A multi-stage gradient structure nonwoven fabric

Abstract

The present application provides a kind of non-woven fabric of multistage gradient structure, including skin layer and flow guide layer, the hydrophilicity of the flow guide layer is stronger than the hydrophilicity of the skin layer, the mass ratio of the skin layer and the flow guide layer is 1:2~3;The skin layer is made of fine fiber multilayer laying.The present application designs non-woven fabric into the structure with skin layer and flow guide layer, wherein the hydrophilicity of the flow guide layer is stronger than the hydrophilicity of the skin layer, under the action of wettability gradient and gravity, liquid can flow from the non-hydrophilic end of skin layer to the hydrophilic end of flow guide layer, reduce liquid back seepage to skin layer surface, thereby greatly reduce back seepage amount, improve dryness.

Description

Technical Field

[0001] This invention relates to the field of nonwoven fabric technology, and more specifically to a nonwoven fabric with a multi-level gradient structure. Background Technology

[0002] Currently, the surface materials used in sanitary napkins and diapers on the market are generally single-material structures. These surface materials often have drawbacks such as slow absorption, large backflow, and insufficient fluffiness, resulting in a poor user experience. Therefore, it is necessary to design a new type of surface material that utilizes the different properties of materials and the structures formed between them to improve the aforementioned problems. Summary of the Invention

[0003] To address the technical deficiencies in the prior art, this invention proposes a nonwoven fabric with a multi-level gradient structure, which solves the aforementioned technical problems and meets practical needs. The specific technical solution is as follows:

[0004] A nonwoven fabric with a multi-level gradient structure includes a skin-friendly layer and a flow-guiding layer, wherein the hydrophilicity of the flow-guiding layer is stronger than that of the skin-friendly layer, and the mass ratio of the skin-friendly layer to the flow-guiding layer is 1:2~3.

[0005] The skin-friendly layer is composed of multiple layers of fine fibers, which are composed of the following components in the indicated mass ratios: 96-98% polypropylene polymer and 2-4% softening masterbatch;

[0006] The flow guiding layer is made of coarse fibers, antibacterial fibers, and indicator fibers interwoven together. The coarse fibers are composed of the following components in the indicated mass ratio: 40-50% polyethylene polymer, 50-60% polyester polymer, and 0.2-0.3% multiple hydrophilic finishing agent.

[0007] Specifically, the fine fibers have a denier of 1.6 to 1.8D, and the coarse fibers have a denier of 2 to 2.2D.

[0008] Specifically, the skin-friendly layer is configured as a two-layer structure, wherein the mass of the upper layer is less than that of the lower layer, and the fiber density of the upper layer is less than that of the lower layer.

[0009] Specifically, the mass ratio of the upper layer to the lower layer is 1:1.5~2.

[0010] Specifically, the soft masterbatch is a polypropylene homopolymer, and the fine fibers also contain 0.01~0.5% of an additive, which is oleic acid amide.

[0011] Specifically, the fine fibers also include 0.5% to 1% of a weak hydrophilic finishing agent, the main component of which is glyceryl stearate.

[0012] Specifically, the antibacterial fiber is made by spinning an inorganic antibacterial agent containing silver, copper, or zinc ions into the fiber raw material.

[0013] Specifically, the indicator fiber is made by immersing the fiber in litmus solution and then drying it.

[0014] A method for preparing a nonwoven fabric includes the following steps:

[0015] S1 Skin-Friendly Layer Production: Polypropylene polymer and soft masterbatch are mixed evenly and then transferred to a screw extruder for heating. The heated and molten melt is filtered, metered and evenly mixed and distributed into a spinneret. The melt is then pressurized and spun into nascent fibers. The nascent fibers are stretched by a stretching device to obtain fine fibers and guided onto a web forming curtain. After thermal bonding, a skin-friendly layer is formed.

[0016] The S2 flow guide layer is made by opening and mixing two-component fibers composed of polyethylene polymer and polyester polymer. The fibers are spun by a spinning machine, with high-melting-point polyester as the core layer and low-melting-point polyethylene as the sheath layer. The fiber cross-section forms a concentric circular structure. After carding, the fibers are stripped by stripping rollers and transferred to the carding machine doffer. They are output as a fiber web and sprayed with hydrophilic finishing agent multiple times for hydrophilic treatment. The treated fiber web is then heated and bonded to obtain coarse fibers, which are then interwoven with antibacterial fibers and indicator fibers to form the flow guide layer.

