Cooling water-jet nonwoven fabric and its application in cooling wet wipes

Abstract

This invention relates to the field of functional nonwoven materials technology and provides a cooling spunlace nonwoven fabric composed of a three-layer gradient functional composite fiber web structure. It is integrally formed through a quadruple network mechanism of physical entanglement, gradient melt bonding, ion-gated reversible crosslinking, and microfibrillated cellulose reinforcement. Simultaneously, it employs a dual cooling design combining fiber body copolymerization modification and embedded phase change materials. The three-layer gradient functional composite fiber web structure includes a tough skeleton layer, a cooling and moisture-absorbing synergistic layer, and a radiation-cooling skin-friendly surface layer. The nonwoven fabric also includes a gradient melt bonding network, an ion-gated reversible crosslinking network, a boron nitride thermally conductive skeleton, and a three-gradient intelligent response coating. This achieves a wet strength of at least 1.3 kN / m for washable wipes with less than 35% residual heat after washing. The dual cooling design embeds all cooling components within the fiber body, solving the problems of powder and lint shedding and cooling effect attenuation in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of functional nonwoven materials technology, and more specifically, to cooling spunlace nonwoven fabric and its application in cooling wipes. Background Technology

[0002] Nonwoven fabric, also known as non-woven cloth, is a type of fabric formed without spinning or weaving. It is a sheet, web, or pad made of oriented or randomly arranged fibers bonded together by friction, cohesion, or bonding. Spunlace nonwoven fabric is an important type of nonwoven fabric, utilizing high-pressure micro-jet water jets sprayed onto one or more layers of fiber webs, causing the fibers to entangle and solidify into a fabric. It has advantages such as softness, good drape, and no lint, and is widely used in medical and hygiene, personal care, and cleaning fields. Cooling spunlace nonwoven fabric is a functional product developed from traditional spunlace nonwoven fabric. The cooling function was initially achieved mainly by introducing inorganic powders with high thermal conductivity (such as mica powder, jade powder, etc.) into the fibers or by coating with cooling auxiliaries through finishing processes. Among them, mica and jade-like mineral powders, with their higher thermal conductivity than traditional textile fibers, can quickly absorb heat upon skin contact, generating a cooling sensation. Furthermore, by adding phase change materials (such as paraffin-based phase change microcapsules) to the surface or interior of nonwoven fabrics, the latent heat absorbed or released during phase transitions can be utilized to achieve temperature regulation within a certain time range. In recent years, with the increasing consumer demand for summer cooling and cleaning products, spunlace nonwoven fabrics that combine cleaning and wiping functions with a cooling experience have gradually become a key focus of industry research and development.

[0003] In the application of cooling spunlace nonwoven fabric in refreshing wet wipes, existing technologies mainly achieve the cooling effect through two approaches. The first approach involves using the prepared cooling spunlace nonwoven fabric as the wipe base material, then impregnating it with a liquid formula containing chemical cooling agents such as menthol, borneol, and alcohol. This chemical stimulation acts on the skin's cold receptors to produce a cooling sensation. The second approach involves directly adding cooling functional components during the nonwoven fabric manufacturing process. For example, cooling powders such as mica and jade powder can be adhered to the fiber surface through coating or impregnation, or phase change microcapsules can be incorporated into the nonwoven fabric to create a base material with cooling properties, which is then compounded with the wet wipe's medicinal liquid. Regarding the wipe's structural design, existing products mostly adopt a single-layer uniform structure or a simple double-layer composite structure, with the fiber ratio primarily consisting of a polyester and viscose blend. Some products employ a hot-rolling reinforcement process to improve lint shedding; to extend the duration of the cooling sensation, some solutions utilize microencapsulation technology to encapsulate the cooling agents. In the field of flushable wipes, there are technical solutions that optimize fiber selection and hydroentangling processes, enabling the wipes to be disintegrated and dispersed by the shear force of water flow after use, thereby avoiding clogging of drainage pipes.

[0004] Currently, the cooling wipes industry faces the challenge of achieving a cooling sensation through methods limited to chemical stimulation or simple physical cooling. The vast majority of products rely on chemical cooling agents such as menthol and alcohol, with the cooling effect typically lasting only 2 to 5 minutes. Some improved solutions use phase change microcapsules as a physical cooling method, but due to the weak binding force between the microcapsules and fibers, a large amount is lost during long-term soaking in the wipe's soaking liquid, resulting in a significant decrease in the cooling effect. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a cooling spunlace nonwoven fabric and its application in cooling wipes.

[0006] The specific technical solution is as follows: Cooling spunlace nonwoven fabric, which is composed of a three-layer gradient functional composite fiber network structure, and is integrally formed through a quadruple network mechanism of physical entanglement, gradient melt bonding, ion-gated reversible crosslinking and microfibrillated cellulose reinforcement. At the same time, it adopts a dual cooling design of fiber body copolymerization modification and embedded phase change material synergistically.

[0007] The three-layer gradient functional composite fiber network structure includes:

[0008] The tough skeleton layer is composed of Lyocell fibers and trilobal polylactic acid fibers in a ratio of 55-70 wt% Lyocell fibers. Microfibrillated cellulose is dispersed between the Lyocell fibers and the trilobal polylactic acid fibers, forming a biodegradable and tough skeleton layer.

[0009] The cooling and moisture-wicking synergistic layer is made of graphene, boron nitride and mica composite copolymer modified Lyocell fiber, bamboo pulp fiber and carboxymethylated seaweed fiber blend; and the skin of the copolymer modified Lyocell fiber is embedded with phase change nanocapsules.

[0010] The radiation-cooled skin-friendly surface layer is made of a blend of high-moisture-strength viscose fiber, cooling viscose fiber with embedded natural menthol nanocapsules, and radiation-cooling fiber with surface grafted silica submicron spheres; the silica submicron spheres have a particle size of 6-10μm and have high emissivity in the atmospheric window 8-13 μm band.

[0011] The nonwoven fabric also contains:

[0012] The gradient melt-bonded network is formed by polylactic acid fibers with trilobal cross-sections forming discrete point-like bonding points with a gradient distribution along the thickness direction under the action of staged pulsed hot airflow. The density of bonding points on the surface layer is 30%-50% of that of the tough skeleton layer.

[0013] An ion-gated reversible crosslinking network is formed by a carboxyl-containing pH / ionic strength dual-responsive alginate derivative and multivalent metal ions forming crosslinking bridges on the fiber surface of a three-layer gradient functional composite fiber network structure. The crosslinking remains closed under the conditions of pH 4.5-6.5 of the impregnation solution and dissociates in response to the conditions of pH 6.8-7.5 of flowing water.

[0014] The boron nitride thermally conductive framework consists of hexagonal boron nitride nanosheets fixed to the fiber surface of a three-layer gradient functional composite fiber network structure through electrostatic self-assembly and hydrogen bonding. The lateral dimensions of the hexagonal boron nitride nanosheets are 200-800 nm, forming a three-dimensional thermally conductive pathway with the phase change nanocapsules embedded in the fiber and the copolymerized modified fiber.

[0015] The three-gradient smart response coating is applied to the skin-friendly surface of the radiation-cooled coating. The three-gradient smart response coating consists of a three-layer structure: a fast-release microcapsule shell, a medium-release microcapsule shell, and a sustained-release microcapsule shell. The fast-release microcapsule shell is a temperature-sensitive polymer that accelerates release at temperatures above 32°C.

