JP3098340B2 - Method for producing polyester false twisted yarn - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester false twisted yarn, and more particularly to a method for controlling a surging phenomenon due to an oil agent adhering to the surface of a cooling plate, preventing abrasion with time, and improving fluff and yarn breakage. The present invention relates to a method for producing a polyester false-twisted yarn capable of obtaining a polyester false-twisted yarn having a high drapability and a dry touch with no twist spots at a processing speed of 1000 m / min or more.

[0002]

2. Description of the Related Art Hitherto, a method for producing a polyester false twisted yarn having a high drape property and a dry touch as a differentiating material has been produced by various methods (for example, Japanese Patent Application Laid-Open No. 57-19335). And JP-A-3-161533), all of which have a low-speed false twist, that is, a yarn speed of 100 m / min to 700 m / min at most. Moreover, the false twisting of polyester unstretched yarn containing a large amount of titanium dioxide, a heater, a concern wear damage to the guide, the Ru is avoided in the industry was normal. Even faster processing (1
(2,000 m / min or more), the processing fluff in the false twisting process frequently occurred, and the yarn was broken, and the operation production was impossible.

More specifically, conventionally, when performing false twisting of polyester fiber, a heater for heat setting is used in a portion where a true twist is inserted by a false twisting tool (spindle, friction disk, belt, etc.). However, this heater is a contact-type hot plate having a groove and a curvature. The heater length varies depending on the processing speed. The heater length of a commercially available processing machine is about 1 m at a processing speed of about 100 m / min, and 1.5 m at a processing speed of about 400 m / min.
The heater is designed to be 2.5 m at about 0 m / min, and the basic idea of these heater designs is to make the heater temperature 250 ° C. or less and to set the heat setting time at least 0.17 seconds or more. .

On the other hand, in order to further improve productivity in recent years, the false twisting speed tends to be gradually increased.

[0005] Higher speeds of 1000 m / min or more, large-yarn packaging, and continuity due to advances in transfer tail technology have been attempted.
Continuity is regarded as important in terms of ensuring stable quality. The points of false twist processing equipment that hinder continuous productivity are represented by two points: 1) dirt on the inner surface of the heater (yarn section) 2) dirt on the cooling plate disposed between the heater and the twisting unit. Aging quality change or aging, processing,
The thread is broken. In order to cope with such speeding-up, in the conventional false twisting, the heater length is increased or the heater temperature is increased in order to prevent a decrease in the heat setting property in accordance with an increase in the processing speed.

As a result, the equipment becomes enormous, and the yarn guide becomes bent.
Heat treatment-Insufficient cooling makes it impossible to maintain the quality of conventional processed yarn. Further, in the case of the contact type heating type, if the heater length is long, the contact resistance of the yarn is increased and fluff is likely to be generated, and it becomes difficult to process fine fine yarn and high speed processing.

Further, during false twisting, the yarn is twisted at a high speed, so that if the heating zone is long, the yarn will fall out of the yarn running groove, and if the processing speed is increased, ballooning will be formed on the twisted yarn. Occurs, and yarn breakage increases, and stable production cannot be maintained. Also, a surging phenomenon occurs at a relatively low yarn speed, and it is difficult to perform high-speed and stable false twisting.

As a countermeasure, in order to maintain processing stability during high-speed processing, adjustment is performed by reducing the number of twists and increasing the processing tension, particularly the twisting tension (T ₁ ), as compared with low-speed processing. However, this does not provide good processed yarn properties.

On the other hand, when the heater temperature is increased, the gradient of the temperature rise curve of the yarn becomes steep, and the yarn is heated at a high temperature for a short time. It becomes difficult to control the difference (intra-weight, inter-weight difference).

In addition to this, in a method in which the first heater is a non-contact heater and is processed at a temperature of 350 ° C. to 800 ° C. (Japanese Patent Publication No. 2-60769), a high heat shrinkage [T. C is 25 to 35%. C] is advantageous to obtain a twisted yarn, but it is disadvantageous for obtaining a false twisted yarn having a low heat shrinkage (generally, TC is 15 to 25%). That is, if processing is performed at a heater temperature of less than 350 ° C., a low T.V.
C-processed yarn is obtained. In this case, when the yarn is broken due to entangled fluff, etc., the molten polymer adheres to the guide etc. in the heater and it does not easily turn into ash.
There was a problem (the molten polymer adhered, making it difficult to clean, and the mere cleaning alone could not sufficiently remove the adhered polymer, so that the thread would break immediately after the next threading).
Work productivity is reduced and the conventional operation production level cannot be maintained.