[0017] S3 bonding: bonding the skin-friendly layer to the fluid-guiding layer.

[0018] Specifically, in step S1, the heating temperature is 210~240℃; the melt is pressurized and spun into nascent fibers at a pressure of 3~4MPa; and a hot rolling mill is used to perform thermal bonding at 100~140℃ and a linear pressure of 50~50MPa, so that the fine fibers are interwoven and bonded together.

[0019] Specifically, in step S2, the fibers after opening and mixing are conveyed to a carding machine for carding. The working roller speed is 90~130m / min and the cylinder speed is 1000~1100m / min, so that most of the fibers are arranged in the direction of machine output, and the number of fibers in the web is 6~6.5 in the longitudinal / transverse direction. The processed web is then placed in an oven at 120~140℃ for hot air penetration bonding.

[0020] Specifically, in step S3, water-based acrylic pressure-sensitive adhesive is first applied to the rougher side of the flow-guiding layer by coating, and then bonded to the rougher side of the skin-friendly layer. The two are then pressed together by a laminating machine to obtain a non-woven fabric.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. The nonwoven fabric with a multi-level gradient structure and its preparation method of the present application are designed to have a skin-friendly layer and a flow-guiding layer. The flow-guiding layer is more hydrophilic than the skin-friendly layer. The skin-friendly layer is a non-hydrophilic end or a weakly hydrophilic end, and the flow-guiding layer is a hydrophilic end or a strongly hydrophilic end. Under the action of wettability gradient and gravity, liquid can flow from the weakly hydrophilic skin-friendly layer to the hydrophilic end of the strongly hydrophilic flow-guiding layer, reducing liquid back-seepage to the surface of the skin-friendly layer, thereby significantly reducing back-seepage and improving dryness.

[0023] 2. The nonwoven fabric of this application can be used in products such as diapers, and the addition of antibacterial fibers and indicator fibers enhances the antibacterial ability and diaper indicator ability of the nonwoven fabric. Detailed Implementation

[0024] The embodiments of the present invention will be described below with reference to relevant examples. The embodiments of the present invention are not limited to the following examples, and the present invention relates to relevant necessary components in this technical field, which should be regarded as well-known technology in this technical field and can be known and mastered by those skilled in this technical field.

[0025] Example 1

[0026] This embodiment provides a nonwoven fabric with a multi-level gradient structure, including a skin-friendly layer and a flow-guiding layer. The skin-friendly layer is the non-hydrophilic end, and the flow-guiding layer is the hydrophilic end. The mass ratio of the skin-friendly layer to the flow-guiding layer is 1:2~3. Under the action of wettability gradient and gravity, liquid can flow from the non-hydrophilic end of the skin-friendly layer to the hydrophilic end of the flow-guiding layer, achieving the effect of liquid infiltration.

[0027] The skin-friendly layer is made of finely woven fibers laid in multiple layers. The fine fibers are made of polypropylene polymer, softening masterbatch, and additives, with a fiber denier of 1.6~1.8D and a mass ratio of 97% polypropylene polymer, 2.9% softening masterbatch, and 0.1% additives. The carrier of the softening masterbatch is polypropylene homopolymer, and the additive is oleamide. The main active ingredient is oleamide. Through the intervention of oil molecules, the intermolecular forces between macromolecular chain segments are weakened, making the chain segments easier to move and thus making the skin-friendly layer softer.

[0028] The manufacturing process of the skin-friendly layer is as follows: The polypropylene polymer and softening masterbatch, in the above-mentioned mass ratio, are drawn into a screw extruder and heated to a temperature of 210-240℃. The molten melt is then filtered, metered, and fed into the spinning box for uniform mixing and distribution into the spinneret. The melt is then pressurized and spun into nascent fibers at a pressure of 3-4 MPa. These nascent fibers are then stretched by a drawing device to obtain fine fibers with a denier of approximately 1.6-1.8D, which are then guided onto a forming screen. To obtain finer fibers at the same basis weight, resulting in a higher fiber distribution density and stronger pore size in the skin-friendly layer, the mass ratio of the upper and lower layers can be set to 1:2. This makes the fiber density of the upper layer lower than that of the lower layer, creating a differential capillary effect and further accelerating the liquid penetration of the skin-friendly layer. Simultaneously, because the upper layer of the skin-friendly layer has a lower density than the lower layer, the capillary effect of the liquid from bottom to top is weakened, effectively reducing backflow and improving dryness. Two spinning machines are set up to spin simultaneously, and the resulting fibers are laid on a web forming curtain and conveyed to a hot rolling mill for thermal bonding at 100~140℃ and 50~50MPa linear pressure, so that the fine fibers are interwoven and bonded to form a skin-friendly layer.

