A nanofiber spinning nozzle

Abstract

The present application discloses a nanofiber spinning nozzle, comprising: a spinneret, a substrate, and an airflow accelerator plate; the substrate and the airflow accelerator plate are symmetrically arranged on both sides of the spinneret, and a melt flow channel is provided in the center of the spinneret; the airflow accelerator plate is located below the spinneret and the substrate and is provided with an airflow acceleration channel inside; wherein, an airflow channel is formed between the first inclined wall surface on the outside of the spinneret and the second inclined wall surface on the inside of the substrate, and the airflow channel is connected to the air supply cavity. The present application increases the airflow velocity on the airflow channel by setting the wall shape of the airflow channel between the spinneret and the air plate to a Laval nozzle structure; at the same time, the parallel throat of the airflow acceleration channel extends the throat, which can reduce the momentum loss of the jet, maintain a higher airflow velocity and airflow temperature over a longer distance, and make the airflow more stable, so that the fiber can be more stably stretched to a greater extent, which is ultimately conducive to obtaining uniform ultrafine nanofibers.

Description

Technical Field

[0001] The present application belongs to the technical field of nonwoven meltblown equipment, and specifically relates to a nanofiber spinning nozzle. Background Art

[0002] Nonwoven fabrics, also known as non-woven fabrics, are a new type of textile fabric that has emerged in recent decades. Meltblown nonwovens, with their excellent breathability and comfort, have broad application prospects and occupy a large share of the textile market. Meltblowing technology, used in the production of nonwoven fabrics, is a key area in the textile industry and a key method for producing microfiber nonwovens. In the meltblowing process, a high-speed, high-temperature airflow sprays a molten polymer, rapidly stretching it to form microfibers. The molten polymer is then deposited on a screen some distance from the die, where it is bonded to form the nonwoven material.

[0003] Meltblown nozzles are core components of meltblown nonwovens equipment. High-speed, high-temperature gas flows through the nozzle's airflow channel, exerting a strong drafting force on the polymer melt, stretching it into micron- or even nanometer-sized meltblown fibers. The flow field beneath the nozzle not only determines the final meltblown fiber diameter but also significantly influences its internal structure, such as molecular chain orientation and crystallinity, and thus fiber strength. Different nozzle structures produce varying airflow fields, which in turn affect the fiber-forming process. The structure and dimensions of the nozzle's internal airflow channel are also crucial factors influencing the flow field and energy consumption.

[0004] The new melt-blown nozzle can stretch and refine the polymer melt by the high-speed airflow, replacing the traditional melt-blown nozzle with a parallel inner wall structure, such as Figure 5 In the meltblown nonwoven process, the polymer melt is stretched into ultrafine fibers by a high-speed, high-temperature airflow. The structure of the jet nozzle, the velocity of the flow field, the temperature distribution, and the airflow stability have a significant impact on the polymer stretching and the final fiber diameter.

[0005] Relevant scholars have called the Laval nozzle (such as Figure 1 ) is used in the melt-blowing process. For example, Chinese patent CN104947208B discloses a spinneret and a spinning device for preparing nanofibers, and its structure is as follows Figure 2 As shown, the spinning device includes a nozzle, a Laval tube-shaped inner hole is provided in the nozzle, a liquid inlet is connected to the throat of the Laval tube-shaped inner hole, one end of the Laval tube-shaped inner hole is a spinning orifice, and the other end of the Laval tube-shaped inner hole is an air inlet. This structure causes the spinning melt or spinning solution to touch the Laval nozzle structure and partially adhere to the narrow throat or expansion section, resulting in the inability to continue the spinning process, thereby affecting the spinning quality; Chinese patent CN113355753B discloses a supersonic spinning nozzle structure, the structure of which is as follows Figure 3As shown, the Laval airflow acceleration channel includes, from top to bottom, a reducing section channel in which the channel width gradually decreases from large to small, a throat channel, and an expanding section channel in which the channel width gradually expands from small to large. For each supersonic airflow generating component, the height of the expanding section channel is not lower than the height of the spinneret. Near the throat channel, the airflow velocity can reach supersonic speed. However, it is difficult to effectively increase the airflow velocity on the center line directly below the spinneret. When the height of the expanding section channel is not lower than the height of the spinneret, the gas coming out of the Laval airflow throat channel rapidly weakens and decreases, and the airflow velocity reaching the center line directly below the spinneret does not increase significantly. A higher energy consumption is required to achieve the ideal effect. Figure 4 The figure shows the existing meltblown structure proposed by relevant scholars. Subsonic, high-temperature, and high-speed air flows are ejected from the jet orifice, converge, and accelerate below the spinneret to form a supersonic drafting airflow. However, the airflow pressure fluctuates greatly and is extremely unstable when the high-temperature, high-speed airflow merges into the supersonic drafting airflow in the expansion section. This makes the drafting force extremely unstable, and the spun fibers easily adhere to the throat and the inner wall of the expansion section. These defects make the spinning process unsustainable. The accumulation of adhered fibers further exacerbates the airflow instability. This repetitive cycle greatly affects spinning efficiency and product quality. Summary of the Invention

