Absorption core production optimization method and short fiber absorption core

Abstract

The invention relates to the technical field of fiber production, in particular to an absorption core production optimization method and a short fiber absorption core, the method aims at an absorption core which is sequentially provided with a liquid guide area and a liquid absorption area in the forward osmosis direction, the performance is improved by dynamically adjusting technological parameters, and the method comprises the steps that firstly, the absorption core is produced based on an initial fiber orientation angle and material spraying parameters; monitoring a liquid transverse diffusion area of a liquid guide area surface layer in real time to obtain a liquid forward osmosis index; dynamically adjusting the material spraying parameters of the current period according to the index, and adjusting the fiber orientation angle of the next period; finally, production optimization is implemented based on the dynamic material spraying parameters and the dynamic fiber orientation angle, and synchronous optimization of fast absorption and low reverse osmosis of the absorption core is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber production, in particular to an absorbent core production optimization method and a short fiber absorbent core. BACKGROUND

[0002] The core function of women's sanitary napkins, diapers and other absorbent products is to quickly absorb and lock liquid, keeping the surface dry. The absorbent core is usually composed of fiber materials (such as fluff pulp, composite short fibers) and high molecular absorbent resin (SAP) through air-laid nonwoven process.

[0003] Currently, product development and process optimization in this field face many challenges. The mainstream method relies heavily on traditional "trial and error" and offline testing. Before production, process parameters (such as air flow equipment wind pressure, wind speed, SAP spraying amount, etc.) are mainly set based on historical experience. After production, offline and destructive performance testing (such as absorption speed, backflow amount testing) is performed on the finished product, and the process parameters are manually adjusted according to the test results, and the cycle is repeated until the performance meets the standard. This mode has significant defects: first, the development cycle is long and cannot meet the rapid market response demand; second, the serious lag of offline testing leads to a large number of unqualified products in the production process, causing huge waste of raw materials and costs; third, excessive reliance on individual experience of technical personnel makes process adjustment lack consistency and scientificity, ultimately leading to large fluctuations in product performance and poor batch stability.

[0004] More importantly, the optimization of absorbent core performance generally stays at the macro level, such as adjusting the overall ratio of SAP and fiber, overall density or fiber structure. However, the absorption and flow guiding performance of the absorbent core is determined by the complex microstructure inside the material. The existing production process lacks effective means to monitor and quantify these key structural features online, and cannot establish a quantitative relationship between these microstructures and the final macro performance. Therefore, process adjustment is largely blind, and it is difficult to fundamentally and systematically improve the overall performance of the product, especially to achieve the two performance goals of "fast absorption" and "low backflow" which are mutually restrictive, which has been a technical bottleneck in the industry. SUMMARY

[0005] Therefore, the purpose of the present application is to overcome the difficulty of achieving high absorption and low backflow performance of the absorbent body by blindly adjusting the material ratio or overall density in the prior art, and to provide an absorbent core production optimization method and a short fiber absorbent core, which synchronously optimizes the fast absorption and low backflow performance of the absorbent body by introducing online measurement of the liquid lateral diffusion area of the liquid guiding area surface layer and a double-loop control mechanism.

[0006] In a first aspect, to solve the above-mentioned technical problems, the present invention provides an optimized method for the production of an absorbent core, wherein the absorbent core comprises a liquid guiding zone and a liquid absorption zone sequentially along the forward permeation direction, and the optimized production method includes: The absorbent core is produced according to initial process parameters, including fiber orientation angle and spray parameters for controlling the distribution of absorbent resin. Monitor the lateral diffusion area of ​​the liquid on the surface of the liquid guiding zone to obtain the positive liquid permeation index; Adjust the spraying parameters of the current production cycle according to the liquid positive penetration index to obtain dynamic spraying parameters; The fiber orientation angle for the next production cycle is adjusted according to the liquid forward permeation index to obtain a dynamic fiber orientation angle; The production of the suction core is optimized based on the dynamic spraying parameters and dynamic fiber orientation angle.

[0007] Preferably, adjusting the spraying parameters of the current production cycle according to the liquid forward penetration index includes: if the liquid lateral diffusion area of ​​the surface layer of the liquid guiding zone is greater than the target diffusion area within a set time, then increasing the spraying amount and / or spraying speed of the absorbent resin.

[0008] Preferably, increasing the amount and / or speed of the absorbent resin sprayed includes adjusting the longitudinal distribution and mass fraction of the absorbent resin in the positive permeation direction of the absorbent core to a target range, wherein the target range is configured such that the mass of the absorbent resin enriched in the liquid absorption zone accounts for 70% to 85% of the total mass of the absorbent resin, and the mass fraction of the absorbent resin in the liquid absorption zone is 60% to 80%.

[0009] Preferably, the spraying parameters include the screw speed of the absorbent resin sprayer; adjusting the spraying parameters for the current production cycle according to the liquid forward penetration index to obtain dynamic spraying parameters includes: calculating the deviation between the liquid lateral diffusion area of ​​the absorbent core layer and the target diffusion area; inputting the deviation into a PID controller to obtain the screw speed adjustment amount; and summing the current screw speed of the absorbent resin sprayer with the screw speed adjustment amount to obtain the dynamic spraying parameters.

