TPU waterproof fabric and preparation method thereof

Abstract

The application relates to the technical field of textile materials, and specifically provides a TPU waterproof fabric and a preparation method thereof. The preparation method comprises the following steps: TPU granules are melt-extruded, and TPU micro-fiber deposition is formed by a melt-blowing process to form a non-woven fabric; a TPU resin composition is subjected to melt plasticizing treatment, and a breathable film is formed by a film blowing process; TPU hot melt adhesive is arranged on the composite surface of the breathable film to form a hot melt adhesive layer; the non-woven fabric and the breathable film are laminated and hot-pressed to obtain a composite material; and the TPU waterproof fabric is obtained after cooling and setting. According to the application, the melt-blowing formed TPU non-woven fabric and the film-blowing formed TPU breathable film are combined, a continuous water-blocking structure is formed by using the TPU breathable film, liquid water is prevented from passing through the fiber pores in the non-woven fabric while the air permeability and elastic support effect of the TPU non-woven fabric are retained.

Description

Technical Field

[0001] This invention relates to the field of textile materials technology, and more specifically, to a TPU waterproof fabric and its preparation method. Background Technology

[0002] TPU material possesses excellent elasticity, abrasion resistance, bending resistance, and processing properties, and can be manufactured into TPU nonwoven fabric through meltblown technology. During meltblown molding, molten TPU is extruded through spinnerets and stretched into TPU microfibers under the action of high-speed hot air. These fibers then randomly deposit, overlap, and entangle to form a web. The resulting TPU nonwoven fabric exhibits good softness and elasticity, with numerous pores remaining between the fibers, allowing air and water vapor to pass through. Therefore, it is suitable for textile materials requiring a certain level of breathability and elasticity.

[0003] However, TPU meltblown nonwoven fabrics primarily rely on the random overlapping of microfibers to form a fiber network. The pores between these fibers are typically interconnected, making it difficult to create a continuous and complete water-blocking structure. When liquid water comes into contact with the nonwoven fabric surface, it easily penetrates the fabric along the pores between fibers under capillary action or external water pressure, and further permeates the fabric. Therefore, while existing TPU meltblown nonwoven fabrics can balance breathability, softness, and elasticity, their hydrostatic pressure resistance is low, making it difficult to meet the waterproofing requirements of applications such as waterproof clothing, protective equipment, and outdoor textile materials.

[0004] Existing technologies can reduce the permeability of liquid water by increasing the basis weight of nonwoven fabrics, reducing the porosity between fibers, or subjecting nonwoven fabrics to high-temperature hot pressing. However, increasing the basis weight of nonwoven fabrics increases material usage and product weight, while excessive hot pressing can easily cause large-area softening and bonding of TPU microfibers, compacting the fiber network and reducing air permeability, softness, and elasticity. Therefore, how to achieve stable liquid water barrier properties while preserving the original air permeability and elasticity of TPU meltblown nonwoven fabrics is a technical problem of ongoing concern in this field. Summary of the Invention

[0005] The present invention aims to provide a TPU waterproof fabric and its preparation method.

[0006] To address the above problems, this invention provides a method for preparing a TPU waterproof fabric, comprising the following steps: S100: TPU granules are melt-extruded and then melt-blown to form TPU microfibers, which are then deposited into a web to form a nonwoven fabric. S200: The TPU resin composition is melt-plasticized and then blown into a breathable film using a blown film process. S300. Apply TPU hot melt adhesive to the composite surface of the breathable membrane to form a hot melt adhesive layer. S400: Non-woven fabric and breathable membrane are laminated together and hot-pressed together through a hot melt adhesive layer to combine the non-woven fabric and breathable membrane into a composite material. S500, the composite material is cooled and shaped to obtain TPU waterproof fabric.

[0007] In the above technical solution, in S100, the TPU granules include first TPU granules and second TPU granules, and the nonwoven fabric is obtained through the following steps: S110. The first TPU granules are melted and extruded, and then formed into first TPU microfibers through a first melt-blowing process, so that the first TPU microfibers are deposited into a network to form the main support layer. S120. The second TPU granules are melt-extruded and formed into second TPU microfibers through a second melt-blowing process, so that the second TPU microfibers are deposited on one side of the main support layer to form an interface thermal activation layer. The Vicat softening temperature of the second TPU granules is lower than that of the first TPU granules, and the interface thermal activation layer and the hot melt adhesive layer are positioned opposite each other.

[0008] In the above technical solution, in S110, the first TPU granules include hydrolysis-resistant polyether TPU, and the Vicat softening temperature of the first TPU granules is 130~160℃; and / or the melt extrusion temperature of the first TPU granules is 195~225℃; and / or the high-speed hot air temperature in the first meltblown process is 210~240℃; and / or the basis weight of the main support layer is 30~120g / m³. 2 .

[0009] In the above technical solution, in S120, the second TPU granules include polyether TPU resin, the Vicat softening temperature of which is 90~120℃; and / or the melt extrusion temperature of the second TPU granules is 180~215℃; and / or the high-speed hot air temperature used in the second meltblown process is 195~230℃; and / or the basis weight of the interface thermally activated layer is 5~30g / m². 2 Furthermore, the weight of the interface thermally activated layer accounts for 8 to 22% of the total weight of the main support layer and the interface thermally activated layer.

