JP2000220033A - Polyester conjugate fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject conjugate fiber which is prepared by laminating plural components different in viscosity in the fiber axial direction and having comfortable stretch back properties when formed into a woven or a knitted fabric without using a polyurethane-based yarn by establishing a specific relationship between the breaking elongation and the shrinkage stress. SOLUTION: This conjugate fiber is obtained by laminating two components different in viscosity in the fiber axial direction and has the breaking elongation and the shrinkage stress in a relationship of the formula Y>= 6.0×(1/X)) [Y is the shrinkage stress (g/d); X is the breaking elongation (%)] and further >=5 crimps/cm number of developed crimps. The difference in intrinsic viscosity ΔIV of the two components is preferably 0.12-0.35 and the intrinsic viscosity of the low-viscosity component is preferably 0.45-0.55. Furthermore, the intrinsic viscosity of the high-viscosity component is preferably 0.60-0.85 and the compounding ratio of the high-viscosity component to the low-viscosity component is preferably (40/60) to (70/30) expressed in terms of weight ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester composite fiber having a crimp developing performance, and more particularly, to a composite fiber comprising two components having different viscosities and having stretch-back properties when formed into a woven or knitted fabric. The present invention relates to a polyester composite fiber which can be used as a high-grade woven or knitted fabric having both large swelling and resilience.

[0002]

2. Description of the Related Art In general, synthetic fibers such as polyesters and polyamides are widely used for clothing to industrial purposes because of their excellent characteristics. Among them, polyester fibers are widely used from apparel to industrial use because of their excellent functions such as strength, dimensional stability, and easy care property.

[0003] In particular, polyester fibers are provided with crimpability, stretchability, antistatic property, antifouling property, cool feeling, heat storage property, permeability prevention, heat retention property, light weight property, antibacterial property, color development with diversification of uses. The development of woven and knitted fabrics that are highly sensitive from functionalities such as fineness, ultrafineness, napping, softness, and drape are being actively performed. For example, JP-A-2-307924 proposes a bulky processed yarn in which false twisted and crimped yarn and polyester yarn are entangled with air to form a loop or a tarmi. Although this processed yarn is bulked by loops and lumps present on the surface, the yarn forming the so-called core inside the yarn does not have a swelling feeling, and therefore has a bulky property in the state of the processed yarn. However, the fabric obtained by knitting and weaving could not be provided with stretchback properties and swelling. Japanese Unexamined Patent Publication (Kokai) No. 3-193945 discloses a method for producing a composite yarn having anti-wrinkling properties and bulkiness and capable of obtaining a woven fabric having an ultra-soft texture. The resulting fiber is a flat yarn that does not exhibit crimping, and thus has a problem that the stretchability of the woven fabric is insufficient and the feeling of wearing is impaired.

[0004] Various methods have been adopted to impart excellent stretchability to the woven fabric. For example, there is a method in which a polyurethane yarn having excellent elasticity is used as a yarn constituting a woven fabric. However, this polyurethane yarn has a hard texture as a unique property of polyurethane,
Therefore, there is a drawback that the texture of the fabric is reduced or the drape property of the fabric is reduced. To avoid this drawback, weaving a woven fabric using a combination of a polyurethane yarn and a polyester yarn has also been performed. However, there is a difference in the dyeability between the polyurethane yarn and the polyester yarn, so that the dyeing process becomes complicated when dyeing the fabric, or the yarn is dyed in a desired color (often a dark color). However, there is a drawback that it becomes difficult.

On the other hand, Japanese Patent Application Laid-Open No. 4-240231 discloses a mixed yarn comprising a polyester multifilament having a difference in dry heat shrinkage and a conjugate filament having spontaneous elongation. However, since the conjugate filaments are spontaneously elongated by heat treatment, the mixed filaments have a flat multifilament in the core and a conjugate filament in the sheath when formed into a fabric, resulting in insufficient stretchability due to crimping. There was a problem that the feel was bad and the wearing feeling was impaired.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a comfortable stretch-back property without using a polyurethane yarn, especially when used for a high-quality woven or knitted fabric. The present invention relates to a polyester composite fiber which can be used as a high-grade woven or knitted fabric having both large swelling and resilience.

