Quick-absorption sanitary towel and preparation method thereof

Abstract

The invention relates to the technical field of hygienic products, and discloses a rapid-absorption sanitary napkin and a preparation method thereof.The rapid-absorption sanitary napkin comprises a surface layer which is a flow guide layer subjected to water repellent treatment and comprises polypropylene and polyethylene bi-component fibers in the mass ratio of 55-65: 35-45; the middle layer comprises a three-dimensional convex flow guide grid and an absorption core body, the absorption core body comprises SAP and fluff pulp, and the SAP accounts for 50-60% by mass; the bottom layer is a breathable waterproof film which is formed by compounding a polyethylene base material and a non-woven fabric, and the base material comprises 15-25wt% of calcium carbonate particles; the protruding height of the flow guide grid ranges from 0.5 mm to 2.0 mm, and the width of the flow guide groove ranges from 0.3 mm to 0.8 mm. Through structural innovation of the flow guide layer and gradient design of the absorption core body, the synergism of the liquid absorption rate and the reverse osmosis prevention performance is remarkably improved; through combination of directional micropore forming of the breathable film and coupling optimization of technological parameters, long-acting breathability is synchronously achieved, the structure is stable, the environmental adaptability is enhanced, and the performance bottleneck of traditional hygienic products is broken through.

Description

Technical Field

[0001] This invention relates to the field of hygiene products technology, and in particular to a fast-absorbing sanitary napkin and its preparation method. Background Technology

[0002] In the field of hygiene products, traditional sanitary napkins often present an irreconcilable contradiction between liquid absorption rate and anti-backflow performance. Conventional absorbent layers often use a single-material fiber web, whose uneven surface energy distribution leads to low liquid diffusion efficiency and a tendency for localized saturation, causing side leakage. The absorbent core generally uses uniformly distributed absorbent resin, which can improve overall absorbency, but under high load conditions, it is prone to structural collapse due to concentrated expansion stress, resulting in backflow.

[0003] Existing breathable membranes mostly rely on mechanical perforation or chemical foaming processes, resulting in a lack of directional control over the pore structure, making it difficult to simultaneously achieve breathability and waterproof performance. Furthermore, the isolated parameter control mode in the manufacturing process leads to insufficient interfacial bonding strength between functional layers, making them prone to interlayer delamination under complex usage environments and affecting product lifespan. These systemic defects limit the performance of hygiene products under extreme usage scenarios, urgently requiring technological breakthroughs through material innovation and process synergy. Summary of the Invention

[0004] The purpose of this invention is to provide a fast-absorbing sanitary napkin and its preparation method, which solves the problem in the prior art that it is difficult to synergistically optimize sanitary napkins in terms of fast liquid absorption, effective backflow prevention and long-lasting breathability.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a fast-absorbing sanitary napkin, comprising: a surface layer: a water-repellent guiding layer comprising polypropylene and polyethylene bicomponent fibers in a mass ratio of 55-65:35-45; a middle layer: comprising a three-dimensional raised guiding grid and an absorbent core, wherein the absorbent core comprises SAP and fluff pulp, and the SAP mass percentage is 50-60%. Bottom layer: Breathable and waterproof membrane, made of polyethylene substrate and non-woven fabric, wherein the substrate contains 15-25 wt% calcium carbonate particles; The height of the guide grille protrusion is 0.5–2.0 mm, and the width of the guide groove is 0.3–0.8 mm.

[0006] Preferably, the flow guiding layer is subjected to plasma treatment, and the treatment parameters include: Argon / Oxygen flow ratio: 7.5–8.5:1.5–2.5; Processing time: 3.5–4.5 min; Power density 0.8~1.2W / cm2.

[0007] Preferably, the absorbent core has a gradient distribution structure, with the SAP content gradually changing from 55-58% in the surface layer to 50-53% in the bottom layer along the thickness direction, and the interlayer density difference is 0.05-0.15 g / cm3.

