Weakly acidic skin-friendly spunlace nonwoven fabric and preparation method thereof

Abstract

This invention belongs to the field of nonwoven fabrics, specifically a weakly acidic, skin-friendly spunlace nonwoven fabric, comprising a surface layer, a middle layer, and a bottom layer, which are fixedly connected by hydroentanglement and ultrasonic patterned welding. The surface layer is composed of a mixture of copolymerized modified polylactic acid short fibers, chitosan short fibers, and locally hydrophobically treated copolymerized modified polylactic acid short fibers. Dual-mode sustained-release composite microcapsules are loaded in localized areas of the surface layer. The surface layer has a microscopic wetting pattern formed by alternating hydrophilic and hydrophobic fiber regions. The bottom layer is composed of a core-sheath structure of polylactic acid and polybutylene succinate bicomponent composite short fibers. The surface of the nonwoven fabric has multiple concave points formed by ultrasonic patterning, and the inner walls of these concave points are enriched with dual-mode sustained-release composite microcapsules. This allows the hydrophobic region to push liquid towards the hydrophilic region, while the concave points in the hydrophilic region provide low-resistance channels for vertical penetration. The hydrophilic microcapsules enriched on the inner walls of the concave points further enhance the liquid absorption dynamics of this region.

Description

Technical Field

[0001] This invention relates to the field of nonwoven fabrics, specifically a weakly acidic, skin-friendly spunlace nonwoven fabric and its preparation method. Background Technology

[0002] Nonwoven fabric, also known as non-woven textile, is a flexible sheet material formed by directly binding fibers into a web through mechanical, thermal, or chemical means, without traditional spinning and weaving processes. Due to its short production process, wide raw material adaptability, and strong product functional designability, nonwoven fabrics are widely used in medical and health, personal care, beauty and skincare, packaging and filtration, and other fields. Spunlace nonwoven fabric, in particular, is a type of nonwoven material formed by using high-pressure micro-jet water jets to entangle and bind the fiber web together. Compared to chemical bonding methods, the spunlace process does not require the addition of adhesives, thus preserving the original softness and cleanliness of the fibers to the greatest extent; compared to needle punching, spunlace fabric has a finer and smoother surface. Therefore, spunlace nonwoven fabric is widely recognized as the most suitable substrate for skin-friendly products that come into direct contact with the skin, and products made from it, such as soft towels, wet wipes, mask base fabrics, sanitary napkins, and diaper top layers, have become mainstream choices in the consumer market.

[0003] With rising living standards and increased health awareness, consumers' demands for skin-friendly nonwoven fabrics have evolved from basic softness and lint-free properties to a focus on skin-friendly microenvironment regulation. Medical research shows that healthy human skin is covered by an acidic protective film formed by sebum, sweat, and keratinocyte degradation products, with a pH value generally in the slightly acidic range of 4.5-6.5. This slightly acidic environment effectively inhibits the colonization and proliferation of pathogenic bacteria such as Escherichia coli and Staphylococcus aureus, while maintaining the integrity of the sebum film and the ecological balance of the skin's surface flora. Based on this mechanism, slightly acidic skin-friendly spunlace nonwoven fabrics have emerged. Currently, the mainstream technical approaches to achieving weakly acidic properties in nonwoven fabrics in industrial production fall into two main categories: one is to introduce weakly acidic substances into the fiber raw material, such as using polylactic acid fibers, which are inherently weakly acidic, or mixing organic acids such as citric acid and lactic acid into the spinning solution to prepare weakly acidic fibers; the other is to attach acidic functional additives to the finished fabric surface through methods such as padding or spraying during the finishing process of nonwoven fabrics. The weakly acidic nonwoven fabrics prepared by these two methods, to a certain extent, meet the market's basic demand for products that are gentle and skin-friendly.

[0004] As consumers' demands for skin-friendly products increase and actual usage scenarios become more complex, existing weakly acidic skin-friendly spunlace nonwoven fabric technology is gradually revealing several insurmountable shortcomings. The most prominent issue is the instability of the weakly acidic properties. In products using finishing processes, water-soluble acids such as citric acid and lactic acid adhere only to the fiber surface through physical adsorption, lacking a strong chemical bond with the fiber itself. Upon contact with body fluids, the surface acid layer is easily washed away and diluted, causing the pH value to rapidly rise from the weakly acidic range to neutral or even alkaline, thus losing its protective function. Even if some products claim to use microencapsulation technology for sustained release, existing single-shell microcapsules suffer from poor encapsulation stability, premature rupture during storage or transportation, and uncontrollable release of acidic substances. Conventional weakly acidic nonwoven fabrics are mostly homogeneous hydrophilic structures. When in contact with liquids, droplets spread evenly in all directions on the surface, resulting in a large lateral spreading area. Moisture remains at the skin-fabric interface for a long time, causing significant stickiness and stuffiness. Some improvement solutions attempt to press embossed patterns on the fabric to guide the flow of liquid, but relying solely on macroscopic embossing has limited effect in suppressing lateral diffusion of the surface layer and cannot fundamentally establish a directional vertical transmission channel for the liquid. As a result, the improvement in dryness performance has not met expectations.

[0005] The aforementioned problems make it difficult for existing weakly acidic, skin-friendly spunlace nonwoven fabrics to meet consumers' increasingly demanding quality requirements in terms of long-lasting weak acidity maintenance and efficient moisture wicking and drying. These issues also constitute key technical challenges that the industry urgently needs to overcome. Summary of the Invention

[0006] To address the problems in the background art, and to achieve the above objectives, the present invention provides the following technical solution:

[0007] A weakly acidic, skin-friendly spunlace nonwoven fabric includes a top layer, an intermediate layer, and a bottom layer sequentially stacked along the thickness direction. The top layer, intermediate layer, and bottom layer are fixedly connected by spunlace entanglement and ultrasonic patterned welding. The top layer is composed of a mixture of copolymerized modified polylactic acid short fibers, chitosan short fibers, and locally hydrophobically treated copolymerized modified polylactic acid short fibers. Dual-mode sustained-release composite microcapsules are loaded in localized areas of the top layer. The top layer has a micro-wetness formed by alternating hydrophilic and hydrophobic fiber regions. The wet pattern features hydrophobic fiber regions composed of copolymerized modified polylactic acid short fibers that have undergone localized hydrophobic treatment; dual-mode sustained-release composite microcapsules are concentrated in the hydrophilic fiber regions, forming a microcapsule enrichment gradient along the hydrophilic and hydrophobic interface; the middle layer is composed of a mixture of cotton fibers, viscose fibers, lyocell fibers, and super-absorbent fibers; the bottom layer is composed of bicomponent composite short fibers of polylactic acid and polybutylene succinate with a core-sheath structure, the sheath layer of the core-sheath being low-melting-point polybutylene succinate, and the core layer being high-melting-point polylactic acid;

