JPH101825A - Method for producing polyester composite fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a discharge amount per unit time, that is, to improve productivity by using a specific polymer as a core component when producing a polyester fiber. The purpose is to remedy the drawbacks of high speed spun fibers. SOLUTION: Polyester is provided for a sheath component, and a polymer having a greater temperature dependence of elongational viscosity than the sheath component is provided for a core component,
The composite ratio of the core component to the entire composite fiber is 1 to 10% by weight.
And a spinning speed of 8
A method for producing a polyester composite fiber, wherein necking occurs at a necking magnification of 7 times or less at 000 to 15000 m / min.

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 composite fiber consisting essentially of polyester, which can improve the productivity.

[0002]

2. Description of the Related Art Polyester fibers have various excellent properties including mechanical properties, and are therefore widely used in apparel and industrial materials.
Conventionally, in order to obtain polyester fibers, a so-called two-step method in which a polymer is melt-spun and then drawn is generally used. In general, a fiber that has just been melt-spun has not developed the internal structure of the fiber, and is inferior in mechanical properties and dimensional stability. Therefore, the structure is formed and fixed by drawing in a separate step. The draw ratio depends on the melt spinning conditions, particularly the spinning speed, and setting an excessively large ratio leads to yarn breakage and a reduction in texture, so there is a limit to the draw ratio. Also,
The productivity in the spinning process largely depends on the discharge amount per unit time. When obtaining a fiber having a desired fineness, if the draw ratio is limited as described above, the fineness of the undrawn fiber, that is, the discharge amount of spinning, is naturally limited, and there is a limit to the productivity improvement in the two-step method.

In recent years, in particular, polyethylene terephthalate (hereinafter abbreviated as PET) has a take-up speed of 5000 m / min or more, and has a practically strong elongation characteristic in one step without stretching, and a heat shrinkage rate of two steps. A process for obtaining a fiber having a lower dimensional stability than a conventionally drawn yarn has been industrially adopted. In addition, since the productivity in the spinning process largely depends on the discharge amount per unit time, the higher the speed, the higher the productivity.

However, in the case of PET, a spinning speed of 70
When the speed is higher than 00 m / min, the strength decreases. 33, T-208 (197
7). In particular, when the spinning speed is 8000 m / min or more, thread breakage and the like frequently occur and not only poor spinning property, but also
Since the remarkable decrease in the elongation characteristic occurs, it cannot be put to practical use.

[0005] For this reason, various attempts have been made to improve the spinnability and high elongation characteristics of ultrahigh-speed spun fibers. For example, Japanese Patent Application Laid-Open No. 1-148808 discloses a method in which a heating cylinder is used, and the necking magnification is 5 times or more. However, in this method, the spinning speed is 10,000 m /
The elongation of the fiber obtained in minutes is too low, only 18%, and cannot be put to practical use. Japanese Unexamined Patent Publication No. Hei 6-93512 discloses a method in which a heating shroud is provided immediately below a base, the temperature of the shroud is gradually lowered, and the necking magnification is reduced to 3 times or less. With this technology, the spinning speed is 10,000m /
When the additional test was performed for more than one minute, it was found that the improvement of the high elongation property was insufficient. Furthermore, in the method using a heating shroud, it is necessary to increase the heating temperature or lengthen the heating length in order to enhance the effect, and the yarn sway becomes large due to the rising airflow due to heating, causing unevenness of fineness and stains. There was a problem that became easy. Further, there has been a problem that the energy for heating is increased and the cost is rather increased, and the size of the apparatus becomes excessively large, and the workability of spinning is deteriorated.

Further, Japanese Patent Application Laid-Open No. 62-263309, 263
No. 314,263315 discloses a method utilizing airflow. However, when a venturi-type airflow imparting device is used, the elongation of the fiber obtained at a spinning speed of 10,000 m / min is too low. On the other hand, when an airflow applying device using a thin tube is used, only a low-strength fiber is obtained at a spinning speed of 10,000 m / min, and the heat shrinkage is too high at about 60%. Moreover, when airflow is used for ultra-high-speed spinning, it is difficult to control turbulence in the airflow imparting device, and there is a problem that spots and fineness unevenness frequently occur. In addition, the size of the device becomes excessively large, and the workability such as threading becomes extremely poor, which causes a decrease in productivity.

