A method for improving the uniformity of pulp molding

Abstract

The application discloses a method for improving the uniformity of pulp molding, which comprises the following steps: a pulp pretreatment step, an electrostatic adsorption forming step, a wet blank transferring and pre-dewatering step, a hot-pressing setting step and a post-treatment step. The method can significantly improve the thickness uniformity of the pulp molding product, greatly reduce the fiber loss rate, effectively inhibit narrow-site pulp holding, improve the efficiency, and improve the precision and performance of the product.

Description

Technical Field

[0001] This invention relates to the field of pulp molding technology, specifically to a method for improving the uniformity of pulp molding. This method effectively improves the uniformity of the thickness of pulp molded products through the synergistic effect of electrostatic adsorption and additives. Background Technology

[0002] Pulp molding products are an environmentally friendly packaging material. Their traditional production process relies on vacuum adsorption to transfer fiber pulp onto the surface of a molding die. Since the intensity of vacuum adsorption is the same in every direction, the resulting pulp molding product should theoretically have a uniform thickness. However, during the adsorption process, uneven thickness can occur due to factors such as pulp flow rate and gravity. This unevenness becomes more pronounced as the cavity of the product deepens.

[0003] In particular, when the mold structure design includes narrow sections, the slurry flow rate drops sharply at these sections. Due to inertia, fibers deviate from the main fluid path and aggregate towards the center of the structure, forming a reverse concentration gradient of "low concentration surrounding high concentration." This can easily lead to abnormal fiber aggregation and localized thickening. Currently, to address this issue, a two-stage slurry suction process is typically employed. The first suction completes the basic molding, forming a thin slurry layer to reduce fiber aggregation at narrow sections and prevent slurry trapping. A second suction completes the entire suction process. However, this two-stage suction process extends the production cycle and reduces production line efficiency.

[0004] Therefore, this process has significant drawbacks in practical applications: during the adsorption molding process, the fibers in the slurry are easily unevenly distributed due to the influence of fluid dynamics, gravity settling, and mold structure (especially deep cavities and narrow areas). Specifically, in deep cavity areas (depth ≥ 15 cm), fiber settling results in a thickness ratio of the bottom to the flat area typically ≥ 1.25, leading to poor uniformity; in narrow areas of the mold, the slurry flow rate drops sharply, and fibers accumulate due to inertia, forming localized thickening ("slurry trapping" phenomenon); furthermore, the fiber loss rate of traditional processes is relatively high, generally between 10% and 15%.

[0005] Therefore, there is an urgent need for an efficient pulp molding method that can fundamentally improve fiber distribution uniformity, reduce fiber loss, and adapt to complex mold structures. Summary of the Invention

[0006] This invention aims to overcome the aforementioned shortcomings of the prior art and provide a method for improving the uniformity of pulp molding. This method modifies the pulp by adding additives, controls the interaction forces between fibers within the pulp in stages, and combines this with a zoned gradient electric field design to achieve precise control over fiber migration and adsorption processes, thereby significantly improving the uniformity of product thickness and greatly reducing fiber loss.

[0007] The technical solution of the present invention is as follows:

[0008] A method for improving the uniformity of pulp molding includes the following steps: Step 1. Slurry Pretreatment 1.1. Adjust the mass percentage concentration of the plant fiber pulp to 0.3%-0.5%. First, add 0.6%-0.8% of the oven-dry fiber mass of anionic dispersant sodium polyacrylate. Stir at 45-50℃ with a 1%-2% NaOH aqueous solution at a pH of 7.5-8.0 to reduce the Zeta potential on the fiber surface from -15 to -30mV to about -38 to -42mV, thereby establishing an electrostatic repulsion barrier to prevent fiber flocculation. 1.2. Then, cationic polyacrylamide (CPAM) is added in two stages: First, 0.3% of the oven-dry fiber mass of CPAM is added, and the mixture is stirred at a high speed of 1000 to 1400 rpm for 2 to 4 minutes to form open micro-flocs with a "chain loop-chain tail" bridging structure; then, 0.2% of the oven-dry fiber mass of CPAM is added, and the stirring speed is reduced to 300 to 800 rpm for 1 to 2 minutes to strengthen the micro-floc network structure to resist shear disturbances in subsequent processes. 1.3. Then add pH-responsive microcapsules at a weight of 0.5%-1.0% of the oven-dry fiber mass, maintain the slurry temperature at 55±2℃, and keep the stirring speed at 100 to 400 rpm / min to form a pretreated slurry.

