A composite surface layer of sanitary products and preparation method thereof

Abstract

The present invention provides a composite surface layer of sanitary products and a preparation method thereof, belonging to the technical field of sanitary napkins, the composite surface layer of sanitary products comprises a skin-friendly surface layer, an absorbent and a leak-proof bottom layer, the skin-friendly surface layer is a mesh elastic non-woven fabric made of spiral fibers by a hot air process, the mesh elastic non-woven fabric is provided with 3D embossing, the absorbent comprises a substrate, a water-absorbing powder fixed to the substrate by an adhesive, the water-absorbing powder comprises the following components by weight: 40-44 parts of sodium polyacrylate, 5-7 parts of polyacrylamide and 6-8 parts of modified fiber; the modified fiber is a core-shell structure with a smooth surface. The present invention ensures that the composite surface layer of sanitary products has excellent water absorption and water retention capabilities.

Description

Technical Field

[0001] The invention belongs to the technical field of sanitary napkins, and in particular relates to a composite surface layer of a sanitary product and a preparation method thereof. Background Art

[0002] Sanitary napkins are also called sanitary napkins. They are mainly made of cotton pulp and high molecular absorbents. They are used to absorb the menstrual blood that flows out of the vagina during menstruation. The structure of sanitary napkins can be divided into three parts: skin-friendly surface layer, absorbent body and leak-proof bottom layer. At the same time, each layer of material is bonded with hot melt adhesive.

[0003] Existing absorbent materials generally use polymer water-absorbing materials such as sodium polyacrylate. When sodium polyacrylate meets water, it dissociates into positively charged low-molecular ions and negatively charged polymer ions. Due to the mutual electrical repulsion between the negatively charged polymer ions, the polymer network bundles gradually stretch out from the mutually entangled state, thereby causing osmotic pressure inside and outside the network structure, and water molecules diffuse into the network structure in an osmotic manner to form a sol. The gel formed by sodium polyacrylate absorbing water has excellent water retention capacity, can retain moisture, and is not easy to lose.

[0004] However, sodium polyacrylate hydrogel is composed of a sodium polyacrylate polymer network, which is formed by chemical or physical cross-linking. This cross-linked network is relatively weak and cannot effectively resist external force and swelling pressure. It is easy to break or shatter under the action of external force or swelling pressure, making it easy to lose water and affect the use effect. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a composite surface layer of a sanitary product and a preparation method thereof, so as to ensure that the composite surface layer of the sanitary product has excellent water absorption and water retention capabilities.

[0006] In order to achieve the above-mentioned purpose, in a first aspect, the present invention provides a composite surface layer of a sanitary product, comprising a skin-friendly surface layer, an absorbent body and a leak-proof bottom layer, wherein the skin-friendly surface layer is a mesh elastic non-woven fabric made of spiral fibers by a hot air process, and the mesh elastic non-woven fabric is provided with 3D embossing, and the absorbent body comprises a substrate and a water-absorbing powder fixed to the substrate by an adhesive, wherein the water-absorbing powder comprises the following components by weight: 40-44 parts of sodium polyacrylate, 5-7 parts of polyacrylamide and 6-8 parts of modified fiber; the modified fiber is a core-shell structure with a smooth surface.

[0007] Furthermore, the preparation method of the modified fiber is as follows:

[0008] A1. Weigh sodium carboxymethyl cellulose, graphene and chitosan in a mass ratio of 1:(3-5):(4-6) respectively;

[0009] A2, prepare the chitosan weighed in A1 into a solution with a mass fraction of 6-8% with deionized water;

[0010] A3, adding the graphene weighed in A1 to the solution 1 obtained in A2, stirring, and ultrasonically dispersing to obtain a solution 2;

[0011] A4, prepare the sodium carboxymethyl cellulose weighed in A1 into a solution with a mass fraction of 1-1.5% with deionized water;

[0012] A5, stirring the solution 3 obtained in A4, and vertically squeezing the solution 2 obtained in A3 into the solution 3 with a syringe, filtering, and drying to obtain the modified fiber.

[0013] Furthermore, in A1, sodium carboxymethyl cellulose, graphene and chitosan are weighed in a mass ratio of 1:4:5.

[0014] Furthermore, in A2, the mass fraction of solution 1 is 7%.

[0015] Furthermore, in A4, the mass fraction of solution three is 1.2%.

