Polyethylene non-woven fabric prepared by flash evaporation method and preparation method of polyethylene non-woven fabric

Abstract

The invention relates to the technical field of non-woven fabrics, in particular to a polyethylene flash-evaporation non-woven fabric and a preparation method thereof.The preparation method comprises the steps that ethylene and 1-butene are subjected to a polymerization reaction through a vapor phase method to obtain polyethylene resin, the polyethylene resin and a performance additive are mixed and then extruded and granulated, and HDPE resin for the flash-evaporation non-woven fabric is obtained; the modification additive at least comprises a lubricant, an anti-blocking agent and a stabilizer; uniformly dissolving HDPE resin for the flash non-woven fabric, low-melting-point HDPE resin and ultra-high molecular weight polyethylene resin in a solvent to obtain a spinning solution; spraying the spinning solution from a decompression nozzle to obtain polyethylene fibers; the polyethylene fiber is spread, drafted and extruded to obtain a polymer sheet; the polymer sheet is subjected to water bath, drying and hot rolling forming, and the non-woven fabric is obtained. The polyethylene non-woven fabric prepared by the flash evaporation method has the characteristics of high tensile strength, high tearing strength, high modulus, high layering peel strength, good air permeability and good bacterium blocking performance.

Description

Technical Field

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

[0002] Flash-spun polyethylene nonwoven fabric uses 100% high-density polyethylene as raw material, prepares a uniform spinning solution under high temperature and high pressure conditions, sprays it from a pressure-reducing nozzle to obtain continuous ultrafine fibers, and the ultrafine fibers are formed into a web by swinging and hot-rolled to obtain polyethylene nonwoven fabric. Flash-spun nonwoven fabric is composed of continuous and ultrafine fibers, endowing the nonwoven fabric with excellent mechanical properties, waterproof properties and air permeability.

[0003] Flash-spun nonwoven fabric is formed by a continuous fiber web with a certain width swinging regularly to form a whole nonwoven fabric with a certain width, and is stacked by dozens of fiber webs arranged in different directions along the thickness direction of the nonwoven fabric. The structure and properties of each layer of fiber web are crucial for the barrier properties of flash-spun nonwoven fabric. The fluidity and molecular structure of the polymer resin determine the diameter distribution of the fiber web, the thermal behavior of the polymer resin determines the interfacial bonding situation between the fiber webs, the structure of the nozzle determines the expansion ratio of the fiber web, that is, the opening width of the fiber web, and the structure of the fiber-swinging assembly determines the spatial distribution of the fiber web along the width direction of the nonwoven fabric. In order to improve the barrier properties of flash-spun nonwoven fabric, it is necessary to improve the mechanical properties, uniformity and stability of flash-spun nonwoven fabric at the same time.

[0004] The patent application with the publication number CN1938459A uses at least two polymers with different melting points or softening points to prepare nonwoven fabric, but the method disclosed in this invention is through simple physical mixing, resulting in poor compatibility between the two polymers and unable to effectively control the distribution uniformity of multiple polymers in the spinning solution and fibers; the patent application with the publication number CN112549713A uses fibers with a linear density of 300-400 dtex to prepare nonwoven fabric, which has a large linear density and poor web-forming uniformity of the nonwoven fabric, and is not conducive to preparing a uniform nonwoven fabric; the patent application with the publication number US3578739A discloses a device for applying static charges to the fiber structure, using static electricity to increase the opening width and achieve a uniform web-forming effect. However, the existing preparation methods of flash-spun nonwoven fabric still cannot simultaneously improve the mechanical properties, uniformity and barrier properties of the nonwoven fabric. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention provides a polyethylene flash-spun nonwoven fabric and a preparation method thereof. During the preparation process of the polyethylene flash-spun nonwoven fabric, the opening width of the fiber bundle unfolding is wide, the fiber diameter distribution range is wide, the internal fiber spatial distribution of the nonwoven fabric is uniform, the fibers are firmly bonded to each other, and it has the characteristics of high tensile strength, high tear strength, high modulus, high delamination peel strength, good air permeability, good antibacterial property and good uniformity.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A preparation method of polyethylene flash-spun nonwoven fabric, and the preparation method is as follows: S1. Preparation of HDPE resin for flash-spun nonwoven fabric: Ethylene and 1-butene are polymerized by a gas-phase method to obtain a polyethylene resin, and the polyethylene resin is mixed with a modification aid and then extruded and pelletized to obtain the HDPE resin for flash-spun nonwoven fabric; the modification aid at least includes a lubricant, an antiblocking agent, and a stabilizer; S2. Preparation of spinning solution: The HDPE resin for flash-spun nonwoven fabric, 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; S3. Preparation of polymer fibers and polymer sheets: The spinning solution is sprayed out from a pressure-reducing nozzle to obtain polyethylene fibers; the polyethylene fibers are spread, drawn, and extruded to obtain polymer sheets; S4. Preparation of nonwoven fabric: The polymer sheets are subjected to water bath, drying, and hot rolling to form the nonwoven fabric.

[0007] Further, the lubricant is at least one of aliphatic amides such as oleic acid amide and erucic acid amide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin wax, polyethylene wax, glycerol monostearate, and ethoxylated fatty amine; The antiblocking agent is at least one of silicon dioxide, talcum powder, diatomaceous earth, and hydrotalcite; The stabilizer is at least one of organic tin stabilizers, metal soap antioxidants, phosphite antioxidants, phenolic antioxidants, and phosphite antioxidants.

[0008] Further, the modification aid further 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.

[0009] Further, in step S1, during the polymerization reaction, hydrogen is used as a molecular weight regulator, isopentane is used as an induced condenser, and a titanium-based catalyst or a chromium-based catalyst is used for catalyzing the polymerization reaction.

[0010] Further, the density of the HDPE resin for flash-spun nonwoven fabric is 0.95 ± 0.005 g / cm 3 ; the melt index is 1 ± 0.3 g / 10 min, at 190 °C / 2.16 kg; the molecular weight and molecular weight distribution are as follows: Mw = 130,000 - 250,000 g / mol, Mn = 20,000 - 60,000 g / mol, Mw / Mn = 2 - 5; the Vicat softening point of the low-melting-point HDPE resin is ≤ 125 °C, the melting point is ≤ 131 °C, and the molecular weight is: Mw = 80,000 - 130,000 g / mol. The molecular weight of the ultra-high molecular weight polyethylene resin is: Mw = 1,000,000 - 7,000,000 g / mol.

[0011] Further, in step S2, the mass ratio of the HDPE resin for flash-spun nonwoven fabric, the low-melting-point HDPE resin, and the ultra-high molecular weight polyethylene resin is (40% - 80%):(10% - 50%):10%.

[0012] Further, the specific process of step S2 is: mixing a solvent and a gas to prepare a first mixed solvent, mixing the HDPE resin for flash-spun nonwoven fabric, the low-melting-point HDPE resin, the ultra-high molecular weight polyethylene resin, and a gas uniformly to prepare a second mixed solution, and under the conditions of heating and pressurization, mixing the first mixed solvent and the second mixed solution uniformly, heating and pressurizing the mixture until the temperature and pressure are stable, and then reducing the pressure and lowering the temperature 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.

[0013] Further, in step S3, the pressure-reducing nozzle includes a pressure-reducing chamber inlet, a pressure-reducing chamber, a pressure-reducing chamber outlet, and a spinneret passage, and the aspect ratio of the pressure-reducing chamber inlet and the pressure-reducing chamber outlet is: length / diameter = (3 - 15) / 1; A combing and separating component is provided inside the pressure-reducing chamber. The combing and separating component includes a combing column and a dispersion plate. The dispersion plate is fixedly connected to the inside of the pressure-reducing chamber. A plurality of dispersion holes are provided on the dispersion plate, and the spinning solution is ejected from the pressure-reducing chamber outlet 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.

[0014] Further, 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 wire laying assembly, and a multi-component cooperation box body. The multi-component cooperation box body includes a spinning box, a channel cavity, and an air flow combing area. The channel cavity communicates with the lower part of the spinning box. The air flow combing area is located below the channel cavity, and the air flow combing area communicates with the spinning box through a connecting pipe. After the polyethylene fibers are horizontally ejected from the decompression nozzle, they hit the wire laying assembly. After being reflected by the surface of the wire laying assembly, the polyethylene fibers fall into the multi-component cooperation box body, are stretched in the multi-component cooperation box body and uniformly formed into a web, and the fiber web is extruded to obtain a polymer sheet. The Venturi effect generated by the high spinning speed in the multi-component cooperation box body forms a negative pressure in the spinning box area, thereby realizing the self-circulation of the air flow between the spinning box and the air flow combing area, combing the disordered air flow during the fiber bundle distribution process, and improving the spreading width of the spun fibers and the uniformity of the cross-web.

