Water-based polyurethane reinforced low-grammage waterproof and breathable non-woven fabric and adult incontinence products

Abstract

This invention belongs to the technical field of nonwoven materials for hygiene products, and relates to a water-based polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric and adult incontinence products. The nonwoven fabric comprises materials with a basis weight of 8-18 g / m². 2 The nonwoven fabric comprises a spunbond nonwoven substrate and an aqueous polyurethane reinforcing coating formed on at least one side thereof; the coating is formed by roller-dot or strip-discontinuous coating, including nodal reinforcements located at fiber intersection areas and unsealed breathable areas between adjacent nodal reinforcements, the nodal reinforcements penetrating into the thickness direction of the substrate and forming a locally consolidated structure, and the unsealed breathable areas retaining through-breathable pores. This nonwoven fabric can be used as a waterproof and breathable outer layer for adult diapers or adult pull-ups, and may not require a separate PE waterproof membrane layer.

Description

Technical Field

[0001] This invention belongs to the technical field of nonwoven materials for hygiene products, specifically relating to a water-based polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric and adult incontinence products using this nonwoven fabric. Background Technology

[0002] Adult incontinence products typically consist of a liquid-permeable top layer, an absorbent core, and a waterproof outer layer surrounding the absorbent core. The waterproof outer layer needs to prevent liquid from seeping out of the absorbent core while also possessing a certain degree of breathability or moisture permeability to reduce stuffiness or dampness while wearing the garment. In existing adult diapers and pull-ups, the waterproof outer layer often uses water-repellent non-woven fabric, breathable PE film, or a composite structure of non-woven fabric and PE film. Some products use PE film as the liquid barrier layer, while products with higher comfort requirements typically use a composite of non-woven fabric and breathable film to balance appearance, feel, and barrier performance.

[0003] In existing technologies, there are methods for forming diaper bottom films by combining low-basis-weight nonwoven fabric with a waterproof and breathable functional layer. For example, Chinese patent CN105063896B discloses a method for preparing a waterproof and breathable diaper bottom film, wherein the substrate layer is a nonwoven fiber layer with a breathability of 100-700 CFM and a thickness of 5-20 GSM, and the waterproof and breathable layer is a nanofiber stack layer, which is formed on the nonwoven fiber layer by electrospinning. This method can form a composite structure with waterproof and breathable functions in the diaper bottom film.

[0004] However, existing solutions of the above types still mainly rely on additional waterproof and breathable functional layers to achieve liquid barrier properties. For electrospun nanofiber layers, certain requirements are placed on equipment, process control, and solvent handling. While PE breathable membrane composite structures can provide a barrier effect, they increase the amount of membrane material used. Furthermore, when using low-basis-weight outer materials, simply reducing the nonwoven fabric basis weight can easily lead to a decrease in the tensile strength, abrasion resistance, and processing stability of the outer layer. On the other hand, if a continuous coating is directly formed on the surface of low-basis-weight nonwoven fabric to improve waterproofness, the continuous membrane layer can easily seal the pores between fibers in the nonwoven fabric, reducing the material's air permeability and moisture permeability, thus affecting moisture release when wearing adult incontinence products.

[0005] Therefore, for waterproof and breathable outer layers of adult incontinence products, there is still a need for a material structure that can improve the bond strength of nonwoven fibers under low basis weight conditions, reduce or avoid the use of independent PE waterproof membrane layers, and at the same time retain breathable pores. This structure should not simply rely on continuous membrane coverage, but should form local reinforcements in the fiber intersection areas, and retain unsealed breathable areas between adjacent reinforced areas. This allows the low basis weight nonwoven fabric to meet the requirements of outer layer processing and wearability while possessing a structural basis that balances waterproofness, breathability, and strength. Summary of the Invention

[0006] The purpose of this invention is to provide a water-based polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric and an adult incontinence product, so as to improve the joint bonding stability, waterproofness and breathability retention of the low-weight nonwoven fabric without setting an independent PE waterproof membrane layer.

[0007] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution.

[0008] In a first aspect, the present invention provides a waterborne polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric, comprising a spunbond nonwoven fabric substrate and a waterborne polyurethane reinforcing coating formed on at least one side of the spunbond nonwoven fabric substrate; the basis weight of the spunbond nonwoven fabric substrate is 8-18 g / m³. 2 The waterborne polyurethane reinforced coating is formed by applying and drying waterborne polyurethane emulsion through roller dot or strip intermittent coating. The waterborne polyurethane reinforced coating includes node reinforcement sections located in the fiber cross regions and unsealed breathable areas located between adjacent node reinforcement sections. The node reinforcement sections penetrate into the thickness direction of the spunbond nonwoven fabric substrate, and the penetration depth is 20% to 70% of the thickness of the spunbond nonwoven fabric substrate. The unsealed breathable areas retain through-breathable pores. The node reinforcement sections and the unsealed breathable areas together form a discontinuous waterproof and breathable reinforced structure, so that when the waterborne polyurethane reinforced low-basis-weight waterproof and breathable nonwoven fabric is used as the outer layer of adult incontinence products, there is no need to set an independent PE waterproof membrane layer.

[0009] As a further improvement, the node reinforcement at least partially covers the overlap position of adjacent fibers and forms a dot-like or short strip-like consolidation structure between adjacent fibers, the consolidation structure causing the adjacent fibers to form a local bonding point at the overlap position.

