EP4417740A1

EP4417740A1 - Method of manufacturing false-twisted processed yarn

Info

Publication number: EP4417740A1
Application number: EP24152072.5A
Authority: EP
Inventors: Takahiro Tsuji; Hiroshi Nomura; Yoshimitsu Demizu; Koki KIMURA; Ryosuke SAKUHANA; Kinzo Hashimoto; Yasushi Hayashi
Original assignee: TMT Machinery Inc
Current assignee: TMT Machinery Inc
Priority date: 2023-02-20
Filing date: 2024-01-16
Publication date: 2024-08-21
Anticipated expiration: 2044-01-16
Also published as: EP4417740B1; CN118516791A; TW202434768A; JP2024118131A

Abstract

An object of the present invention is to increase the maximum speed at which a false-twisted processed yarn can be produced.

In a method of manufacturing the false-twisted processed yarn Yf by using a false-twist texturing machine 1, a raw yarn Yr is a partially oriented yarn formed of PET synthetic fibers. When the partially oriented yarn is not false-twisted, the partially oriented yarn has a pre-processing elongation of less than 100%, a boiling water shrinkage of 3.7% to 25%, and a strength of 2.9 cN/dtex or more. In this regard, the pre-processing elongation is the residual elongation. Furthermore, the raw yarn Yr is false-twisted at a processing speed of 1100 m/min or more while being heated and drawn.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a false-twisted processed yarn.
Patent Literature 1 ( Japanese Laid-Open Patent Publication No. 2016-141912 ) discloses a method of manufacturing a false-twisted processed yarn obtained by false-twisting a yarn (raw yarn) formed of filaments made of synthetic fibers. To be more specific, the running raw yarn is twisted while being heated and drawn. The false-twisted processed yarn is formed in this way, and is still wavy in shape even after being untwisted. Typically, a partially oriented yarn in which the orientation of polymers forming the filaments is partially adjusted (i.e., the polymers are partially oriented) is used as the raw yarn. The partially oriented yarn (POY) is produced by, e.g., a spinning apparatus of Patent Literature 2 ( Japanese Laid-Open Patent Publication No. 2008-138301 ).

SUMMARY OF THE INVENTION

Typically, when (i) the raw yarn which is POY is false-twisted and (ii) the running speed (processing speed) of the yarn is arranged to be higher than the maximum speed, the yarn starts to vibrate (i.e., surging occurs) so that false twisting cannot be properly performed. There have recently been demands for further improvement in production efficiency of false-twisted processed yarns.
An object of the present invention is to increase the maximum speed at which a false-twisted processed yarn can be produced.
According to a first aspect of the invention, a method of manufacturing a false-twisted processed yarn is a method of manufacturing the false-twisted processed yarn with use of a false-twist texturing machine which is able to false-twist a running raw yarn while heating and drawing the raw yarn. The false-twist texturing machine includes: a heater configured to heat the raw yarn; a drawing device configured to draw the raw yarn heated by the heater; and a false-twisting device which is provided downstream of the heater in a yarn running direction and which is configured to false-twist the raw yarn. In this regard, the raw yarn is a partially oriented yarn formed of PET synthetic fibers. When the partially oriented yarn is not false-twisted, the partially oriented yarn has a pre-processing elongation of less than 100%, a boiling water shrinkage of 3.7% to 25%, and a strength of 2.9 cN/dtex or more. In this regard, the pre-processing elongation is the residual elongation, and the raw yarn is false-twisted at a processing speed of 1100 m/min or more while being heated and drawn.
In the false-twist texturing machine, the raw yarn is twisted by the false-twisting device. In this regard, surging occurs mainly in the case where the yarn slips in the false-twisting device so as to be repeatedly loosened and tensioned. Typically, the higher the running speed (processing speed) of the yarn in the false-twisting device is, the more likely the yarn is to slip in the false-twisting device. When the processing speed exceeds the maximum speed, the surging occurs. The inventors of the subject application found that the maximum speed was increased in the case where the false-twisted processed yarn was manufactured with use of the raw yarn which was not false-twisted and which had a low residual elongation (hereinafter, this will be referred to as the pre-processing elongation) of less than 100% and a low boiling water shrinkage of 3.7% to 25%. In other words, even when such a raw yarn was false-twisted at a high processing speed of 1100 m/min or more, the occurrence of surging was suppressed. The inventors of the subject application considered the reasons of this as follows.
The low pre-processing elongation and the low boiling water shrinkage mean that, typically, the orientation of polymers forming the raw yarn and the crystallization of the raw yarn have progressed. When such a raw yarn is false-twisted, high tension (hereinafter, this will be referred to as the processing tension) is applied to the raw yarn immediately on the upstream side of the false-twisting device in the yarn running direction. To be more specific, the processing tension is mainly determined by (i) orientation relaxation of the raw yarn and (ii) a resistance force of the raw yarn against drawing. The orientation relaxation is caused as the raw yarn is heated by the heater. Typically, as the orientation of the raw yarn is relaxed, the raw yarn running on the upstream side of the false-twisting device in the yarn running direction is thermally contracted. When the thermal contraction force is large, the processing tension is high. The crystallization has progressed at a part of the raw yarn, and the orientation relaxation is not caused at this part. Instead, because this part has high rigidity, the above-described resistance force is large at this part. When this resistance force is large, the processing tension is high.
Because of these two factors, when (i) the pre-processing elongation of the raw yarn is less than 100% and (ii) the boiling water shrinkage of the raw yarn is 25% or less, the processing tension is high. It is therefore possible to suppress loosening of the yarn during false twisting. It is also possible to suppress the occurrence of surging. Meanwhile, when the boiling water shrinkage is excessively low (i.e., when the crystallization of the raw yarn has progressed too far), high torsional stress is caused when the raw yarn is about to be false-twisted. When the torsional stress is excessively high, an elastic restoring force of the yarn against the torsional stress is also excessively high. As a result, in the false-twisting device, the yarn is likely to slip in the same direction as the torsional stress. In order to suppress this slip of the yarn, the inventors of the subject application considered that the boiling water shrinkage needed to be high to some degree (specifically, to be higher than 3.7%).
The raw yarn has a high strength of 2.9 cN/dtex or more. With this arrangement, even when high tension is applied to the raw yarn, breakage of the raw yarn is suppressed. It is therefore possible to suppress the generation of fluff and/or the yarn breakage during the false twisting.
As such, the maximum speed at which the false-twisted processed yarn can be produced is increased.
According to a second aspect of the invention, the method of the first aspect is arranged such that the pre-processing elongation of the raw yarn is 80% or more.
Typically, when the crystallization of one raw yarn has progressed too far, the pre-processing elongation of this raw yarn is excessively low. When the crystallization of the raw yarn has progressed too far, the above-described torsional stress is likely to be high so that, in the false-twisting device, the yarn is likely to slip in the same direction as the torsional stress. As a result, the maximum speed may be decreased. It is therefore preferable that the pre-processing elongation is 80% or more.
According to a third aspect of the invention, the method of the first or second aspect is arranged such that the boiling water shrinkage of the raw yarn which is not false-twisted is 3.7% or more and 10% or less.
This aspect increases the above-described resistance force. It is therefore possible to increase the processing tension.
According to a fourth aspect of the invention, the method of any one of the first to third aspects is arranged such that the orientation degree of the raw yarn which is not false-twisted is measured by means of Raman spectroscopy and is 1.23 or more and 1.38 or less.
Typically, when the orientation of the raw yarn has progressed too far, the crystallization of the raw yarn tends to progress too far. According to this aspect, the orientation degree is not too high and not too low. Therefore, while the processing tension is increased, the above-described torsional stress is suppressed from being excessively high.
According to a fifth aspect of the invention, the method of any one of the first to fourth aspects is arranged such that the crystallizing degree of the raw yarn which is not false-twisted is 26% or more and 38% or less.
According to this aspect, the crystallizing degree is not too high and not too low. Therefore, while the processing tension is increased, the above-described torsional stress is suppressed from being excessively high.
According to a sixth aspect of the invention, the method of any one of the first to fifth aspects is arranged such that the target elongation which is a target value of the residual elongation of the formed false-twisted processed yarn is set to be 18% or more and 26% or less.
This aspect makes it possible to manufacture the false-twisted processed yarn whose residual elongation is typical.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a profile of a false-twist texturing machine configured to embody a method of manufacturing (manufacturing method) false-twisted processed yarns in the present embodiment.
FIG. 2 is a schematic diagram of the false-twist texturing machine, expanded along paths of yarns.
FIG. 3 shows a spun yarn winding system for producing raw yarns.
FIG. 4(a) is a table showing, e.g., conditions of manufacturing (manufacturing conditions) the raw yarns in Examples and Comparative Examples, and FIG. 4(b) is a table showing, e.g., conditions of false twisting (false-twisting conditions) in those Examples and those Comparative Examples.
FIG. 5(a) is a table showing, e.g., manufacturing conditions of the raw yarns in other Examples and other Comparative Examples, and FIG. 5(b) is a table showing, e.g., false-twisting conditions in those Examples and those Comparative Examples.
FIG. 6(a) is a table showing, e.g., manufacturing conditions of the raw yarns in other Examples and other Comparative Examples, and FIG. 6(b) is a table showing, e.g., false-twisting conditions in those Examples and those Comparative Examples.
FIG. 7 is a graph which schematically shows the relationship between the composition ratio of the molecular structure of each raw yarn and the spinning speed of each raw yarn.
FIG. 8(a) is a graph showing the correlation between the maximum speed of the false twisting and the residual elongation (described later) of each raw yarn, and FIG. 8(b) is a graph showing the correlation between the maximum speed of the false twisting and the processing tension (described later) of each raw yarn.
FIG. 9(a) is a graph showing the correlation between the maximum speed of the false twisting and the boiling water shrinkage of each raw yarn, and FIG. 9(b) shows an enlargement of a part of the graph of FIG. 9(a).
FIG. 10(a) is a graph showing the correlation between the boiling water shrinkage and residual elongation of each raw yarn, and FIG. 10(b) is a graph showing the correlation between the residual elongation and spinning speed of each raw yarn.
FIG. 11(a) is a graph showing the correlation between the maximum speed of the false twisting and the degree of orientation (orientation degree) of each raw yarn, and FIG. 11(b) is a graph showing the correlation between the maximum speed of the false twisting and the degree of crystallizing (crystallizing degree) of each raw yarn.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe an embodiment of the present invention. For the sake of convenience, a direction perpendicular to the sheet of FIG. 1 is referred to as a base longitudinal direction. Furthermore, a left-right direction on the sheet of FIG. 1 is referred to as a base width direction. An up-down direction on the sheet of FIG. 1, i.e., a direction orthogonal to both the base longitudinal direction and the base width direction is referred to as an up-down direction (a vertical direction) in which the gravity acts. In this regard, the base longitudinal direction and the base width direction are substantially in parallel to a horizontal direction. A direction in which each later-described yarn Y runs is referred to as a yarn running direction.