[0016] In a further technical solution, the microfibrillated cellulose has a fiber diameter of 10-100 nm, an aspect ratio of 50-200, and is added at 1%-5% of the total fiber mass, forming nanoscale bridging reinforcement in the fiber entanglement network.

[0017] In a further technical solution, the graphene, boron nitride and mica composite copolymer modified Lyocell fiber has a mass ratio of graphene nanosheets, hexagonal boron nitride nanosheets and mica powder of 1:2:6, and the total amount of the three added is 8%-15% of the fiber mass of the three-layer gradient functional composite fiber network structure. It is prepared by dry-jet wet spinning process after blending with Lyocell spinning solution.

[0018] In a further technical solution, the core material of the phase change nanocapsule is a binary eutectic mixture of n-tetradecane and n-octadecane; the phase change temperature of the phase change nanocapsule is 26-30℃, and the particle size of the phase change nanocapsule is 200-800 nm; the shell material of the phase change nanocapsule is silicon dioxide, with a phase change enthalpy of not less than 150 J / g, and a loading of 5%-12 wt% in the Lyocell fiber skin.

[0019] In a further technical solution, the pH / ionic strength dual-responsive alginate derivative used in the ion-gated reversible crosslinking network is sodium carboxyethyl alginate; the degree of substitution of sodium carboxyethyl alginate is 0.6-1.2, forming a bridge with the mixed crosslinking system of calcium ions and magnesium ions, and the content of alginate derivative is 0.8%-3.5% of the total weight of the nonwoven fabric.

[0020] A further technical solution involves the three-layer gradient functional composite fiber web structure being integrally formed through a process of high- and low-pressure segmented hydroentangling and localized variable-density point pressure reinforcement: the tough skeleton layer is formed using 120-160 bar high-pressure hydroentangling, the cooling and moisture-absorbing synergistic layer is formed using 70-100 bar medium-pressure hydroentangling, and the radiant cooling skin-friendly surface layer is formed using 40-60 bar low-pressure hydroentangling; after physical entanglement, it is reinforced by lattice-type variable-density point pressure, wherein the point pressure in the central area is 40-60 bar, the point pressure in the edge area is 20-30 bar, the lattice spacing is 4-8 mm, and the edge lattice spacing is 1.5-2 times that of the central area.

[0021] In a further technical solution, the three-gradient intelligent response coating comprises: a fast-release microcapsule shell made of poly(N-isopropylacrylamide-polyethylene glycol) copolymer with a phase transition temperature of 32°C and a shell thickness of 40-80 nm; a mid-release microcapsule shell made of ethyl cellulose with a shell thickness of 150-300 nm; and a sustained-release microcapsule shell made of silica with a shell thickness of 400-800 nm. The thickness ratio of the three layers—fast-release, mid-release, and sustained-release microcapsule shells—is 1:2:3.

[0022] A cooling wipe, comprising the application of the aforementioned cooling spunlace nonwoven fabric; the impregnation solution of the cooling wipe is a weakly acidic buffer system containing the following components:

[0023] Xylitol 1.0% (w / v) - 3.0% (w / v);

[0024] Erythritol 0.5% (w / v) - 1.5% (w / v);

[0025] Panthenol 0.3% (w / v) - 0.6% (w / v);

[0026] Witch hazel extract 0.2% (w / v) - 0.4% (w / v);

[0027] Glycerin 2% (w / v) - 5% (w / v);

[0028] Sodium hyaluronate 0.05% (w / v) - 0.15% (w / v);

[0029] Calcium lactate 0.2% (w / v) - 0.8% (w / v);

[0030] Magnesium gluconate 0.1% (w / v) - 0.3% (w / v);

[0031] Capryloyl hydroxamic acid 0.3% (w / v) - 0.5% (w / v);

[0032] The impregnation solution has a pH value of 5.0-6.2 and does not contain ethanol, menthol, or borneol.

[0033] A further technical solution involves the following: the cooling spunlace nonwoven fabric undergoes a secondary low-temperature plasma treatment before impregnation with the impregnation liquid. The power of the secondary low-temperature plasma treatment is 200-300 W, the time is 5-10 s, and the atmosphere is a mixture of argon and oxygen at a volume ratio of 4:1. The impregnation process employs a gradient negative pressure impregnation process. The first stage of the gradient negative pressure impregnation process has a negative pressure of -0.04 MPa and a negative pressure time of 5 s; the second stage of the gradient negative pressure impregnation process has a negative pressure of -0.02 MPa and a negative pressure time of 8 s. After cutting, the edges are treated with ultrasonic micro-sealing at a power of 80-120 W for 2-3 s. The packaging after the secondary low-temperature plasma treatment uses a five-layer composite film containing an ethylene-vinyl alcohol copolymer layer, and the five-layer composite film contains an oxygen absorber and a desiccant.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. A three-layer gradient functional composite fiber network structure (a tough skeleton layer, a cooling and moisture-wicking synergistic layer, and a radiative cooling skin-friendly surface layer), combined with a quadruple network mechanism (physical entanglement, microfibrillated cellulose reinforcement, gradient melt bonding, and ion-gated reversible crosslinking), further enhanced by a dual cooling design (fiber bulk copolymerization modification and embedded phase change materials), a boron nitride thermally conductive skeleton, and a three-gradient intelligent response coating; the three-layer gradient functional composite fiber network structure integrates toughness support, cooling and moisture-wicking antibacterial properties, and skin-friendly radiative cooling in a layered design, overcoming the limitations of existing homogeneous structures that cannot simultaneously achieve a soft surface layer, a functional middle layer, and a strong bottom layer; the quadruple network mechanism interpenetrates at three levels from the nanoscale (microfibrillated cellulose reinforcement bridging) to the microscale (gradient melt bonding) to the molecular level (ion-gated reversible crosslinking), achieving a wet strength of at least 1.3 for the washable wipes. kN / m and less than 35% of the residue is dispersed; the dual cooling design embeds all the cooling components into the fiber body, solving the problems of powder and lint shedding and cooling attenuation in existing technologies; the radiation cooling surface layer introduces passive radiation cooling with an 8-13 μm atmospheric window to the field of wet wipes for the first time, achieving continuous cooling without energy consumption; the boron nitride thermal skeleton and the three-gradient intelligent response coating form a complete thermal management closed loop from the inside to the outside.

[0036] 2. Microfibrillated cellulose forms nanoscale bridging at fiber intersections with minimal addition (1%-5%). Its huge specific surface area provides a large number of hydrogen bonding sites, which increases the strength of nonwoven fabric by an additional 15%-25% in the wet state without affecting its washability. When flushing, the microfibrillated cellulose disperses along with the main fibers without forming permanent agglomerates. Compared with the shortcomings of existing washable wipes that rely solely on physical entanglement and have insufficient strength, microfibrillated cellulose nano-reinforcement achieves a leap in strength at an extremely low cost.

[0037] 3. Graphene provides ultra-high in-plane thermal conductivity, boron nitride provides interlayer thermal conductivity and a smooth, skin-feeling feel, and mica provides a cooling sensation upon contact. The synergy of these three components makes the thermal conductivity of modified Lyocell fibers 3-5 times that of conventional viscose. Compared with existing single mica or jade powder modification schemes, the graphene-boron nitride-mica ternary composite system constructs a multi-dimensional thermal conductivity network of "in-plane, interlayer, and contact," which significantly improves the cooling efficiency.

