Method for preparing curled nanofibers based on spinneret-orifice-free melt-blowing process and application of curled nanofibers

Abstract

The invention relates to the technical field of melt-blowing spinning, and provides a method for preparing curled nanofibers based on a spinneret-orifice-free melt-blowing process and application of the curled nanofibers. The method comprises the following steps: placing a molten thermoplastic polymer in pores of a moving grid, and drawing the molten thermoplastic polymer in the pores through the moving grid by hot air flow to form the curled nanofibers at one time, the temperature of the pores in contact with the molten thermoplastic polymer is higher than or equal to the temperature of the melt; the hot air flow is output from an air outlet of the air supply assembly, the airflow speed of the hot air flow at the air outlet is 250-320 m / s, and the temperature of the hot air flow at the air outlet is higher than or equal to the temperature of the molten thermoplastic polymer. By regulating and controlling the pore structure, the motion state and the speed of the hot air flow, the nanofiber with the curled structure can be prepared through a one-step method, the universality is high, and the application range is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of meltblown spinning, and particularly to a method for preparing crimped nanofibers based on a nozzleless meltblown process and its application. Background Art

[0002] Three-dimensional crimped fiber cotton materials have structural advantages such as low bulk density, high porosity, fluffiness, and soft handfeel, and can be applied in fields such as sound absorption and noise reduction, cold protection and heat preservation, oil absorption and pollution reduction, etc., and have extremely high application value. The existing technology mainly uses multi-component raw materials for melt spinning technology for processing, and utilizes the performance differences of different components to achieve the three-dimensional crimp of fibers. For example, the rigid polymers and elastic polymers used in technologies such as CN118531562A and CN118241377A. However, the deficiencies of such technologies include: 1. Most of the fibers are micron-scale fibers with a thick fiber diameter, which limits the further improvement of the properties such as low bulk density, high porosity, fluffiness, and soft handfeel of the fiber cotton material; 2. Since the principle of fiber crimping in melt spinning technology is based on the performance differences of two polymers, generally there are relatively strict requirements for the selected elastomeric polymer raw materials, which limits the popularization and application of this technology.

[0003] On this basis, a melt spinning technology based on a single component has also been proposed in the existing technology to achieve the three-dimensional crimp of fibers. For example, CN111118623A proposes a cotton-like polyester fiber and its preparation method, using the FDY process and the POY process, and setting the shape of the spinneret hole as a three-leaf shape (the three leaves are in a T shape) in the FDY process for spinning, so that the coils on the surface of the prepared polyester cotton-like fiber are in a three-dimensional self-crimped form. However, this method still cannot easily reduce the fiber diameter to the nanoscale, and the process is still very complex.

[0004] There is an urgent need in the art for a meltblown spinning method for ultrafine crimped nanofibers with less restrictions on polymer types and a simple process, and to improve its application performance by virtue of the unique crimped structure and nanoscale of the fiber cotton. In view of this, the present invention is proposed. Summary of the Invention

[0005] The present invention provides a method for preparing crimped nanofibers based on a nozzleless meltblown process and its application. Turbulence is formed by hot air flowing through a number of pores in a moving state, so that the molten thermoplastic polymer located in the number of pores is stretched by the hot air flow to form the crimped nanofibers at one time. The crimped nanofibers can be of a single component, and moreover, the method of the present invention has low requirements for polymer types and a simple process.

[0006] Furthermore, the method of the present invention can regulate the pore structure, the moving state, and the hot air flow velocity, and can obtain crimped structure nanofibers with a higher crimp number and a lower fiber diameter.

[0007] Specifically, in the first aspect, the present invention provides a method for preparing curled nanofibers based on a meltblowing process, comprising: a hot air flow passes through a plurality of pores in motion to form turbulence, so that the molten thermoplastic polymer located in the plurality of pores is stretched by the hot air flow to form the curled nanofibers at one time.

[0008] The temperature of the pores in contact with the molten thermoplastic polymer is higher than or equal to the temperature of the molten thermoplastic polymer; The hot air flow is output from the air outlet of the air supply component, the air flow velocity of the hot air flow at the air outlet is 250~320m / s, the temperature of the hot air flow at the air outlet is higher than or equal to the temperature of the molten thermoplastic polymer, and the distance between the air outlet and the pore is less than 3cm.

[0009] The running direction of the pores in the moving state does not coincide with the airflow direction of the hot airflow.

[0010] According to the method for preparing curly nanofibers based on a spinneretless melt-blowing process provided by the present invention, the temperature of the molten thermoplastic polymer is 250-300°C.

[0011] Preferably, the receiving distance of the curled nanofibers is 20 to 80 cm.

[0012] Preferably, the thermoplastic polymer is selected from polypropylene (PP), polylactic acid (PLA), polyethylene terephthalate (PET), polyamide 6 (PA6) or polyamide 66 (PA66).

[0013] Preferably, the curled nanofibers are single-component nanofibers.

[0014] According to the method for preparing curly nanofibers based on a spinneret-free melt-blowing process provided by the present invention, the plurality of pores are located on a screen, and the rotation speed of the screen is 2-6 rpm; The mesh number of the sieve is 40-100.

[0015] According to the method for preparing curly nanofibers based on a spinneret-free melt-blowing process provided by the present invention, the screen is located in a first melt-blowing spinning device, and the first melt-blowing spinning device comprises: frame; A melt processing mechanism, disposed on the frame, for outputting the molten thermoplastic polymer and forming the hot air flow to perform the stretching on the molten thermoplastic polymer; Driving mechanism; A rotating positioning mechanism is provided on the frame and is connected to the driving mechanism. The driving mechanism drives the rotating positioning mechanism to rotate. A screen is disposed opposite to the outlet end of the melt treatment mechanism and is connected to the rotating positioning mechanism. The rotating positioning mechanism positions the screen and drives the screen to rotate. A plurality of micropores are uniformly distributed on the screen. The plurality of micropores are used for the molten thermoplastic polymer on the screen, and the micropores extending along the axial direction further form a diversion channel. The hot air flow performs stretching on the molten thermoplastic polymer through the diversion channel.

[0016] According to the method for preparing coiled nanofibers based on the non-spinneret meltblowing process provided by the present invention, the air supply assembly includes: An air compressor for forming the air flow velocity of the hot air flow; An air knife is connected to the air compressor, and a second heating unit is provided between the air compressor and the air knife. The second heating unit is used for heating the air flow to form the temperature of the hot air flow. The edge of the air knife is the air outlet.

[0017] According to the method for preparing coiled nanofibers based on the non-spinneret meltblowing process provided by the present invention, the several pores are located on a roller, and the rotational speed of the roller is 2 - 5 rpm. The through holes on the roller are slits with a width of less than 0.05 cm or micropores with a pore diameter of less than 0.05 cm.

