Cellulose-based hydrogels and their preparation methods

Abstract

This invention relates to a cellulose-based hydrogel and its preparation method. The raw materials for preparation include a first cellulose derivative, a second cellulose derivative, and a crosslinking agent. The viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000–6000 cps, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30–700 cps. The first cellulose derivative comprises 70%–95% of the total mass of the first and second cellulose derivatives. The above-mentioned cellulose-based hydrogel uses first and second cellulose derivatives with different viscosities within a specific viscosity range as the main crosslinking raw materials, while simultaneously controlling the mass content of the first cellulose derivative. These, along with the crosslinking agent, are used as raw materials for crosslinking reactions. This eliminates the need for additional chemical modification of the cellulose derivatives by introducing other chemical reagents, thus obtaining a cellulose-based hydrogel with both high water absorption and storage modulus.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a cellulose-based hydrogel and its preparation method. Background Technology

[0002] Hydrogels are three-dimensional networks composed of hydrophilic polymer chains. They can swell in hydrophilic media without losing their structure and are insoluble in both organic and inorganic solvents due to the crosslinking between the polymer chains. Rheologically, hydrogels exhibit viscoelasticity, and sometimes pure elasticity. Furthermore, hydrogels possess a highly porous structure, allowing a matrix to be loaded into the gel matrix and released according to the diffusion coefficient of the matrix through the gel network. Hydrogels can be synthesized based on any water-soluble polymer and have a wide range of chemical compositions and physical properties. The polymer network resulting from crosslinking swells in aqueous solutions until the thermodynamic forces of expansion are completely offset by the elastic and recoil forces exerted by the crosslinking. The water retention capacity of the hydrogel network depends on the structure of the polymer network itself and the solution environment conditions, such as the temperature, pH, and ionic strength of the aqueous solution in contact with the polymer. Under given environmental conditions, the water absorption capacity and storage modulus of the hydrogel are the two most important variables for evaluation because they affect the hydrogel's diffusion, optical, acoustic, and surface properties.

[0003] Cellulose-based hydrogels are a type of hydrogel with a physical or chemical cross-linked network structure, prepared from cellulose or its derivatives. Due to their green and non-toxic origin, low cost, and unique characteristics not found in other hydrogels, such as high water absorption, strong water retention, and easy degradation and metabolism within the digestive system, cellulose-based hydrogels have wide applications in the food, health, biopharmaceutical, and medical device industries. However, cellulose-based hydrogels also have some problems or shortcomings. As is well known, increased water absorption generally leads to a decrease in storage modulus; therefore, high water absorption can result in low storage modulus, thus limiting their application in various fields.

[0004] The water absorption and storage modulus of the polymer network of cellulose-based hydrogels can be adjusted according to the crosslinking density. However, water absorption and storage modulus are theoretically inversely proportional. Increasing the crosslinking density of the hydrogel can significantly increase the storage modulus, but it will affect the water absorption and energy absorption of the hydrogel. Summary of the Invention

[0005] Therefore, it is necessary to provide a cellulose-based hydrogel that has both high water absorption capacity and high storage modulus, and a method for preparing the same.

[0006] The present invention is achieved through the following technical solution.

[0007] In one aspect, the present invention provides a cellulose-based hydrogel, the raw materials for which preparation includes a first cellulose derivative, a second cellulose derivative, and a crosslinking agent;

[0008] Wherein, the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000-6000 cps, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30-700 ps; in the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative is 70%-95%.

[0009] In some embodiments, the first cellulose derivative and the second cellulose derivative are both cellulose ethers, and the first cellulose derivative and the second cellulose derivative are the same type of cellulose ether or different types of cellulose ethers.

[0010] In some embodiments, the first cellulose derivative and the second cellulose derivative are each independently selected from at least one of methylcellulose, carboxymethylcellulose, carboxymethylcellulose salt, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose.

[0011] In some embodiments, the first cellulose derivative is carboxymethyl cellulose salt; the second cellulose derivative is selected from at least one of carboxymethyl cellulose, carboxymethyl cellulose salt, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0012] In some embodiments, the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3500–4800 cps.

