Method for improving hardness of BC bacterial cellulose membrane by using silicon dioxide

Abstract

The invention discloses a method for improving the hardness of a BC bacterial cellulose membrane by using silicon dioxide, and relates to the technical field of bio-based material modification. The preparation method comprises the following steps: S1, preparation of a BC bacterial cellulose membrane; S2, preparation of a silicon dioxide dispersion liquid; and S3, composite treatment. According to the preparation method, the nano silicon dioxide is applied to hardness improvement of the corn straw-based BC bacterial cellulose membrane for the first time, gaps of cellulose fibers can be effectively filled through the high hardness and the nano size of the silicon dioxide, a rigid supporting network is formed, and through the combination of the surfactant and ultrasonic dispersion, the mechanical properties of the membrane are improved. The problem of agglomeration of nano silicon dioxide in a cellulose system is solved, uniform distribution of nano silicon dioxide in the membrane is realized, the hardness improvement effect is ensured, a water-based dispersion liquid and mild treatment conditions are adopted in the whole process, toxic chemical reagents are not used, and the biodegradability and safety of the BC membrane are reserved.

Description

Technical Field

[0001] The present invention relates to the technical field of bio-based material modification, and specifically to a method for improving the hardness of BC bacterial cellulose membranes by using silicon dioxide. Background Art

[0002] In clinical medicine, vacuum blood collection tubes have been widely used in fields such as blood analysis, providing clinical doctors with a basis for clinical diagnosis. They mainly use the pressure difference between the human body's blood pressure and the pressure inside the tube to extract blood samples. This method can also be used to collect dairy samples. Its good vacuum performance and controllable dosage can meet the requirements of domestic dairy collection.

[0003] Bacterial cellulose (BC) is a natural nanomaterial synthesized by microbial fermentation. It has the advantages of high purity, biocompatibility and degradability. Using corn straw as raw material to prepare BC bacterial cellulose membrane can not only realize the resource utilization of agricultural waste, but also reduce production costs.

[0004] However, pure BC bacterial cellulose membranes have a low hardness problem. The main reason is that the interaction between the cellulose fibers inside is weak and there is a lack of a rigid support structure. This makes the material easily deformed when subjected to pressure or friction, limiting its application in scenarios with high mechanical performance requirements.

[0005] Currently, methods for improving the hardness of BC membranes mainly include physical compounding (such as adding inorganic particles) and chemical cross-linking (such as using aldehyde reagents). However, these methods have problems such as poor dispersibility, easy agglomeration, and high toxicity of chemical reagents. Moreover, it is difficult to balance the hardness improvement with the original biocompatibility and degradability of the material.

[0006] The specific defects are as follows:

[0007] 1. Insufficient hardness of BC membrane: BC bacterial cellulose membrane made from corn straw has low hardness. The interaction between the cellulose fibers inside is weak, and it lacks a rigid support structure. As a result, it is easily deformed when subjected to pressure or friction. This makes it unable to meet the application requirements of packaging, construction, electronic devices and other fields that have high requirements for material hardness.

[0008] 2. Reinforcement agent dispersion problem: Although nano-scale reinforcement agents such as silica can theoretically increase the hardness of the material, they tend to agglomerate in the cellulose system and are difficult to disperse evenly, resulting in an inability to fully exert the reinforcement effect. How to achieve uniform dispersion of the reinforcement agent in the BC membrane is one of the key technical bottlenecks in improving the hardness;

[0009] 3. Balance between cost and environmental protection: In the process of improving the hardness of BC membranes, it is necessary to develop low-cost, green and environmentally friendly modification processes. It is necessary to reduce production costs to achieve industrial application, avoid the introduction of toxic and hazardous substances, ensure the biosafety and degradability of the materials, and meet the requirements of sustainable development;

[0010] In response to the above problems, the inventors proposed a method of using silica to increase the hardness of BC bacterial cellulose membrane to solve the above problems. Summary of the Invention

[0011] In order to solve the above problems, the purpose of the present invention is to provide a method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide.

