Siloxane-carbon powder dual-modified sugarcane-based coating material, preparation method and application thereof, coated controlled-release fertilizer and preparation method thereof

Abstract

The invention provides a siloxane-carbon powder dual-modified sugarcane-based coating material, a preparation method and application thereof, a coated controlled-release fertilizer and a preparation method thereof, and belongs to the field of fertilizer preparation. The preparation method comprises the following steps: mixing bagasse, an activator and acid, carrying out an activation reaction, mixing the obtained liquefied bagasse, siloxane modified carbon powder, an isocyanate compound and an organic metal catalyst, and carrying out a modification reaction to obtain the siloxane-carbon powder dual modified bagasse-based coating material. According to the invention, agricultural waste bagasse is used as a raw material to prepare a film coating material, the bagasse is activated, the activity of groups in the liquefied bagasse is increased through an activation mode, and the compatibility with a green curing agent and hydrophobic groups is increased; siloxane modified carbon powder is adopted for dual modification, so that the hydrophobic property of the coating material is improved; the coated fertilizer prepared from the obtained coating material can accurately regulate and control the nutrient release rate, the use efficiency of the fertilizer is improved, and high-value utilization of agricultural wastes is further realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer preparation, and in particular to a siloxane-carbon powder dual-modified sugarcane-based coating material, a preparation method and application thereof, and a coated controlled-release fertilizer and a preparation method thereof. Background Art

[0002] Slow- and controlled-release fertilizers, through specific regulatory mechanisms, can slow the rate of nutrient release to align it with crop growth needs, significantly extending the effective nutrient supply cycle. Among these, coated fertilizers have become one of the most promising research areas in this field, due to their outstanding performance in improving nutrient utilization efficiency and reducing environmental impact. These fertilizers, through their physical barrier properties, achieve precise control over nutrient release, providing an effective solution to the many challenges associated with traditional fertilization methods.

[0003] Coated fertilizers can be divided into three categories based on the properties of their coating materials: inorganic coatings, organic polymer coatings, and environmentally friendly types. Inorganic coated fertilizers, represented by sulfur-coated fertilizers, achieve a slow-release effect by forming a poorly soluble inorganic coating on the surface of fertilizer particles. These fertilizers are characterized by readily available raw materials, low production costs, and no harmful residues in the soil. Some also have antibacterial properties. However, the coating lacks flexibility and is prone to damage, resulting in excessive nutrient release and a lack of sustained supply of nutrients throughout the crop's growth cycle. Organic polymer-coated fertilizers use synthetic polymers as coating materials. While these materials can form a stable coating structure, their reliance on petrochemical raw materials is not only expensive but also poses resource constraints. Furthermore, most polymers are difficult to degrade in the natural environment, and long-term accumulation can cause soil pollution. Environmentally friendly coated fertilizers use biomass as the coating matrix. These offer significant advantages, including renewable raw materials, high cost-effectiveness, good environmental compatibility, and biodegradability. They meet coating process requirements without impacting the environment, presenting broad application prospects.

[0004] However, existing coated fertilizers have problems such as complex preparation process, high cost and difficulty in degradation in soil. Summary of the Invention

[0005] The purpose of the present invention is to provide a siloxane-carbon powder dual-modified sugarcane-based coating material, its preparation method and application, coated controlled-release fertilizer and its preparation method. The degradable coating material has a simple preparation process, low cost, good environmental compatibility and ideal controlled-release performance. It can be used as the coating layer of the controlled-release fertilizer, and can fully utilize the sugarcane bagasse, accurately control the nutrient release rate, and improve the fertilizer utilization efficiency.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a siloxane-carbon powder dual-modified sugarcane-based coating material, comprising the following steps:

[0008] mixing bagasse, an activating agent and an acid to perform an activation reaction to obtain liquefied bagasse;

[0009] The liquefied bagasse, siloxane-modified carbon powder, isocyanate compound and organometallic catalyst are mixed to carry out modification reaction to obtain a siloxane-carbon powder dual-modified bagasse-based coating material;

[0010] The preparation method of the siloxane-modified carbon powder comprises the following steps:

[0011] Carbon powder, anhydrous ethanol and methyltriethylsilane are mixed and silane-modified to obtain siloxane-modified carbon powder.