[0013] And / or, the first cellulose derivative and the second cellulose derivative are the same cellulose ether, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30-500 cps; or, the first cellulose derivative and the second cellulose derivative are different cellulose ethers, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30-280 cps.

[0014] In some embodiments, the crosslinking agent includes at least one of oxalic acid, tartaric acid, malonic acid, maleic acid, succinic acid, citric acid, phthalic acid, pyromellitic acid, ethylenediaminetetraacetic acid, and carboxyl-terminated multi-arm polyethylene glycol.

[0015] In some embodiments, the crosslinking agent has a mass content of 0.1% to 5% relative to the total mass of the cellulose.

[0016] In some embodiments, the raw materials for preparation further include a third cellulose derivative, wherein the viscosity of the third cellulose derivative in a 1 wt% aqueous solution at 25°C is >6000 cps;

[0017] And / or, the raw materials for preparation further include a fourth cellulose derivative, wherein the viscosity of the fourth cellulose derivative in a 1 wt% aqueous solution at 25°C is ≥1000 cps and <3000 cps.

[0018] Another aspect of the present invention provides a method for preparing a cellulose-based hydrogel, comprising the following steps:

[0019] A first cellulose derivative, a second cellulose derivative, a crosslinking agent, and water are mixed to obtain a mixed solution; and

[0020] The mixed solution was heat-treated to dry and then subjected to a cross-linking reaction to obtain the cellulose-based hydrogel.

[0021] Wherein, the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000-6000 cps, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30-700 cps. The first cellulose derivative and the second cellulose derivative may be of the same or different types. In the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative is 70%-95%.

[0022] In some embodiments, the total mass content of the first cellulose derivative and the second cellulose derivative in the mixed solution is 1% to 4%.

[0023] The aforementioned cellulose-based hydrogel uses a first cellulose derivative and a second cellulose derivative with different viscosities within a specific viscosity range as the main crosslinking raw materials. The mass content of the first cellulose derivative is controlled and used together with the crosslinking agent as raw materials for preparation. Through the crosslinking reaction, the low molecular weight second cellulose derivative reduces intramolecular crosslinking in the hydrogel and increases the degree of intermolecular crosslinking. Without introducing other chemical reagents to perform additional chemical modification on the cellulose derivative, a cellulose-based hydrogel with both high water absorption and high storage modulus can be obtained. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] One embodiment of the present invention provides a cellulose-based hydrogel, the raw materials for which include a first cellulose derivative, a second cellulose derivative and a crosslinking agent.

[0028] The viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000–6000 cps, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30–700 cps. The mass content of the first cellulose derivative in the total mass of the first and second cellulose derivatives is 70%–95%.

[0029] It is understood that, in the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative can be 70%, 72%, 75%, 78%, 80%, 83%, 84%, 85%, 90%, 92%, or 95%. Further, in the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative is preferably 75% to 95%, more preferably 85% to 95%.

[0030] The aforementioned cellulose-based hydrogels possess a three-dimensional network cross-linked structure at the molecular level. This three-dimensional network cross-linked structure can be formed through chemical cross-linking or physical interactions.

[0031] The aforementioned cellulose-based hydrogels contain at least a three-dimensional network structure formed by chemical cross-linking. This cellulose-based gel with a three-dimensional network structure can only swell in a solvent and cannot completely dissolve. The chemical cross-linking is achieved by a cross-linking agent containing bi / multifunctional groups reacting chemically with the hydroxyl groups and / or other groups on the molecular chains of the aforementioned cellulose derivatives to form a cross-linked network.

[0032] Among them, physical interactions include entanglement between cellulose derivative molecular chains, hydrogen bonding between cellulose derivative molecules or between cellulose derivative molecules and water, and ionic interactions.

