Bacterial cellulose-based biodegradable material, method for preparing same, and use thereof

Abstract

The application discloses a kind of bacterial cellulose-based biodegradable materials and its preparation method and application.The method is prepared by EC-BC material by soaking in the ethanol solution of ethyl cellulose after making bacterial cellulose film into the shape required.The EC-BC material of the application has excellent mechanical property, stability in liquid environment, recyclability, lower water absorption, stronger heat resistance, biodegradability, cost effectiveness and non-toxicity, can be made into various shapes, and is suitable for catering supplies and food packaging materials and other fields.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biodegradable materials, and relates to a bacterial cellulose-based biodegradable material and a preparation method and application thereof. BACKGROUND

[0002] Plastics are widely used due to their convenience, practicality, hygiene and decoration. However, they pose significant challenges: (1) high consumption rate; (2) they are small in size and light in weight, leading to a short service life (a few minutes to a few hours) and a long degradation time of up to 500 years; (3) discarded plastics are harmful to the environment and ecosystems, and pose a threat to the growth of animals and plants. Studies have shown that plastic products continuously release microplastics, which can pose a threat to human health through ingestion. Plastics are particularly harmful to marine life due to their sharp edges. Traditional waste management methods, such as recycling, landfilling and incineration, have limited effectiveness, and harmful gases are produced during the incineration process.

[0003] Biopolymers as plastic alternatives to petroleum have received great attention. Biopolymers are divided into natural types (such as cellulose, starch, seaweed and chitosan) and synthetic types (including polylactic acid (PLA), polypropylene (PP), polyvinyl chloride (PVC)). Cellulose, as the most abundant biomass in nature, is a basic ingredient for manufacturing biodegradable functional materials, and its abundant supply, cost-effectiveness, light weight, high durability and sustainability make it an excellent alternative to traditional plastics. However, paper, mainly composed of plant cellulose, has the disadvantages of low strength and easy deformation, affecting user experience. These challenges are due to the hydrophilicity of cellulose. Current solutions include coating the surface of paper with waterproof wax, which increases costs and hinders large-scale production. Surface modification by coatings such as polyethylene (PE) or polypropylene (PP), while commonly used to improve water resistance, reduces biodegradability. In summary, there is an urgent need to develop biodegradable functional materials that can maintain strong mechanical properties and water stability to effectively replace plastic products.

[0004] Ethyl cellulose (EC), a linear polysaccharide polymer, is formed by replacing the hydroxyl groups in the cellulose backbone with ethyl ether. EC is odorless, non-toxic, colorless and tasteless, and has excellent biocompatibility, adhesion, film-forming property and thermoplasticity. Unlike hydrophilic cellulose, which absorbs water due to its hydroxyl groups, EC naturally repels water and absorbs oil. In addition, EC is known for its biodegradability, strong mechanical strength, thermal stability, etc. These properties make EC widely used in the cosmetics, food, pharmaceutical and other industries.

[0005] Currently, there are direct filtration and doctor blade coating processes for preparing bacterial cellulose (BC) and EC pure cellulose composite materials (Yijia Deng, Shaofeng Wu, Tianxue Zhu, et al.; Ecological packaging: Creating sustainable solutions with all-natural bio-degradable cellulose materials; Giant; 2024). First, a BC aqueous suspension is vacuum filtered to prepare a BC film, and then a thin layer of EC is coated on the surface of the BC film using a doctor blade coating method. Since EC and BC both have long-chain cellulose structures, the hydrophilic hydroxyl groups of EC can form hydrogen bonds with BC at the interface, enhancing adhesion, and the lipophilic ethyl groups can effectively block water molecules, improving the wettability of the composite material. After demolding, a biodegradable and environmentally friendly EC-BC cellulose food packaging material can be obtained. However, in the above-mentioned direct filtration and doctor blade coating process, the amount of EC attached to some parts of the BC material may be insufficient due to factors such as operation method and solution flowability, forming local weak points. In addition, the doctor blade coating method requires precise control of the thickness and uniformity of the coating, and the direct filtration method has high requirements for filtration equipment and operating conditions, making it difficult to achieve process standardization and large-scale production. SUMMARY

[0006] The purpose of the present application is to provide a bacterial cellulose-based biodegradable material and its preparation method and application. The present application uses bacterial cellulose and ethyl cellulose with relatively uniform diameter and length, and a strong hydrophobic agent to form hydrogen bonds between celluloses, to prepare a bacterial cellulose-based biodegradable material with low porosity, strong mechanical properties, good biodegradability, and good hydrophobic effect.