On the other hand, there have been attempts to improve the high elongation characteristics of ultrahigh-speed spun fibers by polymer modification. JP-A-62-21
No. 816 discloses a method in which the molecular chain end of PET is blocked with a metal sulfonate group and spun. However, in this case, the fiber obtained at a spinning speed of 10,000 m / min has too low elongation. In addition, the cost of raw materials rises due to polymer modification. Japanese Patent Application Laid-Open No. 62-21817 discloses a method of blending small amounts of different polymers.
Also in this case, the fiber obtained at a spinning speed of 10,000 m / min has low strength. In addition, in this technique, since the heterogeneous polymer is exposed on the fiber surface, there is a risk that whitening occurs during dyeing. Further, when the heterogeneous polymer is a polymer having a low softening point, such as polymethyl methacrylate or polystyrene, there is a problem that, for example, a high temperature treatment such as false twisting causes fusion.

As described above, it was impossible to obtain fibers having practically high elongation characteristics by ultrahigh-speed spinning with the conventional technology.

[0009] By the way, Journal of the Fiber Society of Japan, vol. 51, p
408 shows that the orientation of PET is reduced in the core-sheath composite spinning in which 50% by weight of polystyrene is disposed in the sheath portion. However, in the report, the spinning speed was 7
No description is made about necking in ultra-high-speed spinning at a spinning speed of about 8000 m / min or more. Further, the fiber obtained at a spinning speed of 7000 m / min has a birefringence of the PET portion of about 0.016 and has a low orientation due to the absence of a crystalline reflection peak observed by wide-angle X-ray diffraction. Moreover, a fiber which is an amorphous fiber and has practically high elongation characteristics as it is has not been obtained. Further, it is expected from the following examples that it is extremely difficult to develop necking without breaking yarn in a polyester fiber in which a large amount of polystyrene is composited as in this technique.

For example, when an undrawn polyester yarn having 30% by weight of polystyrene as a core is drawn, the core polystyrene is partially cut into a thick yarn.
No. 0-157617 and others. Therefore, if necking occurs in a composite undrawn polyester fiber in which a large amount of polystyrene is disposed in the sheath, it is expected that the sheath will be cut. Even if spinning is possible, if the content of the different polymer is high, the properties of the different polymer are strongly exhibited, and a material having substantially excellent mechanical properties of PET fiber cannot be obtained.

[0011]

The object of the present invention is to improve the productivity by ultra-high-speed spinning, to solve the above-mentioned problems, and to provide fibers having high strength and elongation characteristics stably and with good productivity.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to provide a sheath component comprising polyester, a core component comprising a polymer having a higher temperature dependence of elongational viscosity than the sheath component, and providing a core material with respect to the entire composite fiber. A polyester core-sheath conjugate fiber having a conjugate ratio of 1 to 10% by weight is spun, and a spinning speed of 8000 to 1
A necking is generated at a necking magnification of 7 times or less at 5000 m / min.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyester as a sheath component, P is used.
ET, polybutylene terephthalate, polyethylene naphthalate and the like can be mentioned, and PET is most commonly used and is preferred. Further, the polyester may be one in which a part of the diol component and a part of the acid component are each substituted with another copolymerizable component in a range of 15 mol% or less. They may also contain additives such as matting agents, flame retardants, antistatic agents, pigments and the like.

The core component polymer is a polymer including a polymer in which the temperature dependence of the extensional viscosity is higher than that of the sheath component. The relative comparison of the temperature dependence of the elongational viscosity here can be performed, for example, as follows. That is, the polymers to be compared are separately spun under the same spinning conditions (spinning machine, pack, spinneret hole diameter, number of filaments, cooling conditions, spinning speed, etc.) so that the final fiber diameter is the same, and the respective yarn speeds are adjusted. Alternatively, the fiber diameter is measured along the spinning line. Then, it can be determined that the more deformable the upstream of the spinning line, the higher the temperature dependence of the elongational viscosity.

The specific core component polymer having a higher temperature dependence of the extensional viscosity than the sheath component includes polystyrene-based polymers, polyacrylate-based polymers, acrylate-styrene copolymerized polymers, and polymethylpentene-based polymers. Polystyrene-based polymers are preferable because they are easy to handle and exhibit good strength and elongation characteristics and heat shrinkage characteristics.

In the range where the polymer species is the same, the higher the viscosity of the core component polymer, the greater the effect of the present invention. Therefore, for example, in the case of general-purpose polystyrene, the melt flow rate (hereinafter, abbreviated as MFR) is set to 2.5 or less, whereby a further effect is obtained. The MFR measurement method is I
Specified in SOR1133.