[0029] The flow guiding layer is made of coarse fibers, antibacterial fibers, and indicator fibers interwoven together. The number distribution ratio of coarse fibers, antibacterial fibers, and indicator fibers is 20~50:1~2:1. The denier of coarse fibers, antibacterial fibers, and indicator fibers is 2~2.2D. The coarse fibers are arranged longitudinally, while the antibacterial fibers and indicator fibers are arranged transversely.

[0030] The coarse fiber is composed of the following components by weight percentage: 45% polyethylene polymer, 54.8% polyester polymer, and 0.2% hydrophilic finishing agent. The main active ingredient of the hydrophilic finishing agent is glyceryl stearate, which increases the hygroscopicity and water absorption of the fiber by reducing the surface tension of the fiber surface. The nonwoven fabric treated with the hydrophilic finishing agent has strong penetration ability and liquid surface diffusion. The antibacterial fiber is composed of the following components by weight percentage: 45% polyethylene polymer, 54.8% polyester polymer, and 0.2% silver ion antibacterial agent. The antibacterial fiber has excellent antibacterial properties and can resist the adhesion of bacteria on clothing, thus keeping users away from germs. The indicator fiber is made by mixing and spinning 45% polyethylene polymer and 55% polyester polymer, then soaking in litmus solution and drying. It uses the principle that uric acid changes color when it comes into contact with an indicator to remind parents to change the diaper by changing the color.

[0031] The fabrication process of the flow guide layer is as follows:

[0032] ① Production of coarse fibers: A two-component fiber composed of polyethylene polymer and polyester polymer is opened and mixed, and then spun through a spinning machine to form a fiber structure with a high-melting-point polyester core layer and a low-melting-point polyethylene sheath layer. The fiber cross-section forms a concentric circular structure with a denier of 2~2.2D. Further, fibers with high wet modulus and good elasticity can be used as raw materials to improve wet stability. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130m / min, and the cylinder speed to 1000~1100m / min, so that most of the fibers are aligned in the machine's output direction, resulting in a fiber count of approximately 6~6.5 fibers / mm in the web. After carding, the fibers are stripped by the stripping roller and transferred to the doffer, output in a longitudinally aligned manner. A hydrophilic finishing agent is then sprayed onto the coarse fibers for hydrophilic treatment.

[0033] ② Production of antibacterial fibers: Polyester polymer and silver ion antibacterial agent are mixed evenly, and then mixed with polyethylene polymer to form a two-component fiber. The mixture is then spun through a spinning machine to form a fiber structure with a high-melting-point polyester core layer and a low-melting-point polyethylene sheath layer. The fiber cross-section forms a concentric circular structure with a denier of 2~2.2D. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130m / min, and the cylinder speed is 1000~1100m / min, so that most of the fibers are aligned with the output direction of the machine, and the number of fibers in the web is approximately 0.2~0.25 fibers / mm in the transverse direction. After carding, the fibers are stripped by the stripping roller and transferred to the doffer, and output in a transverse arrangement to produce antibacterial fibers.

[0034] ③ Production of indicator fibers: A two-component fiber composed of polyethylene and polyester polymers is opened and mixed, then spun using a spinning machine to form a fiber structure with a high-melting-point polyester core and a low-melting-point polyethylene sheath. The fiber cross-section forms a concentric circular structure, with a denier of 2~2.2D. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130 m / min, and the cylinder speed to 1000~1100 m / min, ensuring that most of the fibers are aligned in the machine's output direction. The fiber count in the web is approximately 0.2~0.25 fibers / mm laterally. After carding, the fibers are stripped by a stripping roller and transferred to a doffer, outputting in a laterally aligned manner. They are then impregnated in litmus solution for 30 minutes, and finally dried to produce indicator fibers.

