A cellulose ester honeycomb porous membrane and a preparation method thereof

Abstract

The present invention relates to the technical field of porous membrane preparation, and particularly relates to a cellulose ester honeycomb porous membrane and a preparation method thereof. The steps are as follows: I. Preparation of cellulose ester: First, dissolve microcrystalline cellulose to obtain a cellulose solution; then add 10-undecenoyl chloride and pyridine to the cellulose solution for an esterification reaction to obtain a reaction mixture; pour the reaction mixture into methanol, precipitate the product, and obtain the lower-layer precipitate through centrifugal separation; then disperse the lower-layer precipitate in a volatile organic solvent to obtain an organic solvent solution of cellulose ester. II. Preparation of honeycomb porous membrane: Pour the organic solvent solution of cellulose ester into a mold, and then place it in a closed high-humidity device. After the volatile organic solvent and water have evaporated completely, a cellulose ester honeycomb porous membrane can be obtained. The present invention first prepares hydrophobic cellulose ester by a one-step esterification method, and then prepares a honeycomb porous membrane with hydrophobicity, uniform pore size, and ordered porous structure through a breath figure method.

Description

Technical Field

[0001] The present invention relates to the technical field of porous membrane preparation, and particularly relates to a cellulose ester honeycomb porous membrane and a preparation method thereof. Background Art

[0002] Microporous thin films with an ordered structure have many unique advantages, such as a large specific surface area, uniform pore size, and high surface roughness, etc., making them have a very broad application prospect in various aspects such as optoelectronic devices, biomaterials, sensors, template materials, separation and filtration, etc.

[0003] Cellulose, as the most abundant natural polymer compound in nature, has the advantages of being renewable, biodegradable, biocompatible, inexpensive and easily available. In the current situation where the energy crisis and environmental problems are becoming increasingly severe, cellulose is considered an important raw material in the future chemical industry and new material development fields. Cellulose membranes have characteristics such as being safe, non-toxic, and biodegradable, and show great application potential in optical devices, biomaterials, chemical catalysis, etc., thus being widely used. The patents with publication numbers CN110237722A and CN113248778A disclose the preparation of cellulose membranes using cellulose, but the pores of the obtained cellulose membranes are disorderly arranged and the pore sizes are uneven, making it difficult to meet the requirements of optoelectronic devices, biomaterials, sensors, template materials, separation and filtration, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a cellulose ester honeycomb porous membrane and a preparation method thereof. First, a hydrophobic cellulose ester is prepared by a one-step esterification method, and then a hydrophobic, honeycomb porous membrane of cellulose ester with uniform pore size and ordered porous structure is prepared by the breath figure method.

[0005] To achieve the above purpose, the technical solution of the present invention is a preparation method of a cellulose ester honeycomb porous membrane, including the following steps:

[0006] I. Preparation of Cellulose Ester

[0007] ①. Dissolve microcrystalline cellulose to obtain a cellulose solution;

[0008] ②. Add 10-undecenoyl chloride and pyridine to the cellulose solution for an esterification reaction to obtain a reaction mixture;

[0009] ③. Pour the reaction mixture into methanol to precipitate the product, and then perform centrifugal separation to obtain the lower layer precipitate;

[0010] ④. Disperse the lower layer precipitate in a volatile organic solvent to obtain an organic solvent solution of cellulose ester;

[0011] II. Preparation of Honeycomb Porous Membrane

[0012] Pour the organic solvent solution of cellulose ester into a mold, and then place it in a closed high-humidity device. After the volatile organic solvent and water have evaporated completely, a cellulose ester honeycomb porous membrane can be obtained.

[0013] Further, in step ①, first dry the microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then add the absolutely dry microcrystalline cellulose to N,N-dimethylacetamide, heat to 120 - 140 °C, and add lithium chloride after heating for 30 - 40 min under continuous stirring; then cool the reaction system to room temperature and continue stirring for 3 h until the microcrystalline cellulose dissolves to obtain a cellulose solution.