[0008] Preferably, the breathable and waterproof membrane comprises oriented micropores with a pore size of 50 to 200 μm, a micropore aspect ratio of 3:1 to 5:1, and a pore density of 800 to 1200 pores / cm2.

[0009] Preferably, a transition layer is provided between the flow guide grid and the absorption core, the transition layer comprising 40-50 wt% SAP and 50-60 wt% fluffy fiber, with a basis weight of 25-35 g / m2.

[0010] A method for preparing a fast-absorbing sanitary napkin includes: a) Pretreatment and three-dimensional forming of the flow guide layer; b) Gradient composite of the absorber core; c) Microporous fabrication of breathable membrane; d) Multi-layered composite structure; e) Post-treatment activation.

[0011] Preferably, a) includes: The electrode spacing during plasma treatment is 25–35 mm; Hot pressing temperature: 140–160℃; Molding pressure: 1.8–2.5 MPa; The pressure holding time is 8–12 seconds.

[0012] Preferably, the SAP processing in b) includes: Curing in three stages using gradient: 50±2℃ / 30±2min→80±2℃ / 20±1min→110±5℃ / 10±0.5min; Humidity balancing treatment: Place in a 65±5%RH environment for 2±0.2h.

[0013] Preferably, in c) : CO2 foaming agent injection rate: 0.8–1.2 g / (min·m2); Longitudinal stretching rate: 1.2–1.5 m / min; Temperature gradient control: 80±5℃→120±5℃→90±3℃.

[0014] Preferably, e) includes: Infrared processing: wavelength 2.5–3.5 μm, irradiation dose 15–20 kJ / m²; Electron beam crosslinking: dose 8–12 kGy, beam current density 0.5–0.8 mA / cm²; Aging treatment: Store at 40±2℃ / 60±5%RH for 24±0.5h.

[0015] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention significantly improves the diffusion efficiency of liquid on the surface of sanitary napkins through innovative diversion layer structure design and surface modification technology. The synergistic effect of the bicomponent fibers in the diversion layer and the geometric optimization of the three-dimensional diversion grid ensure that liquid quickly penetrates into the absorbent core, avoiding the dampness and discomfort caused by surface retention.

[0016] 2. This invention utilizes a gradient distribution design of the absorbent core combined with a multi-stage curing process to achieve a synergistic improvement in absorption capacity and water-locking performance. The highly cross-linked absorbent resin on the surface rapidly captures liquid, while the low-cross-linked region at the bottom inhibits backflow through capillary action, effectively solving the problem of easy saturation and leakage in traditional uniform structures.

[0017] 3. The microporous directional molding technology of the breathable membrane of this invention, through stress-induced phase separation, forms highly breathable channels while ensuring waterproofness. This structural design avoids the strength loss caused by traditional mechanical perforation, ensuring efficient moisture removal during use and reducing stuffiness.

[0018] 4. This invention achieves an optimal balance between surface wettability and structural stability of the guide layer through parameter coupling design of plasma treatment and hot pressing. The synergistic post-treatment process of electron beam crosslinking and infrared activation further enhances the material's interfacial bonding and aging resistance.

[0019] 5. Through optimized humidity balancing and aging processes, this invention ensures that the product maintains stable absorption performance under varying temperature and humidity conditions. The dynamic response design of the flow guiding layer and the absorption core allows it to maintain efficient liquid management capabilities even under pressure or movement. Detailed Implementation

[0020] The present invention will now be described in further detail.

