Preparation method and application of a thermosensitive bio-based controlled-release compound fertilizer

Abstract

The present invention discloses a preparation method and application of a temperature-sensitive bio-based controlled-release compound fertilizer. The present invention uses castor oil and lignin, which are widely available and renewable resources, as main raw materials, and prepares modified lignin polyol and modified castor oil polyol through modification technology. The coating material prepared using these two polyols can improve the hydrophobicity of the coating while improving thermal stability. After adjusting the ratio of polyol to isocyanate, the prepared polyurethane has a higher degree of cross-linking, which can reduce the micropores on the surface of the membrane shell and increase the mechanical strength. The bio-based controlled-release compound fertilizer prepared using this material can effectively reduce the impact of temperature changes on the release period, improve the consistency of fertilizer nutrient release and crop fertilizer requirements, and at the same time, the controlled-release period can still reach 3 to 5 months, which can meet the nutrient needs of most crops.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer preparation, and in particular to a preparation method and application of a temperature-sensitive bio-based controlled-release compound fertilizer. Background Art

[0002] It is estimated that once applied to agricultural soil, up to 50% of traditional fertilizers will be lost (i.e. due to leaching and / or evaporation), or remain in the soil matrix due to low crop nutrient utilization rate. Controlled-release fertilizers can overcome these two problems. Controlled-release fertilizers have the advantages of being able to provide nutrients for a long time, one-time fertilization, no need for topdressing, and improving fertilizer utilization rate. However, in general commercial controlled-release fertilizers, nutrients will be released faster in an environment with high ground temperature, and the expected nutrient controlled-release period will not be achieved. The growth of flowers is very sensitive to nutrient supply. For example, in the early stage of growth, excessive nutrient supply will inhibit its growth and development, and more seriously, it will cause root burning and seedling burning. In the vigorous growth period, insufficient nutrient supply will cause it to lose fertilizer and grow slowly. At present, the ground temperature is high when flowers are cultivated in some areas, which is a challenge to the application of controlled-release fertilizers in flowers with longer growth cycles. On the other hand, most controlled-release fertilizer coating materials are often derived from petrochemical polymers. Since such materials are expensive and resources are non-renewable, their large-scale promotion and application in agriculture are limited.

[0003] At present, renewable bio-based synthetic polymer coated controlled-release fertilizers have shown broad application prospects in replacing petrochemical polymer coated controlled-release fertilizers. Several recognized environmentally friendly bio-based materials, including starch, cellulose and its derivatives, lignin, alginate, chitosan, biochar, etc., have been widely used in the production of coated controlled-release fertilizers. However, most of these materials have hydrophilic components, and the release period of coated controlled-release fertilizers directly prepared with them is difficult to reach more than 60 days, which cannot meet the long-term demand of flowers for fertilizers; on the other hand, when the soil temperature is around 30°C, the micropores on the outer shell of the coating of such materials will absorb water, which will further accelerate the release of fertilizers, resulting in a mismatch between nutrient release and plant absorption. Therefore, it is urgent to develop environmentally friendly bio-based coated controlled-release fertilizers with scientific controlled release and high temperature resistance. Summary of the invention

[0004] In order to overcome the above-mentioned defects and deficiencies in the prior art, the present invention provides a preparation method and application of a temperature-sensitive bio-based controlled-release compound fertilizer.

[0005] The first object of the present invention is to provide a method for preparing a coating material for bio-based controlled-release compound fertilizer.

[0006] The second object of the present invention is to provide a coating material prepared by the above-mentioned preparation method.

[0007] The third object of the present invention is to provide a method for preparing a bio-based controlled-release compound fertilizer.

[0008] The fourth object of the present invention is to provide a bio-based controlled-release compound fertilizer prepared by the above-mentioned preparation method.

[0009] Therefore, the present invention claims the following:

[0010] A method for preparing a coating material for a bio-based controlled-release compound fertilizer, characterized in that it comprises the following steps:

[0011] S11. Castor oil, methanol and NaOH are thoroughly mixed, and after sufficient reaction, the pH is adjusted to 6.5 to 7.5, and the liquid is separated by solid-liquid separation, and the modified castor oil polyol is obtained after vacuum drying;

[0012] S12. The concentrated sulfuric acid, lignin and water are thoroughly mixed and reacted to obtain lignin polyol;

[0013] S13. The concentrated sulfuric acid, the lignin polyol and phenol described in step S12 are thoroughly mixed, and after sufficient reaction, acetone is added to dissolve the product, and the modified lignin polyol is obtained after purification and vacuum drying;

[0014] S14. The modified castor oil polyol of step S11 and the modified lignin polyol of step S13 are mixed thoroughly to obtain a bio-based mixed polyol after sufficient reaction;

[0015] S15. The bio-based mixed polyol, the blocking agent and the catalyst described in step S14 are fully mixed and reacted to obtain the coating material.

