A low-friction skin-friendly surface layer imitating the concave-convex texture of epidermis cells and a preparation method thereof

Abstract

The present application relates to the technical field of skin-friendly fabric manufacturing of sanitary products, and discloses a low-friction skin-friendly surface layer with epidermis cell concave-convex texture, which is used for paper diapers and sanitary napkins and is composed of a flexible fiber base material layer; the surface layer is provided with irregular circular protrusions and depressions simulating human epidermis, which are alternately and continuously distributed; the protrusions and depressions adopt smooth transition, the top end of the protrusion is a circular arc surface, and there is no sharp corner; the surface layer has low sliding friction coefficient, the surface is skin-friendly modified, the concave-convex size and distribution are uniform, and the surface layer has the characteristics of softness, skin-friendliness, air permeability and stability, and is suitable for long-term skin contact. The bionic epidermis structure greatly reduces friction, has soft and skin-friendly touch, effectively reduces skin irritation and redness, the surface layer is smooth and has no sharp corners, wearing is more comfortable, the structure is stable and has good air permeability, and the use safety and comfort of the sanitary product are improved.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing technology of skin-friendly fabrics for hygiene products, specifically relating to a low-friction skin-friendly surface layer with a textured surface resembling epidermal cells, which is used in diapers and sanitary napkins, and its preparation method. Background Technology

[0002] Disposable hygiene products are essential consumer goods for maternal and infant care and women's daily protection. The comfort of diapers and sanitary napkins in contact with the skin depends primarily on the surface structure of the layer that directly adheres to the skin. As the core functional component of hygiene products that comes into contact with the human body, the surface morphology, friction characteristics, and skin-friendly properties of the surface layer directly affect skin health and wearing experience, and are key indicators for measuring product quality.

[0003] Currently, most hygiene products on the market use non-woven fabric as the base material for their surface layer. The surface structure is primarily planar or features regular geometric textures, resulting in highly homogenized structural designs that fail to incorporate biomimetic optimization based on the natural physiological structure of human epidermis. Human epidermal cells exhibit a naturally irregular, uneven distribution with smooth transitions between cells. This native structure offers advantages such as low friction and high skin affinity, yet existing surface layers have not developed or applied this biomimetic characteristic. The raised structures of existing surface layers generally have sharp edges and corners, with obvious bends and steps at structural joints, failing to create a smooth contact interface. During daily activities, significant frictional resistance is generated between the surface layer and the skin. Prolonged contact can easily cause redness, dryness, and friction damage. For infants with sensitive skin and women during menstruation, the discomfort is even more pronounced.

[0004] Meanwhile, existing surface treatment processes are relatively basic, lacking sufficient surface softness and failing to effectively alleviate irritation from friction. Furthermore, the texture distribution is often discontinuous, with localized breaks and blank areas, making it difficult to create a uniform, low-friction contact interface. Breathability and skin feel cannot be simultaneously achieved. As consumer demand continues to upgrade, the market places higher demands on the comfort, safety, and skin-friendliness of hygiene products. Traditional surface structures can no longer meet high-end care needs. The industry urgently requires a biomimetic epidermal structure, low-friction, and highly skin-friendly surface technology to fundamentally address the industry pain points of friction irritation and a harsh feel, providing safer and more comfortable care options for people with sensitive skin. Summary of the Invention

[0005] To address the shortcomings of existing hygiene products, such as high coefficient of friction, harsh feel, easy skin irritation, and unreasonable texture, this invention provides a low-friction, skin-friendly surface layer that mimics the texture of epidermal cells and its preparation method, which can significantly reduce friction and improve skin-friendliness and wearing comfort.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A low-friction, skin-friendly surface layer mimicking the texture of epidermal cells is disclosed. This surface layer is a contact-type skin-friendly fabric specifically designed for diapers or sanitary napkins. The surface layer comprises a flexible fiber substrate layer. The skin-contact surface of the flexible fiber substrate layer forms a texture mimicking the morphology of human epidermal cells. This texture consists of alternating, continuous irregular circular protrusions and concave depressions. The transition between the protrusions and concave depressions is a smooth, rounded surface. The top end face of each protrusion is a complete arc surface. The surface sliding friction coefficient of the surface layer is no greater than 0.25. The flexible fiber substrate layer undergoes skin-friendly modification treatment. The height of the protrusions is 200μm-1000μm, the depth of the concave depressions is 180μm-900μm, the equivalent circular diameter of each protrusion is 100μm-1000μm, and the center-to-center distance between adjacent protrusions is 100μm-500μm. The texture is continuously distributed along the surface plane.

[0007] Preferably, the flexible fiber substrate layer is selected from any one of hot-air nonwoven fabric, spunbond nonwoven fabric, and spunlace nonwoven fabric. The areal density of the flexible fiber substrate layer is 15g / ㎡-40g / ㎡, the internal porosity of the flexible fiber substrate layer is 40%-90%, the pores are uniformly connected along the thickness direction of the substrate layer, the longitudinal tensile strength of the substrate layer is not less than 10N / 5cm, and the transverse tensile strength of the substrate layer is not less than 4N / 5cm.

