Preparation method of high-basis-weight dispersible non-woven fabric

Abstract

The embodiment of the invention provides a preparation method of a high-basis-weight dispersible non-woven fabric. The preparation method comprises the following steps: S10, forming a dry matrix; s20, the dry base body is locally wetted to form a locally wetted body; according to local wetting, a regularly-distributed wetting point array is formed on the surface of the dry base body, and the distribution density of wetting points on the surface of the dry base body is 4-12 / cm, and S30, structural reconstruction is conducted on a local wetting body to form the high-basis-weight dispersible non-woven fabric; according to the structural reconstruction, a fluffy weakening structure is formed in a region corresponding to a wetting point through secondary drying induction, and the fluffy structure is induced through local accurate wetting and secondary drying induction, so that the strength maintenance and the rapid dispersion capability of the non-woven fabric are both considered.

Description

Technical Field

[0001] This invention relates to a high basis weight washable nonwoven fabric, and particularly to a method for preparing a washable nonwoven fabric with a basis weight of 85 g / m² or higher. Background Technology

[0002] Washable nonwoven fabrics, as a material that balances the convenience of modern life with environmental protection requirements, have shown great promise in various fields such as wet wipes, hygiene products, and medical dressings. The core technological challenge lies in meeting the strength and toughness required during production and use, while ensuring that the product can quickly and thoroughly disperse in water after use, thus avoiding clogging of drainage systems. These two performance indicators—strength and washability—present a significant and irreconcilable inherent contradiction in materials science and engineering practice. This contradiction is the primary obstacle to the development of washable nonwoven fabric technology and a key problem that those skilled in the art have long strived to solve.

[0003] Currently, mainstream washable nonwoven fabric technologies mainly revolve around three aspects: fiber selection and modification, adhesive systems, and structural design and processing technology. Regarding fiber selection and modification, the industry commonly uses hydrophilic or biodegradable fibers such as wood pulp fibers, viscose fibers, and lyocell fibers. These fibers have good water absorption and biodegradability, which facilitates rapid dispersion of the product after use. By adjusting parameters such as fiber length, fineness, and crimp, and by performing surface hydrophilic modification, fiber dispersibility can be further improved. Shorter fibers disperse more easily in water but reduce the strength of the nonwoven fabric; finer fibers have better softness and water absorption but increase production costs; crimped fibers can increase entanglement between fibers, improving the strength of the nonwoven fabric but reducing its dispersibility. Surface hydrophilic modification can introduce hydrophilic groups onto the fiber surface, increasing the affinity between the fiber and water, thereby promoting dispersion. When the bonding force between fibers is strong enough to meet the mechanical stress requirements of high-speed operation on the production line, such as stretching and winding, its dispersion speed in water is often limited.

[0004] In terms of adhesive system technology, water-soluble or water-dispersible adhesives are commonly used, such as polyvinyl alcohol, starch derivatives, and acrylate copolymers. These adhesives can adjust the strength and dispersibility of nonwoven fabrics by controlling their dosage, distribution, and dissolution rate, but it is still difficult to balance washability and strength.

[0005] In terms of structural design and processing technology, the main aspects include layered structure design, local embossing or perforation, and optimization of hydroentangling process parameters. Layered structure design refers to combining different types of fibers or adhesives to form multiple layers with specific functions. For example, soft, absorbent fibers can be used in the surface layer, high-strength fibers in the middle layer, and easily dispersible fibers in the bottom layer, thereby achieving comprehensive optimization of strength, softness, and dispersibility. Local embossing or perforation refers to forming specific patterns or holes on the surface of the nonwoven fabric to improve its dispersibility. For example, grid-like or dotted patterns can be pressed onto the surface of the nonwoven fabric to reduce the bonding force between fibers; tiny holes can be punched into the surface of the nonwoven fabric to promote water penetration. Optimization of hydroentangling process parameters refers to controlling the degree of fiber entanglement by adjusting parameters such as water spray pressure, spray angle, and spray frequency of the hydroentangling machine, thereby adjusting the strength and dispersibility of the nonwoven fabric. Using multi-layered structures or complex embossed patterns increases the complexity of the production line, leading to increased equipment investment and decreased production efficiency. While traditional hydroentangling processes can create fiber entanglement, they struggle to achieve precise and controllable localized weakening. This means that, while maintaining overall strength, the impact of water flow cannot effectively target and disrupt specific areas, limiting the improvement in dispersibility. Adjusting hydroentangling parameters may only shorten dispersion time, but not achieve a qualitative leap. When the basis weight exceeds 85 g / m², even with the aforementioned structural design and process optimization, the entanglement and hydrogen bonding forces between fibers become too strong, making it difficult for water flow to effectively penetrate and disrupt the fibers. This leads to a sharp decline in dispersibility, with FTTS dispersion potentially falling below 60%. Designing a reasonable structure and optimizing processing parameters to achieve the optimal balance between strength, dispersibility, production efficiency, and cost-effectiveness is the main challenge facing structural design and processing technology.