(Overall Structure of False-Twist Texturing Machine)

To begin with, the following will describe the overall structure of a false-twist texturing machine 1 configured to embody a manufacturing method of false-twisted processed yarns Yf in the present embodiment, with reference to FIG. 1 and FIG. 2. FIG. 1 is a profile of the false-twist texturing machine 1. FIG. 2 is a schematic diagram of the false-twist texturing machine 1, expanded along paths of yarns Y (yarn paths).
The false-twist texturing machine 1 is configured to false-twist yarns Y (raw yarns Yr) so as to manufacture false-twisted processed yarns Yf. Each raw yarn Yr is made of, e.g., polyester synthetic fibers. Each raw yarn Yr is, e.g., a multi-filament yarn formed of plural filaments. Alternatively, each raw yarn Yr may be formed of a single filament. Each raw yarn Yr is a typical partially-oriented yarn (POY) in which polymers forming each filament are partially oriented. The raw yarns Yr are formed by a later-described spun yarn winding system 100 (see FIG. 3).
The false-twist texturing machine 1 includes a yarn supplying unit 2, a processing unit 3, and a winding unit 4. The yarn supplying unit 2 is able to supply the yarns Y. The processing unit 3 is configured to take out the yarns Y from the yarn supplying unit 2 and to false-twist the yarns Y. The winding unit 4 is configured to wind the yarns Y processed by the processing unit 3 onto winding bobbins Bw. Components of the yarn supplying unit 2, the processing unit 3, and the winding unit 4 are aligned to form plural lines (see FIG. 2) in the base longitudinal direction. The base longitudinal direction is a direction orthogonal to a yarn running surface (the sheet of FIG. 1) of the yarns Y, on which the yarn paths from the yarn supplying unit 2 to the winding unit 4 via the processing unit 3 are provided.
The yarn supplying unit 2 includes a creel stand 7 retaining yarn supply packages Ps, and is configured to supply the yarns Y (raw yarns Yr) to the processing unit 3. The processing unit 3 is configured to take out the yarns Y from the yarn supplying unit 2 and to process the yarns Y. In the processing unit 3, for example, the following members are provided in this order from the upstream side in the yarn running direction: first feed rollers 11; twist-stopping guides 12; first heaters 13; coolers 14; false-twisting devices 15; second feed rollers 16; interlacing devices 17; third feed rollers 18; a second heater 19; and fourth feed rollers 20. The winding unit 4 includes plural winding devices 21. Each winding device 21 is configured to wind a yarn Y false-twisted by the processing unit 3 onto a winding bobbin Bw, so as to form a wound package Pw. Hereinafter, the yarns Y which have been false-twisted by the processing unit 3 may be referred to as the false-twisted processed yarns Yf.
The false-twist texturing machine 1 includes a main base 8 and a winding base 9 that are spaced apart from each other in the base width direction. The main base 8 and the winding base 9 are substantially identical in length in the base longitudinal direction. The main base 8 and the winding base 9 oppose each other in the base width direction. The false-twist texturing machine 1 includes units termed spans. Each span includes a pair of the main base 8 and the winding base 9. In one span, each device is placed so that the yarns Y running while being aligned in the base longitudinal direction can be simultaneously false-twisted. In the false-twist texturing machine 1, the spans are placed in a left-right symmetrical manner to the sheet, with a center line C of the main base 8 in the base width direction being set as a symmetry axis (i.e., the main base 8 is shared between the left span and the right span). The spans are aligned in the base longitudinal direction.