[0018] According to the method for preparing coiled nanofibers based on the non-spinneret meltblowing process provided by the present invention, the roller is located in a second meltblowing spinning device. The second meltblowing spinning device includes: A melt feeding and heating mechanism for loading the thermoplastic polymer and heating the thermoplastic polymer to a molten state; A melt transfer mechanism is connected to the outlet end of the melt feeding and heating mechanism; A melt output mechanism includes: a roller capable of rotating directionally. The roller is opposite to and close to the outlet of the melt transfer mechanism, and a plurality of the through holes are formed on the surface of the roller; A melt stretching mechanism is arranged facing the roller; When the molten thermoplastic polymer is applied to the surface of the roller through the melt transfer mechanism and enters the through holes, the hot air flow stretches the molten thermoplastic polymer to form a polymer jet through the through holes.

[0019] According to the method for preparing coiled nanofibers based on the non-spinneret meltblowing process provided by the present invention, the air supply assembly includes: An air knife is provided inside the drum, and the air knife is located behind the melt transfer mechanism along the rotation direction of the drum; the melt transfer mechanism is provided outside the drum; the blade edge of the air knife is the air outlet; An air compressor is connected to the air knife and is used to form the air flow velocity of the hot air flow; A second heating unit is provided between the air compressor and the air knife and is used to heat the air flow to form the temperature of the hot air flow. The air flow velocity of the hot air flow at the air outlet is 260 - 320 m / s.

[0020] In a second aspect, the present invention also provides a crimped nanofiber aggregate, which is obtained by the method for preparing crimped nanofibers based on a nozzle - less melt - blowing process as described above; The number of crimps of the crimped nanofiber aggregate is 100 - 700 per cm; the average diameter of the crimped nanofibers is less than 1 μm.

[0021] According to the crimped nanofiber aggregate provided by the present invention, the Cro value of the crimped nanofiber flake is 2 - 6 Clo, the air permeability is 50 - 290 mm / s, and the moisture vapor transmission rate is higher than 5900 g / m 2 / 24 h.

[0022] Preferably, the pore diameter of the crimped nanofiber aggregate is 5 - 30 μm, the porosity is higher than 95%, and the bulk density is 5 - 30 mg / cm 3 .

[0023] The crimped nanofiber aggregate in the present invention can be a two - dimensional film, felt or three - dimensional fiber cotton.

[0024] Preferably, the crimped nanofiber aggregate is formed by stacking fibers with different flexibilities in a composite manner, increasing the compression resistance of the fiber aggregate.

[0025] For example: The crimped nanofibers of material A are stacked to form a three - dimensional fiber cotton a1, and then fibers of material B are continuously stacked on the three - dimensional fiber cotton a1 to form a film or felt b, that is, a composite three - dimensional aggregate 1 of a1 and b is obtained. Another example: Crimped nanofibers of material A are continuously stacked on the composite three - dimensional aggregate 1 to form a film or felt a2, that is, a sandwich - type composite fiber aggregate 2 of a1, b and a2 is obtained.

[0026] When preparing the above - mentioned composite fiber aggregate, the composite spinning can be in the ways of melt - blowing spinning A + melt - blowing spinning B, melt - blowing spinning A + air - feeding cotton B or melt - blowing spinning A + fiber cotton B, etc.

[0027] A method for preparing crimped nanofibers based on a meltblowing process without spinneret holes and its applications provided by the present invention form a turbulent flow by passing hot air through a number of pores in a moving state, so that the molten thermoplastic polymer located in the number of pores can be prepared into nanofibers with a crimped structure in one step through the stretching action of the hot air flow. Compared with the prior art, the method of the present invention does not need to consider the physical property differences of raw material components, can be applied to a single-component polymer raw material system, and does not require post-processing techniques such as deformation and crimping processing, greatly shortening the process flow. The preparation method of the present invention has strong versatility and a wide range of applications.

[0028] The crimped nanofibers prepared by the one-step method of the present invention can achieve small pore diameters and high porosities. At the same time, the refinement of the fiber diameter size at the microscopic level can improve the application performance of the fiber aggregates at the macroscopic level, and its application potential in the fields of filtration and separation, sound absorption and noise reduction, cold protection and warmth retention, textile and clothing fabrics, etc. is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a three-dimensional structural schematic diagram of the first meltblowing spinning device provided in one embodiment of the present invention.

[0031] Figure 2 It is a front view of the first meltblowing spinning device provided in one embodiment of the present invention.

[0032] Figure 3 It is a top view of the first meltblowing spinning device provided in one embodiment of the present invention.

[0033] Figure 4 It is a left view of the first meltblowing spinning device provided in one embodiment of the present invention.

[0034] Figure 5 It is a structural schematic diagram of the melt transfer module and the jet stretching module provided in one embodiment of the present invention.

[0035] Figure 6 It is a bottom view of the melt transfer module and the jet stretching module provided in one embodiment of the present invention.

[0036] Figure 7 It is a structural schematic diagram of the screen and the enclosure provided in one embodiment of the present invention.

[0037] Figure 8 It is a schematic structural diagram of the second meltblown spinning device provided in the first example of the present invention.

[0038] Figure 9 It is a schematic structural diagram of the second meltblown spinning device provided in the second example of the present invention.

[0039] Figure 10 is Figure 8 A schematic structural diagram of the first perspective of the melt feeding and heating mechanism, melt transfer mechanism, melt output mechanism, and melt stretching mechanism in

[0040] Figure 11 is Figure 8 A schematic structural diagram of the second perspective of the melt feeding and heating mechanism, melt transfer mechanism, melt output mechanism, and melt stretching mechanism in

[0041] Figure 12 is Figure 8 A schematic structural diagram of the first perspective of the transfer seat in

[0042] Figure 13 is Figure 8 A schematic structural diagram of the second perspective of the transfer seat in

[0043] Figure 14 is Figure 8 A schematic structural diagram of the air knife of the transfer seat in

[0044] Figure 15 It is a schematic structural diagram of the roller provided in one of the embodiments of the present invention.

[0045] Figure 16 It is a schematic structural diagram of the roller provided in one of the embodiments of the present invention.

[0046] Figure 17 It is a schematic structural diagram of the roller provided in one of the embodiments of the present invention.

[0047] Figure 18 It is a morphological diagram of PLA fibers prepared by the method of Embodiment 1A of the present invention.

[0048] Figure 19 It is an SEM image of the fibers prepared in Example 4A of the present invention.

[0049] Figure 20 It is the thermal insulation performance index of the fiber cotton prepared in Example 4A of the present invention.

[0050] Figure 21 It is the air permeability and moisture permeability of the fiber cotton prepared in Example 4A of the present invention. Among them, the bar chart filled with diagonal lines corresponds to the air permeability, and the bar chart filled with grid shapes corresponds to the moisture permeability.

[0051] Figure 22 It is the SEM image of the fiber prepared in Comparative Example 1A of the present invention.

[0052] Figure 23 It is the physical image of the composite fiber cotton in Example 6A of the present invention.

