Preparation method of cellulose degradable water-absorbent resin

Abstract

The invention relates to the technical field of resin preparation, in particular to a preparation method of cellulose degradable water-absorbent resin, which comprises the following steps: mixing sodium carboxymethyl cellulose with water, heating and stirring to obtain a homogeneous solution; a multi-section temperature curve of a freezing procedure is determined according to solution parameters, the solution is placed in one-way freezing equipment, the temperature of a bottom plate is controlled to range from-60 DEG C to-40 DEG C, and ice crystals directionally grow in the vertical direction of the surface of the solution; adding citric acid into the frozen sample, and reacting for 1-2 hours; heating to 40 + / -5 DEG C under the vacuum pressure of 1-5kPa, drying at constant temperature for 12-36 hours, soaking and washing twice with deionized water, 1 hour each time, finally drying for 6-10 hours, and crushing until the particle size is 0.5-2.0 mm. According to the invention, one-way freezing equipment capable of accurately controlling the freezing rate is adopted, and a magnetic field with specific parameters is applied in a slow cooling stage, so that the growth direction, size and distribution of ice crystals can be more effectively controlled; therefore, a more uniform and controllable pore structure is formed in the final water-absorbent resin.

Description

Technical Field

[0001] The present invention relates to the technical field of resin preparation, and more specifically, it relates to a preparation method of a cellulose-based biodegradable water-absorbing resin. Background Art

[0002] Superabsorbent Polymers (SAPs) are a class of polymer materials with extremely strong water absorption ability, and are widely used in fields such as sanitary products, agricultural water retention, and medical dressings. Although traditional synthetic water-absorbing resins, such as sodium polyacrylate, have excellent water absorption performance, their non-biodegradability brings serious environmental problems. Therefore, the development of biodegradable water-absorbing resins has become a current research hotspot.

[0003] As one of the most abundant natural polymers on the earth, cellulose has good biocompatibility, renewability, and biodegradability, and is an ideal raw material for preparing environmentally friendly water-absorbing resins. Currently, the methods for preparing biodegradable water-absorbing resins using cellulose and its derivatives mainly include the following several types:

[0004] Cellulose graft copolymerization method: This is to graft synthesized hydrophilic monomers (such as acrylic acid, acrylamide, etc.) onto the cellulose backbone by chemical or physical methods, and then crosslink to form a water-absorbing resin. Although this method can significantly improve the water absorption performance of cellulose, since the grafted synthetic polymers are usually difficult to be completely biodegradable, the overall biodegradability of the obtained water-absorbing resin may be affected.

[0005] Cellulose derivative crosslinking method: This method usually first chemically modifies cellulose, such as carboxymethylation, hydroxyethylation, etc., to obtain water-soluble cellulose derivatives, and then crosslinks by adding polyvalent metal ions, organic crosslinking agents or by radiation, etc., to form a water-absorbing gel with a three-dimensional network structure. Sodium carboxymethyl cellulose (CMC-Na) is a commonly used cellulose derivative, and a biodegradable water-absorbing resin with certain water absorption performance can be prepared by crosslinking with a suitable crosslinking agent.

[0006] The water absorption performance of the water-absorbing resin not only depends on its chemical composition, but is also closely related to its internal microstructure and morphology. For example, a porous structure can increase the contact area between the water-absorbing resin and water, which is beneficial to the rapid diffusion and absorption of water molecules. Therefore, in the process of preparing the water-absorbing resin, controlling its internal structure and morphology is crucial for improving the water absorption performance.

[0007] Freeze-drying, as a gentle drying method, is often used to prepare porous materials. In the preparation of certain water-absorbing resins, the freezing and thawing (or sublimation) steps can be used to manipulate the pore structure of the final product. For example, by controlling the freezing rate, the size and distribution of ice crystals can be influenced, thereby affecting the pore size and porosity of the final water-absorbing resin.

[0008] However, in the process of preparing cellulose degradable water-absorbing resin using freeze-drying technology, the existing technology still has some shortcomings in accurately controlling the freezing and thawing methods to optimize the water absorption performance:

[0009] Traditional freezing methods often make it difficult to achieve precise control of the freezing rate, resulting in uneven growth of ice crystals and difficulty in achieving the optimal pore structure.

