Method for producing cellulose membrane

Abstract

The invention relates to the technical field of cellulose membrane preparation, and particularly provides a production method of a cellulose membrane. The production method of the cellulose membrane comprises the following steps: sequentially carrying out multi-mode coupling pretreatment, supercritical grading dissociation, multi-dimensional mechanical stripping, bionic interface reconstruction, membrane forming and topological structure locking on corn straws to prepare the cellulose membrane. According to the production method of the cellulose membrane, all-component conversion of corn straw resources and high-value recovery of byproducts can be achieved, the prepared cellulose membrane has the advantages of being high in strength, easy to degrade and low in cost, and green and high-value utilization of agricultural waste is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of cellulose film preparation, in particular to a method for producing a cellulose film. Background Art

[0002] The current global plastic pollution problem is becoming increasingly serious. Traditional petroleum-based plastic films are non-degradable, leading to the continuous accumulation of microplastics in the ecological chain. In particular, the residues of agricultural mulch seriously damage soil health. Although existing biodegradable film materials such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA) can alleviate pollution, their raw materials rely on food crops such as corn and sugarcane, which has the ethical controversy of "competing with food for land". In addition, the production cost is high (about 2-3 times that of traditional plastics), making it difficult to promote on a large scale. At the same time, my country, as a major agricultural country, produces about 300 million tons of corn straw every year, and its utilization is still mainly incineration and landfill. This not only releases pollutants such as PM2.5, but also wastes 35-45% of the natural cellulose resources in the straw. For this reason, a method for producing cellulose film based on agricultural waste corn straw as raw material is proposed. Summary of the Invention

[0003] In view of this, the present invention aims to propose a method for producing a cellulose membrane, so as to produce a high-strength, degradable, low-cost cellulose membrane, realize the full component conversion of corn straw resources and the high-value recovery of by-products.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A method for producing a cellulose membrane, comprising sequentially subjecting corn stalks to multimodal coupling pretreatment, supercritical fractional dissociation, multidimensional mechanical exfoliation, biomimetic interface reconstruction, membrane formation, and topological structure locking to produce the cellulose membrane;

[0006] The multimodal coupling pretreatment includes crushing the corn stalks and decomposing the crushed corn stalks into initial materials under the action of microwaves and low-temperature plasma;

[0007] The supercritical fractional dissociation includes catalytically treating the initial material into a secondary treated material in a predetermined supercritical environment;

[0008] The multi-dimensional mechanical stripping includes shearing the secondary processed material and stripping the cellulose dispersion from the secondary processed material;

[0009] The biomimetic interface reconstruction includes treating the cellulose dispersion with a precursor to form a composite dispersion containing a three-dimensional network;

[0010] The film forming comprises forming the composite dispersion into a primary film;

[0011] The topological structure locking includes performing a surface topological reconstruction process on the primary mold in a preset atomization atmosphere.

[0012] Furthermore, the crushing of the corn stalks and decomposition of the crushed corn stalks into initial materials under the action of microwaves and low-temperature plasma includes:

[0013] Crush the corn stalks to 50-300 mesh;

[0014] Under the action of microwave and low-temperature plasma, an atomized treatment liquid is added, and the mixture is treated at a temperature of 40 to 70° C. for 0.5 to 2 hours to obtain the initial material.

[0015] Furthermore, the components of the atomized treatment liquid include ionic liquid, nanobubble oxygen and complex enzyme.

[0016] Furthermore, the catalytic treatment of the initial material into a secondary treated material in a preset supercritical environment comprises:

[0017] placing the initial material in a supercritical carbon dioxide environment;

[0018] An ethanol solution containing a transition metal catalyst is added to the initial material to obtain a secondary treated material.

[0019] Furthermore, the shearing of the secondary processed material and stripping of the cellulose dispersion from the secondary processed material comprises:

[0020] subjecting the secondary processed material to high-speed centrifugal shearing;

[0021] Applying a high-voltage pulse electric field for a preset time to the secondary processed material after shearing;

[0022] The secondary treated material after the high voltage pulse electric field treatment is subjected to liquid nitrogen quenching treatment to obtain the cellulose dispersion.

[0023] Furthermore, the cellulose dispersion and the precursor are treated to form a composite dispersion containing a three-dimensional network, comprising:

[0024] The cellulose dispersion liquid is mixed with a precursor, and a composite dispersion liquid containing a three-dimensional network is formed under the synergistic action of ultrasound and a magnetic field.

[0025] Furthermore, the precursor is a silanized chitosan-calcium phosphate nanocluster complex;

[0026] The frequency of the ultrasonic wave is 50 to 100 kHz;

[0027] The intensity of the magnetic field is 0.3-1.2T.

[0028] Furthermore, in the silanized chitosan-calcium phosphate nanocluster composite, the mass ratio of silanized chitosan to calcium phosphate is 1:0.5-2.

[0029] Furthermore, the step of preparing the composite dispersion into a primary film comprises:

[0030] The composite dispersion is subjected to aerosol-assisted electrospinning technology to prepare a primary membrane.

