Surface brightening graphene film chemical fertilizer and preparation method thereof

Abstract

The invention discloses a surface brightening graphene film chemical fertilizer and a preparation method thereof. The film chemical fertilizer is prepared from the following raw materials in parts by weight: 800 to 1200 parts of fertilizer particles, 0.8 to 1.2 parts of silane coupling agent, 0.06 to 0.15 part of graphene, 1.2 to 1.8 parts of zirconium oxide, 0.08 to 0.12 part of polyether modified polysiloxane, 40 to 60 parts of polybutylene terephthalate adipate-polylactic acid copolymer resin, 0.25 to 0.35 part of anti-yellowing agent, 0.15 to 0.25 part of flatting agent, 4 to 6 parts of pearlescent mica powder and 130 to 190 parts of solvent. The comprehensive effects of long-acting brightening, long-term weather resistance and environmental friendliness of the thin film fertilizer can be achieved.

Description

Technical Field

[0001] This application relates to the field of fertilizer technology, and in particular to a surface-brightening graphene film fertilizer and its preparation method. Background Technology

[0002] With the booming development of modern agriculture, especially the high-value cash crop industry (such as high-value fruits and vegetables, and ornamental flowers), market competition for fertilizer products has expanded from simply focusing on intrinsic fertilizer efficacy to extrinsic appearance. Consumers often judge the quality and grade of fertilizer products intuitively by the "surface gloss" of the fertilizer granules. Fertilizer products with uniform granules and a glossy surface can command a market premium of over 20%. Therefore, surface brightening treatment of fertilizers has become a key means to enhance product added value and market competitiveness.

[0003] Currently, the industry's technology for brightening the surface of fertilizers mainly relies on coating the surface of fertilizer granules with a polymer coating. Commonly used film-forming materials include polyvinyl alcohol and polylactic acid. These traditional technologies aim to increase the surface's reflection of light by forming a smooth film, thereby achieving a brightening effect.

[0004] However, coatings made of polyvinyl alcohol and polylactic acid have weak interfacial adhesion with fertilizer granules (especially compound fertilizer granules containing trace elements such as calcium, magnesium, and boron). During subsequent packaging, storage, and long-distance transportation, friction and collisions inevitably occur between the granules, easily leading to coating wear and even peeling. After transportation friction, the coating brightness retention rate is often less than 60%, seriously affecting the visual quality of the product when it reaches the end user. Summary of the Invention

[0005] To improve the long-lasting brightening effect of the coating, this application provides a surface-brightening graphene film fertilizer and its preparation method.

[0006] In a first aspect, this application provides a surface-brightening graphene film fertilizer, employing the following technical solution: A surface-brightening graphene film fertilizer comprises the following raw materials in parts by weight: Fertilizer granules 800-1200 parts, silane coupling agent 0.8-1.2 parts, graphene 0.06-0.15 parts, zirconium oxide 1.2-1.8 parts, polyether modified polysiloxane 0.08-0.12 parts, polybutylene adipate-polylactic acid copolymer resin 40-60 parts, anti-yellowing agent 0.25-0.35 parts, leveling agent 0.15-0.25 parts, pearlescent mica powder 4-6 parts, solvent 130-190 parts.

[0007] By employing the above technical solution, the optical interference effect of graphene and the light scattering properties of zirconium oxide work synergistically, and with the help of a highly transparent polybutylene terephthalate-polylactic acid copolymer resin carrier, efficient brightening of fertilizer surfaces is achieved. Simultaneously, the high strength of graphene and the cross-linked network after resin curing work together to significantly improve the wear resistance of the coating, thus ensuring the long-term weather resistance of the film. A silane coupling agent bridges the film and fertilizer particles, greatly enhancing the interfacial bonding force and effectively preventing film detachment. Furthermore, the polybutylene terephthalate-polylactic acid copolymer resin has good chemical compatibility with trace elements such as calcium and magnesium, and is less prone to coordination reactions that cause yellowing; at the same time, the chemical inertness of graphene and its dense layered structure effectively isolate fertilizer elements from air, providing double protection against yellowing of the coating. In addition, the polybutylene terephthalate-polylactic acid copolymer resin is biodegradable, avoiding soil residue. The synergistic effect of the above components achieves a comprehensive effect of long-lasting brightening, long-term weather resistance and environmental friendliness in film fertilizers.

[0008] Optionally, the weight ratio of graphene to zirconium oxide is 1:(20-40).

[0009] By adopting the above technical solution, this application uses a specific ratio of graphene and zirconium oxide to synergistically construct a robust and wear-resistant brightening protective layer on the surface of fertilizer, thereby significantly improving the durability of surface gloss. At the same time, this ratio helps to form a multi-level "sheet-particle" structure inside the coating, constructing an optimized pore network, thereby achieving a stable and controllable release of nutrients.

