Modified cellulose acetate membrane and preparation method thereof

Abstract

The invention discloses a modified cellulose acetate membrane and a preparation method thereof.The preparation method comprises the specific steps that cellulose acetate is dissolved in a solvent formed by mixing N, N-dimethylacetamide and acetone, then 2-methylimidazole is added to form a uniform and stable spinning precursor solution, and finally the modified cellulose acetate membrane is prepared through an electrostatic spinning method. The fiber membrane prepared by the invention is smooth in fiber surface, relatively uniform in diameter distribution, and good in fiber morphology and porosity. And the preparation process is simple, convenient and feasible, the cost is controllable, the competitiveness in large-scale production and practical application is high, and popularization is facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of membrane materials, and in particular to a modified cellulose acetate membrane and a preparation method thereof. Background Art

[0002] With the increasing emphasis on environmental protection and sustainable development, the development and utilization of renewable energy has become a research hotspot. Osmotic energy, as a renewable energy source, has great potential. However, traditional membrane materials used to collect osmotic energy have many problems, such as insufficient mass transfer of ion exchange membranes and high membrane resistance, which leads to low power density and difficulty in achieving effective energy conversion. In the current research on osmotic energy collection membranes, in order to achieve high ion flux and good ion selectivity, many membranes are designed with complex nanofluid channels, but such membranes are expensive and have complex preparation processes, and are not economically feasible for large-scale power generation. Therefore, it is of great significance to develop an osmotic energy collection membrane material with simple process, low cost and excellent performance.

[0003] Cellulose acetate plays an important role in the field of membrane separation and is one of the ideal candidate materials for the preparation of osmotic energy collection membranes. It has good film-forming properties, excellent chemical stability, good biocompatibility, wide sources, and relatively low cost, which helps to reduce the preparation cost of osmotic energy collection membranes and improve their economic feasibility. However, cellulose acetate membranes themselves also have some shortcomings, such as ion selectivity and flux need to be further improved. Therefore, the modification of cellulose acetate membranes to give full play to its advantages and overcome its shortcomings has become an important direction of current research. Through modification, while retaining the original excellent properties of cellulose acetate, it can be given better ion transmission performance and selectivity, thereby improving the osmotic energy collection efficiency and promoting the development of osmotic energy technology. Summary of the invention

[0004] The object of the present invention is to provide a modified cellulose acetate membrane and a preparation method thereof, so as to produce a film material with a higher permeability energy collection rate through a simple design and a single material modification.

[0005] The present application discloses a modified cellulose acetate film and a preparation method thereof, comprising the following steps:

[0006] S1 Preparation of spinning precursor solution: Weigh cellulose acetate (CA) and add it to a mixed solution of N,N-dimethylacetamide (DMAc) and acetone. After stirring evenly, add 2-methylimidazole and stir in a water bath at 50°C for 2h to obtain a transparent and uniform spinning precursor solution.

[0007] S2 electrospinning: The spinning precursor solution obtained in S1 was added into a 5 ml electrospinning syringe, and after removing the bubbles, it was fixed on the syringe pump, and the modified fiber membrane was prepared using an electrospinning machine;

[0008] S3 drying treatment: the fiber membrane spun in S2 is placed in an oven for drying to obtain a 2-methylimidazole-modified cellulose acetate membrane.

[0009] Preferably, in step S1, the content of cellulose acetate is 10-15 wt %, and the content of 2-methylimidazole is 3-6 wt %.

[0010] Preferably, the mass ratio of DMAc to acetone in the mixed solution of step S1 is 3:2.

[0011] Preferably, the electrospinning parameters of step S2 are: electrospinning machine parameters are 15-20 kV, pushing speed is 0.001 mm / s, temperature is room temperature, relative humidity is 40%, and spinning time is 8 hours.

[0012] Preferably, the drying temperature in step S3 is 60° C. and the drying time is 0.5 h.

[0013] The advantages of the present invention are:

[0014] 1. The embodiment of the present invention introduces 2-methylimidazole as a cross-linking agent to form a three-dimensional network structure in the cellulose acetate film, thereby improving the tensile strength and impact resistance of the cellulose acetate film material. The tensile strength of the modified cellulose acetate film is increased by about 20% or more compared with the unmodified film.

[0015] 2. The embodiment of the present invention has good structural stability, and the chemical bonding or physical action between 2-methylimidazole and cellulose acetate improves its strength and toughness. In complex environments such as long-term immersion in aqueous solution and different temperature and pressure conditions, the fiber structure can be kept intact and not easily broken, deformed or degraded, ensuring stable operation in the osmotic energy collection device, reducing maintenance and replacement costs, and improving system reliability and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 Shown is a SEM image of the modified cellulose acetate membrane obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The following will describe the technical solutions in the embodiments of the present invention in detail in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1

[0020] Preparation of S1 spinning precursor solution: 1.2 g of cellulose acetate with a molecular weight of 50,000 was dissolved in a mixed solution of 4.98 g of N,N-dimethylacetamide and 3.32 g of acetone, and stirred in a water bath at 50°C for 4 hours to obtain a uniform and transparent solution, 0.5 g of 2-methylimidazole was added, and the solution was dissolved for ten minutes to obtain a uniform and transparent dimethylimidazole-modified cellulose acetate spinning precursor solution.