[0009] Step 2. Electrostatic adsorption molding A molding die with partitioned gradient electrodes is immersed in a pretreated slurry for adsorption molding. 2.1. Apply a pre-charging electric field of 7.5 to 8.5 kV to the entire electrode layer of the mold to activate the micro-flocs in the slurry; 2.2. Raising the pH of the slurry to 7.0 to 8.5 triggers the rupture of pH-responsive microcapsules pre-added to the slurry, releasing anionic dispersant sodium polyacrylate and nano-bentonite. The dispersant further restores the fiber zeta potential to approximately -40 to -50 mV, and the nano-bentonite forms a steric barrier. Simultaneously, the electric field strength in the deep cavity region of the mold is increased to 15-18 kV / m. 2.3. Maintain the zoned electric field strength and simultaneously start the vacuum system to complete fiber adsorption and preliminary dehydration under a negative pressure of -0.65MPa to form a wet blank; Step 3. Transfer and pre-dehydration of wet preforms The wet preform is transferred from the suction die to the extrusion die by air pressure difference. During the transfer, a weak electric field of 5kV is maintained to prevent fiber rebound. The wet preform is then pre-dehydrated to reduce the surface moisture content to 60% and the core moisture content to about 75%.

[0010] Preferably, the method according to the invention further includes step 4: hot pressing for shaping. The pre-dehydrated wet blank is placed in a hot press mold. An electrode array is embedded on the surface of the hot press mold and a DC voltage of 3 to 6 kV is applied. At the same time, a 2 MHz radio frequency compensation electric field is applied to the edge area of ​​the mold. Hot pressing is performed at a pressure of 12 MPa and a temperature of 180°C. The DC electrostatic attraction forces the fibers to adhere tightly to the mold contour, while the radio frequency electric field softens the fibers through molecular oscillation, together inhibiting the shrinkage and warping deformation of the product.

[0011] Preferably, the method according to the invention further includes step 5. Post-processing. The shaped product is trimmed, and the trimming mold integrates a negative corona discharge device to reduce burrs on the molten fiber cross-section; finally, the finished product undergoes ion wind neutralization treatment to achieve a surface resistivity of 10. 8 -10 10 Ω.

[0012] Preferably, in step 1.2, 0.3% of the dry fiber mass of CPAM is added first, and the mixture is stirred at a high speed of 1200 rpm for 3 minutes; then 0.2% of the dry fiber mass of CPAM is added, the stirring speed is reduced to 600 rpm, and the mixture is stirred for 2 minutes.

[0013] Preferably, step 2.1 is completed within 0-2 seconds, step 2.2 is performed in the 3rd second, and step 2.2 is completed within 4-6 seconds.

[0014] Preferably, the molding die with partitioned gradient electrodes described in step 2 includes, from the inside out, a base layer, an insulating layer 1, an electrode layer, an insulating layer 2, and a contact layer; The base layer is made of aluminum alloy, which provides mechanical support and disperses stress. The preferred thickness is 9.8 mm. The insulating layer 1 is a PI / AlN / PI composite structure, wherein the bottom layer is polyimide, which can effectively block current leakage and ensure high voltage safety; the middle layer is an aluminum nitride coating, which quickly conducts away adsorbed heat (preventing local breakdown); and the top layer is polyimide. The thickness of the insulating layer 1 is preferably 0.07 mm.

[0015] In the insulating layer 1, the bottom layer is 30μm polyimide (PI, withstand voltage 300kV / mm), the middle layer is 20μm aluminum nitride coating (AlN, thermal conductivity 400W / m·K), and the top layer is 20μm polyimide (PI, Ra<0.1μm).