The core component polymer may be a polymer having a higher temperature dependency of elongational viscosity than the sheath component alone, or a polymer having a higher temperature dependence of the extensional viscosity than the sheath component as long as the effects of the present invention are exhibited. And other polymers such as polyester. As described above, when a blended polymer is used, the composite ratio in the present invention is defined by the weight fraction of the polymer, which has a higher temperature dependence of the extensional viscosity than the sheath component, in the entire composite fiber. The content of the polymer having a higher temperature dependency of elongational viscosity than the sheath component in the blend polymer, that is, the blend ratio is 30 to 70% by weight, and the temperature dependence of the elongational viscosity is higher than that of the sheath component in the entire composite fiber. The high polymer content is 1 to 10% by weight. The term "composite ratio" as used in the present invention refers to the content of polymer having higher temperature dependence of elongational viscosity than the sheath component in the entire composite fiber. However, from the viewpoint of controlling the necking magnification, it is preferable to take care to prevent a completely uniform dispersion in which the blend state reaches the molecular order at this time.

The core-sheath composite shape is not particularly limited, and may be a concentric core-sheath or an eccentric core-sheath, may have a plurality of cores, or may have a sea-island structure. That is, it is necessary that the core component polymer is continuously present in a constant amount in the fiber axis direction and is not exposed on the fiber surface.

The composite ratio of the core component polymer having a high temperature dependence of the extensional viscosity is 1 to 10% by weight based on the entire composite fiber. When the composite ratio is higher than 10% by weight, the core component polymer becomes apparent, and strength dimensional stability and the like are reduced. On the other hand, when the composite ratio is less than 1% by weight, the residence time becomes too long, and decomposition, gelation, etc. may occur, and the spinnability may be reduced. The composite ratio of the core component polymer is preferably 2 to 7% by weight, more preferably 3 to 6% by weight. By making the core-sheath conjugate fiber and using a very small amount of the core component polymer as described above, it is possible to maintain good spinnability even in ultra high speed spinning without adding special operations such as heating and cooling on the spinning wire. What you can do is also a big advantage.

The spinning speed is 8000 m / min or more in order to improve productivity and cause necking. When the spinning speed is as low as less than 8000 m / min, not only the productivity improvement effect is low but also a fiber having practical high elongation characteristics without necking may not be obtained. , Preferably at least 9000 m / min, more preferably at least 10,000 m / min. The upper limit is a winding speed of about 15000 m / min.

The necking magnification is defined by (yarn speed immediately after necking / yarn speed just before necking). In the present invention, it is important that the necking magnification is 7 times or less.
If the necking ratio is larger than this, the fiber is deformed too rapidly, resulting in inferior elongation characteristics. Preferably it is 5 times or less, more preferably 3 times or less.

By employing the spinning method of the present invention, not only the productivity is improved by ultra-high-speed spinning, but also the following high-speed spun fibers conventionally used in industry (spinning speed: about 6,000 m /) as follows. Fibers having excellent properties exceeding the above.

First, a strength of 3.5 cN / dtex (4.0), which was very difficult to obtain conventionally in ultra high speed spinning.
The most characteristic feature is that fibers having characteristics of g / d) or more and elongation of 30% or more can be obtained. Strength 3.
When it is 5 cN / dtex (4.0 g / d) or more, it is possible to prevent yarn breakage in a high-order process and strength reduction due to alkali weight loss. Further, when the elongation is 30% or more, yarn breakage and fluff can be prevented in higher-order steps such as weaving. Further, at the time of winding, when the bobbin is automatically switched, the switching success rate becomes good. If the elongation is 37% or more, the higher process passability and the success rate of automatic switching of bobbins are further improved.

The yield stress is 1.5 cN / dtex.
(1.7 g / d) or more and good impact resistance.
Therefore, the fiber obtained by the present invention can be used for the weft of a water jet loom. High-speed spun fibers that are industrially used have a low yield stress and thus are inferior in impact resistance, and when used for water jet loom wefts, there is a problem that fluff and sink marks occur. The fiber obtained by the present invention solves this problem and has a quality exceeding that of the high-speed spun fiber used industrially.

By the way, since the fiber obtained by the high-speed spinning method of the present invention has a low heat shrinkage, it has good thermal dimensional stability and can solve problems such as generation of wrinkles in the dyeing process. There is also. Furthermore, since it has a high heat shrinkage stress exceeding high-speed spun fibers having a spinning speed of about 6000 m / min, which is used industrially, it can be applied to strongly twisted yarns.

The reason why a fiber having excellent characteristics can be obtained by adopting the present invention is not clearly understood, but is considered as follows.

