Preparation method of ultra-thin spun-bonded non-woven fabric

Abstract

The present application relates to a kind of preparation methods of ultrathin spun-bonded nonwoven fabric, comprising: raw material is metered and then input into screw extruder, and the extruded material is input into metering pump after filtering;Metering pump provides material to spun-bonded box at low speed, and spinneret carries out ultrathin spinning;The spun yarn is cooled and drawn by the air outlet of cooling air box, and the top of air outlet is provided with horizontal baffle, so that the cold air output by air outlet can penetrate into curtain-shaped yarn interior;The yarn after cooling is laid on the conveyor belt of web former, and forms single layer spinning layer;Several groups of spinning modules are evenly arranged along the length direction of conveyor belt of web former, each group of spinning modules carries out the above steps in turn, and the spinning layer on the upstream side of conveyor belt is moved to the position corresponding to next spinning module, then receives a layer of spinning layer, so that the spinning layer formed by several groups of spinning modules is stacked up and down, and forms spun-bonded body;Spun-bonded body is sequentially subjected to hot pressing by hot calender, shaping by winding machine, and slitting by slitting machine, and ultrathin spun-bonded nonwoven fabric product is obtained.

Description

Technical Field

[0001] This invention belongs to the field of ultra-thin spunbond nonwoven fabric production technology, specifically relating to a method for preparing ultra-thin spunbond nonwoven fabric. Background Technology

[0002] Spunbond nonwoven fabric is primarily made of polyester and polypropylene. It is resistant to high and low temperatures, aging, and UV radiation, and boasts high elongation, good stability and breathability, corrosion resistance, sound insulation, mothproofing, and is non-toxic. It is widely used in hygiene products, packaging, and bag fabrics. The lower the basis weight and the thinner the fabric, the more exponentially the manufacturing difficulty increases. Low-basis-weight spunbond nonwoven fabrics have higher product value and can be used to make diapers, sanitary napkins, masks, and protective products, offering greater comfort and appealing to consumers. Furthermore, for the same area, lower basis weight directly reduces product costs. Currently, the basis weight of thin spunbond nonwoven fabrics is around 15 g / m². 2 Around 5 g / m², while the basis weight of ultrathin spunbond nonwoven fabric is around 5 g / m². 2 This is currently the thinnest spunbond nonwoven fabric product achievable in China. However, due to its extremely low basis weight, using traditional spunbond nonwoven fabric production processes and equipment can lead to issues such as broken fibers, uneven web formation, and holes. Furthermore, the production process is highly unstable and prone to producing defective products. Summary of the Invention

[0003] To address the above problems, this invention provides a method for preparing ultrathin spunbond nonwoven fabric, comprising the following steps:

[0004] S1: The raw material is metered and fed into the screw extruder. The material extruded by the screw extruder is filtered through a filter and then fed into the metering pump.

[0005] S2: The metering pump supplies material to the spinneret of the spunbond box at low speed, and the spinneret performs ultra-thin spinning; the speed of the metering pump is 11-16 rpm;

[0006] S3: The filaments sprayed out in step S2 are in the form of a curtain and are cooled and stretched through the air outlet of the cooling air box. A horizontal baffle is provided at the top of the air outlet so that the cold air output from the air outlet can penetrate deep into the curtain and fully cool the filaments.

[0007] S4: The cooled filaments from step S3 are laid flat on the conveyor belt of the web forming machine to form a single-layer spun fabric.

[0008] Several sets of spinnerets are evenly arranged along the length of the web forming machine conveyor belt. Each spinneret includes a screw extruder, a metering pump, a spunbond box and a cooling box. Each set of spinnerets sequentially performs the above steps S1-S4. The spun layer on the upstream side of the conveyor belt moves with the conveyor belt to the position of the next corresponding spinneret, and then receives another spun layer. This allows the spun layers formed by several sets of spinnerets to be superimposed on top of each other to form a spunbond.

[0009] S5: The spunbond obtained in step S4 is successively hot-pressed by a hot rolling mill, shaped by a winding machine, and slit by a slitting machine to obtain the finished ultra-thin spunbond nonwoven fabric.

[0010] Optionally, in step S1, the raw materials include polypropylene and masterbatch, and the masterbatch is selected from one or more of colored masterbatch, anti-aging masterbatch, UV-resistant masterbatch, ultra-soft masterbatch, and smooth masterbatch.

