Process for producing high density fiberboard for shoe heels

Abstract

The application provides a high-density fiberboard production process for shoe heels, comprising the following steps: S1, slicing; S2, screening; S3, biological activation; S4, separating fibers; S5, drying; S6, winnowing; S7, gluing; S8, adding; S9, paving; S10, pre-pressing; S11, hot-pressing; S12, post-processing; S13, cooling; S14, trimming; S15, curing; S16, cutting; and S17, grading and packaging. The high-density fiberboard production process for shoe heels creates an active site for subsequent formaldehyde-free self-adhesion by initiating a biological activation path, fundamentally changes the reactivity of raw materials, replaces pure physical heat softening, saves energy, improves the fiber bonding potential, and guarantees the performance of the high-density fiberboard.

Description

Technical Field

[0001] This invention relates to the field of high-density fiberboard production technology, and specifically to a production process for high-density fiberboard for shoe heels. Background Technology

[0002] High-density fiberboard (HDF) for shoe heels is a high-density composite board made from wood fiber, plant fiber, or recycled pulp, pressed under high temperature and pressure with special adhesives. Its density is much higher than that of ordinary fiberboard, so it has a compact structure, high hardness, and is not easily deformed. It is the main supporting structure inside the shoe heel and is made up of one or more HDF boards spliced / laminated together to form the basic shape and mechanical structure of the shoe heel. Therefore, it is particularly important to adopt a suitable hot-pressing process in the production of HDF for shoe heels.

[0003] The existing production process of high-density fiberboard for shoe heels mostly involves raw material preparation and fiber separation, performance imparting and molding, laying and hot pressing curing, and post-treatment and stabilization. The production of high-density fiberboard for shoe heels is achieved through shaving, screening, cooking, hot grinding, drying, air separation, gluing, moisture-proofing and flame-retardant additives, laying, pre-pressing, hot pressing, cooling, post-treatment, curing and sawing, as well as grading and packaging. However, in actual use, pre-cooking and cooking are only physical softening. After softening, the raw material has poor reactivity and the fiber performance is not fully utilized. Summary of the Invention

[0004] In view of this, the present invention addresses the shortcomings of the prior art by providing a production process for high-density fiberboard for shoe heels. By creating a bio-activation pathway, it creates active sites for subsequent formaldehyde-free self-adhesive bonding, fundamentally changing the reactivity of raw materials, replacing pure physical thermal softening, saving energy and improving fiber bonding potential, and ensuring the performance of high-density fiberboard.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a manufacturing process for high-density fiberboard for shoe heels, comprising the following steps:

[0006] S1, chipping: the standardized cutting of raw materials (wood, plant fibers, etc.); S2, screening: removing impurities such as bark and mud; S3, Bioactivation: The chipped raw material is fed into a closed bioreactor, and a compound enzyme is used to activate the lignin and open up the fiber structure. S4, Fiber separation: The fiber is fed into the steam pressure burst chamber, causing the fiber to burst and separate from the cell level under instantaneous pressure relief; S5, Drying: Rapidly reduce the moisture content of the wet fibers to a suitable range for sizing. S6, air separation: removes excessively coarse or fine fiber clumps to ensure uniform fiber shape; S7, Sizing: In the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization to synthesize a bio-based polymer adhesive layer on the fiber surface in situ. S8, Added: The fiber is passed through an electrostatic atomization chamber, where positively charged nano-alumina and silica composite sol (which has both hardness and flame retardancy) is uniformly adsorbed onto the negatively charged fiber surface, forming a nanoscale coating. S9, Paving: A high-intensity directional electric field is applied to the paving line, causing the burst fibers with excellent aspect ratio to align in a direction along the length of the slab (the direction of force on the future heel) under the action of the electric field. S10, Pre-compression: Initial compression of the slab to expel air and increase density and initial strength; S11, hot pressing: the slab is subjected to five-stage high temperature and high pressure, and the temperature of each stage is independently controllable. The temperature gradient is 230℃→210℃→190℃→180℃→170℃. S12, Post-processing: After the sheet material exits the continuous press, it immediately passes through the liquid nitrogen atomization quenching section to lock the molecular chain morphology, and then enters the ultrasonic stress relief field to eliminate internal residual stress using high-frequency mechanical waves. S13, Cooling board: The high-temperature board material after hot pressing is cooled on a cooling board rack to reduce its temperature to room temperature; S14, Trimming: Trimming rough edges, stacking, preparing for health preservation; S15, Curing: The board is left to stand for more than 48 hours in a selected temperature and humidity environment to allow the internal stress to be fully released and the residual formaldehyde and moisture to further evaporate, so that the performance of the board (especially the dimensional stability) tends to be completely stable. S16, Cutting: Cut the large plate into specifications that are easy to machine later, according to the size required for shoe heel production; S17, Graded Packaging: Strict quality inspection is carried out to remove defective products with delamination, uneven density, thickness exceeding tolerance, or surface defects.