[0008] The surface of the nonwoven fabric has multiple dimples formed by ultrasonic patterning. The dimples extend downward from the surface layer, penetrate the surface layer and at least partially enter the intermediate layer. The bottom of the dimples is permanently fused to the bottom layer by melting and re-curing the polybutylene succinate skin layer of the bottom layer. The position of the dimples corresponds to the micro-wetting pattern of the surface layer, so that the opening of the dimples is located in the hydrophilic fiber region, and the inner wall of the dimples is enriched with the dual-mode sustained-release composite microcapsules. Biodegradable toughening composite micropowder is also uniformly dispersed in the surface layer.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned weakly acidic skin-friendly spunlace nonwoven fabric, comprising the following steps:

[0010] Step 1: Preparation and Web Formation of Surface Fiber Raw Materials

[0011] The copolymerized modified polylactic acid short fibers, chitosan short fibers, and biodegradable toughened composite micro powder are fully opened and mixed, and then carded to obtain the surface layer main fiber network; the copolymerized modified polylactic acid short fibers that have undergone local hydrophobic treatment are opened and carded separately to obtain a hydrophobic fiber network; through patterned web laying, the hydrophobic fiber network is laid on the surface layer main fiber network in island, strip, or grid patterns to form a surface layer fiber network with a wettable pattern of alternating hydrophilic and hydrophobic fiber regions;

[0012] Step 2: Positioning and Loading of Dual-Mode Sustained-Release Composite Microcapsules

[0013] First and second microcapsule suspensions were prepared separately and mixed in a certain proportion to obtain a composite microcapsule suspension with a total mass concentration of 6%-12%. Using a mask matching the surface wettability pattern, the composite microcapsule suspension was sprayed onto the hydrophilic fiber region of the surface fiber mesh through precise positioning atomization spraying at an atomization pressure of 0.2-0.5 MPa. The spraying amount was calculated based on the total microcapsule loading. After spraying, the surface fiber mesh was vacuum dried at 40-50℃ and a vacuum degree of -0.08 to -0.09 MPa for 15-25 min to obtain the functionalized surface fiber mesh.

[0014] Step 3: Preparation of the intermediate fiber web

[0015] Cotton fiber, viscose fiber, lyocell fiber and super absorbent fiber are mixed and opened in a certain proportion, and then combed into a web to obtain the middle layer fiber web;

[0016] Step 4: Preparation of the underlying fiber web

[0017] The core-sheath structure of polylactic acid and polybutylene succinate bicomponent composite short fibers is opened and carded into a web to obtain the bottom fiber web.

[0018] Step 5: Overlay and Hydroentanglement Pre-reinforcement

[0019] Functionalized surface fiber web, intermediate fiber web and bottom fiber web are stacked in sequence to form a three-layer composite fiber web; the three-layer composite fiber web is pre-entangled by high-pressure hydroentanglement, wherein the hydroentanglement adopts gradient pressure: pre-wetting 20-30 bar, main hydroentanglement stage four 50-80 bar, post hydroentanglement 70-95 bar, running speed 20-35 m / min, to obtain pre-reinforced nonwoven fabric.

[0020] Step Six: Ultrasonic Patterning Composite

[0021] The pre-reinforced nonwoven fabric is fed into an ultrasonic composite equipment. The surface of the ultrasonic welding head has an array of raised dots corresponding to the wettability pattern of the surface layer. Under the action of ultrasound, the bottom polybutylene succinate skin melts and flows at the corresponding positions of the raised dots, passes through the intermediate layer and fuses with the surface layer fibers, while forming multiple concave dots. The ultrasonic process parameters are: frequency 25-40kHz, amplitude 15-25μm, roller temperature 110-130℃, roller pressure 0.5-2.0MPa, and composite speed 20-40 m / min.

[0022] Step 7: Post-processing

[0023] The composite nonwoven fabric is dried at 100-120℃ until the moisture content is no more than 5%, then the surface is softened and the edges are trimmed. It is then sterilized with a combination of ultraviolet light and ozone, and aseptically packaged to obtain the finished product.

[0024] Compared with the prior art, the present invention can achieve the following:

[0025] 1. Existing technologies mostly employ homogeneous hydrophilic structures, resulting in severe lateral liquid diffusion. This invention achieves intelligent directional liquid management through the synergistic effect of a triple mechanism: hydrophilic and hydrophobic micro-patterns on the surface layer, concave flow channels, and hydrophilic enrichment of microcapsules. Specifically, the hydrophobic region pushes the liquid towards the hydrophilic region, the concave points in the hydrophilic region provide low-resistance channels for vertical infiltration, and the hydrophilic microcapsules enriched on the inner wall of the concave points further enhance the liquid absorption dynamics in this region. This design, which combines surface energy gradients with physical structure gradients, enables the liquid unidirectional transfer index to reach over 190%, representing a qualitative breakthrough in the existing flow guidance mechanisms.

[0026] 2. Unlike existing technologies that rely on post-coating with water-soluble acids such as citric acid and lactic acid (which are quickly lost upon contact with body fluids), this invention establishes a triple weak acid shield: a weak acid at the fiber molecular level, immediate acid replenishment by fast-release microcapsules, and long-term acid maintenance by slow-release microcapsules. The surface layer copolymerized modified polylactic acid fiber itself is weakly acidic. The first microcapsule ruptures upon contact with the skin to rapidly release lactic acid, establishing an immediate weak acid environment. The second microcapsule achieves long-term maintenance through the slow degradation of the polylactic acid shell. The three mechanisms work synergistically to ensure that the pH drift does not exceed 0.3 after 12 months of storage and 10 washes, completely solving the industry problem of the lack of long-lasting weak acidity.

[0027] 3. This invention achieves proactive time-based skincare through the systematic design of dual-mode sustained-release composite microcapsules. The first microcapsule provides immediate moisturizing and soothing upon contact, while the second microcapsule provides sustained release of skin barrier repair factors such as ceramides and Centella asiatica extract for several hours or even days. The two microcapsules are precisely positioned along the essential pathway of liquid transport (hydrophilic area and concave inner wall), ensuring that the active ingredients are released efficiently at the most needed time and space, transitioning from non-harmful to proactive care.