[0035] ④ The coarse fibers are arranged longitudinally, and the antibacterial fibers and indicator fibers are arranged transversely to form a fiber web. The web is then placed in an oven at 120~140℃ for hot air penetration and bonding. By utilizing the low melting point of the outer layer, a portion of the outer layer melts, and the outer layers between the fibers bond together, thus achieving a web-fixing effect and forming a flow-guiding layer.

[0036] Fabrication of nonwoven fabrics with multi-level gradient structures:

[0037] The skin-friendly layer and the flow-guiding layer are bonded together using a water-based acrylic pressure-sensitive adhesive applied to the flow-guiding layer at a rate of 1-2 g / m². The skin-friendly layer is then placed on top of the water-based acrylic pressure-sensitive adhesive, and the two layers are pressed together using a laminating machine to obtain a multi-gradient nonwoven fabric. The water-based acrylic pressure-sensitive adhesive used here has good bonding performance, dries quickly, is non-toxic and odorless, and possesses excellent pressure-sensitive properties. Because the flow-guiding layer has a loose structure, it allows for better adhesive application; therefore, the adhesive is applied to the rougher side of the flow-guiding layer and then bonded to the rougher side of the skin-friendly layer.

[0038] Test 1: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². Liquid penetration time and backflow were measured according to the test standards GB / T 24218.13 and GB / T 28004.1. The results were compared with those of hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 1 below:

[0039] Table 1 Test Results

[0040]

[0041] Test 2: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². Antibacterial performance was tested according to the test standard of GB / T 20944.2-2007 "Evaluation of Antibacterial Properties of Textiles". The results were compared with those of single-material hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 2 below.

[0042] Table 2 Test Results

[0043]

[0044] Test 3: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². The nonwoven fabric with the multi-gradient structure was wetted with urine (Ph=5.5), and its color change was tested. It was compared with hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 3 below:

[0045] Table 3 Test Results

[0046]

[0047] As can be seen from the test results in Tables 1-3 above, the multi-level gradient structure nonwoven fabric produced in this embodiment reduces the average amount of backflow by about 43% compared with the hydrophilic and fluffy nonwoven fabric made of a single material. This significantly reduces backflow, improves dryness, and also has good antibacterial properties. Furthermore, it utilizes the principle that uric acid changes color when it comes into contact with an indicator, so that when the diaper is made, the color change reminds parents to change the diaper.

[0048] Example 2

[0049] This embodiment provides a nonwoven fabric with a multi-level gradient structure, including a skin-friendly layer and a flow-guiding layer. The skin-friendly layer is a weakly hydrophilic end, and the flow-guiding layer is a strongly hydrophilic end. The mass ratio of the skin-friendly layer to the flow-guiding layer is 1:2~3. Under the action of wettability gradient and gravity, liquid can flow from the weakly hydrophilic end of the skin-friendly layer to the strongly hydrophilic end of the flow-guiding layer, achieving the effect of liquid infiltration.

[0050] The skin-friendly layer is made of finely woven fibers laid in multiple layers. The fine fibers are made of polypropylene polymer, softening masterbatch, and a weak hydrophilic finishing agent. The fiber denier is 1.6~1.8D, and the mass ratio is: 97% polypropylene polymer, 2.5% softening masterbatch, and 0.5% weak hydrophilic finishing agent. The carrier of the softening masterbatch is polypropylene homopolymer, and the main active ingredient of the weak hydrophilic finishing agent is glyceryl stearate. By reducing the surface tension of the fiber surface, it increases the hygroscopicity and water absorption of the fiber. The nonwoven fabric treated with the weak hydrophilic finishing agent has good vertical penetration of liquids, does not diffuse on the surface, and only diffuses after penetrating to the lower layers.