[0010] Optionally, the zirconium oxide is nano-sized zirconium oxide with a particle size of 20-30 nm.

[0011] By adopting the above technical solution, this application uses nano-sized zirconia, which can maximize the light reflection intensity and uniformity of the film surface, and work in synergy with graphene to build a continuous nano-sized pore network inside the coating to ensure the smooth release of nutrients; at the same time, the nano-sized zirconia, as a "sheet-particle" composite structure formed by hard particles and graphene sheets, jointly enhances the wear resistance and mechanical strength of the film.

[0012] Optionally, the nano-sized zirconia is modified nano-sized zirconia, and the preparation steps of the modified nano-sized zirconia include: mixing γ-aminopropyltriethoxysilane and ethanol solution, heating and stirring until uniform, then adding nano-sized zirconia, dispersing, filtering and drying to obtain modified nano-sized zirconia.

[0013] By employing the above technical solution, γ-aminopropyltriethoxysilane is used to modify the surface of nano-zirconia. The active silanol groups (-Si-OH) generated after hydrolysis can covalently bond with the hydroxyl groups on the surface of the nano-zirconia, thus firmly grafting the coupling agent molecules onto the particle surface. The outward-extending organic chains after grafting significantly reduce the surface energy of the particles, effectively preventing the aggregation of nanoparticles due to van der Waals forces. Simultaneously, the amino (-NH2) functional groups at the other end of the coupling agent grafted onto the zirconia surface can form strong interfacial interactions with the molecular chains of polybutylene terephthalate-polylactic acid copolymer resin, thereby constructing a strong "molecular bridge" between the inorganic particles and the organic resin. This significantly improves the interfacial bonding strength between the film and fertilizer particles, thereby enhancing the adhesion of the film.

[0014] Optionally, the weight ratio of the polybutylene adipate-polylactic acid copolymer resin to graphene is (800-1000):1.

[0015] By adopting the above technical solution, this application successfully constructed a stable "sheet-resin" composite structure using a specific ratio of polybutylene adipate-polylactic acid copolymer resin and graphene. This structure achieves efficient brightening while synergistically ensuring the coating's flexibility, wear resistance, and unobstructed nutrient release channels. Specifically, the polybutylene adipate-polylactic acid copolymer resin provides ample dispersion space for the graphene and serves as a highly efficient optical carrier due to its high transparency (≥92%). The dispersed graphene enhances the gloss texture through a unique optical interference effect and achieves microscopic leveling of the fertilizer particle surface through its nanosheet structure.

[0016] Optionally, the anti-yellowing agent is a hindered amine anti-yellowing agent, and the leveling agent is an acrylate leveling agent.

[0017] By employing the above technical solutions, hindered amine anti-yellowing agents can efficiently capture and quench free radicals generated in the coating during ultraviolet irradiation and environmental oxidation, effectively interrupting the chain reaction that leads to polymer aging, thereby fundamentally inhibiting yellowing and chalking of the coating. Meanwhile, acrylate leveling agents can effectively reduce the surface tension of the coating liquid, enhancing its spreading and wetting ability on fertilizer granules, thus promoting automatic leveling of the coating before curing and eliminating potential surface defects such as orange peel and pinholes, resulting in a uniformly thick and extremely smooth paint film. Furthermore, both hindered amine anti-yellowing agents and acrylate leveling agents have extremely low inhibition rates on soil microorganisms, ensuring that soil fertility and crop root activity are not affected.

[0018] Optionally, the solvent is at least one of ethyl acetate and propylene glycol methyl ether.

[0019] By adopting the above technical solution, ethyl acetate has a good solubility for polybutylene adipate-polylactic acid copolymer resin, while propylene glycol methyl ether, as a strong coupling solvent, can not only be well miscible with ethyl acetate, but also effectively wet and disperse graphene and nano-zirconia, which helps to form a uniform and stable coating liquid.

[0020] Secondly, this application provides a method for preparing a surface-brightening graphene film fertilizer, which adopts the following technical solution: A method for preparing a surface-brightening graphene film fertilizer includes the following steps: S1. Fertilizer substrate pretreatment: Mix silane coupling agent, ethanol and water, spray on the surface of fertilizer granules, and dry to obtain fertilizer substrate; S2. Preparation of pre-dispersion: Graphene and zirconium oxide are mixed, and solvent and polyether-modified polysiloxane are added in sequence. The mixture is stirred evenly and ultrasonically dispersed to obtain a pre-dispersion. S3. Preparation of polyester base material: Polybutylene adipate-polylactic acid copolymer resin and solvent are mixed, heated and stirred until completely dissolved, hindered amine anti-yellowing agent and acrylate leveling agent are added, and mixed evenly to obtain polyester base material; S4. Preparation of coating liquid: Add the pre-dispersion to the polyester base material and stir evenly to obtain the bottom liquid; divide the bottom liquid into two parts, add pearlescent mica powder to one part of the bottom liquid and mix evenly to obtain the top liquid; S5. Preparation of film fertilizer: Spray the remaining bottom layer liquid onto the surface of the fertilizer substrate, dry it, then spray the top layer liquid and cure it to obtain the film fertilizer.

