Preparation method of ultrathin spun-bonded non-woven fabric

Abstract

The invention relates to a preparation method of an ultrathin spunbond non-woven fabric, which comprises the following steps: metering raw materials, inputting the raw materials into a screw extruder, filtering the extruded materials, and inputting the filtered materials into a metering pump; the metering pump provides materials for the spunbond box body at a low rotating speed, and the spinneret plate performs ultra-thin spinning; the sprayed silk material is cooled and drafted through an air outlet of the cooling air bellow, and a horizontal air baffle is arranged at the top of the air outlet, so that cold air output by the air outlet can penetrate into the curtain-shaped silk material; spreading the cooled silk material on a conveyor belt of a lapper to form a single-layer spinning layer; a plurality of groups of spinning modules are uniformly distributed in the length direction of the conveyor belt of the lapper, each group of spinning modules sequentially performs the steps, the spinning layer on the upstream side of the conveyor belt moves to the position corresponding to the next spinning module along with the conveyor belt, and then one spinning layer is received, so that the spinning layers formed by the plurality of groups of spinning modules are overlapped up and down to form a spun-bonded body; the spun-bonded body is subjected to hot pressing through a hot rolling mill, shaping through a winding machine and slitting through a slitting machine in sequence, and the ultrathin spun-bonded non-woven fabric finished product is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-thin spunbond non-woven fabric production, and specifically relates to a method for preparing ultra-thin spunbond non-woven fabric. Background Art

[0002] The main materials of spunbond non-woven fabrics are polyester and polypropylene. They are resistant to high and low temperatures, aging and UV rays, have high elongation, good stability and breathability, are corrosion-resistant, sound-proof, moth-proof and non-toxic. They are widely used in the fields of sanitary products, packaging and luggage fabrics. The lower the gram weight of the spunbond non-woven fabric, the thinner the fabric, and the difficulty of preparation increases exponentially. Low-gram-weight spunbond non-woven fabrics have higher product value and can be used to make diapers, sanitary napkins, masks, protective products and other products. They are more comfortable and are loved by consumers. Moreover, for products of the same area, a lower gram weight can directly reduce product costs. At present, the gram weight of thin spunbond non-woven fabrics is 15g / m 2 The weight of ultra-thin spunbond nonwoven fabric is about 5g / m 2 However, due to its extremely low gram weight, if the traditional spunbond nonwoven production process and equipment are used, it will cause broken yarns, uneven web formation, holes, etc., and the production process is extremely unstable and prone to defective products. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for preparing an ultra-thin spunbonded nonwoven fabric, comprising the following steps:

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

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

[0006] S3: The silk material sprayed out in step S2 is in a curtain shape and passes through the air outlet of the cooling bellows for cooling and stretching. A horizontal wind shield is provided on the top of the air outlet so that the cold air output from the air outlet can penetrate into the curtain shape and fully cool the silk material.

[0007] S4: the cooled silk material in step S3 is laid flat on the conveyor belt of the web-forming machine to form a single-layer spinning layer;

[0008] Several groups of spinning modules are evenly arranged along the length direction of the conveyor belt of the web forming machine, and the spinning modules include a screw extruder, a metering pump, a spunbond box and a cooling bellows. Each group of spinning modules sequentially performs the above steps S1-S4, and the spun layer on the upstream side of the conveyor belt moves with the conveyor belt to the position corresponding to the next spinning module, and then takes on another spun layer, so that the spun layers formed by several groups of spinning modules are stacked up and down to form a spunbond body;

[0009] S5: The spunbond body obtained in step S4 is sequentially subjected to hot pressing by a hot calender, shaping by a winder, and slitting by a slitting machine to obtain an ultra-thin spunbond nonwoven fabric product.