[0010] Preferably, the way of obtaining the initial process parameters comprises: step one: obtaining microstructure parameters of the absorbent core sample; the microstructure parameters include the average orientation angle of the liquid guiding zone, the average orientation angle of the liquid absorbing zone, and the mass proportion of the absorbent resin in the liquid absorbing zone; step two: inputting the microstructure parameters into a porous medium fluid model, simulating and calculating the penetration speed and direction of the liquid in the porous medium fluid model by a finite element simulation method, and calculating the liquid lateral diffusion area according to the penetration depth and direction; step three: determining whether the liquid lateral diffusion area reaches a target diffusion area; if yes, step four is performed; step four: inputting the microstructure parameters into a preset process-structure mapping model to obtain the initial process parameters.

[0011] Preferably, if the liquid lateral diffusion area does not reach the target diffusion area, the method further comprises: step five: optimizing the microstructure parameters obtained in step one to generate candidate microstructure parameters; step six: inputting the candidate microstructure parameters into the porous medium fluid model to perform step two to obtain an iterative liquid lateral diffusion area; step seven: determining whether the iterative liquid lateral diffusion area reaches the target diffusion area; if yes, step four is performed; otherwise, steps five to seven are repeatedly performed until the iteration converges.

[0012] Preferably, the candidate microstructure parameters satisfy the following constraints: the average orientation angle θ1 of the liquid guiding zone: 45°≤θ1≤90°; the average orientation angle θ2 of the liquid absorbing zone: 0°≤θ2<45°; and the mass proportion η of the absorbent resin in the liquid absorbing zone: 60%≤η≤85%.

[0013] Preferably, the dynamic fiber orientation angle is obtained by adjusting the fiber orientation angle of the next production cycle according to the liquid forward penetration index, comprising: if the liquid lateral diffusion area of the surface layer of the liquid guiding zone is greater than the target diffusion area within a set time, the fiber orientation angle is increased; and if the liquid lateral diffusion area is less than the target diffusion area, the fiber orientation angle is decreased.

[0014] In a second aspect, to solve the above technical problems, the present application further provides a short fiber absorbent core, comprising an absorbent core body, which is prepared based on the absorbent core production optimization method.

[0015] Preferably, the absorbent core body comprises a liquid guiding zone and a liquid absorbing zone, the average orientation angle of the fibers in the liquid guiding zone is 45°-90°, the average orientation angle of the fibers in the liquid absorbing zone is 0°-45°, the mass of the absorbent resin enriched in the liquid absorbing zone accounts for 70%-85% of the total mass of the absorbent resin, and the mass fraction of the absorbent resin in the liquid absorbing zone is 60%-80%.

[0016] The above technical scheme of the present application has the following beneficial effects compared with the prior art: The absorbent core production optimization method and the short fiber absorbent core have the following beneficial effects.

[0017] The fiber orientation angle is optimized by adjusting the air flow forming net parameters, a high-speed flow guide channel that preferentially transports liquid downward is formed in the flow guide area, the structure has small resistance to liquid and weak capillary action, the main function is to quickly transfer liquid away from the contact point to avoid surface liquid accumulation and solve the problem of rapid absorption; the distribution and enrichment of the absorbent resin are controlled by adjusting the spraying parameters of the absorbent resin to build a strong gel water locking network in the liquid absorption area to solve the problem of liquid locking and anti-seepage, thereby realizing the simultaneous optimization of the rapid absorption and low anti-seepage performance of the absorbent.

[0018] Further, the transverse diffusion area of the surface layer of the liquid guide area is a key indicator that is ahead of time, sensitive and can be obtained online to represent the behavior of liquid in the liquid guide area: if the diffusion area exceeds the standard, it directly indicates that the liquid infiltration is not smooth and the trend of lateral spread, and if no intervention is made, it will eventually lead to anti-seepage and side leakage; according to this key indicator, the fiber orientation angle and the spraying parameters of the absorbent resin are bidirectionally optimized, the production process is actively and accurately stabilized near the optimal state, and the excellent and consistent low anti-seepage and side leakage performance of each product is fundamentally ensured, thereby realizing the precise stability and significant improvement of product performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings: Figure 1 The flowchart of the absorbent core production optimization method in the preferred embodiment of the present application is shown. Figure 2 The flowchart of obtaining initial process parameters in the preferred embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0021] The production of absorbent core mainly adopts air-laid process, which is a process of combining short fibers through air blowing and laying into a web, combining with super absorbent polymer (SAP) particles, and finally forming a non-woven fabric material through reinforcement. The core goal is to build a porous medium with a gradient structure to achieve rapid fluid diversion, absorption and latching. The production process includes the following core steps: Fiber opening and mixing: The packaged composite short fiber bag is scattered by the opening machine to make the fibers fluffy and separated. According to the needs of different functional layers, different specifications (denier, length) of fibers can be proportionally fed into the cotton mixing box for uniform mixing.

