A cellulose-based superabsorbent polymer for tropical crops, its preparation method and application

Abstract

This invention proposes a tropical crop cellulose-based superabsorbent polymer, its preparation method, and its application, belonging to the field of polymer materials technology. By combining tropical crop cellulose and gum arabic with a crosslinking agent to form a cellulose-gum composite aerogel with a covalently crosslinked structure, the composite aerogel is then subjected to allyl functionalization graft modification to obtain an allylated composite aerogel. This allylated composite aerogel is then subjected to a synergistic copolymerization reaction with a crosslinking agent and monomers to prepare a tropical crop cellulose-based superabsorbent polymer that possesses both high water absorption and a stable three-dimensional network structure. This overcomes the defect of traditional superabsorbent materials whose structure easily collapses after water absorption. Furthermore, this invention uses abundant tropical crop fibers as raw materials, and the preparation process is simple and easy to operate, making it applicable to the preparation of agricultural and forestry water-retaining materials or food preservation materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a tropical crop cellulose-based superabsorbent polymer, its preparation method and application. Background Technology

[0002] Traditional superabsorbent polymers (such as polyacrylic acid polymers and polyvinyl alcohol) have broad application prospects in medical and health, agricultural and forestry production, and food preservation fields due to their strong water absorption properties and repeated water absorption capacity. While the production technology for single superabsorbent polymers is relatively mature, the range of raw material choices is limited, and the continuously rising prices of chemical raw materials such as acrylic acid result in high production costs, expensive products, slow promotion and application, and long-term use also poses problems such as non-degradability and environmental pollution.

[0003] Cellulose-based superabsorbent polymers have seen rapid development in recent years. This is due to two main factors: firstly, cellulose is a hydrophilic polyhydroxy compound; secondly, cellulose is a fibrous material with numerous capillaries and a large specific surface area, resulting in excellent water absorption and biocompatibility. Cellulose is an abundant renewable resource in nature and a natural polysaccharide. Utilizing cellulose grafting to prepare superabsorbent materials aligns with environmental protection and sustainable development principles. Cellulose-based superabsorbent materials are biodegradable after long-term use, causing no environmental pollution. However, current cellulose-based superabsorbent materials mostly use wood or crop straw as cellulose raw materials, and the efficient utilization of tropical crop fibers (such as pineapple leaf fiber and sisal fiber) is insufficient. Furthermore, they still suffer from low water absorption and relatively low mechanical strength, making them unsuitable for applications requiring high material strength. For example, patent application CN 112592431 A describes the preparation of a cellulose-grafted acrylic-based superabsorbent hydrogel. However, its preparation process requires a specific atmosphere reaction apparatus and has relatively strict preparation conditions. Furthermore, the resulting superabsorbent hydrogel has a water absorption capacity of only 229.5%, indicating poor polymer water absorption performance. Therefore, although tropical crop fiber resources are abundant, existing technologies are insufficient for cellulose extraction and functional modification, especially lacking targeted design for applications in agricultural and forestry water conservation. Developing cellulose superabsorbent materials based on tropical plant fibers can not only solve the environmental defects of traditional synthetic polymeric superabsorbent materials but also achieve high-value utilization of tropical agricultural resources.

[0004] Therefore, developing a cellulose-based superabsorbent material for tropical crops with high water absorption and good mechanical properties has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a tropical crop cellulose-based superabsorbent polymer, its preparation method, and its applications. This invention employs covalent cross-linking technology, first forming a cross-linked aerogel with peach gum, then modifying the aerogel with allyl functionalization grafting. Through the synergistic copolymerization of the cross-linking agent and monomers, a tropical crop cellulose-based superabsorbent polymer with a network structure possessing both high water absorption and mechanical strength is constructed, overcoming the defect of traditional superabsorbent materials whose structure easily collapses after water absorption. The superabsorbent polymer prepared by this invention contains a cross-linked aerogel structure, which not only gives it a high water absorption ratio and a structure that is not easily collapsed, but also endows the material with superior water retention properties, resulting in a wide range of applications. Furthermore, the preparation method of the tropical crop cellulose-based superabsorbent polymer of this invention is simple.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of the present invention:

[0008] A method for preparing a tropical crop cellulose-based superabsorbent polymer involves forming a cellulose-peach gum composite aerogel with a covalent cross-linked structure by combining tropical crop cellulose and peach gum under the action of a glycerol ether cross-linking agent; subjecting the cellulose-peach gum composite aerogel to allyl functionalization graft modification to obtain an allylated composite aerogel; and then subjecting the allylated composite aerogel to a synergistic copolymerization reaction with an acrylate cross-linking agent and monomers to prepare the tropical crop cellulose-based superabsorbent polymer.

[0009] Furthermore, the preparation method of the tropical crop cellulose-based superabsorbent polymer includes the following steps:

[0010] (1) After dispersing tropical crop cellulose and peach gum in water, the mixture is heated in a water bath and the pH is adjusted to alkaline. The glycerol ether crosslinking agent is added and stirred to react. The reaction product is then freeze-dried to obtain the cellulose-peach gum composite aerogel.

[0011] (2) The cellulose-peach gum composite aerogel was pulverized, dispersed with NaOH solution, and an allyl compound containing an epoxy group was added. The reaction was stirred to obtain an allylated composite aerogel.

[0012] (3) The allylated composite aerogel is dispersed in water, heated in a water bath, and an initiator, monomer solution, and acrylate crosslinking agent are added in sequence to react and obtain a gel product. The gel product is washed and dried to obtain the tropical crop cellulose-based superabsorbent polymer.

