A meltblown nozzle structure that ejects oscillating interaction air flows

Abstract

The application relates to the technical field of spinning processing equipment, in particular to a melt-blowing nozzle structure of jet oscillation interactive airflow. The melt-blowing nozzle structure of jet oscillation interactive airflow comprises a spinneret, a plurality of mutually parallel spinning holes are vertically and downwardly formed in the bottom surface of the extrusion groove of the spinneret, and the spinneret and air knives located on both sides of the spinneret form annular backflow channels. The special air duct die head with the annular backflow channels is adopted, when the fibers are extruded, the alternating airflow blows and sprays the fibers, the distribution space of the fibers in the transverse direction is increased, the drawing force on the fibers is increased, the draw ratio of the fibers is improved, and finer fibers are obtained.

Description

Technical Field

[0001] This application relates to the field of spinning equipment technology, and in particular to a meltblown nozzle structure that sprays an alternating airflow of oscillating jets. Background Technology

[0002] Various microorganisms exist in nature, some of which are pathogens. These pathogens, upon contact with the human body, can cause illness or even death. Therefore, how to protect people from contact with pathogens in certain situations has been a persistent challenge for researchers, designers, and manufacturers of protective clothing.

[0003] To prevent pathogens from invading the human body while ensuring comfort, researchers have invented membrane fabric composites and microfiber stacked materials to create protective materials that can both block pathogens and allow water vapor to escape from the skin. Currently, the widely used spunbond meltblown composite (i.e., SMS fabric) is a type of microfiber composite material. This material employs a multi-layered structure. The upper and lower layers consist of stacked filaments with diameters of tens of micrometers (i.e., spunbond nonwoven fabric) to provide the composite material's physical and mechanical properties. The middle layer is a fiber layer composed of at least one layer of microfiber stacked fabric (i.e., the so-called meltblown layer) to meet the pathogen blocking requirements. These multi-layered composite materials are bonded together using a melt-welding method to form a complete protective fabric.

[0004] Because microfibers have a diameter of approximately 1-10 micrometers, similar to the size of most bacteria, the gaps formed by the fiber stacking are insufficient for bacteria to pass through, thus achieving their barrier function. Limited by the diameter of microfibers, further improvements to their barrier properties are needed for different applications. These improvements include adding electrets during fiber production and applying three-antioxidant treatments to the fabric to further enhance its partial barrier effect against even smaller pathogens, such as various viruses, including COVID-19 and Ebola. If an industrially scalable method can be developed to produce even finer fibers, achieving complete barrier properties against various viruses will become possible.

[0005] The Importance of Biodegradable Microfiber Production: After use, nonwoven fabrics trap dust and impurities that adhere to the surface and penetrate the interior of the filter material. Since the raw materials for filter nonwovens are primarily polypropylene and polyester fibers, they are not recyclable after use. Neither blowing nor washing methods can remove the trapped dust. For this reason, they are typically disposed of as everyday waste, usually through incineration. The post-treatment methods for other special filter nonwovens are also more complex. For example, disposable nonwoven protective clothing used in the nuclear industry must consider the radiation effects of radioactive fallout. Incineration is generally not suitable because it cannot remove radioactive fallout and may even accelerate its spread, posing a significant environmental hazard. The common method is to package the product and transport it to a remote area for deep burial, thus isolating it from human health. However, the half-life of radioactive elements is often decades long, posing a long-term potential threat to soil and the environment.

[0006] Given this environmental consideration, and with environmental protection becoming increasingly important, the need to replace traditional nonwoven filter materials with environmentally friendly materials is urgent. One of the most typical environmentally friendly materials is polyvinyl alcohol (PVA). Because PVA is water-soluble, if disposable nonwoven protective clothing uses PVA as a raw material, the waste can dissolve in hot water after use. The PVA aqueous solution can penetrate into the soil, improving its aggregation properties and being decomposed into carbon dioxide and water by bacteria in the soil. Using water-soluble PVA as a raw material to prepare microfiber nonwoven fabrics for nuclear industry protective clothing not only meets environmental requirements but also saves on post-processing costs.