The first point is that by adopting a specific polymer as the core component of the composite fiber, the yarn speed immediately before necking of the composite fiber is increased as compared with the case of single spinning of polyester, and the necking ratio is reduced. (Fig. 1). The yarn speed profile at a spinning speed of 10,000 m / min is shown in FIG. In the case of PET single spinning, the yarn speed before and after necking was 597 m / min and 8400 m / min, and the necking magnification was 14 times. Is declining. It has never been known that such spinning can be controlled by the composite spinning of polyester and a specific polymer. As described above, since the necking ratio could be reduced, a fiber having practically high elongation characteristics and heat shrinkage characteristics could be obtained for the first time even with an ultrahigh-speed spun fiber having a spinning speed of 8000 m / min or more.

It is considered that the specific core component polymer having the effect of increasing the yarn speed immediately before necking plays the following role. That is, since the elongational viscosity of the core component polymer is higher than the temperature dependency of the polyester, the thinning of the core component polymer proceeds upstream of the position where the polyester is originally thinned on the spinning line, and the core component polymer The polyester is forcibly reduced by the thinning. As a result, the yarn speed immediately before necking is higher than the original yarn speed of the polyester, and as a result, the necking magnification is reduced.

However, such action of the core component polymer is greatly influenced by the degree of temperature dependence of the extensional viscosity and / or the absolute value of the extensional viscosity. Then, the effect of the absolute value of the elongational viscosity can be easily estimated by MFR. The smaller the MFR of the core component polymer, the larger the absolute value of the elongational viscosity, and it can be estimated that the effect is large. However, this estimate is limited to comparisons between polymers of the same type, where the temperature dependence of elongational viscosity is considered to be approximately the same.

Further, the effect of reducing the necking magnification is greatly affected by the composite ratio of the core component polymer. When the MFR is constant, the higher the composite ratio, the higher the effect (Table 1). As described above, since the effect of reducing the necking magnification is greatly affected by the viscosity characteristics and the composite ratio of the core component polymer, the type, MFR, and composite ratio of the core component polymer are adjusted according to the desired fiber characteristics and spinning speed. You need to choose.

The polyester fiber obtained by the present invention can be used as raw silk, or as a twisted or false twisted yarn, for stretch materials such as pantyhose, tights, swimwear, socks, innerwear, sportswear, brushes, campuses and the like. It can be suitably used for conventional applications, clothing applications such as lining, slacks, blousons and blouses, and material applications such as ribbons, tapes and belts.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. In addition, the measuring method in the Example used the following method.

A. Intrinsic viscosity [η] Measured at 25 ° C. in orthochlorophenol.

B. Strength and Elongation According to JIS L1013, a load-elongation curve was determined using a tensile tester manufactured by Orientec Co., Ltd. under the conditions of a sample length of 50 mm and a tensile speed of 50 mm / min. Next, the load value was divided by the initial fineness, which was taken as the strength, and the elongation was divided by the initial sample length to obtain the elongation. Table 1 shows the maximum values of strength and elongation.

C. Yield stress A strength-elongation curve was determined from the strength and elongation described above, and the strength at the first inflection point of the strength-elongation curve was defined as the yield stress as shown in FIG.

D. Thermal Shrinkage Stress Measurement was performed under the following conditions using a thermal stress meter manufactured by Kanebo Engineering Co., Ltd. The sample was a loop of 10 cm × 2. 2.7 × 10 ⁻³ N was added as an initial tension, and the measurement was performed at a heating rate of 150 ° C./min under dry heat and constant length. Then, the generated maximum load was divided by the total fineness of the loop sample to obtain a heat shrinkage stress.

E. Heat shrinkage The fiber was squeezed, immersed in boiling water at 98 ° C. for 15 minutes, and the dimensional change before and after the treatment was measured and calculated from the following equation. Heat shrinkage = [(length before processing−length after processing) / length before processing] × 1
00

F. Necking magnification Malvern laser Doppler velocimeter (Type 62
00), the single yarn running from the front of the chimney was irradiated with laser light to measure the yarn speed. The point where the yarn speed jump was observed was regarded as necking, and the necking magnification was determined from the yarn speeds before and after that as follows. Necking magnification = (yarn speed immediately after necking / yarn speed just before necking)

G. It was measured according to MFR ISO R1133.

H. Periodic spots in the fiber longitudinal direction Continuous heat shrinkage spot measuring system F manufactured by Toray Engineering Co., Ltd.
The continuous wet heat stress was measured at a measurement temperature of 100 ° C. by TA-500. Yarn speed 10m / min, chart speed 6c
m / min.