[0013] Preferably, in step (1), the tropical crop cellulose is extracted from pineapple leaf fiber and / or sisal fiber, and the specific preparation method is as follows:

[0014] The raw fibers (pineapple leaf fibers and / or sisal fibers) were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment, stirred at 80°C for 3 hours, filtered and washed three times with distilled water, then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0015] Preferably, in step (1), the mass ratio of the tropical crop cellulose, gum arabic, and glycerol ether crosslinking agent is (1-1.8):(0.2-1):(0.02-0.2); and / or,

[0016] The glycerol ether crosslinking agent is one or more of ethylene glycol diglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0017] Preferably, in step (1), the pH is adjusted to 11 using NaOH; and / or,

[0018] The stirring reaction is carried out at a temperature of 50°C for 1-4 hours; and / or,

[0019] The freeze-drying process involves freezing the reaction product at -80°C for 24 hours, followed by vacuum freeze-drying for 48 hours.

[0020] Preferably, in step (2), the cellulose-gum composite aerogel is pulverized to an average particle size of 2-5 mm; and / or,

[0021] The ratio of the cellulose-gum composite aerogel, NaOH solution, and epoxy-containing allyl compound is 2g:100mL:0.5g.

[0022] Preferably, in step (2), the epoxy-containing allyl compound is allyl glycidyl ether, glycidyl acrylate, or glycidyl methacrylate; and / or,

[0023] The concentration of the NaOH solution was 40 wt.%.

[0024] Preferably, in step (3), the initiator is one or more of ammonium persulfate, potassium persulfate, and sodium persulfate; and / or,

[0025] The acrylate crosslinking agent is one or more of ethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, and 1,6-hexanediol dimethacrylate; and / or,

[0026] The monomer in the monomer solution is acrylic acid, which exists in the form of an acrylic acid solution during the preparation process. The concentration of the acrylic acid solution is 0.125 g / mL, and the temperature is 0°C; and / or,

[0027] The ratio of the allylated composite aerogel, initiator, monomer solution and acrylate crosslinking agent is 1g:(0.025-0.05)g:40mL:(0.015-0.025)g.

[0028] Preferably, in step (3), the allylated composite aerogel obtained in step (2) is dispersed in water, an initiator is added and nitrogen gas is introduced and stirred at room temperature for 10 minutes, then a monomer solution is added, heated to 60°C and stirred for 15 minutes, then an acrylate crosslinking agent is added and stirred for 2-4 hours to obtain a gel-like product.

[0029] The second technical solution of the present invention:

[0030] A tropical crop cellulose-based superabsorbent polymer was prepared according to the preparation method described above.

[0031] The third technical solution of the present invention:

[0032] Applications of the tropical crop cellulose-based superabsorbent polymer in the preparation of agricultural and forestry water-retaining materials or food preservation materials.

[0033] Preferably, in the field of agricultural and forestry water conservation, cellulose-based superabsorbent polymers for tropical crops can be used as water-retaining agents for agricultural and forestry soils.

[0034] Preferably, in the field of food preservation, the tropical crop cellulose-based superabsorbent polymer can be used as a coating preservation material, such as a lychee coating preservation material. When used as a coating preservation material, the powdered tropical crop cellulose-based superabsorbent polymer needs to be formulated into a uniform coating liquid for use. The concentration of the coating liquid can be 2g / L, 5g / L, 8g / L or 10g / L.

[0035] Compared with the prior art, the present invention has the following advantages and technical effects:

[0036] (1) This invention employs covalent cross-linking technology to form a cross-linked aerogel from tropical crop cellulose and gum arabic. In an alkaline environment, the epoxy groups of diglycidyl ether undergo ring-opening reactions with the abundant hydroxyl groups in cellulose and gum arabic, forming stable covalent ether bonds. This cross-linking structure increases the mechanical strength and structural stability of the aerogel. Subsequently, the composite aerogel is modified by allyl functionalization grafting. Utilizing the characteristic that allyl compounds containing epoxy groups have two active groups, the ring-opening reaction of the epoxy groups is grafted onto the composite aerogel structure, endowing the composite aerogel with allyl cross-linking reactivity. Then, through the synergistic copolymerization reaction of the allylated composite aerogel, cross-linking agent, and monomer, a tropical crop cellulose-based superabsorbent polymer with both high water absorption and a stable three-dimensional network structure is prepared, overcoming the defect of traditional superabsorbent materials whose structure easily collapses after water absorption.

[0037] (2) This invention uses abundant tropical crop fibers as raw materials, and the preparation process is simple and easy to operate. The obtained tropical crop cellulose-based superabsorbent polymer superabsorbent material has excellent water absorption performance and high mechanical strength, and can be applied to the fields of soil water retention in agriculture and forestry or food preservation. Attached Figure Description

[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0039] Figure 1 The images show the FT-IR spectra of tropical crop cellulose, tropical crop cellulose-based superabsorbent polymer, and superabsorbent polymer prepared in Example 1, where a is tropical crop cellulose; b is superabsorbent polymer of Comparative Example 1; and c is superabsorbent polymer based on tropical crop cellulose of Example 1.

[0040] Figure 2 SEM image of the tropical crop cellulose-based superabsorbent polymer prepared in Example 1;

[0041] Figure 3 Thermogravimetric (TG) curves of the water-absorbing polymer samples prepared in Example 1 and Comparative Example 1;

[0042] Figure 4 The results of water absorption performance tests on the water-absorbing polymer samples of the examples and comparative examples are shown.

[0043] Figure 5 The results of water retention performance tests on the water-absorbing polymer samples of the examples and comparative examples are shown.

[0044] Figure 6 The results of the compressive strength test of the water-absorbing polymer samples in the examples and comparative examples are shown. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0049] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0050] This invention proposes a method for preparing a tropical crop cellulose-based superabsorbent polymer. Tropical crop cellulose and gum arabic are reacted with a glycerol ether crosslinking agent to form a cellulose-gum composite aerogel with a covalent crosslinking structure. The aerogel is then subjected to allyl functionalization graft modification to obtain an allylated composite aerogel. The allylated composite aerogel is then subjected to a synergistic copolymerization reaction with an acrylate crosslinking agent and monomers to prepare the tropical crop cellulose-based superabsorbent polymer.

