Method for manufacturing nonwoven fabrics

Abstract

In the case of manufacturing a high-grade product with a single fine-fine filament, or in the case of increasing the number of discharge holes of a spinneret or lengthening the spinneret to improve productivity, in order to prevent the occurrence of filament breakage and stably manufacture nonwoven fabrics, a method for manufacturing nonwoven fabrics is provided, which comprises melt-spinning a thermoplastic polymer from a plurality of discharge holes arranged in the long side direction and the short side direction of a rectangular spinneret, blowing an air flow from the outside to the inside of the long side of a rectangular running area where the obtained plurality of filaments run by a cooling device, and capturing the cooled plurality of filaments into a net-like nonwoven fabric manufacturing method, wherein a suction device having suction ports extending over the entire circumference of the rectangular running area is arranged between the spinneret and the cooling device in the running direction of the filaments, and adjusting the suction flow rate QL per unit length and per unit time in the suction ports on the long side of the rectangular running area and the suction flow rate QS per unit length and per unit time in the suction ports on the short side of the rectangular running area to satisfy 1<QS / QL<5.

Description

Technical Field

[0001] The present invention relates to a method for producing nonwoven fabrics (especially spunbonded nonwoven fabrics) for various applications such as medical and sanitary materials, civil engineering materials, industrial materials, and packaging materials. Background Art

[0002] The manufacturing method of spunbond nonwoven fabrics includes: an open type manufacturing method (hereinafter referred to as the open type), which uses air flow to cool the filaments produced by melt spinning, stretches them through a circular air gun or a slit air gun, and then spreads them on a mesh belt; a closed type manufacturing method (hereinafter referred to as the closed type), which introduces the spun filaments into a cooling chamber and cools them by air flow, and then directly passes the air flow as a stretching wind through a nozzle where the filaments travel, stretches the filaments, and spreads them from the nozzle to the traction belt.

[0003] In either method, when the density of the discharge holes of the spinneret is increased in order to improve productivity, more airflow is required accordingly. In addition, especially in the closed type, when the tensile tension is increased in order to reduce the fiber diameter, it is necessary to increase the airflow. When the airflow is increased in this way, the swing of the silk increases and the number of broken silk increases. Especially in the traveling area (hereinafter referred to as "traveling area" or "rectangular traveling area") where the cross section in the direction intersecting the traveling direction of the filament is a rectangular one, the number of broken silk increases at both ends in the long side direction.

[0004] Furthermore, when the length of the rectangular spinneret is extended in the longitudinal direction in order to improve productivity, the number of filament breakages increases at both ends of the filament running region.

[0005] In addition, in recent years, in order to improve the appearance and skin touch of spunbonded nonwoven fabrics, the development of fine-denier filaments with reduced fiber diameters is being actively carried out, but in this case, the filaments are prone to swinging, especially at both ends of the filament running area. In addition, when manufacturing fine-denier filaments, the discharge amount of the polymer discharged from the discharge holes of the rectangular spinneret is sometimes reduced, but the productivity decreases, so the number of discharge holes per unit area of ​​the rectangular spinneret is usually increased.

[0006] Therefore, as a method for improving yarn breakage, Patent Document 1 discloses that yarn breakage is suppressed by providing a difference in suction flow rate using opposing suction devices disposed on the long sides of a rectangular running region where the yarn runs.

[0007] In addition, Patent Document 2 discloses the following: In the traveling direction of the filament, within the height range of the cooling device, a mechanism for exhausting airflow is provided on the side of the cooling device which is arranged relatively to clamp the traveling filament, thereby suppressing filament breakage at both ends in the long side direction of the rectangular traveling area.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application No. 2019-504218

[0011] Patent document 2: Japanese Patent Application Publication No. 2019-206792. Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, according to the inventors' knowledge, the method of Patent Document 1 has a certain improvement effect on the broken wires in the center of the short side direction of the filament running area, but the problem of the broken wires still easily occurring at both ends of the long side direction of the filament running area.

[0014] In addition, in the method of patent document 2, although the broken wires at both ends of the long side direction of the traveling area of ​​the filament can be suppressed to a certain extent, the effect is not sufficient. Especially in the case of making fine fineness filaments by reducing the amount of polymer discharged from the discharge hole of the spinneret, the turbulent airflow near the spinneret will directly shake the filaments and induce broken wires, but in this method, since the airflow control is performed by a cooling device far away from the spinneret, the effect is not sufficient. In addition, in the traveling direction of the filament within the height range of the cooling device, a new mechanism for exhausting the airflow needs to be set up, so there is a problem of excessive equipment cost. Furthermore, a suction blower is required to exhaust the airflow, so there is a problem of increased power.