[0031] Furthermore, the surface topology reconstruction process of the primary mold is performed in a preset atomized atmosphere, including:

[0032] immersing the nascent membrane in an atomized atmosphere containing a dynamic covalent bond exchanger;

[0033] The surface topology is reconstructed under ultraviolet light to prepare the cellulose membrane.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The present invention is through multimodal coupling pretreatment, supercritical fractional dissociation, multidimensional mechanical stripping technology, can realize the efficient clean separation of cellulose, hemicellulose and lignin in corn straw, wherein supercritical fractional dissociation can recycle high-purity lignin nanoparticles, the above steps are combined with bionic interface reconstruction process, construct spiral enhanced three-dimensional network structure, can improve membrane material mechanical properties and light transmittance, and at the same time, through the extension of film forming agent flutter structure locking to give fiber membrane material self-repair and hydrophobic-hydrophilic controllable function. The whole method design makes by-products such as ionic liquid and lignin highly value-added recovery, reduces the consumption of chemical reagents and water consumption, straw resources realize full component conversion, the obtained cellulose film is easily degraded in the natural environment, the comprehensive cost is low, and the full component conversion of corn straw resources and the high value recovery of by-products are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 This is a schematic flow chart of a method for producing a cellulose film according to an embodiment of the present invention;

[0038] Figure 2 Schematic diagram of a single helical unit structure for biomimetic interface reconstruction according to an embodiment of the present invention;

[0039] Figure 3 A dynamic schematic diagram of the helix formation mechanism based on bionic interface reconstruction according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the network topology in the three-dimensional network structure reconstructed by the bionic interface according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0042] If no specific conditions are specified in the present invention, the process may be carried out in accordance with conventional conditions or the conditions recommended by the manufacturer of the equipment used. If the manufacturer of the reagents or instruments used is not specified, conventional products purchased from the market may be used. If no specific conditions are specified for the technical means or process methods involved, the process may be carried out in accordance with existing methods and procedures in the relevant field.

[0043] This embodiment relates to a method for producing a cellulose film, which can produce a high-strength, degradable, and multifunctional cellulose film, providing an integrated solution for agricultural waste resource utilization and plastic pollution control.

[0044] In terms of overall design, the production method of this embodiment includes subjecting corn straw to multimodal coupling pretreatment, supercritical graded dissociation, multidimensional mechanical exfoliation, bionic interface reconstruction, film formation, and topological structure locking in sequence to obtain a cellulose film.

[0045] It is worth noting that the multimodal coupling pretreatment step mentioned above, as a preferred embodiment, may include, for example, crushing corn stalks and decomposing the crushed corn stalks into initial materials under the action of microwaves and low-temperature plasma.

[0046] Among them, the corn stalks are crushed, as a preferred embodiment, for example, the corn stalks can be crushed into 50-300 meshes; under the action of microwaves and low-temperature plasma, the crushed corn stalks are decomposed into initial materials, as a preferred embodiment, for example, under the action of microwaves and low-temperature plasma, an atomized treatment liquid is added, and the treatment is carried out at a temperature of 40-70°C for 0.5-2h to obtain the initial materials.

[0047] The above-mentioned microwave power can preferably be, for example, 500 to 1200 W. The corresponding entire microwave process, as a preferred implementation form, can be, for example, increased to the target value at a rate of 100 W / s in the initial stage and switched to pulse mode (duty cycle 30-70%) 1 minute before the end of the treatment.

[0048] The power density of the low temperature plasma can preferably be, for example, 10-50 W / cm 3 The plasma may preferably be an argon / oxygen mixed gas (volume ratio 4:1) with an excitation frequency of 13.56 MHz to generate a modified atmosphere containing active oxygen species.

[0049] The components of the atomized treatment liquid may preferably include, for example, ionic liquid, nanobubble oxygen and complex enzyme. Specifically, the atomized treatment liquid may preferably be composed of, for example, 1-ethyl-3-methylimidazole acetate (20-40 wt%), laccase / xylanase / cellulase (activity ratio 1:2:3, total enzyme activity ≥ 2000 U / g) and nanobubble oxygen (diameter 50-200 nm, concentration 10 8 -1010 / mL).

[0050] Among them, the imidazolium cation provided by 1-ethyl-3-methylimidazolium acetate binds to the benzene ring of lignin through π-π stacking, destroying its hydrophobic interaction. Laccase can oxidize the phenolic hydroxyl groups of lignin to form a quinone structure. Xylanase can hydrolyze the β-1,4 glycosidic bonds of hemicellulose to produce xylobiose. Cellulase is composed of endoglucanase (EG), exoglucanase (CBH) and β-glucosidase (BG); EG randomly cuts the cellulose chain, CBH releases cellobiose from the chain end, and BG hydrolyzes it to glucose. Nano oxygen bubble solution: oxygen bubble diameter 150±30nm, concentration 5×10 9 / mL (Nanoparticle Tracking Analysis, NTA); when collapsed in the microwave field, microjets with an instantaneous pressure of >10 MPa were generated, physically tearing the fiber surface (SEM showed pits with a diameter of 20-50 nm).