[0051] In this embodiment of the invention, the preparation method of the tropical crop cellulose-based superabsorbent polymer includes the following steps:

[0052] (1) After dispersing tropical crop cellulose and peach gum in water, the mixture is heated in a water bath and the pH is adjusted to alkaline. The glycerol ether crosslinking agent is added and stirred to react. The reaction product is then freeze-dried to obtain the cellulose-peach gum composite aerogel.

[0053] (2) The cellulose-peach gum composite aerogel was pulverized, dispersed with NaOH solution, and an allyl compound containing an epoxy group was added. The reaction was stirred to obtain an allylated composite aerogel.

[0054] (3) The allylated composite aerogel is dispersed in water, heated in a water bath, and an initiator, monomer, and acrylate crosslinking agent are added in sequence to react and obtain a gel-like product. The gel-like product is washed and dried to obtain the tropical crop cellulose-based superabsorbent polymer.

[0055] In step (1) of the preferred embodiment of the present invention, the tropical crop cellulose is extracted from pineapple leaf fiber and / or sisal fiber, and the specific preparation method is as follows:

[0056] The raw fibers (pineapple leaf fibers and / or sisal fibers) were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment, stirred at 80°C for 3 hours, filtered and washed three times with distilled water, then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0057] In step (1) of the preferred embodiment of the present invention, the mass ratio of tropical crop cellulose, gum arabic, and glycerol ether crosslinking agent is (1-1.8):(0.2-1):(0.02-0.2); and / or,

[0058] The glycerol ether crosslinking agent is one or more of ethylene glycol diglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether.

[0059] Preferably, in step (1), the pH is adjusted to 11 using NaOH; and / or,

[0060] The stirring reaction is carried out at a temperature of 50°C for 1-4 hours; and / or,

[0061] Freeze-drying involves freezing the reaction product at -80°C for 24 hours, followed by vacuum freeze-drying for 48 hours.

[0062] In step (2) of the preferred embodiment of the present invention, the cellulose-gum composite aerogel is pulverized to an average particle size of 2-5 mm; and / or,

[0063] The ratio of cellulose-gum composite aerogel, NaOH solution, and epoxy-containing allyl compound is 2g:100mL:0.5g.

[0064] In step (2) of the preferred embodiment of the present invention, the epoxy-containing allyl compound is allyl glycidyl ether, glycidyl acrylate, or glycidyl methacrylate; and / or,

[0065] The concentration of the NaOH solution is 40 wt.%.

[0066] In step (3) of the preferred embodiment of the present invention, the initiator is one or more of ammonium persulfate, potassium persulfate, and sodium persulfate; and / or,

[0067] The acrylate crosslinking agent is one or more of ethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, and 1,6-hexanediol dimethacrylate; and / or,

[0068] The monomer is acrylic acid, which exists in the form of an acrylic acid solution during preparation. The concentration of the acrylic acid solution is 0.125 g / mL, and the temperature is 0℃; and / or,

[0069] The ratio of allylated composite aerogel, initiator, acrylic solution and acrylate crosslinking agent is 1g:(0.025-0.05)g:40mL:(0.015-0.025)g.

[0070] In step (3) of the preferred embodiment of the present invention, the allylated composite aerogel obtained in step (2) is dispersed in water, an initiator is added and nitrogen gas is introduced and stirred at room temperature for 10 minutes, then an acrylic acid solution is added, heated to 60°C and stirred for 15 minutes, then an acrylate crosslinking agent is added and stirred for 2-4 hours to obtain a gel-like product.

[0071] For example, the tropical crop cellulose-based superabsorbent polymer in this embodiment of the invention specifically includes the following steps:

[0072] (1) Cut the raw fibers (pineapple leaf fibers and / or sisal fibers, including but not limited to the above fibers) into small segments with an average size of 1 mm. Add the powdered material to a 4% NaOH solution for alkali treatment. Stir at 80°C for 3 hours. Then filter and wash with distilled water 3 times. Bleach with sodium hypochlorite. Stir at 70°C for 2 hours. Filter and wash 3 times. Dry at 50°C to obtain powdered tropical crop cellulose.

[0073] (2) Take 1-1.8g of tropical crop cellulose obtained in step (1) and 0.2-1g of peach gum, dissolve them separately in 50mL of water, and after complete dispersion and dissolution, mix the two in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.02-0.2g of glycerol ether crosslinking agent (one or more of ethylene glycol diglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether), stir the reaction for 1-4 hours, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0074] (3) The cellulose-gum composite aerogel obtained in step (2) is crushed into particles with an average particle size of 2-5 mm. 2 g of the crushed cellulose-gum composite aerogel is dispersed in 100 mL of NaOH solution (40 wt%) and stirred in a 50 °C water bath for 30 minutes. Then, 0.5 g of an epoxy-containing allyl compound (allyl glycidyl ether, glycidyl acrylate or glycidyl methacrylate) is added and stirred for 1 hour. After filtration and drying, the allylated composite aerogel is obtained.

[0075] (4) Take 1g of the allylated composite aerogel obtained in step (3) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.025-0.05g of initiator (one or more of ammonium persulfate, potassium persulfate, and sodium persulfate). Purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid with a neutralization degree of 75%) at 0℃. Heat to 60℃ and stir for 15 minutes. Then add 0.015-0.025g of acrylate crosslinking agent (ethylene glycol). The product is prepared by stirring for 2-4 hours to obtain a gel-like product. The product is then removed, cut into pieces, and immersed in anhydrous ethanol for 8 hours to remove unreacted monomers. The product is then dried in a 50°C oven to obtain a tropical crop cellulose-based superabsorbent polymer.