[0007] The technical solution to achieve the purpose of the present application is as follows:

[0008] The preparation method of the bacterial cellulose-based biodegradable material comprises the following steps:

[0009] (1) Prepare an EC ethanol solution with a mass concentration of 1% to 9%;

[0010] (2) Soak the BC film produced by fermentation in anhydrous ethanol, then dry at 50-60°C for 10-12 hours to remove excess water and ethanol in the film, and then use a mold to shape the BC film into the desired shape, and dry at room temperature to obtain a BC material with a specific shape;

[0011] (3) Soak the BC material with a specific shape in the EC ethanol solution for 2-10 hours, and dry naturally to obtain a bacterial cellulose-based biodegradable material (EC-BC).

[0012] Preferably, in step (1), the mass concentration of the ethanol solution of EC is 5%-7%.

[0013] Preferably, in step (3), the reaction time is 8h.

[0014] The application provides the bacterial cellulose-based biodegradable material prepared by the preparation method.

[0015] The application also provides application of the bacterial cellulose-based biodegradable material in preparation of catering supplies or food packaging materials.

[0016] The catering supplies are common products, such as forks, bowls, straws, cups and the like.

[0017] Compared with the prior art, the application has the following advantages:

[0018] (1) The application uses bacterial cellulose and ethyl cellulose as raw materials, both of which are good biological functional materials, have no biological toxicity, have good biodegradability, and have simple and easy-to-operate preparation process. Ethanol is used as a green solvent, which is non-toxic and non-polluting.

[0019] (2) In the preparation process of the application, EC forms firm interlayer connection with the 3D nanofiber network of BC through hydrogen bonds in the soaking process, adjusts the wettability of BC by depositing EC on the surface of BC, and adjusts the hydrophobicity of the bacterial cellulose-based biodegradable material by adjusting the concentration of the EC solution. Combined with the natural drying method, no synthetic adhesive is added, which is simple and environmentally friendly. Moreover, the EC-BC material formed by hydrogen bond combination will not break and scatter after subsequent repeated compression, and its mechanical properties are still good after soaking in various drinks.

[0020] (3) The application uses a soaking process, which can make EC fully penetrate into the interior and surface of BC, thereby forming a relatively uniform composite material structure, improving the overall performance stability of the material, and performing better and more uniformly in water resistance and barrier property to other substances. Whether the overall or local part of the composite material can effectively block the penetration of water and other liquids, thereby improving the service life and performance of the composite material in a humid or liquid contact environment. In addition, parameters such as soaking time and EC solution concentration are relatively easy to control, which facilitates the control of the attachment amount and penetration depth of EC on the EC-BC material, so that the performance of the EC-BC material can be flexibly customized according to different use requirements, such as adjusting the water resistance and mechanical strength of the material, and the standardization and large-scale production of the process are easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1The preparation flow chart of EC-BC straw material (a) and the physical picture (b) and the physical picture of EC-BC paper cup material (c).

[0022] Figure 2 The infrared spectrum of the EC-BC straw material prepared in Example 1-5.

[0023] Figure 3 The TGA graph of five different types of straws (a), the determination graph of the initial decomposition temperature and the fastest decomposition temperature of EC-BC straw material (b) and the comparison graph of the initial decomposition temperature, the fastest decomposition temperature and the residual mass of five straws and EC powder (c).

[0024] Figure 4 The contact angle and the schematic diagram of BC and EC-BC material with different EC content (a) and the comparison diagram of the size change of water contact angle on the sample over time (b).

[0025] Figure 5 The SEM graph of BC and EC.

[0026] Figure 6 The schematic diagram of straw tensile (a), compression (b) and bending (c) test, the tensile stress-strain curve of BC composite straw after soaking for 8h with the change of EC concentration (d), the bending stress-strain curve of five different types of straws (e), the compression stress-strain curve of five different types of straws (f), the surface morphology and cross-section physical picture of BC and EC (g).

[0027] Figure 7 The wear test graph of EC-BC straw material prepared in Example 3.

[0028] Figure 8 The practical application graph of EC-BC and BC straw in drinks.

[0029] Figure 9 The biodegradation test graph of EC-BC straw material prepared in Example 3, raw material, PP, PLA, paper. DETAILED DESCRIPTION

[0030] The application will be further described below in conjunction with specific embodiments and drawings.