[0007] As a further improvement of the present invention, the closed bioreactor in step S3 is equipped with a stirrer, jacket temperature control, online pH monitoring, constant temperature storage tank, high-precision metering pump, atomizing nozzle and controllable hot and humid air circulation system. A compound enzyme is selected, mainly including laccase or lignin peroxidase for activating lignin, and hemicellulase for opening the fiber structure. The temperature in the reaction chamber is controlled at 45-60℃, the pH value is 4.5-5.5 (depending on the enzyme), the treatment time is 30-90 minutes, and the humidity is kept at a high level to keep the moisture content of the wood chips at 50-60%.

[0008] As a further improvement of the present invention, the steam pressure-maintaining and bursting chamber in step S4 includes a high-pressure steam generator, a pressure-maintaining and bursting chamber, an instantaneous pressure relief valve (burst valve), and a fiber receiving chamber. The steam pressure is controlled at 1.2-2.0 MPa, and the pressure-maintaining time is 30-180 seconds. A trace amount of acetic anhydride vapor (or other acetylation reagent) is added to the steam to perform in-situ acetylation of the fiber under high temperature and pressure, replacing the cellulose hydroxyl groups and achieving intrinsic hydrophobicity. After bursting, the fiber yield (length greater than 0.2 mm) is above 85%, and the separated fiber bundles are naturally fluffy with no obviously coarse fiber bundles. The hydrophobic modification goal is to make the fiber contact angle greater than 90 degrees.

[0009] As a further improvement of the present invention, the drying pipe in step S7 is a pulsed airflow drying pipe with a long pipe and a specific turbulence zone. The atomization spraying system includes two constant temperature storage tanks, a servo-driven linkage metering pump, a static mixer, and a high-temperature and high-pressure resistant ultrasonic atomizing nozzle array. The spraying material is formed by online mixing of bio-based polyols (such as lignin pyrolysis products, cashew phenol derivatives, etc.) and natural acid catalysts (such as citric acid, itaconic acid) at a weight ratio of 100:(3-10). In the middle section of the drying pipe, the fiber temperature is 100-120°C and the atomization spraying is carried out. The spraying amount accounts for 8-15% of the weight of the oven-dry fiber. The atomized particle size is required to be less than 50 micrometers. The temperature in the latter part of the pipe is increased to 140-160°C and the fiber residence time is extended by 20-30 seconds to promote the rapid occurrence of esterification / etherification reaction and form a uniform bio-based polymer film on the fiber surface.

[0010] As a further improvement of the present invention, in step S8, a cationic nano-alumina / silica composite sol is used with a solid content of 10-20%, a pH value adjusted to acidic (3-5), and a particle size of less than 50 nm. In the electrostatic atomization deposition chamber, the fibers are negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The fibers pass through in a loose state to ensure that the nanoparticles are uniformly and firmly adsorbed on the fiber surface under the action of Coulomb force. The amount of nano-ceramic added is 1-3% of the weight of the oven-dry fiber, with the goal of forming a dense nanoscale coating on the fiber surface.