[0006] The present application provides a nanofiber spinning nozzle to solve the technical problems of the inability to produce continuously during the spinning process and the fiber adhesion.

[0007] In order to solve the above technical problems, a technical solution adopted in this application is: a nanofiber spinning nozzle, comprising: a spinneret, a substrate and an airflow acceleration plate; the substrate and the airflow acceleration plate are symmetrically arranged on both sides of the spinneret, and a melt flow channel is provided in the center of the spinneret; the airflow accelerator plate is located below the spinneret and the substrate and is provided with an airflow acceleration channel inside; wherein, an airflow channel is formed between the first inclined wall on the outside of the spinneret and the second inclined wall on the inside of the substrate, and the airflow channel is connected to the air supply cavity.

[0008] Furthermore, the air flow channel and the air flow acceleration channel are both configured as axisymmetric Laval nozzle structures, and the central axis of the air flow channel is configured at a fixed angle to the central axis of the melt flow channel.

[0009] Furthermore, the airflow channel includes an airflow steady flow area, an airway contraction area, an airflow throat, an airway expansion area and an airflow buffer area, and the airflow steady flow area and the airflow buffer area are cylindrical; the two sides of the cross section between the airflow steady flow area and the airflow buffer area are arc-shaped, wherein the part where the arc contracts is the airway contraction area, the part where the arc expands is the airway expansion area, and the part with the smallest distance between the arcs is the airflow throat.

[0010] Furthermore, the airflow acceleration channel includes an airflow convergence stabilization zone, a lower airway contraction zone, a parallel throat and a lower airway expansion zone. The airflow convergence stabilization zone is cylindrical, and the edge of the airflow convergence stabilization zone coincides with the lower end point of the second inclined wall. The cross-section of the lower airway contraction zone is symmetrical and contracted arc lines on both sides, the cross-section of the parallel throat is parallel, and the cross-section of the lower airway expansion zone is symmetrical and expanded arc lines on both sides.

[0011] Furthermore, the wire outlet hole below the melt flow channel is connected to the air flow channel; wherein, the first inclined wall surface and the second inclined wall surface are symmetrically arranged.

[0012] Furthermore, the height of the wire outlet hole is higher than the lower end of the base plate.

[0013] Furthermore, the airflow acceleration plate is fixed to the bottom end of the base plate by bolts, and the wire outlet hole is located above the airflow acceleration channel, and the airflow acceleration channel is communicated with the airflow channel.

[0014] The beneficial effects of the present application are: the present application increases the air flow velocity in the air flow channel by setting the wall shape of the air flow channel between the spinneret and the air plate to a Laval nozzle structure; at the same time, the parallel throat of the air flow acceleration channel extends the throat, which can reduce the momentum loss of the jet, maintain a higher air flow velocity and air flow temperature over a longer distance, and make the air flow more stable, so that the fibers can be stretched more stably and to a greater extent, reducing adhesion, which is ultimately conducive to obtaining uniform ultrafine nanofibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the Laval nozzle structure;

[0016] Figure 2 It is a structural diagram of the existing spinning device structure;

[0017] Figure 3 This is a schematic diagram of the structure of an existing supersonic spinning nozzle;