[0006] The aforementioned pain points all point to a core unmet need: the market urgently needs a new type of washable nonwoven fabric that can achieve rapid washability while maintaining sufficient production and usage intensity, and is not limited by basis weight, especially performing well in high basis weight (greater than or equal to 85 g / m²) products, while also taking into account cost-effectiveness and environmental friendliness.

[0007] Therefore, a new technical solution is needed to address the aforementioned technical problems. Summary of the Invention

[0008] The main technical problem addressed by this application is the contradiction between high strength and rapid washability in traditional high-basic-weight nonwoven fabrics, as well as the problems of low dispersion efficiency and complex processes in existing technologies.

[0009] To address the aforementioned technical problems, this application employs a technical solution that induces a fluffy structure through precise local wetting and secondary drying, achieving a balance between maintaining the strength of the nonwoven fabric and its rapid dispersion capability. Specifically, this involves: first, forming a dry matrix; then, spraying discrete point-like water mist through a high-precision needle-shaped nozzle array to locally weaken hydrogen bonds; and finally, forming a pre-defined fluffy weakened area through secondary drying, thereby achieving rapid dispersion while maintaining overall strength.

[0010] Specifically, the method for preparing the high-basic-weight washable nonwoven fabric includes the following steps: S10: Forms a dry matrix; S20: Locally wetting the dry substrate to form a locally wetted body; the local wetting is to form a regularly distributed array of wetting points on the surface of the dry substrate, and the distribution density of wetting points on the surface of the dry substrate is 4 to 12 points / cm².

[0011] S30: Structural reconstruction of locally wetted bodies to form high-basic-weight washable nonwoven fabric; The structural reconstruction involves inducing a fluffy, weakened structure in the region corresponding to the wetting point through secondary drying.

[0012] In step S20, local wetting is achieved by spraying a wetting liquid onto the dry substrate surface via pulse jetting. The pulse jetting time is 0.1–1 ms, the water volume at a single wetting point is 0.3–1 μL, and the diameter of the wetting point ranges from 0.5 to 1.5 mm.

[0013] The method involves localized wetting using a precision liquid application device, which includes a spraying unit. The spraying unit is a piezoelectric micro-nozzle array with a nozzle orifice diameter of 0.1–0.2 mm and a pulse time control accuracy of ±0.05 ms.

[0014] The wetting solution is pure water or an aqueous solution containing 0.01wt% to 0.1wt% surfactant.

[0015] The surfactant is polysorbate 80, and the pH of the wetting solution is 6.5±0.5.

[0016] In step S30, a secondary drying process is carried out by hot air penetration drying. The temperature of the secondary drying is 100-140℃, the time is 1-3 minutes, and the wind speed is 2-5 m / s.

[0017] Step S10 includes the following steps: S101: Provides fiber raw materials; S102: Fiber web formation; S103: Hydroentangled reinforcement; S104: A dry substrate is formed by drying in one step. The drying temperature during the one-step drying is 80-140℃ and the drying time is 0.5-5min. The moisture content of the dry substrate is less than or equal to 8%, and the MDT of the dry substrate is 50-100N / 50mm.

