Composite polyamino acid type water-absorbent resin for agriculture and forestry as well as preparation method and application of composite polyamino acid type water-absorbent resin

Abstract

The invention relates to the technical field of preparation of water-retaining agents, and particularly discloses composite polyamino acid type water-absorbent resin for agriculture and forestry and a preparation method and application thereof. The composite polyamino acid type water-absorbent resin is obtained by cross-linking polyglutamic acid, polyaspartic acid, acrylic acid, a cross-linking agent and an initiator; the cross-linking agent is dinitrogen methylene bisacrylamide; the polyglutamic acid is polyglutamic acid A, polyglutamic acid B or agricultural polyglutamic acid; the molecular weight of the polyglutamic acid A is 2 million to 1 million Dalton; the molecular weight of the polyglutamic acid B is 50,000-100,000 Daltons; the molecular weight of the agricultural polyglutamic acid is 600,000-700,000 Daltons, and the purity is 35% + / -10%; the molecular weight of the polyaspartic acid is 10,000 Daltons or 15,000 Daltons; the volume mass ratio of the acrylic acid to the cross-linking agent is 1 mL: (0.00125 g to 0.00175 g). The water-absorbent resin disclosed by the invention is high in durability and liquid absorption rate, can be repeatedly used, and can reduce the raw material cost and improve the product performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of water retaining agents, and particularly relates to a composite polyamino acid type water-absorbing resin for agriculture and forestry, its preparation method and application. Background Art

[0002] Polyglutamic acid and polyaspartic acid are important polymers that can be degraded by environmental microorganisms. Due to their unique biocompatibility, degradability and excellent water absorption performance, they have received wide attention. Polyglutamic acid is a polypeptide polymerized from glutamic acid monomers. Its molecular structure contains a large number of carboxyl groups, which can form a three-dimensional network structure, having good water absorption and biodegradability. Polyaspartic acid is also a biopolymer material with various excellent properties. It is polymerized from the amino and carboxyl groups of aspartic acid to form a hydrophilic three-dimensional network structure, which can absorb and retain a large amount of water, having remarkable water absorption and water retention capacity. In addition, polyaspartic acid also has good biodegradability, and its degradation products are pollution-free to the environment and can be reused.

[0003] At present, polyglutamic acid can be produced by microbial fermentation technology, and the produced polyglutamic acid has a relatively high molecular weight and excellent polymerization performance. However, its fermentation process is complex and the production cost is high. While polyaspartic acid can currently be prepared on a large scale by chemical synthesis methods, with relatively low production costs and simple preparation methods, but its molecular weight is relatively low. In the prior art, a variety of studies have focused on the preparation of these two polymers and their water-absorbing resins, providing a rich technical basis for the development of new polyamino acid type water-absorbing resins.

[0004] For example, Chinese Patent CN116199912A proposes a preparation method of γ-polyglutamic acid superabsorbent resin. By mixing with nisin and crosslinking to form a gel-like product, it has good water absorption performance and biodegradability. Chinese Patent CN102002234A uses the γ-polyglutamic acid fermentation broth produced by Bacillus subtilis fermentation to prepare a water retaining agent, which is suitable for agriculture and forestry. In addition, Chinese Patent CN111068099A proposes a preparation method of a polyaspartic acid-based water retaining agent. By crosslinking with inorganic mineral materials, the production process is simple and the cost is low. Wang Chuanhai et al. (Preliminary study on the water absorption performance and biological effects of a new water retaining agent material γ-polyglutamic acid [J]. Chinese Journal of Agrometeorology. 2004, 05) studied the water absorption performance and biological effects of γ-polyglutamic acid (γ-PGA). It has a certain water retention capacity and an ideal release effect in the soil, and has an obvious drought-resistant and seedling-promoting effect. Chinese Patent CN112209781A relates to the application of a polyaspartic acid-based water retaining agent in an organic-inorganic compound fertilizer, which is suitable for agricultural planting in arid areas. These studies provide a technical basis for the development of new polyamino acid-based superabsorbent resins. However, most of these methods use single polymers, and there is a lack of a preparation method for compounding polyglutamic acid and polyaspartic acid.

