Preparation method of carboxymethylated bamboo powder multifunctional intelligent response hydrogel material

Abstract

The invention provides a preparation method of a carboxymethylated bamboo powder multifunctional intelligent response hydrogel material, which comprises the following steps: step 1, mixing and stirring bamboo powder, isopropanol and a NaOH solution, then adding chloroacetic acid and stirring, then heating for reaction, and after the reaction is finished, filtering, washing and drying to obtain carboxymethylated bamboo powder; 2, water is added to the carboxymethylated bamboo powder for dissolution, then neutralized acrylic acid, sodium polyaspartate and methacryloylethyl sulfobetaine are added, the mixture is stirred and mixed to be uniform, finally, a cross-linking agent and an initiator are added, a reaction is carried out in the nitrogen atmosphere, washing and drying are carried out after the reaction is finished, and the target compound is obtained. The hydrogel material is the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material. The prepared hydrogel can efficiently absorb and maintain moisture, the maximum water absorption capacity in pure water can reach 926.9 g / g, the hydrogel has responsiveness to pH, the moisture absorption capacity in a salt solution is maintained, and the hydrogel has good application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of highly water-absorbent hydrogels, and in particular to a method for preparing a carboxymethylated bamboo powder multifunctional intelligent response hydrogel material. Background Art

[0002] Bamboo powder is a natural biomass material with wide sources, large output and low price. The introduction of natural polymer materials not only changes the chemical structure of hydrogels and improves their biodegradability, but also has good biocompatibility, low potential toxicity, and less impact on the environment after the product is discarded. The polymer chains dispersed in the aqueous medium are cross-linked through various mechanisms to form hydrogels. As hydrogels contain hydrophilic functional groups in their structure, such as hydroxyl, carboxyl, amide and sulfonic acid groups. These ionized functional groups can repel each other, thereby capturing more water molecules. The cross-linking of hydrogels leads to the formation of an elastic structure, which can be carried out by secondary forces such as hydrogen bonds, hydrophobic or ionic forces, and primary forces such as covalent bonds using cross-linking agents during polymerization. Hydrogels have been widely used in agriculture to improve irrigation efficiency and improve the physical properties of soil because of their unique three-dimensional network structure containing a large number of hydrophilic groups.

[0003] Biomass hydrogel plays an important role in water retention, but its water absorption effect is easily limited by changes in environmental factors, especially in high-salinity environments.

[0004] Therefore, it is necessary to provide a new method for preparing carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material to solve the above problems. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a method for preparing a carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material which can efficiently absorb and retain water, has a water absorption capacity of up to 926.9 g / g in pure water, is responsive to pH and maintains water absorption capacity in a salt solution.

[0006] In order to solve the above technical problems, the preparation method of the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material provided by the present invention comprises the following steps: step 1: mixing bamboo powder, isopropanol and NaOH solution, then adding chloroacetic acid and stirring, then heating to react, filtering after the reaction, washing, and drying to obtain carboxymethylated bamboo powder; step 2: dissolving the carboxymethylated bamboo powder in water, then adding neutralized acrylic acid, sodium polyaspartate and methacryloylethyl sulfobetaine and stirring to mix evenly, finally adding a crosslinking agent and an initiator, reacting under a nitrogen atmosphere, washing after the reaction, and drying to obtain the target compound, i.e., the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material.

[0007] Preferably, in step 1, the mass ratio of bamboo powder to chloroacetic acid is 5:7, and 75 mL of isopropanol is added for every 7 g of chloroacetic acid; and 15.04 mL of 30% sodium hydroxide solution is added for every 75 mL of isopropanol.

[0008] Preferably, in step 1, the reaction temperature is 80° C., and the washing solvent is 80% ethanol and anhydrous ethanol.

[0009] Preferably, in step 2, the cross-linking agent is N,N'-methylenebisacrylamide, and the initiator is ammonium persulfate.