[0018] The fiber raw materials include natural fibers and regenerated fibers. The natural fibers can be wood pulp fibers with a length of 2-4 mm and a proportion of 60-80% in the fiber mixture. The regenerated fibers can be lyocell fibers with a length of 8-15 mm, a linear density of 1.2-1.8 denier, and a proportion of 20-40%.

[0019] The high-basic-weight washable nonwoven fabric has a basis weight greater than or equal to 85 g / m², an MDT strength greater than or equal to 35 N / 50 mm, and an FTTS dispersion rate greater than or equal to 90%.

[0020] Beneficial Effects: This invention provides a method for preparing a high-basic-weight washable nonwoven fabric. S10: Forming a dry substrate; S20: Locally wetting the dry substrate to form a locally wetted body; the local wetting involves forming a regularly distributed array of wetting points on the surface of the dry substrate, with a distribution density of 4-12 wetting points / cm². S30: Structurally reconstructing the locally wetted body to form a high-basic-weight washable nonwoven fabric; wherein the structural reconstruction involves inducing a fluffy, weakened structure in the corresponding region of the wetting points through secondary drying. By precisely wetting locally and inducing a fluffy structure through secondary drying, both the strength of the nonwoven fabric and its rapid dispersion capability are achieved. Attached Figure Description

[0021] Figure 1 A schematic diagram of the preparation method of high basic weight washable nonwoven fabric according to an embodiment of the present invention; Figure 2 Schematic diagram of a precision liquid application device; Figure 3 This is a schematic diagram of a locally wetted body formed by localized wetting of a dry substrate; Illustrated component symbols: Dry substrate 100; wetting point 101; liquid storage unit 21; liquid delivery unit 22; control unit 23; spraying unit 24. Detailed Implementation

[0022] The following disclosure generally relates to techniques for manufacturing washable nonwoven fabrics. More specifically, this disclosure relates to methods for manufacturing high-basic-weight washable nonwoven fabrics. The methods for manufacturing washable nonwoven fabrics disclosed herein include custom treatments of the fiber structure to provide additional or enhanced washability without introducing or adding undesirable material properties or performance. In this way, greater strength and dispersibility can be included in high-basic-weight nonwoven fabrics.

[0023] The core of this invention lies in resolving the contradiction between strength and washability in high-basicity nonwoven fabrics through precise local wetting and structural reconstruction. In one example, the method for manufacturing a washable nonwoven fabric may include the step of forming a dry matrix 100. The dry matrix 100 may include wood pulp fibers and lyocell fibers disposed within a fiber web. The manufacturing method may include the step of locally wetting the dry matrix 100. This local wetting process may include forming wetting points 101 of a predetermined shape on the surface of the dry matrix 100 using a precise liquid application device. The manufacturing method may include the step of structural reconstruction of the locally wetted body. This structural reconstruction may include forming a fluffy shape in the wetted areas through drying-induced processes. In one example, such an arrangement allows the nonwoven fabric to achieve rapid dispersion while maintaining high strength. The synergistic effect of this local wetting and structural reconstruction can significantly improve the dispersion performance and stability of the nonwoven fabric. The precisely controlled wetting points 101 can organically combine the strong and weak areas of the nonwoven fabric, thereby improving product performance, durability, and environmental compatibility.

[0024] Please refer to Figure 1 ,exist Figure 1 The diagram illustrates the overall flow of a method for manufacturing a washable nonwoven fabric according to an embodiment of the present invention, specifically including: S10: Forms dry matrix 100.

[0025] The formation of the dry substrate 100 includes the following specific steps: S101: Provide fiber raw materials.

[0026] The fiber raw materials include natural fibers and regenerated fibers. The natural fibers can be at least one of wood pulp fiber, bamboo fiber, straw pulp fiber, sugarcane pulp fiber, and cotton pulp fiber. Preferably, the natural fiber is wood pulp fiber, with a length ranging from 2 to 4 mm, and accounts for 60% to 80% of the fiber mixture. Wood pulp fiber has good hydrogen bond forming ability and mechanical strength, providing basic structural stability for washable nonwoven fabrics. The regenerated fiber can be lyocell fiber, with a length ranging from 8 to 15 mm, a linear density controlled between 1.2 and 1.8 denier, and accounts for 20% to 40%. Lyocell fiber has excellent wet strength and biodegradability, which helps improve the washability of the product. It is understood that the length and linear density mentioned are average lengths and average linear densities, respectively.