(Processing Unit)

The following will describe the structure of the processing unit 3 with reference to FIG. 1 and FIG. 2. Each first feed roller 11 is configured to unwind a yarn Y from a yarn supply package Ps attached to the yarn supplying unit 2, and to feed the yarn Y to a first heater 13. As shown in FIG. 2, for example, the first feed roller 11 is configured to feed one yarn Y to the first heater 13. Alternatively, the first feed roller 11 may be able to feed adjacent yarns Y to the downstream side in the yarn running direction. Hereinafter, the conveyance speed of conveying the yarn Y by the first feed roller 11 is referred to as a first yarn feeding speed.
Each twist-stopping guide 12 is arranged to prevent the twist of a yarn Y formed by a false-twisting device 15 from being propagated to the upstream side of the twist-stopping guide 12 in the yarn running direction. Each first heater 13 is configured to heat yarns Y fed from some first feed rollers 11 to a predetermined processing temperature. As shown in FIG. 2, for example, the first heater 13 (a heater of the present invention) is able to heat two yarns Y. The number of the yarns Y heated by the first heater 13 is not limited to this. Each cooler 14 is configured to cool a yarn Y heated by a first heater 13. As shown in FIG. 2, for example, the cooler 14 is configured to cool one yarn Y. Alternatively, the cooler 14 may be able to simultaneously cool plural yarns Y.
Each false-twisting device 15 is provided downstream of a first heater 13 and a cooler 14 in the yarn running direction. The false-twisting device 15 is configured to twist a yarn Y. For example, the false-twisting device 15 is a known so-called disc-friction-type false-twisting device. The false-twisting device 15 includes plural discs (not illustrated) arranged to form a helix. These discs are rotationally driven in the same direction. In this way, the yarn Y is twisted by the friction force between the yarn Y and the surface of each disc.
Each second feed roller 16 is configured to feed a yarn Y processed by a false-twisting device 15 to an interlacing device 17. Hereinafter, the conveyance speed of conveying the yarn Y by the second feed roller 16 is referred to as a second yarn feeding speed. In this regard, a speed (hereinafter, this speed is referred to as a processing speed) at which each yarn Y is false-twisted is defined by, e.g., the second yarn feeding speed. The second yarn feeding speed is higher than the first yarn feeding speed. With this arrangement, the yarn Y is drawn and false-twisted between the first feed roller 11 and the second feed roller 16.
A combination of the first feed roller 11 and the second feed roller 16 may be referred to as a drawing device. The ratio of the second yarn feeding speed to the first yarn feeding speed is typically referred to as the draw ratio. The yarn Y is tensioned while running between the first feed roller 11 and the second feed roller 16. In this regard, when the yarn Y runs immediately upstream of the false-twisting device 15 in the yarn running direction, tension is applied to the yarn Y. Hereinafter, for the sake of convenience, this tension may be referred to as the processing tension.
Each interlacing device 17 is configured to interlace a yarn Y. The interlacing device 17 includes, e.g., a known interlace nozzle configured to interlace the yarn Y by means of an airflow. Each third feed roller 18 is configured to feed a yarn Y running on the downstream side of an interlacing device 17 in the yarn running direction, to the second heater 19. As shown in FIG. 2, for example, the third feed roller 18 is configured to feed one yarn Y to the second heater 19. Alternatively, the third feed roller 18 may be able to feed adjacent yarns Y to the downstream side in the yarn running direction. The conveyance speed of conveying the yarn Y by the third feed roller 18 is lower than the conveyance speed of conveying the yarn Y by each second feed roller 16. The yarn Y is therefore relaxed between the second feed roller 16 and the third feed roller 18. The second heater 19 is configured to heat yarns Y fed from some third feed rollers 18. The second heater 19 extends along a vertical direction, and one second heater 19 is provided in one span. Each fourth feed roller 20 is configured to feed a yarn Y heated by the second heater 19 to a winding device 21. As shown in FIG. 2, for example, the fourth feed roller 20 is able to feed one yarn Y to the winding device 21. Alternatively, the fourth feed roller 20 may be able to feed adjacent yarns Y to the downstream side in the yarn running direction. The conveyance speed of conveying the yarn Y by the fourth feed roller 20 is lower than the conveyance speed of conveying the yarn Y by each third feed roller 18. The yarn Y is therefore relaxed between the third feed roller 18 and the fourth feed roller 20.
In the processing unit 3 arranged as described above, the yarn Y drawn between the first feed roller 11 and the second feed roller 16 is twisted by the false-twisting device 15. The twist formed by the false-twisting device 15 propagates to the twist-stopping guide 12, but does not propagate to the upstream side of the twist-stopping guide 12 in the yarn running direction. The yarn Y which is twisted and drawn is heated by the first heater 13 and thermally set. After that, the yarn Y is cooled by the cooler 14. The yarn Y is untwisted on the downstream side of the false-twisting device 15 in the yarn running direction. However, the yarn Y is maintained to be wavy in shape on account of the thermal setting described above (i.e., the crimp contraction of the yarn Y is maintained).
The false-twisted yarn Y is interlaced by the interlacing device 17 while being relaxed between the second feed roller 16 and the third feed roller 18. After that, the yarn Y is guided toward the downstream side in the yarn running direction. Furthermore, the yarn Y is thermally processed by the second heater 19 while being relaxed between the third feed roller 18 and the fourth feed roller 20. Finally, the yarn Y (false-twisted processed yarn Yf) fed from the fourth feed roller 20 is wound by the winding device 21.