[0021] This invention provides a fast-absorbing sanitary napkin and its preparation method, comprising: Surface layer: a water-repellent guiding layer containing polypropylene and polyethylene bicomponent fibers in a mass ratio of 55-65:35-45; Intermediate layer: containing a three-dimensional raised guiding grid and an absorbent core, the absorbent core containing SAP and fluff pulp, with SAP accounting for 50-60% of the mass. Bottom layer: Breathable and waterproof membrane, composed of polyethylene substrate and non-woven fabric, the substrate containing 15-25 wt% calcium carbonate particles; the guide grid has a raised height of 0.5-2.0 mm and a guide channel width of 0.3-0.8 mm. This invention relates to the field of hygiene products, and specifically provides a sanitary napkin that achieves rapid absorption through structural innovation and synergistic process, as well as its preparation method. The core innovation lies in constructing a synergistic system of diversion-absorption-breathability, and through the organic combination of material modification, structural design, and process control, it overcomes the technical bottleneck of traditional sanitary napkins that struggle to simultaneously achieve absorption rate and anti-backflow performance.

[0022] The flow-guiding layer structure mechanism utilizes a three-dimensional flow-guiding grid design with specific geometric parameters. The flow-guiding layer is composed of a two-component polypropylene / polyethylene fiber (55-65:35-45) that has undergone plasma surface modification treatment. The polypropylene component provides rigid support, while the polyethylene component undergoes localized melting and bonding during hot pressing, forming a stable three-dimensional structure. The active groups generated by plasma treatment undergo a grafting reaction with the subsequently coated siloxane-modified acrylate, forming a gradient wettable surface. This design is based on the Young-Laplace equation to regulate liquid osmotic pressure. When the contact angle θ satisfies cosθ>(r1-r2) / h (r1 and r2 are the radii of curvature at the top and bottom of the flow-guiding channel, respectively, and h is the convex height), directional flow guidance can be achieved.

[0023] Absorber core construction mechanism The absorber core adopts a SAP gradient distribution structure, with the surface layer containing more SAP (55-58%) than the bottom layer (50-53%), and the interlayer density difference is controlled at 0.05-0.15 g / cm³. 3 The design establishes an osmotic pressure gradient ΔP = ρgΔh + σ(1 / r1 - 1 / r2), where ρ is the liquid density, Δh is the interlayer height difference, and σ is the surface tension. The higher cross-linking density SAP in the upper layer forms a rapid water absorption network, while the lower cross-linking degree SAP in the lower layer enhances water retention capacity through capillary effect. The axial alignment of the fluff pulp fibers and the particle size distribution of the SAP particles (particle size distribution range PDI = 0.3–0.5) produce a synergistic effect, optimizing pore connectivity.

[0024] Mechanism of breathable membrane formation The breathable membrane was prepared using a stress-induced phase separation method, by controlling the decomposition rate of the CO2 foaming agent (0.8–1.2 g / (min·m). 2 The dynamic equilibrium between the length and diameter ratio (L / D ratio) and the stretching rate (1.2–1.5 m / min) is achieved to form oriented micropores with an aspect ratio of 3:1–5:1 in a polyethylene substrate. This process is based on classical nucleation theory, where the supersaturation S of the system satisfies lnS > 16πγ. 3 / (3k 3 T 3 ρ 2 At a temperature of γ (surface energy, density), the bubble nucleation rate reaches a critical value. Three-zone temperature gradient control (80→120→90℃) allows for preferential orientation of crystal growth along the stretching direction, forming permeable channels with a tortuosity factor τ < 1.5.

[0025] Process synergy mechanism During the preparation process, the plasma treatment power density of the guide layer is 0.8–1.2 W / cm². 2 A correlation equation is established between T and the hot-pressing temperature (140~160℃): T=80+0.5P 2 (T is temperature in °C, P is power in W / cm²) 2 This ensures that the surface-modified layer does not decompose during hot pressing. Humidity balancing treatment of the absorber core (65±5% RH) stabilizes the SAP moisture content in the range of 8–12%, corresponding to a Flory-Huggins interaction parameter χ≈0.4. This keeps the polymer chains in a moderately swollen state, which is beneficial for forming a uniform network structure during subsequent electron beam crosslinking.