[0051] The manufacturing process of the skin-friendly layer is as follows: The polypropylene polymer and softening masterbatch, in the above-mentioned mass ratio, are drawn into a screw extruder and heated to a temperature of 210-240℃. The molten melt is then filtered, metered, and fed into a spinning box for uniform mixing and distribution into the spinneret. The melt is then pressurized and spun into nascent fibers at a pressure of 3-4 MPa. These nascent fibers are then stretched by a drawing device to obtain fine fibers with a denier of approximately 1.6-1.8D, which are then guided onto a forming screen. To obtain finer fibers at the same basis weight, resulting in a higher fiber distribution density and stronger pore size in the skin-friendly layer, the mass ratio of the upper and lower layers can be set to 1:1.5-2, making the fiber density of the upper layer lower than the lower layer. This creates a differential capillary effect, further accelerating the liquid penetration of the skin-friendly layer. Simultaneously, because the upper layer of the skin-friendly layer has a lower density than the lower layer, the capillary effect of the liquid from bottom to top is weakened, effectively reducing backflow and improving dryness. Two spinning machines are set up to spin simultaneously, and the resulting fibers are laid in layers on a forming screen and conveyed to a hot rolling mill for thermal bonding at 100~140℃ and 50~50MPa linear pressure. This allows the fine fibers to be interwoven and bonded together. The fibers are then sprayed with a hydrophilic finishing agent to form a skin-friendly layer.

[0052] The flow guiding layer is made of coarse fibers, antibacterial fibers, and indicator fibers interwoven together. The number distribution ratio of coarse fibers, antibacterial fibers, and indicator fibers is 20~50:1~2:1. The denier of coarse fibers, antibacterial fibers, and indicator fibers is 2~2.2D. The coarse fibers are arranged longitudinally, while the antibacterial fibers and indicator fibers are arranged transversely.

[0053] The coarse fiber is composed of the following components by weight percentage: 45% polyethylene polymer, 54.8% polyester polymer, and 0.2% hydrophilic finishing agent. The main active ingredient of the hydrophilic finishing agent is glyceryl stearate, which increases the hygroscopicity and water absorption of the fiber by reducing the surface tension of the fiber surface. The nonwoven fabric treated with the hydrophilic finishing agent has strong penetration ability and liquid surface diffusion. The antibacterial fiber is composed of the following components by weight percentage: 45% polyethylene polymer, 54.8% polyester polymer, and 0.2% copper ion antibacterial agent. The antibacterial fiber has excellent antibacterial properties and can resist the adhesion of bacteria on clothing, thus keeping users away from germs. The indicator fiber is made by mixing and spinning 45% polyethylene polymer and 55% polyester polymer, then soaking in litmus solution and drying. It uses the principle that uric acid changes color when it comes into contact with an indicator to remind parents to change the diaper by changing the color.

[0054] The fabrication process of the flow guide layer is as follows:

[0055] ① Production of coarse fibers: A two-component fiber composed of polyethylene polymer and polyester polymer is opened and mixed, and then spun through a spinning machine to form a fiber structure with a high-melting-point polyester core layer and a low-melting-point polyethylene sheath layer. The fiber cross-section forms a concentric circular structure with a denier of 2~2.2D. Further, fibers with high wet modulus and good elasticity can be used as raw materials to improve wet stability. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130m / min, and the cylinder speed to 1000~1100m / min, so that most of the fibers are aligned in the machine's output direction, resulting in a fiber count of approximately 6~6.5 fibers / mm in the web. After carding, the fibers are stripped by the stripping roller and transferred to the doffer, output in a longitudinally aligned manner. A hydrophilic finishing agent is then sprayed onto the coarse fibers for hydrophilic treatment.

[0056] ② Production of antibacterial fibers: Polyester polymer and copper ion antibacterial agent are mixed evenly, and then mixed with polyethylene polymer to form a two-component fiber. The mixture is then spun through a spinning machine to form a fiber structure with a high-melting-point polyester core layer and a low-melting-point polyethylene sheath layer. The fiber cross-section forms a concentric circular structure with a denier of 2~2.2D. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130m / min, and the cylinder speed is 1000~1100m / min, so that most of the fibers are aligned with the output direction of the machine, and the number of fibers in the web is approximately 0.2~0.25 fibers / mm in the transverse direction. After carding, the fibers are stripped by the stripping roller and transferred to the doffer, and output in a transverse arrangement to produce antibacterial fibers.