Further, when the processing speed is increased to a high speed of 1000 m / min, the liquid (oil) applied to the yarn is shaken off by the centrifugal force generated by the high-speed rotation and scattered in the form of a mist. There are disadvantages that oil droplets adhere to peripheral devices and contaminate the entire machine, and the original cooling function cannot be sufficiently exerted.

In addition, the running resistance when the yarn passes through the oil droplets and the liquid pool becomes large, and the twist given by the false twisting portion does not go back to the upstream side, that is, the heater, which causes a problem. Therefore, sufficient bulk (crimp) performance cannot be obtained.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems and to provide a non-contact heater which is divided into two parts to be compact (miniaturized) and to perform uniform heat treatment in a short time. The purpose of the present invention is to obtain a polyester false twisted yarn having a high drape property and a dry touch, in which the heat shrinkage is controlled to a desired range, and further suppresses a surging phenomenon in a heater in high-speed processing while cooling. Eliminates the generation of oil droplets due to oil on the plate, suppresses smooth twisting of the running yarn, suppresses the surging phenomenon, and prevents damage and abrasion of the plate over time. The present invention provides a method for producing a polyester false twisted yarn that can be operated and produced, which can be carried out under different conditions.

[0014]

That is, the present invention provides a false twist while stretching an undrawn polyester yarn having a birefringence of 0.03 or more and a titanium dioxide content of 1.5% by weight or more. The false twist is heat-set, then cooled by a cooling plate, and then untwisted, the heat fixing heater is satisfied with the following equations (Equation 1) and (Equation 2) along the yarn traveling direction. The upper heater (HA) has a temperature of 400 ° C. or higher and a non-contact heater divided into two upper and lower stages.
When the heat treatment time is maintained at 0 ° C. or less, the heat treatment time is maintained between 0.01 and 0.04 seconds, the temperature of the lower heater (HB) is maintained at 320 ° C. or less, and the heat treatment time is maintained between 0.03 and 0.08 seconds.
In addition, the bottom of the thread groove as a cooling plate
It has a curvature of at least 2 mm or more in a square cross section and
Has a mirror finish with a core average roughness Ra <0.3 μm,
Cooling play hardened so that Hv is 800 or more
This is a method for producing a polyester false twisted yarn, characterized by performing simultaneous draw-twisting using a fiber.

[0015]

[Equation 3] [Upper stage of first heater (yarn entry side) Heater length: H
A = (0.2-0.5) m]

[0016]

[Equation 4] [Lower tier of first heater (yarn exit side) Heater length: H
B = (0.5-0.8) m]

The undrawn polyester yarn in the present invention is:
It is necessary that the birefringence is 0.03 or more and the content of titanium dioxide is 1.5% by weight or more.

When the birefringence is less than 0.03, the draw ratio must be increased in order to spin the yarn during processing and prevent crimping, and as a result, the polyester false twisted yarn It is difficult to obtain sufficient strength, and processing fluff is likely to occur, and workability (thread breaking) is unstable,
The texture is also impaired.

Furthermore, since the internal structure of the undrawn yarn is unstable, there arises a problem that the dyeing property and other physical properties are remarkably changed (the change over time is large).

Generally, an undrawn yarn having a birefringence of 0.03 or more generally corresponds to a material having a breaking elongation of 170% or less, and is usually obtained by spinning at a spinning speed of 3000 m / min or more.

The undrawn polyester yarn used in the present invention must have a titanium dioxide content of 1.5% by weight or more, preferably 2.0% by weight or more. If the content of titanium dioxide is less than 1.5% by weight, it is not possible to obtain a target false twisted yarn having a high drape property, a non-visual feeling and a dry touch.

If the titanium dioxide content of the polyester unstretched yarn is too high, the titanium dioxide particles agglomerate, causing clogging of the filter or breakage of the yarn during the process of melt molding into fibers. In general, it is used in an amount of not more than 3.5% by weight because the operability is reduced.

Next, the above-described polyester undrawn yarn is subjected to simultaneous drawing and false twisting at a high speed. False twisting of polyester fiber is a so-called one-heater type, and a high-torque, high-crimped yarn obtained by the one-heater type is further heat-set under overfeed or underfeed to obtain low crimpability.
Includes two-heater type for low torque. Less than,
The present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an apparatus suitable for carrying out the present invention, and FIGS. 2 (a), (b) and (c).
FIG. 2 is a plan view, a partial transverse sectional view, and an upper (upper heater) longitudinal sectional view of the first heating device in FIG. 1 respectively.

