Production process of high-density fiberboard for heels

Abstract

The invention provides a production process of a high-density fiberboard for heels. The production process comprises the following steps: S1, chipping; s2, screening is carried out; s3, biological activation; s4, separating fibers; s5, drying; s6, winnowing is conducted; s7, sizing is conducted; s8, adding; s9, paving is conducted; s10, prepressing is carried out; s11, hot pressing; s12, carrying out post-treatment; s13, cooling the plate; s14, finishing is conducted; s15, carrying out health maintenance; s16, cutting is carried out; and S17, grading and packaging. According to the production process of the high-density fiberboard for the heel, a biological activation path is created, active sites are created for subsequent formaldehyde-free self-adhesion, the reaction activity of raw materials is changed fundamentally, pure physical thermal softening is replaced, energy is saved, the fiber binding potential is improved, and the performance of the high-density fiberboard is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-density fiberboard production, in particular to a production process of high-density fiberboard for shoe heels. BACKGROUND

[0002] The high-density fiberboard for shoe heels is a high-density composite board made of wood fiber, plant fiber or recycled pulp, pressed by high temperature and pressure and special adhesive, with density much higher than ordinary fiberboard, so it is compact in structure, high in hardness and not easy to deform. It is the main support inside the shoe heel and is composed of one or several high-density fiberboards spliced / laminated to form the basic shape and mechanical structure of the shoe heel. Therefore, it is particularly important to adopt a suitable hot pressing forming process in the production of high-density fiberboard for shoe heels.

[0003] The existing production process of high-density fiberboard for shoe heels mainly includes raw material preparation, fiber separation, performance imparting, forming, paving, heat curing, post-processing and stabilization, etc. The production of high-density fiberboard for shoe heels is realized by means of slicing, screening, cooking, hot grinding, drying, air selection, gluing, moisture-proof and flame-retardant addition, paving, pre-pressing, hot pressing, cooling, post-processing, curing and sawing and grading packaging. However, in actual use, the pre-cooking and cooking are only physical softening, and after softening, the raw material has poor reactivity and the fiber performance is not fully developed. SUMMARY

[0004] Therefore, the present application provides a production process of high-density fiberboard for shoe heels, which creates active sites for subsequent formaldehyde-free self-adhesion by creating a biological activation path, fundamentally changes the reactivity of raw materials, replaces pure physical thermal softening, saves energy, improves fiber bonding potential and ensures the performance of high-density fiberboard.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a production process of high-density fiberboard for shoe heels, comprising the following steps: S1, slicing: the raw materials (wood, plant fiber, etc.) are cut into standard pieces; S2, screening: removing impurities such as bark and sand; S3, biological activation: the sliced raw materials are sent into a closed bioreactor, composite enzymes are selected to activate lignin and open the fiber structure; S4, fiber separation: the fibers are sent into a steam pressure explosion bin to be separated from the cell layer in an instant pressure relief; S5, drying: the moisture content of the wet fibers is rapidly reduced to a suitable range for gluing; S6, air selection: removing coarse or fine fiber groups to ensure uniform fiber morphology; S7, sizing: in the drying pipeline, atomized injection of a mixture of bio-based polyol and natural acid catalyst, in-situ synthesis of a layer of bio-based polymer sizing on the fiber surface; S8, adding: passing the fiber through an electrostatic atomizing chamber, positively charged nano-alumina and silica composite sol (with hardness and flame retardancy) is uniformly adsorbed to the negatively charged fiber surface, forming a nanoscale coating; S9, paving: applying a high-strength directional electric field on the paving line, so that the long-diameter ratio of the blasting fiber is excellent, and the blasting fiber is arranged in the length direction of the mat (the stress direction of the future shoe heel) under the action of the electric field; S10, pre-pressing: preliminary compression of the mat, air discharge, density increase and initial strength increase; S11, hot pressing: five-stage high temperature and high pressure for the mat, each stage temperature is independently controllable, and the temperature gradient is 230℃→210℃→190℃→180℃→170℃ in turn; S12, post-processing: after the plate material comes out of the continuous press, it immediately passes through the liquid nitrogen atomizing quenching section to lock the molecular chain form, and then enters the ultrasonic stress dissipation field to eliminate the internal residual stress by using high-frequency mechanical waves; S13, cooling plate: cooling the high-temperature plate after hot pressing on the cooling plate rack to reduce the temperature to room temperature; S14, trimming: cutting the edge, stacking, and preparing for aging; S15, aging: placing the plate in a specific temperature and humidity environment for more than 48 hours to fully release the internal stress, further volatilize the residual formaldehyde and water, and make the performance of the plate (especially the dimensional stability) tend to be completely stable; S16, cutting: cutting the large plate into a size convenient for subsequent turning according to the required size of the shoe heel production; S17, grading packaging: strict quality inspection, and removing the substandard products with delamination, uneven density, thickness out-of-tolerance, and surface defects.

