JP2017186716A - Yarn interlacing apparatus and method for producing synthetic fiber using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid interlacing apparatus which suppresses the occurrence of the counterflow of discharge air during interlacing processing against the yarn running direction of a running yarn, and which hardly causes fuzzing and slackening.SOLUTION: A yarn interlacing apparatus 1 includes: a yarn path section for allowing a yarn to pass therethrough and be interlaced therein; fluid jetting holes 15 for jetting a fluid onto the running yarn; a yarn guide slit 16 for allowing the yarn path section and an outside to communicate with each other and for inserting the yarn therethrough; and an air discharge groove 18 on a jetting hole surface or an opposing wall surface, communicating with the outside space of the interlacing apparatus 1 with the yarn path section in between. In the yarn interlacing apparatus 1, the air discharge groove 18 is present in a hollow conical region 25 formed by excluding a second conical region 24 from a first conical region 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a yarn entanglement imparting device and a method for producing a synthetic fiber using the same.

  Conventionally, in a synthetic fiber manufacturing process, a compressed fluid is sprayed onto a yarn to cause entanglement between single yarns, forming an entangled portion and a spread portion, and a yarn having a converging property is widely used as an entangled yarn. Are known. Various yarn entanglement applying devices for forming these entangled yarns have been proposed so far.

  Patent Document 1 has a narrowed portion where the area in the cross section perpendicular to the running direction of the yarn in the yarn path portion is the smallest, and the cross-sectional area is from the narrowed portion toward the entrance / exit portion of the yarn in the yarn path portion. A confounding device that is gently expanding is disclosed.

  Patent Document 2 discloses an entanglement imparting device in which thread guide holes having a circular or oval cross-sectional shape are provided, and discharge holes for leading compressed fluid to the outside are provided at both ends thereof.

JP 2013-227711 A Japanese Patent Laid-Open No. 3-344098

  However, in the entanglement imparting device disclosed in Patent Document 1, since most of the compressed fluid injected to the yarn is exhausted to the outlet side in the running direction of the yarn, the fluid to be exhausted is unstable at a high injection pressure. Fluctuations are likely to occur, the confounding performance is reduced, and it is difficult to stably provide confounding. Further, since the yarn is likely to vibrate due to fluctuations in the exhaust fluid, the yarn collides with the wall surface inside the nozzle, and the damage to the yarn increases.

  In the entanglement imparting device disclosed in Patent Document 2, the discharge holes arranged on the inlet side and the outlet side of the yarn discharge the compressed fluid uniformly on the inlet side and the outlet side. The effect of propelling the strip is small, the backflow of the compressed fluid to the upstream side of the yarn is likely to occur, the yarn is slackened, and the yarn is easily damaged.

  In view of the above problems, the present invention provides a fluid entanglement imparting device that is less likely to cause yarn damage such as fuzz and slack of yarns even in processing from low compression to high compression fluid.

The entanglement processing apparatus for multifilament yarns of the present invention that achieves the above-described problems is as follows.
A yarn path portion through which the yarn passes, a slit portion for introducing the yarn into the yarn path portion, and an injection hole surface and an opposite wall surface facing each other across the yarn path portion. In the entanglement processing apparatus for multifilament yarns, two fluid ejection holes with intersecting axes are opened, and the yarns are entangled at the yarn path portion by the fluid ejected from the two fluid ejection holes.
The ejection hole surface and / or the opposing wall surface is provided with an exhaust groove communicating with the external space of the entanglement processing device across the yarn path portion on the upstream side of the yarn path from the fluid ejection hole,
In a plane including the central axis of the two fluid ejection holes, a ridge line inside the two fluid ejection holes, a region surrounded by the ejection hole surface and the opposite wall surface, or a ridge line and ejection inside the two fluid ejection holes G is the center of gravity of the area surrounded by the hole surface,
A line parallel to the yarn running direction drawn from the center of gravity G to the upstream side of the yarn running direction is defined as CD,
The exhaust groove has a first conical shape region having a vertex as G, a central axis as CD, and an apex angle as θ1, and a second conical shape region as having a vertex as G, the central axis as CD, and the apex angle as θ2. It exists in the excluded hollow cone-shaped region, and the apex angle θ1 (°) of the cone and the apex angle θ2 (°) of the cone satisfy the following expressions (1), (2), and (3).
(1) θ1 <180 °
(2) θ2 ≧ 10 °
(3) θ1> θ2.