[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 protection masterbatch, super soft masterbatch, and smooth masterbatch;

[0011] The melt index of polypropylene is 32-42 g / 10 min, and the deviation of the melt index is small, so that the flow performance of polypropylene after heating and melting is more stable, which is suitable for the preparation of the ultra-thin spunbond nonwoven fabric of the present invention. However, the melt index of polypropylene, the raw material of ordinary spunbond nonwoven fabric, has a large deviation, and the flow performance of polypropylene after melting is greatly reduced, which is not suitable for the preparation of ultra-thin spunbond nonwoven fabric.

[0012] Optionally, in step S1, polypropylene and masterbatch are measured in a ratio required by the ultra-thin spunbond non-woven fabric, and then transported to a screw extruder by vacuum suction for raw material mixing and extrusion. The extruded material is a fluid slurry, which is filtered through a filter to remove impurities, and blocky insolubles or solid impurities are filtered out and removed, and the remaining slurry enters a metering pump.

[0013] Optionally, in step S1, a feed pipe is connected between the filter and the metering pump for conveying the filtered slurry, and a pressure gauge is provided on the feed pipe for measuring the pressure of the filtered slurry; the pressure of the filtered slurry is controlled within the range of 5.5±0.05MPa, that is, the pressure fluctuation of the filtered slurry in the feed pipe is 0.05MPa.

[0014] The present invention increases the pressure sensitivity control, making the spinning screw more stable and less vibrating. The pressure fluctuation is small, resulting in less vibration, which helps the metering pump to work stably at a low speed, and further helps to stabilize the spinning. The pressure of the filtered slurry is controlled by the speed of the screw extruder. The faster the screw speed of the screw extruder, the greater the pressure of the filtered slurry.

[0015] Preferably, in step S2, the speed of the metering pump is 14-16 rpm. Compared with the existing spunbond nonwoven fabric process, the metering pump of the present invention has a very low speed and feeds the material to the spunbond box very slowly, so as to match the very small amount of material used when the spinneret is ultra-thin spinning, which is helpful for producing ultra-thin spunbond nonwoven fabrics.

[0016] Further optionally, in step S2, the spunbond box needs to be subjected to monomer extraction to extract and collect the small molecular monomer gas generated by the spunbond box, and discharge the gas to a waste gas treatment device for filtration and then discharge into the environment.

[0017] Optionally, a cooling system is provided in the preparation method to cool the silk material drafting in step S3 and the spinning layer on the conveyor belt in step S4; the cooling system includes a cooling unit and a plurality of component fans, each component fan corresponds to a group of spinning modules;

[0018] A group of fans includes an air conditioning box, a cooling fan and a suction fan. The cooling unit is respectively connected to each air conditioning box. The air supply port of the air conditioning box is connected to the cooling air box through the cooling fan to provide cold air for the cooling air box for silk drawing. The bottom of the air outlet of the cooling air box is above the conveyor belt, and part of the air outlet of the cooling air box is guided to the conveyor belt of the web forming machine for cooling the spinning layer. A suction fan is provided under the conveyor belt, and the suction fan is connected to the air inlet of the air conditioning box to suck the cold air on the conveyor belt back to the air conditioning box to realize a closed air loop.

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

[0020] The cooling bellows are provided with air outlets on both sides of the cooling channel. The surface of the air outlets is covered with a steel mesh with a mesh number of 100-120. The air outlet of the cooling bellows is filtered and evenly distributed by the steel mesh and blown toward the wire material in the cooling channel more evenly.

[0021] Further optionally, one end of the wind shield is fixedly connected to the top of the corresponding air outlet, and the other end is suspended and points to the opposite wind shield, and the wind shields on both sides of the cooling channel are at the same height;

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

[0023] Further optionally, at least one air collecting duct is provided at the bottom of the spunbond box for collecting cold air overflowing from the top of the cooling channel, and the collected cold air is used for extracting smoke from the spunbond box.

[0024] The present invention is to prepare ultra-thin spunbond non-woven fabrics, the material required for the spunbond box is small, and the speed of the metering pump is required to be extremely low. The silk material sprayed from the spinneret is vertically lowered into the cooling channel, and the cooling air box outlets on both sides of the cooling channel blow air facing the cooling channel to directly cool the silk material. The cold air after cooling the silk material is sent out from the top and bottom of the cooling channel respectively. The cold air output from the top is collected by the air collecting pipe and then reused, and the cold air output from the bottom is blown to the transmission belt to continue cooling the spinning layer on the conveyor belt, which can make full use of the cold capacity.