[0016] Furthermore, in A5, the stirring speed is 100-115 r / min, and the speed of the syringe extruding the second solution is 460-480 mL / min.

[0017] Furthermore, the polyacrylamide is anionic polyacrylamide.

[0018] Furthermore, the substrate is non-woven fabric.

[0019] In a second aspect, the present invention provides a method for preparing the above-mentioned composite surface layer of sanitary products, comprising the following steps:

[0020] S1, mixing sodium polyacrylate, polyacrylamide and modified fiber to obtain water-absorbing powder;

[0021] S2, using an adhesive to fix the water-absorbing powder obtained in S1 on a substrate to obtain an absorbent;

[0022] S3, applying glue to one side of the water-absorbing body obtained in S2 and then covering it with a skin-friendly surface layer, and applying glue to the other side and then adhering it to a leak-proof bottom layer, so as to obtain the composite surface layer of the sanitary product.

[0023] This application has the following beneficial effects:

[0024] 1. The present invention introduces anionic polyacrylamide, which can produce ion adsorption with sodium polyacrylate in aqueous solution to form a complex. This complex increases the cross-linking points of the network structure through the interaction between anionic polyacrylamide and sodium polyacrylate, making the cross-linking points of the network structure more dense, which helps to enhance the liquid absorption and fixation capacity (water absorption and water retention capacity); on this basis, the modified fiber is introduced and evenly dispersed to enhance the overall binding force, especially to play the role of reinforcing the dense cross-linking points and effectively dispersing stress, further enhancing the liquid absorption and fixation capacity (water absorption and water retention capacity).

[0025] 2. In the preparation of modified fibers, a core-shell structure is formed with sodium carboxymethyl cellulose as the shell layer and a mixture of graphene and chitosan as the core layer. Chemical cross-linking occurs between sodium carboxymethyl cellulose and chitosan through electrostatic force or hydrogen bonding to further stabilize the core-shell structure. During the filtration and drying process, the fibers gradually solidify, and finally form core-shell fibers with a smooth surface and a compact structure.

[0026] Although sodium polyacrylate can form a water-absorbing network structure, its own cross-linking points are relatively sparse, resulting in insufficient mechanical strength of the overall network structure; when modified fibers with smooth surfaces are added to this sparse cross-linking network, the surface lacks sufficient adhesion points, so that the modified fibers and the sodium polyacrylate network structure are not tightly bonded; and these modified fibers with smooth surfaces are prone to stress concentration when subjected to force, especially when external forces act on the material, the stress cannot be effectively transferred from the matrix to the fiber, causing the interface between the fiber and the matrix to become the starting point of fracture. In this way, the addition of modified fibers will make the water-absorbing network structure formed by sodium polyacrylate more likely to break and shatter under external forces or swelling pressure, making it easy for water to be lost and reducing the water retention capacity;

[0027] The interaction between anionic polyacrylamide and sodium polyacrylate significantly increases the density of cross-linking points in the network structure, forming a more stable and dense composite network structure. The addition of modified fibers can produce stronger binding force in this composite network structure. Moreover, the modified fibers combined at dense cross-linking points help to disperse and absorb energy more effectively when subjected to stress, reducing the possibility of breakage, thereby further improving the water retention capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 , a comparative trend chart of three test data of the absorption speed (time) of the products obtained in Examples 1-5 of the present invention;

[0029] Figure 2 , a trend chart comparing the absorption speed (time) of the products obtained in Example 1 of the present invention and Comparative Examples 1-4 for three times;

[0030] Figure 3, a comparative trend chart of the water absorption rate test data of the products obtained in Examples 1-5 of the present invention and Comparative Examples 1-4;

[0031] Figure 4 , a comparative trend chart of the re-seepage test data of the products obtained in Examples 1-5 of the present invention and Comparative Examples 1-4. DETAILED DESCRIPTION

[0032] The present application is further described in detail below in conjunction with embodiments.

