Multi-particle-size gradient eco-friendly composite water-retaining agent and preparation method thereof

Abstract

This invention discloses an eco-friendly composite water-retaining agent with a multi-particle-size gradient and its preparation method. It is prepared using raw materials of different particle sizes. By weight, the raw materials consist of: 75-78 parts potassium polyacrylate, 5-6 parts attapulgite, 3-4 parts polysuccinimide, 3-4 parts polyglutamic acid-fucoidan oligosaccharide gel particles, 0.5-0.8 parts carboxymethyl chitosan-modified starch, and 20-25 parts potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained through a cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharides. This invention constructs a biphase gradient structure through a primary water-absorbing framework (coarse particles) and a secondary functional matrix (micro powder). This invention uses a full potassium formulation, which is more environmentally friendly and completely eliminates soil compaction.

Description

Technical Field

[0001] This invention belongs to the field of agricultural drought-resistant and water-retaining materials technology, and relates to an eco-friendly composite water-retaining agent with multiple particle size gradients and its preparation method. Background Technology

[0002] Drought resistance and moisture conservation are crucial aspects of agricultural production. Traditional irrigation methods result in significant water waste and low water utilization rates. Water scarcity is a global problem; therefore, scientifically and fully utilizing existing water resources is essential for agricultural production. Water-retaining agents are one of the main means of addressing this issue.

[0003] Water-retaining agents, also known as water absorbents, are typically made from high-molecular-weight polymers containing numerous hydrophilic groups and possessing a network-like molecular chain structure. Upon contact with water, they undergo electrolysis, dissociating into ions with a strong affinity for water, thus exhibiting extremely strong water absorption and retention properties. Water-retaining agents can rapidly absorb hundreds of times their own weight in water and retain a large amount of moisture, while simultaneously expanding in volume to tens or even hundreds of times their original size. When the moisture content in the environment is low, they slowly release the water back into the soil, shrinking back to their original size, repeating this cycle repeatedly. This process improves the soil's water-holding capacity and enhances soil quality. Furthermore, through their network structure, water-retaining agents can adsorb and fix fertilizer elements in the soil, reducing nutrient loss and promoting plant growth. Therefore, they are widely used in desertification control, agricultural and forestry crop cultivation, and landscaping.

[0004] Most water-retaining agents currently on the market are derived entirely from fossil fuels, resulting in high costs, environmental unfriendliness, and limited functionality, severely restricting their widespread application in ecological agriculture systems. Sodium-based water-retaining agents are a common type, boasting advantages such as high water absorption rate, low cost, and rapid water absorption. However, long-term use leads to sodium ion accumulation in the soil, damaging soil structure, causing compaction, salinization, and inhibiting plant growth. Sodium-based water-retaining agents also suffer from short lifespan, environmental impact, and poor salt tolerance; therefore, reducing their use is imperative.

[0005] In addition, traditional water-retaining agents are mostly single fine powder granules, requiring water to diffuse slowly from the outside to the inside. The initial water absorption rate is slow, making it difficult to cope with sudden droughts or short-term rainfall. Some existing technologies attempt to add inert coarse fillers as a skeleton, but this sacrifices water absorption capacity. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an eco-friendly composite water-retaining agent with multiple particle size gradients and its preparation method. Through the special structure of "large particle active skeleton + micro powder functional matrix", it achieves the synergistic effect of rapid water absorption, high water retention and soil improvement.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. By weight, the composition of each raw material is as follows: 75-78 parts of potassium polyacrylate, 5-6 parts of attapulgite, 3-4 parts of polysuccinimide, 3-4 parts of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.5-0.8 parts of carboxymethyl chitosan-modified starch, and 20-25 parts of potassium humate; wherein, the polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0008] Preferably, the composite water-retaining agent is in granular form with a particle size of 3-4 mm.

[0009] Preferably, the particle size of potassium polyacrylate is 10-20 mesh, the particle size of attapulgite is 80-100 mesh, the particle size of polysuccinimide is 100-200 mesh, the particle size of polyglutamic acid-fucoidan oligosaccharide gel particles is 80-100 mesh, the particle size of carboxymethyl chitosan modified starch is 100-200 mesh, and the particle size of potassium humate is 100-200 mesh.

