Polyethylene flash-steamed nonwoven fabric and preparation method thereof

Abstract

The present invention relates to the technical field of non-woven fabrics, and more particularly to a polyethylene flash non-woven fabric and a preparation method thereof. The preparation method comprises: using a gas phase method to polymerize ethylene and 1-butene to obtain a polyethylene resin, mixing the polyethylene resin with a modifying agent, and then extruding and granulating the mixture to obtain a HDPE resin for the flash non-woven fabric; the modifying agent comprises at least a lubricant, an opening agent, and a stabilizer; uniformly dissolving the HDPE resin for the flash non-woven fabric, a low-melting-point HDPE resin, and an ultra-high molecular weight polyethylene resin in a solvent to obtain a spinning solution; ejecting the spinning solution from a decompression nozzle to obtain polyethylene fibers; spreading, drawing, and extruding the polyethylene fibers to obtain a polymer sheet; and subjecting the polymer sheet to a water bath, drying, and hot rolling to obtain the non-woven fabric. The polyethylene flash non-woven fabric has the characteristics of high tensile strength, high tear strength, high modulus, high delamination peel strength, good air permeability, and good antibacterial properties.

Description

Technical Field

[0001] The invention relates to a polyethylene flash-evaporation nonwoven fabric and a preparation method thereof, belonging to the technical field of nonwoven fabrics. Background Art

[0002] Flash-steamed polyethylene nonwovens are made from 100% high-density polyethylene (HDPE). A uniform spinning solution is prepared under high-temperature and high-pressure conditions. This solution is then ejected from a reduced-pressure nozzle to produce continuous, ultrafine fibers. These fibers are then swung into a web and hot-rolled to form the polyethylene nonwoven. Flash-steamed nonwovens are composed of continuous, ultrafine fibers, endowing the fabric with excellent mechanical, waterproof, and breathable properties.

[0003] Flash-spun nonwovens consist of a continuous web of a defined width that oscillates in a regular pattern to form a single sheet. The fabric is composed of dozens of layers of webs arranged in different directions along its thickness. The structure and properties of each web layer are crucial to the barrier properties of flash-spun nonwovens. The fluidity and molecular structure of the polymer resin determine the diameter distribution of the webs, the thermal behavior of the polymer resin determines the interfacial bonding between the webs, the nozzle structure determines the web expansion ratio (i.e., the width of the web opening), and the structure of the swinging assembly determines the spatial distribution of the webs along the width of the nonwoven. To improve the barrier properties of flash-spun nonwovens, it is also necessary to simultaneously enhance their mechanical properties, uniformity, and stability.

[0004] Patent application number CN1938459A uses at least two polymers with different melting or softening points to prepare nonwoven fabrics. However, the method disclosed in this invention is based on simple physical mixing, which results in poor compatibility between the two polymers and cannot effectively control the distribution uniformity of multiple polymers in the spinning solution and fiber. Patent application number CN112549713A uses 300-400 dtex fibers to prepare nonwoven fabrics, which has a high linear density and poor web uniformity, making it difficult to prepare uniform nonwoven fabrics. Patent application number US3578739A discloses a device for applying electrostatic charge to the fiber structure, using static electricity to increase the fiber opening width and achieve a uniform web formation effect. However, existing flash-steamed nonwoven fabric preparation methods still cannot achieve simultaneous improvement in the mechanical properties, uniformity, and barrier properties of nonwoven fabrics. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a polyethylene flash-steamed nonwoven fabric and a preparation method thereof. During the preparation process of the polyethylene flash-steamed nonwoven fabric, the fiber bundles are unfolded with a wide fiber width, a wide fiber diameter distribution range, the fiber space inside the nonwoven fabric is evenly distributed, the fibers are firmly bonded, and the fabric has the characteristics of high tensile strength, high tear strength, high modulus, high delamination peeling strength, good air permeability, good antibacterial performance, and good uniformity.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a polyethylene flash-evaporated nonwoven fabric, the preparation method comprising:

[0007] S1. Preparation of HDPE resin for flash non-woven fabrics:

[0008] A polyethylene resin is obtained by polymerizing ethylene and 1-butene using a gas phase method. The polyethylene resin is mixed with a modification agent and then extruded and granulated to obtain a HDPE resin for flash non-woven fabrics; the modification agent includes at least a lubricant, an anti-blocking agent, and a stabilizer;

[0009] S2. Preparation of spinning solution:

[0010] Flash non-woven fabric HDPE resin, low melting point HDPE resin, ultra-high molecular weight polyethylene resin, solvent and gas are mixed, heated and dissolved, cooled and dissolved, and uniformly mixed to obtain a spinning solution;

[0011] S3. Preparation of polymer fibers and polymer sheets:

[0012] The spinning solution is ejected from a decompression nozzle to obtain polyethylene fibers; the polyethylene fibers are spread, drawn, and extruded to obtain a polymer sheet;

[0013] S4. Preparation of nonwoven fabrics:

[0014] The polymer sheet is subjected to water bathing, drying, and hot rolling to obtain the nonwoven fabric.

[0015] Furthermore, the lubricant is at least one of aliphatic amides such as oleamide, erucamide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin, polyethylene wax, glycerol monostearate, and ethoxylated fatty acid amines;

[0016] The opening agent is at least one of silicon dioxide, talc, diatomaceous earth, and hydrotalcite;

[0017] The stabilizer is at least one of an organic tin stabilizer, a metal soap antioxidant, a phosphite antioxidant, a phenol antioxidant, and a phosphite antioxidant.

[0018] Furthermore, the modification aid also includes other additives, and the other additives are at least one of polyethylene oxide, sodium alginate, polyacrylamide, carboxymethyl cellulose, aliphatic polyoxyethylene propylene ether, emulsifier OP-10, Tween 60, Tween 80, fatty alcohol polyoxyethylene ether, maleic anhydride grafted polyethylene, Tinuvin 326, Tinuvin 327, Chimassorb 81, Tinuvin1577, Tinuvin 770, Chimassorb 944, nano ZnO, and nano TiO2.

[0019] Furthermore, in step S1, during the polymerization reaction, hydrogen is used as a molecular weight regulator, isopentane is used as an inducing condensing agent, and a titanium-based catalyst or a chromium-based catalyst is used to catalyze the polymerization reaction.

[0020] Furthermore, the density of the HDPE resin used for the flash nonwoven fabric is 0.95±0.005g / cm 3 The melt index is 1±0.3 g / 10 min, 190°C / 2.16 kg. The molecular weight and molecular weight distribution are: Mw = 130,000-250,000 g / mol, Mn = 20,000-60,000 g / mol, and Mw / Mn = 2-5. The low-melting-point HDPE resin has a Vicat softening point of ≤125°C, a melting point of ≤131°C, and a molecular weight of: Mw = 80,000-130,000 g / mol. The ultra-high molecular weight polyethylene resin has a molecular weight of: Mw = 1,000,000-7,000,000 g / mol.

[0021] Furthermore, in step S2, the mass ratio of the flash non-woven fabric HDPE resin, the low melting point HDPE resin, and the ultra-high molecular weight polyethylene resin is (40%-80%): (10%-50%): 10%.

[0022] Furthermore, the specific process of step S2 is as follows: a solvent and a gas are mixed to prepare a first mixed solvent, a flash non-woven fabric HDPE resin, a low melting point HDPE resin, an ultra-high molecular weight polyethylene resin and the gas are mixed to prepare a second mixed solution, the first mixed solvent and the second mixed solution are mixed to be uniform under heating and pressurizing conditions, the mixture is heated and pressurized until the temperature and pressure are stable, and then the pressure and temperature are reduced to promote mixing and dissolution to obtain a uniform spinning solution;

[0023] The solvent is one or more of water, alcohol, acid, amine, ester, ether, ketone, nitrile, amide, halogenated hydrocarbon, aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, and unsaturated hydrocarbon;

[0024] The gas is one or more of carbon dioxide, nitrogen, and argon;

[0025] The first mixed solvent is mixed at a low temperature until the temperature and pressure are stable, and the low temperature is 37-150°C.

[0026] Furthermore, in step S3, the decompression nozzle includes a decompression chamber inlet, a decompression chamber, a decompression chamber outlet, and a spinning tunnel, and the aspect ratio of the decompression chamber inlet and the decompression chamber outlet is: length / diameter=(3-15) / 1;

[0027] A combing and separation assembly is provided inside the decompression chamber, and the combing and separation assembly includes a combing column and a dispersion disk. The dispersion disk is fixedly connected to the inside of the decompression chamber and is provided with a plurality of dispersion holes. The spinning solution is ejected from the outlet of the decompression chamber through the dispersion holes.

[0028] The linear density of the polyethylene fiber is 100-350 dtex; the spinning temperature is 160-210° C.; and the spinning pressure is 8-15 MPa.

[0029] Furthermore, in step S3, a spinning and spreading device is used to prepare polymer fibers and polymer sheets. The spinning and spreading device includes a decompression nozzle, a swinging wire assembly, and a multi-component matching box. The multi-component matching box includes a spinning box, a channel cavity, and an airflow combing area. The channel cavity is connected to the bottom of the spinning box. The airflow combing area is located below the channel cavity and is connected to the spinning box through a connecting pipe.