[0007] Both solution spinning and melt spinning of PVA involve the production load of volatile solvents or plasticizers, making fiber formation difficult and prone to sticking, thus failing to produce products that meet quality requirements. Furthermore, solvent evaporation efficiency directly determines the efficiency of large-scale production. Therefore, solvent evaporation must be carefully considered during solution spinning.

[0008] Meltblown technology principles and drawbacks: Currently, the technology capable of producing nonwoven microfibers is called "meltblown," see [link to related documentation]. Figure 1The process flow of meltblown microfiber nonwoven fabric production equipment is as follows: During the meltblown process, polymer granules are added from the hopper and then melted into polymer melt by the heating and extrusion action of a high-temperature screw. The polymer melt is then metered and extruded from the spinneret through a metering pump. The extruded polymer melt is then blown by a high-temperature, high-speed airflow to be drawn into microfibers. Meltblown fibers have a fineness of 1-10 micrometers and exist in the form of nonwoven fabric. Their applications include protective materials, air conditioning filters, masks, and air purifier filters.

[0009] In traditional meltblown fabric, the two airflows are symmetrical, and their convergence direction is vertically downward. In conventional meltblown fabric, the two airflows are symmetrical, and the airflows along the centerline have a downward convergent velocity. The fiber, after being extruded from the spinneret, falls vertically downward. That is, the fiber is subjected to a downward airflow stretching force. Figure 2 If the fiber direction (fiber axis) is parallel to the airflow direction, the stretching force exerted on the fiber by the airflow is called frictional resistance, Fp. That is, in traditional meltblown processes, fiber stretching relies on the frictional resistance of the airflow. Conversely, if the airflow velocity is perpendicular to the fiber axis, the force exerted on the fiber by the airflow is called pressure resistance, FN. (Reference) Figure 3 Research has revealed that the stretching effect of pressure differential resistance on fibers is significantly greater than that of frictional resistance. A comparison of the Fp and FN forces acting on the same fibers demonstrates that traditional meltblown processes fail to effectively utilize the stretching effect of pressure differential resistance (FN). In conclusion, current industrial-scale meltblown technology cannot surpass the 1-micron limit. Summary of the Invention

[0010] In order to overcome the limitation of 1-micron fiber in existing industrial production technologies, this application provides a meltblown nozzle structure that sprays an alternating airflow of oscillating jets.

[0011] The meltblown nozzle structure with jetting oscillating and alternating airflow provided in this application is achieved through the following technical solution:

[0012] A meltblown nozzle structure for jetting oscillating and alternating airflow includes a spinneret, with an extrusion groove in the center of the bottom surface of the spinneret; a plurality of parallel spinneret holes are vertically and downwardly opened through the bottom surface of the extrusion groove of the spinneret; the structure also includes a spinneret and air knives located on both sides of the spinneret; and an annular reflux channel is formed between the spinneret and the air knives.

[0013] This application employs a special air duct die with a near-annular reflux channel. During fiber extrusion, it generates alternating airflow to blow the fiber, which increases the stretching force on the fiber and improves the fiber stretching ratio, thereby obtaining finer fibers. Furthermore, for the spinning process of water-soluble materials, especially environmentally friendly water-soluble PVA materials, the nozzle structure of this application can significantly improve the evaporation efficiency of solvents (plasticizers, etc.), enabling rapid fiber formation and significantly increasing industrial production.

[0014] Preferably, the surface of the air knife facing the spinneret side has a columnar groove along its length; the air knife has a semi-cylinder located within the columnar groove; the bottom surface of the semi-cylinder is flush with the side of the air knife facing the spinneret; a quasi-annular return channel is formed between the air knife and the semi-cylinder; an air duct is formed between the side of the spinneret and the side of the air knife; the air duct is connected to the quasi-annular return channel; the annular return channel is composed of the quasi-annular return channel and the air duct.