  The synthetic fiber manufacturing method of the present invention manufactures a synthetic fiber to which entanglement is imparted by imparting entanglement to the yarn using the multi-filament yarn entanglement imparting device of the present invention.

  By using the multifilament yarn entanglement imparting device of the present invention, it is possible to suppress the backflow of the compressed fluid in the yarn traveling direction, to prevent yarn damage such as yarn fluff and looseness, and from low compression to high compression fluid. It is possible to add entanglement in the processing.

FIG. 1 is a perspective view schematically showing the structure of the yarn entanglement imparting device of the present invention. FIG. 2 is a view showing the injection hole surface as seen from the ZZ cross section of FIG. 3 is a cross-sectional view taken along a plane including the central axes CA and CB in FIG. FIG. 4 is an enlarged view of the yarn path passing portion of FIG. FIG. 5 is an enlarged view of the first conical shape (FIG. 5- (a)), the second conical shape (FIG. 5- (b)), and the hollow conical shape (FIG. 5- (c)) in FIG. is there. FIG. 6 is a schematic view of a configuration in which the central groove 26 is provided on the injection hole surface 21 and the exhaust groove 18 and the central groove 26 are communicated with each other in the yarn entanglement imparting device of the present invention. FIG. 7 is a view showing the injection hole surface as seen from the ZZ cross section of FIG. 8 is a cross-sectional view taken along a plane including the central axes CA and CB in FIG. FIG. 9 is an enlarged view of the yarn path passing portion of FIG. FIG. 10 shows an example in which there is an exhaust groove on the injection wall surface. It is the figure which showed one example of the process of manufacturing a entangled multifilament yarn by melt-spinning a polyethylene terephthalate multifilament yarn and using it for an entanglement process. FIG. 12 is a schematic diagram illustrating a method for measuring the exhaust pressure P1 on the inlet side and the exhaust pressure P2 on the outlet side of the yarn of the confounding device according to the present invention. FIG. 13 is a graph showing the relationship between the set pressure in Example 1, Example 2 and Comparative Example 1 and the inlet side exhaust pressure P1 and the outlet side exhaust pressure P2 of the confounding imparting device. FIG. 14 is a schematic diagram illustrating the arrangement of the exhaust grooves of the confounding device used in the example.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. Reference is made to FIGS. The yarn entanglement imparting device 1 according to the present invention includes a fluid supply unit 11, a fluid ejection nozzle member 12, a side plate member 13, and a spacer 14. Then, by combining the fluid ejection nozzle member 12, the side plate member 13, and the spacer 14, the yarn passage portion 17 through which the yarn passes and imparts entanglement to the yarn, and the yarn passage portion 17 and the outside communicate with each other. A threading slit 16 for introducing a thread into the path portion 17 is formed inside the entanglement imparting device 1. The surface of the fluid injection nozzle member 12 on the yarn hooking slit 16 side is the injection hole surface 21, and the surface of the side plate member 13 on the yarn hooking slit 16 side is the opposing wall surface 22. When the shape of the injection hole surface 21 or the opposed wall surface 22 is not a flat surface but is uneven or curved, the average line of the roughness curve at the unevenness or curved portion is taken as the average value plane, and the injection hole surface 21 and the opposite wall surface 22 And

  The fluid ejecting nozzle member 12 is formed with two fluid ejecting holes 15 that open to the yarn hooking slit 16 and eject fluid onto the traveling yarn. The two fluid ejection holes 15 are formed so that the central axis CA and the central axis CB intersect. The central axis CA and the central axis CB may intersect before reaching the opposing wall surface 22. The shape of the fluid ejection hole 15 is preferably designed to be a circle or an ellipse, and may be slightly deviated from the circle or ellipse within the range of manufacturing errors. As shown in FIG. 1, the central axes CA and CB may intersect at right angles with the running direction of the yarn, or may be inclined toward the outlet side of the entanglement imparting device 1.