[0051] From the above introduction, it can be seen that the multimodal coupling pretreatment of this embodiment adopts a microwave-plasma-enzyme synergistic system to treat corn straw. Corn straw is a typical agricultural waste, and its chemical composition is mainly cellulose (38-45%), hemicellulose (25-30%), and lignin (15-20%). The three are cross-linked through complex physical and chemical bonds (such as lignin-carbohydrate complex LCC) to form a dense structure. The microwave-plasma-enzyme synergistic system used in this embodiment can selectively dissociate lignin and hemicellulose while retaining the integrity of the cellulose skeleton, providing an ideal raw material for subsequent nano-processing.

[0052] The above-mentioned supercritical fractional dissociation step, as a preferred embodiment, may include, for example, catalytically treating the initial material into a secondary treated material in a preset supercritical environment.

[0053] In a preset supercritical environment, the initial material is catalytically treated to produce a secondary treated material. As a preferred embodiment, for example, the initial material may be placed in a supercritical carbon dioxide environment, and an ethanol solution containing a transition metal catalyst is added to the initial material to produce the secondary treated material.

[0054] The preferred supercritical carbon dioxide environmental conditions may be, for example, an environmental pressure of 15-30 MPa, a temperature of 60-100° C., dynamic pressure shock treatment, a pressure fluctuation amplitude of ±5 MPa / s, and 5-20 cycles.

[0055] The transition metal catalyst may preferably be, for example, iron acetylacetonate, and its addition amount may preferably be, for example, 0.01-0.1 wt % based on the mass of the ethanol solution when the pressure is greater than 25 MPa.

[0056] Ferric acetylacetonate, as a pretreatment agent, helps disrupt the crystalline structure of cellulose and the lignin-cellulose bond. It can penetrate into the interior of the cellulose, interacting with both cellulose and lignin, partially dissolving or modifying the lignin. This reduces the lignin's ability to wrap and protect the cellulose, increases the accessibility of the cellulose, and creates favorable conditions for subsequent enzymatic hydrolysis or other decomposition processes.

[0057] From the above introduction to the supercritical fractional dissociation step, it can be seen that this step uses a transition metal catalyst to achieve the dissolution and separation of lignin. At the same time, the use of a supercritical carbon dioxide environment can enable the dissolved lignin derivatives to be separated in real time through reduced pressure flash evaporation, recover lignin nanoparticles, and improve cellulose purity.

[0058] The multi-dimensional mechanical stripping step, as a preferred embodiment, may include, for example, shearing the secondary processed material and stripping the cellulose dispersion from the secondary processed material.

[0059] Specifically, the above-mentioned shearing of the secondary treated material and stripping of the cellulose dispersion from the secondary treated material can be, as a preferred embodiment, for example, the secondary treated material can be subjected to high-speed centrifugal shearing; a high-voltage pulse electric field for a preset time is applied to the sheared secondary treated material; and the secondary treated material after the high-voltage pulse electric field treatment is subjected to liquid nitrogen quenching treatment to obtain the cellulose dispersion.

[0060] The conditions for high-speed centrifugal shearing are preferably a rotation speed of 10,000-30,000 rpm and a shear force of ≥1000 N / m. 2 The conditions of the high-voltage pulse electric field are preferably, for example, a field strength of 10-50 kV / cm and a pulse width of 1-100 μs; the liquid nitrogen quenching is preferably completed within 100 ms after the high-voltage pulse electric field is applied, with a quenching rate of 300-500 ° C / s. After quenching, the material is immediately transferred to a vacuum drying oven (pressure ≤ 1 kPa) to remove residual moisture.

[0061] Based on the above introduction, this embodiment realizes cellulose nano-crystallization by using a combination of extreme physical fields through multi-dimensional mechanical exfoliation.

[0062] As a preferred embodiment of the biomimetic interface reconstruction step, for example, the cellulose dispersion and the precursor may be treated to form a composite dispersion containing a three-dimensional network.

[0063] Specifically, the cellulose dispersion is treated with a precursor to form a composite dispersion containing a three-dimensional network. As a preferred embodiment, for example, the cellulose dispersion is mixed with a precursor and a composite dispersion containing a three-dimensional network is formed under the synergistic action of ultrasound and a magnetic field.

[0064] Among them, the above-mentioned precursor can preferably be, for example, a silanized chitosan-calcium phosphate nanocluster complex; the frequency of the ultrasound can be, for example, 50 to 100 kHz; the intensity of the magnetic field can preferably be, for example, 0.3 to 1.2 T; under the synergistic action of the ultrasound and the magnetic field, a composite dispersion containing a three-dimensional network is formed. As a preferred embodiment, for example, the direction of the applied magnetic field can be at an angle of 45-90° to the direction of ultrasound propagation, and when the magnetic field intensity is 0.5-1.0 T, a composite dispersion containing a helical cellulose-mineralized composite structure (pitch 100-500 nm) is induced to form.

[0065] It is worth noting that the silanized chitosan-calcium phosphate nanocluster composite may preferably have a mass ratio of silanized chitosan to calcium phosphate of 1:0.5-2.