[0018] Figure 4 This is a structural diagram of an existing Laval nozzle meltblowing device;

[0019] Figure 5 Schematic diagram of an existing traditional meltblown die head;

[0020] Figure 6 This is a schematic structural diagram of an embodiment of a nanofiber spinning nozzle of the present application;

[0021] Figure 7 This is a schematic diagram of the working structure of a nanofiber spinning nozzle according to an embodiment of the present application;

[0022] Figure 8It is a structural schematic diagram of another embodiment of the nanofiber spinning nozzle of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0024] like Figure 6-7 As shown, Figure 6 This is a schematic structural diagram of an embodiment of a nanofiber spinning nozzle of the present application; Figure 7 This is a schematic diagram of the working structure of an embodiment of the nanofiber spinning nozzle of the present application. The nanofiber spinning nozzle includes: a spinneret 1, a substrate 2 and an airflow accelerator plate 3; the substrate 2 and the airflow accelerator plate 3 are symmetrically arranged on both sides of the spinneret 1, and a melt flow channel 101 is provided in the center of the spinneret 1; the airflow accelerator plate 3 is located below the spinneret 1 and the substrate 2 and is provided with an airflow acceleration channel 5 inside; wherein, an airflow channel 4 is formed between the first inclined wall 102 on the outside of the spinneret 1 and the second inclined wall 202 on the inside of the substrate 2, and the airflow channel 4 is connected to the air supply cavity 7. The parallel throat of the airflow acceleration channel 5 in the above design extends the throat, which can reduce the momentum loss of the jet, maintain a higher airflow velocity and airflow temperature over a longer distance, and make the airflow more stable, so that the fiber can be more stably stretched to a greater extent.

[0025] The air flow channel 4 is configured as an axisymmetric Laval nozzle structure, with the central axis of the air flow channel 4 being arranged at a fixed angle to the central axis of the melt flow channel 101. The air flow channel 4 in the above design can pass through the inclined Laval nozzle structure, thereby increasing the air flow velocity.

[0026] Airflow channel 4 includes an airflow stabilization zone 415, an airflow contraction zone 414, an airflow throat 413, an airflow expansion zone 412, and an airflow buffer zone 411. Airflow stabilization zone 415 and airflow buffer zone 411 are cylindrical. The cross-section between airflow stabilization zone 415 and airflow buffer zone 411 is arc-shaped on both sides. The arc contraction area is airflow contraction zone 414, the arc expansion area is airflow expansion zone 412, and the area with the smallest distance between the arcs is airflow throat 413. In the above-described design, the wall shape of airflow channel 4 between spinneret 1 and the air plate is configured as a Laval nozzle structure, thereby increasing the airflow velocity in airflow channel 4.

[0027] The airflow acceleration channel 5 includes an airflow converging and stabilizing area 501, a lower airway contraction area 502, a parallel throat 503, and a lower airway expansion area 504. The airflow converging and stabilizing area 501 is cylindrical, and its edge coincides with the lower endpoint of the second inclined wall 202. The cross-section of the lower airway contraction area 502 is symmetrically arranged with contracting arcs, the cross-section of the parallel throat 503 is parallel, and the cross-section of the lower airway expansion area 504 is symmetrically arranged with expanding arcs. The airflow acceleration channel 5 in this design can further accelerate the airflow.

[0028] The outlet hole 103 below the melt flow channel 101 communicates with the airflow channel 4; the first inclined wall 102 and the second inclined wall 202 are symmetrically arranged. In the above design, an airflow acceleration plate 3 is installed directly below the outlet hole 103. Its internal structure is a Laval airflow acceleration channel 5. The starting point of the parallel line segment of the airflow converging and stabilizing zone 501 of the airflow acceleration channel 5 coincides with the endpoint of the lower portion of the inclined wall inside the spinneret 1. This significantly reduces the reverse velocity and airflow instability in the reverse recirculation zone, thereby weakening the adverse effects of recirculation on the molten polymer.

[0029] The height of the wire outlet hole 103 is higher than the lower end of the base plate 2. The above design can facilitate the molten polymer extruded from the wire outlet hole 103 to be drawn forward and thinned, thereby accelerating the cooling and molding of the molten polymer and entering the airflow acceleration channel 5.