[0022] Air-laid and structure control: This step is completed in an air-laid machine and is the key to controlling the fiber orientation angle and SAP distribution. The core equipment used in this step includes: multi-layer forming head, adjustable airflow system, forming net curtain. Increasing airflow speed / pressure will make the fiber hit the forming net curtain with higher kinetic energy, making the implantation angle more vertical (increasing the orientation angle); on the contrary, reducing the speed will make the fiber lie more easily, reducing the orientation angle. Adjusting the angle between the airflow nozzle and the forming net curtain, the more perpendicular the airflow direction to the net curtain, the larger the fiber orientation angle; the more parallel the airflow direction to the net curtain, the smaller the fiber orientation angle. The movement speed and vibration mode of the net curtain will also affect the final laying angle of the fiber. On the production line, by independently controlling the frequency converters (adjusting the speed) and servo motors (adjusting the angle) of the upper and lower air blowers, the average orientation angle of each layer of fiber can be accurately controlled. The orientation angle is defined as the angle between the fiber main axis (i.e. the length direction of the fiber) and the normal of the X-Y reference plane (i.e. the Z axis), with a value range of 0° to 90°. An orientation angle of 0° means that the fiber is completely lying in the X-Y plane, which is horizontal; an orientation angle of 90° means that the fiber is completely vertical, perpendicular to the X-Y plane; an orientation angle between 0° and 90° means that the fiber is in an inclined state. The average orientation angle describes the statistical average of the overall arrangement direction of all fibers in a region (such as the entire liquid guiding zone or the liquid absorbing zone). The calculation method of the average orientation angle is as follows: first, obtain the two-dimensional or three-dimensional image of the fiber material through micro-CT scanning, use image analysis techniques such as structure tensor method or Fourier transform method to calculate the local direction of the fiber at each pixel point in the image, and then statistically average all the calculated direction vectors in the defined specific region of interest (ROI) (for example, the entire upper layer region) to obtain the dominant direction of this region, i.e. the average orientation angle.

[0023] The core equipment involved in the SAP distribution includes a precision SAP spraying system. The installation position of the SAP spraying head is set after the lower layer of fibers is laid and before the upper layer of fibers is laid. The spraying is started when the lower layer of fibers is laid to a predetermined thickness and is stopped before the upper layer of fibers starts to be laid. In this way, the SAP particles can be accurately sandwiched in the lower layer of fibers, so that the lower layer is enriched. The feeding amount of the SAP per unit time (g / s) is accurately controlled by adjusting the rotation speed of the screw of the SAP spraying machine. The higher the rotation speed, the greater the spraying amount. The system is usually driven by a servo motor, and the control precision is extremely high. In addition, a weak air flow is used to assist the spraying, so that the SAP particles are more evenly distributed in the fiber web and are prevented from being clumped.

[0024] Reinforcing the fabric: the laid fiber web is sent into a hot air oven. The low-melting component (such as the PE skin layer) in the composite staple fiber is melted by heat, forming a firm spot-welding type of bonding at the intersection of the fibers, while the high-melting portion of the SAP particles and the fibers remains unchanged.

[0025] Cooling, setting and winding: the material after hot air bonding is cooled and set by a cooling roller, so that the bonding points are solidified, and then the wide material is cut and wound into a large roll of core material according to the specifications of the subsequent products.

[0026] In a conventional structure of the absorbent core, the large-pore structure required to promote rapid absorption weakens the water-locking ability, resulting in high reverse osmosis; and the high SAP concentration and small-pore structure required to enhance water locking hinder the rapid downward infiltration of liquid, resulting in slow absorption speed. This is an inherent material design contradiction.

[0027] The purpose of the embodiments of the present application is to overcome the difficulty in achieving the performance goals of high absorption and low reverse osmosis of the absorbent body by blindly adjusting the material ratio or the overall density in the prior art, and to provide an absorbent core production optimization method and a staple fiber absorbent core. By introducing online measurement of the liquid lateral diffusion area of the liquid guiding area surface layer and a double-loop control mechanism, the performance of fast absorption and low reverse osmosis of the absorbent body is simultaneously optimized.

[0028] Embodiment one: referring to Figure 1 The embodiments of the present application disclose an absorbent core production optimization method. The produced absorbent core includes a liquid guiding area and a liquid absorbing area along the direction of forward osmosis. Here, the liquid guiding area is close to the use surface area, and the surface layer of the liquid guiding area is the use surface. The liquid absorbing area is away from the use surface area. The production optimization method includes: S100, producing an absorbent core according to initial process parameters, the initial process parameters including a fiber orientation angle and a spraying parameter for controlling the distribution of absorbent resin; S200, monitoring the liquid lateral diffusion area of the surface layer of the liquid guiding area to obtain a liquid forward osmosis index; S300, adjusting the spraying parameter of the current production cycle according to the liquid forward osmosis index to obtain a dynamic spraying parameter; S400, adjusting the fiber orientation angle of the next production cycle according to the liquid forward osmosis index, to obtain a dynamic fiber orientation angle; S500, producing an absorbent core according to the dynamic spraying parameter and the dynamic fiber orientation angle.

[0029] In a specific application scenario, the fiber orientation angle is controlled by a multi-layer directional airflow laying device. The air speed, air pressure and spraying angle of the upper and lower air blowers are independently controlled, so that the upper fibers are planted at a large angle to form a liquid guiding area with a vertical guiding channel, and the lower fibers are laid at a small angle to form a liquid absorbing area with a horizontal water locking network. The distribution of the absorbent resin is realized by a precision screw spraying system. The absorbent resin spraying head is placed after the laying of the lower fibers and before the laying of the upper fibers. The spraying amount of the absorbent resin per unit time is accurately controlled by controlling the screw speed.

[0030] Before the die cutting station of the production line, an online visual detection system is arranged. The system includes a set of high-speed industrial camera, a precision titration device and an image processor. The titration device drops a standard test liquid (such as 0.9% physiological saline) to the edge waste area of the moving core material in a timed and quantitative manner. The high-speed camera is synchronously triggered to capture the dynamic process of the droplet spreading on the material surface and transmit the image to the image processor. The image processor calculates the pixel area of the droplet spreading area by using image algorithms (such as edge detection and threshold segmentation) and converts it into the actual physical area according to the calibration coefficient, i.e. the liquid lateral diffusion area, as the liquid forward osmosis index.