[0030] After being ejected horizontally from the pressure reducing nozzle, the polyethylene fiber hits the swinging wire assembly. After being reflected by the surface of the swinging wire assembly, the polyethylene fiber falls into the multi-component matching box, where it is stretched and uniformly formed into a web. The fiber web is extruded to obtain a polymer sheet.

[0031] The multi-component box uses the Venturi effect generated by high spinning speed to form negative pressure in the spinning box area, thereby realizing self-circulation of air flow between the spinning box and the air flow combing area, combing the turbulent air flow in the distribution process of the yarn bundle, and improving the expansion width of the spinneret fiber and the uniformity of the web laying banner.

[0032] Furthermore, the specific process of preparing the nonwoven fabric in step S4 is as follows: the polymer sheet is subjected to water bath, drying, primary hot pressing, cooling, secondary hot pressing, cooling, and winding to obtain the nonwoven fabric;

[0033] The water bath temperature is 20-50°C, and the water bath is repeated three times; the moisture content of the nonwoven fabric after drying is 10-80%; the primary hot pressing temperature is within the range of ±5°C from the Vicat softening point, and the linear pressure is 5-50 N / mm; the secondary hot pressing temperature is within the range of ±5°C from the melting point, and the linear pressure is 0-20 N / mm.

[0034] The invention also discloses a polyethylene flash-evaporated nonwoven fabric, which is prepared according to the preparation method of the invention.

[0035] The beneficial effects of the present invention are:

[0036] (1) In the preparation method of the present invention, the fiber bundles of the polyethylene flash nonwoven fabric have a wide fiber width, a wide fiber diameter distribution range, uniform fiber bundles in the nonwoven fabric, and strong bonding between fibers. The nonwoven fabric has the characteristics of high tensile strength, high tear strength, high modulus, high delamination peeling strength, good air permeability, good antibacterial performance, and good uniformity.

[0037] (2) The HDPE resin for flash non-woven fabrics used in the preparation method of the present invention adopts a titanium or chromium catalyst, which can effectively control the molecular weight and density of HDPE, facilitate the uniform dissolution of the polymer in the spinning solution, and at the same time facilitate the improvement of the breaking strength and fiber width of the fiber. The raw materials used are low-melting point HDPE resin (low-melting point polyethylene), ultra-high molecular weight polyethylene resin and HDPE resin for flash non-woven fabrics. The Vicat softening temperature of low-melting point polyethylene is lower than that of HDPE resin for flash non-woven fabrics. The low-melting point polyethylene takes longer to stretch and deform after being sprayed out from the nozzle, and the fiber diameter is finer, with a fiber diameter of about 700nm-3um. The low-melting point polyethylene undergoes micro-melting at a lower temperature. When the fiber sheet is hot-pressed once during the hot rolling process, the low-melting point polyethylene undergoes effective micro-melting. The ultra-high molecular weight polyethylene has strong intermolecular cohesion and is not easily stretched into fine fibers. The resulting fiber diameter is about 15um, which is relatively thick. The coarse fiber can improve the mechanical properties and barrier properties of the non-woven fabric. During the secondary hot pressing, the low-melting point polyethylene and conventional polyethylene undergo micro-melting, which can effectively improve the bonding strength between the fibers in the non-woven fabric and the fiber interface, and improve the delamination peeling strength and breaking strength of the non-woven fabric.

[0038] (3) The addition of the modifying agent in the present invention has the effects of volume expansion, lubrication, dispersion and expansion. Adding the modifying agent to the HDPE resin for flash non-woven fabrics can effectively make polyethylene with different melting points, softening points or molecular weights fully mixed and dissolved with each other; the modifying agent can improve the dissolution uniformity between polyethylene and solvent, and improve the dispersion uniformity of the spinning solution; the modifying agent has a lubricating effect, reducing the friction between the spinning solution and the pipeline and nozzle; the modifying agent can also increase the expansion ratio of the spinning solution at the outlet of the pressure reducing nozzle, increase the expansion width of the fiber bundle, and improve the uniformity of the non-woven fabric web.

[0039] (4) During the preparation process of the present invention, the expansion ratio of the fiber bundle ejected from the nozzle is increased by controlling the aspect ratio of the inlet and outlet of the decompression chamber of the decompression nozzle and the combing and separation components. At the same time, the linear density of the ejected fiber bundle is controlled to improve the uniformity of the single-layer web of ultrafine fibers. By using the linear density provided by the present invention, the uniformity of each layer of the fiber web is effectively improved without reducing the production efficiency. By forming a multi-layer web with low linear density, the uniformity of the entire non-woven fabric is improved.

[0040] (5) By using multiple components to coordinate the box and utilizing the Venturi effect generated by high spinning speed, negative pressure is formed in the spinning box area to achieve self-circulation of airflow, combing the turbulent airflow during the distribution of the filament bundles, achieving controllable reflux, greatly improving the spinning rate, and effectively improving the laying efficiency and uniformity.

[0041] (6) In the preparation method described in the present invention, the polymer sheet undergoes multiple water baths to effectively remove harmful substances such as residual solvent, free chlorine, and free hydrogen from the fiber surface, thereby preventing adverse effects on the product in downstream applications. The small amount of water in the polymer sheet quickly transfers heat during the hot pressing process, effectively increasing the heat transfer rate of the sheet and improving the delamination and peeling strength of the nonwoven fabric.

[0042] (7) The present invention adopts two hot pressing processes. The first hot pressing process is performed near the softening point, and the low-melting-point polyethylene fibers are slightly melted by increasing the line pressure, so that effective interface bonding occurs between the fibers in the non-woven fabric. The second hot pressing process is performed near the melting point and uses ultra-low line pressure to cause the fibers to slightly melt but avoid excessive plasticization. The ultra-low line pressure is beneficial to maintaining the tortuous path generated by the fiber structure with a wide diameter distribution inside the non-woven fabric, thereby having the function of blocking and filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the internal structure of the vacuum spinneret;

[0044] Figure 2 This is a schematic diagram of the three-dimensional structure of the spinning and spreading equipment;

[0045] Figure 3 Schematic diagram of the internal structure of the spinning and spreading equipment;

[0046] Figure 4 Schematic diagram of the structure of the swing wire assembly;

[0047] Figure 5 Schematic diagram of the three-dimensional structure of the airflow combing plate;

[0048] Figure 6 This is a schematic diagram of the three-dimensional structure of the airflow combing plate from another angle;

[0049] Figure 7 This is the left view of the swing wire assembly;

[0050] Figure 8 This is a bottom view of the swing wire assembly;

[0051] Figure 9 It is a structural diagram of the combing and separation components;

[0052] Figure 10 This is a microscopic morphology of the polyethylene fiber obtained in Example 1;

[0053] Figure 11 This is a photo of the polyethylene fiber prepared in Example 1;

[0054] Figure 12 Schematic diagram of the movement trajectory of the swing wire assembly and the fiber in Example 1;

[0055] In the figure, 1, decompression chamber inlet; 2, decompression chamber; 3, decompression chamber outlet; 4, spinneret; 5, decompression nozzle; 6, swinging assembly; 7, spinning box; 8, chamber; 9, airflow combing area; 10, connecting pipe; 11, combing and separation assembly;

[0056] 61. Connecting base; 62. Swinging surface; 63. Dispersion surface;

[0057] 91. Airflow combing plate; 92. Ventilation hole;

[0058] 111. Combing column; 112. Dispersion disk; 113. Dispersion hole. DETAILED DESCRIPTION

[0059] The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0061] A method for preparing a polyethylene flash-evaporated nonwoven fabric, the preparation method comprising:

[0062] S1. Preparation of HDPE resin for flash non-woven fabrics:

[0063] A polyethylene resin is obtained by polymerizing ethylene and 1-butene using a gas phase method. The polyethylene resin is mixed with a modification agent and then extruded and granulated to obtain a HDPE resin for flash non-woven fabrics; the modification agent includes at least a lubricant, an anti-blocking agent, and a stabilizer;

[0064] S2. Preparation of spinning solution:

[0065] Flash non-woven fabric HDPE resin, low melting point HDPE resin, ultra-high molecular weight polyethylene resin, solvent and gas are mixed, heated and dissolved, cooled and dissolved, and finally uniformly mixed to obtain a spinning solution;

[0066] S3. Preparation of polymer fibers and polymer sheets:

[0067] The spinning solution is ejected from the decompression nozzle 5 to obtain polyethylene fibers; the polyethylene fibers are spread, drawn, and extruded to obtain a polymer sheet;

[0068] S4. Preparation of nonwoven fabrics:

[0069] The polymer sheet is subjected to water bathing, drying, and hot rolling to obtain the nonwoven fabric.

