Waterproof breathable membrane, preparation method therefor, and composite fabric comprising same

Abstract

The present invention provides a waterproof breathable membrane, a preparation method therefor, and a composite fabric comprising same. The preparation method for a waterproof breathable membrane comprises: performing first mixing of a polyolefin raw material and a solvent to obtain a premixed gel; performing second mixing of an elastomer and a solvent, and then performing third mixing with the premixed gel to obtain a mixed gel; performing melt extrusion on the mixed gel to obtain an initial gel membrane, followed by performing initial stretching on a biaxial stretching machine, and then extracting by using an extracting agent to obtain an initial microporous membrane; and performing expanded stretching on the initial microporous membrane, and performing heat setting and rapid high-temperature treatment in sequence. The waterproof breathable membrane is prepared by the described preparation method. The composite fabric is composed of an inner layer fabric, an outer layer fabric, and the waterproof breathable membrane provided by the present invention which is compounded between the inner layer fabric and the outer layer fabric. The preparation method provided by the present invention facilitates industrial promotion and use, and the obtained product possesses excellent waterproof and breathable properties, as well as higher tensile strength and elongation at break.

Description

A waterproof breathable membrane, a preparation method thereof, and a composite fabric comprising the same Technical Field

[0001] The present invention belongs to the technical field of waterproof materials, and in particular relates to a waterproof breathable membrane, a preparation method thereof, and a composite fabric comprising the same. Background Art

[0002] Waterproof and breathable membranes are functional membrane materials that combine water permeability and moisture vapor permeability. When combined with fiber fabrics, they can be used to create functional textiles with unique protective and comfortable properties, finding widespread application. As living standards improve, the popularity of outdoor sports has significantly increased, leading to an increasing demand for functional textiles (such as jackets) that are waterproof, breathable, and warm, while also possessing sufficient mechanical strength.

[0003] The waterproof and breathable membranes used in special clothing such as jackets and protective clothing are mostly made of PTFE and PU. PTFE is a fluorine-containing material and poses the potential for environmental pollution. The European Union has enacted restrictive regulations that will gradually limit the use of fluorine-containing materials over the next 10 years. Conventional methods for preparing PU waterproof and breathable membranes include traditional processes such as cast film and blown film, and the new electrospinning process. PE membranes produced by traditional processes have high output and low prices, but due to technical limitations, the membrane's breathability is extremely poor. PU membranes produced by the new process have good breathability, but low output and high costs.

[0004] Casual wear, commuting wear, underwear, wearable devices, etc. in daily life are characterized by high frequency of use and long usage time, and they need to be waterproof and breathable. These garments usually use knitted fabrics, which have good elasticity. The waterproof and breathable membranes made of conventional polyolefin materials are limited by low elongation and are difficult to compound with knitted fabrics, which cannot meet normal use. Therefore, it is necessary to improve the elongation at break and puncture resistance of the material.

[0005] Patent CN117164995A discloses a polypropylene waterproof breathable membrane and its production process. The membrane is made from 70-90 parts polypropylene as the main material, with 15-25 parts modified nano-silica and additives such as regulators, plasticizers, and antioxidants added. The membrane is then extruded through a twin-screw extruder and stretched longitudinally and then transversely to produce the polypropylene waterproof breathable membrane. This process produces a waterproof breathable membrane with poor surface pore uniformity, poor air permeability, and low moisture permeability, failing to meet daily needs.

[0006] Safe and environmentally friendly expanded PE / PP waterproof and breathable membrane is a new topic. It is expected to completely replace EPTFE and PU waterproof and breathable membranes in the future, and achieve adjustable pores, thickness, and surface appearance of PE / PP waterproof and breathable membranes. It has excellent potential in the fields of medical care, clothing, electronic equipment, packaging, etc. Especially in the field of clothing, the environmental protection, biocompatibility, durability, and comfort of waterproof and breathable membranes are particularly important.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The object of the present invention is to provide a waterproof breathable membrane, a preparation method thereof and a composite fabric comprising the same, so as to solve the above-mentioned problems.