[0010] In the above technical solution, in S200, the TPU resin composition includes hydrophilic polyether TPU and hydrolysis-resistant polyether TPU; based on the total mass of hydrophilic polyether TPU and hydrolysis-resistant polyether TPU as 100%, the mass ratio of hydrophilic polyether TPU is 70~95%, and the mass ratio of hydrolysis-resistant polyether TPU is 5~30%.

[0011] In the above technical solution, in S300, the hot melt adhesive layer is formed through the following steps: S310. Apply TPU hot melt adhesive to the release surface of the release carrier, so that the TPU hot melt adhesive forms a discontinuously distributed pre-formed adhesive layer on the release surface. S320. The pre-formed adhesive layer and the composite surface of the breathable membrane are placed opposite each other, and a heat transfer treatment is performed to transfer and adhere the pre-formed adhesive layer to the composite surface of the breathable membrane. S330. Cool the heat-transfer treated breathable membrane to keep the TPU hot melt adhesive transferred to the breathable membrane composite surface in a discontinuous distribution state. Then peel off the release carrier to obtain a breathable membrane with a hot melt adhesive layer.

[0012] In the above technical solution, the softening temperature of TPU hot melt adhesive is 70~100℃; and / or the temperature of heat transfer treatment is 85~110℃, the pressure is 0.03~0.12MPa, and the time is 1~5s.

[0013] In the above technical solution, in S400, the temperature of hot pressing composite is 105~125℃, the pressure is 0.15~0.30MPa, and the time is 8~15s.

[0014] In the above technical solution, in S500, the cooling and shaping treatment is carried out while the composite material is in a pressed state. After cooling the composite material to 30~40℃, the pressed state is released. This invention also provides a TPU waterproof fabric, prepared using any of the above-mentioned methods. The TPU waterproof fabric includes a nonwoven fabric, a hot melt adhesive layer, and a breathable membrane.

[0015] Beneficial effects (1) The present invention combines meltblown TPU nonwoven fabric with blown TPU breathable membrane, and uses TPU breathable membrane to form a continuous water-blocking structure on the surface of nonwoven fabric, blocking liquid water from penetrating along the interconnected pores between TPU microfibers, thereby making up for the deficiency that a single TPU meltblown nonwoven fabric is difficult to form an effective waterproof barrier, so that the resulting fabric has stable waterproof performance. (2) The present invention uses TPU hot melt adhesive to connect TPU nonwoven fabric and TPU breathable membrane. TPU hot melt adhesive has good material compatibility with nonwoven fabric and breathable membrane. During hot pressing, it can wet the surface of breathable membrane and embed into the fiber gap on one side of nonwoven fabric composite surface. After cooling, it forms a stable interface connection, reducing the separation of breathable membrane from nonwoven fabric during bending, stretching and use, thereby maintaining the integrity and waterproof stability of continuous water-blocking structure. (3) The present invention sets the TPU hot melt adhesive in a discontinuous form between the nonwoven fabric and the breathable membrane, and keeps it in a compressed state for cooling and shaping after hot pressing. This can achieve a reliable bond between the nonwoven fabric and the breathable membrane, while reducing the full coverage of the nonwoven fabric fiber pores and the surface of the breathable membrane by the hot melt adhesive, and reducing the excessive compaction of the nonwoven fabric during the hot pressing process. This allows the resulting fabric to maintain its original breathability, softness and elasticity while achieving waterproof performance. Detailed Implementation

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0017] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available. Experimental methods in the following examples that do not specify particular conditions should be performed according to conventional methods and conditions, or as selected in the product instructions.

[0018] This invention provides a TPU waterproof fabric and its preparation method. By combining meltblown TPU nonwoven fabric with blown TPU breathable membrane, a continuous water-blocking structure is formed using the TPU breathable membrane. This retains the breathability and elastic support of the TPU nonwoven fabric while preventing liquid water from passing through the fiber pores within the nonwoven fabric, solving the problem that existing TPU meltblown nonwoven fabrics are difficult to waterproof due to the interconnected pores between fibers. The TPU waterproof fabric of this application comprises, along its thickness direction, a nonwoven fabric, a hot melt adhesive layer, and a breathable membrane.

[0019] In a preferred embodiment, the nonwoven fabric of this application is obtained through the following steps: S110. The first TPU granules are melted and extruded, and then formed into first TPU microfibers through a first meltblown process, so that the first TPU microfibers are deposited into a network to form the main support layer. S120. The second TPU granules are melt-extruded and formed into second TPU microfibers through a second melt-blowing process, so that the second TPU microfibers are deposited on one side of the main support layer to form an interface thermal activation layer. The Vicat softening temperature of the second TPU granules is lower than that of the first TPU granules, and the interface thermal activation layer is disposed opposite to the hot melt adhesive layer.

[0020] The main support layer is the main fiber skeleton that constitutes the TPU waterproof fabric, providing thickness retention, tensile support, and morphological stability. The main support layer consists of overlapping first TPU microfibers, some of which are bonded together at the intersections, while maintaining fiber gaps between adjacent fibers, thus forming a continuous fiber web structure in the main support layer.

[0021] Preferably, the first TPU granules comprise hydrolysis-resistant polyether TPU, and the Vicat softening temperature of the first TPU granules is 130-160°C. Before the first meltblown process, the first TPU granules are dried at 80-100°C for 4-6 hours to reduce their moisture content to no more than 0.02%. The dried first TPU granules are melt-extruded at 195-225°C and stretched using high-speed hot air at 210-240°C to deposit the formed first TPU microfibers into a web. The average diameter of the first TPU microfibers is 3-30 μm, and the basis weight of the main support layer is 30-120 g / m². 2 .