[0010] Preferably, the preparation method of the polyglutamic acid-fucoidan oligosaccharide gel particles is as follows, by weight: First, 1 part of γ-polyglutamic acid is dissolved in 10-12 parts of deionized water, then 0.3-0.4 parts of lysine is added and stirred to dissolve, then 0.3-0.4 parts of carbodiimide hydrochloride is added and stirred at 300-400 r / min for 30-40 minutes. The pH is adjusted to 6-6.5 using 0.1 mol / L phosphoric acid solution, then 0.05 parts of fucoidan is added and stirred to mix well. Then, 1% of the total volume of acetic acid solution is quickly poured in and stirred to mix well. The mixture is allowed to stand to form a gel, then pulverized to obtain the final product.

[0011] More preferably, the concentration of the acetic acid solution is 0.1 mol / L.

[0012] Preferably, the preparation method of the carboxymethyl chitosan modified starch by weight is as follows: First, 1 part of corn starch is gelatinized to obtain a gelatinized starch solution. Then, 0.5 to 0.6 parts of carboxymethyl chitosan are added to the gelatinized starch solution, stirred and mixed, and the pH is adjusted to 8 to 9. The mixture is stirred and heated to 70 to 80°C. 8 to 10 parts of corn oil and 0.8 to 1 part of Tween 80 are added, and the mixture is stirred vigorously. 0.8 to 1 part of sodium trimetaphosphate is added, and the mixture is kept warm and stirred to crosslink. The mixture is allowed to stand and separate into layers. The oil layer is removed, and the remaining part is washed with anhydrous ethanol. The solid is filtered, dried, and ground to the required particle size to obtain the final product.

[0013] A further preferred method for gelatinization is as follows: add corn starch to water at 3 to 4 times its weight and gelatinize at 70 to 75°C for 10 to 15 minutes.

[0014] Further preferred, the high-intensity stirring rate is 2000-3000 r / min, and the other stirring rates are 300-400 r / min.

[0015] Further preferably, the pH is adjusted using a 0.1 mol / L sodium hydroxide solution.

[0016] Further preferred, the crosslinking reaction time with heat preservation and stirring is 4 to 5 hours.

[0017] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in 2 to 3 times its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0018] Preferably, in step (1), the mass ratio of sodium hydroxide and crosslinking agent in the polysuccinimide and sodium hydroxide aqueous solution is 3-4:1.7-2.2:0.7-0.9, the mass concentration of sodium hydroxide solution is 10-12%, and the crosslinking agent is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether.

[0019] Preferably, in step (1), the hydrolysis conditions are: stirring and hydrolyzing at 50-60℃ for 35-45 minutes; adjusting the pH to 4.5-5 using 0.1mol / L acetic acid solution; and the cross-linking conditions are: stirring and cross-linking at 50-60℃ for 8-10 hours.

[0020] Preferably, in step (1), the attapulgite is first crushed to 150-200 mesh before being added, and after gelation, it is crushed to 100-150 mesh.

[0021] Preferably, in step (3), the tumbling mixing speed is 25-35 r / min, and high-speed shearing is strictly prohibited to prevent the 10-20 mesh skeleton from being broken, so that the moist micro powder agglomerates can be evenly adhered to and filled in the surface and gaps of the large potassium polyacrylate particles. This forms a premix with "large particles as the core, micro powder as the shell and filler".

[0022] Preferably, in step (4), the pressure of the low-pressure roller extrusion granulator is 0.5 to 1.5 MPa, which needs to be strictly controlled. It is only necessary to bond the micro powder to the skeleton, and high pressure compaction is not allowed to avoid crushing the 10 to 20 mesh potassium polyacrylate skeleton or blocking its swelling channels.

[0023] Preferably, in step (4), the drying conditions are: drying at 50-55°C for 20-24 hours.

[0024] The beneficial effects of this invention are as follows: This invention discloses an eco-friendly composite water-retaining agent with multiple particle size gradients and its preparation method. It is prepared using raw materials with different particle sizes. By weight, the composition of each raw material is as follows: 75-78 parts of potassium polyacrylate, 5-6 parts of attapulgite, 3-4 parts of polysuccinimide, 3-4 parts of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.5-0.8 parts of carboxymethyl chitosan-modified starch, and 20-25 parts of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide.