[0014] Further, in step ②, first heat the cellulose solution to 45 - 55 °C, then add 10-undecenoyl chloride to the cellulose solution, and then add pyridine, and react for 5 - 10 h to obtain a reaction mixture.

[0015] Furthermore, the molar ratio of glucose units to acyl chloride in cellulose is 1:(1 - 3), and the mass ratio of absolutely dry microcrystalline cellulose to the volume of pyridine in the cellulose solution is 1 g:(2 - 4) mL.

[0016] Further, in step ③, the conditions for centrifugal separation are: rotation speed 9000 - 11000 r / min, temperature 3 - 5 °C, and time 10 - 20 min.

[0017] Further, in step ③, disperse the obtained lower-layer precipitate in tetrahydrofuran or dichloromethane, and repeat according to step ③ for 3 - 5 times.

[0018] Preferably, in step ④, the volatile organic solvent is dichloromethane.

[0019] Further, in step ④, the concentration of the organic solvent solution of cellulose ester is 4 - 6 mg / mL.

[0020] Further, in step ②, the humidity of the high-humidity device is 70 - 80%.

[0021] The present invention also provides a cellulose ester honeycomb porous membrane prepared by using the preparation method described in any one of the above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention first prepares a hydrophobic cellulose ester by a one-step esterification method, and then obtains a hydrophobic cellulose ester honeycomb porous membrane with a uniform pore size and an ordered porous structure through a breath figure method, which can be used in optical devices, biomaterials, sensors, template materials, separation and filtration, etc., and has good biodegradability;

[0024] (2) The raw materials for preparing the cellulose ester honeycomb porous membrane of the present invention are rich in sources, environmentally friendly and pollution-free. The preparation method is simple and effective, and the pore size and porosity can be adjusted, which can meet the needs of applications in different fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 SEM image of the cellulose ester honeycomb porous membrane prepared in Example 1 of the present invention;

[0027] Figure 2 SEM image of the cellulose ester honeycomb porous membrane prepared in Comparative Example 1;

[0028] Figure 3 SEM image of the cellulose ester honeycomb porous membrane prepared in Comparative Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] Example 1

[0031] This example provides a cellulose ester honeycomb porous membrane, and its preparation method includes the following steps:

[0032] I. Preparation of cellulose ester

[0033] ① First, commercially available microcrystalline cellulose is dried to obtain absolutely dry microcrystalline cellulose; then 1 g of absolutely dry microcrystalline cellulose is weighed and added to 30 mL of N,N-dimethylacetamide, heated to 130 °C, and after heating for 30 min under continuous stirring, 3 g of lithium chloride is added to the mixture; then the reaction system is cooled to room temperature, and then continuously stirred for 3 h until the microcrystalline cellulose dissolves to obtain a transparent cellulose solution;

[0034] ②. Heat the transparent cellulose solution to 50 °C, then add 2.73 mL of 10-undecenoyl chloride to the cellulose solution, where the molar ratio of glucose units in cellulose to 10-undecenoyl chloride is 1:2. Then add 3 mL of pyridine and react for 7 h to obtain a reaction mixture;

[0035] ③. After the reaction is completed, pour the reaction mixture into methanol. The product precipitates out. Then, under the conditions of a rotation speed of 10000 r / min and a temperature of 4 °C, centrifuge for 15 min, then remove the upper layer liquid, and disperse the lower layer precipitate in tetrahydrofuran to obtain a tetrahydrofuran solution of cellulose ester;

[0036] ④. Repeat the operation of step 3 four times for the tetrahydrofuran solution of cellulose ester, and then disperse the lower layer product in dichloromethane solution to obtain a dichloromethane solution of cellulose ester;

[0037] II. Preparation of honeycomb porous membrane

[0038] ①. Pour 10 mL of a dichloromethane solution of cellulose ester with a concentration of 5 mg / mL into a circular Teflon mold with a diameter of 8 cm;

[0039] ②. Place the mold containing the dichloromethane solution of cellulose ester into a closed high-humidity device. The humidity in the closed space is 75%. After the dichloromethane and water have evaporated completely, a cellulose ester honeycomb porous membrane can be obtained.

