Process for producing melt direct-spun degradable nonwoven fabric for sanitary use

Abstract

The application discloses a kind of melt direct spinning degradable sanitary non-woven fabric manufacturing method, please involve non-woven fabric manufacturing field, including raw material pretreatment, melt preparation, melt filtration and metering, melt direct spinning and drafting, web formation, reinforcement forming, post-processing and the like steps;By optimizing the ratio of degradable raw material, using PLA and PBAT blending arrangement biobased plasticizer, without adding too many chemical modifiers;Melt direct spinning process is used, and the processes such as slice preparation, drying are omitted, combined with double screw extruder heat preservation, spinning waste heat recovery, air circulation utilization and other measures, energy consumption is greatly reduced;By optimizing spinning, drafting, hot rolling and other process parameters, the fiber forming quality and product comprehensive performance are improved.The melt direct spinning degradable sanitary non-woven fabric manufacturing method, manufacturing method process is simple, energy consumption is low, efficiency is high, and the prepared non-woven fabric has good degradability, hygiene safety, softness and air permeability.

Description

Technical Field

[0001] This invention relates to the field of nonwoven fabric manufacturing, specifically a method for manufacturing melt-spun biodegradable sanitary nonwoven fabric. Background Technology

[0002] As a core raw material for disposable hygiene products, nonwoven fabrics for hygiene use are experiencing continuously expanding market demand. However, current mainstream products are generally made from non-degradable polymers such as polypropylene. These materials are difficult to decompose in the natural environment after disposal, leading to significant environmental pressure due to long-term accumulation. The global accumulation of discarded nonwoven fabric products for hygiene is enormous, and their prolonged residence under natural conditions seriously conflicts with global trends in sustainable development and environmental protection. To address this challenge, biodegradable polymers such as polylactic acid (PLA) and polybutylene adipate (PEG) are gaining attention. These materials possess good biocompatibility and biodegradability, and their raw materials are derived from renewable resources, theoretically mitigating the environmental burden. However, current production processes for biodegradable nonwoven fabrics for hygiene largely rely on slicing and spinning. This process requires first preparing biodegradable resin into slices, followed by drying, melt spinning, and other steps, resulting in a lengthy production process, high energy consumption in intermediate stages, and the drying process easily causing resin molecular chain breakage, leading to material performance degradation and affecting the quality stability of the final product.

[0003] Melt spinning, as a potential alternative, can directly utilize the polymerized melt for spinning, eliminating the need for slicing and drying steps, and theoretically has the potential to simplify the process and improve efficiency. However, in practical application to the production of biodegradable sanitary nonwoven fabrics, this technology faces multiple technical obstacles. Biodegradable resins such as polylactic acid have low melt strength and slow crystallization kinetics, which easily lead to fiber breakage and fuzzing during high-speed spinning, resulting in uneven fiber formation and making it difficult to meet the stringent requirements of sanitary nonwoven fabrics for softness, breathability, and structural integrity. Summary of the Invention (a) Technical problems to be solved

[0004] The purpose of this invention is to provide a method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric, in order to solve the problems mentioned in the background art, such as the low melt strength and slow crystallization kinetics of biodegradable resins like polylactic acid, which are prone to fiber breakage and fuzzing during high-speed spinning, resulting in uneven fiber formation and difficulty in meeting the strict requirements of sanitary nonwoven fabrics for softness, breathability and structural integrity. (II) Technical Solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric, comprising the following steps: 1) Raw material pretreatment: The biodegradable resin and bio-based plasticizer are mixed at a mass ratio of 85-95:5-15 and put into a high-speed mixer. The mixture is mixed for 15-25 minutes at 60-80℃ and 200-300 r / min to obtain the mixed raw material. The biodegradable resin is a blend of polylactic acid (PLA) and polybutylene adipate (PBAT), wherein the mass ratio of PLA to PBAT is 70-85:15-30. The bio-based plasticizer is a compound of tributyl citrate (TBC) and epoxidized soybean oil (ESO), wherein the mass ratio of TBC to ESO is 1:0.8-1.2. 2) Melt preparation: The mixed raw materials obtained in step 1) are fed into a twin-screw extruder for melt extrusion to prepare a biodegradable melt. The twin-screw extruder uses segmented temperature control, with the temperatures from the feed inlet to the die head set sequentially to 140–160℃, 160–175℃, 175–185℃, and 180–190℃. The screw speed is 180–250 r / min, and the extrusion pressure is 1.5–2.5 MPa. The barrel of the twin-screw extruder is wrapped with an insulation layer with a thickness of 5–10 mm. 3) Melt filtration and metering: The biodegradable melt prepared in step 2) is filtered through a filtration device with a filtration accuracy of 10-20 μm; the filtered melt is fed into a metering pump with a speed of 50-80 r / min and the melt output is controlled at 5-10 g / min·pore. 4) Melt spinning and drawing: The metered melt is ejected through a spinneret to form a fine melt stream; the spinneret orifice diameter is 0.2–0.4 mm, and the orifice spacing is 1.5–2.5 mm; after the melt stream is ejected, it is drawn using a heated airflow at a temperature of 120–150℃ and a velocity of 8–12 m / s, with a draw ratio of 5–8 times; simultaneously, a low-temperature cooling zone is set below the spinneret, with a cooling airflow temperature of 15–25℃ and a velocity of 5–8 m / s, and the cooling zone is 10–30 mm from the spinneret outlet; the heated airflow is preheated using recovered spinning waste heat, with a preheating efficiency of over 60%; 5) Web formation: The drawn fibers are formed into a web by passing them through an air-jet web forming machine; the negative pressure of the air-jet web forming machine is 0.02-0.05MPa, the web forming speed is 10-20m / min, and the basis weight of the fiber web is controlled to be 20-50g / m². 6) Reinforcement and forming: The fiber web obtained in step 5) is fed into a hot rolling mill for hot rolling reinforcement. The hot rolling temperature is 120-140℃, the hot rolling pressure is 0.3-0.6MPa, and the hot rolling speed is 8-15m / min. 7) Post-processing: Cool, cut and roll up the hot-rolled nonwoven fabric. The cooling temperature is 25-35℃ and the cooling time is 5-10 minutes to obtain the melt-spun biodegradable sanitary nonwoven fabric.