[0025] This invention relates to raw materials with the following particle sizes: potassium polyacrylate (10-20 mesh), attapulgite (80-100 mesh), polysuccinimide (100-200 mesh), polyglutamic acid-fucoidan oligosaccharide gel particles (80-100 mesh), carboxymethyl chitosan-modified starch (100-200 mesh), and potassium humate (100-200 mesh). Potassium polyacrylate has the largest particle size, forming the primary water-absorbing framework within the particles; carboxymethyl chitosan-modified starch acts as a binder; other raw materials or small particles generated during preparation constitute the secondary functional matrix, filling and encapsulating the gaps and surface of the primary water-absorbing framework. Within the primary water-absorbing framework, the 10-20 mesh potassium polyacrylate particles are discretely distributed, and any two adjacent potassium polyacrylate particles are separated by the smaller-sized secondary functional matrix, forming a connected water-absorbing swelling network.

[0026] The functions of the various raw materials involved in this invention are as follows: 1. This invention constructs a biphase gradient structure through a primary water-absorbing skeleton (coarse particles) and a secondary functional matrix (micro powder). In the final granular composite water-retaining agent, the coarse potassium polyacrylate particles occupy the main volume and act as a "swelling engine." Upon contact with water, they first rapidly absorb water and swell, creating a huge space inside the particles to form a connected gel network, which greatly improves the water absorption rate (minute-level response). The secondary functional matrix acts as a "filler" and "reinforcing agent," filling the voids in the large potassium polyacrylate particles and coating the surface of the large particles.

[0027] 2. This invention uses a full potassium formula (potassium polyacrylate + potassium humate), which is more environmentally friendly than sodium-based water-retaining agents and completely eliminates soil compaction. Furthermore, potassium humate provides organic matter and readily available potassium, regulating the rhizosphere microenvironment.

[0028] 3. Attapulgite consists of two parts. One part, with its nanorod crystal structure, is distributed like "steel bars" in the gel layer on the surface of the potassium polyacrylate skeleton, forming an organic-inorganic hybrid reinforcing interface, which significantly enhances the gel strength, prevents excessive softening and disintegration after large particles swell, improves the compressive strength of the particles after water absorption, and has a slow-release water function. The other part participates in the preparation of sodium polyaspartate attapulgite gel particles, further enriching the particle size composition. The gel particles are rich in pore structure, which further improves the water retention performance.

[0029] 4. The present invention incorporates polyglutamic acid-fucoidan oligosaccharide gel particles, which are rich in porous structure and further improve water retention performance.

[0030] 5. This invention uses carboxymethyl chitosan-modified starch as a binder, which is biodegradable and promotes the strong bonding between the primary water-absorbing skeleton and the secondary functional matrix, ensuring structural stability during transportation and application.

[0031] Specifically, the present invention has the following advantages: 1. Rapid water absorption: The 10-20 mesh potassium polyacrylate skeleton breaks the dense structure of the micro powder, allowing water to enter the particle instantly. The water absorption rate is more than 60% higher than that of all micro powder products, making it particularly suitable for sowing in moist conditions.

[0032] 2. High water retention: Small-diameter attapulgite and other micro-powders are evenly dispersed in the gel network, forming an "organic-inorganic hybrid reinforced structure", which makes the particles retain their elasticity after absorbing hundreds of times their weight in water, resist soil pressure, and have a long service life.

[0033] 3. Fertilizer and water synergy: Potassium humate micro powder is in close contact with the water-absorbing skeleton and is released with water to achieve precise supply of "integrated water and fertilizer".

[0034] 4. Ecological safety: Full potassium formula, no sodium ion hazards, does not compact soil; biological binder, no microplastic residue.

[0035] 5. Suitable specifications: The particle size of 3-4mm facilitates mechanized spreading, and the internal structure is stable and not easily pulverized. Detailed Implementation

[0036] The preferred embodiments of the present invention will now be described in detail.