[0011] Polypropylene has a melt index of 32-42 g / 10 min, with a relatively small deviation, resulting in more stable flow properties after melting, making it suitable for the preparation of the ultrathin spunbond nonwoven fabric of this invention. In contrast, the melt index of polypropylene, the raw material for ordinary spunbond nonwoven fabrics, varies greatly, and its flow properties are significantly reduced after melting, making it unsuitable for the preparation of ultrathin spunbond nonwoven fabrics.

[0012] Optionally, in step S1, after the polypropylene and masterbatch are metered according to the required ratio for ultra-thin spunbond nonwoven fabric, they are conveyed to the screw extruder by vacuum suction for raw material mixing and extrusion. The extruded material is a fluid slurry. The slurry is filtered through a filter to remove impurities, such as lumpy insoluble matter or solid impurities. The remaining slurry then enters the metering pump.

[0013] Optionally, in step S1, a feed pipe is connected between the filter and the metering pump to transport the filtered slurry. A pressure gauge is installed on the feed pipe to measure the pressure of the filtered slurry. The pressure of the filtered slurry is controlled within the range of 5.5 ± 0.05 MPa, that is, the pressure fluctuation of the filtered slurry in the feed pipe is 0.05 MPa.

[0014] This invention enhances pressure sensitivity control, making the spinning screw more stable and less prone to vibration. Smaller pressure fluctuations result in less vibration, which helps the metering pump operate stably even at low speeds, further contributing to stable spinning. The pressure of the filtered slurry is controlled by the screw extruder's rotational speed; increasing the screw extruder's speed increases the pressure of the filtered slurry.

[0015] Preferably, in step S2, the metering pump rotates at 14-16 rpm. Compared to existing spunbond nonwoven fabric production processes, the metering pump of this invention operates at an extremely low speed, resulting in very slow material feeding to the spunbond housing. This, combined with the minimal material consumption required for ultra-thin spinneret spinning, facilitates the production of ultra-thin spunbond nonwoven fabrics.

[0016] Alternatively, in step S2, it is also necessary to perform single-molecule smoke extraction on the spunbond box, extract and collect the small molecule monomer gas generated by the spunbond box, and discharge it to the waste gas treatment device for filtration before releasing it into the environment.

[0017] Optionally, the preparation method includes a cooling system to cool the filament stretching in step S3 and the spinning layer on the conveyor belt in step S4; the cooling system includes a cooling unit and several component fans, each component fan corresponding to a set of spinnerets.

[0018] One set of fans includes an air conditioning unit, a cooling fan, and an exhaust fan. The cooling unit is connected to each air conditioning unit. The air outlet of the air conditioning unit is connected to the cooling air box through the cooling fan to provide cold air to the cooling air box for yarn drawing. The bottom of the air outlet of the cooling air box is located above the conveyor belt, guiding part of the air out of the cooling air box to the conveyor belt of the web forming machine for cooling the spun layer. An exhaust fan is installed below the conveyor belt, which is connected to the air inlet of the air conditioning unit to draw the cold air on the conveyor belt back to the air conditioning unit, realizing a closed-loop air path.

[0019] Further optionally, in step S3, a cooling channel is provided below the spinneret of the spunbond box, and a conveyor belt of the web forming machine is provided below the cooling channel. The filaments ejected from the spinneret pass vertically downward through the cooling channel and fall onto the conveyor belt after cooling.

[0020] The cooling channel has air outlets for cooling air boxes on both sides. The surface of the air outlets is covered with wire mesh with a mesh size of 100-120. The air from the cooling air boxes is filtered and evenly distributed into the filaments in the cooling channel by the wire mesh.

[0021] Further optionally, one end of the baffle is fixedly connected to the top of the corresponding air outlet, and the other end is suspended and points to the baffle on the opposite side, with the baffles on both sides of the cooling channel at the same height.

[0022] The distance between the suspended ends of the two baffles and the metering pump speed satisfy the following proportional relationship: 1cm:(1.5-2.0)rpm.

[0023] Optionally, the bottom of the spunbond box is provided with at least one air collection pipe for collecting cold air overflowing from the top of the cooling channel, and the collected cold air is used for individual smoke extraction of the spunbond box.

[0024] This invention aims to prepare ultrathin spunbond nonwoven fabrics. The spunbonding box requires a small amount of material, necessitating extremely low rotational speed of the metering pump. The filaments ejected from the spinneret are vertically lowered into the cooling channel. Air outlets from cooling air boxes on both sides of the cooling channel blow air directly onto the filaments. The cooled air is then delivered from the top and bottom of the cooling channel. The air from the top is collected by an air collection pipe for reuse, while the air from the bottom is blown onto the conveyor belt to further cool the spun layers on the conveyor belt, thus fully utilizing the cooling capacity.

