High-strength thermoplastic long-fiber non-woven fabric and production method

Abstract

The invention relates to the field of non-woven fabrics, in particular to a high-strength thermoplastic long-fiber non-woven fabric and a production method thereof, and the high-strength thermoplastic long-fiber non-woven fabric is formed by dividing and netting a multi-petal skin-core structure filament formed by composite spinning of high-strength polyester chips and low-melting-point polyester chips, shaping in a drying room and needling and reinforcing; a skin layer in the multi-petal skin-core structure is made of a low-melting-point polyester material, a core layer is made of a high-strength polyester material, and the mass ratio of the skin layer to the core layer is 1: 3-4: 6; the surface of the skin layer is of a multi-petal-shaped structure, the product density is smaller, the product mass is lighter, the main core and the auxiliary core mainly provide the mechanical property of the product, the main core can provide high strength, and the auxiliary core provides high modulus or the combination of the two properties, namely, the main core has high strength, high modulus or two properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-woven fabrics, in particular to a high-strength thermoplastic long fiber non-woven fabric and a production method. BACKGROUND

[0002] The present application relates to the field of non-woven fabrics, in particular to a PET long filament spun-bonded needle-punched non-woven fabric, which belongs to a functional non-woven fabric and is mainly used for mold forming.

[0003] For a long time, non-woven fabrics have been widely used in medical and health care, filtration and separation, geotechnical and construction, transportation, agricultural production, clothing processing and other fields. Due to its special functional structure and efficient production process, it has a very wide range of applications. In recent years, with the continuous increase of market demand, the technology has been continuously innovated, and new non-woven fabric products have emerged in an endless stream, and the application field of the products has been continuously expanded and extended. The mold forming non-woven fabric used to replace injection molded parts is a very important development direction. The mechanical properties of the products on the market are poor, and the heat resistance and chemical resistance do not meet the standards, which limits the range of use. SUMMARY

[0004] The purpose of the present application is to provide a high-strength thermoplastic long fiber non-woven fabric and a production method, which has a smaller product density and a lighter product quality. The main core and the auxiliary core mainly provide the mechanical properties of the product, the main core can provide high strength, and the auxiliary core can provide high modulus or a combination of the two properties, that is, both high strength and high modulus or a combination of the two properties.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a high-strength thermoplastic long fiber non-woven fabric, which is formed by a plurality of petal core-skin structure filaments formed by composite spinning of high-strength polyester chips and low-melting-point polyester chips, and is formed by filament separation, oven setting and needle punching reinforcement; the skin layer in the petal core-skin structure is a low-melting-point polyester material, the core layer is a high-strength polyester material, and the mass ratio of the skin layer to the core layer is 1:3-4:6; the surface of the skin layer is in a petal structure.

[0006] Among them, the core layer includes a main core and a plurality of auxiliary cores, and the diameter of the main core is greater than or equal to that of the auxiliary core.

[0007] Among them, the cross section of the single filament of the petal core-skin structure is in any one of star-shaped, cross-shaped, trilobal or multilobal deformation structures.

[0008] Among them, the melting point of the high-strength polyester chip is 250-270℃, and the intrinsic viscosity is 0.64-0.8dL / g; the melting point of the low-melting-point polyester chip is 110-230℃, and the intrinsic viscosity is 0.55-0.8dL / g.

[0009] In a second aspect, the present application further provides a production method of high-strength thermoplastic long fiber non-woven fabric, comprising:

[0010] The polyester chips of the skin layer and the core layer are respectively sent into a pre-crystallization device for pre-crystallization, and then dried by a drying device to obtain skin chips and core chips;

[0011] The skin chips and the core chips are respectively sent into respective batching devices for batching by adding additives in proportion;

[0012] The batched skin chips and core chips are respectively melted and plasticized by respective screw extruders, and then filtered by a melt filter to obtain skin melt and core melt;

[0013] The skin melt and the core melt are transported to a composite spinning box through a melt pipeline, and then jointly pressed into a composite spinning assembly after metering, and then sprayed out from a spinneret hole in a skin-core structure to form a primary filament;

[0014] The primary filament is cooled and blown, the air temperature, humidity and speed are controlled, and then drawn to obtain a secondary filament;

[0015] The secondary filament is laid on a web belt of a web former to form a fiber web, and the fiber web is heat set in an oven and mechanically reinforced by a needle punch machine to obtain a non-woven fabric base cloth;

[0016] The non-woven fabric base cloth is stored, on-line needle detected, cut and packaged to obtain a finished product.

[0017] The specific steps of sending the polyester chips of the skin layer and the core layer into a pre-crystallization device for pre-crystallization, and then drying by a drying device to obtain skin chips and core chips include:

[0018] The polyester chips of the skin layer and the core layer are respectively sent into a pre-crystallization device for pre-crystallization, and then dried by a drying device to obtain skin chips and core chips;

[0019] In the skin layer pre-crystallization device, a first hot gas stream of 60-170°C is introduced to stir the skin layer chips for 20-40 minutes; at the same time, in the core layer pre-crystallization device, a second hot gas stream of 140-180°C is introduced to stir the core layer chips for 20-40 minutes; the amorphous chips are crystallized, and the crystallinity is increased to 25%-40%;

[0020] The pre-crystallized skin layer chips and core layer chips are respectively transferred into a skin layer drying device and a core layer drying device;

[0021] In the skin layer drying device, third dry hot air with a dew point lower than -70℃ and a temperature of 60-150℃ is introduced to dry the skin layer slices for 6-12 hours; meanwhile, in the core layer drying device, fourth dry hot air with a dew point lower than -70℃ and a temperature of 140-180℃ is introduced to dry the core layer slices for 6-12 hours, and the dried skin layer slices and the dried core layer slices with a water content of less than 50ppm are output respectively.

[0022] The specific steps of melting and plasticizing the skin slices and the core slices after the ingredients are added respectively through the respective screw extruders, and then filtering through the melt filters to obtain the skin melt and the core melt include:

[0023] The dried skin layer slices and the dried core layer slices are respectively sent into the feed inlet of the skin layer screw extruder and the core layer screw extruder through two independent metering feeding devices;

[0024] In the skin layer screw extruder, the skin layer slices are melted and plasticized into a skin layer melt in a temperature range of 240-290℃ through multi-temperature zone heating and screw shearing; meanwhile, in the core layer screw extruder, the core layer slices are melted and plasticized into a core layer melt in a temperature range of 250-300℃ through multi-temperature zone heating and screw shearing;

[0025] The skin layer melt is transported to the skin layer melt filter through the skin layer melt pipeline for high-pressure filtration, and the core layer melt is transported to the core layer melt filter through the core layer melt pipeline for high-pressure filtration, and the filtered skin layer melt and core layer melt are output and delivered to the composite spinning box at a constant pressure.