[0012] Preferably, the activator is a mixture of polyethylene glycol and low molecular weight polyol, and the mass ratio of the polyethylene glycol to the low molecular weight polyol is 8 to 10:1;

[0013] The polyethylene glycol includes one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 800; the low molecular weight polyol includes one or more of ethylene glycol, glycerol and 1,2-butanediol;

[0014] The mass ratio of the bagasse to the activator is 3 to 5:20;

[0015] The acid includes one or more of sulfuric acid, phosphoric acid and hydrochloric acid; the concentration of the acid is 16-18.4 mol / L; the mass ratio of the bagasse to the acid is 30-50:5-6.

[0016] Preferably, the activation reaction temperature is 140-170° C., and the time is 70-90 min.

[0017] Preferably, the ratio of the mass of the carbon powder to the volume of methyltriethylsilane is 5-15 g:5 mL; the temperature of the silane modification is 60-80° C., and the time is 2-4 h.

[0018] Preferably, the isocyanate compound includes one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and lysine diisocyanate;

[0019] The organometallic catalyst includes one or more of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, stannous oleate, zinc naphthenate, zinc isooctanoate, bismuth isooctanoate, zirconium nitrate, phenylmercuric propionate and phenylmercuric acetate;

[0020] The mass ratio of the isocyanate compound to the liquefied bagasse is 19 to 21:20;

[0021] The mass ratio of the siloxane-modified carbon powder to the liquefied sugarcane bagasse is 0.1 to 1:5, and the mass ratio of the organic metal catalyst to the liquefied sugarcane bagasse is 0.03 to 0.04:2.

[0022] Preferably, the modification reaction temperature is 65-75° C., and the time is 15-30 minutes.

[0023] The present invention provides a siloxane-carbon powder dual-modified sugarcane-based coating material prepared by the above preparation method.

[0024] The present invention provides application of the above-mentioned siloxane-carbon powder dual-modified sugarcane-based coating material in the field of fertilizer preparation.

[0025] The present invention provides a coated controlled-release fertilizer, comprising a coating material and a fertilizer in a mass ratio of 6.6 to 9.9:200;

[0026] The coating material is the aforementioned silicone-carbon powder dual-modified sugarcane-based coating material;

[0027] The fertilizer includes one or more of urea, sulfur-coated urea, ammonium carbonate, ammonium nitrate, ammonium sulfate, potassium chloride, potassium nitrate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0028] The present invention provides a method for preparing the above-mentioned coated controlled-release fertilizer, comprising the following steps:

[0029] Spraying the dispersion of the aforementioned siloxane-carbon powder dual-modified sugarcane-based coating material on the surface of the fertilizer, and drying to obtain a coated controlled-release fertilizer;

[0030] The mass ratio of the coated controlled-release fertilizer to the fertilizer is 107-110:100.

[0031] Beneficial effects of the present invention:

[0032] This invention uses sugarcane bagasse, an agricultural waste, as the primary raw material to produce a coating material. The bagasse is activated with an activator, increasing the activity of groups in the liquefied bagasse and enhancing its compatibility with green curing agents and hydrophobic groups. Furthermore, siloxane-modified carbon powder is used for dual modification. From a microstructural perspective, the introduction of siloxane-modified carbon powder primarily produces the following effects: increased surface microroughness; and the formation of a low-surface-energy hydrophobic interface on the fertilizer particle surface. The synergistic effect of these two factors creates a stable hydrophobic barrier, effectively enhancing the hydrophobic properties of the coating system. Furthermore, by adjusting the incorporation ratio of the siloxane-modified carbon powder, key parameters of the fertilizer coating system can be effectively controlled: the hydrophobic properties of the coating layer and its physical thickness. This dual regulation mechanism precisely regulates the nutrient release rate, achieving a slow nutrient release rate. This helps improve fertilizer efficiency and further maximize the value of agricultural waste, resulting in significant economic and ecological benefits.