[0025] The baffle plate designed at the top of the air outlet of this invention narrows the air outlet passage at the top of the cooling channel, making it easier for the cold air blown out of the outlet to penetrate the fabric curtain and cool the fabric fibers closer to the center of the cooling channel. Simultaneously, the extremely low speed of the metering pump used for ultra-thin spunbond results in a very low basis weight of the fabric fibers, making the fibers themselves prone to movement. The design of the wire mesh covering the air outlet and the baffle plate ensures that the cooling air is gentler and more uniform, and penetrates the fabric fibers more easily. This reduces the amplitude of fiber movement, making them less likely to stick together or break, thus improving the quality of the fabric and the spun layer, and the stability of the finished product.

[0026] Further optional, in step S3, the temperature of the cold air output from the air outlet is 8-20°C. The inventors unexpectedly discovered that the cooling box provides sufficient cooling for the filament, making the filament form faster and the fibers less likely to break.

[0027] The cooling unit is a magnetic levitation refrigeration unit, which can reduce power consumption, make it more energy-efficient and quieter and more environmentally friendly while ensuring stable cooling effect, and provide faster cooling capacity for the cooling fan.

[0028] The speed of the cold air fan is 500-700 rpm, and the speed of the suction fan is 650-750 rpm; the speed of the fan used for single-unit smoke extraction is 300-500 rpm. Compared with the speed of the fans used to prepare conventional spunbond nonwoven fabrics, the speed of the above three types of fans is lower. This can be combined with the low speed and low wind speed of the metering pump, and can also help to produce finer filaments and maintain the stability of the filaments, making the fibers less prone to breakage, less prone to sticking, and more stable.

[0029] Optionally, in step S5, the temperature of the pressure rollers of the hot rolling mill is 105-125℃, and the pressure inside the hot rolling mill is controlled within the range of 0.4-0.5MPa. The hot rolling mill uses a PLC control system to ensure the stability of the internal pressure of the hot rolling mill, avoid the penetration and heat melting of the extremely low basis weight fabric by high pressure, and improve the strength of the product in all directions; it also avoids the fiber not melting due to low pressure.

[0030] Optionally, the oil supply end of the hot rolling mill is equipped with a filter and pressure regulator. The filter and pressure regulator includes a filter body, an oil inlet pipe and an oil outlet pipe. One end of the oil inlet pipe is connected to the bottom of the filter body and the other end is connected to the outlet of the thermal oil furnace. One end of the oil outlet pipe is connected to the top of the filter body and the other end is connected to the oil supply port of the hot rolling mill.

[0031] The filter body has a filter element inside. The filter element is made of steel wire mesh wound outward in circles with the vertical central axis inside the filter body as the center. It can filter out impurities in hot oil, making the oil pressure more stable and improving the yield. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process flow for the preparation method of the ultrathin spunbond nonwoven fabric described in Example 1.

[0033] Figure 2 This is a schematic diagram of the cooling channel and the air outlets on both sides;

[0034] Figure 3 This is a schematic diagram of the filter voltage regulator in Example 2.

[0035] In the attached diagram, 1-cooling channel, 2-air outlet, 3-baffle plate, 4-wire mesh, 5-filter body, 6-oil inlet pipe, 7-oil outlet pipe, 8-filter element, 9-wire material. Detailed Implementation

[0036] Example 1

[0037] The method for preparing the ultrathin spunbond nonwoven fabric described in this embodiment is as follows: Figures 1-2 As shown, it includes the following steps:

[0038] S1: The raw material is metered and fed into the screw extruder. The material extruded by the screw extruder is filtered through a filter and then fed into the metering pump.

[0039] S2: The metering pump supplies material to the spinneret of the spunbond box at low speed, and the spinneret performs ultra-thin spinning.

[0040] S3: The filaments sprayed out in step S2 are in the form of a curtain and are cooled and stretched through the air outlet 2 of the cooling air box. The top of the air outlet 2 is provided with a horizontal baffle 3 so that the cold air output from the air outlet 2 can penetrate deep into the curtain and fully cool the filaments.

[0041] S4: The cooled filaments from step S3 are laid flat on the conveyor belt of the web forming machine to form a single-layer spun fabric.