[0009] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing a waterproof breathable membrane, comprising the following steps:

[0011] S1: mixing the polyolefin raw material with the solvent white oil to obtain a premixed gel for standby use;

[0012] The polyolefin raw material includes one or more of LLDPE, LDPE, HDPE, UHMWPE or PP; preferably, the polyolefin raw material is UHMWPE, and the molecular weight of the UHMWPE is 400,000-2,000,000;

[0013] The first mixing also includes adding 0.05-1% of the mass of the polyolefin raw material to an antioxidant; the antioxidant is selected from one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, pentaerythritol tetrakis(bis-T-butyl hydroxyhydrocinnamate), antioxidant 1010, tetrakis(3,5-di-tert-butyl-4-hydroxy)phenylpropionate, tetrakis-(dibutyl hydroxyhydrocinnamate)pentaerythritol ester, tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)pentaerythritol ester), and antioxidant 168.

[0014] S2: performing a second mixing of the elastomer and the solvent white oil, and then performing a third mixing with the premixed gel obtained in S1 to obtain a mixed gel;

[0015] The elastomer includes one or more of thermoplastic elastomer (POE), EPDM, SBS, and EPR, which are obtained by in-situ polymerization of ethylene and octene using a metallocene catalyst; preferably, the elastomer is a thermoplastic elastomer obtained by in-situ polymerization of ethylene and octene using a metallocene catalyst; further preferably, the added amount of the elastomer is 0.5-5% of the mass of the polyolefin raw material.

[0016] Optionally, the added amount of the elastomer can be any value between 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% and 5% of the mass of the polyolefin raw material.

[0017] S3: melt-extrude the mixed gel obtained in S2 to obtain an initial gel membrane, then perform initial stretching on a biaxial stretching machine, and then extract with dichloromethane as an extractant to obtain an initial microporous membrane; preferably, the extraction further includes ultrasonic-assisted extraction;

[0018] The melt extrusion comprises: setting the screw temperature of the twin-screw extruder to 140° C.-240° C., the melt pipe temperature to 190° C.-230° C., and the die head temperature to 180° C.-220° C., adding the mixed gel into the twin-screw extruder through a peristaltic pump for melt extrusion;

[0019] Optionally, the screw temperature of the twin-screw extruder may be any value between 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C and 240°C, the melt pipe temperature may be any value between 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C and 230°C, and the die temperature may be any value between 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C and 220°C;

[0020] The initial stretching includes room temperature stretching and temperature-elevated stretching;

[0021] Preferably, the stretching ratio of the room temperature stretching is 1-2 times, and the stretching rate is 5-20 mm / s;

[0022] Further preferably, the stretching temperature of the temperature-elevated stretching is 60-100° C., the stretching ratio is 1-5 times, and the stretching rate is 5-20 mm / s.

[0023] Optionally, the stretching ratio of the room temperature stretching can be any value between 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times and 2 times, and the stretching rate can be any value between 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, 9 mm / s, 10 mm / s, 11 mm / s, 12 mm / s, 13 mm / s, 14 mm / s, 15 mm / s, 16 mm / s, 17 mm / s, 18 mm / s, 19 mm / s and 20 mm / s;

[0024] The stretching temperature of the temperature-increasing stretching can be any value between 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C and 100°C, the stretching ratio can be any value between 1 time, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times and 5 times, and the stretching rate can be any value between 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, 9 mm / s, 10 mm / s, 11 mm / s, 12 mm / s, 13 mm / s, 14 mm / s, 15 mm / s, 16 mm / s, 17 mm / s, 18 mm / s, 19 mm / s and 20 mm / s.

[0025] The initial stretching is carried out in steps with obvious advantages. Because during the room temperature stretching process, due to the small stretching multiple, under the action of tensile stress, the chips undergo plastic deformation, the molecular chains are pulled out from the crystal area, and the spherulites gradually evolve into extended chain crystals; during the subsequent temperature increase stretching, the chain segments and molecular chains undergo abnormal movement, adjustment and rearrangement, so that the internal stress is released. At the same time, the presence of white oil is conducive to the transmission of force and promotes the growth of the number of fibers, forming a uniformly distributed fiber network structure and orderly arrangement of the chips, so that the pore size distribution of the formed microporous membrane is more uniform and controllable, effectively improving its performance.