[0015] Therefore, the object of the present invention is to provide a method for stably manufacturing nonwoven fabrics by preventing the occurrence of yarn breakage even when manufacturing advanced products such as fine-fine filaments, or when increasing the discharge holes of the spinneret or lengthening the rectangular spinneret to improve productivity.

[0016] Means for solving problems

[0017] In order to solve the above-mentioned problems, the present invention is a method for manufacturing a non-woven fabric, which comprises melt-spinning a thermoplastic polymer from a plurality of discharge holes arranged in the long side direction and the short side direction of a rectangular spinneret, using a cooling device to blow air flow from the outside to the inside of the long side of a rectangular travel area where the obtained plurality of filaments travel, and capturing the cooled plurality of filaments into a mesh-like non-woven fabric. In the method for manufacturing the non-woven fabric, a suction device is arranged between the spinneret and the cooling device in the travel direction of the filaments, the suction device has suction ports throughout the entire circumference of the rectangular travel area, and the suction flow rate QL per unit length and per unit time in the suction ports on the long side of the rectangular travel area and the suction flow rate QS per unit length and per unit time in the suction ports on the short side of the rectangular travel area are adjusted in a manner that satisfies 1<QS / QL<5.

[0018] Furthermore, in the method for producing a nonwoven fabric of the present invention, it is preferable to have the following configuration.

[0019] The wind speed blown toward the filaments from the blowing surface of the cooling device is set to 0.5 m / sec or more.

[0020] The density of the discharge holes in the spinneret was set to 2 holes / cm 2 above.

[0021] The shortest distance in the horizontal direction between the outermost discharge hole in the long-side direction of the spinneret and the suction port on the short-side of the rectangular running area is set to 200 mm or less.

[0022] In the present invention, the "thermoplastic polymer" is not limited to thermoplastic polymers such as polyester and polyamide, but also includes cellulose ester-based thermoplastic polymers containing a plasticizer.

[0023] In the present invention, "air flow" means an air flow mainly containing air, but is not limited to (i) ordinary air on the earth, and can also be (ii) components such as oxygen contained in the air, (iii) air containing moisture, (iv) inert gases such as rare gases and nitrogen, (v) steam, (vi) a mixture of the above (i) to (v), etc.

[0024] In the present invention, the so-called "travel area" of the filaments refers to the main route from the thermoplastic polymer melt-spinning from the rectangular spinneret arranged above to the spun filaments being captured in a net shape. As a result of arranging a plurality of spinning holes in the long side direction of the spinneret and spinning a plurality of filaments neatly from these spinning holes, the travel area formed by the plurality of filaments as a whole has a substantially rectangular cross-sectional shape (a cross-sectional shape in a direction intersecting with the travel direction of the filaments). Here, in the travel direction of the filaments, the side close to the spinneret is referred to as "the upper side", and the side close to the net side is referred to as "the lower side".

[0025] In the present invention, the "suction port" refers to an opening for discharging an air flow, and is located above the cooling device and below the discharge port of the spinneret in the running direction of the filaments.

[0026] In the present invention, "discharge hole configuration density" refers to the value obtained by dividing the number of discharge holes by the area of ​​the configuration region of the discharge holes. The greater the configuration density of the discharge holes, the greater the number of discharge holes in the spinneret. It should be noted that the "configuration region" refers to the region inside the outer periphery of the line segment connecting the discharge holes formed by the hole distance of less than 50 times relative to the discharge hole diameter. Fig. 9 This shows an example of a non-perforated area that does not serve as a configuration area.

[0027] Effects of the Invention

[0028] According to the method for manufacturing a nonwoven fabric of the present invention, the suction flow rate of the suction device located between the spinneret and the cooling device in the traveling direction of the filaments is appropriately set, so that the airflow near the spinneret can be controlled to prevent the filaments from breaking, and the nonwoven fabric can be manufactured stably. In addition, even when manufacturing fine-fine filaments of advanced varieties, increasing the number of discharge holes of the spinneret to improve productivity, or lengthening the rectangular spinneret, the nonwoven fabric can be manufactured stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] [ Figure 1 ] Figure 1 This is a schematic perspective view of an example of an apparatus for implementing the method according to the present invention.

[0030] [ Figure 2 ] Figure 2 This is a schematic cross-sectional view (short side) of an example of an apparatus for carrying out the method according to the present invention.

[0031] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view (long side) of an example of an apparatus for carrying out the method according to the present invention.

[0032] [ Figure 4 ] Figure 4This is a schematic diagram showing the air flow pattern (direction, flow rate) just below the spinneret when the method according to the present invention is not implemented.