[0026] Post-treatment activation mechanism Infrared processing (wavelength 2.5–3.5 μm) selectively excites the CH stretching vibration modes (wavenumber 2800–3000 cm⁻¹) in the fiber. -1 This process promotes the rearrangement of interfacial molecular chains. The electron beam irradiation dose (8–12 kGy) is controlled below the critical value of the Charlesby-Pinner equation to ensure a crosslinking density G(X) / G(S) = 0.6–0.8, avoiding material embrittlement caused by excessive crosslinking. Aging treatment allows for sufficient relaxation of internal stress in the material by controlling the free volume fraction.

[0027] Example 1 Preparation of the guide layer Use polypropylene (PP) / polyethylene (PE) bicomponent fibers (mass ratio 60:40) with a fiber fineness of 2.2 dtex.

[0028] Plasma treatment parameters: Argon / Oxygen flow ratio: 8:2; Processing time: 4 minutes; Power density 1.0 W / cm³ 2 ;; Electrode spacing is 30mm.

[0029] Hot pressing parameters: Temperature 150℃; Pressure 2.2 MPa; Pressure holding time: 10 seconds; The height of the molded protrusion is 1.2mm.

[0030] Absorber core preparation SAP content 55wt%, gradient distribution is as follows: Surface layer 57%; Middle layer 55%; The bottom layer accounts for 52%.

[0031] Curing process: First stage: 50℃ / 30 minutes; Second stage: 80℃ / 20 minutes; Third stage: 110℃ / 10 minutes; Humidity balancing: 65% RH environment treatment for 2 hours.

[0032] Breathable membrane processing CO2 foaming agent injection rate: 1.0 g / (min·m) 2 ); Longitudinal stretching rate 1.35 m / min.

[0033] Temperature gradient control: Zone 1, 80℃; Zone 2, 120℃; 90℃ in Zone 3.

[0034] Example 2 Preparation of the guide layer Polypropylene / polyethylene ratio 55:45; Plasma treatment parameters: Argon / Oxygen flow ratio: 7.5:2.5; Processing time: 3.5 minutes; Power density 0.8W / cm³ 2 .

[0035] Hot pressing parameters: Temperature 140℃; Pressure 1.8 MPa; The protrusion height is 0.5mm.

[0036] Absorber core preparation SAP content 50wt%, gradient distribution: 55% of the surface layer; Middle layer 53%; The bottom 50%; Decrease the curing temperature by 2°C and increase the curing time by 2 minutes.

[0037] Breathable membrane processing CO2 injection rate: 0.8 g / (min·m 2 ); Tensile rate: 1.2 m / min; The pore size is controlled at 50μm.

[0038] Example 3 Preparation of the guide layer Polypropylene / polyethylene ratio 65:35; Plasma treatment parameters: Argon / Oxygen flow ratio: 8.5:1.5; Processing time: 4.5 minutes; Power density 1.2W / cm³ 2 .

[0039] Hot pressing parameters: Temperature 160℃; Pressure 2.5 MPa; The protrusion height is 2.0mm.

[0040] Absorber core preparation SAP content 60wt%, gradient distribution: Surface layer 58%; Middle layer 57%; The bottom 53%; Increasing the curing temperature by 5°C reduces the curing time by 0.5 minutes.

[0041] Breathable membrane processing CO2 injection rate: 1.2 g / (min·m 2 ); Tensile rate: 1.5 m / min; The pore size was increased to 200 μm.

[0042] Comparative Example 1: Compared to Example 1, the flow guide layer uses pure polypropylene fiber (the PP / PE two-component structure is eliminated), and the rest are the same.

[0043] Comparative Example 2: Compared with Example 1, the plasma treatment gas for the flow channel was changed to pure argon (the Ar / O2 mixed gas treatment was cancelled), and the rest were the same.

[0044] Comparative Example 3: Compared to Example 1, the absorber core adopts a uniform SAP distribution (eliminating the 55-58% → 52% gradient design), and the rest are the same.

[0045] Comparative Example 4: Compared with Example 1, the breathable membrane adopts a mechanical perforation process (eliminating the stress-induced phase separation method), and the rest is the same.