[0016] Preferably, in step S11, the usage ratio of castor oil, methanol and NaOH is (173-177) g: (48-52) g: 1 g.

[0017] More preferably, the usage ratio of castor oil, methanol and NaOH is 175g:50g:1g.

[0018] Preferably, in step S12, the usage ratio of the concentrated sulfuric acid, lignin and water is 1 g: (14-18) g: (1.4-1.8) mL.

[0019] More preferably, the usage ratio of concentrated sulfuric acid to lignin is 1 g:16 g:1.6 mL.

[0020] Preferably, in step S12, the lignin is guaiacyl lignin.

[0021] Preferably, in step S13, the usage ratio of the concentrated sulfuric acid, lignin polyol, phenol and acetone is 1 g: (3.8-4.2) g: (4.8-5.2) g: (58-62) g.

[0022] More preferably, the usage ratio of concentrated sulfuric acid, lignin polyol, phenol and acetone is 1g:4g:5g:60g.

[0023] Preferably, in step S14, the usage ratio of the modified castor oil polyol to the modified lignin polyol is (6-7) g:(3-4) g.

[0024] More preferably, the usage ratio of the modified castor oil polyol to the modified lignin polyol is 7g:3g.

[0025] Preferably, in step S15, the usage ratio of the bio-based mixed polyol, the blocking agent and the catalyst is 1000 g: (0.5-20) g: (0.1-0.5) g.

[0026] More preferably, the usage ratio of the bio-based mixed polyol, the blocking agent and the catalyst is 1000g:20g:0.1g.

[0027] Preferably, the sealing agent is microcrystalline wax.

[0028] Preferably, the catalyst is one or a mixture of titanate, trifluoromethanesulfonic acid, dibutyltin dilaurate, cupric sulfate, ferrous sulfate, zinc acetate, ferrous sulfate, ferric chloride, stannous acid, zinc chloride, tetraethyl titanate, tin oxide, zinc oxide p-toluenesulfonic acid.

[0029] The coating material prepared by any of the above preparation methods.

[0030] A method for preparing a bio-based controlled-release compound fertilizer comprises preheating the compound fertilizer, then spraying the coating material uniformly on the surface of the compound fertilizer particles, and then spraying a curing agent uniformly on the surface of the compound fertilizer particles.

[0031] Preferably, the amount of the coating material and the curing agent is (1.4-1.8) g: 1 g.

[0032] More preferably, the amount of the coating material and the curing agent is 1.6g:1g.

[0033] Preferably, the curing agent is one or a mixture of polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.

[0034] More preferably, the preheating temperature of the compound fertilizer is 60-65°C.

[0035] More preferably, the preparation method is specifically as follows: after preheating the compound fertilizer to 60-65°C, transferring it to a drum coating machine, and then spraying the above-mentioned coating material evenly on the surface of the rolling compound fertilizer particles, and then spraying the curing agent evenly on the fertilizer surface in the same way. During the entire coating process, the surface temperature of the compound fertilizer particles is maintained at 60-65°C, and after waiting for the coating material and the curing agent to solidify on the fertilizer surface, a uniform polyurethane film material can be formed.

[0036] Preferably, the nutrient ratio of the compound fertilizer is 15-15-15.

[0037] Preferably, the particle diameter of the compound fertilizer is 2 to 4 mm.

[0038] Preferably, the weight percentage of the coating material and the curing agent in the compound fertilizer is 3-4%.

[0039] More preferably, the weight percentage of the coating material and the curing agent in the compound fertilizer is 3.3%.