[0011] As a further improvement of the present invention, the laying machine in step S9 is an electrostatic directional laying machine. A set of parallel plates with tens of thousands of volts DC voltage applied are installed below the laying head of the electrostatic directional laying machine to ensure that the fibers entering the electric field area are in a single layer and uniformly dispersed state. The target density of the board should be controlled at 0.6-0.75 g / cm³ (leaving space for subsequent hot pressing), so that more than 60% of the long fibers in the board are arranged along the machine direction (i.e., the main force direction of the future heel).

[0012] As a further improvement of the present invention, the hot press in step S10 is an integrated microwave continuous hot press, the microwave parameters are 2450MHz or 915MHz industrial frequency band, the temperature difference between the core layer and the surface layer of the board is controlled to be less than 10℃, the degree of curing of the adhesive is greater than 95%, and the density reaches the requirement of 0.9-1.0 g / cm³ or higher for shoe heels.

[0013] As a further improvement of the present invention, in step S12, the liquid nitrogen atomization jet tunnel is located at the press outlet, and the inner wall of the tunnel is covered with liquid nitrogen nozzles. After the plate comes out of the hot press (about 100°C), it is uniformly cooled to below 30°C within 60 seconds in the liquid nitrogen tunnel. The cooling rate needs to be greater than 1°C / second to freeze the molecular chain structure. The cooled plate immediately enters the ultrasonic table and is treated with a sound intensity of 0.5-1.0 per square centimeter within 1-2 minutes. The ultrasonic waves break the residual internal stress chains inside the plate.

[0014] In summary, this application has at least one of the following beneficial technical effects compared with the prior art: Firstly, the raw material is bio-activated pretreatment: after chipping, the wood chips are treated with a specific compound bio-enzyme preparation under mild conditions. The enzyme selectively partially decomposes lignin and hemicellulose, exposing more active hydroxyl groups and phenolic groups, and generating a large number of micropores. Subsequently, formaldehyde-free self-adhesive creates active sites, fundamentally changing the reactivity of the raw material, replacing pure physical heat softening, saving energy and enhancing fiber bonding potential.

[0015] Secondly, steam explosion fiber separation and modification: Bio-activated wood chips are placed in a steam explosion device, where instantaneous pressure release causes the fibers to "explode" and separate at the cellular level. This process not only has low energy consumption but also preserves fiber length well, significantly increasing specific surface area. The explosion process simultaneously achieves fiber acetylation modification, improving hydrophobicity. This integrated separation and modification, replacing thermal grinding with steam explosion, completes separation and moisture-proof chemical modification simultaneously, achieving intrinsic fiber moisture resistance without the need for subsequent paraffin addition.

[0016] Third, in-situ catalytic self-adhesive synthesis: when the burst fiber enters the drying tube, a mixture of bio-based polyol and natural acid catalyst is injected by atomization. At the drying temperature, they react with the active groups on the fiber surface that have been bio-activated and exposed by the burst to undergo esterification and etherification reactions, synthesizing a bio-based polymer adhesive layer on the fiber surface in situ. The adhesive substance is generated by reacting the fiber's own components with the bio-based reagent, which is environmentally friendly and healthy.

[0017] Fourth, nano-ceramic reinforcing agent aerosol deposition: Before installation, the fibers are passed through an electrostatic atomization chamber, where positively charged nano-alumina / silica composite sol (which combines hardness and flame retardancy) is uniformly adsorbed onto the negatively charged fiber surface, forming a nanoscale coating and enhancing the nanoscale structure. This upgrades the functional additive from "physical doping" to a nano-coating that combines "chemical bonding and physical adsorption," significantly improving the board's hardness, wear resistance (crucial for shoe heels), and permanent flame retardant effect.