[0031] The PLC controller receives the measured diffusion area, calculates the difference between the diffusion area and the target value diffusion area, and if the difference is greater than 0 (the diffusion area is too large), it is determined that the guiding is not good and the lower water locking ability needs to be enhanced. The adjustment amount of the absorbent resin spraying equipment spraying parameter, such as the spraying amount or / and the spraying speed, is calculated according to the deviation, and the current spraying parameter is updated according to the adjustment amount. The spraying amount of the absorbent resin is increased in the current production cycle to compensate for the defects of the current product.

[0032] At the same time, the PLC controller records the size and trend of the deviation. A continuous positive deviation indicates that the fiber orientation angle setting is unreasonable (too horizontal) and needs to be corrected from the root cause. The upper blower speed adjustment amount is calculated according to the deviation by using the PID control algorithm. After the current production cycle ends, the blower speed is updated. This new parameter will take effect in the next production cycle, making the fiber arrangement more vertical and improving the guiding performance from the root cause.

[0033] The system continuously runs the steps S200-S400 to form a closed loop. The dynamic spraying parameter ensures that the water locking ability of the product is compensated in real time, and the dynamic fiber orientation angle ensures that the production equipment is continuously calibrated, and the product with the optimal structure is produced.

[0034] The absorbent core production optimization method of the present application actively and accurately stabilizes the production process at the optimal state by monitoring the lateral diffusion area of the surface of the liquid guide area in real time and dynamically adjusting the spray amount of the absorbent resin of the liquid guide area and the fiber orientation angle of the liquid guide area according to the diffusion area, thereby synchronously optimizing the fast absorption and low reverse osmosis performance of the absorbent body.

[0035] On the basis of the above-mentioned embodiments, the spray parameters of the current production cycle are adjusted according to the liquid forward osmosis index, including: if the liquid lateral diffusion area of the surface layer of the liquid guide area within a set time is greater than the target diffusion area, the spray amount and / or spray speed of the absorbent resin is increased.

[0036] In a specific application scenario, the target diffusion area is determined through offline testing and correlation analysis, and the determination method is as follows: a series of absorbent core samples under different process parameters (especially different fiber orientation angles) are produced on a pilot line in the laboratory, and the final performance index of each sample is accurately measured using a standard test method, especially the reverse osmosis amount (measuring reverse osmosis) and the absorption speed; for each sample, the same detection equipment and method as the online are used to measure the liquid lateral diffusion area, and the measured reverse osmosis amount and absorption speed data are correlated with the corresponding diffusion area, a scatter plot is drawn, and the chart will show a trend: there is an optimal diffusion area range, within which the reverse osmosis amount is the lowest and the absorption speed is the fastest, and the median value of this optimal range or the value biased to the safer side (for example, pay more attention to low reverse osmosis, choose a smaller value) is set as the control target diffusion area. The determined target diffusion area is input into the control system of the production line for small-batch trial production to verify whether the produced finished products indeed have the optimal comprehensive performance when the control system stabilizes the diffusion area around the target diffusion area.

[0037] If the liquid lateral diffusion area of the surface layer of the liquid guide area within a set time is greater than the target diffusion area, it means that the liquid does not successfully forward osmosis or downward osmosis (Z direction), but diffuses laterally (X-Y direction) on the surface, indicating that the fiber orientation angle of the upper layer is unreasonable (too horizontal) and an effective vertical flow channel is not formed. At this time, it is too late to adjust the orientation angle of the upper layer of fibers, and the most effective remedial measure is to enhance the water grabbing and locking ability of the lower layer, so that once the liquid finally overcomes the resistance and seeps to the lower layer, it can be firmly locked to prevent reverse osmosis back to the surface. The PLC controller sends an instruction to increase the speed to the servo driver of the SAP sprayer, the servo driver increases the motor speed, and the feeding screw rotates faster, thereby spraying more amount of SAP powder onto the fiber web in unit time.

[0038] When more amount of SAP powder is sprayed onto the fiber web, the SAP mass fraction (enrichment) of this area is significantly improved, and the SAP particles themselves and the composite structure formed with the fine fibers can generate extremely strong capillary force, like a more powerful water pump, actively pumping the liquid from the upper layer. After the SAP encounters liquid, it quickly gels, and these hydrogels are wrapped and fixed by the fiber network, making it difficult to move and re-absorb even under pressure, thereby permanently locking the liquid in the deep layer. Through feedforward control, quickly increase the amount of SAP to compensate for the risk of reverse absorption that may occur due to poor flow guidance, and save the current product that is about to become waste.

[0039] Further, the method of increasing the amount of sprayed absorbent resin and / or the spraying speed includes adjusting the longitudinal distribution of the absorbent resin in the absorbent core in the direction of positive osmosis and the mass fraction to a target range, and the target range is configured such that the mass of the absorbent resin enriched in the liquid absorption area accounts for 70% to 85% of the total mass of the absorbent resin, and the mass fraction of the absorbent resin in the liquid absorption area is 60% to 80%.

[0040] In a specific application scenario, a multi-layer air-laid equipment is used, at least two forming heads are required, (one for laying fibers in the liquid absorption area, and one for laying fibers in the liquid guiding area) and an SAP quantitative spraying system. The first forming head is started to lay a layer of fibers on the forming screen to form the bottom layer of the absorbent core. When the bottom layer of fibers is laid to a predetermined thickness (about 1 / 3 of the total target thickness), the SAP spraying machine is started, and the nozzle of the spraying machine accurately sprays SAP powder on the just-laid, exposed fiber layer in the liquid absorption area. After the SAP spraying is completed, the second forming head is immediately started to begin laying the upper layer of fibers, which will cover the liquid absorption area that has been sprayed with SAP to form the liquid guiding area, and finally form a sandwich structure of fiber-SAP-fiber. When the control system determines that the amount of SAP needs to be increased, the screw speed of the SAP spraying machine is increased, and the increased speed means that the mass of SAP sprayed per unit time is increased. Since the timing and location of spraying are fixed (only sprayed after the liquid absorption area is laid), most of the increased SAP particles are limited within the liquid absorption area. Therefore, increasing the amount of spraying / speed directly leads to the synchronous increase of the mass ratio and mass fraction of SAP in the liquid absorption area.