[0040] A bio-based controlled-release compound fertilizer prepared by any of the above preparation methods.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention discloses a preparation method and application of a temperature-sensitive bio-based controlled-release compound fertilizer. The present invention uses castor oil and lignin, which are widely available and renewable resources, as main raw materials to prepare bio-based polyurethane film materials. Castor oil contains three hydroxyl groups and can easily react with isocyanate to generate biodegradable polyurethane, but the polyurethane material prepared from castor oil has a linear flexible long-chain structure, and its mechanical strength and thermal stability are low, which is difficult to meet the requirements of practical applications. Castor oil has carbon-carbon double bonds, carbon-oxygen double bonds and hydroxyl groups, and can be modified by ester exchange, epoxidation, dehydration, pyrolysis, hydrogenation, ozonolysis, sulfonation and hydrolysis. The modified castor oil can significantly improve water resistance, mechanical strength and thermal stability after forming a prepolymer with other bio-based polyols. The addition of castor oil can also alleviate the shortcomings of uneven molecular weight distribution and poor biocompatibility of other polyols, forming a good complementary effect. Lignin contains hydrophobic benzene ring groups in its structure. Phenolization can increase the hydrophobic groups while improving the antioxidant capacity and the reaction activity of lignin, which can effectively reduce the water absorption capacity of the coating material and shorten the reaction time.

[0043] The present invention prepares modified lignin polyol and modified castor oil polyol by modification technology. The coating material prepared by using these two polyols can improve the hydrophobicity of the coating while improving the thermal stability. After adjusting the ratio of polyol to isocyanate, the prepared polyurethane has a higher degree of crosslinking, which can reduce the micropores on the surface of the membrane shell and increase the mechanical strength. The bio-based controlled-release compound fertilizer prepared by using this material can effectively reduce the impact of temperature changes on the release period, improve the consistency of fertilizer nutrient release and crop fertilizer requirements, and at the same time, the controlled-release period can still reach 3 to 5 months, which can meet the nutrient needs of most crops. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the reaction formula for modification of castor oil.

[0045] Figure 2 This is the reaction formula for lignin modification.

[0046] Figure 3 Schematic diagram of polyurethane synthesis.

[0047] Figure 4 This is the SEM section of the membrane shell of the controlled-release compound fertilizer of Example 2. DETAILED DESCRIPTION

[0048] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0049] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0050] The castor oil used in the examples and comparative examples is castor oil polyol.

[0051] Example 1 Preparation of a temperature-sensitive bio-based controlled-release compound fertilizer

[0052] 1. Preparation of coating material A

[0053] (1) Modified castor oil polyol: 70 g of castor oil, 20 g of methanol and 0.4 g of NaOH were added to a flask, stirred at 70° C. for 2 h using a magnetic stirrer, and the pH was adjusted to 7.0±0.5 using dilute sulfuric acid. The impurities at the bottom were removed by standing and stratification, and the modified castor oil polyol ( Figure 1 ).

[0054] (2) Modified lignin polyol: First, 5 g of concentrated sulfuric acid, 80 g of lignin powder and 8 mL of deionized water were added to a 500 mL three-necked round-bottom flask, and the mixture was stirred continuously at 800 r / min to remove impurities and ash in the lignin. The mixture was dried under vacuum to obtain a lignin polyol. Then, 5 g of concentrated sulfuric acid, 20 g of lignin polyol and 25 g of phenol were added to a 500 mL three-necked round-bottom flask, stirred at 100 °C for 1 h using a magnetic stirrer, 300 g of acetone was added to dissolve the mixture, and the mixture was washed with deionized water until neutral. Finally, the mixture was dried under vacuum to obtain a modified lignin polyol ( Figure 2 ).

[0055] (3) The modified castor oil polyol and the modified lignin polyol were added into a round-bottom flask in a mass ratio of 6:4, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0056] (4) The bio-based mixed polyol, the sealing agent microcrystalline paraffin and the catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65°C for 1 hour using a magnetic stirrer to prepare a coating material A.

[0057] 2. Preparation of controlled-release compound fertilizer

[0058] Preheat the compound fertilizer to 65℃ in an oven and transfer it to the coating machine. Use a spraying device to evenly spray the coating material A on the surface of the compound fertilizer particles. This process lasts for two minutes. Then, spray the coating material B, diphenylmethane diisocyanate, on the fertilizer surface in the same way. During the entire coating process, the surface temperature of the fertilizer particles is maintained at 60℃~65℃. After the coating material solidifies on the fertilizer surface, a uniform polyurethane film material ( Figure 3 ). Coating material A and coating material B are added at a mass ratio of 1.6:1, and the amount of coating material added each time accounts for 1.1% of the mass of the compound fertilizer. The coating process is repeated 3 times to prepare a controlled-release compound fertilizer with a coating amount of 3.3%.

[0059] Example 2 Preparation of a temperature-sensitive bio-based controlled-release compound fertilizer

[0060] The preparation was carried out according to Example 1, except that, in the preparation of the coating material A, the modified castor oil polyol and the modified lignin polyol were added into a round-bottom flask at a mass ratio of 7:3 and mixed for use.