[0010] As a further improvement, the spunbond nonwoven fabric substrate is polypropylene spunbond nonwoven fabric, polylactic acid spunbond nonwoven fabric, polyester spunbond nonwoven fabric, or polypropylene and polylactic acid composite fiber spunbond nonwoven fabric.

[0011] As a further improvement, the waterborne polyurethane emulsion includes at least one of polyester-type waterborne polyurethane, polyether-type waterborne polyurethane, or polycarbonate-type waterborne polyurethane, and contains a crosslinking component for improving wet bonding stability.

[0012] As a further improvement, the crosslinking component is at least one of carbodiimide crosslinking agent, aziridine crosslinking agent, blocked isocyanate crosslinking agent or silane coupling agent, and the mass content of the crosslinking component relative to the solids of waterborne polyurethane is 0.3% to 5%.

[0013] As a further improvement, the dry coating weight of the waterborne polyurethane reinforced coating is 0.8–5.0 g / m². 2Furthermore, the waterborne polyurethane reinforced coating has a surface coverage of 35% to 75% on the surface of the spunbond nonwoven fabric substrate.

[0014] As a further improvement, when the waterborne polyurethane reinforced coating is formed by roller dot coating, the node reinforcement portion is a discrete reinforcement point distributed at intervals along the length and width directions of the nonwoven fabric; when the waterborne polyurethane reinforced coating is formed by strip discontinuous coating, the node reinforcement portion is a reinforcing strip extending along the length direction of the nonwoven fabric and spaced apart along the width direction.

[0015] As a further improvement, no continuous waterborne polyurethane film layer is formed throughout the entire width of the unsealed breathable area, and the through-breathable pores are formed by the inter-fiber pores in the spunbond nonwoven fabric substrate that are not completely filled with waterborne polyurethane.

[0016] In a second aspect, the present invention provides an adult incontinence product, comprising a liquid-permeable surface layer, an absorbent core, and a waterproof and breathable outer layer, wherein the waterproof and breathable outer layer is the water-based polyurethane-reinforced low-grammage waterproof and breathable nonwoven fabric described in the first aspect, and the waterproof and breathable outer layer is disposed on the side of the absorbent core away from the liquid-permeable surface layer.

[0017] Specifically, the adult incontinence product is an adult diaper or adult pull-up diaper, and the water-based polyurethane reinforced coating is located on the side of the spunbond nonwoven fabric substrate facing the absorbent core, or on the side of the spunbond nonwoven fabric substrate away from the absorbent core.

[0018] This invention utilizes a roller-dot or strip-intermittent coating process to create a water-based polyurethane reinforcing coating that forms nodal reinforcements at the fiber cross-sections of a spunbond nonwoven fabric substrate, while retaining unsealed breathable areas between adjacent nodal reinforcements. The nodal reinforcements locally consolidate the overlaps between adjacent fibers, improving the tensile strength and structural stability after rubbing of low-basis-weight spunbond nonwoven fabrics. The unsealed breathable areas preserve the interconnected pores in the substrate, reducing the adverse effects of continuous coating on breathability and moisture permeability. When this nonwoven fabric is used as a waterproof and breathable outer layer for adult diapers or adult pull-ups, the need for a separate PE waterproof membrane layer can be reduced, resulting in a better balance of waterproofness, breathability, softness, and material reduction in the outer layer. This makes it suitable for the preparation of outer layer materials for adult incontinence products. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the layered structure of the waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric of the present invention.

[0020] Figure 2 This is a schematic diagram showing the discontinuous distribution of the waterborne polyurethane reinforced coating of the present invention on the surface of a spunbond nonwoven fabric substrate;

[0021] Figure 3This is a schematic diagram of the structure of an adult incontinence product using the waterborne polyurethane-reinforced low-grammage waterproof and breathable nonwoven fabric of the present invention.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1. Spunbond nonwoven fabric substrate; 2. Waterborne polyurethane reinforced coating; 21. Node reinforcement; 22. Unsealed breathable area; 3. Through-breathing pores; 4. Adult incontinence products; 41. Liquid-permeable surface layer; 42. Absorbent core; 43. Waterproof and breathable outer layer. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are used to illustrate the implementation of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, equivalent substitutions or conventional adjustments made by those skilled in the art based on the disclosure of this specification regarding the types of raw materials, equipment types, coating parameters, and post-treatment conditions can all be used to implement the present invention.

[0025] I. General Description

[0026] 1.1 Low-weight waterproof and breathable non-woven fabric

[0027] like Figure 1 and Figure 2 As shown, this invention provides a waterborne polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric, comprising a spunbond nonwoven fabric substrate 1 and a waterborne polyurethane reinforcing coating 2 formed on at least one side of the spunbond nonwoven fabric substrate 1. The basis weight of the spunbond nonwoven fabric substrate 1 is 8-18 g / m³. 2 The waterborne polyurethane reinforcing coating 2 is formed by applying and drying waterborne polyurethane emulsion through a roller-dot or strip-intermittent coating process. The waterborne polyurethane reinforcing coating 2 includes node reinforcement sections 21 located at fiber intersection areas and unsealed breathable areas 22 located between adjacent node reinforcement sections 21. The node reinforcement sections 21 penetrate into the thickness direction of the spunbond nonwoven fabric substrate 1, with a penetration depth of 20% to 70% of the thickness of the spunbond nonwoven fabric substrate 1. The unsealed breathable areas 22 retain through-holes 3, enabling the resulting nonwoven fabric to possess certain tensile strength, water resistance, and breathability under low basis weight conditions.