[0006] Furthermore, this application also proposes that, in step 1), the melt index of PLA is 150-300 g / 10 min (210 °C, 2.16 kg), and the weight-average molecular weight is 100,000-200,000; the melt index of PBAT is 5-15 g / 10 min (190 °C, 2.16 kg), and the weight-average molecular weight is 80,000-150,000.

[0007] Furthermore, this application also proposes that, in step 1), 0.1 to 0.3 wt% of an antioxidant and 0.05 to 0.1 wt% of a light stabilizer are added to the mixed raw materials; the antioxidant is a hindered phenolic antioxidant and the light stabilizer is a benzotriazole light stabilizer.

[0008] Furthermore, this application also proposes that, in step 4), the spinneret is made of ceramic material.

[0009] Furthermore, this application also proposes that, in step 6), the surface of the hot rolling mill rolls is provided with raised and recessed patterns, the pattern depth being 0.1 to 0.3 mm.

[0010] Furthermore, this application also proposes that, in step 2), the screw of the twin-screw extruder adopts a gradually changing pitch design, with a screw pitch of 40-50 mm in the feeding section, 30-40 mm in the compression section, and 20-30 mm in the metering section.

[0011] Furthermore, this application also proposes that, in step 7), a combination of natural cooling and forced ventilation be used in the post-processing. (III) Beneficial Effects

[0012] Compared with the prior art, the present invention provides a method for manufacturing melt-spun biodegradable sanitary nonwoven fabric, which has the following beneficial effects: This melt-spun biodegradable sanitary nonwoven fabric manufacturing method uses PLA and PBAT blends with bio-based plasticizers. It eliminates the need for excessive chemical modifiers, ensuring melt flowability and fiber forming performance, avoiding issues like broken fibers and fuzz, while also guaranteeing the product's biodegradability and hygiene safety. Under standard composting conditions of 58℃±2℃ and 60-80% humidity, the product exhibits a biodegradability rate of ≥90% within 90 days with no harmful residues, meeting the requirements for sanitary products. Furthermore, the PLA and PBAT blend system balances fiber softness and mechanical properties, solving the problem of poor spinning performance with a single biodegradable resin. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Please see Figure 1 As shown, a method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric includes the following steps: Raw material pretreatment: The biodegradable resin and bio-based plasticizer are mixed at a mass ratio of 85-95:5-15 and put into a high-speed mixer. The mixture is mixed for 15-25 minutes at 60-80℃ and 200-300 r / min to obtain the mixed raw material. The biodegradable resin is a blend of polylactic acid (PLA) and polybutylene adipate (PBAT), wherein the mass ratio of PLA to PBAT is 70-85:15-30. The bio-based plasticizer is a compound of tributyl citrate (TBC) and epoxidized soybean oil (ESO), wherein the mass ratio of TBC to ESO is 1:0.8-1.2. Melt preparation: The mixed raw materials obtained in step 1) are fed into a twin-screw extruder for melt extrusion to prepare a biodegradable melt. The twin-screw extruder uses segmented temperature control, with the temperatures from the feed inlet to the die head set sequentially to 140–160℃, 160–175℃, 175–185℃, and 180–190℃. The screw speed is 180–250 r / min, and the extrusion pressure is 1.5–2.5 MPa. The barrel of the twin-screw extruder is wrapped with an insulation layer with a thickness of 5–10 mm. Melt filtration and metering: The biodegradable melt prepared in step 2) is filtered through a filtration device with a filtration accuracy of 10-20 μm; the filtered melt is fed into a metering pump with a speed of 50-80 r / min and the melt output is controlled to be 5-10 g / min·pore. Melt spinning and drawing: The metered melt is ejected through a spinneret to form a fine melt stream; the diameter of the spinneret orifices is 0.2–0.4 mm, and the orifice spacing is 1.5–2.5 mm; after the melt stream is ejected, it is drawn using a heated airflow at a temperature of 120–150℃ and a velocity of 8–12 m / s, with a draw ratio of 5–8 times; simultaneously, a low-temperature cooling zone is set below the spinneret, with a cooling airflow temperature of 15–25℃ and a velocity of 5–8 m / s, and the cooling zone is 10–30 mm from the spinneret outlet; Web formation: The drawn fibers are formed into a web by passing them through an air-flow web forming machine; the negative pressure of the air-flow web forming machine is 0.02-0.05MPa, the web forming speed is 10-20m / min, and the basis weight of the fiber web is controlled to be 20-50g / m². Reinforcement and forming: The fiber web obtained in step 5) is fed into a hot rolling mill for hot rolling reinforcement. The hot rolling temperature is 120-140℃, the hot rolling pressure is 0.3-0.6MPa, and the hot rolling speed is 8-15m / min. Post-processing: The hot-rolled nonwoven fabric is cooled, cut, and rolled up. The cooling temperature is 25-35℃ and the cooling time is 5-10 minutes to obtain the melt-spun biodegradable sanitary nonwoven fabric product.

[0016] Melt-spun biodegradable sanitary nonwoven fabric refers to a new type of nonwoven material produced using a melt-spun process, possessing biodegradable properties and suitable for the field of sanitary products. This method aims to reduce overall energy consumption by optimizing the production process and parameters.

[0017] Biodegradable resin refers to a polymer material that can decompose into smaller molecules through biological or physicochemical processes under specific environmental conditions, ultimately returning to the natural cycle. In this embodiment, the resin is the main component of the nonwoven fabric, giving the product its biodegradable properties.

[0018] Bio-based plasticizers are additives derived from biomass resources that increase the flexibility of polymer materials and lower their glass transition temperature. The use of these plasticizers helps improve the processing properties of biodegradable resins and the softness of the final product.

[0019] Polylactic acid (PLA) is a biodegradable polymer derived from the fermentation of renewable plant resources such as corn and cassava. It is biocompatible and degradable, but has relatively low melt strength and a slow crystallization rate.

[0020] Polybutylene adipate (PBAT) is a biodegradable aliphatic-aromatic copolyester. This material possesses flexibility and ductility and is often blended with PLA to improve PLA's toughness and processability.

