Composite sms nonwoven fabric and method for manufacturing the same

Abstract

The application discloses a composite SMS non-woven fabric and a preparation method thereof, and relates to the technical field of non-woven fabrics.The composite SMS non-woven fabric comprises a bottom layer, a middle layer and a top layer;the bottom layer and the top layer are spun-bond non-woven fabric layers, and the middle layer is a melt-blown non-woven fabric layer;the bottom layer and the top layer comprise the following preparation raw materials in parts by weight: 90-95 parts of polyester, 3-5 parts of polyethylene imine and 1.5-5 parts of an epoxy chain extender; and the middle layer comprises the following preparation raw materials in parts by weight: 90-95 parts of polyester and 2-5 parts of an additive.The application can enhance the interfacial bonding force between the spun-bond layer and the melt-blown layer, and improve the balance of the longitudinal and transverse mechanical properties of the composite material.

Description

Technical Field

[0001] This application relates to the field of nonwoven fabric technology, and in particular to a composite SMS nonwoven fabric and its preparation method. Background Technology

[0002] Nonwoven fabric, also known as non-woven textile, is a sheet or mesh material formed by arranging fibers in a oriented or random manner through mechanical, chemical, or thermal bonding methods. It is widely used in medical protective equipment, hygiene products, packaging materials, and agricultural coverings. Compared to traditional woven fabrics, nonwoven fabrics have advantages such as shorter production processes, lower costs, and greater functional adjustability, leading to their rapid development in both industrial and civilian sectors.

[0003] In the production process of nonwoven fabrics, spunbond and meltblown processes are two common methods for forming filaments. Spunbond processes involve extruding polymer melt through spinnerets, which is then stretched by airflow to form continuous filaments. After web formation, these filaments are thermally bonded to form a fabric. Meltblown processes utilize high-speed hot airflow to blow the melt into ultrafine fibers, creating a meltblown layer with finer fiber diameters and superior filtration performance. SMS nonwoven fabric (i.e., spunbond-meltblown-spunbond composite nonwoven fabric), formed by alternating spunbond and meltblown layers, combines the mechanical strength of spunbond layers with the filtration performance of meltblown layers, making it an important basic material for medical protective materials (such as surgical gowns, masks, and protective suits).

[0004] However, existing SMS nonwoven fabrics generally suffer from significant differences in mechanical properties between the longitudinal and transverse directions during production. In the longitudinal direction, the fibers are highly oriented during drafting and traction, with the molecular chains tightly packed along the longitudinal axis, giving them high tensile strength. In the transverse direction, however, there is a lack of effective external drafting, and the fibers mainly rely on natural diffusion and interweaving during web formation, resulting in low orientation and mechanical properties far lower than those in the longitudinal direction. This imbalance in properties limits the effectiveness of SMS nonwoven fabrics in applications requiring high isotropy.

[0005] To address the aforementioned issues, current research primarily focuses on raw material modification or equipment structure optimization. For example, Chinese patent application number 202510859171.8 discloses a soft SMS nonwoven fabric that improves the material's softness and functionality by introducing components such as PP / PE copolymers and dopamine-grafted hyperbranched polymers; Chinese patent application number 201920423042.4 proposes a nonwoven fabric cross-laying device, aiming to optimize the fiber web structure through physical means. However, the former still fails to effectively solve the problem of differences in mechanical properties between the transverse and longitudinal directions, while the latter is mainly applicable to needle-punching and hydroentangling processes for short fibers and is difficult to directly apply to the continuous molding of long-filament SMS nonwoven fabrics.

[0006] Therefore, maintaining a balance between the transverse and longitudinal properties of nonwoven fabrics has become a key issue in the current development of SMS nonwoven fabric technology. Summary of the Invention

[0007] To improve the balance of transverse and longitudinal mechanical properties of nonwoven fabrics, this application provides a composite SMS nonwoven fabric and its preparation method.

[0008] In a first aspect, this application provides a composite SMS nonwoven fabric, which adopts the following technical solution: A composite SMS nonwoven fabric includes a bottom layer, a middle layer, and a top layer; the bottom layer and the top layer are spunbond nonwoven fabric layers, and the middle layer is a meltblown nonwoven fabric layer; the bottom layer and the top layer include the following raw materials in parts by weight: 90-95 parts polyester, 3-5 parts polyethyleneimine, and 1.5-5 parts epoxy chain extender; the middle layer includes the following raw materials in parts by weight: 90-95 parts polyester and 2-5 parts additives.

