Preparation method of regenerated cellulose foaming aerogel material with high resilience
The preparation of regenerated cellulose aerogel materials by combining chemical and physical methods with polyols and inorganic strong alkali solutions has been solved, and the problems of insufficient material performance and environmental pollution in traditional methods have been achieved, and the preparation of aerogel materials with high resilience and stable mechanical properties have been achieved. , and the process is environmentally friendly and efficient.
Patent Information
- Application Number
- CN202411733631.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-02-07
AI Technical Summary
The existing plant fiber aerogel materials have shortcomings in terms of mechanical properties and rebound compression properties, and traditional chemical preparation methods have problems such as high costs and environmental pollution.
Regenerated cellulose is prepared by chemical physics combining polyols with inorganic strong alkali solution by freeze-thawing and mechanical dispersion, and chemical cross-linking is used to use polycarboxylic acids to high temperature, and foam it through ionic surfactant, and finally obtained by freeze-drying. Highly resilient regenerated cellulose aerogel material.
It has achieved high resilience and stable mechanical properties, simple process, green and environmentally friendly, and low cost, and the mechanical properties and compression cycle performance of the material have been significantly improved.
Smart Images
Figure CN119391039A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of preparation of plant fiber aerogels, and in particular relates to a method for preparing a high-resilience regenerated cellulose foamed aerogel material. Background Art
[0002] As a new material with great potential, aerogels with high specific surface area and low density show amazing characteristics in many aspects. The three-dimensional porous network structure and easy-to-build preparation strategy give this material a natural advantage in the fields of engineering technology and chemical materials. In modern society, which is gradually paying attention to environmental awareness, aerogel materials prepared from plant fibers with a wide range of sources and green economy have always been favored by many researchers. Because of its rich surface functional groups, good biocompatibility and stable material properties, plant fiber-based aerogels have been widely developed and applied in the fields of energy storage, water resource purification, food preservation, electrical sensors, etc.
[0003] However, in the past research process of using plant fibrils obtained from natural plants as aerogel substrates, problems such as uneven fiber size, uneven pore distribution, and poor binding ability were exposed, resulting in poor mechanical properties and rebound compression properties of the material. In order to improve the pore structure and mechanical properties of plant fiber aerogels, the pretreatment of plant fibrils and the pore design of aerogels have become key modification methods. Among them, the preparation of regenerated cellulose from plant fibrils is an emerging technology, mainly based on chemical methods. However, the chemical preparation method has the problems of expensive reagents, unfriendly to the environment, and low output rate; at the same time, the existing modification process cannot effectively improve the mechanical properties of aerogel materials. To this end, the present invention proposes to use a combination of chemical and physical methods, with plant fibrils as raw materials, green and economical polyols and inorganic strong alkali solutions as dissolving systems, and prepare regenerated cellulose by simple multiple freeze-thaw methods and mechanical dispersion, and obtain wet gel by high-temperature chemical crosslinking of non-toxic and pollution-free polycarboxylic acids, and mechanical foaming of environmentally friendly and efficient ionic surfactants, and finally obtain regenerated cellulose aerogel materials by simple freeze-drying technology. The technology is simple, environmentally friendly, and low-cost, and the prepared regenerated cellulose aerogel material has excellent compression resilience. Summary of the invention
[0004] The purpose of the present invention is to develop a method for preparing a highly resilient regenerated cellulose foamed aerogel material by using a new modification technology. Compared with traditional plant fiber aerogel materials, the aerogel material has more stable mechanical properties and better resilience, and the preparation process is simple, efficient, and environmentally friendly.
[0005] In order to achieve the above object, the present invention adopts the following technical scheme:
[0006] A method for preparing a high resilience regenerated cellulose foamed aerogel material, the specific steps of which are as follows:
[0007] Step 1: Prepare a mixed aqueous solution of polyol and inorganic strong base of appropriate concentration (referred to as dissolving solution);
[0008] Step 2: dissolving the plant fiber in the solution prepared in step 1 at a certain mass fraction, freezing the plant fiber solution at a certain temperature for a period of time, taking it out to thaw at room temperature and mechanically stirring it to obtain a dissolved cellulose solution, then pouring the solution into a mold, freezing it for a period of time, taking it out to thaw at room temperature to obtain a hydrogel;
[0009] Step 3: Soak the hydrogel in a certain volume of deionized water to displace the solvent and regenerate the dissolved cellulose. The pH value of the deionized water is measured and the solution is replaced at regular intervals until the pH value is neutral. The regenerated hydrogel and a certain proportion of deionized water are then uniformly dispersed by multiple high-speed shearing to obtain a regenerated cellulose dispersion with uniform size and good dispersion.