[0042] Three sets of spinnerets are evenly arranged along the length of the web forming machine conveyor belt. Each spinneret includes a screw extruder, a metering pump, a spunbond box, and a cooling air box. Each set of spinnerets sequentially performs the above steps S1-S4. The spun layer on the upstream side of the conveyor belt moves with the conveyor belt to the position of the next corresponding spinneret, and then receives another spun layer. This results in the spun layers formed by several sets of spinnerets being stacked on top of each other (three spun layers) to form a spunbond.

[0043] S5: The spunbond obtained in step S4 is successively hot-pressed by a hot rolling mill, shaped by a winding machine, and slit by a slitting machine to obtain the finished ultra-thin spunbond nonwoven fabric.

[0044] In step S1, the raw materials include polypropylene and masterbatch. The melt index of the polypropylene is 32 g / 10 min, and the masterbatch is a colored masterbatch.

[0045] Polypropylene and masterbatch are metered at a mass ratio of 97:3 and then conveyed to a screw extruder via vacuum suction for raw material mixing and extrusion. The extruded material is filtered to remove impurities before entering a metering pump. The screw temperature is 265℃. A feed pipe is connected between the filter and the metering pump, and a pressure gauge is installed on the feed pipe. The pressure of the filtered slurry is controlled within the range of 5.5±0.05MPa, i.e., pressure fluctuation is 0.05MPa.

[0046] In step S2, the rotation speed of all three metering pumps is 11 rpm.

[0047] In step S2, it is also necessary to perform single-molecule smoke extraction on the spunbond box, extract and collect the small molecule monomer gas generated by the spunbond box, and then discharge this part of the gas into the waste gas treatment device for filtration before being discharged into the environment.

[0048] The preparation method includes a cooling system to cool the filament stretching in step S3 and the spinning layer on the conveyor belt in step S4. The cooling system includes a cooling unit and three sets of fans, with each set of fans corresponding to a set of spinnerets.

[0049] One set of fans includes an air conditioning unit, a cooling fan, and an exhaust fan. The cooling unit is connected to each air conditioning unit. The air outlet of the air conditioning unit is connected to the cooling air box through the cooling fan to provide cold air to the cooling air box for yarn drawing. The bottom of the air outlet 2 of the cooling air box is located above the conveyor belt, guiding part of the air out of the cooling air box to the conveyor belt of the web forming machine for cooling the spun layer. An exhaust fan is installed below the conveyor belt, which is connected to the air inlet of the air conditioning unit to draw the cold air on the conveyor belt back to the air conditioning unit, realizing a closed-loop air path.

[0050] In step S3, a cooling channel 1 is provided below the spinneret of the spunbond box, and a conveyor belt of the web forming machine is provided below the cooling channel 1. The filaments 9 ejected from the spinneret pass vertically downward through the cooling channel 1 and fall onto the conveyor belt after cooling.

[0051] Cooling air outlets 2 are provided on both sides of the cooling channel 1. The surface of the air outlet 2 is covered with wire mesh 4, and the wire mesh 4 has a mesh count of 100.

[0052] One end of the baffle plate 3 is fixedly connected to the top of the corresponding air outlet 2, and the other end is suspended and points to the baffle plate 3 on the opposite side. The baffle plates 3 on both sides of the cooling channel 1 are at the same height.

[0053] The distance between the suspended ends of the two baffles and the metering pump speed satisfy the following ratio: 1cm:1.5rpm, that is, the distance between the suspended ends of the two baffles is 7.33cm.

[0054] The bottom of the spunbond box is equipped with three air collection pipes for collecting the cold air overflowing from the top of the cooling channel 1. The collected cold air is used for individual smoke extraction of the spunbond box.

[0055] In step S3, the temperature of the cold air output from air outlet 2 is 8°C; the cooling unit is a magnetic levitation refrigeration unit.

[0056] The air cooler operates at 500 rpm, the exhaust fan at 650 rpm, and the fan used for individual smoke extraction operates at 300 rpm.

[0057] In step S5, the temperature of the hot rolling mill's pressure rolls is 105℃, and the pressure inside the hot rolling mill is controlled at around 0.4MPa. The hot rolling mill uses a PLC control system to ensure the stability of the internal pressure.

[0058] Comparative Example 1

[0059] The preparation method of the ultrathin spunbond nonwoven fabric described in this comparative example is the same as that in Example 1, except that a baffle plate is not provided at the top of the air outlet.

