A nanocellulose-based degradable planting substrate and a method for preparing the same

Abstract

The application relates to the field of planting materials, in particular to a degradable planting substrate based on nanocellulose and a preparation method thereof, which is prepared from the following raw materials in parts by weight: base particles 80-100 parts, hyperbranched nanocellulose 3-6 parts, sodium alginate 3-6 parts, a crosslinking agent 0.1-0.5 parts, amino montmorillonite 1-3 parts and water 10-20 parts. The prepared planting substrate has higher falling strength, can degrade and slowly release nutrient elements, promotes the growth of flowers, the raw materials are easy to obtain, are environment-friendly and non-toxic, can effectively utilize agricultural and livestock waste, and has good practical value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of planting materials, specifically to a biodegradable planting substrate based on nanocellulose and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the improvement of people's living standards, the demand for greening and ecological environment is increasing. As an important agricultural production method, floriculture not only meets people's aesthetic needs but also improves air quality and the ecological environment. However, traditional floriculture substrates have many problems, such as soil compaction, single nutrient content, and poor water retention, which seriously restrict the growth and development of flowers.

[0003] Currently, the main methods for planting flowers and applying fertilizers are traditional, such as spreading solid granular fertilizers on the substrate surface. This method suffers from low fertilizer utilization and significant nutrient loss, easily leading to nutrient waste and even seedling burn. Furthermore, commonly used soil substrates often fail to meet the high aeration and drainage requirements of flowers, negatively impacting their growth. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a biodegradable planting substrate based on nanocellulose and its preparation method.

[0005] The technical solution adopted is as follows:

[0006] A biodegradable planting substrate based on nanocellulose is made from the following raw materials in parts by weight:

[0007] The matrix consists of 80-100 parts of matrix particles, 3-6 parts of hyperbranched nanocellulose, 3-6 parts of sodium alginate, 0.1-0.5 parts of crosslinking agent, 1-3 parts of aminated montmorillonite, and 10-20 parts of water.

[0008] The hyperbranched nanocellulose is synthesized from polyol, methyl 3-butenoate and double-bonded nanocellulose.

[0009] The matrix particles are composed of decomposed straw, decomposed manure, decomposed peat moss and perlite;

[0010] The mass ratio of the decomposed straw, decomposed manure, decomposed peat moss and perlite is 1-10:1-10:1-10:1-10.

[0011] Furthermore, the polyol is trimethylolpropane, glycerol, or pentaerythritol.

[0012] Furthermore, the preparation method of the hyperbranched nanocellulose is as follows:

[0013] The intermediate is obtained by transesterification of polyol with methyl 3-butenoate, and then grafted onto double-bonded nanocellulose.

[0014] Furthermore, the preparation method of the hyperbranched nanocellulose is as follows:

[0015] Polyol, methyl 3-butenoate, and p-toluenesulfonic acid are mixed and stirred and heated to 80-100℃ for 1-10 hours. The reaction product is washed with saturated sodium bicarbonate solution and dried to obtain a hyperbranched intermediate. The hyperbranched intermediate is mixed with a free radical initiator and heated to 60-100℃. Double-bonded nanocellulose is dissolved in DMSO and added to the mixture for reaction. After the reaction is completed, water is added and the product is finally filtered out.

[0016] Furthermore, the preparation method of the double-bonded nanocellulose is as follows:

[0017] Acrylic acid was dissolved in dichloromethane, and then N'N-carbonyldiimidazole was added. After stirring and reacting, nanocellulose was added and the reaction continued. After the reaction was completed, the product was dialyzed and then freeze-dried at low temperature.

[0018] Furthermore, the molar ratio of the polyol to methyl 3-butenoate is 1:2-4.

[0019] Furthermore, the mass ratio of the intermediate to the double-bonded nanocellulose is 1-10:1-10.

[0020] Furthermore, the crosslinking agent is composed of calcium chloride and citric acid;

[0021] The mass ratio of calcium chloride to citric acid is 1-5:1-5.

[0022] Furthermore, the preparation method of the aminated montmorillonite is as follows:

[0023] Sodium montmorillonite was added to water and stirred to disperse it. Then, amino acid hydrochloride was added and the mixture was heated to reflux for 1-10 hours. After the reaction was completed, the mixture was cooled, the precipitate was collected, washed, and dried.

[0024] Furthermore, the preparation method of the matrix particles is as follows:

[0025] Wheat straw, dried chicken manure, and peat moss are mixed evenly in a mass ratio of 1:1:1 to obtain fermentation raw materials. EM bacteria, cellulase, and xylanase are added to the fermentation raw materials, and fermentation is carried out in a fermentation tank to obtain fermentation products. The fermentation products are mixed evenly with perlite and ammonia, and then pressed into pellets by a pellet mill.