[0027] Furthermore, the choice of fiber raw materials can be adjusted according to specific application requirements. Besides wood pulp fiber and lyocell fiber, other types of natural or synthetic fibers can be added. For example, bamboo fiber has excellent antibacterial properties and biodegradability, making it suitable for medical dressing applications. Cotton fiber has good moisture absorption and comfort, making it suitable for personal care products. Polylactic acid fiber, as a biodegradable synthetic fiber, can provide specific mechanical properties and degradation characteristics.

[0028] S102: Fiber web formation.

[0029] The fiber web forming process can be carried out using a wet web forming method. During the web forming process, the basis weight of the fiber web is controlled within the range of 85 to 200 grams per square meter, and the web forming speed is maintained at 50 to 200 meters per minute.

[0030] S103: Hydroentangled reinforcement.

[0031] The fiber web is reinforced using a hydroentangling device equipped with multiple rows of high-pressure water jet beams. The water jet diameter is controlled within the range of 0.1–0.15 mm, and the water pressure is set to 20–80 bar. The water jets are arranged in 3–5 rows in a staggered pattern to ensure that every area of ​​the fiber web receives uniform hydroentangling impact. The impact of the high-pressure water flow causes the fibers to entangle and form a stable network structure. This hydroentangling reinforcement process improves the mechanical strength of the nonwoven fabric.

[0032] S104: Dry substrate 100 is formed by one-time drying.

[0033] During the first drying cycle, the drying temperature should be controlled within the range of 80–140℃, and the drying time should be 0.5–5 minutes. The final moisture content should be reduced to below 8%. The MDT of the dry substrate after the first drying cycle should be controlled to 50–100 N / 50 mm.

[0034] S20: Locally wet the dry substrate 100 to form a locally wetted body.

[0035] Specifically, the local wetting is the formation of a regularly distributed array of wetting points 101 on the surface of the dry substrate 100 by a precision liquid application device.

[0036] The aforementioned array of wetting points 101 refers to the regular array of wetting points 101 formed on the surface of the dry substrate 100. Specifically, the array of wetting points 101 can be checkerboard, linear, plum blossom, or honeycomb. It is understood that different array arrangements can achieve different balance effects between strength and dispersion.

[0037] Among them, the checkerboard pattern provides the most uniform intensity distribution and is suitable for applications requiring high intensity. The linear pattern facilitates directional dispersion and is suitable for applications requiring rapid decomposition in a specific direction. The quincunx pattern offers a good balance between intensity and dispersibility. The honeycomb pattern achieves the highest dispersion efficiency and is suitable for applications with extremely high dispersion speed requirements.

[0038] Furthermore, the distribution density of wetting points 101 on the surface of the dry substrate 100 is 4–12 per cm². Studies have found that when the density of wetting points 101 is greater than 12 per cm², there is a risk of high-density array droplet fusion during production, especially when the temperature and humidity of the production environment fluctuate, causing surface tension changes greater than 3 mN / m. This makes it difficult to control the wetting point array to remain discrete. Additionally, when the density of wetting points 101 is greater than 12 per cm², the yield rate during the corresponding micropore processing is too low, typically only 75-85%, resulting in excessively high production costs. When the density of wetting points 101 is less than 4 per cm², the liquid penetration path is long, and the FTTS dispersion rate drops below 85%, making it difficult to meet the FTTS dispersion rate requirements.

[0039] Its reference Figure 2 , Figure 2 A precision liquid application device is shown, including a liquid storage unit 21, a liquid delivery unit 22, a control unit 23, and a spraying unit 24.