[0016] The electrode layer is configured into functional regions with different pattern densities, including a high-density comb electrode in the deep cavity region, a grid electrode in the planar region, and a ring electrode in the edge region. The insulating layer 2 is a PI / AlN / PI composite structure, wherein the bottom layer is polyimide, which can effectively block current leakage and ensure high voltage safety; the middle layer is an aluminum nitride coating, which quickly conducts away adsorbed heat (preventing local breakdown); and the top layer is polyimide. The thickness of the insulating layer 2 is preferably 0.07 mm.

[0017] In the insulating layer 2, the bottom layer is 30μm polyimide (PI, withstand voltage 300kV / mm), the middle layer is 20μm aluminum nitride coating (AlN, thermal conductivity 400W / m·K), and the top layer is 20μm polyimide (PI, Ra<0.1μm).

[0018] The contact layer is a 0.03mm thick platinum-plated stainless steel mesh (0.5mm aperture), which directly contacts the slurry. Its conductivity transmits the electric field, and the platinum layer reduces the contact resistance.

[0019] More preferably, the electrode layer is a photolithographic copper foil with a preferred thickness of 0.05 mm. It has three functional zones, and the electric field gradient is achieved through the differentiation of a single electrode layer (non-physical layering), without the need for independent circuit control. Deep cavity region: comb tooth density 120 lines / cm 2 (Line width 0.3mm, spacing 0.5mm), by increasing the electrode edge length, the local electric field strength is increased to 15-18 kV / m to compensate for fiber settling caused by gravity and ensure sufficient adsorption force at the bottom of the deep cavity; Planar area: mesh density 80 lines / cm 2 (Standard mesh electrode aperture 1mm), electric field strength maintained at a base value of 8-10 kV / m to balance energy consumption and adsorption requirements; edge region: annular closed-loop electrode (5mm wide), electric field strength 12 kV / m, closed electric field lines to prevent thickness attenuation caused by boundary effects.

[0020] Preferably, the shell material of the pH-responsive microcapsule in step 1.3 is chitosan, and the core material contains the anionic dispersant and nano-bentonite, which can release the contents by breaking the shell at pH=8.5.

[0021] Preferably, the pH-responsive microcapsules described in step 1.3 are injected into the slurry tank before the electrostatic field of the molding die is activated, and the pH value of the slurry is adjusted to 8.5±0.1 (trigger rupture threshold) by NaOH aqueous solution under stirring conditions.

[0022] Preferably, in step 2, the slurry temperature is maintained at 55±2℃ and the viscosity is controlled at 120±20mPa·s.

[0023] Beneficial effects 1. Significantly improved thickness uniformity: Through the design of a partitioned gradient electric field, especially by applying a reinforced electric field to the deep cavity region, the gravitational settling is effectively compensated, reducing the thickness ratio between the bottom of the deep cavity and the planar region from ≥1.25 in the traditional process to ≤1.03, with the thickness difference reduced by more than 21%.

[0024] 2. Significantly reduced fiber loss rate: The directional adsorption effect of the electrostatic field and the synergistic effect of the additives released by the pH-responsive microcapsules greatly reduce the fiber residue in the pulp tank. The fiber loss rate is reduced from 10%-15% in the traditional process to less than 2%, a reduction of more than 80%.

[0025] 3. Effectively suppresses narrow-position slurry accumulation: The synergistic regulation of electrostatic repulsion and micro-floc structure improves the rheological behavior of slurry in narrow-position regions, prevents abnormal fiber aggregation, and improves the narrow-position stacking thickness ratio from 1.8 to ≤1.2.

[0026] 4. High process integration and improved efficiency: By coordinating electrostatic adsorption, chemical additive control and vacuum dewatering timing, complex processes such as secondary slurry suction are avoided, which improves production efficiency while ensuring quality.

