A melt-blown fabric with micro-porous and folded space microstructure and its production process

Abstract

This invention discloses a meltblown fabric with micropores and folded spatial microstructures and its manufacturing process, belonging to the field of meltblown fabric production and manufacturing technology. The meltblown fabric with micropores and folded spatial microstructures comprises a meltblown fabric formed from polypropylene mesh, on which nanoscale pits are etched. Through chemical etching, this invention, on the one hand, forms fluff at the pores, increasing airflow within the pores; on the other hand, the fluff floating within the pores can better capture pathogens with smaller diameters, thereby further improving the filtration effect of the meltblown fabric.

Description

Technical Field

[0001] This invention relates to the field of meltblown fabric production and manufacturing technology, and in particular to a meltblown fabric with micropores and folded spatial microstructures and its production process. Background Technology

[0002] The core functional layer of a face mask is the meltblown nonwoven material located in the core layer. To improve its filtration and protection effect and maintain low inhalation resistance, corona charging is often used to impart static electricity. However, corona charging only imparts space charge to the meltblown nonwoven material, resulting in poor lateral uniformity of charge density and susceptibility to environmental influences. Furthermore, corona charging can damage the polymer macromolecular chains and generate unsaturated groups, increasing the mobility of charge on the fiber surface and accelerating its decay. Therefore, when this material is used as the core layer in a face mask, its charge gradually disappears during long-term storage, leading to a decrease in the mask's filtration efficiency.

[0003] Meltblown nonwoven materials contain fibers with an average diameter of 1–4 µm, possessing advantages such as small pore size and high porosity. They can achieve good mechanical filtration based on interception, inertial impaction, diffusion, and gravitational deposition effects, making them a widely used air filtration material and the core functional layer of masks. However, most dust particles in the air are submicron-sized (0.1–1 µm), resulting in low filtration efficiency through mechanical filtration and a minimum filtration particle size of approximately 0.3 µm. Therefore, high-efficiency protective masks like KN95 use electrostatically charged meltblown nonwoven materials in their core layer, which further filters fine particulate matter based on electrostatic adsorption mechanisms. Furthermore, airborne bacteria and viruses are typically negatively charged. When they pass through the pores of the charged filter material, the electrostatic field and microcurrent generated by the filter material stimulate protein mutations in the bacteria, thereby killing them.

[0004] Currently, most of the meltblown fabric used in masks on the market is produced by spraying meltblown fabric from a meltblown die onto a conveyor belt to form a web, which is then electrostatically charged through electret treatment. However, the electrostatic discharge caused by long-distance transportation can easily reduce the filtration quality of meltblown fabric produced in this way. In addition, although a denser meltblown mesh can improve the filtration effect, it results in poor air flow, affecting the comfort of wearing the mask and making the production technology more difficult. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing meltblown fabrics, such as the weakening of electrostatic charge leading to low filtration efficiency and airflow, by proposing a meltblown fabric with micropores and folded spatial microstructures and its production process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A meltblown fabric with micropores and folded spatial microstructures includes a meltblown fabric formed from polypropylene wire mesh, on which nanoscale pits are etched.

[0008] To improve the capture effect on bacteria and viruses, preferably, the diameter of the pit is in the range of 100-200 nm.

[0009] A meltblown nonwoven fabric production process includes the following steps:

[0010] Step 1: Preparation stage, a screw extruder is used in conjunction with a metering pump to quantitatively pressurize and deliver the molten polymer;

[0011] Step 2: Melt forming, receiving molten polymer and spraying polymer microfibers through a meltblown die under negative pressure generated by high-speed hot air, and then receiving them by a conveying device to form a web;

[0012] Step 3: Rewinding and slitting, the meltblown fabric after being formed into a web is wound onto the take-up roller;

[0013] Step 4: Microstructure etching. The meltblown fabric roll from step 3 is placed in a vacuum device. The process gas in the vacuum device is excited by the radio frequency power supply to generate high-energy ions to chemically etch the surface of the meltblown fabric roll.

[0014] Step 5: Electret treatment. The meltblown fabric roll with microstructure formed by etching is cleaned with deionized water, dried, and then subjected to corona charging.

