Needleless meltblown spinning device, working method and nanofiber preparation method

Abstract

The present application relates to the technical field of fiber spinning equipment, and particularly relates to a needleless melt-blow spinning device, a working method and a nanofiber preparation method. The needleless melt-blow spinning device comprises a feeding mechanism, a melt heating mechanism, a melt output mechanism, a melt traction mechanism and a fiber collecting mechanism. The melt heating mechanism is used for heating and melting the melt-blow grade resin material; the melt output mechanism comprises a filter screen which passes through the melt heating mechanism, and a polymer melt is scraped and coated in the through hole of the filter screen; the melt traction mechanism is used for blowing a gas flow to the filter screen which passes through the melt heating mechanism, and the polymer melt on the filter screen is hot drawn to form a polymer jet; and the fiber collecting mechanism is used for collecting the polymer fiber. The present application can be used for preparing nanofibers, and overcomes the problems of difficult jet hole processing and high cost in the traditional melt-blow process, and low nanofiber preparation efficiency, and avoids the problem of easy clogging of the jet hole in the traditional melt-blow device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber spinning equipment, in particular to a needle-free melt-blow spinning device, a working method and a nanofiber preparation method. BACKGROUND

[0002] The melt-blow process is an industrialized method of using high-temperature high-speed airflow to draw the polymer melt stream extruded from the spinneret. The traditional melt-blow method is to extrude the melt jet through the spinneret hole with a diameter of 0.1-0.3mm, and the fiber diameter depends on the spinneret hole. The smaller the spinneret hole, the thinner the fiber diameter. The processing precision of the spinneret hole is high, the polishing difficulty is great, and the production cost is high. In the melt-blow production process, problems such as spinneret hole blockage often occur, and it is necessary to stop production for cleaning and polishing, which limits the continuous long-term use of the melt-blow spinning device. Moreover, the fiber diameter obtained by the traditional melt-blow spinning device is mostly 2-5μm, and the limitation of the spinneret hole makes it impossible to prepare nanofibers below 1μm. Existing nanofiber preparation methods such as electrospinning, centrifugal spinning and air spinning all require the use of solvents, most of which are toxic, and solvent recovery is difficult. The spinning process is also susceptible to temperature and humidity, and new technologies such as melt electrospinning have low production efficiency and are difficult to industrialize. Therefore, the development of a needle-free melt-blow spinning device has great research significance and broad application prospects for realizing low-cost processing and batch production of nanofibers. SUMMARY

[0003] The present application provides a needle-free melt-blow spinning device, a working method and a nanofiber preparation method, which solves the defects of difficult nanofiber preparation and high cost of the traditional melt-blow spinning device in the prior art, has the advantages of simple structure and processing, convenient waste cleaning, low cost, no solvent residue and environmental friendliness, and can realize batch production of nanofibers, which has important significance for the industrial production of nanofibers.

[0004] The present application provides a needle-free melt-blow spinning device, comprising:

[0005] A feeding mechanism for feeding melt-blow grade resin material;

[0006] A melt heating mechanism located downstream of the feeding mechanism for heating and melting the melt-blow grade resin material to form a polymer melt with fluidity;

[0007] A melt output mechanism comprising a filter screen capable of directional movement, the filter screen being formed with an array of through holes, the filter screen passing through the melt heating mechanism, and under the directional movement of the filter screen, the polymer melt being coated on the through holes of the filter screen;

[0008] A melt traction mechanism, located downstream of the melt heating mechanism, is used to blow airflow into the filter screen that passes through the melt heating mechanism, thereby thermally stretching the polymer melt on the filter screen to form a polymer jet.

[0009] The fiber collecting mechanism is located downstream of the airflow blowing direction of the melt traction mechanism. After the polymer jet is cooled, it forms polymer fibers, and the fiber collecting mechanism is used to collect the polymer fibers.

[0010] According to the needleless meltblown spinning apparatus provided by the present invention, the melt heating mechanism includes: a first heating plate and a second heating plate arranged opposite to each other, and a filter screen conveying channel is provided between the first heating plate and the second heating plate. The filter screen moves directionally through the filter screen conveying channel, and the first heating plate is arranged close to the discharge port of the feeding mechanism. A feeding hole communicating with the filter screen conveying channel is formed on the first heating plate.

[0011] According to the needleless meltblown spinning apparatus provided by the present invention, the filter conveying channel includes: a first groove structure formed on the side of the second heating plate near the first heating plate, the filter being embedded in the first groove structure, one end of the first groove structure being located below the feeding hole, the bottom wall surface of the first groove structure being inclined, and the bottom wall surface being inclined upward from the end near the feeding hole to the end away from the feeding hole, and the moving direction of the filter being from the end of the bottom wall surface near the feeding hole toward the end away from the feeding hole.

[0012] According to the needleless meltblown spinning device provided by the present invention, the slope of the first tank structure ranges from 3.5% to 8%.

[0013] According to the needleless meltblown spinning apparatus provided by the present invention, the filter conveying channel further includes: a second groove structure formed on the side of the second heating plate near the first heating plate, the second groove structure being located at the end of the first groove structure away from the feeding hole, and the second groove structure being horizontally arranged.

[0014] According to the needleless meltblown spinning device provided by the present invention, the melt output mechanism further includes: a support and a plurality of drive units; each of the drive units is disposed on the support, and the filter screen is connected end to end and tensioned and supported on each of the drive units, and the drive unit is used to drive the filter screen to move in a directional manner.