[0040] The liquid storage unit 21 is used to store a wetting liquid, which is pure water or an aqueous solution containing 0.01 wt% to 0.1 wt% surfactant. The addition of surfactant helps to reduce the surface tension of water and improve the uniformity and controllability of the wetting effect.

[0041] Understandably, the wetting fluid should not contain any adhesives.

[0042] The liquid delivery unit 22 employs a precision peristaltic pump system, which is configured to deliver liquid with a flow control accuracy of ±0.5%. Furthermore, the delivery unit 22 is equipped with a high-efficiency filtration system to prevent nozzle clogging.

[0043] The control unit 23 is based on a closed-loop control system of a programmable logic controller and is configured to monitor and adjust injection parameters in real time.

[0044] The spraying unit 24 adopts a piezoelectric micro-nozzle array with a nozzle orifice diameter of 0.1-0.2 mm and a pulse time control accuracy of ±0.05 ms.

[0045] Understandably, in this embodiment, the formation of wetting points 101 is crucial to the local wetting process. Pure water or an aqueous solution containing 0.01wt% to 0.1wt% surfactant is sprayed onto the surface of the dry substrate 100 via pulse jetting. The pulse duration is controlled within the range of 0.1 to 1 ms, and the water volume at a single wetting point 101 is precisely controlled within 0.3 to 1 μL. Understandably, after the droplets contact the dry substrate 100, they diffuse to 3 to 8 times the nozzle orifice diameter due to fiber capillary action, forming the target wetting point 101 diameter. The final diameter of the wetting points 101 ranges from 0.5 to 1.5 mm, and the spacing between the points can be adjusted within the range of 1 to 10 mm.

[0046] Understandably, the formation of wetting point 101 leads to the local disruption and reconstruction of hydrogen bonds in the dry matrix 100. Specifically, when trace amounts of moisture come into contact with the surface of the dry matrix 100, water molecules form new hydrogen bonds with the hydroxyl groups on the fiber surface, while simultaneously disrupting the existing inter-fiber hydrogen bonds. This localized hydrogen bond reconstruction significantly reduces the fiber bonding strength in the wetting region, creating conditions for subsequent structural reconstruction. Precise control of wetting point 101 ensures the regular distribution of weakened regions, preventing overall structural instability.

[0047] Furthermore, to ensure consistent wetting quality, a machine vision feedback system can be employed. This system includes an industrial camera, an image processing computer, and a control unit.

[0048] The industrial camera is configured for high-speed video recording with a frame rate of ≥1000 frames per second and a resolution of ≥20 megapixels. The image processing computer, based on deep learning algorithms, particularly the U-Net convolutional neural network, analyzes the diameter, roundness, and position parameters of the wetting point in real time. A feedback control mechanism from the machine vision system enables closed-loop control of the wetting point 101's quality. When the parameters of the wetting point 101 deviate from the set values, the control unit dynamically adjusts the spray parameters of the nozzle array, including pulse time, spray pressure, and nozzle position. This real-time adjustment mechanism keeps the error in the diameter of the wetting point 101 within ±5%, significantly improving product consistency and yield.

[0049] Furthermore, the precise liquid application device can also employ ultrasonic atomization technology, electrostatic jetting technology, or laser-induced droplet formation technology. Ultrasonic atomization technology atomizes the liquid into fine droplets through high-frequency vibration, achieving a uniform droplet distribution. Electrostatic jetting technology uses an electric field to control the formation and distribution of droplets, enabling precise position control. Laser-induced droplet formation technology generates droplets through the thermal effect of laser pulses.

[0050] S30: Restructuring the structure of the local wetting body.

[0051] The structural reconstruction involves inducing a fluffy, weakened structure in the wetted area through secondary drying, ultimately achieving a balance between strength and dispersibility. After the local wetting treatment is completed, the locally wetted body undergoes a secondary drying treatment.

[0052] Specifically, secondary drying can be achieved through hot air penetration drying. The temperature of the secondary drying is controlled within the range of 100–140℃, the time is 1–3 minutes, and the air velocity is controlled at 2–5 m / s. Understandably, if the temperature of the secondary drying exceeds 140℃, excessive hydrogen bond reconstruction may occur, thereby damaging the structure of the washable nonwoven fabric.