[0046] Comparative Example 5: Compared to Example 1, SAP curing adopted a single-stage isothermal treatment (110℃ / 60min, gradient curing was cancelled), and the rest were the same.

[0047] Comparative Example 6: Compared to Example 1, the CO2 injection rate was increased to 1.5 g / (min·m²). 2 ), the rest are the same.

[0048] Comparative Example 7: Compared with Example 1, the hot-pressing pressure of the flow guide layer was adjusted to 1.2 MPa, and the rest were the same.

[0049] Test Example 1 Experiment Description: Performance Testing of the Deflector Layer Structure Experimental steps: Sample preparation: Example 1: The flow-guiding layer prepared according to Example 1 Comparative Example 1: Pure Polypropylene Fluidization Layer Comparative Example 2: Pure Argon Plasma Treatment of the Flow Guide Layer Flow rate test: Use 25 mL of simulated liquid (viscosity 3.5 cP, 37℃); The sample is fixed to the test fixture at a 30° angle. The droplet falls freely from a height of 10 cm above the surface; Record the complete penetration time (accurate to 0.1s).

[0050] Diffusion uniformity test: The core gradient composite was repeatedly absorbed using 0.1% methylene blue staining solution. Image analyzer measures the area of ​​the stained region; Calculate the coefficient of variation (CV) for the five tests.

[0051] Reflow test: After loading 500 mL of physiological saline; Apply a pressure of 5 kPa and maintain it for 30 seconds; Weigh the amount of backflow liquid absorbed by the filter paper.

[0052] Experimental data table: The test results of this experiment demonstrate that the innovative design of the flow-guiding layer structure plays a crucial role in the liquid flow performance. Firstly, the application of bicomponent fibers effectively improves the surface hydrophilicity and liquid flow rate of the flow-guiding layer. Particularly in Example 1, the use of a polypropylene / polyethylene bicomponent fiber combination, combined with plasma surface modification technology, results in a flow-guiding layer with excellent liquid affinity and low liquid permeation resistance. This innovative design promotes uniform liquid diffusion within the flow-guiding layer, significantly reduces backflow, and exhibits higher stability during liquid flow.

[0053] Secondly, plasma surface modification (with precise control of parameters such as gas ratio and power density) can improve the roughness of the microstructure of the guide layer surface compared to traditional treatment methods, thereby enhancing the liquid's conductivity and reducing liquid "dripping" caused by low surface energy. Experimental data shows that the plasma-treated guide layer in Example 1 exhibits a significantly higher conductivity rate compared to the untreated sample. In particular, by rationally controlling the gas flow ratio and power density parameters, the surface characteristics of the guide layer can be precisely controlled, further improving liquid transport efficiency and reducing liquid retention on the guide layer surface.

[0054] Finally, the structural design of this invention, through the subtle adjustment of the flow-guiding layer and the synergistic effect of the interlayer structure, enables the liquid to quickly enter the absorbent layer and distribute evenly. This design not only improves the uniformity of liquid distribution but also effectively prevents localized oversaturation caused by liquid concentration. In Example 1, the use of a bicomponent fiber flow-guiding layer and a precisely controlled surface modification process enhances the directionality and stability during liquid transport, providing a more efficient liquid input pathway for the absorbent core. This combined design provides strong support for the overall performance of the product, especially demonstrating a longer service life and greater stability in actual use environments.

[0055] Test Example 2 Experiment Description: Absorber Core Performance Test Experimental steps: Sample preparation: Example 1: Gradient SAP distribution + three-stage curing; Comparative Example 3: Uniform SAP distribution (55%); Comparative Example 5: Single-stage curing (110℃ / 60min).

[0056] Absorption capacity test: Weigh the dried sample (accurate to 0.01g); Immerse in 0.9% physiological saline (25℃) for 60 minutes; Remove and drain until no more water drips, then weigh. Calculate the absorption per unit mass (g / g).