In the drawing, 1 is a first feed roller, 2 is a second feed roller, and a false twist heat setting heater 3 and a twisting device 4 are provided between the first and second rollers. And a cooling plate 5 between the heater 3 and the twisting device 4.
Is provided.

The heater 3 is divided into two parts in the yarn advancing direction. The upper heater HA on the entry side of the yarn and the lower heater HB on the exit side of the yarn are, as shown in FIG. This is a non-contact type heater in which the running yarn y is prevented from contacting the heater main body (heater block) 31 by guides 34 provided at appropriate intervals in the direction. The temperature is above the melting point of the strip. The heating temperature of the lower heater HB on the yarn exit side is usually set to a temperature equal to or higher than the melting point of the yarn.

The length of the upper heater HA divided into two parts of the heater 3 on the yarn entry side is usually 0.2 to 0.5 m, and the length of the lower heater HB on the yarn exit side is usually 0.2 to 0.5 m. 5-0.8m
It is. These upper and lower heaters may be arranged at a slight interval, or may be arranged continuously.

In the present invention, the upper heater HA and the lower heater HB are of a non-contact type, and the former has a length of 0.2 to 0.5.
m, the length of the latter must be 0.5 to 0.8 m. If this arrangement is reversed, the optimized drawing point shifts, making it difficult to uniformly heat the inside of the yarn and easily causing a dyeing difference. In addition, 6 is a package of the supply yarn (highly oriented undrawn yarn), and 7 is a winding device.

The yarn y unwound from the supply yarn package 6 is taken up by the first feed roller 1 and subjected to false twisting by the two-part non-contact heater 3 and the twisting device 4. After the yarn y exiting the heater 3 is cooled and stabilized by the cooling plate 5, it is drawn by the second feed roller 2 after drawing false twisting, and then wound. Further, if necessary, a third feed roller 2 may be provided after the second feed roller 2, and a second heater may be provided between the second feed roller 2 and further heat treatment.

As shown in FIG. 2, the non-contact heater of the present invention needs to be provided with a guide to prevent ballooning due to twisting. In this sense, a complete non-contact heater is not intended. .

The non-contact heater of the specific example shown in FIG. 2 will be described in more detail.
And HB, both of which are provided with two grooves 3 in a heater body 31 in which a sheathed heater (not shown) is provided.
The grooves 32 and 33 are provided with a guide 34 for guiding the yarn.

The grooves of the upper heater HA are provided with guides 34 at intervals of about 2 to 10 cm, and the yarns y are fixed in position along the bottoms of the yarns y by the guides 34 as shown in FIGS. 2B and 2C. I will run. In this case, it is preferable to arrange the bottom portion so as to form a certain curvature in order to ensure stable running of the yarn. The temperature of the upper heater HA is shown in FIG.
As shown in (c), the temperature measured at the center is 40
It is necessary to set the temperature between 0 ° C and 800 ° C.

If the temperature is lower than 400 ° C., when the yarn is broken due to a defect (fuzziness in the wound) of the supplied raw yarn, the molten polymer adheres to the guide or the like, and it does not easily turn into ash, making it difficult to hook the yarn.
Problems arise in operation production (reduction of re-threading performance) and in yield and yield.

Of course, false twisting can be carried out even at a temperature lower than 400 ° C., but in order to obtain the same level of crimp when the upper heater HA is 0.2 to 0.5 m as the conventional product, the processing speed must be reduced. It is also disadvantageous in that it has no merit of high-speed processing and the above-mentioned workability lowers efficiency.

When the temperature is 400 ° C. or higher, the molten polymer decomposes in a short time (several minutes) to form ash, and does not remain as scum. However, when the temperature exceeds 800 ° C., the durability and energy cost of the heater increase, and the heat setting time is shortened, so that a desired heat setting effect cannot be obtained.

Further, the heat treatment time of the upper heater HA is set to 0.0
It is necessary to set the time between 1 second and 0.04 seconds. If the setting time is less than 0.01 second, the crimp rate cannot be sufficiently increased, and the strength of the processed yarn also decreases, which is not preferable. On the other hand, if the time exceeds 0.04 seconds, the processing becomes lightly dyed and spots occur.

