JPH0819565B2 - Method for producing fine denier polyester fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fine denier polyester fiber in which unevenness between single yarns is greatly improved and, when woven, has a good quality as a strongly twisted woven fabric.

<Prior art and its problems> Huain denier polyester fiber having a single yarn denier of 1.4d or less and a filament number of 36 or more has recently been in growing demand in the field of polyester fiber garment, and particularly for raw twisted textured fabrics. Widely used as thread.

Such a fine denier polyester fiber is generally obtained by producing a low orientation undrawn yarn and then drawing it in a separate step. However, in that method, when the filaments are heated and drawn in a bundled state and the number of filaments is large like the fine denier yarn, the heat applied to each single yarn becomes non-uniform, and the yarn unevenness between the single yarns increases. To do. This tendency is further increased in fine denier yarns because the yarns are finer and more sensitive to heat.
This drawn yarn is characterized by a stress variation (CV%) of 10% or more at 5% elongation when the S-S curve of each single yarn constituting the yarn is measured. There is a problem in the uniformity of the woven fabric, which often causes problems such as deterioration of the texture of the woven fabric and deterioration of the woven fabric quality due to uneven dyeing. Further, when such a yarn having a large single-yarn unevenness is woven into a strongly twisted woven fabric, torque unevenness is developed and the quality is degraded. Therefore, in the conventional undrawn yarn spinning-drawing method, the homogeneity cannot be sufficiently satisfied, and a fine denier polyester fiber as a raw yarn for a strong twist woven fabric with good quality has not been obtained.

As a method for obtaining a fine denier yarn other than the undrawn yarn spinning-drawing method, for example, there is a method by high-speed spinning described in JP-A-55-93816. However, such a high-speed spinning method has a problem that the yarn breakage increases, stable production is not possible, and the mechanical properties of the obtained yarn, in particular, the yield point stress is low. Various problems occur.

Further, as another method, in JP-A-56-4715, the melt-spun yarn is cooled to a temperature below the glass transition temperature, then again passed through a heating zone and hot-drawn to obtain a fine dye having good dyeability. An example of obtaining a denier yarn is disclosed.

However, in such a drawing method, unless heat and tension (spinning tension) applied to the yarn in the heating zone are sufficiently controlled,
Uniform stretching cannot be performed. That is, JP-A-56-4715
In the present situation, the fine denier fiber disclosed in Japanese Patent Publication has not reached a level where sufficient homogeneity, in particular, single-yarn unevenness is satisfactory.

<Objects of the Invention> An object of the present invention is to reduce the unevenness between single yarns and to provide high-quality woven fabrics having good mechanical properties and good handability in high-order processability, especially in strong twist applications. It is an object of the present invention to provide a novel fine denier polyester fiber which can be used as a raw yarn for a high-quality woven fabric.

<Structure of the Invention> In the present invention, when a fine denier polyester fiber having a single yarn denier of 1.4d or less and a filament number of 36 or more is produced, the melt-spun polyester fiber is once cooled to a glass transition temperature or lower and then from a spinneret. The yarn is introduced into a heating zone having a cross-sectional area ratio between the inlet and the interior of 0.8 to 2.0 m of 4 or more, and heated gas is introduced from the periphery of the yarn in the heating zone to perform hot drawing. A method for producing a fine denier polyester fiber, which comprises refueling and collecting at 5000 m / min or more.

 Hereinafter, the present invention will be described in more detail.

The polyester in the present invention is mainly a polyester having ethylene terephthalate as a main repeating unit, but may be a polyester having butylene terephthalate as a repeating unit. Also, a polyester obtained by copolymerizing one or more other components in an amount of 15 mol% or less,
Alternatively, it may be polyester containing a small amount of additives.

Further, the fine denier polyester fiber means a fiber having a denier of 1.4d or less and a filament number of 36 or more as a single yarn constituting a yarn. In addition, single yarn denier is 1.1d
Below, the effect is particularly remarkable when the number of filaments is 48 or more. The cross-sectional shape is not particularly limited, and various cross-sections such as circles and triangles are targeted.