[0038] 4. The binary eutectic mixture precisely regulates the phase transition temperature to 26-30℃, which is closer to the comfortable temperature range for the skin; the thermal conductivity of the silica shell (approximately 1.4 W / m·K) is far superior to that of traditional melamine resin (approximately 0.3 W / m·K), increasing the thermal response speed by about 3 times; the specific surface area of ​​the 200-800 nm nano-sized particles is an order of magnitude larger than that of micron-sized capsules, further accelerating heat exchange; embedded in the fiber skin rather than attached to the surface, it hardly leaks out even after long-term immersion in the impregnation liquid, and the cooling sensation decreases by less than 6% after 12 months;

[0039] 5. The introduction of carboxyethyl groups lowers the pKa of the alginate chain. Under the conditions of pH 5.0-6.2 in the impregnation solution, the carboxyl groups are fully protonated to form a stable "egg-box" crosslinking structure, providing approximately 30%-50% wet strength gain. Upon entering a flowing water environment with pH 6.8-7.5, the carboxyethyl groups are gradually deprotonated, increasing charge repulsion and diluting calcium and magnesium ions. The dual response synergistically triggers crosslinking dissociation. The calcium-magnesium mixed crosslinking system has a wider response window and a milder dissociation curve than the single calcium ion crosslinking system.

[0040] 6. High and low pressure segmented hydroentanglement utilizes the energy attenuation effect of water needles to form an entanglement density gradient in the thickness direction. The bottom layer is dense and tough, the middle layer is moderately porous, and the surface layer is soft and fluffy, which solves the problem that the existing single hydroentanglement pressure cannot meet the differentiated needs of each layer. Variable density point pressure reinforcement forms a functional zone in the planar direction with high density reinforcement in the center and low density and flexibility at the edges. The central area bears the main wiping force, while the edge area is flexible and does not scratch the face and is conducive to priority disintegration when rinsing.

[0041] 7. The poly-N-isopropylacrylamide-polyethylene glycol copolymer in the shell of the fast-release microcapsule undergoes a phase transition at 32°C (close to skin temperature), and the shell contraction triggers the pulse release of the cooling agent, simulating a biofeedback mechanism. This is an intelligent temperature-sensitive switch that is different from existing iso-rate sustained-release schemes. The three-layer thickness ratio of 1:2:3 and the release rate ratio of approximately 10:3:1 achieve gradient delivery with rapid response, stable maintenance, and ultra-long endurance.

[0042] 8. Erythritol, with a heat of solubility of -42 cal / g, is greater than that of xylitol, which is -37 cal / g, and is non-cariogenic. The dual-component synergistic effect enhances the physical cooling sensation while maintaining zero chemical irritation, making it the most suitable impregnation solution formulation for substrates with a purely physical cooling sensation. The calcium lactate / magnesium gluconate dual salt system maintains ion-gated cross-linking and is deeply coupled with the function of the substrate. Capryloyl hydroxamic acid replaces the traditional phenoxyethanol / paraben, providing mild and broad-spectrum preservation. Gradient negative pressure impregnation is more uniform and shortens the cycle by about 30% compared to normal pressure immersion. Attached Figure Description

[0043] Figure 1 The wet tensile strength statistics of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention are shown in the figure.

[0044] Figure 2 The following are statistical diagrams of the dry fracture strength of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0045] Figure 3 This is a statistical graph of the continuous cooling power density of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0047] Example 1

[0048] Cooling spunlace nonwoven fabric is composed of a three-layer gradient functional composite fiber network structure and is integrally formed through a quadruple network mechanism of physical entanglement, gradient melt bonding, ion-gated reversible crosslinking and microfibrillated cellulose reinforcement. At the same time, it adopts a dual cooling design with fiber body copolymerization modification and embedded phase change material synergistic.

[0049] The three-layer gradient functional composite fiber network structure includes:

[0050] The tough skeleton layer is composed of Lyocell fibers and trilobal polylactic acid fibers in a ratio of 55-70 wt% Lyocell fibers. Microfibrillated cellulose is dispersed between the Lyocell fibers and the trilobal polylactic acid fibers, forming a biodegradable and tough skeleton layer.

[0051] The cooling and moisture-wicking synergistic layer is made of graphene, boron nitride and mica composite copolymer modified Lyocell fiber, bamboo pulp fiber and carboxymethylated seaweed fiber blend; and the skin of the copolymer modified Lyocell fiber is embedded with phase change nanocapsules to achieve synergistic effect of cooling, moisture-wicking and antibacterial.

[0052] The radiation-cooled skin-friendly surface layer is made of a blend of high-moisture-strength viscose fiber, cooling viscose fiber with embedded natural menthol nanocapsules, and radiation-cooling fiber with surface grafted silica submicron spheres; the silica submicron spheres have a particle size of 6-10μm and have high emissivity in the atmospheric window 8-13 μm band.

[0053] The nonwoven fabric also contains:

[0054] The gradient melt-bonded network is formed by polylactic acid fibers with trilobal cross-sections forming discrete point-like bonding points with a gradient distribution along the thickness direction under the action of staged pulsed hot airflow. The density of bonding points on the surface layer is 30%-50% of that of the tough skeleton layer.

[0055] An ion-gated reversible crosslinking network is formed by a carboxyl-containing pH / ionic strength dual-responsive alginate derivative and multivalent metal ions forming crosslinking bridges on the fiber surface of a three-layer gradient functional composite fiber network structure. The crosslinking remains closed under the conditions of pH 4.5-6.5 of the impregnation solution and dissociates in response to the conditions of pH 6.8-7.5 of flowing water.

[0056] The boron nitride thermally conductive framework consists of hexagonal boron nitride nanosheets fixed to the fiber surface of a three-layer gradient functional composite fiber network structure through electrostatic self-assembly and hydrogen bonding. The lateral dimensions of the hexagonal boron nitride nanosheets are 200-800 nm, forming a three-dimensional thermally conductive pathway with the phase change nanocapsules embedded in the fiber and the copolymerized modified fiber.

[0057] The three-gradient smart response coating is applied to the skin-friendly surface of the radiation-cooled coating. The three-gradient smart response coating consists of a three-layer structure: a fast-release microcapsule shell, a medium-release microcapsule shell, and a sustained-release microcapsule shell. The fast-release microcapsule shell is a temperature-sensitive polymer that accelerates release at temperatures above 32°C.

[0058] A three-layer gradient functional composite fiber network structure (a tough skeleton layer, a cooling and moisture-wicking synergistic layer, and a radiative cooling skin-friendly surface layer), combined with a quadruple network mechanism (physical entanglement, microfibrillated cellulose reinforcement, gradient melt bonding, and ion-gated reversible crosslinking), further enhanced by a dual cooling design (fiber bulk copolymerization modification and embedded phase change materials), a boron nitride thermally conductive skeleton, and a three-gradient intelligent response coating; the three-layer gradient functional composite fiber network structure integrates toughness support, cooling and moisture-wicking antibacterial properties, and skin-friendly radiative cooling into layers, overcoming the limitations of existing homogeneous structures that cannot simultaneously achieve a soft surface, functional middle layer, and strong bottom layer; the quadruple network mechanism interpenetrates from the nanoscale (microfibrillated cellulose reinforcement bridging) to the microscale (gradient melt bonding) to the molecular scale (ion-gated reversible crosslinking), achieving a wet strength of at least 1.3 kN / m for the washable wipes with less than 35% residue after washing; the dual cooling design embeds all cooling components within the fiber bulk, solving the problems of powder and lint shedding and cooling attenuation in existing technologies; the radiative cooling surface layer is the first to incorporate 8-13 The introduction of μm atmospheric window passive radiation cooling into the field of wet wipes enables continuous cooling without energy consumption; the boron nitride thermal conductive skeleton and the three-gradient intelligent response coating form a complete thermal management closed loop from the inside out.