[0021] By adopting the above technical solution, this application first pretreats fertilizer particles with a silane coupling agent, forming an activation layer on the fertilizer surface through chemical bonding to enhance interfacial adhesion; then, graphene and nano-zirconia are pre-dispersed to prevent particle agglomeration and achieve a uniform dispersion; finally, a dual-layer coating strategy of "bottom liquid + top liquid" is used to achieve a gradient distribution of functions. The bottom liquid mainly plays the role of graphene in leveling, strengthening, and constructing nutrient channels; the top liquid provides lubrication, wear resistance, and additional brightening effects on the outermost layer through pearlescent mica powder.

[0022] Optionally, in step S1, the drying temperature is 50-70°C.

[0023] Optionally, in S2, the stirring speed is 8000-12000 rpm and the ultrasonic power is 400-600W.

[0024] Optionally, in step S3, the heating temperature is 50-70℃ and the stirring speed is 300-500rpm.

[0025] Optionally, in step S4, the stirring speed is 400-600 rpm, and the volume ratio of the pre-dispersed material to the polyester base material is 1:(7-9).

[0026] Optionally, in step S5, the drying temperature is 50-70℃, the curing is ultraviolet curing, the ultraviolet wavelength is 365nm, and the ultraviolet curing power is 700-900W.

[0027] Optionally, in step S5, the thickness of the base coat liquid is 0.8-1.2 μm, and the thickness of the top coat liquid is 0.5-0.8 μm.

[0028] Optionally, in step S5, the base coat liquid is applied by electrostatic spraying with an electrostatic field voltage of 50-70kV and an atomization pressure of 0.3-0.5MPa, and the top coat liquid is applied by air spraying with an air spraying pressure of 0.2-0.4MPa.

[0029] Optionally, in step S5, the solvent is condensed at 5-10°C and adsorbed by activated carbon during the solvent spraying process to obtain recovered solvent.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. By leveraging the synergistic effect of graphene's optical interference and zirconium oxide's light scattering properties, and utilizing a highly transparent polybutylene adipate-polylactic acid (PEPA-PLA) copolymer resin carrier, efficient brightening of fertilizer surfaces was achieved. Simultaneously, the high strength of graphene and the cross-linked network after resin curing significantly improved the coating's wear resistance, ensuring the long-lasting brightening effect. A silane coupling agent bridges the gap between the film and fertilizer particles, greatly enhancing interfacial adhesion and effectively preventing film detachment. Furthermore, the PEPA-PLA copolymer resin exhibits good chemical compatibility with trace elements such as calcium and magnesium, minimizing the likelihood of yellowing coordination reactions. Additionally, the chemical inertness and dense layered structure of graphene effectively isolate fertilizer elements from air, providing double protection against yellowing of the coating. Moreover, the PEPA-PLA copolymer resin is biodegradable, preventing soil residue. The synergistic effect of the above components enables the film fertilizer to achieve the comprehensive advantages of long-lasting brightening, long-term weather resistance and environmental friendliness; 2. By using a specific ratio of graphene and zirconium oxide, a robust and wear-resistant brightening protective layer can be synergistically constructed on the surface of fertilizer, thereby significantly improving the durability of surface gloss; at the same time, this ratio helps to form a multi-level "lamella-particle" structure inside the coating, constructing an optimized pore network, thereby achieving stable and controllable release of nutrients. 3. By surface-modifying nano-zirconia with γ-aminopropyltriethoxysilane, the active silanol groups (-Si-OH) generated after hydrolysis can covalently bond with the hydroxyl groups on the surface of nano-zirconia, thus firmly grafting coupling agent molecules onto the particle surface. The outward-extending organic chains after grafting significantly reduce the surface energy of the particles, effectively preventing the aggregation of nanoparticles due to van der Waals forces. Simultaneously, the amino (-NH2) functional groups at the other end of the coupling agent grafted onto the zirconia surface can form strong interfacial interactions with the molecular chains of polybutylene terephthalate-polylactic acid copolymer resin, thereby constructing a strong "molecular bridge" between the inorganic particles and the organic resin. This not only significantly improves the interfacial bonding strength between the film and fertilizer particles, but also enhances the adhesion of the film. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] This application designs a surface-brightening graphene film fertilizer, comprising the following raw materials in parts by weight: Fertilizer granules 800-1200 parts, silane coupling agent 0.8-1.2 parts, graphene 0.06-0.15 parts, zirconium oxide 1.2-1.8 parts, polyether modified polysiloxane 0.08-0.12 parts, polybutylene adipate-polylactic acid copolymer resin 40-60 parts, anti-yellowing agent 0.25-0.35 parts, leveling agent 0.15-0.25 parts, pearlescent mica powder 4-6 parts, solvent 130-190 parts.