[0007]

An object of the present invention is to provide a conjugate fiber in which two components having different viscosities are bonded in the direction of the fiber axis, wherein the elongation at break and the shrinkage stress have the following relationship. This can be achieved by a polyester composite fiber.

Y ≧ {6.0 × (1 / X)} where Y is shrinkage stress (g / d) X is breaking elongation (%)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester composite fiber of the present invention is a bimetal composite fiber in which two-component polymers having different viscosities are bonded in the fiber axis direction. The relationship between the breaking elongation (X) and the shrinkage stress (Y) of the conjugate fiber of the present invention needs to be Y ≧ {6.0 × (1 / X)}. The relationship between the two will be described in detail using an example. For example, when the breaking elongation is 20%, the shrinkage stress is 0.30 g /
This indicates that the shrinkage stress at a break elongation of 30% or more is 0.20 g / d or more, and the shrinkage stress at a break elongation of 40% is 0.15 g / d or more.

The elongation at break of 20% is a value of elongation at break when a composite spun undrawn yarn is drawn at a predetermined draw ratio so as to have an elongation of 20%. Elongation at break 30%, Elongation at break 4
Similarly, 0% is a value when the film is stretched at a predetermined stretching ratio so as to have each elongation. In this case, the relational expression Y ≧
It satisfies {6.0 × (1 / X)}.

For example, when the breaking elongation is 20%, the shrinkage stress is 0.30 g / d or more. When the shrinkage stress is 0.30 g / d or more, the woven or knitted fabric has a crimp developing performance without losing its binding force, and a sufficient stretch back property is obtained. As a result, large bulkiness and tension , Waist and resilience are obtained. This shrinkage stress is preferably at least 0.40 g / d, more preferably at least 0.50 g / d. Similarly,
The shrinkage stress when the elongation at break is 30% is 0.20 g / d or more, and the relational expression Y ≧ ｛6.0 × (1 /
X) Satisfies｝. The range of elongation is preferably 10 to 60% from a practical viewpoint.

The composite fiber of the present invention can be used in various ways depending on the final use. The yarn of the present invention having a high elongation with a breaking elongation of 20% level can be suitably mixed with other polyester fibers. However, other materials other than polyester fibers, such as rayon, acetate, and natural fibers, can be suitably used. The yarn of the present invention having a breaking elongation of the level of 30% is particularly suitable for blending with polyester. In addition, the yarn of the present invention having a breaking elongation of 40% can be suitably used for false twisting and false-twisted mixed fiber because of its high residual elongation.

The elongation at break of the present invention is an elongation measured by an ordinary SS curve.

What is the shrinkage stress of the present invention? Thermal stress measuring device "Type KE-2S" manufactured by Kanebo Engineering Co., Ltd.
Is a value measured by the following method. Sample length 100mm
(200mm in loop) is set on the measuring machine and the initial load 1 /
At 10 g / d, a change in shrinkage force when heated at a heating rate of 2.5 ° C./sec from room temperature to 250 ° C. is detected by a strain meter, and a MAX stress value (g) is read from a chart, and converted to g / d. It is a converted value.

The conjugate fiber of the present invention develops crimp even in a free state after skewing, but has a latent crimp property in which a large number of crimps are developed after boiling water treatment. The number of developed crimps after the boiling water treatment is preferably 5 / cm or more. When it is at least 5 cores / cm, the stretch back property will be good and the bulkiness will be obtained, which is preferable. Further, when formed into a woven or knitted fabric, favorable stretch-back properties are obtained, and bulkiness, tension, waist, and resilience are also obtained, which is preferable. It is more preferably at least 7 cores / cm, even more preferably at least 10 cores / cm.

The number of crimps according to the present invention is a value measured by the method described below. First, a sample cut to a length of 7 cm is subjected to a boiling water treatment at 100 ° C. for 15 minutes in a free state. Next, immediately after being taken out, it is treated with cold water for 1 minute and then naturally dried for 5 hours. The sample after drying is stuck on a sample plate, covered with a slit plate having a width of 1 cm, transferred to a screen with a projector, and the number of crimps is read. 1 for n = 2
Measure 0 samples.