[0010] Preferably, in step 2, the mass percentages of various raw materials are as follows: the amount of sodium polyaspartate added is 5-45% of the mass of acrylic acid, the amount of methacryloylethyl sulfobetaine added is 5-25% of the mass of acrylic acid, the amount of carboxymethylated bamboo powder added is 1-20% of the mass of acrylic acid, the initiator content is 0.75-1.75% of the mass of acrylic acid, the cross-linking agent content is 0.05-0.25% of the mass of acrylic acid, and the neutralization degree of acrylic acid is 60-80%.

[0011] Preferably, in step 2, the reaction temperature is 60°C, the reaction time is 30 minutes, the washing solvent is anhydrous ethanol, and the drying temperature is 60°C.

[0012] The carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material prepared according to the above method can be used for water absorption and retention. Acrylic acid contains a large number of carboxyl groups, which can significantly improve the water absorption and water retention of hydrogels. Sodium polyaspartate is a biodegradable polymer polymerized from the natural amino acid aspartic acid. Methacryloylethyl sulfobetaine is a zwitterionic monomer containing cationic betaine groups and anionic sulfonic acid groups, which can maintain the water absorption capacity of hydrogels through internal charge balance in high-salinity environments. Acrylic acid provides basic water absorption capacity, while sodium polyaspartate further enhances water absorption and salt resistance through chelation. The combination of sodium polyaspartate and methacryloylethyl sulfobetaine can effectively resist the influence of electrolytes on the water absorption performance of hydrogels, so that the hydrogels can still maintain high water absorption in high-salinity environments. At the same time, the mechanical strength of the hydrogel is enhanced through cross-linking reactions, and the durability and stability of the hydrogel are improved.

[0013] The invention improves the water solubility of bamboo powder through carboxymethylation modification, and grafts acrylic acid, environmentally friendly monomer sodium polyaspartate and salt-resistant monomer methacryloylethyl sulfobetaine on carboxymethylated bamboo powder through free radical polymerization reaction, which not only increases the types and quantities of surface hydrophilic functional groups of hydrogel, but also adjusts the network structure of hydrogel, and also solves the problems of poor environmental stimulus response and resistance to salt solution of bio-based highly absorbent hydrogel.

[0014] Compared with the related art, the preparation method of the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material provided by the present invention has the following beneficial effects: (1) The method for preparing the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material improves the water solubility of the bamboo powder by treating the bamboo powder with carboxymethylation, thereby simplifying the process; (2) The carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material (CB-APS) prepared by the preparation method can efficiently absorb and retain water, wherein the maximum water absorption capacity in pure water is 926.9 g / g, and it is responsive to pH environmental stimulation and still has a water retention effect in low-salt solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The reaction synthesis route of the preparation method of the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material provided by the present invention; Figure 2 This is the water absorption capacity diagram of CB-APS under different pH conditions; Figure 3 is the water absorption capacity diagram of CB-APS in different salt solutions; Figure 4 The water holdup diagram of CB-APS at different temperatures. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and multiple embodiments.

[0017] Embodiment 1: 5 g of bamboo powder, 75 mL of isopropanol and 15.04 mL of 30% sodium hydroxide solution were weighed and added into a three-necked flask, and stirred at 30°C for 1 hour; then, 7 g of chloroacetic acid was added into the three-necked flask, and stirring was continued for 30 minutes; then, the reaction temperature inside the three-necked flask was raised to 80°C, and the reaction was carried out at this temperature for 2 hours; after the reaction was completed, the product was separated by filtration, and washed with 80% ethanol and anhydrous ethanol in turn, and finally, the washed product was placed in a 60°C oven to dry, and carboxymethylated bamboo powder (CBP) was obtained; 0.072 g of carboxymethylated bamboo powder was weighed and added to 50 mL of water to dissolve. Subsequently, 60% neutralized acrylic acid (the amount of acrylic acid was 0.1 mol), 0.36 g of sodium polyaspartate and 0.36 g of methacryloylethyl sulfobetaine were added and stirred to mix evenly. 0.0036 g of N,N'-methylenebisacrylamide and 0.054 g of ammonium persulfate were added to the mixture. The mixture was reacted at 60 ° C for 30 minutes under a nitrogen atmosphere. After the reaction, the reactant was washed with anhydrous ethanol to obtain a hydrogel material (CB-APS).