[0010] Existing freeze-drying methods primarily focus on regulating pore size and porosity, but struggle to effectively control the pore orientation. However, in certain applications, such as those requiring rapid water absorption and fluid diversion, water-absorbent resins with oriented pore structures may exhibit superior performance.

[0011] The challenge of balancing biodegradability and high performance: While pursuing high water absorption performance, how to select suitable cellulose derivatives and cross-linking agents and optimize the preparation process to ensure that the resulting water-absorbent resin has good biodegradability remains a challenge.

[0012] Therefore, for the preparation of cellulose degradable water-absorbing resin, developing a new method that can accurately control the freezing and thawing mode to more effectively regulate its internal structure and morphology, thereby further improving its water absorption rate and capacity while ensuring its degradability, is a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0013] To this end, the object of the present invention is to provide a method for preparing a cellulose degradable water-absorbing resin, which has a specific microstructure and excellent water absorption performance by precisely controlling the freezing rate and direction.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] A method for preparing a cellulose degradable water-absorbing resin comprises the following steps:

[0016] S1. Solution preparation: Mix sodium carboxymethyl cellulose with water, heat to 70°C to 85°C, and stir at a speed of 300 rpm to 450 rpm for 1 hour to 1.5 hours to obtain a homogeneous solution; wherein the concentration of sodium carboxymethyl cellulose is 2.0% to 4.0% of the total mass of the solution;

[0017] S2. Freezing parameter setting: Determine the multi-stage temperature curve of the freezing process according to the solution parameters. The freezing process includes:

[0018] Rapid cooling stage: Cool the solution from 20°C to -10°C ± 2°C at a rate of 2°C / min to 8°C / min.

[0019] Nucleation holding stage: Hold at -10°C ± 2°C for 10 min to 45 min.

[0020] Slow cooling stage: Continue to cool to -50°C ± 5°C at a rate of 0.1°C / min to 0.8°C / min.

[0021] Final freezing stage: Hold at -50°C ± 5°C for 4 h to 18 h.

[0022] S3. Directional freezing treatment: Place the solution in a unidirectional freezing device, control the bottom plate temperature at -60°C to -40°C, and make the ice crystals grow directionally along the vertical direction of the solution surface.

[0023] S4. Crosslinking reaction: Add citric acid to the frozen sample. The mass ratio of citric acid to sodium carboxymethylcellulose is 0.5:1 to 1.5:1, and react at 140°C to 160°C for 1 h to 2 h.

[0024] S5. Sublimation drying: Under a vacuum pressure of 1 to 5 kPa, heat up to 40°C ± 5°C at a rate of 0.2°C / min to 1.0°C / min, and keep drying at a constant temperature for 12 h to 36 h until the residual moisture ≤ 5%.

[0025] S6. Post-treatment: Soak and wash with deionized water twice, 1 h each time, and finally dry at 40°C to 50°C for 6 h to 10 h, and crush to a particle size of 0.5 mm to 2.0 mm.

[0026] The present invention is further configured that: glycerol is further added in step S1, and the addition amount of glycerol is 0.1% to 0.5% of the mass of sodium carboxymethylcellulose.

[0027] The present invention is further configured that: the temperature parameters in the freezing stage in step S2 are defined by the following formula:

[0028] The cooling rate R of the slow cooling stage slow and the final freezing temperature T freeze satisfy R slow = 0.02 × |T freeze |, where T freeze is -50°C to -30°C.

[0029] The present invention is further configured that: in the sublimation drying of step S5, the relationship between the heating rate and the final temperature satisfies:

[0030] Heating rate R dry = 0.05×T final , where T final is 30°C to 50°C.

[0031] The present invention is further configured such that: during the directional freezing treatment in step S3, a magnetic field is applied synchronously, the magnetic field strength is 100 Gs to 800 Gs, and the magnetic field direction is perpendicular to the ice crystal growth direction.

[0032] The present invention is further configured such that: the relationship between the magnetic field strength B and the freezing rate Rslow satisfies B = 50×Rslow + 100.

[0033] The present invention is further configured such that: in step S4, a nano-silica modifier is further added, and its addition amount is 0.3% - 1.2% of the mass of sodium carboxymethyl cellulose, and the nano-silica particle size is 20 - 100 nm, and the specific surface area ≥ 200 m² / g.

[0034] The present invention is further configured such that: the magnetic field application adopts a pulse mode, the pulse frequency is 0.5 - 5 Hz, the duty cycle is 30% - 70%, and it is applied throughout the slow cooling stage.