[0015] Preferably, the air duct includes a first air duct section and a second air duct section connected to the first air duct section; the distance of the first air duct section is d1; the distance of the second air duct section is d2; and the distance d1 of the first air duct section is greater than the distance d2 of the second air duct section.

[0016] Preferably, the distance d2 of the second section of the air duct is 0.5-1.5mm; the distance d1 of the first section of the air duct is 0.525-3mm.

[0017] Preferably, the distance d1 of the first section of the air duct is 1.05-2 times the distance d2 of the second section of the air duct.

[0018] Preferably, the length of the air duct is controlled between 25-100mm.

[0019] Preferably, the annular return channel forms an angle α with the first section of the air duct, where α ≤ 90°; the annular return channel forms an angle θ with the second section of the air duct, where θ ≤ 90°.

[0020] Preferably, the included angle α is controlled within the range of 15-90°; the included angle θ is controlled within the range of 17-90°.

[0021] Preferably, the height difference between the lower horizontal plane of the air knife and the spinneret hole at the lower vertex of the spinneret triangle does not exceed ±3.0 mm.

[0022] This application utilizes a meltblown nozzle with an alternating jet of oscillating airflow to generate an alternating jet of oscillating airflow, thereby giving the application the following two advantages: (1) The direction of the combined velocity of the oscillating airflow is at an angle to the vertical axis of the fiber, which allows the fiber to be drawn by pressure resistance FN, while minimizing the use of frictional resistance Fp for drawing, thus increasing the drawing efficiency. (2) The oscillating airflow can make the fiber swing left and right, making whipping motion, which can significantly improve the contact between the fiber and the surrounding air, greatly improving the volatilization of solvent components in the fiber. This alternating oscillating airflow field can also quickly exhaust the humid atmosphere to the surroundings, which can also improve the volatilization efficiency.

[0023] In summary, this application has the following advantages:

[0024] 1. This application uses a special air duct die with an annular reflux channel, which generates alternating airflow to blow the fiber during fiber extrusion, which can increase the stretching force on the fiber and improve the fiber stretching ratio, thereby obtaining finer fibers.

[0025] 2. Regarding the spinning process of water-soluble materials, especially environmentally friendly water-soluble PVA materials, the nozzle structure of this application can significantly improve the evaporation efficiency of solvent (plasticizer, etc.) materials, enabling rapid fiber formation and significantly increasing industrial production. Attached Figure Description

[0026] Figure 1 This is a flow chart of the traditional meltblown spinning process equipment.

[0027] Figure 2 This is a schematic diagram of the forces acting on the fiber in an airflow field.

[0028] Figure 3 This is a comparison diagram of the Fp and FN experienced by the same fiber.

[0029] Figure 4 This is a schematic diagram of the meltblown nozzle structure that sprays an alternating airflow with oscillations in this application.

[0030] Figure 5 This is a top view of the meltblown nozzle that sprays an alternating airflow with oscillations in this application.

[0031] Figure 6 This is a schematic diagram of a traditional meltblown nozzle.

[0032] Figure 7 This is a diagram showing the change in fiber diameter during the mechanical simulation of fiber stretching.

[0033] Figure 8 This is a diagram showing the left-right oscillation motion of fibers at different times under a meltblown nozzle with an alternating jet of oscillating airflow.

[0034] Figure 9This is a diagram showing the left-right oscillation motion of fibers at different times under a traditional meltblown nozzle.

[0035] Figure 10 This is a SEM image of traditional meltblown spun fibers.

[0036] Figure 11 This is a SEM image of meltblown spun fibers produced using the meltblown nozzle with jetting oscillating and alternating airflow described in this application.