  The yarn path portion 17 will be described in more detail with reference to FIG. The yarn path portion 17 is a space extending in the yarn traveling direction in a region surrounded by the inner ridge line of the two fluid ejection holes 15, the ejection hole surface 21 and the opposing wall surface 22. When the inner ridge lines of the two fluid ejection holes 15 intersect before reaching the opposing wall surface 22, the two fluid ejection holes 15 extend in the yarn traveling direction in the region surrounded by the inner ridge lines and the ejection hole surface 21. It is an existing space. The yarn passes through this space, and the yarn causes string vibration behavior to be entangled.

  The shape of the yarn path portion 17 is not limited to a triangle, a square, a hexagon, or the like depending on the arrangement and angle of the two fluid injection holes, or the combination of the injection hole surface 21 and the opposing wall surface 22, but also the injection hole surface 21 and the opposing wall surface. Any shape is conceivable, such as when there is a spherical surface 22. Various shapes are conceivable, such as the injection hole surface 21 and the opposing wall surface 22 expanding from the vicinity of the fluid injection hole 15 toward the exit side in the yarn traveling direction.

  Compressed air injected from the fluid injection hole 15 passes through the yarn path portion 17 to the upstream side in the yarn traveling direction on the injection hole surface 21 or the opposite wall surface 22, or both the injection hole surface 21 and the opposite wall surface 22. An exhaust groove 18 is provided for suppressing backflow.

  The exhaust groove 18 is disposed in a region within the hollow conical shape 25 illustrated in FIG. The hollow conical shape 25 is a region obtained by removing the region of the second conical shape 24 illustrated in FIG. 5B from the region of the first conical shape 23 illustrated in FIG. The first conical shape 23 has G as the center of gravity of the yarn path portion 17 and CD as a line parallel to the yarn traveling direction drawn from the center of gravity G to the upstream side of the yarn traveling direction. A cone having a central axis of CD and an apex angle of θ1 (°). The second conical shape 24 is a cone having an apex G, a central axis CD, and an apex angle θ2 (°). Since θ1 is the apex angle of the first conical shape 23, θ1 <180 °. Since the second conical shape 24 is included in the region of the first conical shape 23, θ1> θ2. Furthermore, θ2 is an angle that satisfies θ2 ≧ 10 °. If θ2 is less than 10 °, the exhaust groove is disposed close to the yarn path, and the running yarn is pulled by the flow of exhaust air that flows out of the exhaust groove to the outside. Uniform entanglement, yarn breakage occurs at the edge that is the boundary between the exhaust groove and the yarn path. Further, when the yarn comes into contact with the edge portion, single yarn breakage, single yarn rolling or turning is likely to occur, resulting in yarn damage and lowering the quality of the yarn.

  Please refer to FIG. FIG. 10 shows various forms in which the exhaust groove 18 is formed on the injection wall surface 21. The exhaust groove 18 only needs to be provided in the region of the hollow conical shape 25, and the shape and depth of the exhaust groove 18 are not particularly limited. Various forms and combinations other than the form shown in FIG. 10 are conceivable.