[0018] Embodiment 2: 5 g of bamboo powder, 75 mL of isopropanol and 15.04 mL of 30% sodium hydroxide solution were weighed and added into a three-necked flask, and stirred at 30°C for 1 hour; then, 7 g of chloroacetic acid was added into the three-necked flask, and stirring was continued for 30 minutes; then, the reaction temperature inside the three-necked flask was raised to 80°C, and the reaction was carried out at this temperature for 2 hours; after the reaction was completed, the product was separated by filtration, and washed with 80% ethanol and anhydrous ethanol in turn, and finally, the washed product was placed in a 60°C oven to dry, and carboxymethylated bamboo powder (CBP) was obtained; 0.36 g of carboxymethylated bamboo powder was weighed and added to 50 mL of water to dissolve; then, 65% neutralized acrylic acid (the amount of acrylic acid was 0.1 mol), 1.08 g of sodium polyaspartate and 0.72 g of methacryloylethyl sulfobetaine were added and stirred to mix evenly. 0.0072 g of N,N'-methylenebisacrylamide and 0.072 g of ammonium persulfate were added to the mixture, and the mixture was reacted at 60 ° C for 30 minutes under a nitrogen atmosphere. After the reaction, the reactant was washed with anhydrous ethanol to obtain a hydrogel material (CB-APS).

[0019] Embodiment three: 5 g of bamboo powder, 75 mL of isopropanol and 15.04 mL of 30% sodium hydroxide solution were weighed and added into a three-necked flask, and stirred at 30°C for 1 hour; then, 7 g of chloroacetic acid was added into the three-necked flask, and stirring was continued for 30 minutes; then, the reaction temperature inside the three-necked flask was raised to 80°C, and the reaction was carried out at this temperature for 2 hours; after the reaction was completed, the product was separated by filtration, and washed with 80% ethanol and anhydrous ethanol in turn, and finally, the washed product was placed in a 60°C oven to dry, and carboxymethylated bamboo powder (CBP) was obtained; 0.72 g of carboxymethylated bamboo powder was weighed and added to 50 mL of water to dissolve; then, 70% neutralized acrylic acid (the amount of acrylic acid was 0.1 mol), 1.80 g of sodium polyaspartate and 1.08 g of methacryloylethyl sulfobetaine were added and stirred to mix evenly; 0.0108 g of N,N'-methylenebisacrylamide and 0.090 g of ammonium persulfate were added to the mixture, and the mixture was reacted at 60 ° C for 30 minutes under a nitrogen atmosphere; after the reaction, the reactant was washed with anhydrous ethanol to obtain a hydrogel material (CB-APS).

[0020] Embodiment 4: 5 g of bamboo powder, 75 mL of isopropanol and 15.04 mL of 30% sodium hydroxide solution were weighed and added into a three-necked flask, and stirred at 30°C for 1 hour; then, 7 g of chloroacetic acid was added into the three-necked flask, and stirring was continued for 30 minutes; then, the reaction temperature inside the three-necked flask was raised to 80°C, and the reaction was carried out at this temperature for 2 hours; after the reaction was completed, the product was separated by filtration, and washed with 80% ethanol and anhydrous ethanol in turn, and finally, the washed product was placed in a 60°C oven to dry, and carboxymethylated bamboo powder (CBP) was obtained; 1.08 g of carboxymethylated bamboo powder was weighed and added to 50 mL of water to dissolve; then, 75% neutralized acrylic acid (the amount of acrylic acid was 0.1 mol), 2.52 g of sodium polyaspartate and 1.44 g of methacryloylethyl sulfobetaine were added and stirred to mix evenly; 0.0144 g of N,N'-methylenebisacrylamide and 0.108 g of ammonium persulfate were added to the mixture, and the mixture was reacted at 60 ° C for 30 minutes under a nitrogen atmosphere; after the reaction, the reactant was washed with anhydrous ethanol to obtain a hydrogel material (CB-APS).