[0009] By adopting the above technical solutions, this application uses polyester as the main raw material, endowing the material with high strength, heat resistance and good dimensional stability. The epoxy chain extenders added to the bottom and top layers can react with the polyester molecular chains, increasing the molecular weight and melt strength of the polyester, making the spunbond fibers more uniform and less defective during the molding process, thus improving the mechanical basis of the fibers in all directions from the material itself. Polyethyleneimine is rich in amine groups, which can not only interact with the surface of polyester fibers, but also significantly enhance the interfacial bonding force between the spunbond layer and the meltblown layer during hot rolling, effectively reinforcing the transverse weak links (such as interlayer slippage or easy fiber peeling) caused by fiber orientation. The additives in the middle layer can endow the meltblown layer with specific functions (such as high-efficiency filtration, antibacterial, etc.) as needed, so that the nonwoven fabric has the advantages of both SMS structural mechanics and function.

[0010] Optionally, the epoxy chain extender is a styrene-glycidyl methacrylate copolymer.

[0011] By adopting the above technical solution and selecting styrene-glycidyl methacrylate copolymer as an epoxy chain extender, the good compatibility between its styrene segments and the polyester matrix, as well as the high reactivity of its epoxy groups with the terminal carboxyl and hydroxyl groups of the polyester, can be fully utilized. During the melt spinning process, the polyester molecular chains are effectively extended and branched, significantly improving the viscosity and strength of the polyester melt, thereby improving the uniformity of the spun web and reducing web defects. At the same time, the copolymer can also moderately adjust the melt flow rate, making it easier for the spunbond layer fibers to form a stable orientation structure when laid at a set angle, and forming a strong interfacial bond with the meltblown layer, further improving the overall mechanical properties and filtration stability of the composite nonwoven fabric.

[0012] Optionally, the weight ratio of the polyethyleneimine and the styrene-glycidyl methacrylate copolymer is (1-3):1.

[0013] By adopting the above technical solution, this application uses a specific weight ratio of polyethyleneimine and styrene-glycidyl methacrylate copolymer to achieve the best synergistic effect between the two in the polyester matrix, thereby effectively balancing overall filtration efficiency and air permeability while improving interlayer peel strength. Specifically, the amino groups of polyethyleneimine can catalyze the reaction between epoxy groups and polyester end groups, promoting efficient chain extension. It can also undergo moderate crosslinking with epoxy groups to form an elastic interfacial network structure. Meanwhile, the epoxy chain extender can compensate for the decrease in molecular weight of the polyester during melt spinning, maintaining a suitable melt viscosity, ensuring uniform formation of the bottom and top layer fibers at the set oblique web-laying angle, and maintaining the vertical orientation of the middle layer meltblown fibers.

[0014] Optionally, the weight-average molecular weight of the polyethyleneimine is 10,000-100,000.

[0015] By adopting the above technical solution, this application uses polyethyleneimine with a specific molecular weight, which can ensure its uniform dispersion in the polyester matrix while fully leveraging its catalytic effect on chain extension and interfacial crosslinking function. This molecular weight range avoids the volatilization or migration of polyethyleneimine during the high-temperature melt spinning process, preventing insufficient effective amine group content and hindering the continuous catalysis of the reaction between epoxy groups and polyester end groups. It also avoids decreased dispersibility in the polyester matrix, preventing localized agglomeration and affecting fiber forming uniformity.

[0016] Optionally, the additive includes an antibacterial agent and an antistatic agent, wherein the antibacterial agent is silver nanoparticles and the antistatic agent is polyethylene glycol monostearate.

[0017] By adopting the above technical solution, adding nano-silver particles as an antibacterial agent to the intermediate layer can destroy the cell membrane of microorganisms and inhibit their reproduction through the slow release of silver ions, so that the composite nonwoven fabric has a long-lasting and stable antibacterial effect. Adding polyethylene glycol monostearate as an antistatic agent to the intermediate layer allows the hydrophilic segments of polyethylene glycol in its molecular chain to migrate to the fiber surface under ambient humidity. By adsorbing water molecules in the air, it forms a continuous conductive water film, effectively reducing the surface resistivity of the material, quickly eliminating the accumulation of static electricity caused by friction, and avoiding the risk of dust adsorption and electrical breakdown.