[0033] The present invention's siloxane-carbon powder dual-modified bagasse-based coating material achieves intelligent regulation of nutrient release rate by controlling the amount of siloxane and carbon powder added. This combined sustained-release and accelerated-release technology precisely matches the nutritional needs of crops at different growth stages, significantly reducing production costs compared to traditional processes. The process is simple and efficient, environmentally friendly, and pollution-free during the coating formation stage, meeting overall clean production requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The infrared spectra of the coating materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown;

[0035] Figure 2 The water contact angle diagrams of the coating materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0036] Figure 3 The graphs show the nitrogen accumulation and release of the coated fertilizers obtained from the coating materials of Examples 1 to 3 and Comparative Examples 1 to 3 at different periods. DETAILED DESCRIPTION

[0037] The present invention provides a method for preparing a siloxane-carbon powder dual-modified sugarcane-based coating material, comprising the following steps:

[0038] mixing bagasse, an activating agent and an acid to perform an activation reaction to obtain liquefied bagasse;

[0039] The liquefied bagasse, siloxane-modified carbon powder, isocyanate compound and organometallic catalyst are mixed to carry out modification reaction to obtain a siloxane-carbon powder dual-modified bagasse-based coating material;

[0040] The preparation method of the siloxane-modified carbon powder comprises the following steps:

[0041] Carbon powder, anhydrous ethanol and methyltriethylsilane are mixed and silane-modified to obtain siloxane-modified carbon powder.

[0042] In the present invention, unless otherwise specified, the raw materials required for preparation are all commercially available products well known to those skilled in the art.

[0043] In the present invention, bagasse is preferably mixed with an activator and an activation reaction is carried out under acidic conditions to obtain liquefied bagasse.

[0044] In the present invention, the bagasse needs to be dried and crushed, and the particle size of the bagasse is preferably 0.074-0.15 mm, and more preferably 0.1-0.15 mm; the bagasse raw material supply is sufficient and easy to obtain, the production cost is low and has a significant competitive advantage, realizes resource recycling, effectively solves the problem of sugar industry waste treatment, significantly reduces the consumption of petrochemical resources, optimizes the production process, and effectively controls the overall cost; at the same time, it improves the comprehensive utilization efficiency of agricultural by-products, also has good environmentally friendly characteristics, and is in line with the concept of green agricultural development.

[0045] In the present invention, the activator is preferably a mixture of polyethylene glycol and a low molecular weight polyol, and the mass ratio of the polyethylene glycol to the low molecular weight polyol is preferably 8 to 10:1, and more preferably 9:1; the polyethylene glycol preferably includes one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 800, and more preferably polyethylene glycol 200; the low molecular weight polyol preferably includes one or more of ethylene glycol, glycerol and 1,2-butanediol, and more preferably glycerol.

[0046] In the present invention, the mass ratio of the bagasse to the activator is preferably 3 to 5:20, more preferably 4 to 5:20.

[0047] In the present invention, the acid preferably includes one or more of sulfuric acid, phosphoric acid and hydrochloric acid, more preferably sulfuric acid; the concentration of the acid is preferably 16 to 18.4 mol / L, more preferably 18.4 mol / L.

[0048] In the present invention, the mass ratio of bagasse to acid is preferably 30-50:5-6, more preferably 8:1.1.

[0049] In the present invention, the rotation speed when the bagasse and the activator are mixed is preferably 200 to 350 rpm, more preferably 350 rpm.

[0050] In the present invention, the activation reaction temperature is preferably 140-170° C., more preferably 160-170° C.; the activation reaction time is 70-90 min, more preferably 70 min.

[0051] The present invention preferably mixes the liquefied bagasse, siloxane-modified carbon powder, isocyanate compound and organometallic catalyst, and conducts a modification reaction under water bath heating conditions to obtain a siloxane-carbon powder dual-modified bagasse-based coating material.

[0052] In the present invention, the method for preparing the siloxane-modified carbon powder preferably comprises the following steps: mixing carbon powder, anhydrous ethanol and methyltriethylsilane, and performing silane modification to obtain the siloxane-modified carbon powder.

[0053] In the present invention, the ratio of the mass of the carbon powder to the volume of methyltriethylsilane is preferably 5-15 g:5 mL, more preferably 10 g:5 mL.