[0033] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0034] Embodiment 1: A composite surface layer of a sanitary product, including three layers: an upper, middle and lower layer, which are a skin-friendly surface layer, an absorbent body and a leak-proof bottom layer. The skin-friendly surface layer is a mesh elastic non-woven fabric made of spiral fibers by a hot air process, and the mesh elastic non-woven fabric is provided with 3D embossing. Specifically, the preparation steps of the skin-friendly surface layer are as follows: the first step is to select spiral short fibers, specifically polypropylene fibers, which have high elasticity; the second step is to use the existing hot air process to melt and fix the contact points between the fibers to form a mesh elastic non-woven fabric; the third step is to use the existing technology to make 3D embossing on the mesh elastic non-woven fabric to increase the height of the mesh elastic non-woven fabric and enhance skin-friendly comfort. Among them, the polypropylene fiber was purchased from Huimin County Taili Chemical Fiber Products Co., Ltd.

[0035] The absorbent includes a substrate and a water-absorbing powder fixed to the substrate by an adhesive. The substrate is a polypropylene non-woven fabric. The adhesive is a hot melt adhesive (7560-2W white) purchased from Minli New Materials (Guangzhou) Co., Ltd. The hot melt adhesive is compatible with the water-absorbing powder and maintains a certain degree of softness and elasticity after curing, and can adapt to the expansion and contraction needs of the material.

[0036] The water-absorbing powder includes components by weight: 42 parts of sodium polyacrylate, 6 parts of anionic polyacrylamide and 7 parts of modified fiber. The three are mixed to obtain. Among them, sodium polyacrylate (80-100 mesh) is purchased from Shandong Ouyuan Bioengineering Co., Ltd. Anionic polyacrylamide, Aisen brand, model FLOPAM FO 4490 SSH, is purchased from Tianjin Biboyuan Technology Development Co., Ltd. The modified fiber is a core-shell structure with a smooth surface.

[0037] The preparation method of the modified fiber is as follows:

[0038] A1. Weigh sodium carboxymethyl cellulose, graphene and chitosan in a mass ratio of 1:4:5. Sodium carboxymethyl cellulose (content 98%) was purchased from Zhengzhou Xuxin Chemical Co., Ltd. Graphene was white graphene oxide powder (TFC-150) purchased from Shaoxing Weiqin Textile Auxiliary Co., Ltd. Chitosan was purchased from Jiangsu Gubei Biotechnology Co., Ltd.

[0039] A2. Prepare the chitosan weighed in A1 into a 7% solution with deionized water. Specific operation: Add acetic acid to water to prepare a 15% acetic acid solution, thereby creating an acidic environment for dissolving chitosan. Add chitosan to an acetic acid solution twice the mass of chitosan, stir thoroughly until completely dissolved, then add deionized water to make up the volume, stir magnetically to ensure that the chitosan is completely dispersed and dissolved, and obtain a 7% chitosan solution.

[0040] A3, add the graphene weighed by A1 to the solution 1 obtained by A2, stir, and ultrasonically disperse to obtain solution 2. Specific operation: First, slowly add graphene to the 7% chitosan solution to avoid local overconcentration and affect the final dispersion effect. Use a magnetic stirrer to perform preliminary stirring at a stirring speed of 50r / min for 30 minutes to ensure that the graphene powder is fully wetted and begins to disperse. Then, ultrasonic dispersion treatment is performed at a power of about 960 watts for 30 minutes. Ultrasonic treatment can effectively break the van der Waals force between graphene aggregates by generating high-frequency vibrations and local hot spots, thereby separating graphene aggregates into fewer layers or single-layer graphene nanosheets to achieve the purpose of dispersion. In addition, a power of about 960 watts will not cause damage to the graphene structure.

[0041] A4, use deionized water to prepare the sodium carboxymethyl cellulose weighed in A1 into a solution with a mass fraction of 1.2%. Specific operation: Pour the weighed sodium carboxymethyl cellulose powder into a container, first add 5% of the total amount of deionized water, use a magnetic stirrer to stir at a stirring speed of 70r / min for 20 minutes, and then slowly stir with a glass rod for a while to ensure that the sodium carboxymethyl cellulose powder is completely wetted and begins to dissolve. Then, slowly add the remaining deionized water, while continuing to stir, to ensure that the stirring is uniform, so that the sodium carboxymethyl cellulose powder is further completely dissolved to form a uniform colloidal solution, that is, a 1.2% sodium carboxymethyl cellulose solution.