[0037] In the diagram, 1 is the spinneret; 10 is the extrusion groove; 100 is the spinneret orifice; 2 is the air knife; 21 is the cylindrical groove; 22 is the semi-cylinder; 23 is the annular return channel; 3 is the channel with an annular return channel; 30 is the air duct; 301 is the first section of the air duct; 302 is the second section of the air duct; and 303 is the single air duct. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. Example

[0039] refer to Figure 4 and 5 This application discloses a meltblown nozzle structure for jetting oscillating and alternating airflow, including a spinneret 1 and air knives 2 located on both sides of the spinneret 1. An extrusion groove 10 is formed in the center of the bottom surface of the spinneret 1. Several parallel spinneret holes 100 are vertically and downwardly formed through the bottom surface of the extrusion groove 10 of the spinneret 1. The height difference between the lower horizontal plane of the air knives 2 and the spinneret hole 100 at the lower apex of the triangle on the spinneret 1 does not exceed ±3.0 mm. An annular return channel 3 is formed between the spinneret 1 and the air knives 2.

[0040] refer to Figure 4 and 5 The air knife 2 has a columnar groove 21 along its length on the surface facing the spinneret 1. The air knife 2 has a semi-cylinder 22 located within the columnar groove 21. The bottom surface of the semi-cylinder 22 is flush with the side of the air knife 2 facing the spinneret 1. A quasi-annular return channel 23 is formed between the air knife 2 and the semi-cylinder 22. An air duct 30 is formed between the side of the spinneret 1 and the side of the air knife 2. The air duct 30 is connected to the quasi-annular return channel 23. The annular return channel 3 is composed of the quasi-annular return channel 23 and the air duct 30.

[0041] refer to Figure 4 and 5The air duct 30 includes a first air duct 301 and a second air duct 302 connected to the first air duct 301. The distance between the first air duct 301 and the second air duct 302 is d1, and the distance between the first air duct 301 and the second air duct 302 is d2; and the distance d1 between the first air duct 301 and the second air duct 302 is greater than the distance d2. Specifically, the distance d2 between the second air duct 302 and the second air duct 302 is 0.5-2 mm, and the distance d1 between the first air duct 301 and the second air duct 302 is 1.05-2.00 times, preferably 1.25 times. The length of the air duct 30 is controlled between 25-100 mm, preferably 25 mm. The annular return channel 23 forms an angle α with the first air duct 301, where α ≤ 90°, and the annular return channel 23 forms an angle θ with the second air duct 302, where θ ≤ 90°. Preferably, the angle is 78°, with the included angle α controlled within the range of 10-90°; the included angle θ controlled within the range of 10-85°.

[0042] This application utilizes a meltblown nozzle that generates an alternating jet of oscillating airflow, thereby giving the application the following two advantages: (1) the direction of the combined velocity of the oscillating airflow is at an angle to the vertical axis of the fiber, as referenced Figure 3-4 This allows the fiber to be drawn by pressure resistance FN, while minimizing the use of friction resistance Fp during drawing will increase the drawing efficiency. (2) The oscillating airflow can make the fiber swing left and right, making whipping motion, which can significantly increase the contact between the fiber and the surrounding air, greatly increasing the volatilization of the solvent components in the fiber. This interactive oscillating airflow field can also quickly exhaust the humid air to the surroundings, which can also improve the volatilization efficiency.

[0043] Comparative Example

[0044] refer to Figure 6 The traditional meltblown nozzle structure includes a spinneret 1 and air knives 2 located on both sides of the spinneret 1, with a single air duct 303 formed between the spinneret 1 and the air knives 2.

[0045] Theoretical proof

[0046] refer to Figure 7 , Figure 7 This is a mechanical simulation of fiber diameter changes during fiber stretching. It verifies that without pressure differential resistance during meltblowing, the resulting fiber diameter will undergo a process of re-increasing, which is detrimental to meltblown products, as finer fibers are required. However, after adding pressure differential resistance from alternating oscillating airflow, the diameter of the polymer melt continuously decreases. (Disturbance: generated by oscillating airflow; No disturbance: no oscillating airflow on the surface).