[0025] The windshield designed at the top of the air outlet of the present invention can narrow the air outlet passage at the top of the cooling channel, so that the cold air blown out of the air outlet can more easily penetrate the silk curtain to cool the silk fibers closer to the center of the cooling channel. At the same time, the extremely low speed of the metering pump used for ultra-thin spunbond makes the weight of the silk fibers extremely low, and the fibers themselves are easy to swing. The steel wire mesh covering the air outlet and the design of the windshield make the cooling air more gentle and uniform, and easier to penetrate the silk fibers, so that the fiber swing amplitude is smaller, and it is not easy to stick together, and it is not easy to break the silk, which improves the quality of the silk and the spinning layer and the stability of the finished product.

[0026] Further optionally, in step S3, the temperature of the cold air output from the air outlet is 8-20° C. The inventor unexpectedly found that the cooling bellows provides sufficient cooling capacity for the silk material, so that the silk material is formed faster and the fibers are not easily broken;

[0027] The cooling unit is a magnetic suspension refrigeration unit, which can reduce power while ensuring a stable refrigeration effect, is more energy-saving, quieter and more environmentally friendly, and provides a faster cooling capacity for the cooling fan;

[0028] The speed of the cooling fan is 500-700rpm, the speed of the suction fan is 650-750rpm; the speed of the fan used for single smoke extraction is 300-500rpm; the speeds of the above three fans are lower than those of fans used to prepare conventional spunbond non-woven fabrics, and can cooperate with the low speed and low wind speed of the metering pump, and can also help produce finer silk fibers and maintain the stability of the silk fibers, making the fibers less likely to break, less likely to stick, and more stable.

[0029] Optionally, in step S5, the temperature of the pressure rollers of the hot rolling mill is 105-125°C, 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 stabilize the internal pressure of the hot rolling mill, thereby avoiding high pressure from penetrating and hot melting extremely low-weight fabrics, thereby increasing the all-directional strength of the product and avoiding low pressure from causing the fibers to not melt.

[0030] Optionally, a filter regulator is provided at the oil supply end of the hot rolling mill, the filter regulator comprising 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] A filter element is provided inside the filter body. The filter element is a steel mesh that is wound outward in circles with the vertical central axis inside the filter body as the center. It can filter out impurities in the hot oil, making the oil pressure more stable and improving the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the process flow of the method for preparing the ultra-thin spunbonded nonwoven fabric described in Example 1;

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

[0034] Figure 3 Schematic diagram of the filter regulator of Example 2.

[0035] In the attached drawings, 1-cooling channel, 2-air outlet, 3-wind shield, 4-wire mesh, 5-filter body, 6-oil inlet pipe, 7-oil outlet pipe, 8-filter element, 9-wire material. DETAILED DESCRIPTION

[0036] Example 1

[0037] The preparation method of the ultra-thin spunbond nonwoven fabric described in this embodiment is as follows: Figure 1-Figure 2 As shown, the following steps are included:

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

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

[0040] S3: The silk material sprayed out in step S2 is in a curtain shape and passes through the air outlet 2 of the cooling bellows for cooling and stretching. A horizontal wind shield 3 is provided on the top of the air outlet 2 so that the cold air output from the air outlet 2 can penetrate into the curtain shape and fully cool the silk material.

[0041] S4: the cooled silk material in step S3 is laid flat on the conveyor belt of the web-forming machine to form a single-layer spinning layer;

[0042] Three groups of spinning modules are evenly arranged along the length direction of the conveyor belt of the web forming machine. The spinning modules include a screw extruder, a metering pump, a spunbond box and a cooling bellows. Each group of spinning modules sequentially performs the above steps S1-S4. The spinning layer on the upstream side of the conveyor belt moves with the conveyor belt to the position corresponding to the next spinning module, and then takes on another spinning layer, so that the spinning layers formed by several groups of spinning modules are superimposed up and down (three spinning layers up and down) to form a spunbond body.