[0015] According to the needleless meltblown spinning device provided by the present invention, each of the driving units includes: a support base and a roller. The support base is fixed on the bracket, and the roller is rotatably disposed on the support base, supporting the filter screen in a quadrilateral structure and driving the filter screen to move in a specific direction.

[0016] According to the needleless meltblown spinning device provided by the present invention, the speed at which the filter screen moves directionally under the drive of the drive unit ranges from 10 to 85 cm / min.

[0017] According to the needleless meltblown spinning apparatus provided by the present invention, the melt traction mechanism includes an air compressor, a heating unit and an air knife, wherein the air compressor is connected to the air knife through the heating unit, and the blade of the air knife faces the location of the filter screen at the outlet end of the melt heating mechanism.

[0018] According to the needleless meltblown spinning device provided by the present invention, the vertical distance between the blade of the air knife and the filter screen ranges from 0.5 to 1.5 cm, and the horizontal distance ranges from 1 to 5 cm.

[0019] According to the needleless meltblown spinning device provided by the present invention, the mesh size of the filter screen ranges from 50 to 200 meshes, and the thickness ranges from 0.1 to 0.3 mm.

[0020] According to the needleless meltblown spinning device provided by the present invention, the through holes in the filter screen are square through holes, and the side length of the square through holes ranges from 0.08 to 0.4 mm. The square through holes serve as airflow microchannels, guiding the airflow ejected by the melt traction mechanism to transition into turbulence.

[0021] According to the needleless meltblown spinning device provided by the present invention, the vertical distance between the fiber collecting mechanism and the filter screen ranges from 15 to 30 cm.

[0022] The present invention also provides a method for operating the needleless meltblown spinning device according to the above embodiments of the present invention, comprising: adding meltblown resin particles to the feeding mechanism, and the meltblown resin particles entering the melt heating mechanism under the influence of gravity;

[0023] The melt heating mechanism heats and melts the meltblown resin particles to form a fluid polymer melt. The directionally moving filter screen passes through the melt heating mechanism, and the polymer melt is scraped into the through holes of the filter screen.

[0024] When the filter screen moves out from the outlet end of the melt heating mechanism, the melt traction mechanism blows hot air towards the filter screen to thermally stretch the polymer melt and form a polymer jet.

[0025] After the polymer jet cools, it forms polymer fibers, which are collected by a fiber collection mechanism.

[0026] According to the working method of the needleless meltblown spinning device provided by the present invention, the step of the melt heating mechanism heating and melting the meltblown resin particles specifically includes:

[0027] The melt heating mechanism heats and melts the meltblown resin particles, maintaining the temperature of the polymer melt between 220°C and 260°C.

[0028] According to the working method of the needleless meltblown spinning device provided by the present invention, the step of the melt traction mechanism blowing hot air towards the filter screen when the filter screen is moved out from the outlet end of the melt heating mechanism specifically includes:

[0029] When the filter screen is removed from the outlet end of the melt heating mechanism, the melt traction mechanism blows an airflow with a temperature of 240℃-310℃ and a flow rate of 246-380m / s toward the filter screen.

[0030] The present invention also provides a method for preparing nanofibers, which prepares nanofibers using the needleless meltblown spinning device in the above embodiments of the present invention or by using the working method of the needleless meltblown spinning device in the above embodiments of the present invention.

[0031] This invention provides a needleless meltblown spinning device, comprising: a feeding mechanism, a melt heating mechanism, a melt output mechanism, a melt traction mechanism, and a fiber collecting mechanism; wherein, the feeding mechanism is used to feed meltblown-grade resin material; the melt heating mechanism, located downstream of the feeding mechanism, is used to heat and melt the meltblown-grade resin material to form a fluid polymer melt; the melt output mechanism includes: a filter screen capable of directional movement, the filter screen having an array of through holes, the filter screen passing through the melt heating mechanism, and the polymer melt being scraped into the through holes of the filter screen under the directional movement of the filter screen; the melt traction mechanism, located downstream of the melt heating mechanism, is used to blow hot airflow onto the filter screen exiting the melt heating mechanism, thermally stretching the polymer melt on the filter screen to form a polymer jet; the fiber collecting mechanism, located downstream of the airflow blowing direction of the melt traction mechanism, forms polymer fibers after the polymer jet cools, and is used to collect the polymer fibers. This invention provides a needleless meltblown spinning device with a simple structure and convenient fiber preparation. The through-holes in the filter screen guide the ejected airflow, promoting turbulence formation and increasing the whipping of the melt jet, thus refining the fibers and obtaining nanofibers. Waste materials remaining in the filter screen and melt heating mechanism are easy to clean, with minimal solvent residue, making it environmentally friendly. The device has low manufacturing costs, overcoming the problems of difficult and costly spinneret processing and low nanofiber preparation efficiency in traditional meltblown processes, and avoiding the problem of easy clogging of spinnerets in traditional meltblown devices.

[0032] The present invention provides a working method for a needleless meltblown spinning device, which has a simple structure, low processing cost and convenience, and can continuously and cyclically prepare fibers. It is expected to realize the mass production of nanofibers, with high fiber preparation efficiency and can meet the needs of nanofiber preparation. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the overall structure of the needleless meltblown spinning device provided in one embodiment of the present invention from a first-view perspective.

[0035] Figure 2 This is a schematic diagram of the overall structure of the needleless meltblown spinning device provided in one embodiment of the present invention from a second perspective.

[0036] Figure 3 This is a schematic diagram of the melt heating mechanism provided in one embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of the structure of the first heating plate provided in one embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the structure of the second heating plate provided in one embodiment of the present invention.

[0039] Figure 6 This is a schematic diagram of the structure of the feeding mechanism and the melt heating mechanism provided in one embodiment of the present invention.