[0053] Figure 24 It is the air permeability and moisture permeability of the composite fiber cotton in Example 6A of the present invention.

[0054] Figure 25 It is the compression and resilience performance of the composite fiber cotton in Example 6A of the present invention.

[0055] Reference numerals: 1: Frame; 2: Driving mechanism; 21: Motor; 22: Active turntable; 23: Transmission belt; 3: Rotating positioning mechanism; 31: Slewing bearing; 4: Screen; 41: Enclosure; 42: Micro holes; 5: Melt feeding and heating module; 51: Screw extruder; 6: Melt transfer module; 61: Strip-shaped spray slot; 7: Jet drawing module; 71: First air knife; 8: Heating mechanism; 9: Connecting body; 100: Melt feeding and heating mechanism; 200: Melt transfer mechanism; 201: Transfer seat; 202: Melt channel; 203: Strip-shaped slot; 204: Third heating unit; 205: Arc surface; 300: Melt output mechanism; 301: Drum; 3011: Circular through hole; 3012: Square grid; 3013: Rectangular grid; 302: Support frame; 303: Driving unit; 304: First pulley; 305: Second pulley; 306: Transmission belt; 307: Rotating shaft; 400: Melt drawing mechanism; 401: Second air knife; 500: Heater. Detailed implementation manners

[0056] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0057] In the description of this embodiment, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this embodiment and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on this embodiment.

[0058] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of this embodiment, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0059] In this embodiment, unless otherwise clearly specified and limited, terms such as "set", "installed", "connected", "connected to", "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this embodiment can be understood according to specific circumstances.

[0060] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0061] Next, in combination with Figures 1 - 25 Describe a method for preparing curly nanofibers based on a non-spinneret meltblowing process and its application of the present invention.

[0062] For those technical details or conditions not specified in the embodiments, they shall be in accordance with the techniques or conditions described in the literature in this field or in accordance with the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through regular channels. Among them, the melt index of the polypropylene particles is 1500, while the melt index of the polylactic acid is 70.

[0063] The following will describe the first meltblown spinning device of the present invention in conjunction with Figures 1 - 7 Describe the first meltblown spinning device of the present invention.

[0064] The following will describe the first meltblown spinning device of the present invention in conjunction with Figures 1 - 7 Describe the first meltblown spinning device of the present invention. The first meltblown spinning device includes: a frame 1, a melt processing mechanism, a driving mechanism 2, a rotating positioning mechanism 3, and a screen 4.

[0065] Among them, the melt processing mechanism is arranged on the frame 1, and is used for outputting a molten thermoplastic polymer and forming a hot air flow to draw the molten thermoplastic polymer; the rotating positioning mechanism 3 is arranged on the frame 1 and is connected to the driving mechanism 2, and the driving mechanism 2 drives the rotating positioning mechanism 3 to rotate; the screen 4 is arranged opposite to the outlet end of the melt processing mechanism and is connected to the rotating positioning mechanism 3, and the rotating positioning mechanism 3 positions the screen 4 and drives the screen 4 to rotate. A plurality of micropores 42 (i.e., pores) are evenly distributed on the screen 4. The plurality of micropores 42 are used for dispersing the molten thermoplastic polymer on the screen 4, and the micropores 42 extending along the axial direction also form a diversion channel. The melt processing mechanism draws the molten thermoplastic polymer through the diversion channel.

[0066] Specifically, the frame 1 serves as the support and installation structure of the device, and the melt processing mechanism, the driving mechanism 2, the rotating positioning mechanism 3, and the screen 4 are all installed on the frame 1. Add meltblown-grade resin into the melt processing mechanism, and through the processes of heating, melting, extruding, and drawing; specifically, first heat the meltblown-grade resin to obtain a molten thermoplastic polymer, extrude the molten thermoplastic polymer onto the screen 4, and draw the molten thermoplastic polymer through the ejected air flow. Finally, collect the drawn fibers below the screen 4.

[0067] The driving mechanism 2 serves as the power source for the rotation of the screen 4, and can drive the screen 4 to rotate clockwise or counterclockwise. During the rotation of the screen 4, the melt is drawn through the screen 4, and the rotation speed should not be too fast or too slow; if the rotation speed is too fast, the melt will not have enough time to be drawn, and if the rotation speed is too slow, the melt will solidify due to the increase in cold viscosity.

[0068] The rotating positioning mechanism 3 is installed on the frame 1 and has the following two functions: 1. Rotating transmission function: The driving mechanism 2 drives the rotating positioning mechanism 3 to rotate, thereby transmitting the rotational motion to the screen 4, and further driving the screen 4 to rotate; 2. Positioning function: The screen 4 is installed in the rotating positioning mechanism 3. Through the positioning function of the rotating positioning mechanism 3 on the screen 4, the problem of the screen 4 running off during rotation is avoided.

[0069] By driving the positioning and rotation of the screen 4 through the rotating positioning mechanism 3, the rotation stability of the screen 4 is improved, and the prepared fibers have high stability, ensuring the continuity of production.

[0070] A plurality of micropores 42 are evenly distributed on the screen 4. The micropores 42 have the following two functions: 1. The plurality of micropores 42 on the screen 4 are used to evenly disperse the molten thermoplastic polymer on the screen 4, and multiple melt jets are formed through the micropores 42; 2. The micropores 42 extending along the axial direction form a diversion channel. The melt processing mechanism stretches the molten thermoplastic polymer through the diversion channel. This diversion channel is an air flow channel. An air flow is blown onto the screen 4 through a jet stretching module (i.e., an air supply component). The air flow passes through the air flow channel and stretches the molten thermoplastic polymer.

[0071] The first meltblown spinning device further includes: a heating mechanism 8, which is arranged on the frame 1 and is arranged upstream of the melt processing mechanism along the rotation direction of the screen 4 for heating the screen 4. Specifically, by arranging the heating mechanism 8 above the screen 4, the screen 4 is preheated. Before the melt falls onto the screen 4, the screen 4 is preheated by the heating mechanism 8 in advance to ensure that when the molten thermoplastic polymer contacts the screen 4, the melt will not increase in viscosity or solidify due to the low temperature of the screen 4, thereby improving the fiber quality.

[0072] The rotating positioning mechanism 3 includes: a slewing bearing 31. The slewing bearing 31 includes an inner bearing ring and an outer bearing ring that are rotatably connected to each other. The outer bearing ring is fixed on the frame 1. The driving mechanism 2 is connected to the outside of the inner bearing ring. The screen 4 is fixed to the inside of the inner bearing ring and rotates synchronously with the inner bearing ring. The rotating positioning mechanism 3 adopts the slewing bearing 31, which has the ability to support the screen 4 and can position the screen 4 inside the inner bearing ring and drive the screen 4 to rotate synchronously. Specifically, the outer bearing ring is fixed on the frame 1, and the rotation of the inner bearing ring relative to the outer bearing ring is realized through rolling elements (such as ball bearings or ball bearings) arranged between the outer bearing ring and the inner bearing ring.