[0006] As a further improvement of the application, the closed bioreactor in step S3 is provided with a stirrer, a jacket temperature control, an on-line pH monitoring, a constant temperature storage tank, a high-precision metering pump, an atomizing nozzle and a controllable humidified air circulation system. Composite enzymes are selected, mainly including laccase or lignin peroxidase for activating lignin, and hemicellulase for opening the fiber structure. The temperature in the reaction bin is controlled at 45-60℃, the pH value is 4.5-5.5 (depending on the enzyme species), the treatment time is 30-90 minutes, and the humidity is kept at a high level, so that the moisture content of the wood chips is maintained at 50-60%.

[0007] As a further improvement of the present application, the steam pressure maintaining explosion bin in step S4 includes a high-pressure steam generator, a pressure maintaining explosion bin, an instantaneous pressure relief valve (explosion valve) and a fiber receiving bin. The steam pressure is controlled at 1.2-2.0 MPa, the pressure maintaining time is 30-180 seconds, a small amount of acetic anhydride steam (or other acetylating reagent) is added in the steam, the fiber is in-situ acetylated at high temperature and high pressure, the hydroxyl group of the cellulose is replaced, the intrinsic hydrophobicity is realized, the fiber yield (length greater than 0.2 mm) of the fiber after explosion is more than 85%, and the separated fiber bundle is naturally fluffy without obvious thick fiber bundle. The hydrophobic modification target is to make the contact angle of the fiber greater than 90 degrees.

[0008] As a further improvement of the present application, the drying pipe in step S7 selects a pulse air flow drying pipe with a long pipe and a specific turbulent flow area. The atomizing 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. Bio-based polyols (such as lignin cracking products, cashew phenolic derivatives, etc.) and environmentally friendly natural acid catalysts (such as citric acid, itaconic acid) are mixed online at a weight ratio of 100:(3-10) to form a spraying material. The fiber temperature is in the interval of 100-120℃ in the middle section of the drying pipe, and the spraying amount accounts for 8-15% of the weight of the absolutely dry fiber. The atomized particle size is required to be less than 50 microns. The temperature of the rear section of the pipe is increased to 140-160℃, and the fiber residence time is extended to 20-30 seconds, so as to promote the rapid occurrence of esterification / etherification reaction and form a uniform bio-based polymer film on the surface of the fiber.

[0009] As a further improvement of the present application, the cationic nano-alumina / silica composite sol is used in step S8, the solid content is 10-20%, the pH value is adjusted to be acidic (3-5), the particle size is less than 50 nm, the fiber is negatively charged by corona discharge in the electrostatic atomization deposition chamber, the nano-sol is positively charged after atomization, and the electric field strength is controlled at 30-80 per meter potential difference; the fiber passes through in a loose state, so as to ensure that the nano-particles are uniformly and firmly adsorbed on the surface of the fiber under the action of coulomb force, and the nano-ceramic addition amount is 1-3% of the weight of the absolutely dry fiber, so as to form a dense nano-scale coating on the surface of the fiber.

