A micro-nano cellulose reinforced plant oil-based degradable plastic and its preparation and recycling method

Abstract

This invention provides a micro / nanocellulose-reinforced plant oil-based biodegradable plastic and its preparation and recycling methods, relating to the fields of light industry and plastic materials technology. The invention involves a ring-opening reaction between epoxidized plant oil and the crosslinking agent aminophenylboronic acid to obtain phenylboronic acid-grafted epoxidized plant oil (ESO-B, ECO-B); oxidation of micro / nanocellulose with sodium periodate to obtain dialdehyde micro / nanocellulose (DACNF); a Schiff base reaction between the obtained DACNF and the crosslinking agent aminophenylboronic acid in ethanol to obtain phenylboronic acid-grafted micro / nanocellulose (DACNF-B); mixing ESO-B or ECO-B with DACNF-B in an organic solvent; evaporating the resulting mixture to remove the solvent to obtain the micro / nanocellulose-reinforced plant oil-based biodegradable plastic; the crosslinking agent is independently aminophenylboronic acid. The micro / nanocellulose-reinforced plant oil-based biodegradable plastic prepared by this invention has the characteristics of high mechanical strength, good thermal stability, good biocompatibility, recyclability, and biodegradability.

Description

Technical Field

[0001] This invention relates to the fields of light industry and plastic materials, and particularly to a micro / nano cellulose-reinforced plant oil-based biodegradable plastic and its preparation and recycling methods. Background Technology

[0002] Plastics are indispensable in daily life, industry, and agriculture; however, the overuse of non-degradable petroleum-based plastics has led to a growing problem of white pollution. Mechanical and chemical methods for recycling petroleum-based plastics are costly, and the plastics age rapidly. To effectively mitigate plastic pollution, there is an urgent need to develop new types of plastics that possess sufficient mechanical strength, can be effectively recycled and reused, and are easily degraded in the natural environment. To date, a large number of biodegradable plastics have been successfully developed, but most of these face development challenges due to high production costs, inferior mechanical properties compared to petroleum-based plastics, and incomplete degradation in the natural environment. Bio-based materials are considered environmentally friendly and sustainable, and have the potential to replace petroleum-based plastics in the future. Epoxidized soybean oil and epoxidized castor oil are low molecular weight (≈1 kDa) liquid vegetable oils containing multiple highly reactive epoxy groups. Due to their cost-effectiveness, good biocompatibility, and ease of degradation, they are widely used in plasticizers and other fields. Through ring-opening reactions with substances containing amino or hydroxyl groups, epoxidized vegetable oils can be cross-linked to produce vegetable oil-based plastics. However, due to permanent chemical cross-linking, these plant oil-based plastics have poor recyclability and are difficult to degrade in the natural environment. Currently, plant oils are difficult to use in the preparation of plastics with high mechanical strength, excellent recyclability, and biodegradability, making the development of biodegradable plant oil-based plastics a significant technical challenge.

[0003] Cellulose is one of the most abundant biomass resources in nature. Furthermore, micro / nano cellulose networks exhibit significant tensile strength and high Young's modulus due to the strong hydrogen bonds between cellulose molecules. However, the numerous hydrophilic hydroxyl groups and hydrogen bond interactions within cellulose molecules lead to insufficient water resistance and processability, thus limiting the widespread use of cellulose-based materials as plastic alternatives. Therefore, using micro / nano cellulose as a reinforcing matrix for polymers is a worthwhile option to explore. Currently, the main technical challenges of using micro / nano cellulose for polymer reinforcement are insufficient dispersibility, interfacial compatibility, and poor binding force. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a micro / nano cellulose-reinforced plant oil-based biodegradable plastic and its preparation and recycling method. This invention uses micro / nano cellulose and epoxidized plant oil as raw materials to prepare a micro / nano cellulose-reinforced plant oil-based biodegradable plastic. The resulting plant oil-based biodegradable plastic has high mechanical strength, good thermal stability, good biocompatibility, and is recyclable and easily degradable.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing micro / nano cellulose-reinforced plant oil-based biodegradable plastics, comprising the following steps:

[0007] Epoxy vegetable oil and aminophenylboronic acid are subjected to a ring-opening reaction to obtain phenylboronic acid-grafted epoxy vegetable oil;

[0008] The epoxidized vegetable oil is epoxidized soybean oil or epoxidized castor oil.

[0009] Micro- and nano-cellulose was oxidized with sodium periodate to obtain dialdehyde micro- and nano-cellulose. The resulting dialdehyde micro- and nano-cellulose was then processed.