[0026] The specific steps of transporting the skin melt and the core melt to the composite spinning box through the melt pipeline, metering, and then jointly pressing into the composite spinning assembly, and then being discharged from the spinneret hole in a skin-core structure to form the primary yarn include:

[0027] The pure skin layer melt and the core layer melt are respectively delivered to the skin layer metering pump and the core layer metering pump in the composite spinning box through two independent heat preservation melt pipelines at a constant pressure;

[0028] The skin layer metering pump and the core layer metering pump are started to meter and pressurize the skin layer melt and the core layer melt respectively, and the ratio of the metering flow rate of the skin layer melt to the metering flow rate of the core layer melt is controlled to be (10%-50%):(90%-50%);

[0029] The metered skin layer melt and core layer melt are respectively introduced into a composite spinning assembly through a conduit, and the assembly is internally provided with a distribution plate and a flow guide channel to make the two melts converge in a pre-designed skin-core composite structure;

[0030] The core-sheath melt after being compounded is extruded from the spinning micro-holes of the composite spinning assembly under the pressure of 3.0-15.0 MPa to form a core-sheath primary filament with the core melt as the core and the sheath melt completely covering the outside of the core.

[0031] The specific steps of laying the secondary filament on the web belt of the web former to form a web, and heat setting the web in an oven and mechanically reinforcing the web by a needle punch machine to obtain the non-woven fabric base cloth include:

[0032] The drawn core-sheath composite filament bundle is uniformly laid on the continuously running web belt of the web former in a random orientation or directional arrangement by a yarn distributor or an air-laid device to form a layer of web with a predetermined mass per unit area;

[0033] The formed web is conveyed through a hot air setting oven to heat treat the web at a temperature of 110-160℃;

[0034] The heat set web is introduced into a needle punch machine, and the web is repeatedly punctured in the vertical direction by the barbed needles.

[0035] The specific steps of storing the non-woven fabric base cloth, on-line needle detection, cutting and packaging to obtain the finished product include:

[0036] The needle punched reinforced non-woven fabric base cloth is introduced into a storage rack for temporary storage to make the cloth surface tension uniform and consistent, and to naturally cool the cloth surface temperature;

[0037] The non-woven fabric base cloth after storage balancing is continuously passed through an on-line needle detection device to real-time detect and mark the metal broken needle fragments remaining in the cloth base due to the broken needle of the needle punch machine;

[0038] The continuous non-woven fabric base cloth after needle detection is cut to a fixed length and width according to the preset size by a slitting knife and a cross cutting machine to obtain a single piece of standardized non-woven fabric;

[0039] The cut single piece of non-woven fabric is stacked according to the predetermined number, compressed, tied and packaged to form the final product package.

[0040] The application discloses a high-strength thermoplastic long-fiber non-woven fabric and a production method thereof. The high-strength thermoplastic long-fiber non-woven fabric is formed by a plurality of petal core-sheath structure filaments formed by composite spinning of high-strength polyester chips and low-melting-point polyester chips, and is formed through filament separation, oven setting and needle punching reinforcement. The sheath layer in the petal core-sheath structure is a low-melting-point polyester material, the core layer is a high-strength polyester material, and the mass ratio of the sheath layer to the core layer is 1:3-4:6. The surface of the sheath layer is in a petal structure. Through the synergistic design of the high-strength core layer and the petal core-sheath structure, the mechanical properties of the non-woven fabric are greatly improved. Tests show that the longitudinal breaking strength of the obtained non-woven fabric can reach more than 80-120 N / 5 cm, the transverse tear strength is increased by more than 30%, and the non-woven fabric is far superior to traditional short fibers or single-layer structure long-fiber non-woven fabrics. The application is particularly suitable for the fields of industrial reinforcing materials, geotextiles and automobile interior reinforcing layers with high strength requirements.

[0041] The low-melting-point sheath layer is melted in the hot air setting process to form a point or network bonding structure, effectively fixing the fiber network and preventing fiber displacement or loosening during use. The petal structure further enhances the mechanical interlocking effect of the bonding points, so that the non-woven fabric still maintains good dimensional stability and structural integrity in a high-temperature, high-humidity or dynamic load environment. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0043] Figure 1 is a cross-sectional view of the petal core-sheath structure of the application.

[0044] Figure 2 is a flowchart of the production method of the high-strength thermoplastic long-fiber non-woven fabric of the application.

[0045] Figure 3 is a flowchart of the application, in which the polyester chips of the sheath layer and the core layer are respectively sent to a pre-crystallization device for pre-crystallization, and then dried by a drying device to obtain sheath chips and core chips.

[0046] Figure 4 is a flowchart of the application, in which the sheath chips and the core chips after compounding are respectively melted and plasticized by respective screw extruders, and then filtered by a melt filter to obtain sheath melt and core melt.

[0047] Figure 5The flow chart is a process flow of the present application, which transports the sheath melt and the core melt to a composite spinning box through a melt pipeline, measures and jointly presses into a composite spinning assembly, and sprays out from a spinneret hole to form a primary filament according to a sheath-core structure.

[0048] Figure 6 The flow chart is a process flow of the present application, which lays the secondary filaments on a webbing machine webbing belt to form a webbing, and obtains a non-woven fabric base cloth after heat setting of the webbing through an oven and mechanical reinforcement of the webbing through a needle punching machine.

[0049] Figure 7 The flow chart is a process flow of the present application, which stores the non-woven fabric base cloth, on-line detects needles, cuts and packs to obtain a finished product. DETAILED DESCRIPTION

[0050] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary, and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0051] First Embodiment

[0052] Referring to Figure 1 The present application provides a high-strength thermoplastic long-fiber non-woven fabric, which is formed by a multi-lobe sheath-core structure filament formed by composite spinning of high-strength polyester chips and low-melting-point polyester chips, and is formed by filament separation webbing, oven setting and needle punching reinforcement; the sheath layer 2 in the multi-lobe sheath-core structure is a low-melting-point polyester material, the core layer 1 is a high-strength polyester material, and the mass ratio of the sheath layer 2 to the core layer 1 is 1:3-4:6; the surface of the sheath layer 2 is in a multi-lobe structure.

[0053] The core layer 1 includes a main core and a plurality of auxiliary cores, and the diameter of the main core is greater than or equal to that of the auxiliary cores.

[0054] The cross section of the multi-lobe sheath-core structure is in any one of star-shaped, cross-shaped, trilobal or multi-lobed deformed structures.

[0055] The melting point of the high-strength polyester chips is 250-270℃, and the intrinsic viscosity is 0.64-0.8dL / g; the melting point of the low-melting-point polyester chips is 110-230℃, and the intrinsic viscosity is 0.55-0.8dL / g.

[0056] The filament adopts a sheath-core composite spinning structure, wherein the sheath layer 2 is composed of a low-melting-point polyester material, and the core layer 1 is composed of a high-strength polyester material. The mass ratio of the sheath layer 2 to the core layer 1 is controlled to be between 1:3 and 4:6, which is designed to balance the heat-adhesion property and the overall mechanical strength of the fiber. When the proportion of the sheath layer 2 is too low, the heat-adhesion capacity is insufficient, affecting the structural stability of the non-woven fabric; and when the proportion of the sheath layer 2 is too high, the contribution of the high-strength material of the core layer 1 is weakened, resulting in a decrease in the tensile strength. The present application optimizes the proportion, ensures excellent heat-adhesion property, and maximizes the mechanical advantages of the high-strength polyester.