[0033] A method for preparing a surface-brightening graphene film fertilizer includes the following steps: S1. Fertilizer substrate pretreatment: Mix silane coupling agent, ethanol and water, spray on the surface of fertilizer granules, and dry at 50-70℃ for 5-10 minutes to obtain fertilizer substrate. S2. Preparation of pre-dispersion: Mix graphene and zirconium oxide, add solvent and polyether-modified polysiloxane in sequence, stir at 8000-12000 rpm for 15-25 min, and ultrasonically disperse at 400-600W for 30-50 min to obtain pre-dispersion; S3. Preparation of polyester base material: Mix polybutylene adipate-polylactic acid copolymer resin and solvent, heat to 50-70℃, stir at 300-500 rpm for 25-35 min, add hindered amine anti-yellowing agent and acrylate leveling agent, mix evenly to obtain polyester base material. S4. Preparation of coating liquid: Add the pre-dispersion to the polyester base material and stir at 400-600 rpm for 50-70 min to obtain the bottom liquid; divide the bottom liquid into two parts, add pearlescent mica powder to one part of the bottom liquid and stir at 400-600 rpm for 25-35 min to obtain the top liquid; S5. Preparation of film fertilizer: The remaining base liquid is sprayed onto the surface of the fertilizer substrate by electrostatic spraying with an electrostatic field voltage of 50-70kV and an atomization pressure of 0.3-0.5MPa. It is then dried at 50-70℃ for 5-15min. Then, the top layer liquid is sprayed by air spraying with an air spraying pressure of 0.2-0.4MPa. Finally, it is cured with ultraviolet light at 365nm and 700-900W for 30-60s to obtain the film fertilizer.

[0034] All raw materials used in the embodiments of this application are commercially available, wherein: Fertilizer granules, 3-5mm in diameter, manufactured by Yunnan Yuntianhua Group Co., Ltd. Silane coupling agent, KH-550, Nanjing Liansilicon Chemical Co., Ltd.; Graphene, 3-4 layers, Beijing Graphene Technology Research Institute; Zirconia, Guangdong Dongfang Zirconium Industry Technology Co., Ltd.; Polyether-modified polysiloxane, RH-T1008, Zhejiang Runhe Organosilicon New Materials Co., Ltd.; Polybutylene adipate terephthalate, Xinjiang Lanshan Tunhe Technology Co., Ltd.; Polylactic acid (PLA), Shanghai Shenxia Biochemical Co., Ltd. Tinuvin 123 anti-yellowing agent, Suqian Liansheng Technology Co., Ltd.; Acrylic leveling agent, Shanghai Huiyan New Materials Co., Ltd.; Pearl mica powder, Global New Materials International Holdings Limited; Ethyl acetate, Baichuan Energy Co., Ltd.; Propylene glycol methyl ether, Yida Chemical Co., Ltd. Specific Implementation

[0035] Preparation Example 1 Preparation of modified nano-sized zirconia: Ethanol and water were mixed at a volume ratio of 1:1 to obtain an ethanol solution; 0.1 g of γ-aminopropyltriethoxysilane was mixed with 100 mL of the ethanol solution, heated to 60 °C, stirred at 500 rpm for 30 min, and then 8 g of nano-sized zirconia (particle size 20-30 nm) was added, ultrasonically dispersed at 300 W for 20 min, filtered and dried to obtain modified nano-sized zirconia.

[0036] Preparation Example 2 Preparation of polybutylene adipate-polylactic acid copolymer resin: 100g of polylactic acid, 100g of polybutylene adipate and 5g of glycerol were mixed and heated to 180℃ and melt-blended at 300r / min for 20min. Then, 2g of diisocyanate was added and melt-blended at 180℃ and 300r / min for another 20min to obtain polybutylene adipate-polylactic acid copolymer resin.