[0010] As a further improvement of the present application, the laying machine in step S9 selects an electrostatic directional laying machine. A group of parallel electrode plates with tens of thousands of volts of direct current voltage are installed below the laying head of the electrostatic directional laying machine, so as to ensure that the fibers entering the electric field area are in a single layer and uniformly dispersed state. The electric field strength between the electrode plates needs to reach 50-150 per meter potential difference, and the target density of the board blank should be controlled at 0.6-0.75 g / cm³ (space is left for subsequent hot pressing), so that more than 60% of the long fibers in the board blank are arranged in the machine direction (i.e. the main stress direction of the future shoe heel).

[0011] As a further improvement of the present application, the hot press in step S10 is selected as an integrated microwave continuous hot press, the microwave parameters are selected as 2450MHz or 915MHz industrial frequency, the temperature difference between the core layer and the surface layer of the board is less than 10℃, the curing degree of the adhesive is greater than 95%, and the density reaches 0.9-1.0g / cm3 or higher required by the heel.

[0012] As a further improvement of the present application, the liquid nitrogen atomization spraying tunnel in step S12 is located at the outlet of the press, the inner wall of the tunnel is covered with liquid nitrogen nozzles, and after the board is discharged from the hot press (about 100℃), it is uniformly cooled to below 30℃ in the liquid nitrogen tunnel within 60 seconds, and the cooling rate needs to be greater than 1℃ / s, so as to freeze the molecular chain structure. The cooled board immediately enters the ultrasonic wave table, and is treated within 1-2 minutes at a power density of 0.5-1.0 per square centimeter, and the ultrasonic wave breaks the residual internal stress chain in the board.

[0013] In summary, the present application has at least one of the following beneficial technical effects compared with the prior art: First, raw material bio-activation pretreatment: after cutting, the wood chips are treated with a specific composite enzyme preparation under mild conditions. The enzyme selectively partially deconstructs lignin and hemicellulose, exposing more active hydroxyl and phenolic groups, and creating a large number of micropores. The subsequent formaldehyde-free self-adhesion creates active sites, fundamentally changing the reactivity of the raw materials, replacing pure physical heat softening, saving energy and improving the potential of fiber bonding.

[0014] Second, steam explosion fiber separation and modification: the bio-activated wood chips are placed in a steam explosion device, and the fibers are separated from the cell layer by instant pressure relief. The process not only saves energy, but also preserves the fiber length and significantly increases the specific surface area. The explosion process simultaneously achieves acetylation modification of the fibers, improving their hydrophobicity. The integrated separation and modification replace heat milling, and the separation and moisture-proof chemical modification are completed simultaneously, achieving intrinsic moisture-proofing of the fibers without the need for subsequent addition of paraffin.

[0015] Third, in-situ catalytic self-adhesive synthesis: when the exploded fibers enter the drying pipe, a mixture of bio-based polyol and natural acid catalyst is atomized and injected. At the drying temperature, they react with the active groups exposed on the fiber surface by bio-activation and explosion to synthesize a layer of bio-based polymer adhesive on the fiber surface. The fiber itself reacts with bio-based reagents to generate adhesive substances, which are environmentally friendly and healthy.

[0016] Fourth, nano-ceramic reinforcing agent aerosol deposition: before paving, make the fiber pass through an electrostatic atomizing chamber, the positively charged nano-alumina / silica composite sol (with hardness and flame retardancy) is uniformly adsorbed to the surface of the negatively charged fiber, forming a nanoscale coating, and the nano-scale structure is enhanced; Upgrade the functional additives from "physical doping" to "chemical bonding and physical adsorption synergistic" nano-coating, greatly improve the hardness, wear resistance (very important for shoe heels) and permanent flame retardant effect of the plate.

[0017] Fifth, electrostatically oriented fiber paving: a high-strength directional electric field is applied on the paving line, and most of the blast fibers with excellent aspect ratio are arranged in the length direction of the plate blank (the stress direction of the future shoe heel); Bionic design, imitate the fiber orientation of natural wood, make the plate have very high bending strength in the grain direction, allow the use of lower density plate blanks to meet the same shoe heel strength requirements, and realize lightweight.