[0041] The proportion of the mass of the absorbent resin enriched in the liquid absorption zone to the total mass of the absorbent resin is defined as: the mass of the absorbent resin contained in the liquid absorption zone in the specific space accounts for the percentage of the total mass of the absorbent resin in the entire absorbent core, which measures the concentration of the absorbent resin in the thickness direction (Z direction). By strictly controlling the spraying time of the absorbent resin (only after the liquid absorption zone is laid and before the liquid guide zone is laid), the absorbent resin is physically locked in the liquid absorption zone. The method for increasing the percentage: ensure the spraying time, increase the total spraying amount of the absorbent resin, because the newly added absorbent resin will only be added to the liquid absorption zone, and there is almost no absorbent resin in the liquid guide zone, so when the total amount of absorbent resin increases, the proportion of the liquid absorption zone will naturally increase.

[0042] The mass fraction of the absorbent resin in the liquid absorption zone is defined as: the mass of the absorbent resin in the liquid absorption zone in the specific space accounts for the percentage of the total mass (the mass of the absorbent resin + the mass of the fiber) in the region, which measures the local concentration and composition of the material in the liquid absorption zone, and directly determines the water locking capacity of the region. It is realized by controlling the ratio of the spraying amount of the absorbent resin to the laying amount of the fiber in the liquid absorption zone. The method for increasing the percentage: increase the spraying amount of the absorbent resin while keeping the fiber feeding amount in the liquid absorption zone unchanged, thereby increasing the mass fraction.

[0043] The mass of the absorbent resin enriched in the liquid absorption zone accounts for 70% to 85% of the total mass of the absorbent resin, which means that most of the absorbent resin is placed in the deep layer far from the surface layer, and the liquid must first pass through the liquid guide zone to contact the absorbent resin, thereby avoiding premature gelation of the absorbent resin on the surface to block the pores, thereby ensuring the smoothness of the liquid guide channel and the rapid absorption speed. At the same time, placing the water locking link in the deep layer greatly shortens the path resistance of the liquid back to the surface, and fundamentally reduces the risk of backflow.

[0044] The mass fraction of the absorbent resin in the liquid absorption zone is 60% to 80%, and the concentration is less than 60%. The distance between the absorbent resin particles is too large, the water locking network is discontinuous, the water locking capacity is insufficient, and it is easy to backflow under pressure. The concentration is higher than 80%, the fiber content is too low, the structural strength is poor, the absorbent resin is easy to migrate and agglomerate, which also affects the water locking effect and material stability. The concentration of 60% to 80% provides the strongest capillary water locking force and gel network structure, which can effectively resist external force (such as human pressure) and lock the liquid firmly.

[0045] On the basis of the above embodiment, the spraying parameters include the screw rotation speed of the absorbent resin spraying machine; the spraying parameters of the current production cycle are adjusted according to the liquid forward osmosis index to obtain dynamic spraying parameters, including: calculating the deviation of the liquid lateral diffusion area of the surface layer of the absorbent core from the target diffusion area; inputting the deviation into a PID controller to obtain a screw rotation speed adjustment amount; and summing the current screw rotation speed of the absorbent resin spraying machine and the screw rotation speed adjustment amount to obtain the dynamic spraying parameters. The PID algorithm can accurately adjust according to the size, duration and trend of the deviation, avoid excessive adjustment or oscillation, and finally stabilize the system near the target value.

[0046] On the basis of the above embodiment, the fiber orientation angle of the next production cycle is adjusted according to the liquid forward osmosis index to obtain a dynamic fiber orientation angle, including: if the liquid lateral diffusion area of the surface layer of the liquid guiding area within a set time is greater than the target diffusion area, the fiber orientation angle is increased; and if the liquid lateral diffusion area is less than the target diffusion area, the fiber orientation angle is decreased.

[0047] In a specific application scenario, the online vision system determines the sequence value of the liquid lateral diffusion area in real time, and the PLC controller does not make a decision based on only one instantaneous value, but calculates the average value in a period of time (such as the past 10 minutes) to eliminate random fluctuation interference and reflect the true trend; the deviation of the average lateral diffusion area from the target diffusion area is calculated, if the deviation is greater than zero, the fiber orientation angle is increased; if the deviation is less than zero, the fiber orientation angle is decreased; otherwise, the current parameter remains unchanged. A PID controller is used, which not only considers the current deviation, but also considers the historical accumulation and trend of the deviation, to calculate a more smooth and accurate adjustment amount, avoiding system oscillation. This adjustment instruction is not immediately executed, but is issued to the equipment before the current production cycle ends and the next production cycle starts, the purpose being to ensure that the process parameters of each production cycle are stable and unchanged, thereby ensuring the consistency of production and accurately evaluating the product quality under the current set of parameters.