  Since the exhaust groove 18 is provided in the region of the hollow conical shape 25 as described above, the compressed air ejected from the fluid ejection hole 15 travels along the yarn Y, as compared with the case where the exhaust groove 18 is not provided. Therefore, the compressed air is appropriately avoided in the exhaust groove 18 and discharged to the external space through the exhaust groove 18. As a result, there is less damage to the yarn such as fluff and looseness of the yarn due to the backflow of compressed air, breakage of single yarn, and confounding is applied not only in the treatment with a low compression fluid but also in the treatment with a high compression fluid. Can do.

  Even if the distance from the center of gravity G to the entrance side and the exit side of the yarn is the same length, the yarn path portion 17 is longer than the distance to the exit side, On the contrary, the distance to the entrance side may be shorter than the distance to the exit side.

  Reference is now made to FIGS. The yarn entanglement imparting device 1 of the present invention preferably has a central groove 26 extending along the yarn path on the injection hole wall surface 21 and / or the opposing wall surface 22. The central groove 26 starts from a position after a distance T from the starting point of the yarn path portion on the upstream side in the yarn traveling direction and reaches the end point of the downstream yarn path portion. The central groove 18 and the exhaust groove 18 communicate with each other. The distance T is preferably L / 10 ≦ T ≦ L / 2, where L is the total length of the yarn path portion. When T is L / 10 or more, it is possible to secure a certain length in a region where the distance between the injection hole surface 21 and the opposing wall surface 22 on the upstream side in the yarn traveling direction is short, so that exhaust air flowing backward to the upstream side is suppressed. can do. As a result, the reverse flow of the yarn to the inlet side in the yarn traveling direction can be more effectively suppressed, and the yarn slack and the yarn on the upstream side of the injection hole surface 21 and the opposing wall surface 21 in the yarn traveling direction can be suppressed. This is preferable because the abrasion can be further reduced and damage such as fluff and single yarn breakage can be further reduced. In addition, when T is L / 2 or less, the region of the central groove 26 can be secured to a certain length, so that the behavior region of the yarn when entangled can be widened, and the behavior range of each single yarn becomes large, This is preferable because a more entangled form can be realized, an increase in the number of entanglements, and a strong binding of the converging portions of each single yarn.

  FIG. 11 is a schematic view of a process for producing a fluid entangled multifilament yarn by melt spinning the polyethylene terephthalate multifilament yarn used in the examples described later and subjecting it to fluid entanglement, and 31 is a spinning nozzle (not shown). This is an oil supply guide for applying an oil agent to a multifilament yarn in order to improve the process passability of the thermoplastic melted polymer. 32 and 33 are first and second hot roller units that draw and convey the multifilament yarn at a take-up speed of around 3,000 m / min, and 34 is a winder that winds the drawn and conveyed multifilament yarn. .

(Examples 1 and 2 and Comparative Example 1)
Hereinafter, the effects of the present embodiment will be described in more detail using examples. First, in the entanglement imparting device, the change in the exhaust pressure of the compressed air exhausted out of the entanglement imparting device in the yarn traveling direction depending on the presence or absence of the exhaust groove was examined.

  FIG. 14 is a diagram illustrating details of the exhaust groove of the confounding device used in the example. Of the ridge lines at both ends of the exhaust groove 18 in the groove width direction, an extension line of the ridge line on the side close to the traveling axis Y of the yarn is defined as a line CE. The line CE intersects at an angle θ3 that is symmetric with respect to the upstream side of the yarn traveling direction across the yarn traveling axis Y, and the center of gravity G is the intersection. The start point of the exhaust groove 18 is separated from the end point of the yarn path portion by a distance L2 on the upstream side in the yarn running direction, and away from the yarn running axis Y by a distance L3 in a direction perpendicular to the yarn running direction. In position. The exhaust groove 18 is formed from the start point toward the downstream side of the yarn traveling direction and away from the yarn traveling axis Y, and communicates with the outside of the entanglement imparting device.