[0021] Tributyl citrate (TBC) is a commonly used bio-based plasticizer with plasticizing effects and biosafety, and is often used in food contact materials and medical materials.

[0022] Epoxidized soybean oil (ESO) is a bio-based plasticizer made by epoxidizing soybean oil. It has plasticizing effect and thermal stability, and is environmentally friendly and non-toxic.

[0023] A twin-screw extruder is a widely used piece of equipment in the processing of polymer materials. It uses two meshing screws rotating inside a barrel to convey, melt, mix, plasticize, and extrude materials. This equipment enables precise mixing and temperature control of the materials.

[0024] Heated airflow stretching refers to using high-temperature airflow to stretch the fine molten stream that has just been ejected from the spinneret, causing its molecular chains to orient, thereby improving the strength and fineness of the fiber.

[0025] The low-temperature cooling zone refers to an area located below the spinneret during the molten flow drawing process. Low-temperature airflow is introduced to rapidly cool the molten flow, thereby promoting fiber solidification and forming.

[0026] An airflow web forming machine is a device that uses airflow to disperse and spread fibers into a uniform fiber web. This device uses negative pressure or airflow impact to form the initial shape of a nonwoven fabric on a collecting web.

[0027] The main technical features of this embodiment are described in detail below: In the raw material pretreatment step, the mixing of biodegradable resin and bio-based plasticizer can be carried out manually or using a low-speed mixing device. The biodegradable resin can consist of a single biodegradable polymer, such as polylactic acid (PLA) or polybutylene adipate (PBAT) alone, or a blend in other proportions. The bio-based plasticizer can also be a single component, such as tributyl citrate (TBC) or epoxidized soybean oil (ESO) alone, or a compound in other proportions. The temperature and speed during the mixing process can also be set to fixed values, rather than being adjusted within a specific range.

[0028] In the melt filtration and metering steps, melt filtration can use a filter screen with a large pore size, or in some cases, the filtration step can be omitted. The metering pump speed can be set to a fixed value, or other types of pumps can be used for melt delivery, such as gear pumps, whose output may be controlled by pressure regulation rather than speed.

[0029] In the melt spinning and drawing steps, the melt stream can be ejected using a metal spinneret, and the melt stream can be drawn using mechanical drawing rollers or by a ambient airflow. A dedicated low-temperature cooling zone is not required below the spinneret; natural cooling relies solely on ambient air. The heating airflow can be generated entirely by external energy sources, without utilizing any waste heat for preheating.

[0030] In the web-forming step, the drawn fibers can be mechanically combed to form a fiber web. The negative pressure, web-forming speed, and basis weight of the air-laid web forming machine can be set to fixed values ​​or controlled within a wide range.

[0031] In the reinforcement forming step, the fiber web can be reinforced using methods such as needle punching or chemical bonding. The hot rolling mill can use smooth-surfaced rolls without any patterns. The temperature, pressure, and speed during the hot rolling process can also be set to fixed values.

[0032] In the post-processing steps, the thermally rolled nonwoven fabric can be cooled solely by natural cooling without forced ventilation. Cutting and winding can be performed manually or using simple mechanical equipment. The cooling temperature and cooling time can also be set to fixed values.

[0033] The following example will provide a more detailed explanation of the above technical solution: First, in the raw material pretreatment stage, a biodegradable resin and a bio-based plasticizer at a mass ratio of 88:12 are fed into a high-speed mixer. The biodegradable resin is a blend of polylactic acid (PLA) and polybutylene adipate (PBAT) at a mass ratio of 75:25, while the bio-based plasticizer is a compound of tributyl citrate (TBC) and epoxidized soybean oil (ESO) at a mass ratio of 1:1. The mixture is stirred for 20 minutes at 65°C and 250 rpm to ensure thorough and uniform dispersion of the raw materials, providing a uniform feed for subsequent melt extrusion. This raw material ratio and thorough premixing help overcome the problems of low melt strength and slow crystallization rate of PLA, laying the foundation for subsequent melt spinning.

[0034] Subsequently, the mixed raw materials are fed into a twin-screw extruder for melt extrusion. The extruder employs segmented temperature control, with temperatures set sequentially from the feed inlet to the die head at 150℃, 165℃, 178℃, and 185℃. The screw speed is set at 200 r / min, and the extrusion pressure is controlled at 2.0 MPa. The extruder barrel is wrapped with an 8mm thick insulation layer, effectively reducing heat loss. Through segmented temperature control and insulation design, the biodegradable resin is ensured to be heated uniformly during the melting process, avoiding localized overheating or degradation, while simultaneously reducing energy consumption in the melt preparation process.

[0035] Next, the prepared biodegradable melt is filtered through a filtration device with a filtration precision set to 15 μm to remove minute impurities and prevent clogging of the spinneret orifices. The filtered melt is then fed into a metering pump, which operates at 65 r / min, controlling the melt output at 7 g / min·orifice. This filtration and metering process ensures consistency in melt quality and subsequent fiber diameter, avoiding filament breakage and fuzzing caused by impurities or flow fluctuations.

[0036] In the melt spinning and drawing stages, the metered melt is ejected through a spinneret, forming a continuous melt stream. The spinneret has a spinneret orifice diameter of 0.3 mm and an orifice spacing of 2.0 mm. Immediately after the melt stream is ejected, it is drawn using a heated airflow at 135℃ and a wind speed of 10 m / s, with a draw ratio of 6. Simultaneously, a low-temperature cooling zone is set 20 mm below the spinneret, with a cooling airflow temperature of 20℃ and a wind speed of 6 m / s. Through the synergistic effect of the heated airflow drawing and the low-temperature cooling zone, the melt stream is rapidly solidified while being stretched, effectively improving the fiber forming quality and mechanical properties. Furthermore, waste heat recovery reduces energy consumption.

[0037] The drawn fibers are web-formed using an air-jet web forming machine. The negative pressure of the air-jet web forming machine is set to 0.03 MPa, the web forming speed is 15 m / min, and the basis weight of the fiber web is controlled at 35 g / m². The air-jet web forming technology ensures the uniform spreading and random distribution of the fibers, forming a fiber web that is soft and breathable.