[0048] In implementation, the fiber orientation angle is indirectly and accurately controlled by adjusting the process parameters of the air-laid equipment, and the flight and implantation posture of the fiber are controlled by adjusting the air flow state. The implementation of the fiber orientation angle adjustment is as follows: 1. Increase the fiber orientation angle (make the fiber more vertical): Increase the rotation speed of the upper fan: increase the air flow speed and pressure, so that the fiber hits the forming screen with higher kinetic energy, and is more like a nail being hammered into the screen, so that the orientation is more perpendicular to the screen plane.

[0049] Adjust the air flow guide plate to make the air flow direction more perpendicular to the screen, so that the flight trajectory of the fiber is more perpendicular, and finally the implantation angle is also more perpendicular.

[0050] 2. Reduce the fiber orientation angle (to make the fibers more horizontal): Reduce the speed of the upper fan: reduce airflow energy, allow the fibers to float in the airflow for a longer time, and make them more likely to lie flat under the influence of gravity, thus depositing in a more horizontal manner.

[0051] Adjust the airflow guide plate to make the airflow direction more parallel to the mesh curtain, allowing the fibers to spread onto the mesh curtain in a near-gliding manner, forming a more horizontal orientation.

[0052] Based on the above embodiments, referring to Figure 2 As shown, the method for obtaining initial process parameters includes: Step 1: Obtaining the microstructure parameters of the absorbent core sample; the microstructure parameters include the average orientation angle of the liquid-conducting region, the average orientation angle of the liquid-absorbing region, and the mass ratio of absorbent resin in the liquid-absorbing region; Step 2: Inputting the microstructure parameters into the porous media fluid model, simulating and calculating the liquid permeation velocity and permeation direction in the porous media fluid model using the finite element method, and calculating the liquid lateral diffusion area based on the permeation depth and permeation direction; Step 3: Determining whether the liquid lateral diffusion area reaches the target diffusion area; if so, proceeding to Step 4; Step 4: Inputting the microstructure parameters into a preset process-structure mapping model to obtain the initial process parameters. If the lateral diffusion area of ​​the liquid does not reach the target diffusion area, the process further includes: Step 5: Optimize the microstructure parameters obtained in Step 1 to generate candidate microstructure parameters; Step 6: Input the candidate microstructure parameters into the porous medium fluid model, execute Step 2, and obtain the iterative lateral diffusion area of ​​the liquid; Step 7: Determine whether the iterative lateral diffusion area of ​​the liquid reaches the target diffusion area. If so, execute Step 4; otherwise, repeat Steps 5 to 7 until the iteration converges.

[0053] In a specific application scenario, step one involves using a micro-CT scanner to perform a high-resolution three-dimensional structural scan on a selected high-performance absorbent core sample. The three-dimensional structural image data obtained from the scan is imported into image processing software to separate fibers, absorbent resin particles, and pores in the image. The segmented fiber image is processed using the structural tensor method to calculate the orientation angle of each fiber. The average values ​​θ1 and θ2 of all fiber direction vectors in two regions are calculated respectively. The three-dimensional structural image data is divided into three layers along the thickness direction. The percentage of the total volume of absorbent resin particles in the bottom layer image data relative to the total volume of absorbent resin particles in the entire sample is calculated as the mass percentage η.

[0054] Step 2: Finite element simulation calculation Step 2: Microstructure parameter extraction Using multi-physical field simulation software (such as COMSOL Multiphysics, ANSYS Fluent), import the microstructure parameters obtained in step one into the simulation software, set up the physical field, run the simulation computational fluid dynamics solver to simulate the infiltration process of the liquid in the porous medium, extract the maximum depth reached by the liquid front at a specific time point, calculate the direction angle of the average flow velocity vector by analyzing the velocity vector field, extract a tangent plane infinitely close to the top surface in the simulation results, identify the area on the tangent plane that is wetted by the liquid, and calculate the area of the region, which is the lateral diffusion area of the liquid.

[0055] Step 3: Performance judgment Compare the simulation calculated lateral diffusion area with the target diffusion area, if the calculated lateral diffusion area is less than or equal to the target diffusion area, it is judged as qualified, and step four is executed.

[0056] Step 4: Process-structure mapping inverse solution On the target production equipment, keep other process parameters unchanged, only change the target air laying parameters, produce multiple groups of absorbent core samples; measure the average fiber orientation angle of each group of samples; establish the first mapping relationship between the target air laying parameters and the average fiber orientation angle; inverse solution to obtain the air laying parameters, that is: take θ1 and θ2 extracted in step two as the target value, substitute it into the first mapping relationship, and inversely calculate the corresponding target air laying parameters. Similarly, measure the mass fraction η of absorbent resin in the liquid absorption area of each group of samples, establish the second mapping relationship between the screw speed and the mass fraction η, and inversely solve the absorbent resin spraying parameters, that is: take η extracted in step two as the target value, substitute it into the second mapping relationship, and inversely calculate the corresponding screw speed. The parameters that control the distribution of absorbent resin can be inversely solved.

[0057] Steps 5-7: Iterative optimization Optimization algorithm: if the simulation result is not up to standard, start optimization, take the fiber orientation angle of the liquid guide area, the fiber orientation angle of the liquid absorption area, and the mass fraction η of the absorbent resin in the liquid absorption area as optimization variables, take (lateral expansion area-target expansion area) 2 As the objective function, automatically generate multiple groups of candidate microstructure parameters, and cyclically execute steps two and three, finally search for a group of microstructure parameter combinations that can make the simulation result up to standard, and then inversely solve the process parameters through step four.