[0057] Absorption rate test: Use 50 mL of simulated liquid (surface tension 72 mN / m); Continuous injection with a liquid column height of 10cm; Record the time to complete absorption (the median of three tests).

[0058] Pressure reverse osmosis test: After adding 500 mL of liquid, let it stand for 5 minutes; Apply 5 kPa pressure for 30 seconds; Absorb the reverse osmosis liquid with pre-weighed filter paper (Whatman No. 1); Calculate the reverse osmosis rate (reverse osmosis volume / total absorption volume).

[0059] Experimental data table: The test results of this experiment demonstrate that the innovative structure and material distribution of the absorbent core play a crucial role in its absorption performance. In particular, in Example 1, the use of a gradient distribution of superabsorbent polymers (SAP) effectively controlled the absorption rate and capacity. The higher SAP content in the surface layer allows for rapid liquid absorption, while the lower SAP content in the bottom layer effectively prevents excessive diffusion of liquid to the bottom. This design not only enhances the layered control of the absorbent layer but also ensures high stability of the overall absorption performance under varying loads.

[0060] Furthermore, by employing a three-stage curing process, combined with crosslinking reactions at different temperatures, different crosslinking densities can be formed in different regions. This process design ensures a balance between the overall stability of the absorbent core and the water absorption rate. In Example 1, the three-stage gradient curing effectively controlled the expansion behavior of the SAP, allowing the core to maintain high structural integrity during liquid absorption. This structure not only avoids the uneven absorption phenomenon caused by conventional uniform curing but also improves the overall strength of the core, enabling it to maintain a low degree of collapse after water absorption.

[0061] Finally, the results of this experiment show that the combination of gradient-distributed SAP and multi-segment curing further enhances the rapid response characteristics of water absorption capacity and maintains good water absorption stability under high load conditions. The mechanism of this design is that, as the absorption process proceeds, the surface SAP expands rapidly first, while the bottom layer provides sufficient support to prevent the entire core structure from losing its original shape due to excessive expansion. Through this structural optimization, the absorbent core of Example 1 can not only absorb a large amount of liquid in a short time, but also effectively reduce the adverse effects caused by volume expansion after water absorption, thereby maintaining excellent absorption performance and stability during long-term use.

[0062] Test Example 3 Experiment Description: Test of Breathable Membrane Performance Experimental steps: Sample preparation: Example 1: Formation of microporous membranes using stress-induced phase separation; Comparative Example 4: Using mechanically perforated membrane; Comparative Example 6: CO2 injection rate increased to 1.5 g / (min·m 2 This exceeds the upper limit of the process.

[0063] Breathability test: According to GB / T5453-1997 standard; Using a pressure differential of 45.4 Pa, test 10 cm. 2 area; Unit: mm / s, record the average of 3 times.

[0064] Hydrostatic pressure test: Refer to AATCC 127 standard; The pressurization rate is 10 cm water column / min; Record the pressure (unit: cmH2O) at the moment the first drop of water penetrates.

[0065] Tensile strength test: Proceed according to GB / T1040.3-2006; Sample size: 50mm × 10mm; Tensile rate: 50 mm / min, taking the longitudinal strength.

[0066] Water vapor transmission rate (WVTR) test: Cup method, set temperature 38℃, humidity 90%RH; Test 24-hour mass loss, unit g / m 2 ·24h.

[0067] Experimental data table: The test results of this experiment demonstrate that the innovative structure and molding process of the breathable membrane play a crucial role in improving the overall product performance. In Example 1, a stress-induced phase separation method was used to generate the microporous membrane. This process can form a uniform pore structure within the membrane, significantly improving its air permeability and water vapor transmission rate. The formation of micropores not only increases the membrane's surface area but also, through precise control of the pore size, effectively prevents liquid leakage while maintaining high air permeability. This design effectively solves the problem of poor air permeability of traditional breathable membranes in high humidity environments and provides the product with better breathable protection.