[0073] The first meltblown spinning device further includes: a plurality of connectors 9; an annular gap is formed between the screen 4 and the inner ring of the bearing. The connectors 9 are evenly arranged in the annular gap at intervals in the circumferential direction, and one end of the connector 9 is connected to the screen 4, and the other end of the connector 9 is connected to the inner ring of the bearing. Preferably, the connector 9 is a triangular connector 9 fixed to the inner side of the inner ring of the bearing, which is distributed at a preset distance along the circumference of the inner ring of the bearing. Through holes are formed in the connector 9, and the connector 9 and the screen 4 are fixed by fasteners to ensure the positioning and synchronous rotation of the screen 4.

[0074] The driving mechanism 2 includes: a motor 21 and a transmission belt 23. The motor 21 is arranged on the frame 1; the output end of the motor 21 is connected to the outer side of the inner ring of the bearing through the transmission belt 23. The motor 21 is fixed on the frame 1, the output shaft of the motor 21 is connected to the driving turntable 22, and the driving turntable 22 is connected to the outer side of the inner ring of the bearing through the transmission belt 23 and drives the inner ring of the bearing to rotate. Specifically, both the inner ring of the bearing and the driving turntable 22 are provided with grooves for installing the transmission belt 23, and the transmission belt 23 is tensioned and assembled in the grooves accordingly to ensure the synchronous transmission between the driving turntable 22 and the inner ring of the bearing.

[0075] The first meltblown spinning device further includes a shroud 41. The shroud 41 is arranged outside the screen 4, and the connector 9 is fixedly connected to the shroud 41. As Figure 7 shown in the structure, the screen 4 is a circular screen 4, and the shroud 41 is an annular shroud 41 fixed on the outer edge of the screen 4 to form an integral structure with the screen 4. The shroud 41 has the following three functions: 1. Facilitate the positioning of the screen 4: The screen 4 is connected to each connector 9 through the shroud 41, which is convenient for assembly; 2. Protect the screen 4: Since the shroud 41 is located outside the screen 4, it prevents the screen 4 from contacting the bearing, thereby reducing the wear of the screen 4; 3. Prevent the melt from being thrown out: The shroud 41 protrudes from the screen 4 in the height direction, thereby preventing the melt from being thrown out of the screen 4 due to the centrifugal force.

[0076] The melt treatment mechanism includes: a melt feeding and heating module 5, a melt transfer module 6, and a jet stretching module 7. Among them, the melt feeding and heating module 5 is used to feed and heat the meltblown resin material; one end of the melt transfer module 6 is connected to the melt feeding and heating module 5, and the other end is arranged facing the screen 4, and is used to spray the molten meltblown resin material onto the screen 4; the jet stretching module 7 faces the screen 4 and is located downstream of the melt transfer module 6, and is used to blow air flow onto the screen 4 and stretch the molten meltblown resin material into a jet through the diversion channel. Specifically, the melt feeding and heating module 5, the melt transfer module 6, and the jet stretching module 7 are all arranged on the frame 1.

[0077] The melt feeding and heating module 5 includes: a screw extruder 51. The screw extruder 51 has at least four heating zones. The temperature range of the first heating zone is 25 - 100 °C, and the temperature ranges of the second to fourth heating zones are 25 - 300 °C; the rotational speed of the screw extruder 51 ranges from 0 to 30 rpm. Specifically, meltblown-grade resin is added into the melt feeding and heating module 5 and heated to melting to form a molten thermoplastic polymer with certain fluidity and viscosity. The above-mentioned heating module includes at least four heating zones to ensure sufficient heating of the resin. The temperature range of the first heating zone is 25 - 100 °C, and the temperature ranges of the second to fourth heating zones are 25 - 300 °C. The heating module conveys the melt by screw rotation, and the rotational speed of the screw ranges below 30 rpm.

[0078] The melt transfer module 6 includes: an L-shaped melt channel, and a strip-shaped spray slot 61 is formed at one end of the L-shaped melt channel facing the screen 4. A first heating unit is provided in the L-shaped melt channel, and the temperature range of the first heating unit is 250 - 350 °C; the vertical distance between the outlet end face of the strip-shaped spray slot 61 and the screen 4 ranges from 0.5 to 2 cm. Specifically, the melt transfer module 6 is an integrated block with an L-shaped melt channel formed inside. One end is a hole connected to the end of the screw extruder 51, and the other end is a strip-shaped spray slot 61. The L-shaped melt channel conveys the melt horizontally, changes the melt spraying direction at the strip-shaped spray slot 61, and sprays the melt downward and towards the screen 4; the melt is first conveyed through the hole to the strip-shaped spray slot 61. At the same time, the inside of this module can be heated to keep the molten melt warm and maintain the fluidity of the melt. The heating temperature of the first heating unit should be equal to or higher than the temperature of the melt feeding and heating module 5. The width of the strip-shaped spray slot 61 is preferably in the range of 1 - 7 mm.

[0079] The jet stretching module 7 includes: an air compressor and a first air knife 71, etc. The air pressure output by the air compressor ranges from 0.2 to 0.5 Mpa; the first air knife 71 is connected to the air compressor, and a second heating unit is provided between the air compressor and the first air knife 71, and the temperature range of the second heating unit is 260 - 350 °C. The vertical distance between the blade edge of the first air knife 71 and the screen 4 ranges from 1 to 3 cm, and the horizontal distance between the first air knife 71 and the melt transfer module 6 ranges from 1 to 2 cm. Preferably, the second heating unit can adopt an air heating package, and a freeze dryer is also provided between the air compressor and the first air knife 71. The first air knife 71 is behind the strip-shaped spray slot 61, the first air knife 71 is arranged in parallel with the strip-shaped spray slot 61, the gap of the first air knife 71 is between 0.08 and 0.32 mm, and the length of the first air knife 71 is greater than or equal to the length of the strip-shaped spray slot 61.

[0080] The first melt-blown spinning device further includes: a fiber collection module, which is located on the side of the screen 4 away from the melt processing mechanism, and is used to collect polymer fibers. Preferably, the fiber collection module is located directly below the first air knife 71, and can be a filter basket or a drum with a mesh, and is used to collect the stretched fibers; the vertical distance between the fiber collection module and the first air knife 71 is in the range of 20 to 80 cm.

[0081] The length of the guide channel formed by the micropores 42 extending along the axial direction on the screen 4 ranges from 0.1 to 0.4 mm. Driven by the rotation and positioning mechanism 3, the screen 4 rotates.

