A kind of cellulose acetate membrane and its preparation method and application

Abstract

The present invention discloses a cellulose acetate membrane, a preparation method thereof, and an application thereof. The present invention relates to the field of fiber membrane technology. The present invention comprises the following steps: S1, debonding, breaking up, and vacuum drying a bleached bamboo pulp sheet, and adding it to an analytically pure acetic anhydride reagent to obtain fully swollen bamboo pulp fibers; S2, adding analytically pure trifluoroacetic acid to the acetic anhydride solution in step S1, subsequently adding acetic acid and stirring, heating the mixture in a water bath, adding deionized water to precipitate solids, filtering, and drying to obtain cellulose acetate; S3, mixing the resulting cellulose acetate with activated polyethylene glycol, subsequently adding sodium benzoate, stirring and mixing again until uniformly mixed, air-drying, dissolving in a chloroform solution to obtain an enhanced cellulose acetate solution, coating, and naturally drying to finally obtain a cellulose acetate membrane. The cellulose acetate membrane prepared by the present invention has good biocompatibility, green degradability, excellent mechanical tensile properties, high light transmittance, and ultraviolet light shielding properties.

Description

Technical Field

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

[0002] Cellulose acetate is a thermoplastic resin derived from cellulose derived from woody biomass, esterified with anhydrides. It is currently the most widely used raw material for membrane production. Its low cost, stable properties, excellent strength, heat resistance, simple preparation process, wide availability, and biodegradability make it widely used in plastics, textiles, films, cigarette filters, packaging, and reverse osmosis membranes. The production of cellulose acetate membranes requires purification of the cellulose from the raw materials. Traditional preparation methods use concentrated sulfuric acid as a catalyst. However, the long reaction time, reaction temperature, and reaction system can cause degradation of the resulting cellulose acetate ester. The concentrated sulfuric acid catalyst is also prone to side reactions with the cellulose to form cellulose sulfate. Residual sulfate groups in the reaction also affect the application of cellulose acetate. Furthermore, the physical properties of cellulose acetate membranes produced from pure cellulose using this method are suboptimal, requiring the addition of other raw materials such as crosslinkers and plasticizers to improve the properties. The production process is complex, energy-intensive, prone to side reactions, and has low yields. Summary of the Invention

[0003] The present invention addresses the above-mentioned shortcomings of the prior art by providing a cellulose acetate membrane, a preparation method, and its application. This method is simple to operate, low-cost, and highly efficient. The resulting cellulose acetate membrane exhibits good biocompatibility, environmentally friendly degradability, excellent mechanical tensile properties, high light transmittance, and UV shielding properties. It has broad application prospects in fields such as optical imaging, food packaging, medical devices, and ground films.

[0004] A method for preparing a cellulose acetate membrane of the present invention comprises the following steps:

[0005] S1. Disintegrate, break up, and vacuum dry the bleached bamboo pulp board, then add the dispersed bamboo pulp fiber to analytical grade acetic anhydride reagent, and stir and mix to obtain fully swollen bamboo pulp fiber;

[0006] S2. Add analytically pure trifluoroacetic acid to the acetic anhydride solution in step S1, then add a certain amount of acetic acid and stir, heat in a water bath for reaction, add deionized water to precipitate solid, filter and dry to obtain cellulose acetate;

[0007] S3. Mix the generated cellulose acetate with the activated polyethylene glycol, then add sodium benzoate, stir and mix evenly again, blow dry, dissolve in chloroform solution to obtain a reinforced cellulose acetate solution, apply it evenly using a mold natural drying method, dry it naturally, and finally obtain a cellulose acetate film.

[0008] Furthermore, in step S1, the bleached bamboo pulp board is soaked in water for 6-8 hours and disintegrated at 10,000-15,000 revolutions.

[0009] Furthermore, in step S1, vacuum drying is set at 50° C.-70° C. for 6-8 hours.