[0035] The present invention is further configured such that: the nano-silica surface is grafted with an amino-silane coupling agent, the grafting rate is 15% - 35%, and the relationship between the modifier addition amount D and the magnetic field strength B satisfies the formula: D(%) = 0.002×B + 0.1.

[0036] The present invention is further configured such that: the water used in step S1 is ultrapure water with a conductivity ≤ 5 μS / cm, and ultrasonic degassing treatment is performed during the stirring process, the ultrasonic frequency is 40 kHz, the power is 300 W, and the treatment time is 10 - 20 minutes.

[0037] Comparing with the deficiencies of the prior art, the beneficial effects of the present invention are:

[0038] By using a unidirectional freezing device capable of precisely controlling the freezing rate and applying a magnetic field with specific parameters during the slow cooling stage, the growth direction, size, and distribution of ice crystals can be controlled more effectively, thereby forming a more uniform and controllable pore structure in the final water-absorbing resin.

[0039] Through the synergistic effect of unidirectional freezing and the magnetic field, a pore channel with a certain directionality is constructed inside the water-absorbing resin. This directional pore structure is more conducive to the rapid diffusion and transmission of water molecules, thereby improving the water absorption speed and flow guiding performance, and is particularly suitable for application scenarios that require rapid water absorption and keeping dry. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a trend graph of the addition amount D of the modifier and the magnetic field strength B. Detailed implementation mode

[0041] A further description of the preparation method of a cellulose-degradable water-absorbing resin of the present invention is as follows:

[0042] This method first prepares a solution, then freezes it through a precisely set multi-stage freezing procedure, and applies a magnetic field with specific parameters during the directional freezing process. Subsequently, a cross-linking reaction is carried out, introducing a nano-silica modifier to enhance the performance, and the water is removed by sublimation drying. Finally, the final product is obtained through post-treatment.

[0043] Step 1: Solution preparation

[0044] Dissolve sodium carboxymethyl cellulose with a concentration of 2.0% - 4.0% in ultrapure water with a conductivity ≤ 5 μS / cm. To further optimize the performance, glycerol accounting for 0.1% - 0.5% of the mass of sodium carboxymethyl cellulose can be added as a plasticizer. Stir (300 r / min - 450 r / min) and heat (70 °C - 85 °C) for 1 h - 1.5 h until a uniform and transparent solution is formed. To remove the gas dissolved in the water, ultrasonic degassing treatment (ultrasonic frequency 40 kHz, power 300 W, treatment time 10 - 20 minutes) is carried out synchronously during the stirring process.

[0045] Step 2: Freezing parameter setting and directional freezing

[0046] Place the prepared solution in a unidirectional freezing device, and precisely control the bottom plate temperature at -60 °C - -40 °C to guide the ice crystals to grow directionally along the vertical direction of the solution surface. During the directional freezing process, a multi-stage temperature curve is used for control, including: a rapid cooling stage (cooling from 20 °C to -10 °C ± 2 °C at a rate of 2 °C / min - 8 °C / min), a nucleation holding stage (holding at -10 °C ± 2 °C for 10 min - 45 min), a slow cooling stage (continuing to cool to -50 °C ± 5 °C at a rate of 0.1 °C / min - 0.8 °C / min), and a final freezing stage (holding at -50 °C ± 5 °C for 4 h - 18 h). The cooling rate R slow and the final freezing temperature T freeze satisfy the empirical formula: R slow = 0.02 × |T freeze |, where T freeze is -50 °C - -30 °C. A magnetic field is applied synchronously throughout the slow cooling stage of the directional freezing, the magnetic field direction is perpendicular to the ice crystal growth direction, the magnetic field intensity is 100 Gs - 800 Gs, and a pulse mode is used, with a pulse frequency of 0.5 - 5 Hz and a duty cycle of 30% - 70%. The relationship between the magnetic field intensity B and the freezing rate R slow satisfies: B = 50 × R slow+100。

[0047] Step 3: Crosslinking and modification

[0048] Add citric acid as a crosslinking agent to the frozen sample. The mass ratio of citric acid to sodium carboxymethylcellulose is 0.5:1 to 1.5:1. To further enhance the performance of the water-absorbing resin, a nano-silica modifier is added synchronously. Its addition amount is 0.3% - 1.2% of the mass of sodium carboxymethylcellulose. The particle size of the nano-silica is 20 - 100 nm, the specific surface area is ≥200 m² / g, and the surface is grafted with an amino-silane coupling agent with a grafting rate of 15% - 35%. The relationship between the addition amount D of the modifier and the magnetic field strength B satisfies the formula: D(%) = 0.002×B + 0.1 (reference Figure 1 ) The mixture is placed under the condition of 140°C - 160°C and reacted for 1 h - 2 h to complete the crosslinking reaction.