[0061] Example 3 Preparation of a temperature-sensitive bio-based controlled-release compound fertilizer

[0062] The preparation was carried out according to Example 1, except that, in the preparation process of coating material A, modified castor oil polyol and modified lignin polyol were added to a round-bottom flask at a mass ratio of 7:3 and mixed for use; in the preparation process of controlled-release compound fertilizer, coating material A and coating material B were added at a mass ratio of 1.4:1.

[0063] Example 4 Preparation of a temperature-sensitive bio-based controlled-release compound fertilizer

[0064] The preparation was carried out according to Example 1, except that, in the preparation process of coating material A, modified castor oil polyol and modified lignin polyol were added to a round-bottom flask at a mass ratio of 7:3 and mixed for use; in the preparation process of controlled-release compound fertilizer, coating material A and coating material B were added at a mass ratio of 1.8:1.

[0065] Comparative Example 1

[0066] 1. Preparation of coating material A

[0067] (1) Modified castor oil polyol: 70 g of castor oil, 20 g of methanol and 0.4 g of NaOH were added into a flask, and reacted at 70° C. for 2 h using a magnetic stirrer. The pH was adjusted to 7.0±0.5 using dilute sulfuric acid, and the impurities at the bottom were removed by standing for stratification. The modified castor oil polyol was obtained after vacuum drying.

[0068] (2) Modified castor oil polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0069] 2. Preparation of controlled-release compound fertilizer

[0070] The preparation was carried out according to the method of step 2 in Example 1.

[0071] Comparative Example 2

[0072] 1. Preparation of coating material A

[0073] (1) Modified castor oil polyol: 70 g of castor oil, 20 g of methanol and 0.4 g of NaOH were added into a flask, and reacted at 70° C. for 2 h using a magnetic stirrer. The pH was adjusted to 7.0±0.5 using dilute sulfuric acid, and the impurities at the bottom were removed by standing for stratification. The modified castor oil polyol was obtained after vacuum drying.

[0074] (2) Lignin polyol: 5 g of concentrated sulfuric acid, 80 g of lignin powder and 8 mL of deionized water were added to a 500 mL three-necked round-bottom flask and stirred continuously at 800 r / min to remove impurities and ash in the lignin. After vacuum drying, lignin polyol was prepared.

[0075] (3) Modified castor oil polyol and lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0076] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0077] 2. Preparation of controlled-release compound fertilizer

[0078] The preparation was carried out according to the method of step 2 in Example 1.

[0079] Comparative Example 3

[0080] 1. Preparation of coating material A

[0081] (1) Castor oil polyol: Commercially available castor oil (product number: C110663, brand: Aladdin reagent) was vacuum dried before use.

[0082] (2) Modified lignin polyol: The preparation method is the same as that of "(2) Modified lignin polyol" in Example 1.

[0083] (3) Castor oil polyol and modified lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0084] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0085] 2. Preparation of controlled-release compound fertilizer

[0086] The preparation was carried out according to the method of step 2 in Example 1.

[0087] Comparative Example 4

[0088] 1. Preparation of coating material A

[0089] (1) Castor oil polyol: Commercially available castor oil was vacuum dried and used.

[0090] (2) Lignin polyol: 5 g of concentrated sulfuric acid, 80 g of lignin powder and 8 mL of deionized water were added to a 500 mL three-necked round-bottom flask and stirred continuously at 800 r / min to remove impurities and ash in the lignin. After vacuum drying, lignin polyol was prepared.

[0091] (3) Castor oil polyol and lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 min using a magnetic stirrer to obtain a bio-based mixed polyol.

[0092] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0093] 2. Preparation of controlled-release compound fertilizer

[0094] The preparation was carried out according to the method of step 2 in Example 1.

[0095] Comparative Example 5

[0096] 1. Preparation of coating material A

[0097] (1) Modified soybean oil polyol: 70 g soybean oil, 20 g methanol and 0.4 g NaOH were added to a flask, and reacted at 70° C. for 2 h using a magnetic stirrer. The pH was adjusted to 7.0±0.5 using dilute sulfuric acid, and the impurities at the bottom were removed by standing and stratification. The modified soybean oil polyol was obtained after vacuum drying.

[0098] (2) Modified lignin polyol: The preparation method is the same as that of "(2) Modified lignin polyol" in Example 1.