[0015] Further, the specific process of preparing the non-woven 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 non-woven fabric. The temperature of the water bath is 20 - 50 °C, and the water bath is carried out 3 times; the moisture content of the non-woven fabric after drying is 10 - 80%; the temperature of the primary hot pressing is ±5 °C at the Vicat softening point, and the linear pressure is 5 - 50 N / mm; the temperature of the secondary hot pressing is ±5 °C at the melting point, and the linear pressure is 0 - 20 N / mm.

[0016] The present invention also discloses a polyethylene flash spinning non-woven fabric, and the non-woven fabric is prepared according to the preparation method described in the present invention.

[0017] The beneficial effects of the present invention are as follows: (1) In the preparation method of the present invention, the fiber bundles of the polyethylene flash spinning non-woven fabric have a wide opening width of fiber bundle expansion, a wide fiber diameter distribution range, uniform spatial distribution of fiber bundles inside the non-woven fabric, firm bonding between fibers, and have the characteristics of high tensile strength, high tear strength, high modulus, high delamination peeling strength, good air permeability, good antibacterial property, and good uniformity.

[0018] (2) The HDPE resin for flash-spun nonwoven fabric used in the preparation method of the present invention, using a titanium-based or chromium-based catalyst, can effectively control the molecular weight and density of HDPE, which is beneficial to the uniform dissolution of the polymer in the spinning solution and is also beneficial to improving the breaking strength and fibrillation width of the fibers. The raw materials are low-melting-point HDPE resin (low-melting-point polyethylene), ultra-high molecular weight polyethylene resin, and HDPE resin for flash-spun nonwoven fabric. The Vicat softening temperature of the low-melting-point polyethylene is lower than that of the HDPE resin for flash-spun nonwoven fabric. After the low-melting-point polyethylene is ejected from the nozzle, the stretching deformation time is longer and the fiber diameter is finer, with the fiber diameter being about 700nm - 3um. The low-melting-point polyethylene undergoes micro-melting at a lower temperature. When the fiber sheet is hot-pressed for the first time during the hot rolling process, the low-melting-point polyethylene undergoes effective micro-melting. The intermolecular cohesive force of the ultra-high molecular weight polyethylene is strong and it is not easily stretched into fine fibers. The fiber diameter obtained is about 15um, which is relatively thick. The thick fibers can improve the mechanical properties and barrier properties of the nonwoven fabric. During the second hot pressing, the low-melting-point polyethylene and the conventional polyethylene undergo micro-melting, which can effectively improve the bonding strength between the fibers and the interface between the fibers in the nonwoven fabric, and improve the delamination peel strength and breaking strength of the nonwoven fabric.

[0019] (3) The addition of the modification additive in the present invention has the effects of compatibilization, lubrication, dispersion, and swelling. Adding the modification additive to the HDPE resin for flash-spun nonwoven fabric can effectively make polyethylenes with different melting points or softening points or molecular weights fully mix and dissolve with each other; the modification additive can improve the dissolution uniformity between the polyethylene and the solvent and improve the dispersion uniformity of the spinning solution; the modification additive has a lubricating effect and reduces the friction between the spinning solution and the pipeline and the nozzle; the modification additive can also increase the expansion ratio of the spinning solution at the outlet of the pressure-reducing nozzle, increase the fiber bundle unfolding width, and improve the web-forming uniformity of the nonwoven fabric.

[0020] (4) During the preparation process of the present invention, by controlling the aspect ratio of the inlet and outlet of the pressure-reducing chamber of the pressure-reducing nozzle and the combing and separating assembly, the expansion ratio of the fiber bundle ejected from the nozzle is increased, and at the same time, the linear density of the ejected fiber bundle is controlled to improve the uniformity of the single-layer web-forming of the ultra-fine fibers. Using the linear density provided by the present invention, the uniformity of each layer of fiber web is effectively improved without reducing the production efficiency. Through multi-layer web-forming with a low linear density, the uniformity of the entire nonwoven fabric is improved.

[0021] (5) By using a multi-component cooperating box body and utilizing the Venturi effect generated by a high spinning speed, a negative pressure is formed in the spinning box area to achieve self-circulation of the air flow, the disordered air flow during the fiber bundle distribution process is combed, and controllable reflux is achieved, greatly improving the spinneret opening rate and effectively improving the laying web efficiency and uniformity.

[0022] (6) In the preparation method of the present invention, the polymer sheet undergoes multiple water baths, effectively removing harmful substances such as residual solvents, free chlorine, and free hydrogen on the fiber surface, and avoiding adverse effects on the downstream applications of the product. A small amount of moisture in the polymer sheet quickly transfers heat during the hot pressing process, effectively improving the heat transfer speed of the sheet and enhancing the delamination and peeling strength of the non-woven fabric.

[0023] (7) The present invention adopts two-stage hot pressing. The first stage is near the softening point, where the micro-molten low-melting polyethylene fibers are bonded by increasing the linear pressure, enabling effective interfacial bonding between the fibers in the non-woven fabric. The second-stage hot pressing temperature is near the melting point, and an ultra-low linear pressure is used to make the fibers undergo micro-melting but avoid over-plasticization. The ultra-low linear pressure is conducive to maintaining the tortuous paths generated by the fiber structure with a wide diameter distribution inside the non-woven fabric, thus having the functions of blocking and filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic internal structure diagram of a decompression spinneret; Figure 2 is a three-dimensional structure diagram of a spinning and spreading device; Figure 3 is a schematic internal structure diagram of a spinning and spreading device; Figure 4 is a schematic structure diagram of a wire laying assembly; Figure 5 is a three-dimensional structure diagram of an air flow carding plate; Figure 6 is a three-dimensional structure diagram of the air flow carding plate from another angle; Figure 7 is a left view of the wire laying assembly; Figure 8 is a bottom view of the wire laying assembly; Figure 9 is a schematic structure diagram of a carding and separating assembly; Figure 10 is a microscopic morphology diagram of the polyethylene fiber prepared in Example 1; Figure 11 is a photograph of the polyethylene fiber prepared in Example 1; Figure 12 is a schematic diagram of the wire laying assembly and the fiber movement trajectory in Example 1; In the figure, 1, inlet of the decompression chamber; 2, decompression chamber; 3, outlet of the decompression chamber; 4, spinneret channel; 5, decompression spinneret; 6, wire laying assembly; 7, spinning box; 8, channel cavity; 9, air flow carding area; 10, connecting pipe; 11, carding and separating assembly; 61, connecting base; 62, swinging surface; 63, dispersing surface; 91, air flow carding plate; 92, ventilation hole; 111. Carding cylinder; 112. Dispersion disc; 113. Dispersion holes. Detailed implementation manners

[0025] The following will give a detailed description of the specific implementation manners of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing the specific implementation manners and do not limit the present invention.

[0027] A preparation method of a polyethylene flash-spun nonwoven fabric, and the preparation method is as follows: S1. Preparation of HDPE resin for flash-spun nonwoven fabric: Ethylene and 1-butene are polymerized by a gas-phase method to obtain a polyethylene resin. After the polyethylene resin is mixed with a modification additive, it is extruded and pelletized to obtain the HDPE resin for flash-spun nonwoven fabric; the modification additive at least includes a lubricant, an antiblocking agent, and a stabilizer; S2. Preparation of spinning solution: The HDPE resin for flash-spun nonwoven fabric, low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin, a solvent, and a gas are uniformly mixed through mixing, heating and dissolving, and cooling and dissolving to finally obtain a spinning solution; S3. Preparation of polymer fibers and polymer sheets: The spinning solution is sprayed out from a decompression nozzle 5 to obtain polyethylene fibers; the polyethylene fibers are spread, drawn, and extruded to obtain polymer sheets; S4. Preparation of nonwoven fabric: The polymer sheets are subjected to a water bath, drying, and hot rolling to form the nonwoven fabric.