[0022] The first TPU granules have a relatively high Vicat softening temperature, which is beneficial for the main support layer to maintain a continuous fiber skeleton during subsequent hot-pressing lamination, reducing excessive softening and compaction of the main support layer. It should be noted that the main support layer may undergo moderate compression or local fiber deformation during hot-pressing lamination. As long as the overlapping first TPU microfibers and the continuous fiber network structure are still retained after hot-pressing lamination, the support structure of the main support layer can be considered to be maintained.

[0023] The interface thermally activated layer is formed in situ on one side of the main support layer using a second TPU granule through a second melt-blowing process, and is located between the main support layer and the TPU hot melt adhesive layer. The interface thermally activated layer includes overlapping second TPU microfibers. Some of the second TPU microfibers enter the fiber gaps on the surface of the main support layer and overlap, entangle, or partially adhere to the first TPU microfibers, thereby forming a fiber-interpenetrating transition area between the main support layer and the interface thermally activated layer. By forming the interface thermally activated layer through in-situ melt-blowing, there is no need to set up a separate adhesive layer between the main support layer and the interface thermally activated layer.

[0024] Preferably, the TPU matrix resin used in the second TPU granules includes polyether TPU resin, with a Vicat softening temperature of 90~120℃, which is lower than that of the first TPU granules. Therefore, during the subsequent hot-pressing process, the second TPU microfibers can soften, compress, and reposition more easily than the first TPU microfibers, while the main support layer can still maintain a continuous fiber skeleton and bear the main support function.

[0025] It should be noted that the interfacial thermal activation referred to in this application means that the second TPU microfibers undergo moderate softening, bending, compression, or position adjustment under the action of hot pressing temperature and pressure, thereby improving the adhesion between the interfacial thermal activation layer and the TPU hot melt adhesive layer, without requiring the second TPU microfibers to completely melt or the interfacial thermal activation layer to be transformed into a continuous and dense film layer.

[0026] When forming the interfacial thermal activation layer, the second TPU granules are pre-dried before being fed into the melt extrusion device. Preferably, the second TPU granules are dried at 70~90℃ for 4~6 hours to ensure that their moisture content is not higher than 0.02%; the melt extrusion temperature of the second TPU granules is 180~215℃, and the high-speed hot air temperature used in the second meltblowing process is 195~230℃. After the second TPU melt is discharged through the spinneret, it is stretched under the action of high-speed hot air to form second TPU microfibers, which are then deposited on one side of the main support layer.

[0027] Preferably, the average diameter of the second TPU microfiber is 2~20μm; the basis weight of the interfacial thermally activated layer is 5~30g / m². 2 Furthermore, the basis weight of the interface thermally activated layer accounts for 8-22% of the total basis weight of the main support layer and the interface thermally activated layer. The aforementioned fiber diameter, basis weight, and basis weight ratio are conducive to forming a continuous interface transition region on the surface of the main support layer, while avoiding an excessively thick interface thermally activated layer that would significantly increase the overall thickness and hot-pressing deformation of the double-layer TPU meltblown structure.

[0028] The breathable membrane of this application is formed by melt-plasticizing a TPU resin composition and then using a blown film process. The breathable membrane is a continuous film layer that prevents liquid water from passing directly through while allowing water vapor to pass through. It should be noted that the breathability referred to in this application mainly refers to the water vapor permeability of the breathable membrane. By forming a continuous water-blocking structure through the TPU breathable membrane, the composite fabric maintains a certain water vapor permeability while preventing liquid water from passing through the fiber pores inside the nonwoven fabric, while simultaneously providing elastic support to the TPU nonwoven fabric.

[0029] Preferably, the TPU resin composition comprises hydrophilic polyether TPU and hydrolysis-resistant polyether TPU. Based on the total mass of hydrophilic polyether TPU and hydrolysis-resistant polyether TPU as 100%, the mass percentage of hydrophilic polyether TPU is 70-95%, and the mass percentage of hydrolysis-resistant polyether TPU is 5-30%. The hydrophilic segments in the hydrophilic polyether TPU can adsorb water vapor on the high-humidity side of the breathable membrane and allow water molecules to diffuse along the polymer segments and intermolecular free volume to the low-humidity side, thus enabling the continuous TPU film layer to block liquid water while allowing water vapor to permeate. The hydrolysis-resistant polyether TPU and hydrophilic polyether TPU together form a continuous film, which can improve the melt strength and bubble stability of the TPU resin composition, enhance the hydrolysis resistance and mechanical strength of the breathable membrane, and reduce the risk of membrane breakage or excessive deformation during blown film, winding, and subsequent hot-pressing lamination. When the mass percentage of hydrophilic polyether TPU is less than 70%, the number of hydrophilic segments in the membrane layer that can participate in water vapor adsorption and diffusion is relatively small, which may result in insufficient water vapor permeability of the breathable membrane. When its mass percentage is higher than 95%, the dimensional stability and mechanical stability of the breathable membrane after moisture absorption may decrease. Controlling the proportions of hydrophilic polyether TPU and hydrolysis-resistant polyether TPU within the above-mentioned range allows the breathable membrane to form a continuous water-blocking structure while balancing water vapor permeability, blown film processing stability, and structural integrity during use.