[0010] Furthermore, in step S1, the mass ratio of the bleached bamboo pulp board to the analytically pure acetic anhydride is 1:3-6.

[0011] Furthermore, in step S1, the swelling is carried out at a temperature of 25-35° C. and the swelling time is 2-3 hours.

[0012] Furthermore, in step S2, the reaction temperature is 45-55° C. in a water bath, and the reaction is heated in a water bath for 2.5-3 hours.

[0013] Furthermore, in step S2, the addition ratio of the bleached bamboo pulp board, analytically pure acetic anhydride and analytically pure trifluoroacetic acid is 1:4-6:14-16.

[0014] Furthermore, in step S3, the activation temperature of polyethylene glycol is 60° C., the addition ratio of bleached bamboo pulp board, polyethylene glycol, and sodium benzoate is 38-42:1-3:1-3; and the mass ratio of bleached bamboo pulp board to analytically pure chloroform is 3:20-30.

[0015] Furthermore, the mass fraction of the bamboo pulp fiber in the mixed acid solution system consisting of trifluoroacetic acid, acetic anhydride, acetic acid and bamboo pulp fiber is 6.2-7%.

[0016] A cellulose acetate membrane prepared by the above preparation method.

[0017] Application of the above-mentioned cellulose acetate film in optical imaging, food packaging, medical equipment and ground film

[0018] The preparation method of the cellulose acetate membrane of the present invention can not only realize the high-value utilization of bamboo resources, but also is applicable to industrial production due to its simple process and low energy consumption, thereby promoting the development of a low-carbon economy.

[0019] The present invention uses bleached bamboo pulp instead of dissolving pulp as the raw material for preparing cellulose acetate, uses trifluoroacetic acid instead of concentrated sulfuric acid as a reaction catalyst, and adds polyethylene glycol and sodium benzoate as reinforcing agents. This method omits the step of purifying cellulose from the raw materials, retains part of the hemicellulose and lignin, and while ensuring the stability of the reaction system and improving the reaction efficiency, allows the bleached bamboo pulp to contain a small amount of lignin while still being able to prepare cellulose acetate film with high light transmittance, possessing a mechanical tensile property of 36.25 MPa, and having added ultraviolet light shielding performance, thereby avoiding excessive energy consumption and reducing costs, and also greatly improving the preparation efficiency of the cellulose acetate film.

[0020] This invention proposes, for the first time, the use of bleached bamboo pulp to produce cellulose acetate membranes. This raw material offers advantages such as widespread availability and low cost. Compared to current methods for producing cellulose acetate, which typically extract cellulose from raw materials or use dissolving pulp, this invention can further promote the development and utilization of bamboo resources, fostering the development of a low-carbon economy. Furthermore, the resulting product is biodegradable and environmentally friendly.

[0021] The preparation method adopted by the present invention has a simple process and low reaction temperature, is applicable to industrial production, has broad application prospects, and has good social and economic benefits.

[0022] The newly prepared cellulose acetate membrane of the present invention has good biocompatibility, green degradability, high light transmittance, and excellent mechanical tensile properties. It can be used in optical imaging, food packaging, medical equipment, ground film and other fields, and has very broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 、 2 This is a scanning electron microscope (SEM) test image of the surface of the newly prepared cellulose acetate membrane of Example 1 of the present invention;

[0024] Figure 3 This is a test chart of the optical properties of the newly prepared cellulose acetate film prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0025] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0026] Example 1

[0027] The preparation method of the cellulose acetate membrane of this embodiment includes:

[0028] Weigh 6g of bleached bamboo pulp board and beat it at 15,000 rpm, then vacuum dry it at 60°C for 8 hours. Add the dispersed bamboo pulp fiber to analytically pure acetic anhydride reagent, with the mass ratio of bamboo pulp fiber to analytically pure acetic anhydride being 1:5, and mix and stir for 3 hours. Add analytically pure trifluoroacetic acid to the acetic anhydride solution, with the addition ratio of bleached bamboo pulp board, analytically pure acetic anhydride and analytically pure trifluoroacetic acid being 1:5:14. Subsequently, add a certain amount of acetic acid and stir, heat in a water bath to react for 3h, add deionized water to precipitate the solid, filter and dry to obtain acetate fiber, mix the generated acetate fiber with activated polyethylene glycol for 1 hour, add sodium benzoate and stir again, and the addition ratio of bleached bamboo pulp board, polyethylene glycol and sodium benzoate is 40:1:1. Dry with forced air at 60°C for 10 hours, dissolve in 60g analytically pure chloroform reagent to obtain a reinforced acetate fiber solution, evenly coat it with a mold natural drying method, and dry it naturally to obtain an acetate fiber film.

[0029] Example 2

[0030] The difference from Example 1 is that:

[0031] The bleached bamboo pulp board of Example 1 was beaten at 10,000 rpm instead of 15,000 rpm, while other processes remained unchanged.

[0032] The preparation method of the novel cellulose acetate membrane of this embodiment comprises:

[0033] Weigh 6g of bleached bamboo pulp board and beat it at 10,000 rpm, then vacuum dry it at 60°C for 8 hours. Add the dispersed bamboo pulp fiber to analytically pure acetic anhydride reagent, with the mass ratio of bleached bamboo pulp board to analytically pure acetic anhydride being 1:5, and mix and stir for 3 hours. Add analytically pure trifluoroacetic acid to the acetic anhydride solution, with the addition ratio of bleached bamboo pulp board, analytically pure acetic anhydride and analytically pure trifluoroacetic acid being 1:5:14. Subsequently, add a certain amount of acetic acid and stir, heat in a water bath to react for 3 hours, add deionized water to precipitate the solid, filter and dry to obtain acetate fiber, mix the generated acetate fiber with activated polyethylene glycol for 1 hour, add sodium benzoate and stir again, and the addition ratio of bleached bamboo pulp board, polyethylene glycol and sodium benzoate is 40:1:1. Dry with forced air at 60°C for 10 hours, dissolve in 60g of analytically pure chloroform reagent to obtain a reinforced acetate fiber solution, evenly coat it using the mold natural drying method, and dry it naturally to finally obtain an acetate fiber film.

[0034] In Example 2, the number of beating times was reduced during the preparation process, resulting in some bamboo pulp fibers not being fully dispersed. Agglomeration occurred during the trifluoroacetic acid soaking process, and the reaction was not complete, resulting in small lumps in the prepared sample. The acetic acid bamboo pulp fiber film formed in Example 2 had a tensile strength of 35.17 MPa and a light transmittance of 76.92% at 550 nm.

[0035] Example 3

[0036] The difference from Example 1 is that:

[0037] The amount of the bleached bamboo pulp board in Example 1 was changed from 6 g to 8 g, while other processes remained unchanged.

[0038] The preparation method of the novel cellulose acetate membrane of this embodiment comprises:

[0039] 8g of bleached bamboo pulp was weighed and beaten at 15,000 rpm, and vacuum dried at 60°C for 8 hours. The dispersed bamboo pulp was added to analytically pure acetic anhydride reagent, with the mass ratio of bleached bamboo pulp to analytically pure acetic anhydride being 4:15, and mixed and stirred for 3 hours. Analytically pure trifluoroacetic acid was added to the acetic anhydride solution, with the addition ratio of bleached bamboo pulp, analytically pure acetic anhydride and analytically pure trifluoroacetic acid being 4:15:42. Subsequently, a certain amount of acetic acid was added and stirred, and the reaction was heated in a water bath for 3 hours. Deionized water was added to precipitate the solid, which was filtered and dried to obtain cellulose acetate. The resulting cellulose acetate was mixed and stirred with activated polyethylene glycol for 1 hour, and sodium benzoate was added and stirred again. The addition ratio of bleached bamboo pulp, polyethylene glycol and sodium benzoate was 40:1:1. The solution was dried at 60°C for 10 hours and dissolved in 60g of analytically pure chloroform reagent to obtain a reinforced cellulose acetate solution. The solution was evenly coated using a mold natural drying method and dried naturally to obtain a cellulose acetate film.