[0049] Step 4: Sublimation drying

[0050] Place the crosslinked sample in a vacuum drying device. Under the condition of a vacuum pressure of 1 - 5 kPa, at a heating rate R dry = 0.05×T final (where T final is 30°C - 50°C), raise the temperature to 40°C ± 5°C and keep it dried at a constant temperature for 12 h - 36 h until the residual moisture ≤ 5%.

[0051] Step 5: Post-treatment

[0052] Soak and wash the dried water-absorbing resin with deionized water twice, 1 hour each time, to remove unreacted substances. Finally, dry it in an oven at 40°C - 50°C for 6 h - 10 h, and crush the dried water-absorbing resin to a particle size of 0.5 mm - 2.0 mm.

[0053] Example 1:

[0054] Dissolve 2.0 g of sodium carboxymethylcellulose in 100 mL of ultrapure water with a conductivity of 3 μS / cm. Add 0.002 g of glycerol (0.1% of the mass of sodium carboxymethylcellulose). Stir at 300 r / min for 1 hour at 70°C and perform ultrasonic degassing for 10 minutes.

[0055] Place the solution in a unidirectional freezing device, and control the bottom plate temperature at -30°C. Rapidly cool it to -12°C, keep it for 10 minutes, and then cool it to -30°C at a rate of R slow = 0.02×|-30°C| = 0.6°C / min and keep it at -30°C for 4 hours. Apply a magnetic field during the slow cooling stage. The magnetic field strength B = 50×0.6 + 100 = 130 Gs, the direction is perpendicular to the ice crystal growth direction, the pulse frequency is 0.5 Hz, and the duty cycle is 30%.

[0056] Add 1.0 g of citric acid (mass ratio is 0.5:1), and add 0.006 g of nano-silica with an amino-silane coupling agent grafted on the surface (grafting rate is 15%) (particle size is 20 nm, specific surface area is 200 m² / g, addition amount D = 0.002×130 + 0.1 = 0.36%). React at 140 °C for 1 hour.

[0057] Under a vacuum pressure of 5 kPa, at a rate of R dry = 0.05×30 = 1.5 °C / min, heat up to 30 °C, and keep drying at a constant temperature for 12 hours.

[0058] Soak and wash with deionized water 2 times, 1 hour each time, and finally dry at 40 °C for 6 hours, and crush to a particle size of 1 mm.

[0059] Example 2:

[0060] Dissolve 3.0 g of sodium carboxymethyl cellulose in 100 mL of ultrapure water with a conductivity of 3 μS / cm. Add 0.012 g of glycerol (accounting for 0.4% of the mass of sodium carboxymethyl cellulose). Stir at 80 °C at 400 r / min for 1.3 hours, and perform ultrasonic degassing treatment for 15 minutes.

[0061] Place the solution in a unidirectional freezing device, and control the bottom plate temperature to -40 °C. Rapidly cool to -10 °C and keep for 30 minutes, then at a rate of R slow = 0.02×|-40 °C| = 0.8 °C / min, cool to -40 °C, and keep at -40 °C for 10 hours. Apply a magnetic field during the slow cooling stage, the magnetic field strength B = 50×0.8 + 100 = 140 Gs, the direction is perpendicular to the ice crystal growth direction, the pulse frequency is 3 Hz, and the duty cycle is 50%.

[0062] Add 3.0 g of citric acid (mass ratio is 1:1), and add 0.024 g of nano-silica with an amino-silane coupling agent grafted on the surface (grafting rate is 25%) (particle size is 60 nm, specific surface area is 250 m² / g, addition amount D = 0.002×140 + 0.1 = 0.38%). React at 150 °C for 1.5 hours.

[0063] Under a vacuum pressure of 3 kPa, at a rate of R dry = 0.05×40 = 2 °C / min, heat up to 40 °C, and keep drying at a constant temperature for 24 hours.