[0076] In step (2) of the preparation process of the tropical crop cellulose-based superabsorbent polymer of the present invention, taking 1,4-butanediol diglycidyl ether as the crosslinking agent as an example, the tropical crop cellulose and peach gum are crosslinked to form an aerogel with a crosslinked structure using covalent crosslinking technology. In an alkaline environment, the epoxy groups of diglycidyl ether open and react with the abundant hydroxyl groups in cellulose and peach gum respectively to form stable covalent ether bonds. This crosslinking structure can increase the mechanical strength and structural stability of the aerogel. The crosslinking structure of the obtained cellulose-peach gum composite aerogel is shown below:

[0077]

[0078] Wherein, R1 is the structural formula of tropical crop cellulose, with n ranging from 100 to 500; R2 is the structural formula of gum arabic, with m ranging from 100 to 200, n ranging from 30 to 50, o ranging from 100 to 200, and p ranging from 10 to 50; R3 is an open-ring 1,4-butanediol diglycidyl ether. When the crosslinking agent is glycerol diglycidyl ether, ethylene glycol diglycidyl ether, or 1,6-hexanediol diglycidyl ether, R3 is replaced by an open-ring glycerol diglycidyl ether, ethylene glycol diglycidyl ether, or 1,6-hexanediol diglycidyl ether.

[0079] In step (3) of the preparation process of the tropical crop cellulose-based superabsorbent polymer of the present invention, the composite aerogel is modified by allyl functionalization grafting. Taking allyl glycidyl ether as an example, the allyl compound containing epoxy groups is grafted onto the composite aerogel structure by the ring-opening reaction of the epoxy group, which in turn endows the composite aerogel with allyl crosslinking activity. The structural schematic of the resulting allylated composite aerogel is shown below:

[0080]

[0081] Wherein, R4 is an open-ring allyl glycidyl ether. When the epoxy-containing allyl compound is glycidyl acrylate or glycidyl methacrylate, R4 is replaced by an open-ring glycidyl acrylate or glycidyl methacrylate.

[0082] In step (4) of the preparation process of the tropical crop cellulose-based superabsorbent polymer of the present invention, the structure of the tropical crop cellulose-based superabsorbent polymer with both high water absorption and stable three-dimensional network structure is prepared by the synergistic copolymerization reaction of allylated composite aerogel, crosslinking agent and monomer, taking 1,4-butanediol dimethacrylate as the crosslinking agent as an example:

[0083]

[0084] in, The allylated composite aerogel long chain or polyacrylic acid long chain obtained in step (3), wherein the polyacrylic acid structural formula is n = 200-2000; R5 is 1,4-butanediol dimethacrylate. When the crosslinking agent is ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol dimethacrylate, or 1,6-hexanediol dimethacrylate, R5 is replaced by ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol dimethacrylate, or 1,6-hexanediol dimethacrylate.

[0085] This invention also proposes a tropical crop cellulose-based superabsorbent polymer, which is prepared according to the above preparation method.

[0086] The tropical crop cellulose-based superabsorbent polymer prepared in the embodiments of the present invention can be used in the field of agricultural and forestry water conservation, for example, as a soil water-retaining agent or a coating preservation material.

[0087] The technical solution of the present invention will be further illustrated by the following embodiments.

[0088] Example 1

[0089] A method for preparing a tropical crop cellulose-based superabsorbent polymer specifically includes the following steps:

[0090] (1) Pineapple leaf fibers were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment. The mixture was stirred at 80°C for 3 hours, then filtered and washed three times with distilled water. The mixture was then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0091] (2) Take 1.2g of tropical crop cellulose obtained in step (1) and 0.8g of peach gum, dissolve them separately in 50mL of water, and after they are completely dispersed and dissolved, mix them in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.02g of crosslinking agent 1,4-butanediol diglycidyl ether, stir and react for 2 hours, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze-dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0092] (3) The cellulose-gum composite aerogel obtained in step (2) is crushed into particles with an average particle size of 2-5 mm. 2 g of the crushed cellulose-gum composite aerogel is dispersed in 100 mL of NaOH solution (40 wt%), stirred in a 50 °C water bath for 30 minutes, and then 0.5 g of allyl glycidyl ether is added. The mixture is stirred and reacted for 1 hour. After filtration and drying, allylated composite aerogel is obtained.

[0093] (4) Take 1g of the allylated composite aerogel obtained in step (3) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.025g of initiator ammonium persulfate, purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid and a neutralization degree of 75%) at 0℃. Heat to 60℃ and stir for 15 minutes. Then add 0.015g of crosslinking agent ethylene glycol dimethacrylate and continue stirring for 4 hours to obtain a gel-like product. Take out the product and cut it into pieces. Soak it in anhydrous ethanol for 8 hours to remove unreacted monomers. Place it in a 50℃ oven to dry and obtain a tropical crop cellulose-based superabsorbent polymer.

[0094] Example 2

[0095] A method for preparing a tropical crop cellulose-based superabsorbent polymer specifically includes the following steps:

[0096] (1) After cutting the sisal fiber into short pieces with an average size of 1 mm, the powder was added to a 4% NaOH solution for alkali treatment. The mixture was stirred at 80°C for 3 hours, then filtered and washed three times with distilled water. The mixture was then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0097] (2) Take 1g of tropical crop cellulose obtained in step (1) and 1g of peach gum, dissolve them separately in 50mL of water, and after they are completely dispersed and dissolved, mix them in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.1g of crosslinking agent ethylene glycol diglycidyl ether, stir and react for 4 hours, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze-dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0098] (3) The cellulose-gum composite aerogel obtained in step (2) is crushed into particles with an average particle size of 2-5 mm. 2 g of the crushed cellulose-gum composite aerogel is dispersed in 100 mL of NaOH solution (40 wt%), stirred in a 50 °C water bath for 30 minutes, and then 0.5 g of glycidyl methacrylate is added. The mixture is stirred and reacted for 1 hour. After filtration and drying, allylated composite aerogel is obtained.