[0018] Sixth, instantaneous cooling and stress relief: after the plate leaves the continuous press, it immediately passes through a liquid nitrogen atomizing quenching section (from 100°C to 30°C in 60 seconds), locks the molecular chain form, and then enters the ultrasonic stress relief field, which uses high-frequency mechanical waves to eliminate internal residual stress within 1 minute; Active stress management. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The flowchart of the production method of the present application. DETAILED DESCRIPTION

[0020] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0021] As shown in Figure 1 A shoe heel high-density fiberboard production process, comprising the following steps: S1, slicing: the raw material (wood, plant fiber, etc.) is cut into standard pieces; S2, screening: remove impurities such as bark and sand; S3, biological activation: the sliced raw material is sent into a sealed bioreactor, and composite enzymes are used to activate lignin and open the fiber structure; S4, separate fibers: send into a steam pressure blast chamber, so that the fibers are separated from the cell layer under instantaneous pressure relief; S5, drying: rapidly reduce the moisture content of the wet fiber to a process range suitable for sizing; S6, air selection: remove too coarse or too fine fiber groups to ensure uniform fiber morphology; S7, sizing: in the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization, and a layer of bio-based polymer sizing is synthesized in situ on the surface of the fiber; S8, add: make the fiber pass through an electrostatic atomization chamber, and the positively charged nano-alumina and silica composite sol (with hardness and flame retardancy) is uniformly adsorbed to the negatively charged fiber surface to form a nano-scale coating; S9, paving: apply a high-strength directional electric field on the paving line, so that the long-diameter ratio of the blasting fiber is excellent, and the blasting fiber is arranged along the length direction of the mat (the stress direction of the future shoe heel) under the action of the electric field; S10, pre-pressing: preliminary compression of the mat to expel air and increase density and initial strength; S11, hot pressing: five-stage high temperature and high pressure is applied to the mat, and the temperature of each stage is independently controllable, and the temperature gradient is 230℃→210℃→190℃→180℃→170℃; S12, post-processing: after the plate material comes out of the continuous press, it immediately passes through a liquid nitrogen atomization quenching section to lock the molecular chain morphology, and then enters an ultrasonic stress relief field to eliminate internal residual stress by using high-frequency mechanical waves; S13, cooling plate: cool the high-temperature plate after hot pressing on the cooling plate rack to reduce the temperature to room temperature; S14, trimming: trim the edges and stack them for curing; S15, curing: place the plate in a specific temperature and humidity environment for more than 48 hours to allow internal stress to be fully released, and residual formaldehyde and moisture to be further volatilized, so that the performance of the plate (especially the dimensional stability) tends to be completely stable; S16, cutting: cut the large plate into a size convenient for subsequent turning according to the required size of the shoe heel production; S17, grading and packaging: strict quality inspection is carried out, and substandard products with delamination, uneven density, thickness deviation, and surface defects are removed.

[0022] The closed bioreactor in step S3 is equipped with a stirrer, a jacket temperature control, an online pH value monitoring, a constant temperature storage tank, a high-precision metering pump, an atomizing nozzle, and a controllable humidified air circulation system. Composite enzymes are selected, mainly including laccase or lignin peroxidase for activating lignin, and hemicellulase for opening the fiber structure. The temperature in the reaction bin is controlled at 45-60℃, the pH value is controlled at 4.5-5.5 (depending on the enzyme species), the treatment time is 30-90 minutes, and the humidity is kept high to maintain the moisture content of the wood chips at 50-60%.

[0023] The steam pressure blast bin in step S4 includes a high-pressure steam generator, a pressure blast bin, an instantaneous pressure relief valve (blasting valve), and a fiber receiving bin. The steam pressure is controlled at 1.2-2.0 MPa, and the pressure maintaining time is 30-180 seconds. A small amount of acetic anhydride steam (or other acetylating reagent) is added to the steam. The fiber is in-situ acetylated at high temperature and high pressure to replace the hydroxyl group of cellulose and realize intrinsic hydrophobicity. The fiber yield (length greater than 0.2 mm) of the fiber after blasting is more than 85%, and the separated fiber bundle is naturally fluffy without obvious thick fiber bundle. The hydrophobic modification target is to make the contact angle of the fiber greater than 90 degrees.