Example 1 and Comparative Example 1 PET having an intrinsic viscosity of 0.63 and polystyrene (MFR =
1.1, Denkastyrol MT-2 manufactured by Denki Kagaku Kogyo Co., Ltd.)
Were separately melted and filtered through a stainless steel non-woven fabric filter having an absolute filtration diameter of 5 μm, and then a polystyrene core and PET were converted into a concentric core-sheath composite having a number of holes of 36.
From the base. At this time, the composite ratio of polystyrene is 5
% By weight. The spinning temperature was adjusted to 300 ° C., and the discharge rate was adjusted to a single yarn fineness of 2.2 dtex. The discharged yarn was cooled by a conventional method after discharge, lubricated after refueling, and wound up by a winding machine via a take-off roller. At this time, the speed (spinning speed) of the take-off roller was 10,000 m / min. Table 1 shows the necking magnification and characteristics of the obtained fiber.

In addition, PET alone spinning was performed under the same conditions as in the above-described composite spinning. Table 1 shows the necking magnification and characteristics of the obtained fiber.

Spinning speed of 100 with polystyrene as the core component
The yarn speed profile at 00 m / min is shown in curve A of FIG. In the case of PET alone spinning speed of 10,000 m / min (Fig. 1
As can be seen from the curve B), the yarn speed immediately before necking increased and the necking magnification decreased.

As can be seen from Table 1, the spinning speed is 1 for PET alone.
Although the fiber obtained at 0000 m / min has low strength and low elongation, it is not practical. However, only a small amount of polystyrene is combined with PET and spun. It can be seen that fibers having high yield stress and moderate heat shrinkage characteristics can be obtained. Further, the strength-elongation curve of the fiber obtained at a spinning speed of 10,000 m / min using polystyrene as a core component is shown in curve A of FIG. 2, and the strength-elongation of the fiber obtained at a spinning speed of PET alone of 10,000 m / min. The curve is shown as curve B in FIG. It can be seen that a good strength-elongation curve is obtained by combining a small amount of polystyrene. Table 2 also shows the number of yarn breaks and the periodic unevenness in the fiber longitudinal direction.
It was also described in. It can be seen that the use of the conjugate fiber makes it possible to obtain a fiber having less unevenness as compared with the blended yarn with a good spinning property.

Example 2 and Comparative Example 2 Polystyrene (MFR = 1.1, Denkastyrol MT-2 manufactured by Denki Kagaku Kogyo Co., Ltd.) and MFR = 2.
1. Styron 685 manufactured by Asahi Kasei Corporation), polymethyl methacrylate (Sumipex MH manufactured by Sumitomo Chemical Co., Ltd.), polymethyl pentene (“TPX” RT1 manufactured by Mitsui Petrochemical Co., Ltd.)
8), and the spinning speed was changed (8000 to 14000).
(m / min), and spinning was performed under the same conditions as in Example 1.
Table 1 shows the type of the selected polymer, spinning speed, necking ratio, and properties of the obtained fiber.

In addition, PET single spinning was performed under the same conditions as in the case of the composite spinning. , Spinning speed (6000, 8000m /
Table 1 shows the properties of the obtained fibers.

Fibers obtained by spinning PET alone at a spinning speed of 8000 m / min have low strength and low elongation and are not practical. On the other hand, when a small amount of a polymer whose elongational viscosity is more temperature-dependent than PET is compounded and spun, a spinning speed of 800
Even at 0 m / min or more, the necking magnification becomes 7 times or less, and it can be seen that a fiber having practical strength and elongation characteristics, high yield stress, and appropriate heat shrinkage characteristics can be obtained. It is also found that the lower the MFR of polystyrene, that is, the higher the viscosity, the lower the necking ratio and the higher the effect at the same spinning speed (Experiments No. 1 and No. 6 and No. 3 and No. 7).
Table 2 also shows the number of yarn breaks and the periodic unevenness in the fiber longitudinal direction. It can be seen that the use of the conjugate fiber makes it possible to obtain a fiber having less unevenness as compared with the blended yarn with a good spinning property.

Example 3 Melt spinning was carried out under the same conditions as in Example 1 except that the composite ratio of polystyrene (denkastyrol MT-2) was 1 to 10% by weight and the spinning speed was changed (Experiment No. 16).
19). Table 1 shows the necking magnification, fiber strength, elongation, yield stress, heat shrinkage stress, and heat shrinkage at each composite ratio. It can be seen that if the composite ratio of polystyrene is 1 to 10% by weight, a fiber having practical strength and elongation characteristics, high yield stress, and appropriate heat shrinkage characteristics can be obtained. Also, the higher the polystyrene composite ratio, the greater the effect of lowering the necking magnification. So 7 and 10
In the case of wt%, the spinning speed was increased.