(Winding Unit)

The following will describe the structure of the winding unit 4 with reference to FIG. 2. The winding unit 4 includes winding devices 21. Each winding device 21 is able to wind, e.g., one yarn Y onto one winding bobbin Bw. The winding device 21 includes a fulcrum guide 31, a traverse device 32, and a cradle 33. The fulcrum guide 31 functions as a fulcrum when the yarn Y is traversed. The traverse device 32 is able to traverse the yarn Y by means of a traverse guide 34. The cradle 33 is configured to rotatably support the winding bobbin Bw. A contact roller 35 is provided in the vicinity of the cradle 33. The contact roller 35 is configured to make contact with a surface of a wound package Pw so as to apply a contact pressure to the surface of the wound package Pw. In the winding unit 4 arranged as described above, the yarn Y fed by the fourth feed roller 20 described above is wound onto the winding bobbin Bw by each winding device 21 so as to form the wound package Pw.

(Spun Yarn Winding System)

The following will describe the spun yarn winding system 100 as one example of a system for producing raw yarns Yr, with reference to FIG. 3. FIG. 3 is a profile which schematically shows the spun yarn winding system 100. For the sake of convenience, a predetermined direction orthogonal to the up-down direction is referred to as a front-rear direction. The front-rear direction is in parallel to the left-right direction on the sheet of FIG. 3. A direction orthogonal to both the up-down direction and the front-rear direction is referred to as a left-right direction. The left-right direction is in parallel to a direction perpendicular to the sheet of FIG. 3.
The spun yarn winding system 100 is configured to wind spun-out yarns Y onto bobbins B, so as to form packages P (yarn supply packages Ps described above). The spun yarn winding system 100 includes a spinning apparatus 101, a cooler 102, a take-up unit 103, and a winding unit 104.
The spinning apparatus 101 is configured to discharge (spin out) molten polymer which is a material of the yarns Y (raw yarns Yr). The cooler 102 is configured to cool and solidify the molten polymer. The molten polymer is solidified and formed as the yarns Y each of which is formed of one or more filaments. An oil applicator (not illustrated) configured to apply oil to each yarn Y is provided below the cooler 102.
The take-up unit 103 is configured to take up the descending yarns Y. The take-up unit 103 includes, e.g., a first godet roller 111 and a second godet roller 112. The first godet roller 111 is provided below the spinning apparatus 101, the cooler 102, and the oil applicator. The first godet roller 111 is configured to take up the yarns Y and to send the yarns Y to the second godet roller 112. For example, the second godet roller 112 is provided above and behind the first godet roller 111. The second godet roller 112 is configured to send the yarns Y to the winding unit 104.
The winding unit 104 is configured to wind the yarns Y onto the bobbins B so as to form the packages P. The winding unit 104 is provided below the second godet roller 112. The winding unit 104 includes fulcrum guides 121, traverse guides 122, a turret 123, two bobbin holders 124, and a contact roller 125.
Each fulcrum guide 121 functions as a fulcrum when a yarn Y is traversed by a traverse guide 122. The fulcrum guides 121 are aligned in the front-rear direction. The fulcrum guides 121 are provided for the respective yarns Y. The traverse guides 122 are provided for traversing the respective yarns Y. The traverse guides 122 are aligned in the front-rear direction. The traverse guides 122 are provided for the respective fulcrum guides 121. The turret 123 is substantially disc-shaped. An axis of the turret 123 is substantially parallel to the front-rear direction. The turret 123 is rotationally driven by an unillustrated turret motor. Each of the two bobbin holders 124 is arranged to support the bobbins B so that the bobbins B are aligned in the front-rear direction. An axis of each bobbin holder 124 is substantially in parallel to the front-rear direction. The two bobbin holders 124 are rotatably supported by the turret 123. When viewed in the front-rear direction, the two bobbin holders 124 oppose each other over a center point of the turret 123. To be more specific, for example, when one bobbin holder 124 is positioned at the highest part of the turret 123, the other bobbin holder 124 is positioned at the lowest part of the turret 123. Each bobbin holder 124 is arranged to rotatably support the bobbins B which are provided for the respective yarns Y. The bobbins B which are provided for the respective yarns Y are attached to each bobbin holder 124 so as to be aligned in the front-rear direction. Each of the two bobbin holders 124 is rotationally driven by an individual winding motor (not illustrated). An axis of the contact roller 125 is substantially in parallel to the front-rear direction. The contact roller 125 is provided immediately above upper one of the two bobbin holders 124. The contact roller 125 is configured to make contact with the surfaces of the packages P supported by upper one of the two bobbin holders 124. With this arrangement, the contact roller 125 applies a contact pressure to the surfaces of the unfinished packages P so as to adjust the shape of each package P.
When upper one of the two bobbin holders 124 is rotationally driven, the yarns Y which are traversed by the traverse guides 122 are wound onto the bobbins B so as to form the packages P. When the formation of the packages P is completed, the turret 123 is rotated so as to switch over the upper and lower positions of the two bobbin holders 124. Because of this, one bobbin holder 124 having been at the lower position is moved to the upper position. As a result, the yarns Y are wound onto the bobbins B attached to this bobbin holder 124 having been moved to the upper position, so as to form packages P. Meanwhile, the other bobbin holder 124 to which the fully-formed packages P are attached is moved to the lower position by the turret 123. These fully-formed packages P are collected by, e.g., an unillustrated package collector. The collected packages P are then attached to the yarn supplying unit 2 of the false-twist texturing machine 1 as the above-described yarn supply packages Ps.
Typically, when the running speed (processing speed) of the yarns Y is arranged to be higher than the maximum speed (this may be referred to as the surging speed) in the false-twist texturing machine 1, the yarns Y start to vibrate (i.e., surging occurs) so that the false-twisted processed yarns Yf cannot properly produced. There have recently been demands for further improvement in production efficiency of the false-twisted processed yarns Yf. As a result of diligent study, the inventors of the subject application found a method of increasing the maximum speed (the maximum speed at which the false-twisted processed yarns Yf can be produced) of false twisting. Hereinafter, the maximum speed of the false twisting may be simply referred to as the maximum speed.