[0040] Figure 7 This is an assembly diagram of the bracket, drive unit, feeding mechanism and melt heating mechanism provided in one embodiment of the present invention.

[0041] Figure 8 This is a schematic diagram of the specific structure of the driving unit provided in one embodiment of the present invention.

[0042] Figure 9 This is a schematic diagram of the specific structure of the melt traction machine provided in one embodiment of the present invention.

[0043] Figure 10 This is a schematic diagram of the structure of the filter, support and drive unit provided in one embodiment of the present invention.

[0044] Figure 11 This is a SEM image of the fiber prepared in Example 1 of this invention.

[0045] Figure 12 This is a diameter distribution diagram of the fibers prepared in Example 1 of the present invention.

[0046] Figure 13This is a SEM image of the fiber prepared in Example 2 of the present invention.

[0047] Figure 14 This is a SEM image of the fiber prepared in Comparative Example 1 of this invention.

[0048] Figure label:

[0049] 100: Feeding mechanism; 200: Melt heating mechanism; 201: First heating plate; 202: Second heating plate; 203: Feeding hole; 204: First tank structure; 205: Second tank structure; 300: Melt output mechanism; 301: Support; 302: Drive unit; 3021: Support base; 3022: Roller; 303: Filter screen; 400: Melt traction mechanism; 401: Air compressor; 402: Heating unit; 403: Air knife. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0051] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0052] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0053] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0055] The following is combined Figures 1 to 14 This invention describes a needleless meltblown spinning apparatus. The needleless meltblown spinning apparatus includes: a feeding mechanism 100, a melt heating mechanism 200, a melt output mechanism 300, a melt traction mechanism 400, and a fiber collecting mechanism (not shown in the figure).

[0056] like Figure 1 and Figure 2 As shown, a feeding mechanism 100 is used to feed meltblown resin material; a melt heating mechanism 200, located downstream of the feeding mechanism 100, is used to heat and melt the meltblown resin material to form a fluid polymer melt; a melt output mechanism 300 includes: a filter screen 303 capable of directional movement, the filter screen 303 having an array of through holes, the filter screen 303 passing through the melt heating mechanism 200, and the polymer melt being scraped into the through holes of the filter screen 303 under the directional movement of the filter screen 303; a melt traction mechanism 400, located downstream of the melt heating mechanism 200, is used to blow airflow into the filter screen 303 that passes through the melt heating mechanism 200, thermally stretching the polymer melt on the filter screen 303 to form a polymer jet; and a fiber collection mechanism, located downstream of the airflow blowing direction of the melt traction mechanism 400, the polymer jet cooling to form polymer fibers, the fiber collection mechanism being used to collect the polymer fibers.

[0057] Specifically, meltblown resin material, preferably meltblown resin particles, is added to the feeding mechanism 100 and fed into the melt heating mechanism 200. The melt heating mechanism 200 heats and melts the meltblown resin particles to form a fluid polymer melt. The filter screen 303 in the melt output mechanism 300 passes through the melt heating mechanism 200 and moves directionally. During the movement of the filter screen 303, the polymer melt inside the melt heating mechanism 200 is scraped into the through holes of the filter screen 303 and adheres to the filter screen 303 as it moves out of the melt heating mechanism 200. The melt traction mechanism 400 blows out a high-temperature, high-speed hot airflow, which sprays the filter screen 303 that has moved out of the melt heating mechanism 200, causing the polymer melt adhering to the filter screen 303 to be thermally stretched to form a polymer jet. The fiber collection mechanism is located below the filter screen 303. The polymer jet cools due to the natural environment and forms polymer fibers, which are collected by the fiber collection mechanism.

[0058] Furthermore, the feeding mechanism 100 can adopt a feeding device such as a hopper or funnel. To match the feeding speed, the bottom diameter and length are designed accordingly based on the amount of resin particles fed, and its width is preferably 0.5-1.5 cm. The melt heating mechanism 200 is mainly used to heat the meltblown resin particles to a molten state. Preferably, the polymer melt temperature is between 220°C and 260°C. The mesh count of the filter screen 303 should not be too low, and the diameter of the through holes should not be too large. It should ensure that the polymer melt can adhere to the through holes and be moved out of the melt heating mechanism 200. The airflow ejected by the melt traction mechanism 400 should be a high-temperature, high-speed hot airflow, with a temperature at least 20°C higher than the polymer melt temperature, thereby thermally tractioning the polymer melt and playing a role in heat preservation or even heating the melt, forming a polymer jet. After the polymer jet moves away from the high-temperature, high-speed hot airflow, it cools at room temperature, forming polymer fibers, which are collected by the fiber collection mechanism. The fiber collection mechanism preferably adopts a single roller, double roller, or collection basket collection device.

[0059] The filter screen 303 has an array of through holes that extend along the thickness direction of the filter screen 303. The through holes have a certain length, meaning that the filter screen 303 has a certain thickness. The through holes can serve as microchannels for guiding the airflow ejected by the melt traction mechanism 400. The array of tiny through holes can help to transform the ejected laminar airflow into turbulent airflow, increase the whipping of the melt jet, and refine the fibers. This provides strong stretching conditions for the preparation of nanofibers.

[0060] Furthermore, based on the required diameter of the fibers, a filter screen 303 with a corresponding mesh count and pore size is designed. This filter is then blown through a melt traction mechanism 400 with an airflow of suitable temperature and flow rate, thereby producing suitable fibers. Based on the parameters of the filter screen 303 and the airflow, nanoscale fibers can be prepared. Moreover, after preparation, the waste remaining on the filter screen 303 can be removed by blowing, and the waste remaining in the melt heating mechanism 200 is also easy to clean.