The larger the number of crimps, the better the stretch back property. However, when the viscosity difference of the polymer to be bonded is small, only a small number of crimps can be obtained, and when the viscosity difference is large, a large number of crimps can be obtained, but yarn breakage occurs frequently during spinning and stretching. It is not suitable for production. The intrinsic viscosity difference ΔIV of the conjugate fiber of the present invention is 0.12 to 0.3.
5 When ΔIV is 0.12 or more, crimping ability is generated when the film is stretched at a predetermined stretching ratio, and the shrinkage stress and the number of crimps can be obtained. More preferably 0.15
It is more preferably 0.20 or more. Also, ΔI
When V is 0.35 or less, it is preferable because yarn breakage during spinning and stretching is small and good crimping and shrinkage stress can be obtained.
More preferably, it is 0.30 or less.

This will be described in more detail. The intrinsic viscosity of the low-viscosity component of the conjugate fiber is 0.45 to 0.55. The lower the intrinsic viscosity of the low-viscosity component, the larger ΔIV is taken, and the greater the number of crimps obtained. Further, when the intrinsic viscosity is 0.45 or more, it is preferable because the raw yarn strength is not reduced and the yarn is not suitable for practical use. Further, the intrinsic viscosity of the low-viscosity component is more preferably 0.47 in consideration of the crimp development, shrinkage stress, raw yarn strength, yarn-making properties, and the like.
０．５0.53.

Next, the intrinsic viscosity of the high viscosity component is 0.60 to
0.85. This high-viscosity component makes the yarn-forming properties of the composite fiber
It is important to select a polymer to be used in combination with a low-viscosity component because it has a significant effect on the elongation properties. A combination of high viscosities with an emphasis on the spinning properties results in poor crimping characteristics.
Further, if the crimping property is considered too important, and ΔIV is taken too large, stable production becomes impossible. From these observations, the lower limit of the intrinsic viscosity of the high-viscosity component is preferably 0.60 or more because practical strength is obtained and crimping properties are also obtained. The upper limit is preferably 0.85 or less, at which good spinnability and good crimping properties can be obtained. More preferably, it is 0.65 to 0.75.

The intrinsic viscosity (IV) referred to here is the temperature 25
At 0 ° C., 0.8 g of a sample material is dissolved in 10 ml of orthochlorophenol (hereinafter referred to as OCP), and the relative viscosity (ηr) is obtained by the following formula using an Ostwald viscometer, and IV is further calculated. ηr = (η / ηo) − (t · d / to · do) IV = 0.0243 ηr + 0.2634 where η: viscosity of polymer solution ηo: viscosity of solvent t: drop time of solution (seconds) d: Density of solution (g / cm ³ ) to: drop time of OCP (second) do: density of OCP (g / cm ³ ) The strength of the composite fiber of the present invention is preferably 2.5 g / d or more,
More preferably, it is 3.0 g / d or more. 2.5g / d strength
With the above, fluff and yarn breakage can be reduced in the original yarn manufacturing process, and yarn breakage also occurs in handling in the high-order processing process,
It is preferable because fluff can be reduced. Further, even if the woven or knitted fabric is dyed and finished including alkali weight reduction, the tear strength of the fabric is preferably reduced as it is small.

The apparent shrinkage of the composite fiber of the present invention is 40%.
The above is preferred. When this value is at least 40%, the stretch-back property will be good and bulkiness, tension, waist, and resilience will be obtained. More preferably, it is 50% or more.

The apparent shrinkage of the present invention is a value measured by the method described below. First of all, it is wound ten times with a tape measure machine without applying tension, and (0.01 g / d × 10 ×
2) Measure the original length (l ₀ ) with a weight of g. next,
Remove the load, set free and perform boiling water treatment at 100 ° C for 15 minutes. Immediately after taking out, it is treated with cold water for 1 minute and then naturally dried for 5 hours. After applying the above-mentioned weight and waiting for 30 seconds, the post-processing length (l ₁ ) is measured. It is calculated from the following equation Apparent shrinkage = (l ₀ −l ₁ ) / l ₀ × 100 The composite ratio of the high-viscosity component and the low-viscosity component of the composite fiber of the present invention is preferably in the range of 40:60 to 70:30. In order to make the number of crimps smaller and more numerous, it is preferable that the composite ratio of the low-viscosity component is equal or slightly larger. On the other hand, in order to obtain the expressed number of crimps and the toughness of the yarn, it is preferable that the composite ratio of the high-viscosity component is equal or higher. The composite ratio that satisfies all the expressed number of crimps, shrinkage stress, and toughness of the yarn is preferably 50:50 to 60:40.