[0028] 4. It abandons chemical crosslinking agents and adhesives, and adopts a fully physical composite process of hydroentangled pre-entanglement and ultrasonic patterned welding; it utilizes the low melting point polybutylene succinate skin of the bottom bicomponent fiber to melt under the action of ultrasonic pinpoint, forming permanent welding concave points that penetrate three layers, while retaining the fluffy softness of nonwoven fabric; it is fully compatible with existing hydroentangled production lines, and only requires the addition of patterned mesh laying, positioning spraying and ultrasonic welding head, making it feasible for large-scale mass production;

[0029] 5. This invention is a system integration of five major technical modules: asymmetric wettability structure, dual-mode microcapsules, molecular-level weak acid fiber, super-hygroscopic intermediate layer, and biodegradable skeleton layer. The modules are not simply superimposed, but produce a significant synergistic effect. That is, the wettability gradient enhances the targeted release efficiency of the microcapsules, the concave structure simultaneously assumes the triple role of welding and fixing, flow channel and microcapsule enrichment carrier, and the toughened micro powder strengthens the surface layer without sacrificing biodegradability.

[0030] 6. Through the triple synergy of hydrophilic and hydrophobic patterns on the surface layer, concave drainage channels, and hydrophilic enrichment of microcapsules, intelligent directional management of liquids is achieved, ensuring long-lasting dryness on the skin contact surface, with a liquid unidirectional transfer index exceeding 190%. The surface layer's copolymerized modified polylactic acid fiber is a molecular-level weak acid, requiring no chemical finishing, thus fundamentally solving the problem of short-lasting weak acidity. The three-layer structure—providing skin-friendliness and drainage on the surface layer, achieving high absorption and water retention in the middle layer, and providing mechanical support on the bottom layer—has clearly defined functional zones, overcoming the functional compromises of homogeneous single-layer fabrics. The bottom layer's core-skin structure provides low-melting-point sites for ultrasonic targeted welding, and the all-physical process eliminates chemical adhesives, achieving a medical-grade level of safety with no irritation. The synergy between chitosan fiber and the weakly acidic environment of polylactic acid achieves broad-spectrum and long-lasting antibacterial effects without adding controversial ingredients such as nano-silver.

[0031] 7. Copolymerized polylactic acid fibers with multi-groove, Y-shaped, or cross-shaped cross sections provide excellent capillary effect and a fluffy, soft feel, balancing moisture-wicking efficiency and skin-friendly touch; the proportion of hydrophobic modified fibers is controlled at 8-18 parts by weight, which can form an effective wettability gradient without affecting the overall skin-friendly comfort of the surface layer.

[0032] 8. The middle layer is made of sodium polyacrylate super absorbent fiber, which can lock in liquids dozens of times its own weight, significantly reducing the risk of liquid backflow. It perfectly complements the moisture absorption of viscose and cotton and the wet strength of Lyocell, giving the middle layer high absorption, high water retention and dimensional stability.

[0033] 9. The three-dimensional geometric parameters and arrangement of the concave dots are precisely matched with their dual functions. The area ratio of 5%-12% ensures sufficient interlayer bonding strength without compromising the fluffiness and breathability of the nonwoven fabric. The enrichment of microcapsules on the inner wall of the concave dots (the density of the first microcapsule is more than 1.5 times that of the second microcapsule) ensures that the effective ingredients are concentrated and released in the high-efficiency range through which the liquid flows.

[0034] 10. Biodegradable toughened composite micro powder is completely biodegradable while improving the strength of the surface layer, thus resolving the contradiction between skin-friendly softness and strong durability;

[0035] 11. This invention provides triple weak acid protection through the molecular-level weak acidity of copolymerized modified polylactic acid short fibers, the rapid release of lactic acid upon skin contact by the first microcapsule, and the sustained release of vitamin A from the polylactic acid shell of the second microcapsule. The synergy of the wettability gradient constructed by the hydrophilic and hydrophobic micro-patterns on the surface layer and the vertical capillary channels formed by the array of concave dots, the concentrated distribution of the first microcapsule in the hydrophilic region and the inner wall of the concave dots to achieve instant skin-releasing moisturizing and soothing, the formation of an enrichment gradient along the hydrophilic-hydrophobic interface by the second microcapsule to achieve long-lasting repair through time-based skin care, the composite water-locking of the middle layer of super absorbent fiber with cotton, viscose, and lyocell, the ultrasonic low-temperature fixed-point welding of the bottom layer of polylactic acid and polybutylene succinate bicomponent fibers, and the fully biodegradable reinforcement of the toughening micropowder. Attached Figure Description

[0036] Figure 1 Statistical graphs of the unidirectional transfer index OMMC for Experimental Example 1 and Comparative Examples 1-3;

[0037] Figure 2 Statistical graphs of longitudinal stiffness for Experimental Example 1 and Comparative Examples 1-3;

[0038] Figure 3 The graph shows the longitudinal wet intensity of Experimental Example 1 and Comparative Examples 1-3. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] A weakly acidic, skin-friendly spunlace nonwoven fabric includes a top layer, an intermediate layer, and a bottom layer stacked sequentially along the thickness direction. The top layer, the intermediate layer, and the bottom layer are fixedly connected by spunlace entanglement and ultrasonic patterned welding.

[0042] The surface layer is composed of copolymerized modified polylactic acid short fibers, chitosan short fibers, and locally hydrophobically treated copolymerized modified polylactic acid short fibers. Dual-mode sustained-release composite microcapsules are loaded in localized areas of the surface layer. The surface layer has a microscopic wettability pattern formed by alternating hydrophilic and hydrophobic fiber regions, with the hydrophobic fiber regions composed of locally hydrophobically treated copolymerized modified polylactic acid short fibers. The dual-mode sustained-release composite microcapsules are concentrated within the hydrophilic fiber regions, forming a microcapsule enrichment gradient along the hydrophilic-hydrophobic interface.

[0043] The middle layer is composed of a mixture of cotton fibers, viscose fibers, lyocell fibers, and super absorbent fibers;

[0044] The bottom layer is composed of two-component composite short fibers of polylactic acid and polybutylene succinate with a core-sheath structure. The sheath layer of the core-sheath structure is low-melting-point polybutylene succinate, and the core layer of the core-sheath structure is high-melting-point polylactic acid.

