High-liquid-conductivity composite sodium polyacrylate water-absorbent resin as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymer absorbing materials, in particular to high-liquid-conductivity composite sodium polyacrylate water-absorbent resin, a preparation method and application. The water-absorbent resin is composed of a sodium polyacrylate matrix, low-melting-point ES fibers (accounting for 5-15% of the mass) activated through plasma or alkali etching and a surface cross-linking agent (such as glycerol and polyethylene glycol). The method comprises the following steps: melting a fiber sheath layer to coat SAP particles through one-time heat treatment (120-150 DEG C, 30-60 minutes), and meanwhile, constructing a surface chemical network by a cross-linking agent to form a physical-chemical dual structure. The composite SAP has excellent transverse drainage rate, wet compressive strength and circulation structure integrity, the liquid distribution efficiency and stability of the absorption core layer are remarkably improved, and the composite SAP is suitable for the field of hygienic products such as paper diapers and sanitary towels.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular absorbent material, and particularly relates to a high-liquid-conducting composite sodium polyacrylate water-absorbing resin, a preparation method and application. BACKGROUND

[0002] Super-absorbent polymer (hereinafter also referred to as SAP) is a kind of cross-linked polymer material which can quickly absorb and firmly lock water or ionic solution in tens or even hundreds of times of its own mass. The most common application scenario of SAP is the absorbent core layer of disposable sanitary products (diapers, sanitary napkins, incontinence pads, etc.). SAP forms hydrogen bonds with water molecules through hydrophilic groups such as sodium carboxylate on the chain segment, and relies on a three-dimensional cross-linked network to avoid dissolution after swelling, so it has both high absorption rate and certain gel strength. However, when the SAP particles are rapidly swollen under high-flow urine impact, a high-elasticity gel wall is first formed on the surface of the particles, blocking the subsequent liquid channel and causing a "gel-blocking" effect. The liquid thus displaces along the surface and side of the core, not only reducing the effective absorption area, but also increasing the risk of side leakage. Literature reports that the gel-blocking phenomenon generally leads to less than 60% utilization rate of the core and increased PMC.

[0003] In addition, the swollen SAP particles lack effective skeletal support, and are easily broken, caked or migrated as a whole when extruded by external force (such as baby turning over, adult walking), further weakening the absorption performance and wearing comfort. Industry statistics show that under a load of 0.3 MPa, the wet-state compressive strength of conventional surface-crosslinked sodium polyacrylate is only 0.5-1.0 MPa, and the gel integrity rate is less than 50% after five cycles of absorption-pressing, which is far lower than the index requirement of anti-pressure > 1.2 MPa and cycle integrity rate ≥ 80% for the latest product design.

[0004] The most common solution is to spray a multi-hydroxy alcohol or an epoxy compound on the surface of the dry SAP particles, and then heat treat at 100-200°C for a certain period of time to form a high-crosslinking-density "shell layer". Surface crosslinking can significantly improve the gel strength and reduce the backflow, but the rigidity and hydrophobicity of the cross-linked layer increase, which will sacrifice the absorption rate and capacity; at the same time, the gel-blocking problem still exists in essence, because the particles are still independent spherical bodies. For example, European Patent EP1860215A2 reports that non-surface-crosslinked SAP fibers are subjected to secondary surface crosslinking, mixed with a crosslinking agent in a ketone solvent and then heated. The absorption capacity (AAP) of the obtained fibers under a negative pressure of 0.6 psi can be increased to ≥13 g / g, but the gel-blocking problem still exists. -1This process can reduce the problem of fibers detaching from the edges of the product. However, the highly cross-linked shell reduces the accessibility of hydrophilic groups, sacrificing the instantaneous absorption rate and maximum absorption capacity; moreover, the fiberization route is costly to prepare and requires additional spinning and solvent drying steps. More importantly, surface cross-linking does not change the fact that the particles are still independently spherical, the glue blockage phenomenon still exists, and the lateral liquid conduction capacity is limited.