[0037] The potassium polyacrylate involved in this invention has a weight-average molecular weight of 8000 kDa and was purchased from Hubei Chengfeng Chemical Co., Ltd. Polysuccinimide, with a weight-average molecular weight of 5000-10000 Da, was purchased from Henan Wokas Biotechnology Co., Ltd. Potassium humate was purchased from Hubei Chengfeng Chemical Co., Ltd. γ-polyglutamic acid, weight-average molecular weight 10,000 Da, was purchased from Shandong Aicai Biotechnology Co., Ltd. Carboxymethyl chitosan was purchased from Shandong Pingju Biotechnology Co., Ltd. Brown alginic oligosaccharides were purchased from Hebei Hongtao Biotechnology Co., Ltd. Lysine, specifically L-lysine, was purchased from Hefei Shengrun Biological Products Co., Ltd. Example 1

[0038] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.5 kg of potassium polyacrylate, 0.5 kg of attapulgite, 0.3 kg of polysuccinimide, 0.3 kg of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.05 kg of carboxymethyl chitosan-modified starch, and 2 kg of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0039] The composite water-retaining agent is in granular form with a particle size of 3 mm.

[0040] The particle size of potassium polyacrylate is 10 mesh, the particle size of attapulgite is 80 mesh, the particle size of polysuccinimide is 100 mesh, the particle size of polyglutamic acid-fucoidan oligosaccharide gel particles is 80 mesh, the particle size of carboxymethyl chitosan modified starch is 100 mesh, and the particle size of potassium humate is 100 mesh.

[0041] The preparation method of polyglutamic acid-fucoidan oligosaccharide gel particles is as follows: First, 1 kg of γ-polyglutamic acid is dissolved in 10 kg of deionized water. Then, 0.3 kg of lysine is added and stirred to dissolve. 0.3 kg of carbodiimide hydrochloride is added and stirred at 300 r / min for 30 minutes. The pH is adjusted to 6 using 0.1 mol / L phosphoric acid solution. 0.05 kg of fucoidan oligosaccharide is added and stirred to mix well. Then, 1% of the total volume of acetic acid solution (concentration of 0.1 mol / L) is quickly poured in and stirred to mix well. The mixture is allowed to stand to form a gel and then pulverized to obtain the final product.

[0042] The preparation method of carboxymethyl chitosan modified starch is as follows: First, 1 kg of corn starch is gelatinized to obtain gelatinized starch solution. Then, 0.5 kg of carboxymethyl chitosan is added to the gelatinized starch solution, stirred and mixed, pH is adjusted to 8, stirred and heated to 70℃, 8 kg of corn oil and 0.8 kg of Tween 80 are added, and the mixture is stirred vigorously. Then, 0.8 kg of sodium trimetaphosphate is added, and the mixture is kept warm and stirred to crosslink the reaction. After standing and separating into layers, the oil layer is removed, and the remaining part is washed with anhydrous ethanol. The solid is then filtered, dried, and ground to the required particle size to obtain the final product.

[0043] The specific method for gelatinization is as follows: add corn starch to water with a weight of 3, and gelatinize at 70°C for 10 minutes.

[0044] The high-power stirring rate is 2000 r / min, and the other stirring rates are 300 r / min.

[0045] The pH was adjusted using a 0.1 mol / L sodium hydroxide solution.

[0046] The cross-linking reaction was carried out under heat and with stirring for 4 hours.

[0047] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in twice its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0048] In step (1), the mass ratio of sodium hydroxide and crosslinking agent in the polysuccinimide and sodium hydroxide aqueous solution is 3:1.7:0.7, the mass concentration of sodium hydroxide solution is 10%, and the crosslinking agent is ethylene glycol diglycidyl ether.

[0049] In step (1), the hydrolysis conditions are: stirring and hydrolyzing at 50℃ for 35 minutes; adjusting the pH to 4.5 using 0.1mol / L acetic acid solution; and stirring and crosslinking conditions are: stirring and crosslinking at 50℃ for 8 hours.

[0050] In step (1), the attapulgite is first crushed to 150 mesh before being added, and after gelation, it is crushed to 100 mesh.

[0051] In step (3), the tumbling mixing speed is 25 r / min.