[0054] In the present invention, the temperature of the silane modification is preferably 60 to 80° C., more preferably 70° C., and the time is preferably 2 to 4 hours, more preferably 3 hours.

[0055] In the present invention, the isocyanate compound preferably includes one or more of toluene diisocyanate, isophorone diisocyanate (IPDI), hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and lysine diisocyanate, and isophorone diisocyanate (IPDI) is more preferred.

[0056] In the present invention, the organometallic catalyst preferably includes one or more of dibutyltin dilaurate (DY-12), stannous octoate, dibutyltin diacetate, stannous oleate, zinc naphthenate, zinc isooctanoate, bismuth isooctanoate, zirconium nitrate, phenylmercuric propionate and phenylmercuric acetate, and is more preferably dibutyltin dilaurate (DY-12).

[0057] In the present invention, the mass ratio of the isocyanate compound to the liquefied bagasse is preferably 19 to 21:20, more preferably 20.7:20.

[0058] In the present invention, the mass ratio of the siloxane-modified carbon powder to the liquefied bagasse is preferably 0.1 to 1:5, more preferably 0.1 to 0.15:5; the mass ratio of the organometallic catalyst to the liquefied bagasse is preferably 0.03 to 0.04:2, more preferably 0.032:2.

[0059] In the present invention, the rotation speed when the liquefied bagasse, siloxane-modified carbon powder, isocyanate compound and organometallic catalyst are mixed is preferably 300 to 500 rpm, more preferably 500 rpm.

[0060] In the present invention, the temperature of the modification reaction is preferably 65 to 75° C., more preferably 70 to 75° C., and the time is preferably 15 to 30 minutes, more preferably 20 to 30 minutes.

[0061] In the present invention, after the modification reaction is completed, the obtained siloxane-carbon powder dual-modified bagasse-based coating solution is preferably spread onto a template and naturally dried to a constant weight to obtain a siloxane-carbon powder dual-modified bagasse-based coating material.

[0062] The present invention provides a siloxane-carbon powder dual-modified sugarcane-based coating material prepared by the above preparation method.

[0063] The present invention provides application of the above-mentioned siloxane-carbon powder dual-modified sugarcane-based coating material in the field of fertilizer preparation.

[0064] The present invention provides a coated controlled-release fertilizer, comprising a coating material and a fertilizer in a mass ratio of 9:200;

[0065] The coating material is the aforementioned silicone-carbon powder dual-modified sugarcane-based coating material;

[0066] The fertilizer includes one or more of urea, sulfur-coated urea, ammonium carbonate, ammonium nitrate, ammonium sulfate, potassium chloride, potassium nitrate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0067] In the present invention, the average particle size of the fertilizer is preferably 2 to 5 mm, more preferably 3 to 5 mm.

[0068] The present invention provides a method for preparing the above-mentioned coated controlled-release fertilizer, comprising the following steps:

[0069] Spraying the dispersion of the aforementioned siloxane-carbon powder dual-modified sugarcane-based coating material on the surface of the fertilizer, and drying to obtain a coated controlled-release fertilizer;

[0070] The mass ratio of the coated controlled-release fertilizer to the fertilizer is 107-110:100.

[0071] In the present invention, the spraying is specifically as follows: adding the fertilizer to the coating machine, preheating the fertilizer, and then spraying the siloxane-carbon powder dual-modified bagasse-based coating solution in the drum coating machine 3 to 6 times, and the residence reaction time after each spraying is preferably 5 to 15 minutes.

[0072] In the present invention, the preheating temperature is preferably 70 to 80° C., more preferably 75 to 80° C.; the preheating time is preferably 10 to 20 minutes, more preferably 10 minutes.

[0073] The technical solutions provided by the present invention are 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.

[0074] The particle size of the bagasse used in Examples 1 to 3 and Comparative Examples 1 to 3 was 0.1 to 0.15 mm;

[0075] The concentration of concentrated sulfuric acid used in Examples 1 to 3 and Comparative Examples 1 to 3 was 18.4 mol / L;

[0076] The preparation method of the siloxane-modified carbon powder used in Examples 1 to 3 comprises the following steps: adding 10 g of carbon powder to 25 mL of anhydrous ethanol and ultrasonically dispersing for 20 minutes to obtain pretreated carbon powder; mixing 5 mL of methyltriethoxysilane with 50 mL of anhydrous ethanol, adding the pretreated carbon powder, performing silane modification at 70° C., magnetically stirring for 3 hours, stirring, ultrasonically dispersing again for 15 minutes, and drying to obtain siloxane-modified carbon powder.