[0033] [ Figure 5 ] Figure 5 This is a schematic diagram showing the state of the airflow just below the spinneret when the method according to the present invention is carried out.

[0034] [ Figure 6 ] Figure 6 This is a schematic diagram showing the arrangement area of ​​the spinneret discharge holes in the spinneret that can be used in the method according to the present invention.

[0035] [ Figure 7 ] Figure 7 It is a schematic side view (short side) showing the form (direction, flow speed) of the airflow in the horizontal center of the airflow outlet surface of the cooling device.

[0036] [ Figure 8 ] Figure 8 It is a schematic side view (short side) showing the state (direction, flow speed) of the airflow near both ends in the horizontal direction of the airflow outlet surface of the cooling device when the method according to the present invention is not implemented.

[0037] [ Fig. 9 ] Fig. 9 This is a schematic diagram showing the arrangement area and the non-perforated area of ​​the spinneret discharge holes in the spinneret that can be used in the method of the present invention. DETAILED DESCRIPTION

[0038] Hereinafter, the method for producing the nonwoven fabric of the present invention will be described in detail with reference to the drawings. Figure 1 1 is a schematic perspective view of a nonwoven fabric manufacturing apparatus used in one embodiment of the present invention. Figure 2 yes Figure 1 ZX cross-sectional view, Figure 3 yes Figure 1 YZ section view. Figure 4 It is an enlarged schematic diagram of one end portion of a rectangular traveling region 11 of filaments, showing the airflow pattern just below the spinneret when the method according to the present invention is not implemented. Figure 5 It is an enlarged schematic diagram of one side end of the rectangular running area 11 of the filaments, showing the shape of the airflow directly below the spinneret when the method of the present invention is implemented. It should be noted that "directly below the spinneret" means the area above the cooling device 3 and below the spinning discharge surface in the running direction of the filaments 8. The side that will become the long side of the spinneret 2 is called the long side direction, and the side that will become the short side is called the short side direction. In addition, Figure 4 , Figure 5In the figure, the direction of the arrow indicates the direction of the airflow, and the length of the arrow indicates the speed of the airflow relatively. In addition, the accompanying drawings are conceptual diagrams for accurately conveying the gist of the present invention and are simplified. Therefore, there is no particular limitation on the manufacturing device for implementing the present invention, and the size ratio and the like can be changed according to the embodiment.

[0039] In a method for producing a nonwoven fabric according to one embodiment of the present invention, for example, Figure 1 , 2 3, a thermoplastic polymer is supplied from a molten resin introduction pipe 1 to a spinneret 2, and is discharged from a plurality of discharge holes arranged on the lower surface of the spinneret 2. At this time, the thermoplastic polymer can be directly supplied from the molten resin introduction pipe 1 to the spinneret 2, or can be introduced into the spinneret 2 via a spinning block (not shown) including a hanger die. Then, the plurality of filaments 8 continuously discharged from the discharge holes are cooled by airflow blown from one direction or two directions of a cooling device 3. The cooling device 3 is arranged on the long side of the spinneret 2, and blows airflow from the outside to the traveling area 11 of the filament.

[0040] Although not shown in the figure here, in the case of the closed type, the airflow is directly squeezed by the nozzle and acts as stretching wind, thereby stretching the filament 8; in the case of the open type, the filament is stretched by passing through a circular air gun or a slit air gun that introduces stretching wind separately, and is deposited in a net shape on the moving collection surface.

[0041] For the spinneret 2, a plurality of discharge holes are arranged on the discharge surface along the width direction of the device (the long side direction of the spinneret 2) and the direction perpendicular thereto (the short side direction of the spinneret 2), and are substantially rectangular. In addition, the cross section perpendicular to the travel direction of the filaments in the traveling area 11 of the filaments melt-spun from the plurality of discharge holes arranged in this way is also substantially rectangular. Here, the so-called "rectangle" is any rectangle that can determine the spinneret 2, the long side direction, and the short side direction of the travel area, and does not need to be a strict rectangle without any bumps. Therefore, the arrangement area 10 of the discharge holes in the discharge surface does not need to be a perfect rectangle, for example, it can also be Figure 6 The shapes shown in (a) to (d) and (g) are shown in FIG. Figure 6 As shown in (e) and (f), even if there is a non-arrangement area where the discharge holes are not arranged in the arrangement area of ​​the discharge holes, it is sufficient as long as the overall shape is a rectangle.

[0042] like Figure 3 As shown, the airflow blowing surface 9 of the cooling device 3 is preferably set to be wider than the width of the filament running area 11 in the long side direction of the rectangular running area of ​​the filament. Near the horizontal end of the airflow blowing surface 9, the pressure change of the ambient atmosphere is easy to occur, and the turbulence of the airflow is large, which easily promotes the swing of the filament. By forming the above-mentioned structure, this situation can be prevented.