[0005] Chinese Patent CN110564146A discloses a preparation method of a chelating resin based on γ-polyglutamic acid and polyaspartic acid. Using γ-polyglutamic acid, polyaspartic acid and an epoxy resin crosslinking agent as raw materials, adjusting the pH of the system with hydrochloric acid, the chelating resin can be prepared by reaction without further chemical modification of the raw materials. The obtained chelating resin has a high water absorption rate and a fast swelling rate. However, the main components used in this patent are γ-polyglutamic acid and polyaspartic acid. There are microorganisms in the soil that can degrade these two substances. The superabsorbent resins mainly composed of these two substances have a relatively fast degradation rate in the soil, are difficult to maintain the water retention performance for a long time in the soil, and the strength of the superabsorbent resin is low. The swelling rate of the washing liquid of the superabsorbent resin in this patent is only about 150 g - 200 g, and its liquid absorption swelling rate is low.

[0006] Therefore, the prior art still fails to fully integrate and develop the cost and performance advantages of polyglutamic acid and polyaspartic acid. Therefore, developing a preparation method of a polyamino acid-based superabsorbent resin with higher efficiency, lower cost and excellent comprehensive performance has certain research value and practical significance. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a composite polyamino acid-based superabsorbent resin for agriculture and forestry, its preparation method and application. This preparation method conducts a crosslinking reaction through polyglutamic acid, polyaspartic acid and acrylic acid, effectively reducing the performance degradation caused by repeated use, and is more efficient and cost-reducing.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a preparation method of an agricultural and forestry composite polyamino acid-based water-absorbing resin, which is prepared by crosslinking polyglutamic acid, polyaspartic acid, acrylic acid, a crosslinking agent and an initiator to obtain the agricultural and forestry composite polyamino acid-based water-absorbing resin; The crosslinking agent is selected from at least one of diazomethylenebisacrylamide, polyethylene glycol diacrylate and ethylene glycol dimethacrylate; The polyglutamic acid is any one of polyglutamic acid A, polyglutamic acid B and agricultural polyglutamic acid; the molecular weight of the polyglutamic acid A is 700,000 - 1,100,000 Daltons, and the purity is 90% - 100%; the molecular weight of the polyglutamic acid B is 50,000 - 100,000 Daltons, and the purity is 90% - 100%; the molecular weight of the agricultural polyglutamic acid is 600,000 - 700,000 Daltons, and the purity is 35% ± 10%; the molecular weight of the polyaspartic acid is 10,000 Daltons or 15,000 Daltons; the volume-mass ratio of the acrylic acid to the crosslinking agent is 1 mL: 0.00125 g - 0.00175 g.

[0009] Preferably, the crosslinking agent is diazomethylenebisacrylamide, and the volume-mass ratio of the acrylic acid to the crosslinking agent is 1 mL: 0.0015 g - 0.00175 g.

[0010] Preferably, the initiator is selected from at least one of potassium persulfate, sodium persulfate and ammonium persulfate.

[0011] More preferably, the initiator is potassium persulfate.

[0012] The polyglutamic acid with a molecular weight of 700,000 - 1,100,000 Daltons and the polyglutamic acid with a molecular weight of 50,000 - 100,000 Daltons are sub-categories of polyglutamic acid, specifically referring to polyglutamic acid obtained by microbial fermentation and through refined extraction, with a purity generally above 90%, and the molecular weight strictly controlled in the range of 700,000 to 1,100,000 Daltons or 50,000 to 100,000 Daltons; while the agricultural polyglutamic acid is a polyglutamic acid obtained by microbial fermentation and through rough extraction, with a purity of about 35% ± 10%, and other components are microbial residues in the fermentation process, and its molecular weight is usually between 600,000 and 700,000 Daltons.

[0013] Preferably, the mass ratio of the polyglutamic acid to the polyaspartic acid is 1:2 - 2:1.

[0014] More preferably, the mass ratio of the polyglutamic acid to the polyaspartic acid is 1:2.

[0015] Preferably, the neutralization degree of the acrylic acid is 70% - 90%.

[0016] Further preferably, the neutralization degree of the acrylic acid is 80%.

[0017] Preferably, the mass ratio of the crosslinking agent to the initiator is 2.5 - 3.5:19 - 25.

[0018] Further preferably, the mass ratio of the crosslinking agent to the initiator is 1:7.