[0018] Optionally, the polyester is at least one of polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate.

[0019] Optionally, the basis weight of the bottom layer is 15-40 g / m³. 2 The weight of the top layer is 10-30 g / m³. 2 The basis weight of the intermediate nonwoven fabric is 10-20 g / m². 2 .

[0020] By adopting the above technical solution, the basis weight of the bottom layer, middle layer, and top layer are controlled at 15-40 g / m². 2 10-20g / m 2 and 10-30g / m 2 Within this range, composite nonwoven fabrics can achieve an optimal balance among various indicators such as longitudinal and transverse mechanical properties, filtration efficiency, air permeability, and softness. Specifically, the higher basis weight of the bottom layer provides sufficient structural support and tensile strength, ensuring the composite material is not easily deformed or damaged during use; the middle layer, as the core filtration layer, has a basis weight of 10-20 g / m². 2 The weight design ensures sufficient fiber packing density for efficient filtration while avoiding a significant decrease in breathability due to excessive thickness; the top layer, as the surface layer, has a weight of 10-30 g / m². 2 The weight of the material provides both good surface smoothness and feel, while controlling the overall material weight while ensuring protective performance.

[0021] Optionally, the fiber diameter of the bottom and top layers is 10~40μm, and the fiber diameter of the intermediate nonwoven fabric is 1~10μm.

[0022] By adopting the above technical solution, the fiber diameter of the bottom and top spunbond nonwoven fabrics is controlled at 10~40μm, and the fiber diameter of the middle layer meltblown nonwoven fabric is controlled at 1~10μm. This allows for the construction of a gradient fiber structure in the composite nonwoven fabric, achieving synergistic optimization of the functions of each layer. Specifically, the coarser fibers (10~40μm) in the bottom and top layers form a loose, porous skeletal network, providing sufficient structural strength and tensile properties to the composite material while ensuring good air permeability. The ultrafine fibers (1~10μm) in the middle layer form a high-density fiber web structure, achieving efficient filtration of fine particles through mechanisms such as inertial impaction, diffusion deposition, and direct interception. This gradient combination of coarse and fine fibers significantly improves filtration accuracy and efficiency while maintaining good mechanical properties. Furthermore, the balance between air permeability resistance and filtration performance can be further optimized by adjusting the fiber diameter ratio.

[0023] Secondly, this application provides a method for preparing composite SMS nonwoven fabric, which adopts the following technical solution: A method for preparing a composite SMS nonwoven fabric includes the following steps: S1. Polyester, polyethyleneimine and epoxy chain extender are mixed, and the mixture is melt extruded, spun, drawn, laid into a web and spunbonded to obtain the bottom layer. The top layer is obtained by the same method as the bottom layer. S2. The polyester and additives are mixed, melted and sprayed out by screw extrusion, and then laid into a web to obtain the intermediate layer; S3. Lay the bottom layer, middle layer and top layer in sequence from bottom to top, and hot roll them to obtain composite SMS nonwoven fabric.

[0024] Optionally, in step S1, the temperature of melt extrusion is 230-285℃.

[0025] Optionally, in step S2, the temperature of melt extrusion is 230-285℃.

[0026] Optionally, in step S3, the hot rolling temperature is 130-155℃.

[0027] Optionally, in step S3, the extrusion direction of the bottom layer forms an angle of 10° to 80° with the nonwoven fabric laying direction; the extrusion direction of the top layer forms an angle of -10° to -80° with the nonwoven fabric laying direction; and the extrusion direction of the middle layer forms an angle of 90° with the nonwoven fabric laying direction.

[0028] Furthermore, the extrusion direction of the bottom layer forms an angle of 10° to 45° with the nonwoven fabric web laying direction; the extrusion direction of the top layer forms an angle of -10° to -45° with the nonwoven fabric web laying direction.