Comparative Example 3 Melt spinning was performed under the same conditions as in Example 1 except that the composite ratio of polystyrene (denkastyrol MT-2) was 0.5 and 12% by weight and the spinning speed was changed (Experiment N).
o. 20-22). Necking magnification, fiber strength, elongation, yield stress, heat shrinkage stress,
Table 1 shows the heat shrinkage. When the composite ratio of polystyrene is 0.
In the case of 5% by weight, a low-strength fiber was obtained even at a spinning speed of 8000 m / min. When the composite ratio was 13% by weight and the spinning speed was 10,000 m / min, necking did not occur on the spinning line, and only fibers having a high heat shrinkage were obtained. On the other hand, when the spinning speed was 15000 m / min, necking occurred on the spinning line and the magnification was sufficiently low as 2 times. However, since the composite ratio was too high, the adverse effect of polystyrene was exhibited, resulting in a low-strength fiber.

Comparative Example 4 Stylon 9403 (M
FR = 4.0) and the composite ratio was 5 or 10% by weight.
The melt spinning was performed under the same conditions as in Example 1 except that the spinning speed was changed (Experiment Nos. 23 to 25). Table 1 shows the necking magnification, fiber strength, elongation, yield stress, heat shrinkage stress, and heat shrinkage at each composite ratio. When the composite ratio was 5% by weight, the necking magnification was 7 times at a spinning speed of 8000 m / min, and a fiber having practical high elongation characteristics was obtained. Only strong fibers were obtained. In addition, a composite ratio of 5
MFR = 4.0, 2.1, 1.1, constant at% by weight
When the spinning speed is 10,000 m / min, the necking magnifications are 9 times, 6 times and 2 times, respectively.
It can be seen that the larger the FR, the lower the effect of lowering the necking magnification (Table 1).

By the way, even when polystyrene having MFR = 4.0 is used as the core component, if the composite ratio is 10% by weight, the necking ratio becomes 7 times at a spinning speed of 10,000 m / min, and a fiber having good strong elongation characteristics can be obtained. I got it.
However, since the effect of lowering the necking ratio is low, it can be seen that it is disadvantageous in comparison with high-viscosity type polystyrene in terms of improving productivity.

Comparative Example 5 PET and polystyrene (Styrone 685) used in Example 1 were kneaded with a 5 wt% biaxial extruder, and melt-spinning was performed under the same conditions as in Example 2. Table 2 shows the number of yarn breakage at that time and the periodic unevenness in the fiber longitudinal direction (Experiment Nos. 26 to 28). In the case of the blend, as compared with the composite, the uneven mixing of the polymer was large and the uneven viscosity was caused by the uneven mixing, so that the spinning was abnormal and the yarn was frequently broken. Spinning speed 1
At 0000 m / min or more, the number of thread breakage was large and sampling was impossible. In addition, the periodic unevenness in the longitudinal direction of the fiber also became worse.

[0053]

[Table 1]

[Table 2]

[0054]

【The invention's effect】 [Brief description of the drawings]

FIG. 1 is a diagram showing a yarn speed profile.

FIG. 2 is a diagram showing a strength-elongation curve of a fiber obtained by the present invention.

FIG. 3 is a view showing yield stress.

Claims (4)

[Claims] Claims: 1. A polyester having a sheath component and a polymer having a greater temperature dependence of elongational viscosity than the sheath component are disposed as a core component;
The composite ratio of the core component to the entire composite fiber is 1 to 10% by weight.
And a spinning speed of 8
A method for producing a polyester composite fiber, wherein necking occurs at a necking magnification of 7 times or less at 000 to 15000 m / min. 2. The polymer according to claim 1, wherein the core component polymer whose elongational viscosity is more temperature-dependent than the sheath component is at least one polymer selected from polystyrene-based polymers, polyacrylate-based polymers, acrylate-styrene copolymerized polymers, and methylpentene-based polymers. The method for producing a polyester composite fiber according to claim 1, wherein 3. The method according to claim 1, wherein the sheath component is substantially polyethylene terephthalate. 4. The method for producing a polyester composite fiber according to claim 2, wherein the melt flow rate of the core component polymer is 2.5 or less.