[0019] Preferably, the preparation method includes: dissolving polyglutamic acid and polyaspartic acid in water and mixing evenly to obtain a mixed solution A; mixing acrylic acid with an NaOH solution to obtain a mixed solution B; mixing the mixed solutions A and B and then adding a crosslinking agent and an initiator to obtain the composite polyamino acid-based water-absorbing resin.

[0020] Preferably, the concentration of the NaOH solution is 4 - 6 mol / L.

[0021] Further preferably, the concentration of the NaOH solution is 5 mol / L.

[0022] The present invention also provides a composite polyamino acid-based water-absorbing resin prepared by the above preparation method.

[0023] On the other hand, the present invention provides an application of the above composite polyamino acid-based water-absorbing resin in the preparation of a water-retaining agent for agricultural or forestry soil.

[0024] Compared with the prior art, the present invention has the following beneficial effects: By carrying out a crosslinking reaction with polyglutamic acid, polyaspartic acid and acrylic acid, the present invention can enhance the strength of the water-absorbing resin, slow down the degradation rate of the water-absorbing resin in the soil, extend the service time of the water-absorbing resin, and the obtained composite polyamino acid-based water-absorbing resin not only reduces the raw material cost but also improves the product performance.

[0025] In the preparation process of the composite water-absorbing resin of the present invention, the mixed molecular structure can form a relatively stable crosslinked network structure, which shows excellent stability in multiple water absorption-dehydration cycles, effectively reducing the performance degradation caused by repeated use. Therefore, the composite water-absorbing resin of the present invention has good durability, can be reused multiple times, reduces the use cost, and improves the economic benefit.

[0026] The polyamino acid-based water-absorbing resin of the present invention has good biodegradability, avoiding the environmental pollution problem of traditional petroleum-based resins (such as polyacrylates). After being used in the soil, it can be naturally decomposed within a certain time, without polluting the soil, and the composite polyamino acid-based water-absorbing resin can be degraded into monomeric amino acids or nitrogen-containing organic compounds, which can be absorbed and utilized by plants, meeting the requirements of green agriculture and sustainable development. This environmentally friendly characteristic makes it have broad application prospects in the fields of ecological restoration and soil improvement.

[0027] The polyamino acid-based superabsorbent resin of the present invention can significantly increase the liquid absorption and swelling rate of the superabsorbent resin by compounding polyglutamic acid and polyaspartic acid and copolymerizing with acrylic acid. It is expected to further optimize the performance of the superabsorbent resin on the basis of the existing technology, meet the requirements of different application scenarios, and provide new technical support for the development of related fields. Detailed implementation manners

[0028] The present invention will be described below through specific examples to make the technical solutions of the present invention easier to understand and master. However, the present invention is not limited thereto. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0029] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. Unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" as used herein include both singular and plural referents. Numerical ranges expressed by endpoints include all values and fractions within the corresponding ranges, as well as the expressed endpoints.

[0030] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0031] Sources of experimental materials: Acrylic acid was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd., with a CAS number of 79-10-7; Polyglutamic acid with a molecular weight of 700,000 - 1,100,000 was purchased from Shandong Freda Biotechnology Co., Ltd., with a production batch number of 20240601 and a purity of 92.3%; Polyglutamic acid with a molecular weight of 50,000 - 100,000 was purchased from Shandong Freda Biotechnology Co., Ltd., with a production batch number of 20240115 and a purity of 92.3%; Agricultural polyglutamic acid was purchased from Shandong Freda Biotechnology Co., Ltd., with a production batch number of 20231210, a purity of 35%, and a molecular weight of 600,000 - 700,000 daltons; Polyaspartic acid with a molecular weight of 10,000: purchased from Hebei Xietong Chemical Co., Ltd., with a production batch number of 20231222; Polyaspartic acid with a molecular weight of 15,000: Purchased from Hebei Xietong Chemical Co., Ltd., production batch number 20231009; Diazomethylenebisacrylamide (MBA) was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd., CAS number 110-26-9; Potassium persulfate: Purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd., CAS number 7727-21-1; 1,4-Butanediol diglycidyl ether CAS number 2425-79-8.