  In this examination, the confounding imparting apparatus shown in FIGS. 1 and 14 was used. Examples 1 and 2 each have the shape of the confounding device shown in FIG. 1, and the exhaust grooves 18 of Examples 1 and 2 have different widths and depths, and Example 1 has a groove width: 1.3 mm and groove depth: 0.65 mm. In Example 2, the groove width is 3.4 mm and the groove depth is 0.6 mm. The distance L2 was 6 mm, the distance L3 was 0.25 mm, and the angle θ3 was 25 °. The injection hole diameter of the fluid injection hole 15 is a circle having a diameter of 0.9 mm, the plane including the central axes CA and CB of the two fluid injection holes 15 is perpendicular to the traveling yarn, and the angle formed by CA and CB is 90 degrees, the yarn path length L was 16 mm, and the injection wall surface and the opposing wall surface were parallel and smooth surfaces that did not expand toward the exit side and the entrance side in the yarn running direction. The spacer thickness H for adjusting the gap between the spray wall surface and the opposing wall surface was 0.3 mm. Comparative Example 1 has a shape without an exhaust groove of the confounding imparting device shown in FIG. 1 and has the same configuration and dimensions as those of Examples 1 and 2 except that there is no exhaust groove.

(1) Exhaust pressure on the outlet side and the inlet side of the confounding device:
The measurement of the exhaust pressure P1 on the inlet side and the exhaust pressure P2 on the outlet side of the yarn path portion of the entanglement imparting device when compressed air was injected from the fluid ejection holes was performed. FIG. 12 shows a schematic diagram when measuring the exhaust pressure. P1 and P2 indicate pressure gauges, and L1 is the distance from the center of gravity G of the yarn path portion 17 of the confounding imparting device to the pressure gauges P1 and P2, respectively. For measurement of the exhaust pressure, a handy manometer PG-100 manufactured by Nidec Copal Electronics Co., Ltd. was used, and the discharge pressure measurement distance L1 was set to 16 mm.

  The set pressure for fluid ejection was set to 0.2, 0.3, 0.4, and 0.5 MPa. Each exhaust pressure measurement result and the maximum value, minimum value, and average value of the exhaust pressure difference (P2-P1) are shown in Table 1. In addition, FIG. 13 shows the measurement results of the set pressure for fluid injection, the exhaust pressure P1 on the inlet side, and the exhaust pressure P2 on the outlet side in Table 1. FIG. 13 is a graph in which the negative side of the vertical axis is the exhaust pressure P1 on the inlet side, and the positive side of the vertical axis is the exhaust pressure P2 on the outlet side.

  The following can be understood from the results of Table 1 and FIG. As shown in FIG. 1, the entanglement imparting device according to the first and second embodiments has an exhaust groove that communicates with the external space of the entanglement processing device with the yarn path portion on the upstream side of the yarn path with respect to the ejection hole surface, Since the exhaust pressure P1 on the inlet side is lower than the exhaust pressure P2 on the outlet side, it can be seen that the flow of compressed air flowing backward to the upstream side of the yarn path can be suppressed. On the other hand, the confounding imparting device of Comparative Example 1 is not provided with an exhaust groove, and the exhaust pressure P1 on the inlet side and the exhaust pressure P2 on the outlet side are almost the same pressure, and the compressed air that flows backward to the upstream side of the yarn path It can be seen that the flow is not suppressed.

(Examples 1-5, Comparative Examples 1-8)
Using the entanglement imparting devices of Examples 1 and 2 and Comparative Example 1, multifilament yarns were actually collected with the outline of the process shown in FIG. Polyethylene terephthalate multifilament yarn having a different cross section of 90 dtex and 72 filaments was melt spun and subjected to fluid entanglement treatment, and the wound multifilament yarn was collected at a winding speed of 3000 m / min. The set pressure for fluid ejection was 0.3 MPa. The number of entangled multifilament yarns and the number of fluffs were measured.