[0010] Rice cellulose and crosslinking agent aminophenylboronic acid were subjected to a Schiff base reaction in ethanol to obtain phenylboronic acid-grafted micro / nano cellulose.

[0011] The phenylboronic acid-grafted epoxidized soybean oil or epoxidized castor oil is crosslinked and mixed with phenylboronic acid-grafted micro / nanocellulose in an organic solvent. The resulting mixed solution is evaporated to remove the solvent, thereby obtaining the micro / nanocellulose-reinforced plant oil-based biodegradable plastic.

[0012] The crosslinking agent is 3-aminophenylboronic acid or p-aminophenylboronic acid.

[0013] Preferably, the molar ratio of the epoxidized vegetable oil to the crosslinking agent is 1:3 to 1:6; the ring-opening reaction is carried out at room temperature for 24 to 48 hours.

[0014] Preferably, the micro / nanocellulose is prepared by grinding bleached coniferous wood fibers with a nanomill, and the sodium periodate oxidation time is 2-4 hours, corresponding to an aldehyde content of 1.7-2.9 mmol / g in the dialdehyde micro / nanocellulose.

[0015] Preferably, the molar ratio of aldehyde group content to aminophenylboronic acid in the dialdehyde micro / nanocellulose is 1:1; the Schiff base reaction is carried out at room temperature for 24 hours, and the reaction solvent is ethanol.

[0016] Preferably, the amount of phenylboronic acid-grafted micro / nanocellulose added is 5% to 20% of the total mass of phenylboronic acid-grafted epoxidized vegetable oil and phenylboronic acid-grafted micro / nanocellulose; the crosslinking reaction is carried out at room temperature for 24 hours; and the crosslinking reaction is carried out in an organic solvent.

[0017] Preferably, the ring-opening reaction and cross-linking reaction are carried out in an organic solvent; the organic solvent is tetrahydrofuran.

[0018] Preferably, the temperature for evaporating and removing the solvent is 40–80°C.

[0019] This invention provides a micro / nano cellulose-reinforced plant oil-based biodegradable plastic prepared by the preparation method described above.

[0020] This invention also provides a method for recycling the micro / nano cellulose-reinforced plant oil-based biodegradable plastics described in the above technical solutions, comprising the following steps:

[0021] The vegetable oil-based biodegradable plastic to be recycled is hot-pressed;

[0022] Alternatively, the micro / nano cellulose-reinforced plant oil-based biodegradable plastic to be recycled can be dissolved in an organic solvent, and the resulting solution can be cast and dried sequentially to obtain the recycled plant oil-based biodegradable plastic.

[0023] Preferably, the hot pressing temperature is 70–90°C, the pressure is 3–5 MPa, and the time is 15–45 min; the organic solvent is ethanol or tetrahydrofuran.

[0024] This invention provides a method for preparing a plant oil-based biodegradable plastic reinforced with micro / nanocellulose, comprising the following steps: reacting epoxidized soybean oil and aminophenylboronic acid in a ring-opening reaction to obtain phenylboronic acid-grafted epoxidized soybean oil (ESO_B); reacting castor oil with hydrogen peroxide to obtain epoxidized castor oil, and then reacting the obtained epoxidized castor oil with aminophenylboronic acid in a ring-opening reaction to obtain phenylboronic acid-grafted epoxidized castor oil (ECO_B); oxidizing micro / nanocellulose with sodium periodate to obtain dialdehyde micro / nanocellulose; and then... Nanocellulose and crosslinking agent aminophenylboronic acid are subjected to a Schiff base reaction in ethanol to obtain phenylboronic acid-grafted micro / nanocellulose (DACNF_B); the phenylboronic acid-grafted epoxidized soybean oil or epoxidized castor oil is crosslinked and mixed with the phenylboronic acid-grafted micro / nanocellulose in an organic solvent, and the resulting mixed solution is evaporated to remove the solvent, to obtain the micro / nanocellulose-reinforced vegetable oil-based biodegradable plastic (DACNF_ESO / DACNF_ECO); the crosslinking agent is 3-aminophenylboronic acid or p-aminophenylboronic acid. This invention uses 3-aminophenylboronic acid or p-aminophenylboronic acid as a crosslinking agent. The active amino groups in the crosslinking agent can crosslink the epoxy groups of the epoxy vegetable oil, resulting in phenylboronic acid-grafted epoxy vegetable oil. The micro / nanocellulose is oxidized with sodium periodate to obtain dialdehyde micro / nanocellulose. The active amino groups in the crosslinking agent can react with the aldehyde groups in the dialdehyde micro / nanocellulose to obtain phenylboronic acid-grafted micro / nanocellulose (DACNF_B). ESO_B / ECO_B and DACNFB are mixed, and during the solvent removal process by heating and evaporation, the phenylboronic acid groups of ESO_B / ECO_B and DACNFB gradually dehydrate and trimerize into a boron-oxygen hexagonal structure. ESO_B / ECO_B and DACNFB are uniformly composited together, generating a three-dimensional network of boron-oxygen hexagonally crosslinked micro / nanocellulose and a crosslinked network of ESO_B / ECO_B and DACNF_B, i.e., a plant oil-based plastic reinforced with micro / nanocellulose having a "reinforced concrete" structure. The beneficial effects of this invention are as follows:

[0025] (1) Thanks to the three-dimensional network of boron-oxygen hexacyclic cross-linked welding of micro-nano cellulose and the high cross-linking density of boron-oxygen hexacyclic cross-linking points, plant oil-based plastics have high mechanical strength and good thermal stability.

[0026] (2) The dynamic reversibility of boron-oxygen hexacyclic rings enables the cross-linking network of plant oil-based plastics to dissociate under certain stimuli. In addition, the raw materials are all green and easily degradable molecules, so this type of plant oil-based plastic can achieve rapid and spontaneous degradation in the soil.

[0027] (3) The present invention prepares biodegradable plastic materials based on physical crosslinking and dynamic chemical crosslinking. Compared with biodegradable materials based on covalent bonds, the internal forces are weak interaction forces, so they have a faster degradation rate and milder degradation conditions. They have rapid and efficient dissociation-recombination performance, and therefore have the characteristics of being recyclable and biodegradable.

[0028] (4) The preparation method provided by the present invention is simple, easy to operate, low in cost, and conducive to large-scale preparation.

[0029] This invention provides a vegetable oil-based biodegradable plastic prepared by the method described above. The vegetable oil-based biodegradable plastic provided by this invention has the characteristics of high mechanical strength, good thermal stability, good biocompatibility, and is recyclable and easily degradable. Example results show that the tensile strength of the vegetable oil-based biodegradable plastic can reach nearly 41 MPa. Even after being immersed in water for 7 days at a high temperature (150℃), the tensile strength of the vegetable oil-based plastic is still higher than 23 MPa. Furthermore, it can be effectively recycled and reprocessed under hot pressing or with the assistance of organic solvents to restore its original mechanical strength and integrity. It can completely degrade in soil, meeting the performance requirements of vegetable oil-based biodegradable plastics in living environments. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the reaction of the DACNF_ESO network in which ESO_B and DACNF_B generate a three-dimensional double cross-linked network in this invention;

[0031] Figure 2 The infrared spectrum of the vegetable oil-based biodegradable plastic prepared in Example 1 is shown.

[0032] Figure 3 This is a statistical diagram showing the morphology and aspect ratio of micro / nanocellulose before and after phenylboronic acid grafting.

[0033] Figure 4 The graph shows the mechanical properties of the vegetable oil-based biodegradable plastics prepared in the example.

[0034] Figure 5 The graph shows the mechanical properties of the vegetable oil-based biodegradable plastic prepared in Example 1 under high temperature conditions.

[0035] Figure 6 These are the mechanical properties of the vegetable oil-based biodegradable plastic prepared in Example 1 after immersion in water for 1 day, 3 days, and 7 days.

[0036] Figure 7 Thermogravimetric analysis (TGA) curves of the biodegradable vegetable oil-based plastic prepared in Example 1;

[0037] Figure 8These are fluorescence images of cells cultured in culture medium for 2 days and 7 days after the vegetable oil-based biodegradable plastic prepared in Example 1 was cultured.

[0038] Figure 9 These are tissue sections of the heart, liver, spleen, lungs, and kidneys from mice in the control group (no plastic implantation) and the experimental group (subcutaneous plastic implantation).

[0039] Figure 10 These are mechanical property graphs of the vegetable oil-based biodegradable plastic prepared in Example 1 before and after hot-pressing welding and before and after recycling. Figure 10 In the diagram, (a) shows the operation of hot-pressing and welding plastic fragments; (b) shows the mechanical properties of the plastic before and after hot-pressing and welding; (c) shows the operation of repeatedly shearing and hot-pressing the plastic for recycling; and (d) shows the plastic properties after the fifth hot-pressing recycling and the fifth melting process.

[0040] Graphs showing the properties of plastics after agent-assisted recycling.