[0028] Specifically, the lubricant is at least one of aliphatic amides such as oleic acid amide and erucic acid amide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin wax, polyethylene wax, glycerol monostearate, and ethoxylated fatty amine; The antiblocking agent is at least one of silica, talcum powder, diatomaceous earth, and hydrotalcite; The stabilizer is at least one of organic tin stabilizers, metal soap antioxidants, phosphite antioxidants, phenolic antioxidants, and phosphite antioxidants; The modified auxiliary agent 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.

[0029] More specifically, in step S1, the total addition amount of the modified auxiliary agent is 0.02%-0.4% of the mass of the polyethylene resin, and the addition amount of each modified auxiliary agent is 0.001%-0.1% of the mass of the polyethylene resin.

[0030] Specifically, in step S1, during the polymerization reaction, hydrogen is used as a molecular weight regulator, isopentane is used as an induced condensing agent, and a titanium-based catalyst or a chromium-based catalyst is used for catalyzing the polymerization reaction.

[0031] More specifically, the catalyst used in the polymerization reaction is at least one of the titanium-based UCAT-A catalyst, the titanium-based UCAT-J catalyst, the chromium-based UCAT-G catalyst, and the chromium-based UCAT-B catalyst.

[0032] More specifically, the polymerization reaction temperature in step S1 is 85°C - 100°C, and the pressure is 20 - 30 atm.

[0033] 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 addition amount of isopentane is 0.5 - 5% of the total weight of the reaction system, the addition amount of the catalyst is 0.01~0.1 wt% of the total weight of the reaction system, and the titanium or chromium content in the catalyst carrier is usually 0.2~2 wt%.

[0034] Specifically, the density of the flash-spun nonwoven HDPE resin is 0.95 ± 0.005 g / cm 3; The melt index is 1 ± 0.3 g / 10 min, at 190 °C / 2.16 kg (testing method: ASTM D1238); the molecular weight and molecular weight distribution are as follows: Mw = 130000 - 250000 g / mol, Mn = 20000 - 60000 g / mol, Mw / Mn = 2 - 5 (testing method: ASTM D5296 - 97). The Vicat softening point of the low - melting - point HDPE resin is ≤ 125 °C, the melting point is ≤ 131 °C, and the molecular weight is: Mw = 80000 - 130000 g / mol. The molecular weight of the ultra - high - molecular - weight polyethylene resin is: Mw = 1000000 - 7000000 g / mol.

[0035] Specifically, in step S2, the mass ratio of the HDPE resin for flash - spun non - woven fabric, the low - melting - point HDPE resin, and the ultra - high - molecular - weight polyethylene resin is (40% - 80%):(10% - 50%):10%, where the total mass of the HDPE resin for flash - spun non - woven fabric, the low - melting - point HDPE resin, and the ultra - high - molecular - weight polyethylene resin is counted as 100%.

[0036] More specifically, the low - melting - point HDPE resin used in the embodiments of the present invention is one or more of Formosa Plastics 8010, SK MD700 of South Korea, LG 2500N of South Korea, and LG YE0815 of South Korea. However, this is not a limitation to 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.

[0037] 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, DSM Dyneema SK78. However, this is not a limitation to the present invention, as long as the ultra - high - molecular - weight polyethylene resin with a molecular weight between 1 million and 7 million is used.

[0038] Specifically, the specific process of step S2 is as follows: Mix the solvent and gas to prepare the first mixed solvent. The first mixed solvent is mixed at a low temperature until the temperature and pressure are stable. The low temperature is 37 - 150 °C, and the preferred temperature is 37 - 100 °C. Mix the HDPE resin for flash - spun non - woven fabric, the low - melting - point HDPE resin, the ultra - high - molecular - weight polyethylene resin, and the gas evenly to prepare the second mixed solution. Under the conditions of heating and pressurization, mix the first mixed solvent and the second mixed solution evenly, and mix them at high temperature and high pressure until the temperature and pressure are stable, and then reduce the pressure and temperature (low temperature and low pressure) to promote the mixing and dissolution to obtain a uniform spinning solution.

[0039] More specifically, the gas is one or both of carbon dioxide and nitrogen, and the solvent is one or several of water, alcohol, acid, amine, ester, ether, ketone, nitrile, amide, halogenated hydrocarbon, aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, and unsaturated hydrocarbon; the weight ratio of the gas in the first mixed solvent is 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 the HDPE resin for flash-spun nonwoven fabric, the low-melting-point HDPE resin, and the ultra-high molecular weight polyethylene resin); the weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is (3-20):1.

[0040] More specifically, the first mixed solvent can be mixed evenly in a reaction kettle or a static mixer; the second mixed solution can be mixed evenly in a screw extruder or a reaction kettle; the mixing of the first mixed solvent and the second mixed solution can be carried out in a screw extruder or a reaction kettle.

[0041] For example, if the first mixed solvent is mixed evenly in a static mixer and the polymer is mixed evenly in a screw extruder, the gas is injected into the extruder through a booster pump at the first injection port to obtain the second mixed solution, and it is 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 the spinning kettle.

[0042] For example, if the first mixed solvent is mixed evenly in a reaction kettle and the polymer is mixed evenly in a screw extruder, the gas is injected into the extruder through a booster pump at the first injection port to obtain the second mixed solution, and it is fully homogenized. The first mixed solvent and the second mixed solution are added to the reaction kettle, and through a stirring paddle or internal circulation by a pump, after further homogenization, the spinning solution is extruded into the spinning kettle.

[0043] 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.

[0044] Specifically, in step S3, as Figure 1 shown, the pressure-reducing nozzle 5 includes a pressure-reducing chamber inlet 1, a pressure-reducing chamber 2, a pressure-reducing chamber outlet 3, and a spinning nozzle channel 4. The aspect ratio of the pressure-reducing chamber inlet 1 and the pressure-reducing chamber outlet 3 is: length / diameter = (3-15) / 1; As Figure 1 and Figure 9 shown, a combing and separating component 11 is provided inside the pressure-reducing chamber 2. The combing and separating component 11 includes a combing column 111 and a dispersion disk 112. The dispersion disk 112 is fixedly connected to the inside of the pressure-reducing chamber 2. A number of dispersion holes 113 are provided on the dispersion disk 112, and the spinning solution is ejected from the pressure-reducing chamber outlet 3 through the dispersion holes 113.

[0045] More specifically, dispersion disks 112 are fixedly provided on both sides of the carding column 111. The outer diameter of the dispersion disk 112 is the same as the inner diameter of the pressure reduction chamber 2, so that the dispersion disk 112 can be directly fixedly arranged on the inner cross-section of the pressure reduction chamber 2. The disk surface of the dispersion disk 112 is perpendicular to the flow direction of the spinning solution in the pressure reduction nozzle 5. Among them, the dispersion disk 112 and the inner wall of the pressure reduction chamber 2 are integrally processed, or can be fixed by means of welding, screws, etc.

[0046] More specifically, both ends of the carding column 111 are fixedly arranged with the middle of the dispersion disk 112. Among them, the carding column 111 and the dispersion disk 112 are integrally processed, or can be connected by welding or threaded connection, as long as the fixed connection between the carding column 111 and the dispersion disk 112 is realized.

[0047] More specifically, the carding column 111 is in the shape of a smooth cylinder, water droplet, gourd, thread shuttle or frustum of a cone. In the embodiment of the present invention, the thread shuttle shape is used.

[0048] More specifically, the overall length of the carding and separating assembly 11 (that is, the distance between the two dispersion disks 112) is 40%-100% of the total length of the pressure reduction chamber 2; the cross-sectional area of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 10%-50% of the cross-sectional area of the pressure reduction chamber 2.

[0049] Preferably, the carding and separating assembly 11 is installed on one side of the pressure reduction chamber 2 close to the pressure reduction chamber inlet 1.

[0050] When the spinning solution enters the pressure reduction chamber 2, the space of the pressure reduction chamber 2 becomes larger and the pressure decreases, and the spinning solution will undergo microphase separation. In the present invention, the carding and separating assembly 11 is added to the pressure reduction chamber 2 to allow the spinning solution to slowly undergo microphase separation, which helps to stabilize the rich solution phase, thereby improving the strength and crystallinity of the fiber; at the same time, the spinning solution flows along the shape of the carding column 111, and the spinning solution fluid generates orientation, which can improve the regularity of the molecular chain and the crystallinity. After the spinning solution is carded by the carding and separating assembly 11 and becomes a fiber, the opening width of the fiber bundle can be increased.