[0005] Another type of modification involves introducing hydrophobic monomers, inorganic particles, or porous solids during the polymerization or drying stage to create microchannels between the swollen gels, reducing adhesion. US Patent 7612016B2 proposes incorporating 0.01-20 wt% of anti-clogging additives (silica gel, mineral salts, or fiber powders) into SAP hydrogels to reduce adhesion between gels. However, hydrophobic / inorganic fillers reduce the concentration of hydrophilic groups and the overall swelling degree of the material, requiring a trade-off between absorption rate and clogging suppression; simultaneously, the additives have limited compatibility with the polymer and are prone to precipitation or migration during repeated suction-pressure cycles.

[0006] To improve liquid transport and structural integrity, the industry commonly uses SAP in combination with cellulose pulp (fluffpulp) or dry-blended with thermoplastic fibers (PE / PP composite short fibers) to form the core. Chinese invention patent CN1105578C reports a water-absorbing material made by treating water-absorbing resin particles, resin powder, and fiber materials at 130°C to bond them together, claiming to maintain absorption properties and improve shape retention; Chinese invention patent CN103061042A proposes to mix thermoplastic adhesive short fibers and superabsorbent short fibers in a ratio of 25-98wt%:2-75wt% and hot-air form them into a web to obtain a sheet-like nonwoven fabric as the absorbent layer.

[0007] The above methods all have limitations:

[0008] Limitation A: Fiber content contradiction - To form a continuous skeleton, the fiber content must be significantly increased, but the non-hydrophilic sheath layer and high-density structure of the fiber will compress the core pores, reducing the instantaneous absorption rate and total absorption.

[0009] Limitation B: Weak interfacial adhesion – The polyethylene sheath of low-melting-point fibers is inert on the surface, and thermal bonding only produces point-like adhesion, which is easily peeled off by the expanding gel in a wet state.

[0010] Limitation C: Multi-step processing - Traditional processes require multiple steps such as "dry mixing → hot bonding → secondary surface cross-linking", resulting in high energy consumption and difficulty in ensuring three-dimensional uniformity.

[0011] Another approach is to fabricate self-supporting fibers from SAP, which can be directly woven or hot-pressed. However, sodium polyacrylate has a high melting point and poor thermoplasticity, requiring large amounts of hydrophilic plasticizers and energy-intensive processes. While EP1860215A2 and related PCT literature have yielded fibers with "excellent pressure absorption performance," their unit cost is significantly higher than granular SAP, and their rapid liquid absorption capacity decreases with increasing fiber linear density. Some studies have increased the gel modulus by introducing hydrophobic monomers, silanes, or fluorocarbon groups into the main chain or side chains; however, this leads to a decrease in ion exchange and absorption rate, and the low-energy surface structure easily affects the affinity with the nonwoven layer.

[0012] In summary, no single modification route can achieve overall optimization in terms of absorption rate, instantaneous absorption rate, lateral / longitudinal liquid conduction, wet strength, and cycle stability. The core technical challenge in the iteration of high-end hygiene products lies in constructing a three-dimensional synergistic structure that can rapidly spread urine while maintaining pore connectivity and resisting external force breakage over a long period. Summary of the Invention

[0013] To address the aforementioned technical problems, this invention aims to provide a composite sodium polyacrylate superabsorbent polymer (SAP) with high liquid conductivity, crack resistance, and structural stability. By simultaneously constructing a physical-chemical dual network using surface-activated low-melting-point ES composite fibers and a surface crosslinking agent in a single heat treatment process, this invention simultaneously solves the technical problems of traditional SAP, such as easy glue blockage after liquid absorption, slow liquid conduction, low gel strength, and easy breakage and clumping after repeated absorption. It significantly improves the lateral liquid conduction rate, wet compressive strength, and effective absorption area to meet the comprehensive performance requirements of high-end disposable hygiene products for "instant absorption—liquid conduction—multiple cycle integrity".