[0099] (4) Take 1g of the allylated composite aerogel obtained in step (3) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.03g of potassium persulfate initiator, purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid and 75% neutralization) at 0℃. Heat to 60℃ and stir for 15 minutes. Add 0.02g of crosslinking agent 1,4-butanediol diacrylate and continue stirring for 3 hours to obtain a gel-like product. Take out the product and cut it into pieces. Soak it in anhydrous ethanol for 8 hours to remove unreacted monomers. Place it in a 50℃ oven to dry and obtain a tropical crop cellulose-based superabsorbent polymer.

[0100] Example 3

[0101] A method for preparing a tropical crop cellulose-based superabsorbent polymer specifically includes the following steps:

[0102] (1) Pineapple leaf fibers were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment. The mixture was stirred at 80°C for 3 hours, then filtered and washed three times with distilled water. The mixture was then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0103] (2) Take 1.5g of tropical crop cellulose obtained in step (1) and 0.5g of peach gum, dissolve them separately in 50mL of water, and after they are completely dispersed and dissolved, mix them in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.12g of crosslinking agent ethylene glycol diglycidyl ether, stir and react for 2 hours, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze-dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0104] (3) The cellulose-gum composite aerogel obtained in step (2) is crushed into particles with an average particle size of 2-5 mm. 2 g of the crushed cellulose-gum composite aerogel is dispersed in 100 mL of NaOH solution (40 wt%), stirred in a 50 °C water bath for 30 minutes, and then 0.5 g of glycidyl acrylate is added. The mixture is stirred and reacted for 1 hour. After filtration, it is dried to obtain allylated composite aerogel.

[0105] (4) Take 1g of the allylated composite aerogel obtained in step (3) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.04g of sodium persulfate initiator, purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid and 75% neutralization) at 0℃. Heat to 60℃ and stir for 15 minutes. Then add 0.018g of crosslinking agent 1,3-butanediol dimethacrylate and continue stirring for 2 hours to obtain a gel-like product. Take out the product and cut it into pieces. Soak it in anhydrous ethanol for 8 hours to remove unreacted monomers. Place it in a 50℃ oven to dry and obtain a tropical crop cellulose-based superabsorbent polymer.

[0106] Example 4

[0107] A method for preparing a tropical crop cellulose-based superabsorbent polymer specifically includes the following steps:

[0108] (1) After cutting the original sisal fiber into short pieces with an average size of 1 mm, the powder was added to a 4% NaOH solution for alkali treatment, stirred at 80°C for 3 hours, then filtered and washed 3 times with distilled water, then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed 3 times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0109] (2) Take 1.8g of tropical crop cellulose obtained in step (1) and 0.2g of peach gum, dissolve them separately in 50mL of water, and after they are completely dispersed and dissolved, mix them in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.2g of crosslinking agent 1,6-hexanediol diglycidyl ether, stir and react for 1 hour, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze-dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0110] (3) The cellulose-gum composite aerogel obtained in step (2) is crushed into particles with an average particle size of 2-5 mm. 2 g of the crushed cellulose-gum composite aerogel is dispersed in 100 mL of NaOH solution (40 wt%), stirred in a 50 °C water bath for 30 minutes, and then 0.5 g of allyl glycidyl ether is added. The mixture is stirred and reacted for 1 hour. After filtration and drying, allylated composite aerogel is obtained.

[0111] (4) Take 1g of the allylated composite aerogel obtained in step (3) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.05g of initiator ammonium persulfate, purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid and a neutralization degree of 75%) at 0℃. Heat to 60℃ and stir for 15 minutes. Then add 0.025g of crosslinking agent 1,4-butanediol dimethacrylate and continue stirring for 2 hours to obtain a gel-like product. Take out the product and cut it into pieces. Soak it in anhydrous ethanol for 8 hours to remove unreacted monomers. Place it in a 50℃ oven to dry and obtain a tropical crop cellulose-based superabsorbent polymer.

[0112] Comparative Example 1

[0113] Same as Example 1, except that the steps of preparing cellulose-gum composite aerogel and allylation modification are omitted. Specifically:

[0114] Add 0.025g of initiator ammonium persulfate to a three-necked flask containing 40mL of distilled water, purge with nitrogen and stir in a room temperature water bath. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid with a neutralization degree of 75%) at 0℃, heat to 60℃ and stir for 15 minutes. Then add 0.015g of crosslinking agent ethylene glycol dimethacrylate and continue stirring for 4 hours to obtain a gel-like product. Remove the product and cut it into pieces. Soak the pieces in anhydrous ethanol for 8 hours to remove unreacted monomers. Dry the pieces in a 50℃ oven to obtain a water-absorbing polymer.

[0115] Comparative Example 2

[0116] Commercially available agricultural and forestry soil water retention agents are products of polyacrylate and polyacrylamide copolymers, in the form of transparent powder granules with a particle size of 20-100 mesh.