[0051] More specifically, in the embodiment of the present invention, 4 fan-shaped dispersion holes 113 are evenly arranged on each dispersion disk 112, and the dispersion holes 113 on the two dispersion disks 112 are arranged in a staggered manner, which is more conducive to the carding and regularization of the dispersion liquid and further improves the fiber bundle opening ability.

[0052] 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.

[0053] More specifically, the diameter of the inlet 1 of the decompression chamber is 0.8 ± 0.5 mm, the diameter of the outlet 3 of the decompression chamber 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.

[0054] More specifically, for the structure of the polyethylene flash-spun nonwoven fabric, a multi-layer web-forming method is adopted, and the nonwoven fabric is composed of more than 2 thin layers. The fibers of each layer are ejected from one spinning solution through one decompression nozzle 5, and the fibers of each thin layer can be the same or slightly different according to the requirements of the present invention.

[0055] Specifically, in step S3, a spinning and spreading device is used to prepare polymer fibers and polymer sheets, as Figures 2 - 3 shown. The spinning and spreading device includes a decompression nozzle 5, a wire laying assembly 6, and a multi-component cooperation box body. The multi-component cooperation box body includes a spinning box 7, a channel cavity 8, and an air flow carding area 9. The channel cavity 8 communicates with the lower part of the spinning box 7. The air flow carding area 9 is located below the channel cavity 8, and the air flow carding area 9 communicates with the spinning box 7 through a connecting pipe 10. The channel cavity 8 and the air flow carding area 9 are connected in sequence in the coaxial vertical direction.

[0056] After the polyethylene fibers are ejected horizontally from the decompression nozzle 5, they hit the wire laying assembly 6. After being reflected by the surface of the wire laying assembly 6, the polyethylene fibers fall into the multi-component cooperation box body, and are stretched and uniformly formed into a web in the multi-component cooperation box body. That is, the spinning dope is formed into filaments through the decompression nozzle 5 and then passes through the negative pressure suction area of the spinning box 7, the channel cavity 8, and the air flow carding area 9 in sequence and is spread on the web-forming device to form a web. Finally, the fiber web is extruded to obtain a polymer sheet. In the multi-component cooperation box body, the Venturi effect generated by the high spinning speed is utilized to form a negative pressure in the area of the spinning box 7, so as to realize the self-circulation of the air flow between the spinning box 7 and the air flow carding area 9, comb the disordered air flow during the fiber bundle distribution process, and improve the width of the spun fiber unfolding and the uniformity of the web cross-section.

[0057] More specifically, the air flow carding area 9 communicates with the spinning box 7 through a plurality of connecting pipes 10. At least two air flow carding plates 91 enclose the air flow carding area 9, as Figures 5 - 6 shown. The air flow carding plate 91 is provided with ventilation holes 92. One end of the connecting pipe 10 communicates with the ventilation hole 92, and the other end of the connecting pipe 10 communicates with the spinning box 7. The air flow in the air flow carding plate 91 enters the spinning box 7 through the connecting pipe 10, so as to reduce the air flow following the fibers downward. When the fibers land on the net, there is no high-speed air flow accompanying them, the fiber landing speed is reduced, and the fibers are more likely to land evenly, improving the web-forming uniformity.

[0058] 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 the connection between the air flow combing area 9 and the spinning box 7, it belongs to the protection scope of the present invention.

[0059] More specifically, as Figure 4 shown, a connecting base 61, a swinging surface 62 and a dispersing surface 63 are provided on the wire swinging assembly 6. The wire swinging assembly 6 is connected to the driving motor through the connecting base 61, and the driving motor drives the wire swinging assembly 6 to swing in the horizontal direction. The installation of the wire swinging assembly 6 and the driving motor can be installed in a conventional manner, and will not be shown in detail in the figure. In addition, the pressure reducing nozzle 5 is fixedly installed in the spinning box 7, and a conventional fixing method can be used Figure 3 and will not be shown in detail herein.

[0060] More specifically, the dispersing surface 63 is semi-conical, and the swinging surfaces 62 are symmetrically arranged on both sides of the dispersing surface 63, and the swinging surface 62 is a flat inclined surface.

[0061] More specifically, as Figure 4 , Figure 7 , Figure 8 shown, the swinging surfaces 62 on both sides of the dispersing surface 63 are symmetrically inclined towards the dispersing surface 63. The inclination angle a of the two swinging surfaces 62 relative to the lower horizontal plane is 65 - 75°, and the inclination angle b of the swinging surface 62 relative to the semi-conical cross-section of the dispersing surface 63 is 160 - 180°. The semi-conical angle of the dispersing surface 63 is a conical arc surface structure.

[0062] More specifically, the swinging frequency of the wire swinging assembly 6 is 3 - 30 times per second, and the swinging amplitude of the wire swinging assembly 6 is ±50 mm (with the central axis of the dispersing surface 63 facing the pressure reducing nozzle 5 as the central position of the swinging amplitude). Under this wire swinging frequency condition, it is more conducive to cooperating with the spinning speed, greatly improving the spreading width of the spun fibers, and effectively improving the cross-web uniformity of the laid web. Among them, the wire swinging assembly 6 and the fiber movement trajectory are as Figure 12 shown.

[0063] More specifically, the gap width between each air flow combing plate 91 and the channel cavity 8 is 1 - 6 cm, which is more conducive to combing the disordered air flow, realizing controllable backflow, and is beneficial to the uniformity of the laid web.

[0064] Specifically, the specific process of preparing the non-woven 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 non-woven fabric; The temperature of the water bath is 20 - 50°C, and the water bath is carried out 3 times; the moisture content of the dried non-woven fabric is 10 - 80%; the temperature of the first hot pressing is ±5°C (120 - 135°C) at the Vicat softening point, and the linear pressure is 5 - 50 N / mm; the temperature of the second hot pressing is ±5°C (130 - 140°C) at the melting point, and the linear pressure is 0 - 20 N / mm.

[0065] Specifically, by changing parameters such as the pattern of the hot pressing roller, the material of the hot pressing roller, and the wrap angle of the non-woven fabric on the roller, the hard and soft structure of the non-woven fabric can be changed, and a hard series of non-woven fabrics as stiff as paper or a soft series of non-woven fabrics as soft as cloth can be produced.

[0066] A polyethylene flash-spun non-woven fabric, and the non-woven fabric is prepared by the preparation method described in the present invention.

[0067] Example 1 S1. Preparation of HDPE resin for flash-spun non-woven fabric: The polymerization of polyethylene adopts the gas phase method. Using ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, and isopentane as the induced condensate, using titanium-based UCAT-J as the catalyst, ethylene and the comonomer undergo a polymerization reaction in a fluidized bed reactor at a temperature of 100°C and a pressure of 20 atm to produce a powdery polyethylene resin. After the powdery polyethylene resin is degassed, a modified additive is added and then extruded into pellets to produce the HDPE resin for flash-spun non-woven fabric. The density of the prepared HDPE resin for flash-spun non-woven fabric: 0.95 g / cm 3 , detection method: ASTM D792; melt index: 1 g / 10 min, 190°C / 2.16 kg, detection method: ASTM D1238; molecular weight and molecular weight distribution: Mw = 150000 g / mol, Mn = 32000 g / mol, Mw / Mn = 4.69, detection method: ASTM D5296-97. The modified additive is: calcium stearate, polyethylene wax, antioxidant 1010, antioxidant 168, Tween 80, Tinuvin 327, nano-TiO2, and the dosage of each modified additive is 0.004 wt% of the mass of the polyethylene resin.

[0068] S2. Preparation of the polymer spinning solution: The solvent dichloromethane and carbon dioxide gas are mixed to prepare a first mixed solvent. The flash non-woven fabric is mixed evenly with HDPE resin, low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin and carbon dioxide to prepare a second mixed solution. Under the conditions of heating and pressurization, the first mixed solvent and the second mixed solution are mixed evenly. They are mixed at 200 °C and 15 Mpa until the temperature and pressure are stable, and then cooled and depressurized to 180 °C and 9 Mpa to promote mixing and dissolution, 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 polymer; based on the total weight of the low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin and HDPE resin for flash non-woven fabric being 100%, the low-melting-point HDPE resin accounts for 10 wt%; the ultra-high molecular weight polyethylene resin accounts for 10 wt%; the HDPE resin for flash non-woven fabric accounts for 80 wt%. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 5:1.