[0052] In step (4), the pressure of the low-pressure double-roller extrusion granulator is 0.5 MPa.

[0053] In step (4), the drying conditions are: drying at 50℃ for 20 hours. Example 2

[0054] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.8 kg of potassium polyacrylate, 0.6 kg of attapulgite, 0.4 kg of polysuccinimide, 0.4 kg of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.08 kg of carboxymethyl chitosan-modified starch, and 2.5 kg of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0055] The composite water-retaining agent is in granular form with a particle size of 4 mm.

[0056] The particle size of potassium polyacrylate is 20 mesh, the particle size of attapulgite is 100 mesh, the particle size of polysuccinimide is 200 mesh, the particle size of polyglutamic acid-fucoidan oligosaccharide gel particles is 100 mesh, the particle size of carboxymethyl chitosan modified starch is 200 mesh, and the particle size of potassium humate is 200 mesh.

[0057] The preparation method of polyglutamic acid-fucoidan oligosaccharide gel particles is as follows: First, 1 kg of γ-polyglutamic acid is dissolved in 12 kg of deionized water. Then, 0.4 kg of lysine is added and stirred to dissolve. 0.4 kg of carbodiimide hydrochloride is added and stirred at 400 r / min for 40 minutes. The pH is adjusted to 6.5 using 0.1 mol / L phosphoric acid solution. 0.05 kg of fucoidan oligosaccharide is added and stirred to mix well. Then, 1% of the total volume of acetic acid solution (concentration of 0.1 mol / L) is quickly poured in and stirred to mix well. The mixture is allowed to stand to form a gel and then pulverized to obtain the final product.

[0058] The preparation method of carboxymethyl chitosan modified starch is as follows: First, 1 kg of corn starch is gelatinized to obtain gelatinized starch solution. Then, 0.6 kg of carboxymethyl chitosan is added to the gelatinized starch solution, stirred and mixed, pH is adjusted to 9, stirred and heated to 80℃, 10 kg of corn oil and 1 kg of Tween 80 are added, and the mixture is stirred vigorously. Then, 1 kg of sodium trimetaphosphate is added, and the mixture is kept warm and stirred to crosslink the reaction. After standing and separating into layers, the oil layer is removed, and the remaining part is washed with anhydrous ethanol. The solid is then filtered, dried, and ground to the required particle size to obtain the final product.

[0059] The specific method for gelatinization is as follows: add corn starch to water at 4 times its weight and gelatinize at 75°C for 15 minutes.

[0060] The high-power stirring rate is 3000 r / min, and the other stirring rates are 400 r / min.

[0061] The pH was adjusted using a 0.1 mol / L sodium hydroxide solution.

[0062] The cross-linking reaction time is 5 hours with heat preservation and stirring.

[0063] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in 3 times its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0064] In step (1), the mass ratio of sodium hydroxide and crosslinking agent in the polysuccinimide and sodium hydroxide aqueous solution is 4:2.2:0.9, the mass concentration of sodium hydroxide solution is 12%, and the crosslinking agent is polyethylene glycol diglycidyl ether.

[0065] In step (1), the hydrolysis conditions are: stirring and hydrolyzing at 60℃ for 45 minutes; adjusting the pH to 5 using 0.1 mol / L acetic acid solution; and the cross-linking conditions are: stirring and cross-linking at 60℃ for 10 hours.

[0066] In step (1), the attapulgite clay is first crushed to 200 mesh before being added, and after gelation, it is crushed to 150 mesh.

[0067] In step (3), the tumbling mixing speed is 35 r / min.

[0068] In step (4), the pressure of the low-pressure double-roller extrusion granulator is 1.5 MPa.

[0069] In step (4), the drying conditions are: drying at 55℃ for 24 hours. Example 3

[0070] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.6 kg of potassium polyacrylate, 0.55 kg of attapulgite, 0.35 kg of polysuccinimide, 0.35 kg of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.07 kg of carboxymethyl chitosan-modified starch, and 2.2 kg of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0071] The composite water-retaining agent is in granular form with a particle size of 3.5 mm.