[0059] Cooling spunlace nonwoven fabric with the following performance indicators: areal density 42-62 g / m² 2 The Q-max (instantaneous cooling coefficient) is not less than 0.28 W / cm². 2 The wet longitudinal tensile strength is not less than 1.3 kN / m, the dry breaking strength is not less than 18 N / 5cm, the moisture absorption rate is not less than 200%, the liquid carrying capacity is not less than 340%, and the continuous cooling power density is not less than 25 W / m³. 2 The average emissivity of the atmospheric window is not less than 0.85, the cooling sensation decreases by no more than 6% over 12 months, the compost degradation rate is not less than 95% over 180 days, and the residual rate after 60 minutes of dispersal is less than 35%.

[0060] The four-fold network mechanism includes:

[0061] First layer of network: physical entanglement and microfibrillated cellulose reinforcement

[0062] Using Lyocell fibers (55-70 wt%) as the primary framework, combined with trilobal polylactic acid fibers, a dense physical entanglement is formed through high-pressure hydroentangling. Microfibrillated cellulose, nanoscale cellulose fibers extracted from wood pulp through high-pressure homogenization, with diameters of 10-100 nm and aspect ratios of 50-200, is introduced. The microfibrillated cellulose is uniformly dispersed within the fiber network, forming nanoscale bridging at fiber intersections, with a maximum diameter of 100 nm. 2The specific surface area of ​​ / g provides a large number of hydrogen bonding sites; the nano-bridging effect of microfibrillated cellulose in wet state can increase the wet strength of nonwoven fabric by an additional 15%-25%, while in the flushing environment, microfibrillated cellulose disperses together with the main fiber and does not form permanent agglomeration; the amount of microfibrillated cellulose added is only 1%-5% of the total fiber mass, and has minimal impact on cost and hand feel.

[0063] Second network: gradient melt bonding

[0064] Polylactic acid fibers with a melting point of 165-175℃ form discrete melt-bonded points with a gradient distribution along the thickness direction of the nonwoven fabric under the action of staged pulsed hot airflow:

[0065] First stage: Temperature 150-160℃, pressure 0.2-0.3 MPa, applied in the direction of radiation cooling of the surface layer, forming low-density adhesive points (area ratio of 3%-7%), keeping the surface layer soft and skin-friendly;

[0066] The second stage involves applying a temperature of 170-180℃ and a pressure of 0.4-0.6 MPa to the tough skeleton layer, forming high-density bonding points (8%-15% of the area) to provide core strength.

[0067] With bonding point diameters of 50-200 μm, it provides additional structural support during use, increasing wet strength to no less than 1.3 kN / m; it gradually degrades with polylactic acid hydrolysis in a water-flushing environment without hindering fiber dispersion; the gradient distribution avoids the "overall hardening" problem of traditional uniform hot pressing.

[0068] Third network: Ion-gated reversible crosslinking

[0069] Sodium carboxyethyl alginate with a degree of substitution of 0.6-1.2 is used to replace ordinary sodium alginate, forming a mixed cross-linking system with calcium and magnesium ions; ion-gated effect:

[0070] In use (ion gate closed): The impregnation solution has a pH of 5.0-6.2 and sufficient calcium and magnesium ion concentrations; the introduction of carboxyethyl groups lowers the pKa of the alginate chain, and the carboxyl groups are fully protonated within this pH range to form a stable egg-shell cross-linked structure with multivalent ions; cross-linking bridges give the fiber network additional wet strength (increasing it by about 30%-50%).

[0071] Flushing state (ion gate open): After entering the flowing water environment, the pH gradually rises to 6.8-7.5 (the drainage system is close to neutral), the carboxyethyl group is gradually deprotonated, the charge repulsion increases, and the egg carton structure opens in an orderly manner; at the same time, calcium and magnesium ions are diluted by a large amount of water, and the concentration drops to below the cross-linking critical value; the two work together to trigger pulsed ion release, and the cross-linking network rapidly dissociates within 15-30 minutes;

[0072] This solution features a "pH / ionic strength dual response" with on / off control: it fully cross-links during use and rapidly dissociates after rinsing; the response time can be adjusted within the range of 10-40 minutes by adjusting the degree of carboxyethyl substitution.

[0073] Fourth layer network: Dual network interoperability and coordination

[0074] The aforementioned triple network forms a three-tiered interpenetrating structure of "microfibrillated cellulose nanobridges, gradient melt bonding, and ion-gated reversible crosslinking (ion-gated alginate)," contributing strength at different scales and playing a role in a time- and stage-specific manner during use and flushing.

[0075] 1. Microfibrillated cellulose nanobridges, with a size of 10-100 nm, provide a basic increase in wet strength (15%-25%) and are dispersed together with the main fibers;

[0076] 2. Gradient melt bonding, with a scale of 50-200 μm, provides core structural support and gradually degrades with PLA hydrolysis (greater than 30 min).

[0077] 3. Ion-gated reversible crosslinking at the molecular level (less than 1 nm) provides additional wet strength (30%-50%) and pH / ion dual-response pulse dissociation (15-30 min).

[0078] The fiber bulk copolymerization modification is a Lyocell fiber copolymerized from graphene, boron nitride, and mica, specifically:

[0079] A dry-jet wet spinning process was employed, in which graphene nanosheets, hexagonal boron nitride nanosheets, and mica powder were blended into the spinning solution at a mass ratio of 1:2:6. Graphene provides ultra-high in-plane thermal conductivity, boron nitride provides an insulating interlayer thermal conduction path and a lubricating feel, and mica powder provides a cooling sensation upon contact. The total addition amount of the three components was 8%-15%, uniformly embedded in the fiber body. The prepared modified Lyocell fiber has a thermal conductivity 3-5 times that of conventional viscose, and a cooling coefficient Q-max ≥ 0.25 W / cm². 2 It feels cool and smooth to the touch.

[0080] The phase change material is a copolymer-modified Lyocell fiber with phase change nanocapsules embedded in its outer layer. The phase change nanocapsules contain:

[0081] A binary eutectic mixture of n-tetradecane and n-octadecane was used as the core material (phase transition temperature 26-30℃, closer to the comfortable temperature range for skin), with silica as the shell material, to form phase transition nanocapsules with a particle size of 200-800 nm (phase transition enthalpy ≥150J / g). The fiber sheath was embedded during the Lyocell spinning stage (the sheath thickness accounts for about 15%-20% of the fiber diameter), with a loading of 5%-12wt%. The silica shell material has better biocompatibility and faster thermal conductivity response than traditional melamine resin (thermal conductivity about 1.4 W / m·K vs about 0.3 W / m·K), and the particle size is reduced from the micrometer level to the nanometer level, the specific surface area is increased, and the thermal response speed is improved by about 3 times.