[0010] Step 4, adding polycarboxylic acid, catalyst and adhesive solution to the regenerated cellulose dispersion respectively, stirring at a low speed and then cross-linking at a high temperature to obtain a cross-linked fiber aqueous solution system;
[0011] Step 5, adding anionic surfactant into the system described in step 4, and preparing regenerated cellulose foamed wet gel by high-speed shear stirring and foaming;
[0012] Step 6, pouring the wet gel in step 5 into a silica gel mold, freezing to form a cryogel, and then performing a vacuum freeze-drying process to obtain a regenerated cellulose foamed aerogel material;
[0013] Furthermore, the step 1 includes the following steps: preparing a mixed aqueous solution of an inorganic strong base with a mass fraction ranging from 8% to 15% and a polyol with a mass fraction ranging from 1% to 4%, and precooling it at -5°C for 3-4 hours for standby use.
[0014] Furthermore, in step 1, the polyol includes pentaerythritol, glycerol, trimethylolethane, xylitol, sorbitol, polyethylene glycol, etc.; the inorganic strong base includes lithium hydroxide, sodium hydroxide, etc.
[0015] Furthermore, the types of plant fibers used for preparing the regenerated cellulose dispersion in step 2 include: one or more plant fibers selected from the group consisting of bamboo fibers, cotton fluff fibers, hardwood fibers, and coniferous wood fibers.
[0016] Furthermore, the fibers used to prepare the regenerated cellulose dispersion in step 2 need to be pretreated as follows: tear the pulp sheet into blocks, and then crush it with a pulverizer to obtain flocculent fibers. Soak it in deionized water for 24 hours, and then vacuum filter it until no droplets fall. Then, soak it in anhydrous methanol and acetone in the same way, and filter it to remove impurities. Finally, dry the filtered fibers in a blast drying oven at 110° C. for 2 hours to obtain dry fibers, and then put them in a sealed bag for standby use.
[0017] Furthermore, the fibers used to prepare the regenerated cellulose dispersion in step 2 are added to the pre-cooled dissolving solution prepared in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 1%-6%, and the solution is allowed to stand at 20° C.-25° C. for 5-8 hours.
[0018] Furthermore, in step 2, the plant fiber solution is placed in a refrigerator at -20°C for 12-18 hours, taken out and thawed at 20-25°C for 5-6 hours, and then mechanically stirred to obtain a dissolved cellulose solution, and the speed of the high-speed shearing machine is 1000-1500rad / min;
[0019] Furthermore, in step 2, the mold is frozen at a temperature of -10-20°C for 12-18 hours, and thawed at 20-25°C for 5-6 hours to obtain the hydrogel.
[0020] Furthermore, in step 3, the volume ratio of the hydrogel to the deionized water should be greater than 1:10, the soaking time is 5-6 hours, and the pH value is measured by a pH tester before each replacement of the deionized water. Subsequently, the regenerated cellulose hydrogel is mixed with a certain proportion of deionized water and mechanically stirred, the high-speed shearing machine is used for 30-50 minutes, the speed is 1500-2000 rad / min, and the concentration of the regenerated cellulose dispersion is 2%-5%.
[0021] Furthermore, the polycarboxylic acid in step 4 is fumaric acid, gluconic acid, phytic acid, quinic acid, citric acid, etc.; the concentration of the polycarboxylic acid is 2%-4% of the total mass; the catalyst is sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate and tetramethylammonium salt, etc.; the catalyst is 30%-50% of the mass of the polycarboxylic acid; the adhesive is chitosan, carboxymethyl cellulose, polyvinyl alcohol, sodium alginate, etc.; the concentration of the adhesive is 1%-4% of the total mass. The components in step 4 are added to the regenerated cellulose dispersion in sequence, dispersed at 500 rad / min for 5 minutes, and heated in a blast drying oven at 100°C for 20-30 minutes.