[0026] This invention also provides a method for preparing a biodegradable planting substrate:

[0027] Mix the crosslinking agent with some water to obtain mixture A. Mix the hyperbranched nanocellulose, sodium alginate, aminated montmorillonite with the remaining water to obtain mixture B. Spray mixture B and mixture A onto the surface of the matrix particles in sequence and then dry.

[0028] It has the following beneficial effects:

[0029] This invention provides a biodegradable planting substrate based on nanocellulose. Hyperbranched nanocellulose, synthesized from polyols, methyl 3-butenoate, and double-bonded nanocellulose, serves as a reinforcing agent. It forms an interpenetrating network structure by crosslinking with sodium alginate, creating a gel coating layer with high mechanical strength and crack resistance on the surface of the matrix particles. The hyperbranched structure optimizes the microstructure of the gel coating layer, enriches its porosity, and improves the air permeability and drainage of the planting substrate. Aminated montmorillonite acts as a physical crosslinking point, guiding the hydrogel to form a uniform porous network and significantly enhancing mechanical strength and deformation resistance within the interpenetrating network structure composed of hyperbranched nanocellulose and sodium alginate. The amino groups it carries can also participate in the crosslinking process, forming a denser microstructure and improving strength.

[0030] The planting substrate of this invention has good air permeability and drainage, meeting the needs of flower roots for high air permeability and drainage, which can effectively improve the growth of flowers. Moreover, through physical encapsulation and chemical bonding, nutrients are slowly released into the soil, improving fertilizer utilization and reducing nutrient loss during migration, effectively reducing the probability of seedling burn. The raw materials used are readily available, environmentally friendly and non-toxic, and can effectively utilize agricultural and livestock waste, which has good practical value and prospects for promotion and application. Attached Figure Description

[0031] Figure 1 The nitrogen accumulation release rate-time curves of the planting substrates of Example 1 and Comparative Examples 1-3 are shown.

[0032] Figure 2 The phosphorus cumulative release rate-time curves of the planting substrates of Example 1 and Comparative Examples 1-3 are shown.

[0033] Figure 3 The potassium cumulative release rate-time curves of the planting substrates of Example 1 and Comparative Examples 1-3 are shown.

[0034] Figure 4 This is a flowchart illustrating the preparation route of hyperbranched nanocellulose in Example 1. Detailed Implementation

[0035] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0036] Example 1:

[0037] A biodegradable planting substrate based on nanocellulose is made from the following raw materials in parts by weight:

[0038] The matrix consists of 90 parts of matrix particles, 4 parts of hyperbranched nanocellulose, 4 parts of sodium alginate, 0.2 parts of calcium chloride, 0.1 parts of citric acid, 2 parts of aminated montmorillonite, and 15 parts of water.

[0039] The preparation method of the matrix particles is as follows:

[0040] Crushed wheat straw, dried chicken manure, and peat moss were mixed evenly in a mass ratio of 1:1:1 to obtain fermentation raw materials. 0.55% EM inoculant, 0.12% cellulase, and 0.06% xylanase were added to the fermentation raw materials. The mixture was fermented in a fermentation tank at 55±5℃ for 10 days to obtain fermentation products. The fermentation products were mixed evenly with perlite and ammonia in a mass ratio of 2:1 and then pressed into granules with a particle size of 2.5mm under a pressure of 15kN in a pellet mill.

[0041] The preparation method of hyperbranched nanocellulose is as follows:

[0042] 0.72 g of acrylic acid was dissolved in 25 ml of dichloromethane, and then 1.62 g of N'N-carbonyldiimidazole was added in several portions. The mixture was stirred at room temperature for 5 h. 1 g of nanocellulose was dispersed in 10 ml of dichloromethane and then added to the reaction solution. The reaction was continued at room temperature for 20 h. After the reaction was completed, the product was dialyzed and then freeze-dried at low temperature to obtain double-bonded nanocellulose. 10 mmol of trimethylolpropane, 30 mmol of methyl 3-butenoate and 0.1 g of p-toluenesulfonic acid were mixed, stirred and heated to 90 °C for 5 h. The reaction product was washed with saturated sodium bicarbonate solution and dried to obtain a hyperbranched intermediate. The hyperbranched intermediate was mixed with the free radical initiator APS and heated to 80 °C. Double-bonded nanocellulose was dissolved in DMSO and added to the mixture for reaction. The mass ratio of hyperbranched intermediate, double-bonded nanocellulose and free radical initiator APS was 1:1:0.01. After reacting for 5 h, 10 times the volume of DMSO of water was added, and the mixture was stirred for 10 h. The precipitated product was filtered off and dried.