[0068] Furthermore, by combining CO2 injection rate and temperature gradient control, the membrane's microstructure was precisely adjusted, resulting in higher porosity and better mechanical strength. This structural design, by controlling the aspect ratio of the micropores, optimizes the balance between membrane flexibility and strength, enhancing the membrane's stability during stretching. Experimental results show that the breathable membrane of Example 1 exhibits significantly improved hydrostatic pressure and tensile strength compared to other comparative samples. The advantage of this process is that it allows the membrane to maintain good breathability under high pressure environments and will not lose its function due to external forces during actual use.

[0069] Finally, the breathable membrane in Example 1 exhibited excellent stability in the damp heat aging test. The stress-induced phase separation method not only optimized the membrane's microporous structure but also controlled its porosity through heat treatment, enabling it to maintain high permeability even under extreme environments. Through this precise membrane structure design, the breathable membrane of Example 1 can maintain a high water vapor transmission rate during long-term use, ensuring that the product continues to provide excellent breathability and protection under hygroscopic or damp conditions. This innovative design significantly improves the membrane's long-term stability and service life, adapting to the practical needs of various environmental conditions.

[0070] Test Example 4 Experiment Description: Process Parameter Verification Test Experimental steps: Sample preparation: Example 1: According to the specified process (hot pressing pressure 2.2MPa, temperature 150℃); Comparative Example 7: The thermal pressure of the flow guide layer was adjusted to 1.2 MPa (exceeding the specified range); Interlayer peel strength test: According to GB / T2790-1995 standard; The peel strength in the transverse and longitudinal directions was tested using an electric stretching machine. Record the maximum peel force (in N) in each direction.

[0071] Fluid guide structure retention rate test: The height of the protrusion was tested after hot pressing; Measure the change in bulge height before and after hot pressing, and calculate the retention rate (unit: %).

[0072] Dimensional stability test: Place the sample in an 85% RH environment for 24 hours; Measure the dimensional changes after removal (unit: mm); Calculate the rate of change of size for each sample.

[0073] Rebound performance test: Apply a pressure of 1 kPa and hold for 30 seconds. After removing the sample, measure the rebound height. Measure the height after rebound and calculate the rebound rate (unit: %).

[0074] Experimental data table: Test Project Example 1 Comparative Example 7 Interlayer peel strength (N) 15.7 10.4 Airflow retention rate (%) 92.4 76.3 Dimensional stability change (%) 0.8 2.1 Rebound performance (%) 94.3 83.7 Longitudinal peel force (N) 18.2 12.3 The test results of this experiment show that process parameters have a significant impact on the structural stability and functionality of the flow guide layer. In Example 1, the precise control of hot-pressing temperature and pressure, especially under a pressure of 2.2 MPa, effectively promoted interlayer adhesion of the flow guide layer, improving its overall strength and structural integrity. This design not only ensures that the flow guide layer can withstand liquid pressure during actual use but also effectively avoids deformation or delamination under high load conditions. This innovative process not only improves the stability of the flow guide layer but also ensures its efficient flow guiding capability during repeated use.

[0075] Furthermore, the improved retention rate of the flow guiding structure is closely related to the refinement of pressure control. In the experiment, Example 1 demonstrated a high retention rate of the flow guiding structure, indicating that the high pressure during the hot-pressing process effectively maintained the microstructural characteristics of the flow guiding layer. Through optimized hot-pressing parameters, the flow guiding layer not only maintained its original microporous structure but also ensured the uniform distribution of liquid within the layer. This structural optimization enables the flow guiding layer to continuously provide a stable flow guiding effect under dynamic conditions, avoiding problems such as liquid accumulation or displacement, thereby improving the product's service life and stability.

