Preparation method of cellulose hydrogel
Through two modification treatments of ionizing radiation and bisulfite solution, cellulose hydrogels have achieved high purity and easy preparation of gelatin, solving the problem that cellulose is difficult to form hydrogels, and using homogeneous treatment and The stabilizer promotes the self-crosslinking of cellulose and the formation of three-dimensional network structures, achieving efficient and environmentally friendly cellulose hydrogel preparation.
Patent Information
- Application Number
- CN202411488837.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-24
- Publication Date
- 2024-12-20
AI Technical Summary
Cellulose is difficult to dissolve in water and other common solvents, which makes it usually used as a reinforcement with a small amount when prepared as a hydrogel, and it is difficult to form hydrogels with high purity.
The cellulose powder is modified by ionizing radiation and is modified again with the bisulfite solution to form a cellulose hydrogel that is easy to form a gel with water. A homogenization treatment and a stabilizer are used to promote self-crosslinking of the cellulose and a three-dimensional network structure.
The cellulose hydrogel is achieved with high purity and easy to make gel-forming, avoiding the use of strong acids, strong alkalis and highly toxic reagents, simple process, easy to prepare on a large scale, and reduces irradiation costs and equipment requirements.
Smart Images
Figure CN119161598A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of gel materials, and in particular relates to a method for preparing a hydrogel. Background Art
[0002] Hydrogel is a three-dimensional network polymer composed of a hydrophilic skeleton with good water retention. Depending on the source of the raw materials, hydrogels can be divided into natural hydrogels and synthetic hydrogels. Natural hydrogels, such as agar and gelatin, are usually derived from natural polymers such as plant polysaccharides and proteins, while synthetic hydrogels, such as sodium polyacrylate gel, are mainly prepared through polymerization reactions. Hydrogels have been widely used in the fields of medicine, cosmetics, and agriculture. For example, medical hydrogels are used as dressings for wound healing and infection prevention. In the agricultural field, they are used to improve soil water retention and increase crop yields. In the cosmetic field, they are used to increase the moisturizing effect of products. Hydrogel ingredients are added to skin care products and cosmetics.
[0003] Cellulose is widely found in plants, animals, algae and fungi. It is the most abundant renewable natural polymer on earth. About 1.5×10 12 Tons. Cellulose-based hydrogels have many excellent properties such as hydrophilicity, degradability, biocompatibility, low cost and non-toxicity, and have broad application prospects in the medical fields such as three-dimensional cell culture, tissue engineering, wound dressings, drug delivery, diagnosis and separation, as well as in the field of food antibacterial preservation materials.
[0004] However, due to the hydrogen bonds within and between cellulose molecules, the contact between hydroxyl groups and water molecules is blocked. In addition, hydrogen bonds give cellulose a rigid structure and induce complex aggregation, which makes cellulose present different hydrophilic / hydrophobic interfaces, making cellulose difficult to dissolve in water and other common solvents, and difficult to prepare as hydrogels. Therefore, current cellulose hydrogels are usually prepared by mixing with other gel-forming substances, such as polyvinyl alcohol, gelatin, sodium alginate, etc., and cellulose is only used as a reinforcing agent with a small amount of addition. Summary of the invention
[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a method for preparing cellulose hydrogel which is easy to gel and has high hydrogel purity.
[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing a cellulose hydrogel comprises the following steps: (1) modifying cellulose powder using ionizing radiation to obtain a first modified cellulose; (2) modifying the first modified cellulose again using a bisulfite solution, and separating the modified cellulose from the bisulfite solution to obtain a second modified cellulose; (3) Mixing the second modified cellulose with water and allowing the mixture to stand to form a gel, thereby obtaining the cellulose hydrogel.
[0007] In the above preparation method, preferably, the second modified cellulose is mixed with water and then homogenized, and the homogenization method includes one or more of ultrasonic homogenization, high-pressure homogenization and ball milling homogenization.
[0008] In the above preparation method, preferably, a stabilizer is added before standing to form a gel, and the stabilizer includes Fe 3+ , Sr 2+ 、Zn 2 + , Ba 2+ and Mg 2+ In the present invention, the stabilizer can be added to make the modified cellulose gel.
[0009] In the above preparation method, preferably, the radiation dose of the ionizing radiation is ≥50 kGy, and the ionizing radiation includes gamma rays, electron beams or X-rays. In the present invention, cellulose powder needs to be modified by ionizing radiation, and the radiation dose needs to meet the requirements. In the present invention, the radiation dose can be selected to be ≥50 kGy. Considering that increasing the radiation dose does not significantly improve the performance of the modified product, the radiation dose can be ≤800 kGy.