[0042] A5, stir the solution three obtained by A4 at a stirring speed of 110r / min, and use a syringe to vertically squeeze the solution two obtained by A3 into the stirring solution three at an extrusion speed of 470mL / min, filter, and dry to obtain modified fiber. In the specific operation, use a syringe to vertically inject solution two into the stirring solution three from above container three. Keep the needle part of the syringe stable and completely immersed in the solution to prevent the solution from splashing or forming air pockets. Accurately control the extrusion speed of the syringe to 470 mL / min, and the constant injection speed helps the uniform mixing and reaction of the two solutions. Continue to stir at a speed of 110r / min during the injection process to ensure that solution two and solution three are fully mixed. The existing vacuum filtration device is used for filtration. A hot air drying oven is used for drying.

[0043] The preparation method of the composite surface layer of the sanitary product specifically comprises the following steps:

[0044] S1. Put sodium polyacrylate, polyacrylamide and modified fiber into a mixer and mix them well to obtain water-absorbing powder.

[0045] S2. The water-absorbing powder obtained in S1 is fixed on the substrate using an adhesive to ensure the strength and durability of the final product, thereby obtaining an absorbent. The mass of the water-absorbing powder used here is equal to the mass of the substrate. In the specific operation, the adhesive is evenly applied on the substrate, and then the water-absorbing powder is evenly spread on the adhesive-coated substrate, and the water-absorbing powder is firmly fixed on the substrate by pressurization / natural drying to form an absorbent.

[0046] S3, glue is applied on one side of the absorbent obtained in S2, and then the skin-friendly surface layer is coated, and glue is applied on the other side, and then the leak-proof bottom layer is adhered, so as to obtain the composite surface layer of the sanitary product. In the specific operation, glue is applied on one side of the absorbent, and then the skin-friendly surface layer material is covered. In other embodiments, cotton or soft non-woven fabric can also be selected to ensure smooth adhesion without bubbles. Glue is also applied on the other side of the absorbent, and then the leak-proof bottom layer material is adhered, and PE film is selected here to prevent liquid leakage.

[0047] Finally, the prepared composite surface layer of sanitary products is placed at room temperature to allow the glue to completely solidify and ensure that the layers are firmly bonded. The completed composite surface layer of sanitary products is then inspected for quality, including tests on bonding strength, water absorption, softness and other indicators to ensure that it meets the requirements of sanitary products.

[0048] Example 2: The difference between this example and Example 1 is that the preparation method of the modified fiber is as follows:

[0049] A1. Weigh sodium carboxymethyl cellulose, graphene and chitosan in a mass ratio of 1:3:4 respectively.

[0050] A2. Use deionized water to prepare a 6% solution of chitosan weighed in A1.

[0051] A3. Add the graphene weighed in A1 to solution 1 obtained in A2, stir, and disperse by ultrasonic to obtain solution 2.

[0052] A4. Use deionized water to prepare a 1% solution of sodium carboxymethyl cellulose weighed in A1.

[0053] A5, stirring the solution 3 obtained by A4 at a stirring speed of 100 r / min, and vertically extruding the solution 2 obtained by A3 into the stirring solution 3 with a syringe at an extrusion speed of 460 mL / min, filtering, and drying to obtain the modified fiber.

[0054] Example 3: The difference between this example and Example 1 is that the preparation method of the modified fiber is as follows:

[0055] A1. Weigh sodium carboxymethyl cellulose, graphene and chitosan in a mass ratio of 1:5:6 respectively.

[0056] A2. Use deionized water to prepare a solution with a mass fraction of 8% chitosan taken in A1.

[0057] A3. Add the graphene weighed in A1 to solution 1 obtained in A2, stir, and disperse by ultrasonic to obtain solution 2.

[0058] A4. Use deionized water to prepare a 1.5% mass fraction solution of sodium carboxymethyl cellulose weighed in A1.

[0059] A5, stirring the solution 3 obtained by A4 at a stirring speed of 115r / min, and vertically squeezing the solution 2 obtained by A3 into the stirred solution 3 with a syringe at an extrusion speed of 480mL / min, filtering, and drying to obtain the modified fiber.

[0060] Example 4: The difference between this example and Example 1 is that the water-absorbing powder comprises the following components by weight: 40 parts of sodium polyacrylate, 5 parts of anionic polyacrylamide and 6 parts of modified fiber.

[0061] Example 5: The difference between this example and Example 1 is that the water-absorbing powder comprises the following components by weight: 44 parts of sodium polyacrylate, 7 parts of anionic polyacrylamide and 8 parts of modified fiber.