[0043] In addition, a suction device 4 is provided between the spinneret 2 and the cooling device 3 in the traveling direction of the filament 8. On the long side of the rectangular traveling area 11 of the filament, a suction device 4 having a suction port 5 is provided on the long side, and on the short side of the traveling area 11, a suction device 6 having a suction port 7 is provided on the short side, and the suction ports are opened all around the rectangular traveling area 11. It should be noted that the suction ports 5 and 7 may be provided in such a manner that they are combined to substantially surround the periphery of the rectangular traveling area 11, such as Figure 3 As shown, it is also possible to configure the ribs partially and slightly block the suction flow. The main purpose of these suction devices is to suck the polymer volatiles, but it is not limited to this.

[0044] In the present invention, the suction flow rate QL per unit length and per unit time in the suction ports 5 on the long sides and the suction flow rate QS per unit length and per unit time in the suction ports 7 on the short sides are adjusted to satisfy the following formula.

[0045] 1<QS / QL<5

[0046] In the manufacture of nonwoven fabrics, the thermoplastic polymer just discharged from the spinneret 2 is in a molten state and the yarn tension is also in an extremely low state, so even a slight air flow disturbance is likely to cause yarn swing. In such a state, i.e., directly below the spinneret, it is preferred that the air flow velocity is low and the time variation of the air flow direction is small.

[0047] However, if the airflow of the cooling device 3 is increased in the case of manufacturing fine-fine filaments, the horizontal center of the airflow outlet surface 9 of the cooling device 3 is as follows: Figure 7 As shown in FIG. 1 , the airflow flows downward as a companion flow generated roughly along the traveling direction of the filament 8. In this regard, from the horizontal direction of the airflow blowing surface 9 of the cooling device 3, the airflow is easily oversupplied relative to the filament accompanying flow near the two ends, such as Figure 8 As shown, a large amount of airflow flows countercurrently with respect to the direction of travel of the filaments 8 and flows into the vicinity of the spinneret. Moreover, just below the spinneret, as shown in FIG. Figure 4 As shown, the airflow flows into the filament running area 11. The airflow toward the filament running area 11 just below the spinneret increases the swing of the filaments, which becomes the root cause of the filament breakage.

[0048] Furthermore, if the amount of polymer discharged from the discharge holes of the spinneret 2 is reduced in order to produce fine-fine filaments, the yarn tension of the filaments 8 decreases, and thus the yarn swing becomes more significant.

[0049] Furthermore, when the number of discharge holes of the spinneret 2 is increased, that is, the arrangement density of the discharge holes is increased in order to improve productivity, the difference in the accompanying flow rate between the center of the long side of the filament running area 11 (that is, the horizontal center of the air flow blowing surface 9 of the cooling device 3) and the end of the long side of the filament running area 11 (that is, the horizontal ends of the air flow blowing surface 9 of the cooling device 3) is enlarged. Therefore, the air flow from the end of the long side with less accompanying flow flows into the center of the long side of the filament running area 11 with more accompanying flow, which causes the filament to swing.

[0050] When the spinneret 2 is elongated, a pressure difference occurs between the center and the end portions in the longitudinal direction of the spinneret 2, and thus the difference in flow rate increases, causing the same problem.

[0051] The inventors of the present application have repeatedly conducted in-depth research on the above-mentioned problems that have not been considered in the prior art, and as a result, discovered the new technology of the present invention. Figure 5 As shown, it is found that by increasing the suction flow rate of the suction port 7 on the short side compared to the suction flow rate at the suction port 5 on the long side of the rectangular travel area 11 between the spinneret 2 and the cooling device 3 and appropriately adjusting it, it is possible to suppress the cooling wind from the cooling device 3, which becomes excessively supplied, from flowing into the filaments directly below the spinneret. Specifically, the suction flow rate QL per unit length and per unit time in the suction port 5 on the long side and the suction flow rate QS per unit length and per unit time in the suction port 7 on the short side satisfy the relationship of 1<QS / QL<5 for adjustment. In the case of 1≥QS / QL, the excess airflow tends to flow to the suction port on the long side, and the airflow tends to flow to the travel area 11 of the filament. In addition, in the case of QS / QL≥5, the suction amount on the short side becomes too large, so at both ends of the travel area 11 of the filament, the filament spreads outward in the long side direction, promoting the swing of the filament. Therefore, in the present invention, by adjusting to satisfy 1<QS / QL<5, the airflow toward the filaments 8 is controlled at both ends in the longitudinal direction of the rectangular travel region 11 just below the spinneret to suppress filament breakage.