[0018] Fifth, electrostatic directional fiber laying: A high-intensity directional electric field is applied to the laying line. Under the action of the electric field, most of the burst fibers with excellent aspect ratio are oriented along the length of the board (the direction of force on the future heel); the structure is biomimetic, mimicking the fiber orientation of natural wood, so that the board has extremely high bending strength in the direction of the grain, allowing the use of lower density boards to achieve the same heel strength requirements, thus achieving lightweighting.

[0019] Sixth, instantaneous cooling and stress relief: After the sheet material leaves the continuous press, it immediately passes through the liquid nitrogen atomization quenching section (reducing from 100°C to 30°C within 60 seconds) to lock the molecular chain morphology, and then enters the ultrasonic stress relief field to eliminate internal residual stress within 1 minute using high-frequency mechanical waves; active stress management. Attached Figure Description

[0020] Figure 1 This is a flowchart of the production method of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, a manufacturing process for high-density fiberboard (HDF) for shoe heels includes the following steps: S1, chipping: the standardized cutting of raw materials (wood, plant fibers, etc.); S2, screening: removing impurities such as bark and mud; S3, Bioactivation: The chipped raw material is fed into a closed bioreactor, and a compound enzyme is used to activate the lignin and open up the fiber structure. S4, Fiber separation: The fiber is fed into the steam pressure burst chamber, causing the fiber to burst and separate from the cell level under instantaneous pressure relief; S5, Drying: Rapidly reduce the moisture content of the wet fibers to a suitable range for sizing. S6, air separation: removes excessively coarse or fine fiber clumps to ensure uniform fiber shape; S7, Sizing: In the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization to synthesize a bio-based polymer adhesive layer on the fiber surface in situ. S8, Added: The fiber is passed through an electrostatic atomization chamber, where positively charged nano-alumina and silica composite sol (which has both hardness and flame retardancy) is uniformly adsorbed onto the negatively charged fiber surface, forming a nanoscale coating. S9, Paving: A high-intensity directional electric field is applied to the paving line, causing the burst fibers with excellent aspect ratio to align in a direction along the length of the slab (the direction of force on the future heel) under the action of the electric field. S10, Pre-compression: Initial compression of the slab to expel air and increase density and initial strength; S11, hot pressing: the slab is subjected to five-stage high temperature and high pressure, and the temperature of each stage is independently controllable. The temperature gradient is 230℃→210℃→190℃→180℃→170℃. S12, Post-processing: After the sheet material exits the continuous press, it immediately passes through the liquid nitrogen atomization quenching section to lock the molecular chain morphology, and then enters the ultrasonic stress relief field to eliminate internal residual stress using high-frequency mechanical waves. S13, Cooling board: The high-temperature board material after hot pressing is cooled on a cooling board rack to reduce its temperature to room temperature; S14, Trimming: Trimming rough edges, stacking, preparing for health preservation; S15, Curing: The board is left to stand for more than 48 hours in a selected temperature and humidity environment to allow the internal stress to be fully released and the residual formaldehyde and moisture to further evaporate, so that the performance of the board (especially the dimensional stability) tends to be completely stable. S16, Cutting: Cut the large plate into specifications that are easy to machine later, according to the size required for shoe heel production; S17, Graded Packaging: Strict quality inspection is carried out to remove defective products with delamination, uneven density, thickness exceeding tolerance, or surface defects.

[0023] The closed bioreactor in step S3 is equipped with a stirrer, jacket temperature control, online pH monitoring, constant temperature storage tank, high-precision metering pump, atomizing nozzle, and controllable hot and humid air circulation system. A compound enzyme is selected, mainly including laccase or lignin peroxidase to activate lignin, and hemicellulase to open the fiber structure. The temperature in the reaction chamber is controlled at 45-60℃, the pH value is 4.5-5.5 (depending on the enzyme), the treatment time is 30-90 minutes, and the humidity is kept high to keep the moisture content of the wood chips at 50-60%.