[0038] The fiber web is then fed into a hot rolling mill for hot rolling reinforcement. The hot rolling temperature is set at 130℃, the hot rolling pressure at 0.4MPa, and the hot rolling speed at 10m / min. The hot rolling process enables the fiber web to acquire the required strength and structural stability while maintaining the soft touch of the nonwoven fabric.

[0039] Finally, the hot-rolled nonwoven fabric is cooled, cut, and wound up. The cooling temperature is controlled at 30℃, and the cooling time is 8 minutes, ultimately yielding the melt-spun biodegradable sanitary nonwoven fabric. The entire manufacturing process, through optimized raw material formulation, process parameter control, and energy recovery and utilization, achieves low-energy production and obtains biodegradable nonwoven fabric that meets the requirements for sanitary products.

[0040] Compared to the non-degradable materials commonly used in existing technologies, this embodiment uses a blend of polylactic acid (PLA) and polybutylene adipate (PBAT) as a biodegradable resin, supplemented with a compound of bio-based plasticizers tributyl citrate (TBC) and epoxidized soybean oil (ESO), thus solving the environmental problem of the difficulty in natural degradation of sanitary non-woven fabrics after disposal. This raw material system is not only biodegradable but also avoids the residue problems that may be caused by traditional chemical modifiers, ensuring the hygiene, safety, and environmental protection attributes of the product.

[0041] Compared to the slicing and spinning processes commonly used in existing biodegradable nonwoven fabric production, this embodiment employs a melt direct spinning process, directly spinning the mixed melt. This process eliminates cumbersome and energy-intensive intermediate steps such as slice preparation and drying, reducing the complexity of the production process and overall energy consumption. For example, in the melt preparation stage, the twin-screw extruder uses segmented temperature control supplemented by an insulation layer to ensure uniform plasticization of the melt while reducing heat loss. This demonstrates higher energy management efficiency compared to traditional processes that may involve single temperature control or lack insulation measures.

[0042] To address the technical bottleneck of low melt strength and slow crystallization rate of biodegradable resins, which leads to easy fiber breakage and fuzzing during high-speed spinning, this embodiment overcomes this limitation through process parameter control. In the melt spinning and drawing steps, by controlling the spinneret diameter, heating airflow temperature and velocity, and draw ratio, and by coordinating the setting of a low-temperature cooling zone, stable drawing and rapid solidification of the melt stream are achieved. This multi-parameter synergistic optimization ensures fiber forming quality, effectively avoiding fiber breakage and fuzzing, thereby obtaining fibers that meet the requirements of softness and breathability for sanitary nonwoven fabrics.

[0043] In some other embodiments, this application proposes a method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric. In the aforementioned embodiments of this application, a method is proposed for manufacturing a melt-spun biodegradable sanitary nonwoven fabric by mixing a biodegradable resin with a bio-based plasticizer, wherein the biodegradable resin is a blend of polylactic acid (PLA) and polybutylene adipate (PBAT). However, in actual production, if the performance parameters of PLA and PBAT are not properly selected, it may lead to poor melt flowability, difficulty in fiber formation, or the final nonwoven fabric's mechanical properties and hand feel failing to meet the requirements of sanitary products, affecting production efficiency and product quality.

[0044] In this regard, this application further proposes that in step 1), the PLA has a melt index of 150-300 g / 10 min (210 °C, 2.16 kg) and a weight-average molecular weight of 100,000-200,000; and the PBAT has a melt index of 5-15 g / 10 min (190 °C, 2.16 kg) and a weight-average molecular weight of 80,000-150,000.

[0045] Melt index (MFI) and weight-average molecular weight (Mw) are key parameters affecting the melt flowability and final mechanical properties of polylactic acid (PLA). MFI measures the melt flowability of a polymer at specific temperatures and pressures; a higher MFI generally indicates a lower molecular weight and better flowability, which is beneficial for spinning. Weight-average molecular weight (Mw) reflects the average length of the polymer molecular chains. Excessively high molecular weight can lead to excessive melt viscosity, making spinning difficult; conversely, excessively low molecular weight can affect the mechanical strength of the fiber. Controlling the PLA's melt index within the range of 150–300 g / 10 min (210℃, 2.16 kg) ensures good flowability during melt spinning, facilitating the formation of fine streams through the spinneret and reducing fiber breakage. Simultaneously, PLA with a weight-average molecular weight of 100,000–200,000 ensures that the prepared fibers possess sufficient tensile strength and toughness, avoiding increased fiber brittleness due to excessively low molecular weight. For example, you can choose commercially available PLA brands such as Ingeo™ Biopolymer 6202D or Luminy® LX175, whose melt index and molecular weight are within this range.

[0046] The melt index and weight-average molecular weight of polybutylene adipate (PBAT) also significantly influence its blending properties with PLA, as well as the flexibility and spinnability of the final fiber. PBAT with a melt index in the range of 5–15 g / 10 min (190°C, 2.16 kg) can form good blends with PLA with a high melt index, ensuring suitable viscosity matching during extrusion and spinning, and reducing phase separation and melt fracture. PBAT with a weight-average molecular weight of 80,000–150,000 can effectively improve the flexibility and tear resistance of the blended fiber while maintaining good spinnability. For example, commercially available PBAT brands such as Ecoflex® FBlend C1200 or WanhuaChem® WHC-PBATC1200 can be selected, as their melt index and molecular weight fall within these ranges.

[0047] This application optimizes the rheological properties of melt during direct spinning by precisely controlling the melt index and weight-average molecular weight of polylactic acid (PLA) and polybutylene adipate (PBAT) in biodegradable resins. Specifically, PLA with a melt index of 150–300 g / 10 min (210℃, 2.16 kg) and a weight-average molecular weight of 100,000–200,000 is selected to ensure good melt flowability at high temperatures, facilitating the formation of uniform fine streams through spinnerets, which is beneficial for subsequent fiber drawing. Simultaneously, PBAT with a melt index of 5–15 g / 10 min (190℃, 2.16 kg) and a weight-average molecular weight of 80,000–150,000 is selected. Its relatively low melt index and moderate molecular weight allow it to form a blend system with PLA that has good viscosity matching, effectively improving the brittleness of PLA, imparting appropriate elasticity to the melt, and preventing breakage or excessive stretching and thinning of the melt during high-speed drawing. This precise selection of material parameters ensures that the mixed raw materials maintain stable processing performance during high-speed mixing, twin-screw extrusion melting, and melt direct spinning and stretching, guaranteeing the continuity and uniformity of the fibers, and ultimately forming a nonwoven fabric with excellent mechanical properties and a soft feel.