[0022] Furthermore, the anionic surfactant in step 5 is sodium dodecyl sulfate, sodium alcohol ether sulfate, sodium lauryl sulfate, calcium lignin sulfonate, sodium lignin sulfonate, etc. After cross-linking, the mixed solution is stirred and foamed by a high-speed shearing machine at 1000-2000 rad / min for 5-10 minutes.
[0023] Furthermore, the freezing temperature of the wet gel in step 6 is in the range of -18-20 degrees Celsius, the freezing time is 18-24 hours, and the vacuum freeze drying time is 48-72 hours.
[0024] Compared with the prior art, the present invention has the following beneficial technical advantages:
[0025] The present invention uses plant fiber as raw material, prepares a regenerated cellulose substrate through a low-cost and low-energy consumption process, and uses safe and environmentally friendly polycarboxylic acid for high-temperature catalytic cross-linking modification, thereby achieving efficient utilization of plant fiber and avoiding environmental pollution. The present invention uses polycarboxylic acid to regulate the foaming degree of anionic surfactants, further improving the pore structure of aerogel materials, and the chemical bonds constructed between polycarboxylic acid, regenerated cellulose and anionic surfactants effectively enhance the mechanical properties and compression cycle performance of aerogel materials. The drugs used in the present invention are environmentally friendly and non-toxic, the process output is efficient, environmentally friendly and degradable, and the application potential is broad and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 These are photos of the regenerated cellulose foamed aerogel materials prepared in Examples 1, 2, 3, and 4 of the present invention;
[0027] Figure 2 This is a SEM electron microscope scanning image of the interior of the regenerated cellulose foamed aerogel prepared in Example 3 of the present invention;
[0028] Figure 3 This is a stress-strain curve of the regenerated cellulose foamed aerogel prepared in Example 3 of the present invention at 80% strain;
[0029] Figure 4 This is the stress-strain curve of the regenerated cellulose foamed aerogel prepared in Example 3 of the present invention after 100 consecutive cycles of compression at 50% strain. DETAILED DESCRIPTION
[0030] The embodiments of the present invention are described in further detail below:
[0031] A method for preparing a regenerated cellulose foamed aerogel material that can be repeatedly compressed from plant fibers comprises the following steps:
[0032] Step 1: prepare a mixed aqueous solution of an inorganic strong base with a mass fraction range of 8%-15% and a polyol with a mass fraction range of 1%-4%, and precool it at -5°C for 3-4 hours for standby use. The polyol includes pentaerythritol, glycerol, trimethylolethane, xylitol, sorbitol, polyethylene glycol, etc.; the inorganic strong base includes potassium hydroxide, sodium hydroxide, etc.
[0033] Step 2: The types of plant fibers used to prepare the regenerated cellulose dispersion are: one or more of bamboo fiber, cotton fluff fiber, hardwood fiber, and coniferous wood fiber, and need to undergo the following pretreatment: tear the pulp board into blocks, and then crush it with a grinder to obtain flocculent fibers. Soak it in deionized water for 24 hours and then vacuum filter it until no droplets fall. Then soak it in anhydrous methanol and acetone in the same way and filter it to remove impurities. Finally, place the filtered fiber in a blast drying oven and dry it at 110°C for 2h to obtain dry fiber, and add the precooled dissolving solution in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 1%-6%, and let it stand at 20°C-25°C for 5-8 hours. The plant fiber solution is then placed in a refrigerator and frozen at -10-20°C for 12-18 hours. After thawing at 20-25°C for 5-6 hours, the dissolved cellulose solution is obtained by mechanical stirring. The speed of the high-speed shearing machine is 1000-1500 rad / min, and the stirring time is 10-20 min. The cellulose solution is then injected into a mold and frozen at -10-20°C for 12-18 hours. Then, the hydrogel is obtained by thawing at 20-25°C for 5-6 hours.
[0034] Step three, soak the hydrogel with at least ten times the volume of deionized water to displace the solvent and regenerate the dissolved cellulose, measure the pH value of the deionized water every 5-6 hours and replace the deionized water until the pH value is neutral, then disperse the regenerated hydrogel and a certain proportion of deionized water by 2-4 high-speed shearing, each dispersion time is 30-50 minutes, the rotation speed is 1500-2000rad / min, and a regenerated cellulose dispersion with uniform size and good dispersion is obtained, and the concentration range is 2%-5%.