[0052] QS / QL is preferably within the range of 1.1<QS / QL<2. In addition, the nonwoven fabric manufacturing device preferably has a mechanism for adjusting the balance of the two suction flow rates. For example, it is preferred to have a damper mechanism that can change the width of the suction ports on the long side and the short side, and the gap of the flow path of the suction airflow.

[0053] It should be noted that, as shown in patent document 2, in the case of arranging a mechanism for discharging airflow within the height range of the cooling device 3 in the direction of travel of the filament 8, the area limited by the height of the cooling device 3, although the airflow flowing into the travel area 11 of the filament can be reduced, the inflow of the airflow directly below the spinneret (the area between the spinneret 2 and the cooling device 3) cannot be fully suppressed. In order to maintain productivity, in particular, it is preferred to reduce the amount of polymer discharged from the discharge hole while increasing the number of discharge holes of the spinneret 2, but in this case, the diameter of the filament 8 just discharged is small, and the tension of the filament is small, so it becomes a state where the filament is prone to swing. Therefore, even if the mechanism for discharging airflow is arranged at the position of the cooling device 3 of patent document 2, the effect cannot be exerted at the position where the filament is most prone to swing. In addition, in the case of having a newly set mechanism for discharging airflow, there is also a problem of increased equipment costs and utility costs. However, according to the present invention, compared with the case of providing a mechanism for exhausting airflow in the cooling device 3 of Patent Document 2, the exhaust amount of airflow can be limited to a minimum, the air volume generated by the cooling device 3 based on the blower can be reduced, and thus the power consumption can be reduced.

[0054] In the present invention, it is preferred that the wind speed from the airflow outlet surface 9 of the cooling device 3 is 0.5 / second or more. By setting it to 0.5 / second or more, the cooling of the filaments can be promoted and the occurrence of broken filaments can be further suppressed. The wind speed is more preferably 2.0m / second or less. By setting it to 2.0m / second or less, the swinging of the filaments and the occurrence of broken filaments can be further suppressed.

[0055] In addition, in particular, for producing filaments with a monofilament fineness of less than 2 dtex by a closed type, a high tensile tension is required, and therefore a larger air volume is required. Therefore, the adjustment of the air volume value supplied from the cooling device 3 is important. The airflow blown out from the cooling device 3 is preferably 80 m / min / m or more per unit length and per unit time in the horizontal direction of the airflow blowing surface 9. Furthermore, in the case of producing filaments with a small monofilament fineness, it is preferably set to a larger air volume.

[0056] Furthermore, in the present invention, the arrangement density of the discharge holes in the spinneret 2 is set to 2 holes / cm 2 As a result, the productivity can be improved while preventing fiber breakage. 2 More than, then the accompanying flow to the traveling direction of the filament 8 increases, therefore need to supply the air volume corresponding to this accompanying flow from the cooling device 3, must increase the air volume of the airflow. That is, as mentioned above, owing to be easy to produce air flow turbulence near the end of the length direction of the traveling area 11 of the filament, so the effect of the present invention is more remarkable.

[0057] In addition, according to the inventor's opinion, by making the outermost discharge hole in the long side direction of the spinneret 2 and the suction port 7 on the short side separate in the horizontal direction, the airflow flowing into the travel area 11 of the filament increases. Therefore, it is preferred that the shortest distance L in the horizontal direction between the outermost discharge hole in the long side direction (i.e., the end of the travel area 11 of the filament) and the discharge hole 7 on the short side is 200 mm or less. Such a setting is preferred from the perspective of reducing equipment costs and shortening the length direction.

[0058] In addition, in the present invention, even within the discharge hole arrangement area, it is preferred that only the area near the outermost discharge holes in the long side direction of the spinneret 2 (preferably only the area within 100 mm inward from the outermost discharge holes) be set to have a discharge hole arrangement density lower than the discharge hole arrangement density in the central part in the long side direction. With such a configuration, the interference frequency between the filaments near the ends in the long side direction of the filament running area 11 where the airflow is easily disturbed can be reduced, and filament breakage can be suppressed. At this time, by reducing the arrangement density of the discharge holes, the number of filaments per unit width is reduced, but by Figure 6 As shown in (g), the arrangement area of ​​the discharge holes can be partially enlarged with respect to the longitudinal direction of the spinneret 2, and the number of filaments per unit width can be maintained.