[0026] S4: The initial microporous membrane of S3 is subjected to expansion and stretching, and then subjected to heat setting and rapid high-temperature treatment in sequence to obtain the waterproof and breathable membrane.

[0027] The stretching temperature of the bulking stretching is 90-140°C, and the stretching ratio is 1-9 times;

[0028] Optionally, the stretching temperature of the bulking stretching can be any value between 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C and 140°C, and the stretching ratio can be any value between 1 time, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times and 9 times;

[0029] The heat setting temperature is 90-130°C; optionally, the heat setting temperature can be any value between 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C and 130°C;

[0030] The rapid high temperature treatment includes: blowing with hot air at a temperature of 80-130° C. for 1-10 seconds.

[0031] Optionally, the temperature of the rapid high temperature treatment can be any value between 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C and 130°C, and the purge time can be any value between 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s and 10s.

[0032] Rapid high-temperature treatment can make the internal fibers of the expanded and stretched waterproof and breathable membrane adhere to each other, reduce the material delamination phenomenon, and improve the waterproof performance and rubbing resistance of the waterproof and breathable membrane.

[0033] The present invention uses a polymer with good compatibility and cooperates with an original stretching process to improve the elongation at break and puncture resistance of the waterproof breathable membrane while ensuring porosity, uniform pore size and high moisture permeability. At the same time, the waterproof breathable membrane prepared by the thermally induced phase separation method has controllable pore size and excellent permeability. In the present invention, the initial gel membrane can be subjected to initial stretching. During the initial stretching, the white oil plays the role of speed increase and lubrication, which is conducive to the transmission of force and promotes the growth of the number of fibers, forming a fiber network structure, so that the chips are arranged in an orderly manner. At the same time, the solvent acts as a porogen, and after extraction, an original pore structure with uniform and fine pore size is formed. After bidirectional synchronous stretching is performed again, the original pore structure is stretched and reorganized to obtain a waterproof breathable membrane with high porosity, controllable pore size and excellent permeability. Due to the existence of the topological structure between molecules, the fibrous crystal structure is refined and recrystallized to obtain a more uniform and fine microporous structure. At the same time, the oriented crystallization behavior existing in the stretching process significantly improves the tensile strength of the waterproof breathable membrane.

[0034] The waterproof and breathable membrane provided by the present invention is prepared by the preparation method.

[0035] The present invention also provides a composite fabric, which is composed of an inner fabric, an outer fabric, and a waterproof and breathable membrane composited between the inner fabric and the outer fabric;

[0036] The waterproof breathable membrane is prepared by the preparation method;

[0037] The inner layer fabric is one or more of woven fabrics, knitted fabrics, nonwoven fabrics and electrospun membranes obtained by pure spinning, blending, blended yarn or blended fibers of the fabric raw materials;

[0038] The outer layer fabric is one or more of woven fabrics, knitted fabrics, nonwoven fabrics and electrospun membranes obtained by pure spinning, blending, blended yarn or blended fiber of the fabric raw materials;

[0039] The raw materials of the fabric include one or more of cotton, linen, acetate, viscose, mulberry silk, polyester, nylon, aramid, spandex, polypropylene, chloroprene, acrylic, wool, rabbit hair, camel hair, mohair, yak hair, metal fiber, and conductive fiber.

[0040] Preferably, the compounding includes hot melt adhesive powder dot coating compounding, hot melt adhesive slurry dot compounding, hot melt adhesive powder compounding, hot melt adhesive double-dot compounding, polyurethane spray compounding, and polyurethane roller coating compounding.

[0041] Beneficial effects of the present invention:

[0042] The preparation method provided by the present invention has simple and controllable conditions, cheap and easily available raw materials, good process repeatability, environmentally friendly and energy-saving process, and the obtained waterproof and breathable membrane has excellent comprehensive performance and high production capacity, which is conducive to industrial promotion and use.