[0058] Traditional methods rely heavily on the production-detection-adjustment cycle, each iteration cycle involves material consumption, equipment energy consumption and long waiting, resulting in long research and development cycle, high cost. The present embodiment shortens the research and development cycle from weeks or even months to days without consuming any entity raw materials through finite element simulation reverse engineering, and the research and development cost is also reduced by orders of magnitude, which means faster product launch speed and enables enterprises to undertake more extensive and in-depth parameter research, thereby giving birth to truly optimized products.

[0059] On the basis of the above-mentioned embodiment, the following constraints are met when generating the candidate microstructure parameters: the average orientation angle θ1 of the liquid guiding area: 45°≤θ1≤90°; the average orientation angle θ2 of the liquid absorbing area: 0°≤θ2<45°; the mass percentage η of the absorbent resin in the liquid absorbing area: 60%≤η≤85%.

[0060] The average orientation angle θ1 of the liquid guiding area: 45°≤θ1≤90°, which requires that the fibers in the liquid guiding area must be arranged at a large angle or nearly perpendicular to the material plane, which is equivalent to constructing a large number of vertical, low-resistance capillary channels in this area. If θ1<45°, if the fibers are too horizontal, a large number of tortuous horizontal channels will be formed, and the liquid will preferentially spread to the surrounding, and the liquid will spread to the edge of the product rather than being absorbed downward, greatly increasing the risk of side leakage. If θ1→90°, the more vertical the fibers, the smaller the resistance to liquid penetration downward, and the faster the liquid penetrates downward, which provides the first guarantee for the dry feeling of the surface; at the same time, the rapid vertical flow reduces the residence time of the liquid on the surface, thereby reducing the horizontal diffusion area from the root.

[0061] The average orientation angle θ2 of the liquid absorbing area: 0°≤θ2<45°: this constraint requires that the fibers in the liquid absorbing area must be arranged at a small angle or nearly parallel to the material plane, which is equivalent to constructing a highly tortuous, densely distributed fiber network in this area. The core function is to slow down, buffer, lock, and provide a stable support skeleton for the absorbent resin. If θ2→0°, the horizontal fiber network greatly prolongs the transmission path of the liquid, acts as a buffer zone, slows down the liquid flow, and provides sufficient time for the absorption of absorbent resin particles. In addition, the dense horizontal fiber network provides a stable three-dimensional support structure for the absorbent resin particles, preventing the migration and agglomeration of the absorbent resin particles after absorption, thereby maintaining the stability of the pore structure.

[0062] The mass percentage η of the absorbent resin in the liquid absorbing area: 60%≤η≤85%: this constraint requires that most of the absorbent resin must be concentrated in the liquid absorbing area, and in this area, the absorbent resin must reach a high concentration and continuous distribution state. The core function is to provide ultimate water locking protection and ensure efficient delivery of liquid to the water locking layer.

[0063] η<60%: If the absorbent resin concentration is too low, the particle spacing is too large, and a continuous and strong water locking network cannot be formed. Liquid may penetrate this area, leading to leakage, and insufficient water locking ability also easily leads to reverse osmosis after pressure.

[0064] η>85%: If the absorbent resin concentration is too high, the fiber content is too low, which will lead to poor structural strength. The absorbent resin is easily displaced and clumped under wetting and pressure, which will block the pores and form a gel block, hindering the subsequent infiltration of liquid, which will also lead to a decrease in absorption speed and liquid accumulation.

[0065] In the range of 60%-85%, the absorbent resin particles can form a strong and continuous water locking network, and can be effectively separated and fixed by the fiber network, thereby achieving the best balance between water locking ability and structural stability.

[0066] Example two: The present application discloses a short fiber absorbent core, comprising an absorbent core body, which is prepared based on an absorbent core production optimization method.

[0067] The short fiber absorbent core of the embodiment of the present application is prepared by the method of example one, based on the same inventive concept and having the same technical effect, which will not be described here.

[0068] Further, the absorbent core body comprises a liquid guiding area and a liquid absorbing area, the average orientation angle of the fibers in the liquid guiding area is 45°-90°, the average orientation angle of the fibers in the liquid absorbing area is 0°-45°, the mass of the absorbent resin enriched in the liquid absorbing area accounts for 70%-85% of the total mass of the absorbent resin, and the mass fraction of the absorbent resin in the liquid absorbing area is 60%-80%.

[0069] In a specific application scenario, the liquid absorbing area (far from the use surface) of the absorbent core body is enriched with SAP particles; and in the liquid absorbing area, the average orientation angle of the composite short fibers is 0° to 45°, forming a horizontal network structure for slowing down the liquid flow rate, extending the SAP absorption time and locking the SAP gel; at the same time, the average orientation angle of the composite short fibers in the liquid guiding area (close to the use surface) is 45° to 90°, forming a vertical flow channel for quickly transmitting liquid downward to the SAP enrichment layer.

[0070] The mass of the absorbent resin enriched in the liquid absorbing area accounts for 70%-85% of the total mass of the absorbent resin, which means that most of the absorbent resin is placed in the deep layer far from the surface layer, and the liquid must first pass through the liquid guiding area to contact the absorbent resin, avoiding premature gelation of the absorbent resin on the surface to block the pores, thereby ensuring the smoothness of the liquid guiding channel and the rapid absorption speed. At the same time, placing the water locking link in the deep layer greatly shortens the path resistance of the liquid reverse osmosis back to the surface, fundamentally reducing the risk of reverse osmosis.