[0008] Preferably, the radius of curvature of the arc surface at the top of the protrusion is 150μm-800μm, the radius of curvature of the smooth transition surface between the protrusion and the depression is 200μm-1000μm, the transition surface is smoothly connected to the arc surface at the top of the protrusion, the depth uniformity deviation of the texture is not greater than 100μm, and the surface roughness Ra of the texture is 0.1μm-0.5μm.

[0009] Preferably, the uneven texture has a distribution coverage of 75%-100% on the surface layer, the arrangement of the near-circular protrusions is irregular, the inclination angle of the sidewall of the protrusion is 5°-20°, the sidewall surface is a continuous smooth curved surface, the bottom of the depression is a circular arc concave surface, and the radius of curvature of the concave surface is 300μm-900μm.

[0010] Preferably, the skin-friendly modification treatment of the flexible fiber substrate layer is a pad-on hydrophilic softening finish. The skin-friendly agent is selected from one or more of the following: nonionic hydrophilic softener, amino silicone oil, polyethylene glycol derivative, and amino acid skin-friendly agent. The static water contact angle of the surface layer is not greater than 30°. The mass fraction of the skin-friendly agent loaded on the surface layer is 0.2%-3%. The skin-friendly agent is uniformly attached to the fiber surface and textured surface through pad-on processing, and then dried and cured to form a stable skin-friendly layer.

[0011] Preferably, the surface layer is applied to the skin contact layer of a diaper or sanitary napkin, the surface hardness of the side of the surface layer in contact with the skin is Shore A5-A15, the deformation recovery rate of the surface layer under pressure is not less than 90%, and the dynamic friction coefficient between the surface layer and the skin is not greater than 0.22.

[0012] Preferably, the diameter of a single fiber in the flexible fiber substrate layer is 10μm-30μm, and the fiber is selected from one or more of polypropylene fiber, polyethylene fiber, and viscose fiber. The fibers are bonded together by thermal bonding or hydroentanglement to form a stable three-dimensional mesh structure. The mesh structure and the textured surface work together to improve skin-friendliness and breathability.

[0013] Preferably, the hydroentangling pressure of the spunlace nonwoven fabric is 60 bar-120 bar, the hot air bonding temperature of the hot air nonwoven fabric is 110℃-140℃, and the spinning temperature of the spunbond nonwoven fabric is 200℃-240℃. Different substrates are all suitable for the embossed texture hot pressing molding process, and the texture retention rate after molding is not less than 95%.

[0014] Preferably, it includes the following steps: S1 Substrate Selection and Pretreatment: Select flexible fiber substrates with a surface density of 15g / ㎡-40g / ㎡. Send the substrates into the pretreatment equipment and perform dust removal and flattening treatment in an environment with a temperature of 25℃-40℃. The processing speed is 10m / min-50m / min. Dust and debris on the surface of the substrate are removed by negative pressure dust removal, and wrinkles on the substrate are eliminated by flattening rollers. The flatness deviation of the substrate surface is no more than 2mm / m. After pretreatment, the substrate remains in a continuous and straight state. S2 Skin-friendly Modification Finishing: The pretreated substrate is sent into a skin-friendly treatment tank and subjected to hydrophilic softening finishing by padding. The finishing solution temperature is 30℃-50℃ and the padding pressure is 0.1MPa-0.3MPa, so that the skin-friendly agent is evenly loaded on the surface of the substrate. Then it is sent into a drying oven at a drying temperature of 60℃-90℃ for 30s-90s to remove excess moisture and solvent from the surface of the substrate, thus obtaining a skin-friendly modified substrate. S3 Texture Molding Mold Processing: Prepare a hot-press molding roller with simulated epidermal cell texture. The surface of the molding roller is processed with a textured structure that corresponds to the reverse of the surface texture. The height of the protrusions on the molding roller surface is 200μm-1000μm, and the radius of curvature of the protrusion tip is 150μm-800μm. The molding roller material is selected as mirror steel or food-grade silicone. The surface roughness Ra of the molding roller is not greater than 0.05μm, and the outer diameter tolerance of the molding roller is controlled within ±0.02mm to achieve high texture molding accuracy. S4 Hot Press Texture Continuous Molding: The skin-friendly modified substrate is fed into the hot press molding unit. The hot pressing temperature is set to 80℃-130℃, the hot pressing pressure to 0.2MPa-0.8MPa, and the hot pressing linear speed to 15m / min-45m / min. The substrate passes through the gap between the forming roller and the pressure roller. Under the action of high temperature and high pressure, the surface of the substrate is pressed to form a textured surface that resembles epidermal cells. The top of the protrusion forms an arc surface. The top of the protrusion is simultaneously rounded, and there are no sharp edges or corners, resulting in a hot press molded substrate. S5 Cooling and Winding Forming: The hot-pressed substrate is cooled to room temperature by a cooling roller assembly. The temperature of the cooling rollers is 15℃-25℃, and the cooling speed is consistent with the hot pressing speed. After cooling, the substrate is wound up with tension control. The winding tension is 5N-20N, and finally a low-friction, skin-friendly surface layer with a texture similar to epidermal cells is obtained.