[0028] In this embodiment, the spunbond nonwoven fabric substrate 1 can be polypropylene spunbond nonwoven fabric, polylactic acid spunbond nonwoven fabric, polyester spunbond nonwoven fabric, or polypropylene and polylactic acid composite fiber spunbond nonwoven fabric. The basis weight of the spunbond nonwoven fabric substrate 1 is lower than that of some nonwoven fabric materials conventionally used for the outer layer of adult incontinence products. To avoid insufficient tensile strength due to low basis weight, this invention uses a water-based polyurethane reinforcing coating 2 to form node reinforcement portions 21 in the fiber cross-section area, creating a dot-like or short-ribbon-like bonded structure between adjacent fibers. This bonded structure is not a continuous film covering the entire width, but rather forms a local bond at and near the fiber overlap location, thereby improving the connection stability of the fiber cross-section area.

[0029] 1.2 Waterborne polyurethane reinforced coating

[0030] The waterborne polyurethane emulsion can be at least one of polyester-type waterborne polyurethane, polyether-type waterborne polyurethane, or polycarbonate-type waterborne polyurethane. To improve the bonding stability between the coating and fibers under wet conditions, a crosslinking component can also be added to the waterborne polyurethane emulsion. The crosslinking component can be at least one of carbodiimide crosslinking agent, aziridine crosslinking agent, blocked isocyanate crosslinking agent, or silane coupling agent. The mass content of the crosslinking component relative to the solids of the waterborne polyurethane can be 0.3% to 5%. If the crosslinking component is too low, the bonding strength of the node reinforcement 21 will not be sufficiently improved after wet rubbing; if the crosslinking component is too high, the coating hardness will increase, which may affect the material's softness. Therefore, the crosslinking component should be selected according to the outer layer feel requirements of adult diapers or adult pull-up pants.

[0031] In this invention, the waterborne polyurethane reinforcing coating 2 is applied using either a roller-dot coating or a strip-discontinuous coating. When using a roller-dot coating, the node reinforcement 21 can be discrete reinforcement points spaced apart along the length and width directions of the nonwoven fabric. When using a strip-discontinuous coating, the node reinforcement 21 can be reinforcing strips extending along the length direction of the nonwoven fabric and spaced apart along the width direction. Regardless of the coating method used, an unsealed breathable area 22 is retained between adjacent node reinforcements 21. A continuous waterborne polyurethane film layer penetrating the entire width is not formed within the unsealed breathable area 22, and the permeable pores 3 are formed by the inter-fiber pores in the spunbond nonwoven fabric substrate 1 that are not completely filled with waterborne polyurethane.

[0032] 1.2.1 Discontinuous waterproof and breathable reinforced structure

[0033] To facilitate control of the discontinuous waterproof and breathable reinforcing structure, in this embodiment, the dry coating amount, surface coverage, and penetration depth of the waterborne polyurethane reinforcing coating 2 can be controlled by adjusting the depth of the indentations on the coating roller, the percentage of indentation area, the coating pressure, the emulsion solid content, the emulsion viscosity, and the drying temperature. The dry coating amount of the waterborne polyurethane reinforcing coating 2 can be 0.8–5.0 g / m³. 2The surface coverage of the waterborne polyurethane reinforced coating 2 on the surface of the spunbond nonwoven fabric substrate 1 can be 35% to 75%.

[0034] Surface coverage can be determined using image analysis methods. A sample of water-based polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric is taken, and low-magnification microscopic images are taken of the coating surface. At least five fields of view are selected, and the projected area of ​​the coating is binarized and calculated using the following formula:

[0035] Surface coverage P = Coating projected area / Total area of ​​measurement area × 100%.

[0036] The penetration depth can be determined by cross-sectional microscopic observation. After the sample is subjected to liquid nitrogen brittle fracture or cryosection, the cross-section is observed, and the maximum depth of penetration of the node reinforcement 21 from the surface into the thickness direction of the spunbond nonwoven fabric substrate 1 is measured and calculated according to the following formula:

[0037] Penetration depth ratio D = Maximum penetration depth of node reinforcement / Thickness of spunbond nonwoven fabric substrate × 100%.

[0038] When the penetration depth ratio D is less than 20%, the waterborne polyurethane mainly remains on the fiber surface, resulting in insufficient consolidation at the fiber intersection areas. When the penetration depth ratio D is greater than 70%, the waterborne polyurethane easily enters too many fiber pores, leading to a reduction in the number of through-hole breathable pores 3. Therefore, this invention controls the penetration depth to 20%–70% of the thickness of the spunbond nonwoven fabric substrate 1, so that the node reinforcement 21 and the unsealed breathable area 22 together form a discontinuous waterproof and breathable reinforcement structure.