[0072] The particle size of potassium polyacrylate is 15 mesh, the particle size of attapulgite is 90 mesh, the particle size of polysuccinimide is 150 mesh, the particle size of polyglutamic acid-fucoidan oligosaccharide gel particles is 90 mesh, the particle size of carboxymethyl chitosan modified starch is 150 mesh, and the particle size of potassium humate is 150 mesh.

[0073] The preparation method of polyglutamic acid-fucoidan oligosaccharide gel particles is as follows: First, 1 kg of γ-polyglutamic acid is dissolved in 11 kg of deionized water. Then, 0.35 kg of lysine is added and stirred to dissolve. 0.35 kg of carbodiimide hydrochloride is added and stirred at 400 r / min for 35 minutes. The pH is adjusted to 6 using 0.1 mol / L phosphoric acid solution. 0.05 kg of fucoidan oligosaccharide is added and stirred to mix well. Then, 1% of the total volume of acetic acid solution (concentration of 0.1 mol / L) is quickly poured in and stirred to mix well. The mixture is allowed to stand to form a gel and then pulverized to obtain the final product.

[0074] The preparation method of carboxymethyl chitosan modified starch is as follows: First, 1 kg of corn starch is gelatinized to obtain gelatinized starch solution. Then, 0.55 kg of carboxymethyl chitosan is added to the gelatinized starch solution, stirred and mixed, pH is adjusted to 8, and the mixture is heated to 75°C. 9 kg of corn oil and 0.9 kg of Tween 80 are added, and the mixture is stirred vigorously. 0.9 kg of sodium trimetaphosphate is added, and the mixture is kept warm and stirred to crosslink. After standing and separating into layers, the oil layer is removed, and the remaining part is washed with anhydrous ethanol. The solid is then filtered, dried, and ground to the required particle size to obtain the final product.

[0075] The specific method for gelatinization is as follows: add corn starch to 3.5 times its weight of water and gelatinize at 72°C for 12 minutes.

[0076] The high-power stirring rate is 3000 r / min, and the other stirring rates are 350 r / min.

[0077] The pH was adjusted using a 0.1 mol / L sodium hydroxide solution.

[0078] The crosslinking reaction time with heat preservation and stirring is 4.5 hours.

[0079] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in 2.5 times its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0080] In step (1), the mass ratio of sodium hydroxide and crosslinking agent in the polysuccinimide and sodium hydroxide aqueous solution is 3.5:2:0.8, the mass concentration of sodium hydroxide solution is 11%, and the crosslinking agent is ethylene glycol diglycidyl ether.

[0081] In step (1), the hydrolysis conditions are: stirring and hydrolyzing at 55℃ for 40 minutes; adjusting the pH to 5 using 0.1 mol / L acetic acid solution; and the cross-linking conditions are: stirring and cross-linking at 55℃ for 9 hours.

[0082] In step (1), the attapulgite clay is first crushed to 200 mesh before being added, and after gelation, it is crushed to 150 mesh.

[0083] In step (3), the tumbling mixing speed is 30 r / min.

[0084] In step (4), the pressure of the low-pressure double-roller extrusion granulator is 1 MPa.

[0085] In step (4), the drying conditions are: drying at 52℃ for 22 hours. Comparative Example 1

[0086] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.5 kg of potassium polyacrylate, 0.5 kg of attapulgite, 0.3 kg of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.05 kg of carboxymethyl chitosan-modified starch, and 2 kg of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0087] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, stir and disperse the carboxymethyl chitosan modified starch of the formula in twice its weight of deionized water to obtain starch solution; (2) Mix the attapulgite clay, polyglutamic acid-fucoidan oligosaccharide gel particles and potassium humate evenly, spray the starch glue solution evenly, add the potassium polyacrylate in the formula under the tumbling mixing condition, mix evenly, and obtain the premix. (3) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0088] The rest is the same as in Example 1. Comparative Example 2

[0089] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.5 kg of potassium polyacrylate, 0.5 kg of attapulgite, 0.3 kg of polysuccinimide, 0.05 kg of carboxymethyl chitosan modified starch, and 2 kg of potassium humate.