[0053] Understandably, during the secondary drying process, the moisture in the wetting area gradually evaporates, causing the fibers in that area to shrink and rearrange. Since the hydrogen bonds in the wetting area have been broken, the fibers cannot form tight bonds during shrinkage, instead forming a loose, porous structure. This fluffy morphology is characterized by a 30-50% increase in inter-fiber porosity and a 40-60% decrease in entanglement density, forming micropores with a pore size of 5-50 micrometers. This structural change allows moisture to penetrate more easily into the fiber interior, accelerating the breaking of hydrogen bonds. When the washable nonwoven fabric comes into contact with water, the moisture first penetrates along these weakened areas. Especially under the impact of water flow, this can lead to the rapid disintegration of local structures, subsequently triggering a chain reaction of dispersion in the overall structure.

[0054] Understandably, structural reconstruction of locally wetted materials can also be achieved using infrared drying, microwave drying, or vacuum drying. Infrared drying, through radiant heating, can achieve rapid and uniform drying, making it particularly suitable for temperature-sensitive materials. Microwave drying utilizes microwave energy to directly heat the moisture inside the material, enabling a drying process from the inside out and facilitating the formation of unique porous structures. Vacuum drying lowers the boiling point of water by reducing ambient pressure, achieving rapid drying at lower temperatures. This technique is particularly suitable for heat-sensitive additives or applications requiring the preservation of specific molecular structures.

[0055] Furthermore, a machine vision feedback control system is employed simultaneously during the localized wetting of the dry substrate 100 to form a locally wetted body. This system uses a high-speed industrial camera installed 30cm downstream of the nozzle array, with a frame rate of 1000 frames per second and 20 million pixels. The image processing system, based on the U-Net convolutional neural network algorithm, can analyze the geometric parameters of the wetting point 101 in real time, including diameter, roundness, and positional deviation. After adopting the machine vision feedback control system, the error in the diameter of the wetting point 101 decreased from ±15% to ±5%, while significantly improving batch-to-batch consistency, increasing the yield from 90% to 97.5%, and improving the FTTS dispersion rate to 93.8%.

[0056] Furthermore, faster dispersion speed can be achieved by adjusting local wetting parameters. Increasing the array density of wetting points 101 from 5mm×5mm to 3mm×3mm, increasing the diameter of a single point from 0.8mm to 1.2mm, and correspondingly increasing the water volume to 1.1μL, this high-density weakening region design can significantly shorten the dispersion time from 120 seconds to less than 95 seconds.

[0057] In this rapid dispersion implementation, the linear density of the fibers and the hydroentangling pressure need to be adjusted accordingly. The linear density of the wood pulp fibers was adjusted to 1.8 denier, the linear density of the lyocell fibers was adjusted to 1.5 denier, and the hydroentangling pressure was increased to 60 bar. These adjustments ensured that the nonwoven fabric maintained sufficient overall strength while increasing the density of the weakened areas. The final product had an MDT strength of 58 N / 50 mm and an FTTS dispersion of 92.9%.

[0058] Additionally, functional additives can be used to enhance specific product properties. For example, adding antibacterial agents can provide long-lasting antibacterial effects, suitable for medical and hygiene applications. Adding fragrances can provide a pleasant user experience, suitable for personal care products. Adding colorants can provide an aesthetically pleasing appearance, meeting diverse aesthetic needs.

[0059] Meanwhile, the selection and optimization of surfactants have a significant impact on wetting effects. Polysorbate 80, as a nonionic surfactant, exhibits excellent wetting properties and biocompatibility. Its molecular structure contains hydrophilic polyoxyethylene segments and hydrophobic stearic acid segments, which can effectively reduce the surface tension of water and improve the uniformity of wetting.

[0060] Optimizing surfactant concentration requires balancing wetting effectiveness and cost-effectiveness. Too low a concentration may result in poor wetting, while too high a concentration increases costs and may affect other product properties. Studies have found that determining a concentration range of 0.01wt% to 0.1wt% can control costs while ensuring wetting effectiveness.