[0024] The steam pressure-maintaining and bursting chamber in step S4 includes a high-pressure steam generator, a pressure-maintaining and bursting chamber, an instantaneous pressure relief valve (burst valve), and a fiber receiving chamber. The steam pressure is controlled at 1.2-2.0 MPa, and the pressure maintenance time is 30-180 seconds. A trace amount of acetic anhydride vapor (or other acetylation reagent) is added to the steam to perform in-situ acetylation of the fiber under high temperature and pressure, replacing the cellulose hydroxyl groups to achieve intrinsic hydrophobicity. After bursting, the fiber yield (length greater than 0.2 mm) is above 85%, and the separated fiber bundles are naturally fluffy with no obviously coarse fiber bundles. The hydrophobic modification target is to make the fiber contact angle greater than 90 degrees.

[0025] In step S7, a pulsed airflow drying pipe is used, featuring a long pipe and a specific turbulence zone. The atomization spraying system includes two constant-temperature storage tanks, a servo-driven metering pump, a static mixer, and a high-temperature, high-pressure resistant ultrasonic atomizing nozzle array. The spraying material is formed by online mixing of bio-based polyols (such as lignin pyrolysis products, cashew phenol derivatives, etc.) and natural acid catalysts (such as citric acid, itaconic acid) at a weight ratio of 100:(3-10). Atomization spraying is performed in the middle section of the drying pipe, where the fiber temperature is between 100-120℃. The spraying amount accounts for 8-15% of the oven-dry fiber weight. The atomized particle size is required to be less than 50 micrometers. The temperature in the latter part of the pipe is increased to 140-160℃, and the fiber residence time is extended by 20-30 seconds to promote rapid esterification / etherification reactions, forming a uniform bio-based polymer film on the fiber surface.

[0026] In step S8, a cationic nano-alumina / silica composite sol with a solid content of 10-20% and a pH value adjusted to acidic (3-5) is used. The particle size is less than 50nm. In the electrostatic atomization deposition chamber, the fibers are negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The fibers pass through in a loose state to ensure that the nanoparticles are uniformly and firmly adsorbed on the fiber surface under the action of Coulomb force. The amount of nano-ceramic added is 1-3% of the weight of the oven-dry fiber. The goal is to form a dense nanoscale coating on the fiber surface.

[0027] In step S9, an electrostatic directional paving machine is selected. A set of parallel plates with tens of thousands of volts DC voltage are installed below the paving head of the electrostatic directional paving machine to ensure that the fibers entering the electric field area are in a single layer and uniformly dispersed state. The target density of the slab should be controlled at 0.6-0.75 g / cm³ (leaving room for subsequent hot pressing), so that more than 60% of the long fibers in the slab are arranged along the machine direction (i.e., the main force direction of the future heel).

[0028] In step S10, an integrated microwave continuous hot press is selected as the hot press. The microwave parameters are 2450MHz or 915MHz industrial frequency band. The temperature difference between the core layer and the surface layer of the board is controlled to be less than 10℃, the adhesive curing degree is greater than 95%, and the density reaches the requirement of 0.9-1.0 g / cm³ or higher for shoe heels.

[0029] In step S12, the liquid nitrogen atomization jet tunnel is located at the press outlet. The inner wall of the tunnel is covered with liquid nitrogen nozzles. After the plate comes out of the hot press (about 100°C), it is uniformly cooled to below 30°C within 60 seconds in the liquid nitrogen tunnel. The cooling rate needs to be greater than 1°C / second to freeze the molecular chain structure. The cooled plate immediately enters the ultrasonic table and is treated with a sound intensity of 0.5-1.0 per square centimeter within 1-2 minutes. The ultrasonic waves break the residual internal stress chains inside the plate.