Furthermore, the multifilament yarn was extract | collected on the same conditions using the confounding provision apparatus of Examples 3-5 and Comparative Examples 2-8 shown below.
Example 3: A constricted portion in which the gap between the injection wall surface and the opposed wall surface becomes shorter between the ejection wall surface and the opposed wall surface in the yarn traveling direction than the fluid ejection hole, and the opposed wall surface is in the yarn traveling direction. Example 2 is the same as Example 2 except that the shape expands toward the exit side and the entrance side. The gap between the injection wall surface and the opposing wall surface in the throttle portion was set to a spacer thickness H of 0.3 mm, and the injection wall surface was parallel to the traveling axis Y of the running yarn and was a smooth surface.
Example 4: The same as Example 2 except that the central groove was arranged. The central groove has a V-groove shape with a volume of 12.6 mm ³ .
Example 5: The same as Example 2 except that the same throttle part as Example 3 is arranged and the same central groove as Example 4 is arranged.
Comparative Example 2: The same as Comparative Example 1 except that the same aperture part as in Example 3 was arranged.
Comparative Example 3: The same as Comparative Example 1 except that Example 4 and the central groove were arranged.
Comparative Example 4 The same as Comparative Example 1 except that the same throttle part as in Example 3 is arranged and the same central groove as in Example 4 is further arranged.
Comparative Examples 5 to 8: The same as Examples 2 to 5 except that the angle θ3 was set to 4 °.

(2) Convergence (measurement and determination of the number of confounding):
The number of entanglement was measured about the polyester thread of the atypical cross section obtained in each Example and the comparative example. As a measuring device, an automatic continuous entanglement tester R-2072 manufactured by Rosshield was used. The pretension is set to 10 cN, the trip tension is set to 17 cN, the number of setting coefficient entangled parts is set to 20, the sample yarn is run, and the yarn length required to count 20 entangled parts (running yarn length) Measurements were made to determine the average length from the entangled part to the next entangled part.

  Further, the average value of the above lengths was converted into the number of entanglements per 1 m of yarn length, and this converted value was obtained as “number of entanglements per 1 m of yarn length”. In the measurement, the average value was obtained by setting the n number to 20 times.

  In the determination of the number of entanglements, the number of entanglements per 1 m of yarn is expressed as “bad” in Table 2 as “bad”, and from 5 to less than 15 as “slightly unachieved” in Table 2, “△” In Table 2, “15” or more and less than 25 are indicated as “good”, and in Table 2, “25” or more are indicated as “best” and in Table 2, “「 ”. “Best” and “good” were accepted, and “slightly not achieved” and “bad” were rejected.

(3) Package quality (measurement and determination of the number of fluff):
The number of fluffs was measured for the polyester yarn having a modified cross section obtained in each of the examples and comparative examples. A fluff counting device DT-105 manufactured by Toray Engineering Co., Ltd. was used as a measuring device. The detection height is set to 0.5 mm by the S-type detector, the unwinding speed of the package is set to 500 m / min, the yarn length of 10,000 m is measured, and the fluff present per 10,000 m length of the yarn is measured as it is. Calculated as a number.

  The number of fluff is judged as “bad” when the number of fluffs per 10,000 m length of yarn is “bad” in Table 2 and as “x” in the range of 4 to less than 6 2 is represented by “Δ”, 2 or more and less than 4 are represented as “good”, “Table 2” is represented by “◯”, and less than 2 are represented as “best” by “◎”. “Best” and “good” were accepted, and “slightly not achieved” and “bad” were rejected.

(4) Overall evaluation:
The overall evaluation reflected the lower evaluation results for both convergence and package quality in the overall evaluation. “Best” and “good” were accepted, and “slightly not achieved” and “bad” were rejected. Table 2 shows the configuration of confounding imparting apparatuses in Examples 1 to 5 and Comparative Examples 1 to 8, and the results of convergence, package quality, and comprehensive evaluation.