[0061] This invention provides a needleless meltblown spinning device, comprising: a feeding mechanism 100, a melt heating mechanism 200, a melt output mechanism 300, a melt traction mechanism 400, and a fiber collecting mechanism; wherein, the feeding mechanism 100 is used to feed meltblown-grade resin material; the melt heating mechanism 200, located downstream of the feeding mechanism 100, is used to heat and melt the meltblown-grade resin material to form a fluid polymer melt; the melt output mechanism 300 includes: a filter screen 303 capable of directional movement, the filter screen 303 having an array of through holes, filtering... The filter screen 303 passes through the melt heating mechanism 200. Under the directional movement of the filter screen 303, the polymer melt is scraped into the through holes of the filter screen 303. The melt traction mechanism 400, located downstream of the melt heating mechanism 200, is used to spray airflow onto the filter screen 303 that passes through the melt heating mechanism 200, thermally stretching the polymer melt on the filter screen 303 to form a polymer jet. The fiber collection mechanism, located downstream of the airflow spraying direction of the melt traction mechanism 400, collects the polymer fibers after the polymer jet cools down. This invention provides a needleless meltblown spinning device with a simple structure and convenient fiber preparation. The through-holes in the filter 303 guide the ejected airflow, promoting turbulence formation and increasing the whipping of the melt jet, thus refining the fibers and obtaining nanofibers. Waste materials remaining in the filter 303 and the melt heating mechanism 200 are easy to clean, with minimal solvent residue, making it environmentally friendly. The device has low manufacturing costs, overcoming the problems of difficult and costly spinneret processing and low nanofiber preparation efficiency in traditional meltblown processes, and avoiding the problem of easy clogging of spinnerets in traditional meltblown devices.

[0062] In one embodiment of the present invention, such as Figures 3 to 6As shown, the melt heating mechanism 200 includes: a first heating plate 201 and a second heating plate 202 arranged opposite to each other, and a filter screen 303 conveying channel is provided between the first heating plate 201 and the second heating plate 202. The filter screen 303 moves directionally through the filter screen 303 conveying channel, and the first heating plate 201 is arranged close to the discharge port of the feeding mechanism 100. A feeding hole 203 communicating with the filter screen 303 conveying channel is formed on the first heating plate 201. In this embodiment, the melt heating mechanism 200 adopts a configuration of two heating plates (i.e., the first heating plate 201 and the second heating plate 202) arranged opposite each other, and there is a filter screen 303 conveying channel between the two heating plates for the filter screen 303 to move through. The two heating plates heat and melt the meltblown resin particles to form a polymer melt. With the cooperation of the two heating plates, the polymer melt is coated on the through holes of the filter screen 303. The movement of the filter screen 303 carries the polymer melt out from the first heating plate 201 and the second heating plate 202. Specifically, the filter 303 conveying channel between the first heating plate 201 and the second heating plate 202 is set with a gap between the two in the thickness direction, and the filter 303 can pass through the gap. The first heating plate 201 (that is, the upper heating plate) is located above the second heating plate 202 (that is, the lower heating plate) and has a feeding hole 203. The feeding hole 203 is connected to the discharge port of the feeding mechanism 100 and is used to receive meltblown resin particles and convey them to the gap position between the first heating plate 201 and the second heating plate 202. The first heating plate 201 and the second heating plate 202 are activated to heat and melt the meltblown resin particles.

[0063] A constant-temperature control chamber is used as the heat source for the first heating plate 201 and the second heating plate 202, with a power of 2-4 kW. Two high-temperature resistant heating wires from the constant-temperature control chamber are used to clamp the second heating plate 202 to heat the heating plate, so that the heating temperature of the polymer melt is 220-260℃. Thermocouples are used to monitor the temperature of the heating plate in real time. The heating plate is made of pure copper or stainless steel, which has good heat preservation effect, and is used to heat polymer resin particles to form polymer melt. An elliptical feeding hole 203 is opened at the top of the first heating plate 201. The size of the feeding hole 203 matches the size of the discharge port at the bottom of the feeding mechanism 100. The second heating plate 202 is fixed to the first heating plate 201 with screws, and a gap is ensured between them in the thickness direction to ensure that the filter screen 303 can move through the gap and allow heat transfer between the first heating plate 201 and the second heating plate 202, maintaining a constant temperature between the upper and lower heating plates.

[0064] In one embodiment of the present invention, the filter screen 303 conveying channel includes: a first groove structure 204 formed on the side of the second heating plate 202 near the first heating plate 201, the filter screen 303 being embedded in the first groove structure 204, one end of the first groove structure 204 being located below the feeding hole 203, the bottom wall surface of the first groove structure 204 being inclined, and the bottom wall surface being inclined upward from the end near the feeding hole 203 to the end away from the feeding hole 203, and the moving direction of the filter screen 303 being from the end of the bottom wall surface near the feeding hole 203 toward the end away from the feeding hole 203. In this embodiment, a first groove structure 204 is formed on the upper surface of the second heating plate 202 (i.e., the lower heating plate). The inlet end of the first groove structure 204 corresponds to the feeding hole 203 of the first heating plate 201 (i.e., the upper heating plate). Meltblown resin particles are fed directly into and stored in the first groove structure 204 through the feeding hole 203. The upper and lower heating plates are activated to heat up, forming a polymer melt with a certain fluidity. Because the bottom wall of the first groove structure 204 slopes upward from the inlet end to the outlet end, the gap between the first reinforcing plate and the second reinforcing plate gradually decreases along the moving direction of the filter screen 303. The polymer melt is gradually scraped and spread evenly in the first groove structure 204 to ensure that the polymer melt in each through hole of the filter screen 303 is uniform. Figure 5 As shown in the figure, the x-direction pointed to by the arrow is the direction in which filter 303 moves.