[0037] Example 1 Mix 0.8g of silane coupling agent, 40mL of ethanol, and 40mL of water, and spray the mixture onto the surface of 800g of fertilizer granules using a fluidized bed spraying device. Dry the mixture at 50℃ for 10min to obtain a fertilizer base material. Mix 0.06g of graphene and 1.2g of zirconium oxide (particle size 0.2-0.5μm), and then add 6.8g of ethyl acetate, 6.8g of propylene glycol methyl ether, and 0.08g of polyether-modified polysiloxane sequentially. Stir at 8000rpm for 25min and ultrasonically disperse at 400W for 50min to obtain a pre-dispersion. Mix 60g of the polybutylene adipate-polylactic acid copolymer resin obtained in Preparation Example 2, 85g of ethyl acetate, and 85g of propylene glycol methyl ether, heat to 50℃, stir at 300rpm for 35min, and then add 0.35g of Tinuvin. 123 anti-yellowing agent and 0.25g acrylate leveling agent were mixed evenly to obtain a polyester base material. The pre-dispersion was added to the polyester base material and stirred at 400rpm for 70min to obtain a base liquid. 4g pearlescent mica powder was added to 40mL of the base liquid and stirred at 400rpm for 35min to obtain a top liquid. The remaining base liquid was sprayed onto the fertilizer substrate surface by electrostatic spraying at an electrostatic field voltage of 50kV and an atomization pressure of 0.3MPa. It was dried at 50℃ for 15min. Then, the top liquid was sprayed by air at an air spraying pressure of 0.2MPa. Finally, it was cured under 365nm, 700W ultraviolet light for 60s to obtain a film fertilizer.

[0038] Example 2 1g of silane coupling agent, 50mL of ethanol, and 50mL of water were mixed and sprayed onto the surface of 1000g of fertilizer granules using a fluidized bed spraying device. The mixture was then dried at 60℃ for 5min to obtain a fertilizer substrate. 0.075g of graphene and 1.5g of zirconium oxide (particle size 0.2-0.5μm) were mixed, and 8.5g of ethyl acetate, 8.5g of propylene glycol methyl ether, and 0.1g of polyether-modified polysiloxane were added sequentially. The mixture was stirred at 10000rpm for 20min and ultrasonically dispersed at 500W for 40min to obtain a pre-dispersion. 50g of the polybutylene adipate-polylactic acid copolymer resin obtained in Preparation Example 2 was mixed with 70g of ethyl acetate and 70g of propylene glycol methyl ether. The mixture was heated to 60℃, stirred at 400rpm for 30min, and 0.3g of Tinuvin was added. 123 anti-yellowing agent and 0.2g acrylate leveling agent were mixed evenly to obtain a polyester base material. The pre-dispersion was added to the polyester base material and stirred at 500rpm for 60min to obtain a base liquid. 5g pearlescent mica powder was added to 50mL of the base liquid and stirred at 500rpm for 30min to obtain a top liquid. The remaining base liquid was sprayed onto the fertilizer substrate surface by electrostatic spraying at an electrostatic field voltage of 60kV and an atomization pressure of 0.4MPa. The substrate was dried at 60℃ for 10min. Then, the top liquid was sprayed by air at an air spraying pressure of 0.3MPa. Finally, the substrate was cured under 365nm, 800W ultraviolet light for 30s to obtain a film fertilizer.

[0039] Example 3 1.2g of silane coupling agent, 60mL of ethanol, and 60mL of water were mixed and sprayed onto the surface of 1200g of fertilizer granules using a fluidized bed spraying device. The mixture was then dried at 70℃ for 5min to obtain a fertilizer substrate. 0.09g of graphene and 1.8g of zirconium oxide (particle size 0.2-0.5μm) were mixed, and 10.2g of ethyl acetate, 10.2g of propylene glycol methyl ether, and 0.12g of polyether-modified polysiloxane were added sequentially. The mixture was stirred at 12000rpm for 15min and ultrasonically dispersed at 600W for 30min to obtain a pre-dispersion. 40g of the polybutylene adipate-polylactic acid copolymer resin obtained in Preparation Example 2, 55g of ethyl acetate, and 55g of propylene glycol methyl ether were mixed, heated to 70℃, stirred at 500rpm for 25min, and 0.25g of Tinuvin were added. 123 anti-yellowing agent and 0.15g acrylate leveling agent were mixed evenly to obtain a polyester base material. The pre-dispersion was added to the polyester base material and stirred at 600rpm for 50min to obtain a base liquid. 6g pearlescent mica powder was added to 60mL of the base liquid and stirred at 600rpm for 25min to obtain a top liquid. The remaining base liquid was sprayed onto the fertilizer substrate surface by electrostatic spraying at an electrostatic field voltage of 70kV and an atomization pressure of 0.5MPa. It was dried at 70℃ for 5min. Then, the top liquid was sprayed by air at an air spraying pressure of 0.4MPa. Finally, it was cured under 365nm, 900W ultraviolet light for 30s to obtain a film fertilizer.