Either the eccentric type or the linear type can be applied to the bonding interface of the high-viscosity component and the low-viscosity component polymer of the conjugate fiber of the present invention. It is preferably a straight line. When the contact angle of the boundary surface with a substantially straight line is α, α is up to ± 20 degrees. With the eccentric type, α is larger than 20 degrees and crescent shape,
Or, those covered with high-viscosity, low-viscosity polymers.

A high-viscosity component constituting the composite fiber of the present invention,
Low-viscosity polymer is easy to handle, easy to develop crimp, easy to change shrinkage difference due to heat treatment to swelling of yarn and fabric, easy to impart drape to fabric, and dimensionally stable From the viewpoint of properties and the like, polyester polymers are preferred.

The high-viscosity component and the low-viscosity component constituting the composite fiber are polyesters. Terephthalic acid or its lower alkyl derivative (alkanol diester having 1 to 4 carbon atoms)
And ethylene glycol, or from terephthalic acid or a lower alkyl derivative thereof and ethylene glycol and at least one other component, or bis-2-hydroxyethylene terephthalate or a lower polymer thereof,
Alternatively, a polyester in which at least 70% of the polyester units obtained from bis-2-hydroxyethylene terephthalate and at least one other component is polyethylene terephthalate.

In this case, examples of the third component include aliphatic dicarboxylic acids such as oxalic acid, adipic acid, azelaic acid and sebacic acid, and aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2-6 naphthalene dicarboxylic acid and diphenic acid. And dicarboxylic acids having an alicyclic ring, such as, for example, 1-2-cyclobutanedicarboxylic acid. However, none of these are limited thereto.

Next, a method for producing the polyester composite fiber of the present invention will be described. The method for producing a conjugate fiber of the present invention is a conjugate fiber comprising a high-viscosity component and a low-viscosity component, and a high-viscosity component and a low-viscosity component are pasted into a side-by-side type with a predetermined composite pack and a composite die using a composite spinning machine. An undrawn yarn is obtained by composite spinning. At this time, the composite ratio of the high viscosity component and the low viscosity component can be obtained by adjusting the ejection amount. The difference in intrinsic viscosity between the two polymers can be freely selected depending on the polymer used. However, as described above, if the viscosity difference is too large, the crimping characteristics are good, but the discharge line bend becomes large due to the flow velocity difference between both components immediately below the die discharge hole, and yarn breakage during spinning frequently occurs. Is preferably within the range. Conversely, if the difference in viscosity is too small, the spinning properties will be good, but the crimping property will be reduced. Therefore, it is preferable to select a viscosity difference within the range of the present invention. To make the bonding boundary straight,
A high-viscosity component is introduced from the vertical direction, and a low-viscosity component is introduced from the horizontal direction, and can be obtained by adjusting the distance from the discharge unit.
To decenter the bonding surface, it is possible to adjust the merging position of the die, but in the case of polymers having a relatively small intrinsic viscosity difference, by introducing both polymers in parallel from the vertical direction and combining them. Can be easily obtained. Thus, an undrawn yarn of the conjugate fiber can be obtained.

The undrawn yarn is drawn by a normal drawing machine to a predetermined breaking elongation to obtain a polyester composite fiber. In order to obtain a conjugate fiber having a breaking elongation of 20%, 30%, or 40%, it is possible to obtain a conjugate fiber at a predetermined draw ratio.

If the elongation at break is less than 10%, many yarn breaks occur during stretching, so that high-magnification stretching is not preferred. If the elongation at break is, for example, 60% or more, the crimping properties and strength of the present invention cannot be obtained, which is not suitable for practical use.

The conjugate fiber of the present invention is used alone as it is for the warp,
It may be used for a weft, or may be used by mixing with other yarns.
In addition, false twisting may be applied, or false twist may be mixed.
A relatively low elongation composite fiber having a breaking elongation of about 30% or less can be suitably used for raw silk as it is. Further, conjugate fibers having a relatively high elongation at break elongation of about 40% or more can be suitably used for false twisting. Also, a real twist may be given, or a real twist may be mixed,
In addition, any combination of these may be used, and any method that exerts the characteristics of the conjugate fiber of the present invention may be used.