[0029] By adopting the above technical solution, this application sets the extrusion direction of the bottom and top layers of spunbond nonwoven fabric at a certain angle to the web laying direction, enabling the fibers to form a stable oblique network structure. This structure works synergistically with the meltblown fibers in the middle layer, which are oriented at 90° perpendicularly. As a result, the composite nonwoven fabric exhibits more balanced mechanical properties such as tensile strength and tear strength in both the longitudinal and transverse directions. Simultaneously, the interlayer bonding force is further enhanced, while maintaining excellent filtration efficiency and air permeability. This angle range avoids the problems of excessively parallel fiber arrangement and excessive differences in longitudinal and transverse strength caused by an excessively small angle, while also preventing the defects of excessive fiber tilting and decreased web laying uniformity caused by an excessively large angle.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. This application uses polyester as the main raw material, endowing the material with high strength, heat resistance, and good dimensional stability; the polyethyleneimine added to the bottom and top layers can significantly enhance the interfacial bonding force between the spunbond layer and the meltblown layer, effectively preventing delamination; at the same time, epoxy chain extenders can improve the melt strength and spinning stability of polyester, so that the composite nonwoven fabric can maintain high strength while possessing excellent structural durability; the additives in the middle layer can impart specific functions to the meltblown layer as needed (such as high-efficiency filtration, antibacterial, etc.), so that the nonwoven fabric not only has the advantages of both SMS structural mechanics and function; 2. By employing a specific weight ratio of polyethyleneimine and styrene-glycidyl methacrylate copolymer, the optimal synergistic effect of the two in the polyester matrix was achieved, thereby effectively balancing overall filtration efficiency and air permeability while improving interlayer peel strength. Specifically, the amino groups of polyethyleneimine catalyze the reaction between epoxy groups and polyester end groups, promoting efficient chain extension. It can also undergo moderate crosslinking with epoxy groups to form an elastic interfacial network structure. Meanwhile, the epoxy chain extender compensates for the decrease in molecular weight of the polyester during melt spinning, maintaining suitable melt viscosity, ensuring uniform formation of the bottom and top layer fibers at the set oblique web-laying angle, and maintaining the vertical orientation of the middle layer meltblown fibers. 3. By setting the extrusion direction of the bottom and top layers of spunbond nonwoven fabric at a certain angle to the web laying direction, a stable oblique network structure can be formed, which works synergistically with the 90° perpendicularly oriented meltblown fibers in the middle layer. This results in a more balanced mechanical property of the composite nonwoven fabric, such as tensile strength and tear strength in both the longitudinal and transverse directions. Simultaneously, the interlayer bonding force is further enhanced, while maintaining excellent filtration efficiency and air permeability. This angle range avoids the problems of excessively parallel fiber arrangement and excessive differences in longitudinal and transverse strength caused by an excessively small angle, while also preventing the defects of excessive fiber tilting and decreased web laying uniformity caused by an excessively large angle. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] This application discloses a composite SMS nonwoven fabric, comprising a bottom layer, a middle layer, and a top layer; the bottom layer and the top layer are spunbond nonwoven fabric layers, and the middle layer is a meltblown nonwoven fabric layer; the bottom layer and the top layer comprise the following raw materials by weight: 90-95 parts polyester, 3-5 parts polyethyleneimine, and 1.5-5 parts epoxy chain extender; the middle layer comprises the following raw materials by weight: 90-95 parts polyester and 2-5 parts additives.

[0033] This application discloses a method for preparing composite SMS nonwoven fabric, including the following steps: S1. Polyester, polyethyleneimine and epoxy chain extender are mixed, melt extruded at 230-285℃, spun, drawn, web laid and spunbonded to obtain the bottom layer, and the top layer is obtained by the same method as the bottom layer. S2. The polyester and additives are mixed, melt-extruded at 230-285℃, and laid into a web to obtain the intermediate layer; S3. Lay the bottom layer, middle layer and top layer in sequence from bottom to top, and hot roll at 50-80Kpa and 130-155℃ to obtain SMS composite nonwoven fabric.

[0034] All raw materials used in the embodiments of this application are commercially available, wherein: Styrene-glycidyl methacrylate copolymer, BASF GmbH, Germany; Polypropylene, Wuhan Xinlianchuang Plastics Co., Ltd.; Polyethyleneimine, weight average molecular weight 70,000, Shanghai Aladdin Biochemical Technology Co., Ltd. Nano-silver particles, Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; Polyethylene glycol monostearate, Shanghai Maclean Biochemical Technology Co., Ltd. Polyethylene terephthalate, Shanghai Jiadeer Chemical Technology Co., Ltd.; Polypropylene terephthalate, Shanghai Jiadeer Chemical Technology Co., Ltd.; Polybutylene terephthalate, Shanghai Jiadeer Chemical Technology Co., Ltd.