[0070] Specifically, the lubricant is at least one of aliphatic amides such as oleamide and erucamide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin wax, polyethylene wax, glycerol monostearate, and ethoxylated fatty acid amines;

[0071] The opening agent is at least one of silicon dioxide, talc, diatomaceous earth, and hydrotalcite;

[0072] The stabilizer is at least one of an organic tin stabilizer, a metal soap antioxidant, a phosphite antioxidant, a phenolic antioxidant, and a phosphite antioxidant;

[0073] The modification aid also includes other additives, and the other additives are at least one of polyethylene oxide, sodium alginate, polyacrylamide, carboxymethyl cellulose, aliphatic polyoxyethylene propylene ether, emulsifier OP-10, Tween 60, Tween 80, fatty alcohol polyoxyethylene ether, maleic anhydride grafted polyethylene, Tinuvin 326, Tinuvin 327, Chimassorb 81, Tinuvin 1577, Tinuvin 770, Chimassorb 944, nano ZnO, and nano TiO2.

[0074] More specifically, in step S1, the total amount of the modification aids added is 0.02%-0.4% of the mass of the polyethylene resin, and the amount of each modification aid added is 0.001%-0.1% of the mass of the polyethylene resin.

[0075] Specifically, in step S1, during the polymerization reaction, hydrogen is used as a molecular weight regulator, isopentane is used as an inducing condensing agent, and a titanium-based catalyst or a chromium-based catalyst is used to catalyze the polymerization reaction.

[0076] More specifically, the catalyst used in the polymerization reaction is at least one of a titanium-based UCAT-A catalyst, a titanium-based UCAT-J catalyst, a chromium-based UCAT-G catalyst, and a chromium-based UCAT-B catalyst.

[0077] More specifically, the polymerization reaction temperature in step S1 is 85° C.-100° C., and the pressure is 20-30 atm.

[0078] More specifically, in the embodiments of the present invention, the purity of ethylene used is ≥99.9%; the purity of 1-butene is ≥99.0%; the purity of hydrogen is ≥95%; the molar ratio of 1-butene to ethylene is (0.02-0.04):1; the amount of isopentane added is 0.5-5% of the total weight of the reaction system, the amount of catalyst added is 0.01~0.1 wt% of the total weight of the reaction system, and the titanium or chromium content in the catalyst support is generally 0.2~2 wt%.

[0079] Specifically, the HDPE resin density of the flash nonwoven fabric is 0.95±0.005g / cm 3 The melt index is 1±0.3 g / 10 min, 190°C / 2.16 kg (test method: ASTM D1238). The molecular weight and molecular weight distribution are: Mw = 130,000-250,000 g / mol, Mn = 20,000-60,000 g / mol, and Mw / Mn = 2-5 (test method: ASTM D5296-97). The low-melting-point HDPE resin has a Vicat softening point of ≤125°C, a melting point of ≤131°C, and a molecular weight of Mw = 80,000-130,000 g / mol. The ultra-high molecular weight polyethylene resin has a molecular weight of Mw = 1,000,000-7,000,000 g / mol.

[0080] Specifically, in step S2, the mass ratio of the HDPE resin for flash non-woven fabrics, the low melting point HDPE resin and the ultra-high molecular weight polyethylene resin is (40%-80%): (10%-50%): 10%, wherein the total mass of the HDPE resin for flash non-woven fabrics, the low melting point HDPE resin and the ultra-high molecular weight polyethylene resin is calculated as 100%.

[0081] More specifically, the low-melting-point HDPE resin used in the embodiments of the present invention is one or more of Formosa Plastics 8010, South Korea SKMD700, South Korea LG2500N, and South Korea LGYE0815. However, this is not a limitation of the present invention. As long as the HDPE resin with a Vicat softening temperature not higher than 122°C and a melting point not higher than 132°C is used, it can be used.

[0082] More specifically, the ultra-high molecular weight polyethylene resin used in the embodiments of the present invention is one or more of Celanese GUR 8110, Ticona GUR 4120, Braskem UTEC 6540, Mitsui HI-ZEX 240M, and DSM Dyneema SK78. However, this is not a limitation of the present invention, and any ultra-high molecular weight polyethylene resin with a molecular weight between 1 million and 7 million can be used.

[0083] Specifically, the specific process of step S2 is as follows: a solvent and a gas are mixed to prepare a first mixed solvent, and the first mixed solvent is mixed at a low temperature (37-150°C, preferably 37-100°C) until the temperature and pressure are stable. A flash non-woven fabric HDPE resin, a low-melting point HDPE resin, an ultra-high molecular weight polyethylene resin, and the gas are uniformly mixed to prepare a second mixed solution. The first mixed solvent and the second mixed solution are uniformly mixed under heating and pressurizing conditions, and mixed at high temperature and high pressure until the temperature and pressure are stable. The pressure and temperature are then reduced (to low temperature and low pressure) to promote mixing and dissolution, thereby obtaining a uniform spinning solution.

[0084] More specifically, the gas is one or two of carbon dioxide and nitrogen, and the solvent is one or more of water, alcohol, acid, amine, ester, ether, ketone, nitrile, amide, halogenated hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and unsaturated hydrocarbons; the weight of the gas in the first mixed solvent accounts for 10-30%; the weight of the gas in the second mixed solution is 80-140% of the total weight of the polymer (the total weight of HDPE resin for flash non-woven fabrics, low melting point HDPE resin and ultra-high molecular weight polyethylene resin); the weight ratio of the first mixed solvent and the second mixed solution in the spinning solution is (3-20):1.

[0085] More specifically, the first mixed solvent can be mixed evenly in a reactor or a static mixer; the second mixed solution can be mixed evenly in a screw extruder or a reactor; the first mixed solvent and the second mixed solution can be mixed in a screw extruder or a reactor.

[0086] After the first mixed solvent is uniformly mixed in a static mixer and the polymer is uniformly mixed in a screw extruder, gas is injected into the extruder through a booster pump at the first injection port to obtain a second mixed solution, which is then fully homogenized. The first mixed solvent is injected into the extruder through a booster pump at the second injection port, and after further homogenization, the spinning solution is extruded into a spinneret.

[0087] After the first mixed solvent is uniformly mixed in the reactor and the polymer is uniformly mixed in the screw extruder, gas is injected into the extruder through a booster pump at the first injection port to obtain a second mixed solution, which is then fully homogenized. The first mixed solvent and the second mixed solution are added to the reactor, circulated within the reactor by a stirring paddle or pump, and after further homogenization, the spinning solution is extruded into the spinneret.

[0088] More specifically, the temperature of the high temperature and high pressure is 180-250° C., and the pressure is 12-18 MPa; the temperature of the low temperature and low pressure is 150-180° C., and the pressure is 6-12 MPa.

[0089] Specifically, in step S3, if Figure 1As shown, the decompression nozzle 5 includes a decompression chamber inlet 1, a decompression chamber 2, a decompression chamber outlet 3, and a spinning tunnel 4. The aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is: length / diameter = (3-15) / 1;

[0090] like Figure 1 and Figure 9 As shown, a combing and separation component 11 is provided inside the decompression chamber 2, and the combing and separation component 11 includes a combing column 111 and a dispersion disk 112. The dispersion disk 112 is fixedly connected to the inside of the decompression chamber 2, and a plurality of dispersion holes 113 are provided on the dispersion disk 112. The spinning liquid is sprayed out from the decompression chamber outlet 3 through the dispersion holes 113.

[0091] More specifically, the dispersion discs 112 are fixedly mounted on both sides of the carding column 111. The outer diameter of the dispersion discs 112 is the same as the inner diameter of the decompression chamber 2, so that the dispersion discs 112 can be directly fixed on the inner cross-section of the decompression chamber 2. The surface of the dispersion discs 112 is perpendicular to the flow direction of the spinning solution in the decompression nozzle 5. The dispersion discs 112 can be integrally formed with the inner wall of the decompression chamber 2, or fixed by welding, screws, or other methods.

[0092] More specifically, the two ends of the combing column 111 are fixedly arranged in the middle of the dispersion disk 112. The combing column 111 and the dispersion disk 112 are integrated, or can be connected by welding or threading, as long as the combing column 111 and the dispersion disk 112 are fixedly connected.

[0093] More specifically, the combing column 111 is in the shape of a smooth cylinder, a teardrop, a gourd, a shuttle or a truncated cone. In the embodiment of the present invention, a shuttle shape is used.

[0094] More specifically, the overall length of the combing and separation assembly 11 (i.e., the distance between the two dispersion plates 112) is 40%-100% of the total length of the decompression chamber 2; the cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution accounts for 10%-50% of the cross-sectional area of the decompression chamber 2.

[0095] Preferably, the combing and separating component 11 is installed on a side of the decompression chamber 2 close to the decompression chamber inlet 1.

[0096] The spinning solution enters the decompression chamber 2, where the space becomes larger and the pressure decreases, causing microphase separation of the spinning solution. The present invention incorporates a combing and separation assembly 11 into the decompression chamber 2, allowing the spinning solution to undergo slow microphase separation, contributing to the stability of the solution-rich phase and thereby improving the strength and crystallinity of the fiber. Simultaneously, the spinning solution flows along the shape of the combing column 111, creating orientation in the spinning solution fluid, which can improve the regularity of the molecular chains and increase the crystallinity. After the spinning solution is combed by the combing and separation assembly 11 and becomes fibers, the fiber width of the fiber bundle can be increased.