  The following can be seen from the results in Table 2. The entanglement imparting devices of Examples 1 to 5 have the same performance as Comparative Examples 1 to 4 with respect to the number of entanglements, but the number of fluffs can be reduced as compared with Comparative Examples 1 to 4. The entanglement imparting devices of Comparative Examples 5 to 8 are the same as those of Examples 2 to 5 except that the angle θ3 is different. However, the number of entanglements is slightly decreasing and the number of fluffs is greatly increased.

1: Entangling device 11: fluid supply unit
12: Fluid ejection nozzle member 13: Side plate member
14: Spacer 15: Fluid injection hole 16: Yarn hooking slit 17: Yarn path 18: Exhaust groove
19: Fluid introduction path 20: Fluid supply path 21: Injection hole surface 22: Opposing wall surface 23: First conical shape 24: Second conical shape 25: Hollow conical shape 26: Central groove 31: Oil supply guide
32: First hot roller unit 33: Second hot roller unit 34: Winding machine G: Center of gravity of the yarn path 17 L: Yarn path length L1: Exhaust pressure measurement distance L2: End of the thread path in the yarn running direction Distance from point to start point of exhaust groove 18 L3: Distance between yarn travel axis Y and parallel line CF T: Distance from yarn path start point upstream of yarn travel direction to center groove start point Y: Yarn Strip running axis H: Spacer thickness CA: Center axis CB of fluid ejection hole 15: Center axis CD of fluid ejection hole 15: Vertical line CE from the center of gravity G toward the upstream side in the yarn running direction CE: Groove width of the exhaust groove 18 Extension line CF of the ridge line on the running axis Y side of the yarn in the direction CF: Parallel lines P1, P2 parallel to the running axis Y of the yarn: Pressure gauge

Claims (3)

A yarn path portion through which the yarn passes, a slit portion for introducing the yarn into the yarn path portion, and an injection hole surface and an opposite wall surface facing each other across the yarn path portion. In the entanglement processing apparatus for multifilament yarns, two fluid ejection holes with intersecting axes are opened, and the yarns are entangled at the yarn path portion by the fluid ejected from the two fluid ejection holes.
The ejection hole surface and / or the opposing wall surface is provided with an exhaust groove communicating with the external space of the entanglement processing device across the yarn path portion on the upstream side of the yarn path from the fluid ejection hole,
In a plane including the central axis of the two fluid ejection holes, a ridge line inside the two fluid ejection holes, a region surrounded by the ejection hole surface and the opposite wall surface, or a ridge line and ejection inside the two fluid ejection holes G is the center of gravity of the area surrounded by the hole surface,
A line parallel to the yarn running direction drawn from the center of gravity G to the upstream side of the yarn running direction is defined as CD,
The exhaust groove has a first conical shape region having a vertex as G, a central axis as CD, and an apex angle as θ1, and a second conical shape region as having a vertex as G, the central axis as CD, and the apex angle as θ2. A multifilament yarn that exists in the hollow cone-shaped region except that the apex angle θ1 (°) of the cone and the apex angle θ2 (°) of the cone satisfy the following expressions (1), (2), and (3): Confounding device.
(1) θ1 <180 °
(2) θ2 ≧ 10 °
(3) θ1> θ2 The injection hole surface and / or the opposing wall surface has a central groove extending along a yarn path,
The central groove starts from a position that has passed a distance T from the yarn path start point on the upstream side in the yarn running direction, and reaches the end point of the downstream yarn path,
The exhaust groove communicates with the central groove;
The said distance T is the entanglement provision apparatus of the multifilament yarn of Claim 1 which satisfy | fills the following formula | equation (4) by making the full length of a yarn path part into L.
(4) L / 10 ≦ T ≦ L / 2   A method for producing a synthetic fiber, wherein a synthetic fiber to which entanglement is imparted is produced by imparting entanglement to the yarn using the multifilament yarn entanglement imparting device according to claim 1.

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