[0035] Example 1 90 kg of polyethylene terephthalate, 5 kg of polyethyleneimine, and 5 kg of styrene-glycidyl methacrylate copolymer were mixed, melt-extruded at 260°C, spun, drawn, web-laid, and spunbonded to obtain a basis weight of 15 g / m². 2 The bottom layer has a fiber diameter of 10μm. 90kg of polypropylene terephthalate, 5kg of polyethyleneimine, and 5kg of styrene-glycidyl methacrylate copolymer are mixed, melt-extruded at 260℃, spun, drawn, web-laid, and spunbonded to obtain a basis weight of 30g / m². 2 The top layer has a fiber diameter of 10μm; 90kg of polypropylene terephthalate, 3kg of nano-silver particles, and 2kg of polyethylene glycol monostearate are mixed, melt-sprayed at 260℃, and laid into a web to obtain a basis weight of 15g / m². 2 A middle layer with a fiber diameter of 1μm; the bottom layer, middle layer, and top layer are laid out sequentially from bottom to top. The extrusion direction of the bottom and top layers forms an angle of 10° and -10° with the nonwoven fabric laying direction, respectively, while the extrusion direction of the middle layer forms an angle of 90° with the nonwoven fabric laying direction. Hot-rolled at 65kPa and 140℃, a basis weight of 60g / m² is obtained. 2 Composite SMS nonwoven fabric.

[0036] Example 2 93 kg of polyethylene terephthalate, 4 kg of polyethyleneimine, and 4 kg of styrene-glycidyl methacrylate copolymer were mixed, melt-extruded at 260°C, spun, drawn, web-laid, and spunbonded to obtain a basis weight of 25 g / m². 2 The bottom layer has a fiber diameter of 25μm. 93kg of polyethylene terephthalate, 4kg of polyethyleneimine, and 4kg of styrene-glycidyl methacrylate copolymer were mixed, melt-extruded at 260℃, spun, drawn, laid into a web, and spunbond to obtain a basis weight of 15g / m². 2 The top layer has a fiber diameter of 25μm; 93kg of polyethylene terephthalate, 2kg of nano-silver particles, and 1.5kg of polyethylene glycol monostearate are mixed, melt-sprayed at 260℃, and then laid into a web to obtain a basis weight of 20g / m². 2 A middle layer with a fiber diameter of 5μm; the bottom layer, middle layer, and top layer are laid out sequentially from bottom to top. The extrusion direction of the bottom and top layers forms an angle of 10° and -10° with the nonwoven fabric laying direction, respectively, while the extrusion direction of the middle layer forms an angle of 90° with the nonwoven fabric laying direction. Hot-rolled at 65kPa and 140℃, a basis weight of 60g / m² is obtained. 2 Composite SMS nonwoven fabric.

[0037] Example 3 95 kg of polybutylene terephthalate, 3 kg of polyethyleneimine, and 3 kg of styrene-glycidyl methacrylate copolymer were mixed, melt-extruded at 260°C, spun, drawn, web-laid, and spunbonded to obtain a basis weight of 40 g / m². 2 The bottom layer has a fiber diameter of 40μm. 95kg of polybutylene terephthalate, 3kg of polyethyleneimine, and 3kg of styrene-glycidyl methacrylate copolymer are mixed, melt-extruded at 260℃, spun, drawn, web-laid, and spunbonded to obtain a basis weight of 10g / m². 2 The top layer has a fiber diameter of 40μm; 95kg of polybutylene terephthalate, 1kg of nano-silver particles, and 1kg of polyethylene glycol monostearate are mixed, melt-sprayed at 260℃ by a screw, and then laid into a web to obtain a basis weight of 10g / m². 2 A middle layer with a fiber diameter of 10μm; the bottom layer, middle layer, and top layer are laid out sequentially from bottom to top. The extrusion direction of the bottom and top layers forms an angle of 10° and -10° with the nonwoven fabric laying direction, respectively, while the extrusion direction of the middle layer forms an angle of 90° with the nonwoven fabric laying direction. Hot-rolled at 65kPa and 140℃, a basis weight of 60g / m² is obtained. 2 Composite SMS nonwoven fabric.