[0099] (3) The modified soybean oil polyol and the modified lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0100] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0101] 2. Preparation of controlled-release compound fertilizer

[0102] The preparation was carried out according to the method of step 2 in Example 1.

[0103] Comparative Example 6

[0104] 1. Preparation of coating material A

[0105] (1) Modified castor oil polyol: commercially available hydrogenated castor oil-based polyol (article number: H196306, brand: Aladdin Reagent) was selected.

[0106] (2) Modified lignin polyol: The preparation method is the same as that in Example 1.

[0107] (3) Modified castor oil polyol and lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0108] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0109] 2. Preparation of controlled-release compound fertilizer

[0110] The preparation was carried out according to the method of step 2 in Example 1.

[0111] Comparative Example 7

[0112] 1. Preparation of coating material A

[0113] (1) Modified castor oil polyol: The preparation method is the same as that in Example 1.

[0114] (2) Modified lignin polyol: 5 g of concentrated sulfuric acid, 80 g of lignin powder and 8 mL of deionized water were added to a 500 mL three-necked round-bottom flask, stirred continuously at 800 r / min to remove impurities and ash in the lignin, and vacuum dried to obtain lignin polyol. Then 5 g of concentrated sulfuric acid, 20 g of lignin polyol and 25 g of propylene oxide were added to a 500 mL three-necked round-bottom flask, stirred at 100 ° C for 1 h using a magnetic stirrer, 300 g of acetone was added to dissolve, washed with deionized water until neutral, and finally vacuum dried to obtain modified lignin polyol.

[0115] (3) Modified castor oil polyol and lignin polyol were added into a round-bottom flask in a mass ratio of 7:3, and stirred at room temperature for 30 minutes using a magnetic stirrer to obtain a bio-based mixed polyol.

[0116] (4) Bio-based mixed polyol, sealing agent microcrystalline paraffin and catalyst dibutyltin dilaurate were added into a round-bottom flask in a mass ratio of 1000:20:0.1, and stirred at 65° C. for 1 h using a magnetic stirrer to prepare coating material A.

[0117] 2. Preparation of controlled-release compound fertilizer

[0118] The preparation was carried out according to the method of step 2 in Example 1.

[0119] Comparative Example 8

[0120] Commercially available 100-day 14-14-14 coated compound fertilizer A was used.

[0121] Comparative Example 9

[0122] Commercially available 100-day 14-14-14 coated compound fertilizer B was used.

[0123] Example 5 Nutrient release of controlled-release compound fertilizer under different temperature conditions

[0124] 1. Experimental Methods

[0125] 10g of the controlled-release compound fertilizer prepared in Examples 1 to 4 and Comparative Examples 1 to 9 were respectively put into 250mL plastic bottles, 200mL of deionized water was added after numbering, and the bottles were placed in different constant temperature incubators (20°C, 25°C, 30°C, and 35°C) for culture and extraction. Samples were taken after 1, 3, 5, 7, 14, 21, and 28 days of culture and every 7 days, and the controlled-release period was when the nitrogen release reached 80%.

[0126] 2. Experimental Results

[0127] The nutrient release of the controlled-release compound fertilizer under different temperature conditions is shown in Tables 1 to 4. Comparing the nutrient release of the controlled-release compound fertilizer prepared in the examples, it can be seen that the optimal mixing ratio of modified castor oil polyol and modified lignin polyol is 7:3, and the optimal mixing ratio of coating material A and coating material B is 1.6:1.

[0128] In general, under different culture temperatures, the controlled-release compound fertilizer prepared in Example 2 has the longest controlled-release period; and as the culture temperature increases, the controlled-release period of the controlled-release compound fertilizer in the example is much lower than that of the controlled-release compound fertilizer in the comparative example. By adding phenol-modified lignin to castor oil polyol, the thermal stability and water resistance of polyurethane can be effectively improved, and the prepared controlled-release compound fertilizer can effectively resist the unstable nutrient release caused by changes in ambient temperature.