[0033] The aforementioned cellulose-based hydrogel uses a first cellulose derivative and a second cellulose derivative with different viscosities within a specific viscosity range as the main crosslinking raw materials. The mass content of the first cellulose derivative is controlled and used together with the crosslinking agent as raw materials for preparation. Through the crosslinking reaction, the low molecular weight second cellulose derivative reduces intramolecular crosslinking in the hydrogel and increases the degree of intermolecular crosslinking. Without introducing other chemical reagents to perform additional chemical modification on the cellulose derivative, a cellulose-based hydrogel with both high water absorption and high storage modulus can be obtained.

[0034] The first and second cellulose derivatives used in the preparation of the aforementioned cellulose-based hydrogels have low viscosity, rapid dissolution rate, high soluble concentration, and simple operation, thus greatly increasing the yield that can be synthesized in a single batch. These cellulose-based hydrogels have significant application value in agriculture, tissue engineering, drug delivery, biosensors, and medical devices.

[0035] The water absorption ratio and storage modulus of the aforementioned cellulose-based hydrogel can be controlled by adjusting the viscosity and content ratio of cellulose derivatives. Similarly, the water absorption ratio and storage modulus can also be controlled by adjusting the molecular weight and content ratio of cellulose derivatives, which should also fall within the protection scope of this invention patent.

[0036] Cellulose derivatives are products resulting from the esterification or etherification of the hydroxyl groups in cellulose polymers with chemical reagents. Based on the structural characteristics of the reaction products, cellulose derivatives include cellulose ethers, cellulose esters, and cellulose ether esters.

[0037] The cellulose derivatives mentioned above may be at least one of cellulose ethers, cellulose esters, and cellulose ether esters.

[0038] Furthermore, the cellulose ether can be selected from at least one of methylcellulose, carboxymethylcellulose, carboxymethylcellulose salt, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose. Even further, the carboxymethylcellulose salt can be sodium carboxymethylcellulose.

[0039] Furthermore, the cellulose ester may be selected from at least one of cellulose nitrate, cellulose acetate, cellulose acetate butyrate, and cellulose xanthate.

[0040] In some embodiments, the first cellulose derivative and the second cellulose derivative are both cellulose ethers, and the first cellulose derivative and the second cellulose derivative may be the same type of cellulose ether or different types of cellulose ethers.

[0041] Furthermore, the first cellulose derivative and the second cellulose derivative are each independently selected from at least one of methylcellulose, carboxymethylcellulose, carboxymethylcellulose salt, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose.

[0042] Furthermore, the first cellulose derivative and the second cellulose derivative are each independently selected from at least one of carboxymethyl cellulose, carboxymethyl cellulose salt, hydroxyethyl cellulose and hydroxypropyl cellulose.

[0043] Furthermore, the first cellulose derivative is a carboxymethyl cellulose salt; the second cellulose derivative is selected from at least one of carboxymethyl cellulose, carboxymethyl cellulose salt, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0044] In one specific example, the first cellulose derivative is a carboxymethyl cellulose salt; the second cellulose derivative is a carboxymethyl cellulose salt.

[0045] It is understood that the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000 cps, 3200 cps, 3500 cps, 3800 cps, 4000 cps, 4500 cps, 4800 cps, 5000 cps, 5500 cps, or 6000 cps. In some embodiments, the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3500–4800 cps.

[0046] It is understood that the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30 cps, 50 cps, 80 cps, 100 cps, 120 cps, 150 cps, 180 cps, 200 cps, 220 cps, 250 cps, 280 cps, 300 cps, 350 cps, 400 cps, 450 cps, 500 cps, 550 cps, 600 cps, 650 cps, or 700 cps. In some embodiments, the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30–500 cps, more specifically 30–300 cps, and even more specifically 30–280 cps.

[0047] Furthermore, when the first cellulose derivative and the second cellulose derivative are the same cellulose ether, it is preferable that the viscosity of the second cellulose derivative in a 2wt% aqueous solution at 25°C is 30-500 cps, more preferably 30-300 cps, and even more preferably 30-280 cps.

[0048] Furthermore, when the first cellulose derivative and the second cellulose derivative are different types of cellulose ethers, it is preferable that the viscosity of the second cellulose derivative in a 2wt% aqueous solution at 25°C is 30–280 cps.