[0010] In the above preparation method, preferably, cellulose is modified by ionizing radiation in air. In the present invention, cellulose powder is irradiated and modified in air alone, and then combined with other methods (such as sodium bisulfite, homogenization, etc.) to finally form a hydrogel, without the need to use other components of the cross-linking sensitizer. Therefore, only one material, cellulose powder, needs to be irradiated, and other materials do not need to be irradiated together (especially cellulose mixed with other reagents requires a large amount of water, and the presence of water may produce a large number of additional reactions, which may affect the final result), thereby greatly reducing the mass of the required irradiated object, greatly reducing the irradiation cost, and improving the irradiation efficiency.
[0011] In the above preparation method, preferably, the bisulfite solution is a sodium bisulfite solution, and the mass concentration of bisulfite in the bisulfite solution is 2-50%. If the concentration of bisulfite is too low, the modification effect is poor, and if the concentration of bisulfite is too high, the bisulfite reaches saturation, and the higher the concentration, the higher the cost, and the effect does not change much.
[0012] In the above preparation method, preferably, the liquid-to-solid ratio of the bisulfite solution to the first modified cellulose is (2.5-50) L: 1 kg. If the liquid-to-solid ratio is too low, stirring is impossible during the reaction, and if the liquid-to-solid ratio is too high, the cost performance is poor.
[0013] In the above preparation method, preferably, when the first modified cellulose is modified again with a bisulfite solution, the modification temperature is 0-50°C and the modification time is ≥30 minutes. If the above modification temperature is too high, the cellulose may be carbonized, which will affect the cellulose gelling.
[0014] In the above preparation method, preferably, the second modified cellulose is separated from the bisulfite solution by centrifugation, filtration, etc.
[0015] In the above preparation method, preferably, when the second modified cellulose is mixed with water, the mass (kg) volume (L) ratio of the second modified cellulose to water is 1: (2-100). If the water ratio is too high, the second modified cellulose is difficult to form a network structure and will not form a gel; if the water ratio is too low, the performance of the gel structure is poor.
[0016] In the above preparation method, preferably, no crosslinking agent is added during the static gelation process. In the present invention, cellulose powder is irradiated and modified in air alone, and then combined with other methods (such as sodium bisulfite, homogenization, etc.) to finally form a hydrogel, without using other components of the crosslinking sensitizer, the reagent dosage is less, and the hydrogel is purer.
[0017] In the above preparation method, preferably, the temperature during standing to form gel is 0-50°C and the standing time is 0.5-48h.
[0018] In the preparation method of the cellulose hydrogel of the present invention, after the cellulose powder is modified by ionizing radiation in the air, the degree of polymerization is reduced, and the chemical structure changes, a new C=O functional group is generated, the hydrophilicity is significantly increased, and the dispersibility in water is significantly improved. When modified again, the bisulfite reacts with the cellulose to further increase the hydrophilicity of the cellulose and simultaneously form self-crosslinking points. The modified cellulose after the two modifications is mixed with water and allowed to stand to form a gel, thereby obtaining a cellulose hydrogel. After the modified cellulose is mixed with water, the degree of polymerization of the cellulose can be further reduced by homogenization, and the physical size can be homogenized, which is more conducive to gelation. When standing to form a gel, a stabilizer is added to reduce the repulsion between the modified cellulose particles, so that the modified cellulose particles are close to each other, and the modified fiber molecules are promoted to crosslink to form a three-dimensional network structure, thereby making it easier to form a hydrogel.
[0019] Compared with the prior art, the advantages of the present invention are: 1. The preparation method of the cellulose hydrogel of the present invention utilizes ionizing radiation to modify cellulose, and then utilizes a bisulfite solution to modify it again. Through the two modifications, the dispersibility of cellulose in water can be significantly improved, and self-crosslinking points can be formed, so that the cellulose hydrogel can be easily prepared.
[0020] 2. The cellulose hydrogel prepared by the preparation method of the cellulose hydrogel of the present invention is a pure cellulose hydrogel, and there is no need to add cellulose as an auxiliary material to other gels to prepare the gel, and the cellulose hydrogel has a high purity.
[0021] 3. The preparation method of the cellulose hydrogel of the present invention avoids the use of strong acids, strong bases and highly toxic reagents, and is a green and environmentally friendly preparation method; at the same time, the process operation is simple, the equipment requirements are not high, and it is easy to prepare on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0023] Figure 1 FT-IR spectra of the first modified cellulose obtained after the cellulose is subjected to different radiation doses in the example.
[0024] Figure 2 FT-Raman spectra of the first modified cellulose obtained after the cellulose is subjected to different radiation doses in the example.
[0025] Figure 3 This is a graph showing the change in degree of polymerization of the first modified cellulose obtained after different radiation doses in the example.
[0026] Figure 4 Graph showing the change in aldehyde content of the first modified cellulose obtained after different radiation doses in the examples.