[0043] The preparation method of aminated montmorillonite is as follows:

[0044] Add 1g of sodium montmorillonite to 50ml of water, stir and disperse for 30min, then add 0.5g of lysine hydrochloride, heat to reflux and react for 10h. After the reaction is complete, cool, collect the precipitate, wash with water and dry.

[0045] The above-mentioned method for preparing biodegradable planting substrate:

[0046] Mix calcium chloride, citric acid, and an appropriate amount of water to obtain mixture A. Mix hyperbranched nanocellulose, sodium alginate, aminated montmorillonite, and the remaining water to obtain mixture B. Load mixture A and mixture B into a pressure sprayer. Place the matrix particles into a coating machine. Use the pressure sprayer to spray mixture B and mixture A onto the surface of the matrix particles in sequence. Finally, use a forced-air heating system to dry.

[0047] Example 2:

[0048] A biodegradable planting substrate based on nanocellulose is made from the following raw materials in parts by weight:

[0049] The matrix consists of 80 parts of matrix particles, 3 parts of hyperbranched nanocellulose, 6 parts of sodium alginate, 0.2 parts of calcium chloride, 0.1 parts of citric acid, 1 part of aminated montmorillonite, and 10 parts of water.

[0050] The preparation methods of the matrix particles, hyperbranched nanocellulose and aminated montmorillonite are the same as in Example 1;

[0051] The above-mentioned method for preparing biodegradable planting substrate:

[0052] Mix calcium chloride, citric acid, and an appropriate amount of water to obtain mixture A. Mix hyperbranched nanocellulose, sodium alginate, aminated montmorillonite, and the remaining water to obtain mixture B. Load mixture A and mixture B into a pressure sprayer. Place the matrix particles into a coating machine. Use the pressure sprayer to spray mixture B and mixture A onto the surface of the matrix particles in sequence. Finally, use a forced-air heating system to dry.

[0053] Example 3:

[0054] A biodegradable planting substrate based on nanocellulose is made from the following raw materials in parts by weight:

[0055] 100 parts matrix particles, 6 parts hyperbranched nanocellulose, 3 parts sodium alginate, 0.2 parts calcium chloride, 0.1 parts citric acid, 3 parts aminated montmorillonite, and 20 parts water;

[0056] The preparation methods of the matrix particles, hyperbranched nanocellulose and aminated montmorillonite are the same as in Example 1;

[0057] The above-mentioned method for preparing biodegradable planting substrate:

[0058] Mix calcium chloride, citric acid, and an appropriate amount of water to obtain mixture A. Mix hyperbranched nanocellulose, sodium alginate, aminated montmorillonite, and the remaining water to obtain mixture B. Load mixture A and mixture B into a pressure sprayer. Place the matrix particles into a coating machine. Use the pressure sprayer to spray mixture B and mixture A onto the surface of the matrix particles in sequence. Finally, use a forced-air heating system to dry.

[0059] Comparative Example 1:

[0060] It is basically the same as Example 1, except that commercially available nanocellulose is used instead of hyperbranched nanocellulose.

[0061] Comparative Example 2:

[0062] It is basically the same as Example 1, except that sodium-based montmorillonite is used instead of aminated montmorillonite.

[0063] Comparative Example 3:

[0064] It is basically the same as Example 1, except that the matrix particles are used directly as the planting substrate.

[0065] Performance testing

[0066] ① Soil column leaching test: The soil column leaching device was 6.5 cm in diameter and 20 cm high. The bottom of the column was sealed with a double-layer nylon net (with a qualitative filter paper sandwiched in the middle) and fixed with rope. The filling method of the soil column was as follows: First, 10 g of perlite was placed at the bottom, and 20 g of the planting substrate from Example 1 and Comparative Examples 1-3 were placed in the middle. Finally, 10 g of perlite was added to the top. After filling the soil column, water was added to each soil column, and leaching was carried out at 10, 20, 30, 40, 50, 60, 70, 80, and 90 days. The leachate was collected, and the nitrogen, phosphorus, and potassium contents in the leachate were determined. The total nitrogen content in the leachate was determined by alkaline potassium persulfate oxidation-ultraviolet spectrophotometry; the total phosphorus content in the leachate was determined by ammonium molybdate spectrophotometry; and the total potassium content in the leachate was determined by flame photometry. The results are shown in [reference needed]. Figure 1-3 .