[0117] Comparative Example 3

[0118] Same as Example 1, except that the allylation modification step is omitted, specifically:

[0119] A method for preparing a tropical crop cellulose-based superabsorbent polymer specifically includes the following steps:

[0120] (1) Pineapple leaf fibers were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment. The mixture was stirred at 80°C for 3 hours, then filtered and washed three times with distilled water. The mixture was then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0121] (2) Take 1.2g of tropical crop cellulose obtained in step (1) and 0.8g of peach gum, dissolve them separately in 50mL of water, and after they are completely dispersed and dissolved, mix them in a beaker, heat and stir in a 50℃ water bath, adjust the pH to 11 with NaOH, stir for 30 minutes, add 0.02g of crosslinking agent 1,4-butanediol diglycidyl ether, stir and react for 2 hours, then place the reaction product in a -80℃ ultra-low temperature freezer for 24 hours, and then freeze-dry in vacuum for 48 hours to obtain cellulose-peach gum composite aerogel;

[0122] (3) Disperse the cellulose-peach gum composite aerogel obtained in step (2) in a three-necked flask containing 40 mL of distilled water, stir for 30 minutes to disperse evenly, add 0.025 g of initiator ammonium persulfate, purge with nitrogen and stir in a water bath at room temperature, add 40 mL of monomer (acrylic acid solution containing 5 g of dry acrylic acid and a neutralization degree of 75%) at 0 °C, heat to 60 °C and stir for 15 minutes, add 0.015 g of crosslinking agent ethylene glycol dimethacrylate, continue stirring for 4 hours to obtain a gel-like product, take out the product and cut it into pieces, soak it in anhydrous ethanol for 8 hours to remove unreacted monomers, place it in a 50 °C oven to dry, and obtain a tropical crop cellulose-based superabsorbent polymer.

[0123] Comparative Example 4

[0124] Same as Example 1, except that the addition of peach gum is omitted. Specifically:

[0125] (1) Pineapple leaf fibers were cut short and crushed into small segments with an average size of 1 mm. The crushed powder was added to a 4% NaOH solution for alkali treatment. The mixture was stirred at 80°C for 3 hours, then filtered and washed three times with distilled water. The mixture was then bleached with sodium hypochlorite, stirred at 70°C for 2 hours, filtered and washed three times, and dried at 50°C to obtain powdered tropical crop cellulose.

[0126] (2) Take 2g of the powdered tropical crop cellulose obtained in step (1) and disperse it in a three-necked flask containing 40mL of distilled water. Stir for 30 minutes to disperse it evenly. Add 0.025g of initiator ammonium persulfate, purge with nitrogen and stir in a water bath at room temperature. After 10 minutes, add 40mL of monomer (acrylic acid solution containing 5g of dry acrylic acid and a neutralization degree of 75%) at 0℃. Heat to 60℃ and stir for 15 minutes. Then add 0.015g of crosslinking agent ethylene glycol dimethacrylate and continue stirring for 4 hours to obtain a gel-like product. Take out the product and cut it into pieces. Soak it in anhydrous ethanol for 8 hours to remove unreacted monomers. Place it in a 50℃ oven to dry to obtain a tropical crop cellulose-based superabsorbent polymer.

[0127] Performance testing

[0128] (1) Fourier Transmission Infrared Spectroscopy (FT-IR) Analysis

[0129] The FT-IR spectra of the tropical crop cellulose obtained in step (1) of Example 1, the tropical crop cellulose-based superabsorbent polymer, and the superabsorbent polymer prepared in Comparative Example 1 are shown below. Figure 1 Where a is tropical crop cellulose; b is the water-absorbing polymer of Comparative Example 1; and c is the tropical crop cellulose-based superabsorbent polymer of Example 1. Figure 1 It can be seen that 1114 cm⁻¹ in the cellulose spectrum of tropical crops -1 1040cm -1 The characteristic peak at this point is the -CH-O-CH absorption peak, which is a characteristic absorption peak of the cellulose structure. In the spectrum of cellulose-based superabsorbent polymers from tropical crops, the characteristic peak extends from 3351 cm⁻¹. -1 Change to 3341cm -1 This is related to the stretching vibration of -OH; a comparison with the polymer spectrum of the unreinforced cellulose-gum composite aerogel in Comparative Example 1 revealed that at 1114 cm⁻¹... -1 1040cm -1 The characteristic peaks of cellulose at 2927 cm⁻¹ were retained, indicating that the cellulose aerogel polymer maintained the structural integrity of cellulose. -1 The peak at 1660 cm⁻¹ is due to -CH₂. -1 The absorption peak at 1321 cm⁻¹ is related to carboxylic acids. -1 -1040cm -1 The peak at 2507 cm⁻¹ is attributed to -COO-, while the peak at 2507 -1 The characteristic peak at 1037 cm⁻¹ is related to the -OH group of carbonyl acid, indicating that the grafting reaction of acrylic acid has been successfully carried out. Furthermore, a comparison with the polymer spectrum of Comparative Example 1 (without cellulose-gum composite aerogel) revealed a peak at 1037 cm⁻¹. -1 and 888cm -1New absorption peaks were observed, which correspond to the stretching vibrations of the -CH-O-CH structure and the stretching vibrations of the =COC- structure, respectively, further indicating that a grafting reaction occurred in the cellulose aerogel during polymerization. This suggests that in the embodiments of the present invention, the allylated composite aerogel, acrylic acid, and crosslinking agent underwent a graft copolymerization reaction to form a stable network structure.

[0130] (2) SEM analysis

[0131] The tropical crop cellulose-based superabsorbent polymer prepared in Example 1 was tested using field emission scanning electron microscopy (FETS) from the Czech Republic's TESCAN MIRALMS. The results are shown in the figure. Figure 2 As can be seen, the polymer has a porous structure inside, indicating that the cross-linked aerogel formed by tropical crop cellulose and peach gum forms a polymer network support structure, which also provides more cavity structures to improve the water absorption performance of the polymer, and the structure is not easy to collapse.