[0027] Figure 5 This is a picture of the cellulose dispersed in water in Comparative Example 1 after being left to stand for 48 hours.
[0028] Figure 6 This is a picture of the modified cellulose in Comparative Example 2 after being dispersed in water and left to stand for 48 hours.
[0029] Figure 7 This is a picture of the modified cellulose in Comparative Example 3 after being dispersed in water and left to stand for 48 hours.
[0030] Figure 8This is a picture of the cellulose dispersed in water in Example 1 after being allowed to stand for 48 hours to form gel. DETAILED DESCRIPTION
[0031] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.
[0032] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.
[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.
[0034] Embodiment 1: A method for preparing a cellulose hydrogel comprises the following steps: (1) 1 kg of cellulose powder was irradiated with gamma rays at a dose of 400 kGy.
[0035] (2) The first modified cellulose in step (1) was mixed with 25 L of 6% sodium bisulfite solution, stirred for reaction, and the reaction temperature was controlled at 25° C. for 2 h.
[0036] (3) Filtering the cellulose obtained in step (2) with a filter membrane pore size of ≤100 nm to obtain a second modified cellulose.
[0037] (4) The second modified cellulose separated in step (3) was mixed with 30 L of water and homogenized by ultrasound at an ultrasonic power of 5000 W for 20 min.
[0038] (5) Add 60 g of barium chloride and 90 g of sodium chloride to the second modified cellulose solution homogenized in step (4), place it at 5° C., and let it stand for 48 hours to form a gel, thereby obtaining a cellulose hydrogel.
[0039] The radiation dose in Example 1 was changed to 0, 200, 400, 600, 800, 1000, and 1200 kGy, respectively. The FT-IR and FT-Raman spectra of the first modified cellulose were as follows: Figure 1 , Figure 2 As shown in the figure, compared with cellulose without radiation modification, cellulose after irradiation has a -1 The generation of a new absorption peak suggests the generation of a C=O functional group. Figure 3is the degree of polymerization of the first modified cellulose obtained after different radiation doses. It can be seen from the figure that radiation can significantly reduce the degree of polymerization of cellulose, and the reduction in the degree of polymerization promotes the improvement of cellulose dispersibility. Figure 4 This is a graph showing the change in aldehyde content of the first modified cellulose after different radiation doses. It can be seen from the graph that the aldehyde content of cellulose increases significantly after radiation, providing conditions for sodium bisulfite modification.
[0040] Embodiment 2: A method for preparing a cellulose hydrogel comprises the following steps: (1) 1 kg of cellulose powder was irradiated with electron beam radiation at a dose of 300 kGy.
[0041] (2) The first modified cellulose in step (1) was mixed with 20 L of a 10% sodium bisulfite solution, and the mixture was stirred for reaction. The reaction temperature was controlled at 23° C. and the reaction was continued for 2 h.
[0042] (3) The cellulose obtained in step (2) was centrifuged and washed at a centrifugal force of 6000 g, and the washing was repeated three times.
[0043] (4) The second modified cellulose separated in step (3) was mixed with water at a ratio of 1:20 and then ball-milled for 3 h at a speed of 300 rpm / min. After ball-milling, the mixture was transferred to 50 L with water and homogenized with ultrasound at a power of 5000 W for 10 min.
[0044] (5) Add 45 g of barium chloride and 30 g of ferric chloride to the second modified cellulose solution homogenized in step (4), place it at 10° C., and let it stand for 48 hours to form a gel, thereby obtaining a cellulose hydrogel, similar to Example 1.
[0045] Embodiment 3: A method for preparing a cellulose hydrogel comprises the following steps: (1) 10 kg of cellulose powder was irradiated with electron beam radiation at a dose of 400 kGy.
[0046] (2) The first modified cellulose in step (1) was mixed with 300 L of 8% sodium bisulfite solution, stirred for reaction, and the reaction temperature was controlled at 22° C. for 3 h.
[0047] (3) Filter the cellulose obtained in step (2), with the pore size of the filter membrane being ≤80 nm.
[0048] (4) The second modified cellulose separated in step (3) was mixed with 30 L of water and homogenized by ultrasound at an ultrasonic power of 40 kW for 5 min. The homogenized liquid was then homogenized twice at 800 bar using a high-pressure homogenizer.
[0049] (5) Add 180 g of magnesium sulfate and 180 g of zinc chloride to the second modified cellulose solution homogenized in step (4), place it at 5° C., and let it stand for 48 hours to form a gel, thereby obtaining a cellulose hydrogel, similar to Example 1.
[0050] Comparative Example 1: In this comparative example, cellulose powder was not modified. 1 kg cellulose powder was directly mixed with 30 L water and homogenized by ultrasound. The ultrasonic power was 5000 W and the homogenization time was 20 min. Then 60 g barium chloride and 90 g sodium chloride were added to the homogenized cellulose solution and placed at 5°C for 48 hours without gelation. The results are as follows: Figure 5 shown.
