Polyethylene non-woven fabric and preparation method thereof, breathable film and preparation device and application thereof

Abstract

The invention belongs to the technical field of preparation of non-woven fabrics and breathable films, and discloses a polyethylene non-woven fabric and a preparation method thereof, a breathable film and a preparation device and application of the breathable film. The polyethylene non-woven fabric is prepared from a spinning solution through electrostatic spray spinning, and when the spinning solution is prepared, supercritical carbon dioxide is firstly used for infiltrating a polyethylene raw material. The preparation method comprises the following steps: 1) infiltrating polyethylene in supercritical carbon dioxide; 2) melting, plasticizing and shearing the infiltrated polyethylene to obtain a spinning solution; (3) after the spinning solution is sprayed out through a die head of a spinning system, under coordinated drafting of a wind field and an electrostatic field, obtained polyethylene fibers are deposited on a receiving mesh belt, and the polyethylene non-woven fabric is formed. The problem that the polyethylene melt is difficult to form fibers is solved, the preparation process is green and environment-friendly, and the obtained non-woven fabric and breathable film have excellent performance.

Description

Technical Field

[0001] This invention belongs to the field of nonwoven fabric and breathable membrane preparation technology. Specifically, it relates to a polyethylene nonwoven fabric, a method for preparing the polyethylene nonwoven fabric, a breathable membrane obtained from the polyethylene nonwoven fabric, an apparatus for preparing the breathable membrane, and the application of the polyethylene nonwoven fabric and the breathable membrane. Background Technology

[0002] High-strength breathable membrane materials possess excellent properties such as waterproofness and breathability, toughness and tear resistance, light weight and puncture resistance, and low dust content. Due to their superior protective performance, they are widely used in medical packaging, protective clothing, surgical gowns, and construction.

[0003] High-strength breathable membranes are primarily made of polyethylene. Polyethylene possesses excellent chemical resistance, abrasion resistance, infrared transmittance, good fatigue resistance, and high impact strength, making it one of the most in-demand materials in the current polymer processing market. However, polyethylene has poor spinnability, high melt viscosity, and is difficult to spin into fibers.

[0004] Conventional methods for preparing polyethylene nonwoven fabrics include dry spinning, wet spinning, centrifugal spinning, electrospinning, flash spinning, and meltblowing. Flash spinning is commonly used for the commercial production of polyethylene nonwoven fabrics, producing high-density polyethylene fibers of 0.5-10 μm. It uses less solvent than dry and wet spinning processes, resulting in advantages such as high strength and lightweight. Electrospinning can also effectively obtain high-strength polyethylene nanofibers, but polyethylene has poor solubility and conductivity, requiring large amounts of organic solvents during the spinning process, leading to low production efficiency and limited industrialization. Meltblowing, as the most commonly used industrial technology for efficiently obtaining micro / nano nonwoven fabrics, offers advantages such as high one-step molding yield. However, its performance is limited by the processing characteristics of polyethylene raw materials, resulting in lower product performance. Summary of the Invention

[0005] To meet the demand of related industries for high-performance polyethylene nonwoven materials, the purpose of this invention is to provide a polyethylene nonwoven fabric and its preparation method, a breathable membrane and its preparation device and application. This invention combines supercritical carbon dioxide impregnation technology, continuous screw extrusion, wind field and electric field coordinated coupling technology, and nonwoven fabric post-processing technology. The resulting polyethylene nonwoven fabric and breathable membrane have good application prospects in medical packaging, radiation refrigeration, protective clothing and other fields.

[0006] A first aspect of the present invention provides a polyethylene nonwoven fabric, which is obtained by electrostatic spinning of a spinning solution, wherein the spinning solution is prepared by first impregnating the polyethylene raw material with supercritical carbon dioxide.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned polyethylene nonwoven fabric, the method comprising the following steps:

[0008] 1) Impregnate polyethylene in supercritical carbon dioxide;

[0009] 2) After the impregnated polyethylene is melted and plasticized, a spinning solution is obtained;

[0010] 3) After the spinning solution is sprayed out through the die head of the spinning system, the polyethylene fibers obtained are deposited on the receiving mesh belt under the coordinated stretching of the wind field and the electrostatic field to form polyethylene nonwoven fabric.

[0011] A third aspect of the present invention provides a breathable membrane, which is obtained by hot pressing and stretching the aforementioned polyethylene nonwoven fabric.