[0057] ③ Production of indicator fibers: A two-component fiber composed of polyethylene and polyester polymers is opened and mixed, then spun using a spinning machine to form a fiber structure with a high-melting-point polyester core and a low-melting-point polyethylene sheath. The fiber cross-section forms a concentric circular structure, with a denier of 2~2.2D. The opened and mixed fibers are then fed into a carding machine for carding. The working roller speed is adjusted to 90~130 m / min, and the cylinder speed to 1000~1100 m / min, ensuring that most of the fibers are aligned in the machine's output direction. The fiber count in the web is approximately 0.2~0.25 fibers / mm laterally. After carding, the fibers are stripped by a stripping roller and transferred to a doffer, outputting in a laterally aligned manner. They are then impregnated in litmus solution for 30 minutes, and finally dried to produce indicator fibers.

[0058] ④ The coarse fibers are arranged longitudinally, and the antibacterial fibers and indicator fibers are arranged transversely to form a fiber web. The web is then placed in an oven at 120~140℃ for hot air penetration and bonding. By utilizing the low melting point of the outer layer, a portion of the outer layer melts, and the outer layers between the fibers bond together, thus achieving a web-fixing effect and forming a flow-guiding layer.

[0059] Fabrication of nonwoven fabrics with multi-level gradient structures:

[0060] The skin-friendly layer and the flow-guiding layer are bonded together using a water-based acrylic pressure-sensitive adhesive applied to the flow-guiding layer at a rate of 1-2 g / m². The skin-friendly layer is then placed on top of the water-based acrylic pressure-sensitive adhesive, and the two layers are pressed together using a laminating machine to obtain a multi-gradient nonwoven fabric. The water-based acrylic pressure-sensitive adhesive used here has good bonding performance, dries quickly, is non-toxic and odorless, and possesses excellent pressure-sensitive properties. Because the flow-guiding layer has a loose structure, it allows for better adhesive application; therefore, the adhesive is applied to the rougher side of the flow-guiding layer and then bonded to the rougher side of the skin-friendly layer.

[0061] Test 1: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². Liquid penetration time and backflow were measured according to the test standards GB / T 24218.13 and GB / T 28004.1. The results were compared with those of hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 4 below.

[0062] Table 4 Test Results

[0063]

[0064] Test 2: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². Antibacterial performance was tested according to the test standard of GB / T 20944.2-2007 "Evaluation of Antibacterial Properties of Textiles". The results were compared with those of single-material hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 5 below:

[0065] Table 5 Test Results

[0066]

[0067] Test 3: The nonwoven fabric with a multi-gradient structure produced by the above method has a basis weight of 20~28 g / m². The nonwoven fabric with the multi-gradient structure was wetted with urine (Ph=5.5), and its color change was tested. It was compared with hydrophilic fluffy nonwoven fabric and hydrophilic thin nonwoven fabric of the same basis weight. The test results are recorded in Table 6 below:

[0068] Table 6 Test Results

[0069]

[0070] As can be seen from the test results in Tables 4-6 above, the multi-level gradient structure nonwoven fabric produced in this embodiment reduces the average amount of backflow by about 41% compared with the hydrophilic and fluffy nonwoven fabric made of a single material. This significantly reduces backflow, improves dryness, and also has good antibacterial properties. Furthermore, it utilizes the principle of uric acid changing color when it encounters an indicator to remind parents to change diapers through color changes when the diapers are made.

[0071] Referring to the test results in Tables 1 and 6 above, and comparing the nonwoven fabrics made in Examples 1 and 2 with the hydrophilic thin nonwoven fabric made of a single material, it can be found that Example 1 has the least amount of backflow, followed by Example 2 and the hydrophilic thin nonwoven fabric, with the difference between each pair being within 5%.

[0072] Based on the comparison of the liquid penetration time of the three, the average liquid penetration time of the nonwoven fabric prepared in Example 2 is slightly faster, followed by the hydrophilic thin nonwoven fabric, the nonwoven fabric prepared in Example 1, and the hydrophilic fluffy nonwoven fabric. The difference between each pair is within 5%.

[0073] In summary, the liquid penetration time and backflow amount of Examples 1 and 2 are comparable to those of the hydrophilic thin nonwoven fabric, with differences within 5%. Compared with the hydrophilic fluffy nonwoven fabric, the liquid penetration time of Examples 1 and 2 is slightly faster, but the backflow amount is significantly reduced, by about 41% to 43%.