[0082] Examples 1A to 4A and Comparative Examples 1A to 3A The first melt-blown spinning device is used to prepare the curled nanofibers, and the specific process is as follows: Turn on the temperature switches of the melt feeding and heating module 5 and the melt transfer module 6, set the temperature parameters of the four heating zones of the screw extruder 51, and make the vertical distance between the outlet end face of the strip spray slit 61 and the screen 4 range to 0.8 cm, and the width of the strip spray slit 61 to 5 mm; then start the air compressor, set the air pressure and temperature to control the temperature and airflow velocity of the hot air flow at the blade of the first air knife 71, wherein the temperature of the hot air flow at the blade of the first air knife 71 is 20°C higher than the temperature of the first heating unit, and the temperature and airflow velocity of the first heating unit are specifically shown in Table 1, start the heating mechanism 8, and after the temperature is constant, the heating temperature of the local area of the screen 4 is the same as the temperature of the molten thermoplastic polymer. Add the melt-blown grade resin raw material (see Table 1 for details) to the feed port of the screw extruder 51, and start the screw to rotate. Next, start the motor 21 for controlling the rotation of the screen 4. The screen is a circle with a diameter of 20 cm. Set the rotation speed of the screen 4 (see Table 1 for details), the mesh size of the screen 4 (see Table 1 for details), and the length of the guide channel formed by the micropores 42 extending axially on the screen 4 according to the diameter of the screen with different mesh sizes; the vertical distance between the screen 4 and the first air knife 71 is 1 cm, the horizontal distance between the first air knife 71 and the outlet end of the L-shaped melt channel is 1 cm, the gap of the first air knife 71 is 0.16 mm, and the vertical distance between the screen 4 and the fiber collection module is 80 cm.

[0083] Table 1

[0084] The curl number and average fiber diameter of the fibers obtained in Examples 1A to 4A and Comparative Examples 1A to 3A were tested, as shown in Table 2.

[0085] Table 2

[0086] Example 6A Basically the same as Example 4A, except that: A PET fiber felt is used as the receiving substrate of the fiber collection module, and polypropylene is deposited on the PET fiber felt to obtain a fiber cotton composed of melt-blown spun A + fiber cotton B.

[0087] Example 7A Basically the same as Example 4A, except that: The PET fiber cotton is dispersed and carded into single fibers by a carding machine, then taken out by a rotating licker-in roller, and blown into the receiving substrate of the fiber collection module by air flow depending on air feeding, to obtain a composite fiber cotton of melt-blown spun A + air-fed B.

[0088] Next, in combination with Figures 8 - 17 Describe the second melt-blown spinning device of the present invention. The second melt-blown spinning device includes: a melt feeding and heating mechanism 100, a melt transfer mechanism 200, a melt output mechanism 300, a melt drawing mechanism 400, etc.

[0089] Among them, the melt feeding and heating mechanism 100 is used to load the thermoplastic polymer and heat the thermoplastic polymer to a molten state; the melt transfer mechanism 200 is connected to the outlet end of the melt feeding and heating mechanism 100; the melt output mechanism 300 includes: a drum 301 capable of rotating in a direction, the drum 301 is opposite to the outlet of the melt transfer mechanism 200 and is arranged close to the melt transfer mechanism 200, and a plurality of through holes are formed on the surface of the drum 301; the melt drawing mechanism 400 is arranged facing the drum 301.

[0090] When the molten thermoplastic polymer is applied to the surface of the drum 301 through the melt transfer mechanism 200 and enters the through holes, the molten thermoplastic polymer is drawn by the melt drawing mechanism 400 to form a polymer jet passing through the through holes.

[0091] Specifically, the melt feeding and heating mechanism 100 can adopt a screw extruder, which has the functions of feeding, heating and extruding at the same time. The screw extruder is used to heat and extrude the melt-blown grade resin to form a molten thermoplastic polymer.

[0092] Furthermore, the screw extruder has at least four heating zones to ensure that the resin is heated sufficiently during the rotation of the screw. The temperature range of the first heating zone is 25~100°C, and the temperature ranges of the second to fourth heating zones are 25~300°C. The melt is conveyed by the rotation of the screw, and the rotation speed of the screw ranges from 0 to 30 rpm.

[0093] Specifically, the molten thermoplastic polymer is transferred to the surface of the roller 301 through the melt transfer mechanism 200. During the transfer process, it can be continuously heated to a specified temperature according to the actual situation to ensure that the temperature of the output molten thermoplastic polymer meets the requirements of meltblown spinning. It is transferred to the position of the roller 301 through the melt transfer mechanism 200 so as to scrape and coat the melt on the surface of the roller 301.

[0094] Specifically, the melt output mechanism 300 includes a roller 301 that can rotate directionally. An array of through-holes is formed on the surface of the roller 301, and the through-holes can be round holes, meshes or slits, etc. Under the clockwise or counterclockwise rotation of the roller 301, the molten thermoplastic polymer is blown out by the hot air flow provided by the melt drafting mechanism 400 through the round holes, meshes or slits, etc. on the surface array.

[0095] Specifically, the melt drafting mechanism 400 (i.e., the air supply component) can eject a hot air flow to draft the molten thermoplastic polymer through the hot air flow. After passing through the through-holes, a polymer jet can be formed, and fibers are formed by drafting under the action of the hot air flow. The position of the melt drafting mechanism 400 is inside the roller 301, and its arrangement direction with the melt transfer mechanism 200 is consistent with the rotation direction of the roller 301, ensuring that during the rotation of the roller 301, it first passes through the melt transfer mechanism 200 and then passes through the melt drafting mechanism 400. After the molten thermoplastic polymer is sprayed onto the surface of the roller 301 through the melt transfer mechanism 200, it can be evenly dispersed into each through-hole, and then, through the hot air flow blowing, the spinning is ensured to be uniform and the spinning efficiency is improved.

[0096] Finally, the melt jet is drafted and solidified to form fibers under the action of the hot air flow and the surrounding cold air; it can be collected by the fiber collection mechanism.

[0097] As Figure 12 and Figure 13 shown, the melt transfer mechanism 200 includes: a transfer seat 201, inside which a melt channel 202 is formed; one end of the melt channel 202 is connected to the outlet end of the melt feeding and heating mechanism 100, and the other end of the melt channel 202 is formed with a strip-shaped slit 203, and the strip-shaped slit 203 is arranged towards the roller 301. Specifically, the transfer seat 201 is connected to the outlet at the end of the screw extruder for receiving the molten thermoplastic polymer, and is transported from one end of the melt channel 202 to the strip-shaped slit 203 at the other end. The extrusion speed of the melt can be controlled by the rotation speed of the screw extruder and the size of the strip-shaped slit 203, and uneven melt coating can be avoided.

[0098] Inside the transfer seat 201, there is a third heating unit 204 for heating the molten thermoplastic polymer in the melt channel 202; and the third heating unit 204 is configured to have a heating temperature greater than or equal to the heating temperature of the melt feeding and heating mechanism 100. Specifically, during the melt transportation and transfer process, there may be heat loss, which increases the melt viscosity and makes it difficult to be drawn. Therefore, a third heating unit 204 is provided inside the transfer seat 201 to ensure that the temperature of the molten thermoplastic polymer output from the melt channel 202 meets the requirements of meltblown spinning. Preferably, the third heating unit 204 uses heating rods, and its temperature range is 250~300°C.