[0049] Furthermore, the degree of substitution of the first cellulose derivative is 0.7, 0.9, and 1.2.

[0050] Furthermore, the degree of substitution of the second cellulose derivative is 0.7, 0.9, and 1.2.

[0051] In some embodiments, the crosslinking agent includes at least one of oxalic acid, tartaric acid, malonic acid, maleic acid, succinic acid, citric acid, phthalic acid, pyromellitic acid, ethylenediaminetetraacetic acid, and carboxyl-terminated multi-arm polyethylene glycol.

[0052] Furthermore, the crosslinking agent has a mass content of 0.1% to 5% relative to the total mass of each cellulose, for example, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0053] It is understood that, in addition to the first and second cellulose derivatives, the raw materials used in the preparation of the above materials may also contain cellulose or cellulose derivatives of other viscosities.

[0054] In some embodiments, the raw materials also include a third cellulose derivative, which has a viscosity of >6000 cps in a 1 wt% aqueous solution at 25°C.

[0055] In some embodiments, the raw materials also include a fourth cellulose derivative, which has a viscosity of ≥1000 cps and <3000 cps in a 1 wt% aqueous solution at 25°C.

[0056] Another embodiment of the present invention provides a method for preparing the above-mentioned cellulose-based hydrogel, comprising the following steps S10 to S20.

[0057] Step S10: Mix the first cellulose derivative, the second cellulose derivative, the crosslinking agent and water to obtain a mixed solution.

[0058] Of the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative is 70% to 95%.

[0059] In some embodiments, the total mass content of the first cellulose derivative and the second cellulose derivative in the mixed solution is 1% to 4%. It is understood that the total mass content of the first cellulose derivative and the second cellulose derivative in the mixed solution can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%.

[0060] Furthermore, in the mixed solution, the total mass content of the first cellulose derivative and the second cellulose derivative is 2% to 4%, and more specifically 3%.

[0061] Furthermore, the mixing step can be carried out at 10°C to 40°C, for example, at room temperature. Furthermore, the mixing time can be 8 hours to 14 hours, for example, 12 hours.

[0062] Step S20: The mixed solution is heat-treated to dry and cross-linked to obtain a cellulose-based hydrogel.

[0063] In some embodiments, the heat treatment temperature is 80–140°C and the time is 0.5–12 h.

[0064] Furthermore, the heat treatment temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, or 140℃. Furthermore, the heat treatment time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h.

[0065] The cellulose-based hydrogel prepared by the above method possesses both high water absorption ratio and high storage modulus. Furthermore, it exhibits pH responsiveness, with its water absorption swelling ratio increasing with increasing pH. Therefore, the water absorption swelling ratio of the above cellulose-based hydrogel is adjustable; specifically, in an aqueous solution with pH = 2.1 ± 0.1, the water absorption ratio can be adjusted within the range of 10 to 140.

[0066] To make the objectives, technical solutions, and advantages of this invention clearer and more concise, the invention is described using the following specific embodiments, but the invention is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of the invention and can be used to describe the invention, but should not be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0067] To better illustrate the present invention, the following embodiments are provided for further explanation. The specific embodiments are as follows.

[0068] Example 1

[0069] Materials: Sodium carboxymethyl cellulose 1 (CMCNa-1, viscosity of 4000 cps in a 1w% aqueous solution at 25℃, degree of substitution 0.9); Sodium carboxymethyl cellulose 2 (CMCNa-2, viscosity of a 2w% aqueous solution at 25℃ as shown in Table 1 below, degree of substitution 0.7). All raw materials were commercially available.

[0070] Preparation steps:

[0071] 1) Add 10L of purified water to a 25L stirred reactor, add 1.5g of CA to the water, and then add 250g of high-viscosity sodium carboxymethyl cellulose 1 and 50g of low-viscosity sodium carboxymethyl cellulose 2 to the solution. Stir thoroughly at 150rpm for 12h at room temperature to make the system uniformly mixed and obtain a mixed solution.