A woven or knitted fabric is produced by using the polyester composite fiber of the present invention, and an alkali weight reduction treatment can be suitably used for a woman's material. Also, in sports applications, alkali reduction is not particularly required, and the weight reduction may be appropriately used depending on the application. The woven or knitted fabric thus obtained has a stretch-back property, and a high-grade new woven or knitted fabric that cannot be obtained by the conventional technology having both large swelling and resilience can be manufactured.

[0032]

The present invention will be described below in detail with reference to examples. In the examples, the evaluation of the product texture is performed as follows. In the table, 〇, 〇, 表 is passed, and × is rejected. 1. Product texture A sensory evaluation was conducted by five skilled persons, mainly based on stretchback properties, bulkiness, and feeling of wearing, with appropriate tension, waist resilience, and drape properties.

◎: excellent 〇: good Δ: acceptable ×: not acceptable Alkali dissolution condition 1 part by weight of the knitted fabric is immersed in 50 parts by weight of a boiling aqueous solution of sodium hydroxide (3% by weight), treated with stirring for a predetermined time, washed with water, and then neutralized with a 1% aqueous solution of acetic acid. Further, it was washed with water and dried. The alkali dissolution treatment time was preliminarily examined and set so as to have a predetermined weight loss rate.
In addition, the calculation of the weight loss rate is performed by setting the knitted tube before and after the treatment at 100 ° C
Was dried in hot air for 20 minutes, and the weight was measured [the weights at this time are A and B], and the weight was determined from the formula {(AB) / A} × 100 = weight loss rate (%). 3. Yarn-making properties The following judgment method was used.

◎: Thread breakage rate of less than 3% 〇: Thread breakage rate of less than 6% △: Thread breakage rate of less than 10% ×: Thread breakage rate of 10% or more-: Not evaluated Higher workability Judged from the yarn breakage of the weaving machine during weaving.

◎: Yarn breakage of the weaving machine is less than 3% 〇: Yarn breakage of the weaving machine is less than 6% △: Yarn breakage of the weaving machine is less than 10% ×: Yarn breakage of the weaving machine Rate: 10% or more-: not evaluated Example 1 A high-viscosity component (A) composed of 100% polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.75;
A low-viscosity component (B) composed of 100% PET having an IV of 0.50 was composite-spun side-by-side at a weight composite ratio of A and B of 50:50. The A, B interface in the cross section of the composite spinning was substantially straight. IV of composite fiber
Was 0.61. This composite fiber was drawn so as to have an elongation of 30% to obtain a drawn yarn of 30D-12F. The physical properties of the yarn are shrinkage stress 0.37 g / d, number of expressed crimps 17 / cm,
The strength was 3.5 g / d. The above composite yarn and 30D-72F
Entangled with drawn yarn of polyester filament of 60
A mixed fiber of D-84F was obtained. The obtained mixed fiber yarn was twisted at 200 times / m to give a mixed fiber twisted yarn.

A plain woven fabric was prepared by using the mixed fiber twisted yarn as a warp and a weft. Next, a crimp development treatment, a 15% alkali weight reduction treatment, and a dye finishing treatment were performed in a usual polyester dyeing process. The obtained plain woven fabric had excellent stretch-back properties and bulkiness, upholstery and waist and resilience, and drape properties, and was a luxurious fabric. Next, the IV difference was changed, and levels 2 to 5 were obtained in the same manner as level 1.
A blouse was sewn using the obtained woven fabric, and a wearing test was performed by five skilled persons to determine a feeling of wearing. Table 1 shows the evaluation results.
Summarized in Level 1 was excellent in all aspects. Level 2
In the experiment in which ΔIV was reduced, the number of crimps expressed and the shrinkage stress were small and the feeling of the product was not sufficient, but was within the allowable range.
Level 3 was an experiment in which ΔIV was increased. In the experiment, the bending of the discharge line at the time of spinning was large, and the spinning property and the high-order workability were lowered. However, the texture of the product was good. Comparative Example 1 Level 4 is a comparative example for clarifying the present invention. At level 4, in the experiment in which ΔIV was less than 0.1, the stretchback property aimed at by the present invention could not be obtained. The results are shown in Table 1.