[0064] Soak and wash with deionized water 2 times, 1 hour each time, and finally dry at 45 °C for 8 hours, and crush to a particle size of 1.0 mm.

[0065] Example 3:

[0066] Dissolve 4.0 g of sodium carboxymethyl cellulose in 100 mL of ultrapure water with a conductivity of 3 μS / cm. Add 0.02 g of glycerol (0.5% of the mass of sodium carboxymethyl cellulose). Stir at 450 r / min at 85 °C for 1.5 hours and perform ultrasonic degassing for 20 minutes.

[0067] Place the solution in a unidirectional freezing device with the bottom plate temperature controlled at -50 °C. Rapidly cool to -8 °C and hold for 45 minutes, then cool to -50 °C at a rate of R slow = 0.02×|-50 °C| = 1.0 °C / min and hold at -50 °C for 18 hours. Apply a magnetic field during the slow cooling stage, with a magnetic field strength B = 50×1.0 + 100 = 150 Gs, perpendicular to the ice crystal growth direction, a pulse frequency of 5 Hz, and a duty cycle of 70%.

[0068] Add 6.0 g of citric acid (mass ratio of 1.5:1), and add 0.048 g of nano-silica with an amino-silane coupling agent grafted on the surface (grafting rate of 35%) (particle size of 100 nm, specific surface area of 300 m² / g, addition amount D = 0.002×150 + 0.1 = 0.4%). React at 160 °C for 2 hours.

[0069] Under a vacuum pressure of 1 kPa, heat at a rate of R dry = 0.05×50 = 2.5 °C / min to 50 °C and keep drying at a constant temperature for 36 hours.

[0070] Soak and wash with deionized water twice, 1 hour each time, and finally dry at 50 °C for 10 hours and crush to a particle size of 1.0 mm.

[0071] Comparative Example 1: Directional freezing without applying a magnetic field:

[0072] The preparation process of this Comparative Example 1 is exactly the same as that of Example 2, including solution preparation, the same multi-stage freezing parameter settings (rapid cooling, nucleation holding, slow cooling, final freezing), the same unidirectional freezing treatment (bottom plate temperature controlled at -50 °C), the same cross-linking reaction (citric acid and nano-silica), and the same sublimation drying and post-treatment steps. The only difference is that no magnetic field is applied during the directional freezing process in Step 3.

[0073] Comparative Example 2: Conventional freezing without adding nano-silica:

[0074] Solution preparation: Follow the steps of Example 2;

[0075] Freezing: The prepared solution was directly placed in an ordinary low-temperature refrigerator (set temperature of about -20 °C) and allowed to stand and freeze for 12 hours. In this process, a unidirectional freezing device was not used, precise bottom plate temperature control was not carried out, the multi-stage temperature curve in the embodiment was not implemented, and no magnetic field was applied;

[0076] Crosslinking: The steps of Example 2 were followed, but the addition of the nano-silica modifier was omitted, and only the same amount of citric acid was used as the crosslinking agent.

[0077] Sublimation drying was carried out according to the steps of Example 2; post-treatment was carried out according to the steps of Example 2.

[0078] Based on the above Examples 1 - 3 and Comparative Examples 1 and 2, the obtained finished products were tested, and the test data are shown in Table 1.

[0079] Table 1

[0080]

[0081] The basis for the test items in the above table is as follows:

[0082] Water absorption ratio (g / g): ASTM D570-98, immersion method: The sample was immersed in deionized water for 24 hours and then weighed to calculate the water absorption ratio.

[0083] Water absorption rate (g / min): By the weighing method, record the change in the water absorption weight of the sample per minute in deionized water and calculate the water absorption rate.

[0084] Porosity (%): The ratio of the pore volume to the total volume of the sample was determined by mercury intrusion porosimetry (MIP) using a mercury intrusion porosimeter.

[0085] Average pore size (μm): Observe the pore morphology of the sample by scanning electron microscopy (SEM) and measure the average pore size.

[0086] Biodegradation rate (%): By culturing for 90 days under composting conditions, determine the percentage of mass loss of the sample.

[0087] Thermal stability (°C): By measuring the decomposition temperature of the sample in a nitrogen atmosphere.