[0012] A fourth aspect of the present invention provides an apparatus for preparing the above-mentioned breathable membrane, the apparatus comprising: a supercritical carbon dioxide reactor, a continuous screw extrusion spinning system, a hot air generation system, a suction system, a high voltage electrostatic generation system, a receiving mesh belt, a traction roller, a hot pressing stretching system, and a take-up roller;

[0013] The outlet of the supercritical carbon dioxide reactor is connected to the inlet of the continuous screw extrusion spinning system. According to the material flow, the receiving mesh belt, traction roller, hot pressing stretching system and take-up roller are sequentially arranged downstream of the continuous screw extrusion spinning system. The suction system is located inside the receiving mesh belt. The hot air generating system and the suction system form an air field. The high-voltage electrostatic generating system provides an electrostatic field. The air field and the electrostatic field work together to act on the polyethylene fibers ejected from the die of the continuous screw extrusion spinning system.

[0014] The fifth aspect of the present invention provides the application of the above-mentioned polyethylene nonwoven fabric and breathable membrane in the fields of medical breathable membrane packaging, protective clothing, construction, radiation refrigeration and filtration.

[0015] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0016] (1) This invention solves the problem of difficult polyethylene spinning, especially the problem of difficult high-density polyethylene spinning, by introducing supercritical carbon dioxide to plasticize polyethylene.

[0017] (2) The preparation of the polyethylene spinning solution of the present invention does not require the use of auxiliary solvents, and the preparation process is green and environmentally friendly, without pollution or harm.

[0018] (3) The nonwoven fabric and breathable membrane of the present invention are prepared in one step. The device has a reasonable structure, simple operation, high efficiency, and is suitable for industrial production.

[0019] (4) The present invention can prepare both non-woven fabric and breathable membrane with a set of equipment. The non-woven fabric fibers are uniform and the breathable membrane fibers are dense, uniform, strong and breathable.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] Figure 1 A front view of the apparatus for preparing the breathable membrane;

[0022] Figure 2 A top view of the apparatus for preparing the breathable membrane;

[0023] Figure 3 This is an electron microscope image of the polyethylene nonwoven fabric of Example 1;

[0024] Figure 4 The image shows an electron microscope image of the polyethylene nonwoven fabric of Example 8.

[0025] Figure 5 This is a fiber electron microscope image of the breathable membrane of Example 8.

[0026] Explanation of reference numerals in the attached drawings: 1—Supercritical carbon dioxide reactor; 2—Electric motor; 3—Control box; 4—Cylinder; 5—Extruder body; 6—Hollow electrode plate; 7—Hot air inlet; 8—First-stage traction roller; 9—Second-stage traction roller; 10—First-stage hot press roller assembly; 11—Second-stage hot press roller assembly; 12—Rewinding roller; 13—Polyethylene nonwoven fabric; 14—Spinneret; 15—Negative pressure suction box; 16—Receiving mesh belt. Detailed Implementation

[0027] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0028] According to a first aspect of the present invention, a polyethylene nonwoven fabric is provided, which is obtained by electrostatic spinning of a spinning solution, wherein the spinning solution is prepared by first impregnating the polyethylene raw material with supercritical carbon dioxide.

[0029] The polyethylene used in this invention can be any type of polyethylene conventionally used in the art. For example, the polyethylene can be selected from at least one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). Preferably, the polyethylene has a melt index of 5-60 g / 10 min at 190°C and a load of 2.16 kg.

[0030] Preferably, the polyethylene nonwoven fabric has a fiber diameter of 1-20 μm and a thickness of 0.1-0.2 mm.

[0031] The water contact angle of the polyethylene nonwoven fabric of the present invention can be in the range of 135°-145°.

[0032] According to a second aspect of the present invention, the present invention provides a method for preparing the above-described polyethylene nonwoven fabric, the method comprising the following steps:

[0033] 1) Impregnate polyethylene in supercritical carbon dioxide;

[0034] 2) After the impregnated polyethylene is melted and plasticized, a spinning solution is obtained;

[0035] 3) After the spinning solution is sprayed out through the die head of the spinning system, the polyethylene fibers obtained are deposited on the receiving mesh belt under the coordinated stretching of the wind field and the electrostatic field to form polyethylene nonwoven fabric.