[0062] Comparative Example 1: The difference between this comparative example and Example 1 is that in the preparation of the water-absorbing powder, the modified fiber is replaced by graphene.

[0063] Specifically, the water-absorbing powder includes the following components by weight: 42 parts of sodium polyacrylate, 6 parts of anionic polyacrylamide and 7 parts of graphene.

[0064] Comparative Example 2: The difference between this comparative example and Example 1 is that the modified fiber is deleted in the preparation of the water-absorbing powder.

[0065] Specifically, the water-absorbing powder comprises the following components by weight: 42 parts of sodium polyacrylate and 6 parts of anionic polyacrylamide.

[0066] Comparative Example 3: The difference between this comparative example and Example 1 is that anionic polyacrylamide is deleted in the preparation of the water-absorbing powder.

[0067] Specifically, the water-absorbing powder comprises the following components by weight: 42 parts of sodium polyacrylate and 7 parts of modified fiber.

[0068] Comparative Example 4: The difference between this comparative example and Example 1 is that in the preparation of the water-absorbing powder, the modified fiber and anionic polyacrylamide are deleted.

[0069] Specifically, the water-absorbing powder is sodium polyacrylate.

[0070] Test example: Test items: 1. Water absorption capacity, including absorption rate and water absorption ratio; 2. Water retention capacity, re-seepage amount.

[0071] Test objects: products obtained from Examples 1-5 and Comparative Examples 1-4.

[0072] Test method and content: 1. Absorption rate: Place the beaker with the test solution in a constant temperature water bath at 26℃ and heat it to a constant temperature of (23±1)℃ for the standard synthetic test solution; take each test object product, place it flat on the laboratory table, and place the experimental long tube at the 2 / 3 position of the front end of the product; take 5mL of the standard synthetic test solution and inject it into the long tube for the first time, record the time from the standard synthetic test solution contacting the product surface to the liquid in the long tube being completely absorbed into the product, and record the data; after an interval of 3 minutes, take 5mL of the standard synthetic test solution for the second time and perform the second test according to the above method, and record the data; after another interval of 3 minutes, take 5mL of the standard synthetic test solution for the third time and perform the third test according to the above method, and record the data. The shorter the time, the higher the absorption rate and the stronger the water absorption capacity.

[0073] Water absorption rate: Weigh each test object separately (mass before water absorption), then put each test object product into distilled water at a depth of 10 cm and a temperature of 23°C, with the surface facing up, gently press the test object product to make it completely immersed, lift it up after 60 seconds, make the test object product completely leave the water surface, hang it vertically for 90 seconds, weigh it (mass after water absorption), and calculate the water absorption rate; do three sets of parallel tests respectively, and calculate the average value. Water absorption rate = (mass after water absorption - mass before water absorption) / mass before water absorption. The larger the water absorption rate, the greater the surface water absorption and the stronger the water absorption capacity.

[0074] Re-seepage amount: After the absorption speed test of each test product is completed, remove the long experimental tube and leave it for 2 minutes; take an appropriate amount of filter paper, weigh it, and then return to zero, press the filter paper and 1 kg of pressure block flat on the surface of the absorption part of the test product, and let it stand for 10 seconds; after 10 seconds, remove the filter paper, weigh the weight of the filter paper, and record the data.

[0075] Test results: See Table 1.

[0076] Table 1. Test data of test examples (absorption rate, water absorption rate and rewet amount)

[0077]

[0078] Result analysis: Analyze examples 1-5 and combine the data in Table 1 and Figure 1 , Figure 3 and Figure 4 It can be seen that the product prepared by the present invention has both excellent water absorption capacity and water retention capacity. In terms of water absorption capacity, the absorption speed is fast, and the water absorption ratio is as high as 50.87 or more; in terms of water retention capacity, the re-seepage amount is as low as less than 0.54.

[0079] Analyze Example 1 and Comparative Examples 1-4 and combine the data in Table 1 and Figure 2-3 It can be seen that in the preparation of the water-absorbent powder of the present invention, the addition of anionic polyacrylamide based on sodium polyacrylate significantly improves the absorption rate and water absorption rate; and the addition of modified fibers can also improve the absorption rate and water absorption rate, especially the water absorption rate, which is relatively obvious; and there is a synergistic effect between the two, which can synergistically improve the water absorption capacity (absorption rate and water absorption rate) of the obtained product.