The lower heater HB serves as a slow cooling zone for the high-temperature set of the upper heater HA for a short time, and its temperature is set to 320 ° C. or lower. When the temperature exceeds 320 ° C., the problem that the molten polymer adheres to the guide occurs as described above.
Is equivalent to For this reason, at the time of thread breakage, there is no adhesion to the guide, re-threading can be performed in a few minutes, and operation productivity is improved.

In this case, the temperature zone for fusing to the guide ranges from approximately 320 ° C. to less than 420 ° C. as shown in FIG.

The temperature of the lower heater HB is preferably set at 200 ° C. or more and 320 ° C. or less, whereby the difference in dyeing between the inner layer and the outer layer of the yarn package is uniformed, and spots are less likely to occur.

At this time, the heat treatment time of the lower heater HB needs to be 0.03 seconds or more and 0.08 seconds or less. If the time is less than 0.03 seconds, surging is likely to occur in addition to the decrease in strength, and poor dyeing tends to occur. On the other hand, 0.
In the region exceeding 08 seconds, processing fluff is generated, which affects the quality.

Further, the fineness of the processed yarn after processing is 20 to 150 d.
e is preferred. If the processing exceeds 150 de after processing, the processing speed must be reduced to obtain the target yarn strength and crimp characteristics (reduction of life due to temporal wear of false twisting tool). Disappears. On the other hand, after processing, at less than 20 de, a load is generated by unwinding from the creel by high-speed processing, and slight tension fluctuation at the time of false twisting tends to cause untwisting,
Further, it is not preferable because spots are easily generated.

In this case, the false twisting tool is a friction disk, and an urethane rubber, a ceramic coated disk or the like is appropriately selected.

As described above, since the set time is shorter than the conventional concept, a conventional (contact) heater having a heater length of 900 m / min uses 2.5 m.
In the same-speed machining, a length of 0.6 to 1.8 m (more preferably 0.6 to 0.7 m) is sufficient in the present invention, and the equipment can be made compact.

Further, in the conventional hot plate type heater, scum is generated over time, and it is necessary to clean the heater in 10 days to 1 month. However, such heater cleaning is not required, so that the rest loss is reduced. . In addition, it is possible to select an oil agent having a good spinning condition even in the oil agent of the supplied raw yarn without considering the scum on the false twist heater, thereby improving the performance.

In the present invention, when the false-twisted yarn after heat setting is cooled by the cooling plate, the bottom of the yarn groove of the cooling plate has at least two cross sections at right angles to the axis.
It is necessary to provide a cooling plate having a curvature of not less than mm, a mirror finish of Ra <0.3 μm, and a hardening treatment so as to have a hardness of Hv800 or more .

The false twisting is performed at a high speed (at a yarn speed of 1000 m / min or more) by the above-described two-part non-contact type high-temperature heater. At this time, the yarn heated by the heating device (heater) enters the cooling plate with an accompanying flow, but the accompanying flow contains moisture and oil (oil), which is cooled by the passage wall surface of the plate. When liquefied, it rapidly liquefies and becomes oil droplets.
Also, the oil agent attached to the yarn is generated by centrifugal force or the like due to high-speed rotation twisting, or squeezed out to become oil droplets. This oil drop
The defect of the original yarn causes a jumping phenomenon when passing through the plate groove, resulting in poor quality (non-crimped yarn occurs, defective spots), which is a problem.

That is, in a normal contact type heater, oil smoke generated by contact and resistance on the heater is exhausted, and desorbed matter of the thread oil agent remains as heater tar. Supported. On the contrary,
In the case of the high-temperature non-contact heater according to the present invention, there is no contact resistance in the heater portion and, of course, no heater tar. However, if the cooling device below the heater is a contact type plate, the oil agent or its desorbed substance adheres to the plate, causing various troubles as described above.

The present invention solves such conventional problems, eliminates the generation of oil droplets due to oil adhering to the cooling plate during high-speed processing, suppresses smooth running of the running yarn, suppresses the surging phenomenon, and the like. Stable processing is possible. For this purpose, in the high-speed false twisting (1000 m / min or more), the bottom of the thread groove of the cooling plate has a curvature (R) of at least 2 mm or more in a cross section perpendicular to the axis as shown in FIG. , Ra <0.3 μm. If the curvature is less than 2 mm, the above-mentioned jumping is likely to occur, and it becomes difficult to clean the groove bottom. This curvature is preferably less than 4 mm. More important is the surface roughness, and Ra must be 0.3 μm or less. If it exceeds 0.3 μm, generation of oil droplets tends to increase with time, and jumping occurs. The preferred range of Ra is 0.1 to 0.3 μm. It is considered that the mechanism of this oil droplet generation is that, for example, in the case of nitriding treatment in which the surface roughness is “rough” and Ra exceeds 0.3 μm, many oil droplets are generated. Oil,
It is presumed that the oil droplet components gradually accumulate and eventually flow out to the wall of the plate passage to cause jumping.