[0031] Example 1

[0032] (1) 0.2367g of EC powder was dissolved in 29.7ml of ethanol solvent, and stirred uniformly with a magnetic stirrer at room temperature environment to prepare an ethanol solution of EC with a mass concentration of 1%;

[0033] (2) The BC film (2.0-2.5 mm thick) was immersed in anhydrous ethanol and placed in an oven at 50°C for 12 hours to remove excess water and ethanol. Subsequently, the film was cut into rectangular pieces of 19 cm x 2 cm. These films were then wound around a glass rod mold (the surface of which was covered with plastic film) to form a ring and rubbed back and forth on a cutting board to further eliminate excess solvent. Finally, the sample was air-dried for 12 hours to obtain a BC straw;

[0034] (3) The BC straw after air-drying was immersed in the EC ethanol solution, reacted for 8 h, and finally naturally dried to obtain a bacterial cellulose-based straw-shaped hydrophobic material.

[0035] Example 2

[0036] This example is substantially the same as Example 1, except that the mass concentration of the EC ethanol solution in step (1) is 3%, specifically: 0.7101 g of EC powder is dissolved in 29.1 ml of ethanol solvent, and stirred with a magnetic stirrer at room temperature until the solution is uniform, to prepare an EC ethanol solution with a mass concentration of 3%.

[0037] Example 3

[0038] This example is substantially the same as Example 1, except that the mass concentration of the EC ethanol solution in step (1) is 5%, specifically: 1.1835 g of EC powder is dissolved in 28.5 ml of ethanol solvent, and stirred with a magnetic stirrer at room temperature until the solution is uniform, to prepare an EC ethanol solution with a mass concentration of 5%.

[0039] Example 4

[0040] This example is substantially the same as Example 1, except that the mass concentration of the EC ethanol solution in step (1) is 7%, specifically: 1.6569 g of EC powder is dissolved in 27.9 ml of ethanol solvent, and stirred with a magnetic stirrer at room temperature until the solution is uniform, to prepare an EC ethanol solution with a mass concentration of 7%.

[0041] Example 5

[0042] This example is substantially the same as Example 1, except that the mass concentration of the EC ethanol solution in step (1) is 9%, specifically: 2.1303 g of EC powder is dissolved in 27.3 ml of ethanol solvent, and stirred with a magnetic stirrer at room temperature until the solution is uniform, to prepare an EC ethanol solution with a mass concentration of 9%.

[0043] Example 6

[0044] This example is substantially the same as Example 1, except for step (2): the bacterial cellulose membrane is cut into appropriate shape and size. According to the designed size of the paper cup, the cut membrane is placed on a specially designed mold, which is shaped as the inner shape of the paper cup. Using the wet hand shaping method, the membrane is shaped to fit the mold and form the shape of the paper cup. Finally, a bacterial cellulose-based paper cup-shaped hydrophobic material is obtained.

[0045] Example 7

[0046] This example is substantially the same as Example 1, except for step (2): the bacterial cellulose membrane is cut into appropriate shape and size. According to the designed size of the paper cup, the cut membrane is placed on a specially designed mold, which is shaped as the inner shape of the paper cup. Using the wet hand shaping method, the membrane is shaped to fit the mold and form the shape of the paper cup. Finally, a bacterial cellulose-based paper cup-shaped hydrophobic material is obtained.

[0047] Figure 2 The infrared spectrum of the bacterial cellulose-based straw-shaped hydrophobic material prepared in Examples 1-5 is shown in the figure. As can be seen from the figure, EC is successfully combined on the surface of BC in the form of hydrogen bonds.

[0048] As shown in Figure 3 (a), the thermal decomposition curves of the five straws show three different stages. The first stage is between about 50°C and 100°C, and the mass loss is nearly 5% due to the evaporation of water caused by temperature change. When the temperature exceeds 300°C, the weight of the sample decreases rapidly with the increase of temperature. In the interval of 350°C to 600°C, the decomposition rate remains stable. After comprehensive calculation, the decomposition onset temperature, decomposition peak temperature and residual mass of each straw are obtained. See Figure 3 (c) for details. Comparison shows that the initial decomposition temperature of EC-BC and BC straws is higher than that of PLA biodegradable straws, indicating that they have excellent thermal stability. In addition, compared with untreated BC straws, EC-treated BC straws show slightly higher initial and peak decomposition temperatures.