[0065] In one embodiment of the present invention, the slope of the first tank structure 204 is in the range of 3.5%-8%. Within this slope range, the first tank structure 204 can ensure that the polymer melt is carried out by the moving filter screen 303, and also ensure that the polymer melt is scraped and spread evenly.

[0066] In one embodiment of the present invention, the filter screen 303 conveying channel further includes: a second trough structure 205 formed on the side of the second heating plate 202 near the first heating plate 201, the second trough structure 205 being located at the end of the first trough structure 204 away from the feeding hole 203, and the second trough structure 205 being horizontally arranged. In this embodiment, the second trough structure 205 is provided at the outlet end of the first trough structure 204, and the second trough structure 205 is used for secondary coating of the polymer melt. Through the primary coating of the first trough structure 204 and the secondary coating of the second trough structure 205, the polymer melt can be uniformly coated. Specifically, the height of the second trough structure 205 is level with the height of the outlet end of the first trough structure 204, and the two are interconnected to allow the polymer melt to flow through and the filter screen 303 to move, and the second trough structure 205 is horizontally arranged. It should be understood that the second tank structure 205 is also a tank structure formed on the second heating plate 202. However, compared with the inclined first tank structure 204, the second tank structure 205 is arranged horizontally and is used for secondary coating.

[0067] In one embodiment of the present invention, the melt output mechanism 300 further includes a support 301 and multiple drive units 302. Each drive unit 302 is mounted on the support 301, and a filter screen 303 is connected end-to-end and tensioned and supported on each drive unit 302. The drive units 302 are used to drive the filter screen 303 to move in a specific direction. In this embodiment, the filter screen 303 is a strip-shaped structure connected end-to-end, tensioned and arranged on each drive unit 302, and the drive units 302 drive the filter screen 303 to move. Because the filter screen 303 has an end-to-end structure, it can move continuously in a cyclical manner, thereby achieving uninterrupted batch production of fibers and improving work efficiency.

[0068] In one embodiment of the present invention, such as Figure 8 As shown, each drive unit 302 includes a support base 3021 and a roller 3022. The support base 3021 is fixed on the bracket 301, and the roller 3022 is rotatably mounted on the support base 3021. The roller supports the filter screen 303 in a quadrilateral structure and drives the filter screen 303 to move in a specific direction. In this embodiment, four drive units 302 are provided to support and drive the filter screen 303, so that the filter screen 303 forms a quadrilateral structure. Preferably, as shown... Figure 10 As shown, the filter screen 303 has a parallelogram structure. Each drive unit 302 consists of a support base 3021 and a roller 3022. The roller 3022 can be driven by a motor, and the roller 3022 rotates, causing the filter screen 303 to move in a specific direction.

[0069] In one embodiment of the present invention, the speed at which the filter screen 303 moves directionally, driven by the driving unit 302, ranges from 10 to 85 cm / min. When the driving unit 302 drives the filter screen 303 to move directionally at a preset speed, the speed range of 10-85 cm / min ensures that the polymer melt is sufficiently and uniformly adhered to each through-hole of the filter screen 303. If the filter screen 303 moves too fast, the polymer melt may be unevenly applied or may be thrown off the filter screen 303; if the filter screen 303 moves too slowly, the polymer melt may affect the fiber preparation efficiency.

[0070] In one embodiment of the present invention, such as Figure 9 As shown, the melt traction mechanism 400 includes an air compressor 401, a heating unit 402, and an air knife 403. The air compressor 401 is connected to the air knife 403 through the heating unit 402, and the blade of the air knife 403 faces the location of the filter screen 303 at the outlet end of the melt heating mechanism 200. In this embodiment, the air compressor 401 provides high-pressure airflow, which is heated into high-temperature airflow in the heating unit 402. The high-temperature, high-speed hot airflow is ejected through the air knife 403 and blows onto the filter screen 303. The high-temperature, high-speed hot airflow passes through the through holes formed by the cylindrical metal wires woven in the upper array of the filter screen 303. According to the Karman vortex street principle, the regular laminar flow is transformed into turbulent flow, increasing the whipping of the melt jet and refining the fibers. The gap width of the air knife 403 used in this embodiment is easily adjustable and can generate supersonic airflow, which is beneficial to increasing the airflow stretching force and realizing the preparation of nanofibers in this invention. Preferably, the heating unit 402 can be an air heater.

[0071] In one embodiment of the present invention, such as Figure 7 , 9 As shown in Figure 10, in addition to the drive unit 302 being mounted on the bracket 301, the feeding mechanism 100, the melt heating mechanism 200, and the heating unit 402 are also mounted on the bracket 301. The bracket 301 provides support and component mounting for the entire device.

[0072] The air knife 403 is made of a material that can withstand a high temperature of at least 260°C, preferably aluminum alloy or stainless steel. The gap between the air knives can be widened or narrowed by adding or removing shims inside the air knife 403 according to the required air velocity, or the air pressure in the output pipe of the air compressor 401 can be adjusted by a pressure reducing valve. Reducing the number of shims or increasing the air pressure can increase the air velocity at the air knife 403 inlet. Preferably, the thickness of each shim is 0.05-0.08 mm. The air knife 403 is preferably made of high-temperature resistant stainless steel; the material of the pipe used for the output airflow is also preferably high-temperature resistant stainless steel.