[0074] Therefore, the gradient structure nonwoven fabric produced by both implementation methods possesses the advantages of both hydrophilic thin nonwoven fabrics and hydrophilic fluffy nonwoven fabrics. For hydrophilic thin nonwoven fabrics, it makes the hand feel fluffy, soft, and cotton-like; for hydrophilic fluffy nonwoven fabrics, it significantly reduces backflow and improves dryness. It is possible to produce a multi-level gradient structure nonwoven fabric that is fluffy, soft, cotton-like, absorbs quickly, and has low backflow.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nonwoven fabric with a multi-level gradient structure, characterized in that, It includes a skin-friendly layer and a diffusing layer, wherein the diffusing layer is more hydrophilic than the skin-friendly layer, and the mass ratio of the skin-friendly layer to the diffusing layer is 1:2~3; The skin-friendly layer is composed of multiple layers of fine fibers, which are composed of the following components in the indicated mass ratios: 96-98% polypropylene polymer and 2-4% softening masterbatch; The skin-friendly layer is configured as a two-layer structure, wherein the mass of the upper layer is less than that of the lower layer, and the fiber density of the upper layer is less than that of the lower layer; the mass ratio of the upper layer to the lower layer is 1:1.5~2. The flow-guiding layer is composed of interwoven coarse fibers, antibacterial fibers, and indicator fibers. The coarse fibers consist of the following components in the indicated mass ratio: 40-50% polyethylene polymer, 50-60% polyester polymer, and 0.2-0.3% hydrophilic finishing agent. The fine fibers have a denier of 1.6 to 1.8D, and the coarse fibers have a denier of 2 to 2.2D. The ratio of the number of coarse fibers, antibacterial fibers, and indicator fibers is 20~50:1~2:1, and the coarse fibers are arranged longitudinally, while the antibacterial fibers and indicator fibers are arranged transversely. The preparation method of nonwoven fabric includes the following steps: S1 Skin-Friendly Layer Production: Polypropylene polymer and soft masterbatch are mixed evenly and then transferred to a screw extruder for heating. The heated and molten melt is filtered, metered and evenly mixed and distributed into a spinneret. The melt is then pressurized and spun into nascent fibers. The nascent fibers are stretched by a stretching device to obtain fine fibers and guided onto a web forming curtain. After thermal bonding, a skin-friendly layer is formed. The S2 flow guide layer is made by opening and mixing two-component fibers composed of polyethylene polymer and polyester polymer. The fibers are spun by a spinning machine, with high-melting-point polyester as the core layer and low-melting-point polyethylene as the sheath layer. The fiber cross-section forms a concentric circular structure. After carding, the fibers are stripped by stripping rollers and transferred to the carding machine doffer. They are output as a fiber web and sprayed with hydrophilic finishing agent multiple times for hydrophilic treatment. The treated fiber web is then heated and bonded to obtain coarse fibers, which are then interwoven with antibacterial fibers and indicator fibers to form the flow guide layer. S3 bonding: bonding the skin-friendly layer to the flow-guiding layer; In step S1, the heating temperature is 210~240℃; the melt is pressurized and spun into nascent fibers at a pressure of 3~4MPa; a hot rolling mill is used to perform thermal bonding at 100~140℃ and a linear pressure of 50MPa, so that the fine fibers are interwoven and bonded together. In step S2, the opened and mixed fibers are fed into a carding machine for carding. The working roller speed is 90~130m / min and the cylinder speed is 1000~1100m / min, so that most of the fibers are arranged in the direction of machine output, and the number of fibers in the web is 6~6.5 fibers / mm in the longitudinal direction. The processed web is then placed in an oven at 120~140℃ for hot air penetration bonding. In step S3, water-based acrylic pressure-sensitive adhesive is first applied to the rougher side of the flow-guiding layer by coating, and then bonded to the rougher side of the skin-friendly layer. The two are then pressed together by a laminating machine to obtain a non-woven fabric.

2. The nonwoven fabric with a multi-level gradient structure according to claim 1, characterized in that, The soft masterbatch is a polypropylene homopolymer, and the fine fibers also include an additive in a mass ratio of 0.01~0.5%, which is oleic acid amide.

3. The nonwoven fabric with a multi-level gradient structure according to claim 1, characterized in that, The antibacterial fiber is made by spinning an inorganic antibacterial agent containing silver, copper, or zinc ions into the fiber raw material.

4. The nonwoven fabric with a multi-level gradient structure according to claim 1, characterized in that, The indicator fiber is made by impregnating the fiber in litmus solution and then drying it.

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