[0030] In the preparation process, the TPU resin composition is preferably dried first, then fed into an extruder for melt plasticization, and extruded through a ring die to form a membrane tube. This membrane tube is then sequentially inflated, drawn, cooled, and wound to obtain a breathable membrane with a thickness of 20-80 μm. By controlling the degree of melt plasticization and the membrane bubble formation state, the thickness of the breathable membrane is kept uniform, reducing pinholes, localized weak areas, and membrane surface wrinkles, thereby ensuring the formation of a continuous and stable water-blocking structure.

[0031] The hot melt adhesive layer of this application is formed through the following steps: S310. The TPU hot melt adhesive is applied to the release surface of the release carrier, so that the TPU hot melt adhesive forms a discontinuously distributed pre-formed adhesive layer on the release surface. S320. The pre-formed adhesive layer and the composite surface of the breathable membrane are positioned opposite each other, and a heat transfer treatment is performed to transfer and adhere the pre-formed adhesive layer to the composite surface of the breathable membrane. S330. The breathable membrane that has undergone the heat transfer treatment is cooled to keep the TPU hot melt adhesive transferred to the composite surface of the breathable membrane in a discontinuous distribution state. Then the release carrier is peeled off to obtain a breathable membrane with the hot melt adhesive layer.

[0032] Preferably, the softening temperature of the TPU hot melt adhesive is 70~100℃. The TPU hot melt adhesive has good compatibility with non-woven fabric and breathable membrane. After softening by heat, it can wet the surface of the breathable membrane and enter some of the fiber gaps on the surface of the interfacial heat-activated layer during the subsequent hot pressing process. After cooling, it stably connects the breathable membrane and the non-woven fabric.

[0033] In S310, TPU hot melt adhesive is applied to the surface of the release carrier in the form of dots, meshes, strips, or spaced areas to form a discontinuously distributed pre-formed adhesive layer. By using the release carrier to predefine the distribution location and coverage area of ​​the hot melt adhesive, excessive penetration along the fiber gaps when the hot melt adhesive is directly applied to the porous nonwoven fabric can be avoided, allowing the hot melt adhesive to be retained more concentratedly at the composite interface between the nonwoven fabric and the breathable membrane.

[0034] In S320, the pre-formed adhesive layer is bonded to the composite surface of the breathable membrane and then heat-transferred for 1-5 seconds at 85-110℃ and 0.03-0.12MPa. During the heat transfer process, the TPU hot melt adhesive softens moderately and adheres to the surface of the breathable membrane. At the same time, by controlling the temperature, pressure, and time, excessive flow of the adhesive layer is reduced, so that the transferred TPU hot melt adhesive still maintains a discontinuous distribution.

[0035] In S330, the heat-transfer treated breathable membrane is cooled to reduce the flowability of the TPU hot melt adhesive before peeling off the release carrier. The cooling process helps to fix the shape and position of the hot melt adhesive, reducing adhesive layer dragging, deformation, or adhesion between adjacent bonded areas during peeling.

[0036] During the subsequent hot-pressing lamination process, the hot melt adhesive layer is heated and softened again, coming into contact with the interfacial thermally activated layer. Some of the hot melt adhesive enters between the second TPU microfibers, while the second TPU microfibers in the interfacial thermally activated layer simultaneously undergo moderate softening and repositioning, thereby increasing the contact area between the hot melt adhesive and the fibers. After cooling and setting, the breathable membrane is stably bonded to the surface of the nonwoven fabric, and its continuous structure prevents liquid water from passing through the fiber pores of the nonwoven fabric.

[0037] In an optional embodiment, the surface of the breathable membrane to be laminated is subjected to surface activation treatment before applying the TPU hot melt adhesive. The surface activation treatment includes corona treatment, which brings the surface wetting tension of the treated surface to 38~45 mN / m. Corona treatment improves the wettability of the breathable membrane surface to be laminated, which is beneficial for the uniform spreading and adhesion of the TPU hot melt adhesive on the membrane surface, reducing shrinkage, missing adhesive dots, and localized insufficient adhesion.

[0038] In step S400, the nonwoven fabric and the breathable membrane are bonded together and then hot-pressed using the hot melt adhesive layer to bond the nonwoven fabric and the breathable membrane, thus obtaining a composite material. Preferably, the hot-pressing temperature is 105~125℃, the pressure is 0.15~0.30MPa, and the time is 8~15s. The hot-pressing temperature is not lower than the softening temperature of the TPU hot melt adhesive, so that the TPU hot melt adhesive can soften upon heating and wet the composite surface of the breathable membrane and the nonwoven fabric.

[0039] In embodiments of nonwoven fabrics comprising a main support layer and an interface thermally activated layer, the hot-pressing composite temperature is preferably higher than the Vicat softening temperature of the second TPU granules and lower than the Vicat softening temperature of the first TPU granules. This allows the second TPU microfibers in the interface thermally activated layer to undergo moderate softening, bending, and repositioning, while the main support layer maintains a continuous fiber skeleton, reducing excessive softening and compaction of the main support layer.

[0040] During hot-press lamination, the TPU hot melt adhesive softens upon heating and comes into contact with the second TPU microfibers on the surface of the interface thermally activated layer. Some of the TPU hot melt adhesive penetrates between the second TPU microfibers, wetting and coating adjacent second TPU microfibers, thus forming a composite interface where the hot melt adhesive layer and the interface thermally activated layer are bonded together. After hot-press lamination, the interface thermally activated layer retains at least part of the second TPU microfiber structure, rather than transforming entirely into a continuous, dense film, to reduce the significant hardening of the interface area due to excessive film formation.