[0027] 5. Improved product precision and performance: The introduction of electrostatic and radio frequency assisted technologies during the hot pressing and shaping stage effectively controls product shrinkage and warping, improves dimensional stability, and can meet the anti-static requirements of electronic product packaging through post-processing. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram illustrating the role of CPAM in the slurry when CPAM is added in the first stage according to the method of the present invention.

[0030] Figure 2 This is a schematic cross-sectional view of the partitioned gradient electrode forming mold used in this invention.

[0031] Figure 3 for Figure 2 A magnified view of a portion of the mold.

[0032] Figure 4 This is a diagram showing the measurement locations of the samples in Example 1. Detailed Implementation

[0033] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather should be interpreted based on the principle of allowing the inventors to appropriately define the terminology for the best interpretation, and based on its meaning and concept corresponding to the technical level of the invention. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention; thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the invention.

[0034] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0035] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0036] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0037] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0038] To clarify the invention, parts irrelevant to the description have been omitted from the drawings, and throughout the specification, the same or similar parts are indicated by the same reference numerals.

[0039] Furthermore, for ease of explanation, the dimensions and thicknesses of each component shown in the accompanying drawings are arbitrarily illustrated; therefore, the invention is not necessarily limited to those shown in the drawings.

[0040] Throughout the specification, when it is said that an element is "connected" to another element, it includes not only "direct connection" but also "indirect connection" between other components. Furthermore, when it is said that an element "comprises" a part, it means that the element may further include other parts rather than exclude them, unless otherwise explicitly stated.

[0041] The terms “first,” “second,” etc., used in this article are used to explain various constituent elements, and they are only used for the purpose of distinguishing one constituent element from another.

[0042] Furthermore, the terminology used herein is for the purpose of explaining exemplary embodiments only and is not intended to limit the invention. Singular expressions also include their plural expressions unless otherwise expressly indicated in the context. Terms such as “comprising,” “equipped with,” or “having” as used herein are used to specify the presence of a practical characteristic, number, step, constituent element, or combination thereof, and should be understood to not exclude the possibility of the addition or presence of one or more other characteristics, numbers, steps, constituent elements, or combinations thereof.

[0043] Furthermore, if a layer or element is referred to as being formed "above" or "on top of" a "layer" or "element", it means that each layer or element is formed directly on that layer or element, or that other layers or elements may be formed between layers, bodies, or substrates.

[0044] The CPAM used in this invention is cationic polyacrylamide, a water-soluble linear polymer copolymerized from acrylamide monomers and cationic monomers. Its molecular chain contains ionizable quaternary ammonium groups and other cationic groups (-N...). + (CH3)3), which ionizes in water to form positively charged polycations, forms ionic bonds with fibers, while the amide groups (-CONH2) form hydrogen bonds with the hydroxyl groups of fibers, thus achieving directional adsorption.

[0045] Sodium polyacrylate, an anionic dispersant, helps establish an electrostatic repulsion barrier. Adding 0.6%-0.8% sodium polyacrylate (pH=8.0) to the slurry, its sulfonic acid groups (-SO3) - The ionized adsorption occurs on the fiber surface, causing the Zeta potential to drop from -15 to -30 mV to -40 mV. The pH is strictly maintained at 7.5-8.0 (adjusted with NaOH) to prevent the potential from rising again due to a decrease in the degree of carboxyl ionization. At this point, the electrostatic repulsion barrier between particles exceeds the van der Waals attraction, effectively preventing fiber aggregation.

[0046] Adding CPAM helps to construct controllable micro-flocs. By establishing appropriate binding forces based on electrostatic repulsion, it solves two major problems in subsequent electric field adsorption: purely dispersed fibers are easily dispersed by fluids; and it improves the migration efficiency of charged fibers in an electric field.

[0047] To avoid excessive local cations (charge neutralization leading to dense flocculation) caused by adding CPAM all at once, it will be added in two stages.