[0030] The production process for high-density fiberboard used in shoe heels is as follows: S1, chipping: The raw materials (wood, plant fibers, etc.) are cut in a standardized manner to ensure uniform subsequent processing. High moisture content helps with subsequent softening. S2, Screening: Remove impurities such as bark and sand. These impurities will significantly reduce the purity, uniformity and final strength of the board, and are a major enemy of shoe heel quality. S3, Bioactivation: The chipped raw material is fed into a closed bioreactor. A compound enzyme is selected, mainly including laccase or lignin peroxidase to activate lignin, and hemicellulase to open the fiber structure. The temperature in the reaction chamber is controlled at 45-60℃, the pH value at 4.5-5.5 (depending on the enzyme), the treatment time is 30-90 minutes, and the humidity is kept high to keep the moisture content of the wood chips at 50-60%, so as to achieve the "activation" of the fiber rather than deep degradation. The treated wood chips should retain their original shape, but the color will be darker and the feel will be softer. S4, Fiber Separation: The fiber is fed into a steam pressure bursting chamber, where it is instantly depressurized and separated from the cell level. This process is energy-efficient, preserves fiber length well, and significantly increases specific surface area. The bursting process simultaneously achieves fiber acetylation modification, enhancing hydrophobicity. Steam pressure is controlled at 1.2-2.0 MPa, and pressure time is 30-180 seconds. Specific parameters are optimized based on the type of raw material and the degree of "activation." A trace amount of acetic anhydride vapor (or other acetylation reagents) is added to the steam, and the fiber is in-situ acetylated under high temperature and pressure to replace the cellulose hydroxyl groups, achieving intrinsic hydrophobicity. After bursting, the fiber yield (length > 0.2 mm) is above 85%, and the separated fiber bundles are naturally fluffy with no obviously large fiber bundles. The hydrophobic modification target is to make the fiber contact angle greater than 90 degrees. S5, Drying: Rapidly reduce the moisture content of the wet fibers to a suitable range for sizing. S6, air separation: removes excessively coarse or fine fiber clumps to ensure uniform fiber shape; S7, Sizing: In the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization to synthesize a bio-based polymer adhesive layer on the fiber surface in situ. At the drying temperature, they undergo esterification and etherification reactions with the active groups on the fiber surface that have been bio-activated and exposed by explosion, and synthesize a bio-based polymer adhesive layer on the fiber surface in situ. S8, Added: The fiber is passed through an electrostatic atomization chamber, where positively charged nano-alumina and silica composite sol (which has both hardness and flame retardancy) is uniformly adsorbed onto the negatively charged fiber surface to form a nanoscale coating. In the deposition chamber, the fiber is negatively charged through corona discharge, and the nano-sol becomes positively charged after atomization. The fiber passes through in a loose state, ensuring that the nanoparticles are uniformly and firmly adsorbed onto the fiber surface under the action of Coulomb force. S9, Laying: A high-intensity directional electric field is applied to the laying line, causing the burst fibers with excellent aspect ratio to align along the length of the board (the future force direction of the heel) under the action of the electric field. The laying speed and fiber flow rate need to be precisely matched to prevent fiber accumulation from affecting the electric field. This ensures that more than 60% of the long fibers in the board are aligned along the machine direction (i.e., the main force direction of the future heel). The degree of orientation can be evaluated online through image analysis technology. S10, Pre-compression: Initial compression of the slab to expel air and increase density and initial strength; S11, Hot Pressing: The slab undergoes five-stage high-temperature and high-pressure treatment, with each stage having an independently controllable temperature. The temperature gradient is 230℃→210℃→190℃→180℃→170℃. The integrated microwave continuous hot press consists of a steel belt conveyor system, a multi-section adjustable pressure frame, and a microwave generator array (magnetron or solid-state microwave source) integrated within the pressure frame. Under the combined action of pressure (5-15 MPa) and microwaves, the total hot pressing time can be shortened to 5-8 minutes per sheet (for continuous production at a certain speed). S12, Post-processing: After the sheet material exits the continuous press, it immediately passes through the liquid nitrogen atomization quenching section to lock the molecular chain morphology. Then it enters the ultrasonic stress relief field, where high-frequency mechanical waves are used to eliminate internal residual stress. After exiting the press (approximately 100°C), the sheet material is uniformly cooled to below 30°C within 60 seconds in the liquid nitrogen tunnel. The cooling rate must be greater than 1°C / second to "freeze" the molecular chain structure and achieve cooling. The cooled sheet material immediately enters the ultrasonic stage and is treated with a sound intensity of 0.5-1.0 per square centimeter within 1-2 minutes. The ultrasonic waves generate a microscopic "massage" effect inside the sheet material, breaking the residual internal stress chains. S13, Cooling board: The high-temperature board material after hot pressing is cooled on a cooling board rack to reduce its temperature to room temperature; S14, Trimming: Trimming rough edges, stacking, preparing for health preservation; S15, Curing: The board is left to stand for more than 48 hours in a selected temperature and humidity environment to allow the internal stress to be fully released and the residual formaldehyde and moisture to further evaporate, so that the performance of the board (especially the dimensional stability) tends to be completely stable. S16, Cutting: Cut the large board into specifications that are easy to machine after the shoe heel production according to the required size. Based on the shoe heel factory's order (heel type, height) and the board quality map, plan the optimal cutting scheme to maximize the yield and supply the board directly to the corresponding production line according to the performance grade. S17, graded packaging: Strict quality inspection is carried out to remove defective products with delamination, uneven density, thickness exceeding tolerance, and surface defects. Through high-speed line scan camera and X-ray tomography, 100% of the internal density distribution, minor defects and fiber orientation are detected.