[0041] In S500, the hot-pressed composite material is cooled and shaped while maintaining the pressure. After cooling the composite material to 30-40°C, the pressure is released, resulting in a TPU waterproof fabric. Maintaining the pressure while cooling restricts relative movement between the nonwoven fabric, hot melt adhesive layer, and breathable membrane, and allows the TPU hot melt adhesive to gradually solidify under confined conditions. This stabilizes the bonding structure between the hot melt adhesive layer, the breathable membrane, and the nonwoven fabric, reducing localized delamination or interlayer displacement caused by the rebound of nonwoven fibers after pressure is released.

[0042] Example 1

[0043] This embodiment provides a TPU waterproof fabric and its preparation method, including the following steps: S110. Hydrolysis-resistant polyether TPU granules with a Vicat softening temperature of 145℃ are dried at 90℃ for 5 hours to ensure a moisture content of no more than 0.02%. The dried TPU granules are then melt-extruded at 210℃ and stretched using high-speed hot air at 225℃ to randomly deposit first TPU microfibers with an average diameter of approximately 12μm into a web, yielding a basis weight of 70g / m². 2 The main support layer; S120. Polyether TPU granules with a Vicat softening temperature of 105℃ are dried at 80℃ for 5 hours to ensure a moisture content of no more than 0.02%. The dried second TPU granules are then melt-extruded at 198℃ and subjected to a second melt-blowing process using high-speed hot air at 212℃ to deposit second TPU microfibers with an average diameter of approximately 8μm on the surface of the main support layer, forming a product with a basis weight of 15g / m². 2 The interface thermally activated layer accounts for 17.65% of the total weight of the main support layer and the interface thermally activated layer; S200: Hydrophilic polyether TPU and hydrolysis-resistant polyether TPU are dried at 80°C for 5 hours to ensure that their moisture content is not higher than 0.02%. The hydrophilic polyether TPU and hydrolysis-resistant polyether TPU are mixed at a mass ratio of 85:15 to obtain a TPU resin composition. The TPU resin composition is fed into a blown film extruder, melt-plasticized at 200°C, extruded through a ring die, and then blown, drawn, and cooled sequentially to obtain a breathable film with a thickness of 40 μm. S310. A polyether-type TPU hot melt adhesive with a softening temperature of 88℃ is selected. The TPU hot melt adhesive is applied to the release surface of the release film in a dotted manner using a gravure roller, resulting in a coating amount of 8g / m². 2 A discontinuous pre-formed adhesive layer with a coverage of 32%; S320. The composite surface of the breathable membrane is corona treated to make its surface wetting tension reach 42mN / m; the pre-formed adhesive layer is bonded to the corona-treated composite surface of the breathable membrane and heat-transferred for 3s at 98℃ and 0.08MPa to transfer and adhere the pre-formed adhesive layer to the composite surface of the breathable membrane. S330. Cool the heat-transfer treated breathable membrane to 35°C, and then peel off the release film to obtain a breathable membrane with a discontinuous hot melt adhesive layer on the composite surface. S400, the interface thermal activation layer and the hot melt adhesive layer are bonded together and hot-pressed at 115℃ and 0.22MPa for 12s to obtain the composite material; S500 After the hot pressing of the composite material is completed, the pressing effect of the double belt on the composite material is not released. The composite material continues to enter the cooling pressing zone and is cooled while maintaining the pressing state. When the composite material is cooled to 35°C, the pressure is released and the material is rolled up to obtain the TPU waterproof fabric.

[0044] Example 2

[0045] This embodiment provides a TPU waterproof fabric and its preparation method, including the following steps: S110. Hydrolysis-resistant polyether TPU granules with a Vicat softening temperature of 130℃ are dried at 80℃ for 4 hours to ensure a moisture content of no more than 0.02%. The dried TPU granules are then melt-extruded at 195℃ and stretched using high-speed hot air at 210℃ to randomly deposit first TPU microfibers with an average diameter of approximately 30μm into a web, yielding a basis weight of 30g / m². 2 The main support layer; S120. The polyether TPU granules with a Vicat softening temperature of 90℃ are dried at 70℃ for 4 hours to ensure a moisture content of no more than 0.02%. The dried second TPU granules are then melt-extruded at 180℃ and subjected to a second melt-blowing process using high-speed hot air at 195℃ to deposit second TPU microfibers with an average diameter of approximately 2μm on the surface of the main support layer, forming a product with a basis weight of 5g / m². 2 The interface thermally activated layer accounts for 14.29% of the total weight of the main support layer and the interface thermally activated layer. S200. Hydrophilic polyether TPU and hydrolysis-resistant polyether TPU are dried at 75°C for 4 hours, and then mixed at a mass ratio of 70:30. The resulting TPU resin composition is melt-plasticized at 190°C and blown, stretched and cooled sequentially to obtain a breathable membrane with a thickness of 20μm. S310. Apply polyether-type TPU hot melt adhesive with a softening temperature of 70℃ to the release surface of the release film in a discontinuous grid pattern to form a coating amount of 3g / m². 2 A discontinuous pre-formed adhesive layer with a coverage of 20%; S320. The composite surface of the breathable membrane is corona treated to make its surface wetting tension reach 38mN / m; the pre-formed adhesive layer is bonded to the composite surface of the breathable membrane and heat-transferred for 1s at 85℃ and 0.03MPa. S330. Cool the heat-transfer treated breathable membrane to 30°C, and then peel off the release film to obtain a breathable membrane with a discontinuous hot melt adhesive layer. S400, the interface thermal activation layer and the hot melt adhesive layer are bonded together and hot-pressed at 105℃ and 0.15MPa for 15s to obtain the composite material; S500: After hot pressing the composite material, continue to maintain the pressed state, cool the composite material to 30°C, then release the pressure and roll it up to obtain TPU waterproof fabric.