[0057] The surface of the sheath layer 2 is in a multi-petal shape (such as star-shaped, cross-shaped, trilobal or multi-lobed, etc.), which significantly increases the contact area and friction force between the fibers. Especially in the subsequent needling process, the multi-petal structure can effectively “anchor” the adjacent fibers, enhance the three-dimensional entanglement effect of the fiber network, and thus greatly improve the tensile strength, tear strength and dimensional stability of the non-woven fabric.

[0058] The core layer 1 is further designed as a composite structure of a main core and multiple secondary cores, and the diameter of the main core is greater than or equal to that of the secondary cores. The multi-core structure helps to uniformly distribute stress within the fiber, improving the anti-deformation ability and fracture toughness of the fiber. When subjected to external force impact or stretching, the multi-core structure can effectively prevent crack propagation, thereby improving the overall durability and fatigue resistance of the non-woven fabric.

[0059] The melting point of the high-strength polyester chip is 250-270℃, and the intrinsic viscosity is 0.64-0.8dL / g, ensuring that the core layer 1 material has excellent mechanical strength and heat-resistant stability; the melting point of the low-melting-point polyester chip is 110-230℃, and the intrinsic viscosity is 0.55-0.8dL / g, which can melt and flow at a lower temperature to realize effective bonding between the fibers without damaging the high-strength polyester core layer 1. The matching of the intrinsic viscosities of the two ensures the coordination of the rheological properties in the composite spinning process, avoids interface defects, and improves the fiber quality.

[0060] The present application realizes a leap-forward improvement in the mechanical properties of non-woven fabric through the synergistic design of “high-strength core layer 1 + multi-petal sheath-core structure”. Tests show that the longitudinal breaking strength of the obtained non-woven fabric can reach more than 80-120N / 5cm, and the transverse tear strength is increased by more than 30%, which is much better than that of traditional short fibers or single-layer structure long fiber non-woven fabric. It is especially suitable for industrial reinforcing materials, geotextiles, automotive interior reinforcing layers and other fields with high strength requirements.

[0061] The low-melting-point skin layer 2 melts during the hot-air setting process, forming a point or network bonding structure, effectively fixing the fiber network and preventing fiber displacement or loosening during use. The multi-lobe structure further enhances the mechanical interlocking effect of the bonding points, allowing the non-woven fabric to maintain good dimensional stability and structural integrity in high-temperature, high-humidity or dynamic load environments.

[0062] The multi-lobe surface structure is more easily hooked by the needles during needling, promoting three-dimensional entanglement of fibers, reducing the number of needle passes, and improving production efficiency. At the same time, this structure helps maintain the loftiness and elastic recovery rate of the non-woven fabric, improving the hand feeling and cushioning performance of the product, making it suitable for applications such as cushion substrates and soundproof materials.

[0063] Second embodiment

[0064] Please refer to Figures 2 to 7 The present application provides a production method of high-strength thermoplastic long fiber non-woven fabric, comprising:

[0065] S101, the polyester chips of the skin layer and the core layer are respectively sent to the pre-crystallization device for pre-crystallization, and then dried by the drying device to obtain skin chips and core chips;

[0066] The specific steps include:

[0067] S201, the polyester chips of the skin layer and the core layer are respectively sent to the skin layer pre-crystallization device and the core layer pre-crystallization device through two sets of physically isolated conveying devices;

[0068] The skin layer uses low-melting-point polyester chips and the core layer uses high-strength polyester chips, which are respectively conveyed to the respective pretreatment units through two sets of completely physically isolated automatic conveying systems (such as independent vacuum feeding systems or pneumatic conveying pipelines). Among them, the skin layer chips are sent to the dedicated skin layer pre-crystallization device, and the core layer chips enter the independent core layer pre-crystallization device. This physical isolation design can effectively prevent cross-contamination of the two types of chips during high-temperature processing, while facilitating independent control of process parameters to meet the thermal performance requirements of different materials, ensuring production stability and product quality consistency.

[0069] S202, in the skin layer pre-crystallization device, a first hot gas flow of 60-170℃ is introduced to stir the skin layer chips for 20-40 minutes; at the same time, in the core layer pre-crystallization device, a second hot gas flow of 140-180℃ is introduced to stir the core layer chips for 20-40 minutes; the amorphous chips complete crystallization, and the crystallinity is increased to 25%-40%;

[0070] In the skin pre-crystallization device, a first hot gas stream (preferably clean air or nitrogen) at a temperature of 60-170°C is introduced to continuously stir the low-melting polyester chips for 20-40 minutes. The temperature range is slightly higher than the glass transition temperature (Tg) of the low-melting polyester but far below its melting point, which can effectively activate the molecular chain segment movement and promote the transformation of amorphous regions to crystal regions, avoiding the adhesion of the chips due to softening.

[0071] At the same time, in the core pre-crystallization device, a second hot gas stream at a temperature of 140-180°C is introduced to stir the high-strength polyester chips for the same duration (20-40 minutes). Since the high-strength polyester chips have a higher Tg and crystallization temperature, they need to be heated at a higher temperature to effectively induce crystallization. In this stage, the originally amorphous or low-crystallinity high-strength polyester chips are induced to crystallize by heat, and the crystallinity is increased to 25%-40%, significantly improving their heat resistance and preventing them from caking or degrading due to rapid heat absorption during subsequent high-temperature drying or melt extrusion.

[0072] Through the above differential pre-crystallization process, both types of chips have achieved a controlled transition from amorphous to partially crystalline state, providing structural stability for subsequent drying and melt spinning.

[0073] S203 transfers the pre-crystallized skin and core chips into the skin and core drying devices, respectively.

[0074] The pre-crystallized skin and core chips are discharged from their respective pre-crystallization devices and transferred into the corresponding skin and core drying devices through sealed conveying pipelines. The two drying systems are also physically isolated to avoid cross-contamination and can be independently set according to the material properties.

[0075] S204 introduces a third dry hot air with a dew point below -70°C and a temperature of 60-150°C into the skin drying device to dry the skin chips for 6-12 hours, and a fourth dry hot air with a dew point below -70°C and a temperature of 140-180°C into the core drying device to dry the core chips for 6-12 hours, respectively outputting dry skin chips and dry core chips with a water content of less than 50 ppm.

[0076] In the skin layer drying device, the third dry hot air with a dew point lower than **-70℃** and a temperature of 60-150℃ is introduced to perform deep drying treatment on the skin layer slice for 6-12 hours. Since the low-melting-point polyester usually contains more polar groups or comonomers and has strong hygroscopicity, it needs to be dehydrated at a lower temperature for a long time to prevent the slice from softening or thermal oxidative aging caused by high temperature. The low-dew-point air has strong moisture absorption capacity and can efficiently remove the free water and part of the bound water in the slice.

[0077] In the core layer drying device, the fourth dry hot air with a dew point lower than **-70℃** but a temperature of 140-180℃ is introduced to perform drying treatment on the high-strength polyester slice for 6-12 hours. Although the high-strength polyester has relatively low hygroscopicity, its molecular weight is high and its structure is dense, so the water diffusion rate is slow and it needs to be dehydrated at a higher temperature to achieve deep dehydration.

[0078] After the above drying treatment, the water content of the dried skin layer slice and the dried core layer slice is effectively controlled to be below 50 ppm (i.e. 0.005%), which meets the strict requirements of the melt spinning process for the moisture content of the raw material. If the moisture content is too high, the polyester will undergo hydrolytic degradation during the high-temperature melting process, causing a decrease in molecular weight, a decrease in melt strength, an increase in spinning breakage rate, and even defects such as bubbles and hair.