[0032] Example 1 (1) Take 1 g of polyglutamic acid with a molecular weight of 700,000 - 1,100,000 and 2 g of polyaspartic acid with a molecular weight of 10,000, dissolve them in 50 mL of aqueous solution and mix well to obtain a mixed solution A; (2) Take 20 mL of acrylic acid in a beaker, slowly add 42.04 mL of 5 mol / L NaOH solution, place the beaker in an ice-water solution and stir rapidly to obtain solution B; (3) Add solution A to solution B and stir well, then keep it at 80 °C in a water bath. Add 0.03 g of cross-linking agent (diazomethylenebisacrylamide (MBA)) and 0.21 g of initiator (potassium persulfate) to the mixed solution of A and B and stir rapidly. After a period of time, they start to cross-link, and then a stable gel-like substance is formed. The obtained gel-like substance continues to cross-link in the water bath for 3 h to obtain the product composite polyamino acid type superabsorbent resin. Cut the product into squares with an area of 0.5 cm × 0.5 cm with scissors, and place them in absolute ethanol for dehydration and removal of other unreacted substances. Then place them in a drying oven at 80 °C for 48 h and crush them into powder with a pulverizer.

[0033] Detection method: Weigh 1 g of the synthesized superabsorbent resin powder and place it in an excess of pure water or 0.9% sodium chloride solution (brine) for liquid absorption. After stabilization, weigh the mass of the superabsorbent resin, which is the liquid absorption ratio of the superabsorbent resin in pure water or brine. After the superabsorbent resin absorbs water, dry it in an oven at 60 °C, then dry it again after absorbing water. Repeat six times, and it is the liquid absorption ratio after 6 repeated uses.

[0034] According to the above detection method, detect the liquid absorption ratios of the composite polyamino acid type superabsorbent resin in Example 1 and other composite polyamino acid type superabsorbent resins in pure water and brine, and test the liquid absorption ratio of 6 repeated water absorptions in pure water. (The difference in the preparation methods of other composite polyamino acid type superabsorbent resins and the composite polyamino acid type superabsorbent resin in Example 1 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 1 specifically).

[0035] Table 1 Comparison of the performance of Example 1 and other composite polyamino acid type superabsorbent resins

[0036] Example 2 The difference from Example 1 is only that: in step (1), the mass of polyglutamic acid is 2 g, the mass of polyaspartic acid is 1 g, and other steps are the same as those in Example 1.

[0037] The product was cut into squares with an area of 0.5 cm × 0.5 cm with scissors and placed in absolute ethanol for dehydration and removal of other unreacted substances. Then it was placed in a drying oven and dried for 48 h at a temperature of 80 °C, and then pulverized into powder with a pulverizer. According to the detection method described in Example 1, the liquid absorption ratios of the composite polyamino acid type water-absorbing resin of Example 2 and other composite polyamino acid type water-absorbing resins in pure water and saline were tested, and the liquid absorption ratios of 6 repeated water absorptions in pure water were also tested. (The difference in the preparation methods of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Example 2 is only the different molecular weights of polyglutamic acid or polyaspartic acid, as shown in Table 2 specifically).

[0038] Table 2 Comparison table of the performance of Example 2 and other composite polyamino acid type water-absorbing resins

[0039] Example 3 The difference from Example 1 is only that: in step (1), the mass of polyglutamic acid is 0.5 g, the mass of polyaspartic acid is 0.5 g; in step (3), the mass of the cross-linking agent is 0.025 g, and the mass of the initiator is 0.19 g, and other steps are the same as those in Example 1.

[0040] The product was cut into squares with an area of 0.5 cm × 0.5 cm with scissors and placed in absolute ethanol for dehydration and removal of other unreacted substances. Then it was placed in a drying oven and dried for 48 h at a temperature of 80 °C, and then pulverized into powder with a pulverizer. According to the detection method described in Example 1, the liquid absorption ratios of the composite polyamino acid type water-absorbing resin of Example 3 and other composite polyamino acid type water-absorbing resins in pure water and saline were tested, and the liquid absorption ratios of 6 repeated water absorptions in pure water were also tested. (The difference in the preparation methods of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Example 3 is only the different molecular weights of polyglutamic acid or polyaspartic acid, as shown in Table 3 specifically).