[0021] Embodiment five: 5 g of bamboo powder, 75 mL of isopropanol and 15.04 mL of 30% sodium hydroxide solution were weighed and added into a three-necked flask, and stirred at 30°C for 1 hour; then, 7 g of chloroacetic acid was added into the three-necked flask, and stirring was continued for 30 minutes; then, the reaction temperature inside the three-necked flask was raised to 80°C, and the reaction was carried out at this temperature for 2 hours; after the reaction was completed, the product was separated by filtration, and washed with 80% ethanol and anhydrous ethanol in turn, and finally, the washed product was placed in a 60°C oven to dry, and carboxymethylated bamboo powder (CBP) was obtained; 1.44 g of carboxymethylated bamboo powder was weighed and added to 50 mL of water to dissolve; then, 80% neutralized acrylic acid (the amount of acrylic acid was 0.1 mol), 3.24 g of sodium polyaspartate and 1.80 g of methacryloylethyl sulfobetaine were added and stirred to mix evenly; 0.018 g of N,N'-methylenebisacrylamide and 0.126 g of ammonium persulfate were added to the mixture, and the mixture was reacted at 60 ° C for 30 minutes under a nitrogen atmosphere; after the reaction, the reactant was washed with anhydrous ethanol to obtain a hydrogel material (CB-APS).

[0022] Orthogonal experiments were conducted on the monomer ratio, neutralization degree, initiator content and crosslinker content of the preparation conditions of the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material. The mass percentages of the above raw materials based on the amount of acrylic acid added (0.1 mol) were as follows: the amount of carboxymethylated bamboo powder was 1%, 5%, 10%, 15% and 20% of the mass of acrylic acid, the neutralization degree of acrylic acid was 60%, 65%, 70%, 75% and 80%, the amount of sodium polyaspartate was 5%, 15%, 25%, 35% and 45% of the mass of acrylic acid, the amount of methacryloylethyl sulfobetaine was 5%, 10%, 15%, 20% and 25% of the mass of acrylic acid, the amount of N,N'-methylenebisacrylamide was 0.05%, 0.10%, 0.15%, 0.2% and 0.25% of the mass of acrylic acid, and the content of ammonium persulfate was 0.75%, 1.00%, 1.25%, 1.50% and 1.75% of the mass of acrylic acid, with a total of 25 groups of experiments.

[0023] The following is an analysis of the test results of the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material (CB-APS) prepared with the optimal result of the embodiment, namely, a carboxymethylated bamboo powder content of 5% (0.36 g), a neutralization degree of acrylic acid of 70%, a sodium polyaspartate content of 35% (2.52 g), a methacryloylethyl sulfobetaine content of 5% (0.36 g), an N,N'-methylenebisacrylamide content of 0.05% (0.0036 g), and an ammonium persulfate content of 0.75% (0.054 g).

[0024] (1) Effect of pH on water absorption capacity As attached Figure 2 As shown in the figure, under acidic conditions, the water absorption rate is low and a large number of carboxyl groups (-COOH) will be protonated to carboxylic acid forms (-COOH + ), resulting in a weakening of the electrostatic repulsion between the groups, but poor water absorption performance. Since the betaine group is relatively stable under acidic conditions, the hydrogel can still maintain a certain hydrophilicity and electrical neutrality in an acidic environment. The water absorption rate is high under neutral and weakly alkaline conditions, showing excellent hydrophilicity and water absorption capacity. Carboxyl, hydroxyl and other groups form a large number of hydrogen bonds and other weak interactions with water molecules. At the same time, the carboxyl groups (-COOH) in the hydrogel are gradually deprotonated to carboxylate ions (-COO - ), which will increase the electrostatic repulsion between carboxyl groups and promote the expansion of the hydrogel network. Strong alkaline hydrogels tend to over-swell and disintegrate, and their water absorption capacity decreases.