[0132] (3) Thermogravimetric analysis

[0133] Thermogravimetric (TG) curves of the water-absorbing polymer samples prepared in Example 1 and Comparative Example 1 were measured in an N2 atmosphere. The results are shown in [Figure number missing]. Figure 3 It can be seen that the thermal decomposition of the samples mainly involves the following processes: the first stage is mainly the evaporation of water in the sample, resulting in a small amount of weight loss; the second stage is between 100℃ and 200℃, where the tropical crop cellulose-based superabsorbent polymer of Example 1 is relatively stable, but the cellulose-free superabsorbent polymer of Comparative Example 1 continues to lose weight; the third stage is between 200℃ and 360℃, where the cross-linked structure within the polymer undergoes fibrous thermal decomposition, producing small molecules, and the weight loss reaches its maximum; the fourth stage is the slow decomposition process of macromolecular residues, with relatively slow weight loss. The pyrolysis temperature of the tropical crop cellulose-based superabsorbent polymer of Example 1 with the maximum weight loss rate is 260℃; the pyrolysis temperature of the superabsorbent polymer of Comparative Example 1 with the maximum weight loss rate is 248℃. Furthermore, the mass loss rate of the sample in Comparative Example 1 is greater than that of the sample in Example 1. This indicates that the tropical crop cellulose-based superabsorbent polymer of the present invention has good stability, and the internal three-dimensional network structure can improve the thermal stability of the superabsorbent polymer to a certain extent.

[0134] (4) Water absorption performance test

[0135] The test samples were prepared in the examples and comparative examples. The samples were crushed, and 0.2g of the sample was placed in a 500mL beaker. 400mL of deionized water was added, and the sample was soaked until it was saturated with water. The sample was then removed and filtered through a 100-mesh filter cloth. The sample particles were then suspended for 20 minutes to remove excess water. The weight of the product after water absorption was measured. The ratio of the weight of the product after water absorption to the mass of the sample before water absorption is the water absorption ratio of the sample.

[0136] The water absorption performance test results of the samples in the examples and comparative examples are shown below. Figure 4 ,Depend on Figure 4 It can be seen that the water absorption ratio of the example sample increased rapidly within 1 hour, and after reaching a certain value after 4 hours, the water absorption ratio tended to saturate, with the maximum water absorption ratio rounded to 828 g / g; the water absorption ratio of the comparative sample basically reached water absorption saturation after 6-8 hours, and the water absorption ratio was lower than that of the example sample; indicating that the example sample has good water absorption performance, and the example sample has a cellulose composite aerogel structure and a three-dimensional network porous structure, which helps to improve its water absorption performance.

[0137] (5) Water retention performance test

[0138] After the samples of the examples and comparative examples were saturated with water, they were placed in weighing bottles and placed at room temperature. The remaining mass was weighed at certain intervals. The percentage difference between the remaining water mass and the saturated water mass at different times was used as an indicator of water retention performance. The total test time was 60 hours.

[0139] The water retention performance test results of the samples in the examples and comparative examples are shown below. Figure 5 ,Depend on Figure 5 It can be seen that after water absorption, the mass of the samples in the examples and comparative examples decreased continuously over time, the water retention rate decreased continuously, and the water loss rate was relatively stable. The water retention rate versus time curve under room temperature conditions tended to be linear. The water retention rate of the comparative example decreased to 50% after 24 hours, while the water retention rate of the examples could still maintain 60% after 24 hours. Compared with the comparative example, the samples in the examples all had better water retention performance, which is related to their own three-dimensional network porous structure.

[0140] (6) Repeated water absorption performance test

[0141] The samples from the examples and comparative examples were placed in deionized water to reach the maximum water absorption saturation, and the water absorption ratio was measured. The saturated water-absorbing samples were then placed in a forced-air drying oven and dried at 80°C until the moisture was completely removed. The experiment was repeated 6 times, and the test results are shown in Table 1.

[0142] Table 1. Results of repeated water absorption performance tests for the examples and comparative examples.

[0143]

[0144] As shown in Table 1, the water absorption ratio of the example samples decreased with the increase of repeated water absorption. The water absorption ratio of the samples remained above 70% of the initial ratio during the second water absorption. After three repeated water absorptions, the water absorption ratio of the water-retaining agent decreased to 40% of the initial ratio. After five water absorptions, the water absorption ratio of the water-retaining agent tended to stabilize. The comparative sample showed a more significant decrease in water absorption ratio. Because the example samples have a three-dimensional network porous structure, the molecular chains shrink and curl after some water molecules are expelled. During repeated water absorption, the contracted molecular chains are more easily unfurled, creating more pores and resulting in better repeated water absorption performance.

[0145] (7) Compression strength test

[0146] Immerse the dried sample (5 mm in length, 5 mm in width, and 5 mm in height) of the example or comparative example in deionized water until it swells to saturation. After absorbing excess water with absorbent paper, place the sample in the compression fixture of a universal testing machine and apply uniform pressure at a speed of 5 mm / min until the sample height is reduced by 80%. Record the compression strength. Measure 3 sets for each sample and take the average value.

[0147] Mechanical analysis of the samples in the examples and comparative cases reveals the structural changes of the material after water absorption, ensuring sufficient strength and stability in practical applications. Compressive strength test results are as follows... Figure 6 As shown, the compressive strength of the example samples is 0.058-0.065 MPa, while that of the comparative samples is 0.022-0.036 MPa. This is because the example samples have a cellulose-peach gum composite aerogel structure and a three-dimensional network structure. Tropical crop cellulose, as a natural polysaccharide fiber material, has significant mechanical support and reinforcement effects. Furthermore, the long molecular chains and carboxyl groups of the superabsorbent polymer increase the crosslinking density of the polymer and enhance the stability of the network structure.