[0024] The drying pipe in step S7 selects a pulse air flow drying pipe with a long pipe and a specific turbulent flow area. The atomizing 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. Bio-based polyols (such as lignin cracking products, cashew phenolic derivatives, etc.) and environmentally friendly natural acid catalysts (such as citric acid, itaconic acid) are mixed online at a weight ratio of 100:(3-10) to form a spraying material. The fiber temperature is in the range of 100-120℃ in the middle section of the drying pipe, and the spraying amount is 8-15% of the weight of the absolute dry fiber. The atomized particle size is required to be less than 50 microns. The temperature of the rear section of the pipe is increased to 140-160℃, and the fiber residence time is extended to 20-30 seconds to promote rapid esterification / etherification reaction and form a uniform bio-based polymer film on the fiber surface.

[0025] In step S8, a cationic nano-alumina / silica composite sol is used, with a solid content of 10-20%, a pH value adjusted to acidity (3-5), and a particle size less than 50 nm. In the electrostatic atomization deposition chamber, the fiber is negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The electric field strength is controlled at 30-80 volts per meter. The fiber passes through in a loose state, ensuring that the nano-particles are uniformly and firmly adsorbed on the fiber surface under the action of Coulomb force. The nano-ceramic addition amount is 1-3% of the weight of the absolute dry fiber, and the target is to form a dense nano-scale coating on the fiber surface.

[0026] In step S9, an electrostatic directional laying machine is selected. A set of parallel plates with tens of thousands of volts of direct current voltage are installed below the laying head of the electrostatic directional laying machine, ensuring that the fibers entering the electric field area are in a single layer and uniformly dispersed state. The electric field strength between the plates needs to reach 50-150 volts per meter, and the target density of the board should be controlled at 0.6-0.75 grams per cubic centimeter (leaving space for subsequent hot pressing), so that more than 60% of the long fibers in the board are arranged in the machine direction (i.e. the main stress direction of the future shoe heel).

[0027] The hot press in step S10 is selected as an integrated microwave continuous hot press, microwave parameters are 2450 MHz or 915 MHz industrial frequency, the temperature difference between the core layer and the surface layer of the board is less than 10℃, the curing degree of the adhesive is greater than 95%, and the density reaches 0.9-1.0 g / cm3 or higher required by the heel.

[0028] The liquid nitrogen atomization spraying tunnel in step S12 is located at the outlet of the press, the inner wall of the tunnel is covered with liquid nitrogen nozzles, the board is uniformly cooled to below 30℃ within 60 seconds in the liquid nitrogen tunnel after being discharged from the hot press (about 100℃), and the cooling rate needs to be greater than 1℃ / s to freeze the molecular chain structure, and the cooled board immediately enters the ultrasonic wave table, and is treated within 1-2 minutes at a power density of 0.5-1.0 per square centimeter, and the ultrasonic wave breaks the residual internal stress chain in the board.