[0038] Comparative Example 1 The difference between this comparative example and Example 3 is that the polybutylene terephthalate in the bottom layer, top layer and middle layer of this comparative example is replaced with polypropylene.

[0039] Comparative Example 2 The difference between this comparative example and Example 3 is that the extrusion direction of the bottom layer in this comparative example forms a 90° angle with the nonwoven fabric web laying direction.

[0040] Comparative Example 3 The difference between this comparative example and Example 3 is that the extrusion direction of the top layer in this comparative example forms a -90° angle with the nonwoven fabric web laying direction.

[0041] Comparative Example 4 The difference between this comparative example and Example 3 is that the polyethyleneimine in Example 3 is replaced by styrene-glycidyl methacrylate copolymer.

[0042] Comparative Example 5 The difference between this comparative example and Example 3 is that the same mass of styrene-glycidyl methacrylate copolymer in Example 3 is replaced with polyethyleneimine in this comparative example.

[0043] Performance Test 1 The mechanical properties of the composite SMS nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 were determined. The transverse and longitudinal tensile strengths and elongation at break of the nonwoven fabrics were tested according to GB / T24218.3-2010 "Textiles - Nonwovens - Test Methods - Part 3: Determination of breaking strength and elongation at break".

[0044] Table 1. Performance of composite SMS nonwoven fabrics in Examples 1-3 and Comparative Examples 1-5

[0045] As shown in Examples 1-3 and Table 1, the composite SMS nonwoven fabrics of Examples 1-3 of this application exhibit a longitudinal tensile strength of ≥580.87 N / 50 mm, a longitudinal elongation at break of ≥28.32%, a transverse tensile strength of ≥440.35 N / 50 mm, and a transverse elongation at break of ≥50.93%. This demonstrates that by setting the angle between the extrusion direction of each nonwoven layer and the web-laying direction, and combining the synergistic effect of polyethyleneimine and epoxy chain extenders, this application can significantly improve the balance of longitudinal and transverse mechanical properties of the composite material.

[0046] As shown in Example 3, Comparative Example 1, and Table 1, the longitudinal tensile strength of the composite SMS nonwoven fabric in Example 3 of this application is 603.85 N / 50 mm, with a longitudinal elongation at break of 30.36%, and the transverse tensile strength is 497.66 N / 50 mm, with a transverse elongation at break of 53.60%, which is significantly better than that of Comparative Example 1. This indicates that by using polyester as the matrix material and working synergistically with polyethyleneimine and epoxy chain extenders, this application can effectively improve the forming quality and interfacial bonding of the fiber network at a specific web-laying angle, significantly improving the transverse strength and elongation at break of the composite nonwoven fabric, and achieving a balanced improvement in both longitudinal and transverse mechanical properties. Compared to Example 3, the polypropylene used in Comparative Example 1 has poor compatibility with polyethyleneimine and epoxy chain extenders, failing to form an effective chain extension and cross-linking structure, resulting in a significant decrease in mechanical properties.

[0047] As shown in Example 3, Comparative Examples 2-3, and Table 1, the composite SMS nonwoven fabric of Example 3 exhibits a longitudinal tensile strength of 603.85 N / 50 mm and a longitudinal elongation at break of 30.36%, and a transverse tensile strength of 497.66 N / 50 mm and a transverse elongation at break of 53.60%, significantly superior to Comparative Examples 2-3. This indicates that by setting a certain angle between the extrusion directions of the bottom and top layers to form a symmetrical oblique fiber network, and then combining it with an intermediate layer at a 90° angle, the present application achieves multi-directional cross-arrangement of fibers between layers, significantly optimizing the isotropy of the fiber network. This results in a substantial increase in transverse strength while maintaining high longitudinal strength, leading to a more balanced mechanical property in both directions. In contrast, in Comparative Examples 2 and 3, only one spunbond layer uses an oblique web formation, while the other layer uses a longitudinal web formation, disrupting the symmetry of the fiber network and causing a significant decrease in transverse strength and a large difference in transverse and longitudinal properties.