[0069] S3. Preparation of polymer fibers and polymer sheets: Preparation of polymer fibers: The uniformly mixed spinning solution is ejected from the pressure-reducing nozzle 5 to obtain a polymer fiber bundle; the pressure-reducing nozzle 5 is composed of a pressure-reducing chamber inlet 1, a pressure-reducing chamber 2, a pressure-reducing chamber outlet 3, and a spinneret passage 4. The aspect ratio of the pressure-reducing chamber inlet 1 and the pressure-reducing chamber outlet 3 is length / diameter = 5:1; the linear density of the polymer fiber bundle is 320 dtex; the spinning temperature is 160 °C, and the spinning pressure is 8 Mpa. The overall length of the carding and separating assembly 11 is 100% of the total length of the pressure-reducing chamber 2; the carding column 111 is in a thread shuttle shape, and the cross-sectional area (at the maximum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 50% of the cross-sectional area of the pressure-reducing chamber 2, and the cross-sectional area (at the minimum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 10% of the cross-sectional area of the pressure-reducing chamber 2.

[0070] Preparation of polymer sheets: After the polymer fibers are horizontally ejected from the pressure-reducing nozzle 5, they hit the wire-swinging assembly 6. After being reflected by the surface of the wire-swinging assembly 6, the fibers fall into the spinning box 7 body with multiple components cooperating. After being drawn by the spinning box 7 body, the polymer fibers are uniformly formed into a web, and a polymer sheet is obtained after extrusion of two layers of fiber webs. The swinging frequency of the wire-swinging assembly 6 is 20 times per second, and the swinging amplitude of the wire-swinging assembly 6 is ±50 mm.

[0071] The multi-component cooperation box body includes a spinning box 7, a channel cavity 8 and an air current combing area 9. The channel cavity 8 communicates with the lower part of the spinning box 7. The air current combing area 9 is located below the channel cavity 8. The air current combing area 9 communicates with the spinning box 7 through a connecting pipe 10. Utilizing the Venturi effect generated by high spinning speed, a negative pressure is formed in the area of the spinning box 7 to realize the self-circulation of air current, comb the disordered air current during the fiber bundle distribution process, realize controllable reflux, greatly increase the spreading width of the spun fibers, and effectively improve the cross-web uniformity of the web.

[0072] S4. Preparation of non-woven fabric: The polymer sheet passes through 3 water baths, and after drying at 100 °C, the moisture content of the non-woven fabric is 80%. The temperature of the first hot pressing is 135 °C, the linear pressure is 10 N / mm, and the vehicle speed is 30 m / min; the temperature of the second hot pressing is 138 °C, the linear pressure is 5 N / mm, and the vehicle speed is 30 m / min. The polyethylene flash-spun non-woven fabric is obtained by winding.

[0073] Example 2 S1. Preparation of HDPE resin for flash-spun non-woven fabric: The polyethylene polymerization adopts the gas phase method. Using 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 titanium-based UCAT-A as the catalyst, ethylene and the comonomer undergo a polymerization reaction in a fluidized bed reactor at a temperature of 90 °C and a pressure of 30 atm to produce a powdery polyethylene resin. After the powdery polyethylene resin is degassed, a modified additive is added and then extruded into pellets to produce the HDPE resin for flash-spun non-woven fabric; the density of the produced HDPE resin for flash-spun non-woven fabric: 0.951 g / cm 3 , detection method: ASTM D792; melt index: 0.95 g / 10 min, 190 °C / 2.16 kg, detection method: ASTM D1238; molecular weight and molecular weight distribution: Mw = 160000 g / mol, Mn = 45000 g / mol, Mw / Mn = 3.55, ASTM D5296-97; among them, the modified additives are: calcium stearate, zinc stearate, calcium isooctanoate, antioxidant 1010, antioxidant 168, silica, carboxymethyl cellulose, Tinuvin 326, nano-ZnO, and the dosage of each modified additive is 0.05 wt% of the mass of the polyethylene resin.

[0074] S2. Preparation of polymer spinning solution: Prepare a first mixed solvent by mixing a solvent (mass ratio of dichloromethane to cyclopentane is 3:1) and carbon dioxide gas. Prepare a second mixed solution by uniformly mixing flash-spun nonwoven fabric with HDPE resin, low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin, and carbon dioxide. Under the conditions of heating and pressurization, uniformly mix the first mixed solvent and the second mixed solution. Mix at 250 °C and 18 Mpa until the temperature and pressure are stable, and then cool and depressurize to 150 °C and 6 Mpa to promote mixing and dissolution to obtain a uniform spinning solution; the weight of the gas in the first mixed solvent is 10% of the weight of the liquid; the weight of the gas in the second mixed solution is 120% of the total weight of the polymer; based on the total weight of the low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin, and HDPE resin for flash-spun nonwoven fabric being 100%, the low-melting-point HDPE resin accounts for 30 wt%; the ultra-high molecular weight polyethylene resin accounts for 10 wt%; the HDPE resin for flash-spun nonwoven fabric accounts for 60 wt%. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 10:1.

[0075] S3. Preparation of polymer fibers and polymer sheets: Preparation of polymer fibers: Spray the uniformly mixed spinning solution from the pressure-reducing nozzle 5 to obtain a polyethylene fiber bundle; the pressure-reducing nozzle 5 consists of a pressure-reducing chamber inlet 1, a pressure-reducing chamber 2, a pressure-reducing chamber outlet 3, and a spinneret channel 4. The aspect ratio of the pressure-reducing chamber inlet 1 and the pressure-reducing chamber outlet 3 is length / diameter = 15:1; the linear density of the polyethylene fiber bundle is 100 dtex; the spinning temperature is 200 °C, and the spinning pressure is 12 Mpa. The overall length of the carding and separating assembly 11 is 40% of the total length of the pressure-reducing chamber 2; the carding column 111 is in the shape of a thread shuttle. The cross-sectional area (at the maximum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 50% of the cross-sectional area of the pressure-reducing chamber 2, and the cross-sectional area (at the minimum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 10% of the cross-sectional area of the pressure-reducing chamber 2.

[0076] Preparation of polymer sheets: After the polymer fibers are horizontally sprayed out from the pressure-reducing nozzle 5, they hit the wire-swinging assembly 6. After being reflected by the surface of the wire-swinging assembly 6, the fibers fall into the spinning box 7 body with multiple components in cooperation. After being drawn by the spinning box 7 body, the polymer fibers are uniformly formed into a web, and a polymer sheet is obtained after extrusion of 4 layers of fiber webs. The swinging frequency of the wire-swinging assembly 6 is 10 times per second, and the swinging amplitude of the wire-swinging assembly 6 is ±50 mm.

[0077] The multi-component cooperation box body includes a spinning box 7, a channel cavity 8, and an air flow combing area 9. The channel cavity 8 communicates with the lower part of the spinning box 7. The air flow combing area 9 is located below the channel cavity 8, and the air flow combing area 9 communicates with the spinning box 7 through a connecting pipe 10. Utilizing the Venturi effect generated by a high spinning speed, a negative pressure is formed in the area of the spinning box 7 to realize the self-circulation of the air flow, comb the disordered air flow during the fiber bundle distribution process, realize controllable backflow, greatly increase the spreading width of the spun fibers, and effectively improve the cross-web uniformity of the laid web.

[0078] S4. Preparation of non-woven fabric: The polymer sheet passes through 3 water baths, and after drying at 80 °C, the moisture content of the non-woven fabric is 20%. The temperature of the first hot pressing is 125 °C, the linear pressure is 50 N / mm, and the machine speed is 50 m / min; the temperature of the second hot pressing is 131 °C, the linear pressure is 7 N / mm, and the machine speed is 50 m / min. The polyethylene flash-spun non-woven fabric is obtained by winding.