In order for the fine denier polyester fiber to give good woven quality and good properties when developed in a strong twist application, the uniformity of each single yarn constituting the yarn is important. If the uniformity between the single yarns is poor, and if there is a large difference between the single yarns that make up the yarn in terms of mechanical properties and heat-setting properties, there will be vertical streaks and weft stripes when the fabric is made, and wind In addition to the occurrence of spots and defects of dyeing spots, the texture of the strongly twisted woven fabric is deteriorated and the quality is deteriorated. In order to evaluate the uniformity between single yarns, macroscopic uniformity evaluation means in the fiber axis direction (for example, Worcester spots, stretch tension, etc.) that have been conventionally used are incomplete. It is necessary to microscopically check the variation in the physical properties of each single yarn. According to the knowledge of the present inventors, as an evaluation means for accurately examining the variation in physical properties between single yarns, stress variation (CV%) at 5% elongation of the SS curve of each single yarn constituting the fiber
Was most effective, and it was found that the fabric quality of the fine denier polyester fiber and the high twisting property can be improved only by controlling the stress variation below a certain level. In other words, the physical property values other than the stress variation cannot clearly evaluate the uniformity of the fabric quality of the fine denier polyester fiber and the characteristics of the strongly twisted fabric.

According to the knowledge of the present inventors, the stress variation (CV%) at the time of 5% elongation of the SS curve of each single yarn constituting the above fiber.
Is 7% or less, which is an essential requirement for improving the fabric quality for strong twist applications and eliminating various fabric defects. In addition, 5% or less is preferable.

The fine denier polyester fiber of the present invention is required to have a yield stress of 2 g / d or more in view of the passability in high-order processes. If the stress at yield point is less than 2 g / d, the yarn will be stretched during weaving and the fabric quality will be degraded.

Furthermore, in the present invention, the elongation of the polyester fiber is 30%.
It must be above. When the elongation is less than 30%, the fluff during spinning increases and the yarn breakage during weaving also increases.

Further, the fine denier polyester fiber of the present invention has an apparently different internal structure from the yarn produced by the high-speed spinning method disclosed in the above-mentioned JP-A-55-93816. As a property showing the difference in internal structure, the fine denier polyester fiber of the present invention has a temperature showing a peak value of shrinkage stress measured while heating the yarn at a temperature of 130 ° C. or higher, and thus the yarn is obtained by the high-speed spinning method. Are distinguished. The high speed spun yarn has a temperature at which the peak value of shrinkage stress is less than 130 ° C., and is very inferior to the polyester fiber of the present invention in the wrinkle development ability in the strong twist application.

The essential first requirement of the method for producing a polyester fiber of the present invention is that once melt-spun polyester fiber is cooled to a glass transition temperature or lower, it is again introduced into a heating zone, and hot drawing is performed in the heating zone to supply oil. It is to take over.
Only by this method, it is possible to draw each single yarn while uniformly applying heat to each single yarn without bundling, and in the conventional drawing method in which the single yarns are bundled at the time of drawing, the applied heat is The yarns of the present invention cannot be obtained because they are not evenly distributed to all the single yarns, resulting in single yarn unevenness. In order to obtain a fine denier yarn having good uniformity as in the present invention, it is necessary to strictly control some conditions involved in the drawing in the heating zone, and the drawing in the conventionally known heating zone is necessary. The method does not yield the yarn of the invention.

The second requirement of the manufacturing method of the present invention is the take-up speed, and the take-up speed is 5000 m / min or more. If it is less than 5000 m / min, the stress variation (CV%) at 5% elongation of the SS curve of each single yarn exceeds 7%, and the texture of the strong twist woven fabric becomes poor. The third requirement is the form of the heating zone, and the ratio of the cross-sectional area between the inlet (preferably the outlet) of the heating zone and the inside is 4 or more, preferably 10 or more and 225 or less. If the ratio of the cross-sectional areas is less than 4, the stress variation (CV%) at 5% elongation of the SS curve of each single yarn exceeds 7%. The fourth requirement is that the heating zone be the distance of its inlet from the base.
If it is less than 0.8 m, the stress at yield point will be less than 2 g / d, and if it exceeds 2 m, the elongation will be less than 30%. In the present invention, by setting the above four conditions, the homogeneity among the single yarns as in the present invention is first achieved, and the yarn having the elongation of 30% or more and the yield point stress of 2 g / d or more is stabilized. It can be manufactured. In the production method of the present invention, it is necessary to further introduce heated gas from around the yarn in the heating zone, and the flow rate thereof is preferably controlled to 10 to 80 N1 / min. Yarn. The heating zone for obtaining the fiber of the present invention is not particularly limited as long as the space in which the yarn runs is heated, but for example, a tube or a tube having a rectangular cross section is used. I can. As a means for increasing the temperature of the atmosphere in the heating zone, a method of electrically heating or heating a heating medium around the heating zone is generally used, but is not limited thereto. The atmosphere temperature in the heating zone is preferably 100 ° C to 200 ° C, and the length is preferably 1 to 2 m.