[0025] (2) Effect of salt solution on water absorption capacity As attached Figure 3 As shown: With the increase in salt concentration, the water retention performance of the hydrogel shows significant changes. The order of the influence of salt types on water absorption performance is NaHCO3 < NaCl < KCl < Na2CO3 < Na2SO4 < MgCl2 < CaCl2; the prepared hydrogel shows excellent water absorption performance and water retention ability at lower salt concentrations. With the increase in salt concentration, especially in salt solutions containing divalent ions (such as MgCl2 and CaCl2), the water absorption performance and water retention ability of the hydrogel decrease significantly. Since the hydrogel contains a large number of hydrophilic groups (such as carboxyl groups, hydroxyl groups, etc.), some water molecules can still interact through hydrogen bonds. At the same time, the zwitterionic property of the betaine group inhibits the occurrence of the salt effect, enabling the hydrogel to maintain good hydrophilicity and water absorption performance in a high-salt environment and reducing the inhibition of electrolytes on water absorption performance. This indicates that the performance of the hydrogel is limited in a high-salt environment, while it has good application potential in a low-salt environment.

[0026] (3) Influence of temperature on water retention rate As shown in the Figure 4 attachment: The prepared hydrogel shows excellent water retention ability at lower temperatures and can maintain a relatively high water retention rate for a long time. The initial water loss is mainly the free water on the surface of the hydrogel. As the temperature increases, the evaporation accelerates, resulting in an increase in the water loss rate. The water retention rates after 8 hours at 35°C, 45°C, 55°C, and 65°C are 81.57%, 64.48%, 52.85%, and 35.42% respectively. Since the hydrogel contains a large number of hydrophilic groups, it can still maintain a certain water retention ability at higher temperatures. Water molecules are bound to the hydrophilic groups in the hydrogel (such as carboxyl groups in carboxymethylated bamboo powder, carboxyl groups in sodium polyaspartate, and betaine groups in methacryloylethyl sulfobetaine, etc.) through hydrogen bonds and other weak interactions. The movement of water molecules is significantly hindered by the steric hindrance and electrostatic attraction of the hydrophilic groups. Therefore, even at higher temperatures, the loss of bound water is relatively small.

[0027] The above are only the embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing a carboxymethylated bamboo powder multifunctional intelligent response hydrogel material, characterized in that: The steps include: Step 1: Mix bamboo powder, isopropanol and NaOH solution, then add chloroacetic acid and stir, then heat to react, filter after the reaction, wash, and dry to obtain carboxymethylated bamboo powder; Step 2: Dissolve the carboxymethylated bamboo powder in water, then add neutralized acrylic acid, sodium polyaspartate and methyl methacryloylethyl sulfobetaine and stir to mix evenly, finally add a crosslinker and an initiator, react under a nitrogen atmosphere, wash and dry after the reaction to obtain the target compound, i.e., the carboxymethylated bamboo powder multifunctional intelligent responsive hydrogel material.

2. The method for preparing the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material according to claim 1, characterized in that: In step 1, the mass ratio of bamboo powder to chloroacetic acid is 5:7, and every 7 g of chloroacetic acid is mixed with 75 mL of isopropanol; every 75 mL of isopropanol is mixed with 15.04 mL of 30% sodium hydroxide solution.

3. The method for preparing the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material according to claim 1, characterized in that: In step 1, the reaction temperature is 80° C., and the washing solvents are 80% ethanol and anhydrous ethanol.

4. The method for preparing the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material according to claim 1, characterized in that: In step 2, the cross-linking agent is N,N'-methylenebisacrylamide, and the initiator is ammonium persulfate.

5. The method for preparing the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material according to claim 1, characterized in that: In step 2, the mass percentages of various raw materials are as follows: the amount of sodium polyaspartate added is 5-45% of the mass of acrylic acid, the amount of methacryloylethyl sulfobetaine added is 5-25% of the mass of acrylic acid, the amount of carboxymethylated bamboo powder added is 1-20% of the mass of acrylic acid, the initiator content is 0.75-1.75% of the mass of acrylic acid, the cross-linking agent content is 0.05-0.25% of the mass of acrylic acid, and the neutralization degree of acrylic acid is 60-80%.

6. The method for preparing the carboxymethylated bamboo powder multifunctional intelligent response hydrogel material according to claim 1, characterized in that: In step 2, the reaction temperature is 60°C, the reaction time is 30 minutes, the washing solvent is anhydrous ethanol, and the drying temperature is 60°C.

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