[0129] Table 1 Nutrient release rate and controlled release period of different controlled-release compound fertilizers in 20℃ pure water culture

[0130]

[0131]

[0132] Table 2 Nutrient release rate and controlled release period of different controlled-release compound fertilizers in 25℃ pure water culture

[0133]

[0134] Table 3 Nutrient release rate and controlled release period of different controlled-release compound fertilizers in 30℃ pure water culture

[0135]

[0136]

[0137] Table 4 Nutrient release rate and controlled release period of different controlled-release compound fertilizers in 35℃ pure water culture

[0138]

[0139] Example 6 Application of different controlled-release compound fertilizers in flower planting

[0140] 1. Experimental Methods

[0141] The experiment was conducted in potted plants at Guangdong Weisheng Liansu Technology Co., Ltd. from June to September 2023. The test area has a subtropical monsoon climate, with rain and heat in the same season. The average daytime temperature during the test period was 33°C, and the maximum daytime temperature could reach 39°C. The test flowers were fragrant sparrows, planted in 140# flower pots, and usually bloomed 3 to 4 months after planting. Therefore, they were selected to verify the effects of controlled-release compound fertilizers with a controlled-release period of 3 to 4 months on crop growth. There were 8 treatments in the experiment (see Table 5), 5 replicates for each treatment, 5 grams of fertilizer per pot, and the aboveground fresh weight, plant height and crown width of the flowers were measured at harvest.

[0142] 2. Experimental Results

[0143] It can be seen from Table 5 that when the flower growth temperature is higher than 30°C, the nutrients of the ordinary 3-4 month controlled-release compound fertilizer begin to be released rapidly in the early and middle stages of flower growth, which cannot meet the nutrient supply of flowers in the middle and late stages, resulting in fertilizer deficiency in the late stages. The fresh weight of the aboveground biomass, plant height and crown width of the control group test flowers at harvest are significantly lower than those in Example 2.

[0144] Table 5 Effects of different controlled-release compound fertilizers on flower growth

[0145]

[0146] Note: The same lowercase letters after the values ​​in the table mean that there is no significant difference among the treatments, and different lowercase letters mean that there is a significant difference among the treatments.

[0147] Example 7 SEM Characterization of Controlled Release Compound Fertilizer

[0148] 1. Experimental Methods

[0149] The controlled-release compound fertilizer prepared in Example 2 was characterized by SEM.

[0150] 2. Experimental Results

[0151] From the SEM image, it can be seen that the film shell section of the controlled-release compound fertilizer prepared in Example 2 has no notch cracks, no obvious pores, and the film shell composition is uniform and the thickness is uniform, which can more effectively prevent moisture from entering the film and extend the nutrient controlled-release period of the coated controlled-release compound fertilizer. The polyurethane film becomes smoother with the addition of modified lignin polyol, and the controlled-release compound fertilizer prepared by blending modified lignin and modified castor oil can have a longer controlled-release period.

[0152] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a coating material for a bio-based controlled-release compound fertilizer, characterized in that: The following steps are involved: S11. Castor oil, methanol and NaOH are mixed thoroughly, and after sufficient reaction, the pH is adjusted to 6.5 to 7.5, and the liquid is separated from the solid and vacuum dried to obtain a modified castor oil polyol; The ratio of castor oil, methanol and NaOH is (173-177) g: (48-52) g: 1 g; S12. The concentrated sulfuric acid, lignin and water are thoroughly mixed and reacted to obtain lignin polyol; The ratio of the concentrated sulfuric acid, lignin and water is 1 g: (14-18) g: (1.4-1.8) mL; S13. The concentrated sulfuric acid, the lignin polyol and phenol in step S12 are thoroughly mixed, and after sufficient reaction, acetone is added to dissolve the product, and the modified lignin polyol is obtained after purification and vacuum drying; The usage ratio of the concentrated sulfuric acid, lignin polyol, phenol and acetone is 1 g: (3.8-4.2) g: (4.8-5.2) g: (58-62) g; S14. The modified castor oil polyol of step S11 and the modified lignin polyol of step S13 are mixed thoroughly to obtain a bio-based mixed polyol after sufficient reaction; The usage ratio of the modified castor oil polyol and the modified lignin polyol is (6-7) g: (3-4) g; S15. The bio-based mixed polyol, the blocking agent and the catalyst described in step S14 are fully mixed and reacted to obtain a coating material; The usage ratio of the bio-based mixed polyol, the blocking agent and the catalyst is 1000 g: (0.5-20) g: (0.1-0.5) g.

2. The coating material prepared by the preparation method according to claim 1.

3. A method for preparing a bio-based controlled-release compound fertilizer, characterized in that: Preheating the compound fertilizer, then spraying the coating material according to claim 2 evenly on the surface of the compound fertilizer particles, and then spraying the curing agent evenly on the surface of the compound fertilizer particles; The dosage of the coating material and the curing agent is (1.4-1.8) g: 1 g.

4. The bio-based controlled-release compound fertilizer prepared by the preparation method according to claim 3.

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