[0012] To solve the above technical problems, the present invention adopts the following technical solution: a method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide, comprising the following steps:

[0013] S1. Preparation of BC bacterial cellulose membrane

[0014] Corn stalks were crushed, treated with alkali to remove lignin and hemicellulose, and then enzymatically hydrolyzed with cellulase to obtain pure cellulose raw material. The raw material was mixed with fermentation medium and inoculated with Acetobacter xylinum. The fermentation was carried out at 28°C and pH 6 for 5 days to obtain BC bacterial cellulose wet film. The wet film was then washed with water and hot-pressed at 80°C to obtain dry film.

[0015] S2. Preparation of silicon dioxide dispersion

[0016] Add nano-silica powder to deionized water to prepare a dispersion with a mass concentration of 1-5%, add 0.5-2% surfactant, and disperse under ultrasonic waves to evenly disperse the silica;

[0017] S3. Composite processing

[0018] The BC bacterial cellulose dry film prepared in S1 was immersed in the silica dispersion of S2 at room temperature, taken out and dried in a vacuum drying oven to constant weight to prepare a silica / BC composite film.

[0019] Preferably, in S1, during the alkali treatment, 5% NaOH solution is used, the treatment is carried out at 60°C for 2 hours, the enzyme dosage of the cellulase is 10 U / g, the pH is 5.5, and the enzymatic hydrolysis is carried out at 50°C for 4 hours.

[0020] Preferably, in S2, the particle size of the nano-silicon dioxide powder is 50-100 nm, the power of the ultrasonic wave is 200-400 W, and the ultrasonic dispersion time is 30-60 h.

[0021] Preferably, in S2, the surfactant is sodium lauryl sulfate.

[0022] Preferably, in S3, the soaking time at room temperature is 1-3 hours, and the drying temperature in the vacuum drying oven is 50-70°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. In this invention, nano-silica is used for the first time to improve the hardness of corn straw-based BC bacterial cellulose membranes. The high hardness and nano-size of silica can effectively fill the gaps between cellulose fibers to form a rigid support network.

[0025] 2. In the present invention, the problem of nano-silica agglomeration in the cellulose system is solved by combining surfactants with ultrasonic dispersion, achieving its uniform distribution in the film and ensuring the hardness improvement effect;

[0026] 3. In the present invention, the entire process adopts water-based dispersion and mild processing conditions, without using toxic chemical reagents, thus retaining the biodegradability and safety of the BC membrane;

[0027] 4. In the present invention, the hardness (Shore hardness) of the silica / BC composite film treated by this method can reach 30-40HA, which is 1-3 times higher than that of pure BC film (10-15HA), meeting the material hardness requirements of packaging, building materials and other fields;

[0028] 5. In the present invention, while improving the hardness, the composite film still maintains good flexibility (elongation at break ≥ 8%) and biocompatibility, and the mechanical strength (tensile strength ≥ 90 MPa) is slightly improved;

[0029] 6. In the present invention, corn straw is used as raw material, combined with low-cost silicon dioxide and environmentally friendly treatment technology, to reduce production costs and meet the needs of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a flow chart of a method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide according to the present invention;

[0032] Figure 2 This is a comparison chart of the hardness of the BC bacterial cellulose membrane of the present invention before and after using silicon dioxide. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0034] Example 1:

[0035] The present invention provides a method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide, comprising the following steps:

[0036] S1. Preparation of BC bacterial cellulose membrane

[0037] Corn stalks were crushed, treated with alkali to remove lignin and hemicellulose, and then treated with 5% NaOH solution at 60°C for 2 hours. Purified cellulose raw material was then obtained by enzymatic hydrolysis with cellulase at a dosage of 10 U / g, pH 5.5, and 50°C for 4 hours. The raw material was mixed with fermentation medium, inoculated with Acetobacter xylinum, and fermented at 28°C and pH 6 for 5 days to obtain BC bacterial cellulose wet film. The wet film was then washed with water and autoclaved at 80°C to obtain dry film.