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] A highly liquid-conducting composite sodium polyacrylate absorbent resin, comprising the following components by weight percentage:

[0016] Sodium polyacrylate particles 80-95%;

[0017] Low-melting-point ES composite fiber 5-20%, wherein the ES composite fiber is a polyethylene / polypropylene sheath-core structure, and the sheath melting point is 100-130℃;

[0018] Surface crosslinking agent 0.01-0.30%;

[0019] The ES composite fibers are subjected to plasma treatment or alkaline etching before addition; after the ES composite fibers are mixed with sodium polyacrylate particles, a surface crosslinking agent is sprayed on them, and they are then heat-treated at a temperature higher than the melting point of the sheath to achieve the following:

[0020] a) The fiber sheath layer is melted and oriented to coat the outer surface of the sodium polyacrylate particles to form a physical anchoring layer;

[0021] b) The surface crosslinking agent undergoes a surface crosslinking reaction at the particle-fiber interface to construct a chemical crosslinking layer;

[0022] c) The physical anchoring layer and the chemical cross-linking layer interweave to form an integrated dual-network structure, resulting in a composite resin with a wet compressive strength ≥1.2MPa and a transverse liquid conduction rate ≥1.5mLs under a 0.3MPa load. -1 Longitudinal penetration time ≤ 6s.

[0023] Preferably, the sodium polyacrylate particles may comprise 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, and 95% by mass percentage; and the melting point ES composite fiber may comprise 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% by mass percentage. Surface crosslinking agent at concentrations of 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.12%, 0.14%, 0.16%, 0.18%, or 0.30%.

[0024] Preferably, the surface crosslinking agent is glycerol and / or polyethylene glycol with a molecular weight of 200-600.

[0025] Preferably, the ES composite fiber is subjected to plasma treatment or alkaline etching to increase the atomic percentage of oxygen-containing functional groups on its surface to 2-5%, followed by heat treatment at 120-150℃ for 30-60 minutes. More preferably, the heat treatment is carried out at 130-140℃ for 40-50 minutes.

[0026] Preferably, the ES composite fiber has an average linear density of 1.0-4.0 dtex and a length of 2-6 mm. More preferably, the ES composite fiber has an average linear density of 1.5-2.5 dtex and a length of 4-5 mm.

[0027] Preferably, the surface crosslinking agent is sprayed together with a blend solution containing 0.5-2.0% silane coupling agent. More preferably, the silane coupling agent is 1.0-1.5%. The silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, γ-glycidylpropyltrimethoxysilane, and methacryloyloxypropyltrimethoxysilane.

[0028] Preferably, the sodium polyacrylate matrix has a neutralization degree of 70-90%. More preferably, the sodium polyacrylate matrix has a neutralization degree of 75-85%.

[0029] Furthermore, the present invention also provides a method for preparing the composite sodium polyacrylate water-absorbing resin, comprising the following steps:

[0030] A) Perform plasma discharge on the ES composite fiber at 50-100W for 3-8 minutes; or etch it with 2-5wt% NaOH solution for 1-3 minutes, then wash and dry.

[0031] B) Mix the fibers obtained in step A) with dried sodium polyacrylate granules at a mass ratio of 5-15:85-95;

[0032] C) Atomize and spray the surface crosslinking agent solution into the mixture so that the crosslinking agent accounts for 0.01-0.30% of the mass of sodium polyacrylate;

[0033] D) Heat-treat the sprayed mixture at 120-150℃ for 30-60 minutes to melt and coat the particles with the fiber sheath and simultaneously complete the cross-linking of the particle surface. After cooling, the target product is obtained.

[0034] Preferably, the heat treatment temperature in step D) is 140-150℃, and the device is turned over in a drum at 5-15 rpm to ensure uniform coating; and / or, 0.5-2.0 wt% of γ-aminopropyltriethoxysilane is added while spraying the crosslinking agent to increase the fiber-particle interface bonding force by ≥30%.

[0035] Furthermore, the present invention also provides the application of the composite sodium polyacrylate absorbent resin in diapers, sanitary napkins or incontinence pads, wherein compared with the same mass of unmodified sodium polyacrylate, the first absorption time of the product is shortened by at least 30%, and the structural integrity rate after 5 repeated absorption-pressing is increased by at least 50%.