[0059] The present invention is a highly versatile invention and can be applied to the manufacture of all known non-woven fabrics. Therefore, the polymer constituting the non-woven fabric is not particularly limited. For example, if an example of a polymer constituting the non-woven fabric is given, polyester, polyamide, polyphenylene sulfide, polyolefin, polyethylene, polypropylene, etc. can be given. Furthermore, within the range that does not damage the spinning stability, etc., the above-mentioned polymer can contain matting agents such as titanium dioxide, silicon oxide, kaolin, anti-coloring agents, stabilizers, antioxidants, deodorants, flame retardants, silk friction reducing agents, coloring pigments, surface modifiers and other functional particles, organic compounds and other additives, and can also include copolymers.

[0060] The polymer constituting the nonwoven fabric may be composed of a single component or a plurality of components. In the case of a plurality of components, for example, a core-sheath type or a side-by-side type structure may be used.

[0061] The cross-sectional shape of the fibers forming the nonwoven fabric is not limited to a circle, and may also be a cross-sectional shape other than a circle (triangular, flat, etc.) or hollow. In addition, the single filament fineness of the nonwoven fabric is not particularly limited. The number of filaments constituting the nonwoven fabric is also not particularly limited, but the smaller the single filament fineness of the nonwoven fabric and the more the number of filaments, the more obvious the difference from the prior art.

[0062] Next, use Figure 1 The apparatus shown is used to specifically describe a preferred method for producing spunbonded nonwoven fabrics.

[0063] exist Figure 1 In the device shown, for example, a polyolefin resin is melt-spun from a spinneret 2. The spinning temperature at this time is preferably 200 to 270° C., more preferably 210 to 260° C., and further preferably 220 to 250° C. By setting the spinning temperature within the above range, excellent spinning stability can be obtained in a stable molten state.

[0064] Next, the filaments 8 melt-spun from the spinneret 2 are cooled by the cooling device 3. The cooling conditions can be appropriately adjusted and adopted in consideration of the discharge rate per single hole of the spinneret 2, the spinning temperature, the atmosphere temperature, and the like.

[0065] Then, the filaments 8 cooled by the cooling device 3 are stretched by applying tension to the filaments 8 by a circular air gun or a slit air gun (not shown), and blown onto a moving collecting surface to form a nonwoven fabric. The traveling speed of the filaments 8 after stretching is preferably 2,000 to 6,000 m / min, more preferably 3,000 to 5,000 m / min, and further preferably 3,500 to 4,500 m / min. The greater the traveling speed after stretching, the more obvious the difference from the prior art. In addition, the single yarn fineness of the filaments 8 after stretching is preferably 0.1 to 3 dtex, more preferably 0.5 to 2 dtex, and further preferably 0.8 to 1.5 dtex.

[0066] Example

[0067] Hereinafter, the effects of the production method of the present invention will be specifically described with reference to Examples. It should be noted that the methods for measuring the characteristic values ​​in the Examples are as follows.

[0068] <Single yarn fineness>

[0069] From the nonwoven fabric obtained by capturing the filaments on the conveyor belt, remove 50 mm from both ends in the width direction, and then randomly collect 10 small samples. Take a surface photo of each small sample with a digital microscope, measure the diameter [μm] of 4 single fibers from each sample, and measure a total of 40 single fibers, and round off the first decimal place after their average value. Based on the obtained average value, the single fiber fineness is calculated using the following formula. It should be noted that in this embodiment, since polypropylene resin is used, the resin density is 0.91g / cm 3 .

[0070] Single fiber fineness [dtex] = (fiber diameter [μm] / 2) 2 ×π×10000[m]×resin density[g / cm 3 ]×10 -6

[0071] <Broken Wire>

[0072] The spinning condition was observed for 5 minutes, the number of fiber breakages per minute was determined, and evaluation was performed based on the following criteria.

[0073] A: No wire breakage (less than 1 time / minute)

[0074] B: There are some broken wires (more than 1 time / minute, less than 3 times / minute)

[0075] C: Wire breakage (more than 3 times / minute)

[0076] <Suction flow rate>

[0077] The suction flow rate using the suction device was measured at normal temperature and humidity using an anemometer (Japan Kanomax Co., Ltd.: MODEL 6501 series, or Aria Tecnica Co., Ltd.: MODEL AF101 / 201), with the anemometer probe set at the center of the suction port height. For the suction device on the long side, the wind speeds at 10 points were taken at equal intervals in the width direction, and their average wind speed V was calculated. L-AVE For the suction device on the short side, take the wind speed at three points at equal intervals in the width direction and calculate their average wind speed V S-AVE Here, the wind speed value at each point is obtained every 1 second for 10 seconds, and the average value is calculated. The value obtained by multiplying the average wind speed of each of the long side and the short side by the area of ​​the suction port is set as the respective suction flow rates QL and QS.