[0077] Example 1

[0078] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heating device, and a condenser, and 30 g of bagasse was added. The mixture was heated to 140° C. and stirred at 350 rpm. 5 g of concentrated sulfuric acid was then added and mixed uniformly for activation reaction. The reaction was continued for 70 min to obtain liquefied bagasse.

[0079] At 500 rpm and 70°C in a water bath, 10.35 g IPDI, 0.06 g DY-12 and 0.2 g siloxane-modified carbon powder were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the resulting siloxane-carbon powder dual-modified bagasse-based coating solution was spread onto a template and naturally dried to constant weight to obtain a siloxane-carbon powder dual-modified bagasse-based coating material, which was recorded as SCPM2.

[0080] Example 2

[0081] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heater, and a condenser, 40 g of bagasse was added, and the mixture was heated to 150° C. with a stirring speed of 350 rpm. 5.5 g of concentrated sulfuric acid was added to the mixture, mixed well, and activated. The mixture was reacted for 70 min to obtain liquefied bagasse.

[0082] At 500 rpm and 70°C in a water bath, 10.35 g IPDI, 0.06 g DY-12, and 0.3 g siloxane-modified carbon powder were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the resulting siloxane-carbon powder dual-modified bagasse-based coating solution was spread onto a template and naturally dried to constant weight to obtain a siloxane-carbon powder dual-modified bagasse-based coating material, designated as SCPM3.

[0083] Example 3

[0084] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heater, and a condenser, 40 g of bagasse was added, and the mixture was heated to 160° C. with a stirring speed of 350 rpm. 5.5 g of concentrated sulfuric acid was added to the mixture, mixed well, and activated for 70 min to obtain liquefied bagasse.

[0085] At 500 rpm and 70°C in a water bath, 10.35 g IPDI, 0.06 g DY-12, and 0.4 g siloxane-modified carbon powder were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the resulting siloxane-carbon powder dual-modified bagasse-based coating solution was spread onto a template and naturally dried to constant weight to obtain a siloxane-carbon powder dual-modified bagasse-based coating material, designated as SCPM4.

[0086] Comparative Example 1

[0087] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heater, and a condenser, 50 g of bagasse was added, and the mixture was heated to 170° C. with a stirring speed of 350 rpm. 6 g of concentrated sulfuric acid was added to the mixture, mixed evenly, and activated for 80 min to obtain liquefied bagasse.

[0088] At 500 rpm and 70°C in a water bath, 10.35 g IPDI and 0.06 g DY-12 were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the resulting bagasse-based coating solution was spread onto a template and naturally dried to constant weight to obtain a bagasse-based coating material, which was recorded as CK.

[0089] Comparative Example 2

[0090] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heater, and a condenser, 50 g of bagasse was added, and the mixture was heated to 170° C. with a stirring speed of 350 rpm. 6 g of concentrated sulfuric acid was added to the mixture, mixed evenly, and activated for 80 min to obtain liquefied bagasse.

[0091] At 500 rpm and 70°C in a water bath, 10.35 g IPDI, 0.06 g DY-12 and 0.3 g carbon powder were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the carbon powder-modified bagasse-based coating solution was spread onto a template and naturally dried to a constant weight to obtain a carbon powder-modified bagasse-based coating material, which was recorded as CPM.

[0092] Comparative Example 3

[0093] 180 g of polyethylene glycol 200 and 20 g of glycerol were added to a reaction kettle equipped with a stirrer, a heater, and a condenser, 50 g of bagasse was added, and the mixture was heated to 170° C. with a stirring speed of 350 rpm. 6 g of concentrated sulfuric acid was added to the mixture, mixed evenly, and activated for 80 min to obtain liquefied bagasse.