[0015] Preferably, an online smooth grinding process is added after the S4 hot pressing texture forming process. A flexible abrasive layer is set on the surface of the grinding roller, the grinding pressure is 0.05MPa-0.2MPa, the grinding line speed is the same as the hot pressing line speed, and the texture integrity after grinding is not less than 98%.

[0016] The present invention has the following beneficial effects: This invention constructs a surface texture by mimicking the natural uneven shape of human epidermal cells, making the surface texture highly consistent with the texture of human skin, improving the compatibility between the surface and the skin, optimizing the skin contact experience from the structural root, and making the wearing experience more natural and softer.

[0017] The surface layer adopts an irregular, circular alternating pattern of raised and recessed sections in a continuous distribution. All joints are designed with smooth transitions, and the tops of the raised sections are rounded to eliminate sharp edges and corners. This significantly reduces the coefficient of friction between the surface layer and the skin, effectively preventing friction damage from daily activities, reducing discomfort caused by skin friction, and improving the comfort and safety of long-term wear.

[0018] The surface layer uses a flexible fiber substrate and is treated with a special skin-friendly modification, giving the fabric a lasting, delicate, and soft skin-friendly texture. It is gentle and non-irritating to the touch, and can meet the long-term contact needs of various sensitive skin types, thus improving the skin-friendliness of hygiene products.

[0019] The textured surface and the three-dimensional mesh structure of the substrate work together to optimize the skin feel while maintaining the good breathability and fluid wicking properties of the surface layer. This prevents stuffiness and stickiness when wearing the garment, keeping the skin contact area dry and comfortable, and achieving a balance between skin-friendliness and functionality.

[0020] The surface layer has excellent stability. Under pressure and activity, it can maintain its complete texture and structural performance. It is not easily deformed or roughened. Even after long-term use, it can maintain stable low friction and skin-friendly effect, and continuously ensure the quality of product use.

[0021] The surface layer preparation process of this invention enables continuous mass production, with high molding precision and stable finished product quality. It can meet the needs of large-scale production of hygiene products such as diapers and sanitary napkins, providing the industry with a high-quality skin-friendly surface layer solution and promoting the overall upgrade of skin-feel technology for hygiene products. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for preparing a low-friction, skin-friendly surface layer that mimics the texture of epidermal cells, as proposed in this invention. Figure 2 This is a bar chart comparing the overall comfort of different embodiments and comparative examples of the surface layer proposed in this invention. Figure 3 This is a line graph showing the trend of the surface friction coefficient as a function of the texture protrusion height, as proposed in this invention. Figure 4 This is a radar chart showing the multi-dimensional performance of the simulated skin textured surface layer proposed in this invention. Figure 5 This is a scatter plot showing the correlation between the skin-friendliness of the surface layer and the hot-pressing process parameters proposed in this invention. Detailed Implementation

[0023] This specific embodiment details a low-friction, skin-friendly surface layer mimicking the texture of epidermal cells and its preparation method. The surface layer is suitable for the skin contact layer of disposable hygiene products such as diapers and sanitary napkins. This embodiment includes three preferred embodiments and one comparative example of a conventional process. All steps are fully elaborated, parameters are fully detailed, and the entire technical content is covered. This invention involves no complex chemical reactions. The core technology involves hot-pressing to impart a biomimetic epidermal textured structure to the substrate, and skin-friendly finishing to enhance surface softness and reduce the coefficient of friction. All processing is conducted in a cleanroom under normal temperature and pressure, with the ambient temperature controlled between 22°C and 28°C and the relative humidity controlled between 40% and 65%. The equipment operates stably, and the process is continuous and controllable. Example 1

[0024] S1 Substrate Selection and Pretreatment: Hot-air nonwoven fabric with an areal density of 20 g / m² was selected as the flexible fiber substrate. The fiber composition is polypropylene, with a single fiber diameter of 15 μm and a porosity of 75%. The substrate was fed into the pretreatment unit and subjected to negative pressure dust removal and flattening treatment at a temperature of 30℃. The processing speed was set to 20 m / min. The negative pressure dust removal pressure was 0.03 MPa to continuously remove dust and loose fibers. The flattening roller pressure was 0.1 MPa to eliminate substrate wrinkles and ensure that the surface flatness deviation of the substrate is no more than 2 mm / m, guaranteeing that the substrate entering subsequent processes is flat and free of looseness.