[0036] Furthermore, the present invention also provides a diaper, sanitary napkin, or incontinence pad product comprising the aforementioned composite sodium polyacrylate absorbent resin.

[0037] This invention utilizes the aforementioned technical solution. Through a synergistic strategy of a single heat treatment using surface-activated low-melting-point ES composite fibers and a multi-hydroxyl surface crosslinking agent, a physical-chemical dual network is formed at the microscopic interface. This achieves a balance between instantaneous liquid conductivity, wet strength, and stability over multiple cycles while maintaining almost no impact on the absorption rate. Its main technical effects are specifically reflected in the following five aspects:

[0038] 1. Significantly improved liquid conductivity and uniform absorption performance: The oxidation degree of the ES fiber surface after plasma / alkali etching is increased (O / C atomic ratio increased to 2-5%). After the sheath melts during heat treatment at 120-150℃, it coats SAP particles and overlaps with each other to form a continuous fiber skeleton network; big forms a capillary channel effect; at the same time, the surface crosslinking agent and the fiber-particle interface condense in situ, and the two networks are connected, ensuring that the pore structure remains connected after swelling. The liquid can complete horizontal diffusion within 3-5s and quickly penetrate to the lower absorber, solving the problem of uneven liquid distribution in traditional SAP with "front-end saturation-back-end drying".

[0039] 2. Significantly enhanced wet mechanical strength and resistance to compressive collapse: The use of a tough skeleton and rigid crosslinking, with the molten sheath providing deformable tough support, and silane coupling forming ester / amide / epoxy ring-opening reaction bonds, creates an "anchor-bond" composite between the skeleton and particles. The gel can still maintain a compressive strength of 1.2–1.8 MPa under an external force of 0.3 MPa. The anti-crosslinking layer effectively limits excessive swelling of particles, and the fiber network prevents gel aggregation and migration. The morphology retention rate after repeated extrusion is ≥85%, which is significantly better than the existing technology.

[0040] 3. Anti-clogging and high effective absorption area: Further addition of silane coupling agents such as KH-550 / KH-560 introduces amino and epoxy active groups at the fiber-gel interface, increasing the density of interfacial crosslinking points while maintaining hydrophilicity and reducing the probability of particles bridging each other; the interweaving of fibers and crosslinking layers forms open pores of 10–40 μm, forming a porous double network, which increases the interparticle spacing by more than 30% compared to traditional methods, allowing urine to spread rapidly and through multiple paths inside the core, increasing the effective absorption area to 80–90%.

[0041] 4. Cyclic absorption-pressure stability and repeated drying ability: After 5 cycles of high flow absorption-60N pressing, the absorption retention rate of the composite SAP is still ≥95%, and the gel powdering rate is <3%; the core backflow amount (mass of exudate under 15kPa surface pressure) is less than 0.3g, which is better than the commercial standard of 0.5g of international first-tier brands.

[0042] 5. Comprehensive advantages in process and cost: Heat treatment, cross-linking, and skeleton construction are completed in the same process, eliminating secondary cross-linking and separate hot bonding steps, reducing production energy consumption by approximately 25% and saving equipment investment by approximately 15%; the total silane addition is ≤2wt%, with a cost impact of <0.03 USD / kg. -1 It is lower than traditional resin powder or high filler solutions.

[0043] In summary, this invention achieves a significant and quantifiable performance leap in five key indicators: liquid conduction rate, vertical penetration, wet compressive strength, effective absorbent area, and cycle stability. It also simplifies the manufacturing process and controls costs. Besides diapers, it is particularly effective for applications requiring high instantaneous absorbency and compressive strength, such as overnight sanitary napkins, high-flow adult incontinence products, and medical pressure ulcer care pads. It provides a comprehensive solution for absorbent core materials in disposable hygiene products that combines high performance and high cost-effectiveness. Detailed Implementation

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0045] Example 1 (E1)