[0041] Table 3 Comparison table of the performance of Example 3 and other composite polyamino acid type water-absorbing resins

[0042] Example 4 The difference from Example 1 is only that: in step (1), the mass of polyglutamic acid is 2 g and the mass of polyaspartic acid is 3 g; in step (3), the mass of the crosslinking agent is 0.035 g and the mass of the initiator is 0.25 g, and other steps are the same as those in Example 1.

[0043] Cut the product into squares with an area of 0.5 cm × 0.5 cm with scissors, and place it in absolute ethanol for dehydration and removal of other unreacted substances. Then place it in a drying oven and dry for 48 h at a temperature of 80 °C, and crush it into powder with a pulverizer. Test the liquid absorption ratio of the composite polyamino acid type water-absorbing resin of Example 4 and other composite polyamino acid type water-absorbing resins in pure water and salt water, and test the liquid absorption ratio of 6 repeated water absorptions in pure water according to the detection method described in Example 1. (The difference in the preparation method of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Example 4 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 4 specifically).

[0044] Table 4 Performance comparison table of Example 4 and other composite polyamino acid type water-absorbing resins

[0045] Example 5 The difference from Example 1 is only that: in step (1), the mass of polyglutamic acid is 3 g and the mass of polyaspartic acid is 2 g; in step (3), the mass of the crosslinking agent is 0.035 g and the mass of the initiator is 0.25 g, and other steps are the same as those in Example 1.

[0046] Cut the product into squares with an area of 0.5 cm × 0.5 cm with scissors, and place it in absolute ethanol for dehydration and removal of other unreacted substances. Then place it in a drying oven and dry for 48 h at a temperature of 80 °C, and crush it into powder with a pulverizer. Test the liquid absorption ratio of the composite polyamino acid type water-absorbing resin of Example 5 and other composite polyamino acid type water-absorbing resins in pure water and salt water, and test the liquid absorption ratio of 6 repeated water absorptions in pure water according to the detection method described in Example 1. (The difference in the preparation method of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Example 5 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 5 specifically).

[0047] Table 5 Performance comparison table of Example 5 and other composite polyamino acid type water-absorbing resins

[0048] Comparative Example 1 (1) Take 1 g of polyglutamic acid with a molecular mass of 700,000 - 1,100,000 and 2 g of polyaspartic acid with a molecular mass of 10,000, dissolve them in 50 mL of aqueous solution and mix evenly to obtain a mixed solution; (2) Keep the mixed solution A in a water bath at 80 °C. Add 0.9 g of crosslinking agent (ethylene glycol diglycidyl ether) to the mixed solution A and stir quickly until evenly mixed. After a period of time, the crosslinking reaction starts between the two, and then a stable gel-like substance is formed. The obtained gel-like substance continues to crosslink in the water bath for 3 h to obtain the product composite polyamino acid type water-absorbing resin.

[0049] Cut the product into squares with an area of 0.5 cm × 0.5 cm using scissors, and place them in absolute ethanol for dehydration and removal of other unreacted substances. Then place them in a drying oven and dry for 48 h at a temperature of 80 °C, and crush them into powder using a pulverizer. Test the liquid absorption ratios of the composite polyamino acid type water-absorbing resin of Comparative Example 1 and other composite polyamino acid type water-absorbing resins in pure water and saline, and test the liquid absorption ratios of 6 repeated water absorptions in pure water according to the detection method described in Example 1. (The difference in the preparation methods of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Comparative Example 1 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 6 specifically).

[0050] Table 6 Comparison table of the performance of the composite polyamino acid type water-absorbing resin of Comparative Example 1 and other composite polyamino acid type water-absorbing resins

[0051] It can be seen from Table 6 that the composite polyamino acid type water-absorbing resin in Comparative Example 1 no longer has the performance of repeated water absorption after 6 repeated uses. And during the preparation process of using agricultural polyglutamic acid, it failed to crosslink effectively with the crosslinking agent and could not form a gel-like water-absorbing resin, so the subsequent detection of the liquid absorption ratio could not be carried out.

[0052] Comparative Example 2 Compared with Example 1, the difference is only that: the crosslinking agent in step (3) is 1,4-butanediol diglycidyl ether, and other steps are the same as those in Example 1.