[0051] Figure 5 The left side is the cellulose sample without any treatment, and the right side is the comparative sample. Figure 5 It can be seen that the dispersibility of cellulose can be significantly improved after ultrasonic homogenization, but the cellulose in this comparative example is not modified and is ultimately difficult to gel.
[0052] Comparative Example 2: In this comparative example, 1 kg of cellulose powder was treated with gamma ray radiation at a dose of 400 kGy, and then mixed with 30 L of water, ultrasonically homogenized at an ultrasonic power of 5000 w for 20 min, and then the homogenized cellulose solution was added with 60 g of barium chloride and 90 g of sodium chloride and placed at 5 ° C for 48 h without gelling. The results are as follows: Figure 6 shown.
[0053] Figure 6 The left side is the cellulose sample without any treatment, and the right side is the comparative sample. Figure 6 It can be seen that the dispersibility of cellulose is significantly improved after γ-ray radiation treatment and ultrasonic homogenization, but the cellulose in this comparative example is not modified by sodium bisulfite and is ultimately difficult to gel.
[0054] Comparative Example 3: In this comparative example, 1 kg of cellulose powder was mixed with 25 L of 6% sodium bisulfite solution, stirred for reaction, the reaction temperature was controlled to be 25 ° C, the reaction was carried out for 2 hours, and then filtered, the filter membrane pore size was ≤ 100 nm, and then ultrasonic homogenized, the ultrasonic power was 5000 w, the homogenization time was 20 minutes, and finally the homogenized cellulose solution was added with 60 g of barium chloride and 90 g of sodium chloride, and then placed at 5 ° C, and stood for 48 hours without gelation. The results are as follows: Figure 7 shown.
[0055] Figure 7 The left side is the cellulose sample without any treatment, and the right side is the comparative sample. Figure 7 It can be seen that the dispersibility of cellulose is significantly improved after being treated with sodium bisulfite solution and ultrasonic homogenization, but the cellulose in this comparative example is not treated with γ-ray radiation and is ultimately difficult to gel.
[0056] The second modified cellulose in Example 1 and the unmodified cellulose were dispersed in water and allowed to stand for 48 hours. The gelling properties were as follows: Figure 8 As shown, the left side of the figure is a schematic diagram of the gelation of unmodified cellulose, and the right side is a schematic diagram of the gelation of the second modified cellulose in Example 1. It can be seen from the figure that the cellulose in Example 1 has significantly better gelation performance after two modification treatments, while the cellulose that has not been modified cannot be gelled.
Claims
1. A method for preparing a cellulose hydrogel, characterized in that: The following steps are involved: (1) modifying cellulose powder using ionizing radiation to obtain a first modified cellulose; (2) modifying the first modified cellulose again using a bisulfite solution, and separating the modified cellulose from the bisulfite solution to obtain a second modified cellulose; (3) Mixing the second modified cellulose with water and allowing the mixture to stand to form a gel, thereby obtaining the cellulose hydrogel.
2. The preparation method according to claim 1, characterized in that: The second modified cellulose is mixed with water and then homogenized. The homogenization method includes one or more of ultrasonic homogenization, high-pressure homogenization and ball milling homogenization.
3. The preparation method according to claim 1, characterized in that: Before standing to form gel, a stabilizer is added, wherein the stabilizer includes Fe 3+ , Sr 2+ 、Zn 2+ , Ba 2+ and Mg 2+ One or more of the .
4. The preparation method according to any one of claims 1 to 3, characterized in that The radiation dose of the ionizing radiation is ≥50 kGy, and the ionizing radiation includes gamma rays, electron beams or X-rays.
5. The preparation method according to any one of claims 1 to 3, characterized in that: Cellulose powder is modified using ionizing radiation in air.
6. The preparation method according to any one of claims 1 to 3, characterized in that: The bisulfite solution is a sodium bisulfite solution, and the mass concentration of bisulfite in the bisulfite solution is 2-50%.
7. The preparation method according to any one of claims 1 to 3, characterized in that: The liquid-to-solid ratio of the bisulfite solution to the first modified cellulose is (2.5-50) L: 1 kg.
8. The preparation method according to any one of claims 1 to 3, characterized in that When the first modified cellulose is modified again with a bisulfite solution, the modification temperature is 0-50° C. and the modification time is ≥30 min.
9. The preparation method according to any one of claims 1 to 3, characterized in that: When the second modified cellulose is mixed with water, the mass volume ratio of the second modified cellulose to water is 1:(2-100).
10. The preparation method according to any one of claims 1 to 3, characterized in that: No cross-linking agent is added during the static gelation process.