[0035] Step 4: Add polycarboxylic acid, catalyst and adhesive solution to the regenerated cellulose dispersion, stir at low speed and then crosslink at high temperature to obtain a crosslinked fiber aqueous solution system. The polycarboxylic acid is fumaric acid, gluconic acid, phytic acid, quinic acid, citric acid, etc.; the concentration of the polycarboxylic acid is 2%-4% of the total mass; the catalyst is sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate and tetramethylammonium salt, etc.; the catalyst is 30%-50% of the mass of the polycarboxylic acid; the adhesive is chitosan, carboxymethyl cellulose, polyvinyl alcohol, sodium alginate, etc.; the concentration of the adhesive is 1%-4% of the total mass; each component is added to the regenerated cellulose dispersion in turn, dispersed for 5 minutes by a high-speed shearing machine at 500rad / min, and then heated at 100°C in a blast drying oven for 20-30 minutes.
[0036] Step 5: adding anionic surfactant to the system described in step 4, and preparing regenerated cellulose foamed wet gel by high-speed shearing and stirring. The anionic surfactant is sodium dodecyl sulfate, sodium alcohol ether sulfate, sodium lauryl sulfate, calcium lignin sulfonate, sodium lignin sulfonate, etc.; the speed of the high-speed shearing machine of the mixed solution after cross-linking is 1000-2000 rad / min, and the stirring time is 5-10min.
[0037] Step six, pour the wet gel described in step five into a silica gel mold, freeze it at -18-20 degrees for 18-24 hours to form a cryogel, and then perform vacuum freeze drying for 48-72 hours to obtain a regenerated cellulose foam aerogel material.
[0038] The present invention is described in further detail below in conjunction with embodiments:
[0039] Example 1
[0040] Step 1: Prepare cellulose dissolving solution: add 12% potassium hydroxide and 2% polyethylene glycol into deionized water and freeze it in a refrigerator at -5°C for 5 hours.
[0041] Step 2: Preparation of dissolved cellulose hydrogel: tear the hardwood fiber pulp into blocks, and then crush it with a pulverizer to obtain flocculent fibers. Soak in deionized water for 24 hours and then vacuum filter until no droplets fall. Then soak and filter with anhydrous methanol and acetone in the same way to remove impurities. Finally, place the filtered fibers in a blast drying oven and dry them at 110°C for 2 hours to obtain dry fibers, and add the pre-cooled dissolving solution in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 3%, and let it stand at 25°C for 6 hours. Then put the plant fiber dissolving solution into a refrigerator and freeze it at minus 15°C for 18 hours. After thawing at 25°C for 6 hours, mechanically stir to obtain a dissolved cellulose solution, the speed of the high-speed shearing machine is 1000rad / min, and the stirring time is 10min; then inject the dissolved cellulose solution into the mold and freeze it at a temperature of minus 20°C for 16 hours, and then thaw it at 25°C for 6 hours to obtain a hydrogel.
[0042] Step 3: Soak the hydrogel in deionized water with a volume 20 times that of the hydrogel, measure the pH value of the deionized water every 5 hours and replace the deionized water until the pH value is neutral, then uniformly disperse the regenerated hydrogel and deionized water through two high-speed shearing processes, each dispersion time is 30 minutes, the rotation speed is 1500 rad / min, and a regenerated cellulose dispersion is obtained, and the concentration is controlled to be 5%.
[0043] Step 4: Add fumaric acid at a concentration of 2% of the total mass, sodium tripolyphosphate at a concentration of 50% of the mass of the polycarboxylic acid, and chitosan at a concentration of 1% of the total mass; each component is added in turn to the regenerated cellulose dispersion, dispersed at a high-speed shearing machine of 500 rad / min for 5 minutes, and then heated at 100°C in a forced air drying oven for 20 minutes to obtain a cross-linked cellulose aqueous solution system with a regenerated cellulose concentration of 3%.
[0044] Step 5: Add sodium lauryl sulfate surfactant to the system described in step 4, and prepare the regenerated cellulose foamed wet gel by high-speed shearing and stirring. The high-speed shearing machine speed is 2000 rad / min, and the stirring time is 10 minutes.