(Processing Conditions Required in False Twisting)

Before describing the manufacturing method of the false-twisted processed yarns Yf in the present embodiment, the following will outline processing conditions required for producing the false-twisted processed yarns Yf by false-twisting (to be more specific, by drawing and false-twisting) the raw yarns Yr.
Before being false-twisted by the false-twist texturing machine 1, each raw yarn Yr has predetermined residual elongation (pre-processing elongation) as a unique characteristic of the raw yarn Yr. The residual elongation of each yarn Y is the elongation of the yarn Y after the yarn Y is pulled and broken under predetermined conditions. In other words, the residual elongation is the elongation ratio of the yarn Y which has been broken to the yarn Y which is not pulled yet. The residual elongation of the raw yarn Yr may vary depending on a manufacturing condition of the raw yarn Yr in the spun yarn winding system 100. The strength of the raw yarn Yr (the pulling force applied to the raw yarn Yr when the raw yarn Yr is broken) may also vary depending on the manufacturing condition of the raw yarn Yr in the spun yarn winding system 100.
The raw yarn Yr is typically required to be false-twisted so that the residual elongation of each false-twisted processed yarn Yf achieves a predetermined target value (hereinafter, this will be referred to as the target elongation). In other words, the raw yarn Yr is typically false-twisted in consideration of the pre-processing elongation and the target elongation. The target elongation may slightly vary depending on the use of the false-twisted processed yarn Yf. The typical target elongation is within the range of 18 to 26%. In false-twist texturing machine 1, the operating conditions of the first feed roller 11, the first heater 13, the cooler 14, the false-twisting device 15, the second feed roller 16, etc. are set as the processing conditions so that the residual elongation of the false-twisted processed yarn Yf achieves the target elongation. For example, the above-described draw ratio is determined (calculated) by the relationship between the pre-processing elongation and the target elongation.

(Cause of Surging)

The following will briefly describe the cause of the surging. As the running yarn Y is unintentionally and repeatedly loosened and tensioned, the surging occurs. The direct cause of the surging is mainly due to the false-twisting device 15. The surging may occur between the first feed roller 11 and the second feed roller 16 in the yarn running direction. For example, the running yarn Y may slip on the surfaces of the discs in the false-twisting device 15 of the friction type. Even when the yarn Y slips in the false-twisting device 15, the yarn Y is able to properly run as long as it is not loosened (i.e., as long as the tension is applied to the yarn Y). However, when the running speed (substantially equal to the second yarn feeding speed) of the yarn Y is high in the false-twisting device 15, the yarn Y is likely to slip. The more frequently the yarn Y slips, the more likely the yarn Y is to be loosened. When the yarn Y is unintentionally loosened and tensioned between the first feed roller 11 and the second feed roller 16, the yarn Y vibrates so as not to properly run. That is, the surging occurs. The second yarn feeding speed at which the surging starts to occur is the above-described maximum speed.
An effective method of suppressing the surging is to increase the tension (i.e., processing tension) of the yarn Y running immediately on the upstream side of the false-twisting device 15 in the yarn running direction. However, as described above, the draw ratio is determined in advance in consideration of the pre-processing elongation and the target elongation. Typically, the higher the draw ratio is, the higher the processing tension may be. However, when the draw ratio is excessively high, the residual elongation of the false-twisted processed yarn Yf is significantly different from the target elongation. Such a false-twisted processed yarn Yf does not qualify as a product.

(Manufacturing Method of False-Twisted Processed Yarn)