[0037]

[Table 1] Example 2 The discharge amount of the composite yarn of Example 1 was changed from 30D to 50D, a drawn yarn of a 50D-120F polyester filament was used in place of a drawn yarn of a 30D-72F polyester filament, and the others were in accordance with Level 1. Was. Level 5
Was excellent in all aspects. Level 6 was an experiment in which the elongation was 20%, and the crimping property and product texture were good. Spinning,
Although it was slightly inferior to the level 5 in high-order workability, it was within the allowable range. Level 7 was an experiment in which the elongation was 40%, and the yarn formability and high order workability were good. Although the crimping characteristics and the feeling of the product were slightly inferior to the level 5, they were within the allowable range. Comparative Example 2 Levels 8 and 9 are comparative examples for clarifying the present invention.
Level 8 was set to an elongation of 20%, but the desired yarn properties could not be obtained. The stretch back property aimed at by the present invention could not be obtained for the product texture. Level 9 was set to an elongation of 40%, but the desired yarn properties could not be obtained. The stretch back property aimed at by the present invention could not be obtained for the product texture. The results are shown in Table 2.

[0038]

[Table 2] Example 3 An experiment was performed according to the level 6 of Example 2 except that the composite ratio of the high viscosity component and the low viscosity component was changed. Level 10 was excellent in all aspects. Level 11 was an experiment in which the high-viscosity component was reduced to 40%, and level 12 was a conversely 70% in the high-viscosity component.
The experiment was increased to All of the spinning properties, higher passability, and the feeling of the product were unsatisfactory as compared with level 10, but were within the allowable range of the present invention. Comparative Example 3 Levels 13 and 14 are comparative examples for clarifying the present invention. Level 13 was an experiment in which the compounding ratio of the high-viscosity component was 35%, and the yarn-making properties, high-order workability, and product feeling were poor.
Level 14 was an experiment in which the high-viscosity component was 75%. The results are shown in Table 3.

[0039]

[Table 3] Example 4 This is an experiment for determining a limit value of a high viscosity component and a low viscosity component. Except that the polymer was changed, it was in accordance with the level 10 of Example 3. Level 15 was excellent in all aspects. Level 16,
17 was slightly unsatisfactory in terms of the spinning properties, higher passability, and product feeling compared to Level 15, but was within the allowable range of the present invention. Comparative Example 4 Level 18 was an experiment in which the IV of the low-viscosity component was reduced to 0.40, the shrinkage stress was small, the strength was low, and yarn breakage occurred frequently during spinning. The product texture was also insufficient. Table 4 shows the results
It was shown to.

[0040]

[Table 4]

[0041]

The high-grade woven fabric which is made of polyester composite fiber, has good yarn-making properties, has a comfortable stretch-back property without using a polyurethane yarn when used for woven or knitted fabric, and has both large swelling and resilience. A knit can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4L041 AA07 BA02 BA05 BA09 BA59 BC04 BC05 BC20 BD14 CA06 DD01 DD04

Claims (6)

[Claims] 1. A polyester composite fiber comprising two components having different viscosities bonded in the fiber axis direction, wherein the elongation at break and the shrinkage stress have the following relationship. Y ≧ {6.0 × (1 / X)} where Y is shrinkage stress (g / d) X is elongation at break (%) 2. The polyester composite fiber according to claim 1, wherein the number of expressed crimps is 5 / cm or more. 3. The limiting viscosity difference ΔIV of the two components is 0.12 to 0.12.
The polyester composite fiber according to claim 1 or 2, wherein the polyester fiber is 0.35. 4. The low viscosity component has an intrinsic viscosity of 0.45 to 0.5.
The polyester composite fiber according to any one of claims 1 to 3, wherein 5. The high viscosity component has an intrinsic viscosity of 0.60 to 0.8.
The polyester composite fiber according to any one of claims 1 to 4, wherein 6. The polyester composite fiber according to claim 1, wherein the composite ratio of the high-viscosity component to the low-viscosity component is 40:60 to 70:30 by weight.