[0036] In this invention, the impregnation is carried out in a reaction vessel with a pressure of 8-15 MPa, a temperature of 70-125°C, and an impregnation time of 6-12 h.

[0037] In this invention, after the polyethylene is impregnated with supercritical carbon dioxide, the carbon dioxide overflows into the micropores of the polyethylene. Preferably, the carbon dioxide content in every 100 grams of polyethylene after impregnation is 10-30g.

[0038] According to the present invention, the hot air temperature of the wind field is 200-290℃, preferably 210-290℃, the wind field intensity is 0.1-0.6MPa, preferably 0.1-0.5MPa, and the electrostatic field intensity is 5-50KV, preferably 20-50KV.

[0039] This invention uses polyethylene as raw material, employing a supercritical carbon dioxide reactor to impregnate the polyethylene material. The impregnated material is then continuously extruded using a screw extruder. At the extrusion end, a synergistic airflow and electrostatic field are applied, utilizing the stretching effect of the airflow and electric field to draw the polyethylene into fibers. These fibers adhere to a receiving mesh belt to form a film, resulting in a polyethylene nonwoven fabric with excellent air permeability.

[0040] According to a specific embodiment of the present invention, the preparation method of polyethylene nonwoven fabric includes: First, selecting an appropriate amount of polyethylene granules and placing them in a burlap mesh bag or other packaging bag with good gas permeability, then placing the wrapped polyethylene material in a supercritical carbon dioxide reactor. The temperature of the supercritical carbon dioxide reactor is set to 70-125℃, and the pressure to 8-15MPa. The polyethylene material is immersed in the supercritical carbon dioxide reactor for 6-12 hours. During the immersion of the polyethylene material, the extruder and blowing system are heated. After the extruder and die reach the predetermined temperature, the temperature is maintained for 1 hour. The pressure valve is adjusted to release the pressure and the material is removed. The immersed polyethylene is added to the feed inlet. The polyethylene is melted and plasticized by a single-screw extruder and then enters the spinneret. Second, the electrostatic generator and suction device are turned on. The melt is stretched into filaments at the tip of the die and deposited onto the receiving mesh belt.

[0041] According to a third aspect of the present invention, a breathable membrane is provided, which is obtained by hot pressing and stretching the aforementioned polyethylene nonwoven fabric.

[0042] This invention enhances the fiber orientation and inter-fiber bonding of nonwoven fabrics through two-stage stretching and hot rolling treatment, thereby improving mechanical strength and obtaining a high-strength breathable membrane.

[0043] Preferably, the air permeability of the breathable membrane is greater than 1 μm / Pa·s, more preferably 10-35 μm / Pa·s, the longitudinal tensile strength is greater than 3.5 kN / m, reaching 5.1 kN / m, and the transverse tensile strength is greater than 2.5 kN / m, reaching 4.5 kN / m.

[0044] In this invention, hot pressing and stretching are performed using two-stage hot pressing rollers. The temperature of the rollers is 80-130℃, the gap between the rollers is 0.05mm-0.30mm, the pressure between the rollers is 3-7MPa, and the speed ratio between the roller pairs is 1.0:1.1-1.0:1.6.

[0045] According to a fourth aspect of the present invention, the present invention provides an apparatus for preparing the above-described breathable membrane, the apparatus comprising: a supercritical carbon dioxide reactor, a continuous screw extrusion spinning system, a hot air generating system, a suction system, a high voltage electrostatic generating system, a receiving mesh belt, a traction roller, a hot pressing stretching system, and a take-up roller;

[0046] The outlet of the supercritical carbon dioxide reactor is connected to the inlet of the continuous screw extrusion spinning system. According to the material flow, the receiving mesh belt, traction roller, hot pressing stretching system and take-up roller are sequentially arranged downstream of the continuous screw extrusion spinning system. The suction system is located inside the receiving mesh belt. The hot air generating system and the suction system form an air field. The high-voltage electrostatic generating system provides an electrostatic field. The air field and the electrostatic field work together to act on the polyethylene fibers ejected from the die of the continuous screw extrusion spinning system.

[0047] Preferably, the traction roller includes a primary traction roller and a secondary traction roller arranged in sequence. The nonwoven fabric deposited on the receiving mesh belt passes through the primary traction roller and the secondary traction roller under the drive of the conveyor belt. After passing through the secondary traction roller, the nonwoven fabric becomes horizontal, preparing for subsequent hot pressing and stretching.