[0045] Step six, pour the wet gel described in step five into a silica gel mold, freeze it at minus 20 degrees for 24 hours to form a cryogel, and then perform vacuum freeze drying for 48 hours to obtain a regenerated cellulose foam aerogel material.
[0046] The density of the regenerated cellulose foamed aerogel material prepared in this embodiment is 0.118 g / cm 3 The compressive strength can reach 76.2 kPa under 80% compression strain, and it can recover to 81% of the initial shape with a recovery time of less than 4 s; the rebound rate reaches 81% after 100 cycles of compression under 50% strain, which proves that the aerogel material prepared in this embodiment has good mechanical properties and durability.
[0047] Example 2
[0048] Step 1: Prepare cellulose dissolving solution: add 10% sodium hydroxide and 3% xylitol into deionized water and freeze it in a refrigerator at -5°C for 5 hours.
[0049] Step 2: Preparation of dissolved cellulose hydrogel: tear the cotton fluff fiber pulp into blocks, and then crush it with a pulverizer to obtain flocculent fibers. Soak in deionized water for 24 hours and then vacuum filter until no droplets fall. Then soak and filter with anhydrous methanol and acetone in the same way to remove impurities. Finally, place the filtered fibers in a blast drying oven and dry them at 110°C for 2 hours to obtain dry fibers, and add the pre-cooled dissolving solution in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 3%, and let it stand at 25°C for 6 hours. Then put the plant fiber dissolving solution into a refrigerator and freeze it at minus 15°C for 18 hours. After thawing at 25°C for 6 hours, mechanically stir to obtain a dissolved cellulose solution, the speed of the high-speed shearing machine is 1500rad / min, and the stirring time is 10min; then inject the dissolved cellulose solution into the mold and freeze it at a temperature of minus 20°C for 16 hours, and then thaw it at 25°C for 6 hours to obtain a hydrogel.
[0050] Step 3: Soak the hydrogel in deionized water with a volume 20 times that of the hydrogel, measure the pH value of the deionized water every 5 hours and replace the deionized water until the pH value is neutral, then uniformly disperse the regenerated hydrogel and deionized water through two high-speed shearing processes, each dispersion time is 30 minutes, the rotation speed is 1500 rad / min, and a regenerated cellulose dispersion is obtained, and the concentration is controlled to be 4%.
[0051] Step 4: Add glucic acid at a concentration of 2.5% of the total mass, tetramethylammonium salt at a concentration of 40% of the mass of the polycarboxylic acid; carboxymethyl cellulose at a concentration of 2% of the total mass; each component is added to the regenerated cellulose dispersion in turn, dispersed at a high-speed shearing machine of 800 rad / min for 5 minutes, and then heated at 100° C. in a forced air drying oven for 20 minutes to obtain a cross-linked cellulose aqueous solution system with a regenerated cellulose concentration of 3%.
[0052] Step 5: Adding the alcohol ether sodium sulfate surfactant to the system described in step 4, and foaming the regenerated cellulose foamed wet gel by high-speed shearing stirring. The high-speed shearing machine speed is 1500 rad / min, and the stirring time is 10 min.
[0053] Step six, pour the wet gel described in step five into a silica gel mold, freeze it at minus 20 degrees for 24 hours to form a cryogel, and then perform vacuum freeze drying for 48 hours to obtain a regenerated cellulose foam aerogel material.
[0054] The density of the regenerated cellulose foamed aerogel material prepared in this embodiment is 0.135 g / cm 3 The compressive strength can reach 80.5 kPa under 80% compression strain, and it can recover to 91% of the initial shape with a recovery time of less than 3 s. The rebound rate reaches 88% after 100 cycles of compression under 50% strain, which proves that the aerogel material prepared in this embodiment has good mechanical properties and durability.
[0055] Example 3
[0056] Step 1: Prepare cellulose dissolving solution: add 9% sodium hydroxide and 1% propylene glycol into deionized water and freeze it in a refrigerator at -5°C for 5 hours.