[0079] Example 3 S1. Preparation of HDPE resin for flash-spun non-woven fabric: The polymerization of polyethylene adopts the gas phase method. Using ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, and isopentane as the induced condensate, using a chromium-based UCAT-G as the catalyst, ethylene and the comonomer undergo a polymerization reaction in a fluidized bed reactor at a temperature of 85 °C and a pressure of 25 atm to generate a powdery polyethylene resin. After degassing the powdery polyethylene resin, a modified additive is added and then extruded and pelletized to produce the HDPE resin for flash-spun non-woven fabric; the density of the prepared HDPE resin for flash-spun non-woven fabric is: 0.948 g / cm 3 , detection method: ASTM D792; melt index: 1.1 g / 10 min, 190 °C / 2.16 kg, detection method: ASTM D1238; molecular weight and molecular weight distribution: Mw = 140000 g / mol, Mn = 33000 g / mol, Mw / Mn = 4.24, detection method: ASTM D5296-97; among them, the modified additives are: oleic acid amide, calcium stearate, polyethylene wax, diatomaceous earth, antioxidant 1076, antioxidant 626, emulsifier OP-10, hydrotalcite, Tinuvin 1577, and the dosage of each additive is 0.01 wt% of the polyethylene dosage.

[0080] S2. Preparation of polymer spinning solution: A first mixed solvent is prepared by mixing a solvent (mass ratio of dichloromethane to hexafluoroisopropanol is 1:1) and carbon dioxide gas. A second mixed solution is prepared by uniformly mixing flash non-woven fabric with HDPE resin, low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin and carbon dioxide. Under the conditions of heating and pressurization, the first mixed solvent and the second mixed solution are uniformly mixed. They are mixed at 190°C and 9.5 Mpa until the temperature and pressure are stable, and then cooled and depressurized to 160°C and 8.3 Mpa to promote mixing and dissolution, obtaining 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, ultra-high molecular weight polyethylene resin and HDPE resin for flash non-woven fabric being 100%, the low-melting-point HDPE resin accounts for 50 wt%; the ultra-high molecular weight polyethylene resin accounts for 10 wt%; the HDPE resin for flash non-woven fabric accounts for 40 wt%. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 20:1.

[0081] S3. Preparation of polymer fibers and polymer sheets: Preparation of polymer fibers: The uniformly mixed spinning solution is ejected from the pressure-reducing nozzle 5 to obtain a polymer fiber bundle; the pressure-reducing nozzle 5 is composed of a pressure-reducing chamber inlet 1, a pressure-reducing chamber 2, a pressure-reducing chamber outlet 3 and a spinneret channel 4. The aspect ratio of the pressure-reducing chamber inlet 1 and the pressure-reducing chamber outlet 3 is length / diameter = 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 carding and separating assembly 11 is 60% of the total length of the pressure-reducing chamber 2; the carding column 111 is in the shape of a thread shuttle. The cross-sectional area (at the maximum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 50% of the cross-sectional area of the pressure-reducing chamber 2, and the cross-sectional area (at the minimum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 10% of the cross-sectional area of the pressure-reducing chamber 2.

[0082] Preparation of polymer sheets: After the polymer fibers are horizontally ejected from the pressure-reducing nozzle 5, they hit the wire-swinging assembly 6. After being reflected by the surface of the wire-swinging assembly 6, the fibers fall into the spinning box 7 body with multi-component cooperation. After being drawn by the spinning box 7 body, the polymer fibers are uniformly formed into a web, and a polymer sheet is obtained after extrusion of 6 layers of fiber webs. The swinging frequency of the wire-swinging assembly 6 is 3 times per second, and the swinging amplitude of the wire-swinging assembly 6 is ±50 mm.

[0083] The multi-component matching box body includes a spinning box 7, a channel cavity 8, and an air current combing area 9. The channel cavity 8 communicates with the lower part of the spinning box 7. The air current combing area 9 is located below the channel cavity 8, and the air current combing area 9 communicates with the spinning box 7 through a connecting pipe 10. Utilizing the Venturi effect generated by a high spinning speed, a negative pressure is formed in the area of the spinning box 7 to achieve self-circulation of the air current, comb the disordered air current during the fiber bundle distribution process, realize controllable backflow, greatly increase the spreading width of the spun fibers, and effectively improve the cross-web uniformity of the laid web.

[0084] S4. Preparation of non-woven fabric: The polymer sheet passes through 3 water baths and is dried at 90 °C. The moisture content of the non-woven fabric is 50%. The temperature of the first hot pressing is 130 °C, the linear pressure is 40 N / mm, and the vehicle speed is 70 m / min. The temperature of the second hot pressing is 140 °C, the linear pressure is 20 N / mm, and the vehicle speed is 70 m / min. The polyethylene flash-spun non-woven fabric is obtained by winding.

[0085] Example 4 S1. Preparation of HDPE resin for flash-spun non-woven fabric: The polymerization of polyethylene adopts the gas phase method. Using ethylene as the main raw material, 1-butene as the comonomer, hydrogen as the molecular weight regulator, and isopentane as the induced condenser, and using a chromium-based UCAT-G as the catalyst, ethylene and the comonomer undergo a polymerization reaction in a fluidized bed reactor at a temperature of 85 °C and a pressure of 25 atm to produce a powdery polyethylene resin. After the powdery polyethylene resin is degassed, a modification additive is added and then extruded into pellets to produce the HDPE resin for flash-spun non-woven fabric; the density of the prepared HDPE resin for flash-spun non-woven fabric is: 0.948 g / cm 3 , detection method: ASTM D792; melt index: 1.1 g / 10 min, 190 °C / 2.16 kg, detection method: ASTM D1238; molecular weight and molecular weight distribution: Mw = 130000 g / mol, Mn = 29000 g / mol, Mw / Mn = 4.48, detection method: ASTM D5296-97; the modification additives are: oleic acid amide, calcium stearate, polyethylene wax, diatomaceous earth, antioxidant 1076, antioxidant 626, emulsifier OP-10, hydrotalcite, Chimassorb 944, nano-ZnO, and the dosage of each additive is 0.01 wt% of the polyethylene dosage.

[0086] S2. Preparation of polymer spinning solution: A first mixed solvent is prepared by mixing a solvent (the mass ratio of cyclopentane to hexafluoroisopropanol is 2:1) and carbon dioxide gas. A second mixed solution is prepared by uniformly mixing flash-spun nonwoven fabric with HDPE resin, low-melting-point HDPE resin, ultra-high molecular weight polyethylene resin, and carbon dioxide. Under the conditions of heating and pressurization, the first mixed solvent and the second mixed solution are uniformly mixed. They are mixed at 190°C and 9.5 Mpa until the temperature and pressure are stable, and then the temperature is lowered and the pressure is reduced to 160°C and 8.3 Mpa to promote mixing and dissolution, obtaining 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, ultra-high molecular weight polyethylene resin, and HDPE resin for flash-spun nonwoven fabric being 100%, in the outer surface fiber web formulation, the low-melting-point HDPE resin accounts for 10 wt%. The ultra-high molecular weight polyethylene resin accounts for 10 wt%. The HDPE resin for flash-spun nonwoven fabric accounts for 80 wt%. In the spinning solution of the inner two-layer fiber web, the low-melting-point HDPE resin accounts for 60 wt%. The HDPE resin for flash-spun nonwoven fabric accounts for 40 wt%. The weight ratio of the first mixed solvent to the second mixed solution in the spinning solution is 20:1.

[0087] S3. Preparation of polymer fibers and polymer sheets: Preparation of polymer fibers: The uniformly mixed spinning solution is ejected from the pressure-reducing nozzle 5 to obtain a polymer fiber bundle. The pressure-reducing nozzle 5 is composed of a pressure-reducing chamber inlet 1, a pressure-reducing chamber 2, a pressure-reducing chamber outlet 3, and a spinneret passage 4. The aspect ratio of the pressure-reducing chamber inlet 1 and the pressure-reducing chamber outlet 3 is length / diameter = 4:1. 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 carding and separating assembly 11 is 100% of the total length of the pressure-reducing chamber 2. The carding column 111 is in the shape of a thread shuttle. The cross-sectional area (at the maximum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 50% of the cross-sectional area of the pressure-reducing chamber 2. The cross-sectional area (at the minimum cross-section) of the carding column 111 perpendicular to the flow direction of the spinning solution accounts for 10% of the cross-sectional area of the pressure-reducing chamber 2.

[0088] Preparation of polymer sheets: After the polymer fibers are horizontally ejected from the pressure-reducing nozzle 5, they hit the wire-swinging assembly 6. After being reflected by the surface of the wire-swinging assembly 6, the fibers fall into the spinning box 7 body with multiple components in cooperation. After being drawn by the spinning box 7 body, the polymer fibers are uniformly formed into a web. The four-layer fiber web is extruded to obtain a polymer sheet. The swinging frequency of the wire-swinging assembly 6 is 30 times per second, and the swinging amplitude of the wire-swinging assembly 6 is ±50 mm.