[0015] Preferably, the process gas in step 4 includes sodium hypochlorite and oxygen.

[0016] To ensure uniform etching of the polypropylene mesh surface, the flow rate of the sodium hypochlorite atomizer is further 800-1500 sccm, and the flow rate of the oxygen gas is 2500-4000 sccm.

[0017] Preferably, the chemical etching time in step 4 is 80-200 s.

[0018] Preferably, the time for cleaning the meltblown fabric with deionized water at room temperature in step 5 is 60-120 seconds.

[0019] Preferably, in step 4, the voltage of the radio frequency power supply is 1500-1900W at high frequency and 80-200W at low frequency.

[0020] To improve etching efficiency, preferably, the vacuum device in step 4 includes: a base box, a placement rack inside the base box, a drive unit on the placement rack, and a bracket slidably connected above the base box. The bracket has a lifting box, which forms a sealed working chamber when it is in contact with the base box. The top of the bracket is equipped with a vacuum pump for creating a vacuum environment in the working chamber, and an RF power supply and a gas supply pipe extending from the top of the lifting box to the inside of the lifting box. A rinsing strip and an electric heating ring are fixedly connected to the top of the lifting box, and a liquid supply pipe connected to the rinsing strip is provided on the top of the bracket.

[0021] Furthermore, the drive unit includes a first motor fixedly connected to the side wall of the base box, the output end of the first motor extending into the base box for driving the take-up roller placed on the placement frame.

[0022] Compared with the prior art, the present invention provides a meltblown fabric with micropores and folded spatial microstructures and its production process, which has the following beneficial effects:

[0023] 1. The production process of this meltblown fabric uses radio frequency power to excite sodium hypochlorite and oxygen to generate accelerated ions that bombard the surface of polypropylene fiber mesh to form meteorite craters and fluff, thereby effectively improving the inactivation and capture effect of meltblown fabric on bacteria and dust. The fluff fills the enlarged pores of the meltblown fabric, improving wearing comfort while ensuring the filtration effect of the meltblown fabric.

[0024] 2. In this meltblown fabric production process, pressurized deionized water is supplied to the rinsing strip through the liquid supply pipe. The deionized water is evenly sprayed onto the surface of the meltblown fabric through the rinsing strip to remove ions remaining during the chemical etching process, ensuring safety in use. At the same time, the winding roller rotates in the opposite direction to ensure that all meltblown fabrics are rinsed. During the rinsing process, the electric heating ring is activated to dry the wound meltblown fabric, which facilitates subsequent electret treatment.

[0025] 3. The meltblown fabric production process uses a first motor to drive the winding roller to rotate synchronously, which makes the meltblown fabric on it more stable and synchronized, further improves the uniformity of chemical etching, and ensures the air flow of the meltblown fabric during use as well as the effect of capturing and eliminating pathogens.

[0026] The parts of this device not described herein are the same as or can be implemented using existing technologies. Through chemical etching, this invention forms fluff at the pores, increasing the airflow in the pores. On the other hand, the fluff floating in the pores can better capture pathogens with smaller diameters, thereby further improving the filtration effect of meltblown fabric. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 1;

[0028] Figure 2 This is a schematic diagram of the structure of the present invention. Figure 2 ;

[0029] Figure 3 This is a schematic diagram of the vacuum device of the present invention. Figure 1 ;

[0030] Figure 4 This is a schematic diagram of the vacuum device of the present invention. Figure 2 .

[0031] In the diagram: 1. Meltblown die head; 2. Screw extruder; 3. Metering pump; 4. Conveying device; 5. Take-up roller; 6. Base box; 601. Placement rack; 602. First motor; 7. Support; 701. Vacuum pump; 702. Radio frequency power supply; 703. Air supply pipe; 704. Liquid supply pipe; 8. Lifting box; 801. Flushing bar; 802. Electric heating ring. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "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 this 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 this invention.