[0039] In this embodiment, the penetration depth of the node reinforcement 21 is controlled by the combined effects of coating liquid viscosity, solid content, coating pressure, coating speed, substrate surface tension, and drying and setting speed. Specifically, the viscosity of the waterborne polyurethane coating liquid at 25°C is controlled to be 450–900 mPa·s, and the solid content is controlled to be 24%–32%. The spunbond nonwoven fabric substrate 1 is subjected to corona treatment or low-power plasma treatment before coating to control its surface tension to be 36–44 mN / m. During roller-dot coating, the coating pressure is controlled to be 0.15–0.35 MPa, and the coating speed is controlled to be 40–80 m / min. During strip intermittent coating, the coating pressure is controlled to be 0.10–0.30 MPa. The coated material enters the hot air drying channel within 5 seconds and is dried at 70–110°C to set the waterborne polyurethane in the fiber cross-section area. Through the above control, the penetration depth of the node reinforcement 21 into the spunbond nonwoven fabric substrate 1 in the thickness direction is maintained at 20% to 70% of the substrate thickness, and an unsealed air-permeable area 22 and a through-hole air-permeable pore 3 are retained between adjacent node reinforcements 21. During the production process, the penetration depth can be sampled and inspected by cross-sectional microscopic observation, and the viscosity of the coating liquid, the coating pressure, or the coating speed can be adjusted according to the inspection results; when the penetration depth is less than 20%, the viscosity of the coating liquid is reduced or the coating pressure is increased; when the penetration depth is greater than 70%, the viscosity of the coating liquid is increased, the coating pressure is reduced, or the coating speed is increased.

[0040] 1.3 Implementation methods for adult incontinence products

[0041] like Figure 3 As shown, the present invention also provides an adult incontinence product 4. The adult incontinence product 4 includes a liquid-permeable surface layer 41, an absorbent core 42, and a waterproof and breathable outer layer 43. The waterproof and breathable outer layer 43 is the aforementioned water-based polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric, and is disposed on the side of the absorbent core 42 away from the liquid-permeable surface layer 41. The adult incontinence product 4 can be an adult diaper or an adult pull-up. The water-based polyurethane-reinforced coating 2 of the waterproof and breathable outer layer 43 can be disposed facing the absorbent core 42 or facing away from the absorbent core 42.

[0042] In one embodiment, the waterborne polyurethane reinforcing coating 2 is disposed towards the absorbent core 42, and the node reinforcement portion 21 forms contact with the outer surface of the absorbent core 42, which helps to reduce the stretching deformation of the low-basis-weight nonwoven fabric during wearing and movement. In another embodiment, the waterborne polyurethane reinforcing coating 2 is disposed towards the side away from the absorbent core 42, which facilitates the formation of a wet-rub resistant and friction-resistant surface on the outer side.

[0043] II. Raw Materials and Equipment

[0044] The polypropylene spunbond nonwoven fabrics used in the following examples were prepared by conventional spunbond processes, with a basis weight of 10 g / m³. 212g / m 2 14g / m 2 and 18g / m 2 The thickness is 0.12–0.20 mm; the polylactic acid spunbond nonwoven fabric has a base weight of 10 g / m³. 2 The thickness is 0.13 mm. The waterborne polyurethane emulsion is an anionic waterborne polyurethane emulsion with a solid content of 35%–40% and a viscosity of 300–1200 mPa·s at 25°C. Carbodiimide crosslinking agents or silane coupling agents are used as crosslinking agents. Nonionic wetting agents are used, associative polyurethane thickeners are used as thickeners, and deionized water is used to adjust the solid content and coating viscosity of the emulsion.

[0045] Coating equipment can be either a roller dot coater or a strip intermittent coater. A roller dot coater includes an anilox roller, a rubber pressure roller, a doctor blade assembly, and a hot air drying tunnel; a strip intermittent coater includes an intermittent liquid supply mechanism, a grooved coating roller, and a hot air drying tunnel. The drying temperature is controlled between 70 and 110°C, and the drying time is 30 to 120 seconds. After drying, the samples are equilibrated for 24 hours at 23°C and 50% relative humidity before testing.

[0046] III. Preparation Process

[0047] The waterborne polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric of this invention can be prepared according to the following steps:

[0048] S1. Substrate preparation: Select a substrate weight of 8-18 g / m³. 2 The spunbond nonwoven fabric substrate 1 is placed in an environment of 23°C and 50% relative humidity for at least 12 hours to equilibrate. If necessary, the substrate can be subjected to corona treatment or low-power plasma treatment to bring the surface tension of the substrate to a range suitable for wetting by the aqueous emulsion.

[0049] S2. Preparation of waterborne polyurethane coating solution: Weigh the waterborne polyurethane emulsion and add deionized water to adjust the solid content to 20%–35%; add 0.3%–5% of crosslinking component relative to the solid content of waterborne polyurethane; add 0.05%–0.3% of wetting agent; adjust the viscosity of the coating solution to a range suitable for roller-dot or strip-intermittent coating with a thickener. Stir the prepared coating solution at low speed for 10–30 minutes and let it stand to defoam.

[0050] S3. Discontinuous Coating: The spunbond nonwoven fabric substrate 1 is fed into a coating device, and the water-based polyurethane coating liquid is applied to at least one side of the spunbond nonwoven fabric substrate 1 in a roller-dot or strip-intermittent manner. The distribution of the nodal reinforcement 21 is controlled by the coating pressure, coating roller line count, coating roller indentation depth, coating speed, and emulsion viscosity, so that it is located in and near the fiber cross-section area and penetrates into the thickness direction of the spunbond nonwoven fabric substrate 1.