[0082] Hexagonal boron nitride thermally conductive framework: Hexagonal boron nitride nanosheets (lateral size 200-800 nm, number of layers 5-20, in-plane thermal conductivity >400 W / m·K) are fixed to the fiber surface through a combination of electrostatic self-assembly and hydrogen bonding. During the impregnation process, the boron nitride nanosheets form a large-area overlapping spread on the fiber surface, constructing a three-dimensional thermally conductive framework that runs continuously from the surface layer to the inner layer. Skin heat is efficiently conducted through the boron nitride framework to the phase change nanocapsules embedded in the fiber and the copolymerized modified fiber cooling component, forming a complete heat flow path of "surface heat conduction, internal heat absorption and bulk heat dissipation".

[0083] A three-layer temperature-sensitive controlled-release coating with a three-gradient intelligent response coating was constructed on the surface of the radiation-cooled skin-friendly layer using a layer-by-layer spraying method:

[0084] Fast-release microcapsule shell (shell thickness 40-80 nm): The shell is a poly(N-isopropylacrylamide)-polyethylene glycol copolymer with a low critical solubility of 32°C; below 32°C, the shell swells and retains water, allowing the cooling agent to be released slowly; upon contact with skin (above 32°C), the shell contracts rapidly, triggering the rapid release of the cooling agent and providing an immediate "cooling shock"; the polyethylene glycol segments provide antifouling and hydrophilic properties;

[0085] Medium-release microcapsule shell (shell thickness 150-300 nm): The shell is made of ethyl cellulose, which has relatively stable sustained-release properties and maintains a stable output of cooling sensation;

[0086] Sustained-release microcapsule shell (shell thickness 400-800 nm): The shell is made of silica, with a dense structure and the slowest release rate, providing an ultra-long-lasting cooling sensation, which lasts for more than 40 minutes.

[0087] With a thickness ratio of 1:2:3 and a release rate ratio of approximately 10:3:1, the three layers achieve an intelligent delivery curve of "rapid response - stable maintenance - ultra-long endurance". The introduction of a thermosensitive shell layer of poly(N-isopropylacrylamide)-polyethylene glycol copolymer enables the coating to adjust the release rate in real time according to skin temperature, which is an original breakthrough that distinguishes it from all existing isotropic sustained-release solutions.

[0088] Further:

[0089] The microfibrillated cellulose has a fiber diameter of 10-100 nm and an aspect ratio of 50-200. The amount added is 1%-5% of the total fiber mass, forming nanoscale bridging reinforcement in the fiber entanglement network.

[0090] Microfibrillated cellulose forms nanoscale bridging at fiber intersections with minimal addition (1%-5%). Its huge specific surface area provides a large number of hydrogen bonding sites, which increases the strength of nonwoven fabric by an additional 15%-25% in the wet state without affecting its washability. When flushing, microfibrillated cellulose disperses along with the main fibers without forming permanent agglomerates. Compared with the shortcomings of existing washable wipes that rely solely on physical entanglement and have insufficient strength, microfibrillated cellulose nano-reinforcement achieves a leap in strength at an extremely low cost.

[0091] In a further technical solution, the graphene, boron nitride and mica composite copolymer modified Lyocell fiber has a mass ratio of graphene nanosheets, hexagonal boron nitride nanosheets and mica powder of 1:2:6, and the total amount of the three added is 8%-15% of the fiber mass of the three-layer gradient functional composite fiber network structure. It is prepared by dry-jet wet spinning process after blending with Lyocell spinning solution.

[0092] Graphene provides ultra-high in-plane thermal conductivity, boron nitride provides interlayer thermal conductivity and a smooth, skin-like feel, and mica provides a cooling sensation upon contact. The synergy of these three components makes the thermal conductivity of modified Lyocell fibers 3-5 times that of conventional viscose. Compared with existing single mica or jade powder modification schemes, the graphene-boron nitride-mica ternary composite system constructs a multi-dimensional thermal conductivity network of "in-plane, interlayer, and contact," significantly improving the cooling efficiency. The dry-jet wet spinning process is more conducive to the uniform dispersion and orientation of nanofillers than traditional wet spinning.

[0093] The core material of the phase change nanocapsule is a binary eutectic mixture of n-tetradecane and n-octadecane; the phase change temperature of the phase change nanocapsule is 26-30℃, and the particle size of the phase change nanocapsule is 200-800 nm; the shell material of the phase change nanocapsule is silicon dioxide, with a phase change enthalpy of not less than 150 J / g, and a loading of 5%-12 wt% in the Lyocell fiber skin.

[0094] The binary eutectic mixture precisely adjusts the phase transition temperature to 26-30℃, which is closer to the comfortable temperature range for the skin; the thermal conductivity of the silica shell (approximately 1.4 W / m·K) is far superior to that of traditional melamine resin (approximately 0.3 W / m·K), increasing the thermal response speed by about 3 times; the specific surface area of ​​the 200-800 nm nano-sized particles is an order of magnitude larger than that of the micron-sized capsules, further accelerating heat exchange; embedded in the fiber skin rather than attached to the surface, it hardly loses its coolness even after long-term immersion in the impregnation liquid, and the cooling sensation decreases by less than 6% after 12 months.

[0095] The pH / ionic strength dual-responsive alginate derivative used in the ion-gated reversible crosslinking network is sodium carboxyethyl alginate; the degree of substitution of sodium carboxyethyl alginate is 0.6-1.2, forming a bridge with the mixed crosslinking system of calcium and magnesium ions, and the content of alginate derivative is 0.8%-3.5% of the total weight of the nonwoven fabric.

[0096] The introduction of carboxyethyl groups lowers the pKa of the alginate chain. Under the conditions of pH 5.0-6.2 in the impregnation solution, the carboxyl groups are fully protonated to form a stable "egg-box" crosslinking structure, providing approximately 30%-50% wet strength gain. Upon entering a flowing water environment with pH 6.8-7.5, the carboxyethyl groups are gradually deprotonated, increasing charge repulsion and diluting calcium and magnesium ions. The dual response synergistically triggers crosslinking dissociation. The calcium-magnesium mixed crosslinking system has a wider response window and a milder dissociation curve than the single calcium ion crosslinking system. Compared with the linear decay of existing calcium alginate that relies solely on dilution dissociation, this scheme achieves a "switch-on" gated response.

[0097] The three-layer gradient functional composite fiber network structure is integrally formed through a process of high and low pressure segmented hydroentangling and local variable density point pressure reinforcement: the tough skeleton layer adopts 120-160 bar high-pressure hydroentangling, the cooling and moisture-absorbing synergistic layer adopts 70-100 bar medium-pressure hydroentangling, and the radiant cooling skin-friendly surface layer adopts 40-60 bar low-pressure hydroentangling; after physical entanglement, it is reinforced by point pressure reinforcement with a lattice type variable density, wherein the point pressure in the central area is 40-60 bar, the point pressure in the edge area is 20-30 bar, the lattice spacing is 4-8 mm, and the edge lattice spacing is 1.5-2 times that of the central area.

[0098] High and low pressure segmented hydroentanglement utilizes the energy attenuation effect of water needles to form an entanglement density gradient in the thickness direction. The bottom layer is dense and tough, the middle layer is moderately porous, and the surface layer is soft and fluffy, which solves the problem that the existing single hydroentanglement pressure cannot meet the differentiated needs of each layer. Variable density point pressure reinforcement forms a functional zone in the planar direction with high density reinforcement in the center and low density and flexibility at the edges. The central area bears the main wiping force, while the edge area is flexible and does not scratch the face and is conducive to priority disintegration when rinsing.