[0046] Using 100g of sodium polyacrylate (SAP) particles with a neutralization degree of 80% as the matrix, 10g of low-melting-point ES composite fiber (1.5dtex×5mm, sheath melting point 125℃) was added. The fiber was first activated and dried in radio frequency plasma (50W, 5min). Then, the activated fiber and SAP were dry-mixed in a rotary drum (30rpm) for 10min. A 4g ethanol / water (80 / 20) atomization solution containing 0.15g glycerol and 1.0g KH-550 was prepared, pre-hydrolyzed at room temperature for 30min, and then uniformly sprayed into the mixture. Finally, the mixture was heat-treated once in a fluidized bed hot air furnace at 145℃ for 45min and then cooled and sieved.

[0047] Example 2 (E2)

[0048] SAP100g is mixed with 5g of ES fiber (soaked in 3wt% NaOH solution at 40℃ for 2min, then rinsed and dried). The spraying solution contains PEG-4000.10g and KH-5500.8g, totaling 4g. Heat treatment conditions: 140℃ for 50min.

[0049] Other technical features are as described in Example 1.

[0050] Example 3 (E3)

[0051] SAP100g and 15g ES fiber (plasma 80W, 6min) are dry-mixed. The spray solution contains 0.12g glycerol, 0.8g KH-550, and 0.4g KH-560. Heat treatment at 150℃ for 40min.

[0052] Other technical features are as described in Example 1.

[0053] Example 4 (E4)

[0054] SAP100g and ES fiber (treated with 2wt% NaOH for 3 min) are dry-mixed. The spray solution contains 0.10g glycerol, 0.6g KH-550, and 0.2g KH-570. Heat treatment is performed at 140℃ for 50 min.

[0055] Other technical features are as described in Example 1.

[0056] Example 5 (E5)

[0057] SAP100g and 12g ES fiber (plasma 60W, 5min) are dry-mixed. The spraying solution contains PEG-4000 0.13g and KH-5600 0.6g. Heat treatment is performed at 145℃ for 45min.

[0058] Other technical features are as described in Example 1.

[0059] Comparative Example 1 (C1)

[0060] Pure SAP particles (without fiber or crosslinking agent) are heat-treated at 145°C for 45 minutes. Other technical features are as described in Example 1.

[0061] Comparative Example 2 (C2)

[0062] Based on C1, only 0.15g of glycerol is sprayed, resulting in no fibers. Other technical features are as described in Example 1.

[0063] Comparative Example 3 (C3)

[0064] Add 3 wt% activated ES fibers. Other technical features are as described in Example 1.

[0065] Comparative Example 4 (C4)

[0066] 20 wt% activated ES fibers were added. Other technical features are as described in Example 1.

[0067] Comparative Example 5 (C5)

[0068] Use 10wt% fiber according to E1, but omit the fiber activation step.

[0069] Comparative Example 6 (C6)

[0070] Follow the E1 process but without spraying glycerol and silane.

[0071] Comparative Example 7 (C7)

[0072] Formulated according to E1 but heat-treated at 100℃ for 60 minutes (below the fiber melting point).

[0073] Comparative Example 8 (C8)

[0074] Follow the E1 formula but heat treat at 175℃ for 30 minutes.

[0075] Comparative Example 9 (C9)

[0076] Replace the ES fibers in E1 with pure PP short fibers of the same length and linear density (melting point 160℃).

[0077] Comparative Example 10 (C10)

[0078] First, perform heat treatment at 145℃ according to E1, then cool it down and spray KH-5501g separately and cure it again at 100℃ for 30 minutes.

[0079] Test case

[0080] All the following tests were conducted in a standard atmosphere at 23℃±2℃ and 50%±5% relative humidity (conditioned for 24 hours).

[0081] 1. Lateral conduction rate

[0082] According to the standard GB / T24218.6-2010 "Textiles - Nonwovens - Test methods - Part 6: Determination of absorbency".