[0051] S4. Drying and Crosslinking: The coated material enters the hot air drying channel and is dried at 70–110°C for 30–120 seconds to evaporate moisture and form node reinforcements 21 in the fiber cross-linking area of ​​the waterborne polyurethane. For systems containing crosslinking components, a short curing zone at 90–120°C can be set in the later stage for 20–90 seconds to improve wet bonding stability.

[0052] S5. Winding and Balancing: After drying, the material is cooled by cooling rollers and then wound up. It is placed at 23°C and 50% relative humidity for 24 hours to obtain waterborne polyurethane reinforced low-grammage waterproof and breathable nonwoven fabric.

[0053] IV. Examples

[0054] 4.1 Example 1

[0055] The selected basis weight is 12g / m³. 2 Polypropylene spunbond nonwoven fabric was used as the substrate of the spunbond nonwoven fabric. 100 parts of polyether-type waterborne polyurethane emulsion were taken, and deionized water was added to adjust the solid content to 28%. 1.2% of carbodiimide crosslinking agent based on the solid content of waterborne polyurethane was added, along with 0.1% of nonionic wetting agent. The viscosity was adjusted to 650 mPa·s with an associative thickener to obtain the coating liquid.

[0056] A roller-coating method was used with a coating speed of 60 m / min and a coating pressure of 0.25 MPa. The drying temperature was set in three stages: 80℃, 95℃, and 105℃, with a total drying time of 70 s. The resulting waterborne polyurethane reinforced coating 2 had a dry coating weight of 2.0 g / m², a surface coverage of 52%, and the penetration depth of the node reinforcement 21 was 42% of the thickness of the spunbond nonwoven fabric substrate 1. Cross-sectional observation showed that the node reinforcement 21 was located in the fiber intersection area and partially covered the overlapping positions of adjacent fibers, with through-holes 3 remaining between adjacent node reinforcement 21.

[0057] 4.2, Example 2

[0058] The selected basis weight is 14 g / m³. 2 Polypropylene and polylactic acid composite fiber spunbond nonwoven fabric was used as the substrate of the spunbond nonwoven fabric. 1. Take 100 parts of polycarbonate-type waterborne polyurethane emulsion, add deionized water to adjust the solid content to 32%, add 0.8% silane coupling agent and 0.8% carbodiimide crosslinking agent based on the solid content of waterborne polyurethane, and adjust the viscosity to 900 mPa·s.

[0059] A discontinuous strip coating method was adopted, with reinforcing strips extending along the length of the nonwoven fabric and spaced apart along its width. The coating speed was 45 m / min, the drying temperature was 85–110 °C, and the total drying time was 90 s. The resulting waterborne polyurethane reinforcing coating 2 had a dry coating weight of 2.8 g / m², a surface coverage of 60%, and the penetration depth of the node reinforcement 21 was 55% of the thickness of the spunbond nonwoven fabric substrate 1. No continuous film layer was formed in the unsealed breathable area 22, and the pores between fibers remained interconnected.

[0060] 4.3, Example 3

[0061] The selected basis weight is 10 g / m³. 2 Polylactic acid spunbond nonwoven fabric was used as the substrate of spunbond nonwoven fabric 1. 100 parts of polyester-type waterborne polyurethane emulsion were taken, and deionized water was added to adjust the solid content to 24%. Carbodiimide crosslinking agent of 1.5% based on the solid content of waterborne polyurethane was added to adjust the viscosity to 480 mPa·s.

[0062] A roller-dot coating method was used, with a coating speed of 70 m / min, a coating pressure of 0.18 MPa, a drying temperature of 75–100 °C, and a total drying time of 60 s. The resulting waterborne polyurethane reinforced coating 2 had a dry coating weight of 1.4 g / m², a surface coverage of 40%, and the penetration depth of the node reinforcement 21 was 28% of the thickness of the spunbond nonwoven fabric substrate 1. This example illustrates that node reinforcement 21 and unsealed breathable areas 22 can still be formed under conditions of lower basis weight and lower coating weight.

[0063] 4.4, Example 4

[0064] The selected basis weight is 18 g / m³. 2 Polypropylene spunbond nonwoven fabric was used as the substrate of spunbond nonwoven fabric 1. 100 parts of polyether-type waterborne polyurethane emulsion were taken, and deionized water was added to adjust the solid content to 35%. 2.0% of a blocked isocyanate crosslinking agent based on the solid content of waterborne polyurethane was added to adjust the viscosity to 1100 mPa·s.

[0065] A roller-coating method was used, with a coating speed of 40 m / min, a coating pressure of 0.30 MPa, a drying temperature of 90–115 °C, and a total drying time of 100 s. The resulting waterborne polyurethane reinforced coating 2 had a dry coating weight of 4.2 g / m³. 2 The surface coverage is 72%, and the penetration depth of the node reinforcement 21 is 65% of the thickness of the spunbond nonwoven fabric substrate 1. This embodiment is used to illustrate that the unsealed breathable area 22 can still be retained under the conditions of higher basis weight, higher coating amount and higher coverage as defined in the claims.

[0066] V. Comparative Examples

[0067] 5.1 Comparative Example 1

[0068] Using the same 12g / m³ as in Example 1 2 A polypropylene spunbond nonwoven fabric, but without a water-based polyurethane reinforcing coating. This comparative example is used to evaluate the strength and water resistance of a low-basis-weight spunbond nonwoven fabric substrate 1 without the formation of node reinforcements 21.