[0031] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 manufacturing process for high-density fiberboard for shoe heels, characterized in that: Includes the following steps: S1, chipping: the raw material is cut into standardized pieces; S2, Screening: Remove bark, mud and sand impurities; S3, Bioactivation: The chipped raw material is fed into a closed bioreactor, and a compound enzyme is used to activate the lignin and open up the fiber structure. S4, Fiber separation: The fiber is fed into the steam pressure burst chamber, causing the fiber to burst and separate from the cell level under instantaneous pressure relief; S5, Drying: Rapidly reduce the moisture content of the wet fibers to a suitable range for sizing. S6, air separation: removes excessively coarse or fine fiber clumps to ensure uniform fiber shape; S7, Sizing: In the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization to synthesize a bio-based polymer adhesive layer on the fiber surface in situ. S8, Added: The fiber is passed through an electrostatic atomization chamber, where positively charged nano-alumina and silica composite sol are uniformly adsorbed onto the negatively charged fiber surface, forming a nanoscale coating. S9, Paving: A high-intensity directional electric field is applied to the paving line, causing the burst fibers with excellent aspect ratio to be oriented along the length of the slab under the action of the electric field; S10, Pre-compression: Initial compression of the slab to expel air and increase density and initial strength; S11, hot pressing: the slab is subjected to five-stage high temperature and high pressure, and the temperature of each stage is independently controllable. The temperature gradient is 230℃→210℃→190℃→180℃→170℃. S12, Post-processing: After the sheet material exits the continuous press, it immediately passes through the liquid nitrogen atomization quenching section to lock the molecular chain morphology, and then enters the ultrasonic stress relief field to eliminate internal residual stress using high-frequency mechanical waves. S13, Cooling board: The high-temperature board material after hot pressing is cooled on a cooling board rack to reduce its temperature to room temperature; S14, Trimming: Trimming rough edges, stacking, preparing for health preservation; S15, Curing: The board is left to stand for more than 48 hours in a set temperature and humidity environment to allow the internal stress to be fully released and the residual formaldehyde and moisture to further evaporate, so that the performance of the board tends to be completely stable. S16, Cutting: Cut the large plate into specifications that are easy to machine later, according to the size required for shoe heel production; S17, Graded Packaging: Strict quality inspection is carried out to remove defective products with delamination, uneven density, thickness exceeding tolerance, or surface defects.

2. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: The closed bioreactor in step S3 is equipped with a stirrer, jacket temperature control, online pH monitoring, constant temperature storage tank, high-precision metering pump, atomizing nozzle, and controllable hot and humid air circulation system. A compound enzyme is selected, mainly including laccase or lignin peroxidase to activate lignin, and hemicellulase to open the fiber structure. The temperature in the reaction chamber is controlled at 45-60℃, the pH value at 4.5-5.5, the treatment time at 30-90 minutes, and the humidity is kept at a high level to keep the moisture content of the wood chips at 50-60%.

3. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: The steam pressure-maintaining explosion chamber in step S4 includes a high-pressure steam generator, a pressure-maintaining explosion chamber, an instantaneous pressure relief valve, and a fiber receiving chamber. The steam pressure is controlled at 1.2-2.0 MPa, and the pressure maintenance time is 30-180 seconds. A trace amount of acetic anhydride vapor is added to the steam, and the fiber is acetylated in situ under high temperature and high pressure to replace the cellulose hydroxyl groups and achieve intrinsic hydrophobicity. After explosion, the fiber yield is above 85%, and the separated fiber bundles are naturally fluffy with no obvious coarse fiber bundles. The hydrophobic modification target is to make the fiber contact angle greater than 90 degrees.

4. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: In step S7, a pulsed airflow drying pipe is selected, which has a long pipe and is designed with a turbulent zone. The atomization spraying system includes two constant temperature storage tanks, a servo-driven linkage metering pump, a static mixer, and a high-temperature and high-pressure resistant ultrasonic atomizing nozzle array. The spraying material is formed by online mixing of bio-based polyol and natural acid catalyst in a weight ratio. In the middle section of the drying pipe, the fiber temperature is in the range of 100-120℃, and the spraying amount accounts for 8-15% of the weight of the oven-dry fiber. The atomized particle size is required to be less than 50 micrometers. The temperature in the latter part of the pipe is increased to 140-160℃, and the fiber residence time is extended by 20-30 seconds to promote the rapid occurrence of esterification / etherification reaction and form a uniform bio-based polymer film on the fiber surface.

5. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: In step S8, a cationic nano-alumina / silica composite sol with a solid content of 10-20%, pH adjusted to acidic, and particle size less than 50 nm is used. In the electrostatic atomization deposition chamber, the fibers are negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The fibers pass through in a loose state to ensure that the nanoparticles are uniformly and firmly adsorbed on the fiber surface under the action of Coulomb force. The amount of cationic nano-alumina / silica composite sol added is 1-3% of the oven-dry fiber weight, and the goal is to form a dense nanoscale coating on the fiber surface.

6. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: In step S9, an electrostatic directional paving machine is selected. A set of parallel plates with tens of thousands of volts DC voltage are installed below the paving head of the electrostatic directional paving machine to ensure that the fibers entering the electric field area are in a single layer and uniformly dispersed state. The target density of the slab should be controlled at 0.6-0.75 g / cm³, so that more than 60% of the long fibers in the slab are arranged along the main force direction of the future heel.

7. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: In step S10, an integrated microwave continuous hot press is selected as the hot press. The microwave parameters are 2450MHz or 915MHz industrial frequency band. The temperature difference between the core layer and the surface layer of the board is controlled to be less than 10℃, the adhesive curing degree is greater than 95%, and the density reaches the requirement of 0.9-1.0 g / cm³ or higher for shoe heels.

8. The manufacturing process of high-density fiberboard for shoe heels as described in claim 1, characterized in that: In step S12, the liquid nitrogen atomization jet tunnel is located at the press outlet. The inner wall of the tunnel is covered with liquid nitrogen nozzles. After the plate comes out of the hot press, it is uniformly cooled to below 30°C within 60 seconds in the liquid nitrogen tunnel. The cooling rate needs to be greater than 1°C / second to freeze the molecular chain structure. The cooled plate immediately enters the ultrasonic table, where the ultrasonic waves break the residual internal stress chains inside the plate.

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