granules at a rate of 5g / min. After spraying, the mixture was further subjected to in-situ polymerization at 75℃ for 30min to allow the film to fully solidify. After the reaction, the mixture was allowed to cool naturally to obtain a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer.
[0052] Example 4
[0053] Polyethylene glycol 400, polycaprolactone diol 830, and glycerol were mixed in a mass ratio of 7:1:1 and placed in a reactor equipped with a stirrer, heating device, and condenser. The mixture was heated to 175°C and stirred at 350 r / min to obtain a homogeneous mixed liquefying agent. Subsequently, 50 g of ethanol lignin that had passed through a 100-mesh sieve was added to 100 g of the mixed liquefying agent, and concentrated sulfuric acid at 2.5% of the mass of ethanol lignin was added as a catalyst. The mixture was reacted at 175°C and atmospheric pressure for 1.2 h to obtain liquefied lignin-based polyol.
[0054] Add 3.5% (by mass) of hexadecyltrimethylammonium bromide to liquefied lignin-based polyol. After stirring and dispersing evenly at 175°C, add montmorillonite and nano-silica (mass ratio of hexadecyltrimethylammonium bromide, montmorillonite, and nano-silica is 3.5:8:4). Continue stirring and reacting at 175°C for 50 min until the mixture is evenly dispersed to obtain a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material.
[0055] 1000g of urea granules with a particle size of 2-4mm were placed in a rotary drum coating machine and preheated at 80℃ for 15min. The coating process was carried out in 5 stages. Each coating stage involved spraying a mixture of 4.545g of coating material, 5.455g of diphenylmethane diisocyanate, and 0.2% (by mass) of stannous octoate catalyst onto the surface of the preheated urea granules at a rate of 4.5g / min. After spraying, an in-situ polymerization reaction was carried out at 80℃ for 30min to allow the film to fully solidify. After the reaction, the mixture was allowed to cool naturally to obtain a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer.
[0056] Example 5
[0057] Polyethylene glycol 600, polycaprolactone diol 2000, and glycerol were mixed in a mass ratio of 9:1:1 and placed in a reactor equipped with a stirrer, heating device, and condenser. The mixture was heated to 165°C and stirred at 350 r / min to obtain a homogeneous mixed liquefying agent. Subsequently, 50 g of alkali lignin that had passed through a 100-mesh sieve was added to 100 g of the mixed liquefying agent, and concentrated sulfuric acid at 1.5% of the mass of the alkali lignin was added as a catalyst. The mixture was reacted at 165°C and atmospheric pressure for 1.5 h to obtain liquefied lignin-based polyol.
[0058] Add 4.8% (by mass) of hexadecyltrimethylammonium bromide to liquefied lignin-based polyol. After stirring and dispersing evenly at 165°C, add opal attapulgite and nano-silica (mass ratio of hexadecyltrimethylammonium bromide, opal attapulgite, and nano-silica is 4.8:9:6). Continue stirring and reacting at 165°C for 1 hour until the mixture is evenly dispersed to obtain a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material.
[0059] 1000g of urea granules with a particle size of 2-4mm were placed in a rotary drum coating machine and preheated at 80℃ for 15min. The coating process was carried out in 7 stages. Each coating stage involved spraying a mixture of 4g of coating material, 6g of diphenylmethane diisocyanate, and 0.2% (by weight of the coating material) of stannous octoate catalyst onto the surface of the preheated urea granules at a rate of 5g / min. After spraying, an in-situ polymerization reaction was carried out at 80℃ for 30min to allow the film to fully solidify. After the reaction, the mixture was allowed to cool naturally to obtain a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer.
[0060] The coated fertilizers (single-layer coated fertilizers) from Examples 1-5 were placed in 100-mesh nylon mesh bags, sealed, and then placed in 300mL plastic bottles. 250mL of deionized water was added, the bottles were sealed, and the bottles were incubated in a 25℃ biochemical incubator. Samples were taken at regular intervals (24h, 3d, 5d, 7d, 10d, 13d, 16d, 19d, 22d, 25d, 28d, 35d, 42d, 49d, 56d…). During sampling, the plastic bottles were inverted three times to ensure consistent liquid concentration. 50mL of the extract was taken, cooled, and the total nitrogen content was determined. The coating thickness and controlled-release performance of different fertilizers are shown in Table 1. The coating thickness is expressed as the percentage of the total mass of the coating material and diphenylmethane diisocyanate relative to the mass of the urea particles. The date corresponding to 80% cumulative nutrient (nitrogen) release is defined as the cumulative nutrient release period (controlled release period) of the fertilizer. The cumulative nitrogen release of the surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizers prepared in Examples 1-5 is as follows: Figure 1 As shown.