[0097] More specifically, in the embodiment of the present invention, each of the dispersion disks 112 is evenly provided with four fan-shaped dispersion holes 113, and the dispersion holes 113 on the two dispersion disks 112 are staggered with each other, which is more conducive to the regular combing of the dispersion liquid and further improves the fiber opening ability of the fiber bundle.

[0098] The linear density of the polyethylene fiber is 100-350 dtex; the spinning temperature is 160-210° C.; and the spinning pressure is 8-15 MPa.

[0099] More specifically, the diameter of the decompression chamber inlet 1 is 0.8±0.5 mm, the diameter of the decompression chamber outlet 3 is 0.6±0.5 mm, the volume of the decompression chamber 2 is 5±3 ml, and the outlet diameter of the decompression nozzle 5 is 6±5 mm.

[0100] More specifically, the polyethylene flash nonwoven fabric is constructed using a multi-layer web-forming method. The nonwoven fabric is composed of two or more thin layers. The fibers of each layer are ejected from a single spinning solution through a single decompression nozzle 5. The fibers of each thin layer can be identical or slightly different depending on the requirements of the present invention.

[0101] Specifically, in step S3, a spinning and spreading device is used to prepare polymer fibers and polymer sheets, such as Figure 2-Figure 3 As shown, the spinning spreading equipment includes a pressure reducing nozzle 5, a swinging wire assembly 6 and a multi-component matching box, and the multi-component matching box includes a spinning box 7, a corridor cavity 8 and an air flow combing area 9. The corridor cavity 8 is communicated with the bottom of the spinning box 7, and the air flow combing area 9 is located below the corridor cavity 8. The air flow combing area 9 is communicated with the spinning box 7 through a connecting pipe 10; the corridor cavity 8 and the air flow combing area 9 are connected in sequence in a coaxial vertical direction.

[0102] After being ejected horizontally from the vacuum nozzle 5, the polyethylene fibers hit the swinging assembly 6. After being reflected by the surface of the swinging assembly 6, the polyethylene fibers fall into the multi-component matching box, where they are drawn and uniformly formed into a web. That is, the spinning solution is formed into fibers by the vacuum nozzle 5, and then passes through the negative pressure suction area of the spinning box 7, the channel cavity 8, and the air flow combing area 9 in sequence, and is then spread on the web forming equipment to form a web. Finally, the fiber web is extruded to obtain a polymer sheet.

[0103] The multi-component box body utilizes the Venturi effect generated by high spinning speed to form a negative pressure in the spinning box 7 area, thereby realizing self-circulation of airflow between the spinning box 7 and the airflow combing area 9, combing the turbulent airflow in the distribution process of the filament bundle, and improving the expansion width of the spinneret fiber and the uniformity of the web laying banner.

[0104] More specifically, the airflow combing area 9 is connected to the spinning box 7 through a plurality of connecting pipes 10; at least two airflow combing plates 91 surround the airflow combing area 9, such as Figure 5-Figure 6 As shown, the airflow carding plate 91 is provided with a vent 92, one end of the connecting pipe 10 is connected to the vent 92, and the other end of the connecting pipe 10 is connected to the spinning box 7. The airflow in the airflow carding plate 91 enters the spinning box 7 through the connecting pipe 10, thereby reducing the airflow following the fibers downward. When the fibers are deposited on the web, there is no high-speed airflow accompanying them, the fiber deposition speed is reduced, the fibers are more easily and evenly deposited on the web, and the web uniformity is improved.

[0105] More specifically, the connecting pipe 10 is a flexible air pipe, but this is not a limitation of the present invention. As long as the connecting pipe 10 can achieve communication between the airflow combing area 9 and the spinning box 7, it falls within the protection scope of the present invention.

[0106] More specifically, Figure 4 As shown, the swing assembly 6 is provided with a connection base 61, a swing surface 62 and a dispersion surface 63. The swing assembly 6 is connected to the drive motor via the connection base 61, and the drive motor drives the swing assembly 6 to swing in the horizontal direction. The swing assembly 6 and the drive motor can be installed in a conventional manner, which is not shown in detail in the figure. In addition, the decompression nozzle 5 is fixedly installed in the spinning box 7, and a conventional fixing method can be used. Figure 3 No more detailed display.

[0107] More specifically, the dispersion surface 63 is semi-conical, and the swing surfaces 62 are symmetrically provided on both sides of the dispersion surface 63 . The swing surfaces 62 are straight inclined surfaces.

[0108] More specifically, Figure 4 、 Figure 7 、 Figure 8 As shown, the swing surfaces 62 on both sides of the dispersion surface 63 are symmetrically inclined toward the dispersion surface 63, and the inclination angle a of the two swing surfaces 62 relative to the lower horizontal plane is 65-75°. The inclination angle b of the swing surface 62 relative to the semi-conical cross-section of the dispersion surface 63 is 160-180°, and the semi-conical angle of the dispersion surface 63 is a conical arc surface structure.

[0109] More specifically, the swing frequency of the swing assembly 6 is 3-30 times per second, and the swing amplitude of the swing assembly 6 is ±50mm (the center position of the swing amplitude is when the central axis of the dispersion surface 63 is facing the pressure reducing nozzle 5). Under this swing frequency condition, it is more conducive to cooperating with the spinning speed, greatly increasing the spread width of the spinning fiber and effectively improving the uniformity of the web laying cross section. Among them, the swing assembly 6 and the fiber movement trajectory are as follows Figure 12 shown.

[0110] More specifically, the width of the gap between each airflow combing plate 91 and the channel cavity 8 is 1-6 cm, which is more conducive to combing the turbulent airflow, achieving controllable backflow, and facilitating the uniformity of the web laying.

[0111] Specifically, the specific process of preparing the non-woven fabric in step S4 is: the polymer sheet is subjected to water bath, drying, primary hot pressing, cooling, secondary hot pressing, cooling, and winding to obtain the non-woven fabric;

[0112] The temperature of the water bath is 20-50°C, and the water bath is performed three times; the moisture content of the non-woven fabric after drying is 10-80%; the temperature of the first hot pressing is within the range of ±5°C of the Vicat softening point (120-135°C), and the linear pressure is 5-50 N / mm; the temperature of the second hot pressing is within the range of ±5°C of the melting point (130-140°C), and the linear pressure is 0-20 N / mm.

[0113] Specifically, by changing the pattern of the hot pressing roller, the material of the hot pressing roller, the wrap angle of the non-woven fabric roller and other parameters, the hard and soft structure of the non-woven fabric can be changed to produce a hard series of non-woven fabrics as stiff as paper or a soft series of non-woven fabrics as soft as cloth.

[0114] A polyethylene flash-evaporated nonwoven fabric is prepared according to the preparation method of the present invention.

[0115] Example 1

[0116] S1. Preparation of HDPE resin for flash non-woven fabrics:

[0117] Polyethylene polymerization is carried out using a gas-phase process, with ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, and isopentane as the induced condensing agent. Using a titanium-based UCAT-J catalyst, the ethylene and comonomer undergo polymerization in a fluidized bed reactor at a temperature of 100°C and a pressure of 20 atm, producing a powdered polyethylene resin. After degassing, the powdered polyethylene resin is added with a modifying agent and extruded into pellets to produce HDPE resin for flash nonwoven fabrics. The resulting HDPE resin has a density of 0.95 g / cm 3Test method: ASTM D792; Melt index: 1 g / 10 min, 190°C / 2.16 kg, test method: ASTM D1238; Molecular weight and molecular weight distribution: Mw = 150,000 g / mol, Mn = 32,000 g / mol, Mw / Mn = 4.69, test method: ASTM D5296-97. Modifying agents include: calcium stearate, polyethylene wax, antioxidant 1010, antioxidant 168, Tween 80, Tinuvin 327, and nano-TiO2. The dosage of each modifying agent is 0.004 wt% of the polyethylene resin.

[0118] S2. Preparation of polymer spinning solution:

[0119] A first mixed solvent is prepared by mixing dichloromethane and carbon dioxide gas. A second mixed solution is prepared by uniformly mixing HDPE resin for flash non-woven fabrics, a low-melting-point HDPE resin, an ultra-high molecular weight polyethylene resin, and carbon dioxide. The first mixed solvent and the second mixed solution are uniformly mixed under heating and pressurizing conditions. Mixing is carried out at 200°C and 15 MPa until the temperature and pressure stabilize. The mixture is then cooled and pressure-reduced to 180°C and 9 MPa to promote mixing and dissolution, thereby obtaining a uniform spinning solution. The weight of the gas in the first mixed solvent is 30% of the weight of the liquid; the weight of the gas in the second mixed solution is 80% of the total weight of the polymers. Based on the total weight of the low-melting-point HDPE resin, the ultra-high molecular weight polyethylene resin, and the HDPE resin for flash non-woven fabrics being 100%, the low-melting-point HDPE resin accounts for 10% by weight, the ultra-high molecular weight polyethylene resin accounts for 10% by weight, and the HDPE resin for flash non-woven fabrics accounts for 80% by weight. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 5:1.

