JPH09316726A - Production of extra fine polyester fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing an extra fine polyester fiber with slight variation in quality such as orientation degree unevenness and suitable as an industrial material. SOLUTION: Polyethylene terephthalate >=0.90 in intrinsic viscosity is melt spun from a spinneret having 200-500 delivery holes, and the delivered filament yarn is passed through a heated atmosphere kept at >=300 deg.C, and then cooled and solidified. The solidified filament yarn 7 is bundled in two stages 1-3m under the spinneret and then taken up at a spin draft rate of 300-500 and a take-up speed of 700-1,500m/min into undrawn yarn <5 denier in single fiber fineness, which is then subjected to multistage drawing, thus obtaining the objective drawn yarn <1 denier in single fiber fineness.

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 an ultrafine polyester fiber which is suitable for obtaining a base cloth or a canvas excellent in flexibility and strength.

[0002]

2. Description of the Related Art Polyester fibers are widely used as industrial materials because of their excellent mechanical properties. However, since the initial modulus is high, there is a disadvantage that the flexibility of the high-density fabric is lowered.

As a method of improving this flexibility, a method of making the fineness of a single yarn to be less than 1 denier is well known, but for industrial use, high tenacity and high toughness are required. It is necessary to increase the intrinsic viscosity. For example, in JP-A-59-1714, a polyester having a high intrinsic viscosity is slow-cooled by providing a heating zone under a spinneret and is spun at a low spinning speed to obtain a low viscosity. A method has been proposed in which an unstretched yarn having an orientation degree is obtained and the unstretched yarn is stretched at a high ratio. However, since the spinning speed is extremely low at about 350 m / min, it is necessary to reduce the discharge hole diameter of the spinneret in order to obtain ultrafine fibers, which easily causes melt fracture and has a problem in spinnability. It was

[0004] In general, in order to obtain ultrafine fibers having a fineness of single yarn of less than 1 denier, undrawn yarn of less than 5 denier is required. However, since such a fiber has a large surface area per unit mass, it is spun. There is also a problem that as the tensile strength applied to the medium fiber becomes higher and the fluctuation range of the tensile strength also greatly increases, unevenness of orientation occurs in the longitudinal direction of the single fiber, resulting in uneven strength. As a method for solving this problem, JP-A-55-132709 proposes a method of converging spun yarns to reduce air resistance applied to the yarns. However, when polyester with high intrinsic viscosity is spun, the melt viscosity of the polymer is large, so the spinning tension applied to the discharged yarn is too high, and it is easy to break the yarn. However, there is a problem in that fusion occurs.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the above-mentioned prior art and stably produces an ultrafine polyester fiber suitable for industrial materials with little variation in quality such as orientation unevenness. Is provided.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventor has found that a polyester having a high intrinsic viscosity is cooled and solidified after passing through a heating atmosphere and then focused in two steps. As a result, they have found that spinning can be carried out without increasing the degree of orientation unevenness, and as a result of further studies, they have reached the present invention.

That is, an object of the present invention is to "in the production of an ultrafine polyester fiber having a single yarn fineness of less than 1 denier, polyethylene terephthalate having an intrinsic viscosity of 0.90 or more and a spinneret having 200 to 500 discharge holes. Melted and discharged, and the discharged yarn is passed through a heating atmosphere maintained at a temperature of 300 ° C. or higher and then cooled and solidified, and the solidified yarn is divided into two stages within 1 to 3 m below the spinneret. Focused, spinning draft rate 300-500, take-up speed 70
It is achieved by a method for producing an ultrafine polyester fiber, which comprises winding at 0 to 1500 m / min to form an undrawn yarn having a single yarn fineness of less than 5 denier, and then drawing the undrawn yarn in multiple stages.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer used in the present invention is intended mainly for polyethylene terephthalate, but is a copolymerized polyethylene terephthalate (usually a copolymer) obtained by copolymerizing a third component within a range not impairing the object of the present invention. Quantity is 10
Mol% or less, preferably 5 mol% or less). Copolymer components preferably used include isophthalic acid, 5-sodium sulfoisophthalic acid, diethylene glycol, neopentyl glycol, bisphenol A with ethylene oxide and the like.

The intrinsic viscosity of the polyethylene terephthalate is preferably 0.75 or more from the viewpoint of the strength and toughness of the fiber in order to use it for industrial materials, and for that purpose, the intrinsic viscosity of the polyethylene terephthalate used for melt spinning is Viscosity is 0.90 or higher, preferably 0.9
It is 5 to 1.00. When the intrinsic viscosity exceeds 1.00, the melt viscosity becomes too high. As a result, when the melt spinning temperature is raised to stably melt and discharge, the polymer is thermally decomposed, and conversely, the strength and toughness of the obtained fiber are reduced. And the spinnability tends to deteriorate.