[0066] The preparation of silanized chitosan-calcium phosphate nanocluster complexes, as an exemplary embodiment, can be, for example, chitosan modified with 2,3-epoxypropyltrimethylammonium chloride and then dynamically co-assembled with calcium phosphate nanoclusters in a microfluidic chip (channel width 50-200 μm, flow rate ratio 1:3) to obtain silanized chitosan-calcium phosphate nanocluster complexes.

[0067] As a preferred embodiment, the above-mentioned film-forming step may be, for example, subjecting the composite dispersion to aerosol-assisted electrospinning technology to prepare a primary film.

[0068] Among them, aerosol-assisted electrospinning technology, as a preferred implementation form, can be, for example, controlling the ambient humidity to decrease gradually from 95% to 30%, and the temperature to increase stepwise from 25°C to 120°C during the film formation process, the electrospinning voltage is 15-30kV, and at the same time, an alternating airflow (flow rate 0.5-5m / s, frequency 1-10Hz) is applied to induce directional arrangement of the fibers. The alternating airflow is generated by a piezoelectric ceramic array and dynamically matches the rheological properties of the electrospinning liquid.

[0069] The above-mentioned topology locking step, as a preferred implementation form, may be, for example, performing a surface topology reconstruction process on the primary mold in a preset atomized atmosphere.

[0070] Specifically, in a preset atomized atmosphere, the primary mold is subjected to surface topology reconstruction. As a preferred implementation form, for example, it may include: immersing the primary film in an atomized atmosphere containing a dynamic covalent bond exchanger, and performing surface topology reconstruction under ultraviolet light irradiation to obtain the cellulose film.

[0071] The dynamic covalent bond exchanger may be, for example, a disulfide bond-terminated polyurethane prepolymer.

[0072] As can be seen from the above introduction, this embodiment can achieve efficient and clean separation of cellulose, hemicellulose and lignin in corn straw through multimodal coupling pretreatment, supercritical graded dissociation, and multidimensional mechanical stripping technology. It also combines the biomimetic interface reconstruction process to construct a spiral-enhanced three-dimensional network structure, improve the mechanical properties and light transmittance of the membrane material, and at the same time, through the locking of the membrane-forming agent structure, give the fiber membrane material self-repair and hydrophobic-hydrophilic controllable functions. The entire method design allows for high-value recovery of by-products such as ionic liquids and lignin, reduces the use of chemical reagents and water consumption, achieves full component conversion of straw resources, and the resulting cellulose membrane is easily degradable in the natural environment with low overall cost, providing an integrated solution for agricultural waste resource utilization and plastic pollution control.

[0073] Based on the above introduction, with respect to the production method of the cellulose film of the present invention, further, in the specific implementation, reference may be made to the following examples.

[0074] Example 1

[0075] This example is a method for producing a cellulose film, which specifically includes the following steps:

[0076] Step S1: Multimodal coupling preprocessing

[0077] 1. Raw material crushing

[0078] Select dry corn stalks (moisture content <8%) and process them into 300 mesh (48 μm) through a three-stage crushing system, with a specific surface area of ​​15 m 2 / g, after using magnetic separation to remove metal impurities, it is ready for use;

[0079] 2. Preparation of atomized treatment fluid

[0080] The enzyme is composed of 1-ethyl-3-methylimidazole acetate (20-40 wt%), laccase / xylanase / cellulase (activity ratio 1:2:3, total enzyme activity ≥ 2000 U / g) and nano oxygen bubbles (diameter 50-200 nm, concentration 10 8 -10 10 The liquid-solid interfacial tension was reduced by adding sodium lignin sulfonate (LS-Na, molecular weight 5000 Da, 0.5%) as a penetration enhancer.

[0081] 3. Microwave-Plasma Synergistic Reaction

[0082] Equipment configuration: quartz reactor, dual-frequency microwave source (2.45GHz / 915MHz), 13.56MHz radio frequency plasma.

[0083] Atomization spray: The pretreatment liquid is sprayed through a two-fluid nozzle (gas-liquid ratio 1:3, compressed air pressure 0.3 MPa) at a speed of 0.5 mL / cm 2 The spray rate evenly covers the surface of the material, and the droplet size is 50-100μm;

[0084] Microwave heating: Initially at 100W / s, increase to 800W and maintain for 60 minutes to penetrate deep fibers.

[0085] Plasma activation: Argon / oxygen (4:1) mixed gas was used to excite reactive oxygen species (mass spectrometry detection OH concentration 3.2×10 16 / cm 3 ), oxidizing the methoxyl groups of the lignin side chains.

[0086] Pulse protection: Switch to pulse mode (duty cycle 50%) 1 minute before the end of treatment to avoid enzyme inactivation and obtain the initial material.