[0072] 2) Add the obtained mixed solution to a stainless steel tray, with each tray weighing about 2500g. Place the tray in a 120℃ oven for 12 hours to dry.

[0073] 3) The obtained dried product is crushed and sieved to obtain the final product.

[0074] Examples 2-3 and Comparative Examples 1-3 are basically the same as Example 1, except that the contents of CMCNa-1 and CMCNa-2 in the mixed solution are different. Example 2 includes Examples 2-1 to 2-6. Specific parameters and performance data are shown in Table 1.

[0075] Table 1

[0076]

[0077] As shown in Table 1, compared with Comparative Examples 1-3, the cellulose-based hydrogels prepared in Examples 1-3 can have both higher water absorption ratio and storage modulus.

[0078] As can be seen from Examples 1, 2-1 and 3, the cellulose-based hydrogel prepared in Example 2-1 can achieve a higher water absorption ratio and a higher storage modulus.

[0079] As can be seen from Examples 2-1 to 2-6, when using sodium carboxymethyl cellulose with different viscosities, the viscosity of low-viscosity sodium carboxymethyl cellulose in a 2w% aqueous solution at 25°C is preferably 30 to 280 cps. Within this range, it is possible to obtain a higher water absorption ratio while also having a higher storage modulus.

[0080] Example 4

[0081] Materials: Sodium carboxymethyl cellulose 1 (CMCNa-1, viscosity of 4000 cps in 1w% aqueous solution at 25℃, degree of substitution 0.9); hydroxyethyl cellulose (HEC, viscosity of 2w% aqueous solution at 25℃ is shown in Table 2); all raw materials used were commercially available.

[0082] Preparation steps:

[0083] 1) Add 10L of purified water to a 25L stirred reactor, add 1.5g of CA to the water, then add 250g of high-viscosity CMCNa and 50g of HEC to the solution, and stir thoroughly at 150rpm for 24h at room temperature to make the system uniformly mixed and obtain a mixed solution.

[0084] 2) Add the obtained mixed solution to a stainless steel tray, with each tray weighing about 2500g. Place the tray in a 120℃ oven for 12 hours to dry.

[0085] 3) The obtained dried product is crushed and sieved to obtain the dried product.

[0086] Examples 5-6 and Comparative Examples 4-6 are basically the same as Example 4, except that the contents of CMCNa-1 and HEC in the mixed solution are different. Example 5 includes Examples 5-1 to 5-5. Specific parameters and performance data are shown in Table 2.

[0087] Table 2

[0088]

[0089] As shown in Table 2, compared with Comparative Examples 4-6, the cellulose-based hydrogels prepared in Examples 4-6 can have both higher water absorption ratio and storage modulus.

[0090] As can be seen from Examples 4, 5-1 and 6, the cellulose-based hydrogel prepared in Example 5-1 can achieve a high water absorption ratio and a higher storage modulus.

[0091] As can be seen from Examples 5-1 to 5-5, when high-viscosity sodium carboxymethyl cellulose and low-viscosity hydroxyethyl cellulose are used, the viscosity of the low-viscosity hydroxyethyl cellulose in a 2w% aqueous solution at 25°C is preferably 30 to 280 cps; more preferably 30 to 150 cps.

[0092] Example 7

[0093] Materials: Sodium carboxymethyl cellulose 1 (CMCNa-1, viscosity of 4000 cps in 1w% aqueous solution at 25℃, degree of substitution 0.9); hydroxypropyl cellulose (HPC, viscosity of 2w% aqueous solution at 25℃ as shown in Table 3); all raw materials used were commercially available.

[0094] Preparation steps:

[0095] 1) Add 10L of purified water to a 25L stirred reactor, add 1.5g of CA to the water, then add 250g of high-viscosity CMCNa and 50g of HPC to the solution, and stir thoroughly at 150rpm for 12h at room temperature to make the system uniformly mixed and obtain a mixed solution.