[0030] The airflow acceleration plate 3 is fixed to the bottom end of the base plate 2 by bolts 6, and the fiber outlet hole 103 is located above the airflow acceleration channel 5, which is connected to the airflow channel 4. The airflow acceleration channel 5 in this design allows high-speed, high-temperature airflow to be generated in the middle, thereby pulling the fibers toward the airflow acceleration channel 5 inside the airflow acceleration plate 3.

[0031] The specific working principle is that during the meltblowing process, high-speed and high-temperature gas enters the air supply cavity 7 from the external air supply equipment and flows into the airflow channel 4. When entering the airflow channel 4, the high-speed and high-temperature airflow first enters the airflow stabilization area 415 to make the airflow uniform and reduce turbulence. Then the airflow enters the airway contraction area 414 to accelerate the airflow, while ensuring that the outlet airflow of the contraction section is uniform, straight and stable. Then it enters the airflow throat 413, a transition section that changes the airflow from subsonic to supersonic, and then enters the airway expansion area 412 and then to the airflow buffer area 411 to accelerate the airflow to supersonic or even hypersonic speed. Then the airflow will rapidly decay and the speed will decrease. At the same time, the high-speed and high-temperature gas ejected from the symmetrical airflow channel 4 on the other side also merges at the wire outlet 103, pulling the molten polymer extruded from the wire outlet 103 forward. In order to obtain high-speed and high-temperature airflow again, a Laval nozzle structure is set in the acceleration plate not far below the outlet hole 103, so that the airflow pulls the fiber toward the airflow acceleration channel 5 inside the airflow acceleration plate 3. After the two airflows merge, they enter the airflow merging stabilization area 501 of the airflow acceleration channel 5, so that the airflow after merging is uniform and turbulence is reduced. Then the airflow enters the lower airway contraction area 502 to accelerate the airflow, while ensuring that the outlet airflow of the contraction section is uniform, straight and stable, and then enters the parallel airflow throat 503. The airflow speed continues to rise to supersonic speed. In this parallel throat, the airflow can maintain a high-speed and high-temperature state for a long distance, which is beneficial to the thinning and stretching of the fiber by the airflow. Finally, the airflow enters the lower airway expansion area 504, so that the airflow is further accelerated and then attenuated and ejected from the airflow outlet.

[0032] like Figure 8 As shown, Figure 8 It is a structural schematic diagram of another embodiment of the nanofiber spinning nozzle of the present application. Two Laval nozzle structures connected in sequence from top to bottom can also be set in the air flow channel 4. The second Laval nozzle 42 has the same structure as the first Laval nozzle 41 but different sizes. The second Laval nozzle 42 is located above the first Laval nozzle 41. The end of the airway expansion area 412 of the second Laval nozzle 42 is connected to the air inlet end of the upper part of the air flow stabilization area 415 of the first Laval nozzle 41. The high-speed and high-temperature airflow enters the air supply cavity 7 from the external air supply equipment, and then flows into the second airflow channel 4 to achieve the first airflow acceleration. The airflow enters the first airflow channel 4 to achieve the second airflow acceleration, and then merges with the high-speed and high-temperature airflow of the airflow channel 4 on the other side to enter the airflow acceleration plate 3. The airflow is accelerated for the third time and finally ejected from the outlet of the airflow acceleration plate 3.

[0033] By arranging multiple Laval nozzle structures in the air flow channel 4, the air flow velocity is greatly improved, the air flow temperature is maintained for a longer time, the air flow is more uniform and stable, so that greater kinetic energy and higher heat act on the melt, and the higher air flow velocity and temperature can effectively reduce the diameter of the fiber, which is conducive to obtaining uniform nanofibers.

[0034] Example 1

[0035] The molten polymer is extruded from the outlet hole 103 in the melt flow channel 101 of the spinneret 1, and at the same time, high-speed and high-temperature airflow is ejected and merged from the outlet ends of the airflow channels 4 on both sides of the spinneret 11, and the high-speed and high-temperature airflow stretches and refines the meltblown filaments.