[0061] Table 1. Coating thickness and controlled-release performance of different coated fertilizers
[0062] Depend on Figure 1 As shown in Table 1, the surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coated fertilizer prepared in this invention has a good controlled-release effect, with an initial nutrient dissolution rate of ≤2% and a cumulative release period of ≥28 days.
[0063] This invention introduces hexadecyltrimethylammonium bromide as a dispersant, which effectively improves the dispersibility of multi-component inorganic nano-minerals in the organic phase. By leveraging the synergistic complementary mechanism of attapulgite and nano-silica in terms of microstructure and function, a dense microscopic barrier network is constructed within the monolayer membrane. The prepared coated fertilizer has an initial nutrient dissolution rate of less than 2% and a cumulative release period of 28-56 days, significantly improving the controlled-release performance and nutrient utilization efficiency of the fertilizer. It also has comprehensive advantages such as being entirely bio-based, environmentally friendly, having a simple preparation process, and significant economic benefits.
[0064] This invention makes full use of renewable biomass resources and inexpensive natural minerals, and optimizes the interface bonding using hexadecyltrimethylammonium bromide. Through a simple one-step coating process, a novel slow-release fertilizer with dense membrane layer, excellent controlled-release performance, low cost, and environmental friendliness is prepared, providing strong technical support for the green and sustainable development of modern agriculture.
[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, characterized in that, It includes the following steps: 1) Polyethylene glycol, polycaprolactone glycol and glycerol are mixed to obtain a mixed liquefying agent; the mixed liquefying agent, lignin and acid catalyst are reacted to obtain liquefied lignin-based polyol; 2) Liquefy lignin-based polyol, hexadecyltrimethylammonium bromide, attapulgite and nano silica are mixed to obtain surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material.
2. The preparation method according to claim 1, characterized in that, The polyethylene glycol comprises one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800; the polycaprolactone diol comprises one or more of polycaprolactone diol 530, polycaprolactone diol 830, and polycaprolactone diol 2000; the lignin is one or more of alkali lignin, lignin sulfonate, and organic solvent lignin; the particle size of the lignin is 60-120 mesh; and the acid catalyst is concentrated sulfuric acid and / or phosphoric acid.
3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of polyethylene glycol, polycaprolactone diol, and glycerol is 6-10:1:1; the mass ratio of the mixed liquefying agent to lignin is 2-5:1; and the mass of the acid catalyst is 1-3% of the lignin mass.
4. The preparation method according to claim 3, characterized in that, Step 1) The mixing temperature is 160~180℃, the mixing is carried out under stirring, the stirring speed is 300~400r / min, the reaction temperature is 160~180℃, and the reaction time is 0.5~1.5h.
5. The preparation method according to claim 3, characterized in that, The mass of the hexadecyltrimethylammonium bromide is 0.5-5% of the mass of the liquefied lignin-based polyol, and the mass ratio of the hexadecyltrimethylammonium bromide, attapulgite, and nano-silica is 0.5-5:5-15:0.5-10. The attapulgite includes one or more of the following: high-quality attapulgite, opal attapulgite, dolomite attapulgite, and montmorillonite attapulgite.
6. The preparation method according to claim 5, characterized in that, Step 2) The mixing temperature is 160~180℃ and the mixing time is 0.5~1.5h.
7. The surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material prepared by the preparation method according to any one of claims 1 to 6.
8. A coated fertilizer prepared from a surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material as described in claim 7, characterized in that, A mixture of surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coating material, isocyanate compounds, and catalyst is sprayed onto the surface of preheated fertilizer granules and subjected to in-situ polymerization to obtain surfactant-assisted multi-component inorganic nano-mineral modified lignin-based coated fertilizer.
9. The coated fertilizer according to claim 8, characterized in that, The temperature of the preheated fertilizer granules is 75~85℃. The mass ratio of surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material to isocyanate compound is 1:0.5~1.
5. The mass of catalyst is 0.1~0.3% of the mass of surfactant-assisted multi-element inorganic nano-mineral modified lignin-based coating material. The number of spraying times is 3~7.
10. The coated fertilizer according to claim 9, characterized in that, The isocyanate compound comprises one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, methylcyclohexyl diisocyanate, and tetramethylphenyldimethyl diisocyanate; the catalyst comprises one or more of dibutyltin dilaurate, stannous octoate, zinc naphthenate, zinc isooctanoate, bismuth carboxylate, bismuth isooctanoate, phenylmercuric propionate, and phenylmercuric acetate; the fertilizer comprises one or more of urea, ammonium nitrate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, and potassium chloride.