[0099] The surface of the transfer seat 201 close to the roller 301 is an arc surface 205 and is adapted to fit on the outer arc wall of the roller 301, and the strip-shaped slit 203 is located on the arc surface 205. Specifically, the radian of the arc surface 205 of the transfer seat 201 is the same as the radian at this position of the roller 301, and the distance between the two arc surfaces 205 ranges from 1 to 5 mm, so as to ensure that the molten thermoplastic polymer output from the strip-shaped slit 203 is evenly coated on the outer wall surface of the roller 301 and ensure uniform spinning. Preferably, the strip-shaped slit 203 is located at the center of the arc surface 205, that is, in the width direction of the roller 301, arc surfaces 205 are formed in front of and behind the strip-shaped slit 203, further ensuring uniform coating of the molten thermoplastic polymer.

[0100] As Figure 15 shown, the through holes are arranged along the circumferential direction of the roller 301 and / or along the width direction of the roller 301. Specifically, according to the size of the through holes, multiple columns of through holes are arranged along the circumferential direction of the roller 301, and multiple rows of through holes are arranged along the width direction of the roller 301, thus forming a through hole array.

[0101] The multiple through holes include: multiple circular through holes 3011, and the multiple circular through holes 3011 are arrayed along the circumferential direction and the width direction of the roller 301. The molten thermoplastic polymer forms local turbulence under the action of the melt drawing mechanism 400 through the circular through holes 3011. Preferably, the diameter of the circular through holes 3011 ranges from 0.01 to 0.05 cm.

[0102] The through holes adopt the form of circular through holes 3011. The following means can be used to improve the local turbulence effect: 1. Geometric shape: Circular holes with as small a size as possible can be used. Smaller hole diameters and larger length-to-diameter ratios (i.e., L / D ratios) can intensify the degree of turbulence; 2. Boundary layer effect: When the molten thermoplastic polymer approaches the wall surface of the circular hole, a thin boundary layer will be formed. The development and separation of this boundary layer have a direct impact on the formation of turbulence.

[0103] 3. Multiphase flow: Since the melt stretching mechanism 400 can eject hot air flow, it forms a multiphase flow with the molten thermoplastic polymer, and the interaction between different phases will also greatly affect the formation of turbulence.

[0104] The local turbulence formed in the form of the above-mentioned round holes has the following characteristics: 1. The turbulence intensity is relatively low, mainly concentrated at the edge of the jet; 2. The fluidity is relatively stable, and the central region may be laminar flow; 3. The turbulence scale is relatively large, mainly in the form of large eddy structures; 4. The pressure loss is relatively small.

[0105] In summary, the local turbulence formed in the form of round holes is mainly located at the edge of the round holes, so it is called local turbulence.

[0106] As Figure 16 and 17 shown, the multiple through holes include: multiple rectangular grids 3013, and the multiple rectangular grids 3013 are arrayed along the circumferential direction and the width direction of the drum 301. The molten thermoplastic polymer forms local turbulence by passing through the rectangular grids 3013 under the action of the melt stretching mechanism 400. Preferably, the length and width of the rectangular grids 3013 are in the range of 0.018 - 0.05 cm. Preferably, the rectangular grids 3013 are rectangular grids.

[0107] In one embodiment of the present invention, the rectangular grid is a square grid 3012, and the side length of the square grid 3012 is in the range of 0.018 - 0.05 cm.

[0108] In the above embodiment, the through holes adopt the grid form of the rectangular grid 3013 or the square grid 3012 to form a uniform and stable turbulence field. The following means can be used to improve the effect of the turbulence field: 1. Grid type: including single grid, double grid or even multi-layer grid, which can generate turbulence with different degrees and characteristics.

[0109] 2. Grid geometry: grids in the shape of square, rectangle or other shapes will affect the isotropic and anisotropic characteristics of turbulence.

[0110] 3. Grid ratio: The ratio of the grid size to the channel width also affects the generated turbulence intensity and its spatial distribution.

[0111] The uniform and stable turbulence field formed in the form of the above-mentioned rectangular grid 3013 or square grid 3012 has the following characteristics: 1. The turbulence intensity is relatively high and evenly distributed; 2. The fluidity is relatively unstable and quickly turns into turbulence; 3. The turbulence scale is small, and the energy is dispersed to small scales; 4. The pressure loss is large.

[0112] In summary, the turbulence formed by the rectangular grid 3013 or the square grid 3012 has a high intensity, uniform distribution, and stable formation. Therefore, the interaction between multiple turbulent flows forms a turbulence field.

[0113] Furthermore, the length direction of the above-mentioned rectangular grid 3013 or square grid 3012 is perpendicular to the length direction of the strip slot 203 of the transfer seat 201.

[0114] The melt drawing mechanism 400 includes: a second air knife 401, which is arranged inside the roller 301, and the second air knife 401 is located behind the melt transfer mechanism 200 along the rotation direction of the roller 301; the melt transfer mechanism 200 is arranged outside the roller 301. Specifically, the second air knife 401 is located inside the roller 301, and both the melt transfer mechanism 200 and the fiber collection mechanism are located outside the roller 301. The molten thermoplastic polymer is smeared on the outer wall of the roller 301 through the melt transfer mechanism 200. After the roller 301 rotates, the molten thermoplastic polymer is drawn into a jet by the hot air flow blown by the second air knife 401.

[0115] The melt drawing mechanism 400 further includes: an air compressor and a fourth heating unit. The air compressor is connected to the second air knife 401; the fourth heating unit is arranged between the air compressor and the second air knife 401 for heating the compressed air. The air compressor is used to provide high-speed compressed air, and the fourth heating unit can use an air heating package to heat the high-pressure and high-speed air.

[0116] The melt drawing mechanism 400 further includes: a freeze dryer, which is arranged between the air compressor and the fourth heating unit for drying the air to avoid the influence of air moisture on meltblown spinning.

[0117] The shortest distance between the second air knife 401 and the roller 301 ranges from 1 to 2 cm; the distance between the second air knife 401 and the melt transfer mechanism 200 on the rotation path of the roller 301 ranges from 1 to 2 cm, the air pressure of the second air knife 401 ranges from 0.2 to 0.5 Mpa, the temperature of the fourth heating unit ranges from 260 to 350 °C, the gap at the outlet of the second air knife 401 is between 0.08 and 0.32 mm, and the length of the second air knife 401 is greater than or equal to the width of the roller 301.

[0118] The melt output mechanism 300 further includes: a support frame 302 and a drive unit 303. The support frame 302 is formed with a through hole for the rotation shaft 307 to pass through; the output shaft of the drive unit 303 passes through the through hole and is connected to the roller 301, and is used to drive the roller 301 to rotate directionally. Preferably, the second meltblown spinning device further includes: a bracket, the support frame 302 is fixed on the bracket, the through hole in the support frame 302 can play a role in positioning the rotation shaft 307, the drive unit 303 provides power to drive the rotation shaft 307 to rotate, and further drives the roller 301 to rotate directionally.