[0080] Analyze Example 1 and Comparative Examples 1-4 and combine the data in Table 1 and Figure 4 It can be seen that in the preparation of the water-absorbing powder of the present invention, the addition of anionic polyacrylamide based on sodium polyacrylate can improve the water retention capacity of the obtained product (the amount of re-seepage is reduced); on this basis (interaction between sodium polyacrylate and anionic polyacrylamide), the addition of modified fibers can further improve the water retention capacity (the amount of re-seepage is reduced).

[0081] If anionic polyacrylamide is not added (only sodium polyacrylate, and there is no interaction between sodium polyacrylate and anionic polyacrylamide), the addition of modified fibers will cause the water retention capacity to decrease instead of increase (increase in re-seepage). The inventor believes that this is because although sodium polyacrylate can form a water-absorbing network structure, its own cross-linking points are relatively sparse, resulting in insufficient mechanical strength of the overall network structure; and when modified fibers with smooth surfaces are added to this sparse cross-linked network, the surface lacks sufficient adhesion points, so that the bond between the modified fibers and the sodium polyacrylate network structure is not tight enough; and these modified fibers with smooth surfaces are prone to stress concentration when subjected to force, especially when external force acts on the material, the stress cannot be effectively transferred from the sodium polyacrylate network structure to the modified fibers, but instead causes the bonding interface between the modified fibers and the sodium polyacrylate network structure to become the starting point of fracture, resulting in easier fracture.

[0082] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0083] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A composite surface layer of a sanitary product, comprising a skin-friendly surface layer, an absorbent body and a leak-proof bottom layer, wherein the skin-friendly surface layer is a mesh elastic non-woven fabric made of spiral fibers by hot air process, and the mesh elastic non-woven fabric is provided with 3D embossing, characterized in that: The absorbent body comprises a substrate and a water-absorbing powder fixed to the substrate by an adhesive, wherein the water-absorbing powder comprises the following components by weight: 40-44 parts of sodium polyacrylate, 5-7 parts of polyacrylamide and 6-8 parts of modified fiber; The modified fiber is a core-shell structure with a smooth surface; The polyacrylamide is anionic polyacrylamide; The preparation method of the modified fiber is as follows: A1. Weigh sodium carboxymethyl cellulose, graphene and chitosan in a mass ratio of 1:(3-5):(4-6) respectively; A2, prepare the chitosan weighed in A1 into a solution with a mass fraction of 6-8% with deionized water; A3, adding the graphene weighed in A1 to the solution 1 obtained in A2, stirring, and ultrasonically dispersing to obtain a solution 2; A4, prepare the sodium carboxymethyl cellulose weighed in A1 into a solution with a mass fraction of 1-1.5% with deionized water; A5, stirring the solution 3 obtained in A4, and vertically squeezing the solution 2 obtained in A3 into the solution 3 with a syringe, filtering, and drying to obtain the modified fiber.

2. The composite surface layer of sanitary products according to claim 1, characterized in that: In A1, sodium carboxymethyl cellulose, graphene and chitosan are weighed in a mass ratio of 1:4:

5.

3. The composite surface layer of sanitary products according to claim 1, characterized in that: In A2, the mass fraction of solution 1 is 7%.

4. The composite surface layer of sanitary products according to claim 1, characterized in that: In A4, the mass fraction of solution three is 1.2%.

5. The composite surface layer of sanitary products according to claim 1, characterized in that: In A5, the stirring speed is 100-115 r / min, and the speed of the syringe extruding solution 2 is 460-480 mL / min.

6. The composite surface layer of sanitary products according to claim 1, characterized in that: The substrate is non-woven fabric.

7. A method for preparing the composite surface layer of a sanitary product according to any one of claims 1 to 6, characterized in that: The steps include: S1, mixing sodium polyacrylate, polyacrylamide and modified fiber to obtain water-absorbing powder; S2, using an adhesive to fix the water-absorbing powder obtained in S1 on a substrate to obtain an absorbent; S3, applying glue to one side of the water-absorbing body obtained in S2 and then covering it with a skin-friendly surface layer, and applying glue to the other side and then adhering it to a leak-proof bottom layer, so as to obtain the composite surface layer of the sanitary product.

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