[0099] The specific high- and low-pressure segmented hydroentangling uses extremely fine high-pressure water needles (approximately 0.08-0.15 mm in diameter) to penetrate the fiber web. The energy of the water needles causes displacement, entanglement, and mechanical cohesion between the fibers, thereby forming a fabric with a certain strength. The principle of applying different pressures in segments is based on three physical effects:

[0100] 1) Water needle energy attenuation effect

[0101] After the high-pressure water jet is ejected from the spray plate, its energy gradually decreases as it penetrates the fiber web; when the high-pressure water jet enters from one side of the tough skeleton layer:

[0102] In the skeleton layer (bottom layer): the energy is highest when the high-pressure water jet just enters, the fiber is subjected to the greatest impact force and displacement, and the entanglement is the tightest; this is where the 120-160 bar high pressure plays its role, fully entangles the Lyocell fiber and the trilobal cross-section polylactic acid fiber, forming a dense high-strength skeleton.

[0103] Reaching the synergistic layer (intermediate layer): the water jet energy has decreased by about 30%-40%; at this point, it corresponds to a medium pressure effect of 70-100 bar, which is sufficient to form an effective entanglement between bamboo pulp fiber, seaweed fiber and copolymer modified fiber, but without excessive compaction, thus preserving the pore structure required for moisture absorption.

[0104] Reaching the skin-friendly surface layer (top layer): The energy of the water injection further decreases to 40%-50% of the initial level, corresponding to a low-pressure effect of 40-60 bar. This only causes the surface fibers to become moderately entangled, maintaining a soft and fluffy feel, while avoiding the inactivation of the SiO2 microspheres used for radiation cooling into the fibers.

[0105] 2) Differences in fiber response

[0106] The three fiber layers respond differently to the energy of high-pressure water jets:

[0107] Lyocell fibers (skeleton layer): have high wet modulus and good fiber rigidity, requiring high energy to fully bend and entangle; 120-160 bar is just enough to trigger its effective entanglement response;

[0108] Bamboo pulp / seaweed fiber (synergistic layer): The fibers are relatively fine and soft, and can entangle with medium energy; 70-100 bar can both entangle and prevent the fibers from breaking.

[0109] Viscose fiber (surface layer): The fiber is soft and more easily deformed when wet; it can entangle at 40-60 bar, and excessive pressure will cause the surface to fray and disrupt the distribution of the radiative cooling spheres;

[0110] 3) Interface interlocking effect

[0111] Although the three layers are segmented hydroentangled, when the hydroneedles pass through the interlayer interface, they will "push" some fibers from one layer into the adjacent layer, forming an interlayer mechanical interlock. The pressure segmented design ensures that the interlayer interlock is strong enough (without delamination), but it does not completely "flatten" the three layers into a homogeneous body (that would defeat the purpose of the gradient structure). The entanglement density between the three layers has a gradient transition in the thickness direction, rather than an abrupt interface, thus avoiding stress concentration that could lead to delamination.

[0112] Localized variable density point pressing reinforcement involves, after hydroentanglement, the fiber web undergoing localized hot or cold pressing reinforcement using a pair of dot-matrix embossing rollers. Specifically:

[0113] 1) Central region: high pressure and dense lattice, resulting in high strength and resistance to deformation.

[0114] The central area is the main force-bearing part when wiping with a wet wipe, and it needs sufficient structural strength. The point pressure of 40-60 bar combined with the dense dot matrix spacing of 4-8 mm forms more and denser fiber melting bonding points in the central area (polylactic acid fibers melt locally under pressure). These bonding points, like "rivets", firmly lock the three-layer fiber network, making the central area less prone to stretching, deformation or tearing during use.

[0115] 2) Edge areas: Low pressure and sparse dot matrix, flexible, sealing the edges without cutting the hands, and easy to disperse.

[0116] The design concept for the edge area is "sealing the edges but not rigidly":

[0117] Lower pressure of 20-30 bar: Polylactic acid fibers only undergo slight softening rather than deep melting, achieving slight bonding and "locking" the fiber ends on the cut surface to prevent lint shedding and edge unraveling;

[0118] Larger dot pitch (1.5-2 times): The number of adhesive points in the edge area is reduced by 50%-75%, maintaining the flexibility of the edges, so that users will not scratch their skin when wiping because the edges are too hard;

[0119] Considerations for washability: The number of adhesive points is directly related to the fiber dispersion efficiency. The fewer adhesive points, the faster the fibers dissociate when flushed. The sparse dot matrix design in the edge area makes it easier for water to "open a gap" at the edge when the wipe is flushed, accelerating the overall dispersion. This is the design logic of "edge-priority dissociation".

[0120] (3) Natural connection of the transition zone

[0121] Between the central and edge areas, the dot density transitions naturally through the gradual engraving of the embossing roller, without forming a clear dividing line between strong and weak areas, thus avoiding stress concentration on a certain circle that could lead to tearing.

[0122] In the three-gradient smart response coating, the fast-release microcapsule shell is made of poly(N-isopropylacrylamide-polyethylene glycol) copolymer with a phase transition temperature of 32°C and a shell thickness of 40-80 nm; the intermediate-release microcapsule shell is made of ethyl cellulose with a shell thickness of 150-300 nm; and the sustained-release microcapsule shell is made of silica with a shell thickness of 400-800 nm. The thickness ratio of the three layers of the fast-release microcapsule shell, intermediate-release microcapsule shell, and sustained-release microcapsule shell is 1:2:3.

[0123] Example 2

[0124] The preparation method of the cooling spunlace nonwoven fabric includes the following steps:

[0125] S1. The fibers of the three-layer gradient functional composite fiber network structure are pretreated respectively. The polylactic acid fiber of the tough skeleton layer and the copolymerized modified Lyocell fiber of the cool and moisture-absorbing synergistic layer are embedded in phase change nanocapsules during the spinning stage.

[0126] S2. After the three-layer fiber web of the three-layer gradient functional composite fiber web structure is combed and laid out, it is stacked in sequence and sent into a hydroentanglement machine for high and low pressure segmented hydroentanglement.

[0127] S3. The hydroentangled three-layer gradient functional composite fiber network structure is treated with staged pulsed hot air flow. The first stage has a temperature of 150-160℃ and a pressure of 0.2-0.3 MPa, which is applied to the surface layer. The second stage has a temperature of 170-180℃ and a pressure of 0.4-0.6 MPa, which is applied to the tough skeleton layer, forming gradient-distributed melt bonding points.

[0128] S4. The three-layer gradient functional composite fiber network structure is sequentially passed through a boron nitride nanosheet dispersion impregnation tank and an ion-gated alginate derivative / metal ion mixed liquid impregnation tank to complete the construction of the thermally conductive skeleton and the reversible cross-linked network, respectively.

[0129] S5. A three-gradient intelligent response coating is formed by sequentially applying fast-release microcapsule shells, intermediate-release microcapsule shells, and sustained-release microcapsule shells to the skin-friendly surface of the radiation-cooled coating layer using a layer-by-layer spraying method.

[0130] S6. After being dried at a low temperature of 80-90℃, hot air setting and low temperature pre-shrinking treatment, the finished cool-feeling spunlace nonwoven fabric is obtained.