[0087] Step S2: Supercritical fractional dissociation

[0088] The initial material was loaded into a high-pressure reactor (Inconel 625 material, pressure resistance 50 MPa), CO2 was introduced until the pressure reached 25 MPa and the temperature reached 80°C, and dynamic pressure shock was performed (fluctuation amplitude ±5 MPa / s, 15 cycles);

[0089] Supercritical CO2 dissolves water to form H2CO3 (pH = 3.2), which hydrolyzes the β-1,4 bonds of hemicellulose to produce xylo-oligosaccharides. Based on the pressure oscillation effect, the cavitation bubbles collapse to produce microjets, tearing the fiber bundles apart.

[0090] When the pressure is greater than 25 MPa, an ethanol solution containing 0.03 wt% ferric acetylacetonate is injected, and the Fe3 + Catalyze H2O2 to generate OH free radicals:

[0091] Fe 3+ +H2O2→Fe 2+ +·OH+OH -

[0092] OH radicals attack the β-O-4 bond of lignin (2D HSQC NMR shows the disappearance of the δC / δH 71.5 / 4.86 signal), and the molecular weight decreases from 15 kDa to 2.3 kDa.

[0093] Flash recovery technology is used to reduce the pressure from 10 MPa / min to 5 MPa, lignin nanoparticles (LNP) are precipitated, and the remaining material is the secondary treatment material.

[0094] The lipid nanoparticles (LNP) obtained above were recovered by a cyclone separator, with a particle size D50=85 nm and a thermal stability of 282° C. (TGA). The recovered lignin nanoparticles can be processed into a flame retardant for preparing flame retardant coatings.

[0095] Step S3: Multidimensional mechanical exfoliation

[0096] First, high-speed centrifugal shearing is used to shear the material after step 2 treatment, and the shear rate reaches 1.2×10 4 s -1 , cutting the fiber bundle into 200-500nm short fibers;

[0097] A high-voltage pulse of 30 kV / cm (pulse width 50 μs, frequency 100 Hz) was then used to apply an electric field of 30 kV / cm to open the hydrogen bond network of the sheared cellulose. The surface Zeta potential increased from -15 mV to -42 mV, forming 2-5 nm micropores. The negative charge enhanced electrostatic repulsion, dispersed the fibers, prevented fiber agglomeration, and promoted the penetration of subsequent modifiers.

[0098] Within 100ms after pulsed electric field treatment, the material was sprayed into -196°C liquid nitrogen (spray speed 20m / s); it was quenched at a rate of 380°C / s to induce the transformation of cellulose Iα crystal form to Iβ (XRD showed that Iβ accounted for 78%). Finally, vacuum drying was used to remove free water to obtain a nanocellulose dispersion (diameter 35±8nm, Zeta potential -42mV).

[0099] Step S4: Bionic interface reconstruction

[0100] This step combines nanocellulose with functional materials through chemical modification, mineralization deposition and physical field coordination to construct a high-strength three-dimensional network.

[0101] 1. Cellulose surface charge characteristics and binding basis

[0102] In step S3, after the cellulose is treated with a high-voltage pulsed electric field, its surface hydroxyl (-OH) groups are partially deprotonated to form a negatively charged surface (Zeta potential -42mV). This negative charge characteristic provides an electrostatic driving force for the subsequent adsorption of positively charged materials.

[0103] 2. Chemical modification of chitosan to enhance interfacial bonding

[0104] 2.1 Original properties of chitosan

[0105] Unmodified chitosan molecules contain free amino groups (-NH2), which can be protonated to -NH3 under acidic conditions. + , Zeta potential is about +15mV (at pH=5.0). However, in a neutral or weakly alkaline environment, its surface positive charge is significantly reduced, making it difficult to effectively adsorb negatively charged cellulose.

[0106] 2.2 Epoxy quaternary ammonium salt grafting modification

[0107] Chitosan was reacted with 2,3-epoxypropyltrimethylammonium chloride (GTA) under alkaline conditions (pH = 9.0) to produce the following covalent bonding:

[0108] Chitosan-NH2+CH2-CH(O)CH2-N + (CH3)3→Chitosan-NH-CH(OH)-CH2-N + (CH3)3 epoxy group opens the ring and combines with chitosan amino group to introduce permanent quaternary ammonium group; quaternary ammonium group (-N + (CH3)3) maintains strong positive charge in a wide pH range, and the Zeta potential of the modified chitosan increases to +28mV (measured at pH=7.0); elemental analysis (nitrogen content increases from 7.2% to 9.8%) and FTIR (1650cm -1 The quaternary ammonium characteristic peak was found at the bottom of the column, confirming that the degree of substitution reached 0.85.

[0109] 2.3 Electrostatic adsorption mechanism

[0110] A positively charged modified chitosan solution (+28mV) and a negatively charged cellulose dispersion (-42mV) were tightly bound together by Coulomb force, forming a chitosan-cellulose complex by electrostatic adsorption. A calcium phosphate nanocluster suspension was added and ultrasonicated to achieve uniform dispersion.

[0111] The Langmuir adsorption model showed that the maximum adsorption capacity reached 120 mg / g (25°C); the electrostatic effect made the chitosan coating layer thicker than 5-10 nm, and it did not fall off after centrifugation (10,000 rpm, 30 min);

[0112] The Coulomb force between positive and negative charges enables the modified chitosan to tightly wrap the cellulose surface; the hydrophilicity of the quaternary ammonium group reduces the van der Waals force between fibers and prevents agglomeration.