[0083] Key steps:

[0084] 1) Mix 15g of sample with 3g of cellulose pulp evenly, spread it into a thin layer of 50mm×250mm and 3mm thickness, sandwich it between 15g of sodium polyacrylate film and 12g of nonwoven fabric to imitate the core layer structure.

[0085] 2) Place the sample horizontally on the liquid conduction test platform, with the liquid inlet 10mm from the front end of the sample;

[0086] 3) Using 20mL min -1 The national standard for the continuous flow pump to deliver 0.9% NaCl solution (the solution is prepared according to GB / T22875-2018 4.2) is publicly available on the platform.

[0087] 4) Record the distance L (mm) and time t (s) that the first 10 mL of liquid moves in the sample using a high-definition camera system;

[0088] 5) Lateral liquid conduction rate V = (L × width × thickness) / t, retain the result for 0.01 mL / s. -1 .

[0089] 2. Longitudinal penetration time

[0090] According to the standard GB / T24218.13-2010 "Textiles - Nonwovens - Test Methods - Part 13: Determination of Liquid Penetration Time", the first penetration time (STT1) is taken as the longitudinal penetration index.

[0091] Key steps:

[0092] 1) Place 5g of sample on a standard absorbent pad (3mm filter paper layer + 10g SAP-free nonwoven fabric);

[0093] 2) Add 1.0 mL of 0.9% NaCl solution (23℃) dropwise from a height of 20 mm using a standard titrator.

[0094] 3) Start timing from the moment the droplet contacts the sample surface and stop when the first wet stain appears on the back side; record the time t (s).

[0095] 4) Repeat each item 5 times and take the arithmetic mean; the result is accurate to 0.1s.

[0096] 3. Wet compressive strength

[0097] Reference standard: GB / T1041-2008 "Determination of compressibility of plastics" (Method A, constant speed compression), combined with the provisions of GB / T22875-2018 on the free liquid absorption saturation conditions of SAP.

[0098] Key steps:

[0099] 1) Take 2.00g of composite SAP and let it absorb freely in 0.9% NaCl solution for 30min, then filter for 5min;

[0100] 2) Collect the gel, put it into a Φ10mm×10mm mold and gently press it into three cylindrical samples;

[0101] 3) On a universal testing machine at 10 mm / min -1 Compress the material at a speed of 50% deformation; read the compressive stress σ (MPa) corresponding to 30% deformation.

[0102] 4) Report the average value, accurate to 0.01 MPa.

[0103] 4. Loop structure integrity rate

[0104] According to the standard GB / T24218.12-2012 "Textiles - Nonwovens - Test Methods - Part 12: Determination of pressure absorption" "Pressure absorption - backflow" procedure, with 5 additional cycles.

[0105] Key steps:

[0106] 1) Lay up 5g of sample according to the above standard and apply a load of 4.83kPa (approximately 50gfcm). -2 ) Absorb 0.9% NaCl under pressure and let stand for 5 minutes;

[0107] 2) Remove the upper pressure block and weigh the wet mass m1; then press with the same pressure for 1 minute and record the mass of the refluxing liquid m2;

[0108] 3) Repeat steps 1–2 five times in total; after the fifth pressing, pass the residual gel through a 1 mm sieve and collect the mass m3 of intact gel on the sieve;

[0109] 4) The integrity rate of the cyclic structure = m3 / m1 (first time) × 100%, with 1% retained.

[0110] 5. Effective absorption area

[0111] Currently, there is no direct national standard. Based on internal control methods, and referencing GB / T24218.6 Image Analysis Process, this revision is as follows:

[0112] 1) Pour 100 mL of 0.05% methylene blue solution into the center of a 10 cm × 10 cm sample using the "lateral liquid transfer" method.

[0113] 2) Immediately after 10 minutes, cut the sample along the vertical section and place it in an optical scanner; resolution 600 dpi;

[0114] 3) Use Image-ProPlus software to perform threshold segmentation on the blue pixels, and calculate the wetted projected area A1 and the total area A0;

[0115] 4) Effective absorption area = A1 / A0 × 100%, round the result to 1%.