[0078] <Wind speed of air flow blown from the air flow outlet of the cooling device to the filament>

[0079] The wind speed of the airflow from the cooling device is measured at normal temperature and humidity using an anemometer (Japan Kanomax Co., Ltd.: MODEL 6501 series, or Aria Tecnica Co., Ltd.: MODEL AF101 / 201). The anemometer probe is set at a position 50 mm from the upper end of the airflow blowing surface, a central position at height, and a position 50 mm from the lower end, and the measurement is performed at 3 points in the height direction and 10 points in the width direction at equal intervals, totaling 3 points × 10 points = 30 points. The average wind speed calculated from the data of each point is set as the wind speed of the airflow from the blowing surface of the cooling device.

[0080] <Flow rate of air flow blown from the cooling device to the filaments>

[0081] The value obtained by multiplying the wind speed of the airflow blown from the blowing surface of the cooling device toward the filaments by the area of ​​the blowing surface is set as the flow rate of the airflow.

[0082] <Discharge Hole Arrangement Density>

[0083] The arrangement density of the discharge holes is defined as follows: When the nozzle holes are arranged in a grid pattern, the lateral pitch of the nozzle holes is Ph (mm), the longitudinal pitch is Pv (mm), and the density is 1 / (Ph×Pv) (number / mm 2 ) to find the arrangement density. In addition, when the nozzle holes are arranged in a staggered manner, the area of ​​the triangle formed by connecting the central axes of three adjacent nozzle holes is set to St (mm 2 ), 0.5 / St(pcs / mm 2 ) to find the configuration density.

[0084] It should be noted that when the nozzle hole arrangement is not regular, the 2500mm 2 Measure the number of nozzle holes contained in the square and divide by 2500mm 2 , so as every 1mm 2 The number of nozzle holes is expressed as follows. Among them, 2500mm with a single side of 50mm 2 When the square portion of includes a non-perforated area, the value obtained by calculating without including the non-perforated area is used.

[0085] In addition, unless otherwise specified, the arrangement density of the discharge holes is calculated near the center of the rectangular discharge area in the long-side direction.

[0086] <The shortest distance between the discharge hole and the suction port in the horizontal direction>

[0087] Among the discharge holes through which the thermoplastic polymer flows out of the spinneret, the horizontal distance between the outermost discharge hole and the suction surface of the suction device on the short side when viewed in the longitudinal direction is set as the shortest distance between the discharge hole and the suction port in the horizontal direction.

[0088] (Examples 1 to 3, Comparative Examples 1 and 2)

[0089] Use with Figure 1 The nonwoven fabric was manufactured by using a closed nonwoven fabric manufacturing device having the mechanism shown in FIG. As the raw material resin, a polypropylene resin having a melt flow rate of 60 g / 10 min under a load of 2.16 kgf (21 N) and a temperature of 230° C. according to ASTM-D1238 was used, the molten resin temperature was set to 240° C., the air velocity of the air flow from the air flow outlet surface of the cooling device was set to 1.0 m / sec, and the air volume per 1 m was set to 95 m 3 / min / m, and the density of the spinneret discharge holes was set to 3.6 holes / cm 2The shortest distance between the discharge hole and the suction port in the horizontal direction was set to 80 mm, the discharge rate per hole was set to 0.46 g / min, and a nonwoven fabric having a single yarn fineness of 1.4 dtex was produced under the conditions shown in Table 1. The test results are shown in Table 1.

[0090] In Comparative Example 1, broken wires occurred at both ends of the long side direction of the running area of ​​the filament. In contrast, in Example 1, the suction flow rate of the suction device on the short side was increased and proper control was performed, thereby significantly reducing the number of broken wires. In Example 2, the suction flow rate on the short side was increased compared to Example 1, so that compared with Example 1, the broken wires at both ends of the long side direction of the rectangular running area were further reduced. In Example 3, the suction flow rate on the short side was further increased compared to Example 2, but at both ends of the long side direction of the rectangular running area, the broken wires increased compared to Example 2. Furthermore, as shown in Comparative Example 2, when the suction flow rate was increased, the broken wires increased significantly.