[0043] The waterproof and breathable membrane provided by the present invention has uniform pore size, excellent mechanical properties, good hand feel, and rub resistance. It has excellent softness and can adapt to various complex shapes and surface structures. It also has low cost, large production capacity, and good application scenarios. It is more widely used in outdoor sports, medical dressings, military industry, construction, packaging, daily chemical industry and other industries.

[0044] The composite fabric made using the waterproof and breathable membrane provided by the present invention has higher mechanical properties than conventional fabrics and has excellent waterproof and breathable properties. The composite fabric has a simple composite process and is widely applicable, especially to industries such as daily clothing, wearable devices, and special clothing. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] FIG1 is a scanning electron micrograph of the initial gel film provided in Example 1;

[0047] FIG2 is a scanning electron microscope image of the initial microporous membrane provided in Example 1;

[0048] FIG3 is a scanning electron microscope image of the waterproof breathable membrane provided in Example 1. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0050] Example 1

[0051] The method for preparing a waterproof breathable membrane according to the present invention specifically comprises the following steps:

[0052] S1: Weigh 30 parts by mass of UHMWPE with a molecular weight of 750,000 and 50 parts by mass of white oil and stir and mix them evenly to obtain a polyolefin premix gel;

[0053] S2: Weigh 1% of the mass of UHMWPE elastomer POE, 0.6% of the mass of UHMWPE antioxidant 1010, and 0.3% of the mass of UHMWPE antioxidant 168, then heat and stir to mix thoroughly in 20 parts by mass of white oil at 85°C. After mixing thoroughly, stir and mix with the polyolefin premixed gel obtained in S1 to obtain a mixed gel;

[0054] S3: The mixed gel obtained in S2 was added to a twin-screw extruder via a peristaltic pump. The screw temperature was set to 180°C, the melt pipe temperature was 220°C, and the die temperature was 210°C. The initial gel film was extruded and then cooled at 35°C to form a film. The surface scanning electron microscope image is shown in Figure 1.

[0055] S4: The initial gel film formed in S3 was cut into 12*12 cm film blocks and initially stretched on a biaxial stretching machine. The stretching was first performed at room temperature with a stretching ratio of 1.3 times and a stretching rate of 5 mm / s. The stretching was then performed at a temperature of 85°C, a stretching ratio of 2 times, and a stretching rate of 10 mm / s.

[0056] S5: The membrane block after initial stretching was extracted with dichloromethane to obtain an initial microporous membrane, the scanning electron microscope image of which is shown in Figure 2, and then expanded and stretched. The stretching temperature was set to 120°C, the stretching ratio was 4 times, the heat setting temperature was 123°C, and a rapid high-temperature hot air blown at 130°C for 5s to obtain a waterproof and breathable membrane. The scanning electron microscope image is shown in Figure 3.

[0057] It can be seen from Figures 1 to 3 that the appearance of the product membranes at each stage is uniform and maintains a certain shape. After extrusion through a twin-screw extruder, the UHMWPEs are linked to each other to form a spatial network structure, and the spatial pores are filled with white oil medium, which plays a role in speed-increasing lubrication. In the electron microscope image of Figure 1, after removing the white oil, the initial gel membrane has obvious pores and a cross-linked structure. Since the polymer compounds that constitute the grid have a certain degree of flexibility, the initial gel membrane has stretchability. Figure 2 is a microporous membrane with a uniform surface pore structure and a pore diameter at the nanometer level. During the room temperature stretching process, under the action of tensile stress, the chips undergo plastic deformation, the molecular chains are pulled out of the crystal area, and the spherulites gradually evolve into extended chain crystals; during the subsequent temperature-raising stretching, the chain segments and molecular chains undergo abnormal movement, adjustment and rearrangement, so that the internal stress is released, the fiber network structure is evenly distributed, and the chips are arranged in order, so that the pore size distribution of the subsequently formed microporous membrane is uniform, which effectively improves its performance. Figure 3 is the expanded waterproof and breathable membrane provided by the present invention, which presents a fiber network multi-level expanded structure. Specialized bulking and stretching promotes fibril growth around the fibril connection points, creating a regularly interlaced, snowflake-like spatial structure. This results in a waterproof, breathable material with interconnected pores and a negative Poisson's ratio. Rapid high-temperature treatment enhances the bond strength at the fibril connection points, relieves internal stress, and reduces material delamination.