To solve the problem above, the inventors of the subject application considered a method of manufacturing a false-twisted processed yarn Yf which qualified as a product and increasing the maximum speed. In this regard, the inventors of the subject application performed the false twisting with use of raw yarns Yr which were manufactured under different manufacturing conditions in the spun yarn winding system 100. To be more specific, the inventors of the subject application prepared the raw yarns Y respectively for Examples 1 to 16 and Comparative Example 1 to 13 as shown in the tables of FIG. 4(a) to FIG. 6(b). How these Examples and these Comparative Examples are divided will be described later. The target thickness of a raw yarn Yr of each Example and that of a raw yarn Yr of each Comparative Example were set in a typical thickness (83 dtex (decitex)). The number of filaments forming the raw yarn Yr is 48 in Examples 1 to 4 and Comparative Examples 1 to 2 (see FIG. 4(a) and FIG. 4(b)). The number of filaments forming the raw yarn Yr is 72 in Examples 5 to 12 and Comparative Examples 3 to 5 (see FIG. 5(a) and FIG. 5(b)). The number of filaments forming the raw yarn Yr is 144 in Examples 13 to 16 and Comparative Examples 6 to 13 (see FIG. 6(a) and FIG. 6(b)).
Each of FIG. 4(a), FIG. 5(a), and FIG. 6(a) is a table showing the manufacturing condition and physical properties of each raw yarn Yr. In the table, a value of the spinning speed is shown as the manufacturing condition of each raw yarn Yr. Furthermore, the following values are shown as the physical properties of each raw yarn Yr: a value of the residual elongation (pre-processing elongation); a value of the strength; a value of the fineness; a value of the boiling water shrinkage; a value of the orientation degree; and a value of the crystallizing degree. The spinning speed (the unit is m/min) is the winding speed at which each yarn Y is wound onto a bobbin B. The residual elongation (the unit is %) was measured by using TENSORAPID (Trademark) which was the strength meter/extensometer of Uster Technologies. Similarly, the strength (the unit is cN/dtex (cN/decitex)) was measured by using TENSORAPID (Registered Trademark) which was the strength meter/extensometer of Uster Technologies. To calculate the fineness, a yarn sample with a predetermined length was obtained by using an electric sizing reel (a machine for winding a yarn to make a hank) of INTEC CO., LTD. After that, the weight of this yarn sample was measured by using a typical scale. In this way, the fineness was calculated as the ratio of the weight of this yarn sample to the length of this yarn sample. In this regard, the unit of the fineness is dtex (decitex). To calculate the boiling water shrinkage (this unit is %), a yarn sample with a predetermined length was heated by using a thermostat bath (this model number is T-22H) of Thomas Kagaku CO., LTD. After that, the boiling water shrinkage was calculated by measuring the length of the heated yarn sample with use of a typical ruler. The orientation degree (dimensionless quantity) was measured by using a RAMAN touch (Registered Trademark) which was the Raman spectrometer of Nanophoton Corporation. The crystallizing degree (this unit is %) was measured by using DSC25 (this is the model number of the product) which was the differential scanning calorimeter of TA Instruments Materials Science. The birefringence is typically measured as the index of orientation degree of a material forming each yarn Y. However, instead of measuring the birefringence, the inventors of the subject application measured the orientation degree by means of Raman spectroscopy. In this regard, the orientation degree and crystallizing degree ware measured only in Examples 1 to 4 and Comparative Examples 1 to 2 just for reference.
As the raw yarns Yr, the inventors of the subject application used PET (i.e., polyester) yarns Y which were manufactured by the spun yarn winding system 100 so as to obtain different values of the residual elongation. In this regard, the residual elongation of each raw yarn Yr is changeable by changing the spinning speed in the spun yarn winding system 100. Typically, when the winding speed is high, molten polymer spun out from the spinning apparatus 101 is easily drawn before being solidified. That is, the higher the winding speed is, the more the residual elongation of each raw yarn Yr tends to be low. As the raw yarns Yr of plural types, the inventors of the subject application prepared (i) raw yarns Yr with the residual elongation of 100% or more and (ii) raw yarns Yr with the residual elongation of less than 100%. It has been said that the raw yarns Yr with the residual elongation of 100% or more are suitable for drawing and the false twisting. Meanwhile, it has been said that the raw yarns Yr with the residual elongation of less than 100% are not suitable for the drawing and the false twisting. Except the spinning speed, the inventors of the subject application performed settings so that the raw yarns Yr had the same typical manufacturing conditions. With this arrangement, the typical false twisting can be performed at least for a conventional raw yarn Yr with the residual elongation of 100% or more. The strength of each raw yarn Yr with the residual elongation of less than 100% was higher than that of each raw yarn Yr with the residual elongation of 100% or more, i.e., higher than 2.9 cN/dtex.
The inventors of the subject application set the manufacturing condition (false-twisting condition) of each false-twisted processed yarn Yf in consideration of the residual elongation (pre-processing elongation described above) and target elongation of each raw yarn Yr which was not false twisted yet. In this regard, the false-twisting conditions of all false-twisted yarns Yf have the same target elongation which is 22%. Each of FIG. 4(b), FIG. 5(b), and FIG. 6(b) is a table showing the false-twisting condition, processability, and physical properties of each false-twisted processed yarn Yf. In the table, a value of the above-described draw ratio is shown as the false-twisting condition of each false-twisted processed yarn Yf. Furthermore, a value of the maximum speed (described later) and a value of the processing tension are shown as the processability of each false-twisted processed yarn Yf. Furthermore, values of the residual elongation strength of each false-twisted processed yarn Yf are shown as the physical properties of each false-twisted processed yarn Yf. The processing tension (the unit is cN) was measured by using a typical tensiometer. The residual elongation and strength of each false-twisted processed yarn Yf were measured by using the same apparatuses which were used for measuring those of each raw yarn Yr.
In addition to the draw ratio, other false-twisting conditions are provided for each false-twisted processed yarn Yf. The inventors of the subject application set the other false-twisting conditions of each false-twisted processed yarn Yf in typical values. It is known that this arrangement makes it possible to false-twist, at least, each raw yarn Yr with the residual elongation of 100% or more so as to obtain a traditional high-quality false-twisted processed yarn.
The inventors of the subject application manufactured each false-twisted processed yarn Yf under a false-twisting condition (the draw ratio) corresponding to each raw yarn Yr. When each false-twisted processed yarn Yf was manufactured, the inventors of the subject application checked the maximum speed by keeping a value of the draw ratio and gradually increasing the processing speed. Under each false-twisting condition (hereinafter, this will be simply referred to as a condition), the highest processing speed at which the surging does not occur is the maximum speed. Traditionally, the maximum speed in the known case at which a traditional normal raw yarn was false-twisted was approximately 1000 m/min. Under some conditions, the processing speed was considerably higher than the maximum speed in the known case.
The inventors of the subject application divided examples with the respective conditions into Examples and Comparative Examples. To be more specific, when the maximum speed was 1100 m/min or more in an example with a condition on the premise that (i) the residual elongation of a raw yarn Yr was less than 100%, (ii) the false twisting was properly performed, and (iii) the yarn quality of a false-twisted processed yarn Yf was appropriate, the inventors of the subject application classified this example as an Example irrespective of the number of filaments forming the raw yarn Yr. Meanwhile, when the maximum speed was less than 1100 m/min in an example with a condition, the inventors of the subject application classified this example as a Comparative Example. That is, when the maximum speed in an example with a condition was simply higher than the maximum speed in the known case, the inventors of the subject application classified this example as an Example. This is how Examples and Comparative Examples are divided in the present embodiment.
When the false twisting was properly performed, problems such as yarn breakage and generation of fluff did not occur during the false twisting. The generation of fluff is a yarn quality defect caused when only some of filaments forming a yarn Y are broken. The yarn breakage is caused when a yarn Y is completely broken, and causes the manufacture of a false-twisted processed yarn Yf to stop. In the present embodiment, the generation of fluff and the yarn breakage did not occur during the false twisting in Examples and Comparative Examples, and the false twisting was properly performed.
When the yarn quality of a false-twisted processed yarn Yf is appropriate, the residual elongation and strength of the false-twisted processed yarn Yf are substantially identical with those of a known false-twisted processed yarn. When the residual elongation of a false-twisted processed yarn Yf was 18 to 26% and the strength of the false-twisted processed yarn Yf was 3.7 or more, the inventors of the subject application determined this false-twisted processed yarn Yf as a false-twisted processed yarn Yf with appropriate yarn quality.
As shown in FIG. 4(a) to FIG. 6(b), when raw yarns Yr with the pre-processing elongation of less than 100% (i.e., raw yarns Yr which were considered to be unsuitable for the drawing and the false twisting) were false-twisted, values of the maximum speed of the false twisting were considerably high. The inventors of the subject application considered the reason of this as follows. To begin with, as described above, the higher the winding speed in the spun yarn winding system 100 is, the lower the residual elongation of each raw yarn Yr is. When one raw yarn Yr is considerably drawn by the spun yarn winding system 100, the residual elongation of this raw yarn Yr is low. When the raw yarn Yr is drawn, the orientation of polymers in the raw yarn Yr is adjusted (the polymers are oriented). In this regard, the crystallization of the polymers progresses along with the orientation of the polymers. The inventors of the subject application considered that there was causality between such phenomenon and the increased values of the maximum speed of the false twisting.
In this regard, the inventors of the subject application also considered that (i) there were three structures of molecules in each raw yarn Yr as described below and (ii) the ratio (hereinafter, this will be referred to as the composition ratio) of mixture of these three structure of the raw yarn Yr varied depending on the spinning speed. The following describes the details with reference to FIG. 7. FIG. 7 is a graph showing the relationship between the composition ratio of the molecular structure of each raw yarn Yr and the spinning speed of each raw yarn Yr. The vertical axis indicates the composition ratio. The transverse axis indicates the spinning speed. As the first structure, each raw yarn Yr may have an unoriented-noncrystalline structure (hereinafter, this will be referred to as the structure S1) in which the polymers are not oriented and not crystallized. As the second structure, the raw yarn Yr may have an oriented-noncrystalline structure (hereinafter, this will be referred to as the structure S2) in which the polymers are oriented and not crystallized. As the third structure, the raw yarn Yr may have an oriented-crystalline structure (hereinafter, this will be referred to as the structure S3) in which the polymers are oriented and crystallized. The structures S1, S2, and S3 are divided by solid lines in the graph of FIG. 7.