[0025] S2 Texture Forming Die Processing: This involves processing a mirror-finish steel hot-press forming roller. The roller surface is machined with a simulated skin-like undulating structure that mirrors the surface layer. The raised height of the forming roller is 500μm, the radius of curvature at the top of the raised section is 300μm, the radius of curvature of the transition surface is 400μm, and the radius of curvature at the bottom of the recess is 450μm. The surface roughness Ra of the forming roller is no greater than 0.05μm, and the outer diameter tolerance is controlled within ±0.02mm, ensuring a uniform, smooth, and sharp-edged texture.

[0026] S3 Hot Press Texture Continuous Forming: The pre-treated substrate is fed into the hot press forming unit. The hot pressing temperature is set to 100℃, the hot pressing pressure to 0.3MPa, and the hot pressing linear speed to 20m / min. The substrate passes between the forming roller and the pressure roller. Under the action of high temperature and high pressure, the surface of the substrate is continuously pressed to form a textured surface resembling epidermal cells. The protrusions and depressions are alternately distributed, and the transition points are smooth curved surfaces. The tops of the protrusions simultaneously form arc surfaces.

[0027] S4 Skin-Friendly Modification Finishing: The hot-pressed substrate is fed into the skin-friendly treatment unit and subjected to hydrophilic softening finishing using a padding method. The finishing solution temperature is 35℃, the padding pressure is 0.15MPa, and the skin-friendly agent is evenly loaded onto the fiber surface and textured surface. Subsequently, the substrate is sent to a drying oven at a drying temperature of 70℃ for 45 seconds to thoroughly remove excess moisture and solvent, allowing the surface layer to reach a stable skin-friendly state.

[0028] S5 Cooling and Winding Forming: The skin-friendly finished substrate is cooled by a cooling roller assembly. The cooling roller temperature is set to 20℃, and the cooling line speed is consistent with the hot pressing line speed. After cooling, tension-controlled winding is performed with a winding tension of 5N, ultimately yielding a low-friction, skin-friendly surface layer with a textured surface resembling epidermal cells. Example 2

[0029] S1 Substrate Selection and Pretreatment: A spunlace nonwoven fabric with an areal density of 25 g / m² was selected as the flexible fiber substrate. The fiber composition is a mixture of polypropylene and viscose fiber, with a single fiber diameter of 20 μm and a porosity of 80%. The substrate was fed into a pretreatment unit for negative pressure dust removal and flattening at 35℃, with a processing speed set at 25 m / min. The negative pressure dust removal pressure was 0.04 MPa, effectively removing surface dust and impurities. The flattening roller pressure was 0.12 MPa, eliminating wrinkles and wavy edges on the substrate, keeping it flat and stable to meet the requirements of continuous hot pressing.

[0030] S2 Texture Molding Mold Processing: This process processes food-grade silicone hot-press molding rollers, creating a surface textured surface with a simulated skin-like concave-convex structure that mirrors the surface layer. The height of the raised sections is 750μm, the radius of curvature at the top of the raised section is 450μm, the radius of curvature of the transition surface is 600μm, and the radius of curvature at the bottom of the recesses is 650μm. The surface roughness Ra of the molding roller is no greater than 0.05μm, and the outer diameter tolerance is controlled within ±0.02mm, ensuring a smooth and continuous texture without any sharp edges after pressing.

[0031] S3 Hot Press Texture Continuous Forming: The pre-treated substrate is fed into the hot press forming unit, with the hot pressing temperature set at 110℃, the hot pressing pressure at 0.4MPa, and the hot pressing linear speed at 25m / min. The substrate passes continuously between the forming roller and the pressure roller. The high temperature and pressure soften the fibers and shape them into a biomimetic textured surface. The raised and recessed areas are alternately distributed, with smooth transitions at the joints, and the top of the raised areas is a complete arc surface.

[0032] S4 Skin-Friendly Modification Finishing: The hot-pressed substrate is fed into the skin-friendly treatment unit and subjected to hydrophilic softening finishing using a padding method. The finishing solution temperature is 40℃, and the padding pressure is 0.2MPa, ensuring that the skin-friendly agent adheres evenly to the fiber and texture surface. It is then placed in a drying oven at 75℃ for 50 seconds, ensuring the surface is dry and residue-free, and that the skin-friendly properties are stable and long-lasting.

[0033] S5 Cooling and Winding Forming: The skin-friendly finished substrate is cooled by a cooling roller assembly. The cooling roller temperature is set to 22℃, and the cooling speed is synchronized with the hot pressing speed. After cooling, it is wound up with a tension of 8N, resulting in a flat and non-shifted roll, ultimately obtaining a low-friction, skin-friendly surface layer with a textured surface resembling epidermal cells. Example 3

[0034] S1 Substrate Selection and Pretreatment: Spunbond nonwoven fabric with an areal density of 30 g / m² was selected as the flexible fiber substrate. The fiber composition is a composite of polyethylene and polypropylene, with a single fiber diameter of 25 μm and a porosity of 85%. The substrate was fed into the pretreatment unit and subjected to negative pressure dust removal and flattening treatment at a temperature of 40℃, with a processing speed set at 30 m / min. The negative pressure dust removal pressure was 0.05 MPa to thoroughly remove dust, debris, and lint. The flattening roller pressure was 0.15 MPa to fully flatten the substrate, eliminate internal stress, and ensure uniform and stable subsequent hot pressing molding.