[0119] The second meltblown spinning device further includes: a first pulley 304, a second pulley 305 and a transmission belt 306. The first pulley 304 is coaxially connected to the output shaft of the drive unit 303; the second pulley 305 is coaxially connected to the rotation shaft 307; the transmission belt 306 is respectively connected to the first pulley 304 and the second pulley 305. The drive unit 303 can adopt a motor, and its output shaft drives the first pulley 304 to rotate, further driving the transmission belt 306 to move, so that the second pulley 305 rotates synchronously, thereby driving the rotation shaft 307 and the roller 301 to rotate. The rotational speed of the motor ranges from less than 10 rpm. If the speed is too fast, the melt will not have enough time for stretching. If the speed is too slow, the viscosity of the melt will increase due to cooling and solidify. Therefore, it is preferable to preheat the roller 301 at a position in front of the melt transfer mechanism 200 to reduce the possibility of melt cooling. A heater 500 can be provided at a corresponding position on the roller 301, and the heating temperature of the heater 500 is greater than or equal to the temperature of the first heating unit 204..

[0120] The second meltblown spinning device further includes: a fiber collection mechanism, which is arranged in the outlet direction of the melt stretching mechanism 400 and is located outside the roller 301. Preferably, the fiber collection mechanism can be a filter basket with mesh holes, the roller 301 or a reciprocating mesh belt, and is used to collect the stretched fibers. The vertical distance between the melt stretching mechanism 400 and the fiber collection mechanism is in the range of 20 - 80 cm, and the obtained fiber form can be in the form of a film, felt or fluffy cotton.

[0121] Based on the above structure, the second meltblown spinning device of the present invention can form the following several structural examples: Example 1: Such as Figure 8As shown in the figure, the outlet end of the melt transfer mechanism 200 has an arc matching the drum 301, and its position is at the upper left outside the drum 301. The inner diameter of the drum 301 is 16 cm. The arc structure at the outlet end of the melt transfer mechanism 200 (i.e., the arc surface 205 of the transfer seat 201) is as close as possible to the arc surface of the drum 301. Preferably, the distance between the two arc surfaces is 3 mm. A heating rod is installed in the hole of the transfer seat 201. Its self-heating function enables the melt to maintain a certain temperature and fluidity during the transfer process through the transfer seat 201. The heating temperature of the transfer seat 201 is 10° higher than the temperature of the melt feeding and heating mechanism 100; the front end of the transfer seat 201 has a melt inlet matching the screw extruder, and the rear end has a strip-shaped slit 203 for melt extrusion. The length of the strip-shaped slit 203 is less than the width of the drum 301. The melt output mechanism 300 includes a directionally rotating drum 301, a motor, and a support frame 302. The drum 301 is installed on the support frame 302 and rotates clockwise by the motor relying on a synchronous pulley. The surface of the drum 301 has through holes in the shape of an array of rectangular grids 3013. The cross-section of the through holes is perpendicular to the direction of the strip-shaped slit 203 in the transfer seat 201. The length of the rectangular grid 3013 is 0.05 cm, the width is 0.02 cm, and the length along the axial direction of the through hole is 2 mm. During the directional rotation of the drum 301, the molten thermoplastic polymer is smeared on the surface of the drum 301 through the strip-shaped slit 203 of the closely attached transfer seat 201; the speed of the drum 301 depends on the motor. If the rotation speed is too fast, the melt will not have enough time to be stretched. If the rotation speed is too slow, the viscosity of the melt will increase due to cooling and solidify. Therefore, the drum 301 is preheated at a position in front of the melt transfer mechanism 200, specifically at the lower left, to reduce the possibility of melt cooling. In the melt stretching mechanism 400, the position of the second air knife 401 is inside the drum 301 and perpendicular to the tangent plane of the drum 301.

[0122] Example 2: As Figure 9 shown, different from Example 1, the surface of the drum 301 is composed of an array of square grids 3012, replacing the rectangular grid 3013 in Embodiment 1. The melt transfer mechanism 200 is located at the upper right outside the drum 301, and the fibers are collected on a reciprocating mesh belt perpendicular to the direction of the second air knife.

[0123] Example 3: Different from Example 1, the surface of the drum 301 is composed of an array of round holes, replacing the rectangular grid 3013 in Embodiment 1. The melt transfer mechanism 200 is located at the lower right outside the drum 301, and the position of the second air knife 401 is inside the drum 301. The fibers fall into the fiber collection mechanism from top to bottom.

[0124] Embodiment 1B The second meltblown spinning device described in Example 1 above is used to prepare crimped nanofibers, and the specific process is as follows: Turn on the temperature switch of the melt feeding and heating mechanism 100, and set the temperature parameters of the four heating zones to 50°C, 190°C, 230°C, and 260°C respectively. The temperature of the transfer seat 201 is set to 270°C, and the temperature of the heater 500 is set to 280°C. After the temperature reaches the set value and stabilizes, set the screw speed; then start the air compressor, and set the air pressure and temperature to control the temperature and air flow velocity of the hot air flow at the outlet of the second air knife 401, where the temperature of the hot air flow at the outlet of the second air knife 401 is 295°C, and the air flow velocity is shown in Table 3 specifically. After the temperature is constant, start and set the rotation speed of the drum as shown in Table 3 specifically. Add the meltblown grade resin raw material (shown in Table 3 specifically) to the feeding port of the screw extruder. The gap between the second air knife 401 and the drum 301 is 1 cm, the rotational path distance between the second air knife and the transfer mechanism 200 is 1 cm, the gap of the second air knife 401 is 0.24 mm, and the horizontal distance between the drum 301 and the reciprocating collecting mesh belt is 80 cm.

[0125] Example 2B It is basically the same as Example 1B, except that: the rotation speed of the drum is shown in Table 3 specifically.

[0126] Example 3B The second meltblown spinning device described in Example 2 above is used to prepare crimped nanofibers, and the specific process is basically the same as that of Example 1B, except that: the side length of the grid on the surface of the drum 301 is 0.02 cm.

[0127] Example 4B The second meltblown spinning device described in Example 3 above is used to prepare crimped nanofibers, and the specific process is basically the same as that of Example 1B, except that: the diameter of the round hole on the surface of the drum 301 is 0.015 cm.

[0128] Comparative Example 1B It is basically the same as Example 1B, except that: the width of the rectangular grid 3013 is shown in Table 3 specifically.

[0129] Comparative Example 2B It is basically the same as Example 1B, except that: the rotation speed of the drum is shown in Table 3 specifically.

[0130] Table 3

[0131] Test the crimp number and average fiber diameter of the fibers obtained in Examples 1B - 4B and Comparative Examples 1B - 2B above, as shown in Table 4 specifically.