[0038] S2. Preparation of silicon dioxide dispersion

[0039] 2 g of nano-silica was added to 200 mL of deionized water, 1 g of sodium lauryl sulfate was added, and the mixture was dispersed under 300 W ultrasonic waves for 40 min to prepare a dispersion with a mass concentration of 1%;

[0040] S3. Composite processing

[0041] The BC membrane was immersed in the dispersion at room temperature for 2 hours, taken out and dried in a vacuum drying oven at 60°C to constant weight. After testing, the Shore hardness of the composite membrane was 32HA and the tensile strength was 92MPa.

[0042] Example 2:

[0043] The present invention provides a method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide, comprising the following steps:

[0044] S1. Preparation of BC bacterial cellulose membrane

[0045] Corn stalks were crushed, treated with alkali to remove lignin and hemicellulose, and then treated with 5% NaOH solution at 60°C for 2 hours. Purified cellulose raw material was then obtained by enzymatic hydrolysis with cellulase at a dosage of 10 U / g, pH 5.5, and 50°C for 4 hours. The raw material was mixed with fermentation medium, inoculated with Acetobacter xylinum, and fermented at 28°C and pH 6 for 5 days to obtain BC bacterial cellulose wet film. The wet film was then washed with water and autoclaved at 80°C to obtain dry film.

[0046] S2. Preparation of silicon dioxide dispersion

[0047] Prepare a 3% silica dispersion with 6 g of silica, 200 mL of deionized water, and 1.5 g of surfactant, and disperse under ultrasonic pressure at 400 W for 50 min.

[0048] S3. Composite processing

[0049] The treatment process is the same as that of Example 1. After testing, the Shore hardness of the composite film reaches 38HA and the elongation at break is 9%.

[0050] The hardness of pure BC bacterial cellulose membrane without adding silicon dioxide was tested, and the Shore hardness was 12HA, which proved that the method of the present invention significantly improved the hardness of the membrane.

[0051] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for increasing the hardness of BC bacterial cellulose membrane using silicon dioxide, characterized in that: The following steps are involved: S1. Preparation of BC bacterial cellulose membrane Corn stalks were crushed, treated with alkali to remove lignin and hemicellulose, and then enzymatically hydrolyzed with cellulase to obtain pure cellulose raw material. The raw material was mixed with fermentation medium and inoculated with Acetobacter xylinum. The fermentation was carried out at 28°C and pH 6 for 5 days to obtain BC bacterial cellulose wet film. The wet film was then washed with water and hot-pressed at 80°C to obtain dry film. S2. Preparation of silicon dioxide dispersion Add nano-silica powder to deionized water to prepare a dispersion with a mass concentration of 1-5%, add 0.5-2% surfactant, and disperse under ultrasonic waves to evenly disperse the silica; S3. Composite processing The BC bacterial cellulose dry film prepared in S1 was immersed in the silica dispersion of S2 at room temperature, taken out and dried in a vacuum drying oven to constant weight to prepare a silica / BC composite film.

2. A method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide as claimed in claim 1, characterized in that: In S1, during the alkali treatment, 5% NaOH solution was used at 60°C for 2 hours, and the cellulase enzymatic hydrolysis was performed at a dosage of 10 U / g, pH 5.5, and 50°C for 4 hours.

3. A method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide as claimed in claim 1, characterized in that: In S2, the particle size of the nano-silicon dioxide powder is 50-100 nm, the power of the ultrasonic wave is 200-400 W, and the ultrasonic dispersion time is 30-60 h.

4. A method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide according to claim 1, characterized in that: In S2, the surfactant is sodium lauryl sulfate.

5. A method for improving the hardness of BC bacterial cellulose membrane using silicon dioxide as claimed in claim 1, characterized in that: In S3, the soaking time at room temperature is 1-3 hours, and the drying temperature in the vacuum drying oven is 50-70°C.

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