[0048] According to the present invention, the hot pressing stretching system includes a primary hot pressing roller group and a secondary hot pressing roller group arranged sequentially. The two hot pressing roller groups are hot pressing roller pairs, which can be steel rollers or point rollers. The stretching effect can be achieved by adjusting the speed difference between the roller pairs. The gap between the upper and lower rollers of the hot pressing roller pairs is adjustable, and the gap is not less than 0.05 mm.

[0049] The continuous screw extrusion spinning system, hot air generation system, suction system, and high-voltage electrostatic generation system in this invention can all adopt conventional configurations in the prior art, as long as they can achieve the corresponding functions.

[0050] The screw of the continuous screw extrusion spinning system of the present invention includes, but is not limited to, a corrugated screw capable of generating pressure, with an internal pressure of 8 MPa or higher in the extruder.

[0051] The suction system inside the receiving mesh belt of this invention facilitates the deposition of drawn fibers onto the receiving mesh belt. The receiving mesh belt is connected to the take-up roller, and the nonwoven fabric is collected into a roll by the take-up roller after being deposited onto the receiving mesh belt.

[0052] The die head in this invention can be a multi-hole die head, a slit die head, or a micro die head. The aperture of the multi-hole die head is 0.2mm-0.3mm.

[0053] The hot air generation system, the suction system, and the high-voltage electrostatic generation system of this invention constitute a wind farm coordinated system. The hot air temperature range is 200-290℃, the wind field intensity is 0.1-0.6MPa, and the electrostatic field intensity is 5KV-50KV.

[0054] According to the present invention, the hot air outlet of the hot air generating system is located on the upper and lower sides of the mold head, and hot air is blown out from the upper and lower sides of the mold head. The electrostatic field is applied between the mold head and the receiving mesh belt.

[0055] The preparation of the breathable membrane in this invention includes: starting the traction roller and hot-press stretching system; after the polyethylene nonwoven fabric is collected by the receiving mesh belt, it passes through the primary guide roller and the secondary traction roller, entering a horizontal state awaiting hot pressing. The gap between the rollers in the hot pressing zone is set to approximately 0.1 mm, the temperature is around 80℃-120℃, and a certain speed difference between the two stages of hot pressing rollers can be adjusted, with the roller speed ranging from 400-1600 mm / min. After hot pressing and stretching, a polyethylene membrane with high strength and breathability is obtained, which is finally collected by the collection device.

[0056] According to a fifth aspect of the present invention, the present invention provides the application of the above-described polyethylene nonwoven fabric and breathable membrane in the fields of medical breathable membrane packaging, protective clothing, construction, radiation refrigeration and filtration.

[0057] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0058] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0059] The sources of raw materials and the data testing methods used in the following examples and comparative examples are as follows:

[0060] High-density polyethylene M691, LG Corporation of South Korea.

[0061] Longitudinal and transverse tensile strength: tested according to YY / T 0698.9-2009;

[0062] Air permeability: Tested according to ISO 5636.5:2013, using the Bentssen method;

[0063] Membrane uniformity: Take 5 points along the width and 5 points along the length of the nonwoven fabric and test the thickness of the nonwoven fabric according to ISO 4593. A thickness deviation of <10% is considered non-uniform.

[0064] Example 1

[0065] use Figure 1 and Figure 2 The preparation apparatus shown is used to prepare nonwoven fabrics and breathable membranes. The apparatus specifically consists of a supercritical carbon dioxide reactor 1, an electric motor 2, a control box 3, a material cylinder 4, an extruder body 5, a hollow electrode plate 6, a hot air inlet 7, a primary traction roller 8, a secondary traction roller 9, a primary hot press roller group 10, a secondary hot press roller group 11, a negative pressure suction box 12, a spinneret 14, a suction box 15, and a receiving mesh belt 16. After being impregnated in a supercritical carbon dioxide reactor 1, the material is fed into an extruder through a feed cylinder 4. The end of the extruder is connected to a spinneret 14. Two hot air inlets 7 are arranged above the spinneret, and a hollow electrode plate 6 is located below the spinneret. Under the stretching effect of hot air and an electric field, the fiber bundles are deposited onto a receiving mesh belt 16 below the hollow electrode plate 6. Inside the receiving mesh belt is a suction box 15. The nonwoven fabric passes through a primary traction roller 8 and a secondary traction roller 9 sequentially from the receiving mesh belt 16. Behind the traction rollers are a primary hot press roller group 10 and a secondary hot press roller group 11. After passing through the hot press roller group, the nonwoven fabric forms a high-strength and dense fiber structure. Finally, the nonwoven fabric is collected by a take-up roller 12.