In the present invention, the heating gas is introduced into the heating zone, but the introduction of the heating gas is preferably blown out uniformly around the running yarn at a low flow rate. For example, a nonwoven fabric of metal fibers, a rectifying filter, or a porous material. It is preferable to introduce it through metal or the like. The temperature of the heated gas may be 80 ° C or higher, but 100 to 300 ° C is particularly preferable. Furthermore, the introduction of the heated gas is performed in the upper part of the heating zone so as to be substantially orthogonal to the running direction of the yarn, and then the heated gas is run along the running direction of the yarn in order to improve the uniformity of the yarn. Is effective and preferable.

As described above, the conventional undrawn yarn spinning-drawing fine denier yarns and the fine denier yarns drawn by the heating zone during the spinning process disclosed in JP-A-56-4715 are The variation in stress (CV%) at 5% elongation of the S-S curve of the single yarn constituting the fiber defined in the present invention is 9 to 10% or more, which does not reach the present invention.

This is because in the conventional drawing method of undrawn yarn, when the number of filaments increases like a fine denier yarn, the individual yarns overlap each other during heating and drawing, resulting in a temperature difference between the single yarns.
It is considered that the drawing points are different among the single yarns.

In the drawing method in the spinning process disclosed in Japanese Patent Application Laid-Open No. 56-4715, since each single yarn is not gripped between the rollers, it is inevitable that there is a difference in temperature rising behavior between the single yarns. This is because there is a difference in the drawing behavior, and a fine denier multifilament yarn excellent in uniformity cannot be obtained simply by providing a heating zone.

That is, the single yarns constituting the multifilament are heated to the same temperature at substantially the same position by the above-mentioned method, and the single yarns have the same physical property value by applying the same tension. This is the only way that a uniform yarn can be obtained. It is important to use the above-mentioned stress variation (CV%) in order to correctly grasp the yarn having such characteristics.
The object of the present invention can be achieved by controlling the following.

<Effects of the Invention> As described above, the fine denier polyester fiber of the present invention is a fiber in which unevenness between single yarns is significantly small and controlled to have good uniformity, and has good mechanical properties.
It has the following advantages.

1. Stable with no fluff or yarn breakage during spinning, and low-cost production is possible.

2. It is possible to manufacture high-quality woven and knitted products with good high-order process passing properties.

3. When used as a strong twist textured fabric, a high quality strong twist textured fabric with good texture is obtained.

The physical property values specified in the present invention are obtained under the following measurement conditions.

A. Stress variation at 5% elongation of each single-thread S-S curve (CV%) Divide into each single yarn that constitutes polyester fiber, and test each single yarn with a test length of 2 cm and a pulling speed of 2 cm / min. S
The curve is measured, the stress at 5% elongation of the SS curve of each single yarn is obtained, and the CV% is calculated by the following formula.

B. Elongation and yield point stress An SS curve is obtained using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd. under the conditions of a test length of 20 cm and a pulling speed of 10 cm / min, and the elongation and yield point stress are obtained.

C. Temperature of peak value of heat shrinkage stress Using a heat shrinkage stress measuring device manufactured by Kanebo Engineering, trial length 10 cm (loop actual length 20 cm), heating rate 150 ° C /
The heat shrinkage stress curve is obtained under the conditions of a load of 0.03 g / d and the temperature is read by reading the temperature corresponding to the maximum stress value of the curve.

Example 1 Polyethylene terephthalate was melted at 290 ° C. and the number of holes was 4
Ejection was performed from 8 nozzles (hole diameter 0.18 mmφ). The discharge rate was 27.8 g / min. 25m / min, 20 ℃ for the yarn discharged from the die
After cooling the blown yarn to a room temperature by blowing the cooling air of 1 m, the length of 1 m provided at 1.2 m below the mouthpiece, the inlet diameter 6 mmφ,
A yarn was introduced into a heating cylinder with an internal diameter of 32 mmφ (cross-sectional area ratio of the inlet and the interior was 28.4). The wall temperature of the heating cylinder was 200 ° C., and heated air was introduced from the side (upper part) of the heating cylinder close to the base (upper part) through a rectifying filter. The set temperature of the heated air was 250 ° C and the flow rate was 25 N / min.