[0067] in Figure 1 The nitrogen accumulation release rate-time curves of the planting substrates in Example 1 and Comparative Examples 1-3 are shown below. Figure 1 It is evident that the nutrient release time of the planting substrate prepared in Example 1 of this invention is long, which allows the nutrients to exert their maximum fertilizer effect or utilization rate.

[0068] in Figure 2 The graphs showing the cumulative phosphorus release rate over time for the planting substrates of Example 1 and Comparative Examples 1-3 are provided. Figure 2It is evident that the nutrient release time of the planting substrate prepared in Example 1 of this invention is long, which allows the nutrients to exert their maximum fertilizer effect or utilization rate.

[0069] in Figure 3 The figures show the potassium cumulative release rate-time variation curves of the planting substrates in Example 1 and Comparative Examples 1-3, respectively. Figure 3 It is evident that the nutrient release time of the planting substrate prepared in Example 1 of this invention is long, which allows the nutrients to exert their maximum fertilizer effect or utilization rate.

[0070] ②The planting substrates in Examples 1-3 and Comparative Examples 1-3 were used as samples for testing. A certain amount of samples were dropped freely from a height of 5m onto a steel plate. Each group underwent 5 repeated drop tests and was then sieved with a 10-mesh sieve. The mass of the sieved particles was accurately weighed. The drop strength was expressed as the percentage of the mass of the sieved particles to the mass of the sample, and calculated according to formula (1).

[0071] S = (m1 / m2) × 100;

[0072] S is the drop strength (%), m1 is the mass of the particles remaining on the sieve (g), and m2 is the mass of the sample (g).

[0073] Each experiment was conducted five times, and the average data were recorded in Table 1, as shown below:

[0074]

[0075] As shown in Table 1 above, the planting substrate prepared by the present invention has high drop strength and can maintain its shape and is not easily crushed during transportation and use;

[0076] The comparison between Example 1 and Comparative Example 1 shows that, compared with commercially available nanocellulose, the addition of hyperbranched nanocellulose can significantly improve the drop strength of the planting substrate.

[0077] The comparison between Example 1 and Comparative Example 2 shows that, compared with sodium-based montmorillonite, the addition of aminated montmorillonite can significantly improve the drop strength of the planting substrate.

[0078] A comparison between Example 1 and Comparative Example 3 shows that the drop strength of the matrix particles is greatly improved after coating.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biodegradable planting substrate based on nanocellulose, characterized in that, Made from the following parts by weight of raw materials: The matrix consists of 80-100 parts of matrix particles, 3-6 parts of hyperbranched nanocellulose, 3-6 parts of sodium alginate, 0.1-0.5 parts of crosslinking agent, 1-3 parts of aminated montmorillonite, and 10-20 parts of water. The hyperbranched nanocellulose is synthesized from polyol, methyl 3-butenoate and double-bonded nanocellulose. The preparation method of the hyperbranched nanocellulose is as follows: The intermediate is obtained by transesterification of polyol with methyl 3-butenoate, and then grafted onto double-bonded nanocellulose. The molar ratio of the polyol to methyl 3-butenoate is 1:2-4; The mass ratio of the intermediate to the double-bonded nanocellulose is 1-10:1-10; The polyol is trimethylolpropane, glycerol, or pentaerythritol; The preparation method of the double-bonded nanocellulose is as follows: Acrylic acid was dissolved in dichloromethane, then N'N-carbonyldiimidazole was added, the reaction was stirred, and nanocellulose was added to continue the reaction. After the reaction was completed, the product was dialyzed and then freeze-dried at low temperature. The matrix particles are composed of decomposed straw, decomposed manure, decomposed peat moss and perlite; The mass ratio of the decomposed straw, decomposed manure, decomposed peat moss and perlite is 1-10:1-10:1-10:1-10; The crosslinking agent is composed of calcium chloride and citric acid; The mass ratio of calcium chloride to citric acid is 1-5:1-5; The preparation method of the aminated montmorillonite is as follows: Sodium montmorillonite was added to water and stirred to disperse it. Then, amino acid hydrochloride was added and the mixture was heated to reflux for 1-10 hours. After the reaction was completed, the mixture was cooled, the precipitate was collected, washed, and dried.

2. A method for preparing a biodegradable planting substrate as described in claim 1, characterized in that, Mix the crosslinking agent with some water to obtain mixture A. Mix the hyperbranched nanocellulose, sodium alginate, aminated montmorillonite with the remaining water to obtain mixture B. Spray mixture B and mixture A onto the surface of the matrix particles in sequence and then dry.

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