[0076] Finally, optimization of dimensional stability and resilience performance shows that the hot-pressing process and pressure control in Example 1 can reduce the dimensional changes of the guide layer during use to a certain extent. Especially in humid and hot environments, the guide layer of Example 1 exhibits a low rate of dimensional change, indicating that the hot-pressing process effectively improves the dimensional stability of the guide layer. This result further verifies that by reasonably adjusting the hot-pressing parameters, the structural stability and long-term performance of the guide layer under different environmental conditions can be significantly improved. This innovative design enables the guide layer to better adapt to changes in the external environment in practical applications and maintain excellent performance over a long period of time.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fast-absorbing sanitary napkin, characterized in that, include: Surface layer: Water-repellent guiding layer, containing two-component fibers of polypropylene and polyethylene, with a mass ratio of 55-65:35-45; Intermediate layer: includes a three-dimensional raised flow guide grid and an absorbent core, wherein the absorbent core contains SAP and fluff pulp, with SAP accounting for 50-60% by mass; Bottom layer: Breathable and waterproof membrane, made of polyethylene substrate and non-woven fabric, wherein the substrate contains 15-25 wt% calcium carbonate particles; The height of the guide grille protrusion is 0.5–2.0 mm, and the width of the guide groove is 0.3–0.8 mm.

2. The quick-absorbing sanitary napkin according to claim 1, characterized in that, The flow guide layer is subjected to plasma treatment, and the treatment parameters include: Argon / Oxygen flow rate ratio: 7.5–8.5:1.5–2.5; processing time: 3.5–4.5 min; power density: 0.8–1.2 W / cm³ 2 .

3. The quick-absorbing sanitary napkin according to claim 1, characterized in that, The absorber core exhibits a gradient distribution structure, with the SAP content gradually changing from 55-58% in the surface layer to 50-53% in the bottom layer along the thickness direction, and the interlayer density difference being 0.05-0.15 g / cm³. 3 .

4. The quick-absorbing sanitary napkin according to claim 1, characterized in that, The breathable and waterproof membrane comprises oriented micropores with a pore size of 50–200 μm, an aspect ratio of 3:1–5:1, and a pore density of 800–1200 pores / cm². 2 .

5. The quick-absorbing sanitary napkin according to claim 1, characterized in that, A transition layer is provided between the flow guide grid and the absorbent core. The transition layer contains 40-50 wt% SAP and 50-60 wt% fluffy fiber, with a basis weight of 25-35 g / m³. 2 .

6. A method for preparing a fast-absorbing sanitary napkin, used to prepare a fast-absorbing sanitary napkin according to any one of claims 1-5, characterized in that, include: a) Pretreatment and three-dimensional forming of the flow guide layer; b) Gradient composite of the absorber core; c) Microporous fabrication of breathable membrane; d) Multi-layered composite structure; e) Post-treatment activation.

7. The method for preparing a fast-absorbing sanitary napkin according to claim 6, characterized in that, a) includes: an electrode spacing of 25-35 mm during plasma treatment; a hot pressing temperature of 140-160℃; a forming pressure of 1.8-2.5 MPa; and a holding time of 8-12 s.

8. The method for preparing a fast-absorbing sanitary napkin according to claim 6, characterized in that, The SAP treatment in b) includes: three-stage gradient curing: 50±2℃ / 30±2min→80±2℃ / 20±1min→110±5℃ / 10±0.5min; humidity balancing treatment: placed in a 65±5%RH environment for 2±0.2h.

9. The method for preparing a fast-absorbing sanitary napkin according to claim 6, characterized in that, In c), the CO2 foaming agent injection rate is 0.8–1.2 g / (min·m). 2 Longitudinal stretching rate: 1.2–1.5 m / min; Temperature gradient control: 80±5℃→120±5℃→90±3℃.

10. The method for preparing a fast-absorbing sanitary napkin according to claim 6, characterized in that, The above (e) includes: infrared processing: wavelength 2.5–3.5 μm, irradiance 15–20 kJ / m². 2 Electron beam crosslinking: dose 8–12 kGy, beam current density 0.5–0.8 mA / cm² 2 Aging treatment: Store in an environment of 40±2℃ / 60±5%RH for 24±0.5h.

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