[0046] Example 3

[0047] This embodiment provides a TPU waterproof fabric and its preparation method, including the following steps: S110. Hydrolysis-resistant polyether TPU granules with a Vicat softening temperature of 160℃ are dried at 100℃ for 6 hours to ensure a moisture content of no more than 0.02%. The dried TPU granules are then melt-extruded at 225℃ and stretched using high-speed hot air at 240℃ to randomly deposit first TPU microfibers with an average diameter of approximately 5μm into a web, yielding a basis weight of 120g / m². 2 The main support layer; S120. Polyether TPU granules with a Vicat softening temperature of 115℃ are dried at 90℃ for 6 hours to ensure a moisture content of no more than 0.02%. The dried second TPU granules are then melt-extruded at 215℃ and subjected to a second melt-blowing process using high-speed hot air at 230℃ to deposit second TPU microfibers with an average diameter of approximately 5μm on the surface of the main support layer, forming a product with a basis weight of 30g / m². 2 The interface thermal activation layer accounts for 20% of the total weight of the main support layer and the interface thermal activation layer; S200. Hydrophilic polyether TPU and hydrolysis-resistant polyether TPU are dried at 90°C for 6 hours, and then mixed at a mass ratio of 95:5. The resulting TPU resin composition is melt-plasticized at 210°C and blown, stretched and cooled sequentially to obtain a breathable membrane with a thickness of 80μm. S310. Apply polyether-type TPU hot melt adhesive with a softening temperature of 100℃ to the release surface of the release film in a spaced strip pattern to form a coating amount of 15g / m². 2 A discontinuous pre-formed adhesive layer with a coverage of 45%; S320. The composite surface of the breathable membrane is corona treated to make its surface wetting tension reach 45mN / m; the pre-formed adhesive layer is bonded to the composite surface of the breathable membrane and heat-transferred for 5s at 110℃ and 0.12MPa. S330. Cool the heat-transfer treated breathable membrane to 40°C, and then peel off the release film to obtain a breathable membrane with a discontinuous hot melt adhesive layer. S400: The interface thermally activated layer and the hot melt adhesive layer are stacked opposite each other and hot-pressed at 125℃ and 0.30MPa for 8s to obtain the composite material. S500: After the composite material is hot-pressed, keep it in the pressed state, cool the composite material to 40°C and then release the pressure to obtain TPU waterproof fabric.

[0048] Comparative Example 1 This comparative example provides a TPU waterproof fabric and its preparation method, which is the same as in Example 1, except that only S110 and S120 are performed, that is, S200, S310~S330, S400 and S500 are no longer performed.

[0049] Comparative Example 2 This comparative example provides a TPU waterproof fabric and its preparation method, which is the same as in Example 1, except that: S120 is not performed, i.e., the interfacial heat-activated layer is not formed, and the basis weight of the main support layer is adjusted to 85 g / m². 2 The total weight of the nonwoven fabric was made the same as in Example 1.

[0050] Comparative Example 3 This comparative example provides a TPU waterproof fabric and its preparation method, which is the same as in Example 1, except that in S120, the second TPU granules are made of the same hydrolysis-resistant polyether TPU as the first TPU granules, with a Vicat softening temperature of 145°C. Specifically, the second TPU granules are dried at 90°C for 5 hours, melt-extruded at 210°C, and stretched using high-speed hot air at 225°C to form a fabric with a basis weight of 15 g / m². 2 The second TPU meltblown fiber layer.

[0051] Comparative Example 4 This comparative example provides a TPU waterproof fabric and its preparation method. The preparation method is the same as in Example 1, except that steps S310~S330 are omitted, and the coating amount is 8g / m². 2 A 32% coverage TPU hot melt adhesive is applied directly to the surface of the interface heat-activated layer in a dotted manner, and then hot-pressed and laminated with the breathable membrane.

[0052] Comparative Example 5 This comparative example provides a TPU waterproof fabric and its preparation method, which is the same as in Example 1, except that in S310, the TPU hot melt adhesive is applied to the surface of the release film in a full-width continuous manner, and the hot melt adhesive coating amount is still 8g / m². 2 The coverage rate is 100%.

[0053] Comparative Example 6 This comparative example provides a TPU waterproof fabric and its preparation method. The preparation method is the same as that in Example 1, except that in S500, the pressure is released immediately after the hot-pressing composite is completed, and the composite material is allowed to cool naturally to room temperature in a pressure-free state.

