Nanofiber melt-blown cloth and preparation method thereof

Abstract

The invention discloses a nanofiber melt-blown fabric and a preparation method thereof. The preparation method comprises the following steps: (1) mixing a polymer material and electret master batch, and performing melt extrusion through an extruder; (2) performing hot air spraying on the melt through a spinneret plate; (3) enabling the fiber sprayed by the spinneret plate to enter a heat-preservation drafting area, and refining the diameter of the fiber under the action of hot air; the distance of the heat preservation drafting area is 500-800 mm, and the hot air temperature of the heat preservation drafting area is 180-220 DEG C; (4) the fibers passing through the heat preservation drafting area enter a cooling area again, and are cooled and solidified under the action of cooling air; and (5) receiving the cooled and cured fibers through a receiving web curtain to form a web, and carrying out electret treatment to obtain the nanofiber melt-blown cloth. The heat preservation drafting area and the cooling area are additionally arranged between the spinneret plate and the receiving web curtain, so that melt can be drafted and refined in a longer receiving web curtain distance, effective control over the fiber diameter is achieved, and nanoscale fibers are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of meltblown cloths, and in particular to a nanofiber meltblown cloth and a preparation method thereof. Background Art

[0002] At present, there are many methods for preparing nanofibers, among which electrospinning, two-component spinning and melt-blowing technology are widely considered to be the most efficient means of preparing nanofibers. However, although these methods have their own characteristics and advantages, they also have some shortcomings. For example, the two-component spinning method faces problems such as high equipment cost, complex spinneret structure design, and limited applicable raw materials. Electrospinning technology is currently mainly limited to laboratory environments, with problems such as low production efficiency and difficulty in large-scale production and application. In addition, the stretching rate is low and the spinning distance is short during the electrospinning process, resulting in imperfect polymer orientation extension and low fiber strength, which faces many challenges in practical applications; at the same time, the use of organic solvents is expensive, difficult to recycle, and easy to cause environmental pollution. In contrast, the melt-blown spinning process has achieved remarkable results in practical applications.

[0003] The meltblowing method melts the polymer at high temperature and then uses a high-speed airflow to spray it into fibers. This method has the advantages of high production efficiency, low cost, and uniform fiber structure, so it has become an important means of producing fine filtration and separation media materials. However, although the meltblowing spinning process is relatively mature, it still faces technical difficulties in further reducing the fiber diameter. In the production and manufacturing process of traditional meltblown non-woven fabrics, after the polymer melt is extruded from the spinneret, it is stretched and rapidly thinned under the action of hot air on both sides. Subsequently, these melt streams will quickly solidify after contacting the cold air to form fine fibers. These fine fibers are usually 2-5μm, and can only reach about 1.5μm when they are extremely fine, which is difficult to meet the demand for nano-scale fibers in some fields. At present, there have been studies on the production of nano-scale fibers by reducing the aperture of the spinneret, but the spinneret with a small aperture has extremely high requirements for production accuracy, and the spinneret with a small aperture is easy to be blocked during use, resulting in high cost and low service life of the spinneret.

[0004] Therefore, it has become an urgent need to develop an efficient, economical and simple method for preparing nanofiber meltblown fabrics to break through the limitations of existing technologies and meet market demand. Summary of the invention

[0005] The present invention aims to overcome the above-mentioned problems existing in the melt-blowing process in the prior art, and provides a nanofiber melt-blown cloth and a preparation method thereof, by adding a heat preservation stretching zone and a cooling zone, so that the melt can be stretched and refined over a longer receiving mesh curtain distance, thereby achieving effective control of the fiber diameter and obtaining nano-scale fibers.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) mixing the polymer material and the electret masterbatch and then melting and extruding them through an extruder; (2) allowing the melt to be sprayed with hot air through a spinneret; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced by the action of hot air; the distance of the heat preservation and stretching zone is 500 to 800 mm, and the hot air temperature in the heat preservation and stretching zone is 180 to 220°C; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; (5) The cooled and solidified fibers are received by a receiving mesh curtain to form a web, and then subjected to electret treatment to obtain the nanofiber meltblown cloth.

[0007] The traditional meltblowing process is limited in the preparation of nanofibers. The main reason is that when the fiber is stretched to microns, the temperature of the hot air flow on both sides decreases, the wind speed decreases, and the melt is cooled and cannot be stretched again. On the basis of the existing meltblowing process, the present invention adds a heat preservation stretching zone and a cooling zone between the spinneret and the receiving mesh curtain. The setting of the heat preservation stretching zone ensures that there is a temperature maintenance zone after the melt is ejected from the spinneret hole, so that the melt can be fully stretched and refined within a relatively long distance (for example, 500mm to 800mm), and then cooled and received into a web. This treatment method can significantly slow down the cooling rate of the fiber, so that it can complete the adjustment and optimization of the structure in a longer time. At the same time, the precise stretching and refinement of the fiber can be achieved by accurately controlling the hot air temperature and speed in the heat preservation stretching zone.