[0069] 5.2 Comparative Example 2

[0070] Using the same 12g / m³ as in Example 1 2 Polypropylene spunbond nonwoven fabric and the same waterborne polyurethane emulsion are used, but a continuous waterborne polyurethane film is formed by a doctor blade coating method. The dry coating weight is 2.0 g / m². 2 The surface coverage is 95%. This comparative example is used to evaluate the effect of continuous membrane layers on air permeability.

[0071] 5.3 Comparative Example 3

[0072] Using the same 12g / m³ as in Example 1 2 Polypropylene spunbond nonwoven fabric and the same waterborne polyurethane coating solution were used, but the coating pressure was reduced and the coating speed was increased, allowing the waterborne polyurethane to remain primarily on the substrate surface. The resulting coating dry coating weight was 2.0 g / m². 2 The surface coverage was 50%, and the penetration depth was 12% of the thickness of the spunbond nonwoven fabric substrate. This comparative example was used to evaluate the impact of a penetration depth of less than 20% on the node consolidation effect.

[0073] 5.4, ​​Comparative Example 4

[0074] Using the same 12g / m³ as in Example 1 2 Polypropylene spunbond nonwoven fabric and the same waterborne polyurethane emulsion were used, but the emulsion viscosity and coating pressure were increased, causing the coating liquid to penetrate too many fiber pores. The resulting coating dry coating weight was 6.2 g / m². 2 The surface coverage was 82%, and the penetration depth was 85% of the thickness of the spunbond nonwoven substrate. This comparative example was used to evaluate the effects of excessive penetration and high coverage on the retention of air permeability pores.

[0075] 5.5, Comparative Example 5

[0076] It adopts the outer composite structure of conventional adult diapers, including 18g / m² 2 Polypropylene spunbond nonwoven fabric with 18g / m 2 Breathable PE membrane composite layer. This comparative example is used to evaluate the performance of the present invention without a separate PE waterproof membrane layer.

[0077] VI. Testing Methods

[0078] 6.1 Basis Weight Test

[0079] The standard basis weight test method for nonwoven fabrics was used. Five 100mm × 100mm samples were cut from each group of samples, weighed, and converted to g / m³. 2 Take the average value.

[0080] 6.2 Thickness Test

[0081] The thickness of the samples was measured using a thickness gauge under a pressure of 2 kPa. Five locations were tested for each group of samples, and the average value was taken.

[0082] 6.3 Surface Coverage Test

[0083] The samples were observed under a microscope at 50x magnification. Five fields of view were randomly selected from each group of samples, and the projected area of ​​the waterborne polyurethane coating was identified using image analysis software. The average value was calculated as "surface coverage P = coating projected area / total area of ​​measurement area × 100%".

[0084] 6.4 Penetration Depth Test

[0085] The samples were frozen and sectioned for cross-sectional microscopic observation. Ten node reinforcement sections 21 were selected from each group of samples. The maximum penetration depth of the node reinforcement section 21 from the coating surface to the thickness direction was measured, and the average value was calculated according to "penetration depth ratio D = maximum penetration depth of node reinforcement section / thickness of spunbond nonwoven fabric substrate × 100%".

[0086] 6.5 Tensile strength test

[0087] The tensile properties of nonwoven fabrics were tested according to standard testing methods. The sample width was 50 mm, the clamping distance was 100 mm, and the tensile speed was 100 mm / min. The longitudinal tensile strength and transverse tensile strength were tested separately. Five samples were tested in each group, and the average value was taken.

[0088] 6.6 Hydrostatic Pressure Resistance Test

[0089] The hydrostatic pressure tester was used to test the water pressure resistance of the samples. The water pressure rise rate was 60 cmH2O / min, and the water pressure value at the third seepage point was recorded. Each group of samples was tested 5 times, and the average value was taken.

[0090] 6.7 Air permeability test

[0091] An air permeability tester was used to measure the airflow per unit area under a specified pressure difference. Five locations were tested for each sample, and the average value was taken. Since different devices may use different units, the following data are expressed in mm / s.

[0092] 6.8 Moisture permeability test

[0093] Water vapor transmission rate was tested using the cup method at a temperature of 38℃ and a relative humidity of 90% for 24 hours. Results are expressed in g / (m³).2 ·24h) indicates.

[0094] 6.9 Performance retention test after kneading

[0095] The sample was rubbed alternately longitudinally and transversely 20 times, and then its hydrostatic pressure resistance and air permeability were tested. Performance retention was calculated using the following formula:

[0096] Performance retention rate = Performance value after kneading / Performance value before kneading × 100%.

[0097] Among them, the hydrostatic pressure resistance retention rate and air permeability retention rate are calculated according to the corresponding indicators.

[0098] 6.10. Adult Incontinence Drug Simulation Test

[0099] The materials obtained in the examples and comparative examples were used as the waterproof and breathable outer layer 43, and were used together with the same liquid-permeable surface layer 41 and the same absorbent core 42 to prepare a simulated adult incontinence product. The absorbent core 42 was composed of fluff pulp and superabsorbent resin, with the total absorption capacity kept consistent. The simulated sample was laid flat on the test platform, and 0.9% sodium chloride aqueous solution was added to the central area three times, 100 mL each time, with an interval of 10 min. 30 min after the addition was completed, the outside of the waterproof and breathable outer layer 43 was observed for any liquid seepage, and the moisture level on the outside of the sample was recorded. Five samples were tested in each group.