[0060] Example 2

[0061] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in Example 1, except that, as Figure 3 As shown, the oil supply end of the hot rolling mill is equipped with a filter and pressure regulator. The filter and pressure regulator includes a filter body 5, an oil inlet pipe 6 and an oil outlet pipe 7. One end of the oil inlet pipe 6 is connected to the bottom of the filter body 5 and the other end is connected to the outlet of the thermal oil furnace. One end of the oil outlet pipe 7 is connected to the top of the filter body 5 and the other end is connected to the oil supply port of the hot rolling mill.

[0062] The filter body 5 is equipped with a filter element 8 inside. The filter element 8 is made of steel wire mesh 4 wound outward in circles with the vertical central axis inside the filter body 5 as the center. It can filter out impurities in hot oil, making the oil pressure more stable and improving the yield.

[0063] Example 3

[0064] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in Example 2, except that the melt index of the raw material polypropylene is 42 g / 10 min.

[0065] Example 4

[0066] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in Example 2, except that the melt index of the raw material polypropylene is 43 g / 10 min.

[0067] Example 5

[0068] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2. The difference is that in step S1, the pressure of the filtered slurry is controlled within the range of 5.5 ± 0.2 MPa, that is, the pressure fluctuation is 0.2 MPa.

[0069] Example 6

[0070] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2, except that the metering pump speed is 16 rpm in step S2.

[0071] Example 7

[0072] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2, except that the speed of the metering pump in step S2 is 14 rpm.

[0073] Comparative Example 2

[0074] The preparation method of the ultrathin spunbond nonwoven fabric described in this comparative example is the same as that in Example 2, except that the speed of the metering pump in step S2 is 17 rpm.

[0075] Example 8

[0076] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2. The difference is that the distance between the suspended ends of the two baffles and the speed of the metering pump satisfies the following ratio: 1cm:2.0rpm, that is, the distance between the suspended ends of the two baffles is 5.5cm.

[0077] Example 9

[0078] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2. The difference is that the distance between the suspended ends of the two baffles and the speed of the metering pump satisfy the following ratio: 1cm:1.4rpm, that is, the distance between the suspended ends of the two baffles is 7.86cm.

[0079] Example 10

[0080] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2. The difference is that in step S3, the temperature of the cold air output from the air outlet is 20°C, the speed of the cold air fan is 700 rpm, the speed of the suction fan is 750 rpm, and the speed of the fan used for individual smoke extraction is 500 rpm.

[0081] Example 11

[0082] The preparation method of the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in embodiment 2. The difference is that in step S3, the temperature of the cold air output from the air outlet is 21°C, the speed of the cold air fan is 710 rpm, the speed of the suction fan is 760 rpm, and the speed of the fan used for individual smoke extraction is 510 rpm.

[0083] Table 1 Comparison of yield rates of ultrathin spunbond nonwoven fabrics produced in the examples and comparative examples.

[0084]

[0085]

[0086] The yield rate is equal to the quality of the qualified products produced divided by the quality of the raw materials input.

[0087] All of the above examples and comparative examples can produce a weight of 5 g / m³. 2 The table above shows the preparation method of ultra-thin spunbond nonwoven fabric provided by this invention. A lower metering pump speed, combined with suitable cold air temperature, cold air fan speed, suction fan speed, and the speed of the fan used for individual smoke extraction, along with high-quality polypropylene raw materials and suitable post-filtration pressure, enables stable production of ultra-thin spunbond nonwoven fabric. Furthermore, the design of the cooling channel and air outlet, as well as the design of the filter voltage regulator, effectively improves the product yield.