[0096] 2) Add the obtained mixed solution to a stainless steel tray, with each tray weighing about 2500g. Place the tray in a 120℃ oven for 12 hours to dry.

[0097] 3) The obtained dried product is crushed and sieved to obtain the dried product.

[0098] Examples 8-9 and Comparative Examples 8-9 are basically the same as Example 4, except that the contents of high-viscosity CMCNa-1 and HPC in the mixed solution are different. Example 8 includes Examples 8-1 to 8-4. Specific parameters and performance data are shown in Table 3.

[0099] Table 3

[0100]

[0101]

[0102] As shown in Table 3, compared with Comparative Examples 7-9, the cellulose-based hydrogels prepared in Examples 7-9 can have both higher water absorption ratio and storage modulus.

[0103] As can be seen from Examples 7, 8-1 and 9, the cellulose-based hydrogel prepared in Example 8-1 can achieve a higher water absorption ratio and a higher storage modulus.

[0104] As can be seen from Examples 8-1 to 8-5, when using high-viscosity sodium carboxymethyl cellulose and low-viscosity hydroxypropyl cellulose, the viscosity of the low-viscosity hydroxypropyl cellulose in a 2w% aqueous solution at 25°C is preferably 50 to 280 cps; more preferably 50 to 150 cps.

[0105] Comparative Example 10

[0106] Materials: Sodium carboxymethyl cellulose 3 (CMCNa-3, with a viscosity of 8000 cps in a 1w% aqueous solution at 25℃ and a degree of substitution of 0.9), purchased from a relevant domestic manufacturer.

[0107] 1) Add 10L of purified water to a 25L stirred reactor, add 1.5g of CA to the water, and then add 150g of CMCNa-3 to the solution. Stir thoroughly at 150rpm for 48 hours at room temperature to ensure the system is mixed evenly and obtain a mixed solution.

[0108] 2) Add the obtained mixed solution to a stainless steel tray, with each tray weighing about 2500g. Place the tray in a 120℃ oven for 12 hours to dry.

[0109] 3) The obtained dried product is crushed and sieved to obtain the final product.

[0110] Comparative Example 10, Examples 2, 5, and 8, have specific parameters as shown in Table 4 below. In Table 4, the single-batch dissolution amount refers to the total amount of each cellulose derivative, and the stirring dissolution time refers to the time required to achieve uniform mixing of the system.

[0111] Table 4

[0112] Group Single batch dissolution amount Dissolving time by stirring Water absorption ratio Storage modulus (Pa) Comparative Example 10 150g 48h 105 1000 Example 2-1 300 g 12h 110 1500 Example 5-1 300 g 12h 140 1200 Example 8-1 300 g 12h 130 1400

[0113] As can be seen from the comparison, the medium and low viscosity cellulose derivative raw materials in the embodiments of the present invention have a short raw material dissolution time, a high soluble concentration, and a high single batch yield. Furthermore, by using a strategy of high and low molecular weight or high and low viscosity, products with better water absorption ratio and storage modulus than those in Comparative Example 10 can be prepared.

[0114] The test methods for water absorption ratio and storage modulus of the above embodiments and comparative examples are as follows.

[0115] (I) Water absorption ratio test procedure:

[0116] A. Weigh 0.250±0.005g of sample, record the actual mass as m1, and add the sample to a beaker.

[0117] B. Add 40.0±1.0 ml of an aqueous solution with a pH of 2.1±0.1 to the beaker.

[0118] C. Place the beaker on a magnetic stirrer and stir gently at room temperature for 30 ± 2 minutes without creating vortices.

[0119] D. Filter the resulting suspension with a lint-free cloth and let it stand for 10±1 minutes to allow the solution to be fully filtered.

[0120] E. Collect the remaining substance with a medicine spoon, weigh it, and record its mass as m2.

[0121] The water absorption ratio (MUR) is calculated using the following formula: MUR = (m2 - m1) / m1. At least three tests should be conducted, and the average value is the water absorption ratio.