[0089] The multi-component cooperation box body includes a spinning box 7, a channel cavity 8 and an air flow combing area 9. The channel cavity 8 communicates with the lower part of the spinning box 7. The air flow combing area 9 is located below the channel cavity 8. The air flow combing area 9 communicates with the spinning box 7 through a connecting pipe 10. Utilizing the Venturi effect generated by high spinning speed, a negative pressure is formed in the area of the spinning box 7 to realize the self-circulation of air flow, comb the disordered air flow during the fiber bundle distribution process, realize controllable backflow, greatly increase the spreading width of the spun fibers, and effectively improve the cross-web uniformity of the laid web.

[0090] S4. Preparation of non-woven fabric: The polymer sheet passes through 3 water baths and is dried at 90°C. The moisture content of the non-woven fabric is 50%. The temperature of the first hot pressing is 130°C, the linear pressure is 40 N / mm, and the vehicle speed is 70 m / min. The temperature of the second hot pressing is 140°C, the linear pressure is 20 N / mm, and the vehicle speed is 70 m / min. The polyethylene flash-spun non-woven fabric is obtained by winding.

[0091] Comparative Example 1 The polyethylene flash-spun non-woven fabric is prepared by the same method as in Example 1, except that: in step S2, the dosage ratio of the low-melting-point HDPE resin is increased. In this Comparative Example 1, the low-melting-point HDPE resin accounts for 60 wt%; the HDPE resin used for flash-spun non-woven fabric accounts for 30 wt%; and the ultra-high molecular weight polyethylene resin accounts for 10 wt%.

[0092] Comparative Example 2 The polyethylene flash-spun non-woven fabric is prepared by the same method as in Example 1, except that: in step S1, no modifying additive is added.

[0093] Comparative Example 3 The polyethylene flash-spun non-woven fabric is prepared by the same method as in Example 1, except that: in step S1, no titanium-based catalyst or chromium-based catalyst is added during the polymerization reaction, and a metallocene catalyst is used.

[0094] Comparative Example 4 The polyethylene flash-spun non-woven fabric is 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 remain unchanged (the same as in Example 1), but the aspect ratio of the decompression chamber inlet 1 and the decompression chamber outlet 3 is length / diameter = 1:1.

[0095] Comparative Example 5 The polyethylene flash-spun non-woven fabric is prepared by the same method as in Example 1, except that: in this Comparative Example 5, in the spinning and spreading equipment used, the air flow combing area is not communicated with the spinning box through a connecting pipe.

[0096] Comparative Example 6 The polyethylene flash-spun nonwoven fabric was prepared by the same method as in Example 1, except that in step S4 of Comparative Example 6, only the second hot pressing was used and the first hot pressing was not carried out.

[0097] Comparative Example 7 The polyethylene flash-spun nonwoven fabric was prepared by the same method as in Example 1, except that the swing frequency of the filament laying assembly 6 was 50 times per second. The effective width was 80 mm, which could not meet the requirements of large-size sterilization bags.

[0098] Comparative Example 8 The polyethylene flash-spun nonwoven fabric was prepared by the same method as in Example 1, except that the swing frequency of the filament laying assembly 6 was 1 time per second. The width was large, the cross-web basis weight distribution was uneven, and there were many holes.

[0099] Comparative Example 9 The polyethylene flash-spun nonwoven fabric was prepared by the same method as in Example 1, except that the swing amplitude of the filament laying assembly 6 was ±80 mm. The width was large, the cross-web basis weight distribution was uneven, and there were many holes.

[0100] Comparative Example 10 The polyethylene flash-spun nonwoven fabric was prepared by the same method as in Example 1, except that there was no carding and separating assembly 11 in the decompression chamber 2.

[0101] Performance tests were carried out on the products prepared in the above examples and comparative examples, and the test methods involved were as follows.

[0102] I. HDPE detection: Melt index; ASTM D 1238; Density: ASTM D 792, ASTM D 4703; Molecular weight: The test standard is ASTM D5296-97. A high-temperature gel permeation chromatograph was used for determination at 160 °C. 1,2,4-Trichlorobenzene was used as the solvent, the flow rate was 1 mL / min, the guard column: PLGEL 10 um guard×1, the separation column: PLGEL 10 um mixed-B×2, and narrow-distribution styrene was used as the standard sample.

[0103] II. Fiber detection Test method for linear density: A 250 g weight was hung on a fiber, the length of the fiber was 1800 mm, and the weight of this fiber was weighed. The linear density = fiber weight / 1.8×10000. Repeat 10 times and take the average value to obtain the linear density of the fiber.

[0104] Test method for fibrillation width: After the fibers were deposited on the web, the width of the fibers was measured from the web surface, and the average value of the widths of 10 fibers was taken.

[0105] Cross-direction quantitative distribution detection method: Samples are taken sequentially from one side of the cross-direction along the CD direction to the other side, and circles with an area of 100 cm 2 are cut. After taking 10 groups, the average basis weight and basis weight fluctuation are calculated.

[0106] Fiber strength detection method: Twist 10 turns for every 2.54 cm of sample length, with a standard test distance of 50.8 mm and a tensile speed of 101.6 mm / min. Take the maximum breaking force and elongation at break. The breaking strength is obtained by dividing the maximum breaking force by the linear density.

[0107] 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.

[0108] III. Nonwoven fabric detection methods: Laminated peel strength: FZ / T 80007.1-2006; Basis weight: GB / T 451.2-2002; Thickness: GB / T 451.3-2003; Tensile strength and elongation at break: GB / T 12914-2018; Tear strength: GB / T 455-2002; Gurley air permeability: TAPPI T460; Microbial barrier performance: ASTM F1608; Mullen burst strength: ASTM D774; Spencer puncture resistance: ASTM D3420; Moisture vapor transmission rate: TAPPI T523; Hydrostatic pressure: GB / T 4744; Opacity: TAPPI T425 Bendtsen air permeability: ISO 5636-3.

[0109] The specific test results are shown in Tables 1-3 below.

[0110] Table 1 Test results of nonwoven fabric and fiber performance indicators for Examples 1-4

[0111] Table 2 Test results of nonwoven fabric and fiber performance indicators for Comparative Examples 1-5

[0112] Table 3 Test results of nonwoven fabric and fiber performance indicators for Comparative Examples 6-10

[0113] As can be seen from the above table data: For the nonwoven fabrics prepared by the preparation method described in the present invention in Examples 1-4, the fibrillation width of the fiber bundles is wide, the fiber diameter distribution range is wide, the internal fiber spatial distribution of the nonwoven fabric is uniform, the fibers are firmly bonded to each other, and it has the characteristics of high tensile strength, high tear strength, high modulus, high delamination peel strength, good air permeability, good antibacterial property, and good uniformity. Figure 10 Figure 5 shows the microscopic morphology of the polyethylene fibers obtained in Example 1. Figure 11 Figure 7 is a photograph of the polyethylene fibers obtained in Example 1. From Figure 10 and Figure 11 it can be seen that: The fiber diameter distribution obtained by the preparation method described in the present invention is wider, the standard deviation of the fiber diameter is large, the thinnest fiber diameter is about 700 nm, the thickest is about 15 μm, and the fibers with different diameters have better barrier performance against microorganisms.

[0114] The cross-web basis weight distribution of the fiber web in Example 1 is shown in Table 4 below. Among them, the MD direction refers to the direction along the product production, the CD direction refers to the direction perpendicular to the production direction, and CD positions 1 to 12 refer to taking a sample every 15 cm from one end of the cross-web along the CD direction for basis weight measurement; sampling along the MD direction means taking a sample every 20 cm along the MD direction for basis weight measurement; it can be seen from Table 4 that the basis weight in Example 1 is evenly distributed in the entire cross-web direction and the basis weight fluctuation is small.

[0115] Table 4 Cross-web basis weight distribution of Example 1

[0116] From the comparison of the experimental results between Comparative Example 1 and Example 1, it can be seen that: The flash-spun nonwoven fabric uses HDPE resin to improve the fibrillation width and mechanical properties of the fibers. The Vicat softening temperature of the low-melting-point polyethylene is lower than that of the HDPE resin for flash-spun nonwoven fabrics. After the low-melting-point polyethylene is ejected from the pressure-reducing nozzle 5, the stretching deformation time is longer and the fiber diameter is finer. The low-melting-point polyethylene undergoes micro-melting at a lower temperature and plays a bonding role during the hot pressing process, which helps to improve the delamination peel strength of the nonwoven fabric. Excessive low-melting-point polyethylene in Comparative Example 1 will reduce the average fiber diameter, cause excessive fusion of the fibers in the nonwoven fabric, deteriorate the air permeability of the nonwoven fabric, and reduce the mechanical properties after hot pressing.