[0041] Figure 11 This is a graph showing the degradation effect of the vegetable oil-based plastic prepared in Example 1 in soil; Detailed Implementation

[0042] This invention provides a method for preparing vegetable oil-based biodegradable plastics, comprising the following steps:

[0043] Epoxy vegetable oil and aminophenylboronic acid are subjected to a ring-opening reaction to obtain phenylboronic acid-grafted epoxy vegetable oil;

[0044] The epoxidized vegetable oil is epoxidized soybean oil or epoxidized castor oil.

[0045] Micro- and nano-cellulose were oxidized with sodium periodate to obtain dialdehyde micro- and nano-cellulose. The obtained dialdehyde micro- and nano-cellulose and the cross-linking agent aminophenylboronic acid were subjected to a Schiff base reaction in ethanol to obtain phenylboronic acid-grafted micro- and nano-cellulose.

[0046] The phenylboronic acid-grafted epoxidized soybean oil or epoxidized castor oil is crosslinked and mixed with phenylboronic acid-grafted micro / nanocellulose in an organic solvent. The resulting mixed solution is evaporated to remove the solvent, thereby obtaining the micro / nanocellulose-reinforced plant oil-based biodegradable plastic.

[0047] The crosslinking agent is 3-aminophenylboronic acid or p-aminophenylboronic acid.

[0048] Unless otherwise specified, all raw materials mentioned in this invention are commercially available products well known to those skilled in the art.

[0049] This invention involves a ring-opening reaction between epoxidized vegetable oil and aminophenylboronic acid to obtain phenylboronic acid-grafted epoxidized vegetable oil. The epoxidized vegetable oil used in this invention has no particular requirements and can be any epoxidized vegetable oil well-known to those skilled in the art. In this invention, the crosslinking agent is 3-aminophenylboronic acid or p-aminophenylboronic acid, having phenyl, amino, and boric acid groups. The molar ratio of the epoxidized vegetable oil to the crosslinking agent is preferably 1:3 to 1:6. In this invention, the ring-opening reaction is preferably carried out in an organic solvent, preferably tetrahydrofuran. The amount of organic solvent used is not particularly important, as long as it allows the ring-opening reaction to proceed smoothly. In this invention, the ring-opening reaction temperature is preferably room temperature, specifically 25°C. The ring-opening reaction time is preferably 24 to 48 hours, more preferably 24 to 36 hours. The ring-opening reaction is preferably carried out under stirring conditions. Specifically, the ring-opening reaction involves the active amino group in the crosslinking agent crosslinking the epoxy groups of the epoxidized vegetable oil to obtain phenylboronic acid-grafted epoxidized vegetable oil.

[0050] In this invention, epoxidized soybean oil is used as the reactant, and 3-aminophenylboronic acid is used as the crosslinking agent. The reaction formula for the ring-opening reaction is shown in Formula 1:

[0051]

[0052] This invention oxidizes micro / nanocellulose to dialdehyde micro / nanocellulose, and then reacts the obtained dialdehyde micro / nanocellulose with aminophenylboronic acid via a Schiff base reaction to obtain phenylboronic acid-grafted micro / nanocellulose. The micro / nanocellulose of this invention is prepared by grinding bleached coniferous wood fibers using a nanomill with a grinding disc gap of -100 μm and a grinding cycle of 20 times. The preferred sodium periodate oxidation time is 2–4 h, and the optimized reaction temperature is 45 °C, corresponding to an aldehyde content of 1.7–2.9 mmol / g in the dialdehyde micro / nanocellulose. A more preferred sodium periodate oxidation time is 2 h, corresponding to an aldehyde content of 1.7 mmol / g in the dialdehyde micro / nanocellulose. This invention does not have specific requirements regarding the source of the micro / nanocellulose; bleached coniferous wood fibers well-known to those skilled in the art can be used. The crosslinking agent of this invention is 3-aminophenylboronic acid or p-aminophenylboronic acid. Preferably, the crosslinking agent is directly added to the dialdehyde micro / nanocellulose for the Schiff base reaction. In this invention, the molar ratio of aldehyde group content to aminophenylboronic acid in the dialdehyde micro / nanocellulose is preferably 1:1 to 1:1.5, more preferably 1:1; the Schiff base reaction temperature is room temperature, specifically 25°C; the reaction time is preferably 12 to 24 hours, more preferably 24 hours; and the reaction solvent is preferably ethanol. Specifically, the grafting reaction involves a Schiff base reaction between the active amino group in the crosslinking agent and the aldehyde group in the dialdehyde micro / nanocellulose to obtain phenylboronic acid-grafted micro / nanocellulose.