[0045] The surface of the nonwoven fabric has multiple dimples formed by ultrasonic patterning. The dimples extend downward from the surface layer, penetrate the surface layer and at least partially enter the intermediate layer. The bottom of the dimples is permanently fused to the bottom layer by melting and re-curing the polybutylene succinate skin layer of the bottom layer. The position of the dimples corresponds to the micro-wetting pattern of the surface layer, so that the opening of the dimples is located in the hydrophilic fiber region, and the inner wall of the dimples is enriched with the dual-mode sustained-release composite microcapsules.

[0046] The surface layer also contains biodegradable toughening composite micro powder evenly dispersed.

[0047] Through the triple synergy of hydrophilic and hydrophobic patterns on the surface layer, concave drainage channels, and hydrophilic enrichment of microcapsules, intelligent directional management of liquids is achieved, ensuring long-lasting dryness on the skin contact surface, with a liquid unidirectional transfer index exceeding 190%. The surface layer's copolymerized modified polylactic acid fiber is a molecular-level weak acid, requiring no chemical finishing, thus fundamentally solving the problem of short-lasting weak acidity. The three-layer structure, with its clear functional zones—a surface layer providing skin-friendliness and drainage, a middle layer achieving high absorption and water retention, and a bottom layer providing mechanical support—overcomes the functional compromises of homogeneous single-layer fabrics. The bottom layer's core-skin structure provides low-melting-point sites for ultrasonic targeted welding, and the all-physical process eliminates chemical adhesives, achieving a medical-grade level of safety with no irritation. The synergy between chitosan fiber and the weakly acidic environment of polylactic acid achieves broad-spectrum and long-lasting antibacterial effects without adding controversial ingredients such as nano-silver.

[0048] Furthermore, the dual-mode sustained-release composite microcapsule includes a first microcapsule and a second microcapsule;

[0049] The first microcapsule comprises a capsule wall and a core material A. The capsule wall is a chitosan-sodium alginate ion-crosslinked gel. The core material A is a mixture of lactic acid, sodium hyaluronate, and panthenol, with a mass ratio of 1:2-3:1-1.5. The first microcapsule has a particle size of 2-5 μm and ruptures upon contact with skin moisture or friction, rapidly releasing the core material A.

[0050] The second microcapsule comprises an inner capsule wall, an outer capsule wall, and a core material B. Core material B is encapsulated within the inner and outer capsule walls. The inner capsule wall is composed of chitosan-sodium alginate, and the outer capsule wall is composed of polylactic acid. Core material B is a mixture of ceramide, Centella asiatica extract, and vitamin E acetate, with a mass ratio of 2:1:0.5-1. The second microcapsule has a particle size of 5-8 μm and an outer capsule wall thickness of 0.4-1.0 μm, used to delay the release of core material B. The mass ratio of the first microcapsule to the second microcapsule is 1:1.5-3.

[0051] The dual-mode sustained-release microcapsule system achieves timed and batched release of both instant release upon contact with the skin and sustained release through the shell. The first microcapsule releases lactic acid, sodium hyaluronate, and panthenol upon contact with the skin, providing instant weak acid reinforcement and moisturizing soothing. The second microcapsule releases ceramide, centella asiatica extract, and vitamin E acetate through the slow degradation of the polylactic acid outer shell, continuously repairing the skin barrier.

[0052] The surface layer has the following fiber composition:

[0053] Copolymer-modified polylactic acid short fiber: 40-65 parts by weight;

[0054] Chitosan short fibers: 25-45 parts by weight;

[0055] Copolymerized modified polylactic acid short fibers with localized hydrophobic treatment: 8-18 parts by weight;

[0056] Among them, the copolymer-modified polylactic acid short fiber is polylactic acid-polycaprolactone block copolymer fiber or polylactic acid-polybutylene succinate block copolymer fiber; the cross section of the copolymer-modified polylactic acid short fiber is multi-groove, Y-shaped or cross-shaped, and its single fiber fineness is 1.0-1.5 dtex and its length is 35-40 mm;

[0057] The degree of deacetylation of chitosan short fibers is not less than 90%, and the fineness of its single fibers is 1.2-1.8 dtex, with a length of 35-40 mm;

[0058] The copolymerized modified polylactic acid short fibers, after being partially hydrophobically treated, have organosiloxane grafted onto their surface after plasma activation. The water contact angle of the fiber surface is not less than 115°, and the fineness of the single fiber is 1.0-1.5 dtex, and the length is 35-40 mm.

[0059] The total loading of the dual-mode sustained-release composite microcapsules is 6%-15% of the total mass of the surface fiber.

[0060] Copolymerized polylactic acid fibers with multi-grooved, Y-shaped, or cross-shaped cross sections provide excellent capillary effect and a fluffy, soft feel, balancing moisture-wicking efficiency and skin-friendly touch; the proportion of hydrophobic modified fibers is controlled at 8-18 parts by weight, which can form an effective wetting gradient without affecting the overall skin-friendly comfort of the surface layer; the microcapsule loading range of 6%-15% balances skin care efficacy and cost control.

[0061] The fiber composition of the intermediate layer is as follows:

[0062] Cotton fiber: 25-35 parts by weight;

[0063] Viscose fiber: 20-35 parts by weight;

[0064] Lyocell fiber: 20-30 parts by weight;

[0065] Super absorbent fiber: 8-15 parts by weight;

[0066] Among them, the super absorbent fiber is a sodium polyacrylate cross-linked super absorbent fiber with a pure water absorption rate of not less than 60 g / g, a physiological saline absorption rate of not less than 20 g / g, and a fiber length of 30-40 mm.

[0067] The cotton fiber is combed cotton fiber, with a fiber length of 25-32 mm;

[0068] The viscose fiber has a fineness of 1.5-1.8 dtex and a length of 40-45 mm;

[0069] The lyocell fibers have a fineness of 1.3-1.5 dtex and a length of 35-40 mm.

[0070] The middle layer incorporates sodium polyacrylate super-absorbent fibers, which can lock in liquids dozens of times their own weight, significantly reducing the risk of liquid backflow. This perfectly complements the moisture absorption of viscose and cotton and the wet strength of lyocell, giving the middle layer high absorption, high water retention, and dimensional stability.

[0071] In the core-sheath structure of the bottom layer, the polylactic acid and polybutylene succinate bicomponent composite short fibers have a melting point of 105-120℃ for the polybutylene succinate in the sheath layer and a melting point of 160-175℃ for the polylactic acid in the core layer. The mass ratio of the sheath layer to the core layer is 30-45:70-55. The fiber fineness of the core-sheath structure is 2.0-2.8 dtex, and the length is 45-52 mm.