[0057] Step 2: Preparation of dissolved cellulose hydrogel: tear the cotton fluff fiber pulp into blocks, and then crush it with a pulverizer to obtain flocculent fibers. Soak in deionized water for 24 hours and then vacuum filter until no droplets fall. Then soak and filter with anhydrous methanol and acetone in the same way to remove impurities. Finally, place the filtered fibers in a blast drying oven and dry them at 110°C for 2 hours to obtain dry fibers, and add the pre-cooled dissolving solution in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 4%, and let it stand at 25°C for 5 hours. Then put the plant fiber dissolving solution into a refrigerator and freeze it at minus 20°C for 18 hours. After thawing at 25°C for 6 hours, mechanically stir to obtain a dissolved cellulose solution. The speed of the high-speed shearing machine is 800rad / min, and the stirring time is 15min. Then inject the dissolved cellulose solution into the mold and freeze it at a temperature of minus 20°C for 16 hours, and then thaw it at 25°C for 6 hours to obtain a hydrogel.
[0058] Step 3: Soak the hydrogel in deionized water with a volume 20 times that of the hydrogel, measure the pH value of the deionized water every 5 hours and replace the deionized water until the pH value is neutral, then uniformly disperse the regenerated hydrogel and deionized water through two high-speed shearing processes, each dispersion time is 30 minutes, the rotation speed is 1500 rad / min, and a regenerated cellulose dispersion is obtained, and the concentration is controlled to be 6%.
[0059] Step 4: Add phytic acid at a concentration of 2% of the total mass, sodium pyrophosphate at 50% of the mass of the polycarboxylic acid, and polyvinyl alcohol at 3% of the total mass; each component is added in turn to the regenerated cellulose dispersion, dispersed at a high-speed shearing machine of 1000 rad / min for 5 minutes, and then heated at 100°C in a forced air drying oven for 20 minutes to obtain a cross-linked cellulose aqueous solution system with a regenerated cellulose concentration of 3%.
[0060] Step 5: Add sodium lignin sulfonate surfactant to the system described in step 4, and prepare regenerated cellulose foamed wet gel by high-speed shearing and stirring. The high-speed shearing machine speed is 500 rad / min, and the stirring time is 15 minutes.
[0061] Step six, pour the wet gel described in step five into a silica gel mold, freeze it at minus 20 degrees for 24 hours to form a cryogel, and then perform vacuum freeze drying for 48 hours to obtain a regenerated cellulose foam aerogel material.
[0062] The density of the regenerated cellulose foamed aerogel material prepared in this embodiment is 0.129 g / cm 3 The compressive strength can reach 84.1 kPa under 80% compression strain, and can recover to 86% of the initial shape with a recovery time of less than 2 s; the rebound rate reaches 91% after 100 cycles of compression under 50% strain, which proves that the aerogel material prepared in this embodiment has good mechanical properties and durability.
[0063] Example 4
[0064] Step 1: Prepare cellulose dissolving solution: add 13% sodium hydroxide and 1.5% sorbitol into deionized water and freeze it in a refrigerator at -5°C for 5 hours.
[0065] Step 2: Preparation of dissolved cellulose hydrogel: Tear the bamboo fiber pulp into blocks, and then crush it with a pulverizer to obtain flocculent fibers. Soak in deionized water for 24 hours and then vacuum filter until no droplets fall. Then soak and filter with anhydrous methanol and acetone in the same way to remove impurities. Finally, place the filtered fibers in a blast drying oven and dry them at 110°C for 2 hours to obtain dry fibers, and add the pre-cooled dissolving solution in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 4%, and let it stand at 25°C for 5 hours. Then put the plant fiber dissolving solution into a refrigerator and freeze it at minus 20°C for 18 hours. After thawing at 25°C for 6 hours, mechanically stir to obtain a dissolved cellulose solution, the speed of the high-speed shearing machine is 800rad / min, and the stirring time is 15min; then inject the dissolved cellulose solution into the mold and freeze it at a temperature of minus 20°C for 16 hours, and then thaw it at 25°C for 6 hours to obtain a hydrogel.
[0066] Step 3: Soak the hydrogel in deionized water with a volume 20 times that of the hydrogel, measure the pH value of the deionized water every 5 hours and replace the deionized water until the pH value is neutral, then uniformly disperse the regenerated hydrogel and deionized water through two high-speed shearing processes, each dispersion time is 30 minutes, the rotation speed is 1500 rad / min, and a regenerated cellulose dispersion is obtained, and the concentration is controlled to be 5%.