[0071] The mass fraction of the absorbent resin in the liquid absorption zone is 60% to 80%. When the concentration is lower than 60%, the distance between the absorbent resin particles is too large, the water locking network is discontinuous, the water locking capacity is insufficient, and the reverse penetration is easy after being pressed. When the concentration is higher than 80%, the fiber content is too low, the structural strength is poor, the absorbent resin is easy to migrate and agglomerate, and the water locking effect and the material stability are also affected; the concentration of 60% to 80% provides the strongest capillary water locking force and the gel network structure, which can effectively resist external force (such as human body pressure) and lock the liquid.

[0072] Obviously, the above embodiments are only examples for clearly illustrating, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An optimized method for producing an absorbent core, wherein the absorbent core comprises, sequentially along the forward osmosis direction, a liquid guiding zone and a liquid absorption zone, characterized in that... The production optimization method includes: The absorbent core is produced according to initial process parameters, including fiber orientation angle and spray parameters for controlling the distribution of absorbent resin. Monitor the lateral diffusion area of ​​the liquid on the surface of the liquid guiding zone to obtain the positive liquid permeation index; Adjust the spraying parameters of the current production cycle according to the liquid positive penetration index to obtain dynamic spraying parameters; The fiber orientation angle for the next production cycle is adjusted according to the liquid forward permeation index to obtain a dynamic fiber orientation angle; The production of the suction core is optimized based on the dynamic spraying parameters and dynamic fiber orientation angle.

2. The optimized production method for absorber cores according to claim 1, characterized in that... Adjusting the spraying parameters of the current production cycle according to the liquid forward penetration index includes: if the liquid lateral diffusion area of ​​the surface layer of the liquid guiding zone is greater than the target diffusion area within a set time, then increasing the spraying amount and / or spraying speed of the absorbent resin.

3. The optimized production method for absorber cores according to claim 2, characterized in that... The method of increasing the spraying amount and / or spraying speed of the absorbent resin includes: adjusting the longitudinal distribution and mass fraction of the absorbent resin in the positive permeation direction of the absorbent core to a target range, wherein the target range is configured such that the mass of absorbent resin enriched in the liquid absorption zone accounts for 70% to 85% of the total mass of the absorbent resin, and the mass fraction of absorbent resin in the liquid absorption zone is 60% to 80%.

4. The method for optimizing the production of absorber cores according to any one of claims 1-3, characterized in that... The spraying parameters include the screw speed of the absorbent resin sprayer; the spraying parameters for the current production cycle are adjusted according to the liquid positive penetration index to obtain dynamic spraying parameters, including: Calculate the deviation between the liquid lateral diffusion area of ​​the absorber core layer and the target diffusion area; The deviation is input into the PID controller to obtain the screw speed adjustment. The dynamic spraying parameters are obtained by summing the current screw speed of the absorbent resin sprayer with the screw speed adjustment amount.

5. The optimized production method for absorber cores according to claim 1, characterized in that... The methods for obtaining the initial process parameters include: Step 1: Obtain the microstructure parameters of the absorbent core sample; the microstructure parameters include the average orientation angle of the liquid-conducting region, the average orientation angle of the liquid-absorbing region, and the mass percentage of absorbent resin in the liquid-absorbing region; Step 2: Input the microstructure parameters into the porous medium fluid model, and use the finite element method to simulate and calculate the liquid permeation velocity and permeation direction in the porous medium fluid model, and calculate the liquid lateral diffusion area based on the permeation depth and permeation direction; Step 3: Determine whether the lateral diffusion area of ​​the liquid has reached the target diffusion area; if so, proceed to Step 4. Step 4: Input the microstructure parameters into a preset process-structure mapping model to obtain the initial process parameters.

6. The optimized production method for absorber cores according to claim 5, characterized in that... If the lateral diffusion area of ​​the liquid does not reach the target diffusion area, then the method further includes: Step 5: Optimize the microstructure parameters obtained in Step 1 to generate candidate microstructure parameters; Step 6: Input the candidate microstructure parameters into the porous medium fluid model, execute Step 2, and obtain the iterative liquid lateral diffusion area; Step 7: Determine whether the lateral diffusion area of ​​the liquid in the iteration has reached the target diffusion area. If so, proceed to step 4; otherwise, repeat steps 5 to 7 until the iteration converges.

7. The method for optimizing the production of absorber cores according to claim 5 or 6, characterized in that... The following constraints must be satisfied when generating candidate microstructure parameters: The average orientation angle θ1 of the liquid-conducting region is 45°≤θ1≤90°; The average orientation angle θ2 of the liquid absorption area is: 0°≤θ2<45°; The mass percentage η of absorbent resin in the liquid absorption zone is 60% ≤ η ≤ 85%.

8. The method for optimizing the production of absorber cores according to claim 1, characterized in that... The fiber orientation angle for the next production cycle is adjusted according to the liquid forward permeation index to obtain a dynamic fiber orientation angle, including: if the liquid lateral diffusion area of ​​the surface layer of the liquid guiding zone is greater than the target diffusion area within a set time, the fiber orientation angle is increased; if the liquid lateral diffusion area is less than the target diffusion area, the fiber orientation angle is decreased.

9. A short fiber absorbent core, comprising an absorbent core body, characterized in that... The absorber core is prepared based on the absorber core production optimization method as described in any one of claims 1-9.

10. The short fiber absorbent core according to claim 9, characterized in that... The absorbent core includes a liquid guiding region and a liquid absorbing region. The average fiber orientation angle in the liquid guiding region is 45°~90°. The average fiber orientation angle in the liquid absorbing region is 0°~45°. The mass of absorbent resin enriched in the liquid absorbing region accounts for 70%~85% of the total mass of absorbent resin, and the mass fraction of absorbent resin in the liquid absorbing region is 60%~80%.

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