[0072] The bottom layer is a two-component composite short fiber of polylactic acid and polybutylene succinate. The low temperature characteristic of the polybutylene succinate in the outer layer (105-120℃) provides an ideal melting point for ultrasonic welding, avoiding thermal damage to the polylactic acid core layer, surface layer, and intermediate layer fibers caused by high temperature. The setting of the outer layer to core layer ratio can ensure sufficient welding strength.

[0073] The multiple concave dots are arranged in a matrix, rhomboid lattice, or regular hexagonal honeycomb pattern. The diameter of the concave dot opening is 0.5-1.5 mm, the depth of the concave dot is 0.3-0.9 mm, the center distance between adjacent concave dots is 3-8 mm, and the total area of ​​the concave dot region accounts for 5%-12% of the total surface area of ​​the nonwoven fabric.

[0074] The fiber density on the inner wall of the concave area is greater than that in the non-concave area, forming a capillary channel extending from the surface layer through the intermediate layer to the bottom layer; on the side wall of the concave area, the number density of the first microcapsule is more than 1.5 times that of the non-concave area, and the number density of the second microcapsule is more than 2 times that of the non-concave area.

[0075] The three-dimensional geometric parameters and arrangement of the concave dots are precisely matched with their dual functions. The area ratio of 5%-12% ensures sufficient interlayer bonding strength without compromising the fluffiness and breathability of the nonwoven fabric. The enrichment of microcapsules on the inner wall of the concave dots (the density of the first microcapsule is more than 1.5 times that of the second microcapsule) ensures that the effective ingredients are concentrated and released in the efficient range through which the liquid flows.

[0076] The biodegradable toughened composite micro powder is composed of polylactic acid, polyhydroxyalkanoate and nanocellulose, with a mass ratio of polylactic acid, polyhydroxyalkanoate and nanocellulose of 5-7:2-4:1. The average particle size of the biodegradable toughened composite micro powder is 1-5 μm. The amount of biodegradable toughened composite micro powder added is 2%-5% of the total mass of the surface fiber.

[0077] Biodegradable toughened composite micro powder improves the surface strength while being completely biodegradable, resolving the contradiction between skin-friendly softness and strong durability, with the overall material biodegradability rate remaining above 90%.

[0078] The basis weight of the surface layer is 15-25 g / m². 2 The basis weight of the intermediate layer is 25-45 g / m³. 2 The base layer has a basis weight of 15-25 g / m², and the finished product has a total basis weight of 55-95 g / m². 2 .

[0079] The aqueous extract of the weakly acidic, skin-friendly spunlace nonwoven fabric has a pH value of 5.2-6.2. After being stored in a sealed container at room temperature for 12 months, the pH value drift is no higher than 0.2. After 10 simulated water washes, the pH value drift is no higher than 0.3. The longitudinal dry tensile strength is no less than 32 N / 5 cm, and the longitudinal wet tensile strength is no less than 18 N / 5 cm. The liquid transfer index is no less than 190%.

[0080] The inhibition rate against Escherichia coli and Staphylococcus aureus is not less than 99%, and the inhibition rate against Candida albicans is not less than 90%; the irritation index in the skin occlusion patch test is not higher than 0.3; and the overall biodegradability rate is not less than 90%.

[0081] Example 2

[0082] The purpose of this embodiment is to provide a method for preparing the aforementioned weakly acidic, skin-friendly spunlace nonwoven fabric, comprising the following steps:

[0083] Step 1: Preparation and Web Formation of Surface Fiber Raw Materials

[0084] The copolymerized modified polylactic acid short fibers, chitosan short fibers, and biodegradable toughened composite micro powder are fully opened and mixed, and then carded to obtain the surface layer main fiber network; the copolymerized modified polylactic acid short fibers that have undergone local hydrophobic treatment are opened and carded separately to obtain a hydrophobic fiber network; through patterned web laying, the hydrophobic fiber network is laid on the surface layer main fiber network in island, strip, or grid patterns to form a surface layer fiber network with a wettable pattern of alternating hydrophilic and hydrophobic fiber regions;

[0085] Step 2: Positioning and Loading of Dual-Mode Sustained-Release Composite Microcapsules

[0086] First and second microcapsule suspensions were prepared separately and mixed in a certain proportion to obtain a composite microcapsule suspension with a total mass concentration of 6%-12%. Using a mask matching the surface wettability pattern, the composite microcapsule suspension was sprayed onto the hydrophilic fiber region of the surface fiber mesh through precise positioning atomization spraying at an atomization pressure of 0.2-0.5 MPa. The spraying amount was calculated based on the total microcapsule loading. After spraying, the surface fiber mesh was vacuum dried at 40-50℃ and a vacuum degree of -0.08 to -0.09 MPa for 15-25 min to obtain the functionalized surface fiber mesh.

[0087] Step 3: Preparation of the intermediate fiber web

[0088] Cotton fiber, viscose fiber, lyocell fiber and super absorbent fiber are mixed and opened in a certain proportion, and then combed into a web to obtain the middle layer fiber web;

[0089] Step 4: Preparation of the underlying fiber web

[0090] The core-sheath structure of polylactic acid and polybutylene succinate bicomponent composite short fibers is opened and carded into a web to obtain the bottom fiber web.

[0091] Step 5: Overlay and Hydroentanglement Pre-reinforcement

[0092] Functionalized surface fiber web, intermediate fiber web and bottom fiber web are stacked in sequence to form a three-layer composite fiber web; the three-layer composite fiber web is pre-entangled by high-pressure hydroentanglement, wherein the hydroentanglement adopts gradient pressure: pre-wetting 20-30 bar, main hydroentanglement stage four 50-80 bar, post hydroentanglement 70-95 bar, running speed 20-35 m / min, to obtain pre-reinforced nonwoven fabric.

[0093] Step Six: Ultrasonic Patterning Composite

[0094] The pre-reinforced nonwoven fabric is fed into an ultrasonic composite equipment. The surface of the ultrasonic welding head has an array of raised dots corresponding to the wettability pattern of the surface layer. Under the action of ultrasound, the bottom polybutylene succinate skin melts and flows at the corresponding positions of the raised dots, passes through the intermediate layer and fuses with the surface layer fibers, while forming multiple concave dots. The ultrasonic process parameters are: frequency 25-40kHz, amplitude 15-25μm, roller temperature 110-130℃, roller pressure 0.5-2.0MPa, and composite speed 20-40 m / min.

[0095] Step 7: Post-processing

[0096] The composite nonwoven fabric is dried at 100-120℃ until the moisture content is no more than 5%, then the surface is softened and the edges are trimmed. It is then sterilized with a combination of ultraviolet light and ozone, and aseptically packaged to obtain the finished product.