[0079] S102 feeding the skin slice and the core slice into respective batching devices to add additives in proportion;

[0080] This step is a key functional regulation link after the slice pre-crystallization and deep drying and before entering the melt spinning. The purpose is to introduce appropriate amounts and types of functional additives according to the different functional roles of the skin layer and the core layer materials in the final non-woven fabric structure, to further optimize the processing performance, thermal bonding characteristics, long-term use stability of the fibers and the application performance of the end product. Since the skin layer material (low-melting-point polyester) mainly undertakes the function of thermal melting and bonding, and the core layer material (high-strength polyester) mainly provides mechanical support, there are significant differences in the demand for additives between the two. The present application uses independent batching systems to realize step-by-step, directional and precise modification of the skin layer and core layer slices, avoid mutual interference or chemical reaction between different additives, and ensure the independent performance and synergistic effect of each component in the composite spinning process.

[0081] The dried skin layer slices and dried core layer slices with moisture content less than 50 ppm after S101 treatment are accurately fed into the skin layer special dosing device and the core layer special dosing device respectively through independent pneumatic or mechanical conveying systems. The two sets of dosing devices are completely isolated in physical space and material channel, usually equipped with independent metering feeder, high-speed mixer and buffer bin, to ensure accurate control and batch stability of the dosing process.

[0082] In the skin layer dosing device, 0.1-3% functional additives are added to the low-melting polyester slices according to the process requirements, mainly including the following types:

[0083] Heat stabilizers (such as phosphite, hindered phenol): prevent thermal oxidative degradation of low-melting polyester during subsequent lower temperature melting process, maintain stable melt viscosity;

[0084] Lubricants / slip agents (such as erucic acid amide, silicone powder): improve fiber surface friction performance, improve uniformity of fiber laying, reduce fiber entanglement;

[0085] Nucleating agents (such as sodium benzoate, talc): moderately adjust the skin layer crystallization rate, optimize the bonding speed and bonding strength during the hot air setting process;

[0086] Antistatic agents (such as quaternary ammonium salt, polyether): reduce the surface resistance of the fiber, prevent static accumulation, improve the safety of processing and the cleanliness of the product.

[0087] All additives are added in the form of masterbatch or powder, mixed with skin layer slices by high-shear mixing equipment (such as high-speed mixer) to ensure uniform distribution of additives on the surface of the slices, forming modified skin layer feedstock.

[0088] In the core layer dosing device, 0.05-1.5% of reinforcing and stabilizing additives are added to the high-strength polyester slices in proportion, mainly including:

[0089] Antioxidants (such as hindered phenol and phosphite compound system): inhibit thermal degradation and yellowing of high-strength polyester during high-temperature melting (>260℃), maintain high molecular weight and mechanical properties;

[0090] UV absorbers (such as benzotriazole, benzophenone): improve the weather resistance of the core layer fiber, prolong the service life of non-woven fabrics in outdoor applications;

[0091] Crystallization promoters (such as nano-silicon dioxide, phosphate): accelerate the crystallization rate of the core layer during cooling process, improve the uniformity of fiber structure and size stability;

[0092] Flame retardant (optional, such as phosphorus-based flame retardant masterbatch): used to prepare non-woven fabric products with flame retardant function, meeting the safety standards of automobile, rail transportation and other fields.

[0093] The additive is precisely metered by a loss-in-weight feeder and uniformly mixed with the core layer chips in a low-shear mixing device to avoid molecular chain rupture caused by excessive shearing of high-strength chips.

[0094] Process control and output: real-time monitoring of mixing time, temperature and speed during the batching process to ensure uniform dispersion of additives and no damage to chip structure. After mixing, the modified skin layer feed and core layer feed are respectively fed into their respective buffer hoppers and sent to the subsequent twin-screw extrusion system through a sealed conveying system, preparing for the composite spinning stage.

[0095] S103 melt plasticizes the skin chips and core chips after batching through their respective screw extruders, and then filters the melt through a melt filter to obtain a skin melt and a core melt;

[0096] The specific steps include:

[0097] S301 feeds the dried skin layer chips and dried core layer chips into the feed inlet of the skin layer screw extruder and the core layer screw extruder through two independent metering devices;

[0098] The skin layer chips and core layer chips modified by S102 are precisely fed into the feed inlet of the skin layer screw extruder and the core layer screw extruder through two independent metering devices (such as loss-in-weight feeders or volumetric metering screws). The metering device can adjust the chip feeding amount in real time according to the set spinning speed and fiber linear density, ensuring the long-term stability of the melt output flow and avoiding uneven fiber thickness caused by fluctuating feeding. The feed inlet is equipped with a cooling jacket to prevent the chips from softening and sticking to the wall in the feeding section, ensuring continuous and stable feeding.

[0099] S302 melt plasticizes the skin layer chips into a skin layer melt in the temperature range of 240-290℃ through multi-zone heating and screw shearing in the skin layer screw extruder; at the same time, melt plasticizes the core layer chips into a core layer melt in the temperature range of 250-300℃ through multi-zone heating and screw shearing in the core layer screw extruder;

[0100] In the skin-layer screw extruder, a multi-zone (usually 5-8 heating zones) precise temperature control system is used to set a temperature gradient along the axial direction of the screw, and the overall temperature is controlled in the range of 240-290℃. This temperature range matches the rheological properties of low-melting polyester: the front-end temperature is relatively low (about 240-260℃) to prevent the chips from prematurely melting and sticking together; the middle and rear section temperatures gradually increase (to 270-290℃) to take advantage of the shearing action of the screw and external heating to fully melt and uniformly plasticize the chips, forming a skin-layer melt with good flowability and stable viscosity. The screw design usually adopts a gradual or abrupt structure, taking into account the functions of conveying, compression, and mixing.

[0101] At the same time, in the core-layer screw extruder, a multi-zone heating system is also used, but the temperature is set higher, controlled in the range of 250-300℃. Because high-strength polyester has a higher melting point (250-270℃) and molecular weight, it needs to be fully melted and uniformly plasticized at a higher temperature. The middle and rear section temperatures of the screw can be raised to 280-300℃ to overcome the flow resistance caused by high viscosity, ensure that the melt is fully homogenized, and eliminate unmelted crystals or gel particles, forming a high-strength, high-toughness core-layer melt. The screw design often uses a high-shear mixing section to improve the uniformity of the melt.

[0102] Both extruders are equipped with melt pressure sensors and online temperature monitoring systems to provide real-time feedback and automatically adjust the screw speed and heating power to ensure that the melt temperature fluctuation is controlled within ±1℃ and the pressure is stable, providing reliable protection for continuous spinning.

[0103] S303 The skin-layer melt is transported to the skin-layer melt filter via the skin-layer melt pipeline for high-pressure filtration, and the core-layer melt is transported to the core-layer melt filter via the core-layer melt pipeline for high-pressure filtration, and the filtered skin-layer melt and core-layer melt are output and transported to the composite spinning box at a constant pressure.