In this regard, the raw yarn Yr may include an unoriented-crystalline structure in which the polymers are not oriented and are crystallized. However, because the raw yarn Yr runs in the spun yarn winding system 100 while being pulled to some degree, the raw yarn Yr is highly unlikely to include the unoriented-crystalline structure. This structure is therefore not detailed.
As shown in FIG. 7, when the spinning speed is very low in an example with a condition, a large part of the raw yarn Yr has the structure S1 (indicated by a two-dot chain line L1). As compared to this, when the spinning speed is slightly high in an example with a condition, the ratio of a part corresponding to the structure S2 increases and that of a part corresponding to the structure S1 decreases in the raw yarn Yr (indicated by a two-dot chain line L2) . As compared to this, when the spinning speed is relatively high in an example with a condition, the structure S3 appears in the raw yarn Yr (indicated by a two-dot chain line L3). As compared to this, when the spinning speed is high in an example with a condition, the ratio of a part corresponding to the structure S3 increases and that of a part corresponding to the structure S1 and that of a part corresponding to the structure S2 decrease in the raw yarn Yr (indicated by a two-dot chain line L4) . As compared to this, when the spinning speed is very high in an example with a condition, a large part of the raw yarn Yr has the structure S3 (indicated by a two-dot chain line L5).
By being heated, the structure S2 (oriented-noncrystalline structure) of the raw yarn Yr is likely to turn into the structure S1 (unoriented-noncrystalline structure) so that a large thermal contraction may be generated because of orientation relaxation. Meanwhile, a structural change caused by heating is unlikely to occur in the structure S3 (oriented-crystalline structure) of the raw yarn Yr. Therefore, a thermal contraction force is unlikely to be generated. However, because the structure S3 of the raw yarn Yr has high rigidity, stress is likely to be caused when external force is applied. The inventors of the subject application considered that the characteristics of these structures of the raw yarn Yr affected each other in a complicated manner so that (i) the processing tension varied depending on the pre-processing elongation of the raw yarn Yr and (ii) the maximum speed of the false twisting also varied.
In many examples of the present embodiment, raw yarns Yr were manufactured at the high spinning speed. In each of the raw yarns Yr, the ratio of a part corresponding to the structure S1 and that of a part corresponding to the structure S2 are relatively low and that of a part corresponding to the structure S3 is relatively high. Therefore, the inventors of the subject application focused on the ratio of a noncrystalline structure (the structure S1 or the structure S2) of the raw yarn Yr to a crystalline structure (the structure S3) of the raw yarn Yr in addition to the pre-processing elongation of the raw yarn Yr. This ratio is significantly reflected on the boiling water shrinkage which is one physical property of the raw yarn Yr.
The following will describe the correlation between items with reference to the graphs of FIG. 8(a) to FIG. 11(b). FIG. 8(a) is a graph showing the correlation between the maximum speed of the false twisting and the residual elongation of each raw yarn Yr. FIG. 8(b) is a graph showing the correlation between the maximum speed of the false twisting and the processing tension. FIG. 9(a) is a graph showing the correlation between the maximum speed of the false twisting and the boiling water shrinkage of each raw yarn Yr. FIG. 9(b) shows an enlargement of a part of the graph of FIG. 9(a). FIG. 10(a) is a graph showing the correlation between the boiling water shrinkage and residual elongation of each raw yarn Yr. FIG. 10(b) is a graph showing the correlation between the residual elongation and spinning speed of each raw yarn Yr. FIG. 11(a) is a graph showing the correlation between the maximum speed of the false twisting and the orientation degree of each raw yarn Yr. In this regard, FIG. 11(a) shows a correlation between the maximum speed of the false twisting and the orientation degree of each raw yarn Yr. This correlation (indicated by a dashed line) is estimated by interpolation. FIG. 11(b) is a graph showing the correlation between the maximum speed of the false twisting and the crystallizing degree of each raw yarn Yr. In this regard, FIG. 11(b) shows a correlation between the maximum speed of the false twisting and the crystallizing degree of each raw yarn Yr. This correlation (indicated by a dashed line) is estimated by interpolation.
As shown in FIG. 8(a), when the pre-processing elongation (residual elongation) of the raw yarn Yr is approximately 90 to 100%, the maximum speed is highest. In regard to the pre-processing elongation of 90% or less, the lower the pre-processing elongation is, the lower the maximum speed tends to be. Especially, when the pre-processing elongation is 80% or less, the maximum speed tends be 1100 m/min or less. In this regard, the pre-processing elongation at which the maximum speed is highest varies depending on the number of filaments forming the raw yarn Yr. Therefore, the pre-processing elongation is unlikely to be closely related to the maximum speed. The inventors of the subject application thus considered that the pre-processing elongation of 80% or more was not a prerequisite for the maximum speed of 1100 m/min or more.
As shown in FIG. 8(b), the higher the processing tension is, the higher the maximum speed tends to be. This tendency is more or less consistent with the above-described opinion of the inventors. However, when the processing tension is excessively high, the decrease in maximum speed tends to start. The inventors of the subject application thus considered that the maximum speed was not determined only by the processing tension.
As shown in FIG. 9(a), when the boiling water shrinkage of the raw yarn Yr is approximately 10%, the maximum speed is highest. Typically, the further the crystallization of the raw yarn Yr progresses, the higher the boiling water shrinkage is. This tendency regarding the maximum speed does not actually depend on the number of filaments forming the raw yarn Yr. The inventors of the subject application thus considered that the maximum speed was determined mainly by the boiling water shrinkage. FIG. 9(a) and FIG. 9(b) showed that, when the boiling water shrinkage was 3.7 to 40%, the maximum speed was 1100 m/min or higher.
For reference, as shown in FIG. 10(a), the higher the boiling water shrinkage of the raw yarn Yr is, the higher the residual elongation (pre-processing elongation) tends to be. This typical tendency means that, in the raw yarn Yr, the higher the ratio of a part corresponding to the structure S3 is, the more difficultly the raw yarn Yr is drawn. As shown in FIG. 10(a), when the boiling water shrinkage is approximately 25% or less, the pre-processing elongation is less than 100%.
For reference, as shown in FIG. 10(b), the higher the spinning speed of the raw yarn Yr is, the lower the residual elongation (pre-processing elongation) of the raw yarn Yr tends to be. However, a specific relationship between the spinning speed and the pre-processing elongation varies depending on the number of filaments forming the raw yarn Yr. According to the graph of FIG. 10(b), it is therefore possible to presume that the spinning speed and the pre-processing elongation are not the main factors to determine the maximum speed.
For reference, as shown in FIG. 11(a), the orientation degree of the raw yarn Yr is preferably 1.23 or more and 1.38 or less so that the maximum speed is 1100 m/min or more.
For reference, as shown in FIG. 11(b), the crystallizing degree of the raw yarn Yr is preferably 26% or more and 38% or less so that the maximum speed is 1100 m/min or more.
As described above, when the pre-processing elongation of the raw yarn Yr is less than 100%, a total of (i) a thermal contraction force because of the orientation relaxation in the crystallized raw yarn Yr and (ii) a resistance force of the raw yarn Yr against the drawing is presumably large. Therefore, when (i) the pre-processing elongation of the raw yarn Yr is less than 100% and (ii) the boiling water shrinkage of the raw yarn Yr is 25% or less, the processing tension applied to the raw yarn Yr is high. Because of this, even when the second yarn feeding speed is high, loosening of the yarn Y is suppressed. The occurrence of surging is also suppressed. Meanwhile, when the boiling water shrinkage is excessively low (i.e., when the crystallization of the raw yarn Yr has progressed too far), high torsional stress is caused when the yarn Y is about to be false-twisted. When the torsional stress is excessively high, an elastic restoring force of the yarn Y against the torsional stress is also excessively high. As a result, in the false-twisting device 15, the yarn Y is likely to slip in the same direction as the torsional stress. In order to suppress the torsional stress and the slip of the yarn Y, the boiling water shrinkage needs to be high to some degree (specifically, to be higher than 3.70).
As described above, when a partially oriented yarn whose pre-processing elongation is less than 100%, whose boiling water shrinkage is 3.7% or more and 25% or less, and which is formed of PET synthetic fibers is used as the raw yarn Yr, the maximum speed is considerably high. In this case, even when the processing speed is set to be 1100 m/min or more, the occurrence of surging is suppressed. The boiling water shrinkage of the raw yarn Yr is preferably 3.7% or more and 10% or less. This increases the above-described resistance force.
It has been said that (i) the generation of fluff and the yarn breakage are likely to occur in a partially oriented yarn whose pre-processing elongation is less than 100% and (ii) such a partially oriented yarn is not appropriate for the drawing and the false twisting. Nevertheless, the generation of fluff and the yarn breakage did not occur in Examples. This is presumably because the raw yarn Yr which is not false-twisted has a high strength of 2.9 cN/dtex or more. The strength of the raw yarn Yr needs to be higher than 2.9 cN/dtex so that the generation of fluff and the yarn breakage do not occur even when high tension is applied to the raw yarn Yr.
The pre-processing elongation is preferably 80% or more.
The target elongation is preferably 18% or more and 26% or less. The orientation degree of the raw yarn Yr which is not false-twisted is measured by the Raman spectrometer, and is preferably 1.23 or more and 1.38 or less. The crystallizing degree of the raw yarn Yr is preferably 26% or more and 38% or less.
As described above, the raw yarn Yr whose pre-processing elongation is less than 100% and whose boiling water shrinkage is 3.7% or more and 25% or less is false-twisted. With this arrangement, the processing tension is high. It is therefore possible to suppress the loosening of the yarn Y. It is also possible to suppress the occurrence of surging. The raw yarn Yr has a high strength of 2.9 cN/dtex or more. With this arrangement, even when high tension is applied to the raw yarn Yr, breakage of the raw yarn Yr is suppressed. It is therefore possible to suppress the generation of fluff and/or the yarn breakage. This makes it possible to increase the maximum speed at which the false-twisted processed yarn Yf can be produced.
When the pre-processing elongation is excessively low, the maximum speed may be decreased. Therefore, the pre-processing elongation is preferably 80% or more.
The boiling water shrinkage of the raw yarn Yr is preferably 3.7% or more and 10% or less. This increases the above-described resistance force. It is therefore possible to increase the processing tension.
The orientation degree of the raw yarn Yr is measured by means of Raman spectroscopy, and is 1.23 or more and 1.38 or less. As such, the orientation degree is not too high and not too low. With this arrangement, while the processing tension is increased, the above-described torsional stress is suppressed from being excessively high.
The crystallizing degree of the raw yarn Yr is 26% or more and 38% or less. As such, the crystallizing degree is not too high and not too low. With this arrangement, while the processing tension is increased, the above-described torsional stress is suppressed from being excessively high.
The target elongation is 18% or more and 26% or less. It is therefore possible to manufacture the false-twisted processed yarn Yr whose residual elongation is typical.
The following will describe modifications of the above-described embodiment. The members identical with those in the embodiment above will be denoted by the same reference numerals and the explanations thereof are not repeated.

