JPH05247768A - Production of self-extensible thick-thin yarn and production of differently shrinkable blended yarn - Google Patents

Abstract

PURPOSE:To provide a yarn giving a web which gives a sufficient swelling touch and a new touch when the web is produced and subsequently subjected to a treatment such as a thermal treatment and which gives a dyed state highly different from conventional webs when the web is dyed. CONSTITUTION:A self-extensible thick-thin yarn 1b and a highly shrinkable yarn 2 are blended and interlaced with each other to produce a differently shrinkable blended yarn 3, where the self-extensible thick-thin yarn is produced by imparting the self-extensible property to a synthetic thick-thin yarn 1a whose fiber crystals are irregularly disposed along its longitudinal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-expanding thick yarn obtained by imparting self-expanding property to a synthetic fiber thick yarn in which the crystal of the fiber is unevenly oriented along the longitudinal direction, and a method for producing the same. The present invention relates to a method for producing a heterogeneous shrinkage mixed yarn using the self-expanding thick thin yarn, and in particular, the self-expanding thick thin yarn is stretched by subjecting a fabric to a treatment such as heat treatment, It is characterized in that it has sufficient bulkiness, and that this self-expanding thick thin yarn appears on the surface so that a fabric having a texture and a touch unprecedented can be obtained.

[0002]

2. Description of the Related Art Conventionally, when an undrawn yarn spun in an undrawn state is drawn at a natural draw ratio or less, uneven orientation occurs in the crystal of the fiber along the longitudinal direction, resulting in a thick fiber in the drawn yarn. It has been known that a synthetic fiber thick and thin yarn in which a portion and a thin fiber portion are generated can be obtained.

When the synthetic fiber thick yarn thus obtained is dyed, the thick fiber portion with low crystal orientation is dyed darkly, while the thin fiber portion with advanced crystal orientation is dyed lightly. As a result, a shade is produced in the dyeing, so that a fabric is manufactured by using this synthetic fiber thick and thin yarn, and then this fabric is dyed to obtain a marbling fabric having a shade unevenness.

[0004] In the past, yarns of different shrinkability were mixed and entangled to produce a different shrinkage mixed yarn.

When the different shrinkage mixed fiber thus produced is subjected to a treatment such as a heat treatment, a difference in shrinkage appears between the yarns constituting the different shrinkage mixed yarn, so that such a different shrinkage mixing occurs. It has been performed that a fabric is manufactured using a yarn and then the fabric is subjected to a treatment such as heat treatment to give a bulging feeling to the fabric.

Here, as such a different shrinkage mixed yarn,
Conventionally, different shrinkage mixed fibers obtained by producing two kinds of yarns having different heat shrinkages by different heat treatment conditions in a drawing process and winding and twisting two kinds of yarns having different heat shrinkages A yarn, a different shrinkage mixed yarn in which a high shrinkage yarn obtained by a high speed spinning method and a low shrinkage yarn obtained by a usual method are mixed, and the like are generally used.

However, in the above-described different shrinkage mixed yarn, there is little difference in shrinkage ratio between the yarns when subjected to a treatment such as heat treatment. Therefore, such different shrinkage mixed yarn is used. However, even if a fabric is manufactured by applying the heat treatment to the fabric, a fabric having a sufficient bulging feeling cannot be obtained.

Therefore, in the prior art, Japanese Patent Laid-Open No. 2-53
As disclosed in Japanese Patent No. 926, a different shrinkage mixed yarn in which a self-stretchable filament and a shrinkable filament are twisted together and wound up has been developed.

[0009] Here, when such a different shrinkage mixed fiber yarn is subjected to a treatment such as heat treatment, the filament having self-expandability expands, while the filament having shrinkability contracts, so that the shrinkage ratio of both is decreased. The difference becomes large, and when a fabric is manufactured using this heterogeneous shrinkage mixed yarn, and then this fabric is subjected to a treatment such as heat treatment, filaments having self-expandability are lifted to obtain a fabric having a sufficient swelling feeling. It became so.