[0088] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a cellulose-degradable water-absorbing resin, characterized in that, It includes the following steps: S1. Solution preparation: Mix sodium carboxymethylcellulose with water, heat it to 70°C - 85°C, and stir at a speed of 300 r / min - 450 r / min for 1 h - 1.5 h to obtain a homogeneous solution; wherein the concentration of sodium carboxymethylcellulose is 2.0% - 4.0% of the total mass of the solution; S2. Freezing parameter setting: Determine the multi-stage temperature curve of the freezing program according to the solution parameters. The freezing program includes: Rapid cooling stage: Cool the solution from 20°C to -10°C ± 2°C at a rate of 2°C / min - 8°C / min; Nucleation holding stage: Hold at -10°C ± 2°C for 10 min - 45 min; Slow cooling stage: Continue to cool to -50°C ± 5°C at a rate of 0.1°C / min - 0.8°C / min; Final freezing stage: Hold at -50°C ± 5°C for 4 h - 18 h; S3. Directional freezing treatment: Place the solution in a unidirectional freezing device, control the bottom plate temperature at -60°C - -40°C, and make the ice crystals grow directionally along the vertical direction of the solution surface; S4. Crosslinking reaction: Add citric acid to the frozen sample, and the mass ratio of citric acid to sodium carboxymethylcellulose is 0.5:1 - 1.5:1, and react at 140°C - 160°C for 1 h - 2 h; S5. Sublimation drying: Under a vacuum pressure of 1 - 5 kPa, heat it to 40°C ± 5°C at a rate of 0.2°C / min - 1.0°C / min, and keep drying at a constant temperature for 12 h - 36 h until the residual moisture ≤ 5%; S6. Post-treatment: Soak and wash with deionized water twice, 1 h each time, and finally dry at 40°C - 50°C for 6 h - 10 h, and crush to a particle size of 0.5 mm - 2.0 mm.

2. The preparation method of a cellulose-degradable water-absorbing resin according to claim 1, characterized in that, In step S1, glycerol is also included, and the addition amount of glycerol is 0.1% - 0.5% of the mass of sodium carboxymethylcellulose.

3. The preparation method of a cellulose-degradable water-absorbing resin according to claim 1, characterized in that, In step S2, the temperature parameters of the freezing stage are limited by the following formula: The cooling rate R during the slow cooling stage slow and the final freezing temperature T freeze satisfy R slow = 0.02 × |T freeze |, where T freeze is from -50°C to -30°C.

4. The preparation method of a cellulose-degradable water-absorbing resin according to claim 3, characterized in that, In the sublimation drying of step S5, the relationship between the heating rate and the final temperature satisfies: Heating rate R dry = 0.05 × T final , where T final is 30°C to 50°C.

5. The preparation method of a cellulose-degradable water-absorbing resin according to claim 3, characterized in that, In the directional freezing treatment of step S3, a magnetic field is applied synchronously, the magnetic field intensity is 100 Gs - 800 Gs, and the magnetic field direction is perpendicular to the ice crystal growth direction.

6. The preparation method of a cellulose-degradable water-absorbing resin according to claim 5, characterized in that, The magnetic field strength B and the freezing rate R slow satisfy the relationship B = 50×R slow + 100.

7. The preparation method of a cellulose-degradable water-absorbing resin according to claim 1, characterized in that, In step S4, a nano-silica modifier is also added, and its addition amount is 0.3% - 1.2% of the mass of sodium carboxymethylcellulose, and the nano-silica particle size is 20 - 100 nm, and the specific surface area ≥ 200 m² / g.

8. The preparation method of a cellulose-degradable water-absorbing resin according to claim 6, characterized in that, The magnetic field application adopts a pulse mode, the pulse frequency is 0.5 - 5 Hz, the duty cycle is 30% - 70%, and it is applied throughout the slow cooling stage.

9. The preparation method of a cellulose-degradable water-absorbing resin according to claim 7, characterized in that, The nano-silica surface is grafted with an amino-silane coupling agent, the grafting rate is 15% - 35%, and the relationship between the modifier addition amount D and the magnetic field intensity B satisfies the formula: D(%) = 0.002×B + 0.

1.

10. The preparation method of a cellulose-degradable water-absorbing resin according to claim 1, characterized in that, The water used in step S1 is ultrapure water with a conductivity ≤ 5 μS / cm, and ultrasonic degassing treatment is carried out during the stirring process, the ultrasonic frequency is 40 kHz, the power is 300 W, and the treatment time is 10 - 20 minutes.

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