[0113] 3. In situ mineralization of calcium phosphate nanoclusters

[0114] 3.1 Confined synthesis and directional deposition:

[0115] Inject CaCl2 and Na2HPO4 solutions into the microfluidic chip at a flow rate ratio of 1:3:

[0116] The laminar flow effect in the microchannel achieves molecular mixing with a residence time of 15ms, avoiding disordered nucleation; the nano-confined space inhibits grain growth and generates monodisperse hydroxyapatite (Ca 10 (PO4)6(OH)2) nanoclusters;

[0117] 3.2 Directed mineralized sedimentation

[0118] Modified chitosan phosphate groups (-PO4 3- ) and Ca 2+ Preferential binding guides the directional deposition of calcium phosphate along the fiber surface.

[0119] Ca 2+ Preferentially adsorbed on the surface of the chitosan coating to form the initial nucleation point; PO4 3- Epitaxial growth is driven by local supersaturation, and the cellulose microfibrils are arranged axially to achieve crystal growth and produce a precursor.

[0120] 4. Magnetic Field-Ultrasonic Cooperative Assembly of 3D Networks

[0121] 4.1 Magnetic field response of composite dispersion

[0122] Place the mixed solution of cellulose dispersion and precursor (containing cellulose-chitosan-calcium phosphate) in a 0.8T magnetic field:

[0123] Cellulose molecular chains have diamagnetic anisotropy (Δχ=1.2×10 -6 ) are arranged along the direction of the magnetic field; the magnetic field force drives the fibers to form a preliminary orderly arrangement;

[0124] 4.2 Ultrasonic dynamic control

[0125] Applying 80kHz ultrasonic waves (power density 50W / L) and alternating pressure waves (peak value > 10kPa) causes the fiber to twist periodically, forming a helical structure with a pitch of 220±30nm:

[0126] The calcium phosphate nanoclusters are preferentially embedded in the concave surface of the spiral, through the Ca 2+ The dual action of coordination and hydrogen bonding with the cellulose hydroxyl groups fixes the position, ultimately forming a continuous three-dimensional network. This network has a compression modulus of 4.8GPa, and the helical arrangement imparts axial conductivity (1.5×10-3S / m), making it a composite dispersion.

[0127] Step S5: Film formation

[0128] In this stage, the composite dispersion prepared in step S4 is used as raw material and converted by aerosol electrospinning technology to obtain a primary membrane.

[0129] 1. Adaptation of electrospinning liquid properties

[0130] The composite dispersion has a solids content of 5.2 wt% (i.e., 5.2 g of solids per 100 g of solution), and its flow characteristics exhibit "shear thinning"—when an external force (such as stirring or airflow shear) is applied, the solution viscosity decreases, facilitating uniform atomization. This characteristic is described by the power law exponent n = 0.55 (n < 1 indicates shear thinning). The solution has an initial viscosity of 5000 cP (25°C) and needs to be stretched into fibers using a high-voltage electric field (20 kV), while an alternating airflow (flow rate of 2 m / s) is used to control the fiber arrangement.

[0131] 2. Electric field stretching and fiber forming

[0132] A high-voltage electric field is applied to the electrospinning nozzle, and the composite dispersion forms a "Taylor cone" (the tip of the droplet is stretched into a cone) under the action of the electric field force. Because the composite dispersion contains calcium phosphate nanoclusters (which enhance dielectric properties), the electric field effect is more efficient, and the jet speed reaches 120m / s. During the jet flight, the solvent (DMAC) evaporates, and the fiber transitions from liquid to solid:

[0133] During the fiber forming process, the initial humidity is 95% to slow solvent evaporation and prevent fiber breakage. The humidity is then gradually reduced to 30% (with the temperature paused after every 15% drop) to ensure uniform fiber solidification. The initial temperature is gradually increased from 25°C to 120°C, inducing the sol-gel transition at 60°C and locking the glassy structure at 100°C to prevent fiber adhesion. The final fiber diameter is stabilized at 120±5nm.

[0134] 3. Airflow assistance and fiber orientation

[0135] During fiber forming, a piezoelectric ceramic array is arranged to generate an alternating airflow, the direction of which is perpendicular to the composite dispersion jet direction. When in a low-viscosity solution (n < 0.6), the alternating airflow frequency is 1-3 Hz, and gentle disturbance is used to avoid jet breakage. When in a high-viscosity solution (n ≥ 0.6), the alternating airflow frequency is 5-10 Hz, which enhances shear force to suppress "bead string" defects.

[0136] The transverse airflow induces the jet to swing, so that the fibers are arranged along the direction of the airflow. The airflow accelerates the diffusion of the solvent, and the humidity is reduced from 95% to 30% (the temperature is paused for 10 minutes every 15% drop), avoiding the pore closure caused by surface crusting and forming a primary membrane.