[0008] Preferably, the polymer material in step (1) is selected from at least one of polypropylene, polyamide, polyester, polylactic acid and polyurethane.

[0009] Preferably, in step (1), the mass ratio of the polymer material to the electret masterbatch is 95:5 to 97:3.

[0010] Preferably, the extrusion temperature in step (1) is 200-260° C., and the screw speed of the extruder is 30-50 rpm.

[0011] Preferably, the nozzle temperature of the spinneret in step (2) is 230-300°C.

[0012] Preferably, the hot air velocity at the nozzle in step (2) is 180-210 m / s.

[0013] Preferably, the hot air velocity in the heat-insulating stretching zone in step (3) is 140 to 170 m / s.

[0014] Preferably, the distance between the cooling zones in step (4) is 100 to 200 mm.

[0015] Preferably, the temperature of the cooling zone in step (4) is 24-36°C.

[0016] Preferably, the cooling air speed in step (4) is 0.8 to 1.2 m / s.

[0017] The present invention also provides a nanofiber meltblown cloth prepared by the method.

[0018] Preferably, the average fiber diameter is 500 to 800 nm. The average fiber diameter of the meltblown fabric obtained by the present invention is between 500 and 800 nanometers, and has excellent filtration efficiency.

[0019] Therefore, the present invention has the following beneficial effects: (1) Adding a heat preservation stretching zone and a cooling zone in the melt-blowing process allows the melt to be stretched and refined over a longer receiving mesh curtain distance; (2) By precisely adjusting the hot air temperature and wind speed in the heat preservation and drawing zone, the fiber diameter can be effectively controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the melt-blowing device used in the present invention.

[0021] Figure 2 It is a front view of the position of the meltblowing device used in the present invention on the equipment.

[0022] Figure 3 It is a structural diagram of the position of the meltblowing device used in the present invention on the equipment.

[0023] In the figure: 1-spinneret, 2-insulation drawing zone, 3-cooling zone, 4-nanofiber meltblown cloth, 5-receiving mesh curtain, 6-hot air, 7-cooling air.

[0024] Figure 4 This is a SEM image of the nanofiber meltblown fabric obtained in Example 3 of the present invention.

[0025] Figure 5 It is a SEM picture of the nanofiber meltblown cloth obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art.

[0028] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with specific implementation methods, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention rather than to limit the claims of the present invention.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0031] Overall embodiment: A use such as Figure 1 to Figure 3 The method for preparing nanofiber meltblown cloth by the meltblowing device shown comprises the following steps: (1) mixing the polymer material and the electret masterbatch and then melting and extruding them through an extruder; (2) allowing the melt to pass through the spinneret 1 for hot air spraying; (3) The fibers ejected from the spinneret enter the heat preservation and drawing zone 2, where the fiber diameter is reduced by the action of hot air 6; the distance of the heat preservation and drawing zone is 500 to 800 mm, and the hot air temperature of the heat preservation and drawing zone is 180 to 220°C; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone 3 and is cooled and solidified under the action of the cooling air 7; (5) The cooled and solidified fibers are received by a receiving mesh curtain 5 to form a web, and then subjected to electret treatment to obtain the nanofiber meltblown cloth 4.

[0032] As a specific implementation, the polymer material described in step (1) is selected from at least one of polypropylene, polyamide, polyester, polylactic acid, and polyurethane.

[0033] As a specific implementation, in step (1), the mass ratio of the polymer material to the electret masterbatch is 95:5 to 97:3.

[0034] As a specific implementation, the extrusion temperature in step (1) is 200-260° C., and the screw speed of the extruder is 30-50 rpm.

[0035] As a specific implementation, the nozzle temperature of the spinneret in step (2) is 230-300°C.

[0036] As a specific implementation, the hot air velocity at the nozzle in step (2) is 180-210 m / s.

[0037] As a specific implementation, the hot air velocity in the heat preservation and stretching zone in step (3) is 140 to 170 m / s.

[0038] As a specific implementation, the distance of the cooling zone in step (4) is 100 to 200 mm.

[0039] As a specific implementation, the temperature of the cooling zone in step (4) is 24-36°C.

[0040] As a specific implementation, the cooling wind speed in step (4) is 0.8 to 1.2 m / s.