[0073] In one embodiment of the present invention, the vertical distance between the blade of the air knife 403 and the filter screen 303 ranges from 0.5 to 1.5 cm, and the horizontal distance ranges from 1 to 5 cm, to ensure that the hot airflow passes through the through holes of the filter screen 303, effectively forming turbulence and providing heat preservation or even heating for the melt. The distance between the blade of the air knife 403 and the filter screen 303 should not be too large, as this will cool the melt and affect the generation of turbulence; the distance should also not be too small, otherwise, the blade of the air knife 403 may come into contact with the polymer melt, or the polymer melt may splash onto the blade of the air knife 403 during the blowing process.

[0074] In one embodiment of the present invention, the mesh count of the filter 303 is in the range of 50-200 mesh, the thickness is in the range of 0.1-0.3 mm, and the wire diameter is in the range of 0.08-0.18 mm.

[0075] In one embodiment of the present invention, the through holes in the filter screen 303 are square through holes, with the side length of the square through holes ranging from 0.08 to 0.4 mm. The square through holes serve as microchannels for airflow, guiding the airflow ejected by the melt traction mechanism 400 to transition into turbulence. By arranging small-diameter square through holes, on the one hand, microchannels for airflow are provided, forming turbulence and increasing the whipping of the melt jet, thus refining the fibers; on the other hand, the small diameter and uniform array distribution of the square through holes enable the preparation of nanoscale fibers while ensuring the continuity of fiber preparation.

[0076] In one embodiment of the present invention, the vertical distance between the fiber collecting mechanism and the filter screen 303 is in the range of 15-30 cm. At this distance, the ejected polymer jet can solidify into polymer fibers under ambient cooling. If the distance between the fiber collecting mechanism and the filter screen 303 is too small, the polymer jet cannot be cooled sufficiently, and the polymer fibers will not form completely; if the distance between the fiber collecting mechanism and the filter screen 303 is too large, the collected fibers will be more dispersed, and the collection efficiency will be low.

[0077] The present invention also provides a method for operating the needleless meltblown spinning device according to the above embodiments of the present invention. The method specifically includes the following steps:

[0078] S1. Meltblown resin particles are added to the feeding mechanism 100. Due to gravity, the meltblown resin particles enter the melt heating mechanism 200.

[0079] S2. The melt heating mechanism 200 heats and melts the meltblown resin particles to form a fluid polymer melt. The directionally moving filter screen 303 passes through the melt heating mechanism 200, and the polymer melt is scraped into the through holes of the filter screen 303.

[0080] S3. When the filter screen 303 moves out from the outlet end of the melt heating mechanism 200, the melt traction mechanism 400 blows hot air towards the filter screen 303 to thermally stretch the polymer melt and form a polymer jet.

[0081] S4. After the polymer jet cools, it forms polymer fibers, which are collected by a fiber collection mechanism.

[0082] Specifically, meltblown resin particles are added to the feeding mechanism 100. Under the influence of gravity, the resin particles fall through the feeding hole 203 of the first heating plate 201 (upper heating plate), which communicates with the bottom of the feeding mechanism 100, into the second heating plate 202 (lower heating plate). Both heating plates contain resistance wires, and a constant temperature control box regulates the temperature of the heating plates. The heating plates heat and melt the polymer resin particles, forming a fluid polymer melt. The gap between the upper and lower heating plates gradually decreases along the running direction of the filter screen 303. The filter screen 303 is supported in a quadrilateral shape by four rollers 3022 on the support 301 and moves directionally. The filter screen 303 shuttles between the upper and lower heating plates. Between the heating plates, a reciprocating motion is performed. The moving speed of the filter screen 303 is controlled by a servo drive and a motor to ensure stable operation. The directional moving filter screen 303 passes through the upper and lower heating plates, and the polymer melt is scraped and coated into the array of through holes of the filter screen 303. The gradually decreasing gap between the heating plates scrapes and spreads the polymer melt evenly. The compressed air generated by the air compressor 401 passes through the air heater to generate a high-temperature and high-speed airflow. The high-temperature and high-speed airflow enters the air knife 403 and thermally stretches the polymer melt on the filter screen 303 directly below the air knife 403 to form a polymer jet. The polymer jet is naturally cooled by the ambient room temperature air to form polymer fibers, which are collected by the fiber collection mechanism.

[0083] The present invention provides a working method for a needleless meltblown spinning device, which has a simple structure, low processing cost and convenience, can continuously and cyclically prepare fibers, can realize mass production of fibers, has high fiber preparation efficiency, and can meet the needs of nanofiber preparation.

[0084] In one embodiment of the present invention, the step of heating and melting the meltblown resin particles by the melt heating mechanism 200 in step S2 specifically involves: the melt heating mechanism 200 heating and melting the meltblown resin particles, and maintaining the temperature of the polymer melt between 220°C and 260°C. At this temperature, it is ensured that the meltblown resin particles are sufficiently heated and in a molten state, so as to achieve meltblown spinning.

[0085] In one embodiment of the present invention, in step S3 above, when the filter screen 303 moves out from the outlet end of the melt heating mechanism 200, the melt traction mechanism 400 blows hot air towards the filter screen 303, specifically: when the filter screen 303 moves out from the outlet end of the melt heating mechanism 200, the temperature of the airflow blown by the melt traction mechanism 400 towards the filter screen 303 is 20°C-50°C higher than the melt, that is, 240°C-310°C, and the flow rate is 246-380m / s. Under the blowing of this high-temperature and high-speed airflow, not only is the melt heated, but the polymer jet in the through holes of the filter screen 303 is also thermally stretched, which is beneficial to fiber formation.