In the present invention, the above-mentioned polymer is 265
After melting at a temperature of 300 to 300 ° C., preferably 275 to 290 ° C., 200 discharge holes having a hole diameter of 0.35 to 0.55 mm are formed.
˜500, preferably 250 to 350 spinnerets are melt-discharged at a spinning temperature of 290 to 310 ° C. at a rate such that the undrawn yarn has a single yarn fineness of less than 5 denier. Here, it is desirable to select the hole diameter of the die so that the linear velocity of discharge from the die is 2.3 m / min or more, and if the linear velocity is less than 2.3 m / min, fineness unevenness is likely to occur. If the number of the discharge holes is less than 200, the effect of the two-stage focusing described below will not be exhibited, so that the object of the present invention cannot be achieved. It is easy for fusion to occur.

In order to obtain ultrafine fibers of less than 1 denier, the melt-extruded yarns have a temperature of 300 ° C or higher, preferably 30 ° C.
After passing through a heating atmosphere maintained at a temperature of 0 to 450 ° C., it is cooled and solidified. When the atmospheric temperature is lower than 300 ° C., the spinning tension cannot be kept low, the spinnability is lowered, the maximum draw ratio of the undrawn yarn obtained is also lowered, and the tenacity of the drawn yarn is also lowered. Is not preferable. The length of the heating atmosphere region varies depending on the heating atmosphere temperature condition, but is usually preferably 300 to 500 mm. Further, the heating atmosphere temperature is preferably set in two or more stages in the heating atmosphere region for the purpose of enhancing the strength. For example, 370 to 400 ° C. from below the die to 100 mm below the die and 330 to 380 from 100 to 300 mm below the die. C., 300 to 350.degree. C. up to 300 to 500 mm below the base.

It is important that the yarn passed through the heating atmosphere is blown with cooling air to be cooled and solidified, and then the cooled yarn is focused in two steps within 1 to 3 m below the spinneret. When attempting to focus in one stage, the spinning tension per denier applied to a single yarn becomes high when the focusing position is too far from the spinneret, and the fluctuation of the spinning tension becomes large when spinning ultrafine fibers. Will cause fineness unevenness and orientation unevenness. If the focusing position is raised to avoid this, the single yarn will be fused before the fluctuation of the spinning tension is suppressed, which is not preferable. When the focusing position of the first stage is less than 1 m below the spinneret,
The fineness unevenness is rather enlarged by the friction between the yarn and the bundling device, which is not preferable, and when the focusing position of the second stage is 3 m or more below the spinneret, the effect of suppressing the spinning tension becomes insufficient. Therefore, the object of the present invention cannot be achieved.

Although the spinning tension becomes smaller and the fluctuation thereof becomes smaller as the bundle diameter of the first stage becomes smaller, the spinning tension difference occurs between the single yarns and the single yarns are fused when they are rapidly bundled at once. Occurs. Therefore, the convergent diameter of the first stage is 1/5 to 1/15, especially 1/7 to 1/12 of the outermost diameter of the spinneret discharge hole group (minimum circle radius including all discharge hole groups). Is preferable, and the focusing diameter of the second stage is 1 cm.
The following is preferable. And the first stage focusing position and 2
It is desirable that the distance from the stage focus position is 10 to 50 cm. The material of the focusing device is not particularly limited as long as it has a small friction with the yarn, but for example, a material having a satin finished surface or ceramic is preferable. The shape is preferably a round hole, and a snail shape is particularly preferable because it is easy to use.

The bundled yarn has a spinning draft ratio of 300-.
It is important that the filament is drawn at a spinning speed of 500 to 700 to 1500 m / min to form an undrawn yarn having a single yarn fineness of less than 5 denier. Here, when the draft ratio is less than 300, the spinning tension (extension stress) applied to the unsolidified yarn in the heating atmosphere becomes insufficient and fusion occurs between the single yarns. On the other hand, when it exceeds 500, the spinning tension becomes too high, and the yarn breakage easily occurs. Spinning speed is 700m
If it is less than / minute, the discharge linear velocity for obtaining an undrawn yarn of less than 5 denier becomes too low, and stable spinning cannot be performed. On the other hand, when it exceeds 1500 m / min, the spinning tension becomes too high and single yarn breakage easily occurs. When the single yarn fineness of the undrawn yarn is 5 denier or more, the draw ratio must be increased in order to obtain a drawn yarn having a single yarn fineness of less than 1 denier, and stable drawing cannot be performed. The object of the invention cannot be achieved.