[0048] The first step involves adding 0.3% CPAM. By controlling the appropriate cationization, physical bridging rather than charge neutralization is achieved to form micro-flocs. CPAM molecules have a long-chain linear structure. When cationic groups adsorb onto negatively charged sites on the fiber surface, they form initial anchoring points. Neutral segments curl into arc or ring structures due to hydrophobic interactions and extend into the liquid phase. Unadsorbed segments extend freely in the slurry, capturing neighboring fibers and forming a "chain loop-chain tail" bridging structure. The second stage involves adding 0.2% CPAM to the slurry to strengthen the "fiber-CPAM-fiber" network, enhance the tensile strength of the mesh structure, and reinforce it against fluid shear and electric field disturbances.

[0049] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0050] Example 1 Taking the production of an electronic device buffer bracket with a depth of 15cm as an example, the implementation process of the present invention will be explained.

[0051] 1. Pulp Preparation: Bamboo pulp fibers are crushed, ground, and prepared into a suspension with a mass percentage concentration of 0.4%. The mixture is heated to 48°C in a mixing tank, and sodium polyacrylate (an anionic dispersant) at 0.7% of the oven-dry fiber mass is added. The pH is adjusted to 7.8 with a 1% NaOH solution, and the mixture is stirred at 900 rpm for 5 minutes. Next, CPAM at 0.3% of the oven-dry fiber mass is added, and the mixture is stirred at 1200 rpm for 3 minutes. Then, the same type of CPAM at 0.2% of the oven-dry fiber mass is added, and the mixture is stirred at 600 rpm for 2 minutes. Finally, pH-responsive microcapsules (chitosan shell containing sodium polyacrylate dispersant and nano-bentonite) at 0.8% of the total pulp mass are added.

[0052] 2. Molds and equipment: using, for example Figure 2 and 3 The diagram shows a partitioned gradient electrode mold. The electrode layers are fabricated using photolithography; the deep cavity region uses a comb-like electrode with 120 lines / cm², the planar region uses a grid electrode with 80 lines / cm², and the edge region uses a 5mm wide annular electrode. The insulating layer 2 is a 0.07mm thick PI / AIN / PI composite structure. The contact layer is a 0.03mm thick platinum-plated stainless steel mesh with 0.5mm aperture. The slurry tank is equipped with a precision temperature control and pH monitoring system.

[0053] 3. Electrostatic Adsorption Molding: Immerse the mold to a depth of 50 mm in the slurry tank (slurry temperature maintained at 55℃, viscosity approximately 130 mPa·s). Control the process according to the preset time sequence: 0-2s, apply an 8 kV electric field throughout the entire process; at 3s, add a small amount of 1% NaOH solution to raise the slurry pH to 8.5, triggering microcapsule rupture, and simultaneously raise the voltage in the deep cavity to 15 kV; 4-6s, maintain the zoned electric field and simultaneously turn on the vacuum pump to maintain a negative pressure of -0.65 MPa for adsorption and dehydration.

[0054] 4. Subsequent processes: After air pressure transfer and pre-dehydration, the wet blank enters the hot press. The upper mold of the hot press is embedded with an electrode array, and a 5kV DC voltage is applied, with an additional 2MHz, 200W radio frequency field applied to the edge area. It is hot-pressed and shaped at 12MPa and 180℃. Finally, the finished product is obtained after charged edge trimming and ion air treatment.

[0055] Testing revealed that the thickness ratio between the bottom of the deep cavity and the flat area of ​​the bracket was 1.02, the overall fiber loss rate was 1.8%, there was no slurry trapping in the narrow areas, the product dimensions were stable, and there was no warping.

[0056] Table 1 shows the test data for different regions (bottom of deep cavity / sidewall / edge / planar area) of the sample measured using a universal testing machine. The measurement locations are referenced below. Figure 4 The annotation is in the middle. For example, Figure 4The three measurement points 1, 2 and 3 marked in the figure correspond to thickness 1, thickness 2 and thickness 3 in Table 1, that is, three measurement points are taken at the bottom, middle and top of the product respectively for measurement.