However, in the case where a fabric is manufactured by using the different shrinkage mixed filament yarn in which the filament having the self-expandability and the filament having the shrinkability are twisted, and the fabric is subjected to a treatment such as heat treatment. However, the texture of the fabric, the dyeing state when dyed, and the like are not significantly different from those of the fabric produced using the conventional different-shrink mixed yarn, and are not satisfactory in the sense of providing a new fabric. It was

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to develop a new yarn in order to obtain a fabric having a texture and a dyed state which are very different from those of conventional fabrics.

According to the present invention, when the cloth is subjected to a heat treatment or the like, it has a sufficient swelling feeling and has a texture which is not present in the conventional cloth. An object of the present invention is to provide a yarn capable of obtaining a fabric having a dyed state which is very different from that of the fabric.

[0013]

In order to solve the above-mentioned problems, the present invention is a synthetic fiber thick and thin yarn in which the crystal of the fiber is unevenly oriented along the longitudinal direction and has a self-expanding property. We have developed a self-expanding thick yarn.

Here, the crystal orientation unevenness in the above-mentioned synthetic fiber thick and thin yarn has a birefringence (Δn) of 20 to 50 × 10 ⁻³ in the chic portion and a birefringence of 90 to in the thin portion.
It is preferably about 120 × 10 ⁻³ .

Further, in producing the synthetic fiber thick and thin yarns in which the crystals of the fibers have uneven orientation along the longitudinal direction, generally, an undrawn yarn spun at a low speed of 1000 to 1600 m / min is used, At a temperature below the glass transition temperature of the unstretched yarn, preferably 10 to 60 ° C., more preferably 30 to 55 ° C.
A low draw of about 1.6 times is performed to obtain a synthetic fiber thick and thin yarn in which the crystal unevenness of the fiber is oriented.

The method for obtaining the synthetic fiber thick and thin yarns is not particularly limited to the above-mentioned method, and the spinning draft at the time of spinning is lowered, and the synthetic fiber thick yarn is drawn at a low draw ratio. Fiber thick yarn may be manufactured.

When imparting self-stretchability to the synthetic fiber thick and thin yarn obtained as described above, the above-mentioned synthesis is generally performed at a temperature of 60 ° C. or lower, preferably 30 to 50 ° C. The fiber thin yarn is subjected to a medium stretching of about 1.5 to 2.5 times, and then the synthetic fiber thick yarn thus stretched is heat-treated in a relaxed state. When the drawn synthetic fiber thick and thin yarn is heat-treated, it is generally heat-treated at a high temperature of 200 to 280 ° C.

Further, in the present invention, the self-expanding thick thin yarn having self-expandability and the highly shrinkable yarn produced as described above are mixed and entangled to produce a different shrinkage mixed yarn. I decided to do it.

Here, the self-expanding thick and thin yarns and the mixed fibers,
As a highly shrinkable yarn to be entangled, when the heterogeneous mixed mixed yarn is subjected to a treatment such as heat treatment, it shows a sufficient difference in shrinkage with the self-expanding thick yarn, In order to have a high bulkiness, a yarn having a heat shrinkage of 10% or more is generally used.

[0020]

In the self-expanding thick yarn according to the present invention, as described above, the synthetic fiber thick yarn in which the crystal of the fiber is unevenly oriented along the longitudinal direction is stretched and then heat treated in a relaxed state. Since it is designed to give extensibility,
When the self-expanding thick yarn is subjected to a treatment such as heat treatment, the self-expanding thick yarn becomes elongated.

When the self-expanding thick thin yarn and the highly shrinkable yarn are mixed and entangled to produce a different shrinkage mixed yarn,
When this different shrinkage mixed yarn is subjected to a treatment such as heat treatment, the above-mentioned self-expanding thick thin yarn is expanded, while the above-mentioned highly shrinkable yarn is greatly shrunk, and the above-mentioned self-expanding thick thin yarn is largely lifted. , The different shrinkage mixed filament yarn becomes sufficiently bulky.

When a cloth is produced by using such a different-shrink mixed yarn, and the cloth is subjected to a heat treatment or the like, the self-expanding thick thin thread is stretched as described above, while the above-mentioned high shrinkage is caused. The elastic yarns are largely shrunk, the self-expanding thick and thin yarns are largely floated, and a fabric having sufficient bulkiness can be obtained.

When this cloth is dyed, the thick fiber portion having poor crystal orientation in the above-described self-expanding thick yarn is dyed darkly, while the thin fiber portion having advanced crystal orientation is dyed lightly, This self-expanding thick and thin yarn has a difference in color tone.