From the above, it can be seen that the oil droplet component is entrained into the yarn by setting the surface roughness Ra of the “smoothness” to be 0.3 μm or less as the surface roughness. p. u Confirmed in the measurement results.

More preferably, as a forcible forcible suction means, suction is conducted to the yarn running surface of the cooling plate from the running surface to the back surface, and the suction is sucked into the hollow portion inside the cooling plate, and the separation device is passed through the suction nozzle. It may be discharged and removed. In this case, it is needless to say that the surface roughness Ra is preferably 0.3 μm or less. Furthermore, high-speed false twisting of polyester undrawn yarn having a content of titanium dioxide of 1.5% by weight or more is particularly remarkable and requires a hardening treatment of a cooling plate having a surface hardness of Hv 800 or more. This is to prevent the generation of fluff due to abrasion with time. Hv is preferably Hv 1200 or less. When Hv exceeds 1200, oil droplets are easily generated due to surface coating. The surface coating is usually a permanent mirror, preferably tufted SUS316L.

The cooling mode will be described below with reference to the drawings.

A cooling plate 5 is provided between the heater 3 and the twisting device 4 in FIG.

In FIG. 4, the cooling plate 5 is composed of a vertically long contact type cooling plate having a thread running path in which a curved concave portion is formed.
As shown in the figure, a curvature (R) of 2 mm or more is shown.

The yarn y heated by the heater 3 enters the cooling plate 5 with an accompanying flow.

After being cooled and stabilized by the cooling plate 5, the yarn untwisted by the twisting device 4 is taken up by the second feed roller 2 and then wound up by the winding device 7.

The temperature of the heater 3 is set according to the processing speed, the yarn fineness and the like as described above.
When processing at a high speed of 000 m / min or more, the upper heater is set to 550 ° C. and the lower heater is set to 300 ° C.

As described above, according to the present invention, during high-speed machining, particularly at a high speed of 1000 m / min or more, the generation of oil droplets on the cooling plate surface is suppressed, and the surging phenomenon and the process condition over time are suppressed. In addition, the generation of fluff due to the deterioration of the twist, the unevenness of the twist, and the abrasion damage of the plate and the like are eliminated, and a remarkable effect that the high-speed and stable false twisting becomes possible is achieved.

[0057]

The present invention will be described more specifically with reference to the following examples.

Here, the crimp ratio TC is 150 de.
Skein and treated in a boiling water with a light load of 2 mg per denier for 20 minutes, then air dried all day and night in a room of 20 ° C. and 65% RH, then 200 mg per denier
After applying a heavy load for 1 minute, the length after standing for 1 minute is L ₀ , then remove the heavy load and change to a light load, measure L ₁ after 1 minute,
It is calculated by the following equation. TC (%) = (L ₀ −L ₁ ) × 100 / L ₀

Examples 1 to 3 and Comparative Examples 1 to 6 When the content of titanium dioxide was 2.0% by weight and the spinning speed was 3100
Birefringence Δn = 0.040, elongation 15 spun at m / min
0%, 130 denier / 36 filament of round cross section
The stretched polyester multifilament yarn was stretched by the simultaneous drawing false twisting apparatus as shown in FIG.
High-speed false twisting (Example 1) was performed at 00 m / min.

The length of the upper stage heater HA of the non-contact type first heater on the yarn entry side is 0.3 m, the set temperature is 550 ° C., the heat treatment time is 0.018 seconds, and the non-contact type first heater on the yarn exit side is The length of the lower heater HB of one heater is 0.7 m, and the set temperature is 30.
The polyester filament yarn was processed at a speed of 1000 m / min so that the fineness after processing was 75 denier (drawing ratio = 1.78) while maintaining the heat treatment time at 0 ° C. and 0.042 seconds.