[0043] S5: The spunbond body obtained in step S4 is sequentially subjected to hot pressing by a hot calender, shaping by a winder, and slitting by a slitting machine to obtain an ultra-thin spunbond nonwoven fabric product.

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

[0045] After the polypropylene and masterbatch are metered at a mass ratio of 97:3, they are transported to the screw extruder by vacuum suction for raw material mixing and extrusion. The extruded material is filtered through a filter to remove impurities and then enters the metering pump. The screw temperature is 265°C. A feed pipe is connected between the filter and the metering pump, and a pressure gauge is provided on the feed pipe. The pressure of the filtered slurry is controlled within the range of 5.5±0.05MPa, that is, the pressure fluctuation is 0.05MPa.

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

[0047] In step S2, the spunbond box needs to be subjected to monomer extraction to extract and collect the small molecular monomer gas generated by the spunbond box, and then the gas is uniformly discharged to the exhaust gas treatment device for filtration and then discharged into the environment.

[0048] The preparation method is provided with a cooling system to cool the silk material drafting in step S3 and the spinning layer on the conveyor belt in step S4; the cooling system includes a cooling unit and three components of fans, each component of the fans corresponds to a group of spinning modules;

[0049] A group of fans includes an air conditioning box, a cooling fan and a suction fan. The cooling unit is connected to each air conditioning box respectively. The air supply port of the air conditioning box is connected to the cooling air box through the cooling fan to provide cold air for the cooling air box for silk drawing. The bottom of the air outlet 2 of the cooling air box is above the conveyor belt, and part of the air outlet of the cooling air box is guided to the conveyor belt of the web forming machine for cooling the spinning layer. A suction fan is provided under the conveyor belt, and the suction fan is connected to the air inlet of the air conditioning box to suck the cold air on the conveyor belt back to the air conditioning box to realize a closed air loop.

[0050] In step S3, a cooling channel 1 is provided below the spinneret of the spunbond box, and a conveyor belt of a 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 being cooled.

[0051] Air outlets 2 of cooling air boxes are respectively arranged on both sides of the cooling channel 1. The surface of the air outlet 2 is covered with a steel mesh 4, and the mesh number of the steel mesh 4 is 100 meshes.

[0052] One end of the windshield 3 is fixedly connected to the top of the corresponding air outlet 2, and the other end is suspended and points to the opposite windshield 3, and the windshields 3 on both sides of the cooling channel 1 are at the same height;

[0053] The distance between the suspended ends of the two wind shields and the rotation speed of the metering pump meet the following proportional relationship: 1 cm: 1.5 rpm, that is, the distance between the suspended ends of the two wind shields is 7.33 cm.

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

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

[0056] The speed of the cooling fan is 500rpm, the speed of the suction fan is 650rpm; the speed of the fan for single-unit smoke extraction is 300rpm.

[0057] In step S5, the temperature of the hot rolling mill's rollers is 105°C, the pressure inside the hot rolling mill is controlled at about 0.4 MPa, and the hot rolling mill uses a PLC control system to stabilize the internal pressure of the hot rolling mill.

[0058] Comparative Example 1

[0059] The method for preparing the ultra-thin spunbonded nonwoven fabric described in this comparative example is the same as that of Example 1, except that no wind shield is provided at the top of the air outlet.

[0060] Example 2

[0061] The method for preparing the ultra-thin spunbonded nonwoven fabric described in this embodiment is the same as that in embodiment 1, except that Figure 3 As shown, a filter regulator is provided at the oil supply end of the hot rolling mill, and the filter regulator comprises 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] A filter element 8 is provided inside the filter body 5. The filter element 8 is a steel 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 the hot oil, making the oil pressure more stable and improving the yield rate.