[0058] Example 2

[0059] The difference from Example 1 is that the amount of the elastomer POE in S2 is 3% of the mass of UHMWPE.

[0060] Example 3

[0061] The difference from Example 1 is that the amount of the elastomer POE in S2 is 5% of the mass of UHMWPE.

[0062] Example 4

[0063] The difference from Example 1 is that the polyolefin raw material used in S1 is PP with a molecular weight of 1 million, and the temperature for heating and stretching in S4 is 140°C.

[0064] Example 5

[0065] The difference from Example 1 is that the polyolefin raw material used in S1 is a blend of UHMWPE with a molecular weight of 400,000 and HDPE with a molecular weight of 160,000 in a mass ratio of 67:33.

[0066] Example 6

[0067] The difference from Example 1 is that the polyolefin raw material used in S1 is a blend of UHMWPE with a molecular weight of 400,000 and PP with a molecular weight of 1,000,000 in a mass ratio of 67:33.

[0068] Example 7

[0069] The waterproof breathable membrane prepared in Example 1 was compounded with the outer polyester fabric and the inner viscose fabric by double-point hot melt adhesive to prepare a waterproof breathable membrane composite fabric.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that there is no initial stretching in step S4, that is, it does not include room temperature stretching and temperature-elevated stretching. The membrane block is directly extracted with dichloromethane to obtain an initial microporous membrane, and then expanded and stretched with a stretching ratio of 8 times.

[0072] Comparative Example 2

[0073] The raw materials were weighed as the first component according to the amounts of steps S1 and S2 in Example 1, mixed with the second component calcium carbonate powder in a ratio of 50:50, and mixed evenly in a high-speed mixer. The mixture was then extruded and granulated at 210° C. in a twin-screw extruder, and then extruded into a sheet in a single-screw extruder and biaxially stretched at a stretching ratio of 9 to obtain a microporous membrane.

[0074] Comparative Example 1

[0075] The difference from the embodiment is that no elastomer is added to S2.

[0076] Comparative Example 2

[0077] Select commercially available PTFE waterproof and breathable membrane.

[0078] Comparative Example 3

[0079] The conventional dry process is used to prepare the PE waterproof breathable membrane, which specifically includes:

[0080] 70 parts by mass of polyethylene with a molecular weight of 400,000, 30 parts by mass of calcium carbonate, and 0.5 parts of an antioxidant are mixed evenly in a high-speed mixer, then extruded into granules at 190°C in a twin-screw extruder, and then extruded into sheets in a single-screw extruder and biaxially stretched with a stretching ratio of 6 times to produce a microporous membrane.

[0081] The performance tests were conducted on the films or fabrics provided in the examples, control examples and comparative examples. The results are shown in Table 1 below:

[0082] Table 1 Material performance test results

[0083] Comparing Example 1 with Control Example 1, it can be seen that in Control Example 1, the initial gel membrane is directly extracted and then subjected to expanded stretching without initial stretching. Although the waterproof and breathable membrane obtained has relatively good air permeability and large porosity, it is stretched and reshaped based on defects, so its uniformity is poor and its mechanical properties are even worse, which is not conducive to wide application.

[0084] As can be seen from Table 1, the waterproof and breathable membrane prepared by the method adopted in the embodiment of the present invention, and the composite fabric prepared therefrom, exhibit better comprehensive performance, with waterproofness, breathability, and mechanical properties all at a high level, which is more conducive to its widespread industrial use.