Claims

1. A method for preparing an ultrathin spunbond nonwoven fabric, characterized in that, Includes the following steps: S1: The raw material is metered and fed into the screw extruder. The material extruded by the screw extruder is filtered through a filter and then fed into the metering pump. S2: The metering pump supplies material to the spinneret of the spunbond box at low speed, and the spinneret performs ultra-thin spinning; the speed of the metering pump is 14-16 rpm; S3: The filaments sprayed out in step S2 are in the form of a curtain and are cooled and stretched through the air outlet of the cooling air box. A horizontal baffle is provided at the top of the air outlet so that the cold air output from the air outlet can penetrate deep into the curtain and fully cool the filaments. S4: The cooled filaments from step S3 are laid flat on the conveyor belt of the web forming machine to form a single-layer spun fabric. Several sets of spinnerets are evenly arranged along the length of the web forming machine conveyor belt. Each spinneret includes a screw extruder, a metering pump, a spunbond box and a cooling box. Each set of spinnerets sequentially performs the above steps S1-S4. The spun layer on the upstream side of the conveyor belt moves with the conveyor belt to the position of the next corresponding spinneret, and then receives another spun layer. This allows the spun layers formed by several sets of spinnerets to be superimposed on top of each other to form a spunbond. S5: The spunbond obtained in step S4 is successively hot-pressed by a hot rolling mill, shaped by a winding machine, and slit by a slitting machine to obtain the finished ultra-thin spunbond nonwoven fabric. In step S1, the raw materials include polypropylene and masterbatch, and the melt index of polypropylene is 32-42 g / 10min. A cooling channel is provided below the spinneret of the spunbond box, and air outlets of cooling air boxes are respectively provided on both sides of the cooling channel. The surface of the air outlets is covered with wire mesh. One end of the baffle is fixedly connected to the top of the corresponding air outlet, and the other end is suspended and points to the baffle opposite. The baffles on both sides of the cooling channel are at the same height. The distance between the suspended ends of the two baffles and the metering pump speed satisfy the following proportional relationship: 1cm:(1.5-2.0)rpm; In step S1, after the polypropylene and masterbatch are metered, they are conveyed to the screw extruder by vacuum suction for raw material mixing and extrusion. The extruded material is filtered to remove impurities before entering the metering pump. The pressure of the filtered slurry is controlled within the range of 5.5±0.05MPa.

2. The method for preparing ultrathin spunbond nonwoven fabric according to claim 1, characterized in that, The preparation method includes a cooling system to cool the filament stretching in step S3 and the spinning layer on the conveyor belt in step S4. The cooling system includes a cooling unit and several component fans, with each component fan corresponding to a set of spinnerets. One set of fans includes an air conditioning unit, a cooling fan, and an exhaust fan. The cooling unit is connected to each air conditioning unit. The air outlet of the air conditioning unit is connected to the cooling air box through the cooling fan to provide cold air to the cooling air box for yarn drawing. The bottom of the air outlet of the cooling air box is located above the conveyor belt, guiding part of the air out of the cooling air box to the conveyor belt of the web forming machine for cooling the spun layer. An exhaust fan is installed below the conveyor belt, which is connected to the air inlet of the air conditioning unit to draw the cold air on the conveyor belt back to the air conditioning unit, realizing a closed-loop air path.

3. The method for preparing ultrathin spunbond nonwoven fabric according to claim 2, characterized in that, Below the cooling channel is a conveyor belt for a web forming machine. The filaments ejected from the spinneret pass vertically downward through the cooling channel and fall onto the conveyor belt after cooling. The wire mesh has a mesh count of 100-120.

4. The method for preparing ultrathin spunbond nonwoven fabric according to claim 3, characterized in that, In step S3, the temperature of the cold air output from the air outlet is 8-20℃; The cooling unit is a magnetic levitation refrigeration unit, which can reduce power consumption, make it more energy-efficient and quieter and more environmentally friendly while ensuring stable cooling effect, and provide faster cooling capacity for the cooling fan. The speed of the air cooler is 500-700 rpm, and the speed of the exhaust fan is 650-750 rpm; the speed of the fan used for single-unit smoke extraction is 300-500 rpm.

5. The method for preparing ultrathin spunbond nonwoven fabric according to claim 1, characterized in that, In step S5, the temperature of the pressure rolls of the hot rolling mill is 105-125℃, the pressure inside the hot rolling mill is controlled within the range of 0.4-0.5MPa, and the hot rolling mill uses a PLC control system to ensure the stability of the internal pressure of the hot rolling mill.

6. The method for preparing ultrathin spunbond nonwoven fabric according to claim 1, characterized in that, The hot rolling mill is equipped with a filter and pressure regulator at the oil supply end. The filter and pressure regulator includes a filter body, an oil inlet pipe and an oil outlet pipe. One end of the oil inlet pipe is connected to the bottom of the filter body and the other end is connected to the outlet of the thermal oil furnace. One end of the oil outlet pipe is connected to the top of the filter body and the other end is connected to the oil supply port of the hot rolling mill. The filter body has a filter element inside. The filter element is made of steel wire mesh wound outward in circles with the vertical central axis inside the filter body as the center. It can filter out impurities in hot oil, making the oil pressure more stable and improving the yield.

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