[0120] S3. Preparation of polymer fibers and polymer sheets:

[0121] Preparation of polymer fibers: A uniformly mixed spinning solution is ejected from a decompression nozzle 5 to produce a polymer fiber bundle. The decompression nozzle 5 comprises a decompression chamber inlet 1, a decompression chamber 2, a decompression chamber outlet 3, and a spinning tunnel 4. The aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is 5:1. The polymer fiber bundle has a linear density of 320 dtex. The spinning temperature is 160°C, and the spinning pressure is 8 MPa. The overall length of the combing and separation assembly 11 is 100% of the total length of the decompression chamber 2. The combing column 111 is in the shape of a linear shuttle. The cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its largest cross-sectional area) accounts for 50% of the cross-sectional area of the decompression chamber 2, and the cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its smallest cross-sectional area) accounts for 10% of the cross-sectional area of the decompression chamber 2.

[0122] Preparation of polymer sheet: After being ejected horizontally from a decompression nozzle 5, polymer fibers strike an oscillating assembly 6. After being reflected by the surface of the oscillating assembly 6, the fibers fall into a multi-component spinning box 7. After being drawn by the spinning box 7, the polymer fibers form a uniform web. The two-layer web is extruded to produce a polymer sheet. The oscillating assembly 6 oscillates at a frequency of 20 times per second, with an amplitude of ±50 mm.

[0123] The multi-component matching box includes a spinning box 7, a channel cavity 8 and an airflow combing area 9. The channel cavity 8 is communicated with the bottom of the spinning box 7. The airflow combing area 9 is located below the channel cavity 8. The airflow combing area 9 is communicated with the spinning box 7 through a connecting pipe 10. The Venturi effect generated by the high spinning speed is used to form a negative pressure in the spinning box 7 area to achieve self-circulation of the airflow, comb the turbulent airflow in the distribution process of the filament bundle, realize controllable reflux, greatly increase the expansion width of the spinneret fiber, and effectively improve the uniformity of the web laying banner.

[0124] S4. Preparation of nonwoven fabrics:

[0125] The polymer sheet was passed through three water baths and dried at 100°C to a nonwoven fabric with a moisture content of 80%. The first hot press was performed at 135°C, a linear pressure of 10 N / mm, and a speed of 30 m / min. The second hot press was performed at 138°C, a linear pressure of 5 N / mm, and a speed of 30 m / min. The resulting polyethylene flash-steamed nonwoven fabric was then rolled up.

[0126] Example 2

[0127] S1. Preparation of HDPE resin for flash non-woven fabrics:

[0128] Polyethylene polymerization adopts the gas phase method, with ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, isopentane as the induced condensing agent, and titanium-based UCAT-A as the catalyst. Ethylene and the comonomer undergo polymerization in a fluidized bed reactor at a temperature of 90°C and a pressure of 30 atm to produce powdered polyethylene resin. After degassing, the powdered polyethylene resin is added with a modification agent and then extruded and granulated to produce HDPE resin for flash non-woven fabrics. The density of the obtained HDPE resin for flash non-woven fabrics is 0.951 g / cm 3, test method: ASTM D792; melt index: 0.95g / 10min, 190℃ / 2.16kg, test method: ASTM D1238; molecular weight and molecular weight distribution: Mw=160000g / mol, Mn=45000g / mol, Mw / Mn=3.55, ASTM D5296-97; the modifying agents include: calcium stearate, zinc stearate, calcium isooctanoate, antioxidant 1010, antioxidant 168, silica, carboxymethyl cellulose, Tinuvin 326, and nano-ZnO. The amount of each modifying agent is 0.05wt% based on the mass of the polyethylene resin.

[0129] S2. Preparation of polymer spinning solution:

[0130] A first mixed solvent was prepared by mixing a solvent (methylene chloride:cyclopentane in a mass ratio of 3:1) with carbon dioxide gas. A second mixed solution was prepared by uniformly mixing HDPE resin for flash non-woven fabrics, a low-melting-point HDPE resin, an ultra-high molecular weight polyethylene resin, and carbon dioxide. The first mixed solvent and the second mixed solution were uniformly mixed under heating and pressurizing conditions. Mixing was performed at 250°C and 18 MPa until the temperature and pressure stabilized. The mixture was then cooled and pressure-reduced to 150°C and 6 MPa to promote mixing and dissolution, resulting in a uniform spinning solution. The weight of the gas in the first mixed solvent accounted for 10% of the weight of the liquid; the weight of the gas in the second mixed solution accounted for 120% of the total weight of the polymers. Based on the combined weight of the low-melting-point HDPE resin, the ultra-high molecular weight polyethylene resin, and the HDPE resin for flash non-woven fabrics as 100%, the low-melting-point HDPE resin accounted for 30% by weight, the ultra-high molecular weight polyethylene resin accounted for 10% by weight, and the HDPE resin for flash non-woven fabrics accounted for 60% by weight. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution was 10:1.

[0131] S3. Preparation of polymer fibers and polymer sheets:

[0132] Preparation of polymer fibers: A uniformly mixed spinning solution is ejected from a decompression nozzle 5 to produce a polyethylene fiber bundle. The decompression nozzle 5 comprises a decompression chamber inlet 1, a decompression chamber 2, a decompression chamber outlet 3, and a spinning tunnel 4. The aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is 15:1. The polyethylene fiber bundle has a linear density of 100 dtex. The spinning temperature is 200°C, and the spinning pressure is 12 MPa. The overall length of the combing and separation assembly 11 is 40% of the total length of the decompression chamber 2. The combing column 111 is in the shape of a linear shuttle. The cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its largest cross-sectional area) accounts for 50% of the cross-sectional area of the decompression chamber 2, and the cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its smallest cross-sectional area) accounts for 10% of the cross-sectional area of the decompression chamber 2.

[0133] Preparation of polymer sheet: After being ejected horizontally from a decompression nozzle 5, polymer fibers strike an oscillating assembly 6. After being reflected by the surface of the oscillating assembly 6, the fibers fall into a multi-component spinning box 7. After being drawn by the spinning box 7, the polymer fibers form a uniform web. The four-layer web is extruded to produce a polymer sheet. The oscillating assembly 6 oscillates at a frequency of 10 times per second, with an amplitude of ±50 mm.

[0134] The multi-component matching box includes a spinning box 7, a channel cavity 8 and an airflow combing area 9. The channel cavity 8 is communicated with the bottom of the spinning box 7. The airflow combing area 9 is located below the channel cavity 8. The airflow combing area 9 is communicated with the spinning box 7 through a connecting pipe 10. The Venturi effect generated by the high spinning speed is used to form a negative pressure in the spinning box 7 area to achieve self-circulation of the airflow, comb the turbulent airflow in the distribution process of the filament bundle, realize controllable reflux, greatly increase the expansion width of the spinneret fiber, and effectively improve the uniformity of the web laying banner.

[0135] S4. Preparation of nonwoven fabrics:

[0136] The polymer sheet was passed through three water baths and dried at 80°C to a nonwoven fabric with a moisture content of 20%. The first hot press was performed at 125°C, a linear pressure of 50 N / mm, and a speed of 50 m / min. The second hot press was performed at 131°C, a linear pressure of 7 N / mm, and a speed of 50 m / min. The resulting polyethylene flash-steamed nonwoven fabric was then rolled up.

[0137] Example 3

[0138] S1. Preparation of HDPE resin for flash non-woven fabrics: Polyethylene polymerization adopts the gas phase method, with ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, isopentane as the induced condensing agent, and chromium-based UCAT-G as the catalyst. Ethylene and the comonomer undergo polymerization reaction in a fluidized bed reactor at a temperature of 85°C and a pressure of 25 atm to produce powdered polyethylene resin. After degassing, the powdered polyethylene resin is added with a modifying agent and then extruded and granulated to produce HDPE resin for flash non-woven fabrics. The density of the obtained HDPE resin for flash non-woven fabrics is 0.948 g / cm 3, test method: ASTM D792; melt index: 1.1g / 10min, 190℃ / 2.16kg, test method: ASTM D1238; molecular weight and molecular weight distribution: Mw=140000g / mol, Mn=33000g / mol, Mw / Mn=4.24, test method: ASTM D5296-97; the modifying additives are: oleamide, calcium stearate, polyethylene wax, diatomaceous earth, antioxidant 1076, antioxidant 626, emulsifier OP-10, hydrotalcite, Tinuvin 1577, and the amount of each additive is 0.01wt% of the amount of polyethylene.

[0139] S2. Preparation of polymer spinning solution: A solvent (dichloromethane:hexafluoroisopropanol in a mass ratio of 1:1) and carbon dioxide gas are mixed to prepare a first mixed solvent, and a HDPE resin for flash non-woven fabrics, a low-melting point HDPE resin, an ultra-high molecular weight polyethylene resin, and carbon dioxide are uniformly mixed to prepare a second mixed solution. The first mixed solvent and the second mixed solution are uniformly mixed under heating and pressurizing conditions, and the mixture is mixed at 190°C and 9.5 MPa until the temperature and pressure are stable. The mixture is then cooled and pressurized to 160°C and 8.3 MPa to promote mixed dissolution and obtain a uniform spinning solution. The weight of the gas in the first mixed solvent is 20% of the weight of the liquid; the weight of the gas in the second mixed solution is 100% of the total weight of the polymer; based on the total weight of the low-melting point HDPE resin, the ultra-high molecular weight polyethylene resin, and the HDPE resin for flash non-woven fabrics as 100%, the low-melting point HDPE resin accounts for 50wt%; the ultra-high molecular weight polyethylene resin accounts for 10wt%; and the HDPE resin for flash non-woven fabrics accounts for 40wt%. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 20:1.