[0040] The prepared cellulose ester honeycomb porous membrane was analyzed by scanning electron microscopy, and the results are as Figure 1 shown. It can be seen that the pore size of the prepared cellulose ester honeycomb porous membrane is uniform and arranged in an orderly manner, and the average pore size is 39.71 μm.

[0041] Example 2

[0042] This example provides a cellulose ester honeycomb porous membrane, and its preparation method includes the following steps:

[0043] I. Preparation of cellulose ester

[0044] ①. First, dry commercial microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then weigh 1 g of absolutely dry microcrystalline cellulose and add it to 30 mL of N,N-dimethylacetamide, heat to 130 °C, and add 3 g of lithium chloride to the mixture after heating for 30 min under continuous stirring; then cool the reaction system to room temperature and continue to stir for 3 h until the microcrystalline cellulose dissolves to obtain a transparent cellulose solution;

[0045] ②. Heat the transparent cellulose solution to 50 °C, then add 1.37 mL of 10-undecenoyl chloride to the cellulose solution, where the molar ratio of glucose units in cellulose to 10-undecenoyl chloride is 1:1. Then add 3 mL of pyridine and react for 10 h to obtain a reaction mixture;

[0046] ③. After the reaction is completed, pour the reaction mixture into methanol, and the product will precipitate. Then, under the conditions of a rotation speed of 10,000 r / min and a temperature of 4 °C, centrifuge for 15 min, then remove the upper layer liquid, and disperse the lower layer precipitate in tetrahydrofuran to obtain a tetrahydrofuran solution of cellulose ester;

[0047] ④. Repeat the operation of step 3 four times for the tetrahydrofuran solution of cellulose ester, and then disperse the lower layer product in dichloromethane solution to obtain a dichloromethane solution of cellulose ester;

[0048] II. Preparation of honeycomb porous membrane

[0049] ①. Pour 10 mL of a dichloromethane solution of cellulose ester with a concentration of 5 mg / mL into a circular Teflon mold with a diameter of 8 cm;

[0050] ②. Place the mold containing the dichloromethane solution of cellulose ester in a closed high-humidity device. The humidity of the closed space is 75%. After the dichloromethane and water have evaporated completely, a honeycomb porous membrane of cellulose ester can be obtained.

[0051] For the prepared honeycomb porous membrane of cellulose ester, micropores with uniform pore size and arranged in an orderly manner can be seen through a scanning electron microscope, and the average pore size is 30.68 μm.

[0052] Example 3

[0053] This example provides a honeycomb porous membrane of cellulose ester, and its preparation method includes the following steps:

[0054] I. Preparation of cellulose ester

[0055] ①. First, dry commercial microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then weigh 1 g of absolutely dry microcrystalline cellulose and add it to 30 mL of N,N-dimethylacetamide, heat to 130 °C, and add 3 g of lithium chloride to the mixture after heating for 30 min under continuous stirring. Then cool the reaction system to room temperature and continue to stir for 3 h until the microcrystalline cellulose dissolves to obtain a transparent cellulose solution;

[0056] ②. Heat the transparent cellulose solution to 50 °C, then add 4.1 mL of 10-undecenoyl chloride to the cellulose solution, where the molar ratio of glucose units in cellulose to 10-undecenoyl chloride is 1:3. Then add 3 mL of pyridine and react for 5 h to obtain a reaction mixture;

[0057] ③. After the reaction is completed, pour the reaction mixture into methanol, and the product will precipitate. Then, centrifuge for 15 min at a rotation speed of 10000 r / min and a temperature of 4 °C, and then remove the upper layer liquid. Disperse the lower layer precipitate in tetrahydrofuran to obtain a tetrahydrofuran solution of cellulose ester;