[0131] The poly-N-isopropylacrylamide-polyethylene glycol copolymer in the shell of the fast-release microcapsule undergoes a phase transition at 32°C (close to skin temperature), and the shell contraction triggers the pulse release of the cooling agent, simulating a biofeedback mechanism. This is a smart temperature-sensitive switch that is different from existing isoproximal sustained-release schemes. The three-layer thickness ratio of 1:2:3 and the release rate ratio of approximately 10:3:1 enable gradient delivery with rapid response, stable maintenance, and ultra-long endurance.

[0132] Example 3

[0133] A cooling wipe, comprising the application of the aforementioned cooling spunlace nonwoven fabric; the impregnation solution of the cooling wipe is a weakly acidic buffer system containing the following components:

[0134] Xylitol 1.0% (w / v) - 3.0% (w / v);

[0135] Erythritol 0.5% (w / v) - 1.5% (w / v);

[0136] Panthenol 0.3% (w / v) - 0.6% (w / v);

[0137] Witch hazel extract 0.2% (w / v) - 0.4% (w / v);

[0138] Glycerin 2% (w / v) - 5% (w / v);

[0139] Sodium hyaluronate 0.05% (w / v) - 0.15% (w / v);

[0140] Calcium lactate 0.2% (w / v) - 0.8% (w / v);

[0141] Magnesium gluconate 0.1% (w / v) - 0.3% (w / v);

[0142] Capryloyl hydroxamic acid 0.3% (w / v) - 0.5% (w / v);

[0143] The impregnation solution has a pH value of 5.0-6.2 and does not contain ethanol, menthol, or borneol.

[0144] A further technical solution involves the following: the cooling spunlace nonwoven fabric undergoes a secondary low-temperature plasma treatment before impregnation with the impregnation liquid. The power of the secondary low-temperature plasma treatment is 200-300 W, the time is 5-10 s, and the atmosphere is a mixture of argon and oxygen at a volume ratio of 4:1. The impregnation process employs a gradient negative pressure impregnation process. The first stage of the gradient negative pressure impregnation process has a negative pressure of -0.04 MPa and a negative pressure time of 5 s; the second stage of the gradient negative pressure impregnation process has a negative pressure of -0.02 MPa and a negative pressure time of 8 s. After cutting, the edges are treated with ultrasonic micro-sealing at a power of 80-120 W for 2-3 s. The packaging after the secondary low-temperature plasma treatment uses a five-layer composite film containing an ethylene-vinyl alcohol copolymer layer, and the five-layer composite film contains an oxygen absorber and a desiccant.

[0145] The shelf life of the cooling wipes is 24 months under normal temperature (10-30℃) and relative humidity (40%-60%). After use, the residual rate is less than 35% after rinsing in running water for 60 minutes. After disposal, the biodegradability rate is not less than 95% under 180-day composting conditions.

[0146] With a heat of solubility of -42 cal / g erythritol greater than that of -37 cal / g xylitol and without causing tooth decay, the dual-component synergistic effect enhances the physical cooling sensation while maintaining zero chemical irritation, making it the most suitable impregnation solution formulation for substrates with a purely physical cooling sensation; the calcium lactate / magnesium gluconate dual salt system maintains ion-gated cross-linking and is deeply coupled with the function of the substrate; octanoyl hydroxamic acid replaces the traditional phenoxyethanol / paraben, providing mild and broad-spectrum preservation; gradient negative pressure impregnation is more uniform and shortens the cycle by about 30% compared to normal pressure immersion.

[0147] Comparative Example 1

[0148] Using purely physical entanglement and mica-jade powder modification, without microfibrillated cellulose reinforcement, ion-gated crosslinking, radiation cooling layer, or gradient bonding, the resulting nonwoven fabric exhibits a wet tensile strength of only 0.55 kN / m and a Q-max of 0.22 W / cm². 2 It is non-dispersible.

[0149] Comparative Example 2

[0150] A phase change system employing a triple network (physical entanglement, thermally induced self-adhesion, and contact unfolding reversible crosslinking) and phase change nanocapsules was developed, eliminating the need for microfibrillated cellulose reinforcement, ion gating, and radiation cooling. The resulting nonwoven fabric exhibited a wet tensile strength of 1.26 kN / m and a Q-max of 0.28 W / cm². 2 Continuous cooling power density 22 W / m 2 The residual rate after rinsing is 36%.

[0151] The performance comparison analysis of Example 1, Comparative Example 1, and Comparative Example 2 is shown in Table 1 below:

[0152] Table 1

[0153] Example 1 Comparative Example 1 Comparative Example 2 <![CDATA[Areal density (g / m 2 )]]> 55 50 55 Wet tensile strength (kN / m) 1.42 0.55 1.26 Dry fracture strength (N / 5cm) 20.2 14.0 17.5 <![CDATA[Q-max(W / cm 2 )]]> 0.29 0.22 0.28 <![CDATA[Cooling sensation power density (W / m 2 )]]> 25 15 22 Atmospheric window emissivity 0.86 - - Moisture absorption rate (%) 203 180 190 180-day compost degradation rate (%) 95.8 32 93.5 Cooling sensation decreases by 24 months (%) 5.0 15 6.0 60min Dispersion Residue (%) 29 Do not break 36

[0154] Through Table 1 and Figure 1-3 It is clear that the performance of Example 1 is superior to that of Comparative Example 1 and Comparative Example 2.

[0155] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cooling spunlace nonwoven fabric, characterized in that, Composed of a three-layer gradient functional composite fiber network structure, it is integrally formed through a quadruple network mechanism of physical entanglement, gradient melt bonding, ion-gated reversible crosslinking and microfibrillated cellulose reinforcement. At the same time, it adopts a dual cooling design that combines fiber body copolymerization modification and embedded phase change material. The three-layer gradient functional composite fiber network structure includes: The tough skeleton layer is composed of Lyocell fibers and trilobal polylactic acid fibers in a ratio of 55-70 wt% Lyocell fibers. Microfibrillated cellulose is dispersed between the Lyocell fibers and the trilobal polylactic acid fibers, forming a biodegradable and tough skeleton layer. The cooling and moisture-wicking synergistic layer is made of graphene, boron nitride and mica composite copolymer modified Lyocell fiber, bamboo pulp fiber and carboxymethylated seaweed fiber blend; and the skin of the copolymer modified Lyocell fiber is embedded with phase change nanocapsules. The radiation-cooled skin-friendly surface layer is made of a blend of high-moisture-strength viscose fiber, cooling viscose fiber with embedded natural menthol nanocapsules, and radiation-cooling fiber with surface grafted silica submicron spheres; the silica submicron spheres have a particle size of 6-10 μm and have high emissivity in the atmospheric window 8-13 μm band. The nonwoven fabric also contains: The gradient melt-bonded network is formed by polylactic acid fibers with trilobal cross-sections forming discrete point-like bonding points with a gradient distribution along the thickness direction under the action of staged pulsed hot airflow. The density of bonding points on the surface layer is 30%-50% of that of the tough skeleton layer. An ion-gated reversible crosslinking network is formed by a carboxyl-containing pH / ionic strength dual-responsive alginate derivative and multivalent metal ions forming crosslinking bridges on the fiber surface of a three-layer gradient functional composite fiber network structure. The crosslinking remains closed under the conditions of pH 4.5-6.5 of the impregnation solution and dissociates in response to the conditions of pH 6.8-7.5 of flowing water. The boron nitride thermally conductive framework consists of hexagonal boron nitride nanosheets fixed on the surface of a three-layer gradient functional composite fiber network structure through electrostatic self-assembly and hydrogen bonding. The lateral dimensions of the hexagonal boron nitride nanosheets are 200-800 nm, forming a three-dimensional thermally conductive pathway with the phase change nanocapsules embedded in the fiber and the copolymerized modified fiber. The three-gradient smart response coating is applied to the skin-friendly surface of the radiation-cooled coating. The three-gradient smart response coating consists of a three-layer structure: a fast-release microcapsule shell, a medium-release microcapsule shell, and a sustained-release microcapsule shell. The fast-release microcapsule shell is a temperature-sensitive polymer that accelerates release at temperatures above 32°C.