[0049] Figure 4The results of (a) show that the water contact angle increases with increasing EC concentration. The water contact angle reaches a maximum of 110 ± 0.8° when the EC concentration is 5 g / 100 ml. The water contact angles of other samples BC, 1EC-BC, 3EC-BC, 7EC-BC and 9EC-BC are 84 ± 1.4°, 92 ± 1.3°, 101 ± 0.7°, 97 ± 0.3° and 95 ± 1.7°, respectively. This observed trend is due to the enhanced deposition of EC on the surface of the cellulose-based straw, which in turn increases their hydrophobicity. The size change of the contact angle of BC and EC-BC straws over time on the sample was then recorded, as shown in Figure 4 (b) shows that the water contact angle of EC-BC has a downward trend due to the presence of cellulose hydroxyl groups, but within half an hour, the surface water contact angle only decreases by 12%. This is because the thin EC layer blocks the contact of BC with water molecules, preventing BC from over-swelling, thus maintaining the low water absorption and high water contact angle of EC-BC.

[0050] Figure 5 The SEM images of BC and EC show that the surface morphology of the BC straw gradually becomes smooth with increasing EC, indicating that EC greatly improves the surface porosity of the bacterial cellulose film.

[0051] Figure 6 The schematic diagram of the material mechanics experiment shows that the bending performance of EC-BC material is the strongest. After being soaked for 30 minutes, the bending strength of BC material decreases to 3.0 mPa, while the strength of EC-BC material remains at 7.5 mPa, highlighting the hydrophobic effect of EC.

[0052] Figure 7 The wear test diagram of the EC-BC straw material prepared in Example 3 shows that wear resistance is crucial for evaluating the stability of hydrophobic coatings. The EC-BC modified material curve initially decreases rapidly and then stabilizes, with the water contact angle remaining at about 98° after 40 cm of friction. This mechanical stability is attributed to strong polymer bonds.

[0053] Figure 8 The practical application diagram of EC-BC and BC straws in drinks shows that the EC-BC straw remains intact without signs of bending or cracking, whether immersed in cold water or hot tea at 90°C for up to two hours. Similarly, when immersed in beverages such as soda, charcoal, and milk for 120 minutes, the hydrophobic EC-BC straw does not soften or bend, in sharp contrast to the BC straw, which softens and bends due to capillary action and its porous composition. Importantly, the hydrophobic EC-BC straw does not exhibit capillary phenomena; under liquid, the surface only leaves a small amount of residue without complete wetting, indicating its practical feasibility.

[0054] Figure 9 For comparison of biodegradability of BC, EC-BC, paper, PLA and PP in soil, photo observation and calculation showed that BC exhibited the highest degradation performance, which was attributed to their full natural origin without synthetic additives. In contrast, the degradation effect of EC was not as good as BC, which might be due to the introduction of ethoxyl groups during the preparation of EC-BC. Compared with hydroxyl groups, ethoxyl groups are not easily degraded by microorganisms, thereby affecting the overall degradation performance. Poly-lactic acid cannot be naturally degraded within 21 days, requiring specific composting conditions, which brings challenges in recycling and potential environmental problems. Commercial paper is usually made by adding various chemicals as stabilizers or coatings, which can cause the degradation rate of paper to decrease and the degradation performance to deteriorate.

Claims

1. Process for the preparation of a bacterial cellulose-based biodegradable material, characterized in that, The method comprises the following steps: (1) preparing an ethyl cellulose ethanol solution with a mass concentration of 1% to 9%; (2) soaking the bacterial cellulose film produced by fermentation in anhydrous ethanol, and then drying at 50 to 60 ℃ for 10 to 12 hours to remove the excess water and ethanol in the film, and then using a mold to make the bacterial cellulose film into a desired shape, and drying at room temperature to obtain a bacterial cellulose material with a specific shape; (3) soaking the bacterial cellulose material with a specific shape in the ethyl cellulose ethanol solution for 2 to 10 hours, and naturally drying to obtain a bacterial cellulose-based biodegradable material.

2. The production method according to claim 1, characterized by, In step (1), the mass concentration of the ethyl cellulose ethanol solution is 5% to 7%.

3. The production method according to claim 1, characterized by, In step (3), the reaction time is 8 hours.

4. The bacterial cellulose-based biodegradable material prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the bacterial cellulose-based biodegradable material according to claim 4 in preparing catering supplies or food packaging materials.

6. Use according to claim 5, characterized in that, The catering supplies are forks, bowls, straws or cups.

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