[0053] In this invention, taking 3-aminophenylboronic acid as the crosslinking agent as an example, the reaction formula of the grafting reaction is shown in Formula 2:

[0054]

[0055] After obtaining phenylboronic acid-grafted epoxy vegetable oil (ESO_B / ECO_B) and phenylboronic acid-grafted micro / nanocellulose (DACNF_B), this invention mixes the phenylboronic acid-grafted epoxy vegetable oil and phenylboronic acid-grafted micro / nanocellulose in an organic solvent. The resulting mixed solution is heated to evaporate and remove the solvent, yielding the plant oil-based biodegradable plastic (DACNF_ESO / DACNF_ECO). In this invention, the amount of phenylboronic acid-grafted micro / nanocellulose added is 5% to 20% of the total mass of the phenylboronic acid-grafted epoxy vegetable oil and phenylboronic acid-grafted micro / nanocellulose, specifically 5%, 10%, 15%, or 20%. By controlling the amount of phenylboronic acid-grafted micro / nanocellulose added within the range of 5% to 20%, this invention enables the plant oil-based biodegradable plastic to possess high mechanical strength. The crosslinking reaction is carried out at room temperature for 24 hours in an organic solvent. Preferably, the ring-opening reaction and cross-linking reaction are carried out in an organic solvent; the organic solvent is tetrahydrofuran. Specifically, in actual operation, no post-treatment is required after the ring-opening reaction and grafting reaction; the resulting ring-opening reaction solution and cross-linking reaction suspension can be directly mixed. The mixing is preferably stirring. This invention does not have special requirements on the speed and time of stirring, as long as the mixture is uniform. In this invention, the temperature for heating and evaporating to remove the solvent is preferably 40-60°C, more preferably 50°C, and the time for heating and evaporating to remove the solvent is based on the complete removal of the solvent. During the process of heating to remove the solvent, the phenylboronic acid groups of ESO_B / ECO_B and DACNF_B gradually dehydrate and trimerize into a boron-oxygen hexagonal structure. ESO_B / ECO_B and DACNF_B are uniformly composited together to generate a boron-oxygen hexagonal cross-linked welded micro / nano cellulose three-dimensional network and a cross-linked network of ESO_B / ECO_B and DACNF_B, that is, a micro / nano cellulose-reinforced plant oil-based plastic with a "reinforced concrete" structure. Figure 1 A schematic diagram of the reaction for generating a three-dimensional cross-linked DACNF_ESO network for the ESO_B and DACNF_B.

[0056] This invention provides a micro / nano cellulose-reinforced plant oil-based biodegradable plastic prepared by the preparation method described above.

[0057] The micro-nano cellulose-reinforced plant oil-based biodegradable plastic provided by this invention possesses high mechanical strength, good thermal stability, good biocompatibility, and is recyclable and easily degradable. In soil, moisture and microorganisms enter the plastic, causing some boron-oxygen hexacyclic rings in the plant oil-based plastic to dissociate, thereby generating easily degradable low-molecular-weight biomass molecules (ESO / ECO and DACNF). This process of material dissociation into low-molecular-weight molecules continues, thus achieving complete degradation. The micro-nano cellulose-reinforced plant oil-based biodegradable plastic provided by this invention can replace commonly used plastic products, such as films and packaging bags.

[0058] This invention also provides a method for recycling the micro / nano cellulose-reinforced plant oil-based biodegradable plastics described in the above technical solutions, comprising the following steps:

[0059] The micro-nano cellulose-reinforced plant oil-based biodegradable plastic to be recycled is hot-pressed;

[0060] Alternatively, the micro / nanocellulose-reinforced plant oil-based biodegradable plastic to be recycled can be dissolved in an organic solvent, and the resulting solution can be cast and dried sequentially to obtain the recycled micro / nanocellulose-reinforced plant oil-based biodegradable plastic.

[0061] In this invention, the preferred hot-pressing temperature is 70–90°C, the preferred pressure is 3–5 MPa, and the preferred time is 15–45 min. The specific operation of the hot-pressing is as follows: the micro-nano cellulose-reinforced plant oil-based biodegradable plastic fragments to be recycled are overlapped or stacked together, and then hot-pressed. In this invention, the preferred organic solvent is ethanol or tetrahydrofuran, more preferably tetrahydrofuran. This invention does not have special requirements for the amount of organic solvent used; it is sufficient to completely dissolve the micro-nano cellulose-reinforced plant oil-based biodegradable plastic to be recycled. The dissolution can be carried out at room temperature. This invention does not have special requirements for the specific casting operation; casting methods well known to those skilled in the art can be used. In this invention, the micro-nano cellulose-reinforced plant oil-based biodegradable plastic can be recycled and reprocessed through hot pressing or with the assistance of an organic solvent, restoring its original mechanical strength and integrity, and reshaping it into large-area, defect-free plastic materials.