[0132] Table 4

[0133] Furthermore, the fiber morphology prepared in Example 1A is as Figure 18 shown.

[0134] Furthermore, to verify the industrial application prospect of the method shown in Example 4A of the present invention, specifically, spinning for 2 hours according to the parameters of Example 4A to obtain 400 g of fiber cotton.

[0135] Furthermore, test the microstructure of the fiber cotton with a grammage of 150 - 600 g / m 2 prepared by the method shown in Example 4A of the present invention, as Figure 19 shown, and test its heat preservation performance and thermal and moisture comfort. The results are as Figure 20 and 21 shown. The fiber cotton has good heat preservation performance, the Clo value is between 2.1 and 5.4 Clo, the air permeability is between 57 and 185 mm / s, and the moisture permeability is as high as 5900 g / m 2 / 24 h or more.

[0136] Furthermore, test the microstructure of the fiber cotton prepared by the method shown in Comparative Example 1A of the present invention, as Figure 22 shown. The fibers are relatively thick, mostly micron-sized, and have less crimp.

[0137] Furthermore, the physical picture of the composite fiber cotton prepared in Example 6A is as Figure 23 shown, and test the application performance of the composite fiber cotton prepared in Example 6A. The results are as Figures 24 - 25 shown. The Clo value of this composite fiber cotton is 2.9 Clo, the air permeability is as high as 290 mm / s, and the moisture permeability is higher than 7000 g / m 2 / 24 h; at the same time, the PET fibers in this fiber cotton have good elasticity, making this fiber cotton have excellent compression resilience.

[0138] Perform performance tests on the fiber aggregates prepared in the above examples of the present invention. The test results show that: the grammage of the fiber cotton prepared can reach 150 - 600 g / m 2 , and test its heat preservation performance and thermal and moisture comfort. It is found that the fiber cotton has good heat preservation performance, the Clo value is between 2 and 6 Clo, the air permeability is between 50 and 290 mm / s, and the moisture permeability is higher than 5900 g / m 2 / 24 h.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing coiled nanofibers based on a meltblowing process without spinneret holes, characterized in that, Comprising: The hot air stream passes through a number of pores in a moving state to form a turbulent flow, causing the molten thermoplastic polymer located in the number of pores to be stretched by the hot air stream to form the curled nanofibers at one time; The temperature at the pores in contact with the molten thermoplastic polymer is higher than or equal to the temperature of the molten thermoplastic polymer; The hot air stream is output from the air outlet of the air supply assembly. The air flow velocity of the hot air stream at the air outlet is 250 - 320 m / s. The temperature of the hot air stream at the air outlet is higher than or equal to the temperature of the molten thermoplastic polymer. The distance between the air outlet and the pores is below 3 cm.

2. The method for preparing crimped nanofibers based on a non-spinneret meltblowing process according to claim 1, wherein The temperature of the molten thermoplastic polymer is 250 - 300 °C.

3. The method for preparing crimped nanofibers based on the meltblowing process without spinneret holes according to claim 1 or 2, characterized in that, The number of pores is located on the screen, and the rotation speed of the screen is 2 - 6 rpm; The mesh number of the screen is 40 - 100.

4. The method for preparing curly nanofibers based on the non-spinneret meltblowing process according to claim 3, characterized in that, The screen is located in the first meltblown spinning device, and the first meltblown spinning device includes: A frame; A melt treatment mechanism, provided on the frame, for outputting the molten thermoplastic polymer and forming the hot air stream to perform the stretching on the molten thermoplastic polymer; A driving mechanism; A rotation positioning mechanism, provided on the frame and connected to the driving mechanism, and driven by the driving mechanism to drive the rotation positioning mechanism to rotate; A screen, oppositely arranged with the outlet end of the melt treatment mechanism and connected to the rotation positioning mechanism. The screen is positioned by the rotation positioning mechanism and driven to rotate. A plurality of micropores are evenly distributed on the screen. The plurality of micropores are used for the molten thermoplastic polymer dispersed on the screen, and the micropores extending along the axial direction also form a diversion channel. The hot air stream performs stretching on the molten thermoplastic polymer through the diversion channel.

5. The method for preparing crimped nanofibers based on the meltblowing process without spinneret holes according to claim 4, characterized in that, The air supply assembly includes: An air compressor, for forming the air flow velocity of the hot air stream; An air knife, connected to the air compressor, and a second heating unit is provided between the air compressor and the air knife. The second heating unit is used for heating the air stream to form the temperature of the hot air stream; The edge of the air knife is the air outlet.

6. The method for preparing crimped nanofibers based on a nozzleless meltblowing process according to claim 1 or 2, characterized in that, The number of pores is located on the drum, and the rotation speed of the drum is 2 - 5 rpm; The through holes on the drum are slits with a width below 0.05 cm or micropores with a pore diameter below 0.05 cm.

7. The method for preparing crimped nanofibers based on the non-spinneret meltblowing process according to claim 6, characterized in that, The drum is located in the second meltblown spinning device, and the second meltblown spinning device includes: A melt feeding and heating mechanism, for loading the thermoplastic polymer and heating the thermoplastic polymer to the molten state; A melt transfer mechanism, connected to the outlet end of the melt feeding and heating mechanism; A melt output mechanism, including: a drum capable of rotating in a direction, the drum is opposite to and close to the outlet of the melt transfer mechanism, and a plurality of the through holes are formed on the surface of the drum; A melt stretching mechanism, facing the drum; When the molten thermoplastic polymer is applied to the surface of the drum through the melt transfer mechanism and enters the through holes, the molten thermoplastic polymer is stretched by the hot air stream to pass through the through holes to form a polymer jet.

8. The method for preparing crimped nanofibers based on the meltblowing process without spinneret holes according to claim 7, wherein, The air supply assembly includes: An air knife is provided inside the drum, and the air knife is located behind the melt transfer mechanism along the rotation direction of the drum; the melt transfer mechanism is provided outside the drum; the blade edge of the air knife is the air outlet. An air compressor is connected to the air knife and is used to form the air flow velocity of the hot air flow; the air flow velocity of the hot air flow at the air outlet is 260 - 320 m / s. A second heating unit is provided between the air compressor and the air knife and is used to heat the air flow to form the temperature of the hot air flow.

9. A coiled nanofiber aggregate, characterized in that, Obtained by the method for preparing curly nanofibers based on the non-spinneret meltblowing process according to any one of claims 1 - 8; The number of curls of the curly nanofiber aggregate is 100 - 700 curls / cm, and the average diameter of the curly nanofibers is less than 1 μm.

10. The crimped nanofiber aggregate according to claim 9, wherein The Cro value of the crimped nanofiber floc is 2 to 6 Clo, the air permeability is 50 to 290 mm / s, and the moisture permeability is higher than 5900 g / m 2 / 24 h.

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