[0100] VII. Test Results

[0101] 7.1 Parameter Settings

[0102] The structural parameters of the test examples and comparative examples are shown in Table 1.

[0103] Table 1 Structural Parameters

[0104]

[0105] As shown in Table 1, in Examples 1 to 4, the waterborne polyurethane reinforced coating 2 forms node reinforcement 21 and unsealed breathable area 22 within the scope defined in the claims. Comparative Example 2 forms a continuous film layer and does not have unsealed breathable area 22; although the surface coverage of Comparative Example 3 is close to that of Example 1, the penetration depth is less than 20%; the penetration depth of Comparative Example 4 is greater than 70%, and the coating enters too many fiber pores.

[0106] 7.2 Comparison of physical properties

[0107] The results of the basic physical performance tests are shown in Table 2.

[0108] Table 2 Basic Physical Properties

[0109]

[0110] As shown in Table 2, compared with Comparative Example 1, the longitudinal tensile strength, transverse tensile strength, and hydrostatic pressure resistance of Examples 1-4 are all improved. Comparative Examples 2 and 4 have higher hydrostatic pressure resistance, but their air permeability and moisture permeability decrease significantly, indicating that continuous membrane layers or excessive penetration reduce the permeable pores 3. Due to insufficient penetration depth, the waterborne polyurethane in Comparative Example 3 did not fully enter the fiber cross-section area, resulting in lower tensile strength and hydrostatic pressure resistance than Example 1.

[0111] 7.3 Comparison of performance retention capabilities

[0112] The results of the performance retention test after kneading are shown in Table 3.

[0113] Table 3 Results of performance retention after kneading

[0114]

[0115] In Table 3, the hydrostatic pressure retention rate is calculated as the ratio of the hydrostatic pressure after rubbing to the hydrostatic pressure before rubbing. For example, the hydrostatic pressure retention rate of Example 1 is 322 / 360 × 100% = 89.4%. Examples 1 to 4 maintained a high hydrostatic pressure retention rate and a high air permeability after rubbing, indicating that the solidified structure formed by the node reinforcement 21 in the fiber cross-section area can still retain a certain degree of waterproof and breathable performance after rubbing. The hydrostatic pressure retention rate of Comparative Example 3 is relatively low, indicating that when the coating mainly stays on the surface, the waterproof performance decreases significantly after rubbing.

[0116] 7.4. Terminal Product Simulation Testing

[0117] The results of the simulated use test of adult incontinence products are shown in Table 4.

[0118] Table 4 Results of simulated use test of adult incontinence products

[0119]

[0120] As shown in Table 4, no liquid seepage was observed on the outer surface of Examples 1, 2, and 4 when used as simulated adult incontinence products. Example 3, due to its lower substrate weight and coating amount, showed localized wet marks at the edge of one sample, but it was still superior to the uncoated Comparative Example 1. Example 3, using a lower substrate weight and lower dry coating amount, is suitable for the outer layer of adult incontinence products with light to moderate absorbency or high breathability requirements. For high absorbency or overnight adult incontinence products, combinations of parameters from Examples 1, 2, or 4 can be used. Although no liquid seepage was observed in Comparative Examples 2 and 4, their breathability was low, consistent with the results in Table 2. Comparative Example 5 relies on an independent PE waterproof membrane layer for waterproofing, and its material structure differs from the scheme of this invention that does not include an independent PE waterproof membrane layer.

[0121] As can be seen from the above embodiments, the present invention uses a roller-dot or strip-intermittent coating method to form node reinforcement portions 21 in the fiber cross-section area of ​​the spunbond nonwoven fabric substrate 1, and retains unsealed breathable areas 22 between adjacent node reinforcement portions 21. The node reinforcement portions 21 are used to improve the fiber connection stability of the low basis weight spunbond nonwoven fabric substrate 1; the unsealed breathable areas 22 are used to retain through-breathable pores 3. The two work together to enable the material to be used as a waterproof and breathable outer layer 43 of adult incontinence products 4 without the need for a separate PE waterproof membrane layer.

[0122] This invention does not achieve waterproofing by forming a full-width continuous film on the surface of low-basis-weight nonwoven fabric. Instead, it achieves waterproofing by controlling the discontinuous distribution of the waterborne polyurethane reinforced coating 2, the penetration depth of the node reinforcement 21, and the retention state of the unsealed breathable area 22, so that the coating has both fiber node consolidation and porosity retention functions. Compared with uncoated low-basis-weight spunbond nonwoven fabric, this invention improves the tensile strength and hydrostatic pressure resistance of the material; compared with continuously coated waterborne polyurethane film layers, this invention retains higher air permeability and moisture permeability; and compared with composite outer layers with independent PE waterproof membrane layers, this invention reduces the need for independent PE waterproof membrane layers.

[0123] In practical applications, the waterproof and breathable outer layer 43 can be connected to other layers of the adult incontinence product 4 via hot pressing, adhesive bonding, or ultrasonic bonding. The connection area can be located in the edge sealing area, waistband area, or leg opening leak-proof area to avoid completely sealing the main breathable area corresponding to the absorbent core 42. The liquid-permeable surface layer 41 can be made of hydrophilic nonwoven fabric, and the absorbent core 42 can be formed by a combination of fluff pulp, superabsorbent resin, a diversion layer, and a covering layer.