[0137] Step S6: Topology Locking

[0138] 1. Dynamic covalent cross-linking:

[0139] The nascent membrane was placed in an atomizing atmosphere containing disulfide-terminated polyurethane (molecular weight 3500Da, atomized particle size 1-10μm) and ultraviolet light (365nm, 30mW / cm 2) excites sulfur free radicals, triggering a dynamic bond exchange reaction. The sulfur free radicals attack the hydroxyl groups on the cellulose surface to form a reversible covalent bond (-SS-), achieving self-repair of scratches.

[0140] 2. Fluorine element gradient deposition

[0141] During ultraviolet irradiation, 10 vol% carbon tetrafluoride gas is introduced simultaneously, and plasma dissociation generates CF3 free radicals, forming a fluorine content gradient on the membrane surface (XPS shows a surface fluorine content of 18 at%, and an internal fluorine content of 5 at%), achieving a hydrophobic-hydrophilic Janus function (contact angle 152° / 85°).

[0142] 3. Post-processing:

[0143] After the membrane material is washed with a pH=4 buffer solution, unreacted cross-linking agent is recovered by ultrafiltration, and the preparation of the cellulose membrane is completed.

[0144] Example 2

[0145] This example 2 is a method for producing a cellulose film, which specifically includes the following steps:

[0146] The production method of this example is basically the same as that of Example 1. The only difference is that in step S1 of this example 2, the multimodal coupling pretreatment is performed by reducing the microwave power to 600W (800W in Example 1), extending the treatment time to 90 minutes, maintaining the ionic liquid concentration at 30wt%, and increasing the nano-oxygen bubble concentration to 1×101 0 The other steps were the same as those in Example 1.

[0147] Example 3

[0148] This example 3 is a method for producing a cellulose film, which specifically includes the following steps:

[0149] The production method of this example is basically the same as that of Example 1, except that in step S2 of this Example 3, supercritical fractional dissociation is performed, the CO2 pressure is increased to 28 MPa (25 MPa in Example 1), the temperature is 85°C, the pressure fluctuation amplitude is ±7 MPa / s, the number of cycles is increased to 18 times, and the amount of catalyst (ferric acetylacetonate) added is adjusted to 0.05 wt%. The other steps are the same as in Example 1.

[0150] Comparative Example 1

[0151] This comparative example 1 is a method for producing a cellulose film, which specifically comprises the following steps:

[0152] The production method of this comparative example is basically the same as that of Example 1, except that, in step S1 of the multimodal coupling pretreatment in this comparative example 1, 1-ethyl-3-methylimidazole acetate is removed, and only water and enzyme system are used. The other steps are the same as those in Example 1.

[0153] Comparative Example 2

[0154] This comparative example 2 is a method for producing a cellulose film, which specifically includes the following steps:

[0155] The production method of this comparative example is basically the same as that of Example 1, with the only difference being that in step S4 of this comparative example 2, the bionic interface is reconstructed by turning off the magnetic field and relying only on ultrasonic treatment without magnetic field-assisted assembly. The other steps are the same as those of Example 1.

[0156] Comparative Example 3

[0157] This comparative example 3 is a method for producing a cellulose film, which specifically includes the following steps:

[0158] The production method of this comparative example is basically the same as that of Example 1, with the only difference being that, in step S5 of film formation in this comparative example 3, aerosol assistance and dynamic airflow are eliminated, and conventional single-needle electrospinning (constant temperature and humidity) is used. The other steps are the same as those in Example 1.

[0159] The comprehensive performance comparison results of the above examples and comparative examples are shown in the following table:

[0160] Comprehensive performance comparison table

[0161] index Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (MPa) 108 105 110 48 60 72 Light transmittance (%) 91.5 92 90 75 88 85 Degradation cycle (days) 60 65 55 ＞120 70 80 Fiber diameter uniformity 4.2％ 5.1％ 3.8％ 25％ 15％ 18％

[0162] By comparing the performance results of Examples 1-3 with those of Comparative Examples 1-3, it can be seen that the multimodal coupling pretreatment (ionic liquid + nano oxygen bubbles + enzyme synergy) and supercritical CO2 dynamic dissociation (25 MPa pressure shock) treatment steps can significantly improve the performance of the cellulose membrane.

[0163] Specifically, it can be seen that Example 1 achieves lignin nanoparticles (D50 = 85 nm, TGA 282°C) by using the ionic liquid [EMIM]OAc (contact angle reduced from 75° to 60°) and nano-oxygen bubble microjet (pit diameter 20-50 nm) in step S1, and the produced cellulose has a tensile strength of 108 MPa. Compared with Comparative Example 1, which removes 1-ethyl-3-methylimidazolium acetate and uses only water and an enzyme system, the strength of the produced cellulose is 48 MPa, an increase of 125%.

[0164] As can be seen from the above comprehensive performance comparison table, in Example 2, the microwave power in the multimodal coupling pretreatment step was reduced to 600 W (800 W in Example 1), the treatment time was extended to 90 minutes, the ionic liquid concentration was maintained at 30 wt%, and the nano oxygen bubble concentration was increased to 1 × 10 10 After the reaction temperature was adjusted to 500 nm / mL, the comprehensive performance of the produced cellulose membrane had no significant change compared with Example 1.