[0061] Besides polysorbate 80, other types of surfactants can be considered. For example, polyoxyethylene ether surfactants have stronger wetting ability and are suitable for difficult-to-wet fiber materials. Amino acid surfactants have excellent biocompatibility and biodegradability, making them suitable for medical and food contact applications. Furthermore, the pH value of the wetting solution is also a factor affecting wetting performance. An appropriate pH value can optimize the performance of the surfactant and improve the wettability of the fiber surface.

[0062] Temperature also has a significant impact on the wetting process. Appropriately increasing the temperature of the wetting solution can reduce the liquid viscosity and improve the wetting speed and uniformity. However, excessively high temperatures may lead to over-wetting or affect the properties of the fiber material. Optimizing the wetting solution temperature can further improve the wetting effect.

[0063] The preparation method of the washable nonwoven fabric of the present invention will be further described below with reference to specific embodiments. Example

[0064] S401: Forms a dry matrix.

[0065] S4011: Provides fiber raw materials: 70wt% wood pulp fiber (length 2-4mm) and 30wt% lyocell fiber (length 12mm, linear density 1.4 denier); the wood pulp fiber and lyocell fiber are added to the opening machine in proportion and mixed, with a mixing uniformity deviation ≤3%.

[0066] S4012: Provides fiber raw materials: A fiber web with a basis weight of 90±2g / m² is formed by wet web forming.

[0067] Mesh forming equipment: Inclined mesh forming machine (working width 2.5m, speed 80m / min).

[0068] S4013: Hydroentangled reinforcement.

[0069] Water pressure impacts the fiber web, with a water needle spacing of 1.2 mm and a processing time of 0.5 s.

[0070] Hydroentangling equipment: 5 rows of high-pressure hydro-needle beams (hydro-needle hole diameter 0.12mm, pre-needle water pressure 25Bar, main needle 45Bar).

[0071] S4014: Dry substrate is formed by drying in one step.

[0072] Dry with hot air at 120℃ for 3 minutes until the moisture content is <8%, forming a dry substrate.

[0073] S402: Locally wet the dry substrate to form a locally wetted body.

[0074] Precision liquid application device: piezoelectric needle nozzle array (nozzle orifice diameter 0.1±0.005mm). Control system: PLC control unit (pulse time accuracy ±0.01ms); Array configuration: Fuji Dimatix Q-Class modular printhead array (PQ-512), arranged in a 5mm×5mm square array with a spacing error of ±0.1mm; Spray parameters: pulse time 0.5ms, droplet diameter 0.8±0.1mm, single-point water volume 0.5±0.05μL, spray parameters are calibrated in real time by temperature and humidity sensors.

[0075] Wetting solution: 0.01wt% polysorbate 80 (pH 6.5±0.5) added to pure water.

[0076] S403: Restructuring the structure of the local wetting body.

[0077] Hot air penetrates and dries; Secondary drying temperature: 135±2℃; Drying time: 2 ± 0.2 min; Wind speed: 3±0.5m / s. Example

[0078] S501: Form dry matrix, same as in Example 1, at a speed of 60 m / min.

[0079] S502: Locally wet the dry substrate to form a locally wetted body.

[0080] Precision liquid application device: Same as in Example 1; Control system: Same as in Example 1; Array design: 10 points / cm² cellular array; Wetting point diameter: 0.5±0.05mm; Single-point water volume: 0.3±0.05μL; Wetting solution: An aqueous solution containing 0.01 wt% polysorbate 80 (pH 6.5±0.5); S503: Restructuring the structure of the local wetting body.

[0081] Low-temperature heated roller drying; Temperature: 80±5℃; Drying time: 5 ± 0.5 min; Auxiliary measures: 2kW infrared preheating unit (wavelength 2.5~5μm).

[0082] Comparative Example 1: The method shown in CN113718548A.