[0021] S2 electrospinning: The solution obtained in S1 was sucked into a 5 mL syringe, and after removing the bubbles, it was fixed on the syringe pump, and the modified fiber membrane was prepared using an electrospinning machine. The electrospinning machine parameters were set to 18 kV, a feed speed of 0.001 mm / s, room temperature, relative humidity of 40%, and spinning for 8 h.

[0022] S3 Drying treatment: The fiber membrane obtained in S2 was placed in a 60°C oven and dried for 0.5 h to obtain a 2-methylimidazole-modified cellulose acetate membrane.

[0023] Comparative Example 1

[0024] Except that 2-methylimidazole was not added in step S1, the rest was consistent with Example 1, and finally an unmodified cellulose acetate membrane was obtained.

[0025] Example 2

[0026] Step S1 in Example 1 is changed to: 1.4 g of cellulose acetate with a molecular weight of 50,000 is dissolved in a mixed solution of 4.98 g of N,N-dimethylacetamide and 3.32 g of acetone, stirred in a water bath at 50° C. for 4 h to obtain a uniform transparent solution, 0.3 g of 2-methylimidazole is added, and the solution is dissolved for 10 minutes to obtain a uniform and transparent dimethylimidazole-modified cellulose acetate spinning precursor solution. The rest is consistent with Example 1, and a uniformly distributed modified cellulose acetate film is obtained.

[0027] Example 3

[0028] Step S1 in Example 1 is changed to: 1.1 g of cellulose acetate with a molecular weight of 50,000 is dissolved in a mixed solution of 4.98 g of N,N-dimethylacetamide and 3.32 g of acetone, stirred in a water bath at 50° C. for 4 h to obtain a uniform transparent solution, 0.6 g of 2-methylimidazole is added, and the solution is dissolved for 10 minutes to obtain a uniform and transparent dimethylimidazole-modified cellulose acetate spinning precursor solution. The rest is consistent with Example 1, and a uniformly distributed modified cellulose acetate film is obtained.

[0029] The morphology of Example 1 was analyzed by scanning electron microscopy. Figure 1 As shown: It can be seen that the spun nanofibers are evenly distributed, and the modified 2-methylimidazole is wrapped in the fibers. The obtained fiber membrane has a smooth fiber surface, a relatively uniform diameter distribution, and good fiber morphology and porosity, which indicates that the preparation method can be used to obtain a nanofiber membrane with good fiber morphology. This shows that by cross-linking 2-methylimidazole with cellulose acetate, the prepared nanofiber membrane presents a continuous and evenly distributed fiber state.

[0030] The samples of Examples 1-3 and Comparative Example 1 were tested, and the results are as follows:

[0031] sample Tensile strength(MPa) Elongation at break (%) Comparative Example 1 35.4 16 Example 1 44.6 28 Example 2 39.7 21 Example 3 42.5 25

[0032] These performance indicators show that the modified cellulose acetate membrane is superior to the unmodified cellulose acetate membrane in mechanical properties such as tensile strength, and is more suitable for a wide range of fields such as filtration, separation, biomedicine, and flexible electronics.

[0033] This implementation mode is only an exemplary description of this patent and does not limit its protection scope. Personnel in this field may also make partial changes to it. As long as it does not exceed the spirit of this patent, it shall be regarded as an equivalent replacement of this patent and shall be within the protection scope of this patent.

Claims

1. A modified cellulose acetate film and a preparation method thereof, characterized in that: The steps include: S1 Preparation of spinning precursor solution: Weigh cellulose acetate and add it to a mixed solution of N,N-dimethylacetamide and acetone. After stirring evenly, add 2-methylimidazole and stir in a water bath at 50°C for 2h to obtain a transparent and uniform spinning precursor solution. S2 electrospinning: The spinning precursor solution obtained in S1 was added into a 5 ml electrospinning syringe, and after removing the bubbles, it was fixed on the syringe pump, and the modified fiber membrane was prepared using an electrospinning machine; S3 Drying treatment: The fiber membrane spun in S2 is placed in an oven for drying to obtain a 2-methylimidazole-modified cellulose acetate membrane.

2. The method for preparing the modified cellulose acetate film according to claim 1, characterized in that: In the step S1, the content of cellulose acetate is 10-15 wt %, and the content of 2-methylimidazole is 3-6 wt %.

3. The method for preparing the modified cellulose acetate film according to claim 1, characterized in that: The mass ratio of N,N-dimethylacetamide to acetone in the mixed solution of step S1 is 3:

2.

4. The method for preparing the modified cellulose acetate film according to claim 1, characterized in that: The electrospinning parameters of step S2 are: electrospinning machine parameters are 15-20 kV, pushing speed is 0.001 mm / s, temperature is room temperature, relative humidity is 40%, and spinning time is 8 h.

5. The method for preparing the modified cellulose acetate film according to claim 1, characterized in that: The drying temperature of step S3 is 60° C. and the drying time is 0.5 h.

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