Further, when the treatment such as the heat treatment and the dyeing are combined, the self-expanding thin yarn having a difference in the dark and light dyeing between the thick fiber portion and the thin fiber portion is greatly lifted up and has a texture which has never been obtained before. Thus, it becomes possible to obtain a fabric in a dyed state which is very different from that of the conventional fabric.

[0025]

EXAMPLES Examples of the present invention will be specifically described below, and comparative examples will be given to clarify that the yarns according to the examples of the present invention are excellent.

(Example 1) In this example, polyethylene terephthalate (semi-dal) having an intrinsic viscosity [η] of 0.640 was melted and spun at a spinning temperature of 293 ° C.
The yarn spun through the individual spinning holes is taken up at a take-up speed of 1470 m / min and wound up,
An unstretched multifilament yarn of 75 denier / 36 filament was obtained. The above intrinsic viscosity [η]
Was measured at 20 ° C. in a mixed solvent in which phenol and tetrachloroethane became 6: 4.

Next, as shown in FIG. 1, the undrawn multifilament yarn 1 wound as described above.
Of the multifilament yarn 1 thus drawn out by the first supply roller 11 rotating at a peripheral speed of 416 m / min, and guided to the second supply roller 12 rotating at a peripheral speed of 420 m / min at a temperature of 45 ° C. After passing through the second supply roller 12, the multifilament yarn 1
The multi-filament yarn 1 is heated by the heater 14 at a temperature of 135 ° C. so as not to come into contact with the heater 14 and is rotated at a peripheral speed of 596 m / min.
Then, the film was drawn to 1.43 times and stretched 1.43 times, and then it was wound up.

When the unfiltrated multifilament yarn 1 is subjected to a drawing treatment in this way, the crystal orientation of the fibers becomes uneven, and a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion is obtained. Was given.

Next, as shown in FIG. 2, a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion, which has been drawn and wound as described above, has a peripheral speed of 416 m / mi.
After being pulled out by the first supply roller 11 rotating at n, the synthetic fiber thick yarn 1a is guided to the third supply roller 13 rotating at a peripheral speed of 832 m / min, so that the synthetic fiber thick yarn 1a is After being drawn 0.000 times, the synthetic fiber thick yarn 1a thus drawn is heated so as not to come into contact with the heater 14, and the synthetic fiber thick yarn 1a is heated by the heater 14 at a temperature of 265 ° C. It is guided to the draw roller 15 rotating at 624 m / min (relaxation rate 0.75), and the synthetic fiber thick and thin yarn 1a is heat-treated in a relaxed state to impart self-stretchability, thus imparting self-stretchability. The self-expanding thick thin yarn 1b was wound up.

When the self-expanding thick yarn 1b thus obtained was subjected to a dry heat treatment at 160 ° C., the self-expanding thick yarn 1b was elongated by 4.7%.

(Example 2) In this example, the undrawn multifilament yarn 1 obtained in the same manner as in Example 1 was used.

In this embodiment, the undrawn multifilament yarn 1 is drawn out by the first supply roller 11 rotating at a peripheral speed of 416 m / min as shown in FIG. The drawn multifilament yarn 1 is guided to a second supply roller 12 rotating at a peripheral speed of 420 m / min, passed through the second supply roller 12 at a temperature of 45 ° C., and then the multifilament yarn 1
The multi-filament yarn 1 is heated by the heater 14 at a temperature of 135 ° C. so as not to come into contact with the heater 14 and is rotated at a peripheral speed of 832 m / min.
After drawing it to 2.00 and drawing it to 2.00 times, this was taken up to obtain synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion due to uneven orientation of fiber crystals.

Next, as shown in FIG. 2, a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion, which has been drawn and wound as described above, has a peripheral speed of 416 m / mi.
After being pulled out by the first supply roller 11 rotating at n, the synthetic fiber thick yarn 1a is guided to the third supply roller 13 rotating at a peripheral speed of 603 m / min to make the synthetic fiber thick yarn 1a 1 After being stretched to 45 times, the synthetic fiber thick yarn 1a thus stretched is prevented from coming into contact with the heater 14, and the synthetic fiber thick yarn 1a is heated at a temperature of 265 ° C.
The peripheral speed of 4
It is guided to the draw roller 15 rotating at 52 m / min (relaxation rate 0.75), and the synthetic fiber thick and thin yarn 1a is heat-treated in a relaxed state to impart self-stretchability, thus imparting self-stretchability. The self-expanding thick thin yarn 1b was wound up.