[0086] The present invention also provides a method for preparing nanofibers. This method utilizes the needleless meltblown spinning apparatus described in the above embodiments of the present invention to prepare fibers, or employs the operating method of the needleless meltblown spinning apparatus according to the present invention to prepare fibers.

[0087] Example 1:

[0088] Polypropylene nanofibers were prepared using the needleless meltblown spinning device described in the above embodiments. The raw material used was polypropylene granules with a melt index of 1500. The equipment parameters were as follows: the heating plate temperature was 260℃; in this example, the moving speed of the metal filter 303 was controlled by motor adjustment; the width of the metal filter 303 was 4cm and the mesh size was 100 mesh; to achieve effective fiber stretching, in this embodiment, the running speed of the metal filter 303 was 15cm / min by adjusting the speed of the servo driver and the motor; the width of the air knife 403 was 5cm and the gap width of the air knife 403 was 0.05mm; the thickness of the gasket used was 0.05mm, slightly larger than the width of the metal filter 303, to ensure that the air velocity was uniform in the width direction of the metal filter 303; the air pressure in the airflow pipe was 0.4MPa; the temperature of the air heater was set to 280℃, which was 20℃ higher than the melt temperature, to keep the melt on the filter 303 warm; and the distance between the filter 303 and the receiving basket was 30cm. The morphology and diameter distribution of PP fibers prepared using the parameters in this embodiment are referenced. Figure 11 and Figure 12 As shown in the SEM image and fiber diameter distribution diagram, the prepared PP fiber has a smooth surface and its diameter is in the range of 200-600nm, with most of the fiber diameters being at the nanoscale.

[0089] Example 2:

[0090] Fibers were prepared using a needleless meltblown spinning apparatus with different parameters, essentially the same as in Example 1, except that the metal filter 303 used had a mesh size of 150 and a diameter of 0.11 mm, and the operating speed of the metal filter 303 was 20 cm / min. All other parameters were the same as in Example 1. Due to the increased mesh size, the through-holes in the metal filter 303 became smaller, resulting in a slight increase in melt extrusion pressure. To ensure the polymer stream flowed down the filter, the airflow pressure was increased to 0.45 MPa. Because the operating speed of the metal filter 303 was faster, a small portion of the polymer stream was not fully stretched, leading to increased fiber diameter non-uniformity. The uniformity was worse than in Example 1, with diameters ranging from 100 to 768 mm. Figure 13 This is a SEM image of the fiber product in Example 2.

[0091] Example 3:

[0092] Fibers were prepared using a needleless meltblown spinning device with different parameters, which was basically the same as in Example 1, except that the polymer used was polylactic acid (NatureWorks6252D), the heating plate temperature was set to 235°C, the air pressure was 0.3MPa, the airflow temperature was 270°C, the viscosity of polylactic acid was higher than that of polypropylene, and in this example, the metal filter screen selected was 303 mesh with a mesh number of 80 and a wire diameter of 0.1mm. The resulting fiber diameter was relatively large, ranging from 500 to 800nm.

[0093] Comparative Example 1

[0094] Polypropylene (PP) was spun using a commercial meltblown spinning device, with spinning parameters basically the same as in Example 1. The meltblown screw extruder used was an SJ35, with the temperatures of the die barrel heating zones one through four being 175°C, 190°C, 215°C, and 240°C, respectively, and the die temperature being 260°C. Polypropylene masterbatch was added to the hopper, and polypropylene fibers were extruded through the die and collected on a horizontally running mesh belt. The screw diameter was 35 mm, the spinneret orifice size was 0.2 mm, the aspect ratio was set, the air temperature was set to 280°C, the air pressure was adjusted to 0.4 MPa via a pressure reducing valve, and the receiving distance was set to 30 cm. The morphology of the PP fibers prepared using the parameters of Comparative Example 1 was used as a reference. Figure 14 As shown, the prepared PP fibers have a smooth surface and a diameter in the range of 2-5 μm, which are micron-sized fibers.

[0095] Comparative Example 2

[0096] Polylactic acid (PLA) was spun using a commercial meltblown spinning device, with spinning parameters basically the same as in Example 3. The meltblown screw extruder used was an SJ35, with the temperatures of the die barrel heating zones one through four being 160°C, 200°C, 215°C, and 235°C, respectively. The die temperature was 235°C. PLA masterbatch was added to the hopper, and PLA fibers were ejected through the die and collected on a horizontally running mesh belt. The screw diameter was 35 mm, the spinneret orifice size was 0.2 mm, the air temperature was set to 270°C, the air pressure was adjusted to 0.3 MPa via a pressure reducing valve, and the receiving distance was set to 30 cm. The fibers prepared using the parameters of Comparative Example 2 had diameters ranging from 3 to 5.8 μm, classifying them as micron-sized fibers.