[0036] The spinneret in this embodiment is a common meltblowing die, such as Figure 5 The specific dimensions shown are: a 60° air channel angle, a 0.6mm air slot outlet width, a 1mm spinneret top width, a 1.3atm gas pressure at the top of the air slot inlet, a 540K wall temperature, and a 500K gas temperature. Simulation analysis shows that along the centerline of the melt, the maximum air velocity is 175m / s. Within the fiber stretching zone within 25mm of the spinneret top, the average gas velocity is 105.8m / s, and the average gas temperature is 421K.

[0037] Example 2

[0038] The molten polymer is extruded from the outlet hole 103 of the melt flow channel 101 of the spinneret 1, and at the same time, a high-speed and high-temperature airflow is ejected and merged from the outlet ends of the airflow channel 4 on the right and left sides of the spinneret 1, and the high-speed and high-temperature airflow stretches and refines the meltblown filaments.

[0039] The spinneret structure of this embodiment, in which the die is not equipped with an accelerator plate 3 and has a single Laval nozzle airflow channel, has an airflow buffer zone 411 with a length of 0.5 mm and a width of 2.5 mm, an airflow throat 413 with a width of 2 mm, an airflow contraction zone 414 with a length of 5 mm, and an airflow stabilization zone 415 with a width of 7.5 mm and a length of 5 mm. The gas pressure at the upper inlet of the gas slot is 1.3 atm, the wall temperature is 540 K, and the gas temperature is 500 K. Simulation analysis shows that the maximum airflow velocity along the centerline of the melt is 264.6 m / s. In the fiber stretching zone within 25 mm from the top of the spinneret, the average gas velocity is 227.7 m / s, and the average gas temperature is 502 K. Compared with the conventional die in Example 1, the die structure of this embodiment has a maximum airflow velocity of 51.2%, an average velocity in the main stretching zone of 115.2%, and an average gas temperature of 19.2%.

[0040] Example 3

[0041] The molten polymer is extruded from the outlet hole 103 of the melt flow channel 101 of the spinneret 1, and at the same time, a high-speed and high-temperature airflow is ejected and merged from the outlet ends of the airflow channel on the right and left sides of the spinneret 1. The high-speed and high-temperature airflow stretches and refines the melt-blown filaments, and enters the airflow acceleration channel 5 of the airflow acceleration plate 3 to further refine the fibers, and finally obtain uniform nanofibers.

[0042] The spinneret structure in this embodiment is as follows: Figure 6 As shown, in this embodiment, the die head is equipped with an acceleration plate and has a single Laval nozzle airflow channel. The length of the airflow buffer zone 411411 is 0.5 mm, the width is 2.5 mm, the width of the airflow throat 413413 is 2 mm, the length of the airway contraction area 414 is 5 mm, the width of the airflow steady flow area 415 is 7.5 mm, the length is 5 mm, the airflow converging stable area 501 is 3 mm long, the width is 2.14 mm, the length of the lower airway contraction area 502 is 3 mm, the length of the parallel throat 503 is 11 mm, the width is 1.5 mm, the length of the lower airway expansion area 504 is 12.4 mm, and the width of its outlet section is 2.5 mm; the pressure of the gas at the upper inlet of the gas slot is 1.3 atm, the wall temperature is 540 K, and the gas temperature is 500 K. After simulation analysis, the maximum air flow velocity along the center line direction of the melt movement is 442.8 m / s. In the fiber stretching area within 25 mm from the top of the spinneret, the average gas velocity is 327.2 m / s, and the average gas temperature is 506 K. The die structure in this embodiment increases the maximum air flow velocity by 152.6% compared with the traditional die in Example 1, the average velocity in the main stretching zone is increased by 209.3%, and the average gas temperature is increased by 20.2%.

[0043] Example 4

[0044] The molten polymer is extruded from the outlet hole 103 of the melt flow channel 101 of the spinneret 1, and at the same time, a high-speed and high-temperature airflow is ejected and merged from the outlet ends of the first airflow channel, the second airflow channel on the right side and the third airflow channel and the fourth airflow channel on the left side of the spinneret 1. The high-speed and high-temperature airflow stretches and refines the melt-blown filaments, and enters the airflow acceleration channel 5 of the airflow acceleration plate 3 to further refine the fibers, and finally obtain uniform nanofibers.