[0058] ④. Repeat the steps of the tetrahydrofuran solution of cellulose ester 4 times according to step 3, and then disperse the lower layer product in dichloromethane solution to obtain a dichloromethane solution of cellulose ester;

[0059] II. Preparation of honeycomb porous membrane

[0060] ①. Pour 10 mL of dichloromethane solution of cellulose ester with a concentration of 5 mg / mL into a circular Teflon mold with a diameter of 8 cm;

[0061] ②. Place the mold containing the dichloromethane solution of cellulose ester into a closed high-humidity device. The humidity of the closed space is 75%. After the dichloromethane and water have evaporated completely, a cellulose ester honeycomb porous membrane can be obtained.

[0062] For the prepared cellulose ester honeycomb porous membrane, micropores with uniform pore size and orderly arrangement can be seen through a scanning electron microscope, and the average pore size is 45.77 μm.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for preparing a cellulose ester honeycomb porous membrane, including the following steps:

[0065] I. Preparation of cellulose ester

[0066] ①. First, dry commercial microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then weigh 1 g of absolutely dry microcrystalline cellulose and add it to 30 mL of N,N-dimethylacetamide. Heat to 130 °C and heat for 30 min under continuous stirring, then add 3 g of lithium chloride to the mixture; then cool the reaction system to room temperature and continue stirring for 3 h until the microcrystalline cellulose dissolves to obtain a transparent cellulose solution;

[0067] ②. Heat the transparent cellulose solution to 100 °C, then add 3.96 mL of stearoyl chloride to the cellulose solution, where the molar ratio of glucose units in cellulose to stearoyl chloride is 1:2, and then add 3 mL of pyridine and react for 1 h to obtain a reaction mixture;

[0068] ③. After the reaction is completed, pour the reaction mixture into methanol to precipitate the product. Then, centrifuge for 15 min at a rotation speed of 10,000 r / min and a temperature of 4 °C, and then remove the upper layer of liquid. Disperse the lower layer of precipitate in tetrahydrofuran to obtain a tetrahydrofuran solution of cellulose ester;

[0069] ④. Repeat step 3 four times with the tetrahydrofuran solution of cellulose ester, and then disperse the lower layer of product in dichloromethane solution to obtain a dichloromethane solution of cellulose ester;

[0070] II. Preparation of honeycomb porous membrane

[0071] ①. Pour 10 mL of a dichloromethane solution of cellulose ester with a concentration of 5 mg / mL into a circular Teflon mold with a diameter of 8 cm;

[0072] ②. Place the mold containing the dichloromethane solution of cellulose ester into a closed high-humidity device with a humidity of 75% in the closed space. After dichloromethane and water have completely evaporated, a cellulose ester honeycomb porous membrane can be obtained.

[0073] Comparative Example 2

[0074] Comparative Example 2 provides a method for preparing a cellulose ester honeycomb porous membrane, which includes the following steps:

[0075] I. Preparation of cellulose ester

[0076] ①. First, dry commercial microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then weigh 1 g of absolutely dry microcrystalline cellulose and add it to 30 mL of N,N-dimethylacetamide, heat to 130 °C, and add 3 g of lithium chloride to the mixture after heating and continuously stirring for 30 min; then cool the reaction system to room temperature and continue to stir for 3 h until the microcrystalline cellulose dissolves to obtain a transparent cellulose solution;

[0077] ②. Heat the transparent cellulose solution to 50 °C, and then add 1.7 mL of hexanoyl chloride to the cellulose solution, where the molar ratio of glucose units in cellulose to hexanoyl chloride is 1:2, and then add 3 mL of pyridine and react for 5 h to obtain a reaction mixture;

[0078] ③. After the reaction is completed, pour the reaction mixture into methanol to precipitate the product. Then, centrifuge for 15 min at a rotation speed of 10,000 r / min and a temperature of 4 °C, and then remove the upper layer of liquid. Disperse the lower layer of precipitate in tetrahydrofuran to obtain a tetrahydrofuran solution of cellulose ester;