[0041] Embodiment 1: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 550 mm, the hot air temperature in the heat preservation and stretching zone is 210°C, and the hot air speed is 160 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received into a web through a receiving mesh curtain, and after electret treatment, a weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.94μm, and the filtration efficiency is 99.9915% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0042] Embodiment 2: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 600 mm, the hot air temperature in the heat preservation and stretching zone is 210°C, and the hot air speed is 160 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received by a receiving mesh curtain to form a web having a gram weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.72μm, and the filtration efficiency is 99.9973% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0043] Embodiment 3: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 650 mm, the hot air temperature in the heat preservation and stretching zone is 210°C, and the hot air speed is 160 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received by a receiving mesh curtain to form a web having a gram weight of 30 g / m 2 Nanofiber meltblown cloth; SEM image of nanofiber meltblown cloth Figure 4As shown in , the average fiber diameter is 0.64 μm and the filtration efficiency is 99.99983% (test conditions: high efficiency and ultra-high efficiency filter paper test bench, 32 L / min, 0.3 μm NaCl).

[0044] Embodiment 4: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 255° C., and the hot air velocity at the nozzle was 180 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 700 mm, the hot air temperature in the heat preservation and stretching zone is 210°C, and the hot air speed is 160 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received by a receiving mesh curtain to form a web having a gram weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.66μm, and the filtration efficiency is 99.99965% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0045] Embodiment 5: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 650 mm, the hot air temperature in the heat preservation and stretching zone is 190°C, and the hot air speed is 140 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received into a web through a receiving mesh curtain, and after electret treatment, a weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.81μm, and the filtration efficiency is 99.9935% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0046] Embodiment 6: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced by the action of hot air; the distance of the heat preservation and stretching zone is 650 mm, the hot air temperature in the heat preservation and stretching zone is 200 ° C, and the hot air speed is 150 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received into a web through a receiving mesh curtain, and after electret treatment, a weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.76μm, and the filtration efficiency is 99.9968% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0047] Embodiment 7: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is reduced under the action of hot air; the distance of the heat preservation and stretching zone is 650 mm, the hot air temperature in the heat preservation and stretching zone is 220°C, and the hot air speed is 170 m / s; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; the distance of the cooling zone is 150 mm, the temperature of the cooling air is 26 ° C, and the cooling air speed is 0.9 m / s; (5) The cooled and solidified fibers are received into a web through a receiving mesh curtain, and after electret treatment, a weight of 30 g / m 2 Nanofiber meltblown cloth; the average fiber diameter of the nanofiber meltblown cloth is 0.68μm, and the filtration efficiency is 99.9976% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32L / min, 0.3μm NaCl).

[0048] Comparative Example 1: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret are received by a receiving mesh curtain to form a web, and after electret treatment, a weight of 30 g / m 2 The distance between the spinneret and the receiving mesh curtain is 200 mm; the SEM image of the nanofiber meltblown cloth is as follows Figure 5 As shown in , the average fiber diameter is 2.07 μm and the filtration efficiency is 99.9767% (test conditions: high efficiency and ultra-high efficiency filter paper test bench, 32 L / min, 0.3 μm NaCl).

[0049] Comparative Example 2: A method for preparing a nanofiber meltblown cloth comprises the following steps: (1) Polypropylene (Basel Metocene MF650Y) and electret masterbatch (added in an amount of 4 wt% of polypropylene) were mixed and melt-extruded through a twin-screw extruder at a temperature of 235° C. and a screw speed of 35 rpm; (2) passing the melt through a spinneret (aperture 0.25 mm, hole spacing 0.4 mm) for hot air jetting; the nozzle temperature of the spinneret was 265° C., and the hot air velocity at the nozzle was 190 m / s; (3) The fibers ejected from the spinneret are received by a receiving mesh curtain to form a web having a gram weight of 30 g / m 2 The distance between the spinneret and the receiving mesh curtain is 500 mm; the average fiber diameter of the nanofiber meltblown cloth is 2.26 μm, and the filtration efficiency is 99.6765% (test conditions: high-efficiency and ultra-high-efficiency filter paper test bench, 32 L / min, 0.3 μm NaCl).

[0050] The process parameters in the above embodiments and comparative examples and the performance indicators of the obtained nanofiber meltblown fabrics are shown in Table 1.

[0051] Table 1: Process parameters and nanofiber meltblown fabric performance data table.

[0052] From the above results, it can be seen that in Examples 1 to 7, the method of the present invention is adopted, and a heat preservation and drawing zone and a cooling zone are set between the spinneret and the receiving mesh curtain, and the average diameter of the fibers in the obtained meltblown cloth can be less than 1 μm. In Comparative Example 1, a heat preservation and drawing zone and a cooling zone are not set between the spinneret and the receiving mesh curtain, and the diameter of the fibers in the obtained meltblown cloth is significantly increased compared with that in the embodiment, and the filtration efficiency is difficult to meet the requirements of some high-precision filtration fields.