[0097] Furthermore, in step two, the pattern of the mask is consistent with the wettability pattern and the hydrophobic pattern of the surface layer, and the opening area corresponds to the hydrophilic fiber area; the thickness of the mask is 0.2-0.5 mm, and the opening accuracy is ±0.1 mm.

[0098] In step six, the bump array pattern of the ultrasonic welding head corresponds to the center of the hydrophilic region or the hydrophilic-hydrophobic interface line in the surface wettability pattern and the surface hydrophobic pattern, offset by 0-1 mm, so as to ensure that the concave opening falls on the hydrophilic region or interface.

[0099] This invention provides triple weak acid protection through the molecular-level weak acidity of copolymerized modified polylactic acid short fibers, the immediate release of lactic acid upon skin contact by the first microcapsule, and the sustained release of vitamin A from the polylactic acid shell of the second microcapsule. The synergistic effect of the wettability gradient constructed by the hydrophilic-hydrophobic micro-pattern on the surface layer and the vertical capillary channels formed by the array of concave dots, along with the concentrated distribution of the first microcapsule in the hydrophilic region and the inner wall of the concave dots for immediate skin-releasing moisturizing and soothing, and the formation of an enrichment gradient along the hydrophilic-hydrophobic interface by the second microcapsule for long-lasting repair, provides time-based skincare. The middle layer features super-absorbent fibers combined with cotton, viscose, and lyocell for water locking. The bottom layer consists of ultrasonic low-temperature fixed-point welding of polylactic acid and polybutylene succinate bicomponent fibers, and the toughening micropowder provides fully biodegradable reinforcement.

[0100] Experimental Example 1

[0101] The weakly acidic, skin-friendly spunlace nonwoven fabric of Example 1 was prepared using the preparation method in Example 2; specifically:

[0102] Surface layer: 50 parts of polylactic acid-polycaprolactone copolymer modified short fibers (cross-shaped cross section, 1.2 dtex × 38 mm), 35 parts of chitosan short fibers (93% deacetylation, 1.5 dtex, length 38 mm), and 3 parts of biodegradable toughening micro-powder (polylactic acid, polyhydroxyalkanoate, and nanocellulose in a mass ratio of 6:3:1, particle size 3 μm), mixed and carded into a web, basis weight 20 g / m². 2 Ten portions of hydrophobically modified PLA short fibers (water contact angle 120°, 1.2 dtex, length 38 mm) were individually carded into a web and then laid on the main web in a diamond lattice (dot diameter 3 mm, center-to-center distance 6 mm).

[0103] Microcapsules: 3 parts of the first microcapsule (chitosan-sodium alginate wall, core material: lactic acid:sodium hyaluronate:panthenol = 1:2:1); 6 parts of the second microcapsule (bilayer, core material:ceramide:centella asiatica extract:vitamin E acetate = 2:1:0.5). The total suspension concentration was 8%. The microcapsules were sprayed onto the hydrophilic region using a mask, atomized at 0.3 MPa, and vacuum dried at 50°C for 20 min.

[0104] Middle layer: 30 parts combed cotton, 30 parts viscose, 25 parts lyocell, and 15 parts super absorbent fiber, blended and carded into a web, with a weight of 35 g / m². 2 .

[0105] Bottom layer: 100 parts of bicomponent short fibers of polylactic acid and polybutylene succinate with a core-sheath structure (polybutylene succinate sheath melting point 110℃, sheath to core ratio 40:60, 2.2 dtex, length 48 mm), weight 20 g / m². 2 .

[0106] Hydroentanglement: Pre-wetting 25 bar, main hydroentanglement 55-75 bar (four stages), post hydroentanglement 90 bar, speed 28 m / min.

[0107] Ultrasonic composite: The center of the welding head protrusion corresponds to the center of the hydrophilic rhomboid area, with a frequency of 30kHz, an amplitude of 20μm, a temperature of 120℃, a pressure of 1.2MPa, a speed of 28 m / min, and a concave diameter of approximately 0.8 mm and a depth of 0.5 mm.

[0108] Post-treatment: Dry at 110℃, then UV + ozone sterilize for 12 min.

[0109] Comparative Example 1: It has hydrophilic and hydrophobic patterns and dimples, but no microcapsules and toughening micropowder, and no super-absorbent fibers in the middle layer.

[0110] Comparative Example 2: The surface layer is a homogeneous mixture without a pattern, finished with added lactic acid, without pits or super-absorbent fibers, and is a conventional hydroentangled composite.

[0111] Comparative Example 3: Commercially available mildly acidic soft towels (labeled as containing citric acid, made of pure cotton).

[0112] All experiments were conducted under standard atmospheric conditions (20±2℃, 65±4%RH). The samples were Experimental Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0113] Experiment 1: pH stability (refer to GB / T 7573-2009)

[0114] The initial pH value, the pH value after 12 months of sealed storage, and the pH value after 10 simulated water washes were tested; the water washes were performed according to the gentle program of GB / T 8629-2017 at 38℃; the specific results are shown in Table 1 below:

[0115] Table 1

[0116] sample initial pH pH drift after 12 months pH shift after 10 washes Experimental Example 1 5.6 5.5（0.1） 5.4（0.2） Comparative Example 1 5.7 5.5（0.2） 5.3（0.4） Comparative Example 2 5.5 6.2（0.7） 6.6（1.1） Comparative Example 3 5.8 6.4（0.6） 6.8（1.0）

[0117] Table 1 shows that the pH shift in Experimental Example 1 was minimal, demonstrating the effectiveness of the triple weak acid shield; Comparative Example 1 relied on molecular-level weak acid and showed a slight increase after washing; Post-treatment and commercially available products showed significant pH shifts and lost their weak acidity.

[0118] Experiment 2: Antibacterial long-term effect (refer to GB / T 20944.3-2008 shaking method)

[0119] The inhibition rates against Escherichia coli and Staphylococcus aureus were tested initially and after 12 months of storage; the specific results are shown in Table 2 below:

[0120] Table 2

[0121] sample Initial E. coli inhibition rate E. coli inhibition rate after 12 months Initial Staphylococcus aureus inhibition rate Staphylococcus aureus inhibition rate after 12 months Experimental Example 1 99.6% 99.3% 99.5% 99.1% Comparative Example 1 99.4% 98.0% 99.2% 97.5% Comparative Example 2 95.0% 85.0% 94.0% 82.0% Comparative Example 3 94.5% 80.0% 93.0% 78.0%

[0122] As shown in Table 2, the long-lasting antibacterial effect achieved by this invention, relying on the weakly acidic environment of chitosan and polylactic acid, is significantly superior to the control product that relies on acidity and other additives, achieving over 99% antibacterial efficacy without the need for nano-silver.