[0083] Fiber raw materials: 70wt% wood pulp fiber, 15wt% lyocell fiber and 5wt% Tencel; Web forming equipment: Wet web forming machine (working width 2.5m, linear speed 100m / min) Hydroentangling equipment: 5 rows of high-pressure water needle beams, with injection pressures set at 30±2 bar, 35±3 bar, 40±2 bar, 45±3 bar, and 50±2 bar respectively.

[0084] Drying equipment: Hot air circulating oven (the temperatures of the first, second, and third ovens are set to 105±2℃, 120±2℃, and 135±2℃, respectively).

[0085] Comparative Example 2: The method shown in US6749718.

[0086] Fiber composition: 40% NBKP wood pulp (beating degree 740 cc), 30% viscose fiber (1.2 denier × 5 mm, water dispersible), 30% microfibrillated cellulose (MFC, diameter 0.01 μm, viscosity 6000 mPa·s).

[0087] Process: Wet web forming → Three-layer hydroentanglement reinforcement (water pressure 3920 kPa, energy 0.4 kW / m²) → Drying. Note: All test conditions were 23±2℃ and 50±5%RH.

[0088] Based on the test results above, the washable nonwoven fabrics obtained in Examples 1 and 2 can simultaneously meet the balance between MDT strength and dispersion performance under high basis weight, that is, simultaneously meet the target of MDT strength greater than 35N / 50mm and FTTS dispersion rate greater than 90%.

[0089] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing high-basic-weight washable nonwoven fabric, characterized in that, Includes the following steps: S10: Forms a dry matrix; S20: Locally wetting the dry substrate to form a locally wetted body; the local wetting is to form a regularly distributed array of wetting points on the surface of the dry substrate, and the distribution density of the wetting points on the surface of the dry substrate is 4 to 12 points / cm². S30: Structural reconstruction of locally wetted bodies to form high-basic-weight washable nonwoven fabric; The structural reconstruction involves inducing a fluffy, weakened structure in the region corresponding to the wetting point through secondary drying.

2. The preparation method according to claim 1, characterized in that, In step S20, local wetting is achieved by spraying wetting liquid onto the dry substrate surface via pulse jetting, wherein the pulse jetting time is 0.1 to 1 ms, the water volume at a single wetting point is 0.3 to 1 μL, and the diameter of the formed wetting point ranges from 0.5 to 1.5 mm.

3. The preparation method according to claim 2, characterized in that, Local wetting is achieved by a precision liquid application device, which includes a spraying unit, which is a piezoelectric micro-nozzle array with a nozzle orifice diameter of 0.1–0.2 mm and a pulse time control accuracy of ±0.05 ms.

4. The preparation method according to claim 2, characterized in that, The wetting solution is pure water or an aqueous solution containing 0.01wt% to 0.1wt% surfactant.

5. The preparation method according to claim 4, characterized in that, The surfactant is polysorbate 80, and the pH of the wetting solution is 6.5±0.

5.

6. The preparation method according to claim 2, characterized in that, In step S30, a secondary drying process is carried out by hot air penetration drying. The temperature of the secondary drying is 100-140℃, the time is 1-3 minutes, and the wind speed is 2-5 m / s.

7. The preparation method according to claim 2, characterized in that, Step S10 includes the following steps: S101: Provides fiber raw materials; S102: Fiber web formation; S103: Hydroentangled reinforcement; S104: A dry substrate is formed by drying in one step. The drying temperature during the one-step drying is 80-140℃ and the drying time is 0.5-5min. The moisture content of the dry substrate is less than or equal to 8%, and the MDT of the dry substrate is 50-100N / 50mm.

8. The preparation method according to claim 7, characterized in that, The fiber raw materials include natural fibers and regenerated fibers. The natural fibers can be wood pulp fibers with a length of 2-4 mm and a proportion of 60-80% in the fiber mixture. The regenerated fibers can be lyocell fibers with a length of 8-15 mm, a linear density of 1.2-1.8 denier, and a proportion of 20-40%.

9. The preparation method according to claim 1, characterized in that, The high basis weight washable nonwoven fabric has a basis weight greater than or equal to 85 g / m², an MDT strength greater than or equal to 35 N / 50 mm, and an FTTS dispersion rate greater than or equal to 90%.

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