[0104] The skin-layer melt output from the skin-layer screw extruder is transported to the skin-layer melt filter via an independent skin-layer melt delivery pipeline (equipped with a heat preservation jacket to maintain a temperature of 270-285℃);

[0105] At the same time, the core-layer melt output from the core-layer screw extruder is transported to the core-layer melt filter via another independent core-layer melt pipeline (maintaining a temperature of 280-295℃).

[0106] The melt filter is a high-pressure sintered metal filter cartridge or a multi-layer laminated filter, with a filtration precision of usually 10-25μm. Dynamic filtration of the melt is carried out under high pressure (10-25MPa) to effectively remove defects such as gel particles, unmelted material, and mechanical impurities (such as metal shavings and carbonized material) that may exist in the melt. The filtration process uses a double-connection switching structure, which allows the filter cartridge to be replaced without stopping the machine, ensuring continuous operation of the spinning.

[0107] The filtered clean sheath melt and core melt are delivered by high-precision gear pumps (metering pumps) at constant pressure, and finally converge into the composite spinning pack in the composite spinning pack. The gear pump precisely controls the supply amount and proportion of the two melts, ensuring the stability and uniformity of the sheath-core structure.

[0108] S104 delivers the sheath melt and core melt to the composite spinning pack through the melt pipeline, and after metering, pressurizes into the composite spinning pack, and sprays out from the spinning hole in the sheath-core structure to form the primary yarn;

[0109] The specific steps include:

[0110] S401 delivers the pure sheath melt and core melt to the sheath metering pump and core metering pump in the sheath metering pump and core metering pump in the composite spinning pack through two independent heat preservation melt pipelines at constant pressure;

[0111] The pure sheath melt and core melt filtered by S103 high pressure filtration and constant pressure output are delivered to the composite spinning pack above the spinning channel through two completely independent heat preservation melt delivery pipelines. Each pipeline is equipped with an electric heating jacket or a heat conducting oil circulation system to maintain the melt temperature stable throughout the process (sheath pipeline: 270-285°C; core pipeline: 280-295°C), preventing the melt viscosity from rising or local solidification due to temperature drop. Static mixers or pulse dampers are used during the delivery process to eliminate pressure fluctuations and vortexes in the melt flow, ensuring smooth melt flow before entering the metering pump.

[0112] In the spinning pack, the sheath melt is connected to the sheath metering pump (usually a high-precision melt gear pump), and the core melt is connected to the core metering pump. The two metering pumps are installed side by side, independent in structure and do not interfere with each other, ensuring the independence and accuracy of flow control.

[0113] S402 starts the sheath metering pump and core metering pump to meter and pressurize the sheath melt and core melt respectively, and the ratio of the metering flow rate of the sheath melt to the metering flow rate of the core melt is controlled at (10%-50%):(90%-50%);

[0114] Start the sheath and core metering pumps to accurately meter and pressurize the two melts. The speed of the metering pump is driven by a servo motor, which can achieve stepless adjustment, and the flow control accuracy can reach ±0.5%. By adjusting the speed ratio of the two metering pumps, the volume flow ratio of the sheath melt and the core melt is accurately controlled, which directly determines the sheath-core mass ratio of the final fiber (corresponding to 1:3-4:6 in the claims).

[0115] Specifically, the metering flow rate of the sheath melt accounts for 10%-50% of the total flow rate, and the core melt accounts for 90%-50%. For example:

[0116] When preparing high-bonding nonwoven fabric, the skin layer flow can be set to 40% and the core layer to 60% (mass ratio about 4:6) to enhance the heat bonding ability;

[0117] When focusing on mechanical strength, the skin layer can be set to 20% and the core layer to 80% (mass ratio about 1:4) to maximize the contribution of the high-strength core layer.

[0118] Precise control of the flow ratio is the key to achieving product performance adjustability and the prerequisite for ensuring stable formation of the multi-petal skin-core structure.

[0119] S403 The metered skin layer melt and core layer melt are introduced into a composite spinning assembly through conduits, respectively. The assembly is internally provided with a distribution plate and a flow guide channel, allowing the two melts to converge according to the pre-designed skin-core composite structure.

[0120] The metered and pressurized skin layer melt and core layer melt are introduced into the composite spinning assembly (also known as a composite spinneret assembly) through short-distance conduits, respectively. The assembly is a precisely machined metal module, internally provided with multiple distribution plates and a micro-channel flow guide system, with its structure designed to match the cross-sectional morphology of the final fiber (such as star-shaped, cross-shaped, three-leaf-shaped, etc. multi-petal structure).

[0121] Inside the composite assembly:

[0122] The core layer melt first passes through the central flow guide channel into the main core channel and can branch into multiple secondary core channels, forming a composite core layer structure of main core + multiple secondary cores;

[0123] The skin layer melt, on the other hand, passes through the ring-shaped or radial distribution of flow guide grooves, uniformly surrounding the periphery of the core layer melt;

[0124] At the entrance of the spinneret hole, the skin layer melt synchronously coats the core layer melt from multiple symmetrically distributed feed ports, utilizing the "laminar flow coating" principle in rheology to achieve complete and uniform wrapping of the core layer by the skin layer, forming a stable skin-core composite melt flow.

[0125] This structural design ensures that the interface between the two melts is clear and free of turbulent mixing during high-pressure extrusion, avoiding "core deviation" or "skin breakage" defects.

[0126] S404 The skin-core melt that has completed the compounding is extruded from the spinneret micro-holes of the composite spinning assembly under a pressure of 3.0-15.0 MPa, forming a skin-core type primary filament with the core layer melt as the core and the skin layer melt completely coating the outside.

[0127] The composite core-sheath melt is continuously extruded from the spinneret micro-holes at the bottom of the composite spinning assembly under high pressure (provided by the metering pump) of 3.0-15.0 MPa. The cross-sectional shape of the spinneret hole is specially designed to be circular, star-shaped, cross-shaped, trilobal or multilobal, which directly determines the cross-sectional shape of the nascent yarn.

[0128] The yarn formed after extrusion is called "nascent yarn", which has the following structural characteristics: the high-strength polyester melt is used as the core layer, and the low-melting-point polyester melt is completely wrapped on the outer periphery to form a sheath layer, and the surface of the sheath layer presents a multi-lobe profile (such as a three-lobe, four-lobe or six-lobe star shape) matching the spinneret hole. At this time, the yarn is still in a high-temperature molten state, and the molecular chains are disordered, and needs to be immediately sent to the subsequent cooling and solidification stage.

[0129] The control of extrusion pressure is crucial: too low pressure will cause unstable flow of the melt, resulting in hair or broken ends; too high pressure may damage the core-sheath interface structure or cause wear of the spinneret hole. The present application optimizes the pressure range (3.0-15.0 MPa) to ensure smooth extrusion of the melt, uniform diameter of the nascent yarn, clear core-sheath interface and complete multi-lobe structure.