[0034] Example 1:

[0035] A meltblown fabric with micropores and folded spatial microstructures is formed on a conveyor belt by polypropylene filaments ejected through a meltblown die 1, creating a mesh with uniform pores ranging from 0.2µm to 1µm. This ensures smooth breathing when made into a mask while also providing a certain degree of folding capability, preventing the breakage of the separating ribs between the pores when the meltblown fabric is bent. This effectively ensures that even after multiple uses, the electrostatically charged meltblown fabric mesh still has a high filtration and sterilization effect against bacteria and dust. Furthermore, meteorite craters with a diameter of 100-200nm are formed on the surface of the separating ribs between the pores of the mesh through chemical etching.

[0036] Here, the diameter of the pit can be 100nm, 130nm, 180nm, 200nm, etc., depending on the frequency of contact with the process gas and the voltage of the RF power supply 702 during the chemical etching process.

[0037] Even with the weakening of electrostatic charge on meltblown fabric during long-distance transport, meteorite craters can still capture and contain pathogens with diameters of 100nm and above using weak electrostatic charge. Compared to the traditional direct electret electrostatic method, it has a stronger and more lasting filtration and sterilization effect. Especially in the airflow areas of the pores, during the chemical etching process, on the one hand, fluff will form in the pores, increasing the airflow. On the other hand, the fluff floating in the pores can better capture pathogens with smaller diameters, thereby further improving the filtration effect of meltblown fabric.

[0038] Example 2:

[0039] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4 A meltblown fabric production process, mainly used to produce meltblown fabric formed from polypropylene wire mesh with meteorite crater holes, involves the following steps:

[0040] Step 1: Preparation stage. First, the heated and molten polypropylene is extruded using a screw extruder 2 and then quantitatively pressurized through a pipeline. A metering pump 3 is installed on the pipeline to measure the flow rate of the pressurized polymer solution conveyor belt, which facilitates subsequent control of the spraying speed of the meltblown die head 1 and the conveying speed of the finished product by the conveying device 4.

[0041] Step 2: Melt forming. Accurately metered molten polypropylene is fed into the meltblown die head 1. A receiving groove is set at the top of the meltblown die head 1, and multiple sets of equally spaced spray holes are set at the bottom of the meltblown die head 1. Air blowing points are set on both sides of the spray holes, which are continuously supplied with air by a pump and an air storage tank. During the continuous air supply by the pump, a negative pressure area is formed below the spray holes, thereby guiding the polypropylene solution in the receiving groove above to spray out. Here, components such as electric heating are set in the air storage tank to heat the air inside and prevent the polypropylene filaments carried by the sprayed filaments from solidifying too quickly. A control valve is set on the pipe that supplies air from the air storage tank to the meltblown die head 1 for centralized control in the central control room. The polypropylene microfibers sprayed from the spray holes fall below, and the conveying device 4, which consists of a conveyor belt and a drive motor, continuously transports the falling high-temperature polypropylene fibers and makes the microfibers intertwine and gradually form a web according to the spray direction of the spray head, thereby forming the basic part of the meltblown cloth.

[0042] Step 3: Rewinding and slitting. The meltblown fabric that has been formed into a web on the conveyor belt is wound onto the winding roller 5. Before winding, the polypropylene fibers can be allowed to cool down to prevent them from sticking together again. Of course, a fan can also be used to accelerate cooling and improve winding efficiency, thereby quickly forming a meltblown fabric roll.

[0043] Step 4: Microstructure etching. Place the meltblown fabric roll from Step 3 into a vacuum device. Set the voltage of the RF power supply 702 to 1500W for high frequency and 80W for low frequency, or 1900W for high frequency and 200W for low frequency, etc. The specific selection parameters are determined based on the total mass of the meltblown fabric. The greater the mass, the higher the etching precision required. In this case, a range with a smaller difference between high and low frequencies is selected to ionize the mixture of sodium hypochlorite and oxygen in the vacuum. This causes charged ions to be accelerated and continuously collide with gas molecules, producing a cascade effect. The resulting plasma continuously impacts the surface of the polypropylene mesh, forming meteorite craters on its surface. During the chemical etching process, the time is maintained at three levels: 80s, 150s, and 200s. The specific time is determined according to the required mass of the meltblown fabric to be etched, so as to ensure that the meltblown fabric on the take-up roller 5 can be circulated to the end and to ensure the uniformity of chemical etching.