[0029] The production process of high-density fiberboard for heels is as follows: S1, chip: the raw materials (wood, plant fibers, etc.) are standardized cut to ensure uniformity in subsequent processing, and high water content helps subsequent softening; S2, screening: remove bark, sand and other impurities, which can significantly reduce the purity, uniformity and final strength of the board, and are the enemy of heel quality; S3, biological activation: the chipped raw materials are sent into a closed biological reactor, and composite enzymes are 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 controlled at 4.5-5.5 (depending on the enzyme type), the treatment time is 30-90 minutes, and the humidity is kept high, so that the moisture content of the wood chips is maintained at 50-60%, the fiber is "activated" instead of deep degradation, and the treated wood chips should maintain the original form, but the color is darker and the hand feeling is softer; S4, separate fibers: send into a steam pressure explosion chamber, so that the fibers are separated from the cell layer under instantaneous pressure relief, not only low energy consumption, but also good preservation of fiber length and significant increase of specific surface area, and the explosion process realizes in-situ acetylation modification of the fibers, improves hydrophobicity, the steam pressure is controlled at 1.2-2.0 MPa, and the pressure maintaining time is 30-180 seconds. The specific parameters are optimized according to the type of raw materials and the degree of "activation", a small amount of acetic anhydride steam (or other acetylation reagents) is added in the steam, the fibers are acetylated in-situ at high temperature and high pressure, the hydroxyl groups of the cellulose are replaced, and the intrinsic hydrophobicity is realized. The fiber yield (length>0.2mm) after explosion is more than 85%, and the separated fiber bundle is naturally fluffy without obvious thick fiber bundle, and the hydrophobic modification target is to make the contact angle of the fiber greater than 90 degrees; S5, drying: rapidly reduce the moisture content of the wet fiber to a suitable range for sizing; S6, air selection: remove too coarse or too fine fiber groups to ensure uniform fiber morphology; S7, sizing: in the drying pipeline, a mixture of bio-based polyol and natural acid catalyst is injected by atomization, and a layer of bio-based polymer sizing is synthesized in situ on the fiber surface. At the drying temperature, they undergo esterification and etherification reactions with the active groups exposed on the fiber surface by bioactivation and blasting, and a layer of bio-based polymer sizing is synthesized in situ on the fiber surface; S8, addition: make the fiber pass through an electrostatic atomization chamber, positively charged nano-alumina and silica composite sol (with hardness and flame retardancy) are uniformly adsorbed to the negatively charged fiber surface to form a nanoscale coating. In the deposition chamber, the fiber is negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The fiber passes through in a loose state to ensure that the nano-particles are uniformly and firmly adsorbed to the fiber surface under the action of coulomb force; S9, paving: apply a high-strength directional electric field on the paving line to make the blasting fiber with excellent aspect ratio directionally arrange along the length direction of the mat (the stress direction of the future shoe heel). The paving speed and fiber flow need to be accurately matched to prevent fiber accumulation from affecting the electric field effect, so that more than 60% of the long fibers in the mat are arranged along the machine direction (i.e. the main stress direction of the future shoe heel). The orientation degree can be evaluated online through image analysis technology; S10, pre-pressing: preliminary compression of the mat to expel air, increase density and initial strength; S11, hot pressing: five-stage high temperature and high pressure for the mat, each stage temperature is independently controllable, temperature gradient is 230℃→210℃→190℃→180℃→170℃, integrated microwave continuous hot press is composed of steel belt conveying system, multiple component zone adjustable pressure frame, and microwave generator array (magnetron or solid-state microwave source) integrated in the pressure frame. Under the combined action of pressure (5-15 MPa) and microwave, the total hot pressing time can be shortened to 5-8 minutes per piece (continuous production at a certain speed); S12, post-processing: after the mat comes out of the continuous press, it immediately passes through a liquid nitrogen atomization quenching section to lock the molecular chain morphology, and then enters an ultrasonic stress relief field to eliminate internal residual stress using high-frequency mechanical waves. The mat is cooled to below 30℃ within 60 seconds in the liquid nitrogen tunnel after coming out of the press (about 100℃), with a cooling rate greater than 1℃ / s to "freeze" the molecular chain structure for cooling. The cooled mat immediately enters an ultrasonic wave station and is treated with a sound intensity of 0.5-1.0 per square centimeter of power density within 1-2 minutes. Ultrasonic waves produce a micro "massage" effect inside the mat, breaking the residual internal stress chain; S13, cooling: cool the high-temperature mat after hot pressing on the cooling rack to reduce the temperature to room temperature; S14, trimming: cutting off the edges, stacking, and preparing for aging; S15, aging: placing the board in a specific temperature and humidity environment for more than 48 hours to fully release internal stress, further volatilize residual formaldehyde and moisture, and make the performance of the board (especially dimensional stability) tend to be completely stable; S16, cutting: cutting the large board into a size convenient for subsequent turning according to the required size of the heel production, planning the optimal cutting scheme according to the order of the heel factory (heel type, height) and the quality atlas of the board, maximizing the yield, and supplying the board directly to the corresponding production line according to the performance grade; S17, grading and packaging: strict quality inspection, removing substandard products such as delamination, uneven density, thickness out-of-tolerance, and surface defects, and 100% detecting internal density distribution, minor defects, and fiber orientation through high-speed linear array cameras and X-ray tomography.