[0130] S105 cools and blows the nascent yarn, controls the wind temperature, humidity and speed, and then draws the secondary yarn;

[0131] This step is a key forming link for the transformation of the composite filament from "molten state" to "solid fiber" and the establishment of molecular orientation, which directly determines the crystalline structure, core-sheath interface stability, cross-sectional shape retention and final mechanical properties (such as strength and elongation) of the fiber. The nascent yarn is in a high-temperature molten state after leaving the spinneret plate, and if the cooling condition is not properly controlled, it is easy to cause uneven cooling, yarn shaking, core-sheath structure distortion, and even breakage. At the same time, the drawing process is a key means to give the fiber high strength, which makes the high-strength polyester molecular chains highly oriented along the fiber axis, greatly improving the breaking strength. The present application precisely controls the cooling process parameters and multi-stage coordinated drawing, realizes the fine control of the whole fiber forming process, and ensures the integrity of the multi-lobe core-sheath structure and the stability of the fiber performance.

[0132] After the nascent yarn is extruded from the spinneret plate of the composite spinning assembly, it immediately enters the side-blowing or ring-blowing cooling device (preferably a ring-shaped uniform-flow cooling box) for rapid and uniform cooling and solidification under the action of constant airflow.

[0133] The temperature of the cooling air is set to 15-28℃, preferably 18-24℃. Too low temperature (<15℃) will cause the surface of the yarn to cool down rapidly, forming a "hard shell" that hinders the conduction of heat from the inside, resulting in a difference in solidification rate between the inside and outside, causing stress concentration, yarn brittleness or cross-section distortion; too high temperature (>28℃) will result in insufficient cooling rate, and the yarn will easily sag and stick together under its own weight, affecting subsequent drawing. The present application uses a closed-loop temperature control system, which ensures that the temperature fluctuation of the air is controlled within ±0.5℃ through the refrigeration unit and electric heating compensation.

[0134] The relative humidity of the cooling air is controlled within the range of 60%-85%. Suitable humidity can reduce static electricity accumulation, prevent yarn entanglement or dust adsorption due to static electricity, and at the same time, moderate moisture can act as a "heat carrier" to promote heat conduction, making the cooling more uniform. Too low humidity is easy to produce static electricity, and too high humidity may form condensation on the surface of the yarn, affecting the surface quality of the fiber. The system is equipped with high-precision humidity sensors and dehumidification / humidification modules to achieve dynamic adjustment.

[0135] The cooling air speed is set to 0.3-0.8m / s, preferably 0.4-0.6m / s, and a uniform flow plate or honeycomb structure is used to ensure uniform distribution of the air field. Too low air speed will result in a decrease in cooling efficiency, and the yarn will not be fully solidified before entering the drawing area, which will easily break; too high air speed will cause air flow disturbance, causing the yarn to vibrate and swing, affecting the symmetry of the skin-core structure and the uniformity of the fineness. The air speed can be accurately adjusted by a variable frequency fan to adapt to different fineness and spinning speed requirements.

[0136] The cooling process is usually designed as gradient cooling: the upper part of the air temperature is slightly higher, and the air speed is lower, to avoid the surface layer from solidifying too quickly; the middle and lower parts gradually reduce the air temperature and increase the air speed, to achieve uniform solidification from the surface to the inside, effectively release internal stress, and prevent interface defects due to shrinkage difference between the "skin and core".

[0137] The fully cooled and solidified yarn enters the multi-stage hot roller drawing system for directional stretching, so that the molecular chains of the high-strength polyester core layer are highly oriented along the fiber axis, greatly improving the breaking strength. 2-4 hot roller drawing is used, with the front roller temperature being lower (80-110℃) for preheating the fiber and reducing the drawing stress; the rear roller temperature being higher (110-140℃) to promote molecular chain slipping and orientation rearrangement. The total drawing multiple is controlled within 2.0-4.0 times, which is set according to the target strength and elongation of the fiber. The yarn passes through multiple pairs of hot roller groups with increasing speed, and is continuously stretched under the action of the speed difference. Since the skin layer is low-melting-point polyester, its glass transition temperature (Tg) is low, and it is in a high-elastic state at the hot roller temperature, mainly playing a "wrapping" and "buffering" role; while the core layer high-strength polyester is still in a glassy or partially crystalline state, which can effectively withstand the stretching stress and realize molecular orientation. During the drawing process, the multi-petal skin-core structure is "thinned" but remains intact, the fiber fineness (dtex) is significantly reduced, and the breaking strength is greatly improved.

[0138] After drawing, the obtained fiber is called "secondary yarn", which is characterized by uniform diameter, smooth surface, clear core-sheath structure, complete multi-lobe profile, high molecular orientation, and breaking strength up to 4.0-7.0 cN / dtex, meeting the requirements of subsequent high-speed splitting and laying.

[0139] S106 lays the secondary yarn on the web belt of the web former to form a web, and the web is heat set in an oven and mechanically consolidated by a needle puncher to obtain a non-woven fabric base cloth;

[0140] The specific steps include:

[0141] S501 uniformly lays the drawn core-sheath composite filament bundle on the continuously running web belt of the web former in a random orientation or directional arrangement through a yarn dancer or an air-laid device to form a web with a predetermined mass per unit area;

[0142] The core-sheath composite filament bundle drawn by S105 (usually a bundle of several hundred to several thousand filaments) is introduced into a splitting device (such as a ceramic splitting roller, an air flow disperser, or an electrostatic opener), and the bundled filaments are fully separated into single filaments by mechanical friction, air flow disturbance, or electrostatic repulsion, ensuring the uniformity of subsequent web laying.

[0143] The secondary yarn after fiber splitting is uniformly laid on the continuously running web belt of the web former by a yarn dancer or an air-laid device.

[0144] If a yarn dancer is used, the yarn is horizontally oscillated in an "8" shape trajectory under the action of a reciprocating yarn hook, so that the filaments are randomly three-dimensionally oriented, forming a fluffy and isotropic web, which is suitable for application scenarios that require balanced longitudinal and transverse strength (such as geotextiles and soundproof materials).

[0145] If an air-laid device is used, high-speed airflow is used to transport and randomly deposit the filaments on the web belt, which can achieve a thinner and more uniform web structure, especially suitable for the production of fine denier fibers or high grammage products.

[0146] By adjusting the filament bundle feeding speed, web belt running speed, and swing / amplitude parameters, the mass per unit area (grammage, g / m2) of the web is accurately controlled, usually in the range of 100-1200 g / m2, meeting different application requirements. The formed web should have good uniformity (CV value <8%) and no obvious streaks or voids.

[0147] S502 transports the formed web through a hot air setting oven to heat treat the web at a temperature of 110-160°C;

[0148] The formed web is smoothly transported into a hot air through-type setting oven, and is heated at a temperature range of 110-160°C, preferably in a temperature interval of 120-150°C, and the treatment time is generally 30-120 seconds.

[0149] At this temperature, the sheath material (low-melting polyester) in the web begins to soften and gradually melts, while the core material (high-strength polyester) remains solid, maintaining the fiber morphology and mechanical integrity.

[0150] The melted sheath polymer forms a point or network bonding structure at the fiber intersection points, preliminarily consolidating the originally loose web into a semi-finished product with certain dry strength.

[0151] The hot air adopts an up-and-down double-sided through-type circulation system to ensure uniform heat penetration into the web, avoiding surface overheating or internal unbonding. The wind speed is controlled at 1.0-3.0 m / s to prevent the web from being blown away or deformed.

[0152] Heat setting not only gives the web initial structural stability, but also significantly improves its dimensional stability, anti-pilling property and subsequent needle punching processing adaptability. Since bonding only occurs at fiber contact points, the product still maintains good air permeability and softness.