[0140] S3. Preparation of polymer fibers and polymer sheets:

[0141] Preparation of polymer fibers: A uniformly mixed spinning solution is ejected from a decompression nozzle 5 to produce a polymer fiber bundle. The decompression nozzle 5 comprises a decompression chamber inlet 1, a decompression chamber 2, a decompression chamber outlet 3, and a spinning tunnel 4. The aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is 3:1. The linear density of the polymer fiber bundle is 200 dtex. The spinning temperature is 180°C, and the spinning pressure is 10 MPa. The overall length of the combing and separation assembly 11 is 60% of the total length of the decompression chamber 2. The combing column 111 is in the shape of a linear shuttle. The cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its largest cross-sectional area) accounts for 50% of the cross-sectional area of the decompression chamber 2, and the cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its smallest cross-sectional area) accounts for 10% of the cross-sectional area of the decompression chamber 2.

[0142] Preparation of polymer sheet: After being ejected horizontally from a decompression nozzle 5, polymer fibers strike an oscillating assembly 6. After being reflected by the surface of the oscillating assembly 6, the fibers fall into a multi-component spinning box 7. After being drawn by the spinning box 7, the polymer fibers are uniformly formed into a web. The six-layer web is extruded to produce a polymer sheet. The oscillating assembly 6 oscillates at a frequency of three times per second, with an amplitude of ±50 mm.

[0143] The multi-component matching box includes a spinning box 7, a channel cavity 8 and an airflow combing area 9. The channel cavity 8 is communicated with the bottom of the spinning box 7. The airflow combing area 9 is located below the channel cavity 8. The airflow combing area 9 is communicated with the spinning box 7 through a connecting pipe 10. The Venturi effect generated by the high spinning speed is used to form a negative pressure in the spinning box 7 area to achieve self-circulation of the airflow, comb the turbulent airflow in the distribution process of the filament bundle, realize controllable reflux, greatly increase the expansion width of the spinneret fiber, and effectively improve the uniformity of the web laying banner.

[0144] S4. Preparation of nonwoven fabrics:

[0145] The polymer sheet was passed through three water baths and dried at 90°C to a nonwoven fabric with a moisture content of 50%. The first hot press was performed at 130°C, a linear pressure of 40 N / mm, and a speed of 70 m / min. The second hot press was performed at 140°C, a linear pressure of 20 N / mm, and a speed of 70 m / min. The resulting polyethylene flash-spun nonwoven fabric was then rolled up.

[0146] Example 4

[0147] S1. Preparation of HDPE resin for flash non-woven fabrics: Polyethylene polymerization adopts the gas phase method, with ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, isopentane as the induced condensing agent, and chromium-based UCAT-G as the catalyst. Ethylene and the comonomer undergo polymerization reaction in a fluidized bed reactor at a temperature of 85°C and a pressure of 25 atm to produce powdered polyethylene resin. After degassing, the powdered polyethylene resin is added with a modifying agent and then extruded and granulated to produce HDPE resin for flash non-woven fabrics. The density of the obtained HDPE resin for flash non-woven fabrics is 0.948 g / cm 3, test method: ASTM D792; melt index: 1.1g / 10min, 190℃ / 2.16kg, test method: ASTM D1238; molecular weight and molecular weight distribution: Mw=130000g / mol, Mn=29000g / mol, Mw / Mn=4.48, test method: ASTM D5296-97; the modifying additives are: oleamide, calcium stearate, polyethylene wax, diatomaceous earth, antioxidant 1076, antioxidant 626, emulsifier OP-10, hydrotalcite, Chimassorb 944, nano-ZnO, and the amount of each additive is 0.01wt% of the amount of polyethylene.

[0148] S2. Preparation of polymer spinning solution: A solvent (cyclopentane: hexafluoroisopropanol in a mass ratio of 2:1) and carbon dioxide gas are mixed to prepare a first mixed solvent, and a HDPE resin for flash non-woven fabrics, a low-melting point HDPE resin, an ultra-high molecular weight polyethylene resin, and carbon dioxide are uniformly mixed to prepare a second mixed solution. The first mixed solvent and the second mixed solution are uniformly mixed under heating and pressurizing conditions, and the mixture is mixed at 190°C and 9.5 MPa until the temperature and pressure are stable. The mixture is then cooled and pressurized to 160°C and 8.3 MPa to promote mixed dissolution and obtain a uniform spinning solution. The weight of the gas in the first mixed solvent is 20% of the weight of the liquid; the weight of the gas in the second mixed solution is 100% of the total weight of the polymer; based on the total weight of the low-melting point HDPE resin, the ultra-high molecular weight polyethylene resin, and the HDPE resin for flash non-woven fabrics as 100%, in the outer layer fiber web formula, the low-melting point HDPE resin accounts for 10wt%; the ultra-high molecular weight polyethylene resin accounts for 10wt%; and the HDPE resin for flash non-woven fabrics accounts for 80wt%. The spinning solution for the inner two-layer fiber web consists of 60% by weight of low-melting-point HDPE resin and 40% by weight of HDPE resin for flash nonwoven fabric. The weight ratio of the first mixed solvent to the second mixed solvent in the spinning solution is 20:1.

[0149] S3. Preparation of polymer fibers and polymer sheets:

[0150] Preparation of polymer fibers: A uniformly mixed spinning solution is ejected from a decompression nozzle 5 to produce a polymer fiber bundle. The decompression nozzle 5 comprises a decompression chamber inlet 1, a decompression chamber 2, a decompression chamber outlet 3, and a spinning tunnel 4. The aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is 4:1. The polymer fiber bundle has a linear density of 200 dtex. The spinning temperature is 180°C, and the spinning pressure is 10 MPa. The overall length of the combing and separation assembly 11 is 100% of the total length of the decompression chamber 2. The combing column 111 is in the shape of a linear shuttle. The cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its largest cross-sectional area) accounts for 50% of the cross-sectional area of the decompression chamber 2, and the cross-sectional area of the combing column 111 perpendicular to the flow direction of the spinning solution (at its smallest cross-sectional area) accounts for 10% of the cross-sectional area of the decompression chamber 2.

[0151] Preparation of polymer sheet: After being ejected horizontally from a decompression nozzle 5, polymer fibers strike an oscillating assembly 6. After being reflected by the surface of the oscillating assembly 6, the fibers fall into a multi-component spinning box 7. After being drawn by the spinning box 7, the polymer fibers form a uniform web. The four-layer web is extruded to produce a polymer sheet. The oscillating assembly 6 oscillates at a frequency of 30 times per second, with an amplitude of ±50 mm.

[0152] The multi-component matching box includes a spinning box 7, a channel cavity 8 and an airflow combing area 9. The channel cavity 8 is communicated with the bottom of the spinning box 7. The airflow combing area 9 is located below the channel cavity 8. The airflow combing area 9 is communicated with the spinning box 7 through a connecting pipe 10. The Venturi effect generated by the high spinning speed is used to form a negative pressure in the spinning box 7 area to achieve self-circulation of the airflow, comb the turbulent airflow in the distribution process of the filament bundle, realize controllable reflux, greatly increase the expansion width of the spinneret fiber, and effectively improve the uniformity of the web laying banner.

[0153] S4. Preparation of nonwoven fabrics:

[0154] The polymer sheet was passed through three water baths and dried at 90°C to a nonwoven fabric with a moisture content of 50%. The first hot press was performed at 130°C, a linear pressure of 40 N / mm, and a speed of 70 m / min. The second hot press was performed at 140°C, a linear pressure of 20 N / mm, and a speed of 70 m / min. The resulting polyethylene flash-spun nonwoven fabric was then rolled up.

[0155] Comparative Example 1

[0156] The same method as in Example 1 was used to prepare a polyethylene flash nonwoven fabric, except that the amount of the low-melting point HDPE resin was increased in step S2. In this comparative example 1, the low-melting point HDPE resin accounted for 60 wt %; the HDPE resin for the flash nonwoven fabric accounted for 30 wt %; and the ultra-high molecular weight polyethylene resin accounted for 10 wt %.

[0157] Comparative Example 2

[0158] The polyethylene flash nonwoven fabric was prepared by the same method as in Example 1, except that no modifying agent was added in step S1.

[0159] Comparative Example 3

[0160] The polyethylene flash nonwoven fabric was prepared by the same method as in Example 1, except that no titanium catalyst or chromium catalyst was added during the polymerization reaction in step S1, and a metallocene catalyst was used.

[0161] Comparative Example 4

[0162] The polyethylene flash nonwoven fabric was prepared by the same method as in Example 1, except that the diameters of the decompression chamber inlet 1 and the decompression chamber outlet 3 remained unchanged (the same as in Example 1), but the aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 was length / diameter = 1:1.