[0030] The above is the preferred embodiment of the present application, and it should be noted that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A process for producing high density fiberboard for shoe heels, characterized by: Includes the following steps: S1, chipping: the standardized cutting of raw materials (wood, plant fibers, etc.); S2, Screening: Remove 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 specific 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.

2. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: 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%.

3. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: The steam pressure blast bin in step S4 includes a high-pressure steam generator, a pressure blast bin, an instantaneous pressure relief valve (blasting valve), and a fiber receiving bin. The steam pressure is controlled at 1.2-2.0 MPa, and the pressure maintaining time is 30-180 seconds. A small amount of acetic anhydride steam (or other acetylating reagent) is added to the steam. The fiber is acetylated in situ at high temperature and high pressure to replace the hydroxyl group of cellulose and realize intrinsic hydrophobicity. The fiber yield (length greater than 0.2 mm) of the fiber after blasting is more than 85%, and the separated fiber bundle is naturally fluffy without obvious thick fiber bundle. The hydrophobic modification target is to make the contact angle of the fiber greater than 90 degrees.

4. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: The drying pipe in step S7 is a pulse airflow drying pipe with a long pipe and a specific turbulent zone. The atomizing 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. Bio-based polyols (such as lignin cracking products and cashew phenol derivatives) and environmentally friendly natural acid catalysts (such as citric acid and itaconic acid) are mixed online at a weight ratio of 100:(3-10) to form a spraying material. The fiber temperature is 100-120℃ in the middle section of the drying pipe, and the spraying amount is 8-15% of the weight of the absolute dry fiber. The atomized particle size is required to be less than 50 microns. The temperature of the rear section of the pipe is raised to 140-160℃, and the fiber residence time is extended to 20-30 seconds to promote rapid esterification / etherification reaction and form a uniform bio-based polymer film on the fiber surface.

5. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: In step S8, a cationic nano-alumina / silica composite sol is used, with a solid content of 10-20%, a pH value adjusted to acidity (3-5), and a particle size of less than 50 nm. In the electrostatic atomization deposition chamber, the fiber is negatively charged by corona discharge, and the nano-sol is positively charged after atomization. The electric field strength is controlled at 30-80 volts per meter. The fiber passes through in a loose state, ensuring that the nano-particles are uniformly and firmly adsorbed on the fiber surface under the action of Coulomb force. The nano-ceramic addition amount is 1-3% of the weight of the absolute dry fiber, and the goal is to form a dense nano-scale coating on the fiber surface.

6. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: In step S9, an electrostatic directional laying machine is used. A set of parallel plates with tens of thousands of volts of direct current voltage 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 electric field strength between the plates needs to reach 50-150 volts per meter, and the target density of the board should be controlled at 0.6-0.75 grams per cubic centimeter (leaving space for subsequent hot pressing), so that more than 60% of the long fibers in the board are arranged in the machine direction (i.e., the main stress direction of the future heel).

7. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: In step S10, an integrated microwave continuous hot press is used. The microwave parameters use 2450 MHz or 915 MHz industrial frequency bands. 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 0.9-1.0 grams per cubic centimeter or higher required for the heel.

8. The process for producing high density fiberboard for shoe heels according to claim 1, wherein: The liquid nitrogen atomizing spray tunnel in step S12 is located at the exit of the press. The inner wall of the tunnel is covered with liquid nitrogen spray heads. After the plate material is discharged from the hot press (about 100℃), it is uniformly cooled to below 30℃ within 60 seconds in the liquid nitrogen tunnel, and the cooling rate needs to be greater than 1℃ / second, so as to freeze the molecular chain structure. The cooled plate material immediately enters the ultrasonic wave table, and is processed within 1-2 minutes at a power density of 0.5-1.0 per square centimeter. The ultrasonic wave breaks the residual internal stress chain in the plate material.

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