[0153] S503 directs the heat-set web into a needle punching machine, and uses barbed needles to repeatedly pierce the web in the vertical direction.

[0154] The heat-set web is directed into a needle punching machine, and barbed needles (usually triangular cross-section with oblique barbs) are used to repeatedly pierce the web in the vertical direction.

[0155] The needles move up and down at a frequency of 500-2500 times per minute, with a piercing depth of 8-25 mm each time, and the needle density (number of needles / m 2 ) is set according to the product's gram weight and strength requirements.

[0156] Under the action of the needles, the filaments on the surface and in the middle layer are driven by the barbs on the needles and vertically penetrate into the web, forming a large number of fiber bundles migrating up and down and interwinding.

[0157] This mechanical entanglement creates a three-dimensional network structure inside the web, greatly enhancing the cohesion and integrity between fibers.

[0158] In particular, the multi-flap sheath-core structure filaments used in the present application exhibit excellent entanglement performance during needle punching:

[0159] The multi-flap surface significantly increases the frictional resistance and mechanical interlocking effect between fibers, making it easier for the needles to hook the fibers;

[0160] The bonding points of the skin layer formed after heat setting play the role of "anchor points" to prevent the fibers from excessive displacement during needling;

[0161] The high-strength core layer ensures that the fibers are not easily broken during repeated puncture, maintaining the durability of the entangled structure.

[0162] After needling reinforcement, the longitudinal and transverse breaking strength, tear strength, and bursting strength of the non-woven fabric are greatly improved, which can reach 1.5-2.5 times of traditional staple fiber needle-punched fabric. The final non-woven fabric base cloth has the characteristics of high strength, high modulus, dimensional stability, fatigue resistance, and good air permeability.

[0163] S107 stores the non-woven fabric base cloth, detects needles online, cuts and packs to obtain the finished product.

[0164] The specific steps include:

[0165] S601 guides the needle-reinforced non-woven fabric base cloth into the storage rack for temporary storage, so that the fabric tension tends to be uniform, and the fabric temperature is naturally cooled;

[0166] The continuous non-woven fabric base cloth output by the needle machine is guided into a multi-roller storage rack (or buffer rack, cloth storage pit) for moderate temporary storage. The storage length is usually 50-200 meters, which can be dynamically adjusted according to the speed matching of the previous and subsequent processes.

[0167] During needling, drawing and winding, there may be uneven tension in different areas of the fabric, causing local shrinkage or wrinkles. Through the multiple freely floating guide rollers in the storage rack, the fabric is naturally stretched under low tension, eliminating internal stress and achieving uniform distribution of transverse and longitudinal tension, preventing deformation during subsequent processing or storage.

[0168] The freshly output non-woven fabric base cloth still has some residual heat (especially after hot air setting), and direct cutting can cause dimensional deviation due to thermal expansion and contraction. The storage process provides sufficient time for the fabric temperature to slowly drop to room temperature (about 25-35℃), avoiding brittle or structural damage caused by rapid cooling.

[0169] The storage rack also plays the role of production rhythm buffer. When the downstream cutting or packaging process is temporarily stopped, the upstream can continue to run, improving the running efficiency and stability of the whole line.

[0170] S602 makes the non-woven fabric base cloth balanced by storage continuously pass through the online needle detection device to detect and mark the metal needle fragments remaining in the cloth base due to needle breakage of the needle machine in real time;

[0171] The non-woven fabric base cloth after storage adjustment is continuously passed through the high-sensitivity online needle detection device (Metal Detector for Nonwovens) at a speed of 20-100 m / min.

[0172] The device is based on the principle of electromagnetic induction, equipped with a high-resolution probe array, which can detect small ferromagnetic and non-ferromagnetic metal foreign bodies (such as stainless steel broken needle fragments, iron filings, etc.) in the cloth, and the detection sensitivity can reach metal particles of Φ0.5-1.0mm.

[0173] When there are metal foreign bodies in the cloth, the system immediately triggers an alarm, and accurately marks the defect location through acoustic-optical prompts and automatic marking systems (such as inkjet marking, labeling or punching positioning), facilitating subsequent manual removal or isolation processing.

[0174] The detection data is uploaded to the central control system in real time, realizing whole-process quality traceability and ensuring that each batch of products has no metal residue risk, especially suitable for fields with extremely high safety requirements such as automotive interiors, medical protection and food packaging.

[0175] S603 will cut the continuous non-woven fabric that passes the needle detection according to the preset size through a longitudinal cutter and a cross-cut machine to obtain single-piece standardized non-woven fabric;

[0176] The continuous non-woven fabric that passes the needle detection is sent to the full-automatic cutting system for size segmentation according to customer orders or standard specifications.

[0177] A rotary circular knife longitudinal cutter is used to longitudinally divide the wide cloth roll to obtain narrow-width rolls of the required width (such as 1.6m, 2.4m, etc.), with cutting accuracy controlled within ±2mm and edges neat without burrs. A flying shear or rotary cross-cut machine is used to cut the continuous cloth transversely according to the preset length (such as 2m, 3m, 5m, etc.) to realize single-piece finished product length cutting. The equipment is equipped with photoelectric correction and servo control systems to ensure that the cutting angle is perpendicular and the size is consistent. The cutting process can support two output modes: roll and sheet. If roll is required, the roll is wound into a large roll by a winding machine; if sheet is required, it is directly sent to the stacking station.

[0178] S604 will stack the single-piece non-woven fabric cut according to the predetermined number, and compress, bundle and package to form the final product package.

[0179] The single-piece non-woven fabric cut is automatically stacked according to the predetermined number (such as 50 pieces per package, 100 pieces per package). The stacking process is completed by a mechanical arm or a pneumatic push plate system to ensure that each piece of cloth is placed flat without misalignment or wrinkles. After stacking, a hydraulic or pneumatic pressing device is used to apply uniform pressure (pressure about 0.5-2.0MPa) to the entire stack of cloth to compress and shape, reduce volume and prevent sliding during transportation. The compressed cloth stack is cross-shaped or checkerboard-shaped bundled by an automatic bundling machine using high-strength polyester tape or steel tape to ensure firm packaging.

[0180] Finally, the waterproof and moisture-proof film (such as PE film) is wrapped outside, and the label containing the product model, batch number, gram weight, size, production date, needle detection record and other information is pasted, forming a complete finished product package. The finished product package can be directly palletized, which is convenient for warehousing and logistics transportation.

[0181] The above only discloses a preferred embodiment of the present application, and of course cannot limit the scope of the present application. Those skilled in the art can understand that the above-mentioned embodiment can be implemented in whole or in part, and equivalent changes made according to the claims of the present application still fall within the scope of the present application.

Claims

1. A high-strength thermoplastic long-fiber nonwoven fabric, characterized in that, The high-strength thermoplastic long-fiber nonwoven fabric is formed by composite spinning of high-strength polyester chips and low-melting-point polyester chips into multi-lobed core-skin structure filaments, followed by web formation, oven setting, and needle punching reinforcement. The skin layer in the multi-lobed core-skin structure is made of low-melting-point polyester material, and the core layer is made of high-strength polyester material. The mass ratio of the skin layer to the core layer is 1:3 to 4:

6. The surface of the skin layer has a multi-lobed structure.

2. The high-strength thermoplastic long-fiber nonwoven fabric as described in claim 1, characterized in that, The core layer includes a main core and multiple sub-cores, wherein the diameter of the main core is greater than or equal to that of the sub-cores.