[0047] Experiments have shown

[0048] refer to Figure 8Using the meltblown nozzle with jet oscillation and interactive airflow provided in this application, the fiber is spun in a left-right oscillation pattern, with the left-right oscillation motion of the fiber at different times.

[0049] refer to Figure 9 Using a traditional meltblown nozzle, the movement of the fiber at different times (no left-right oscillation occurred).

[0050] refer to Figure 10 The SEM images of the spun fibers obtained using the meltblown nozzle with jet oscillating interactive airflow provided in this application show that the spun fibers obtained using the meltblown nozzle with jet oscillating interactive airflow provided in this application can break through the 1-micron limitation.

[0051] refer to Figure 11 The image of the spun fiber obtained using a traditional meltblown nozzle is shown in the SEM image, but the SEM image of the spun fiber obtained using a traditional meltblown nozzle cannot break through the 1-micron limit.

[0052] In summary, this application employs a special air duct die with a near-annular reflux channel, which generates alternating airflow to blow the fiber during extrusion. This increases the stretching force on the fiber and improves the fiber stretching ratio, resulting in finer fibers. Furthermore, for the spinning process of water-soluble materials, especially environmentally friendly water-soluble PVA materials, the nozzle structure of this application can significantly improve the evaporation efficiency of solvents (plasticizers, etc.), enabling rapid fiber formation and significantly increasing industrial production output.

[0053] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A meltblown nozzle structure for jetting oscillating and alternating airflow, comprising a spinneret (1), wherein an extrusion groove (10) is provided in the center of the bottom surface of the spinneret (1); a plurality of parallel spinneret holes (100) are vertically and downwardly penetrating the bottom surface of the extrusion groove (10) of the spinneret (1), characterized in that: It also includes a spinneret (1) and air knives (2) located on both sides of the spinneret (1), with an annular return channel (3) formed between the spinneret (1) and the air knives (2); the surface of the air knives (2) facing the side of the spinneret (1) has a columnar groove (21) along its own length direction; the air knives (2) are provided with a semi-cylinder (22) located in the columnar groove (21); the bottom surface of the semi-cylinder (22) is flush with the side of the air knives (2) facing the spinneret (1); an annular return channel (23) is formed between the air knives (2) and the semi-cylinder (22); an air duct (30) is formed between the side of the spinneret (1) and the side of the air knives (2); the air duct (30) The annular return channel (3) is connected to the annular return channel (23); the annular return channel (3) is composed of the annular return channel (23) and the air duct (30); the air duct (30) includes a first section air duct (301) and a second section air duct (302) connected to the first section air duct (301); the distance of the first section air duct (301) is d1; the distance of the second section air duct (302) is d2; and the distance d1 of the first section air duct (301) is greater than the distance d2 of the second section air duct (302); the distance d2 of the second section air duct (302) is 0.5-1.5mm; the distance d1 of the first section air duct (301) is 0.525-3mm.

2. The meltblown nozzle structure for jetting oscillating and alternating airflow according to claim 1, characterized in that: The distance d1 of the first section of the air duct (301) is 1.05-2 times the distance d2 of the second section of the air duct (302).

3. The meltblown nozzle structure for jetting oscillating and alternating airflow according to claim 1, characterized in that: The length of the air duct (30) is controlled between 25-100mm.

4. The meltblown nozzle structure for jetting oscillating and alternating airflow according to claim 1, characterized in that: The annular return channel (23) forms an angle α with the first section of the air duct (301), where α ≤ 90°; the annular return channel (23) forms an angle θ with the second section of the air duct (302), where θ ≤ 90°.

5. The meltblown nozzle structure for jetting oscillating and alternating airflow according to claim 4, characterized in that: The included angle α is controlled within the range of 15-90°; the included angle θ is controlled within the range of 17-90°.

6. The meltblown nozzle structure for jetting oscillating and alternating airflow according to claim 1, characterized in that: The height difference between the lower horizontal plane of the air knife (2) and the spinneret hole (100) at the lower vertex of the triangle of the spinneret plate (1) does not exceed ±3.0mm.

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