[0090] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in twice its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite and the amount of potassium humate in the formula evenly, spray the starch glue solution evenly, add the amount of potassium polyacrylate in the formula under the tumbling mixing condition, mix evenly, and obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0091] The rest is the same as in Example 1. Comparative Example 3

[0092] An eco-friendly composite water-retaining agent with multiple particle size gradients is prepared using raw materials of different particle sizes. The composition of each raw material is as follows: 7.5 kg of potassium polyacrylate, 0.5 kg of attapulgite, 0.3 kg of polysuccinimide, 0.3 kg of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.05 kg of gelatinized starch, and 2 kg of potassium humate. The polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

[0093] The preparation method of gelatinized starch is as follows: 1 kg of corn starch is gelatinized to obtain a gelatinized starch solution, which is then dried and ground to the desired particle size. The specific method of gelatinization is as follows: corn starch is added to water at 3 times its weight and gelatinized at 70°C for 10 minutes.

[0094] The preparation method of the aforementioned eco-friendly composite water-retaining agent with multiple particle size gradients includes the following specific steps: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the amount of gelatinized starch in the formula is stirred and dispersed in twice its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

[0095] The rest is the same as in Example 1. Experimental Example

[0096] The composite water-retaining agents obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to relevant tests, including: 1. Water absorption rate (average rate within 5 minutes): Take 1g (m1) of composite water-retaining agent and mix it with 1000mL of tap water for 5 minutes to obtain water-retaining agent gel. After filtering the water-retaining agent gel through a 0.18mm sieve, weigh it m2. Water absorption rate = (m2-m1) / 5m1.

[0097] 2. Water absorption ratio: Take 1g (m3) of composite water-retaining agent and 1000mL of tap water and mix for 30 minutes to obtain water-retaining agent gel. After filtering the water-retaining agent gel through a 0.18mm sieve, weigh it as m4. Water absorption ratio = (m4-m3) / m3.

[0098] 3. Tensile strength: Tested using an electronic universal testing machine (Shimadzu AGX-V2).

[0099] 4. Soil hardness: Mix the composite water-retaining agent and fine dry soil at a mass ratio of 1:10, spread evenly on the surface of the test soil, turn it into the soil layer to a depth of 8cm, water thoroughly, and use a soil hardness meter to measure the hardness of the test soil on the 30th day (20 points, 20cm interval between points, take the average value).

[0100] The test results are shown in Table 1.

[0101] Table 1 Example 1 85.32 500.1 358 4.71 Example 2 85.55 501.5 359 4.69 Example 3 86.02 502.6 362 4.65 Comparative Example 1 70.37 440.6 328 5.02 Comparative Example 2 68.45 432.8 340 4.98 Comparative Example 3 80.96 483.2 310 4.80 As shown in Table 1, the composite water-retaining agents obtained in Examples 1 to 3 have high water retention performance and high strength.

[0102] In Comparative Example 1, polysuccinimide was omitted from the raw material composition; in Comparative Example 2, polyglutamic acid-fucoidan oligosaccharide gel particles were omitted from the raw material composition; and in Comparative Example 3, carboxymethyl chitosan-modified starch was replaced with gelatinized starch. The water retention performance and strength of the composite water-retaining agent were significantly worse, indicating that the raw materials of the present invention synergistically improve the water retention performance and strength.

[0103] Finally, it should be noted that the above preferred 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 through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. An eco-friendly composite water retaining agent of multi-particle size gradient, characterized by, It is prepared using raw materials of different particle sizes. By weight, the composition of each raw material is as follows: 75-78 parts of potassium polyacrylate, 5-6 parts of attapulgite, 3-4 parts of polysuccinimide, 3-4 parts of polyglutamic acid-fucoidan oligosaccharide gel particles, 0.5-0.8 parts of carboxymethyl chitosan modified starch, and 20-25 parts of potassium humate; wherein, the polyglutamic acid-fucoidan oligosaccharide gel particles are obtained by cross-linking reaction of γ-polyglutamic acid and fucoidan oligosaccharide as raw materials.