[0066] The preparation method of nonwoven fabric and breathable membrane includes: 1. Placing polyethylene granules in a supercritical carbon dioxide reactor 1, heating and pressurizing the reactor. After the pressure and temperature stabilize, impregnate the raw material for about 6 hours. 2. Preheating the extruder 5, hot air, and spinneret 14, adding the impregnated high-density polyethylene M691 through the barrel 4 into the extruder 5, and depositing it onto the receiving mesh belt 16 through the spinneret 14 and hollow electrode plate 6 to obtain the desired product. Figure 3 The polyethylene nonwoven fabric shown is shown. 3. Start the primary traction roller 8 and the secondary traction roller 9. The nonwoven fabric is stretched into the hot-pressing stretching area. By setting the temperature and rotation speed of the primary hot-pressing roller group 10 and the secondary hot-pressing roller group 11, the nonwoven fabric is hot-pressed and differentially stretched, thereby forming a nonwoven fabric as shown. Figure 5 The high-strength breathable membrane shown has dense and high-strength fibers. The high-strength breathable membrane is eventually collected into a roll by the take-up roller 12.

[0067] The supercritical carbon dioxide reactor is set to a temperature of 100℃ and a pressure of 12MPa; the extruder is set to a temperature of 235℃; the hot air inlet has an air pressure of 0.4MPa and a temperature of 265℃; the primary hot press roller assembly is set to a temperature of 85℃, the secondary hot press roller assembly is set to a temperature of 80℃, the roller pressure is 5MPa, the roller gap is 0.1mm, and the roller speed ratio is 1:1.2.

[0068] Example 2

[0069] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 90°C, and the temperature of the second-stage hot press roller assembly is set to 85°C. Everything else is the same.

[0070] Example 3

[0071] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 95°C, and the temperature of the second-stage hot press roller assembly is set to 90°C. Everything else is the same.

[0072] Example 4

[0073] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 100°C, and the temperature of the second-stage hot press roller assembly is set to 95°C. Everything else is the same.

[0074] Example 5

[0075] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 105°C, and the temperature of the second-stage hot press roller assembly is set to 100°C. Everything else is the same.

[0076] Example 6

[0077] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 110°C, and the temperature of the second-stage hot press roller assembly is set to 105°C. All other aspects are the same.

[0078] Example 7

[0079] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 115°C, and the temperature of the second-stage hot press roller assembly is set to 110°C. Everything else is the same.

[0080] Example 8

[0081] The difference from Example 1 is that the temperature of the primary hot press roller assembly is set to 120°C, and the temperature of the secondary hot press roller assembly is set to 115°C. All other aspects are the same. The resulting polyethylene nonwoven fabric is as follows: Figure 4 As shown, the breathable membrane is as follows Figure 5 As shown.

[0082] Example 9

[0083] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 125°C, and the temperature of the second-stage hot press roller assembly is set to 120°C. Everything else is the same.

[0084] Example 10

[0085] The difference from Example 1 is that the temperature of the first-stage hot press roller assembly is set to 130°C, and the temperature of the second-stage hot press roller assembly is set to 125°C. All other aspects are the same.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that supercritical carbon dioxide impregnation was not used, and the impregnation step is omitted. Everything else is the same. HDPE cannot form a continuous, stable jet, making direct spinning difficult.

[0088] The performance of the breathable membranes prepared in each embodiment and comparative example was tested, and the results are shown in Table 1.

[0089] Table 1

[0090]

[0091] This invention employs a supercritical carbon dioxide reactor to pre-impregnate polyethylene raw materials. The impregnated material is then continuously extruded using a screw extruder. At the extrusion end, a synergistic airflow and electric field are applied, utilizing the stretching effect of the airflow and electric field to draw the polymer into fibers. These fibers adhere to a receiving mesh belt to form a film, resulting in a polyethylene nonwoven fabric with excellent breathability. Multi-stage stretching and hot rolling treatments enhance the fiber orientation and inter-fiber adhesion of the nonwoven fabric, improving the mechanical strength of the breathable membrane and yielding a high-strength breathable membrane. Polyethylene without supercritical carbon dioxide impregnation cannot be spun into fibers and therefore cannot be used to make nonwoven fabrics or breathable membranes.