Under this condition, the yarn drawn in the heating zone was drawn out from the heating zone and was taken up at a take-up speed of 5000 m / min to obtain a yarn of 50 denier 48 filament.

The stress variation (CV%) at 5% elongation of the SS curve of each single yarn of the obtained yarn is 4.53%, the strength is 4.9 g / d, the elongation is 36%,
Yield point stress 2.6g / d, temperature of peak value of heat shrinkage stress 168 ℃
It was.

The woven fabric obtained by plain-fabricating the fine denier polyester fiber had good quality. Even when used as a strongly twisted fabric, it had a good texture and a good quality with no defects.

Comparative Example 1 In Example 1, the heating zone was removed, otherwise Example 1 was used.
Under the same conditions as above, the discharge rate was set to 24.8 g / min, the take-up speed was set to 1500 m / min, and an undrawn yarn was obtained.
Hot roller drawing was carried out at 83 ° C. to obtain a drawn yarn of 50 denier 48 filament. 5 of the SS curve of each single yarn of this drawn yarn
The stress variation during the% stretching was 10.35%, the elongation was 35% and the yield stress was 3.0 g / d. A plain-woven fabric using this yarn had defects of uneven spots in some places. In addition, the strongly twisted woven fabric produced by using this yarn was found to have wrinkled spots everywhere and was of low quality.

Comparative Example 2 The heating zone in Example 1 was removed, otherwise Example 1 was used.
Under the same conditions as above, the discharge rate was 33.1 g / min, the take-up speed was 6000 m / min, and a 50-denier 48 filament yarn was obtained by the high-speed spinning method.

The stress variation at 5% elongation of the SS curve of each single yarn of this yarn was 3.59%, the elongation was 50%, and the stress at yield point was 1.3 g / d. The temperature of the peak value of heat shrinkage stress was 99 ° C.

The woven fabric plain-woven using this yarn was out of the range of the stress of the yield point of the present invention, and thus the vertical and horizontal stripe defects were conspicuous and the quality was low. Moreover, the temperature of the peak value of heat shrinkage stress is less than 130 ° C.
Almost no wrinkles were raised and there was a problem in quality.

Example 2 A yarn of 50 denier 48 filament was obtained under the same conditions as in Example 1 except that the position of the heating cylinder was changed as shown in Table 1.
The physical properties of the obtained yarn, the spinnability, and the ability to pass through higher-order processes are shown in Table 1.

As is clear from Table 1, when the elongation is less than 30%, the spinnability and the high-order passability are remarkably reduced.

Example 3 A yarn of 50 denier 48 filament was obtained under the same conditions as in Example 1 except that the discharge rate, the take-up speed, the heating air flow rate, and the cross-sectional area ratio between the heating cylinder inlet and the inside were changed as shown in Table 2. Table 2 also shows the stress variation (CV%) elongation at 5% elongation of SS of each single yarn of the obtained yarns, the yield point stress, and the properties of the strongly twisted woven fabric using the yarns.

As is clear from Table 2, No. 5,6,7,8 in which the stress variation of the S-S curve of each single yarn at the time of 5% elongation exceeds 7%, the quality as a strongly twisted woven fabric is poor and unpreferable. It was

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-4715 (JP, A) JP-A-54-138613 (JP, A) JP-A-55-93816 (JP, A) JP-B-58- 42286 (JP, B2)

Claims (1)

[Claims] 1. When producing a fine denier polyester fiber having a single yarn denier of 1.4 d or less and a filament number of 36 or more, the melt-spun polyester fiber is once cooled to a glass transition temperature or less, and then 0.8 to 2.0 m from a spinneret. The yarn is introduced into the heating zone having a ratio of the cross-sectional area of the inlet to the inside of which is 4 or more, and the heated gas is introduced from the periphery of the yarn in the heating zone to thermally draw and refuel, A method for producing a fine denier polyester fiber, which is characterized in that it is collected at 5000 m / min or more.