[0062] The following detailed description, in conjunction with embodiments, illustrates the micro / nano cellulose-reinforced plant oil-based biodegradable plastics provided by the present invention, as well as their preparation and recycling methods. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0063] Example 1

[0064] A micro / nano cellulose-reinforced plant oil-based biodegradable plastic is prepared as follows:

[0065] At room temperature, epoxidized soybean oil (ESO) and 3-aminophenylboronic acid were stirred in tetrahydrofuran (THF) to carry out a ring-opening reaction. The molar ratio of epoxidized soybean oil (ESO) to 3-aminophenylboronic acid was 1:3, and the ring-opening reaction time was 24 h. The product was a reaction solution of phenylboronic acid grafted epoxidized soybean oil (ESO_B).

[0066] Micro-nanocellulose (CNF) was oxidized with sodium periodate for 2 h at a reaction temperature of 45 °C to obtain dialdehyde micro-nanocellulose (DACNF) with an aldehyde content of 1.7 mmol / g. The dialdehyde micro-nanocellulose was then reacted with 3-aminophenylboronic acid in ethanol at room temperature for 24 h at a molar ratio of aldehyde to amino groups of 1:1. The amino groups reacted with the aldehyde groups in the dialdehyde micro-nanocellulose in a Schiff base reaction to obtain phenylboronic acid-grafted micro-nanocellulose (DACNF_B).

[0067] The reaction solution of ESO_B and the suspension of DACNF_B were mixed at 20% of the total mass of DACNF_B and ESO_B, and stirred to obtain a uniform suspension. Most of the THF solvent was evaporated at room temperature, and then heated to 50°C to further remove residual THF. During this process, the phenylboronic acid groups of ESO_B and DACNF_B gradually dehydrated and trimerized into a boron-oxygen hexacyclic structure, generating a three-dimensional cross-linked DACNF_ESO network, namely the micro / nanocellulose-reinforced plant oil-based biodegradable plastic (DACNF_ESO, denoted as DACNF0.2_ESO0.8).

[0068] The morphology of the micro / nano cellulose and the performance of the micro / nano cellulose-reinforced plant oil-based biodegradable plastic film prepared in Example 1 were tested, as follows:

[0069] (1) Morphological scale detection:

[0070] The morphology of micro / nanocellulose before and after phenylboronic acid grafting was observed by atomic force microscopy, and the aspect ratio of the micro / nanocellulose was statistically analyzed. The results are as follows: Figure 2 As shown, after grafting with phenylboronic acid, micro- and nano-cellulose exhibited slight flocculation and a reduced aspect ratio, but still maintained good dispersion and fibrillation.

[0071] (2) Infrared detection:

[0072] Infrared detection was performed on the biodegradable DACNF0.2_ESO0.8 plastic film with a thickness of approximately 200 μm obtained in Example 1, and the results are as follows: Figure 3 As shown, a new peak of 705 cm⁻¹ appeared in the FTIR spectrum of DACNF0.2_ESO0.8 plastic, indicating that a boron-oxygen hexacyclic structure was formed in DACNF0.2_ESO0.8 plastic.

[0073] (3) Mechanical property testing:

[0074] The mechanical properties of the biodegradable DACNF_ESO plastic with a thickness of approximately 200 μm obtained in Example 1 were tested, and the results are as follows: Figure 4 As shown, the tensile strength of DACNF0.2_ESO0.8 plastic reached approximately 41 MPa.

[0075] (4) Mechanical property testing in high-temperature environments and after water absorption saturation:

[0076] The DACNF0.2_ESO0.8 plastic was subjected to tensile testing at 150℃; its mechanical properties were then tested after immersing it in water for 7 days. The results are as follows. Figure 5 and Figure 6 As shown, DACNF0.2_ESO0.8 plastic exhibits higher tensile strength (37MPa and 23MPa) under high temperature conditions and when saturated with water, which is higher than the tensile strength of HDPE used in daily life.

[0077] (5) Thermal stability test:

[0078] Thermogravimetric analysis was performed on the biodegradable vegetable oil-based plastic obtained in Example 1, and the results are as follows: Figure 7 Thermogravimetric analysis (TGA) curves are shown. (From...) Figure 7 It can be seen that the decomposition temperature of DACNF0.2_ESO0.8 plastic reaches ~184.2℃ when the weight loss is 5%, which confirms the excellent thermal stability of DACNF0.2_ESO0.8 plastic.