[0116] 6. Experimental Data

[0117] All data below were obtained according to the test methods described above (GB / T 24218 series, GB / T 1041-2008, GB / T22875-2018, etc.). At room temperature of 23℃ and relative humidity of 50%, five parallel samples were measured for each indicator, and the coefficient of variation (CV) was ≤4%. The following values ​​are the arithmetic mean of the five measurements; the standard deviation is in parentheses. A two-tailed t-test (α = 0.05) was subsequently used to compare the examples and corresponding comparative examples. For any description of "extremely significant difference," P < 0.01.

[0118]

[0119] 1. Cyclic structure integrity rate = mass of gel that remains intact after the fifth absorption-pressure cycle ÷ mass of gel after the first absorption × 100%.

[0120] 7. Verification of key elements

[0121] deviation factor typical comparative example performance degradation phenomenon description Fiber content < 5 wt% C3 liquid permeability ≤1.23, compression resistance ≤0.93 channel skeleton deficiency fiber content >15wt% C4 liquid permeability only 1.28, absorption capacity decreased core layer too dense, liquid absorption blocked no fiber activation C5 compression resistance ↓, integrity rate ↓ weak interface bonding, skeleton peeling no surface crosslinking agent C6 compression resistance ≤0.75 lack of chemical reinforcement low / high heat treatment temperature C7 / C8 fiber not fused or overburned no dual network or structure brittle fracture non-low melting point fiber C9 performance similar to C5 no coating and reticulation stepwise crosslinking C10 low compression resistance and integrity rate synchronous process cannot be replaced

[0122] 8. Data Explanation and Technical Effect Analysis

[0123] 1) Significantly improved instantaneous liquid conduction capacity: In the examples, the lateral liquid conduction rate ranged from 1.53 to 2.02 mL / s. -1 The highest control ratio was only 1.28 mL s -1 (C4). Compared with C1 and C2 without fibers, the liquid conduction rate of E1–E5 increased by 50%–100% (P<0.01), proving that the activated ES fibers form continuous capillary channels after melt coating at 120–150℃, which greatly accelerates the lateral diffusion of liquid.

[0124] 2) Longitudinal penetration time is reduced by half: the penetration time of the example is 4–5 s; C1 reaches 10 s. The same drop of liquid penetrates the core layer more quickly, indicating that the physical-chemical dual network significantly reduces glue blockage and maintains pore connectivity.

[0125] 3) Wet mechanical strength increased by 1.5–3 times: the compressive strength of the example was 1.31–1.78 MPa; C1 was only 0.61 MPa. Compared with C2 (0.89 MPa) which only has surface crosslinking, it is still 40–100% higher, verifying the synergistic strengthening effect of "melted skeleton + surface crosslinking".

[0126] 4) Effective absorption area increased by 15–25 percentage points: absorption area of ​​E1–E5 is 83–90%; the comparative ratio is generally 65–72%. This indicates that glue blockage is significantly suppressed, core layer utilization is greatly improved, and the service life can be extended and side leakage reduced under the same absorbent core basis weight.

[0127] 5) Significantly enhanced cycle stability: The cycle structure integrity rate of the example is 85–89%, while that of C1 is only 45%. The fiber-crosslinked dual network limits excessive particle swelling and prevents gel migration, meeting the stringent "repeated dryness" requirements of nighttime diapers and adult incontinence products.

[0128] This invention, using a composite SAP, simultaneously achieves a lateral fluid transfer rate ≥1.5 mL / s. -1 The material exhibits a wet compressive strength ≥1.3MPa, an effective absorbent area ≥80%, and a cycle integrity rate ≥85%, significantly outperforming existing technologies. While maintaining a substantially unchanged absorbency ratio, this invention solves the problems of easy clogging, poor strength, and cycle breakage associated with traditional SAP (Super Absorbent Polymer) materials. It can be directly applied to high-end diapers, sanitary napkins, and medical pads, achieving product performance upgrades and reducing the amount of absorbent core required per unit.