[0048] As shown in Example 3, Comparative Examples 4-5, and Table 1, the composite SMS nonwoven fabric of Example 3 exhibits a longitudinal tensile strength of 603.85 N / 50 mm and a longitudinal elongation at break of 30.36%, and a transverse tensile strength of 497.66 N / 50 mm and a transverse elongation at break of 53.60%, significantly superior to Comparative Examples 4-5. This indicates that the present application achieves effective chain extension and moderate crosslinking during melt spinning through the synergistic effect of polyethyleneimine and epoxy chain extenders, significantly improving the processing stability of the polyester melt and the fiber forming quality, thereby obtaining a high-strength, high-elongation, and well-balanced composite nonwoven fabric at a specific web-laying angle. In Comparative Example 4, the reaction efficiency of the simple epoxy chain extender is low, resulting in insufficient increase in melt viscosity and decreased spinning stability and interlayer bonding. In Comparative Example 5, the simple polyethyleneimine fails to effectively compensate for the polyester molecular weight during spinning, leading to lower melt viscosity and poorer fiber forming uniformity.

[0049] Examples 4-7 Based on Example 3, the difference is that the extrusion direction of the bottom layer and the top layer are at different angles with the web laying direction of the nonwoven fabric, while the other steps are the same as in Example 3.

[0050] Example 4 The difference between this embodiment and embodiment 3 is that the extrusion direction of the bottom layer forms a 30° angle with the web laying direction of the nonwoven fabric, and the extrusion direction of the top layer forms a -30° angle with the web laying direction of the nonwoven fabric.

[0051] Example 5 The difference between this embodiment and Embodiment 3 is that the extrusion direction of the bottom layer forms a 45° angle with the web laying direction of the nonwoven fabric, while the extrusion direction of the top layer forms a -45° angle with the web laying direction of the nonwoven fabric.

[0052] Example 6 The difference between this embodiment and embodiment 3 is that the extrusion direction of the bottom layer forms a 60° angle with the web laying direction of the nonwoven fabric, while the extrusion direction of the top layer forms a -60° angle with the web laying direction of the nonwoven fabric.

[0053] Example 7 The difference between this embodiment and embodiment 3 is that the extrusion direction of the bottom layer forms an 80° angle with the web laying direction of the nonwoven fabric, while the extrusion direction of the top layer forms a -80° angle with the web laying direction of the nonwoven fabric.

[0054] Examples 8-9 Based on Example 5, except for the weight ratio of polyethyleneimine and styrene-glycidyl methacrylate copolymer, the other components and preparation methods are the same as in Example 5, and the total weight of polyethyleneimine and styrene-glycidyl methacrylate copolymer remains unchanged.

[0055] Example 8 The difference between this embodiment and embodiment 5 is that the weight ratio of polyethyleneimine and styrene-glycidyl methacrylate in this embodiment is 2:1. Specifically, the weight of polyethyleneimine is 4 kg and the weight of styrene-glycidyl methacrylate is 2 kg.

[0056] Example 9 The difference between this embodiment and embodiment 5 is that the weight ratio of polyethyleneimine and styrene-glycidyl methacrylate in this embodiment is 3:1. Specifically, the weight of polyethyleneimine is 4.5 kg and the weight of styrene-glycidyl methacrylate is 1.5 kg.

[0057] Performance Test 2 The mechanical properties of the composite SMS nonwoven fabrics prepared in Examples 3-9 were determined. The test methods were the same as those in Performance Test 1, and the test results are shown in Table 2 below.

[0058] Table 2 Performance of Composite SMS Nonwoven Fabrics in Examples 3-9

[0059] As shown in Examples 3-7 and Table 2, the longitudinal tensile strength of the composite SMS nonwoven fabric in Example 5 of this application is 620.33 N / 50 mm, the longitudinal elongation at break is 32.01%, and the transverse tensile strength is 539.68 N / 50 mm, with a transverse elongation at break of 54.83%, which is significantly better than Examples 3-4 and Examples 6-7. This indicates that by controlling the angles between the extrusion directions of the bottom and top layers and the web-laying direction of the nonwoven fabric to 45° and -45° respectively, this application enables the fibers to form the most stable oblique network structure. This, in synergy with the M layer at a 90° angle, achieves multi-directional cross-arrangement of fibers between layers, maximizing the isotropy of the fiber network. This results in a significant increase in transverse strength while maintaining high longitudinal strength, achieving the optimal balance between longitudinal and transverse mechanical properties. Compared to Example 5, the included angle in Example 3 is too small, the fiber arrangement is still biased towards the longitudinal direction, and the improvement in transverse strength is limited; compared to Example 5, the included angle in Example 7 is too large, the fibers are excessively tilted, the uniformity of web laying decreases, resulting in an overall decrease in mechanical properties.