When the self-expanding thick thin yarn 1b thus obtained was subjected to a dry heat treatment at 160 ° C., the self-expanding thick thin yarn 1b was elongated by 3.3%.

(Example 3) In this example as well, the undrawn multifilament yarn 1 obtained in the same manner as in the case of Example 1 above was used.

In this embodiment, the undrawn multifilament yarn 1 is drawn out by the first supply roller 11 rotating at a peripheral speed of 416 m / min as shown in FIG. The drawn multifilament yarn 1 is guided to a second supply roller 12 rotating at a peripheral speed of 420 m / min, passed through the second supply roller 12 at a temperature of 45 ° C., and then the multifilament yarn 1
The multi-filament yarn 1 is heated by the heater 14 at a temperature of 135 ° C. so as not to come into contact with the heater 14, and the draw roller 1 is rotated at a peripheral speed of 1019 m / min.
After being guided to No. 5 and drawn to 2.45 times, this was taken up to obtain a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion due to uneven orientation of the fiber crystals.

Next, as shown in FIG. 2, a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion, which has been drawn and wound as described above, has a peripheral speed of 416 m / mi.
After being drawn out by the first supply roller 11 rotating at n, the synthetic fiber thick yarn 1a is guided to the third supply roller 13 rotating at a peripheral speed of 437 m / min, and the synthetic fiber thick yarn 1a After being stretched to .05 times, the synthetic fiber thick yarn 1a stretched in this way is heated by the heater 14 at a temperature of 265 ° C. so that the synthetic fiber thick yarn 1a does not come into contact with the heater 14. It is guided to the draw roller 15 rotating at a speed of 334 m / min (relaxation rate: 0.764), and the synthetic fiber thick and thin yarn 1a is heat-treated in a relaxed state to impart self-expandability, thus imparting self-extendability. The prepared self-expanding thick thin yarn 1b was wound up.

When the thus obtained self-expanding thick thin yarn 1b was subjected to dry heat treatment at 160 ° C., the self-expanding thick thin yarn 1b was elongated by 2.7%.

(Comparative Example 1) In this comparative example, the same polyethylene terephthalate (semi-dal) used in each of the above Examples was used, and this was melted and spun through 48 spinning holes at a spinning temperature of 293 ° C. Then, the thus spun yarn was drawn at a take-up speed of 1480 m / min and wound up to obtain an undrawn multifilament yarn of 90 denier / 48 filaments.

Then, as shown in FIG. 3, the unstretched multifilament yarn 1 wound as described above is
First supply roller 2 rotating at a peripheral speed of 1080 m / min
The multifilament yarn 1 thus drawn out is brought into contact with a heater 23 having a temperature of 111 ° C. to heat the multifilament yarn 1, and then the second supply roller 22 rotating the multifilament yarn 1 at a peripheral speed of 2646 m / min. And pass through this second supply roller 22 at a temperature of 66 ° C.,
The above multifilament yarn 1 is drawn 2.45 times, and this is wound up, and orientation unevenness occurs in the crystal of the fiber, and a synthetic fiber thick thin yarn 1a having a thick fiber portion and a thin fiber portion.
Got

When the synthetic fiber thick yarn 1a thus obtained was subjected to dry heat treatment at 160 ° C., the synthetic fiber thick yarn 1a contracted by 5.0%.

(Embodiment 4) In this embodiment, a method for producing a different shrinkage mixed yarn by mixing and entanglement of a self-expanding thick thin yarn and a highly shrinkable yarn will be described.

Here, in this example, as in the case of Example 1 above, a composite having a thick fiber portion and a thin fiber portion produced by drawing the multifilament yarn 1 in an undrawn state. While using the thick fiber yarn 1a,
As the highly shrinkable yarn 2, a modified polyester (semi-dal) obtained by copolymerizing polyethylene terephthalate with isophthalic acid in an amount of 8.0 mol% was used. A modified polyester of 50 denier / 24 filament was obtained by spinning the polyester in a conventional manner. The multifilament yarn 2 was used.