[0044] Step 5: Electret treatment. The meltblown fabric roll with microstructure formed by etching is cleaned with room temperature deionized water for 60-120 seconds to ensure that ions are removed from the surface of the meltblown fabric and improve the safety of its use. Then the meltblown fabric is dried and corona charged to make it carry space charge.

[0045] Here, when the flow rate of the sodium hypochlorite atomizer is 800 sccm, the oxygen supply flow rate is 2500 sccm; when the flow rate of the sodium hypochlorite atomizer is 1000 sccm, the oxygen supply flow rate is 3000 sccm; and when the flow rate of the sodium hypochlorite atomizer is 1500 sccm, the oxygen supply flow rate is 4000 sccm. The specific flow rate ratio is determined based on the quality of the meltblown fabric on the take-up roller 5.

[0046] The vacuum device in step 4 includes: a base box 6 with an open top, base platforms on both sides of the base box 6, and a lead screw driven by a second motor rotatably connected inside the base platforms. Two pairs of semi-circular placement racks 601 are arranged inside the base box 6. A take-up roller 5 with meltblown fabric wound on it is placed on one pair of placement racks 601, and an empty take-up roller 5 is placed on the other pair of placement racks 601. One end of the meltblown fabric is wound around the empty take-up roller 5.

[0047] Additionally, a bracket 7 is threaded onto the lead screw. The bracket 7 has a lifting box 8 that slides up and down driven by a cylinder, hydraulic cylinder, or electric slide. The lifting box 8 has an open bottom and contains a flushing strip 801 and multiple sets of electric heating rings 802 at its top. A liquid supply pipe 704 connected to the flushing strip 801 is located at the top of the bracket 7. By controlling the rotation of the second motor's electric lead screw, the lifting box 8 can be moved above or to the side of the base box 6 to facilitate the placement of the take-up roller 5. After the take-up roller 5 is placed, the lifting box 8 can be lowered so that its lower opening fits tightly against the upper opening of the base box 6, forming a sealed working chamber. A vacuum pump 701 is located at the top of the bracket 7 to create a vacuum environment within the working chamber. After the air in the working chamber is extracted, sodium hypochlorite and oxygen are supplied to the working chamber through the air supply pipe 703. Then, the RF power supply 702 is started. The RF power supply 702 generates an alternating electric field between two plates in the working chamber, which ionizes the gas. During the ionization process, the two take-up rollers 5 are rotated synchronously, so that the meltblown cloth is wound from one set of take-up rollers 5 to another set of take-up rollers 5. The winding time is maintained at 80-200s, thereby realizing chemical etching. Subsequently, the gas inside the working chamber is extracted again, and pressurized deionized water is supplied to the rinsing strip 801 through the liquid supply pipe 704. The deionized water is evenly sprayed onto the surface of the meltblown cloth through the rinsing strip 801 to remove the ions remaining during the chemical etching process and ensure the safety of use. At the same time, the take-up rollers 5 are rotated synchronously in the opposite direction so that all meltblown cloth can be rinsed. During the rinsing process, the electric heating ring 802 is started to dry the wound meltblown cloth, which is convenient for subsequent electret treatment.

[0048] Here, the meltblown fabric can be directly subjected to corona electret treatment in the working chamber, or electret treatment can be performed later to ensure that the meltblown fabric carries space charge.

[0049] For the synchronous drive of the two sets of take-up rollers 5, we can operate manually, or we can fix two first motors 602 to the side wall of the base box 6. The output end of the first motor 602 extends into the base box 6, and magnetic material can be set at the output end to ensure better stability and synchronization when it contacts the take-up roller 5 and drives it to rotate, further improving the uniformity of chemical etching, ensuring the air flow of meltblown cloth during use, and the effect of capturing and eliminating pathogens.