[0079] (6) Biocompatibility testing:

[0080] The 200 μm thick DACNF0.2_ESO0.8 plastic film prepared in Example 1 was cut into small pieces and immersed in a certain volume of DMEM culture medium. This culture medium was then used to culture normal human hepatocytes (HepG2 cells) for 2 days and 7 days, and cell viability was observed and statistically analyzed to reflect the cytotoxicity of the vegetable oil-based biodegradable plastic. Simultaneously, to further verify the in vivo toxicity of the vegetable oil-based biodegradable plastic, the plastic was implanted in situ into the subcutaneous tissue of mice for two weeks. The effects of plastic implantation on the physiological condition of the mice were then studied by analyzing organ tissue sections (heart, liver, spleen, lung, and kidney) from the experimental group mice. A control group without plastic implantation was also included.

[0081] Figure 8 These are fluorescence images of cells cultured in culture medium for 2 days and 7 days after the vegetable oil-based plastic prepared in Example 1 was cultured. Figure 8It can be seen that the cells cultured in the control group and experimental group for 2 days and 7 days both had high cell activity, and no dead cells were observed, proving that the plant oil-based plastic has no cytotoxicity.

[0082] Figure 9 These are tissue sections (scale bar 100 μm) of the heart, liver, spleen, lung, and kidney from mice in the control group (no plastic implantation) and the experimental group (subcutaneous plastic implantation). It can be seen that the morphology of the tissue sections from the experimental group mice is basically the same as that of the control group, and no obvious inflammatory reactions or other problems were observed. Therefore, this proves that the plastic has high biocompatibility and is non-toxic.

[0083] (7) Recyclability test:

[0084] The DACNF0.2_ESO0.8 plastic film with a thickness of 200μm prepared in Example 1 was further cut into fragments. The fragments were then overlapped and hot-pressed at 85°C and 5MPa for 30 minutes. Alternatively, the fragments were dissolved in THF at room temperature, then cast and dried (i.e., solvent-assisted recovery) to reshape them into large-area, defect-free plastic sheets to obtain the recycled product.

[0085] Figure 10 The graph shows the properties of the DACNF0.2_ESO0.8 plastic prepared in Example 1 before and after reprocessing and recycling. Figure 10 In the diagram, (a) shows the operation of hot-pressing and welding the plastic, (b) shows the mechanical properties of the plastic before and after hot-pressing and welding, (c) shows the operation of repeatedly shearing and hot-pressing the plastic for recycling, and (d) shows the plastic properties after the fifth hot-pressing recycling and the plastic properties after the fifth solvent-assisted recycling. Testing showed that the performance of the recycled product was comparable to the mechanical properties of the raw material before recycling (the vegetable oil-based biodegradable plastic obtained in Example 1). Compared with biodegradable materials based on covalent bonds, the vegetable oil-based biodegradable plastic material prepared by this invention, based on physical crosslinking and dynamic chemical crosslinking, exhibits faster degradation speed and milder degradation conditions due to the weak internal interaction forces, and possesses rapid and efficient dissociation-recombination performance, thus demonstrating recyclability.

[0086] (8) Degradation performance testing:

[0087] The degradation performance of the plant oil-based biodegradable plastic reinforced with micro / nano cellulose prepared in Example 1 was tested, and the results were as follows:

[0088] Cut 200μm thick DACNF0.2_ESO0.8 plastic into small pieces, about 5cm×5cm, weigh them, and then bury them in the soil to place them in the natural environment. Figure 11The image shows the degradation effect of the plant oil-based plastic in soil in Example 1. After 20 days in the soil, the DACNF0.2_ESO0.8 plastic film changed from smooth and flat to uneven. After 40 days in the soil, the DACNF0.2_ESO0.8 plastic film began to break, and holes appeared in some areas. As the degradation time increased to 60 days, the film had broken into fragments with a size of less than 1 cm. After 80 days, no fragments were observed in the soil, proving that the film had completely degraded.

[0089] Examples 2-3 and Comparative Examples 1-4

[0090] The preparation steps of Examples 2-3 and Comparative Examples 1-4 are the same as those of Example 1, except that the content of DACNF_B and the ratio of epoxidized soybean oil to 3-aminophenylboronic acid are different.