[0048] In one specific implementation, in the raw material pretreatment step 1), the biodegradable resins selected are polylactic acid (PLA) with a melt index of 200 g / 10 min (210℃, 2.16 kg) and a weight-average molecular weight of 150,000, and polybutylene adipate (PBAT) with a melt index of 10 g / 10 min (190℃, 2.16 kg) and a weight-average molecular weight of 120,000. The PLA and PBAT are blended at a mass ratio of 80:20 and mixed with a bio-based plasticizer at a mass ratio of 90:10. The mixture is then fed into a high-speed mixer and mixed for 20 min at 70℃ and 250 r / min to obtain a mixed raw material. Subsequently, this mixed raw material is fed into a twin-screw extruder for melt extrusion to prepare a biodegradable melt. Following subsequent melt filtration and metering, melt spinning and stretching, web formation, reinforcement molding, and post-treatment steps, the final product is a melt-spun biodegradable sanitary nonwoven fabric.

[0049] In some embodiments described above in this application, a method for preparing melt-spun nonwoven fabric by mixing biodegradable resin with bio-based plasticizer is proposed. However, biodegradable resin is prone to thermal oxidative degradation during high-temperature processing, which leads to a decline in material properties. At the same time, the nonwoven fabric prepared may also age faster due to ultraviolet radiation during storage and use, affecting its mechanical properties and service life.

[0050] In this regard, this application further proposes that in step 1), 0.1 to 0.3 wt% of an antioxidant and 0.05 to 0.1 wt% of a light stabilizer are added to the mixed raw materials; the antioxidant is a hindered phenolic antioxidant and the light stabilizer is a benzotriazole light stabilizer.

[0051] Antioxidants are substances that can inhibit or delay the oxidation reaction of polymers. During polymer processing and use, polymer chains can break or cross-link due to factors such as heat, oxygen, and shear stress, leading to deterioration of material properties. Antioxidants protect polymers by interrupting the oxidation chain reaction through methods such as capturing free radicals and decomposing hydrogen peroxide. In addition to hindered phenolic antioxidants, common antioxidants include phosphite antioxidants and thioether antioxidants, which can be used alone or in combination to provide more comprehensive protection. Light stabilizers are substances that can absorb or shield ultraviolet light, thereby inhibiting or delaying the photoaging reaction of polymers. Polymers undergo photo-oxidative degradation under ultraviolet radiation, leading to discoloration, embrittlement, and decreased mechanical properties. Light stabilizers protect polymers from ultraviolet damage by absorbing ultraviolet energy and converting it into harmless heat energy, or by capturing free radicals and quenching excited-state molecules. In addition to benzotriazole light stabilizers, common examples include hindered amine light stabilizers (HALS) and salicylate light stabilizers. Hindered phenolic antioxidants are a class of primary antioxidants, primarily acting as free radical scavengers. They possess sterically hindered phenolic hydroxyl structures, enabling them to react with reactive free radicals such as alkyl and peroxy radicals generated during polymer oxidation, generating stable free radicals that terminate the oxidation chain reaction and effectively inhibit the thermal oxidative degradation of the polymer. Benzotriazole light stabilizers are a class of ultraviolet (UV) absorbers, primarily absorbing UV radiation. They have a unique molecular structure that efficiently absorbs UV radiation in the 290-400 nm wavelength range, converting the absorbed energy into heat through intramolecular proton transfer and other mechanisms. This prevents UV energy from directly affecting the polymer molecular chain, effectively protecting the polymer from photoaging.

[0052] The solution in this application achieves comprehensive protection of the biodegradable material throughout the entire manufacturing process and subsequent use by adding a specific proportion of antioxidants and light stabilizers to the mixed raw material of biodegradable resin and bio-based plasticizer in the aforementioned raw material pretreatment step 1). Specifically, when the biodegradable resin and bio-based plasticizer are mixed in a high-speed mixer, 0.1–0.3 wt% of hindered phenolic antioxidants and 0.05–0.1 wt% of benzotriazole light stabilizers are added simultaneously. The hindered phenolic antioxidants play a role in processing steps such as high-temperature, high-shear mixing, melt extrusion, direct spinning, and hot rolling. By capturing free radicals, they effectively inhibit the thermal oxidative degradation of the biodegradable resin under these harsh conditions, thereby maintaining the stability of the polymer's molecular weight and mechanical properties. At the same time, the benzotriazole light stabilizers are uniformly dispersed in the material during the mixing stage. In subsequent storage and use of the final nonwoven fabric product, they can efficiently absorb ultraviolet light, preventing photo-oxidative damage to the biodegradable resin caused by ultraviolet light, thereby delaying the aging process of the nonwoven fabric. This strategy of introducing protective additives during the raw material pretreatment stage ensures that antioxidants and light stabilizers are fully and uniformly dispersed throughout the polymer matrix, providing continuous and effective protection for subsequent processing and the performance of the final product. It avoids problems such as processing interruption, unstable product performance, and shortened service life caused by material degradation.

[0053] The following is a specific example. In the raw material pretreatment process of step 1), when biodegradable resin (PLA to PBAT at a mass ratio of 75:25) and bio-based plasticizer (TBC to ESO at a mass ratio of 1:1) are mixed at a mass ratio of 85:15, an additional 0.2 wt% antioxidant and 0.08 wt% light stabilizer are added. The antioxidant can be pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], a typical hindered phenolic antioxidant. The light stabilizer can be 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, a typical benzotriazole light stabilizer. These additives, along with the biodegradable resin and bio-based plasticizer, are added to a high-speed mixer and mixed for 20 minutes at 70°C and 250 rpm to ensure thorough and uniform dispersion, forming a mixed raw material with good stability.