(1) In the embodiment above, the target elongation is 18% or more and 26% or less. However, the disclosure is not limited to this. The target elongation may be less than 18%, or may be more than 26%.
(2) The pre-processing elongation of the raw yarn Yr may be less than 80% as long as the boiling water shrinkage of the raw yarn Yr is 3.7% or more and 25% or less.
(3) The orientation degree of the raw yarn Yr is measured by means of Raman spectroscopy, and may not be within the range of 1.23 to 1.38.
(4) The crystallizing degree of the raw yarn Yr may not be within the range of 26% to 38%.
(5) The above-described manufacturing method of the false-twisted processed yarn Yr may be used not only in the false-twist texturing machine 1, but also in a known false-twist texturing machine (not illustrated) differently structured.

Claims

A method of manufacturing a false-twisted processed yarn (Yf) with use of a false-twist texturing machine (1) which is able to false-twist a running raw yarn (Yr) while heating and drawing the raw yarn (Yr),
the false-twist texturing machine (1) including:
a heater (13) configured to heat the raw yarn (Yr);

a drawing device (11, 16) configured to draw the raw yarn (Yr) heated by the heater (13); and

a false-twisting device (15) which is provided downstream of the heater (13) in a yarn running direction and which is configured to false-twist the raw yarn (Yr),

the raw yarn (Yr) being a partially oriented yarn formed of PET synthetic fibers, when the partially oriented yarn is not false-twisted, the partially oriented yarn having a pre-processing elongation of less than 100%, a boiling water shrinkage of 3.7% to 25%, and a strength of 2.9 cN/dtex or more, the pre-processing elongation being the residual elongation, and

the raw yarn (Yr) being false-twisted at a processing speed of 1100 m/min or more while being heated and drawn.
The method according to claim 1, wherein, the pre-processing elongation of the raw yarn (Yr) is 80% or more.
The method according to claim 1 or 2, wherein, the boiling water shrinkage of the raw yarn (Yr) which is not false-twisted is 3.7% or more and 10% or less.
The method according to any one of claims 1 to 3, wherein, the orientation degree of the raw yarn (Yr) which is not false-twisted is measured by means of Raman spectroscopy and is 1.23 or more and 1.38 or less.
The method according to any one of claims 1 to 4, wherein, the crystallizing degree of the raw yarn (Yr) which is not false-twisted is 26% or more and 38% or less.
The method according to any one of claims 1 to 5, wherein, the target elongation which is a target value of the residual elongation of the formed false-twisted processed yarn (Yf) is set to be 18% or more and 26% or less.