[0063] Example 3

[0064] The method for preparing the ultra-thin spunbond nonwoven fabric described in this embodiment is the same as that in Embodiment 2, except that the melt index of the raw material polypropylene is 42 g / 10 min.

[0065] Example 4

[0066] The method for preparing the ultra-thin spunbond nonwoven fabric described in this embodiment is the same as that in Embodiment 2, except that the melt index of the raw material polypropylene is 43 g / 10 min.

[0067] Example 5

[0068] The method for preparing the ultrathin spunbond nonwoven fabric described in this embodiment is the same as that in Embodiment 2, except 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 method for preparing the ultra-thin spunbonded nonwoven fabric described in this embodiment is the same as that in Embodiment 2, except that in step S2, the rotation speed of the metering pump is 16 rpm.

[0071] Example 7

[0072] The method for preparing the ultra-thin spunbond nonwoven fabric described in this embodiment is the same as that in Embodiment 2, except that in step S2, the rotation speed of the metering pump is 14 rpm.

[0073] Comparative Example 2

[0074] The method for preparing the ultra-thin spunbonded nonwoven fabric described in this comparative example is the same as that of Example 2, except that in step S2, the rotation speed of the metering pump is 17 rpm.

[0075] Example 8

[0076] The preparation method of the ultra-thin spunbond nonwoven fabric described in this embodiment is the same as that of Embodiment 2, except that the spacing between the suspended ends of the two windshields and the rotation speed of the metering pump satisfy the following proportional relationship: 1 cm: 2.0 rpm, that is, the spacing between the suspended ends of the two windshields is 5.5 cm.

[0077] Example 9

[0078] The preparation method of the ultra-thin spunbond nonwoven fabric described in this embodiment is the same as that of Embodiment 2, except that the spacing between the suspended ends of the two windshields and the rotation speed of the metering pump satisfy the following proportional relationship: 1cm:1.4rpm, that is, the spacing between the suspended ends of the two windshields is 7.86cm.

[0079] Example 10

[0080] The preparation method of the ultra-thin spunbond non-woven fabric described in this embodiment is the same as that of Embodiment 2, except that, in step S3, the temperature of the cold air output from the air outlet is 20°C, the rotation speed of the cold air fan is 700rpm, the rotation speed of the suction fan is 750rpm; the rotation speed of the fan used for single-body extraction is 500rpm.

[0081] Embodiment 11

[0082] The preparation method of the ultra-thin spunbond non-woven fabric described in this embodiment is the same as that in Embodiment 2, except that, in step S3, the temperature of the cold air output from the air outlet is 21°C, the rotation speed of the cold air fan is 710rpm, the rotation speed of the suction fan is 760rpm; the rotation speed of the fan used for single-body extraction is 510rpm.

[0083] Table 1 Comparison of the yield of ultra-thin spunbonded nonwoven fabrics produced in the embodiments and comparative examples

[0084]

[0085]

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

[0087] The above embodiments and comparative examples can produce a weight of 5g / m 2 As can be seen from the above table, the preparation method of the ultra-thin spunbond non-woven fabric provided by the present invention, the relatively low metering pump speed, the appropriate cold air temperature, the cold air fan speed, the suction fan speed, the fan speed for single smoke extraction, the high-quality polypropylene raw material, and the appropriate pressure after filtration can stably produce ultra-thin spunbond non-woven fabrics. In addition, the design of the cooling channel and the air outlet of the present invention, as well as the design of the filter stabilizer, can effectively improve the yield rate of the product.