[0067] Step 4: Add quinic acid at a concentration of 1.5% of the total mass, sodium hexametaphosphate at 50% of the mass of the polycarboxylic acid; sodium alginate at 3% of the total mass; each component is added to the regenerated cellulose dispersion in turn, dispersed at a high-speed shearing machine of 1500 rad / min for 10 minutes, and then heated at 100°C in a forced air drying oven for 20 minutes to obtain a cross-linked cellulose aqueous solution system with a regenerated cellulose concentration of 3%.
[0068] Step 5: Add calcium lignin sulfonate surfactant to the system described in step 4, and prepare regenerated cellulose foamed wet gel by high-speed shearing and stirring. The high-speed shearing machine speed is 500 rad / min, and the stirring time is 15 minutes.
[0069] Step six, pour the wet gel described in step five into a silica gel mold, freeze it at minus 20 degrees for 24 hours to form a cryogel, and then perform vacuum freeze drying for 48 hours to obtain a regenerated cellulose foam aerogel material.
[0070] The density of the regenerated cellulose foamed aerogel material prepared in this embodiment is 0.141 g / cm3 The compressive strength can reach 82.7 kPa under 80% compression strain, and it can recover to 88% of the initial shape with a recovery time of less than 3 s. The rebound rate reaches 87% after 100 cycles of compression under 50% strain, which proves that the aerogel material prepared in this embodiment has good mechanical properties and durability.
[0071] Table 1 Performance comparison of aerogel materials of implementation one, two, three and four
[0072]
[0073] The photos of the regenerated cellulose foamed aerogel materials prepared in Example 1, Example 2, Example 3 and Example 4 are shown in FIG. Figure 1 The SEM image of the material is as follows: Figure 2 Due to the foaming and foam stabilizing properties of anionic surfactants, the material has a dense and uniform layered network structure. The mechanical properties and durability of regenerated cellulose foam aerogel materials are as follows Figure 3 , 4 Due to the chemical covalent bonds and hydrogen bonds between polycarboxylic acids, anionic surfactants and cellulose, the prepared regenerated cellulose active foaming aerogel material has good mechanical properties and compression resilience.
[0074] The method for determining each parameter in the above embodiment is as follows:
[0075] Density: Measure the size of the sample material three times with a vernier caliper and take the average value to calculate its volume V. Use an electronic balance to weigh the mass m of the sample and calculate the material density according to formula (1):
[0076]
[0077] Compressive strength at 80% strain: Perform compression test on the material using a universal testing machine, export the test data and read the stress value corresponding to when the strain value reaches 80% in the stress-strain curve of the sample material, and take the average value of three experimental data.
[0078] Resilience under 80% strain: Before the test, measure the thickness of the sample material three times and take the average value (H0), then use a universal testing machine to perform a 50% strain compression test on the sample material, and measure its thickness three times 10S after the sample material recovers and take the average value (H1). According to the formula
[0079]
[0080] Recovery time: Use a universal testing machine to compress the material to 50% strain, quickly release it and start timing until the material recovers to the maximum recovery amount. Repeat three times and take the average time as the recovery time.
[0081] 100 times compression rebound rate at 50% strain: The test method is similar to the rebound rate at 80% strain. The difference is that the H1 value represents the thickness of the material tested after being compressed 100 times continuously at 50% strain using a universal testing machine. The 100 times compression rebound rate at 50% strain is calculated using formula (2).
[0082] The above embodiments only express several implementation methods of the present invention. These descriptions are relatively specific and detailed, but it cannot be understood that the protection scope of the present invention is limited thereto. It should be said that for professionals in this field, many variations and improvements can be made on the basis of the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.