[0057] Table 1

[0058] Example 2 The difference between this embodiment and Example 1 is that the fiber used is bagasse pulp, the anionic dispersant addition is 0.65%, the total CPAM addition is 0.5% (the two-stage addition ratio remains 0.3% + 0.2% of the oven-dry fiber mass, the same as in Example 1), and the pulp concentration is 0.35%. During adsorption molding, the electric field strength in the deep cavity region is adjusted to 17 kV / m. The thickness uniformity and fiber loss rate of the final product are comparable to those of Example 1, indicating that the present invention has good adaptability to different plant fiber raw materials.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the uniformity of pulp molding, comprising the following steps: Step 1. Slurry Pretreatment 1.

1. Adjust the mass percentage concentration of the plant fiber pulp to 0.3%-0.5%. First, add 0.6%-0.8% of the oven-dry fiber mass of anionic dispersant sodium polyacrylate. Stir at 45-50℃ with a 1%-2% NaOH aqueous solution, strictly controlling the pH value to 7.5-8.0, so that the Zeta potential of the fiber surface drops from -15~-30mV to -38 to -42mV, establishing an electrostatic repulsion barrier to prevent fiber flocculation. 1.

2. Then, cationic polyacrylamide (CPAM) is added in two stages: First, 0.3% of the oven-dry fiber mass of CPAM is added, and the mixture is stirred at a high speed of 1000 to 1400 rpm for 2 to 4 minutes to form open micro-flocs with a "chain loop-chain tail" bridging structure; then, 0.2% of the oven-dry fiber mass of CPAM is added, and the stirring speed is reduced to 300 to 800 rpm for 1 to 2 minutes to strengthen the micro-floc network structure to resist shear disturbances in subsequent processes. 1.

3. Then add pH-responsive microcapsules at a concentration of 0.5%-1.0% of the oven-dry fiber mass, maintain the slurry temperature at 55±2℃, and keep the stirring speed at 100 to 400 rpm / min to form a pretreated slurry; Step 2. Electrostatic adsorption molding A molding die with partitioned gradient electrodes is immersed in a pretreated slurry for adsorption molding. 2.

1. Apply a pre-charging electric field of 7.5 to 8.5 kV to the entire electrode layer of the mold to activate the micro-flocs in the slurry; 2.

2. Raising the pH of the slurry to 7.0 to 8.5 triggers the rupture of pH-responsive microcapsules pre-added to the slurry, releasing anionic dispersant sodium polyacrylate and nano-bentonite. The dispersant further restores the fiber zeta potential to -40 to -50 mV, and the nano-bentonite forms a steric barrier. Simultaneously, the electric field strength in the deep cavity region of the mold is increased to 15-18 kV / m. 2.

3. Maintain the zoned electric field strength and simultaneously start the vacuum system to complete fiber adsorption and preliminary dehydration under a negative pressure of -0.65MPa to form a wet blank; Step 3. Transfer of wet preform and pre-dehydration The wet preform is transferred from the suction die to the extrusion die by air pressure difference. During the transfer, a weak electric field of 5kV is maintained to prevent fiber rebound. The wet preform is then pre-dehydrated to reduce the surface moisture content to 60% and the core moisture content to about 75%.

2. The method according to claim 1, characterized in that, The method further includes step 4: hot pressing and shaping. The pre-dehydrated wet blank is placed in a hot press mold. An electrode array is embedded on the surface of the hot press mold and a 5kV DC voltage is applied. At the same time, a 2MHz radio frequency compensation electric field is applied to the edge area of ​​the mold. Hot pressing is performed at a pressure of 12MPa and a temperature of 180℃. The DC electrostatic attraction forces the fibers to adhere tightly to the mold contour, while the radio frequency electric field softens the fibers through molecular oscillation, thus jointly inhibiting the shrinkage and warping deformation of the product.

3. The method according to claim 1, characterized in that, The method further includes step 5. Post-processing. The shaped product is trimmed, and the trimming mold integrates a negative corona discharge device to reduce burrs on the molten fiber cross-section; finally, the finished product undergoes ion wind neutralization treatment to achieve a surface resistivity of 10. 8 -10 10 Ω.