[0091] [Table 1]

[0092]

[0093] (Examples 4 to 6, Comparative Examples 3 and 4)

[0094] In Comparative Example 3, a Figure 1 The nonwoven fabric was manufactured by using an open type nonwoven fabric manufacturing device with the structure shown in FIG. As the raw material resin, a polypropylene resin having a melt flow rate of 60 g / 10 min under a load of 2.16 kgf (21 N) and a temperature of 230° C. according to ASTM-D1238 was used, the molten resin temperature was set to 230° C., the air velocity of the air flow from the air flow outlet surface of the cooling device was set to 0.7 m / s, and the air volume per 1 m was set to 34 m 3 / min / m, and the density of the spinneret discharge holes was set to 3.0 holes / cm 2 The shortest distance between the discharge hole and the suction port in the horizontal direction was set to 80 mm, the discharge rate per hole was set to 0.40 g / min, and a nonwoven fabric having a single yarn fineness of 1.0 dtex was produced under the conditions shown in Table 2. The test results are shown in Table 2.

[0095] Comparative Example 4 and Examples 4 to 6 were also carried out in the same manner as in Comparative Example 3 except that the conditions were changed as shown in Table 2. Nonwoven fabrics were produced.

[0096] In Comparative Example 3, an attempt was made to obtain a web, but filament breakage frequently occurred. In Comparative Example 4, by increasing the flow rate of the air current compared to Comparative Example 3, the frequency of filament breakage decreased, but filament breakage still occurred. On the other hand, in Example 4, by increasing the suction flow rate of the suction device on the short side compared to Comparative Examples 3 and 4, the number of filament breakages was significantly reduced. Additionally, in Example 5, the shortest distance L in the horizontal direction between the discharge hole through which the thermoplastic polymer flows out and the suction port on the short side was increased from Example 4 to 180 mm, enabling stable spinning. Furthermore, in Example 6, the shortest distance L in the horizontal direction between the discharge hole and the suction port was increased to 220 mm, and as a result, a little filament breakage occurred at both ends in the longitudinal direction of the rectangular traveling region.

[0097] [Table 2]

[0098]

[0099] Industrial Applicability

[0100] The present invention relates to a method for suppressing filament breakage in the spinning process that occurs during the production of non-woven fabrics, particularly spunbond non-woven fabrics. The non-woven fabric obtained by this production method can be applied to industrial material films, diapers, sanitary products, medical masks, pollen protection masks, sanitary materials such as medical gowns and curtains, wire wrapping tapes, automotive materials, liquid filtration filters, liner papers, car wash brushes and other industrial materials, food packaging materials, wrapping cloths, yarns, shoe materials, heaters, tea bags, cleaning covers and other daily materials, overall covering materials (original Japanese: べたがけ材), agricultural materials such as agricultural capital pots, roofing materials, civil engineering stabilizing sheets, heat insulation materials, floor materials, building envelopes and other building materials, civil engineering materials, etc., but its application scope is not limited to these.

[0101] Explanation of Reference Numerals

[0102] 1 Melted resin inlet pipe

[0103] 2 Spinneret

[0104] 3 Cooling device

[0105] 4 Suction device on the long side

[0106] 5 Suction port on the long side

[0107] 6 Suction device on the short side

[0108] 7 Suction port on the short side

[0109] 8 Filament

[0110] 9 Air flow blowing surface of the cooling device

[0111] 10 Configuration area of the spinneret discharge holes

[0112] 11 Filament travel area

[0113] 12 Non-perforated area of ​​the spinneret

[0114] L is the shortest distance in the horizontal direction between the outermost discharge hole in the long-side direction of the spinneret and the suction port on the short-side side of the rectangular running area.

Claims

1. A method for producing a nonwoven fabric, comprising: spinning a thermoplastic polymer from a plurality of discharge holes arranged in the long and short directions of a rectangular spinneret, blowing an air flow from the outside to the inside of a rectangular running area where the plurality of filaments are running by a cooling device, and capturing the cooled plurality of filaments into a net-like shape. In the manufacturing method of the nonwoven fabric, a suction device is arranged between the spinneret and the cooling device in the traveling direction of the filaments, the suction device has suction ports all around the entire periphery of the rectangular traveling area, and the suction flow rate QL per unit length and per unit time in the suction ports on the long sides of the traveling area of ​​the rectangle and the suction flow rate QS per unit length and per unit time in the suction ports on the short sides of the traveling area of ​​the rectangle are adjusted in such a way that they satisfy the following formula: 1<QS / QL<5.

2. The method for producing a nonwoven fabric according to claim 1, in, The wind speed blown from the blowing surface of the cooling device to the filaments is set to 0.5 m / sec or more.

3. The method for producing a nonwoven fabric according to claim 1 or 2, in, The arrangement density of the discharge holes in the spinneret was set to 2 holes / cm 2 above.

4. The method for producing a nonwoven fabric according to any one of claims 1 to 3, in, The shortest distance in the horizontal direction between the outermost discharge hole in the long-side direction of the spinneret and the suction port on the short-side side of the rectangular running area is set to 200 mm or less.

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