[0045] The spinneret structure in this embodiment is as follows: Figure 8As shown, in this embodiment, the die head is equipped with an accelerator plate and has two Laval nozzle air flow channels. The length of the air flow buffer zone 411 of the first Laval air channel 41 is 1 mm, the width is 1 mm, the width of the air flow throat 413 is 0.8 mm, the length of the air channel contraction zone 414 is 2 mm, the width of the air flow steady zone 415 is 2.5 mm, and the length is 2 mm. The length of the air flow expansion zone 412 of the second Laval air channel 42 is 1.7 mm, the width of the air flow throat 413 is 2 mm, and the air channel contraction zone 414 is 0.8 mm. 414 is 5 mm long, the airflow stabilization zone 415 is 7.5 mm wide and 5 mm long, the airflow converging stabilization zone 501 is 3 mm long and 2.14 mm wide, the lower airway contraction zone 502 is 3 mm long, the parallel throat 503 is 11 mm long and 1.5 mm wide, and the lower airway expansion zone 504 is 12.4 mm long, with an outlet width of 2.5 mm. The gas pressure at the upper inlet of the gas slot is 1.3 atm, the wall temperature is 540 K, and the gas temperature is 500 K. Simulation analysis shows that along the centerline of the melt, the maximum airflow velocity is 576.5 m / s. In the fiber stretching zone within 25 mm from the top of the spinneret, the average gas velocity is 264.2 m / s, and the average gas temperature is 509 K. The die structure of this embodiment increases the maximum airflow velocity by 229.4% compared to the conventional die in Example 1, the average velocity in the main stretching zone by 149.2%, and the average gas temperature by 20.9%.

[0046] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A nanofiber spinning nozzle, characterized in that: include: Spinneret, base plate and air flow acceleration plate; The substrate and the airflow acceleration plate are symmetrically arranged on both sides of the spinneret, and a melt flow channel is provided in the center of the spinneret; the airflow acceleration plate is fixed to the bottom of the substrate by bolts, and an airflow acceleration channel is provided inside; wherein, an airflow channel is formed between the first inclined wall surface on the outer side of the spinneret and the second inclined wall surface on the inner side of the substrate, and the airflow channel is connected to the air supply cavity; wherein, the airflow acceleration channel includes a parallel throat and a lower airway expansion area; the length of the parallel throat is 11 mm and the width is 1.5 m; the airflow channel and the airflow acceleration channel are both arranged as axially symmetrical Laval nozzle structures, and the central axis of the airflow channel is set at a fixed angle to the central axis of the melt flow channel; the wire outlet is located above the airflow acceleration channel, and the airflow acceleration channel is connected to the airflow channel; The airflow channel includes an airflow stabilization area, an airway contraction area, an airflow throat, an airway expansion area, and an airflow buffer area. The airflow stabilization area and the airflow buffer area are cylindrical. The two sides of the cross section between the airflow stabilization area and the airflow buffer area are arc-shaped. The part where the arc contracts is the airway contraction area, the part where the arc expands is the airway expansion area, and the part with the smallest distance between the arcs is the airflow throat. The airflow acceleration channel includes an airflow convergence stabilization zone, a lower airway contraction zone, a parallel throat and a lower airway expansion zone. The airflow convergence stabilization zone is cylindrical, and the edge of the airflow convergence stabilization zone coincides with the lower end point of the second inclined wall. The cross-section of the lower airway contraction zone is symmetrical and contracted arc lines on both sides, the cross-section of the parallel throat is parallel, and the cross-section of the lower airway expansion zone is symmetrical and expanded arc lines on both sides.

2. The nanofiber spinning nozzle according to claim 1, characterized in that: The wire outlet hole below the melt flow channel is communicated with the air flow channel; wherein the first inclined wall surface and the second inclined wall surface are symmetrically arranged.

3. The nanofiber spinning nozzle according to claim 2, characterized in that: The height of the wire outlet hole is higher than the lower end of the base plate.

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