[0054] In other embodiments, this application proposes a method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric. This method includes steps such as raw material pretreatment, melt preparation, melt filtration and metering, melt spinning and drawing, web formation, reinforcement molding, and post-treatment. In the melt spinning and drawing step, the melt is extruded through a spinneret to form a melt stream. However, in actual production, traditional spinnerets operate under high temperature and pressure for extended periods, making them susceptible to melt corrosion and mechanical wear. This can lead to deformation or blockage of the spinneret orifices, affecting the uniformity and stability of the melt stream, ultimately reducing fiber quality and production efficiency.

[0055] In this regard, this application further proposes that in the above-mentioned melt spinning and drawing steps, the spinneret is made of ceramic material and the spinneret hole adopts a rounded transition design.

[0056] Specifically, the use of ceramic material for the spinneret means that the main material of the spinneret is made of inorganic non-metallic materials sintered at high temperatures. Ceramic materials typically possess excellent high-temperature resistance, corrosion resistance, and wear resistance; for example, alumina ceramics, zirconia ceramics, or silicon carbide ceramics can be selected. These ceramic materials can maintain good chemical stability and mechanical strength under high-temperature melt extrusion environments, effectively resisting the erosion and wear of the melt on the spinneret, thereby ensuring the geometric accuracy and service life of the spinneret orifices.

[0057] In some of the embodiments described above in this application, a step of feeding the fiber web into a hot rolling mill for hot rolling reinforcement is proposed. However, in the process of implementation, if the surface of the rolls of the hot rolling mill is designed to be smooth, the resulting nonwoven fabric may have a uniform overall density, lack the necessary fluffiness and softness, and the surface may also be relatively uniform, making it difficult to meet the higher requirements of hygiene nonwoven fabrics for comfort, breathability and appearance.

[0058] In this regard, this application further proposes that in step 6), the surface of the hot rolling mill rolls is provided with a raised or recessed pattern, and the pattern depth is 0.1 to 0.3 mm.

[0059] Specifically, the embossed pattern on the roll surface refers to the creation of raised and recessed geometric shapes on the working surface of the rolls used in hot rolling mills to reinforce and shape the fiber web, through specific processing techniques. These patterns can be regularly arranged, such as dots, lines, grids, diamonds, or waves, or they can be irregular patterns designed according to specific needs. Their function is to ensure that during the hot rolling process, when the fiber web is subjected to pressure and heat, some areas experience higher pressure and temperature, forming denser bonds, while other areas remain relatively loose, thus macroscopically giving the nonwoven fabric a specific physical structure and surface texture. This design can effectively improve the softness, breathability, liquid absorption, and appearance of the nonwoven fabric. Implementation methods can include: forming a pre-defined embossed pattern on the roll surface through mechanical engraving, laser etching, chemical etching, or electrical discharge machining; or coating the roll surface with a high-temperature resistant material with a specific texture. The pattern depth refers to the vertical distance between the raised and recessed parts of the embossed pattern on the roll surface. This depth range is optimized to ensure that effective bonding and texture are formed during hot rolling without excessively damaging the fibers or degrading the nonwoven fabric's performance. A shallow depth may result in indistinct texture and poor bonding, while an excessive depth can cause fiber breakage, reduced fabric strength, and even impact production efficiency. Therefore, a depth range of 0.1–0.3 mm balances the nonwoven fabric's mechanical strength, softness, breathability, and aesthetics. This depth can be controlled using precision machining equipment, such as CNC milling machines, grinding machines, or laser processing equipment, to ensure the accuracy of the pattern dimensions.

[0060] The solution proposed in this application involves creating raised and recessed patterns on the surface of the rolls in a hot rolling mill and precisely controlling the pattern depth. This results in a selective, localized contact between the rolls and the fiber web during hot rolling reinforcement, rather than a uniform planar contact. When the fiber web passes through the raised and recessed rolls, the raised portions of the rolls apply greater local pressure and heat to the fiber web, causing the fibers in these areas to melt and form dense bonding points, thus giving the nonwoven fabric the necessary structural strength. Simultaneously, the recessed portions of the rolls apply less pressure to the fiber web, keeping the fibers in these areas relatively loose, thereby preserving the nonwoven fabric's bulk and softness. The pattern depth setting of 0.1–0.3 mm ensures an appropriate difference between the bonding points and non-bonded areas, guaranteeing sufficient bonding strength while avoiding excessive compaction that could lead to a stiffer feel or reduced air permeability in the nonwoven fabric. This differentiated hot rolling process allows the final nonwoven fabric to maintain good mechanical properties while significantly improving its softness, bulkiness, breathability, and surface texture, thereby meeting the higher requirements for comfort and functionality of sanitary nonwoven fabrics.

[0061] The following is a specific example. In one implementation, in step 6), the fiber web formed by the air-laid web forming machine is fed into a hot rolling mill for hot rolling reinforcement. This hot rolling mill is equipped with rolls whose surfaces are engraved with raised and recessed patterns. For example, the roll surface can have a dotted pattern, where each raised point has a diameter of approximately 0.5 mm, a dot spacing of 1.5 mm, and a pattern depth controlled at 0.2 mm. During hot rolling, the fiber web passes through the rolls at a temperature of 130°C, a pressure of 0.4 MPa, and a speed of 10 m / min. The raised portions of the rolls apply localized high pressure and high temperature to the fiber web, causing the polylactic acid (PLA) and polybutylene adipate (PBAT) fibers in these areas to melt and bond together, forming strong bonding points. The fiber areas corresponding to the recessed portions of the rolls experience less pressure, maintaining the fluffy structure of the fibers. This treatment method results in a final nonwoven fabric with sufficient strength, a clear raised and recessed texture, a softer touch, and good breathability.

[0062] In some of the embodiments described above in this application, during the melt preparation process, if the screw design of the twin-screw extruder is unreasonable when processing mixed raw materials, it may lead to uneven stress on the material during extrusion, excessive shear heat, or a narrow residence time distribution, thereby affecting the uniformity and stability of the melt and reducing the quality and production efficiency of the final nonwoven fabric product.