[0040] The film fertilizers obtained in Examples 1-3 were tested for 60° angle gloss, brightness uniformity, adhesion, acid and alkali resistance, temperature resistance, 6-month degradation rate in soil, and 60-day nutrient release rate. The test items and methods are as follows: 60° angle gloss: The 60° angle gloss of the film fertilizer was tested using a gloss meter.

[0041] Brightness uniformity: The brightness uniformity of the film fertilizer was tested using a gloss meter.

[0042] Adhesion: The adhesion of the film on the fertilizer film was tested according to GB / T 9286-2021 "Cross-cut test for paints and varnishes".

[0043] Acid and alkali resistance: The integrity rate of the film fertilizer was obtained by soaking the film in a simulated pH 4-10 leachate for 30 days.

[0044] Temperature resistance test: According to GB / T 2423.22-2012 "Environmental testing - Part 2: Test methods - Test N: Temperature change", the film fertilizer was placed in an environment of -10℃ for 30 minutes, and then placed in an environment of 60℃ for 30 minutes. The temperature transition time from -10℃ to 60℃ was within 30 minutes. 2 hours was one cycle. The above steps were repeated for 10 cycles to obtain the film peeling rate on the film fertilizer.

[0045] Degradation rate in soil over 6 months: The soil biodegradation rate of film fertilizer in soil over 6 months was determined in accordance with GB / T 19277.1-2011 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions by measuring carbon dioxide released".

[0046] Nutrient release rate over 60 days: The nutrient release rate of film fertilizer over 60 days was tested according to the standard "HG / T3931-2007 Slow-release Fertilizer".

[0047] The test results of Examples 1-3 obtained according to the above test methods are shown in Table 1: Table 1 Performance testing of film-coated fertilizers in Examples 1-3 detection indicators Example 1 Example 2 Example 3 60° angle gloss (GU) 89 88 87 Brightness uniformity (%) 98 97 96 Adhesion Level 2 Level 2 Level 2 Acid and alkali resistance (%) 97 96 95 Temperature resistance to change (%) 0.7 0.8 0.9 Soil biodegradation rate (%) after 6 months 64 62 60 Nutrient release rate (%) over 60 days 97 96 95 As shown in Examples 1-3 and Table 1, the film fertilizers of Examples 1-3 exhibit a gloss level of over 87 GU at a 60° angle, a brightness uniformity of over 96%, an adhesion grade of 2, acid and alkali resistance of over 95%, a temperature change resistance of over 0.7%, a soil biodegradation rate of over 60% after 6 months, and a nutrient release rate of over 97% after 60 days. This indicates that the film fertilizer of this application possesses excellent long-lasting brightening and long-term weather resistance, and is environmentally friendly. Specifically, the optical interference effect of graphene and the light scattering characteristics of zirconium oxide work synergistically to achieve highly efficient brightening of the fertilizer surface. Simultaneously, the high strength of graphene and the cross-linked network after resin curing significantly improve the wear resistance of the coating, thus ensuring the long-lasting brightening effect. The film and fertilizer particles are bridged by a silane coupling agent, greatly enhancing the interfacial bonding force and effectively preventing film detachment. Furthermore, the polybutylene adipate-polylactic acid copolymer resin is biodegradable, avoiding soil residue. The synergistic effect of the above components achieves a comprehensive effect of long-lasting brightening, long-term weather resistance and environmental friendliness in film fertilizers.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is that the equivalent mass of polybutylene terephthalate-polylactic acid copolymer resin in Example 1 is replaced with polylactic acid resin.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that the equivalent mass of polybutylene adipate-polylactic acid copolymer resin in Example 1 is replaced with polybutylene adipate resin.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that the graphene in Example 1 is replaced with zirconium oxide.

[0051] Comparative Example 4 The difference between this comparative example and Example 1 is that the zirconium oxide in Example 1 is replaced with graphene in this comparative example.

[0052] The film fertilizers obtained in Example 1 and Comparative Examples 1-4 were tested for gloss at a 60° angle, brightness uniformity, adhesion, acid and alkali resistance, temperature resistance, degradation rate in soil over 6 months, and nutrient release rate over 60 days. The test results are shown in Table 2. Table 2 Performance testing of film-coated fertilizers in Examples 1 and 1-4 detection indicators Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 60° angle gloss (GU) 89 78 84 72 75 Brightness uniformity (%) 98 88 94 82 89 Adhesion Level 2 Level 3 Level 1 Level 4 Level 3 Acid and alkali resistance (%) 97 85 92 88 90 Temperature resistance to change (%) 0.7 5.2 1.5 3.8 2.5 Degradation rate in soil over 6 months (%) 64 61 35 58 60 Nutrient release rate (%) over 60 days 97 88 94 82 84 As shown in Example 1, Comparative Examples 1-2, and Table 2, the film of Example 1 exhibits a brightness uniformity of 98%, an adhesion grade of 2, an acid and alkali resistance of 97%, a temperature change resistance of 0.7%, and a degradation rate of 64% in soil after 6 months, significantly superior to Comparative Examples 1-2. Compared to polybutylene adipate-polylactic acid copolymer resin, polylactic acid resin is brittle and has poor flexibility, resulting in a significant reduction in the film's adhesion, abrasion resistance, and anti-detachment properties; while polybutylene adipate-polylactic acid resin, although possessing better flexibility and film-forming properties, has a slower biodegradation rate.