2. The composite water retaining agent according to claim 1, characterized by, The particle size of potassium polyacrylate is 10-20 mesh, the particle size of attapulgite is 80-100 mesh, the particle size of polysuccinimide is 100-200 mesh, the particle size of polyglutamic acid-fucoidan oligosaccharide gel particles is 80-100 mesh, the particle size of carboxymethyl chitosan modified starch is 100-200 mesh, and the particle size of potassium humate is 100-200 mesh.

3. The composite water-retaining agent according to claim 1, characterized in that, The preparation method of the polyglutamic acid-fucoidan oligosaccharide gel particles by weight is as follows: First, 1 part of γ-polyglutamic acid is dissolved in 10-12 parts of deionized water, then 0.3-0.4 parts of lysine is added and stirred to dissolve. Then, 0.3-0.4 parts of carbodiimide hydrochloride is added and stirred at 300-400 r / min for 30-40 minutes. The pH is adjusted to 6-6.5 using 0.1 mol / L phosphoric acid solution. Then, 0.05 parts of fucoidan oligosaccharide are added and stirred to mix well. Finally, 1% of the total volume of acetic acid solution is quickly poured in and stirred to mix well. The mixture is allowed to stand to form a gel and then pulverized to obtain the final product.

4. The composite water-retaining agent according to claim 1, characterized in that, The preparation method of the carboxymethyl chitosan modified starch by weight is as follows: First, 1 part of corn starch is gelatinized to obtain a gelatinized starch solution. Then, 0.5-0.6 parts of carboxymethyl chitosan are added to the gelatinized starch solution, stirred and mixed, and the pH is adjusted to 8-9. The mixture is stirred and heated to 70-80°C. 8-10 parts of corn oil and 0.8-1 part of Tween 80 are added, and the mixture is stirred vigorously. 0.8-1 part of sodium trimetaphosphate is added, and the mixture is kept warm and stirred to crosslink. The mixture is allowed to stand and separate into layers. The oil layer is removed, and the remaining part is washed with anhydrous ethanol. The solid is filtered, dried, and ground to the required particle size to obtain the final product.

5. A method for preparing an eco-friendly composite water-retaining agent with a multi-particle size gradient as described in any one of claims 1 to 4, characterized in that, The specific steps are as follows: (1) First, add the amount of polysuccinimide in the formula to the sodium hydroxide solution, hydrolyze it to obtain a sodium polyaspartate solution, adjust the pH, then add 1 / 3 of the amount of attapulgite, stir and mix well, continue to add crosslinking agent, stir to crosslink and gel, crush it to obtain sodium polyaspartate attapulgite gel particles. (2) Then, the carboxymethyl chitosan modified starch of the formula amount is stirred and dispersed in 2 to 3 times its weight of deionized water to obtain starch solution; (3) Then mix the sodium polyaspartate attapulgite gel particles with the remaining amount of attapulgite, the amount of polyglutamic acid-fucoidoglycolic acid gel particles and potassium humate evenly, spray the starch slurry evenly, add the amount of potassium polyacrylate under tumbling mixing conditions, mix evenly to obtain the premix. (4) Finally, the premixed material is fed into a low-pressure double-roller extrusion granulator for granulation, drying and screening to obtain the composite water-retaining agent.

6. The preparation method according to claim 5, characterized in that, In step (1), the mass ratio of sodium hydroxide and crosslinking agent in the polysuccinimide and sodium hydroxide aqueous solution is 3-4:1.7-2.2:0.7-0.9, the mass concentration of sodium hydroxide solution is 10-12%, and the crosslinking agent is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether.

7. The preparation method according to claim 5, characterized in that, In step (1), the hydrolysis conditions are: stirring and hydrolyzing at 50-60℃ for 35-45 minutes; adjusting the pH to 4.5-5 using 0.1mol / L acetic acid solution; and stirring and crosslinking conditions are: stirring and crosslinking at 50-60℃ for 8-10 hours.

8. The preparation method according to claim 5, characterized in that, In step (3), the tumbling mixing speed is 25-35 r / min.

9. The preparation method according to claim 5, characterized in that, In step (4), the pressure of the low-pressure double-roller extrusion granulator is 0.5 to 1.5 MPa.

10. The preparation method according to claim 5, characterized in that, In step (4), the drying conditions are: drying at 50-55℃ for 20-24 hours.