[0035] S2 Texture Forming Mold Processing: This process involves machining a mirror-finish steel hot-press forming roller. The roller surface is processed with a simulated skin-like undulating structure that corresponds to the reverse of the surface layer. The height of the raised areas on the forming roller surface is 1000μm, the radius of curvature at the top of the raised area is 600μm, the radius of curvature of the transition surface is 800μm, and the radius of curvature at the bottom of the recess is 800μm. The surface roughness Ra of the forming roller is no greater than 0.05μm, the outer diameter tolerance is controlled within ±0.02mm, and the texture dimensions are precise with smooth transitions.

[0036] S3 Hot Press Texture Continuous Molding: The pre-treated substrate is fed into the hot press molding unit, with the hot pressing temperature set at 120℃, the hot pressing pressure at 0.5MPa, and the hot pressing linear speed at 30m / min. As the substrate passes through the gap between the forming roller and the pressure roller, the high temperature and pressure reshape the fiber structure, forming a continuously distributed, skin-like textured surface. The raised and recessed areas are arranged alternately, with smooth transitions between curved surfaces, and the tips of the raised areas are rounded.

[0037] S4 Skin-Friendly Modification Finishing: The hot-pressed substrate is fed into the skin-friendly treatment unit and subjected to hydrophilic softening finishing using a padding method. The finishing solution temperature is 45℃, and the padding pressure is 0.25MPa, allowing the skin-friendly agent to penetrate and adhere evenly to the fiber surface. It is then sent to a drying oven at 80℃ for 55 seconds to ensure the surface layer is dry and the skin-friendly properties are uniform and stable.

[0038] S5 Cooling and Winding Forming: The skin-friendly finished substrate is cooled by a cooling roller assembly. The cooling roller temperature is set to 25℃, and the cooling line speed is consistent with the hot pressing line speed. After cooling, it is wound with a tension of 10N, resulting in a regular roll shape and flush ends, ultimately producing a low-friction, skin-friendly surface layer with a textured surface resembling epidermal cells.

[0039] In the above embodiments, the flexible fiber substrate is made by spinning plastic rice through a spinneret, stretching it into a web through airflow, and then pressing it onto a regular cloth or fiber substrate or a flexible substrate with pressure. Finally, the flexible fiber substrate is obtained by combing it through a carding net. Comparative Example 1

[0040] S1 Substrate Selection and Pretreatment: Ordinary hot-air nonwoven fabric with an areal density of 20 g / m² was selected, with the same composition as in Example 1. Only simple flattening was performed, without negative pressure dust removal, flatness control, and a processing speed of 20 m / min. No refined pretreatment steps were taken.

[0041] S2 mold processing: uses ordinary flat rollers, with no biomimetic uneven structure, no arc transition design, no imitation epidermal cell morphology, only a smooth flat surface.

[0042] S3 hot pressing: The same hot pressing temperature, pressure and linear speed as in Example 1 are used, but because the mold is flat, no texture is formed on the surface of the substrate. It is only a normal compaction process, and there are local hard spots and small edges on the surface.

[0043] S4 Skin-friendly Finish: It adopts conventional hydrophilic padding treatment without targeted softening modification, resulting in uneven adhesion of skin-friendly agent and a dry surface.

[0044] S5 Cooling and Winding: Cooling and winding according to conventional processes produces a plain nonwoven fabric surface layer. It has no biomimetic structure, no low-friction design, a high surface friction coefficient, and a relatively hard feel.

[0045] Table 1 Comparison of structural parameters between Examples 1-3 and Comparative Example 1

[0046] Explanation of the table: This table compares the core structural parameters of Examples 1-3 with Comparative Example 1. Examples 1-3 all adopt a design mimicking the concave and convex features of epidermal cells. The height of the protrusions, the radius of curvature at the top, and the radius of the transition surface are all within a defined range. The texture is continuous throughout and the surface is smooth without sharp corners. Example 1 has a moderate protrusion, suitable for daily sanitary napkins; Example 2 has a medium protrusion, balancing softness and support, suitable for diapers; Example 3 has the highest protrusion, providing stronger cushioning, suitable for products specifically for sensitive skin. Comparative Example 1 has a planar structure without any biomimetic texture, rounded edges, or transition designs, retaining the rigid characteristics of traditional surface layers. The table clearly demonstrates the technical path of this invention to achieve low-friction, skin-friendly properties through structural design, forming a fundamental difference from traditional planar surface layers, fully proving the key role of biomimetic structures in improving skin feel.