[0091] The molar ratio of epoxidized soybean oil to crosslinking agent, the content of DACNF_B, and the mechanical strength of the resulting vegetable oil-based biodegradable plastics in each embodiment and comparative example are as follows: Figure 4 As shown in Table 1:

[0092] Table 1 shows the molar ratio of epoxy vegetable oil and crosslinking agent, the content of DACNF_B, and the mechanical strength of the resulting plastics in the examples and comparative examples.

[0093] Table 1 shows the mechanical strength of the plastics obtained in the examples and comparative examples.

[0094]

[0095] In Table 1, the tensile strength and tensile strain of ESO_B plastics are ~12 MPa and ~55%, respectively. With increasing DACNF_B content, the fracture strength of DACNF_ESO plastics increases significantly, while its elongation at break decreases slightly. Among DACNF_ESO plastics, DACNF0.2_ESO0.8 plastic exhibits the highest tensile strength, approximately 41 MPa. With increasing DACNF_B content, both fiber crosslinking and dynamic chemical crosslinking of the DACNF_ESO network increase significantly, thus increasing the strength of DACNF_ESO while correspondingly decreasing its elongation at break.

[0096] As can be seen from the above embodiments, the present invention uses epoxidized vegetable oil and micro / nano cellulose as raw materials to prepare vegetable oil-based biodegradable plastics. The obtained vegetable oil-based biodegradable plastics have the characteristics of high mechanical strength, good thermal stability, good biocompatibility, and are recyclable and biodegradable.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a micro / nano cellulose-reinforced plant oil-based biodegradable plastic, comprising the following steps: Epoxy vegetable oil and aminophenylboronic acid are subjected to a ring-opening reaction to obtain phenylboronic acid-grafted epoxy vegetable oil; The epoxidized vegetable oil is epoxidized soybean oil or epoxidized castor oil; Micro- and nano-cellulose were oxidized with sodium periodate to obtain dialdehyde micro- and nano-cellulose. The obtained dialdehyde micro- and nano-cellulose and the cross-linking agent aminophenylboronic acid were subjected to a Schiff base reaction in ethanol to obtain phenylboronic acid-grafted micro- and nano-cellulose. The phenylboronic acid-grafted epoxidized soybean oil or epoxidized castor oil is crosslinked and mixed with phenylboronic acid-grafted micro / nanocellulose in an organic solvent. The resulting mixed solution is evaporated to remove the solvent, thereby obtaining the micro / nanocellulose-reinforced plant oil-based biodegradable plastic. The crosslinking agent is 3-aminophenylboronic acid or p-aminophenylboronic acid; The molar ratio of the epoxidized vegetable oil to aminophenylboronic acid is 1:3 to 1:6; the ring-opening reaction is carried out at room temperature for 24 to 48 hours. The aldehyde content of the dialdehyde micro / nanocellulose is in a molar ratio of 1:1 to aminophenylboronic acid; the Schiff base reaction is carried out at room temperature for 24 hours, and the reaction solvent is ethanol. The amount of phenylboronic acid-grafted micro / nanocellulose added is 5% to 20% of the total mass of phenylboronic acid-grafted epoxidized vegetable oil and phenylboronic acid-grafted micro / nanocellulose; the cross-linking reaction is carried out at room temperature for 24 hours; the cross-linking reaction is carried out in an organic solvent.

2. The production method according to claim 1, characterized by, The micro / nanocellulose is prepared by grinding bleached coniferous wood fibers with a nanomill; the sodium periodate oxidation time is 2-4 hours, corresponding to an aldehyde content of 1.7-2.9 mmol / g in the dialdehyde micro / nanocellulose.

3. The method of claim 1, wherein, The ring-opening reaction and cross-linking reaction are carried out in an organic solvent; the organic solvent is tetrahydrofuran.

4. The method of claim 1, wherein, The temperature for evaporation and solvent removal is 40–80℃.

5. The preparation method according to any one of claims 1 to 4 yields a micro / nano cellulose-reinforced plant oil-based biodegradable plastic.

6. The process for recycling the micro- or nano-cellulose reinforced biodegradable plastics based on vegetable oils according to claim 5, characterized in that, Includes the following steps: The micro-nano cellulose-reinforced plant oil-based biodegradable plastic to be recycled is hot-pressed; Alternatively, the micro / nano cellulose-reinforced plant oil-based biodegradable plastic to be recycled can be dissolved in an organic solvent, and the resulting solution can be cast and dried sequentially to obtain the recycled plant oil-based biodegradable plastic.

7. The recycling method according to claim 6, characterized in that, The hot pressing temperature is 70–90°C, the pressure is 3–5 MPa, and the time is 15–45 min; the organic solvent is ethanol or tetrahydrofuran.

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