[0060] As shown in Examples 5, 8-9, and Table 2, the composite SMS nonwoven fabric of Example 8 has a longitudinal tensile strength of 636.22 N / 50 mm and a longitudinal elongation at break of 32.74%, and a transverse tensile strength of 551.84 N / 50 mm and a transverse elongation at break of 55.67%, which are significantly better than those of Examples 5 and 9. This indicates that the present application uses a specific weight ratio of polyethyleneimine and styrene-glycidyl methacrylate copolymer to achieve optimal synergy between the two. The amine groups of polyethyleneimine can fully catalyze the reaction between the epoxy groups and the polyester end groups, promoting efficient chain extension, and can also form a suitable interfacial crosslinking network with the epoxy groups; at the same time, the styrene-glycidyl methacrylate copolymer can effectively compensate for the decrease in molecular weight of polyester during melt spinning, maintain a suitable melt viscosity, and ensure uniform fiber formation at an oblique web-laying angle.

[0061] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A composite SMS nonwoven fabric, characterized in that, The product comprises a bottom layer, a middle layer, and a top layer; the bottom and top layers are spunbond nonwoven fabric layers, and the middle layer is a meltblown nonwoven fabric layer; the bottom and top layers comprise the following raw materials by weight: 90-95 parts polyester, 3-5 parts polyethyleneimine, and 1.5-5 parts epoxy chain extender; the middle layer comprises the following raw materials by weight: 90-95 parts polyester and 2-5 parts additives; the epoxy chain extender is a styrene-glycidyl methacrylate copolymer. The preparation method of the composite SMS nonwoven fabric includes the following steps: S1, mixing polyester, polyethyleneimine, and epoxy chain extender, followed by melt extrusion, spinning, drawing, web laying, and spunbonding to obtain a bottom layer, and obtaining a top layer using the same method as the bottom layer; S2, mixing polyester and additives, followed by melt spraying and web laying to obtain an intermediate layer; S3, laying the bottom layer, intermediate layer, and top layer sequentially from bottom to top, and hot-rolling to obtain the composite SMS nonwoven fabric; in step S3, the extrusion direction of the bottom layer forms an angle of 10~80° with the web laying direction of the nonwoven fabric; the extrusion direction of the top layer forms an angle of -10~-80° with the web laying direction of the nonwoven fabric; the extrusion direction of the intermediate layer forms an angle of 90° with the web laying direction of the nonwoven fabric; the extrusion directions of the bottom layer and the top layer are respectively set with a certain angle, forming a symmetrical oblique fiber network.

2. The composite SMS nonwoven fabric according to claim 1, characterized in that, The weight ratio of the polyethyleneimine and the styrene-glycidyl methacrylate copolymer is (1-3):

1.

3. The composite SMS nonwoven fabric according to claim 1, characterized in that, The weight-average molecular weight of the polyethyleneimine is 10,000-100,000.

4. The composite SMS nonwoven fabric according to claim 1, characterized in that, The additives include an antibacterial agent and an antistatic agent, wherein the antibacterial agent is silver nanoparticles and the antistatic agent is polyethylene glycol monostearate.

5. The composite SMS nonwoven fabric according to claim 1, characterized in that, The polyester is at least one of polyethylene terephthalate, propylene terephthalate, and butylene terephthalate.

6. The composite SMS nonwoven fabric according to claim 1, characterized in that, The basis weight of the bottom layer is 15-40 g / m³. 2 The weight of the top layer is 10-30 g / m³. 2 The basis weight of the intermediate nonwoven fabric is 10-20 g / m². 2 .

7. The composite SMS nonwoven fabric according to claim 1, characterized in that, The extrusion direction of the bottom layer forms an angle of 10° to 45° with the nonwoven fabric laying direction; the extrusion direction of the top layer forms an angle of -10° to -45° with the nonwoven fabric laying direction.

Images