[0053] Test the liquid absorption ratios of the composite polyamino acid type water-absorbing resin of Comparative Example 2 and other composite polyamino acid type water-absorbing resins in pure water and saline, and test the liquid absorption ratios of 6 repeated water absorptions in pure water according to the detection method of Example 1. (The difference in the preparation methods of other composite polyamino acid type water-absorbing resins and the composite polyamino acid type water-absorbing resin of Comparative Example 2 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 7 specifically).

[0054] Table 7 Comparison table of the performance of the composite polyamino acid type water-absorbing resin of Comparative Example 2 and other composite polyamino acid type water-absorbing resins

[0055] As can be seen from Table 7, the liquid absorption ratio of the composite polyamino acid-based superabsorbent resin in Comparative Example 2 is relatively low, and the performance of repeated water absorption after 6 repeated uses is also relatively low. Moreover, for the superabsorbent resin prepared using agricultural polyglutamic acid, after 6 repeated uses, the structure of the superabsorbent resin has dispersed and it no longer has the ability to absorb liquid.

[0056] Comparative Example 3 Compared with Example 1, the only difference is that: the content of the cross-linking agent in step (3) is 0.05 g, and the other steps are the same as those in Example 1.

[0057] According to the detection method of Example 1, the liquid absorption ratios of the composite polyamino acid-based superabsorbent resin in Comparative Example 3 and other composite polyamino acid-based superabsorbent resins in pure water and salt water were detected, as well as the liquid absorption ratio of repeated water absorption 6 times in pure water was tested. (The difference in the preparation methods of other composite polyamino acid-based superabsorbent resins and the composite polyamino acid-based superabsorbent resin in Comparative Example 3 is only the molecular weight of polyglutamic acid or polyaspartic acid, as shown in Table 8 specifically).

[0058] Table 8 Comparison table of the performance of Comparative Example 3 and other composite polyamino acid-based superabsorbent resins

[0059] As can be seen from Table 8, the liquid absorption ratio of the composite polyamino acid-based superabsorbent resin in Comparative Example 3 is relatively low, and the performance of repeated water absorption after 6 repeated uses is also relatively low. This is mainly because when the content of the cross-linking agent is too high, it causes excessive cross-linking of the superabsorbent resin, and the smaller mesh of the superabsorbent resin results in a lower liquid absorption ratio.

[0060] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A preparation method of a composite polyamino acid-based water-absorbing resin for agriculture and forestry, characterized in that: An agricultural and forestry composite polyamino acid superabsorbent resin is prepared by crosslinking polyglutamic acid, polyaspartic acid, acrylic acid, a crosslinking agent and an initiator; The crosslinking agent is selected from at least one of diazomethylenebisacrylamide, polyethylene glycol diacrylate and ethylene glycol dimethacrylate; the polyglutamic acid is any one of polyglutamic acid A, polyglutamic acid B and agricultural polyglutamic acid; the molecular weight of the polyglutamic acid A is 700,000 - 1,100,000 daltons and the purity is 90% - 100%; the molecular weight of the polyglutamic acid B is 50,000 - 100,000 daltons and the purity is 90% - 100%; the molecular weight of the agricultural polyglutamic acid is 600,000 - 700,000 daltons and the purity is 35% ± 10%; the molecular weight of the polyaspartic acid is 10,000 daltons or 15,000 daltons; the volume-to-mass ratio of the acrylic acid to the crosslinking agent is 1 mL: 0.00125 g - 0.00175 g.

2. The preparation method according to claim 1, wherein: The mass ratio of the polyglutamic acid to the polyaspartic acid is 1:2 - 2:

1.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the polyglutamic acid to the polyaspartic acid is 1:

2.

4. The preparation method according to claim 1, characterized in that: The neutralization degree of the acrylic acid is 70% - 90%.

5. The preparation method according to claim 1, wherein: The initiator is selected from at least one of potassium persulfate, sodium persulfate and ammonium persulfate; the crosslinking agent is diazomethylenebisacrylamide.

6. The preparation method according to claim 5, characterized in that: The initiator is potassium persulfate.

7. A composite polyamino acid superabsorbent resin prepared by the preparation method according to any one of claims 1 - 6.

8. Use of the composite polyamino acid superabsorbent resin according to claim 7 in the preparation of a water retainer for agricultural or forestry soil.

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