2. The cooling spunlace nonwoven fabric according to claim 1, characterized in that, The microfibrillated cellulose has a fiber diameter of 10-100 nm and an aspect ratio of 50-200. The amount added is 1%-5% of the total fiber mass, forming nanoscale bridging reinforcement in the fiber entanglement network.

3. The cooling spunlace nonwoven fabric according to claim 1, characterized in that, In the graphene, boron nitride and mica composite copolymer modified Lyocell fiber, the mass ratio of graphene nanosheets, hexagonal boron nitride nanosheets and mica powder is 1:2:6, and the total amount of the three added is 8%-15% of the fiber mass of the three-layer gradient functional composite fiber network structure. It is prepared by dry-jet wet spinning process after blending with Lyocell spinning solution.

4. The cooling spunlace nonwoven fabric according to claim 1, characterized in that, The core material of the phase change nanocapsule is a binary eutectic mixture of n-tetradecane and n-octadecane; the phase change temperature of the phase change nanocapsule is 26-30℃, and the particle size of the phase change nanocapsule is 200-800 nm; the shell material of the phase change nanocapsule is silicon dioxide, with a phase change enthalpy of not less than 150 J / g, and a loading of 5%-12 wt% in the Lyocell fiber skin.

5. The cooling spunlace nonwoven fabric according to claim 1, characterized in that... The ion-gated reversible crosslinking network uses a pH / ionic strength dual-responsive alginate derivative, sodium carboxyethyl alginate; the degree of substitution of sodium carboxyethyl alginate is 0.6-1.2, forming a bridge with the mixed crosslinking system of calcium and magnesium ions, and the content of alginate derivative is 0.8%-3.5% of the total weight of the nonwoven fabric.

6. The cooling spunlace nonwoven fabric according to claim 1, characterized in that, The three-layer gradient functional composite fiber network structure is integrally formed through a process of high and low pressure segmented hydroentangling and local variable density point pressure reinforcement: the tough skeleton layer is made of 120-160 bar high-pressure hydroentangling, the cooling and moisture-absorbing synergistic layer is made of 70-100 bar medium-pressure hydroentangling, and the radiant cooling skin-friendly surface layer is made of 40-60 bar low-pressure hydroentangling; after physical entanglement, it is reinforced by point pressure reinforcement with a lattice type variable density point pressure, wherein the point pressure in the central area is 40-60 bar, the point pressure in the edge area is 20-30 bar, the point spacing is 4-8 mm, and the point spacing in the edge area is 1.5-2 times that in the central area.

7. The cooling spunlace nonwoven fabric according to claim 1, characterized in that, In the three-gradient smart response coating, the fast-release microcapsule shell is made of poly(N-isopropylacrylamide-polyethylene glycol) copolymer with a phase transition temperature of 32°C and a shell thickness of 40-80 nm; the intermediate-release microcapsule shell is made of ethyl cellulose with a shell thickness of 150-300 nm; and the sustained-release microcapsule shell is made of silica with a shell thickness of 400-800 nm. The thickness ratio of the three layers of the fast-release microcapsule shell, intermediate-release microcapsule shell, and sustained-release microcapsule shell is 1:2:

3.

8. The cooling spunlace nonwoven fabric according to claim 7, characterized in that, Its preparation method includes the following steps: S1. The fibers of the three-layer gradient functional composite fiber network structure are pretreated respectively. The polylactic acid fiber of the tough skeleton layer and the copolymerized modified Lyocell fiber of the cool and moisture-absorbing synergistic layer are embedded in phase change nanocapsules during the spinning stage. S2. After the three-layer fiber web of the three-layer gradient functional composite fiber web structure is combed and laid out, it is stacked in sequence and sent into a hydroentanglement machine for high and low pressure segmented hydroentanglement. S3. The hydroentangled three-layer gradient functional composite fiber network structure is treated with staged pulsed hot air flow. The first stage has a temperature of 150-160℃ and a pressure of 0.2-0.3 MPa, which is applied to the surface layer. The second stage has a temperature of 170-180℃ and a pressure of 0.4-0.6 MPa, which is applied to the tough skeleton layer, forming gradient-distributed melt bonding points. S4. The three-layer gradient functional composite fiber network structure is sequentially passed through a boron nitride nanosheet dispersion impregnation tank and an ion-gated alginate derivative / metal ion mixed liquid impregnation tank to complete the construction of the thermally conductive skeleton and the reversible cross-linked network, respectively. S5. A three-gradient intelligent response coating is formed by sequentially applying fast-release microcapsule shells, intermediate-release microcapsule shells, and sustained-release microcapsule shells to the skin-friendly surface of the radiation-cooled coating layer using a layer-by-layer spraying method. S6. After being dried at a low temperature of 80-90℃, hot air setting and low temperature pre-shrinking treatment, the finished cool-feeling spunlace nonwoven fabric is obtained.

9. A cooling wet wipe, characterized in that, The application includes the cooling spunlace nonwoven fabric as described in any one of claims 1-8; the impregnation solution of the cooling wipe is a weakly acidic buffer system containing the following components: Xylitol 1.0% (w / v) - 3.0% (w / v); Erythritol 0.5% (w / v) - 1.5% (w / v); Panthenol 0.3% (w / v) - 0.6% (w / v); Witch hazel extract 0.2% (w / v) - 0.4% (w / v); Glycerin 2% (w / v) - 5% (w / v); Sodium hyaluronate 0.05% (w / v) - 0.15% (w / v); Calcium lactate 0.2% (w / v) - 0.8% (w / v); Magnesium gluconate 0.1% (w / v) - 0.3% (w / v); Capryloyl hydroxamic acid 0.3% (w / v) - 0.5% (w / v); The impregnation solution has a pH value of 5.0-6.2 and does not contain ethanol, menthol, or borneol.

10. The cooling wipes according to claim 7, characterized in that, The cooling spunlace nonwoven fabric undergoes a secondary low-temperature plasma treatment before impregnation in the impregnation solution. The power of the secondary low-temperature plasma treatment is 200-300 W, the time is 5-10 s, and the atmosphere is a mixture of argon and oxygen in a volume ratio of 4:

1. The impregnation adopts a gradient negative pressure impregnation process. The first stage of the gradient negative pressure impregnation process has a negative pressure of -0.04 MPa and a negative pressure time of 5 s. The second stage of the gradient negative pressure impregnation process has a negative pressure of -0.02 MPa and a negative pressure time of 8 s. After cutting, the edges are treated with ultrasonic micro-sealing at a power of 80-120 W for 2-3 s. The packaging after the low-temperature plasma secondary treatment uses a five-layer composite film containing an ethylene-vinyl alcohol copolymer layer. The five-layer composite film contains an oxygen absorber and a desiccant.

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