Claims
1. A method for preparing a high resilience regenerated cellulose foamed aerogel material, characterized in that: The following steps are involved: Step 1: Prepare a mixed aqueous solution of polyol and inorganic strong base of appropriate concentration (referred to as dissolving solution); Step 2: dissolving the plant fiber in the solution prepared in step 1 at a certain mass fraction, freezing the plant fiber solution at a certain temperature for a period of time, taking it out to thaw at room temperature, and mechanically stirring it to obtain a dissolved cellulose solution, then pouring the solution into a mold, freezing it for a period of time, and taking it out to thaw at room temperature to obtain a hydrogel; Step 3: Soak the hydrogel in a certain volume of deionized water to displace the solvent and regenerate the dissolved cellulose. The pH value of the deionized water is measured and the solution is replaced at regular intervals until the pH value is neutral. The regenerated hydrogel and a certain proportion of deionized water are then uniformly dispersed by multiple high-speed shearing to obtain a regenerated cellulose dispersion with uniform size and good dispersion. Step 4: adding polycarboxylic acid, catalyst and adhesive solution to the regenerated cellulose dispersion respectively, stirring at a low speed and then cross-linking at a high temperature to obtain a cross-linked fiber aqueous solution system; Step 5: adding anionic surfactant to the system described in step 4, and preparing regenerated cellulose foamed wet gel by high-speed shear stirring and foaming; Step 6: pouring the wet gel in step 5 into a silica gel mold, freezing to form a cryogel, and then performing a vacuum freeze-drying process to obtain a regenerated cellulose foamed aerogel material; Vacuum freeze drying treatment: Place in a vacuum freeze dryer and freeze dry for 2-3 days.
2. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: The step 1 comprises the following steps: preparing a mixed aqueous solution of an inorganic strong base with a mass fraction ranging from 8% to 15% and a polyol with a mass fraction ranging from 1% to 4%, and precooling it at -5°C for 3 to 4 hours for standby use. The polyol includes pentaerythritol, glycerol, trimethylolethane, xylitol, sorbitol, polyethylene glycol, etc.; the inorganic strong base includes lithium hydroxide, sodium hydroxide, etc.
3. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: The types of plant fibers used to prepare the regenerated cellulose dispersion in the step 2 include: one or more plant fibers selected from bamboo fiber, cotton fluff fiber, hardwood fiber, and coniferous wood fiber. The fibers need to be pretreated as follows: tear the pulp board into blocks, and then crush them with a grinder to obtain flocculent fibers. Soak in deionized water for 24 hours and then vacuum filter until no droplets drip. Then, soak and filter with anhydrous methanol and acetone in the same way to remove impurities. Finally, place the filtered fibers in a blast drying oven and dry them at 110°C for 2 hours to obtain dry fibers. Then, add the precooled dissolving solution prepared in step 1 to prepare a plant fiber dissolving solution with a mass fraction of 1%-6%, and let it stand at 20°C-25°C for 5-8 hours.
4. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: In the step 2, the plant fiber solution is placed in a refrigerator at -20°C for 12-18 hours, taken out and thawed at 20-25°C for 5-6 hours, and mechanically stirred to obtain a dissolved cellulose solution, and the speed of the high-speed shearing machine is 1000-1500rad / min; the mold freezing temperature is minus 10-20°C for 12-18 hours, and thawed at 20-25°C for 5-6 hours to obtain a hydrogel.
5. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: In the step 3, the volume ratio of the hydrogel to the deionized water should be greater than 1:10, the soaking time is 5-6 hours, and the pH value is measured by a pH tester before each replacement of the deionized water. After the pH value reaches neutral, the regenerated cellulose hydrogel is mixed with a certain proportion of deionized water and mechanically stirred, and the high-speed shearing machine is used for 30-50 minutes at a speed of 1500-2000 rad / min, and the concentration of the regenerated cellulose dispersion is 2%-5%.
6. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: The polycarboxylic acid in step 4 is fumaric acid, gluconic acid, phytic acid, quinic acid, citric acid, etc., and the concentration of the polycarboxylic acid is 2%-4% of the total mass; the catalyst is sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate and tetramethylammonium salt, etc., and the catalyst is 30%-50% of the mass of the polycarboxylic acid; the adhesive is chitosan, carboxymethyl cellulose, polyvinyl alcohol, sodium alginate, etc., and the concentration of the adhesive is 1%-4% of the total mass. The above components are added to the regenerated cellulose dispersion in sequence, dispersed at 500 rad / min for 5 minutes, and heated in a blast drying oven at 100°C for 20-30 minutes.
7. The method for preparing a high resilience regenerated cellulose foamed aerogel material according to claim 1, characterized in that: The anionic surfactant in step 5 is sodium dodecyl sulfate, sodium alcohol ether sulfate, sodium dodecyl sulfate, sodium lauryl sulfate, calcium lignin sulfonate, sodium lignin sulfonate, etc.; After cross-linking, the mixed solution is passed through a high-speed shearing machine at 1000-2000 rad / min and stirred for foaming for 5-10 minutes.