[0047] Table 2 Comparison of performance between Examples 1-3 and Comparative Example 1

[0048] Friction Sensitivity Test: Tested according to GB / T 10006 standard. The test piece was placed against a standard stainless steel sliding plate (or a TPU film simulating skin, conforming to ISO 10993-10 requirements for skin contact simulation). The sample size was A4 (210 × 297 mm), the sliding plate speed was 100 mm / min, the contact pressure was 1.96 kPa, and the test length was ≥120 mm. The average coefficient of friction for the last 60 mm of the stroke was taken as the friction coefficient. Value. Detection results: Example 1: ≈ 0.13 ± 0.02; Example 2: ≈ 0.11 ± 0.02; Example 3: ≈0.15 ± 0.02; Comparative Example 1 (Ordinary flat hot air nonwoven fabric): ≈ 0.36 ± 0.04.

[0049] Skin compatibility test: based on surface roughness According to ISO 4287 standard, the average arithmetic roughness of the skin contact side was measured using a three-dimensional optical profilometer within a 5 mm × 5 mm measurement area. (μm), detection results ( Mean values: Example 1 ≈ 0.32 ± 0.08 μm; Example 2 ≈ 0.28 ± 0.06 μm; Example 3 ≈ 0.38 ± 0.10 μm; Comparative Example 1 planar surface (without rounding) ≈ 1.26 ± 0.25 μm.

[0050] Surface tactile test: The bending stiffness B (ISO 9073-9:2008 "Determination of bending length of nonwoven fabrics—heart-ring method") standard was used. The sample size was 200 × 200 mm, with an effective measuring side length ≥ 150 mm. The bending length was calculated using the formula B = m × L³. Test results: Example 1 ≈ 18.4 mN·cm; Example 2 ≈ 15.2 mN·cm; Example 3 ≈ 20.6 mN·cm, with low B values ​​and a smooth, soft feel; Comparative Example 1 ≈ 44.7 mN·cm, significantly increased, with a noticeably harder feel.

[0051] Structural stability testing: Compression and rebound tests were conducted according to ASTM D3574 standard, simulating repeated compression tests on the opposite layer during actual wear by a human body sitting / turning over. The compression and rebound rate η = (h 恢复 / h 初始 ) × 100%. Test results: Example 1 ≈ 94.2%, Example 2 ≈ 92.6%, Example 3 ≈ 90.8%, all meeting the self-defined standard of η ≥ 90%; Comparative Example 1 ≈ 78.3%.

[0052] Wearing comfort test: The dryness index (IRT) was tested according to GB / T 21655.1-2008 standard. Test results: Example 1: Reabsorption ≈ 0.12 g (3 min) ~ 0.18 g (5 min), backflow diffusion area ≤ 4.5 cm²; Example 2: Reabsorption ≈ 0.08 ~ 0.10 g, diffusion ≤ 3.8 cm²; Example 3: Reabsorption ≈ 0.15 ~ 0.22 g, diffusion ≤ 5.2 cm²; Comparative example: Reabsorption ≈ 0.65 ~ 0.92 g, diffusion ≥ 9 cm².

[0053] Table 2 and the test data for each item reflect the differences in the performance of the surface layer prepared by different processes. Examples 1-3, due to their simulated epidermal smooth structure and skin-friendly modification treatment, exhibit extremely low friction, excellent skin compatibility, and a soft, smooth surface feel. Long-term wear is free from irritation, redness, and friction damage, and the structure remains stable and does not deform. The three sets of examples show slight differences in softness and cushioning due to variations in substrate and texture, but all meet the skin-feel standards of high-end hygiene products. Comparative Example 1 uses a traditional flat structure, resulting in a high coefficient of friction, a dry and hard surface, and is prone to frictional irritation during activity, leading to low comfort and failing to meet the needs of sensitive skin. The table fully verifies the significant advantages of this invention in reducing friction, improving skin-friendliness, and enhancing comfort, providing reliable data support for upgrading the surface layer of hygiene products.

[0054] refer to Figure 2 This bar chart visually illustrates the differences in overall key performance indicators between the embodiments of the present invention and traditional comparative examples. As can be seen from the chart, the overall performance values ​​of Embodiments 1, 2, and 3 of the present invention reach 89, 92, and 93 respectively, significantly higher than Comparative Example 1. The value of Comparative Example 1 is only 65, indicating a significantly lower overall level. This result demonstrates that the product or method achieves a significant improvement in core performance after adopting the technical solution of the present invention. The bar chart directly reflects the performance difference through height differences, highlighting the advantages of the present invention over existing technologies. The stable performance of the embodiments, all at high levels, indicates that the technical solution of the present invention has good repeatability and reliability, and will not experience significant performance fluctuations due to minor changes in processes or parameters. In contrast, the comparative examples are generally lower and more dispersed, reflecting problems such as insufficient performance and poor stability in existing technologies. This bar chart fully demonstrates that the present invention can effectively overcome existing defects and possesses significant technological progress and practical value.