[0124] To adapt to different absorption capacities and wearing scenarios of adult incontinence products 4, the coating amount and coverage of the waterborne polyurethane reinforced coating 2 can be adjusted within the scope of the technical solution of this invention. For mild to moderate incontinence products, a lower basis weight substrate and a lower dry coating amount can be used to improve softness and breathability; for overnight or high-absorbency adult diapers, a higher basis weight substrate and a higher dry coating amount can be used to improve hydrostatic pressure resistance and retention performance after rubbing. Regardless of the parameter combination used, the penetration depth of the node reinforcement 21 should be maintained at 20% to 70% of the thickness of the spunbond nonwoven fabric substrate 1, and the unsealed breathable area 22 should retain through-breathable pores 3.

[0125] In summary, this invention achieves a waterproof and breathable outer layer 43 suitable for adult incontinence products 4 through the structural coordination between a low-basis-weight spunbond nonwoven fabric substrate 1, a waterborne polyurethane reinforcing coating 2, node reinforcement sections 21, unsealed breathable areas 22, and through-hole breathable pores 3. Those skilled in the art can prepare and verify the waterborne polyurethane-reinforced low-basis-weight waterproof and breathable nonwoven fabric of this invention based on the raw materials, process parameters, test methods, and example data disclosed in this specification.

Claims

1. A water-based polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric, characterized in that, It includes a spunbond nonwoven fabric substrate and an aqueous polyurethane reinforcing coating formed on at least one side of the spunbond nonwoven fabric substrate; the basis weight of the spunbond nonwoven fabric substrate is 8-18 g / m³. 2 The waterborne polyurethane reinforced coating is formed by applying and drying waterborne polyurethane emulsion through roller dot or strip intermittent coating. The waterborne polyurethane reinforced coating includes node reinforcement sections located in the fiber cross regions and unsealed breathable areas located between adjacent node reinforcement sections. The node reinforcement sections penetrate into the thickness direction of the spunbond nonwoven fabric substrate, and the penetration depth is 20% to 70% of the thickness of the spunbond nonwoven fabric substrate. The unsealed breathable areas retain through-breathable pores. The node reinforcement sections and the unsealed breathable areas together form a discontinuous waterproof and breathable reinforced structure, so that when the waterborne polyurethane reinforced low-basis-weight waterproof and breathable nonwoven fabric is used as the outer layer of adult incontinence products, there is no need to set an independent PE waterproof membrane layer.

2. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, The node reinforcement at least partially covers the overlap position of adjacent fibers and forms a dot-like or short strip-like consolidation structure between adjacent fibers, the consolidation structure causing the adjacent fibers to form a local bonding point at the overlap position.

3. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, The spunbond nonwoven fabric substrate is polypropylene spunbond nonwoven fabric, polylactic acid spunbond nonwoven fabric, polyester spunbond nonwoven fabric, or polypropylene and polylactic acid composite fiber spunbond nonwoven fabric.

4. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, The waterborne polyurethane emulsion includes at least one of polyester-type waterborne polyurethane, polyether-type waterborne polyurethane, or polycarbonate-type waterborne polyurethane, and contains a crosslinking component for improving wet bonding stability.

5. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 4, characterized in that, The crosslinking component is at least one of carbodiimide crosslinking agent, aziridine crosslinking agent, blocked isocyanate crosslinking agent or silane coupling agent, and the mass content of the crosslinking component relative to the solids of waterborne polyurethane is 0.3% to 5%.

6. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, The dry coating weight of the waterborne polyurethane reinforced coating is 0.8–5.0 g / m². 2 Furthermore, the waterborne polyurethane reinforced coating has a surface coverage of 35% to 75% on the surface of the spunbond nonwoven fabric substrate.

7. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, When the waterborne polyurethane reinforced coating is formed by roller dot coating, the node reinforcement is a discrete reinforcement point distributed at intervals along the length and width directions of the nonwoven fabric; when the waterborne polyurethane reinforced coating is formed by strip discontinuous coating, the node reinforcement is a reinforcing strip extending along the length direction of the nonwoven fabric and spaced apart along the width direction.

8. The waterborne polyurethane-reinforced low-weight waterproof and breathable nonwoven fabric according to claim 1, characterized in that, No continuous waterborne polyurethane film layer is formed throughout the entire width of the unsealed breathable area, and the through-breathable pores are formed by the inter-fiber pores in the spunbond nonwoven fabric substrate that are not completely filled with waterborne polyurethane.

9. An adult incontinence product, characterized in that, It includes a liquid-permeable surface layer, an absorbent core, and a waterproof and breathable outer layer, wherein the waterproof and breathable outer layer is a water-based polyurethane-reinforced low-grammage waterproof and breathable nonwoven fabric as described in any one of claims 1 to 8, and the waterproof and breathable outer layer is disposed on the side of the absorbent core away from the liquid-permeable surface layer.

10. The adult incontinence product according to claim 9, characterized in that, The adult incontinence product is an adult diaper or an adult pull-up diaper, and the water-based polyurethane reinforced coating is located on the side of the spunbond nonwoven fabric substrate facing the absorbent core, or on the side of the spunbond nonwoven fabric substrate away from the absorbent core.

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