When the modified polyester multifilament yarn 2 was dry heat treated at 160 ° C., it was 30.6%.
Contracted.

In order to impart self-expandability to the synthetic fiber thick thin yarn 1a, as shown in FIG. 4, the synthetic fiber thick thin yarn 1a is rotated at a peripheral speed of 41 as in the case of the first embodiment.
After being pulled out by the first supply roller 11 rotating at 6 m / min, this synthetic fiber thick and thin thread 1a is rotated at a peripheral speed of 832 m.
The synthetic fiber thick yarn 1a is guided to the third supply roller 13 rotating at a rotation speed of / min and drawn 2.00 times, and the synthetic fiber thick yarn 1a thus drawn does not come into contact with the heater 14. In this way, the synthetic fiber thick thin yarn 1a is heated to the temperature 2
Heated by the heater 14 at 65 ° C., and then the peripheral speed 62
The synthetic fiber thick yarn 1a is heat-treated in a relaxed state by being guided to the draw roller 15 rotating at 4 m / min (relaxation rate 0.75) to obtain the same self-expanding thick yarn 1b as in Example 1 above. It was

Then, the self-expanding thick thin yarn 1b to which the self-expanding property is imparted in this way and the above-mentioned highly shrinkable modified polyester multifilament yarn 2 are combined and guided to the entanglement device 16, and In the entanglement device 16, the self-expanding thick thin yarn 1b and the highly shrinkable modified polyester multifilament yarn 2 were entangled, and then wound up to obtain a different shrinkage mixed fiber 3.

Here, when the different shrinkage mixed yarn 3 thus obtained is subjected to the dry heat treatment, the self-expanding thick thin yarn 1b imparted with the self-expanding property is expanded by 4.7% while the above The highly-shrinkable modified polyester multifilament yarn 2 of 3) shrank by 30.6%, and the difference in shrinkage between them was 35.3%.

When the different shrinkage mixed fiber 3 of this Example 4 is heat-treated as described above, the different shrinkage mixed fiber 3 becomes
As shown in FIG. 5, the self-expanding thick thin yarn 1b having the thick fiber portion and the thin fiber portion was greatly lifted from the highly shrinkable modified polyester multifilament yarn 2.

(Comparative Example 2) In this comparative example, the synthetic fiber thick thin yarn 1a obtained in the above-mentioned Comparative Example 1 was obtained by applying this synthetic fiber thick thin yarn 1a to the above-mentioned Example 4 without imparting self-stretchability. The above-mentioned entanglement device 1 which is combined with the highly shrinkable modified polyester multifilament yarn 2 used in
6, the entanglement device 16 entangles the synthetic fiber thick and thin yarns 1a and the modified polyester multifilament yarns 2 and then winds them to obtain a different shrinkage mixed yarn.

When the heterogeneous-shrink mixed yarn thus obtained is subjected to dry heat treatment, the above-mentioned synthetic fiber thick and thin yarn 1a shrinks without stretching. Therefore, the different-shrink mixed yarn of Example 4 shown in FIG. Like the yarn 3, the self-extending thick thin yarn 1b having a thick fiber portion and a thin fiber portion did not float more than the highly shrinkable modified polyester multifilament yarn 2.

When a cloth is manufactured by using the differently shrinkage mixed yarn 3 of Example 4, and the cloth is heat-treated, the self-expanding thick thin thread 1b is stretched as described above, while the above-mentioned high The shrinkable modified polyester multifilament yarn 2 is greatly shrunk, and the self-expanding thin yarn 1b having a thick fiber portion and a thin fiber portion is largely floated on the surface of the fabric, showing sufficient bulkiness and A fabric having a texture very different from that of the above fabric was obtained.

Further, when this cloth is dyed, the thick fiber portion in which the crystal orientation is not sufficiently performed in the above-mentioned self-extending thick yarn 1b is dyed deeply, while the fine fiber in which the crystal orientation is advanced. The part was dyed lightly, and the self-expanding thick and thin yarn 1b had a difference in dark and light dyeing, and a fabric having a dyeing state very different from that of the conventional fabric was obtained.