[0094] At 500 rpm and 70°C in a water bath, 10.35 g IPDI, 0.06 g DY-12, and 2 g siloxane were added to 12 mL of liquefied bagasse (containing 10 g of liquefied bagasse) for a modification reaction. The reaction lasted for 20 min. 5 mL of the siloxane-modified bagasse-based coating solution was spread onto a template and naturally dried to constant weight to obtain a siloxane-modified bagasse-based coating material, which was recorded as SM.

[0095] Characterization and performance testing

[0096] 1. The bagasse-based coating materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were tested using infrared spectroscopy. The results are shown in Table 1. Figure 1 ;

[0097] Depend on Figure 1 It can be seen that the siloxane-modified carbon powder successfully introduced hydrophobic functional groups, including Si-O-Si bonds and Si-CH3 groups, and their content is positively correlated with the hydrophobic property. Compared with comparative examples 1 to 3, the siloxane-modified samples SCPM2, SCPM3, and SCPM4 have a higher hydrophobicity than the control samples 1 to 3 at 1000-1100 cm -1New characteristic absorption peaks appeared across the wavenumber range, while the intensity of existing peaks significantly increased. This phenomenon fully confirms that the siloxane treatment significantly altered the chemical structure of the carbon powder. Furthermore, the intensity of the characteristic peaks showed a regular increasing trend with increasing addition of modified carbon powder. This dose-response relationship indicates a direct correlation between modifier dosage and the density of functional groups on the material's surface.

[0098] 2. The water contact angles of the bagasse-based coated solid materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were measured using a contact angle meter. The bagasse-based coated solid materials were cut into appropriate sizes and fixed on a measuring platform. A droplet was placed on the surface of the material. After the droplet shape stabilized, a picture was taken to measure the contact angle. The results are shown in FIG. Figure 2 ;

[0099] Depend on Figure 2 It can be seen that the contact angle of the control group CK in Comparative Example 1 without adding carbon powder is 65.6°, while the contact angle of the sample CPM in Comparative Example 2 with 0.3g of ordinary carbon powder added is increased to 77.1°. This difference confirms that the introduction of carbon materials can indeed enhance the hydrophobic properties of the coating layer. Further analysis found that the sample SCPM2 in Example 1 with 0.2g of siloxane-modified carbon powder added exhibited even better hydrophobic properties, with a contact angle of 82.1°, significantly higher than that of the ordinary carbon powder sample, indicating that the carbon powder treated with siloxane has an advantage in improving the hydrophobicity of the coating. More importantly, as the amount of siloxane carbon powder added increases, the water contact angle first increases and then decreases, reaching the optimal hydrophobicity at 0.3g: the contact angle of the SCPM3 sample (109.3°) > SCPM4 (91.9°) > SCPM2 (82.3°).

[0100] 3. The coating materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are made into coated fertilizers, which specifically comprises the following steps:

[0101] Start the coating machine, set the temperature to 75°C and the speed to 380 rpm. After it remains stable, place 200 g of urea fertilizer with a diameter of 3 mm in the drum for preheating. After the temperature reaches a constant 75°C, maintain it for 10 minutes.

[0102] 6 mL of the bagasse-based coating solution (containing 3 g of bagasse-based coating material) prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively weighed and evenly added dropwise to the surface of urea in the drum, and reacted for 5 minutes;

[0103] Repeatedly add the bagasse-based coating solution for a total of 3 sprayings, and then cool to room temperature to obtain the bagasse-based coated fertilizer;

[0104] The controlled release performance of the obtained coated fertilizer was tested according to the national standard GBT23348-2009, and the nitrogen accumulation and release of the coated fertilizer obtained from the coating materials of Examples 1 to 3 and Comparative Examples 1 to 3 at different periods were measured. The results are shown in FIG. Figure 3 and Table 1;

[0105] Table 1 Initial nutrient release rate and nutrient controlled release period of coated fertilizers of Examples 1 to 3 and Comparative Examples 1 to 3

[0106] Serial number Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial nutrient release rate / % 3.86 0.96 2.17 12.66 3.05 1.59 Nutrient controlled release period / d 31 62 31 12 28 48