[0054] Performance testing The samples obtained in Examples 1-3 and Comparative Examples 1-6 were placed in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours and then the following performance tests were conducted. The results are shown in Tables 1-3. Initial peel strength: The sample was cut longitudinally into specimens with a width of 25 mm and a length of 200 mm. The nonwoven fabric and the breathable membrane were pre-separated to form a clamping end. The sample was peeled at 180° under the condition of a tensile speed of 100 mm / min. The average force in the stable peeling stage was taken as the initial peel strength. The results are shown in Table 1. Peel strength after damp heat aging: The sample was placed in a constant temperature and humidity environment of 70±2℃ and 95±3% for 168h. After being taken out, it was conditioned in an environment of 20±2℃ and 65±4% for 24h. The peel strength after damp heat aging was then measured according to the initial peel strength. The results are shown in Table 1. Peel strength after washing: The sample was washed for 5 cycles using a standard washing program at 40℃. After washing, the sample was conditioned for 24 hours at a temperature of 20±2℃ and a relative humidity of 65±4%. The peel strength after washing was then measured according to the initial peel strength. The results are shown in Table 1. Table 1

[0055] As shown in Table 1, all embodiments of the present invention exhibit high interfacial bonding strength and maintain a high retention rate after damp heat aging and washing. Comparative Example 2 lacks an interfacial thermal activation layer; the TPU hot melt adhesive layer directly contacts the main support layer. Under the same hot pressing conditions, the softening and repositioning of the surface fibers of the main support layer are relatively low, and the hot melt adhesive does not adequately wet and coat the fibers. Comparative Example 3 uses the same high Vicat softening temperature TPU as the main support layer for its interfacial layer, which cannot preferentially undergo thermal activation during hot pressing, resulting in a lower peel strength than Example 1. Example 4: Hot melt adhesive was directly applied to the surface of the porous interfacial heat-activated layer. Some of the hot melt adhesive migrated into the nonwoven fabric along the fiber gaps, reducing the effective amount of adhesive actually retained at the interface between the nonwoven fabric and the breathable membrane. Comparative Example 5: A full-width continuous adhesive layer was used, which had a higher initial peel strength. However, the continuous adhesive layer imposed greater restrictions on the deformation of the composite fabric, and the retention rate after wet heat and washing was lower than that of Example 1. Comparative Example 6: The pressure was released immediately after hot pressing. Before the hot melt adhesive had fully cured, it was affected by fiber rebound and interlayer displacement, resulting in a decrease in the interfacial bonding stability after aging and washing.

[0056] Main support layer thickness retention rate: After S120 is completed, pre-composite samples are taken from each sample; after composite is completed, post-composite samples are cut from the corresponding TPU waterproof fabric; the samples are frozen and sectioned to obtain a cross section perpendicular to the fabric surface, and observed with an optical microscope to measure the thickness of the main support layer before and after composite. The results are shown in Table 2. Table 2

[0057] As shown in Table 2, the present invention, by setting an interface thermal activation layer on the surface of the main support layer, allows the interface thermal activation layer to preferentially soften and deform during hot pressing, enabling the hot melt adhesive to form an interface bond with the nonwoven fabric, while reducing the transmission of hot pressing force to the deeper part of the main support layer. In Comparative Example 2, no interface thermal activation layer was set, and the hot melt adhesive directly contacted the main support layer, resulting in a more direct application of hot pressing force to the surface of the main support layer and an increase in the compaction degree of the main support layer. In Comparative Example 3, the interface layer was difficult to preferentially activate at the hot pressing temperature, and more hot pressing pressure was transmitted to the main support layer. In Comparative Example 4, the hot melt adhesive directly entered the fiber gaps of the interface thermal activation layer and the surface of the main support layer, which also increased the local compaction of the fiber web. In Comparative Example 5, a full-width continuous adhesive layer was used, resulting in a larger stress area during hot pressing and a further decrease in the thickness retention rate of the main support layer. In Comparative Example 6, the pressure was released immediately after hot pressing, and the main support layer was able to generate a certain degree of rebound, so the thickness retention rate was not significantly reduced.

[0058] Bending stiffness test: The bending properties of each sample were determined by the inclined plane method. The test was conducted in accordance with GB / T 18318.1-2009 "Determination of bending properties of textiles - Part 1: Inclined plane method". The bending stiffness of the sample in the longitudinal and transverse directions was measured and the average value was calculated. The results are shown in Table 3. Water vapor transmission rate: The water vapor transmission performance of the sample was determined by the permeation cup method. The test was conducted for 24 hours at a temperature of 38±1℃ and a relative humidity of 90±2%. The water vapor transmission rate per unit area of ​​the sample within 24 hours was calculated based on the change in mass of the permeation cup. The results are shown in Table 3. Hydrostatic pressure test: The test was conducted according to GB / T 4744-2013 "Test and evaluation of waterproof performance of textiles - hydrostatic pressure method". The breathable membrane side of the sample was brought into contact with water, and the water pressure was continuously increased at a rate of 6.0±0.3kPa / min. The hydrostatic pressure at the third water droplet on the back side of the sample was recorded. The results are shown in Table 3. Hydrostatic pressure after repeated bending: The sample was bent back and forth around a cylinder with a diameter of 10 mm 1000 times, and then its hydrostatic pressure was measured according to the hydrostatic pressure test. The results are shown in Table 3. Table 3

[0059] As shown in Table 3, the TPU waterproof fabric prepared in the embodiments of the present invention has low bending stiffness, maintains good hydrostatic pressure performance, and maintains good waterproof performance after repeated bending. Comparative Example 1, consisting solely of TPU microfiber deposition forming a nonwoven fabric, exhibits high water vapor permeability and low bending stiffness. However, liquid water easily permeates through the interconnected fiber pores, resulting in a significantly lower hydrostatic pressure compared to Example 1. Comparative Examples 2 and 3 primarily utilize a continuous breathable membrane for initial hydrostatic pressure. However, due to insufficient interfacial bonding, repeated bending easily leads to localized detachment and stress concentration, resulting in a noticeable decrease in hydrostatic pressure. In Comparative Example 4, hot melt adhesive is directly applied to the porous nonwoven fabric surface, with some adhesive entering the fiber pores, leading to a decrease in water vapor permeability and reduced uniformity of interfacial bonding. Comparative Example 5 employs a full-width continuous adhesive layer, which maintains a high hydrostatic pressure. However, the continuous adhesive layer restricts the water vapor transfer area and fabric bending deformation, resulting in the lowest water vapor permeability and the highest bending stiffness. Comparative Example 6, lacking cooling and shaping during pressing, experiences interfacial relaxation before the hot melt adhesive cures, resulting in a significantly lower hydrostatic pressure after repeated bending compared to Example 1.