[0163] Comparative Example 5

[0164] The same method as in Example 1 was used to prepare a polyethylene flash nonwoven fabric, except that in the spinning and spreading equipment used in Comparative Example 5, the airflow carding zone was not connected to the spinning box through a connecting pipe.

[0165] Comparative Example 6

[0166] The polyethylene flash nonwoven fabric was prepared by the same method as in Example 1, except that in step S4 of this comparative example 6, only the second hot pressing was performed, and the first hot pressing was not performed.

[0167] Comparative Example 7

[0168] The same method as in Example 1 was used to prepare a polyethylene flash nonwoven fabric, except that the swing frequency of the swing wire assembly 6 was 50 times per second. The effective width was 80 mm, which could not meet the requirements of large-sized sterilization bags.

[0169] Comparative Example 8

[0170] The same method as in Example 1 was used to prepare a polyethylene flash nonwoven fabric, except that the swing frequency of the swinging wire assembly 6 was 1 time per second. The fabric had a large width, uneven weight distribution across the width, and many holes.

[0171] Comparative Example 9

[0172] The same method as in Example 1 was used to prepare a polyethylene flash nonwoven fabric, except that the swing amplitude of the swinging wire assembly 6 was ±80 mm. The fabric had a large width, uneven weight distribution across the width, and many holes.

[0173] Comparative Example 10

[0174] The polyethylene flash nonwoven fabric was prepared by the same method as in Example 1, except that: there was no carding and separation component 11 in the decompression chamber 2 .

[0175] The performance tests were conducted on the products prepared in the above examples and comparative examples, and the test methods involved are as follows.

[0176] 1. HDPE testing:

[0177] Melt index; ASTM D 1238;

[0178] Density: ASTM D 792, ASTM D 4703;

[0179] Molecular weight: Test standard ASTM D5296-97, using high temperature gel chromatography analyzer, 160℃, 1,2,4-trichlorobenzene as solvent, flow rate 1 mL / min, guard column: PLGEL 10 um guard × 1, separation column: PLGEL 10 um mixed-B × 2, narrow distribution styrene as the standard.

[0180] 2. Fiber Testing

[0181] Linear density test method: Take a fiber and drop a 250g weight on it. The length of the fiber is 1800mm. Weigh the weight of the fiber. Linear density = fiber weight / 1.8×10000. Repeat 10 times and take the average value to get the linear density of the fiber.

[0182] Fiber width detection method: After the fiber is on the mesh, measure the fiber width from the mesh surface and take the average value of the width of 10 fibers.

[0183] Banner quantitative distribution test method: Sample from one side of the banner along the CD direction to the other side in sequence, with a cutting area of 100cm 2 After taking 10 groups of circles, the average quantitative and quantitative fluctuations were calculated.

[0184] Fiber strength test method: Twist the sample 10 times for every 2.54 cm of length, the standard test distance is 50.8 mm, the tensile speed is 101.6 mm / min, the maximum breaking force and elongation are taken, and the maximum breaking force is divided by the linear density to obtain the breaking strength.

[0185] Fiber diameter detection: Using a scanning electron microscope, measure the diameters of 100 random fibers of the same sample, and calculate the average fiber diameter and diameter distribution.

[0186] 3. Nonwoven fabric testing methods:

[0187] Delamination peel strength: FZ / T 80007.1-2006;

[0188] Quantitative: GB / T 451.2-2002;

[0189] Thickness: GB / T 451.3-2003;

[0190] Tensile strength and elongation: GB / T 12914-2018;

[0191] Tear strength: GB / T 455-2002;

[0192] Gurley air permeability: TAPPI T460;

[0193] Microbial barrier performance: ASTM F1608;

[0194] Mullen bursting strength: ASTM D774;

[0195] Spencer puncture resistance: ASTM D3420;

[0196] Moisture vapor transmission rate: TAPPI T523;

[0197] Hydrostatic pressure: GB / T 4744;

[0198] Opacity: TAPPI T425

[0199] Bendtsen air permeability: ISO 5636-3.

[0200] The specific test results are shown in Tables 1 to 3 below.

[0201] Table 1 Test results of nonwoven fabric and fiber performance indicators of Examples 1-4

[0202]

[0203] Table 2 Test results of nonwoven fabric and fiber performance indicators of comparative examples 1-5

[0204]

[0205] Table 3 Test results of nonwoven fabric and fiber performance indicators of comparative examples 6-10

[0206]

[0207] From the data in the above table, it can be seen that the fiber bundles of the non-woven fabrics prepared by the preparation method of Examples 1-4 using the present invention have a wide spread width, a wide fiber diameter distribution range, uniform fiber space distribution inside the non-woven fabric, and firm bonding between the fibers. They have the characteristics of high tensile strength, high tear strength, high modulus, high delamination peeling strength, good air permeability, good antibacterial performance, and good uniformity. Figure 10 This is the microscopic morphology of the polyethylene fiber obtained in Example 1. Figure 11 This is a photo of the polyethylene fiber obtained in Example 1. Figure 10 and Figure 11 It can be seen that the fiber diameter distribution obtained by the preparation method of the present invention is wider, the standard deviation of the fiber diameter is large, the thinnest fiber diameter is about 700nm, and the thickest is about 15um. Fibers with different diameters have better barrier properties against microorganisms.

[0208] The cross-sectional quantitative distribution of the fiber web in Example 1 is shown in Table 4 below, where the MD direction refers to the direction along which the product is produced, the CD direction refers to the direction perpendicular to the production direction, and CD positions 1 to 12 refer to sampling at intervals of 15 cm from the end of one side of the cross-sectional area along the CD direction. Sampling along the MD direction refers to sampling at intervals of 20 cm along the MD direction. As can be seen from Table 4, the quantitative distribution of Example 1 is uniform across the entire cross-sectional area, with minimal quantitative fluctuation.

[0209] Table 4 Banner quantitative distribution of Example 1

[0210]

[0211] Comparing the experimental results of Comparative Example 1 and Example 1, it can be seen that the use of HDPE resin in flash-steamed nonwoven fabrics improves the fiber width and mechanical properties. The Vicat softening temperature of low-melting-point polyethylene is lower than that of HDPE resin used in flash-steamed nonwoven fabrics. Low-melting-point polyethylene takes longer to stretch and deform after being ejected from the decompression nozzle 5, resulting in a finer fiber diameter. Low-melting-point polyethylene undergoes micro-melting at lower temperatures, acting as a bonding agent during the hot pressing process, helping to improve the delamination and peel strength of the nonwoven fabric. However, the excessive amount of low-melting-point polyethylene in Comparative Example 1 reduces the average fiber diameter, causes excessive fiber welding within the nonwoven fabric, degrades the air permeability of the nonwoven fabric, and reduces the mechanical properties after hot pressing.

[0212] From the comparison of the experimental results of Comparative Example 2 and Example 1, it can be seen that the modifying auxiliary agent has the effects of volume expansion, lubrication, dispersion and expansion. Comparative Example 2 does not add the modifying auxiliary agent, and there is a risk of nozzle clogging during the spinning process. The fiber opening width of Comparative Example 2 is low, and the barrier performance, uniformity and mechanical properties of the non-woven fabric obtained are poor.

[0213] Comparing the experimental results of Comparative Example 3 and Example 1, it can be seen that the use of titanium-based or chromium-based catalysts can effectively control the density, fluidity, molecular weight distribution, crystallinity, and branching structure of HDPE resin, thereby improving the uniformity and mixing efficiency of the polymer in the spinning solution. Changing the catalyst in Comparative Example 3 resulted in a significant decrease in fiber width, coarsening of the fiber diameter, and deterioration in the uniformity and barrier properties of the nonwoven fabric. Furthermore, the resin produced in Comparative Example 3 exhibited significant wall buildup in the mixer, resulting in a low yield and prone to clogging of the equipment and spinning line.

[0214] From the comparison of the experimental results of Comparative Example 4 and Example 1, it can be seen that after the aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 of the decompression nozzle 5 becomes 1:1, the expansion ratio of the fiber bundle ejected from the decompression nozzle 5 becomes smaller, the fiber opening width becomes lower, the linear density of the ejected fiber bundle becomes larger, the uniformity of the non-woven fabric deteriorates, and the barrier performance deteriorates.

[0215] From the comparison of the experimental results of Comparative Example 5 and Example 1, it can be seen that: the airflow combing area is connected to the spinning box through a connecting pipe, so as to realize self-circulation of the airflow, comb the turbulent airflow in the distribution process of the filament bundle, realize controllable reflux, greatly improve the spinning development rate, effectively improve the web laying efficiency and uniformity, and the comparative example 5 has poor web uniformity, poor barrier performance, and poor mechanical properties of the non-woven fabric.