[0053] And it can be seen from the data of Examples 1 to 4 that, using the method of the present invention, within a certain range, increasing the distance of the heat preservation and drawing zone is beneficial to the thinning of the fiber (Examples 1 to 3), but when the heat preservation and drawing distance increases to a certain extent, the diameter of the fiber does not change significantly when the heat preservation and drawing distance is further increased (Example 4). This is because when the fiber is stretched and thinned to a certain extent and continues to be stretched and thinned, the fiber is easy to be blown off and flying flowers appear, and the temperature and wind speed at the nozzle need to be properly adjusted. In Comparative Example 2, the heat preservation and drawing zone and the cooling zone are not set between the spinneret and the receiving mesh curtain. Although the receiving distance is increased compared with Comparative Example 1, the diameter of the fiber does not decrease. This is because when the heat preservation and drawing zone is not set between the spinneret and the receiving mesh curtain, the fiber has cooled down in the later stage and cannot be stretched again.

[0054] From the data of Examples 5 to 7, it can be seen that when the hot air temperature and hot air speed in the heat preservation and drawing zone gradually increase (Examples 5, 6, and 3), it is beneficial to the thinning of the fiber, but when the hot air temperature and speed increase to a certain extent (Example 7), the fiber diameter does not change significantly; this is because when the hot air temperature and speed are high, the fiber is prone to broken fibers and flying flowers, as well as more fiber paralleling. Therefore, the hot air temperature and speed in the heat preservation and drawing zone need to be controlled within an appropriate range.

[0055] Based on the existing melt-blowing process, the present invention adds a heat preservation and stretching zone and a cooling zone between the spinneret and the receiving mesh curtain. The setting of the heat preservation and stretching zone allows the melt to have a temperature maintenance zone after it is ejected from the spinneret hole, so that the melt can be fully stretched and refined over a relatively long distance, and then cooled and received into a web. This treatment method can significantly slow down the cooling speed of the fiber, so that the structure can be adjusted and optimized in a longer time. At the same time, the precise stretching and refinement of the fiber can be achieved by accurately controlling the hot air temperature and speed in the heat preservation and stretching zone.

[0056] The above content is a further detailed description of the technical solution of the present invention in combination with a specific preferred implementation method, and should not be understood as a limitation on the applicable scope of the present invention. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be deemed to fall within the scope of patent protection determined by the claims submitted for the present invention.

Claims

1. A method for preparing a nanofiber meltblown cloth, characterized in that: The steps include: (1) Mixing the polymer material and the electret masterbatch and then melting and extruding them through an extruder; (2) The melt is sprayed with hot air through a spinneret; (3) The fibers ejected from the spinneret enter the heat preservation and stretching zone, where the fiber diameter is refined under the action of hot air; the distance of the heat preservation and stretching zone is 500-800 mm, and the hot air temperature in the heat preservation and stretching zone is 180-220 °C; (4) After passing through the heat preservation and drawing zone, the fiber enters the cooling zone and is cooled and solidified under the action of cooling air; (5) The cooled and solidified fibers are received by a receiving mesh curtain to form a web, and then subjected to electret treatment to obtain the nanofiber meltblown fabric.

2. The method for preparing the nanofiber meltblown cloth according to claim 1, characterized in that: The polymer material described in step (1) is at least one selected from polypropylene, polyamide, polyester, polylactic acid, and polyurethane.

3. The method for preparing the nanofiber meltblown cloth according to claim 1 or 2, characterized in that: The extrusion temperature in step (1) is 200-260° C., and the screw speed of the extruder is 30-50 rpm.

4. The method for preparing the nanofiber meltblown cloth according to claim 1, characterized in that: The nozzle temperature of the spinneret in step (2) is 230-300°C.

5. The method for preparing the nanofiber meltblown cloth according to claim 1 or 4, characterized in that: In step (2), the hot air velocity at the nozzle is 180-210 m / s.

6. The method for preparing the nanofiber meltblown cloth according to claim 1, characterized in that: The hot air velocity in the heat preservation and stretching zone in step (3) is 140-170 m / s.

7. The method for preparing the nanofiber meltblown cloth according to claim 1, characterized in that: The distance of the cooling zone in step (4) is 100~200mm.

8. The method for preparing the nanofiber meltblown cloth according to claim 1 or 7, characterized in that: In step (4), the temperature of the cooling air is 24-36° C., and the cooling air speed is 0.8-1.2 m / s.

9. A nanofiber meltblown cloth, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 8.

10. The nanofiber meltblown cloth according to claim 9, characterized in that: The average fiber diameter is 500~800nm.

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