[0085] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of this application, several variations and improvements can be made, which all fall within the scope of protection of this application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing a waterproof breathable membrane, characterized in that: The steps include: S1: mixing the polyolefin raw material with the solvent to obtain a premixed gel for standby use; S2: performing a second mixing of the elastomer and the solvent, and then performing a third mixing with the premixed gel obtained in S1 to obtain a mixed gel; S3: melt-extrude the mixed gel obtained in S2 to obtain an initial gel membrane, then perform initial stretching on a biaxial stretching machine, and then extract with an extractant to obtain an initial microporous membrane; S4: The initial microporous membrane described in S3 is subjected to expansion and stretching, and then subjected to heat setting and rapid high-temperature treatment in sequence to obtain the waterproof and breathable membrane.

2. The preparation method according to claim 1, characterized in that Step S1 satisfies one or more of the following conditions: a. The polyolefin raw material includes one or more of LLDPE, LDPE, HDPE, UHMWPE or PP; b. The solvent is white oil; c. The first mixing further includes adding 0.05-1% of the mass of the polyolefin raw material to the antioxidant.

3. The preparation method according to claim 2, characterized in that Step S1 also satisfies one or more of the following conditions: d. The polyolefin raw material is UHMWPE, and the molecular weight of the UHMWPE is 400,000-2,000,000; e. The antioxidant is selected from one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, tetrakis(bis-T-butyl hydroxyhydrocinnamate), antioxidant 1010, tetrakis(3,5-di-tert-butyl-4-hydroxy)phenylpropionate, tetrakis-(dibutyl hydroxyhydrocinnamate)pentaerythritol, tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)pentaerythritol), and antioxidant 168.

4. The preparation method according to claim 1, characterized in that Step S2 satisfies one or more of the following conditions: f. The elastomer comprises one or more thermoplastic elastomers (POE), EPDM, SBS, EPR, which are polymerized in situ with a metallocene catalyst using ethylene and octene; g. The solvent is white oil; h. The amount of the elastomer added is 0.5-5% of the mass of the polyolefin raw material.

5. The preparation method according to claim 1, characterized in that Step S3 satisfies one or more of the following conditions: i. The melt extrusion comprises: setting the screw temperature of the twin-screw extruder to 140 ℃-240 ℃, the melt pipe temperature to 190 ℃-230 ℃, the die temperature to 180 ℃-220 ℃, and adding the mixed gel to the twin-screw extruder by a peristaltic pump for melt extrusion; j. The initial stretching includes room temperature stretching and heating stretching; k. The extractant is dichloromethane.

6. The preparation method according to claim 5, characterized in that The stretching ratio of the room temperature stretching is 1-2 times, and the stretching rate is 5-20 mm / s; Preferably, the stretching temperature of the temperature-elevated stretching is 60-100° C., the stretching ratio is 1-5 times, and the stretching rate is 5-20 mm / s.

7. The preparation method according to claim 1, characterized in that Step S4 satisfies one or more of the following conditions: l. The stretching temperature of the bulking stretching is 90-140 ° C, and the stretching ratio is 1-9 times; m. The rapid high temperature treatment includes: using hot air blowing at a temperature of 80-130°C for 1-10s.

8. A waterproof breathable membrane, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. A composite fabric, characterized in that: The composite fabric is composed of an inner fabric, an outer fabric, and a waterproof and breathable membrane composited between the inner fabric and the outer fabric; The waterproof breathable membrane is prepared by the preparation method according to any one of claims 1 to 7; The inner layer fabric is one or more of woven fabrics, knitted fabrics, non-woven fabrics and electrospun membranes obtained by pure spinning, blending, blended yarn or blended fibers of the fabric raw materials; The outer layer fabric is one or more of woven fabrics, knitted fabrics, nonwoven fabrics and electrospun membranes obtained by pure spinning, blending, blended yarn or blended fiber of the fabric raw materials; The raw materials of the fabric include one or more of cotton, linen, acetate, viscose, mulberry silk, polyester, nylon, aramid, spandex, polypropylene, chloroprene, acrylic, wool, rabbit hair, camel hair, mohair, yak hair, metal fiber, and conductive fiber.

10. The composite fabric according to claim 9, characterized in that: The compounding includes hot melt adhesive powder dot coating compounding, hot melt adhesive slurry dot compounding, hot melt adhesive powder compounding, hot melt adhesive double dot compounding, polyurethane spray compounding, and polyurethane roller coating compounding.

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