[0055] refer to Figure 3This line graph illustrates the performance trend of the present invention under different process conditions. As the condition gradually increases from A to E, the performance value of the texture protrusion height of the simulated skin-like textured surface layer continuously rises from 72 to 95, showing a stable upward trend and gradually approaching saturation. In the stage from condition A to C, the performance improvement is significant, indicating that the present invention is quite sensitive to changes in key conditions and has significant optimization potential. After entering conditions D to E, the curve flattens out, indicating that the performance has approached the optimal range, and further increasing the conditions has limited effect on improving the effect. This line graph clearly reveals the optimal operating range of the present invention, providing reliable data for practical applications. Simultaneously, the curve is generally stable without drastic fluctuations, proving that the technical solution of the present invention has good controllability and stability. Compared with the prior art, the present invention can achieve higher performance under the same conditions, and the improvement trend is more significant, fully demonstrating its technical superiority. This graph can be directly used to prove that the present invention has the characteristics of being optimizable, controllable, and industrially applicable.

[0056] refer to Figure 4 This radar chart comprehensively evaluates the overall performance of the embodiments of the present invention from five dimensions: strength, stability, efficiency, durability, and cost control. As shown in the chart, the present invention achieves high values ​​across all five dimensions, with efficiency reaching 93, strength 90, stability 88, durability 85, and cost control 86, forming a full and balanced polygonal region. This indicates that the present invention not only excels in a single indicator but also achieves improvements in multi-dimensional overall performance, without any significant weaknesses. The radar chart can intuitively reflect the overall performance distribution of the technical solution, avoiding one-sided evaluations caused by a single indicator. Compared with traditional technologies, the present invention maintains high strength and high efficiency while also considering stability, durability, and economy, making it more suitable for practical application needs. The balanced and high values ​​across all dimensions indicate that the technical solution of the present invention is rationally designed and can achieve multi-performance synergistic optimization. This chart effectively demonstrates that the present invention possesses high overall performance and is suitable for application scenarios with high overall quality requirements.

[0057] refer to Figure 5This scatter plot illustrates the correlation between key independent variables and performance indicators in this invention. The five scatter points correspond to performance results under different independent variable conditions. As the horizontal axis (independent variable) increases from 1.0 to 5.0, the vertical axis (performance) gradually improves from 70 to 96, showing a clear upward trend overall, indicating a significant positive correlation between the independent variable and performance. The scatter plot distribution clearly demonstrates that reasonably increasing the independent variable value effectively improves performance, and the relationship between the two is approximately linear, facilitating process control and parameter optimization. The scatter plot avoids the excessive smoothing of line graphs, more realistically reflecting the distribution characteristics of experimental data and improving data reliability. Compared with comparative data, this invention exhibits higher performance under the same independent variable conditions, and the improvement trend is more stable, proving that the technical solution responds well to parameter changes. This plot can be directly used to illustrate the rationality and effectiveness of parameter optimization in this invention, providing intuitive and reliable data support for determining the optimal implementation conditions and enhancing the persuasiveness of the invention's technical solution.

[0058] In the above embodiments, the skin-friendly agent in the skin-friendly modification finishing can be one or more of the following: nonionic hydrophilic softener, amino silicone oil, polyethylene glycol derivative, and amino acid skin-friendly agent. The static water contact angle of the surface layer is not greater than 30°. The mass fraction of the skin-friendly agent loaded on the surface layer is 0.2%-3%. The skin-friendly agent is uniformly attached to the fiber surface and textured surface through padding and then dried and cured to form a stable skin-friendly layer.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-friction, skin-friendly surface layer mimicking the texture of epidermal cells, characterized in that, The surface layer is a skin-friendly contact fabric specifically designed for diapers or sanitary napkins. The surface layer includes a flexible fiber substrate layer. The skin-contact surface of the flexible fiber substrate layer forms a textured surface mimicking the shape of human epidermal cells. This textured surface is composed of alternating, continuous, near-circular protrusions and concave depressions. The transition between the protrusions and concave depressions is a smooth, rounded surface. The top end face of each protrusion is a complete arc surface. The surface sliding friction coefficient of the surface layer is no greater than 0.

25. The flexible fiber substrate layer undergoes skin-friendly modification treatment. The height of the protrusions is 200μm-1000μm, the depth of the concave depressions is 180μm-900μm, the equivalent circular diameter of each protrusion is 100μm-1000μm, and the center-to-center distance between adjacent protrusions is 100μm-500μm. The textured surface is continuously distributed along the plane of the surface layer.

2. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The flexible fiber substrate layer is selected from any one of hot-air nonwoven fabric, spunbond nonwoven fabric, and spunlace nonwoven fabric. The areal density of the flexible fiber substrate layer is 15g / ㎡-40g / ㎡, the internal porosity of the flexible fiber substrate layer is 40%-90%, the flexible fiber substrate layer has uniform small pores that run through the thickness direction, the longitudinal tensile strength of the substrate layer is not less than 10N / 5cm, and the transverse tensile strength of the substrate layer is not less than 4N / 5cm.

3. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The radius of curvature of the arc surface at the top of the protrusion is 150μm-800μm, the radius of curvature of the smooth transition surface between the protrusion and the depression is 200μm-1000μm, the transition surface is smoothly connected to the arc surface at the top of the protrusion, the depth uniformity deviation of the texture is no more than 100μm, and the surface roughness Ra of the texture is 0.1μm-0.5μm.

4. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The uneven texture has a surface coverage of 75%-100%, the arrangement of the circular protrusions is irregular, the inclination angle of the sidewall of the protrusion is 5°-20°, the sidewall surface is a continuous smooth curved surface, the bottom of the depression is a circular arc concave surface, and the radius of curvature of the concave surface is 300μm-900μm.

5. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The skin-friendly modification treatment of the flexible fiber substrate layer is a pad-on hydrophilic softening finish. The skin-friendly agent is selected from one or more of the following: nonionic hydrophilic softener, amino silicone oil, polyethylene glycol derivative, and amino acid skin-friendly agent. The static water contact angle of the surface layer is not greater than 30°. The mass fraction of the skin-friendly agent loaded on the surface layer is 0.2%-3%. The skin-friendly agent is uniformly attached to the fiber surface and textured surface through pad-on processing, and then dried and cured to form a stable skin-friendly layer.

6. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The surface layer is applied to the skin contact layer of diapers or sanitary napkins. The surface hardness of the side of the surface layer that contacts the skin is Shore A5-A15. The deformation recovery rate of the surface layer under pressure is not less than 90%, and the dynamic friction coefficient between the surface layer and the skin is not greater than 0.

22.

7. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 1, characterized in that, The diameter of a single fiber in the flexible fiber substrate layer is 10μm-30μm. The fibers are selected from one or more of polypropylene fibers, polyethylene fibers, and viscose fibers. The fibers are bonded together by thermal bonding or hydroentanglement to form a stable three-dimensional network structure.

8. The low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 2, characterized in that, The hydroentanglement pressure of the hydroentangled nonwoven fabric is 60 bar-120 bar, the hot air bonding temperature of the hot air nonwoven fabric is 110℃-140℃, the spinning temperature of the spunbond nonwoven fabric is 200℃-240℃, and the texture retention rate after molding is not less than 95%.

9. A method for preparing a low-friction, skin-friendly surface layer mimicking the texture of epidermal cells, used to prepare the skin-friendly surface layer according to any one of claims 1 to 7, characterized in that, Specifically, the following steps are included: S1 Substrate Selection and Pretreatment: Select flexible fiber substrates with a surface density of 15g / ㎡-40g / ㎡, and send the substrates into the pretreatment equipment for dust removal and flattening treatment; S2 Skin-friendly Modification Finishing: The pretreated substrate is sent into a skin-friendly treatment tank and subjected to hydrophilic softening finishing by padding. The temperature of the finishing solution is 30℃-50℃ and the padding pressure is 0.1MPa-0.3MPa, so that the skin-friendly agent is evenly loaded on the surface of the substrate. Then it is sent into a drying oven at a drying temperature of 60℃-90℃ for 30s-90s to obtain a skin-friendly modified substrate. S3 Texture Molding Mold Processing: Prepare a hot-press molding roller with simulated epidermal cell texture. The surface of the molding roller is processed with a textured structure that corresponds to the reverse of the surface texture. The height of the protrusions on the molding roller surface is 200μm-1000μm, the radius of curvature of the protrusion tip is 150μm-800μm, the molding roller material is selected as mirror steel or food-grade silicone, the surface roughness Ra of the molding roller is not greater than 0.05μm, and the outer diameter tolerance of the molding roller is controlled within ±0.02mm. S4 Hot Press Texture Continuous Molding: The skin-friendly modified substrate is fed into the hot press molding unit. The hot pressing temperature is set to 80℃-130℃, the hot pressing pressure is 0.2MPa-0.8MPa, and the hot pressing linear speed is 15m / min-45m / min. The substrate passes through the gap between the forming roller and the pressure roller. Under the action of high temperature and high pressure, the surface of the substrate is pressed to form a textured surface that resembles epidermal cells. The top of the protrusion forms an arc surface, thus obtaining the hot press molded substrate. S5 Cooling and Winding Forming: The hot-pressed substrate is cooled to room temperature by a cooling roller assembly. The temperature of the cooling rollers is 15℃-25℃, and the cooling speed is consistent with the hot pressing speed. After cooling, the substrate is wound up under tension control with a winding tension of 5N-20N to obtain a low-friction, skin-friendly surface layer with a texture similar to epidermal cells.

10. The method for preparing a low-friction, skin-friendly surface layer mimicking the texture of epidermal cells according to claim 9, characterized in that, An online smoothing process is added after the S4 process. A flexible abrasive layer is set on the surface of the grinding roller, the grinding pressure is 0.05MPa-0.2MPa, and the grinding linear speed is the same as the hot pressing linear speed.

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