[0117] From the comparison of the experimental results between Comparative Example 2 and Example 1, it can be seen that: The modifying additive has the functions of compatibilization, lubrication, dispersion, and swelling. In Comparative Example 2, no modifying additive is added, and there is a risk of nozzle blockage during the spinning process. The fibrillation width in Comparative Example 2 is low, and the barrier performance, uniformity, and mechanical properties of the prepared nonwoven fabric are poor.

[0118] It can be seen from the comparison of the experimental results between Comparative Example 3 and Example 1 that the use of a titanium-based catalyst or a chromium-based catalyst can effectively control the density, fluidity, molecular weight distribution, crystallinity, branched chain structure, etc. of the HDPE resin, thereby improving the uniformity and mixing efficiency of the polymer in the spinning solution. After changing the catalyst in Comparative Example 3, the fiber opening width becomes significantly worse, the fiber diameter is thick, and the uniformity and barrier properties of the non-woven fabric become worse. At the same time, it is found that the resin prepared in Comparative Example 3 adheres severely to the wall of the mixer, the production rate is low, and it is easy to block the equipment and the spinning pipeline.

[0119] It can be seen from the comparison of the experimental results between Comparative Example 4 and Example 1 that after the aspect ratio of the inlet 1 and the outlet 3 of the decompression chamber 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, and the uniformity and barrier properties of the non-woven fabric become worse.

[0120] It can be seen from the comparison of the experimental results between Comparative Example 5 and Example 1 that the air flow carding area is communicated with the spinning box through a connecting pipe, so as to realize the self-circulation of the air flow, card the disordered air flow during the fiber bundle distribution process, realize the controllable reflux, greatly improve the spinning opening rate, effectively improve the web-forming efficiency and uniformity. The web-forming uniformity, barrier property and mechanical property of the non-woven fabric in Comparative Example 5 are poor.

[0121] It can be seen from the comparison of the experimental results between Comparative Example 6 and Example 1 that for the first time near the softening point, by increasing the line pressure, the slightly molten low-melting polyethylene fibers are bonded, so that effective interfacial bonding occurs between the fibers in the non-woven fabric; for the second time, the hot pressing temperature is near the melting point, and an ultra-low line pressure is adopted to make the fibers slightly melt but avoid over-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, so as to have the functions of barrier and filtration. Comparative Example 6 did not adopt the first hot pressing, and the internal bonding of the non-woven fabric was insufficient, resulting in poor barrier performance, low delamination peeling strength and poor mechanical properties of the non-woven fabric.

[0122] It can be seen from the comparison of the experimental results between Comparative Example 7 and Example 1 that the swing frequency affects the width of the fiber falling. When the swing frequency is slow, the web-forming width is large; when the swing frequency is fast, the web-forming width is narrow. Using the swing frequency of Comparative Example 8, the swing frequency is fast and the web-forming width is narrow. The effective width of the obtained 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.

[0123] It can be seen from the comparison of the experimental results between Comparative Example 8 and Example 1 that the swing frequency of the wire laying assembly 6 is related to the width of the product and the ratio of the tensile strength of the product in the MD and CD directions. The effective width of Comparative Example 8 is 2300 mm, the web forming uniformity is poor, and the barrier performance is poor. The effective width of Example 1 is 1600 mm. The difference in the numerical values of the tensile strength of the product in the MD and CD directions in Example 1 is small (MD / CD = 1.05), while the difference in the numerical values of the tensile strength of the product in the MD and CD directions in Comparative Example 8 is large (MD / CD = 0.59), and the mechanical properties of the product are anisotropic.

[0124] It can be seen from the comparison of the experimental results between Comparative Example 9 and Example 1 that the swing amplitude is related to the web forming width and the web forming uniformity. When the swing amplitude is small, the web forming width is small and the web forming uniformity is good; when the swing amplitude is large, the web forming width is large and the web forming uniformity is poor. The effective width of Comparative Example 9 is 2200 mm, the web forming uniformity is poor, and the barrier performance is poor. The effective width of Example 1 is 1800 mm. When the swing amplitude of the wire laying assembly 6 increases, the cross-directional basis weight distribution is uneven and there are many holes.

[0125] It can be seen from the comparison of the experimental results between Comparative Example 10 and Example 1 that after the spinning solution passes through the carding and separating assembly 11, it helps the spinning solution to undergo microphase separation, thereby improving the strength and crystallinity of the fibers; through the carding of the carding and separating assembly 11, the opening width of the fiber bundle can be increased. The opening width of the fiber bundle in Comparative Example 10 is narrow, the fiber strength is low, the mechanical properties of the non-woven fabric are reduced, and both the uniformity and the barrier performance decline.

[0126] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the various technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0127] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention shall be subject to 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 nonwoven fabrics: A gas phase method is used to polymerize ethylene and 1-butene to obtain polyethylene resin, and the polyethylene resin is mixed with a modification auxiliary agent and then extruded and granulated to obtain a HDPE resin for flash non-woven fabrics; the modification auxiliary agent at least includes a lubricant, an opening agent and a stabilizer; S2. Preparation of spinning solution: HDPE resin for flash nonwoven 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 bathing, drying and hot rolling to obtain the nonwoven fabric.

2. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, characterized in that: The lubricant is at least one of aliphatic amides such as oleic acid amide, erucic acid amide, calcium stearate, zinc stearate, calcium isooctanoate, paraffin, polyethylene wax, glycerol monostearate, and ethoxylated fatty acid amines; The opening agent is at least one of silicon dioxide, talcum powder, 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, characterized in that: 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, characterized in that: 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, 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, characterized in that: 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%.

6. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, characterized in that: The specific process of step S2 is: mixing a solvent and a gas to prepare a first mixed solvent, mixing a flash non-woven fabric HDPE resin, a low melting point HDPE resin, an ultra-high molecular weight polyethylene resin and a gas to uniformly prepare a second mixed solution, mixing the first mixed solvent and the second mixed solution uniformly under heating and pressurizing conditions, heating and pressurizing the mixture until the temperature and pressure are stable, and then reducing the pressure and temperature to promote mixed 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.

7. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, characterized in that: In step S3, the decompression nozzle comprises a decompression chamber inlet, a decompression chamber, a decompression chamber outlet, and a spinning channel, and the aspect ratio of the decompression chamber inlet and the decompression chamber outlet is: length / diameter=(3-15) / 1; A combing and separation component is provided inside the decompression chamber, and the combing and separation component includes a combing column and a dispersion disk, the dispersion disk is fixedly connected to the inside of the decompression chamber, and the dispersion disk is provided with a plurality of dispersion holes, through which the spinning solution is sprayed out from the outlet of the decompression chamber; 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.

8. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, characterized in that: In step S3, a spinning and spreading device is used to prepare polymer fibers and polymer sheets, wherein the spinning and spreading device comprises a decompression nozzle, a swinging wire assembly and a multi-component matching box, wherein the multi-component matching box comprises a spinning box, a channel cavity and an airflow combing area, wherein the channel cavity is communicated with the bottom of the spinning box, the airflow combing area is located below the channel cavity, and the airflow combing area is communicated with the spinning box through a connecting pipe; After the polyethylene fiber is horizontally ejected from the pressure reducing nozzle, it hits the swing wire assembly. After being reflected by the surface of the swing wire assembly, the polyethylene fiber falls into the multi-component matching box, and is evenly formed into a web after being drawn in the multi-component matching box. The fiber web is extruded to obtain a polymer sheet. The multi-component box uses the Venturi effect produced 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.

9. The method for preparing a polyethylene flash nonwoven fabric according to claim 1, characterized in that: 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 temperature of the water bath is 20-50°C, and the water bath is repeated 3 times; the moisture content of the nonwoven 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, and the line pressure is 5-50N / mm; the temperature of the second hot pressing is within the range of ±5°C of the melting point, and the line pressure is 0-20 N / mm.

10. A polyethylene flash nonwoven fabric, characterized in that: The nonwoven fabric is prepared according to the preparation method according to any one of claims 1 to 9.

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