The undrawn yarn obtained has a glass transition point of 1 or more.
After the first stage drawing to 3.0 to 4.0 times at a temperature of 15 ° C or less, the total draw ratio is 4.5 to 120 ° C at a temperature of 120 to 270 ° C.
It is desirable that the film be stretched in multiple stages so as to be 5.5 times. .
Here, when the first-stage drawing temperature is lower than the glass transition point, stable drawing cannot be carried out. On the contrary, when the first-stage drawing temperature exceeds 115 ° C., crystallization of the polyester proceeds, so that the drawing ratio can be increased. It becomes difficult to obtain ultrafine fibers having a denier less than 1 denier. In particular, in order to obtain a high-strength ultrafine polyester fiber of 8 g / de or more, it is important to carry out multi-stage drawing.

The stretching may be a separate stretching method in which a spun unstretched yarn is once wound and then stretched in a separate step, or a direct stretching method in which it is continuously stretched without being once wound.

[0017]

In the manufacturing method of the present invention, the spun yarn is treated with 3
Since the thinned and cooled and solidified yarns are bundled in two stages while passing through an atmosphere heated and held at 00 ° C or higher, the spinning tension applied to the single yarn does not become so large, and The fluctuation range can be reduced. As a result, 1
It is possible to stably produce ultrafine fibers having a denier or less and to obtain high quality fibers.

Since the drawing conditions are multi-step drawing of two or more steps, high-magnification drawing is possible and high-strength ultrafine fibers can be stably obtained.

[0019]

EXAMPLES The present invention will be described in more detail with reference to examples.

[Examples 1 to 3, Comparative Examples 1 to 5] Intrinsic viscosity (measured at 30 ° C using orthochlorophenol as a solvent)
A polyethylene terephthalate chip having a viscosity of 0.62 was subjected to solid-state polymerization at 220 ° C. under reduced pressure to obtain a chip having an intrinsic viscosity shown in Table 1. This solid-state polymerized chip was melted under the conditions shown in Table 1, introduced into a spinning pack, filtered, and then discharged from the spinneret shown in Table 1 at a rate shown in Table 1 to form a heating region having a temperature set in Table 1. After passing through, it was cooled and solidified with cooling air of 15 to 50 ° C., and the first stage focusing guide with an inner diameter of 30 mm and the second stage with an inner diameter of 3 mm were installed at the positions shown in Table 1 from the die surface. After being converged by the focusing guide, it was taken up once with the draft rate and the take-up speed shown in Table 1 and wound up. The heating region temperatures at the positions of 10 cm, 30 cm, and 40 cm below the die at this time are also shown in Table 1.

The undrawn yarn thus obtained was preheated by a preheating roller at 95 ° C., then drawn in the first stage at the ratio shown in Table 1, and then 27
A non-contact heating bath at 0 ° C. was passed for 1 second to carry out the second stage drawing so that the total draw ratio was the ratio shown in Table 1, followed by relaxation heat setting and winding to obtain a drawn yarn. The results are shown together in Table 1.

[0022]

[Table 1]

[0023]

According to the method of the present invention, since the spinning tension is not so large and the fluctuation range thereof is small, it is possible to extremely stably produce ultrafine fibers of 1 denier or less,
Moreover, the quality unevenness is extremely small.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a melt spinning apparatus of the present invention.

FIG. 2 is a schematic view showing an example of a conventional melt spinning apparatus.

[Explanation of Codes] 1 Spinneret 2 Spinneret pack 3 Spinneret 4 Dowsome box 5 Heater 6 Cooling air blower 7 Thread 8 Focusing device 9 Air exhaust 10 Oiling roller 11 Winder

Claims (3)

[Claims] 1. When producing an ultrafine polyester fiber having a single yarn fineness of less than 1 denier, polyethylene terephthalate having an intrinsic viscosity of 0.90 or more is melted and discharged from a spinneret having 200 to 500 discharge holes, and the discharge is performed. 3 yarns
After passing through a heating atmosphere maintained at a temperature of 00 ° C. or higher, the solidified yarn is cooled and solidified, and
Focused in 2 stages between ~ 3m, spinning draft rate 30
A method for producing an ultrafine polyester fiber, which comprises drawing an undrawn yarn having a single yarn fineness of less than 5 denier by drawing at 0 to 500 and a drawing speed of 700 to 1500 m / min, and then drawing the undrawn yarn in multiple stages. 2. The method for producing an ultrafine polyester fiber according to claim 1, wherein the distance between the first-stage focusing position and the second-stage focusing position is 10 to 50 cm. 3. The method for producing an ultrafine polyester fiber according to claim 1, wherein the bundle diameter of the first stage is 1/5 to 1/15 of the outermost diameter of the spinneret discharge hole group.