[0040] During the preparation process of Example 3, the reactants were not completely reacted, and the product system was clearly stratified. The cellulose acetate membrane formed in Example 3 had a tensile property of 35.33 MPa and a light transmittance of 84.48% at 550 nm.

[0041] Example 4

[0042] The difference from Example 1 is that:

[0043] The mass ratio of the soaked bamboo pulp fiber in Example 1 to analytically pure acetic anhydride was changed from 1:5 to 1:3, while other processes remained unchanged.

[0044] The preparation method of the novel cellulose acetate membrane of this embodiment comprises:

[0045] Weigh 6g of bleached bamboo pulp, beat it at 15,000 rpm, and vacuum dry it at 60°C for 8 hours. Add the dispersed bleached bamboo pulp to analytical grade acetic anhydride reagent at a solid-to-liquid ratio of 1:3g / mL and mix and stir for 3 hours. Analytically pure trifluoroacetic acid was added to the acetic anhydride solution, and the addition ratio of bleached bamboo pulp board, analytically pure acetic anhydride and analytically pure trifluoroacetic acid was 1:5:14. Subsequently, a certain amount of acetic acid was added and stirred, and the reaction was heated in a water bath for 3 hours. Deionized water was added to precipitate the solid, and the solid was filtered and dried to obtain acetate fiber. The generated acetate fiber was mixed and stirred with activated polyethylene glycol for 1 hour, and sodium benzoate was added and stirred again. The addition ratio of bleached bamboo pulp board, polyethylene glycol and sodium benzoate was 40:1:1. It was dried with forced air at 60°C for 10 hours and dissolved in 60g of analytically pure chloroform reagent to obtain an enhanced acetate fiber solution. It was evenly coated using a mold natural drying method and naturally dried to finally obtain an acetate fiber film.

[0046] The mass ratio of the soaked bleached bamboo pulp board in Example 1 to analytically pure acetic anhydride was changed from 1:5 to 1:3. During the preparation process, a small amount of bamboo pulp fibers after the bleached bamboo pulp board was not completely soaked, resulting in an incomplete final reaction and the production of a small amount of insoluble matter. The tensile properties of the cellulose acetate film prepared in Example 4 were 35.47 MPa, and the transmittance at 550 nm was 74.77%.

[0047] like Figure 1 、 2 As shown in the scanning electron microscope image of the cellulose acetate membrane prepared in Example 1 of the present invention, the surface of the cellulose acetate membrane is flat and smooth, indicating that the bamboo pulp fiber is completely dissolved; the surface of the cellulose acetate membrane is dense and compact, and is regular, indicating that the cellulose acetate forms a denser structure during the precipitation and film-forming process, and has more excellent mechanical properties.

[0048] Table 1 Tensile performance test table of each example

[0049]

[0050] Depend on Figure 3 It can be seen that there is an absorption peak at 280nm. This change is caused by the fact that the bamboo pulp fibers after decomposition contain a small amount of lignin and hemicellulose. Lignin contains functional groups such as aromatic groups, phenolic hydroxyl groups, ketone groups, and carboxyl groups. In addition, due to intramolecular hydrogen bonding and conjugation, the chromophores in the lignin structure can also absorb, giving the lignin excellent UV shielding properties. Compared with cellulose acetate films prepared from pure cellulose, the cellulose acetate films prepared in this invention have a light transmittance of over 74%, and the UV shielding rate can reach up to 58.12%.