Claims

1. A method for preparing an ultra-thin spunbonded nonwoven fabric, characterized in that: The following steps are involved: S1: The raw materials are metered and fed into a screw extruder. The materials extruded by the screw extruder are filtered through a filter and then fed into a metering pump; S2: The metering pump supplies materials to the spinneret of the spunbond box at a low speed, and the spinneret performs ultra-thin spinning; the speed of the metering pump is 11-16rpm; S3: The silk material sprayed out in step S2 is in a curtain shape and passes through the air outlet of the cooling bellows for cooling and stretching. A horizontal wind shield is provided on the top of the air outlet so that the cold air output from the air outlet can penetrate into the curtain shape and fully cool the silk material. S4: the cooled silk material in step S3 is laid flat on the conveyor belt of the web-forming machine to form a single-layer spinning layer; Several groups of spinning modules are evenly arranged along the length direction of the conveyor belt of the web forming machine, and the spinning modules include a screw extruder, a metering pump, a spunbond box and a cooling bellows. Each group of spinning modules sequentially performs the above steps S1-S4, and the spun layer on the upstream side of the conveyor belt moves with the conveyor belt to the position corresponding to the next spinning module, and then takes on another spun layer, so that the spun layers formed by several groups of spinning modules are stacked up and down to form a spunbond body; S5: The spunbond body obtained in step S4 is sequentially subjected to hot pressing by a hot calender, shaping by a winder, and slitting by a slitting machine to obtain an ultra-thin spunbond nonwoven fabric product.

2. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: In step S1, the raw materials include polypropylene and masterbatch, and the melt index of the polypropylene is 32-42 g / 10 min.

3. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: In step S1, after the polypropylene and the masterbatch are metered, they are transported to a screw extruder by vacuum suction for raw material mixing and extrusion. The extruded material is filtered through a filter to remove impurities and then enters a metering pump; the pressure of the filtered slurry is controlled within the range of 5.5±0.05MPa.

4. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: In step S2, the rotation speed of the metering pump is 14-16 rpm.

5. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: The preparation method is provided with a cooling system to cool the silk material drafting in step S3 and the spinning layer on the conveyor belt in step S4; the cooling system includes a cooling unit and a plurality of component fans, each component fan corresponding to a group of spinning modules; A group of fans includes an air conditioning box, a cooling fan and a suction fan. The cooling unit is respectively connected to each air conditioning box. The air supply port of the air conditioning box is connected to the cooling air box through the cooling fan to provide cold air for the cooling air box for silk drawing. The bottom of the air outlet of the cooling air box is above the conveyor belt, and part of the air outlet of the cooling air box is guided to the conveyor belt of the web forming machine for cooling the spinning layer. A suction fan is provided under the conveyor belt, and the suction fan is connected to the air inlet of the air conditioning box to suck the cold air on the conveyor belt back to the air conditioning box to realize a closed air loop.

6. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 5, characterized in that: A cooling channel is provided below the spinneret of the spunbond box, and a conveyor belt of a 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 being cooled. Air outlets of cooling air boxes are respectively arranged on both sides of the cooling channel, and the surface of the air outlets is covered with a steel mesh with a mesh number of 100-120.

7. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 6, characterized in that: One end of the windshield is fixedly connected to the top of the corresponding air outlet, and the other end is suspended and points to the opposite windshield, and the windshields on both sides of the cooling channel are at the same height; The distance between the suspended ends of the two wind shields and the rotation speed of the metering pump meet the following proportional relationship: 1 cm: (1.5-2.0) rpm.

8. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 6, characterized in that: In step S3, the temperature of the cold air output from the air outlet is 8-20°C; The cooling unit is a magnetic suspension refrigeration unit, which can reduce power while ensuring a stable refrigeration effect, is more energy-saving, quieter and more environmentally friendly, and provides a faster cooling capacity for the cooling fan; The speed of the cooling fan is 500-700rpm, the speed of the suction fan is 650-750rpm; the speed of the fan used for single-unit smoke extraction is 300-500rpm.

9. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: In step S5, the temperature of the hot rolling mill's rollers is 105-125°C, 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 stabilize the internal pressure of the hot rolling mill.

10. The method for preparing the ultra-thin spunbonded nonwoven fabric according to claim 1, characterized in that: The oil supply end of the hot rolling mill is provided with a filter regulator, which 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; A filter element is provided inside the filter body. The filter element is a steel mesh that is wound outward in circles with the vertical central axis inside the filter body as the center. It can filter out impurities in the hot oil, making the oil pressure more stable and improving the yield rate.

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