[0216] Comparing the experimental results of Comparative Example 6 and Example 1, we can see that the first hot pressing process, near the softening point, increases linear pressure to bond the slightly melted, low-melting-point polyethylene fibers, resulting in effective interfacial bonding between the fibers within the nonwoven fabric. The second hot pressing process, at a temperature near the melting point and using ultra-low linear pressure, achieves micro-melting of the fibers while avoiding excessive plasticization. This ultra-low linear pressure helps maintain the tortuous pathways created by the widely distributed fiber structure within the nonwoven fabric, thus achieving barrier and filtration functions. Comparative Example 6 omitted the first hot pressing process, resulting in insufficient internal bonding within the nonwoven fabric, resulting in poor barrier properties, low delamination peel strength, and poor mechanical properties.

[0217] From the comparison of the experimental results of Comparative Example 7 and Example 1, it can be seen that the swing frequency affects the width of the falling fibers. The slower the swing frequency, the larger the web width; the faster the swing frequency, the narrower the web width. The swing frequency of Comparative Example 8 is used, the faster the swing frequency, and the narrower the web width. The effective width of the resulting non-woven fabric is 80 mm, which cannot meet the requirements of large-size sterilization bags. The effective width of Example 1 is 1800 mm.

[0218] A comparison of the experimental results for Comparative Example 8 and Example 1 reveals that the oscillation frequency of the oscillating wire assembly 6 is related to the product width and the ratio of the product's tensile strength in the MD / CD directions. Comparative Example 8, with an effective width of 2300 mm, exhibits poor web uniformity and barrier properties, while Example 1 has an effective width of 1600 mm. The difference in tensile strength between the MD and CD directions for Example 1 is small (MD / CD = 1.05), while the difference in tensile strength between the MD and CD directions for Comparative Example 8 is large (MD / CD = 0.59), indicating anisotropic mechanical properties.

[0219] Comparing the experimental results of Comparative Example 9 and Example 1, it can be seen that the swing amplitude is related to the web width and web uniformity. Small swing amplitudes result in a smaller web width and better web uniformity, while large swing amplitudes result in a larger web width and poor web uniformity. Comparative Example 9 has an effective width of 2200 mm, poor web uniformity, and poor barrier performance, while Example 1 has an effective width of 1800 mm. Increasing the swing amplitude of the swing wire assembly 6 results in uneven web weight distribution and more holes.

[0220] Comparing the experimental results of Comparative Example 10 and Example 1, it can be seen that the spinning solution, after passing through the carding and separation assembly 11, facilitates microphase separation of the spinning solution, thereby improving the strength and crystallinity of the fibers. Furthermore, the carding of the spinning solution by the carding and separation assembly 11 can increase the spread width of the fiber bundle. However, the fiber bundle of Comparative Example 10 has a narrow spread width and low fiber strength, resulting in reduced mechanical properties, uniformity, and barrier properties of the nonwoven fabric.

[0221] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. 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.

[0222] For those skilled in the art, several variations and improvements may be made without departing from the scope of the present invention, which all fall within the scope of protection of the present invention. The scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for preparing a polyethylene flash nonwoven fabric, characterized in that: The preparation method is: S1. Preparation of HDPE resin for flash non-woven fabrics: A polyethylene resin is obtained by polymerizing ethylene and 1-butene using a gas phase method. The polyethylene resin is mixed with a modification agent and then extruded and granulated to obtain a HDPE resin for flash non-woven fabrics; the modification agent includes at least a lubricant, an anti-blocking agent, and a stabilizer; S2. Preparation of spinning solution: HDPE resin for flash non-woven fabric, low melting point HDPE resin and ultra-high molecular weight polyethylene resin are mixed with solvent and gas, heated and dissolved, cooled and dissolved, and uniformly mixed to obtain spinning solution; S3. Preparation of polymer fibers and polymer sheets: The spinning solution is ejected from a decompression nozzle to obtain polyethylene fibers; the polyethylene fibers are spread, drawn, and extruded to obtain a polymer sheet; S4. Preparation of nonwoven fabrics: The polymer sheet is subjected to water bath, drying, and hot rolling to obtain the nonwoven fabric; In step S2, the mass ratio of HDPE resin for flash non-woven fabric, low melting point HDPE resin, and ultra-high molecular weight polyethylene resin is (40%-80%): (10%-50%): 10%; In step S3, the decompression nozzle includes a decompression chamber inlet, a decompression chamber, a decompression chamber outlet, and a spinning tunnel, and the aspect ratio of the decompression chamber inlet and the decompression chamber outlet is: length / diameter=(3-15) / 1; A combing and separation assembly is provided inside the decompression chamber, and the combing and separation assembly includes a combing column and a dispersion disk. The dispersion disk is fixedly connected to the inside of the decompression chamber and is provided with a plurality of dispersion holes. The spinning solution is ejected from the outlet of the decompression chamber through the dispersion holes. The linear density of the polyethylene fiber is 100-350 dtex; the spinning temperature is 160-210° C.; and the spinning pressure is 8-15 MPa.

2. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: The lubricant is at least one of oleamide, erucamide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin wax, polyethylene wax, glycerol monostearate, and ethoxylated fatty acid amine; The opening agent is at least one of silicon dioxide, talc, diatomaceous earth, and hydrotalcite; The stabilizer is at least one of an organic tin stabilizer, a metal soap antioxidant, a phosphite antioxidant, a phenolic antioxidant, and a phosphite antioxidant; The modification aid also includes other additives, which are at least one of polyethylene oxide, sodium alginate, polyacrylamide, carboxymethyl cellulose, aliphatic polyoxyethylene propylene ether, emulsifier OP-10, Tween 60, Tween 80, fatty alcohol polyoxyethylene ether, maleic anhydride grafted polyethylene, Tinuvin 326, Tinuvin 327, Chimassorb 81, Tinuvin 1577, Tinuvin 770, Chimassorb 944, nano ZnO, and nano TiO2.

3. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: In step S1, during the polymerization reaction, hydrogen is used as a molecular weight regulator, isopentane is used as an inducing condensing agent, and a titanium-based catalyst or a chromium-based catalyst is used to catalyze the polymerization reaction.

4. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: The HDPE resin density of the flash nonwoven fabric is 0.95±0.005 g / cm 3 ; Melt index is 1±0.3g / 10min, 190℃ / 2.16kg; Molecular weight and molecular weight distribution are: Mw=130000-250000g / mol, Mn=20000-60000g / mol, Mw / Mn=2-5; The Vicat softening point of the low-melting point HDPE resin is ≤125℃, the melting point is ≤131℃, the molecular weight is: Mw=80000-130000g / mol, and the molecular weight of the ultra-high molecular weight polyethylene resin is: Mw=1000000-7000000g / mol.

5. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: The specific process of step S2 is as follows: a solvent and a gas are mixed to prepare a first mixed solvent; a flash non-woven fabric HDPE resin, a low melting point HDPE resin, an ultra-high molecular weight polyethylene resin and the gas are mixed to prepare a second mixed solution; the first mixed solvent and the second mixed solution are mixed to prepare a second mixed solution under heating and pressurizing conditions; the mixture is heated and pressurized until the temperature and pressure are stable; and then the pressure and temperature are reduced to promote mixing and dissolution to obtain a uniform spinning solution; The solvent is one or more of water, alcohol, acid, amine, ester, ether, ketone, nitrile, amide, halogenated hydrocarbon, aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, and unsaturated hydrocarbon; The gas is one or more of carbon dioxide, nitrogen, and argon; The first mixed solvent is mixed at a low temperature until the temperature and pressure are stable, and the low temperature is 37-150°C.

6. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: In step S3, polymer fibers and polymer sheets are prepared using a spinning and spreading device, wherein the spinning and spreading device includes a decompression nozzle, a swinging wire assembly, and a multi-component coordinated box, wherein the multi-component coordinated box includes a spinning box, a channel cavity, and an airflow combing area, wherein the channel cavity is connected to the bottom of the spinning box, and the airflow combing area is located below the channel cavity and is connected to the spinning box through a connecting pipe; After being ejected horizontally from the pressure reducing nozzle, the polyethylene fiber hits the swinging wire assembly. After being reflected by the surface of the swinging wire assembly, the polyethylene fiber falls into the multi-component matching box, where it is stretched and uniformly formed into a web. The fiber web is extruded to obtain a polymer sheet. The multi-component box uses the Venturi effect generated by high spinning speed to form negative pressure in the spinning box area, thereby realizing self-circulation of air flow between the spinning box and the air flow combing area, combing the turbulent air flow in the distribution process of the yarn bundle, and improving the expansion width of the spinneret fiber and the uniformity of the web laying banner.

7. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, wherein: The specific process of preparing the nonwoven fabric in step S4 is as follows: the polymer sheet is subjected to water bath, drying, primary hot pressing, cooling, secondary hot pressing, cooling, and winding to obtain the nonwoven fabric; The water bath temperature is 20-50°C, and the water bath is repeated three times; the moisture content of the nonwoven fabric after drying is 10-80%; the primary hot pressing temperature is within the range of ±5°C from the Vicat softening point, and the linear pressure is 5-50 N / mm; the secondary hot pressing temperature is within the range of ±5°C from the melting point, and the linear pressure is 0-20 N / mm.

8. A polyethylene flash-steamed nonwoven fabric, characterized in that: The nonwoven fabric is prepared according to the preparation method according to any one of claims 1 to 7.

Images