[0097] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A needleless meltblown spinning device, characterized in that, include: Feeding mechanism (100) is used to feed meltblown resin material; The melt heating mechanism (200), located downstream of the feeding mechanism (100), is used to heat and melt the meltblown resin material to form a fluid polymer melt; The melt output mechanism (300) includes: a filter screen (303) capable of directional movement, the filter screen (303) having an array of through holes, the filter screen (303) passing through the melt heating mechanism (200), and under the directional movement of the filter screen (303), the polymer melt is scraped into the through holes of the filter screen (303); The melt traction mechanism (400), located downstream of the melt heating mechanism (200), is used to spray airflow onto the filter screen (303) that passes through the melt heating mechanism (200) to thermally stretch the polymer melt on the filter screen (303) to form a polymer jet; The fiber collecting mechanism is located downstream of the gas flow direction of the melt traction mechanism (400). After the polymer jet is cooled, polymer fibers are formed. The fiber collecting mechanism is used to collect the polymer fibers. The melt heating mechanism (200) includes a first heating plate (201) and a second heating plate (202) arranged opposite to each other, and a filter screen (303) conveying channel is provided between the first heating plate (201) and the second heating plate (202). The filter screen (303) moves directionally through the filter screen (303) conveying channel. The first heating plate (201) is located near the discharge port of the feeding mechanism (100), and a feeding hole (203) communicating with the filter screen (303) conveying channel is formed on the first heating plate (201). The filter screen (303) conveying channel includes: a first groove structure (204) formed on the side of the second heating plate (202) near the first heating plate (201), the filter screen (303) is embedded in the first groove structure (204), one end of the first groove structure (204) is located below the feeding hole (203), the bottom wall of the first groove structure (204) is inclined, and the bottom wall is inclined upward from the end near the feeding hole (203) to the end away from the feeding hole (203), and the moving direction of the filter screen (303) is from the end of the bottom wall near the feeding hole (203) toward the end away from the feeding hole (203).

2. The needleless meltblown spinning device according to claim 1, characterized in that, The slope of the first trough structure (204) ranges from 3.5% to 8%.

3. The needleless meltblown spinning device according to claim 1, characterized in that, The filter screen (303) conveying channel further includes: a second trough structure (205) is formed on the side of the second heating plate (202) close to the first heating plate (201), the second trough structure (205) is located at the end of the first trough structure (204) away from the feeding hole (203), and the second trough structure (205) is horizontally arranged.

4. The needleless meltblown spinning device according to claim 1, characterized in that, The melt output mechanism (300) further includes: Support (301); Multiple drive units (302) are provided on the bracket (301). The filter screen (303) is connected end to end and tensioned and supported on each drive unit (302). The drive unit (302) is used to drive the filter screen (303) to move in a specific direction.

5. The needleless meltblown spinning device according to claim 4, characterized in that, Each of the drive units (302) includes: a support base (3021) and a roller (3022). The support base (3021) is fixed on the bracket (301), and the roller (3022) is rotatably disposed on the support base (3021), supporting the filter screen (303) in a quadrilateral structure and driving the filter screen (303) to move in a specific direction.

6. The needleless meltblown spinning apparatus according to claim 4, characterized in that, Driven by the drive unit (302), the speed at which the filter screen (303) moves in a directional manner ranges from 10 to 85 cm / min.

7. The needleless meltblown spinning device according to claim 1, characterized in that, The melt traction mechanism (400) includes an air compressor (401), a heating unit (402), and an air knife (403). The air compressor (401) is connected to the air knife (403) through the heating unit (402). The blade of the air knife (403) faces the location of the filter screen (303) at the outlet end of the melt heating mechanism (200).

8. The needleless meltblown spinning apparatus according to claim 7, characterized in that, The vertical distance between the blade of the air knife (403) and the filter screen (303) ranges from 0.5 to 1.5 cm, and the horizontal distance ranges from 1 to 5 cm.

9. The needleless meltblown spinning apparatus according to any one of claims 1 to 8, characterized in that, The mesh size of the filter (303) ranges from 50 to 200 meshes, and the thickness ranges from 0.1 to 0.3 mm.

10. The needleless meltblown spinning device according to claim 9, characterized in that, The filter screen (303) has square through holes with a side length ranging from 0.08 to 0.4 mm. The square through holes serve as airflow microchannels, guiding the airflow ejected by the melt traction mechanism (400) to transition into turbulence.

11. The needleless meltblown spinning apparatus according to any one of claims 1 to 8, characterized in that, The vertical distance between the fiber collecting mechanism and the filter screen (303) ranges from 15 to 30 cm.

12. A method of operating the needleless meltblown spinning device according to any one of claims 1 to 11, characterized in that, include: Meltblown resin particles are added to the feeding mechanism (100), and under the influence of gravity, the meltblown resin particles enter the melt heating mechanism (200). The melt heating mechanism (200) heats and melts the meltblown resin particles to form a fluid polymer melt. The directionally moving filter screen (303) passes through the melt heating mechanism (200), and the polymer melt is scraped into the through holes of the filter screen (303). When the filter screen (303) moves out from the outlet end of the melt heating mechanism (200), the melt traction mechanism (400) blows hot air towards the filter screen (303) to thermally stretch the polymer melt and form a polymer jet; After the polymer jet cools, it forms polymer fibers, which are collected by a fiber collection mechanism.

13. The operating method of the needleless meltblown spinning device according to claim 12, characterized in that, The step of the melt heating mechanism (200) heating and melting the meltblown resin particles specifically includes: The melt heating mechanism (200) heats and melts the meltblown resin particles, and maintains the temperature of the polymer melt between 220°C and 260°C.

14. The operating method of the needleless meltblown spinning device according to claim 12, characterized in that, The step of the filter screen (303) being moved out of the outlet end of the melt heating mechanism (200) and the melt traction mechanism (400) blowing hot air towards the filter screen (303) is specifically as follows: When the filter screen (303) moves out of the outlet end of the melt heating mechanism (200), the melt traction mechanism (400) blows an airflow with a temperature of 240℃-310℃ and a flow rate of 246-380 m / s toward the filter screen (303).

15. A method for preparing nanofibers, characterized in that, Nanofibers are prepared using the needleless meltblown spinning apparatus according to any one of claims 1 to 11 or by the working method of the needleless meltblown spinning apparatus according to any one of claims 12 to 14.

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