4. The method according to claim 1, characterized in that, In step 1.2, first add 0.3% of the dry fiber mass of CPAM and stir at a high speed of 1200 rpm for 3 minutes; then add 0.2% of the dry fiber mass of CPAM, reduce the stirring speed to 600 rpm, and stir for 2 minutes.

5. The method according to claim 1, characterized in that, Step 2.1 is completed within 0-2 seconds, Step 2.2 is implemented in the 3rd second, and Step 2.2 is completed within 4-6 seconds.

6. The method according to claim 1, characterized in that, The molding die with partitioned gradient electrodes described in step 2 includes, from the inside out, a base layer, an insulating layer 1, an electrode layer, an insulating layer 2, and a contact layer. Preferably, the base layer is made of aluminum alloy to provide mechanical support and distribute stress, and its thickness is preferably 9.8 mm. Preferably, the insulating layer 1 is a PI / AlN / PI composite structure, wherein the bottom layer is polyimide, which can effectively block current leakage and ensure high voltage safety; the middle layer is an aluminum nitride coating, which can quickly conduct away adsorbed heat and prevent local breakdown; the top layer is polyimide, and the thickness of the insulating layer 1 is preferably 0.07 mm; More preferably, in the insulating layer 1, the bottom layer is 30μm polyimide, the middle layer is 20μm aluminum nitride coating, and the top layer is 20μm polyimide; Preferably, the electrode layer is configured as functional regions with different pattern densities, including a high-density comb electrode in the deep cavity region, a grid electrode in the planar region, and a ring electrode in the edge region; Preferably, the insulating layer 2 is a PI / AlN / PI composite structure, wherein the bottom layer is polyimide, which can effectively block current leakage and ensure high voltage safety; the middle layer is an aluminum nitride coating, which quickly conducts away adsorbed heat and prevents local breakdown; the top layer is polyimide, and the thickness of the insulating layer 1 is preferably 0.07 mm; More preferably, in the insulating layer 2, the bottom layer is 30μm polyimide, the middle layer is 20μm aluminum nitride coating, and the top layer is 20μm polyimide; Preferably, the contact layer is a platinum-plated stainless steel mesh that directly contacts the slurry. Its conductivity transmits the electric field, and the platinum layer reduces the contact resistance. The thickness is preferably 0.03 mm, and the aperture is preferably 0.5 mm.

7. The method according to claim 1, characterized in that, The electrode layer is a photolithographic copper foil with a thickness of 0.05 mm and has three functional zones. The electric field gradient is achieved through the differentiation of a single electrode layer, without the need for independent circuit control; Deep cavity region: comb tooth density 120 lines / cm 2 With a line width of 0.3 mm and a spacing of 0.5 mm, the local electric field strength is increased to 15-18 kV / m by increasing the electrode edge length, compensating for fiber settling caused by gravity and ensuring sufficient adsorption force at the bottom of the deep cavity; Planar area: mesh density 80 lines / cm 2 The standard grid electrode has a pore size of 1mm and maintains an electric field strength of 8-10 kV / m to balance energy consumption and adsorption requirements. The edge region has a ring-shaped closed-loop electrode with a width of 5mm and an electric field strength of 12 kV / m to close the electric field lines and prevent thickness attenuation caused by boundary effects.

8. The method according to claim 1, characterized in that, The shell material of the pH-responsive microcapsule mentioned in step 1.3 is chitosan, and the core material contains the anionic dispersant and nano-bentonite, which can release the contents by breaking the shell at pH=8.

5.

9. The method according to claim 1, characterized in that, The pH-responsive microcapsules described in step 1.3 are injected into the slurry tank before the electrostatic field of the molding die is activated, and the pH value of the slurry is adjusted to 8.5±0.1 with NaOH aqueous solution under stirring conditions.

10. The method according to claim 1, characterized in that, In step 2, the slurry temperature is maintained at 55±2℃ and the viscosity is controlled at 120±20mPa·s.

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