[0122] (II) Storage Modulus Test Procedure:

[0123] 1) Sample preparation

[0124] A. Weigh 0.250±0.005g of the sample and place it in 40.0±1.0ml of aqueous solution with a pH of 2.1±0.1. Stir gently at 37℃ without creating a vortex.

[0125] B. Filter the sample using a cleanroom cloth. Pour the sample onto the raised cleanroom cloth to filter out the liquid.

[0126] C. Spread out the lint-free cloth and then spread the sample out to allow the liquid to filter quickly.

[0127] D. Place the lint-free cloth containing the sample on a paper towel (3 layers) and let it stand for 5 seconds.

[0128] E. Remove the lint-free cloth containing the sample from the paper towel and let it sit on the table for 5 minutes.

[0129] F. Samples were taken for storage modulus testing.

[0130] 2) Storage modulus test

[0131] A. Select a serrated anti-slip parallel plate with a diameter of 20mm and set the spacing between the parallel plates to zero.

[0132] B. Set the following parameters: parallel plate spacing is 1.0 mm, oscillation mode, frequency scan (0.159~4.77Hz / 0.999~29.97rad / s), and take 10 points for each order of magnitude.

[0133] C. Raise the upper parallel plate, take an appropriate amount of sample and place it on the lower parallel plate, so that after the upper parallel plate is reset, the sample can fill the gap and avoid overflowing the lower parallel plate as much as possible.

[0134] D. The sample does not stick to the edges.

[0135] E. Control the sample stage temperature at 37℃ and keep the sample for 5 minutes.

[0136] F. Begin the test.

[0137] G. After the test, record the storage modulus values ​​corresponding to 10 rad / s and 3 Hz. At least three tests should be performed, and the average value should be taken as the storage modulus value.

[0138] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0139] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A cellulose-based hydrogel, characterized in that, Its raw materials include a first cellulose derivative, a second cellulose derivative, and a crosslinking agent; Wherein, the viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3000~6000 cps; the first cellulose derivative and the second cellulose derivative are the same cellulose ether, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30~500 cps; or, the first cellulose derivative and the second cellulose derivative are different cellulose ethers, and the viscosity of the second cellulose derivative in a 2 wt% aqueous solution at 25°C is 30~280 cps; in the total mass of the first cellulose derivative and the second cellulose derivative, the mass content of the first cellulose derivative is 75%~95%; The first cellulose derivative is carboxymethyl cellulose salt; the second cellulose derivative is selected from at least one of carboxymethyl cellulose, carboxymethyl cellulose salt, hydroxyethyl cellulose and hydroxypropyl cellulose.

2. The cellulose-based hydrogel as described in claim 1, characterized in that, The viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3500~4800 cps.

3. The cellulose-based hydrogel as described in claim 2, characterized in that, The viscosity of the first cellulose derivative in a 1 wt% aqueous solution at 25°C is 3500~4500 cps.

4. The cellulose-based hydrogel as described in claim 1, characterized in that, The first cellulose derivative and the second cellulose derivative are the same cellulose ether, and the viscosity of the second cellulose derivative in a 2wt% aqueous solution at 25°C is 30~300cps.

5. The cellulose-based hydrogel according to any one of claims 1 to 4, characterized in that, The crosslinking agent includes at least one of oxalic acid, tartaric acid, malonic acid, maleic acid, succinic acid, citric acid, phthalic acid, pyromellitic acid, ethylenediaminetetraacetic acid, and carboxyl-terminated multi-arm polyethylene glycol.

6. The cellulose-based hydrogel according to any one of claims 1 to 4, characterized in that, The crosslinking agent has a mass content of 0.1% to 5% relative to the total mass of each cellulose.

7. A method for preparing a cellulose-based hydrogel as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A first cellulose derivative, a second cellulose derivative, a crosslinking agent, and water are mixed to obtain a mixed solution; and The mixed solution is heat-treated to dry and then subjected to a cross-linking reaction to obtain the cellulose-based hydrogel.

8. The preparation method according to claim 7, characterized in that, In the mixed solution, the total mass content of the first cellulose derivative and the second cellulose derivative is 1% to 4%.

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