[0079] ④. Repeat step 3 four times with the tetrahydrofuran solution of cellulose ester, and then disperse the lower layer of product in dichloromethane solution to obtain a dichloromethane solution of cellulose ester;

[0080] II. Preparation of Honeycomb Porous Membrane

[0081] ① Pour 10 mL of a dichloromethane solution of cellulose ester with a concentration of 5 mg / mL into a circular Teflon mold with a diameter of 8 cm;

[0082] ② Place the mold containing the dichloromethane solution of cellulose ester into a closed high-humidity device. The humidity in the closed space is 75%. After the dichloromethane and water have completely evaporated, a cellulose ester honeycomb porous membrane can be obtained.

[0083] Perform scanning electron microscope analysis on the cellulose ester honeycomb porous membranes prepared in Comparative Example 1 and Comparative Example 2. As shown in Figure 2 and Figure 3 , it can be seen that the micropores of the porous membranes prepared in Comparative Example 1 and Comparative Example 2 are both irregularly arranged, and the pore sizes are different. The pore size of the micropores in Comparative Example 1 is about 50 microns, and the pore size of the micropores in Comparative Example 2 is about 20 microns.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a cellulose ester honeycomb porous membrane, characterized in that, It includes the following steps: I. Preparation of cellulose ester ① First, dry microcrystalline cellulose to obtain absolutely dry microcrystalline cellulose; then add the absolutely dry microcrystalline cellulose into N,N-dimethylacetamide, heat to 120 - 140 °C, add lithium chloride after heating for 30 - 40 min under continuous stirring; then cool the reaction system to room temperature and continue stirring for 3 h until the microcrystalline cellulose dissolves to obtain a cellulose solution; ② First, heat the cellulose solution to 45 - 55 °C, then add 10-undecenoyl chloride to the cellulose solution, and then add pyridine, react for 5 - 10 h to obtain a reaction mixture; ③ Pour the reaction mixture into methanol to precipitate the product, and then centrifuge to obtain the lower-layer precipitate; ④ Disperse the lower-layer precipitate in a volatile organic solvent to obtain an organic solvent solution of cellulose ester; II. Preparation of honeycomb porous membrane Pour the organic solvent solution of cellulose ester into a mold, and then place it in a closed high-humidity device. After the volatile organic solvent and water have evaporated completely, a cellulose ester honeycomb porous membrane can be obtained.

2. The preparation method of the cellulose ester honeycomb porous membrane according to claim 1, characterized in that: The molar ratio of glucose units in cellulose to acyl chloride is 1:(1 - 3), and the mass ratio of absolutely dry microcrystalline cellulose in the cellulose solution to the volume of pyridine is 1 g:(2 - 4) mL.

3. The method for preparing a cellulose ester honeycomb porous membrane according to claim 1, characterized in that: In step I③, the conditions for centrifugation are: rotation speed 9000 - 11000 r / min, temperature 3 - 5 °C, time 10 - 20 min.

4. The method for preparing a cellulose ester honeycomb porous membrane according to claim 1, wherein: In step I③, disperse the obtained lower-layer precipitate in tetrahydrofuran or dichloromethane and repeat step I③ 3 - 5 times.

5. The method for preparing a cellulose ester honeycomb porous membrane according to claim 1, characterized in that: In step I④, the volatile organic solvent is dichloromethane.

6. The preparation method of the cellulose ester honeycomb porous membrane according to claim 1, characterized in that: In step I④, the concentration of the organic solvent solution of cellulose ester is 4 - 6 mg / mL.

7. The method for preparing the cellulose ester honeycomb porous membrane according to claim 1, wherein: In step II, the humidity of the high-humidity device is 70 - 80%.

8. A cellulose ester honeycomb porous membrane prepared by the preparation method according to any one of claims 1 - 7.

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