[0060] In summary, this invention forms a continuous water-blocking structure through a TPU breathable membrane and improves the stability of the composite interface by utilizing an interfacial thermal activation layer, a discontinuous heat transfer adhesive layer, and compression cooling. This allows the resulting TPU waterproof fabric to achieve waterproof performance while maintaining good water vapor permeability, softness, and repeated bending stability. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this invention; therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a TPU waterproof fabric, characterized in that, Includes the following steps: S100: TPU granules are melt-extruded and formed into TPU microfibers through a melt-blowing process, and the TPU microfibers are deposited into a web to form a nonwoven fabric; S200: The TPU resin composition is melt-plasticized and then blown into a breathable film using a blown film process. S300. Apply TPU hot melt adhesive to the composite surface of the breathable membrane to form a hot melt adhesive layer. S400. The nonwoven fabric and the breathable membrane are bonded together and hot-pressed together through the hot melt adhesive layer to combine the nonwoven fabric and the breathable membrane to obtain a composite material. S500: Cool and shape the composite material to obtain the TPU waterproof fabric.

2. The preparation method according to claim 1, characterized in that, In S100, the TPU granules include first TPU granules and second TPU granules, and the nonwoven fabric is obtained through the following steps: S110. The first TPU granules are melted and extruded, and then formed into first TPU microfibers through a first melt-blowing process, so that the first TPU microfibers are deposited into a network to form the main support layer. S120. The second TPU granules are melt-extruded and formed into second TPU microfibers through a second melt-blowing process, so that the second TPU microfibers are deposited on one side of the main support layer to form an interface thermal activation layer. The Vicat softening temperature of the second TPU granules is lower than that of the first TPU granules, and the interface thermal activation layer is disposed opposite to the hot melt adhesive layer.

3. The preparation method according to claim 2, characterized in that, In S110, The first TPU granules comprise hydrolysis-resistant polyether TPU, and the Vicat softening temperature of the first TPU granules is 130~160℃; and / or The melt extrusion temperature of the first TPU granules is 195~225℃; and / or In the first meltblown process, the high-speed hot air temperature is 210~240℃; and / or The main support layer has a weight of 30~120g / m³. 2 .

4. The preparation method according to claim 2, characterized in that, In S120, The second TPU granules comprise polyether TPU resin, wherein the Vicat softening temperature of the polyether TPU resin is 90~120°C; and / or The melt extrusion temperature of the second TPU granules is 180~215℃; and / or The second meltblown process uses high-speed hot air at a temperature of 195~230℃; and / or The basis weight of the interface thermally activated layer is 5~30 g / m². 2 Furthermore, the weight of the interface thermally activated layer accounts for 8-22% of the total weight of the main support layer and the interface thermally activated layer.

5. The preparation method according to claim 1, characterized in that, In S200, the TPU resin composition includes hydrophilic polyether TPU and hydrolysis-resistant polyether TPU; Based on the total mass of the hydrophilic polyether TPU and the hydrolysis-resistant polyether TPU as 100%, the mass percentage of the hydrophilic polyether TPU is 70-95%, and the mass percentage of the hydrolysis-resistant polyether TPU is 5-30%.

6. The preparation method according to claim 1, characterized in that, In S300, the hot melt adhesive layer is formed by the following steps: S310. The TPU hot melt adhesive is applied to the release surface of the release carrier, so that the TPU hot melt adhesive forms a discontinuously distributed pre-formed adhesive layer on the release surface. S320. The pre-formed adhesive layer and the composite surface of the breathable membrane are positioned opposite each other, and a heat transfer treatment is performed to transfer and adhere the pre-formed adhesive layer to the composite surface of the breathable membrane. S330. The breathable membrane that has undergone the heat transfer treatment is cooled to keep the TPU hot melt adhesive transferred to the composite surface of the breathable membrane in a discontinuous distribution state. Then the release carrier is peeled off to obtain a breathable membrane with the hot melt adhesive layer.

7. The preparation method according to claim 6, characterized in that, The softening temperature of the TPU hot melt adhesive is 70~100℃; and / or The heat transfer process is performed at a temperature of 85~110℃, a pressure of 0.03~0.12MPa, and a time of 1~5s.

8. The preparation method according to claim 1, characterized in that, In S400, the temperature of the hot-pressing composite is 105~125℃, the pressure is 0.15~0.30MPa, and the time is 8~15s.

9. The preparation method according to claim 1, characterized in that, In S500, the cooling and shaping process is carried out while the composite material is kept in a pressed state, and the pressed state is released after the composite material is cooled to 30~40°C.

10. A TPU waterproof fabric, characterized in that, The TPU waterproof fabric is prepared by the preparation method according to any one of claims 1 to 9, and the TPU waterproof fabric includes a non-woven fabric, a hot melt adhesive layer and a breathable membrane.

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