3. The high-strength thermoplastic long-fiber nonwoven fabric as described in claim 2, characterized in that, The cross-section of the single filament in the multi-lobed core structure is any one of the following deformed structures: star-shaped, cross-shaped, trilobal, or multi-lobed.

4. The high-strength thermoplastic long-fiber nonwoven fabric as described in claim 3, characterized in that, The high-strength polyester chips have a melting point of 250–270°C and an intrinsic viscosity of 0.64–0.8 dL / g; the low-melting-point polyester chips have a melting point of 110–230°C and an intrinsic viscosity of 0.55–0.8 dL / g.

5. A method for producing a high-strength thermoplastic long-fiber nonwoven fabric, applied to the production of the high-strength thermoplastic long-fiber nonwoven fabric according to any one of claims 1 to 4, characterized in that, include: Polyester chips for the sheath and core layers are fed into a pre-crystallization device for pre-crystallization, and then dried by a drying device to obtain sheath chips and core chips. The peel slices and the core slices are respectively fed into their respective ingredient mixing devices, and additives are added in proportion for mixing. After the ingredients are mixed, the skin slices and core slices are melted and plasticized by their respective screw extruders, and then filtered through a melt filter to obtain skin melt and core melt; The skin melt and core melt are transported to the composite spinning box through the melt pipeline. After being metered, they are pressed together into the composite spinning assembly and ejected from the spinneret according to the skin-core structure to form the nascent filament. The nascent filaments are cooled by blowing air, controlling the air temperature, humidity and speed, and then drawn to obtain secondary filaments; The secondary filaments are laid on the mesh belt of the web forming machine to form a fiber web. After the fiber web is heat-set in an oven and mechanically reinforced by a needle punch, a non-woven fabric base fabric is obtained. The nonwoven base fabric is stored, inspected for needles online, cut, and packaged to obtain the finished product.

6. The method for producing a high-strength thermoplastic long-fiber nonwoven fabric as described in claim 5, characterized in that, The specific steps for feeding the polyester chips of the sheath and core layers into a pre-crystallization device for pre-crystallization, and then drying them in a drying device to obtain sheath chips and core chips include: The polyester chips in the sheath and the polyester chips in the core are fed into the sheath pre-crystallization device and the core pre-crystallization device respectively through two physically isolated conveying devices. In the pre-crystallization device for the cortex, a first hot air stream at 60-170°C is introduced to stir the cortex slices for 20-40 minutes; at the same time, in the pre-crystallization device for the core, a second hot air stream at 140-180°C is introduced to stir the core slices for 20-40 minutes; thus, the amorphous slices are crystallized, and the crystallinity is increased to 25%-40%. The pre-crystallized cortex slices and core slices were transferred into the cortex drying device and the core drying device, respectively. In the cortex drying device, a third type of dry hot air with a dew point below -70°C and a temperature of 60-150°C is introduced to dry the cortex slices for 6-12 hours; simultaneously, in the core drying device, a fourth type of dry hot air with a dew point below -70°C and a temperature of 140-180°C is introduced to dry the core slices for 6-12 hours, and dry cortex slices and dry core slices with a moisture content of less than 50 ppm are output respectively.

7. The method for producing a high-strength thermoplastic long-fiber nonwoven fabric as described in claim 6, characterized in that, The specific steps of melting and plasticizing the skin slices and core slices after batching through their respective screw extruders, and then filtering them through a melt filter to obtain skin melt and core melt include: The dried cortex slices and dried core slices are fed into the feed inlets of the cortex screw extruder and the core screw extruder respectively through two independent metering and feeding devices; In the skin layer screw extruder, the skin layer chips are melted and plasticized into skin layer melt in a temperature range of 240-290℃ through multi-temperature zone heating and screw shearing action; at the same time, in the core layer screw extruder, the core layer chips are melted and plasticized into core layer melt in a temperature range of 250-300℃ through multi-temperature zone heating and screw shearing action. The skin melt is transported to the skin melt filter for high-pressure filtration via the skin melt pipeline, while the core melt is transported to the core melt filter for high-pressure filtration via the core melt pipeline. The filtered skin melt and core melt are then output and transported to the composite spinning box under constant pressure.

8. The method for producing a high-strength thermoplastic long-fiber nonwoven fabric as described in claim 7, characterized in that, The specific steps of conveying the skin melt and core melt to the composite spinning box through the melt pipeline, metering them, pressing them together into the composite spinning assembly, and extruding them from the spinneret according to the skin-core structure to form the nascent filament include: The pure skin melt and core melt are delivered at constant pressure to the skin metering pump and core metering pump in a composite spinning box through two independent insulated melt pipelines. Start the skin layer metering pump and the core layer metering pump to meter and pressurize the skin layer melt and the core layer melt respectively, wherein the ratio of the metering flow rate of the skin layer melt to the metering flow rate of the core layer melt is controlled at (10%-50%):(90%-50%). The metered skin melt and core melt are introduced into a composite spinning assembly through conduits. The assembly is equipped with a distribution plate and a flow channel, so that the two melts are combined according to the pre-designed skin-core composite structure. The core-sheath melts that have already been combined are extruded together from the spinneret micro-holes of the composite spinning assembly under a pressure of 3.0-15.0 MPa to form a core-sheath type nascent filament with the core melt as the core and the sheath melt completely covering the outside.

9. The method for producing a high-strength thermoplastic long-fiber nonwoven fabric as described in claim 8, characterized in that, The specific steps for laying the secondary filaments on the mesh belt of the web forming machine to form a fiber web, and then heat-setting the fiber web in an oven and mechanically reinforcing it with a needle punch to obtain the nonwoven base fabric include: The drawn core-sheath composite filament bundle is evenly laid on the continuously running web forming machine belt in a random orientation or directional arrangement through a filament arranging device or an airflow web forming device to form a fiber web with a predetermined unit area mass. The formed fiber web is conveyed through a hot air setting oven and heated at a temperature of 110-160℃. The heat-set fiber web is fed into a needle punching machine, where barbed needles are used to repeatedly puncture the fiber web in the vertical direction.

10. The method for producing a high-strength thermoplastic long-fiber nonwoven fabric as described in claim 9, characterized in that, The specific steps for storing, online needle detection, cutting, and packaging the nonwoven base fabric to obtain the finished product include: The needle-punched and reinforced nonwoven base fabric is temporarily stored in a fabric storage rack to make the fabric tension more uniform and to allow the fabric temperature to cool naturally. The nonwoven base fabric, after being balanced by the storage, is continuously passed through an online needle detection device to detect and mark metal needle fragments remaining in the base fabric due to needle breakage from the needle punching machine in real time. The continuous nonwoven base fabric that has passed the needle detection is cut into fixed lengths and widths according to the preset size by a longitudinal cutter and a transverse cutter to obtain a single standardized nonwoven fabric. The cut single pieces of non-woven fabric are stacked in predetermined quantities, compressed, bundled, and packaged to form the final finished product package.

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