In Examples 2 and 3 and Comparative Examples 3 to 6, Table 2 was used.
False twisting was performed under the conditions described. On the other hand, in Comparative Examples 1 and 2,
Is a conventional simultaneous draw-twisting apparatus as shown in FIG. 5, which uses the same raw yarn as in Example 1 and has a heater having a length of 2.5 mm.
Heat treatment at 220 ° C. using a contact type heater of m, 700 m / min speed (Comparative Example 1), 1000 m / min speed (Comparative Example 2) so that the denier after processing becomes 75 denier.
Processed with.

The properties of the false twisted yarns obtained from these Examples and Comparative Examples are shown in Tables 1 and 2.

[0063]

[Table 1]

[0064]

[Table 2]

As is clear from Tables 1 and 2, in the conventional technique of high-speed processing (Comparative Example 2 at 1000 m / min) same as that of the present invention, all of the strength, elongation and TC were inferior, and all the properties were inferior. Was also inferior. Further, the false twisted yarn of Comparative Example 2 had many fluffs, and the yarn was frequently broken during the operation, so that stable processing for a long time was impossible.

Comparative Example 1 is a quality characteristic, false twisting apparatus which is usually commercially available in the prior art.

[0067]

According to the present invention, the heating device can be significantly shortened, and when processing at a high speed of about 1000 m / min, the length can be reduced to less than half the conventional length, and the equipment can be downsized. A uniform and sufficient heat treatment can be performed.

Further, it is possible to improve the re-threading property at the time of thread breakage, to enable operational production, to increase the control range of the crimped TC, and to make it versatile. In addition, by shortening the heating device, the contact resistance of the yarn is small and the generation of fluff is reduced, and the surging phenomenon at the time of high-speed false twisting can be suppressed, so that high-speed and stable false twisting can be performed.
In addition, high-speed processing that has not been experienced before, especially 1000 m /
Elimination of oil droplets due to oil adhering to the cooling plate more than minutes, ensuring smooth twisting of running yarn, prevention of surging phenomenon and jumping, and eliminating processing fuzz due to plate damage and wear over time. This has a remarkable effect that high-speed and stable false twisting can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus suitable for practicing the present invention.

FIG. 2A is a plan view of a first heating device of FIG. 1; (B) It is a partial cross-sectional view of the first heating device of FIG. (C) It is an upper side longitudinal cross-sectional view of the 1st heating apparatus of FIG.

FIG. 3 is a graph showing a relationship between a heater temperature and TC workability.

FIG. 4A is an enlarged front view of the cooling plate of FIG. 1; (B) It is an expanded cross-sectional view of the cooling plate of (a). (C) It is explanatory drawing which shows the curvature of the groove part of the cooling plate of (a).

FIG. 5 is a schematic view of a contact heater type medium-speed false twister showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st feed roller 2 2nd feed roller 3 Heater for false twist heat setting 4 Twisting device 5 Cooling plate 32 Groove 33 Groove 34 Guide

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) D02G 1/02 101 D02G 1/02

Claims (2)

(57) [Claims] 1. A polyester unstretched yarn having a birefringence of 0.03 or more and a titanium dioxide content of 1.5% by weight or more is subjected to false twist while being stretched, and the false twist is heat-set. When cooling by a cooling plate and then untwisting, the heat setting heater is divided into two, an upper stage and a lower stage, which satisfy the following expressions (Equation 1) and (Equation 2) along the yarn traveling direction. The temperature of the upper heater (HA) is 400 ° C. or more and 800 ° C. or less, the heat treatment time is 0.01 second or more and 0.04 second or less, and the temperature of the lower heater (HB) is 32.
0 ° C. or less, the heat treatment time is maintained at 0.03 seconds or more and 0.08 seconds or less, and as the cooling plate,
The bottom is at least 2 mm or more in a section perpendicular to the axis.
Mirror surface having a curvature of and a center line average roughness Ra <0.3 μm
It has a finish and has a hardening treatment so that the hardness Hv is 800 or more.
A method for producing a polyester false-twisted yarn, comprising simultaneously performing drawing and false-twisting using a cooled cooling plate . [Equation 1] [Upper stage of first heater (yarn entry side) Heater length: H
A = (0.2-0.5) m] [Equation 2] [Lower stage of first heater (yarn exit side) Heater length: H
B = (0.5-0.8) m] 2. The simultaneous drawing false twisting process is performed at a yarn speed of 1000 m.
The method for producing a polyester false twisted yarn according to claim 1, which is performed at a rate of at least / minute .