[0053] As shown in Example 1, Comparative Examples 3-4, and Table 2, the film of Example 1 has a 60° angle gloss of 89 GU, a brightness uniformity of 98%, an adhesion grade of 1, an acid and alkali resistance of 97%, a temperature change resistance of 0.7%, and a degradation rate of 64% in soil over 6 months, which is significantly better than that of Comparative Examples 3-4. While the light scattering effect of pure oxalic acid can make the fertilizer surface appear "bright white," it reduces gloss and brightness uniformity and fails to form a "layer-particle" composite reinforcing network, resulting in a significant reduction in the film's adhesion and weather resistance. Pure graphene will give the film a dull gloss, and the graphene may be stacked too densely, making the coating brittle and affecting adhesion and nutrient release performance.

[0054] Examples 4-5 Based on Example 1, except for the weight ratio of graphene and zirconium oxide, the total weight of graphene and zirconium oxide remains unchanged, and the other components and preparation methods are the same as in Example 1.

[0055] Example 4 The difference between this embodiment and Embodiment 1 is that the weight ratio of graphene to zirconium oxide in this embodiment is 1:15. Specifically, the weight of graphene is 0.098g and the weight of zirconium oxide is 1.477g.

[0056] Example 5 The difference between this embodiment and Embodiment 1 is that the weight ratio of graphene to zirconium oxide in this embodiment is 1:10. Specifically, the weight of graphene is 0.143g and the weight of zirconium oxide is 1.432g.

[0057] The film fertilizers obtained in Examples 1 and 4-5 were tested for gloss at a 60° angle, uniformity of brightness, adhesion, acid and alkali resistance, temperature resistance, degradation rate in soil over 6 months, and nutrient release rate over 60 days. The test results are shown in Table 3. Table 3 Performance testing of film-coated fertilizers in Examples 1 and 4-5 detection indicators Example 1 Example 4 Example 5 60° angle gloss (GU) 89 91 88 Brightness uniformity (%) 98 99 97 Adhesion Level 2 Level 2 Level 2 Acid and alkali resistance (%) 97 98 96 Temperature resistance to change (%) 0.7 0.5 0.8 Nutrient release rate (%) over 60 days 97 98 96 As shown in Examples 1, 4-5, and Table 3, the film fertilizer of Example 4 has a 60° angle gloss of 91 GU, a brightness uniformity of 99%, an acid and alkali resistance of 98%, a temperature change resistance of 0.5%, and a 60-day nutrient release rate of 98%, which are higher than those of Examples 1 and 5. An excessively high graphene content can lead to an increase in coating density, thereby affecting gloss and nutrient release; an excessively high zirconium oxide content may disrupt the continuity and flexibility of the resin film, resulting in a decrease in the coating's temperature change resistance.

[0058] Example 6 The difference between this embodiment and embodiment 4 is that in this embodiment, the zirconium oxide of equal mass in embodiment 4 is replaced with nano-sized zirconium oxide, and the particle size of nano-sized zirconium oxide is 20-30nm.

[0059] Example 7 The difference between this embodiment and Example 6 is that in this embodiment, the nano-sized zirconium oxide in Example 6 is replaced with the modified nano-sized zirconium oxide obtained in Preparation Example 1.

[0060] The film fertilizers obtained in Examples 4 and 6-7 were tested for gloss at a 60° angle, uniformity of brightness, adhesion, acid and alkali resistance, temperature resistance, degradation rate in soil over 6 months, and nutrient release rate over 60 days. The test results are shown in Table 4. Table 4 Performance testing of film-coated fertilizers in Examples 4 and 6-7 detection indicators Example 4 Example 6 Example 7 60° angle gloss (GU) 91 93 94 Brightness uniformity (%) 99 99 99 Adhesion Level 2 Level 2 Level 1 Acid and alkali resistance (%) 98 99 99 Temperature resistance to change (%) 0.5 0.3 0.2 Nutrient release rate (%) over 60 days 98 99 99 As shown in Examples 4, 6-7, and Table 4, the film fertilizer of Example 7 exhibits a 60° angle gloss of 94 GU, a temperature resistance of 0.2%, and an adhesion grade of 1, significantly superior to Examples 4 and 6. Nanoscale zirconia can improve the light reflection intensity of the film surface and enhance temperature resistance through the "sheet-particle" composite structure formed with graphene sheets. Surface modification of nanoscale zirconia with γ-aminopropyltriethoxysilane is beneficial to the interfacial bonding strength between the film and fertilizer particles, thereby improving the adhesion of the film.