[0123] Experiment 3: Liquid unidirectional transfer and dryness (AATCC 195-2017)

[0124] The instantaneous aspiration time, unidirectional transport index OMMC, and 30-second reabsorption were tested; the specific results are shown in Table 3 below:

[0125] Table 3

[0126] sample Instantaneous absorption time (s) OMMC 30s reabsorption (g) Experimental Example 1 0.7 225% 0.01 Comparative Example 1 1.0 190% 0.03 Comparative Example 2 2.8 75% 0.14 Comparative Example 3 3.2 60% 0.17

[0127] Through Table 3 and Figure 1 It can be seen that the triple mechanism of hydrophilic and hydrophobic patterns, dimples and microcapsules hydrophilic enrichment in Experiment Example 1 makes OMMC as high as 225%, which basically achieves unidirectional irreversible liquid conduction and has a far superior dryness.

[0128] Experiment 4: Dry and wet mechanical properties (refer to GB / T 24218.3-2010)

[0129] Table 4

[0130] sample Longitudinal stiffness (N / 5cm) Longitudinal wet strength (N / 5cm) Wet strength retention rate Experimental Example 1 37 22 59.5% Comparative Example 1 33 18 54.5% Comparative Example 2 24 11 45.8% Comparative Example 3 19 7 36.8%

[0131] Through Table 4, Figure 2 and Figure 3 It can be seen that the toughening micro powder, lyocell and the underlying skeleton work together to improve dry and wet strength, with a wet strength retention rate of nearly 60%, which is far superior to existing products.

[0132] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0133] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A weakly acidic, skin-friendly spunlace nonwoven fabric, characterized in that, It includes a top layer, an intermediate layer and a bottom layer stacked sequentially along the thickness direction, wherein the top layer, the intermediate layer and the bottom layer are fixedly connected by hydroentanglement and ultrasonic patterned welding; The surface layer is composed of copolymerized modified polylactic acid short fibers, chitosan short fibers, and locally hydrophobically treated copolymerized modified polylactic acid short fibers. Dual-mode sustained-release composite microcapsules are loaded in localized areas of the surface layer. The surface layer has a microscopic wettability pattern formed by alternating hydrophilic and hydrophobic fiber regions, with the hydrophobic fiber regions composed of locally hydrophobically treated copolymerized modified polylactic acid short fibers. The dual-mode sustained-release composite microcapsules are concentrated within the hydrophilic fiber regions, forming a microcapsule enrichment gradient along the hydrophilic-hydrophobic interface. The middle layer is composed of a mixture of cotton fibers, viscose fibers, lyocell fibers, and super absorbent fibers; The bottom layer is composed of two-component composite short fibers of polylactic acid and polybutylene succinate with a core-sheath structure. The sheath layer of the core-sheath structure is low-melting-point polybutylene succinate, and the core layer of the core-sheath structure is high-melting-point polylactic acid. The surface of the nonwoven fabric has multiple dimples formed by ultrasonic patterning. The dimples extend downward from the surface layer, penetrate the surface layer and at least partially enter the intermediate layer. The bottom of the dimples is permanently fused to the bottom layer by melting and re-curing the polybutylene succinate skin layer of the bottom layer. The position of the dimples corresponds to the micro-wetting pattern of the surface layer, so that the opening of the dimples is located in the hydrophilic fiber region, and the inner wall of the dimples is enriched with the dual-mode sustained-release composite microcapsules. The surface layer also contains biodegradable toughening composite micro powder evenly dispersed.

2. The weakly acidic skin-friendly spunlace nonwoven fabric according to claim 1, characterized in that, The dual-mode sustained-release composite microcapsule comprises a first microcapsule and a second microcapsule; The first microcapsule comprises a capsule wall and a core material A. The capsule wall is a chitosan-sodium alginate ion-crosslinked gel. The core material A is a mixture of lactic acid, sodium hyaluronate, and panthenol, with a mass ratio of 1:2-3:1-1.

5. The first microcapsule has a particle size of 2-5 μm and ruptures upon contact with skin moisture or friction, rapidly releasing the core material A. The second microcapsule comprises an inner capsule wall, an outer capsule wall, and a core material B. Core material B is encapsulated within the inner and outer capsule walls. The inner capsule wall is composed of chitosan-sodium alginate, and the outer capsule wall is composed of polylactic acid. Core material B is a mixture of ceramide, centella asiatica extract, and vitamin E acetate, with a mass ratio of 2:1:0.5-1. The second microcapsule has a particle size of 5-8 μm, and the outer capsule wall has a thickness of 0.4-1.0 μm, which is used to delay the release of core material B. The mass ratio of the first microcapsule to the second microcapsule is 1:1.5-3.

3. The weakly acidic, skin-friendly, spunlace nonwoven fabric according to claim 1, characterized in that, The surface layer has the following fiber composition: Copolymer-modified polylactic acid short fiber: 40-65 parts by weight; Chitosan short fibers: 25-45 parts by weight; Copolymerized modified polylactic acid short fibers with localized hydrophobic treatment: 8-18 parts by weight; Among them, the copolymer-modified polylactic acid short fiber is polylactic acid-polycaprolactone block copolymer fiber or polylactic acid-polybutylene succinate block copolymer fiber; the cross section of the copolymer-modified polylactic acid short fiber is multi-groove, Y-shaped or cross-shaped, and its single fiber fineness is 1.0-1.5 dtex and its length is 35-40 mm; The degree of deacetylation of chitosan short fibers is not less than 90%, and the fineness of its single fibers is 1.2-1.8 dtex, with a length of 35-40 mm; The copolymerized modified polylactic acid short fibers, after being partially hydrophobically treated, are grafted with organosiloxanes after plasma activation. The water contact angle of the fiber surface is not less than 115°, and the fineness of the single fiber is 1.0-1.5 dtex, and the length is 35-40 mm. The total loading of the dual-mode sustained-release composite microcapsules is 6%-15% of the total mass of the surface fiber.