[0063] In this regard, this application further proposes that in step 2), the screw of the twin-screw extruder adopts a gradually changing pitch design, with a screw pitch of 40-50 mm in the feeding section, 30-40 mm in the compression section, and 20-30 mm in the metering section.

[0064] Gradual pitch design refers to a screw pitch that gradually changes across different zones. This design optimizes material conveying, mixing, shearing, and venting based on the material's needs at different stages within the extruder (e.g., feeding, compression, melting, metering). For example, a larger pitch in the feeding section facilitates full filling and conveying of the material; a smaller pitch in the compression section aids in compaction and melting; and a smaller pitch in the metering section provides stable extrusion pressure and flow. Besides gradual pitch design, screws can also employ constant pitch designs or use reverse thread elements in certain zones to enhance mixing. The feeding section is the first area after material enters the extruder, and its primary function is to receive and convey solid or semi-solid materials. A larger pitch (e.g., 40–50 mm) provides greater free volume, facilitating full filling, reducing resistance as the material enters the extruder, and ensuring stable and continuous conveying to subsequent zones. Furthermore, a larger pitch helps reduce shearing in the feeding section, preventing premature thermal degradation of the material. In addition to a 40–50 mm pitch range, the pitch in the feed section can also be designed to be 50–60 mm or 30–40 mm, depending on the material's bulk density and flowability. The compression section, located after the feed section, is the key area where the material gradually transforms from a solid or semi-solid state to a molten state. The pitch gradually decreases from the larger value in the feed section to 30–40 mm, causing the screw channel volume to gradually shrink, thus creating a squeezing effect on the material, promoting compaction, degassing, and melting. This compression helps increase the material's density, remove air, and enhance shearing and mixing between materials, thereby accelerating the melting process and improving melt homogeneity. Besides the 30–40 mm pitch range, the pitch in the compression section can also be designed to be 25–35 mm or 35–45 mm, depending on the material's melting characteristics and required shear strength. The metering section is the last area of ​​the extruder, and its main function is to provide stable pressure and flow rate for the melt, ensuring that the melt is uniformly extruded from the die. Smaller pitches (e.g., 20–30 mm) provide higher shear rates and smaller screw channel volumes, resulting in stable pumping of the melt, effectively eliminating pressure fluctuations in the melt, and ensuring precise control of extrusion volume and stability of melt quality. In addition to the 20–30 mm pitch range, the metering section pitch can also be designed to other ranges such as 15–25 mm or 25–35 mm, depending on the required extrusion pressure and flow accuracy.

[0065] This application's solution employs a gradually varying screw pitch design in the twin-screw extruder, specifically defining the pitch ranges of the feeding, compression, and metering sections. This achieves precise control over the material transport, melting, and metering of the biodegradable resin and bio-based plasticizer mixture during extrusion. Specifically, in the feeding section, a larger screw pitch of 40–50 mm ensures sufficient filling and stable transport of the mixture, preventing blockage or uneven heating upon entering the extruder. Subsequently, in the compression section, the screw pitch decreases to 30–40 mm, allowing the material to be gradually compacted under the screw's thrust, expelling internal air, and accelerating melting under shearing action to form a homogeneous melt. Finally, in the metering section, the screw pitch further decreases to 20–30 mm, providing stable pumping pressure and precise flow control for the melt, ensuring that the melt is extruded from the spinneret at a constant rate and pressure. This gradual pitch design, combined with segmented temperature control, allows the material to experience optimal temperature and shear duration throughout the extrusion process. This effectively prevents overheating and degradation of the material and incomplete melting, ensuring the uniformity and stability of the biodegradable melt and providing high-quality raw materials for subsequent direct spinning.

[0066] As a specific implementation method, a Coperion ZSK series co-rotating twin-screw extruder can be used in the melt preparation process. The extruder screw can be designed with a gradually changing pitch, with the feed section pitch set to 45mm to ensure smooth entry and initial conveying of the mixed raw materials. The subsequent compression section has a 35mm pitch for effective compaction and melting of the material. At the end of the extruder, the metering section, the pitch can be set to 25mm to provide stable melt pressure and precise extrusion rate. The extruder barrel can be electrically heated for segmented temperature control and wrapped with an 8mm thick insulation layer to reduce heat loss.

[0067] Through the above technical solution, in the manufacturing method of melt-spun biodegradable sanitary nonwoven fabric, the twin-screw extruder adopts a gradually changing screw pitch design, and the screw pitches of the feeding section, compression section, and metering section are optimized. This design makes the material conveying, mixing, melting, and metering processes inside the extruder more efficient and stable. Specifically, the gradually changing screw pitch design can effectively avoid the problems of uneven stress and excessive shear heat during the extrusion process, thereby reducing the degradation risk of biodegradable resin and improving the uniformity and stability of the melt. At the same time, the precise screw pitch configuration helps to achieve precise control of melt output and pressure, providing a high-quality melt for subsequent melt-spun fabric, thereby improving the fiber uniformity and mechanical properties of the final nonwoven fabric product and helping to reduce overall energy consumption.

[0068] In some embodiments described above in this application, the hot-rolled nonwoven fabric needs to undergo cooling treatment to stabilize its structure and prepare it for subsequent cutting and winding. However, a single cooling method may have limitations. For example, purely natural cooling may be inefficient, leading to a longer production cycle; while over-reliance on forced cooling may cause unnecessary energy consumption and may even affect product quality due to uneven cooling.

[0069] In this regard, this application further proposes that in step 7), a combination of natural cooling and forced ventilation be used in the post-processing.

[0070] Natural cooling refers to the process of gradually lowering the temperature of nonwoven fabric through heat exchange with the surrounding environment due to the temperature difference. Its characteristic is that it does not require additional energy input to drive airflow. This can be achieved by placing the heat-rolled nonwoven fabric in a room-temperature environment or slowly conveying it, allowing its surface to exchange heat with the air through convection and radiation, or by placing it on a material surface with good heat dissipation properties. Forced ventilation, on the other hand, uses external mechanical equipment, such as fans or blowers, to generate directional airflow, accelerating heat dissipation from the nonwoven fabric surface and thus improving cooling efficiency. This can be achieved by placing fans in the cooling area to blow air directly onto the nonwoven fabric, or by constructing a ventilation duct system to guide airflow across the nonwoven fabric surface. Combining these two cooling methods means flexibly utilizing or synergistically applying natural cooling and forced ventilation according to actual needs and process stages to achieve optimal cooling effect and energy consumption balance.