[0092] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A polyethylene nonwoven fabric, characterized in that, The polyethylene nonwoven fabric is obtained by electrostatic spinning of a spinning solution. The spinning solution is prepared by first impregnating the polyethylene raw material with supercritical carbon dioxide. Preferably, the polyethylene nonwoven fabric has a fiber diameter of 1-20 μm, a thickness of 0.1-0.2 mm, and a water contact angle range of 135°-145°.

2. The polyethylene nonwoven fabric according to claim 1, wherein, The polyethylene is selected from at least one of high-density polyethylene, low-density polyethylene and linear low-density polyethylene; the melt index of polyethylene at 190°C and 2.16 kg load is 5-60 g / 10 min.

3. The method for preparing polyethylene nonwoven fabric according to claim 1 or 2, characterized in that, The preparation method includes the following steps: 1) Impregnate polyethylene in supercritical carbon dioxide; 2) After the impregnated polyethylene is melted and plasticized, a spinning solution is obtained; 3) After the spinning solution is sprayed out through the die head of the spinning system, the polyethylene fibers obtained are deposited on the receiving mesh belt under the coordinated stretching of the wind field and the electrostatic field to form polyethylene nonwoven fabric.

4. The method for preparing polyethylene nonwoven fabric according to claim 3, wherein, The impregnation is carried out in a reaction vessel at a pressure of 8-15 MPa and a temperature of 70-125°C for 6-12 hours. Preferably, the carbon dioxide content in each 100 grams of polyethylene after impregnation is 10-30 g.

5. The method for preparing polyethylene nonwoven fabric according to claim 3, wherein, The hot air temperature of the wind field is 210-290℃, the wind field intensity is 0.1-0.5MPa, and the electrostatic field intensity is 20-50KV.

6. A breathable membrane, characterized in that, The breathable membrane is made from the polyethylene nonwoven fabric as described in claim 1 or 2 by hot pressing and stretching. Preferably, the breathable membrane has an air permeability greater than 1 pm / Pa·s, a longitudinal tensile strength greater than 3.5 kN / m, and a transverse tensile strength greater than 2.5 kN / m.

7. The breathable membrane according to claim 6, wherein, Hot pressing and stretching are performed using two-stage hot pressing rollers. The temperature of the rollers is 80-130℃, the gap between the rollers is 0.05mm-0.30mm, the pressure between the rollers is 3-7MPa, and the speed ratio between the rollers is 1.0:1.1-1.0:1.

6.

8. The apparatus for preparing the breathable membrane according to claim 6 or 7, characterized in that, The preparation apparatus includes: a supercritical carbon dioxide reactor, a continuous screw extrusion spinning system, a hot air generation system, a suction system, a high-voltage electrostatic generation system, a receiving mesh belt, a traction roller, a hot pressing and stretching system, and a take-up roller; The outlet of the supercritical carbon dioxide reactor is connected to the inlet of the continuous screw extrusion spinning system. According to the material flow, the receiving mesh belt, traction roller, hot pressing stretching system and take-up roller are sequentially arranged downstream of the continuous screw extrusion spinning system. The suction system is located inside the receiving mesh belt. The hot air generating system and the suction system form an air field. The high-voltage electrostatic generating system provides an electrostatic field. The air field and the electrostatic field work together to act on the polyethylene fibers ejected from the die of the continuous screw extrusion spinning system. Preferably, the traction roller includes a primary traction roller and a secondary traction roller arranged in sequence; the hot pressing and stretching system includes a primary hot pressing roller group and a secondary hot pressing roller group arranged in sequence.

9. The apparatus for preparing a breathable membrane according to claim 8, wherein, The die head is a multi-hole die head, a slit die head, or a micro die head; the aperture of the multi-hole die head is 0.2mm-0.3mm; The hot air outlet of the hot air generating system is located on the upper and lower sides of the mold head, and the electrostatic field is applied between the mold head and the receiving mesh belt.

10. The application of the polyethylene nonwoven fabric of claim 1 or 2 and the breathable membrane of claim 6 or 7 in the fields of medical breathable membrane packaging, protective clothing, construction, radiation refrigeration and filtration.

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