[0148] (8) Coating preservation test

[0149] The powdered superabsorbent polymer prepared in Example 1 was formulated into homogeneous hydrogel aqueous solutions (coating agents) with concentrations of 2 g / L, 5 g / L, 8 g / L, and 10 g / L. Freshly purchased lychees were washed with clean water and dried. The lychees were then immersed in the above hydrogel aqueous solutions for 20 seconds. At the same time, lychees were soaked in distilled water (coating agent concentration of 0 g / L) as a blank control. Three sets of experiments were performed in parallel. After the coated lychees were dried in a ventilated place, they were placed in a well-ventilated and dark indoor place for 4 days. Various physicochemical indicators of the lychees were measured. At the same time, fresh lychees were used to measure physicochemical indicators as a fresh control group. The weight loss rate was determined by weighing method; the vitamin C content was determined according to GB / T6195-1986 "2,6-dichlorophenolindophenol sodium salt titration method"; the soluble solids were determined according to agricultural standard NY / T2637-2014 "Determination of soluble solids content in fruits and vegetables". The test results are shown in Table 2.

[0150] Table 2 Results of the preservation experiment using powdered superabsorbent polymer coatings of different concentrations

[0151]

[0152] Table 2 shows that the superabsorbent polymer prepared in Example 1 of this invention can be used as a coating agent to preserve lychees. Different concentrations of the superabsorbent polymer coating agent can reduce the weight loss rate of lychees while maintaining their flavor. When the coating agent concentration is 5 g / L, all physicochemical properties of the lychee reach their optimal values. The weight loss rate of lychees decreases with increasing coating agent concentration. However, when the concentration exceeds 5 g / L, further increasing the amount of coating agent slows the decline in weight loss. This is mainly because the superabsorbent resin itself contains a large number of carboxyl hydrophilic groups; the higher the concentration of the coating agent, the stronger the water absorption capacity, and the more intense the water loss inside the fruit, thus preventing a significant decrease in the weight loss rate of the lychee. When the concentration of the coating agent is too low, the film layer covering the surface of the lychee is too thin and cannot play a protective role; when the concentration of the coating agent is too high, the film layer on the surface of the lychee is too thick, which may hinder the entry of oxygen, causing anaerobic respiration inside the lychee, leading to internal fermentation, decay and deterioration, and thus aggravating the rot and spoilage of the fruit.

[0153] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing a high water-absorbing polymer of a tropical plant cellulose, characterized by, The cellulose-tannin composite aerogel with covalent cross-linking structure is formed by tropical crop cellulose and peach gum under the action of glycerol ether cross-linking agent; the allyl functionalized grafted modification is carried out on the cellulose-tannin composite aerogel to obtain an allylated composite aerogel; and the allylated composite aerogel is subjected to synergistic copolymerization reaction with an acrylic ester cross-linking agent and a monomer to prepare the tropical crop cellulose-based superabsorbent polymer.

2. The method for preparing a hot crop cellulose-based superabsorbent polymer according to claim 1, characterized by, The method comprises the following steps: (1) After the tropical crop cellulose and peach gum are dispersed with water, heating is carried out in a water bath and the pH is adjusted to be alkaline, the glycerol ether cross-linking agent is added and stirred, and then the reaction product is freeze-dried to obtain the cellulose-tannin composite aerogel; (2) The cellulose-tannin composite aerogel is crushed, dispersed with NaOH solution and added with an epoxy group-containing allyl compound to obtain an allylated composite aerogel through stirring reaction; (3) After the allylated composite aerogel is dispersed with water, heating is carried out in a water bath and an initiator, a monomer solution and an acrylic ester cross-linking agent are sequentially added to obtain a gel-like product, and after the gel-like product is washed and dried, the tropical crop cellulose-based superabsorbent polymer is obtained.

3. The method for producing a hot crop cellulose-based superabsorbent polymer according to claim 2, characterized by, In step (1), the mass ratio of the tropical crop cellulose, peach gum and glycerol ether cross-linking agent is (1-1.8):(0.2-1):(0.02-0.2); and / or, The glycerol ether cross-linking agent is selected from one or more of ethylene glycol diglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether.

4. The method for preparing the tropical crop cellulose-based superabsorbent polymer according to claim 2, characterized in that, In step (1), the pH is adjusted to 11 with NaOH; and / or, The stirring reaction is carried out at a temperature of 50°C for 1-4 hours.

5. The method for preparing the tropical crop cellulose-based superabsorbent polymer according to claim 2, characterized in that, In step (2), the dosage ratio of the cellulose-tannin composite aerogel, NaOH solution and epoxy group-containing allyl compound is 2g:100mL:0.5g.

6. The method for preparing the tropical crop cellulose-based superabsorbent polymer according to claim 2, characterized in that, In step (2), the epoxy group-containing allyl compound is selected from allyl glycidyl ether.

7. The method for preparing the tropical crop cellulose-based superabsorbent polymer according to claim 2, characterized in that, In step (3), the initiator is selected from one or more of ammonium persulfate, potassium persulfate and sodium persulfate; and / or, The acrylic ester cross-linking agent is selected from one or more of ethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate and 1,6-hexanediol dimethacrylate; and / or, The monomer solution is an acrylic acid solution; and / or, The dosage ratio of the allylated composite aerogel, initiator, monomer solution and acrylic ester cross-linking agent is 1g:(0.025-0.05)g:40mL:(0.015-0.025)g.

8. The method for preparing the tropical crop cellulose-based superabsorbent polymer according to claim 2, characterized in that, The specific step of step (3) is: dispersing the allylated composite aerogel with water, adding initiator and passing nitrogen, stirring at room temperature for 10 minutes, then adding the monomer solution, heating to 60℃ and stirring, reacting for 15 minutes, then adding the acrylic ester crosslinking agent and continuing to stir, and reacting for 2-4 hours to obtain a gel product.

9. A tropical crop cellulose-based superabsorbent polymer, characterized by, The tropical crop cellulose-based superabsorbent polymer is prepared according to the preparation method of the tropical crop cellulose-based superabsorbent polymer in any one of claims 1-8.

10. Use of the tropical crop cellulose-based superabsorbent polymer in claim 9 in the preparation of agricultural and forestry water-retaining materials or food fresh-keeping materials.

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