[0051] Table 2 Optical performance test table of each example

[0052] Project Name Example 1 Example 2 Example 3 Example 4 Transmittance% at 550nm 81.4 76.92 84.48 74.77 UV shielding rate% 200-400nm 44.98 56.12 43.62 58.12

[0053] The dissolving system adopted by the present invention is applicable to bleached bamboo pulp board. After the bamboo pulp board is debonded, the bamboo pulp fiber can be effectively separated and broomed in the beating process. Since the surrounding pH value is lower than other dissolving systems, the hydrolysis of the bamboo pulp fiber can be curbed. The method for preparing cellulose acetate used by the present invention can efficiently dissolve the bamboo pulp fiber. The trifluoroacetic acid used is an organic acid containing a carboxyl group. It accelerates the dissolution rate during the dissolution process, destroys the hydrogen bonds between the original bamboo pulp fiber chains, thereby forming stronger cross-linked hydrogen bonds. The prepared cellulose acetate film has excellent mechanical properties, and the bleached bamboo pulp board contains a small amount of lignin inside. Lignin contains functional groups such as aromatic groups and phenolic hydroxyl groups and has the function of shielding ultraviolet rays. In order to improve the performance of preparing the film, activated polyethylene glycol and sodium benzoate are added. The two are evenly dispersed with the cellulose acetate mixture, and the mechanical properties of the cellulose acetate film are more excellent after filling.

[0054] Any matters not mentioned above shall be subject to the existing technology.

[0055] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cellulose acetate film, characterized in that: The following steps are involved: S1. Disintegrate, break up, and vacuum dry the bleached bamboo pulp board, then add the dispersed bamboo pulp fiber to analytical grade acetic anhydride reagent, and stir and mix to obtain fully swollen bamboo pulp fiber; S2, adding analytically pure trifluoroacetic acid to the acetic anhydride solution containing bamboo pulp fiber in step S1, subsequently adding a certain amount of acetic acid and stirring, heating in a water bath to react, adding deionized water to precipitate solids, filtering, and drying to obtain acetate fiber; S3. The generated cellulose acetate is mixed with the activated polyethylene glycol, and sodium benzoate is subsequently added. The mixture is stirred again until uniform, air-dried, and dissolved in analytical grade chloroform reagent to obtain an enhanced cellulose acetate solution. The solution is evenly coated using a mold natural drying method and naturally dried to finally obtain a cellulose acetate membrane. The activation temperature of polyethylene glycol is 60°C.

2. The method for preparing a cellulose acetate film according to claim 1, wherein: In step S1, the bleached bamboo pulp board is soaked in water for 6-8 hours and debonded at 10,000-15,000 revolutions; and vacuum dried at 50° C.-70° C. for 6-8 hours.

3. The method for preparing a cellulose acetate film according to claim 1, wherein: In step S1, the mass ratio of the bleached bamboo pulp board to analytically pure acetic anhydride is 1:3-6.

4. The method for preparing a cellulose acetate film according to claim 1, wherein: In the step S1, the swelling is carried out at a temperature of 25-35° C. and the swelling time is 2-3 h.

5. The method for preparing a cellulose acetate film according to claim 1, wherein: In step S2, the reaction is heated in a water bath at a temperature of 45-55° C. for 2.5-3 hours.

6. The method for preparing a cellulose acetate film according to claim 1, wherein: In step S2, the ratio of the added amount of bamboo pulp fiber, analytically pure acetic anhydride and analytically pure trifluoroacetic acid is 1:4-6:14-16.

7. The method for preparing a cellulose acetate film according to claim 1, wherein: In step S3, the addition ratio of the bleached bamboo pulp board, polyethylene glycol, and sodium benzoate is 38-42:1-3:1-3; and the mass ratio of the bleached bamboo pulp board to analytically pure chloroform is 3:20-30.

8. The method for preparing a cellulose acetate film according to claim 1, wherein: The mass fraction of the bamboo pulp fiber in the mixed acid solution system consisting of trifluoroacetic acid, acetic anhydride, acetic acid and bamboo pulp fiber is 6.2-7%.

9. A cellulose acetate film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the cellulose acetate film according to claim 9 in optical imaging, food packaging, medical equipment and ground film.

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