[0071] In the aforementioned manufacturing method, the nonwoven fabric reaches a high temperature after hot rolling, requiring effective cooling to ensure stable physical properties and facilitate subsequent cutting and winding operations. Combining natural cooling with forced ventilation allows for optimized control of the cooling process. Specifically, natural cooling, as a basic and gentle cooling method, continuously dissipates heat from the nonwoven fabric, helping to avoid internal stress concentration or deformation that may occur due to excessively rapid cooling. Simultaneously, forced ventilation, based on factors such as production line speed, nonwoven fabric thickness, and ambient temperature, significantly improves cooling efficiency by enhancing air convection in stages or areas requiring rapid cooling, effectively compensating for the inefficiency of natural cooling. For example, when the nonwoven fabric immediately leaves the hot rolling mill, its temperature is highest; at this time, forced ventilation can be moderately increased to quickly remove most of the heat. As the nonwoven fabric temperature gradually decreases, the intensity of forced ventilation can be gradually reduced, or the subsequent cooling process can rely primarily on natural cooling. This combined approach makes the cooling process more flexible and controllable, adaptable to different production conditions and product requirements, and effectively reduces overall energy consumption while ensuring cooling effectiveness.

[0072] The following is a concrete example. After the nonwoven fabric undergoes hot rolling reinforcement, it first enters a cooling channel. This channel contains multiple horizontally or vertically arranged industrial fans. The airflow generated by these fans forces the nonwoven fabric into a cooling environment, rapidly reducing its initial high temperature. Subsequently, the nonwoven fabric continues to travel on a conveyor belt into a longer natural cooling zone. In this zone, the nonwoven fabric primarily dissipates heat through natural convection and radiation with the ambient air, without the need for additional airflow. Throughout the cooling process, temperature sensors can monitor the nonwoven fabric's temperature in real time. Based on a preset cooling curve, the intensity of forced ventilation can be dynamically adjusted by controlling the start / stop and fan speed, thereby achieving precise temperature control.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric, characterized in that: Includes the following steps: 1) Raw material pretreatment: The biodegradable resin and bio-based plasticizer are mixed at a mass ratio of 85-95:5-15 and put into a high-speed mixer. The mixture is mixed for 15-25 minutes at 60-80℃ and 200-300 r / min to obtain a mixed raw material. The biodegradable resin is a blend of polylactic acid (PLA) and polybutylene adipate (PBAT), wherein the mass ratio of PLA to PBAT is 70-85:15-30. The bio-based plasticizer is a compound of tributyl citrate (TBC) and epoxidized soybean oil (ESO), wherein the mass ratio of TBC to ESO is 1:0.8-1.

2. 2) Melt preparation: The mixed raw materials obtained in step 1) are fed into a twin-screw extruder for melt extrusion to prepare a biodegradable melt; the twin-screw extruder adopts segmented temperature control, with the temperature from the feed inlet to the die head set sequentially to 140-160℃, 160-175℃, 175-185℃, and 180-190℃, the screw speed to be 180-250 r / min, and the extrusion pressure to be 1.5-2.5 MPa; the barrel of the twin-screw extruder is wrapped with an insulation layer with a thickness of 5-10 mm; 3) Melt filtration and metering: The biodegradable melt prepared in step 2) is filtered through a filtration device with a filtration accuracy of 10-20 μm; the filtered melt is fed into a metering pump with a speed of 50-80 r / min and the melt output is controlled at 5-10 g / min·pore. 4) Melt spinning and drawing: The metered melt is ejected through a spinneret to form a fine melt stream; the diameter of the spinneret orifices is 0.2-0.4 mm, and the orifice spacing is 1.5-2.5 mm; after the melt stream is ejected, it is drawn using a heated airflow at a temperature of 120-150℃ and a velocity of 8-12 m / s, with a draw ratio of 5-8 times; at the same time, a low-temperature cooling zone is set below the spinneret, with a cooling airflow temperature of 15-25℃ and a velocity of 5-8 m / s, and the cooling zone is 10-30 mm away from the spinneret outlet; 5) Web formation: The drawn fibers are formed into a web by passing them through an air-jet web forming machine; the negative pressure of the air-jet web forming machine is 0.02-0.05MPa, the web forming speed is 10-20m / min, and the basis weight of the fiber web is controlled to be 20-50g / m². 6) Reinforcement and forming: The fiber web obtained in step 5) is fed into a hot rolling mill for hot rolling reinforcement. The hot rolling temperature is 120-140℃, the hot rolling pressure is 0.3-0.6MPa, and the hot rolling speed is 8-15m / min. 7) Post-processing: Cool, cut and roll up the hot-rolled nonwoven fabric. The cooling temperature is 25-35℃ and the cooling time is 5-10 minutes to obtain the melt-spun biodegradable sanitary nonwoven fabric.

2. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 1), the PLA has a melt index of 150-300 g / 10 min (210℃, 2.16 kg) and a weight-average molecular weight of 100,000-200,000; the PBAT has a melt index of 5-15 g / 10 min (190℃, 2.16 kg) and a weight-average molecular weight of 80,000-150,000.

3. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 1), 0.1-0.3 wt% of antioxidant and 0.05-0.1 wt% of light stabilizer are added to the mixed raw materials; the antioxidant is a hindered phenolic antioxidant and the light stabilizer is a benzotriazole light stabilizer.

4. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 4), the spinneret is made of ceramic material.

5. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 6), the surface of the hot rolling mill rolls is provided with raised and recessed patterns, with a pattern depth of 0.1 to 0.3 mm.

6. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 2), the screw of the twin-screw extruder adopts a gradually changing pitch design, with a screw pitch of 40-50 mm in the feeding section, 30-40 mm in the compression section, and 20-30 mm in the metering section.

7. The method for manufacturing a melt-spun biodegradable sanitary nonwoven fabric according to claim 1, characterized in that, In step 7), a combination of natural cooling and forced ventilation is used in the post-treatment process.

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