[0050] The properties of the meltblown fabric produced using the above process are as follows:

[0051] 1. Thickness: 0.36mm; CV value: 4.2%;

[0052] 2. Air permeability: 422mm / s;

[0053] 3. Mass per unit area: 26.3 g / m²; CV value: 1.9%;

[0054] 4. Salt filtration efficiency: 986.62%, filtration resistance: 3.41 Pa.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A meltblown fabric production process for preparing meltblown fabric with micropores and folded spatial microstructures, wherein the meltblown fabric is formed from polypropylene mesh, and nanoscale pits are etched on the surface of the polypropylene mesh, characterized in that... Includes the following steps: Step 1: In the preparation stage, a screw extruder (2) is used in conjunction with a metering pump (3) to quantitatively pressurize the molten polymer; Step 2: Melt forming, receiving molten polymer and spraying polymer ultrafine fibers through the meltblown die (1) under the negative pressure generated by high-speed hot air, and receiving them into a web by the conveying device (4); Step 3: Rewinding and slitting, the meltblown fabric after being formed into a web is wound onto the take-up roller (5); Step 4: Microstructure etching. The meltblown fabric roll from step 3 is placed in a vacuum device, and the process gas in the vacuum device is excited by the radio frequency power supply (702) to generate high-energy ions to chemically etch the surface of the meltblown fabric roll. Step 5: Electret treatment, the meltblown fabric roll with microstructure formed by etching is cleaned with deionized water, dried and then corona charged. In step 4, the process gas includes sodium hypochlorite and oxygen. The flow rate of the sodium hypochlorite atomizer is 800-1500 sccm, and the flow rate of the oxygen gas is 2500-4000 sccm. The chemical etching time in step 4 is 80-200 s. The voltage of the RF power supply (702) in step 4 is 1500-1900 W at high frequency and 80-200 W at low frequency. The vacuum device in step 4 includes: A base box (6) is provided, and two pairs of placement racks (601) are provided inside the base box (6). A drive unit is provided on each placement rack (601). And, a bracket (7) that is slidably connected above the base box (6). The bracket (7) is provided with a lifting box (8). When the lifting box (8) is in contact with the base box (6), a sealed working cavity is formed. The top of the bracket (7) is provided with a vacuum pump (701) for creating a vacuum environment in the working cavity, a radio frequency power supply (702) whose output end extends into the lifting box (8), and a gas supply pipe (703). A flushing strip (801) and an electric heating ring (802) are fixedly connected to the top of the lifting box (8). The top of the bracket (7) is also provided with a liquid supply pipe (704) connected to the flushing strip (801). The drive unit includes a first motor (602) fixedly connected to the side wall of the base box (6), the output end of the first motor (602) extending into the base box (6) for driving the take-up roller (5) placed on the placement rack (601). Place the take-up roller (5) with meltblown fabric on one pair of placement racks (601), and place an empty take-up roller (5) on the other pair of placement racks (601). Wrap one end of the meltblown fabric around the empty take-up roller (5), and then control the lifting box (8) to descend, tightly fitting it with the upper opening of the base box (6) to form a sealed working chamber. After the air in the working chamber is extracted by the vacuum pump (701), sodium hypochlorite and oxygen are supplied to the working chamber through the air supply pipe (703). Then, the radio frequency power supply (702) is started. The radio frequency power supply (702) generates an alternating electric field in the working chamber, causing gas-electric separation and ionization. During the process, two take-up rollers (5) are rotated synchronously so that the meltblown fabric is wound from one take-up roller (5) to the other take-up roller (5) to achieve chemical etching. Then, the gas inside the working chamber is extracted again, and pressurized deionized water is supplied to the rinsing strip (801) through the liquid supply pipe (704). The deionized water is evenly sprayed onto the surface of the meltblown fabric through the rinsing strip (801) to remove the ions remaining during the chemical etching process. At the same time, the take-up rollers (5) are rotated synchronously in the opposite direction so that all meltblown fabrics can be rinsed. During the rinsing process, the electric heating ring (802) is activated to dry the wound meltblown fabric.

2. The meltblown nonwoven fabric production process according to claim 1, characterized in that, The diameter of the pit ranges from 100 to 200 nm.

3. The meltblown nonwoven fabric production process according to claim 1, characterized in that, In step 5, the time for rinsing the meltblown fabric with deionized water at room temperature is 60-120 seconds.

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