[0107] Depend on Figure 3 As shown in Table 1, the initial dissolution rate of the silicone-carbon powder dual-modified bagasse-based coated fertilizer prepared by the present invention is 3 to 13 times lower than that of the control example, and the controlled-release period is increased by 2.8 to 3.2 times. This is mainly attributed to the fact that the present invention increases the activity of the groups in the liquefied bagasse through activation, thereby increasing the compatibility with the green curing agent and the hydrophobic group. The nutrient control period of the silicone-carbon powder dual-modified bagasse-based coated fertilizer prepared by the present invention is 31 to 62 days. By adjusting the content of the modified carbon powder, silicone-carbon powder dual-modified bagasse-based coated fertilizer with a corresponding controlled-release period can be prepared to meet the nutrient needs of different crops, effectively improving fertilizer utilization efficiency.

[0108] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a siloxane-carbon powder dual-modified sugarcane-based coating material, characterized in that: The following steps are involved: mixing bagasse, an activating agent and an acid to perform an activation reaction to obtain liquefied bagasse; The liquefied bagasse, siloxane-modified carbon powder, isocyanate compound and organometallic catalyst are mixed to carry out modification reaction to obtain a siloxane-carbon powder dual-modified bagasse-based coating material; The preparation method of the siloxane-modified carbon powder comprises the following steps: Carbon powder, anhydrous ethanol and methyltriethylsilane are mixed and silane-modified to obtain siloxane-modified carbon powder.

2. The preparation method according to claim 1, characterized in that The activator is a mixture of polyethylene glycol and low molecular weight polyol, and the mass ratio of the polyethylene glycol to the low molecular weight polyol is 8 to 10:1; The polyethylene glycol includes one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 and polyethylene glycol 800; the low molecular weight polyol includes one or more of ethylene glycol, glycerol and 1,2-butanediol; The mass ratio of the bagasse to the activator is 3 to 5:20; The acid includes one or more of sulfuric acid, phosphoric acid and hydrochloric acid; the concentration of the acid is 16-18.4 mol / L; the mass ratio of the bagasse to the acid is 30-50:5-6.

3. The preparation method according to claim 2, characterized in that The activation reaction temperature is 140-170° C., and the activation reaction time is 70-90 minutes.

4. The preparation method according to claim 1, characterized in that The ratio of the mass of the carbon powder to the volume of methyltriethylsilane is 5-15 g:5 mL; the temperature of the silane modification is 60-80° C., and the time is 2-4 hours.

5. The preparation method according to claim 1, characterized in that The isocyanate compound includes one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate and lysine diisocyanate; The organometallic catalyst includes one or more of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, stannous oleate, zinc naphthenate, zinc isooctanoate, bismuth isooctanoate, zirconium nitrate, phenylmercuric propionate and phenylmercuric acetate; The mass ratio of the isocyanate compound to the liquefied bagasse is 19 to 21:20; The mass ratio of the siloxane-modified carbon powder to the liquefied sugarcane bagasse is 0.1 to 1:5, and the mass ratio of the organic metal catalyst to the liquefied sugarcane bagasse is 0.03 to 0.04:

2.

6. The preparation method according to claim 5, characterized in that The modification reaction temperature is 65-75° C. and the reaction time is 15-30 minutes.

7. A sugarcane-based coating material dually modified with silicone and carbon powder prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the siloxane-carbon powder dual-modified sugarcane-based coating material according to claim 7 in the field of fertilizer preparation.

9. A coated controlled-release fertilizer, characterized in that: including coating material and fertilizer in a mass ratio of 6.6 to 9.9:200; The coating material is the silicone-carbon powder dual-modified sugarcane-based coating material according to claim 7; The fertilizer includes one or more of urea, sulfur-coated urea, ammonium carbonate, ammonium nitrate, ammonium sulfate, potassium chloride, potassium nitrate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

10. The method for preparing the coated controlled-release fertilizer according to claim 9, characterized in that: The following steps are involved: Spraying the dispersion of the siloxane-carbon powder dual-modified sugarcane-based coating material according to claim 7 on the surface of the fertilizer, and drying to obtain a coated controlled-release fertilizer; The mass ratio of the coated controlled-release fertilizer to the fertilizer is 107-110:100.

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