[0165] Although Example 3 increased the CO2 pressure in the supercritical fractional dissociation step to 28 MPa and added a catalyst (0.05 wt% ferric acetylacetonate), the overall performance of the cellulose membrane finally produced had no significant advantages over the cellulose membrane of Example 1, with only a slightly better fiber diameter uniformity.

[0166] The bionic interface reconstruction step of Comparative Example 2 is not assisted by a magnetic field, and the lack of fiber orientation causes the transmittance to drop to 88% (91.5% in Example 1). Comparative Example 3 only uses conventional electrospinning technology to form a film, and the fiber uniformity of the obtained cellulose film is only 18% and the strength is 72MPa. However, Example 1 achieves balanced performance of 91.5% transmittance, 60 days degradation cycle and 4.2% fiber uniformity through bionic interface reconstruction (chitosan quaternization Zeta potential +28mV, calcium phosphate compression modulus 4.8GPa) and aerosol electrospinning regulation (fiber diameter 120±5nm). Comparing Comparative Examples 2 and 3, the comprehensive performance of cellulose in Example 1 is the best.

[0167] In summary, the cellulose film produced by the cellulose production method of the present invention has high strength, is easy to degrade, and has low cost, providing an integrated solution for agricultural waste resource utilization and plastic pollution control.

[0168] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for producing a cellulose film, characterized in that: The production method comprises sequentially subjecting corn stalks to multimodal coupling pretreatment, supercritical graded dissociation, multidimensional mechanical exfoliation, biomimetic interface reconstruction, film formation, and topological structure locking to produce a cellulose film; The multimodal coupling pretreatment includes crushing the corn stalks and decomposing the crushed corn stalks into initial materials under the action of microwaves and low-temperature plasma; The supercritical fractional dissociation includes catalytically treating the initial material into a secondary treated material in a predetermined supercritical environment; The multi-dimensional mechanical stripping includes shearing the secondary processed material and stripping the cellulose dispersion from the secondary processed material; The biomimetic interface reconstruction includes treating the cellulose dispersion with a precursor to form a composite dispersion containing a three-dimensional network; The film forming comprises forming the composite dispersion into a primary film; The topological structure locking includes performing a surface topological reconstruction process on the primary mold in a preset atomization atmosphere.

2. The method for producing a cellulose film according to claim 1, wherein The crushing of the corn stalks and decomposition of the crushed corn stalks into initial materials under the action of microwaves and low-temperature plasma comprises: Crush the corn stalks to 50-300 mesh; Under the action of microwave and low-temperature plasma, an atomized treatment liquid is added, and the mixture is treated at a temperature of 40 to 70° C. for 0.5 to 2 hours to obtain the initial material.

3. The method for producing a cellulose film according to claim 2, wherein: The components of the atomized treatment liquid include ionic liquid, nano bubble oxygen and complex enzyme.

4. The method for producing a cellulose film according to claim 3, wherein: The catalytic treatment of the initial material into a secondary treated material in a preset supercritical environment comprises: placing the initial material in a supercritical carbon dioxide environment; An ethanol solution containing a transition metal catalyst is added to the initial material to obtain a secondary treated material.

5. The method for producing a cellulose film according to claim 4, wherein: The shearing of the secondary processed material and stripping the cellulose dispersion from the secondary processed material comprises: subjecting the secondary processed material to high-speed centrifugal shearing; Applying a high-voltage pulse electric field for a preset time to the secondary processed material after shearing; The secondary treated material after the high voltage pulse electric field treatment is subjected to liquid nitrogen quenching treatment to obtain the cellulose dispersion.

6. The method for producing a cellulose film according to claim 5, wherein: The step of treating the cellulose dispersion with a precursor to form a composite dispersion containing a three-dimensional network comprises: mixing the cellulose dispersion with a precursor; Under the synergistic effect of ultrasound and magnetic field, a composite dispersion containing a three-dimensional network is formed.

7. The method for producing a cellulose film according to claim 6, wherein: The precursor is a silanized chitosan-calcium phosphate nanocluster complex; The frequency of the ultrasonic wave is 50 to 100 kHz; The intensity of the magnetic field is 0.3-1.2T.

8. The method for producing a cellulose film according to claim 7, wherein: In the silanized chitosan-calcium phosphate nanocluster composite, the mass ratio of silanized chitosan to calcium phosphate is 1:0.5-2.

9. The method for producing a cellulose film according to claim 6, wherein: The method of preparing the composite dispersion into a primary film comprises: The composite dispersion is subjected to aerosol-assisted electrospinning technology to prepare a primary membrane.

10. The method for producing a cellulose film according to claim 9, characterized in that: The surface topology reconstruction process of the primary mold in a preset atomizing atmosphere includes: immersing the nascent membrane in an atomized atmosphere containing a dynamic covalent bond exchanger; The surface topology is reconstructed under ultraviolet light to prepare the cellulose membrane.

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