[0061] Examples 8-9 Based on Example 7, except for the weight ratio of polybutylene adipate-polylactic acid copolymer resin and graphene, the other components and preparation methods are the same as in Example 4.

[0062] Example 8 The difference between this embodiment and Embodiment 7 is that the weight ratio of polybutylene adipate-polylactic acid copolymer resin and graphene in this embodiment is 900:1. Specifically, the weight of polybutylene adipate-polylactic acid copolymer resin is 54g and the weight of graphene is 0.06g.

[0063] Example 9 The difference between this embodiment and Embodiment 7 is that the weight ratio of polybutylene adipate-polylactic acid copolymer resin and graphene in this embodiment is 800:1. Specifically, the weight of polybutylene adipate-polylactic acid copolymer resin is 48g and the weight of graphene is 0.06g.

[0064] The film fertilizers obtained in Examples 7-9 were tested for gloss at a 60° angle, uniformity of brightness, adhesion, acid and alkali resistance, temperature resistance, degradation rate in soil over 6 months, and nutrient release rate over 60 days. The test results are shown in Table 5. Table 5 Performance testing of film-coated fertilizers in Examples 7-9 As shown in Examples 7-9 and Table 5, the film fertilizer of Example 8 has a gloss level of 95 GU at a 60° angle and a temperature resistance of 0.1%, which is significantly better than that of Examples 7 and 9. Too low a resin content may lead to a decrease in graphene dispersion, thereby affecting light reflection and resulting in reduced gloss and brightness uniformity. Too high a resin content will soften the coating, leading to reduced acid and alkali resistance and temperature resistance.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A surface-brightening graphene film fertilizer, characterized in that, The raw materials include the following parts by weight: Fertilizer granules 800-1200 parts, silane coupling agent 0.8-1.2 parts, graphene 0.06-0.15 parts, zirconium oxide 1.2-1.8 parts, polyether modified polysiloxane 0.08-0.12 parts, polybutylene adipate-polylactic acid copolymer resin 40-60 parts, anti-yellowing agent 0.25-0.35 parts, leveling agent 0.15-0.25 parts, pearlescent mica powder 4-6 parts, solvent 130-190 parts.

2. The surface-brightening graphene film fertilizer according to claim 1, characterized in that, The weight ratio of graphene to zirconium oxide is 1:(20-40).

3. The surface-brightening graphene film fertilizer according to claim 1, characterized in that, The zirconium oxide is nano-sized zirconium oxide with a particle size of 20-30 nm.

4. The surface-brightening graphene film fertilizer according to claim 3, characterized in that, The nanoscale zirconia is modified nanoscale zirconia. The preparation steps of the modified nanoscale zirconia include: mixing γ-aminopropyltriethoxysilane and ethanol solution, heating and stirring until uniform, then adding nanoscale zirconia, dispersing, filtering and drying to obtain modified nanoscale zirconia.

5. The surface-brightening graphene film fertilizer according to claim 1, characterized in that, The weight ratio of the polybutylene adipate-polylactic acid copolymer resin and graphene is (800-1000):

1.

6. The surface-brightening graphene film fertilizer according to claim 1, characterized in that, The anti-yellowing agent is a hindered amine anti-yellowing agent, and the leveling agent is an acrylate leveling agent.

7. The surface-brightening graphene film fertilizer according to claim 1, characterized in that, The solvent is at least one of ethyl acetate and propylene glycol methyl ether.

8. A method for preparing a surface-brightening graphene film fertilizer according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix silane coupling agent, ethanol and water, spray the mixture onto the surface of fertilizer granules, and dry to obtain fertilizer base material. S2. Mix graphene and zirconium oxide, add solvent and polyether-modified polysiloxane, stir evenly, and ultrasonically disperse to obtain a pre-dispersion. S3. Mix polybutylene adipate-polylactic acid copolymer resin and solvent, heat and stir until completely dissolved, add hindered amine anti-yellowing agent and acrylate leveling agent, mix evenly to obtain polyester base material; S4. Add the pre-dispersed material to the polyester base material and stir evenly to obtain the bottom liquid; divide the bottom liquid into two parts, add pearlescent mica powder to one part of the bottom liquid and mix evenly to obtain the top liquid; S5. Spray the remaining bottom layer liquid onto the surface of the fertilizer substrate, dry it, then spray the top layer liquid and cure it to obtain the film fertilizer.

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