[0129] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A highly liquid-conducting composite sodium polyacrylate water-absorbing resin, characterized in that, The absorbent resin contains the following components by weight percentage: Sodium polyacrylate granules 80-95%; Low-melting-point ES composite fiber 5-20%, wherein the ES composite fiber is a polyethylene / polypropylene sheath-core structure, and the sheath melting point is 100-130℃; Surface crosslinking agent 0.01-0.30%; The ES composite fibers are subjected to plasma treatment or alkaline etching before addition; after the ES composite fibers are mixed with sodium polyacrylate particles, a surface crosslinking agent is sprayed on them, and they are then heat-treated at a temperature higher than the melting point of the sheath to achieve the following: a) The fiber sheath layer is melted and oriented to coat the outer surface of the sodium polyacrylate particles to form a physical anchoring layer; b) The surface crosslinking agent undergoes a surface crosslinking reaction at the particle-fiber interface to construct a chemical crosslinking layer; c) The physical anchoring layer and the chemical cross-linking layer intertwine to form an integrated double network structure, so that the resulting composite resin has a wet compressive strength ≥1.2MPa, a transverse liquid conduction rate ≥1.5mLs⁻¹, and a longitudinal penetration time ≤6s under a 0.3MPa loading.

2. The highly liquid-conducting composite sodium polyacrylate water-absorbing resin according to claim 1, characterized in that, The surface crosslinking agent is glycerol and / or polyethylene glycol with a molecular weight of 200-600.

3. The highly liquid-conducting composite sodium polyacrylate water-absorbing resin according to claim 1, characterized in that, The ES composite fiber is subjected to plasma treatment or alkaline etching to increase the atomic percentage of oxygen functional groups on its surface to 2-5%, and then heat-treated at 120-150℃ for 30-60 minutes.

4. The highly liquid-conducting composite sodium polyacrylate water-absorbing resin according to claim 1, characterized in that, The average linear density of the ES composite fiber is 1.0-4.0 dtex, and the length is 2-6 mm.

5. The highly liquid-conducting composite sodium polyacrylate water-absorbing resin according to claim 1, characterized in that, The surface crosslinking agent is sprayed together with a blend solution containing 0.5-2.0% silane coupling agent.

6. The highly liquid-conducting composite sodium polyacrylate water-absorbing resin according to claim 1, characterized in that, The sodium polyacrylate matrix has a neutralization degree of 70-90%.

7. A method for preparing the composite sodium polyacrylate superabsorbent polymer according to any one of claims 1-6, characterized in that, Includes the following steps: A) Perform plasma discharge on the ES composite fiber at 50-100W for 3-8 minutes; or etch it with 2-5wt% NaOH solution for 1-3 minutes, then wash and dry. B) Mix the fibers obtained in step A) with dried sodium polyacrylate granules at a mass ratio of 5-15:85-95; C) Atomize and spray the surface crosslinking agent solution into the mixture, so that the crosslinking agent accounts for 0.01-0.30% of the mass of sodium polyacrylate; D) Heat-treat the sprayed mixture at 120-150℃ for 30-60 minutes to melt and coat the particles with the fiber sheath and simultaneously complete the cross-linking of the particle surface. After cooling, the target product is obtained.

8. The method according to claim 7, characterized in that, The heat treatment temperature in step D) is preferably 140-150℃, and the device is turned over in a drum at 5-15 rpm to ensure uniform coating; and / or, 0.5-2.0 wt% of γ-aminopropyltriethoxysilane is added while spraying the crosslinking agent to increase the interfacial bonding force of the fiber-particle interface by ≥30%.

9. The application of the composite sodium polyacrylate absorbent resin according to any one of claims 1-6 in diapers, sanitary napkins, or incontinence pads, characterized in that, Compared with the same mass of unmodified sodium polyacrylate, the first absorption time of the product is shortened by at least 30%, and the structural integrity after 5 repeated absorption-pressing is improved by at least 50%.

10. A diaper, sanitary napkin, or incontinence pad product, characterized in that, The product includes the composite sodium polyacrylate superabsorbent polymer as described in any one of claims 1-6.

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