[0053]

As described above in detail, according to the present invention, the synthetic fiber thick and thin yarns having uneven orientation in the crystal of the fibers are stretched along the longitudinal direction and then heat-treated in a relaxed state to be self-expanding. Since the self-expanding thick yarn is produced by applying the above, the self-expanding thick yarn itself becomes elongated when the self-expanding thick yarn is subjected to a treatment such as heat treatment.

In the present invention, the self-expanding thick and thin yarns and the highly shrinkable yarns are mixed and entangled to produce a different shrinkage mixed yarn. When a treatment such as heat treatment is applied, the self-expanding thick yarns are stretched, while the highly shrinkable yarns are largely shrunk, and the self-expanding thick yarns are greatly lifted, resulting in a different shrinkage mixed yarn. It came to show sufficient bulkiness.

Further, when a cloth is manufactured by using the different shrinkage mixed yarn thus manufactured, and the cloth is subjected to a heat treatment or the like, the self-expanding thick and thin threads are elongated, while the high shrinkability The yarn shrinks greatly and the self-expanding thick yarn floats up from the highly shrinkable yarn to give a fabric exhibiting sufficient bulkiness. When this fabric is dyed, the self-expanding thick yarn is crystallized. The thick fiber portion with poor orientation was dyed deeply, while the thin fiber portion with advanced crystal orientation was dyed lightly, and this self-expandable thick thin yarn had a difference in shade.

In addition, when the above-mentioned cloth is subjected to a combination of treatment such as heat treatment and dyeing, the self-expanding thick and thin yarn having a difference in shade between the thick fiber portion and the thin fiber portion is greatly lifted. Now, it is possible to obtain a fabric having a texture which is unprecedented and a dyeing state which is very different from that of the conventional fabric.

[Brief description of drawings]

FIG. 1 shows an example of the present invention in which an unstretched multifilament yarn is stretched so as to cause unevenness of orientation in a fiber crystal, and a synthetic fiber thick yarn having a thick fiber portion and a thin fiber portion is obtained. It is a schematic explanatory drawing which showed the state manufactured.

FIG. 2 is a schematic explanatory view showing a state in which the synthetic fiber thick yarn obtained in FIG. 1 is drawn and then heat-treated in a relaxed state to produce a self-expanding thick yarn.

FIG. 3 is a comparative example 1 in which an unstretched multifilament yarn is stretched so as to cause unevenness of orientation in the crystal of the fiber to produce a synthetic fiber thick yarn having a thick fiber portion and a thin fiber portion. It is a schematic explanatory drawing which showed the state.

[Fig. 4] In Example 4, while imparting self-expandability to the synthetic fiber thick thin yarn, the self-expandable thick thin yarn and the highly shrinkable modified polyester multifilament yarn were mixed and entangled to cause different shrinkage. It is a schematic explanatory drawing which showed the state which manufactures a mixed fiber.

FIG. 5 is a partially enlarged explanatory view showing a state of each yarn after heat-treating the differently shrinkage mixed yarn obtained in Example 4.

[Explanation of symbols]

 1 Unstretched yarn 1a Synthetic fiber thick and thin yarn 1b Self-expanding thick and thin yarn 2 Highly shrinkable yarn 3 Different shrinkage mixed yarn

Claims (3)

[Claims] 1. A self-expanding thick yarn, which is a synthetic fiber thick yarn in which the crystal of the fiber is unevenly oriented along the longitudinal direction, and which is provided with self-expanding property. 2. A synthetic fiber yarn, which has been spun in an unstretched state, is stretched at a temperature not higher than the glass transition temperature and at a low draw ratio of 1.1 to 2.5 times, and the crystals of the fiber have uneven orientation. A method for producing a self-stretching synthetic fiber thick yarn, which comprises producing a thick fiber yarn, stretching the synthetic fiber thick yarn, and then heat-treating in a relaxed state to impart self-stretchability. 3. A self-expanding synthetic fiber thick yarn obtained by imparting self-expanding property to a synthetic fiber thick thin yarn in which the crystal of fibers is unevenly oriented along the longitudinal direction is mixed with a highly shrinkable yarn. A method for producing a heterogeneous shrinkage mixed yarn, which comprises entanglement of fibers.