4. The weakly acidic, skin-friendly, spunlace nonwoven fabric according to claim 1, characterized in that, The fiber composition of the intermediate layer is as follows: Cotton fiber: 25-35 parts by weight; Viscose fiber: 20-35 parts by weight; Lyocell fiber: 20-30 parts by weight; Super absorbent fiber: 8-15 parts by weight; Among them, the super absorbent fiber is a sodium polyacrylate cross-linked super absorbent fiber with a pure water absorption rate of not less than 60 g / g, a physiological saline absorption rate of not less than 20 g / g, and a fiber length of 30-40 mm. The cotton fiber is combed cotton fiber, with a fiber length of 25-32 mm; The viscose fiber has a fineness of 1.5-1.8 dtex and a length of 40-45 mm; The lyocell fibers have a fineness of 1.3-1.5 dtex and a length of 35-40 mm.

5. The weakly acidic, skin-friendly, spunlace nonwoven fabric according to claim 1, characterized in that, In the core-sheath structure of the bottom layer, the polylactic acid and polybutylene succinate bicomponent composite short fibers have a melting point of 105-120℃ for the polybutylene succinate in the sheath layer and a melting point of 160-175℃ for the polylactic acid in the core layer. The mass ratio of the sheath layer to the core layer is 30-45:70-55. The fiber fineness of the core-sheath structure is 2.0-2.8 dtex, and the length is 45-52 mm.

6. The weakly acidic, skin-friendly, spunlace nonwoven fabric according to claim 1, characterized in that, The multiple concave dots are arranged in a matrix, rhomboid lattice, or regular hexagonal honeycomb pattern. The diameter of the concave dot opening is 0.5-1.5 mm, the depth of the concave dot is 0.3-0.9 mm, the center distance between adjacent concave dots is 3-8 mm, and the total area of ​​the concave dot region accounts for 5%-12% of the total surface area of ​​the nonwoven fabric. The fiber density on the inner wall of the concave area is greater than that in the non-concave area, forming a capillary channel extending from the surface layer through the intermediate layer to the bottom layer; on the side wall of the concave area, the number density of the first microcapsule is more than 1.5 times that of the non-concave area, and the number density of the second microcapsule is more than 2 times that of the non-concave area.

7. The weakly acidic, skin-friendly, spunlace nonwoven fabric according to claim 1, characterized in that, The biodegradable toughened composite micro powder is composed of polylactic acid, polyhydroxyalkanoate and nanocellulose, with a mass ratio of polylactic acid, polyhydroxyalkanoate and nanocellulose of 5-7:2-4:

1. The average particle size of the biodegradable toughened composite micro powder is 1-5 μm. The amount of biodegradable toughened composite micro powder added is 2%-5% of the total mass of the surface fiber.

8. A method for preparing a weakly acidic, skin-friendly spunlace nonwoven fabric according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Preparation and Web Formation of Surface Fiber Raw Materials The copolymerized modified polylactic acid short fibers, chitosan short fibers, and biodegradable toughened composite micro powder are fully opened and mixed, and then carded to obtain the surface layer main fiber network; the copolymerized modified polylactic acid short fibers that have undergone local hydrophobic treatment are opened and carded separately to obtain a hydrophobic fiber network; through patterned web laying, the hydrophobic fiber network is laid on the surface layer main fiber network in island, strip, or grid patterns to form a surface layer fiber network with a wettable pattern of alternating hydrophilic and hydrophobic fiber regions; Step 2: Positioning and Loading of Dual-Mode Sustained-Release Composite Microcapsules First and second microcapsule suspensions were prepared separately and mixed in a certain proportion to obtain a composite microcapsule suspension with a total mass concentration of 6%-12%. Using a mask matching the surface wettability pattern, the composite microcapsule suspension was sprayed onto the hydrophilic fiber region of the surface fiber mesh through precise positioning atomization spraying at an atomization pressure of 0.2-0.5 MPa. The spraying amount was calculated based on the total microcapsule loading. After spraying, the surface fiber mesh was vacuum dried at 40-50℃ and a vacuum degree of -0.08 to -0.09 MPa for 15-25 min to obtain the functionalized surface fiber mesh. Step 3: Preparation of the intermediate fiber web Cotton fiber, viscose fiber, lyocell fiber and super absorbent fiber are mixed and opened in a certain proportion, and then combed into a web to obtain the middle layer fiber web; Step 4: Preparation of the underlying fiber web The core-sheath structure of polylactic acid and polybutylene succinate bicomponent composite short fibers is opened and carded into a web to obtain the bottom fiber web. Step 5: Overlay and Hydroentanglement Pre-reinforcement Functionalized surface fiber web, intermediate fiber web and bottom fiber web are stacked in sequence to form a three-layer composite fiber web; the three-layer composite fiber web is pre-entangled by high-pressure hydroentanglement, wherein the hydroentanglement adopts gradient pressure: pre-wetting 20-30 bar, main hydroentanglement stage four 50-80 bar, post hydroentanglement 70-95 bar, running speed 20-35 m / min, to obtain pre-reinforced nonwoven fabric. Step Six: Ultrasonic Patterning Composite The pre-reinforced nonwoven fabric is fed into an ultrasonic composite equipment. The surface of the ultrasonic welding head has an array of raised dots corresponding to the wettability pattern of the surface layer. Under the action of ultrasound, the bottom polybutylene succinate skin melts and flows at the corresponding positions of the raised dots, passes through the intermediate layer and fuses with the surface layer fibers, while forming multiple concave dots. The ultrasonic process parameters are: frequency 25-40kHz, amplitude 15-25μm, roller temperature 110-130℃, roller pressure 0.5-2.0MPa, and composite speed 20-40 m / min. Step 7: Post-processing The composite nonwoven fabric is dried at 100-120℃ until the moisture content is no more than 5%, then the surface is softened and the edges are trimmed. It is then sterilized with a combination of ultraviolet light and ozone, and aseptically packaged to obtain the finished product.

9. The method for preparing a weakly acidic, skin-friendly spunlace nonwoven fabric according to claim 8, characterized in that, In step two, the pattern of the mask is consistent with the wettability pattern and the hydrophobic pattern of the surface layer, and the opening area corresponds to the hydrophilic fiber area; the thickness of the mask is 0.2-0.5 mm, and the opening accuracy is ±0.1 mm.

10. The method for preparing a weakly acidic, skin-friendly spunlace nonwoven fabric according to claim 8, characterized in that, In the step six, the convex dot array pattern of the ultrasonic welding head is offset 0-1 mm from the center of the hydrophilic region or the hydrophilic-hydrophobic interface in the surface layer wettability pattern and the surface layer hydrophobic pattern, so as to ensure that the concave dot opening falls in the hydrophilic region or the interface.

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